Secondary battery and secondary battery module

Abstract

The present invention provides, at a lower cost, a secondary battery that has a weak part which makes it possible to address a sudden increase in the internal pressure of the battery. This secondary battery comprises an electrode laminate, an electrolyte, and a box-shaped case that is made of resin and that houses the electrode laminate and the electrolyte. The box-shaped case has a stripe-shaped recessed portion. The stripe-shaped recessed portion functions as a weak part that can be destroyed preferentially and in a localized manner when internal pressure rises excessively due to gas produced inside the battery.

Description

[Technical field]

[0001] The present invention relates to a secondary battery and a secondary battery module. [Background technology]

[0002] Alkaline secondary batteries such as nickel-zinc batteries are much safer than secondary batteries that use non-aqueous electrolytes containing flammable organic solvents because they use aqueous electrolytes such as potassium hydroxide. However, in order to further improve the safety of alkaline secondary batteries, it is desirable to assume the worst possible abnormality as a risk and take all possible measures against it. One of the worst possible abnormalities is the generation of hydrogen due to decomposition of the aqueous electrolyte, which may lead to hydrogen combustion due to ignition caused by a short circuit or the like.

[0003] Therefore, a stacked-cell type alkaline secondary battery that can minimize damage caused by a sudden increase in the internal pressure of the battery due to hydrogen combustion or the like has been proposed. For example, Patent Document 1 (WO2021 / 024681) discloses an alkaline secondary battery that includes a stacked battery in which multiple single cell elements having the configuration of an alkaline secondary battery are stacked, and a resin box-shaped case in which the stacked battery is housed vertically, and proposes providing a fragile part with a reduced thickness and a predetermined area ratio on the lid of the box-shaped case. According to this configuration, when the internal pressure of the battery suddenly increases due to hydrogen combustion or the like, the fragile part is preferentially and locally destroyed before the box-shaped case is destroyed as a whole, so that the overall destruction of the box-shaped case can be avoided, and as a result, safety can be improved.

[0004] In order to achieve even greater capacity and power output, it is common to arrange a plurality of battery units, each having a stacked battery built therein, into a battery module. In this regard, the above-mentioned Patent Document 1 also discloses an alkaline secondary battery module that includes a module case, which is a metal container with a lid, and a plurality of alkaline secondary batteries housed in the module case. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2021 / 024681 Summary of the Invention

[0006] Providing a weak portion with a reduced thickness as disclosed in Patent Document 1 in a box-shaped case leads to an increase in manufacturing costs. Therefore, it is desired to realize a function equivalent to that of a weak portion at a lower manufacturing cost.

[0007] The inventors have now discovered that by providing a striated recess in a box-shaped case, this recess can function as a weak part that can be broken preferentially and locally in the event of an excessive increase in internal battery pressure, and as a result, a secondary battery having a weak part can be provided at lower cost.

[0008] Therefore, an object of the present invention is to provide a secondary battery having a weak portion capable of coping with a sudden increase in internal battery pressure at a lower cost.

