U.S. patent application number 13/901157 was filed with the patent office on 2013-09-26 for lead-zinc battery.
The applicant listed for this patent is John E. STAUFFER. Invention is credited to John E. STAUFFER.
Application Number | 20130252083 13/901157 |
Document ID | / |
Family ID | 49212127 |
Filed Date | 2013-09-26 |
United States Patent
Application |
20130252083 |
Kind Code |
A1 |
STAUFFER; John E. |
September 26, 2013 |
LEAD-ZINC BATTERY
Abstract
A rechargeable battery is provided such that the positive
electrode comprises lead, the negative electrode zinc, and the
electrolyte is an aqueous solution of an alkali metal bisulfate.
Upon discharge, lead dioxide is reduced to lead sulfate, zinc is
oxidized to zinc oxide, and the electrolyte is converted to an
alkali metal hydroxide. The reactions are reversed when the battery
is charged.
Inventors: |
STAUFFER; John E.;
(Greenwich, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STAUFFER; John E. |
Greenwich |
CT |
US |
|
|
Family ID: |
49212127 |
Appl. No.: |
13/901157 |
Filed: |
May 23, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13649602 |
Oct 11, 2012 |
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13901157 |
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12608201 |
Oct 29, 2009 |
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13649602 |
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11249223 |
Oct 13, 2005 |
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12608201 |
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10756015 |
Jan 13, 2004 |
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11249223 |
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Current U.S.
Class: |
429/188 |
Current CPC
Class: |
H01M 4/38 20130101; H01M
10/26 20130101; H01M 10/36 20130101; H01M 2300/0002 20130101; Y02E
60/10 20130101; H01M 10/44 20130101; H01M 10/06 20130101; H01M
8/186 20130101; Y02E 60/50 20130101; H01M 10/22 20130101; H01M
4/244 20130101 |
Class at
Publication: |
429/188 |
International
Class: |
H01M 10/22 20060101
H01M010/22 |
Claims
1. A storage battery comprising: a positive electrode of lead
dioxide that upon discharge is reduced to divalent lead sulfate; a
negative electrode of zinc that upon discharge is oxidized to zinc
oxide; and an electrolyte comprising an aqueous solution of an
alkali metal bisulfate that upon discharge is converted to an
alkali metal hydroxide.
2. A storage battery as defined in claim 1 wherein the electrolyte
further includes a buffering agent selected from the group
consisting of borates, silicates and phosphates.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 13/649,602 filed on Oct. 11, 2012, which is a
continuation-in-part of U.S. application Ser. No. 12/608,201 filed
on Oct. 29, 2009 currently pending, which is a continuation-in-part
of U.S. application Ser. No. 11/249,223 filed on Oct. 13, 2005 and
abandoned, which in turn is a continuation of U.S. application Ser.
No. 10/756,015 filed on Jan. 13, 2004 and abandoned. In addition,
this application is a continuation-in-part of U.S. patent
application Ser. No. 11/167,535 filed on Jun. 27, 2005, now U.S.
Pat. No. 7,947,391, which is a continuation-in-part of U.S. patent
application Ser. No. 10/756,015 filed on Jan. 13, 2004 and
abandoned.
FIELD OF THE INVENTION
[0002] The present invention relates to a novel type of storage
battery which is distinguished by its unique electrochemistry. The
positive electrode comprises, in the charged state, lead dioxide
and the negative electrode highly pure zinc. The electrolyte
consists of an aqueous solution of an alkali metal bisulfate salt.
Various buffering agents, including borates, silicates, and
phosphates, may be added to the electrolyte. Upon discharge the
lead dioxide is reduced to a divalent lead compound and zinc is
oxidized to zinc oxide, and the electrolyte is converted to an
alkali metal hydroxide.
BACKGROUND OF THE INVENTION
[0003] The most common storage battery, found in almost every
vehicle, is the lead-acid battery. This battery comprises a lead
dioxide positive electrode, a lead metal negative electrode, and
sulfuric acid for the electrolyte. Its chief advantage is low cost.
Nevertheless, it has limited energy density and the electrolyte is
extremely corrosive. Furthermore, sufficient acid is required to
react with the electrodes during discharge. Maintenance-free types
avoid the loss of evolved gases, as disclosed in U.S. Pat. No.
