JP2003282051A - Electrode for cell, and cell using electrode for cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient electrode for cells of which the internal resistance is low and the cell using this electrode for cells. <P>SOLUTION: The electrode for cells is formed by combining a powdered active material 15 with current collector bodies 10, which have electrical conductivity. If a value computed by dividing the volume of a void, which is obtained by subtracting the real volume of the active material 15 from the volume of the apparent volume of the active material 15, further by the volume of the apparent volume of the active material 15, is to be a percentage of voids, the above percentage of voids is to become 5% or more and 20% or less. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery electrode and a battery using the battery electrode, and more particularly to a battery electrode having a low internal resistance and high performance, and a battery using the battery electrode. It is about.

[0002]

2. Description of the Related Art Conventionally, when a negative electrode plate for a nickel-hydrogen battery is manufactured, a paste-like substance obtained by mixing a powder of an active material such as a hydrogen storage alloy with a binder or a conductive material is used as an electrode current collector. Is applied to a foamed metal porous body to fill three-dimensional pores, or it is applied to a perforated metal porous plate such as punching metal or metal lath, dried, and then rolled. It is manufactured by In this case, the porosity of the negative electrode plate of the nickel hydrogen battery is about 25.
%. In addition, the porosity is the void obtained by subtracting the actual volume of the electrode component other than the current collector (including the active material, the binder, and the conductive material) from the apparent volume of the electrode component other than the current collector. Is a value obtained by dividing the volume of the void by the apparent volume of the electrode constituent member other than the current collector.

[0003]

However, in the battery electrode having a porosity of about 25% as shown in the above-mentioned prior art, the electrical resistance inside the electrode is large, and this is one of the causes for lowering the discharge capacity. There was a problem of becoming.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a high-performance battery electrode having a low internal resistance, and a battery using the battery electrode.

[0005]

In order to solve the above-mentioned problems, the invention described in claim 1 is an electrode for a battery formed by bonding a powdery active material to a conductive current collector. That is, the volume of voids obtained by subtracting the actual volume of the active material from the apparent volume of the active material, further, when the value calculated by dividing by the apparent volume of the active material is the porosity, The porosity is characterized by being 5% or more and 20% or less. According to this battery electrode, the porosity is 5
% To 20%.

According to a second aspect of the present invention, a binder or conductive material having conductivity is added to the active material, and the addition rate of the binder or conductive material is 0 in terms of volume ratio. Alternatively, it is characterized by being 10% or less. According to this battery electrode, a binder or a conductive material having a conductivity of 0 or 10% or less in volume ratio is added to the active material.

The invention as set forth in claim 3 is characterized in that the binder or the conductive material has an average particle diameter smaller than that of the active material. According to this battery electrode, the average particle size of the binder or the conductive material is set smaller than the average particle size of the active material.

In the invention described in claim 4, a non-conductive binder is added to the active material, and the addition rate of the binder is 0 or 10% or less in volume ratio. Is characterized by. According to this battery electrode, a non-conductive binder having a volume ratio of 0 or 10% or less is added to the active material.

The invention described in claim 5 is characterized in that, in the step of forming the battery electrode, rolling is performed at least once by the electric current rolling method. According to this battery electrode, the electric rolling method is adopted as the forming process of the battery electrode.

According to a sixth aspect of the present invention, in the electric current rolling method, the electric current α is expressed by a unit width current (A / m).
m) and v are rolling speeds (mm / s), α = i ² /
v is satisfied, and the energizing current α is 2.5 × 10
It is characterized by being set to a value of ⁵ (A ² · sec) / mm ³ or less. According to this battery electrode, the energizing current α is 2.5 × 10 ⁵ (A ² · sec) during the energizing rolling.
/ Mm ³ or less.

The invention described in claim 7 is characterized in that the electric current rolling method is carried out in a vacuum atmosphere having a pressure of 1 × 10 ^-2 Pa or less. According to this battery electrode, the electric current rolling method is carried out in a vacuum atmosphere having a pressure of 1 × 10 ⁻² Pa or less.

The invention described in claim 8 is characterized in that the electric current rolling method is carried out in an inert atmosphere. According to this battery electrode, the electric current rolling method is carried out in an inert atmosphere.

