In situ synthesis and cell performance of a Si/C core-shell/ball-milled graphite composite for lithium ion batteries

A high-capacity silicon-carbon core-shell (Si/C) supported by ball-milled graphite (BMG) was synthesized in situ using a hydrosilylation reaction and tested as an anode material for lithium ion batteries (LIBs) in the investigation of the effects of dual buffer layers of carbon shell and BMG. The Si/C/BMG sample effectively absorbed high volumetric expansion/contraction generated during charge/discharge process due to the assistance of dual elastic buffers of carbon shell and BMG. As a result, after 50 charge/discharge cycles, the Si/C/BMG electrodes still had a very high capacity of 1615 mAh/g, whereas raw Si, Si/C, and a mechanical mixture of Si/C and BMG were less than 500 mAh/g. The results of various electrochemical characterization techniques revealed that the dual buffer layers were favorable in decreasing electron and ion transfer resistance. It was also shown from ex situ TEM results that the carbon layers behaved as anti-amorphization layers decreasing the amorphization rate of crystalline Si during the alloying/dealloying of Li with Si.