TW202019819A - Fabrication method of combining nitrogen-doped porous graphene and supercapacitor exhibiting high volumetric energy density and high volumetric power density - Google Patents

Abstract

A fabrication method of combining nitrogen-doped porous graphene and a supercapacitor is disclosed. The present invention is a supercapacitor having high volumetric energy and high power density, which includes an upper and a lower cover, a spring lamination, a working electrode, a separator membrane, a counter electrode and an organic liquid electrolyte. A button cell disclosed in the present invention is CR2032, the working electrode and the counter electrode are coated with a composite coating paste prepared through mixing activated carbon/nitrogen-doped porous graphene/a conductive additive/a binder on a aluminum substrate, a cellulose separator membrane produced by the Nippon Kodoshi Corporation is selected as the separator membrane, and 1M TEABF4/PC is selected to be used as the organic liquid electrolyte. The supercapacitor fabricated by the present invention is able to produce capacitance value as high as 122F/g, and the power density can be as high as 31kW/Kg.

Description

Nitrogen-doped porous graphene combined ultra-high capacitor and manufacturing method thereof

The invention relates to a nitrogen-doped porous graphene combined ultra-high capacitor and a preparation method thereof. The ultra-high capacitor has high volume energy and power density.

For electrode materials of energy storage devices, the chemical modification technology of graphene is a very effective and feasible method to improve the electrochemical performance of electrode materials. Chemical doping (Doping) technology is one of the generally effective methods used to adjust the electronic properties of graphene. It uses doping other atoms, such as nitrogen atoms, to chemically modify graphene so that the graphene surface has specific functional groups. This changes the electrical properties of graphene.

Nitrogen-doped graphene uses the effect of chemical doping to replace nitrogen atoms or functional groups containing nitrogen with carbon atoms in the original graphene lattice. Nitrogen atoms with lone electron pairs can be mixed with sp _{2 of} graphene The carbon lattice structure of the orbital region forms a bond, so that the graphene surface has nitrogen functional groups to form nitrogen-doped graphene. Due to the strong electronegativity of nitrogen atoms, it will affect the surrounding carbon atoms, causing changes in the electrical properties of graphene.

Due to the doping effect of nitrogen atoms, the electrical structure of graphene changes. In terms of performance, nitrogen-doped graphene has many properties that are different from pure graphene, such as increased conductivity, changes in energy band, The improvement of electrocatalytic activity makes nitrogen-doped graphene widely used in various fields, including field effect transistors, lithium ion batteries, fuel cells, photocatalysts, sensors and The application of supercapacitors has good development feasibility.

The current methods for preparing nitrogen-doped graphene can be roughly divided into two categories: direct synthesis and post-synthesis treatment. The direct synthesis method uses small molecules containing carbon and nitrogen to directly synthesize nitrogen-doped graphene. Such methods currently mainly include chemical vapor desposition (CVD) and direct current arc (Arc-discharge). , Hydrothermal (Hydrothermal), etc.; and the post-synthesis treatment method is to use graphene oxide (GO) or graphene through plasma treatment (Plasma treatment), chemical treatment (Hydrazine hydrate treatment) or thermal treatment (Thermal treatment) and other methods with high activity and energy to carry out chemical modification, in the above methods, often using nitrogen-containing compounds such as ammonia, pyridine, acetonitrile, melamine, urea, etc. as a nitrogen source for chemical doping to make the original crystal The carbon atoms in the lattice are replaced by nitrogen atoms to form a structure with a nitrogen-bonding functional group.

However, there is currently no simple and time-saving method for preparing nitrogen-doped porous graphene. Therefore, the present invention provides a simple and rapid method for preparing nitrogen-doped porous graphene, which utilizes rapid temperature rise and continuous introduction of nitric oxide (NO gas) In one step, nitrogen-doped porous graphene is prepared and added to the activated carbon electrode material to prepare high-performance supercapacitors. Nitrogen-doped porous graphene not only has the effect of improving the conductivity and capacity of the electrode, in addition, the use of this method can reduce the residue of functional groups, and simplify the complicated preparation steps to achieve a fast and convenient process method.

The reason is that, in view of this, the inventor upholds many years of rich design development and practical production experience in the relevant industry, studies and improves on existing technologies and deficiencies, provides a nitrogen-doped porous graphene combined ultra-high capacitor and its manufacturing method, In order to achieve the purpose of better practical value.

