WO2023162333A1

WO2023162333A1 - Secondary battery and secondary battery module

Info

Publication number: WO2023162333A1
Application number: PCT/JP2022/039697
Authority: WO
Inventors: 淳宣松矢
Original assignee: 日本碍子株式会社
Priority date: 2022-02-25
Filing date: 2022-10-25
Publication date: 2023-08-31

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

Secondary battery and secondary battery module

The present invention relates to secondary batteries and secondary battery modules.

Alkaline secondary batteries, such as nickel-zinc batteries, use an aqueous electrolyte such as an aqueous solution of potassium hydroxide, and are significantly safer than secondary batteries that use a non-aqueous electrolyte containing a flammable organic solvent. It is expensive. However, in order to further improve the safety of alkaline secondary batteries, it is desirable to assume the worst possible abnormal situation as a risk and take all possible measures against it. As the worst possible abnormal situation, it is conceivable that hydrogen is generated by the decomposition of the aqueous electrolytic solution, and hydrogen combustion is caused by ignition due to short circuit or the like.

Therefore, a laminated battery-type alkaline secondary battery has been proposed that can minimize the damage caused by a rapid increase in the internal pressure of the battery due to hydrogen combustion or the like. For example, Patent Document 1 (WO2021/024681) describes a laminated battery in which a plurality of unit cell elements having the structure of an alkaline secondary battery are laminated, and a resin box-shaped case in which the laminated battery is accommodated in the vertical direction. is disclosed, and it is proposed to provide a fragile portion with a reduced thickness in the lid portion of the box-shaped case with a predetermined thickness and area ratio. According to this configuration, when the internal pressure of the battery rises rapidly due to hydrogen combustion or the like, the fragile portion is preferentially and locally destroyed before the entire box-shaped case is destroyed. damage can be avoided, and as a result, safety can be improved.

In addition, in order to further increase the capacity and output, it is common practice to arrange a plurality of battery units each containing a laminated battery to form 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 accommodated in the module case. ing.

WO2021/024681

Providing a box-shaped case with a weakened portion having a reduced thickness as disclosed in Patent Document 1 causes an increase in manufacturing cost. Therefore, it is desired to achieve the same function as the fragile portion at a lower manufacturing cost.

The present inventors have recently found that by providing the box-shaped case with a streak-shaped recess, the recess can function as a fragile portion that can be preferentially and locally destroyed when the internal pressure of the battery is excessively increased. As a result, the inventors have found that a secondary battery having a fragile portion can be provided at a lower cost.

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

According to the present invention, the following aspects are provided.
[Aspect 1]
an electrode laminate;
an electrolyte;
A box-shaped case made of resin that accommodates the electrode laminate and the electrolytic solution;
A secondary battery comprising
The box-shaped case has a streak-shaped recess, and the streak-shaped recess functions as a fragile portion that can be preferentially and locally destroyed when the internal pressure is excessively increased by the gas generated in the battery. , secondary battery.
[Aspect 2]
The secondary battery according to aspect 1, wherein the streaky concave portion is a weld line.
[Aspect 3]
The box-shaped case has a bottom, a pair of long side walls parallel to the electrode laminate, a pair of short side walls perpendicular to the electrode laminate, and a lid, 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.
[Aspect 4]
The secondary battery according to any one of aspects 1 to 3, wherein the secondary battery is selected from the group consisting of nickel-hydrogen secondary batteries, lead-acid batteries, and alkaline secondary batteries.
[Aspect 5]
The secondary battery according to aspect 4, wherein the secondary battery is an alkaline secondary battery, and the alkaline secondary battery is a nickel-zinc secondary battery.
[Aspect 6]
The secondary battery according to any one of aspects 1 to 5, wherein the electrode laminate includes a positive electrode layer, a negative electrode layer, and a separator separating the positive electrode layer and the negative electrode layer from each other.
[Aspect 7]
7. The second embodiment according to aspect 6, wherein the electrode laminate 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 form a multilayer cell as a whole. next battery.
[Aspect 8]
The secondary battery according to any one of modes 1 to 7, further comprising a pressure release valve capable of releasing gas in the box-shaped case at a predetermined operating pressure or higher.
[Aspect 9]
The secondary battery according to aspect 8, wherein the bursting pressure of the fragile portion is higher than the operating pressure of the pressure relief valve.
[Aspect 10]
a module case, which is a container with a lid made of metal;
a plurality of secondary batteries according to any one of aspects 1 to 9, which are accommodated in parallel in the module case;
A secondary battery module with
[Aspect 11]
11. The secondary battery module according to aspect 10, wherein the plurality of box-shaped cases each have the streak-shaped concave portion on the same side surface.
[Aspect 12]
The secondary battery module according to aspect 11, wherein a side wall of the module case facing the surface having the streaky recess is reinforced.
[Aspect 13]
The secondary battery module according to

