U.S. patent application number 13/475720 was filed with the patent office on 2012-09-13 for surface treated steel sheet for battery case, battery case and battery using the case.
This patent application is currently assigned to Toyo Kohan Co., Ltd.. Invention is credited to Yoshitaka Honda, Hitoshi Ohmura, Tatsuo Tomomori.
Application Number | 20120231329 13/475720 |
Document ID | / |
Family ID | 29536166 |
Filed Date | 2012-09-13 |
United States Patent
Application |
20120231329 |
Kind Code |
A1 |
Ohmura; Hitoshi ; et
al. |
September 13, 2012 |
SURFACE TREATED STEEL SHEET FOR BATTERY CASE, BATTERY CASE AND
BATTERY USING THE CASE
Abstract
A surface treated steel sheet for a battery case, which has a
diffusion layer of a nickel-phosphorus alloy or a
nickel-cobalt-phosphorus alloy formed on the outermost layer of the
inside surface of a plated steel sheet for a battery case; a
battery case which is produced through forming the surface-treated
steel sheet having a diffusion layer of a nickel-phosphorus alloy
or a nickel-cobalt-phosphorus alloy by the deep drawing method, the
DI forming or the DTR forming: and a battery using the battery
case. The battery case can be used for producing a battery
excellent in battery characteristics.
Inventors: |
Ohmura; Hitoshi;
(Kudamatsu-shi, JP) ; Tomomori; Tatsuo;
(Kudamatsu-shi, JP) ; Honda; Yoshitaka;
(Kudamatsu-shi, JP) |
Assignee: |
Toyo Kohan Co., Ltd.
Chiyoda-ku
JP
|
Family ID: |
29536166 |
Appl. No.: |
13/475720 |
Filed: |
May 18, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13041207 |
Mar 4, 2011 |
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13475720 |
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10511844 |
Oct 19, 2004 |
7923145 |
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PCT/JP03/04869 |
Apr 17, 2003 |
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13041207 |
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Current U.S.
Class: |
429/176 ;
429/163 |
Current CPC
Class: |
Y10T 428/12937 20150115;
H01M 2/0257 20130101; Y10T 428/12951 20150115; C25D 5/50 20130101;
C25D 5/14 20130101; Y02E 60/10 20130101; H01M 2/0287 20130101; Y10T
428/12944 20150115; C23C 12/02 20130101; H01M 2/0285 20130101; Y10T
428/12972 20150115; C23C 30/00 20130101; C23C 10/28 20130101; H01M
2/0292 20130101 |
Class at
Publication: |
429/176 ;
429/163 |
International
Class: |
H01M 2/02 20060101
H01M002/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 22, 2002 |
JP |
2002-119679 |
Claims
1. A surface treated steel sheet for a battery case comprising: a
steel sheet having a first surface and a second surface, said first
surface to be used as the inner surface of the battery case and the
second surface to be used as the outer surface of the battery case;
a first diffusion layer of a nickel-cobalt phosphorous alloy formed
as an uppermost layer over said first surface of the battery case;
a second diffusion layer of iron-nickel between said first
diffusion layer and said steel sheet; a nickel layer formed as an
upper layer over the second surface; and an iron-nickel diffusion
layer between said nickel layer and said steel sheet, wherein the
first diffusion layer contains Ni.sub.3P, the cobalt content in the
first diffusion layer is within a range from 5 to 30% by weight,
the phosphorus content in the first diffusion layer is within a
range from 1 to 12% by weight, a thickness of the first diffusion
layer is in the range of 0.1 to 2 .mu.m, and a thickness of the
nickel layer is in the range of 0.2 to 3 .mu.m.
2. The surface treated steel sheet for a battery case according to
claim 1, wherein the surface treated steel sheet further comprises
an intermediate nickel layer between said first diffusion layer and
said second diffusion layer.