[0009] According to the present invention, the following aspects are provided. [Aspect 1] An electrode stack; An electrolyte; a resin box-shaped case in which the electrode stack and the electrolyte are contained; A secondary battery comprising: The box-shaped case has a streak-like recess, and the streak-like recess functions as a weak part that can be broken preferentially and locally when internal pressure increases excessively due to gas generated within the battery. [Aspect 2] 2. The secondary battery of embodiment 1, wherein the streak-like recess is a weld line. [Aspect 3] 3. The secondary battery of claim 1, wherein the box-shaped case has a bottom, a pair of long side wall portions parallel to the electrode stack, a pair of short side wall portions perpendicular to the electrode stack, and a lid, and the striated recess is provided in at least one of the short side wall portions, at least one of the long side wall portions, or the lid. [Aspect 4] A secondary battery according to any one of aspects 1 to 3, wherein the secondary battery is selected from the group consisting of a nickel-metal hydride secondary battery, a lead storage battery, and an alkaline secondary battery. [Aspect 5] 5. The secondary battery of embodiment 4, wherein the secondary battery is an alkaline secondary battery, the alkaline secondary battery being a nickel-zinc secondary battery. [Aspect 6] A secondary battery according to any one of aspects 1 to 5, wherein the electrode stack includes a positive electrode layer, a negative electrode layer, and a separator that isolates the positive electrode layer and the negative electrode layer from each other. [Aspect 7] 7. The secondary battery of claim 6, wherein the electrode stack has a plurality of unit cells each including the positive electrode layer, the separator, and the negative electrode layer, whereby the plurality of unit cells as a whole form a multi-layer cell. [Aspect 8] The secondary battery according to any one of aspects 1 to 7, further comprising a pressure relief valve capable of releasing gas within the box-shaped case at or above a predetermined operating pressure. [Aspect 9] 9. The secondary battery of claim 8, wherein the fragile portion has a burst pressure higher than an operating pressure of the pressure relief valve. [Aspect 10] a module case which is a metal container with a lid; A plurality of secondary batteries according to any one of Aspects 1 to 9 housed in parallel with each other in the module case; A secondary battery module comprising: [Aspect 11] 11. The secondary battery module according to aspect 10, wherein each of the plurality of box-shaped cases has the stripe-like recesses on the same side surface. [Aspect 12] 12. The secondary battery module of claim 11, wherein a side wall of the module case facing the surface having the streak-like recesses is reinforced. [Aspect 13] 13. The secondary battery module of claim 11, wherein the module case has a burst pressure higher than the burst pressure of the fragile portion. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view illustrating an example of a secondary battery according to the present invention. [Diagram 2] 2 is a top view showing a schematic positional relationship between the secondary battery and a module side wall shown in FIG. 1. FIG. [Diagram 3] FIG. 1 is a cross-sectional view that illustrates an example of the internal structure of a secondary battery according to the present invention. [Figure 4] 4 is a schematic cross-sectional view of the secondary battery shown in FIG. 3 taken along line AA'. FIG. [Diagram 5] FIG. 4 is a perspective view that illustrates a schematic view of an electrode stack of the secondary battery illustrated in FIG. [Figure 6] 4 is a cross-sectional view that illustrates a schematic diagram of an electrode stack of the secondary battery illustrated in FIG. [Figure 7] 1 is a schematic cross-sectional view showing an example of a secondary battery module according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] secondary battery The present invention relates to a secondary battery. The secondary battery in the present invention is preferably a nickel-hydrogen secondary battery, a lead storage battery, or an alkaline secondary battery, and more preferably an alkaline secondary battery. The alkaline secondary battery is not particularly limited as long as it is a secondary battery using an alkaline electrolyte (typically an aqueous alkali metal hydroxide solution), but a zinc secondary battery using zinc as the negative electrode is preferable. Examples of zinc secondary batteries include nickel-zinc secondary batteries, silver oxide zinc secondary batteries, manganese oxide zinc secondary batteries, and various other alkaline zinc secondary batteries, and nickel-zinc secondary batteries are particularly preferable. Therefore, although the following description may refer to the configuration of zinc secondary batteries such as nickel-zinc secondary batteries, the present invention is not limited to zinc secondary batteries.

[0012] 1 to 6 show an example of a secondary battery 10 according to the present invention. The secondary battery 10 includes an electrode laminate 11, an electrolytic solution 18, and a resin box-shaped case 20 in which the electrode laminate 11 and the electrolytic solution 18 are accommodated. The electrode laminate 11 and the electrolytic solution 18 are accommodated in the box-shaped case 20. The box-shaped case 20 has a streak-like recess 20a, which functions as a weak part that can be broken preferentially and locally when the internal pressure of the secondary battery 10 rises excessively due to gas generated in the secondary battery 10. By providing the box-shaped case 20 with the streak-like recess 20a in this way, the recess 20a can be made to function as a weak part that can be broken preferentially and locally when the internal pressure of the battery rises excessively, and as a result, a secondary battery having a weak part can be provided at a lower cost.

[0013] As described above, providing a box-shaped case with a weakened portion with a reduced thickness as disclosed in Patent Document 1 leads to an increase in manufacturing costs. That is, such a conventional weakened portion is formed, for example, by forming a recessed rupture portion and a through hole in the lid portion, and fitting and welding a separately manufactured thin rupture plate to the rupture portion, so that additional work steps such as forming and processing the rupture portion, manufacturing the rupture plate, and fitting and welding these members must be performed, which increases manufacturing costs. In contrast, according to the secondary battery 10 of the present invention, by a very simple method of only providing the box-shaped case 20 with a streaky recess 20a, this recess 20a can be made to function as a weakened portion that can be broken preferentially and locally when the battery internal pressure rises excessively (for example, in the direction indicated by the arrow B in FIG. 1). It is believed that the streaky recess 20a makes it easier to disperse the pressure when the recess 20a is ruptured, and promotes preferential and localized destruction. As a result, the secondary battery 10 having the weakened portion can be provided at a lower cost.

