Constructing stable cathode interfaces with halide–sulfide dual electrolytes for all-solid-state lithium batteries with enhanced electrochemical performance

Abstract

Interfacial instability between Ni-rich layered oxide cathodes and sulfide electrolytes remains a major bottleneck hindering the development of high-performance all-solid-state lithium batteries (ASSLBs). Conventional coating materials often suffer from low ionic conductivity and poor mechanical deformability, necessitating complex processing or additional interlayers. Halide electrolytes offer good stability, ionic conductivity, and softness, but their poor reductive stability with lithium metal limits their use as standalone solid electrolytes in full cells. In this work, we propose a dual-electrolyte composite cathode strategy by introducing a halide electrolyte, Li₃InCl₆ (LIC), as a functional surface coating for LiNi_0.8Co_0.1Mn_0.1O₂ (NCM). The nanosized Li₃InCl₆ particles synthesized by freeze-drying exhibit high ionic conductivity and uniform particle size distribution, making them effective as interfacial buffer layers. The optimized 15% LIC@NCM composite cathode delivers a high initial capacity of 189 mA h g⁻¹ with a coulombic efficiency of 84.4% at 0.1 C, along with remarkable cycling stability, retaining 114 mA h g⁻¹ after 250 cycles at 0.5 C. Comprehensive electrochemical and spectroscopic analyses confirm that the Li₃InCl₆ coating effectively mitigates interfacial degradation, suppresses side reactions, and facilitates ion transport across the composite interface. This study offers a facile and scalable interface engineering strategy using halide electrolytes to simultaneously enhance lithium-ion transport and interfacial stability in sulfide-based ASSLBs.