JP7516086B2 - Secondary batteries and module batteries - Google Patents

Description

The present invention relates to secondary batteries and module batteries.

In a zinc secondary battery, positive and negative plates are stacked to form a laminate. The laminate is housed in a case. The case has two main surfaces that are separated from each other and sandwich the laminate. The case also has a side that extends from the end of one main surface to the end of the other main surface.

For example, in the zinc secondary battery described in Patent Document 1, positive and negative electrode plates are alternately stacked (paragraph 0012). The battery element is housed in a case (paragraph 0031). The case has two main surfaces that are separated from each other and sandwich the battery element (Figure 3). The case also has a side surface that extends from the end of one main surface to the end of the other main surface (Figure 3).

International Publication No. 2019/077953

In zinc secondary batteries, over time and/or after repeated charging and discharging, the internal pressure inside the case can increase, causing the case to expand and break.

To prevent the case from expanding and breaking, it is effective to thicken the case walls to increase the strength of the case. However, if the case walls are made thicker, the weight and volume of the case will increase, which in turn increases the weight and volume of the zinc secondary battery, decreasing the energy density of the zinc secondary battery.

This problem also occurs with secondary batteries other than zinc secondary batteries.

The present invention was made in consideration of this problem. The purpose of the present invention is to increase the strength of the case provided for the secondary battery without significantly increasing the weight and volume of the secondary battery.

The present invention relates to a secondary battery and a module battery including the secondary battery.

The secondary battery comprises a laminate, a case and a lid.

The laminate comprises a positive plate and a negative plate. The negative plate is stacked on top of the positive plate.

The case has an opening. The case houses the laminate.

The lid covers the opening.

The first and second main surfaces of the case are spaced apart from each other with the laminate sandwiched between them. The side surface of the case extends from an end of the first main surface to an end of the second main surface of the case. The side surface of the case has a honeycomb rib structure.

According to the present invention, the honeycomb rib structure formed on the side surface of the case improves the strength of the case, thereby making it possible to increase the strength of the case provided for the secondary battery without significantly increasing the weight and volume of the secondary battery.

The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

1 is a perspective view illustrating a secondary battery according to a first embodiment; 1 is a cross-sectional view illustrating a secondary battery according to a first embodiment; 1 is a cross-sectional view illustrating a secondary battery according to a first embodiment; 1 is a front view illustrating a secondary battery according to a first embodiment; 1 is a side view illustrating a schematic diagram of a secondary battery according to a first embodiment; FIG. 4 is a side view illustrating a schematic diagram of a secondary battery according to a first modified example of the first embodiment. FIG. 4 is a side view illustrating a secondary battery according to a second modified example of the first embodiment. FIG. 11 is a side view illustrating a schematic diagram of a secondary battery according to a third modified example of the first embodiment. 1 is a cross-sectional view illustrating a schematic view of a main portion of a stacked battery included in a secondary battery of a first embodiment. FIG. 2 is a side view illustrating a module battery according to the first embodiment.

1 First embodiment 1.1 Secondary battery Fig. 1 is a perspective view that illustrates a secondary battery of the first embodiment. Fig. 2 and Fig. 3 are cross-sectional views that illustrate the secondary battery of the first embodiment. Fig. 2 illustrates a cross section taken along the line B-B in Fig. 3. Fig. 3 illustrates a cross section taken along the line A-A in Fig. 2.

The secondary battery 1 shown in Figures 1, 2, and 3 is a zinc secondary battery, and is preferably a nickel-zinc secondary battery. The secondary battery 1 may be a secondary battery other than a zinc secondary battery.

As shown in Figures 1, 2, and 3, the secondary battery 1 includes a case 11 and a lid 12. As shown in Figures 2 and 3, the secondary battery 1 also includes a stacked battery 13, a positive electrode current collector 14, and a negative electrode current collector 15.

The case 11 houses the stacked battery 13, the positive electrode current collector 14, and the negative electrode current collector 15. The case 11 has an opening 11a. The lid 12 closes the opening 11a. In this way, the case 11 and the lid 12 form a sealed container having a sealed space. In addition, the stacked battery 13, the positive electrode current collector 14, and the negative electrode current collector 15 are arranged in the sealed space.

As shown in FIG. 2, the stacked battery 13 includes a stacked body 101, a plurality of positive electrode current collector tabs 102, and a plurality of negative electrode current collector tabs 103. Therefore, the secondary battery 1 includes a stacked body 101. The secondary battery 1 also includes a plurality of positive electrode current collector tabs 102 and a plurality of negative electrode current collector tabs 103.

The multiple positive electrode current collector tabs 102 protrude from the laminate 101 in a first direction DXP. The multiple negative electrode current collector tabs 103 protrude from the laminate 101 in a second direction DXN. The second direction DXN is opposite to the first direction DXP. The tips of the multiple positive electrode current collector tabs 102 are aggregated. The tips of the multiple negative electrode current collector tabs 103 are aggregated.

As described above, the case 11 houses the stacked battery 13. Therefore, the case 11 houses the stack 101. The case 11 also houses a plurality of positive electrode current collecting tabs 102 and a plurality of negative electrode current collecting tabs 103.

As shown in Figures 1, 2 and 3, the lid 12 includes a lid body 111, a positive terminal 112 and a negative terminal 113.

The positive terminal 112 and the negative terminal 113 pass through the lid body 111.

The positive terminal 112 is connected to one end of the positive collector plate 14. The positive collector plate 14 is connected to the tips of the aggregated multiple positive collector tabs 102. The negative terminal 113 is connected to one end of the negative collector plate 15. The negative collector plate 15 is connected to the tips of the aggregated multiple negative collector tabs 103. As a result, the positive terminal 112 is electrically connected to the multiple positive collector tabs 102 via the positive collector plate 14. The negative terminal 113 is electrically connected to the multiple negative collector tabs 103 via the negative collector plate 15. As a result, a charging current can be passed from the positive terminal 112 to the negative terminal 113 via the positive collector plate 14, the multiple positive collector tabs 102, the laminate 101, the multiple negative collector tabs 103, and the negative collector plate 15. In addition, a discharge current can flow from the negative terminal 113 to the positive terminal 112 via the negative current collector plate 15, the multiple negative current collector tabs 103, the laminate 101, the multiple positive current collector tabs 102, and the positive current collector plate 14.

