A simple and green self-conversion method to construct silicon hollow spheres for high-performance Li-ion battery anodes

Silicon (Si) anode has garnered attention as a potential replacement for high energy density lithium-ion battery anodes. Its commercial application, however, is still hindered by the issues of rapid capacity attenuation due to large volume change during (de)lithiation process, complex preparation process, and high cost. In this work, a simple and green strategy was proposed to fabricate carbon-coated hollow porous silicon spheres (Hp-Si@C) by a self-conversion method and subsequent magnesiothermic reduction. The synthesis of Hp-Si@C by this method used inexpensive tetraethyl orthosilicate precursors and did not involve the use of additional sacrificial template, complicated CVD and toxic hydrofluoric acid, which was simple, inexpensive, green and scalable. NaCl was introduced as a heat scavenger to avoid the formation of SiC and maintain the hollow morphology of the pre-cursor. The electrochemical behaviors of Hp-Si@C were investigated by in situ electrochemical characterization. The structure of Hp-Si@C defined fast ion transport routes and provided expansion space during lithiation process, endowing it with stable cycling performance and fast electrochemical reaction kinetics. Hp-Si@C had a delithiation capacity of 1228 mAh g-1 with a capacity retention of 69% at 2 A g-1, and a rate capacity of 865 mAh g- 1at 10 Ag- 1.