JP2006310264A - Plated steel plate for battery case, battery case using plated steel plate for battery case, and battery using battery case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plated steel plate for battery case having no possibility of separation and cracks of the plate layer at forming process into battery case, superior in corrosion resistance to alkali solution, and having excellent battery characteristics, and a battery case using the plated steel plate for battery case, and a battery using the battery case. <P>SOLUTION: A plated steel plate in which bismuth plating is applied on the side of battery case inner face of steel plate and cobalt plating is applied on top of it, or a plated steel plate in which nickel plating is applied, and bismuth plating is applied on top of it, and further, cobalt plating is applied on the top, or a plated steel plate in which nickel plating is applied, then, heat treatment is applied, and bismuth plating is applied on top of it, and further, cobalt plating is applied on the top is formed to make the plated steel plate for battery case, and by forming process into battery case, it is applied to a battery. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plated steel sheet for battery containers, a battery container using the plated steel sheet for battery containers, and a battery using the battery container.

  In recent years, along with the development of portable AV equipment and mobile phones such as digital cameras, CDs, MD players, liquid crystal televisions, game machines, etc., alkaline batteries as primary batteries, nickel-metal hydride batteries as secondary batteries, lithium as operating power sources for heavy loads Ion batteries are often used. In these batteries, there is a demand for higher performance such as higher output and longer life, and battery containers filled with positive and negative electrode active materials are also required to have improved performance as important components of the battery. Yes. For example, in the case of an alkaline battery, a surface-treated steel sheet for a battery container in which a nickel-phosphorus alloy layer is formed on the inner surface of the battery case in order to improve the corrosion resistance against an alkaline solution that is an electrolytic solution for the purpose of extending the life. Has been proposed (see, for example, Patent Document 1).

  In addition, in order to prevent the high capacity of the battery and the deterioration of heavy load characteristics after storage, a nickel-silver alloy plating layer or a nickel-chromium alloy plating layer is formed on the rolled steel plate material on the surface that becomes the inner surface of the can, A method of reducing the internal resistance of the battery by reducing the internal resistance of the battery by increasing the contact area with the positive electrode mixture or conductive film by forming fine cracks by press drawing and ironing to form fine irregularities, After a nickel plating layer is formed and a silver plating layer is formed thereon, heat treatment is performed to form a nickel-silver plating layer, thereby reducing the plating crystals and increasing the hardness, further increasing the spacing between cracks. Thus, a battery can has been proposed in which the contact area with the positive electrode mixture or the conductive coating is further increased to reduce the internal resistance of the battery (see, for example, Patent Document 3).

  However, since the nickel-phosphorus alloy layer directly formed on the steel plate surface used for the battery container inner surface is hard and brittle, when forming into a container by drawing or drawing ironing, the underlying steel is exposed and electrolyzed. There is a possibility that the corrosion resistance to the alkaline solution which is a liquid may be lowered. Similarly, in the battery cans described in Patent Document 2 and Patent Document 3, if a fine crack is generated by press drawing, the steel base may be exposed and the corrosion resistance against the alkaline solution used for the electrolyte may be reduced. is there.

Prior art document information relating to the present application includes the following.
International Publication WO99 / 03161 Pamphlet JP-A-11-102671 JP 2001-325924 A

  In the present invention, when the battery container is pressed by drawing or squeezing and ironing, micro cracks that do not reach the steel substrate occur in the plating layer on the battery container inner surface side, and the positive electrode mixture of the alkaline battery and Improved adhesion and contact resistance of the battery container, and can sufficiently exhibit excellent battery performance after long-term storage, a battery container using the plated steel sheet for the battery container, and the battery container It aims at providing the battery using this.

In order to achieve the object of the present invention, the plated steel sheet for battery containers of the present invention is characterized in that a bismuth layer and a cobalt layer are formed in order from the bottom on the steel sheet on the side that is the inner surface of the battery container. A plated battery for a battery container (Claim 1), or a battery container plating, wherein a nickel layer, a bismuth layer, and a cobalt layer are formed in order from the bottom on a steel sheet on the side of the battery container that is the inner surface of the battery container. An iron-nickel alloy layer, a nickel layer, a bismuth layer, and a cobalt layer are formed in order from the bottom on a steel plate (Claim 2), or a steel plate on the side that is the inner surface of the battery case. Plated steel sheet (Claim 3),
Any one of the plated steel sheets for battery containers, wherein an iron-nickel alloy layer, a bismuth layer, and a cobalt layer are formed in order from the bottom on the steel sheet on the side that becomes the battery container inner surface of the steel sheet (Claim 4). It is.

