CN114068197A - Modified electrode and preparation method and application thereof - Google Patents
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/48—Conductive polymers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/66—Current collectors
- H01G11/68—Current collectors characterised by their material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
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- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
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- Battery Electrode And Active Subsutance (AREA)
- Electric Double-Layer Capacitors Or The Like (AREA)
Abstract
The invention relates to a modified electrode and a preparation method and application thereof, wherein the modified electrode comprises the following components: the current collector loaded with carbon-based active substances is used as an electrode, and the polymer film is coated on the surface of the electrode; the polymer film is formed by in-situ polymerization of small molecular organic monomers by an electrochemical method; the small molecular organic monomer at least comprises a carbon-carbon double bond and a group containing a heteroatom, wherein the group containing the heteroatom is selected from at least one of carboxyl, hydroxyl, carbonyl, aldehyde group, sulfonic group, phosphoric group, nitro, amino, sulfydryl, amido, ester group, halogenated group and cyanamide group.
Description
Technical Field
The invention relates to a modification method of an electrochemical energy storage material, in particular to a modified electrode and a preparation method and application thereof, and particularly relates to a method for improving a voltage window of a water system super capacitor by electrochemically depositing a micromolecule organic monomer containing carbon-carbon double bonds and polymers of alkali metal salts and alkaline earth metal salts thereof on the surface of the electrode in situ, belonging to the field of materials.
Background
The electrochemical energy storage technology is an important technology influencing the production and life of human beings, and obtains wide attention from the industrial and academic fields. Lithium ion batteries and supercapacitors are two representative types of energy storage devices in the field of electrochemical energy storage. Compared with the traditional secondary battery, the lithium ion battery has the advantages of high open-circuit voltage, large energy density, long service life and the like, and can be applied to the fields of portable electronic equipment such as mobile phones, video cameras, notebook computers and the like, military equipment, medical equipment and the like. However, the energy density of the traditional lithium battery is high (250 Wh kg)-1) But the power density is lower (< 1kW kg)-1) And the application of the lithium ion battery in high-power equipment and fields is limited. In the field of high-power energy storage, the super capacitor has unique advantages, and the power density of the super capacitor can reach 15kW kg-1However, since the surface energy storage is usually carried out by using an electric double layer, the energy density is too low (< 20Wh kg)-1) And the requirement of high energy density in practical application is difficult to meet, so that a novel super capacitor device with high energy density is urgently needed to be developed, and the application market of the super capacitor device is further expanded.
The energy density E and power density P of the supercapacitor can be determined by E-0.5 CV2And P ═ V2/4RESRCalculated respectively, where C is the specific capacitance of the active material, V is the voltage window of the device, and RESRIs the equivalent series resistance of the device. Through the calculation formula, two ways for improving the energy density of the super capacitor are found, namely, improving the specific capacity C of the active material and improving the voltage window of the device. The carbon material is the most typical active material of a supercapacitor, and commercial supercapacitor carbon materials such as YP-50 with a capacity of 200F g-1In the previous work, the capacity of 855F g is designed and prepared-1The nitrogen-doped ordered mesoporous carbon (Science,2015,350,1508-1513.) improves C by more than 4 times. The size of the voltage window V is another important factor influencing the energy density of the super capacitor, and the device can be greatly improved by improving V under the condition that C is constantThe energy density of the super capacitor is improved by 1 time, and the energy density of the super capacitor is improved by 4 times, so that the development of the high-voltage super capacitor is significant.
Carbon-based supercapacitors generally do not have a distinct redox peak due to the principle of electric double layer energy storage, and therefore the voltage of the devices is mainly determined by the electrolyte used, and can be divided into two categories, namely water-based supercapacitors and organic supercapacitors. The water system super capacitor has the advantages of good safety, good rate performance, environmental friendliness, low cost and the like, but is limited by the electrolysis of water, the voltage window of the water system super capacitor is usually lower, the voltage window of a symmetrical device in strong acid (such as sulfuric acid) and strong alkali (such as potassium hydroxide) electrolyte is only 1.0-1.2V, and the voltage window can reach as high as-1.8V due to the influence of the activity of water and the like in neutral lithium sulfate electrolyte. Due to the low voltage window, the energy density of the water system super capacitor is low, commercial YP-50 carbon material is used as an active material, and the energy density is only 8-14 Wh kg-1Even if high-capacity nitrogen-doped carbon is adopted, the energy density can only reach 40-60 Wh kg-1Much lower than lithium batteries. The voltage window of the super capacitor can reach 3V-4V by adopting non-aqueous electrolyte such as organic electrolyte or ionic liquid, and the energy density can be improved to 60-90Wh kg by adopting commercial active carbon material-1. However, the high-voltage non-aqueous super capacitor has the problems of high electrolyte price, poor safety, environmental friendliness and the like, the specific capacity of the carbon material in the electrolyte is generally less than half of that of the carbon material in the aqueous electrolyte, the improvement of energy density caused by high voltage is weakened, and the ionic conductivity of the electrolyte is generally only 10mS cm-1Far below that of aqueous electrolytes>100mS cm-1The rate performance of the device is poor, and the cycling stability of the device is reduced due to the oxidation problem of the carbon material under high voltage.
Therefore, the development of a high-voltage supercapacitor based on an aqueous electrolyte is an optimal path for simultaneously achieving high energy density, high power density, high safety and low cost, and theoretically, by constructing a water-blocking but ion-conducting polymer film on the surface of an electrode, the direct contact between the electrode and water can be isolated, so as to inhibit the decomposition of water, but how to achieve the aqueous high-voltage supercapacitor still has the following problems: (1) how to break through the limitations of thermodynamics and kinetics, inhibit the electrolysis of water under high voltage, and increase the voltage window to more than 2V; (2) how to solve the problem of oxidation of an active substance carbon material under high voltage; (3) how to controllably prepare a uniform water-blocking and ion-conducting sublayer on the surface of an electrode; (4) how to achieve stability of the polymer film during cycling; (5) how to ensure that the specific capacity and the rate capability of the material are not lost under the condition of improving the voltage of a device.
Disclosure of Invention
Based on the problems of the water system super capacitor, the invention aims to provide a modified electrode, a preparation method thereof and application thereof in the water system super capacitor so as to improve the voltage window of the water system super capacitor.
In a first aspect, the present invention provides a modified electrode comprising: the current collector loaded with carbon-based active substances is used as an electrode, and the polymer film is coated on the surface of the electrode; the polymer film is formed by in-situ polymerization of small molecular organic monomers by an electrochemical method, wherein the small molecular organic monomers at least comprise a carbon-carbon double bond and a group containing a heteroatom, wherein the group containing the heteroatom is selected from at least one of carboxyl, hydroxyl, carbonyl, aldehyde group, sulfonic group, phosphoric group, nitro group, amino group, sulfydryl, amido, ester group, halogenated group and cyanamide group, and is preferably selected from at least one of small molecular organic monomers containing the carbon-carbon double bond, alkali metal salts of the small molecular organic monomers containing the carbon-carbon double bond and alkaline earth metal salts of the small molecular organic monomers containing the carbon-carbon double bond.
