A high face capacity zinc-bromine redox flow battery

Abstract

The application relates to a high surface capacity zinc-bromine double liquid flow battery, belonging to the field of liquid flow batteries. The zinc-bromine double liquid flow battery is improved in a negative electrode structure, and the structure of the negative electrode is that a non-conductive plastic fiber film is clamped in the middle of two carbon felts. The method is simple in operation, low in cost, obvious in effect, significantly improves the surface capacity of the battery, and effectively improves the energy density of the zinc-bromine single liquid flow battery.

Description

Technical Field

[0001] This invention relates to a high areal capacity zinc-bromine dual-flow battery. Background Technology

[0002] Zinc-bromine dual-flow energy storage battery is a new type of low-cost, high-efficiency, and environmentally friendly flow energy storage battery. It has advantages such as high energy density and current efficiency, simple and easy-to-operate device, long service life, and low cost. It is mainly used in grid peak shaving, renewable energy power generation such as wind and solar power, electric vehicles and other fields.

[0003] For zinc-bromine flow batteries, because the battery separator uses a porous ion-conducting membrane, during the charging process at the negative electrode, zinc dendrites grow along the micropores of the separator and continue to grow to the positive electrode. When these zinc dendrites come into contact with the positive electrode, a short circuit occurs, preventing the battery stack from operating. To avoid this short circuit between the positive and negative electrodes, the battery's charging capacity must be reduced. These issues are the main reasons limiting the relatively low capacity of zinc-bromine batteries. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a high-area-capacity zinc-bromine dual-flow battery. This invention combines the electrode structure characteristics of the zinc-bromine dual-flow battery by making the negative electrode into a structure of two carbon felts sandwiching a non-conductive plastic fiber membrane. During the battery charging process, zinc is induced to deposit on the two carbon felts respectively, thereby increasing the amount of zinc deposited and thus increasing the battery capacity.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-area-capacity zinc-bromine dual-flow battery includes a separator, a negative electrode, and a negative electrode current collector. The negative electrode is composed of two carbon felts with equal cross-sectional areas sandwiched between two non-conductive porous plastic fiber membranes of equal area. The carbon felt closer to the negative electrode current collector is called the main carbon felt, and the carbon felt closer to the separator is called the secondary carbon felt.

[0007] A non-conductive plastic fiber membrane is installed between two carbon felt pieces;

[0008] The pore size range of the porous plastic fiber membrane is 0.2µm to 2µm, preferably 0.5µm to 1µm;

[0009] The porosity of the porous plastic fiber membrane ranges from 50% to 70%, preferably from 55% to 65%.

[0010] The thickness of the porous plastic fiber membrane ranges from 1 mm to 2 mm, preferably from 1.2 to 1.5 mm;

[0011] The thickness of the main carbon felt is 2mm to 3mm, preferably 2.3mm to 2.8mm; the thickness of the secondary carbon felt is 0.5mm to 1mm, preferably 0.6mm to 0.9mm.

[0012] Furthermore, the material of the non-conductive plastic fiber membrane includes one or more of GF, PE, PP, and PVC.

[0013] Furthermore, two carbon felts with equal cross-sectional areas refer to carbon felts with the same surface shape and size;

[0014] Equal area means that the surface shape and size of the plastic fiber membrane are the same as those of the carbon felt.

[0015] Furthermore, the zinc-bromine dual-flow battery includes an electrolyte storage tank, in which the electrolyte circulates within the chambers containing the positive and negative electrodes of the zinc-bromine dual-flow battery.

[0016] Furthermore, the positive and negative electrolytes of the zinc-bromine dual-flow battery are both neutral aqueous solutions containing zinc ions. The zinc and bromine raw materials are zinc bromide. The zinc ion concentration in the positive and negative electrolytes is the same, and the supporting electrolyte KCl concentration is also the same. The zinc ion concentration in the electrolyte is 2-4 mol / L, and the KCl concentration is 2-5 mol / L. Furthermore, the positive and negative electrolytes in the electrolyte storage tank of the zinc-bromine dual-flow battery flow to the positive and negative electrodes respectively via pumps, and a diaphragm is installed between the positive and negative electrodes.

[0017] Furthermore, the zinc-bromine dual-flow battery includes a positive current collector and a positive electrode. The positive electrode is a carbon felt electrode, which has the same surface shape and size as the negative carbon felt, and the same thickness as the negative main carbon felt.

