JP2000192281A - Surface treated steel sheet for electric cell case, its production, electric cell case using the surface treated steel sheet and electric cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart stable and low contact resistance and to improve cell characteristics by discontinuously forming nickel plated layers on one side of the surfaces of a low carbon steel sheet, then anodically electrolyzing the one side of the surfaces in an acidic solution in order to form many small pits at exposed steel parts and forming a nickel plated layer onto the both surfaces of the steel sheet. SOLUTION: Discontinuous nickel plated layers 1 having a mass of deposit of 0.05-0.50 g/m2 are formed on one side of the surfaces of an aluminum killed low carbon steel sheet 3, whose surface has been cleaned by dewaxing and removing iron oxides. The discontinuously nickel plated surface is anodically electrolyzed in an acidic solution having a pH of 2-5 at a bath temp. of about 30-60 deg.C and at a current density of about 10-60 A/dm2 for about 0.3-5 sec in order to solve only exposed steel parts 2 and form many small pits 4. Thereafter, both surfaces of the steel sheet 3 having many small pits on its one surface are subjected to nickel plating for forming nickel plated layer having a mass of deposit of 9-45 g/cm2. If necessary, the adherability is enhanced by forming a nickel-iron diffusion layer between nickel plated layer and the steel sheet by heating at 450-700 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface-treated steel sheet used for a battery case, a method for manufacturing the same, a battery case using the above-described surface-treated steel sheet for a battery case, and a battery using the same. More specifically, a surface-treated steel sheet suitable for a battery case processed into a cylindrical shape with a bottom using a forming method such as drawing, a method for manufacturing the same, and a battery case using the surface-treated steel sheet for the battery case, and And a battery using the same.

[0002]

2. Description of the Related Art In recent years, battery cases, such as alkaline manganese batteries and nickel cadmium batteries, in which a strongly alkaline electrolytic solution is filled, are as follows: (1) A cold-rolled steel plate is formed into a bottomed cylindrical battery case by deep drawing. Forming and then barrel plating nickel, the so-called post-plating method, or (2) so-called pre-plating method of forming a nickel-plated cold-rolled steel sheet into a bottomed cylindrical battery case by deep drawing or the like, Being manufactured. The reason why nickel plating is applied to the battery case is that nickel has excellent corrosion resistance to strong alkali such as potassium hydroxide in the battery case in which the alkaline electrolyte is sealed, and the battery is connected to the external terminal. And that the contact resistance is stable.

[0003] The post-plating method in which a cold-rolled steel sheet is formed into a battery case and then nickel is barrel-plated is a method in which the plating thickness at each part of the case, particularly the nickel plating applied to the inner surface of the battery case is reduced to a uniform thickness. Since it is difficult to ensure a stable thickness, a so-called pre-plating method of forming a nickel-plated cold-rolled steel sheet into a battery case in recent years has become mainstream.

In these nickel-plated battery cases, (1) a conductive material such as carbon is applied to the inner surface of the battery case for the purpose of improving various characteristics such as short-circuit current and discharge characteristics of the battery. 2) Various measures have been taken such as providing fine irregularities on the inner surface of the battery case to improve the contact with the positive electrode mixture.

[0005] Also, various ideas have been devised for plating applied on cold-rolled steel sheets. For example, Japanese Unexamined Patent Publication No.
No. 46 discloses a steel plate surface corresponding to the inner surface of a battery case.
It discloses that a nickel-tin alloy layer having a thickness of 0.15 to 3 μm can be formed to stably maintain a low contact electric resistance even under a strong alkaline environment in a battery. Further, JP-A-8-150501 discloses that a steel plate surface corresponding to the inner surface of a battery case is nickel-plated to a thickness of 0.5 to 5 μm, and then anodized in an acid solution of 1 to 10% by weight. It is disclosed that a cathode treatment is performed later, or a cathode treatment is performed and then an anodization treatment is performed to roughen a nickel plating surface to improve battery performance.

