锰掺杂磷酸铁锂的合成和电化学性能研究

Synthesis of Mn-doped LiFePO_4 Cathode Materials and Their Electrochemical Performance

针对磷酸铁锂本征电导率较低、倍率性能较差问题,在以十六烷基三甲基溴化铵为模板、柠檬酸为螯合剂的协同作用下,先共沉淀后水热合成,然后在惰性气氛中高温煅烧形成高结晶度的橄榄石相锰掺杂磷酸铁锂LiFe_((1-x))Mn_xPO_4(0≤x≤0.5),研究了水热反应温度和表面活性剂对产物的影响.利用扫描电镜和X线衍射对材料的形貌和晶体结构进行表征,测试了材料的电化学性能.研究结果表明Mn成功掺杂到晶格中的Fe位,并有效改善了材料的离子电导率,使倍率性能提高约10%.

Aiming at the low intrinsic electronic conductivity and unsatisfactory rate performance of LiFePO4, a series of LiFe（1-x）MnxPO4 （0≤x≤0.5） with adjustable Mn doping content are synthesized by hydrothermal reaction followed by calcination through the synergistic mechanism including both templating and chelating effects contributed by cetyltrimethyl ammonium bromide （CTAB） and citric acid. The roughness of the sample particle surface can be controlled by citric acid chelation. The Mn ions were con- firmed to be homogeneously substituted at the iron sites and no impurity phase was detected through XRD analysis. The rate performance of LiFe（1--x）Mn^PO4 with x=0.1 or 0.2 has increased about 10% compared to that of LiFePO4, which suggests that proper Mn doping in crystal is beneficial to improve material intrinsic conductivity and facilitate the Li-ion transfer.