The laminate 101 has a plate-like shape. The case 11 has a rectangular box-like shape. The case 11 has a side wall 121, a side wall 122, a side wall 123, a side wall 124, and a bottom wall 125. The side wall 121 and the side wall 122 are parallel to the laminate 101. The side wall 123, the side wall 124, and the bottom wall 125 are perpendicular to the laminate 101. The side wall 121 and the side wall 122 face each other with the laminated battery 13, the positive electrode collector plate 14, and the negative electrode collector plate 15 in between. The side wall 123 and the side wall 124 face each other with the laminated battery 13, the positive electrode collector plate 14, and the negative electrode collector plate 15 in between. The opening 11a and the bottom wall 125 face each other with the laminated battery 13, the positive electrode collector plate 14, and the negative electrode collector plate 15 in between. Side wall 123, side wall 124, and bottom wall 125 connect the end of side wall 121 and the end of side wall 122. Opening 11a is formed between the end of side wall 121 and the end of side wall 122.

The case 11 and the lid body 111 are made of an insulator that is resistant to the electrolyte. The insulator is preferably a resin, more preferably a polyolefin resin, an acrylonitrile butadiene styrene (ABS) resin, or a modified polyphenylene ether resin, and particularly preferably an ABS resin or a modified polyphenylene ether resin.

The positive electrode terminal 112 and the negative electrode terminal 113 are made of electrical conductors.

1.2 Rib Structure FIG. 4 is a front view that illustrates a schematic diagram of the secondary battery of the first embodiment.

As shown in Figures 1, 3, and 4, the case 11 has a first main surface 11p and a second main surface 11q. The first main surface 11p and the second main surface 11q are the outer surfaces of the side walls 121 and 122, respectively. The first main surface 11p and the second main surface 11q are separated from each other with the stacked battery 13, the positive electrode current collector 14, and the negative electrode current collector 15 in between. Therefore, the first main surface 11p and the second main surface 11q are separated from each other with the stacked body 101 in between.

As shown in FIG. 1 and FIG. 4, a rib structure 131 is formed on the first main surface 11p. In the first embodiment, the rib structure 131 is a slit rib structure. When the rib structure 131 is a slit rib structure, the rib structure 131 includes a plurality of slit-shaped ribs 132. The plurality of slit ribs 132 are arranged in a direction DX parallel to the first direction DXP and the second direction DXN. Each of the plurality of slit ribs 132 extends linearly in a direction DY perpendicular to the first direction DXP and the second direction DXN. The rib structure 131 may be a rib structure other than the slit rib structure. For example, the rib structure 131 may be a dot rib structure, or a rib structure in which the slit rib structure and the dot rib structure are mixed. The dot rib structure includes a plurality of dot ribs. The plurality of dot ribs are arranged two-dimensionally. A rib structure similar to the rib structure 131 is also formed on the second main surface 11q.

Figure 5 is a side view that typically illustrates a secondary battery of the first embodiment. Figure 6 is a side view that typically illustrates a secondary battery of a first modified example of the first embodiment. Figure 7 is a side view that typically illustrates a secondary battery of a second modified example of the first embodiment. Figure 8 is a side view that typically illustrates a secondary battery of a third modified example of the first embodiment.

As shown in Figures 1, 2 and 5, the case 11 has a first side 11r and a second side 11s. The first side 11r and the second side 11s are the outer surfaces of the side wall 123 and the side wall 124, respectively. The first side 11r and the second side 11s extend from the end of the first main surface 11p to the end of the second main surface 11q. The first side 11r and the second side 11s are separated from each other with the stacked battery 13, the positive electrode current collector 14 and the negative electrode current collector 15 in between. Therefore, the first side 11r and the second side 11s are separated from each other with the stacked body 101 in between.

The first side surface 11r is formed with a rib structure 135 as shown in FIG. 1 and FIG. 5. In the first embodiment, the rib structure 135 is a honeycomb rib structure with a 1-2 arrangement in which one or two unit lattices are arranged in the direction DZ perpendicular to the direction DX and the direction DY. The rib structure 135 may be a honeycomb rib structure with an arrangement other than the 1-2 arrangement. For example, the rib structure 135 may be a honeycomb rib structure with a 2-3 arrangement in which two or three unit lattices are arranged in the direction DZ as shown in FIG. 6. The rib structure 135 may be a rib structure other than the honeycomb rib structure. For example, the rib structure 135 may be a lattice rib structure with a single row lattice in which one unit lattice is arranged in the direction DZ as shown in FIG. 7. The rib structure 135 may also be a lattice rib structure with a double row lattice in which two unit lattices are arranged in the direction DZ as shown in FIG. 7.

As shown in Figures 2, 3, and 5, the case 11 has a bottom surface 11t. The bottom surface 11t is the outer surface of the bottom wall 125. The bottom surface 11t extends from the end of the first main surface 11p to the end of the second main surface 11q. The bottom surface 11t and the opening 11a are separated from each other, sandwiching the stacked battery 13, the positive electrode current collector plate 14, and the negative electrode current collector plate 15. Therefore, the bottom surface 11t and the opening 11a are separated from each other, sandwiching the stacked body 101.

A rib structure similar to rib structure 135 may be formed on bottom surface 11t.

1.3 Stacked Battery FIG. 9 is a cross-sectional view that diagrammatically illustrates a main portion of a stacked battery provided in the zinc secondary battery of the first embodiment.

As shown in FIG. 9, the stacked battery 13 includes a plurality of coated positive electrodes 141 and a plurality of coated negative electrodes 142. The number of the coated positive electrodes 141 and the number of the coated negative electrodes 142 can be increased or decreased depending on the specifications of the secondary battery 1.

