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The extremely low room-temperature ionic conductivity of solid-state polymer electrolytes (SPEs) ranging from 10-7 to 10-5 S cm-1 seriously restricts their practical application in solid-state lithium metal batteries (LMBs). Herein,...

Piezoelectric polymers hold great potential for various electromechanical applications, but only show low performance, with |d33 | < 30 pC/N. We prepare a highly piezoelectric polymer (d33 = −62 pC/N) based on a biaxially oriented poly(vinylidene fluoride) (BOPVDF, crystallinity = 0.52). After unidirectional poling, macroscopically aligned samples with pure β crystals are achieved, which show a high spontaneous polarization (Ps) of 140 mC/m2. Given the theoretical limit of Ps,β = 188 mC/m2 for the neat β crystal, the high Ps cannot be explained by the crystalline-amorphous two-phase model (i.e., Ps,β = 270 mC/m2). Instead, we deduce that a significant amount (at least 0.25) of an oriented amorphous fraction (OAF) must be present between these two phases. Experimental data suggest that the mobile OAF resulted in the negative and high d33 for the poled BOPVDF. The plausibility of this conclusion is supported by molecular dynamics simulations.

Oriented amorphous fraction in biaxially oriented poly(vinylidene fluoride) gives it significantly enhanced dielectric and ferroelectric properties.