[0014] The structure and shape of the streak-like recess 20a are not particularly limited as long as it can function as a weak portion that can be preferentially and locally broken when the battery internal pressure rises excessively. A particularly preferred streak-like recess 20a is a weld line. The term "weld line" is a general technical term in the field of injection molding, and is defined as a linear mark that appears at the joining portion of molten resin in a mold during injection molding. Since the box-shaped case 20 is made of resin, the weld line can be formed at the same desired position every time by controlling the position of the inlet (gate) through which the resin is poured when the box-shaped case 20 is injection molded, the injection conditions, and the design of the rib structure on the outer surface of the box-shaped case 20. Therefore, by utilizing the weld line as the streak-like recess 20a, a weak portion can be formed by an extremely simple and low-cost method. In fact, the inventors have found that in the box-shaped case 20 (case body and lid 20e) manufactured by injection molding, weld lines tend to form the starting point of breakage when the internal pressure rises, and that in a high-temperature storage evaluation test, a penetrating crack originating from the weld line occurs, from which internally generated gas leaks. The technical value of this embodiment lies in the fact that the weld line, which would normally be considered a molding defect, is deliberately utilized as the streak-like recess 20a to function as a weak part.

[0015] The box-shaped case 20 typically has a bottom 20b, a pair of long side walls 20c parallel to the electrode laminate 11, a pair of short side walls 20d perpendicular to the electrode laminate 11, and a lid 20e. In this case, the striated recess 20a is preferably provided on at least one of the short side walls 20d, at least one of the long side walls 20c, or the lid 20e, and is particularly preferably provided on at least one of the short side walls 20d. By determining the striated recess 20a at a predetermined position in this manner, it is sufficient to reinforce only a specific position (for example, the side wall of the module case 102 adjacent to the recess 20a as shown by the arrow B in FIG. 2) of a structure (for example, the module case 102 shown in FIG. 2) existing around the box-shaped case 20 in preparation for the rupture of the recess 20a. The method of reinforcing such a structure is not particularly limited, and the side wall may be thickened as shown in FIG. 2, or a reinforcing member may be provided on the side wall.

[0016] The electrode laminate 11 is a laminate including a plurality of electrode layers. Typically, the electrode laminate 11 includes a positive electrode layer 12, a negative electrode layer 14, and a separator 16 that separates the positive electrode layer 12 and the negative electrode layer 14 from each other. Therefore, the electrode laminate 11 can be said to be a battery element that functions as a secondary battery 10 by being permeated with an electrolyte 18. In particular, as shown in Figs. 5 and 6, the electrode laminate 11 is preferably in the form of a positive / negative electrode laminate including a plurality of positive electrode layers 12, a plurality of negative electrode layers 14, and a plurality of separators 16, and is laminated so that the unit of the positive electrode layer 12 / separator 16 / negative electrode layer 14 is repeated. That is, the electrode laminate 11 preferably has a plurality of unit cells 10a including the positive electrode layer 12, the separator 16, and the negative electrode layer 14, and the plurality of unit cells 10a as a whole form a multi-layer cell. This is a so-called assembled battery or stacked battery configuration, and is advantageous in that it can provide high voltage and large current.

[0017] The positive electrode layer 12 may include a positive electrode active material layer. The positive electrode active material constituting the positive electrode active material layer may be appropriately selected from known positive electrode materials according to the type of 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. Alternatively, in the case of an air-zinc secondary battery, an air electrode may be used as the positive electrode. The positive electrode layer 12 may further include a positive electrode current collector (not shown). The positive electrode current collector preferably has a positive electrode current collector tab 12b extending in a predetermined direction (for example, upward) from an end (for example, an upper end) of the positive electrode layer 12. A preferred example of the positive electrode current collector is a nickel porous substrate such as a foamed nickel plate. In this case, for example, a paste containing an electrode active material such as nickel hydroxide is uniformly applied onto a nickel porous substrate and dried to preferably produce a positive electrode plate consisting of a positive electrode / positive electrode current collector. At that time, it is also preferable to perform a press treatment on the dried positive electrode plate (i.e., positive electrode / positive electrode current collector) to prevent the electrode active material from falling off and improve the electrode density. The positive electrode layer 12 shown in FIG. 6 includes a positive electrode current collector (e.g., nickel foam), but is not shown. This is because in the case of a nickel-zinc secondary battery, the positive electrode current collector is completely integrated with the positive electrode active material, and therefore the positive electrode current collector cannot be depicted separately. The positive electrode current collector tab 12b may be made of the same material as the positive electrode current collector, or may be made of a different material. When the positive electrode current collector is a nickel porous substrate such as a nickel foam plate, it can be processed into a tab shape by pressing it. In any case, the positive electrode current collector tab 12b may be extended by adding another current collecting member such as a tab lead to such a tab. In any case, it is preferable that a plurality of positive electrode current collector tabs 12b are joined to one positive electrode terminal 26 or a member electrically connected thereto to form a positive electrode tab joint (not shown). This allows current collection to be performed with a simple configuration and with good space efficiency, and also makes it easier to connect to the positive electrode terminal 26. The positive electrode current collecting tab 12b can be joined to a member such as a terminal by using a known joining method such as ultrasonic welding (ultrasonic joining), laser welding, TIG welding, or resistance welding.

