Battery module

Abstract

The purpose of the present invention is to provide a battery module with which it is possible to pressurize a battery with a simple structure. This battery module comprises: a module housing; a battery assembly that is housed in the module housing in a vertical direction and is composed of a plurality of secondary batteries having a vertically long shape and being juxtaposed in parallel to each other; a pair of end plates that are provided on both sides of the battery assembly and face each other in the direction in which the plurality of secondary batteries are juxtaposed; and a plurality of rods that are provided perpendicular to the pair of end plates and connect the pair of end plates. Each of the rods has an extension part that extends passing through at least one end plate, and an energization means that biases at least one end plate toward the other end plate is provided in each extension part of the rod.

Description

Battery module

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

[0002] Stacked batteries, which are made by combining a plurality of unit cells, are widely used to obtain high voltages and large currents. A stacked battery has a configuration in which a plurality of unit cells connected in series or parallel are housed in a single battery container. For example, Patent Document 1 (WO 2017 / 086278) discloses a zinc secondary battery in which a plurality of electrode cartridges each including an electrode and a separator (particularly an LDH separator, which will be described later) are housed in a sealed container.

[0003] In addition, in order to further increase capacity and power output, it is common to arrange multiple battery units each incorporating a stacked battery to form a battery module. For example, Patent Document 2 (WO 2018 / 173110) discloses a battery module in which multiple rectangular parallelepiped battery units are housed within a frame structure, and it is stated that it is preferable that multiple alkaline secondary battery cells (e.g., nickel-zinc secondary batteries and zinc-air secondary batteries) are housed within the battery unit in the form of a battery pack or battery module. Furthermore, Patent Document 3 (WO 2021 / 024664) discloses a battery module including a metal module housing having a closed internal space and multiple longitudinally elongated secondary batteries housed vertically in the internal space and arranged parallel to each other.

[0004] In battery modules in which multiple battery units are arranged, it is known that each battery unit shrinks or expands during charging, etc., and battery modules with a structure to suppress battery unit expansion have also been proposed. For example, Patent Document 4 (Japanese Patent Laid-Open Publication No. 2023-156612) discloses a battery case including a case that houses multiple stacked battery cells and an elastic member housed within the case that biases the multiple battery cells in the stacking direction. It is claimed that this configuration can suppress battery cell expansion. Furthermore, Patent Document 5 (Japanese Patent No. 6915358) discloses a battery module that includes an array of multiple battery cells, a pair of end plates that sandwich the array in the battery cell arrangement direction, and a connecting rod that connects the pair of end plates. It discloses that an elastic member is disposed between one of the end plates and the array. Patent Document 4 claims that the placement of the elastic member can suppress deformation or damage to the end plates and connecting rods when battery cells expand.

[0005] In zinc secondary batteries, such as nickel-zinc secondary batteries and air-zinc secondary batteries, metallic zinc precipitates from the negative electrode in the form of dendrites during charging, penetrates the pores of separators such as nonwoven fabrics, and reaches the positive electrode, resulting in a short circuit. Such short circuits caused by zinc dendrites shorten the repetitive charge-discharge life. To address this problem, batteries have been proposed that include a layered double hydroxide (LDH) separator that selectively allows hydroxide ions to pass through while preventing the penetration of zinc dendrites. For example, Patent Document 6 (WO 2013 / 118561) discloses a nickel-zinc secondary battery in which an LDH separator is provided between the positive and negative electrodes. Patent Document 7 (WO 2016 / 076047) also discloses a separator structure including an LDH separator fitted or bonded to a resin outer frame, and discloses that the LDH separator has such high density that it is gas- and / or water-impermeable. This document also discloses that an LDH separator can be composited with a porous substrate. Furthermore, Patent Document 8 (WO 2016 / 067884) discloses various methods for forming a dense LDH membrane on the surface of a porous substrate to obtain a composite material (LDH separator). This method includes a step of uniformly attaching a starting substance capable of providing a starting point for LDH crystal growth to the porous substrate, and then subjecting the porous substrate to hydrothermal treatment in a raw material aqueous solution to form a dense LDH membrane on the surface of the porous substrate. Furthermore, Patent Document 9 (WO 2019 / 069762) discloses a method for efficiently producing a negative electrode structure suitable for zinc secondary batteries (particularly stacked batteries) that can prevent zinc dendrite extension by covering or enveloping the entire negative electrode active material layer with a liquid-retaining member and an LDH separator.

[0006] Furthermore, although they cannot be called LDHs, LDH-like compounds are known as hydroxides and / or oxides with a layered crystal structure similar to LDHs, and they exhibit hydroxide ion conductive properties similar enough to be collectively referred to as hydroxide ion conductive layered compounds together with LDHs. For example, Patent Document 10 (WO 2020 / 255856) discloses a hydroxide ion conductive separator comprising a porous substrate and a layered double hydroxide (LDH)-like compound that plugs the pores of the porous substrate, wherein the LDH-like compound is a hydroxide and / or oxide with a layered crystal structure containing Mg and one or more elements, including at least Ti, selected from the group consisting of Ti, Y, and Al. This hydroxide ion conductive separator is said to have superior alkali resistance compared to conventional LDH separators and to be able to more effectively suppress short circuits caused by zinc dendrites.

