IMPROVED ELECTROCHEMICAL PERFORMANCE OF Al DOPED Li AND Mn-RICH LAYERED CATHODES FOR Li-ION BATTERIES

High capacity cathode materials are essential to increase the energy density of currently used Li-ion batteries. In recent years, Li and Mn-rich layered cathodes xLi₂MnO₃.(1-x)LiMO₂ (M=Mn, Co and Ni) are considered as promising cathode materials for high energy Li-ion batteries because of their high specific capacities ≥ 250 mAh g^-1. However, these cathode materials suffer from capacity fading as well as discharge voltage decay upon prolonged cycling due to a structural layered-to-spinel transformation [1, 2]. In this study, Al doped Li and Mn-rich Li_1.2Ni_0.16Mn_0.54Al_0.02Co_0.08O₂ and Li_1.2Ni_0.16Mn_0.51Al_0.05Co_0.08O₂ cathode materials are synthesized by self-combustion reaction (SCR) and tested for Li-ion batteries. The electrochemical performance, including specific capacity, average voltage and rate capability of these two cathode materials are compared with un-doped cathode Li_1.2Ni_0.16Mn_0.56Co_0.08O₂. Substitution of Mn with Al results in a decrease in their specific capacity but increases their stability upon cycling. The optimized Al doped cathode Li_1.2Ni_0.16Mn_0.51Al_0.05Co_0.08O₂ retains about 96 % capacity as compared to 68 % for Li_1.2Ni_0.16Mn_0.56Co_0.08O_2. This Al doping also prevents from the decrease in the average discharge voltage upon cycling, which is the critical drawback of these Li and Mn rich cathode materials. The structural analysis of cycled electrode by Raman spectra suggests that Al has a stabilizing effect on the layered LiMO₂ phase resulting in better electrochemical performance of Al doped cathode material as compared to the un-doped one.

1. M. Gu, I. Belharouak, J. Zheng, H. Wu, J. Xiao, A. Genc, K. Amine, S. Thevuthasan, D. R. Baer, J-G. Zhang, N. D. Browning, J. Liu, C. Wang, ACS Nano 2013, 7, 760-767.
2. P. K. Nayak, J. Grinblat, M. Levi, B. Markovsky, D. Aurbach, J. Electrochem. Soc. 2014, 161, A1534-A1547.