In the present disclosure, the polymer film formed in situ on the surface of the electrode by an electrochemical method has an ultra-thin thickness and a dense structure, and can isolate the direct contact between the surface of the electrode and water in the electrolyte, and further effectively inhibit the electrolysis of water, thereby improving the voltage window of the electrode. The selection of small molecule organic monomers has two requirements: (1) the water-soluble polymer (2) has ionic conductivity after being formed into a polymer.
Preferably, the first and second liquid crystal display panels are,the carbon-based active substance is at least one of graphene, carbon nanotubes, YP-50 active carbon and a nitrogen-doped carbon material (such as nitrogen-doped graphene); the current collector is selected from one of iron foil, iron mesh, titanium foil, titanium mesh, three-dimensional graphene, graphite paper and carbon felt, and is preferably carbon felt; the loading amount of the carbon-based active substance in the electrode before modification is 0-20 mg/cm2Preferably 1mg/cm2。
Preferably, the polymer film is uniformly deposited on the surface of the electrode, and the thickness of the polymer film is 2nm to 35nm, preferably 15 nm. The thickness of the resulting polymer film can be controlled by electrochemical means.
Preferably, the small-molecule organic monomer is at least one selected from acrylic acid and alkali metal salts and alkaline earth metal salts thereof, methacrylic acid and alkali metal salts and alkaline earth metal salts thereof, acrylic sulfonic acid and alkali metal salts and alkaline earth metal salts thereof, methacrylic sulfonic acid and alkali metal salts and alkaline earth metal salts thereof, acrylamide, methacrylamide, butenol, methyl methacrylate, amino propylene, triethylene tetramine, acrolein, acrylonitrile, ethylene phosphoric acid, mercaptopropene and nitroethylene, and is preferably lithium acrylate; the molecular weight of the small molecular organic matter monomer is less than 1000.
In a second aspect, the invention provides a method for preparing the modified electrode, wherein a current collector loaded with a carbon-based active material is used as a working electrode, an aqueous solution containing a small molecular organic monomer is used as an electrolyte, and a cyclic voltammetry method, a potentiostatic method or a pulse voltage method is used for exciting a carbon-carbon double bond in the small molecular organic monomer containing the carbon-carbon double bond to perform a polymerization reaction on the surface of the working electrode to form a polymer film, so as to obtain the modified electrode.
In the present disclosure, through electrochemical induction (or excitation), electrons generated by an electrochemical device are used as a radical initiator on the surface of an electrode, carbon-carbon double bonds in small organic monomers are opened, and an addition reaction is repeatedly performed between molecules to connect a plurality of monomers, so that a polymer macromolecule layer is formed on the surface of the electrode. By the method, the micromolecule organic monomer containing carbon-carbon double bonds and alkali metal salt and alkaline earth metal salt thereof are subjected to in-situ polymerization on the surface of the electrode, so that a layer of uniform and compact polymer film is formed on the surface of the electrode, the polymer film is tightly combined on the surface of the electrode and is not easy to fall off or damage, and the method is superior to the method for carrying out in-situ coating by a chemical method and the method for directly carrying out ex-situ coating by using a polymer. Moreover, the electrochemical in-situ coating of the polymer with electronic insulation and ionic conduction on the surface of the electrode can realize the direct contact of the surface of the electrode and aqueous electrolyte, thereby inhibiting the oxygen evolution reaction of the electrode at high potential (more than 1.23V vs. RHE) and the hydrogen evolution reaction at low potential (less than 0V vs. RHE), improving the voltage window of the electrode coated with the polymer in a three-electrode test system, effectively inhibiting the oxide of a carbon material at high voltage and improving the cycle stability of the material.
Preferably, the concentration of the aqueous solution containing the small-molecule organic monomer is 0.01mol/L to 10mol/L, and preferably 2 mol/L.
Preferably, the parameters of cyclic voltammetry include: the lower voltage limit of the scanning range is 0V to-3V, the upper voltage limit is 0V to 3V, the scanning speed is 1mV/s to 500mV/s, and the number of scanning circles is 1 circle to 200 circles; preferably, the parameters of cyclic voltammetry include: the scanning range is-1.6V, the scanning speed is 50mV/s, and the number of scanning turns is 20 turns.
Preferably, the parameters of the potentiostatic method include: the voltage is 0V to-3V, and the constant voltage time is 5s-36000 s; preferably, the parameters of the potentiostatic method are-1.6V and constant voltage 360 s.
Preferably, the parameters of the pulse voltage method include: the pulse voltage is pressed down within the range of 0V to-3V, the constant voltage time is 1s-360s, the pulse voltage is pressed down within the range of 0V to 3V, the constant voltage time is 1s-360s, the number of cycles is 2-500 cycles, preferably, the pulse voltage is pressed down within the range of-1.6V, the constant voltage time is 10s, the pulse voltage is pressed up within the range of 1.6V, the constant voltage time is 10s, and the number of cycles is 30 cycles.
In a third aspect, the present invention provides an aqueous high-voltage supercapacitor comprising the above-described modified electrode.
According to the invention, by utilizing the method for electrochemically depositing the polymer of the micromolecule organic monomer containing the carbon-carbon double bond and the salt thereof on the surface of the electrode in situ, the electrode with the polymer layer uniformly coated on the surface of the electrode can be obtained, the polymer layer is favorable for inhibiting the oxygen production and the low-voltage hydrogen production of the electrode under the high voltage, the voltage window is wider than that of an uncoated electrode, an aqueous high-voltage super capacitor device can be assembled by taking out and cleaning two same electrodes after the polymer coating treatment, the device can adopt an aqueous solution of lithium sulfate as an electrolyte, the concentration is 0.5mol/L to 3mol/L, the pH application range is wider (the pH range is 2 to 10), and the voltage window of the device can be improved by 0.4V to 1.4V from 1.0V to 1.6V compared with the untreated electrode, and can reach 2.0V to 3.0V.
Preferably, the device voltage of the water system high-voltage super capacitor can reach 3.0V at most when 2mol/L lithium sulfate aqueous solution with the pH value of 6-8 is used as electrolyte.
Preferably, the device voltage of the water system high-voltage super capacitor can reach 1.8V at most when a 0.5mol/L sulfuric acid aqueous solution with the pH value of 0 is used as an electrolyte.
