CN115939475A - Simple low-cost method for reducing concentration polarization of flow battery and application - Google Patents

Simple low-cost method for reducing concentration polarization of flow battery and application Download PDF

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CN115939475A
CN115939475A CN202211564945.7A CN202211564945A CN115939475A CN 115939475 A CN115939475 A CN 115939475A CN 202211564945 A CN202211564945 A CN 202211564945A CN 115939475 A CN115939475 A CN 115939475A
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electrode
flow battery
concentration polarization
electrolyte
electrodes
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李全龙
鲁志颖
石振家
张雅薇
宋清爽
吴琼
冯伟
张宇哲
胡伊宁
汪平
李超
王世宇
张鸣镝
仇馨茹
徐广民
吕晨光
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Dalian Rongke Power Co Ltd
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Dalian Rongke Power Co Ltd
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Abstract

The invention belongs to the field of flow batteries and discloses a simple method for reducing concentration polarization of a flow battery and application thereof, wherein electrodes with different n block body densities rho are sequentially arranged in an electrolyte reaction area of a positive electrode and a negative electrode along the flowing direction of the electrolyte, the sum of the combined areas of the n electrodes is consistent with the area of the electrolyte reaction area, n is more than or equal to 2 and less than or equal to 10,0.07g/cm 3 ≤ρ≤0.15g/cm 3 . The method for reducing the concentration polarization of the flow battery is simple to operate, low in cost, obvious in effect and suitable for large-scale popularization; can reduce the shape constraint of the galvanic pile, improve the effective utilization rate of the ion exchange membrane and the bipolar plate material to a certain extent, and does not need to bring additional pump consumption.

