Battery module

Abstract

Provided is a battery module capable of suppressing decreases in battery performance. The battery module comprises: a monoblock housing; a plurality of electrode stacks that are vertically accommodated in the monoblock housing and each include a positive electrode plate, a positive electrode tab lead, a negative electrode plate, a negative electrode tab lead, and a hydroxide ion conductive separator; a plurality of connection terminals whereby adjacent electrode stacks among the plurality of electrode stacks are connected in series; and an electrolyte solution. The monoblock housing has a bottom section, a pair of long side wall sections, a pair of short side wall sections, a plurality of partition walls, and a lid section. A plurality of ribs in contact with the positive electrode plates or the negative electrode plates are provided spaced apart from each other on both surfaces of each of the partition walls. A positive electrode contact area ratio which is the ratio of the contact area between the positive electrode plates and the plurality of ribs to the plan view area of the positive electrode plates and / or a negative electrode contact area ratio which is the ratio of the contact area between the negative electrode plates and the plurality of ribs to the plan view area of the negative electrode plates are each 20% or more.

Description

Battery module

[0001] The present disclosure relates to a battery module.

[0002] In order to obtain high voltage and large current, stacked batteries made by combining a plurality of single cells are widely adopted. A stacked battery has a configuration in which a stack of a plurality of single cells connected in series or parallel is housed in one battery container. For example, Patent Document 1 (WO2017 / 086278) discloses a zinc secondary battery in which a plurality of electrode cartridges provided with electrodes and separators are housed in a sealed container.

[0003] Further, in order to achieve further increased capacity and higher output, it is also common to modularize a battery module by arranging a plurality of battery units incorporating stacked batteries. For example, Patent Document 2 (WO2018 / 173110) discloses a battery module in which a plurality of rectangular parallelepiped battery units are housed in a frame structure. In the battery unit, it is preferable that single cells of a plurality of alkaline secondary batteries (for example, nickel-zinc secondary batteries and zinc-air secondary batteries) are housed in the form of an assembled battery or a battery module.

[0004] In a battery module in which a plurality of battery units such as zinc secondary batteries are arranged, it is known that each battery unit expands due to charge and discharge, and a battery module having a structure capable of pressurizing the battery unit has been proposed to suppress such expansion. For example, Patent Document 3 (WO2021 / 024664) discloses a battery module including a metal module housing having a closed internal space and a plurality of secondary batteries (for example, nickel-zinc secondary batteries) having a vertically long shape that are housed vertically in the internal space and juxtaposed parallel to each other. According to Patent Document 3, by bringing a shielding plate into contact with both ends or one end of a group of juxtaposed secondary batteries, the secondary batteries can be pressurized from the outside to maximize battery performance.

[0005] Incidentally, in the field of sealed lead-acid batteries, a battery case is used which is manufactured by integrally molding resin or the like and has a monoblock structure in which multiple cell chambers are partitioned by partition walls. For example, Patent Document 4 (Japanese Patent No. 3807206) discloses a sealed lead-acid battery in which a monoblock battery case divided into 19 or more cell chambers houses cells having a positive electrode, a negative electrode, and a separator in each cell chamber.

[0006] WO2017 / 086278WO2018 / 173110WO2021 / 024664 Patent No. 3807206 Publication WO2013 / 118561WO2016 / 076047WO2016 / 067884WO2019 / 069762WO2020 / 255856

[0007] In modularized zinc secondary batteries, applying a monoblock housing structure offers advantages in terms of reducing the number of parts and lightening the module. However, when such a monoblock housing is manufactured by integral molding (e.g., injection molding), ribs are often formed on the internal partition walls of the housing for ease of molding. In zinc secondary batteries, it is desirable to suppress expansion by applying external pressure to the electrodes. When using a monoblock housing, the contact area between the partition wall and the electrodes is limited to the locations where ribs are present. As a result, the pressure applied to the electrodes may become uneven, potentially degrading battery performance.

[0008] The present inventors have now discovered that by housing multiple electrode stacks as single cell elements within a single monoblock housing and connecting them in series, and by bringing ribs provided on the partition wall of the monoblock housing into contact with the positive and / or negative electrode plates at a predetermined area ratio, it is possible to suppress the degradation of battery performance.

[0009] Therefore, an object of the present invention is to provide a battery module that can suppress the deterioration of battery performance.

[0010] The following aspects are provided according to this disclosure. [Aspect 1] A monoblock housing, a plurality of vertically elongated electrode stacks housed vertically within the monoblock housing and arranged parallel to each other, wherein each of the electrode stacks includes: a positive electrode plate including a positive electrode active material layer and a positive electrode current collector, a positive electrode tab lead extending from the end of the positive electrode plate, a negative electrode plate provided opposite the positive electrode plate and including a negative electrode active material layer and a negative electrode current collector, a negative electrode tab lead extending from the end of the negative electrode plate at a position not overlapping with the positive electrode tab lead, and a hydroxide ion conductive separator that isolates the positive electrode plate and the negative electrode plate in a manner that allows hydroxide ions to conduct; a plurality of connection terminals for connecting adjacent electrode stacks in the plurality of electrode stacks in series via the positive electrode tab lead and / or the negative electrode tab lead; and an electrolyte filled within the monoblock housing in which the electrode stacks are immersed. The monoblock housing has a bottom, a pair of longitudinal side walls parallel to the stacking direction of the electrode stack, a pair of short side walls perpendicular to the stacking direction of the electrode stack, a plurality of partitions provided parallel to the pair of short side walls and dividing the internal space of the monoblock housing into a plurality of compartments capable of accommodating the plurality of electrode stacks spaced apart from each other, a plurality of ribs spaced apart from each other are provided on both sides of each partition to contact the positive electrode plate or the negative electrode plate, and the positive electrode contact area ratio, which is the ratio of the contact area between the positive electrode plate and the plurality of ribs to the planar area of ​​the positive electrode plate, and / or the negative electrode contact area ratio, which is the ratio of the contact area between the negative electrode plate and the plurality of ribs to the planar area of ​​the negative electrode plate, is 20% or more. [Aspect 2] The battery module according to aspect 1, wherein the positive electrode contact area ratio and / or the negative electrode contact area ratio is 50% or less. [Aspect 3] The battery module according to aspect 1 or 2, wherein the plurality of ribs are arranged parallel to each other in the vertical direction. [Aspect 4] The battery module according to any one of aspects 1 to 3, wherein the plurality of ribs are arranged at equal intervals from each other.[Aspect 5] A battery module according to any one of aspects 1 to 4, wherein the number of ribs on each face of the partition wall is 8 or more. [Aspect 6] A battery module according to any one of aspects 1 to 5, wherein each of the ribs has a width of 5 to 15 mm. [Aspect 7] A battery module according to any one of aspects 1 to 6, wherein each of the ribs has a height of 0.2 to 3.0 mm. [Aspect 8] A battery module according to any one of aspects 1 to 7, wherein the tops of the ribs form a flat surface. [Aspect 9] A battery module according to any one of aspects 1 to 8, wherein the plurality of electrode stacks are not housed in individual single cell cases, but are housed in the plurality of compartments in an exposed state.