aspect

11 or 12, wherein the module case has a higher burst pressure than the weak portion.

1 is a perspective view schematically showing an example of a secondary battery according to the present invention; FIG. FIG. 2 is a top view schematically showing the positional relationship between the secondary battery and the side wall of the module shown in FIG. 1; 1 is a cross-sectional view schematically showing an example of the internal structure of a secondary battery according to the present invention; FIG. 4 is a diagram schematically showing a cross section of the secondary battery shown in FIG. 3 taken along line A-A'; FIG. FIG. 4 is a perspective view schematically showing an electrode laminate of the secondary battery shown in FIG. 3; FIG. 4 is a cross-sectional view schematically showing an electrode laminate of the secondary battery shown in FIG. 3; 1 is a schematic cross-sectional view showing an example of a secondary battery module according to the present invention; FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to secondary batteries. The secondary battery in the present invention is preferably a nickel-hydrogen secondary battery, a lead-acid battery, or an alkaline secondary battery, 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 a negative electrode is preferred. Examples of zinc secondary batteries include nickel-zinc secondary batteries, silver-zinc oxide secondary batteries, manganese-zinc oxide secondary batteries, and various other alkaline zinc secondary batteries. Nickel-zinc secondary batteries are particularly preferred. be. Therefore, although the following description may refer to the construction of zinc secondary batteries such as nickel-zinc secondary batteries, the present invention is not limited to zinc secondary batteries.

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 box-shaped resin case 20 that accommodates the electrode laminate 11 and the electrolytic solution 18 . The box-shaped case 20 accommodates the electrode laminate 11 and the electrolytic solution 18 . The box-shaped case 20 has a streak-shaped recess 20a, and the streak-shaped recess 20a is a fragile portion that can be preferentially and locally destroyed when the internal pressure is excessively increased by the gas generated in the secondary battery 10. function as By providing the box-shaped case 20 with the streaky recess 20a in this manner, the recess 20a can function as a fragile portion that can be preferentially and locally destroyed when the internal pressure of the battery is excessively increased. , a secondary battery having a fragile portion can be provided at a lower cost.

As described above, providing a box-shaped case with a weakened portion having a reduced thickness as disclosed in Patent Document 1 leads to an increase in manufacturing cost. That is, such a conventional fragile portion is formed, for example, by forming a depression-shaped rupture portion and a through hole in the lid portion, and fitting and welding a separately manufactured thin rupture plate to the rupture portion. , the formation and processing of the rupture portion, the fabrication of the rupture plate, and the fitting and welding of these members, which increase the manufacturing cost. On the other hand, according to the secondary battery 10 of the present invention, the box-shaped case 20 is provided with the streak-like recessed portion 20a by a very simple method, and the recessed portion 20a is opened when the internal pressure of the battery is excessively increased (for example, It can act as a preferentially locally destructible weakened portion (in the direction indicated by arrow B in FIG. 1). It is believed that the streak-like shape of the recessed portions 20a makes it easier to disperse the pressure when the recessed portions 20a are cleaved, and promotes preferential and local breakage. As a result, secondary battery 10 having a fragile portion can be provided at a lower cost.