[0007] WO2017 / 086278WO2018 / 173110WO2021 / 024664JP Patent Publication No. 2023-156612Patent Publication No. 6915358WO2013 / 118561WO2016 / 076047WO2016 / 067884WO2019 / 069762WO2020 / 255856

[0008] As described above, it is desirable to suppress expansion of a battery module by pressurizing the battery unit. However, conventional battery modules such as those disclosed in Patent Documents 4 and 5 tend to have an increased number of components due to the pressurization of the battery unit, which poses a problem from the perspective of reducing the size and weight of the module.

[0009] The inventors have now discovered that by connecting a pair of end plates that sandwich a battery assembly with multiple rods that penetrate at least one of the end plates and providing a biasing means on the extension portion of each rod, it is possible to provide a battery module that is capable of pressurizing the batteries with a simple structure.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a battery module that is capable of applying pressure to batteries with a simple structure.

[0011] The present disclosure provides the following aspects. [Aspect 1] A battery module comprising: a module housing; a battery assembly consisting of a plurality of longitudinally elongated secondary batteries housed vertically within the module housing and arranged parallel to one another; a pair of end plates provided on both sides of the battery assembly and facing each other in the direction in which the plurality of secondary batteries are arranged side by side; and a plurality of rods provided perpendicular to the pair of end plates and connecting the pair of end plates, each of the rods having an extension portion that extends through at least one of the end plates, and each of the extension portions of the rods being provided with a biasing means that biases the at least one end plate toward the other end plate. [Aspect 2] The battery module according to Aspect 1, wherein each of the pair of end plates has a height greater than the battery assembly, and the rods include an upper rod located above the battery assembly and two lower rods located on or below the bottom surface of the battery assembly. [Aspect 3] The battery module according to Aspect 1 or 2, wherein the number of rods is three. [Aspect 4] The battery module according to Aspect 2 or 3, wherein the battery assembly is placed on the two lower rods. [Aspect 5] The battery module according to any one of Aspects 2 to 4, wherein the secondary battery has a groove on its bottom surface that fits the cross-sectional shape of the lower rod along the axial direction of the lower rod. [Aspect 6] The battery module according to any one of Aspects 1 to 5, wherein the biasing means is a spring attached to surround the outer periphery of the extension portion of the rod. [Aspect 7] The battery module according to Aspect 6, wherein an end of the spring away from the end plate is restricted by a fastening member fixed to an end of the rod, thereby biasing the end plate in contact with the spring in a direction away from the fastening member. [Aspect 8] The battery module according to any one of Aspects 1 to 7, wherein the secondary battery is an alkaline secondary battery comprising: a stacked battery in which a plurality of unit cell elements having the configuration of an alkaline secondary battery are stacked; and a box-shaped resin case in which the stacked battery is housed in a vertical orientation.[Aspect 9] The battery module according to Aspect 8, wherein the alkaline secondary battery is a zinc secondary battery. [Aspect 10] The battery module according to Aspect 9, wherein the zinc secondary battery is a nickel-zinc secondary battery. [Aspect 11] The battery module according to any one of Aspects 8 to 10, wherein the unit cell element comprises: a positive electrode plate including a positive electrode active material layer; a negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound; an LDH separator including a layered double hydroxide (LDH) and / or an LDH-like compound; and an electrolyte, wherein the positive electrode active material layer and the negative electrode active material layer are isolated from each other via the LDH separator. [Aspect 12] The battery module according to aspect 11, wherein the LDH separator comprises an LDH and / or an LDH-like compound and a porous substrate, and the LDH and / or the LDH-like compound fills the pores of the porous substrate so that the LDH separator exhibits hydroxide ion conductivity and gas impermeability.

[0012] 1 is a perspective view showing an example of a battery module of the present invention. It is a front view showing a battery assembly, end plates, and rods in the battery module shown in FIG. 1. It is a front view showing an example of a secondary battery having a groove on the bottom surface in the battery module shown in FIG. 1. It is an enlarged view of the groove portion of the secondary battery shown in FIG. 3. It is a schematic cross-sectional view of the secondary battery shown in FIG. 3. It is a schematic cross-sectional view of the secondary battery shown in FIG. 5 along line AA'. It is a perspective view showing a stacked battery constituting the secondary battery shown in FIG. 5. It is a schematic cross-sectional view showing a stacked battery constituting the secondary battery shown in FIG. 5. It is a perspective view showing an example of a positive electrode plate or a negative electrode plate in the secondary battery shown in FIG. 5. It is a perspective view showing a configuration of the positive electrode plate or the negative electrode plate shown in FIG. 9 covered with a hydroxide ion conductive separator or a liquid-retaining member. It is a perspective view showing an example of a conventional battery module. It is a front view showing a battery assembly, end plates, and rods in the battery module shown in FIG. 11.

