Secondary battery and method for manufacturing a secondary battery

Abstract

To facilitate an impregnation of an electrolyte to an electrode plate at a liquid injection of the electrolyte.SOLUTION: A positive electrode plate 2 is constructed so that the following equation is satisfied: an uneven width ΔW1≥an uneven width ΔW3 in the case where when a positive electrode bonding layer 22 filled in a positive electrode collector 21 is divided into a plurality of regions containing an upper side region Wt1 and a lower side region Wt3 in a vertical direction in an end part 22d of the positive electrode bonding layer 22, a mean uneven width of the end part 22d of the positive electrode bonding layer 22 in the upper side region Wt1 is an uneven width ΔW1 and a mean uneven width of the end part 22d of the positive electrode bonding layer 22 of the lower side region Wt3 is an uneven width ΔW3. An electrolyte accumulated above an electrode group at a liquid injection of the electrolyte can be easily impregnated from the end part 22d in the upper region.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] This invention relates to a secondary battery and a method for manufacturing a secondary battery, and more specifically, to a secondary battery in which the electrolyte penetrates the electrode plates well during manufacturing, and to a method for manufacturing a secondary battery. [Background technology]

[0002] Electric vehicles (including hybrid vehicles, etc.) equipped with electric motors drive the motors using electricity stored in secondary batteries. Among such secondary batteries, alkaline secondary batteries, such as nickel-metal hydride batteries, are widely used in vehicles because they are safe and capable of high-current charging and discharging. Figure 1 is a perspective view showing the external structure of such a nickel-metal hydride battery. Figure 2 is a perspective view including a partial cross-sectional structure of a part of the battery module of such a nickel-metal hydride battery 1. Figure 3 is a cross-sectional view of an electrode group 6 provided in such a nickel-metal hydride battery 1. In the battery module of such an automotive nickel-metal hydride battery 1, electrode plates are manufactured by coating a composite material layer containing active material onto a current collector, and as shown in Figure 3, an electrode group 6, in which a large number of positive electrode plates 2 and negative electrode plates 3 are stacked with separators 4 in between, is housed in a battery case 15 as shown in Figure 2. Electrolyte 5 is poured from above into the battery case 15 in which the electrode groups 6 are housed. Multiple battery cells 12 configured in this way are connected in series, as shown in Figure 1 (for example, 6 cells).

[0003] In the manufacturing process of such secondary batteries, when coating the composite layer containing the active material onto the current collector, a certain height may occur at the edges of the composite layer. Using such electrodes may affect the productivity and performance of the secondary battery.

[0004] Therefore, the invention disclosed in Patent Document 1 provides an electrode plate having a coated region with an active material layer and an uncoated region without an active material layer, with a first buffer region having a non-linear uneven shape in plan view at the boundary between the coated region and the uncoated region. As a result, in a secondary battery equipped with a large electrode group formed by stacking positive and negative electrodes, it was possible to create an electrode plate that is less prone to problems such as peeling or cracking of the active material layer and wear or cracking of the current collector. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2014 / 034708 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, in such secondary batteries, the manufacturing process generally involves inserting the electrode plate group into the battery case and then pouring the electrolyte from the top. In the automotive nickel-metal hydride battery 1, as shown in Figure 2, the electrode group 6 is inserted into the battery case 15, but for miniaturization purposes, no unnecessary gaps are provided around it. As a result, when the electrolyte 5 is poured, it tends to accumulate on top of the electrode group 6. This has resulted in a problem where the electrolyte 5 does not easily penetrate the positive electrode plate 2, which is the electrode plate of the electrode group 6.

[0007] The problem that the present invention's secondary battery and its manufacturing method aim to solve is to facilitate the penetration of the electrolyte into the electrode plates when the electrolyte is injected. [Means for solving the problem]

[0008] To solve the above problems, the secondary battery of the present invention comprises an electrode group formed by stacking a positive electrode plate having a positive electrode current collector made of a plate-shaped porous metal and a positive electrode composite layer containing a positive electrode active material and filled in the positive electrode current collector, a negative electrode plate and a separator, the electrode group is housed in a battery case and filled with an electrolyte, and the electrode group is provided with a positive electrode plate configured such that when the filled positive electrode composite layer is divided vertically into a plurality of regions including an upper region and a lower region, the average unevenness width of the end of the positive electrode composite layer in the upper region is an unevenness width ΔW1 and the average unevenness width of the end of the positive electrode composite layer in the lower region is an unevenness width ΔW3.

[0009] In other words, ΔW1, ΔW2, and ΔW3 each represent the average value within the divided region. The average is... In this invention It is the arithmetic mean, for example, Least squares mean or weighted mean can also be used. Similarly, the average values ​​for coating width Wp and standard coating width Ws should also be shown.

[0010] In the aforementioned unevenness widths ΔW1 and ΔW3, it is preferable that the unevenness width ΔW1 / unevenness width ΔW3 ≥ 5. An intermediate region may be provided between the upper region and the lower region, and when the average unevenness width of the intermediate region is ΔW2, the unevenness width ΔW1 ≥ unevenness width ΔW2 ≥ unevenness width ΔW3 may be set.

[0011] In the upper region Wt1, it is preferable that the relationship between the unevenness width ΔW1 and the horizontal coating width Wp be ΔW1 / Wp ≥ 0.015. Furthermore, it is even more preferable that ΔW1 / Wp ≤ 0.025.

[0012] In the lower region Wt3, it is preferable that the relationship between the unevenness width ΔW3 and the horizontal coating width Wp is ΔW3 / Wp ≤ 0.01. In the aforementioned electrode group, more than 1 / 4 of the total number of positive electrode plates can be positive electrode plates of a secondary battery with the above configuration.

[0013] The positive electrode current collector can preferably be made of a foam made of nickel or a nickel alloy. The foam has a basis weight of 200 g / m². 2 ] or more, 400[g / m 2 It is preferable that the pore size is 300 [μm] or less and 600 [μm] or less.

[0014] Furthermore, the upper region Wt1, the intermediate region Wt2, and the lower region Wt3 may be divided into three equal parts in the vertical direction, or multiple intermediate regions Wt2 may be provided, and the upper region Wt1, the multiple intermediate regions Wt2, and the lower region Wt3 may each be divided equally in the vertical direction.

[0015] Furthermore, the present invention relates to a method for manufacturing a secondary battery comprising an electrode group formed by stacking a positive electrode plate having a positive electrode current collector made of a plate-shaped porous metal and a positive electrode composite layer containing a positive electrode active material and filled in the positive electrode current collector, a negative electrode plate, and a separator, wherein the electrode group is housed in a battery case and an electrolyte is poured into it, and the method for manufacturing a secondary battery comprises a coating step of intermittently coating the positive electrode current collector with a positive electrode composite paste containing a solvent for forming the positive electrode composite layer, starting from one surface of the positive electrode current collector. The coating process is characterized in that the positive electrode composite paste does not fall off the positive electrode current collector due to gravity, and the positive electrode composite layer to be coated is divided into multiple regions including an upper region and a lower region in the vertical direction, and at the end of the positive electrode composite layer in the width direction, the unevenness width ΔW1 is set to the average unevenness width ΔW1 of the positive electrode composite layer in the upper region Wt1 and the unevenness width ΔW3 of the positive electrode composite layer in the lower region Wt3, and the unevenness width ΔW1 is set to the average unevenness width ΔW3.

[0016] The above adjustment is performed when the shear rate of the positive electrode composite paste is 10 [s -1 In this case, the viscosity can be set to 50 m[Pa·s] or more and 2000 [mPa·s] or less. Furthermore, the above adjustment can be made by setting the discharge amount in region Wt1 to 102% or more of the discharge amount in region Wt3.

[0017] Further, the adjustment can be achieved by adjusting the clearance G, which is the clearance between the nozzle that discharges the positive electrode composite paste in the coating process and the positive electrode current collector.

Advantages of the Invention

[0018] According to the secondary battery and its manufacturing method of the present invention, it is possible to make the electrolyte easily penetrate into the electrode plate when injecting the electrolyte.

