JP5110889B2 - Nickel metal hydride secondary battery - Google Patents

Description

  The present invention relates to a nickel metal hydride secondary battery.

Nickel metal hydride secondary batteries are used as a power source for various electric and electronic devices including portable devices such as mobile phones and laptop computers.
In this nickel-metal hydride secondary battery, an electrode group in which a positive electrode plate and a negative electrode plate are wound in a spiral shape with a separator between them is formed on a cylindrical conductive bottomed outer can that is open at one end. Either one is accommodated in contact with the inner wall of the outer can. For this reason, the outer can itself becomes a terminal of one of the poles. Then, an alkaline electrolyte is injected into the outer can and allowed to permeate the electrode group, and the opening of the outer can is sealed by the lid and assembled. The lid includes a terminal to which a pole opposite to the electrode plate in contact with the inner wall of the outer can is electrically connected.

As a positive electrode plate, a porous substrate such as a metal punching metal substrate or a nickel-plated foam plate is filled with a paste formed by kneading a powder of nickel hydroxide as an active material, a conductive material, a binder and water. In this way, a material holding an active material is used. As the separator evening, for example, a nonwoven fabric made of polyolefin fiber, nylon fiber or the like is used.
Further, as the negative electrode plate, for example, a nickel punching substrate having a predetermined hole area ratio (percentage of the hole area in the substrate area), particles of hydrogen storage alloy such as LaNi ₅ , MmNi ₅ (Mm is Misch metal), A paste in which a paste formed by kneading a conductive material, a binder and water is applied and dried to hold the hydrogen storage alloy particles is used.

On the other hand, as the alkaline electrolyte, for example, a mixed solution of sodium hydroxide and lithium hydroxide, a mixed solution of potassium hydroxide and lithium hydroxide, or the like is used.
Such nickel-metal hydride secondary batteries are required to achieve both battery voltage securing and battery life when discharged with a large current, and to further increase the capacity within a limited battery volume.
Therefore, in Patent Document 1 and Patent Document 2, a layer (inner layer) made of hydrogen storage alloy particles having a small particle diameter is formed in the vicinity of the punching metal substrate, and the hydrogen storage alloy particles having a large particle diameter are formed on the inner layer. A negative electrode plate having a two-layer structure in which layers (outer layers) are stacked is disclosed.

In this negative electrode plate, the battery voltage, that is, the discharge capacity is secured by arranging the hydrogen storage alloy particles having a small particle diameter in the inner layer. And battery life is ensured by arrange | positioning a hydrogen storage alloy particle with a large particle diameter in an outer layer. That is, by increasing the gas absorption capacity and suppressing the increase in battery internal pressure, deterioration of the battery life due to the decrease in alkaline electrolyte is prevented.
Moreover, what is necessary is just to increase the active material of a positive electrode plate in order to raise the capacity | capacitance of a battery. As means for that, since the size of the outer can that accommodates the electrode group is constant, it is known that the spiral electrode group is highly dense and the separator is thin.
JP 11-233105 A JP 2002-216749 A

However, when hydrogen storage alloy particles having a large particle diameter are arranged on the surface of the negative electrode plate as in Patent Document 1 while increasing the density of the electrode group and thinning the separator, an internal short circuit is likely to occur. This is because, although the distance between the positive electrode plate and the negative electrode plate is short, the unevenness on the surface of the negative electrode plate becomes large, so that the positive electrode plate and the negative electrode plate easily break through the separator and come into contact with each other.
In addition, when the negative electrode plate has a two-layer structure, the hydrogen storage alloy particles having a small particle size must be applied after the hydrogen storage alloy particles having a small particle size are applied, which complicates the manufacturing process.

  The present invention has been made based on the above-described circumstances, and its purpose is to suppress the occurrence of an internal short circuit and to have a long life even if the electrode group is made denser or the separator is made thinner, and further easy to manufacture. The object is to provide a nickel metal hydride secondary battery.