[0006] However, recently, with the rapid spread of various portable electric devices such as portable telephones, further improvement of characteristics such as capacity and output of a battery used therein has been demanded. Also, the contact resistance based on the surface condition of the inner surface of the battery case has a great influence. However, the above-mentioned improvement does not always bring about a sufficient improvement in characteristics. In other words, the method disclosed in Japanese Patent Application Laid-Open No. 7-122246 is to form fine irregularities on the inner surface of the battery case by generating cracks in the hard nickel-tin alloy layer when forming the plated steel sheet into the battery case. However, the size and density of cracks generated depending on the processing method and processing degree are different, and it is difficult to obtain stable battery performance. The method disclosed in Japanese Patent Application Laid-Open No. 8-150501 is a method in which a nickel plating layer itself is surface-dissolved by anodic treatment to roughen the surface, and the degree of surface roughening is small, and the contact with the positive electrode mixture is improved. It is difficult to obtain a necessary degree of unevenness.

[0007]

SUMMARY OF THE INVENTION In the present invention, a surface-treated steel sheet for a battery case, which is capable of providing a stable low contact resistance when formed into a battery case and improving the battery characteristics, a method for producing the same, and An object of the present invention is to provide a battery case using the above-mentioned surface-treated steel sheet for a battery case, and a battery using the same.

[0008]

The surface-treated steel sheet for a battery case of the present invention comprises a low-carbon steel sheet having a discontinuous nickel plating layer formed on one side thereof, and then anodizing the one side in an acidic solution to expose the steel sheet. The method is characterized in that a portion is melted to generate a large number of fine pits, and then a nickel plating layer is formed on both surfaces, and has a large number of fine pits on one surface. Further, a nickel-iron alloy layer may be formed between the low carbon steel sheet and the nickel plating layer.

The method for producing a surface-treated steel sheet for a battery case according to the present invention comprises the steps of: adhering 0.05 to 0.50 g to one surface of a low carbon steel sheet;
/ M ^2, a thin and discontinuous nickel plating is applied to partially expose the base steel.
After anodic electrolysis in an acidic solution of No. 5 to dissolve only the exposed steel plate portion to generate a large number of fine pits on the steel plate surface, nickel plating is performed on both surfaces with an adhesion amount of 9 to 45 g / m ² to cover the entire steel plate surface. It is characterized by coating. Further, the discontinuous nickel plating is applied to one surface of the low carbon steel sheet, and then a large number of minute pits are generated on the exposed steel sheet surface. Then, after nickel plating is applied to both surfaces, 450 to 700
C. to diffuse nickel and iron to improve the corrosion resistance and moldability of the battery case.

[0010] The battery case of the present invention is obtained by forming the above-mentioned surface-treated steel sheet for a battery case into a bottomed cylindrical shape such that one surface having a large number of minute pits faces the inner surface side. And the battery of this invention is manufactured using this battery case.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
First, as a steel sheet serving as a substrate of the surface-treated steel sheet for a battery case of the present invention, niobium is used for ordinary aluminum-killed low-carbon steel or ultra-low carbon steel having a carbon content of 0.003% by weight or less.
Use non-aging ultra-low carbon steel with a small amount of titanium added. The cold-rolled steel sheet used as the substrate is prepared by pickling, cold-rolling, electrolytic degreasing,
Obtained by performing annealing and temper rolling.

Next, a small amount of discontinuous nickel plating is applied to one surface of the cold-rolled steel sheet obtained as described above. After electrolytic degreasing in a hot alkaline aqueous solution by a conventional method to remove fats and oils remaining on the surface, electrolytic treatment or immersion treatment in a hydrochloric acid or sulfuric acid aqueous solution is performed to remove iron oxide on the surface. On one side of the steel sheet whose surface has been cleaned in this manner, 0.05 to 0.5.
Nickel plating is applied with an adhesion amount of 50 g / m ² . The nickel plating may be electroless plating, but electroplating using a known nickel plating bath such as a Watts bath, a chloride bath, and a sulfamic acid bath is preferable because the amount of deposition can be strictly controlled. Nickel plating may be either matte plating, semi-glossy plating using a plating bath in which an organic brightener is added to the plating bath, or bright plating.

