长寿命及高功率锂离子电池用多孔石墨烯/聚偏氟乙烯功能层复合隔膜

A graphene/PVDF/PP multilayer composite separator for long-life and high power lithium-ion batteries

隔膜是锂离子电池的重要组成部分,对隔膜进行材料及结构的优化可以提高锂离子电池的性能。通过在普通商用聚丙烯(PP)隔膜表面构建多孔石墨烯/聚偏氟乙烯功能层的方式获得了复合隔膜材料,通过涂布及常温液相处理的方法调控涂层的孔隙结构,使复合隔膜对电解液的吸附性能明显提高,功能层使复合隔膜具有优异的离子透过性和单侧(石墨烯层)导电性。与采用普通聚丙烯隔膜相比,功能层复合隔膜在低倍率(0.5 C)下的电极材料容量发挥相当。而在高倍率(5 C)下,功能层复合隔膜下,电池容量发挥非常突出,并且600次循环后的容量保持率接近100%,而采用常规PP隔膜,电池材料则容量快速衰减失效。

The separator is an important part of lithium-ion batteries and its optimization from both material and structural consid-erations can improve the performance of the battery. We prepared multilayer separators by coating a slurry containing graphene and PVDF in N-methylpyrrolidone on one side of a commercial polypropylene （PP） separator,fol low ed by water trea tment at 60 ℃ for 6 h and vacuum drying at 60℃ for 12 h to manipulate the pores tructure of the comp o s ite layer. Results indic a te that the discharge capacities of batteries using PP and the composite separator were nearly the same at a low rate of 0.5 C. However,th ecapacity of the former at a high rate of 5 C fades quickly while that of the latter remains almost unchanged after 600 cycles. The composite sepa-rators have a high absorption and wettability of the electrolyte, resulting in an improved conductivity.