| Lithium ion batteries gradually replace the traditional energy, such as coal, oil. With its high energy density, good safety, light quality. Anode materials play a key role for the lithium ion batteries. At present, Anode materials, high nickel, ternary materials, LiFePO4, LiCoO2, LiMn2O4 are used widely. Compared with the other kinds of anode materials, spinel LiMn2O4 (LMO) cathode material has the advantages with low cost, environmental friendly, good safety. So it gains popularity of researchers and enterprises. This paper mainly adopts coprecipitation preparation of precursor, and then under the high temperature solid phase reaction.Doping elements is studied, and the synthesis temperature, crystal structure and electrochemical properties of the coating to the LMO.XRD, SEM, TEM, XPS, AAS, particle size distribution test by laser approach, electrochemical titration technique for Mn oxidation states, dQ/dV-V frofiles and galvanostatic charge-discharge tests were carried out for insight into the comprehensive electrochemical performance of as-prepared materials. The experimental results show the following aspects:The doping of Ni and Cr for Mn can not prevent Mn2+from being oxidized into Mn3+in solution process, yet do not change their final crystal structures of spinel with or without doping. Although the first charge and discharge capacity decreased but it improves circulation performance after doping, especially at the same time with the comparison of Cr, Ni co-doping. Li, Al doping also doesn’t change samples’crystal structure, but prevent samples from growing up obviously, the article size of Li, Al doping decrease about 4 μm compared to pure LiMn2O4. However, Li, Al doping improves the cycle performance and the first discharge capacity of samples effectively. When the Al3+content increased to 0.1, the capacity retention is the most perfect, it is 94.2%after 50 cycles, the results indicate Li, Al doping stabilize the spinel structure.The experimental results show that appears oxygen deficiencies in the samples sintered at higher temperatures, and they enrich with the elevated temperatures. As fine particulate samples being sintered at temperature above 750℃, oxygen deficiencies occur significantly in lattice, company withMn3+enrichment and Mn4+depletion, so result in a slight lattice expansion, lessen the structural stability, and deteriorate the cycleability of doped materials. Samples with small oxygen deficiency show a good cycle performance because of its destructive effect couldn’t past to the positive effect of Li, Al doping, and synthesis temperature higher than 750 ℃, the positive effect of Li, Al doping couldn’t past to the destructive effect of oxygen deficiency, so show a bad cycle performance, especially sintered at 900 ℃, the capacity retention reduce to 84% after 50 cycles. In addition, it also shows small samples with higher specific capacity than theoretically. But they can increase oxygen deficiency and lead to a bad cycle performance.For AIF3-coating of Al0.1 cathode materials, it appear coating layer in the surface of samples, in addition, AlF3-coating it do not change the samples’ crystal structure and improve its cycle performance effectively, the capacity retention reaches 99% with sintering temperature at 400℃ after 50 cycles. For AlPO4-coating, because of the high treatment temperature, Al3+formed interstitial doping to pristine materials, then the lattice constant increasing, and form a small content of well-conducted Li3PO4 in the surface. Therefore, APO4-coating has high capacity and good cycle performance. The capacity retention is 98.6% of P70 after 50 cycles,.In this paper, the influence of Li-Al co-doping on the material electrochemical performance are studied. In addition, it studies that different materials coating on pristine material and study the influence mechanism of the electrochemical properties.
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