JP3497754B2 - Surface-treated steel sheet for battery case, method of manufacturing the same, battery case using surface-treated steel sheet for battery case, and battery using same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 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 to be processed into a bottomed tubular shape by using a forming method such as drawing, a manufacturing method thereof, and a battery case using the surface-treated steel sheet for a battery case, and the same. Relates to a battery using.

[0002]

2. Description of the Related Art In recent years, as a battery case for encapsulating a particularly strong alkaline electrolyte such as an alkaline manganese battery or a nickel cadmium battery, (1) a cold-rolled steel plate is formed into a cylindrical battery case with a bottom by deep drawing. Either by so-called post-plating method of forming and then barrel-plating nickel, (2) so-called pre-plating method of forming a nickel-plated cold-rolled steel sheet into a cylindrical battery case with a bottom by deep drawing, 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 that encloses alkaline electrolyte, The contact resistance is stable when connecting to.

The post-plating method in which a cold-rolled steel sheet is formed into a battery case and then barrel-plated with nickel is used. Since it is difficult to stably secure the thickness, a so-called pre-plating method has recently been used, in which a cold-rolled steel sheet plated in advance with nickel is formed into a battery case.

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

In addition, various contrivances have been made regarding the plating applied to the cold rolled steel sheet. For example, Japanese Patent Laid-Open No. 7-1222
No. 46 discloses a steel plate surface corresponding to the inner surface of the battery case.
It is disclosed that a nickel-tin alloy layer having a thickness of 0.15 to 3 μm is formed, and the contact electric resistance can be stably kept low even in a strong alkaline environment in the battery. Further, in Japanese Patent Laid-Open No. 8-150501, a steel plate surface corresponding to the inner surface of the 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 the nickel plating surface is roughened by subjecting it to cathodic treatment or cathodic treatment followed by anodizing to improve the battery performance.

However, recently, due to the rapid spread of various portable electric devices such as mobile phones, further improvement in characteristics such as capacity and output of batteries used therein has been demanded. The contact resistance based on the surface condition of the inner surface of the battery case has a great influence. However, the above improvement cannot always bring about a sufficient improvement in characteristics. That is, the method disclosed in JP-A-7-122246 is to form fine irregularities on the inner surface of the battery case by causing cracks in the hard nickel-tin alloy layer when the plated steel sheet is formed into the battery case. However, it is difficult to obtain stable battery performance because the size and density of the cracks that are generated differ depending on the processing method and the degree of processing. The method of Japanese Patent Laid-Open No. 8-150501 discloses a method in which the nickel plating layer itself is surface-dissolved by anodizing to roughen the surface, so that the degree of roughening is small and the contact with the positive electrode mixture is improved. It is difficult to obtain the required degree of unevenness.

[0007]

DISCLOSURE OF THE INVENTION In the present invention, a surface-treated steel sheet for a battery case, which provides stable low contact resistance when formed into a battery case and can improve battery characteristics, a method for producing the same, and An object of the present invention is to provide a battery case using the surface-treated steel sheet for battery case, and a battery using the battery case.

[0008]

The surface-treated steel sheet for a battery case of the present invention is an exposed steel sheet obtained by forming a discontinuous nickel plating layer on one surface of a low carbon steel sheet and subjecting the one surface to anodic electrolysis in an acidic solution. It is characterized in that a portion is melted to form a large number of minute pits, and then nickel plating layers are formed on both surfaces, and that a large number of minute pits are formed on one side. Further, a nickel-iron alloy layer may be formed between the low carbon steel plate and the nickel plating layer.

The method for producing a surface-treated steel sheet for a battery case according to the present invention is applied to one surface of a low carbon steel sheet in an amount of 0.05 to 0.50 g.
/ M ² thin and discontinuous nickel plating is applied to partially expose the base steel, and then the one surface is adjusted to pH 2 to
After anodic electrolysis in the acidic solution of No. 5 to dissolve only the exposed steel plate portion to generate a large number of minute pits on the steel plate surface, nickel plating is applied to both surfaces at an adhesion amount of 9 to 45 g / m ² to cover the entire steel plate surface. It is characterized by coating. In addition, the above discontinuous nickel plating is applied to one surface of the low carbon steel plate, then a large number of minute pits are formed on the exposed steel plate surface, and then nickel plating is applied to both surfaces, and then 450 to 700.
The nickel and iron may be diffused by heating to ℃ to improve the corrosion resistance and moldability of the battery case.