3. A battery case comprising the surface-treated steel sheet
according to claim 1, wherein the battery case is obtained by a
drawing forming method, drawing and ironing (DI) forming method, or
drawing thin and redraw (DTR) forming method.
4. A battery comprising a battery case according to claim 3,
including a positive electroactive substance and a negative
electroactive substance on the inside of the battery case.
Description
[0001] This is a divisional of application Ser. No. 13/041,207,
filed Mar. 4, 2011, which is a divisional of Ser. No. 10/511,844,
filed Oct. 19, 2004 (now U.S. Pat. No. 7,923,145, issued Apr. 12,
2011), which is the U.S. National Phase application of
International Application No. PCT/JP03/04869, filed Apr. 17, 2003,
such applications claiming the benefit under 35 USC .sctn.119 of
the filing date of Application No. 2002-119679 filed in Japan on
Apr. 22, 2002, the contents of each of which are incorporated
herein by reference.
TECHNICAL FIELD
[0002] The present invention concerns a surface treated steel sheet
for battery case, a battery case and a battery using the case.
BACKGROUND ART
[0003] Heretofore, in battery cases for sealing strongly alkaline
solutions of alkali-manganese batteries as primary batteries or
nickel-cadmium batteries as secondary batteries and, further,
nickel hydrogen batteries for which growth of demand has been
expected in recent years as new secondary batteries, a so-called
post-plating method of applying barrel plating after pressing cold
rolled steel sheets, or a so-called pre-plating method of pressing
a nickel plated steel sheets into a battery case have been adopted,
for which many proposals have been made for the improvement and the
present inventors have also proposed an excellent surface treated
steel sheet for battery cases with low internal resistance
(International Publication No. WO95/11527).
[0004] Further, in recent years, as a press forming method for
battery cases, a DI (drawing and ironing) forming method has also
been used as a wall thinning method instead of a multi-stage deep
drawing method for increasing the battery capacity (JP-B No.
7-99686). The DI forming method or DTR (drawing thin and redraw)
forming method can fill more positive electrode and negative
electrode active substances by as much as the additional volume
created by the side wall being thinner than the bottom, to increase
the capacity of the battery, as well as also provide a merit
capable of improving the pressure proofness of the battery since
the case bottom is thick.
[0005] By the way, while the DI forming method or the DTR forming
method is a forming method effective to the increase of the battery
capacity as described above, since the deformation resistance of a
material is larger compared that with the existent multi-stage deep
draw forming method in view of the forming ability, it involves a
disadvantage with respect to the continuous forming property.
[0006] Further, it has been required for alkali-manganese batteries
in recent years that they are excellent in performance such as
internal resistance, short circuit current and discharge
characteristics.
[0007] A battery case manufactured by a deep draw forming method,
DI forming method or DTR forming method comprises a nickel layer or
an iron-nickel layer as the surface layer on the inner surface but
has a limit in view of the battery performance and improvement has
been demanded.
[0008] The present invention has a technical subject of providing a
battery case excellent in the battery performance and a surface
treated steel sheet that can be used suitably to the manufacture of
the battery case.
DISCLOSURE OF THE INVENTION
[0009] Then, the present inventors have found that when a battery
case manufactured by a deep draw forming method, a DI forming
method or a DTR forming method has a heat treated phosphorus
containing diffusion layer at the surface layer on the inner
surface of a can, it is excellent in battery performance such as
internal resistance or short-circuit current.
[0010] A surface treated steel sheet for a battery case according
to claim 1 is characterized in that a diffusion layer of a
nickel-phosphorus alloy is formed at a surface on the inner side of
the battery case.
[0011] A surface treated steel sheet for a battery case according
to claim 2 is characterized in that an iron-nickel diffusion layer
is formed as a lower layer and a diffusion layer of a
nickel-phosphorus alloy is formed as an upper layer at a surface on
the inner side, and an iron-nickel diffusion layer is formed as a
lower layer and a nickel layer is formed as an upper layer at a
surface on the outer side of the battery case.