Brief Description of the Drawings

[0019] [Figure 1] It is a perspective view showing the external structure of the nickel-hydrogen storage battery of this embodiment. [Figure 2] It is a perspective view including a partial cross-sectional structure of a part of the battery module of the nickel-hydrogen storage battery of this embodiment. [Figure 3] It is a cross-sectional view of the electrode group provided in the nickel-hydrogen storage battery of this embodiment. [Figure 4] It is a flowchart showing the manufacturing process of the nickel-hydrogen storage battery of this embodiment. [Figure 5] It is a flowchart showing the manufacturing process of the positive electrode plate of the nickel-hydrogen storage battery of this embodiment. [Figure 6] It is a schematic diagram showing a cross-section in the width direction W of the positive electrode plate of the nickel-hydrogen storage battery of this embodiment. [Figure 7] It is a schematic diagram showing the surface on the coating side of the positive electrode plate of the nickel-hydrogen storage battery of this embodiment. [Figure 8] It is a schematic diagram showing the surface opposite to the coating side of the positive electrode plate of the nickel-hydrogen storage battery of this embodiment. [Figure 9] It is a schematic diagram showing another example of the positive electrode plate of the nickel-hydrogen storage battery of this embodiment. [Figure 10] It is a schematic diagram showing the state of penetration of the electrolyte when injecting the electrolyte into the nickel-hydrogen storage battery of this embodiment. [Figure 11] It is a comparison table of an example of the composition of a conventional positive electrode composite paste and an example of the composition of the positive electrode composite paste of this embodiment. [Figure 12] It is a perspective view showing the coating machine in this embodiment. [Figure 13] (a) A perspective view showing the coating process in this embodiment. (b) An enlarged cross-sectional view of the position where the die nozzle applies the positive electrode composite paste to the positive electrode current collector. [Figure 14] (a) is a plan view showing the positional relationship between the nickel substrate, the first support part, and the second support part. (b) is a cross-sectional view showing the nickel substrate supported by the first support part and the second support part before the paste is applied. (c) is an enlarged cross-sectional view of (b). [Figure 15] This is a schematic diagram showing one side of the positive electrode plate of a conventional nickel-metal hydride battery. [Figure 16] This is a schematic diagram showing the other side of the positive electrode plate of a conventional nickel-metal hydride battery. [Figure 17] This is a schematic diagram showing the state of electrolyte penetration during the injection of electrolyte into a conventional nickel-metal hydride battery. [Modes for carrying out the invention]

[0020] Hereinafter, the secondary battery of the present invention and its manufacturing method will be described with reference to Figures 1 to 14 using one embodiment of the nickel-metal hydride storage battery and its manufacturing method. In this application, the nickel-metal hydride storage battery 1 will be described with the upward direction in Figure 1 being referred to as "up".

[0021] (Configuration of this embodiment) <Outline of this embodiment> The nickel-metal hydride battery 1 of this embodiment includes an electrode group 6 consisting of a positive electrode plate 2 having a positive electrode current collector 21 and a positive electrode composite material layer 22 (see Figure 6) filled therein, a negative electrode plate 3, and a separator 4, as shown in Figure 3.

[0022] Figure 17 is a schematic diagram showing the state of electrolyte 5 penetration during injection in a conventional nickel-metal hydride battery 1. In the nickel-metal hydride battery 1, the electrode group 6 shown in Figure 3 is housed in the battery case 15 of each battery cell as shown in Figure 2. Then, the electrolyte 5 is injected from above. The injected electrolyte 5 temporarily remains above the electrode group 6. At this time, the electrode group 6 housed in the battery case 15 is housed with almost no gaps between it and the battery case 15 so as not to create any wasted space. In addition, the stacked positive electrode plate 2, negative electrode plate 3, and separator 4 are stacked closely together. For this reason, the electrolyte 5 does not easily penetrate into the interior of the electrode group 6 or into the gaps with the battery case 15, as shown by the thin arrows.

[0023] Figure 15 is a schematic diagram showing one side of the positive electrode plate 2 of a conventional nickel-metal hydride battery 1. Figure 16 is a schematic diagram showing the other side of the positive electrode plate 2 of a conventional nickel-metal hydride battery 1. Conventionally, both sides were coated. In addition, battery performance can be improved by increasing the area in which the positive electrode composite layer 22 faces the negative electrode composite layer. For this reason, it was thought that the positive electrode composite layer 22 should be coated onto the positive electrode current collector 21 with as little gap as possible. Furthermore, if there are irregularities on the end 22d of the positive electrode composite layer 22, the positive electrode composite layer 22 is likely to fall off, so it was thought that irregularities should not be formed on the end 22d of the positive electrode composite layer 22.

[0024] Therefore, in the conventional positive electrode plate 2 shown in Figures 15 and 16, the end portion 22d of the positive electrode composite layer 22 is close to the inner surface 21m of the peripheral edge of the positive electrode current collector 21, and the width Wv0 of the unpainted portion is narrow. In addition, the width ΔW of the unevenness at the end portion 22d of the positive electrode composite layer 22 is uniform and small.

[0025] Therefore, as shown in Figure 17, there was a problem in that the electrolyte 5 that remained at the top of the electrode group 6 did not easily penetrate the positive electrode plate 2. Figure 7 is a schematic diagram showing the coated surface 22a of the positive electrode plate 2 of the nickel-metal hydride battery 1 of this embodiment. Figure 8 is a schematic diagram showing the surface 22c of the positive electrode plate 2 of the nickel-metal hydride battery 1 of this embodiment, opposite to the coated surface.

[0026] In this embodiment, the positive electrode composite layer 22 formed in the positive electrode current collector 21 is divided equally in the vertical direction into three regions: an upper region Wt1, an intermediate region Wt2, and a lower region Wt3. At the end 22d in the width direction W (horizontal direction) of the positive electrode composite layer 22, the average unevenness width of the positive electrode current collector in the upper region Wt1 is defined as the unevenness width ΔW1. The average unevenness width of the positive electrode current collector in the intermediate region Wt2 is defined as the unevenness width ΔW2. The average unevenness width of the positive electrode current collector in the lower region Wt3 is defined as the unevenness width ΔW3. In this case, the configuration is such that unevenness width ΔW1 ≥ unevenness width ΔW3. Also, unevenness width ΔW1 ≥ unevenness width ΔW2 ≥ unevenness width ΔW3.

[0027] <Main functions of this embodiment> Figure 10 is a schematic diagram showing the state of electrolyte 5 penetration during the injection of electrolyte into the nickel-metal hydride battery 1 of this embodiment.

[0028] In this embodiment, the positive electrode plate 2 is configured as described above. Therefore, the average unevenness width ΔW1 of the upper region Wt1 is greater than the average unevenness width ΔW3 of the lower region Wt3. The fact that the unevenness width ΔW1 is greater than the unevenness width ΔW3 means that the length of the end portion 22d of the positive electrode composite layer 22 in the upper region Wt1 is longer. The fact that the end portion 22d is longer means that the critical interface between the positive electrode composite layer 22 in the upper region Wt1 and the electrolyte 5 in the lower region Wt3 is wider for the positive electrode composite layer 22 in the upper region Wt1. Here, if the configuration of the positive electrode composite layer 22 is the same and the permeability to the electrolyte 5 is also the same, then the larger the critical area with the electrolyte 5, the easier it is for the electrolyte 5 to penetrate.

[0029] As shown in Figure 10, the electrolyte 5 that remains above the electrode group 6 of this embodiment penetrates the uncoated portion between the end 22d of the upper region Wt1 and the inner surface 21m of the peripheral edge of the positive electrode current collector 21 via the separator 4, as shown in Figure 3. Subsequently, the electrolyte 5 penetrates from this uncoated portion of width Wv1 to the end 22d of the positive electrode composite layer 22.

[0030] As described above, the critical area where the end 22d of the positive electrode composite layer 22 in the upper region Wt1 is in contact with the electrolyte 5 is larger than the critical area between the end 22d of the positive electrode composite layer 2 in the lower region Wt3 and the electrolyte 5. Therefore, the electrolyte 5 lingering above the electrode group 6 in this embodiment shown in Figure 10 penetrates the positive electrode composite layer 22 more easily than the electrolyte 5 lingering above the electrode group 6 in the conventional technology shown in Figure 17.

[0031] <Main effects of this embodiment> In the nickel-metal hydride battery 1 of this embodiment, because it has such a configuration, when the electrolyte 5 is injected during the manufacturing process of the nickel-metal hydride battery 1, the electrolyte 5 can efficiently penetrate the end portion 22d of the positive electrode composite layer 22 in the upper region Wt1.

[0032] Furthermore, the width Wv1 of the uncoated portion of the upper region Wt1 of the positive electrode plate 2 shown in Figure 7 is wider than the width Wv0 of the uncoated portion of the positive electrode plate 2 shown in Figure 15. As a result, the absorption of the electrolyte 5 by the positive electrode plate 2 as a whole can be improved, and the internal resistance (DC-IR) can be reduced.

[0033] The nickel-metal hydride battery 1 of this embodiment and its manufacturing method will be described in detail below. <Configuration of Nickel-Metal Hydride Battery 1> Figure 1 is a perspective view showing the external structure of the nickel-metal hydride battery 1 of this embodiment.

[0034] <Battery Module> As shown in Figure 1, the nickel-metal hydride battery 1 is configured as a battery module equipped with multiple battery cells 12. The nickel-metal hydride battery 1 is a sealed battery with a rectangular plate-like exterior. It comprises a battery case 13 that forms an integrated battery case capable of housing multiple (in this case, six) battery cells 12, and a lid 14 that seals the opening of the battery case 13. The battery case 13 houses six battery cells 12 electrically connected in series in a battery case 15 (see Figure 2). The power of these battery cells 12 is taken out from the positive electrode connection terminal 13a and the negative electrode connection terminal 13b provided on the battery case 13.