The battery case of the present invention is obtained by forming the surface-treated steel sheet for a battery case described above into a bottomed cylindrical shape with one surface having the large number of minute pits being the inner surface side. The battery of the present invention is manufactured using this battery case.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
First, as a steel plate that serves as a substrate of the surface-treated steel plate for a battery case of the present invention, a normal aluminum killed low carbon steel, or an ultra low carbon steel having a carbon content of 0.003% by weight or less, niobium,
Non-aging ultra-low carbon steel with a small amount of titanium added is used. The cold-rolled steel sheet as the substrate is a hot-rolled steel sheet made of these low-carbon steels, according to a conventional method, pickling, cold rolling, electrolytic degreasing,
It can be obtained by annealing and temper rolling.

Next, a slight 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 standard method to remove the oil and fat remaining on the surface, electrolytic treatment or immersion treatment in a hydrochloric acid or sulfuric acid aqueous solution is performed to remove the iron oxide on the surface. On one side of the steel plate whose surface is cleaned in this way, 0.05 to 0.
Nickel plating is performed 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, or a sulfamic acid bath is preferable because the adhesion amount can be strictly controlled. The nickel plating may be matte plating, semi-bright plating using a plating bath in which an organic brightening agent is added to the plating bath, or bright plating.

The coating weight is 0.05 to 0.50 g / m
^The reason for defining ² is that the amount of adhesion does not completely cover the entire surface of the steel sheet, resulting in discontinuous plating and partially exposing the surface of the steel sheet. By providing the exposed portion on the surface of the steel sheet in this manner, it becomes possible to generate only minute pits by dissolving only the exposed portion of the steel sheet by anodizing in the next acidic solution. When 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 is reduced 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 plate surface is locally exposed is formed on the steel plate surface.

Next, this discontinuous nickel-plated surface is subjected to anodic electrolysis in an acidic solution of pH 2-5. pH is 2
If less than, nickel will also dissolve together with the steel,
The desired minute pit cannot be formed. On the other hand, when the pH exceeds 5, nickel is hardly dissolved, the melting of steel does not proceed, and clear pits are not formed. The acidic solution is not particularly limited as long as the pH of the bath is within the above range, but it is difficult to stably control the pH within the above range by only diluting an acid such as hydrochloric acid or sulfuric acid. It is preferable to use a salt of ammonium chloride, sodium sulfate, ammonium sulfate, or a solution in which a weak acid such as boric acid or acetic acid is appropriately added to these salts. Adjust the pH as above and adjust the bath temperature to 30
Current density 10-60 using acidic solution
Anodic electrolysis is carried out under the conditions of A / dm ² and energization time of 0.3 to 5 seconds.

FIG. 2 (a) is a schematic sectional view of a steel sheet plated with discontinuous nickel under the above conditions. Steel plate 3
The figure shows a state in which discontinuous nickel plating 1 is formed with the steel plate exposed portion 2 left above. FIG. 2 (b) is a schematic cross-sectional view when anodic electrolysis is further performed. This shows a state in which the exposed portion of the steel sheet is preferentially melted by anodic electrolysis and a large number of minute pits 4 are formed.

In this way, the adhesion amount of 9 to 45 g / m ² is applied to both surfaces of the steel sheet having a large number of minute pits formed on one surface.
To plate nickel. As the nickel plating bath, the plating bath used for the discontinuous plating can be applied as it is. That is, a known Watt bath, a chloride bath, a plating bath for dull plating such as a sulfamic acid bath, a semi-bright plating in which an organic brightening agent is further added to these plating baths, or a plating bath for bright plating Can be used.

