U.S. patent application number 12/088011 was filed with the patent office on 2009-07-16 for positive electrode current collector for lead accumulator.
This patent application is currently assigned to GS YUASA CORPORATION. Invention is credited to Isamu Kurisawa.
Application Number | 20090181306 12/088011 |
Document ID | / |
Family ID | 37899802 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090181306 |
Kind Code |
A1 |
Kurisawa; Isamu |
July 16, 2009 |
POSITIVE ELECTRODE CURRENT COLLECTOR FOR LEAD ACCUMULATOR
Abstract
In a positive electrode current collector for a lead-acid
battery including a coating of tin dioxide formed on the surface of
a current collector substrate of titanium or a titanium alloy, the
half width of a peak with the maximum intensity among peaks of tin
dioxide in the x-ray diffraction pattern of the positive electrode
current collector for a lead-acid battery is 1.degree. or
lower.
Inventors: |
Kurisawa; Isamu; (Kyoto,
JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
GS YUASA CORPORATION
Kyoto-shi, Kyoto
JP
|
Family ID: |
37899802 |
Appl. No.: |
12/088011 |
Filed: |
September 29, 2006 |
PCT Filed: |
September 29, 2006 |
PCT NO: |
PCT/JP2006/319488 |
371 Date: |
March 25, 2008 |
Current U.S.
Class: |
429/225 ;
429/231.5 |
Current CPC
Class: |
Y10T 29/10 20150115;
Y02E 60/10 20130101; H01M 4/68 20130101; Y10T 29/49115 20150115;
H01M 4/66 20130101; H01M 4/662 20130101; H01M 4/667 20130101; H01M
4/82 20130101 |
Class at
Publication: |
429/225 ;
429/231.5 |
International
Class: |
H01M 4/56 20060101
H01M004/56; H01M 4/58 20060101 H01M004/58 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2005 |
JP |
2005-285131 |
Claims
1: A positive electrode current collector for a lead-acid battery
comprising a coating of tin dioxide formed on the surface of a
current collector substrate of titanium or a titanium alloy,
wherein the half width of a peak with the maximum intensity among
peaks of tin dioxide in the x-ray diffraction pattern of said
positive electrode current collector for a lead-acid battery is
1.degree. or lower.
2: A positive electrode current collector for a lead-acid battery
comprising a coating of tin dioxide formed on the surface of a
current collector substrate of titanium or a titanium alloy,
wherein crystals of said tin dioxide are selectively oriented in 1
or more and 4 or less of the crystal planes.
3: The positive electrode current collector for a lead-acid battery
according to claim 2, wherein said crystal planes oriented are a
(110) plane, a (101) plane, a (200) plane, a (211) plane, a (220)
plane, a (310) plane, a (112) plane, or (301) plane.
4: The positive electrode current collector for a lead-acid battery
according to claim 1, wherein said coating contain antimony or
fluorine.
5: A lead-acid battery comprising said positive electrode current
collector according to claim 1.
6: The lead-acid battery comprising said positive electrode current
collector according to claim 4.
7: The positive electrode current collector for a lead-acid battery
according to claim 2, wherein said coating contain antimony or
fluorine.
8: The lead-acid battery comprising said positive electrode current
collector according to claim 7.
9: The positive electrode current collector for a lead-acid battery
according to claim 3, wherein said coating contain antimony or
fluorine.
10: The lead-acid battery comprising said positive electrode
current collector according to claim 9.
11: A lead-acid battery comprising said positive electrode current
collector according to claim 2.
12: A lead-acid battery comprising said positive electrode current
collector according to claim 3.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a positive electrode
current collector for a lead-acid battery having a coating on the
surface.
[0003] 2. Description of the Related Art
[0004] A lead-acid battery has a low energy density as compared
with a nickel-metal hydride battery and a lithium ion battery. One
of the causes is that lead or a lead alloy to be used as a positive
electrode current collector is thick and heavy. Therefore, use of
titanium or a titanium alloy (hereinafter, referred to as titanium
or the like) for the positive electrode current collector and
formation of a conductive oxide layer of tin dioxide or the like as
a coating on the surface of titanium or the like have been proposed
(reference to Japanese Patent Application Laid-Open (JP-A) No.
55-64377 and Japanese Patent No. 3482605). It is because use of
titanium or the like makes a positive electrode current collector
lightweight because of the lower specific gravity of titanium or
the like than that of lead.
[0005] However, in the case where a positive electrode current
collector made of solely titanium or the like is used for a
lead-acid battery, although hard, titanium or the like is slightly
dissolved in diluted sulfuric acid, which is an electrolytic
solution, and accordingly there occurs a problem. Therefore, a tin
dioxide which is insoluble in diluted sulfuric acid, which is an
electrolytic solution, is formed as a coating on the surface of
titanium or the like.
[0006] Moreover, in the case of forming tin dioxide on the surface
of titanium or the like, there are advantageous points: (i) tin
dioxide shows high electrochemical stability when it is positive
electrode potential in an electrolytic solution; (ii) voltage
decrease by existence of the coating of tin dioxide with low
conductivity can be suppressed by titanium or the like with high
conductivity; and (iii) since the melting point of titanium or the
like is high, it can stand firing around 500.degree. C. in a step
of forming a tin dioxide coating.
