Abstract
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.