Electrochemical behavior of elemental alloy anodes in solid-state batteries

Abstract

Lithium alloy anodes in the form of dense foils offer significant potential advantages over lithium metal and particulate alloy anodes for solidstate batteries (SSBs). However, the reaction and degradation mechanisms of dense alloy anodes remain largely unexplored. Here, we investigate the electrochemical lithiation/delithiation behavior of 12 elemental alloy anodes in SSBs with Li 6 PS 5 Cl solid-state electrolyte (SSE), enabling direct behavioral comparisons. The materials show highly divergent first-cycle Coulombic efficiency, ranging from 99.3% for indium to ∼20% for antimony. Through microstructural imaging and electrochemical testing, we identify lithium trapping within the foil during delithiation as the principal reason for low Coulombic efficiency in most materials. The exceptional Coulombic efficiency of indium is found to be due to unique delithiation reaction front morphology evolution in which the high-diffusivity LiIn phase remains at the SSE interface. This study links composition to reaction behavior for alloy anodes and thus provides guidance toward better SSBs.

Intimate Protective Layer via Lithiation Sintering for All-Solid-State Lithium Metal Batteries

“…Various alloy metals, including indium (In), − silver (Ag), − silicon (Si), aluminum (Al), and magnesium (Mg), , have been explored for use as protective layers or host materials. These metals exhibit the potential to function as lithium-ion conductors, featuring remarkable Li ion diffusion coefficients achieved by alloying with Li metals. − Among these options, the Li-Si alloy stands out due to its exceptionally high Li concentration and superior electrochemical stability with SE, making it a promising candidate. − Despite its potential physicochemical properties, the effective Li-Si alloy protective layer in ASSLMBs has not yet been developed because the formation of uniform protective layers over large areas is challenging due to the limited electrochemical lithiation of Si particles …”