[0007] As a method for forming the tin dioxide coating on the
surface of a current collector substrate are generally employed a
dip coating method and a spin coating method. Specifically, the
coating of tin dioxide is formed by applying a raw material
solution containing tin on titanium or the like and thereafter
heating them. Further, a technique of forming a tin dioxide coating
on the surface of a glass substrate by a spray method is also
proposed (e.g., Japanese Patent No. 3271906, or J. J. Rowlette,
American Chemical Society, 1052 (1986))
[0008] In Japanese Patent No. 3271906, in a first step, a first raw
material solution obtained by dissolving an organic compound such
as dibutyltin diacetate in an organic solvent is atomized in a
spray form on the surface of a heated glass substrate. At that
time, in order to avoid a factor of crystallinity decrease, an
element such as antimony and fluorine having outermost electrons in
a number higher by one than that of tin or oxygen is not added to
the first raw material solution. The sprayed first raw material
solution is thermally decomposed on the surface of the heated glass
substrate to form an undercoating layer selectively oriented to a
specified crystal plane. Next, a second raw solution obtained by
adding an element having outermost electrons in a number higher by
one than that of tin or oxygen to the first raw solution is
atomized in a spray form on the surface of the undercoating
layer.
SUMMARY OF THE INVENTION
[0009] However, in the case where a lead-acid battery is produced
using a current collector substrate of titanium or the like having
a coating of tin dioxide on the surface, there is a problem that
the life performance of the lead-acid battery is inferior. The
inventors of the present invention have made investigations on its
cause and accordingly have made it clear that the crystallinity of
tin dioxide formed as a coating affects the life performance.
Conventionally, no attention has been paid to the crystallinity of
tin dioxide in form of the coating.
[0010] According to the dip coating method and spin coating method
described in the paragraphs of Related Art described above, in the
case of forming tin dioxide on a current collector substrate of
titanium or the like, the applied raw material solution is
thermally decomposed from a surface side far from the current
collector substrate. Therefore, crystal cores are produced in
crystal planes having various directions on the surface side of the
raw material solution and along with the proceeding of the thermal
decomposition, crystals are respectively grown from the crystal
cores. If the crystals of various crystal planes are grown, points
where the crystals of different crystal planes are adjacent to one
another are increased to increase crystal strains. As a result, the
crystallinity decreases.
[0011] Further, in the case where the crystallinity decreases,
points where the distance between a tin atom and an oxygen atom is
not as in a standard crystal state are increased to lower the
chemical stability. Accordingly, the life performance of a
lead-acid battery using the current collector substrate
deteriorates.
[0012] Under the above-mentioned state of the problems, the present
invention aims to solve the problems according to the following
means.
[0013] A positive electrode current collector for a lead-acid
battery of the present invention is a positive electrode current
collector for a lead-acid battery including a coating of tin
dioxide formed on the surface of a current collector substrate of
titanium or a titanium alloy and is characterized in that the half
width of a peak with the maximum intensity among peaks of tin
dioxide in the x-ray diffraction pattern of the positive electrode
current collector for a lead-acid battery is 1.degree. or
lower.
[0014] In the case where a lead-acid battery is produced using such
a positive electrode current collector, the life performance of the
lead-acid battery becomes excellent. The results of specific
experiments will be described later.
[0015] As titanium is used titanium (JIS 1 type) or titanium (JIS 2
type). As a titanium alloy are used Ti-5Al-2.5V, Ti-3Al-2.5V, and
Ti-6Al-4V.
[0016] In the x-ray diffractometry of the present application,
while x-ray (CuK.alpha. ray) is radiated to a specimen, scanning is
carried out at an incident angle .theta. in a prescribed range and
during that time, the intensity of diffracted x-ray is counted. If
a diffraction angle 2.theta. is plotted in an abscissa axis and
diffraction intensity is plotted in an ordinate axis, the x-ray
diffraction pattern is obtained. According to the x-ray diffraction
pattern, based on the crystal structure of tin dioxide coating
which is a specimen and the wavelength of radiated x-ray, the types
of crystal planes corresponding to the diffraction angles 2.theta.
at which the peaks of the x-ray diffraction intensity appear can be
specified. In this application, 2.theta. is set in a range of
26.6.degree. to 108.4.degree..
[0017] The term "peaks" means hill-like parts in the x-ray
diffraction pattern. The respective peaks correspond to crystal
planes. The term "half width" means a diffraction angular width of
the peak curve in the x-ray diffraction intensity at which the
intensity (x-ray diffraction intensity at a summit in the peak
curve) of the peak becomes 1/2. If the half width is narrow, the
peak has a sharp hill-like shape and the crystallinity of the
crystal plane can be said to be high. On the other hand, if the
half width is broad, the peak has gentle hill-like shape with a
spread toward the bottom and the crystallinity of the crystal plane
can be said to be low.
[0018] In order to produce such a positive electrode current
collector for a lead-acid battery, a production method described
below may be employed.