  Moreover, the battery container of this invention is a battery container (Claim 5) formed by shape | molding the plated steel plate for battery containers in any one of the said (Claims 1-4) to a bottomed cylindrical shape. And the battery of this invention is a battery (Claim 6) using the battery container of said (Claim 5).

  The plated steel sheet for battery containers of the present invention is plated with bismuth on the inner surface of the battery container, then plated with cobalt, or nickel plated, and then coated with bismuth. And then a plated steel sheet with cobalt plating on it, or further with nickel plating, followed by heat treatment, then with bismuth plating on it, and then with cobalt plating on it. The plated steel sheet for battery containers according to any one of claims 1 to 4 can be obtained. Moreover, it becomes possible to provide the battery excellent in the discharge performance after a battery preservation | save by using the battery container formed by shape | molding the plated steel plate for battery containers.

  The bismuth layer or bismuth alloy layer formed on the battery container inner surface of the plated steel sheet for battery containers of the present invention is hard and brittle, so that when the battery container is molded, minute cracks are generated on the inner surface of the battery container. In addition, the adhesion when contacting the positive electrode mixture directly or through the conductive material applied to the inner surface of the battery container is improved, and deterioration of the contact resistance after storage is suppressed, and it is caused by micro cracks. The contact resistance is reduced by the small unevenness and the heavy load discharge performance is improved. In addition, by forming a cobalt layer on the bismuth layer, it is possible to further improve the conductivity, and also improve the powdering resistance of the plating surface when forming into a battery container. It becomes. Bismuth plating is prone to smut, so when forming into a battery container, smut, which is a bismuth oxide, adheres to and accumulates on the mold, making continuous molding impossible. The technique of the present invention for forming a cobalt layer thereon can solve the above-mentioned problems caused by bismuth smut. Furthermore, in the alkaline (potassium hydroxide) electrolyte solution, since there is little deterioration of cobalt conductivity over time (increased contact resistance), the positive electrode mixture due to micro-cracking of the brittle bismuth layer in the molding process of the battery container It has also been clarified by the present invention that the discharge performance after storage of the battery is improved in combination with the improvement of the adhesion of the battery.

  The contents of the present invention will be described below. As a steel plate used as a substrate for the plated steel plate for battery containers of the present invention, general-purpose low carbon aluminum killed steel (carbon content 0.01 to 0.15 wt%), or non-aging ultra-low carbon added with niobium or titanium. Aluminum killed steel (carbon content less than 0.01% by weight) is used. These steel hot-rolled plates are pickled to remove surface scales, then cold-rolled by a conventional method, and then subjected to electrolytic cleaning, annealing, and temper rolling as a substrate. Alternatively, an unannealed material that has been cold-rolled and then subjected to electrolytic cleaning can be used as a substrate. In this case, after the nickel plating process, the diffusion heat treatment of the nickel plating layer that also serves as the annealing of the steel substrate is performed by one heat treatment.

First, nickel plating is performed on one surface, which is the outer surface of a battery container of a steel plate as a substrate. For nickel plating, it is preferable to use a matte bath or a semi-gloss bath containing an organic additive. The plating thickness of the nickel plating is preferably 4.5 to 25 g / m ² . When the nickel plating thickness is less than 4.5 g / m ² , the corrosion resistance on the outer surface of the battery container is insufficient, and when it exceeds 25 g / m ² , the corrosion resistance reaches saturation, which is uneconomical.

Next, one side which is the inner surface of the battery container of the battery container is subjected to bismuth plating on the steel plate directly or after nickel plating. Bismuth plating dissolves in high-concentration potassium hydroxide aqueous solution, which is an electrolytic solution, but bismuth is an electrochemically noble metal, and manganese dioxide, which is a positive electrode active material, coexists with manganese dioxide rather than bismuth. The inventors have found through experiments that the bismuth of the plating film formed on the steel sheet does not dissolve and does not cause gas generation, which is an important factor harmful to the battery structure. When the bismuth layer is directly formed on the steel substrate, the coating amount is preferably 5 to ²⁰ g / m ² . If it is less than 5 g / m ² , the crack reaches the steel substrate when it is formed into a battery container and cannot sufficiently cover the steel substrate, and the steel substrate is exposed and comes into contact with the electrolyte. As a result, oxides are formed to increase the contact resistance, and the risk of gas generation increases. As the amount of coating increases, micro cracks when forming into a battery container will not reach the steel substrate and the steel substrate will not be exposed. However, if it exceeds 20 g / m ² , the improvement effect will reach saturation. It becomes uneconomical.