The coated positive electrode 141 includes a positive electrode 151 and a positive electrode coating 152, as shown in FIG. 9. The positive electrode 151 includes a positive electrode plate 161 and a positive electrode current collector tab 102, as shown in FIG. 9. The coated negative electrode 142 includes a negative electrode 153 and a negative electrode coating 154, as shown in FIG. 9. The negative electrode 153 includes a negative electrode plate 163 and a negative electrode current collector tab 103, as shown in FIG. 9. Therefore, the laminate 101 includes a plurality of positive electrode plates 161 and a plurality of negative electrode plates 163. The plurality of positive electrode plates 161 and the plurality of negative electrode plates 163 are stacked in a direction DZ perpendicular to the first main surface 11p and the second main surface 11q.

The multiple coated positive electrodes 141 and the multiple coated negative electrodes 142 are stacked on top of each other. Therefore, the multiple positive electrode plates 161 and the multiple negative electrode plates 163 are stacked on top of each other. The coated positive electrodes 141 and the coated negative electrodes 142 are arranged alternately. Therefore, the positive electrode plates 161 and the negative electrode plates 163 are arranged alternately. The coated positive electrodes 141 and the coated negative electrodes 142 adjacent to each other constitute one battery that constitutes the stacked battery 13.

The multiple positive electrode current collector tabs 102 protrude from the laminate 101 in the first direction DXP. When viewed in plan from the stacking direction DZ, the multiple positive electrode current collector tabs 102 protrude from the same position of the laminate 101. Therefore, when viewed in plan from the stacking direction DZ, the multiple positive electrode current collector tabs 102 are arranged in the same position. This allows the tips of the multiple positive electrode current collector tabs 102 to be aggregated to electrically connect the multiple positive electrode current collector tabs 102 to each other. In addition, the multiple negative electrode current collector tabs 103 protrude from the laminate 101 in the second direction DXN. When viewed in plan from the stacking direction DZ, the multiple negative electrode current collector tabs 103 protrude from the same position of the laminate 101. Therefore, when viewed in plan from the stacking direction DZ, the multiple negative electrode current collector tabs 103 are arranged in the same position. This allows the tips of multiple negative electrode current collecting tabs 103 to be aggregated and electrically connected to each other.

The positive electrode coating 152 covers the positive electrode 151. The negative electrode coating 154 covers the negative electrode 153.

As shown in FIG. 9, the positive electrode plate 161 includes a positive electrode collector 171 and a positive electrode active material layer 172. Also, as shown in FIG. 9, the negative electrode plate 163 includes a negative electrode collector 174 and a negative electrode active material layer 175. Therefore, each of the positive electrode plates 161 includes a plurality of positive electrode collectors 171. Also, each of the positive electrode plates 161 includes a plurality of positive electrode active material layers 172. Also, each of the negative electrode plates 163 includes a plurality of negative electrode collectors 174. Also, each of the negative electrode plates 163 includes a plurality of negative electrode active material layers 175.

The positive electrode active material layer 172 is disposed on the positive electrode current collector 171. The negative electrode active material layer 175 is disposed on the negative electrode current collector 174. Therefore, the multiple positive electrode active material layers 172 are disposed on the multiple positive electrode current collectors 171, respectively. The multiple negative electrode active material layers 175 are disposed on the multiple negative electrode current collectors 174, respectively.

The positive electrode current collector tab 102 is connected to the positive electrode current collector 171. The negative electrode current collector tab 103 is connected to the negative electrode current collector 174. Therefore, the multiple positive electrode current collector tabs 102 are connected to the multiple positive electrode current collectors 171, respectively. The multiple negative electrode current collector tabs 103 are connected to the multiple negative electrode current collectors 174, respectively. As a result, the multiple positive electrode current collector tabs 102 are electrically connected to the multiple positive electrode current collectors 171, respectively. The multiple negative electrode current collector tabs 103 are electrically connected to the multiple negative electrode current collectors 174, respectively.

The positive electrode current collector tab 102 may be a tab lead having a base portion that is overlapped with the positive electrode current collector 171 and connected to the positive electrode current collector 171 and a tip portion that is not overlapped with the positive electrode current collector 171, or may be a tab made of the same material as the material constituting the positive electrode current collector 171 and continuing from the positive electrode current collector 171. The negative electrode current collector tab 103 may be a tab lead having a base portion that is overlapped with the negative electrode current collector 174 and connected to the negative electrode current collector 174 and a tip portion that is not overlapped with the negative electrode current collector 174, or may be a tab made of the same material as the material constituting the negative electrode current collector 174 and continuing from the negative electrode current collector 174.

The positive electrode coating 152 includes a positive electrode side liquid retaining member 191. The negative electrode coating 154 includes a negative electrode side liquid retaining member 192 and a separator 193.

The positive electrode current collector 171 has a plate or foil shape. The positive electrode current collector 171 is made of a conductor. The conductor is preferably made of nickel or a nickel alloy. The positive electrode current collector 171 is preferably made of a porous material, and more preferably made of a foam. This makes it possible to increase the area of the interface where the positive electrode current collector 171 and the positive electrode active material layer 172 come into contact with each other, thereby increasing the efficiency of current collection.

The reason why the positive electrode collector 171 is drawn with a dashed line in FIG. 9 is that if the positive electrode collector 171 is made of a porous material, the positive electrode active material contained in the positive electrode active material layer 172 will penetrate into the pores of the positive electrode collector 171, making it difficult to draw the positive electrode collector 171 and the positive electrode active material layer 172 separately from each other.

The positive electrode active material layer 172 includes a positive electrode active material. The positive electrode active material preferably includes at least one selected from the group consisting of nickel hydroxide and nickel oxyhydroxide. The positive electrode active material layer 172 is formed, for example, by uniformly applying a paste including a positive electrode active material and a dispersion medium onto the positive electrode current collector 171 to form a coating film, and evaporating the dispersion medium from the formed coating film. The positive electrode active material layer 172 and the paste may include a binder. A press process may be performed on the composite including the positive electrode current collector 171 and the positive electrode active material layer 172. This can prevent the positive electrode active material layer 172 from falling off, and can improve the electrode density of the positive electrode 151.

