Electrochemical performance of F-doped lithium-rich layered oxide
The lithium-rich manganese-based cathode materials have broad application prospects,but the cycle stability is poor.To enhance the electrochemical stability of materials,an F-doping concentration gradient experiment is set up.By optimizing the raw material preparation ratio during the acrylic acid polymerization process,Li1.2Ni0.13Co0.13Mn0.54O2-xFx material is prepared using the polymer-pyrolysis method.The effect of F-doping ratios on the microstructure and electrochemical stability of cathode materials is investigated,and the capacity release of different oxidation-reduction reactions during the initial cycle of charge and discharge is quantitatively analyzed.The phase compositions and morphology of the samples are observed by XRD and SEM.The electrochemical performance of the samples is analyzed by galvanostatic charge-discharge and electrochemical impedance tests.The electrochemical stability of lithium-rich manganese-based cathode materials can be improved by F-doping.When x=0.03,the sample LMNC-F 0.03 exhibits a distinct layered structure with a low degree of cation mixing and optimal electrochemical stability.After 100 cycles at 0.5 C rate in 2.0-4.8 V,the specific discharge capacity is 186.97 mAh/g,with a capacity retention rate of 85.76%,a median voltage retention rate of 84.93%;the average specific discharge capacity at 2.0 C rate is 147.68 mAh/g.
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