Extending the Cycling Life of Lithium-Ion Batteries with Silicon/Graphite Composite Anodes by Automatic External Stress Regulation

The operational mode and buffering materials significantly affect the electrochemical performance, mechanical properties, and structural integrity of lithium-ion batteries with silicon/graphite composite anodes. This study conducts a comprehensive cycle life test under a constant-gap mode and introduces foam as a buffering material to analyze the capacity retention rate, pressure evolution, and microstructural changes in detail. The results from the constant-gap mode show that the battery reaches the end of its life after 540 cycles, while the Coulombic efficiency remains approximately 100%. In addition, the maximum pressure of the battery increases from just over 900 N initially to more than 2200 N at the end of cycling, indicating a significant increase in the pressure. Due to the excessive external pressure, the surface of the aged electrode becomes smooth, and the particles are in close contact. Hence, foams are introduced to automatically regulate the external pressure. After introducing the foam as a buffering medium, the battery life is extended to 650 cycles, with an increase ratio of 20%. An increase in the charging capacity during the constant-voltage phase is observed, indicating an increase in the electrochemical resistance. The buffering effect of the foam significantly reduces the pressure variations and fluctuations during cycling before it reaches its deformation limit. In addition, the active particles on the aged electrode exhibit a more dispersed distribution without significant damage, indicating a relative structural stability. This work highlights the scientific and engineering importance of using foam buffering in a constant-gap mode to increase the lifespan, pressure management, and structural integrity of lithium-ion batteries with silicon-based anodes.