| With the rapid development of electronic facilities as well as energy and environmental concerns, people have made high demands on batteries. Li-ion batteries are widely used for their favorable advantages of high voltage, big specific capacity, long cycling life and non-pollution. Transition metal oxides with high inserted potential are used as cathode material of Li-ion batteries generally. At present, layered compounds LiCo02 , LiNi02 and spinel LiMn204 are extensively studied. However, the application of commercialized LiCo02 is limited due to the lackness and high expense of raw material Co, especially in power battery and large-scale energy storage device. The industrialization of LiNi02 can not come true .because the conditions of control are out of reach on preparation. Spinel LiMnA is considered as the most promising positive material for Li-ion batteries because of its high voltage ,high safety, low cost,easy recycle and environmental affinity.Based on summarizing Li-ion Batteries , some pertinent data and looking into the status quo about spinel LiMnA research at home and abroad , it' s known that the deficiency of the material lies in inhomogeneity .motley phase .instability as well as poor reversibility. Now, many studies and methods , such as sol-gel, welt-impreghation and Pechini method, etc, have been making to synthesize LiMn204 cathode material by reserchers. To some extent, the properties of the material are improved. Nevertheless, these methods are not u,sed- for mass production because of complicated technics or high cost. So the emphasis of our investigations is to develop a technics which can both be fit for industrialization and synthesize spinel LiMn204 with excellent electrochemical characteristics.For adapting to the need of industrialization and improving the properties of materials,the method of mechanical activation has introduced on the basis of traditional calcinations at high temperature.The stardardspinel LiMn204 is prepared by the mechanical activation-high temperature solidsynthesis method.The thermodynamic property , the physical-chemistry performance and the producing techniques of .battery have been studied by means of thermogravimetry (TG), differential scanning calorimetry (DSC), x-ray diffraction(XRD) , scanning electric microscopy (SEM) as well as various electrochemical analysis methods.Studies show that synthesis temperature, calcinations time, recipe of raw materials, heat treatment and particle size of products are main factors affecting the performances of LiMn204 cathode materials. With the increment of synthesis temperature and time, the structure and crystal of products are getting to perfect. But the samples synthesized at 1100 "C appears the phenomena of sinter and microcrystal growth. When the time of constant temperature exceeds 24 hours,the heating time has little influence on the performance of products. The standard spinel structure of LiMn204 can be obtained at the Li/Mn mole ratio of 0. 95~1. 05/2, especially, at the ratio of 1.05/2, the synthesized samples have better electrochemical characteristics.The materials synthesized by two steps heat treatment have preferable performance. Comparing the two continuous calcination method with the two discontinuous calcination, the former is the better. With prolongation of ball milling time, particle size decreases, but specific surface area increases. Small and narrow particle size distribution benifit diffusion of Li-ion.Also, the production techniques of Li-ion battery is discussed, the influence of important working proceduces (including the preparing, the doping, the assembling , etc.) on battery performance is analysed and the recipe of cathode materials is optimized. The results give that the positive plate takes on preferable charge-discharge properties only when the amount of additive of PVDF and acetylene black is suitable. When the amount of PVDF and acetylene black is 7~10% and 8%, the positive plate obtained possesses optimum properties in our studies. |
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