Accelerating Desolvation Kinetics on Hard Carbon Anodes With a Graphitic Carbon Nitride Nanosieve for High-Performance Sodium-Ion Batteries

Sluggish desolvation kinetics at the interface pose a critical bottleneck for hard carbon (HC) anodes, severely limiting their rate capability and fast-charging performance. This study addresses this fundamental challenge by constructing a graphitic carbon nitride (g-C₃N₄) nanosieve to establish an active, geometry-regulated interphase. The proposed mechanism relies on an adsorption-capture-promotion process, whereby pyridinic nitrogen sites facilitate the spontaneous desolvation of Na⁺ through strong electrostatic interactions. Theoretical calculations reveal that these sites release an adsorption energy of 3.41 eV, which overcompensates for the 1.39 eV desolvation enthalpy to convert hindered ion transfer into a spontaneous process. Multi-scale characterization identifies a self-optimizing amorphization-to-crystallization transition of the g-C₃N₄ layer and solid electrolyte interphase (SEI) during cycling. This structural evolution sustains a thin and highly crystalline interface, which reduces charge transfer resistance to ensure long-term stability. The optimized 10 wt.% g-C₃N₄-coated HC (HC@10%CN) anode delivers 145 mAh g⁻¹ at 8 A g⁻¹ and demonstrates 94.7% capacity retention after 500 cycles at 1 A g⁻¹. The full cell paired with Na₃V₂(PO₄)₃ achieves stable reversibility at 6 A g⁻¹ to validate the practical potential of this configuration. This work establishes active interfacial adsorption as a universal design framework for high-rate energy storage.