Examinations on 2.5 V Li[Li1/3Ti5/3]O4/Li[Li0.1Al0.1Mn1.8]O4 cells at −10, 25, and 55 °C for the first-generation 12 V lead-free batteries

Electrochemical behaviors of 2.5 V Li[Li1/3Ti5/3]O4 (LTO)/Li[Li0.1Al0.1Mn1.8]O4 (LAMO) cells for the first-generation 12 V lead-free battery were examined at −10, 25, and 55 °C. The LTO/LAMO cells showed the same rechargeable capacity in temperature ranging from −10 to 55 °C when the cells were examined at 0.5 mA cm−2 in cell potential ranging from 0 to 3.0 V. Capacity fading after 250 cycles was negligibly small at −10 °C. Rechargeable capacities, however, faded 5% at 25 °C and 15% at 55 °C after 250 cycles. In the discharged LTO/LAMO cell after 250 cycles at 55 °C, the state of charge (SOC) of the positive electrode was 16% while SOC of the negative electrode was 0%, indicated that the capacity fading was due to an imbalance in SOC between the positive and negative electrodes. To understand the progress of an imbalance in SOC, the LTO/LAMO cell with a lithium auxiliary electrode was fabricated and examined at 55 °C for 400 cycles, and the possible origin of capacity fading was discussed.

► Electrochemical behaviors of 2.5 V LTO/LAMO cells were examined at −10, 25, and 55 °C. ► Capacity fading after 250 cycles was negligibly small at −10 °C. ► Rechargeable capacities faded 5% at 25 °C and 15% at 55 °C after 250 cycles. ► The capacity fading was due to the imbalance in SOCs between the positive and negative electrodes.