Bipolar lead-acid battery

Abstract

To maintain and improve a battery capacity while avoiding deterioration of a battery performance and an invitation of the early life caused by the contact of an electrolyte solution with a current collector.SOLUTION: A bipolar lead-acid battery includes: a positive electrode active material layer 111b; a negative electrode active material layer 112b; a current collector 111 made of lead or a lead alloy and in contact with one or both of the positive electrode active material layer 111b and the negative electrode active material layer 112b; and a separator 113 disposed between the positive electrode active material layer 111b and the negative electrode active material layer 112b facing each other. The positive electrode active material layer 111b or the negative electrode active material layer 112b covers a surface in contact with the current collector 111 and at least part of an end part of the current collector 111.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a bipolar lead-acid battery. [Background technology]

[0002] In recent years, the number of power generation facilities that utilize natural energy sources such as solar and wind power has been increasing. Since it is not possible to control the amount of power generated in such power generation facilities, storage batteries are used to level the power load. That is, when the amount of power generated is greater than the amount consumed, the difference is charged to the storage battery, and when the amount of power generated is less than the amount consumed, the difference is discharged from the storage battery. Lead-acid batteries are widely used as the storage batteries from the viewpoints of economy, safety, and the like. For example, the following Patent Document 1 describes a known example of such a conventional lead-acid battery.

[0003] In the lead-acid battery described in Patent Document 1, a resin substrate (bipolar plate) is attached to the inside of a frame (rim) made of resin in a picture-frame shape. A positive electrode lead layer and a negative electrode lead layer are provided on one side and the other side of the substrate. A positive electrode active material layer is adjacent to the positive electrode lead layer. A negative electrode active material layer is adjacent to the negative electrode lead layer. In addition, a glass mat (electrolytic layer) containing an electrolyte is disposed inside a frame-shaped resin spacer. Then, multiple frames and spacers are alternately stacked and assembled.

[0004] Furthermore, the positive electrode lead layer and the negative electrode lead layer are directly bonded inside a plurality of perforations formed in the substrate. That is, the lead-acid battery described in Patent Document 1 is a bipolar lead-acid battery in which a plurality of substrates having perforations (communicating holes) connecting one side to the other side and cell members are alternately stacked. The cell members have a positive electrode in which a positive electrode active material layer is provided on the positive electrode lead layer, a negative electrode in which a negative electrode active material layer is provided on the negative electrode lead layer, and an electrolytic layer interposed between the positive and negative electrodes. The positive electrode lead layer of one cell member and the negative electrode lead layer of the other cell member are immersed inside the perforations of the substrate and bonded, thereby connecting the cell members in series. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6124894 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a structure like the lead-acid battery in Patent Document 1 is adopted, for example, the lead layer for the positive electrode (positive electrode current collector) may be corroded by sulfuric acid contained in the electrolyte, and a film of corrosion products (lead oxide) may be formed on the surface of the positive electrode current collector. Then, there is a risk that the growth of this film of corrosion products may cause elongation (growth) in the positive electrode current collector.

[0007] Furthermore, if this growth causes the positive electrode current collector and adhesive layer to peel off and the positive electrode current collector to roll up, electrolyte may penetrate the interface between the positive electrode current collector and adhesive layer, the interface between the adhesive layer and the substrate, or the interface between the positive electrode current collector and the positive electrode active material layer, potentially further promoting corrosion of the positive electrode current collector by sulfuric acid. In this case, electrolyte may reach the negative electrode side from the positive electrode side through the perforations (communicating holes) that connect the positive electrode and negative electrode sides. This phenomenon causes so-called liquid leakage, resulting in reduced battery performance and a shorter lifespan.

[0008] Furthermore, if the electrolyte penetrates not only the interface between the positive electrode current collector and the positive electrode active material layer but also the interface between the positive electrode current collector and the adhesive layer, corrosion will progress on both sides of the positive electrode current collector. Furthermore, in the case of a lead-acid battery in which active material layers are arranged on both sides of the current collector, corrosion by sulfuric acid will progress not only on the surface of one current collector on the positive electrode side but also on the surface of the other current collector on the negative electrode side, and corrosion will progress on both sides of the current collector. In these situations, corrosion progresses faster than corrosion on either surface, resulting in a shorter lifespan of the storage battery.

[0009] Furthermore, the lead-acid battery has an excellent volumetric energy density due to its stacked cell components, but if there is a limit to the overall size of the lead-acid battery, it is necessary to thin each component constituting the cell components, such as the current collector, in order to make the lead-acid battery compact. However, thinning the current collector makes it more susceptible to corrosion due to contact with the electrolyte, which may lead to the above-mentioned deterioration of battery performance.

[0010] On the other hand, while it is possible to slow down the progression of this corrosion by, for example, lowering the specific gravity of the electrolyte, this approach would reduce the overall capacity of the lead-acid battery, so there is a trade-off between the lifespan and capacity of lead-acid batteries.

[0011] The present invention aims to provide a bipolar lead-acid battery that can maintain and improve battery capacity while avoiding deterioration in battery performance and premature end of life caused by contact of the electrolyte with the current collector. [Means for solving the problem]

[0012] A bipolar lead-acid battery according to one embodiment of the present invention includes a positive electrode active material layer, a negative electrode active material layer, a current collector made of lead or a lead alloy in contact with either or both of the positive electrode active material layer and the negative electrode active material layer, and a separator disposed between the positive electrode active material layer and the negative electrode active material layer facing each other, wherein the positive electrode active material layer or the negative electrode active material layer covers the surface in contact with the current collector and at least a portion of the end of the current collector. [Effects of the Invention]