  In order to achieve the above-described object, according to the present invention, a cylindrical outer can having conductivity, and the outer can are accommodated together with an alkaline electrolyte, and the positive electrode plate and the negative electrode plate are spirally arranged through a separator. In a nickel metal hydride secondary battery comprising an electrode group formed by winding, the negative electrode plate includes a metal substrate having a plurality of holes, and hydrogen storage alloy particles held on the substrate, and the hydrogen Among the storage alloy particles, the average particle diameter of the first hydrogen storage alloy particles located in the holes is larger than the thickness of the substrate and the second hydrogen storage alloy particles located outside the holes. A nickel metal hydride secondary battery characterized by being larger than the average particle diameter is provided.

Preferably, the average particle diameter of the second hydrogen storage alloy particles is set by rolling the substrate to which the raw material particles that are common raw materials of the first and second hydrogen storage alloy particles are attached. The average particle size of the hydrogen storage alloy particles is made smaller (claim 2).
Preferably, the average particle diameter of the raw material particles is in the range of 1.5 to 2.5 times the thickness of the substrate (Claim 3).

In the nickel hydride secondary battery according to claim 1 of the present invention, the average particle size of the second hydrogen storage alloy particles located outside the hole is smaller than the average particle size of the first hydrogen storage alloy particles.
In this case, since the second hydrogen storage alloy particles are arranged on the surface of the negative electrode plate, the unevenness of the surface of the negative electrode plate is small. For this reason, even if the electrode group is made highly dense or the separator is thinned, when the electrode group is formed or when the electrode group is accommodated in the outer layer can, the positive electrode plate and the negative electrode plate break through the separator to each other. Contact is prevented.

In this nickel metal hydride secondary battery, the average particle diameter of the first hydrogen storage alloy particles disposed in the hole of the substrate is larger than the thickness of the substrate.
In this case, since the first hydrogen storage alloy particles have a small contact area with the alkaline electrolyte, the first hydrogen storage alloy particles hardly corrode and maintain a good gas absorption capacity for a long period of time. For this reason, an abnormal increase in the battery internal pressure is suppressed for a long period of time, and a decrease in the alkaline electrolyte due to leakage is prevented.

Therefore, according to the nickel metal hydride secondary battery, a long-life and high-capacity battery in which the occurrence of an internal short circuit is suppressed is realized.
In the nickel-metal hydride secondary battery according to claim 2, the average particle size of the second hydrogen storage alloy particles is smaller than the average particle size of the first hydrogen storage alloy particles by rolling the substrate on which the raw material particles are adhered. To be. That is, some of the raw material particles are broken by rolling to become second hydrogen storage alloy particles.

In this case, it is not necessary to separately attach the first and second hydrogen storage alloy particles to the substrate. As a result, the nickel hydride secondary battery is easy to manufacture.
In the nickel-metal hydride secondary battery according to claim 3, the average particle size of the raw material particles is in the range of 1.5 times to 2.5 times the thickness of the substrate, so that the average particle size of the second hydrogen storage alloy particles is internal. It becomes an appropriate size from the viewpoint of the balance between the suppression of short circuit and the extension of life. As a result, according to the nickel metal hydride secondary battery, it is possible to reliably suppress internal short circuit and extend the life.

FIG. 1 shows a cylindrical nickel-metal hydride secondary battery according to an embodiment of the present invention.
The nickel metal hydride secondary battery includes a cylindrical outer can 2 having one end opened, and the outer can 2 has conductivity. In the outer can 2, a substantially cylindrical electrode group 4 is accommodated together with an alkaline electrolyte (not shown). The electrode group 4 swirls a strip-shaped negative electrode plate 6 and a positive electrode plate 8 via a separator 10, respectively. It is formed by winding in a shape. The outer periphery of the electrode group 4 is formed by the outermost peripheral portion of the negative electrode plate 6, and the outermost peripheral portion of the negative electrode plate 6 is in contact with the inner wall of the outer can 2.

  The opening of the outer can 2 is closed by a lid body 14, and the lid body 14 includes a substantially circular lid plate 16 having a valve hole 16a at the center. The outer peripheral portion of the cover plate 16 is fixed by caulking the opening edge of the outer can 2 via an insulating gasket 18. The valve body 20 which stuck together is arrange | positioned. A cylindrical positive terminal 22 with a flange is fixed on the outer surface of the cover plate 16 so as to cover the valve body 20, and a compression coil spring 24 that biases the valve body 20 is provided in the positive terminal 22. Contained.