[0035] <Internal structure of nickel-metal hydride battery> Figure 2 is a partial perspective view of the battery module of the nickel-metal hydride battery 1, including its cross-sectional structure. As shown in Figure 2, the battery case 13 and lid 14 are made of polypropylene (PP) and polyphenylene ether (PPE), which are resin materials resistant to alkaline electrolyte 5. Inside the battery case 13, partition walls 18 are formed to separate multiple battery cells 12, and the portion separated by these partition walls 18 becomes a battery case 15 for each battery cell 12. Electrode groups 6 are housed within these partitioned battery cases 15, and the alkaline electrolyte 5, which is an aqueous electrolyte mainly composed of potassium hydroxide (KOH), is filled into the cases.

[0036] A through-hole 17 is formed in the upper part of the partition wall 18, which is used to connect each battery cell 12. Two connecting protrusions, one protruding from the upper part of the positive electrode current collector plate 27 and the other protruding from the upper part of the negative electrode current collector plate 37, are welded together through the through-hole 17 by spot welding or the like. This electrically connects the electrode groups 6 of adjacent battery cells 12 in series. Of the through-holes 17, the through-holes 17 located on the outside of each of the battery cells 12 at both ends are fitted with a positive electrode connection terminal 13a or a negative electrode connection terminal 13b (see Figure 1) above the longitudinal end of the battery case 13. The positive electrode connection terminal 13a is welded to the connecting protrusion of the positive electrode current collector plate 27. The negative electrode connection terminal 13b is welded to the connecting protrusion of the negative electrode current collector plate 37. The total output of the series-connected electrode group 6, i.e., the multiple battery cells 12, is taken out from the positive electrode connection terminal 13a and the negative electrode connection terminal 13b.

[0037] <Electrode group 6> Figure 3 is a cross-sectional view in the width direction W of the electrode group 6 provided in the nickel-metal hydride battery 1 of this embodiment. As shown in Figure 3, the electrode group 6 is constructed by stacking rectangular positive electrode plates 2 and negative electrode plates 3 with a separator 4 in between. In this case, the direction in which the positive electrode plate 2, negative electrode plate 3 and separator 4 are stacked is the thickness direction D.

[0038] The positive electrode plate 2 and negative electrode plate 3 of the electrode group 6 are provided with lead portions that protrude from opposite sides of the electrode plates in the planar direction. A positive electrode current collector plate 27 is joined to the side edge of the lead portion 21l (see Figures 6 and 7) of the positive electrode plate 2 by spot welding or the like. Similarly, a negative electrode current collector plate 37 is joined to the side edge of the lead portion (not shown) of the negative electrode plate 3 by spot welding or the like.

[0039] <Configuration of positive electrode plate 2> Figure 6 is a schematic diagram showing a cross-section in the width direction W of the positive electrode plate 2 of the nickel-metal hydride battery 1 of this embodiment. The positive electrode plate 2 has a positive electrode current collector 21 and a positive electrode composite material layer 22 filled in the positive electrode current collector 21. The positive electrode composite material layer 22 has a positive electrode active material and additives (conductive material, binder, thickener, etc.).

[0040] <Positive electrode current collector 21> The positive electrode current collector 21 is formed in the shape of a rectangular plate made of a three-dimensional porous metal, nickel or a nickel alloy foam, which serves as the substrate. The periphery of the positive electrode current collector 21 is compressed and has a higher density, and functions as a frame that maintains the shape of the positive electrode current collector 21. In addition, because the porous structure of the periphery is compressed and the air permeability is reduced, the absorption of the electrolyte 5 from the surface is worse compared to the central part. The positive electrode current collector 21 has the function of a carrier that supports the positive electrode composite material layer 22 in the space formed by its three-dimensional mesh-like structure, and the function of a current collector that collects current from the positive electrode active material in the positive electrode composite material layer 22.

[0041] The positive electrode current collector 21 uses foamed nickel, which is a type of foamed metal. Foamed nickel has numerous pores inside and can be easily compressed. The method for manufacturing foamed nickel is not particularly limited, but for example, it can be manufactured by applying nickel plating to the surface of a foamed urethane skeleton and then burning off the foamed urethane.

[0042] Figure 7 is a schematic diagram showing the coated surface 22a of the positive electrode plate of the nickel-metal hydride battery of this embodiment. As shown in Figures 6 and 7, the lead portion 21l is formed by welding a metal material such as iron to the center of one of the long sides of the rectangular positive electrode current collector 21 in the length direction L. This lead portion 21l is provided in the center of the thickness direction D of the positive electrode current collector 21.

[0043] The lead portion 21l is formed by welding a metal member, such as iron, to a frame portion that is compressed and has high density and strength on one of the long sides of the positive electrode current collector 21. A connection surface is formed on one surface of this metal member. The lead portion 21l is connected to the positive electrode connection terminal 13a of the adjacent battery cell 12 by a connection projection that protrudes from its upper part.

[0044] In this embodiment, it is desirable that the thickness of the positive electrode current collector 21 before the coating process (S13) be 0.5 mm or more and 1.0 mm or less. It is desirable that the foamed nickel used has an average pore size of 300 μm or more and 6000 μm or less. Furthermore, the basis weight of the positive electrode composite layer 22 filled into the positive electrode current collector 21 should be 200 g / m². 2 ] or more, 400[g / m 2 It is desirable to use the following:

[0045] <Positive electrode composite paste 25> The positive electrode composite paste 25, which forms the positive electrode composite layer 22, contains positive electrode active material particles mainly composed of nickel hydroxide, a conductive material made of cobalt (Co), a thickener, a binder, and a solvent such as water.

[0046] Figure 11 is a comparison table showing an example of the composition of a conventional cathode composite paste and an example of the composition of the cathode composite paste 25 of this embodiment. As shown in Figure 11, the composition (wt%) of the positive electrode composite paste 25 of this embodiment, excluding the solvent water, is preferably as follows: Nickel hydroxide as the positive electrode active material is preferably 85 wt% to 95 wt%. Cobalt (Co) as the conductive material is preferably 5 wt% to 10 wt%. Zinc oxide is preferably 0.5 wt% to 1.5 wt% for adjusting the potential. Yttrium oxide is preferably 0.5 wt% to 1.5 wt%. Carboxymethylcellulose (CMC) as a thickener is preferably 0.01 wt% to 0.2 wt%. Sodium alginate is preferably 0.01 wt% to 0.2 wt% as a thickener. Furthermore, a fluorine-based binder is preferred in an amount of 0.05 (wt%) or more and 0.3 (wt%) or less.

[0047] While "fluorine-based binders" exhibit desirable performance as binders, they have the problem of segregation on the electrode surface during drying. In this embodiment, this problem is solved, making it possible to use fluorine-based binders. Details will be described later.

[0048] The positive electrode composite paste 25 of this embodiment is made by forming a paste from a positive electrode active material, conductive material, binder, thickener, etc., with a solvent such as water. The viscosity V [mPa·s] is adjusted by the solvent and thickener, and in this embodiment, 50 to 2000 [mPa·s] is desirable, and for example, it is adjusted to 500 [mPa·s]. Note that this value is for a shear rate of 10 [s -1 This shows the value in the case of ].

[0049] <Features of the positive electrode composite paste 25 of this embodiment> As shown in Figure 11, conventional cathode composite pastes do not contain sodium alginate as a thickening agent. Therefore, the viscosity [mPa·s] is not adjusted. Furthermore, they differ in that they do not contain polyvinylidene fluoride (PVDF), a fluorine-based binder. As a result, the binding strength is low.

[0050] <Cathode active material> Examples of positive electrode active materials include particulate materials mainly composed of nickel oxides such as nickel hydroxide and nickel oxyhydroxide.

[0051] <Conductive material> The conductive material is a metal or a metallic compound, such as cobalt compounds including metallic cobalt (Co), cobalt monoxide (CoO), or cobalt oxyhydroxide (CoOOH), which coat the surface of a nickel oxide. Cobalt oxyhydroxide, which has high conductivity, is preferred because it forms a conductive network within the positive electrode, thereby increasing the utilization rate of the positive electrode.

[0052] <Thickening agent> Examples of thickening agents include glucose-based substances such as xanthan gum, and acrylic-based substances such as sodium acrylate.

[0053] <Binding agent> The material contains a fluorine-based binder. Examples of fluorine-based binders include organic solvent-based polyvinylidene fluoride (PVDF) and aqueous dispersants. While fluorine-based binders have good binding properties, they tend to segregate on the surface of the positive electrode composite layer 22. In this embodiment, even if such segregation occurs, the structure facilitates the penetration of the electrolyte 5 into the positive electrode composite layer 22. Therefore, in this embodiment, even fluorine-based binders that tend to segregate can be effectively utilized.

[0054] Furthermore, other examples of binding agents include latex-based materials such as Rubron (a registered trademark of Daikin Industries, Ltd.) and polyethylene oxide (PEO). <Solvent> In this embodiment, water (H2O) is used as the solvent. The solvent, along with the thickener, is used to adjust the viscosity of the cathode composite paste 25. The amount added is adjusted while taking into account the value of the unevenness width ΔW1 and the relationship ΔW1 / Wp.

[0055] <Positive electrode composite layer 22> The positive electrode composite paste 25 described above is coated and filled into the positive electrode current collector 21, and after drying and shaping press, the positive electrode composite layer 22 is formed. Further details will be described later.

