A theoretical method to assess cyclability of intercalation electrode materials using DFT

Density functional theory is widely used to theoretical investigation and comparison of electrode materials. In this paper, we propose novel theoretical approach to evaluate cyclability of intercalation electrode materials. Crystal structure of an intercalation electrode material have to be stable after deintercalation, which is called “structural stability”. Capability of an electrode to endure many cycles is called as “cyclability”. We suggest that changing in properties in atomic scale under intercalation/deintercalation (cycling) is responsible for low cyclability, while changing in cell parameters and unit cell properties is responsible for the primitive structural stability. Also, thermodynamic stability of the electrode polymorph after deintercalation can be another parameter of structural stability. We use layered oxides and spinel electrode materials, to verify the here proposed approach, respectively, for atomic forces and magnetic moment. As a consideration in analysis of calculated forces, LiCoO2 is estimated to have the most stable cycling in the family. According to the results, Fe atoms in LiFeO2 would experience huge changes in the force value after (de)lithiation, causing low cyclability, as observe in experiments. In term of changes in magnetic moment under (de)lithiation, our calculations show significant changes of magnetic moment for LiMn2O4, which justifies its low cyclability observed in the experimental studies.