Lithium-ion battery has become the new safe and pollution free green energy

and has the advantages of high work voltage

high energy density

low self discharge rate and long cycle life. Separator as an essential part of the battery plays a key role in the performance of the battery.Its main function is to keep the positive and negative electrodes apart to prevent electrical short circuit and at the same time allow rapid transport of ionic charge carriers needed to complete the circuit during the passage of current in an electrochemical cell.Despite the widespread use of separator

a great need still exists for improving performance

increasing life

and reducing cost.In this paper

the composite membrane based on poly(vinylidene fluoride)(PVDF)and a polyethylene terephthalate (PET)non-woven matrix was prepared by coating PVDF/NMP solution on the matrix under the optimal condition.The pore structure in the PVDF region was generated by immersion precipitation of the polymer solution.Physical properties and battery performance of composite membrane were compared with those of the Celgard separator.The results showed that the composite membrane had bigger pore size and better pore distribution

porosity of 48.5%

ionic conductivity of 0.346 mS·cm-1 and tolerance of 250.8℃.The capacity of Li-ion battery made with the composite membrane was 48.7 mA·h and was maintained at about 77.9% of the initial value on the 100th cycle at room temperature.The battery also showed good performance at different discharge rates and could meet the requirements of practical application.