[0056] <Negative electrode plate 3> The negative electrode plate 3 includes a plate-shaped negative electrode current collector 31 made of rectangular perforated metal or the like. The negative electrode current collector 31 is both a mechanical substrate and a current collector that collects current from the negative electrode active material. It also includes a hydrogen storage alloy (MH) coated on the negative electrode current collector 31. The type of hydrogen storage alloy is not particularly limited, but for example, it may be an alloy of mischmetal, which is a mixture of rare earth elements, and nickel, or a part of the alloy in which metals such as aluminum, cobalt, or manganese are replaced. The negative electrode plate 3 is coated with a negative electrode composite paste. The negative electrode composite paste is made by adding a thickening agent such as carbon black and a binder such as styrene-butadiene copolymer to a hydrogen storage alloy and processing it into a negative electrode composite paste. The negative electrode plate 3 is manufactured by filling the negative electrode composite paste into the negative electrode current collector 31, which is made of a core material such as perforated metal, and then drying, rolling, and cutting it.

[0057] <Separator 4> Separator 4 is made of a nonwoven fabric of an olefin resin such as polypropylene, or, if necessary, this fabric has been treated with a hydrophilic treatment such as sulfonation.

[0058] These positive electrode plate 2, negative electrode plate 3, and separator 4 are used to manufacture a battery module. <Electrolyte 5> The electrolyte 5 is held within the separator 4 and conducts ions between the positive electrode plate 2 and the negative electrode plate 3. The electrolyte 5 is, for example, an alkaline aqueous solution with potassium hydroxide (KOH) as the main solute component. The electrolyte 5 also penetrates into the positive electrode composite layer 22 and reacts with the positive electrode active material within the positive electrode composite layer 22. Therefore, the penetration of the electrolyte 5 into the positive electrode composite layer 22 is a factor that affects the performance of the battery.

[0059] <Manufacturing process for nickel-metal hydride battery 1> Figure 4 is a flowchart showing the manufacturing process of the nickel-metal hydride battery 1 of this embodiment. Next, the manufacturing method of the nickel-metal hydride battery 1 of this embodiment, which has the configuration described above, will be explained with reference to Figure 4. The manufacturing process of the nickel-metal hydride battery 1 consists of a source process (S1), an electrode group manufacturing process (S2), an electrode group assembly process (S3), a liquid injection process (S4), a sealing process (S5), and an inspection process (S6).

[0060] In the source process (S1), the battery elements, namely the positive electrode plate 2, the negative electrode plate 3, and the separator 4, are manufactured. In the electrode group manufacturing process (S2), the positive electrode plate 2, the negative electrode plate 3, and the separator 4 manufactured in the source process (S1) are stacked, and the positive electrode current collector plate 27 and the negative electrode current collector plate 37 are welded to manufacture the electrode group 6 as shown in Figure 3. In the electrode group assembly process (S3), the electrode group 6 manufactured in the electrode group manufacturing process (S2) is housed in each of the battery cases 15 of the integrated battery case 13, as shown in Figure 2. The electrode groups 6 housed in each of the battery cases 15 are then electrically connected by welding or other means, and the positive electrode connection terminal 13a and the negative electrode connection terminal 13b (see Figure 1) are attached. In the electrolyte injection process (S4), the electrolyte 5 is injected into each of the battery cases 15 of the battery case 13 from above. In the sealing process (S5), the lid 14 is attached to the battery case 13, which has been filled with electrolyte in the electrolyte filling process (S4), and sealed. This completes the assembly of the nickel-metal hydride battery 1, which is the battery module of this embodiment. In the inspection process (S6), the assembled nickel-metal hydride battery 1 undergoes initial charging, aging, internal resistance (DC-IR) testing, OCV testing, self-discharge testing, etc. Only those that pass these tests become the nickel-metal hydride battery module 1 as a product.

[0061] <Manufacturing process for positive electrode plate 2> Figure 5 is a flowchart showing the manufacturing process of the positive electrode plate of the nickel-metal hydride battery according to this embodiment. Next, the manufacturing process of the positive electrode plate 2 will be described in detail with reference to Figure 5. This manufacturing process of the positive electrode plate 2 is a part of the source process (S1) of the nickel-metal hydride battery 1.

[0062] The manufacturing process for the positive electrode plate consists of the positive electrode current collector manufacturing process (S11), the positive electrode composite paste manufacturing process (S12), the coating process (S13), the drying process (S15), and the shaping and pressing process (S16).

[0063] <Positive electrode current collector manufacturing process (S11)> The positive electrode current collector manufacturing process (S11) is the process for manufacturing the positive electrode current collector 21. First, a positive electrode current collector 21 of a predetermined size is cut from a long sheet of foamed nickel by a cutting process. Next, the peripheral portion of the positive electrode current collector 21, which has been shaped to a predetermined thickness in a shaping and pressing process, is compressed to shape it to a predetermined length and width. The shaped peripheral portion of the positive electrode current collector 21 is compressed and crushed, increasing its density. This increased density increases its mechanical strength, allowing it to maintain its shape as the frame of the positive electrode current collector 21. Furthermore, this peripheral portion is compressed and crushed, which crushes the spaces in the porous foamed nickel, reducing its permeability and making it difficult for the electrolyte 5 to be absorbed.

[0064] A lead portion 21l, as shown in Figures 6 and 7, is welded to the center of one of the longer sides of the periphery of the positive electrode current collector 21. <Cathode composite paste manufacturing process (S12)> In the positive electrode composite paste manufacturing process (S12), the positive electrode composite paste 25 described above is manufactured. The positive electrode composite paste 25 is made by mixing positive electrode active material particles, conductive material, binder, thickener, etc. with a solvent to form a paste with a predetermined viscosity V [mPa·s].

[0065] <Coating process (S13)> In the coating process (S13), the positive electrode composite paste 25 manufactured in the positive electrode composite paste manufacturing process (S12) is coated onto the positive electrode current collector 21 manufactured in the positive electrode current collector manufacturing process (S11) and filled into the positive electrode current collector.

[0066] Figure 12 is a perspective view showing a coating machine 8, which is an example of a coating apparatus in this embodiment. Figure 13(a) is a perspective view showing the coating process (S13) in this embodiment. <Coating machine 8> As shown in Figure 12, the coating machine 8 for applying the positive electrode composite paste 25 to the positive electrode current collector 21 comprises a die nozzle 81 for applying the positive electrode composite paste 25 to the positive electrode current collector 21, a support member 85, and a stage 86.

[0067] <Die nozzle 81> As shown in Figure 13(b), the die nozzle 81 comprises a die 82 and a nozzle 83. The die 82 stores the positive electrode mixture paste 25 supplied from a supply unit (not shown), such as a tank, through a supply pipe at high pressure. The nozzle 83 has a discharge port at its tip facing the upper surface 21j of the positive electrode current collector 21. Here, the upper surface 21j refers to the surface that is facing upward in the coating process (S13), unlike in Figures 1 and 2, and refers to the surface on the coated side surface 22a of the positive electrode mixture layer 22. The same applies to the lower surface 21k. The discharge port is spaced apart from the upper surface 21j by a predetermined clearance gap G. The nozzle 83 extends in the second direction Y (width direction W of the positive electrode current collector 21), and its discharge port is partitioned to correspond to the coating areas 21a to 21d, intermittently discharging the positive electrode mixture paste 25 onto the upper surfaces 21j of the coating areas 21a to 21d. The positive electrode composite paste 25 discharged from the discharge port flows down to the upper surface 21j.

[0068] The die nozzle 81 is equipped with a pressing roller 84 in the area of ​​the nozzle 83 that is not coated with the positive electrode mixture paste 25 when dispensing the positive electrode mixture paste 25 onto the upper surface 21j of the positive electrode current collector 21. The pressing roller 84 contacts the upper surface 21j just before the nozzle 83 applies the positive electrode mixture paste 25 to the upper surface 21j, pressing the positive electrode current collector 21 toward the support member 85. As a result, the pressing roller 84 removes the waviness of the positive electrode current collector 21 and maintains a constant distance between the nozzle 83 and the upper surface 21j.

[0069] <Support member 85> The support member 85 supports the coating area 21a to 21d from the lower surface 21k side until the positive electrode composite paste 25 is applied to the upper surface 21j of the positive electrode current collector 21 by the nozzle 83.

[0070] Figure 14(a) is a plan view showing the positional relationship between the nickel substrate, the first support, and the second support. Figure 14(b) is a cross-sectional view showing the nickel substrate supported by the first and second support before the paste is applied. Figure 14(c) is an enlarged cross-sectional view of (b).

[0071] As shown in Figures 14(a) to (c), the support member 85 comprises a first support portion 85a, an insertion portion 85b, and a connecting portion 85c. The first support portion 85a supports each of the coating areas 21a to 21d by contacting them from the lower surface 21k side. The insertion portion 85b is provided between adjacent first support portions 85a. The connecting portion 85c (see Figure 13(a)) connects the first support portions 85a that are separated from each other by the insertion portion 85b in the second direction Y (see Figure 12). The support member 85 has a comb-like shape overall.

