| In this paper, based on layered Li Mn O2 as the starting point, the materials were systematically studied, the results are as follows:1. This paper determines to use nitrate, nickel nitrate, lithium hydroxide prepared precursor to the raw materials for the co precipitation method, and then mixed with lithium hydroxide of high temperature sintering are layered lithium manganate cathode material.2. Study influence of sintering temperature and holding time on the crystallization and morphology of materials and electrochemical performance. TG analysis is first used to determine the approximate temperature of sintering for 750-950℃. From the SEM can be observed in the sample at low temperature particle aggregation for polyhedral ball shape, when the temperature reached 950℃ lead to crystal plane distance decreases, the increase of crystallinity, collapse, sample particle structure particle melting. The attachment is formed on the particle surface. The electrochemical properties of the graph we can see that from 750℃ to 850℃, with the temperature rise, gradually increased testing battery capacity, and capacity variation trend to 950℃ test battery from 850℃ is also gradually reduced. Research results showed that, layer-like Li Ni0.5Mn0.5O2 cathode material in air atmosphere of best sintering temperature for 850℃, the holding time is obtained with a 10 h sample has a maximum discharge capacity and the cycle performance of the best, the crystal is also more complete, more uniform particle size.3. By doping metal ions and other elements to reduce the content of Mn3+ to reduce the effect of Jahn-Teller is a very effective method. This paper has chosen the Ni doped. The research results show that when Ni2+:Mn2+=1:1 Li Ni0.5Mn0.5O2 materials exhibit the most excellent electrochemical performance, capacity and chemical cycle performance of the material is improved obviously.4. With the increase of the amount of lithium, layered structure materials tended to be complete, but when the lithium content too much to maintain the metal ionic crystal structure is reduced, the battery capacity is gradually decay. The final determination of n Li:n(Ni+Mn) =1:1, that is the amount of lithium is excessive to the standard with the content of 10%.5. This paper using the homemade LPAN was coated on the Li Ni0.5Mn0.5O2, explores the best coating content at the same time, find the optimal sintering temperature. This chapter studies from 800℃ to 900℃ between the precursor after electrochemical performance of carbon coated after the results show that the coating LPAN materials charge discharge capacity and cycle stability are greatly improved.The temperature is 830℃ centigrade coating content is 13%, the ideal of electrochemical performance of coating of the layered lithium manganese oxide anode material, after 50 cycles at 204.5m Ah.g-1 capacity. At the same time, the results also shows that when the temperature reaches 900℃, battery capacity decreased obviously, which showed that high temperature destroys the crystal structure of the material form, can not reach the purpose to improve the electrochemical performance of material.6. The properties of composite materials of different content and Li2 Mn O3 and Li NixMn1-xO2, the result of 0.5Li1.1Ni0.4Mn0.6O2 and 0.5Li2 Mn O3 after 30 cycles, the capacity was 190 m Ah.g-1, 0.5 Li Ni0.3Mn0.7O2·0.5Li2 Mn O3 after 40 charge discharge cycle capacity of 224.6m Ah.g-1.7. The research on Li Ni0.5Mn0.5O2 based coating modification, and thus on the Li2 Mn O3 and Li MO2 solid solution composite modification of similar. The results indicate that the temperature is the key factor affecting the electrochemical performance of the material, crystalline materials at too low a temperature effect of sintering process, the temperature is too high for the LPAN coating is extremely unfavorable, the temperature at 800℃to 900℃coated LPAN are beneficial to improve the electrochemical properties of the materials, especially at about 850℃, based on raw materials coated with the content of 20%, the electrochemical cycle stability improved obviously. |
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