Preparations and Sodium Storage Properties of Ni3S2@CNT Composite
- 2020年第26卷 
采用一步固相煅烧工艺制备了碳纳米管原位封装Ni3S2纳米颗粒（Ni3S2@CNT）,并研究了其作为钠离子电池（SIBs）负极材料的电化学性能. 通过X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、循环伏安测试、恒流充放电以及交流阻抗等研究了Ni3S2@CNT的物相结构、形貌特征以及电化学性能. 电化学测试表明,材料在100 mA·g -1电流密度下,放电容量可以达到541.6 mAh·g -1,甚至在2000 mA·g -1的大电流密度下其放电比容量也可以维持在274.5 mAh·g -1. 另外,材料在100 mA·g -1电流密度下,经过120周充放电循环后其放电和充电比容量仍然可以保持在374.5 mAh·g -1和359.3 mAh·g -1,说明其具有良好倍率性能和循环稳定性能. 良好的电化学性能归因于这种独特的碳纳米管原位封装Ni3S2纳米颗粒结构. 碳纳米管不但可以提高复合材料的导电性,也可以缓冲Ni3S2纳米颗粒在反复充放电过程中产生的体积膨胀效应,明显改善了Ni3S2@CNT负极复合材料的电化学性能.Transition metal sulfides (TMSs)-based electrode materials with highly reversible sodium storage have attracted extensive attentions as one of the most prospective electrode materials for sodium ion batteries (SIBs). However, low cycling stability and rate property caused by large volume expansion and poor electronic conductivity during the electrochemical reaction still hamper their further practical application. In this work, in-situ encapsulated Ni3S2 nanoparticles in carbon nanotubes (Ni3S2@CNT) have been successfully fabricated as an anode material for high-performance SIBs by a one-step solid-phase calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry, and galvanostatic discharge/charge experiments and electrochemical impedance spectroscopy (EIS) were used to characterize the morphology, phase structure and electrochemical performance of the Ni3S2@CNT material. When evaluated as an anode material for sodium ion batteries, the Ni3S2@CNT composite exhibited excellent rate performance (the discharge specific capacity reached 541.6 mAh·g -1 at a current density of 100 mA·g -1, the discharge specific capacity could maintain at 274.5 mAh·g -1, even at a large current density of 2000 mA·g -1) and good cycle stability (the discharge and charge specific capacities still maintained at 374.5 mAh·g -1 and 359.3 mAh·g -1, respectively, at a current density of 100 mA·g -1 after 120 cycles). Remarkable cycling performance and rate capability could attribute to the synergistic effect between Ni3S2 nanoparticles and this unique carbon nanotube structure. The nanoscale size of the Ni3S2 particles could reduce the Na-ions diffusion path as well as increase the contact area between the electrode and the electrolyte. More importantly, in-situ generated carbon nanotube structure not only helped to improve the electronic conductivity of materials, but also buffered the volume effect of Ni3S2 nanoparticles during discharge and charge cycling. At the same time, the smart structure designed and fabrication method reported here provide a new way for in-situ preparation of high-performacne host materials for SIBs, and other high-end energy storage and conversion applications in the future.