Poly(lithium borate ester) Binder for Fast Charging Lithium-Ion Battery Enabled by Functionalized Solid Electrolyte Interphase

A single lithium-ion conductive poly(lithium borate ester) water-soluble binder (PAA-MBLi) was utilized in the graphite anode with the motive of tuning the solid electrolyte interphase (SEI) and enhancing the ionic conductivity. The prelithiated binder and the boron-functionalized SEI enhanced the Li-ion kinetics with a low SEI and charge-transfer resistance, low activation energy, and a high diffusion coefficient. These enhancements enabled fast charging with a discharge capacity of 72 mAh/g at 5C and a capacity retention of 82.9% after 1400 cycles. The anodic half cells with PAA-MBLi exhibited a capacity retention of 80.4% after 750 cycles at 1C with a maximum capacity of 323 mAh/g. It also showed a 95.8% capacity retention after 100 cycles with a high mass loading of 5.55 mg/cm2 at 0.2C and an appreciable initial Coulombic efficiency of 83.9%, indicating a thin SEI with minimum irreversible capacity loss. The PAA-MBLi binder exhibited a remarkable ionic conductivity of 8.160 × 10–5 S cm–1 and a high lithium transference number of 0.831 at 25 °C. The PAA-MBLi binder is also expected to reduce HF formation in the cell by consuming the fluoride ions and forming a B–F bond in the SEI, as indicated by the X-ray photoelectron spectroscopy spectra.