It has been studied that in order to prevent lifespan reduction and gas generation in secondary battery cathode materials, the size of silicon must be reduced to 5 nm or less and uniformly dispersed in conductive carbon particles. Related technologies have also been developed, and it is expected that this will serve as an opportunity to further activate the development of silicon cathode materials in the future.

UNIST (President Yong-Hoon Lee) Department of Energy and Chemical Engineering, led by Professor Jae-Pil Cho, recently published a review paper in 'Nature Energy'. The paper deeply analyzed the characteristics and issues that silicon anode materials, which are receiving the most attention as secondary battery materials, must secure in order to be used in commercial batteries.

Silicon anode materials experience breakage due to expansion and contraction of volume more than five times that of graphite during charging and discharging. This accelerates the decomposition reaction with the electrolyte and forms a thick surface film, which inhibits the movement of lithium ions and reduces the lifespan.

The silicon material used in the cathode of electric vehicle batteries is SiOx, a type of micron-sized particle, and contains less than 5% of the material, but the initial efficiency of the material used is in the 80% range, and its conductivity is low, making fast charging problematic.

The research team pointed out that the silicon materials under development have an initial efficiency of less than 86%, which is lower than that of graphite at 94%, which reduces the efficiency of the anode. They also analyzed that as the silicon material particles get larger, the efficiency decreases, and the phenomenon of breakage caused by expansion and contraction of the volume accelerates, leading to a rapid decrease in the lifespan and gas generation.

The research team stated in this paper that the only solution is a technology that reduces the size of silicon to less than 5 nm and uniformly disperses it on conductive carbon particles. In a paper published in December 2021, they developed a synthesis technology that reduces the size of silicon particles to less than 1 nm by depositing raw materials on carbon composite particles in a gaseous phase. They confirmed that the initial efficiency of this material was implemented at more than 90% and the lifespan was greatly improved.

Professor Jae-pil Cho said, “Currently, the evaluation methods for silicon anode materials reported in professional academic journals are somewhat limited, making it difficult to determine whether they have commercial potential, etc.” He added, “I expect that this paper will lead to more active development of silicon anode materials that can be applied for commercialization.”

This review paper was written at the invitation of the editor-in-chief of Nature Energy, a prestigious academic journal in the energy field, and Professor Seong Jae-kyung of Gyeongsang National University participated as a co-corresponding author. The paper was published on August 28 (local time).