Graphene integrated water system energy storage device and application thereof

Abstract

The invention discloses a graphene integrated water system energy storage device and application thereof, and belongs to the technical field of battery manufacturing. The preparation method comprises the following steps: (1) preparing a graphene modified electrolyte: adding high-purity water, inorganic salt and TEMPO or a derivative thereof into graphene oxide slurry, and mixing the high-purity water, the inorganic salt and the TEMPO or the derivative thereof; 2) mixing the graphene oxide slurry, the additional carbon material powder and high-purity water to form slurry, blade-coating the slurry to form a film, and forming aerogel to prepare an electrode; and 3) assembling the graphene modified electrolyte, an electrode and a diaphragm into an energy storage device. According to the graphene integrated water system energy storage device and the application thereof, the graphene modified electrolyte effectively inhibits the shuttle effect and side reaction, and the coulombic efficiency of the system is remarkably improved; the three-dimensional porous structure of the aerogel electrode accommodates electrolyte ions and limits the diffusion of the electrolyte ions, so that the specific capacity is improved; through the synergistic effect of the two, the energy storage device has excellent electrochemical performance, is convenient to assemble and high in safety, and has huge application value in the field of large-scale energy storage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery manufacturing, and particularly relates to a graphene integrated aqueous energy storage device and application thereof. BACKGROUND

[0002] In recent years, aqueous energy storage devices with aqueous solution as electrolyte have been widely studied due to their low cost, high safety and environmental friendliness. More importantly, their excellent ionic conductivity (about 1 S cm -1 ) allows ions to migrate efficiently between the positive and negative electrodes, thus achieving high power density and energy density. However, since the migration rate of ions in the active electrode material is much lower than that in the electrolyte, the energy density of the system mainly depends on the reaction depth of ions in the electrode material, that is, the greater the energy density, the greater the reaction depth, and the longer the migration time of ions in the electrode material, thus reducing the power density. Therefore, the aqueous energy storage device with electrode redox reaction to transfer charge faces the problem of difficult coexistence of energy density and power density.

[0003] By introducing a redox mediator into the electrolyte, the charge transfer process is extended from the electrode to the entire electrochemical energy storage device, which can to some extent alleviate the above problems. When the concentration of the redox mediator in the electrolyte is increased, the migration rate of the mediator based on concentration polarization is improved, and the amount of the mediator participating in charge transfer is also increased, so the power density and energy density are both improved. Among all the redox mediators, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and its derivatives show outstanding application potential. It not only has excellent stability in neutral solution, but also has bipolarity. During charging, it can not only be oxidized as a positive electrode, but also be reduced as a negative electrode, so that a symmetric energy storage device with a single electrolyte can be constructed, greatly simplifying the preparation process of the energy storage device. However, after charging, the TEMPO + oxidized in the positive electrode region will diffuse to the electrolyte or even the other electrode, and this shuttle effect will cause irreversible capacity loss and reduce the coulombic efficiency; and the TEMPO - reduced in the negative electrode region is extremely easy to be attacked by protons to generate TEMPOH which cannot be oxidized, so that it cannot be discharged. Therefore, there is an urgent need for an electrolyte additive to modify and modify the system, and a three-dimensional porous electrode with high conductivity to be assembled into an integrated aqueous energy storage device. SUMMARY

[0004] In view of the above problems existing in the prior art, the purpose of the present application is to provide a technical scheme of a graphene integrated aqueous energy storage device and application thereof, wherein the graphene modified electrolyte effectively inhibits the shuttle effect and side reactions, and significantly improves the coulombic efficiency of the system; the three-dimensional porous structure of the aerogel electrode accommodates electrolyte ions and limits their diffusion, thereby improving the specific capacity; the synergistic effect of the two makes the energy storage device have excellent electrochemical performance, is convenient to assemble, is high in safety, and has great application value in the field of large-scale energy storage.

[0005] The graphene integrated aqueous energy storage device is characterized in that the following method is used for preparation: 1) Preparation of graphene modified electrolyte: graphene oxide slurry is added to high-purity water for dilution, and after stirring, inorganic salt and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) or its derivative are added, and the mixture is continuously stirred until uniform, and the mass fraction of graphene oxide in the electrolyte is 0.025%-0.15%; 2) Preparation of graphene composite aerogel electrode: graphene oxide slurry, additional carbon material powder and high-purity water are mixed to form a slurry, the slurry is scraped to form a film, and the film is subjected to freeze-drying and heat treatment to form an aerogel for making an electrode; 3) Device assembly: the graphene modified electrolyte, the graphene composite aerogel electrode and the separator are assembled into an energy storage device.

