Abstract:

Lithium titanium oxide (LTO) batteries offer high safety, rapid charge-discharge capabilities, and long cycle life, presenting significant potential for application in energy storage and frequency modulation markets. However, research on high-rate cyclic aging under different state-of-charge (SOC) ranges remains limited. This study addresses the requirements of short-term, high-frequency energy storage scenarios by investigating commercial LTO batteries. The evolution of electrochemical performance in LTO batteries cycled under different SOC upper and lower limit conditions at a rate of 4 C was examined. Using non-destructive analysis methods such as incremental capacity curves and differential voltage curves, the dominant mechanisms of thermodynamic capacity decay were analyzed. Experimental results indicate that as the upper SOC limit increases or the lower SOC limit decreases, the cycling capacity of LTO batteries significantly decreases. Meanwhile, the compensation of lithium insertion depth in the negative electrode within high SOC ranges and the repair effect during constant voltage charging improve cycling stability in high SOC ranges compared with low SOC ranges. Analysis of the charge curves reveals a strong correlation between capacity degradation and SOC interval conditions. The loss of active lithium is the primary factor contributing to capacity degradation during cycling in 0%—100% SOC, 0—80% SOC, and 80%—100% SOC ranges. In contrast, in the 20%—100% SOC range, capacity degradation is mainly caused by the loss of active material in the positive electrode. When cycled in the low SOC range (0—20%), the contributions of active lithium loss and positive electrode active material loss to capacity decay are comparable. These findings elucidate the influence of SOC range on high-rate cycling capacity degradation in LTO batteries, providing theoretical guidance for their application in short-term, high-frequency energy storage scenarios.

Key words: lithium titanium oxide batteries, state-of-charge range, cyclic aging, capacity fade