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

Abstract

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 SixCuy alloys with different weight compositions are synthesized by a simple ball-milling process. Among the SixCuy 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.