Sulfide-based all-solid-state batteries (ASSBs) have emerged as promising candidates for next-generation energy storage systems owing to their superior safety and energy density. A conductive agent is necessarily added in the cathode composite of ASSBs to facilitate electron transport therein, but it causes the decomposition of the solid electrolyte and ultimately the shortening of lifetime. To resolve this dilemmatic situation, herein, we report a rationally designed solution-processible coating of zinc oxide (ZnO) onto vapor-grown carbon fiber as a conductive agent to reduce the contact between the carbon additive and the solid electrolyte and still maintain electron pathways to the active material. ASSBs with the carbon additive with an optimal coating of ZnO have markedly improved cycling performance and rate capability compared to those with the bare conductive agent, which can be attributed to hindering the decomposition of the solid electrolytes. The results highlight the usefulness of controlling the interparticle contacts in the composite cathodes in addressing the challenging interfacial degradation of sulfide-based ASSBs and improving their key electrochemical properties.
Keywords: all-solid-state batteries; conductive carbon additive; solvothermal synthesis; sulfide solid electrolyte; surface coating.