Here, we report that in situ MoS₂ and S cathodes (MGC) prepared by simple decomposition of (NH₄)₂MoS₄ facilitate direct formation of Li₂S and suppress the long-term problem associated with polysulphide shuttling in Li–S batteries. For comparison, we prepared ex situ MoS₂ and S cathodes (EMS) with a similar S/MoS₂ 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 MoS₂ 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 MoS₃ and possible electrochemical reactions pertaining to Li⁺ insertion in MoS₂ and S. Based on DFT studies, MoS₃ undergoes stoichiometric decomposition to stable MoS₂ and S. Furthermore, electrochemical analysis confirmed the redox activity of MoS₂ and S at 1.3 and 1.8 V against Li/Li⁺, respectively.

中文翻译：

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先进的Li-S电池稳健的MoS ₂和S阴极的高效合成和表征：结合实验和理论研究

在这里，我们报告说，通过简单分解（NH ₄）₂ MoS ₄制备的原位MoS ₂和S阴极（MGC）有助于Li ₂ S的直接形成，并抑制了与Li–S电池中多硫化物穿梭有关的长期问题。为了进行比较，我们准备了具有类似S / MoS _2的异位MoS ₂和S阴极（EMS）摩尔比与原位制备的阴极的摩尔比。在最初的几个循环后，EMS阴极的放电容量下降了80％，而组装的MGC电池的初始放电容量为1649 mA h / g，在C / 3和C / 3时达到了接近元素硫的理论容量（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 ₂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速率下也是如此。进行密度泛函理论（DFT）计算以了解中间MoS ₃的结构稳定性以及与Li ⁺插入MoS ₂和S中有关的可能的电化学反应。基于DFT研究，MoS ₃进行化学计量分解，生成稳定的MoS ₂和S。此外，电化学分析证实，MoS ₂和S分别在1.3和1.8 V下对Li / Li ⁺的氧化还原活性。