Organic electrode materials face two outstanding issues in the practical applications in lithium-ion batteries (LIBs), dissolution and poor electronic conductivity. Herein, we fabricate a nanocomposite of an anthraquinone carboxylate lithium salt (LiAQC) and graphene to address the two issues. LiAQC is synthesized via a green and facile one-pot reaction and then ball-milled with graphene to obtain a nanocomposite (nr-LiAQC/G). For comparison, single LiAQC is also ball-milled to form a nanorod (nr-LiAQC). Together with pristine LiAQC, the three samples are used as cathodes for LIBs. Results show that good cycling performance can be obtained by introducing the -CO2Li hydrophilic group on anthraquinone. Furthermore, the nr-LiAQC/G demonstrates not only a high initial discharge capacity of 187 mAh g-1 at 0.1 C but also good cycling stability (reversible capacity: ∼165 mAh g-1 at 0.1 C after 200 cycles) and good rate capability (the average discharge capacity of 149 mAh g-1 at 2 C). The superior electrochemical properties of the nr-LiAQC/G profit from graphene with high electronic conductivity, the nanorod structure of LiAQC shortening the transport distance for lithium ions and electrons, and the introduction of the -CO2Li hydrophilic group decreasing the dissolution of LiAQC in the electrolyte. Meanwhile, density functional theory calculations support the roles of graphene and -CO2Li groups. The fabrication is general and facile, ready to be extended to other organic electrode materials.
Keywords: dissolution; electronic conductivity; hydrophilic group; lithium-ion batteries; nanorod; organic cathodes.