High performance sodium-ion battery anode using biomass derived hard carbon with engineered defective sites

Defective hard carbons are deliberated as promising candidates for sodium-ion battery (SIB) anodes of this decade. Recently, several groups have discussed the structure-property correlation which correlates the slope capacity in charge/discharge profile curves to the binding of sodium-ions on the structural defective sites of the hard carbon. In order to validate these correlations, herein we report for first time the preparation of defective hard carbon materials from Borassus flabellifer male inflorescence via controlled thermal activation process using Nitrogen (N2) and Carbon dioxide (CO2) gas mixtures and its subsequent usage as anode material in sodium-ion battery. When used as sodium-ion battery anode, the prepared hard carbon displayed outstanding reversible discharge/charge capacities of 413/358 mAh g−1 and superior initial capacity retention of 86.6%, which is the highest ever reported value to date alongwith a overwhelming cycling stability. The notable improvements can be correlated to the broken edges present in the hard carbon surface as well as the randomly distributed micro-nano structured pores in the system as revealed by the morphological characterizations. Thus, the reported research work paves way in developing novel low cost and high performance micro-nano structured defective hard carbon anode materials for Sodium-ion batteries.