A comprehensive cognition for the capacity fading mechanism of FeS2 in argyrodite-based all-solid-state lithium battery

Sulfide solid state electrolyte (SSE) possesses high ionic conductivity and great processability but suffers from narrow electrochemical window. Conversion sulfide cathode FeS 2 has higher specific capacity and moderate redox potential, making it appropriate toward sulfide SSE. However, the complex reaction pathway and capacity fading mechanism in FeS 2 are rarely studied, especially in all-solid-state lithium battery (ASSLB). Herein, argyrodite sulfide SSE is paired with FeS 2 to investigate the electrochemical reaction pathways and the capacity fade mechanism. Instead of single conversion reaction, an anionic redox driven reaction of FeS 2 is revealed. The oxidization of Li 2 S vanishes and large quantity of inactive Li 2 S accumulates to cause the interfacial deterioration, along with the stress concentration during cycling, which leads to the rapid capacity fade of FeS 2 . Finally, a simple strategy of slurry-coated composite electrode with highly conductive network is proposed to direct the uniform deposition of Li 2 S and alleviate the stress concentration.