|Publication number||US20060035145 A1|
|Application number||US 11/249,223|
|Publication date||Feb 16, 2006|
|Filing date||Oct 13, 2005|
|Priority date||Jan 13, 2004|
|Also published as||CA2491534A1, EP1555710A1, US7682737, US20050153203, US20070238022|
|Publication number||11249223, 249223, US 2006/0035145 A1, US 2006/035145 A1, US 20060035145 A1, US 20060035145A1, US 2006035145 A1, US 2006035145A1, US-A1-20060035145, US-A1-2006035145, US2006/0035145A1, US2006/035145A1, US20060035145 A1, US20060035145A1, US2006035145 A1, US2006035145A1|
|Original Assignee||Stauffer John E|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (1), Classifications (25)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation of U.S. application Ser. No. 10/756,015 filed under attorney docket no. STF-122-A on Jan. 13, 2004, currently pending.
The present invention relates to a novel type of storage battery which is distinguished by its unique electrochemistry. The positive electrode comprises lead dioxide and the negative electrode zinc. The electrolyte consists of an alkaline aqueous solution of an alkali metal hydroxide or tetramethyl ammonium hydroxide to which various buffers, including carbonates, borates, silicates, and phosphates, may be added. Upon discharge the lead dioxide is reduced to lead oxide and the zinc is oxidized to zinc oxide.
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 a 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.
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.
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 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 accompanying figure.
A storage battery is fabricated from a positive electrode of lead and a negative electrode of zinc. During charging some lead is converted to lead dioxide. Upon discharge lead dioxide is reduced to lead oxide and 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.
The electrolyte of a cell is alkaline. Aqueous solutions of bases provide the alkalinity. These bases include ammonia and the hydroxides of the alkali metals, namely, lithium, sodium, potassium and cesium. In addition, tetramethyl ammonium hydroxide may be employed.
Certain additives have been found to be effective buffers in the electrolyte. These additives include carbonates, borates, silicates and phosphates. They may be introduced by the corresponding acids or their respective salts.
The electrodes of a practical embodiment of the invention may be configured as sheets, fibers, or particles thereby to maximize 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.
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 lead oxide during discharge. The negative electrode comprises zinc which is oxidized to zinc oxide when the cell is discharged. The electrolyte is alkaline such that the solution contains an excess of hydroxyl ions. The electrode reactions during discharge can be represented by the following equations:
In the above reaction, zinc hydroxide may be an intermediate in the formation of zinc oxide. When these equations are combined, the reaction for the cell is:
In the overall reaction, there is no change in the average composition of the electrolyte during discharge although there may be concentration gradients.
During recharging of the cell, the reactions are reversed. Thus, lead oxide 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.
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 its open-circuit voltage.
The use of lead in an alkaline cell may seem questionable because lead in the +2 oxidation state commonly forms plumbous salts containing the positive divalent ion Pb++. However, by the action of hydroxides on plumbous compounds it is possible to form the negative ion HPbO2 − which is soluble in aqueous solutions. Accordingly Pb(OH)2 is regarded as an amphoteric hydroxide. In a similar manner, concentrated solutions of alkali hydroxides act upon the dioxide PbO2 to form plumbate ions, PbO4−4 and PbO3 −2, which are likewise soluble.
In view of these considerations, one goal of the research on new cells was to control the concentration hydroxides in the electrolyte. This result was made possible by employing solutions of sodium carbonate which react as follows:
In place of carbonates, borates can be employed to similar advantage. Boric acid is a weak acid, much more mild than carbonic acid. Thus, its salts tend to hydrolyze in solution. The following equation shows the reaction of potassium meta borate in solution to form potassium hydroxide and potassium tetra borate.
Carbonates and borates are effective not only in controlling the alkalinity of the electrolyte, but they also form insoluble salts with lead and zinc. In this manner the corrosion of such electrodes can be minimized. Not only are carbonates and borates helpful in this regard, but other salts are likewise effective. Both silicates and phosphates form insoluble salts with lead and zinc.
Alkalinity can be provided by compounds of the alkali metals including lithium, sodium, potassium, and cesium. Lithium has certain limitations inasmuch as its carbonate and phosphate are almost insoluble in water. Cesium provides a very strong base but the cost of this material limits its potential applications. While ammonium hydroxide is basic in solution, its volatility restricts its use. Finally, tetramethyl ammonium hydroxide is known to be strongly alkaline, approaching that of sodium hydroxide and potassium hydroxide.
The present invention covers the use of aqueous solutions for the electrolyte. These solutions have the advantage of superior electrical conductivities. Although use of organic solvents including alcohols and glycols is feasible, their performance is inferior.
The configuration of a lead-zinc cell is not restricted. For purposes of testing various combinations of electrodes and electrolytes, a simple cell was assembled from a glass jar and strips of metals separated, as need be, by a polypropylene sheet. A workable battery, however, would necessarily be designed with the maximum surface areas for the electrodes and minimum volume of electrolyte. Such geometric designs as parallel plates, either flat or spirally wound, are appropriate. Alternatively, particles of lead and zinc either alone or interspersed with graphite may be employed. In this manner, the capacity of the cell can be increased and its internal resistance minimized.
To gain a greater appreciation of the present invention,
Applications of a secondary battery as provided by the present invention are almost limitless. The largest application is in vehicles including automobiles powered by new hybrid motors. Other uses include portable electronic devices such as cell phones and laptop computers.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US1955115 *||Sep 6, 1930||Apr 17, 1934||Drumm Battery Company Ltd||Storage battery|
|US3862861 *||May 30, 1972||Apr 7, 1987||Title not available|
|US4830718 *||Apr 17, 1987||May 16, 1989||John Stauffer||Removal of sulfur dioxide (SO2) from waste gases and recovery as sulfuric acid|
|US5344529 *||Jun 15, 1993||Sep 6, 1994||Stauffer John E||Bipolar process for removal of sulfur dioxide from waste gases|
|US5512144 *||Mar 28, 1995||Apr 30, 1996||John E. Stauffer||Pulse method for sulfur dioxide electrolysis|
|US5705050 *||Apr 29, 1996||Jan 6, 1998||Sampson; Richard L.||Electrolytic process and apparatus for the controlled oxidation and reduction of inorganic and organic species in aqueous solutions|
|US6235167 *||Dec 10, 1999||May 22, 2001||John E. Stauffer||Electrolyzer for the production of sodium chlorate|
|US6391186 *||Oct 10, 2000||May 21, 2002||John E. Stauffer||Electrochemical process for removing ions from solution|
|US20030190524 *||May 6, 2003||Oct 9, 2003||Jeffrey Phillips||Positive and negative interactive electrode formulation for a zinc-containing cell having an alkaline electrolyte|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7550231 *||Aug 7, 2007||Jun 23, 2009||Stauffer John E||Tin-zinc secondary battery|
|U.S. Classification||429/206, 429/207, 429/229, 429/225|
|International Classification||H01M10/24, H01M10/22, H01M10/26, H01M4/38, H01M4/56, H01M4/42, H01M10/20|
|Cooperative Classification||Y02T10/7016, H01M10/26, Y02E60/124, Y02E60/126, H01M4/56, H01M10/08, H01M4/244, H01M2300/0014, H01M10/20|
|European Classification||H01M4/56, H01M4/24C, H01M10/08, H01M10/20, H01M10/26|