A ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material and a preparation method thereof, and a pseudo-capacitive capacitor

Abstract

The application relates to the field of electrochemical energy storage, in particular to a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material and a preparation method thereof, and a pseudo-capacitive capacitor. The ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material is prepared through a series of steps of in-situ growth of uniformly distributed ruthenium nanoparticles with a particle size of 1-3 nm on surface-modified cellulose nanofibers, vacuum filtration and drying to form a self-supporting three-dimensional network structure, and low-temperature annealing to oxidize the ruthenium nanoparticles. The preparation method can overcome the problems of easy agglomeration and easy falling-off of ruthenium dioxide particles in current industrial preparation, and the prepared electrode material has good flexibility and extremely low self-weight, and can guarantee excellent specific capacitance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemical energy storage, in particular to a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material and a preparation method thereof, and a pseudo-capacitive capacitor. BACKGROUND

[0002] With the rise of portable and wearable electronic devices such as medical implants, microsensors, and electronic skin, new demands have been put forward for energy storage devices. Lightweight, flexible, and green energy storage devices with high energy density, high power density, and fast charging and discharging capabilities are key components of portable and mobile electronic products. Compared with secondary batteries, supercapacitors have the advantages of high power density, long cycle stability, and high safety, and can be used as a substitute or supplement for secondary batteries in applications requiring high power output or fast energy collection.

[0003] According to the different charge storage mechanisms, supercapacitors can be divided into double-layer capacitors relying on ion adsorption and pseudo-capacitive capacitors based on fast surface redox reactions. Pseudo-capacitive capacitors have both double-layer formation and surface redox reactions, and have higher energy density than double-layer capacitors.

[0004] At present, the commonly used pseudo-capacitive electrode materials mainly include transition metal oxides, hydroxides, transition metal sulfides, phosphides, or conductive polymers, etc. Among them, ruthenium dioxide is considered as one of the most ideal pseudo-capacitive electrode materials due to its similar conductivity to metal and good electrochemical stability. However, the high price and scarcity of ruthenium dioxide, as well as its easy aggregation and easy shedding, limit its application in industrial production. In addition, commercially manufactured ruthenium tantalum capacitors generally use the method of casting electrode slurry on a metal tantalum foil current collector, such as Chinese patent publication CN 102891013 A and CN 106024408, etc. The capacitors produced in this way are not only hard, but also heavy and bulky, which cannot meet the needs of portable and wearable electronic devices. SUMMARY

[0005] Therefore, the present application provides a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material and a preparation method thereof, and a pseudo-capacitive capacitor. The preparation method of the present application can overcome the problems of easy aggregation and easy shedding of ruthenium dioxide particles in current industrial production, and the electrode material prepared has good flexibility and extremely low self-weight, while ensuring excellent specific capacitance.

[0006] The present application provides a preparation method of a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material, comprising the following steps:

[0007] A) dispersing nanocellulose in a solvent to obtain a nanofiber dispersion;

[0008] B) dissolving the hydrated ruthenium trichloride in a solvent to obtain a ruthenium trichloride solution;

[0009] C) mixing the nanofiber dispersion obtained in step A) with the ruthenium trichloride solution obtained in step B) to obtain a mixed solution;

[0010] D) performing a heating reaction on the mixed solution obtained in step C), then washing the obtained product, dispersing the washing product in a solvent, filtering, and freeze-drying to obtain a thin film;

[0011] E) performing an annealing treatment on the thin film obtained in step D) to obtain a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material;

[0012] Preferably, the mass ratio of the nanocellulose used in step A) to the hydrated ruthenium trichloride used in step B) is 30:(20-30).

[0013] Preferably, in step C), the mixing is performed by dropwise adding the nanofiber dispersion obtained in step A) to the ruthenium trichloride solution obtained in step B).

[0014] Preferably, in step C), after the nanofiber dispersion obtained in step A) and the ruthenium trichloride solution obtained in step B) are fully contacted, stirring is performed.

[0015] Preferably, in step C), the stirring is performed at a rate of 300-600 rpm for 2-4 h.

[0016] Preferably, in step D), the heating reaction is performed at a temperature of 80-150°C for 12-24 h.

[0017] Preferably, in step E), the annealing treatment is performed at a temperature of 60-160°C for 2-12 h.

[0018] Preferably, in step E), the annealing is performed in an air atmosphere or an oxygen atmosphere.

[0019] Preferably, in step A), the solvent is water; and the amount of nanocellulose used is 30 mg, and the amount of solvent used is 30-90 mL.

