Controllable and Large-Scale Preparation of High-Purity Nano-Silicon and Its Electrochemical Performance

Silicon (Si) has become one of the hot spots in the research of anode materials in lithium-ion batteries (LIBs) for its highest lithium intercalation capacity among known elements. However, the large volume expansion (similar to 300%) of Si due to the lithium intercalation restricts its application in LIBs. Nano-crystalized is an effective solution to resolve the volume expansion. In this study, nano-Si which can be used for high energy storage lithium-ion battery was prepared from metallurgical Si by two steps method of high-energy electron beam evaporation and deposition and mechanical grinding. According to scanning electron microscopy (SEM) observation, the molten Si deposits into Si nanofibers with a linear diameter of about 40 nm after evaporation under the action of high-energy electron beam, and then the nanofibers gather into Si nanobundles. And the size distribution of nano-Si particles is uniform after mechanical grinding. The results of electrochemical tests show that the first reversible capacity is 1292.4 mAh/g, and the charge transfer impedance fitting value is 51.36 Omega, under the condition of the nano-Si purity reaches more than 99.96% and the discharge density is 100 mA/g. The experimental result indicates that this method can be applied to the controllable and large-scale preparation of nano-Si, and has certain guiding significance for Si in the future industrial production of LIBs.