Unlocking Charge Transfer Limitation in NASICON Structured Na₃V₂(PO₄)₃ Cathode via Trace Carbon Incorporation

NASICON-type cathode with remarkable ionic conductivity is perspective candidate for fast-charging sodium-ion battery. However, severely restricted by low electrical conductivity and poor interfacial kinetics, it usually delivers poor charge transfer kinetics. Different from traditional carbon compositing with high carbon contents, herein, a trace carbon incorporation tactic is proposed based on a typical NASICON-structured Na₃V₂(PO₄)₃. First, particle-growth process of Na₃V₂(PO₄)₃ is regulated via incorporating carbon dot, significantly reducing its particle size to shorten charge diffusion path. Second, electrical conductivity of Na₃V₂(PO₄)₃ is improved without sacrificing its high electrochemical activity due to the incorporated trace carbon content (0.76 wt.%). Third, Na₃V₂(PO₄)₃-electrolyte interface structure is optimized by abundant functional groups from the incorporated carbon dot, enabling a thin and stable NaF-rich CEI layer to boost interface kinetics. As a result, carbon dot endows Na₃V₂(PO₄)₃ with ultrastable cyclability up to 20 k cycles (capacity retention of 98.4%) and excellent rate capability (up to 200 C) in half cell, as well as high energy density (368.7 Wh kg⁻¹) and fast charging property (≈110.2 s per charging with 250.8 Wh kg⁻¹ input) in full cell. This study carves a new path for developing fast-charging cathode, as is increasingly desired for present energy storage applications.