[0019] The positive electrode current collector for a lead-acid
battery of the present invention is a positive electrode current
collector for a lead-acid battery having a coating of tin dioxide
formed on the surface of a current collector substrate of titanium
or a titanium alloy and is characterized in that the
above-mentioned crystals of tin dioxide are selectively oriented in
1 or more and 4 or less of the crystal planes.
[0020] In the case where a lead-acid battery is produced using such
a positive electrode current collector, the life performance of the
lead-acid battery becomes excellent. Results of specific
experiments will be described later.
[0021] Herein, the phrase "selectively oriented in the crystal
planes" means the case that the texture coefficient TC of the
crystal planes is 1 or more. For example, the texture coefficient
TC of a (110) plane is 1 or more, it can be expressed that the
crystal is oriented in the (110) plane. A calculation method of the
texture coefficient TC will be described in a first embodiment.
[0022] The present invention is characterized in that the oriented
crystal planes as described above are a (110) plane, a (101) plane,
a (200) plane, a (211) plane, a (220) plane, a (310) plane, a (112)
plane, or a (301) plane.
[0023] In the case where titanium or the like has an oriented tin
dioxide coating on the above-mentioned crystal plane, the life
performance of the lead-acid battery produced using the positive
electrode current collector becomes excellent.
[0024] The present invention is characterized in that the coating
contains antimony or fluorine in the positive electrode current
collector for a lead-acid battery.
[0025] Since the coating contains antimony or fluorine, the
conductivity of the coating is remarkably improved. In the case
where the conductivity of the coating is high, since the inner
resistance of the lead-acid battery is lowered, the life
performance of the lead-acid battery becomes further excellent and
the effect of the present invention is more apparently caused. In
the case of comparison of antimony with fluorine, antimony is
better.
[0026] A positive electrode current collector for a lead-acid
battery having a coating on the surface of a current collector
substrate of the present invention is produced by the following
method. That is, the production method involves a step of
intermittently spraying a raw material solution obtained by
dissolving a tin compound in a solvent to the surface of a heated
current collector substrate made of titanium or a titanium
alloy.
[0027] Accordingly, a coating of tin dioxide with high
crystallinity is formed on the surface of titanium or the like. As
a result, in the case where a lead-acid battery is produced using
the positive electrode current collector produced by this
production method, the life performance of the lead-acid battery
becomes excellent.
[0028] In this production method, as the tin compound, organotin
compounds such as dibutyltin diacetate, tributoxytin, and the like
and inorganic tin compounds such as tin tetrachloride may be
employed. As a solvent, an organic solvent such as ethanol,
butanol, and the like may be employed. To add antimony to the raw
material solution obtained by dissolving a tin compound in a
solvent, a method of mixing a chloride of antimony may be
employed.
[0029] In execution of the production method, it is required to
heat the current collector substrate in order to thermally
decompose the tin compound in the raw material solution when the
raw material solution is sprayed to the current collector
substrate. The temperature suitable for the heating depends on the
type of the tin compound. For example, in the case of using a raw
material solution obtained by mixing an antimony chloride solution
(solvent:ethanol) with a dibutyl tin diacetate solution
(solvent:ethanol), the temperature is 400.degree. C. or higher. It
is preferably 450.degree. C. or higher and most preferably
500.degree. C. or higher.
[0030] At the time of spraying the raw material solution to the
surface of the current collector substrate, spraying is repeated at
intervals, so that the temperature is not decreased. That is,
spraying is carried out intermittently.
[0031] The thickness of the coating of tin dioxide to be formed by
one time spraying is required to be 5 nm or thinner. It is because
a coating of tin dioxide with high crystallinity can be obtained by
the production method by which such a thin coating is layered.
Further, it is because crystals of tin dioxide to be formed on the
surface of titanium or the like can be selectively oriented in one
or more and 4 or less of the crystal planes.
[0032] In order to form such a thin coating, it is preferable to
adjust a spraying amount at one time is 0.4 cc or less. It is
because, although it depends on other conditions for the
production, 0.4 cc or less of the spraying amount is suitable for
layering the coating of 5 nm or thinner.
[0033] The reason for the possibility of obtaining high
crystallinity by layering of the coating formed in such a thin
thickness is not clearly understood. However, it is probably
attributed to that titanium oxide existing on the surface of the
current collector substrate and oxides of titanium and tin formed
in the initial stage of the coating formation become an undercoat
layer and tin dioxide forming the coating is epitaxially grown. In
this connection, tin dioxide cannot be selectively oriented in
specified crystal planes by a conventional dip coating method.
Therefore, tin dioxide does not show high crystallinity.
[0034] In execution of the production method, it is preferable for
the raw material solution to contain antimony or fluorine.
Existence of antimony or fluorine in the coating improves the
conductivity of the coating. In the case where the coating has high
conductivity, since the inner resistance of the lead-acid battery
is lowered, the life performance of the lead-acid battery becomes
further excellent. In the case of comparison of antimony with
fluorine, antimony is better.
[0035] The lead-acid battery of the present invention is
characterized in that the battery is provided with the
above-mentioned positive electrode current collector. Accordingly,
since the life performance of the positive electrode current
collector is heightened, the lead-acid battery with high energy
density and a long life can be provided in a low cost.
