Speaker
Description
The Era of the IoT and the paradigm of Sustainable Energy boosted the search for self-powered devices that harvest and store energy to satisfy the electrical needs of the generation of autonomous wearable electronics.1,2 Thermally-chargeable supercapacitors are a clean energy technology that is able to convert the waste thermal energy into electrical energy (as a power source) and, simultaneously, store that energy (as an energy storage system). These hybrid devices allow converting the waste thermal energy provided from low-grade heat sources (e.g., human body) into electrical energy by a thermally-induced migration of electrolyte ions towards the device electrodes based on the Soret effect.1–3
Herein, we report on the fabrication of a thermally-chargeable textile supercapacitor (TCSC) composed of two multiwalled carbon nanotube-coated cotton electrodes (MWCNT@cotton) and an all-solid-state ionic polyelectrolyte (PVA/H3PO4). The MWCNT@cotton electrodes were prepared by directly coating the cotton substrates with a MWCNTs dispersion through a scalable textile industry process. The ionic conductivity of PVA/H3PO4 electrolyte was tuned by doping the PVA matrix with different wt% of H3PO4, unveiling an ionic conductivity value of 39 mS/cm for a PVA/H3PO4 ratio of 1:1 (m/m). The TCSC was fabricated by sandwiching the ionic electrolyte between the MWCNTs/cotton electrodes. The thermally-induced power generation of the TCSC was evaluated, reaching a Soret coefficient of ~2 mV/K (up to 30 mV for an applied temperature gradient of 25 K). Concerning the energy storage features, the TCSC presented an electric double-layer charge storage mechanism, affording a working voltage of 2.27 V and an energy density of 4.33 Wh/kg at a power density of 620 W/kg. The high flexibility and the efficient performance of the TCSC, combined with the scalable and cost-effective fabrication process, make this device a feasible solution to satisfy the challenges of autonomous wearable electronics.
Acknowledgements: This work was funded by FEDER – European Regional Development Fund through COMPETE 2020 – Operational Programme for Competitiveness and Internationalization (POCI) and by Portuguese funds through Fundação para a Ciência e a Tecnologia (FCT)/MCTES under Program PT2020 in the framework of the projects PTDC/CTM-TEX/31271/2017 and NORTE-01-0145-FEDER-022096. This work was also funded by projects UIDB/50006/2020 and UIDB/04968/2020 through FCT/MCTES. R.S.C. thanks the MSc. grant funding from FEDER through project POCI-01-0247-FEDER-039833. A.L.P. thanks the junior researcher contract funded by European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 863307 (H2020-FETOPEN-2018-2019-2020-01). C.P. thanks FCT for FCT Investigator contract IF/01080/2015.
References
[1] X. Pu et al., Chem. Sci. 2021, 12 (1), 34–49.
[2] A.L. Pires et. al., ACS Appl. Electron. Mater. 2021, 3 (2), 696–703.
[3] M. Falk et al., Biosens. Bioelectron. 2019, 126 (July 2018), 275–291.