One category of the invention is to provide an ultra-high capacitor. According to a specific embodiment of the present invention, the ultra-high capacitor of the present invention includes an electrode having an active material of nitrogen-phosphorus doped porous graphene, and an organic electrolyte.

Further, the organic solvents of the organic electrolyte include ethylene carbonate (PC), acetonitrile (AN), N,N-dimethyl amide (NMP), dimethyl acetamide (DMA), tetra Any one or a combination of hydrofuran (THF); the cations of the organic electrolyte include quaternary ammonium salt (R ₄ N ⁺ ), lithium salt (Li+), quaternary phosphorus salt (R ₄ P ⁺ ) aromatic microphone sit salt (EMI) according to any one or a combination of; the anion of an organic electrolytic solution comprising ^{_{CO 4 -, BF 4 -,}} PF 4 -, AsF 6 -, (CF 3 SO 2) 2NB - It is any one or a combination of anions, tetraethyl ammonium tetrafluoroborate (TEMABF ₄ , TMABOB, TMADFOB), etc.

Among them, the active material is deposited on the conductive substrate by means of doctor blade coating.

In summary, the ultra-high capacitor of the present invention using nitrogen-doped porous graphene as an organic electrolyte has good volume energy and power density performance. Nitrogen-doped porous graphene is added to the activated carbon electrode to improve the energy density and power density performance of ultra-high capacitors. The energy density of the ultra-high capacitor prepared by the invention can be as high as 21Wh/Kg, and the volume power density can be as high as 31kW/Kg.

The above summary, the following detailed description and the drawings are intended to further explain the ways, means and effects of this creation to achieve the intended purpose. The other purposes and advantages of this creation will be explained in the subsequent description and drawings.

1‧‧‧Ultra high capacitor

11‧‧‧ isolation film

12‧‧‧Working electrode

13‧‧‧Spring leaf

15‧‧‧Top cover

16‧‧‧ Lower cover

17‧‧‧ counter electrode

S ₁ ~ S ₃ , S ₁₁ ~ S ₁₃ , S ₂₁ ~ S ₂₆ , S1 ~ S3, S4 ~ S6

FIG. 1 is a schematic diagram of an explosion of an ultra-high capacitor according to an embodiment of the invention.

FIG. 2 is a graph showing the surface morphology of (a) graphene and (b) nitrogen-doped porous graphene.

FIG. 3 is a graph showing the cycle life comparison of graphene and nitrogen-doped porous graphene on an activated carbon electrode.

Fig. 4 is a flow chart showing a method for manufacturing an ultra-high capacitor.

FIG. 5 is a flow chart showing the preparation method of the working electrode and the counter electrode.

6 is a flow chart of preparation of graphite oxide.

7 is a flow chart showing a method for preparing an active material containing nitrogen-doped porous graphene.

FIG. 8 is a flowchart showing a method for preparing active material without doped graphene.

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail with reference to the accompanying drawings and examples. It is worth noting that these embodiments are only representative embodiments of the present invention, and the specific methods, devices, conditions, materials, etc. exemplified therein are not intended to limit the present invention or the corresponding embodiments.

In the description of this specification, the description referring to the terms “a specific embodiment”, “another specific embodiment” or “partial specific embodiment” means that the specific features, structures, materials or characteristics described in conjunction with the embodiment include In at least one embodiment of the invention. In this manual, The schematic representation of the above terms does not necessarily refer to the same embodiment. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments.

In the description of the present invention, it should be understood that the terms "portrait, landscape, up, down, front, back, left, right, top, bottom, inside, outside" and other indicated orientation or positional relationship are based on the drawings The orientation or positional relationship shown is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limit.

