Low-Frequency Random Vibration-Induced Cycling Degradation Behavior and Mechanisms of Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries because of their low cost and abundant resources. However, the effect of prior low-frequency mechanical vibration on subsequent cycling degradation remains poorly understood. This study investigates commercial 26,700 cylindrical SIBs subjected to low-frequency random vibration pre-treatment followed by stationary cycling. Capacity evolution, DCIR, EIS, IC analysis, and post-cycling SEM observations were used to compare control and vibration-pretreated cells. Vibration pre-treatment produced a slight initial increase in discharge capacity, accompanied by temporarily reduced polarization and increased electrochemical accessibility. During subsequent cycling, the vibration-pretreated cells exhibited faster capacity fade and greater internal-resistance growth, with larger DCIR differences in the low- and high-SOC regions. EIS and IC results indicate aggravated interfacial polarization, charge-transfer limitation, diffusion limitation, and reaction heterogeneity. SEM observations after cycling reveal more pronounced surface irregularities and crack-like features in the vibration-pretreated electrodes, particularly on the anode, consistent with the electrochemical degradation trends. Together, the electrochemical measurements and post-cycling surface observations show that prior low-frequency vibration increased the subsequent degradation of the tested commercial 26,700 cells.