If the amount of plating adhered to the inner surface of the battery case is less than 9 g / m ^2, corrosion resistance to the strongly alkaline electrolyte filled in the battery case is insufficient and iron ions are dissolved from the base steel sheet, which is preferable. Absent. On the other hand, 45
When the coating amount is more than g / m ² , the battery characteristics such as corrosion resistance do not cause any problems, but it is not advantageous in terms of productivity and cost. The amount of plating adhered to the outer surface of the battery case may be such that sufficient corrosion resistance can be obtained in the use atmosphere, and the same amount as the inner surface or a smaller amount than the inner surface can be used.

Although it is possible to directly process the nickel-plated steel sheet produced as described above to form a battery case, after nickel-plating both sides, 4
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 of 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, while when the heating temperature exceeds 700 ° C, the degree of softening becomes remarkable and it becomes necessary to re-roll to recover the strength. It is practically preferable that after the above diffusion heat treatment is performed, temper rolling is performed at a mild reduction rate of about 1 to 2% to suppress the occurrence of stretcher strain.

The surface-treated steel sheet for battery case of the present invention thus obtained is formed into a cylindrical shape with a bottom to obtain a battery case. As the processing method for forming into a bottomed cylindrical shape, drawing, drawing and ironing (DI processing), thinning drawing (DTR processing) that bends back to reduce the thickness during drawing, and ironing during bending back Any method such as a processing method in which processing is used in combination to reduce the thickness can be applied. A battery case molded into a bottomed cylindrical shape by using such a processing method is filled with an electrode plate, an active material, a separator, and the like together with an electrolytic solution, and a lid is caulked and sealed to obtain a battery.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to 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% by weight, balance: Fe plate thickness: 0.25 mm
After cold rolling and annealing the low carbon steel sheet of, the concentration: 30 g /
l, temperature: 85 ° C., aqueous sodium hydroxide solution, current density: 5 A / dm ² , energization time: 5 seconds, followed by cathodic electrolysis to degrease and wash with water, concentration: 50 g / l, temperature: 30 ° C.
The steel sheet surface was cleaned by immersing it in the sulfuric acid aqueous solution of 5 seconds, pickling it, and washing it with water. Then, the following plating bath (Watts bath) was used on one surface thereof, the energization time was changed under the following conditions, and nickel plating was performed with the deposition amount shown in Table 1 to obtain a single-sided discontinuous plated steel sheet.

Next, only on one surface of the single-sided discontinuously plated steel sheet plated with nickel, salt (sodium sulfate) or weak acid (boric acid) was added to an acidic solution having the basic composition shown below, and the results are shown in Table 1. An acidic solution having the indicated pH was prepared, and the energization time was changed under the following conditions for anodic electrolysis to form fine pits.

The same plating bath as above was used on both sides of the single-sided porous steel sheet having fine pits formed on one side as described above, and the same plating conditions as above were used except for the energizing time.
A sample was obtained by nickel plating with the adhesion amount shown in.

A part of the sample thus obtained was composed of hydrogen: 5.5% by volume and the balance of nitrogen, and had a dew point of -35.
A nickel-iron diffusion layer was formed by heating under the conditions shown in Table 1 in a non-oxidizing atmosphere at 0 ° C.

[Evaluation of Micro Pits] The states of the micro pits formed on the surface of these samples were observed using a scanning electron microscope under the conditions shown below, and evaluated according to the criteria shown below. (Observation conditions) Observation site: 5 areas of each sample Observation field of view: 5 cm x 6 cm (magnification: 500 times) (Evaluation criteria) A: Formation of more than 40 minute pits is observed. ◯: Formation of 20 to 40 minute pits is recognized. Δ: Formation of 10 to 20 minute pits is recognized. X: Formation of less than 10 minute pits is recognized.

