Bipolar battery

Abstract

To keep the pressure applied from a separator to a positive electrode active material layer and a negative electrode active material layer high by controlling the density of the separator disposed between the positive electrode active material layer and the negative electrode active material layer, and improve the adhesion between a positive electrode current collector and a positive electrode active material layer, thereby delaying the decrease in capacity and extending the lifespan.SOLUTION: A bipolar storage battery includes: a positive electrode active material layer 111b; a negative electrode active material layer 112b; a current collector made of lead or a lead alloy in contact with either 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 and in contact with the positive electrode active material layer 111b and the negative electrode active material layer 112b. In the separator 113, a ratio of the mass of the separator 113 to the volume of a region A sandwiched between the positive electrode active material layer 111b and the negative electrode active material layer 112b is 0.215 g / cm3 or more and 0.350 g / cm3 or less.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a bipolar storage 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] The lead-acid battery described in Patent Document 1 includes bipolar plates each having a positive electrode active material layer and a negative electrode active material layer provided on one side and the other side of a conductive metal substrate. The bipolar plates are sandwiched between a pair of end plates, and a separator is provided between each pair of adjacent bipolar plates.

[0004] Furthermore, regarding the separator, for example, in the manufacturing process of a lead-acid battery disclosed in Patent Document 2 below, when the separator is sandwiched between the positive electrode active material layer and the negative electrode active material layer, a pressure of, for example, 20 kPa is applied in the thickness direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special table number 2014-530450 [Patent Document 2] Patent Publication No. 2022-085750 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional lead-acid batteries, for example, when the positive electrode current collector is formed in a grid shape, the positive electrode active material layer is three-dimensionally connected to the positive electrode current collector so as to surround the grid shape, and therefore, the electrolyte is less likely to penetrate between the positive electrode current collector and the positive electrode active material layer.

[0007] In contrast, in a lead-acid battery having a bipolar plate configuration, for example, the positive electrode current collector and the positive electrode active material layer are connected in a planar (two-dimensional) manner. Therefore, if, for example, an electrolyte penetrates between the positive electrode current collector and the positive electrode active material layer, the adhesion between the positive electrode current collector and the positive electrode active material layer deteriorates. Furthermore, if the electrolyte reaches the negative electrode side connected through the perforations, a liquid junction may occur.

[0008] One possible reason for this phenomenon is that the pressure exerted by the separator on the positive electrode active material layer is reduced, but Patent Document 1 mentioned above does not mention this point.

[0009] In the case of the valve-regulated lead-acid battery described in Patent Document 2, the pressure applied to the separator when it is sandwiched between the positive electrode active material layer and the negative electrode active material layer is as described above. On the other hand, in the case of a bipolar lead-acid battery such as that disclosed in Patent Document 1, the pressure applied to the separator is greater than the pressure described in Patent Document 2.

[0010] The present invention aims to provide a bipolar lead-acid battery that can delay the decrease in capacity and extend its lifespan by controlling the density of the separator disposed between the positive electrode active material layer and the negative electrode active material layer, thereby maintaining high pressure applied from the separator to the positive electrode active material layer and the negative electrode active material layer and improving adhesion between the positive electrode current collector and the positive electrode active material layer. [Means for solving the problem]

[0011] 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 and in contact with the positive electrode active material layer and the negative electrode active material layer, wherein the ratio of the mass of the separator to the volume of a region sandwiched between the positive electrode active material layer and the negative electrode active material layer is 0.215 g / cm. 3 More than 0.350g / cm 3 The following is the result. [Effects of the Invention]

[0012] A bipolar lead-acid battery according to one aspect 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 and in contact with the positive electrode active material layer and the negative electrode active material layer, wherein the ratio of the mass of the separator to the volume of a region sandwiched between the positive electrode active material layer and the negative electrode active material layer is 0.215 g / cm 3 More than 0.350g / cm 3 By adopting such a configuration, the density of the separator disposed between the positive electrode active material layer and the negative electrode active material layer can be controlled, thereby maintaining a high pressure applied from the separator to the positive electrode active material layer and the negative electrode active material layer, and improving the adhesion between the positive electrode current collector and the positive electrode active material layer, thereby delaying the decrease in capacity and extending the lifespan. [Brief explanation of the drawings]

[0013] [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]1 is a table showing specifications of examples of separators that can be used in a bipolar lead-acid battery according to an embodiment of the present invention, together with specifications of comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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 in the scope and spirit of the invention, and are also included in the scope of the inventions and their equivalents as set forth in the claims.