[0013] Battery Module FIGS. 1 and 2 show one embodiment of the battery module of the present invention. The battery module 100 shown in FIGS. 1 and 2 includes a module housing 102, a battery assembly 104, a pair of end plates 106, and multiple rods 108. The battery assembly 104 is composed of multiple secondary batteries 10. The number of secondary batteries 10 constituting the battery assembly 104 is not particularly limited and may be determined appropriately to achieve the desired capacity and output. Each of the multiple secondary batteries 10 has a vertically elongated shape, is housed vertically within the module housing 102, and is arranged parallel to one another. The type of secondary battery 10 is not particularly limited, but is preferably an alkaline secondary battery such as a nickel-zinc secondary battery, which will be described later. A pair of end plates 106 (hereinafter, sometimes referred to as "one end plate 106a" and "the other end plate 106b" as necessary) are provided on both sides of the battery assembly 104 and face each other in the direction in which the multiple secondary batteries 10 are arranged side by side. The rods 108 are disposed perpendicular to the pair of end plates 106 and connect the pair of end plates 106. As shown in FIG. 2 , each of the rods 108 has an extension E that extends through at least one of the end plates 106 a. The extension E of each rod 108 is provided with a biasing means 110 that biases one end plate 106 a toward the other end plate 106 b. In this way, by connecting the pair of end plates 106 that sandwich the battery assembly 104 with the rods 108 so that they penetrate at least one of the end plates 106 a, and by providing the biasing means 110 on the extension E of each rod 108, it is possible to provide a battery module 100 that is capable of applying pressure to the battery assembly 104 with a simple structure.

[0014] As mentioned above, it is known that in battery modules in which multiple secondary batteries are arranged, the secondary batteries shrink or expand during charging, etc. That is, secondary batteries such as nickel-zinc batteries have the characteristic of shrinking due to structural changes in the positive or negative electrodes during charging. Therefore, even if multiple secondary batteries are arranged without gaps and each battery is pressurized, the pressure decreases due to the shrinkage of the secondary batteries. As a result, there is a concern that gas generated during charging and discharging may accumulate in the container, causing certain secondary batteries to expand, increasing the resistance of the battery module.

[0015] To address this issue, battery modules with structures designed to suppress expansion of secondary batteries have been proposed, but these have problems in terms of reducing size and weight. As an example, a battery module 200 with springs directly attached to end plates is shown in FIGS. 11 and 12 . This battery module 200 includes a module housing 202, a battery assembly 204 housed in the module housing 202, a pair of end plates 206 that sandwich the battery assembly 204, and multiple rods 208 that connect the pair of end plates 206. A spring 210 is fixed between one of the end plates 206 and an additional plate-like member 211. As described above, conventional battery modules 200 tend to require many additional components to apply pressure to the battery assembly 204. In contrast, the battery module 100 of the present invention includes the biasing means 110 on the extension E of the rod 108, as described above. This eliminates the need for an additional plate-like member to secure the biasing means 110, allowing the battery module to be constructed with a reduced number of components. As a result, the battery module can be made smaller and lighter. Even so, during charging, the biasing means 110 allows one end plate 106a of the battery module 100 to move toward the other end plate 106b in response to the contraction of the secondary batteries 10, thereby allowing for continuous pressure application to the battery assembly 104. Furthermore, during discharging, the biasing means 110 can absorb expansion of the secondary batteries 10.

[0016] The module housing 102 is a container capable of housing the battery assembly 104, a pair of end plates 106, and multiple rods 108. Although not shown in FIG. 1 , the module housing 102 may further include a top lid in addition to a container body having a bottom and sidewalls. To ensure sufficient pressure resistance, heat resistance, and strength, the module housing 102 is preferably constructed of both the container body and the top lid from metal plates. Preferred examples of the metal plate constituting the module housing 102 include steel plates and stainless steel plates. The thickness of the metal plate constituting the container body of the module housing 102 may be determined appropriately based on the allowable weight as long as the desired pressure resistance and strength are ensured, but is preferably 0.8 to 2.5 mm, more preferably 1.0 to 2.0 mm. Meanwhile, the thickness of the metal plate constituting the top lid is preferably 1.0 to 3.0 mm, more preferably 1.5 to 2.5 mm. The top lid is preferably fixed to the container body using bolt and nut fastening, since this allows the top lid to be removed when necessary (for example, when replacing or maintaining the secondary battery 10) while ensuring sufficient pressure resistance. If the module housing 102 is a container with a lid, it is desirable not to make it a completely sealed container so that internal pressure can be released to the outside. For example, the module housing 102 preferably has a structure that allows internal pressure to be released to the outside at a location facing or communicating with the internal space above the secondary battery 10.

[0017] It is desirable to form a flow path within the module housing 102 for air flow to cool the secondary battery 10. Preferably, an air intake (not shown) is provided at one end of the module housing 102, while an exhaust port (not shown) is provided at the other end of the module housing 102, and a fan is attached to the exhaust port. The fan may be a small ventilation fan. With this configuration, operating the fan causes air to flow within the module housing 102, thereby cooling the secondary battery 10.

