LEAD STORAGE CELL
5 TECHNICAL FIELD
[0001] The present invention relates to lead storage cells, more particularly to a lead
storage cell including electrode plate units, each including a positive electrode plate, a
negative electrode plate, and a separator. The positive electrode plate is a positive electrode
grid filled with paste including powder. The main component of this powder is lead oxide.
10 The negative electrode plate is a negative electrode grid filled with paste including powder
and carbon black. The main component of this powder is lead oxide. The separator is
provided between the positive electrode plate and the negative electrode plate.
BACKGROUND ART
15 [0002] There is a constant demand for economical lead storage cells with high durability,
which serve as starter batteries for automobiles. Such a lead storage cell includes a battery
box including a plurality of cell compartments. Each of the cell compartments includes an
electrode plate unit including a positive electrode plate, a negative electrode plate, and a
separator. The positive electrode plate is a positive electrode grid filled with paste of lead
20 suboxide powder. The negative electrode plate is a negative electrode grid filled with paste
of lead suboxide powder and carbon black. The separator is provided between the positive
electrode plate and the negative electrode plate. The abutting electrode plate units are
connected in series. The level of an electrolyte poured into the battery box is higher than
that of the electrode plate unit. A lid is closed to seal the battery box.
25 [0003] For a long-life lead storage cell, the negative electrode plate often includes a
conductive agent such as carbon black to improve the charge acceptance of the negative
electrode plate. In addition, the conductivity depends on the surface area and the amount of
the carbon black. The surface area of the CB is often measured with the amount of dibutyl
phthalate (DBP) oil absorption.
5 [0004] PATENT DOCUMENTS 1-4 disclose that a negative electrode plate includes
carbon black having a large amount of DBP oil absorption (or a large specific surface) to
make a long-life lead storage cell. In particular, PATENT DOCUMENTS 2 and 4 disclose
in detail that the CB and a lignin compound are used together to improve the charge
acceptance of the negative electrode plate. This CB has a DBP oil absorption of 100-300
10 mllg or 450-550 mllg. The lignin compound is approximately 0.1-0.6 mass percent relative
to a negative electrode active material.
CITATION LIST
PATENT DOCUMENT
15 [0005] PATENT DOCUMENT 1 : Japanese Unexamined Patent Publication No. H05-
174825
PATENT DOCUMENT 2: Japanese Unexamined Patent Publication No. 2002-063905
PATENT DOCUMENT 3 : Japanese Unexamined Patent Publication No. 2006- 196 19 1
PATENT DOCUMENT 4: Japanese Unexamined Patent Publication No. 2007-273367
20
SUMMARY OF THE INVENTION
TECHNICAL PROBLEM
[0006] However, it has been found that the lead storage cell does not work effectively
under certain conditions. For example, the lead storage cell with the techniques of
25 PATENT DOCUMENTS 1-4 does not start the engine of the vehicle that has been left under
a relatively low SOC for a long time. It is an object of the present invention to provide a
lead storage cell that is so excellent in discharging under severe conditions as to start an
engine of a vehicle that has been left for a long time.
5 SOLUTION TO THE PROBLEM
[0007] To solve the above problem, the lead storage cell of the present invention includes
electrode plate units, each including a positive electrode plate, a negative electrode plate, and
a separator. The positive electrode plate is a positive electrode grid filled with paste
including powder of lead oxide as a main component. The negative electrode plate is a
10 negative electrode grid filled with paste including powder of lead oxide as a main component,
and including carbon black. The positive electrode plate faces the negative electrode plate.
The separator is provided between the positive electrode plate and the negative electrode
plate. The positive electrode grid includes gates, each being generally diamond-shaped and
being more than or equal to 50 mm2 and less than or equal to 100 mm2 in area. The carbon
15 black has a DBP oil absorption of more than or equal to 140 mllg and less than or equal to
340 mllg.
[0008] The amount of DBP oil absorption can be measured according to the method of JIS
K6221 (1982) 6.1.2.A. The term "main component" means that the component occupies
more than or equal to 50%. The term "generally diamond-shaped" covers not only a strict
20 diamond shape, but also a shape termed a diamond shape in an expanded metal.