[0015] [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.

[0016] As shown in FIG. 1, a bipolar lead-acid battery 100 according to an embodiment of the present invention has 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.

[0017] 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.

[0018] In the following, as shown in FIG. 1 and FIG. 2 described later, the stacking direction of the cell members 110 is defined as the Z direction (for example, the vertical direction in FIG. 1), and the directions perpendicular to the Z direction and perpendicular to each other are defined as the X direction and the Y direction.

[0019] 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.

[0020] 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.

[0021] On the other hand, the negative electrode lead foil 112a is provided on the other surface of the bipolar plate 120 (the surface facing downward in the drawing of FIG. 1) by an adhesive 150 (described later) provided between the other surface of the bipolar plate 120 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).

[0022] The separator 113 is made of, for example, a glass fiber mat impregnated with an electrolyte solution containing sulfuric acid. Alternatively, the separator may be made of, for example, a glass mat containing organic fibers, such as an AGM (All Glass Mat), instead of a glass fiber mat.

[0023] The separator 113 is provided so as to be sandwiched between the positive electrode active material layer 111b provided on one bipolar plate 120 and the negative electrode active material layer 112b provided on the other bipolar plate 120 facing each other.

[0024] 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 laminated in this order in the cell member 110. Details of the separator 113 in this embodiment of the present invention will be described later.

[0025] 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.

[0026] The bipolar lead-acid battery 100 according to the embodiment of the present invention has a battery configuration in which the cell members 110 are connected in series by stacking a plurality of bipolar plates 120, each of which is a cell member 110 formed by sandwiching a separator 113 between a positive electrode 111 and a negative electrode 112, and a pair of bipolar plates 120 that sandwich the cell member 110, and the outermost layer is assembled with a first end plate 130 and a second end plate 140.

[0027] The dimensions in the X and Y directions of the positive electrode lead foil 111a are larger than those of the positive electrode active material layer 111b. Similarly, the dimensions in the X and Y directions of the negative electrode lead foil 112a are larger than those of the negative electrode active material layer 112b. Furthermore, the dimension (thickness) in the Z direction of the positive electrode lead foil 111a is larger (thicker) than that of the negative electrode lead foil 112a, and the dimension (thicker) of the positive electrode active material layer 111b is larger (thicker) than that of the negative electrode active material layer 112b.

[0028] 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.

[0029] 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.

[0030] 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, 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.

[0031] 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.

[0032] 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.

[0033] 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. When multiple bipolar plates 120 are stacked with the frame bodies 122 and the pillar portions 123 in contact with each other, a space C is formed between the substrates 121, and the dimension of the space C in the Z direction is maintained by the pillar portions 123 in contact with each other.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] A conductor 160 is disposed in the through-hole 121a of the substrate 121 of the bipolar plate 120, and 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.

[0038] A cover plate 170 is provided on the outer edge of the positive electrode lead foil 111a to cover the outer edge. However, although not shown in Fig. 1, a cover plate 170 may also be provided on the outer edge of the negative electrode lead foil 112a. Therefore, the cover plate 170 is provided on both the positive electrode side and the negative electrode side, or on either one of them.

[0039] 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 perpendicularly 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).

[0040] 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, but the number corresponds to the number of pillars 123 of the bipolar plate 120 that are to come into contact with the pillars 133.

[0041] 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).

[0042] This forms a space C between the substrate 121 of the bipolar plate 120 and the substrate 131 of the first end plate 130, and 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.

[0043] 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.

[0044] 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.

[0045] The positive electrode lead foil 111a of the cell member 110 is placed in the recess 131b of the substrate 131 of the first end plate 130 via an adhesive 150. Similarly to the substrate 121 of the bipolar plate 120, a cover plate 170 is fixed to one surface of the substrate 131 with the adhesive 150, and the outer edge of the positive electrode lead foil 111a is covered with the cover plate 170, even at the boundary with the periphery of the recess 131b.

