JP3115574B2 - Battery - Google Patents

Description

The present invention relates to a battery. In particular, it relates to a battery using a hydrogen storage alloy.

(B) Conventional technology Conventional batteries include a positive electrode mixture powder containing a positive electrode active material,
A powdery separator is placed between the negative electrode mixture powder containing the hydrogen storage alloy of the negative electrode active material, and pressed integrally to obtain a three-layer tablet-shaped battery element, which is supplied with an electrolytic solution. Then, the current collector was placed in a welded button-shaped container, swaged and sealed.

Further, in the nickel-hydrogen battery, a positive electrode active material powder containing nickel oxide as a positive electrode active material was applied or impregnated on a substrate such as a nickel-plated iron punching metal or a nickel porous body. Thereafter, a chemical conversion treatment is performed electrochemically in an alkaline electrolyte such as an aqueous solution of potassium hydroxide, and then punched or cut into a predetermined size to form a positive electrode layer, which is welded to a can of a battery container.

On the other hand, a negative electrode mixture powder containing a hydrogen storage alloy of a negative electrode active material is attached to the same substrate as the positive electrode, and chemically converted in an alkaline electrolyte such as an aqueous potassium hydroxide solution. Punched or cut out to the size of the negative electrode layer and welded to the lid of the battery container. And
After the separator was inserted between the positive electrode layer and the negative electrode layer, and the above-mentioned alkaline electrolyte was supplied, the can and the lid were closed by caulking or the like.

(C) Problems to be Solved by the Invention A battery comprising a negative electrode containing the above-mentioned hydrogen storage alloy has a slight difference in the internal resistance of the battery due to a slight difference in the amount of the negative electrode mixture powder used or a contact resistance at the electrode interface. Due to this difference, the charge-discharge characteristics of the battery tend to vary, making it difficult to produce a battery exhibiting uniform charge-discharge characteristics at a high yield.

The present invention has been made in order to solve the problems of the conventional battery described above, and it is an object of the present invention to provide a battery which can simplify the manufacturing process, exhibit uniform charge / discharge characteristics, and can be manufactured at a high yield. It is assumed that.

(D) Means for Solving the Problems According to the present invention, a positive electrode layer, a separator layer impregnated with an electrolytic solution, and a negative electrode layer are sequentially laminated and sealed in a battery container. The present invention provides a battery comprising, as a constituent material, a hydrogen storage alloy powder plated with nickel and copper in this order.

Further, according to the present invention, a positive electrode layer, a separator layer impregnated with an electrolytic solution, and a negative electrode layer are sequentially laminated and sealed in a battery container, and the negative electrode layer includes nickel and copper in this order from the surface side. There is provided a battery characterized by comprising, as a constituent material, a mixture of a plated hydrogen storage alloy powder and a hydrogen storage alloy powder whose surface is plated with nickel.

The negative electrode layer is formed by plating nickel and copper on the surface of the hydrogen storage alloy powder in which nickel and copper are plated in this order from the surface side, or hydrogen storage alloy powder in which nickel and copper are plated in this order from the surface side. Of hydrogen storage alloy powder. These hydrogen storage alloys are for discharging and charging a battery by oxidation of hydrogen or reduction reaction of hydrogen ions.Hydrogen storage alloys whose surfaces are sequentially plated with nickel and copper are, for example, Ti. _x Ni (1
≦ x ≦ 2), a powder of TiFe, LaNi5, MmNi5, etc. was first subjected to nickel plating by, for example, electroless plating, vacuum deposition, etc., and then further subjected to copper plating and degassing. Thereafter, it can be manufactured by absorbing hydrogen in a hydrogen atmosphere, and a hydrogen storage alloy having a surface plated with nickel is not subjected to the step of applying copper plating in the method of manufacturing, and the others are manufactured in the same manner as in the above-described manufacturing. It can be produced in the same manner as in the method. The negative electrode layer, using a mixture of a hydrogen storage alloy whose surface is plated with nickel and copper in order or a hydrogen storage alloy whose surface is plated with nickel,
Further, if necessary, a conductive agent and a binder may be mixed to form a powder of the negative electrode layer, which may be formed by, for example, pressure molding. This mixture amount is usually 20% by weight or more for hydrogen storage alloys whose surfaces are plated with nickel and copper in order. Hydrogen storage alloys whose surfaces are plated with nickel are usually
It is usually 80% by weight or less, and each of the conductive agent and the binder is usually 20% by weight or less.

