Lithiation/Delithiation Properties of Lithium Silicide Electrodes in Ionic-Liquid Electrolytes

We investigated the impact of electrolyte difference on lithiation and delithiation properties of a Li1.00Si electrode to improve the Coulombic efficiency (CE) of Si-based electrodes. The results of X-ray diffraction, Raman spectroscopy, and soft X-ray emission spectroscopy demonstrated that a portion of the Li in Li1.00Si desorbed by simply immersing the electrode in an ionicliquid electrolyte, that is, the phase transition of Li1.00Si to Si occurred. In contrast, this phenomenon was not confirmed in an organic-liquid electrolyte. Instead, the desorbed Li was consumed for the formation of a surface film; thus, the Li in LiiooSi did not elute into the electrolyte. The addition of vinylene carbonate (VC) to the ionic-liquid electrolyte suppressed the phase transition of Li Li1.00Si to Si. Although the Li1.00Si electrode showed a low initial CE and poor cycling performance in a VC-free electrolyte, the electrode exhibited a high CE and a remarkable cycle life in the VC-added electrolyte. It was considered that no desorption of the mechanically added Li in Li1.00Si contributed to the superior cycle life; thus, the characteristic ductility, malleability, and high electrical conductivity of lithium silicide should improve the electrochemical performance.

Automated summary

The study found that immersing the Li1.00Si electrode in an ionic liquid electrolyte causes part of the Li to desorb and transition to Si, while adding vinylene carbonate (VC) to the electrolyte can suppress this phase transition. Additionally, the desorbed Li was mainly used for the formation of a surface film, rather than eluting into the electrolyte from Li1.00Si.