ETRI Develops 'Ultrathin Solid Electrolyte Film' for All-Solid-State Secondary Batteries

The Electronics and Telecommunications Research Institute (ETRI) has succeeded in developing an ultrathin solid electrolyte film, one of the core technologies for all-solid-state secondary batteries.

On the 17th, ETRI announced that it developed a separator using a binder material that easily fibrillates when mechanical force is applied, through a solvent-free mixing process with solid electrolyte powder.

In general, in all-solid-state secondary battery research, when manufacturing separators using solid electrolytes, it is common to increase the thickness of the film (several hundred ㎛ to 1 mm) to enhance durability. However, the thicker the film, the greater the loss in energy density.

On the other hand, ETRI applied a binder material that exhibits fibrillation behavior under mechanical shear (force) and succeeded in manufacturing an ultrathin solid electrolyte film of 18 ㎛ thickness, close to the thickness of commercially available lithium-ion battery separators, using a dry process.

They also significantly reduced the cell volume, creating a high-energy-density and high-performance all-solid-state secondary battery. Compared to a 1 mm thick thick-film solid electrolyte membrane, the energy density was increased by more than 10 times.

Through this research, ETRI expects to develop high-energy-density all-solid-state secondary batteries by producing solid electrolyte films close to the thickness of already commercialized polymer separators, improving ion transfer speed during charging and discharging, while significantly reducing cell volume and weight.

Additionally, they revealed the correlation between the molecular weight of the binder material and the degree of strong entanglement, presenting a process standard for the development of optimized ultrathin solid electrolyte films.

All-solid-state secondary batteries are attracting attention as next-generation secondary batteries. The reason for this attention is that by changing the medium for ion transfer inside the battery from liquid to solid materials, risks such as fire, explosion, and leakage are fundamentally eliminated, significantly enhancing safety.

The solid electrolyte film is considered a core material in all-solid-state secondary batteries, serving to prevent direct contact between the cathode and anode while allowing ion transfer.

Meanwhile, this research was conducted with support from the ETRI Future Fundamental Creative Research Laboratory project, the Ministry of Trade, Industry and Energy’s ‘Development of Lithium-based Next-generation Secondary Battery Performance Enhancement and Manufacturing Technology’ project, and the National Research Council of Science & Technology’s Global TOP Strategic Research Group project. The research involved Dr. Dongok Shin and Dr. Youngsam Park of ETRI as corresponding authors, and Seokyun Yoon, a combined master’s and doctoral student at UST, as the first author.

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