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 m²  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.