Direct chitin conversion to N-doped amorphous carbon nanofibers for high-performing full sodium-ion batteries

Currently, renewable and low-cost electrode materials are being intensively pursued to meet the development of sustainable electrochemical energy-storage systems. Chitin, which is the second most abundant biopolymer throughout the natural world and can be sourced cheaply from the exoskeletons of arthropods and shells of cephalopods, has many attractive properties such as renewability, nontoxicity, intrinsically fibrous structure and high nitrogen content. In this study, nitrogen-doped amorphous carbon nanofibers (NACF) fabricated by direct pyrolysis of chitin, were used as the anode material in sodium-ion batteries (SIBs) for the first time. The NACF electrode delivered a high reversible capacity of 320.6 mA h g⁻¹ with excellent rate capability and long cyclability. The superior electrochemical performance can mainly be attributed to synergistic effects of the unique one-dimensional mesoporous nanofibers facilitating the transmission of electrons/electrolyte, and the N-doped amorphous nanostructure increasing electrical conductivity and number of active sites. Furthermore, a sodium-ion full cell was constructed by coupling the NACF electrode with a Prussian blue cathode, and it delivered 115 mA h g⁻¹ while retaining 90% of the capacity after 200 cycles. Our work will hopefully inspire the research community to explore other advanced materials with value-added attributes that can be generated by appropriate treatment of renewable bio-waste.