[0020] Preferably, in step B), the solvent is water; and the amount of hydrated ruthenium trichloride used is 20-30 mg, and the amount of solvent used is 30 mL.

[0021] Preferably, in step B), the solvent is water; and the amount of hydrated ruthenium trichloride used is 20-30 mg, and the amount of solvent used is 30 mL.

[0022] The present application also provides a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material prepared by the method described in the above technical solution.

[0023] The application also provides a pseudo-capacitance capacitor, wherein the electrode material is the above-mentioned ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material.

[0024] The ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material is prepared through a series of steps of in-situ growth of uniformly distributed ruthenium nanoparticles on nanocellulose, vacuum suction filtration and drying to form a self-supporting three-dimensional network structure, and low-temperature annealing to oxidize the ruthenium nanoparticles. The application uses in-situ growth technology to firmly anchor the ruthenium dioxide nanoparticles on the surface of the modified wood cellulose nanofiber with rich surface groups, overcoming the shortcoming of easy falling of active substances. At the same time, the surface-modified cellulose nanofiber has a large specific surface area and a three-dimensional network structure, and has good matching with ruthenium dioxide, can fully expose the active sites of ruthenium dioxide, maximize the pseudo-capacitance activity of ruthenium dioxide, and play the energy storage performance with low ruthenium loading, overcoming the high cost problem of using ruthenium dioxide as raw material in the prior art. Moreover, the nanocellulose substrate has a small density and a high aspect ratio, and can form a lightweight and flexible self-supporting material through winding, avoiding the use of adhesive and effectively reducing the weight of the electrode material and the energy storage device. Moreover, the nanocellulose is derived from cellulose, which is the most widely existing in nature, is cheap and easy to obtain, and is sustainable, and is an ideal material for developing green energy storage equipment. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0026] Figure 1 The schematic diagram of the appearance of the ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material obtained in Example 1 is shown in the figure.

[0027] Figure 2 The mechanical property effect diagram of the product obtained in each example and the comparative example is shown in the figure.

[0028] Figure 3 The TEM diagram of the ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material obtained in Example 1 is shown in the figure.

[0029] Figure 4 The XRD diagram of the product obtained in each example and the comparative example is shown in the figure.

[0030] Figure 5 The thermogravimetric analysis curve diagram of the product obtained in each example and the comparative example is shown in the figure.

[0031] Figure 6 Raman spectra of the products obtained in each example and comparative example;

[0032] Figure 7 Specifically, the specific embodiments of the present application are described in detail below. DETAILED DESCRIPTION

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application.

[0034] In this document, the terms "technology features" and "technical solutions" are used in an open-ended manner, including both closed technical solutions consisting of listed features and open technical solutions containing listed features.

[0035] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] In this document, when referring to a range of values, unless otherwise specified, the range of values is considered to be continuous and includes the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Further, when the range is referring to integers, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be interpreted as including any and all sub-ranges subsumed therein.

[0037] In this document, when referring to a range of values, if only the right endpoint is followed by a unit, it means that the units of the left endpoint and the right endpoint are the same. For example, 150-450 W means that the units of the left endpoint "150" and the right endpoint "450" are both W.

[0038] The present application provides a preparation method of a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material, comprising the following steps:

[0039] A) dispersing nanocellulose in a solvent to obtain a nanofiber dispersion;

[0040] B) dissolving hydrated ruthenium trichloride in a solvent to obtain a ruthenium trichloride solution;

[0041] C) mixing the nanofiber dispersion obtained in step A) with the ruthenium trichloride solution obtained in step B) to obtain a mixed solution;

[0042] D) heating the mixed solution obtained in step C) to perform a reaction, then washing the obtained product, dispersing the washing product in a solvent, filtering, and freeze-drying to obtain a thin film;

[0043] E) annealing the film obtained in step D) to obtain a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material;

[0044] Wherein, step A) and step B) are not limited in order.

[0045] [About step A]:

[0046] A) dispersing the nanocellulose in a solvent to obtain a nanofiber dispersion.

[0047] In the present application, the source of the nanocellulose is not particularly limited, and can be a commercially available product or prepared according to conventional methods in the art, for example, can be prepared from lignocellulose by the tempo oxidation method.

[0048] In the present application, the solvent is preferably water, more preferably deionized water.