[0036] As described above, in the case where a lead-acid battery is
produced using a positive electrode current collector according to
the present invention, the life performance of the lead-acid
battery becomes excellent.
[0037] The present application is based on Japanese Patent
Application (JP-A No. 2005-285131) filed on Sep. 29, 2005, the
disclosure of which is hereby incorporated by reference in its
entirety.
[0038] Finally, the relevancy of the present invention and the
above-mentioned Japanese Patent No. 3271906 will be described.
Japanese Patent No. 3271906 discloses a production method of
forming a tin dioxide coating with high crystallinity on the
surface of a glass substrate. However, the production method
described in Japanese Patent No. 3271906 does not relate to a
positive electrode current collector for a lead-acid battery. The
production method including a first stage and a second stage
described in Japanese Patent No. 3271906 is combined with titanium
or the like, which is a current collector substrate of a positive
electrode current collector to be used in the present invention,
since the conductivity of the undercoat layer formed in the first
stage becomes too low, only a positive electrode current collector
which cannot be practically usable as the positive electrode
current collector is obtained. The production cost is also
increased.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a view showing an x-ray diffraction pattern of a
tin dioxide coating in a positive electrode current collector
according to Example of the present invention;
[0040] FIG. 2 is a view showing the results of a life test
according to Example of the present invention;
[0041] FIG. 3 is a vertical cross sectional view showing the
structure of a cell using the current collector substrate of
titanium for a positive electrode plate according to Example of the
present invention;
[0042] FIG. 4 is a vertical cross sectional view showing the
structure of a lead-acid battery having four combined cells shown
in FIG. 3 according to Example of the present invention;
[0043] FIG. 5 is a view showing an x-ray diffraction pattern of a
positive electrode current collector, in which the heating
temperature of the current collector substrate is changed,
according to Example of the present invention;
[0044] FIG. 6 is a view showing a relation between the half width
of a peak with the maximum intensity among peaks of tin dioxide in
the x-ray diffraction pattern of the positive electrode current
collector and the life performance; and
[0045] FIG. 7 is a view showing a relation between the number of
crystal planes having oriented tin dioxide crystals and the life
performance.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(1) First Embodiment
(1.1) Production of Positive Electrode Current Collector
[0046] In Example 1, a mixed solution of a dibutyltin diacetate
solution (solvent: ethanol) and an antimony chloride solution
(solvent: ethanol) was used as a raw material solution. In this
case, the amount of dibutyltin diacetate was adjusted to be 2.5% by
mass on the basis of tin dioxide in the entire raw material
solution. Further, the amount of antimony chloride was adjusted to
be 2.5% by mass on the basis of antimony to tin dioxide.
[0047] The raw material solution was intermittently sprayed to the
surface of a flat plate-like current collector substrate heated to
450.degree. C. At the time of spraying, the spraying intervals were
controlled so as to keep the temperature of the current collector
substrate at 450.degree. C. Accordingly, thermal decomposition is
caused on the surface of the current collector substrate to form a
coating of tin dioxide. The obtained substrate was set as a
positive electrode current collector of Example 1.
[0048] Next, to compare with Example 1, a positive electrode
current collector of a conventional example 1 was produced. The
conventional example 1 was produced by a dip coating method using a
raw material solution prepared by dissolving tin tetrachloride,
antimony trichloride, and a small amount of hydrochloric acid in
propanol. That is, a flat plate-like current collector substrate
similar to that of Example 1 was immersed in the raw material
solution, pulled up at 30 cm/min, dried for 15 minutes, and
thereafter kept still in an electric furnace heated to 500.degree.
C. for 30 minutes to form a tin dioxide coating. The obtained
substrate was set as a positive electrode current collector of the
conventional example 1.
(1.2) Results of X-Ray Diffractometry
[0049] FIG. 1 shows the x-ray diffraction pattern of the positive
electrode current collector of Example 1 and the x-ray diffraction
pattern of the positive electrode current collector of the
conventional example 1. The XRD peak of Example 1 is sharp as
compared with that of the conventional example 1.
[0050] Table 1 shows the half width of a peak with the maximum
intensity in Example 1 and the conventional example 1. The crystal
plane of the peak with the maximum intensity is a (200) plane for
Example 1 and a (110) plane for the conventional example 1.
TABLE-US-00001 TABLE 1 Crystal plane Half width Conventional
example 1 (110) 2.21.degree. Example 1 (200) 0.68.degree.
[0051] As shown in Table 1, in the conventional example 1, the half
width of the peak of the (110) plane in which the intensity was the
maximum was rather higher than lo. On the other hand, in Example 1,
the half width of the peak of the (200) plane in which the
intensity was the maximum was sufficiently lower than 10.
[0052] Accordingly, in the case of the tin dioxide coating of the
conventional example 1, it is supposed that the crystallinity of
the coating is low and points where the distance between a tin atom
and an oxygen atom is not as in a standard crystal state are many.
On the other hand, in the case of the tin dioxide coating of
Example 1, it is supposed that the crystallinity of the coating is
high and points where the distance between a tin atom and an oxygen
atom is as in a standard crystal state are many.
