Boosting Charge transport kinetics by MXene/Na4Fe3(PO4)2P2O7 hetero-structure toward high-rate and stable sodium ion batteries

Sodium-ion batteries (SIBs) show great potential for energy storage, but currently suffer from low cycling stability and volume expansion in the electrode. This study proposes a composite cathode material composed of sodium iron pyrophosphate (NFPP) and MXene via electrostatic self-assembly. The crumpled MXene nanosheets serve as conductive scaffolds, uniformly encapsulating NFPP particles, which effectively mitigates volume expansion and boosts charge transport kinetics by MXene/NFPP hetero-structure. The MXene nanosheets effectively prevent direct contact between NFPP particles and the electrolyte, thereby suppressing NFPP dissolution in the electrolyte and improving cycling stability. And the NFPP/MXene composite cathode surface morphology remained relatively smooth after cycling, and alleviating volume expansion. Furthermore, to prevent the surface of MXene self-restacking, the MXene ratio in the NFPP/MXene composite was optimized. The NFPP/MXene-5 cathode demonstrates superior cycling durability, delivering a specific capacity of 62.7 mAh·g −1 after 1,000 cycles at 1 A·g −1 , accompanied by 76.9% capacity retention. Experimental tests and theoretical calculations confirm the composite’s superior adsorption capability and high-rate performance, providing valuable insights for designing high-rate and stable sodium ion batteries.