South Korean researchers put the solid in solid-state batteries

Lin Yu-chun, Taipei; Samuel Howarth, DIGITIMES Asia 0

A solid-state battery research project supported by the South Korean government has discovered methods to enhance the stability of solid-state batteries. The discoveries will reportedly promote the development of safer battery systems and the team's results have been published in the online edition of the academic journal ACS Energy Letters.

South Korean media reported that the Energy Chemical Engineering Department research team at the Ulsan National Institute of Science and Technology (UNIST) announced that they have they had clarified the interrelation between the thermal stability of the cathode of a rechargeable battery and halide solid electrolytes. The team's research was aimed at creating more stable solid-state batteries.

Currently, the widely used lithium-ion batteries are filled with organic liquid electrolytes that pose risks of fire and explosion. To mitigate these risks, the industry has begun seeking suitable alternatives, with non-flammable inorganic solid electrolytes gaining attention, known as all-solid-state batteries (ASSBs).

Among inorganic solid electrolytes, sulfide solid electrolytes are highly favored in next-generation solid-state battery development. However, sulfide solid electrolytes exhibit thermal stability issues due to explosive decomposition between the electrolyte and electrodes.

UNIST looked to halide solid electrolytes for a solution to the problem. Halide solid electrolytes demonstrate better oxidative stability than sulfides and are primarily used in cathodes and composites.

The UNIST research team combined the most representative halide solid electrolyte, lithium indium chloride (Li3InCl6), with a charged nickel-cobalt-manganese cathode (NCM 622; with a ratio of 60% nickel, 20% cobalt, and 20% manganese) to create a composite for thermal stability assessment. They confirmed a higher decomposition temperature at the onset, enhancing battery stability, and significantly reducing oxygen release to mitigate explosion risks.

Through their experiments, the research team discovered that the oxygen generated from the cathode does not transform into gas but disappears during an endothermic reaction with lithium indium chloride. Furthermore, substituting lithium zirconium chloride (Li2ZrCl6) or using lithium cobalt oxide (LiCoO2) as the cathode material yields similar results, the report said.

The research team said the discovery offers a new research direction for improving the thermal stability of solid-state batteries, serving as a critical criterion for designing safe battery systems. The focus of this study was on the interaction between solid electrolytes and electrodes, facilitating the design and development of more stable solid electrolytes.