Further, the lid 14 includes a circular current collecting plate 26 disposed near one end of the electrode group 4, and the current collecting plate 26 is welded to the positive electrode plate 8. A positive electrode lead 28 extends integrally from the current collector plate 26, and the tip end side of the positive electrode lead 28 is welded to the inner surface of the lid plate 16.
FIG. 2 shows a schematic enlarged cross section of a part of the negative electrode plate 6, and the negative electrode plate 6 has a metal substrate 30 having conductivity. The substrate 30 also has a strip shape, and the substrate 30 is formed with innumerable holes 30a over the entire area. The holes 30 a are arranged in a predetermined pattern and open on both surfaces of the substrate 30. As the substrate 30, for example, a punching metal or an expanded metal can be used.

In addition, the negative electrode plate 6 has countless hydrogen storage alloy particles 32 held by the substrate 30. As the hydrogen storage alloy particles 32, particles of a hydrogen storage alloy such as LaNi ₅ and MmNi ₅ (Mm is Misch metal) can be used.
In FIG. 2, although the conductive material and the binder are omitted, the hydrogen storage alloy particles 32 are adhered to the substrate 30 by the binder together with the conductive material as necessary.

  Here, the hydrogen storage alloy particles 32 are roughly classified into first hydrogen storage alloy particles 32a and second hydrogen storage alloy particles 32b. The first hydrogen storage alloy particles 32a are located in the holes 30a of the substrate 30, and the second hydrogen storage alloy particles 32b are located outside the holes 30a. And the average particle diameter of the 1st hydrogen storage alloy particle 32a is larger than the thickness of the board | substrate 30, and is larger than the average particle diameter of the 2nd hydrogen storage alloy particle 32b.

In addition, since the average particle diameter of the 1st hydrogen storage alloy particle 32a is larger than the depth of the hole 30a, being located in the hole 30a means that at least one part is enclosed by the hole 30a. .
The negative electrode plate 6 described above can be manufactured, for example, as follows.
First, a paste formed by kneading raw material particles, a conductive material, a binder, and water, which are common raw materials of the first hydrogen storage alloy particles 32a and the second hydrogen storage alloy particles 32b, is applied to the substrate 30. dry. As a result, the raw material particles adhere to the substrate 30. Then, after rolling the board | substrate with which raw material particle adhered, it cut | judged to a predetermined dimension and the negative electrode plate 6 is obtained.

The average particle diameter of the raw material particles is preferably in the range of 1.5 to 2.5 times the thickness of the substrate 30. In other words, the average particle diameter of the first raw material particles is preferably in the range of 1.5 to 2.5 times the thickness of the substrate 30.
In this method of manufacturing the negative electrode plate 6, during rolling, some of the raw material particles are broken to become the second hydrogen storage alloy particles 32b, and the remainder of the raw material particles are not broken and are directly broken into the first hydrogen storage alloy particles 32a. Become. That is, the raw material particles existing outside the holes 30a of the substrate 30 are pulverized and densified. On the other hand, the raw material particles located in the holes 30a are compressed without being crushed, and the degree of densification is small.

In the nickel hydride secondary battery of the above-described embodiment, the average particle size of the second hydrogen storage alloy particles 32b located outside the hole 30a is smaller than the average particle size of the first hydrogen storage alloy particles 32a.
In this case, since the second hydrogen storage alloy particles 32 b are arranged on the surface of the negative electrode plate 6, the unevenness on the surface of the negative electrode plate 6 is small. For this reason, even if the electrode group 4 is made highly dense or the separator is thinned, the positive electrode plate 8 and the negative electrode plate 6 are not used when the electrode group 4 is formed or when the electrode group 4 is accommodated in the outer layer can 2. It is prevented that the separator 10 breaks through and comes into contact with each other.

In this nickel metal hydride secondary battery, the average particle diameter of the first hydrogen storage alloy particles 32 a disposed in the holes 30 a of the substrate 30 is larger than the thickness of the substrate 30.
In this case, since the first hydrogen storage alloy particles 32a have a small contact area with the alkaline electrolyte, the first hydrogen storage alloy particles 32a are hardly corroded and maintain a good gas absorption capacity over a long period of time. For this reason, an abnormal increase in the battery internal pressure is suppressed for a long period of time, and a decrease in the alkaline electrolyte due to leakage is prevented.

