Efficient energy storage in mustard husk derived porous spherical carbon nanostructures

An environment-friendly synthesis of highly porous spherical carbon nanostructures (PSCNs), in situ doped with N and S, from mustard seed waste has been accomplished. The synthesised PSCNs have an interconnected network, abundant active interfaces, heteroatom rich content, and notably high porosity/surface area which are favourable for fast ion transport and efficient charge storage. This active material (PSCN), when employed as a lithium-ion battery (LIB) half-cell anode, shows a specific charge capacity of 714 mA h g⁻¹ at a current density of 100 mA g⁻¹ even after 550 cycles with 112% capacity retention and high restoration capability. Furthermore, PSCN//LiFePO₄ full cell LIBs show an excellent performance with a highly reversible capacity of ∼195 mA h g⁻¹ at a current density of 50 mA g⁻¹ for 400 cycles. The PSCN electrode also exhibited a specific capacitance of 257.8 F g⁻¹ at a current density of 0.1 A g⁻¹ with ∼93% capacity retention after 10 000 cycles, when used as an electrochemical supercapacitor in aqueous 3 M KOH electrolyte. This work shows the preparation of high value and advanced carbon nanostructured material from renewable bio-mass waste for high-performance electrochemical energy storage applications.