Ultra-high energy density thin-film capacitors with high power density using BaSn0.15Ti0.85O3/Ba0.6Sr0.4TiO3 heterostructure thin films J. Power Sources (IF 6.945) Pub Date : 2018-12-10 Shihui Yu, Chunmei Zhang, Muying Wu, Helei Dong, Lingxia Li
Ultra-high energy storage performance of lead-free ferroelectric materials has been achieved at room temperature by heterostructure composite based on environment-friendly BaSn0.15Ti0.85O3 and Ba0.6Sr0.4TiO3 thin films. The dielectric constant and loss tangent of BaSn0.15Ti0.85O3 layers grown on the Ba0.6Sr0.4TiO3 layers respectively are calculated as 402 and 0.0137 at 100 kHz. The interfacial layer between BaSn0.15Ti0.85O3 and Ba0.6Sr0.4TiO3 layers can improve the dielectric constant and reduce the loss tangent of heterostructures. The electrical breakdown strength can be significantly enhanced by the interfacial layer, and the influence mechanism is proposed. Ultra-high energy storage density as high as 43.28 J/cm3, is obtained at a sustained high bias electric field of 2.37 MV/cm with a power density of 6.47 MW/cm3 and an efficiency of 84.91% in the BaSn0.15Ti0.85O3/Ba0.6Sr0.4TiO3 heterostructure thin films.
Reproducibility and robustness of microbial fuel cells technology J. Power Sources (IF 6.945) Pub Date : 2018-12-08 Sara Mateo, Pablo Cañizares, Manuel Andrés Rodrigo, Francisco Jesús Fernández-Morales
This work focuses on the evaluation of the robustness and reproducibility of the behaviour of microbial fuel cells (MFCs). Up to 112 MFCs were operated simultaneously under the same conditions, finding that the probability of high performance, maximum power, maximum current and internal resistance is 95%, 90%, 96% and 94% respectively. Reproducibility of stacks was also evaluated by testing different electrical connections, finding that when evaluating the performance of 7 stacks of 16 MFCs each connected in parallel and different combinations of series/parallel, the maximum power varies only between 1 and 2 mW. Results obtained also helps to demonstrate that the performance of the bioelectrochemical devices evaluated mainly depended on the internal resistance. All these information is of a great significance for future developments of the technology because it is a real first step in the characterization of the robustness of the bioelectrochemical technology.
Acceptor-doped La1.9M0.1Ce2O7 (M = Nd, Sm, Dy, Y, In) proton ceramics and in-situ formed electron-blocking layer for solid oxide fuel cells applications J. Power Sources (IF 6.945) Pub Date : 2018-12-08 Bo Zhang, Zhibing Zhong, Taiping Tu, Kewen Wu, Kaiping Peng
In the present work, La1.9M0.1Ce2O7 (M = Nd, Sm, Dy, Y, In) powders are synthesized by citric acid-nitrate sol-gel combustion method. The effects of the acceptor dopant on the phase structure, microstructure and electrical properties of La1.9M0.1Ce2O7 ceramics are investigated. All La1.9M0.1Ce2O7 ceramics possess a single-phase fluorite structure. It turns out that the In-doped ceramic exhibits the highest electrical conductivity of 0.82 × 10−2 and 2.03 × 10−2 S cm−1 at 700 °C both in dry air and wet 5% H2Ar atmospheres, respectively. Furthermore, in order to eliminate the internal short circuit resulting from the reduction of Ce4+ to Ce3+, a novel NiBaCe0.5Zr0.3Dy0.2O3-δ composite is applied and evaluated as the anode for the fuel cell based on La1.9In0.1Ce2O7 electrolyte. Raman and scanning electron microscope and energy dispersive spectrometer analyses indicate that a Ba-containing electron-blocking layer is formed in-situ at the anode/electrolyte interface. The new structured fuel cell with NiBaCe0.5Zr0.3Dy0.2O3-δ anode and La1.9In0.1Ce2O7 electrolyte exhibit significantly improved open circuit voltage of 1.005 V along with maximum power density of 546 mW cm−2 at 700 °C using humidified hydrogen fuel. The results demonstrate that La1.9In0.1Ce2O7 electrolyte and NiBaCe0.5Zr0.3Dy0.2O3-δ anode can be considered as the promising candidates for solid oxide fuel cells applications.
Carbon particles co-doped with N, B and Fe from metal-organic supramolecular polymers for boosted oxygen reduction performance J. Power Sources (IF 6.945) Pub Date : 2018-12-07 Yuntong Li, Zhongyu Li, Yuzhe Wu, Haiyang Wu, Hong Zhang, Tong Wu, Conghui Yuan, Yiting Xu, Birong Zeng, Lizong Dai
Rational design of high-efficiency and cost-effective nonprecious metal-based catalysts with outstanding oxygen reduction reaction (ORR) performance, is of great importance to replace platinum-based electrocatalysts in fuel cell. Herein, a novel N, B and Fe co-doped carbon materials (Fe-NBC) electrocatalyst is designed through the pyrolysis of a metal-organic coordination polymer precursor, which is formed from the coordination between dendrimer-like terpyridinic monomer and Fe3+. The as-prepared Fe-NBC catalyst exhibits superior ORR activity with an onset potential of 0.98 V and a half-wave potential of 0.86 V, which are comparable to that of the Pt/C catalyst. The formation of Fe-Nx moieties is considered to be the most important factor for the improved ORR activity of Fe-NBC. Besides, Fe-NBC catalyst displays a better methanol tolerance as well as durability (5 mV negative shift of E1/2, after 1000 cycles) in comparison with Pt/C (12 mV negative shift of E1/2, after 1000 cycles). This work provides a facile protocol for the design and fabrication of multi-element co-doped carbon materials. Moreover, the excellent ORR performance of these N, B and Fe co-doped carbon materials may be a potential candidate to replace Pt-based catalyst in fuel cells.
Enhanced electronic conductivity and sodium-ion adsorption in N/S co-doped ordered mesoporous carbon for high-performance sodium-ion battery anode J. Power Sources (IF 6.945) Pub Date : 2018-12-07 Jianqi Ye, Hanqing Zhao, Wei Song, Na Wang, Mengmeng Kang, Zhong Li
The unique interconnected mesoporous structure and high specific surface area facilitate the diffusion and absorption of Na+, making ordered mesoporous carbon a promising candidate for the anode of sodium-ion batteries. However, low electronic conductivity and scanty defects cause unsatisfied sodium storage capacity. Heteroatoms doping is regarded as an efficient strategy to modify the physicochemical properties of carbonaceous materials and in this work, nitrogen and sulfur are simultaneously doped into the framework of ordered mesoporous carbon via a one-step thermal treatment. The N/S co-doped samples possess an enhanced electronic conductivity, rich defects, and improved Na+ adsorption capability, realizing a superior capacity of 419 mA h g−1 at 0.1 A g−1 after 150 cycles and retaining 220 mA h g−1 at 5 A g−1 even after 3000 cycles. As a consequence, the facile synthetic route and excellent sodium storage properties make N/S co-doped ordered mesoporous carbon show great prospect for the application of sodium-ion batteries anode material.
An evolutionary framework for lithium-ion battery state of health estimation J. Power Sources (IF 6.945) Pub Date : 2018-12-07 Lei Cai, Jinhao Meng, Daniel-Ioan Stroe, Guangzhao Luo, Remus Teodorescu
Battery energy storage system expands the flexibility of the electricity grid, which facilitates the extensive usage of renewable energies in industrial applications. In order to ensure the techno-economical reliability of the battery energy storage system, managing the lifespan of each battery is critical. In this paper, a novel evolutionary framework is proposed to estimate the Lithium-ion battery state of health, which uniformly optimizes the two key processes of establishing a data driven estimator. The features in the degradation process of a battery are conveniently measured by a group of current pulses, which last only few seconds. The proposed evolutionary framework selects the most efficient combination of the short-term features from the current pulse test, and guarantees an optimal training process simultaneously. A hybrid encoding technology is applied to mix the feature extraction and the parameters of support vector regression in one chromosome. With the benefit of the proposed evolutionary framework, the battery state of health is estimated by using support vector regression and genetic algorithm in a more efficient way. A mission profile corresponding to batteries providing the primary frequency regulation service to the power system is used to cycle two Lithium-ion batteries for the validation of the proposed method.
Effect of compression on the water management of polymer electrolyte fuel cells: An in-operando neutron radiography study J. Power Sources (IF 6.945) Pub Date : 2018-12-07 Y. Wu, J.I.S. Cho, X. Lu, L. Rasha, T.P. Neville, J. Millichamp, R. Ziesche, N. Kardjilov, H. Markötter, P. Shearing, D.J.L. Brett
In-depth understanding of the effect of compression on the water management in polymer electrolyte fuel cells (PEFCs) is indispensable for optimisation of performance and durability. Here, in-operando neutron radiography is utilised to evaluate the liquid water distribution and transport within a PEFC under different levels of compression. A quantitative analysis is presented with the influence of compression on the water droplet number and median droplet surface area across the entire electrode area. Water management and performance of PEFCs is strongly affected by the compression: the cell compressed at 1.0 MPa demonstrates ∼3.2% and ∼7.8% increase in the maximum power density over 1.8 MPa and 2.3 MPa, respectively. Correlation of performance to neutron radiography reveals that the performance deviation in the mass transport region is likely due to flooding issues. This could be ascribed to the loss of the porosity and increased tortuosity factor of the gas diffusion layer under the land at higher compression pressure. The size and number of droplets formed as a function of cell compression was examined: with higher compression pressure, water droplet number and median droplet surface area rapidly increase, showing the ineffective water removal, which leads to fuel starvation and the consequent performance decay.
