聚磷腈原位改性复合锂电隔膜的制备与性能

Preparation and properties of polyphosphazene modified composite separator for lithium-ion battery

锂离子电池要求隔膜具有良好的亲液性和耐热性。本文设计原位限域聚合法,利用聚(环三磷腈-4,4-磺酰基二苯酚)微球(PZSMS)修饰聚偏氟乙烯(PVDF)纤维基膜,通过单体与引发剂分别引入的策略调控PZSMS的尺寸和分布,促进PVDF纤维表面连续包覆层的形成,获得新型复合膜。对隔膜的理化性能(孔道结构、力学性能、电解液性能和耐热性)和电池性能(循环性能、倍率性能)进行系统研究。结果表明:在优化条件下,复合膜的吸液率和离子电导率分别达到433%和1.47 mS/cm,拉伸强度大于25 MPa,且在150℃、0.5 h内热收缩率低于2%,优于PVDF基膜及市售聚乙烯隔膜(PE)隔膜。在钴酸锂/石墨电池中,优化的复合膜显示出较好的电池充放电性能,如8.0 C时的放电容量为0.5 C时的76%,200次循环后放电容量保持率为97%。因此,原位限域聚合法制备的PZSMS修饰PVDF纤维膜在锂离子电池中显示出较好的应用前景。

Separators with superior electrolyte property and thermal stability are in urgent need for lithium-ion batteries(LIBs).This work designed a space-confined polymerization method to fabricate an advanced composite separator,in which poly(cyclotriphosphazene-co-4,4-sulfonyldiphenol)microspheres(PZSMS)grow directly in poly(vinylidene fluoride)(PVDF)membrane as the substrate.To regulate the size and distribution of PZSMS,triethylamine vapor as acid-binding agent is introduced into PVDF membrane separately from the polymeric monomers.The physical-chemical properties and battery performances of PPCS were systematically characterized,such as the structure,tensile strength,electrolyte property and thermal resistance as well as the charge-discharge performance.The results show that under the optimized conditions,the liquid absorbency and ionic conductivity of the composite membrane reach 433%and 1.47 mS/cm,respectively,the tensile strength is greater than 25 MPa,and the thermal shrinkage rate is lower than 2%at 150℃and 0.5 h,which is better than that of PVDF based membrane and commercial polyethylene(PE)membrane.The LiCoO2/graphite cells with optimized separators exhibit satisfactory discharge capacity retention of 76%at 8.0 C compared with that at 0.5 C and preferable cycling stability with a capacity retention of 97%after 200 cycles.Therefore,PZSMS modified PVDF fibrous membrane prepared by space-confined polymerization method shows a good application prospect in lithium-ion batteries.