Silicon carbon nanohybrids with expandable space: A high-performance lithium battery anodes

摘要

The theoretical capacity of the silicon electrode is very high, but the large volume change of Si during the charge and discharge processes leads to a fast capacity fading and thus a poor cycling stability. Here, in order to overcome this shortcoming, a new method for preparing silicon electrode materials was proposed. We employed a facile Chemical Vapor Deposition (CVD) process to produce uniform carbon layer to cover the silicon spheres, etched a space between the carbon layer and the silicon nucleus to accommodate the expansion of silicon during charging and discharging, and thus a well-designed chain-like Si@void@C electrode material was prepared. The thickness of the carbon shell was tuned simply by adjusting CVD deposition time. The stability of such silicon electrode was proved to be significantly enhanced. By a comparative study on Si@void@C, Si@C and the commercial pure Si without carbon coating, we have demonstrated that the thin but stable carbon shell and the rationally designed void space in the Si@void@C structure have greatly positive influences on the electrochemical performance. As a result, the chain-like Si@void@C-15 exhibits a reversible capacity of 983 mA h g(-1) after 200 cycles and a high capacity retention up to 94%, indicating an excellent cycling stability. Good rate performance is also demonstrated.