[0012] A surface treated steel sheet for a battery case according
to claim 3 is characterized in that an iron-nickel diffusion layer
is formed as a lower layer, a nickel layer is formed as an
intermediate layer and a diffusion layer of a nickel-phosphorus
alloy is fanned as an upper layer at a surface on the inner side,
and an iron-nickel diffusion layer is formed as a lower layer and a
nickel layer is formed as an upper layer at a surface on the outer
side of the battery case. The diffusion layer of the
nickel-phosphorus alloy preferably contains Ni.sub.3P. Further, the
thickness of the nickel-phosphorus alloy is preferably within a
range from 0.1 to 2 .mu.m. Further, it is preferred that the
phosphorus content of the nickel-phosphorus alloy is within a range
from 1 to 12% by weight.
[0013] A surface treated steel sheet for a battery case according
to claim 7 is characterized in that a diffusion layer of a
nickel-cobalt-phosphorus alloy is formed at a surface on the inner
face side of the battery case.
[0014] A surface treated steel sheet for a battery case according
to claim 8 is characterized in that an iron-nickel diffusion layer
is formed as a lower layer and a diffusion layer of a
nickel-cobalt-phosphorus alloy is formed as an upper layer at a
surface on the inner side, and an iron-nickel diffusion layer is
formed as a lower layer and a nickel layer is formed as an upper
layer at a surface on the outer side of the battery case.
[0015] A surface treated steel sheet for a battery case according
to claim 9 is characterized in that an iron-nickel diffusion layer
is formed as a lower layer, a nickel layer is formed as an
intermediate layer, and a diffusion layer of a
nickel-cobalt-phosphorus alloy is formed as an upper layer at the
surface on the inner side, and an iron-nickel diffusion layer is
formed as a lower layer and a nickel layer is formed as an upper
layer at the surface on the outer side of the battery case. The
thickness of the nickel-cobalt-phosphorus alloy is preferably
within a range from 0.1 to 2 .mu.m. Further, the
nickel-cobalt-phosphorus alloy preferably has a cobalt content in a
range of from 5 to 30% by weight, and a phosphorus content in a
range of from 1 to 12% by weight.
[0016] A battery case according to claim 12 is characterized in
that a diffusion layer of a nickel-phosphorus alloy is formed on
the inner surface.
[0017] A battery case according to claim 13 is characterized in
that an iron-nickel diffusion layer is formed as a lower layer and
a nickel-phosphorus alloy layer is formed as an upper layer at the
inner surface, and an iron-nickel diffusion layer is formed as a
lower layer and a nickel layer is formed as an upper layer at the
outer surface thereof.
[0018] A battery case according to claim 14 is characterized in
that an iron-nickel diffusion layer is formed as a lower layer, a
nickel layer is formed as an intermediate layer and a
nickel-phosphorus alloy layer is formed as an upper layer at the
inner surface, and an iron-nickel diffusion layer is formed as a
lower layer and a nickel layer is formed as an upper layer at the
outer surface thereof. The diffusion layer of the nickel-phosphorus
alloy previously contains Ni.sub.3P. Further, the nickel-phosphorus
alloy has a phosphorus content preferably within a range from 1 to
12% by weight.
[0019] A battery case according to claim 17 is characterized in
that a diffusion layer of a nickel-cobalt-phosphorus alloy is
formed at the inner surface.
[0020] A battery case according to claim 18 is characterized in
that an iron-nickel diffusion layer is formed as a lower layer and
a diffusion layer of a nickel-cobalt-phosphorus alloy is formed as
an upper layer at the inner surface, and an iron-nickel diffusion
layer is formed as a lower layer and a nickel layer is formed as an
upper layer at a surface on the outer side.
