UNIST Solves Lithium-Ion Battery Electrode Instability
Preventing silicon-based cathode degradation due to volume expansion
Removing hydrofluoric acid suppresses nickel dissolution and extends service life.


As demand for large-capacity batteries, including those for electric vehicles (EVs), increases, research is actively underway to replace the electrodes of commercial lithium-ion batteries with high-capacity materials such as silicon and high-nickel.

However, the silicon cathode has weak mechanical durability as its volume increases more than three times during charging and discharging, and the high-nickel cathode is also chemically unstable.

A research team consisting of Professors Choi Nam-soon and Kwak Sang-kyu of the Department of Energy and Chemical Engineering at Ulsan National Institute of Science and Technology (UNIST) and Professor Hong Seong-yu of the Department of Chemistry announced on the 14th that they have developed a battery electrolyte additive that solves the instability of electrode materials, a challenge in the development of large-capacity lithium-ion batteries.

The research team developed two functional electrolyte additives (△DMVC-OCF3, △DMVC-OTMS) that form a stable and flexible polymer protective film on silicon-based cathodes and effectively remove hydrofluoric acid, a cause of battery deterioration. Its performance was also confirmed by introducing it to a lithium-ion battery with a high-capacity silicon-based cathode and a nickel-rich anode.

The additives prevent deterioration due to volume expansion of the silicon-based anode (DMVC-OCF3) and suppress nickel dissolution from the nickel-rich anode through hydrofluoric acid removal (DMVC-OTMS), thereby extending battery life. The protective film formed on the silicon anode increases lithium-ion permeability, enabling rapid battery charging.

The research team added two types of additives to a large-capacity battery composed of a high-nickel cathode and a silicon-mixed cathode, and confirmed that it maintained 81.5% of its initial capacity even after 400 charge and discharge cycles. This is a 10% to 30% improvement in performance compared to commercial additives such as fluoroethylene carbonate (FEC) or vanylene carbonate (VC).

“Even in experiments where the battery was fast-charged in less than 20 minutes, only a 1.9% capacity loss was observed after 100 cycles,” added co-first author Sewon Park, a doctoral candidate in the Department of Energy and Chemical Engineering at UNIST.

The results of this study, which was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP)'s 'Energy Technology Development Project' and the National Research Foundation of Korea (NRF)'s 'Climate Change Response Technology Development Project', were introduced as an influential paper (Editor's Highlights) in the February 5th issue of the international academic journal 'Nature Communications'.