[0006] The graphene integrated aqueous energy storage device is characterized in that in step 1), the mass fraction of graphene oxide in the electrolyte is 0.05%-0.1%.

[0007] The graphene integrated aqueous energy storage device is characterized in that in step 1), the inorganic salt is at least one of LiCl, NaCl, KCl, NH4Cl, MgCl2 and CaCl2, and the concentration is 0.1mol / L-3mol / L, preferably 0.5mol / L-2mol / L, and more preferably 1mol / L-1.5mol / L.

[0008] The graphene integrated aqueous energy storage device is characterized in that in step 1), the derivative of TEMPO is at least one of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO-OH), 4-methoxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-MeO-TEMPO), 4-carboxylic acid-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO-COOH), 4-carboxylic acid methyl-2,2,6,6-tetramethylpiperidin-1-oxyl (4-COOMe-TEMPO), 4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl (4-NH2-TEMPO), 4-acetylamino-2,2,6,6-tetramethylpiperidin-1-oxyl (4-AcNH-TEMPO), 4-sulfonic acid-2,2,6,6-tetramethylpiperidin-1-oxyl (4-SO3H-TEMPO), and the concentration of TEMPO or the derivative thereof in the electrolyte is 0.01 mol / L-3 mol / L, preferably 0.1 mol / L-1 mol / L, and more preferably 0.2 mol / L-0.5 mol / L.

[0009] The graphene integrated aqueous energy storage device is characterized in that in step 2), the solid content of the graphene oxide slurry is 5-20 mg / mL, preferably 10-15 mg / mL; the graphene oxide is a single-layer structure, and the flake diameter is 1-30 μm, preferably 5-20 μm.

[0010] The graphene integrated aqueous energy storage device is characterized in that in step 2), the mass ratio of graphene oxide to additional carbon material powder is 5-9:3, preferably 7:3, and high-purity water is added to make the solid content of the composite slurry 0.5-2%. The mass ratio of graphene oxide to additional carbon material is a key design, the large graphene oxide flake layer serves as a macroscopic framework, and is built into a shape; and the fibrous or particulate material such as carbon nanotube acts as a steel bar and a filler, and is inserted between the graphene flake layers to prevent the re-stacking of the graphene flake layers and to increase the mechanical strength and toughness of the structure. The solid content limitation of the composite slurry ensures the structural integrity: if the solid content is too low, the solid components for building the framework in the slurry are too few, and a continuous and stable three-dimensional network cannot be formed after freeze-drying, and the structure is easy to collapse; if the solid content is too high, the slurry is too viscous, and the flake layers are stacked too closely, which reduces the porosity and is not conducive to the electrolyte infiltration and ion transmission.

[0011] The graphene integrated aqueous energy storage device is characterized in that in step 2), the additional carbon material is at least one of activated carbon, carbon nanotube and conductive carbon black.

[0012] The graphene integrated water-based energy storage device is characterized in that, in step 2), the thickness of the slurry coating film is 0.1-5 mm, preferably 1-2 mm; the freeze-drying time is 6-24 hours, preferably 10-15 hours, and the freezing temperature is -50℃ to -70℃; the heat treatment is carried out in an inert atmosphere, the heat treatment temperature is 500-1500℃, preferably 800-1100℃, and the holding time is 0.5-3 hours, preferably 1-2 hours.

[0013] The graphene integrated water energy storage device is characterized in that, in step 3), the membrane is one of glass fiber membrane, perfluorosulfonic acid ion exchange membrane, cellulose-based membrane, and PVDF-modified PP membrane.

[0014] The application of the graphene integrated aqueous energy storage device in the fabrication of button batteries, pouch batteries, cylindrical batteries, and flexible supercapacitors.

