| The lithium-rich manganese-based materials have received much attention due to their high discharge capacity. However, many problems, such as low initial columbic efficiency and poor rate performance, have to be solved before these materials are practically used in commercial lithium-ion batteries. These problems are closely related to the electrochemical activity of Li2Mn03in materials. A highly activated Li2MnO3contribute to the capacity of lithium-rich manganese-based cathode material. Better understanding of the structure and the electrochemical behavior of Li2Mn03itself is helpful for the development of high-performance lithium-rich manganese-based cathode material.In this paper, Li2MnO3were synthesized from two different raw materials by solid state reaction. The dependence of stacking faults on the synthesis temperature was studied by X-Ray diffraction (XRD) and electron beam diffraction (SAED). The results show that the higher the synthesis temperature, the less the stacking faults. Morphology of samples sintered at low temperature are aggregates of nano plate, which grow to larger particles with increasing temperature. The sample sintered at750℃for twenty hours (SS750-20) are spherical assembly of nano plates. The average particle size reaches43μm and the tap density is1.78g/cm3, which is helpful to obtaining high energy density.The electrochemical test suggested that well crystallized Li2Mn03contain less stacking fault and give a low discharge capacity. The sample sintered at900℃for twenty hours (SS900-20) even haven’t been activated after100cycles. However, materials with high degrees of stacking faults show high electrochemical activity. Sample SS750-20(The sample sintered at750℃for twenty hours) delivers its first charge/discharge capacity up to203.9/139.3mAh g-1, and it remains169.2mAh g-1after70cycles. And those poor crystallized Li2Mn03, which were calcinated at low temperature, didn’t show high capacity as desired.Analysis suggested Li2MnO3will gradually transform to spinel during the electrochemical cycling. The speed of spinel transition is related to the calcinating temperature. The Li2MnO3cathode material calcined at low temperature is easy to transform to spinel during cycling. However, it is difficult in the material sintered at high temperature due to its good crystallinity. The capacity of many samples increased in cycle. Part of it come from the electrochemical activity of the spinel, and due to the progressively activation of Li2MnO3The formation of Li2CO3and its effect on electrochemical performance have studied in detailed. The results suggest that Li2CO3has been generated during calcination, by reaction of LiOH and cathode material with CO2in atmosphere. The XRD dates implied that Li2CO3in power decomposed gradually with increasing sintering temperature. And excess lithium is in favor of forming Li2CO3The Li2CO3formed in solid state reaction could in the form of particle or on the surface of material. The lithium impurities on surface can be rinsed away by water washing and the pH will change accordingly. Both washed and unwashed samples have large irreversible capacity in first cycle. The exist of Li2CO3also increased the surface film resistance and charge transfer resistance, which is impeded the transportion of lithium ions.
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