UCLA

Energy storage remains a critical factor in the widespread adoption of renewable energy sources. While lithium-ion batteries have played a significant role, increasing their capacity using alternative materials is essential. In this context, microcrystalline silicon is a promising candidate for the anode due to its theoretically tenfold higher capacity compared to traditional graphite. However, its significant volume expansion during charge and discharge cycles hinders practical application due to mechanical breakdown and rapid loss of capacity. A novel approach to mitigate this issue is by incorporating trace amounts of aluminum into the micro-crystalline silicon electrode model. Density functional theory (DFT) is applied to establish a theoretical framework elucidating how grain boundary sliding, a key mechanism involved in preventing mechanical failure, is facilitated by the presence of trace aluminum at grain boundaries. This, in turn, reduces stress accumulation within the material, reducing the likelihood of failure. To validate the theoretical predictions, capacity retention experiments were performed on undoped and Al-doped micro-crystalline silicon samples by Shu-Ting Ko at the University of California San Diego (UCSD) in the research group of Prof. Jian Luo. The results demonstrate significantly reduced capacity fading in the doped sample, corroborating the theoretical framework and showcasing the potential of aluminum doping for improved Li-ion battery performance.