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 (approximate to 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.