固相-碳热还原法制备高密度LiFePO4/C复合材料及其电化学性能

以无机Fe2O3和有机柠檬酸铁(FeC6H5O7·5H2O)两种价廉的三价铁化合物为铁源, 利用柠檬酸铁中的柠檬酸根为碳源和还原剂, 通过固相-碳热还原法成功制备了高密度LiFePO4/C复合材料. 采用热重与差示扫描量热法研究了反应历程, 并利用X射线衍射、扫描电镜、激光粒度分布仪、振实密度测试仪和恒流充放电技术对材料的微观结构和物理化学性能进行了表征. 研究结果表明, 在700 ℃下焙烧制备的材料结晶良好、粒径大小适中, 具有优良的电化学性能和较高的振实密度. 该材料在17 mA·g-1电流密度下充放电可以得到129 mAh·g-1的首次放电比容量, 20周循环后比容量基本无衰减. 其晶粒由纳米颗粒和微米颗粒组成, 呈多峰的粒径分布, 振实密度达1.41 g·cm-3.

Electrochemical Performance of High-Density LiFePO4/C Composites Synthesized by Solid State-Carbothermal Reduction Method

High-density LiFePO4/C composites were successfully synthesized by a solid state-carbothermal reduction method using Fe2O3 and citrate ferric as Fe3+ precursors in which the citrate acid radical acted as both reducing agent and carbon source. The reaction mechanism was investigated using thermogravimetric and differential scanning calorimetry (TG-DSC). The structures and physicochemical properties of the LiFePO4/C composites were characterized by X-ray diffraction, scanning electron microscopy, laser particle-size distribution measurement, tap-density testing and galvanostatic charge-discharge. Results indicated that the material calcined at 700 ℃ possessed a crystal olivine structure, a moderate particle size, excellent electrochemical performance and a high tap-density. It had a high initial discharge capacity of 129 mAh·g-1 at 17 mA·g-1 charge-discharge current density without decaying after twenty cycles. This material, which had a multi-peak particle size distribution, consisted of nanometer-sized and micrometer-sized particles and had high tap-density of 1.41 g·cm-3.