[0018] The pair of end plates 106 are plate-like members provided on both sides of the battery assembly 104 and sandwich the multiple secondary batteries 10. Typically, as shown in FIG. 2 , one end plate 106a is positioned to abut against one outermost secondary battery 10, and the other end plate 106b is positioned to abut against the other outermost secondary battery 10, thereby sandwiching the battery assembly 104. Then, a biasing means 110 provided on the extension portion E of the rod 108 biases one end plate 106a toward the other end plate 106b, thereby pressurizing the battery assembly 104 in a direction in which the multiple secondary batteries 10 are juxtaposed. The material of the end plates 106 is not particularly limited, but is typically metal.

[0019] Each of the pair of end plates 106 preferably has a height greater than that of the battery assembly 104. Specifically, the height of the end plate 106 is preferably greater than 1.0 times the height of the battery assembly 104 (including components such as terminals and pressure relief valves extending from the upper surface), more preferably 1.1 to 1.5 times, and even more preferably 1.1 to 1.3 times. This allows the upper rod 108a to be positioned above the battery assembly 104, and the lower rod 108b to be positioned on or below the bottom surface of the battery assembly 104, as described below. From the perspective of uniformly pressurizing the secondary battery 10, the end plate 106 preferably has a width equal to or greater than that of the secondary battery. Furthermore, one end plate 106a preferably has through-holes through which the rods 108 can be inserted, more preferably an upper through-hole through which the upper rod 108a can be inserted and a lower through-hole through which the lower rod 108b can be inserted. The sizes of these through-holes are not particularly limited, as long as they are compatible with the cross-sectional shape of the rods 108. For example, if the rod 108 is cylindrical, the inner diameter of the through hole may be larger than the outer diameter of the rod 108. The other end plate 106b may also have a through hole similar to that of the one end plate 106a.

[0020] The rod 108 is a rod-shaped member that is disposed perpendicular to the surfaces of the pair of end plates 106 that sandwich the battery assembly 104 and connects the pair of end plates 106. The rod 108 has an extension portion E that extends through at least one of the end plates 106a. The rod 108 may also extend through not only one end plate 106a but also the other end plate 106b. In this case, it is preferable that the movement of the other end plate 106b be restricted by a fastening member 112 provided at or near the end of the rod 108 so that the other end plate 106b does not come off the rod 108. The material of the rod 108 is not particularly limited, but is typically metal. The dimensions of the rod 108 may be determined appropriately depending on the size of the battery assembly 104 and the end plates 106, and are not particularly limited.

[0021] The rods 108 preferably include an upper rod 108a located above the battery assembly 104 and two lower rods 108b located on or below the bottom surface of the battery assembly 104. In this case, it is particularly preferable for the battery assembly 104 to be mounted on the two lower rods 108b. This configuration ensures excellent heat dissipation and allows the secondary battery 10 to be efficiently cooled. Furthermore, since there is no need to provide a separate breathable spacer such as a frame or rail on the bottom surface of the module housing 102, the battery module can be constructed more simply. When the battery assembly 104 is mounted on the lower rods 108b, as shown in FIGS. 3 and 4 , a groove G that fits the cross-sectional shape of the lower rods 108b is preferably formed on the bottom surface of the secondary battery 10 (i.e., the bottom 20a of the box-shaped case) along the axial direction of the lower rods 108b. This effectively prevents the secondary batteries 10 from falling off the lower rods 108b and scattering, even if the battery module 100 is subjected to vibration or impact. The number of rods 108 may be two or more, but from the viewpoint of reducing the weight of the battery module 100 with a simple configuration with a small number of parts, it is particularly preferable to have three rods (for example, one upper rod 108a and two lower rods 108b).

[0022] The biasing means 110 is provided on the extension portion E of the rod 108 and biases one end plate 106a toward the other end plate 106b. The biasing means 110 may be configured in any suitable manner as long as it performs the required function. However, the biasing means 110 is preferably a spring, particularly preferably a coil spring such as a compression coil spring. That is, the biasing means 110 is preferably a spring mounted so as to surround the outer periphery of the extension portion E of the rod 108. In this case, as shown in FIG. 2 , the end of the spring away from the end plate 106 is preferably restricted by a fastening member 112 fixed to the end of the rod 108. This allows the end plate 106a, which the spring contacts, to be biased in a desired direction away from the fastening member 112. The material, wire diameter, inner diameter, number of turns, and other factors of the spring (e.g., a coil spring) may be appropriately determined depending on the size of the rod 108, the load applied to the battery assembly 104, and other factors, and are not particularly limited. The fastening member 112 is not particularly limited, but a preferred example is a nut.

[0023] Alkaline Secondary Battery As mentioned above, the preferred secondary battery 10 used in the battery module 100 of the present invention is an alkaline secondary battery such as a nickel-zinc secondary battery. FIG. 5 shows a preferred example of an alkaline secondary battery of the present invention. The alkaline secondary battery 10 shown in FIG. 5 includes a stacked battery 11 and a box-shaped case 20 in which the stacked battery 11 is housed vertically. The box-shaped case 20 is made of resin. As shown in FIGS. 7 and 8 , the stacked battery 11 is formed by stacking multiple single cell elements 10 a having the configuration of an alkaline secondary battery, and is advantageous in that it can provide high voltage and large current.

