The use of novel VDF–HFP–CTFE terpolymers in lithium-ion polymer cells

Porous polymer films and plasticised polymer films of vinylidene fluoride (VDF)–hexafluoropropylene (HFP)–chlorotrifluoroethylene (CTFE) terpolymers have been fabricated from a range of solvents. Significant 2EC/PC solvent uptake was measured at 60 °C for VDF–HFP–CTFE terpolymer films but structural integrity was maintained. 0.625 Ah soft packaged graphite—LiCoO2 test cells have been fabricated containing porous VDF–HFP–CTFE terpolymer films as separator. Ninety-eight percent of Rated Capacity was measured at 2C rate. Four hundred and fifty-four cycles were obtained at C rate to 80% of Rated Capacity. Thin 4–5 μm plasticised VDF–HFP–CTFE terpolymer films have also been produced.