Preparation method of low-self-discharge aminated activated carbon for supercapacitor

Abstract

The invention discloses a preparation method of low-self-discharge aminated activated carbon for a supercapacitor, and belongs to the technical field of supercapacitors. The preparation method comprises the following steps: by taking commercial activated carbon as a raw material, sequentially adding a catalyst, the activated carbon and an amino reagent into a beaker according to a certain proportion, uniformly mixing, and then putting a uniform mixed solution into a reaction kettle for homogeneous reaction; and after the reaction is completed, washing with deionized water and absolute ethyl alcohol, and drying to obtain the aminated activated carbon. In the system, the introduction of the catalyst induces a cross-coupling reaction, so that the occurrence of side reaction is effectively avoided, and the directional introduction of amino functional groups on the surface of the activated carbon is promoted. The surface charge state is optimized through activated carbon surface amination, the adsorption capacity of activated carbon to charged ions is improved, then self-discharge caused by diffusion-controlled non-Faraday reaction is effectively restrained, when the initial voltage is 3.0 V, after standing is conducted for 40 hours, the voltage retention rate is larger than 76%, and low self-discharge of the supercapacitor is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of supercapacitors, and particularly relates to a preparation method of low-self-discharge aminated activated carbon for supercapacitors. BACKGROUND

[0002] Supercapacitors are energy storage devices between dielectric capacitors and lithium-ion batteries, and have the advantages of high power density, long cycle life, wide working temperature range and safety and reliability. Thanks to these advantages, supercapacitors still have important applications in power grid frequency modulation, rail transit, elevator kinetic energy recovery and military equipment fields, which cannot be replaced.

[0003] The energy storage process of supercapacitors mainly depends on the physical adsorption and desorption of charged ions on the surface of the electrode. Porous carbon materials with high specific surface area are considered to be the preferred electrode materials of supercapacitors. In the energy storage process, the charged ions need to pass through the complex pore structure from the surface of the material to the micropores in the interior of the material to achieve higher energy density. However, the self-discharge problem of supercapacitors is relatively serious. The self-discharge phenomenon of supercapacitors can be attributed to three aspects: (1) Ohmic leakage. Micro-short circuits may exist between the positive and negative electrodes of supercapacitors, causing charge loss and leading to self-discharge of supercapacitors. (2) Charge redistribution. In the process of rapid charging, due to the complex pore structure of the porous carbon electrode, the charged ions cannot fully diffuse into the deep micropores but accumulate at the pore mouth. After the external voltage is turned off, the ions can still spontaneously diffuse into the deep micropores, causing self-discharge of supercapacitors. (3) Diffusion-controlled non-Faraday process. In the presence of an external electric field, the adsorption of ions on the surface of the electrode will form a double layer. At this time, there is a concentration gradient of ions from the electrode surface to the electrolyte bulk phase. When the external voltage is turned off, the concentration gradient acts as a driving force to drive the ions to spontaneously diffuse away from the electrode surface, causing self-discharge of supercapacitors. Ohmic leakage and charge redistribution can be eliminated by adjusting the charging protocol, while the diffusion-controlled non-Faraday process cannot be effectively eliminated. The self-discharge phenomenon of supercapacitors is relatively serious and unavoidable, which limits the extended application of supercapacitors in the field of backup power supplies.

[0004] CN118969516A uses freeze-thaw method to prepare piezoelectric ion gel as electrolyte, and applies external pressure to supercapacitor. Due to the dense cross-linked network and piezoelectric potential generated by ion gel under pressure, the spontaneous movement of ions is hindered, and the self-discharge caused by spontaneous diffusion of ions is reduced. Although this technology can inhibit self-discharge to some extent, the slow ion diffusion in the gel electrolyte phase will significantly reduce the power density of the supercapacitor. CN118782396A uses gel sol method to prepare Nb2O5@TiO2 composite material. The best composite method is obtained by testing the synergy coefficient and self-discharge inhibition behavior of the sample. This method can inhibit the self-discharge of supercapacitor, but will cause pseudo-capacitance, which will significantly reduce the cycle life of supercapacitor. CN117292949A proposes a soft and hard heterogeneous structure of porous carbon material. The microstructure of the porous carbon is reasonably controlled through precursor nitrogen doping, carbonization, impurity removal and activation processes. The porous carbon prepared by this technology has inhibitory effect on self-discharge, but the preparation process is long and large-scale production is difficult. In summary, it is still a serious challenge to effectively inhibit the self-discharge performance of supercapacitor under simple and easy scale process conditions, and to fully balance other electrochemical performances. SUMMARY