The secondary battery 1 includes a positive electrode side liquid retaining member 191. The positive electrode side liquid retaining member 191 has a sheet-like shape. The positive electrode side liquid retaining member 191 covers the entire positive electrode active material layer 172. The positive electrode side liquid retaining member 191 may encase the entire positive electrode active material layer 172. The positive electrode side liquid retaining member 191 retains the electrolyte. This allows the electrolyte to spread throughout the entire positive electrode active material layer 172. The positive electrode side liquid retaining member 191 is preferably made of a nonwoven fabric, a water-absorbent resin, a liquid retaining resin, a porous sheet, or a spacer, and more preferably made of a nonwoven fabric. By making the positive electrode side liquid retaining member 191 made of a nonwoven fabric, the electrode reaction in the positive electrode 151 can be promoted, and the coated positive electrode 141 can be manufactured at low cost. The positive electrode side liquid retaining member 191 preferably has a thickness of 0.01 mm or more and 0.20 mm or less. This allows the positive electrode side liquid retaining member 191 to retain a sufficient amount of electrolyte while preventing the coated positive electrode 141 from becoming too large in size.

The negative electrode current collector 174 has a plate, foil, or mesh shape. The negative electrode current collector 174 is made of a conductor. The conductor is preferably made of copper. The negative electrode current collector 174 is preferably made of foil, expanded metal, or punched metal, and more preferably made of expanded metal. By making the negative electrode current collector 174 of expanded metal, a sufficient amount of the negative electrode active material layer 175 can be held on the negative electrode current collector 174.

The negative electrode active material layer 175 includes a negative electrode active material. The negative electrode active material preferably includes at least one selected from the group consisting of zinc, zinc oxide, zinc alloy, and zinc compound, more preferably includes at least one selected from the group consisting of zinc, zinc oxide, and calcium zincate, and particularly preferably includes zinc and zinc oxide. The negative electrode active material preferably has a powdery property. This makes it possible to increase the surface area where the negative electrode active material is exposed. This makes it possible to increase the current that can be passed through the negative electrode 153. The negative electrode active material layer 175 is formed, for example, by applying a coating material containing a powder of the negative electrode active material onto the negative electrode current collector 174. The negative electrode active material layer 175 and the coating material may include a binder. The binder includes, for example, polytetrafluoroethylene particles. A press process may be performed on the composite including the negative electrode current collector 174 and the negative electrode active material layer 175. This makes it possible to suppress the negative electrode active material layer 175 from falling off, and to improve the electrode density of the negative electrode 153. The negative electrode active material layer 175 may have a gel-like property. When the negative electrode active material layer 175 has a gel-like property, the negative electrode active material layer 175 contains an electrolyte and a thickener in addition to the negative electrode active material. The thickener preferably contains polyvinyl alcohol, polyacrylate, carboxymethyl cellulose (CMC) or alginic acid, and more preferably contains polyacrylate. When the thickener contains polyacrylate, the chemical resistance of the thickener to the electrolyte having strong alkalinity can be increased.

When the negative electrode active material contains a zinc alloy, the self-dissolution rate of zinc in a strongly alkaline electrolyte can be slowed down. This makes it possible to suppress the generation of hydrogen gas in the negative electrode 153. This makes it possible to improve the safety of the secondary battery 1. The zinc alloy is preferably a mercury- and lead-free zinc alloy. The zinc alloy preferably contains 0.01% by mass to 0.1% by mass of indium, 0.005% by mass to 0.02% by mass of bismuth, and 0.0035% by mass to 0.015% by mass of aluminum. When the zinc alloy contains indium and bismuth, the discharge performance of the negative electrode 153 can be improved.

When the negative electrode active material contains a zinc alloy and has a powdery nature, the negative electrode active material preferably has an average particle size of 3 μm or more and 100 μm or less in the short axis. This makes it possible to increase the surface area where the negative electrode active material is exposed, and also makes it easier to uniformly mix the negative electrode active material, electrolyte, and gelling agent, making it easier to handle the negative electrode active material when manufacturing the secondary battery 1.

The secondary battery 1 includes a negative electrode side liquid retaining member 192. The negative electrode side liquid retaining member 192 has a sheet-like shape. The negative electrode side liquid retaining member 192 covers the entire negative electrode active material layer 175. The negative electrode side liquid retaining member 192 may encase the entire negative electrode active material layer 175. The negative electrode side liquid retaining member 192 retains the electrolyte. This allows the electrolyte to spread throughout the entire negative electrode active material layer 175. The negative electrode side liquid retaining member 192 is preferably made of a nonwoven fabric, a water-absorbent resin, a liquid retaining resin, a porous sheet, or a spacer, and more preferably made of a nonwoven fabric. By making the negative electrode side liquid retaining member 192 out of a nonwoven fabric, the electrode reaction in the negative electrode 153 can be promoted, and the coated negative electrode 142 can be manufactured at low cost. The negative electrode side liquid retaining member 192 preferably has a thickness of 0.01 mm or more and 0.20 mm or less, more preferably 0.02 mm or more and 0.20 mm or less, particularly preferably 0.02 mm or more and 0.15 mm or less, more preferably 0.02 mm or more and 0.10 mm or less, and most preferably 0.02 mm or more and 0.06 mm or less. By having the negative electrode side liquid retaining member 192 have a thickness in these ranges, it is possible to hold a sufficient amount of electrolyte in the negative electrode side liquid retaining member 192 while keeping the overall size of the coated negative electrode 142 compact and efficient.

