Static zinc-bromine battery with multi-layer composite integrated electrode

Abstract

The invention relates to the technical field of electrochemical energy storage, in particular to a static zinc-bromine battery with a multi-layer composite integrated electrode, which comprises a positive electrode end plate, a single battery unit and a negative electrode end plate which are sequentially arranged in a laminated manner, and is characterized in that the single battery unit comprises a first current collector, the multi-layer composite integrated electrode and a second current collector; the first current collector and the second current collector are respectively arranged on two opposite sides of the multi-layer composite integrated electrode; the multi-layer composite integrated electrode is formed by sequentially and alternately compositing and arranging a plurality of conductive layers and non-conductive barrier layers, and the total number of the conductive layers and the non-conductive barrier layers is not less than three. A rich three-dimensional confinement space is provided for zinc deposition through a multi-layer alternating structure of the conductive layers and the non-conductive barrier layers, and high-load and compact deposition of zinc in the conductive layers with high porosity is allowed, so that the unit area capacity of the battery is improved, and the bottleneck of low surface capacity of a traditional static battery is overcome.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to a static zinc-bromine battery with a multilayer composite integrated electrode. Background Technology

[0002] With the accelerated global energy transition towards renewable energy and the large-scale grid connection of intermittent power sources such as solar and wind power, there is an urgent need for efficient, long-duration, low-cost, and highly safe electrochemical energy storage technologies. Among various energy storage systems, zinc-bromine flow batteries have become a highly promising technology in the field of large-scale electrochemical energy storage due to their advantages such as high theoretical energy density, abundant and inexpensive zinc / bromine raw material reserves, and intrinsic safety with no risk of explosion.

[0003] Typical zinc-bromine flow batteries rely on the deposition / dissolution of zinc (negative electrode) and the redox reaction of bromide ions / bromine (positive electrode) to store and release energy. During charging, zinc ions are electrodeposited as metallic zinc at the negative electrode, while bromide ions are oxidized to elemental bromine at the positive electrode and combine with the solid bromine complexing agent in the electrolyte; the discharge process is the reverse. However, traditional zinc-bromine flow batteries typically require two independent electrolyte circulation systems and an ion-selective separator. The circulation system is used to transport active materials and regulate thermal management, and its use often introduces additional energy consumption, equipment complexity, and the risk of electrolyte leakage, while also increasing maintenance costs. The ion-selective separator is used to mitigate the cross-diffusion of bromine species and the growth of zinc dendrites, but it itself suffers from high cost, high internal resistance, and easy aging, limiting the battery's cycle life.

[0004] To simplify systems and reduce costs, the concept of membrane-free static zinc-bromine batteries has emerged. These batteries eliminate external circulation pipelines and ion-selective separators, placing the positive and negative electrolytes together in a single chamber. However, this design also brings new technical challenges: First, the diffusion of bromine species (especially elemental bromine and its complexes) to the negative electrode cannot be effectively blocked, leading to severe chemical self-discharge and a sharp decline in coulombic efficiency and cycle life. Second, without physical constraints, zinc tends to form dendritic deposits on the surface of the conductive substrate of the negative electrode, which can easily cause electrode short circuits. Furthermore, the mass transfer process within the static system is limited, causing the battery to typically operate at a lower areal capacity, making it difficult to meet the needs of high-energy-density energy storage applications. For example, in Chinese patent CN108134141B, an attempt was made to alleviate self-discharge through gravity separation (inverted battery) and carbon felt adsorption. However, in practical applications, the battery can only operate at a low areal capacity, which makes it unable to meet the high energy density requirements. In addition, there is a lack of effective physical barriers, and the liquid bromine complex generated at the positive electrode is easy to diffuse to the negative electrode, making it difficult to effectively solve the problems of chemical self-discharge and low coulombic efficiency. Summary of the Invention

[0005] This application provides a static zinc-bromine battery with a multilayer composite integrated electrode to solve the problems of low areal capacity, severe self-discharge, difficult dendrite problem, and dependence on specific placement methods in the prior art.

[0006] This application provides a static zinc-bromine battery with a multilayer composite integrated electrode, comprising a positive electrode plate, a single cell unit, and a negative electrode plate stacked sequentially, wherein: The single cell unit includes a first current collector, a multilayer composite integrated electrode, and a second current collector, wherein the first current collector and the second current collector are respectively disposed on opposite sides of the multilayer composite integrated electrode; The multilayer composite integrated electrode is composed of multiple conductive layers and non-conductive resistive layers arranged alternately, and the total number of conductive layers and non-conductive resistive layers is not less than three.

