Restrained Li|Garnet Interface Contact Deterioration Manipulated by Lithium Modification for Solid‐State Batteries

Abstract Garnet solid state electrolytes (SSEs) have emerged as propitious candidates for solid‐state batteries (SSBs) with exceptional ionic conductivity and excellent (electro)chemical stability. However, the Li|garnet interface contact deterioration still remains a major challenge resulting in Li dendrite propagation. Herein, a method is proposed to strengthen the adhesion of garnet SSE and Li by incorporating Sr 3 N 2 into the Li metal. Density functional theory (DFT) calculations reveal that the interfacial formation energy of Li|garnet is decreased by the obtained Li‐Sr‐N (LSN) composite, which can enable a shift from poor contact to intimate bonding at the Li|garnet interface and a homogenous Li + flux as well as electric field distribution. Simultaneously, the produced Li 3 N and LiSrN, which are known for their strong Li adsorption affinity and rapid Li + transfer kinetics, actively govern the Li plating process. Thereby this rational design brings a notable reduction in interfacial impedance (4.5 Ω cm 2 ), along with the increased critical current density (1.3 mA cm −2 ) and enhanced cycle stability (1200 h at 0.3 mA cm −2 ). Furthermore, The LFP|garnet|LSN full cell has demonstrated remarkable cycling performance (95.9% capacity retention after 200 cycles at 1 C) and favorable rate capability (150.2 mAh g −1 at 0.1 C and 134.9 mAh g −1 at 1 C). The research provides a new sight into lithium modification that can restrain Li|garnet interface deterioration and lay the groundwork for future advancements in high‐performance garnet‐ based SSBs.