Flow battery with improved electrode assembly and electrolyte distribution

Abstract

The present application relates to an electrode assembly and a flow battery with improved electrolyte distribution. The present invention discloses an electrode assembly for a flow battery, the electrode assembly comprising a porous electrode material, a frame surrounding the porous electrode material, at least one distribution tube embedded in the porous electrode material having an inlet for supplying electrolyte to the porous electrode material, and at least another distribution tube embedded in the porous electrode material having an outlet for discharging electrolyte from the porous material. The wall of the distribution tube is preferably provided with holes or pores to allow the electrolyte to be evenly distributed within the electrode material. The distribution tube provides the required electrolyte flow path length within the electrode material to minimize the shunt current flowing between the flow battery cells of the battery pack.

Description

[0001] This application is a divisional application of an application with an application date of November 15, 2016, application number 201680066397.1, and invention name “Liquid flow battery with improved electrode assembly and electrolyte distribution”. Technical Field

[0002] The present invention relates to an electrode assembly for a flow battery having a construction that allows improved electrolyte distribution within the electrode material, and to a flow battery including such an electrode assembly. Background Art

[0003] Flow batteries, also known as redox flow batteries, convert electrical energy into chemical energy, which can be stored and then converted back into electrical energy for release when needed.

[0004] Flow batteries differ from other electrochemical devices, such as fuel cells, by using a liquid electrolyte that participates in a reversible electrochemical reaction. Fuel cells use gaseous fuels to produce energy, they do not store energy, whereas flow batteries do not produce any energy, they store and release energy. This is the basic difference between fuel cells and flow batteries, but there are many other differences between these two types of electrochemical cells, some of which are further described here.

[0005] Basic flow batteries, such as Figure 1 The basic flow battery shown by reference numeral 10 in the figure includes a redox flow battery cell 11 having a negative electrode 12 and a positive electrode 14 separated by a diaphragm 16. A negative electrode liquid electrolyte 17 is delivered to the negative electrode from a storage tank 18, and a positive electrode liquid electrolyte 19 is delivered to the positive electrode from a storage tank 20 to promote an electrochemically reversible redox reaction. The diaphragm can be a microporous diaphragm or an ion exchange membrane that separates the electrodes and prevents the electrolytes from mixing, but allows selected ions to pass through to complete the redox reaction. As shown, the flow battery includes a first collector plate 22 and a second collector plate 24, each of which is arranged adjacent to the porous electrode 12 and the porous electrode 14, respectively. The porous electrode is composed of a material that is conductive and catalytically active relative to the liquid electrolyte 17 and the liquid electrolyte 19 and is preferably corrosion-resistant. The collector plate is preferably made of a material that is highly conductive and chemically stable in the highly acidic environment within the flow battery cell. The collector plates are coupled to conductors 26 and 28 which complete a circuit either through a power source 30 (for charging) or to an electrical load 32 (for discharging) via an electrical switch 34 .

[0006] Figure 1The positive electrode and negative electrode in the liquid flow battery cell 11 are separated by a separator. The liquid flow battery group usually includes more than one liquid flow battery cell, depending on the design capacity of the liquid flow battery, and two adjacent liquid flow battery cells are separated by bipolar plates. During operation, liquid electrolytes 17 and 19 are delivered to the liquid flow battery cell group to convert electrical energy into chemical energy or chemical energy into electrical energy, which can be released by electrically connecting to an electrical load.

[0007] In some flow batteries, each electrolyte flows completely through the porous electrodes from the inlet to the outlet of each cell. In this type of flow battery, high pressure drops may occur due to the flow resistance through the porous material of the electrodes. In other flow batteries, the liquid electrolyte flows through channels set on either side of the bipolar plates and diffuses into the adjacent electrodes. This type of design provides less pressure drop because the electrolyte flows unrestricted through the flow channels, but the performance is relatively low due to the uneven distribution of the electrolyte into the electrodes.

[0008] Some flow batteries with flow field channels in the bipolar plates address this problem by changing the design of the flow field in an attempt to achieve a relatively uniform distribution of electrolyte within the electrodes and prevent any electrolyte concentration gradients in the electrodes.

[0009] For example, to address this problem, U.S. Patent Application No. 20120244395 describes a flow field having interdigitated channels whose outlets or inlets are at least partially blocked, thereby forcing the electrolyte to flow through the liquid porous electrode under the ribs of the channel. It is claimed that, as described above, forcing the liquid electrolyte to flow through the electrode under the ribs provides a lower pressure drop than flowing completely through the electrode as in some flow-through arrangements of flow batteries, and has the benefit of enhancing electrolyte exposure to the electrode.

[0010] In other designs, such as described in international patent application WO 2016 / 072254, the bipolar plate is provided with longitudinal grooves formed or cut into the molded plate, which produce electrolyte supply channels and electrolyte discharge channels, which help to reduce the deformation of the plate frame caused by the pressure imbalance between the supply side and the discharge side. The bipolar plate further includes an electrolyte guide portion between the electrolyte supply channel and the electrolyte discharge channel, which guides the electrolyte flow to the electrode. The electrolyte supply channel and the electrolyte discharge channel are covered by a plastic protective plate, which helps to guide the electrolyte flow to the electrode. The applicant states that better performance will be obtained if the electrolyte guide portion is provided with grooves to promote better distribution of the electrolyte to the electrode. Each electrode of the battery cell in this prior art document, such as a positive electrode or a negative electrode, is not formed in one piece, but is divided into at least two parts, each part facing an electrolyte guide portion on the bipolar plate. The electrode parts are placed at a certain distance from the electrolyte supply channel and the electrolyte discharge channel to form an electrolyte guide area, and these electrolyte guide areas are only allowed to partially cover the electrolyte supply channel and the electrolyte discharge channel. The design disclosed in this prior art document is complex, involving electrodes comprising several parts, a plastic protective plate covering electrolyte circulation grooves cut or formed into the bipolar plates, and an arrangement that requires appropriate positioning of the electrode parts so that the electrode parts do not interfere with the electrolyte circulation channels.