Preferably, the energy density and the power density of the device of the water system high-voltage super capacitor calculated on the basis of the mass of the active substances are both improved by more than 100 percent and respectively reach 127Wh kg-1And 237kW kg-1。
Has the advantages that:
in the invention, a polymer of micromolecule organic monomers containing carbon-carbon double bonds and salts thereof can be uniformly coated with a layer of electronically insulating and ionically conductive water-blocking polymer layer on the surface of an electrode loaded with active substances through electrochemical in-situ deposition on the surface of the electrode, the electrolysis of water of the electrode in the electrochemical process is inhibited, so that the voltage window of the electrode is widened, the electrode coated with the polymer can be used for assembling a water system high-voltage super capacitor, the voltage window of the water system super capacitor is improved from 1.0-1.6V by 0.4V to 1.4V to 2.0V to 3.0V, and better specific capacity and rate performance of materials can be kept, so that the energy density and the power density of the water system super capacitor are both improved by more than 100 percent and can reach 127Wh kg at most-1And 237kW kg-1Cycling 1000000 cycles of capacity retention under optimum conditionsThe rate can reach 93.8%, the energy density reaches the level similar to that of a lithium ion battery, the power density and the cycle stability are far superior to those of the lithium ion battery, and the requirements of the market on a high-performance super capacitor can be met.
Drawings
Fig. 1 is a partial enlarged view of a CV curve (a) negative voltage curve (b) positive voltage curve (c) overall variation of the CV curve with the number of electrodeposition cycles in the process of in situ deposition of lithium polyacrylate through an electrode surface in example 1;
FIG. 2 is a graph of transmission electron micrographs of polymer film thickness corresponding to different CV wraps of lithium polyacrylate deposited in situ on the electrode surface in example 1, showing the relationship between (a) 5 wraps, (b) 10 wraps, (c) 15 wraps, (d) 20 wraps, (e) 30 wraps, (f) 50 wraps, (g) 100 wraps, (h) 200 wraps, and (i) the number of wraps and the thickness of the polymer film;
FIG. 3 is a transmission electron micrograph of a polymer film prepared in example 1 before and after cycling (a) a freshly prepared polymer film cycled for 15 cycles and (b) a lithium sulfate electrolyte in the range of-1.2V to 1.0V after CV cycling 2000 times at a scanning rate of 50 mV/s;
FIG. 4 is a graph showing the variation of the in-situ deposition of lithium polyacrylate by CV method on a carbon felt electrode loaded with YP-50 active material in example 2;
FIG. 5 is a graph comparing (a) voltage window and (b) rate performance in a three-electrode system after electrodeposition of lithium polyacrylate in example 2;
FIG. 6 is a schematic diagram of an aqueous supercapacitor assembled by electrodes in example 2 and a structure thereof;
fig. 7 is a cyclic voltammetry curve of the aqueous high-voltage supercapacitor assembled in example 2, which shows that the voltage thereof can reach 2.4V, 2.6V, 2.8V and 3.0V from left to right, respectively, and the voltage window thereof can reach 3V at most;
FIG. 8 is a graph of the cycling stability of the assembled lithium polyacrylate coated supercapacitor device of example 2, where PAA-Li2SO4Showing the device assembled of polymer-coated electrodes, Li2SO4Showing the assembly of electrodes without polymer encapsulationA device;
fig. 9 is a graph showing the variation of lithium polyacrylate deposited in situ by CV method and (b) CV curves of the polymer-coated electrode in lithium sulfate electrolyte of different pH on the carbon felt electrode loaded with nitrogen-doped carbon active material in example 3;
fig. 10 is a CV curve of a symmetrical device assembled by in-situ deposition of lithium polyacrylate by a CV method on a carbon felt electrode loaded with a nitrogen-doped carbon active material in example 3 and a comparison thereof with an uncoated device (b) constant current charge and discharge curve;
FIG. 11 is a graph of the cycling stability of the assembled lithium polyacrylate coated supercapacitor device of example 3;
FIG. 12 is a graph comparing the energy density and power density of assembled lithium polyacrylate coated supercapacitor devices of examples 2 and 3 with other energy storage devices;
FIG. 13 is a graph comparing the capacity retention at different loadings of the assembled lithium polyacrylate coated electrode of example 4 and uncoated electrode;
FIG. 14 is a CV curve for the device assembled from the electrodes coated with lithium polyacrylate of different thickness and uncoated electrodes assembled in the sulfuric acid electrolyte of example 5, wherein "1" is uncoated, "2" is coated for 20 circles, and "3" is coated for 30 circles;
FIG. 15 is a CV curve for the device assembled from the assembled lithium polyacrylate coated over-thick electrode of example 6 and the uncoated electrode in a lithium sulfate electrolyte, where "1" is uncoated and "2" is coated for 40 cycles;
FIG. 16 is the electrochemical properties of the electrodes coated with lithium polyacrylate of different thickness of example 7, (a) constant current charging and discharging curves of the coated 50 rings and uncoated electrodes in lithium sulfate electrolyte, the current density being 0.1A/g; (b) a multiplying power performance curve of the electrode coated with different turns and (c) an alternating current impedance curve;
FIG. 17 is a graph showing (a) a current change curve with time and (b) a CV curve of a device assembled after coating, in which the surface of the electrode in example 16 was coated with magnesium polyacrylate by a potentiostatic method;
FIG. 18 is a graph showing (a) a change in current with time and (b) a CV curve of a device assembled after coating, in which the surface of the electrode in example 17 was coated with magnesium polyacrylate by a pulse voltage method;
FIG. 19 is a CV curve of a device assembled by coating different polymers on the surface of an electrode in a comparative example, (a) a CV curve of a device coated with PVDF in a comparative example 1 and CV curves of a device coated with PVA (b) and PEG (c) in a comparative example 2;
FIG. 20 is a CV curve of a device assembled by electrodes in comparative example 3 using polyacrylic acid PAA as a binder and YP-50 as an active material;
fig. 21 is a CV curve of a device assembled by electrodes after coating with polyacrylic acid instead of acrylic acid monomer in comparative example 4 and a comparison thereof with an uncoated device and a device coated with acrylic acid, (a) is with sulfuric acid as an electrolyte (wherein 1 is polyacrylic acid coated, 2 is acrylic acid in-situ coated, and 3 is uncoated), (b) is with lithium sulfate as an electrolyte (wherein 1 is polyacrylic acid coated, 2 is uncoated, and 3 is acrylic acid in-situ coated).
Detailed Description
The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.
In the disclosure, aiming at the current situation that the current commercial energy storage device is insufficient under the high-rate working condition, a polymer film (modified electrode) of a micromolecule organic monomer containing a carbon-carbon double bond and a salt thereof is deposited in situ on the surface of an electrode through electrochemistry, and the voltage window of the water system super capacitor is greatly expanded.