Synergic effect of ionic liquid grafted titanate nanotubes on the performance of anion exchange membrane fuel cell J. Power Sources (IF 6.945) Pub Date : 2018-12-06 Vijayakumar Elumalai, Dharmalingam Sangeetha
Titanate nano tubes, prepared by hydrothermal method, are covalently bonded with a basic ionic liquid (1-Methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride) resulting in an ion exchange behaviour. The ionic liquid bonded Titanate nano tubes are characterised by SEM, TEM, XRD studies for their nano tube morphology and covalent bond between them which are confirmed by solid state NMR and FTIR. This synthesised filler, in various concentrations (1, 3, 5 and 7 wt%), are incorporated into quaternised polysulfone leading to the fabrication of nano composite membranes with high ion exchange capacity. The fabricated nano composite membranes are characterised by SEM, XRD, water uptake, ion exchange capacity and hydroxyl conductivity studies to evaluate their suitability as an electrolyte in alkaline fuel cell applications. Upon testing these membranes in fuel cell setup with platinum anode and silver cathode, amongst the various composites, the membrane with 5% wt filler exhibits the most optimum properties for application in alkaline fuel cells with a power density of 302 mW/cm2. The existence of ion exchange behaviour as well as the hollow nature of titanate nano tubes leads to synergistic effect in conducting the hydroxyl ions via both Grotthus (through water molecules) and hopping (through ion exchange groups) mechanisms.
Modelling voltametric data from electrochemical capacitors J. Power Sources (IF 6.945) Pub Date : 2018-12-05 Hannah M. Fellows, Marveh Forghani, Olivier Crosnier, Scott W. Donne
Linear and cyclic voltammetry are common method for the characterization of electrochemical capacitor electrodes. Herewith we describe an approach to modelling voltametric data to provide more detailed information about the electrode under study. The model is based upon the response of a series arrangement of a resistor and capacitor to a linearly changing potential to simulate a double layer capacitor. Also included is a term to account for redox processes in localized domains, electrode instability at the extremes of potential, as well as electrode resistance, each of which represent behaviour commonly encountered in electrochemical capacitors. Development of the model is presented, together with its application to the aqueous manganese dioxide electrode.
Co-Ni-MoSx yolk-shell nanospheres as superior Pt-free electrode catalysts for highly efficient dye-sensitized solar cells J. Power Sources (IF 6.945) Pub Date : 2018-12-04 Xing Qian, Hongyu Liu, Yixuan Huang, Zejia Ren, Yating Yu, Chong Xu, Linxi Hou
Transition metal chalcogenides with yolk-shell nanostructures are a family of promising electrocatalytic materials with complex interior construction and remarkable structural tenability. In this work, a sequence of yolk-shell transition metal sulfide nanospheres (Co-Ni-MoSx, Co-MoSx and Ni-MoSx) are prepared as superior Pt-free catalysts for dye-sensitized solar cells. This yolk-shell structure, consisting of a thin shell and an inner porous core, exposes more active sites and provides more contact regions between the electrolyte and catalyst. By comparing with the ternary Co-MoSx and Ni-MoSx nanospheres, the quaternary Co-Ni-MoSx nanospheres have advantages of the relatively larger surface area, favourable chemical composition, higher conductivity and excellent catalytic performance for expediting the reduction of I3− in solar cells. Particularly, as for Co-Ni-MoSx, a splendid power conversion efficiency of 9.76% is achieved under a standard irradiation, which is much better than that of Pt (8.24%).
Strong synergetic electrochemistry between transition metals of α phase Ni−Co−Mn hydroxide contributed superior performance for hybrid supercapacitors J. Power Sources (IF 6.945) Pub Date : 2018-12-04 Yuying Zhu, Chenghao Huang, Chao Li, Meiqiang Fan, Kangying Shu, Hai Chao Chen
Electroactive materials with high electrochemical activity, good rate capability and excellent cycling stability are urgently needed for hybrid supercapacitors, but achieving those performances at the same time is still a big challenge. Here, α phase nickel−cobalt−manganese hydroxide (NiCoMn−OH) with a flower-like structure is synthesized and used as the battery materials for hybrid supercapacitor. The NiCoMn−OH exhibits strong synergetic electrochemistry between the transition metals, which contributes better charge storage performances. The NiCoMn−OH shows a specific capacity of 757 C g−1 at 1 A g−1 and retains 369 C g−1 at very high specific current of 50 A g−1, which are both much higher than the corresponding bimetal and nomometal hydroxides. Therefore, both high electrochemical activity and rate capability have been achieved. The α phase NiCoMn−OH also exhibits a long-term cycling stability because the specific role of Co, maintaining 100% of the specific capacity after 1200 cycles. The hybrid supercapacitor based on NiCoMn−OH also shows high specific capacity of 219 C g−1 at 1 A g−1, high rate performance of 53% capacity retention when the specific current increases 25 times and ultralong cycling stability of 83% capacity retention after 12,000 cycles.
High capacity semi-liquid lithium sulfur cells with enhanced reversibility for application in new-generation energy storage systems J. Power Sources (IF 6.945) Pub Date : 2018-12-04 Daniele Di Lecce, Vittorio Marangon, Almudena Benítez, Álvaro Caballero, Julián Morales, Enrique Rodríguez-Castellón, Jusef Hassoun
Semi-liquid configuration of sulfur cell is proposed as simple strategy to develop high-energy lithium battery. Two solutions of Li2S8 in diethylene glycol dimethyl ether (DEGDME), containing either lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium trifluoromethansulfonate (LiCF3SO3) and lithium nitrate (LiNO3), are studied as catholytes for Li/S cells exploiting the polysulfides electrochemical reaction at about 2.2 V vs. Li+/Li. X-ray photoelectron spectroscopy (XPS) and thermal analyses, respectively, reveal composition and high-temperature stability of the catholyte solutions. Ad hoc study conducted by impedance spectroscopy, voltammetry, and galvanostatic techniques suggests well suitable characteristics in terms of Li+-transport ability, electrochemical stability window, and electrode/electrolyte interphase features. Cells with sulfur loading ranging from about 3 to 6 mg cm−2 into the solution are successfully studied with remarkable performances in terms of current rates, efficiency and cycle life. Hence, the lithium cells based on the catholyte deliver maximum capacity of the order of 1100 mAh gS−1 at C/10 rate and stable capacity of about 800 mAh gS−1 at C/3 rate with Coulombic efficiency exceeding 99%. Therefore, the catholyte solutions studied herein are considered as a very promising candidates for high-energy storage in next generation systems, such as the intriguing hybrid and electric vehicles.
An easy-to-implement multi-point impedance technique for monitoring aging of lithium ion batteries J. Power Sources (IF 6.945) Pub Date : 2018-12-04 Xing Zhou, Zhengqiang Pan, Xuebing Han, Languang Lu, Minggao Ouyang
The need for a quick yet informative technique for diagnosing the lithium-ion batteries is escalating. Conventional impedance-based diagnosis methods are usually time-demanding for a complete electrochemical impedance spectroscopy measurement and involve complicated calculations to extract battery information, which therefore have limited applications in battery monitoring. In this study, we propose a multi-point impedance technique, involving impedance measurement on three characteristic frequency points and being able to separate ohmic, contact and solid electrolyte interphase resistances. The characteristic frequency points are calibrated using distribution of relaxation time method. This multi-point impedance technique holds potential for large-scale high-throughput battery monitoring and screening.
Effect of nonionic surfactant as an electrolyte additive on the performance of aluminum-air battery J. Power Sources (IF 6.945) Pub Date : 2018-12-03 M.A. Deyab
In this work, the aluminum-air battery performance is improved by adding nonionic surfactant (nonoxynol-9) to battery electrolyte (4.0 M NaOH). The efficiency of nonoxynol-9 is determined using hydrogen gas evolution and electrochemical measurements. The surface analysis is explored using scan electron microscope and energy dispersive X-ray spectroscopy. Battery performance is investigated at 20 mA cm−2. The results show that the battery performance is significantly improved by adding nonoxynol-9. This is due to the low corrosion rate of aluminum in 4.0 NaOH solution resulted from physical adsorption of nonoxynol-9 on aluminum surface. The surfactant suppresses the hydrogen gas evolution and increases the anode utilization and capacity density. The maximum inhibition efficiencies of nonoxynol-9 from hydrogen gas evolution and electrochemical measurements are 85.6% and 92.8%, respectively at 2.0 mM. Nonoxynol-9 behaves as a cathodic-type inhibitor and its adsorption complies with Freundlich type isotherm. The adsorption of surfactant on the aluminum surface is emphasized by surface analysis.
Tetragonal LiMn2O4 as dual-functional pseudocapacitor-battery electrode in aqueous Li-ion electrolytes J. Power Sources (IF 6.945) Pub Date : 2018-12-03 Mozaffar Abdollahifar, Sheng-Siang Huang, Yu-Hsiang Lin, Hwo-Shuenn Sheu, Jyh-Fu Lee, Meng-Lin Lu, Yen-Fa Liao, Nae-Lih Wu
The development of low-cost electrode with high capacity and long cycle-life is an essential issue for energy storage devices. Herein a unique nanostructured tetragonal LiMn2O4 (TLMO) electrode exhibiting mixed pseudocapacitor and battery behaviors in Li ion-containing aqueous electrolytes is derived via a novel in-situ low-temperature ion-exchange method from nanocrystalline ZnMn2O4. The complementary actions between the pseudocapacitance and battery properties enable TLMO to substantially outperform, in terms of the combination of high capacity, long cycle stability and suppressed self-discharge, its counterparts having only either one of the electrochemical behaviors, along with many other notable pseudocapacitive materials. The phase transformation mechanism during the ion-exchange process and charge-storage mechanisms are revealed using operando/in situ synchrotron X-ray analyses. This study may open up a new design concept in charge-storage electrode materials.
