KR100462128B1 - Spirally-rolled electrodes with separator, the batteries therewith, and electrode for batteries - Google Patents

Abstract

An electrode group is fabricated by winding a cathode composed of a plurality of thin anode plates and / or a cathode composed of a plurality of thin cathode plates spirally with a separator interposed therebetween. Moreover, after inserting such an electrode group in a battery case and injecting electrolyte solution, the battery sealed with the cap is produced.

Description

Spirally-rolled electrodes with separator, the batteries therewith, and electrode for batteries}

The present invention relates to a reduction in battery capacity variation and an improvement in cycle life of secondary batteries composed of concentric or elliptic spiral electrode groups, particularly cylindrical sealed secondary batteries or square secondary batteries.

In recent years, in a relatively small battery, a spiral electrode that enables high-rate discharge by widening the opposing area of the positive electrode and the negative electrode, regardless of the conventional battery, button-type, or coin-shaped battery, regardless of the primary battery and the secondary battery. A group is employ | adopted a lot as an electrode structure method. However, a secondary battery is usually employed in applications requiring considerable high rate discharge, and the electrode group is composed of nickel / cadmium batteries (Ni / Cd batteries) and nickel-hydrogen batteries (Ni). / MH batteries) and lithium ion batteries (Li-ion batteries) are used in almost all cylindrical sealed batteries and square sealed batteries, accounting for more than 55% of Japan's total battery production. Therefore, hereinafter, a small secondary battery will be described as an example.

Many battery systems were naturally culled, and by 1990, battery systems representing industrial production-scale secondary batteries were condensed into lead-acid batteries and Ni / Cd batteries. In particular, the latter battery system is a small secondary battery power source, and the market has been remarkably expanded due to the rapid spread of portable electronic devices such as CDs and camcorders in the 1980s. The great reason is that Ni / Cd cells have a higher energy density than that of lead batteries, that is, they are small and suitable for weight reduction.

In the 1990s, however, higher energy density Ni / MH cells were developed, followed by lighter Li-ion cells, which began to enter the Ni / Cd cell market. In the form of these new battery systems, in the case of Ni / MH batteries, small cylindrical sealed batteries such as Ni / Cd batteries are mainstream, and Li-ion batteries are used in both small cylindrical sealed batteries and rectangular sealed batteries. have.

In addition to the above-mentioned consumer use, mobile power supply markets such as hybrid electric vehicle (HEV) and electric assist vehicle have been developed recently. Cylindrical sealed Ni / MH batteries, which are slightly larger than consumer use, but belong to small size, are mainly used. It started to be.

The electrode group structure of these cells is basically the same structure of Ni / Cd, Ni / MH and Li-ion cells, and the same structure. One thin rectangular plate anode and one thin rectangular plate anode are synthetic resins. It is an electrode group structure wound almost in a concentric circle with the separator interposed therebetween.

In the case of a rectangular sealed battery of a Li-ion battery, the same spiral electrode group structure is basically the same, but an elliptical spiral shape that is not concentric but rather flat is inserted, and a structure in which one is inserted into a closed rectangular case is generally used. I adopt it.

In addition, in the rectangular sealed battery of a Ni / Cd battery or a Ni / MH battery, a structure in which a plurality of plate-shaped positive electrodes are alternately stacked is employed, but this type has a small market share at present. That is, in the small secondary battery, it can be said that the spiral of the electrode group structure is mainstream regardless of the battery system.

In order to more specifically describe the prior art of such a spiral electrode group structure, an example of a small cylindrical hermetic Ni / MH battery will be described below.

Ni / MH batteries use nickel oxide powder (mainly nickel oxyhydroxide) for the positive electrode and hydrogen storage alloy powder such as MmNi _{5 for the} negative electrode as the active material and the semi-active material, respectively, and have a battery voltage of 1.2 V per cell. to be. Here, the semi-curable material is a material that electrochemically absorbs and releases hydrogen or lithium. The active material to be absorbed and released may be released as an active material as a result, and may be included as an active material in a semi-active material, or may be included as a compound of a material different from the active material.

These active materials and semi-rigid materials are generally used as one thin plate-shaped electrode, each of which is filled with a three-dimensional gas or a two-dimensional core material or is bound together with a binder and then press-molded as necessary. After the two electrodes were spirally wound with a nonwoven fabric made of polyolefin resin fibers imparting hydrophilicity, an electrode group was formed. Then, the electrode was inserted into a cylindrical metal case with one side closed, and an alkali electrolyte solution was injected therein. The gasket made of synthetic resin is used as a complete battery by blocking the inlet with a cap having a positive electrode terminal and a safety valve. In addition to the Ni / Cd battery and Li-ion battery, the battery has a battery capacity that is regulated by the charge and discharge capacity of the positive electrode. In other words, the variation in battery capacity cannot be denied in error due to a slight difference in the utilization rate of the active material, but almost corresponds to the variation in the weight of the active material charged or arrived at one positive electrode.

As described above, since the small-sized secondary battery was originally used for applications requiring high rate discharge, a spiral electrode group structure was needed. However, in recent Ni / MH batteries, the market for mobile power supplies requiring higher rate discharge is required. With the development of, the spiral electrode group structure using an extremely long electrode than the conventional one has attracted attention.

In this application, since the power supply voltage is used at a high voltage of several hundred volts, which is much higher than in the prior art, many cells are used in succession in the 1.2V battery. For example, in recent years, the HEV battery, which has been in recent years, is used in which 240 cells or 120 cells of a D-size cylindrical sealed Ni / MH battery are continuously connected.

