• Bi@NC composite anode delivers high specific capacity (300 mAh g−1 at 0.5 A g−1) and exceptional rate capability up to 75 A g−1.
• The anode exhibits outstanding cycling stability over 12,000 cycles, addressing kinetic imbalance in sodium-ion capacitors.
• Three-electrode tests confirm reduced kinetic gap with activated carbon cathode, enabling high energy/power densities.
• The fabricated SIC achieves maximum energy density of 115 Wh kg−1, peak power density of 45,535 W kg−1, and cycle life exceeding 8,000 cycles.