Since the bismuth alloy layer is hard and brittle, in order to suppress the exposure of the steel substrate due to the occurrence of microcracks when being molded into the battery container, the nickel layer or / and the lower layer on the steel substrate as the underlayer of the bismuth layer It is more preferable to form an iron-nickel alloy layer. The nickel plating is preferably provided with a coating amount of 5 to 25 g / m ² . If the coating amount is less than 5 g / m ² , the steel substrate exposure suppression effect is insufficient, and even if the coating amount exceeds 25 g / m ² , the steel substrate exposure suppression effect is saturated and economically undesirable. When a nickel layer and / or an iron-nickel alloy layer is provided as the base of the bismuth layer, the bismuth plating is preferably a coating amount of 1 to 10 g / m ² . If it is less than 1 g / m ² , the battery performance is not improved, and if it exceeds 10 g / m ² , the improvement effect reaches saturation and becomes uneconomical.

In this invention, it can be set as the outstanding formation material for batteries by providing a cobalt layer in the outermost surface by the side which becomes a battery container inner surface. As the coating amount of the cobalt plating, good electric conductivity and low gas generation can be brought about in the range of 0.25 to 5 g / m ² . If it is less than 0.25 g / m ² , the effect of improving the battery performance is insufficient, and if it exceeds 5 g / m ² , the improvement effect reaches saturation and cobalt is expensive, which is uneconomical.

  When heat treatment is performed after nickel plating, diffusion heat treatment is performed using either a box-type annealing method or a continuous annealing method. The heat treatment is performed under such a condition that a part or all of the nickel plating layer is converted into an iron-Nicke diffusion layer (alloy layer). That is, when the box-type annealing method is used, heating at less than 450 ° C. does not soften the nickel plating layer, and at the same time, no iron-nickel diffusion layer (alloy layer) is formed. On the other hand, when heated at a temperature exceeding 700 ° C., the iron-nickel diffusion layer (alloy layer) is sufficiently formed, but the steel substrate becomes too soft. For this reason, the heat treatment temperature is 450 to 650 ° C, preferably 500 to 600 ° C. The heating time is preferably soaking for 1 to 6 hours in the above temperature range. When using a continuous annealing method, it is preferable to set it as the heating time of 1 to 5 minutes at the heating temperature of 600-850 degreeC. By controlling the thickness of the nickel plating layer and the heat treatment conditions, a plated steel sheet for battery containers having the cross-sectional configuration shown in FIGS. 1 to 4 is obtained. In addition, FIGS. 1-4 shows the upper layer structure from the steel base of the side used as the battery container inner surface. The layer structure on the side corresponding to the outer surface of the battery container is a nickel layer on the steel base, an iron-nickel diffusion layer (alloy layer) on the steel base, or an iron-nickel diffusion layer (alloy layer) on the steel base. A nickel layer is formed thereon.

  In these plated steel sheets, when heat treatment is performed after nickel plating, temper rolling is usually performed at a rolling rate of 1.0 to 1.5% to obtain the plated steel sheet for battery containers of the present invention. If the stretcher strain generated during processing does not hinder, temper rolling can be omitted. In addition, it may replace with the plating layer only of nickel plating on the single side | surface used as the outer surface of the battery container of a steel plate, and may form each plating layer similar to the above given to the other one side used as the inner surface of a battery container.

  The battery container of the present invention is obtained by subjecting the above-described plated steel sheet for a battery container to a drawing process, a drawing ironing process (DI processing method), a drawing stretch processing method (DTR processing method), or a drawing process as a stretching process. It is obtained by forming into a bottomed cylindrical shape using the processing method used in combination. As the cylindrical shape, the bottom surface is a circle, an ellipse, or a polygonal shape such as a rectangle or a square, and is molded into a cylindrical shape with the side wall height appropriately selected according to the application. The battery container thus obtained is filled with a positive electrode mixture, a negative electrode active material, and the like to obtain a battery.