The invention described in claim 9 is characterized in that the battery electrode according to any one of claims 1 to 8 is used. According to the battery using the battery electrode, the battery electrode according to any one of claims 1 to 8 is adopted as the battery.

[0014]

DETAILED DESCRIPTION OF THE INVENTION (Embodiment of Battery Electrode)
Embodiments of the present invention will be described based on illustrated examples.
As shown in FIG. 1, the negative electrode plate 1 of the nickel-hydrogen battery comprises a current collector 10 and a hydrogen storage alloy powder 15 which is an active material. Further, although not shown, a binder and a conductive material such as carbon powder may be appropriately mixed with the active material.

As the material used as the current collector 10, in addition to simple metals such as nickel, copper and aluminum,
Compounds such as metal oxides and sulfides, or a mixture of a plurality of metals, a plating material and the like can be mentioned. Depending on the form of the current collector, a foamed porous body, punching metal,
Alternatively, a solid foil is appropriately applied, but it is not particularly limited, and in this embodiment, an embossed nickel foil is used. Further, as the active material fixed to the current collector 10, a hydrogen storage alloy is adopted in the present embodiment, but the active material powder usually corresponds to the type of battery or electrode to be applied, and zinc, lead, etc. , Elemental metals such as iron, cadmium, aluminum and lithium, metal hydroxides such as nickel hydroxide, zinc hydroxide, aluminum hydroxide and iron hydroxide, lithium cobalt oxide, lithium nickel oxide, lithium manganate, and A lithium composite oxide such as lithium vanadate, manganese dioxide, a metal oxide such as lead dioxide, a conductive polymer such as polyalinine, polyacene, or the like can be adopted and is not particularly limited.

The negative electrode plate 1 is manufactured by pressure-bonding or coating the hydrogen-absorbing alloy powder 15 on the current collector 10 and then rolling. In this embodiment, three types of manufacturing methods are adopted. That is, the hydrogen storage alloy powder 15 is rolled by the powder rolling method to the current collector 10 and is rolled again by the electric current rolling method (hereinafter referred to as production method A), and the hydrogen storage alloy powder 15 is processed by the powder rolling method. A manufacturing method in which the current collector 10 is rolled and a rolling process is performed again by a normal rolling method (hereinafter, referred to as a manufacturing method B), and further, a hydrogen storage alloy powder 15 is applied to the current collector 10 by a dipping method, The manufacturing method (hereinafter, referred to as manufacturing method C) of rolling by the rolling method of No.

In the manufacturing method A, first, nickel powder (average particle diameter of 1 μm or less) as a conductive material is used as the hydrogen storage alloy powder 15
(Average particle size 30 μm), and the mixture is pressed onto both sides of the current collector 10 by a powder rolling method to form a preform. Next, the preform is rolled again by the electric current rolling method to form the negative electrode plate 1. In the electric current rolling method, the negative electrode plates having different porosities were manufactured by appropriately changing the load, atmosphere, and electric current.

In the manufacturing method B, the preform is rolled again by the usual rolling method to form the negative electrode plate 1. Negative electrode plates having different porosities were manufactured by appropriately changing the amount of nickel powder added and the load during rerolling.

In the manufacturing method C, an aqueous solution in which a non-conductive resin is dispersed is mixed with the hydrogen storage alloy powder 15 as a binder,
The mixture is applied to both sides of the current collector 10 by a dipping method,
After drying, the preform is molded. Next, the preform is rolled by a usual rolling method to form the negative electrode plate 1. The amount of the non-conductive binder added and the load during re-rolling were appropriately changed to manufacture negative electrode plates having different porosities.

FIG. 2 shows the relationship between the porosity of the negative electrode plate and the discharge capacity ratio in this embodiment. The discharge capacity ratio is shown by point A in the figure, and the non-conductive binder is added in a volume ratio of 5%, and the production method C is used.
In the negative electrode plate 1a manufactured in 1., the discharge capacity value is 100% when the porosity is 25%.

