Study On Oxalate Co-precipitation Synthesis And Doping Of Lini_0.8Co_0.1Mn_0.1O₂and Its Properties

Lithium-ion batteries(LIB) with the highest work voltage and energy density, longer cycle life and better safty are used to power portable electronic devices such as mobile phones, laptop computers, power tools, EV/HEV/PHEV and a variety of handheld and portable devices. The application of commercialized LiCoO2is limited due to the lackness and relative toxicity of cobalt. It is accepted that3M(mixed cobalt/nickel/manganese oxides) battery cathode materials is a promising candidate to replace the commercialized LiCoO2for the lithium ion batteries.In this paper, LiM0.8Co0.1Mn0.1O2and Cr3+, Ti4+doping of LiNi0.8Co0.1Mn0.1O2have been synthesized by oxalate co-precipitation and post-sintering in O2. The crystalline structure, morphology and electrochemical character of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM), charge-discharge experiments, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).The result of oxalate co-precipitation synthesis of LiNi0.8Co0.1Mn0.1O2processes in PH=5.5showed that the discharge capacity of material first increased and than decreases with the increases of sintering temperature, sintering time and Li/(Ni+Co+Mn) mole ratios. All of them, sintering temperature was lower than750℃, materials which has not obvious layered structure and orderly degree is not high could be indexed in XRD patterns. LiNi0.8Co0.1Mn0.1O2prepared with sintering temperature800℃, sintering time12h and Li/(Ni+Co+Mn) mole ratios1.05showed the largest discharge capacity of175.4,140.6,117.4mAh·g-1at0.5C,1C,2C respectively, corresponding to the capacity of114.4,90.6,51.2mAh·g-1after50cycles. It showed serious capacity fading.The result of XRD, SEM, CV and EIS showed that a small amount of Cr3+, Ti4+was in the form of solid solution into the crystal lattice of LiNi0.8Co0.1Mn0.1O2, that they could form electronic defects in LiNi0.8Co0.1Mn0.1O2to improve the degree of the disorder of crystal lattice atoms, reduce the polarization and charge transfer resistance, improve the lithium ion diffusion coefficient, so the electrochemical properties of the material were improved. The initial discharge capacities of LiCr0.01Nio.79Co0.1Mn0.1O2and LiTi0.02Ni0.78Co0.1Mn0.1O2are144.4mAh·g-1and143.3mAh·g-1at2C with a capacity retention rate more than70.0%and86.95%after50cycles respectively.