摘要
锂硫电池中基于常规环状S_8分子的正极研究非常普遍,然而硫的另一类同素异形体链状硫,相应的电化学研究却非常有限。这里,我们将硫链装入单壁和双壁碳纳米管中,作为一模型体系,研究链状硫在锂硫电池中的电化学嵌脱锂过程。电化学测试证明链状硫具有高电化学活性,电化学反应与环状S_8有鲜明区别。借助多种原位和半原位分析手段,我们发现链状硫的锂化-去锂化为固相反应机理,并且长硫链在电化学反应过程中变为短硫链(图1)。固相反应的优势是循环过程中的结构稳定性,其缺点是缓慢的动力学。由于电化学反应过程中硫链自发缩短,动力学过程自发得到优化。短链硫的电平台较高,动力学优于长链硫。~([1])关于链状硫电化学的研究是对现有锂硫电池中硫电化学理论的有益补充,为今后开发基于链状硫的硫正极提供了理论指导。
We use 1D S chains confined in single-walled or double-walled carbon nanotubes as a model system to study the electrochemistry of S chains in Li-S batteries.The electrochemical test attests to the high electrochemical activity and extinctive electrochemistry of S chains compared with conventional S_8.We discover a solid-phase lithiation/delithiation mechanism of S chains and S chains degradation to short chains during reaction.The advantage of is structure cycling stability while the disadvantage is a sluggish kinetics.Intriguingly,the kinetic process is improved spontaneously when S chains become short.The short S chains exhibit higher discharge plateaus and better kinetics.The electrochemistcal study of S chains provides good supplement to the existing knowledge of S electrochemistry in Li-S batteries and will pave the way for new S cathodes based on S chains.
引文
[1]Yang,C.-P.;Yin,Y.-X.;Guo,Y.-G.;Wan L.-J.J.Am.Chem.Soc.2015,137:2215.
