Porous carbon-coated ball-milled silicon as high-performance anodes for lithium-ion batteries

Si-based anodes are promising candidates for high-performance lithium-ion batteries (LIBs) because they can offer the highest theoretical capacity over conventional graphite-based anodes used in commercial LIBs. However, the large volume change of Si upon cycling results in the degradation of structural integrity and electrode rapid capacity decay. These issues limit the practical applications of Si-based anodes in LIBs. Therefore, porous Si electrodes exhibiting excellent electrochemical performance can be used as anodes in high-energy density LIBs. In this work, we used commercially cheap microsized Si powders to synthesize porous Si via high-energy ball milling and etching processes. The milling time has a significant impact on the morphology, crystallinity, and electrochemical performance of the as-prepared samples. Structural and morphological analyses indicate that the high-energy ball milling greatly reduces the particle size of Si, and on the other hand increases the specific surface area. Porous Si electrodes with pore size of 20nm were successfully prepared. The 2h-milled porous Si coated with a uniform carbon layer of 4.5nm exhibits high reversible capacities of 1016.1 and 834.1mAhg(-1) at 1000 and 2000mAg(-1), respectively, over 200 cycles with high coulombic efficiency (>99.5%), as well as stable cycling. The preparation process is simple, and can be regarded as an alternative route for synthesizing high-performance Si-based anodes for LIBs.