In such a case, a battery having a small capacity not only regulates the overall battery capacity but also is susceptible to damage such as overdischarge and overcharge, and as a result, the capacity of the entire power supply may be reduced and the cycle life may be shortened. In particular, it can be said to be a fatal problem in such a use. Therefore, the small capacity variation between each battery used has become more important than ever in the reliability of the power supply.

For this reason, in the positive electrode which regulates battery capacity especially in a cylindrical sealed type Ni / MH battery, improvement of the following three items is examined in order to reduce the capacity | variation variation.

1. Improvement of method or apparatus for reducing variation in filling or arrival of active material powder.

2. Measure the weight of all electrodes and select electrodes of approximately equal weight.

3. Measure the discharge capacity of all batteries, and select batteries of approximately equal weight.

In addition, as described above, in this application, since a high rate discharge is required beyond conventional batteries, the positive electrode is used thinner than the conventional one. Because of this, the expansion of the positive electrode, which occurs as the charge and discharge are repeated, causes a part of the electrode group to be easily deformed in a concentric circle. In some cases, the risk of the electrode deforming part breaks through the separator and causes a new short circuit. did. In addition, such a risk is also a shape that can be seen in a Li-ion battery, in which electrode thinning is already progressing.

In short, in a Ni / MH battery or a Li-ion battery using a spiral electrode group structure, when the long electrode is used due to the thinning of the electrode, which is a means for miniaturizing and reducing the battery, it is necessary to expand the electrode due to charge and discharge. As a result, the spiral electrode group is remarkably deformed, and in some cases, the battery often causes fine short circuits.

However, in the first improvement to reduce the variation of the battery capacity, the quantitative filling or quantitative deposition per unit area of the active material powder based on Ni (OH) ₂ is considerably advanced, for example, the conventional ± 7 to 10 Although the% deviation decreased to about 3 to 5%, it is still insufficient for a HEV power supply that uses several hundred cells continuously. In the second improvement, the active material charge can be managed at a certain weight width by ranking according to the weight, the battery capacity can be managed at a certain width, but the variation of the overall capacity is still not reduced. In the third improvement, the accuracy is further increased by measuring the battery capacity in the same manner as the second improvement. However, obtaining the correct battery capacity requires many cycles of discharge amount and is cumbersome, and as with the second improvement above, the overall capacity variation still does not decrease. In addition, in the above-mentioned prevention of fine short circuits, no new measures for solving fine short circuits have yet been reported.

MEANS TO SOLVE THE PROBLEM This invention solves the said subject, Comprising: It is the battery provided with the spiral electrode group which has very small capacitance deviation, and can suppress a micro short circuit, and this spiral electrode group, The hybrid electricity which uses several hundred batteries connected continuously is used. It is an object of the present invention to provide a secondary battery having a very high reliability and a long lifespan for a high reliability of a power supply used for a mobile power source such as an automobile (HEV).

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the electrode group for cylindrical sealed type Ni / MH batteries which concerns on one Embodiment of this invention.

2 is a configuration diagram of an electrode group for a cylindrical hermetic Ni / MH battery according to one embodiment of the present invention.

3A is two nickel positive electrode plates for a cylindrical hermetic Ni / MH battery according to one embodiment of the present invention.

3B is two nickel positive electrode plates for a cylindrical hermetic Ni / MH battery according to one embodiment of the present invention.

4 is a cross-sectional view of an electrode group for a cylindrical hermetically sealed Ni / MH battery using the nickel positive electrode plate shown in FIG. 3B which is one embodiment of the present invention.

5 is a configuration diagram of a cylindrical sealed Ni / MH battery according to one embodiment of the present invention.

6A is a view showing a discharge capacity distribution of 500 cells of an example battery.

6B is a view showing a weight distribution of a positive electrode used in an example battery 500 cells.

7 shows an ironing-drawing machining process.

8 is an enlarged cross-sectional view of a battery case manufactured by an ironing-drawing process.

9 is an electrode plate subjected to 1C chamfering.

10 is a partially enlarged perspective view of a metal thin plate that is a base.

11 is a plan view of a metal thin plate that is a substrate.

FIG. 12 is a conceptual view of unevenness of the metal thin plate that is a substrate in the AB section of FIG.

13A shows two nickel positive plates provided with sheet-like materials.

13B shows two nickel positive plates provided with sheet-like materials.

<Description of the symbols for the main parts of the drawings>

1: anode

1-a: One of two anodes

1-b: One of two anodes

2: cathode

2-a: one of two cathodes

2-b: one of two cathodes

3: The separator which consists of a nonwoven fabric of polypropylene fiber.

4: bipolar plate lead

4 ': positive plate lead

5: negative plate lead

6: current collector metal plate of positive electrode plate

6 ': current collector metal plate of negative electrode plate

7: positive lead terminal

7 ': negative lead terminal

8: positive terminal

9: rubber valve body

10: nylon gasket

11: metal case

12: spindle

13: bottom cylinder

14: Mold

15: electrical case side wall surface

16: battery case bottom

17 metal foil

18: convex portion

19: recess

20: hole

21: trailing edge of the electrode of the winding start side

22: shear edge of the electrode close to

23: sheet shape

24: sheet shape

R: thickness

The present invention relates to a battery assembly for a battery in which a positive electrode and a negative electrode are spirally wound around a separator, wherein the positive electrode and / or the negative electrode are constituted by a combination of a plurality of electrode plates. And / or each of the combinations in the negative electrode is configured such that the total weight of the active material or the quasi-active material as the main material is almost constant, and each electrode plate of the plurality of electrodes is successively wound at intervals and wound around the battery electrode group. By employing, these problems are solved simultaneously.