[0021] A battery case according to claim 19 is characterized in
that an iron-nickel diffusion layer is formed as a lower layer, a
nickel layer is formed as an intermediate layer and a diffusion
layer of nickel-cobalt-phosphorus alloy is formed as an upper layer
at the inner surface, and an iron-nickel diffusion layer is formed
as a lower layer and a nickel layer is formed as an upper layer at
a surface of the outer side. The nickel-cobalt-phosphorus alloy
preferably has a cobalt content within a range of from 5 to 30% by
weight, and a phosphorus content within a range of from 1 to 12% by
weight.
[0022] A battery case according to claim 21 is characterized in
that it is obtained by a draw forming method, DI forming method or
DTR forming method.
[0023] A battery case according to claim 22 is characterized by
using a battery case according to any one of claims 12 to 21 and
filling a positive electrode active substance and a negative
electrode active substance to the inside of the battery case.
Best Mode for Practicing the Invention
[0024] Surface treated steel sheets according to the present
invention are to be described.
(Steel Sheet)
[0025] As a raw material for plated sheet, low carbon aluminum
killed steel is preferably used usually. Further, non-aging ultra
low carbon steel with addition of niobium, boron or titanium is
also used. Usually, steel hoops applied with cold rolling and then
electrolytic cleaning, annealing and temper rolling are used as the
starting sheet.
(Nickel Plating)
[0026] Non-bright nickel plating was conducted by using the
following sulfate bath. The plating thickness at the surface on the
inner side of the case is preferably within a range from 0.5 to 3
.mu.m. In a case where it is less than 0.5 .mu.m, iron leaching
increases to worsen the battery performance. Further, it may exceed
3 .mu.m but this is excessively thick and not economical. It is
preferably within a range from 0.2 to 3 .mu.m on the outer side. In
a case where it is less than 0.2 .mu.m, corrosion resistance is
poor and rust tends to occur. Further, it may exceed 3 .mu.m but it
is excessively thick and uneconomical.
[0027] Bath Composition:
TABLE-US-00001 Nickel sulfate (NiSO.sub.4.cndot.6H.sub.2O) 300 g/L
Nickel chloride (NiCl.sub.2.cndot.6H.sub.2O) 45 g/L Boric acid
(H.sub.3BO.sub.3) 30 g/L
Bath pH: 4 (adjust with sulfuric acid) Stirring: air stirring Bath
temperature: 60.degree. C. Anode: S pellets (trade name of products
manufactured by INCO Co., spherical) charged in a titanium basket
and covered with a polypropylene bag were used.
[0028] Further, the following plating bath is used for the
semi-bright nickel plating. The semi-bright nickel plating may be
conducted instead of the first non-bright nickel plating.
(Semi-Bright Nickel Plating)
[0029] Semi-bright nickel plating was conducted by properly adding
an unsaturated alcohol polyoxyethylene adduct and an unsaturated
carboxylic acid formaldehyde as a semi-brightening agent to the
nickel sulfate bath. The range for the plating thickness may be
identical with that in the case of the non-bright nickel
plating.
[0030] Bath Composition:
TABLE-US-00002 Nickel sulfate (NiSO4.cndot.6H2O) 300 g/L Nickel
chloride (NiCl2.cndot.6H2O) 45 g/L Boric acid (H3BO3) 30 g/L
Unsaturated alcohol polyoxyethylene adduct 3.0 g/L Unsaturated
carboxylic acid formaldehyde 3.0 g/L
Bath pH: 4 (adjust with sulfuric acid) Stirring: air stirring Bath
temperature: 60.degree. C. Anode: S pellets (trade name of products
manufactured by INCO Co., spherical) charged in a titanium basket
and covered with a polypropylene bag were used.
(Nickel-Phosphorus Alloy Plating)
[0031] The starting material sheet was applied with alkali
electrolysis degreasing, water washing, sulfuric acid pickling
(dipping) and pre-treatment after water washing, and then
nickel-phosphorus alloy plating is conducted on one side of a steel
sheet. Further, it may be applied on the non-bright nickel plating
or semi-bright nickel plating. The bath for the nickel-phosphorus
alloy plating may be any of known plating baths such as watt bath,
sulfamate bath or chloride bath in the invention.
