| Recently, it was found that the performance of layered LiNi1/3Co1/3Mn1/3O2 was similar to that of LiCoO2, and even better than LiCoO2 at certain aspects, such as high-temperature performance and safety performance. The LiNi1/3CO1/3Mn1/3O2 material has the development trends to be used as the cathode of dynamic batteries. Therefore, this superior and cheap positive material would replace LiCoO2. However, many studies showed that in lithium-ion battery, the harmful interactions between electrolytes and layered nickel-oxide-based cathode materials could lead to capacity fading rapidly during cycling. To overcome this problem, basing on the synthesis of LiNi1/3CO/3Mn1/3O2, we used electrostatic self-assembly method to modify this material by TiO2, and also applied another coating materials (LiCoO2 and AlPO4) to modify LiCo1/3Ni1/3Mn1/3O2. XRD, XPS, SEM and electrochemical performance tests were used to characterize the products. In our work, "zero strain" material Li4/3Ti5/3O4 was used as anode material and LiCo1/3Ni1/3Mn1/3O2 as cathode to assemble Li4/3Ti5/3O4/LiCo1/3Ni1/3Mn1/3O2 test cells, and the electrochemical performance were researched in non-water system. The supercapacitor can be made with two different layered intercalation compounds as the anode and cathode electrodes, which was a new subject. The simulative symmetry electrochemical supercapacitor assembled by LiCo1/3Ni1/3Mn1/3O2 material in our work, and the electrochemical behavior was studied in water-based system.In the first chapter, the current survey on the lithium ion batteries cathode materials, especially on layered LiCo1/3Ni1/3Mn1/3O2 material was introduced and the correlative scientific problems needed to solve were brought forward.In the second chapter, the LiCo1/3Ni1/3Mn1/3O2 cathode material for lithium ion batteries was synthesized by semi-solid-state method under 850℃for 20h in air. XRD analysis, SEM and electrochemical tests were used to characterize the structure, appearance and electrochemical performances of the aimed material. The XRD indicated that the diffraction lines of the obtained LiCo1/3Ni1/3Mn1/3O2 could be indexed based on a hexagonalα-NaFeO2 structure (space group R3m). The SEM showed that the synthesized material has a very narrow grain size distribution with uniform particle size (d≈0.2μm). Electrochemical performances research indicated that the LiCo1/3Ni1/3Mn1/3O2 cycled between 2.7～4.3V had charge/discharge capacity of 172.4/156.1 mAh/g, 162.0/154.5 mAh/g, 162.7/155.7 mAh/g, 163.2/155.9 mAh/g and 161.7/154.2 mAh/g in the previous five cycles respectively and had good cycle properties.To avoid the harmful interactions between LiCo1/3Ni1/3Mn1/3O2 and electrolyte, the LiCo1/3Ni1/3Mn1/3O2 cathode materials were modified by applying surface coating of TiO2, using electrostatic self-assembly method. The TiO2-coated material with excellent layered structure had uniform size about 6μm and exhibited spherically porous morphology due to aggregating by small grains. The initial charge-discharge capacity of TiO2-coated LiCo1/3Ni1/3Mn1/3O2 was 168.8/157.0 mAh/g. 20th cycle later, the discharge capacity was 141.1 mAh/g, and the cyclic efficiency was 98.5%. Compared with the uncoated sample, the electrochemical performance of TiO2-coated LiCo1/3Ni1/3Mn1/3O2 was improved.In the fourth chapter , we also employed surface coating of LiCoO2 and AlPO4 to modify the LiCo1/3Ni1/3Mn1/3O2 cathode materials at the different conditions. The coated-LiCo1/3Ni1/3Mn1/3O2 was tested by XRD, SEM and lectrochemical test. The results showed that 10% and 30%LiCoO2-coated LiCo1/3Ni1/3Mn1/3O exhibited better performance than AlPO4-coated sample. After 10 cycles, the discharge capacity of 10%LiCoO2-coated LiCo1/3Ni1/3Mn1/3O2 was 135.6mAh/g. For the 30% LiCoO2-coated sample, with the average size of 0.3um, delivered 140.1 mAh/g in the 10th cycle.In the fifth chapter, Li4/3Ti5/3O4/LiCo1/3Ni1/3Mn1/3O2 lithium ion battery was obtained by using LiCo1/3Ni1/3Mn/3O2 as cathode and Li4/3Ti5/3O4 as anode material. The initial charge and discharge capacity of the battery was 344.0 mAh/g and 200.0 mAh/g, respectively. The capacity faded sharply to 102.2 mAh/g at 4th cycle.In the sixth chapter, substituting the organic electrolyte to inorganic salt solution is another approach to avoid the harmful reaction between LiCo1/3Ni1/3Mn1/3O2 and electrolyte. In our work, the simulative symmetry electrochemical supercapacitor assembled by LiCo1/3Ni1/3Mn1/3O2, and the electrochemical behavior was studied in water-based system. The results indicated the charge and discharge curves of this simulative capacitor is similar to that of supercapacitor. In 1 mol/L NaNO3 solution, first discharge capacity of the capacity was 91.4 F/g, 30 cycles later, the capacity decreased to27.7 F/g, and 22.2 F/g in 70th cycle, and it was better than that Li2SO4 solution.In the last chapter, the author summarized the whole dissertation and brought forward some suggestion for future research work of LiCo1/3Ni1/3Mn1/3O2 cathode material.
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