Iron sulfides draw much attention as electrode candidates for sodium-ion batteries (SIBs) due to the rich chemical stoichiometries and high capacity. However, they usually exhibit poor cycling performance due to the large volume change during sodiation/desodiation process. In this work, we embed Fe7S8 nanoparticles into sulfur, nitrogen-doped carbon (S/N–C) nanofibers through electrospinning/sulfurization processes. The heteroatom doped carbon matrixes could effectively protect the Fe7S8 from structural collapse, obtaining a stable cycling performance. Moreover, the conductive matrixes with 1D structure can facilitate the diffusion of electrons, leading to good rate capability. As results, the as-designed Fe7S8@S/N–C nanofibers present a discharge capacity of 347 m Ah g−1 after 150 cycles at 1 A g−1 and a high rate capacity of 220 m Ah g−1 at 5 A g−1 in virtue of unique structural characteristics.

Despite the success of proton exchange membrane fuel cell (PEMFC) in aeronautic applications, there is still limited data on its behaviour. Hence, this paper explores effects of load profile on PEMFC State of Health (SoH) by testing under simulated flight stages at nominal and extreme temperatures. The key findings are that the cruise mode (CR) are the least aggressive mode while the idling mode (ID) and the variable load demand (VL) (namely, climbing, flying and descending) show comparable performance in terms of catalyst activity losses and Pt particle growth, except at extreme temperature for the ID. However, the post-mortem analysis reveals that the VL cause membrane thinning and loose fluoride particles to redeposit on the membrane and the GDL layers while the high voltage during the ID collapse the cathode catalyst layer. The take-off and landing (TL) are the most aggressive at both temperatures causing severe damage to the catalyst and notable delamination between the membrane layer and the gas diffusion layer (GDL). The study concludes that cruise mode has milder operating conditions, which qualified it to be the benchmark test, while the most aggressive TL operating conditions need to be refined in order to optimize PEMFC performance.

This paper presents cycle aging results of a commercial lithium-ion cell from a comprehensive, 29 month aging study and follows up on calendar aging results published previously [1]. We use a widely used commercial LiFePO4/graphite cell from Sony/Murata, which promises long calendar and cycle lifetime, that would make it suitable for stationary battery applications. The evolution of the cells’ capacity and impedance are shown in a static cycle aging study for 19 test points with different combinations of temperature, C-rate, depth of discharge and state of charge. Based on the measurement data shown herein and the calendar aging model presented in the previous paper, a semi-empirical combined aging model is presented for the capacity loss and resistance increase. Two dynamic load profiles are used to experimentally validate the combined aging model. Absolute model errors below 1% for the capacity loss and below 2% for the resistance increase in both dynamic load profiles demonstrate that the combined aging model can predict the lifetime of LiFePO4/graphite battery cells for different applications and varying operation conditions adequately. In the cycle experiments, an unexpectedly strong, but partly reversible capacity loss is observed with shallow cycles at medium states of charge.

LIBs with improved specific capacity even more than theoretical capacity that is provided by poly (vinylidene fluoride) and silicon dioxide (PVDF/SiO2) nanofiber composite membrane separator is presented in our study. The experiment results are in agreement with simulation analysis that Si can substitute P in the LiFePO4 during the charge-discharge process and lead a great electrochemical performance. It provides a new approach to significantly improve the overall electrochemical performance. This can be described as the capacity of 175 mAh/g at 0.1 C; 160.7 mAh/g at 0.5 C and subsequent residual capacity is 168.6 mAh/g at 0.2 C after long-term cycles of 300 times and the coulombic efficiency is 98.22%. Meanwhile, the PVDF/SiO2 separators are exhibited higher porosity (131.33%) and electrolyte uptake (1514.79%) than commercial PP separator, and also evaluated reduced interfacial resistance and higher thermal property that the initial decomposition temperature is 389.05 °C. The PVDF/SiO2 separators with better performance than commercial separator apply to conventional lithium-ion batteries leads to improved electrochemical performance obviously, and can be more prospective for LIBs after multiple modified preparations.

