Rate-dependent electrochemical degradation of NCA /graphite-Si lithium-ion batteries under mechanical vibration

Li-ion batteries (LIBs), which serve as the primary energy source for electric vehicles (EVs), are routinely exposed to mechanical vibrations during real-world operation. While such vibrations are often overlooked, they may profoundly affect battery aging behavior over time. In this study, commercial cylindrical NCA /graphite-Si LIBs underwent vibration (20 Hz, 0.7 mm)-coupled aging experiments at discharge rates of 0.5C, 1C, and 2C, followed by electrochemical characterization to elucidate vibration-induced degradation. Our findings reveal that vibration alters both the structural integrity of the cathode and the interfacial electrochemical dynamics at the anode, ultimately affecting capacity retention. Notably, these effects are highly sensitive to the discharge rate. On the cathode side, degradation is linked to the disruption of active material integrity and the loss of crystal lattice ordering; on the anode side, changes are closely tied to the morphology and chemical composition of the solid electrolyte interphase (SEI) layer. The discharge rate emerges as a critical parameter that governs not only the extent but also the direction of vibration-induced degradation. At lower rates vibration appears to stabilize internal structures and reduce capacity loss. However, when the discharge rate surpasses a certain threshold(1C), the combined mechanical and electrochemical stresses accelerate deterioration, leading to faster capacity fade. These results underscore the importance of considering discharge rate-vibration coupling in the design and durability assessment of LIBs for applications in vibration-rich environments.