Abstract:

Silicon, with its high specific capacity and low voltage platform, is considered one of the most promising anode materials for lithium-ion batteries. However, the significant volume expansion of silicon electrodes during lithiation/delithiation processes, along with the associated material fracturing and pulverization, limits its rate performance and cycling stability. Existing studies have demonstrated that applying external loads to the silicon electrode during cycling can effectively enhance the cycling performance of silicon-based batteries. This study proposes a macroscopic control method, namely applying external mechanical loads to enhance the capacity retention of silicon electrode lithium-ion batteries. We employed a custom-designed in-situ loading device connected with a battery cycling tester and CR2032 button cells as the experimental objects, the effectiveness of this method was confirmed through charge-discharge cycling tests. The experimental results demonstrate that applying a 0.2 MPa axial external load on the surface of CR2032 cells effectively suppress the expansion of silicon electrodes during charge-discharge processes and regulate the internal state of the battery. After 50 charge-discharge cycles, the capacity retention rate increases from 59% without external loads to 70%. Additionally, due to the different stress states of silicon electrode active material particles during lithiation and delithiation processes, we propose a new control method, namely applying a 0.1 MPa external load during the lithiation stage and a 0.2 MPa load during the delithiation stage in the cycling process. Experimental results demonstrate that this method can further improve the cycling performance of silicon-based lithium-ion batteries. Moreover, scanning electron microscopy imaging of the electrode surface also supports this conclusion. The method of applying external mechanical loads used in this study provides important insights for improving the performance of silicon-based electrode lithium-ion batteries from a macroscopic perspective.

Key words: Lithium battery, silicon electrode, external load, electrochemical performance