LiFePO_4/C复合材料的制备和氧化过程

Preparation and oxidation process of LiFePO_4/C composites

采用XRD测试技术对不同煅烧温度下所得的LiFePO4/C(LFP/C)产物和不同温度氧化处理LFP/C的产物进行了研究,并结合差热分析(DTA)对含碳LFP前驱体和700℃煅烧制备的LFP/C样品的测试结果,研究了LFP/C的制备过程和LFP/C在空气气氛下的氧化过程。实验结果表明,含碳LFP前驱体在350～400℃区间完全分解。当煅烧温度提升至400℃时,含碳LFP前驱体分解产生的FeO、Li4P2O7和H4P2O7反应生成LFP。当煅烧温度升至600℃时可得到无杂相的LFP。进一步提高反应温度有利于LFP结晶度的提高。LFP的最佳煅烧温度应控制在700℃左右。LFP/C样品中的LFP在250～550℃区间被氧化为β-Li3Fe2(PO4)3和α-Fe2O3。LFP/C样品中的碳在750℃时被完全氧化。从提高实验准确度考虑,采用热重法对LFP/C进行碳含量测定时应尽可能将测试温度覆盖到750℃。

LiFePO4/C（LFP/C） samples have been synthesized at different calcination temperatures,and LFP/C oxidation products have also been prepared by oxidizing LFP/C at different temperatures.The oxidation process in atmosphere of LFP/C was analyzed with XRD and differential thermal analysis（DTA） for the carbonaceous LFP precursor and LFP/C samples calcinated at 700 ℃.The experimental results show that the carbonaceous LFP precursor was decomposed completely in the range of 350–400 ℃.LFP was produced by FeO,Li4P2O7and H4P2O7which were decomposed from the carbonaceous LFP precursor when the calcination temperature increased to 400 ℃.LFPwithout impurity phase was obtained when the calcination temperature reached 600 ℃.Increasing reaction temperature could contribute to improvement of crystallinity of LFP.The optimal calcination temperature of LFP was around 700 ℃.LFP in LFP/C sample was oxidized toβ-Li3Fe2（PO4）3andα-Fe2O3between 250 ℃ and 550 ℃.The carbon in LFP/C sample was oxidized completely at 750 ℃.Inconsiderationofexperimentalaccuracy,thetesttemperatureshouldbecontrolledto750℃asfaraspossiblewhentestingcarbon content of LFP/C with the thermal gravimetric method.