The specific process comprises the following steps: the current collector (as an electrode) loaded with carbon-based active substances is put into an aqueous solution (electrolyte) of a micromolecule organic monomer containing carbon-carbon double bonds and salts thereof, and the micromolecule organic monomer containing the carbon-carbon double bonds and the salts thereof are deposited on the surface of the electrode through double bond polymerization and crosslinking by an electrochemical method to form a uniform polymer film. In addition, the electrode treated by the method can isolate the direct contact of the surface of the electrode and water in the electrolyte of the water system super capacitor due to the polymer film, so that the electrolysis of the water is effectively inhibited, the voltage window of the electrode is finally improved, the better specific capacity and rate performance of the material are kept, and the energy density and the power density of the water system super capacitor device can be improved by over 100 percent.
In alternative embodiments, the small organic molecule monomer containing a carbon-carbon double bond and salts thereof includes at least organic small molecules containing one carbon-carbon double bond and one group containing a heteroatom (e.g., carboxyl, hydroxyl, carbonyl, aldehyde, sulfonic, phosphoric, nitro, amino, thiol, amide, ester, halide, cyanamide, etc.) and having a molecular weight of < 1000. For example, acrylic acid and salts thereof, methacrylic acid and salts thereof, acrylic sulfonic acid and salts thereof, methacrylic sulfonic acid and salts thereof, acrylamide and salts thereof, methacrylamide and salts thereof, butenol and salts thereof, and the like. The salts generally refer to alkali metal salts or alkaline earth metal salts corresponding to small organic monomers. The concentration of the aqueous solution of the small molecular organic monomer containing the carbon-carbon double bond and the salt thereof can be 0.01mol/L to 10mol/L, and preferably, the monomer of the small molecular organic monomer containing the carbon-carbon double bond and the salt thereof is lithium acrylate, and the concentration is preferably 2 mol/L.
In the present invention, the electrode is composed of a carbon-based active material and a current collector. Wherein, the carbon-based active material is a carbon material for electrochemical super capacitor, and can be a purchased commercial product or a self-made nitrogen-doped graphene (the self-made nitrogen-doped graphene is generally a conventional material, and the preparation method thereof can be referred to document 1(Science,2015,350,1508 1513) and related patents (for example, application numbers 201910419557.1, 201911029332.1, 201910403912.6, 201910408208.X, etc.). the current collector for electrode can be one or more combinations of iron foil, iron mesh, titanium foil, titanium mesh, three-dimensional graphene, graphite paper or carbon felt.
In the present invention, the electrochemical method may be cyclic voltammetry, potentiostatic method, pulsed voltage method, or the like.
In alternative embodiments, the parameters of cyclic voltammetry include: the lower voltage limit of the scanning range is 0V to-3V, and the upper voltage limit is 0V to 3V; the scanning speed is 1mV/s to 500 mV/s; the number of scanning turns is 1 to 200 turns. The obtained polymer film is uniformly deposited on the surface of the electrode, and the thickness of the polymer film is controllable in the range of 2 nm-35 nm, preferably 15 nm.
In alternative embodiments, the parameters of the potentiostatic method include: the voltage is 0V to-3V, and the constant voltage time is 5s-36000 s; preferably, the parameters of the potentiostatic method are-1.6V and constant voltage 360 s.
In an alternative embodiment, the parameters of the pulsed voltage method include: the pulse voltage is pressed down within the range of 0V to-3V, the constant voltage time is 1s-360s, the pulse voltage is pressed down within the range of 0V to 3V, the constant voltage time is 1s-360s, the number of cycles is 2-500 cycles, preferably, the pulse voltage is pressed down within the range of-1.6V, the constant voltage time is 10s, the pulse voltage is pressed up within the range of 1.6V, the constant voltage time is 10s, and the number of cycles is 30 cycles.
In the disclosure, the modified electrode is used for assembling a symmetrical device of a water system high-voltage super capacitor, the energy density of the symmetrical device can be improved to the level of a lithium ion battery, the symmetrical device has extremely high power density and cycle stability, the advantages of two devices of the lithium ion battery and the super capacitor are achieved, and the symmetrical device has strong innovation and wide application prospect.
The aqueous high-voltage supercapacitor can adopt an aqueous solution of lithium sulfate as an electrolyte, and the concentration of the aqueous solution is 0.5mol/L to 3 mol/L. The voltage window of the water-based high-voltage supercapacitor can be increased by 0.4V to 1.4V from 1.0-1.6V to a level of 2.0V to 3.0V (preferably, the voltage window can be increased to 3.0V) compared to the untreated electrode. In addition, the water system high-voltage super capacitor can have a large voltage window and capacity in a lithium sulfate electrolyte with the pH value ranging from 2 to 10 (preferably, the pH value ranges from 6 to 8) and can keep proton energy storage characteristics. Compared with an unmodified device, the water system high-voltage supercapacitor can keep better specific capacity and rate capability of materials, the specific capacity loss rate of the materials is less than 20%, and the material ratio is 10A g-1The specific loss rate under high multiplying power is less than 20%. The energy density and the power density of the device calculated based on the mass of the carbon-based active substance are both improved by more than 100 percent and respectively reach 127Wh kg-1And 237kW kg-1。
The preparation method of the water system high-voltage super capacitor has strong universality, does not need too fine regulation and control and a large amount of additives, and has the potential and value of industrial mass production.
Sample characterization
The method comprises the steps of collecting morphology and ultrastructure information of a sample by using a scanning electron microscope and a transmission electron microscope, collecting element and distribution information of the sample by using an X-ray energy spectrometer, carrying out in-situ electrochemical deposition and electrochemical performance characterization analysis of an electrode by using an electrochemical workstation, and characterizing the electrode performance of the sample by using a blue-ray battery testing system.
The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.
Example 1
The method comprises the following steps of firstly, attempting electrochemical in-situ deposition of a polymer containing a micromolecular organic monomer with a carbon-carbon double bond and a salt thereof on a blank carbon felt (CCF) current collector without loading an active substance, putting the blank carbon felt electrode into a 2mol/L lithium acrylate solution to serve as a working electrode, Ag/AgCl to serve as a reference electrode, graphite to serve as a counter electrode, and carrying out in-situ deposition of lithium polyacrylate on the surface of the electrode by adopting a Cyclic Voltammetry (CV), wherein a scanning range is set to be-2V, a scanning speed is set to be 50mV/s, and the number of scanning turns is 1, 2, 5, 10, 15, 20, 30, 50, 100 and 200 turns in sequence. As shown in fig. 1, the electrochemical window of the electrode gradually widened from 1.94V to 3.45V as the number of CV cycles increased. As shown in fig. 2, transmission electron microscopy characterization shows that the thickness of the polymer layer on the surface of the carbon felt is gradually increased with the increase of the number of cycles, the thickness of the polymer layer is controllable within the range of 2nm to 35nm, the thickness of the polymer layer is hardly increased after reaching 35nm, the in-situ deposited polymer layer has good stability in the subsequent cycle process, and the polymer layer is not changed after being cycled for 2000 times (fig. 3).
