Unraveling Failure Mechanism of Indium Anodes in all‐Solid‐State Batteries

ABSTRACT Alloy‐based anodes, particularly indium (In) are emerging as promising candidates for achieving long‐cycle life in all‐solid‐state lithium batteries (ASSLBs), due to their dendrite‐free characteristics and ability to stabilize the anode interface. However, their practical applications remain hindered by limitations in the failure of In anodes under high current densities and areal capacities, where the incomplete understanding of the underlying failure mechanism limits the optimization strategies. Herein, we employ advanced characterization techniques to systematically investigate the failure mechanisms of In anodes under high current densities and areal capacities. Our findings reveal that alloying and dealloying processes involve an electro‐chemo‐mechanical coupling failure mechanism and further exacerbate performance degradation. By elucidating these failure mechanisms, our work provides critical insights and rational surface protection strategies by ALD coating with Al 2 O 3 layer for enhancing the interfacial stability and performance of alloy anodes in ASSLBs. The maximum cycling capacity of the Li/In asymmetric cell at 0.5 mA/cm 2 was enhanced from 0.2 to 2 mAh/cm 2 (>200 cycles). This work paves the way for the development of durable, high‐energy‐density batteries.