[0018] The positive electrode layer 12 may contain at least one additive selected from the group consisting of silver compounds, manganese compounds, and titanium compounds, which can promote a positive electrode reaction that absorbs hydrogen gas generated by a self-discharge reaction. The positive electrode layer 12 may further contain cobalt. Cobalt is preferably contained in the positive electrode layer 12 in the form of cobalt oxyhydroxide. In the positive electrode layer 12, cobalt functions as a conductive additive, thereby contributing to an improvement in charge / discharge capacity.

[0019] The negative electrode layer 14 may include a negative electrode active material layer 14a. For example, in the case of a zinc secondary battery, 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 included in any form of zinc metal, zinc compound, or zinc alloy, so long as it has an electrochemical activity suitable for the negative electrode. Preferred examples of the negative electrode material include zinc oxide, zinc metal, calcium zincate, and the like, with a mixture of zinc metal and zinc oxide being more preferred. The negative electrode active material may be configured in a gel form, or may be mixed with the electrolyte 18 to form a negative electrode mixture. 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 the thickener include polyvinyl alcohol, polyacrylate, CMC, alginic acid, and the like, with polyacrylic acid being preferred because of its excellent chemical resistance to strong alkalis.

[0020] As the zinc alloy, a zinc alloy containing no mercury or lead, 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 preferable because it has an 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 improve safety by suppressing hydrogen gas generation by slowing down the self-dissolution rate in an alkaline electrolyte.

[0021] The shape of the negative electrode material is not particularly limited, but it is preferably in powder form, which increases the surface area and allows for high-current discharge. The average particle size of the negative electrode material is preferably in the range of 3 to 100 μm in minor axis in the case of a zinc alloy, and within this range, the large surface area makes it suitable for high-current discharge, and it is easy to mix uniformly with the electrolyte and gelling agent, and is easy to handle when assembling a battery.

[0022] The negative electrode layer 14 may further include a negative electrode collector 14b. The negative electrode collector 14b is preferably provided inside and / or on the surface of the negative electrode active material layer 14a, except for a portion extending as a negative electrode collector tab 14c. That is, the negative electrode active material layer 14a may be provided on both sides of the negative electrode collector 14b, or the negative electrode active material layer 14a may be provided only on one side of the negative electrode collector 14b. The negative electrode collector tab 14c extends from an end (e.g., the upper end) of the negative electrode layer 14 in a predetermined direction (e.g., upward) at a position that does not overlap with the positive electrode collector tab 12b. The negative electrode collector tab 14c is preferably provided at a position that does not overlap with the positive electrode collector tab 12b. The negative electrode collector tab 14c may be made of the same material as the negative electrode collector 14b, or may be made of a different material. In either case, the negative electrode current collecting tab 14c may be extended by adding another current collecting member such as a tab lead to such a tab. In either case, it is preferable to form the negative electrode tab joint 30 by joining a plurality of negative electrode current collecting tabs 14c to one negative electrode terminal 28 or a member electrically connected thereto. This allows current collection to be performed with a simple configuration and with good space efficiency, and also makes it easier to connect to the negative electrode terminal 28. The joining of the negative electrode current collecting tab 14c to a member such as a terminal may be performed using a known joining method such as ultrasonic welding (ultrasonic joining), laser welding, TIG welding, or resistance welding.

[0023] The negative electrode current collector 14b is preferably a metal plate having a plurality (or a large number) of 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 preferably copper expanded metal, copper punched metal, and combinations thereof, and particularly preferably copper expanded metal. In this case, for example, a mixture containing zinc oxide powder and / or zinc powder, and optionally a binder (e.g., polytetrafluoroethylene particles) can be applied onto the copper expanded metal to preferably prepare a negative electrode plate consisting of a negative electrode / a negative electrode current collector. In this case, it is also preferable to perform a press treatment on the negative electrode plate (i.e., a negative electrode / a negative electrode current collector) after drying to prevent the electrode active material from falling off and improve the electrode density. The expanded metal is a mesh-shaped metal plate obtained by pressing and expanding a metal plate while making staggered cuts using an expander, and shaping the cuts into a diamond or tortoiseshell shape. Punching metal, also known as perforated metal, is a metal plate with holes punched into it. Metal mesh is a metal product with a wire mesh structure, and is different from expanded metal and punching metal.

