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

Abstract

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.

Electrospun polar-nanofiber PVDF separator for lithium–sulfur batteries with enhanced charge storage capacity and cycling durability

“…33 Many methods have been developed to prepare b-phase PVDF, such as solvent casting, electrospinning, annealing, polymer stretching, and incorporation of filler materials. Electrospinning of PVDF nanofibers has become one of the most promising techniques 30,34 and can provide membranes with high porosity, high specific surface area and controllable pore size, and can improve the wettability for electrolytes. In the electrospinning method, a PVDF solution in organic solvent is prepared and loaded into a spinneret with a hollow needle, which is then placed under a high electric field (B10 6 V m À1 ).…”

“…Our previous studies concerned development of polar PVDF separator for supercapacitor use. 34 The membrane separators optimised for supercapacitors similarly needed to display very high porosity and electrolyte uptake, and they were consequently optimised to that end. It was the research hypothesis in the current study that such separators would then also act to limit polysulfide shuttling, and this is what is tested and proved here.…”

All‐in‐one Biomass‐Based Flexible Supercapacitors with High Rate Performance and High Energy Density

“…[1][2][3] Their electrochemical performance mainly depends on three key components including electrodes, separator, and electrolyte. [4,5] Thus far, traditional SCs usually use metal oxides, [6] carbon materials [7] or conductive polymers [8] as electrode materials, commercial glass fiber (GF) [9] or polyolefin-based membrane (PL) [10] as the separator, and liquid-based solutions (e.g., aqueous/organic solutions, [11,12] and ionic liquids [13] ) as electrolyte. This configuration presents three main drawbacks: The toxic metal-oxides/polymers-based electrodes and corrosive liquid-based electrolytes used in commercial SCs have some safety and environmental concerns, [14][15][16][17] this is especially the case for the next-generation SCs for wearable and scalable electronics.…”

Conjugated supercapacitor with suppressed self‐discharge constructed by pairs of prelithiated Nb2O5@C with optimized elemental and phase purity in the carbon shell

“…[19] Charge redistribution is due to the charge transfer caused by the uneven distribution of charge in the pores of the electrode. [20] Accordingly, current strategies to suppress self-discharge for supercapacitors are mainly focused on optimizing the structure of each component in the device including modifying the structure of the electrodes, the electrolytes, or the separators. [13,[21][22][23][24][25][26] Fundamentally, the selfdischarge of one electrode is accompanied by the departure of the charge carrier from the electrode, which is intuitively coupled with the property of the electrolyte and the counter electrode.…”