CN109841799B

CN109841799B - An activated carbon electrode and its preparation and application

Info

Publication number: CN109841799B
Application number: CN201711214158.9A
Authority: CN
Inventors: 阎景旺; 张华民; 席耀宁; 李先锋; 孙海涛; 霍玉龙
Original assignee: Dalian Institute of Chemical Physics of CAS; Fengfan Co Ltd
Current assignee: Dalian Institute of Chemical Physics of CAS; Fengfan Co Ltd
Priority date: 2017-11-28
Filing date: 2017-11-28
Publication date: 2021-07-06
Anticipated expiration: 2037-11-28
Also published as: CN109841799A

Abstract

The invention relates to an activated carbon electrode, which adopts carbon felt as a 3D current collector, and electrode materials are filled in pores of the carbon felt; the thickness of the carbon felt is 0.1-30mm, the porosity of the carbon felt is 50-99%, the diameter of fibers forming the carbon felt is 0.01-0.5mm, and the electrode material is composed of capacitance activated carbon, a conductive agent and a bonding agent. The composite material is used for internal parallel lead-carbon batteries and all-carbon cathode lead-carbon batteries and has the advantages of low cost, high energy density, strong high-power discharge capacity and the like.

Description

Activated carbon electrode and preparation and application thereof

Technical Field

The invention relates to the field of lead-carbon batteries, in particular to an active carbon electrode and application thereof in a lead-carbon battery.

Background

The lead-carbon battery is a novel energy storage device formed by combining a super capacitor and a lead-acid storage battery. The lead-acid storage battery is used as an energy source, the super capacitor is used as pulse power, and the performance of the battery is improved, so that the defect that the common valve-controlled lead-acid storage battery cannot be used under various complex use conditions is overcome. In the lead-carbon battery, the two energy storage modes of the super capacitor and the lead-acid battery are integrated in an internal combination mode, and a special external electronic control circuit is not needed, so that the size of the battery is controlled, the system is simplified, and the energy storage cost is reduced. In addition, the lead-carbon battery also has the following characteristics: meanwhile, the energy-saving capacitor has the advantages of high specific energy of the storage battery and high specific power of the capacitor; the service life of the pulse heavy current charge and discharge is long, and the life cycle of the lead-carbon battery is four times longer than that of the existing lead-acid battery; the low-temperature large-current discharge is better than that of a common battery; the sulfation phenomenon of the negative electrode can be greatly relieved; the lead-acid storage battery production line is easy to manufacture, and can be used for producing lead-carbon batteries by slightly modifying the existing lead-acid storage battery production line; the reliability is high; the manufacturing cost is low. Therefore, the appearance and development of the lead-carbon battery technology can lead the lead-acid storage battery to meet new development opportunities.

Lead-carbon batteries can be roughly divided into three types according to different technical schemes: the lead-Carbon battery (Pb-C battery, Carbon-enhanced VRLA) adopts a technical scheme that a small amount of Carbon materials are doped into a lead negative electrode (internal mixing type), the super battery (ultra battery) adopts a technical scheme that a battery electrode and a super capacitor electrode are mutually connected in parallel (internal parallel type) as a negative electrode, and the lead-Carbon battery (all-Carbon negative electrode type lead-Carbon battery) completely adopts a super capacitor electrode as a negative electrode.

The concept of an internal parallel lead-carbon battery (also known as a super battery) was first proposed in 2003 by l.t.lam et al, the federal scientific and industrial research organization in australia. Subsequently, the national laboratory of sandia, the international association of advanced lead-acid batteries, the federal scientific and industrial research organization in australia, manufactured by eastern state of america, Ecoult in australia and the japanese gule river battery in japan have developed research, development and testing of super batteries. Granted the patent obtained in 2004 by the japan gule river battery company, research and commercial development work of super batteries began. The cathode of the gulhe super battery is of a sandwich structure in which the surfaces of the two sides of a spongy lead negative plate are covered with active carbon layers. The vehicle-mounted performance test shows that the charging recovery capacity of the super battery is improved by 30% compared with that of the traditional lead-acid storage battery due to the existence of the capacitor layer. The service life of a super battery under an undercharge condition (80% state of charge) is twice that of a conventional lead-acid battery.

