In-Depth Investigation of Manganese Dioxide as Pseudocapacitive Electrode in Lithium- and Sodium-Doped Ionic Liquids

Thibaud Guillemin (1, 2) , Camille Douard (1, 2) , Anthony Impellizzeri (1) , Christopher Ewels (1) , Bernard Humbert (1) , Christophe Lethien (3, 2, 4, 5) , Scott Wilfred Donne (6) , Jean Le Bideau (1, 2) , Thierry Brousse (2, 1)

1 IMN - Institut des Matériaux de Nantes Jean Rouxel
2 RS2E - Réseau sur le stockage électrochimique de l'énergie
3 IEMN - Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520
4 IUF - Institut universitaire de France
5 CSAM - IEMN - Circuits Systèmes Applications des Micro-ondes - IEMN
6 UoN - University of Newcastle [Callaghan, Australia]

We investigate the contribution of pseudocapacitance to the overall capacitance of MnO2 electrodes in pure and alkaline-doped ionic liquids via two spectroscopic methods: step potential electrochemical spectroscopy (SPECS) and in situ Raman spectroscopy. For both characterization methods, thin-film electrodes of birnessite-like amorphous MnO2 were cycled in Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, pure or doped with lithium or sodium. SPECS allows determination of the influence of the electrolyte composition on the electrochemical behavior of the MnO2 electrodes. Pseudocapacitive charge storage can account for over half of the total capacitance with alkaline-doped ionic liquids. In situ Raman spectroscopy provided insight into the reversible ion intercalation in the MnO2 structure, which appears to be controlled by EMIm+ cations. These findings are supported by density functional theory calculations, which further help unveil the charge storage mechanism in birnessite-like amorphous MnO2 thin films operated in pure and alkaline-doped ionic liquids.

Mots clés: Raman spectroscopy; supercapacitor; MnO2; Ionic liquid; Pseudocapacitance; Density Functional Theory; Step potential electrochemical spectroscopy

Domaines: Matériaux; Autre

Thibaud Guillemin, Camille Douard, Anthony Impellizzeri, Christopher Ewels, Bernard Humbert, et al.. In-Depth Investigation of Manganese Dioxide as Pseudocapacitive Electrode in Lithium- and Sodium-Doped Ionic Liquids. Journal of The Electrochemical Society, 2023, 170 (10), pp.100531. ⟨10.1149/1945-7111/ad0180⟩. ⟨hal-04239177⟩