[0007] Preferably, the single-cell unit further includes an electrode frame for encapsulating and fixing the edge of the multilayer composite integrated electrode.

[0008] Preferably, there are multiple single battery cells, at least one, and the multiple single battery cells are stacked in series between the positive terminal plate and the negative terminal plate.

[0009] Preferably, when there are multiple single-cell units, the second current collector of the current single-cell unit also serves as the first current collector of the next single-cell unit.

[0010] Preferably, when the total number of conductive layers and non-conductive resistive layers in the multilayer composite integrated electrode is an odd number, its outermost layer is always a conductive layer.

[0011] Preferably, the conductive layer has a resistivity of less than or equal to 10. -6 It is made of porous material with Ω·m.

[0012] Preferably, the non-conductive resistive separator has a resistivity greater than or equal to 10. 8 It is made of porous material with Ω·m.

[0013] Preferably, the thickness of the conductive layer and the non-conductive resistive barrier layer are each independently between 0.1 mm and 10 mm.

[0014] Preferably, the multiple conductive layers and the non-conductive resistive barrier layer are combined to form an integral structure through hot pressing, bonding or needle punching processes.

[0015] Preferably, the negative terminal plate is further provided with an inlet for injecting electrolyte and an outlet for discharging gas.

[0016] The beneficial effects of this application are as follows: The static zinc-bromine battery with multilayer composite integrated electrode of this application provides a rich three-dimensional confined space for zinc deposition through the multilayer alternating structure of conductive layer and non-conductive resistive separator. This allows zinc to be deposited in a high-load and dense manner within the high-porosity conductive layer, thereby improving the battery's capacity per unit area and overcoming the bottleneck of low areal capacity in traditional static batteries.

[0017] Furthermore, by employing a non-conductive resistive separator as a built-in physical barrier, an electronically insulated region that allows ion penetration and transport is constructed inside the battery, thereby effectively blocking the macroscopic diffusion of bromine species to the negative electrode side, reducing the self-discharge rate under static conditions, and improving the coulombic efficiency of the battery. At the same time, the confined deposition mode guided by this structure can also suppress the growth of zinc dendrites, thereby suppressing the risk of internal short circuits caused by them and extending cycle life.

[0018] In particular, by adopting this fully static integrated design structure, the expensive ion exchange membrane and complex, energy-intensive external pumping circulation system in traditional zinc-bromine flow batteries are eliminated, simplifying the system structure of the battery stack. This reduces raw material costs, equipment manufacturing costs, and system operation and maintenance complexity, while also reducing potential failure points. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 A schematic diagram of the planar structure of a static zinc-bromine battery with a multilayer composite integrated electrode provided in the embodiments of this application; Figure 2 This is an exploded schematic diagram of the three-dimensional structure of the static zinc-bromine battery of this application; Figure 3 This is a schematic diagram showing the disassembled structure of the multilayer composite integrated electrode of this application; Figure 4 A comparison chart of typical charge-discharge curves of a conventional membrane-free static zinc-bromine battery (Comparative Example 1) and those of Examples 8 and 10 in this application. Figure 5 This is a schematic diagram of the long-cycle performance of Embodiment 10 in this application.

[0021] Figure label: 1. Positive electrode plate; 2. First current collector; 3. Electrode frame; 4. Multilayer composite integrated electrode; 41. Conductive layer; 42. Non-conductive insulating layer; 5. Negative electrode plate; 51. Liquid inlet; 52. Exhaust port; 6. Second current collector Detailed Implementation The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The following is combined Figures 1-5 This describes a static zinc-bromine battery with a multilayer composite integrated electrode provided in the embodiments of this application.

[0023] Reference Figure 1 and Figure 2 As shown in the embodiment of this application, the static zinc-bromine battery with a multilayer composite integrated electrode mainly includes a positive terminal plate 1, a single cell unit, and a negative terminal plate 5 stacked sequentially. The negative terminal plate 5 is also provided with an inlet 51 for injecting electrolyte and an outlet 52 for discharging gas. Each single cell unit includes a first current collector 2, a multilayer composite integrated electrode 4, a second current collector 6, and an electrode frame 3 for encapsulating and fixing the edge of the multilayer composite integrated electrode 4. The first current collector 2 and the second current collector 6 are respectively located on opposite sides of the multilayer composite integrated electrode 4. At least one single cell unit is provided; when multiple single cell units are provided, they are stacked in series between the positive terminal plate 1 and the negative terminal plate 5. Furthermore, when multiple single cell units are provided, the second current collector 6 of the current single cell unit also serves as the first current collector 2 of the next single cell unit.