The separator 193 has a sheet-like shape. The separator 193 preferably covers or encases the negative electrode active material layer 175 by sandwiching the negative electrode side liquid retaining member 192. One or two sides of the outer edge of the separator 193 are open to allow the negative electrode current collector tab 103 to protrude. The separator 193 includes a porous substrate and a hydroxide ion conductive layered compound that blocks the pores of the porous substrate. The hydroxide ion conductive layered compound is a layered double hydroxide (LDH) and/or a layered double hydroxide (LDH)-like compound. In this specification, the separator 193 is defined as a separator that includes an LDH and/or an LDH-like compound and selectively passes hydroxide ions by utilizing the hydroxide ion conductivity of the LDH and/or the LDH-like compound. In this specification, "LDH-like compounds" are hydroxides and/or oxides with a layered crystal structure similar to LDH, which may not be called LDH, and can be considered equivalent to LDH. However, in a broad sense, "LDH" can be interpreted as including not only LDH but also LDH-like compounds. Separator 193 has LDH and/or LDH-like compounds filling the pores of the porous substrate so as to exhibit hydroxide ion conductivity and gas impermeability (and thus function as separator 193 exhibiting hydroxide ion conductivity).

The denseness of the separator can be evaluated by the He permeability. That is, the separator has a He permeability per unit area of 10 cm/min·atm or less, more preferably 5.0 cm/min·atm or less, and even more preferably 1.0 cm/min·atm or less. A separator having a He permeability within such a range can be said to have extremely high denseness. Therefore, a separator having a He permeability of 10 cm/min·atm or less can prevent the passage of substances other than hydroxide ions at a high level. For example, in the case of a zinc secondary battery, the permeation of Zn (typically the permeation of zinc ions or zincate ions) in the electrolyte can be suppressed very effectively. The He permeability is measured through a process of supplying He gas to one side of the separator to allow the He gas to permeate the separator, and a process of calculating the He permeability to evaluate the denseness of the hydroxide ion conductive separator. The He permeability is calculated by the formula F/(P×S) using the amount of He gas permeated per unit time F, the pressure difference P applied to the separator when He gas permeates, and the membrane area S through which He gas permeates. By evaluating the gas permeability using He gas in this way, it is possible to evaluate the presence or absence of denseness at an extremely high level, and as a result, it is possible to effectively evaluate a high level of denseness such as not allowing substances other than hydroxide ions (especially Zn, which causes zinc dendrite growth) to permeate as much as possible (permeating only a very small amount). This is because He gas has the smallest structural unit among the wide variety of atoms or molecules that can constitute gas, and has extremely low reactivity. In other words, He does not form molecules and constitutes He gas with He atoms alone. In this regard, since hydrogen gas is composed of H ₂ molecules, He atoms alone are smaller as gas structural units. In the first place, H ₂ gas is dangerous because it is a flammable gas. By adopting the index of He gas permeability defined by the above formula, it is possible to easily and objectively evaluate the denseness regardless of the difference in sample size and measurement conditions. In this way, it is possible to easily, safely, and effectively evaluate whether a separator has a sufficiently high denseness suitable for a zinc secondary battery separator.

As described above, the separator includes a porous substrate and LDH and/or an LDH-like compound (hereinafter collectively referred to as a hydroxide ion conductive layered compound). The hydroxide ion conductive layered compound is connected between the upper and lower surfaces of the separator, thereby ensuring the hydroxide ion conductivity of the separator. In the separator, the pores of the porous substrate are blocked by the hydroxide ion conductive layered compound, but the pores of the porous substrate do not need to be completely blocked, and a small amount of residual pores may be present.

LDH is composed of a plurality of hydroxide basic layers and intermediate layers interposed between the plurality of hydroxide basic layers. The hydroxide basic layers are mainly composed of metal elements (typically metal ions) and OH groups. The intermediate layers of LDH are composed of anions and H ₂ O. The anions are monovalent or higher anions, preferably monovalent or divalent ions. Preferably, the anions in LDH include OH ^- and/or CO ₃ ^2- . Furthermore, LDH has excellent ionic conductivity due to its inherent properties. In general, LDH is known to be represented by the basic composition formula M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ^n- _x/n ·mH ₂ O (wherein M ²⁺ is a divalent cation, M ³⁺ is a trivalent cation, A ^n- is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more). In the above basic composition formula, M ²⁺ can be any divalent cation, with preferred examples including Mg ²⁺ , Ca ²⁺ and Zn ²⁺ , and more preferably Mg ²⁺ . M ³⁺ can be any trivalent cation, with preferred examples including Al ³⁺ or Cr ³⁺ , and more preferably Al ³⁺ . ^{A n-} can be any anion, with preferred examples including OH ^- and CO ₃ ^2- . Therefore, in the above basic composition formula, it is preferred that M ²⁺ includes Mg ²⁺ , M ³⁺ includes Al ³⁺ , and A ^n- includes OH ^- and/or CO ₃ ^2- . n is an integer of 1 or more, and is preferably 1 or 2. x is 0.1 to 0.4, and is preferably 0.2 to 0.35. m is any number that means the number of moles of water, and is a real number of 0 or more, typically greater than 0 or 1 or more. However, the above basic composition formula is merely a formula of a "basic composition" typically exemplified for LDH, and the constituent ions can be appropriately replaced. For example, in the above basic composition formula, a part or all of M ³⁺ may be replaced with a cation having a valence of 4 or more (e.g., Ti ⁴⁺ ), and in that case, the coefficient x/n of the anion A ^n- in the above general formula may be appropriately changed.

