Fire-safe all-solid-state batteries move closer to commercialization

The Korea Research Institute of Standards and Science (KRISS, President Lee Ho Seong) has developed a key materials technology that accelerates the commercialization of all-solid-state batteries (ASSBs)—next-generation batteries designed to intrinsically eliminate the risks of fire and explosion.

The Emerging Material Metrology Group at KRISS demonstrated ultra-dense, large-area solid electrolyte membranes by applying a method that coats solid electrolyte powders with multifunctional compounds, reducing production costs to one-tenth of conventional levels.

Lithium-ion secondary batteries, which are widely used in electric vehicles (EVs) and energy storage systems (ESS), rely on flammable liquid electrolytes, making them vulnerable to fires and explosions. Once ignited, such fires are particularly difficult to extinguish. In recent years, a series of incidents—including a fire at a government data center operated by the National Information Resources Service (NIRS) and explosions involving EV batteries—has further underscored the urgent need for safer lithium battery technologies.

All-solid-state batteries (ASSBs) replace liquid electrolytes with non-flammable solid electrolytes, fundamentally improving battery safety. Among them, oxide-based all-solid-state batteries have attracted significant attention as a promising next-generation solution due to their high energy density and the absence of risks associated with toxic gas release, which can occur in sulfide-based systems.

Oxide-based all-solid-state batteries primarily employ garnet-type solid electrolytes as their core materials. Garnet-type solid electrolytes exhibit high ionic conductivity and excellent chemical stability; however, due to their intrinsic material properties, the fabrication of high-performance electrolyte membranes requires a high-temperature sintering process, in which the powder is compacted at temperatures exceeding 1,000 °C.

A major challenge during this sintering process is the evaporation of lithium, a key constituent of the solid electrolyte membrane. Lithium loss compromises the structural stability of the electrolyte, making large-area fabrication difficult, and leads to significant degradation in material quality, including reduced ionic conductivity and increased interfacial resistance, due to changes in chemical composition.

To mitigate lithium evaporation, conventional approaches have relied on covering the electrolyte membrane with a large quantity of mother powder—a lithium-containing electrolyte material—during sintering. However, this method results in more than ten times the amount of mother powder being discarded compared to the actual electrolyte membrane produced, significantly increasing production costs and posing a major barrier to commercialization.

The research team fully addressed this challenge by developing a fabrication technique that thinly coats solid electrolyte powders with Li–Al–O–based (lithium–aluminum–oxide) multifunctional compounds.

The resulting surface coating layer supplies lithium during the sintering process while preventing lithium evaporation, and simultaneously enhances interparticle bonding through a soldering-like effect, thereby maximizing the densification of the electrolyte membrane.

Using this approach, the team achieved a record-high density exceeding 98.2% without employing any expensive mother powder, producing high-strength solid electrolyte membranes free from chemical and mechanical defects, with ionic conductivity improved by more than twofold compared to conventional materials.

In addition, the electronic conductivity of the solid electrolyte membrane was reduced by more than 20 times, significantly lowering the risk of internal current leakage and thereby enhancing both the efficiency and safety of all-solid-state batteries.

Notably, the research team successfully fabricated large-area solid electrolyte membranes with an area of 16 cm²—more than ten times larger than conventional laboratory-scale pellets—while achieving an exceptional yield of 99.9%.

Dr. Baek Seung-Wook, Principal Research Scientist of the Emerging Material Metrology Group at KRISS, stated,

“This achievement fully resolves long-standing materials and manufacturing challenges that have remained unsolved for more than two decades in garnet-type solid electrolyte research. By dramatically reducing production costs, our technology is expected to significantly accelerate the commercialization of oxide-based all-solid-state batteries and drive technological innovation in the energy storage systems (ESS) and electric vehicle markets.”

Dr. Kim Hwa-Jung, a Postdoctoral Researcher in the Emerging Material Metrology Group at KRISS, noted,

“At present, Korea relies entirely on imports for garnet-type solid electrolyte pellets, which cost more than USD 550 per unit for a diameter of just 1 cm. This technological breakthrough is expected to open the door to domestic production of high-value next-generation battery materials.”

This research was conducted in collaboration with Professor Park Hyeokjun’s team from the Department of Materials Science and Engineering at Korea University. The work was supported by the Ministry of Science and ICT and the National Research Foundation of Korea (NRF) under the Nano and Materials Technology Development Program, and was published in the January issue of Materials Today (Impact Factor: 22.0; JCR top 3.5%).