Effect of Pressure on Si-Based Anode Performance in All-Solid-State Batteries

Abstract

The effects of pressures on electrochemical performance, micro-morphology, surface elemental valence, and cell impedance of nano-silica-based anode all-solid-state lithium batteries (ASLBs) are investigated in this study. The cell under various applied pressures is measured using electrochemical charge/discharge tests, X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance test (EIS), and X-ray spectroscopy (XPS). The results indicate that the first cycle lithium insertion capacity reaches its highest value of 3554.5 mAh·g−1 when the Si-based anode undergoes charge and discharge at a rate of 0.1C under a pressure of 100 MPa. Moreover, the coulombic efficiency (CE) at a pressure of 300 MPa reaches a high value of 92.67%, which significantly surpasses the 88.11% under 100 MPa. Meanwhile, higher pressure significantly enhances the cycling performance of Si-based anode, with a capacity of 2268 mAh·g−1 after 100 cycles of charging and discharging at 0.3C under 300 MPa, and a capacity retention rate of 80.21%. SEM images and XPS demonstrated that higher pressures block Si expansion and inhibit crack formation in the Si-based anode, and meanwhile the lower pressure would lead to severe decomposition of Li6S5Cl in the electrode after long-term cycling and hence resulting in more SEI generation in the Si-based anode. The XPS results demonstrate that. The EIS test results show that the impedance of solid-state batteries is lower under a pressure of 300 MPa, indicating an improved interface of the ASLBs.