JP2007250420A - Core body for secondary battery electrode with excellent adhesiveness and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive core body for a secondary battery electrode in which an excellent adhesiveness between a nickel porous sintered material and a steel plate of a core body is obtained, and also to provide its manufacturing method. <P>SOLUTION: The core body for a secondary battery electrode is composed of: a perforated steel plate; a plating layer formed on the steel plate and composed of a Ni-Fe alloy; and a conductive carbon fiber layer formed on the plating layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a core for a secondary battery electrode applied to a secondary battery such as a nickel-cadmium battery or a nickel-hydrogen battery, and a method for manufacturing the same.

  Conventionally, in a nickel-cadmium or nickel-hydrogen secondary battery, an electrode using a porous metal sintered body having a large specific surface area is used in order to allow a large current to be taken out. This sintered body is non-oxidized by pressing nickel powder or applying slurry-like nickel powder onto a core body, which is a punched steel sheet with a thickness of 80 μm or less plated with nickel. Manufactured by sintering at a temperature around 1000 ° C. in an atmosphere. By this heat treatment, a nickel-plated sintered body having a porosity in which a nickel-bonded punched steel sheet and nickel powder are joined by solid phase diffusion of nickel and bonded to each other and a network is formed. An electrode for a secondary battery bonded to a steel plate is manufactured.

  However, in a secondary battery electrode having a structure in which a porous metal sintered body and a metal core are joined only by solid phase diffusion, the adhesion is not sufficient, so that the electrode is wound around a cylindrical battery case. When assembled, the nickel porous sintered body may be peeled off or dropped from the steel plate as the core body, or the active material may fall off, and the dropped sintered body or active material may break through the separator and cause a short circuit.

Therefore, in Patent Document 1, a Ni-Co-P alloy layer or a Co-P layer is formed on the surface of a steel sheet, or a Co layer or a Co-P layer is further formed after forming a Ni layer or a Ni-P layer. A technique for improving the adhesion between the nickel porous sintered body and the steel sheet has been proposed.
International Publication No. WO01 / 004971 Pamphlet

  However, in the technique described in Patent Document 1, it is necessary to use an expensive metal called Co, which causes a significant increase in cost and does not necessarily provide excellent adhesion between the porous nickel sintered body and the steel plate. .

  The present invention has been made in view of such circumstances, and is inexpensive and surely capable of obtaining excellent adhesion between a nickel porous sintered body and a steel plate as a core, and a core for a secondary battery electrode and its An object is to provide a manufacturing method.

  The above-mentioned object is a two-layered structure composed of a perforated steel sheet, a plating layer made of Ni or Ni-Fe alloy formed on the steel sheet, and a conductive carbon film formed on the plating layer. This is achieved by the secondary battery electrode core.

  The C content of the steel sheet is preferably 0.05% by mass or less.

  Examples of conductive carbon films include diamond-like carbon films (diamond-like carbon (DLC) films: hard amorphous carbon films with a ps3 bond of about 10% or more, resulting in a hardness of about 10 GPa or more) ).

  The core for a secondary battery electrode of the present invention is manufactured by, for example, a method of forming a conductive carbon film by plasma CVD after forming a plated layer made of Ni or Ni-Fe alloy on a perforated steel sheet it can.

  According to the present invention, it is possible to manufacture a core for a secondary battery electrode that is inexpensive and reliably obtains excellent adhesion between a nickel porous sintered body and a steel plate as a core. Moreover, by using the core for secondary battery electrodes of the present invention, the charge / discharge characteristics of nickel-cadmium or nickel-hydrogen secondary batteries can also be improved.

  The present inventors have examined the improvement in adhesion between the nickel porous sintered body and the steel sheet as the core. As a result, a conductive layer is formed on the perforated steel sheet having a plated layer made of Ni or Fe-Ni alloy. It has been found that forming a carbon film is extremely effective. Although this cause is not necessarily clear, it is thought to be due to a so-called anchor effect in which a nickel sintered body enters a gap between carbon films and mechanical bonding is strengthened. Further, since only the carbon film is formed, there is no significant increase in cost.

