Li-In-S composite foil with built-in electric fields to stabilize Li/Li6PS5Cl interface for long-life all-solid-state batteries

Sulfides-based all-solid-state lithium batteries show great potential due to their high safety and high energy density, yet severely suffer from sulfide electrolytes/Li interfacial instability and short cycle life. Here we propose a Li-In-S composite foil comprising Li2S, LixIn, and LiInS2 to stabilize the Li/Li6PS5Cl interface by constructing built-in electric fields, thereby enabling long-life all-solid-state lithium batteries. The work function difference between Li2S and LixIn generates built-in electric fields at the heterointerface, which traps the interfacial electrons and restricts their transfer to Li6PS5Cl, thereby suppressing the interfacial side reactions. Simultaneously, the built-in electric fields promote Li+ adsorption and diffusion inhibiting lithium dendrite growth. Li symmetrical cells display high critical current density over 4 mA cm−2 and Li plating/stripping stability over 2000 h at 1 mA cm−2. The assembled full cells with LiCoO2 and LiNi0.8Co0.1Mn0.1 (NCM811) demonstrate high capacity retention of 93% over 2000 cycles at 1 C and 87.7% over 1000 cycles at 1 C, respectively. Moreover, Li-In-S|Li6PS5Cl|NCM811 full cell shows rate capability up to 4 C. This work offers useful insights into the design of stable interfaces in all-solid-state batteries. Sulfide-based all-solid-state lithium batteries severely suffer from sulfide electrolyte/Li interfacial instability. Here, authors propose an In and S doping into Li metal to stabilize the Li/Li6PS5Cl interface by constructing built-in electric fields, thereby enabling long-life all-solid-state lithium batteries.