Cycle-Stage-Dependent Pressure Regulation: An Operando Strategy for Improving Capacity Retention of High-Capacity Silicon Anodes

Silicon is a promising anode material for next-generation lithium-ion batteries due to its high theoretical capacity. However, severe volume expansion during cycling leads to structural degradation, unstable solid electrolyte interphase formation, and rapid capacity fading. In this study, we first investigated the correlation between capacity degradation and direct current internal resistance in silicon-based CR2032 half-cells and explored the effect of external mechanical loading on electrode structural evolution and electrochemical performance. Based on the results, a regulation strategy of applying external pressure after 50 charge/discharge cycles to suppress further accumulation of damage was proposed. Cycling tests, along with theoretical modeling, electrochemical impedance spectroscopy testing, and scanning electron microscopy observation, were conducted to validate this approach and delve into its underlying mechanisms. The results show that external loading significantly reduces charge transfer resistance and, to a lesser extent, SEI resistance, thereby improving capacity retention and cycling stability. Surface morphology analysis reveals that mechanical pressure suppresses crack propagation and minimizes active material detachment. Numerical modeling confirms that external pressure increases the contact area between both electrode layers and active material particles, reducing interfacial contact resistance and enhancing electronic conductivity within the electrode. However, the beneficial effects diminish at higher pressures due to increased particle-level stress. These findings highlight the importance of optimizing mechanical loading to enhance electrode performance while avoiding additional mechanical degradation.