[0024] In some specific embodiments, such as Figure 3 As shown, the multilayer composite integrated electrode 4 is composed of multiple conductive layers 41 and non-conductive resistive layers 42 arranged alternately. The total number of conductive layers 41 and non-conductive resistive layers 42 is not less than three, preferably an odd number of layers. When the total number of conductive layers 41 and non-conductive resistive layers 42 in the multilayer composite integrated electrode 4 is an odd number of layers, the number of conductive layers is one more than the number of non-conductive resistive layers, so that the outermost layer is a conductive layer 41. Thus, the opposite sides of the multilayer composite integrated electrode 4 that are in contact with the current collector are both conductive layers 41.

[0025] In some specific embodiments, the conductive layer 41 is made of material with a resistivity less than or equal to 10. -6 It is made of porous material with Ω·m, preferably conductive carbon felt, graphite felt, porous metal material or composite material thereof; The non-conductive resistive separator 42 is made of materials with a resistivity greater than or equal to 10. 8 It is made of porous material with an Ω·m content, preferably hydrophilic non-conductive polymer felt, glass fiber felt or ceramic fiber felt; Furthermore, the thickness of the conductive layer 41 and the non-conductive resistive barrier layer 42 are each independently selected and set between 0.1 mm and 10 mm.

[0026] In some specific embodiments, the multilayer composite integrated electrode 4 can be preformed by processes such as cutting, stacking, hot pressing or bonding. The adjacent conductive layer 41 and the non-conductive resistive spacer 42 can be composited into an integrated structure by any one or more processes such as hot pressing, bonding or needle punching, and then uniformly compressed and set in the electrode frame 3. The electrode frame 3 is used to fix and seal the edge of the multilayer composite integrated electrode 4, and to provide the necessary compression and positioning for the composite conductive layer 41 and the non-conductive resistive spacer 42 inside.

[0027] Among them, the multilayer composite integrated electrode 4 uses a porous conductive layer 41 as the negative electrode reaction site. Unlike the flat current collector in the prior art, its porous structure provides a huge specific surface area and rich three-dimensional confined space for zinc deposition, allowing zinc to be deposited in a high-porosity conductive layer with high loading and dense deposition, thereby significantly improving the unit area capacity of the battery and overcoming the bottleneck of low surface capacity of traditional static batteries. Meanwhile, by employing a non-conductive resistive separator 42 as a built-in physical barrier, an electronically insulated region that allows ion penetration and transport is constructed inside the battery. This effectively blocks the macroscopic diffusion of bromine species to the negative electrode side, significantly reducing the self-discharge rate under static conditions and improving the battery's coulombic efficiency. Furthermore, this barrier layer can guide and confine the deposition behavior of zinc, forcing zinc ions to be reduced within specific conductive layer regions, preventing their disordered growth on a single plane, thereby inhibiting dendrite formation and extending cycle life. This application adopts a novel fully static integrated battery structure design, which completely eliminates the expensive ion exchange membrane and complex, energy-intensive external pumping circulation system in traditional zinc-bromine flow batteries. This not only greatly simplifies the structure of the battery stack and system, simplifies the assembly process, and reduces potential failure points, but also significantly reduces raw material costs, equipment manufacturing costs, and system operation and maintenance complexity. Furthermore, because this application employs a physical barrier layer to suppress diffusion, the battery in this application does not need to be placed upside down as in existing technologies, making its installation direction more flexible. The multilayer composite integrated electrode 4 can also be prefabricated using mature material processes, such as simple processes like cutting, stacking, hot pressing, or bonding, making it easy to achieve standardized and large-scale production. Its integrated structure also avoids the difficult problems of aligning the film and electrode and sealing in traditional batteries, improving assembly consistency and reliability.

[0028] Specifically, this application also provides the following specific embodiments: Example 1 First, a multilayer composite integrated electrode with a three-layer structure of "conductive layer-non-conductive resistive barrier layer-conductive layer" is prepared.

[0029] Specifically, a 4mm thick conductive graphite felt is used as the first conductive layer; a 2mm thick non-conductive polymer felt is used as the second non-conductive insulating layer 42; and a 2mm thick conductive graphite felt is used as the third conductive layer. The three layers are stacked sequentially and then hot-pressed at 120°C and 0.2MPa for 10 minutes to form an integrated three-layer composite electrode. All electrode materials are cut to a uniform standard size of 6cm × 8cm.

