Patent Application
20100062347
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1. Technical Field of the Invention
The preferred embodiment relates generally to a rechargeable zinc cell with a longitudinally-folded separator and method of use thereof, and more specifically a rechargeable zinc cell with a longitudinally-folded separator comprising a zinc negative electrode, a positive electrode, an electrolyte and a separator, wherein the separator comprises at least two wicking layers with a microporous layer in the center thereof, and wherein the separator is folded longitudinally to wrap around the zinc negative electrode, thereby improving cell cycle life and inhibiting dendrite growth.
2. Description of Related Art
The increase of environmental regulations, surging oil prices and the proliferation of electronic devices have given rise to new growing markets for battery and/or energy technologies. Batteries are well known in the art for supplying portable energy to electrical circuits and comprise four principal components: a negative electrode, a positive electrode, an electrolyte and a separator. The negative electrode provides electrons to an external electrical circuit (anodic reaction) during the discharge process. The positive electrode accepts electrons from the external circuit (cathodic reaction) during the discharge process. The separator keeps the negative electrode and the positive electrode insulated electrically, while the electrolyte disposed within the separator provides ionic conduction.
Currently, there exists a large variety of battery technologies, one of which is the nickel-cadmium battery. The nickel-cadmium battery comprises a nickel positive electrode that comprises primarily nickel hydroxide and a cadmium negative electrode that comprises primarily cadmium metal. During the discharge process, hydroxyl ions (OH−) in the electrolyte combine with the metallic cadmium (Cd) to form Cd(OH)2 releasing the electrons to the external circuit via the negative electrode (anode, during discharge). Also during the discharge process, the positive electrode, or cathode, accepts electrons from the external circuit, thereby converting the charged nickel oxyhydroxide (NiOOH) to nickel hydroxide (Ni(OH)2). There are several benefits associated with the nickel-cadmium battery. Such benefits include extended operating life, long storage life, and operation at both high and low temperatures. However, the nickel-cadmium battery also has disadvantages. For example, nickel-cadmium batteries cannot keep up with increasing market performance requirements and they are not environmental friendly. Accordingly, there is a need for batteries that have the advantageous properties of nickel-cadmium batteries, but are also environmentally benign.
Another battery technology is the nickel-zinc technology, which has the potential to fulfill various application needs. Nickel-zinc batteries have superior electrochemical properties, which have long been acknowledged and are well documented. For example, in comparison to nickel-cadmium or nickel-metal hydride cells, nickel-zinc cells have higher open circuit voltages (i.e., 1.7 volts vs. 1.4 volts) and potentially can provide significantly higher energy density.
While there are several benefits associated with nickel-zinc batteries, there are also disadvantages. For example, zinc dendrite growth is a common problem in nickel-zinc batteries and is a common source of rechargeable battery failure. It is a phenomenon that occurs during battery recharging, whereby active material, namely, zinc hydroxide Zn(OH)2, is reduced from its oxidized state and deposited onto a substrate (e.g., electrode being charged) as zinc metal (Zn) Depending on the charging conditions, the metal may be deposited in a dendrite form, and has the potential to penetrate the separator and short the cell by providing an electrical bridge between the negative and positive electrodes. Accordingly, there is a need for zinc batteries that overcome dendrite growth.
Further, zinc electrodes may also be subject to shape change or densification, wherein, through cycling, more active material is deposited typically toward the center of the electrode resulting in a generally convex shape (although on occasions increased zinc deposition has been noted at the corners of zinc electrodes). This results in different current density requirements on different areas of the electrode, reducing efficiency of utilization of active material.
