Si Anode Materials for Li-Ion Batteries

Abstract

Silicon is regarded as one of the most promising anode materials because of its theoretical specific capacity (4200mAh/g) compared to commercially available graphite anodes (370mAh/g). However, Si electrodes suffer considerable volume expansion of up to 300% during electrochemical lithiation, leading to electrode cracking and pulverization of the Si, causing rapid capacity degradation. Various approaches had been used for using nanostructured Si materials have been applied to solve this problem, since the interval distance between nano structures and internal spaces in them can act as structural buffer space to accommodate the volume expansion of Si. Although some of the nanostructured Si materials achieved considerably high capacity and cyclability, they are usually prepared by complicate and high cost synthetic process which are difficult to extend to large scale. The other approach is using active/inactive alloys as an efficient way to reduce volume expansion and improve cycling performance. The volume expansion of Si can be suppressed by the presence of inactive components, resulting in the maximum energy density at a given volume expansion. Literature has also shown commercially available and low-cost Si alloys can serve as high capacity Li-storage anodic host materials with certain cyclability. If such Si alloy compounds can be made with required chemical stoichiometry and structural architecture though a simple mechanochemical process. Wildcat Discovery Technologies is developing facile synthesis pathway to prepare Si-alloy active/inactive material. Our approach utilized high-throughput combinatorial research to optimize synthesis process, Si-alloy composition and electrode component to improve the cycling performance of the anode material. Here we demonstrate that with optimized synthesis process, varied active Si and inactive alloy composition reveal a strong correlation between capacity and cyclability.