Li Yuyun, Lei Dongyuan, Yang Shixun, Chen Jiqun, Zhao Zirui, Guo Junming, Xiang Mingwu, Liu Xiaofang, Bai Wei
National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials, Yunnan Minzu University, Kunming, 650500, China.
Key Laboratory of Green-chemistry Materials in University of Yunnan Province, Yunnan Minzu University, Kunming, 650500, China.
Dalton Trans. 2022 Nov 1;51(42):16206-16214. doi: 10.1039/d2dt02625b.
Lithium-sulfur batteries are expected to be prospective candidates of high-energy-storage systems due to their high theoretical specific capacity. However, poor electrical conductivity, severe polysulfide shuttle effect and low sulfur utilization generally cause inferior electrochemical performance, hence hindering the practical development. In this study, common makeup cotton derived self-supporting porous carbon fibers (SPCFs) are prepared by a facile simultaneous activation/pyrolysis process accompanied by the effectively regulation of a KHCO activator. The as-prepared SPCF materials have mutually cross-linked porous skeletons with an ultrahigh specific surface area of 2124.9 m g and a large pore volume of 1.01 cm g, whilst exhibiting robust flexibility. When directly used as a self-supporting carbon current collector for encapsulating sulfur, the interconnected and abundant porous carbon fibers can not only immobilize soluble polysulfides, but also form a highly conductive network for the favorable redox transformation of adsorbed polysulfides. Moreover, the voids between the carbon skeletons can alleviate the volume change of sulfur cathodes during charge/discharge. Owing to these structure merits, the optimized SPCF-based sulfur cathode with a sulfur loading of 3.0 mg cm shows a high coulombic efficiency of approximately 99% and delivers a first discharge capacity of 778 mA h g at 0.2 C. Even at a relatively high current rate of 0.5 C, the reversible capacity of 450 mA h g can be obtained after 300 cycles. The above-mentioned self-supporting porous carbon current collectors provide a guidance for high-performance lithium-sulfur batteries.
锂硫电池因其高理论比容量有望成为高储能系统的潜在候选者。然而，导电性差、严重的多硫化物穿梭效应和低硫利用率通常会导致较差的电化学性能，从而阻碍其实际发展。在本研究中，通过一种简便的同时活化/热解过程，并有效调控KHCO活化剂，制备了源自普通化妆棉的自支撑多孔碳纤维（SPCFs）。所制备的SPCF材料具有相互交联的多孔骨架，比表面积高达2124.9 m²/g，孔体积大至1.01 cm³/g，同时展现出强大的柔韧性。当直接用作封装硫的自支撑碳集流体时，相互连接且丰富的多孔碳纤维不仅可以固定可溶性多硫化物，还能形成一个高导电网络，有利于吸附的多硫化物进行氧化还原转变。此外，碳骨架之间的空隙可以缓解硫阴极在充放电过程中的体积变化。由于这些结构优点，硫负载量为3.0 mg/cm²的优化后的基于SPCF的硫阴极显示出约99%的高库仑效率，在0.2 C下首次放电容量为778 mA h/g。即使在0.5 C的相对高电流速率下，300次循环后仍可获得450 mA h/g的可逆容量。上述自支撑多孔碳集流体为高性能锂硫电池提供了指导。