Several attempts have been made to reduce dendrite formation in nickel-zinc batteries. For example, Adler et al. (U.S. Pat. Nos. 5,453,336 and 5,302,475) teach utilizing alkali metal-based fluoride salts and carbonate salts to reduce the shape change of the zinc electrode during recharging. Spaziante et al. (U.S. Pat. No. 4,181,777) disclose an additive such as polysaccharide or sorbitol to prevent zinc dendrite formation during electrical charge of the battery. Berchielli et al. (U.S. Pat. No. 4,041,221) disclose inorganic titanate as an additive in the anode. Rampel (U.S. Pat. No. 3,954,501) discloses enhanced gas recombination, capacity and cycle life in a rechargeable electrolytic cell with the inclusion of a fibrous interconnecting network of an unsintered, uncoalesced, hydrophobic linear fluorocarbon polymer. Collien et al. (U.S. Pat. No. 6,087,030) disclose a zinc anode, including a reaction rate-enabling metal compound such as indium, gallium, germanium, tin, along with aqueous potassium hydroxide. Larsen et al. (U.S. Pat. No. 4,857,424) disclose an alkaline zinc electrochemical cell including a zinc corrosion and hydrogen gas inhibiting quantity of a siliconated, film-forming organic wetting agent. Charkey (U.S. Pat. No. 4,022,953) disclose a zinc electrode structure including cadmium, such as metallic cadmium or a cadmium compound electrochemically convertible to metallic cadmium dispersed in the zinc material, the metallic cadmium having a certain particle dimension and surface area. Charkey et al. (U.S. Pat. No. 5,863,676) disclose use of a calcium-zincate constituent in a zinc electrode. Charkey (U.S. Pat. No. 5,556,720) disclose use of barium hydroxide (Ba(OH)2)or strontium hydroxide (Sr(OH)2) material and a conductive matrix including a metallic oxide material which is more electropositive than zinc, such as lead oxide (PbO), bismuth oxide (Bi2O3), cadmium oxide (CdO), gallium oxide (Ga2O3), or thallium oxide (Tl2O3). Charkey (U.S. Pat. No. 4,415,636) disclose cadmium particulate matter dispersed in the zinc material of the anode. Charkey (U.S. Pat. No. 4,332,871) disclose a zinc electrode including a cement additive distributed therein. Schrenk et al. (U.S. Pat. No. 4,791,036) disclose use of an anode current collector made from a silicon bronze alloy for minimizing gassing during overcharging. Lastly, Gibbard et al. (U.S. Pat. No. 4,552,821) disclose a sealed, rechargeable nickel-zinc cell in the form of a wound roll, such that the cell is under compression.
While there are several different approaches in preventing dendrite formation in nickel-zinc batteries, as referenced above, none of the references incorporate a wrapped anode process for jelly-roll structured nickel-zinc batteries. Generally, in battery manufacturing processes, especially in cylindrical batteries, it is unavoidable that some active material drops from cathode or anode or both. When the dropped active material touches the cell can (or in the event that any cathode material touches the anode or any anode material touches the cathode) shorting will occur and gas will be released. Therefore, the battery cell may become useless or even dangerous (if heating occurs from the electrical short or if the cell loses its physical integrity due to excess pressure within the cell). Additionally, separators are often not wrapped around electrodes, merely being disposed between the positive and negative electrodes, wherein the electrodes may contact the cell can.
During charging, the exposed portion of the anode has more tendency to form zinc dendrites. I.e., dendrites grow around the open anode and easily touch the adjacent cathode or even the cell can. If the positive electrode also touches the can a short will occur. Accordingly, there is a need for an effective way to prevent dendrite growth from the exposed portion of the anode.
Therefore, it is readily apparent that there is a need for cells that provide high electrical energy density and that prevents the growth of zinc dendrites and/or shape change, while still maintaining high power density capability and environmental friendliness.
Briefly described, in a preferred embodiment, the preferred embodiment overcomes the above-mentioned disadvantages and meets the recognized need for such an apparatus by providing a rechargeable zinc cell with a longitudinally-folded separator comprising a zinc negative electrode, a positive electrode, an electrolyte and a separator, wherein the separator is folded longitudinally to wrap under the zinc negative electrode around an edge thereof, and wherein the zinc negative electrode, the positive electrode, the electrolyte and the separator are wound into a jelly roll and contained in a can having a positive terminal connected to the positive electrode and a negative terminal connected to the negative electrode.