[0046] 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.

[0047] 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).

[0048] The planar shape of substrate 141 is rectangular, and the four end faces of substrate 141 are covered with frame 142, and substrate 141, frame 142, and column 143 are integrally formed from, for example, the above-mentioned thermoplastic resin. The number of column 143 protruding from one surface of substrate 141 may be one or more, but the number corresponds to the number of column 123 of bipolar plate 120 that comes into contact with column 143.

[0049] In the Z direction, the dimension of the frame body 142 is larger than the dimension (thickness) of the substrate 131, 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).

[0050] This forms a space C between the substrate 121 of the bipolar plate 120 and the substrate 141 of the second end plate 140, and 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] As described above, the cover plate 170 may be fixed to one side of the substrate 141 with the adhesive 150, and the outer edge of the negative electrode lead foil 112a may be covered by the cover plate 170 even at the boundary with the peripheral edge of the recess 141b.

[0055] 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.

[0056] 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.

[0057] Next, the structure of separator 113 according to the embodiment of the present invention will be described with reference to Fig. 2 as well as Fig. 1. Fig. 2 is an enlarged cross-sectional view showing a portion of the structure of bipolar lead-acid battery 100 according to the embodiment of the present invention.

[0058] As shown in Figures 1 and 2, separator 113 in this embodiment of the present invention is arranged between positive electrode active material layer 111b and negative electrode active material layer 112b that face each other when stacked, and has an area that contacts at least positive electrode active material layer 111b and negative electrode active material layer 112b.

[0059] Specifically, the "region" here refers to region A surrounded by a dashed line in separator 113 shown in Fig. 2. That is, region A is a region that comes into contact with positive electrode active material layer 111b and negative electrode active material layer 112b when space forming members adjacent in the Z direction are joined to each other, and is subjected to pressure from positive electrode active material layer 111b and negative electrode active material layer 112b.

[0060] Separator 113 in the embodiment of the present invention further includes a region B (hereinafter referred to as "non-contact region") that does not contact positive electrode active material layer 111b and negative electrode active material layer 112b that sandwich separator 113. As shown in Fig. 2, non-contact region B is a region of separator 113 that does not contact positive electrode active material layer 111b and negative electrode active material layer 112b and protrudes in the X direction.

[0061] Therefore, unlike region A, non-contact region B is a region to which no pressure is applied from the positive electrode active material layer 111b and the negative electrode active material layer 112b even when adjacent space forming members in the Z direction are joined to each other.

[0062] However, although the non-contact region B is defined in this way here, when pressure is applied to the separator 113, the surrounding area of ​​the pressured region also sinks in the Z direction due to the properties of the material of the separator 113. Therefore, in reality, at the boundary with the region A where the separator 113 in the non-contact region B comes into contact with the positive electrode active material layer 111b and the negative electrode active material layer 112b, strictly speaking, the positive electrode active material layer 111b and the negative electrode active material layer 112 may be in a state where pressure is applied from the positive electrode active material layer 111b and the negative electrode active material layer 112b.

[0063] At the same time, at the boundary between non-contact region B and region A, the positive electrode active material layer 111b and the negative electrode active material layer 112b are in contact with each other even in non-contact region B, which is thought to contribute to improving the adhesion between the positive electrode active material layer 111b and the negative electrode active material layer 112b and the separator 113.

[0064] However, although there may be an area in non-contact region B where pressure from the positive electrode active material layer 111b and the negative electrode active material layer 112b is applied, this area is very narrow and its contribution to adhesion is considered to be negligible compared to region A. Therefore, in the embodiment of the present invention, as described above, non-contact region B refers to an area of ​​separator 113 that does not contact positive electrode active material layer 111b and negative electrode active material layer 112b, protrudes in the X direction, and is not subjected to pressure from positive electrode active material layer 111b and negative electrode active material layer 112b.

[0065] 1 and 2, however, mainly show the structure of the right side of the pillar portion 123 of the bipolar lead-acid battery 100. Therefore, in Fig. 2, the non-contact area B is depicted as protruding to the right side of the drawing, and the protruding state on the left side of the drawing is not depicted.

