Surface modification of cathodes with nanosized amorphous MnO2 coating for high-power application in lithium-ion batteries

In this paper, we discuss the surface modification of spinel LiMn2O4 cathodes by MnO2 particles via a simple precipitation method at room temperature, without any heat treatment. Nanosized MnO2 particles with an amorphous structure were formed and distributed evenly on the parent cathode, without severe agglomeration. Electrochemical measurements at ambient temperature revealed that the MnO2-coated LiMn2O4 electrode exhibited superior rate capability as compared to the pristine LiMn2O4 electrode. Based on the capacity at low currents, the surface-modified electrode delivered 62% capacity, whereas the pristine LiMn2O4 electrode maintained 8% capacity during fast discharging for 3 min at 20 C-rate. Surface coating with nano-MnO2 enhanced the electrochemical properties such as storage characteristics, particularly at elevated temperatures. X-ray photoelectron spectroscopy data showed that the improved performance of the coated electrode was mainly because of the suppressed side reaction between the cathode and the electrolyte.