Engineering of carbon anodes by laser irradiation for advanced sodium-ion batteries

Sodium-ion batteries (NIBs) represent an attractive alternative to Li-ion batteries due to sodium-abundant sources, lower cost, and better safety characteristics. However, the limited sodium-ion intercalation into graphite anodes has motivated researchers to search for new anode materials of NIBs. Herein, we demonstrate that laser-irradiated fly ash carbon (FAC), which is a waste by-product of the oil-burning process, can be a promising carbon anode of NIBs. The laser irradiation approach yields three synergistic benefits: (1) introducing carbonyl and carboxylic functional groups that increase adsorption capacity, (2) structurally transforming amorphous carbon into graphitic nanoplatelets to boost dynamic intercalation, and (3) enabling an additive and binder-free electrode to increase gravimetric energy density. The laser-irradiated fly ash carbon (LFAC) anode exhibits an excellent specific charge capacity of 356 mAh/g at 0.1 A/g, which is significantly higher than that of the FAC anode (119 mAh/g). At the end of the cycling measurement, the LFAC anode delivers a capacity of 250 mAh/g, which is three times higher than the untreated FAC anode (80 mAh/g).