[0005] In view of the key problems of intrinsic self-discharge of supercapacitor and difficulty in optimizing high performance indicators, the purpose of the present application is to provide a preparation method of low self-discharge aminated activated carbon for supercapacitor. The catalyst initiates cross-coupling reaction to introduce amino groups on the surface of activated carbon electrode. Amino groups are electron-rich groups that can provide more negative charges on the surface of activated carbon, thereby improving the ability of the electrode surface to adsorb cations. Therefore, a more compact and stable double-layer structure is constructed on the electrode surface, which inhibits the spontaneous diffusion of ions driven by concentration gradient, thereby effectively inhibiting the self-discharge of supercapacitor, and having no obvious influence on the electrochemical performance such as capacity and rate of supercapacitor.

[0006] To solve the above technical problems, the following technical solutions are adopted in the present application:

[0007] A low self-discharge aminated activated carbon for supercapacitor, the specific surface area of the aminated activated carbon is 1500 m 2 / g~2000 m 2 / g, the N element content is 0.5%~1.5%, the aminated activated carbon is a typical disordered structure, and the defect content I D / I G is 0.9~1.1.

[0008] Further, the Zeta potential is about 0 mV~5 mV when the 1 M SBPBF4 organic electrolyte is used as the medium, the zero charge potential is about 0.20 V~0.30 V vs Ag in the 1 M SBPBF4 organic electrolyte system, and the surface potential measured by the Kelvin probe microscope is about 50 mV~60 mV.

[0009] A preparation method of low self-discharge amino-functionalized activated carbon for supercapacitors, the activated carbon is screened, impurities are removed, and drying treatment is performed, then the treated activated carbon is mixed with a catalyst and an amino reagent by magnetic stirring, homogeneous reaction is performed, after the reaction is completed, the product is washed by filtration with anhydrous ethanol and deionized water in sequence, and dried to obtain the amino-functionalized activated carbon.

[0010] Further, the activated carbon is selected from at least one of coconut shell carbon, nutshell carbon, wooden carbon, columnar carbon, coal carbon, and starch-based carbon.

[0011] Further, the catalyst is selected from at least one of 2-(7-azabenzotriazol)-N,N,N',N'-tetramethyluronium hexafluorophosphate, oxo-benzotriazol-tetramethyluronium hexafluorophosphate, 6-chlorobenzotriazol-1,1,3,3-tetramethyluronium hexafluorophosphate, oxo-benzotriazol-N,N,N',N'-tetramethyluronium tetrafluoroborate, oxo-(N-succinimidyl)-bis(dimethylamino)carbonium tetrafluoroborate, tris(2-aminoethyl)-tris-nitroisourea, oxo-(7-azabenzotriazol-1-yl)-bis(tetrahydropyrrolyl)carbonium hexafluorophosphate, and oxo-(benzotriazol-1-yl)-bis(tetrahydropyrrolyl)carbonium hexafluorophosphate.

[0012] Further, the amino reagent is selected from at least one of ethylamine, ethylenediamine, diethylamine, 1,2-propanediamine, 1,3-propanediamine, mercaptoethylamine, and aniline.

[0013] Further, the use amounts of the treated activated carbon, the catalyst, and the amino reagent are 2 g, 12 g, and 120 mL respectively.

[0014] Further, the temperature of the homogeneous reaction is 80℃, and the reaction time is 1~10h.

[0015] Further, the screening, impurity removal, and drying treatment specifically include screening the activated carbon through a 300-mesh sieve, removing residual impurities by washing with ethanol and deionized water in sequence, and drying in an 80℃ oven.

[0016] Further, the stirring time of the magnetic stirring is 5 min~30 min.

[0017] Further, the filter paper for the suction filtration is made of cellulose material, has a pore size of 20 μm, and a thickness of 160 μm, and the suction filtration and washing time is 1-5 hours.