[0024] The separator 16 is preferably a hydroxide ion conductive separator. The hydroxide ion conductive separator 16 is provided so as to isolate the positive electrode layer 12 and the negative electrode layer 14 in a manner that allows hydroxide ion conductivity. For example, as shown in FIG. 6, the negative electrode layer 14 may be covered or wrapped with the hydroxide ion conductive separator 16. This makes it possible to manufacture a zinc secondary battery (particularly a stacked battery thereof) capable of preventing zinc dendrite extension extremely easily and with high productivity, without the need for a complicated sealing joint between the hydroxide ion conductive separator 16 and the battery container. However, a simple configuration in which the hydroxide ion conductive separator 16 is disposed on one side of the positive electrode layer 12 or the negative electrode layer 14 may also be used.

[0025] The hydroxide ion conductive separator 16 is not particularly limited as long as it is a separator capable of isolating the positive electrode layer 12 and the negative electrode layer 14 in a hydroxide ion conductive manner, but is typically a separator that includes a hydroxide ion conductive solid electrolyte and selectively passes hydroxide ions solely by utilizing hydroxide ion conductivity. A preferred hydroxide ion conductive solid electrolyte is a layered double hydroxide (LDH) and / or an LDH-like compound. Therefore, the hydroxide ion conductive separator 16 is preferably an LDH separator. In this specification, an "LDH separator" is defined as a separator that includes an LDH and / or an LDH-like compound and selectively passes hydroxide ions solely by utilizing the hydroxide ion conductivity of the LDH and / or the LDH-like compound. In this specification, an "LDH-like compound" is a hydroxide and / or oxide with a layered crystal structure similar to LDH, which may not be called LDH, and can be said to be equivalent to LDH. However, in a broad sense, "LDH" can be interpreted as including not only LDH but also LDH-like compounds. The LDH separator is preferably composited with a porous substrate. Therefore, the LDH separator preferably further comprises a porous substrate, and is composited with the porous substrate in a form in which the pores of the porous substrate are filled with LDH and / or LDH-like compounds. That is, in a preferred LDH separator, the pores of the porous substrate are blocked with LDH and / or LDH-like compounds so as to exhibit hydroxide ion conductivity and gas impermeability (and therefore 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 is incorporated over the entire thickness of the porous substrate made of a polymer material. For example, a known LDH separator as disclosed in Patent Document 1 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.

[0026] As shown in FIGS. 1 to 6, each of the positive electrode layer 12, the negative electrode layer 14, and the separator 16 is preferably arranged vertically, whereby the multilayer cells are preferably multilayered in the horizontal direction. Also, it is preferable that the positive electrode current collecting tab 12b and the negative electrode current collecting tab 14c extend upward.

[0027] The electrode laminate 11 may further include a liquid retention member 17. The liquid retention member 17 is preferably provided at a position in contact with the positive electrode layer 12 and / or the negative electrode layer 14. For example, not only the hydroxide ion conductive separator 16 but also the liquid retention member 17 may be interposed between the positive electrode layer 12 and the negative electrode layer 14. And, as shown in FIG. 6, it is preferable that the positive electrode layer 12 and / or the negative electrode layer 14 is covered or wrapped by the liquid retention member 17. However, a simple configuration in which the liquid retention member 17 is disposed on one side of the positive electrode layer 12 or the negative electrode layer 14 may also be used. In any case, by interposing the liquid retention member 17, the electrolytic solution 18 can be uniformly present between the positive electrode layer 12 and / or the negative electrode layer 14 and the hydroxide ion conductive separator 16, and the transfer of hydroxide ions between the positive electrode layer 12 and / or the negative electrode layer 14 and the hydroxide ion conductive separator 16 can be efficiently performed. The liquid retention member 17 is not particularly limited as long as it can hold the electrolytic solution 18, but is preferably a sheet-like member. Preferred examples of the liquid retention member 17 include non-woven fabric, water-absorbing resin, liquid-retaining resin, porous sheet, and various spacers, and particularly preferably non-woven fabric in terms of being able to produce an electrode structure with low cost and good performance. The liquid retention member 17 or the non-woven fabric preferably has a thickness of 10 to 200 μm, more preferably 20 to 200 μm, still more preferably 20 to 150 μm, particularly preferably 20 to 100 μm, and most preferably 20 to 60 μm. When the thickness is within the above range, a sufficient amount of the electrolytic solution 18 can be retained in the liquid retention member 17 while suppressing the overall size of the positive electrode structure and / or the negative electrode structure compactly without waste.

