Alkaline battery

Abstract

To provide an alkaline battery capable of improving discharge performance by ensuring the filling amount of a negative electrode mixture to the inside of a separator.SOLUTION: An alkaline battery 1 includes: a bottomed cylindrical positive electrode can 2 having a bottom face 16 on which a positive electrode terminal 17 is formed; a positive electrode mixture 3 provided inside the positive electrode can 2; a separator 7 provided on the inner peripheral side of the positive electrode mixture 3 and having a first cylindrical part 70 with a cylindrical shape and a bottom 73 closing an opening of the first cylindrical part 70; and a negative electrode mixture 5 filling the inner peripheral side of the first cylindrical part 70. The first cylindrical part 70 has an inner layer 71 provided on the inner peripheral side and an outer layer 72 provided on the outer peripheral side. The bottom 73 has a lid part 73a covering the opening of the first cylindrical part 70 and a second cylindrical part 73b extending from an outer edge of the lid part 73a. The distance between an inner layer side end 71a and the bottom face 16 is different from the distance between an outer layer side end 72a and the bottom face 16, so that a step is formed between the inner layer 71 and the outer layer 72, and the second cylindrical part 73b is fitted in a step part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to alkaline batteries. [Background technology]

[0002] The alkaline battery includes a cylindrical cathode can with a bottom. A cylindrical cathode mixture is provided inside the cathode can, and is coaxial with the cathode can. A gel-like anode mixture is filled inside the cathode mixture. The alkaline battery also includes a separator between the cathode mixture and the anode mixture. The separator has a first cylindrical portion formed coaxially with the positive electrode can and in contact with the inner peripheral surface of the positive electrode mixture, and a bottom portion closing an opening on one end side of the first cylindrical portion.

[0003] For example, as disclosed in Patent Document 1, the first cylindrical portion of the separator is formed by stacking a cylindrical inner layer and an outer layer. The bottom portion is formed by having a lid portion that covers an opening on one end side of the cylindrical portion and a second cylindrical portion that rises from the outer edge of the lid portion toward the first cylindrical portion. The stacking of the first cylindrical portion and the second cylindrical portion prevents leakage of the negative electrode mixture from the gap between the first cylindrical portion and the bottom portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-120721 Summary of the Invention [Problem to be solved by the invention]

[0005] However, where the first cylindrical portion overlaps with the second cylindrical portion, the number of layers increases, as the second cylindrical portion overlaps in addition to the inner and outer layers. Because the outer surface of the first cylindrical portion abuts against the inner surface of the positive electrode mixture and cannot move outward, the inner surface of the first cylindrical portion indents inward by the amount of the increased number of layers. This reduces the amount of negative electrode mixture that can be packed inside the separator, resulting in a problem of reduced discharge performance.

[0006] The disclosed technology aims to provide an alkaline battery that can ensure the amount of negative electrode mixture filled inside the separator and thereby improve discharge performance. [Means for solving the problem]

[0007] An alkaline battery according to one embodiment of the present disclosure includes a cylindrical cathode can with a bottom and a cathode terminal formed on the bottom surface, a cylindrical cathode mixture provided inside the cathode can and coaxial with the central axis of the cathode can, a separator having a cylindrical first tube portion provided coaxially with the central axis on the inner circumferential side of the cathode mixture, and a bottom portion that closes the opening of the first tube portion that is on the cathode terminal side, and a gelled anode mixture filled on the inner circumferential side of the first tube portion of the separator, The bottom portion has a lid portion that covers the opening of the first tubular portion that faces the positive electrode terminal, and a second tubular portion that extends from the outer edge of the lid portion in a direction opposite to the positive electrode terminal side. The inner layer side end, which is the end of the inner layer that faces the positive electrode terminal, and the outer layer side end, which is the end of the outer layer that faces the positive electrode terminal, have different distances from the bottom surface, forming a step between the inner layer and the outer layer, and the second tubular portion is fitted into the step portion. [Effects of the Invention]