Two-dimensional (2D) organic-inorganic hybrid Ruddlesden-Popper (RP) perovskite materials have attracted considerable attention due to their unique performance and enhanced stability for photovoltaic and photoluminescent devices. However, the optoelectronic properties of 2D all-inorganic RP perovskites remains unclear because of hard-to-experiment synthesis. Therefore, the two-dimensionality how to affect the photoelectric properties of all-inorganic perovskites remains unclear. In this study, we investigate the electrical and optical properties, including the band structures, carrier mobility, optical absorption spectra, and exciton-binding energies for newly synthesized all-inorganic 2D-layered RP perovskite Cs2PbI2Cl2 using density functional theory. The results demonstrate the thickness-dependence of photoelectric properties in 2D-layered RP perovskite Cs2PbI2Cl2. The carrier mobilities and absorption coefficients in the visible spectrum of Cs2PbI2Cl2 are smaller than those of MAPbI3 and Si crystal photovoltaic materials, whereas the exciton-binding energies increase with the decrease in the number of layers, which are obviously higher than those of MAPbI3 and Si crystal. The results show that Cs2PbI2Cl2 is a good material for luminescent devices rather than for photovoltaic cells. This study provides a theoretical basis for other ultra-thin two-dimensional perovskite materials with potential applications in photoluminescent devices.

Low electronic conductivity and drastic volume change during cycling of transition metal oxides, as anodes for lithium ion batteries (LIBs), lead to rapid capacity decay and poor structural stability. Herein, nanostructured NiCo2O4 anchored on carbon sheets was synthesized by a facile hydrothermal method with following thermal treatment. The wrinkled carbon substrate in the composite derives from the carbonization of pomelo peels, which can be mass-produced for the large-scale application. This composite shows mesoporous structures with high specific surface areas and intimate NiCo2O4/carbon interfaces, which favors the alleviation of the volume expansion/shrink during charging/discharging process and improves the electron/mass transport, enhancing the capability and stability for LIBs. This composite delivers a high reversible capacity of 473.7 mA h g−1 after 210 cycles at a current density of 500 mA g−1. A long cycle life of up to 1100 cycles at 2000 mA g−1 is achieved with the retention capacity of 363 mA h g−1. The electrode also exhibits excellent rate capability and can regain its original capacities as reversing to the low current densities. This work highlights the biomass-derived carbon-supported metal oxides as an environmentally friendly and economic strategy for advanced LIBs.

The available capacity of a lithium battery reflects its actual capacity under certain constraints. It serves as an important deciding factor for the electric vehicles’ energy management system. Online estimation allows the construction of a mathematical model with easily measurable variables as input to estimate the main variables that are difficult to measure in a complex environment. Current research applies the trained model of another battery to the current testing battery. Due to differences across batteries, the same model is unable to deliver an accurate description of the chemical processes of the same type of batteries. In order to solve the problem of model adaptability, an iterative EKF-GPR method is proposed based on the full charging curve of the battery being estimated and the daily charging voltage, current and time data based on the assumption that there are no abrupt changes in the lithium battery charging curves. The method is to establish a model for the estimation of the available current charging capacity of the lithium battery. It converts macro-time machine learning into the prediction and estimation of single charging curve on the micro-time scale, thus guaranteeing the accuracy of available capacity estimation models for any batch of batteries.

The commercialization of Li–S batteries is impeded by their short lifespan and poor rate capability resulting from the shuttle effect and sluggish reaction kinetics. Herein, we develop a bi-functional cathode substrate for Li–S batteries made of well-distributed boron carbide nanoparticles decorated activated cotton fiber (B4C-ACF), in which B4C nanoparticles serve as not only robust chemically anchoring sites to trap the polysulfides, but also afford abundant active sites for efficient sulfur conversion reactions. Meanwhile, the ACF network provides fast electron pathways for the conversion reactions and acts as the current collector. As a result, the novel cathode substrate enables a Li–S battery to deliver an initial capacity of as high as 1415 mAh g−1 at 0.1 C, and an extra-high reversible capacity of 928 mAh g−1 at 3 C with an areal sulfur loading of 3.0 mg cm−2. More strikingly, the B4C-ACF substrate-based battery could be stably operated for 3000 cycles with a high coulombic efficiency of 99.24% and a capacity decay rate of as low as 0.012% per cycle at 1 C, demonstrating that the B4C-ACF substrate holds great potential in realizing the mass production of advanced Li–S batteries.