Description

Simple low-cost method for reducing concentration polarization of flow battery and application
Technical Field
The invention relates to the field of flow batteries, in particular to a simple method for reducing concentration polarization of a flow battery and application thereof.
Background
The flow battery is a novel energy storage technology, and has been developed to a certain extent in the field of energy storage in recent years. In the flow battery, electrolyte is an energy unit and a medium for storing electric energy, and a galvanic pile is a power unit and a place where active substances in the electrolyte participate in conversion of the electric energy and the chemical energy. Energy loss during the conversion of electrical energy and chemical energy in a flow battery is inevitable. The energy loss of the energy storage system is mainly the energy loss of the galvanic pile in the charging and discharging process and the energy loss caused by the operation of auxiliary equipment (a circulating pump, refrigeration equipment, lighting equipment and the like), and in the charging and discharging process of the galvanic pile, besides side reactions, various polarization losses are the most main sources of the energy loss. For the flow battery, polarization loss is mainly divided into ohmic polarization, electrochemical polarization and concentration polarization, wherein the ohmic polarization mainly consists of various conductive materials and contact resistance, the electrochemical polarization is mainly determined by the electron transfer rate of the electrochemical reaction, and the concentration polarization is mainly determined by whether reactants are sufficient or not and the mass transfer rate. For concentration polarization, in the practical application process, the method for reducing the concentration polarization mainly shortens the flowing distance of the electrolyte in the galvanic pile (namely, a short-flow structure) and improves the flow rate of a pump, so that the active substances after reaction can be quickly transferred. However, the short-flow structure can restrict the shape of the stack to a certain extent (the length and the width are larger), and under the condition of the same area dosage of the ion exchange membrane and the bipolar plate, the utilization rate of the ion exchange membrane and the bipolar plate with the short-flow structure is relatively low; increasing the flow rate of the pump increases the energy consumption of the pump, which causes additional energy loss and limits the pump in practical use. Therefore, the development of a new method for reducing concentration polarization is one of the main directions in the field.
Disclosure of Invention
In order to make up for the defects of the prior art, the invention provides a simple low-cost method for reducing concentration polarization of a flow battery, so that the concentration polarization in the running process of the flow battery is reduced, and the voltage efficiency and the energy efficiency of the battery are improved.
In the prior art, a whole electrode with consistent bulk density is placed in an electrolyte reaction area, when a galvanic pile is assembled, the electrode is placed on the electrolyte reaction area, the position of the electrode is limited by a part framed by the middle of an electrode frame, and the size of the middle of the electrode frame is consistent with that of the electrolyte reaction area. In the invention, the electrodes formed by splicing a plurality of electrodes with different bulk densities have the overall outer dimension consistent with the dimension of an electrolyte reaction area, the other electrodes are kept unchanged, the electrodes are limited by an electrode frame, and the electrodes can be fixed by external pressure and the limiting action of the electrode frame when a galvanic pile is assembled.
In order to achieve the purpose, the technical scheme of the invention is as follows:
in the simple low-cost method for reducing concentration polarization of the flow battery, electrodes with different n block body densities rho are sequentially arranged in the electrolyte reaction regions of a positive electrode and a negative electrode along the electrolyte flowing direction, and the sum of the combined areas of the n electrodes is consistent with the area of the electrolyte reaction region.
Further, the value range of n is: n is more than or equal to 2 and less than or equal to 10. It should be noted that under similar conditions, increasing the value of n will increase the efficiency of the cell to some extent, which is more helpful to reduce concentration polarization due to more careful distribution of the electrode to the electrolyte, but the value of n is not suggested to be a relatively larger value, because increasing the value of n means increasing the number of electrodes, which will increase the difficulty of assembling the stack to some extent and reduce the working efficiency, and the appropriate value of n can be selected according to the factors such as the size of the stack, the density and the area of the electrode body in practical work.
Further, the bulk densities ρ of the electrodes having different n bulk densities ρ arranged in this order along the electrolyte flow direction are decreased in this order.
Furthermore, the bulk density of each electrode is the density of the assembled and compressed galvanic pile and meets the requirement of 0.07g/cm 3 ≤ρ≤0.15g/cm 3 。
Further, the electrode is a porous carbon material electrode.
Further, the electrodes are carbon felt electrodes, carbon fiber cloth electrodes, carbon paper electrodes, foam carbon electrodes, 3D printing carbon electrodes and the like.
Another object of the present invention is to protect the electrode prepared by the above method from being applied to the field of redox flow batteries.
In order to make the solution easier to understand, it is further explained here:
in the conventional flow battery, in order to ensure that the electrolyte can be uniformly distributed in each unit of the galvanic pile, the electrode can be completely contacted with the electrolyte to participate in reaction, and no dead zone exists, the electrolyte is fed in and discharged out in a downward mode. Thus at the lowermost part of the electrode (close to the electrolyte inlet)) The active material participating in the reaction is most sufficient, in order to ensure the maximum degree of reaction, the electrode should provide more active sites and a larger contact area with the electrolyte, at the moment, the electrode with larger bulk density meets the requirement, the concentration of the active material participating in the reaction is reduced along with the reaction of the active material and the upward transmission of the electrolyte, the requirement on the number of the active sites of the electrode is reduced, and lower resistance is needed to transmit the electrolyte out of the pile, at the moment, the electrode with lower bulk density can play a role. That is, the electrode body has a high density, provides more active sites, has a larger contact area with the electrolyte, and is beneficial for the active material to participate in the reaction, but at the same time, the high density of the electrode body also increases the resistance to the liquid, which can hinder the electrolyte from transmitting; the electrode body has low density, can provide relatively few (but enough) active sites, has small resistance to the electrolyte, contributes to quick transmission of the electrolyte, and reduces concentration polarization of the flow battery. It is worth mentioning that the material of the electrode is preferably carbon felt, and the decrease of the density of the carbon felt may reduce the bulk resistance of the carbon felt to a certain extent, but since the carbon felt is an electronic conductor, the resistance of the carbon felt itself is very low (< 0.2 Ω · cm) 2 ) So that the reduction in bulk density does not substantially affect the ohmic polarization of the cell.
Compared with the prior art, the invention has the following beneficial effects:
the method for reducing the concentration polarization of the flow battery is simple to operate, low in cost, obvious in effect and suitable for large-scale popularization;
the method for reducing the concentration polarization of the flow cell can reduce the constraint of the shape of the galvanic pile, improve the effective utilization rate of the materials of the ion exchange membrane and the bipolar plate to a certain extent and avoid additional pump consumption.
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FIG. 1 is a schematic view of an assembly structure of a bipolar plate, an electrode frame and an electrode in example 1 of the present invention;
