Improving Electrochemical Performances of Li-Rich Layered Mn-Based Oxide Cathodes through K2Cr2O7 Solution Treatment

The chemical pretreatment is usually an efficient strategy for improving the electrochemical performance and reducing the voltage fading of the Li-rich Mn-based materials. Herein the different concentration K2Cr2O7 solution pretreatment and subsequent annealing processes are applied in the modification of the layered porous Li-rich Mn-based Li1.2Mn0.54Ni0.13Co0.13O2. The changes of the structure and electrochemical properties of the sample before/after modification are investigated by Raman spectrometer, transmission electron microscopy, powder X-ray diffractometer, and galvanostatic charge/discharge tests. It has been found that K2Cr2O7 solution treatment and subsequent annealing can not only form the spinel phase on the surface of the layered porous Li-rich Mn-based particles but also lead Cr doping on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 and thus distinctly improve the cyclic stability and the rate capability of the sample. Especially, the layered porous Li-rich Mn-based Li1.2Mn0.54Ni0.13Co0.13O2 after 0.1 mol L–1 K2Cr2O7 treatment represents a distinctly high initial Coulombic efficiency of 91%, enhanced rate capability of 129.3 mAh g–1 even at a rate of 10 C, and good cyclic stability with capacity retention of 86% after 200 cycles at a rate of 0.5 C.