三维双金属硫化物Co9S8/MoS2/C异质结用于增强钠离子存储

A bimetallic sulfide Co9S8/MoS2/C heterojunction in a three-dimensional carbon structure for increasing sodium ion storage

  • 摘要: 钠离子电池(SIBs)的阳极材料一直备受研究关注,但缓慢的动力学行为和较大的体积变化限制了其在实际应用中的推广。为了克服这些问题,本研究利用金属有机框架和MoS2的优异性能,设计并制备了具有稳定骨架结构的复合材料。以Co-ZIF为前驱体,添加Mo源材料,在高温硫化烧结的过程中,构建了花状的Co9S8/MoS2/C复合材料,探究其在不同温度条件下的结构和电化学性能。此外,通过密度泛函理论(DFT)分析了Co9S8(001)/MoS2异质结对扩散动力学的影响。结果表明,电子结构在异质结构的界面处发生了重塑,Co9S8/MoS2表现出典型的金属性和显著增强的电子导电性。在所有样品中,700 °C合成的阳极材料Co9S8/MoS2/C具有更稳定的结构和优异的电化学性能。当电流密度从4000恢复到40 mA g−1时,Co9S8/MoS2/C-700的放电容量可以从368 mAh g−1完全恢复到571 mAh g−1,并稳定在543 mAh g−1。综上所述,本研究提供了一些关于异质结材料合理制备的思路,有助于设计高性能的金属钠离子电池负极复合材料。

     

    Abstract: The synthesis of high-rate and long-life anode materials for sodium ion batteries (SIBs) has attracted much attention. However, the slow kinetics and large increase in volume of the batteries remain major problems. Both metal-organic frameworks and MoS2 have shown properties suitable for SIBs, making research on their composite systems an attractive area of research. We report the formation of flower-like Co9S8/MoS2/C composites by a simultaneous vulcanization-carbonization process using MoCl5 as the Mo source and a 2-methylimidazole cobalt salt as the Co and C precursor at different temperatures(600, 700 and 800 °C)in sublimed sulfur. The effect of the heterojunction on the diffusion kinetics was analyzed using density functional theory. The results indicate that the electronic structure is different at the interface in the heterogeneous structure, exhibiting typical metallic properties and better electronic conductivity. In addition, the anode material Co9S8/MoS2/C synthesized at 700 °C had the most stable structure and best electrochemical performance of the three samples. Notably, the discharge capacity of Co9S8/MoS2/C-700 fully recovered from 368 to 571 mAh g−1 and then stabilized at 543 mAh g−1 when the current density was restored from 4 000 to 40 mA g−1. This work demonstrates the preparation of heterojunction materials for composite anode materials as a step to producing high-performance metal SIBs.

     

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