For example, it is particularly preferable that the hydroxide basic layer of the LDH contains Mg, Al, Ti, and OH groups, since it exhibits excellent alkali resistance. In this case, the hydroxide basic layer may contain other elements or ions as long as it contains Mg, Al, Ti, and OH groups. For example, the LDH or hydroxide basic layer may contain Y and/or Zn. Also, when the LDH or hydroxide basic layer contains Y and/or Zn, the LDH or hydroxide basic layer may not contain Al or Ti. However, it is preferable that the hydroxide basic layer contains Mg, Al, Ti, and OH groups as main components. That is, it is preferable that the hydroxide basic layer is mainly composed of Mg, Al, Ti, and OH groups. Therefore, the hydroxide basic layer is typically composed of Mg, Al, Ti, OH groups, and in some cases, unavoidable impurities. The atomic ratio of Ti/Al in the LDH, as determined by energy dispersive X-ray analysis (EDS), is preferably 0.5 to 12, more preferably 1.0 to 12. Within the above range, the effect of suppressing short circuits caused by zinc dendrites (i.e., dendrite resistance) can be more effectively realized without impairing ion conductivity. For the same reason, the atomic ratio of Ti/(Mg+Ti+Al) in the LDH, as determined by energy dispersive X-ray analysis (EDS), is preferably 0.1 to 0.7, more preferably 0.2 to 0.7. In addition, the atomic ratio of Al/(Mg+Ti+Al) in the LDH is preferably 0.05 to 0.4, more preferably 0.05 to 0.25. Furthermore, the atomic ratio of Mg/(Mg+Ti+Al) in the LDH is preferably 0.2 to 0.7, more preferably 0.2 to 0.6. It is preferable to perform the EDS analysis using an EDS analyzer (e.g., X-act, manufactured by Oxford Instruments) by 1) capturing an image at an accelerating voltage of 20 kV and a magnification of 5,000x, 2) performing a three-point analysis in point analysis mode with an interval of about 5 μm, 3) repeating the above 1) and 2) once more, and 4) calculating the average value of the total six points.

Alternatively, the hydroxide base layer of the LDH may contain Ni, Al, Ti, and OH groups. In this case, the hydroxide base layer may contain other elements or ions as long as it contains Ni, Al, Ti, and OH groups. However, it is preferable that the hydroxide base layer contains Ni, Al, Ti, and OH groups as main components. That is, it is preferable that the hydroxide base layer is mainly composed of Ni, Al, Ti, and OH groups. Therefore, the hydroxide base layer is typically composed of Ni, Al, Ti, OH groups, and sometimes unavoidable impurities. The atomic ratio of Ti/(Ni+Ti+Al) in the LDH determined by energy dispersive X-ray analysis (EDS) is preferably 0.10 to 0.90, more preferably 0.20 to 0.80, even more preferably 0.25 to 0.70, and particularly preferably 0.30 to 0.61. Within the above range, both alkali resistance and ion conductivity can be improved. Therefore, the hydroxide ion conductive layered compound may contain so much Ti that it produces not only LDH but also titania as a by-product. In other words, the hydroxide ion conductive layered compound may further contain titania. The inclusion of titania is expected to increase hydrophilicity and improve wettability with the electrolyte (i.e., improve conductivity).

The LDH-like compound may not be called LDH, but is a hydroxide and/or oxide of a layered crystal structure similar to LDH, and preferably contains Mg and one or more elements including at least Ti selected from the group consisting of Ti, Y, and Al. In this way, by using an LDH-like compound that is a hydroxide and/or oxide of a layered crystal structure containing at least Mg and Ti as a hydroxide ion conductive material instead of a conventional LDH, a hydroxide ion conductive separator that is excellent in alkali resistance and can more effectively suppress short circuits caused by zinc dendrites can be provided. Therefore, a preferred LDH-like compound is a hydroxide and/or oxide of a layered crystal structure containing Mg and one or more elements including at least Ti selected from the group consisting of Ti, Y, and Al. Therefore, a typical LDH-like compound is a composite hydroxide and/or oxide of Mg, Ti, optionally Y, and optionally Al, and particularly preferably a composite hydroxide and/or oxide of Mg, Ti, Y, and Al. The above elements may be replaced with other elements or ions to the extent that the basic properties of the LDH-like compound are not impaired, but it is preferable that the LDH-like compound does not contain Ni.

The LDH-like compound can be identified by X-ray diffraction. Specifically, when X-ray diffraction is performed on the surface of the separator, a peak derived from the LDH-like compound is typically detected in the range of 5°≦2θ≦10°, more typically in the range of 7°≦2θ≦10°. As described above, LDH is a substance having an alternating laminate structure in which exchangeable anions and H ₂ O exist as intermediate layers between stacked hydroxide basic layers. In this regard, when LDH is measured by X-ray diffraction, a peak due to the crystal structure of LDH (i.e., the (003) peak of LDH) is essentially detected at a position of 2θ=11 to 12°. In contrast, when an LDH-like compound is measured by X-ray diffraction, a peak is typically detected in the above-mentioned range shifted to the lower angle side from the above-mentioned peak position of LDH. In addition, the interlayer distance of the layered crystal structure can be determined by the Bragg formula using 2θ corresponding to the peak derived from the LDH-like compound in X-ray diffraction. The interlayer distance of the layered crystal structure constituting the LDH-like compound determined in this manner is typically 0.883 to 1.8 nm, and more typically 0.883 to 1.3 nm.

The atomic ratio of Mg/(Mg+Ti+Y+Al) in the LDH-like compound determined by energy dispersive X-ray analysis (EDS) is preferably 0.03 to 0.25, more preferably 0.05 to 0.2. The atomic ratio of Ti/(Mg+Ti+Y+Al) in the LDH-like compound is preferably 0.40 to 0.97, more preferably 0.47 to 0.94. The atomic ratio of Y/(Mg+Ti+Y+Al) in the LDH-like compound is preferably 0 to 0.45, more preferably 0 to 0.37. The atomic ratio of Al/(Mg+Ti+Y+Al) in the LDH-like compound is preferably 0 to 0.05, more preferably 0 to 0.03. Within the above range, the alkali resistance is more excellent, and the effect of suppressing short circuits caused by zinc dendrites (i.e., dendrite resistance) can be more effectively realized. Incidentally, LDH conventionally known for LDH separators can be expressed by a basic composition of the general formula: M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ^n- _{x/n.mH 2} O (wherein M ²⁺ is a divalent cation, M ³⁺ is a trivalent cation, A ^n- is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more). In contrast, the above atomic ratio in LDH-like compounds generally deviates from the above general formula of LDH. For this reason, it can be said that LDH-like compounds generally have a composition ratio (atomic ratio) different from that of conventional LDH. The EDS analysis is preferably performed using an EDS analyzer (e.g., X-act, manufactured by Oxford Instruments) by 1) capturing an image at an accelerating voltage of 20 kV and a magnification of 5,000 times, 2) performing three-point analysis in a point analysis mode with an interval of about 5 μm, 3) repeating the above 1) and 2) once more, and 4) calculating the average value of the total six points.