[0049] In the present application, the ratio of the amount of nanocellulose to the amount of solvent is preferably 30 mg:(30-90) mL, and can be 30 mg:30 mL, 30 mg:40 mL, 30 mg:50 mL, 30 mg:60 mL, 30 mg:70 mL, 30 mg:80 mL, 30 mg:90 mL.

[0050] In the present application, the dispersion of nanocellulose in the solvent is preferably ultrasonic dispersion. In the present application, the power of the ultrasonic dispersion is preferably 150-450 W, and can be 150 W, 200 W, 250 W, 300 W, 350 W, 400 W, 450 W. The time of the ultrasonic dispersion is preferably 5-20 min, and can be 5 min, 10 min, 15 min, 20 min. After the above ultrasonic dispersion, a uniformly dispersed nanofiber dispersion is obtained.

[0051] [About step B]:

[0052] B) dissolving the hydrated ruthenium trichloride in a solvent to obtain a ruthenium trichloride solution.

[0053] In the present application, the solvent is preferably water, more preferably deionized water.

[0054] In the present application, the ratio of the amount of hydrated ruthenium trichloride to the amount of solvent is preferably (20-30) mg:30 mL, and can be 20 mg:30 mL, 25 mg:30 mL, 30 mg:30 mL.

[0055] [About step C]:

[0056] C) mixing the nanofiber dispersion obtained in step A) with the ruthenium trichloride solution obtained in step B) to obtain a mixture.

[0057] In the present application, when the nanofiber dispersion solution obtained in step A) is mixed with the ruthenium trichloride solution obtained in step B), the mass ratio of the surface-modified cellulose nanofiber used in step A) to the hydrated ruthenium trichloride used in step B) is preferably controlled to be 30:(20-30), and can be specifically 30:20, 30:21, 30:22, 30:23, 30:24, 30:25, 30:26, 30:27, 30:28, 30:29, or 30:30. In the present application, the above ratio can ensure excellent specific capacitance of the material and avoid aggregation of ruthenium dioxide, thereby maintaining flexibility and extremely low self-weight of the electrode. If the proportion of the hydrated ruthenium trichloride is too low, the specific capacitance of the material is poor. If the proportion of the hydrated ruthenium trichloride is too high, aggregation of ruthenium dioxide is easily caused, which not only cannot effectively expose the active surface, but also destroys the flexibility of the electrode and increases the self-weight thereof.

[0058] In the present application, the mixing method is preferably that the nanofiber dispersion solution obtained in step A) is added dropwise to the ruthenium trichloride solution obtained in step B). The dropwise addition is preferably carried out in multiple batches. The dropwise addition amount of each batch is preferably 10%-20% of the total mass of the nanofiber dispersion solution, and can be specifically 10%, 15%, or 20%. After the dropwise addition of each batch is completed, a certain interval of time is set, and the next batch is added dropwise. The interval of time between the dropwise addition of each batch is preferably 2-5 min, and can be specifically 2 min, 3 min, 4 min, or 5 min. In the present application, stirring is carried out during the above mixing process. The stirring rate is preferably 300-600 rpm, and can be specifically 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, or 600 rpm.

[0059] In the present application, after the nanofiber dispersion solution obtained in step A) and the ruthenium trichloride solution obtained in step B) are completely contacted (for example, after all the dropwise addition is completed), stirring is carried out. The stirring rate is preferably 300-600 rpm, and can be specifically 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, or 600 rpm. The stirring time is preferably 2-4 h, and can be specifically 2 h, 3 h, or 4 h. After the above treatment, a mixed solution is obtained. In the present application, the above dropwise addition in multiple batches and stirring treatment can uniformly anchor the ruthenium ions on the surface of the cellulose nanofiber.

[0060] [About step D]:

[0061] D) The mixed solution obtained in step C) is subjected to a heating reaction, and then the obtained product is washed, dispersed in a solvent, filtered, and freeze-dried to obtain a thin film.

[0062] In the present application, the heating reaction can be carried out in a reaction kettle, that is, after the mixed solution obtained in step C) is transferred into a reaction kettle to carry out the hydrothermal reaction. In the present application, the temperature of the heating reaction is preferably 80-150℃, and can be specifically 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃. The time of the heating reaction is preferably 12-24h, and can be specifically 12h, 14h, 16h, 18h, 20h, 22h, 24h.

[0063] In the present application, after the above heating reaction, the obtained product is washed. The washing is preferably centrifugal washing. The washing agent used in the washing is preferably water, and more preferably deionized water.