[0011] Generally speaking, another characteristic problem of flow batteries is that the electrolyte supply port of the flow battery cell is a conductive path for current to leak from one battery cell to the next battery cell in the battery cell group. For example, in fuel cells, the shunt current through the fluid path caused by the ion-conductive electrolyte is not a problem, but it is something that needs to be solved in flow batteries. This problem can be solved by increasing the effective resistance along the flow path entering and leaving the battery cell to reduce the current leakage between the battery cells. One way to achieve increased resistance is to increase the ratio of the electrolyte flow path length to the cross-sectional area, which is usually accomplished by increasing the electrolyte flow path within the frame around the electrode. The increase in the length of the electrolyte flow path must be balanced with the need to reduce the electrolyte pressure drop when the electrolyte flows through the battery cell, thereby reducing the electrolyte pumping energy loss and achieving uniform flow distribution in each battery cell.

[0012] During assembly, the flow battery cell stack is placed between two end plates and the flow battery cells are held together in contact by compressive forces applied to the end plates. The compressive forces required to assemble a flow battery stack are less than, for example, those required to assemble a fuel cell stack. In a flow battery, the stack typically has a plastic frame and metal or plastic end plates held together with metal rods and nuts. Since plastics and metals have very different coefficients of thermal expansion, springs are required in the clamping system to ensure that the desired stack compression force remains constant during temperature fluctuations.

[0013] In view of the known difficulties associated with existing systems, there is a need for a flow battery that allows for better distribution of electrolyte throughout the electrodes and reduces the risk of shunt currents in the stack by using simple and efficient construction of electrode assemblies and battery cell stack assemblies. Summary of the invention

[0014] The present invention describes an electrode assembly for a flow battery, the electrode assembly comprising a porous electrode material, a frame surrounding the porous electrode material, at least one distribution tube embedded in the porous electrode material having an inlet for supplying electrolyte to the porous electrode material, and at least another distribution tube embedded in the porous electrode material having an outlet for discharging electrolyte from the porous electrode material. The frame and the distribution tube are made of a non-conductive plastic material.

[0015] In a preferred embodiment of the electrode assembly according to the invention, the distribution tube extends between the first side of the frame and the second side of the frame beyond a midpoint between the two sides of the frame.

[0016] In a first embodiment of the invention, the distribution tubes having an inlet for supplying electrolyte to the porous electrode material each have an outlet sealed to the frame, and the distribution tubes having an outlet for discharging electrolyte from the porous electrode material each have an inlet sealed to the frame.

[0017] The distribution tube is a hollow tube having an internal flow passage and a wall surrounding the internal passage. In a preferred embodiment, the wall of the hollow tube is made of a solid material provided with holes to allow the electrolyte to flow through the wall of the distribution tube into the porous electrode material. Alternatively, the wall of the hollow tube can be made of a porous material to allow the electrolyte to flow through the wall of the distribution tube.

[0018] In a second embodiment of the invention, the distribution tubes having an inlet for supplying electrolyte to the electrode material each have an outlet leading to the porous electrode material, and the distribution tubes having an outlet for discharging electrolyte from the electrode material each have an inlet leading to the porous electrode material. In such embodiments, the distribution tubes are hollow tubes having an internal flow passage and a wall surrounding the internal passage, and the wall of at least one of the hollow tubes can be made of a solid material. In such embodiments, the wall of the hollow tube can also be made of a porous material or a solid material provided with at least one hole to allow the electrolyte to be better distributed within the porous electrode material.

[0019] In some embodiments of the electrode assembly of the present invention, the distribution tube is a hollow tube having an internal flow passage made of a porous material having a higher porosity than the porosity of the tube wall.

[0020] Generally, the dispensing tube has a circular cross-section. Alternatively, as described herein, the dispensing tube may have a triangular cross-section.

[0021] In a preferred embodiment, the distribution tube is completely embedded in the porous electrode material. However, in other embodiments, the distribution tube is only partially embedded in the porous electrode material.

[0022] In some embodiments of the present invention, the distribution tubes of the electrode assembly may be hollow tubes having a serpentine shape, and the wall of each distribution tube may be made of a solid material provided with at least one hole or of a porous material to allow the electrolyte to be distributed within the porous electrode material.

[0023] Embodiments of the electrode assemblies described herein may include a plurality of distribution tubes evenly distributed over an area of ​​electrode material. In some embodiments, at least some of the distribution tubes of the electrode assembly have the same cross-sectional flow area or are equal in length.

[0024] The distribution tube of the electrode assembly of the present invention can be made of polyethylene or polypropylene or other conductive materials compatible with the highly acidic environment within the flow battery, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethyl vinyl acetate (EVA), PE copolymers, UHMW PE, thermoplastic polyurethane, polyethersulfone, polycarbonate, and polycarbonate alloys.

[0025] The present invention also relates to a flow battery comprising at least one flow battery cell, the flow battery cell comprising a negative electrode assembly and a positive electrode assembly having the above-mentioned construction and features. Each flow battery cell further comprises a separator separating the positive electrode assembly and the negative electrode assembly, and a first bipolar plate and a second bipolar plate, each bipolar plate being adjacent to a corresponding electrode assembly.

[0026] In addition, the present invention also describes a liquid flow battery, which includes a liquid flow battery cell group enclosed in a cylindrical plastic shell provided with two end plates, and the liquid flow battery cell group is connected to the inner wall of the cylindrical plastic shell, whereby the cylindrical plastic shell compresses the liquid flow battery cell in the radial direction and the two end plates compress the liquid flow battery cell in the axial direction. The fuel cell cells in the battery cell group are separated by bipolar plates, and each liquid flow battery cell includes a positive electrode assembly and a negative electrode assembly separated by a diaphragm, and each electrode assembly includes a porous electrode material surrounded by a frame. The cylindrical plastic shell and the two end plates encapsulating the fuel cell cell group are made of non-conductive material.

[0027] In a preferred embodiment, the material of the cylindrical plastic shell and the end plates has the same or about the same coefficient of thermal expansion as the frame material. For example, the material of the frame, the cylindrical plastic shell and the end plates may be polyethylene or polypropylene.