[0032] The thickness of the nickel-phosphorus alloy plating is
preferably within a range from 0.1 to 2 .mu.m. In a case where it
is less than 0.1 .mu.m, many pinholes are present in the
nickel-phosphorus alloy plating layer to increase nickel exposure
on the surface of a battery can and increase formation of nickel
and iron oxides which is not preferred. It may exceeds 2 .mu.m but
this is not economical.
[0033] Referring to the formation of nickel-phosphorus alloy
plating, nickel-phosphorus alloy plating is conducted by adding
phosphorus acid to a watt bath. In a specific example, phosphorus
acid is added as H.sub.3PO.sub.3 while varying the amount within a
range from 5 to 20 g/l to 250 g/l of nickel sulfate (hexa-hydrate),
45 g/l of nickel chloride and 30 g/l of boric acid to control the
amount of phosphorus crystallized in the nickel layer. Preferably,
the bath temperature is from 40 to 70.degree. C. and the pH is from
1.5 to 2.5. In this case, the thickness of the plating layer is
preferably from 0.1 to 2 .mu.m.
(Nickel-Cobalt-Phosphorus Alloy Plating)
[0034] The starting material sheet is applied with alkali
electrolysis degreasing, water washing, sulfuric acid pickling
(dipping) and pre-treatment after water washing and then
nickel-cobalt-phosphorus alloy plating is conducted on one side of
a steel sheet. Further, it may be applied on the non-bright nickel
plating or semi-bright nickel plating. The bath for the
nickel-phosphorus alloy plating may be any of known plating baths
such as watt bath, sulfamate bath and chloride bath.
[0035] The thickness of the nickel-cobalt-phosphorus alloy plating
is preferably within a range from 0.1 to 2 .mu.m. In a case where
it is less than 0.1 .mu.m, many pinholes are present in the
nickel-cobalt-phosphorus alloy plating to increase nickel exposure
on the surface of a battery can and increase formation of nickel
and iron oxides which is not preferred. It may exceeds 2 .mu.m but
this is not economical.
[0036] Referring to the formation of nickel-cobalt-phosphorus alloy
plating, nickel-cobalt-phosphorus alloy plating is conducted by
adding phosphorus acid to a watt bath. In a specific example, 1 to
40 g/l of cobalt sulfate and 5 to 20 g/l of phosphorus acid as
H.sub.3PO.sub.3 are added while varying the amounts to 250 g/l of
nickel sulfate (hexa-hydrate), 45 g/l of nickel chloride and 30 g/l
of boric acid, to control the amount of phosphorus and cobalt
crystallized in the nickel layer. Preferably, the bath temperature
is from 40 to 70.degree. C. and pH is from 1.5 to 2.5. In this
case, the thickness of the plating layer is preferably from 0.1 to
2 .mu.m.
(Diffusion Treatment)
[0037] After conducting the plating described above, a diffusion
treatment by heat treatment is conducted. As the condition for the
diffusion treatment, a non-oxidative atmosphere or a reducing
atmosphere is preferred and it may be conducted, for example, in a
non-oxidative atmosphere comprising 5% hydrogen and remaining
nitrogen gas. The diffusion treatment may be conducted also by
using known facilities such as a box-type annealing furnace or a
continuous annealing furnace. The diffusion treatment is conducted
at a temperature within a range from 300 to 800.degree. C. A
temperature within a range from 350 to 800.degree. C. is more
preferred. It may be conducted for a period of time in a range
where the nickel plating layer in the lower layer is entirely
converted into an iron-nickel alloy layer or the nickel plating
layer remains partially. Although the reason is not apparent, it
may be considered that characteristics are satisfactory in view of
the formation of Ni.sub.3P.
EXAMPLE
[0038] The present invention is to be described more specifically
by way of examples.
