Implanting Non‐Lithiated Metal into Fluoride/Nitride Hybrid Matrix Enabling Tailored Lithium/Garnet Interface Chemistry for Durable Solid‐State Lithium Batteries

Abstract Garnet‐type Li ₇ La ₃ Zr ₂ O ₁₂ has been regarded as a promising electrolyte for solid‐state lithium batteries due to its high ionic conductivity and wide potential window. Unfortunately, the critical dendrite infiltration endows garnet with great limitations toward practical applications. Herein, a hybrid interlayer consisting of Ni nanocrystals encircled by fluoride/nitride matrix with mixed ionic‐electronic conductivity is in situ established to tailor Li/garnet interface chemistry via synergetic conversion reactions between NiF ₂ /LiNO ₃ and Li. Specifically, the inner non‐lithiated metallic Ni nanocrystal exhibits no obsession of alloy hardening during high‐temperature aging or long‐term cycling, reliably retaining its basic role of uniformizing interfacial electric‐field distribution. In addition, the outer fluoride/nitride bulk with balanced ionic conductivity and interface energy toward Li inhibits the electron tunneling and dendrite invasion from the Li anode. Consequently, a dendrite‐free Li plating/stripping can be achieved even at a critical current density of as high as 1.5 mA cm ⁻² . Besides, the resultant solid‐state LiNi _0.6 Co _0.2 Mn _0.2 O ₂ /Li cell based on such interface engineering displays an initial discharge capacity of 159 mAh g ⁻¹ , followed by a high capacity retention of 77.4% after 300 cycles. This study provides a novel strategy for the construction of mixed‐conductivity interlayers by implanting non‐lithiated metal particles into inorganic‐rich fast ion conductors to reinforce the Li/garnet interface.