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

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.