Combination of high performance organic cathode Calix[4]quinone and practical biocarbon in sodium-ion batteries

Highlights

• Biocarbon PPL is used as immobilization material for Calix[4]quinone (C4Q) cathode SIBs for the first time.

• PPL not only serves as a kind of immobilization material but conductive agent.

• The content of active substances is greatly increased.

• High specific capacity and good cycling performance of C4Q/PPL are achieved.

Abstract

Nowadays, sodium-ion batteries (SIBs) have received extensive attention for their abundant resources and low price. Some quinone compounds have the advantages of high specific capacity, diverse structures, environmental friendliness and good redox reversibility, are ideal cathode materials. Calix[4]quinone (C4Q) with a high theoretical specific capacity of 446 mA h g⁻¹ is synthesized as cathodes, while it is still puzzled over low conductivity and high dissolution rate in organic electrolytes. In this study, a kind of economical and practical biocarbon-PPL with porous tubular structures is prepared by pyrolysis of Physalis Peruviana L. Calyx to immobilize C4Q in SIBs for the first time. The C4Q/PPL cathode presents an initial capacity of 435 mA h g⁻¹ with stable cyclability (195 mA h g⁻¹ after 100 cycles at 0.1 C) and great rate performance (170 mA h g⁻¹ at 1 C).

Introduction

At present, the lithium-ion batteries (LIBs) are mainly used in small energy storage devices for their high safety, stable cycling performance and high voltage [[1], [2], [3]]. However, they cannot be widely applied in large energy storage equipment for the lack of lithium resources and low capacity. In the 21 Century, the concepts of resource conservation, eco-friendly and sustainable development require us to find a suitable candidate to replace lithium [4,5]. Sodium, belongs to the same main group with lithium, has not only similar physical and chemical properties with lithium, but also earth-abundant resources, sodium-ion batteries (SIBs) are powerful competitors to solve resource and cost problems [[6], [7], [8], [9], [10], [11], [12]]. In addition, organic materials are also in line with the development strategy of environmental protection and efficiency [[13], [14], [15]]. Especially various quinone compounds with relatively long development history from the 1970s have attracted much attention on account of their rich resources, structure diversity, sustainability, strong redox reaction and high specific capacity in comparison with traditional inorganic materials [[16], [17], [18]].

Thus, investigating the performances of SIBs with quinones cathodes is a big hotspot. However, small molecular quinones are highly soluble in organic electrolytes due to their small molecular weight, leading to poor cycling stability. For example, anthraquinone (AQ) displays a fast capacity decrease from 178 to 126 mA h g⁻¹ after 50 cycles in SIBs [19]. Similarly, when these small structure quinones are made into macromolecular polymers, their dissolution rate will be remitted, but if too many inactive structures are introduced in the polymerization process, their specific capacity will decrease. Like pyrene-4,5,9,10-tetraone (PYT), when it is polymerized as polymer-bound pyrene-4,5,9,10-tetraone (PPYT), the theoretical specific capacity drops from 408 to 262 mA h g⁻¹ [20].

Thus, the key to solving the dissolution problem is to synthesize large structure quinone compounds by connecting several basic quinone units with fewer junction units. Huang synthesized calix[4]quinone (C4Q) consisted of four p-quinone units linked by four “-CH₂-” that offers eight active electrochemical sites, the redox mechanism is shown as Fig. 1 [21]. It has a capacity of up to 446 mA h g⁻¹, as do the pillar[5]quinone (P5Q) and calix[6]quinone (C6Q) with the same structural units as C4Q [[22], [23], [24]].

Unfortunately, the poor conductivity and high solubility of these above mentioned quinones have been alleviated, but are still far from sufficient. The point is to effectively perfect their flaws. Zheng [25] applied CMK-3 (an ordered mesoporous carbon) to immobilize C4Q in SIBs. It presents a good result with a high initial capacity of 438 mA h g⁻¹ and a retention rate of 50% after 50 cycles. Yan [26] prepared C4Q/CMK-3/SWCNTs nanocomposites with three-dimensional conductive network structures which deliver a high capacity of 290 mA h g⁻¹ after 100 cycles at 0.1 C. However, CMK-3 and SWCNTs are much expensive, seeking alternative carbon materials with cost-effectiveness and excellent properties is an efficient cost-cutting measure for SIBs.

Biocarbon is an ideal candidate since its merits of wide source of raw materials, low cost and reproducibility. At present, a variety of biocarbon, such as grapefruit peel and kinds of leaves, have been made into carbon materials with different morphologies and properties, which have been widely used in many fields [[27], [28], [29], [30], [31]].

Hence, in this study, PPL (with Physalis Peruviana L. Calyx as raw materials) with porous tubular structures has been found to solve above problems. When it is applied to immobilize C4Q, both the high dissolution rate and low conductivity issues for LIBs are eased. The simple flow chart of C4Q/PPL composites (m:m = 1:1) is presented in Fig. 1. It obtains a high initial capacity of 437 mA h g⁻¹ and maintains at 228 mA h g⁻¹ after 100 cycles at 0.1 C [32]. Even more noteworthy, this system also shows excellent results in SIBs, its initial capacity is as high as 435 mA h g⁻¹ (98% of C_theo), and keeps at 195 mA h g⁻¹ after 100 cycles at 0.1 C with great rate performance of 170 mA h g⁻¹ at 1 C. Its cheapness and availability make SIBs more practical.