Please refer to FIG. 1, which is an exploded schematic view of an ultra-high capacitor 1 according to an embodiment of the present invention. According to a specific embodiment of the present invention, the ultra-high capacitor 1 of the present invention may be a two-pole ultra-high capacitor, which includes an upper cover 16, a spring piece 13, a counter electrode 17, an isolation film 11, a working electrode 12, and a lower cover 15 And an organic electrolyte (not shown) contained between the upper cover 16 and the lower cover 15. The working electrode 12 and the counter electrode 17 are disposed between the upper cover 16 and the lower cover 15. Both the working electrode 12 and the counter electrode 17 have an active material and conductive substrate of nitrogen-doped porous graphene, and the active material is deposited on the conductive substrate, and Nitrogen-doped porous graphene is a porous graphene surface doped with more than 3 at% nitrogen. The separator 11 is disposed between the working electrode 12 and the counter electrode 17, and the organic electrolyte is accommodated between the upper cover 16 and the lower cover 15. The organic solvent of the organic electrolyte may include ethylene carbonate (PC) and acetonitrile (AN) , N,N-dimethylamide (NMP), dimethylacetamide (DMA), tetrahydrofuran (THF), etc., or any combination thereof. The cation of the organic electrolyte may include any one or a combination of quaternary ammonium salt (R ₄ N ⁺ ), lithium salt (Li+), quaternary phosphorus salt (R ₄ P ⁺ ), and aromatic imidate (EMI). Anionic organic electrolytic solution comprising ^{_{CO 4 -, BF 4 -,}} PF 4 -, AsF 6 -, (CF 3 SO 2) 2 NB -, alkylamine salts four _{tetraethyl ammonium tetrafluoroborate (TEMABF 4, TMABOB} , TMADFOB) , etc. Any one or combination of them.

The model of the button battery in this embodiment is CR2032. The working electrode 12 and the counter electrode 17 are both coated with an aluminum substrate containing an active material, that is, the working electrode 12 may be the same as the counter electrode 17, but it is not limited thereto. In another embodiment, the counter electrode 17 may only be a conductive substrate, such as an aluminum substrate or a stainless steel substrate. In another embodiment, the active material on the conductive substrate may be non-nitrogen and phosphorus doped porous graphene, such as nitrogen doped porous graphene, phosphorus doped porous graphene, porous graphene, graphene, nano Carbon materials such as rice carbon tubes and activated carbon. The separator is made of Nippon Kodoshi Corporation's cellulose separator. The organic electrolyte is 1M TEABF ₄ /PC.

In this embodiment, the components of the ultra-high capacitor 1 can be processed separately before packaging. Before assembling, the upper cover 16, the lower cover 15 and the spring sheet 13 must be immersed in 95% alcohol for ultrasonic shock cleaning for one hour, and then placed in an 80°C oven under general atmosphere to bake overnight. The aluminum substrate will be wiped clean with alcohol.

In an embodiment, please refer to FIG. 4, a method for manufacturing an ultra-high capacitor 1 includes the following steps: S ₁ : preparing an active material including nitrogen-doped porous graphene. S ₂ : Deposit an active substance on the conductive substrate to form the working electrode 12 and the counter electrode 17. S ₃ : Adsorb organic electrolyte on the surfaces of the working electrode 12 and the counter electrode 17. Please refer to FIG. 5, and the preparation method of the working electrode 12 and the counter electrode 17 may include the following steps: S ₁₁ : Activated carbon, nitrogen-doped porous graphene, conductive carbon black, thickener, adhesive at a weight percentage of 89.5: 1.5:5:1.5:2.5 ratio, and add appropriate amount of deionized water to mix the slurry uniformly by mortar or hand grinding. S ₁₂ : The uniformly mixed slurry is coated on the aluminum substrate by a blade coater, the blade thickness can be 50 μm, and the coating speed of the blade coater can be 300 rpm. S ₁₃ : Put the aluminum substrate coated with the paste into an oven and bake it in a vacuum state at 90°C for 3 hours, then cool down, and cut it to form the working electrode 12 and the counter electrode 17 as described The size of the cut area is 1.33 cm ² . Among them, the conductive carbon black can be Super P (Super P), the thickener is carboxymethyl cellulose (CMC), the adhesive is styrene-butadiene copolymer (SBR), and used The solvent system is deionized water.

After that, the above components are assembled inside the glove box (under a protective atmosphere) to form the above-mentioned two-pole ultra-high capacitor. Before the working electrode 12 and the counter electrode 17 are put into the glove box, the working electrode 12 and the counter electrode 17 are put into an oven and baked in a vacuum state of 100° C. for 3 hours and then cooled down to remove moisture. Immediately after the temperature is lowered, the working electrode 12 and the counter electrode 17 are sent to the glove box. Then, inside the glove box, the ultra-high capacitor 1 is assembled in the order of the lower cover 15, the working electrode 12, the separator 11 (simultaneously dripping the electrolyte), the counter electrode 17, the spring piece 13 and the upper cover 16 (as shown in FIG. 1) .

Further, the ultra-high capacitor 1 after the assembly can be electrically activated to electrically activate the working electrode 12 to which the organic electrolyte is adsorbed. The activation condition is from the open circuit potential, the current density is 1A/g, the potential window is 2.7V, and the constant current is charged and discharged for 3 cycles.