The structure and shape of the streak-shaped concave portion 20a are not particularly limited as long as it can function as a fragile portion that can be preferentially and locally destroyed when the internal pressure of the battery is excessively increased. A particularly preferable streaky recess 20a is a weld line. A "weld line" is a general technical term in the field of injection molding, and is defined as a linear trace that appears at the junction of molten resins in a mold during injection molding. Since the box-shaped case 20 is made of resin, by controlling the position of the inlet (gate) into which the resin is poured and the injection conditions when the box-shaped case 20 is injection molded, and by designing the rib structure of the outer surface of the box-shaped case 20, A weld line can be formed at the same desired position each time. Therefore, by utilizing the weld line as the streak-like concave portion 20a, the weak portion can be formed by an extremely simple and low-cost method. In fact, the present inventor found that the box-shaped case 20 (the case body and the lid portion 20e) produced by injection molding has a weld line, which is likely to cause breakage when the internal pressure rises. It is known that a penetrating crack originating from is generated and the internally generated gas leaks from there. It can be said that the technical value of this embodiment is that the weld line, which should be called a molding defect, is intentionally utilized as the streak-like recessed portion 20a to function as a weak portion.

The box-shaped case 20 typically includes a bottom portion 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 streak-like recess 20a is preferably provided in at least one of the short side walls 20d, at least one of the long side walls 20c, or the lid 20e, and particularly preferably in at least one of the short side walls 20d. be. By setting the streak-shaped recessed portion 20a at a predetermined position in this way, a structure existing around the box-shaped case 20 (for example, the module case 102 shown in FIG. 2) can be positioned at a specific position (for example, an arrow in FIG. Only the side walls of the module case 102 adjacent to the recess 20a, as indicated at B), need be reinforced against rupture of the recess 20a. A 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.

The electrode laminate 11 is a laminate including a plurality of electrode layers. Typically, the electrode stack 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 the secondary battery 10 when the electrolyte 18 is permeated. In particular, the electrode laminate 11 includes a plurality of positive electrode layers 12, a plurality of negative electrode layers 14, and a plurality of separators 16, as shown in FIGS. It is preferably in the form of a positive/negative electrode laminate in which 14 units are stacked repeatedly. That is, the electrode laminate 11 preferably has a plurality of unit cells 10a each including the positive electrode layer 12, the separator 16, and the negative electrode layer 14, so that the plurality of unit cells 10a as a whole form a multi-layer cell. This is a so-called assembled battery or laminated battery configuration, and is advantageous in that a high voltage and a large current can be obtained.

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 a zinc-air secondary battery, the air electrode may be used as the positive electrode. The cathode layer 12 may further include a cathode current collector (not shown). The positive electrode current collector preferably has a positive electrode current collecting tab 12b that extends in a predetermined direction (eg, upward) from the end (eg, upper end) of the positive electrode layer 12 . Preferred examples of the positive electrode current collector include nickel porous substrates such as foamed nickel plates. In this case, for example, a positive electrode plate composed of a positive electrode/positive current collector can be preferably produced by uniformly applying a paste containing an electrode active material such as nickel hydroxide onto a nickel porous substrate and drying the paste. . In this case, it is also preferable to press the dried positive electrode plate (that is, the positive electrode/positive electrode current collector) to prevent the electrode active material from falling off and improve the electrode density. Although the positive electrode layer 12 shown in FIG. 6 includes a positive electrode current collector (for example, nickel foam), it is not shown. This is because, in the case of the nickel-zinc secondary battery, the positive electrode current collector is integrated with the positive electrode active material, and thus the positive electrode current collector cannot be drawn separately. The positive electrode collector tab 12b may be made of the same material as the positive electrode collector, or may be made of a different material. When the positive electrode current collector is a nickel porous substrate such as a foamed nickel plate, it can be processed into a tab shape by pressing. In any case, such a tab may be supplemented with another current collecting member such as a tab lead to extend the positive electrode current collecting tab 12b. In any case, it is preferable that a plurality of positive electrode current collecting tabs 12b are joined to one positive electrode terminal 26 or a member electrically connected thereto to form a positive electrode tab joining portion (not shown). By doing so, current collection can be performed with good space efficiency with a simple configuration, and connection to the positive electrode terminal 26 is also facilitated. The positive electrode current collecting tab 12b and a member such as a terminal may be joined using a known joining method such as ultrasonic welding (ultrasonic joining), laser welding, TIG welding, or resistance welding.

