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In order to reduce the corrosion of LiNi0.5Mn1.5O4 by an electrolyte, an innovative method of in situ coating of AlPO4 was proposed in this paper, which effectively improved the high-temperature cycling performance of the electrode. The effects of AlPO4 coating with different mass fractions on the structure, morphology, and electrochemical properties of LiNi0.5Mn1.5O4 were investigated. Through analysis and testing, it is found that each coating amount has no obvious effect on the spinel structure of the material. When the coating content is 1.0%, the sample has higher capacity, better rate performance, and excellent cycle stability at a high temperature (55 °C). It is also found from the data of the alternating current impedance test that the Li+ diffusion of the material is the most favorable when the coating amount is 1.0%, and the capacity retention rate reaches about 90% after 50 cycles at a 1 C rate. The results show that compared with the traditional coating method, the AlPO4 coating layer of the LiNi0.5Mn1.5O4 material obtained by in situ coating is more uniform (the layer thickness is about 4.2 nm), which more effectively blocks the contact between the LiNi0.5Mn1.5O4 electrode and electrolyte, reduces the erosion of the electrolyte to LiNi0.5Mn1.5O4, inhibits the oxygen loss in the material, and is more conducive to lithium-ion diffusion.

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Currently, LiMnPO4 is a highly prevalent cathode material in lithium-ion batteries. However, its low conductivity and Li+ diffusion rate limit its practical application. To overcome these inherent defect, we have modified its properties by doping Fe at the Mn site. In the LiMn1-xFexPO4 system, the total density of states of electrons near the Fermi level and the energy band of the Fermi surface are obtained by first-principles calculation. The adjustment of the energy band width immediately influences the electronic conductivity of LiMn1-xFexPO4 system, which is positively related to the electrochemical performance. According to the results of first-principles calculation, we speculated that x=1/4 was the optimal doping concentration. Then, the LiMn1-xFexPO4/C systems were compounded by hydrothermal method to verify the first-principles’ hypothesis. The electrochemical tests show that the LiMn3/4Fe1/4PO4/C material has the best cycle performance and rate performance. At the condition of 0.05 C rate, this material possesses an initial discharge capacity of 142.5 mAh/g. with the capacity retention maintained 93.9% after 100 cycles. The theoretical calculation in consistent with the experimental findings, which accounts for the fact that the first-principles strategy is very effective in the research and development of lithium-ion batteries.

LiNi 0.5 Mn 1.5 O 4 (LNMO) cathode material is burnt in two-stage roasting process for lithium battery. Carried out X-ray diffraction (XRD), scanner transmission electron microscope (SEM), laser grain fineness distribution and precise measurement of photoelectric catalysis, and qualitatively analyzed the LNMO cathode material. The SEM image shows that the LNMO battery cathode material is combined with μm-level particles (10 μm in diameter). The XRD pattern shows that the structure of the prepared LNMO cathode material belongs to the Fd3m space group. After being burned at 650 C for 8 hours and refrigerated milling, it is burned again at 1000 C for 8 hours. At this time, the LNMO cathode material prepared by quenching has the best photocatalytic properties. In the range of 3.5 to 5.1 V, the original charge-discharge volume of the prepared battery cathode material is shown as 130.3 mAh g −1 at a speed of 1.0 C. After 100 cycles, the sample saves 96.7% (1.0 C) of the original volume. At 1025 C, at different speeds in the discontinuance voltage range of 3.5 to 5.1 V, the charge and discharge quantity of the negative electrode raw materials obtained by individuals can be maintained at about 133.6 (0.2 C), 129.9 (1.0 C), 129 (2.0 C), respectively.

The LiMnPO 4 material has the advantages of abundant raw materials, safety and environmental protection, low price, high theoretical capacity, high stable working voltage platform and so on, showing great potential in lithium-ion batteries. Dissimilar metal ion doping can essentially improve the electronic conductivity of LiMnPO 4 and the material's charge and discharge performance, which is an ideal method to improve the electrochemical performance of LiMnPO 4 . In this paper, the optimal doping concentration of Mg-doped solid solution material was calculated by first principles. At the same time, the corresponding content of LiMn 1Àx Mg x PO 4 /C cathode material was synthesized by hydrothermal method for experimental verification, so as to prepare the

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