A free-standing, self-assembly ternary membrane with high conductivity for lithium-ion batteries

A kind of self-assembly ternary membrane, comprising the hyperbranched polyether, PVDF-HFP and ionic liquid, has been successfully prepared, and the resulting polymer electrolytes were fabricated for applications in lithium-ion batteries. The crystallinity and glass transition temperature (T _g) of the prepared polymer electrolytes were found to decrease with increase of the ionic liquid content, which were confirmed by XRD and DSC thermal analysis. The thermal stability and conductivity could be improved with addition of ionic liquid in the polymer electrolyte. The polymer electrolyte membranes were thermally stable at 320 °C, and the ionic conductivity can reach to 1.37 × 10 ^{- 3} S·cm ^{- 1} at room temperature. The electrochemical tests showed that the electrochemical stability of as-prepared polymer electrolyte was up to 4.9 V (vs. Li/Li ⁺), and the Li/LiFePO ₄ cell with the kind of polymer electrolyte delivered the initial discharge capacity of 101.6 mAh·g ^{- 1}.