U.S. patent application number 15/491926 was filed with the patent office on 2017-08-03 for flooded lead-acid battery and method of making the same.
The applicant listed for this patent is TROJAN BATTERY COMPANY, LLC. Invention is credited to Gordon C. Beckley, Marvin C. Ho, Colin Smith, Charles E. Snyder.
Application Number | 20170222215 15/491926 |
Document ID | / |
Family ID | 41133571 |
Filed Date | 2017-08-03 |
United States Patent
Application |
20170222215 |
Kind Code |
A1 |
Beckley; Gordon C. ; et
al. |
August 3, 2017 |
FLOODED LEAD-ACID BATTERY AND METHOD OF MAKING THE SAME
Abstract
Positive active material pastes for flooded deep discharge
lead-acid batteries, methods of making the same and lead-acid
batteries including the same are provided. The positive active
material paste includes lead oxide, a sulfate additive, and an
aqueous acid. The positive active material paste contains from
about 0.1 to about 1.0 wt % of the sulfate additive. Batteries
using such positive active material pastes exhibit greatly improved
performance over batteries with conventional positive active
material pastes.
Inventors: |
Beckley; Gordon C.;
(Grayson, GA) ; Ho; Marvin C.; (Yorba Linda,
CA) ; Smith; Colin; (Grayson, GA) ; Snyder;
Charles E.; (Placentia, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TROJAN BATTERY COMPANY, LLC |
Santa Fe Springs |
CA |
US |
|
|
Family ID: |
41133571 |
Appl. No.: |
15/491926 |
Filed: |
April 19, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
14230799 |
Mar 31, 2014 |
|
|
|
15491926 |
|
|
|
|
13760673 |
Feb 6, 2013 |
8722249 |
|
|
14230799 |
|
|
|
|
12275158 |
Nov 20, 2008 |
8404382 |
|
|
13760673 |
|
|
|
|
61043377 |
Apr 8, 2008 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/685 20130101;
H01M 2004/028 20130101; Y02T 10/70 20130101; B05D 7/14 20130101;
C22C 11/08 20130101; H01M 4/20 20130101; B22D 21/007 20130101; H01M
4/73 20130101; Y02E 60/10 20130101; Y02P 70/50 20151101; B05D 1/26
20130101; H01M 10/06 20130101; H01M 4/48 20130101; H01M 4/364
20130101; H01M 4/14 20130101; H01M 4/56 20130101; B22D 25/02
20130101; H01M 2220/20 20130101 |
International
Class: |
H01M 4/20 20060101
H01M004/20; H01M 4/68 20060101 H01M004/68; H01M 4/73 20060101
H01M004/73; B05D 7/14 20060101 B05D007/14; B22D 25/02 20060101
B22D025/02; C22C 11/08 20060101 C22C011/08; B05D 1/26 20060101
B05D001/26; H01M 4/56 20060101 H01M004/56; B22D 21/00 20060101
B22D021/00 |
Claims
1.-20. (canceled)
21. A method for making a positive plate for a flooded lead-acid
battery comprising: casting a positive electrode grid from a
lead-antimony alloy; applying a positive active material paste
directly to the cast positive electrode grid, the positive active
material paste comprising lead oxide, a binder, and tin sulfate,
wherein the tin sulfate is present the positive active material
paste in an amount from about 0.1 wt % to about 1 wt % on a dry
basis.
22. The method of claim 21 wherein the tin sulfate is present in
the positive active material paste in an amount from about 0.15 wt
% to about 0.2 wt % on a dry basis.
23. The method of claim 21 wherein the tin sulfate is present in
the positive active material paste in an amount of about 0.18 wt %
on a dry basis.
24. The method of claim 21 wherein the lead-antimony alloy
comprises between about 2 wt % and 6 wt % of antimony.
Description
CROSS REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/760,673 filed on Feb. 6, 2013, which is a
continuation of U.S. patent application Ser. No. 12/275,158, filed
on Nov. 20, 2008, now issued as U.S. Pat. No. 8,404,382, which
claims the benefit of U.S. Provisional Application No. 61/043,377,
filed on Apr. 8, 2008, the entire contents of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to flooded or wet cell
lead-acid electrochemical batteries, and more particularly to
positive active material pastes for use in such batteries and to
methods of making and using the same.
BACKGROUND OF THE INVENTION
[0003] A typical flooded lead-acid battery includes positive and
negative electrode grids and an electrolyte. The electrode grids,
while primarily constructed of lead, are often alloyed with
antimony, calcium, or tin to improve their mechanical
characteristics. Antimony is generally a preferred alloying
material for deep discharge batteries.
