In Situ Formation of “Dimethyl Sulfoxide/Water‐in‐Salt”‐Based Chitosan Hydrogel Electrolyte for Advanced All‐Solid‐State Supercapacitors

Abstract

Biodegradable hydrogel electrolytes are particularly attractive in the fabrication of all‐solid‐state supercapacitors due to environmental benignity and avoiding of leakage. The introduction of “water‐in‐salt” (WIS) electrolytes into hydrogels will further broaden the electrochemical stability window of aqueous supercapacitors significantly. Meanwhile, the addition of an organic co‐solvent can effectively overcome the inevitable salt precipitation and extend the temperature adaptability. Herein, an in situ cross‐linking approach was demonstrated without any extra binder to obtain a “dimethyl sulfoxide/water‐in‐salt”‐based (DWIS) chitosan hydrogel electrolyte. Interestingly, the addition of 4–7 mol L−1 of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salts not only conforms to the criterion of WIS, but also promoted the successful gelation through the supramolecular complexation between Li+‐solvated complexes and chitosan chains. A hydrogel‐based all‐solid‐state supercapacitor was fabricated using the DWIS chitosan hydrogel as the electrolyte and separator while nitrogen‐doped graphene hydrogel (NG) was used as the electrode. The optimized supercapacitor with a wide operating voltage of 2.1 V showed a high specific capacitance of 107.6 F g−1 at 1 A g−1, remarkable capacitance retention of 80.1 % after 5000 cycles, a superior energy density of 62.9 Wh kg−1 at a power density of 1025.5 W kg−1, and excellent temperature stability in the range of −20 to 70 °C. These findings suggest that the as‐prepared hydrogel electrolyte holds great potential in the practical application of high‐performance solid‐state energy storage devices.

Bio Based Batteries

“…[69] Further developments to combine classical gel electrolytes with WISE are shown in ref. [70], (Figure 4b) where chitosan is used to form a gel network in the presence of two miscible solvents (water and DMSO) and a fluorinated salt, to make a 2.1 V supercapacitor construction, where both anode and cathode materials derive from graphene oxide in hydrogel formats. Thus the nanostructure of both electrodes and electrolytes is defined by the polymer physics of gels.…”

Photoassisted Reduction Synthesis of Pt@SnO2/Graphene Catalysts with Excellent Activities toward Methanol Oxidation

“…Graphene oxide (GO) was prepared by oxidation of graphite powder following a modified Hummers’ method as described previously. − In a typical synthetic process for the growth of SnO 2 in graphene frameworks, a facile hydrothermal method and subsequent calcination were adopted. First, 50 mg of SnCl 2 precursor was dissolved in 5 mL of ethanol and then mixed with 10 mL of GO solution (5 mg mL –1 ) with the aid of vigorous ultrasound for 30 min.…”

Recent Advancements on Biopolymer‐ Based Flexible Electrolytes for Next‐Gen Supercaps and Batteries: A Brief Sketch

“…This exceptional performance was accredited to the ultra‐high porosity of the membrane which not only provided sufficient space for the storage of electrolyte but also brought forth additional channels for the transmission of ions. On top of this, ability to retain the capacity was found to be much higher in the case of the LPM‐ Li 2 SO 4 electrolyte with 88 % retention even after 10,000 cycles at 1.8 V accompanying an energy density of 16.08 W h Kg −1 while the supercapacitor based on liquid electrolyte only had a capacity retention of 53 % due to the inhibition of activity of water resulting from several physical and chemical effects [73] …”

“…(d) Freeze dried LPM ‐based hydrogel electrolyte using Li 2 SO 4 (e) Ionic conductiviy of LPM membranes prepared via different conditions using Li 2 SO 4 as conducting additive. Reproduced with permission [73] . Copyright, Wiley, 2020.…”