PEG crosslinked poly(vinylbenzene boronic acid) polymer electrolytes for Li-ion batteries

• Crosslinked boron containing polymers with different PEG side chains were produced.
• PEGME chains increased the thermal stability and segmental mobility.
• The ionic conductivity depends on side chain length as well as the Li+ content.

Poly(4-vinylbenzeneboronic acid), PVBBA was synthesized via free-radical polymerization of 4-vinylbenzeneboronic acid (4-VBBA) and followed by crosslinking with polyethylene glycol (PEG) with different molecular weights to produce boron containing crosslinked polymers. Prior to crosslinking, the materials were doped with CF3SO3Li at several stoichiometric ratios to get PVBBAPEGX-Y where X is the molecular weight of PEG and Y is the EO/Li ratio. The materials were characterized by using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). The ionic conductivity of these novel crosslinked electrolytes was studied by dielectric-impedance spectroscopy. Li-ion conductivity of these polymer electrolytes depends on the length of the side units as well as the doping ratio. PVBBAPEG200-10 illustrated a satisfactory ionic conductivity of 3.1 × 10−5 S/cm at 20 °C and 1.8 × 10−3 S/cm at 100 °C.