Specifically, the term means a shape of an expanded metal including a bonding portion that is
regarded as not a side but an angle.
[0009] The positive electrode grid may include gates, each being generally diamondshaped
and being more than or equal to 65 mm2 and less than or equal to 85 mm2 in area.
25 [0010] The carbon black may have a DBP oil absorption of more than or equal to 150 mllg
and less than or equal to 200 mllg.
[0011] The carbon black may be more than or equal to 0.05 mass percent and less than or
equal to 0.7 mass percent relative to a negative electrode active material.
[0012] The carbon black may be more than or equal to 0.1 mass percent and less than or
5 equal to 0.5 mass percent relative to a negative electrode active material.
[0013] The level of an electrolyte may be higher than that of the electrode plate unit.
ADVANTAGES OF THE INVENTION
[0014] The lead storage cell of the present invention is a long-life lead storage cell for
10 vehicles. This lead storage cell that has been left for a long time after a repeat of a start of
the engine can still start the engine. This lead storage cell has excellent discharge
characteristics under server conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
15 [0015] [FIG. 1 ] FIG. 1 illustrates a main portion of a lead storage cell of an embodiment.
[FIG. 21 FIG. 2(a) illustrates one example of a positive electrode grid of the
embodiment. FIG. 2(b) is an enlarged view of a part of the positive electrode grid.
DESCRIPTION OF EMBODIMENTS
20 [0016] Before an embodiment, the story behind the present invention will be described.
[0017] A negative electrode plate with an appropriate amount of carbon black that has a
large amount of DBP oil absorption (or a high conductivity) surely has an improved charge
acceptance, and lengthens the life of a lead storage cell. However, it has been found that a
lead storage cell including such a negative electrode plate combined with a positive electrode
25 plate produced at random does not obtain desirable discharge characteristics under special,
severe conditions. For example, this battery that has been left under a relatively low SOC
for a long time cannot start a vehicle. The inventors have found a cause of such a
disadvantage, and made the present invention. The following is the detailed descriptions of
its mechanisms etc.
5 [0018] Lithium ion secondary batteries or nickel hydrogen storage batteries include paste
of an active material. This paste includes a thickener such as polyvinylidene fluoride
(PVDF) or carboxymethyl cellulose (CMC). Thus, this paste has a high flowability and is
convenient for filling and applying. In other words, a current collector includes the active
material having a small variability per unit area. In contrast, lead storage cells include a
10 positive electrode plate with paste of lead suboxide powder, purified water, and dilute sulfuric
acid. The main component of the lead suboxide powder is lead oxide. This paste does not
include a thickener while only including, e.g., acrylic resin fiber or polyethylenetelephthalate
(PET) resin fiber. Thus, this paste has a low flowability as plaster does, and is inconvenient
for filling and applying. In other words, a current collector includes the active material
15 having has a large variability per unit area.
[0019] The lead storage cell includes positive electrode plates and negative electrode
plates. These positive electrode plates and negative electrode plates are made from positive
electrode grids and negative electrode grids, respectively. These positive electrode grids and
negative electrode grids are made of a lead or a lead alloy. Each grid includes an upper
20 frame and a mesh. The upper frame includes an edge connected with a strap. The mesh
includes a plurality of gates that are generally diamond-shaped. The positive electrode
plates and the negative electrode plates include this mesh filled with the above paste.
[0020] As described above, the paste on the positive electrode of the lead storage cell has a
lower flowability than those of the other batteries have. Thus, the paste is inconvenient for
25 filling. It is very difficult to appropriately apply such paste on a grid including excessively
small gates (small spaces) or a grid including excessively large gates (large spaces). The
amount of the active material (lead suboxide powder) per unit area of the positive electrode
plate filled with the paste under such conditions varies in the inside of a single gate or over
multiple gates.
