Flexible sodium-ion capacitors boosted by high electrochemically-reactive and structurally-stable Sb₂S₃ nanowire/Ti₃C₂T_x MXene film anodes

The rapid development of portable, foldable, and wearable electronic devices requires flexible energy storage systems. Sodium-ion capacitors (SICs) combining the high energy of batteries and the high power of supercapacitors are promising solutions. However, the lack of flexible and durable electrode materials that allow fast and reversible Na⁺ storage hinders the development of flexible SICs. Herein, we report a high-capacity, free-standing and flexible Sb₂S₃/Ti₃C₂T_x composite film for fast and stable sodium storage. In this hybrid nano-architecture, the Sb₂S₃ nanowires uniformly anchored between Ti₃C₂T_x nanosheets not only act as sodium storage reservoirs but also pillar the two-dimensional (2D) Ti₃C₂T_x to form three-dimensional (3D) channels benefiting for electrolyte penetration. Meanwhile, the highly conductive Ti₃C₂T_x nanosheets provide rapid electron transport pathways, confine the volume expansion of Sb₂S₃ during sodiation, and restrain the dissolution of discharged sodium polysulfides through physical constraint and chemical absorption. Owing to the synergistic effects of the one-dimensional (1D) Sb₂S₃ nanowires and 2D MXenes, the resultant composite anodes exhibit outstanding rate performance (553 mAh·g⁻¹ at 2 A·g⁻¹) and cycle stability in sodium-ion batteries. Moreover, the flexible SICs using Sb₂S₃/Ti₃C₂T_x anodes and active carbon/reduced graphene oxide (AC/rGO) paper cathodes deliver a superior energy and power density in comparison with previously reported devices, as well as an excellent cycling performance with a high capacity retention of 82.78% after 5,000 cycles. This work sheds light on the design of next-generation low-cost, flexible and fast-charging energy storage devices.