Ion conductivity of polymer electrolytes derived from poly (p-phenylene terephthalamide)

Polymer electrolytes that exhibit lithium-ion conductivity of the order of 10−3 S cm−1 and excellent mechanical strength are prepared by impregnating aqueous gel films of poly (p-phenylene terephthalamide) (PPTA) with polyethylene glycol (PEG), polycarbonate in propylene carbonate (polyC·PC), or ethylene carbonate (EC), removing water, and soaking the impregnated polymer in lithium salt solution. The lithium-ion conductivity of the PPTA/PEG systems increases rapidly with the concentration of the LiBF4 in the lithium salt solution LiBF4/PC:EC:BL (25:25:50), to a maximum of 2.2 × 10−3S cm−1 at 0.8 M LiBF4, then decreases gradually between 1 and 2 M. This suggests that the ion conductivity is the result of LiBF4 uptake at the amide bond sites of the PPTA. With LiPF6/PC:EC:BL (25:25:50) in the range 0.8 to 1.5 M LiPF6 the PPTA/PEG systems exhibit a similar high conductivity. The PPTA/polyC·PC and the PPTA/EC systems also display high lithium-ion conductivities with the LiBF4 solutions.