[0072] <First support part 85a> Four first support parts 85a are provided, corresponding to the coating areas 21a to 21d. Each first support part 85a extends in the first direction X and is spaced parallel to each other. In each first support part 85a, the support surface that supports the coating areas 21a to 21d is preferably a flat surface that can provide stable support and is easily slidable against the lower surface 21k of the coating areas 21a to 21d. This makes it easier for the first support part 85a to dislodge from below the coating areas 21a to 21d.

[0073] The tip opposite to the connecting portion 85c that connects each first support portion 85a is located at least below the press roller 84. This allows each first support portion 85a to work in cooperation with the press roller 84 to firmly grip the positive electrode current collector 21. More preferably, the tip of the first support portion 85a may also be long enough to be located below the nozzle 83. That is, the first support portion 85a may be configured to contact and support the lower surface 21k of the coating area 21a to 21d until the positive electrode mixture paste 25 penetrates from the upper surface 21j to the lower surface 21k of the positive electrode current collector 21. This allows the first support portion 85a to support the lower surface 21k of the coating area 21a to 21d until just before it comes into contact with the penetrating positive electrode mixture paste 25.

[0074] <Insertion section 85b> The insertion portion 85b, located between adjacent first support portions 85a, is a slit that penetrates in the thickness direction D, extends in the first direction X, and has an open end below the nozzle 83.

[0075] <Stage 86> Stage 86 is configured such that a support member 85 and a die nozzle 81 synchronized with the support member 85 are movable in a first direction X. Stage 86 is provided with a second support portion 85d on the support surface of the support member 85.

[0076] <Second support part 85d> As shown in Figure 14(c), the support member 85 is a member positioned between the die nozzle 81 and the stage 86. The insertion portion 85b of this support member 85 is through which the second support portion 85d provided on the stage 86 is inserted, so that the second support portion 85d can support the lower surface 21k of the uncoated areas 21e to 21i of the positive electrode current collector 21. That is, the width of each insertion portion 85b (the distance between adjacent first support portions 85a) is, for example, a width through which the second support portion 85d can be inserted, and is slightly wider than the width of the second support portion 85d.

[0077] The die nozzle 81 and the support member 85 are connected via a connecting mechanism (not shown) that includes a connecting member, and move synchronously in the direction of movement indicated by the arrow, which is one of the first directions X relative to the positive electrode current collector 21. In other words, the positive electrode current collector 21 and the stage 86 do not move, while the die nozzle 81 and the support member 85 move in the direction of movement indicated by the arrow relative to the positive electrode current collector 21 and the stage 86.

[0078] The second support portion 85d is inserted into the insertion portion 85b of the support member 85 and supports the lower surface 21k of the positive electrode current collector 21 with its tip surface. For example, the second support portion 85d has a length corresponding to the first direction X of the positive electrode current collector 21 on which it is placed (the length of the uncoated region 21e to 21i in the first direction X). In the second support portion 85d, the support surface that supports the uncoated region 21e to 21i is preferably a flat surface that is less slippery with respect to the lower surface 21k of the uncoated region 21e to 21i. This prevents the positive electrode current collector 21 from being dragged along and moving in the direction indicated by the arrow on the support member 85.

[0079] <Operation of coating machine 8> Specifically, before the positive electrode composite paste 25 is applied to the upper surface 21j of the positive electrode current collector 21, the lower surfaces 21k of the applied areas 21a to 21d are supported by the first support part 85a, and the lower surfaces 21k of the unapplied areas 21e to 21i are supported by the second support part 85d. Then, the die nozzle 81 and the support member 85 move in the direction indicated by the arrows relative to the positive electrode current collector 21 and the stage 86. As a result, in the portion of the positive electrode current collector 21 to which the positive electrode composite paste 25 has been applied, only the lower surfaces 21k of the unapplied areas 21e to 21i are supported by the second support part 85d. The space between the lower surfaces 21k of the applied areas 21a to 21d and the stage 86 becomes a gap when the first support part 85a is removed, preventing the positive electrode composite paste 25 that has penetrated to the lower surface 21k of the positive electrode current collector 21 from coming into contact with the stage 86. Furthermore, by inserting the second support portion 85d into the insertion portion 85b, the second support portion 85d also functions as a guide rail for the support member 85 that moves relative to the stage 86, and the insertion portion 85b also functions as a guide groove into which the guide rail is inserted. Note that the guiding mechanism for the support member 85 relative to the stage 86 can also be provided in addition to the insertion portion 85b.

[0080] When the positive electrode composite paste 25 is applied to the upper surface 21j of the positive electrode current collector 21, the support member 85 moves relative to the positive electrode current collector 21 in the direction indicated by the arrow. Therefore, the positive electrode current collector 21 may be dragged and moved by the movement of the support member 85 in the direction indicated by the arrow. To address this, the second support portion 85d is equipped with a holding means to hold the positive electrode current collector 21 so that it does not move in the direction indicated by the arrow. The holding means is a vacuum suction pad or a magnetic suction pad that holds the positive electrode current collector 21 on the second support portion 85d.

[0081] <Coating Procedure> Figure 13(b) is an enlarged cross-sectional view showing the position where the die nozzle 81 applies the positive electrode composite paste 25 to the positive electrode current collector 21. The coating process (S13) is carried out using the coating machine 8 described above. The coating procedure will be explained with reference to Figure 13.

[0082] As shown in Figures 13(a) and 13(b), the die nozzle 81 and the support member 85 move synchronously and sequentially in the direction indicated by the arrows. As a result, the first support portion 85a of the support member 85 retracts sequentially from below the upper surface 21j of the coating area 21a to 21d, and thereafter, the positive electrode composite paste 25 penetrates from the upper surface 21j to the lower surface 21k. This prevents contact between the positive electrode composite paste 25 on the lower surface 21k and the first support portion 85a. In other words, after the positive electrode composite paste 25 is applied, only the uncoated area 21e to 21i of the positive electrode current collector 21 is supported by the second support portion 85d of the stage 86.

[0083] The positive electrode current collector 21 is coated with the positive electrode composite paste 25 through the process described above. <Positive electrode composite paste 25 in coating process (S13)> In the coating process (S13), as described above, the die nozzle 81 applies the positive electrode composite paste 25 to the positive electrode current collector 21.

[0084] As shown in Figure 13(b), when the positive electrode composite paste 25 is discharged from the upper surface 21j of the positive electrode current collector 21, the positive electrode composite paste 25 is coated on the upper surface 21j of the positive electrode current collector 21 with a coating width Wp, as shown in Figures 6 and 7. The coated positive electrode composite paste 25 penetrates and fills the interior of the positive electrode current collector 21. At this time, due to its viscosity V [mPa·s], surface tension, and wettability, as shown in Figure 6, the width W of the positive electrode composite paste 25 gradually decreases as it penetrates downwards due to gravity from the coating width Wp. Finally, at the lower surface 21k, the coating width becomes Ws.

[0085] As shown in Figure 7, the coated positive electrode composite paste 25 is applied to a coating width Wp, but at this time, the end 22d in the width direction W is not a straight line along the length direction L, but rather has a wavy, random unevenness in the width direction W. This is caused by the skeletal structure of the positive electrode current collector 21 and the unevenness of the positive electrode composite paste 25 absorbed therein. Therefore, the coating width Wp and coating width Ws are the average of these unevennesses. This averaging is Like this embodiment You can use the arithmetic mean, or any other method of averaging.

[0086] The average width of the irregularities at this time is defined as the irregularity width ΔW. In this embodiment, the penetration of the electrolyte 5 into the positive electrode composite layer 22 is improved by controlling and adjusting this irregularity width ΔW. In this embodiment, the "coating width Wp" and "coating width Ws" are the trajectory of a straight line obtained by averaging the "undulation width ΔW" for each of the upper region Wt1, the intermediate region Wt2, and the lower region Wt3.

[0087] Next, Figure 8 is a schematic diagram showing the surface 22c of the positive electrode composite layer 22 of the positive electrode plate 2 of the nickel-metal hydride battery 1 of this embodiment, opposite to the coated side. As shown in Figure 6, the width of the positive electrode composite paste 25 that is coated and penetrates the positive electrode current collector 21 narrows by the time it reaches the bottom surface 21k. Therefore, on the surface 22c opposite to the coated side shown in Figure 8, the width of the positive electrode composite layer 22 is the coating width Ws.

[0088] <Coating amount of positive electrode composite paste 25 [g / s]> The coating amount in this embodiment is set as follows. In this embodiment, as described above, the unevenness width ΔW1 in the upper region Wt1 is configured to be larger than the unevenness width ΔW3 in the lower region Wt3.

[0089] Therefore, the inventors have found that, as one method for controlling the unevenness width ΔW1 in the upper region Wt1, the more the viscosity V [mPa·s] of the positive electrode composite paste 25 is within a predetermined range, and the greater the coating amount [g / s] within that range, the larger the unevenness width ΔW becomes.

[0090] Therefore, when the average coating amount Q3 [g / s] in the lower region Wt3 was set to 100%, the average coating amount Q1 [g / s] in the upper region Wt1 was set to 102.4%, which is excessive. At this time, the average coating amount Q2 [g / s] in the intermediate region Wt2 was set to 101.2% of Q3, which is the midpoint between the two.