[0013] According to the present invention, a bipolar lead-acid battery is provided, which comprises a positive electrode active material layer, a negative electrode active material layer, a current collector made of lead or a lead alloy in contact with either or both of the positive electrode active material layer and the negative electrode active material layer, and a separator disposed between the opposing positive electrode active material layer and the negative electrode active material layer, wherein the positive electrode active material layer or the negative electrode active material layer covers the surface in contact with the current collector and at least a portion of the edge of the current collector. By adopting such a configuration, it is possible to provide a bipolar lead-acid battery that can maintain or improve battery capacity while avoiding deterioration in battery performance and premature end of life caused by contact of the current collector with the electrolyte. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing the structure of a bipolar lead-acid battery according to an embodiment of the present invention. [Figure 2] 1 is an enlarged cross-sectional view showing a portion of the structure of a bipolar lead-acid battery according to an embodiment of the present invention. [Figure 3] FIG. 2 is a plan view showing the relationship between a positive electrode lead foil and a positive electrode active material layer in a bipolar lead-acid battery according to an embodiment of the present invention. [Figure 4] FIG. 4 is a plan view showing a first modified example of the relationship between the positive electrode lead foil and the positive electrode active material layer shown in FIG. 3 in the bipolar lead-acid battery according to the embodiment of the present invention. [Figure 5] FIG. 4 is a plan view showing a second modified example of the relationship between the positive electrode lead foil and the positive electrode active material layer shown in FIG. 3 in the bipolar lead-acid battery according to the embodiment of the present invention. [Figure 6]FIG. 4 is a plan view showing a third modified example of the relationship between the positive electrode lead foil and the positive electrode active material layer shown in FIG. 3 in the bipolar lead-acid battery according to the embodiment of the present invention. [Figure 7] 4 is an enlarged cross-sectional view of a positive electrode lead foil and a positive electrode active material layer in a bipolar lead-acid battery according to an embodiment of the present invention, taken along line AA in FIG. 3. FIG. [Figure 8] FIG. 4 is a cross-sectional view showing another structure of the positive electrode lead foil and the positive electrode active material layer in the bipolar lead-acid battery according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that each embodiment described below shows an example of the present invention. Furthermore, various modifications and improvements can be made to each of these embodiments, and such modifications and improvements can also be included in the present invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the inventions described in the claims and their equivalents. Note that the following description will use a lead-acid battery as an example from among various storage batteries.

[0016] [Overall structure] First, the overall configuration of a bipolar lead-acid battery according to an embodiment of the present invention will be described. Fig. 1 is a cross-sectional view showing the structure of a bipolar lead-acid battery 100 according to an embodiment of the present invention.

[0017] As shown in FIG. 1, a bipolar lead-acid battery 100 according to an embodiment of the present invention includes a plurality of cell members 110, a plurality of bipolar plates (space forming members) 120, a first end plate (space forming member) 130, and a second end plate (space forming member) 140.

[0018] 1 shows a bipolar lead-acid battery 100 in which three cell components 110 are stacked, but the number of cell components 110 is determined by the battery design. The number of bipolar plates 120 is also determined by the number of cell components 110.

[0019] 1 and 2, which will be described later, the stacking direction of the cell members 110 is defined as the Z direction (the vertical direction in FIG. 1 or FIG. 2), and directions perpendicular to the Z direction and perpendicular to each other are defined as the X direction and the Y direction. The Z direction, which is the stacking direction of the cell members 110, is parallel to the vertical direction.

[0020] The cell member 110 includes a positive electrode 111, a negative electrode 112, and an electrolyte layer (separator) 113. The positive electrode 111 includes a positive electrode lead foil 111a, which is a positive electrode current collector made of lead or a lead alloy, and a positive electrode active material layer 111b. The negative electrode 112 includes a negative electrode lead foil 112a, which is a negative electrode current collector made of lead or a lead alloy, and a negative electrode active material layer 112b.

[0021] This positive electrode lead foil 111a is provided on one surface of the bipolar plate 120 by an adhesive 150 (described later) provided between one surface of the bipolar plate 120 (the surface facing upward in the drawing of FIG. 1) and the positive electrode lead foil 111a. Therefore, on one surface of the bipolar plate 120, an adhesive layer (adhesive 150), the positive electrode lead foil 111a, and the positive electrode active material layer 111b are laminated in this order.

[0022] On the other hand, the negative electrode lead foil 112a is attached to the other surface of the bipolar plate 120 by an adhesive 150 (described later) provided between the other surface of the bipolar plate 120 (the surface facing downward in the drawing of FIG. 1) and the negative electrode lead foil 112a. Therefore, on the other surface of the bipolar plate 120, an adhesive layer (adhesive 150), the negative electrode lead foil 112a, and the negative electrode active material layer 112b are laminated in this order. The positive electrode 111 and the negative electrode 112 are electrically connected via a conductor 160 (described later).

[0023] In this way, the cell member 110 is provided with a plurality of current collectors (positive electrode lead foil 111a and negative electrode lead foil 112a). Therefore, the positive electrode active material layer 111b contacts one of the plurality of current collectors (positive electrode lead foil 111a). Also, the negative electrode active material layer 112b contacts the other of the plurality of current collectors (negative electrode lead foil 112a).

[0024] The separator 113 is made of, for example, a glass fiber mat impregnated with an electrolyte solution containing sulfuric acid. The separator 113 is sandwiched between a positive electrode active material layer 111b provided on one of the opposing bipolar plates 120 and a negative electrode active material layer 112b provided on the other bipolar plate 120. In the cell member 110, the positive electrode lead foil 111a, the positive electrode active material layer 111b, the separator 113, the negative electrode active material layer 112b, and the negative electrode lead foil 112a are layered in this order.

[0025] In the bipolar lead-acid battery 100 according to the embodiment of the present invention, an electrolyte having a specific gravity of 1.30 or more and 1.38 or less can be used. As described above, in conventional lead-acid batteries, it has been difficult to use an electrolyte with a high specific gravity due to corrosion caused by contact with the electrolyte, and as a result, it has been difficult to increase the overall capacity of the lead-acid battery.

[0026] However, as will be described later, in the bipolar lead-acid battery 100 according to the embodiment of the present invention, the active material layer is formed and arranged so as to cover at least a part of the end of the current collector, thereby reducing corrosion of the current collector due to contact with the electrolyte. Therefore, even if the specific gravity of the electrolyte is increased, corrosion is unlikely to occur, and it is possible to achieve both retardation of corrosion and maintenance or improvement of capacity.

[0027] The electrolyte used in the bipolar lead-acid battery 101 according to the embodiment of the present invention may contain, for example, Mg ions, Al ions, and Na ions in the range of 0.2 mol / L or less and boron in the range of 0.5 mol / L or less. The inclusion of these ions in the electrolyte improves charge acceptance and makes it easier to control stratification of the electrolyte.