[0028] The liquid flow battery cell group has a rectangular outer shape, and its corners are connected to the inner surface of the cylindrical plastic shell to form four compartments between the liquid flow battery cell group and the cylindrical plastic shell. More specifically, the corners of the liquid flow battery cell group are connected to the inner wall of the cylindrical plastic shell through a seal to form four sealed compartments between the liquid flow battery cell group and the cylindrical plastic shell for allowing positive electrolyte and negative electrolyte to flow therethrough. Two of the compartments are used to allow positive electrolyte to flow therethrough, and the other two compartments are used to allow negative electrolyte to flow therethrough.

[0029] In some embodiments, as described above, a flow battery cell group enclosed in a cylindrical housing provided with two end plates for compressing the flow battery cell in radial and axial directions, respectively, includes a flow battery cell having an electrode assembly having a configuration described in the present invention, more specifically, the electrode assembly includes a porous electrode material, a frame surrounding the porous electrode material, at least one distribution pipe embedded in the porous electrode material having an inlet for supplying electrolyte to the porous electrode material, and at least another distribution pipe embedded in the porous electrode material having an outlet for discharging electrolyte from the porous electrode material. Such an electrode assembly may have any of the features described in the present invention.

[0030] A method of manufacturing an electrode assembly for a flow battery according to the present invention is also described, the method comprising the steps of:

[0031] - positioning the porous electrode material within the frame;

[0032] - inserting a positioning pin into the porous electrode material through a hole provided in the frame surrounding the porous electrode material;

[0033] - positioning the dispensing tube in the porous material and relative to the frame by inserting the positioning pin into the porous electrode material and sliding the dispensing tube through the hole provided in the frame and the hole provided in the porous electrode material; and

[0034] - Sealing the distribution tube in the hole of the frame.

[0035] In another embodiment, a method of manufacturing an electrode assembly for a flow battery includes the following steps:

[0036] a. securing at least one distribution tube to the electrode frame;

[0037] b. positioning the porous electrode material on the distribution tube next to the electrode frame; and

[0038] c. Compressing the electrode frame, the distribution tube, and the porous electrode material to at least partially embed the distribution tube within the porous electrode material.

[0039] In all embodiments, when the electrode assembly of the flow battery is an electrode assembly including some distribution tubes whose inlets or outlets must be closed, respectively, the method of manufacturing the electrode assembly further includes sealing ends of the distribution tubes to prevent electrolyte from flowing through the inlets or outlets thereof.

[0040] Also described is a method for manufacturing a flow battery, the method comprising the steps of:

[0041] a. securing at least one distribution tube to the electrode frame;

[0042] b. sequentially placing an electrode frame having a distribution tube, an electrode material, a diaphragm, another electrode material, and another electrode frame having a distribution tube in a stacked manner;

[0043] c. Repeating steps a) and b) until the desired number of flow battery cells in the flow battery cell group is reached; and

[0044] d. Compressing the set of components formed in steps a) to c) to at least partially embed the distribution tube within the porous electrode material.

[0045] When the electrode assembly includes some distribution tubes whose inlets or outlets must be closed, respectively, the method of manufacturing the flow battery further includes sealing ends of those distribution tubes to prevent the electrolyte from flowing through the inlets or outlets thereof.

[0046] A method of manufacturing a flow battery is also disclosed, wherein the flow battery comprises a flow battery cell group enclosed in a cylindrical plastic casing provided with two end plates, and wherein the method comprises the following steps:

[0047] a. Provide a cylindrical plastic shell and two end plates;

[0048] b. placing the liquid flow battery cell group in the cylindrical plastic housing so that the liquid flow battery cell is connected to the inner wall of the cylindrical plastic housing and the cylindrical plastic housing compresses the liquid flow battery cell in a radial direction; and

[0049] c. Compressing the liquid flow battery cell group in the axial direction between the two end plates. The present application provides the following:

[0050] 1). An electrode assembly for a flow battery, comprising:

[0051] -Porous electrode materials;

[0052] - a frame surrounding the porous electrode material;

[0053] - at least one first distribution tube embedded in the porous electrode material, the first distribution tube having an inlet for supplying electrolyte to the porous electrode material; and

[0054] at least one second distribution tube embedded in the porous electrode material, the second distribution tube having an outlet for draining electrolyte out of the porous electrode material,

[0055] Wherein, the frame and the distribution pipe are made of non-conductive plastic material.

[0056] 2). The electrode assembly as described in 1), wherein the first distribution tube and the second distribution tube extend between the first side of the frame and the second side of the frame beyond the midpoint between the two sides of the frame.

[0057] 3). An electrode assembly as described in 1), wherein the first distribution tube has an outlet sealed to the frame, and the second distribution tube has an inlet sealed to the frame, and wherein the first distribution tube and the second distribution tube are hollow tubes, each hollow tube having an internal flow passage and a wall surrounding the internal passage, wherein the wall of the hollow tube is made of a solid material provided with holes to allow the electrolyte to flow through the wall of the distribution tube into the porous electrode material.

[0058] 4). An electrode assembly as described in 1), wherein the first distribution tube has an outlet sealed to the frame, and the second distribution tube has an inlet sealed to the frame, and wherein the first distribution tube and the second distribution tube are hollow tubes, each hollow tube having an internal flow passage and a wall surrounding the internal passage, wherein the wall of the hollow tube is made of a porous material to allow the electrolyte to flow through the wall of the distribution tube into the porous electrode material.

[0059] 5). The electrode assembly as described in 1), wherein the first distribution pipe has an outlet leading to the porous electrode material, and the second distribution pipe has an inlet leading to the porous electrode material.

[0060] 6). An electrode assembly as described in 5), wherein the first distribution tube and the second distribution tube are hollow tubes, each hollow tube having an internal flow passage and a wall surrounding the internal passage, wherein the wall of at least one of the hollow tubes is made of solid material.

[0061] 7). An electrode assembly as described in 5), wherein the first distribution tube and the second distribution tube are hollow tubes having an internal flow passage and a wall surrounding the internal passage, wherein the wall of at least one of the hollow tubes is made of a porous material to allow the electrolyte to be distributed within the porous electrode material.

[0062] 8). An electrode assembly as described in 5), wherein the first distribution tube and the second distribution tube are hollow tubes, each hollow tube having an internal flow passage and a wall surrounding the internal passage, wherein the wall of each hollow tube is made of a solid material having at least one hole to allow the electrolyte to be distributed in the porous electrode material.