As shown in FIG. 2, the negative electrode plate 1a manufactured by the manufacturing method C and the nickel powder which is the conductive material, which is the present embodiment, is added by 5% in volume ratio of the non-conductive binder. Negative electrode plate 1b manufactured by the manufacturing method A by adding 10% in volume ratio
And the negative electrode plate 1c manufactured by the manufacturing method B without adding the nickel powder and 5% by volume of the nickel powder,
The negative electrode plate 1d manufactured in step 1 and nickel powder in a volume ratio of 10
%, And with the negative electrode plate 1e manufactured by the manufacturing method B, in all cases, as the porosity decreases, the electric resistance inside the electrode decreases from the porosity of 20% or less, and the electric resistance decreases. As a result, the discharge capacity increases and the discharge capacity ratio becomes maximum when the porosity is 10 to 12.5%. Further, when the porosity is 5% or less, the discharge capacity ratio decreases.

In general, the voids present in the electrodes cause an increase in electrical resistance. Therefore, by reducing the voids, the electrical resistance inside the electrodes can be lowered. On the other hand, the voids are indispensable for diffusing the electrolytic solution into the electrode. Therefore, if the voids are made less than necessary, the diffusion of the electrolytic solution will be deteriorated and the battery performance will be deteriorated. That is, as shown in FIG. 2, it is efficient to set the porosity to about 5 to 20% in terms of volume ratio, and it is particularly preferable to set it to about 7.5 to 15% in terms of volume ratio.

The conductive material and the binder may be used either alone or as a mixture of both. In Figure 3,
(1) A case where nickel powder as a conductive material is added and a negative electrode plate is manufactured by a manufacturing method B, (2) A case where a non-conductive binder is added and a negative electrode plate is manufactured by a manufacturing method C, and (3)
The porosity of the negative electrode plate was 1 as compared with the case where the negative electrode plate was manufactured by the manufacturing method C by adding the non-conductive binder and the nickel powder.
The relationship between the volume ratio of the added amount and the discharge capacity ratio in the present embodiment in the case of 2.5% is shown. The discharge capacity ratio has the same definition as the discharge capacity ratio shown in FIG. In addition, (3) above
In the manufacturing method, the amount of non-conductive binder added was 5% in volume ratio, and the amount of nickel powder added was appropriately changed by the amount shown on the horizontal axis in the figure.

When the conductive material is used, for example, when nickel powder is used as the conductive material as in the manufacturing method of (1) and the nickel powder is mixed with the hydrogen storage alloy powder 15 or the like, the average nickel powder is Since the particle size is smaller than the average particle size of the hydrogen storage alloy powder 15, it has an effect of reducing the porosity of the negative electrode plate, and it is possible to reduce the electric resistance and increase the discharge capacity.

However, when the amount of nickel powder added is increased, the weight of the hydrogen storage alloy per unit volume is reduced, so that when compared with a negative electrode plate having the same porosity and no conductive material added, Battery performance is reduced. As shown in FIG. 3, the addition amount of the nickel powder is 1 in terms of volume ratio.
If it is mixed as 0% or more, the discharge capacity ratio is greatly reduced. Therefore, the addition amount of the conductive material is preferably 10% or less. Furthermore, it is more desirable to set the addition amount to 2.5% or less.

When a non-conductive binder is used as the binder, the non-conductive binder has the effect of increasing the electrical resistance of the electrode, but on the other hand, it prevents the active material from falling off. Is effective, and the addition of a small amount has a significant effect depending on the purpose of use. As shown in FIG. 3, when the non-conductive binder is added at a volume ratio of 10% or more and mixed, the discharge capacity ratio sharply decreases. Therefore, the addition amount of the non-conductive binder is preferably 10% or less. Furthermore, it is more desirable to set the addition amount to 2.5% or less.

Further, as shown in FIG. 2, if a current rolling method in which current is applied between rolls during rolling is adopted as a method for reducing the porosity, the hardness in the vicinity of the contact point on the surface of the active material is reduced. The contact resistance between the active materials can be reduced. Therefore, it is possible to reduce the electric resistance of the electrode and increase the discharge capacity as compared with a negative electrode plate having the same porosity, which is manufactured by a rolling method in which electricity is not applied.

FIG. 4 shows that in the above-mentioned electric current rolling method, the pressure is 1 × 10 ⁻² Pa or less in a vacuum atmosphere and the pressure is 1 ×
The porosity of the negative electrode plate is set to 12.5% and the conductive material nickel powder is set to 10% in an air atmosphere of about 10 ⁵ Pa.
The relationship between the energizing current α and the discharge capacity ratio in the present embodiment when added is shown. The energizing current α is expressed by the unit width current (A
/ Mm) and v is the rolling speed (mm / s), α = i
It is a value that satisfies the formula of ² / v. Further, the discharge capacity ratio has the same definition as the discharge capacity ratio shown in FIGS.