Continuing the description with the cylindrical sealed Ni / MH battery as an example, at least the positive electrode for regulating the battery capacity of the battery adopts a constitution method in which a plurality of positive electrode plates are used successively (continuously). Among them, the weight sum of the plurality of positive electrode plates is adjusted to a constant value, and the amount of active material of each battery is adjusted to suppress the variation in battery capacity, and also to decrease the distance between each positive electrode plate when winding successively. Absorbs deformation of the electrode group due to electrode expansion due to repetition.

As a result, a capacity deviation between the cells can be extremely reduced, and at the same time, a cylindrical sealed Ni / MH battery in which fine short circuits are unlikely to occur can be obtained. In addition, the cylindrical battery case has a bottom thickness (t ₂ ) with respect to the side wall thickness (t ₁ ). By using a battery case having a ratio (t ₁ / t ₂ ) of 1.5 or more, i.e., a case having a thin sidewall surface, with the electrode group, especially when used in a mobile power supply, it has a great effect on weight reduction and high capacity. will be. In addition, by reducing the capacity deviation, there is a margin in capacity balance between the positive electrode and the negative electrode generated at the battery design stage, and as a result, a high capacity cylindrical sealed Ni / MH battery can be obtained.

Although this invention is not specifically limited to Ni / MH battery, Embodiment of this invention is described, referring a figure as an example of a cylindrical sealed type Ni / MH battery.

In the cylindrical sealed Ni / MH battery, as shown in FIG. 5, the plate-shaped anode 1 and the thinner plate-shaped cathode 2, which generally have a thickness of less than 1 mm, are made of synthetic resin fibers. It is wound in a spiral with the interposed between and inserted into the metal case (11).

Next, after the alkaline electrolyte is injected into this electrode group, the inlet is sealed through the gasket 10 by the cap. The cap also serves as a positive electrode terminal 8, and is provided with a safety valve 9 for extracting gas when the battery internal pressure rises abnormally.

Typically, an electrode group consisting of one positive electrode, one negative electrode, and a separator includes two positive electrode plates 1-a and 1-b and two negative electrode plates 2-a and 2, as shown in FIG. 1 or 2 in the present invention. -b is wound in a spiral in series with each separator 3 in between.

Prior to this electrode group configuration, each of the two electrodes is selected and combined such that the weight is close to a substantially constant weight, that is, an average weight value. In addition, appropriate intervals y and x are formed between the two positive electrode plates constituting the positive electrode and the two negative electrode plates constituting the negative electrode. At this time, it is preferable that a substantially constant weight exists in the range of +/- 1 weight%.

Such a positive electrode and a negative electrode can adjust the weight of each electrode close to the average value, that is, the total weight of the active material and the smoothing material can be adjusted to a predetermined value, so that the battery capacity of each battery is very well matched. In addition, as described above, the expansion, ie, elongation, of the electrode caused by repetition of charge and discharge causes a significant deformation in the spiral electrode group using a thin positive anode, and in some cases, a fine short circuit. In some cases, deformation can be absorbed by forming the interval y or x between the electrode plates as in the present invention, and this problem can be largely suppressed.

In the above, an example of a cylindrical sealed Ni / MH battery, for example, has been described with two positive electrodes and two negative electrodes. However, as described above, only a plurality of positive electrodes for regulating battery capacity may be used, or both positive electrodes may be used. good. In addition, theoretically equivalent effects can be expected in Li-ion batteries that already employ very thin anodes.

In the positive electrode and the negative electrode of the battery electrode group of the present invention, at least two corners (corners) of the plurality of electrode plates constituting the positive electrode and the negative electrode are chamfered. It is preferable that four corners which are all corners of an electrode plate are chamfered more preferably. Two corners of the electrode plate are chamfered. When the two corners of the electrode plate are chamfered, it is preferable that the two corners on the side corresponding to the adjacent electrodes are chamfered at appropriate intervals, but the entire sides of the electrode plates facing each other in a circular shape or an ellipse shape. You may cut. In the case where at least two corners of each of the plurality of electrode plates constituting the positive electrode and the negative electrode are chamfered, the electrode plate is elongated according to repetition of charge and discharge, so that the substrate in the electrode plate, that is, the metal porous plate or the metal thin plate. This is because the corners of the chip may be inserted into the separator or torn. Although the chamfering process is not particularly limited, the 1C chamfering process, which is a process of which the radius of curvature is 1 mm according to a known method, is performed in view of the balance between the prevention of chipping or tearing and the ease of processing. Is preferable when.

Although it demonstrated also above, each electrode plate of the electrode comprised from the some in this invention is wound one after another by the other electrode plate spaced apart in the winding direction with respect to one electrode plate. The interval must set the distance at which the electrode plate is not able to rise further by contacting the adjacent electrode plate according to the elongation according to repetition of charge and discharge. Since this interval is determined by the material of the active material used, the packing density, the gas strength (thickness of the metal thin plate), the length of the electrode plate winding direction, etc., it is difficult to limit the numerical value, but the active material material is 10 to 20%. In the general case of expansion, it is generally 1 to 5% of the length of the electrode plate. If it is narrower than 1%, it is not preferable because it causes deformation such as rising more after contact with the adjacent electrode, and there is a risk of fine short circuiting. If it is larger than 5%, the active material is markedly reduced to decrease the battery capacity. It is a problem. In the cylindrical sealed Ni / MH battery, it is preferable that the positive electrode and the negative electrode are 1.0 to 5.0 mm in the case of the thin nickel positive electrode and the thin metal hydride negative electrode.

The positive electrode and the negative electrode of the battery electrode group of the present invention are wound in a spiral concentric or elliptical shape with a separator interposed therebetween, and may be wound substantially as a concentric circle or an ellipse, and do not need to be completely wound in a concentric circle or an ellipse.