The conductive agent is an electron conductive substance added to secure the electron conductivity of the negative electrode layer, and includes, for example, acetylene black, graphite, carbon black, nickel powder, and the like.Acetylene black and graphite are preferable. . The binder is a substance added to enhance the binding properties of the two powders. Examples of the binder include carboxymethylcellulose, polytetrafluoroethylene, carboxymethylcellulose salt, polyvinyl alcohol, polyethylene, agar, methylcellulose and the like.

Next, an example of a method for manufacturing a button-shaped battery in which a negative electrode capacity is controlled using a three-layer tablet-shaped battery element will be specifically described with reference to the drawings, but the present invention is not limited to this example.

In FIG. 1, reference numeral 1 denotes a molding die, reference numeral 2 denotes a push bar for pressing and molding the powder put into the die, and reference numeral 3 denotes a receiving stand for the molding die 1. The pedestal 3 is vertically movable within the molding die 1 to adjust the depth of the molding die 1.

First, the powder 4 of the positive electrode layer is put into the molding die 1 set in such a state (FIG. 1), and then the powder 4 of the positive electrode layer is lightly pressed with the push rod 2 to level the ground. The powder 5 of the layer is put on the powder 4 of the positive electrode layer placed in the molding die 1. The state is shown in FIG. Then push rod 2
And lightly pressurize the powder 5 of the separator layer to level the ground.

Next, the negative electrode layer powder 6 is put on the separator layer powder 5 placed in the molding die 1. This state is shown in FIG. Next, the powder 4 of the positive electrode layer, the powder 5 of the separator layer, and the powder 6 of the negative electrode layer placed in the molding die 1
To form a single piece. The state is shown in FIG. Thereafter, the molded body (three-layer tablet-shaped battery element) is taken out of the molding die 1. The order of charging the powder of the positive electrode layer and the powder of the negative electrode layer into the molding die 1 may be reversed. The powder of the positive electrode layer contains a positive electrode active material, a conductive agent, and a binder. Examples of the positive electrode active material include oxidizing agents such as manganese dioxide, nickel oxide, tungsten trioxide, lead dioxide, and molybdenum trioxide, and manganese dioxide and nickel oxide are preferred. The conductive agent and the binder may be the same as those used for the negative electrode layer, and are usually mixed in the powder of the positive electrode layer in an amount of 3 to 20% by weight.

The powder of the separator layer contains an electrolyte support and a binder. The electrolyte support may be any as long as it has an insulating property. Examples of the electrolyte support satisfying this condition include silicon dioxide and aluminum oxide. As the binder suitable for the present invention, the same binder as that used for the negative electrode layer is selected. The binder is added in an amount of not more than 40 parts by weight, as needed, with respect to 100 parts by weight of the electrolyte support.

Next, as shown in FIG. 5, the molded body (three-layer tablet-shaped battery element) is placed in a battery container 9 on which a current collecting net 7 has been welded in advance and a gasket 8 has been placed. Thereafter, the electrolytic solution 10 is supplied and impregnated.

Finally, as shown in FIG. 6, a lid 11 to which the current collecting net 7 is welded is attached to the battery container 9, and the battery container 7 and the lid 11 are caulked and sealed to form a battery.

(E) Action The nickel plating layer applied to the surface of the hydrogen storage alloy prevents oxidation of the hydrogen storage alloy, and the copper plating layer prevents overdischarge and flattens the discharge curve.