5 [0021] PATENT DOCUMENTS 1-4 disclose that the carbon black having a large amount
of DBP oil absorption and a high conductivity and the lignin in an appropriate amount not
only improve the charge acceptance of the negative electrode plate, but also form a uniform
conductive network, thereby reducing the resistance to a charge transfer, and improving the
responsivity to discharging.
10 [0022] In contrast, the positive electrode plate with an excessively small or excessively
large gate area is unable to distribute the active material equally. Thus, such a positive
electrode plate has a stronger resistance to a charge transfer than the above improved negative
electrode plate does.
[0023] In this situation, the inventors have found the following. The lead storage cell
15 with the above improved negative electrode plate is a long-life battery. However, this
battery on a vehicle that has been left for a long time from a certain low SOC might generate
a dark current discharge (a discharge of an extremely weak current for maintaining a memory
in a device). In this case, an uneven distribution of the active material in the positive
electrode plate produces a significant effect. This is because the positive electrode plate and
20 the negative electrode plate show an uneven distribution of a charging/discharging reaction,
i.e., because lead sulfate (PbS04), which is a reaction product, is unevenly generated on
certain portions of the positive electrode plate and the negative electrode plate.
[0024] Specifically, the inside of the positive electrode plate has a portion of a high weight
ratio of the positive electrode grid (i.e., a portion of a low weight ratio of the active material).
25 In this portion, the dark current discharge reaction proceeds more smoothly than in the other
portions. Thus, this portion serves as a strong resistance, thereby preventing a start of the
engine. Such an effect is unable to be found without exposing the lead storage cell to the
dark current discharge for a long time. This lead storage cell includes the carbon black
having a DBP oil absorption of 140-340 ml/g, and thus includes the negative electrode plate
5 having an improved charge acceptance.
[0025] From this finding, the inventors have studied a positive electrode grid convenient
for a uniform filling of an active material paste for the positive electrode plate. Then, they
have found that a mesh including gates, each being 50-100 mm2 in area, preferably 65-85
mm2 allows the positive electrode plate to have a great uniformity of filling of paste and a
10 small distribution variability of an active material. This finding provides a long-life lead
storage cell that is able to start an engine even when exposed to the dark current discharge for
a long time after the SOC has been reduced by a repeat of a start of the engine.
[0026] The carbon black having a DBP oil absorption of 150-200 mllg is more
advantageous. The carbon black having a DBP oil absorption of more than or equal to 150
15 ml/g makes the charge acceptance of the negative electrode plate high. The carbon black
having a DBP oil absorption of less than or equal to 200 ml/g keeps the structure of the active
material solid. Accordingly, the life characteristics are further improved.
[0027] The carbon black of 0.05-0.7 mass percent, preferably 0.1-0.5 mass percent relative
to the negative electrode active material is more advantageous. The amount of more than or
20 equal to 0.05 mass percent makes the charge acceptance of the negative electrode plate high.
The amount of less than or equal to 0.7 mass percent keeps the structure of the active material
solid. Accordingly, the life characteristics are further improved.
[0028] Moreover, the so-called liquid electrolyte lead storage cell is more advantageous.
The level of an electrolyte of this liquid electrolyte lead storage cell is higher than that of the
25 electrode plate unit so that the whole electrode plate unit is soaked in the electrolyte. The
liquid electrolyte lead storage cell (as a starter battery for, in particular, an idle reduction
vehicle) has many opportunities to repeat a large current discharge such as a start of the
engine and to reduce the SOC. This battery that is mounted on a vehicle also has many
opportunities to be exposed to a dark current discharge.
