Performance Degradation and Gassing of Li₄Ti₅O₁₂/LiMn₂O₄ Lithium-ion Cells

Batteries comprised of LiMn₂O₄ cathodes (LMO) and Li₄Ti₅O₁₂ anodes (LTO) have potential advantages in terms of cost, safety, and power for transportation applications. In this manuscript, we present results from a cycle and calendar life study of 2 Ah LTO/LMO cells held at temperatures of 30°C, 45°C, and 60°C for 5 months. The cells held at elevated temperatures had measurable loss of capacity and severe loss of power. The LTO anodes harvested from the cells were found to have developed a coating during testing comprised of manganese, phosphorous, and fluorine, which likely resulted in the decreased cycling and power performances. In addition, there was significant gas generation inside of the cells predominantly consisting of hydrogen. We report on the initial diagnostics of the power loss and gas generation for these LTO/LMO cells.