The all-carbon cathode lead-carbon battery was originally developed by Axion in the United states, and is a mixed type energy storage device with active carbon as a cathode and lead dioxide as an anode, and the company refers to the battery as a lead-carbon battery. Axion's lead-carbon battery is actually a hybrid supercapacitor. Unlike lead-acid batteries, the reaction that takes place on the negative electrode of the battery is as follows,

since the following reaction no longer occurs on the negative electrode of the lead-carbon battery,

so that the sulfation of the negative electrode can be fundamentally avoided, thereby prolonging the service life of the negative electrode.

Due to the fact that the lead-carbon battery works in an acid environment, if the technical scheme that the active carbon electrode plate is introduced into the negative electrode is adopted in the internal parallel lead-carbon battery, the selection of the active carbon electrode current collector becomes very difficult. The same problem exists for the activated carbon negative electrode of an all-carbon negative electrode lead-carbon battery. Due to the corrosion problem, common metal materials cannot be directly used as a current collector of an activated carbon electrode used in an acidic environment, and noble metal materials, although the corrosion resistance can meet the requirement, are too high in price and also have no practical value. In addition, since the specific capacity of the activated carbon is much lower than that of the lead paste, the surface density of the active material of the activated carbon electrode is more than tens of milligrams per square centimeter in order to match the capacity of the battery electrode. The surface density of the activated carbon electrode prepared by the traditional coating method is generally about 10 mg per square centimeter, and the thickness of the activated carbon layer is further increased, so that the activated carbon layer is cracked or peeled, and the ohmic resistance of the electrode is increased. In order to solve the problems, the Axon all-carbon cathode lead-carbon battery cathode adopts a copper sheet with an anti-corrosion protective layer as a current collector. And coating active carbon layers on two sides of the current collector to form a sandwich structure. By adopting the structure, the usage amount of lead can be reduced, the weight of the battery can be reduced, and the charge acceptance and the cycle life of the battery can be improved. The technical scheme has the defects that a large amount of copper is consumed, so that the cost of the lead-carbon battery is greatly increased. In addition, the thickness of the activated carbon electrode, i.e., the areal density of the active material, is limited. Increasing the surface density of the active material of the activated carbon electrode also increases the electron transfer resistance of the electrode, thereby increasing the ohmic drop of the cathode of the lead-carbon battery and influencing the exertion of the capacitive performance of the battery.

Disclosure of Invention

The invention aims to solve the problems of the surface density of active substances of the traditional active carbon electrode, overlarge ohmic impedance of the high-surface-density active carbon electrode and overhigh cost caused by using a metal material as a current collector, and provides a low-cost active carbon electrode with ultrahigh surface density of the active substances, which is suitable for an internal parallel lead-carbon battery and an all-carbon negative lead-carbon battery, a preparation method thereof and application methods of the active carbon electrode in the internal parallel lead-carbon battery and the all-carbon negative lead-carbon battery.

The carbon felt is used as a 3D current collector, and electrode materials are filled in pores of the carbon felt. The thickness of the carbon felt is 0.1-30mm, and the preferable thickness is 1-15 mm. The porosity of the carbon felt is 50 to 99%, preferably 80 to 99%. The diameter of the fibers constituting the carbon felt is 0.01 to 0.5mm, preferably 0.05 to 0.2 mm. The surface density of the active substance is 0.1-5 g/cm²Preferably 0.2 to 2.5g/cm²。

The electrode material is composed of capacitance active carbon, conductive agent and adhesive. Capacitance activated carbon: conductive carbon black: (70-95) adhesive: (5-20): (1-10).

The conductive agent is one, two or three of conductive carbon black, acetylene black, superfine graphite powder and titanium black. The adhesive includes an aqueous adhesive and an organic adhesive.

The water-based adhesive is a mixed dispersion of Styrene Butadiene Rubber (SBR), carboxymethyl cellulose (CMC) and water. The SBR and CMC content in the mixture is 1-60 wt%. SBR: DMC (10-95): (95-5).