Microfluidic water splitting cell using 3D NiFe2O4 hollow spheres J. Power Sources (IF 6.945) Pub Date : 2018-12-03 A. Martínez-Lázaro, A. Rico-Zavala, F.I. Espinosa-Lagunes, Julieta Torres-González, L. Álvarez-Contreras, M.P. Gurrola, L.G. Arriaga, J. Ledesma-García, E. Ortiz-Ortega
The present research work shows a simple method to synthesize 3D NiFe2O4 hollow spheres by a hydrothermal route and its application as catalyst for water splitting in an alkaline microfluidic system. The NiFe2O4 was developed by a simple mechanism from the urea hydrolysis reaction and later subjected to a hydrothermal process to carry out a single-step synthesis, obtaining novel 3D hollow nanospheres with doubles, triples and quadruples shells. 3D NiFe2O4 with large surface area and stability showed a catalytic activity for the oxygen evolution reaction (OER) comparable with the commercial material commonly employed IrO2. The NiFe2O4-based material was used as an anode and cathode in a microfluidic water splitting device, where the H2 production was 2.5 and 2.7 × 10−5 mg s−1 for 3D NiFe2O4 hollow spheres and IrO2Pt/C, respectively.
The construction of rod-like polypyrrole network on hard magnetic porous textile anodes for microbial fuel cells with ultra-high output power density J. Power Sources (IF 6.945) Pub Date : 2018-12-03 Fei Li, Dong Wang, Qiongzhen Liu, Bo Wang, Weibing Zhong, Mufang Li, Ke Liu, Zhentan Lu, Haiqing Jiang, Qinghua Zhao, Chuanxi Xiong
This study attempts to prompt the formation of microorganism films on flexible textile-based anodes and enhances the performance of living microorganisms by introducing magnetic properties to the anodes. A magnetic and electrically conductive anode for a microbial fuel cell is designed and fabricated by encapsulating uniformly dispersed SrFe12O19 nanoparticles into the poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibers and forming a three-dimensional (3D) polypyrrole (PPy) network on the surface of flexible composite nanofiber based fabric. A dual-chamber MFC equipped with the magnetized anode shows a maximum power density of 3317 mW m−2, which is significantly larger than that of the non-magnetized anode (2471 mW m−2). This study demonstrates that the hard-magnetic anode providing an inherent magnetic field can greatly promote bio-electrochemical reaction rates of E. coli, and decrease the anode charge transfer resistance in a MFC system.
A modelling and simulation study of soluble lead redox flow battery: Effect of presence of free convection on the battery characteristics J. Power Sources (IF 6.945) Pub Date : 2018-12-03 Mahendra Nandanwar, Sanjeev Kumar
In this paper, we develop a mathematical model for soluble lead redox flow battery. The model accounts for simultaneous effect of forced convection and induced free convection in electrolyte domain of the battery. It predicts existence of dominant free convection over the forced convection in vicinity of the electrodes. The predictions suggests that both, electrode kinetics and ion transfer assisted by free convection alone, controls charge-discharge characteristics of the battery. The free convection augments ion transfer rate to the electrodes. By virtue of this, limiting current density at the electrodes increases to twice the theoretical limit under forced convection. The predictions coherently explains Collins et al. ‘s observations of high charge efficiencies when charging currents are higher than the theoretical limit. Also, the model consistently explains Pletcher et al. ‘s observation of insensitivity of the battery characteristics to the electrolyte flow rate. The model predicts satisfactory battery performance even at microscopic (μL s−1) flow rates which opens up the possibility for significant reduction in electrolyte pumping cost.
Evaluation of convective heat transfer coefficient and specific heat capacity of a lithium-ion battery using infrared camera and lumped capacitance method J. Power Sources (IF 6.945) Pub Date : 2018-12-03 Xiaoxuan Zhang, Reinhardt Klein, Anantharaman Subbaraman, Sergei Chumakov, Xiaobai Li, Jake Christensen, Christian Linder, Sun Ung Kim
The electrochemical performance of lithium-ion batteries is highly temperature dependent. An accurate determination of battery thermal parameters is crucial for research including cell thermal analysis, safety design, and multiphysics simulations. This work explores the possibility to use a lumped capacitance model based experimental approach to measure the battery convective heat transfer coefficient and specific heat capacity. In this approach, the transient temperature of the battery and its can (by removing the jellyroll) is measured with an infrared radiation camera. When the Biot number of the battery Bi ≪1, the lumped capacitance model can be used to determine cell specific heat capacity through the measured battery surface temperature, where the convective heat transfer coefficients of both the can and the battery are the same and the specific heat capacity of the can is known. As an example, the specific heat capacity of LG G5 smartphone batteries is measured to demonstrate the proposed approach. The specimens are tested under both natural and forced convection conditions. The measured cell specific heat capacity is very consistent between these two convection conditions.
Bis(trimethylsilyl) 2-fluoromalonate derivatives as electrolyte additives for high voltage lithium ion batteries J. Power Sources (IF 6.945) Pub Date : 2018-12-03 Hailong Lyu, Yunchao Li, Charl J. Jafta, Craig A. Bridges, Harry M. Meyer, Albina Borisevich, Mariappan Parans Paranthaman, Sheng Dai, Xiao-Guang Sun
Three trimethylsilyl based malonate esters, bis(trimethylsilyl) 2-methyl-2-fluoromalonate (BTMSMFM), bis(trimethylsilyl) 2-ethyl-2-fluoromalonate (BTMSEFM) and bis(trimethylsilyl) 2-propyl-2-fluoromalonate (BTMSPFM), have been used as additives in 1.0 M LiPF6/ethylene carbonate (EC)-dimethyl carbonate (DMC)-diethyl carbonate (DEC) (1-1-1, by v) baseline electrolyte for LiNi0.80Co0.15Al0.05O2 (NCA) based high voltage lithium ion batteries. The NCA half-cells with 5 wt% BTMSMFM exhibit higher capacity retention than that in the baseline electrolyte at different upper cut off voltages, that is, 4.2, 4.3, 4.4 and 4.5 V vs. Li/Li+. Scanning electron microscope (SEM) show that the additive successfully prevents the formation of thick solid electrolyte interphase (SEI) films on the surface of the NCA electrodes. X-ray diffraction (XRD) further reveals that the crystal structure of NCA is also maintained in the electrolyte with 5 wt% BTMSMFM at high cut off voltages. Besides beneficial to NCA cathode, the BTMSMFM additive also ensures better cycling performance of the graphite based half-cells and NCA/graphite full-cells, and thus is a promising additive for application in rechargeable lithium ion batteries.
A survey on driving prediction techniques for predictive energy management of plug-in hybrid electric vehicles J. Power Sources (IF 6.945) Pub Date : 2018-12-02 Yang Zhou, Alexandre Ravey, Marie-Cécile Péra
Driving prediction techniques (DPTs) are used to forecast the distributions of various future driving conditions (FDC), like velocity, acceleration, driver behaviors etc. and the quality of prediction results has great impacts on the performance of corresponding predictive energy management strategies (PEMSs), e.g., fuel economy (FE), lifetime of battery etc. This survey presents a comprehensive study on existing DPTs. Firstly, a review on prediction objectives and major types of prediction algorithms are presented. Then a comparative study on various prediction approaches is carried out and suitable application scenarios for each approach are provided according to their characteristics. Moreover, prediction accuracy-affecting factors are analyzed and corresponding approaches for dealing with mis-predictions are discussed in detail. Finally, the bottlenecks of current researches and future developing trends of DPTs are given. In general, this paper not only gives a comprehensive analysis and review of existing DPTs but also indicates suitable application scenarios for each prediction algorithm and summarizes potential approaches for handling the prediction inaccuracies, which will help prospective designers to select proper DPTs according to different applications and contribute to the further performance enhancements of PEMSs for hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs).
Clean energy from human sweat using an enzymatic patch J. Power Sources (IF 6.945) Pub Date : 2018-12-02 R.A. Escalona-Villalpando, E. Ortiz-Ortega, J.P. Bocanegra-Ugalde, Shelley D. Minteer, J. Ledesma-García, L.G. Arriaga
The development of devices capable of generating energy through biofluids, such as sweat, is an effort to integrate flexible devices that can be powered and used on the skin. A patch-type completely enzymatic biofuel cell (p-EBFC) is developed using bilirubin oxidase- and lactate oxidase-based electrodes as biocathode and bioanode respectively, where both enzymes are immobilized on flexible Toray carbon paper-modified. The evaluation of the half-cells shows that the bioelectrodes had good catalytic activity towards the oxygen reduction and lactic acid oxidation reactions using natural human sweat. The wireless p-EBFC on the skin is capable to delivery an open circuit voltage of 0.55 ± 0.03 V and a short circuit current of 140 ± 4 μA cm−2. Also, the p-EBFC maintains its performance of 20 μW cm−2 and 30 μA cm−2 continuously for 30 min in a sweat delivery from the arm of a healthy volunteer during workouts. In addition, a wireless device is incorporated in order to monitor via a cell phone the energy produced in real time.
Collection optimization of photo-generated charge carriers for efficient organic solar cells J. Power Sources (IF 6.945) Pub Date : 2018-12-01 Yang Sun, Shudi Lu, Rui Xu, Kong Liu, Ziqi Zhou, Shizhong Yue, Muhammad Azam, Kuankuan Ren, Zhongming Wei, Zhijie Wang, Shengchun Qu, Yong Lei, Zhanguo Wang
Collection of photo-generated charge carriers is of significance in organic photovoltaic devices. Herein, we focus on systematically exploring the effective methods to improve the charge collection efficiency in organic solar cells based on PBDB-T: ITIC. In the active layer, we observe that the energy level bending at the interface of acceptor/donor is influential to the recombination of charge carriers. For extracting electrons efficiently, we propose that using SnO2 instead of ZnO as the electron conducting layer is advantageous in improving short-circuit current (Jsc), power conversion efficiency (PCE), and particularly stability. To unveil the dynamics of hole collection, we use different metals as the anode and find out that enlarging the work function of the anode close to the highest occupied molecular orbital (HOMO) of the donor is beneficial for enhancing the open-circuit voltage (Voc), Jsc, fill factor (FF) and thus PCE. The optimized device delivers a PCE of 10.77%. Insights on how to efficiently extract photo-generated charge carriers are elaborated systematically.
