Flexible energy storage device based on gylcerol gel electrolyte
A flexible energy storage device with a glycerol-based gel electrolyte is provided. The flexible energy storage device can include a pair of electrodes separated by the gel electrolyte. The electrolytes can be in gel form, bendable and stretchable in a device. The gel electrolyte can include glycerol, redox-active molybdenum-containing ions, and a secondary ionic substance. The secondary ionic substance can include a salt. The gel electrolyte can have a density of 1.4 to 1.9 g/cm 3 and an ionic conductivity of 2.3×10 −4 to 3.2×10 −4 Scm −1 . The flexible energy storage device may retain greater than 95% of an unbent energy storage capacity when bent at an angle of 10 to 170°.
1. A flexible energy storage device, comprising:
a pair of electrodes separated by a gel electrolyte, the gel electrolyte comprising glycerol, redox-active molybdenum-containing ions, and a secondary ionic substance,
wherein the flexible energy storage device retains greater than 75% of an unbent energy storage capacity when bent at an angle of 10 to 170°.
2. The flexible energy storage device of claim 1 , wherein the glycerol is present in an amount of 40 to 98 wt %, based on a total weight of gel electrolyte.
3. The flexible energy storage device of claim 1 , wherein the redox-active molybdenum-containing ions are present in an amount of 1 to 25 wt %, based on a total weight of gel electrolyte.
4. The flexible energy storage device of claim 1 , wherein the redox-active molybdenum-containing ions are molybdate anions.
5. The flexible energy storage device of claim 1 , wherein the secondary ionic substance is present in an amount of 1 to 35 wt %, based on a total weight of gel electrolyte.
6. The flexible energy storage device of claim 1 , wherein the secondary ionic substance is at least one selected from the group consisting of a hydroxide salt, a halide salt, a sulfate salt, a nitrate salt, a perchlorate salt, a tetrafluoroborate salt, a difluoro(oxalato)borate salt, a hexafluorophosphate salt, and a bis(trifluoromethanesulfonyl)imide salt.
7. The flexible energy storage device of claim 1 , wherein the secondary ionic substance is an alkali metal hydroxide.
8. The flexible energy storage device of claim 7 , wherein the alkali metal hydroxide is potassium hydroxide.
9. The flexible energy storage device of claim 1 , wherein the gel electrolyte is substantially free of water.
10. The flexible energy storage device of claim 1 , wherein the gel electrolyte is substantially free of polymer additives.
11. The flexible energy storage device of claim 1 , wherein the gel electrolyte has a density of 1.4 to 1.9 g/cm 3 .
12. The flexible energy storage device of claim 1 , wherein the gel electrolyte has an ionic conductivity of 2.3×10 −4 to 3.2×10 −4 Scm −1 .
13. The flexible energy storage device of claim 1 , wherein one or both of the electrodes are carbon electrodes.
14. The flexible energy storage device of claim 1 , wherein the energy storage device is a supercapacitor, a fuel cell, or a battery.
15. The flexible energy storage device of claim 14 , wherein the flexible energy storage device is a supercapacitor having a specific capacitance of 275 to 350 F/g.
16. The flexible energy storage device of claim 14 , wherein the flexible energy storage device is a supercapacitor having an energy density of 40 to 50 Wh/kg.
17. A method of forming the flexible energy storage device of claim 1 , the method comprising:
mixing the secondary ionic substance and the glycerol at 25 to 75° C. to produce an ion-containing mixture;
adding to the ion-containing mixture a salt comprising the redox-active molybdenum-containing ions to form an uncured gel;
vacuum-drying the uncured gel to form the gel electrolyte;
disposing the gel electrolyte on a first electrode such that the gel electrolyte forms a uniform film covering an entirety of a top surface of the first electrode; and
placing onto the gel electrolyte a second electrode such that the second electrode is separated from the first electrode by the gel electrolyte to form the flexible energy storage device.
18. The method of claim 17 , wherein one or both of the electrodes are carbon electrodes prepared by uniformly depositing on a conductive electrode support a film comprising activated carbon, conductive carbon, and a binder such that an entirety of a top surface of the conductive electrode support is individually covered by the film to form a carbon electrode.
19. A gel electrolyte, comprising:
40 to 98 wt % glycerol;
1 to 25 wt % redox-active molybdenum-containing ions; and
1 to 35 wt % a secondary ionic substance,
wherein the gel electrolyte is substantially free of water, and
wherein the gel electrolyte has a density of 1.4 to 1.9 g/cm 3 and an ionic conductivity of 2.3×10 −4 to 3.2×10 −4 Scm −1 .