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Enhancing the Li Storage Capacity and Initial Coulombic Efficiency for Porous Carbons by Sulfur Doping

Ning, Guoqing, Ma, Xinlong, Zhu, Xiao, Cao, Yanming, Sun, Yuzhen, Qi, Chuanlei, Fan, Zhuangjun, Li, Yongfeng, Zhang, Xin, Lan, Xingying, Gao, Jinsen
ACS Applied Materials & Interfaces 2014 v.6 no.18 pp. 15950-15958
anodes, batteries, carbon, carbonization, magnesium sulfate, nanomaterials, sulfur
Here, we report a new approach to synthesizing S-doped porous carbons and achieving both a high capacity and a high Coulombic efficiency in the first cycle for carbon nanostructures as anodes for Li ion batteries. S-doped porous carbons (S-PCs) were synthesized by carbonization of pitch using magnesium sulfate whiskers as both templates and S source, and a S doping up to 10.1 atom % (corresponding to 22.5 wt %) was obtained via a S doping reaction. Removal of functional groups or highly active C atoms during the S doping has led to formation of much thinner solid-electrolyte interface layer and hence significantly enhanced the Coulombic efficiency in the first cycle from 39.6% (for the undoped porous carbon) to 81.0%. The Li storage capacity of the S-PCs is up to 1781 mA h g–¹ at the current density of 50 mA g–¹, more than doubling that of the undoped porous carbon. Due to the enhanced conductivity, the hierarchically porous structure and the excellent stability, the S-PC anodes exhibit excellent rate capability and reliable cycling stability. Our results indicate that S doping can efficiently promote the Li storage capacity and reduce the irreversible Li combination for carbon nanostructures.