The organic binder is a solution of polyvinylidene fluoride (PVDF) and CMC dissolved in N-methylpyrrolidone (NMP) or N, N-Dimethylformamide (DMF). Wherein, the PVDF is DMC (5-95): (95-5), NMP: DMF ═ (5-95): (95-5), (PVDF + DMC): (NMP: DMF) ═ 3-70: (30-97).

The negative electrode of the internal parallel lead-carbon battery is formed by connecting a negative plate of the lead-acid battery and the active carbon electrode plate with ultrahigh active substance surface density in parallel, the positive electrode adopts a positive plate of the lead-acid battery, and the positive plate and the negative plate are separated by a PE film or a glass fiber (AGM) separator. The sheet ratio of the negative plate of the lead-acid battery to the active carbon electrode plate is 1: 10-10: 1, and the preferable ratio is 1: 4-4: 1. The internal parallel type lead-carbon battery adopts dilute sulfuric acid as electrolyte, and the concentration of the dilute sulfuric acid is 10-50 wt%, and the preferable concentration is 20-40 wt%. The liquid level of the dilute sulphuric acid in the battery is 0.1-30mm higher than the pole plate, so as to ensure that the battery is in a liquid-rich working condition.

The all-carbon negative electrode lead-carbon battery is completely composed of the active carbon electrode plate with the ultrahigh active material surface density, a negative plate of the lead-acid battery is not used, a positive plate of the lead-acid battery is used as a positive electrode, and the positive plate and the negative plate are alternately arranged and are separated by a PE film or an AGM separator. The all-carbon cathode lead-carbon battery adopts dilute sulfuric acid as electrolyte, and the concentration of the dilute sulfuric acid is 10-50 wt%, and the preferable concentration is 20-40 wt%. The liquid level of the dilute sulphuric acid in the battery is 0.1-30mm higher than the pole plate, so as to ensure that the battery is in a liquid-rich working condition.

1) Pretreatment of the carbon felt: placing the carbon felt in mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid, heating to 50-90 ℃, performing ultrasonic treatment for 0.1-60min, filtering and separating, washing with deionized water to be neutral, and drying to remove water;

2) preparation of the adhesive: and weighing SBR and CMC in proportion for the water-based adhesive, adding the SBR into deionized water, stirring uniformly, adding the CMC, heating and stirring for 4-10 hours until the CMC is completely dissolved to form the colloidal adhesive. For the organic adhesive, PVDF, CMC, NMP and DMF are weighed in proportion. Uniformly mixing NMP and DMF, adding PVDF and CMC, and fully stirring until the PVDF and CMC are completely dissolved to form a colloidal adhesive.

2) Preparing electrode slurry: weighing the capacitive activated carbon, the conductive agent and the water system or organic system adhesive according to the mass ratio requirement, mixing the capacitive activated carbon, the conductive agent and the water system or organic system adhesive, and uniformly stirring to obtain viscous electrode slurry.

3) Introduction of electrode slurry: firstly, placing the carbon felt obtained in the step 1) on a vacuum vibration table paved with filter paper or filter membrane, then uniformly pouring a certain amount of electrode slurry on the carbon felt, starting the vibration table to discharge the gas in the carbon felt, and enabling the electrode slurry to permeate into the carbon felt as much as possible. And starting a vacuum pumping system, pumping the residual electrode slurry amount into the carbon felt, and removing most of moisture in the electrode slurry amount in the carbon felt.

4) Drying the electrode plate: and drying the obtained electrode slice together with the filter paper or the filter membrane to remove water in the electrode slice. The drying temperature is 40-150 deg.C, preferably 60-120 deg.C.

5) Pressing the electrode plate: and removing the filter paper or the filter membrane, and pressing the electrode plate under certain pressure to improve the density of the electrode plate. The pressure range for pressing the electrode plate is 0.1-100atm, and preferably 0.2-10 atm.

The beneficial effects brought by the technical scheme of the invention

The carbon felt is formed by interweaving carbon fibers with the diameters ranging from nanometer to micron, the high-conductivity carbon fibers form a 3D electronic conduction network, and the carbon fibers are used as a current collector, so that the surface density of active substances of the active carbon electrode can be obviously improved on the basis of not increasing the ohmic impedance of the electrode, and the active carbon electrode plate capable of being matched with the electrode capacity of a lead-acid battery is obtained.