The coating weight is 0.05 to 0.50 g / m.
^The reason for defining as ² is that with this amount of adhesion, the entire surface of the steel sheet is not completely covered, resulting in discontinuous plating and the surface of the steel sheet is partially exposed. By providing the exposed portion on the surface of the steel sheet in this manner, it is possible to dissolve only the exposed portion of the steel sheet by anodic treatment in the next acidic solution to generate minute pits. If the coating weight is less than 0.05 g / m ² , the exposed area of the steel sheet is too large, and it is difficult to obtain fine pits. On the other hand, when the coating weight exceeds 0.50 g / m ² , the exposed portion of the steel sheet decreases, and it becomes difficult to obtain a large number of fine pits. In this way, as shown in FIG. 1, a discontinuous nickel plating layer in which the steel sheet surface is locally exposed is formed on the steel sheet surface.

Next, the surface subjected to the discontinuous nickel plating is subjected to anodic electrolysis in an acidic solution having a pH of 2 to 5. pH 2
If less, nickel will also dissolve along with the steel,
The desired minute pit cannot be formed. On the other hand, when the pH exceeds 5, nickel hardly dissolves, the dissolution of steel does not progress, and clear pits are not formed. The acidic solution is not particularly limited as long as the pH of the bath is in the above range, but it is difficult to stably manage the pH in the above range only by diluting an acid such as hydrochloric acid or sulfuric acid. , Ammonium chloride, sodium sulfate, ammonium sulfate and the like, and a liquid obtained by appropriately adding a weak acid such as boric acid and acetic acid to these salts. Adjust the pH as above and adjust the bath temperature to 30
Current density of 10 to 60 using an acidic solution adjusted to
The anodic electrolysis is performed under the conditions of A / dm ² and an energizing time of 0.3 to 5 seconds.

FIG. 2A is a schematic cross-sectional view showing a case where the steel sheet is subjected to discontinuous nickel plating under the above conditions. Steel plate 3
The state where discontinuous nickel plating 1 is formed leaving exposed steel plate portion 2 on the upper side is shown. FIG. 2B is a schematic cross-sectional view when anodic electrolysis is further performed. This shows a state in which the exposed portion of the steel plate is preferentially melted by anodic electrolysis, and a number of minute pits 4 are formed.

In this way, the steel sheet having a large number of fine pits formed on one side has an adhesion amount of 9 to 45 g / m ^{2 on} both sides.
With nickel. As the nickel plating bath, the plating bath used for the discontinuous plating described above can be applied as it is. That is, any of known plating baths for matte plating such as a Watts bath, a chloride bath, and a sulfamic acid bath, semi-glossy plating obtained by adding an organic brightener to these plating baths, and plating baths for bright plating. May be used.

When the amount of plating on the inner side of the battery case is less than 9 g / m ^2, iron ions are dissolved from the base steel sheet because the corrosion resistance to the strong alkaline electrolyte filled in the battery case is insufficient and iron is dissolved. Absent. On the other hand, 45
If the plating amount exceeds g / m ² , there is no problem in battery characteristics such as corrosion resistance, but it is not advantageous in terms of productivity and cost. The amount of plating on the outer surface of the battery case may be such that sufficient corrosion resistance can be obtained in the use atmosphere, and may be the same as the inner surface or less than the inner surface.

The nickel-plated steel sheet prepared as described above can be processed as it is to form a battery case.
By heating to 50 to 700 ° C. to form a nickel-iron spreading layer between the nickel plating layer and the steel sheet, the corrosion resistance and adhesion between the nickel plating layer and the steel sheet, particularly the adhesion when forming into a battery case Can be improved. When the heating temperature is lower than 450 ° C., it takes a long time to form the diffusion layer. On the other hand, when the heating temperature is higher than 700 ° C., the degree of softening becomes remarkable, and it is necessary to recover the strength by re-rolling. After the above diffusion heat treatment, it is practically preferable to perform temper rolling at a light reduction rate of about 1 to 2% to suppress the occurrence of stretcher strain.

