化学学报 ›› 2023, Vol. 81 ›› Issue (6): 620-626.DOI: 10.6023/A23030083 上一篇    下一篇

研究论文

钴取代多金属氧酸盐作为可溶性介质提升锂硫电池性能

李子奇, 刘力玮, 毛承晖, 周常楷, 夏旻祺, 沈桢, 郭月, 吴强*(), 王喜章, 杨立军, 胡征*()   

  1. 南京大学化学化工学院 介观化学教育部重点实验室 南京 210023
  • 投稿日期:2023-03-18 发布日期:2023-05-23
  • 基金资助:
    国家自然科学基金(21832003); 及江苏省前沿引领技术基础研究专项(BK20212005)

Cobalt-Substituted Polyoxometalates as Soluble Mediators to Boost the Lithium-Sulfur Battery Performance

Ziqi Li, Liwei Liu, Chenghui Mao, Changkai Zhou, Minqi Xia, Zhen Shen, Yue Guo, Qiang Wu(), Xizhang Wang, Lijun Yang, Zheng Hu()   

  1. Key Laboratory of Mesoscopic Chemistry of Ministry of Education, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023
  • Received:2023-03-18 Published:2023-05-23
  • Contact: * E-mail: wqchem@nju.edu.cn, Zhenghu@nju.edu.cn
  • Supported by:
    National Natural Science Foundation of China(21832003); Natural Science Foundation of Jiangsu Province, Major Project(BK20212005)

锂硫电池(LSB)因具有理论能量密度高、成本低及环境友好等特点, 是前景光明的下一代高能量二次电池, 目前面临着可溶性多硫化锂(Li2Sn, 8≥n>2)的穿梭效应以及S8↔Li2S转化反应的极化效应等挑战性问题. 以钴取代多金属氧酸盐(Cobalt-substituted polyoxometalates, Co-POMs)作为可溶性介质, 通过化学吸附使可溶性多硫化锂“固化”, 通过催化作用促进S8↔Li2S的转化反应, 有效抑制了穿梭与极化效应, 从而提升了LSB性能. 添加Co-POMs的LSB在2 A•g-1下循环400圈后仍具有565 mAh•g-1的比容量, 库伦效率接近100%, 在5 A•g-1的倍率测试下展现出518 mAh•g-1的放电比容量, 优于添加了四丁基铵-POMs的LSB, 远优于没添加可溶性介质的LSB. 本研究提供了一种利用兼具吸附和催化功能的量子点可溶性介质提升LSB性能的新策略.

关键词: 锂硫电池, 可溶性介质, 钴取代多金属氧酸盐, 化学吸附, 催化转化

Lithium-sulfur battery (LSB) is a kind of promising next-generation high-energy secondary battery due to its high theoretical energy density, low cost and environmental friendliness. Many studies have been devoted to solve the challenging problems faced by LSB such as the shuttle effect of soluble lithium polysulfides (Li2Sn, 8≥n>2) and the polarization effect of sluggish S8↔Li2S conversion. Currently, the main strategies to cope with these challenges include cathode structure design, separator modification and electrolyte regulation, etc., all of which can suppress the shuttle and polarization effects to some extend and thereby optimize the performance of LSB. Adding soluble mediators into electrolytes is a convenient approach, and the key is to develop advanced soluble mediators with synergic functions of inhibiting the polysulfides shuttle and promoting the sulfur/sulfides conversion kinetics. Polyoxometalates (POMs) have unique redox properties and are widely used in the fields of photocatalysis, fuel cells, supercapacitors and rechargeable batteries. POMs have excellent electrochemical stability, and their redox reaction potentials well match the potentials of sulfur/sulfides conversion reactions. Therefore, the utilization of POMs in LSB has great prospect, but is still in its infancy. Herein, cobalt-substituted polyoxometalates (Co-POMs) are used as the soluble mediator of LSB for the first time, which can solidify the soluble polysulfides by chemical adsorption and promote the reversible conversion of S8↔Li2S by electrocatalysis simultaneously, which effectively suppress the shuttle and polarization effects, leading to the improved performance of LSB. The LSB with Co-POMs remains the high specific capacity of 565 mAh•g-1 after 400 cycles at 2 A•g-1 and the coulombic efficiency close to 100%. At a high rate of 5 A•g-1, it still shows a discharge capacity of 518 mAh•g-1, obviously better than the LSB with tetrabutylammonium-POMs or without mediators. This study provides a new strategy to improve the LSB performance by developing advanced quantum dot-type soluble mediators with dual-functional adsorption and electrocatalysis.

Key words: lithium-sulfur battery, soluble mediator, cobalt-substituted polyoxometalate, chemical adsorption, catalytic conversion