Fixing Cu7S4 nanocrystals on flexible carbon nanotube film for distinguished sodium storage performance

Sodium-ion batteries (SIBs) have been identified as capable alternatives with great promise to lithium-ion batteries (LIBs) on account of affordable cost and satisfactory natural abundance of metallic sodium. However, they may suffer volume expansion of the active material and eventually the disintegration of the microstructure during the process of charge and discharge, giving rise to inferior reversible capacity and poor cyclic stability. In this work, we germinate nanoscale Cu7S4 on the carbon nanotube film innovatively by hydrothermal, which may be the first time Cu7S4 has been grown on such a thin film interwoven with innumerable carbon nanotubes and apply to the anode of SIBs to the best of our knowledge. The freestanding composite electrode without any binder and conductive auxiliary retains 553 mA h g(-1) after 300 cycles at 1A g(-1). Furthermore, ex situ characterization is employed to make a thorough inquiry of phase transitions and the relationship with the kinetics of Na-ion diffusion by the combination with galvanostatic intermittent titration technique (GITT) in the whole electrochemical process. We anticipate our work can provide a promising scheme for the research of the energy supply system of flexible wearable devices.

Automated summary

In this study, nanoscale Cu7S4 was grown innovatively on a carbon nanotube film using hydrothermal method and applied to the anode of sodium-ion batteries, demonstrating reliable cyclic stability. In situ characterization and galvanostatic intermittent titration technique were employed to investigate phase transitions and the dynamics of sodium-ion diffusion, providing a promising scheme for research in the energy supply system of flexible wearable devices.