During the electric current rolling, the temperature of the negative electrode plate during the rolling process rises as the electric current is applied between the rolls (not shown), and the oxidation reaction occurs violently. Therefore, as shown in FIG.
When the electric current rolling is performed in the atmosphere, the discharge capacity ratio decreases as the electric current α increases, and the performance of the battery decreases significantly. Therefore, in the electric current rolling, for example, when the pressure is 1 × 10 ⁻² , it is possible to pass a large amount of current.
It is desirable to carry out under a vacuum atmosphere of Pa or less or under an inert atmosphere.

Further, if the energizing current α is increased too much, the physical properties of the active material itself are changed and the discharge capacity is lowered. Therefore, from FIG. 4, the energizing current α is 2.5 × 10 ⁵
By setting the value to (A ² · sec) / mm ³ , it becomes possible to efficiently increase the discharge capacity.

(Embodiment of Battery) Next, referring to FIG. 5, a cylindrical secondary battery P using the negative electrode D1 adopting the negative electrode plate 1 is shown.
A perspective view of (for example, a nickel hydrogen battery) is shown. In this cylindrical secondary battery P, the negative electrode D1 and the positive electrode D2 are spirally multi-wound with the separator 3 sandwiched therebetween, and the battery case 4 is formed.
It is housed in the (negative electrode terminal) and is immersed in the electrolyte solution filled in the battery case 4. An opening is formed at the upper end of the battery case 4, and the positive electrode terminal 5 is provided at the center of the opening and is sealed by a sealing plate 6 that is insulated from the battery case 4. Further, the negative electrode D1 is connected to the battery case 4, the positive electrode D2 is connected to the positive electrode terminal 5, and the negative electrode D1 and the positive electrode D2 form a series circuit via the electrolytic solution.

The present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention. For example, the following modifications are possible.

(1) In this embodiment, the electrode plate is a negative electrode for a nickel hydrogen battery, but it may be a positive electrode for a nickel hydrogen battery. Further, for example, it may be an electrode for another battery such as a lithium-ion battery, and in this case, a substance as an active material is appropriately selected.

(2) In this embodiment, the rolling method and the electric current rolling method are adopted as the method for reducing the porosity. However, in addition to these methods, the electric current pressing method, the warm pressing method, and the
A warm rolling method or the like may be adopted. Also, before rolling
When the method of applying the active material to the current collector is adopted, the method of application may be the dipping method, the doctor blade method or the like.

(3) Although FIG. 5 shows the cylindrical secondary battery P, a negative battery as the above-mentioned electrode is formed into a prismatic battery mounted in a battery case by alternately laminating a negative electrode with a positive electrode sandwiching an insulating material. Can also be applied.

[0036]

As described above, according to the invention described in claim 1, since the porosity is set to 5% or more and 20% or less, the electric resistance inside the electrode can be reduced, Moreover, it becomes possible to efficiently diffuse the electrolytic solution into the electrode.

According to the second aspect of the invention, since the active material is added with a binder or a conductive material having a volume ratio of 0 or 10% or less, the unit of the hydrogen storage alloy. It is possible to suppress reduction in weight per volume and suppress deterioration in discharge capacity, that is, battery performance.

According to the invention described in claim 3, since the average particle size of the binder or the conductive material is set smaller than the average particle size of the active material, there is an effect of reducing the porosity of the electrode. It is possible to reduce the electric capacity and increase the discharge capacity.

According to the invention described in claim 4, since the non-conductive binder having a volume ratio of 0 or less than 10% is added to the active material, it has the effect of increasing the electric resistance of the electrode. It is possible to suppress the deterioration of the discharge capacity, that is, the battery performance while suppressing and dropping the active material.

According to the invention described in claim 5, since the electric current rolling method is adopted as the step of forming the battery electrode,
The hardness in the vicinity of the contact point on the surface of the active material can be reduced, and the contact resistance between the active materials can be reduced. Furthermore, the electric resistance of the electrodes can be reduced, and the discharge capacity can be increased.

