Reducing Surface Roughness to Achieve Li<sub>2</sub>CO<sub>3</sub>‐Existent Lithiophilic Interface in Garnet‐Type Solid‐State Batteries
Jiaxu Zhang, Changhong Wang, Jiamin Fu, Minghao Ye, Huiyu Zhai, Jun Li, Gangjian Tan, Xinfeng Tang, Xueliang Sun
Abstract
Abstract The presence of Li 2 CO 3 has been identified as the cause of poor lithophilicity in garnet‐type Li 7 La 3 Zr 2 O 12 (LLZO) solid‐state batteries. A Li 2 CO 3 ‐free garnet is expected to enhance the Li/LLZO interface contact. However, permanently eradicating regenerative Li 2 CO 3 from the LLZO surface is extremely challenging and the influence of regenerated Li 2 CO 3 is often ignored. Herein, it is found that glossy Li 2 CO 3 pellets can also be perfectly wetted by molten Li, contradicting the common belief that Li 2 CO 3 is lithiophobic. Therefore, reducing the surface roughness of LLZO allows it to be directly wetted by lithium metal, regardless of the presence of Li 2 CO 3 . Additionally, smooth LLZO exhibits better air stability due to its reduced active area. The symmetric cell with a smooth LLZO pellet shows a low interfacial impedance of 2 Ω cm 2 and a high critical current density of 1.4 mA cm − 2 at 25 °C. This work highlights the surface physics of garnet which significantly influences its interface properties, apart from surface chemistry.