Effect of High-Valent Metal-Ion Doping on the Properties of NCM-523 Li-Ion Battery Materials

In recent years, rechargeable Li-ion batteries have received immense attention as these materials are among the most promising candidates as renewable energy alternatives.[1,2] LiNi_1-x-yCo_xMn_yO₂ is arguably the most important of currently available cathode materials for Li-ion battery due to their stability and high operating voltage.[3,4] In these materials, there are various challenging issues like stability, capacity fading etc.[5] In this work, we show that the performance of LiNi_0.5Co_0.2 Mn_0.3O₂ (NCM-523) can be improved by 1% doping by the high-valent metal ion, Mo. We perform density functional theory calculations to study the most favourable doping site in NCM-523. We find that replacing Ni with Mo is the most favourable process, possibly due to the similar ionic radius of Mo⁶⁺ and Ni³⁺. We also observe that the average Ni-O bond length is slightly larger in the case of Mo-doped NCM-523, compared to the undoped system, in agreement with XANES experiment. Further, it is observed that there is an increase in Ni²⁺ ions and a concomitant decrease in Ni³⁺ ions due to Mo-doping. This change in oxidation states is ascribed to a charge-compensation effect.

Keywords: Li-ion battery, DFT, doping, NCM cathode materials.

References:

1. J-M. Tarascon and M. Armand, Nature, 414, 359 (2001).
2. Saiful Islam and C. A. J. Fisher, Chem. Soc. Rev., 43, 185 (2014).
3. Dixit, M. Kosa, O. S. Lavi, B. Markovsky, D. Aurbach and D. T. Major, Phys.Chem.Chem.Phys., 18, 6799 (2016).
4. Schipper, E. M. Erickson, C. Erk, J. Y. Shin, F. F. Chesneau, and D. Aurbach, Journal of The Electrochemical Society, 164 (1) A6220 (2017).
5. Schipper, M. Dixit, D. Kovacheva, M. Talianker, O. Haik, J. Grinblat, E. M. Erickson, C. Ghanty, D. T. Major, B. Markovsky and D. Aurbach, J. Mater. Chem. A, 4,16073 (2016).