Abstract: 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.

Key words: composite membrane, immersion precipitation, ionic conductivity, electrochemical property, pore structure

摘要： 采用浸没沉淀相转化法,以聚酯(PET)无纺布为底膜,在其上涂覆聚偏氟乙烯(PVDF)制备复合隔膜,应用于动力锂离子二次电池隔膜。将制备的复合隔膜与Celgard隔膜进行了孔结构分析、电化学性质、热性能等理化性质及电池性能检测对比。结果显示,复合隔膜孔径尺寸较大且分布均一,孔隙率达到48.5%,可以承受250.8℃的高温,离子电导率达0.346 mS·cm^-1,使用该隔膜的锂离子电池具有很好的倍率特性,初次放电容量达48.7 mA·h,循环100次后仍保持77.9%的容量,其性能与市售Celgard隔膜基本相当,能满足实际应用的要求。

关键词: 复合隔膜, 浸没沉淀法, 离子电导率, 电化学性质, 孔结构