And secondly, the carbon felt is used as a 3D current collector, the thickness of the activated carbon electrode, namely the load of active substances in unit area, can be flexibly adjusted according to the requirements of the internal parallel type lead-carbon battery and the all-carbon negative electrode lead-carbon battery on the capacity of the activated carbon electrode, so that the working conditions of the anode and the cathode of the two lead-carbon batteries are optimized.

In addition, the carbon felt is small in unit area weight, and the carbon felt is used as a current collector, so that the capacity of the internal parallel type lead-carbon battery and the capacity of the full-carbon negative electrode lead-carbon battery can be remarkably improved on the premise of keeping the weight of the battery unchanged, or the weight of the internal parallel type lead-carbon battery and the weight of the full-carbon negative electrode lead-carbon battery can be remarkably reduced on the premise of keeping the capacity of the battery unchanged.

Compared with a 2D current collector adopting metal copper as an active carbon electrode in the Axion, the invention has the advantages of low cost, high energy density and strong high-power discharge capacity.

In addition, the ultrahigh-surface-density activated carbon electrode obtained by using the carbon felt as the 3D current collector has the advantages of simple preparation process, easiness in scale amplification and realization of industrial production.

Drawings

FIG. 1 is a cyclic voltammogram of an ultra-high areal density activated carbon electrode prepared in example 1 in 30% dilute sulfuric acid;

FIG. 2 is a constant current charge and discharge curve of the ultra-high surface density activated carbon electrode prepared in example 1 in 30% dilute sulfuric acid;

fig. 3 cycle life test results of the internal parallel type lead-carbon battery prepared in example 3;

fig. 4 shows cycle life test results of lead-acid batteries prepared in comparative examples.

Detailed Description

Example 1

500ml of 95% concentrated sulfuric acid and 500ml of 36.5% concentrated nitric acid are added successively to a 2L beaker and stirred until mixed uniformly. Cutting a carbon felt with a thickness of 5mm into a rectangle with a length of 10cm and a width of 1cm, adding into the mixed acid, heating to 60 ℃ while stirring, and preserving heat for 10 min. And taking out the carbon felt, repeatedly washing the carbon felt with deionized water until the pH value is 6-7, and drying the carbon felt in an electrothermal blowing drying oven at 95 ℃ for 2 hours. 30g of SBR emulsion is weighed, added into 1200ml of deionized water and stirred uniformly. And then weighing 30g of CMC, adding the CMC into the prepared SBR dispersion liquid, heating to 40 ℃, and stirring for 6 hours until the CMC is completely dissolved to obtain the SBR-CMC adhesive. 42.5g of active carbon and 5g of acetylene black are weighed, added into 200ml of deionized water in sequence, stirred uniformly, then 50g of SBR-CMC binder is added, and the electrode slurry is obtained after full stirring. And (3) closely arranging 10 cut carbon felts, placing the carbon felts on a vacuum vibration table paved with filter paper or filter membrane, then uniformly pouring 60g of electrode slurry at one end of the carbon felt to enable the width of the carbon felt covered by the electrode slurry to be 1cm, starting the vibration table to vibrate for 3min to enable gas in the carbon felt to be discharged, and enabling the amount of the electrode slurry to permeate into the carbon felt as much as possible. And starting a vacuum pump, and pumping for 5min to pump the residual electrode slurry into the carbon felt and remove most of water in the electrode slurry in the carbon felt. The obtained wet pole piece and the filter paper are placed in an electric heating blast for dryingDrying at 80 deg.C for 120min in a box. And finally, removing the filter paper, applying pressure of 2atm to the electrode plate by using an oil press, and keeping the pressure for 5min so as to improve the density of the electrode plate. The area of the pressed carbon electrode is 1.23cm²The thickness is 4.3mm, and the activated carbon supporting amount is 0.35g/cm²The thickness of the active material of the electrode active carbon electrode prepared on the metal foil by the coating method is generally 20-30 μm, and the supporting amount is 8-15mg/cm². The results of cyclic voltammetry test and constant current charge and discharge test of the prepared ultra-high surface density activated carbon electrode in 30 wt% dilute sulfuric acid by using three electrodes are respectively shown in fig. 1 and fig. 2. As can be seen from FIG. 1, the cyclic voltammetry curves of the activated carbon electrode prepared in this example still maintained a shape similar to a rectangle at a sweep rate of 100mV/s, indicating that the capacitance performance of the activated carbon as the active material in the electrode performed well. As can be seen from fig. 2, when the electrode is charged and discharged with a constant current at a high current density of 1A/g, the potential of the activated carbon electrode prepared in this embodiment changes linearly with the charging and discharging time, and the IR drop at the transition point in the charging and discharging process is very low and can be almost ignored, which indicates that the electrode not only has very high rate performance, but also has very low resistance, and can meet the requirements of internal parallel and all-carbon cathode lead-carbon batteries on the surface capacity, internal resistance and rate performance of the activated carbon electrode.