[0028] In the bipolar lead-acid battery 100 according to the embodiment of the present invention having such a configuration, as described above, the bipolar plate 120, the positive electrode lead foil 111a, the positive electrode active material layer 111b, the negative electrode lead foil 112a, and the negative electrode active material layer 112b constitute a bipolar electrode. A bipolar electrode is an electrode that functions as both a positive electrode and a negative electrode in one sheet.

[0029] The bipolar lead-acid battery 100 according to the embodiment of the present invention is formed by stacking a plurality of cell members 110, each of which has a separator 113 interposed between a positive electrode 111 and a negative electrode 112, and bipolar plates 120 arranged in pairs to sandwich the cell member 110. The outermost layer is assembled with a first end plate 130 and a second end plate 140, thereby forming a battery configuration in which the cell members 110 are connected in series.

[0030] The dimensions of the positive electrode lead foil 111a in the X and Y directions are smaller than the dimensions of the positive electrode active material layer 111b in at least a portion thereof because the positive electrode active material layer 111b covers a portion thereof. Similarly, the dimensions of the negative electrode lead foil 112a in the X and Y directions are smaller than the dimensions of the negative electrode active material layer 112b in at least a portion thereof because the negative electrode active material layer 112b covers a portion thereof.

[0031] The dimension (thickness) in the Z direction is larger (thicker) for the positive electrode lead foil 111a than for the negative electrode lead foil 112a, and the positive electrode active material layer 111b is larger (thicker) than for the negative electrode active material layer 112b.

[0032] The multiple cell members 110 are stacked and arranged at intervals in the Z direction, and the substrates 121 of the bipolar plates 120 are arranged in these intervals. In other words, the multiple cell members 110 are stacked with the substrates 121 of the bipolar plates 120 sandwiched between them.

[0033] In this way, the plurality of bipolar plates 120, the first end plate 130, and the second end plate 140 are space forming members for forming a plurality of spaces (cells) C that individually accommodate a plurality of cell members 110.

[0034] That is, the bipolar plate 120 is a space-forming member that covers both the positive electrode 111 side and the negative electrode 112 side of the cell member 110 and includes a substrate 121 having a rectangular planar shape, and a frame body 122 that surrounds the side surface of the cell member 110 and covers the four end faces of the substrate 121.

[0035] 1, the bipolar plate 120 further includes pillars 123 that protrude perpendicularly from both sides of the substrate 121. The number of pillars 123 protruding from each side of the substrate 121 may be one or more.

[0036] The substrate 121, frame 122, and column 123 that make up the bipolar plate 120 are integrally formed from, for example, a thermoplastic resin. Examples of the thermoplastic resin that forms the bipolar plate 120 include acrylonitrile-butadiene-styrene copolymer (ABS resin) and polypropylene. These thermoplastic resins have excellent moldability and sulfuric acid resistance. Therefore, even if the bipolar plate 120 comes into contact with an electrolyte, the bipolar plate 120 is unlikely to decompose, deteriorate, or corrode.

[0037] In the Z direction, the dimension of the frame body 122 is larger than the dimension (thickness) of the substrate 121, and the dimension between the protruding end faces of the pillar portions 123 is the same as the dimension of the frame body 122. Then, by stacking multiple bipolar plates 120 with the frame bodies 122 and the pillar portions 123 in contact with each other, a space C is formed between the substrates 121. The dimension of the space C in the Z direction is maintained by the pillar portions 123 in contact with each other.

[0038] The positive electrode lead foil 111a, the positive electrode active material layer 111b, the negative electrode lead foil 112a, the negative electrode active material layer 112b, and the separator 113 are respectively formed with through holes 111c, 111d, 112c, 112d, and 113a through which the columnar portion 123 passes.

[0039] The substrate 121 of the bipolar plate 120 has a plurality of through-holes 121a penetrating the plate surface. A first recess 121b is formed on one surface of the substrate 121, and a second recess 121c is formed on the other surface. The depth of the first recess 121b is greater than the depth of the second recess 121c. The dimensions of the first recess 121b and the second recess 121c in the X and Y directions correspond to the dimensions of the positive electrode lead foil 111a and the negative electrode lead foil 112a in the X and Y directions.

[0040] The substrate 121 of the bipolar plate 120 is disposed between adjacent cell members 110 in the Z direction. The positive electrode lead foil 111a of the cell member 110 is disposed in the first recess 121b of the substrate 121 of the bipolar plate 120 via an adhesive 150. The negative electrode lead foil 112a of the cell member 110 is disposed in the second recess 121c of the substrate 121 of the bipolar plate 120 via an adhesive 150.

[0041] A conductor 160 is disposed in the through-hole 121a of the substrate 121 of the bipolar plate 120. Both end faces of the conductor 160 are in contact with and joined to the positive electrode lead foil 111a and the negative electrode lead foil 112a. That is, the positive electrode lead foil 111a and the negative electrode lead foil 112a are electrically connected by the conductor 160. As a result, all of the multiple cell members 110 are electrically connected in series.

[0042] Here, the relationship between the current collectors and the active material layers in the bipolar lead-acid battery 100 according to the embodiment of the present invention will be described with reference to Fig. 2 to Fig. 8. Fig. 2 is an enlarged cross-sectional view showing a portion of the structure of the bipolar lead-acid battery 100 according to the embodiment of the present invention. Specifically, Fig. 2 shows the area surrounded by a dashed line in the cross-sectional view of the bipolar lead-acid battery 100 in Fig. 1.

[0043] That is, FIG. 2 shows the substrate 121, positive electrode lead foil 111a, and positive electrode active material layer 111b on the positive electrode side, with the ends of the positive electrode lead foil 111a and positive electrode active material layer 111b enlarged.

[0044] The following explanation also applies to, for example, the ends of the negative electrode lead foil 112a and the negative electrode active material layer 112b on the negative electrode side. However, here, the explanation will be given using the ends of the positive electrode lead foil 111a and the positive electrode active material layer 111b on the positive electrode side as an example.

[0045] 2, adhesive 150 is applied to the first recess 121b of the substrate 121, and the positive electrode lead foil 111a is placed above it in the Z direction. Note that here, for convenience, the surface of the positive electrode lead foil 111a that faces the first recess 121b with the adhesive 150 interposed therebetween is referred to as the first surface 111aa.