[0008] According to one aspect of the alkaline battery disclosed in the present application, it is possible to provide an alkaline battery that can ensure the amount of negative electrode mixture filled inside the separator and thereby improve discharge performance. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a partially enlarged cross-sectional view of the positive electrode terminal side of an alkaline battery according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of the separator according to the first embodiment. [Figure 3] FIG. 3 is a plan view showing the material of the first cylindrical portion in the first embodiment. [Figure 4] FIG. 4 is a partially enlarged cross-sectional view of the positive electrode terminal side of the alkaline battery according to the second embodiment. [Figure 5] FIG. 5 is a partially enlarged cross-sectional view of the positive electrode terminal side of the alkaline battery of the comparative example. [Figure 6] FIG. 6 is a diagram showing the results of the evaluation test. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the alkaline battery disclosed in the present application will be described in detail with reference to the drawings. However, the alkaline battery disclosed in the present application is not limited to the following embodiments.

[0011] First Embodiment 1 is a partially enlarged cross-sectional view of the positive electrode terminal side of an alkaline battery according to Embodiment 1. The alkaline battery 1 according to Embodiment 1 includes a positive electrode can 2, a positive electrode mixture 3, a negative electrode mixture 5, and a separator 7.

[0012] The positive electrode can 2 is made of a conductor such as a metal. The positive electrode can 2 is formed in a cylindrical shape with a bottom, and has a side surface 15 and a bottom surface 16. The side surface 15 is formed in a cylindrical shape. The bottom surface 16 is formed integrally with the side surface 15 so as to close one end of the side surface 15. A positive electrode terminal 17 is formed in the center of the bottom surface 16. The positive electrode terminal 17 is formed so as to protrude from the inside to the outside of the positive electrode can 2. The cross-sectional view shown in FIG. 1 can also be considered a cross-sectional view cut along a plane including the central axis 10 of the positive electrode can 2.

[0013] The positive electrode mixture 3 contains manganese dioxide (MnO2), graphite (C), an aqueous potassium hydroxide solution, and a binder. The binder contains, for example, a polymer compound, and forms a solid by bonding powders of manganese dioxide (MnO2) and graphite (C). The positive electrode mixture 3 is formed in a cylindrical shape. The positive electrode mixture 3 is disposed inside the positive electrode can 2 so that its outer surface faces the inner circumferential surface of the side surface 15 of the positive electrode can 2. The positive electrode mixture 3 is in close contact with the positive electrode can 2 so that the manganese dioxide (MnO2) and graphite (C) are electrically connected to the positive electrode can 2.

[0014] The negative electrode mixture 5 contains zinc powder, a potassium hydroxide aqueous solution, and a gelling agent, and is in a gel state. The negative electrode mixture 5 is disposed inside the positive electrode mixture 3. The zinc powder contained in the negative electrode active material may be replaced with zinc alloy powder formed from a zinc alloy containing zinc.

[0015] The other end of the positive electrode can 2 is open. The alkaline battery 1 also includes a current collector unit made up of a current collector rod inserted into the negative electrode mixture 5, a gasket that supports the current collector rod and closes the opening of the positive electrode can 2, and a negative electrode terminal plate joined to the current collector rod; however, illustrations and detailed descriptions of these components are omitted.

[0016] The separator 7 is made of an insulator such as vinylon or pulp. FIG. 2 is a perspective view of the separator in the first embodiment. The separator 7 is formed in a cylindrical shape with a bottom. The separator 7 has a first cylindrical portion 70 and a bottom portion 73. The first cylindrical portion 70 is formed in a cylindrical shape. The separator 7 is disposed inside the positive electrode can 2 so that the first cylindrical portion 70 is disposed coaxially with the central axis 10 of the positive electrode can 2. The first cylindrical portion 70 is disposed between the positive electrode mixture 3 and the negative electrode mixture 5. That is, inside the positive electrode can 2, the positive electrode mixture 3 is disposed on the outside of the first cylindrical portion 70, and the negative electrode mixture 5 is filled inside the first cylindrical portion 70. The negative electrode mixture 5 is insulated from the positive electrode can 2 by the first cylindrical portion 70.

