Si-based composite interconnected by multiple matrices for high-performance Li-ion battery anodes

To obtain anode materials with high performance Li-ion batteries, a nanostructured Si-based composite, including Si, a Li-inactive conducting Cu₃Si matrix, and multiple carbon-based matrices (carbon nanotube, graphite, and a pyrolytic carbon coating) is developed by facile step-by-step combination of solid-state synthetic technologies. First, various Si_xCu_y alloys with different weight compositions are synthesized by a simple ball-milling process. Among the Si_xCu_y alloys, Si₈₀Cu₂₀, which is comprised of Si and Cu₃Si, displays the highest electrochemical performance. To further improve the electrochemical performance of Si-Cu₃Si, an interconnected composite with 1D-structured CNT and 3D-structured graphite, Si-Cu₃Si-CNT/G, is prepared via an additional ball-milling process. The Si-Cu₃Si-CNT/G composite is finally coated via the pyrolysis of polyvinyl chloride, thus forming the carbon-coated Si-Cu₃Si-CNT/G-C composite. This final product, Si-Cu₃Si-CNT/G-C, is comprised of well-dispersed nanocrystalline Si and Cu₃Si (Li-inactive conducting matrix) within the multiple interconnected carbon matrices. The Si-Cu₃Si-CNT/G-C displays excellent electrochemical performance, with a high first reversible capacity of 1237 mA h g⁻¹, a high initial coulombic efficiency of 82.8%, a long cycle durability of 1084 mAh g⁻¹ over 100 cycles, and a high rate capability of ~1000 mAh g⁻¹ at 1C-rate, which confirms its commercial application as a high-performance Si-based anode for Li-ion batteries.