Extreme Fast Charging Capability in Graphite Anode via a Lithium Borate Type Biobased Polymer as Aqueous Polyelectrolyte Binder

Desolvation of lithium ions and diffusion of Li+ through the solid electrolyte interface (SEI) play an important role in determining the extreme fast-charging ability of graphite for electric vehicle (EV) application. For this reason, a novel aqueous borate type bio-based polymer with inherent Li ions was designed as an SEI forming binder for graphite. The low lying LUMO energy level enabled the preferential reduction of the binder prior to the degradation of the electrolyte or salt to form a thinner and highly conducting borate rich SEI. A robust boron rich SEI and a binder with inherent Li ions improved the kinetics with low activation energy for lithiation/desolvation (22.56 kJ/mol), lower SEI resistance, and a high Li+ diffusion coefficient across the graphite galleries (7.24 × 10–9 cm2 s–1). Anodic half-cells with the novel binder delivered a discharge capacity of 73 mAh/g at 10 C, which is three times higher than the those of the polyvinylidene fluoride (PVDF) and sodium carboxymethyl cellulose/polystyrene-polybutadiene rubber (CMC-SBR) counterparts, with a high capacity retention for more than 1000 cycles.