[0018] The zinc-bromine dual-flow battery comprises, in sequence, a positive current collector, a positive electrode, a separator, a secondary carbon felt, a plastic fiber membrane, a main carbon felt, and a negative current collector.

[0019] This invention relates to a zinc-bromine dual-flow battery, which improves the negative electrode structure. The negative electrode consists of two carbon felts sandwiched between a non-conductive plastic fiber membrane. During battery charging, elemental zinc preferentially grows between the carbon felt and the plastic fiber membrane on the side closer to the current collector. Because the carbon felt near the membrane is non-conductive and separated by the plastic fiber, no elemental zinc grows on it. Zinc preferentially grows on the carbon felt near the current collector. As charging time increases, elemental zinc gradually accumulates on the carbon felt near the current collector until zinc dendrites pierce the non-conductive plastic fiber membrane. After piercing the membrane, the zinc dendrites contact the carbon felt near the membrane, making it conductive. Subsequently, elemental zinc is deposited on the carbon felt near the membrane, thus increasing the amount of elemental zinc deposited and consequently increasing the battery capacity.

[0020] The aforementioned fiber membrane can be composed of one or more of the following materials: GF, PE, PP, and PVC. When assembling the battery, it simply needs to be placed sequentially between the two carbon felts of the negative electrode (the area of ​​the carbon felt is equal to the area of ​​the plastic fiber membrane). This method is simple to operate, low in cost, and highly effective, significantly improving the battery's surface capacity and effectively increasing the energy density of the zinc-bromine single-flow battery.

[0021] The beneficial effects of this invention are:

[0022] This invention addresses the problem of zinc-bromine single-flow batteries where, during charging, zinc dendrites at the negative electrode grow through the micropores of the separator to the positive electrode, contacting it and causing a short circuit, thus limiting battery capacity. The invention solves this problem by constructing the negative electrode as two carbon felts sandwiched between a non-conductive plastic fiber membrane. During charging, this induces zinc to deposit on both carbon felts, thereby increasing the amount of zinc deposited and ultimately improving battery capacity.

[0023] Plastic fibers possess advantages such as oxidation resistance, insulation, density, porosity, water absorption, and low cost. In the initial stages of battery charging, the plastic fiber membrane effectively insulates the two carbon felts at the negative electrode, allowing elemental zinc to deposit on the carbon felt closest to the current collector. Due to its porous structure, as zinc accumulates to a certain amount, it grows through the micropores of the plastic fiber membrane, reaching and conducting the carbon felt near the separator. Subsequently, elemental zinc deposits on the carbon felt closest to the separator. This provides a larger deposition space for the zinc negative electrode, increasing the amount of zinc deposited and thus increasing battery capacity. This method is low-cost, fast-acting, and simple to operate. It quickly and efficiently solves the problems of low capacity and low energy density in zinc-bromine single-phase flow batteries, promoting their development. Attached Figure Description

[0024] Figure 1 This is a diagram of the electrode structure of a zinc-bromine dual-flow battery.

[0025] Figure 2 It is the negative electrode structure of the battery. Detailed Implementation

[0026] This invention, combining the electrode structure characteristics of a zinc-bromine dual-flow battery, makes the negative electrode a structure of two carbon felts sandwiching a non-conductive plastic fiber membrane, as shown below. Figure 2 As shown, during battery charging, zinc is induced to deposit on two carbon felts, thereby increasing the amount of zinc deposited and thus increasing the battery capacity.

[0027] Example 1

[0028] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP (nitrogen bromide-methyl-ethylpyrrolidone). The single cell consists of the following components stacked sequentially: positive electrode plate, positive graphite plate, positive electrode frame, carbon felt (placed within the central cavity of a hollow annular positive electrode frame), separator, negative electrode secondary carbon felt (0.8 mm thick), PE fiber membrane (pore size range 0.5 μm–0.9 μm, porosity 60%, thickness 1.3 mm), negative electrode primary carbon felt (2.7 mm thick) (the negative electrode secondary carbon felt, PE fiber membrane, and negative electrode primary carbon felt are stacked within the central cavity of a hollow annular negative electrode frame), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within two closed cavities formed by the positive and negative electrode frames, the positive and negative current collectors (graphite plates), and the battery separator, respectively. The electrolytes flow within these cavities using positive and negative electrode circulation pumps. The charge / discharge current density is 40 mA / cm². 2 The electrode structure of a zinc-bromine dual-flow battery is as follows: Figure 1 As shown, the maximum charging surface capacity is 230mAh / cm². 2 Battery performance is shown in Table 2.