When the separator is incorporated in a zinc secondary battery, it separates the positive and negative plates in a manner that allows hydroxide ion conduction. A preferred separator is gas-impermeable and/or water-impermeable. In other words, it is preferable that the separator is so dense that it has gas-impermeability and/or water-impermeability. In this specification, "gas-impermeable" means that, as described in WO 2016/076047 and WO 2016/067884, even if helium gas is brought into contact with one side of the object to be measured in water at a differential pressure of 0.5 atm, no bubbles due to helium gas are generated from the other side. In addition, in this specification, "water-impermeable" means that water that has come into contact with one side of the object to be measured does not penetrate to the other side, as described in WO 2016/076047 and WO 2016/067884. That is, the separator being gas-impermeable and/or water-impermeable means that the separator is dense enough to prevent gas or water from passing through, and is not a porous film or other porous material that is water-permeable or gas-permeable. In this way, the separator selectively passes only hydroxide ions due to its hydroxide ion conductivity, and can function as a battery separator. Therefore, it is extremely effective in preventing short-circuiting between the positive and negative electrodes by physically preventing the penetration of the separator by zinc dendrites generated during charging. Since the separator has hydroxide ion conductivity, it is possible to efficiently move hydroxide ions required between the positive and negative plates, thereby realizing charge and discharge reactions in the positive and negative plates.

As described above, the separator comprises a hydroxide ion conductive layered compound and a porous substrate (typically consisting of a porous substrate and a hydroxide ion conductive layered compound), with the hydroxide ion conductive layered compound blocking the pores of the porous substrate so that the separator is hydroxide ion conductive and gas impermeable (and therefore functions as a hydroxide ion conductive separator). It is particularly preferred that the hydroxide ion conductive layered compound is incorporated throughout the entire thickness of the porous substrate. The thickness of the separator is preferably 3 to 80 μm, more preferably 3 to 60 μm, and even more preferably 3 to 40 μm.

The porous substrate is preferably made of a polymer material. The polymer porous substrate has the following advantages: 1) flexibility (so it is difficult to break even if it is thinned); 2) it is easy to increase the porosity; 3) it is easy to increase the conductivity (because the thickness can be reduced while increasing the porosity); and 4) it is easy to manufacture and handle. In addition, by taking advantage of the advantage derived from the flexibility of 1), 5) it is also possible to easily fold or seal and bond the hydroxide ion conductive separator including the porous substrate made of the polymer material. Preferred examples of polymer materials include polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, fluororesin (tetrafluorinated resin: PTFE, etc.), cellulose, nylon, polyethylene, and any combination thereof. More preferably, from the viewpoint of a thermoplastic resin suitable for hot pressing, polystyrene, polyethersulfone, polypropylene, epoxy resin, polyphenylene sulfide, fluororesin (tetrafluorinated resin: PTFE, etc.), nylon, polyethylene, and any combination thereof. All of the above-mentioned various preferred materials have alkali resistance as a resistance to the electrolyte of the battery. Particularly preferred polymer materials are polyolefins such as polypropylene and polyethylene, which have excellent hot water resistance, acid resistance, and alkali resistance, and are low cost, and are most preferably polypropylene or polyethylene. It is particularly preferred that the hydroxide ion conductive layered compound is incorporated throughout the entire thickness of the polymeric porous substrate (for example, most or almost all of the pores inside the polymeric porous substrate are filled with the hydroxide ion conductive layered compound). As such a polymeric porous substrate, a commercially available polymeric microporous membrane can be preferably used.

The method for producing the LDH separator is not particularly limited, and the LDH separator can be produced by using the conditions (particularly the LDH raw material composition) of the already known methods for producing LDH separators (or LDH-containing functional layers and composite materials) (see, for example, WO 2013/118561, WO 2016/076047, WO 2016/067884, WO 2019/124270, and WO 2019/124212) as is or by appropriately modifying them. For example, an LDH separator can be produced by (1) preparing a porous substrate, (2) applying i) a mixed sol of alumina and titania (when forming LDH), or ii) a solution containing titania sol (or further yttrium sol and/or alumina sol) (when forming LDH-like compound) to the porous substrate and drying the coated substrate to form a titania-containing layer, (3) immersing the porous substrate in a raw aqueous solution containing magnesium ions (Mg ²⁺ ) and urea (or further yttrium ions (Y ³⁺ )), and (4) subjecting the porous substrate to hydrothermal treatment in the raw aqueous solution to form a hydroxide ion-conducting layered compound on and/or in the porous substrate. In addition, it is considered that the presence of urea in the above step (3) causes ammonia to be generated in the solution by hydrolysis of urea, thereby increasing the pH value, and that the coexisting metal ions form hydroxides and/or oxides to obtain a hydroxide ion-conducting layered compound (i.e., LDH and/or LDH-like compound). In addition, since the hydrolysis is accompanied by the generation of carbon dioxide, when LDH is formed, LDH in which the anion is of the carbonate ion type can be obtained.

In particular, when preparing a separator in which the hydroxide ion conductive layered compound is incorporated throughout the entire thickness of the polymeric porous substrate, it is preferable to apply the mixed sol solution to the substrate in (2) above in such a manner that the mixed sol solution penetrates the entire or most of the substrate. In this way, most or almost all of the pores in the porous substrate can be filled with the hydroxide ion conductive layered compound. Examples of preferred application methods include dip coating and filtration coating, and dip coating is particularly preferred. The amount of the mixed sol solution attached can be adjusted by adjusting the number of applications of dip coating, etc. The substrate to which the mixed sol solution has been applied by dip coating, etc., can be dried and then subjected to the above steps (3) and (4).