[0091] As a result, the unevenness width ΔW3 in the lower region Wt3 was 0.1 [mm], while the unevenness width ΔW2 in the intermediate region Wt2 was 0.3 [mm], and the unevenness width ΔW1 in the upper region Wt1 was larger at 0.5 [mm].

[0092] In this embodiment, it was found that the desired ΔW1 can be obtained when the coating amount Q1 in the upper region Wt1 is within the range of Q1 / Q3 ≥ 1.02 relative to the coating amount Q3 in the lower region Wt3. In this embodiment, the coating amount [g / s] is adjusted by the discharge pressure of the positive electrode mixture paste 25.

[0093] <Another example of coating amount Q> In this embodiment, the coating amount [g / s] is adjusted by the discharge pressure of the positive electrode mixture paste 25. However, depending on the configuration of the positive electrode current collector 21, the configuration of the positive electrode mixture paste 25, and its viscosity V [mPa·s], it has been found that even by discharging at a constant discharge pressure, the value of the unevenness width ΔW1 in the upper region Wt1 can be increased.

[0094] Therefore, we found that the value of the unevenness width ΔW1 in the upper region Wt1 can be controlled and adjusted not only by the discharge pressure but also by the viscosity V [mPa·s]. Specifically, when the positive electrode composite paste 25 has a relatively low viscosity, the paste flow is turbulent at the beginning of discharge, and the unevenness width ΔW1 becomes large. However, as the positive electrode composite paste 25 discharged to the positive electrode current collector 21 becomes uneven in width ΔW2 and then ΔW3, ΔW steadily decreases. As a result, even with the same discharge pressure, the unevenness width ΔW3 in the lower region Wt3 becomes smaller than the unevenness width ΔW1 in the upper region Wt1.

[0095] <Gap G> Furthermore, the inventors have found that the width ΔW1 of the unevenness in the upper region Wt1 can also be controlled and adjusted by the gap G.

[0096] As shown in Figure 13(b), a predetermined clearance, or gap G, is set between the discharge portion at the lower end of the nozzle 83 of the die nozzle 81 and the positive electrode current collector 21. If this gap G is made small, even with the same discharge rate [g / s], the discharge pressure of the discharged positive electrode composite paste 25 is more easily transmitted to the surface of the positive electrode current collector 21. As a result, the positive electrode composite paste 25 on the surface of the positive electrode current collector 21 is more likely to become disordered, and the unevenness width ΔW1 becomes larger.

[0097] On the other hand, when the gap G is large, even with the same discharge rate [g / s], the discharge pressure of the discharged positive electrode composite paste 25 is less likely to be transmitted to the surface of the positive electrode current collector 21, and the positive electrode composite paste 25 is coated onto the positive electrode current collector 21 by gravity. As a result, the disturbance of the positive electrode composite paste 25 on the surface of the positive electrode current collector 21 is reduced, and the unevenness width ΔW1 becomes smaller.

[0098] Thus, the gap G, which is the clearance between the discharge portion at the lower end of the nozzle 83 of the die nozzle 81 and the positive electrode current collector 21, affects the size of the unevenness width ΔW that is formed. <Depth ΔW and coating width Wp> As described above, the control and adjustment of the unevenness width ΔW1 of the upper region Wt1 is performed as described above. The coating width Wp is also taken into consideration when determining the unevenness width ΔW1, as shown below.

[0099] When the width of the positive electrode composite paste 25 on the positive electrode current collector 21 in the upper region Wt1 is defined as the coating width Wp of the positive electrode composite layer 22, the relationship between this width and the unevenness width ΔW1 of the edge 22d of the positive electrode composite layer 22 is as follows. Here, the coating width Wp is the average width in the upper region Wt1. If the relationship ΔW1 / Wp is sufficiently large, the critical interface between the edge 22d of the positive electrode composite layer 22 and the electrolyte 5 can be sufficiently large. Therefore, the critical interface can allow sufficient electrolyte 5 to penetrate.

[0100] Specifically, in this embodiment, the relationship is set to "ΔW1 / Wp≧0.015". More preferably, ΔW1 / Wp≧0.016. On the other hand, if the relationship ΔW1 / Wp is too large, the irregularities in the surface become larger, and the end portion 22d of the positive electrode composite layer 22 may overlap the lead portion 21l. Furthermore, if the irregularities in the surface become too large, it can cause the end portion 22d of the positive electrode composite layer 22 to fall off.

[0101] Therefore, in this embodiment, the preferred value of the relation ΔW1 / Wp is set to ΔW1 / Wp ≤ 0.025. Furthermore, the relationship ΔW3 / Wp in the lower region Wt3 can be a relatively small value because its contribution to the penetration of the electrolyte 5 is small. Conversely, in the lower region Wt3, when inserted into the battery case 15, it comes into contact with its inner surface, but the contact distance is longer than in the upper region Wt1. Therefore, the end portion 22d of the positive electrode composite layer 22 is prone to detachment due to contact with the inner surface of the battery case 15. For this reason, it is preferable that the unevenness width ΔW3 is small in the lower region Wt3.

[0102] Therefore, in this embodiment, a preferred value for the relation ΔW3 / Wp is set to ΔW3 / W≦0.01. More preferably, ΔW3 / Wp≦0.005. <Depth ΔW of the unevenness of the positive electrode composite layer 22 opposite the coated side> The above describes the unevenness width ΔW of the positive electrode composite layer 22 on the coated surface 22a, but a similar approach can be considered for the positive electrode composite layer 22 on the opposite side of the coated surface. In other words, the unevenness width ΔW1 in the upper region Wt1 is set to be large, and the unevenness width ΔW3 in the lower region Wt3 is set to be small. A detailed explanation is omitted here, and specific numerical values ​​are not given, but an optimized setting can be made in the nickel-metal hydride battery 1 by a person skilled in the art.

[0103] <Preparation of positive electrode composite paste 25 (S14)> In the coating process (S13), as described above, a predetermined relationship ΔW1 / Wp is defined between the unevenness width ΔW1 of the edge 22d of the upper region Wt1 of the positive electrode composite layer 22 on the target coated surface 22a and the coating width Wp. After the coating process (S13), the positive electrode composite layer 22 is inspected to see if it is properly constructed. If the inspection reveals that the positive electrode composite layer 22 is not properly constructed (S14: NO), the process returns to the positive electrode composite paste manufacturing process (S11). The discharge rate [g / s], viscosity V [mPa·s], and shear rate [s] of the positive electrode composite paste 25 are then determined. -1 Adjust the gap G, etc. If the positive electrode composite layer 22 is appropriate (S14: YES), proceed to the drying process (S15).

[0104] Thus, in this embodiment, by monitoring the unevenness width ΔW1 and the relationship ΔW1 / Wp and resetting the conditions, it is possible to always manufacture a positive electrode plate 2 with a predetermined unevenness width ΔW1 and relationship ΔW1 / Wp.

[0105] Furthermore, the adjustment of the positive electrode composite paste 25 (S14) does not necessarily have to be performed continuously; for example, it can be done for each production lot in which the composition changes. <Drying process (S15)> In the drying process (S15), the positive electrode composite paste 25 applied to the positive electrode current collector 21 in the coating process (S13) is dried by methods such as hot air, cold air, or infrared irradiation to evaporate the solvent and harden the positive electrode composite paste 25, thereby forming the positive electrode composite layer 22.

[0106] <Shaping and pressing process (S16)> In the drying process (S15), the positive electrode composite paste 25 is hardened to form the positive electrode composite layer 22. Then, the positive electrode plate 2 is pressed to a predetermined thickness using a roller press machine (not shown) and its surface shape is adjusted.

[0107] This completes the manufacturing process for the positive electrode plate 2. The process then proceeds to the electrode group manufacturing process (S2), where the negative electrode plate 3 and separator 4 manufactured in the source process (S1) are stacked, and the positive electrode current collector plate 27 and negative electrode current collector plate 37 are welded together to manufacture the electrode group 6.

[0108] (Operation of this embodiment) <Experimental Examples and Comparative Examples> Next, the operation of the nickel-metal hydride battery 1 and its manufacturing method according to this embodiment will be described. In this embodiment, the following comparative experiment was conducted. The electrode group 6 used in the experiment comprises 12 positive electrode plates 2 and 13 negative electrode plates 3.

[0109] In the comparative example, the conventional nickel-metal hydride battery 1, as shown in Figures 15 and 16, the unevenness width ΔW of the conventional technology is equal to the unevenness width ΔW3 of the lower region Wt3 of this embodiment shown in Figures 7 and 8. In other words, the unevenness width ΔW of the conventional nickel-metal hydride battery 1 is always equal to ΔW3.

[0110] On the other hand, in the experimental example, three of the twelve positive electrode plates 2 in the comparative example, corresponding to 1 / 4 of the original plate 2, were replaced with positive electrode plates 2 that had the same unevenness width ΔW3 as shown in Figures 7 and 8: upper region Wt1, intermediate region Wt2, and lower region Wt3.

