JP2006134795A - Alkaline storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline hydrogen storage battery adapted to large-current application by improving current-collecting efficiency by enhancing conductivity from a non-filling part of a filling type electrode to a collector. <P>SOLUTION: This alkaline storage battery is provided with a spiral electrode group composed by rolling strip-like positive and negative electrode plates each having a non-filling part having no active material along at least one of long sides thereof formed thereon by interlaying a separator, and by welding flat plate-like collectors to its both end faces. The alkaline storage battery is characterized in that at least one of the positive and negative electrode plates is a filling type electrode having a three-dimensional metal porous body as a core material, the non-filling parts of the filling type electrodes are molded so as to contact with each other on end faces of the spiral electrode group, and each collector is provided with a fixed blade on a surface to be welded to the end face of the filling type electrode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a nickel metal hydride storage battery capable of charging and discharging a large current.

  Alkaline storage batteries such as nickel-cadmium storage batteries or nickel metal hydride storage batteries have been widely used as various power sources. In particular, in recent years, nickel-metal hydride storage batteries have been desired to be further improved in high-rate discharge characteristics from fields that require charging and discharging with a large current, such as electric vehicles, hybrid vehicles, and electric tools.

  Among these, even the most popular electric tools are using nickel metal hydride storage batteries from nickel-cadmium storage batteries. In the nickel-metal hydride storage battery, a three-dimensional metal porous body such as a foamed nickel substrate is used for at least one core material of the positive and negative electrode plates, and this core material is a filled electrode filled with an active material. When a positive electrode is used as a filling electrode, it can be filled with nickel hydroxide powder as an active material at a high density, so that the capacity can be increased and the manufacturing method is easy, so that it is widely deployed.

  However, in the three-dimensional metal porous body, the skeleton forming the porous body is about several tens of μm to 100 μm, and the skeleton is intertwined in three dimensions, so that the conductivity per volume is low.

Alkaline batteries for large currents generally have a tabless structure as a current collecting structure (a structure in which an unfilled portion where no active material is present is provided along the long side of the strip electrode, and a flat plate current collector is welded thereto. However, the securing of the welding strength between the electrode end face and the current collector, that is, the area of the welding point, affects the battery performance. Therefore, Patent Document 1 proposes a method of securing the welding strength by increasing the number of welding points while improving the conductivity by providing unevenness at the tip after compressing the unfilled portion of the electrode in the width direction.
Japanese Patent Laid-Open No. 10-228908

  However, although the method of Patent Document 1 can secure the welding strength between the electrode and the current collector, the filled electrode collects current only with a cross-sectional area of one three-dimensional metal porous body, so that it contacts with the current collector. The area cannot be increased any more, and there is a limit to improving the conductivity regardless of the welding strength.

  The present invention solves such a problem, and an alkaline hydrogen storage battery adapted to high current use by increasing the conductivity from the unfilled portion of the filled electrode to the current collector and improving the current collection efficiency. It is to provide.

  Based on the above problems, the present invention winds a strip-like positive and negative electrode plate provided with an unfilled portion free of active material along at least one of the long sides through a separator, and a flat current collector is obtained. An alkaline storage battery having a spiral electrode group welded to both end faces, wherein at least one of the positive and negative electrode plates is a filled electrode having a three-dimensional metal porous body as a core material. The present invention relates to an alkaline storage battery characterized in that the filling portion is shaped so as to be in contact with each other at the end face of the spiral electrode group, and the current collector is provided with a fixed blade on the surface welded to the end face of the filling electrode.

When the unfilled portion of the filled electrode is bent at a substantially right angle, the thickness of the current collector is substantially increased, and when it is folded in multiple, the resistance of the unfilled portion itself is decreased. In either case, the filled electrode The conductivity from the unfilled portion to the current collector is improved, and the unfilled portion itself has the same function as the current collector. Further, since the unfilled portion is a porous body, the fixed blade of the current collector bites in and the number of welding points can be secured, so that a welding strength equal to or higher than that obtained when a plate-like core material is used can be obtained. The synergistic effect of these two effects makes it possible to obtain current collection efficiency suitable for large current applications.

  By adopting the current collecting structure of the present invention, it is possible to improve the conductivity from the unfilled portion of the filled electrode to the current collector, which was a conventional problem, and to obtain a welding strength equal to or higher than that of the plate-like core material. Therefore, a high-performance high-current nickel-metal hydride storage battery having high current collection efficiency can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  1 and 4 are partial cross-sectional structural views of the alkaline storage battery of the present invention, FIGS. 2 and 5 are schematic perspective views of the positive electrode, and FIGS. 3 and 6 are cross-sectional structural views of the electrode plate group. The positive electrode composed of the active material filled portion 1 and the unfilled portion 11 or 12 is a filled electrode having a three-dimensional metal porous body as a core material. The positive electrode is wound together with the negative electrode 3 via a separator 4 and has a spiral electrode group. Become. At the end face of the spiral electrode group, the unfilled portions 11 or 12 of the positive electrode are in contact with each other and are welded to the flat positive electrode current collector 5. The surface to be welded to the end face of the filling electrode of the positive electrode current collector is provided with a fixed blade, which will be described in detail later. This electrode group is inserted into a case 10 that also serves as a negative electrode terminal.

