Domestic researchers have developed a technology to produce sulfide-based solid electrolytes, a key material for all-solid-state batteries, more quickly and with better quality. This is expected to accelerate mass production of all-solid-state batteries.
Hah Yoon-cheol, head of the Next-Generation Battery Research Center at Korea Electrotechnology Research Institute (KERI), noted on the 10th that his research team developed an 'upgraded co-precipitation method' to make sulfide-based solid electrolytes for all-solid-state batteries faster and with better quality. The research findings were published in the international journal 'Energy Storage Materials' in December of last year, and a patent application has recently been filed.
All-solid-state batteries replace the 'electrolyte' that transports ions between the anode and cathode with a solid that has a significantly lower risk of fire or explosion instead of a liquid. However, the solid electrolyte has limitations due to difficult manufacturing processes and high costs.
In this regard, the research team proposed a 'co-precipitation method' in 2021 to manufacture solid electrolytes in bulk by putting raw materials into a container all at once without expensive lithium sulfide. This technology can greatly reduce raw material costs compared to existing methods and does not require high-energy milling or evaporation processes. The technology has been transferred to Daejoo Electronic Materials, a domestic electric and electronic materials specialized corporation.
In this study, in collaboration with Korea Advanced Institute of Science and Technology (KAIST) and Daejoo Electronic Materials, the researchers successfully developed an optimized upgraded co-precipitation method that can reduce solid electrolyte production time from 14 hours to 4 hours while dramatically improving quality.
The co-precipitation method is centered on dissolving the raw materials evenly in the solution, precipitating it, and then filtering it. The research team developed a technology to rapidly and homogenously dissolve various raw materials by mixing lithium, sulfur, and catalysts in appropriate ratios.
Professor Byeon Hye-ryeong of KAIST led the chemical analysis of each intermediate product that occurs depending on the solubility of lithium, with the help of researchers from Professor Baek Moo-hyun's team at the same university and Professor Seo Jong-cheol's team at Pohang University of Science and Technology (POSTECH), revealing the precise molecular structure of the intermediates. Based on this, Daejoo Electronic Materials integrated relevant technologies into the continuous process to be applied in actual production of solid electrolytes.
As a result, it was possible to significantly reduce the production time of solid electrolytes while also improving their quality. Existing manufacturing methods had shown low ion conductivity during the mass production process, which was problematic. By applying the newly developed co-precipitation method, it was possible to achieve a value exceeding that of liquid electrolytes' ion conductivity. When this solid electrolyte was applied to a pouch cell of an all-solid-state battery with a capacity of 700mAh, a higher energy density than conventional lithium-ion batteries was achieved. Additionally, in experiments where the all-solid-state battery was charged and discharged 1,000 times, it maintained more than 80% of its capacity, showing stable longevity.
Director Hah Yoon-cheol asserted, 'The significance of the existing achievement is that it was the first in the world to introduce co-precipitation technology into solid electrolyte manufacturing. The upgraded version realizes optimization through a detailed analysis of the principles of co-precipitation and produces even better results,' he said, adding, 'This will be a catalyst that opens the era of mass production of all-solid-state batteries at an affordable expense.'
Reference materials
Energy Storage Materials(2024), DOI: https://doi.org/10.1016/j.ensm.2024.103938