Theoretical prediction of surface stability and morphology of LiNiO2 cathode for Li ion battery

Abstract: As the layered oxide with large Ni content is considered as a promising cathode with high capacity, its surface structure is highly required to be explored for tailoring complicated surface phenomena. Here, we comprehensively examine the salient features of surface stability and morphology of LiNiO2 material as the representative of Ni-rich layered oxides using density functional calculations. Our study reveals that the Li exposed surfaces give lower surface energies than the oxygen surfaces irrespective of facets, and Ni exposed ones are the least stable. Also, the equilibrium morphology can be varied from truncated trigonal bipyramid type to truncated egg shape according to the chemical potential whose range is confined by the phase diagram. Moreover, it is found that the electrochemical window of stable facets strongly depend on the surface elements rather than facet directions. On the contrary to stable Li surfaces, the oxygen exposure on the surface considerably lowers the Fermi level similar to the level of electrolyte, which can accelerate an oxidative decomposition of the electrolyte on the cathode surface.