Optimizing the operation strategy of solid-conversion sulfur cathodes for achieving high total capacity contribution throughout the lifespan

Abstract

Solid-solid sulfur conversion reaction caused by cathode electrolyte interphase (CEI) can effectively prevent the dissolution of lithium polysulfides and theoretically improve the cycle stability of lithium-sulfur (Li–S) batteries. However, once the volume of reduction products (Li2S) exceeds the maximal volume of hosts, the as-formed CEI will be destroyed and significantly shorten the cycle life. In this study, we report a simple capacity control strategy to obtain a stable CEI which can greatly increase the total capacity contribution of Li–S batteries throughout the whole lifespan. By adjusting the discharging condition, Li–S cells achieve a prolonged cycle life over 950 cycles and a remarkable total capacity of 289 Ah g−1 based on sulfur during the whole lifetime. Meanwhile, it is also found that the cycle life depends to a great extent on lithium anodes. This discharging strategy and understanding on the solid phase sulfur conversion under CEI mechanism can advance progress for the development of Li–S batteries.