[0053] Next, the texture coefficient TC of each crystal plane in
Example 1 and the conventional example 1 was calculated. The
results are shown in Table 2.
[0054] Herein, "texture coefficient TC" is an index for evaluating
orientation of a crystal plane which can be calculated according to
the following expression (1). In the expression (1), I(hkl) is an
x-ray diffraction intensity in a (hkl) plane; I.sub.0 (hkl) is a
standard intensity of each crystal plane of a tin dioxide obtained
according to JCPDS (No. 41-1445). N denotes the number of
diffraction lines. Herein, calculation was carried out using
diffraction line number N=31 (2.theta.=26.6.degree. to
108.4.degree.). Accordingly, if the texture coefficient TC is 1 or
lower, no crystal orientation occurs in the crystal plane and if it
is 31, the maximum value, the crystal is completely oriented in the
crystal plane and it means that the orientation becomes higher as
the texture coefficient TC is further higher than 1.
[0055] However, in the calculation method according to the
following expression (1), even if a crystal with high orientation
is not actually formed in a crystal plane with a small standard
intensity, 1 or higher texture coefficient TC is sometimes given by
the calculation. Accordingly, the following crystal planes were
selected; a (110) plane, a (101) plane, a (200) plane, a (211)
plane, a (220) plane, a (310) plane, a (112) plane, and a (301)
plane; which are crystal planes having standard intensity of 10 or
higher in the case where the standard intensity of a (110) plane
having the highest standard intensity obtained from the JCPDS was
set to be 100 and the texture coefficient TC was calculated only
for 8 kinds of them according to the expression (1) to employ the
resulting values as the orientation indications.
Expression 1
TABLE-US-00002 [0056] TABLE 2 (1) TC = I ( h k 1 ) I 0 ( h k 1 ) 1
N N I ( h k 1 ) I 0 ( h k 1 ) ##EQU00001## Crystal plane of tin
Texture coefficient TC dioxide (hkl) Conventional example 1 Example
1 (110) 0.53 0.32 (101) 0.33 0.52 (200) 0.71 3.21 (211) 0.36 0.68
(220) 0.56 0.28 (310) 0.52 0.68 (112) 0.55 0.42 (301) 0.42 1.34
[0057] As shown in Table 2, the texture coefficient TC of each
crystal plane was sufficiently lower than 1 in the case of the tin
dioxide coating of the conventional example 1 and the crystal was
not selectively oriented in any crystal plane and the crystallinity
was thus inferior. On the other hand, since the texture coefficient
TC of the (200) plane and the (301) plane was 1 or higher and
crystal was selectively oriented in these two types of crystal
planes in the case of the tin dioxide coating of Example 1.
(1.3) Life Test
[0058] FIG. 2 shows a life test using positive electrode current
collectors of Example 1 and the conventional example 1. The method
of the life test was as follows.
[0059] At first, according to a common production method of a
lead-acid battery, an active material paste was produced by
kneading a lead powder, water, and sulfuric acid. Thereafter, the
active material paste was packed in a frame with 10 mm in
diameter.times.8 mm in thickness and dried to obtain active
material pellet. The pellet was put in a diluted sulfuric acid
solution with a concentration of 20% and electric current at 50 mA
was applied to carry out formation and charging.
[0060] The active material pellet was formed in a flat plate-like
shape and put on the positive electrode current collectors of
Example 1 and the conventional examples 1 and 2 and while being
press-bonded by pressure around 100 kPa, these active material
pellet and positive electrode current collectors were immersed in a
diluted sulfuric acid solution with a concentration of 40% to
obtain positive electrode plates. A lead plate was used as a
negative electrode plate.
[0061] Respective test cells were assembled using the
above-mentioned positive electrode plates and negative electrode
plate. Constant voltage of 2.3 V was applied to the respective test
cells to carry out a constant voltage overcharging test at
650.degree. C. in a vapor phase.
[0062] The test cells were periodically taken out of the test
environments and left at room temperature for 24 hours. Thereafter,
discharge at 150 mA was carried out to measure the positive
electrode capacities. The moment the measured positive electrode
capacity became below 50% of the initial value was determined to be
the time of termination. The days until the time the life was
terminated was defined as the life performance (days).
[0063] The results of the life test according to the
above-mentioned method are shown in FIG. 2. FIG. 2 also shows the
results of a test carried out for comparison of a positive
electrode current collector of a conventional example 2 obtained by
electrodepositing a lead dioxide layer on the surface of the tin
dioxide coating formed in the conventional example 1. The tin
dioxide layer was carried out by electrodeposition by applying
electric current at current density of 5 to 10 mA/cm.sup.2 and a
temperature of 40 to 50.degree. C. in a 4 to 5 N sodium hydroxide
solution in which lead hydroxide was saturated.
[0064] According to FIG. 2, the life performance of the positive
electrode current collector of the conventional electrode 1 was
shorter than 100 days. On the other hand, the life performance of
the positive electrode current collector of Example 1 exceeded 400
days. Even beyond 400 days, decrease of the positive electrode
capacity was slight. The life performance of the positive electrode
current collector of the conventional example 2 slightly exceeded
200 days.