[0004] In a flooded lead-acid battery, positive and negative active
material pastes are coated on the positive and negative electrode
grids, respectively, forming positive and negative plates. The
positive and negative active material pastes generally comprise
lead oxide (PbO or lead (II) oxide.) The electrolyte typically
includes an aqueous acid solution, most commonly sulfuric acid.
Once the battery is assembled, the battery undergoes a formation
step in which a charge is applied to the battery in order to
convert the lead oxide of the positive plates to lead dioxide
(PbO.sub.2 or lead (IV) oxide) and the lead oxide of the negative
plates to lead.
[0005] After the formation step, a battery may be repeatedly
discharged and charged in operation. During battery discharge, the
positive and negative active materials react with the sulfuric acid
of the electrolyte to form lead (II) sulfate (PbSO.sub.4). By the
reaction of the sulfuric acid with the positive and negative active
materials, a portion of the sulfuric acid of the electrolyte is
consumed. However, the sulfuric acid returns to the electrolyte
upon battery charging. The reaction of the positive and negative
active materials with the sulfuric acid of the electrolyte during
discharge may be represented by the following formulae.
[0006] Reaction at the negative electrode:
Pb(s)+SO.sub.4.sup.2-(aq)PbSO.sub.4(s)+2e.sup.-
[0007] Reaction at the positive electrode:
PbO.sub.2(s)+SO.sub.4.sup.2-(aq)+4H.sup.++2e.sup.-PbSO.sub.4(s)+2(H.sub.-
2O)(l)
As shown by these formulae, during discharge, electrical energy is
generated, making the flooded lead-acid battery a suitable power
source for many applications. For example, flooded lead-acid
batteries may be used as power sources for, electric vehicles such
as forklifts, golf cars, electric cars, and hybrid cars. Flooded
lead-acid batteries are also used for emergency or standby power
supplies, or to store power generated by photovoltaic systems.
[0008] To charge a flooded lead-acid battery, the discharge
reaction is reversed by applying a voltage from a charging source.
During charging, the lead sulfate reacts with oxygen molecules from
ionized water to produce lead and lead dioxide. The lead dioxide is
deposited on the positive electrode and the lead is deposited on
the negative electrode.
[0009] The lead dioxide deposited on the positive electrode is
known to exist in two different crystalline structures,
.alpha.-PbO.sub.2 and .beta.-PbO.sub.2. Of these, .alpha.-PbO.sub.2
tends to have a larger size crystal providing lower surface area
over .beta.-PbO.sub.2 which has a smaller size crystal with higher
surface area. In batteries, the larger crystal size and lower
surface area of .alpha.-PbO.sub.2 tends to lower initial battery
capacity, but provides longer life compared to the smaller crystal
size and larger surface area of .beta.-PbO.sub.2 which tends to
provide higher initial battery capacity, but shorter battery life.
Upon initial formation, the positive active material paste of a
typical deep discharge flooded lead-acid battery tends to exhibit
an .alpha.-PbO.sub.2 to .beta.-PbO.sub.2 ratio of about 1.2 or
higher.
[0010] The addition of tin sulfate to positive electrode in flooded
batteries is known, but is generally limited to use in batteries
that use positive electrodes made of lead-calcium alloys. Batteries
using lead-calcium alloy positive electrode grids are known to
suffer from the development of a poorly defined corrosion layer at
the surface of the grid which can limit battery life. It has been
suggested that the addition of tin to the alloy from which the grid
is made, or the application of tin to the surface of a grid will
form a tin-enriched layer at the surface of the grid, and in doing
so, will improve the properties of the corrosion layer at the
interface surface of the grid. However, it is also generally
recognized that positive electrode grids of a lead-antimony alloy
have well defined corrosion layers, and therefore, would not
benefit from the formation of a tin-enriched layer. Moreover, it is
also generally recognized that any tin provided at the positive
electrode grid will tend to migrate to the negative electrode grid
during battery use, and in doing so, will change the half potential
of the negative electrode grid and adversely affect the recharge
characteristics of the battery.
