An enhanced poly(vinylidene fluoride) matrix separator with high density polyethylene for good performance lithium ion batteries

A sponge-like poly(vinylidene fluoride)/high density polyethylene (PVDF/HDPE) separator exhibiting high ionic conductivity and transference number of Li⁺ ion for lithium ion battery has been prepared by non-solvent induced phase separation (NIPS) method. HDPE fillers with size smaller than 250 nm are prepared with moderated reverse phase emulsion. The ion conductivity of PVDF/HDPE separator saturated with 1.0 M LiPF₆–ethylene carbonate (EC)/dimethyl carbonate (DMC)/ethyl methyl carbonate (EMC) (1:1:1, v/v/v) can be up to 2.54 mS cm^?1 at 25 °C, which is higher than that of pristine PVDF separator (1.85 mS cm^?1). The transference number of lithium ion with PVDF/HDPE separator is 0.495, better than that with commercial PP separator (0.33) and pristine PVDF separator (0.27). What is more, LiCoO₂/Li cells assembled with PVDF/HDPE separator show good C-rate and cycling performance which indicates great potential in serving as a good candidate of polymer separator for lithium ion batteries application.