[0065] Herein, the life performance of the normal lead-acid battery
measured in the constant voltage overcharging test at 65.degree. C.
is around 120 days in the case of a common product and it is around
240 days in the case of a product planed to have a long life.
Accordingly, it can be said that the cycle life performance of the
lead-acid battery using the positive electrode current collector of
Example 1 is remarkably excellent as compared with those of these
common product and product planed to have a long life.
(1.4) Production of Cell, Production of Lead-Acid Battery, and Life
Test of Lead-Acid Battery
[0066] A cell 1 was produced using the positive electrode current
collector of Example 1. A cell 1 was produced using the positive
electrode current collector of the conventional example 1
[0067] The structure of the cell 1 is shown in FIG. 3. A battery
case 4 is an insulating frame body for an air-tightly housing a
positive electrode active material 5, a separator 6, and a negative
electrode active material 7 and sandwiched between a positive
electrode current collector 2 and a negative electrode current
collector 3. The battery case 4 is provided with a gas discharge
port 4a communicated to the outside. The aperture part of the gas
discharge port 4a is provided with a control valve 8. The positive
electrode active material 5, the separator 6, and the negative
electrode active material 7 are arranged in the inside of the
battery case 4. The positive electrode active material 5, the
separator 6, and the negative electrode active material 7 are
impregnated with an electrolyte solution containing diluted
sulfuric acid as a main component.
[0068] The positive electrode current collector 2 was provided with
the positive electrode active material 5 to produce a positive
electrode plate. Herein, the positive electrode active material 5
was a plate-like active material containing mainly lead dioxide
(PbO.sub.2). The negative electrode current collector 3 was a
copper plate (thickness: 0.1 mm) plated with lead (thickness: 20 to
30 .mu.m). The negative electrode current collector 3 was provided
with the negative electrode active material 7 to produce a negative
electrode plate. Herein, the negative electrode active material 7
was a plate-like active material of mainly sponge-like metal lead.
The separator 6 was like a mat produced from glass fibers. The
positive electrode plate and the negative electrode plate were
layered with the separator interposed therebetween and housed in a
container. The container was covered with a cover and the
electrolyte solution was injected to produce the cell 1 of a
lead-acid battery.
[0069] Next, a lead-acid battery of Example 1 was produced using
four cells 1 produced using the positive electrode current
collector of Example 1. Further, a lead-acid battery of the
conventional example 1 was produced using four cells 1 produced
using the positive electrode current collector of conventional
example 1. The configuration example is shown in FIG. 4. The
lead-acid batteries are lead-acid batteries for an uninterruptible
power supply apparatus (hereinafter, referred to lead-acid battery
for UPS using UPS as abbreviation of Uninterruptible Power Supply).
The lead-acid battery produced using the positive electrode current
collector of the present invention was remarkably excellent in the
life performance and therefore was particularly useful for UPS.
[0070] The negative electrode current collector 3 of the cell 1 was
set on the positive electrode current collector 2 of another cell
and in such a manner, four cells 1 were layered and connected in
series. The pressing members 9 and 10 made of a conductive material
such as a metal plate were set on the top and the bottom of the
four cells 1. The circumferences of the cells were surrounded with
an auxiliary frame material 11 of an insulating material such as a
resin or the like. The pressing members 9 and 10 were fixed
respectively in the top and bottom end faces of the auxiliary frame
material 11 with a plurality of screws 12 to firmly press, pinch,
and fix the four cells 1. These pressing members 9 and 10 were
directly press-bonded with the positive electrode current collector
2 and the negative electrode current collector 3 and therefore,
they could be used as positive and negative electrode
terminals.
[0071] Herein, in the respective pinched and fixed cells 1, the
separators 6 were in compressed state. Due to the repulsive force,
the positive electrode active material 5 was pushed to the positive
electrode current collectors 2 at gauge pressure of around 250 kPa
and the negative electrode active material 7 was pushed to the
negative electrode current collectors 3. To obtain the pressing
force by the separators 6, the material and the thickness for the
separators 6 may be adjusted properly. The pressing force can be
changed properly in accordance with the structure, the capacity,
and the size of the cells 1. Generally, the charge discharge
performance can be stabilized by applying gauge pressure of around
100 to 400 kPa.
[0072] With respect to the lead-acid batteries of Example 1 and the
conventional example 1 (nominal capacities are both 2.3 Ah), the
energy density per weight at the time of discharge at 0.5 A and the
life performance were compared. As a result, the energy density per
weight was 50 Wh/kg for both. The life performance was 15 months
for Example 1 and 7 months for the conventional example. The life
performance of Example 1 was remarkably excellent as compared with
that of the conventional example 1.
(1.5) Production Cost
[0073] The cost to produce the positive electrode current collector
of Example 1 and the cost to produce the positive electrode current
collector of the conventional example 2 are estimated. Both are
compared. As a result, the cost for producing the positive
electrode current collector of Example 1 is about one fifth of that
of the conventional example 2. In the conventional example 2, since
the lead dioxide layer was electrodeposited further on the surface
of the tin dioxide coating formed by the dip coating method, the
production efficiency was low. The production method of the
invention can be said to be excellent as compared with the
conventional production method.
