Preparation and Improved Electrochemical Performance of Li[Li(1/3-x/3)CrxMn(2/3-2x/3)]O2 Nanoparticles Quenched in Iced Water

Li[Li(1/3-x/3)CrxMn(2/3-2x/3)]O-2 (x = 0, 0.2, 0.5 and 0.8) nanoparticles are synthesized at 900 degrees C and quenched in iced water. The crystal structure, diffusion ability of lithium ions and the improved electrochemical properties are studied by X-ray diffraction, Rietveld refinement, and electrochemical techniques. The lithium diffusion ability of Li[Li(1/3-x/3)CrxMn(2/3-2x/3)]O-2 are defined by cyclic voltammetry (CVs) profiles with various sweep rates and electrochemical impedance spectra (EIS). Li[Li(1/3-x/3)CrxMn(2/3-2x/3)]O-2 (x = 0.2) with the biggest diffusion coefficients, delivers 254.5 mAh g(-1) and retains 90% of the initial capacity after 50 cycles. The redox peaks appeared near 3.3 V after the initial cycle, is attributed to the pair of Mn3+/Mn4+, corresponding to the improved capacity of Li[Li(1/3-x/3)CrxMn(2/3-2x/3)]O-2 (x = 0.2). For Li[Li(1/3-x/3)CrxMn(2/3-2x/3)]O-2 (x = 0.8) with large Cr content, the absence of the redox reaction Mn3+/Mn4+ and more inactive phase of LiCrO2 result in the lowest discharge capacity. Proper Cr substitution activates and improves the electrochemical performance of Li[Li(1/3-x/3)CrxMn(2/3-2x/3)]O-2 and keeps the stable lattice structure during charge and discharge.