[0017] The first tubular portion 70 has an inner layer 71 that is cylindrical and provided on the inner circumferential side of the first tubular portion 70, and an outer layer 72 that is cylindrical and provided on the outer circumferential side of the first tubular portion 70. In other words, the outer layer 72 is provided on the outer circumferential side of the inner layer 71.

[0018] The distance from the bottom surface 16 of the positive electrode can 2 to the inner layer side end 71a, which is the end of the inner layer 71 that faces the positive electrode terminal 17, and the distance from the bottom surface 16 to the outer layer side end 72a, which is the end of the outer layer 72 that faces the positive electrode terminal 17, are different. More specifically, the distance X2 between the outer layer side end 72a and the bottom surface 16 is greater than the distance X1 between the inner layer side end 71a and the bottom surface 16. In other words, the inner layer side end 71a protrudes more toward the positive electrode terminal 17 than the outer layer side end 72a. Due to this difference in distance, a step is formed between the inner layer 71 and the outer layer 72 at the end of the first tubular portion 70 that faces the positive electrode terminal 17.

[0019] FIG. 3 is a plan view showing the material of the first cylindrical portion in the first embodiment. For example, the first cylindrical portion 70 can be formed by rolling a single sheet as shown in FIG. 3 into a cylindrical shape so that the wall surface is doubled by an inner layer 71 and an outer layer 72. As shown in FIG. 3, a rectangular sheet is prepared, and a portion of the region that will become the outer layer 72 on the positive electrode terminal 17 side is removed to obtain the first cylindrical portion 70 in which the inner layer side end 71a protrudes further toward the positive electrode terminal 17 than the outer layer side end 72a. Here, the removed portion 74 removed from the rectangular sheet is discarded. Because the size of the removed portion 74 is proportional to the amount of protrusion of the inner layer side end 71a, a smaller amount of protrusion of the inner layer side end 71a is preferable from the viewpoint of reducing raw materials.

[0020] 1 and 2, the bottom portion 73 has a lid portion 73a and a second cylindrical portion 73b. The lid portion 73a is formed in a circular shape and covers the opening at the end of the first cylindrical portion 70 on the positive electrode terminal 17 side. The outer diameter of the lid portion 73a is approximately the same as the outer diameter of the outer layer 72. The lid portion 73a is in contact with the bottom surface 16 inside the positive electrode can 2. The negative electrode mixture 5 is insulated from the positive electrode can 2 by the lid portion 73a.

[0021] The second tubular portion 73b is formed to extend from the outer edge of the lid portion 73a in a direction opposite to the positive electrode terminal 17 side. The second tubular portion 73b is formed in a cylindrical shape. The lid portion 73a and the second tubular portion 73b are formed integrally. With the lid portion 73a covering the opening of the first tubular portion 70, the second tubular portion 73b fits into the step between the inner layer 71 and the outer layer 72. This causes the second tubular portion 73b to overlap the first tubular portion 70, making it less likely that the negative electrode mixture 5 filled inside the separator will leak from the gap between the first tubular portion 70 and the bottom portion 73. In addition, the tip of the second tubular portion 73b abuts against the outer layer side end portion 72a.

[0022] The area where the first tubular portion 70 and the second tubular portion 73b do not overlap has a two-layer structure of an inner layer 71 and an outer layer 72. The area where the first tubular portion 70 and the second tubular portion 73b overlap also has a two-layer structure of an inner layer 71 and a second tubular portion 73b. Therefore, any part of the separator 7 that is formed into a cylindrical shape has a two-layer structure.

[0023] An electrolyte solution is poured into the positive electrode can 2. The electrolyte solution is an aqueous solution containing potassium hydroxide (KOH). The electrolyte solution permeates the positive electrode mixture 3, the negative electrode mixture 5, and the separator 7.

[0024] Second Embodiment 4 is a partially enlarged cross-sectional view of the positive electrode terminal side of the alkaline battery of embodiment 2. In embodiment 2, differences from alkaline battery 1 of embodiment 1 will be described.