fig. 2 is a schematic view of an electrode frame and an electrode structure in embodiment 1 of the present invention;
fig. 3 is a schematic view of an electrode frame and an electrode structure in embodiment 2 of the present invention;
fig. 4 is a schematic view of an electrode frame and an electrode structure in embodiment 3 of the present invention;
fig. 5 is a schematic view of an electrode frame and an electrode structure in embodiment 4 of the present invention.
Detailed Description
The following examples are provided to further illustrate the present invention in order to better understand the present invention, but the present invention is not limited to the following examples. Unless otherwise specified, the experimental methods used in the present invention are conventional methods, and the experimental devices, materials, reagents, etc. used therein are commercially available.
The embodiment of the invention is illustrated by selecting the full-vanadium redox flow battery with the most mature technical process, but the specific type of the redox flow battery is not limited, and the application of the method for reducing the concentration polarization of the redox flow battery in other types of redox flow batteries is also within the protection scope of the invention.
The performance test conditions of the all-vanadium redox flow battery pile are as follows: graphite carbon felts of different bulk densities produced by Liaoyang gold grain carbon materials GmbH are used as reaction electrodes, and positive and negative electrolytes are VO 2+ /VO 2 + And V 2+ /V 3+ The battery operating temperature was 37 ℃.
In the invention, the total size of the n electrodes is consistent with the size of the electrolyte reaction area, the width of each electrode can be the same or different, and the width ratio of each electrode is not required. The example of the same width of each electrode in the following embodiments is merely for convenience of explanation.
Example 1
The electrode numbers, dimensions and bulk density are shown in table 1.
Table 1 carbon felt electrode parameters in example 1
Figure BDA0003986220590000041
Assembled into a 44-power-saving stack at 100mA/cm 2 Electric fluid density ofAnd carrying out constant-current charging and discharging (average discharging power is 5 kW), and selecting data of a fifth cycle as initial performance data. Note that the size of the ion exchange membrane and the bipolar plate is the same as the size of the outer edge of the electrode frame.
Example 2
The electrode numbers, dimensions and bulk densities are shown in table 2.
Table 2 carbon felt electrode parameters in example 2
Figure BDA0003986220590000042
Assembled into a 44-power-saving stack at 100mA/cm 2 Constant current charging and discharging (average discharging power 5 kW) are carried out on the electrofluid density, and data of a fifth cycle are selected as initial performance data. Note that the size of the ion exchange membrane and the bipolar plate is the same as the size of the outer edge of the electrode frame.
Example 3
The electrode numbers, dimensions and bulk densities are shown in table 3.
Table 3 carbon felt electrode parameters in example 3
Figure BDA0003986220590000043
Figure BDA0003986220590000051
Assembled into a 44-power-saving stack at 100mA/cm 2 Constant current charging and discharging (average discharging power 5 kW) are carried out on the electrofluid density, and data of a fifth cycle are selected as initial performance data.
Example 4
The electrode numbers, dimensions and bulk densities are shown in table 4.
Table 4 carbon felt electrode parameters in example 4
Figure BDA0003986220590000052
Assembled into a 40-power-saving stack at 100mA/cm 2 Constant current charging and discharging (average power 5 kW) are carried out on the electrofluid density, and data of a fifth cycle are selected as initial performance data. Note that the size of the ion exchange membrane and the bipolar plate is the same as the size of the outer edge of the electrode frame.
Comparative example 1
Using the same electrode frame structure as in example 1 or 2, the electrodes were changed to 200mm by 460mm in size and 0.07g/cm in bulk density 3 The single carbon felt is assembled into a 44-power-saving stack under the condition of not changing other conditions and the power consumption is 100mA/cm 2 Constant current charging and discharging (average discharging power 5 kW) are carried out on the electrofluid density, and data of a fifth cycle are selected as initial performance data.
Comparative example 2
Using the same electrode frame structure as in example 1 or 2, the electrodes were changed to 200mm by 460mm in size and 0.12g/cm in bulk density 3 The single carbon felt is assembled into a 44-power-saving stack under the condition of not changing other conditions, and the power is supplied at 100mA/cm 2 Constant current charging and discharging are carried out on the electrofluid density (the average discharging power is 5 kW), and data of a fifth cycle are selected as initial performance data.
Comparative example 3
Using the same electrode frame structure as in example 1 or 2, the electrodes were changed to 200mm by 460mm in size and 0.15g/cm in bulk density 3 The single carbon felt is assembled into a 44-power-saving stack under the condition of not changing other conditions and the power consumption is 100mA/cm 2 Constant current charging and discharging are carried out on the electrofluid density (the average discharging power is 5 kW), and data of a fifth cycle are selected as initial performance data.
Comparative example 4
Using the same electrode frame structure as in example 3, the electrodes were changed to 300mm X335 mm in size and 0.07g/cm in bulk density 3 The single carbon felt is assembled into a 40-power-saving stack under the condition of not changing other conditions and the power consumption is 100mA/cm 2 Constant current charging and discharging are carried out on the electrofluid density (the average discharging power is 5 kW), and data of a fifth cycle are selected as initial performance data.
Comparative example 5
Using the same electrode frame structure as in example 3, the electrodes were changed to 300 mm. Times.335 mm in sizeBulk density of 0.12g/cm 3 The single carbon felt is assembled into a 40-power-saving stack under the condition of not changing other conditions and the power consumption is 100mA/cm 2 Constant current charging and discharging (average discharging power 5 kW) are carried out on the electrofluid density, and data of a fifth cycle are selected as initial performance data.
Comparative example 6
Using the same electrode frame structure as in example 3, the electrodes were changed to 300mm X335 mm in size and 0.15g/cm in bulk density 3 The single carbon felt is assembled into a 40-power-saving stack under the condition of not changing other conditions and the power consumption is 100mA/cm 2 Constant current charging and discharging (average discharging power 5 kW) are carried out on the electrofluid density, and data of a fifth cycle are selected as initial performance data.
TABLE 5 test data for examples 1-3 and comparative examples 1-6 stacks
Figure BDA0003986220590000071
As can be seen from examples 1-3 and comparative examples 1-3 (or example 4 and comparative examples 4-6), under other conditions such as the same electrode frame, the concentration polarization of the stack can be remarkably reduced and the voltage efficiency and the energy efficiency can be improved by using the method of the invention; from comparative examples 1-3 and comparative examples 4-6, it can be seen that when the flow distance of the electrolyte in the stack is increased, i.e. the short-flow structure is not used (comparative examples 4-6), the effective area utilization ratio (under the premise of the same total used area) of the ion exchange membrane and the bipolar plate is increased (from 61.3% to 67.0%), and under the condition, from example 4 and comparative examples 1-3, the stack efficiency can still reach or even exceed the effect of the short-flow structure stack when the stack does not use the short-flow structure by adopting the method of the present invention, which shows that the method of the present invention is effective for reducing the concentration polarization of the flow battery, improving the voltage efficiency and the energy efficiency of the battery, and can get rid of the shape constraint of the stack to a certain extent.
The above are typical examples and comparative examples of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to substitute or change the technical solution and its concept of the present invention within the technical scope of the present invention.

