Spinel Lithium Manganese Oxide Wet Chemical Synthesis And Its Performance Testing,

The spinel LiMn₂O₄ and cobalt-doped or chrome-doped lithium manganese oxides of the cathode for rechargeable lithium-ion batteries was synthesized by wet chemical process which is considered as a most promising method for the synthesis of spinel lithium manganese oxides. Based on the theoretical analysis and experimental study, the influence of technological conditions on the chemical composition and the powder characteristics, such as particle size, morphology, structure and so on, was systematically investigated by modern Analytical methods of XRD, SEM, BET, TGA/DTA and so onThe changes of the structure, particle size ,morphology and specific surface area of the products prepared in different systems of salts were discussed. The results suggest that the precursors from different systems of salts have similar characteristic and the system of nitrate be in favor of embedded Li+ inserting manganese oxides.The characteristic of different products at different calcinating temperatures and time was investigated. The results show that perfect spinel LiMn₂O₄ crystals can be obtained from the precursor of LiMn2O4 after being calcinated. It is founded that calcinating temperature has great influence on the crystal structure of LiMn2O4. With the elevating of the temperature, the crystal structure becomes more perfect and the particle size gets larger. A spinel LiMn2O4 with regular crystal structure and well-distributed particle size can be obtained after being calcinated for 4 h at 700 "C. However, it is also observed that the calcinating time has less effect on the perfection of the LiMn2O4 structure and the samples maintain the same XRD patterns when the calcinating time is prolonged at the same temperature.Cobalt-doped or chrome-doped lithium manganese oxides were prepared by the wet chemical process and the circling performance of the products were studied. The results shown that the Cobalt-doped or chrome-doped spinel has the same structure as spinel LiMn2O4 and is more slender and uniformity.A test cell was tested, presented by using the sample Lii.o4Mn1.96O4or Li1.05Mn1.95O4 as cathode active material. Electrical properties of samples were depicted by charging and discharging curves respectively. Emphasis was placed on the two kind of electrolytes, 1M UC1O4/EC+DEC (1:1wt) 1MLiPF6/EC+DEC(1:1wt).The electrochemical properties of the sample Lii.o4Mni.96O4or Lii.osMni.95O4 used asa cathode active mater of a test cell were examined in both IM LiQO4/EC+DEC (l:lwt)å’Œ1M LiPF6/EC+DEC(l:lwt) electrolytes. The battery with LiClO4 electrolyte has higher capacity and more stable performance than that with LiPFe electrolyte. When the sample Lii.o5Mni.95O4 is in the electrolyte of IM LiCKVEC+DEC (1:1 wt), the first discharge capacity is 118.0mAh/g, and the sixth discharge capacity isl!2.9 mAh/g. At the same condition, the capacity of the sample Lii.osMni.9sO4 respectively is 104.9 mAh/g and 80.2 mAh/g in the first circle and the second circle.The results of constant-current cyclic test show that the cycling stability of the cobalt-doped or chrome-doped lithium manganese oxides is more stable than the spinel LiMnaCU- For example, the first discharge capacity of the sample Lii.wCr0.03Mn1.93O4 in the IM LiPF6/EC+DEC(l:lwt) is 115.4mAh/g, and the second discharge capacity is 113.0 mAh/g. Compared with Li-rich spinel Li1.04Cr0.03Mn1.93O4 and Lii.osMni.95O4, the cobalt-doped or chrome-doped spinel has higher capacity and more stable circling performance.