A solution-processed cobalt-doped nickel oxide for high efficiency inverted type perovskite solar cells J. Power Sources (IF 6.945) Pub Date : 2018-11-30 Ju Ho Lee, Young Wook Noh, In Su Jin, Sang Hyun Park, Jae Woong Jung
Optimal interfaces play an important role in determining the efficiency of perovskite solar cells. Despite nickel oxide is a promising hole transport material in perovskite solar cells, electrical conductivity and surface properties of pristine nickel oxide are not satisfactory for achieving high efficiency perovskite solar cells. Here, we demonstrate that cobalt doping significantly improves not only the electrical conductivity but also the interfaces of nickel oxide hole transport layer. As a result, the hole extraction, transport and collection properties are significantly improved in the device using cobalt-doped nickel oxide as a hole transport layer. Also, it reveals that cobalt-doped nickel oxide reduces the trap-sites of interfaces of perovskite/hole transport layer, leading to suppressed charge recombination in the devices. As a result, the devices using cobalt-doped nickel oxide achieve as high as 17.52% without severe hysteresis, which is attributed to better band alignment, superior hole extraction and decreased resistance, as compared to pristine nickel oxide-based devices.
Modeling of oxygen reduction reaction in porous carbon materials in alkaline medium. Effect of microporosity J. Power Sources (IF 6.945) Pub Date : 2018-11-30 Atsushi Gabe, Ramiro Ruiz-Rosas, Carolina González-Gaitán, Emilia Morallón, Diego Cazorla-Amorós
The role of porosity, and more specifically, microporosity, in the performance of carbon materials as Oxygen Reduction Reaction (ORR) catalysts in alkaline medium still has to be clarified. For this purpose, a highly microporous KOH-activated carbon and a microporous char have been prepared and their ORR performance in alkaline media were compared to that of two commercial carbon blacks with low and high surface areas, respectively. Interestingly, all carbon materials show a two-wave electrocatalytic process, where the limiting current and the number of electron transferred increase when going to more negative potentials. The limiting current and onset potential of the second wave is positively related to the amount of microporosity, and H2O2 electrochemical reduction tests have confirmed that the second wave could be related to the catalytic activity towards this reaction. In accordance to these findings, a model is developed that takes into account narrow and wide micropores in both charge transfer reactions and the mass transfer rate of O2 and H2O2. This model successfully reproduces the experimental electrochemical response during ORR of the analyzed porous carbon materials and suggests the important role of narrow micropores in H2O2 reduction.
Freestanding oxidized poly(acrylonitrile-co-vinylpyrrolidone)/SnCl2 nanofibers as interlayer for LithiumSulfur batteries J. Power Sources (IF 6.945) Pub Date : 2018-12-01 Elif Ceylan Cengiz, Osman Ozturk, Serap Hayat Soytas, Rezan Demir-Cakan
LithiumSulfur batteries are one of the most promising energy storage systems among the next generation batteries due to their high energy density and the natural abundance of sulfur. Nevertheless, some limitations hinder their implementation to the marketplace which are mostly linked to the shuttle effect resulting fast capacity lost and lithium poisoning by dissolved polysulfides. One of the possible solutions is the use of polysulfide adsorptive interlayers between anode and cathode to inhibit the shuttle effect protecting lithium anode. In this work, oxidized poly(acrylonitrile-co-vinylpyrrolidone) nanofibers containing SnCl2 (oPANVP/SnCl2) are used as an interlayer to enhance the performance of LiS cells. Unlike most of the current literature, the electrospun nanofiber mats are oxidized at 200 °C under air, but not further pyrolyzed to benefit from the functional groups and the partial formation of SnOx. 700 mAh g−1 discharge capacity is obtained at C/5 after 100 cycles by using oPANVP/SnCl2, which is higher than the cells with oPANVP and without interlayer. The improved capacity is mostly associated with the complementary adsorption effect of SnCl2 particles, partially formed SnOx and functional groups of oPANVP. Polysulfide adsorption effect of SnCl2, SnOx, and nitrogen- and oxygen-rich functional groups of oPANVP is proven by X-Ray Photoelectron Spectroscopy.
A data-driven remaining capacity estimation approach for lithium-ion batteries based on charging health feature extraction J. Power Sources (IF 6.945) Pub Date : 2018-11-30 Peiyao Guo, Ze Cheng, Lei Yang
Capacity degradation monitoring of lithium batteries is necessary to ensure the reliability and safety of electric vehicles. However, capacity of cell is related to its complex internal physicochemical reactions and thermal effects and cannot be measured directly. A data-driven remaining capacity estimation approach for lithium-ion batteries based on charging health feature extraction is presented in this work. The proposed method utilizes rational analysis and principal component analysis to extract and optimize health features of charging stage which adapt to various working conditions of battery. The remaining capacity estimation is realized by relevance vector machine and validations of different working conditions are made with six battery data sets provided by NASA Prognostics Center of Excellence. The results show high efficiency and robustness of the proposed method.
Biomass-derived 3D hierarchical N-doped porous carbon anchoring cobalt-iron phosphide nanodots as bifunctional electrocatalysts for LiO2 batteries J. Power Sources (IF 6.945) Pub Date : 2018-11-30 Kailing Sun, Jing Li, Lulu Huang, Shan Ji, Palanisamy Kannan, Du Li, Lina Liu, Shijun Liao
Developing lithium-oxygen batteries with high reversibility and long cyclability requires an electrocatalyst with superior catalytic activity and excellent stability to achieve an efficient cathode. Herein, a three-dimensional hierarchically porous carbon framework embedded with cobalt-iron-phosphide nanodots nanocomposite is fabricated via a lyophilization-pyrolysis-phosphorization process. The synthetic catalyst displays excellent performances towards both the oxygen reduction reaction and the oxygen evolution reaction. With our optimal sample, the half-wave potential for the oxygen reduction reaction is up to 0.83 V versus reversible hydrogen electrode, and its potential for the oxygen evolution reaction at a current density of 10 mA cm−2 is as low as 1.53 V in 0.1 M KOH solution. The catalyst also exhibits improved electrochemical performances in a rechargeable lithium-oxygen battery, including a high specific capacity (11969 mAh g−1 at 100 mA g−1) and a long cycle life (141 cycles at a cut-off capacity of 1000 mAh g−1). All of these results make our catalyst a promising candidate for the development of highly efficient electrocatalysts for the rechargeable lithium-oxygen batteries.
Correlation between long range and local structural changes in Ni-rich layered materials during charge and discharge process J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Shiyao Zheng, Chaoyu Hong, Xiaoyun Guan, Yuxuan Xiang, Xiangsi Liu, Gui-Liang Xu, Rui Liu, Guiming Zhong, Feng Zheng, Yixiao Li, Xiaoyi Zhang, Yang Ren, Zonghai Chen, Khalil Amine, Yong Yang
Ni-rich cathode materials can deliver higher energy density with a lower cost compared with other conventional layered oxide materials. However, the cycling performance of Ni-rich materials needs further improvement, and the irreversible phase transformation related to the cell failure is not fully understood yet. Although an H1H2H3 structural change process is revealed, a more specific explanation about the difference of these hexagonal phases is needed for deeper comprehension and further targeted modification of Ni-rich materials. In this work, the different phase transformation mechanisms of LiNi0.6Co0.2Mn0.2O2 (NCM622) and LiNi0.8Co0.1Mn0.1O2 (NCM811) are investigated by C X-ray diffraction (XRD) measurement, and the relationship between structural change and capacity degradation is discussed, showing that H3 phase can be harmful for cycling. In addition, 6Li solid state nuclear magnetic resonance (ss-NMR) experiments are carried out for detecting the Li chemical environment at different state of charge, and the data can be associated with structural change obtained from in operando XRD results. From the analysis mentioned above, a new explanation of H1/H2/H3 is given, and a relationship between long range and local structural change has been put forward for the first time.
Hybrid powertrain, energy management system and techno-economic assessment of rubber tyre gantry crane powered by diesel-electric generator and supercapacitor energy storage system J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Pedro J. Corral-Vega, Luis M. Fernández-Ramírez, Pablo García-Triviño
This paper describes and evaluates a hybrid propulsion system based on diesel generator and supercapacitors (SCs) as energy storage system (ESS) for a rubber tyre gantry (RTG) container crane, which currently operates within the yard of the Algeciras port terminal (Spain) powered by diesel electric generator for supplying the electric drives and motors (hoist and trolley). The SCs, which are connected to the DC bus through a bidirectional DC/DC converter, are controlled by a control strategy based on the DC-bus voltage. The SCs reference current is limited depending on their state-of-charge (SOC). All main components and control strategy of the RTG crane are modelled and simulated in SimPowerSystems. The current and hybrid configuration are simulated and compared under the real working cycle of the RTG crane. The results show the technical viability, the validity of the proposed control strategy, the improvements in the energy efficiency and diesel fuel consumption, and the economic viability of the hybrid propulsion system for the RTG crane.