According to the invention described in claim 6, at the time of electric rolling, the electric current α is 2.5 × 10 ⁵ (A ² · se).
Since the value is set to c) / mm ³ or less, the discharge capacity can be efficiently increased without changing the physical properties of the active material itself.

According to the invention described in claim 7, since the electric current rolling method is carried out in a vacuum atmosphere having a pressure of 1 × 10 ^-2 Pa or less, it is compared with the case where electric current rolling is carried out in the atmosphere. As a result, the energizing current α can be increased, and the decrease in discharge capacity can be suppressed.

According to the invention described in claim 8, since the electric current rolling method is carried out in an inert atmosphere, the electric current α should be increased as compared with the case where the electric current rolling is carried out in the atmosphere. It becomes possible to suppress the decrease in discharge capacity.

According to the invention described in claim 9, since the battery electrode according to any one of claims 1 to 8 is adopted for the battery, the battery having a low internal resistance and high performance is obtained. It becomes possible to

[Brief description of drawings]

FIG. 1 is a schematic view showing a negative electrode plate in an embodiment of a battery electrode of the present invention.

FIG. 2 is a relationship diagram of the void ratio and the discharge capacity ratio of the negative electrode plate in the embodiment of the battery electrode of the present invention.

FIG. 3 is a relationship diagram of a volume ratio of a binder addition amount and a discharge capacity ratio in an embodiment of a battery electrode of the present invention.

FIG. 4 is a diagram showing a relationship between a passing current α and a discharge capacity ratio in the embodiment of the battery electrode of the present invention.

FIG. 5 is a perspective view of a cylindrical secondary battery using a negative electrode in the embodiment of the battery electrode of the present invention.

[Explanation of symbols]

1 Negative electrode plate 10 Current collector 15 Active material α energizing current

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomotoshi Mochizuki             Stone, Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa             Kawashima Harima Heavy Industries Co., Ltd. Machinery and plant opening             In the departure center (72) Inventor Hiroki Yoshizawa             Stone, Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa             Kawashima Harima Heavy Industries Co., Ltd. Machinery and plant opening             In the departure center F-term (reference) 4E002 AA08 AB03 AD01 BD08 CB01                 5H017 AA02 AA03 AS02 BB01 BB16                       BB17 CC03 CC25 EE01 HH02                       HH04 HH07 HH09 HH10                 5H050 AA12 BA14 BA15 CA02 CA03                       CA07 CA20 CB02 CB11 CB12                       CB16 DA04 DA10 DA11 FA13                       FA17 GA02 GA03 GA07 GA08                       GA22 GA26 GA27 HA01 HA07                       HA09 HA15 HA17 HA20

Claims (9)

[Claims] 1. A battery electrode formed by binding a powdery active material to a conductive current collector, which is obtained by subtracting the actual volume of the active material from the apparent volume of the active material. If the value calculated by dividing the volume of voids to be generated by the apparent volume of the active material is the porosity, the porosity is
An electrode for a battery, which is 5% or more and 20% or less. 2. A binder or conductive material having conductivity is added to the active material, and the addition ratio of the binder or conductive material is 0 or 10% or less in volume ratio. The battery electrode according to claim 1. 3. The battery electrode according to claim 1, wherein an average particle size of the binder or the conductive material is smaller than an average particle size of the active material. 4. The non-conductive binder is added to the active material, and the addition ratio of the binder is 0 or 10% or less in volume ratio. The battery electrode described. 5. The battery electrode according to claim 1, wherein the electrode for battery is rolled by an electric rolling method at least once in the step of forming the battery electrode. 6. The electric current α in the electric current rolling method
Is the unit width current (A / mm), v is the rolling speed (mm
/ S), the equation α = i ² / v is satisfied, and the energizing current α is set to a value of 2.5 × 10 ⁵ (A ² · sec) / mm ³ or less. The battery electrode according to claim 5. 7. The electric current rolling method has a pressure of 1 × 10 ⁻² P
The battery electrode according to claim 5 or 6, which is carried out in a vacuum atmosphere of a or less. 8. The battery electrode according to claim 5, wherein the electric current rolling method is performed in an inert atmosphere. 9. A battery comprising the battery electrode according to claim 1.