In Situ Conversion Reaction Triggered Alloy@Antiperovskite Hybrid Layers for Lithiophilic and Robust Lithium/Garnet Interfaces

Abstract Garnet‐type electrolytes demonstrate promising prospects in the field of solid‐state lithium batteries owing to their superior ionic conductivity and high (electro)chemical stability toward Li metal, whereas the critical issue of Li dendrite growth and even infiltration throughout garnets limits their practical applications. Herein, a hybrid interlayer consisting of Li 3 Bi alloy embedded in antiperovskite‐type Li 3 OCl matrix is in situ constructed at Li/Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 interface by taking the conversion reaction of BiOCl with Li metal. The lithiophilic nature of such interlayer enables an intimate contact of garnet against Li metal, guaranteeing a dramatically reduced interfacial resistance of 27 Ω cm 2 . In addition, the inside electron‐conducting Li 3 Bi nanoparticles homogenize the interfacial potential distribution, while the outside ion‐conducting Li 3 OCl matrix with a bandgap of 5.06 eV blocks electron tunneling from Li bulk. Profiting from such synergistic effect, the resultant Li symmetric cell displays a high critical current density of 1.1 mA cm −2 , along with an ultralong cycling life of 1000 h at 0.5 mA cm −2 . Furthermore, the corresponding solid LiNi 0.6 Co 0.2 Mn 0.2 O 2 /Li cell delivers a high cycling stability for 150 times accompanied by a capacity retention of 82%. This study puts forward a potential solution for construction of functional layers at Li/garnet interfaces by making use of in situ conversion reaction.