The thus obtained surface-treated steel sheet for a battery case of the present invention is formed into a bottomed cylindrical shape to obtain a battery case. Examples of the processing method for forming a cylinder with a bottom include drawing, drawing and ironing (DI processing), thinning drawing (DTR processing) in which bending is performed at the time of drawing to reduce the thickness, and ironing is performed at the time of bending and returning. Any method such as a processing method for reducing the thickness by using the processing in combination can be applied. An electrode plate, an active material, a separator, and the like are filled together with an electrolytic solution into a battery case formed into a bottomed cylindrical shape formed by using such a processing method, and a lid is crimped to form a battery.

[0020]

The present invention will be described in more detail with reference to the following examples. (Example) [Preparation of sample] C: 0.04% by weight, Mn: 0.21% by weight, Si: 0.01% by weight, P: 0.013% by weight, S:
0.010% by weight, Al: 0.064% by weight, N: 0.0
03 wt%, balance: thickness of Fe: 0.25 mm
After cold rolling and annealing a low carbon steel sheet of
1, temperature: 85 ° C., aqueous sodium hydroxide solution, current density: 5 A / dm ² , energization time: 5 seconds, cathodic electrolysis for 5 seconds, degreased, washed with water, concentration: 50 g / l, temperature: 30 ° C.
For 5 seconds in an aqueous sulfuric acid solution, and pickled and washed with water to clean the surface of the steel sheet. Next, nickel plating was performed on one surface of the steel sheet using the following plating bath (watt bath) under the following conditions and the energizing time was changed, and the nickel plating was performed with the adhesion amount shown in Table 1 to obtain a single-side discontinuous plated steel sheet.

Next, a salt (sodium sulfate) or a weak acid (boric acid) was added to an acidic solution having the following basic composition on only one side of the nickel-plated single-side discontinuous-plated steel sheet. An acidic solution having the indicated pH was prepared, and anodic electrolysis was performed under the following conditions while changing the energization time to form minute pits.

The same plating bath was used on both sides of the single-sided porous steel sheet having fine pits formed on one side as described above, and the plating conditions were the same except for the energizing time.
Nickel plating was performed with the adhesion amount shown in Table 1 to obtain a sample.

A part of the sample thus obtained was composed of 5.5% by volume of hydrogen and the remainder of nitrogen, and had a dew point of -35.
Heating was performed in a non-oxidizing atmosphere at a temperature shown in Table 1 to form a nickel-iron diffusion layer.

[Evaluation of micro pits] The state of the micro pits formed on the surface of these samples was observed using a scanning electron microscope under the following conditions, and evaluated according to the following criteria. (Observation conditions) Observation site: 5 places for each sample Observation visual field area: 5 cm x 6 cm (magnification: 500 times) (Evaluation criteria) A: Formation of more than 40 micro pits is observed. ：: Formation of 20 to 40 minute pits is observed. Δ: 10 to 20 minute pits were formed. X: Formation of less than 10 minute pits is observed.

[Evaluation of battery characteristics] (Preparation of battery case)
Outer diameter: 13.8 m by punching into an 8 mm disc, 10 steps of drawing and bending and bending back (DTR processing)
m, Case wall thickness: 0.20mm, height 45mm LR
It was formed into a case for a 6-type battery. Next, 80 parts by weight of graphite and 20 parts by weight of epoxy resin were diluted with methyl ethyl ketone, sprayed on the inner surface of the battery case, and heated at 150 ° C. for 15 minutes.
After drying for a minute, a conductive film was formed. The amount of graphite attached was determined to be about 20 mg / can by measuring the difference between the weight of the can after drying and the weight of the can before spray coating.

(Preparation of Battery) Using the battery case prepared as described above, an alkaline manganese battery was prepared as follows. First, manganese dioxide and graphite
Samples were collected at a ratio of 0: 1, and potassium hydroxide having a concentration of 8 mol was added thereto and mixed to prepare a positive electrode mixture. Next, this positive electrode mixture was pressure-pressed in a mold to form a donut-shaped positive electrode mixture pellet having a predetermined size, and was press-inserted into a battery case having a conductive film formed on the inner surface. Next, the negative electrode plate obtained by spot welding the negative electrode current collecting rod was attached to the battery case. Next, a separator made of vinylon nonwoven fabric was inserted along the inner periphery of the pellet pressed into the battery case, and a negative electrode gel made of potassium hydroxide saturated with zinc particles and zinc oxide was inserted into the battery case. Further, an insulator gasket was mounted on the negative electrode plate, and the gasket was mounted in a battery case, and then caulked to obtain an alkaline manganese battery shown in FIG.