[0063] 9). An electrode assembly as described in 1), wherein the first distribution tube and the second distribution tube are hollow tubes, each hollow tube having an internal flow passage and a wall surrounding the internal passage, wherein the internal flow passage of at least one of the first distribution tube or the second distribution tube is made of a porous material, and the porosity of the porous material is higher than the porosity of the wall.

[0064] 10). The electrode assembly as described in 1), wherein at least one of the first distribution tube or the second distribution tube has a circular cross-section.

[0065] 11). The electrode assembly as described in 1), wherein at least one of the first distribution tube or the second distribution tube has a triangular cross-section.

[0066] 12). The electrode assembly as described in 1), wherein at least one of the first distribution tube or the second distribution tube is completely embedded in the porous electrode material.

[0067] 13). The electrode assembly as described in 1), wherein at least one of the first distribution tube or the second distribution tube is partially embedded in the porous electrode material.

[0068] 14). An electrode assembly as described in 1), wherein at least one of the first distribution tube or the second distribution tube is a hollow tube having a serpentine shape, and the wall of the hollow tube is made of a solid material provided with at least one hole to allow the electrolyte to be distributed in the porous electrode material.

[0069] 15). The electrode assembly as described in 1), wherein at least one of the first distribution tube or the second distribution tube is a hollow tube having a serpentine shape, and the wall of the hollow tube is made of a porous material to allow the electrolyte to be distributed in the porous electrode material.

[0070] 16). The electrode assembly as described in 1) comprises a plurality of first distribution tubes and a plurality of second distribution tubes, wherein the plurality of first distribution tubes and the plurality of second distribution tubes are evenly distributed over the area of ​​the porous electrode material.

[0071] 17). The electrode assembly as described in 1) comprises a plurality of first distribution tubes and a plurality of second distribution tubes having the same cross-sectional flow area.

[0072] 18). The electrode assembly as described in 1), wherein the length of the first distribution tube is equal to the length of the second distribution tube.

[0073] 19). The electrode assembly as described in 1), wherein the first distribution pipe and the second distribution pipe are made of polyethylene or polypropylene.

[0074] 20) A liquid flow battery, the liquid flow battery comprising at least one liquid flow battery unit, the liquid flow battery unit comprising:

[0075] - a negative electrode assembly and a positive electrode assembly,

[0076] - a separator separating the positive electrode assembly and the negative electrode assembly, and

[0077] - a first bipolar plate and a second bipolar plate, each bipolar plate being adjacent to a respective electrode assembly,

[0078] Wherein, at least one of the negative electrode assembly or the positive electrode assembly is the electrode assembly as described in 1).

[0079] 21). A liquid flow battery, comprising a group of liquid flow battery cells separated by bipolar plates, each liquid flow battery cell comprising a positive electrode assembly and a negative electrode assembly separated by a diaphragm, each electrode assembly having a porous electrode material surrounded by a frame, wherein the liquid flow battery cell group is enclosed in a cylindrical plastic shell provided with two end plates, the liquid flow battery cell group is connected to the inner wall of the cylindrical plastic shell, and wherein the cylindrical plastic shell and the two end plates are made of non-conductive material, and the cylindrical plastic shell compresses the liquid flow battery cell in a radial direction, and the two end plates compress the liquid flow battery cell in an axial direction.

[0080] 22) The flow battery of 21), wherein the material of the cylindrical plastic shell and the end plates has a thermal expansion coefficient approximately the same as that of the material of the frame.

[0081] 23). The flow battery as described in 22), wherein the material of the frame, the cylindrical plastic shell and the end plate is polyethylene or polypropylene.

[0082] 24). A flow battery as described in 21), wherein the flow battery cell group has a rectangular outer shape, and its corners are connected to the inner surface of the cylindrical plastic shell to form four compartments between the flow battery cell group and the cylindrical plastic shell.

[0083] 25). A liquid flow battery as described in 24), wherein the corners of the liquid flow battery cell group are connected to the inner wall of the cylindrical plastic shell through seals to form four sealed compartments between the liquid flow battery cell group and the cylindrical plastic shell for allowing positive electrode electrolyte and negative electrode electrolyte to flow therethrough.

[0084] 26). A liquid flow battery, comprising a liquid flow battery cell group having an electrode assembly as described in 1), wherein the liquid flow battery cell group is enclosed in a cylindrical plastic shell provided with two end plates, the cylindrical plastic shell and the two end plates are made of non-conductive material, and hold the liquid flow battery cells together and compress them in radial and axial directions.

[0085] 27) A flow battery as described in 26), wherein the material of the cylindrical plastic shell and the end plates has a thermal expansion coefficient approximately the same as that of the material of the frame.

[0086] 28) A liquid flow battery as described in 26), wherein the liquid flow battery cell group has a rectangular outer shape, and its corners are connected to the inner surface of the cylindrical plastic shell to form four compartments between the liquid flow battery cell group and the cylindrical plastic shell.

[0087] 29). A liquid flow battery as described in 26), wherein the corners of the liquid flow battery cell group are connected to the inner surface of the cylindrical plastic shell by seals to form four sealed compartments between the liquid flow battery cell group and the cylindrical plastic shell, two of which are used to allow positive electrode electrolyte to flow therethrough, and the other two compartments are used to allow negative electrode electrolyte to flow therethrough.

[0088] 30). A method for manufacturing an electrode assembly for a flow battery, comprising the following steps:

[0089] - positioning the porous electrode material within the frame;

[0090] - inserting a positioning pin into the porous electrode material through a hole provided in the frame surrounding the porous electrode material;

[0091] - positioning the dispensing tube in the porous material and relative to the frame by inserting the positioning pin into the porous electrode material and sliding the dispensing tube through the hole provided in the frame and the hole provided in the porous electrode material; and

[0092] - Sealing the distribution tube in the hole of the frame.

[0093] 31). The method as described in 30) further includes sealing the end of at least one distribution tube to prevent the electrolyte from flowing through its inlet or outlet.