[0030] Subsequently, referring to Figure 1 As shown, the positive terminal plate 1, the first current collector 2, the electrode frame 3 containing the aforementioned integrated three-layer composite electrode, the second current collector 6, and the negative terminal plate 5 are sequentially aligned and stacked, and sealed with uniform pressure using four corner bolts. The first current collector 2 and the second current collector 6 are both graphite plates approximately 1 mm thick. The electrode frame 3 is made of insulating polypropylene, and its inner frame dimensions match the dimensions of the fabricated three-layer composite electrode, forming a complete multi-layer integrated composite electrode 4. The bottom of the negative terminal plate 5 is also machined with a liquid inlet 51, and the top is machined with an exhaust port 52.

[0031] Using deionized water as a solvent, a mixed solution containing 2M zinc bromide (ZnBr2), 1M zinc chloride (ZnCl2), 1M potassium chloride (KCl), and 1M tetraethylammonium bromide (TEAB) was prepared as the electrolyte. The electrolyte was slowly injected into the inlet 51 using a syringe pump until the electrolyte completely wetted the electrode and overflowed from the vent 52. The inlet 51 and the vent 52 were then sealed.

[0032] Examples 2-5 (Conductive Layer Thickness Gradient Experiment) The difference from Example 1 is that the thickness of the conductive layer 41, which is the main reaction region of the positive electrode, is changed. The thickness of the first conductive layer 41 in Examples 2-5 is 1 mm (Example 2), 2 mm (Example 3), 3 mm (Example 4), and 5 mm (Example 5), respectively. Constant current charge-discharge tests were conducted on the batteries in Examples 1, 2, 3, 4, and 5 above at an ambient temperature of 25°C, with the charge-discharge current density set at 10 mA cm⁻¹. -2 The charging time was 1 hour; the discharge cutoff voltage was 0.5 V. The test results are shown in Table 1. Table 1. Constant current charge-discharge test results for Examples 1-5

[0033] Test results show that as the thickness of the first conductive layer increases, both the coulombic efficiency and voltage efficiency of the battery improve. The battery performance is optimal when the thickness is 4mm, with an energy efficiency of 81.93%, which can be selected as the basis for subsequent comparisons.

[0034] Examples 6-9 (Thickness Gradient Experiment of Non-Conductive Interlayer) The difference from Example 1 is that the thickness of the non-conductive resistive interlayer 42 located in the second layer is adjusted. The thicknesses of the non-conductive resistive interlayer 42 in Examples 6-9 are 1 mm (Example 6), 3 mm (Example 7), 4 mm (Example 8), and 5 mm (Example 9), respectively. Constant current charge-discharge tests were conducted on the batteries in Examples 1, 6, 7, 8, and 9 at an ambient temperature of 25°C, with the charge-discharge current density set at 10 mA cm⁻¹. -2 The charging time was 1 hour; the discharge cutoff voltage was 0.5V. The test results are shown in Table 2. Table 2 shows the constant current charge-discharge test results for Examples 1, 6, 7, 8, and 9.

[0035] Test results show that as the thickness of the non-conductive resistive separator 42 in the second layer increases, the coulombic efficiency of the battery improves and the voltage efficiency decreases slightly. When its thickness is 4mm, the battery's overall performance is the best, and it can be selected as the basis for subsequent comparisons.

[0036] Example 10 (Five-layer structure) The difference from Embodiment 8 is that the multilayer composite integrated electrode 4 in this embodiment adopts a five-layer structure of "conductive layer - non-conductive resistive barrier layer - conductive layer - non-conductive resistive barrier layer - conductive layer". Specifically: A 4mm thick conductive graphite felt is used as the first conductive layer. A 4mm thick non-conductive polymer felt is used as the second non-conductive resistive insulating layer. A 2mm thick conductive graphite felt is used as the third conductive layer; A 2mm thick non-conductive polymer felt is used as the fourth non-conductive resistive insulating layer. A 2mm thick conductive graphite felt was used as the fifth conductive layer.

[0037] Comparative Example 1 (Traditional Static Structure Without Diaphragm) The difference from Example 8 is that the second layer (non-conductive separator) and the third layer (conductive layer) in the multilayer composite integrated electrode 4 are removed, the first conductive layer is retained, and a cavity space of the same thickness (6mm) is retained at the original positions of the second and third layers to assemble a conventional membrane-free static zinc-bromine battery.