Metal-air desalination battery: Concurrent energy generation and water desalination J. Power Sources (IF 6.945) Pub Date : 2018-11-29 M. Ghahari, S. Rashid-Nadimi, H. Bemana
The concept of a self-powered water desalination device with the capability of simultaneous electricity generation is introduced. The as-fabricated metal-air desalination battery takes the advantage of integration of ion selective membranes with an aluminum-air battery in a three-chamber cell. The maximum power density of 2.83 W m−2 at 6.58 A.m−2 current density and 0.43 V output voltage is obtained using natural saltwater as the electrolyte. The as-fabricated device decreases the salinity of Caspian saltwater by 37.8% with 10 mW h energy generation in 14-h operation. The obtained results are promising to present considerable room for improvement of the as-fabricated device.
A facile method to intimately contacted nanocomposites as thermoelectric materials: Noncovalent heterojunctions J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Fengrui Liu, Xiaoyan Zhou, Chengjun Pan, Lei Wang
We develop a facile method to intimately contacted hybrid organic-inorganic nanocomposites as thermoelectric materials. By utilizing branched alkyl naphthalimide molecules as the organic component, monodispersed single walled carbon nanotubes are tethered via strong Van der Waals' forces between the two components (i.e., forming heterojunctions). Comparing with using the linear alkyl naphthalimide molecules as the organic component, this leads to much more intimate contact between the two components, which is identified by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. Consequently, the carrier transport is promoted much more at the interface of the branched composites and the thermoelectric properties are enhanced much more compared with those of the linear composites who possess the weaker interactions. The maximum value of the power factor reaches 158.8 μWm−1K−2 while only 85.0 μWm−1K−2 for the linear ones. Because naphthalimide molecules are noncovalently connected to single walled carbon nanotubes, a complex chemical synthesis is avoided, enhancing the use of hybrid nanocomposites in the new energy-related applications, especially the environmentally-friendly applications. We envision that this general, robust and unconventional strategy could be used to create other nanocomposites for use in a variety of applications.
A new breakthrough for graphene/carbon nanotubes as counter electrodes of dye-sensitized solar cells with up to a 10.69% power conversion efficiency J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Fei Yu, Yan Shi, Wenhao Yao, Sheng Han, Jie Ma
A three-dimensional graphene/single-walled carbon nanotube counter electrode is developed for dye-sensitized solar cells via a drop-coating method. The resulting graphene/single-walled carbon nanotube counter electrode show satisfactory transmittance (56.6%) compared with that of bare fluorine-doped tin oxide glass (84.71%) at 670 nm. The obtained graphene/single-walled carbon nanotube counter electrode exhibits an excellent power conversion efficiency of 9.24%. When a mirror was set under the cells, the power conversion efficiency increased to 10.56%. Unexpectedly, in the stability test, its power conversion efficiency reached a maximum of 10.69%. This excellent performance was attributed to the three-dimensional structure, which had a large specific surface area. The cyclic voltammetry results indicate that the graphene/single-walled carbon nanotube had a higher catalytic I3− capability than that of Pt counter electrode, whereas the electrochemical impedance spectroscopy and Tafel test results prove that the graphene/single-walled carbon nanotube have a smaller resistance, which is consistent with the I-V characterization. We determine that the three-dimensional graphene/single-walled carbon nanotube counter electrode may have broad application prospects in dye-sensitized solar cells as a Pt-free material.
Humidity-insensitive fabrication of efficient perovskite solar cells in ambient air J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Feng Wang, Zongbiao Ye, Hojjatollah Sarvari, So Min Park, Ashkan Abtahi, Kenneth Graham, Yuetao Zhao, Yafei Wang, Zhi David Chen, Shibin Li
Fabrication of perovskite solar cells (PSCs) is highly humidity-sensitive. In this paper, humidity-insensitive fabrication (HIF) of efficient CH3NH3PbI3 (MAPbI3) PSCs using an antisolvent method is demonstrated. Characterizations including scanning electron microscope (SEM), X-ray diffraction (XRD), UV–vis absorption and steady-state photoluminescence (PL) of the MAPbI3 films prepared in a glovebox(∼0% RH) and 50% RH ambient air using the antisolvent method are carried out. The quality of the MAPbI3 films shows no obvious difference in these two cases. By analyzing the crystallization processes, the greatly suppressed influence of humidity is ascribed to the rapid crystallization process due to the antisolvent method. The photovoltaic performances and storage stability of MAPbI3 PSCs prepared at a series of relative humidity (RH) levels below 60% are found similar. Their average power conversion efficiency (PCE) is over 15% with the best PCE of 16.9%. In addition, the influence of absorbed water in the hydrophilic precursor to MAPbI3 films and associated solar cells is investigated. The influence of equal molar absorbance of H2O is found ignorable. It is concluded that antisolvent method is an ideal HIF route for fabrication of efficient PSCs in ambient air and may pave the way for massive and low-cost manufacturing of solar panels.
A comparative study of planar and mesoporous perovskite solar cells with printable carbon electrodes J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Wei Chen, Xingtian Yin, Meidan Que, Haixia Xie, Jie Liu, Chenhui Yang, Yuxiao Guo, Yutao Wu, Wenxiu Que
Devices with printable carbon electrodes are promising directions for the commercialization of perovskite solar cells. Most of perovskite solar cells employ mesoporous device structures when using printable carbon as the counter electrodes. Here, we carry a comparative study of planar and mesoporous perovskite solar cells with carbon electrodes. The device efficiency is significantly reduced from 11.37% to 5.27% when the mesoporous TiO2 film is removed from the device structure. Compared with the planar device, smaller carrier transport resistance and bigger carrier recombination resistance are demonstrated for the mesoporous device. Results suggest that the presence of mesoporous TiO2 enables an efficient electron extraction from the perovskite absorber, which remits the serious carrier recombination in the hole transport layer free device due to the hole accumulation. Therefore, the electron extraction efficiency is crucial in these hole transport layer free devices with carbon electrodes. This study helps to develop further optimization of low temperature carbon-based perovskite solar cells for higher reproducibility and higher device performance.
Brownian-snowball-mechanism-induced hierarchical cobalt sulfide for supercapacitors J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Yucheng Zhao, Zhe Shi, Tianquan Lin, Liumin Suo, Chao Wang, Jing Luo, Zhangshun Ruan, Chang-An Wang, Ju Li
Transition metal sulfides with hierarchical (ball in ball) micro/nanoporous structures have drawn wide spread interests for various applications, such as energy storage, catalysis, solar cells, owing to their unique features and intriguing properties. However, precise control of synthesizing process for hierarchical porous nanospheres of transition metal sulfides remains a big challenge. In addition, the charging and discharging process of transition metal sulfides in electrochemical storage is still a black box. Herein we design and precise control of synthesizing a transition metal sulfide with hierarchical porous nanosphere structure, namely cobalt sulfide hierarchical porous nanospheres (HPNs). Brownian snowball mechanism is put forward to explain the formation mechanism of CoS samples, which is supported by first-principles calculations. The proposed Brownian snowball mechanism helps us understand the formation process and facilitates comprehensive and precise manipulation, a key requirement for industrial scale-up. The CoS hierarchical porous nanospheres with a specific surface area of approximately 140 m2/g possess a total specific capacitance of 1310 F/g and 932 F/g at a current density of 5 A/g when used as electrode materials for electrochemical capacitors. The capacitance reflected hybrid electrical energy storage and is separated into double layer charging and the Faradaic contribution from the OH− ions reactions with surface atoms. It is demonstrated that Faradaic capacitance dominates in CoS hierarchical porous nanospheres exceeding 770 F/g by an analysis of the voltammetric sweep data.
New design of polyvalent ammonium salts for a high-capacity electric double layer capacitor J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Yuki Maruyama, Shoko Marukane, Takashi Morinaga, Saika Honma, Toshio Kamijo, Ryo Shomura, Takaya Sato
We have newly designed five kinds of polyvalent solute that have two to four quaternary ammonium functional groups in one cation. Their molecular structure is designed to be as compact as possible, with either two or three cationic groups on a linear molecular structure, or three or four cationic moieties on three strands in a star-shape. The prepared solutes have a bis(trifluoromethylsulfonyl)imide anion in common and a flexible molecular structure that can easily adsorb onto the electrode surface of an electric double layer capacitor (EDLC). Since a single polyvalent solute molecule can accumulate more electric charge by adsorption than can a monovalent solute, a high capacitance is possible even at a low solute concentration compared with conventional cells. We evaluated some electrochemical properties of these polyvalent solutes as an electrolyte and their EDLC performance, including initial capacitance, rate characteristics and cycle durability. All the polyvalent solutes had a potential window of 5 V or more, and in particular the divalent salt showed a capacitor performance equivalent to that of the monovalent salt even at half salt concentration in the electrolyte. On the other hand, the trivalent and tetravalent solutes had a lower charge utilization rate compared with a monovalent solute.
Biomass-derived robust three-dimensional porous carbon for high volumetric performance supercapacitors J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Xiaoguang Liu, Changde Ma, Jiaxin Li, Beata Zielinska, Ryszard J. Kalenczuk, Xuecheng Chen, Paul K. Chu, Tao Tang, Ewa Mijowska
The inherent low volumetric performance of two-dimensional (2D) carbon materials hinders their practical usage in portable devices. Three-dimensional (3D) carbon materials derived from sustainable biomass have been widely investigated but also suffer from the moderate volumetric performance. In this work, using biomass (jujube) as carbon precursor, robust 3D porous carbon with a high particle density of 1.06 gcm−3 is synthesized through high-temperature carbonization and subsequent activation. In three-electrode system, the electrode exhibits an ultrahigh volumetric capacitance of 476 Fcm−3 in 6 M KOH electrolyte, which is much higher than previously reported results. The symmetrical two-electrode supercapacitor delivers excellent rate capability (75% capacitance retention at 20 Ag−1) as well as superior cycle stability (91% capacitance retention after 10,000 cycles) in 1 M H2SO4 electrolyte. Furthermore, an energy density as high as 13 WhL−1 at a power density of 477 WL−1 is demonstrated in 1 M Li2SO4 electrolyte. The high volumetric performance of our biomass-derived porous carbon meets the requirements of portable devices and the fabrication process can be scaled up easily to industrial levels.
