物理化学学报 >> 2019, Vol. 35 >> Issue (2): 193-199.doi: 10.3866/PKU.WHXB201801241

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NiCo2S4六角片作为钠离子电池负极材料的电化学性能及储钠动力学

赵明宇,朱琳,付博文,江素华,周永宁,宋云*()   

  • 收稿日期:2018-01-11 发布日期:2018-07-10
  • 通讯作者: 宋云 E-mail:songyun@fudan.edu.cn
  • 基金资助:
    国家自然科学基金(51601040);国家自然科学基金(51572948);国家自然科学基金(51502039)

Sodium Ion Storage Performance of NiCo2S4 Hexagonal Nanosheets

Mingyu ZHAO,Lin ZHU,Bowen FU,Suhua JIANG,Yongning ZHOU,Yun SONG*()   

  • Received:2018-01-11 Published:2018-07-10
  • Contact: Yun SONG E-mail:songyun@fudan.edu.cn
  • Supported by:
    National Natural Science Foundation of China(51601040);National Natural Science Foundation of China(51572948);National Natural Science Foundation of China(51502039)

摘要:

通过共沉淀以及后续的气相硫化成功制备了横向边长约为2 μm,纵向厚度约为30 nm的NiCo2S4六角片,并研究了其作为钠离子电池负极材料的电化学性能。电化学性能测试结果显示在1000 mA·g-1的电流密度下,NiCo2S4电极循环60次后仍然可保持约387 mAh·g-1的可逆比容量。此外,NiCo2S4电极还具有良好的倍率性能,在200、400、800、1000和2000 mA·g-1的电流密度下,容量分别为542、398、347、300和217 mAh·g-1。通过进一步动力学机制分析发现,NiCo2S4电极的良好的倍率性能得益于其二维片层状结构诱导产生的赝电容。上述结果表明,NiCo2S4纳米六角片是一种极具潜力的钠离子电池负极材料。

关键词: 钠离子电池, NiCo2S4纳米片, 负极材料, 储钠性能, 赝电容

Abstract:

As a potential substitute for commercial lithium ion batteries (LIBs), sodium ion batteries (NIBs) have attracted increasing interest during the last decade. However, compared to the LIBs, the sluggish kinetics of sodium ion diffusion in NIBs due to its larger ionic radius results in deteriorated electrochemical performances, which hinders the future development and application of NIBs. Therefore, exploring anode materials that exhibit a novel kinetic mechanism is desired. Recently, extremely rapid kinetics has been realized by introducing the pseudocapacitance effect into battery systems; this effect generally refers to faradaic charge-transfer reactions, including surface or near-surface redox reactions, and fast bulk ion intercalation. To obtain a pseudocapacitance effect in battery systems, the critical step involves the rational design of a two-dimensional structure with a high conductivity. In this regard, the bimetallic sulfide thiospinel NiCo2S4 stands out by virtue of its high conductivity (1.25 × 106 S·m-1) at room temperature, which is at least two orders of magnitude higher than that of the oxide counterpart (NiCo2O4). Herein, NiCo2S4 hexagonal nanosheets with a large lateral dimension of ~2 μm and thickness ~30 nm have been successfully synthesized through coprecipitation followed by a vapor sulfidation method. As the anode material in NIBs, the NiCo2S4 nanosheets deliver a reversible capacity of 387 mAh·g-1 after 60 cycles at a current density of 1000 mA·g-1. Additionally, the NiCo2S4 nanosheets exhibit high reversible capacities of 542, 398, 347, 300, and 217 mAh·g-1 at the current densities 200, 400, 800, 1000, and 2000 mA·g-1, respectively. Ex situ X-ray diffraction analysis has been employed to reveal that the sodium ion storage process is a result of a combined Na+ intercalation and conversion reaction between Na+ and NiCo2S4. Further quantitative analysis of the kinetics has verified the extrinsic pseudocapacitance mechanism of the Na+ storage process, in which the capacitive contribution enlarges as the current density increases. The observed capacitive contribution of NiCo2S4 electrode is as high as 71% at a scan rate of 0.4 mV·s-1. This is closely attributed to the modified thin-sheet structure of NiCo2S4 and hybridization with graphene that account for the superior high-rate performance with long-term cyclability. These intriguing results shed light on a new strategy for the structural design of electrode materials for advanced NIBs. Moreover, this vapor transformation route can be extended to the preparation of other transition metal disulfides with high electrochemical activities, such as FeCo2S4, ZnCo2S4, CuCo2S4, etc.

Key words: Sodium ion battery, NiCo2S4 nanosheets, Anode material, Sodium storage capalibity, Pseudocapacitance

MSC2000: 

  • O646