Synthesis of Hard Carbons from Argan Shell for Na-Ion Batteries
Hard carbon is one of attractive materials for negative electrode of sodium-ion batteries. Herein, we report a new hard carbon, synthesized via carbonization of argan shell biomass, delivering the enhanced capacity higher than 330 mAh g-1 based upon reversible sodium insertion. We prepared hard carbon under different conditions of high-temperature treatment and pretreatment of the biomass. The graphitization degree of hard carbon increased as the carbonization temperature increases, simultaneously the reversible capacity for sodium storage was significantly influenced by the carbonization temperatures. Structural characterization revealed the difference in the structure of hard carbon synthesized at different carbonization temperatures, which supports to elucidate the correlation between the capacity increase and the micropore size available for sodium storage. Composite electrodes of the argan hard carbon with sodium polyacrylate binder was tested in non-aqueous sodium half cells. The electrodes delivered the reversible capacity as high as 300 mAh g-1 at a current density of 25 mA g-1 with a superior reversibility and capacity retention of 94.1% after 70 cycles. By carbonization of argan shell biomass treated with HCl aqueous solution, we successfully demonstrate higher reversible capacity of 333 mAh g-1 and excellent capacity retention of 96.0 % after 100 cycles.