The positive electrode layer 12 may contain at least one additive selected from the group consisting of silver compounds, manganese compounds, and titanium compounds. can promote Moreover, 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 aid, thereby contributing to an improvement in charge/discharge capacity.

The negative electrode layer 14 can include a negative electrode active material layer 14a. For example, in the case of a zinc secondary battery, the negative electrode active material forming the negative electrode active material layer 14a contains at least one selected from the group consisting of zinc, zinc oxide, zinc alloys and zinc compounds. Zinc may be contained in any form of zinc metal, zinc compound, and zinc alloy as long as it has electrochemical activity suitable for the negative electrode. Preferred examples of the negative electrode material include zinc oxide, zinc metal, calcium zincate, etc., and a mixture of zinc metal and zinc oxide is more preferred. The negative electrode active material may be configured in a gel form, or may be mixed with the electrolytic solution 18 to form a negative electrode mixture. For example, a gelled negative electrode can be easily obtained by adding an electrolytic solution and a thickener to the negative electrode active material. Examples of the thickener include polyvinyl alcohol, polyacrylate, CMC, alginic acid, etc. Polyacrylic acid is preferable because of its excellent chemical resistance to strong alkali.

As the zinc alloy, it is possible to use a zinc alloy that does not contain mercury and lead, which is known as a zinc-free zinc alloy. For example, a zinc alloy containing 0.01 to 0.1% by mass of indium, 0.005 to 0.02% by mass of bismuth, and 0.0035 to 0.015% by mass of aluminum has the effect of suppressing hydrogen gas generation. Therefore, it is preferable. Indium and bismuth are particularly advantageous in terms of improving discharge performance. The use of a zinc alloy for the negative electrode slows down the rate of self-dissolution in an alkaline electrolyte, thereby suppressing the generation of hydrogen gas and improving safety.

Although the shape of the negative electrode material is not particularly limited, it is preferably powdered, which increases the surface area and enables high-current discharge. In the case of a zinc alloy, the average particle size of the preferred negative electrode material is in the range of 3 to 100 μm in minor axis. It is easy to mix uniformly with the agent, and is easy to handle during battery assembly.

The negative electrode layer 14 may further include a negative electrode current collector 14b. The negative electrode current collector 14b is preferably provided inside and/or on the surface of the negative electrode active material layer 14a except for the portion extending as the negative electrode current collecting tab 14c. That is, the negative electrode active material layer 14a may be arranged on both sides of the negative electrode current collector 14b, or the negative electrode active material layer 14a may be arranged only on one side of the negative electrode current collector 14b. good. Then, the negative electrode current collector 14c extends from the end (eg, upper end) of the negative electrode layer 14 in a predetermined direction (eg, upward) at a position that does not overlap the positive electrode current collector tab 12b. The negative electrode current collecting tab 14c is preferably provided at a position not overlapping the positive electrode current collecting 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 any case, such a tab may be supplemented with another current collecting member such as a tab lead to extend the negative electrode current collecting tab 14c. In any case, it is preferable that a plurality of negative electrode current collecting tabs 14c are joined to one negative electrode terminal 28 or a member electrically connected thereto to constitute the negative electrode tab joining portion 30. FIG. By doing so, current collection can be performed with good space efficiency with a simple configuration, and connection to the negative electrode terminal 28 is facilitated. The bonding between the negative electrode current collecting tab 14c and a member such as a terminal may be performed using a known bonding method such as ultrasonic welding (ultrasonic bonding), laser welding, TIG welding, resistance welding, or the like.

From the viewpoint of fixing the negative electrode active material to the current collector, it is preferable to use a metal plate having a plurality (or a large number) of openings as the negative electrode current collector 14b. 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, especially Copper expanded metal is preferred. In this case, for example, a mixture comprising zinc oxide powder and/or zinc powder and, if desired, a binder (for example, polytetrafluoroethylene particles) is applied onto a copper expanded metal to form a negative electrode composed of a negative electrode/a negative electrode current collector. Plates can be preferably made. At that time, it is also preferable to press the dried negative electrode plate (that is, the negative electrode/negative electrode current collector) to prevent the electrode active material from falling off and to improve the electrode density. The expanded metal is a mesh-like metal plate obtained by expanding a metal plate with zigzag cuts by an expander and forming the cuts into a diamond shape or a tortoiseshell shape. A perforated metal is also called a perforated metal, and is made by punching holes in a metal plate. A metal mesh is a metal product with a wire mesh structure, and is different from expanded metal and perforated metal.

