Density functional theory study of lignin, carboxymethylcellulose and unsustainable binders with graphene for electrodes in lithium-ion batteries
Electrodes are the fundamental components in lithium-ion batteries to develop high-performance device systems. The fabrication process of electrodes involves a mixing of active materials, a nonconductive polymeric binder material, and an electrically conductive additive. Binders play a critical role during the electrochemical process, which tightly holds the active materials together within the electrode to provide a long-cycle life. The present study investigates the strength of the interaction for different binders such as vinylidene fluoride (VDF), pyrrole (PY), styrene-butadiene (SB), acrylonitrile (AN), tetrafluoroethylene (TFE), carboxymethylcellulose (CMC), and lignin monomers, coumarylalcohol (LCmA), coniferylalcohol (LCnA), and sinapylalcohol (LSiA), using density functional theory calculations. The result reveals that sustainable binders (CMC, LCmA, LiCnA, and LSiA) exhibit higher interaction energy than unsustainable binders (VDF, PY, SB, AN, and TFE). The highest interaction energy is obtained for the graphene-LiSiA system, followed by graphene-LCnA and graphene-LCmA. Comparing the orientation of the binders on the graphene surface, all binders make a face-to-face arrangement with graphene. This interaction is greatly enhanced for those binders that possess aromatic rings with functional groups (methoxy and hydroxyl). These results provide significant insights for the use of lignocellulosic biomass materials such as lignin and cellulose as binders in energy devices toward more sustainability.