[0064] In the present application, after the above washing, the washed product is dispersed in a solvent. The solvent is preferably water, and more preferably deionized water. After the above dispersion, filtration is carried out. The filtration is preferably suction filtration. After suction filtration, the product is trapped on the filter material, and then freeze-drying is carried out to form a thin film.

[0065] [About step E]:

[0066] E) annealing treatment is carried out on the thin film obtained in step D) to obtain a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material.

[0067] In the present application, the annealing treatment is carried out in an air atmosphere or an oxygen atmosphere.

[0068] In the present application, the temperature of the annealing treatment is preferably 60-160℃, and can be specifically 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, and more preferably 150℃. The time of the annealing treatment is preferably 2-12h, and can be specifically 2h, 4h, 6h, 8h, 10h, and more preferably 2h. After the above annealing treatment, a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material is obtained.

[0069] The present application also provides a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material prepared by the preparation method described in the above technical solution.

[0070] The present application also provides a pseudo-capacitance capacitor, in which the electrode material is the ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material described in the above technical solution.

[0071] In the present application, the pseudo-capacitor is a sandwich structure assembled in the order of a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material, a diaphragm and a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material; that is, a symmetric pseudo-capacitor supercapacitor is constructed by using the ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material. The ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material is preferably pre-soaked in an electrolyte. The soaking time is preferably 10-60 min, and can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, and more preferably 30 min. The diaphragm is preferably an NKK-TF4030 diaphragm. The diaphragm is preferably pre-dropped with an electrolyte. The electrolyte is preferably an H2SO4 electrolyte. The concentration of the electrolyte is preferably 0.5-2.0 M, and can be 0.5 M, 1.0 M, 1.5 M, 2.0 M, and more preferably 1.0 M.

[0072] The ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material provided by the present application is prepared through a series of steps such as in-situ growth of uniformly distributed ruthenium nanoparticles on nanocellulose, vacuum suction filtration and drying to form a self-supporting three-dimensional network structure, and low-temperature annealing to oxidize the ruthenium nanoparticles. The present application uses in-situ growth technology to firmly anchor ruthenium dioxide nanoparticles on the surface of modified wood cellulose nanofiber with abundant surface groups, overcoming the shortcoming of easy shedding of active substances. At the same time, the surface-modified cellulose nanofiber has a large specific surface area and a three-dimensional network structure, and has good matching with ruthenium dioxide, can fully expose the active sites of ruthenium dioxide, and maximize the pseudo-capacitance activity of ruthenium dioxide. Moreover, the nanocellulose substrate used has a small density and a high aspect ratio, and can form a lightweight and flexible self-supporting material through winding, avoiding the use of adhesives and effectively reducing the weight of the electrode material and energy storage device. Moreover, the nanocellulose is derived from cellulose, which is the most widely existing in nature, and is cheap and easy to obtain, and has sustainability, and is an ideal material for developing green energy storage equipment.

[0073] The preparation method of the present application is simple, the reaction conditions are mild, and is suitable for large-scale production and practical application. The cellulose nanofiber used as the electrode support material is cheap and easy to obtain, and the active material ruthenium dioxide realizes energy storage performance with the lowest loading amount, and the large-scale production cost is controllable. The active material is firmly loaded in an in-situ form, solving the problem of easy agglomeration and easy shedding of ruthenium dioxide particles in current industrial preparation. The biomass support substrate used has the characteristics of lightweight and high strength, and the prepared electrode composite material has good flexibility and extremely low self-weight, improves the specific capacitance while maintaining excellent mechanical properties, and can meet the requirements of portable and wearable electronic devices for energy storage devices.

[0074] To further understand the present invention, preferred embodiments are described below with reference to examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims. In the following examples and comparative examples, nanocellulose is obtained from bleached coniferous wood pulp via the tempo oxidation method.

[0075] Example 1

[0076] A) Add 30 mg of dry cellulose nanoparticles to 40 mL of deionized water and sonicate them in an ultrasonic grinder (300 W, 10 min) to obtain a uniformly dispersed cellulose nanoparticle dispersion.

[0077] B) Dissolve 30 mg of hydrated ruthenium trichloride powder in 30 mL of deionized water and stir thoroughly to obtain a homogeneous ruthenium trichloride aqueous solution.

[0078] C) At a stirring speed of 500 rpm, the nanofiber dispersion obtained in step A) is slowly added dropwise in multiple batches to the ruthenium trichloride aqueous solution obtained in step B). The amount added in each batch is 10% of the total mass of the nanofiber dispersion, and the interval between each batch is 5 min. After the addition is complete, the mixture is stirred at 500 rpm for 2 h to obtain a mixture.