[0046] Furthermore, the surface of the positive electrode active material layer 111b opposite to the surface in contact with the separator 113, which is the surface of the positive electrode lead foil 111a (current collector) in contact with the positive electrode lead foil 111a (current collector), i.e., the surface of the positive electrode lead foil 111a facing the positive electrode active material layer 111b, is referred to as the second surface 111ab for convenience.

[0047] 2, the end 111ac of the positive electrode lead foil 111a connecting the first surface 111aa and the second surface 111ab is arranged to face the rising portion 121ba rising upward in the Z direction from the first recess 121b on the substrate 121. Therefore, when the positive electrode active material layer 111b is not arranged above the positive electrode lead foil 111a in the Z direction, a gap exists between the end 111ac of the positive electrode lead foil 111a and the rising portion 121ba.

[0048] Then, the positive electrode active material layer 111b is placed on the upper part of the positive electrode lead foil 111a in the Z direction. When the positive electrode active material layer 111b is placed in contact with the second surface 111ab of the positive electrode lead foil 111a, the positive electrode active material layer 111b is also placed in the gap between the end portion 111ac and the rising portion 121ba of the positive electrode lead foil 111a.

[0049] That is, the positive electrode active material layer 111b is arranged in contact with the second surface 111ab of the positive electrode lead foil 111a at the upper part in the Z direction, and its end is formed in a flange shape and is arranged in the above-mentioned gap formed between the end 111ac of the positive electrode lead foil 111a and the rising portion 121ba.

[0050] That is, as shown in FIG. 2, when the positive electrode active material layer 111b is provided, the end 111ac and the rising portion 121ba of the positive electrode lead foil 111a are arranged in positions facing each other with the flange portion 111ba of the positive electrode active material layer 111b in between.

[0051] Therefore, the positive electrode lead foil 111a has an end 111ac surrounded by the flange portion 111ba of the positive electrode active material layer 111b. The first surface 111aa of the positive electrode lead foil 111 is bonded to the first recess 121b via the adhesive 150, and the second surface 111ab is in contact with the positive electrode active material layer 111b. Therefore, as shown in FIG. 2, the positive electrode lead foil 111a is entirely covered by the adhesive 150 (first recess 121b (substrate 121)) or the positive electrode active material layer 111b.

[0052] Fig. 3 is a plan view showing the relationship between the positive electrode lead foil 111a and the positive electrode active material layer 111b in a bipolar lead-acid battery 100 according to an embodiment of the present invention. In Fig. 3, the positive electrode lead foil 111a is shown by a dashed line because it is covered by the positive electrode active material layer 111b. On the other hand, the positive electrode active material layer 111b is shown by a solid line because it covers the positive electrode lead foil 111a.

[0053] A flange portion 111ba is formed around the entire periphery of the end portion of the positive electrode active material layer 111b, and the flange portion 111ba is in contact with an end portion 111ac of the positive electrode lead foil 111a.

[0054] As shown in FIG. 3, the flange portion 111ba of the positive electrode active material layer 111b may cover the entire periphery of the positive electrode lead foil 111a, or may be formed to cover only a portion of the end portion 111ac of the positive electrode lead foil 111a.

[0055] Here, a case where the flange portion 111ba of the positive electrode active material layer 111b is formed so as to cover a part of the end portion 111ac of the positive electrode lead foil 111a will be described with reference to FIGS.

[0056] Fig. 4 is a plan view showing a first modified example of the relationship between the positive electrode lead foil 111a and the positive electrode active material layer 111b shown in Fig. 3 in the bipolar lead-acid battery 100 according to the embodiment of the present invention. In the positive electrode active material layer 111b shown in Fig. 4, the flange portion 111ba covers the entire periphery of the end portion 111ac of the positive electrode lead foil 111a, but the shape of the flange portion 111ba on the left side in the X direction in particular is different from the shapes of the other three sides.

[0057] That is, the distance in the Y direction of the flange portion 111ba on the left side in the X direction is formed to be longer than the distance in the Y direction of the end portion 111ac of the positive electrode lead foil 111a on the left side in the X direction that is arranged in an opposing position.

[0058] Furthermore, the distance from the outer edge of the flange portion 111ba of the positive electrode active material layer 111b to the end 111ac of the positive electrode lead foil 111a located at the opposing position may be different for each side. For example, in the flange portion 111ba of the positive electrode active material layer 111b shown in Fig. 4, the distance between the flange portion 111ba on the left side in the X direction and the end 111ac located at the left side in the X direction and located at the opposing position to the flange portion 111ba is greater than the distance between the flange portion 111ba on the other three sides and the end 111ac of the positive electrode lead foil 111a located at the opposing position.

[0059] Next, Fig. 5 is a plan view showing a second modified example of the relationship between the positive electrode lead foil 111a and the positive electrode active material layer 111b shown in Fig. 3 in the bipolar lead-acid battery 100 according to the embodiment of the present invention. The flange portion 111ba of the positive electrode active material layer 111b shown in Fig. 5 covers a part of the end portion 111ac of the positive electrode lead foil 111a.

[0060] Specifically, the flange portions 111ba on the two X-direction sides cover part of the center of the end portion 111ac of the positive electrode lead foil 111a, which corresponds to the two X-direction sides. Therefore, the two Y-direction sides of the positive electrode lead foil 111a and the two X-direction sides near the two Y-direction sides are not covered by the flange portions 111ba.

[0061] Furthermore, the flange portion 111ba of the positive electrode active material layer 111b may be shaped to cover only one side of the end portion 111ac of the positive electrode lead foil 111a. Fig. 6 is a plan view showing a third modified example of the relationship between the positive electrode lead foil 111a and the positive electrode active material layer 111b shown in Fig. 3 in the bipolar lead-acid battery 100 according to the embodiment of the present invention.

[0062] 6 is formed so as to cover only the end 111ac of the positive electrode lead foil 111a on the left side in the X direction, and the end 111ac of the other three sides is not covered by the flange portion 111ba. From the above, the relationship between the flange portion of the active material layer and the end of the current collector in the embodiment of the present invention may be such that the active material layer is disposed so as to cover at least a part of the end of the current collector.

