Effect of Element Substitution on Electrochemical Performance of Silicide/Si Composite Electrodes for Lithium-Ion Batteries

Si is a promising candidate for application as an active material for negative electrodes in lithium-ion batteries. However, its practical use is limited due to the large change in Si volume during cycling. It was previously reported that binary silicide/Si composite electrodes exhibit better electrochemical performance than a Si-alone electrode. Silicide has been found to have several properties, including mechanical characteristics, low electrical resistivity, moderate reactivity with Li+, and high thermodynamic stability, which alleviate the stress from Si. To improve the performance of the composite electrodes, it is essential to carefully modify these properties by element substitution. In this study, a Cr1–xVxSi2/Si composite was synthesized and its electrochemical performance was investigated. The changes in the properties of CrSi2 after V substitution were also evaluated. The Cr0.5V0.5Si2/Si electrode exhibited a longer cycle life than the CrSi2 and VSi2 electrodes, indicating that the element substitution contributed to an improvement in cycle life. Due to a larger crystal lattice arising from VSi2 and a smaller charge repulsion resulting from CrSi2, Li was found to easily diffuse into Cr0.5V0.5Si2. Hence, Li could readily move between the Si phases via the Cr0.5V0.5Si2 phase. It was speculated that the homogeneous storage of Li in the Si phase resulted in no local stress and suppression of severe electrode disintegration. Overall, it was concluded that the Cr0.5V0.5Si2/Si electrode exhibited a longer cycle life.