Hereinafter, the present invention will be described in detail with reference to examples.
[Creation of plated steel sheets for battery containers]
As the plating substrate, hot-rolled low carbon aluminum killed steel (I) or extremely low carbon aluminum killed steel (II) whose chemical composition is shown in Table 1 is used, and the battery container is subjected to the steps shown in the following a) to d). A plated steel sheet was created.
B) Low carbon aluminum killed steel (I) → Cold rolling → Electrolytic cleaning → Annealing (box annealing or continuous annealing) → Temper rolling → Nickel plating (outside) → Bismuth plating → Cobalt plating b) Low carbon aluminum killed steel ( I) → cold rolling → electrolytic cleaning → annealing (box annealing or continuous annealing) → temper rolling → nickel plating → bismuth plating → cobalt plating c) low carbon aluminum killed steel (I) → cold rolling → electrolytic cleaning → annealing (Box annealing or continuous annealing) → Temper rolling → Nickel plating → Diffusion heat treatment (Box annealing or continuous annealing) → Temper rolling → Bismuth plating → Cobalt plating d) Extremely low carbon aluminum killed steel (II) → Cold rolling → Electrolytic cleaning → Nickel plating → Annealing and diffusion heat treatment (continuous annealing) → Temper rolling → Bismuth plating → Cobalt plating b) Nickel plating in the process is outside the substrate container Only one side as a, b) is nickel plated-d) process both sides of a substrate, bismuth plating and cobalt plating was applied only to one side of the container inner surface of the substrate.

The hot rolled sheet of the above steel grade I or II is subjected to cold rolling and electrolytic cleaning by a conventional method to obtain a cold rolled sheet having a thickness of 0.25 mm, and in the case of steel grade I, box annealing. Annealing was performed in a furnace at a soaking temperature of 500 to 600 ° C. for 8 hours of soaking time. Next, bismuth plating, nickel plating, and cobalt plating were performed under the following conditions. In the case of steel type II, after nickel plating, annealing was performed in a continuous annealing furnace at a heating temperature of 780 ° C. for a heating time of 2 minutes. Next, bismuth plating and cobalt plating were performed under the following conditions.
<Bismuth plating>
Bath composition LMP-bismuth (Okuno Pharmaceutical Co., Ltd.) 200g / L
LMP-acid bismuth (Okuno Pharmaceutical Co., Ltd.) 100g / L
LMP-SG (Okuno Pharmaceutical Co., Ltd.) 10g / L
Anode Bismuth plate Stirring Circulation of plating bath pH 0.3 to 0.7
Bath temperature 40-45 ° C
Current density 5A / dm ²

<Nickel plating>
Bath composition Nickel sulfate 300g / L
Nickel chloride 35g / L
Boric acid 40g / L
Pit inhibitor (sodium lauryl sulfate) 0.4mL / L
Anode Nickel Pellet (Titanium basket filled with S pellets from INCO Corporation and equipped with polypropylene anode bag)
Stirring air stirring
pH 4.0-4.6
Bath temperature 55-60 ° C
Current density 10A / dm ²

<Silver plating>
Bath composition Cobalt sulfate 300g / L
Cobalt chloride 30g / L
Sodium chloride 25g / L
Boric acid 45g / L
Anode Insoluble anode with platinum plating on titanium plate Stirring Circulation of plating bath pH 3.7 to 4.3
Bath temperature 50 ° C
Current density 2.5A / dm ²

  C) When performing diffusion heat treatment after nickel plating in the step shown in FIG. 5B, when using a box annealing method, soaking temperature is 500 to 650 ° C. and soaking time is 6 to 8 in a nitrogen-hydrogen protective gas atmosphere. Time heat treatment was applied. Further, in the process shown in d), when the diffusion heat treatment of the plating layer that also serves as the annealing of the steel substrate is performed after nickel plating in one heat treatment, a continuous annealing method is used, and the heating temperature is 780 ° C. and the heating time is 1 A heat treatment of ˜2 minutes was performed.

Samples (sample numbers 1 to 12) of the plated steel sheets for battery containers shown in Tables 2 and 3 were prepared as described above. Further, a sample (Sample No. 13) that has been subjected to nickel plating for comparison using the low carbon aluminum killed steel (I), a sample that has been subjected to thermal diffusion treatment after the nickel plating (Sample No. 14), and after the nickel plating has been performed Then, a sample (sample number 15) subjected to nickel-phosphorus alloy plating and a sample (sample number 16) subjected to heat treatment after nickel-phosphorus alloy plating following nickel plating were prepared. Nickel-phosphorus alloy plating was performed under the following conditions.
<Nickel-phosphorus alloy plating>
Bath composition Nickel sulfate 300g / L
Nickel chloride 45g / L
Boric acid 40g / L
Phosphorous acid 10g / L
Anode Nickel Pellet (Titanium basket filled with S pellets from INCO Corporation and equipped with polypropylene anode bag)
Stirring air stirring
pH 1.5-2.0
Bath temperature 55-60 ° C
Current density 10A / dm ²

[Create battery container]
After punching blanks with a diameter of 57 mm from the samples of Sample Nos. 1 to 16, an outer diameter of 13 was obtained by ten-stage drawing so that the side on which only the iron-nickel alloy layer and the nickel layer were provided was the outer surface of the container. It was molded into a cylindrical LR6 type battery (AA size battery) container having a height of 4 mm and a height of 49.3 mm.