  On the other hand, the negative electrode 3 uses a plate-shaped core material, and an unfilled portion of the negative electrode active material is welded to the negative electrode current collector 9. The positive electrode current collector 5 is electrically connected to a sealing plate 7 also serving as a positive electrode terminal via a lead 8, and the negative electrode current collector 9 is electrically connected to a case 10. Thereafter, an electrolytic solution is injected, and the sealing plate 7 and the case 10 are caulked to constitute the alkaline storage battery of the present invention.

Here, the porosity (ratio of voids) of the three-dimensional metallic porous material used in the present invention is not particularly limited, but is about 70 to 98%, preferably about 94 to 98% before filling with the active material. In this case, the average diameter of the voids is 100 to 300 μm in terms of a circle. When the material is nickel, the weight per unit area (metal weight per unit area) is 200 to 700 g / m ² .

  The active material filled in the three-dimensional metal porous body used in the present invention is not particularly limited and any known active material is used. For example, in the case of a positive electrode, nickel hydroxide is used. Unless this active material is particularly limited, the powder is mixed with an appropriate conductive material or binder to form a paste.

  Further, the manufacturing method of the unfilled portion 11 or 12 is not particularly limited. However, it is preferable to compress and compress in advance so as not to clog the active material along at least one of the long sides in the final electrode shape (band shape). preferable. Thereafter, the three-dimensional metal porous body is filled with the paste, and after drying, the electrode plate is press-pressed to a predetermined thickness, and then cut into a predetermined dimension to produce a filled electrode.

The unfilled portions 11 or 12 of the present invention are molded so as to contact each other when the spiral electrode group is formed. By firmly adhering the unfilled portions of the filled electrode, the conductivity from the unfilled portion to the current collector is improved. Specifically, it can be roughly divided into a case where the unfilled portion 11 is compression-molded as shown in FIG. 1 and a case where the unfilled portion 12 is bent at a substantially right angle as shown in FIG. In the case of the unfilled portions 11, the resistance decreases as the contact area density between the unfilled portions 11 increases. In the case of the unfilled portion 12, the thickness of the positive electrode current collector 5 is substantially increased. In any of these cases,
This is preferable because the conductivity from the positive electrode to the positive electrode current collector 5 is improved.

  Here, when the thickness of the unfilled portion 11 or 12 when welding the positive electrode current collector 5 is A, the thickness of the positive electrode is B, the thickness of the negative electrode 3 is C, and the thickness of the separator 4 is D, (B + C + 2D) ≦ It is preferable to satisfy the relationship of A ≦ 1.2 × (B + C + 2D) from the viewpoint of firmly adhering adjacent unfilled portions 11 or 12 to each other. In the case of A <(B + C + 2D), the adhesion between adjacent unfilled portions 11 or 12 is lowered, and the effect of the present invention is hardly exhibited. In the case of A> 1.2 × (B + C + 2D), the repulsive force when the unfilled portions 11 or 12 are brought into close contact with each other becomes excessive, and the electrode group is easily deformed.

  FIG. 10 is a schematic perspective view of a configuration of the electrode plate group and a current collector with a fixed blade. The current collector of the present invention (the positive electrode current collector 5 in FIGS. 1 to 6) needs to be provided with a fixed blade 14. Specifically, in addition to the shape shown in FIG. 10, any shape that can bite into the unfilled portion 11 or 12, which is a porous body, may be used, and high conductivity can be obtained by increasing the contact area between the two. be able to.

  In the above description, only the positive electrode has been described as a filling electrode. However, it goes without saying that the effects of the present invention are equally exhibited when only the negative electrode is a filling electrode or when both the positive and negative electrodes are filling electrodes. Furthermore, since the positive electrode current collector 5 only needs to have the fixed blade 14, it may have a rectangular shape (for a square battery) in addition to the disk shape (for a cylindrical battery) described above.

  Hereinafter, a cylindrical nickel-metal hydride storage battery comprising the spiral electrode group as an example will be described with reference to the drawings.