Compact and low loss electrochemical capacitors using a graphite / carbon nanotube hybrid material for miniaturized systems J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Qi Li, Shuangxi Sun, Anderson D. Smith, Per Lundgren, Yifeng Fu, Peng Su, Tao Xu, Lilei Ye, Litao Sun, Johan Liu, Peter Enoksson
With the establishment of the internet of things (IoT) and the rapid development of advanced microsystems, there is a growing demand to develop electrochemical capacitors (ECs) to replace bulky electrolytic capacitors on circuit boards for AC line filtering, and as a storage unit in energy autonomous systems. For this purpose, ECs must be capable of handling sufficiently high signal frequencies, display minimum energy loss through self-discharge and leakage current as well as maintaining an adequate capacitance. Here, we demonstrate ECs based on mechanically flexible, covalently bonded graphite/vertically aligned carbon nanotubes (graphite/VACNTs) hybrid materials. The ECs employing a KOH electrolyte exhibit a phase angle of −84.8°, an areal capacitance of 1.38 mF cm−2 and a volumetric capacitance (device level) of 345 mF cm−3 at 120 Hz, which is among the highest values for carbon based high frequency ECs. Additionally, the performance as a storage EC for miniaturized systems is evaluated. We demonstrate capacitive charging/discharging at μA current with a gel electrolyte, and sub-μA leakage current reached within 50 s, and 100 nA level equilibrium leakage within 100 s at 2.0 V floating with an ionic liquid electrolyte.
Catalytic CeO2 washcoat over microchanneled supporting cathodes of solid oxide electrolysis cells for efficient and stable CO2 reduction J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Jingjing Wang, Tengpeng Wang, Libo Yu, Tao Wei, Xun Hu, Zhengmao Ye, Zhi Wang, C.E. Buckley, Jianfeng Yao, George E. Marnellos, Dehua Dong
Infiltration is an effective way to improve porous electrode performance of solid oxide cells while the preparation procedure and catalyst stability still remain challenging. The microchannel structure of cathodes enables the implementation of catalysts into conventional Ni-based cathode supports of solid oxide electrolysis cells via the infiltration process to accelerate CO2 electrolysis. Infiltrating a CeO2 colloid precursor to prepare catalytic washcoat has been demonstrated as a more efficient catalyst preparation and resulted in a more stable CO2 electrolysis performance, compared with infiltrating conventional nitrate precursors. The catalytic CeO2 washcoat possesses a uniform particle size distribution and strong adhesion to the cathode scaffold surface. The optimization of the infiltration process results in a remarkable stability of CO2 electrolysis performance during cell operation for 334 h owing to the stable catalyst microstructure.
Co-sputtered nanocomposite nickel cermet anode for high-performance low-temperature solid oxide fuel cells J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Yonghyun Lim, Hojae Lee, Soonwook Hong, Young-Beom Kim
Nickel-samaria-doped ceria (Ni-SDC) nanocomposite anodes with various compositions are fabricated by co-sputtering technique. The film compositions are effectively controlled by adjusting the applied power to the SDC target while applying a constant power to the Ni target. The microstructure, crystallinity and electrical conductivity of the deposited films are analyzed and their optimal composition is investigated based on fuel cell performance and electrochemical impedance spectroscopy (EIS) analysis. Among various deposition conditions, the lowest polarization resistance is achieved at Ni-SDC 80W condition, which is attributed to the difference in the film composition and expected reaction site densities. Thin film fuel cells with the optimal nickel cermet anode are fabricated on a nanoporous supporting structure to achieve a high cell performance and compared with noble Pt electrode. The fuel cell with the optimal nickel cermet anode yields a maximum power density of 178 mW/cm2 and polarization resistance of 0.55 Ω cm2 at 450 °C, which is significantly improved from the reference Pt anode cell (113 mW/cm2 and 1.69 Ω cm2). Impedance analysis clearly demonstrates that the enhancement in the cell performance originates from the difference in the polarization resistance, resulting from the expanded reaction sites owing to the mixed ion electronic conducting characteristics of the nickel cermet nanocomposite anode.
Dynamic behavior and control strategy study of CO2/H2O co-electrolysis in solid oxide electrolysis cells J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Yuqing Wang, Aayan Banerjee, Olaf Deutschmann
The co-electrolysis of CO2 and H2O in high temperature solid oxide electrolysis cells (SOECs) is a promising energy storage method for intermittent renewable energy sources. In this paper, a three-dimensional (3D) continuum model of a 3-kW 40-cell planar SOEC stack is employed to study the dynamic behavior and control strategy under variable working conditions. The dynamic responses of stack power, current density, output H2/CO ratio and stack temperature are evaluated for a scaled real-time wind power input over a whole day. The fluctuation of the wind power input leads to SOEC stack temperature fluctuation, which illustrates the need for temperature control. Two representative cases with voltage step changes in both endothermic and exothermic operation modes are studied to predict the temperature control by the variation of excess air ratio. The effects of excess air ratio on both the steady-state temperature gradient and the transient temperature variation rate are analyzed in both cases. The temperature fluctuation is successfully controlled by applying an excess air ratio profile that changes with the wind power input.
Error of Darcy's law for serpentine flow fields: Dimensional analysis J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Xuyang Zhang, Xu Zhang, Hidetaka Taira, Hongtan Liu
A serpentine flow field is commonly used in both fuel cells and redox flow batteries. Accurate prediction of mass transfer in the porous gas/liquid diffusion layer (GDL/LDL) is essential for both flow field design optimization and pressure drop predictions. Darcy's law has been widely used to predict fluid flow through GDL/LDL in fuel cells and flow batteries. However, since the inertial effect is neglected in the Darcy's law, significant errors can arise when it is applied to serpentine flow fields. In this work, dimensional analyses are performed using both the Buckingham Pi-theorem and the analytical models developed earlier based on Darcy's law and modified Darcy's law. From the Pi-theorem, four and five non-dimensional parameters are obtained from the Darcy's law and the modified Darcy's law, respectively. The variations of Darcy's law errors in predicting under-land cross-flow rate with each of the non-dimensional parameters are studied. By comparing the coefficient of each term of the two models, two independent Pi-terms for under-land cross-flow rate are obtained. The criterion for applicability of Darcy's law is developed based on the two Pi-terms. The model predicted errors of Darcy's law compared very well with experimental data, thus further confirms the applicability of developed criterion.
Studying mass transport dynamics in polymer electrolyte membrane fuel cells using concentration-alternating frequency response analysis J. Power Sources (IF 6.945) Pub Date : 2018-11-29 A. Sorrentino, T. Vidakovic-Koch, K. Sundmacher
In the present contribution an experimental validation and a measurement routine of a new electrochemical method to study dynamics of electrochemical processes, the so-called concentration alternating frequency response analysis (cFRA) is presented. In cFRA the electrical response of the cell (current or potential) to periodic perturbation of specific reactant feeds is studied by means of linear system analysis. For the example of a polymer electrolyte fuel cell (PEMFC) we show that cFRA, in contrast to classical electrochemical impedance spectroscopy (EIS), detects selectively the effect of the dynamics of mass transport of reactants and products inside the different layers of the PEMFC. Moreover, cFRA can be used to diagnose the humidification state of the fuel cell cathode. Finally, procedures to improve the diagnostic skills of the proposed cFRA technique are discussed and directions of future work are recommended.
Unraveling the composition-activity relationship of PtRu binary alloy for hydrogen oxidation reaction in alkaline media J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Gongwei Wang, Wenzheng Li, Nian Wu, Bing Huang, Li Xiao, Juntao Lu, Lin Zhuang
The research and development of hydrogen oxidation reaction catalysts in alkaline media is a prerequisite for the commercialization of alkaline polymer electrolyte fuel cell. PtRu bimetallic catalyst was found to be more active towards HOR than Pt in alkaline, but the composition-activity relationship of PtRu alloys is still lacking. Herein, a series of PtRu alloy planar electrodes with 14 different compositions were prepared in a high-throughput fashion using an improved magnetron sputtering method. The atomic ratio of Pt was controlled from 6.7% to 99.7% within the samples. The corresponding electro-catalytic activities towards the HOR in alkaline were systematically measured by rotating disc electrode method. A volcano-shape relationship between the HOR exchange current density and the Ru atomic fraction was revealed, and maximum activity was observed at ca. 55% content of Ru. The enhancement in electro-catalytic activity is attributed to a reduction in the electronic charge density of Pt upon Ru doping.
Highly durable polybenzimidazole composite membranes with phosphonated graphene oxide for high temperature polymer electrolyte membrane fuel cells J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Ebrahim Abouzari-Lotf, Masoumeh Zakeri, Mohamed Mahmoud Nasef, Mikio Miyake, Pooria Mozarmnia, Nur Anati Bazilah, Noor Fatina Emelin, Arshad Ahmad
Polymer electrolyte membranes with highly stable phosphoric acid loading continue to pose a challenge for the development of durable high temperature polymer electrolyte membrane fuel cells. A new class of highly conductive and durable composite membranes is prepared for high temperature fuel cell application under anhydrous conditions. 2,6-Pyridine functionalized polybenzimidazole (Py-PBI) is used as substrate for hosting phosphoric acid moiety. A highly dispersible phosphonated graphene oxide (PGO) introduced to Py-PBI substrate at different levels prior to acid doping and conductivity, durability and fuel cell performance of developed membranes are evaluated. A proton conductivity as high as 76.4 × 10−3 S cm−1 is achieved at 140 °C under anhydrous condition. A strong correlation is found between the content of PGO and the stability of the acid content despite similarity in doping level. In general, the conductivity is obviously more stable in the PGO containing membranes. A Pt-catalyzed fuel cell using the developed composite membranes show a peak power density >359 mW cm−2 at 120 °C under anhydrous condition which is above 75% improvements compared to the membranes without the phosphonated filler. This work demonstrates that the adopted membrane preparation strategy and their observed properties pave the way for highly conductive and durable proton conducting membranes.