[0066] Although not shown in the drawing, the separator 113 may have a non-contact region B in the Y direction where it does not come into contact with the positive electrode active material layer 111b and the negative electrode active material layer 112b.

[0067] Instead of the separator 113 in the embodiment of the present invention, a separator may be used in which, when adjacent space-forming members in the Z direction are joined to each other, the entire area of ​​the separator is in contact with the positive electrode active material layer 111b and the negative electrode active material layer 112b that are arranged in opposing positions.

[0068] That is, in such a separator, no non-contact region B is generated, and the regions facing the positive electrode active material layer 111b and the negative electrode active material layer 112b all become region A. Therefore, the separator 113 used in the bipolar lead-acid battery 100 only needs to have regions in contact with at least the positive electrode active material layer 111b and the negative electrode active material layer 112b, regardless of whether or not the non-contact region B is present.

[0069] In the separator 113 according to the embodiment of the present invention, the ratio of the dry mass of the separator 113 to the volume of the separator 113 in the region A is 0.215 g / cm 3 More than 0.350g / cm 3 The following is the result.

[0070] Here, when a bipolar electrode is provided, as in the bipolar lead-acid battery 100 according to the embodiment of the present invention, it is necessary to maintain good adhesion between the positive electrode lead foil 111a and the positive electrode active material layer 111b, and between the negative electrode lead foil 112a and the negative electrode active material layer 112b, as described above, in order to avoid a decrease in the capacity of the bipolar lead-acid battery 100 and to extend its lifespan.

[0071] Therefore, in order to ensure adhesion between the positive electrode lead foil 111a and the positive electrode active material layer 111b, and between the negative electrode lead foil 112a and the negative electrode active material layer 112b, the density of the separator 113 of the bipolar lead-acid battery 100 according to the embodiment of the present invention is controlled. This is because if the density can be kept high, the group pressure can be kept high. That is, the higher the density of the separator 113, the higher the group pressure, whereas if the density of the separator 113 is low, the group pressure will be low.

[0072] A cell member 110 is disposed in the space C of the bipolar lead-acid battery 100. As will be described later, when the bipolar lead-acid battery 100 is manufactured and before the frames of adjacent space-forming members are joined, for example, a positive electrode active material layer 111b is disposed on the positive electrode lead foil 111a, and a separator 113 is further disposed so as to be in contact with the positive electrode active material layer 111b.

[0073] In this state, the height in the Z direction of the placed separator 113 is greater than the height in the Z direction of the frame body of the adjacent space forming member. Therefore, these frame bodies are joined by applying a large pressure to the separator 113 to crush it. When the adjacent space forming members are joined together and the cell member 110 is placed in the space C, the pressure applied to the separator 113 is referred to as "group pressure."

[0074] As explained above, the separator 113 according to the embodiment of the present invention has a region (region A) that is in contact with the positive electrode active material layer 111b and the negative electrode active material layer 112b and receives pressure from them. By increasing the collective pressure applied to region A, the density in region A is increased, and adhesion between the positive electrode active material layer 111b and the positive electrode lead foil 111a and adhesion between the negative electrode active material layer 112b and the negative electrode lead foil 112a are ensured.

[0075] However, as described above, non-contact area B is not in contact with the positive electrode active material layer 111b or the negative electrode active material layer 112b and is not subjected to pressure from these layers. Because of the non-contact, non-contact area B does not contribute to ensuring adhesion between the positive electrode active material layer 111b and the positive electrode lead foil 111a or between the negative electrode active material layer 112b and the negative electrode lead foil 112a.

[0076] Therefore, the target for controlling the density of separator 113 is region A. Therefore, separator 113 according to the embodiment of the present invention is formed so that the density of region A and the density of non-contact region B are different from each other.

[0077] 3 is a table showing the specifications of examples of the separator 113 that can be used in the bipolar lead-acid battery 100 according to the embodiment of the present invention, along with the specifications of comparative examples. That is, the table shows the results of experiments in which the density of the separator 113 was changed in multiple ways, and the shown specifications are values ​​in region A of the separator 113.

[0078] 3, Comparative Example 1 is shown at the top row, Comparative Example 2 is shown at the bottom row, and seven examples are shown between the two Comparative Examples, while nine items are shown in order from left to right in the column direction.