In the positive electrode and / or negative electrode constituting the battery electrode group of the present invention, the thickness of the electrode plate is 0.5 mm or less. It is desirable to be located near the center of the. FIG. 10 is a partially enlarged perspective view of a substrate made of a metal thin plate formed by forming anhydrous fine uneven parts. The convex part 18 and the recessed part 19 are formed in the metal thin plate 17. FIG. Fig. 11 is a partially enlarged plan view when a myriad of metal thin plates formed by forming a myriad of fine uneven parts is observed from one side direction. 11, the convex part 18 and the recessed part 19 are formed in the metal thin plate 17, and the hole 20 is formed in each. In particular, since the substrate constituting the electrode plate is a substrate made of a metal thin plate formed by forming a number of fine uneven portions, it is not limited to the nickel anode, but it is a nickel anode for an alkaline storage battery, especially a thin electrode having a thickness of 500 μm or less. When used for nickel anodes, an electrode using an inexpensive and lightweight conductive electrode body that can be processed by mechanical operation without sintering or plating can be obtained, and also has excellent charge / discharge characteristics and integrity of active material powder, etc. Since it is excellent, it is possible to obtain a cylindrical hermetic and square nickel-hydrogen storage battery (Ni / MH battery) which is inexpensive, lightweight, has excellent high rate discharge characteristics, and has a long service life. FIG. 12 is a conceptual diagram of the irregularities of the metal thin plate 17 in the AB section of FIG. 11. The convex portion 18 and the concave portion 19 are preferably 200 mu m or less from the center of the thickness direction of the metal thin plate because of excellent discharge characteristics. The convex portion and the concave portion, It is preferable to have a thickness of 200 µm or less because the current collecting capability of the entire electrode can be increased.

The metal thin plate is not particularly limited as long as it is a thin metal plate that can be used as a substrate of the electrode. However, the metal thin plate is treated using a metal plate in which fine particles are collided, a metal plate processed using a metal mold having irregularities, and an electrolytic metal deposition method. Any one of the metal sheets obtained by colliding fine particles with a metal thin plate obtained by electrolytic deposition of unevenness, or a metal thin plate processed by using a metal mold provided with unevenness, or a metal thin plate electrolytically precipitated by numerous metal irregularities by electrolytic metal deposition. Preference is given to using.

In the case of using a metal thin plate in which fine particles collide with each other, the metal thin plate is not particularly limited as long as it can collide the fine particles with the metal thin plate to form anhydrous fine irregularities on the metal thin plate. The method of blowing out fine particles having an average particle diameter of 1 to 50 μm into the thin plate by compressed air (blasting method) is easy to form a myriad of fine hollow irregularities in the metal thin plate, and a new metal surface appears to be annealed. It is preferable because there is no need. Although the fine particles are not particularly limited, hollow fine irregularities can be easily formed on the metal thin plate by using hard fine particles represented by metal oxides such as aluminum oxide or zirconium oxide, glass beads, or the like. Especially, it is especially preferable to use aluminum oxide powder. Although it does not specifically limit as a method of making the said microparticles collide with a metal foil, It is preferable to use the method (blast method) which blows out microparticles | fine-particles using the compressed air of 2.5-6 atmospheres of air pressure using a well-known blast apparatus. At this time, although fine particles may be blown out on one side of the metal thin plate, it is preferable to blow out fine particles on both sides, since it is easy to form irregularities.

When using the metal thin plate processed using the metal mold | die provided with an unevenness | corrugation as said metal thin plate, a nickel foil of 20-50 micrometers in thickness can be provided in which the myriad unevenness | corrugation is almost alternately alternately interlocked in the upper and lower metal mold | die, and can be engaged. It is preferable to obtain a three-dimensionally conductive electrode base by pressurizing between the molds because of ease of operation. In addition, when using the metal thin plate which electrolytically deposited innumerable unevenness | corrugation by the electrolytic metal precipitation method as the said metal thin plate, since it is inexpensive and easy to manufacture, the said electroconductive electrode base body can also be obtained by the electrolytic metal precipitation method. For example, in a conventional electrolytic cell in which an aqueous solution of pH 2.0 mainly containing nickel sulfate is preserved, a nickel gas having a thickness of 20 µm having a myriad of irregularities on the surface of a cathode can be obtained by electrolytic precipitation. This nickel gas can also be obtained as a long continuous foil having numerous irregularities on the surface by using a rotary drum having irregularities on the surface of the cathode. Usually, the nickel gas is usually obtained as an electrode gas after annealing at about 850 ° C. to obtain mechanical strength. In addition, fine fine irregularities are sufficiently formed on the hollow uneven surface again by colliding fine particles again to the metal thin plate treated using a mold having unevenness, or to a thin metal plate electrolytically precipitated with countless unevenness by the electrolytic metal precipitation method. It is also possible to obtain a metal thin plate having improved adhesion to the active material powder and the like.

The metal thin plate constitutes a positive electrode and / or a negative electrode of the electrode group for batteries of the present invention as a base, but in the electrode in which the metal thin plate is used as a base, the metal thin plate is preferably disposed near the center of the electrode in the thickness direction. In addition, the positive electrode and the negative electrode are preferably 0.5 mm or less because the high rate discharge characteristics are improved.

Each electrode plate of an electrode composed of a combination of a plurality of electrode plates in the battery electrode group of the present invention may be combined so that the total weight of the active material or the semi-active material is almost constant, and is limited to the case where the shapes of the electrode plates are the same. However, it is preferable that the area of the electrode plates is the same in each of the electrodes. The reason for this is that when each electrode plate is the same area, all the electrode plates enter one normal distribution, which facilitates the selective combination of the light and heavy electrodes, but conversely, when the area is different, two or more normal distributions are achieved. This is because the weight fitting becomes cumbersome.