The separator 16 is preferably a hydroxide ion conducting separator. A hydroxide ion-conducting separator 16 is provided to separate the positive electrode layer 12 and the negative electrode layer 14 so as to conduct hydroxide ions. For example, as shown in FIG. 6, the negative electrode layer 14 may be covered or wrapped with a hydroxide ion conductive separator 16 . This eliminates the need for complicated sealing bonding between the hydroxide ion conductive separator 16 and the battery container, and makes it possible to manufacture a zinc secondary battery (especially a laminated battery thereof) that can prevent zinc dendrite extension in a very simple and costly manner. It becomes possible to produce with productivity. However, a simple configuration in which the hydroxide ion conductive separator 16 is arranged on one side of the positive electrode layer 12 or the negative electrode layer 14 may also be used.

The hydroxide ion-conducting separator 16 is not particularly limited as long as it can separate the positive electrode layer 12 and the negative electrode layer 14 so that hydroxide ions can be conducted, but typically includes a hydroxide ion-conducting solid electrolyte. , is a separator that allows hydroxide ions to pass through exclusively by utilizing hydroxide ion conductivity. Preferred hydroxide ion-conducting solid electrolytes are layered double hydroxides (LDH) and/or LDH-like compounds. Therefore, hydroxide ion conducting separator 16 is preferably an LDH separator. As used herein, the term "LDH separator" refers to a separator containing LDH and/or LDH-like compounds, which selectively removes hydroxide ions by exclusively utilizing the hydroxide ion conductivity of LDH and/or LDH-like compounds. defined as passing through In the present specification, "LDH-like compounds" are hydroxides and/or oxides of layered crystal structure similar to LDH, although they may not be called LDH, and can be said to be equivalents of LDH. However, as a broad definition, "LDH" can be interpreted as including not only LDH but also LDH-like compounds. The LDH separator is preferably composited with the porous substrate. Therefore, it is preferable that the LDH separator further includes a porous substrate, and the LDH and/or the LDH-like compound are combined with the porous substrate in a form in which the pores of the porous substrate are filled. That is, preferred LDH separators are those in which LDH and/or LDH-like compounds are porous so as to exhibit hydroxide ion conductivity and gas impermeability (and thus function as LDH separators exhibiting hydroxide ion conductivity). block the pores of the base material. The porous substrate is preferably made of a polymeric material, and it is particularly preferable that the LDH is incorporated throughout the entire thickness direction of the porous substrate made of polymeric material. For example, a known LDH separator as disclosed in Patent Document 1 can be used. The thickness of the LDH separator is preferably 5-100 μm, more preferably 5-80 μm, still more preferably 5-60 μm, particularly preferably 5-40 μm.

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 so that the multi-layer cell is multi-layered in the horizontal direction. Moreover, it is preferable that the positive electrode current collecting tab 12b and the negative electrode current collecting tab 14c extend upward.

The electrode laminate 11 may further include a liquid retaining member 17 . The liquid retaining 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 retaining member 17 may be interposed between the positive electrode layer 12 and the negative electrode layer 14 . Then, 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 with the liquid retaining member 17 . However, a simple configuration in which the liquid retaining member 17 is arranged on one surface side of the positive electrode layer 12 or the negative electrode layer 14 may be employed. In any case, by interposing the liquid retaining member 17, the electrolytic solution 18 can be evenly 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 negative electrode layer 14 and the hydroxide ion conductive separator 16 can be performed efficiently. The liquid holding 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-retaining member 17 include non-woven fabric, water-absorbing resin, liquid-retaining resin, porous sheet, and various spacers, but non-woven fabric is particularly preferable because it enables the production of an electrode structure with good performance at low cost. be. The liquid retaining member 17 or the nonwoven 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, most preferably 20 μm. ~60 μm. When the thickness is within the above range, a sufficient amount of the electrolytic solution 18 can be retained in the liquid retaining member 17 while keeping the overall size of the positive electrode structure and/or the negative electrode structure compact without waste.