Therefore, according to the nickel metal hydride secondary battery, a long-life and high-capacity battery in which the occurrence of an internal short circuit is suppressed is realized.
Moreover, in the manufacturing method of the negative electrode plate 6 of the nickel hydride secondary battery described above, the average particle size of the second hydrogen storage alloy particles 32b is obtained by rolling the substrate 30 to which the raw material particles are adhered, thereby The average particle diameter of the alloy particles 32a is made smaller. That is, some of the raw material particles are broken by rolling to become the second hydrogen storage alloy particles 32b.

In this case, it is not necessary to adhere the first and second hydrogen storage alloy particles 32a and 32b to the substrate 30 separately. As a result, the nickel-hydrogen secondary battery is easy to manufacture.
In addition, in the above-described nickel-metal hydride secondary battery, the average particle size of the raw material particles is in the range of 1.5 times to 2.5 times the thickness of the substrate 30, so that the average particle size of the second hydrogen storage alloy particles 32 b is increased. The diameter becomes an appropriate size. As a result, according to the nickel metal hydride secondary battery, the suppression of internal short circuit and the extension of the service life are reliably achieved.

1. Production of Negative Electrode Plate As compared with 10 parts by mass of LaNi ₅ powder having the average particle size shown in Table 1 as raw material particles, 0.05 parts by mass of carbon black powder as a conductive material, 0.005 parts by mass of carboxymethylcellulose binder and water 2.5 Pace porridge was prepared by mixing parts by mass.
What apply | coated this paste to the punching metal board | substrate was cut after rolling with a roller rolling apparatus after drying the paste, and produced the negative electrode plate of Examples 1-4 and Comparative Examples 1 and 2. The punched metal substrate is a SPCC steel plate having a thickness of 45 μm and an aperture ratio of 43%, which is successively subjected to Ni plating treatment and heat treatment of 1 μm thickness.

In addition, a hole in a punching metal substrate filled with a paste containing raw material particles with an average particle size of 30 μm, and other portions coated with a paste containing raw material particles with an average particle size of 90 μm are dried by roller rolling after the paste is dried. A negative electrode plate of Comparative Example 3 was produced by rolling with an apparatus and then cutting. This rolling was performed so that raw material particles having an average particle diameter of 90 μm were not broken.
Further, a punching metal substrate coated with a paste containing raw material particles having an average particle size of 90 μm was cut with a roller rolling device after the paste was dried, and then cut to produce a negative electrode plate of Comparative Example 4. This rolling was also performed in the same manner as in Comparative Example 3 so that the raw material particles inside and outside the hole of the punching metal substrate were not broken.

2. Production of Positive Electrode Plate A paste was prepared by mixing 1 part by mass of cobalt monoxide powder as a conductive material, 0.3 part by mass of a carboxymethylcellulose binder and 5 parts by mass of water with 10 parts by mass of nickel hydroxide powder.
A porous nickel-plated foam metal substrate filled with this paste was dried and then formed by rolling and then cut to form a positive electrode plate.

3. Preparation of battery Prepare two separators made of polypropylene nonwoven fabric, laminate them in the order of separator, positive electrode plate, separator and negative electrode plate, place a winding core on one end of the bottom layer separator, and make the negative electrode plate outside I wound it. In this way, a spiral electrode group in which the negative electrode plate is located on the outermost layer was formed and housed in a SFCC cylindrical outer can coated with Ni. Thereafter, the current collector plate was welded and the alkaline electrolyte was injected, and then the outer can was closed with a lid to produce a nickel metal hydride secondary battery.

4). Evaluation of Battery (1) Short-circuit failure The number of short-circuit failures was inspected by 10,000 for each of the obtained batteries of Examples 1 to 4 and Comparative Examples 1 to 4. The results are shown in Table 1.
(2) Cycle life characteristics
-1V charge with -ΔV control (-ΔV = 5mV) and discharge to 1V with 1C as one cycle, charge and discharge were repeated until the discharge capacity dropped to 60% of the initial discharge capacity, and the number of cycles was counted . The results are shown in Table 1.

