Prelithiation of Alloy Anodes via Roll Pressing for Solid‐State Batteries

Solid‐state batteries with alloy‐type negative electrodes can feature enhanced energy density and safety compared to conventional Li‐ion batteries. However, diffusional Li trapping within Li alloys often causes low initial Coulombic efficiency and leads to capacity loss with cycling. Here, a general roll‐pressing prelithiation method compatible with a variety of alloy‐type negative electrodes (silicon, aluminum, tin, and multi‐phase alloys) is introduced, which is shown to improve performance in solid‐state batteries. By warm‐rolling lithium foil of controlled thickness with various alloy‐type electrodes, both slurry‐cast and foil‐type electrodes can be uniformly prelithiated via direct chemical reaction. The prelithiated electrodes exhibit enhanced specific capacity and extended cycle life in batteries with Li 6 PS 5 Cl solid‐state electrolyte. Prelithiated multi‐phase foil electrodes with a tailored interface are shown to exhibit superior cycling stability down to 2 MPa stack pressure. This prelithiation technique offers a pathway to overcome intrinsic challenges in alloy anodes for solid‐state batteries.