13A and 13B, the battery electrode group of the present invention has a resin film, porous material on the surface of the rear end portion 21 of the electrode at least on the side of winding and the front edge portion 22 of the electrode next to the electrode. The sheet-like article 23 or the sheet-like article 24 selected from the group consisting of a resin film, a woven fabric and a nonwoven fabric may be disposed. Since the electrodes of the positive electrode and the negative electrode are expanded and stretched in accordance with the repetition of charging and discharging, a minute short circuit is likely to occur because a part of the electrode substrate protrudes and breaks the separator. In the electrode substrate constituting the electrode of the battery electrode group, the breakage of the separator by the electrode substrate is provided by disposing the sheet shape on the surface of the rear end side of the electrode on the winding start side and the front edge side of the electrode close to it. Can be easily prevented. The sheet-like article is preferably a sheet-shaped material selected from the group consisting of a resin film, a porous resin film, a woven fabric and a nonwoven fabric because it can easily prevent the breakthrough. It is preferable to use a polyolefin resin film as the resin film. As the porous resin film, it is preferable to use a porous polyolefin resin film subjected to hydrophilic treatment, and as a woven fabric, it is preferable to use a thin polyamide woven fabric, and as the nonwoven fabric, it is preferable to use a thin polyolefin-based or polyamide-based nonwoven fabric. . As shown in FIG. 13A, the sheet-like article may be divided into two and formed into an electrode plate 1-a and an electrode plate 1-b, respectively, but as shown in FIG. The rear edge 21 and the front edge 22 of 1-a and the electrode plate 1-b may be simultaneously covered with one sheet-like material. Furthermore, although the sheet-like thing is clearly shown to be arrange | positioned at the surface of the electrode plate 1-a and the electrode plate 1-b in FIG. 13, it is also arrange | positioned at the back surface.

The battery electrode group of the present invention is an almost concentric battery electrode group in which a thin nickel positive electrode and a thin metal hydride negative electrode are spirally wound with a separator interposed therebetween, wherein the thin nickel positive electrode is sequentially wound on a plurality of positive electrode plates, The thin metal hydride negative electrode is sequentially wound with one or a plurality of negative electrode plates, so that the sum of the active material weight and / or the weight of the semi-active material of each electrode plate in an electrode composed of a plurality of electrode plates is maintained at a substantially constant value. A plurality of electrode plates are combined, and the plurality of electrode plates in the electrode composed of the plurality of electrode plates are wound in succession at intervals, and the thicknesses of the electrodes on the side starting from the plurality of electrode plates of the electrode composed of the plurality of electrode plates are different. It is thinner than the electrode of the wound side, As a battery electrode group It can be applied to the form.

In the above-described aspect of the battery electrode group of the present invention, the thickness of the electrode on the side of the winding start of each of the plurality of electrode plates is thinner than the electrode on the side of the winding, whereby the polarization radius of the winding occurs at the portion where the winding starts. Since the crack of the electrode which can be easily controlled can be controlled and relatively many conductive electrode bodies are contained, heat radiation can be reduced, which is preferable.

The present invention provides a secondary battery in which the battery electrode group is sealed in a battery case, and the positive lead and the sealing plate are connected by a method such as spot welding, and then the sealing plate is sealed by a caulking method at the opening of the battery case. It is about.

The secondary battery in the present invention can be obtained by encapsulating the battery electrode group of the present invention in a container of a battery case having a desired outline size such as D, C, AA, AAA, AAAA, or the like.

In the battery case of the secondary battery of the present invention, when the secondary battery of the present invention is used for applications requiring high capacity and weight reduction, such as HEV batteries, the thickness of the bottom portion with respect to the thickness t ₁ of the side wall surface is used. (t ₂₎ ratio (t ₂ / t ₁₎ of 1.5 or more preferable to use light weight battery case, and also preventing cracks caused by spot welding to the pressure resistance of the side wall to afford and bottom portion of the container of More preferably, the ratio t ₁ / t ₂ of the thickness t ₂ of the bottom portion to the thickness t ₁ of the side wall surface is about 2.0 from the viewpoint of making it more certain. When the secondary battery of the present invention is used for a HEV battery or the like, the positive terminal of another secondary battery adjacent to the bottom of the battery case of the secondary battery is connected by welding or through a metallic connector, depending on the usage. Therefore, the bottom of the battery case is not deformed or dissolved, and a thickness capable of withstanding spot welding with the above-mentioned inter-cell connection connector is required, so that the thickness of the bottom portion with respect to the thickness t ₁ of the side wall surface in the battery case is required. (t ₂₎ the ratio (t ₂ / t ₁₎ the by 1.5 or more, the side wall of the battery case has a thickness and the bottom thickness of the substantially compared to the same conventional battery case, which can withstand the bottom of the thickness of the spot welding By securing the thickness and thinning the side wall surface, it is possible to reduce the battery case by about 30% without changing the material, and at the same time increase the inner volume. High capacity of the secondary battery is possible. In addition, the welding is a known welding method, the welding temperature of the spot welding portion is performed in the range of 1000 to 3000 ℃.

In the secondary battery according to the present invention, when used in a battery case of AAAA size in which the ratio (t ₂ / t ₁ ) of the thickness t ₂ of the bottom portion to the thickness t ₁ of the side wall surface is 1.5 or more. In case of using a battery case (t ₂ / t ₁ = 182) having a thickness of 0.2 mm at the bottom and a thickness of 0.11 mm at the side wall, the thickness of the bottom is about 0.2 mm and the thickness of the side wall at about 0.2 mm is the same material. It is possible to improve the battery capacity by about 5% as compared with the case where a battery case ((t ₂ / t ₁ = 1) of mm is used.

