Ultrafast High-Volumetric Sodium-Ion Capacitors Based on Compact Nanoarchitectured Carbon Electrodes

Ultrafast carbon electrodes with high-volumetric capacities are crucial for the fast-developing sodium-ion capacitors (SICs) but have rarely been achieved due to the negative correlation between electrode density and ion transport kinetics. Here, a top-down strategy to achieve a compact carbon architecture with topological ion transport/diffusion pathways to address this obstacle is reported. The resulting freestanding carbon electrode exhibits a notable volumetric capacity of 242 mAh cm-3 at 0.05 A g-1 and unprecedented high-rate capability of 107 mAh cm-3 at 50 A g-1. It achieves an optimal balance between energy density (60.2 Wh L-1) and power density (12859 W L-1) in a SIC device. The ultrafast and high-volumetric performance is attributed to the synergistic effect of architecture-enhanced rapid ion transport/diffusion and carbon nanostructure-driven fast Na+ storage mechanisms involving adsorption/desorption, surface-redox and solvated Na+ co-intercalation reactions. The nanoarchitectured carbon electrodes show greatly improved Na+ diffusion coefficients throughout the potential range, resulting in an extremely short characteristic time (0.013 s) for fast Na+ storage. Compact electrodes of carbon nanoparticles with a pore-interconnected architecture have been fabricated by a strategy of processing bulk nanostructured precursor. The combination of nanosized active units and ion-conductive pore architecture enables fast sodium-ion transport/storage kinetics, achieving an extremely short characteristic time (0.013 s) and fast sodium-ion storage (107 mAh cm-3 at 50 A g-1). image