(1.6) Others
[0074] In Example 1, dibutyltin diacetate was used for the raw
material solution. However, even in the case where an organic tin
compound such as tributoxytin or an inorganic tin compound such as
tin tetrachloride was used, if the half width of a peak with the
maximum intensity among peaks of tin dioxide in the x-ray
diffraction pattern of the positive electrode current collector was
1.degree. or lower, the life performance of the lead-acid battery
using the positive electrode current collector was excellent.
[0075] Not limited to the case the selectively oriented crystal
planes were (200) plane and (301) plane as Example 1, even in the
case where the planes were, for example, (110) plane, (101) plane,
and (211) plane, the same results were obtained. That is, it was
confirmed that the orientation did not depend on the types of
crystal planes.
[0076] Although at least one crystal plane is necessary for
selective orientation, even in the case of 2 to 4 crystal planes,
the same results of the test were obtained regardless of the
combinations of these crystal planes. However, in the case of
orientation in 5 or more crystal planes, the points where the
crystals of different crystal planes were adjacent to each other
were increased and therefore the crystallinity was not sufficiently
heightened and consequently, similar to the case of the
conventional example 1, the life performance was not excellent.
[0077] In the lead-acid battery of the first embodiment, an example
in which four cells 1 were combined was employed. However, the
lead-acid battery may be composed using only one or the lead-acid
battery may be composed by combining an arbitrary number of 2 or
more of cells 1. Further, although the screws 12 were employed for
pressing the cells 1 by the pressing member 9 and 10 in the
lead-acid battery, the fixation means is arbitrary. For example, it
may be caulking.
(2) Second Embodiment
(2.1) Production of Positive Electrode Current Collector
[0078] Positive electrode current collectors were produced while
changing the heating temperature of the current collector
substrates when the raw material solution was intermittently
sprayed to 300.degree. C., 350.degree. C., 380.degree. C.,
400.degree. C., 420.degree. C., 450.degree. C., or 450.degree. C.
At the time of spraying, the heating temperature was prevented from
lowering. The raw material solution to be used was the same raw
material solution as in the above-mentioned first embodiment.
[0079] The case where the heating temperature of the current
collector substrate was 300.degree. C. was set to be Comparative
Example 1; the case of 350.degree. C. was set to be Comparative
Example 2; the case of 380.degree. C. was set to be Comparative
Example 3; the case of 400.degree. C. was set to be Example 2-1;
the case of 420.degree. C. was set to be Example 2-2; the case of
450.degree. C. was set to be Example 2-3; and the case of
500.degree. C. was set to be Example 2-4.
(2.2) Results of X-Ray Diffractometry
[0080] In the x-ray diffraction patterns of the positive electrode
current collectors of Comparative Examples 1, 2, and 3 and Examples
2-1, 2-2, 2-3, and 2-4, the crystal planes of peaks with the
maximum intensity among peaks of tin dioxide and the half width of
the peaks are shown in Table 3.
TABLE-US-00003 TABLE 3 Surface temperature of current collector
substrate Crystal plane Half width Comparative example 1
300.degree. C. (200) 2.80.degree. Comparative example 2 350.degree.
C. (200) 1.31.degree. Comparative example 3 380.degree. C. (200)
1.10.degree. Example 2-1 400.degree. C. (200) 1.00.degree. Example
2-2 420.degree. C. (200) 0.91.degree. Example 2-3 450.degree. C.
(200) 0.68.degree. Example 2-4 500.degree. C. (200)
0.64.degree.
[0081] Further, the x-ray diffraction patterns of tin dioxide
coatings in the positive electrode current collectors of
Comparative Example 1, Example 2-1, and Example 2-4 are shown in
FIG. 5. The encircled peaks in FIG. 5 were attributed to
titanium.
[0082] In the x-ray diffraction pattern of Comparative Example 1,
the peak curves of the respective crystal planes were very gentle
slopes. The half width of the peak of the (200) plane was wide. The
crystallinity was supposed to be very low.
[0083] On the other hand, in the x-ray diffraction pattern of
Example 2-1, the peak curves of the respective crystal planes were
steep. The half width of the peak of the (200) plane was narrow.
The crystallinity was supposed to be high. In the x-ray diffraction
pattern of Example 2-4, the peak curves of the respective crystal
planes were steeper. The half width of the peak of the (200) plane
was narrower. The crystallinity was supposed to be very high.
[0084] As shown in Table 3, in the case where the heating
temperature was 300.degree. C. (Comparative Example 1), 350.degree.
C. (Comparative Example 2), or 380.degree. C. (Comparative Example
3), the crystallinity was low and the half width was higher than
10. In the case where the heating temperature was 400.degree. C. in
Example 2-1, the half width was 1.00.degree.. Further, in the case
where the heating temperature was 420.degree. C. in Example 2-2,
the half width was 0.91.degree.. Further, in the case where the
heating temperature was as high as 450.degree. C. (Example 2-3) and
500.degree. C. (Example 2-4), the crystallinity was sufficiently
high and the half width was sufficiently low than 10.