[0024] As shown in Figures 5 and 6, the box-shaped case 20 has a bottom 20a, a pair of long side walls 20b parallel to the battery stack 11, a pair of short side walls 20c perpendicular to the battery stack 11, and a lid 20d. The box-shaped case 20 (e.g., the lid 20d) may have a pressure relief valve for releasing gas. Although not shown in Figures 5 and 6, the battery stack 11 is formed by stacking a plurality of cell elements 10a, i.e., an assembly of a plurality of cell elements 10a, as shown in Figure 8. The box-shaped case 20 is typically cuboid in basic shape, but it does not need to be a perfect cuboid. As long as the overall general shape is box-shaped, it may have partially curved surfaces or uneven surfaces.

[0025] The box-shaped case 20 is preferably made of resin. The resin constituting the box-shaped case 20 is preferably a resin that is resistant to alkali metal hydroxides such as potassium hydroxide, more preferably a polyolefin resin, an ABS resin, or a modified polyphenylene ether, and even more preferably an ABS resin or a modified polyphenylene ether.

[0026] The alkaline secondary battery 10 is not particularly limited as long as it is a secondary battery that uses an alkaline electrolyte (typically, an aqueous alkali metal hydroxide solution), but is preferably a zinc secondary battery that uses zinc as the negative electrode. Therefore, it may be a nickel-zinc secondary battery, a silver-zinc oxide secondary battery, a manganese-zinc oxide secondary battery, or any other type of alkaline zinc secondary battery. For example, it is preferable that the positive electrode contains nickel hydroxide and / or nickel oxyhydroxide, thereby making the zinc secondary battery a nickel-zinc secondary battery.

[0027] The alkaline secondary battery 10 (i.e., zinc secondary battery) shown in FIGS. 5 to 10 includes a cell element 10a, which includes a positive electrode plate 12, a negative electrode plate 14, a layered double hydroxide (LDH) separator 16, and an electrolyte (not shown). The positive electrode plate 12 includes a positive electrode active material layer 12a and, optionally, a positive electrode current collector 12b. The negative electrode plate 14 includes a negative electrode active material layer 14a and, optionally, a negative electrode current collector 14b. The negative electrode active material layer 14a includes at least one material selected from the group consisting of zinc, zinc oxide, a zinc alloy, and a zinc compound. The positive electrode active material layer 12a and the negative electrode active material layer 14a are separated from each other by the LDH separator 16. For example, the LDH separator 16 preferably covers or encases the entire negative electrode active material layer 14a. In this specification, an "LDH separator" is defined as a separator containing LDH and / or an LDH-like compound, which selectively passes hydroxide ions by utilizing the hydroxide ion conductivity of the LDH and / or LDH-like compound. In this specification, an "LDH-like compound" may not be called an LDH, but is a hydroxide and / or oxide with a layered crystal structure similar to LDH, and can be considered an equivalent of LDH. However, in a broad sense, "LDH" can be interpreted as including not only LDH but also LDH-like compounds. Typically, the positive electrode active material layer 12 a, the negative electrode active material layer 14 a, and the LDH separator 16 each have a quadrilateral shape (typically a square shape).

[0028] Preferably, the alkaline secondary battery 10 further includes a positive electrode tab lead 13 extending upward from the end of the positive electrode plate 12, and a negative electrode tab lead 15 extending upward from the end of the negative electrode plate 14 at a position that does not overlap with the positive electrode tab lead 13. As shown in Fig. 5, the alkaline secondary battery 10 further includes a positive electrode terminal 22 and a negative electrode terminal 24, and it is preferable that the positive electrode terminal 22 and the negative electrode terminal 24 extend from the lid portion 20d.

[0029] The positive electrode plate 12 includes a positive electrode active material layer 12a. The positive electrode active material constituting the positive electrode active material layer 12a may be selected from known positive electrode materials depending on the type of zinc secondary battery, and is not particularly limited. 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 12a may contain at least one additive selected from the group consisting of silver compounds, manganese compounds, and titanium compounds, which can promote the positive electrode reaction that absorbs hydrogen gas generated by the self-discharge reaction. The positive electrode active material layer 12a may also contain cobalt. Cobalt is preferably contained in the positive electrode plate 12 in the form of cobalt oxyhydroxide. In the positive electrode active material layer 12a, cobalt functions as a conductive additive, thereby contributing to improved charge / discharge capacity. Alternatively, in the case of an air-zinc secondary battery, an air electrode may be used as the positive electrode.

[0030] The positive electrode plate 12 preferably further includes a positive electrode current collector 12b. A preferred example of the positive electrode current collector 12b is a nickel porous substrate such as a foamed nickel plate. In this case, a positive electrode plate consisting of a positive electrode / positive electrode current collector can be preferably produced, for example, by uniformly applying a paste containing an electrode active material such as nickel hydroxide to the nickel porous substrate and drying it. In this case, it is also preferred to press the dried positive electrode plate (i.e., the positive electrode / positive electrode current collector) to prevent the electrode active material from falling off and improve the electrode density. When the positive electrode current collector 12b is a nickel porous substrate such as a foamed nickel plate, the uncoated area of ​​the positive electrode current collector 12b may be pressed into a tab shape.

