Energy storage device and supercapacitor

1. An energy storage device, comprising:

a plurality of electric charge supercapacitors connected in parallel;

wherein each of the electric charge supercapacitors is an asymmetric nanocomposite supercapacitor, comprising:

a first electrode;

a second electrode;

a porous separator between the first and second electrodes;

wherein the porous separator is coated with an electrolyte and is at least one selected from the group consisting of a polypropylene membrane and a glass fiber membrane;

wherein the first electrode comprises:

a first substrate at least partially coated on one face with a first mixture of a first binding compound and at least one carbonaceous material selected from the group consisting of graphite, graphene, activated carbon, reduced graphene oxide, and highly reduced graphene oxide (HRG);

wherein the second electrode comprises:

a second substrate at least partially coated on one face with a second mixture of a second binding compound and monoclinic tungsten-oxide (m-WO 3 ) nanoplates;

wherein the face of the first substrate and the face of the second substrate coated with the carbonaceous material and m-WO 3 nanoplates, respectively, are separated by and in direct contact with the porous separator; and

wherein the first and second substrates are formed from at least one material selected from the group consisting of copper, nickel, and steel.

2. The energy storage device of claim 1 , wherein:

the electrolyte is at least one selected from a group consisting of a hydrogen halide, sulfuric acid, nitric acid, perchloric acid, chloric acid, an alkali metal salt, and an alkaline earth salt; and

the binding compound is at least one selected from a group consisting of polyvinylidene fluoride and n-methylpyrrolidone.

3. The energy storage device of claim 1 , wherein:

the first mixture comprises 10-20 wt % of the first binding compound and 80-90 wt % of the carbonaceous material based on the total weight of the first binding compound, and the carbonaceous material; and

the second mixture comprises 10-20 wt % of the second binding compound and 80-90 wt % of the m-WO 3 nanoplates based on the total weight of the binding compound, and the m-WO 3 nanoplates.

4. The energy storage device of claim 1 , wherein:

the carbonaceous material is HRG;

the HRG is substantially crystalline and in layered sheet form having 2-20 layers;

the sheets have an average d-spacing of 0.25-0.45 nm;

the HRG comprises at most 5% oxygen based on the total atomic weights of carbon, hydrogen, and oxygen in the HRG.

5. The energy storage device of claim 1 , wherein:

the m-WO 3 nanoplates are substantially monoclinic crystalline phase;

the platelets have an average d-spacing of 0.3-0.5 nm;

the platelets have an average length of 50-200 nm, an average width of 10-150 nm, and an average thickness of 5-20 nm; and

wherein the O and W elements are homogeneously distributed throughout the nanoplates.

6. The energy storage device of claim 1 , wherein:

the carbonaceous material is HRG;

the HRG has a surface area of 500-800 m 2 /g; and

the m-WO 3 nanoplates have a surface area of 150-250 m 2 /g.

7. The energy storage device of claim 1 , wherein:

the thickness of the coating of the carbonaceous material on the first substrate and the m-WO 3 nanoplates on the second substrate is less than 500 nm each.

8. The energy storage device of claim 1 , wherein:

the first electrode has a specific capacitance of at least 440 F/g at a current density of 0.5 A/g.

9. The energy storage device of claim 1 , wherein:

the second electrode has a specific capacitance of at least 310 F/g at a current density of 0.5 A/g.

10. The energy storage device of claim 1 , having:

a specific capacitance of at least 380 F/g at a current density of 0.5 A/g;

wherein the carbonaceous material is HRG.

11. The energy storage device of claim 10 , wherein:

at least 90% of the initial specific capacitance is maintained after 5000 charge-discharge cycles.

12. The energy storage device of claim 10 , having:

an energy density of at least 90 Wh/kg at a power density of 500 W/kg.

13. The energy storage device of claim 1 , wherein:

the supercapacitor is operated up to 1.8 V.

14. A wearable device comprising the energy storage device of claim 1 , wherein:

the energy storage device is electrically connected to a sensor; and

the energy storage device functions as a battery.

15. The energy storage device of claim 1 , comprising:

2-10 of the asymmetric nanocomposite supercapacitors.