Zinc-based flow battery structure

Abstract

The zinc-based flow battery structure comprises a current collector, a positive electrode, a diaphragm, a negative electrode and a current collector which are sequentially arranged, more than two through holes are formed in the negative electrode, a non-conductive adhesive layer is coated on the surface of one side, close to the negative electrode, of a current collector plate at the position corresponding to the through holes, and the projection of the through holes on the current collector plate is located on the non-conductive adhesive layer. The problem that the surface capacity of the zinc-based flow battery is limited is solved, and the energy density of the battery is further improved. The method is simple to operate and easy to implement.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to the field of zinc-based liquid flow batteries. Background Art

[0002] With the increasing depletion of fossil energy, the development and utilization of renewable energy such as wind energy and solar energy has become the focus of attention of all countries. Since wind energy and solar energy are discontinuous and unstable due to factors such as weather, this will have an impact on the power grid during the process of renewable energy power generation and grid connection, affecting the power supply quality and grid stability. Energy storage technology can solve this problem and ensure the efficient and stable operation of renewable energy power generation and grid connection. Energy storage technology is mainly divided into two categories: physical energy storage and chemical energy storage. Among them, chemical energy storage represented by flow batteries has the most advantages in large-scale energy storage due to its many advantages such as independent power and capacity, rapid response, simple structure, easy design, long cycle life, and environmental friendliness.

[0003] Zinc-based flow batteries have attracted widespread attention in the industry due to their rich active material resources, high energy density and low system cost. Among them, zinc-based flow batteries with carbon felt, graphite felt and other electrode materials have become a research hotspot due to their high working current density and good cycle stability. Since zinc deposition in zinc-based flow batteries with porous materials such as carbon felt and graphite felt as electrodes mainly occurs on the electrode surface close to the diaphragm, a common problem of this type of zinc-based flow batteries is that as the battery surface capacity gradually increases, the zinc deposition on the electrode surface becomes more and more dense, and the resistance of zinc ions diffusing to the surface of the deposited zinc becomes greater and greater, resulting in increased battery polarization and decreased battery performance; in severe cases, zinc dendrites may even pierce the diaphragm, causing battery failure. Summary of the invention

[0004] Technical problem to be solved by the present invention (purpose of the invention)

[0005] Since zinc deposition in zinc-based flow batteries using porous materials such as carbon felt and graphite felt as electrodes mainly occurs on the electrode surface close to the diaphragm, a common problem of such zinc-based flow batteries is that as the battery surface capacity gradually increases, zinc deposition on the electrode surface becomes more and more dense, and the resistance of zinc ions diffusing to the surface of deposited zinc becomes greater and greater, resulting in increased battery polarization and decreased battery performance; in severe cases, zinc dendrites may even pierce the diaphragm and cause battery failure. In the present invention, a through hole is used in the negative electrode, and a non-conductive glue is applied to the surface of the current collector at the through hole position to promote the diffusion of zinc ions to the surface of deposited zinc, reduce ion transmission resistance, reduce battery polarization, and improve battery performance and cycle life.

[0006] The complete technical solution provided by the present invention is described in detail with reference to the accompanying drawings.

[0007] The method for reducing battery polarization at high surface capacity of zinc-based liquid flow batteries and improving battery performance and cycle life is to add through holes in the negative electrode.

[0008] A zinc-based liquid flow battery structure, comprising a current collector, a positive electrode, a separator, a negative electrode, and a current collector arranged in sequence, characterized in that:

[0009] There are more than two through holes on the negative electrode, and a non-conductive adhesive layer is coated on the surface of the current collector at the corresponding position of the through holes close to the negative electrode, so that the projection of the through holes on the current collector is on the non-conductive adhesive layer.

[0010] The opening positions of more than two through holes are evenly distributed on the electrode surface.

[0011] The cross-sectional area of ​​each through hole parallel to the negative electrode surface is 0.1-0.5cm 2 , preferably 0.1-0.4cm 2 , more preferably 0.3-0.4cm 2 .

[0012] The opening ratio of through holes on the negative electrode surface (the ratio of the sum of the through hole areas on the negative electrode surface to the electrode surface area) is 5%-20% of the electrode surface area, preferably 10%-15%.

[0013] The non-conductive adhesive can be classified into one or more of polyester resin adhesive, epoxy resin adhesive, polyurethane adhesive, polybutadiene resin adhesive, silicone resin adhesive, polyester imide resin adhesive and polyimide resin adhesive according to the composition of the main resin;

[0014] After applying the non-conductive glue, the projection of the through hole on the current collecting plate is placed on the non-conductive glue, and the shape and size of the non-conductive glue corresponding to each through hole are the same or equivalent to the port of the through hole close to the current collecting plate.

[0015] The thickness of the non-conductive adhesive coating is 0.5-3 mm, preferably 0.5-1 mm;

[0016] The thickness of the negative electrode is 3-6 mm, preferably 4-5 mm.

