Improving the cycling stability of Li2MnO3 by surface treatment

An electrochemically stable and cobalt-free cathode material is prepared by impregnating Li2MnO3 with nickel nitrate and subsequent calcination at 650 °C. X-ray diffraction and scanning electron microscopy reveal a phase pure material with a homogenous distribution of nickel over the particle surface. Structural changes related to the treatment before and after cycling as well as electrochemical performance are investigated. The surface modified samples exhibit improved cycling stability and rate capability. In particular, the material with a nickel content of 5.7 wt% shows 173 mAh g−1 at rate C/10 and 104 mAh g−1 at rate 3C. Furthermore, a constant capacity of 155 mAh g−1 is obtained at rate C/5. Derivative plots of galvanostatic curves in combination with Raman spectroscopy depict a reduced transition from a layered to spinel-like structure compared with pristine Li2MnO3, while ICP measurements reveal a drastically decreased dissolution of manganese.