Alkaline storage battery

Abstract

To provide an alkaline storage battery that improves battery performance.SOLUTION: A positive electrode plate and a negative electrode plate are overlapped and wound. A first separator is subjected to first hydrophilic treatment, impregnated with an electrolyte, and arranged on the opposite side of the spiral center of the positive electrode plate between the positive electrode plate and the negative electrode plate. A second separator is subjected to second hydrophilic treatment different from the first hydrophilic treatment, impregnated with an electrolyte that has a liquid content with a liquid content ratio relative to a liquid content of the first separator of 83% or more, and arranged on the spiral center of the positive electrode plate, between the positive electrode plate and the negative electrode plate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an alkaline storage battery. [Background technology]

[0002] Alkaline storage batteries include nickel-metal hydride batteries and nickel-cadmium batteries. In alkaline storage batteries, a separator is placed between the positive and negative electrodes. The separator is subjected to a hydrophilic treatment to improve its hydrophilicity with the alkaline electrolyte.

[0003] There are various types of hydrophilic treatments, including fluorine gas treatment, sulfonation treatment, corona discharge treatment, and graft polymerization treatment. Separators with sulfone groups introduced through sulfonation treatment contribute to suppressing self-discharge and improving capacity retention. However, separators that have undergone sulfonation treatment have characteristics such as reduced mechanical strength and poor electrolyte retention.

[0004] Therefore, in order to further improve the performance of alkaline storage batteries, a configuration has been proposed in which a separator that has been subjected to a different type of hydrophilic treatment is used together with a separator that has been subjected to a sulfonation treatment. In this way, by using two types of separators that have been subjected to two different types of hydrophilic treatment in an alkaline storage battery, it is possible to adjust the characteristics, quality, and safety.

[0005] In alkaline storage batteries, the amount of alkaline electrolyte contained in the separator may be reduced in order to prevent leakage or increase capacity.

[0006] Previously, storage battery technologies have been proposed, such as using ultrasonic waves to turn the separator at the beginning of the winding, which does not face the positive electrode, into a film to increase the liquid content of the other parts, and joining two types of separators together using ultrasonic welding to minimize the amount of separator with low liquid retention. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-20439 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-69887 Summary of the Invention [Problem to be solved by the invention]

[0008] However, if there is a difference in the amount of alkaline electrolyte held in the two separators, especially if the design is for a small amount of alkaline electrolyte, the separator with better electrolyte retention will absorb the alkaline electrolyte held in the other separator, causing an increase in internal resistance. High internal resistance reduces the capacity that can be extracted at high voltage, making the operation of the device using the battery unstable.

[0009] Furthermore, in a technology that uses ultrasonic waves to turn the separator at the beginning of winding into a film and increase the electrolyte content in other parts, it is difficult to suppress the increase in internal resistance due to the difference in electrolyte content between the two types of separators, as opposed to a configuration that uses two types of separators, and it is difficult to improve battery performance.Furthermore, in a technology that uses ultrasonic welding to connect two types of separators and reduce the amount of separator with low electrolyte retention, it is difficult to suppress the increase in internal resistance and it is difficult to improve battery performance, as it does not take into account the electrolyte content of the different types of separators.

[0010] The disclosed technology has been made in view of the above, and aims to provide an alkaline storage battery that improves battery performance. [Means for solving the problem]

[0011] In one embodiment of the alkaline storage battery disclosed herein, positive and negative electrode plates are alternately arranged in a concentric circle. A first separator is subjected to a first hydrophilization treatment, is impregnated with an electrolyte, and is arranged between the positive and negative electrode plates and outside the circle formed by the positive electrode plates. A second separator is subjected to a second hydrophilization treatment, is impregnated with an electrolyte amount such that the ratio of the amount of electrolyte impregnated in the first separator to the amount of electrolyte impregnated in the first separator is 83% or more, and is arranged between the positive and negative electrode plates and inside the circle formed by the positive electrode plates. [Effects of the Invention]

[0012] In one aspect, the present invention can improve battery performance. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a partially cutaway view of an alkaline storage battery according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the results of comparison between the alkaline storage battery according to the example and the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0014] Examples of the electricity storage device disclosed in the present application will be described in detail below with reference to the drawings. Note that the electricity storage device disclosed in the present application is not limited to the following examples.

