| Spinel LiMn2O4 is one of the most promising cathode for lithium ion battery for its high working voltage,high satfy and low pollution. However, the commercial applications of LiMn2O4 are badly blocked by its poor cycling performance.According to its characteristic, LiMn2O4 was prepared and doped and characterized by x-ray diffraction(XRD), Electrochemical Impedance Spectroscopy(EIS), Cyclic Voltammetry, constant current charge/discharge techniques. The experiments showed that the LiMn2O4 prepared by critic acid method revealed pure spinel phase and better performance with initial discharge capacity of 115.49mAh·g-1. When doped by C, the sample gave the largest discharge capacity of 128.82mAh·g-1 and remained 120mAh·g-1 after 30 cycles with the C content of 30%, which indicated better cycling performance than the sample without C. Based on traits of Cr, the Mn was doped by Cr and the working voltage reached 5V. The LiCr0.5Mn1.5O4 with x=0.5 displayed the best electrochemical performance by showing the initial discharge capacity of 145.85mAh·g-1 and remained 121.33mAh·g-1 after 30 cycles. When coupled as cathode with AC anode in hybrid capacitor, the higher discharge capacity and perfect cycling performance were both obtained. The working voltage was found to reach 2.5V and the preferable ratio of AC in cathode was tested to be 5%. The initial discharge capacitance was 32.89F·g-1 and remained 32.27F·g-1 after 1000cycles with the loss of 1.89%.
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