Example 2

500ml of 95% concentrated sulfuric acid and 500ml of 36.5% concentrated nitric acid are added successively to a 2L beaker and stirred until mixed uniformly. Cutting a carbon felt with the thickness of 1cm into a rectangle with the length of 10cm and the width of 1cm, putting the rectangle into mixed acid, heating to 60 ℃ while stirring, and preserving heat for 10 min. And taking out the carbon felt, repeatedly washing the carbon felt with deionized water until the pH value is 6-7, and drying the carbon felt in an electrothermal blowing drying oven at 95 ℃ for 2 hours. 30g of SBR emulsion is weighed, added into 1200ml of deionized water and stirred uniformly. And then weighing 30g of CMC, adding the CMC into the prepared SBR dispersion liquid, heating to 40 ℃, and stirring for 6 hours until the CMC is completely dissolved to obtain the SBR-CMC adhesive. 42.5g of active carbon and 5g of acetylene black are weighed, added into 200ml of deionized water in sequence, stirred uniformly, then 50g of SBR-CMC binder is added, and the electrode slurry is obtained after full stirring. Closely arranging the cut carbon felts, and placing the carbon felts in a vacuum oscillator paved with filter paper or filter membraneAnd moving the table, uniformly pouring 120g of electrode slurry at one end of the carbon felt to enable the width of the carbon felt covered by the electrode slurry to be 1cm, starting the vibration table to vibrate for 3min to discharge gas in the carbon felt, and enabling the electrode slurry to permeate into the carbon felt as much as possible. And starting a vacuum pump, and pumping for 5min to pump the residual electrode slurry into the carbon felt and remove most of water in the electrode slurry in the carbon felt. And (3) placing the obtained wet pole piece and filter paper in an electric heating air blast drying oven, and drying at 80 ℃ for 120 min. And finally, removing the filter paper, applying pressure of 2atm to the electrode plate by using an oil press, and keeping the pressure for 5min so as to improve the density of the electrode plate. The area of the pressed carbon electrode is 1.32cm²The thickness is 8.6mm, and the loading of the active carbon is 0.76g/cm². The prepared ultrahigh surface density activated carbon electrode is subjected to cyclic volt-ampere test and constant current charge and discharge test in 30 wt% dilute sulfuric acid by adopting three electrodes. As a result, under the sweep rate of 100mV/s, the cyclic voltammetry curve of the activated carbon electrode prepared in the embodiment still maintains the shape similar to a rectangle, which indicates that the capacitance performance of the activated carbon serving as an active substance in the electrode plays a good role. The electrode prepared by the embodiment has the advantages that the potential of the electrode linearly changes along with the charging and discharging time, and the IR drop at the conversion part in the charging and discharging process is 0.05V under the constant current charging and discharging at the high current density of 1A/g, so that the electrode not only has high rate performance, but also has low resistance, and can meet the requirements of internal parallel type and all-carbon cathode lead-carbon batteries on the surface capacity, the internal resistance and the rate performance of the active carbon electrode.

