锂离子电池负极材料用针状焦的石墨化机理及其储锂行为

Graphitization Mechanisms and Electrochemical Performance of Needle Coke Anode for Li-ion Battery

通过考察煤系针状焦在700～2800℃热处理过程中石墨微晶结构的变化规律及其电化学性能,并结合TG-DTG、XRD、SEM、XPS表征方法以及充放电、循环伏安曲线特征,分析了针状焦的石墨化机理及其储锂机制.研究结果表明,随热处理温度的升高,针状焦的类石墨微晶在不断长大的同时,还存在微晶在径/轴向的排列、石墨层间位错线的消失、晶界间C-C六圆环的形成、晶界的消失以及石墨层"褶皱"的平面化等复杂过程,且每个过程的驱动力不同.针状焦经过2800℃石墨化后,可获得较低的Li+充放电电位和稳定的充放电平台,且反复充放电40次后的有效嵌锂容量为305mAh/g.

Effects of heat-treatment temperature on the microstructure and electrochemical properties of coal based nee-dle coke were investigated by TG-DTG,XRD,SEM,XPS analysis and the charge/discharge,cyclic voltammetry curves.The graphitization mechanism of needle coke is suggested as well as the Li＋ extraction-insertion behaviors.With the heat-treatment temperature increasing,the graphite-like crystal grows continuously attended with a complicated process,including the arrangement of crystal along radial/axial direction,dislocation dispersion among graphite layers,hexagonal carbon formation,crystal edge dispersion and folded graphite layer turning to plane.Meanwhile,the driving-forces are far different for different process.When needle coke is graphitized at 2800℃,it exhibits a lower charge/discharge potential and stable charge/discharge platform,and the insertion capacitance of Li＋ can maintain at 305mAh/g even after charge/discharged for 40 cycles.