Dopant Based Stabilization of LiCoO2: Insight from First-Principles Calculations

LiCoO₂ is widely used as cathode material for Li-ion batteries (1). However, the usable specific capacity of LiCoO₂ is limited to approximately half of its theoretical capacity. This limitation comes from the mechanical failure of the cathode when more than 50% of Li is deintercalated. The stability of LiCoO₂ and its electrochemical performance can be improved by coating its surface with inner metal oxides (2). Such approach has been used for different cathode materials, but the origin of the stabilization effect is poorly understood. The enhanced stability of the cathodes has been rationalized invoking many effects, e.g., i) the inner metal oxides act as a physical barrier to prevent cathode-electrolyte reactions (3), and ii) the layered structure of the cathode material is stabilized by the migration of metal ions from the coating oxides (1). To have a better understanding of the stabilization mechanism, we have performed Density Functional Theory calculations of LiCoO₂doped with inner metal ions (Figure 1). Such calculations allow us to study how the migration of metal ions from the coating oxides modify the structure of the cathode materials.

Acknowledgments.Research supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division.

Reference:

1. H. Li, Z. Wang, L. Chen, and X. Huang, Adv. Mater., 21, 4593–4607 (2009).

2. Z. Chen, Y. Qin, K. Amine, and Y.-K. Sun, J. Mater. Chem., 20, 7606–7612 (2010).

3. J.-S. Kim et al., J. Electrochem. Soc., 151, A1755–A1761 (2004).

Figure 1. Schematic of some possible sites for metal dopants in LiCoO₂: the left and central panels show the dopant on Li and Co sites, respectively, and the right panel shows substitution on both Li and Co sites.