Norbornene-Functionalized Plant Oils for Biobased Thermoset Films and Binders of Silicon-Graphite Composite Electrodes

We herein report the functionalization of plant oil with norbornene (NB) and subsequent polymerization to prepare biobased thermoset films and biobased binders for silicon/mesocarbon microbead (MCMB) composite electrodes for use in lithium-ion batteries. A series of NB-functionalized plant oils were prepared as biobased thermoset films via ring-opening metathesis polymerization (ROMP) in the presence of a second-generation Grubbs catalyst with tunable thermomechanical properties. Increasing the catalyst loading and cross-linking agent increased cross-link density, storage modulus (E'), and glass transition temperature (T _g), while the numbers of unreacted or oligomeric components in the films were reduced. High number of NB rings per triglyceride in the plant oil encouraged monomer incorporation to form a polymer network, therefore accounting for the high T _g and E' values. Furthermore, the NB-functionalized plant oil and 2,5-norbornadiene (NBD) were copolymerized as bioderived binders for silicone/MCMB composite electrodes of lithium-ion batteries via ROMP during electrode preparation. Cell performance investigation showed that the silicone/MCMB composite electrode bearing the NBD-cross-linked NB-functionalized plant oil binder exhibited a higher C-rate and cycle-life performance than that using a conventional poly(vinylidene fluoride) (PVDF) binder. Finally, the electrode based on the bioderived binder exhibited a high specific charge capacity of 620 mA h g^-1 at 0.5 C.