[0015] (First embodiment) Fig. 1 is a partially cutaway view of an alkaline storage battery according to an embodiment. As shown in Fig. 1, the alkaline storage battery 1 is, for example, a AAA-sized cylindrical battery. In the alkaline storage battery 1, an electrode group 7 is housed together with an alkaline electrolyte in an outer can 2 having a cylindrical shape with a bottom and an open top, and the top is sealed with a sealing body 8. The electrode group 7 is formed by stacking a positive electrode plate 3, a separator 5, a negative electrode plate 4, and a separator 6 in this order and winding them into a spiral shape.

[0016] The bottom wall 9 of the outer can 2 is conductive and functions as a negative electrode terminal. The sealing body 8 includes a lid plate 10 and a positive electrode terminal 11. The lid plate 10 is conductive and has a gas vent hole 12 in the center, and a rubber valve body 13 that closes the gas vent hole 12 is disposed on the outer surface of the lid plate 10. The lid plate 10 is disposed on the open end of the outer can 2 via a ring-shaped gasket 14, and the opening edge of the outer can 2 is crimped to close the opening. A positive electrode terminal 11 is attached to the lid plate 10.

[0017] The electrode group 7 is composed of a strip-shaped positive electrode plate 3, a negative electrode plate 4, and separators 5 and 6. The electrode group 7 is spirally wound in a state in which the separator 5 is sandwiched between the positive electrode plate 3 and the negative electrode plate 4 and the separator 6 is disposed on the surface of the negative electrode plate 4 opposite the separator 5, forming a substantially cylindrical shape. That is, the positive electrode plate 3 and the negative electrode plate 4 face each other with the separators 5 and 6 sandwiched between them, and are overlapped in the radial direction of the outer can 2.

[0018] In the exterior can 2, a positive electrode lead 15 is disposed between one end of the electrode group 7 and the cover plate 10, and each end of the positive electrode lead 15 is electrically connected to the positive electrode plate 3 and the cover plate 10, respectively.

[0019] The positive electrode plate 3 comprises a conductive positive electrode substrate having a porous structure and a positive electrode mixture held in the pores of the positive electrode substrate and on the surface of the positive electrode substrate. The positive electrode substrate may be, for example, a nickel-plated mesh-like, sponge-like, or fibrous metal body or foamed nickel.

[0020] The positive electrode mixture contains positive electrode active material particles, a conductive material, a positive electrode additive, and a binder. The positive electrode active material particles are nickel hydroxide (Ni(OH)2) particles or higher-order nickel hydroxide particles. It is preferable that at least one of zinc, magnesium, and cobalt is solid-dissolved in these nickel hydroxide particles.

[0021] The negative electrode plate 4 has a strip-shaped conductive negative electrode core, and a negative electrode mixture is supported on this negative electrode core. The negative electrode core is made of a sheet-shaped metal material with distributed through holes, such as a punched iron sheet with a nickel-plated surface. When held on the negative electrode core, the negative electrode mixture forms a negative electrode mixture layer.

[0022] The negative electrode mixture contains particles of a hydrogen storage alloy, a negative electrode additive, a conductive material, and a binder. The hydrogen storage alloy is an alloy that can absorb and release hydrogen, which is a negative electrode active material. A general hydrogen storage alloy can be used as the hydrogen storage alloy. Here, in this embodiment, the hydrogen storage alloy is preferably a rare earth-Mg-Ni based hydrogen storage alloy that contains rare earth elements, Mg, and Ni.

[0023] The separator 6 is subjected to hydrophilic treatment. In this embodiment, the separator 6 is a nonwoven fabric made of polypropylene fibers that have been subjected to sulfonation treatment.

[0024] Separator 5 is subjected to a hydrophilic treatment different from that of separator 6. In this embodiment, separator 5 is a nonwoven fabric made of fluorine-treated polypropylene fibers.

[0025] Both fluorine treatment and sulfonation treatment can obtain the desired liquid retention by forming hydrophilic functional groups on the surface of water-repellent polyolefin fibers. Liquid retention is an index that indicates the ease of retaining alkaline electrolyte, and the higher the liquid retention, the easier it is to retain and hold alkaline electrolyte. Both fluorine treatment and sulfonation treatment can adjust the liquid retention by changing the amount of functional groups generated, and changing the liquid retention can change the amount of liquid impregnation.

[0026] The liquid retention of separators 5 and 6 can be measured by the following procedure. We will use separator 5 as an example. First, separator 5 is cut to the specified dimensions and its mass (W) is measured. Next, separator 5 is immersed in water and allowed to absorb liquid for about an hour, and then removed. After 10 minutes, the mass (W1) of separator 5 is measured. Then, the liquid retention is calculated by (W1-W) / W×100.