[0028] When the positive electrode layer 12 and / or the negative electrode layer 14 are covered or wrapped with the liquid retaining member 17 and / or the separator 16, it is preferable that the outer edges of the liquid retaining member 17 and / or the separator 16 are closed (except for the edges from which the positive electrode current collector tab 12b and the negative electrode current collector tab 14c extend). In this case, it is preferable that the closed edge of the outer edge of the liquid retaining member 17 and / or the separator 16 is realized by folding the liquid retaining member 17 and / or the separator 16, or by sealing the liquid retaining members 17 together and / or the separators 16 together. Examples of preferable sealing methods include adhesives, heat welding, ultrasonic welding, adhesive tape, sealing tape, and combinations thereof. In particular, since the LDH separator including a porous base material made of a polymer material has an advantage of being flexible and therefore easy to bend, it is preferable to form the LDH separator into a long shape and fold it to form a state in which one side of the outer edge is closed. Thermal welding and ultrasonic welding may be performed using a commercially available heat sealer or the like, but in the case of sealing between LDH separators, it is preferable to perform thermal welding and ultrasonic welding by sandwiching the outer peripheral portion of the liquid retaining member 17 between the LDH separators constituting the outer peripheral portion, in order to perform more effective sealing. On the other hand, the adhesive, adhesive tape, and sealing tape may be commercially available products, but it is preferable to use those containing a resin having alkali resistance in order to prevent deterioration in an alkaline electrolyte. From this viewpoint, examples of preferable adhesives include epoxy resin adhesives, natural resin adhesives, modified olefin resin adhesives, and modified silicone resin adhesives, and among them, epoxy resin adhesives are more preferable because they are particularly excellent in alkali resistance. An example of a product of an epoxy resin adhesive is the epoxy adhesive Hysol (registered trademark) (manufactured by Henkel).

[0029] It is preferable that the outer edge of one side, which is the upper end of the separator 16, is open. This open-top structure 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 is highly dense and allows only hydroxide ions to pass through, so O 2In this respect, the top-opening type structure allows O 2 can escape above the positive electrode layer 12 and be sent to the negative electrode layer 14 side through the upper open portion, thereby 2 The negative electrode active material Zn can be oxidized to ZnO by this oxygen reaction cycle. By using the open-top electrode laminate 11 in a sealed zinc secondary battery, the overcharge resistance can be improved. Even if the outer edge of one side that is the upper end of the separator 16 or the liquid-retaining member 17 is closed, the same effect as that of the open-type configuration can be expected by providing a vent hole in a 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 when sealing, a part of the outer edge may be left unsealed so that a vent hole is formed.

[0030] The electrolyte 18 preferably contains an aqueous solution of an alkali metal hydroxide. In FIG. 6, the electrolyte 18 is only partially illustrated because it is distributed throughout the positive electrode layer 12 and the negative electrode layer 14. Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, lithium hydroxide, and ammonium hydroxide, with potassium hydroxide being more preferable. In order 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 be present in the form of a positive electrode mixture and / or a negative electrode mixture. In addition, the electrolyte may be gelled to prevent leakage of the electrolyte. As the gelling agent, it is preferable to use a polymer that absorbs the solvent of the electrolyte and swells, and polymers such as polyethylene oxide, polyvinyl alcohol, and polyacrylamide, or starch are used.

[0031] The lid 20e is preferably provided with a pressure release valve 32 capable of releasing gas in the box-shaped case 20 at a predetermined operating pressure or higher. In this case, it is preferable that the burst pressure (or operating pressure) of the fragile portion (recess 20a) is higher than the operating pressure of the pressure release valve 32. In this way, the fragile portion (recess 20a) can be broken only in an abnormal situation where the internal pressure rises to a level that the pressure release valve 32 can no longer handle, without impairing the function of the pressure release valve 32. In other words, the pressure release valve 32 is intended to handle gradual pressure changes, such as gradually discharging accumulated gas during normal battery operation, while the fragile portion (recess 20a) is intended to release abnormal pressure when pressure rises suddenly in an abnormal situation.

