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Ma Cheng, a professor at the University of Science and Technology of China, has developed a new sulfide solid electrolyte for all-solid-state batteries. While possessing the inherent advantages of sulfide solid electrolytes, this material is cheaper than other sulfide solid electrolytes and thus more suitable for commercialization. The relevant research findings were recently published in German Applied Chemistry. All-solid-state batteries are expected to overcome the bottleneck faced by lithium-ion batteries in balancing range and safety, thereby breaking through the current “ceiling” of battery technology. Solid-state electrolytes are the key to successfully constructing all-solid-state batteries. Scientists believe that among the three types of solid electrolytes—oxides, sulfides, and halides—it is the sulfides, with their excellent properties, that hold the greatest potential for enabling the practical use of all-solid-state batteries. However, the cost of sulfide solid-state electrolytes generally exceeds $195 per kilogram, which is far higher than the $50 per kilogram required for commercialization. The root of this problem lies in the fact that the synthesis of solid sulfide electrolytes requires a large amount of expensive lithium sulfide, whose price is no less than $650 per kilogram. Researchers have tried various methods to reduce the cost of lithium sulfide, but long-term efforts have shown that achieving this goal is quite difficult. To this end, Ma Cheng no longer focused on reducing the cost of lithium sulfide; instead, he developed a sulfide solid electrolyte that does not use lithium sulfide as a raw material—lithium oxysulfide. This solid electrolyte is synthesized using inexpensive raw materials such as hydrated lithium hydroxide and phosphorus sulfide, with a cost of only 14.42 dollars per kilogram. This is less than 8% of the cost of raw materials used for other sulfide-based solid electrolytes, and it is well below the 50 dollars per kilogram requirement for commercial use, making it highly cost-competitive. At the same time, lithium oxysulfide retains the unique advantages of sulfide solid electrolytes: extremely low density and good compatibility with anodes. These characteristics cannot be achieved simultaneously in oxide and halide solid electrolytes. The density of lithium oxysulfide is only 1.7 grams per cubic centimeter, which is lower than that of halide and oxide solid electrolytes. In addition, lithium oxysulfide is highly compatible with both lithium metal and silicon ； The symmetric battery composed of it and lithium metal can undergo stable cycling at room temperature for over 4,200 hours, while the all-solid soft-pack battery made up of it, a silicon anode, and a high-nickel ternary cathode retains 89.29% of its capacity after 200 cycles at 60 degrees Celsius. Ma Cheng said, “Our work shows that the cost issue of sulfide solid electrolytes is not insurmountable.” As a new material, lithium phosphoxysulfide is expected to see further improvements in its performance, and we are continuing to work toward that goal. ” The reviewers believe that the all-solid-state battery composed of lithium phosphoxysulfide possesses \"excellent cycle performance\", and their findings are of great significance for the commercialization of all-solid-state batteries.