Important consideration for interface engineering of carbon-based materials in sulfide all-solid lithium-ion batteries

All-solid-state lithium-ion batteries (ASSLBs) offer superior performance and enhanced safety compared to the existing liquid-based lithium-ion batteries (LIBs). However, recently, an issue has emerged in ASSLBs in which carbon materials accelerate the deterioration of the sulfide solid electrolytes (SSEs), thereby reducing electrochemical performance. In this paper, we present approach for carbon materials that can enhance compatibility with solid electrolytes in ASSLBs. The compatibility between carbon and solid electrolyte is improved by removing amorphous carbon on the carbon surface, which unavoidably forms on the surface during carbon material synthesis, covering about 5 similar to 7 nm on the highly crystalline graphite surface. The evaluation of ASSLBs revealed significant differences in electrochemical performance depending on pristine graphite (P-Gr), which had amorphous carbon adsorbed on the surface, and surface-crystallized graphite (SC-Gr) where amorphous carbon was removed. Interestingly, there was no significant difference in electrochemical performance observed in LIBs. The improved electrochemical properties were closely associated with the quantity of Li2S, Li- phosphide, and SEI layer formed by the decomposition of the solid electrolyte during charging and discharging, subsequently affecting interfacial resistance between graphite and SSEs. In addition, stable electrochemical performance was achieved in both half-cell and full-cell evaluations due to the suppressed degradation of the solid electrolyte and the stable interface. This was observed despite reducing the proportion of the solid electrolyte within the anode composite from 40 % to 20 %. We anticipate that improving the interface compatibility between crystalline carbon and the solid electrolyte will broaden the applications of carbon materials in solid-state electrolytes, advancing the development of ASSLBs that meet specific electrochemical performance criteria.