Aging of LNMO-Based Lithium Ion Battery Pouch Cells

Abstract

Cobalt-free cathode materials are a key factor for building more sustainable and costeffective batteries. One promising cobalt-free material is the high-voltage spinel LNMO (LiNi0.5Mn1.5O4) due to its high energy density and high operating voltage of 4.7 V. However, the high operating voltage has also its drawbacks. Commonly used carbonate-based electrolytes oxidize at high voltages, leading to the continuous formation of a cathodeelectrolyte interface (CEI). Additionally, LNMO is prone to transition metal dissolution which not only leads to a reduced stability of the cathode active material but due to migration and deposition of the transition metals on the anode surface also to an altered solid electrolyte interface (SEI) formation and significant impedance rise of the anode.1 Both ageing mechanisms provoke increased lithium loss and high resistances and thus a poor cycling performance.2, 3 In the Horizon 2020 LC-BAT5 project HYDRA, LNMO-based prototype pouch cells are developed and built. Herein, their performance and cycling behavior are analyzed by electrochemical methods such as differential voltage analysis and impedance spectroscopy to investigate the influence of upper cut-off voltage, charge and discharge current rate as well as temperature on the degradation. We thereby reveal the main degradation modes as a function of the cycling conditions and derive solutions on how to increase the cycle life. 1. C. Zhan, T. Wu, J. Lu and K. Amine, Energy Environ. Sci., 11 (2), 243-257 (2018). 2. J. Ma, P. Hu, G. Cui and L. Chen, Chem. Mater., 28 (11), 3578-3606 (2016). 3. W. Li, Y.-G. Cho, W. Yao, Y. Li, A. Cronk, R. Shimizu, M. A. Schroeder, Y. Fu, F. Zou, V. Battaglia, A. Manthiram, M. Zhang and Y. S. Meng, J. Power Sources, 473, (2020)