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

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, Li_xIn, 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 Li_xIn 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 LiNi_0.8Co_0.1Mn_0.1 (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.