In addition, please refer to FIG. 7, the foregoing preparation method of the active material containing nitrogen-doped porous graphene may include the following steps: S1: graphite oxide (GO) is put into a high-temperature furnace; S2: 50c.c./min Nitrogen oxide gas, one of the gas flow rates for one hour; S3: After heating to 900°C at a heating rate of 40°C/min and holding the temperature for 1 hour, the temperature is naturally reduced to room temperature to prepare the activity containing nitrogen-doped porous graphene substance.

In order to prove the benefits of nitrogen-doped porous graphene, the present invention also prepared graphene active material as a control group. The preparation process of the graphene active material is to put graphite oxide in a nitrogen environment (50sccm) for heat treatment, and the heating rate and temperature holding time are the same as the preparation process of the nitrogen-doped porous graphene. In addition, the ratio of the slurry and the preparation of the working electrode are also the same as the nitrogen-phosphorus-doped porous graphene active material of the present invention.

Further, please refer to FIG. 8, the preparation method of undoped graphene active material includes the following steps: S4: graphite oxide (GO) is put into a high-temperature furnace; S5: nitrogen gas with a gas flow rate of 50 c.c./min Hours; S6. After heating to 900°C at a heating rate of 40°C/min and holding the temperature for 1 hour, the active material can be prepared by naturally cooling to room temperature without being doped with graphene.

The above preparation process of graphite oxide, please refer to FIG. 6, which may include the following steps: S ₂₁ : In a fume hood, mix the sulfuric acid and nitric acid mixed acid solution in an ice bath for 15 minutes, then add commercially available natural graphite ( (Purity 99.999%, above 150mesh) and continue stirring for 15 minutes; S ₂₂ : Slowly add potassium perchlorate, its purpose is to avoid excessive oxidation reaction caused by excessive heating rate or solution splash, and stir in an ice bath for 96 hours; S ₂₃ : Add 4 liters of deionized water, stir and dilute, then filter, and then wash with hydrochloric acid until no sulfate ion (SO ₄ ^2- ) remains in the solution; S ₂₄ : Wash it with deionized water until the pH is neutral After drying; S ₂₅ : soak the above product in 65% alcohol solution for 12 hours, and then wash it with deionized water several times after filtering; S ₂₆ : filter the solution and put it in a 90°C oven to dry overnight, you can get Graphite oxide.

Please refer to Table 1 for graphs of carbon, oxygen, and nitrogen in graphene and nitrogen-doped porous graphene. The atomic percentage of carbon, oxygen, and nitrogen in nitrogen-doped porous graphene is 89:8:3. Nitrogen-doped porous graphene is a porous graphene surface doped with more than 3 at% nitrogen.

Please refer to FIG. 2, the nitrogen-doped porous graphene is overall fluffy, and it can be observed that the surface has many fine holes.

The electrochemical characteristic measurement of the present invention uses a potentiostat (manufacturer is Solartron), adopts the chronopotentiometric measurement method, and sets the measurement potential window to 0~2.5V. By outputting a fixed current, the super The change of the potential of the capacitor with time. Use this to measure and compare the evaluation of specific capacitance, energy density, and power density.

Please refer to Table 2 for a comparison of the specific capacitance values of graphene and nitrogen-doped porous graphene at different current densities for activated carbon electrodes. Compared with undoped graphene, nitrogen-doped porous graphene is 50A/ Under constant current charge and discharge conditions, g has excellent electrical performance. The electrical capacity of undoped porous graphene is only 21F/g, while the electrical capacity of nitrogen-doped porous graphene can reach 40F/g. Its excellent fast charge and discharge characteristics can be mainly attributed to nitrogen doping, which can provide free electrons and increase the concentration of electrons to improve the conductivity, so that it has better performance under high-speed charge and discharge environment. Under the condition of 50A/g constant current charge and discharge, the power density can be further estimated to be as high as 31kW/Kg.

Please refer to Figure 3, after 6000 cycles of activated carbon supercapacitors (ACs), the capacity retention rate is about 81%; and the activated carbon supercapacitors with undoped graphene are 78%; AC with nitrogen doping The porous graphene activated carbon supercapacitor is 81%. The addition of a small amount of graphene in the present invention has little effect on the cycle stability of the overall electrode material.

