A method has been developed to produce solid electrolytes for all-solid-state batteries faster and with better quality, which is expected to contribute to the commercialization of all-solid-state batteries in the future.

Dr. Ha Yoon-cheol's team at the Next Generation Battery Research Center of the Korea Electrotechnology Research Institute (KERI) has developed an 'upgraded co-precipitation method' to produce sulfide-based solid electrolytes for all-solid-state batteries faster and with better quality.

All-solid-state batteries are a next-generation battery technology that significantly reduces the risk of fire or explosion by replacing the electrolyte with a solid rather than a liquid.

Dr. Ha Yoon-cheol's team attracted attention in 2021 for developing a co-precipitation method that could mass-produce raw materials by putting them into a container all at once without expensive lithium sulfide (Li2S), and this technology was transferred to Daejoo Electronic Materials Co., Ltd.

Afterwards, KERI collaborated with the Korea Advanced Institute of Science and Technology (KAIST) and Daejoo Electronic Materials Co., Ltd. to elucidate the mechanism of the coprecipitation phenomenon and develop an upgraded coprecipitation method to shorten the solid electrolyte production time and improve quality.

The core of the precipitation method is the process of dissolving the raw material in a solution, precipitating it, and then filtering it.

The research team mixed lithium, sulfur, and a catalyst in an appropriate ratio to achieve the sequential dissolution process of lithium. Intermediate products were analyzed and applied to the solid electrolyte synthesis process to optimize the rapid and homogeneous dissolution and coprecipitation of various raw materials.

Professor Hye-Ryeong Byun's team at KAIST led the chemical analysis of intermediate products generated during the lithium dissolution process, and with the help of Professor Moo-Hyun Baek's team at the same university and Professor Jong-Cheol Seo's team at POSTECH, they elucidated the exact molecular structure.

Based on this, Daejoo Electronic Materials Co., Ltd. applied the relevant technology to the actual solid electrolyte mass production process. As a result, an upgraded co-precipitation method was created that drastically reduced the solid electrolyte production time from 14 hours to 4 hours.

The solid electrolyte synthesized using the upgraded co-precipitation method also has improved quality. Unlike the existing manufacturing method that showed low ionic conductivity during the mass production process, the solid electrolyte using this method showed an ionic conductivity of 5.7 mS/cm, which exceeds that of the liquid electrolyte (approximately 4 mS/cm).

In addition, by applying it to an all-solid-state battery pouch cell with a capacity of 700 mAh, it achieved an energy density (352 Wh/kg) higher than that of commercial lithium-ion batteries, and confirmed a stable lifespan by maintaining more than 80% of the capacity even after 1,000 charge/discharge cycles.

The results of this study were published in the internationally renowned academic journal in the energy field, 'Energy Storage Materials', and the research team confirmed that this technology can be applied to the production of various functional coating films and completed a patent application.

Dr. Ha Yoon-cheol said, “This achievement is the result of detailed analysis of the principles of the co-precipitation method and realization of optimization,” and “It will open an era of mass production of all-solid-state batteries at low cost.”

Meanwhile, KERI is a government-funded research institute under the National Research Council of Science and Technology of the Ministry of Science and ICT, and this research was conducted as a KERI basic project and the Ministry of Trade, Industry and Energy's material and component technology development project.