[0079] D) Transfer the mixture obtained in step C) to a reaction vessel and hydrothermally react at 80°C for 16 hours. Then, centrifuge and wash the obtained product, and then redisperse the washings in deionized water, filter, freeze dry, and obtain a thin film.

[0080] E) The film was annealed in air at 150°C for 2 hours to obtain a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material. This product mainly consists of ruthenium dioxide and lignocellulose nanofibers, with ruthenium dioxide accounting for 52.3% of the total mass.

[0081] test:

[0082] The appearance of the obtained ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material is as follows: Figure 1 As shown in the figure, it exhibits excellent flexibility. Simultaneously, this electrode material has a low density; experimental results show its density to be 1.2 g·cm³. -3 Mechanical properties such as Figure 2 As shown, the prepared self-supporting electrode film was repeatedly tested at room temperature and 50% humidity. The average tensile strength was 21 MPa and the average elongation at break was 1.2%.

[0083] The microstructure of the obtained ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material is as follows: Figure 3As shown, it can be seen that it is a three-dimensional network structure, proving that the method of the present application does not destroy the three-dimensional network structure of nanocellulose, and the nanofiber surface is densely coated with ruthenium dioxide nanoparticles, and there is no ruthenium dioxide particle agglomeration, so excellent mechanical properties can be obtained. As can also be seen from the TEM diagram, the size of the ruthenium oxide particles is 1-3 nm, and the average distance between the particles is less than 2 nm, so that electrons can tunnel, realizing the circuit conduction of the electrode.

[0084] The XRD of the obtained ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material is as shown in Figure 4 The characterization results show that the ruthenium dioxide particles therein are in a non-crystalline state, and the amorphous ruthenium dioxide particles can achieve higher capacitive activity than the crystalline form.

[0085] Example 2

[0086] According to the implementation of Example 1, except that the amount of hydrated ruthenium trichloride powder in step B) is 20 mg.

[0087] The obtained product is mainly composed of ruthenium dioxide and wood cellulose nanofiber, and the mass ratio of ruthenium dioxide is 33.4%.

[0088] The density of the obtained ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material is 1.09 g·cm -3 ; The mechanical properties are as shown in Figure 2 The average tensile strength is 35 Mpa, and the average elongation at break is 2.9% after repeated testing of the prepared self-supporting electrode film at room temperature and humidity of 50%.

[0089] Comparative Example 1

[0090] According to the implementation of Example 1, except that the amount of hydrated ruthenium trichloride powder in step B) is 15 mg.

[0091] The obtained product is mainly composed of ruthenium dioxide and wood cellulose nanofiber, and the mass ratio of ruthenium dioxide is 24.7%.

[0092] Comparative Example 2

[0093] According to the implementation of Example 1, except that the amount of hydrated ruthenium trichloride powder in step B) is 12 mg.

[0094] The obtained product is mainly composed of ruthenium dioxide and wood cellulose nanofiber, and the mass ratio of ruthenium dioxide is 22.9%.

[0095] Comparative Example 3

[0096] According to the implementation of Example 1, except that the amount of hydrated ruthenium trichloride powder in step B) is 10 mg.

[0097] The obtained product mainly consists of ruthenium dioxide and lignocellulose nanofiber, and the mass percentage of ruthenium dioxide is 16.7%.

[0098] Product test:

[0099] (1) Thermogravimetric analysis

[0100] The thermogravimetric analysis was performed on the samples of Example 1-2, Comparative Example 1-3 and the blank sample without adding ruthenium trichloride hydrate powder, and the results are shown in Table 1. Figure 5 As can be seen from the thermogravimetric curves of the samples, the mass percentages of ruthenium dioxide in the products of Example 1-2 and Comparative Example 1-3 are 52.3%, 33.4%, 24.7%, 22.9% and 16.7%, respectively.

[0101] (2) Raman test

[0102] The Raman test was performed on the products of Example 1-2 and Comparative Example 1-3, and the results are shown in Table 2. Figure 6 As can be seen from the Raman characteristic peaks, the particles in the obtained samples are ruthenium dioxide, and the peak intensity increases with the increase of the mass percentage of ruthenium dioxide.