[0011] Figure 1 is a perspective view showing an example of a battery module of the present invention. Figure 1 is a schematic cross-sectional view of the battery module shown. Figure 1 is a perspective view showing the internal structure of the monoblock housing in the battery module shown. Figure 1 is a perspective view showing an example of multiple electrode stacks connected in series in the battery module shown. Figure 4 is a schematic perspective view showing the specific configuration of the electrode stack shown. Figure 4 is a schematic cross-sectional view showing the specific configuration of the electrode stack shown. Figure 4 is a perspective view showing an example of a positive electrode plate or negative electrode plate in the electrode stack shown. Figure 7 is a perspective view showing a positive electrode plate or negative electrode plate covered with a hydroxide ion conductive separator or liquid-retaining member. Figure 1 is a schematic top view showing the configuration of the nickel-zinc secondary battery made in Example 1. Figure 2 is a schematic top view showing the configuration of the nickel-zinc secondary battery made in Example 2. Figure 3 is a graph showing the initial charge and discharge capacities measured for the nickel-zinc secondary batteries of Examples 1 to 5. Figure 4 is an image of the appearance of the negative electrode plate in the fully charged state in the nickel-zinc secondary battery of Example 1. Figure 4 is an image of the appearance of the negative electrode plate in the fully charged state in the nickel-zinc secondary battery of Example 2.

[0012] Figures 1 to 4 show one embodiment of the battery module of the present invention. The battery module 10 shown in Figures 1 to 4 comprises a monoblock housing 12, a plurality of electrode stacks 14, a plurality of connection terminals 30, and an electrolyte 34. The plurality of electrode stacks 14 are housed vertically within the monoblock housing 12 and are arranged parallel to each other. The electrode stacks 14 have an elongated shape, that is, when the electrode stack is viewed in cross-section, the length in the height direction (height H shown in Figure 4) is longer than the length in the thickness direction (thickness T shown in Figure 4). As shown in Figures 5 to 8, each of the electrode stacks 14 includes a positive electrode plate 16, a positive electrode tab lead 18, a negative electrode plate 20, a negative electrode tab lead 22, and a hydroxide ion conductive separator 24. Details of each element constituting the electrode stack 14 will be described later. The connection terminals 30 connect adjacent electrode stacks in the plurality of electrode stacks 14 in series via the positive electrode tab lead 18 and / or the negative electrode tab lead 22. The electrolyte 34 is filled into the monoblock housing 12, and the electrode stack 14 is immersed in it. The monoblock housing 12 has a bottom portion 12a, a pair of longitudinal side walls 12b parallel to the stacking direction of the electrode stack 14, a pair of short side walls 12c perpendicular to the stacking direction of the electrode stack 14, a lid portion 12d, and a plurality of partition walls 12e. As shown in Figure 3, the plurality of partition walls 12e are provided parallel to the pair of short side walls 12c, and divide the internal space of the monoblock housing 12 into a plurality of compartments capable of accommodating the plurality of electrode stacks 14 spaced apart from each other. A plurality of ribs 12f that contact the positive electrode plate 16 or the negative electrode plate 20 are provided spaced apart from each other on both sides of each partition wall 12e. Furthermore, the positive electrode contact area ratio, which is the ratio of the contact area between the positive electrode plate 16 and the plurality of ribs 12f to the planar area of ​​the positive electrode plate 16, and / or the negative electrode contact area ratio, which is the ratio of the contact area between the negative electrode plate 20 and the plurality of ribs 12f to the planar area of ​​the negative electrode plate 20, are 20% or more. In this specification, the positive electrode plate and / or the negative electrode plate may be referred to as "electrodes," and the positive electrode contact area ratio and / or the negative electrode contact area ratio may be referred to as "electrode contact area ratio."In this way, by housing multiple electrode stacks 14 as single cell elements within a single monoblock housing 12 and connecting them in series, and by bringing the ribs 12f provided on the partition wall 12e of the monoblock housing into contact with the positive electrode plate 16 and / or negative electrode plate 20 at a predetermined area ratio, a decrease in battery performance can be suppressed.

