Nanostructured organic electrode materials grown on graphene with covalent-bond interaction for high-rate and ultra-long-life lithium-ion batteries

Nanostructured organic tetralithium salts of 2, 5-dihydroxyterephthalic acid (Li₄C₈H₂O₆) supported on graphene were prepared via a facile recrystallization method. The optimized composite with 75 wt.% Li₄C₈H₂O₆ was evaluated as an anode with redox couples of Li₄C₈H₂O₆/Li₆C₈H₂O₆ and as a cathode with redox couples of Li₄C₈H₂O₆/Li₂C₈H₂O₆ for Li-ion batteries, exhibiting a high-rate capability (10 C) and long cycling life (1, 000 cycles). Moreover, in an all-organic symmetric Li-ion battery, this dual-function electrode retained capacities of 191 and 121 mA·h·g^–1 after 100 and 500 cycles, respectively. Density functional theory calculations indicated the presence of covalent bonds between Li₄C₈H₂O₆ and graphene, which affected both the morphology and electronic structure of the composite. The special nanostructures, high electronic conductivity of graphene, and covalent-bond interaction between Li₄C₈H₂O₆ and graphene contributed to the superior electrochemical properties. Our results indicate that the combination of organic salt molecules with graphene is useful for obtaining high-performance organic batteries.