(Battery A1)
A foamed nickel substrate having a thickness of 0.4 mm, a width of 54 mm, a length of 1000 mm, and a nickel basis weight of 450 g / m ² , 100 parts by weight of a spherical nickel hydroxide powder (average particle diameter of 10 to 20 μm) as an active material, A portion (width) which becomes a non-filled portion by kneading 10 parts by weight of cobalt hydroxide powder (average particle diameter 0.2 μm) and 2 parts by weight of zinc oxide powder (average particle diameter 0.2 μm) into a paste form 4 mm) was filled and dried so as not to clog the active material. After drying, it was pressure-formed with a roll press so that the filling portion had a thickness of 0.27 mm. Thereafter, the unfilled portion was pressure-molded as shown in FIG. 2 so that the unfilled portion was thicker than the active material filled portion (average thickness 0.79 mm). The coating type negative electrode (thickness 0.19 mm) 3 using a known hydrogen storage alloy as an active material is shifted on the positive electrode so that each unfilled portion protrudes upward or downward, and is subjected to a hydrophilic treatment. The electrode group was configured by winding through a polypropylene separator (thickness: 0.1 mm).

  Next, a flat disk-shaped current collector was electrically resistance-welded from above to each plain part of the positive and negative electrode plates. Here, a positive electrode current collector equipped with a fixed blade shown in FIG. 10 was used.

Here, the thicknesses of the respective portions are the positive electrode unfilled portion A = 0.79, the positive electrode filled portion B = 0.27, the negative electrode C = 0.19, and the separator D = 0.1. ). 0.79 = 1.2 × (0.27 + 0.19 + 2 × 0.1) (Formula 1)
After inserting the electrode group into the case, the negative electrode current collector is resistance-welded to the inner bottom of the case, the positive electrode current collector and the sealing plate are electrically connected using a lead, and an alkaline electrolyte is injected. A cylindrical nickel-metal hydride storage battery with a capacity of 6.5 Ah was formed by sealing with a sealing plate equipped with a safety valve. This is designated as battery A1.

(Battery B1)
A battery B1 is configured as the battery A1 except that the shape of the positive electrode current collector is as shown in FIG. 11 without a fixed blade.

(Batteries A0, A2-4, B0, B2-4)
The width of the unfilled portion is 5 mm, 3.5 mm, 3.0 mm, 2.5 mm, and this is folded back multiple times, and the average thickness of the unfilled portion is 0.92 mm, 0.73 mm, 0.66 mm, A filled positive electrode similar to the batteries A1 and B1 was prepared except that the thickness was 0.59 mm.

Here, the thickness of each part excluding the positive electrode unfilled portion is an unpositive electrode filled portion B = 0.27, a negative electrode C = 0.19, and a separator D = 0.1. Therefore, when the positive electrode unfilled portion A = 0.92, the relationship between the thicknesses of the respective portions was as shown in (Formula 2).
0.92 = 1.4 × (0.27 + 0.19 + 2 × 0.1) (Formula 2)
In the case where the positive electrode unfilled portion A = 0.73, the relationship between the thicknesses of the respective portions was as shown in (Formula 3). 0.73 = 1.1 × (0.27 + 0.19 + 2 × 0.1) (Formula 3)
In the case where the positive electrode unfilled portion A = 0.66, the relationship between the thicknesses of the respective portions was as shown in (Formula 4). 0.66 = 1.0 × (0.27 + 0.19 + 2 × 0.1) (Formula 4)
When the positive electrode unfilled portion A = 0.59, the relationship between the thicknesses of the respective portions was as shown in (Formula 5).
0.59 = 0.9 × (0.27 + 0.19 + 2 × 0.1) (Formula 5)
A battery A1 (A = 0.92) and A2 (A = A = A2) are constructed in the same manner as the battery A1 except that a positive electrode current collector with a fixed blade shown in FIG. 10 is welded to these electrode groups. 0.73), A3 (A = 0.66), and A4 (A = 0.59).

  Also, batteries B0 (A = 0.92) and B2 (A, respectively) having the same configuration as the battery B1 except that a positive electrode current collector without a fixed blade (see FIG. 11) was welded to these electrode groups. = 0.73), B3 (A = 0.66), and B4 (A = 0.59).

  However, in the batteries A0 and B0, when the electrode plate group was wound, the diameter of the unfilled portion was too large, and the electrode group deformed frequently when the case was inserted.

(Batteries R1, R2)
As shown in FIGS. 7 to 9, the positive electrode unfilled portion 13 is configured in the same manner as the battery R1 and the battery B1 except that the positive electrode unfilled portion 13 is simply compression molded without being folded repeatedly. This is battery R2.

