Reducing Fire Risk and Cutting Costs...KIST Develops "Sodium All-Solid-State Battery" [Reading Science]

Realizing 4.5 V high-voltage operation...Simultaneous improvements in ESS safety and cost stability

A Korean research team has developed a sodium all-solid-state battery technology that can simultaneously address the recurring fire accidents and cost burden issues associated with lithium-ion battery-based energy storage systems (ESS).

On February 12, a research team led by Dr. Ryu Seungho at the Energy Storage Research Center of the Korea Institute of Science and Technology (KIST) announced that it has developed a sodium-based all-solid-state battery technology that dramatically enhances fire safety by applying a nonflammable solid electrolyte.

Stable operation of sodium all-solid-state batteries at high voltages achieved. Sodium all-solid-state batteries employing a solid electrolyte have a stabilized electrode-electrolyte interface, maintaining stable charge-discharge performance at high voltages while improving discharge capacity and energy density. Provided by the research team.

Lithium-ion batteries are widely used in electric vehicles and ESS due to their high energy density, but the liquid electrolyte they use inherently poses a fire risk. In particular, large-scale ESS facilities have suffered repeated fire accidents, turning safety and operating costs into major social issues.

The research team replaced the flammable liquid electrolyte with a nonflammable solid electrolyte and used sodium, which is inexpensive and abundantly available, thereby securing both safety and economic feasibility. Sodium is not concentrated in specific countries, giving it advantages in terms of supply stability and raw material cost volatility.

Exceeding the 4 V limit to operate at 4.5 V...Improved energy density

The team also addressed the "energy density limit" that had been a barrier to the commercialization of sodium all-solid-state batteries. Whereas conventional lithium-ion batteries experience electrolyte decomposition and lifespan degradation at around 4.2 V and above, the researchers introduced fluorine (F) into the solid electrolyte and designed it to maintain structural stability even under high-voltage conditions.

As a result, they demonstrated stable operation up to 4.5 V, surpassing the 4 V level that conventional sodium all-solid-state batteries had struggled to exceed. This means that more energy can be stored in a battery of the same size, and it is significant in that the battery has secured sufficient durability for repeated charging and discharging even at high voltages.

Stable sodium all-solid-state battery at high voltage. At high voltages, sodium-ion batteries experience interfacial degradation and gas generation due to decomposition of the liquid electrolyte, but sodium all-solid-state batteries maintain a stable interface and operate reliably even at high voltages. Provided by the research team.

This technology is assessed as having elevated sodium all-solid-state batteries from the experimental stage to a level suitable for large-scale ESS applications. It is expected to contribute to meeting the growing demand for power storage driven by the expansion of renewable energy, as it can be applied more safely even in environments where installation had been restricted due to fire concerns, such as power plants and industrial complexes.

Dr. Ryu Seungho said, "It is meaningful that we have realized a sodium all-solid-state battery that operates stably even in high-voltage environments," adding, "We hope that sodium all-solid-state batteries, with their low cost and high safety, will emerge as a new alternative for large-scale energy storage systems."

This research was carried out with support from the Ministry of Science and ICT, and the results were published in the international journal "ACS Energy Letters" (IF 18.9).