Bifunctional electrocatalysts for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are developed with perovskite-type oxide catalyst and antimony-doped tin oxide (ATO) as an oxidation-resistant conductive additive to increase the stability under an oxidizing atmosphere. In conventional carbon-supported catalysts, carbon plays an important role not only in increasing electric conductivity but also in catalyzing the first 2-electron reaction of the ORR. The ATO-mixed catalyst itself requires a perovskite-type oxide (ABO3) catalyst that is active in the first step of the ORR, such as La0.6Ca0.4MnO3 (LCMO), because of the poor ORR activity of ATO. On the other hand, OER performance strongly depends on the composition of the perovskite oxide and La0.6Ca0.4CoO3 (LCCO) shows high OER activity. Here, La0.6Ca0.4Co0.7Mn0.3O3 (LCCMO), in which Co and Mn are mixed at the B site of the perovskite-type oxide, mixed with ATO is proposed as a carbon-free bifunctional catalyst that shows activity for both the ORR and OER. The activity and durability of gas-diffusion air electrodes with the bifunctional catalysts are evaluated in zinc–air batteries, and the results suggest that the catalyst with ATO achieved similar charge-discharge performance and a longer lifetime compared to the conventional catalyst with carbon.

Solid Oxide Electrolysis Cells offer great promise for efficient recycle and cost-effective conversion of carbon dioxide. However, the conventional Ni/YSZ and some other fuel electrodes suffer some technological limitations such as the use of protecting gas CO/H2. Here we demonstrate the efficient electrochemical reduction of carbon dioxide without flowing any protecting gases based on the porous cathode with La0.3Sr0.7Ti0.3Fe0.7O3-δ(LSTF) nanostructured composite which is infiltrated into a scandia-stabilized zirconia scaffold together with ceria. The infiltrated porous electrode provides excellent performance for CO2 electrolysis. By I–V measurement and electrochemical impedance spectroscopic characterization, it shows that the current densities during electrolysis below a cell voltage of 2 V is between 1.20 and 4.44 A cm−2, increasing with temperature increase over the temperature range of 700–850 °C, and the cell with configuration of LSTF/CeO2|ScSZ|LSM/ScSZ possesses low electrode polarization resistances (Rp) within different voltage ranges, for example, Rp = 0.18 Ω cm2 at an applied voltage of 2.0 V, which is one order of magnitude lower than other reported electrode materials such as La0.2Sr0.8TiO3+δ. Moreover, a combination of short-term stability test for 48 h and cyclic stability test of LSTF/CeO2 are also estimated, and the results show that the nanostructured LSTF/CeO2 is highly effective for CO2 electrolysis.

In this work, a cost-competitive oxide system of Ni-substituted Sr1-xTi0.3Fe0.6Ni0.1O3-δ (STFN, x = 0, 0.02, 0.05), is evaluated as Solid Oxide Fuel Cell cathode. All STFN oxides present cubic perovskite structure with maximum conductivities over 22 S/cm in air. The introduction of Sr deficiency yields higher oxygen vacancy and lower thermal expansion coefficient. As a result, the cathode polarization resistance of 0.107 Ω cm2 is obtained for Sr0.95Ti0.3Fe0.6Ni0.1O3-δ (STFN-95) at 750 °C and pO2=0.21atm, with weak oxygen partial pressure dependence. Specially, STFN-95 presents higher stability with slower Rp increasing rate in lower oxygen partial pressure of 0.14 atm than in 0.21 atm, which greatly facilitates the cathode practical application in SOFC stack under high air utilization condition. Finally, a stable operation of 400 h is achieved using STFN-95 cathode on anode supported single cell at 750 °C, without showing Sr and other elements diffusions.