[0017] The positive and negative electrode materials of the battery are both carbon felt or graphite felt; the current collector is a graphite plate.

[0018] The zinc-based flow battery includes a zinc-bromine flow battery, a zinc-iodine flow battery, a zinc-nickel flow battery or a zinc-manganese flow battery.

[0019] Beneficial effects brought by the technical solution of the present invention

[0020] 1. In the present invention, a through hole is used in the negative electrode, and a non-conductive glue is applied on the surface of the current collector at the through hole position, so as to promote the diffusion of zinc ions to the surface of the deposited zinc, reduce the ion transmission resistance, reduce the battery polarization, and improve the battery performance and cycle life.

[0021] 2. Solve the problem of limited surface capacity of zinc-based liquid flow batteries and further improve battery energy density.

[0022] The method is simple to operate and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of battery structure; wherein 1 end plate 2 positive electrode current collector 3 positive electrode 4 separator 5 negative electrode 6 negative electrode current collector 7 end plate;

[0024] Figure 2 Schematic diagram of the holes opened on the carbon felt electrode. DETAILED DESCRIPTION

[0025] A zinc-based liquid flow battery structure, comprising a current collector, a positive electrode, a separator, a negative electrode, and a current collector arranged in sequence, characterized in that:

[0026] A through hole is provided on the negative electrode, and a non-conductive adhesive layer is coated on the surface of the current collecting plate at the position corresponding to the through hole and close to the negative electrode, so that the projection of the through hole on the current collecting plate is on the non-conductive adhesive layer.

[0027] The opening positions of the through holes are evenly distributed on the electrode surface.

[0028] After applying the non-conductive glue, the projection of the through hole on the current collecting plate is placed on the non-conductive glue, and the shape and size of the non-conductive glue corresponding to each through hole are the same as or equal to or slightly larger than the port area of ​​the through hole close to the current collecting plate, and correspond one to one.

[0029] Example 1

[0030] The cycling performance experiment of zinc-bromine flow battery was carried out with 2MZnBr2+3MKCl+0.8M N-ethyl bromide, methylpyrrolidine (MEP) as electrolyte. The graphite plate was used as current collector. The positive and negative electrodes of the battery were both carbon felt with a thickness of 5mm. The negative electrode of the carbon felt was provided with through holes, and the opening positions were evenly distributed on the electrode surface. Epoxy non-conductive glue (i.e. epoxy resin glue, Wuxi Resin Plant of Bluestar Chemical New Materials Co., Ltd., Ex-20) was applied on the surface of the current collector plate close to the negative electrode at the corresponding position of the through hole, so that the projection of the through hole on the current collector plate was on the epoxy non-conductive glue, and the thickness of the non-conductive glue was 0.5mm. The diaphragm was PE film, the electrolyte flow rate was 60ml / min, and the current density was 40mA / cm 2 , discharge to 0.1V. Electrode area 48cm 2The battery performance tests were conducted on batteries with different opening ratios and single hole areas.

[0031] The battery performance is as follows:

[0032]

[0033] The through-hole area is defined as the surface area of ​​the through-hole on the carbon felt electrode;

[0034] The total open porosity is defined as the percentage of the total through-hole area to the surface area of ​​the carbon felt electrode.

[0035] When the total opening rate is 10%, the battery VE increases with the increase of single hole area. This is mainly because the increase of single hole area helps to accelerate the mass transfer of electrolyte, reduce the concentration polarization of battery and thus improve the battery VE. When the single hole area is greater than 0.4cm 2 When the through-hole area is 0.4cm, the battery CE and VE decrease. This is mainly due to the excessively large electrode opening area, which leads to the destruction of the electrode conductive network and the increase of battery polarization. In addition, due to the influence of VE, the battery discharge power increases first and then decreases. 2 The battery power is highest when

[0036] The single hole area is 0.4cm 2 When the total porosity increases, the battery VE decreases. This is mainly due to the decrease in the electrode reaction active area and the increase in battery polarization as the porosity increases. When the porosity is 5%, the battery surface capacity is 100mAh / cm 2 This is mainly due to the low open porosity. As the surface capacity increases, the diffusion resistance of the electrolyte to the electrode surface increases, and the battery polarization increases. In addition, as the total open porosity increases, the effective area of ​​the electrode decreases, resulting in a gradual decrease in the battery discharge power.

[0037] Example 2

[0038] The cycling performance experiment of zinc-bromine flow battery was carried out with 2MZnBr2+3MKCl+0.8M N-ethyl bromide, methylpyrrolidine (MEP) as electrolyte. The graphite plate was used as current collector. The positive and negative electrodes of the battery were both carbon felt with a thickness of 5mm. A through hole was provided on the negative electrode of the carbon felt, and the opening positions were evenly distributed on the electrode surface. Epoxy non-conductive glue (i.e. epoxy resin glue, Wuxi Resin Plant of Bluestar Chemical New Materials Co., Ltd., Ex-20) was applied on the surface of the current collector plate close to the negative electrode at the corresponding position of the through hole, so that the projection of the through hole on the current collector plate was on the epoxy non-conductive glue. The thickness of the non-conductive glue was 0.5mm, 1mm, 1.5mm, 2mm, and 3mm respectively. The diaphragm was PE film, the electrolyte flow rate was 60ml / min, and the current density was 40mA / cm 2 , discharge to 0.1V. Electrode area 48cm2 . Through hole area 0.4cm 2 , the total opening rate is 10%.

