Dual-Function ZnO-Li3TaO4 Surface Modification of Single-Crystalline Ni-Rich Cathodes for All-Solid-State Batteries

Herein, we introduce a ZnO–Li3TaO4 composite coating designed to stabilize single-crystalline LiNi0.95Co0.03Mn0.015Al0.005O2 (sNCMA) in ASSBs with Li6PS5Cl. This dual-function coating establishes a Ta-rich surface layer and Zn-doped near-surface regions, as verified by detailed analyses, including atom probe tomography and transmission electron microscopy. The ZnO-Li3TaO4 coating markedly enhances both interfacial and structural stabilities, showcasing an exceptional performance in sNCMA|Li6PS5Cl|(Li–In) cells at 30 °C (initial discharge capacity of 196 mA h g–1 with 82.7% capacity retention after 1000 cycles), exceeding the performance of both uncoated or only Li3TaO4-coated sNCMA (only 82.5 or 84.2%, respectively, after 200 cycles). The protective role of ZnO-Li3TaO4 is corroborated by electrochemical impedance spectroscopy and ex situ X-ray photoelectron spectroscopy. Finally, density functional theory calculations and comparative tests with oxidatively inert Li2ZrCl6 catholytes elucidate the enhanced performance mechanism, specifically, the suppression of Ni2+ migration by Zn doping, emphasizing the importance of cathode structural stability in all-solid-state batteries.