SUMMARY OF THE INVENTION
[0011] An embodiment of the present invention is directed to an
improved positive active material paste for a flooded deep
discharge lead-acid battery of the type that includes lead-antimony
alloy positive electrode grids. Such a positive active material
paste includes lead oxide, a metal sulfate additive, and sulfuric
acid. The positive active material paste may optionally include a
binder such as polyester fiber. According to one embodiment, the
metal sulfate is tin sulfate. For such an embodiment, the metal
sulfate additive may be present in the paste in an amount of about
0.2 wt % or less on a dry basis. In another embodiment, the tin
sulfate additive is present in the paste in an amount of about 0.18
wt % on a dry basis. Upon battery formation, the lead oxide of the
paste is converted to lead dioxide, and it is believed the metal
sulfate is similarly converted to an oxide of the metal.
[0012] In an embodiment of the invention, the molar ratio of lead
to metal (or metal oxide) for the positive active material paste
ranges from about 200:1 to about 825:1. In one exemplary
embodiment, the molar ratio of lead to the metal (or metal oxide)
is greater than about 450:1 (corresponding to an initial amount of
tin sulfate (when tin sulfate is the additive) of about 0.22 wt %
on a dry basis). In another embodiment, the lead to metal additive
molar ratio of the positive active material paste is between about
450:1 and about 650:1 (corresponding to an initial amount of tin
sulfate (when tin sulfate is the additive) ranging from about 0.15
to about 0.22 wt. % on a dry basis). In yet another embodiment, the
lead to metal additive molar ratio of the positive active material
paste is about 500:1 (corresponding to an initial amount of tin
sulfate (when tin sulfate is the additive) of about 0.2 wt % on a
dry basis).
[0013] For embodiments where tin is used as the metal additive, the
tin may be provided to the paste as tin sulfate. For such
embodiments, the lead to tin weight ratio of the positive active
material paste may be greater than about 800:1 (corresponding to an
initial amount of tin sulfate of about 0.22 wt % on a dry basis).
In another embodiment, the lead to tin weight ratio of the positive
active material paste is between about 800:1 and about 1100:1
(corresponding to an initial amount of tin sulfate ranging from
about 0.15 to about 0.22 wt % on a dry basis). In yet another
embodiment, the lead to tin weight ratio of the positive active
material paste is about 900:1 (corresponding to an initial amount
of tin sulfate of about 0.19 wt % on a dry basis).
[0014] Without being bound by theory, it is believed that after
battery formation, the resulting paste has a smaller crystal
structure and therefore a higher surface area after curing when
compared to conventional positive active material pastes.
Furthermore, the inclusion of a metal additive, such as tin, in a
weight ratio of about 900:1 can lower the .alpha.-PbO.sub.2 to
.beta.-PbO.sub.2 ratio of the formed battery to between about 0.8
and 1.0, resulting in a battery with both high initial capacity and
long battery life.
[0015] The metal additive is generally provided as a metal sulfate
in the positive active material paste prior to formation. Suitable
sulfates other than tin sulfate may include sulfates of zinc
(ZnSO.sub.4), titanium oxide (TiOSO.sub.4), calcium (CaSO.sub.4),
potassium (K.sub.2SO.sub.4), bismuth (Bi.sub.2(SO.sub.4).sub.3) and
indium (In.sub.2(SO.sub.4).sub.3).
[0016] Another embodiment of the invention is directed to a method
for preparing a positive active material paste for a flooded deep
discharge lead-acid battery of the type that includes lead-antimony
alloy grids. Such a method includes mixing lead oxide, a binder
such as polyester fiber, and a sulfate additive to form a dry
mixture, adding water to the dry mixture and wet-mixing the
resulting mixture. Acid is then added to form the positive active
material paste.
[0017] In another embodiment of the present invention, a flooded
deep discharge lead-acid battery includes the positive active
material paste. Such a flooded deep discharge lead-acid battery
includes a positive electrode grid alloyed with antimony. The
positive active material paste as described above is applied to the
positive electrode grid. In one embodiment, for example, the
positive electrode grid includes from about 2 to about 11 wt %
antimony. In another embodiment, the positive electrode grid
includes from about 2 to about 6 wt % antimony. While some amount
of antimony is desirable to improve the mechanical characteristics
of the grid, if too much antimony is added, it can cause
undesirable gassing of the finished battery, and can also drive up
the cost of the grid. Consequently, there are benefits to alloys
with low antimony content.