(F) Examples Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 A positive electrode mixture was prepared by mixing 20 parts by weight of γ-manganese dioxide, 2 parts by weight of acetylene black as a conductive agent, and 1 part by weight of polytetrafluoroethylene powder and sodium carboxymethylcellulose as a binder. Powder. Take 200 mg of this and put it into a molding die with an inner diameter of 15 mm, and press lightly with a push rod from above.

The separator mixture is a powder obtained by mixing 20 parts by weight of α-alumina powder as an electrolyte support and 1 part by weight of carboxymethyl cellulose as a binder. 200mg of this
And put it on the positive electrode mixture placed in the molding die, and gently press with a push rod from above.

The negative electrode mixture is obtained by applying nickel plating to the surface of TiNi powder by electroless plating, and then applying copper plating on the surface, and then applying gaseous hydrogen in a pressure vessel at 25 ° C and 1 atmosphere. This powder is obtained by mixing 10 mg each of acetylene black as a conductive agent and carboxymethylcellulose as a binder with 180 mg of a hydrogen storage alloy absorbed overnight. This is put on a separator mixture placed in a molding die, and pressed from above with a push rod at a pressure of 200 kgw / cm ² to obtain a molded body. Thus, a green compact having a three-layer structure, which is a battery content, is obtained and taken out from the molding die.

Next, the battery content is placed in a battery container, 100 μl of a 30% by weight aqueous solution of potassium hydroxide is added, the cap is closed, and the cap is closed by caulking. In this way, battery (A) is
Make pieces. This battery (A) has a capacity of 2 kΩ as shown in FIG.
The constant load discharge curve was selected to have higher voltage flatness than the comparative example described later, and as shown in Table 1, the discharge time (capacity up to 0.5 V when 2 KΩ constant load discharge was performed at 25 ° C.) ) Was measured for 10 samples, and it was found that the samples had excellent capacity uniformity.

Comparative Example 1 In Example 1, the surface of the TiNi powder was nickel-plated, and further plated with copper. Then, instead of using a hydrogen storage alloy storing hydrogen, unplated TiNi powder was used. A battery (B) was produced in the same manner as in Example 1 except for the above.

The battery (B) was measured for constant-load discharge characteristics and capacity at 2 KΩ in the same manner as in Example 1. As a result, the flatness of the discharge voltage was low, and variations were observed in the capacity.

(G) Effects of the Invention According to the present invention, it is possible to provide a battery having excellent flatness of discharge voltage and uniform capacity. Further, since the capacity is uniform, the production yield of this battery can be improved.

[Brief description of the drawings]

1 to 6 are explanatory views of the manufacturing process of the battery of the present invention, and FIGS. 7 and 8 are diagrams of 2 KΩ constant load discharge curves of the batteries manufactured in the example of the present invention and the comparative example, respectively. It is. DESCRIPTION OF SYMBOLS 1 ... Molding die, 2 ... Push rod, 5 ... Powder of separator layer, 6 ... Powder of negative electrode layer, 7 ... Net for current collection, 8 ... Gasket, 9 ... Battery container, 10 ... ... electrolyte, 11 ... lid.

(56) References JP-A-61-168866 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/38 H01M 4/24-4/26

Claims (3)

(57) [Claims] 1. A positive electrode layer, a separator layer impregnated with an electrolytic solution, and a negative electrode layer are sequentially laminated and sealed in a battery container. The negative electrode layer is formed by plating nickel and copper in this order from the surface side. A hydrogen storage alloy powder as a constituent material. 2. A positive electrode layer, a separator layer impregnated with an electrolytic solution, and a negative electrode layer are sequentially laminated and sealed in a battery container. The negative electrode layer is formed by plating nickel and copper in this order from the surface side. A battery comprising a mixture of a hydrogen storage alloy powder and a hydrogen storage alloy powder whose surface is plated with nickel. 3. The negative electrode layer contains 20% by weight or more of a hydrogen storage alloy powder having nickel and copper plated in this order from the surface side, and 80% by weight or less of a hydrogen storage alloy powder having nickel plated on the surface. The battery according to claim 2, which is contained at a ratio of: