Eco‐Friendly Synthesis of 3D Disordered Carbon Materials for High‐Performance Dual Carbon Na‐Ion Capacitors

An eco‐friendly and sustainable salt‐templating approach was proposed for the production of anode materials with a 3D sponge‐like structure for sodium‐ion capacitors using gluconic acid as carbon precursor and sodium carbonate as water‐removable template. The optimized carbon material combined porous thin walls that provided short diffusional paths, a highly disordered microstructure with dilated interlayer spacing, and a large oxygen content, all of which facilitated Na ion transport and provided plenty of active sites for Na adsorption. This material provided a capacity of 314 mAh g(−1) at 0.1 A g(−1) and 130 mAh g(−1) at 10 A g(−1). When combined with a 3D highly porous carbon cathode (S (BET) ≈2300 m(2) g(−1)) synthesized from the same precursor, the Na‐ion capacitor showed high specific energy/power, that is 110 Wh kg(−1) at low power and still 71 Wh kg(−1) at approximately 26 kW kg(−1), and a good capacity retention of 70 % over 10000 cycles.