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, their outer edges (sides from which the positive electrode current collecting tab 12b and the negative electrode current collecting tab 14c extend) except) preferably closed. In this case, the liquid-retaining member 17 and/or the separator 16 has a closed outer edge by bending the liquid-retaining member 17 and/or the separator 16 or by sealing the liquid-retaining members 17 and/or the separators 16 together. preferably. Preferred examples of sealing techniques include adhesives, heat welding, ultrasonic welding, adhesive tapes, sealing tapes, and combinations thereof. In particular, an LDH separator containing a porous substrate made of a polymeric material has the advantage of being easy to bend because of its flexibility. It is preferred to form closed sides. Thermal welding and ultrasonic welding may be performed using a commercially available heat sealer or the like. However, in the case of sealing between LDH separators, the outer peripheral portion of the liquid retaining member 17 should be sandwiched between the LDH separators forming the outer peripheral portion. It is preferable to perform heat welding and ultrasonic welding by using the same method because more effective sealing can be performed. On the other hand, commercially available adhesives, adhesive tapes, and sealing tapes may be used, but those containing an alkali-resistant resin are preferable in order to prevent deterioration in an alkaline electrolyte. From this point of view, examples of preferable adhesives include epoxy resin adhesives, natural resin adhesives, modified olefin resin adhesives, and modified silicone resin adhesives. It is more preferable because it is particularly excellent in alkalinity. A product example of the epoxy resin-based adhesive includes the epoxy adhesive Hysol (registered trademark) (manufactured by Henkel).

It is preferable that the outer edge of one side, which is the upper end of the separator 16, 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 be generated in the positive electrode layer 12, but the LDH separator has a high degree of denseness that substantially allows only hydroxide ions to pass. Impervious to _O2 . In this respect, according to the configuration of the top open type, in the box-shaped case 20, 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 In ₂ , Zn of the negative electrode active material can be oxidized and returned to ZnO. Through such an oxygen reaction cycle, overcharge resistance can be improved by using the electrode laminate 11 with an open top in a sealed zinc secondary battery. Note that even when the outer edge of one side, which is the upper end of the separator 16 or the liquid retaining member 17, is closed, by providing a ventilation hole in a part of the closed outer edge, the same structure as the open type can be obtained. expected to be effective. For example, a ventilation hole may be opened after sealing the outer edge of one side, which is the upper end of the LDH separator, or a part of the outer edge may be unsealed so that a ventilation hole is formed during sealing. good.

The electrolytic solution 18 preferably contains an aqueous alkali metal hydroxide solution. The electrolytic solution 18 is only shown locally in FIG. Examples of alkali metal hydroxides include potassium hydroxide, sodium hydroxide, lithium hydroxide and ammonium hydroxide, with potassium hydroxide being more preferred. Zinc compounds such as zinc oxide and zinc hydroxide may be added to the electrolytic solution in order to suppress self-dissolution of zinc and/or zinc oxide. As described above, the electrolyte may be mixed with the positive electrode active material and/or the negative electrode active material to exist in the form of a positive electrode mixture and/or a negative electrode mixture. Also, the electrolyte may be gelled to prevent leakage of the electrolyte. As the gelling agent, it is desirable to use a polymer that absorbs the solvent of the electrolytic solution and swells, and polymers such as polyethylene oxide, polyvinyl alcohol and polyacrylamide, and starch are used.

It is preferable that the lid portion 20e is provided with a pressure release valve 32 capable of releasing the gas inside the box-shaped case 20 at a predetermined operating pressure or higher. In this case, it is preferable that the bursting pressure (or operating pressure) of the fragile portion (recess 20 a ) is higher than the operating pressure of the pressure release valve 32 . By doing so, the fragile portion (recess 20a) can be destroyed only in an abnormal situation in which the internal pressure rises to the extent that the pressure relief valve 32 cannot cope with it, without impairing the function of the pressure relief valve 32 . That is, the pressure relief valve 32 copes with gradual pressure changes such as gradually discharging accumulated gas during normal battery operation, whereas the fragile portion (recess 20a) responds to a sudden pressure rise in an abnormal situation. It is for releasing the abnormal pressure of time.

