Zhang Xinxin, Zhou Xiaocheng, Wang Yu, Li Yafei
Jiangsu Key Laboratory of New Power Batteries, Jiangsu Collaborative Innovation Centre of Biomedical Functional Materials, School of Chemistry and Materials Science, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
Phys Chem Chem Phys. 2023 Apr 5;25(14):10097-10102. doi: 10.1039/d3cp00042g.
Developing efficient cathode materials with good conductivity to restrain the shuttle effect and promote the reaction kinetics has been a key scientific issue for the development of lithium-sulfur (Li-S) batteries. Here, by means of first-principles computations, we demonstrate that the NbS monolayer is a promising cathode anchoring material for Li-S batteries. It has a metallic feature that improves the conductivity of sulfur and lithium polysulfides (LiPSs) and promotes the electron transfer ability. The discharge products LiPSs are strongly anchored on the NbS monolayer without structural distortion, which effectively alleviates the shuttle effect. Remarkably, the reductions of sulfur to soluble LiPSs are spontaneous exothermic reactions while the subsequent reductions to insoluble LiPSs are endothermic reactions with low Gibbs free energy barriers (0.09-0.18 eV) and reaction activation barriers (0.83-0.93 eV), ensuring the rapid discharge process. In addition, the barriers of LiS decomposition and Li atom diffusion are only 0.64 and 0.18 eV, respectively, which improve the reaction kinetics in the charging process and the cycling life of batteries. These results suggest that the NbS monolayer can be utilized as a promising anchoring material for Li-S batteries to achieve high reversible capacity and conversion efficiency.
开发具有良好导电性的高效正极材料以抑制穿梭效应并促进反应动力学，一直是锂硫（Li-S）电池发展的关键科学问题。在此，通过第一性原理计算，我们证明了NbS单层是一种有前景的用于Li-S电池的正极锚定材料。它具有金属特性，可提高硫和多硫化锂（LiPSs）的导电性，并促进电子转移能力。放电产物LiPSs牢固地锚定在NbS单层上而无结构畸变，这有效地减轻了穿梭效应。值得注意的是，硫还原为可溶性LiPSs是自发放热反应，而随后还原为不溶性LiPSs是具有低吉布斯自由能垒（0.09 - 0.18 eV）和反应活化能垒（0.83 - 0.93 eV）的吸热反应，确保了快速放电过程。此外，LiS分解和Li原子扩散的能垒分别仅为0.64和0.18 eV，这提高了充电过程中的反应动力学以及电池的循环寿命。这些结果表明，NbS单层可作为一种有前景的用于Li-S电池的锚定材料，以实现高可逆容量和转换效率。