[0079] The nine items are, in order, "mass (g)", "volume (cc)", "density (g / cm 3 )," "Rated (Ah)," "10HR (Ah)," "Discharge capacity relative to rated capacity (%)," "Judgment," "Separator porosity (%)," and "Amount of liquid that the separator can hold (cc)."

[0080] As described above, the target for density control in the separator 113 is the region A, and therefore the "mass (g)", "volume (cc)", and "density (g / cm 3 )" is the value in region A. From the mass and volume in region A, the density range in each comparative example and example is "0.207 g / cm 3" or "0.400g / cm 3 " is included in the scope of

[0081] Here, the "mass (g)" of region A of the separator is measured as follows. That is, a bipolar lead-acid battery equipped with the separator to be measured is disassembled, and the separator is sampled. That is, the region of the separator whose mass is to be measured, i.e., the portion corresponding to region A, is cut out. At this time, the separator contains an electrolyte.

[0082] The separator cut out in this way contains electrolyte. Therefore, it is washed with water for at least 12 hours to remove the electrolyte. This is because if sulfuric acid components of the electrolyte remain on the separator, the measured mass will be larger than the actual mass of the separator.

[0083] Since the separator has been washed with water, it is then dried after washing. For example, it is dried in a gas phase at 60°C for at least 24 hours. The mass of the dried separator is then measured. Note that it is desirable that the moisture content of the separator when measuring the mass is less than 1%.

[0084] Next, we will explain how to measure the "volume (cc)." The volume of the separator can be calculated by multiplying the "area where the positive electrode active material layer or the negative electrode active material layer contacts the separator" by the "inter-electrode pitch."

[0085] Here, the "area" is determined as follows. First, the cell components of a bipolar lead-acid battery are cut in a direction perpendicular to the stacking direction (Z direction in FIG. 2), i.e., in the X direction shown in FIG. 2. This makes it possible to expose the XY plane of the separator, i.e., the surface where the positive electrode active material layer or the negative electrode active material layer contacts the separator. Then, the area where the positive electrode active material layer or the negative electrode active material layer contacts the separator is measured.

[0086] If the contact area between the positive electrode active material layer and the separator is different from the contact area between the negative electrode active material layer and the separator, the smaller area is used as the contact area between the active material layer and the separator.

[0087] 2, the presence of the non-contact region B means that when the active material layer and the separator are placed opposite each other, the separator has a larger area than the active material layer. Therefore, for example, the area can be measured using the trace of the active material layer remaining on the separator.

[0088] Next, we will explain how to measure the "inter-electrode pitch." As shown in Figure 2, a bipolar lead-acid battery equipped with the separator to be measured is cut so that the Z direction (the stacking direction of the cell components) is exposed. Then, the distance between the position where the positive electrode active material layer and the separator contact each other and the position where the negative electrode active material layer and the separator contact each other is measured. However, since measuring the distance at only one location may result in variations in the value, the distance is measured at multiple locations, for example, three or more locations. The multiple measured distances are then averaged, and this average value is used as the "inter-electrode pitch."

[0089] Then, using the thus measured and calculated "area of ​​contact between the positive electrode active material layer or the negative electrode active material layer and the separator" and "inter-electrode pitch", the volume of region A is calculated based on the above-mentioned formula.

[0090] Returning to the table shown in Fig. 3, "Rated (Ah)" indicates the performance of the bipolar lead-acid battery 100 used in each comparative example and example. As is clear from the "Rated (Ah)" column, in the experiments, all bipolar lead-acid batteries 100 showing a value of "50" were used except for Example 4.

[0091] "10HR (Ah)" is the 10-hour rate capacity, and a higher value indicates better performance. "Discharge capacity relative to rated capacity (%)" is a value that indicates how much discharge capacity has been achieved relative to the rated capacity, and a higher value indicates that more current has been extracted. "Judgment" indicates the result of a judgment made based on the results of each of these items obtained through experiments.

[0092] Furthermore, "separator porosity (%)" indicates the ratio of the volume of voids capable of containing water to the volume of region A of separator 113. In other words, the larger this value, the greater the amount of electrolyte that can be held in region A of separator 113. On the other hand, as the density of region A of separator 113 increases, the porosity tends to decrease, and therefore the amount of electrolyte that can be injected also decreases.