According to its major aspects and broadly stated, the preferred embodiment in its preferred form is a rechargeable zinc cell with a longitudinally-folded separator comprising a zinc negative electrode, a positive electrode, an electrolyte and a separator disposed between the electrodes, wherein the separator is folded longitudinally around one edge of the zinc negative electrode. The electrolyte comprises KOH in a range between approximately 1% to approximately 55%, LiOH in a concentration between approximately 0.1% to approximately 30%, KAcet, CsCO3, In2(SO4)3 and approximately 150 ppm of K2SnO3. Alternatively, the electrolyte comprises KOH in a range between approximately 1% to approximately 55%, approximately 15% of CsAcet and 150 ppm of In2(SO4)3.
The separator comprises at least two wicking layers with a microporous layer or other dendrite-blocking separator layer disposed therebetween. The wicking layers comprise a non-woven polypropylene material or a non-woven nylon. The separator is folded over the long dimension of the zinc negative electrode. As such, the zinc negative electrode is completely covered by the separator, such that both sides of the zinc negative electrode are in contact with at least one of the wicking layers of the separator. The positive electrode is disposed on top of the separator and is in contact with one of the wicking layers. The zinc negative electrode, the positive electrode, the electrolyte and the separator are then rolled together to form a jelly roll such that the portion of the separator wrapped under the long edge of the electrode is at the bottom of the jelly roll. The jelly roll comprises a negative terminal in electrical communication with the zinc negative electrode and a positive terminal in electrical communication with the positive electrode. The jelly roll is contained in a can having a cover insulated from the can by a seal ring. The negative terminal is in electrical communication with the cover and the positive terminal is in electrical communication with the can. The separator is folded along the long edge of the zinc negative electrode to insulate the zinc negative electrode from the can.
Additionally, the preferred embodiment is a method of constructing a rechargeable zinc cell with a longitudinally-folded separator. The method comprises the steps of obtaining a zinc negative electrode, a positive electrode, an electrolyte and a separator having two wicking layers with a microporous layer or other dendrite blocking layer disposed therebetween. The zinc negative electrode is placed in contact with one of the wicking layers of the separator, such that a first side of the zinc negative electrode is fully covered by the separator. The separator is then longitudinally folded around along the long edge of the zinc negative electrode. A positive electrode is then placed on the separator/negative electrode stack. The negative electrode, the positive electrode and the separator are then wound into a jelly roll structure. The jelly roll structure comprises a negative terminal in electrical communication with the zinc negative a positive terminal in electrical communication with the positive electrode. The jelly roll structure is then placed into a cell housing comprising a can, a seal and a cover. Additionally, the preferred embodiment is a rechargeable cell further containing KAcet.
More specifically, the prior art teaches a configuration comprising a generally rectangular zinc negative electrode and a separator. The zinc negative electrode comprises a first end, a second end, a first edge, a second edge, a front surface, a back surface and a tab. The separator is generally rectangular in shape and comprises a top half, a bottom half, a first edge, a second edge, a fold line, a first end and a second end. The separator further comprises a wicking layer. The zinc negative electrode is disposed on the bottom half of the separator, wherein the second end of the zinc negative electrode is proximate the second end of the separator. The back surface of the zinc negative electrode is in contact with the wicking layer of the separator. The prior art embodiment teaches folding the separator along the fold line with the first end disposed, after folding, proximate the second end of the separator, such that the separator extends beyond the outer dimensions of the zinc negative electrode, and the tab extends beyond the separator.