Tracking the evolution of mechanical degradation in fuel cell membranes using 4D in situ visualization J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Yadvinder Singh, Robin T. White, Marina Najm, Tylynn Haddow, Vivian Pan, Francesco P. Orfino, Monica Dutta, Erik Kjeang
Mechanical degradation occurs in fuel cell membranes due to the dynamic environmental conditions of operational duty cycles, and is regarded as a critical determinant of fuel cell durability and lifetime. Imaging-based failure analysis is typically employed to characterize structural and morphological aspects of the degradation, and 3D visualization capability of X-ray computed tomography is effectively expanding the scope of this analysis. This work further leverages the additional non-destructive and non-invasive attributes of this visualization technique to capture 4D information pertaining to the evolution of mechanical degradation in fuel cell membranes. A custom fuel cell fixture is utilized to periodically track identical membrane locations during the course of its mechanical degradation, which is generated through an accelerated stress test. The predominant fatigue-driven membrane crack development process is found to proceed non-linearly in time and is spatially concentrated under the uncompressed channel regions. Membrane cracking location is shown to be strongly correlated with beginning-of-life MEA defects, namely, electrode cracks and delamination. In situ crack propagation rates are quantified and the presence of a ‘crack closure’ effect during mechanical membrane degradation is demonstrated. Unlike crack initiation, crack propagation in the membranes does not appear to be significantly influenced by electrode morphology.
Hierarchical NiCo2O4 nanowire array supported on Ni foam for efficient urea electrooxidation in alkaline medium J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Linna Sha, Ke Ye, Gang Wang, Jiaqi Shao, Kai Zhu, Kui Cheng, Jun Yan, Guiling Wang, Dianxue Cao
NiCo2O4 nanowire arrays grown on Ni foam (NiCo2O4/NF) are synthesized by a simple template-free hydrothermal route followed by a thermal treatment in the air at 400 °C. The as-prepared Ni foam substrate exhibits homogeneous and porous nanowire arrays, which providing a number of active sites and electronic transmission channels for urea electrooxidation. The electroactivity of NiCo2O4/NF electrode toward the oxidation of urea in alkaline solution is evaluated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) measurements. Results show that the as-obtained electrode delivers an outstanding electrocatalytic activity and stability for urea electrooxidation. The NiCo2O4/NF electrode delivers a low open potential at 0.19 V versus Ag/AgCl with a corresponding current density of 570 mA cm−2 in 5 mol L−1 KOH and 0.33 mol L−1 urea electrolytes. Meanwhile, detailed investigation is made for the electrocatalytic oxidation of urea by varying several reaction parameters, such as scan rate, urea and KOH concentrations. Benefiting from the unique structure and synergistic effects of Ni and Co, the NiCo2O4/NF electrode exhibit superior electrocatalyst activity and is considered to be a promising candidate catalysis material for direct urea fuel cell.
Ternary CoAuPd and binary AuPd electrocatalysts for methanol oxidation and oxygen reduction reaction: Enhanced catalytic performance by surface reconstruction J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Lai-Ming Luo, Wei Zhan, Rong-Hua Zhang, Di Chen, Qing-Yun Hu, Yi-Fei Guo, Xin-Wen Zhou
Two kinds of ternary cobalt gold palladium (CoAuPd) and three kinds of binary AuPd alloy nanocatalysts are synthesized by co-reduction and successive reduction method. The CoAuPd nanocatalysts obtained by the successive reduction method possess a hollow structure with some solid nanospheres, nanodendrites and show much better catalytic activity for methanol oxidation reaction (MOR) (1.26 mA cm−2) than another CoAuPd NCs (1.14 mA cm−2) and binary AuPd nanocatalysts (0.85 mA cm−2). CO adsorption and electrochemical dealloying method can restructure nanocatalyst surface and improve MOR and oxygen reduction reaction (ORR) activities. Electrochemical dealloying reconstructs the hollow CoAuPd alloy to a CoAuPd@AuPd core-shell structure with pinholes and the dealloyed NCs exhibits better MOR (1.92 mA cm−2) and ORR (6.3 mA cmGEO−2) catalytic activities than the initial CoAuPd nanocatalysts (1.26 mA cm−2 for MOR and 3.4 mAcmGEO−2 for ORR). Accelerated durability tests (ADT) quantify the changes of stability before and after the surface reconstruction. The ternary CoAuPd nanocatalysts have excellent durability before and after surface reconstruction (current density decrease 14.04% for MOR and 0.3 mA cmGEO−2 for ORR) in alkaline medium.
Palladium decorated porous nickel having enhanced electrocatalytic performance for hydrazine oxidation J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Lin-Song Wu, Xiao-Ping Wen, He Wen, Hong-Bin Dai, Ping Wang
Crucial to enabling hydrous hydrazine as a viable fuel is the development of high-performance electrocatalysts. Herein, we report the synthesis of a palladium decorated porous nickel electrocatalyst using a combination of the dealloying and galvanic replacement methods. The obtained electrocatalyst shows outstanding catalytic activity and good long-term durability towards hydrazine oxidation. The mechanistic reason for the improved electrocatalytic performance is discussed based on the structural characterization and controlled experiments. Our study demonstrates that the electrocatalytic properties of catalyst can be improved by enhancing the number of active sites and its intrinsic activity.
Increased power generation in supercapacitive microbial fuel cell stack using FeNC cathode catalyst J. Power Sources (IF 6.945) Pub Date : 2018-11-30 Carlo Santoro, Mounika Kodali, Najeeb Shamoon, Alexey Serov, Francesca Soavi, Irene Merino-Jimenez, Iwona Gajda, John Greenman, Ioannis Ieropoulos, Plamen Atanassov
The anode and cathode electrodes of a microbial fuel cell (MFC) stack, composed of 28 single MFCs, were used as the negative and positive electrodes, respectively of an internal self-charged supercapacitor. Particularly, carbon veil was used as the negative electrode and activated carbon with a Fe-based catalyst as the positive electrode. The red-ox reactions on the anode and cathode, self-charged these electrodes creating an internal electrochemical double layer capacitor. Galvanostatic discharges were performed at different current and time pulses. Supercapacitive-MFC (SC-MFC) was also tested at four different solution conductivities. SC-MFC had an equivalent series resistance (ESR) decreasing from 6.00 Ω to 3.42 Ω in four solutions with conductivity between 2.5 mScm−1 and 40 mScm−1. The ohmic resistance of the positive electrode corresponded to 75–80% of the overall ESR. The highest performance was achieved with a solution conductivity of 40 mS cm−1 and this was due to the positive electrode potential enhancement for the utilization of Fe-based catalysts. Maximum power was 36.9 mW (36.9 W m−3) that decreased with increasing pulse time. SC-MFC was subjected to 4520 cycles (8 days) with a pulse time of 5 s (ipulse 55 mA) and a self-recharging time of 150 s showing robust reproducibility.
Anomalous power enhancement of biophotovoltaic cell J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Min Jung Kim, Seoung Jai Bai, Jae Ryoun Youn, Young Seok Song
The photosynthetic activities of cyanobacteria have been employed in various energy related fields such as energy harvesting and water-splitting based energy conversion. However, the output powers obtained from the photo-bioelectrochemical cells have lower efficiency than those from other artificial materials. It is reported in this study that Synechococcus sp.-iron oxide nanoparticles (γ-Fe2O3 and Fe3O4)- neodymium iron boride magnet complexes enable great energy harvesting performance by both synergistic combination effect of the natural and artificial photocatalysts and formation of an effective electron transfer conduit to the electrode. A green LED bulb is turned on as the result of the energy harvesting. During the light illumination, electrons are transported through the electrode, yielding a peak power density of 0.806 and 0.534 W/m2 for Synechococcus sp.-γ-Fe2O3- neodymium iron boride magnet and Synechococcus sp.-Fe3O4- neodymium iron boride magnet complexes, respectively. The difference in the power output arises from the distinct electrochemical interactions among the cell, iron oxide nanoparticles, and NdFeB depending on the type of the nanoparticles. The approach introduced in this study can boost solar energy harvesting remarkably by combining natural photocatalysts with artificial ones.
Impact of flow recirculation and anode dimensions on performance of a large scale microbial fuel cell J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Ruggero Rossi, Patrick J. Evans, Bruce E. Logan
Many design and operational parameters that can impact power generation in microbial fuel cells (MFCs), such as flow over the electrodes, can only be effectively examined in larger-scale systems. A maximum power density of 0.101 ± 0.006 W m−2 (0.74 ± 0.05 W m−3) was obtained in an 85-L MFC with graphite fiber brushes (5.1 cm diameter, 61 cm long) and flat air cathode (0.62 m2 exposed area; anode-cathode spacing of 1.3 cm) in batch mode. Recirculating the anolyte diagonally through the chamber (entering the top right side of the reactor and exiting the bottom left side) further improved performance by 17% to 0.118 ± 0.006 W m−2, at a hydraulic retention time (HRT) of 22 min (3.9 L min−1), compared to static flow conditions. This power density was also higher than that obtained with parallel flow through the chamber (more evenly distributed using a manifold; 0.109 ± 0.009 W m−2). Reducing the diameter of the anode brushes from 5.1 cm to 2.5 cm did not improve the anode performance. These results demonstrate the importance of electrode spacing and hydraulic flow on large-scale MFC performance.