It is preferable to perform a pressing process on the separator obtained by the above method. In this way, a separator with even better density can be obtained. The pressing method may be, for example, roll pressing, uniaxial pressing, CIP (cold isostatic pressing), etc., and is not particularly limited, but roll pressing is preferable. This pressing is preferably performed while heating, since it softens the polymeric porous substrate, thereby allowing the pores of the polymeric porous substrate to be sufficiently blocked with the hydroxide ion conductive layered compound. For example, in the case of polypropylene or polyethylene, it is preferable to heat the substrate to a temperature of 60 to 200°C to sufficiently soften the substrate. By performing pressing such as roll pressing in such a temperature range, the residual pores in the separator can be significantly reduced. As a result, the separator can be made extremely dense, and therefore short circuits caused by zinc dendrites can be more effectively suppressed. When performing roll pressing, the shape of the residual pores can be controlled by appropriately adjusting the roll gap and roll temperature, thereby allowing a separator with the desired density to be obtained.

The secondary battery 1 includes an electrolyte. The electrolyte is preferably an aqueous solution of hydroxide. The hydroxide is preferably an alkali metal hydroxide or ammonium hydroxide, more preferably an alkali metal hydroxide, particularly preferably potassium hydroxide, sodium hydroxide or lithium hydroxide, and most preferably potassium hydroxide. A zinc compound may be dissolved in the electrolyte. The zinc compound is preferably zinc oxide or zinc hydroxide. When a zinc compound is dissolved in the electrolyte, it is possible to suppress the zinc and/or zinc oxide constituting the negative electrode active material layer 175 from self-dissolving in the electrolyte. A gelling agent may be added to the electrolyte. The gelling agent is preferably made of a polymer that absorbs a solvent contained in the electrolyte and swells, and more preferably made of polyethylene oxide, polyvinyl alcohol, polyacrylamide or starch. When a gelling agent is added to the electrolyte, it is possible to suppress the electrolyte from gelling and leaking from the case 11. The electrolyte and the positive electrode active material may be mixed to form a positive electrode mixture. The electrolyte and the negative electrode active material may be mixed to form a negative electrode mixture.

1.4 Effect of rib structure The distribution of displacement in the direction DX of the first side 11r and the second side 11s when the internal pressure inside the case 11 rises to a specific internal pressure was investigated by simulation for each of the following cases: when the rib structure 135 is not formed on the first side 11r and the second side 11s; when a single-row lattice rib structure is formed on the first side 11r and the second side 11s; when a double-row lattice rib structure is formed on the first side 11r and the second side 11s; when a 1-2 honeycomb rib structure is formed on the first side 11r and the second side 11s; and when a 2-3 honeycomb rib structure is formed on the first side 11r and the second side 11s. The relative value of the displacement amount at the maximum displacement point P is shown in Table 1.

As shown in Table 1, the amount of displacement at the maximum displacement point P is smaller when the rib structure 135 is formed, and is significantly smaller when the rib structure 135 is a honeycomb rib structure. Therefore, the rib structure 135 can increase the strength of the case 11 provided for the secondary battery 1 without significantly increasing the weight and volume of the secondary battery 1, and the rib structure 135 being a honeycomb rib structure can increase the strength of the case 11 provided for the secondary battery 1 without significantly increasing the weight and volume of the secondary battery 1.

1.5 Battery Module FIG. 10 is a side view that diagrammatically illustrates the battery module of the first embodiment.

The module battery 2 shown in FIG. 10 comprises a plurality of single cells 21, a pressure member 22, and a bottom member 23.

Each of the multiple cells 21 is the secondary battery 1 described above.

The multiple single cells 21 are arranged in an arrangement direction DZ perpendicular to the first principal surface 11p and the second principal surface 11q.

The pressure member 22 applies pressure to the multiple cells 21 in the arrangement direction DZ.

This restricts the displacement of the first principal surface 11p and the second principal surface 11q, and prevents damage to the case 11 due to the displacement of the first principal surface 11p and the second principal surface 11q.

The bottom member 23 supports the multiple single cells 21. The bottom member 23 supports the bottom surfaces 11t of the multiple single cells 21.

This restricts the displacement of the bottom surface 11t, preventing damage to the case 11 caused by the displacement of the bottom surface 11t.

The displacement of the open first side 11r and second side 11s is suppressed by the rib structure 135. This makes it possible to suppress damage to the case 11 due to the displacement of the first side 11r and second side 11s.

Although this invention has been described in detail, the above description is illustrative in all respects and does not limit the invention. It is understood that countless variations not illustrated can be envisioned without departing from the scope of this invention.

REFERENCE SIGNS LIST 1 secondary battery 11 case 12 lid 13 stacked battery 14 positive electrode current collector plate 15 negative electrode current collector plate 101 stacked body 102 positive electrode current collector tab 103 negative electrode current collector tab 131 rib structure 135 rib structure 161 positive electrode plate 163 negative electrode plate 171 positive electrode current collector 2 module battery 21 single cell 22 pressure member 23 bottom member

Claims (3)

A laminate including a positive electrode plate and a negative electrode plate overlapped on the positive electrode plate;
a case having an opening and housing the laminate;
A lid that closes the opening;
Equipped with
The case is
A first major surface;
a second main surface spaced apart from the first main surface across the laminate;
a side surface having a honeycomb rib structure formed thereon from an end of the first main surface to an end of the second main surface;
having
The positive electrode plate and the negative electrode plate are stacked in a direction perpendicular to the first main surface and the second main surface.
Secondary battery. 2. The secondary battery of claim 1 , wherein the secondary battery is a zinc secondary battery. A plurality of unit cells arranged in an arrangement direction perpendicular to the first main surface and the second main surface;
a pressing member that presses the plurality of unit cells in the arrangement direction;
a bottom member on which the plurality of unit cells are placed;
Equipped with
Each of the plurality of single cells is a secondary battery according to claim 1 or 2 ,
the case has a bottom surface extending from an end of the first main surface to an end of the second main surface and spaced apart from the opening with the laminate therebetween;
The bottom member is a module battery that supports the bottom surfaces of the plurality of single cells.

Images