It will be noted that in the prior art configuration the first edge and the second edge of the zinc negative electrode are open to contact externally because the top half and the bottom half of the separator merely cover, but do not seal, the first and second edge of the zinc negative electrode. Accordingly, the first and second edges of the zinc negative electrode may move beyond the first and second edges of the separator and thereby make contact with an external container once the electrodes are wound and placed in a cell. Further, loose material from the zinc negative electrode may migrate beyond the first and second edges of the separator and provide electrical communication between the zinc negative electrode and any container therearound.
It will be recognized by those skilled in the art that the zinc negative electrode may be made by techniques known in the art. For example, a powdered mixture of the desired materials and a binder may be rolled onto a suitable current collector, such as, for exemplary purposes only, a copper screen. Prior techniques have utilized calcium hydroxide as a further component of the negative electrode mixture. However, it is not necessary to include calcium hydroxide in the preferred embodiment and it is preferred that the zinc negative electrode is essentially free of calcium hydroxide. Additionally, it should be recognized by those skilled in the art that a variety of housing materials for fabricating zinc electrode is known, wherein typically, the binder material utilized is inert in the cell environment and is incorporated in an amount sufficient to hold the mixture together.
The preferred embodiment is a configuration comprising a zinc negative electrode and a separator. The zinc negative electrode comprises a first end, a second end, a first edge, a second edge, a front surface, a back surface and a tab. The separator comprises two wicking layers with a microporous layer or other dendrite blocking separator layer disposed therebetween. The separator also comprises a longitudinal fold line, a first edge, a second edge, a first end, a second end, a front surface and a back surface. The longitudinal fold line is approximately parallel and disposed between the first edge and the second edge of the separator. The zinc negative electrode is disposed on the front surface of the separator between the longitudinal fold line and the second edge of the separator. The first edge of the zinc negative electrode is disposed approximately parallel to the longitudinal fold line of the separator. The separator is folded along the longitudinal folding line such that the first edge of the separator is disposed proximate the second edge of the separator. Thus, the front surface and the back surface of the zinc negative electrode are in contact with one of the wicking layers. Accordingly, the separator extends past the first end, the second end, the first edge, the second edge of the negative electrode, and the tab of the zinc negative electrode extends beyond the first edge and the second edge of the separator.
It will be noted that, contrary to the prior art embodiment discussed herein above, the preferred embodiment results in the first edge of the zinc negative electrode being completely surrounded by the separator. As such, the first edge can no longer contact a container once the electrodes and separator are wound and placed in a cell. Further, any material that sloughs off the first edge will be retained in the longitudinal fold line and can no longer provide electrical communication between the zinc negative electrode and any container therearound.
The material utilized for the separator should comprise a membrane having relatively fine, uniformly-sized pore structure to preferably facilitate wicking and electrolyte permeation therethrough, while reducing or eliminating dendrite penetration therethrough. The material employed should possess sufficient flexibility and strength characteristics to endure adequately any shape change and/or electrode expansion, and for the preferred embodiment a composite membrane is utilized comprising two the wicking layers on either side of a microporous layer. As one illustrative example, without limitation, the microporous layer may comprise commercially available CELGARD polypropylene film, while the wicking layers could comprise non-woven nylon or polypropylene material.
The preferred embodiment further comprises a separator membrane formed from at least two polymers impregnated into a non-woven substrate, wherein the at least two polymers form an interpenetrating matrix network. The polymers comprise, for exemplary purposes only, PVA or fluoro-substituted PVA as a first polymer, and a water soluble, KOH insoluble, film-forming polymer as a second polymer, wherein the second polymer comprises, for exemplary purposes only, polymeric acids sulphates, phosphates and their cationic salts. An alternate embodiment could further include nanosized particles that are insoluble in potassium hydroxide.