[0093] The "amount of liquid that the separator can hold (cc)" indicates the amount of electrolyte that can be injected into the separator in each comparative example and example. Since the above-mentioned tendency is observed between the density of the separator 113 and the amount of electrolyte, the separator used in the bipolar lead-acid battery of comparative example 1, in which the density of the separator 113 in region A is the lowest, holds the largest amount of electrolyte. Conversely, the separator used in the bipolar lead-acid battery of comparative example 2, in which the density of the separator 113 in region A is the highest, holds the smallest amount of electrolyte.

[0094] The results of tests conducted on bipolar lead-acid batteries equipped with the nine types of separators described above are as follows. First, let us look at the comparative examples. In the case of comparative example 1, the density in region A of the separator 113 was 0.207 g / cm 3 ", the rating is "50Ah", the 10-hour rate capacity is "43.2%", and the discharge capacity is "86%". The result is "X".

[0095] This is presumably because the density of the separator 113 in the region A is low, and the collective pressure that tightly adheres the positive electrode active material layer 111b to the positive electrode lead foil 111a is weak, which is why the positive electrode lead foil 111a is peeled off from the positive electrode active material layer 111b, resulting in a low discharge capacity.

[0096] On the other hand, in Comparative Example 2, the density of the separator 113 in the region A was 0.400 g / cm 3 ", the rating is "50Ah", the 10-hour rate capacity is "45.6%", and the discharge capacity is "91%". The result is "X", just like in Comparative Example 1.

[0097] In the case of Comparative Example 2, unlike Comparative Example 1, the density of region A of separator 113 is high. However, because the density is high, the amount of electrolyte that can be held in separator 113 is small. That is, compared to Comparative Example 1, the "liquid volume" of Comparative Example 1 is "310 cc," while that of Comparative Example 2 is "245 cc." This is presumably why the discharge capacity decreased.

[0098] Next, looking at the Examples, all seven Examples were judged to be good. Only Example 7 was judged to be "Good", but this is because the discharge capacity was slightly lower than the other Examples. As a result, the ratio of the dry mass of the separator 113 to the volume of the separator 113 in the region A was 0.215 g / cm. 3 More than 0.350g / cm 3 Those having a density within the following ranges can be more preferably used.

[0099] Furthermore, a more preferable range for the porosity in region A of separator 113 is 0.69 or more and 0.83 or less. If the porosity is within this range, the separator can retain an amount of electrolyte sufficient to ensure the required performance as discharge capacity.

[0100] [Manufacturing method] The bipolar lead-acid battery 100 of this embodiment can be manufactured, for example, by a method including the steps described below. Although a cover plate 170 may also be provided on the negative electrode side, the following description will be given taking as an example a case where the cover plate 170 is provided only on the positive electrode side.

[0101] <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.

[0102] 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.

[0103] Next, the substrate 121 is placed on a workbench with the first recess 121b side facing up. Then, adhesive 150 is applied to the outer edge of the positive electrode lead foil 111a and to the upper surface of the substrate 121 that will become the edge of the first recess 121b, and a cover plate 170 is placed on top of that and the adhesive 150 is cured. In this way, the cover plate 170 is fixed over the outer edge of the positive electrode lead foil 111a and over the portion of the substrate 121 that is continuous with that outer edge (the peripheral edge of the first recess 121b).

[0104] 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.

[0105] <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 up. Then, adhesive 150 is applied to the recess 131b, and the positive electrode lead foil 111a is placed in the recess 131b and the adhesive 150 is cured. 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. The adhesive 150 is cured, and the positive electrode lead foil 111a is attached to one surface of the substrate 131.

[0106] Next, adhesive 150 is applied to the outer edge of the positive electrode lead foil 111a and to the upper surface of the substrate 131, which will be the edge of the recess 131b. A cover plate 170 is placed on this adhesive 150 and the adhesive 150 is cured. This fixes the cover plate 170 over the outer edge of the positive electrode lead foil 111a and the portion of the substrate 131 that is continuous with the outer edge. This results in an end plate with positive electrode lead foil.