The capacities of the wind turbines, solar photovoltaic (PV) panels, and lithium-ion (Li-ion) batteries composing an off-grid system are optimized. The model of the Li-ion batteries considers the capacity fading and temperature variation. A case study on Jeju Island demonstrates the capacity factors of the onshore and offshore wind energy, and solar PV energy. The optimal capacities of the onshore and offshore wind turbines, solar PV panels, and Li-ion batteries are evaluated as 16 MW, 1532 MW, 6076 MW, and 14,651 MWh, respectively, without capacity fading. The corresponding life cycle cost (LCC) and levelized cost of electricity (LCOE) are evaluated as 84.3 BUSD and 0.42 USD kWh−1, respectively. With capacity fading, the optimal capacities of the onshore and offshore wind turbines, solar PV panels, and Li-ion batteries are estimated as 2 MW, 1947 MW, 5072 MW, and 16,927 MWh, respectively. The corresponding LCC and LCOE are nearly invariant. The maximum temperature of the Li-ion batteries is estimated for different cooling conditions. The convection coefficients are suggested for negligible performance degradation and preventing thermal runaway. Finally, sensitivity analysis is conducted for different renewables penetrations, the portion of electric vehicles (EVs), and demand reduction during summer.

NiS2 is a promising anode material for sodium-ion batteries (SIBs) and capacitors (SICs). However, the sluggish Na+ diffusion and large volume change of bulk NiS2 during sodiation/de-sodiation lead to poor rate capability and fast capacity decay, limiting its practical application. Herein, we design and prepare well-oriented NiS2 nanosheets on porous carbon microtubes (denoted as NiS2/pCMT) as a novel anode material for SIBs/SHCs. The unique porous hollow carbon tubes and NiS2 nanosheets can well relieve the repeated stress/strain and maintain the structural integrity of the composite anode during long-term charging/discharging. As a confirmation, a modelled SHC is constructed by using the NiS2/pCMT composite as anode and coupling with an activated carbon cathode, delivering a high energy density of 136 Wh kg−1 and good cycling stability. The first-principles density functional theory (DFT) calculations confirm that the NiS2 nanosheets surface has a high chemical affinity towards Na+ ions, promising the concentration of Na+ ion on/nearby the surface for fast redox reactions during sodiation/de-sodiation of NiS2. This work provides some new insights for the design and fabrication novel composite electrode materials for applications in beyond lithium-ion batteries/capacitors.

Anode supported (ASC) and electrolyte supported cells (ESC) represent the most common cell concepts in solid oxide fuel cell (SOFC) technology. In ASCs, mechanical manageability is provided by a porous nickel/yttria-stabilized zirconia (Ni/YSZ) substrate, whereas in ESCs a self-supporting dense YSZ electrolyte is applied. Naturally, the electrical loss contributions arising in ASCs and ESCs differ in quantity, leading to different temperature profiles within planar SOFC stacks. A two-dimensional, finite element method model was developed which considers the underlying chemical and physical processes, and calculates both the electrical performance and the thermal distribution of planar SOFC stack layers operated with reformate fuels. It was then validated by comparing simulation results with extensively measured (i) temperature profiles in SOFC stacks, (ii) gas composition changes along the fuel gas channel of planar ASCs, and (iii) current-voltage characteristics in a temperature range from 650 °C to 800 °C. The subsequent numerical study reveals (i) the different performances of ASC and ESC, (ii) the impact of operation conditions on performance and temperature profile and (iii) how the individual loss contributions generate temperature distributions in the stack layer.

An inert-supported cell (ISC) was developed by Bosch with the aim of lowering the manufacturing costs of SOFCs and thus increasing their marketability and prolonging their lifetime. This ISC concept uses forsterite, a manganese silicate doped with Zn and Ca, as support material. The cell can be described as air side inert-supported cell, since forsterite faces the air compartment. Forsterite was chosen as a support material, as it is abundant and therefore relatively inexpensive. All functional layers are subsequently applied and co-sintered at T < 1300 °C to further reduce cell manufacturing costs. At present, LSM is used as a cathode. However, the performance of the cell is drastically reduced due to the formation of a Zn–Mn spinel at the triple-phase boundaries during co-firing. Based on these findings, seven different cathodes were synthesized to identify a cathode that is less reactive with forsterite. In order to investigate their reactivity, different types of samples were prepared: mixed pellets, double-layered pellets and screen-printed cathode inks on forsterite green substrates. These samples and their cross sections were then investigated by using XRD, SEM, EDX, and WDX. Their reactivity was as follows (ascending order): LSFM > LSF > LSC > PSCF > LSCF > LCCF.