[0013] As mentioned above, applying a monoblock housing structure to a modularized zinc secondary battery offers advantages in terms of reducing the number of parts and lightening the module. On the other hand, when such a monoblock housing is manufactured by integral molding (e.g., injection molding), ribs are often formed on the internal partition walls of the housing for ease of molding. In zinc secondary batteries, however, the electrodes can expand due to charging and discharging, which can degrade battery performance. Therefore, it is desirable to suppress the expansion by applying external pressure to the electrodes. In the case of a monoblock housing, the contact area between the partition wall and the electrodes is limited to the locations where ribs are present. In particular, the ribs that are inevitably formed on the partition walls are generally narrow, and the number of ribs per surface is small, resulting in a very small contact area between the ribs and the electrodes. As a result, the pressure applied to the electrodes becomes uneven, leading to uneven electrode reactions, which may reduce battery performance (e.g., initial charge / discharge capacity). This problem is unique to zinc secondary batteries and could not occur in sealed monoblock lead-acid batteries. In contrast, the battery module 10 of the present invention has a large electrode contact area ratio of 20% or more, which allows the electrodes to be uniformly pressurized by the ribs 12f. As a result, the electrode reaction becomes uniform, and it is believed that the deterioration of battery performance can be effectively suppressed. Furthermore, in the battery module 10, multiple electrode stacks 14 are not housed in individual single cell cases, but are instead housed in multiple compartments inside the monoblock housing 12 in an exposed state. This reduces the number of parts and makes the module lighter.

[0014] As described above, the monoblock housing 12 has a bottom portion 12a, a pair of longitudinal side walls 12b, a pair of transverse side walls 12c, a lid portion 12d, and a plurality of partition walls 12e, with ribs 12f provided on both sides of each partition wall 12e. In particular, it is preferable that the partition walls 12e, including the bottom portion 12a, longitudinal side walls 12b, transverse side walls 12c, and ribs 12f, form a single block structure as the main body that houses the electrode stack 14 and the electrolyte 34. That is, it is preferable that the main body is not assembled from multiple parts, but is a single molded product formed by a method such as injection molding. The size of the monoblock housing 12 can be determined according to the dimensions and number of electrode stacks 14 to be housed. Furthermore, it is preferable that ribs are also provided on the inner surface of the short side wall portion 12c, which allows for more effective pressurization of the electrodes that come into contact with the inner surface of the short side wall portion 12c, that is, the electrodes located on the outside of the electrode stacks 14 installed at both ends of the group of electrode stacks. The ribs provided on the inner surface of the short side wall portion 12c may be similar to the ribs 12f provided on the partition wall 12e.

[0015] The partition wall 12e divides the internal space of the monoblock housing 12 (i.e., the space in which the electrode stack 14 and electrolyte 34 are housed) into multiple compartments in which multiple electrode stacks 14 can be housed spaced apart from each other. The number of partition walls 12e can be determined according to the number of electrode stacks 14 to be housed. The thickness of each partition wall 12e is not particularly limited, but from the viewpoint of preventing deformation due to electrode expansion and effectively applying pressure, and from the viewpoint of integral moldability, it is preferably 2 to 8 mm, more preferably 2 to 5 mm.

[0016] The ribs 12f provided on the partition wall 12e are provided to equalize the pressure on the positive electrode plate 16 and / or the negative electrode plate 20, as described above. Therefore, the positive electrode contact area ratio and / or negative electrode contact area ratio described above are 20% or more, preferably 20 to 50%, more preferably 22 to 45%, and even more preferably 24 to 40% from the viewpoint of improving moldability during integral molding (e.g., injection molding). Each of the electrode stacks 14 may have a plurality of positive electrode plates 16 and a plurality of negative electrode plates 20, as will be described later. In this case, it is sufficient that the electrode contact area ratio between each of the electrodes located at both ends of the electrode stack 14 and the ribs 12f is within the above range. As an example, if the electrodes located at both ends of the electrode stack 14 are a positive electrode plate 16 and a negative electrode plate 20, respectively, it is desirable that both the positive electrode contact area ratio and the negative electrode contact area ratio are within the above range. As another example, if the number of negative electrode plates 20 is greater than the number of positive electrode plates 16, and as a result both electrodes located at both ends of the electrode laminate 14 are negative electrode plates 20, it is desirable that the negative electrode contact area ratio between one negative electrode plate 20 and the rib 12f, and the negative electrode contact area ratio between the other negative electrode plate 20 and the rib 12f, are both within the above range. Furthermore, contact between the rib 12f and the positive electrode plate 16 and / or negative electrode plate 20 may be indirect, via a hydroxide ion conductive separator 24 or a liquid-retaining member 28 described later. Note that if the positive electrode plate 16 and / or negative electrode plate 20 have an uncoated region U where no active material exists, as described later, the uncoated region U shall not be included in the calculation of the positive electrode contact area ratio and the negative electrode contact area ratio. In other words, the positive electrode contact area ratio means the ratio of the contact area between the positive electrode plate 16 (excluding the uncoated area U) and the multiple ribs 12f to the planar area of ​​the positive electrode plate 16 (excluding the uncoated area U), and the negative electrode contact area ratio means the ratio of the contact area between the negative electrode plate 20 (excluding the uncoated area U) and the multiple ribs 12f to the planar area of ​​the negative electrode plate 20 (excluding the uncoated area U).

[0017] The electrode contact area ratio can be controlled, for example, by adjusting the width and number of ribs 12f. From this viewpoint, each rib 12f preferably has a width of 5 to 15 mm, more preferably 6 to 13 mm, and even more preferably 7 to 11 mm. Each rib 12f preferably has a height of 0.2 to 3.0 mm, more preferably 0.3 to 2.5 mm, and even more preferably 0.4 to 2.0 mm. The number of ribs 12f per face of the partition wall 12e is preferably 8 or more, more preferably 8 to 12, and even more preferably 8 to 10.

[0018] As shown in Figure 3, it is preferable that multiple ribs 12f are provided parallel to each other in the vertical direction on each surface of the partition wall 12e, and it is more preferable that the multiple ribs 12f are provided at equal intervals from each other. This makes it possible to make the pressure on the electrodes even more uniform. Furthermore, it is preferable that the tops of the ribs 12f form flat surfaces, which increases the contact surface with the electrodes and makes it possible to apply pressure to the electrodes even more uniformly.

