A sulfide Li3PS4 (LPS) solid electrolyte is reversibly oxidized and reduced by mixing carbon additives in all-solid-state cells. Because LPS is an electronic insulator similar to S and Li2S, LPS functions as an active material at an interface between LPS and carbon. In this study, composite electrodes composed of LPS and one of various carbon conductive additives were prepared by ballmilling to investigate electrochemical performances of LPS, electrical effective conductivities, and a contact area between LPS and carbon in the LPS-carbon composite electrodes. The rate performance of all-solid-state cells with LPS-carbon composite electrodes was mainly affected by the ionic effective conductivity and the contact area of the composite electrodes. In various carbons, activated carbon was the most promising carbon to achieve the high electrical effective conductivities and the large contact area in the LPS-carbon composite electrode prepared by ballmilling.

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