5 [0029] (Embodiment)
FIG. I illustrates a main portion (an electrode plate unit) of a lead storage cell of
this embodiment. FIG. 2 illustrates one example of a positive electrode grid of this
embodiment. An electrode plate unit 1 includes a positive electrode plate la, a negative
electrode plate lb, and a separator lc. The positive electrode plate la is a positive electrode
10 grid filled with paste of lead suboxide powder, purified water, and dilute sulfuric acid. The
main component of this lead suboxide powder is lead oxide. The negative electrode plate lb
is a negative electrode grid filled with paste of lead suboxide powder, purified water, dilute
sulfuric acid, carbon black, barium sulfate, and lignin. The main component of this lead
suboxide powder is also lead oxide. The carbon black, the barium sulfate, and the lignin
15 serve as additives. The separator I c is provided between the positive electrode plate 1 a and
the negative electrode plate lb. A battery box 2 includes a plurality of cell compartments 3
separated by partitions 2a. Each of the cell compartments 3 accommodates the electrode
plate unit 1. The electrode plate unit 1 is connected with a strap 4 (that is connected with a
connection member 5). This connection member 5 is connected through the partition 2a
20 with a next connection member 5 having the opposite polarity. In this manner, the electrode
plate units 1 are connected in series as many as the number of the cell compartments 3.
Each of the connection members 5 located on both ends of the series does not abut the
connection member 5 having the opposite polarity. These connection members 5 on both
ends are connected with binding posts (not shown). A lid 6 including a pair of bushings (not
25 shown) is closed to seal the battery box 2. The bushings engage with the binding posts of
the cell compartments 3 on both ends. The binding posts and the bushings are integrated by,
e.g., welding to serve as a pair of terminals 7. A vent hole (not shown) is provided directly
above each of the cell compartments 3. An electrolyte (not shown) is poured from this vent
hole so that the level of the electrolyte is higher than that of the electrode plate unit 1. Then,
5 the vent holes are sealed with vent plugs 6a. Then, the lead storage cell is charged under a
predetermined condition.
[0030] The positive electrode grid 8 of this embodiment is made of a lead or a lead alloy.
This grid includes an upper frame 9 and a mesh. The upper frame 9 includes an edge 9a
connected with the connection member 5. The mesh includes a plurality of gates 10 that are
10 generally diamond-shaped. A lower h e may be provided on a lower part of the mesh to
keep the structure solid. The negative electrode grid (not shown) has the same structure as
the positive electrode grid 8.
[0031] This embodiment has two features. First, the gate 10 of the mesh of the positive
electrode grid 8 is 50-100 mm2 in area, preferably 65-85 mm2. Second, the carbon black of
15 the negative electrode plate lb has a DBP oil absorption of 140-340 ml/g, preferably 150-200
ml/g.
[0032] Unlike a lithium ion secondary battery or a nickel hydrogen storage battery, a lead
storage cell includes paste, of lead suboxide powder, that does not include a thickener (PVDF,
CMC, etc.). Thus, this paste has a low flowability as plaster does, and is inconvenient for
20 filling and applying. In other words, the current collector includes the active material having
a large variability per unit area. It is impossible to appropriately apply such paste on a grid
including excessively small gates 10 (small spaces) or a grid including excessively large gates
10 (large spaces). Thus, the amount of the active material (lead suboxide powder) per unit
area of the electrode plate varies in the inside of a single gate 10 or over multiple gates 10.
25 [0033] PATENT DOCUMENTS 1-4 disclose that the carbon black having a large amount
of DBP oil absorption and a high conductivity, and the lignin in an appropriate amount not
only improve the charge acceptance of the negative electrode plate, but also form a uniform
conductive network, thereby reducing the resistance to a charge transfer, and improving the
responsivity to discharging.
5 [0034] In contrast, the positive electrode plate la that is a positive electrode grid 8
including gates 10, each being excessively small or excessively large in area is unable to
distribute the active material equally due to the filling variability. Thus, such a positive
electrode plate has a stronger resistance to a charge transfer than the above improved negative
electrode plate 1 b does.
10 [0035] The lead storage cell with the above improved negative electrode plate I b is a longlife
battery. However, this battery on a vehicle that has been left for a long time from a
certain low SOC might generate a dark current discharge. In this case, an uneven
distribution of the active material in the positive electrode plate la produces a significant
effect. Specifically, the inside of the positive electrode plate la has a portion of a high
15 weight ratio of the positive electrode grid 8 (more specifically, a grid (a strand) including a
mesh), i.e., a portion of a low weight ratio of the active material. In this portion, the dark
current discharge reaction proceeds more smoothly than in the other portions. Thus, this
portion serves as a strong resistance to the reaction, thereby preventing a restart of the engine.