3,862,861, but their cycle-life is still restricted.
[0004] The search for alternatives to the lead-acid battery has
been ongoing. As far back as 1934, Drumm disclosed the nickel
oxide-zinc battery and the silver oxide-zinc battery. (U.S. Pat.
No. 1,955,115) Both of these batteries employ zinc as the negative
electrode and caustic potash as the electrolyte. Nickel oxide or
silver oxide serves as the positive electrode. These batteries have
improved energy densities and for many uses are a good
compromise.
[0005] The ideal storage battery would combine the best features of
existing batteries with none of the drawbacks. The need for such a
battery is apparent for backup power systems and in mobile
applications. Therefore, it is an object of the present invention
to provide an improved storage battery, one that is both economical
and highly efficient. These and other objects, features, and
advantages of the invention will be recognized from the following
description and the accompanying figure.
SUMMARY OF THE DISCLOSURE
[0006] A storage battery is fabricated from a positive electrode of
lead and a negative electrode of highly pure zinc. During charging,
some lead is converted to lead dioxide. Upon discharge, lead
dioxide is reduced to a divalent lead compound, more particularly,
lead sulfate. Zinc is oxidized to zinc oxide. These reactions are
reversible such that the battery fulfills both functions of a
secondary battery: supplying electricity on demand and storing or
accumulating surplus electricity.
[0007] The electrolyte of the cell is an aqueous solution of a salt
selected from the group of alkali metal bisulfates. The alkali
metals include lithium, sodium, potassium, rubidium, and cesium.
Any combination of these metals may be used. Upon discharge, the
electrolyte is converted to an alkali metal hydroxide.
[0008] Certain additives have been found to be effective buffers in
the electrolyte. These additives include borates, silicates, and
phosphates.
[0009] The electrodes of a practical embodiment of the invention
may be configured as sheets, fibers, or particles, thereby to
maximize the electrode surface area. Interspersed particles of a
carbonaceous material may be used to improve the electrical
conductivity. A gelling agent may be added to immobilize the
electrolyte. As required, a separator may be employed between the
positive and negative electrodes to prevent a short circuit.
BRIEF DESCRIPTION OF THE DRAWING
[0010] FIG. 1 is a rendering of a prototype of a lead-zinc battery
according to the present invention, illustrating the principal
components of the cell.
WRITTEN DESCRIPTION
[0011] The chemistry of the lead-zinc battery is important in order
to gain an understanding of its operation. A positive electrode
comprises lead dioxide, which is reduced to divalent lead sulfate
during discharge. The negative electrode comprises zinc, which is
oxidized to zinc oxide when the cell is discharged. The electrolyte
is an aqueous solution of an alkali metal bisulfate. In the special
case where the alkali metal is sodium, the electrode reactions
during discharge can be represented by the following equations.
[0012] Positive electrode:
[0012]
PbO.sub.2+NaHSO.sub.4+H.sub.2O+2e.sup.-.fwdarw.PbSO.sub.4+NaOH+2O-
H.sup.- (1) [0013] Negative electrode:
[0013] Zn+2OH.sup.-.fwdarw.ZnO+H.sub.2O+2e.sup.- (2) [0014] When
these equations are combined, the overall reaction for the cell is
obtained as follows:
[0014] PbO.sub.2+NaHSO.sub.4+Zn.fwdarw.PbSO.sub.4+ZnO+NaOH (3)
[0015] During recharging of the cell, the reactions are reversed.
Thus, lead sulfate is oxidized to lead dioxide and zinc oxide is
reduced to zinc metal. The emf necessary for charging is supplied
by an external power source. The discharge-recharge cycle can be
repeated endlessly, thus fulfilling the function of a storage
battery.
[0016] A particularly difficult challenge in designing new
batteries is identifying electrode materials that will undergo
electrochemical reactions and still withstand corrosion by the
electrolyte. Although theory is helpful in this respect, empirical
data are required to prove the effectiveness of materials--both for
the electrodes and the electrolyte. One measure of the relative
performance of a cell is the open-circuit voltage.