[0015] Compared with the prior art, the present invention has the following advantages: 1) Synergistic effect, significantly improving coulombic efficiency: This invention creatively introduces graphene oxide into both the electrolyte and the electrode. The graphene in the electrolyte can adsorb redox media, regulate its reaction kinetics, and effectively suppress its shuttle and side reactions. Meanwhile, the three-dimensional porous graphene composite aerogel electrode not only provides an excellent conductive network, but its abundant internal cavities can also accommodate a large amount of electrolyte and restrict the free diffusion of redox media. The synergistic effect of these two elements significantly improves coulombic efficiency and cycle stability. Experiments show that the coulombic efficiency can be increased from 61.4% to 83.0%.

[0016] 2) Integrated design with excellent performance: Through the synergistic design of electrodes and electrolytes, the device has both high energy density and high power density. The lightweight and high specific surface area of ​​the graphene composite aerogel electrode ensures high specific capacity.

[0017] 3) All preparation stages covered by this invention can be operated efficiently and smoothly using industrial-grade equipment. This innovative design ensures the efficiency, safety and environmental friendliness of the production process, laying a solid foundation for large-scale production and thus precisely meeting the urgent needs of the commercial electrochemical energy storage device market. Attached Figure Description

[0018] Figure 1 This is a SEM image of the graphene composite aerogel prepared in Example 1 of the present invention. Figure 2 The graph shows a comparison of the CV curves of the graphene integrated flexible supercapacitors prepared in Examples 1-3 and Comparative Example 1 at a scan rate of 5 mV / s. Figure 3The graphene-integrated flexible supercapacitors prepared in Examples 1-3 and Comparative Example 1 of this invention operate at 20 mA / cm². 2 A comparison of charge and discharge curves at different current densities. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. The scope of protection is not limited to these embodiments. Any technical solutions that fall within the scope of the present invention should be protected by the present invention.

[0020] Example 1: 1) Preparation of graphene-modified electrolyte: Add 0.5g of monolayer graphene oxide slurry (sheet diameter 5-20μm) with a solid content of 10mg / mL to an appropriate amount of high-purity water and stir to dilute. Then add 10mmol of NaCl and 2mmol of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxygen radical (TEMPO-OH), continue stirring until homogeneous, and make up to a final volume so that the mass fraction of graphene oxide in the electrolyte is 0.05% to obtain the graphene-modified electrolyte. 2) Preparation of graphene composite aerogel electrode: 35 ml of 10 mg / mL monolayer graphene oxide slurry and 150 mg of hydroxylated carbon nanotubes were mixed evenly with high-purity water to make the solid content of the composite slurry 1%. The composite slurry was coated into a 2 mm thick film using a coating machine. After pre-freezing at -10℃, it was placed in a freeze dryer for 12 h at a freezing temperature of -60℃. After removing the moisture, it was placed in a tube furnace and heated to 1000℃ and held for 2 h to form a composite aerogel. 3) Device assembly: Assemble the above-mentioned graphene-modified electrolyte, graphene composite aerogel electrode and glass fiber diaphragm into an energy storage device: supercapacitor.

[0021] Example 2: 1) Preparation of graphene-modified electrolyte: 0.25g of monolayer graphene oxide slurry with a solid content of 10mg / mL was added to an appropriate amount of high-purity water and stirred to dilute. Then, 10mmol of MgCl2 and 2mmol of 4-carboxylic acid-2,2,6,6-tetramethylpiperidine-1-oxygen radical (TEMPO-COOH) were added and stirred until homogeneous. After adjusting the volume, the mass fraction of graphene oxide in the electrolyte was 0.025%, thus obtaining the graphene-modified electrolyte. 2) Preparation of graphene composite aerogel electrode: 50 ml of 5 mg / mL single-layer graphene oxide slurry and 150 mg of hydroxylated carbon nanotubes were mixed evenly with high-purity water to make the solid content of the composite slurry 0.5%. The composite slurry was coated into a 5 mm thick film using a coating machine. After pre-freezing at -10℃, it was placed in a freeze dryer for 24 h at a freezing temperature of -50℃. After removing the moisture, it was placed in a tube furnace and heated to 1100℃ and held for 3 h to form a composite aerogel. 3) Device assembly: Assemble the above-mentioned graphene-modified electrolyte, graphene composite aerogel electrode and glass fiber membrane into an energy storage device.