Such an effect is unable to be found without exposing the lead storage cell to the dark current
20 discharge for a long time. This lead storage cell includes the carbon black having a DBP oil
absorption of 140-340 mllg, and thus includes the negative electrode plate lb having an
improved charge acceptance.
[0036] The positive electrode grid 8 convenient for a uniform filling of an active material
paste for the positive electrode plate 1 a includes a mesh including gates, each being 50-1 00
25 mm2 in area, preferably 65-85 mm2. The positive electrode plate la including this mesh has
a great uniformity of filling of paste and a small distribution variability of the active material.
This positive electrode plate la combined with the negative electrode plate lb including the
carbon black having a DBP oil absorption of 140-340 mllg provides a long-life lead storage
cell that is able to start an engine even when exposed to the dark current discharge for a long
5 time after the SOC has been reduced by a repeat of a start of the engine.
[0037] The carbon black of the negative electrode plate lb preferably has a DBP oil
absorption of 150-200 mllg. The carbon black having a DBP oil absorption of more than or
equal to 150 mllg makes the charge acceptance of the negative electrode plate lb high. The
carbon black having a DBP oil absorption of less than or equal to 200 mug keeps the structure
10 of the active material solid. Accordingly, the life characteristics are further improved.
[0038] The negative electrode plate lb preferably includes the carbon black of 0.05-0.7
mass percent, preferably 0.1-0.5 mass percent relative to the negative electrode active
material. The amount of more than or equal to 0.05 mass percent makes the charge
acceptance of the negative electrode plate lb high. The amount of less than or equal to 0.7
15 mass percent keeps the structure of the active material solid. Accordingly, the life
characteristics are further improved.
[0039] Moreover, the so-called liquid electrolyte lead storage cell is preferable. The level
of an electrolyte of this liquid electrolyte lead storage cell is higher than that of the electrode
plate unit 1. The liquid electrolyte lead storage cell (as a starter battery for, in particular, an
20 idle reduction vehicle) has many opportunities to repeat a large current discharge such as a
start of the engine and to reduce the SOC. This battery that is mounted on a vehicle also has
many opportunities to be exposed to a dark current discharge. Thus, this liquid electrolyte
lead storage cell is advantageous for this embodiment.
[0040] In this embodiment, a preferable amount of lignin compound of the negative
25 electrode plate lb is not limited to 0.1-0.6 mass percent of PATENT DOCUMENTS 1-4
relative to the negative electrode active material. A matter of first priority of this
embodiment is the responsivity to discharging of the positive electrode plate 1 a. In such an
embodiment, the amount of lignin compound improving the charge acceptance of the negative
electrode plate 1 b is more dominant than the quality of the conductive network of the positive
5 electrode plate 1 a (the size of the gate 10 of the mesh of the positive electrode grid 8).
[0041] FIG. 2 illustrates that the area of the gate 10 of the mesh varies from the upper
frame 9 to the bottom. Note that the maximum of this area is less than or equal to the double
of the minimum. In this case, the average of this area may serve as "the area of the gate 10."
Only a portion, of the mesh, that is in contact with the upper frame 9 includes gates 10, each
10 having half a generally diamond-shaped area. These gates are few in number, and produce
no noticeable effect. Thus, these gates are not defined as "the area of the gate 10" in this
embodiment.
[0042] The area of the gate 10 in FIG. 2(b) is calculated by A x B. The area of the gate
10 is controlled by adjusting a mold that is used to produce the positive electrode grid 8 by the
15 casting method. The area of the gate 10 is also controlled by adjusting a cutting width and
an expansion dimension of a lead alloy sheet, which is a raw material.
