| Lithium manganese oxide spinel is considered as a most promising positive material for lithium-ion secondary batteries because of its low cost and environmental harmlessness. However, this material prepared by most of the methods reported has been shown to exhibit inhomogeneity and poor reversibility as well as severe capacity fading when circling at high temperature.In this paper, two wet chemical synthetic routes were devised to change the physical properties of the crystalline product and improving the charge-discharge performance of lithium manganese oxide spinel. The synthesis of Li1+xMn2O4 and Li1+xMyMn2-x-yO4 (M=Co, Cr), which are good candidates for the cathode of the lithium ion battery, via two wet chemical routes, called the solution oxidizing method and the mechanical activation-wet chemical method were reported. The physical properties of the samples, such as composition, structure, crystal grain and powder morphology, et al., were systematically investigated and characterized by means of modern method, such as X-ray diffraction, thermal gravimetric analysis (TG), differential thermal analysis (DTA), scanning electron microscope (SEM) and so on. The circling performances of the materials were tested preliminarily.It was shown that an Li-Mn-O compound precursor with a composition of spinel Li1+xMn2-x04 and an amorphous structure was synthesized via the solution oxidizing method, in which the Mn( II) salts, as the manganese raw material, were oxidizing by oxidant H2O2, et al. in existence of lithium salts. It was then converted into a positive material with a perfect crystal structure after heat treatment. A well-crystalloid spinel Li1+xMn2-x04 and Li1+xMyMn2-x-yO4 (M=Co, Cr) compounds were prepared successfully from aqueous solution by mechanical activation-wet chemical method, in which the MnO2 (EMD), as a manganese raw material, were directly reacted with lithium salts which is carried out usually at high temperature of 700-800℃. The lithium content in the sample, which determines the phase of the sample, is sensitive to the amount of lithium salts added. The main phase in the sample is a cubic spinel Li1+xMn2-xO4 when its lithium content ranges from 3.78%wt ~ 4.35%wt, while the main phase is layered LiMnO2 as the lithium content is up to 5.80%wt. Almost all of the samples ranging from Li 3.78%wt to Li 5.80%wt can be converted to a single-phase spinel after heat treatment at 500~700'C for 4~8h, and their spinel characteristic diffraction lines in the XRD patterns shift to higher diffraction angles, indicating a decrease of the cubic spinel lattice constant with the increase of the lithium constants. Furthermore, the heating temperature has an influence on both the structure and the crystal grain size. The higher the temperature (<800癈), the more perfect the crystal structure. The growing of the crystal grain during heating can be described using Turnbull equation. The temperature has an small influence on the growing velocity of the crystal grain at the temperature lower than 400 ℃ but anlarger influences at the temperature higher than 400. However, the heating time (>4h) is little influence on the sample structure. It can be seen from the SEM that the samples from wet chemical technique is a nanopowerder with a regular morphology and well-distributed particle size less than 0.1 um. Therefore, lithium manganese oxide spinel with special non-stoichiometric composition and structure can be synthesized easily by adjusting and controlling the parameters of the novel wet chemical technology. Two spinel compounds doped Co3+ or Cr3 with chemical formula, respectively, of Lii.o2Coo.o4Mni.94O4 and Lii.o4Cro.o3Mni.93O4 were obtained directly by novel mechanical activation-wet chemical method, which have the same cubic spinel structure as LixMn2O4. Also, three Li-rich Li-Mn-O spinel compounds, respectively with Li/Mn mole ratio of 0.502 (B-17)> 0.531 (B-27X 0.608 (B-37) , have been prepared by the same process. Based on the results of XRD examination, chemical analysis for elements Li and Mn, and th...
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