Production Conditions The O <sub> 4 Spinel Of Limn <sub> 2 </ Sub> </ Sub> Electrode Performance Impact

Spinel LiMn₂O₄ thin films were prepared by spin-coating the lithium/manganese acetates-containing precursor solution on a stainless steel substrate at different annealing temperature.The structure and morphology of the thin films were investigated by XRD and SEM. The electrochemical property was also investigated by charge-discharge test and CV. The results showed that the structure, morphology and electrochemical property of the thin films were highly related to the annealing temperature. The surface morphology of thin films annealed at 500℃, 650℃, 700℃and 750℃respectively all took on a wrinkle-like microstructure; with annealing at 650℃or lower, the surface morphology was homogeneous and crack-free. The sizes of grains increased notably with the rise of annealing temperature, and so did the crystallization. When the annealing temperature was raised to 650℃, the film was pure spinel LiMn₂O₄ with a thickness of 3.6μm and had optimal electrochemical property: its initial discharge special capacity was 35.9μAhcm^-2μm^-1 at 50μAcm^-2. After 20 cycles, the discharge special capacity turned to 33.8μAhcm^-2μm^-1, and 93.6% of capacity was kept.Electrochemical impedance spectroscopies of dinsertion of Li ion in spinel LiMn₂O₄ with graphite conductive material KS-6, carbon black conductive material Super P and a mixture of KS-6 and Super P with a mass ratio of 1:1 as conductive agents respectively was studied, and according to the influence on electrode processes of spinel LiMn₂O₄ by different conductive agents, different equivalent circuit models were used to fit the experimental electrochemical impedance spectroscopies. The fitting results were in agreement with the experimental results and exchange current density was also calculated. The results indicated that the LiMn₂O₄ with binary conductive agents had the minimum impedance R_ct, and the max exchange current density during the deinsertion of Li ion in spinel LiMn₂O₄. The results of the charge-discharge test showed that the LiMn₂O₄ with binary conductive agents had better discharge capacity at the same discharge rate and higher capacity retention rate after 20 cycles at 60℃than those of LiMn₂O₄ with single conductive agents.The electrochemical property at 60℃and thermal stability of 18650 batteries with LiMn₂O₄ or LiMn₂O₄/LiNi_1/3Co_1/3Mn_1/3O₂ composite cathode material as cathodes were investigated by charge-discharge, CV, EIS, TG/DSC. The results indicated that the capacity retain LiMn₂O₄ and LiMn₂O₄/LiNi_1/3Co_1/3Mn_1/3O₂ batteries were 64.03% and 83.12% after 150 cycles at 60℃; the impedance of batteries with composite cathode at 3.9V after 50, 100 and 150 cycles shift lower during cycles, weather that of batteries with LiMn₂O₄ become a little bigger. The result of XRD for cathodes and anodes showed that the crystal structure of spinel LiMn₂O₄ in composite cathode changed more than that of LiMn₂O₄ cathode at 4.2 V during cycles. TG/DSC results showed that for the thermal stability of whole batteries with LiMn₂O₄ or composite material, anodes played an important role during cycles at 60℃; for the whole batteryLiMn₂O₄/LiNi_1/3Co_1/3Mn_1/3O₂ batteries showed better thermal stability during cycles.