The Spinel LiMn <sub>, 2 </ Sub> O <sub> 4 </ Sub> Preparation And Battery Production Technology And Performance

With the rapid development of electronic facilities as well as energy and environmental concerning, people make high demands on batteries. Lithium-ion batteries are widely used for their favorable advantages of high voltage, big specific capacity, long cycling life and non-pollution. Transitional metal oxides with high inserted potential are usually used as cathode material of Li-ion batteries. At present, layered compounds LiCoO₂, LiNiO₂ and spinel LiMn₂O₄ are extensively studied. Spinel LiMn₂O₄ is considered as one of the most promising cathode materials for Li-ion batteries because of its high voltage, high safety, low cost, easy recycling and environmental affinity among these materials.Based on summarizing Li-ion batteries, some correlative materials and analysing the status quo about spinel LiMn₂O₄ research domestic and abroad, it's known that the deficiency of the material lies in inhomogeneity, instability, fast fading as well as poor reversibility. Now, many preparation methods,such as sol-gel, welt-impreghation and Pechini method have been used to synthesize LiMn₂O₄ cathode material by reserchers. To some extent, the properties of the material are improved. Nevertheless, these methods are not used for mass production because of complicated technics or high cost. So the emphasis of our investigations is to develop a techniques that can both be fit for industrialization and synthesize LiMn₂O₄ with excellent performances.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 solid state reaction. The spinel LiMn₂O₄ cathode material was prepared by the mechanical activation—solid state synthesis method, and was modified by ion doping and surface coating. The producing technique and performances of lithium-ion batteries were studied, the 10Ah power lithium-ion batteries were trial-produced on the basis of the material synthesized. The thermodynamic property, the physical-chemistry characteristics and the performances of batteries were analysed by means of thermogravimetry(TG), differential scanning calorimetry(DSC), X-ray diffraction (XRD), scanning electric microscopy(SEM), energy dispersive spectrometer (EDS), inductively coupled plasmas-atomic emission spectroscopy (ICP-AES), atomicabsorption spectrum (AAS) as well as various electrochemical analysis methods.The thermal analysises of LiM^C^ synthesis materials show the overall reaction is composed of three reactions, namely the decomposition of Li2CO3, the decomposition of MnC>2 as well as the composition of LijO and Mn2C>3. The mechanical activation — solid state synthesis method can enhance rawmaterial homogeneity, reduce reaction temperature, stabilize crystalline structure and improve product performances.The main factors influencing LiM^C^ electrochemical properties are synthesis temperature, Li/Mn mole ratio, ballmilling time and retenion time in turn through four factors and three levels perpendicular experiments of the hydro-ballmilling—solid state synthesis method. Compared with different reaction reagents, the Li2CO3 is batter Li source and electrolytic MnO2 is batter Mn source. When the sintering atmosphere is O2, the performances of products are batter, and the mechanism of physical and chemic action is analysed. Appropriate briqutting pressure can increase contact area and accelerate reaction, but excessive pressure may hinder the dissolution and diffusion of gas, which will postpone reaction rate. The mixing method firstly added Li2CC>3 can reduce the particle size difference and homogeneity of raw materials, thereby attaining the best discharge specific capacity 129.12mAh/g. The materials synthesized by two steps solid state reaction have preferable performance. Comparing the two continuous calcination method with the two discontinuous calcination, the former is the better.Ultrasonic technique was firstly applied to prepare spinel LiM^C^ cathode material, and the effects of different ultrasonic conditions on the performances of spinel LiMn2O4 were investigated. Compared with hydro-ballmilling, the mechanical activating effect is stronger, which is profit for accelerating nucleation and controlling crystal growth. The samples disposed by ultrasonic have well formed crystal shape and particle distribution. With the increase of frequency, power and time, the electro-chemical performances of products are improved. Ultrasonic cavitation effect is enhanced in turn from distilled water, absolute ethanol to acetone in different medium, respectively.The lattice parameter reduced and the average valence of manganese increased when Co or Cr cation doped in LiM^Cv As the doping cotent increases, the dischargespecific capacity of samples is reduces, but the structural stability and cycle performance are improved. Although F-doped samples have higher specific capacity, the increase of Jahn-Teller distortion and Mn dissolution lead to poor cycle performance. The materials have not only high reversible capacity but also well cycleability by F-Co or F-Cr ion co-doping. The properties of LiCo0.09Mn1.91O3.92F0.08 cathode material are best, the specific capacity is 119.16mAh/g, the capacity loss is 2.79% after 20th cycle.The well clad coated on parent material can be synthesized by a sol-gel method, the materials modified consist of exterior clad, doping transition layer and interior parent material. LiCoCVcoated LiCo0.09Mn1.91O392F0.08 powers with smooth appearance improve the resist ability of corrosion and decrease the dissolution of Mn to electrolyte. With the L1COO2 content increasing, the specific capacity and cycle performance of samples are improved. The capacity fading rate is 3.57% after 50th cycle capacity at 55 °C high temperature, so the capacity loss is suppressed distinctly.Also, the composition and production technique of Li-ion batteries were discussed, the influence of important working procedures (including slurrying, coating, assembling, forming, etc.) on battery performance was analysed.and the main materials used were optimized. The 083448 prismatic lithium-ion battery was produced, the cathode material was LiCoO2/LiMn2O4 composite material, the anode material was carbonaceous mesophase spheres(CMS), the electrolyte injected was 1 M L1PF6 in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) at the volume ratio of 1:1. The battery have well rate and temperature characteristics, excellent cycle life (the capacity loss is 5.41% after 300 cycles), lower internal resistance and reliable security, which have achieved the performance requirements of the same kind battery.The lOAh tentative battery was produced by self-making electrode winder for power lithium-ion batteries, the core prerared by the machine have well overlap, flatting and compactness. The testing results show that the power battery has higher specific energy density(the volume energy density is 181.74Wh/L, the mass energy density is 111.57Wh/kg) and preferable cycleability(the capacity loss is 1.38% after 15 cycles at 0.5C rate, the capacity loss is 7.39% after 46 cycles at 1C rate).