[0032] Secondary Battery Module It is preferable to configure a secondary battery module using a plurality of secondary batteries 10. FIG. 7 shows a preferable embodiment of the secondary battery module. The secondary battery module 100 shown in FIG. 7 includes a module case 102 and a plurality of secondary batteries 10. The module case 102 is a metal container with a lid. The plurality of secondary batteries 10 are accommodated in the module case 102 parallel to each other (for example, with the long side wall portions 20c facing each other). By accommodating the secondary batteries 10 in the module case 102, which is a metal container with a lid, even if the weak portion (recess 20a) ruptures due to hydrogen combustion in the secondary battery 10 (for example, a nickel-zinc secondary battery), various troubles associated with the rupture (sudden rise in internal pressure, scattering of debris, leakage of electrolyte, fire, abnormal heat, etc.) can all be prevented within the module case 102, and the safety outside the module case 102 can be sufficiently ensured.

[0033] As described above with reference to Fig. 2, it is preferable that each of the multiple box-shaped cases 20 has a stripe-shaped recess 20a on the same side (for example, one side of the short side wall portion 20d). It is also preferable that the side wall of the module case 102 facing the surface having the stripe-shaped recess 20a is reinforced. By determining the stripe-shaped recess 20a at a predetermined position in this manner, it is sufficient to reinforce only the side wall of the module case 102 corresponding to the stripe-shaped recess 20a in preparation for the recess 20a bursting. Therefore, it is possible to provide a secondary battery module 100 that is low cost and highly safe.

[0034] From the viewpoint of effectively preventing an internal pressure rise accompanying the rupture of the recess 20a within the module case 102, it is preferable that the burst pressure of the module case 102 (particularly, the side wall or top cover facing the recess 20a) is higher than the burst pressure of the recess 20a. By doing so, even if hydrogen combustion occurs in the module case 102, causing the recess 20a of one secondary battery 10 (e.g., a nickel-zinc secondary battery) to burst, various troubles accompanying the rupture (sudden rise in internal pressure, scattering of debris, leakage of electrolyte, fire, abnormal heat generation, etc.) can all be reliably prevented within the module case 102 (particularly, the side wall or top cover 102b facing the recess 20a), and the safety of the outside of the module case 102 can be sufficiently ensured.

[0035] The module case 102 is a metal container with a lid, and includes a container body 102a and an upper lid 102b. That is, in order to ensure sufficient pressure resistance, heat resistance, and strength, the module case 102 is made of both the container body 102a and the upper lid 102b made of metal plates. In particular, since the upper lid 102b is disposed near the recess 20a, it is desired that the upper lid 102b has sufficient pressure resistance, heat resistance, and strength to withstand the pressure and temperature at the time of the rupture of the recess 20a. From this viewpoint, preferred examples of the metal plate constituting the upper lid 102b include a steel plate and a stainless steel plate. In addition, the thickness of the metal plate constituting the upper lid 102b is preferably 1.0 to 3.0 mm, more preferably 1.5 to 2.5 mm. On the other hand, preferred examples of the metal plate constituting the container body 102a include a steel plate and a stainless steel plate. The thickness of the metal plate constituting the container body 102a may be appropriately determined in consideration of the allowable weight as long as the desired pressure resistance or strength is ensured, but is preferably 0.8 to 2.5 mm, and more preferably 1.0 to 2.0 mm. From the viewpoint of preventing the rise in internal pressure caused by the rupture of the recess 20a in the module case 102, it is desirable that the top cover 102b is firmly fixed to the container body 102a. The top cover 102b is preferably fixed to the container body by bolt and nut fastening, since it is possible to remove the top cover 102b when necessary (for example, when replacing or maintaining the secondary battery 10) while ensuring sufficient pressure resistance. Although the module case 102 is a container with a lid, it is desirable not to make it a completely sealed container so that the internal pressure can be released to the outside. For example, the module case 102 preferably has a structure that releases the internal pressure to the outside at a location facing or communicating with the internal space above the secondary battery 10.

