What is it about?

Intrinsic p-type conductivity was observed in an otherwise aliphatic epoxy backbone through derivatization with stable radicals. The conductive potential of this combined radical-epoxy material was further investigated by prospecting for energy storage systems. This work identifies macroradical epoxy composites with 10% (w/w) conductive carbon as viable devices in supercapacitor application. In cross-linking, the appropriate selection of the diamine spacer has a profound impact on the curing and the resulting conformation of the polymer. The short-chain diamine spacer 1,2-diaminoethane exhibits the best supercapacitor performance yielding a maximum specific capacitance of 195 F g−1 at 1.0 A g−1. The specific capacitance remains at 99% at 1.0 A g−1 after repeatedly charging and discharging 10,000 times. The observed cycling stability is rare for materials exhibiting pseudocapacitance. This better performance than a reference conventional epoxy composite is attributed to the overall contributions of the electric double layer and pseudocapacitance effect with the effective utilization of the nanoscale porous polymeric structure. Furthermore, the pseudocapacitance is significantly enhanced by using the short-chain diamine spacer due to the closer radical-to-radical interactions and the excellent dispersibility of the added conductive particles.

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Why is it important?

• Macroradical epoxies have promising energy-storage prospects. • Macroradical epoxy composite electrodes are viable supercapacitors. • Superior cycling performance is observed, rare for pseudocapacitors. • Rheology and small-angle x-ray scattering correlate with electrode chemistry. • Magnets used during cross-linking are valuable in distinguishing morphology.

Perspectives

In this paper, the viability of macroradical epoxy monomer for supercapacitor applications, exhibiting excellent electrochemical properties and cycling stability compared to traditional epoxy-based systems of similar design, was demonstrated. The curing profile and nanomorphology have been investigated and relate the effect of the crosslinker chain length to observed capacitor performance. Insights into the impact of the diamine crosslinkers were obtained from oscillatory rheological and small-angle X-Ray scattering (SAXS) measurements using simple mathematical equations. Magnets employed during cross-linking proved valuable in distinguishing the SAXS results. In my opinion, the combined techniques applied in this study are novel and will benefit other researchers in analyzing related polymers. Furthermore, the insights gained from this work will aid other researchers in designing energy storage systems based on 3D cross-linked macroradicals.

Dr Jaworski C. Capricho
Henkel AG und Co KGaA

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This page is a summary of: Porous macroradical epoxy-based supercapacitors, Polymer, September 2022, Elsevier, DOI: 10.1016/j.polymer.2022.125356.
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