  Examples of the conductive carbon film include the diamond-like carbon film described above. The diamond-like carbon film can be formed by plasma CVD at 20 to 300 ° C. for 10 to 200 minutes in a hydrocarbon atmosphere using a microwave as a plasma generation source. From the viewpoint of adhesion, the thickness of the carbon film is preferably 0.1 to 2 μm.

To form a plating layer made of Ni or Ni-Fe alloy on a steel plate, it can be performed under normal plating conditions, for example, pH 4 to 250 g / liter nickel sulfate, 40 g / liter nickel chloride, 25 g / liter. A Ni plating layer can be formed at a current density of 15 A / dm ² using a plating bath at 5 and 50 ° C. If the thickness of the plating layer is less than 0.5 μm, corrosion in the battery becomes a problem. On the other hand, if the thickness exceeds 3 μm, the adhesiveness deteriorates, so 0.5 to 3 μm is preferable. In the Ni—Fe alloy plating layer, the adhesion of the obtained carbon film can be brought to a more preferable level by containing 50% or less of Fe.

  In the steel sheet used for the core for a secondary battery electrode of the present invention, the C content is preferably 0.05% by mass or less in order to improve the adhesion of the plating layer made of Ni or Ni—Fe alloy. Other steel plate components are not particularly limited, but in particular, by mass%, C: 0.005% or less, Si: 0.05% or less, Mn: 0.5% or less, P: 0.05% or less, N: 0.005% or less, sol .Al: A steel plate composed of 0.0001 to 0.1%, the balance Fe and inevitable impurities is suitable. Such a steel sheet can be produced, for example, by subjecting a slab composed of the above components to hot rolling, pickling, cold rolling and annealing once or multiple times.

  Contains by mass: C: 0.0030%, Si: 0.01%, Mn: 0.14%, P: 0.01%, S: 0.0028%, sol.Al: 0.0002%, N: 0.0018%, the balance being Fe and inevitable The steel made of impurities was cast, and the obtained slab was hot-rolled to a thickness of 2.0 mm, pickled, and cold-rolled and annealed twice to obtain a steel plate having a thickness of 0.08 mm.

  A number of 1mm diameter holes were formed in the annealed steel plate by punching, then a Ni plating layer with a thickness of 3μm was formed, and the above diamond-like carbon film was carbonized using a microwave as a plasma generation source. A core for a secondary battery electrode was produced by plasma CVD at 100 ° C. for 60 minutes in a hydrogen atmosphere. At this time, the thickness of the diamond-like carbon film was 0.5 μm. Then, the porous nickel sintered compact was formed in this core for secondary battery electrodes, and the electrode was manufactured. As a comparison, an electrode in which a porous nickel sintered body was directly formed on a Ni plating layer without forming a diamond-like carbon film was also produced. The manufactured electrode was bent at a bending diameter of 1 mm and 180 degrees, and the degree of peeling of the nickel sintered body from the core was visually evaluated.

  As a result, the core for a secondary battery electrode on which the diamond-like carbon film according to the present invention was formed had no peeling and was excellent in adhesion. On the other hand, in the core for a secondary battery electrode in which the diamond-like carbon film for comparison was not formed, peeling was observed on the entire surface of the core.

Claims (4)

  A core for a secondary battery electrode, comprising: a perforated steel sheet; a plating layer made of Ni or a Ni-Fe alloy formed on the steel sheet; and a conductive carbon film formed on the plating layer. body.   2. The core for a secondary battery electrode according to claim 1, wherein the C content of the steel sheet is 0.05% by mass or less.   3. The secondary battery electrode core according to claim 1, wherein the conductive carbon film is a diamond-like carbon film. A method for producing a core for a secondary battery electrode, wherein a conductive carbon film is formed by a plasma CVD method after forming a plated layer made of Ni or a Fe-Ni alloy on a perforated steel sheet.
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