Optimization of acetonitrile/water content in hybrid deep eutectic solvent for graphene/MoS2 hydrogel-based supercapacitors
1T-MoS2@rGO-H based supercapacitor worked in a wide operating voltage of 2.3 V and achieved the maximum energy density of 31.2 Wh kg−1 at a power density of 1164 W kg−1. Further, the device exhibited 91% capacitance retention after 20,000 cycles. [Display omitted] •Flame-retardant hybrid DES electro...
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Veröffentlicht in: | Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2021-02, Vol.405, p.126706, Article 126706 |
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Zusammenfassung: | 1T-MoS2@rGO-H based supercapacitor worked in a wide operating voltage of 2.3 V and achieved the maximum energy density of 31.2 Wh kg−1 at a power density of 1164 W kg−1. Further, the device exhibited 91% capacitance retention after 20,000 cycles.
[Display omitted]
•Flame-retardant hybrid DES electrolyte was developed with a wide potential window (2.3 V).•Addition of co-solvent led to the superior conductivity and low viscosity.•1T-MoS2-rGO hydrogel exhibited higher energy and power density in the hybrid electrolyte.•The capacitance retention of 91% was achieved even after 20,000 cycles of GCD.
Herein, we are the first to develop a co-solvent-in-deep eutectic solvent (DES) system by mixing water and acetonitrile with a typical DES electrolyte consisting of acetamide and lithium perchlorate. The addition of co-solvents not only solves the problems of high viscosity and low conductivity of DES but also provides some unique properties. For example, the presence of water improves the flame-retardant property of the DES electrolyte. In contrast, the addition of acetonitrile further improves the ionic conductivity without compromising a wide electrochemical stability window (ESW). The effects of the amount of co-solvent in DES and the optimal molar ratio between co-solvents have been investigated. When the molar ratio of acetonitrile to water is 4.4:1, hybrid DES shows the best physical properties, including a wide ESW (2.55 V), superior conductivity (15.6 mS cm−1), and low viscosity (5.82 mPa·s). Furthermore, a series of spectroscopic measurements have been performed to understand the interaction among electrolyte components. It was found that water molecules were strongly coordinated to Li+ ions, and such interaction was not affected by the presence of acetonitrile molecules. On the other hand, we have demonstrated using hydrogel consisting of 1T-MoS2 and reduced graphene oxide (rGO) as the electrode materials for supercapacitors. This hydrogel inherited the porous structure of rGO hydrogel and the high conductivity of 1T-MoS2. Finally, high voltage symmetric supercapacitors have been fabricated by using hybrid DES and hydrogel as the electrolyte and electrode, respectively. An optimized supercapacitor works at a wide operating voltage of 2.3 V and achieves the maximum energy density of 31.2 Wh kg−1 at a power density of 1164 W kg−1. Furthermore, this device exhibited 91% capacitance retention after 20,000 cycles. |
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ISSN: | 1385-8947 1873-3212 |
DOI: | 10.1016/j.cej.2020.126706 |