锂硫电池隔膜改性增强电池循环稳定性

Modification of separator to enhance cycle perfomance for lithium-sulfur batteries

关键词:  锂硫电池  玻璃纤维隔膜  循环稳定性  多硫化锂  锰催化剂

Key words:  lithium-sulfur battery  glass fiber separator  cycle stability  lithium polysulfides  Mn catalyst

摘要:

目的 对比玻璃纤维和聚丙烯隔膜用于锂硫电池的性能差异，并通过催化剂改性隔膜提升锂硫电池循环稳定性能。方法 通过循环充放电实验考查不同隔膜锂硫电池性能，利用循环伏安法、线性扫描伏安法及扫描电镜研究隔膜对多硫化锂氧化还原反应动力学的影响，进一步研究锰催化剂改性隔膜对锂硫电池性能的提升效果及作用原理。结果 在1 C放电倍率、150次循环条件下，玻璃纤维隔膜锂硫电池放电比容量由聚丙烯隔膜的428 mAh/g提升至477 mAh/g，充放电效率从96.9%提升至98.6%，容量保持率从66.8%提升至85.1%。利用锰催化剂修饰玻璃纤维隔膜，经500次循环电池仍保有597 mAh/g的容量和99.7%的充放电效率，循环稳定性能大幅提升。结论 玻璃纤维隔膜的大孔隙结构有利于多硫化锂及锂离子在电解液传递，可提高锂离子的传递效率，但也会加强穿梭效应而导致电池容量降低；同时，多硫化锂及锂离子的快速传质有助于诱导形成致密SEI膜以保护锂负极，提升电池循环稳定性；此外，在锰催化剂修饰下，锰?玻璃纤维隔膜能实现电池容量和循环稳定性双重提升，减少充放电过程中的能量损耗。

Abstract:

Objective Separators are crucial components for suppressing the shuttle effect in lithium-sulfur batteries. This study compares the performance differences of lithium-sulfur batteries using glass fiber and polypropylene separators and explores the cycling stability improvement of lithium-sulfur batteries through catalyst-modified separators. Method This paper investigated the performance of lithium-sulfur batteries with different separators through cyclic charge-discharge experiments, and uses cyclic voltammetry, linear sweep voltammetry, and scanning electron microscopy to study the impact of separators on the redox kinetics of lithium polysulfides, and further researched the performance enhancement and mechanism of lithium-sulfur batteries with Mn catalyst-modified separators. Result Under the conditions of 1 C and 150 cycles, the discharge specific capacity of lithium-sulfur batteries with glass fiber separators increased from 428 mAh/g of polypropylene separators to 477 mAh/g, the charge-discharge efficiency increased from 96.9% to 98.6%, and the capacity retention rate increased from 66.8% to 85.1%. With Mn catalyst modification of the glass fiber separator, the battery still maintained a capacity of 597 mAh/g and a charge-discharge efficiency of 99.7% after 500 cycles, which significantly improving the cycle stability. Conclusion The large pore structure of the glass fiber separator is beneficial for the transmission of lithium polysulfides and lithium ions in the electrolyte, which can improve the transfer efficiency of lithium ions but also strengthen the shuttle effect leading to a reduction in battery capacity. At the same time, the rapid mass transfer of lithium polysulfides and lithium ions helps to induce the formation of a dense SEI film to protect the lithium anode and enhance the cycle stability of the battery; in addition, with Mn catalyst modification, the Mn-glass fiber separator can achieve dual enhancement of battery capacity and cycle stability, and reduce energy loss during the charge-discharge process.