[0038] Constant current charge-discharge tests were conducted on the batteries in Examples 8, 10, and Comparative Example 1 at an ambient temperature of 25°C, with the charge-discharge current density set at 10 mA cm⁻¹. -2 The charging time is 6 hours; the discharge cut-off voltage is 0.5V. Reference Figure 4 As shown, in the charge-discharge behavior test, the battery in Comparative Example 1 exhibited a short charge-discharge curve plateau and severe polarization due to severe mass transfer limitations and significant self-discharge side reactions. It also showed low voltage efficiency, rapid voltage rise and short circuit at the end of charging, and rapid decay of the discharge plateau. In contrast, the batteries in Examples 8 and 10 displayed significantly longer and flatter charge-discharge voltage plateaus, indicating that they could achieve higher capacity, reversible zinc deposition and bromine reaction, with less polarization.

[0039] Reference Figure 5 As shown, in the cycle performance test, the battery in Comparative Example 1 performed better at 60 mAh cm⁻¹. -2 Under conditions where the battery capacity is insufficient, it cannot operate normally and cannot undergo long-cycle testing. The battery in Example 8 exhibits severe polarization after the initial few cycles, resulting in rapid performance degradation and a cycle life typically less than 20 cycles. In contrast, the battery in Example 10 demonstrates superior overall performance, capable of stable operation for over 200 cycles, with a coulombic efficiency of approximately 95%, a voltage efficiency of approximately 86%, and an energy efficiency of approximately 82%.

[0040] The test results fully demonstrate that the integrated electrode structure, which alternates between conductive layer 41 and non-conductive resistive separator layer 42, successfully achieves precise control of zinc deposition space and effective physical suppression of bromine diffusion in a simplified system without a static diaphragm or pumping. While simplifying the system structure, it achieves a balance between high areal capacity, high coulombic efficiency, and long cycle life.

[0041] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0042] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0043] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0044] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A static zinc-bromine battery with a multilayer composite integrated electrode, characterized in that, It includes a positive terminal plate (1), a single battery cell, and a negative terminal plate (5) stacked in sequence, wherein: The single cell unit includes a first current collector (2), a multilayer composite integrated electrode (4), and a second current collector (6), wherein the first current collector (2) and the second current collector (6) are respectively disposed on opposite sides of the multilayer composite integrated electrode (4); The multilayer composite integrated electrode (4) is composed of multiple conductive layers (41) and non-conductive resistive layers (42) arranged alternately in sequence, and the total number of conductive layers (41) and non-conductive resistive layers (42) is not less than three.

2. The static zinc-bromine battery with a multilayer composite integrated electrode according to claim 1, characterized in that, The single cell also includes an electrode frame (3) for encapsulating and fixing the edge of the multilayer composite integrated electrode (4).

3. The static zinc-bromine battery with a multilayer composite integrated electrode according to claim 2, characterized in that, One or more single battery cells are provided, and multiple single battery cells are stacked in series between the positive terminal plate (1) and the negative terminal plate (5).

4. The static zinc-bromine battery with a multilayer composite integrated electrode according to claim 3, characterized in that, When there are multiple single battery cells, the second current collector (6) of the current single battery cell also serves as the first current collector (2) of the next single battery cell.

5. The static zinc-bromine battery with a multilayer composite integrated electrode according to claim 4, characterized in that, When the total number of conductive layers (41) and non-conductive resistive insulating layers (42) in the multilayer composite integrated electrode (4) is an odd number, its outermost layer is always a conductive layer (41).

6. The static zinc-bromine battery with a multilayer composite integrated electrode according to claim 5, characterized in that, The conductive layer (41) has a resistivity of less than or equal to 10. -6 It is made of porous material with Ω·m.

7. The static zinc-bromine battery with a multilayer composite integrated electrode according to claim 6, characterized in that, The non-conductive resistive separator (42) has a resistivity greater than or equal to 10. 8 It is made of porous material with Ω·m.

8. The static zinc-bromine battery with a multilayer composite integrated electrode according to claim 7, characterized in that, The thickness of the conductive layer (41) and the non-conductive resistive barrier layer (42) are each independently between 0.1 mm and 10 mm.

9. The static zinc-bromine battery with a multilayer composite integrated electrode according to claim 1, characterized in that, Multiple conductive layers (41) and non-conductive resistive separators (42) are combined to form an integral structure through hot pressing, bonding or needle punching processes.

10. The static zinc-bromine battery with a multilayer composite integrated electrode according to claim 1, characterized in that, The negative terminal plate (5) is also provided with an inlet (51) for injecting electrolyte and an outlet (52) for discharging gas.

Images