Point defects and their impact on electrochemical performance in Na<sub>0.44</sub>MnO<sub>2</sub> for sodium-ion battery cathode application
Chung-Hyok Rim, Chol-Hun Jang, Kwang-Han Kim, Chol Ryu, Chol‐Jun Yu
Abstract
approach, we determine the formation energies of elementary defects and defect complexes depending on the sets of atomic chemical potentials, corresponding to a certain thermodynamic condition for the synthesis of stable NMO. Sodium interstitials are found to have the lowest formation energies in the relevant ranges of temperature and pressure. Other intrinsic point defects such as oxygen vacancies, sodium vacancies and manganese antisites can also be formed with proper formation energies and have an impact on the cathode performance. Compared to the perfect system, oxygen vacancies lower the electrode voltage, whereas manganese vacancies and antisites increase the voltage. We find that most point defects and defect complexes improve the sodium ion diffusivity, highlighting a proper control of defect formation for enhancing the performance of sodium-ion batteries.