Impact of Electrode Thickness and Temperature on the Rate Capability of Li4Ti5O12/LiMn2O4 Cells

Growing demand for stationary energy storage systems requires the development of low cost, long cycle life, safe batteries. Lithium-ion batteries (LiBs) utilizing Li4Ti5O12 (LTO) anode and LiMn2O4 (LMO) cathode are promising candidates providing critical-material-free chemistry, high power capability, and long lifespan. However, their low energy density is a major drawback. In this work, we evaluate the rate performance of LTO/LMO cells fabricated with electrode loadings from 1.7 to 4.2 mAh cm-2 toward the development of high energy density and low cost LTO/LMO cells. The operating temperature is varied from 30 C to 55 C to evaluate the impact of electrode thickness vs temperature limitations on the electrode utilization. In addition, Newman modeling is performed to provide detailed understandings of the cell performance. Combining experimental and simulated results, we show the rate capability of the thicker electrodes is limited by the electrolyte transport. When the cells are discharged by applying pulsed current, Li+ ion depletion is mitigated and the discharge capacity increases. Thus, high energy density LTO/LMO cells for BTMS applications can operate more efficiently when intermittent rest is applied. Finally, overcoming electrolyte transport limitations will be the key to enabling the development of high energy density LTO/LMO cells using thick electrodes.