[0018] When compared to a conventional flooded deep discharge
lead-acid battery of similar size and weight that does not include
a metal additive in the positive active material paste, a flooded
deep discharge lead-acid battery that includes a metal additive in
the positive active material paste tends to retain a higher
capacity over the life of the battery. Therefore, a battery of the
present invention can provide higher total power output over the
battery's life compared to a conventional battery.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other features and advantages of the present
invention will be better understood by reference to the following
detailed description when considered in conjunction with the
attached drawings, in which:
[0020] FIG. 1 is a schematic sectional view of a flooded deep
discharge lead-acid battery according to one embodiment of the
present invention; and
[0021] FIGS. 2 through 4 are graphs comparing the cycle life of
flooded deep discharge lead-acid batteries according to embodiments
of the present invention to a control battery in which no additive
is used.
DETAILED DESCRIPTION
[0022] According to one embodiment of the invention, a positive
active material paste for a flooded deep discharge lead-acid
battery includes lead oxide, a sulfate additive, and an aqueous
acid solution. The sulfate additive may be any suitable metal or
metal oxide sulfate compound, nonlimiting examples of which include
SnSO.sub.4, ZnSO.sub.4, TiOSO.sub.4, CaSO.sub.4, K.sub.2SO.sub.4,
Bi.sub.2(SO.sub.4).sub.3 and In.sub.2(SO.sub.4).sub.3.
[0023] According to embodiments of the invention, enough sulfate
additive is provided to the paste to yield a lead to metal (or
metal oxide) molar ratio ranging from about 90:1 to about 1000:1,
and in one embodiment, for examples the molar ratio of lead to the
metal (or metal oxide) ranges from about 99:1 to about 997:1. In
one exemplary embodiment, enough additive is supplied such that the
lead to metal (or metal oxide) molar ratio of the positive active
material paste is greater than about 450:1. In another embodiment,
the lead to metal (or metal oxide) molar ratio of the positive
active material paste is between about 450:1 and about 650:1. In
yet another embodiment, the lead to metal additive molar ratio of
the positive active material paste is about 500:1.
[0024] In some embodiments of the invention, enough sulfate
additive is provided to the paste to yield a lead to metal (or
metal oxide) weight ratio ranging from about 170:1 to about 1750:1,
and in one embodiment, for example the weight ratio of lead to the
metal (or metal oxide) ranges from about 173:1 to about 1741:1. In
one exemplary embodiment, enough additive is supplied such that the
lead to metal (or metal oxide) weight ratio of the positive active
material paste is greater than about 750:1. In another embodiment,
the lead to metal (or metal oxide) weight ratio of the positive
active material paste is between about 750:1 and about 1150:1. In
yet another embodiment, the lead to metal additive molar ratio of
the positive active material paste is about 870:1.
[0025] For embodiments where tin is used as the metal in the
additive (i.e., the additive is tin sulfate), the lead to tin
weight ratio of the positive active material paste may be greater
than about 800:1. In another embodiment, the lead to tin weight
ratio of the positive active material paste is between about 800:1
and 1100:1. In yet another embodiment, the lead to tin weight ratio
of the positive active material paste is about 900:1 which
corresponds to an initial amount of tin sulfate of about 0.2 wt %
in the positive active material paste applied to the positive grid
prior to battery formation.
[0026] In order to provide a lead to metal (or metal oxide) molar
ratio within the ranges discussed above, in one embodiment, the
sulfate additive is provided to the paste in an amount ranging from
about 0.1 to about 1 wt % on a dry basis. In another embodiment,
the sulfate additive is provided to the paste in an amount of about
0.2 wt % on a dry basis. When using SnSO.sub.4 as the sulfate
additive, addition of more than about 1 wt % in the positive paste
prior to battery formation may cause undesirable tin migration to
the negative electrode grid. Adding high amounts of additive may
also be cost prohibitive. Based on an amount of additive provided
to the paste of about 0.2 wt % on a dry basis, and depending on the
purity of the additive (which varies), the lead to metal (or metal
oxide) molar ratio may range from about 200:1 to about 825:1, and
in one embodiment ranges from about 201:1 to about 823:1.
[0027] Surprisingly, according to an embodiment of the present
invention, the small amount of metal added to the positive active
material provides significant improvements in battery performance.
In addition, the small amount of metal additive does not tend to
cause any significant tin poisoning at the negative electrode as
might have been expected.
[0028] Without being bound by theory, it is believed that the
inclusion of the metal additive in the positive active material
paste according to embodiments of the present invention changes the
crystal structure of the positive active material paste. As a
result, it is believed that the active material has a higher
surface area on which electrochemical reactions can occur.
Accordingly, the deep discharge batteries having the uniform
crystal structure and higher active material surface area can
withstand deep discharge with less deterioration in the charge
capacity over the life of the battery, thus improving
performance.