(3) Results (i) When the average particle diameter of the raw material particles is 90 μm, the number of short-circuit defects in Example 2 is smaller than those in Comparative Examples 3 and 4. This is because in Example 2, the raw material particles outside the holes were broken and made smaller, so that the irregularities on the surface of the negative electrode plate were smaller than in Comparative Examples 3 and 4. That is, in Comparative Examples 3 and 4, the unevenness on the surface of the negative electrode plate was large, the distance between the positive electrode plate facing the convex part was shortened, and a short circuit failure occurred.
(Ii) In Comparative Examples 1 and 2 and Examples 1 to 4, the short-circuit failure increases as the average particle diameter of the raw material particles arranged outside the holes in the substrate increases. This is because the raw material particles are pulverized by rolling, but the negative electrode plate using raw material particles having a large average particle size has larger irregularities on the surface of the negative electrode plate than the negative electrode plate using raw material particles having a small average particle size. It is.

(Iii) On the other hand, in Comparative Examples 1 and 2 and Examples 1 to 4, the cycle life tends to increase as the average particle size of the raw material particles increases, but the average particle size is 70 μm or more. In 1-4, the cycle life improvement rate is small. The cycle life is not improved even when the average particle size is increased in this way, because the alloy on the punching metal substrate is pulverized in rolling forming, and as a result, a paste containing raw material particles having a small average particle size is applied. It is because it becomes the same. Of course, this result varies depending on the hardness of the hydrogen storage alloy and the capability of the roller rolling device.
(Iv) In Examples 1 and 2, the number of short-circuit defects is smaller than in Examples 3 and 4, and the number of short-circuit defects is substantially the same as in Comparative Examples 1 and 2. On the other hand, the cycle life of Examples 1 and 2 is longer than that of Comparative Examples 1 and 2. From this, it is understood that the average particle diameter of the raw material particles is preferably in the range of 1.5 times to 2.5 times in consideration of the balance between short circuit failure and cycle life.

The present invention is not limited to the above-described embodiments and examples, and various modifications are possible. For example, in one embodiment, the negative electrode plate 6 is in contact with the inner wall of the outer can 2. The electrode group may be formed so that the positive electrode plate 8 contacts the inner wall of the outer can 2.
Moreover, the structure of the cover body 14 is not specifically limited, You may change the valve body 20 and the compression coil spring 24 to the column-shaped valve body which consists of an elastic body.

  Furthermore, the outer can 2 may have a cylindrical shape other than the cylindrical shape, and may be, for example, a rectangular tube shape or an elliptical column shape.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a nickel hydride secondary battery according to an embodiment of the present invention with a part thereof expanded and a part with a longitudinal section. FIG. 2 is an enlarged cross-sectional view schematically showing a part of a negative electrode plate used in the battery of FIG. 1.

Explanation of symbols

6 Negative electrode plate 30 Substrate 30a Hole 32 Hydrogen storage alloy particle 32a First hydrogen storage alloy particle 32b Second hydrogen storage alloy particle

Claims (3)

Nickel metal hydride provided with a cylindrical outer can having conductivity, and an electrode group that is housed together with an alkaline electrolyte in the outer can and formed by spirally winding a positive electrode plate and a negative electrode plate through a separator. In the next battery,
The negative electrode plate includes a metal substrate having a plurality of holes, and hydrogen storage alloy particles held on the substrate,
Of the hydrogen storage alloy particles, the first hydrogen storage alloy particles located in the holes have an average particle diameter larger than the thickness of the substrate, and the second hydrogen storage alloys located outside the holes. A nickel-metal hydride secondary battery characterized by being larger than the average particle diameter of the particles.   The average particle diameter of the second hydrogen storage alloy particles is determined by rolling the substrate to which the raw material particles, which are common raw materials of the first and second hydrogen storage alloy particles, are rolled. The nickel-metal hydride secondary battery according to claim 1, wherein the nickel-hydrogen secondary battery is made smaller than an average particle diameter of the alloy particles.   The nickel metal hydride secondary battery according to claim 2, wherein the average particle diameter of the raw material particles is in the range of 1.5 to 2.5 times the thickness of the substrate.

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