[0063] 3 to 6 are all formed in a generally rectangular shape. However, the active material layer and the current collector are not limited to such shapes, and the shapes of the active material layer and the current collector are not important as long as the active material layer is disposed so as to cover at least a portion of the edge of the current collector.

[0064] Next, the relationship between the active material layer and the current collector will be described using numerical values. Fig. 7 is an enlarged cross-sectional view of the positive electrode lead foil 111a and the positive electrode active material layer 111b in the bipolar lead-acid battery 100 according to the embodiment of the present invention, taken along line AA in Fig. 3.

[0065] In addition, in Figure 7, the positive electrode lead foil 111a and the positive electrode active material layer 111b are also taken as an example, but the same relationship applies when the negative electrode lead foil 112a and the negative electrode active material layer 112b, which have the same relationship as the positive electrode lead foil 111a and the positive electrode active material layer 111b described so far, are provided on the negative electrode side.

[0066] 7, the flange portion 111ba of the positive electrode active material layer 111b covers the end portion 111ac of the positive electrode lead foil 111a. First, the ratio in the X direction will be described. If the length in the X direction of the positive electrode active material layer 111b including the flange portion 111ba is L1 and the length in the X direction of the positive electrode lead foil 111a is L2, then the ratio (L2 / L1) of the length L2 of the positive electrode lead foil 111a to the length L1 of the positive electrode active material layer 111b is 0.60 or more and 0.98 or less.

[0067] Regarding the length L2 in the X direction of the positive electrode lead foil 111a, the ratio when the length of L2 can be made as short as possible is 0.60, taking into account the relationship with the through-hole 121a and other parts constituting the cell member 110. On the other hand, the ratio when L2 is made as long as possible in the X direction is 0.98. The reason why the length of L2 is not the same as the length of L1 is that it is necessary to provide the flange portion 111ba on the positive electrode active material layer 111b, as described above.

[0068] Specific numerical values regarding the relationship between the X-direction length L1 of the positive electrode active material layer 111b and the X-direction length L2 of the positive electrode lead foil 111a are as follows. First, the X-direction length L1 of the positive electrode active material layer 111b is assumed to be, for example, 290 mm. In this case, the X-direction length L2 of the positive electrode lead foil 111a is 174 mm when the ratio is set to the smallest value of "0.60." Then, if the X-direction length of the flange portion 111ba in contact with the end portion 111ac of the positive electrode lead foil 111a is assumed to be equal, the X-direction length L3 of the flange portion 111ba is 58 mm.

[0069] On the other hand, if the ratio is set to the maximum of 0.98, the length L2 of the positive electrode lead foil 111a in the X direction is approximately 285 mm. If the length of the flange portion 111ba in contact with the end portion 111ac of the positive electrode lead foil 111a in the X direction is the same, the length L3 of the flange portion 111ba in the X direction is approximately 2.5 mm.

[0070] The protrusion width of the positive electrode active material layer 111b from the end 111ac of the positive electrode lead foil 111a, i.e., the ratio of the length indicated by the length L3 shown in FIG. 7, is preferably less than 3% of the length L2 of the positive electrode lead foil 111a in the X direction.

[0071] If the positive electrode active material layer 111b protrudes from the end portion 111ac of the positive electrode lead foil 111a by more than 3%, the amount of the active material layer in the positive electrode active material layer 111b that does not contact the positive electrode lead foil 111a increases too much, which raises concerns about a decrease in current collection efficiency.

[0072] Next, the length (thickness) L4 in the Z direction of the positive electrode active material layer 111b is set in relation to the length (thickness) in the Z direction of the positive electrode lead foil 111a, and for example, it is sufficient that it is at least twice the length (thickness) in the Z direction of the positive electrode lead foil 111a.

[0073] Therefore, if the length (thickness) in the Z direction of the positive electrode lead foil 111a is, for example, 0.25 mm, the length L4 in the Z direction of the positive electrode active material layer 111b is set to 0.5 mm. The length (thickness) in the Z direction of the flange portion 111ba is the same as the length (thickness) in the Z direction of the positive electrode lead foil 111a, so the length (thickness) in the Z direction of the flange portion 111ba is 0.75 mm.

[0074] In this way, by covering at least a portion of the edge of the current collector with the active material layer, it is possible to reduce the possibility of the electrolyte contacting the edge of the current collector and causing corrosion. As a result, it is possible to avoid a decrease in battery performance and premature end of life. This also makes it possible to use an electrolyte with a high specific gravity, thereby maintaining and improving battery capacity.

[0075] So far, we have described an embodiment in which a flange portion 111ba is formed on the positive electrode active material layer 111b, and the flange portion 111ba covers the end portion 111ac of the positive electrode lead foil 111a. However, the following structure can also be considered as a method for preventing corrosion due to contact of the electrolyte with the positive electrode lead foil 111a. Fig. 8 is a cross-sectional view showing another structure of the positive electrode lead foil 111a and the positive electrode active material layer 111b in a bipolar lead-acid battery 100 according to an embodiment of the present invention.

[0076] 8, the first surface 111aa of the positive electrode lead foil 111a is provided in the first recess 121b via an adhesive 150a. The second surface 111ab of the positive electrode lead foil 111a is in contact with the positive electrode active material layer 111b. This is in accordance with the arrangement of the substrate 121, positive electrode lead foil 111a, and positive electrode active material layer 111b described above.

[0077] What differs from the structures described so far is that the adhesive 150 is provided so as to rise upward in the Z direction from the first recess 121b, and this rising adhesive portion 150a covers the end portion 111ac of the positive electrode lead foil 111a. The flange portion 111ba of the positive electrode active material layer 111b is disposed between the rising adhesive portion 150a and the rising portion 121ba.

[0078] That is, adhesive 150 is placed by a method such as screen printing in first recess 121b of substrate 121. By employing such a method, adhesive 150 can be provided in first recess 121b with almost no gaps.

[0079] Then, the positive electrode lead foil 111a is placed above the adhesive 150 in the Z direction. At this time, the positive electrode lead foil 111a is not simply placed on the adhesive 150, but is pressed downward in the Z direction to more firmly attach it to the substrate 121. As a result, the adhesive 150 that has protruded from between the positive electrode lead foil 111a and the first recess 121b moves upward in the Z direction from the first recess 121b so as to cover the end 111ac of the positive electrode lead foil 111a, forming a rising adhesive portion 150a.