[0036] It is desirable to form a flow path for air flow to cool the secondary battery 10 in the module case 102. Preferably, an intake port 102c is provided at one end of the module case 102, while an exhaust port 102d is provided at the other end of the module case 102, and a fan 108 is attached to the exhaust port 102d. The fan 108 may be a small ventilation fan. According to this configuration, air flows through the module case 102 by operating the fan 108, and the secondary battery 10 can be cooled. In order to efficiently cool the secondary battery 10, it is preferable to provide a shielding plate 104 in the module case 102 to partition an intake flow path 110 that supplies air from the intake port 102c to the lower side of the secondary battery 10, and an exhaust flow path 112 that guides the air that has escaped upward through the gap between the secondary batteries 10 to the exhaust port 102d. In this case, the gaps between the secondary batteries 10 also form a flow path, but when the box-shaped case 20 has a rib R, the rib R serves as a spacer, which can form a vertical vent hole, thereby ensuring excellent heat dissipation. In order to ensure and not impede the exhaust flow path 112, it is preferable that the lid portion 28e of the box-shaped case 20 is spaced a predetermined distance from the upper lid 102b, with a preferred distance being 10 to 50 mm, and more preferably 20 to 30 mm. Similarly, in order to ensure and not impede the intake flow path 110, it is preferable that the bottom portion 28b of the box-shaped case 20 is spaced a predetermined distance from the bottom surface of the container body 102a, with a preferred distance being 3 to 20 mm, and more preferably 5 to 15 mm. In order to hold the bottom portion 28b of the box-shaped case 20 higher than the bottom surface of the module case 102, it is preferable to provide a breathable spacer such as a frame or rail on the bottom surface of the module case 102, and place the secondary battery 10 (i.e., the box-shaped case 20) on it.

[0037] It is preferable that a fire spread prevention material 106 is provided between adjacent secondary batteries 10 (i.e., box-shaped cases 20). Since the box-shaped cases 20 are made of resin, if the box-shaped cases 20 are adjacent to each other, there is a possibility that if a fire breaks out in one box-shaped case 20, the fire may spread to the other box-shaped cases 20. However, by interposing the fire spread prevention material 106 between adjacent box-shaped cases 20, such fire spread can be suppressed. In order to more effectively realize this fire spread suppression effect, it is particularly preferable that the side end of the fire spread prevention material 106 reaches the side wall of the module case 102, thereby isolating the adjacent box-shaped cases 20 from each other so that fire cannot spread. However, it is preferable that the upper end of the fire spread prevention material 106 does not reach the upper cover 102b of the module case 102, and is set to be approximately the same height as the secondary battery 10 so as not to obstruct the exhaust flow path 112 inside the module case 102. Similarly, it is preferable that the lower end of the fire spread prevention material 106 does not reach the bottom surface of the container body 102a, but is set at the same height as the bottom surface of the secondary battery 10, and is configured so as not to obstruct the intake flow path 110 inside the module case 102. As the fire spread prevention material 106, various known fire spread prevention materials can be used, for example, an embossed mica plate.

Claims

1. An electrode stack; An electrolyte; a resin box-shaped case in which the electrode stack and the electrolyte are contained; A secondary battery comprising: the box-shaped case has a streak-like recess, and the streak-like recess functions as a fragile part that can be broken preferentially and locally when internal pressure increases excessively due to gas generated within the battery; The secondary battery, wherein the streak-like recess is a weld line.

2. 2. The secondary battery according to claim 1, wherein the box-shaped case has a bottom, a pair of long side wall portions parallel to the electrode stack, a pair of short side wall portions perpendicular to the electrode stack, and a lid portion, and the striated recess is provided in at least one of the short side wall portions, at least one of the long side wall portions, or the lid portion.

3. 3. The secondary battery according to claim 1, wherein the secondary battery is selected from the group consisting of a nickel-metal hydride secondary battery, a lead-acid battery, and an alkaline secondary battery.

4. 4. The secondary battery according to claim 3, wherein the secondary battery is an alkaline secondary battery, the alkaline secondary battery being a nickel-zinc secondary battery.

5. 3. The secondary battery according to claim 1, wherein the electrode stack comprises a positive electrode layer, a negative electrode layer, and a separator that separates the positive electrode layer and the negative electrode layer from each other.

6. 6. The secondary battery according to claim 5, wherein the electrode stack has a plurality of unit cells each including the positive electrode layer, the separator, and the negative electrode layer, whereby the plurality of unit cells as a whole form a multi-layer cell.

7. 3. The secondary battery according to claim 1, further comprising a pressure relief valve capable of releasing gas within the box-shaped case at or above a predetermined operating pressure.

8. The secondary battery according to claim 7 , wherein the burst pressure of the fragile portion is higher than an operating pressure of the pressure relief valve.

9. a module case which is a metal container with a lid; A plurality of secondary batteries according to claim 1 or 2 housed in parallel with each other in the module case; A secondary battery module comprising:

10. The secondary battery module according to claim 9 , wherein each of the plurality of box-shaped cases has the stripe-like recess on a surface on the same side.

11. The secondary battery module according to claim 10 , wherein a side wall of the module case facing the surface having the streak-like recess is reinforced.

12. The secondary battery module according to claim 10 , wherein a burst pressure of the module case is higher than a burst pressure of the fragile portion.

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