In summary, the ultra-high capacitor of the present invention using nitrogen-doped porous graphene as an organic electrolyte has good volume energy and power density performance. Nitrogen-doped porous graphene is added to the activated carbon electrode to improve the energy density and power density performance of ultra-high capacitors. The energy density of the ultra-high capacitor prepared by the invention can be as high as 21Wh/Kg, and the volume power density can be Up to 31kW/Kg.

The above-mentioned embodiments are merely illustrative of the characteristics and effects of the present invention, rather than limiting the scope of the essential technical content of the present invention. Anyone who is familiar with this skill can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the rights of the present invention should be as listed in the scope of patent application mentioned later.

1‧‧‧Ultra high capacitor

11‧‧‧ isolation film

12‧‧‧Working electrode

13‧‧‧Spring leaf

15‧‧‧Top cover

16‧‧‧ Lower cover

17‧‧‧ counter electrode

Claims (13)

An ultra-high capacitor, comprising: an upper cover and a lower cover; a working electrode and a pair of electrodes, both having an active material of nitrogen-doped porous graphene, arranged between the upper cover and the lower cover; an isolation film, It is arranged between the working electrode and the pair of electrodes; and an organic electrolyte is accommodated between the upper cover and the lower cover. The ultra-high capacitor as described in item 1 of the patent application scope, wherein the organic solvent of the organic electrolyte includes ethylene carbonate (PC), acetonitrile (AN), N,N-dimethyl amide (NMP), di Either or any combination of methyl acetamide (DMA) and tetrahydrofuran (THF). The ultra-high capacitor as described in item 1 of the patent application scope, wherein the cation of the organic electrolyte contains quaternary ammonium salt (R ₄ N ⁺ ), lithium salt (Li+), quaternary phosphorus salt (R ₄ P ⁺ ), aromatic Any one or a combination of iminium salt (EMI). The ultra-capacitor in item 1 of the scope of the patent, wherein the organic electrolyte contains anions ^{_{CO 4 -, BF 4 -,}} PF 4 -, AsF 6 -, (CF 3 SO 2) 2 NB -, four Any one or combination of tetraethyl ammonium tetrafluoroborate (TEMABF ₄ , TMABOB, TMADFOB). The ultra-high capacitor as described in item 1 of the patent application scope, wherein the working electrode and the pair of electrodes both include a conductive substrate, and the active material is deposited on the conductive substrate. The ultra-high capacitor as described in item 1 of the patent application range, wherein the nitrogen-doped porous graphene is a porous graphene surface doped with nitrogen at least 3 at%. An ultra-high capacitor preparation method includes the following steps: Preparing an active material containing nitrogen-doped porous graphene; depositing the active material on a conductive substrate to form a working electrode and a pair of electrodes; and adsorbing an organic electrolyte on the surfaces of the working electrode and the pair of electrodes . The preparation method as described in item 7 of the patent application scope, wherein the organic solvent of the organic electrolyte includes ethylene carbonate (PC), acetonitrile (AN), N,N-dimethyl amide (NMP), dimethyl Ethylacetamide (DMA), tetrahydrofuran (THF), or any combination thereof. The preparation method as described in item 7 of the patent application scope, wherein the cation of the organic electrolyte contains quaternary ammonium salt (R ₄ N ⁺ ), lithium salt (Li+), quaternary phosphorus salt (R ₄ P ⁺ ), aromatic Any one or a combination of sitting salt (EMI). The application of the method of preparation of patentable scope of item 7, wherein the organic electrolyte contains anions ^{_{CO 4 -, BF 4 -,}} PF 4 -, AsF 6 -, (CF 3 SO 2) 2 NB -, four Any one or combination of tetraethyl ammonium tetrafluoroborate (TEMABF ₄ , TMABOB, TMADFOB). For example, in the preparation method of claim 7, the active substance is deposited on the conductive substrate by doctor blade coating. For example, the preparation method of claim 7 in the patent application scope, in which the preparation of the active material containing nitrogen-doped porous graphene, including the following sub-steps: Put graphite oxide (GO) into a high-temperature furnace, pass into 50c.c. /min gas flow rate of nitrogen oxide gas for one hour, and after the temperature is raised to 900°C at a heating rate of 40°C/min and held for 1 hour, the temperature is naturally reduced to room temperature to form the active material. For example, the preparation method of item 7 of the patent application scope further includes the following steps: electrically activating the working electrode adsorbed with the organic electrolyte.

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