[0094] 32). A method for manufacturing an electrode assembly for a flow battery, comprising the following steps:

[0095] a. securing at least one distribution tube to the electrode frame;

[0096] b. positioning the porous electrode material on the distribution tube next to the electrode frame; and

[0097] c. Compressing the electrode frame, the distribution tube, and the porous electrode material to at least partially embed the distribution tube within the porous electrode material.

[0098] 33). A method for manufacturing a flow battery, comprising the following steps:

[0099] a. securing at least one distribution tube to the electrode frame;

[0100] b. sequentially placing an electrode frame having a distribution tube, an electrode material, a diaphragm, another electrode material, and another electrode frame having a distribution tube in a stacked manner;

[0101] c. Repeating steps a) and b) until the desired number of flow battery cells in the flow battery cell group is reached; and

[0102] d. Compressing the set of components formed in steps a) to c) to at least partially embed the distribution tube within the porous electrode material.

[0103] 34). The method as described in 33) further includes sealing the end of at least one distribution tube to prevent the electrolyte from flowing through its inlet or outlet.

[0104] 35). A method for manufacturing a flow battery as described in 21), comprising the following steps:

[0105] a. Provide a cylindrical plastic shell and two end plates;

[0106] b. placing the liquid flow battery cell group in the cylindrical plastic housing so that the liquid flow battery cell is connected to the inner wall of the cylindrical plastic housing and the cylindrical plastic housing compresses the liquid flow battery cell in a radial direction; and

[0107] c. Compressing the flow battery cell stack in the axial direction between the two end plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0108] The drawings illustrate specific preferred embodiments of the present invention, but should not be considered to limit the spirit or scope of the present invention in any way.

[0109] Figure 1 An example of a conventional flow battery is shown.

[0110] Figure 2A A schematic diagram of an electrode assembly according to a preferred embodiment of the present invention is shown.

[0111] Figure 2B Shown along line AA through Figure 2A A cross section of an electrode assembly is shown in FIG.

[0112] Figure 2C Shown through Figure 2A A longitudinal cross section of an electrode assembly is shown in FIG.

[0113] Figure 2D A cross-sectional view through one of the distribution pipes of the invention is shown, with particular reference to Figure 2A , Figure 2B and Figure 2C The embodiment shown in .

[0114] Figure 3 A cross-sectional view through an electrode assembly according to a second embodiment of the present invention is shown.

[0115] Figure 4 A cross-sectional view through an electrode assembly according to another embodiment of the present invention is shown.

[0116] Figure 5 A method of making the electrode assembly of the present invention is presented.

[0117] Fig. 6A A view showing a distribution tube having a triangular cross section that can be used in the electrode assembly of the present invention, Figure 6B Such an electrode assembly is shown.

[0118] Figure 6C and Fig.6D Demonstrated manufacturing capabilities such as Figure 6B Steps in a method of manufacturing a flow battery cell stack of an electrode assembly using a distribution tube having a triangular cross-section are shown.

[0119] Fig. 7A and Figure 7B Systems and methods for compressing and sealing a stack of flow battery cells in a flow battery are presented. DETAILED DESCRIPTION

[0120] Certain terms are used in this specification and are intended to be interpreted according to the definitions provided below. Additionally, terms such as "a", "an", and "comprising" should be considered open ended.

[0121] Herein, in the context of a quantitative amount, the term "about" should be interpreted as ranging from as high as 20% to as low as 20%.

[0122] The term "fully embedded" is used herein to describe a distribution tube that is placed within the porous material of the electrode such that the outer surface of the tube is surrounded by the electrode material.

[0123] The term "partially embedded" is used herein to describe a distribution tube that is placed within the porous material of the electrode, wherein at least a portion of the outer surface of the distribution tube is not surrounded by the electrode material.

[0124] Figure 2A FIG. 4 shows a schematic diagram of an electrode assembly according to a preferred embodiment of the present invention. The electrode assembly 40 includes a porous electrode material 42 surrounded by a frame 44 and a distribution tube 46 embedded in the porous electrode material 42. In this embodiment, the distribution tube 46 is completely embedded in the porous electrode material, such as Figure 2B , which shows a cross section of the electrode assembly 40 along line AA.

[0125] like Figure 2CAs further shown in the figure, both ends of each distribution tube 46 are located in holes 45 provided in the frame 44. Some distribution tubes, such as the distribution tube indicated by the mark 41, are designed to allow electrolyte to flow from the storage tank to the electrode material, while other distribution tubes, such as the distribution tube indicated by the mark 43, are designed to allow electrolyte to flow from the electrode material to the storage tank. The distribution tube 41 has an open inlet 41A and a sealed outlet 41B, which is fluidly connected to the electrolyte supply flow 50A in the operating battery pack. The distribution tube 43 has a sealed inlet 43A and an outlet 43B, which leads to an electrolyte discharge flow 50B of the electrolyte tank in the operating battery pack. Due to the configuration of the distribution tube, in the operating liquid flow battery, the electrolyte can flow from the tube 41 through the electrode material to the distribution tube 43, as indicated by the arrow D and further explained below.

[0126] like Figure 2D As shown, the distribution tube 46 having a tubular shape has an internal passage 54 through which the electrolyte flows in one direction B, and a wall 56 surrounding the internal passage. The internal passage of the distribution tube may be as shown in FIG. Figure 2D The open passages shown may alternatively be filled with a material having a high porosity, more specifically a material having a porosity higher than that of the electrode material. In any case, the internal passages of the distribution tubes must allow the electrolyte to flow along the tubes at a low pressure differential, preferably along the entire length of the tubes. Figure 2C and Figure 2D As shown, the wall 56 of the distribution tube may include a plurality of holes 58 that allow electrolyte to flow from the internal passage to the electrode material, such as Figure 2C and Figure 2D As shown by arrow D in the figure, the electrolyte is distributed on the electrode material or the electrolyte flows from the electrode material to the inside of the distribution tube, such as Figure 2C The holes 58 may be evenly distributed along the length of the tube to allow for even distribution of electrolyte over the electrode material, or as will be readily appreciated by one skilled in the art, the density of the holes may vary depending on the area of ​​the electrode material requiring more or less electrolyte. Alternatively, the wall 56 of the distribution tube 46 may be a porous sleeve having pores the size of which allow the electrolyte to flow through the sleeve at a higher pressure differential than that existing in the internal passage.

