Doped Spinel Of Limn <sub> 2 </ Sub> O <sub> 4 </ Sub> Experimental Study And Synthesis

Nowadays, with the rapid development of science and technology, communication, network, people have made higher demands on cheap and long life-span batteries. Li-ion batteries has been the study hotspot for people for their favorable advantages of low cost, high energy density, high voltage, light-duty, long cycling life and non-pollution. Spinel LiMn₂O₄ is considered as the most promising positive cathode material for Li-ion batteries because of its high voltage, high safety, low cost, and low contaminated, but its poor cycle performance and stability in high temperature blocked severely the commercialize process. This article summarized the work principle, develop course and of Li-ion Batteries, and summarized the study status of several cathode materials;analyzed the reason about attenuation of Spinel LiMn₂O₄ and illuminated some existing synthesize methods of LiMn₂O₄ to improve the performance of this cathode materials.It was studied the doping and synthesizing of Spinel LiMn₂O₄ adopting two ways. The materials was analyzed by modern means of x-ray diffraction (XRD) scanning electric microscopy (SEM-EDS) and the electrochemical properties was tested.: (1) The compound Li_1.05Mn_2-xM_xO₄(M=Mg, Ni, Al)doping with cations and Li_1.05Mn_1.9M_0.1O_3.5F_0.5 (M=Mg Ni Al) doping with cations and anions was synthesized by the way of machine ball-milling-solid phase in high temperature. The results showed that the electrical properties of the batteries with Li_1.05Mn_2-xM_xO₄(M=Al Mg Ni) doping different cations showed same laws when the batteries were charging and discharging: The specific capacity decrease with the increasing of the amount of doping ions. The circling stability of Spinel Li_1.05Mn₂O₄ are better than those of the pure phase LiMn₂O₄. among the other cation-doping compounds. The optimal doping amount of Ni was 0.08, Al was 0.04, Mg was 0.10. In the studies, the first discharge specific capacity of Li_1.05Mn_1.90Ni_0.1O_3.5F_0.5 Li_1.05Mn_1.90Mg_0.1O_3.5F_0.5 and Li_1.05Mn_1.90Al_0.1O_3.5F_0.5 co-doping were as follows separately: 95.64mAh/g, 113.46mAh/g and 109.19mAh/g and the holding ? ratio of capacity after 15 times cycling were separately 97.19%, 91.18% and 88.98%: The ,highest specific capacity of U1.05Mn1.90Nio.1O3.5Foj of the second cycling process reached 138.86mAh/g. The effect of the co-doping Ui.o5Mni.9oMgo.i03.5Fo.5 is the best. (2) Microwave heat technology was adopted to try to find the appropriate experiments conditions and to preparare excellent performance LiMn2O4 as cathode material, thereby to conquer disadvantage of long time of sintering and uneven of granularity distribution of the way of solid phase in high temperature. The optimal condition to synthesize spinel LiMn2C>4 was explored using family micro-wave oven because the power of microwave and heating time are foremost factors. Studies showed that it was appropriate to heat 10 minutes at 700-800°C or preservation 20 minutes at 600°C to prepare pure phase spinel LiMn2C>4, the latter is better controlling condition. It was found that the stable cycling performance of the cathode material of spinel LiMn2O4 prepared by the way of microwave chemistry possess is better than that of the samples prepared by the way of solid phase in high temperature, but the specific capacity is unideal, the best result of the experiments is only 73mAh/g.