[0019] As shown in Figure 1, it is preferable that outer wall ribs 12g are provided on the outer surface of each short side wall portion 12c to reinforce the monoblock housing 12 and improve its strength. This makes it possible to further suppress the expansion of the electrodes. That is, when the electrodes expand, the short side wall portion 12c side of the monoblock housing corresponding to the main surface of the electrode stack 14 is pressed. In this respect, the monoblock housing 12 is reinforced by the outer wall ribs 12g provided on the outer surface of each short side wall portion 12c, thereby preventing deformation of the housing. As a result, expansion can be suppressed by pressurizing the electrode stack 14 with the monoblock housing 12 without using additional restraining parts or the like.

[0020] It is preferable that the outer wall ribs 12g are integrally molded together with the bottom portion 12a, the longitudinal side wall portion 12b, the transverse side wall portion 12c, and the partition wall 12e. From the viewpoint of improving the yield during the molding of the monoblock housing 12 (for example, during injection molding), it is preferable that the outer wall ribs 12g are provided on the outer surface of the transverse side wall portion 12c so as to form a repeating pattern of squares or hexagons when viewed from above, and more preferably so as to form a repeating pattern of hexagons. In particular, it is preferable that the outer wall ribs 12g are provided on the transverse side wall portion 12c so as to form a honeycomb pattern. Having such a three-dimensional structure for the outer wall ribs 12g makes it possible to further improve the strength of the housing while reducing its weight, and as a result, the expansion of the electrodes can be suppressed more effectively.

[0021] The height of the outer wall rib 12g is preferably 5 to 15 mm, more preferably 6 to 14 mm, and even more preferably 8 to 12 mm. The thickness of the outer wall rib 12g is preferably 2 to 10 mm, more preferably 3 to 9 mm, and even more preferably 4 to 8 mm. Furthermore, in each of the short side wall portions 12c, the ratio of the planar area occupied by the outer wall rib 12g to the planar area of ​​the short side wall portion 12c is preferably 10 to 40%, more preferably 15 to 40%, and even more preferably 20 to 40%. By controlling the shape of the outer wall rib 12g to fall within these ranges, it is possible to achieve a better balance between weight reduction and strength improvement of the monoblock housing 12.

[0022] The monoblock housing 12 is preferably made of an alkali-resistant material, and is particularly preferably made of an alkali-resistant resin from the viewpoint of integral moldability and weight reduction. Examples of resins that make up the monoblock housing 12 include polypropylene resin, polyolefin resin, ABS resin, and modified polyphenylene ether. The monoblock housing 12 (for example, the lid portion 12d) may also have a pressure relief valve for releasing gas inside the housing at a predetermined operating pressure or higher. The operating pressure of the pressure relief valve is preferably 50 kPa or less, which effectively prevents damage to the housing (especially a resin housing).

[0023] The configuration of the electrode stack 14 will be described below with reference to Figures 5 to 8. The electrode stack 14 shown in Figures 5 to 8 includes a positive electrode plate 16, a positive electrode tab lead 18, a negative electrode plate 20, a negative electrode tab lead 22, and a hydroxide ion conductive separator 24. The positive electrode plate 16 includes a positive electrode active material layer 16a and a positive electrode current collector 16b. The positive electrode tab lead 18 extends from the end of the positive electrode plate 16. The negative electrode plate 20 is provided opposite the positive electrode plate 16 and includes a negative electrode active material layer 20a and a negative electrode current collector 20b. The negative electrode active material layer 20a includes at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compounds. The negative electrode tab lead 22 extends from the end of the negative electrode plate 20 at a position that does not overlap with the positive electrode tab lead 18. The hydroxide ion conductive separator 24 isolates the positive electrode plate 16 and the negative electrode plate 20 in a manner that allows hydroxide ions to conduct. Typically, the positive electrode plate 16, the negative electrode plate 20, and the hydroxide ion conductive separator 24 are each quadrilateral in shape (typically square). The number of electrode stacks 14 housed in the monoblock housing 12 is not particularly limited, but is preferably six or more, and more preferably six to eight.

[0024] The electrode stack 14 is a stack containing multiple electrode layers. That is, as shown in Figures 5 and 6, the electrode stack 14 preferably has the configuration of a positive-negative electrode stack in which multiple positive electrode plates 16, multiple negative electrode plates 20, and multiple hydroxide ion conductive separators 24 are stacked in a repeating manner. That is, the electrode stack 14 preferably contains multiple unit cells 14a, each having a pair of positive electrode plates 16 and negative electrode plates 20 together with a hydroxide ion conductive separator 24, thereby forming a multilayer cell as a whole. This is the configuration of a so-called battery pack or stacked battery, which is advantageous in that high voltage and high current can be obtained. The electrode stack 14 preferably has the configuration of a nickel-zinc secondary battery, a silver-zinc secondary battery, a manganese-zinc secondary battery, or various other types of alkali-zinc secondary batteries.

[0025] The positive electrode plate 16 includes a positive electrode active material layer 16a. The positive electrode active material constituting the positive electrode active material layer 16a is not particularly limited and can be appropriately selected from known positive electrode materials depending on the type of zinc secondary battery. For example, in the case of a nickel-zinc secondary battery, a positive electrode containing nickel hydroxide and / or nickel oxyhydroxide may be used. In this case, the positive electrode active material layer 16a may also contain an additive which is at least one selected from the group consisting of silver compounds, manganese compounds, and titanium compounds, thereby promoting a positive electrode reaction that absorbs hydrogen gas generated by the self-discharge reaction. Furthermore, the positive electrode active material layer 16a may further contain cobalt. It is preferable that the cobalt is included in the positive electrode plate 16 in the form of cobalt oxyhydroxide. In the positive electrode active material layer 16a, cobalt functions as a conductive additive, thereby contributing to an improvement in charge-discharge capacity. Alternatively, in the case of an air-zinc secondary battery, an air electrode may be used as the positive electrode.

