LiMn 2O 4电极材料的碳包覆改性电化学性能研究.docx

硕十学位论文 硕十学位论文 摘要 次后容量衰减率分别为O．3％和O．5％。利用交流阻抗技术及Zview软 件对所得阻抗谱进行拟合，可以得出包覆与未包覆电极材料的电荷转 移电阻分别为16．28Q和45．02fl，Li+的扩散系数分别为3．62x10‘12 cm2．s‘1和1．46x 1 0’13 cm2．s一。 关键词：尖晶石LiMn204，碳包覆，球形，电化学性能，电极过程动 力学 U 硕十学位论文 硕十学位论文 ABSTRACT AB STRACT Carbon—coated spinel LiMn204 compostte cathode was synthesized by melt impregnating method using LiN03，electrolytic manganese(EMD) and as·-prepared carbon xerogel as raw material for Li··ion baaery．The crystalline structure，morphology and elements of particles were analyzed by X—ray diffraction(XRD)，scanning electromicroscopy(SEM)and energy-dispersion X—ray spectroscopy(EDX)．The results showed that the material obtained is pure spinel—type phase and the particles of carbon-coated LiMn204 have no aggregation，the carbon content was 4．53 、以．％in cathode material．The carbon—coated LiMn204 cathode showed excellent cycling performance at different C rates．The reason was that carbon film coated on the grains ensured a good electronic contact， restraining the dissolving of Mn and polarization on electrode surface during charge—diacharge．The electrochemical AC impedance spectroscopy showed that the electrical conductivity of LiMn204 cathodes Was enhanced and the charge transfer resistance reduced obviously during electrochemical reaction process． LiMn204 and its carbon-coated materials were synthesized by euecitc sel f-mixing method using glucose as carbon source．Galvanostatic charge／discharge tests of carbon·coated and uncoated cathode were carried out at 0．2C rate at room temperature．and the initial discharge capacity were 11 8．2 mAh’g_and ll 2．2 mAh。g．。，respectively,the coulomb efficiency were 94．9％and 94％，respectively．Li十diffusion coefficients which were calculated by cyclic voltammetry measurement， were 5．2x lO-13cm2．s。1 and 1．7x 10-t3cm2．