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

Abstract

Herein, we introduce a ZnO–Li₃TaO₄ composite coating designed to stabilize single-crystalline LiNi_0.95Co_0.03Mn_0.015Al_0.005O₂ (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.