Size-controlled wet-chemical synthesis of sulfide superionic conductors for high-performance all-solid-state batteries

The escalating concerns surrounding the safety issues tied to the flammability of organic liquid electrolytes in conventional lithium-ion batteries have catalyzed the evolution and advancement of all-solid-state batteries (ASSBs) integrated with solid electrolytes (SEs). Among various SE materials, sulfide-based lithium argyrodite has risen to prominence owing to its high ionic conductivity and ease of processability. Despite the wet-chemical processing method being considered advantageous for the synthesis of sulfide SEs, due to its inherent simplicity, potential scalability, and cost-effectiveness, certain challenges persist. These primarily pertain to achieving high ionic conductivity and mitigating interfacial resistance between the electrode and the SEs. Addressing these challenges, this study presents a novel, scalable, and cost-efficient wet synthesis approach to produce superionic conductive sulfide-based SEs. This method involves careful regulation of the nucleation rate and strategic substitution of elements to control particle size and enhance ionic conductivity. The resultant Li5.5PS4.5Cl1.5 SEs synthesized show a uniform size distribution (average particle diameter = 7 μm), coupled with a high ionic conductivity of 4.98 mS cm−1. This level of ionic conductivity is either comparable to or exceeds those produced through dry processes. The ability to control particle size optimizes the contact interface between the electrode and the electrolyte, reducing interfacial resistance and increasing discharge capacity. Consequently, this method paves the way for mass production of high-quality sulfide SEs. The findings of this study serve to further the development of high-performing ASSBs, making them suitable for implementation in high output power and long cruising distance electric vehicles, pushing the envelope for battery-powered transportation solutions.