Examples 1 to 8, Comparative Examples 1 to 4
[0039] A low carbon aluminum killed steel sheet of 0.25 mm
thickness after cold rolling and annealing was uses as a starting
sheet for plating. The steel chemical composition of the starting
sheet for plating is as described below.
[0040] C, 0.04% (% means % by weight. Here and hereinafter),
[0041] Mn: 0.19%, Si: 0.01%, P: 0.012%, S: 0.009%,
[0042] Al: 0.064%, N, 0.0028%,
[0043] The steel sheet described above was applied with alkali
electrolysis degreasing under the following conditions.
(Alkali Electrolysis Degreasing)
[0044] Electrolysis Condition
[0045] Bath composition: Caustic soda 30 g/l
[0046] Current density: 5 A/dm.sup.2 (anodic treatment).times.10
sec
[0047] Current density: 5 A/dm.sup.2 (cathodic treatment).times.10
sec
[0048] Bath temperature: 70.degree. C.
[0049] Subsequently, after applying sulfuric acid pickling
(sulfuric acid 50 g/l, bath temperature 30.degree. C., dipping 20
sec), non-brightness nickel plating or semi-brightness nickel
plating is applied to both sides of a steel sheet, then
nickel-phosphorus alloy plating or nickel-cobalt-phosphorus alloy
plating was applied to a surface corresponding to the inner side of
a battery case and, further, a diffusion treatment was conducted by
a heat treatment under the conditions shown in Table 1 for
examples. Non-bright nickel plating or semi-bright nickel plating
was applied to both sides of a steel sheet, under the conditions
shown in Table 1 and then nickel-phosphorus alloy plating or
nickel-cobalt-phosphorus alloy plating was not applied for
comparative examples. For comparative examples 1 to 2, a diffusion
treatment was conducted by a heat treatment under the conditions
shown in Table 1. Ni plating in Table 1 was conducted as non-bright
nickel plating for Examples 3 to 6 and Comparative Examples 2 to 3
and semi-bright nickel plating was applied to others.
TABLE-US-00003 TABLE 1 Preparation conditions for examples and
comparative examples, and battery characteristics Battery case
inner side Battery case Ni--P or Ni--Co--P alloy outer side Battery
characteristics Example or Ni plating plating Ni-- plating Heat
treatment condition Discharge Comparative Ni Ni P Co Ni after Ni--P
plating or IR SCC characteristic Example (g/m.sup.2) (g/m.sup.2)
(%) (%) (g/m.sup.2) Ni--Co--P plating (m.OMEGA.) (A) (min) Example
1 4.5 0.9 1.1 -- 17.5 550.degree. C. .times. 1 hr.sup. 151 8.0 15.8
2 8.9 2.6 4.2 -- 18.2 400.degree. C. .times. 1 min 149 8.1 16.1 3
17,.5 4.7 7.8 -- 17.5 450.degree. C. .times. 1 min 145 8.2 17.3 4
16.8 8.8 11.9 -- 18.3 600.degree. C. .times. 30 sec 148 8.2 17.0 5
4.6 1.0 0.25 5.3 26.3 550.degree. C. .times. 1 hr.sup. 150 8.0 16.1
6 9.2 2.5 1.54 9.8 27.1 400.degree. C. .times. 1 min 146 8.3 17.9 7
17.2 4.6 0.28 18.8 9.1 450.degree. C. .times. 1 min 152 7.9 15.9 8
16.9 8.6 5.3 28.5 9.5 600.degree. C. .times. 30 sec 141 8.6 18.3
Comp. 1 4.5 -- -- -- 17.9 550.degree. C. .times. 1 hr.sup. 161 6.6
14.2 Example 2 8.5 -- -- -- 26.4 780.degree. C. .times. 4 min 169
5.8 13.4 3 7.9 -- -- -- 17.9 -- 159 6.2 14.3 4 17.7 -- -- -- 17.9
-- 162 6.1 14.0
(Preparation of Battery Case)
[0050] In the formation of a battery case by a DI forming method,
the surface treated steel sheet described above of 0.38 mm
thickness was used and after cupping from a blank diameter of 41 mm
diameter to 20.5 mm diameter, redraw and two step wringing were
applied by a DI forming machine into a shape of 13.8 mm outer
diameter, 0.20 mm of case wall thickness, and 56 mm of height.