[0029] In particular, the inclusion of tin as the metal of the
additive in the positive active paste at a lead to tin weight ratio
of about 900:1 can lower the .alpha.-PbO.sub.2 to .beta.-PbO.sub.2
ratio to between about 0.8 and 1.0. Such a balance of
.alpha.-PbO.sub.2 to .beta.-PbO.sub.2 has surprisingly shown to
result in a battery with both high initial capacity and long
battery life. It has further been shown that at sulfate levels
higher than about 0.2 wt %, the porosity of the positive active
paste material increases. Such an increase in porosity normally
tends to adversely affect battery performance. Higher porosity
indicates a higher volume of pores, enabling the electrolyte to
more easily penetrate inside the active material solid matrix.
Although this may improve initial battery performance, the positive
active material will expand and shrink during charge and discharge
(cycling), and the highly porous structure will decrease the
mechanical strength and shorten the cycle life of the active
material.
[0030] According to another embodiment of the present invention, a
method for preparing a positive active material paste includes
mixing lead oxide, a binder such as polyester fiber, and a metal
sulfate additive to form a dry mixture. Water is then added to the
dry mixture and the mixture is wet-mixed for a period of time.
After wet-mixing, acid is added and mixing continues.
[0031] In one embodiment, as shown somewhat schematically in FIG.
1, a single cell flooded deep discharge lead-acid battery 10
includes the positive active material paste as set forth above. The
battery includes a plurality of positive electrode grids 12, and a
plurality of negative electrode grids 14. Each positive electrode
grid is coated with a positive active material paste 16 as set
forth above to form a positive plate. Each negative electrode grid
is coated with a negative active material paste 18 to form a
negative plate. The coated positive and negative electrode grids
are arranged in an alternating stack within a battery case 22 using
a plurality of separators 24 to separate each electrode grid from
adjacent electrode grids and prevent short circuits. A positive
current collector 26 connects the positive electrode grids and a
negative current collector 28 connects the negative electrode
grids. An electrolyte solution 32 fills the battery case, and
positive and negative battery terminal posts 34, 36 extend from the
battery case to provide external electrical contact points used for
charging and discharging the battery. The battery case includes a
vent 42 to allow excess gas produced during the charge cycle to be
vented to atmosphere. A vent cap 44 prevents electrolyte from
spilling from the battery case. While a single cell battery is
illustrated, it should be clear to one of ordinary skill in the art
that the invention can be applied to multiple cell batteries as
well.
[0032] According to one embodiment, the positive electrode grids
are made from a lead-antimony alloy. In one embodiment, the
electrode grids are alloyed with about 2 wt % to about 11 wt %
antimony. In another embodiment, the electrode grids are alloyed
with between about 2 wt % and about 6 wt % antimony.
[0033] The negative electrode grids are similarly made from an
alloy of lead and antimony, but generally include less antimony
than the alloy used for the positive electrode grids. The negative
electrode grids also tend to be somewhat thinner than the positive
electrode grids. Such negative electrode grids are well known in
the art. The negative electrode grids are coated with a negative
active material that includes lead oxide and an expander as is also
well known in the art. Upon battery formation, the lead oxide of
the negative active material is converted to lead.
[0034] Suitable electrolytes include aqueous acid solutions. In one
embodiment, the electrolyte comprises a concentrated aqueous
solution of sulfuric acid having a specific gravity of about 1.1 to
about 1.3 prior to battery formation. The separators are made from
any one of known materials. Suitable separators are made from wood,
rubber, glass fiber mat, cellulose, poly vinyl chloride, and
polyethylene.
[0035] According to some embodiments, the completed battery may be
aged after formation. In particular, after initial charging (i.e.,
battery formation), the battery may be allowed to stand without use
for an aging period. The aging period may range from about 2 months
to about 6.5 months. Batteries according to embodiments of the
present invention that have been aged after formation have
surprisingly exhibited better results than their non-aged
counterparts. These results are shown in FIG. 2, discussed in
detail below relative to Examples 2 and 3.
[0036] The present invention will now be described with reference
to the following examples. These examples are provided for
illustrative purposes only, and are not intended to limit the scope
of the present invention.
EXAMPLE 1
Positive Active Material Paste and Positive Plate Formation
[0037] A positive active material paste was made by first mixing
2400 lbs of lead oxide powder and 2 lbs of polyester fiber in a
mixer. To that mixture, 4.40 lbs of tin sulfate was added while
mixing continued. Then, specified amounts of water and acid were
added and mixing continued until a positive active material paste
was formed. The positive paste included lead oxide, polyester
fiber, water, and aqueous sulfuric acid. The paste density was
about 4.5 g/cc, which is considered a high density paste and
suitable for cycling applications. The resulting paste was gray in
color and had a tin sulfate concentration of about 0.18 wt % on a
dry basis.
