Coherent Integration of Organic Gel Polymer Electrolyte and Ambipolar Polyoxometalate Hybrid Nanocomposite Electrode in a Compact High-Performance Supercapacitor

Abstract

We report a gel polymer electrolyte (GPE) supercapacitor concept with improved pathways for ion transport, thanks to a facile creation of a coherent continuous distribution of the electrolyte throughout the electrode. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was chosen as the polymer framework for organic electrolytes. A permeating distribution of the GPE into the electrodes, acting both as integrated electrolyte and binder, as well as thin separator, promotes ion diffusion and increases the active electrode–electrolyte interface, which leads to improvements both in capacitance and rate capability. An activation process induced during the first charge–discharge cycles was detected, after which, the charge transfer resistance and Warburg impedance decrease. We found that a GPE thickness of 12 μm led to optimal capacitance and rate capability. A novel hybrid nanocomposite material, formed by the tetraethylammonium salt of the 1 nm-sized phosphomolybdate cluster and activated carbon (AC/TEAPMo12), was shown to improve its capacitive performance with this gel electrolyte arrangement. Due to the homogeneous dispersion of PMo12 clusters, its energy storage process is non-diffusion-controlled. In the symmetric capacitors, the hybrid nanocomposite material can perform redox reactions in both the positive and the negative electrodes in an ambipolar mode. The volumetric capacitance of a symmetric supercapacitor made with the hybrid electrodes increased by 40% compared to a cell with parent AC electrodes. Due to the synergy between permeating GPE and the hybrid electrodes, the GPE hybrid symmetric capacitor delivers three times more energy density at higher power densities and equivalent cycle stability compared with conventional AC symmetric capacitors.

An acrylate-based quasi-solid polymer electrolyte incorporating a novel dinitrile poly(ethylene glycol) plasticizer for lithium-ion batteries

“…The almost rectangular shapes of the CV profiles at low scan rates indicate that a capacitive behavior is the dominating factor of the electrode/electrolyte kinetics, which is caused by charge accumulation (double layer charging current) in the absence of an electrode reaction (Faradaic current) [50]. Dependence of the capacitance on the scan rate is noticeable: The rectangular shapes of the CV profiles become more distorted at higher scan rates, which is a factor of the resistive nature of the material and the polarization influence [51]. Figure 12b shows the calculated capacitance as a function of the scan rate.…”

Polyoxometalate intercalated MXene with enhanced electrochemical stability

“…CTAMX-PW12 does not present larger b-values even though PW12 clusters are dispersed homogeneously at the nanoscale. This is quite surprising at first glance, because in other studies (such as activated carbon/POMs, 26,42 reduced graphene oxide/POMs, 43 polypyrrole hydrogel wrapped CNT/POMs, 44 and metal-organic framework/POMs [45][46][47] ) where the POMs clusters are nano-dispersed (bright dots detected in HAADF-STEM), the b-values are close to 1, revealing that the redox reactions of the nano-dispersed PW12 clusters are surface capacitive. The electrochemical behaviours of CTAMX-PW12 seem to be contrary to these other studies.…”

Hybrid polymer gels for energy applications

“…Zhu, Gomez-Romero, and coworkers reported a GPE-based supercapacitor concept with improved pathways for ion transport, by the creation of a coherent continuous distribution of the electrolyte throughout the electrode. 263 In this work, PVDF-HFP was chosen as the polymer framework for organic electrolytes. A permeating distribution of the gel polymer electrolyte into the electrodes played a multifarious role as an integrated electrolyte and binder, as well as a thin separator.…”