Constructing a Superlithiophilic 3D Burr‐Microsphere Interface on Garnet for High‐Rate and Ultra‐Stable Solid‐State Li Batteries

Garnet-type solid-state electrolyte (SSE) Li6.5 La3 Zr1.5 Ta0.5 O12 attracts great interest due to its high ion conductivity and wide electrochemical window. But the huge interfacial resistance, Li dendrite growth, and low critical current density (CCD) block the practical applications. Herein, a superlithiophilic 3D burr-microsphere (BM) interface layer composed of ionic conductor LiF-LaF3 is constructed in situ to achieve a high-rate and ultra-stable solid-state lithium metal battery. The 3D-BM interface layer with a large specific surface area shows a superlithiophilicity and its contact angle with molten Li is only 7° enabling the facile infiltration of molten Li. The assembled symmetrical cell reaches one of the highest CCD (2.7 mA cm-2 ) at room temperature, an ultra-low interface impedance of 3 Ω cm2 , and a super-long cycling stability of 12 000 h at 0.1-1.5 mA cm-2 without Li dendrite growth. The solid-state full cells with 3D-BM interface show outstanding cycling stability (LiFePO4 : 85.4%@900 cycles@1 C; LiNi0.8 Co0.1 Mn0.1 O2 :89%@200 cycles@0.5 C) and a high rate capacity (LiFePO4 :135.5mAh g-1 at 2 C). Moreover, the designed 3D-BM interface is quite stable after 90 days of storage in the air. This study offers a facile strategy to address the critical interface issues and accelerate the practical application of garnet-type SSE in high performance solid-state lithium metal batteries.