Example 2
Will be negativeCarbon felt electrode loaded with YP-50 type activated carbon (the loading amount of YP-50 type activated carbon is 1 mg/cm)2) Placing the solution into 2mol/L lithium acrylate solution as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and depositing lithium polyacrylate on the surface of the electrode in situ by Cyclic Voltammetry (CV), wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 20 cycles, as shown in FIG. 4. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the lithium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of about 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, and testing the electrochemical characteristics of the in-situ coated lithium polyacrylate rear electrode, wherein as shown in a in figure 5, the electrochemical window of the coated lithium polyacrylate rear electrode is enlarged, and compared with 0-0.8V in the sulfuric acid electrolyte and-0.8V in the lithium sulfate electrolyte before the coating of the olefine acid polymer, the voltage range of the coated electrode can be expanded to-1.2-1V, and the specific capacitance is maintained. Fig. 5 b shows that the rate performance of the electrode coated with lithium polyacrylate is better and the specific capacity is increased due to the large voltage window. According to the mode shown in fig. 6, a water system super capacitor soft package device is assembled by using 2mol/L lithium sulfate as electrolyte, the voltage of the device can reach 3.0V at most (fig. 7), and the voltage is calculated according to the mass of the active material (wherein, the specific capacity C of the active material is S/(2 mv. delta. V) or I.DELTA.t/m.DELTA.V, wherein S is the integral area of a cyclic voltammetry curve, m is the mass of the active material, V is the sweeping speed, Δ V is a voltage window, I is current, Δ t is charging and discharging time, and E is 0.5 CV)2And P ═ V2/4RESRCalculated respectively, where C is the specific capacitance of the active material, V is the voltage window of the device, and RESRIs the equivalent series resistance of the device) has energy density and power density of 28Wh kg-1And 34kW kg-1The capacity was 93.8% over 100000 cycles (fig. 8), significantly higher than 12.5Wh kg for the uncoated electrode assembled device-1、25.5kW kg-1And 100000 cycles of capacity retention 85.7%. Therefore, the method plays an important role in improving the energy density, the power density and the cycle stability of the same material.
Example 3
Loading a carbon felt electrode loaded with a self-made nitrogen-doped carbon material (the loading amount of the self-made nitrogen-doped carbon material is 1 mg/cm)2The used nitrogen-doped carbon material is nitrogen-doped graphene, the doping amount of the nitrogen element is 11.9 at%) is put into 2mol/L lithium acrylate solution to serve as a working electrode, Ag/AgCl serves as a reference electrode, graphite serves as a counter electrode, lithium polyacrylate is deposited in situ on the surface of the electrode by adopting Cyclic Voltammetry (CV), the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning turns is 15 circles, as shown in a in figure 9. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the lithium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of about 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, and testing the electrochemical characteristics of the in-situ coated lithium polyacrylate rear electrode, wherein as shown in a b in fig. 9, the electrochemical window of the coated lithium polyacrylate rear electrode is enlarged, and compared with 0-0.8V in the sulfuric acid electrolyte and-0.8V in the lithium sulfate electrolyte before the olefine acid polymer is not coated, the voltage range of the coated electrode can be expanded to-1.2-1V, and the capacity is maintained. In addition, polyacrylic acid is weak acid and can be used as a proton storage pool and a pH buffering agent, so that the electrode can keep a wide window and stable capacity in a wide range of pH 2-10. According to the mode shown in FIG. 6, 2mol/L lithium sulfate is used as electrolyte to assemble a water-system supercapacitor soft package device, and the voltage of the device can reach 3.0V at most. The energy density and the power density of the 2.4V device respectively reach 127Wh kg according to the mass calculation of the active substance-1And 237kW kg-1(fig. 10), cycle 60000 times capacity 84.5% (fig. 11), significantly higher than 63Wh kg for the uncoated electrode assembled device-1、44kW kg-1And 100000 cycles of capacity retention 73.3%. As shown in fig. 12, the energy density of the device can reach a level similar to that of a lithium ion battery, but the power density and the cycle stability of the device are far superior to those of the lithium ion battery, and the device has important practical application value.
Example 4
Loading carbon-based active substance YP-50 type active carbon with different loading amounts (the loading amount of the YP-50 type active carbon is 1-12 mg/cm)2In order of 1mg/cm2、2mg/cm2、4mg/cm2、6mg/cm2、8mg/cm2、10mg/cm2、12mg/cm2) The loaded carbon felt electrode is put into 2mol/L lithium acrylate solution to be used as a working electrode, Ag/AgCl is used as a reference electrode, graphite is used as a counter electrode, lithium polyacrylate is deposited in situ on the surface of the electrode by adopting Cyclic Voltammetry (CV), the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning circles is 20 circles. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the lithium acrylate monomer adhered on the electrode. And then placing the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated lithium polyacrylate rear electrode, wherein the electrochemical window of the coated lithium polyacrylate rear electrode is enlarged, and compared with 0-0.8V in sulfuric acid electrolyte and-0.8V in the lithium sulfate electrolyte before no coating of an olefine acid polymer, the voltage range of the coated electrode can be expanded to-1.2-1V, and the specific capacitance is maintained. Fig. 13 shows that even at high loading, the in situ electrochemical deposition of polyacrylic acid can maintain a higher level of electrode capacity at high loading than electrodes that are not coated with polyacrylic acid, and thus coating with polyacrylic acid is beneficial for increasing the volumetric energy density of the device.
Example 5
A carbon felt electrode loaded with YP-50 type active carbon (the loading amount of the YP-50 type active carbon is 1 mg/cm)2) Putting the material into 2mol/L lithium acrylate solution as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and depositing lithium polyacrylate on the surface of the electrode in situ by adopting a Cyclic Voltammetry (CV), wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning circles is 15 and 30. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the lithium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 0.5mol/L sulfuric acid electrolyte with the pH value of about 0, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated lithium polyacrylate rear electrode, and enlarging the electrochemical window of the coated polyacrylic acid rear electrode. The electrodes are respectively assembled into a water system superCapacitor devices were tested for electrochemical performance, as shown in fig. 14, the in-situ deposition CV of 20 cycles resulted in a thinner polymer layer and 30 cycles resulted in a thicker polymer layer, thus the device voltage window with the thinner polyacrylic layer was increased from 1.2V to 1.4V and the capacity was maintained, while the device voltage with the thicker polyacrylic layer could be increased to 1.8V, but the capacity was reduced.