[0080] Therefore, the end 111ac of the positive electrode lead foil 111a is covered by the rising adhesive portion 150a and the flange portion 111ba, since the rising adhesive portion 150a of the adhesive 150 and the flange portion 111ba of the positive electrode active material layer 111b are disposed between the end 111ac and the rising portion 121ba of the substrate 121. By adopting such a structure, it is possible to further reduce the possibility that the electrolyte will come into contact with the positive electrode lead foil 111a and cause corrosion.

[0081] From the above, when it is said that the positive electrode active material layer 111b "covers" the positive electrode lead foil 111a, it means that the positive electrode active material layer 111b not only covers the opposing surface of the positive electrode lead foil 111a that is opposite the surface of the positive electrode active material layer 111b that contacts the separator 113 and is in contact with the positive electrode lead foil 111a, i.e., the second surface 111ab described above, but also covers the end of the positive electrode lead foil 111a extending beyond the second surface 111ab of the positive electrode lead foil 111a. Moreover, the positive electrode active material layer 111b covers at least a part of the opposing surface (second surface 111ab) and the end of the positive electrode lead foil 111a.

[0082] In the above description, the active material layer provided with the flange portion is the positive electrode active material layer 111b, and the object at least part of the end of which is covered by the flange portion 111ba is the positive electrode lead foil (positive electrode current collector) 111a. This is because, in the case of a bipolar lead-acid battery, corrosion often occurs on the surface of the positive electrode lead foil 111a. Therefore, it is required that at least a part of the end of the positive electrode lead foil 111a be covered by the positive electrode active material layer 111b provided with the flange portion 111ba at its end.

[0083] However, corrosion may also occur on the surface of the negative electrode current collector. Therefore, at least a portion of the end of the negative electrode lead foil (negative electrode current collector) 112a may be covered with a negative electrode active material layer 112b having a flange at the end. Alternatively, the end of the positive electrode lead foil 111a and the end of the negative electrode lead foil 112a may be covered with a positive electrode active material layer 111b and a negative electrode active material layer 112b having a flange, respectively.

[0084] In the above description, the end of the positive electrode lead foil 111a, which has been described as an object at least partially covered by the flange portion 111ba of the positive electrode active material layer 111b, is, for example, the end that is the peripheral portion of the positive electrode lead foil 111a arranged near the frame 122, as shown in Fig. 2. However, the term "end" includes not only the end of the positive electrode lead foil 111a but also the through-hole 111c where the column portion 123 and the positive electrode lead foil 111a contact.

[0085] Therefore, the through hole 111d of the positive electrode active material layer 111b can be configured as a flange portion and arranged in the portion of the through hole 111c of the positive electrode lead foil 111a between the through hole 111c and the column portion 123. This reduces the possibility that the electrolyte will infiltrate from the portion of the through hole 111c of the positive electrode lead foil 111a and corrode the positive electrode lead foil 111a.

[0086] 1, the first end plate 130 is a space-forming member that includes a substrate 131 that covers the positive electrode side of the cell member 110, and a frame 132 that surrounds the side surface of the cell member 110. The first end plate 130 also includes a pillar portion 133 that protrudes vertically from one surface of the substrate 131 (the surface facing the substrate 121 of the bipolar plate 120 that is arranged closest to the positive electrode side).

[0087] The planar shape of the substrate 131 is rectangular, and the four end faces of the substrate 131 are covered with a frame 132. The substrate 131, frame 132, and pillars 133 are integrally formed from, for example, the above-mentioned thermoplastic resin. The number of pillars 133 protruding from one surface of the substrate 131 may be one or more. However, the number corresponds to the number of pillars 123 of the bipolar plate 120 that are to come into contact with the pillars 133.

[0088] In the Z direction, the dimension of the frame body 132 is larger than the dimension (thickness) of the substrate 131, and the dimension between the protruding end faces of the column portions 133 is the same as the dimension of the frame body 132. The first end plate 130 is stacked with the frame body 132 and the column portions 133 in contact with the frame body 122 and the column portions 123 of the bipolar plate 120 arranged on the outermost side (positive electrode side).

[0089] This forms a space C between the substrate 121 of the bipolar plate 120 and the substrate 131 of the first end plate 130. The Z-direction dimension of the space C is maintained by the pillar portions 123 of the bipolar plate 120 and the pillar portions 133 of the first end plate 130, which are in contact with each other.

[0090] The positive electrode lead foil 111a, positive electrode active material layer 111b, and separator 113 of the cell member 110 arranged on the outermost side (positive electrode side) have through holes 111c, 111d, and 113a formed therein, respectively, for allowing the columnar portion 133 to pass therethrough.

[0091] A recess 131b is formed on one surface of the substrate 131 of the first end plate 130. The dimensions of the recess 131b in the X and Y directions correspond to the dimensions of the positive electrode lead foil 111a in the X and Y directions.

[0092] The positive electrode lead foil 111a of the cell member 110 is disposed in the recess 131b of the substrate 131 of the first end plate 130 via the adhesive 150. As in the case of the positive electrode lead foil 111a and the positive electrode active material layer 111b in the substrate 121 of the bipolar plate 120 described above, the flange portion 111ba of the positive electrode active material layer 111b is disposed in the gap between the end portion 111ac of the positive electrode lead foil 111a and the rising portion 131ba of the substrate 131 of the opposing first end plate 130.

[0093] Therefore, by arranging the flange portion 111ba in the gap, the end portion 111ac of the positive electrode lead foil 111a is covered with the flange portion 111ba of the positive electrode active material layer 111b.

[0094] The first end plate 130 also includes a positive electrode terminal (not shown in FIG. 1) electrically connected to the positive electrode lead foil 111a in the recess 131b.

[0095] The second end plate 140 is a space-forming member that includes a substrate 141 that covers the negative electrode side of the cell member 110, and a frame 142 that surrounds the side surface of the cell member 110. The second end plate 140 also includes a column portion 143 that protrudes vertically from one surface of the substrate 141 (the surface facing the substrate 121 of the bipolar plate 120 that is arranged on the most negative electrode side).