[0043] The numerical value of DBP oil absorption of the carbon black may be specified
with only one material. For example, the value of 178 ml/g may be specified with only
"WLCAN (a trademark) XC-72" (BK) of Cabot Corporation. The BK has a DBP oil
20 absorption of 178 ml/g. Alternatively, the numerical value may be varied with multiple
materials. For example, the BK and "KETJENBLACK (a trademark) EC" (KB) of Lion
Corporation may be appropriately mixed to specify any value of 178-350 ml/g. The KB has
a DBP oil absorption of 350 ml/g.
Examples
25 [0044] (Example 1)
A positive electrode plate la including an edge 9a and an upper frame 9 was
produced as follows. An expanded sheet serving as a positive electrode grid 8 was produced
by expanding a calendered sheet of a lead-calcium alloy by the reciprocating method and
adjusting a cutting width and an expansion dimension of the calendered sheet. The positive
5 electrode grid 8 includes a mesh including a plurality of gates 10. Each of the gates 10 is
generally diamond-shaped and 50 mm2 in area. A paste was produced by mixing lead
suboxide powder, sulfuric acid, and purified water. The main component of the lead
suboxide powder was lead oxide. The positive electrode grid 8 was filled with this paste.
Then, this positive electrode grid 8 was cut in the predetermined dimension and was dried.
10 [0045] A negative electrode plate lb including an edge 9a and an upper frame 9 was
produced as follows. An expanded sheet serving as a negative electrode grid was produced
by expanding a calendered sheet of a lead-tin-calcium alloy by the reciprocating method.
Lignin compound of 0.15 mass percent, barium sulfate of 1.0 mass percent, and carbon black
of 0.3 weight percent relative to the lead suboxide powder were added to the negative
15 electrode grid. The main component of the lead suboxide powder was lead oxide. The
average of DBP oil absorption of the carbon black was 185 mug by mixing BK and KB.
The negative electrode grid was filled with a paste produced by mixing sulfuric acid with
purified water. Then, this negative electrode grid was cut in the predetermined dimension
and was dried.
20 [0046] An electrode plate unit 1 was produced by providing the positive electrode plate 1 a
and the negative electrode plate lb face to face, and providing a microporous separator 1 c
between the positive electrode plate la and the negative electrode plate lb. The
microporous separator Ic was mainly made of a polyethylene resin. A battery box 2 of
polypropylene (PP) included six cell compartments 3 separated by partitions 2a. Each of the
25 six electrode plate units 1 was accommodated in each of the cell compartments 3. The
electrode plate units 1 were connected in series together through straps 4 and connection
members 5. Binding posts of the electrode plate units 1 on both ends were connected to one
of polarities.
[0047] The battery box 2 was sealed by a lid 6. This lid 6 was made of PP and included
5 bushings. A pair of terminals 7 were produced by engaging, welding, and integrating the
binding posts and the bushings. A predetermined dilute s u l h c acid (an electrolyte) was
poured from a vent hole provided directly above each of the cell compartments 3 so that the
level of the electrolyte was higher than that of the electrode plate unit 1. The vent hole was
sealed with a vent plug 6a. Then, the battery was charged under a predetermined condition.
10 In this manner, 80D26 defined by JIS D5 103 (lead-acid starter battery) was produced.
[0048] (Examples 2-5)
Lead storage cells were all produced in a similar manner of Example 1 except for
the area of the gate 10 of the mesh of the positive electrode grid 8. The area of the gate 10
was 65 mrn2 (Example 2), 75 mm2 (Example 3), 85 mm2 (Example 4), or 100 mm2 (Example
15 5).
[0049] (Comparison Examples 1 and 2)
Lead storage cells were all produced in a similar manner of Example 1 except for
the area of the gate 10 of the mesh of the positive electrode grid 8. The area of the gate 10
was 45 mm2 (Comparison Example 1) or 1 10 mm2 (Comparison Example 2).
20 [0050] (Comparison Example 3)
A lead storage cell was all produced with the positive electrode grid 8 of Example 3
in a similar manner of Example 3 except for an average of DBP oil absorption of carbon black
added to the negative electrode paste. The "Denkablack (a trademark)" (DB) of DENKI
KAGAKU KOGYO has a DBP oil absorption of 115 mllg. The DB and BK were mixed
25 together and used as carbon black having the average of 130 mllg.