(Measurement of Internal Resistance) The characteristics of the battery prepared as described above were evaluated by measuring the internal resistance. After the battery was prepared, it was left at 20 ° C. for 1 hour and then stored at 60 ° C. for 4 weeks. After that, an AC milliohm tester was connected between the positive electrode and the negative electrode, and the AC impedance method (frequency: 1 kHz) was used.
The internal resistance was measured using z). Table 1 shows the results.

[0028]

[Table 1]

[0029]

The surface-treated steel sheet for a battery case according to the present invention comprises:
The battery has a large number of fine pits on its inner surface, and when a battery case is formed by molding this surface-treated steel sheet for a battery case into a battery case, the battery has low internal resistance and exhibits excellent battery characteristics.

[Brief description of the drawings]

FIG. 1 is a view showing a steel sheet surface on which a discontinuous nickel plating layer is formed in which the steel sheet surface is locally exposed.

FIG. 2 (a) is a schematic cross-sectional view of a plated steel sheet in which discontinuous nickel plating is applied to a steel sheet, and FIG. 2 (b) is further subjected to anodic electrolysis on the discontinuous nickel plated steel sheet to form minute pits. It is a schematic cross section of the steel plate which was set.

FIG. 3 is a schematic cross-sectional view of an alkaline manganese battery prepared using a battery case formed by processing the surface-treated steel sheet for a battery case of the present invention.

[Explanation of symbols]

1: nickel plating layer, 2: exposed part of steel sheet, 3: steel sheet, 4: micro pits 5, alkaline manganese battery, 6: battery case, 7:
8: negative electrode current collector rod 9: negative electrode plate, 10: gasket, 11: separator, 1
2: Negative electrode gel

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01M 2/02 H01M 2/02 E // H01M 6/08 6/08 A 10/30 10/30 Z F term (reference ) 4K023 AA12 BA06 BA08 CA09 DA02 DA07 DA08 4K024 AA03 AB07 BA03 BB18 DA02 DA04 DB01 DB07 GA16 5H011 AA04 BB03 CC06 DD00 DD18 KK04 5H024 AA03 BB11 CC02 CC14 DD01 EE01 EE03 5H028 AA03 BB03 BB03 CC

Claims (6)

[Claims] 1. After forming a discontinuous nickel plating layer on one side of a low carbon steel sheet, the one side is subjected to anodic electrolysis in an acidic solution to dissolve the exposed steel sheet portion to generate a large number of fine pits. A surface-treated steel sheet for a battery case, comprising a plurality of fine pits on one side, having nickel plating layers formed on both sides. 2. A nickel-iron alloy layer is formed between the low carbon steel sheet and the nickel plating layer.
Surface treated steel sheet for battery case according to 4. 3. A low carbon steel sheet having a coating amount of 0.05 to 0.5 on one surface.
Discontinuous nickel plating is performed at 50 g / m ² , and then one side is subjected to anodic electrolysis in an acidic solution having a pH of 2 to 5 to form a large number of fine pits on the surface of the exposed steel sheet. ^{2. A} method for producing a surface-treated steel sheet for a battery case, wherein nickel plating is performed in Step 2. 4. A low carbon steel sheet is subjected to discontinuous nickel plating on one side according to claim 3, then a large number of fine pits are formed on the exposed steel sheet surface, and then nickel plating is performed on both sides. A method for producing a surface-treated steel sheet for a battery case, wherein nickel and iron are diffused by heating to 450 to 700 ° C. 5. A battery case obtained by forming the surface-treated steel sheet for a battery case according to claim 1 or 2 into a bottomed cylindrical shape such that one surface having the plurality of minute pits faces the inner surface. . 6. A battery using the battery case according to claim 5.