[0027] In this embodiment, the fluorine treatment is performed so that the amount of alkaline electrolyte contained in the separator 6 in the completed alkaline storage battery 1 is 83% or more of the amount of alkaline electrolyte contained in the separator 5.

[0028] The electrode group 7 is housed in the outer can 2 so that the negative electrode side is in contact with the bottom wall 9 of the outer can 2 .

[0029] After a predetermined amount of alkaline electrolyte is poured into the outer can 2, the opening of the outer can 2 is sealed. The alkaline electrolyte is impregnated into the positive electrode plate 3, the negative electrode plate 4, and the separators 5 and 6, and is involved in the electrochemical reaction, i.e., the charge-discharge reaction, between the positive electrode plate 3 and the negative electrode plate 4. As the alkaline electrolyte, for example, an alkaline electrolyte containing NaOH as a main solute is used.

[0030] The alkaline storage battery 1 produced as described above is subjected to an initial activation process to make the alkaline storage battery 1 usable.

[0031] Next, the performance of the alkaline storage battery 1 according to this embodiment will be described in comparison with a comparative example. Fig. 2 is a diagram showing the results of a comparison between the alkaline storage battery according to this embodiment and the comparative example.

[0032] Table 100 shown in Figure 2 compares Comparative Examples P1 to P4 with Examples #1 and #2. Here, AAA-sized 750 mAh alkaline storage batteries are used. Furthermore, alkaline storage batteries are fabricated using hydrophilically treated separators and 0.800 g of alkaline electrolyte.

[0033] Table 100 shows the battery characteristics, capacity retention, and internal resistance measurements for the alkaline storage batteries fabricated in each example, including the number of charge / discharge cycles required to reach the end of life and the rate at which leakage occurred. The capacity retention is the result of placing the batteries in a 60°C environment for 7 days. Table 100 also shows the total amount of electrolyte absorbed per unit area of ​​the inner and outer separators of the positive electrode, as well as the amount of electrolyte absorbed per unit area of ​​each separator.

[0034] The outer separator is a separator arranged on the outer side of the positive electrode when viewed from the center of the alkaline storage battery, and corresponds to separator 5 in Fig. 1. The inner separator is a separator arranged on the inner side of the positive electrode when viewed from the center of the alkaline storage battery, and corresponds to separator 5 in Fig. 1. Here, the terms "inner separator" and "outer separator" will be used for Comparative Examples P1 to P4, and the terms "separators 5" and "6" will be used for Examples #1 and #2.

[0035] Comparative Example P1 is an example where fluorine treatment C was applied to both the outer separator and the inner separator. Comparative Example P2 is an example where sulfonation treatment S was applied to both the outer separator and the inner separator. Comparative Example P3 is an example where fluorine treatment A was applied to the outer separator and sulfonation treatment S was applied to the inner separator. Comparative Example P4 is an example where fluorine treatment B was applied to the outer separator and sulfonation treatment S was applied to the inner separator.

[0036] Example #1 is an example in which separator 5 was subjected to fluorine treatment C and separator 6 was subjected to sulfonation treatment S. Example #1 is an example in which separator 5 was subjected to fluorine treatment D and separator 6 was subjected to sulfonation treatment S.

[0037] Here, A to D represent liquid retention properties, and the liquid retention properties of the fluorine treatments A to D are expressed as A>B>C>D.

[0038] The electrolyte content can be calculated by the following procedure. For example, after the test, the alkaline storage battery is disassembled and the weights of the inner separator and outer separator, or separator 5 and separator 6, are measured. Next, the alkaline electrolyte is drained from each separator, and the batteries are dried and then weighed. The electrolyte content can then be calculated by calculating the difference between the respective measurement results.

[0039] In Comparative Example P1, the same fluorine treatment C was applied to both the outer separator and the inner separator, so the amount of alkaline electrolyte per unit area was 32 g / m 2 The total amount of alkaline electrolyte per unit area of ​​the inner and outer separators is 32 g / m 2 Since the liquid content of the inner separator and the outer separator is the same, the liquid content of the outer separator is 100% compared to the liquid content of the inner separator.