Secondary Battery Module It is preferable to construct a secondary battery module using a plurality of secondary batteries 10 . FIG. 7 shows a preferred embodiment of a secondary battery module. A 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 lidded container made of metal. A plurality of secondary batteries 10 are accommodated in the module case 102 parallel to each other (for example, the long side walls 20c face each other). By housing the secondary battery 10 in the module case 102, which is a metal container with a lid, hydrogen combustion in the secondary battery 10 (for example, a nickel-zinc secondary battery) causes the fragile portion (recess 20a) to form. Even if the module ruptures, various troubles associated with the rupture (rapid rise in internal pressure, scattering of fragments, electrolyte leakage, fire, abnormal heat generation, etc.) can all be prevented within the module case 102. Safety can be sufficiently ensured.

As described above with reference to FIG. 2, each of the plurality of box-shaped cases 20 has the streaky recess 20a on the same side surface (for example, one surface of the short side wall portion 20d). preferable. Moreover, it is preferable that the side wall of the module case 102 facing the surface having the streak-like recessed portion 20a is reinforced. By positioning the streak-like recesses 20a at predetermined positions, it is sufficient to reinforce only the side walls of the module case 102 corresponding to the streak-like recesses 20a in case the recesses 20a burst. Therefore, the secondary battery module 100 can be provided at low cost and with high safety.

From the viewpoint of effectively stopping the increase in internal pressure within the module case 102 due to the bursting of the recess 20a, the bursting pressure of the module case 102 (especially the side wall or the upper lid facing the recess 20a) is preferably higher than the bursting pressure of the recess 20a. . By doing so, even if hydrogen combustion occurs to cause the recess 20a of one secondary battery 10 (for example, a nickel-zinc secondary battery) to explode in the module case 102, various troubles (increased internal pressure) due to the explosion will occur. Rapid rise, scattering of fragments, leakage of electrolyte, fire, abnormal heat generation, etc.) can be reliably prevented from occurring inside the module case 102 (in particular, the side wall facing the recess 20a or the upper lid 102b). Safety can be sufficiently ensured.

The module case 102 is a lidded container made of metal, and includes a container body 102a and an upper lid 102b. That is, in order to secure sufficient pressure resistance, heat resistance, and strength, the module case 102 includes both the container main body 102a and the upper lid 102b made of a metal plate. In particular, since the upper cover 102b is arranged near the recess 20a, it is desired to have sufficient pressure resistance, heat resistance and strength to withstand the pressure and temperature when the recess 20a bursts. From this point of view, preferred examples of the metal plate forming the upper lid 102b include a steel plate and a stainless steel plate. Moreover, the thickness of the metal plate forming 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 forming the container main body 102a include a steel plate and a stainless steel plate. Further, the thickness of the metal plate forming the container body 102a may be appropriately determined in consideration of the allowable weight as long as the desired pressure resistance or strength can be secured. It is preferably 1.0 to 2.0 mm. From the viewpoint of preventing an increase in internal pressure within the module case 102 due to the rupture of the recess 20a, it is desired that the upper lid 102b is firmly fixed to the container body 102a. The fixing of the upper lid 102b to the container body is performed by bolt-nut connection, because the upper lid 102b can be removed when necessary (for example, during replacement or maintenance of the secondary battery 10) while ensuring sufficient pressure resistance. preferable. Although the module case 102 is a container with a lid, it is desirable not to make it a completely closed container so that the internal pressure can escape to the outside. For example, the module case 102 preferably has a structure that releases internal pressure to the outside at a location that faces or communicates with the internal space above the secondary battery 10 .