[0107] <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 of 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.

[0108] <The process of stacking and joining plates> First, the first end plate 130, to which the positive electrode lead foil 111a and cover plate 170 are fixed, is placed on a workbench with the positive electrode lead foil 111a facing up. The positive electrode active material layer 111b is then placed inside the cover plate 170 and 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. Next, the separator 113 and the negative electrode active material layer 112b are placed on top of the positive electrode active material layer 111b.

[0109] Next, the bipolar plate 120 with the positive and negative electrode lead foils is placed with the negative electrode lead foil 112a side facing downwards on the first end plate 130 in this state. At this time, the column parts 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 parts 133 of the first end plate 130. Then, the frame 122 of the bipolar plate 120 is placed on the frame 132 of the first end plate 130.

[0110] As described above, the separator 113 used here is sufficient as long as it has at least the region A in contact with the positive electrode active material layer 111b and the negative electrode active material layer 112b. Therefore, the presence or absence of the non-contact region B is not an issue.

[0111] In addition, the ratio of the dry mass of the separator 113 to the volume of the separator 113 in the region A is 0.215 g / cm 3 More than 0.350g / cm 3 Furthermore, it is more preferable that the porosity is 0.69 or more and 0.83 or less.

[0112] 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.

[0113] 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.

[0114] Next, the positive electrode active material layer 111b, separator 113, and negative electrode active material layer 112b are placed in this order on the assembly thus obtained, in which the bipolar plate 120 is joined to the first end plate 130. Thereafter, another bipolar plate 120 with positive and negative electrode lead foils is placed with the negative electrode lead foil 112a side facing downward.

[0115] In this state, the combined body is fixed, and another bipolar plate 120 with lead foil for positive and negative electrodes is vibration-welded while being vibrated in the diagonal direction of the substrate 121. This vibration welding process is continued until the required number of bipolar plates 120 are joined onto the first end plate 130.

[0116] 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.

[0117] 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.

[0118] In the above explanation, the stacking order is described as starting from the first end plate 130 to the second end plate 140, but the stacking order may also be reversed, starting from the second end plate 140 to the first end plate 130.

[0119] The collective pressure applied to the cell member 110 (separator 113) after all the space forming members have been joined is, for example, 100 kPa.

[0120] <Injection and chemical conversion process> In the process of stacking and joining the plates, a joint structure is formed by vibration welding the opposing surfaces of the frame bodies, and through-holes are formed by the cutouts of the opposing frame bodies. Then, a lid is attached to the bipolar lead-acid battery 100 so as to cover the through-hole.

[0121] By injecting a predetermined amount of electrolyte from the communication port provided in the lid, the electrolyte is injected into the space C via the through-hole. This allows the separator 113 to be impregnated with the electrolyte. Then, by performing chemical formation under predetermined conditions, the bipolar lead-acid battery 100 can be manufactured.

[0122] As mentioned above, the embodiments of the present invention have been described using a bipolar lead-acid battery as an example. However, if the above description also applies to other storage batteries that use metals other than lead for the current collector plates, this does not mean that the application of the above description is excluded. [Explanation of symbols]

[0123] 100···Bipolar lead-acid battery 110 Cell member 111...Positive electrode 112...Negative electrode 111a...Lead foil for positive electrode 111aa...Void part 112a...Lead foil for negative electrode 111b...Active material layer for positive electrode 112b...Active material layer for negative electrode 113 Separator 120···Bipolar Plate 121....Bipolar plate substrate 121a... Through hole in substrate 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 160 Conductor 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 and in contact with the positive electrode active material layer and the negative electrode active material layer, In the separator, the ratio of the mass of the separator to the volume of the region sandwiched between the positive electrode active material layer and the negative electrode active material layer is 0.215 g / cm ３ More than 0.350g / cm ３ A bipolar lead-acid battery characterized by the following:

2. 2. The bipolar lead-acid battery according to claim 1, wherein the region is in contact with the positive electrode active material layer and the negative electrode active material layer and is subjected to pressure from the positive electrode active material layer and the negative electrode active material layer.

3. 3. The bipolar lead-acid battery according to claim 1, wherein the porosity of the separator in the region is 0.69 or more and 0.83 or less.

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