【摘要】 采用溶胶凝胶法,以LiOH,Fe2C2O4和NH4H2PO4为原材料,以乙二醇为络合剂和碳源,通过对合成LiFePO4的前驱体在不同温度和时间的分步煅烧,获得了兼具良好结晶性、亚微米颗粒尺寸和含适量原位引入Fe2P的LiFePO4/C复合材料,该材料作为锂离子电池正极材料表现出优良的倍率性能.采用X射线衍射、扫描电子显微镜、元素分析等方法和恒电流充放电等测试技术对获得的LiFePO4/C材料的结构和电化学性能进行研究.结果表明,分步联合煅烧是综合实现适量Fe2P相的原位引入、LiFePO4颗粒尺寸控制和提高LiFePO4结晶性的有效途径,其显著提高了LiFePO4/C材料的高倍率性能.经600℃煅烧20 h再经700℃煅烧4 h获得的含4wt%Fe2P和3wt%C的LiFePO4/C复合正极材料,在1,10和20 C放电条件下的放电容量分别达到140,110和100 mAh/g.更多还原

【Abstract】 LiFePO4/C composite with high crystallinity,sub-micron particle size and suitable content of in-situ introduced Fe2P was synthesized by a sol-gel method,in which LiOH,Fe2C2O4and NH4H2PO4were used as starting materials,and ethylene glycol was used as complexing agent and carbon source.The precursor of LiFePO4was calcined at a comparatively low temperature for relatively long time combined a following calcination at a comparatively high temperature for relatively short time.The composite shows high-rate capability as cathode material for lithium-ion batteries.The structure and the electrochemical properties of the LiFePO4/C composites synthesized by different calcination parameters were analyzed by X-ray diffraction,scanning electron microscopy,element analysis and electrochemical testing of galvanostatic charge-discharge,etc.The results show that the step-wise calcination at different temperatures for different times is an effective approach to obtain suitable amount of in-situ Fe2P,control the particle size and enhance the crystallinity of LiFePO4,which results in a significant improvement in the high-rate capability of LiFePO4.The LiFePO4/C composite synthesized at a calination temperature of 600°C for 20 h followed by a further calcination at 700°C for 4 h has 4wt% Fe2P and 3wt% C.The composite possesses discharge capacities of 140,110 and 100 mAh/g at discharge rates of 1,10 and 20 C,respectively.更多还原