HIGH ENERGY ALL-SOLID-STATE LITHIUM SECONDARY BATTERIES COMBINING SULFUR-BASED CATHODES WITH ARGYRODITE ELECTROLYTE

Abstract

Among the known fast Li+-ion conducting solids, thiophosphates and especially lithium argyrodites Li6PS5X (X= Cl, Br) are promising solid electrolytes due to their high ionic conductivities and electrochemical stability. We could clarify that lithium argyrodite phase formation starts at low temperature, while lattice parameters, halide content, ordering and consequently ionic conductivities vary with annealing temperature. All-solid-state lithium batteries (ASSLBs) were realized combining argyrodites with various sulfur-based cathodes. ASSLBs using CuS or Cu-Li2S as cathode experience fast capacity fading regardless of the preparation method for the composite cathode, as Cu+ partly substitutes for Li+ in argyrodites yielding CuyLi6-yPS5Br at the intermediate discharge state. Eliminating this detrimental effect of Cu+, S/Li6PS5Br/In-Li batteries achieve an enhanced cyclic performance with reversible capacity of 1080 mAh/g after 50 cycles. In MoS2/Li6PS5Br/In-Li batteries the initial discharge product, well-dispersed Mo metal nanoparticles, enhance the electronic conductivity in the thereby formed Li/S battery further reducing capacity fading.