A 3D Cross‐Linking Lithiophilic and Electronically Insulating Interfacial Engineering for Garnet‐Type Solid‐State Lithium Batteries

Abstract Solid‐state batteries (SSBs) promise high energy density and strong safety due to using nonflammable solid‐state electrolytes (SSEs) and high‐capacity Li metal anode. Ta‐substituted Li 7 La 3 Zr 2 O 12 (LLZT) SSE possesses superior ionic conductivity and stability with Li metal, yet the interfacial compatibility and lithium dendrite hazards still hinder its applications. Herein, an interfacial engineering is demonstrated by facile acid‐salt (AS) treatment on LLZT, constructing a 3D cross‐linking LiF‐LiCl (CF) network. Such structure facilitates Li wetting via capillary permeation. Notably, CF as electronically insulting phases block the electrons through the interface and ulteriorly suppress the dendrite formation. The assembled Li symmetric cell exhibited a low interfacial impedance (11.6 Ω cm 2 ) and high critical current densities (CCDs) in the time‐constant mode, 1.8 mA cm −2 at 25 °C and 3.6 mA cm −2 at 60 °C, respectively. Meanwhile, by exploring the capacity‐constant mode of CCD measurement, the concept of critical areal capacity (CAC) is first proposed, obtaining its values of ≈0.5 mAh cm −2 at 25 °C and 1.2 mAh cm −2 at 60 °C. Moreover, the safety‐enhanced hybrid SSBs matched with LiFePO 4 and LiNi 0.6 Co 0.2 Mn 0.2 O 2 deliver a remarkable rate and cycling performances, validating the feasibility of this interfacial engineering in various SSB systems.