The material of the battery case of the secondary battery of the present invention is not particularly limited, but in the alkaline storage battery, nickel plating is applied to iron in view of electrolytic solution resistance, and in lithium secondary batteries, in order to reduce weight in addition to iron, Preference is given to using aluminum or aluminum alloys.

The battery case can be manufactured by a known method such as a deep drawing process, but the side wall surface is made thin so that the ratio of the thickness t ₂ of the bottom portion to the thickness t ₁ of the side wall surface (t ₂ / It is preferable to produce by ironing-drawing processing in order to form t ₁ ) of 1.5 or more. When manufacturing a deep drawing process in which the battery case is divided into several times to get closer to the desired battery case shape, the thickness of the bottom portion and the side wall surface is generally the same, but the ironing-drawing process is performed by using a single metal member. Since the bottomed cylindrical container is formed by extrusion processing by the spindle, the battery case can be easily formed into a battery case having a desired side wall thickness by adjusting the distance between the spindle and the mold.

In the battery case of the secondary battery of the present invention, it is preferable that a thickness portion is formed inside the battery case along the boundary between the side surface of the battery case and the bottom portion in order to ensure mechanical strength. In the portion indicated by R in FIG. 8, the outer portion of the tip of the spindle used for fabricating the battery case is chamfered to easily form the thickness portion of the corresponding battery case. Although a slight chamfered spindle is used, the effect is obtained. However, in the case of AA size battery case, 1C chamfering is appropriate without causing a decrease in battery capacity.

The ratio of the present invention secondary battery by using the electrode to reduce the weight of the battery, but the side wall is very thin, the thickness of the side wall of the bottom thickness (t ₁₎ portion (t ₂₎ at (t ₂ By using a battery case having / t ₁ ) of 1.5 or more, a lighter secondary battery can be provided.

Hereinafter, specific examples of the present invention will be described.

(Preparation Example of Electrode Paste)

3 parts by weight and 2 parts by weight of cobalt oxide and zinc oxide were added to commercially available spherical nickel hydroxide powders (100 parts by weight) in which cobalt and zinc were dissolved in 1 wt% and 3 wt% as solid solutions. 25 wt% of the aqueous solution which melt | dissolved 0.5 wt% of carboxymethyl cellulose and 0.1 wt% of polyvinyl alcohols was added to this mixture, and knead | mixed, and the paste for nickel positive electrodes was obtained.

(Production example of a battery case)

As Production Example 1, as shown in Fig. 7, a nickel-plated steel sheet (plating thickness of 1 μm) having a thickness of about 0.3 mm was formed by ironing-drawing once by a known spindle 12. The bottomed cylindrical container 13 which is C size formed according to the (drawing) process was obtained. Specifically, the outer diameter is 25mm, side thickness 0.19mm, and bottom thickness 0.3mm. In addition, in order to suppress the decrease in the physical strength of the boundary between the side and the bottom portion, it is preferable to form the thickness portion R inside the boundary.

As Production Example 2, a bottomed cylindrical AA size battery case was obtained in the same manner as in Production Example 1, except that a nickel plated steel sheet (plating thickness of 1 μm) having a thickness of about 0.25 mm was formed in a circle. Specifically, the outer diameter is 14 mm, the side thickness is 0.16 mm, and the bottom thickness is 0.25 mm.

(Example 1)

A commercially available foamed nickel porous body, in which a nickel foil was welded to one edge in the longitudinal direction in advance, was filled with the same paste as in Example 1, and then pressed after drying to obtain a thickness of 0.4 mm as shown in Fig. 3A, A positive electrode plate having a width of 40 mm and a length of 230 mm was obtained. Next, the weights of all of the positive electrode plates were measured, classified by weight in eight stages, and two positive electrode plates were selected so as to be close to the weight average value, to form a battery positive electrode.

The electrode group shown in FIG. 1 was formed between this anode and a polypropylene nonwoven fabric having a hydrophilic treatment of a metal hydride cathode having a thickness of 0.25 mm, a width of 40 mm, and a length of 580 mm using a general-purpose MmNi _5- based alloy. did. At the time of winding, as shown by y in the figure, the two positive plates were formed in a spiral with a spacing of 3 mm. In addition, although the negative electrode also shows the example comprised from two electrode plates in FIG. 1, in this Example 1, it was set as one negative electrode. At this time, as shown in FIG. 4, the nickel foil 4 'provided in the anode 1 protrudes from the separator 3, and the donut-shaped metal plate 6 which cut out the lead terminal 7 welded to a cap is carried out. ) Is welded. Therefore, the two positive plates have a structure leading to the metal plate at a plurality of welding points, and the impedance is greatly reduced.

Here, all the weight distributions of 300 test plates of 300 positive plates 10 times were almost normally distributed, with a deviation of ± 7% in the range of ± 3σ. Among the positive electrodes, each of which was separated into eight stages to be closer to the average value, by measuring 500 trillion weights randomly, as shown in FIG. 6B, it was possible to suppress the distribution within ± 1% from the average value.

This electrode group was inserted into a case for the C-sized cylindrical hermetically sealed battery prepared in Production Example 1, and the aqueous solution of about 30wt% KOH was poured into and sealed to prepare a C-sized cylindrical hermetically sealed Ni / MH battery shown in FIG. Then, 500 cells of this C-size battery were charged with 120% of the theoretical capacity 4500mAh of the positive electrode at 0.1C, discharged from 0.5C to 1.0V, then charged again to 0.5C / 120%, and discharged to 1.0C / 1.0V. The discharge capacity distribution at the time of repeating 2 cycles is shown in FIG. As a result, the battery capacity could be suppressed to within ± 1.5%. In the case of a general-purpose (widely used) battery that does not use two positive electrodes, it can be seen that the deviation can be greatly reduced because the deviation is about ± 8%.

