ACS Appl Mater Interfaces. 2019 Oct 2;11(39):35729-35737. doi: 10.1021/acsami.9b11967. Epub 2019 Sep 23.
Here, we report that in situ MoS and S cathodes (MGC) prepared by simple decomposition of (NH)MoS facilitate direct formation of LiS and suppress the long-term problem associated with polysulphide shuttling in Li-S batteries. For comparison, we prepared ex situ MoS and S cathodes (EMS) with a similar S/MoS mole ratio to that of in situ-prepared cathodes. Discharge capacity of EMS cathodes dropped by 80% after first few cycles, while assembled MGC cells demonstrated an initial discharge capacity of 1649 mA h/g, achieving close to theoretical capacity of elemental sulfur (1675 mA h/g) at C/3 and a reversible capacity of 1500 mA h/g was obtained in further cycles. The MoS nanostructure evolution after initial discharge helped in extending the cycle life of assembled cells even at a high C rate. Density functional theory (DFT) calculation was performed to understand the structural stability of intermediate MoS and possible electrochemical reactions pertaining to Li insertion in MoS and S. Based on DFT studies, MoS undergoes stoichiometric decomposition to stable MoS and S. Furthermore, electrochemical analysis confirmed the redox activity of MoS and S at 1.3 and 1.8 V against Li/Li, respectively.
在这里，我们报告说，通过简单分解（NH）MoS 制备的原位 MoS 和 S 阴极（MGC）有利于直接形成 LiS，并抑制了 Li-S 电池中与多硫化物穿梭相关的长期问题。为了进行比较，我们用类似于原位制备的阴极的相似 S/MoS 摩尔比制备了异位 MoS 和 S 阴极（EMS）。EMS 阴极在几个循环后放电容量下降了 80%，而组装的 MGC 电池的初始放电容量为 1649 mA h/g，在 C/3 时达到了单质硫的理论容量（1675 mA h/g），在进一步的循环中获得了 1500 mA h/g 的可逆容量。初始放电后 MoS 纳米结构的演变有助于延长组装电池的循环寿命，即使在高 C 率下也是如此。进行了密度泛函理论（DFT）计算，以了解中间 MoS 的结构稳定性和与 MoS 和 S 中 Li 插入相关的可能电化学反应。基于 DFT 研究，MoS 经历了化学计量分解，生成稳定的 MoS 和 S。此外，电化学分析证实了 MoS 和 S 在 1.3 和 1.8 V 相对于 Li/Li 的氧化还原活性。
