Suppression of Self‐Discharge in Aqueous Supercapacitor Devices Incorporating Highly Polar Nanofiber Separators

One of the major problems limiting the applications of electric double‐layer (EDLC) supercapacitor devices is their inability to maintain their cell voltage over a significant period. Self‐discharge is a spontaneous decay in charged energy, often resulting in fully depleted devices in a matter of hours. Here, a new method for suppressing this self‐discharge phenomenon is proposed by using directionally polarized piezoelectric electrospun nanofiber films as separator materials. Tailored engineering of polyvinylidene fluoride (PVDF) nanofiber films containing a small concentration of sodium dodecyl sulfate (SDS) results in a high proportion of polar β phases, reaching 38 ± 0.5% of the total material. Inducing polarity into the separator material provides a reverse‐diode mechanism in the device, such that it drops from an initial voltage of 1.6 down to 1 V after 10 h, as opposed to 0.3 V with a nonpolarized, commercial separator material. Thus, the energy retained for the polarized separator is 37% and 4% for the nonpolarized separator, making supercapacitors a more attractive solution for long‐term energy storage.