[0025] In the alkaline battery 1 of the second embodiment, the distance X1 between the end of the inner layer end 71a and the bottom surface 16 of the separator 7 is greater than the distance X2 between the outer layer end 72a and the bottom surface 16. In other words, the outer layer end 72a protrudes more toward the positive electrode terminal 17 than the inner layer end 71a. Due to this difference in distance, a step is formed between the inner layer 71 and the outer layer 72 at the end of the first tubular portion 70 on the positive electrode terminal 17 side.

[0026] In the alkaline battery 1 of the second embodiment, the outer diameter of the lid portion 73a of the separator 7 is approximately the same as the outer diameter of the inner layer 71. Furthermore, with the lid portion 73a covering the opening of the first cylindrical portion 70, the second cylindrical portion 73b fits into the step between the inner layer 71 and the outer layer 72. This allows the second cylindrical portion 73b to overlap the first cylindrical portion 70, making it less likely that the negative electrode mixture 5 filled inside the separator will leak from the gap between the first cylindrical portion 70 and the bottom portion 73. Furthermore, the tip of the second cylindrical portion 73b abuts against the end of the inner layer 71.

[0027] The area where the first tubular portion 70 and the second tubular portion 73b do not overlap has a two-layer structure of an inner layer 71 and an outer layer 72. The area where the first tubular portion 70 and the second tubular portion 73b overlap also has a two-layer structure of an outer layer 72 and the second tubular portion 73b. Therefore, any part of the separator 7 that is formed into a cylindrical shape has a two-layer structure.

[0028] Comparative Example 5 is a partially enlarged cross-sectional view of the positive electrode terminal side of an alkaline battery of the comparative example. In the alkaline battery 111 of the comparative example, there is no difference in the distance from the bottom surface 16 between the inner layer side end 71a and the outer layer side end 72a. Meanwhile, as in the first and second embodiments, a second cylindrical portion 73b is formed on the outer edge of the lid portion 73a of the separator 7. The end of the first cylindrical portion 70 on the positive electrode terminal 17 side is inserted into the second cylindrical portion 73b. At the overlapping portion between the first cylindrical portion 70 and the second cylindrical portion, the inner layer 71, the outer layer 72, and the second cylindrical portion 73b overlap to form a three-layer structure.

[0029] Furthermore, since the second tubular portion 73b abuts against the inner peripheral surface of the positive electrode mixture 3 and cannot move further outward, the first tubular portion 70 (inner layer 71 and outer layer 72) is positioned further inward than the two-layer structure portion of the separator 7.

[0030] Therefore, compared to the alkaline batteries 1 of the first and second embodiments, in which all cylindrically formed portions of the separator 7 have a two-layer structure, the alkaline battery 1 of the comparative example has a reduced internal volume of the separator 7 in the three-layer structure portion, resulting in less negative electrode mixture 5 being filled.

[0031] [Evaluation Test of Comparative Examples and Examples] Evaluation tests were conducted using comparative examples 1 and 2 having the structure of alkaline battery 111 shown in the comparative example, examples 1 to 4 having the structure of alkaline battery 1 shown in embodiment 1, and examples 5 to 8 having the structure of alkaline battery 1 shown in embodiment 2.

[0032] 6 is a diagram showing the results of the evaluation test. First, the parameters of the alkaline batteries 1, 111 of Comparative Examples 1 and 2 and Examples 1 to 8 shown in FIG. 6 will be described.

[0033] In Comparative Examples 1 and 2 and Examples 1 to 8, the separator 7 is made of paper (pulp). The thickness of the inner layer 71, outer layer 72, lid portion 73a, and second tubular portion 73b of the separator 7 is 0.3 mm.

[0034] Dimension A (see also Figures 1, 4, and 5) is the distance along the central axis 10 between the inner layer side end 71a and the outer layer side end 72a, whichever protrudes toward the positive electrode terminal 17, and the one that does not protrude. Dimension B is the distance along the central axis 10 between the inner layer side end 71a and the outer layer side end 72a, whichever does not protrude, and the lid portion 73a. Dimension C is the length along the central axis 10 of the cylindrical portion of the separator 7 that has a three-layer structure. In Examples 1 to 8, there is no portion that has a three-layer structure, so dimension C is 0 mm.