In Comparative Example 1, the electrode group was constituted in the same manner as in Example 1 except that the distance between the two positive plates was 0.5 mm. As Comparative Example 2, an electrode group was constructed in the same manner as in Example 1 except that the distance between the two positive plates was 1 mm. In addition, except having used one anode, it carried out similarly to Example 1, and comprised the electrode group, and it was set as the comparative example 3.

In the electrode groups of Example 1 and Comparative Examples 1 to 3, the electrode group was inserted into a case of the C-cylindrical sealed battery manufactured in Production Example 1, and about 30 wt% of KOH aqueous solution was injected after sealing and sealed. A cylindrical sealed Ni / MH battery of size C shown in 5 was fabricated, and each 100 cell was charged at 1C for 15 hours, and after 1 hour of rest, the cycle of discharging the 1C battery pressure to 1.0 V was repeated until a set cycle. A charge and discharge cycle test was conducted.

In Example 1 and Comparative Examples 1 to 3, Example 1 when the gap between the positive electrode plates is 3 mm, and Comparative Example 1 when the distance between the positive electrode plates is 0.5 mm is m and the distance between the positive electrode plates is 1 mm. The result is shown in Table 1 using the comparative example 3 which is the case where Example 2 uses n and one positive electrode as o. In addition, in the sum total number column of Table 1, it shows that a molecule totaled the number of paragraphs of each setting cycle, and the denominator shows the sum of the number of test cells used for the cycle test.

Set cycle number of charge / discharge cycle test Short circuit sum 100 200 300 400 500 One 0 0 0 0 0 0/500 m 0 0 0 0 One 1/500 n One 2 One 4 8 16/500 o One One 3 6 9 18/500

As a result, it can be seen that the effect of significantly reducing the fine short circuit even at intervals of 1mm, when 3mm apart can not see the fine short circuit at all after 500 cycles, all 500 cells were able to withstand normal charging and discharging. As described above, it can be said that the local deformation of the spiral electrode group was alleviated as a result of the absorption of the elongation of the electrode due to the charge / discharge due to the decrease of almost 3 mm interval after 500 cycles of charge and discharge. . Therefore, although it can be predicted that the same effect can be obtained even if the space | interval is further extended, about 5 mm or less is preferable, since the battery capacity decreases with increasing space | interval.

In this embodiment, the positive electrode is composed of two positive electrode plates, but except for the troublesome problem of weak angles, the larger the number, the more the deviation can be reduced, and also the propagation of the spiral electrode group can be reduced. . This means that as the number of negative electrodes also increases, the variation in capacity of the battery can be further reduced.

In addition, when the thickness of the nickel positive electrode plate on the winding start side is thinner than the winding end side, it is preferable because cracks occurring at the winding start portion with a small radius radius can be suppressed and are easy to wind concentrically.

In addition, by adopting the same method of construction of the electrode group as in the present embodiment, the capacity ratio of the positive electrode in the battery design does not require a large margin as in a conventional battery, and a space in the battery can be spared. It is possible to increase the battery capacity.

Also, in the same manner as in the present embodiment, the variation in battery capacity can be adapted to a Li-ion battery that uses an ultra-thin electrode one by one in advance, and the gap formed between the electrode plates is a general-purpose Li-ion battery. It can be said that the effect of reducing the deformation of the spiral electrode group can be seen in

(Example 2)

A commercially available foamed nickel porous body in which a nickel lead is welded in advance is filled with a paste according to the preparation example, and then pressurized after drying to obtain a thickness of about 0.4 mm, a width of about 40 mm, and a length of about as shown in FIG. 3B. A 75 mm positive plate was obtained.

Next, the weight of the whole positive electrode plate was measured, the weight was separated by eight stages, and the two positive electrode plates were selected so as to be close to the weight average value to obtain a battery positive electrode.

As shown in Fig. 2, a polypropylene nonwoven fabric having a hydrophilicity is provided between the anode and one metal hydride cathode having a thickness of about 0.25 mm, a width of about 40 mm, and a thickness of about 200 mm using a general-purpose MmNi _5- based alloy. The electrode group was comprised. At the time of winding, as shown by y in the figure, the two positive plates were spirally formed with a gap of 3 mm. In addition, although the negative electrode also shows the example which consists of two electrode plates in FIG. 2, in this Example 2, it was set as one negative electrode.

The electrode group in Example 2 was inserted into a case for the AA size cylindrical sealed battery manufactured in Production Example 2, and the aqueous solution of about 30 wt /% KOH was poured into and sealed, and the AA size cylindrical sealed type shown in FIG. Ni / MH was obtained. In this case as well, similarly to Example 1, the capacity variation between the batteries was very small and the capacity variation of 500 cells was within ± 1.5%. There was also the effect of preventing fine short circuits.

In addition, when the positive electrode is composed of a plurality of positive electrode plates and the negative electrode is composed of a plurality of negative electrode plates, it is slightly troublesome, but the effect is smaller, as in Example 1, and the deformation of the spiral electrode group can be reduced.

As described above, according to the present invention, a Ni / MH battery having a spiral electrode group or the like may have a very small capacity variation between batteries, and as a result, the average capacity may be increased, and the charge / discharge cycle may be repeated. The occurrence of minute short circuits can be prevented, and a lightweight secondary battery suitable for a mobile power source such as a hybrid electric vehicle (HEV) or an electric assist bicycle can be provided.