Finally, an upper portion was trimmed to prepare an LR6 type batter
case with 49.3 mm height. In the DI forming method, surface treated
steel sheets in Examples 1 to 3 and Comparative Example 1 and
Comparative Example 4 were used.
[0051] In the preparation of a battery case by a DTR forming
method, a surface treated steel sheet of 0.25 mm thickness was used
and, punched into 58 mm blank diameter and an LR6 type battery case
having 13.8 mm outer diameter, 0.20 mm case wall thickness and 49.3
mm height was prepared by punching into 58 mm blank diameter,
several drawing and redraw forming. Surface treated steel sheets in
Examples 4 to 6 and Comparative Example 2 were used in the DTR
forming method.
[0052] Further, in the preparation of a battery case by a deep draw
forming method, a plated steel sheet of 0.25 mm thickness was used
and punched into 57 mm blank diameter, and an LR6 type battery case
of 49.3 mm height was prepared by drawing for several times and by
re-drawing into a shape of 13.8 mm outer diameter, 0.25 mm of case
wall thickness and 49.3 mm height. In the deep draw forming method,
surface treated steel sheets in Examples 7 to 8 and Comparative
Example 3 were used.
(Preparation of Battery)
[0053] After preparing the battery case as described above, size AA
(LR-6) alkali manganese batteries were manufactured as described
below.
[0054] At first, manganese dioxide and graphite were sampled at a
ratio of 10:1 by weight, to which potassium hydroxide (8 mol) was
admixed to prepare a positive electrode mix. Then, the positive
electrode mix was pressed under compression in a molding die to
prepare a positive electrode mix pellets of a doughnut shape of a
predetermined size which was press inserted into the battery case.
Then, a negative electrode plate having a negative electrode
collector spot welded thereto was mounted to the battery case.
[0055] Then, a separator comprising non-woven fabrics made of
vinylon was inserted along the inner circumference of the pellets
which were press bonded to the battery case, and a negative
electrode gel comprising 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, inserted into the battery case and then caulked to
manufacture a completed product of an alkali manganese cell.
[0056] For the batteries manufactured as described above, the
battery performance was evaluated as described below. The results
are shown in Table 1.
[Evaluation for Internal Resistance (IR)]
[0057] After aging the manufactured batteries at 80.degree. C. for
3 days, the internal resistance (IR) was measured by the AC
impedance method. Lower internal resistance shows better
characteristics.
[Evaluation for Short-Circuit Current (SCC)]
[0058] After aging the manufactured batteries at 80.degree. C. for
3 days, an ampere meter was connected to the battery to establish a
closed circuit and the current value of the battery was measured,
which was defined as a short circuit current (SCC). Larger short
circuit current shows better characteristics.
[Discharge Characteristics]
[0059] After aging the manufactured batteries at 80.degree. C. for
3 days, the battery was discharged at a constant current of 1 A and
the discharge time till it reached 0.9 V was measured and the
discharge time was defined as discharge characteristics. Longer
discharge time shows better characteristics.
INDUSTRIAL APPLICABILITY
[0060] A battery case obtained by the deep draw forming method, the
DI forming method or the DTR forming method having a diffusion
layer of a nickel-phosphorus alloy, or a nickel-cobalt-phosphorus
alloy at the outermost surface on the inner side has better battery
performance (internal resistance, short circuit current and
discharge characteristics) compared with a battery case having a
nickel layer or a nickel-iron layer at the surface on the inner
side of existent battery cases.
* * * * *