Unravelling the electrochemical evolution mechanism of In 2 O 3 anode in long‐cycle all‐solid‐state lithium batteries with sulfide electrolytes

In sulfide‐based all‐solid‐state lithium batteries (ASLBs), the development of high‐capacity anode materials with stable interfaces to sulfide solid‐state electrolytes (SSEs) is critical. Here, In 2 O 3 is explored as an anode material for ASLBs for the first time, demonstrating exceptional interfacial stability and electrochemical performance. The In 2 O 3 anode, with a substantial mass loading of 7.64 mg cm −2 , sustains a charge‐specific capacity of 528.0 mAh g −1 (4.03 mAh cm −2 ) at a current density of 0.76 mA cm −2 over 500 cycles, with a capacity retention of 81.2%. Additionally, it exhibits remarkable long‐term cycling stability (2900 cycles) under a high current density of 3.82 mA cm −2 , with an exceptionally low decay rate of 0.016% per cycle. The charge–discharge mechanism of the In 2 O 3 anode is elucidated in detail, revealing that the electrochemical evolution of In 2 O 3 in ASLBs involves not only the alloying/dealloying process of indium (In) but also a conversion reaction between In and Li 2 O. Notably, as cycling progresses, the conversion reaction of In and Li 2 O diminishes, with the reversible alloying/dealloying process becoming predominant. This work offers valuable insights for advancing oxide anode materials in sulfide‐based ASLBs.