[0026] The positive electrode plate 16 further includes a positive electrode current collector 16b. A preferred example of the positive electrode current collector 16b is a porous nickel substrate such as a foamed nickel plate. In this case, for example, a positive electrode plate consisting of a positive electrode and a positive electrode current collector can be preferably manufactured by uniformly applying a paste containing an electrode active material such as nickel hydroxide onto the porous nickel substrate and drying it. At that time, it is also preferable to press the positive electrode plate (i.e., positive electrode / positive electrode current collector) after drying to prevent the electrode active material from falling off and to improve the electrode density. If the positive electrode current collector 16b is a porous nickel substrate such as a foamed nickel plate, the uncoated area of ​​the positive electrode current collector 16b may be processed into a tab shape by pressing it.

[0027] As shown in Figure 7, the positive electrode plate 16 may have an uncoated region U along its upper end where the positive electrode active material layer 16a is absent. In such a case, it is preferable that the positive electrode tab lead 18 is welded to the positive electrode current collector 16b in the uncoated region U, and that the insulating tape 26 is attached to the uncoated region U so that the welded portion W is covered with insulating tape 26. This makes it difficult for the tip of the positive electrode tab lead 18 to penetrate the hydroxide ion conductive separator 24 or the liquid retention member 28, and even if it does penetrate them and come into contact with the positive electrode plate 16, the insulating tape 26 functions as an insulating material, making a short circuit less likely.

[0028] The positive electrode tab lead 18 is preferably provided so as to extend upward from the end of the positive electrode plate 16. The positive electrode tab lead 18 is not particularly limited and can be made of commercially available thin metal. As shown in Figure 6, it is preferable that multiple positive electrode tab leads 18 are joined to a single connection terminal 30 or a member electrically connected to it to form a positive electrode tab joint 19. This allows for a simple configuration and space-efficient current collection, and also facilitates connection to the connection terminal 30. The joining of the positive electrode tab lead 18 to the positive electrode current collector 16b, connection terminal 30, and other members can be performed using known joining methods such as ultrasonic welding (ultrasonic bonding), laser welding, TIG welding, or resistance welding.

[0029] The negative electrode plate 20 includes a negative electrode active material layer 20a. The negative electrode active material constituting the negative electrode active material layer 20a includes at least one selected from the group consisting of zinc, zinc oxide, zinc alloys, and zinc compounds. Zinc may be included in any form of zinc metal, zinc compounds, or zinc alloys, as long as it has electrochemical activity suitable for a negative electrode. Preferred examples of negative electrode materials include zinc oxide, zinc metal, calcium zincate, etc., but a mixture of zinc metal and zinc oxide is more preferred. The negative electrode active material may be configured in a gel state, or it may be mixed with an electrolyte to form a negative electrode composite material. For example, a gelled negative electrode can be easily obtained by adding an electrolyte and a thickener to the negative electrode active material. Examples of thickeners include polyvinyl alcohol, polyacrylate, CMC, alginic acid, etc., but polyacrylic acid is preferred because it has excellent chemical resistance to strong alkalis.

[0030] As the zinc alloy, a mercury- and lead-free zinc alloy known as a mercury-free zinc alloy can be used. For example, a zinc alloy containing 0.01 to 0.1 mass% indium, 0.005 to 0.02 mass% bismuth, and 0.0035 to 0.015 mass% aluminum is preferred because it has a hydrogen gas generation suppression effect. In particular, indium and bismuth are advantageous in that they improve discharge performance. Using a zinc alloy as the negative electrode can improve safety by suppressing hydrogen gas generation through slowing the self-dissolution rate in an alkaline electrolyte.

[0031] The shape of the negative electrode material is not particularly limited, but it is preferably in powder form, as this increases the surface area and allows it to handle high-current discharge. The preferred average particle size of the negative electrode material is in the range of 3 to 100 μm in the short diameter for zinc alloys. Within this range, the surface area is large, making it suitable for handling high-current discharge, and it is also easy to uniformly mix with the electrolyte and gelling agent, resulting in good handling during battery assembly.

[0032] The negative electrode plate 20 further includes a negative electrode current collector 20b. The negative electrode active material layer 20a may be arranged on both sides of the negative electrode current collector 20b, or the negative electrode active material layer 20a may be arranged on only one side of the negative electrode current collector 20b. From the viewpoint of fixing the negative electrode active material to the current collector, it is preferable to use a metal plate having multiple (or many) openings for the negative electrode current collector 20b. Preferred examples of such a negative electrode current collector 20b include expanded metal, perforated metal, metal mesh, and combinations thereof, more preferably copper expanded metal, copper perforated metal, and combinations thereof, and particularly preferably copper expanded metal. In this case, for example, a negative electrode plate consisting of a negative electrode / negative electrode current collector can be preferably manufactured by coating a mixture containing zinc oxide powder and / or zinc powder, and optionally a binder (e.g., polytetrafluoroethylene particles), onto copper expanded metal. In this process, it is also preferable to press the dried negative electrode plate (i.e., negative electrode / negative electrode current collector) to prevent the electrode active material from falling off and to improve electrode density. Expanded metal is a mesh-like metal sheet made by expanding a metal sheet using an expansion machine, which cuts the sheet in a staggered pattern, and then shaping the cuts into a diamond or tortoise shell pattern. Perforated metal, also known as perforated metal, is a metal sheet with holes punched into it. Metal mesh is a metal product with a wire mesh structure and is different from expanded metal and perforated metal.