[0031] 9 , the positive electrode plate 12 may have an uncoated region U along the upper edge of the positive electrode plate 12 where the positive electrode active material layer 12a is not present. In such a case, it is preferable that the positive electrode tab lead 13 is welded to the positive electrode current collector 12b in the uncoated region U, and insulating tape 18 is attached to the uncoated region U so that the welded portion W is covered with the insulating tape 18. This makes it difficult for the tip of the positive electrode tab lead 13 to penetrate the LDH separator 16 or the liquid retention member 17, and even if the tip penetrates them and comes into contact with the positive electrode plate 12, the insulating tape 18 functions as an insulator, making it difficult for a short circuit to occur.

[0032] The positive electrode tab lead 13 is preferably provided so as to extend from the end of the positive electrode plate 12. The positive electrode tab lead 13 may be a commercially available metal foil, and is not particularly limited. As shown in FIG. 8 , a plurality of positive electrode tab leads 13 are preferably joined to one positive electrode terminal 22 or a member electrically connected thereto to form a positive electrode tab joint 26. This allows for space-efficient current collection with a simple configuration and facilitates connection to the positive electrode terminal 22. The positive electrode tab lead 13 may be joined to members such as the positive electrode current collector 12b and the positive electrode terminal 22 using a known joining method such as ultrasonic welding (ultrasonic welding), laser welding, TIG welding, or resistance welding.

[0033] The negative electrode plate 14 includes a negative electrode active material layer 14a. The negative electrode active material constituting the negative electrode active material layer 14a includes at least one selected from the group consisting of zinc, zinc oxide, zinc alloys, and zinc compounds. Zinc may be contained in any form, such as 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, and calcium zincate, with a mixture of zinc metal and zinc oxide being more preferred. The negative electrode active material may be in a gel form or may be mixed with an electrolyte to form a negative electrode composite. 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, and alginic acid, with polyacrylic acid being preferred due to its excellent chemical resistance to strong alkalis.

[0034] 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 the effect of suppressing hydrogen gas generation. In particular, indium and bismuth are advantageous in terms of improving discharge performance. The use of a zinc alloy for the negative electrode can suppress hydrogen gas generation and improve safety by slowing the rate of self-dissolution in alkaline electrolyte.

[0035] The shape of the negative electrode material is not particularly limited, but is preferably in powder form, which increases the surface area and enables it to withstand large current discharge. In the case of a zinc alloy, the average particle size of the negative electrode material is preferably in the range of 3 to 100 μm in minor axis. Within this range, the large surface area makes it suitable for withstanding large current discharge, and it is also easy to mix uniformly with the electrolyte and gelling agent, making it easy to handle during battery assembly.

[0036] The negative electrode plate 14 preferably further includes a negative electrode current collector 14b. The negative electrode active material layer 14a may be disposed on both sides of the negative electrode current collector 14b, or may be disposed on only one side of the negative electrode current collector 14b. The negative electrode current collector 14b is preferably a metal plate having multiple (or many) openings from the viewpoint of fixing the negative electrode active material to the current collector. Preferred examples of such a negative electrode current collector 14b include expanded metal, punched metal, metal mesh, and combinations thereof. More preferred are copper expanded metal, copper punched metal, and combinations thereof, with copper expanded metal being particularly preferred. In this case, a negative electrode plate consisting of a negative electrode and a negative electrode current collector can be preferably produced by applying a mixture containing zinc oxide powder and / or zinc powder, and optionally a binder (e.g., polytetrafluoroethylene particles), to a copper expanded metal. In this case, 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 improve the electrode density. Expanded metal is a mesh-like metal plate obtained by expanding a metal plate while making staggered cuts using an expander, and then shaping the cuts into a diamond or tortoiseshell shape. Perforated metal is also called perforated metal, and is a metal plate with holes punched out by a punching process. Metal mesh is a metal product with a wire mesh structure and is different from expanded metal and perforated metal.

[0037] 9 , the negative electrode plate 14 may have an uncoated region U along the upper edge of the negative electrode plate 14 where the negative electrode active material layer 14a is not present. In such a case, it is preferable that the negative electrode tab lead 15 is welded to the negative electrode current collector 14b in the uncoated region U, and insulating tape 18 is attached to the uncoated region U so that the welded portion W is covered with the insulating tape 18. This makes it difficult for the tip of the negative electrode tab lead 15 to penetrate the LDH separator 16 or the liquid retention member 17, and even if the tip penetrates them and comes into contact with the negative electrode plate 14, the insulating tape 18 functions as an insulator, making it difficult for a short circuit to occur.

[0038] The negative electrode tab lead 15 is preferably provided so as to extend from the end of the negative electrode plate 14 at a position where it does not overlap with the positive electrode tab lead 13 (see FIG. 7 ). The negative electrode tab lead 15 may be a commercially available metal foil, and is not particularly limited. As shown in FIG. 8 , it is preferable that a plurality of negative electrode tab leads 15 are joined to one negative electrode terminal 24 or a member electrically connected thereto to form a negative electrode tab joint 28. This allows for space-efficient current collection with a simple configuration and facilitates connection to the negative electrode terminal 24. The joining of the negative electrode tab lead 15 to members such as the negative electrode current collector 14b and the negative electrode terminal 24 may be performed using a known joining method such as ultrasonic welding (ultrasonic welding), laser welding, TIG welding, or resistance welding.