[Evaluation of Battery Characteristics] (Preparation of Battery Case) The samples shown in Table 1 were blank diameter: 5
Outer diameter: 13.8 m by punching into a 8 mm disk and drawing 10 steps and bending and bending back processing (DTR processing)
m, case wall thickness: 0.20 mm, height 45 mm LR
It was molded into a case for a 6-type battery. Next, 80 parts by weight of graphite and 20 parts by weight of epoxy resin are diluted with methyl ethyl ketone and sprayed on the inner surface of the battery case.
Minute drying was performed to form a conductive film. The amount of graphite adhered was 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, 1 manganese dioxide and graphite
It was sampled at a ratio of 0: 1, and potassium hydroxide having a concentration of 8 mol was added and mixed to prepare a positive electrode mixture. Next, this positive electrode mixture was pressure-pressed in a mold to prepare donut-shaped positive electrode mixture pellets having a predetermined size, which was then pressure-inserted into a battery case having a conductive film formed on its inner surface. Next, the negative electrode plate obtained by spot-welding the negative electrode current collector rod was attached to the battery case. Next, a separator made of vinylon non-woven fabric was inserted into the battery case along the inner circumference of the pellet, 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 attached to the negative electrode plate, and this was placed in the battery case, followed by caulking to obtain the 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 preparing the battery, leave it at 20 ° C. for 1 hour, then store at 60 ° C. for 4 weeks. After keeping for a while, connect an AC milliohm tester between the positive electrode and the negative electrode, and use the AC impedance method (frequency: 1 kH
The internal resistance was measured using z). The results are shown in Table 1.

[0028]

[Table 1]

[0029]

The surface-treated steel sheet for battery case of the present invention is
The battery has a large number of minute pits on its inner surface, and the surface-treated steel sheet for a battery case is formed into a battery case to produce a battery, which has low internal resistance and excellent battery characteristics.

[Brief description of drawings]

FIG. 1 is a diagram showing a steel sheet surface on which a discontinuous nickel plating layer is formed, where the steel sheet surface is locally exposed.

FIG. 2 (a) is a schematic cross-sectional view of a plated steel sheet obtained by performing discontinuous nickel plating on the steel sheet, and FIG. 2 (b) is a view showing that the discontinuous nickel plated steel sheet is further subjected to anodic electrolysis to form fine pits. It is a schematic cross-sectional view of a steel plate.

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

[Explanation of symbols]

1: Nickel plated layer, 2: Steel plate exposed portion, 3: Steel plate, 4: Micro pits 5: Alkaline manganese battery, 6: Battery case, 7:
Positive electrode mixture, 8: Negative electrode collector rod 9, Negative electrode plate, 10: Gasket, 11: Separator, 1
2: Negative electrode gel

Continuation of front page (51) Int.Cl. ⁷ identification code FI H01M 2/02 H01M 2/02 E (56) Reference JP-A-7-300695 (JP, A) JP-A-6-346284 (JP, A ) Japanese Patent Laid-Open No. 5-21044 (JP, A) International Publication 97/044835 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C25D 5/00-7/12 H01M 2/02

Claims (6)

(57) [Claims] 1. After forming a discontinuous nickel plating layer on one surface of a low carbon steel sheet, the one surface is subjected to anodic electrolysis in an acidic solution to dissolve exposed steel sheet portions to form a large number of fine pits, and thereafter, A surface-treated steel sheet for a battery case, characterized in that it has a large number of fine pits on one side, which is formed by forming nickel plating layers on both sides. 2. A nickel-iron alloy layer is formed between the low carbon steel plate and the nickel plating layer.
The surface-treated steel sheet for a battery case according to. 3. The amount of adhesion on one surface of the low carbon steel plate is 0.05 to 0.5.
After applying discontinuous nickel plating at 50 g / m ² and then subjecting one side to anodic electrolysis in an acidic solution of pH 2 to 5 to form a large number of fine pits on the exposed steel plate surface, the amount of adhesion on both sides is 9 to 45 g / m 2. ^{2. A} method for producing a surface-treated steel sheet for a battery case, which comprises applying nickel plating in ² . 4. A low carbon steel plate 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 plate surface, and then nickel plating is applied to both sides, A method for producing a surface-treated steel sheet for a battery case, which comprises heating to 450 to 700 ° C. to diffuse nickel and iron. 5. A battery case formed by forming the surface-treated steel sheet for battery case according to claim 1 or 2 into a bottomed tubular shape with one surface having the large number of minute pits being the inner surface side. . 6. A battery using the battery case according to claim 5.