Example 6
A carbon felt electrode loaded with YP-50 type activated carbon (the loading amount of the YP-50 type activated carbon is 1 mg/cm)2) Putting the material into 2mol/L lithium acrylate solution as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and depositing lithium polyacrylate on the surface of the electrode in situ by adopting a Cyclic Voltammetry (CV), wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 40. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the lithium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH of 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated lithium polyacrylate rear electrode, and enlarging the electrochemical window of the coated polyacrylic acid rear electrode. The electrodes are respectively assembled into a water system super capacitor device, electrochemical characteristics of the water system super capacitor device are tested, as shown in FIG. 15, when the CV of in-situ deposition is 40 circles, a polymer layer is thicker, and therefore the voltage of the device with the thicker polyacrylic acid layer can be increased to 2.4V, but the capacity is reduced.
Example 7
A carbon felt electrode loaded with YP-50 type active carbon (the loading amount of the YP-50 type active carbon is 1 mg/cm)2) Putting the material into 2mol/L lithium acrylate solution as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and depositing lithium polyacrylate on the surface of the electrode in situ by adopting a Cyclic Voltammetry (CV), wherein the scanning range is set to be-1.6V, the scanning speed is set to be 50mV/s, and the number of scanning circles is 20 circles, 30 circles and 50 circles. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the lithium acrylate monomer adhered on the electrode. Then the treated electrode is put into 2mol/L lithium sulfate electrolyte with the pH value of 6-8, Ag/AgCl is used as a reference electrode, graphite is used as a counter electrode,the electrochemical characteristics of the in-situ coated lithium polyacrylate rear electrode are tested, and as shown in fig. 16, a is a constant current charging and discharging curve of the electrode coated with CV for 50 circles under a small current density of 0.1A/g, it can be found that the electrode coated with CV for 50 circles and the electrode not coated have similar specific capacities under the small current density, which indicates that the in-situ coated lithium polyacrylate does not reduce the specific capacity of the active material. However, as shown in b in fig. 16, comparing the electrodes with different numbers of coating turns, it can be found that the rate performance of the electrode coated with lithium polyacrylate is close to that of the electrode not coated when the number of coating turns is 20, but when the number of coating turns is too large, such as 30 turns and 50 turns, the electrode has higher capacity at low rate, but the performance of high rate is rapidly reduced, which indicates that the too thick lithium polyacrylate film greatly reduces the mass transfer rate on the surface of the electrode, which is not favorable for the high rate performance of the material. Fig. 16 c is an ac impedance spectrum of electrodes with different numbers of wraps, from which it can be seen that an increase in the number of wraps makes the slope of the low-frequency end of the electrode smaller, illustrating that ion diffusion deviates from the surface capacitance type mass transfer process and is biased toward bulk diffusion of the battery, which is consistent with a decrease in the rate performance of the electrode.
Example 8
A carbon felt electrode loaded with YP-50 type activated carbon (the loading amount of the YP-50 type activated carbon is 1 mg/cm)2) Putting the mixture into a magnesium acrylate solution of 2mol/L as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and in-situ depositing lithium polyacrylate on the surface of the electrode by adopting a Cyclic Voltammetry (CV), wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 20. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the magnesium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated magnesium polyacrylate rear electrode, enlarging the electrochemical window of the coated magnesium polyacrylate rear electrode, expanding the voltage range to-1.2-1V, and keeping the specific capacitance. After the electrode is coated with the magnesium polyacrylate, the rate performance is better, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is used as electrolyte to assemble a water system super capacitor soft package device, and the voltage of the device is the highestThe high voltage can reach 2.6V, and the energy density and the power density calculated according to the mass of the active substances respectively reach 24Wh kg-1And 32kW kg-1The capacity retention rate after 50000 times of circulation is 92 percent.
Example 9
A carbon felt electrode loaded with YP-50 type activated carbon (the loading amount of the YP-50 type activated carbon is 1 mg/cm)2) Putting the material into 0.1mol/L magnesium acrylate solution as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and adopting Cyclic Voltammetry (CV) to deposit lithium polyacrylate on the surface of the electrode in situ, wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 20. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the magnesium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of about 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated magnesium polyacrylate rear electrode, enlarging the electrochemical window of the coated magnesium polyacrylate rear electrode, expanding the voltage range to-1.0-0.9V, and keeping the specific capacitance. After the electrode is coated with the magnesium polyacrylate, the rate performance is better, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is used as electrolyte to assemble a water system super capacitor soft package device, the voltage of the device can reach 2.2V at most, and the energy density and the power density calculated according to the mass of active substances respectively reach 20Wh kg-1And 30kW kg-1The capacity retention rate after 50000 times of circulation is 92 percent.
Example 10
A carbon felt electrode loaded with YP-50 type activated carbon (the loading amount of the YP-50 type activated carbon is 1 mg/cm)2) Putting the mixture into 10mol/L magnesium acrylate solution as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and in-situ depositing lithium polyacrylate on the surface of the electrode by adopting a Cyclic Voltammetry (CV), wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 20. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the magnesium acrylate monomer adhered on the electrode. Then, the treated electrode is placed into 2mol/L lithium sulfate electrolyte with the pH value of 6-8, Ag/AgCl is used as a reference electrode, and graphite is used as a pairAnd testing the electrochemical characteristics of the in-situ coated magnesium polyacrylate rear electrode, wherein the electrochemical window of the coated magnesium polyacrylate rear electrode is enlarged, the voltage range can be expanded to-1.4-1.2V, and the specific capacitance is maintained. After the electrode is coated with the magnesium polyacrylate, the rate performance is better, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is used as electrolyte to assemble a water system super capacitor soft package device, the voltage of the device can reach 2.8V at most, and the energy density and the power density calculated according to the mass of active substances respectively reach 10Wh kg-1And 5kW kg-1The capacity retention rate of 50000 times of circulation is 80%, and the energy density and the power density are low mainly because the ion transmission speed is too slow due to the excessive thickness of the polymer film.
Example 11
Carrying out three-dimensional graphene electrode loaded with YP-50 type active carbon (the loading amount of the YP-50 type active carbon is 1 mg/cm)2) Putting the mixture into a magnesium acrylate solution of 2mol/L as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and in-situ depositing lithium polyacrylate on the surface of the electrode by adopting a Cyclic Voltammetry (CV), wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 20. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the magnesium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of about 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated magnesium polyacrylate rear electrode, enlarging the electrochemical window of the coated magnesium polyacrylate rear electrode, expanding the voltage range to-1.2-1.0V, and keeping the specific capacitance. After the electrode is coated with the magnesium polyacrylate, the rate performance is better, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is used as electrolyte to assemble a water system super capacitor soft package device, the voltage of the device can reach 2.6V at most, and the energy density and the power density calculated according to the mass of the active substance respectively reach 28Wh kg-1And 35kW kg-1The capacity retention rate is 95% after 50000 times of circulation.
