复合碳源包覆对LiFePO_4/C正极材料性能的影响

Effects of the sources of composite carbon on the performance of LiFePO_4/C cathode materials

采用固相合成法在惰性气氛下合成了LiFePO4/C复合正极材料,采用比表面积(SSA)、X射线衍射(XRD)、扫描电镜(SEM)以及电化学测试等手段对合成样品进行了结构表征和性能测试;考察了采用蔗糖、柠檬酸、蔗糖与炭黑掺杂、蔗糖柠檬酸与炭黑掺杂等不同碳源对最终复合正极材料性能的影响。结果表明,当采用蔗糖柠檬酸与炭黑的复合碳源时,正极材料在碳含量相近的情况下比表面积得到了控制,粒度分布和振实密度没有明显的变化,0.1C比容量达154 mAh/g,1C比容量达到了142 mAh/g;但是采用复合碳源,材料的初始内阻和极化程度有所增大。

Olivine LiFePO4/C composite cathode materials have been synthesized by a solid state method in an inert atmosphere. The physical parameters, crystal structure and electrochemical performance were characterized by specific surface area measurements, X-ray diffraction, scanning electron microscopy and electrochemical performance testing. The effects of using different combinations of carbon sources-sucrose, acetylene black and citric acid-on the performance of the as-synthesized cathode materials were investigated and the origins of the observed differences were analyzed. The results demonstrated that when a composite carbon source （sucrose, acetylene black and citric acid） was used, the tap density and particle size （D50） of the materials were comparable to the corresponding values obtained with the same amount of a single carbon precursor, but the specific surface area was reduced. The initial discharge capacity of the material derived from the composite carbon source was higher-154 mAh/g at room temperature and a discharge rate of 0.1C, and 142 mAh/g at discharge rate of 1C-but the values of initial impedance and polarization were also increased.