Improving the lithium storage performance of micro-sized SiO particles by uniform carbon interphase encapsulation and suitable SiO2 buffer component

l Uniform carbon interphase is encapsulated inside the SiO x particles. l SiO 2 buffer components are rationally adjusted to stabilize nano-sized Si microcrystals. l Enhanced cycle-life, initial reversible specific capacity and rate capability for Si-based anodes. Silicon anode material has a high specific capacity for high-energy-density lithium-ion batteries, but the pulverization issue during cycling has limited its cycle life in the practical application. Herein, we demonstrate a micro-sized SiO x /C composite with an average particle size of 1.12 µm, suitable SiO 2 content and uniform carbon encapsulation as a potential anode material for lithium-ion storage. The residual SiO 2 component, which is carefully tuned by changing the amounts of hydrofluoric acid, severs as a buffer layer to alleviate the volume change of active Si particles and maintain the structural integrity. Furthermore, the encapsulated carbon component inside and outside the SiO x rather than isolated surface coating can greatly increase the electronic conductivity, cycle stability and reaction reversibility of Li-ions storage. As a result, the designed SiO x /C composite as an anode exhibits a high initial coulombic efficiency of 78.2 % with a high reversible capacity of 2298 mAh g −1 , stable cycle performance with more than 716 mAh g −1 over 300 cycles and impressive rate capability (786 mAh g −1 at 2000 mA g −1 ). The SiO x /C hybrid anode demonstrates the importance of the SiO 2 buffer matrix and carbon location in Si-based anode materials for developing high-energy-density and long-life lithium-ion battery.