[0127] like Figure 2CAs shown, the ends of the distribution tubes are sealed in holes 45 of frame 44 to prevent any electrolyte flow except for the dedicated paths through distribution tubes 41 and 43. The electrolyte flows through the open inlet of distribution tube 41 and through the internal passage 54 of the tube, and is distributed to the electrode material through holes 58 as shown by arrow D, reaches distribution tube 43 within the electrode material placed near distribution tube 41, and enters the internal passage of distribution tube 43 through holes 58 provided in the tube wall as shown by arrow E. Due to the lower pressure difference between the ends of the distribution tubes, the electrolyte flows to the outlet 43B of the distribution tube and flows into the electrolyte exhaust stream 50B, returning to the electrolyte tank.

[0128] Those skilled in the art will recognize that the dimensions of the distribution tube, the dimensions of the internal passage, and the dimensions of the holes in the walls of the distribution tube, or the porosity of the material occupying the internal passage and the porosity of the wall material, respectively, are calculated to allow electrolyte to flow through the internal passage with a low pressure differential and to allow electrolyte to flow into the electrode material.

[0129] exist Figure 2A and Figure 2B In the embodiment, the distribution tubes are shown as being evenly distributed along the entire surface of the electrode material and across the entire area of ​​the electrode assembly. It should be understood that although the same frequency and spacing between the distribution tubes are generally preferred for achieving and making the electrolyte flow evenly through the porous electrode material, in some other embodiments, the frequency and spacing between the distribution tubes may vary. For example, when a non-uniform electrolyte distribution is preferred, the distribution tubes do not span the entire area of ​​the electrode material. Also in the current illustration of this embodiment, all tubes are presented as having the same size (e.g., cross-section). In other embodiments, each distribution tube may have a different cross-sectional size, or some distribution tubes may have different cross-sectional sizes. Similarly, some distribution tubes may have a wall material with more holes or more holes than other distribution tubes.

[0130] Figure 3 A second embodiment of the present invention is shown. In this embodiment, the electrode assembly 140 includes a porous electrode material 142 surrounded by a frame 144 and a Figure 2B The distribution tube 146 is completely embedded in the electrode material in a similar manner to the distribution tube shown in FIG. Figure 3 Only four distribution tubes 146 are shown. Those skilled in the art will readily appreciate that a greater number of distribution tubes may be used, and that the distribution tubes may be evenly distributed over the entire surface of the electrode material, or their density and frequency may vary from one region of the electrode assembly to another region depending on the desired electrolyte distribution.

[0131] exist Figure 3In FIG. 1 , the electrode assembly 140 is shown in an operational state as it would be used in a flow battery and, more specifically, in fluid communication with an electrolyte supply and exhaust. Figure 3 As shown, a distribution pipe 141 has an inlet 141A leading to the electrolyte supply flow 150A and an outlet 141B leading to the electrode material and not connected to the discharge fluid of the electrolyte 150B. The adjacent distribution pipe 143 has an inlet 143A leading to the electrode material and an outlet 143B connected to the discharge fluid of the electrolyte 150B. As in the aforementioned embodiment, the distribution pipe 146 has a wall and an internal passage, the only difference being that, in this second embodiment, the wall of the distribution pipe does not have to be provided with a hole or pore that allows the electrolyte flow path tubular wall. As shown by the arrow, when the electrolyte leaves through the outlet of the tube located in the electrode material, the electrolyte is distributed on the electrode material. The electrolyte then enters a tube in the nearby tube, which has an inlet leading to the electrode material and leaves the distribution pipe by the end of the tube connected to the electrolyte discharge flow. In this arrangement, compared with the solution of providing a unique branch length with the supply / discharge channel in the frame in the prior art, the current branch length is almost entirely arranged in the electrode assembly.

[0132] In some other embodiments, the distribution tube 146 may be provided with holes or walls of higher porosity, preferably towards the end of the tube that opens into the electrode material, as desired.

[0133] In some embodiments, the end of the distribution tube 146 connected to the electrode frame can protrude to the outside of the frame through the hole 145. Figure 3 As shown, the length of the distribution tubes may vary. Some tubes may have equal lengths (eg, l1 = l2), while other tubes may have different lengths (eg, l1 may be different from l3 and different from l4).

[0134] Figure 3 The electrode assembly shown in has a midpoint line CC. In a preferred embodiment, the distribution tube 146 extends beyond the midline for better distribution of the electrolyte over the electrode material.

[0135] In all embodiments of the present disclosure, the frame of the electrode assembly may be an injection molded frame provided with holes to allow the distribution tube to pass through the electrode material.

[0136] Figure 4 Another embodiment of the present invention is shown. Figure 4Only two distribution tubes are shown, but those skilled in the art will readily appreciate that in other embodiments, more than two distribution tubes may be provided. Distribution tube 241 has a serpentine shape with an inlet 241A connected to electrolyte supply stream 250A and a sealed outlet 241B, and distribution tube 243 also has a serpentine shape with a sealed inlet 243A and an outlet 243B leading to electrolyte exhaust stream 250B. In this embodiment, as described with respect to Figure 2A and Figure 2B As discussed, the distribution tube is provided with holes or apertures in the tube wall and, for ease of manufacture, is provided by combining the following Figure 6C and Fig.6D A further approach is presented in which the tubes are only partially embedded in the electrode material.

[0137] exist Figure 3 In the alternative embodiment shown, the distribution pipe 146 with an inlet or outlet to the electrode material can also have a similar Figure 4 The serpentine shape shown.

[0138] In all the embodiments presented herein, the dispensing tube may have a circular cross-sectional shape or may have any other shape, e.g. Fig. 6A The triangular shape shown in .

[0139] Figure 5 Demonstrates the manufacture of a Figure 2A , Figure 2C and Figure 3 Method of electrode assembly of the illustrated embodiment: The dispensing tube 46 is inserted into the porous electrode material 42 through the hole 45 provided in the frame 44 using the positioning pin 53 .