[0111] The negative electrode plate 3 consists of 13 negative electrodes made of AB5-type hydrogen storage alloy, common to both the experimental and comparative examples. Furthermore, there are no differences between the experimental and comparative examples other than the replacement of the positive electrode plate 2. Nickel-metal hydride battery 1 was fabricated using these experimental and comparative examples, and its DC-IR (direct current resistance) was compared. The positions of the three positive electrode plates 2 were randomly changed, and the DC-IR was measured multiple times.

[0112] As a result, the DC-IR of the nickel-metal hydride battery 1 in the experimental example was approximately 1% lower than the DC-IR of the nickel-metal hydride battery 1 in the comparative example. <Effects of experimental examples> As described above, the DC-IR of the nickel-metal hydride battery 1 in the experimental example was approximately 1% lower than that of the nickel-metal hydride battery 1 in the comparative example. It is clear that this is due to the difference in the configuration of the positive electrode plate 2. Specifically, in the three positive electrode plates 2 replaced in the experimental example, the width Wv1 of the uncoated portion of the upper region Wt1 is larger than the width Wv0 of the uncoated portion of the portion corresponding to the upper region of the comparative example. Therefore, when the electrolyte 5 is injected from above the battery case 13 during injection, it remains above the electrode group 6, and it is thought that one of the reasons is that it easily penetrates from the portion with a width Wv1 of the uncoated portion of the upper region Wt1 to the portion in contact with the end 22d of the positive electrode composite layer 22. The peripheral portion of the positive electrode current collector 21 is compressed to give it a frame function and has a high density, making it difficult for the electrolyte to penetrate. It is thought that the electrolyte 5 first penetrates the separator 4, and then penetrates the uncoated portion with width Wv1 of the upper region Wt1. In the comparative example, the uncoated portion with width Wv0 of the upper region has a narrow gap between the end portion 22d of the positive electrode composite layer 22 and the inner surface 21m of the peripheral edge, making it difficult for much of the electrolyte 5 to penetrate.

[0113] In the experimental example, the end portion 22d of the positive electrode composite layer 22 has a wide critical interface in contact with the electrolyte 5 that has penetrated into the uncoated portion Wv1 of the upper region Wt1. Therefore, the positive electrode plate 2 replaced in the experimental example allows the electrolyte 5 to penetrate the positive electrode composite layer 22 more easily than the positive electrode plate 2 in the comparative example.

[0114] For the reasons stated above, the DC-IR of the nickel-metal hydride battery 1 in the experimental example is considered to be approximately 1% lower than the DC-IR of the nickel-metal hydride battery 1 in the comparative example.

[0115] (Effects of this embodiment) (1) In the nickel-metal hydride battery 1 and its manufacturing method of this embodiment, the electrolyte 5 can be easily permeated into the positive electrode plate 2 when the electrolyte 5 is injected.

[0116] (2) A positive electrode composite layer 22 is formed on the positive electrode current collector 21, and the formed positive electrode composite layer 22 is divided equally in the vertical direction into three regions: an upper region Wt1, an intermediate region Wt2, and a lower region Wt3. At the end 22d of the positive electrode composite layer 22 in the width direction W, the average unevenness width of the end 22d of the positive electrode composite layer 22 in the upper region Wt1 is defined as the unevenness width ΔW1. Similarly, the average unevenness width of the end 22d of the positive electrode composite layer 22 in the intermediate region Wt2 is defined as the unevenness width ΔW2. The average unevenness width of the end 22d of the positive electrode composite layer in the lower region Wt3 is defined as the unevenness width ΔW3. In this case, the configuration is such that the unevenness width ΔW1 ≥ the unevenness width ΔW3.

[0117] Therefore, the surface area of ​​the end portion 22d of the positive electrode composite layer 22 in the upper region Wt1 becomes larger, resulting in better absorption when criticality is reached with the electrolyte 5. As a result, when the electrolyte accumulates above the electrode group 6, the electrolyte 5 can easily penetrate the positive electrode plate 2.

[0118] (3) The difference between the unevenness width ΔW1 and the unevenness width ΔW3 was set to be ΔW1 / ΔW3 ≥ 5. Therefore, the penetration of the electrolyte 5 is increased, and at the same time, the shedding of the end portion 22d of the positive electrode composite layer 22 can be suppressed.

[0119] (4) In the upper region Wt1, the relationship between the unevenness width ΔW1 and the coating width Wp of the coated surface 22a is set to ΔW1 / Wp≧0.015, thereby improving the penetration of the electrolyte 5 in the upper region Wt1. If ΔW1 / Wp≧0.016, the penetration of the electrolyte 5 can be further improved. Also, if ΔW1 / Wp≦0.025, the detachment of the positive electrode active material and the overflow of the positive electrode composite paste 25 can be suppressed.

[0120] (5) In the lower region Wt3, the relationship between the uneven width ΔW3 and the coating width Wp in the horizontal direction is set such that ΔW3 / Wp ≤ 0.01, so that the dropout of the end portion 22d of the positive electrode composite material layer 22 can be suppressed. If ΔW3 / Wp ≤ 0.005, it can be further suppressed.

[0121] (6) In the electrode group 6, if the number of all positive electrode plates 2 is 1 / 4 or more of the total number of positive electrode plates 2 configured in the present embodiment, the penetration of the electrolytic solution 5 can be improved, and the internal resistance can be significantly improved. (7) The basis weight of the positive electrode current collector 21 is 200 [g / m 2 or more and 400 [g / m 2 or less, and the pore diameter is 300 [μm] or more and 600 [μm] or less, so that a desired positive electrode composite material layer 22 can be formed.

[0122] (8) In the manufacturing method of the nickel-hydrogen storage battery 1 of the present embodiment, the shear rate of the positive electrode composite material paste 25 is 10 [s -1 or less, and the viscosity is 50 m[Pa·s] or more and 2000 [mPa·s] or less. By controlling the viscosity of the positive electrode composite material paste 25 in this way, a desired ΔW1 can be achieved.

[0123] (9) The discharge amount of the positive electrode composite material paste 25 in the upper region Wt1 is set to be 102% or more of that in the lower region Wt3. By controlling the discharge amount of the positive electrode composite material paste 25 in this way, a desired ΔW1 can be achieved.

[0124] (10) The gap G, which is the clearance between the nozzle 83 for discharging the positive electrode composite material paste 25 in the coating process (S13) and the positive electrode current collector 21, is adjusted. By controlling the gap G in this way, a desired ΔW1 can be achieved.

[0125] (Alternative example) The present invention can be implemented as follows regardless of the above embodiment. ○Figure 9 is a schematic diagram showing another example of the positive electrode plate 2 of the nickel-metal hydride battery 1 of this embodiment. In this embodiment, for the sake of simplicity of explanation, Figures 7 and 8 describe the plate as being equally divided into three regions: the upper region Wt1, the intermediate region Wt2, and the lower region Wt3. However, as shown on the right side of Figure 9, for example, the plate may also be divided into a total of five regions: the upper region Wt1, the lower region Wt3, the intermediate region Wt21, the intermediate region Wt22, and the intermediate region 23, in order to manage the unevenness width ΔW.

[0126] ○Although not shown in the diagram, for example, the upper region Wt1 can be defined as the top 25% region, the lower region Wt3 as the bottom 25% region, and the remaining 50% as the intermediate region Wt2. In other words, in this embodiment, the division of the region is particularly for managing, controlling, and adjusting the unevenness width ΔW in the upper part, so any unequal division is possible.

[0127] Furthermore, as shown on the left side of Figure 9, the intermediate region Wt2 can be omitted, and the upper 20% can be designated as the upper region Wt1, with the remaining 80% as the lower region Wt3. ○In this embodiment, the viscosity V [mPa·s] of the positive electrode mixture paste 25 is adjusted by the blending of water, which is the solvent, and a thickening agent to form a positive electrode mixture layer 22 having a desired unevenness width ΔW1 and a desired relationship ΔW1 / Wp. However, it is not limited to adjusting the viscosity V [mPa·s], and any method that can achieve the desired unevenness width ΔW and the desired relationship ΔW1 / Wp is acceptable. In short, it is sufficient if the unevenness width ΔW and the relationship ΔW / Wp are used as indicators and adjusted by means related to them so that they become the set unevenness width ΔW and relationship ΔW / Wp.

[0128] ○Examples of this include the discharge rate [g / s] and the gap G. Furthermore, the configuration of the positive electrode current collector 21 can be mentioned. Specifically, the desired unevenness width ΔW1 and the desired relationship ΔW1 / Wp may be achieved by changing the size, shape, material, etc., of the mesh structure of the positive electrode current collector 21.

[0129] ○Alternatively, the composition of the positive electrode mixture paste 25, other than its viscosity, and the positive electrode active material may be changed. For example, the type and diameter of the positive electrode active material in the positive electrode mixture paste 25 can be changed to control the settling rate of the positive electrode active material particles. In addition, the wettability (water repellency) between the positive electrode mixture paste 25 and the frame of the positive electrode current collector 21 can be adjusted to control the spreading and turbulence of the positive electrode mixture paste 25.

[0130] ○By changing the temperature [°C] of the positive electrode composite paste 25, the viscosity can also be changed. Also, the shear rate [s -1 By controlling [this factor], viscosity can also be adjusted indirectly.