[005 11 (Examples 6-8)
Lead storage cells were all produced with the positive electrode grid 8 of Example 3
in a similar manner of Example 3 except for an average of DBP oil absorption of carbon black
added to the negative electrode paste. The DB and BK were mixed together and used as
5 carbon black having the average of 140 ml/g (Example 6), 150 mug (Example 7), or 170 mug
(Example 8).
[0052] (Examples 9-1 1)
Lead storage cells were all produced with the positive electrode grid 8 of Example 3
in a similar manner of Example 3 except for an average of DBP oil absorption of carbon black
10 added to the negative electrode paste. The BK and KB were mixed together and used as
carbon black having the average of 200 ml/g (Example 9), 270 ml/g (Example lo), or 340
ml/g (Example 1 I).
[0053] (Comparison Example 4)
A lead storage cell was all produced with the positive electrode grid 8 of Example 3
15 in a similar manner of Example 3 except for the amount of DBP oil absorption of carbon
black added to the negative electrode paste. Only KB was used as carbon black having 350
1 [0054] (Examples 12-1 7)
1 Lead storage cells were all produced with the positive electrode grid 8 of Example 3
( 20 in a similar manner of Example 3 except for the amount of carbon black added to the negative
1 electrode paste. The carbon black was 0.03 mass percent (Example 12), 0.05 mass percent
( (Example 13), 0.1 mass percent (Example 14), 0.5 mass percent (Example 15), 0.7 mass
( percent (Example 16), or 0.8 mass percent (Example 17) relative to lead suboxide powder (a
negative electrode active material).
k5 [0055] (Example 18)
A lead storage cell was all produced with the positive electrode grid of Example 3
in a similar manner of Example 3 except for the amount of lignin compound added to the
negative electrode paste. The amount of lignin compound was 0.05 mass percent.
[0056] A complex cycle life test for combination of a dark current discharge and an engine
5 start was conducted on each of these lead storage cells. Specifically, this test where a fourminute
discharge of the "light-load life test" of JIS D5103 was replaced with a two-minute
discharge was conducted in a thermostat at 80°C. More specifically, each sample was
discharged at 25A for two minutes and at a constant voltage of 14.8V (the maximum current
of 25A) for ten minutes. This cycle was repeated 480 times. Every 480 cycles, the sample
10 in a thermostat at 25°C was discharged at 0.1A for two weeks. Then, the sample was
discharged at 490A for 30 seconds. Then, the sample having the terminal voltage of less
than or equal to 7.2V was assessed as dead. Table 1 shows conditions and results.
[0057] [Tablel]
Example
Example
Example
Example
Example
Example
Example
Example
Example
Example
Example
Example
Gate Area
(-2lgate)
50
65
75
85
100
75
75
75
75
75
75
75
1
2
3
4
5
6
7
8
9
10
11
12
Life
Characteristics
(Cycle
Numbers)
5760
6240
7200
6240
5760
5760
6240
6240
6240
5760
5760
5760
Lignin
Amount
(mass %)
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
Carbon Black
DBP Oil Absorption
( d g )
185
185
185
185
185
140
150
170
200
270
340
185
Amount
(mass %)
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.03
[0058] The positive electrode grid 8 of Comparison Example 1 includes the gate 10 that is
45 rnm2 in area. The positive electrode grid 8 of Comparison Example 2 includes the gate
10 that is 1 10 mm2 in area. The samples of these comparison examples have poor
Comparison
Example 1 45 185 0.3
Comparison
Example 2 110 185 0.3
Comparison
Example 3 75 130 0.3
Comparison
Exam~le 4 75 350 0.3
5 startability after the dark current discharge. Such a gate 10 that is excessively large or
excessively small varies the uniformity of filling of the paste of an active material (the
distribution of an active material). If the negative electrode plate lb has a good conductive
network in its inside, this variation reduces the resistance to the dark current discharge
performed from a low SOC.
