SiO2掺杂介孔碳纳米球及其锂硫电池的特性

SiO2-Doped Mesoporous Carbon Nanospheres and Performances of Its Lithium-Sulfur Batteries

为了增加对锂硫电池在循环期间产生的多硫化物的吸附能力,用软模板法在溶液中通过自组装得到了SiO2掺杂介孔碳球,其中极性SiO2可以很好地吸附多硫化物,提高锂硫电池的循环性能。扫描电子显微镜(SEM)和透射电子显微镜(TEM)表征结果表明合成的介孔碳球分散性良好,粒径约为250 nm,具有封闭在内部的孔径约为20 nm的球形孔,封闭的孔结构可以为防止多硫化物流失提供良好的物理屏障。同时氮气吸附和脱附测试结果表明介孔碳球具有很高的比表面积(523 m2/g)和孔体积(0.67 cm3/g),热重分析仪(TGA)数据表明SiO2的质量分数为9.4%,灌硫后硫的质量分数为60%。电化学测试结果表明,在167.5 mA/g的电流密度下,SiO2掺杂介孔碳球的首次循环比容量为1173 mA·h/g,100次循环后比容量仍可达到770 mA·h/g,库仑效率保持在99%。在1675 mA/g的大电流密度下循环了500次后比容量从660 mA·h/g下降到550 mA·h/g,平均每次循环的比容量衰减率仅为0.036%。

In order to increase the adsorption capacity of polysulfides generated during the cycling of lithium-sulfur batteries,SiO2-doped mesoporous carbon spheres were obtained by self-assembly in a solution using a soft template method,in which polar SiO2 could adsorb polysulfides to improve the cycling performances of lithium-sulfur batteries.The characterization results of scanning electron microscopy(SEM)and transmission electron microscopy(TEM)show that the synthesized mesoporous carbon spheres with a particle size of about 250 nm have good dispersibility,and the spherical pores with a pore diameter of about 20 nm are enclosed inside the mesoporous carbon spheres.The closed pore structure can provide a good physical barrier to prevent the loss of polysulfides.At the same time,the nitrogen adsorption and desorption test results show that mesoporous carbon sphere has a high specific surface area(523 m2/g)and a pore volume of 0.67 cm3/g.The thermogravimetric analyzer(TGA)data show that the mass fraction of SiO2 is 9.4%,and the mass fraction of the sulfur after sulfur impregnation is 60%.The electrochemical test results show that at a current density of 167.5 mA/g,the first cycle specific capacity of the SiO2-doped mesoporous carbon spheres is 1 173 mA·h/g.After 100 cycles,the specific capacity can still reach 770 mA·h/g,and the Coulomb efficiency is maintained at 99%.After 500 cycles under a large current density of 1 675 mA/g,the specific capacity decreases from 660 mA·h/g to 550 mA·h/g,and the average specific capacity decay rate per cycle is only 0.036%.