Computational Analysis of Coupled Anisotropic Chemical Expansion in Li2-XMnO3-δ

During the activation and charge process, vacancies are generated in the Li2MnO3 component in lithium-rich layered cathode materials. The chemical expansion coefficient tensor associated with oxygen vacancies, lithium vacancies and a Li-O vacancy pair were calculated for Li2-xMnO3-delta. The chemical expansion coefficient was larger for oxygen vacancies than for lithium vacancies in most directions. Additionally, the chemical expansion coefficient for a Li-O vacancy pair was shown to not be a linear sum of the chemical expansion coefficients of the two vacancy types, suggesting that the oxygen vacancies and lithium vacancies in Li2-XMnO3-delta exhibit a coupling effect.