[0033] As shown in Figure 7, the negative electrode plate 20 may have an uncoated region U along its upper end where the negative electrode active material layer 20a is absent. In such a case, it is preferable that the negative electrode tab lead 22 is welded to the negative electrode current collector 20b in the uncoated region U, and that the insulating tape 26 is attached to the uncoated region U so that the welded portion W is covered with insulating tape 26. This makes it difficult for the tip of the negative electrode tab lead 22 to penetrate the hydroxide ion conductive separator 24 or the liquid retention member 28, and even if it does penetrate them and come into contact with the negative electrode plate 20, the insulating tape 26 functions as an insulating material, making a short circuit less likely.

[0034] The negative electrode tab lead 22 is preferably provided so as to extend upward from the end of the negative electrode plate 20 at a position that does not overlap with the positive electrode tab lead 18 (see Figure 5). The negative electrode tab lead 22 is not particularly limited and can be made of commercially available thin metal. As shown in Figure 6, it is preferable that multiple negative electrode tab leads 22 are joined to a single connection terminal 30 or a member electrically connected thereto to form a negative electrode tab joint 23. This allows for current collection with a simple configuration and space efficiency, and also facilitates connection to the connection terminal 30. The joining of the negative electrode tab lead 22 to the negative electrode current collector 20b, connection terminal 30, and other members can be performed using known joining methods such as ultrasonic welding (ultrasonic bonding), laser welding, TIG welding, or resistance welding.

[0035] The hydroxide ion conductive separator 24 is provided to isolate the positive electrode plate 16 and the negative electrode plate 20 in a manner that allows hydroxide ions to conduct. For example, as shown in Figure 8, the positive electrode plate 16 and / or the negative electrode plate 20 (preferably the negative electrode plate 20) may be covered or enclosed by the hydroxide ion conductive separator 24. This eliminates the need for complicated sealing and bonding between the hydroxide ion conductive separator 24 and the housing, making it possible to manufacture zinc secondary batteries and their stacked batteries that can prevent zinc dendrite extension very simply and with high productivity. However, a simpler configuration in which the hydroxide ion conductive separator 24 is arranged on one side of the positive electrode plate 16 or the negative electrode plate 20 is also acceptable.

[0036] The hydroxide ion conductive separator 24 is not particularly limited as long as it is a separator capable of separating the positive electrode plate 16 and the negative electrode plate 20 in a manner that allows hydroxide ions to conduct, but typically it is a separator that contains a hydroxide ion conductive solid electrolyte and selectively passes hydroxide ions by exclusively utilizing its hydroxide ion conductivity. A preferred hydroxide ion conductive solid electrolyte is a layered double hydroxide (LDH) and / or an LDH-like compound. Therefore, it is preferable that the hydroxide ion conductive separator 24 is an LDH separator. In this specification, "LDH separator" is defined as a separator containing LDH and / or an LDH-like compound that selectively passes hydroxide ions by exclusively utilizing the hydroxide ion conductivity of the LDH and / or LDH-like compound. In this specification, "LDH-like compound" is a hydroxide and / or oxide with a layered crystalline structure similar to LDH, which may not be called LDH, and can be considered an equivalent of LDH. However, in a broader sense, "LDH" can also be interpreted as encompassing not only LDH but also LDH-like compounds. The LDH separator is preferably compounded with a porous substrate. Therefore, the LDH separator is preferably compounded with the porous substrate in a form in which LDH and / or LDH-like compounds fill the pores of the porous substrate. That is, in a preferred LDH separator, the LDH and / or LDH-like compounds block the pores of the porous substrate so as to exhibit hydroxide ion conductivity and gas impermeability (and thus function as an LDH separator exhibiting hydroxide ion conductivity). The porous substrate is preferably made of a polymer material, and it is particularly preferable that the LDH is incorporated throughout the entire thickness of the polymer material porous substrate. For example, known LDH separators such as those disclosed in Patent Documents 5 to 9 can be used. The thickness of the LDH separator is preferably 5 to 100 μm, more preferably 5 to 80 μm, even more preferably 5 to 60 μm, and particularly preferably 5 to 40 μm.

[0037] It is preferable that not only a hydroxide ion conductive separator 24 but also a liquid-retaining member 28 is interposed between the positive electrode plate 16 and the negative electrode plate 20. Furthermore, as shown in Figure 8, it is preferable that the positive electrode plate 16 and / or the negative electrode plate 20 are covered or wrapped by the liquid-retaining member 28. However, a simpler configuration in which the liquid-retaining member 28 is placed on one side of the positive electrode plate 16 or the negative electrode plate 20 is also acceptable. In any case, by interposing the liquid-retaining member 28, the electrolyte can be evenly distributed between the positive electrode plate 16 and / or the negative electrode plate 20 and the hydroxide ion conductive separator 24, and the transfer of hydroxide ions between the positive electrode plate 16 and / or the negative electrode plate 20 and the hydroxide ion conductive separator 24 can be efficiently performed. The liquid-retaining member 28 is not particularly limited as long as it is a member capable of holding electrolyte, but it is preferable that it is a sheet-like member. Preferred examples of the liquid-retaining member 28 include nonwoven fabric, superabsorbent resin, liquid-retaining resin, porous sheet, and various spacers, but nonwoven fabric is particularly preferred because it allows for the production of a low-cost, high-performance negative electrode structure. The liquid-retaining member 28 or nonwoven fabric preferably has a thickness of 10 to 200 μm, more preferably 20 to 200 μm, even more preferably 20 to 150 μm, particularly preferably 20 to 100 μm, and most preferably 20 to 60 μm. With a thickness within the above range, a sufficient amount of electrolyte can be retained within the liquid-retaining member 28 while keeping the overall size of the positive electrode structure and / or negative electrode structure compact and without waste.

