In Situ Growth of Iron Sulfide on Fast Charge Transfer V2C-MXene for Superior Sodium Storage Anodes

Due to the upstream pressure of lithium resources, low-cost sodium-ion batteries (SIBs) have become the most potential candidates for energy storage systems in the new era. However, anode materials of SIBs have always been a major problem in their development. To address this, V2C/Fe7S8@C composites with hierarchical structures prepared via an in situ synthesis method are proposed here. The 2D V2C-MXene as the growth substrate for Fe7S8 greatly improves the rate capability of SIBs, and the carbon layer on the surface provides a guarantee for charge-discharge stability. Unexpectedly, the V2C/Fe7S8@C anode achieves satisfactory sodium storage capacity and exceptional rate performance (389.7 mAh g(-1) at 5 A g(-1)). The sodium storage mechanism and origin of composites are thoroughly studied via ex situ characterization techniques and first-principles calculations. Furthermore, the constructed sodium-ion capacitor assembled with N-doped porous carbon delivers excellent energy density (135 Wh kg(-1)) and power density (11 kW kg(-1)), showing certain practical value. This work provides an advanced system of sodium storage anode materials and broadens the possibility of MXene-based materials in the energy storage.

Automated summary

Due to the pressure on lithium resources, low-cost sodium-ion batteries (SIBs) have emerged as the most potential candidates for energy storage systems in the new era. This study proposes V2C/Fe7S8@C composites with hierarchical structures, prepared through an in situ synthesis method, to address the problem of anode materials in SIBs development. The V2C-MXene growth substrate greatly improves the rate capability of SIBs, while the carbon layer ensures charge-discharge stability. The V2C/Fe7S8@C anode achieves satisfactory sodium storage capacity and exceptional rate performance, making it a promising material for energy storage.