Claims (16)

In a concentric or elliptic battery electrode group in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween, (1) the positive electrode and / or the negative electrode is configured according to a combination of a plurality of electrode plates selected from electrode plates classified by weight after measuring the weight of the electrode plate; (2) each of the combinations in the positive electrode and / or the negative electrode is configured such that the total weight of the active material or the smooth material, which is the main material, becomes almost constant; (3) A spiral electrode group for batteries, characterized in that each electrode plate of a plurality of electrodes is wound in succession at intervals. The method of claim 1, The positive electrode and / or the negative electrode, (a) the electrode plate has a thickness of 0.5 mm or less; (b) A spiral electrode group for a battery, wherein a substrate made of a metal thin plate which is formed three-dimensionally by forming a myriad of fine uneven parts is provided at almost the center of the thickness direction of the electrode plate. According to claim 2, wherein the three-dimensional metal thin plate, (m) a metal sheet in which fine particles are collided, (n) a metal sheet which is formed by unevenness by pressurizing between unevenly opposed molds or by pressing between dies; (o) a metal sheet obtained by electrolytic deposition of innumerable irregularities by the electrolytic metal deposition method, or (p) Metals obtained by colliding fine particles with metal foils which are pressurized between molds with concave-convex convexities or by passing through the molds while forming concavities and convexities, or metal foils with electrolytic deposition of innumerable concavities and convexities by an electrolytic metal deposition method. The spiral electrode group for batteries which is any one of thin plates. 3. The battery spiral electrode group according to claim 2, wherein the metal thin plate contains nickel (Ni), copper (Cu), aluminum (Al) or a compound containing these metals as a main component. The sheet-shaped material selected from the group consisting of a resin film, a porous resin film, a woven fabric, and a nonwoven fabric is installed on at least the rear edge portion of the electrode before the start of winding and the front edge portion of the electrode close to it. Spiral electrode group for batteries, characterized in that. 2. The battery spiral electrode group according to claim 1, wherein each of the plurality of electrode plates constituting the positive electrode and / or the negative electrode has a lead terminal or a terminal corresponding to the lead terminal. The electrode according to claim 1, wherein at least each of the electrodes constituting the positive electrode and / or the negative electrode is separated into both sides extending along an end edge of the winding direction, and the active material or the softening material of the positive electrode or the negative electrode is removed. A spiral electrode group for batteries, wherein a core material is exposed beyond the separator. A thin nickel positive electrode and a thin metal hydride negative electrode are almost concentric circular battery electrode groups wound around a separator, (1) the thin nickel anode is wound by successively winding a plurality of positive electrode plates; (2) the thin metal hydride cathode is wound by successively winding one or a plurality of negative electrode plates; (3) in the electrode composed of the plurality of electrode plates, the plurality of electrode plates are combined so as to keep the sum of the weights of the active materials and / or the smooth material of each electrode at a substantially constant value, (4) in the electrode consisting of a plurality of electrode plates are wound in succession with a plurality of electrode plates, (5) A spiral electrode group for batteries, characterized in that the electrode thickness before the winding of the plurality of electrode plates in the electrode composed of the plurality of electrode plates is thinner than the electrode on the wound side. The battery spiral electrode group according to claim 8, wherein at least two corners (corners) of each of the plurality of electrode plates constituting the positive electrode and the negative electrode are chamfered. 9. The spiral electrode group for batteries according to claim 8, wherein a spacing of the plurality of electrode plates constituting the positive electrode and the negative electrode is in a range of 1.0 to 5.0 mm in the electrode group configuration. 9. The spiral electrode group for a battery according to claim 8, wherein the plurality of electrodes constituting the positive electrode and / or the plurality of electrodes constituting the negative electrode each have substantially the same area. A secondary battery in which a positive electrode and a negative electrode are spirally wound in a battery case with a concentric or elliptical battery electrode group wound around a separator. The electrode group for batteries, (1) The said positive electrode and / or the said negative electrode are comprised by the combination of the several electrode plate classified by the weight after measuring the weight of an electrode plate, (2) each of the combinations in the positive electrode and / or the negative electrode is configured such that the total weight of the active material or the smooth material, which is the main material of the electrode plate, becomes almost constant; (3) A secondary battery characterized in that various electrode plates in an electrode composed of a plurality of electrodes are wound successively at intervals. The method of claim 12, wherein the battery case has a thickness to withstand the thickness of the bottom portion (t ₂₎ welding, side ratio (t ₂ / t of the thickness (t ₂₎ of the bottom portion of the thickness (t ₁₎ of the wall _A secondary battery, characterized in that ₁ ) is 1.5 or more. The secondary battery according to claim 12, wherein a thickness portion is formed inside the battery case at a boundary between the side wall surface of the battery case and the bottom portion. The secondary battery according to claim 12, wherein the positive terminal of the adjacent secondary battery is welded directly or through a metal connector to the bottom of the battery case. As a positive electrode and / or negative electrode for a battery, (a) the electrode plate has a thickness of 0.5 mm or less; (b) a substrate made of a three-dimensional metal thin plate is formed in almost the center of the thickness direction of the electrode plate, forming a myriad of fine irregularities; The three-dimensional metal thin plate is (m) a metal sheet in which fine particles are collided, (n) a metal sheet obtained by electrolytic deposition of innumerable irregularities by the electrolytic metal deposition method, or (o) Metals obtained by colliding fine particles with metal foils which are pressurized between molds with concave-convex convexities or by passing through the molds while forming concavities and convexities, or metal foils with electrolytic deposition of innumerable irregularities by electrolytic metal deposition. A battery electrode using any one of metal thin plates in a thin plate as a base.