Tag Archive for: supercapacitors

Publication on AWSensors technology

Understanding Electrolyte Ion Size Effects on the Performance of Conducting Metal–Organic Framework Supercapacitors

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Authors: Jamie W. Gittins, Kangkang Ge, Chloe J. Balhatchet, Pierre-Louis Taberna, Patrice Simon, Alexander C. Forse

Journal: Journal of the American Chemical Society

Abstract:

Layered metal–organic frameworks (MOFs) have emerged as promising materials for next-generation supercapacitors. Understanding how and why electrolyte ion size impacts electrochemical performance is crucial for developing improved MOF-based devices. To address this, we investigate the energy storage performance of Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with a series of 1 M tetraalkylammonium tetrafluoroborate (TAABF4) electrolytes with different cation sizes. Three-electrode experiments show that Cu3(HHTP)2 exhibits an asymmetric charging response with all ion sizes, with higher energy storage upon positive charging and a greater charging asymmetry with larger TAA+ cations. The results further show that smaller TAA+ cations demonstrate superior capacitive performances upon both positive and negative charging compared to larger TAA+ cations. To gain further insights, electrochemical quartz crystal microbalance measurements were performed to probe ion electrosorption during charging and discharging. These reveal that Cu3(HHTP)2 has a cation-dominated charging mechanism, but interestingly indicate that the solvent also participates in the charging process with larger cations. Overall, the results of this study suggest that larger TAA+ cations saturate the pores of the Cu3(HHTP)2-based electrodes. This leads to more asymmetric charging behavior and forces solvent molecules to play a role in the charge storage mechanism. These findings significantly enhance our understanding of ion electrosorption in layered MOFs, and they will guide the design of improved MOF-based supercapacitors.

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Publication on AWSensors technology

Highly Ordered Graphene Polydopamine Composite Allowing Fast Motion of Cations: Toward a High-Performance Microsupercapacitor

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Authors: Adnane Bouzina, René Meng, Cyrille Bazin, Hubert Perrot, Ozlem Sel, Catherine Debiemme-Chouvy

Journal: Adv. Mater. Interfaces (2023)

 

Abstract

The simple and eco-friendly preparation of microsupercapacitor remains a great challenge. Here are presented the preparation and the characterizations of an all-solid symmetric micro-supercapacitor based on a new composite formed of highly ordered graphene sheets due to the presence of polydopamine between the layers, which present a d-spacing of 0.356 nm. This graphene-polydopamine composite is prepared by electroreduction of graphene oxide (GO) followed by the electrooxidation of dopamine added into the initial solution, i.e., after GO reduction. In Na2SO4 solution, this composite material shows excellent capacitance and stability even at a high scan rate (2 V s−1) and a very low relaxation time (τ0) of 62 ms. This value is in very good agreement with the high transfer kinetic and low transfer resistance values of the ions implied in the charge storage process (Na+·2H2O and Na+) determined by ac-electrogravimetry. Finally, it is shown that the all-solid micro-supercapacitor (interdigitated electrodes obtained using a CO2 laser and Na2SO4/PVA hydrogel) prepared with this new composite delivers a remarkable energy density of 6.36 mWh cm−3 for a power density of 0.22 W cm−3 and exhibits excellent cycling stability (98% of retention after 10 000 cycles at 2 V s−1).

 

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Gravimetric and dynamic deconvolution of global EQCM response of carbon nanotube based electrodes by Ac-electrogravimetry

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Authors: F. Escobar-Teran, A. Arnau, J.V. García, Y. Jiménez, H. Perrot, O. Sel

Journal: Electrochemistry communications (2016)

The capacity charge storage of carbon nanotube (CNT) based electrodes was investigated by ac-electrogravimetry which couples fast quartz crystal microbalance (QCM) and electrochemical impedance spectroscopy (EIS). In contact with an aqueous NaCI electrolyte, evidence was found that there are two types of cations (Na+.H2O and H+) electroadsorbed with different kinetics for cathodic potentials and the Cl– ionsfor anodic potentials together with free water molecules. The reconstruction of the total mass response from independent ac-electrogravimetry measurements agrees perfectly well with the global EQCM response. Our findings reveal the unique sensitivity of the ac-electrogravimetry to provide a fair gravimetric and dynamic deconvolution of the global EQCM responses.

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