Claims (7)

1. A simple low-cost method for reducing concentration polarization of a flow battery is characterized in that electrodes with different n block densities rho are sequentially arranged in electrolyte reaction areas of a positive electrode and a negative electrode along the flowing direction of electrolyte, and the sum of the combined areas of the n electrodes is consistent with the area of the electrolyte reaction area.
2. The simple low-cost method for reducing concentration polarization of a flow battery as claimed in claim 1, wherein the value range of n is: n is more than or equal to 2 and less than or equal to 10.
3. The simple and low-cost method for reducing concentration polarization of a flow battery as claimed in claim 1, wherein the n electrodes with different bulk densities ρ arranged in sequence along the electrolyte flow direction have sequentially reduced bulk densities ρ.
4. The simple low-cost method for reducing concentration polarization of the flow battery as claimed in claim 1, wherein the bulk density is the density after the stack is assembled and compressed, and the density meets 0.07g/cm 3 ≤ρ≤0.15g/cm 3 。
5. The simple and low-cost method for reducing concentration polarization of a flow battery as claimed in claim 1, wherein said electrode is a porous carbon material electrode.
6. The simple and low-cost method for reducing concentration polarization of a flow battery as claimed in claim 1, wherein the electrode is a carbon felt electrode, a carbon fiber cloth electrode, a carbon paper electrode, a foam carbon electrode, or a 3D printed carbon electrode.
7. The electrode prepared by the simple low-cost method for reducing the concentration polarization of the flow battery according to claim 1 is suitable for the field of redox flow batteries.
CN202211564945.7A 2022-12-07 2022-12-07 Simple low-cost method for reducing concentration polarization of flow battery and application Pending CN115939475A (en)

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