fig5

Figure 5. (A and B) Na⁺ diffusion coefficients calculated from the GITT potential profiles under discharge/charge processes; (C) EIS analysis after ten cycles; (D) Sodium storage diagram of AFR-HCs. GITT: Galvanostatic intermittent titration technique; EIS: electrochemical impedance spectroscopy; AFR: aminophenol formaldehyde resin; HCs: hard carbons.