[0140] In the first step of the method, the electrode material 42 is placed in the frame 44, and then the positioning pins 53 are inserted through the holes 45 from either side of the frame and through the electrode material to reach the holes 45 on the opposite side of the frame. In the next step, the distribution tube 46 slides through the holes 45 and through the holes set in the electrode material by inserting the positioning pins. These pins help position the distribution tube in the electrode material and in the holes of the frame. Next, the distribution tube is seal welded relative to the holes in the frame, and some inlets / outlets of the distribution tube are sealed to prevent any fluid communication with the electrolyte in the operating liquid flow battery.

[0141] The dispensing tube may be made of, for example, polypropylene (PP) or polyethylene (PE), which are low-cost materials and can be easily sealed into the frame edge, which reduces the cost of the overall manufacturing process.

[0142] Fig. 6A , Figure 6B , Figure 6C and Fig.6DAnother embodiment of an electrode assembly and a method for manufacturing the same according to the present invention are presented. Fig. 6A and Figure 6B The embodiment shown in Figure 2A and Figure 2C , except that the distribution tube 346 has a triangular cross-section and is only partially embedded in the electrode material, as further explained herein. The distribution tube 346 is preferably provided with holes 358 along its entire length, such as Fig. 6A Detailed description, and although not shown, for Figure 6B , Figure 6C and Fig.6D The distribution tubes 341 and 343 in the embodiment are further suggested. Some of the distribution tubes 341 have an inlet 341A and a sealed outlet 341B that are fluidly connected to an electrolyte inlet channel 351A provided in the electrode frame 344 (and respectively to an electrolyte supply channel 350A in an operating flow battery), while other distribution tubes 343 have a sealed inlet 343A and an outlet 343B that are fluidly connected to an electrolyte discharge channel 351B provided in the electrode frame 344 (and respectively to an electrolyte discharge channel 350B in an operating flow battery). Electrolyte is supplied to the electrode assembly through the electrolyte supply channel 350A, which is fluidly connected to an electrolyte storage tank in the flow battery, and electrolyte is discharged from the electrode assembly back to the electrolyte storage tank through the electrolyte discharge channel 350B.

[0143] Figure 6B The manufacturing method of the embodiment is Figure 6C and Fig.6D As shown in Figure 6B As shown, the distribution tubes 346 are first connected to the frames 344, and then the components of the battery pack are arranged one above the other on a flat surface so that each assembly consisting of the distribution tubes and the frames to which these distribution tubes are connected is connected to and placed next to the electrode material 342, which is separated by the separator 359, and each frame 344 with a distribution tube 346 is separated from the next frame with a distribution tube by a bipolar plate 360. Figure 6C The uncompressed battery cell group 370 so formed is shown in FIG.

[0144] The next step includes compressing the battery cell group 370 so that the distribution tube 346 is pressed from the top to the bottom into the electrode material 342, as shown in FIG. Fig.6D as demonstrated and ensures good connections between battery cell group components.

[0145] like Fig.6D As shown, in this embodiment, in the compressed battery cell stack, the distribution tube is only partially embedded in the electrode material, whereby the surface of the distribution tube indicated by reference numeral 380 is in contact with the bipolar plate and is not surrounded by the electrode material.

[0146] Figure 6C and Fig.6D The fabrication method presented is particularly recommended for embodiments such as Figure 4 The illustrated embodiments include serpentine distribution tubes that would be difficult to assemble using the previous manufacturing methods described herein.

[0147] Fig. 7A and Figure 7B Systems and methods for compressing and sealing a flow battery cell group in a flow battery are shown. The battery may include, for example, a flow battery having an electrode assembly having a configuration described in an embodiment of the present invention. The system uses a cylindrical plastic shell 90 encapsulating a flow battery cell group 92, and is provided with two end plates 91 and an end plate 95, the cylindrical plastic shell and the end plate holding the flow battery cells in the flow battery cell group together while sealing all flow battery cell group components. The cylindrical plastic shell compresses the flow battery cell group in a radial direction, while the end plate compresses the flow battery cell group in an axial direction. Although the cylindrical plastic shell 90 is shown as having a circular internal cross-section, it will be readily understood by those skilled in the art that such an internal cross-section may be modified as long as the inner surface of the cylindrical plastic shell contacts the corners or edges of the flow battery cell group. In addition, even though the flow battery cell group shown here has a square shape, other flow battery cell groups may also have different shapes (e.g., rectangular).

[0148] The four corners of the liquid flow battery cell group are sealed relative to the inner surface of the cylindrical shell 90 with a seal 93 to form four sealed compartments 95A, 95B, 95C and 95D between the liquid flow battery cell group and the inner surface of the cylindrical plastic shell. Compartment 95A and compartment 95B represent, for example, a positive electrolyte supply compartment and a positive electrolyte discharge compartment, respectively, and compartment 95C and compartment 95D represent a negative electrolyte supply compartment and a negative electrolyte discharge compartment, respectively. Although this compression system works better for a liquid flow battery cell group including electrodes having the structure described in the present invention, it can also be used with a liquid flow battery cell group having a known structure in the prior art. The compression system is particularly compatible with liquid flow battery cells having an electrode assembly, in which the battery cell inlet / outlet branch length is generated by a distribution tube within the electrode material, as shown in the embodiments described herein, where such battery cell branch length does not need to be accommodated in the electrode frame periphery.

[0149] The material of the plastic cylindrical shell 90 and the end plates 91 and 95 of the present compression system has the same or approximately the same thermal expansion coefficient as the material of the electrode frame 94. Since the cylindrical plastic shell has the same or approximately the same thermal expansion coefficient as the frame, the cylindrical plastic shell provides a good seal at the corners of the flow battery pack at various operating temperatures, and since both the cylindrical plastic shell and the end plates have the same or approximately the same thermal expansion coefficient as the frame, there is no need to use tie rods and springs commonly used in the prior art to compensate for different thermal expansion coefficients while maintaining compression of the flow battery pack. In the present compression system, the compression of the flow battery cells remains constant over the typical storage and operating temperature range of the flow battery cell pack (e.g., which can vary between -40 degrees and 70 degrees).

