LIAN Fang，FAN Zunhao，LI Jingyi，WANG Zixin

School of Materials Science and Engineering， University of Science and Technology Beijing， Beijing 100083， China

Abstract

Significance Sulfide solid electrolytes （SSEs） have become one of the most promising materials for the industrialization of solid-state batteries， owing to their high ionic conductivity at room temperature and unique mechanical properties. However， in terms of material types， the development of SSEs still faces a series of challenges， including poor chemical stability， severe electrode interface side reactions， mechanical contact loss， and the absence of large-scale production technologies. Over the past decade，many approaches have been proposed to address the above issues. This review focuses on particle size reduction and particle coating/modification to improve the chemical stability and electrochemical performance of SSEs.

Progress Small-sized sulfide particles have lower electrochemical/mechanical strain energy， which suppresses mechanical deactivation/degradation. Due to the unique mechanical processing and low-temperature crystallization characteristics of sulfides，mechanical ball milling and mechanochemical solid solution synthesis methods are currently effective for obtaining small-sized sulfides. However， the crystallinity of sulfides is changed during the mechanical ball milling process， and the Li⁺ionic conductivity decreases. In contrast， the liquid-phase synthesis method has the advantages of lower synthesis temperature， shortened synthesis procedure， production of fine sulfide particles， and simultaneous modification， which is expected to be employed for low-cost large-scale preparation of sulfide electrolyte powders. However， sulfides are unstable in air and solvents， limiting the solvents available for liquid-phase sulfide synthesis. The residual solvents and generated impurities are detrimental to the performance of sulfide electrolytes. Therefore， exploring more feasible processes for large-scale production of sulfide powders will be crucial for the industrialization of sulfide-based solid-state batteries in the future. The surface state and chemical sensitivity of sulfide particles can be precisely controlled by coating and surface modifying， which can significantly suppress the reactivity of particles under humid and oxidized conditions， improve the interface compatibility between SSEs and electrode materials， and reduce the electronic conductivity. In the future development of sulfide electrolyte， it is important to explore coating materials and their coating techniques to further improve interface stability without compromising ionic conductivity.

Conclusions and Prospects By optimizing the synthesis methods and modifying the particle surface， sulfide electrolyte have made great progress in the application for solid-state batteries. It is vital to further enhance the performance of sulfide materials for solid-state batteries. Future studies can focus on the strategies for producing electrolyte membranes and exploring composite electrode designs to ensure compatibility with production equipment and processes of liquid lithium-ion batteries.

Keywords：particle； sulfide； solid electrolyte； solid-state battery； preparation