10 [0059] The carbon black of Comparison Example 3 has a DBP oil absorption of less than
140 mllg. The carbon black of Comparison Example 4 has more than 340 mllg of DBP oil
absorption. The samples of these comparison examples have poor life characteristics. To
0.15 4320
0.15 4320
0.15 3840
0.15 3 840
improve the life characteristics with a high charge acceptance of the negative electrode, the
carbon black needs to have an appropriate range of the amount of DBP oil absorption. An
15 excessively small amount of DBP oil absorption causes an insufficient conductive network in
the negative electrode plate lb. An excessively large amount of DBP oil absorption reduces
the retention of the active material in the negative electrode plate 1 b.
[0060] In contrast to these comparison examples, the samples of the other examples
include the gates 10, each being 50-100 mm2 in area. These samples also include the carbon
20 black having a DBP oil absorption of 140-340 mllg. Accordingly, these samples have both
good life characteristics and a good startability after the dark current discharge. The gate 10
that is 65-85 mm2 in area and the carbon black having 150-200 mllg of oil absorption are
17
more advantageous to the life characteristics and startability.
[0061] From the results of life characteristics, the carbon black is preferably 0.05-0.7 mass
percent relative to the negative electrode active material, and more preferably 0.1-0.5 mass
percent. It is conceivable that the effect on the life characteristics by the amount of carbon
5 black is based on the same mechanism of the amount of DBP oil absorption of carbon black.
[0062] The lignin compound of Example 3 is 0.15 mass percent relative to the negative
electrode active material. The lignin compound of Example 18 is 0.05 mass percent relative
to the negative electrode active material. The samples of these examples have the same
startability after the dark current discharge. A matter of first priority of this embodiment is
10 to adjust the balance of the conductive network between the positive electrode plate la and
the negative electrode plate lb. Thus, the lignin compound that does not directly relate to
this matter is not advantageous (but advantageous to only the charge acceptance).
INDUSTRIAL APPLICABILITY
15 [0063] The lead storage cell of the present invention, which is widely applicable to starter
batteries on vehicles, is industrially very useful.
DESCRIPTION OF REFERENCE CHARACTERS
[0064] 1 Electrode Plate Unit
20 la Positive Electrode Plate
1 b Negative Electrode Plate
1 c Separator
2 Battery Box
2a Partition
25 2b Side Wall
Cell Compartment
Strap
Connection Member
Lid
Vent Plug
Terminal
Positive Electrode Grid
Upper Frame
Edge
Gate
CLAIMS
1. A lead storage cell, comprising:
electrode plate units, each including a positive electrode plate, a negative electrode
5 plate, and a separator, wherein
the positive electrode plate is a positive electrode grid filled with paste including
powder of lead oxide as a main component,
the negative electrode plate is a negative electrode grid filled with paste including
powder of lead oxide as a main component, and including carbon black,
10 the positive electrode plate faces the negative electrode plate,
the separator is provided between the positive electrode plate and the negative
electrode plate,
the positive electrode grid includes gates, each being generally diamond-shaped,
and being more than or equal to 50 mm2 and less than or equal to 100 mm2 in area, and
15 the carbon black has a DBP oil absorption of more than or equal to 140 mllg and
less than or equal to 340 mllg.
2. The lead storage cell of claim 1, wherein
the positive electrode grid includes gates, each being generally diamond-shaped,
20 and being more than or equal to 65 mm2 and less than or equal to 85 mm2 in area.
3. The lead storage cell of claim 1, wherein
the carbon black has a DBP oil absorption of more than or equal to 150 mllg and
less than or equal to 200 mllg.
25
4. The lead storage cell of claim 1, wherein
the carbon black is more than or equal to 0.05 mass percent and less than or equal to
0.7 mass percent relative to a negative electrode active material.
5. The lead storage cell of claim 4, wherein
the carbon black is more than or equal to 0.1 mass percent and more than or equal to
0.5 mass percent relative to the negative electrode active material.
6. The lead storage cell of claim 1, wherein
10 a level of an electrolyte is higher than that of the electrode plate unit.