[0150] Another advantage of the present compression system is that the four sealed compartments formed between the cylindrical plastic shell and the flow battery cell stack frame can contain any internal leaks between frames in the flow battery cell stack or between frames and other components of the flow battery cells (e.g., diaphragms, bipolar plates, electrode materials).

[0151] The above-described compression system may be used in flow batteries, where the compression forces required to act on the flow battery cells in the flow battery cell stack are typically much lower than, for example, fuel cells.

[0152] Figure 7B , showing how a flow battery cell stack 92 is slid within a cylindrical plastic housing 90, and the resulting assembly is then positioned between end plates 91 and 95 and assembled together.

[0153] The distribution tube of the present invention can be made of any non-conductive material that is compatible with the electrolyte chemistry. For example, for vanadium flow batteries, the distribution tube can be made of low-cost materials such as polypropylene (PP) or polyethylene (PE) and can be easily sealed into the frame edge. Other materials for the distribution tube can be polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethyl vinyl acetate (EVA), PE copolymers, UHMW PE, thermoplastic polyurethane, polyethersulfone, polycarbonate and polycarbonate alloys, etc. Examples of commercial tubes that can be used in this application are plastic porous tubes used in medical or industrial filtration systems, such as those made of or Parker Production of plastic porous pipes.

[0154] In all embodiments presented herein, the electrode material is porous, but can have a uniform porosity throughout its volume, or the porosity of the electrode material can vary with specific regions of the electrode material having a higher porosity than other regions to promote electrochemical reactions in those specific regions.

[0155] In the embodiments described herein, the distribution tube is completely embedded in the electrode material, which is interpreted to mean that the distribution tube is completely surrounded by the electrode material, such as Figure 2A and Figure 2B , or may be partially embedded in the electrode material, which is interpreted to mean that at least a portion of the tube surface is not surrounded by the electrode material and is exposed to the bipolar plates but not to the electrode material in the assembled stack, such as Figure 6B and Figure 6C As shown in .

[0156] Throughout this disclosure, the electrode frame is shown as a rectangular shape with right angles. Those skilled in the art will readily appreciate that in other embodiments, the electrode frame may have other shapes, such as a rectangular shape with rounded corners, etc. In some figures, the electrode material (e.g., 42, 142, 242) is not shown as a porous material, but those skilled in the art will appreciate that this is for the purpose of simplifying the drawings, and in all figures, the implied porous electrode material is shown as Fig.6D The electrode material 342 in.

[0157] In all of the embodiments described herein, the separator separating the negative electrode assembly and the positive electrode assembly in the flow battery cell of the battery can be a microporous separator or an ion exchange membrane.

[0158] In all embodiments described herein, the bipolar plates separating the electrodes are not provided with a frame and / or features for circulating, directing or regulating the flowing electrolyte as described in some prior art documents, because the electrolyte circulation is achieved by the distribution tubes fully or partially embedded in the electrode material. The bipolar plates presented in the present invention only have the function of separating the distribution tubes and / or the electrodes, while being conductive.

[0159] An example of a flow battery according to the present invention is a vanadium flow battery, which is a rechargeable flow battery that uses vanadium ions in different oxidation states to store chemical potential energy.

[0160] An advantage of the present invention is that an electrode assembly having the construction described herein provides improved electrolyte distribution with low pressure drop across the electrode material and provides shunt current control without requiring additional frame area or material to accommodate extended branch lengths. The electrode assembly of the present invention is easy to manufacture, does not require some high tolerance positioning and / or attachment of the electrodes relative to the electrolyte distribution channels, does not require the bipolar plates to be permanently attached or bonded to the plastic battery cell frame as in the prior art, but uses low-cost materials and manufacturing techniques suitable for mass production. In addition, in the design disclosed in the present invention, due to the positioning and design of the distribution tubes within the electrode material, the electrolyte flow rate and reaction rate may be increased, and the electrode properties (porosity, electrolyte distribution, etc.) can be changed to achieve higher energy efficiency and current density than solutions known in the prior art.

[0161] Although specific elements, embodiments and applications of the present invention have been shown and described, it should be understood that the present invention is certainly not limited thereto, as modifications may be made by those skilled in the art without departing from the spirit and scope of the present disclosure, especially in light of the foregoing teachings. Such modifications should be considered to be within the purview and scope of the appended claims.

Claims

1. A flow battery comprising a group of flow battery cells separated by bipolar plates, each flow battery cell comprising a positive electrode assembly and a negative electrode assembly separated by a separator, each electrode assembly having a porous electrode material surrounded by a frame, wherein: The liquid flow battery cell group is enclosed in a cylindrical plastic shell provided with two end plates, the liquid flow battery cell group is connected to the inner wall of the cylindrical plastic shell, and wherein the cylindrical plastic shell and the two end plates are made of non-conductive material, and the cylindrical plastic shell compresses the liquid flow battery cells in the radial direction, and the two end plates compress the liquid flow battery cells in the axial direction, Wherein, the liquid flow battery cell group has a rectangular outer shape, and its corners are connected to the inner surface of the cylindrical plastic shell to form four compartments between the liquid flow battery cell group and the cylindrical plastic shell, and wherein the corners of the liquid flow battery cell group are connected to the inner wall of the cylindrical plastic shell through seals to form four sealed compartments between the liquid flow battery cell group and the cylindrical plastic shell for allowing positive electrode electrolyte and negative electrode electrolyte to flow therethrough.

2. The flow battery according to claim 1, wherein: The material of the cylindrical plastic housing and the end plates has approximately the same coefficient of thermal expansion as the material of the frame.

3. The flow battery according to claim 2, wherein: The material of the frame, the cylindrical plastic housing and the end plates is polyethylene or polypropylene.

4. The flow battery according to any one of claims 1 to 3, wherein: The flow battery does not include tie rods and springs.

5. A method for manufacturing a flow battery according to any one of claims 1 to 4, comprising the following steps: a. Provide a cylindrical plastic shell and two end plates; b. placing the liquid flow battery cell group in the cylindrical plastic housing so that the liquid flow battery cell is connected to the inner wall of the cylindrical plastic housing and the cylindrical plastic housing compresses the liquid flow battery cell in a radial direction; as well as c. Compressing the flow battery cell stack in the axial direction between the two end plates.

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