Fast expansion of graphite into superior three-dimensional anode for microbial fuel cells J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Luye Chen, Youzhi Li, Jiani Yao, Gaoming Wu, Bin Yang, Lecheng Lei, Yang Hou, Zhongjian Li
Bioanodes are core components that affect the performance of microbial fuel cells. In this paper, a superior three-dimensional graphite foam electrode is prepared with rapid gasification of liquid nitrogen and expanding a graphite foil into an expanded graphite foam. With following thermal treatment, thermal treated expanded graphite foam is also prepared. The characterization results indicate that no doping or oxidation occurs during the preparation, which retains a good conductivity and biocompatibility. Microbial fuel cells equipped with expanded graphite foam and thermal treated expanded graphite foam exhibit significantly higher output voltage and power density than graphite foil. Furthermore, cyclic voltammetry and electrochemical impedance spectroscopy are further conducted to investigate the electrochemical performance of different anode materials. Results confirm that the bioelectrochemical activities are enhanced on the fabricated electrodes. Electrochemical active surface area measurement reveals that, other than surface area increase, the graphene-like electrode morphology promotes electron transfer processes. This fast and easy fabrication strategy allows massive production of three-dimensional graphite foam based high performance anodes for microbial fuel cells.
In-situ fabrication of nitrogen-doped carbon nanosheets containing highly dispersed single iron atoms for oxygen reduction reaction J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Yuchuan Liu, Baobing Huang, Xuefei Zhang, Xing Huang, Zailai Xie
Iron and nitrogen co-doped carbons show great potential for high-performance electrochemical oxygen reduction reaction. However, the rational design of atomically dispersed iron over nitrogen-doped carbons with activity comparable to that of Pt-C is still challenging. Herein, we develop a new approach that enables the direct formation of intrinsically nitrogen-functionalized two-dimensional sheet-like carbons containing a high concentration of single Fe atoms. This strategy only involves one-step pyrolysis of both, guanine and iron nitrate, without using any guiding agent and sacrificial template. The electrochemistry tests demonstrate an excellent ORR performance of the prepared Fe-Nx-C catalyst with a half-wave potential of 0.85 V and a limited current density of −6.5 mA/cm2 in alkaline medium, outperforming the commercial Pt-C and most of previously reported Fe-Nx-C catalysts. We believe that the emergence of superior ORR performance is mostly attributed to the uniform dispersion of single Fe atoms at the molecular level and the formation of abundant coordinated Fe-Nx sites. In addition, the high surface area, optimal porosity and defective structure (particularly the defects at the edge) of the two-dimensional carbons are also beneficial for the improved ORR activity.
High performance of AuPt deposited on Ni nanoparticles in ethylene glycol oxidation J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Nan Cai, Jialu Wu, Rulin Dong, Changchun Jin
The electrochemical deposition of small amounts of Au and Pt on the surface of Ni nanoparticles supported on reduced graphene oxide and the electrooxidation of ethylene glycol on the AuPt-decorated Ni/reduced graphene oxide catalysts in alkaline solution are investigated. By selecting a short deposition time, a low concentration of metal precursors, and a positive applied potential, AuPt loadings of less than 1.0 μg cm−2 are obtained. Physical and electrochemical characterizations of AuPt/Ni/reduced graphene oxide reveal a much lower content of Pt relative to Au. However, AuPt/Ni/reduced graphene oxide behaves similar to monometallic Pt/reduced graphene oxide rather than to Au/reduced graphene oxide in ethylene glycol oxidation, while Ni/reduced graphene oxide and Pt-decorated Ni/reduced graphene oxide show no activity. Compared to Pt/reduced graphene oxide or Au/reduced graphene oxide, the peak intensities of AuPt/Ni/reduced graphene oxide are somewhat higher in terms of the glassy carbon substrate, but are significantly higher in terms of the AuPt mass loading. Another attractive feature of AuPt/Ni/reduced graphene oxide is low cost resulted from the low AuPt loading. The result of this study indicates that decorating the surface of non-noble metal with a small amount of two noble metals is an efficient method to fabricate highly active catalysts.
Mechanical behavior and Weibull statistics based failure analysis of vanadium flow battery stacks J. Power Sources (IF 6.945) Pub Date : 2018-11-29 Jing Xiong, Shaoliang Wang, Xiangrong Li, Zhigang Yang, Jianguo Zhang, Chuanwei Yan, Ao Tang
Stack reliability is of great importance in commercialization of vanadium redox flow battery (VFB) since practical VFB stacks are prone to undergo material failure and electrolyte leakage caused by unreliable stack design and improper assembling conditions. A comprehensive evaluation of mechanical behavior and analysis of stack failure is thus highly valued for material fabrication, stack design and assembly. In this study, mechanical behavior and Weibull statistics based failure analysis of the VFB stacks are investigated. The Weibull parameters of two key components are firstly determined from tensile strength tests, which, in combination with finite element analysis of the stack mechanical behavior, are subsequently used to calculate the stack failure probability at specified clamping forces for two different stack designs that both contains 20 individual cells. The results demonstrate that the stack failure probability can be significantly reduced by properly decreasing the clamping forces for both designs, while adding a thick plate to the middle of the stack can effectively lower the probability of failure thus offering a superior stack mechanical performance and a prolonged stack life cycle. Such an approach to analyze stack failure can be readily accessed by flow battery engineers for design and assembly of commercial VFB stacks.
Nonaqueous vanadium disproportionation flow batteries with porous separators cycle stably and tolerate high current density J. Power Sources (IF 6.945) Pub Date : 2018-11-29 James D. Saraidaridis, Charles W. Monroe
Vanadium acetylacetonate, or V(acac)3, provides a model chemistry for investigating the performance of nonaqueous disproportionation flow batteries. A flow reactor was developed to implement studies of efficiency, energy capacity, and power capability with respect to electrolyte flow rate and current density. Reactors incorporating a porous separator allowed V(acac)3 to be cycled without appreciable capacity fade at current densities up to 100 mAcm−2. Experiments at the lowest flow rate, 12.5 mLmin–1, revealed limitations imposed by residence time within the reactor, which manifested as high charging overpotentials. These overpotentials vanish above 25 mLmin–1. A higher flow rate of 50 mLmin–1 yielded performance similar to cells at 25 mLmin–1, but could improve performance at current densities above 100 mAcm−2. Extrapolation of power density's dependence on current suggests a maximum power of 0.22 Wcm−2 for cells run at 206 mAcm−2. Energy efficiency passes through a maximum of 71% at 40 mAcm−2 and the corresponding energy density suggests that the chemistry can, in principle, deliver above 13 WhL−1 in acetonitrile solutions and above 24 WhL−1 in mixed-solvent solutions with higher V(acac)3 solubility. A V(acac)3 cell run at 40 mAcm−2 is shown to exhibit stable capacity and performance for more than 150 cycles.
Graphene oxide-carbon nanotubes aerogels with high sulfur loadings suitable as binder-free cathodes for high performance lithiumsulfur batteries J. Power Sources (IF 6.945) Pub Date : 2018-11-30 Juan Luis Gómez-Urbano, Juan Luis Gómez-Cámer, Cristina Botas, Teófilo Rojo, Daniel Carriazo
Herein we report a simple approach for the preparation of graphene oxide-carbon nanotube-sulfur composites. The self-standing composites can be easily prepared by freeze drying a frozen graphene oxide-carbon nanotube suspension, and then impregnated with sulfur by melt diffusion. Composites obtained in this way are physicochemically characterized by elemental analysis, X-ray diffractometry (XRD), electron microscopy and gas adsorption, showing a three dimensional macroporous graphene-based architecture in which sulfur is homogeneously distributed. The performance of self-standing composites with sulfur loadings over 4.0 mg cm−2 is evaluated as binder-free positive electrodes for Lithium-Sulfur (Li-S) batteries. Results show that the incorporation of just 2 wt.% of CNTs significantly improves both the specific capacity and capacity retention compared to the results shown by the CNT-free samples, and slightly improves the performance of thermally reduced samples. More importantly, reversible specific capacity values over 500 mAh g−1 at a rate of 0.1C after 100 charge/discharge cycles are obtained for either thermally reduced and CNT containing samples, which in terms of areal capacity correspond to values over 2.0 mAh cm−2.
Room temperature ionic liquid (RTIL)-based electrolyte cocktails for safe, high working potential Li-based polymer batteries J. Power Sources (IF 6.945) Pub Date : 2018-11-30 Jijeesh Ravi Nair, Francesca Colò, Arefeh Kazzazi, Margherita Moreno, Dominic Bresser, Rongying Lin, Federico Bella, Giuseppina Meligrana, Sébastien Fantini, Elisabetta Simonetti, Giovanni Battista Appetecchi, Stefano Passerini, Claudio Gerbaldi
In this work, we report novel room temperature ionic liquid (RTIL)-based electrolytes to be used with high-energy cathode, lithium-rich nickel manganese cobalt oxide (Li[Li0.2Mn0.56Ni0.16Co0.08]O2, LiR-NMC) in Li-ion batteries. The physical and electrochemical characteristics of the newly developed materials are thoroughly detailed, also by means of post-cycling electrochemical impedance spectroscopy (EIS) analysis of the resulting lab-scale lithium cells upon long-term, constant-current cycling (>1200 cycles). In addition, an innovative polymer electrolyte is developed encompassing the best performing RTIL-based electrolyte mixture, which is investigated in terms of its physico-chemical features, ion transport and electrochemical behaviour by EIS, cyclic voltammetry and constant-current (galvanostatic) cycling. The polymer electrolyte is obtained via facile, rapid and easily up-scalable UV-induced free radical polymerization (UV curing) technique, being a low-cost and solvent-free approach compared to other existing film formation techniques. The versatile fabrication method along with the use of appropriate materials may turn high-voltage, solid state and ageing resistant batteries into industrial reality in the coming years, as underlined by the excellent electrochemical response of the lithium polymer cell.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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