Space‐Confined Fabrication of MoS 2 @Carbon Tubes with Semienclosed Architecture Achieving Superior Cycling Capability for Sodium Ion Storage

High rate and good cycling capability are always difficult for sodium ion anode materials owing to the unstable electrode structure induced by reversibly intercalation of large‐sized sodium ions. In this paper, based on the unique nanotube arrays of crab shells, a novel space‐confined growth of MoS 2 nanosheets in carbon nanotubes is reported to fabricate MoS 2 @carbon nanotube (MoS 2 @CT) with a semienclosed architecture. Due to the space‐confined effect, MoS 2 sheets are nanosized with poor stacking feature, which are anchored on the inner surface of carbon tubes. The semienclosed architecture built of carbon nanotubes and abundant MoS 2 nanosheets enhances the stability and integrity of the electrode structure during cycles. Thereby, the coupling effect of stable structure and MoS 2 with fast kinetics achieves a comprehensive performance improvement of the MoS 2 @CT anode materials. Particularly for cycling capability, it delivers a capacity of 170 mAh g −1 after 10 000 cycles at a high current density of 10 A g −1 , which is comparable for most previously reported cases. The assembled Na‐ion hybrid supercapacitors device delivers a high energy density of 82 Wh kg −1 at a power density of 2000 W kg −1 after 5000 cycles with an 89% retention.