Influence of the crystallographic orientation of silicon nanowires in a carbon matrix on electrochemical performance as negative electrode materials for lithium-ion batteries

In this study, we report the effect of the crystallographic orientation of silicon nanowires (SiNWs) on electrochemical performance as a negative electrode material. We synthesize vertically aligned SiNWs from differently oriented Si substrates with axial orientations of Si <100>, <110>, and <111> by the metal-assisted chemical etching method. To investigate the influence of a carbon matrix on SiNWs, various ratios of carbon/SiNWs are incorporated into negative electrode materials. The electrochemical performance of the <110>-SiNWs is greatly improved by increasing the carbon/SiNWs ratio from 0.5 to 2 compared to <100> and <111>-SiNWs. The electrochemical results reveal that a reversible capacity of more than 3200 mAh g−1 at a current rate of 0.1 C was obtained by using <110>-SiNWs with a carbon/SiNWs ratio of 2. The enhanced electrochemical performance is attributed to the relatively large interspacing between atoms along the <110> direction, which is much larger than those along the <100> and <111> directions. We also suggest that a large amount of carbon accommodates the volume expansion that occurs during the Li alloying/dealloying processes with Si and increases the electronic conductivity.

► The electrochemical performance of SiNW depending on substrate orientation was investigated.
► The discharge capacity of <110>-SiNWs was greatly improved with an increasing carbon/SiNWs ratio.
► Large amount of carbon accommodates the volume expansion of SiNW and increased the electronic conductivity.