[0039] The performance of batteries coated with non-conductive adhesive coatings of different thicknesses were tested respectively.

[0040]

[0041]

[0042] As the thickness of the non-conductive adhesive coating increases, the battery VE decreases. This is mainly because the increase in the thickness of the non-conductive adhesive coating affects the mass transfer of the electrolyte in the through-holes, thereby increasing the polarization of the battery.

[0043] Comparative Example 1

[0044] The zinc-bromine flow battery cycle performance experiment was carried out with 2MZnBr2+3MKCl+0.8MMEP as the electrolyte. The graphite plate was the current collector. The positive and negative electrodes of the battery were both carbon felt with a thickness of 5mm. There were no through holes on the carbon felt electrodes. The diaphragm was a PE film, the electrolyte flow rate was 60ml / min, and the current density was 40mA / cm 2 , discharge to 0.1V. Electrode area 48cm 2 .

[0045] The battery surface capacity can reach 80mAh / cm 2 , further increasing the battery surface capacity will cause zinc dendrites to pierce the diaphragm, leading to battery failure. This is mainly because as the battery surface capacity gradually increases, the zinc deposition on the electrode surface becomes more and more dense, and the resistance of zinc ions diffusing to the surface of the deposited zinc becomes greater and greater, resulting in increased battery polarization.

[0046] Comparative Example 2

[0047] The zinc-bromine flow battery cycle performance experiment was carried out with 2MZnBr2+3MKCl+0.8MMEP as the electrolyte. The graphite plate was the current collector. The positive and negative electrodes of the battery were both carbon felt. The thickness of the carbon felt was 5mm. There were through holes on the carbon felt electrodes, and the opening positions were evenly distributed on the electrode surface. The surface of the current collector was not coated with non-conductive glue at the through hole position. The diaphragm was PE film, the electrolyte flow rate was 60ml / min, and the current density was 40mA / cm 2 , discharge to 0.1V. Electrode area 48cm 2 . Through hole area 0.4cm 2 , the total opening rate is 10%.

[0048] During the operation of the battery, zinc falls off and blocks the battery, causing battery failure. This is mainly due to the fact that the surface of the current collector at the through-hole position is not coated with non-conductive glue, and zinc is deposited on the surface of the graphite plate current collector. When zinc is deposited on the graphite plate as the substrate, the bonding force between zinc and the graphite plate is poor, resulting in zinc falling off.

Claims

1. A zinc-based liquid flow battery structure, comprising a current collector, a positive electrode, a separator, a negative electrode, and a current collector arranged in sequence, characterized in that: There are more than two through holes on the negative electrode, and a non-conductive adhesive layer is coated on the surface of the current collector at the corresponding position of the through holes close to the negative electrode, so that the projection of the through holes on the current collector is on the non-conductive adhesive layer.

2. The structure according to claim 1, characterized in that: The opening positions of more than two through holes are evenly distributed on the electrode surface.

3. The structure according to claim 1, characterized in that: The cross-sectional area of ​​each through hole parallel to the negative electrode surface is 0.1-0.5cm 2 , preferably 0.1-0.4cm 2 , more preferably 0.3-0.4cm 2 .

4. The structure according to claim 1 or 3, characterized in that: The opening ratio of through holes on the negative electrode surface (the ratio of the sum of the through hole areas on the negative electrode surface to the electrode surface area) is 5%-20% of the electrode surface area, preferably 10%-15%.

5. The structure according to claim 1, characterized in that: The non-conductive adhesive can be classified into one or more of polyester resin adhesive, epoxy resin adhesive, polyurethane adhesive, polybutadiene resin adhesive, silicone resin adhesive, polyester imide resin adhesive and polyimide resin adhesive according to the composition of the main resin; After applying the non-conductive glue, the projection of the through hole on the current collecting plate is placed on the non-conductive glue, and the shape and size of the non-conductive glue corresponding to each through hole are the same or equivalent to the port of the through hole close to the current collecting plate.

6. The structure according to claim 1 or 5, characterized in that: The thickness of the non-conductive adhesive coating is 0.5-3 mm, preferably 0.5-1 mm; The thickness of the negative electrode is 3-6 mm, preferably 4-5 mm.

7. The structure according to claim 1, characterized in that: The positive and negative electrode materials of the battery are both carbon felt or graphite felt; the current collector is a graphite plate.

8. The structure according to claim 1, characterized in that: The zinc-based flow battery includes a zinc-bromine flow battery, a zinc-iodine flow battery, a zinc-nickel flow battery or a zinc-manganese flow battery.

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