[0022] Example 3: 1) Preparation of graphene-modified electrolyte: 1.5g of monolayer graphene oxide slurry with a solid content of 10mg / mL was added to an appropriate amount of high-purity water and stirred to dilute. Then, 10mmol of LiCl and 2mmol of 4-sulfono-2,2,6,6-tetramethylpiperidine-1-oxy free radical (4-SO3H-TEMPO) were added and stirred until homogeneous. After adjusting the volume, the mass fraction of graphene oxide in the electrolyte was 0.15%, thus obtaining the graphene-modified electrolyte. 2) Preparation of graphene composite aerogel electrode: 22 ml of 20 mg / mL monolayer graphene oxide slurry and 150 mg of hydroxylated carbon nanotubes were mixed with high-purity water to make the solid content of the composite slurry 2%. The composite slurry was coated into a 0.1 mm thick film using a coating machine. After pre-freezing at -10℃, it was placed in a freeze dryer for 6 h at a freezing temperature of -70℃. After removing the moisture, it was placed in a tube furnace and heated to 800℃ and held for 0.5 h to form a composite aerogel. 3) Device assembly: Assemble the above-mentioned graphene-modified electrolyte, graphene composite aerogel electrode and glass fiber membrane into an energy storage device.

[0023] In this invention, the inorganic salt can be selected from any one of LiCl, NaCl, KCl, NH4Cl, MgCl2, and CaCl2, and the concentration can be selected from 0.1 mol / L to 3 mol / L according to actual needs, which can also produce the energy storage device described in this invention. The energy storage device described in this invention can also be made into button batteries, pouch batteries, cylindrical batteries, and flexible supercapacitors.

[0024] Comparative Example 1: 1) The conventional electrolyte preparation method is as follows: Add 10 mol of NaCl and 2 mmol of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxo radical (TEMPO-OH) to 10 ml of high-purity water, and stir for a certain period of time until homogeneous. 2) The preparation method of the graphene composite aerogel electrode is as follows: 35 ml of aqueous graphene oxide slurry with a concentration of 10 mg / mL, 150 mg of hydroxylated carbon nanotubes, and 10 ml of high-purity water are mixed evenly. The composite slurry is coated into a 2 mm thick film using a coating machine. After pre-freezing at low temperature, it is placed in a freeze dryer for 12 h. After removing moisture, it is heated to 1000 ℃ in a tube furnace and held at that temperature for 2 h to form a composite aerogel.

[0025] 3) Assemble the above-mentioned integrated aqueous graphene electrolyte, graphene composite aerogel electrode and glass fiber diaphragm into a flexible supercapacitor.

[0026] Figure 1 This is a SEM image of the graphene composite aerogel prepared in Example 1 of the present invention. The graphene sheets are about 10 μm in size, and the sheets are interwoven to form a three-dimensional porous structure. Carbon nanotubes with a size of tens of nanometers are filled between the sheets, which greatly increases the specific surface area of ​​the aerogel and is beneficial to the adsorption and reaction of redox electrolyte media.

[0027] Figure 2 This indicates that when no monolayer graphene oxide is introduced into the electrolyte, the current at high potential continuously increases with increasing voltage, suggesting that the TEMPO-OH after the reaction... + The TEMPO-OH molecules diffuse continuously into the liquid phase of the electrolyte, making it difficult for a reverse reaction to occur during discharge, thus reducing the coulombic efficiency. After introducing monolayer graphene oxide, a significant oxidation peak appears at high potential, indicating that the TEMPO-OH molecules after the reaction... + Confined near the electrode, the graphene exhibits a larger reverse current during discharge, indicating improved coulombic efficiency. Even when the graphene mass fraction reaches 0.15%, the reverse current remains even greater, but no significant reduction peak appears, suggesting that excess graphene hinders ion migration, thereby suppressing the electrochemical reaction kinetics. This conclusion can also be supported by the GCD curves of both materials. Figure 3 As confirmed by [the study], the charging capacities were 187.8, 159.5, 166.2, and 131.5 mAh g⁻¹ when no monolayer graphene oxide was introduced, and when the mass fraction of monolayer graphene oxide was 0.025%, 0.05%, and 0.15%, respectively. -1 The discharge capacities were 115.4, 116.3, 138.0, and 98.7 mAh g, respectively. -1 Therefore, the coulombic efficiencies are 61.4%, 73.0%, 83.0%, and 75.1%, respectively, which demonstrates the effectiveness of the strategy. The performance is optimal when the graphene mass fraction is 0.05%, which also proves that the graphene integrated water energy storage device has great development potential and application value.