(2.2) Results of Life Performance
[0085] For lead-acid batteries produced using the positive
electrode current collectors of Comparative Examples 1, 2, and 3
and Examples 2-1, 2-2, 2-3, and 2-4, the life performance test was
carried out. The method for the life performance was the same as in
the first embodiment.
[0086] Results of the life performance test are shown in FIG. 6.
The abscissa axis of FIG. 6 shows the half width of XRD peak with
the maximum intensity and the ordinate axis shows the life
performance. The definition of the life performance is described in
the first embodiment.
[0087] The life performance of the positive electrode current
collectors of Examples 2-1, 2-2, 2-3, and 2-4 exceeded 400 days.
However, the life performance of the positive electrode current
collectors of Comparative Examples 1, 2, and 3 was 200 days or
shorter.
[0088] According to the above-mentioned results, in the case where
the half width of peak with the maximum intensity among peaks of
tin dioxide became 1.degree. or lower in the x-ray diffraction
pattern of the positive electrode current collector, the life
performance became excellent.
(3) Third Embodiment
[0089] In a third embodiment, how the number of selectively
oriented crystal planes affected the life performance of the
lead-acid battery was investigated.
(3.1) Production of Positive Electrode Current Collector
[0090] The spraying amount of the raw material solution per one
time in the production process affects the number of the
selectively oriented crystal planes. Further, whether annealing
treatment is carried out or not for titanium to which spraying is
carried out also affects the number of the selectively oriented
crystal planes. Therefore, titanium which was not annealed and
titanium which was annealed were used to produce positive electrode
current collectors. The spraying amount of the raw material
solution per one time was variously changed. Hereinafter, specific
explanation will be given.
[0091] Using titanium which was not annealed as a current collector
substrate, the raw material solution was intermittently sprayed. In
the case of spraying, the spraying amount per one time was changed
to be 0.2 cc, 0.4 cc, 0.6 cc, and 0.8 cc to form a titanium dioxide
coating on the current collector substrate. The heating temperature
of the current collector substrate was 550.degree. C.
[0092] Further, using titanium which was annealed in vacuum
atmosphere as a current collector substrate, a titanium dioxide
coating was formed on the current collector substrate by adjusting
the spraying amount per time to be 0.2 cc and 0.4 cc. The raw
material solution was the same as in Example 1.
(3.2) Results of X-Ray Diffractometry
[0093] In the case where the spraying amount was 0.2 cc/time, there
were 2 selectively oriented crystal planes. In the case where the
spraying amount was 0.4 cc/time, there were 4 selectively oriented
crystal planes. In the case where the spraying amount was 0.6
cc/time, there were 5 selectively oriented crystal planes.
[0094] As described above, as the spraying amount was increased
more, the number of the selectively oriented crystal planes was
increased more. It is supposed to be because the heating
temperature was high and the ambient temperature in the periphery
of the current collector substrate was so sufficiently increased as
to cause the thermal decomposition and also because, similarly to
the case of a dip coating method, due to the increased thickness of
the liquid film of the raw material solution sprayed to the surface
of the current collector substrate, crystals were contained which
were grown using crystal cores in crystal planes in various
directions produced in the liquid film without using the crystal on
the surface of the current collector substrate as the undercoating
layer.
[0095] In the case of using the current collector substrate of
titanium which was annealed in vacuum atmosphere, in the case where
the spraying amount per one time was set to be 0.2 cc, there was
one selectively oriented crystal plane and in the case where it was
set to be 0.4 cc, there were three selectively oriented crystal
planes.
[0096] The above-mentioned results are collectively shown in Table
4.
TABLE-US-00004 TABLE 4 Current collector Spraying amount per Number
of selectively substrate one time oriented crystal planes Titanium
not annealed 0.2 cc 2 0.4 cc 4 0.6 cc 5 0.8 cc 6 Titanium annealed
in 0.2 cc 1 vacuum atmosphere 0.4 cc 3
(3.3) Results of Life Performance
[0097] The life performance test was carried out for 5 kinds of
positive electrode current collectors produced in the third
embodiment. The method of the life performance test was the same as
in Example 1.
[0098] The results of the life performance test are shown in FIG.
7. In FIG. 7, the abscissa axis shows the number of the selectively
oriented crystal planes and the ordinate axis shows the life
performance.
[0099] According to FIG. 7, in the case where the number of the
selectively oriented crystal planes was 1 or more and 4 or less,
the life performance was excellent. However, in the case where the
number of the selectively oriented crystal planes was 5 or more,
the life performance was considerably inferior as compared with
that in the case where the number was 4 or less. There was
significant difference of life performance between the case of 4
and the case of 5.
[0100] It is supposed that the life performance was inferior in the
case where the number of the selectively oriented crystal planes
was 5 or more because the points where crystals of different
crystal planes are adjacent to one another are increased and
therefore the chemical stability is lowered.
[0101] The present invention relates to a positive electrode
current collector for a lead-acid battery having a coating on the
surface. A lead-acid battery equipped with the positive electrode
current collector shows extremely excellent life performance.
Accordingly, the present invention can be applied widely in
industrial spheres.
* * * * *