[0103] (3) Specific capacitance test:

[0104] Preparation of pseudo-capacitive capacitor: the ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material was immersed in 1M H2SO4 electrolyte at room temperature for 30 min, and then taken out for standby. A 1M H2SO4 electrolyte (dropping amount: 0.06 mL / cm 2 ) was added on the surface of a commercially available NKK-TF4030 separator. The above-mentioned immersed ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material and the separator with added electrolyte were assembled into a pseudo-capacitive capacitor with a sandwich structure.

[0105] The capacitor was scanned with a voltage scan rate of 1 mv·s -1 , 2 mv·s -1 , 5 mv·s -1 , 10 mv·s -1 , 25 mv·s -1 , 50 mv·s -1 , 100 mv·s -1 and 1000 mv·s -1 , respectively. The test results of each example and comparative example are shown in Table 3. Figure 7 As can be seen, the specific capacitances of the electrodes with the mass percentages of ruthenium dioxide of 16.7%, 22.9%, 24.7%, 33.4% and 52.3% are 20.7 F·g -1 , 39.1 F·g -1, 57.4 F·g -1 , 176.1 F·g -1 and 730.6 F·g -1 When the voltage sweep rate is increased from 1 mv·s -1 to 50 mv·s -1 , the specific capacitance of the electrodes with 33.4% and 52.3% ruthenium dioxide by weight (i.e. the electrodes of Example 1-2) decreases by less than 20%, still maintaining a high specific capacitance. It can be seen that after loading the ruthenium dioxide particles, the surface of the insulating lignocellulose nanofibers gradually forms a conductive electron path, and electron transmission and ion transmission are carried out through the three-dimensional network of the interwoven lignocellulose nanofibers.

[0106] From the above test results, it can be seen that the specific capacitance of the product obtained in Example 1-2 of the present application reaches 176.1 F·g -1 , which maintains excellent specific capacitance effect; at the same time, compared with the prior art, the product obtained in the present application has excellent flexibility; and the present application firmly loads in situ, solving the problems of easy agglomeration and easy falling off of ruthenium dioxide particles in current industrial preparation; in addition, it has a low self-weight and still maintains excellent mechanical properties.

[0107] The principles and implementations of the present application are described herein by applying specific examples, and the above description of the examples is only used to help understand the method of the present application and its core idea, including the best mode, and also enables any person skilled in the art to practice the present application, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application. The scope of protection of the present application patent is defined by the claims, and can include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material, characterized by, The method comprises the following steps: A) dispersing nanocellulose in a solvent to obtain a nanofiber dispersion; B) dissolving hydrated ruthenium trichloride in a solvent to obtain a ruthenium trichloride solution; C) adding the nanofiber dispersion obtained in step A) dropwise to the ruthenium trichloride solution obtained in step B) to obtain a mixture; wherein the dropwise adding is in batches; the amount of each batch is 10-20% of the total mass of the nanofiber dispersion; after each batch is added, the next batch is added after a certain interval; the interval between each batch is 2-5 min; D) performing a heating reaction on the mixture obtained in step C), then washing the obtained product, dispersing the washing product in a solvent, filtering, and freeze-drying to obtain a thin film; wherein the heating reaction is performed in a reaction kettle; the temperature of the heating reaction is 80-150°C; E) performing an annealing treatment on the thin film obtained in step D) to obtain a ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material; wherein the annealing is performed in an air or oxygen atmosphere; the temperature of the annealing treatment is 60-160°C; The mass ratio of the nanocellulose used in step A) to the hydrated ruthenium trichloride used in step B) is 30:(20-30). wherein steps A) and B) are not limited in order.

2. The production method according to claim 1, characterized by, In step C), after the nanofiber dispersion obtained in step A) and the ruthenium trichloride solution obtained in step B) are fully contacted, stirring is performed; the stirring rate is 300-600 rpm, and the stirring time is 2-4 h.

3. The preparation method according to claim 1, characterized in that, In step D), the heating reaction time is 12-24 h.

4. The method of claim 1, wherein, In step E), the annealing treatment time is 2-12 h.

5. The preparation method of claim 1, wherein in step A), the solvent is water; the amount of nanocellulose used is 30 mg, and the amount of solvent used is 30-90 mL; in step B), the solvent is water; the amount of hydrated ruthenium trichloride used is 20-30 mg, and the amount of solvent used is 30 mL.

6. A ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material prepared by the preparation method of any one of claims 1-5.

7. A pseudo-capacitance capacitor, characterized by The electrode material is the ruthenium dioxide-cellulose nanofiber composite self-supporting electrode material of claim 6.

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