| Lithium ion battery is a new generation green non-pollution battery when it was used in the 1990s. It is widely used in portale electron apparatus and cars, due to its highlighs, such as high voltage, low discharge rate by itself, little volume, light weight and nonmemeory effect, but the cathode materials for lithium ion batteries are the key to constrain its whole performance. The lithium ion batteries which was earliest used are almost selected LiCoO2 as the cathode material, because Co is shortage, high cost and toxity, it is necessary to find other cathode materials to replace it. Respectively, Ni and Mn have low cost and nontoxity, therefore the cathode materials including Ni and Mn have attracted wide attention. For inverse spinel type LiNiVO4, it also attracts many research workers interests due to its high voltage (4.8V, vs.Li).Layered LiNiO2 can be used as 4V batteries, its theoretic cycle capacity is 275 mAh -g-1. But the conditions of synthesis are very rigorous, there is a high potential energy from Ni2+ to Ni3+, the oxidize process is hardly complete. Aim at this situation, we successly use a new method to synthesize it. This method is not reported until now, which is simple and easily controlled. LiNiO2 was prepared by reaction of stoichiometric calculation amounts of thoroughly-mixed Liand preoxidation nanometer-scale Ni3O2 (OH) 4 powders in 02 at the temperature of 700 for 6h. The products were tested by XRD, XPS, SEM and electrochemistry methods. It was shown that product was LiNiO2 single-phase, and the valence of nickel was +3; the average size of it was 40nm; its initial charge specific capacity is leSmAh-g-1 and the coulomb efficiency is 90%; the second charge specific capacity is 160mAh-g-1 and the coulomb efficiency is 96%.The theoretic cycle capacity of LiMnO2 is 286 mAh g-1, which has attracted a great deal of people to research. Aim at the impurity of LiMnO2 which was synthesized by the predecessor and the phase change during the electrochemical process, we try several methods, including wet moist chemical method, liquid state method, solide state method and liquid dipping method. At the same time, we study the synthesis of LiMnC>2 in defferent atmosphere, for example air, argon and nitrogen. LiMnOa has been synthesized from self-synthesized material Y -Mn203 by wet moist chemical method under different sinter conditions in argon. The material was analyzed by XRD, SEM. It is shown by XRD that material is LiMnO2 single phase in 450 keeping 5h, then in 600癈 sintering 6h in argon. SEM study shows that the grains of LiMnO2 are uniformity. In terms of the unstability of it, we take dopping and coating measures to restrain it. The dopping elements include Cr, Al, Co and Ni, and LiCoO2 is used as the coating material. Through XRD ananysis, we can know only dopping Al can form LiMnO2, the product of coating LiCoO2 forms the main phase LiMn2O4Although LiNiV04 has high voltage as cathode materials, it is difficult to Ni3+ from Ni2+, which makes it hard in the first charge. In order to improve its cycle performance and reduce capacity loss, we have synthesized series of lithium nickel manganese vanadate by using the moist chemical method in the reaction conditions of different temperature and calcination time. The structure characterization and element analysis tests are preformed by means of XRD , IR, Raman and XPS. The results showed that the vanadium element exists as a form of V04 and the manganese element in +3 value resides in the octahedral coordinatedinterstices to replace the +2 value nickel element, the optimum reaction condition is at 750癈 forlOh. The XRD results indicate that the most limited molar amount of Mn substituting for Ni is 0.4 in the compound. By using Scherrer formula for determining the product's sizes, we can calculate the sizes of the products being 42~56nm.We use dimethylglyoxine direct color matching method to determine the content of Ni in the results. Mn in LiMnO2 does not exist all Mn[III], there is still a little Mn (IV), it is Mn[II... |