[0040] In Comparative Example P1, the alkaline storage battery had a life of 400 cycles, with no leakage and a good cycle life. The internal resistance was also good at 44.0 mΩ. However, the capacity retention rate was a low 73.5%. This was because the battery did not use a sulfonated separator, resulting in a low capacity retention rate.

[0041] In Comparative Example P2, the same sulfonation treatment S was applied to both the outer separator and the inner separator, so the amount of alkaline electrolyte per unit area was 28 g / m 2 The total amount of alkaline electrolyte per unit area of ​​the outer and inner separators is 28 g / m 2 Since the liquid content of the inner separator and the outer separator is the same, the ratio of the liquid content of the outer separator to the liquid content of the inner separator is 100%.

[0042] Comparative Example P2 uses a sulfonated separator, resulting in a high capacity retention rate of 80.5% and good self-discharge characteristics. However, the sulfonated separator has poor electrolyte retention and can only hold a small amount of alkaline electrolyte, resulting in a low total electrolyte capacity and a high internal resistance of 46.2 mΩ. Furthermore, the battery life is low at 340 cycles, and the leakage rate is high at 2 / 10 cells.

[0043] In Comparative Example P3, the outer separator was subjected to fluorine treatment A, and the amount of alkaline electrolyte per unit area was 55 g / m 2 In addition, the inner separator is sulfonated, and the amount of alkaline electrolyte per unit area is 10 g / m 2 The total amount of alkaline electrolyte per unit area of ​​the outer and inner separators is 34 g / m 2 The ratio of the liquid content of the outer separator to that of the inner separator is 19%, which is less than 83%.

[0044] In Comparative Example P3, no leakage occurred. The capacity retention rate was high, at 80.0%, which was a good result. However, although the total electrolyte content was high, the electrolyte retention capacity of the outer separator was high, and the electrolyte in the inner separator was removed, resulting in a high internal resistance of 49.0 mΩ. The battery life was also low at 50 cycles.

[0045] In Comparative Example P4, the outer separator was subjected to fluorine treatment B, and the amount of alkaline electrolyte per unit area was 37 g / m 2 In addition, the inner separator is sulfonated, and the amount of alkaline electrolyte per unit area is 24 g / m 2 The total amount of alkaline electrolyte per unit area of ​​the outer and inner separators is 31 g / m 2 The ratio of the liquid content of the outer separator to the liquid content of the inner separator is 65%, which is less than 83%.

[0046] In Comparative Example P4, no leakage occurred. The capacity retention rate was high, at 80.0%, which was a good result. However, although the total electrolyte content was high, the electrolyte retention capacity of the outer separator was still high, and the electrolyte in the inner separator was absorbed, resulting in a high internal resistance of 45.8 mΩ. Furthermore, the battery life was short at 360 cycles.

[0047] In contrast, in Example #1, the separator 5 was subjected to fluorine treatment C, and the amount of alkaline electrolyte per unit area was 33 g / m 2 In addition, the separator 6 is subjected to sulfonation treatment S, and the amount of alkaline electrolyte per unit area is 27 g / m 2 The total amount of alkaline electrolyte contained in the separator 5 and the separator 6 per unit area is 30 g / m 2 The ratio of the liquid content of separator 6 to that of separator 5 is 90%, which is 83% or more.

[0048] In Example #1, the characteristics of the separators 5 and 6, which had been subjected to two types of hydrophilization treatment, were utilized, and the alkaline storage battery 1 had a life of 380 cycles and no leakage. The capacity retention rate was high at 80.0%, and the self-discharge characteristics were good. Furthermore, the liquid content of both separators 5 and 6 was high, and the internal resistance was good at 44.5 mΩ.

[0049] In Example #2, the separator 5 was subjected to fluorine treatment D, and the amount of alkaline electrolyte per unit area was 30 g / m 2 In addition, the separator 6 is subjected to sulfonation treatment S, and the amount of alkaline electrolyte per unit area is 27 g / m 2 The total amount of alkaline electrolyte contained in the separator 5 and the separator 6 per unit area is 29 g / m 2 The ratio of the liquid content of separator 6 to that of separator 5 is 92%, which is 83% or more.

[0050] In Example #2, the characteristics of the separators 5 and 6, which had been subjected to two types of hydrophilization treatment, were utilized, and the alkaline storage battery 1 had a life of 390 cycles and no leakage. The capacity retention rate was high at 80.0%, and the self-discharge characteristics were good. Furthermore, the liquid content of both separators 5 and 6 was high, and the internal resistance was good at 44.3 mΩ.

