MXene-Bonded hollow MoS2/Carbon sphere strategy for high-performance flexible sodium ion storage

Sodium-ion batteries, as a promising alternative to the lithium-ion battery, have attracted extensive attention. However, due to the larger ion radius and higher standard reduction potential, the sodium-ion batteries still face poor cycle stability and relatively low energy density problems. In this work, a carbon sphere-supported Nb2CTx MXene/MoS2 hierarchical structure has been designed and synthesized through hydrothermal and electrostatic self-assembly methods. The design strategy successfully improves the utilization efficiency of the MoS2 carbon sphere as a support skeleton and reducing the diffusion path length of Na ions, leading to an improved specific capacity and rate performance. Moreover, Nb2CTx sheets also effectively inhibit the capacity attenuation caused by MoS2 shedding, thus achieving the long cycle life of the sodium-ion battery. As a result, the carbon-supported MXene/MoS2 anode delivers an ultrahigh reversible capacity, long cycling stability, and superior capacity retention rate. Notably, the carbon-supported MXene/MoS2 anode can also obtain a considerable capacity of 196 mAh g−1 at a current density of 20 A g−1. The full cell of SIBs was assembled, and the flexibility of the battery was tested. The density functional theory simulation results show that the sodium ion has a smaller diffusion barrier under this material design strategy.