Speaker
Description
Hybrid supercapacitors are energy storage devices combining a negative carbon electrode (capacitive storage) and a positive electrode of transition metal oxide/hydroxide (faradic or pseudocapacitive storage). Those devices can reach high power density, but they need to be improved in terms of energy density [1]. Previous studies carried out in the laboratory have shown that positive electrodes based on nanocomposites of lamellar cobalt and manganese oxyhydroxides ( β(III)-CoOOH and Birnessite type δ-MnO2 ) prepared by exfoliation/restacking are promising, especially at high rate [1]. The main objective of this work is to optimize the final nanocomposite by changing the morphology of the initial cobalt and manganese hydroxides. A series of mixed Mn/Co materials was therefore studied in order to highlight the combinations of initial morphologies generating the best interaction, likely to lead to high stability during cycling as well as to optimal electrochemical performance. Playing on the synthesis conditions (various precipitation processes or HT synthesis), three different morphologies of initial δ-MnO2 birnessite were obtained (nano-platelets, veils and micro-platelets) and two for β(III)-CoOOH (platelets with different size). By combining all the Mn and Co precursors, we obtained six different exfoliated/restacking materials, which all show electrochemical performances better than the additional capacities of Mn and Co precursors. This is the combination with the MnO2 veals and the more divided β(III)-Co that leads to the highest capacity and synergy, thanks to a more homogeneous distribution of nanoobjects , due to the smaller size of the primary particles of the initial materials.
[1] P. Simon, Science 2014, 343 (6176), 1210−1211
[2] C. Tang, ACS Appl. Energy Mater. 2019, 2, 11, 7832–7842
| Speaker Country | France |
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