First Principles Calculations of Transition Metal Containment in Li-Ion Cathode Materials with Surface Coatings

In Li-ion cells, transition metal (TM) dissolution from the cathode active material into the electrolyte can accelerate degradation of capacity and power.[1-4]  Containment of TMs in cathode particles using surface coatings is one strategy for improving durability.  To achieve TM containment, coatings must have low TM solubility and must not react with the cathode active material to form new phases that contain TMs.  We use Density Functional Theory to investigate TM containment in cathode particles composed of an active material and a coating material.  We consider Li_xMn₂O₄, Li_xNiO₂, Li_xMnO₂, Li₂MnO₃, and Li_xMPO₄ (M = Mn, Fe, and Ni) active materials, and we consider Al₂O₃, MgO, ZnO, Li₃PO₄, Li₄P₂O₇, and LiMPO₄ (M = Mn, Fe, and Ni) coating materials.  For each particle type, we calculate transition metal solubility in the coating, and we identify reactivity or stability between the coating and the active material.  We find that TM containment is somewhat sensitive to temperature and is very sensitive to the cathode state of charge.  Although most cathode-coating combinations are not stable either during heat treatment or during battery operation, we identify several combinations that are stable under both of these conditions.

[1] A. Blyr, C. Sigala, G. Amatucci, D. Guyomard, Y. Chabre, and J. M. Tarascon, J. Electrochem. Soc. 145, 194-209, (1998).

[2] J. Vetter, P. Novak, M.R. Wagner, C. Veit, K.-C. Moller, J.O. Besenhard, M. Winter, M. Wohlfahrt-Mehrens, C. Vogler, and A. Hammouche, J. Power Sources, 147, 269–281 (2005).

[3] K. Amine, J. Liu, and I. Belharouak, Electrochem. Comm., 7, 669–673 (2005).

[4] C. Zhan, J. Lu, A. J. Kropf, T. Wu, A. N. Jansen, Y.-K. Sun, Q.Qiu, and K. Amine, Nature Comm., 4, 1–8 (2013).