锂硫电池硫-导电炭黑复合正极材料的研究

Research on sulfur-conductive carbon black composite as cathode materials for the lithium-sulfur battery

采用富含微孔的导电炭黑BP2000和无孔导电炭黑VXC72作为导电载体材料,分别与单质硫进行复合制备硫-导电炭黑复合材料,研究微孔孔隙对硫-导电炭黑复合材料电化学性能的影响。通过扫描电子显微镜法(SEM)、X-射线衍射光谱法(XRD)、低温氮气吸附法对该材料进行了结构表征,利用循环伏安扫描和恒电流充放电技术对复合材料的电化学性能进行了测试。结果表明:硫与导电炭黑复合后,能较好地改善单质硫的导电性和电化学性能,具有高比表面积微孔结构的炭黑BP2000因其高吸附性可限制聚硫离子的溶解和扩散,表现出较高的比容量和较好的大电流充放电能力。样品S/BP2000在100 mA/g充放电时,首周放电比容量达1 274.4 mAh/g,硫的利用率达到了76.1%;在1 600mA/g的大电流密度充放电时,其放电容量明显高于S/VXC72与单质硫电极,并表现出较好的倍率性能;经过120次循环后充放电效率保持在99.1%,较之普通硫电极其电化学性能得到显著改善。

In order to investigate the effect of sulfur-conductive carbon black composite on the sulfur cathode electrochemical performance of lithium-sulfur battery, sulfur-carbon composite material was prepared by thermally treating a mixture of elemental sulfur with a commercial microporous carbon black BP2000 and nonporous carbon black VXC72, respectively. The sulfur/carbon composite was characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and low-temperature nitrogen adsorption method tests. The electrochemical performance of the composite as cathode material was evaluated by the galvanostatic method and cyclic voltammetry （CV）. It is found that the sulfur-carbon composite material can improve the conductivity of the elemental sulfur and electrochemical performance. S/BP2000 composite can deliver a high specific capacity of 1 274.4 mAh/g at the first discharge and the utilization of sulfur reached 76.1%. Meanwhile, at a large current density（1 600 mA/g）, S/BP2000 composite showed good rate capability and maintained a charge-discharge efficiency of 99.1% after 120 cycles, these demonstrated that the narrow micropores of BP2000 due to strong adsorption could minimize the dissolution and diffusion of poly-sulfides. Therefore, the electrochemical properties of the sulfur cathode with the addition of BP2000 were remarkably improved.