Impact on electronic correlations on the structural stability, magnetism, and voltage ofLiCoPO4battery

We present a study of the structural stability of the lithium-orthophosphate oxide ${\mathrm{LiCoPO}}_4$ using density-functional theory within the local-density (LDA), generalized gradient and $\mathrm{LDA}+U$ approximation. We show that both enhanced localization and anisotropic effects provided within the $\mathrm{LDA}+U$ approximation are essential to reproduce the experimentally observed magnetic structure, lattice parameters, and stability of the lithiated and nonlithiated compound. Within this approximation, the intercalation voltage of 4.6 eV as well as the insulator character of the lithiated and nonlithiated compounds are recovered. Moreover, we found that the $\mathrm{LDA}+U$ approximation induces a strong transfer of charge from the $t_{2g}$-like to the $e_g$-like orbitals of Co as well as a significant shift of the ${\mathrm{LiPO}}_4$ band. Both effects are competing with each other and determine most of the peculiar properties of the ${\mathrm{LiCoPO}}_4$ and ${\mathrm{CoPO}}_4$ compounds.