[0018] A supercapacitor, wherein the active material of the positive and negative electrodes of the supercapacitor comprises the amino-functionalized activated carbon material.

[0019] The amino-functionalized activated carbon prepared above is prepared into an electrode, which is used to assemble a supercapacitor, so as to perform subsequent self-discharge performance test and other electrochemical performance test.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] (1) Advancement of the method. The amino-functionalization reaction used in the present application is a catalyst-induced cross-coupling type reaction, which has the advantages of less side reactions and easy control. By using this method, amino groups can be introduced to the surface of activated carbon in a directional manner, which can avoid the introduction of other forms of N elements and the introduction of other impurity elements.

[0022] (2) Advancement of the principle. The present application adopts an electrode surface amino-functionalization strategy to inhibit the self-discharge of supercapacitors driven by diffusion-controlled non-Faradic reactions. The diffusion-controlled non-Faradic reaction self-discharge is driven by the concentration gradient and potential gradient at the double layer, and the adsorption ability of charged ions on the electrode surface as resistance. The amino-functionalization strategy effectively improves the adsorption ability of ions on the electrode surface, thereby effectively inhibiting the self-discharge of supercapacitors. This strategy effectively inhibits the self-discharge of supercapacitors while having no obvious effect on other electrochemical performances.

[0023] (3) Suitable for large-scale production. The material used in the present application is a widely commercialized porous carbon material, which is low in cost. The reaction process is simple, fast and efficient, and the reactants (catalyst and amino-functionalization reagent) are water-soluble, without impurities remaining. The method of the present application has the advantages of low cost, simple preparation method and equipment, and easy control of operation process, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 The self-discharge curves of Comparative Example 1, Example 2, Example 5 and Example 8 are shown.

[0026] Figure 2Charge-discharge curves of Comparative Example 1, Example 2, Example 5 and Example 8.

[0027] Figure 3 Rate capability curves of Comparative Example 1, Example 2, Example 5 and Example 8.

[0028] Figure 4 EIS curves of Comparative Example 1, Example 2, Example 5 and Example 8. DETAILED DESCRIPTION

[0029] For a more complete understanding of the present application, we will make a comprehensive and detailed description of it. However, the present application has multiple implementations and is not limited to the specific examples listed herein. The presentation of these examples aims to deepen the overall understanding of the disclosure of the present application.

[0030] Example 1

[0031] The present embodiment provides a low self-discharge aminated activated carbon for supercapacitors;

[0032] The specific surface area of the aminated activated carbon material is 1720 m 2 / g, the N element content is 0.5%~1.5%, the material is a typical disordered structure, and the defect content I D / I G is 0.9~1.1.

[0033] The surface of the aminated activated carbon material is rich in negative charges, the Zeta potential is about -5 mV (1 M SBPBF4 organic electrolyte as medium), the zero charge potential is about 0.2 V vs Ag (1 M SBPBF4 organic electrolyte system), and the surface potential measured by Kelvin probe force microscopy is about 53 mV.

[0034] The present embodiment also provides a preparation method of the aminated activated carbon material, which comprises the following steps:

[0035] (1) The activated carbon is passed through a 300-mesh sieve, washed with ethanol and deionized water in turn to remove residual impurities, and dried in an 80 ℃ oven;

[0036] (2) A certain proportion of dried activated carbon is mixed with an amino reagent ethylenediamine and a catalyst 2-(7-azabenzotriazol)-N,N,N',N'-tetramethyluronium hexafluorophosphate, stirred and dispersed in a fume hood to obtain a uniform mixture;

[0037] (3) The uniform mixture is transferred to a polytetrafluoroethylene-lined reaction kettle in a fume hood, reacted in a homogeneous reactor at 80 ℃ for 2 hours, and cooled to room temperature after the reaction is completed;

[0038] (4) The cooled mixture is sequentially filtered and washed with ethanol and deionized water, and after the washing is completed, the obtained activated carbon material is transferred to a 80 ℃ oven for drying, to obtain an amino-functionalized activated carbon.

[0039] Example 2

[0040] The difference between this example and Example 1 is that the reaction time in step (3) in the homogeneous reactor is 5 hours.