[0038] When the positive electrode plate 16 and / or the negative electrode plate 20 are covered or enclosed by a liquid-retaining member 28 and / or a hydroxide ion conductive separator 24, it is preferable that their outer edges (except for the edges from which the positive electrode tab lead 18 and the negative electrode tab lead 22 extend) are closed. In this case, it is preferable that the closed edges of the outer edges of the liquid-retaining member 28 and / or the hydroxide ion conductive separator 24 are achieved by bending the liquid-retaining member 28 and / or the hydroxide ion conductive separator 24, or by sealing the liquid-retaining members 28 with each other and / or the hydroxide ion conductive separators 24 with each other. Preferred sealing methods include adhesives, heat welding, ultrasonic welding, adhesive tapes, sealing tapes, and combinations thereof. In particular, LDH separators containing a porous substrate made of polymer material have the advantage of being flexible and therefore easy to bend, so it is preferable to form the LDH separator in a long shape and bend it to form a closed state on one side of the outer edge. Heat welding and ultrasonic welding can be performed using commercially available heat sealers, but in the case of sealing LDH separators together, it is preferable to perform heat welding and ultrasonic welding by sandwiching the outer periphery of the liquid-retaining member 28 between the LDH separators that constitute the outer periphery, as this allows for more effective sealing. On the other hand, commercially available adhesives, adhesive tapes, and sealing tapes can be used, but it is preferable to use those containing alkali-resistant resins to prevent deterioration in alkaline electrolytes. From this viewpoint, examples of preferred adhesives include epoxy resin adhesives, natural resin adhesives, modified olefin resin adhesives, and modified silicone resin adhesives, among which epoxy resin adhesives are more preferred due to their particularly excellent alkali resistance. An example of an epoxy resin adhesive product is the epoxy adhesive Hysol (registered trademark) (manufactured by Henkel).

[0039] The connection terminals 30 are preferably joined (e.g., by welding) to the positive electrode tab lead 18 and / or the negative electrode tab lead 22, thereby connecting adjacent electrode stacks 14 in a plurality of electrode stacks 14 in series. As shown in Figure 2, each of the connection terminals 30 may be formed by joining (e.g., by welding) terminals having an L-shape. As shown in Figure 4, it is typical that the electrode stacks 14 at both ends of a group of electrode stacks 14 are each provided with pole terminals 32 for electrical connection to an external circuit.

[0040] The electrolyte 34 preferably contains an aqueous alkali metal hydroxide solution. Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide, but potassium hydroxide is more preferred. To suppress the self-dissolution of zinc and / or zinc oxide, zinc compounds such as zinc oxide and zinc hydroxide may be added to the electrolyte. The electrolyte 34 may be mixed with the positive electrode active material and / or negative electrode active material to exist in the form of a positive electrode composite and / or negative electrode composite. Furthermore, the electrolyte 34 may be gelled to prevent leakage of the electrolyte 34. As a gelling agent, it is desirable to use a polymer that absorbs the solvent of the electrolyte 34 and swells, and polymers such as polyethylene oxide, polyvinyl alcohol, polyacrylamide, and starch can be used.

[0041] As shown in Figure 2, it is preferable that the entire electrode stack 14 is immersed in the electrolyte 34. For example, the length L from the lower end to the upper end of the negative electrode plate 20. １ The length L from the lower end of the negative electrode plate 20 to the liquid surface of the electrolyte 34. ２ The percentage of (= (L ２ / L １ The immersion rate, expressed as (x 100), is preferably 104% or more, more preferably 107% or more, and even more preferably 109% or more. By doing so, the amount of oxygen present in the internal space of the monoblock housing 12 that dissolves into the electrolyte 34 is reduced, and the oxidation of zinc in the negative electrode active material layer 20a is suppressed, thereby improving the battery life.

[0042] The present invention will be described more specifically by the following examples. However, the present invention is not limited to the following examples.

[0043] Examples 1 to 5 To confirm the influence of ribs contacting the electrodes on battery performance, the nickel-zinc secondary battery was fabricated and evaluated as follows. Note that the nickel-zinc secondary batteries fabricated in these examples have a single-cell configuration that houses a laminate with the minimum necessary number of electrode plates for simplicity of evaluation. However, by forming a laminate in which the single-cell elements are adapted to the above-described monoblock housing 12 and accommodating a plurality of them in series connection, the battery module of the present invention can be fabricated.

[0044] (1) Fabrication of nickel-zinc secondary battery The nickel-zinc secondary battery 110 shown in FIGS. 9 and 10 was fabricated as follows. First, as single-cell elements, the following positive electrode plate, positive electrode current collector tab, negative electrode plate, negative electrode current collector tab, LDH separator, and electrolytic solution were prepared. - Positive electrode plate: A foam nickel with a positive electrode paste containing nickel hydroxide and a binder filled in the pores and dried (there is an uncoated portion where the positive electrode paste is not applied in the vicinity of one side of the end of the foam nickel), height 120 mm (excluding the uncoated portion), width 180 mm - Positive electrode current collector tab: The uncoated portion of the foam nickel constituting the positive electrode plate was compressed by roll pressing to form a tab, and a tab lead (made of pure nickel) was ultrasonically welded to this tab and extended. - Negative electrode plate: A negative electrode paste containing ZnO powder, metallic Zn powder, polytetrafluoroethylene (PTFE), and propylene glycol was pressure-bonded to a current collector (copper expanded metal) (there is an uncoated portion where the negative electrode paste is not applied in the vicinity of one side of the end of the copper expanded metal), height 120 mm (excluding the uncoated portion), width 180 mm - Negative electrode current collector tab: A tab lead (made of copper) was ultrasonically welded to the uncoated portion of the copper expanded metal. - LDH separator: Ni-Al-Ti-LDH (layered double hydroxide) was precipitated by hydrothermal synthesis in the pores and on the surface of a polyethylene microporous membrane and roll-pressed. - Electrolytic solution: 5.4 mol% potassium hydroxide aqueous solution

[0045] As the battery case 112, a box-shaped case made of a modified polyphenylene ether resin was prepared. The battery case 112 includes a pair of restraint plates 112a for fixing the electrode laminate 114. While the restraint plate 112a of Example 1 has no ribs (see FIG. 9), a plurality of ribs 112b whose tops form flat surfaces are provided in the restraint plates 112a of Examples 2 to 5 in parallel in the vertical direction and at equal intervals (see FIG. 10). The width of each of the ribs 112b in Examples 2 to 5 and the number of ribs 112b per restraint plate were as shown in Table 1.