[0029] Example 2

[0030] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (0.7 mm thick), GF fiber membrane (pore size range 0.6–0.9 μm, porosity 63%, thickness 1.4 mm), negative electrode main carbon felt (2.5 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 220mAh / cm². 2 Battery performance is shown in Table 2.

[0031] Example 3

[0032] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (0.9 mm thick), PP fiber membrane (pore size range 0.7–0.9 μm, porosity 65%, thickness 1.5 mm), negative electrode main carbon felt (2.8 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 220mAh / cm². 2 Battery performance is shown in Table 2.

[0033] Example 4

[0034] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode auxiliary carbon felt (0.5 mm thick), PE fiber membrane (pore size range 0.2 μm–0.5 μm, porosity 50%, thickness 1 mm), negative electrode main carbon felt (2 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 200mAh / cm². 2 Battery performance is shown in Table 2.

[0035] Example 5

[0036] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode auxiliary carbon felt (1 mm thick), PE fiber membrane (pore size range 1 μm–2 μm, porosity 70%, thickness 2 mm), negative electrode main carbon felt (3 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm².2 The maximum charging surface capacity is 240mAh / cm². 2 Battery performance is shown in Table 2.

[0037] Comparative Example 1

[0038] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (0.8 mm thick), PE fiber membrane (pore size range 2.5 μm–3 μm, porosity 65%, thickness 1.4 mm), negative electrode main carbon felt (2.7 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 110mAh / cm². 2 Battery performance is shown in Table 2.

[0039] As shown in Table 2 regarding battery performance, the non-conductive plastic fiber membrane installed between the main carbon felt and the secondary carbon felt of the negative electrode has too large a pore size. Zinc will accumulate rapidly in the membrane pores, which means that the plastic fiber membrane is not enough to block the zinc from contacting the secondary carbon felt for a long time. As a result, the main carbon felt does not deposit enough zinc. Because the zinc deposited on the main carbon felt quickly pierces the non-conductive fiber membrane, the secondary carbon felt becomes conductive, and zinc begins to deposit on the secondary carbon felt. The main carbon felt does not play its role in transferring the zinc deposition site, so the battery surface capacity is not improved.

[0040] Comparative Example 2

[0041] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (0.7 mm thick), PE fiber membrane (pore size range 0.6 μm–1 μm, porosity 64%, thickness 2.5 mm), negative electrode main carbon felt (2.5 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 220mAh / cm². 2 Battery performance is as described in section 2.

[0042] As shown in Table 2 regarding battery performance, when the thickness of the plastic fiber membrane between the main and auxiliary carbon felts of the negative electrode is too large, the zinc, which preferentially accumulates on the main carbon felt, is difficult to penetrate the plastic fiber membrane. This results in zinc continuously accumulating on the main carbon felt. Although the capacity may increase, the battery performance will decrease. Because the deposition sites of zinc on the main carbon felt are close to the separator, the distance between the positive and negative electrodes is larger than that on the auxiliary carbon felt, leading to greater battery polarization and thus lower battery performance.

[0043] Comparative Example 3

[0044] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (0.7 mm thick), GF fiber membrane (pore size range 0.05–0.15 μm, porosity 63%, thickness 1.4 mm), negative electrode main carbon felt (2.5 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 220mAh / cm². 2 Battery performance is shown in Table 2.

[0045] As shown in Table 2 regarding battery performance, the non-conductive plastic fiber membrane installed between the main carbon felt and the secondary carbon felt of the negative electrode has too small a pore size. Zinc dendrites have difficulty penetrating the plastic fiber membrane, causing zinc to deposit continuously on the main carbon felt. The deposition sites between the main carbon felt and the plastic fiber membrane are far from the positive electrode, increasing battery polarization and thus degrading performance. Even if zinc dendrites do penetrate the plastic fiber membrane, the number of penetration points is relatively small, resulting in uneven current distribution on the negative carbon felt. This affects zinc deposition on the secondary carbon felt, increasing polarization and reducing the amount of zinc deposited. Overall, the battery is oversized and has low performance.

[0046] Comparative Example 4

[0047] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (0.6 mm thick), GF fiber membrane (pore size range 0.5–0.7 μm, porosity 64%, thickness 0.5 mm), negative electrode main carbon felt (2.6 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 220mAh / cm². 2 Battery performance is shown in Table 2.