[0041] The rest of the preparation method and parameters remain the same as in Example 1.

[0042] Example 3

[0043] The difference between this example and Example 1 is that the reaction time in step (3) in the homogeneous reactor is 8 hours.

[0044] The rest of the preparation method and parameters remain the same as in Example 1.

[0045] Example 4

[0046] The difference between this example and Example 1 is that the amino reagent in step (2) is 1,2-propanediamine.

[0047] The rest of the preparation method and parameters remain the same as in Example 1.

[0048] Example 5

[0049] The difference between this example and Example 4 is that the reaction time in step (3) in the homogeneous reactor is 5 hours.

[0050] The rest of the preparation method and parameters remain the same as in Example 4.

[0051] Example 6

[0052] The difference between this example and Example 4 is that the reaction time in step (3) in the homogeneous reactor is 8 hours.

[0053] The rest of the preparation method and parameters remain the same as in Example 4.

[0054] Example 7

[0055] The difference between this example and Example 1 is that the amino reagent in step (2) is aniline.

[0056] The rest of the preparation method and parameters remain the same as in Example 1.

[0057] Example 8

[0058] The difference between this example and Example 7 is that the reaction time in step (3) in the homogeneous reactor is 5 hours.

[0059] The rest of the preparation method and parameters are consistent with Example 7.

[0060] Example 9

[0061] The difference between this example and Example 7 is that the reaction time in step (3) in the homogeneous reactor is 8 hours.

[0062] The rest of the preparation method and parameters are consistent with Example 7.

[0063] Comparative Example 1

[0064] This comparative example uses a commercial activated carbon material (YP-50F from Kureha, Japan) without additional treatment.

[0065] Performance test:

[0066] Super capacitor preparation: After mixing the activated carbon, conductive carbon black and binder evenly, coat on the aluminum current collector, dry, then compact, cut and weigh to obtain two electrode pieces with equal mass. Then assemble and seal the electrode pieces, cellulose diaphragm and prepared electrolyte in the glove box to obtain the super capacitor device.

[0067] The test process of the super capacitor is as follows: (1) pre-cycling. In a constant temperature chamber at 25°C, pre-cycle 10 times, and the voltage interval is set to 0.1 V-3.0 V. The cycle program is to charge at a current density of 0.1 A / g, then constant voltage charge for 1 hour, and then discharge at a current density of 0.1 A / g. (2) Self-discharge test. Perform self-discharge test in a constant temperature chamber at 25°C. The test program is to charge and discharge for two cycles, then charge to 3.0 V and keep constant voltage at 3.0 V for 3 hours, where the current density is 0.1 A / g. Finally, stand for 40 hours, and record the voltage change of the super capacitor during the standing process.

[0068] The test results are shown in Table 1.

[0069]

[0070] Analysis: From the test results in Table 1, it can be seen that the aminated activated carbon can effectively inhibit the self-discharge of the super capacitor. This is because the surface of the activated carbon is aminated, which can inhibit the specific adsorption of anions on the electrode surface, thereby improving the adsorption capacity of cations on the electrode surface, which is beneficial to inhibit the self-discharge of the negative electrode.

[0071] From Examples 1-3, it can be seen that increasing the amination reaction time can improve the ability to inhibit self-discharge, but continuously prolonging the reaction time will not continuously improve the self-discharge performance.

[0072] It can be seen from Example 2, Example 5 and Example 8 that different amino reagents can achieve the purpose of amination of the surface of activated carbon, indicating the universality of the scheme.

[0073] The self-discharge curves of Comparative Example 1, Example 2, Example 5 and Example 8 are shown in Figure 1

[0074] It can be seen from the test results of Figure 2 that the specific capacitances of Comparative Example 1, Example 2, Example 5 and Example 8 are almost unchanged. It can be seen from the test results of Figure 3 that the rate performance of Comparative Example 1, Example 2, Example 5 and Example 8 is very small. It can be seen from the test results of Figure 4 that the impedances of Comparative Example 1, Example 2, Example 5 and Example 8 are almost consistent. The above data show that the strategy of inhibiting the self-discharge of supercapacitors by amination of the electrode surface has no obvious influence on the specific capacitance, rate performance and impedance performance, indicating that the scheme can effectively balance other electrochemical performances of supercapacitors.

