A Universal Self‐Propagating Synthesis of Aluminum‐Based Oxyhalide Solid‐State Electrolytes

Inorganic solid‐state electrolytes (SSEs) play a vital role in high‐energy all‐solid‐state batteries (ASSBs). However, the current method of SSE preparation usually involves high‐energy mechanical ball milling and/or a high‐temperature annealing process, which is not suitable for practical application. Here, a facile strategy is developed to realize the scalable synthesis of cost‐effective aluminum‐based oxyhalide SSEs, which involves a self‐propagating method by the exothermic reaction of the raw materials. This strategy enables the synthesis of various aluminum‐based oxyhalide SSEs with tunable components and high ionic conductivities (over 10‐3 S cm‐1 at 25 °C) for different cations (Li+, Na+, Ag+). It is elucidated that the amorphous matrix, which mainly consists of various oxidized chloroaluminate species that provide numerous sites for smooth ion migration, is actually the key factor for the achieved high conductivities. The application of these aluminum‐based oxyhalide SSEs synthesized by our approach further pushes forward their practical application considering their easy synthesis, low cost, and low weight that ensures high‐energy‐density ASSBs.