Carbon/C3N4 heterostructures constructed from lignin toward enhanced lithium-ion storage.

Lithium-ion batteries (LIBs) are widely used in portable energy storage. The capacity of commercial graphite is difficult to improve due to the stoichiometry limit of LiC₆ of graphite, thus new anodes need to be developed to meet the demand of high-energy–density LIB. The growing interest in graphitized carbon nitride (g-C₃N₄) stems from its structural resemblance to graphite and its capacity to offer abundant adsorption and intercalation sites. However, g-C₃N₄, as a semiconductor, has a low lithium transfer rate due to its poor conductivity and high diffusion resistance. Improving the electron transport rate of g-C₃N₄ and reducing the adsorption energy barrier of Li⁺ in g-C₃N₄ are the keys to improving the electrochemical performances of g-C₃N₄. In this study, lignin and melamine were homogeneously mixed using the spray drying method, followed by the preparation of covalently bonded C₃N₄/LC material through a one-step carbonization process. The uniform dispersion of g-C₃N₄ in amorphous carbon can improve the conductivity and reduce the diffusion energy barrier of Li⁺. As a result, the C₃N₄/LC-x anode has better electrochemical behavior, including higher reversible capacity, better rate performance, and cycle stability. Highlights: • The covalently bonded C₃N₄/LC-x material was prepared through a one-step carbonization method. • The uniform dispersion of g-C₃N₄ in amorphous carbon could improve the electronic conductivity and reduce the diffusion energy barrier of Li⁺ ions. • C₃N₄/LC-2 showed high reversible capacity, ideal rate performance, and cycle life. [ABSTRACT FROM AUTHOR]