[0039] The LDH separator 16 is provided to separate the positive electrode active material layer 12a and the negative electrode active material layer 14a in a manner that allows hydroxide ion conductivity. For example, as shown in Figures 8 and 10, the positive electrode plate 12 and / or the negative electrode plate 14 (preferably the negative electrode plate 14) may be configured to be covered or wrapped with the LDH separator 16. This eliminates the need for a complicated sealing joint between the LDH separator 16 and the battery container, making it possible to produce a zinc secondary battery (particularly a stacked battery thereof) that can prevent zinc dendrite extension extremely easily and with high productivity. However, a simple configuration in which the LDH separator 16 is disposed on one side of the positive electrode plate 12 or the negative electrode plate 14 may also be used.

[0040] As described above, the LDH separator 16 contains LDH and / or an LDH-like compound. The LDH separator 16 is preferably composited with a porous substrate. Therefore, the LDH separator preferably further includes a porous substrate, and is composited with the porous substrate in a form in which the LDH and / or LDH-like compound fills the pores of the porous substrate. That is, in a preferred LDH separator 16, the pores of the porous substrate are filled with the LDH and / or LDH-like compound 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 preferred that the LDH and / or LDH-like compound be incorporated throughout the entire thickness of the porous substrate made of a polymer material. 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.

[0041] It is preferable that not only the LDH separator 16 but also a liquid-retaining member 17 be interposed between the positive electrode plate 12 and the negative electrode plate 14. As shown in FIGS. 8 and 10 , it is preferable that the positive electrode plate 12 and / or the negative electrode plate 14 be covered or wrapped with the liquid-retaining member 17. However, a simple configuration in which the liquid-retaining member 17 is disposed on one side of the positive electrode plate 12 or the negative electrode plate 14 may also be used. In either case, the interposition of the liquid-retaining member 17 allows the electrolyte to be evenly distributed between the positive electrode plate 12 and / or the negative electrode plate 14 and the LDH separator 16, thereby enabling efficient exchange of hydroxide ions between the positive electrode plate 12 and / or the negative electrode plate 14 and the LDH separator 16. The liquid-retaining member 17 is not particularly limited as long as it is a material capable of retaining the electrolyte, but is preferably a sheet-like material. Preferred examples of the liquid-retaining member 17 include nonwoven fabric, water-absorbent resin, liquid-retaining resin, porous sheet, and various spacers, but nonwoven fabric is particularly preferred because it allows for the production of a high-performance negative electrode structure at low cost. The liquid-retaining member 17 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. A thickness within the above range allows a sufficient amount of electrolyte to be retained within the liquid-retaining member 17 while keeping the overall size of the positive electrode structure and / or negative electrode structure compact and efficient.

[0042] When the positive electrode plate 12 and / or the negative electrode plate 14 are covered or wrapped with the liquid retention member 17 and / or the LDH separator 16, their outer edges are preferably closed (except for the edges from which the positive electrode tab lead 13 and the negative electrode tab lead 15 extend). In this case, the closed edges of the outer edges of the liquid retention member 17 and / or the LDH separator 16 are preferably realized by folding the liquid retention member 17 and / or the LDH separator 16, or by sealing the liquid retention members 17 together and / or the LDH separators 16 together. Preferred examples of sealing methods include adhesives, heat welding, ultrasonic welding, adhesive tape, sealing tape, and combinations thereof. In particular, LDH separators including a porous substrate made of a polymer material have the advantage of being flexible and therefore easily bendable. Therefore, it is preferable to form the LDH separator into a long shape and then fold it to close one edge of the outer edge. Thermal welding and ultrasonic welding can be performed using a commercially available heat sealer, etc., but when sealing LDH separators together, it is preferable to perform thermal welding and ultrasonic welding by sandwiching the outer periphery of the liquid-retaining member 17 between the LDH separators that make up the outer periphery, as this provides more effective sealing. Commercially available adhesives, adhesive tapes, and sealing tapes can be used, but those containing alkali-resistant resins are preferred to prevent deterioration in alkaline electrolyte. From this perspective, preferred examples of adhesives include epoxy resin-based adhesives, natural resin-based adhesives, modified olefin resin-based adhesives, and modified silicone resin-based adhesives. Of these, epoxy resin-based adhesives are particularly preferred due to their excellent alkali resistance. An example of a product of an epoxy resin-based adhesive is the epoxy adhesive Hysol® (manufactured by Henkel).