  About each battery comprised as mentioned above, after charging at 20 degreeC 650mA for 16 hours, it discharged at 1300mA and confirmed nominal capacity. Both batteries had a capacity of 6500 mAh. Next, in order to measure the dynamic resistance of the battery, the battery was charged for 3 hours and 25 minutes at 20 ° C. and 2 A corresponding to 50% of the battery nominal capacity. It was 1.36V when it left still for 1 hour after charge and the voltage was measured. Each of these batteries was discharged at 15A, 30A, and 60A for 10 seconds, and the voltage at that time was measured. The duration between discharges for 10 seconds was 5 seconds.

  The dynamic resistance of this battery was determined from Ohm's law (IR = E). Here, I is current (A), R is dynamic resistance (generally called DC resistance), E is an open circuit voltage when standing in a charged state, and a closed circuit after 10 seconds. This is the difference in voltage, and the smaller the voltage drop when a current is passed, the smaller the DC resistance and the higher the output. The calculation results are shown in Table 1.

Each battery of the present invention (A0 to A3) as compared with batteries R1 to R2 and A4 that are not molded so that the unfilled portions are in contact with each other, and batteries B0 to B4 that are not provided with a fixed blade on the positive electrode current collector In this case, the unfilled parts are in contact with each other at the end face of the spiral electrode group, and the fixed blade of the positive electrode current collector bites into that part, so that the current collection and conductivity of the electrode plate are improved in each stage. As a result, the DC resistance can be reduced by nearly 20%, and the high-rate discharge characteristics are dramatically improved.

  What was comprised similarly to battery A0-A4 and battery B0-B4 including the thickness of each site | part except having pressure-molded the unfilled part like FIG. Are batteries Y0 to Y4. However, in the batteries X0 and Y0, when the electrode plate group was wound, the unfilled portion was bent up and down, and the unevenness of the end face of the group became conspicuous, and spark failure occurred frequently when welding the current collector.

  About each battery comprised as mentioned above, the same evaluation and calculation as Example 1 were performed. The results are shown in Table 2.

As in Example 1, the batteries R1 to R2 and X4 that are not molded so that the unfilled portions are in contact with each other, and the batteries Y0 to Y4 that do not have a fixed blade on the positive electrode current collector, In the batteries (X0 to X3), the unfilled portions are in contact with each other at the end face of the spiral electrode group, and the fixed blade of the positive electrode current collector bites into the portion, so that the current collecting property and conductivity of the electrode plate As a result, the DC resistance can be reduced by nearly 20%, and the high-rate discharge characteristics are dramatically improved.

  According to the present invention, since the DC resistance can be lowered, it can be applied as a battery such as an electric tool, an electric vehicle, a hybrid vehicle, or a backup power source that requires a large current discharge instantaneously, which requires a large current charge / discharge. it can.

The partial cross section figure which shows the structure of the alkaline storage battery in the Example of this invention The schematic perspective view which shows the positive electrode plate after the unfilling part shaping | molding in the Example of this invention. Sectional structure diagram showing the configuration of the electrode plate group in the embodiment of the present invention The partial cross section figure which shows the structure of the alkaline storage battery in the Example of this invention The schematic perspective view which shows the positive electrode plate after the unfilling part shaping | molding in the Example of this invention. Sectional structure diagram showing the configuration of the electrode plate group in the embodiment of the present invention Partial cross-sectional structure diagram showing the configuration of an alkaline storage battery in a conventional example Schematic perspective view showing the positive electrode plate after forming the unfilled portion in the conventional example Cross-sectional structure diagram showing configuration of electrode plate group in conventional example (A) Schematic perspective view before welding of configuration of electrode plate group and current collector with fixed blade in embodiment of the present invention (b) Schematic perspective view after welding (A) Structure of electrode plate group in conventional example and schematic perspective view before current collector welding (b) schematic perspective view after welding

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode active material filling part 2 Case 3 Negative electrode 4 Separator 5 Positive electrode collector 7 Sealing plate 8 Lead 9 Negative electrode collector 11, 12, 13 Unfilled part 14 Fixed blade

Claims (2)

A spiral electrode formed by winding a strip-like positive and negative electrode provided with an unfilled portion where no active material exists along at least one of the long sides through a separator, and welding a flat plate current collector to both end faces thereof An alkaline storage battery comprising a group,
At least one of the positive and negative electrode plates is a filled electrode having a three-dimensional metal porous body as a core material,
The unfilled portion of the filled electrode is molded so as to be in contact with each other at the end face of the spiral electrode group,
The alkaline storage battery, wherein the current collector is provided with a fixed blade on a surface welded to an end surface of the filling electrode. When the thickness of the unfilled part after the filling electrode molding is A, the thickness of the filling electrode filling part is B, the thickness of the other electrode is C, and the thickness of the separator is D, (B + C + 2D) ≦ A ≦ The alkaline storage battery according to claim 1, wherein a relationship of 1.2 × (B + C + 2D) is satisfied.