[0035] Next, evaluation tests performed on the alkaline batteries 1 of Comparative Examples 1 and 2 and Examples 1 to 8 will be described. First, as an impact resistance test, a JIS vibration test (see JIS C8514 6.2.2.3) was conducted to check for a decrease in open circuit voltage (OCV). The results of the impact resistance test are indicated by whether or not there was a decrease in OCV. If there was a decrease in OCV, it is believed that the negative electrode mixture 5 had leaked to the outside of the separator 7, causing an internal short circuit.

[0036] Furthermore, as a discharge performance test, continuous discharge at 100 mA was performed with an end voltage of 0.9 V (average value of N=9). The results of the discharge performance test are shown as relative values ​​of the discharge time of the target alkaline battery when the discharge time of Comparative Example 1 is set to 100.0. If the relative value to Comparative Example 1 is greater than 100.0, it is considered that the inner volume of the separator 7 is larger than that of Comparative Example 1, which increases the amount of negative electrode mixture 5 filled, thereby improving discharge performance.

[0037] The amount of paper waste indicates the amount of paper that is wasted when the first tubular portion 70 is formed using a single rectangular sheet as shown in FIG. 3, i.e., the area of ​​the cut-out portion 74. In Comparative Examples 1 and 2, the cut-out portion 74 is not generated. Among Examples 1 to 4, Example 1 has the smallest area of ​​the cut-out portion 74, and the area of ​​the cut-out portion 74 increases in the order of Example 2, Example 3, and Example 4. Among Examples 5 to 8, Example 5 has the smallest area of ​​the cut-out portion 74, and the area of ​​the cut-out portion 74 increases in the order of Example 6, Example 7, and Example 8.

[0038] <Evaluation of Examples 1 to 4 Having the Structure of Alkaline Battery 1 Described in Embodiment 1> In Examples 1 and 2, where dimension B was smaller than 3 mm, the OCV decreased, but the discharge time was longer and the discharge performance improved compared to Comparative Examples 1 and 2. In addition, the area of ​​the cut-out portion 74 was smaller than in Examples 3 and 4, resulting in less paper waste.

[0039] Furthermore, in Examples 1 and 2 in which the dimension B was 3 mm or more, there was no decrease in OCV and no leakage of the negative electrode mixture 5. Furthermore, the discharge time was longer than in Comparative Examples 1 and 2, and the discharge performance was also improved.

[0040] <Evaluation of Examples 5 to 8 Having the Structure of Alkaline Battery 1 Described in Embodiment 2> Furthermore, in Examples 5 and 6, where dimension B was smaller than 3 mm, the OCV decreased, but the discharge time was longer and the discharge performance improved compared to Comparative Examples 1 and 2. In addition, the area of ​​the cut-out portion 74 was smaller than in Examples 7 and 8, resulting in less paper waste.

[0041] Furthermore, in Examples 7 and 8, in which the dimension B was 3 mm or more, there was no decrease in OCV and no leakage of the negative electrode mixture 5. Furthermore, the discharge time was longer than in Comparative Examples 1 and 2, and the discharge performance was improved.

[0042] <Summary of evaluation> In any of Examples 1 to 4 and Examples 5 to 8, the discharge performance is improved by increasing the amount of negative electrode mixture filled compared to Comparative Examples 1 and 2. That is, whether the inner layer 71 or the outer layer 72 is protruded toward the positive electrode terminal 17, the discharge performance can be improved.

[0043] Furthermore, by setting the dimension B to 3 mm or more as in Examples 3 and 4 and Examples 7 and 8, the OCV does not decrease, and therefore leakage of the negative electrode mixture 5 can be prevented while improving the discharge performance.

[0044] Furthermore, when the dimension B is set to be smaller than 3 mm as in Examples 1, 2, 5, and 6, it is possible to reduce the amount of paper that is discarded and to reduce raw materials.

