Stability of the Argyrodite Electrolyte in Li–In Based All-Solid-State Batteries

Li–In alloy has been largely used as a working anode in all-solid-state full cells. Incorporating indium can help stabilize the interface by suppressing the decomposition of the solid electrolyte. However, the Li–In phase diagram is complex and involves multiple phases depending on the composition. Understanding the relationship between the Li–In composition and electrochemical performance as well as identifying the root causes of cell failure is crucial for advancing this technology. Here, we present a compressive analysis of the impact of the Li–In composition on the interfacial stability of the argyrodite electrolyte in all-solid-state batteries. The Li0.5In alloy, composed of LiIn and In phases, significantly improves the interfacial stability. In contrast, when using the Li–In or Li metal anode, we observe the accumulation of large Li deposits within the solid electrolyte as well as a thick interface composed of Li2S, leading to a shortened cycle life. The Li0.5In anode enables a high critical current density of 2.0 mA cm–2 and extends cycling for 1000 h at 0.5 mA cm–2. Additionally, a reversible capacity of 120 mAh g–1 is achieved over 700 cycles in the LiCoO2|Li6PS5Cl|Li0.5In full cell.