[0046] The prepared positive electrode plate and negative electrode plate were opposed to each other through an LDH separator to form an electrode laminate 114, and this electrode laminate 114 was vertically accommodated in the battery case 112 so as to contact the restraint plate 112a (in the case of Example 1) or the ribs 112b (in the case of Examples 2 to 5). After injecting an electrolytic solution into the battery case 112 to impregnate the positive electrode plate and the negative electrode plate, the lid was closed and sealed. Thus, the nickel-zinc secondary battery 110 was assembled.

[0047]

[0048] (2) Measurement of initial charge-discharge capacity The initial charge-discharge capacity of the fabricated nickel-zinc secondary battery 110 was measured as follows. Using a charge-discharge device (manufactured by Toyo System Co., Ltd., TOSCAT3100), the fabricated nickel-zinc secondary battery was subjected to formation with 0.1 C charging and 0.2 C discharging. Thereafter, one 0.5 C charge-discharge cycle was performed, and the charging capacity and discharging capacity at this time were recorded.

[0049] FIG. 11 shows a graph of the initial charge-discharge capacity measured for the fabricated nickel-zinc secondary battery 110. As is clear from the results shown in FIG. 11, it can be seen that in Examples 4 and 5 where the contact area ratio between the ribs and the electrode is 20% or more, the decrease in the initial charge-discharge capacity is significantly suppressed as compared with Examples 2 and 3 where the contact area ratio between the ribs and the electrode is less than 20%.

[0050] For reference, Figures 12 and 13 show the appearance of the negative electrode plate in the nickel-zinc secondary battery 110 manufactured in Example 1 and Example 2 when fully charged, respectively. As is clear from these figures, in the nickel-zinc secondary battery 110 of Example 2, color unevenness was observed in the areas between the ribs, confirming that the electrode reaction was non-uniform.

[0051] 10: Battery module, 12: Monoblock housing, 12a: Bottom, 12b: Long side wall, 12c: Short side wall, 12d: Cover, 12e: Partition, 12f: Rib, 12g: Outer wall rib, 14, 114: Electrode stack, 14a: Unit cell, 16: Positive electrode plate, 16a: Positive electrode active material layer, 16b: Positive electrode current collector, 18: Positive electrode tab lead, 19: Positive electrode tab joint, 20: Negative electrode plate, 20a: Negative electrode active material layer, 20b: Negative electrode current collector, 22: Negative electrode tab lead, 23: Negative electrode tab joint, 24: Hydroxide ion conductive separator, 26: Insulating tape, 28: Liquid retention member, 30: Connection terminal, 32: Electrode column terminal, 34: Electrolyte, 110: Nickel-zinc secondary battery, 112: Battery case, 112a: Retaining plate, 112b: Rib, U: Unpainted area, W: Welded joint

Claims

1. A monoblock housing, a plurality of vertically elongated electrode stacks housed vertically within the monoblock housing and arranged parallel to each other, wherein each of the electrode stacks includes: a positive electrode plate including a positive electrode active material layer and a positive electrode current collector, a positive electrode tab lead extending from the end of the positive electrode plate, a negative electrode plate provided opposite the positive electrode plate and including a negative electrode active material layer and a negative electrode current collector, a negative electrode tab lead extending from the end of the negative electrode plate at a position not overlapping with the positive electrode tab lead, and a hydroxide ion conductive separator that isolates the positive electrode plate and the negative electrode plate in a manner that allows hydroxide ion conduction, a plurality of connection terminals for connecting adjacent electrode stacks in the plurality of electrode stacks in series via the positive electrode tab lead and / or the negative electrode tab lead, and an electrolyte filled within the monoblock housing in which the electrode stacks are immersed, wherein the monoblock housing is A battery module having a bottom, a pair of longitudinal side walls parallel to the stacking direction of the electrode stack, a pair of short side walls perpendicular to the stacking direction of the electrode stack, a plurality of partitions provided parallel to the pair of short side walls and dividing the internal space of the monoblock housing into a plurality of compartments capable of accommodating the plurality of electrode stacks spaced apart from each other, a plurality of ribs spaced apart from each other are provided on both sides of each partition to contact the positive electrode plate or the negative electrode plate, and the positive electrode contact area ratio, which is the ratio of the contact area between the positive electrode plate and the plurality of ribs to the planar area of ​​the positive electrode plate, and / or the negative electrode contact area ratio, which is the ratio of the contact area between the negative electrode plate and the plurality of ribs to the planar area of ​​the negative electrode plate, is 20% or more.

2. The battery module according to claim 1, wherein the positive electrode contact area ratio and / or the negative electrode contact area ratio is 50% or less.

3. The battery module according to claim 1 or 2, wherein the plurality of ribs are arranged parallel to each other in the longitudinal direction.

4. The battery module according to claim 3, wherein the plurality of ribs are provided at equal intervals from one another.

5. The battery module according to claim 3, wherein the number of ribs on each surface of the partition wall is eight or more.

6. The battery module according to claim 1 or 2, wherein each of the ribs has a width of 5 to 15 mm.

7. The battery module according to claim 1 or 2, wherein each of the ribs has a height of 0.2 to 3.0 mm.

8. The battery module according to claim 1 or 2, wherein the top of the rib forms a flat surface.

9. The battery module according to claim 1 or 2, wherein the plurality of electrode stacks are not housed in individual single cell cases, but are housed in the plurality of compartments in an exposed state.

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