Effects of cationic substitution on structural defects in layered cathode materials LiNiO2

Abstract

The electrochemical properties of layered rock salt cathode materials are strongly influenced by defects. The three most common defects in LiNiO₂-based compounds, namely extra Ni, Li–Ni anti-site and oxygen vacancy defects have been investigated. The calculated defect formation energies are very low in LiNiO₂, consistent with the difficulty in synthesizing stoichiometric defect-free LiNiO₂. A systematic study is conducted to examine the effect of Co, Mn and Al substitution on defect formation. It is shown that the presence of Ni²⁺ in the Li layer can be rationalized using ideas of superexchange interactions. In addition, a correlation between oxygen vacancy formation energy and oxygen charge is noted. This explains the better thermal stability obtained by early transition metal or Al substitutions.