[0028] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A graphene-integrated water-based energy storage device, characterized in that... Prepared using the following method: 1) Preparation of graphene-modified electrolyte: Dilute graphene oxide slurry in high-purity water, stir, add inorganic salt and 2,2,6,6-tetramethylpiperidine-1-oxygen radical (TEMPO) or its derivative, and continue stirring to mix evenly. The mass fraction of graphene oxide in the electrolyte is 0.025%-0.15%. 2) Preparation of graphene composite aerogel electrode: Graphene oxide slurry, additional carbon material powder and high-purity water are mixed to form a slurry, the slurry is coated into a film, and the film is freeze-dried and heat-treated to form an aerogel for use in making electrodes; 3) Device assembly: Assemble graphene-modified electrolyte, graphene composite aerogel electrode and diaphragm into energy storage device.

2. The graphene-integrated water-based energy storage device as described in claim 1, characterized in that... In step 1), the mass fraction of graphene oxide in the electrolyte is 0.05%-0.1%.

3. The graphene-integrated water-based energy storage device as described in claim 1, characterized in that... In step 1), the inorganic salt is at least one of LiCl, NaCl, KCl, NH4Cl, MgCl2, and CaCl2, with a concentration of 0.1 mol / L-3 mol / L, preferably 0.5 mol / L-2 mol / L, and more preferably 1 mol / L-1.5 mol / L.

4. The graphene-integrated water-based energy storage device as described in claim 1, characterized in that... In step 1): the derivatives of TEMPO are 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxo radicals (TEMPO-OH), 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxo radicals (4-MeO-TEMPO), 4-carboxylic acid-2,2,6,6-tetramethylpiperidine-1-oxo radicals (TEMPO-COOH), 4-carboxylic acid methyl ester-2,2,6,6-tetramethylpiperidine-1-oxo radicals (4-COOMe-TEMPO), and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxo radicals. The electrolyte contains at least one of 4-acetamino-2,2,6,6-tetramethylpiperidine-1-oxygen radical (4-NH2-TEMPO), 4-acetamino-2,2,6,6-tetramethylpiperidine-1-oxygen radical (4-AcNH-TEMPO), and 4-sulfonic acid-2,2,6,6-tetramethylpiperidine-1-oxygen radical (4-SO3H-TEMPO), wherein the concentration of TEMPO or its derivative in the electrolyte is 0.01 mol / L to 3 mol / L, preferably 0.1 mol / L to 1 mol / L, and more preferably 0.2 mol / L to 0.5 mol / L.

5. The graphene-integrated water-based energy storage device as described in claim 1, characterized in that... In step 2): the solid content of the graphene oxide slurry is 5-20 mg / mL, preferably 10-15 mg / mL; the graphene oxide has a single-layer structure and a sheet diameter of 1-30 μm, preferably 5-20 μm.

6. The graphene-integrated water-based energy storage device as described in claim 1, characterized in that... In step 2), the mass ratio of graphene oxide to additional carbon material powder is 5-9:3, preferably 7:3, and high-purity water is added to make the solid content of the composite slurry 0.5-2%.

7. The graphene-integrated water-based energy storage device as described in claim 1, characterized in that... In step 2): the additional carbon material is at least one of activated carbon, carbon nanotubes, and conductive carbon black.

8. The graphene-integrated water-based energy storage device as described in claim 1, characterized in that... In step 2): the thickness of the slurry film is 0.1-5 mm, preferably 1-2 mm; the freeze-drying time is 6-24 hours, preferably 10-15 hours, and the freezing temperature is -50℃ to -70℃; the heat treatment is carried out in an inert atmosphere, the heat treatment temperature is 500-1500℃, preferably 800-1100℃, and the holding time is 0.5-3 hours, preferably 1-2 hours.

9. The graphene-integrated water-based energy storage device as described in claim 1, characterized in that... In step 3): the membrane is one of glass fiber membrane, perfluorosulfonic acid ion exchange membrane, cellulose-based membrane, and PVDF-modified PP membrane.

10. The application of the graphene integrated aqueous energy storage device as described in claim 1 in the preparation of button batteries, pouch batteries, cylindrical batteries, and flexible supercapacitors.

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