Co3S4@polyaniline nanotubes as high-performance anode materials for sodium ion batteries

Abstract

In this study, by employing Co₃S₄ nanotubes prepared by a facile self-template hydrothermal route based on the Kirkendall effect, Co₃S₄@polyaniline (Co₃S₄@PANI) nanotubes, in which polyaniline is uniformly coated on both exterior and inner surfaces of Co₃S₄ nanotubes, have been fabricated through in situ oxidative polymerization. Benefiting from the highly conductive and mechanically robust polyaniline shell, the conductivity and stability of the composite have been significantly improved. As a result, Co₃S₄@PANI nanotubes demonstrate much better electrochemical performance than bare Co₃S₄ nanotubes as sodium ion battery anode materials, with a high capacity of 252.5 mA h g⁻¹ after 100 cycles at the current density of 200 mA g⁻¹. In contrast, although a specific capacity of the bare Co₃S₄ nanotubes in the first cycle achieved was 815.3 mA h g⁻¹, it rapidly decayed to 192.9 mA h g⁻¹ at the 20^th cycle and further reduced to 58.2 mA h g⁻¹ after 100 cycles. Furthermore, Co₃S₄@PANI nanotubes showed a high discharge capacity of 170.1 mA h g⁻¹ after 400 cycles with a large current density of 4000 mA g⁻¹. The excellent electrochemical properties of Co₃S₄@PANI nanotubes were ascribed to the combination of Co₃S₄ and PANI and the stability of the composite structure.