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

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 20th 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.