关键词: Ni₃S₂@CNT复合材料, 负极材料, 高性能, 钠离子电池

Abstract:

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.

Key words: Ni₃S₂@CNT composite, anode material, high performance, sodium ion battery