Mechanofusion-derived Si-alloy/graphite composite electrode materials for Li-ion batteries

Abstract

Silicon–graphite composites are extremely promising negative electrode materials for Li-ion batteries. However, simple and effective methods to synthesize silicon–graphite composites with engineered structures are needed to realize this technology in practical applications. Here, we show that the environmentally friendly and low-cost dry mechanofusion (MF) process can effectively synthesize silicon alloy–graphite composites, in which silicon alloy particles can be well dispersed and embedded between graphite layers. This results in increased tap density and reduced surface area. The special structure provides a way to buffer volume expansion and contraction of the silicon alloy during lithiation and delithiation. As a result of this hierarchical arrangement, superior cyclability and rate capability are achieved compared to simple mixtures, with capacities of 950 mA h g⁻¹ (i.e. 1473 A h L⁻¹) and 900 mA h g⁻¹ (i.e. 1432 A h L⁻¹) at 2C and 4C, respectively.