Experimental and theoretical investigation on boron, phosphorus dual doped hard carbon as anode for sodium-ion battery

In recent years, hard carbon has gained immense attention as the most potential candidate for anode in sodium- ion batteries. However, low capacity and rate performance limits its industrial application. Herein, experimental and theoretical studies have been conducted to study the effect of boron, phosphorus dual doping on hard carbon an anode in sodium ion batteries. The study confirmed that B, P dual doping can boost the electrochemical characteristics of the hard carbon. It shows a superior capacity (224 mAh g- 1 at 20 mA), enhanced rate performance and a better retention (88.17 % at 20 mA after 200 cycles). Besides, density functional theory (DFT) reveals that the band gap of the hard carbon reduces from 5.36 eV in pristine hard carbon to 1.874 eV after B, P dual doped hard carbon which may increase the electronic conductivity of the anode. It also reveals that the volume expansion of the hard carbon during sodiation decreases after optimal doping which increases the cyclic stability of the anode. The assembled full-cell exhibits an excellent electrochemical performance. Our detailed investigation shows that B, P dual doped hard carbon can be considered as potential candidate for high energy density anode for sodium-ion battery.