[0131] Furthermore, a desired unevenness width ΔW1 and a desired relationship ΔW1 / Wp may be achieved by changing the discharge speed, discharge pressure, discharge port shape, and transport speed from the coating machine 8. ○Of course, these can be combined to achieve the desired unevenness width ΔW1 and the desired relationship ΔW1 / Wp.

[0132] ○In the experimental example, only 3 out of 12 positive electrode plates 2 were used with a predetermined unevenness width ΔW1 and relation ΔW1 / Wp, but the experiment can also be carried out by replacing all of them, not just 3 plates. ○Although the nickel-metal hydride battery 1 of this embodiment has been described using a vehicle drive battery as an example, the battery's applications are not limited and can be used in aircraft, ships, and even for stationary applications. Furthermore, as long as the present invention can be implemented, it is not limited to nickel-metal hydride batteries and can be implemented with other secondary batteries.

[0133] ○Some of the drawings are schematic diagrams illustrating the nickel-metal hydride battery 1 of this embodiment, and the quantities and dimensional balance of the components may not always be accurate, and some may be exaggerated.

[0134] ○The flowcharts shown in Figures 4 and 5 are illustrative examples, and the steps can be added, deleted, rearranged, or modified. For example, the order of the positive electrode current collector manufacturing process (S11) and the positive electrode composite paste manufacturing process (S12) does not matter.

[0135] The numerical values ​​such as the viscosity V [mPa·s] of the positive electrode composite paste are illustrative examples in the embodiments, and the present invention is not intended to be limited to these values ​​or ranges. Those skilled in the art can optimize them to suit the configuration of the nickel-metal hydride battery 1.

[0136] It goes without saying that the present invention can be implemented by those skilled in the art by adding, deleting, or modifying its configuration, as long as it does not deviate from the scope of the claims. [Explanation of Symbols]

[0137] 1… Nickel-metal hydride battery 2…Positive plate 3… Negative plate 4... Separator 5...Electrolyte 6...Electrode group 8…Coating machine 9...Vacuum suction device 12…Battery cell 13…Battery case (integrated battery case) 13a... Positive terminal 13b... Negative terminal 14... Lid 15...Battery container 16…Opening 17…Through hole 18...Bulkhead 21...Positive electrode current collector 21a~21d...Coating area 21e~21i...Uncoated area 21j…Top surface 21k…Bottom side 21l…Lead section 21m...Inner surface of the periphery 22…Positive electrode composite layer 22a...Coated surface 22b…Inside (the positive electrode composite layer) 22c…The surface opposite the coated side 22d... End in the width direction W 25… Positive electrode composite paste 25e…Top surface 25f…bottom surface 27…Positive electrode current collector plate 31...Negative electrode current collector 37... Negative electrode current collector plate 81…Die nozzle 82...Dai 83… Nozzle 84...Pressing roller 85...Support member 85a...first support part 85b... Insertion part 85c...Connection part 85d…Second support part 86… Stage 91... Adhesive pads L...Length direction (coating direction) W...Width direction (shorter side direction) D...Thickness direction Wp…(Coating width on the coating side) Ws…(Coating width opposite to the coating side) Wo… (Conventional technology) coating width ΔW… (Width of irregularities at the edge of the positive electrode composite layer in the width direction W) ΔW1…Width of irregularities (in the upper region) ΔW2… (Width of irregularities in the intermediate region) ΔW3…Width of irregularities (in the lower region) ΔW / Wp…relationship Wt1…upper area Wt2…middle area Wt3…Lower area Wv1… (Width of the unpainted portion of the upper area) Wv2… (Width of the unpainted portion in the intermediate area) Wv3… (Width of the unpainted portion of the lower area) Wv0… (Width of the uncoated portion of the conventional technology) V…Viscosity [mPa·s] Q... Coating amount [cm] 3 / s] Q0...Conventional coating amount [cm 3 / s] Q1…(Average coating amount in the upper region Wt1) [g / s] Q2…(Average coating amount in the intermediate region Wt2) [g / s] Q3…(Average coating amount in the lower region Wt3) [g / s] G... Gap P1... Points P2... Points P3... Points P4... Points

Claims

1. The electrode group comprises a positive electrode plate having a positive electrode current collector made of a plate-shaped porous metal and a positive electrode composite layer containing a positive electrode active material filled in the positive electrode current collector, a negative electrode plate, and a separator, all of which are stacked together. The electrode group is housed in a battery case, and the battery case has an opening at its top and a lid that seals the opening. Electrolyte is poured in from the side of the opening at the top of the battery case. A secondary battery characterized in that the electrode group includes a positive electrode plate configured such that, when the filled positive electrode composite layer is divided vertically into a plurality of regions including an upper region Wt1 and a lower region Wt3, the average unevenness width of the edges of the positive electrode composite layer in the width direction is the unevenness width ΔW1, and the average unevenness width of the edges of the positive electrode composite layer in the upper region Wt1 is the unevenness width ΔW3, and the average unevenness width of the edges of the positive electrode composite layer in the lower region Wt3 is the unevenness width ΔW1 > unevenness width ΔW3.

2. The secondary battery according to claim 1, characterized in that the unevenness width ΔW1 and the unevenness width ΔW3 are such that the unevenness width ΔW1 / unevenness width ΔW3 ≥ 5.

3. An intermediate region Wt2 is provided between the upper region Wt1 and the lower region Wt3, and the average unevenness width of the intermediate region Wt2 is ΔW2, The secondary battery according to claim 1 or 2, characterized in that the unevenness width ΔW1 > unevenness width ΔW2 > unevenness width ΔW3.

4. In the upper region Wt1, the relationship between the unevenness width ΔW1 and the horizontal coating width Wp is ΔW1 / Wp≧0.015 A secondary battery according to any one of claims 1 to 3, wherein the above conditions are met.

5. In the upper region Wt1, the relationship between the unevenness width ΔW1 and the horizontal coating width Wp is ΔW1 / Wp≦0.025 A secondary battery according to any one of claims 1 to 3, wherein the above conditions are met.

6. In the lower region Wt3, the relationship between the unevenness width ΔW3 and the coating width Wp in the horizontal direction is ΔW3 / Wp≦0.01 A secondary battery according to any one of claims 1 to 5, wherein the above conditions are met.

7. A secondary battery characterized in that, in the electrode group, 1 / 4 or more of the total number of positive electrode plates are positive electrode plates of the secondary battery described in claim 1.

8. The secondary battery according to any one of claims 1 to 7, characterized in that the positive electrode current collector is made of a foam made of nickel or a nickel alloy.

9. The aforementioned foam has a basis weight of 200 g / m². ２ ] or more, 400 [g / m ２ The secondary battery according to claim 8, characterized in that it is less than or equal to 300 [μm] and has a pore size of 300 [μm] or more and 600 [μm] or less.

10. The secondary battery according to claim 3, characterized in that the upper region Wt1, the intermediate region Wt2, and the lower region Wt3 are divided into three equal parts in the vertical direction.

11. The secondary battery according to claim 3, characterized in that a plurality of intermediate regions Wt2 are provided, and the upper region Wt1, the plurality of intermediate regions Wt2, and the lower region Wt3 are each equally divided in the vertical direction.

12. The electrode group comprises a positive electrode plate having a positive electrode current collector made of a plate-shaped porous metal and a positive electrode composite layer containing a positive electrode active material and filled in the positive electrode current collector, a negative electrode plate, and a separator, all of which are stacked together. A method for manufacturing a secondary battery, wherein the electrode group is housed in a battery case, and the battery case has an opening at its top and a lid that seals the opening, and an electrolyte is poured in from the side of the opening at the top of the battery case, The process includes a coating step of intermittently coating the positive electrode current collector with a positive electrode mixture paste containing a solvent for forming the positive electrode mixture layer, starting from one surface of the positive electrode current collector. In the coating process described above, the positive electrode composite paste does not fall off the positive electrode current collector due to gravity, and A method for manufacturing a secondary battery, characterized by dividing the positive electrode composite layer to be coated into a plurality of regions in the vertical direction, including an upper region Wt1 and a lower region Wt3, and adjusting the edges in the width direction of the positive electrode composite layer such that, when the average unevenness width of the positive electrode composite layer in the upper region Wt1 is the unevenness width ΔW1 and the average unevenness width of the positive electrode composite layer in the lower region Wt3 is the unevenness width ΔW3, the unevenness width ΔW1 > unevenness width ΔW3.

13. The above adjustment is performed when the shear rate of the positive electrode composite paste is 10 [s] －１ The method for manufacturing a secondary battery according to claim 12, characterized in that the viscosity is 50 m[Pa·s] or more and 2000 [mPa·s] or less when [condition is met].

14. The method for manufacturing a secondary battery according to claim 12 or 13, characterized in that the adjustment makes the discharge amount of the upper region Wt1 102% or more of that of the lower region Wt3.

15. The method for manufacturing a secondary battery according to any one of claims 12 to 14, characterized in that the adjustment is made by adjusting the gap G, which is the clearance between the nozzle that dispenses the positive electrode mixture paste in the coating process and the positive electrode current collector.

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