[0038] The positive active material paste was applied to identical
positive electrode grids using a Mac Engineering & Equipment
Co. commercial pasting machine to form pasted positive plates. The
positive electrode grids were cast using a Wirtz Manufacturing Co.
grid casting machine using a lead-antimony alloy with 4.5%
antimony. Each positive electrode grid was pasted with positive
active material paste. The resulting positive plates were then
dried in a flash drying oven according to well known methods. The
dried positive plates were then cured by a two-step process in a
curing chamber, first at 100% humidity for sixteen hours, and the
plates were then dried under high temperature without humidity
until the moisture content inside the plate was below 4%.
COMPARATIVE EXAMPLE 1
Conventional Positive Active Material Paste and Plate Formation
[0039] A positive active material paste and positive plates
identical to those described at Example 1 were made using the
method described at Example 1 with the exception that no metal
sulfate additive was included in the positive active material
paste.
EXAMPLES 2-3
Battery Assembly
[0040] According to Examples 2 and 3, the positive plates formed
according to Example 1 were assembled into twelve production
batteries of the type manufactured and sold by Trojan Battery
Corporation as Model T105 (3-cell, 6-volt, deep discharge lead-acid
battery, a type commonly used in electric golf cars). In other
words, with the exception that the positive plates of Example 1
were used instead of conventional positive plates, all other
components and manufacturing steps were identical to those employed
in making conventional Model T105 batteries. In particular,
individual cell groups were formed by stacking eight positive
plates of Example 1 and nine conventional negative plates in an
alternating arrangement with conventional separators between them.
The negative plates comprised negative electrode grids made from an
alloy of 2.75 wt % antimony in lead. Each negative electrode grid
was pasted with negative paste comprising lead oxide, deep cycle
expander, polyester fiber, water, and aqueous sulfuric acid. The
negative paste density was about 4.3 g/cc, which represents a
typical negative paste in the lead acid battery industry. The
positive plates were then dried in a flash drying oven and cured
using the same procedures as were used for the negative plates. The
separators used were rubber separators made by Microporous
Products, L.P. The deep cycle expander was provided by Atomized
Products Group, Inc.
[0041] The tabs of the negative plates of each cell group were
welded together using known procedures as were the tabs of the
positive plates of each cell group. For each battery, three cell
groups were interconnected in series as is well-known in the
assembly of three-cell batteries, and the combination of three cell
groups was inserted into a battery case. The case was then sealed
and the battery terminals were welded into place. The assembled
batteries were then filled with aqueous sulfuric acid and covers
were placed over the vents. For each of Examples 2 and 3, the
assembled batteries were connected in series, and within thirty
minutes of filling the batteries with acid, the battery formation
step was initiated. According to the battery formation step, a
charge was applied to the series of batteries using a constant
current formation procedure to form the plates. The formation was
terminated until the total charge energy reached about 190 to about
220% of the theoretical charge energy based on the quantity of
positive active material and charging efficiency. The final
specific gravity of the aqueous sulfuric acid inside the batteries
was about 1.275. The formed batteries were then placed on a shelf
for a 21 day pre-condition period before performing cycle tests.
After pre-conditioning, a number of the formed batteries were aged
on the shelf for an additional six months.
COMPARATIVE EXAMPLE 2
Conventional Battery Assembly
[0042] For Comparative Example 2, batteries identical to those of
Examples 2 and 3 were constructed, except that the conventional
positive plates of Comparative Example 1 were used in the
assembly.
[0043] For a first test, six conditioned batteries of Example 2
were compared against six conventional batteries of Comparative
Example 2 immediately after conditioning. In particular, the six
batteries of Example 2 were set up in series on one test circuit
while the six batteries of Comparative Example 2 were set up in
series on another test circuit. For a second test, the six
batteries of Example 3 were aged for another six months before
being set up in series on yet another test circuit.
[0044] For the tests, the batteries were repeatedly discharged and
charged using standard procedures as established by Battery Council
International. In particular, the batteries were discharged at a
constant 75 amps down to a cut-off voltage of 1.75 V per cell. For
each circuit, the total discharged capacity for each discharge
cycle was determined in Ampere-hours. Once the batteries of a
circuit were discharged, the circuit was rested for 30 minutes
before recharging. After the rest step, the batteries were
recharged using a three-step I-E-I charge profile up to 110% of the
capacity discharged on the immediately preceding discharge cycle.