[0051] From the above, the following can be confirmed: When the same type of hydrophilic treatment is applied to the inner and outer separators, as in Comparative Examples P1 and P2, the properties of the alkaline storage battery deteriorate due to the weaknesses of the hydrophilic treatment applied compared to when different hydrophilic treatments are applied. Therefore, it is preferable to apply different hydrophilic treatments to the inner and outer separators to make use of the characteristics of each.

[0052] Furthermore, if different hydrophilic treatments are applied, differences in the liquid retention capacity of each may result in differences in the liquid content. If there is a difference in the liquid content between the inner separator and the outer separator, the internal resistance increases and the life of the alkaline storage battery is shortened. In contrast, as in Examples #1 and #2, the liquid retention capacity of the fluorinated separator 5 is reduced, and the ratio of the liquid content between separator 5 and separator 6 is set to 83% or more, thereby minimizing the difference, thereby improving the internal resistance. Improving the internal resistance can extend the life of the alkaline storage battery 1.

[0053] As described above, in the alkaline storage battery 1 according to this embodiment, the separators 5 and 6 are subjected to different hydrophilic treatments, and the ratio of the liquid content between them is set to 83% or more. By performing different hydrophilic treatments, it is possible to extend the battery life while suppressing leakage, and to improve self-discharge characteristics. Furthermore, by setting the ratio of the liquid content between the separators 5 and 6 to 83% or more, and thereby reducing the difference, the internal resistance is improved.

[0054] In the above description, the separator 6 was subjected to a fluorine treatment and the separator 5 was subjected to a sulfonation treatment to achieve different hydrophilic treatments. However, the type of hydrophilic treatment is not limited to this. Separators 5 and 6 may also be hydrophilized by combining fluorine treatment, sulfonation treatment, plasma treatment, surfactant treatment, or graft polymerization treatment. Regardless of the combination, the internal resistance can be improved by setting the ratio of the amount of electrolyte content to the amount of electrolyte content at 83% or more. To further improve the performance of the alkaline storage battery 1, sulfonation treatment and graft polymerization treatment are treatments that improve self-discharge characteristics, and it is preferable to combine these treatments with other hydrophilic treatments. In particular, the combination of fluorine treatment and sulfonation treatment described in the examples is most preferable because it allows a large amount of alkaline electrolyte to be poured without leakage, extends cycle life, and provides good self-discharge characteristics.

[0055] Furthermore, in the examples, separator 6 was fluorinated and separator 5 was sulfonated, so that the liquid content of separator 5 was 83% or more of the liquid content of separator 6, but the liquid content of separator 5 and separator 6 may be reversed. That is, separator 5 may be fluorinated and separator 6 may be sulfonated, so that the liquid content of separator 6 is 83% or more of the liquid content of separator 5. [Explanation of symbols]

[0056] 1 alkaline storage battery 2 outer can 3 positive electrode plate 4 negative plates 5,6 Separator 7 electrode group 8 Sealing body 9 Bottom Wall 10 Lid plate 11 Positive terminal 12 Gas vent hole 13 Valve body 14 Gasket

Claims

1. a positive electrode plate and a negative electrode plate that are stacked and wound; a first separator that has been subjected to a first hydrophilization treatment, is impregnated with an electrolyte, and is disposed between the positive electrode plate and the negative electrode plate on the opposite side from the center of the spiral of the positive electrode plate; a second separator that has been subjected to a second hydrophilization treatment different from the first hydrophilization treatment, that contains an electrolyte in an amount such that the ratio of the amount of electrolyte contained in the first separator to the amount of electrolyte contained in the first separator is 83% or more, and that is disposed between the positive electrode plate and the negative electrode plate and toward the center of the spiral of the positive electrode plate; An alkaline storage battery comprising:

2. the first hydrophilization treatment is any one of a fluorine treatment, a sulfonation treatment, a plasma treatment, a surfactant treatment, and a graft polymerization treatment; The second hydrophilization treatment is a treatment other than the first hydrophilization treatment, among fluorine treatment, sulfonation treatment, plasma treatment, surfactant treatment, and graft polymerization treatment.

2. The alkaline storage battery according to claim 1 .

3. the first hydrophilization treatment is a fluorine treatment, the second hydrophilization treatment is a sulfonation treatment, The liquid content of the second separator is 83% or more of the liquid content of the first separator.

2. The alkaline storage battery according to claim 1 .

Images