[0017] In its choice of electrolyte, the present invention has a
decided advantage over the prior art. Instead of using an
electrolyte comprising a strong alkali like potassium hydroxide or
a strong acid like sulfuric acid, the present invention employs an
aqueous solution of an alkali metal bisulfate salt. Such an
electrolyte is a good ionic conductor but is relatively mild under
operating conditions. It therefore avoids problems of electrode
corrosion that plague existing batteries.
[0018] Notwithstanding the superior performance of the electrolyte
of the present invention, there may be a need for better control
over the pH of the solution. In this case, a buffering agent may be
added to the electrolyte. Such compounds as borates, silicates, and
phosphates can be effective in this application. These salts have
the added benefit of forming insoluble compounds with the lead and
zinc.
[0019] The selection of the alkali metal bisulfate for use in the
electrolyte is of interest. In aqueous solutions, sulfuric acid is
a strong acid but only for the dissociation of one proton. Thus, a
solution of alkali metal bisulfate is acidic but to a lesser
extent. Such a solution contains alkali metal ions and bisulfate
ions. Solutions of alkali metal sulfates are essentially
neutral.
[0020] The electrolyte environment is important for the electrodes.
The positive lead electrode is stable because of the insolubility
of lead sulfate. On the other hand, the relatively high electrode
potential of zinc indicates that that this metal should dissolve in
acids. In fact, that is the case with ordinary zinc that contains
impurities. However, pure zinc resists corrosion because of an
effect known as over-voltage. Thus, the present invention
contemplates the use of high quality zinc in excess of 99.9% for
the negative electrode.
[0021] The selection of the alkali metal bisulfate for use in the
electrolyte is also of interest. Bisulfates of any one of the
alkali metals can be used including lithium, sodium, potassium,
rubidium, and cesium. As one progresses from lithium to cesium in
this series, the electronegativity decreases. This phenomenon will
affect the ionic nature of the salts, and therefore can be expected
to influence the battery's performance.
[0022] Another factor in considering the choice of alkali metal is
the solubility of its bisulfate. For example, the solubility of
potassium bisulfate at 0.degree. C. is 36.3 gm. per 100 ml. water,
whereas the solubility of sodium bisulfate at the same temperature
is 50 gm. Greater solubility has an advantage by aiding the
compactness of the battery.
[0023] The configuration of a lead-zinc cell of the present
invention is not restricted. The distinctive features, however, can
be appreciated from a drawing of a prototype as shown in FIG. 1.
The cutaway perspective shows the electrodes arranged as flat
parallel plates. The lead positive electrodes 1 and the zinc
negative electrodes 2 are kept apart by separators 3. These parts
are immersed in the electrolyte 4, which is contained in casing 5.
This sectional view also shows the electrical leads attached to the
electrodes.
EXAMPLES
[0024] (1) A glass jar 4.5 in. high was used for the cell. A
plastic divider kept the electrodes apart. The positive electrode
was a strip of lead 1.5 in. wide by 5 in. high. The negative
electrode was a sheet of zinc 1.75 in. wide by 3.5 in. long, which
had been recovered from a dry cell. The electrolyte was prepared by
dissolving 48.1 gm. of sodium bisulfate monohydrate, reagent grade
in 200 ml. water. After charging the cell for 8 minutes at 3.0
volts, an open circuit potential of 2.65 volts was observed. The
cell was discharged, producing a current of 100 milliamps through a
flashlight bulb. After repeated cycling, the electrodes showed no
corrosion.
[0025] (2) The same cell as used in example (1) was employed except
the negative electrode comprised a rod of zinc 99.9999 percent
(metals basic) pure. The electrolyte was formulated by dissolving
33.0 gm. of potassium bisulfate, 97% in 200 ml. of water. After
charging the cell for 11 minutes at 3.0 volts, an open circuit
potential of 2.6 volts was observed. At the end of the run, the
zinc rod appeared slightly tarnished but otherwise in excellent
condition. The lead electrode was also in perfect condition.
[0026] While the invention has been described in connection with
certain embodiments, it is to be understood that the invention is
not to be limited to the disclosed embodiments but, on the
contrary, is intended to cover various modifications and equivalent
arrangements included within the spirit and scope of the appended
claims, which scope is to be accorded the broadest interpretation
so as to encompass all such modifications and equivalent structures
as is permitted under the law.
* * * * *