[0048] As shown in Table 2, when the thickness of the plastic fiber film between the main and auxiliary carbon felts of the negative electrode is too thin, the zinc element that is preferentially accumulated on the main carbon felt of the negative electrode can easily puncture the plastic fiber film. This results in too little zinc element being deposited on the main carbon felt, and most of the zinc is deposited on the auxiliary carbon felt. Compared with Comparative Example 1, the battery capacity is reduced.

[0049] Comparative Example 5

[0050] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (0.6 mm thick), GF fiber membrane (pore size range 0.5–0.8 μm, porosity 63%, thickness 1.5 mm), negative electrode main carbon felt (1 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 220mAh / cm². 2 Battery performance is shown in Table 2.

[0051] As shown in Table 2 regarding battery performance, when the thickness of the main carbon felt on the negative electrode is too thin, elemental zinc cannot be uniformly deposited on it. This reduces the overall thickness of the negative electrode, increases electrolyte flow resistance, worsens fluidity, and increases concentration polarization, thus affecting the amount of zinc deposited. Uneven zinc deposition on the main carbon felt leads to excessive zinc dendrite accumulation in some areas, which rapidly penetrates the plastic fiber membrane. This results in insufficient zinc deposition on the main carbon felt, with most zinc deposited on the secondary carbon felt, leading to a decrease in battery capacity compared to Comparative Example 1.

[0052] Comparative Example 6

[0053] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of the following components in sequence: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (0.1 mm thick), GF fiber membrane (pore size range 0.6–0.9 μm, porosity 65%, thickness 1.5 mm), negative electrode main carbon felt (2.5 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 220mAh / cm². 2 Battery performance is shown in Table 2.

[0054] As shown in Table 2 regarding battery performance, when the thickness of the negative electrode sub-carbon felt is too thin, zinc dendrites penetrating from the plastic fiber membrane can also pierce the sub-carbon felt and contact the separator, essentially rendering the sub-carbon felt ineffective. Battery capacity depends on the amount of elemental zinc deposited between the main carbon felt and the plastic fiber membrane. The disordered growth of zinc dendrites between the sub-carbon felt and the separator makes it easy for them to pierce the separator. Therefore, both battery capacity and performance are affected and reduced accordingly, and battery stability is also reduced.

[0055] Comparative Example 7

[0056] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. A single cell consists of the following layers stacked sequentially: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (0.8 mm thick), PE fiber membrane (pore size range 0.5 μm–0.9 μm, porosity 60%, thickness 1.3 mm), negative electrode main carbon felt (3.5 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode end plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within two closed cavities formed by the positive and negative electrode frames, the positive and negative current collectors (graphite plates), and the battery separator, respectively. The electrolytes flow within these cavities using positive and negative electrode circulation pumps. The charge / discharge current density is 40 mA / cm². 2 The electrode structure of a zinc-bromine dual-flow battery is as follows: Figure 1 As shown, the maximum charging surface capacity is 220mAh / cm². 2 Battery performance is shown in Table 2.

[0057] As shown in Table 2, when the thickness of the negative electrode carbon felt is too thick, it increases the distance between the positive and negative electrodes, which increases the ohmic polarization of the battery and leads to a decrease in battery voltage efficiency.

[0058] Comparative Example 8

[0059] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. A single cell consists of the following layers stacked sequentially: positive electrode plate, positive electrode graphite plate, positive electrode frame, carbon felt, separator, negative electrode secondary carbon felt (1.5 mm thick), PE fiber membrane (pore size range 0.5 μm–0.9 μm, porosity 60%, thickness 1.3 mm), negative electrode main carbon felt (2.7 mm thick), negative electrode frame, negative electrode graphite plate, and negative electrode end plate. Except for the end plate and electrode frame, all components are 6 x 6 cm in size. 2 The positive and negative electrolytes are sealed within two closed cavities formed by the positive and negative electrode frames, the positive and negative current collectors (graphite plates), and the battery separator, respectively. The electrolytes flow within these cavities using positive and negative electrode circulation pumps. The charge / discharge current density is 40 mA / cm². 2 The electrode structure of a zinc-bromine dual-flow battery is as follows: Figure 1 As shown, the maximum charging surface capacity is 220mAh / cm². 2 Battery performance is shown in Table 2.

[0060] As shown in Table 2, when the thickness of the negative electrode carbon felt is too thick, compared with Comparative Example 7, the overall thickness of the negative electrode increases, which affects the battery electrode spacing. As the electrode spacing increases, the battery polarization increases, and the performance decreases significantly.