[Create battery]
Using this battery container, an alkaline manganese battery was prepared as follows. Manganese dioxide and graphite were collected at a ratio of 10: 1, and potassium hydroxide (10 mol) was added and mixed to prepare a positive electrode mixture. Next, this positive electrode mixture was pressed in a mold to form a doughnut-shaped positive electrode mixture pellet having a predetermined size, and was press-inserted into a battery container having a conductive material mainly composed of graphite powder applied on the inner surface. Next, the negative electrode plate spot-welded with the negative electrode current collector rod was attached to the battery container. Next, a separator made of vinylon woven fabric is inserted along the inner periphery of the positive electrode mixture beret pressure-inserted into the battery container, and a negative electrode gel made of potassium hydroxide saturated with zinc particles and zinc oxide is inserted into the battery container. Filled in. Further, an insulating gasket was attached to the negative electrode plate and inserted into the battery container, followed by caulking to prepare an alkaline manganese battery.

[Characteristic evaluation]
The characteristics of the batteries prepared using the battery containers prepared from the samples Nos. 1 to 16 as described above were evaluated as follows.

<Short-circuit current>
After leaving the battery at 80 ° C. for 3 days, an ammeter was connected to the battery, a closed circuit was provided, and the current value was measured, which was defined as a short-circuit current. It shows that a characteristic is so favorable that a short circuit current is large.

<Discharge characteristics (1.5 A discharge)>
After the battery was left at 80 ° C. for 3 days, the battery was discharged to a constant current of 1.5 A, and the time until the end voltage reached 0.9 V was measured as the discharge time. The longer the discharge time, the better the discharge characteristics.

<Intermittent discharge characteristics>
As an evaluation of the double-added intermittent discharge, an operation of discharging at 2A for 0.5 seconds and then discharging at 0.25A at 29.5 seconds is defined as one cycle, and this cycle is repeated until the voltage reaches 1.0V. Was measured. A high number of cycles indicates that the intermittent discharge characteristics are good. These evaluation results are shown in Table 4.

  As shown in Table 4, the plated steel sheet for battery containers of the present invention has any of short-circuit current, discharge characteristics (1.5 A discharge), and intermittent discharge characteristics compared to plated steel sheets for battery containers that do not form a bismuth layer and a cobalt layer. Also superior to.

  A bismuth layer and a cobalt layer formed thereon are formed on a steel plate, or an iron-nickel alloy layer or / and a nickel layer and a bismuth layer formed thereon and a cobalt layer formed thereon. The plated steel sheet for battery containers according to the present invention is free from peeling or cracking of the plating layer when it is formed into a container by drawing or drawing ironing, and the surface is excellent in alkali resistance and conductivity. Therefore, it can be suitably applied as a container for a high-performance battery excellent in battery characteristics such as discharge characteristics and a high-performance battery.

Sectional drawing which shows an example of an upper layer structure from the steel base of the side used as the battery container inner surface of the plated steel plate for batteries of this invention. Sectional drawing which shows another example of an upper layer structure from the steel base of the side used as the battery container inner surface of the plated steel plate for batteries of this invention. Sectional drawing which shows another example of an upper layer structure from the steel base of the side used as the battery container inner surface of the plated steel plate for batteries of this invention. Sectional drawing which shows another example of an upper layer structure from the steel base of the side used as the battery container inner surface of the plated steel plate for batteries of this invention.

Claims (6)

A plated steel sheet for a battery container, wherein a bismuth layer and a cobalt layer are formed in order from the bottom on the steel sheet on the side of the steel container that is the inner surface of the battery container. A plated steel sheet for a battery container, wherein a nickel layer, a bismuth layer, and a cobalt layer are formed in order from the bottom on the steel sheet on the side that is the battery container inner surface of the steel sheet. An iron-nickel alloy layer, a nickel layer, a bismuth layer, and a cobalt layer are formed in order from the bottom on a steel plate on the side that is the inner surface of the battery case of the steel plate. An iron-nickel alloy layer, a bismuth layer, and a cobalt layer are formed in order from the bottom on a steel plate on the side that is the inner surface of the battery case of the steel plate. The battery container formed by shape | molding the plated steel plate for battery containers of any one of Claims 1-4 in a bottomed cylindrical shape. A battery comprising the battery container according to claim 5.

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