Improvement of the rate capability of all-solid-state cells with Fe-based polysulfide positive electrode materials by modifying the microstructure.

We successfully prepared an Fe- and Li-containing polysulfide positive electrode material (Li 8 FeS 5 -Li 2 FeS 2 composite) that shows a high specific capacity (>500 mA h g -1 ) with improved rate capability in all-solid-state cells. High-resolution TEM analysis indicated the coexistence of small crystallites of high-conductivity Li 2 FeS 2 and FeS, as well as low-crystallinity Li 2 S, in the composite, and this microstructure is responsible for the improved battery performance.