[0061] Comparative Example 9

[0062] The battery electrolyte is 2 mol / L ZnBr2 + 3 mol / L KCl + 0.8 M MEP. The single cell consists of, in sequence: positive electrode plate, positive graphite plate, positive electrode frame, carbon felt, separator, negative carbon felt (3 mm thick), negative electrode frame, negative graphite plate, and negative electrode plate. Except for the end plates and electrode frames, all components are 6x6 cm in size. 2 The positive and negative electrolytes are sealed within a closed cavity formed by the positive and negative electrode frames, the positive current collector (graphite plate), and the battery separator. The electrolyte flows within the positive and negative electrode cavity using a positive and negative electrode circulation pump. The charge / discharge current density is 40 mA / cm². 2 The maximum charging surface capacity is 220mAh / cm². 2 Battery performance is shown in Table 2.

[0063] This comparative example is a traditional zinc-bromine dual-flow battery structure, with only one carbon felt electrode as the negative electrode. As can be seen from the battery performance, the traditional battery structure is limited by the space for zinc deposition at the negative electrode, resulting in a low battery capacity. Zinc can only be deposited between the carbon felt and the separator.

[0064] Table 1

[0065]

[0066]

[0067] Table 2 Battery Performance

[0068]

Claims

1. A high areal capacity zinc-bromine dual-flow battery, comprising a separator, a negative electrode, and a negative electrode current collector, characterized in that: The negative electrode is composed of two carbon felts with equal cross-sectional areas sandwiching a non-conductive porous plastic fiber membrane with equal area. The carbon felt closer to the negative electrode current collector is called the main carbon felt, and the carbon felt closer to the membrane is called the secondary carbon felt. A non-conductive plastic fiber membrane is installed between two carbon felt pieces; The pore size range of the porous plastic fiber membrane is 0.2µm to 2µm, preferably 0.5µm to 1µm; The porosity of the porous plastic fiber membrane ranges from 50% to 70%, preferably from 55% to 65%. The thickness of the porous plastic fiber membrane ranges from 1 mm to 2 mm, preferably from 1.2 to 1.5 mm; The thickness of the main carbon felt is 2mm to 3mm, preferably 2.3mm to 2.8mm; the thickness of the secondary carbon felt is 0.5mm to 1mm, preferably 0.6mm to 0.9mm.

2. The high areal capacity zinc-bromine dual-flow battery according to claim 1, characterized in that: The material of the non-conductive plastic fiber membrane includes one or more of GF, PE, PP, and PVC.

3. The high areal capacity zinc-bromine dual-flow battery according to claim 1, characterized in that: Two carbon felts with equal cross-sectional areas refer to carbon felts with the same surface shape and size; Equal area means that the surface shape and size of the plastic fiber membrane are the same as those of the carbon felt.

4. The high areal capacity zinc-bromine dual-flow battery according to claim 1, characterized in that: The zinc-bromine dual-flow battery includes an electrolyte storage tank, in which the electrolyte circulates within the chambers containing the positive and negative electrodes of the zinc-bromine dual-flow battery.

5. The high areal capacity zinc-bromine dual-flow battery according to claim 1 or 4, characterized in that: The positive and negative electrode electrolytes of the zinc-bromine dual-flow battery are both neutral aqueous solutions containing zinc ions. The zinc and bromine raw materials are zinc bromide. The zinc ion concentrations in the positive and negative electrode electrolytes are the same, and the supporting electrolyte KCl concentration is the same. The zinc ion concentration in the electrolyte is 2-4 mol / L, and the KCl concentration is 2-5 mol / L.

6. The high areal capacity zinc-bromine dual-flow battery according to claim 1, 4, or 5, characterized in that, In a zinc-bromine dual-flow battery, the positive and negative electrolytes in the electrolyte storage tank flow to the positive and negative ends respectively via pumps, and a diaphragm is installed between the positive and negative electrodes.

7. The high areal capacity zinc-bromine dual-flow battery according to claim 1, characterized in that, The zinc-bromine dual-flow battery includes a positive current collector and a positive electrode. The positive electrode is a carbon felt electrode, which has the same surface shape and size as the negative carbon felt, and its thickness is the same as the thickness of the negative main carbon felt. The zinc-bromine dual-flow battery comprises, in sequence, a positive current collector, a positive electrode, a separator, a secondary carbon felt, a plastic fiber membrane, a main carbon felt, and a negative current collector.

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