In this 3-step charge profile, the first step employs a constant
start current in which charge current to the batteries is
maintained at a constant value (in this case 17.7 A) during the
initial charge stage until the battery voltage per cell reaches a
specified level (in this case 2.35 VPC). In the second step, the
battery voltage is maintained at a steady voltage while being
charged with decreasing current. In the third step, a lower
constant current is delivered to the batteries (in this case 4.5
A). Such a charge profile is abbreviated in this specification as
"IEI 7.7 A-2.35VPC-4.5 A-110%." Once recharged, the battery circuit
was rested for two hours before being discharged. These steps were
repeated until the batteries failed to deliver 50% of the
manufacturer's rated capacity on a discharge cycle. Defective
batteries may have been removed from the string during cycle life
testing, not exceeding removal of 50% of the total batteries in the
circuit. Also, no replacement batteries were added during
testing.
[0045] The results of the tests are shown in FIG. 2, which graphs
capacity per cycle against the number of cycles, where the capacity
per cycle is corrected for temperature using standardization
procedures set forth by Battery Council International. FIG. 2 shows
the effect of additive on 6V golf lead acid batteries. Batteries
with additive show better performance than control batteries. In
addition, as shown in FIG. 2, the batteries that were aged an
additional six months performed significantly better than their
non-aged counterparts. The curve fitting was based on the
polynomial regression function of the Microsoft Excel program.
[0046] As illustrated by FIG. 2, the batteries of the present
invention exhibit consistently higher ampere hour discharge and
sustained peak capacity for longer periods of time. Moreover, the
battery circuit using batteries according to Example 2 exhibited
consistently higher ampere-hour discharge per cycle. The Example 3
batteries have delivered higher performance than the Example 2
batteries. This is due to a longer aging period, which helps
produce more sulfates inside the PAM (positive active material)
matrix and improves utilization of the PAM during cycling. The
total ampere-hour capacity over the life of the test batteries is
summarized in Table 1.
TABLE-US-00001 TABLE 1 Total Accumulated Average Ampere- Test
Cycles Ampere-Hours Hours per cycle Example 2 512 69,763 136
Example 3 515 74,539 145 Comparative 525 62,266 119 Example 2
EXAMPLE 4 AND COMPARATIVE EXAMPLE 3
[0047] For Example 4, the positive plates formed according to
Example 1 were assembled into six production batteries of the type
manufactured and sold by Trojan Battery Corporation as Model J305P
(3-cell, 6-volt, deep discharge lead-acid batteries of a type
commonly used in scrubber & floor machine batteries). For
Comparative Example 3, batteries identical to those of Example 4
were constructed, except that the conventional positive plates of
Comparative Example 1 were used in the assembly.
[0048] The results of the tests are shown in FIG. 3 which graphs
capacity per cycle against the number of cycles, where the capacity
per cycle is corrected for temperature using standardization
procedures set forth by Battery Council International. FIG. 3 shows
the effect of additive on 6V scrubber batteries. Batteries with
additive show better performance than the control batteries. The
curve fitting was based on the polynomial regression function of
the Microsoft Excel program.
[0049] As illustrated by FIG. 3, the batteries of the present
invention exhibit consistently higher ampere hour discharge and
sustained peak capacity for longer periods of time. Moreover, these
test results re-confirm the conclusions gained from FIG. 2 that the
batteries of the present invention show similar effects and
benefits on different models of lead acid battery products. The
total ampere-hour capacity over the life of the test batteries is
summarized in Table 2.
TABLE-US-00002 TABLE 2 Total Accumulated Average Ampere- Test
Cycles Ampere-Hours Hours per cycle Example 4 392 78,695 201
Comparative 315 61,268 194 Example 3
EXAMPLES 5-11 AND COMPARATIVE EXAMPLE 4
[0050] For Examples 5-11, positive active material pastes were
prepared including various additive salts as set forth in Table 3.
For Comparative Example 4, a conventional positive active material
paste was prepared without any additive. The positive active
material pastes were prepared in a lab scale mixer. Each positive
active material paste was made by first mixing 10 lbs of lead oxide
powder and 3.8 grams of polyester fiber in a mixer. To that
mixture, 9.08 grams of additive was added while mixing continued.
