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High-performance flexible sodium-ion batteries based on carbon sphere-supported hierarchical Nb2CTx MXene/MoS 2 composites, which excellent specific capacity, cycle stability and rate performance. It has a specific capacity of 196 mAh g-1 at a current density of 20 A g-1. In addition, this design scheme can also be extended to other application scenarios. [Display omitted] • Hollow carbon sphere could make electrode three-dimensional. • MXene-bonded 3D hierarchical structure could reduce the charge transfer path. • Nb 2 CT x /MoS 2 @CS anode have outstanding cycle stability for Na ion storage. • MXene-bonded electrode have certain flexibility. Hand-made Nb 2 CT x /MoS 2 @CS//NVP full battery could reach to 90° bending. 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 Nb 2 CT x MXene/MoS 2 hierarchical structure has been designed and synthesized through hydrothermal and electrostatic self-assembly methods. The design strategy successfully improves the utilization efficiency of the MoS 2 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, Nb 2 CT x sheets also effectively inhibit the capacity attenuation caused by MoS 2 shedding, thus achieving the long cycle life of the sodium-ion battery. As a result, the carbon-supported MXene/MoS 2 anode delivers an ultrahigh reversible capacity, long cycling stability, and superior capacity retention rate. Notably, the carbon-supported MXene/MoS 2 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. [ABSTRACT FROM AUTHOR]

A facile structural refining for Sb film anode is firstly applied in SIBs by increasing the working pressure. Compared with Sb@0.2Pa and Sb@1Pa, the Sb@3Pa anode exhibits improved performance, stemming from its refined architecture. Surprisingly, the progressive in-situ electrochemically-driven Cu-Sb alloying can be probed upon cycling onward and further clarified by operando XRD, ex-situ SEM and DFT calculations. • A scalable structural refining for sputtered Sb film via altering working pressure. • The Sb@3Pa anode exhibits better performance owing to refined structure. • The (de)sodiation mechanism of Sb anodes was probed utilizing operando XRD. • In-situ electrochemically-driven Cu-Sb alloying is firstly observed in SIBs. Sb is a promising anode for sodium ion batteries (SIBs) but held back from practical application owing to its pulverization induced by dramatic volumetric variation. Herein, we propose a simple pressure-induced regulation strategy to efficiently refine nanoscale column-channel architecture of Sb layer by magnetron sputtering, which is easily manipulated and reproductive in practical conditions. The refining process under high working pressure can be ascribed to the synergistic effects from the shadow effect, the low kinetic energy of sputtered Sb atoms and high diffusion barrier on substrate. As benchmarked with Sb@0.2Pa and Sb@1Pa electrodes, the Sb@3Pa anode exhibits significantly enhanced electrochemical performance owing to structural refining effect generated by the elevated working pressure, effectively accelerating the ion/electron transfer and mitigating the volumetric variations. Notably, the progressive in-situ electrochemically-driven alloying in Sb layer on the Cu substrate to form Cu x Sb with the gradient Cu/Sb content is detected and further rationalized by operando XRD, ex-situ SEM and DFT calculations. Simultaneously, the formed Cu-Sb layer yields a novel (de)sodiation mechanism of Cu x Sb 1−x ↔ Na y Cu x Sb 1−x ↔ Na 3 Cu x Sb 1−x after the 1st discharge. [ABSTRACT FROM AUTHOR]