Example 3

500ml of 95% concentrated sulfuric acid and 500ml of 36.5% concentrated nitric acid are added successively to a 2L beaker and stirred until mixed uniformly. Cutting a carbon felt with the thickness of 5mm into a rectangle with the length of 8cm and the width of 5cm, putting the carbon felt into mixed acid, heating to 60 ℃ while stirring, and preserving heat for 10 min. And taking out the carbon felt, repeatedly washing the carbon felt with deionized water until the pH value is 6-7, and drying the carbon felt in an electrothermal blowing drying oven at 95 ℃ for 2 hours. 10g of PVDF was weighed out and added to 1200ml of a mixture of NMP and DMF (95: 5 by volume) and stirred until completely dissolved. Then 10g of CMC is weighed and added into the NMP solution of PVDF, and the mixture is stirred until the CMC is completely dissolved, so that the PVDF-CMC adhesive is obtained. 42.5g of active carbon and 5g of acetylene black are weighed, 150g of PVDF-CMC is added for bondingAnd fully stirring the mixture to obtain the electrode slurry. And (3) placing the cut carbon felt on a vacuum vibration table paved with filter paper or filter membrane, then uniformly pouring 100g of electrode slurry onto the carbon felt to cover the whole carbon felt surface, starting the vibration table to vibrate for 3min to discharge gas in the carbon felt, and enabling the electrode slurry to permeate into the carbon felt as much as possible. And starting a vacuum pump, and pumping for 5min to pump the residual electrode slurry into the carbon felt and remove most of water in the electrode slurry in the carbon felt. And (3) placing the obtained wet pole piece and filter paper in an electric heating air blast drying oven, and drying at 80 ℃ for 120 min. And finally, removing the filter paper, applying pressure of 2atm to the electrode plate by using an oil press, and keeping the pressure for 5min so as to improve the density of the electrode plate. The area of the pressed carbon electrode is 43cm²The thickness is 4.2mm, and the activated carbon supporting amount is 0.38g/cm². The activated carbon electrode and the positive and negative electrodes of the lead-acid battery prepared in the embodiment are adopted to construct a 4.4Ah three-positive-two-battery negative-two-activated-carbon negative internal parallel type lead-carbon battery according to the stacking sequence of the activated carbon negative electrode, the positive electrode of the lead-acid battery, the negative electrode of the lead-acid battery, the positive electrode of the activated carbon negative electrode of the lead-acid battery and the activated carbon. The battery uses a PE separator and is operated under a rich solution working condition. The cycle life test of the prepared internal parallel lead-carbon battery is carried out according to the method specified by SBAS0101-2014 'lead-acid battery for start and stop vehicles' standard, and the result is shown in figure 3. It can be seen that the cycle life of the lead-carbon battery reached 54000 times, which is 3 times longer than that of the lead-acid battery prepared in the comparative example.

Example 4

500ml of 95% concentrated sulfuric acid and 500ml of 36.5% concentrated nitric acid are added successively to a 2L beaker and stirred until mixed uniformly. Cutting a carbon felt with the thickness of 1cm into a rectangle with the length of 8cm and the width of 5cm, putting the rectangle into mixed acid, heating to 60 ℃ while stirring, and preserving heat for 10 min. And taking out the carbon felt, repeatedly washing the carbon felt with deionized water until the pH value is 6-7, and drying the carbon felt in an electrothermal blowing drying oven at 95 ℃ for 2 hours. 30g of SBR emulsion is weighed, added into 1200ml of deionized water and stirred uniformly. And then weighing 30g of CMC, adding the CMC into the prepared SBR dispersion liquid, heating to 40 ℃, and stirring for 6 hours until the CMC is completely dissolved to obtain the SBR-CMC adhesive. 42.5g of activated carbon and 5g of acetylene black are weighed,and sequentially adding the mixture into 125ml of deionized water, uniformly stirring, adding 50g of SBR-CMC binder, and fully stirring to obtain the electrode slurry. And placing the cut carbon felt on a vacuum vibration table paved with filter paper or filter membrane, then uniformly pouring 300g of electrode slurry onto the carbon felt to cover the whole carbon felt surface, starting the vibration table to vibrate for 3min to discharge gas in the carbon felt, and enabling the electrode slurry to permeate into the carbon felt as much as possible. And starting a vacuum pump, and pumping for 5min to pump the residual electrode slurry into the carbon felt and remove most of water in the electrode slurry in the carbon felt. And (3) placing the obtained wet pole piece and filter paper in an electric heating air blast drying oven, and drying at 80 ℃ for 120 min. And finally, removing the filter paper, applying pressure of 2atm to the electrode plate by using an oil press, and keeping the pressure for 5min so as to improve the density of the electrode plate. The area of the pressed carbon electrode is 43cm²The thickness is 8.3mm, and the loading of the active carbon is 0.75g/cm². The activated carbon electrode plates and the lead-acid battery positive plates prepared by the embodiment are alternately stacked to construct a 4.4Ah 'three-positive-four-negative' all-carbon negative-electrode lead-carbon battery. The battery uses a PE separator and is operated under a rich solution working condition. The service life test is carried out according to the standard, and the charge-discharge cycle life reaches 72000 times, which is far higher than the cycle life of the traditional lead-acid battery (18000 times) and is also higher than the cycle life of the internal parallel lead-carbon battery prepared in the example 3 (64000 times).

