Mechanistic Insight into Ultrafast Kinetics of Sodium Cointercalation in Few-Layer Graphitic Carbon

Fast-charging sodium ion batteries remain deeply challenged by the lack of suitable carbonaceous anodes that exhibit intercalation plateau with fast kinetics. Here we develop a few-layer graphitic carbon with nanoscale architecture, which enables shortened Na⁺ ion diffusion path and fast formation of fully intercalated phase at the same time. Combined in situ Raman and electrochemical test reveal that this graphitic carbon with highly crystalline few layers follows surface-controlled intercalation rather than typical diffusion-controlled kinetics observed in natural graphite. As a result, a few-layer graphitic carbon anode maintains the reversible capacity of 106 mAh g^-1 at 10 A g^-1 and achieves 87% capacity retention even after 10 000 cycles at 1 A g^-1. This work provides new insight on the Na storage mechanism in fast-charging graphitic carbon as well as the design of carbon anodes for high-rate sodium ion batteries.