[0096] The planar shape of the substrate 141 is rectangular, and the four end faces of the substrate 141 are covered with a frame 142. The substrate 141, frame 142, and pillars 143 are integrally formed from, for example, the above-mentioned thermoplastic resin. The number of pillars 143 protruding from one surface of the substrate 141 may be one or more. However, the number corresponds to the number of pillars 123 of the bipolar plate 120 that are to come into contact with the pillars 143.

[0097] In the Z direction, the dimension of the frame body 142 is larger than the dimension (thickness) of the substrate 141, and the dimension between the protruding end faces of the two pillar portions 143 is the same as the dimension of the frame body 142. The second end plate 140 is stacked with the frame body 142 and the pillar portions 143 in contact with the frame body 122 and the pillar portions 123 of the bipolar plate 120 arranged on the outermost side (negative electrode side).

[0098] This forms a space C between the substrate 121 of the bipolar plate 120 and the substrate 141 of the second end plate 140. The Z-direction dimension of the space C is maintained by the pillar portions 123 of the bipolar plate 120 and the pillar portions 143 of the second end plate 140, which are in contact with each other.

[0099] The negative electrode lead foil 112a, the negative electrode active material layer 112b, and the separator 113 of the cell member 110 arranged on the outermost side (negative electrode side) have through holes 112c, 112d, and 113a formed therein, respectively, for allowing the column portion 143 to pass therethrough.

[0100] A recess 141b is formed on one surface of the substrate 141 of the second end plate 140. The dimensions of the recess 141b in the X and Y directions correspond to the dimensions of the negative electrode lead foil 112a in the X and Y directions.

[0101] The negative electrode lead foil 112a of the cell member 110 is placed in the recess 141b of the substrate 141 of the second end plate 140 via adhesive 150. The second end plate 140 also includes a negative electrode terminal (not shown in FIG. 1) that is electrically connected to the negative electrode lead foil 112a in the recess 141b.

[0102] Here, when joining opposing bipolar plates 120 together, the first end plate 130 and the opposing bipolar plate 120, or the second end plate 140 and the opposing bipolar plate 120, various welding methods can be used, such as vibration welding (vibration welding), ultrasonic welding, and hot plate welding. Of these, vibration welding involves welding by vibrating the surfaces to be joined while applying pressure, and has a fast welding cycle and good reproducibility. Therefore, vibration welding is more preferably used.

[0103] The objects to be welded include not only the frames arranged at opposing positions on the opposing bipolar plate 120, first end plate 130, and second end plate 140, but also the respective pillars.

[0104] [Manufacturing method] The bipolar lead-acid battery 100 of this embodiment can be manufactured, for example, by a method including the steps described below.

[0105] <Manufacturing process of bipolar plates with lead foil for positive and negative electrodes> First, the substrate 121 of the bipolar plate 120 is placed on a workbench with the first recess 121b facing upward. Then, adhesive 150 is applied to the first recess 121b, and the positive electrode lead foil 111a is placed in the first recess 121b. At this time, the column portion 123 of the bipolar plate 120 is passed through the through hole 111c of the positive electrode lead foil 111a. The adhesive 150 is cured, and the positive electrode lead foil 111a is attached to one surface of the substrate 121.

[0106] Next, the substrate 121 is placed on a workbench with the second recess 121c facing upward, and the conductor 160 is inserted into the through-hole 121a. Then, adhesive 150 is applied to the second recess 121c, and the negative electrode lead foil 112a is placed in the second recess 121c. At this time, the column portion 123 of the bipolar plate 120 is passed through the through-hole 112c of the negative electrode lead foil 112a. The adhesive 150 is cured, and the negative electrode lead foil 112a is attached to the other surface of the substrate 121.

[0107] Next, resistance welding is performed to connect the conductor 160 to the positive electrode lead foil 111a and the negative electrode lead foil 112a, thereby obtaining the bipolar plate 120 with positive and negative electrode lead foils. The required number of bipolar plates 120 with positive and negative electrode lead foils are prepared.

[0108] <Production process of end plates with lead foil for positive electrodes> The substrate 131 of the first end plate 130 is placed on a workbench with the recess 131b facing upward. Adhesive 150 is then applied to the recess 131b, and the positive electrode lead foil 111a is placed in the recess 131b and the adhesive 150 is allowed to harden. At this time, the column portion 133 of the end plate 130 is passed through the through hole 111c of the positive electrode lead foil 111a. This results in an end plate with positive electrode lead foil. The adhesive 150 is allowed to harden, and the positive electrode lead foil 111a is attached to one surface of the substrate 131.

[0109] <Manufacturing process of end plates with lead foil for negative electrodes> The substrate 141 of the second end plate 140 is placed on a workbench with the recess 141b facing up. Adhesive 150 is then applied to the recess 141b, and the negative electrode lead foil 112a is placed in the recess 141b and the adhesive 150 is cured. At this time, the column portions 143 of the second end plate 140 are passed through the through holes 112c in the negative electrode lead foil 112a. The adhesive 150 is cured to obtain the second end plate 140 in which the negative electrode lead foil 112a is attached to one surface of the substrate 141.

[0110] <The process of stacking and joining plates> First, the first end plate 130 to which the positive electrode lead foil 111a is fixed is placed on a workbench with the positive electrode lead foil 111a facing up. Then, the positive electrode active material layer 111b is placed inside the cover plate 170, which is then placed on top of the positive electrode lead foil 111a. At this time, the column portions 133 of the first end plate 130 are passed through the through holes 111d of the positive electrode active material layer 111b.

[0111] Furthermore, the flange portion 111ba formed at the end of the positive electrode active material layer 111b is disposed between the end 111ac of the positive electrode lead foil 111a and the rising portion 121ba of the substrate 121. By disposing the flange portion 111ba in such a position, the end 111ac of the positive electrode lead foil 111a is covered with the positive electrode active material layer 111b.

[0112] Next, the separator 113 and the negative electrode active material layer 112b are placed on the positive electrode active material layer 111b. The bipolar plate 120 with the positive and negative electrode lead foils is placed on the first end plate 130 in this state, with the negative electrode lead foil 112a side facing downward. At this time, the column portions 123 of the bipolar plate 120 are passed through the through holes 113a of the separator 113 and the through holes 112d of the negative electrode active material layer 112b, and placed on the column portions 133 of the first end plate 130.

