Hollow Carbon and MXene Dual-Reinforced MoS with Enlarged Interlayers for High-Rate and High-Capacity Sodium Storage Systems.

Sodium-ion batteries (SIBs) and sodium-ion capacitors (SICs) are promising candidates for cost-effective and large-scale energy storage devices. However, sluggish kinetics and low capacity of traditional anode materials inhibit their practical applications. Herein, a novel design featuring a layer-expanded MoS is presented that dual-reinforced by hollow N, P-codoped carbon as the inner supporter and surface groups abundant MXene as the outer supporter, resulting in a cross-linked robust composite (NPC@MoS/MXene). The hollow N, P-codoped carbon effectively prevents agglomeration of MoS layers and facilitates shorter distances between the electrolyte and electrode. The conductive MXene outer surface envelops the NPC@MoS units inside, creating interconnected channels that enable efficient charge transfer and diffusion, ensuring rapid kinetics and enhanced electrode utilization. It exhibits a high reversible capacity of 453 mAh g, remarkable cycling stability, and exceptional rate capability with 54% capacity retention when the current density increases from 100 to 5000 mA g toward SIBs. The kinetic mechanism studies reveal that the NPC@MoS/MXene demonstrates a pseudocapacitance dominated hybrid sodiation/desodiation process. Coupled with active carbon (AC), the NPC@MoS/MXene//AC SICs achieve both high energy density of 136 Wh kg at 254 W kg and high-power density of 5940 W kg at 27 Wh g, maintaining excellent stability.