Polyvinyl formal based single-ion conductor membranes as polymer electrolytes for lithium ion batteries

Novel single-ion conductor polymer (SCP) membranes based on oxalate-chelated borate structure grafted polyvinyl formal (PVFM) were developed herein. The membranes and their application as polymer electrolytes for lithium-ion batteries were characterized by Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetry (TG), differential scanning calorimetry (DSC), stress-strain test, electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and charge/discharge test. Results show that the novel SCP membranes exhibit good thermal stability and excellent mechanical strength of 11-34 MPa; the obtained gel polymer electrolytes (GPEs) from propylene carbonate (PC) plasticized SCP membranes show ionic conductivity of 10−6-10−5 S cm−1 between 15 and 60 °C, wide electrochemical stability window of >5 V (vs. Li+/Li) and good matching properties with Li/LiFePO4 cells. The PVFM based SCP membrane shows promising characteristics as polymer electrolytes for lithium-ion batteries.