The non-invasive investigation of lithium-ion batteries is of great importance, e.g. for improvement of electrode materials or monitoring the state of health (SOH) in stationary or mobile applications. Electrochemical impedance spectroscopy (EIS) is a powerful tool for this task. Once the predominant processes in the impedance spectra are assigned to their corresponding electrode (i.e. anode or cathode), a tracking of both electrode's SOH becomes possible. In a previous work, this assignment has been performed. Two predominant processes were found: the impedance of the solid electroly interphase (SEI) and the NMC's charge transfer. In this work, this information is used for a non-invasive yet separate investigation of anode and cathode degradation throughout aging. Cells have been aged for about 700 days (calendric aging) or about 3000 full cycle equivalents (cyclic aging) at three different operating points each. A combination of impedance spectra analysis, differential voltage analysis (DVA) and post mortem analysis (PMA) determines the main aging mechanisms. Calendric aging: SEI-growth, CEI-growth, cathode-dissolution. Cyclic aging: anode's and cathode's particle-cracking, cathode-dissolution and possibly CEI-growth.

An important issue towards cell individual battery monitoring is the employment of new sensor technologies and efficient algorithms to enlarge the diagnostic capabilities of battery systems. Especially for the onboard application in electric vehicles, impedance spectroscopy is one of the most promising methods to gather useful information about the battery. In this paper, a new framework for onboard impedance spectroscopy on cell level is developed, which incorporates a passive method without the need of an additional active signal generation. The derived estimator is based on the weighted overlapped segment averaging algorithm and is optimized for the application in a battery management system. The theoretical considerations are experimentally examined with a battery module consisting of parallel connected cells. Therefore, a battery test rig with high bandwidth is designed to enable a realistic replication of road driving scenarios. Statistical quality criterions for the online validation of impedance spectra using linear Kramers-Kronig tests are established and verified with corresponding experiments. A significant comparison with reference measurements based on the accuracy of estimated model parameters shows very good agreement. Next to model parameter estimation, diverse other application scenarios for the monitoring and diagnosis of battery systems based on impedance data are outlined.

The inhomogeneous distribution of electrolyte over the porous electrode is one of the main issues hindering vanadium flow battery performance, limiting the system power density. Moreover, the interplay between fluid dynamics in distribution channels and morphology of porous electrodes is not well understood at local level throughout the cell active area, where local reactant starvation may occur and further limit system performance. Therefore, a systematic local characterization is fundamental to improve the understanding of system operation and to enhance system power density. This work discusses the implementation of a 10 regions macro-segmented flow battery with 25 cm2 active area, that permits the local measurement of polarisation curves and impedance spectra. Both positive and negative symmetric cells, as well as all-vanadium configuration, are adopted, combining carbon paper electrodes of different thickness with single serpentine and interdigitated distributors. The characterization evidences that single serpentine presents poor performance towards cell outlet, while interdigitated geometry is limited in the central region of active area. In most of the investigated operating conditions, single serpentine induces a more heterogeneous operation, especially if coupled with thinner electrode and positive electrolyte. Moreover, the representativeness at local level of symmetric cells compared to all-vanadium one is analysed and discussed.

Cell voltage reversal resulted from hydrogen starvation at the anode is one of the factors that exacerbate the overall degradation of proton exchange membrane fuel cells (PEMFCs). An effective mitigation strategy is to involve oxygen evolution reaction (OER) catalysts into the anode to facilitate water electrolysis against carbon corrosion. As such, this paper aims to study the influence of relative humidity (RH) on the performance and durability of reversal-tolerant-anodes (RTAs) during hydrogen starvation. An advanced segmented technique is employed to examine the coupling reactions by simultaneously measuring current density, RH and temperature in a fuel cell with a large active area. It is found that the inlet of RTAs undergoes degradation earlier than the outlet and the membrane electrode assembly (MEA) with a RTA has an optimal humidity during cell reversal. Results also show that the failure of the RTA MEA is due to a loss of electron conduction medium rather than the deactivation of the OER catalyst. In addition, this work highlights the importance of plate flow field design and the OER catalyst gradient design of the RTA MEA.

