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https: //doi. org/10.1007/s11595-020-2304-7

Salt-washing Improvement of the Electrochemical Properties of Zeolite-sulfur Cathode for Lithium-sulfur Batteries HE Yanjia1△, DU Zibo1△, SU Yong1, YU Junxi1, CHEN Feifan1, XIE Shuhong2*, PAN Jun'an2*

(1. Hunan Provincial Key Laboratory of Thin Film Materials and Devices, Xiangtan University, Xiangtan 411105, China; 2. Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China)

Abstract: We displayed that the low-cost natural zeolite with molecular sieve structure can be used as the carrier of sulfur in lithium-sulfur batteries. Meanwhile, a simple salt-washing method was implemented on zeolite for dredging the internal microchannel to improve the ability of adsorption, ion exchange and sulfur loading. The experimental results show that the first specific discharge capacities of zeolite/S and salt-washed zeolite/S cathode under 0.2 C current density are 950.7 and 1 116.8 mAh/g, respectively, and corresponding discharge capacities remain at 350.6 and 604.2 mAh/g after 300 cycles. The first specific discharge capacity of salt-washed zeolite/S composite is 17.5% higher than that sample without salt-washing, and the corresponding ionic conductivity is improved. Key words: zeolite; salt-washing; internal microchannel; lithium-sulfur battery

1 Introduction Presently, researches on rechargeable batteries have been focused on the high energy density, long cycling life, low cost, and low environmental impact. Among all known rechargeable battery systems, the lithium-sulfur (Li-S) batteries are one of the most promising candidates, since elemental sulfur (S) has one of the highest theoretical capacities for Listorage (1 672 mAh/g), resulting in a higher specific energy compared to conventional Li-ion batteries[1,2]. Nevertheless, the practical application of Li-S batteries is limited by many disadvantages. The most serious one is the dissolution of lithium polysulfides in electrolyte, resulting in the reduction of battery capacity and © Wuhan University of Technology and Springer-Verlag GmbH Germany, Part of Springer Nature 2020 (Received: Apr. 10, 2019; Accepted: July 23, 2019) HE Yanjia(何妍佳): E-mail: [email protected]; DU Zibo(杜子博): E-mail: [email protected] △These authors are co-first authors, and they contribute equally to the work *Corresponding authors: XIE Shuhong(谢淑红): Prof.; E-mail: [email protected]; PAN Jun'an(潘俊安): Ph D; E-mail: pja3330@ xtu.edu.cn Funded by the National Natural Science Foundation of China(Nos.11627801, 51772254, 11502225, and 51375017), and the Natural Science Foundation of Hunan Province of China(No.2019JJ50578)

shorter cycle life [3-5]. To solve this problem, much attention had been devoted to porous nanomaterials, such as carbon nanotube[6], carbon nanofibers (CNF)[7], mesoporous carbon CMK-3 [2], mesoporous silica [8] and so on, due to their high specific surface area and good adsorption ability. For example, Jix