China University of Science and Technology develops all-solid-state lithium battery electrolyte with cost performance

Professor Ma Cheng of the University of Science and Technology of China has developed a new solid electrolyte, which has similar comprehensive performance to the most advanced sulfide and chloride solid electrolyte, but the cost is less than 4% of the latter, which is suitable for industrial application. On June 27, the results were published in the internationally renowned academic journal Nature-Communications.

Comprehensive comparison of the cost and performance of lithium zirconium oxychloride and other types of solid electrolytes. Photo courtesy of China University of Science and Technology

All-solid-state lithium batteries can overcome the serious safety shortcomings of current commercial lithium-ion batteries, while further improving energy density, which is a disruptive technology for the new energy vehicle and energy storage industry. However, because the core material of all-solid-state lithium batteries, solid electrolytes, is difficult to balance performance and cost, industrialization still faces huge obstacles.

In order to meet the needs of practical applications, the solid-state electrolyte of an all-solid-state lithium battery needs to meet at least three conditions at the same time: high ionic conductivity (more than 1 millisiemens per centimeter at room temperature), good deformability (more than 90% dense at 250 to 350 MPa), and low enough cost (less than $50 per kilogram). However, the currently widely studied oxide, sulfide, chloride solid electrolytes cannot meet these conditions at the same time.

In this study, Ma Cheng no longer focused on any of the above oxides, sulfides, and chlorides, but turned to oxychlorides and designed and synthesized a new solid electrolyte – lithium zirconium oxychloride. This material has a strong cost advantage. If it is synthesized with hydrated lithium hydroxide, lithium chloride and zirconium chloride, its raw material cost is only 11.6 US dollars per kilogram, which well meets the above requirements of 50 US dollars per kilogram. If zirconium oxychloride hydrate, lithium chloride and zirconium chloride are synthesized, the cost of lithium zirconium oxychloride can be further reduced to about $7 per kilogram, which is far lower than the current most cost-effective solid electrolyte lithium zirconium chloride ($10.78 per kilogram), and less than 4% of sulfide and rare earth-based and indium-based chloride solid electrolytes.

While having a strong cost advantage, the comprehensive performance of lithium zirconium oxychloride is comparable to the most advanced sulfide and chloride solid electrolytes. Its room-temperature ionic conductivity is as high as 2.42 millisiemens per centimeter, exceeding the 1 millisiemens per centimeter required for the application, and is among the top of the various solid electrolytes currently reported. At the same time, its good deformability makes the material 94.2% dense at a pressure of 300 MPa, which can well meet the application needs, and is also better than the sulfide and chloride solid electrolyte known for its easy deformability (less than 90% dense at the same pressure).

The experiment proved that the all-solid-state lithium battery composed of lithium zirconium oxychloride and high-nickel ternary cathode demonstrated excellent performance: under the condition of 12 minutes of fast charging, the battery still managed to cycle stably at room temperature for more than 2,000 cycles.

According to the researchers, lithium zirconium oxychloride can achieve similar performance to the most advanced sulfide and chloride solid electrolytes at the lowest cost, which is of great significance to the industrialization of all-solid-state lithium batteries.

The reviewers considered the discovery “very novel and original” and considered the lithium zirconium oxychloride material “promising” and “beneficial to the commercialization of solid-state battery technology.” (Source: Wang Min, China Science News)

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