Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA.
Chemistry. 2013 Jun 24;19(26):8621-6. doi: 10.1002/chem.201300886. Epub 2013 May 13.
The cathodic reactions in Li-S batteries can be divided into two steps. Firstly, elemental sulfur is transformed into long-chain polysulfides (S8 ↔ Li2S4), which are highly soluble in the electrolyte. Next, long-chain polysulfides undergo nucleation reaction and convert into solid-state Li2S2 and Li2S (Li2S4 ↔ Li2S) by slow processes. As a result, the second-step of the electrochemical reaction hinders the high-rate application of Li-S batteries. In this report, the kinetics of the sulfur/long-chain-polysulfide redox couple (theoretical capacity=419 mA h g(-1)) are experimentally demonstrated to be very fast in the Li-S system. A Li-S cell with a blended carbon interlayer retains excellent cycle stability and possesses a high percentage of active material utilization over 250 cycles at high C rates. The meso-/micropores in the interlayer are responsible for accommodating the shuttling polysulfides and offering sufficient electrolyte accessibility. Therefore, utilizing the sulfur/long-chain polysulfide redox couple with an efficient interlayer configuration in Li-S batteries may be a promising choice for high-power applications.
锂硫电池的阴极反应可以分为两步。首先，单质硫转化为长链多硫化物（S8 ↔ Li2S4），它们在电解液中高度溶解。然后，长链多硫化物通过缓慢的成核反应转化为固态 Li2S2 和 Li2S（Li2S4 ↔ Li2S）。因此，电化学反应的第二步阻碍了锂硫电池的高倍率应用。在本报告中，实验证明硫/长链多硫化物氧化还原对（理论容量=419 mA h g-1）在锂硫系统中的动力学非常快。具有混合碳夹层的锂硫电池在高 C 率下经过 250 次循环后仍保持出色的循环稳定性和高活性材料利用率（超过 90%）。夹层中的介孔/微孔负责容纳穿梭多硫化物，并提供足够的电解质可达性。因此，在锂硫电池中利用具有高效夹层结构的硫/长链多硫化物氧化还原对可能是高功率应用的一个有前途的选择。