It is desirable to form a flow path for flowing air in order to cool the secondary battery 10 in the module case 102 . Preferably, one end of the module case 102 is provided with an intake port 102c, while the other end of the module case 102 is provided with an exhaust port 102d, and a fan 108 is attached to the exhaust port 102d. Fan 108 may be a small ventilation fan. According to this configuration, by operating fan 108 , air flows through module case 102 and secondary battery 10 can be cooled. In order to efficiently cool the secondary battery 10, a shield plate 104 is provided in the module case 102, an air intake passage 110 for supplying air from an air intake 102c to the lower side of the secondary battery 10, and a secondary It is preferable to separate the exhaust passage 112 that guides the air that escapes upward through the gaps between the batteries 10 to the exhaust port 102d. In this case, the gaps between the secondary batteries 10 also constitute flow paths, but if the box-shaped case 20 has ribs R, the ribs R serve as spacers, thereby forming vertical ventilation holes. , and excellent heat dissipation can be ensured. In order to secure the exhaust flow path 112 and not block it, the lid portion 28e of the box-shaped case 20 is preferably separated from the upper lid 102b by a predetermined distance, preferably 10 to 50 mm, more preferably 20 to 30 mm. . Similarly, in order to secure the air intake channel 110 and not block it, the bottom 28b of the box-shaped case 20 is preferably separated from the bottom surface of the container body 102a by a predetermined distance, preferably 3 to 20 mm, 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, a ventilable spacer such as a frame or rail is provided on the bottom surface of the module case 102, and the secondary battery 10 (that is, the box-shaped case) is placed thereon. A case 20) is preferably arranged.

A fire spread prevention material 106 is preferably provided between adjacent secondary batteries 10 (that is, 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, if one box-shaped case 20 catches fire, the other box-shaped cases 20 may catch fire. However, such fire spread can be suppressed by interposing the fire spread prevention material 106 between the adjacent box-shaped cases 20 . In order to realize this fire spread suppression effect more effectively, the side ends of the fire spread prevention material 106 reach the side walls of the module case 102, thereby separating the adjacent box-shaped cases 20 from each other so that the fire cannot spread. is particularly preferred. However, the upper end of the fire spread prevention material 106 does not reach the upper lid 102b of the module case 102, and is set at approximately the same height as the secondary battery 10 so as not to obstruct the exhaust flow path 112 in the module case 102. preferably Similarly, the lower end of the fire spread prevention material 106 does not reach the bottom surface of the container body 102a, and is set at the same height as the bottom surface of the secondary battery 10, so as not to block the intake flow path 110 inside the module case 102. preferably. As the fire spread prevention material 106, various known fire spread prevention materials can be used, such as an embossed mica plate.

Claims

an electrode laminate;
an electrolyte;
A box-shaped case made of resin that accommodates the electrode laminate and the electrolytic solution;
A secondary battery comprising
The box-shaped case has a streak-shaped recess, and the streak-shaped recess functions as a fragile portion that can be preferentially and locally destroyed when the internal pressure is excessively increased by the gas generated in the battery. , secondary battery.
The secondary battery according to claim 1, wherein the streak-shaped recess is a weld line.
The box-shaped case has a bottom, a pair of long side walls parallel to the electrode laminate, a pair of short side walls perpendicular to the electrode laminate, and a lid, 3. The secondary battery according to claim 1, wherein the 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.
The secondary battery according to claim 1 or 2, wherein the secondary battery is selected from the group consisting of nickel-hydrogen secondary batteries, lead-acid batteries, and alkaline secondary batteries.
The secondary battery according to claim 4, wherein said secondary battery is an alkaline secondary battery, and said alkaline secondary battery is a nickel-zinc secondary battery.
The secondary battery according to claim 1 or 2, wherein the electrode laminate includes 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.
7. The electrode laminate according to claim 6, wherein the electrode laminate 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 form a multi-layer cell as a whole. secondary battery.
The secondary battery according to claim 1 or 2, further comprising a pressure release valve capable of releasing gas in the box-shaped case at a predetermined operating pressure or higher.
The secondary battery according to claim 8, wherein the bursting pressure of said fragile portion is higher than the operating pressure of said pressure relief valve.
a module case, which is a container with a lid made of metal;
a plurality of secondary batteries according to claim 1 or 2, which are accommodated in parallel with each other in the module case;
A secondary battery module with
11. The secondary battery module according to claim 10, wherein the plurality of box-shaped cases each have the streak-shaped recesses on the same side surface.
The secondary battery module according to claim 11, wherein the sidewall of the module case facing the surface having the streaky recess is reinforced.
The secondary battery module according to claim 11, wherein the bursting pressure of the module case is higher than the bursting pressure of the fragile portion.