Example 12
Graphite paper electrode loaded with YP-50 type activated carbon (YP-50 type activated carbon load)The amount is 1mg/cm2) Putting the mixture into a magnesium acrylate solution of 2mol/L as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and in-situ depositing lithium polyacrylate on the surface of the electrode by adopting a Cyclic Voltammetry (CV), wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 20. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the magnesium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of about 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated magnesium polyacrylate rear electrode, enlarging the electrochemical window of the coated magnesium polyacrylate rear electrode, expanding the voltage range to-1.4-1.2V, and keeping the specific capacitance. After the electrode is coated with the magnesium polyacrylate, the rate performance is better, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is used as electrolyte to assemble a water system super capacitor soft package device, the voltage of the device can reach 3V at most, and the energy density and the power density calculated according to the mass of the active substance respectively reach 30Wh kg-1And 36kW kg-1The capacity retention rate of 50000 times of circulation is 94%.
Example 13
Graphite paper electrodes loaded with YP-50 type activated carbon (the loading of YP-50 type activated carbon is 2 mg/cm)2) Putting the electrode into 2mol/L propylene sulfonic acid solution as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and adopting Cyclic Voltammetry (CV) to deposit the polypropylene sulfonic acid on the surface of the electrode in situ, wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 20. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the propene sulfonic acid monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated polypropylene sulfonic acid rear electrode, enlarging the electrochemical window of the coated polypropylene sulfonic acid rear electrode, expanding the voltage range to-1.2V, and keeping the specific capacitance. The multiplying power performance of the electrode coated with the polypropylene sulfonic acid is good, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is taken as electrolyteThe water system super capacitor soft package device is assembled, the voltage of the device can reach 2.8V at most, and the energy density and the power density calculated according to the mass of the active substance respectively reach 31Wh kg-1And 37kW kg-1The capacity retention rate after 50000 times of circulation is 93%.
Example 14
Graphite paper electrodes loaded with YP-50 type activated carbon (the loading of YP-50 type activated carbon is 2 mg/cm)2) Putting the electrode into 2mol/L methacrylic sulfonic acid solution as a working electrode, Ag/AgCl as a reference electrode, graphite as a counter electrode, and adopting Cyclic Voltammetry (CV) to deposit the polymethacrylic acid on the surface of the electrode in situ, wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 20. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the methacrylic sulfonic acid monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated polymethacrylic acid rear electrode, enlarging the electrochemical window of the coated polymethacrylic acid rear electrode, expanding the voltage range to-1.4-1.2V, and keeping the specific capacitance. After the electrode is coated with the polymethacrylic sulfonic acid, the multiplying power performance is better, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is used as electrolyte to assemble a water system super capacitor soft package device, the voltage of the device can reach 3V at most, and the energy density and the power density calculated according to the mass of the active substance respectively reach 28Wh kg-1And 30kW kg-1The capacity retention rate after 50000 times of circulation is 96 percent.
Example 15
Graphite paper electrodes loaded with YP-50 type activated carbon (the loading of YP-50 type activated carbon is 2 mg/cm)2) Putting the electrode into 2mol/L methacrylic acid solution as a working electrode, Ag/AgCl as a reference electrode and graphite as a counter electrode, and depositing polymethacrylic acid on the surface of the electrode in situ by adopting a Cyclic Voltammetry (CV), wherein the scanning range is set to be-1.6V, the scanning speed is 50mV/s, and the number of scanning cycles is 20. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the methacrylic acid monomer adhered on the electrode. Then the above-mentioned points are treatedAnd placing the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated polymethacrylic acid rear electrode, enlarging the electrochemical window of the coated polymethacrylic acid rear electrode, expanding the voltage range to-1.2V, and keeping the specific capacitance. The multiplying power performance of the electrode coated with the polymethacrylic acid is better, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is used as electrolyte to assemble a water system super capacitor soft package device, the voltage of the device can reach 2.5V at most, and the energy density and the power density calculated according to the mass of the active substance respectively reach 26Wh kg-1And 33kW kg-1The capacity retention rate is 90% after 50000 times of circulation.
Example 16
Graphite paper electrodes loaded with YP-50 type activated carbon (the loading of YP-50 type activated carbon is 2 mg/cm)2) Putting into 2mol/L magnesium acrylate solution as working electrode, Ag/AgCl as reference electrode, graphite as counter electrode, and depositing magnesium polyacrylate in situ on the surface of the electrode by potentiostatic method at-1.6V for 320 s. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the magnesium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of about 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated magnesium polyacrylate rear electrode, enlarging the electrochemical window of the coated magnesium polyacrylate rear electrode, expanding the voltage range to-1.0-1.2V, and keeping the specific capacitance. After the electrode is coated with the magnesium polyacrylate, the rate performance is better, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is used as electrolyte to assemble a water system super capacitor soft package device, the voltage of the device can reach 2.0V at most, and the energy density and the power density calculated according to the mass of active substances respectively reach 20Wh kg-1And 25kW kg-1The capacity retention rate after 50000 times of circulation is 91 percent.
Example 17
Graphite paper electrodes loaded with YP-50 type activated carbon (the loading of YP-50 type activated carbon is 2 mg/cm)2) Put in 2mol/LThe magnesium acrylate solution is used as a working electrode, Ag/AgCl is used as a reference electrode, graphite is used as a counter electrode, the magnesium polyacrylate is deposited in situ on the surface of the electrode by adopting a pulse voltage method, the pulse voltage is set to be-1.6V, the constant voltage time is 10s, the pulse voltage is set to be 1.6V, the constant voltage time is 10s, and the number of cycles is 30. And after the in-situ deposition is finished, washing the electrode by using deionized water to remove the magnesium acrylate monomer adhered on the electrode. And then, putting the treated electrode into 2mol/L lithium sulfate electrolyte with the pH value of about 6-8, taking Ag/AgCl as a reference electrode and graphite as a counter electrode, testing the electrochemical characteristics of the in-situ coated magnesium polyacrylate rear electrode, enlarging the electrochemical window of the coated magnesium polyacrylate rear electrode, expanding the voltage range to-1.2V, and keeping the specific capacitance. After the electrode is coated with the magnesium polyacrylate, the rate performance is better, and the specific capacity is increased due to the large voltage window. 2mol/L lithium sulfate is used as electrolyte to assemble a water system super capacitor soft package device, the voltage of the device can reach 2.4V at most, and the energy density and the power density calculated according to the mass of the active substance respectively reach 26Wh kg-1And 32kW kg-1The capacity retention rate of 50000 times of circulation is 94%.
Comparative example 1
In the comparative example 1, polyvinylidene fluoride PVDF is dissolved in N-methyl pyrrolidone to prepare a solution of 20mg/mL, then a carbon felt electrode loaded with YP-50 type activated carbon is placed in the carbon felt electrode to be fully soaked, then the carbon felt electrode is taken out and dried to obtain a PVDF-coated electrode, as shown in a in figure 19, a water system super capacitor soft package device is assembled by using 2mol/L lithium sulfate as electrolyte, the voltage of the device is 2.2V, and the energy density and the power density calculated according to the mass of the active material are respectively 1Wh kg-1And 0.01kW kg-1The reason for the low energy density and power density is mainly that PVDF is not able to conduct protons efficiently.