Two high temperature polymer exchange membrane fuel cells (HT-PEM FCs) were operated under repeated starvation/regeneration steps for 550 min (DPS-1) and 12 days (DPS-2). Concerning the investigation of the irreversible degradation under fuel (H2) starvation the focus was put on the electrochemical characteristics during regeneration, since during this step the system operates under normal conditions. Electrochemical impedance spectroscopy (EIS) and distribution of relaxation times (DRT) analysis were used as electrochemical characterization methods. DRT analysis of selected impedance spectra during regeneration steps for the first seven days revealed an intensity increase of the charge transfer kinetics of the cathode (ca. 10 Hz) and the anode (ca. 100 Hz). From day 3 on, an additional peak at 300–800 Hz appeared likely pointing to the formation of surface oxides at the anode side. The EIS and DRT results were verified with Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM), Microcomputed Tomography (μ-CT) and Transmission Electron Microscopy (TEM). While TEM indicated advanced Pt particle agglomeration pointing to carbon corrosion, μ-CT measurements showed an increase of void volume fraction and a decrease of the tortuosity value. The combined results show that the anode gas outlet region of the FC is more degraded than the inlet region.

18650-type cells with 2.5 Ah capacity are cycled at both 25 °C and 0 °C separately, and at 25 °C two charging protocols (constant current, and constant current-constant voltage charge) are used. Differential voltage analysis (dV/dQ) and alternating current (AC) impedance are mainly used to investigate battery degradation mechanisms quantitatively. The dV/dQ suggests that active cathode loss and loss of lithium inventory (LLI) are the dominating degradation factors. Significant microcracks are observed in the fatigued cathode particles from the scanning electron microscopy (SEM) images. Crystal structure parameters of selected fatigued batteries at fully charged state are determined by in situ high-resolution neutron powder diffraction. Obvious increases of ohmic resistance and solid electrolyte interphase (SEI) resistance occur when the battery capacity fade falls beneath 20%. Continuous charge transfer resistance and Warburg impedance coefficient (W.eff) increase are observed in the course of cycling. Correlation analysis is performed to bridge the gap between material loss as well as LLI and impedance increase. The increase of the charge transfer resistance is related to both active cathode loss and LLI, and a functional relationship is revealed between LLI and W.eff regardless of the used cycling protocols.

Reliable development of Li-ion Batteries requires a good understanding of the correlation between electrochemical performances and accurate aging interfaces phenomena. The present study focuses on the SEI characterization formed at both electrodes surface in LiMn2O4/Li4Ti5O12 (LMO/LTO) cells, depending on the cycling temperature, which is one of the major stress factors for batteries. LMO/LTO cells were cycled at 25 °C, 40 °C and 60 °C over 100 cycles and the chemical composition of surface layers was investigated by XPS, SAM and ToF-SIMS at the end of the 100th cycles. LTO electrodes are covered by surface layers since the first cycle (inducing an irreversible capacity loss) and the SEI thickness increases with the cycling temperature; moreover, organic (alkyl-carbonates, polyethylene oxides, oxalates) and inorganic species (LiF and (fluoro)-phosphates) of the solid interphase are present in different proportions depending on the temperature; more fluorophosphates are especially observed at 60 °C due to a higher chemical degradation of LiPF6 salt. Finally, small amounts of manganese, heterogeneously spread over the LTO electrode surface, are found at different oxidation states at higher temperatures; for the first time, metallic Mn0 was detected at the LTO surface after cycling at 60 °C which could explain the important capacity loss of the system at this temperature.

High theoretical specific capacity and low electrochemical potential offered by lithium metal make it the definitive anode material for lithium batteries. Yet, unrelenting growth of dendrites forestalls the use of Li metal anode in commercial applications. To overcome this issue, we demonstrate the formation of a multi-phase composite protective layer consists of LixSi alloy, Si-linked organic oligomers and LiCl on the lithium anode surface. Due to its inherent ionic conductivity and chemical stability, the composite film can not only inhibit the formation of lithium dendrites by facilitating uniform Li-ion distribution, but also prevent unfavorable side reactions. The improved electrochemical performance is demonstrated by symmetric cells with the composite layer cycling at 1 mA cm−2 stably for 2200 h. Protected lithium anode coupled with LiFePO4 achieves high rate performance and better capacity retention after 400 cycles at 1C. Furthermore, cells with protected lithium anode and Li4Ti5O12 cathode (high areal loading of 14.9 mg cm−2) shows 91% capacity retention after 400 cycles at 0.5 C. The effective and scalable way to stabilize lithium anode with the multi-phase composite protective layer may serve as good references for development of advanced lithium metal batteries.