Optimizing Lithium Nucleation Overpotential in Anode‐Free Garnet‐Based Hybrid Solid‐State Batteries

Abstract Anode‐free solid‐state lithium batteries promise high‐energy‐density storage but remain limited by unstable interfaces between the solid electrolyte and in situ‐formed lithium. In this work, a hybrid solid–liquid electrolyte strategy is developed using a localized high‐concentration electrolyte containing AlCl ₃ and LiPO ₂ F ₂ , a trilayer garnet‐type Li _6.4 Ga _0.1 La _2.9 Ba _0.1 Zr _1.6 Ta _0.4 O ₁₂ solid electrolyte. This configuration forms a mechanically stable and ionically conductive solid‐liquid electrolyte interphase, enabling 81% Coulombic efficiency after 300 cycles at 2 mA cm ⁻² and 1 mAh cm ⁻² in Cu/Li half‐cells. A single‐layer anode‐free hybrid solid‐state pouch cell demonstrated excellent long‐term cycling performance, retaining 75% of its initial capacity after 400 cycles at 1C (1.25 mA cm ⁻² ), with a Coulombic efficiency of 99% without external pressure and at room temperature. At the lab scale, this hybrid electrolyte approach shows both scalability and performance, providing a potential practical pathway to next‐generation anode‐free hybrid solid‐state lithium batteries.