리튬/유황전지용 미세기공 탄소나노섬유를 이용한 양극소재에 관한 연구
리튬유황전지 탄소나노섬유 양극;
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Recently, the demand of batteries with high energy density for energy storage systems and electronic vehicles are growing and lithium-sulfur (Li-S) batteries have attracted great attentions. Li-S batteries have a high theoretical capacity (1675 mAh/g) and a high energy density (2600 Wh/kg), which is three to five times higher than recent lithium ion batteries. In addition, sulfur is abundant in nature and non-toxic, making it promising candidates for the next generation energy storage. However, there are still many problems that challenge the practical application of Li-S batteries. The insulating nature of sulfur and its reduction product lithium sulfide leads to the low active material utilization. More severe problem is that the intermediates, lithium polysulfides, are soluble in the liquid electrolyte and shuttle between the cathode and anode, generating loss of active material and corrosion of lithium anode. Herein, an attempt to solve these problems using a carbon nanofiber-sulfur composite has performed. A carbon nanofiber was prepared by electrospinning method with polyacrylonitrile (PAN) solution with different SiO2 content. An activation process with KOH to generate micropores was then carried out and the KOH concentration used was controlled to obtain the carbon nanofiber with best pore systems. A carbon nanofiber with high surface area of 2287.2 m2/ganda high pore volume of 2.27 cm3/gpossessing an average pore size of about 4.6 nm were synthesized for confining sulfur. The carbon nanofiber-sulfur composite was prepared by a two-step thermal treatment at 155 °C for 12 h and at 300 °C for another 20 h. The Li-S cells with the carbon nanofiber-sulfur composite obtained a high specific capacity of about 837 mAh/g at C/5 rate after 50 cycles of charge/discharge. It proves the superiority of this highly porous carbon nanofiber used as a conductor and vessel for sulfur encapsulation.