Effects of Fluorine Doping on Electrochemical Performance of Spinel-Layered Li3Mn3O7.5-xFx as Cathode Materials for Li-Ion Batteries

Abstract

A simple synthesis procedure for solid-state reactions at an intermediate temperature (500°C) is applied to synthesize F-doped spinel-layered 0.5Li2MnO3•0.5Li4Mn5O12 (Li3Mn3O7.5-xFx with x = 0, 0.05, 0.1, and 0.2). The F-doping does not affect the crystal structure or the morphology of the pristine sample. However, F-doping increases the Mn3+ content, leading to an improved electronic conductivity and a lower charge-transfer resistance. In addition, F-doping also reduces the difference of voltage between the oxidation and reduction processes, and enhances the Li+ diffusion coefficient (with a maximum four times higher than that of the pristine sample). Consequently, the capacity and rate capability of the cathode are improved by F-doping (the x = 0.1 sample can provide a high capacity of 300 mAh g−1 at C/10).