Comparative examples

A lead-acid battery with the rated capacity of 4.4Ah is assembled by adopting a three-positive-two-negative structure and using a negative plate of the lead-acid battery, a positive plate of the lead-acid battery and a PE diaphragm. 80g of the mixture is mixed with the specific gravity of 1.18g/cm³The diluted sulfuric acid is injected into the assembled lead-acid battery and is formed at 40 ℃. Pouring out sulfuric acid in the formed battery, and injecting 40g of sulfuric acid with the specific gravity of 1.36g/cm³And obtaining the rich-solution lead-acid battery by using the dilute sulfuric acid. The prepared rich-solution lead-acid battery was subjected to cycle life test by the method specified in SBA S0101-2014 "start-stop vehicle lead-acid battery" standard, and the results are shown in fig. 4. The result shows that when the discharge termination voltage is lower than 1.2V, the charge-discharge cycle life test of the battery is terminated. The charge-discharge cycle life of the rich-solution lead-acid battery prepared by the embodiment is 5 major cycles, namely 18000 times.

Claims

1. An activated carbon electrode, characterized in that: adopting a carbon felt as a 3D current collector, and filling electrode materials in pores of the carbon felt; the thickness of the carbon felt is 0.1-30 mm; the porosity of the carbon felt is 50-99%; the diameter of the fiber forming the carbon felt is 0.01-0.5 mm;

the electrode material is composed of capacitance active carbon, a conductive agent and an adhesive; capacitance activated carbon: conductive agent: the mass ratio of the adhesive is (70-95): (5-20): (1-10), the surface density of the capacitance activated carbon on the electrode is 0.1-5 g/cm²；

The preparation process comprises the following steps:

1) pretreatment of the carbon felt: placing the carbon felt in mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid, and heating to 50-90 DEG^oC, performing ultrasonic treatment for 0.1-60min, filtering and separating, washing to be neutral by using deionized water, and drying to remove water; the concentrations of concentrated sulfuric acid and concentrated nitric acid which form the mixed acid are 95-98 wt% and 65-68 wt% respectively, and the mass ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1: 9-9: 1;

2) preparation of the adhesive: weighing SBR and CMC in proportion for the water-based adhesive, adding the SBR into deionized water, stirring uniformly, adding the CMC, heating and stirring for 4-10h until the CMC is completely dissolved to form a colloidal adhesive;

or, for the organic adhesive, firstly weighing PVDF, CMC, NMP and DMF in proportion, uniformly mixing NMP and DMF, then adding PVDF and CMC, fully stirring until the PVDF and CMC are completely dissolved to form a colloidal adhesive;

3) preparing electrode slurry: weighing capacitive activated carbon, a conductive agent and a water system or organic system adhesive according to the mass ratio requirement, mixing the capacitive activated carbon, the conductive agent and the water system or organic system adhesive, and uniformly stirring to obtain viscous electrode slurry;