[0045] [Summary of effects] The alkaline battery 1 according to the first and second embodiments includes a cylindrical cathode can 2 with a bottom and a cathode terminal 17 formed on the bottom surface 16, a cylindrical cathode mixture 3 provided inside the cathode can 2 and coaxial with the central axis 10 of the cathode can 2, a separator 7 having a cylindrical first tubular portion 70 provided coaxially with the central axis 10 on the inner circumferential side of the cathode mixture 3, and a bottom portion 73 that closes the opening of the first tubular portion 70 on the side of the cathode terminal 17, and a gelled anode mixture 5 filled on the inner circumferential side of the first tubular portion 70 of the separator 7, and the first tubular portion 70 is provided on the inner circumferential side. The bottom 73 has an inner layer 71 and an outer layer 72 provided on the outer periphery of the inner layer, and a lid portion 73a that covers the opening of the first tubular portion 70 on the positive terminal 17 side, and a second tubular portion 73b that extends from the outer edge of the lid portion 73a in a direction opposite to the positive terminal 17 side.The inner layer side end 71a, which is the end of the inner layer 71 on the positive terminal 17 side, and the outer layer side end 72a, which is the end of the outer layer 72 on the positive terminal 17 side, have different distances from the bottom surface 16, forming a step between the inner layer 71 and the outer layer 72, and the second tubular portion 73b is fitted into the step portion.

[0046] This allows any part of the cylindrical portion of the separator 7 to have a two-layer structure, thereby increasing the internal volume of the separator 7. Therefore, the amount of negative electrode mixture 5 filled inside the separator 7 can be increased, thereby improving discharge performance.

[0047] Furthermore, the distance from the inner layer side end 71a to the positive electrode terminal 17 may be smaller than that from the outer layer side end 72a. Furthermore, the distance from the outer layer side end 72a to the positive electrode terminal 17 may be smaller than that from the inner layer side end 71a. In either case, the amount of negative electrode mixture 5 filled inside the separator 7 can be increased, thereby improving discharge performance.

[0048] The distance between the lid portion 73a and either the inner layer side end portion 71a or the outer layer side end portion 72a, whichever is further from the positive electrode terminal 17, may be 3 mm or more. This makes it possible to prevent leakage of the negative electrode mixture 5 from between the first cylindrical portion 80a and the bottom portion 73. [Explanation of symbols]

[0049] 1,111 alkaline batteries 2 Positive electrode can 3 Positive electrode mixture 5. Negative electrode mixture 7 Separator 70 First cylindrical part 71 Inner layer 71a Inner layer end 72 Outer layer 72a Outer layer side end 73 Bottom 73a Lid 73b Second cylindrical part 10 Center axis

Claims

1. a cylindrical positive electrode can with a bottom and a positive electrode terminal formed on the bottom surface; a cylindrical positive electrode mixture provided inside the positive electrode can and coaxial with a central axis of the positive electrode can; a separator including a cylindrical first tube portion provided coaxially with the central axis on the inner circumferential side of the positive electrode mixture, and a bottom portion that closes an opening of the first tube portion that is on the positive electrode terminal side; a gelled negative electrode mixture filled on the inner circumferential side of the first cylindrical portion of the separator, the first cylindrical portion has an inner layer provided on an inner circumferential side and an outer layer provided on an outer circumferential side of the inner layer, the bottom portion has a lid portion that covers an opening of the first tubular portion that is on the positive electrode terminal side, and a second tubular portion that extends from an outer edge of the lid portion in a direction opposite to the positive electrode terminal side, a step is formed between the inner layer and the outer layer by a difference in distance from the bottom surface between an inner layer side end, which is an end of the inner layer that is on the positive electrode terminal side, and an outer layer side end, which is an end of the outer layer that is on the positive electrode terminal side; The alkaline battery has the second cylindrical portion fitted into the stepped portion.

2. 2. The alkaline battery according to claim 1, wherein the distance between the inner layer end and the positive electrode terminal is smaller than that between the inner layer end and the positive electrode terminal.

3. 2. The alkaline battery according to claim 1, wherein the distance between the outer layer end and the positive electrode terminal is smaller than that between the inner layer end and the positive electrode terminal.

4. 4. The alkaline battery according to claim 2, wherein the distance between the lid and one of the inner layer side end and the outer layer side end, whichever is further from the positive electrode terminal, is 3 mm or more.

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