碳纳米管膜具有丰富的孔道结构、大比表面积、高导电性及优异的柔性,可通过负载硫形成柔性碳纳米管/硫复合膜,用于锂硫电池正极材料。为了提高锂硫电池的循环稳定性,抑制“穿梭效应”,通过浮动催化化学气相沉积法(FCCVD)分别制备了氮掺杂和硼掺杂的碳纳米管膜(N-CNT膜和B-CNT膜),然后通过浸渍工艺负载硫后得到掺杂型碳纳米管/硫复合柔性自支撑正极膜。微观表征显示:复合膜中硫和碳纳米管在纳米尺度复合均匀。复合膜均具有良好导电性:CNT正极电导率为4.62S/m,N-CNT正极电导率为0.86S/m,B-CNT正极电导率为1.29S/m。作为锂硫电池正极,B-CNT正极表现出最佳性能:在0.2C倍率下首次放电容量达到1197.3mAh/g,200次循环后容量保持在950.2mAh/g,1C倍率下放电比容量仍旧保持在615.5mAh/g。分析认为:碳纳米管良好的导电性和丰富的孔结构同时提供了高效的电子和离子传输通道;硼原子掺杂向碳纳米管引入极性,增强了碳纳米管网络对聚硫离子的吸附作用,抑制了“穿梭效应”。可为高比容、高循环稳定性锂硫电池正极材料研发提供解决思路。
Carbon nanotube(CNT) film has a rich pore structure,large specific surface area,high conductivity and excellent flexibility.It can be loaded with sulfur to form a flexible CNT/S composite film,which is used as a cathode material for lithium-sulfur(Li/S) batteries.In order to improve the cycle stability of Li/S batteries and suppressed the “shuttle effect”,nitrogen-doped and boron-doped CNT films (N-CNT film and B-CNT film) were prepared by floating catalytic chemical vapor deposition (FCCVD).and then load sulfur through immersion process to obtain doped CNT/S composite flexible self-supporting cathode film.The microscopic characterization shown that S and CNT in the composite film were uniformly composited at the nanometer scale.The films had good conductivity:the conductivity of the CNT cathode was 4.62S/m,the conductivity of the N-CNT cathode was 0.86S/m,and the conductivity of the B-CNT cathode was 1.29S/m.As a Li/S battery cathode,B-CNT cathode shown the best performance:the first discharge capacity reached 1197.3mAh/g at 0.2C rate,the capacity remained at 950.2mAh/g after 200 cycles,and the discharge specific capacity stayed at 615.5mAh/g at 1 C rate.The analysis believed that the good conductivity and abundant pore structure of CNT also provided efficient electron and ion transmission channels.Boron atom doping introduced polarity to the CNT,which enhanced the adsorption of polysulfide ions by the CNT network function,and inhibited the “shuttle effect”.The results provided solutions for the research and development of Li/S battery cathode materials with high specific volume and high cycle stability.
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