A Korean research team has crossed, for the first time, the "5-volt (V)" barrier long regarded as the biggest technical limit of all-solid-state batteries. All-solid-state batteries are drawing attention as next-generation batteries that store more energy than conventional lithium-ion batteries and have a lower risk of explosion.
The higher the voltage of a battery, the more energy it can hold. But until now, materials inside batteries became unstable and easily degraded above 5V, so most stayed around 4V. This made it difficult to further boost performance. The same was true for all-solid-state batteries.
The research team led by Jeong Yun-seok, a professor in the Department of Chemical and Biomolecular Engineering at Yonsei University, said on the 14th that it developed a new material to solve this problem with the teams of Nam Gyeong-wan, a professor at Dongguk University, and Seo Dong-hwa, a professor at KAIST. The findings were published on the 3rd in the international journal Nature Energy.
The core material the team created is a solid electrolyte called "LiCl–4Li₂TiF₆." An electrolyte serves as the pathway for electricity inside a battery, and this material operates stably even at high voltages above 5V. In addition, the speed at which electricity flows (ionic conductivity) became much faster than before.
This electrolyte also protects the surface of the cathode inside the battery. Simply put, it acts as a "protective film" that prevents unstable reactions that can occur when electricity flows, improving both the battery's lifespan and performance.
The team applied the material to several types of high-voltage batteries for experiments. As a result, while maintaining stability, it stored more than twice as much charge (258mAh/g) as before. It also showed high output and stable operation in a pouch-type all-solid-state battery close to commercialization, demonstrating the technology's practical potential.
The team also confirmed that the technology can be applied to nickel-cobalt-manganese (NCM) batteries, which are already widely used in industry, and lithium-excess manganese batteries. In other words, it is not limited to a specific experimental cell and can be expanded to various battery systems.
This achievement combines fluoride with conventional, low-cost chloride electrolytes to enhance both stability and performance, and is regarded as a key technology that could accelerate the commercialization of all-solid-state batteries.
Jeong said, "This research is not just about developing a new material but presents a new design direction for realizing high-voltage all-solid-state batteries," adding, "It will be a key technology that accelerates the commercialization of all-solid-state batteries and a breakthrough that can replace existing sulfide-based electrolytes, which face safety concerns."
References
Nat Energy (2025), DOI: https://doi.org/10.1038/s41560-025-01865-y