Internal resistance and heat generation of soft package Li₄Ti₅O₁₂ battery during charge and discharge

The resistance and heat generation of soft package Li₄Ti₅O₁₂ batteries in two different lifecycle (One was cycled 2100 times at 55 °C and swollen, the other is a new one) were studied in this paper. The ohmic resistance, polarization resistance and electrochemical impedance spectroscopy of these two cells were investigated. Accelerating rate calorimeter was used to study the generated heat at the C-rates of 0.5 C, 2 C and 5 C in charging and discharging processes. The amount of total generated heat, reversible and irreversible were obtained. The results showed that ohmic resistance of the swollen battery was higher than that of the new one, while polarization resistance tended to be smaller. The heat produced during discharge was greater than that by charge. In single charge or discharge process, the heat generation rate of the swollen battery was higher than that of the new one at all C-rates. The swollen battery released more reversible heat in charging process, especially at a lower state of charge.