Comparative example 2
In the comparative example 2, PVA or PEG is dissolved in water to prepare a solution of 20mg/mL, then the carbon felt electrode loaded with YP-50 type active carbon is put in the solution to be fully soaked, and then the carbon felt electrode is taken out and dried to obtain the PVA/PEG coated electrode, as shown in b-c in figure 19, and 2mol/L lithium sulfate is used as electrolyte to assemble a water system super electrodeCapacitor soft package device, voltage of the device 2.4V, energy density calculated according to active material mass and power density of 15Wh kg respectively-1And 3kW kg-1The reasons for the low energy density and power density are mainly that PVA/PEG conducts protons slowly and the polarization of the device is strong.
Comparative example 3
In comparative example 3, polyacrylic acid is used as a binder, mixed with YP-50, and loaded on a carbon felt to form an electrode, as shown in fig. 20, 2mol/L lithium sulfate is used as an electrolyte to assemble a water-based flexible package device for a supercapacitor, and the voltage of the device is not yet 1.8V, which indicates that the voltage window of the supercapacitor cannot be widened by only using polyacrylic acid as the binder and not uniformly coating the polyacrylic acid on the surface of the electrode.
Comparative example 4
In this comparative example 4, magnesium polyacrylate was dissolved in water to prepare an electrolyte, Ag/AgCl was used as a reference electrode, graphite was used as a counter electrode, and Cyclic Voltammetry (CV) was used, in which a scanning range was set to-1.6V, a scanning speed was set to 50mV/s, and the number of scanning cycles was set to 20 cycles. After the completion, the electrode was rinsed with deionized water to remove the magnesium polyacrylate adhered to the electrode. 0.5mol/L sulfuric acid and 2mol/L lithium sulfate are respectively used as electrolyte to assemble the water system super capacitor soft package device. As in fig. 21, the voltage window of the device was not significantly changed compared to the untreated device, indicating that polyacrylic acid that had been polymerized did not enable in situ deposition of polyacrylic acid on the electrode surface to increase the voltage window. Only by taking olefine acid monomers and salts thereof as in-situ electrochemical deposition, the surface of the electrode can be uniformly coated with polyacrylic acid, and the voltage window can be improved. Therefore, the electrochemical in-situ deposition olefinic acid polymer on the surface of the electrode disclosed by the invention has uniqueness and advancement.
Claims (10)
1. A modified electrode, comprising: the current collector loaded with carbon-based active substances is used as an electrode, and the polymer film is coated on the surface of the electrode; the polymer film is formed by in-situ polymerization of small molecular organic monomers by an electrochemical method; the small molecule organic monomer at least comprises a carbon-carbon double bond and a group containing a heteroatom, wherein the group containing the heteroatom is at least one selected from carboxyl, hydroxyl, carbonyl, aldehyde group, sulfonic group, phosphoric group, nitro group, amino group, sulfydryl, amido, ester group, halogenated group and cyanamide group, and is preferably at least one selected from the group consisting of a small molecule organic monomer containing a carbon-carbon double bond, alkali metal salt of the small molecule organic monomer containing the carbon-carbon double bond and alkaline earth metal salt of the small molecule organic monomer containing the carbon-carbon double bond.
2. The modified electrode of claim 1, wherein the carbon-based active material is at least one of graphene, carbon nanotubes, YP-50 activated carbon, and nitrogen-doped carbon material; the current collector is selected from one of iron foil, iron mesh, titanium foil, titanium mesh, three-dimensional graphene, graphite paper and carbon felt; the loading amount of the carbon-based active substance in the electrode is 0-12 mg/cm2。
3. The modified electrode according to claim 1 or 2, wherein the thickness of the polymer thin film is 2nm to 35nm, preferably 15 nm.
4. The modified electrode according to any one of claims 1 to 3, wherein the small-molecule organic monomer is selected from at least one of acrylic acid and alkali metal salts and alkaline earth metal salts thereof, methacrylic acid and alkali metal salts and alkaline earth metal salts thereof, acrylic sulfonic acid and alkali metal salts and alkaline earth metal salts thereof, methacrylic sulfonic acid and alkali metal salts and alkaline earth metal salts thereof, acrylamide, methacrylamide, butenol, methyl methacrylate, amino propene, triethylene tetramine, acrolein, acrylonitrile, ethylene phosphoric acid, mercapto propene and nitroethylene, preferably lithium acrylate; the molecular weight of the small molecular organic matter monomer is less than 1000.
5. A method for preparing the modified electrode as claimed in any one of claims 1 to 4, wherein a current collector loaded with carbon-based active materials is used as a working electrode, an aqueous solution containing a small molecular organic monomer is used as an electrolyte, and a carbon-carbon double bond in the small molecular organic monomer containing the carbon-carbon double bond is excited by cyclic voltammetry, potentiostatic method or pulse voltage method to perform a polymerization reaction on the surface of the working electrode to form a polymer film, thereby obtaining the modified electrode.
6. The method according to claim 5, wherein the concentration of the aqueous solution containing the small organic monomer is 0.01mol/L to 10mol/L, preferably 2 mol/L.
7. The method according to claim 5 or 6, wherein the parameters of cyclic voltammetry comprise: the lower voltage limit of the scanning range is 0V to-3V, the upper voltage limit is 0V to 3V, the scanning speed is 1mV/s to 500mV/s, and the number of scanning circles is 1 circle to 200 circles; preferably, the parameters of cyclic voltammetry include: the scanning range is-1.6V, the scanning speed is 50mV/s, and the number of scanning turns is 20 turns.
8. The method according to claim 5 or 6, wherein the parameters of potentiostatic method comprise: the voltage is 0V to-3V, and the constant voltage time is 5 seconds to 36000 seconds; preferably, the parameters of the potentiostatic method are-1.6V and the constant pressure time is 360 seconds.
9. The method according to claim 5 or 6, wherein the parameters of the pulsed voltage method comprise: the pulse voltage is pressed down within the range of 0V to-3V, the constant voltage time is 1 second to 360 seconds, the pulse voltage is pressed down within the range of 0V to 3V, the constant voltage time is 1 second to 360 seconds, the number of cycles is 2 to 500 cycles, preferably, the pulse voltage is pressed down within the range of-1.6V, the constant voltage time is 10 seconds, the pulse voltage is pressed up within the range of 1.6V, the constant voltage time is 10 seconds, and the number of cycles is 30 cycles.
10. A high-voltage aqueous supercapacitor comprising the modified electrode according to any one of claims 1 to 4.
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