[0075] The contents not described in detail in the specification of the present application belong to the prior art known to those skilled in the art. Although the above describes the specific embodiments of the present application in a descriptive manner, so as to facilitate those skilled in the art to understand the present application, it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, it is obvious that various changes are within the spirit and scope of the present application defined and determined by the appended claims, and all the inventions utilizing the concept of the present application are within the scope of protection.​

Claims

1. A low self-discharge aminated activated carbon for supercapacitors, characterized by: The specific surface area of the amino-functionalized activated carbon is 1500 m 2 / g~2000 m 2 / g, the N element content is 0.5%~1.5%, the amino-functionalized activated carbon is a typical disordered structure, the defect content I D / I G is 0.9~1.

1.

2. The low self-discharge amino-functionalized activated carbon for supercapacitors according to claim 1, characterized by: The Zeta potential is about 0 mV~5 mV when the 1 M SBPBF4 organic electrolyte is used as a medium, the zero charge potential is about 0.20 V~0.30 V vs Ag in the 1 M SBPBF4 organic electrolyte system, and the surface potential measured by a Kelvin probe microscope is about 50 mV~60 mV.

3. A method for preparing low self-discharge aminated activated carbon for supercapacitors, characterized by: The activated carbon is screened, impurities are removed, and drying treatment is performed, then the treated activated carbon is mixed with a catalyst and an amino reagent by magnetic stirring, and a homogeneous reaction is performed, after the reaction is completed, the treated activated carbon is sequentially extracted and washed by deionized water and anhydrous ethanol, and dried to obtain an aminated activated carbon.

4. The method for preparing low self-discharge amino-activated carbon for supercapacitors according to claim 3, characterized in that: The activated carbon is at least one of coconut shell carbon, nutshell carbon, wood carbon, columnar carbon, coal carbon, and starch-based carbon.

5. The method for preparing low self-discharge amino-activated carbon for supercapacitors according to claim 3, characterized in that: The catalyst is at least one of 2-(7-azabenzotriazol)-N,N,N',N'-tetramethyluronium hexafluorophosphate, oxo-benzotriazol-tetramethyluronium hexafluorophosphate, 6-chlorobenzotriazol-1,1,3,3-tetramethyluronium hexafluorophosphate, oxo-benzotriazol-N,N,N',N'-tetramethyluronium tetrafluoroborate, oxo-(N-succinimidyl)-bis(dimethylamino)carbonium tetrafluoroborate, tris(2-aminoethyl)-tris-nitroisourea, oxo-(7-azabenzotriazol-1-yl)-bis(tetrahydropyrrolyl)carbonium hexafluorophosphate, and oxo-(benzotriazol-1-yl)-bis(tetrahydropyrrolyl)carbonium hexafluorophosphate.

6. The method for preparing low self-discharge amino-activated carbon for supercapacitors according to claim 3, characterized in that: The amino reagent is at least one of ethylamine, ethylenediamine, diethylamine, 1,2-propanediamine, 1,3-propanediamine, mercaptoethylamine, and aniline.

7. The method according to claim 3, wherein the method is characterized by: The treated activated carbon, the catalyst, and the amino reagent are respectively 2 g, 12 g, and 120 mL.

8. The method for preparing low self-discharge amino-activated carbon for supercapacitors according to claim 3, characterized by: The homogeneous reaction is performed at a temperature of 80℃ for 1~10h.

9. The method according to claim 3, wherein the method is characterized by: The screening, impurity removal, and drying treatment are specifically that the activated carbon is screened through a 300-mesh screen, residual impurities are removed by sequentially extracting and washing with ethanol and deionized water, and drying is performed in an oven at 80℃; the magnetic stirring is performed for 5 min~30 min. The filter paper used for the extraction and washing is cellulose material, has a pore size of 20 μm and a thickness of 160 μm, and the extraction and washing time is 1~5h.

10. An ultracapacitor characterized by: The active material of the positive and negative electrodes of the supercapacitor comprises the aminated activated carbon material prepared by the preparation method of any one of claims 3~9.

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