Then, water was added to the dry mixture and mixing continued for
one minute. Finally, an aqueous solution of sulfuric acid was added
and mixing continued until a positive active material paste was
formed. The resulting paste was gray in color and had an additive
concentration of about 0.20 wt % on a dry basis.
[0051] The positive active material pastes prepared above were
manually applied to substantially identical positive electrode
grids to form pasted positive plates. The positive electrode grids
were made as described in Example 1, and were used in a 2-volt
single cell jar for cycle life testing. Each positive electrode
grid weighed 144+/-5 grams and was pasted with 278+/-3 grams of
positive active material paste. The resulting positive plates were
then cured by a two-step process in a lab scale curing chamber.
TABLE-US-00003 TABLE 3 Metal (or Metal Oxide) Metal Metal Salt
Amount Pb:Metal (or (or Metal (or Metal (wt % Metal Oxide) Example
Oxide) Oxide) Salt dry basis) Molar Ratio Example 5 Sn SnSO.sub.4
0.20% 500 Example 6 TiO TiOSO.sub.4 0.20% 334 Example 7 Ca
CaSO.sub.4 0.20% 314 Example 8 K K.sub.2SO.sub.4 0.20% 201 Example
9 In In.sub.2(SO.sub.4).sub.3.cndot.xH.sub.2O 0.20% 729 Example 10
Zn ZnSO.sub.4.cndot.7H.sub.2O 0.20% 663 Example 11 Bi
Bi.sub.2(SO.sub.4).sub.3 0.20% 823
[0052] The single cells made for Examples 5-11 and Comparative
Example 4 were tested in the same manner as the Example 2
batteries. The total ampere-hour capacity over the life of the test
batteries is summarized in Table 4.
TABLE-US-00004 TABLE 4 Metal (or Metal Total Accumulated Average
Ampere- Example Oxide) Cycle Ampere-Hours Hours per cycle Example
5* Sn 169 23,101 137 Example 6 TiO 200 23,068 115 Example 7 Ca 200
25,938 130 Example 8 K 200 25,681 128 Example 9 In 200 25,980 130
Example 10 Zn 200 24,667 123 Example 11 Bi 200 24,996 125
Comparative N/A 200 25,630 128 Example 4 *Testing was stopped
prematurely due to equipment failure.
EXAMPLES 12 AND 13 AND COMPARATIVE EXAMPLE 5
[0053] For Examples 12 and 13, positive active material pastes were
prepared including various tin sulfate contents as set forth in
Table 5. The quantities of acid and water needed to be adjusted as
the additive content increased. The density of the positive paste
changed due to the adjustment of acid/water quantity. The densities
of the positive paste for each mix varied from about 4.3 to about
4.7 g/cc. For Comparative Example 5, a conventional positive active
material paste was prepared without any metal additive. The
positive active material pastes prepared as above were manually
applied to substantially identical positive electrode grids to form
pasted positive plates. The positive electrode grids were made as
described in Example 1, and were used in 2-volt single cell jars
for cycle life testing. Each positive electrode grid weighed
144+/-5 grams and was pasted with 278+/-3 grams of positive active
material paste. The resulting positive plates were then cured under
the same conditions as Examples 5-11.
TABLE-US-00005 TABLE 5 Tin Sulfate Amount Pb:Sn Pb:Sn Example (wt %
dry basis) Weight Ratio Molar Ratio Example 12 0.2% 870 498 Example
13 1.0% 173 99 Comparative 0.0% N/A N/A Example 5
[0054] The single cells made for Examples 12 and 13 and Comparative
Example 5 were tested in the same manner as the Example 2
batteries. The total ampere-hour capacity over the life of the test
batteries is summarized in Table 6. The results of the tests are
shown in FIG. 4 which graphs capacity per cycle against the number
of cycles, where the capacity per cycle is corrected for
temperature as mentioned above. As illustrated by FIG. 4, the
batteries of the present invention exhibit consistently higher
ampere hour discharge energy than conventional batteries.
TABLE-US-00006 TABLE 6 Tin Sulfate Average Amount Total Accumulated
Ampere- Example (wt % dry) Cycle Ampere-Hours Hours per cycle
Example 12* 0.2% 169 23,101 137 Example 13 1.0% 200 29,296 147
Comparative 0.0% 200 25,630 128 Example 5 *Testing was stopped
prematurely due to equipment failure.
[0055] While the present invention has been illustrated and
described with reference to certain exemplary embodiments, those of
ordinary skill in the art would appreciate that various
modifications and changes can be made to the described embodiments
without departing from the spirit and scope of the present
invention, as defined in the following claims.
* * * * *