4) introduction of electrode slurry: firstly, placing the carbon felt obtained in the step 1) on a vacuum vibration table paved with filter paper or filter membrane, then uniformly pouring electrode slurry on the carbon felt, starting the vibration table to discharge gas in the carbon felt, enabling the electrode slurry to permeate into the carbon felt, vibrating for 10 s-10 min, then starting a vacuum air pumping system, enabling the air pumping time to be 10 s-30 min, and pumping all the electrode slurry into the carbon felt to obtain an electrode;

5) and (3) drying the electrode: drying the obtained electrode together with filter paper or filter membrane to remove water; drying at 40-150 deg.C^oC；

6) And (3) electrode pressing: removing the filter paper or filter membrane, and pressing the electrode into tablets under a certain pressure, wherein the pressure range for pressing is 0.1-100 atm.

2. The activated carbon electrode of claim 1, wherein:

the thickness of the carbon felt is 1-15 mm; the porosity of the carbon felt is 80-99%; the diameter of the fiber forming the carbon felt is 0.05-0.2 mm;

the surface density of the capacitance active carbon on the electrode is 0.2-2.5 g/cm²。

3. The activated carbon electrode of claim 1, wherein:

wherein the conductive agent is one or more of conductive carbon black, acetylene black, superfine graphite powder and titanium black;

the adhesive is water-based adhesive or organic adhesive;

the water system adhesive is a mixed dispersion formed by Styrene Butadiene Rubber (SBR), carboxymethyl cellulose (CMC) and water; the mass content of SBR and CMC in the mixture is 1-60 wt%, wherein SBR: the mass ratio of CMC is (10-95): (95-5);

the organic adhesive is a solution formed by dissolving polyvinylidene fluoride (PVDF) and CMC in N-methyl pyrrolidone (NMP) and N, N-dimethyl amide (DMF); wherein the mass ratio of PVDF to CMC is (5-95): (95-5), NMP: the mass ratio of DMF is (5-95): (95-5), (PVDF + CMC): the mass ratio of (NMP + DMF) is (3-70): (30-97).

4. A method for producing an activated carbon electrode according to claim 1 or 2, characterized in that:

1) pretreatment of the carbon felt: placing the carbon felt in mixed acid consisting of concentrated sulfuric acid and concentrated nitric acid, and heating to 50-90 DEG^oC, ultrasonic 0.1-60min, filtering, separating, washing with deionized water to neutrality, and drying to remove water; the concentrations of concentrated sulfuric acid and concentrated nitric acid which form the mixed acid are 95-98 wt% and 65-68 wt% respectively, and the mass ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1: 9-9: 1;

5. Use of an activated carbon electrode according to claim 1 or 2, characterized in that: the active carbon electrode is used as a negative electrode and applied to an internal parallel type lead-carbon battery or an all-carbon negative electrode lead-carbon battery.

6. Use according to claim 5, characterized in that: the negative electrode of the internal parallel lead-carbon battery is formed by connecting a negative plate of the lead-acid battery and an active carbon electrode in parallel, the positive electrode adopts a positive plate of the lead-acid battery, and the positive electrode and the negative electrode are separated by a PE film or glass fiber (AGM) separator; the sheet ratio of the negative plate of the lead-acid battery to the active carbon electrode is 1: 10-10: 1; the internal parallel type lead-carbon battery adopts dilute sulfuric acid as electrolyte, and the concentration of the dilute sulfuric acid is 10-50 wt%; the liquid level of the dilute sulphuric acid in the battery is 0.1-30mm higher than the pole plate, so as to ensure that the battery is in a liquid-rich working condition.

7. Use according to claim 5, characterized in that: the negative electrode of the all-carbon negative lead-carbon battery is an active carbon electrode, the positive electrode of the all-carbon negative lead-carbon battery is a positive plate of the lead-acid battery, and the positive electrode and the negative electrode are separated by a PE film or an AGM separator; the all-carbon cathode lead-carbon battery adopts dilute sulfuric acid as electrolyte, and the concentration of the dilute sulfuric acid is 10-50 wt%; the liquid level of the dilute sulphuric acid in the battery is 0.1-30mm higher than the pole plate, so as to ensure that the battery is in a liquid-rich working condition.