[0113] Then, the frame 122 of the bipolar plate 120 is placed on the frame 132 of the first end plate 130 .

[0114] As described above, the negative electrode active material layer 112b may have a flange 112ba formed thereon. When such a negative electrode active material layer 112b is used, the frame 122 of the bipolar plate 120 is placed on the frame 132 of the first end plate 130 so that the flange 112ba is positioned between the end of the negative electrode lead foil 112a and the rising portion 121ba of the substrate 121.

[0115] In this state, the first end plate 130 is fixed, and vibration welding is performed while vibrating the bipolar plate 120 in the diagonal direction of the substrate 121. As a result, the frame 122 of the bipolar plate 120 is joined onto the frame 132 of the first end plate 130. In addition, the pillars 123 of the bipolar plate 120 are joined onto the pillars 133 of the first end plate 130.

[0116] As a result, the bipolar plate 120 is joined onto the first end plate 130. The cell member 110 is placed in the space C formed by the first end plate 130 and the bipolar plate 120, with the positive electrode lead foil 111a exposed on the upper surface of the bipolar plate 120.

[0117] Next, the positive electrode active material layer 111b, the separator 113, and the negative electrode active material layer 112b are placed in this order on the assembly thus obtained, in which the bipolar plate 120 is joined onto the first end plate 130.

[0118] As described above, when the flange portion 111ba is formed on the positive electrode active material layer 111b or the flange portion is formed on the negative electrode active material layer 112b, these flange portions are assembled so as to be positioned between the rising portion 121ba of the substrate 121 and the end of the current collector.

[0119] Thereafter, another bipolar plate 120 with positive and negative lead foils is placed with the negative lead foil 112a side facing downward. In this state, the combined assembly is fixed, and vibration welding is performed on the other bipolar plate 120 with positive and negative lead foils while vibrating it in the diagonal direction of the substrate 121. This vibration welding process is continued until the required number of bipolar plates 120 are joined on the first end plate 130.

[0120] Finally, the positive electrode active material layer 111b, separator 113, and negative electrode active material layer 112b are placed in this order on the uppermost bipolar plate 120 of the combined assembly in which all the bipolar plates 120 are joined together. Then, a second end plate 140 is placed with the negative electrode lead foil 112a side facing downward.

[0121] In this state, the combined assembly is fixed, and vibration welding is performed while vibrating the second end plate 140 in the diagonal direction of the substrate 141. As a result, the second end plate 140 is joined onto the uppermost bipolar plate 120 of the combined assembly to which all the bipolar plates 120 have been joined.

[0122] In the above description, the layers are stacked in order from the first end plate 130 to the second end plate 140. However, the stacking order may be reversed, from the second end plate 140 to the first end plate 130.

[0123] <Injection and chemical conversion process> In the stacking and joining process of the plates described above, a joining structure is formed by vibration welding of the opposing surfaces of the frame bodies. Then, a predetermined amount of electrolyte is injected into each space C through a through-hole (not shown), and the separator 113 is impregnated with the electrolyte. Then, by performing chemical formation under predetermined conditions, the bipolar lead-acid battery 100 can be manufactured.

[0124] As described above, in the embodiment of the present invention, a flange portion is provided at the end of the active material layer, and the flange portion covers at least a part of the end of the current collector, thereby making it possible to provide a bipolar lead-acid battery that can maintain and improve battery capacity while avoiding deterioration in battery performance and premature end of life that occur when the electrolyte comes into contact with the current collector.

[0125] The bipolar lead-acid battery described above includes, as an example, a stack of spaced-apart cell members, each including a positive electrode having a positive current collector and a positive active material layer, a negative electrode having a negative current collector and a negative active material layer, and a separator interposed between the positive and negative electrodes, the cell members being stacked at intervals, a space-forming member including a substrate covering at least one of the positive and negative sides of the cell members and a frame surrounding the side surfaces of the cell members, through holes penetrating the substrate, and conductors inserted into the through holes to establish electrical continuity between the positive and negative electrodes. However, the bipolar lead-acid battery may be, for example, a bipolar lead-acid battery in which a positive active material layer and a negative active material layer are provided on both sides of a single current collector.

[0126] In the embodiments of the present invention described so far, it has been assumed that the flange portion 111ba of the positive electrode active material layer 111b is arranged in contact with (or in close contact with) the end portion 111ac and the rising portion 121ba of the positive electrode lead foil 111a, which are arranged opposite each other, as shown in Fig. 2. However, instead of this state, the entire flange portion 111ba may not be in contact with (or not be in close contact with) the end portion 111ac, and may be arranged so that there is a slight gap between part of the flange portion 111ba and the end portion 111ac. [Explanation of symbols]

[0127] 100···Bipolar lead-acid battery 110 Cell member 111...Positive electrode 112...Negative electrode 111a...Lead foil for positive electrode 111aa···First Side 111ab...Second Side 111ac...end 112a...Lead foil for negative electrode 111b...Active material layer for positive electrode 111ba···Flange part 112b...Active material layer for negative electrode 113 Separator 120···Bipolar Plate 121....Bipolar plate substrate 121a... Through hole in substrate 121b... First recess 121ba....Rising section 122....Bipolar plate frame 130 First end plate 131... First end plate substrate 132 First end plate frame 140...Second end plate 141... Second end plate substrate 142... Second end plate frame 150···Adhesive 150a...Starting adhesive part 160 Conductor 160a...Outer wall C···Cell (space that houses the cell components)

Claims

1. a positive electrode active material layer; a negative electrode active material layer; a current collector made of lead or a lead alloy in contact with either or both of the positive electrode active material layer and the negative electrode active material layer; a separator disposed between the positive electrode active material layer and the negative electrode active material layer facing each other, a positive electrode active material layer or a negative electrode active material layer covering a surface in contact with the current collector and at least a part of an end of the current collector;

2. 2. The bipolar lead-acid battery according to claim 1, wherein the positive electrode active material layer or the negative electrode active material layer is disposed so as to cover the entire periphery of the end of the current collector.

3. 3. The bipolar lead-acid battery according to claim 1, wherein the specific gravity of the electrolyte impregnated into the separator is 1.30 or more and 1.38 or less.

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