[0043] It is preferable that the outer edge of one side of the LDH separator 16, which is the upper end, is open. This open-top configuration makes it possible to deal with the problem of overcharging in nickel-zinc batteries and the like. That is, when a nickel-zinc battery or the like is overcharged, oxygen (O ２ ) may occur, but the LDH separator has such a high density that it allows only hydroxide ions to pass through, so O ２In this respect, the open-top structure allows O ２ can escape above the positive electrode plate 12 and be sent to the negative electrode plate 14 side through the upper open portion, thereby ２ The Zn in the negative electrode active material can be oxidized and returned to ZnO by this oxygen reaction cycle. By using the open-top stacked battery 11 in a sealed zinc secondary battery, overcharge resistance can be improved. Even if the outer edge of one side that is the upper end of the LDH separator 16 or the liquid retention member 17 is closed, the same effect as the open-type configuration can be expected by providing a vent hole in part of the closed outer edge. For example, the vent hole may be opened after sealing the outer edge of one side that is the upper end of the LDH separator, or part of the outer edge may be left unsealed during sealing so that the vent hole is formed.

[0044] The electrolyte preferably contains an aqueous solution of alkali metal hydroxide. The electrolyte is not shown because it is distributed throughout the positive electrode plate 12 (particularly the positive electrode active material layer 12a) and the negative electrode plate 14 (particularly the negative electrode active material layer 14a). Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide, with potassium hydroxide being preferred. To suppress the self-dissolution of zinc and / or zinc oxide, a zinc compound such as zinc oxide or zinc hydroxide may be added to the electrolyte. As described above, the electrolyte may be mixed with the positive electrode active material and / or the negative electrode active material to form a positive electrode composite and / or a negative electrode composite. The electrolyte may also be gelled to prevent leakage of the electrolyte. A polymer that absorbs the solvent in the electrolyte and swells is preferably used as the gelling agent. Examples of suitable gelling agents include polymers such as polyethylene oxide, polyvinyl alcohol, and polyacrylamide, as well as starch.

[0045] 10: secondary battery, 10a: single cell element, 11: stacked battery, 12: positive electrode plate, 12a: positive electrode active material layer, 12b: positive electrode current collector, 13: positive electrode tab lead, 14: negative electrode plate, 14a: negative electrode active material layer, 14b: negative electrode current collector, 15: negative electrode tab lead, 16: LDH separator, 17: liquid retaining member, 18: insulating tape, 20: box-shaped case, 20a: bottom, 20b: long side wall portion, 20c: short side wall portion, 20d: lid portion, 22: positive electrode terminal, 24 : negative electrode terminal, 26: positive electrode tab joint, 28: negative electrode tab joint, 100, 200: battery module, 102, 202: module housing, 104, 204: battery assembly, 106, 206: end plate, 108, 208: rod, 108a: upper rod, 108b: lower rod, 110: biasing means, 112: fastening member, 210: spring, 211: additional plate-like member, E: extension, G: groove, U: uncoated area, W: welded joint

Claims

1. A battery module comprising: a module housing; a battery assembly consisting of a plurality of vertically elongated secondary batteries housed vertically within the module housing and arranged parallel to one another; a pair of end plates provided on both sides of the battery assembly and facing each other in the direction in which the plurality of secondary batteries are arranged side by side; and a plurality of rods provided perpendicular to the pair of end plates and connecting the pair of end plates, wherein each of the rods has an extension portion that extends through at least one of the end plates, and the extension portion of each of the rods is provided with a biasing means that biases the at least one end plate toward the other end plate.

2. The battery module according to claim 1, wherein each of the pair of end plates has a height greater than that of the battery assembly, and the rods include an upper rod located above the battery assembly and two lower rods located on or below the bottom surface of the battery assembly.

3. The battery module according to claim 2, wherein the number of rods is three.

4. The battery module according to claim 2, wherein the battery assembly is placed on the two lower rods.

5. The battery module according to claim 4, wherein the secondary battery has a groove on its bottom surface that fits the cross-sectional shape of the lower rod along the axial direction of the lower rod.

6. The battery module according to any one of claims 1 to 5, wherein the biasing means is a spring attached so as to surround the outer periphery of the extension of the rod.

7. A battery module as described in claim 6, wherein the end of the spring away from the end plate is restricted by a fastening member fixed to the end of the rod, thereby biasing the end plate in contact with the spring in a direction away from the fastening member.

8. The battery module according to any one of claims 1 to 5, wherein the secondary battery is an alkaline secondary battery comprising: a stacked battery in which a plurality of unit cell elements having the configuration of an alkaline secondary battery are stacked; and a box-shaped resin case in which the stacked battery is housed in a vertical position.

9. The battery module according to claim 8, wherein the alkaline secondary battery is a zinc secondary battery.

10. The battery module according to claim 9, wherein the zinc secondary battery is a nickel-zinc secondary battery.

11. The battery module according to claim 9, wherein the unit cell elements comprise: a positive electrode plate including a positive electrode active material layer; a negative electrode plate including a negative electrode active material layer including at least one selected from the group consisting of zinc, zinc oxide, zinc alloys, and zinc compounds; an LDH separator including a layered double hydroxide (LDH) and / or an LDH-like compound; and an electrolyte, wherein the positive electrode active material layer and the negative electrode active material layer are isolated from each other via the LDH separator.

12. The battery module of claim 11, wherein the LDH separator comprises an LDH and / or an LDH-like compound and a porous substrate, and the LDH and / or LDH-like compound fills the pores of the porous substrate so that the LDH separator exhibits hydroxide ion conductivity and gas impermeability.

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