Study of the Delithiation of LiMn0.2Co0.8O2 Cathode Material for Lithium Batteries

Abstract

Samples of LiCo0.8Mn0.2O2 were synthesized by a wet-chemical method using citric acid as a chelating agent, and were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and magnetism. Transmission Electron Microscope (TEM) revealed particles with a mean size of 100 nm. We observe that the material has ability to free lithium ions from its structure by chemical process, which is analogous to the first step of the charge transfer process in an electrochemical cell. Both the concentration of Mn3+-Mn4+ pairs and that of Mn4+-Mn4+ pairs formed in the delithiation process have been determined, together with that of the Mn3+-Mn3+ pairs. The results indicate a random distribution of the Li ions that are removed from the matrix upon delithiation, which then undergo a diffusion process. Testing the material as cathode in lithium batteries revealed about 170 mAh g-1 capacity, with a lower polarization and a high columbic efficiency.