As a further illustrative example, without limitation, it is satisfactory to utilize an aqueous potassium hydroxide solution containing approximately 10% to 30% by weight of potassium hydroxide (KOH), optionally approximately 1% by weight of lithium hydroxide (LiOH), approximately 5% by weight of potassium acetate (KAcet), approximately 5% by weight of cesium carbonate CsCO3, between 8% and 15% by weight of cesium acetate (CsAcet), approximately 150 ppm of potassium stannate (K2SnO3)and approximately between 150 and 200 ppm of indium sulphate In2(SO4)3. It is desirable to utilize initially an electrolyte saturated with zinc oxide (ZnO) so as to suppress initial dissolution of zinc oxide from the electrode into the electrolyte. As is known in the sealed electrochemical cell art, the amount of electrolyte utilized should be restricted sufficiently so that an effective oxygen recombination reaction will be provided at the zinc electrode. In the preferred embodiment, the necessary electrolyte can be added to the open space in the core of the jelly roll wound cell element prior to the sealing of the cell.
A positive electrode comprises a first end, a second end, a first edge, a bottom edge, a front surface, a back surface and a tab. The positive electrode is disposed onto the construction, wherein the construction comprises the configuration of the separator longitudinally folded around the zinc negative electrode. The first edge of the positive electrode is approximately parallel the longitudinal folding line. The tab of positive electrode extends beyond the longitudinal fold line of the separator. The tab is disposed near the longitudinal fold line, such that the tab of the positive electrode and the tab of the zinc negative electrode are on opposite sides of the construct. The back surface of the positive electrode is in contact with the wicking layer of the separator, such that the construct is wound into a jelly roll, such that the back surface of the positive electrode is in contact with the wicking layer of the positive electrode, and nearly all of the front surface of the positive electrode is in contact with the wicking layer of the positive electrode. It should be recognized that the preferred embodiment comprises the zinc negative electrode and the positive electrode being in contact with the wicking layers serve to impart longer cell life cycle, particularly at high discharge rates of about 2 C or higher.
The negative electrode, the separator and the positive electrode are rolled together to form a jelly roll. The jelly roll is contained in housing, thereby forming a cell. The jelly roll comprises the zinc negative electrode, the positive electrode, the separator, a top and a bottom. The top comprises the tab of zinc negative electrode and the bottom comprises the tab of positive electrode. The bottom is formed along the longitudinal folding line, and the separator comprises the wicking layers and the microporous layer. The housing comprises a can, a seal and a cover. The cover comprises a negative terminal and the can comprises a positive terminal. The bottom of the jelly roll is disposed proximate the bottom of the can, such that the positive electrode tab is connected to the positive terminal, such as via, for exemplary purposes only, welding. Similarly, the top of the jelly roll is disposed proximate the cover, and the tab is connected to the cover forming a negative terminal, such as via, for exemplary purposes only, welding. It should be recognized by those skilled in the art that the preferred embodiment comprises the negative terminal disposed proximate the top of the housing to prevent the zinc negative electrode from contacting the housing. It should also be recognized in the art that the cell of the preferred embodiment may be utilized in either prismatic or cylindrical design, as desired for the particular application. Likewise, capacity of the cell may vary within wide limits, the size being dictated by the requirements of the particular application. As one example, a cylindrical sub-C size cell may suitably have a capacity of, for example, 1.5 Ampere-hours.
Additionally, the preferred embodiment allows extended cycle life of cells. As depicted, the discharge capacity of the cells of this invention is maintained substantially higher than the discharge capacity of a conventional nickel-zinc cell up to one hundred cycles or more.
Lastly, the zinc negative electrode tab is connected to the cover to reduce metal surface area in electrical communication with the zinc electrode, thereby reducing generation of hydrogen gas, which does not readily recombine within the cell. If hydrogen gas is generated, having no place to recombine, pressure within the cell will increase, leading to possibly hazardous consequences. Accordingly, in the preferred embodiment, the zinc negative electrode is in electrical communication with the cover and the positive electrode is in electrical communication with the can. Oxygen gas generated at the positive electron near end of charge and in overcharge readily combines at the zinc electrode under optimal conditions, thereby reducing the tendency for excess pressure due to oxygen.
Accordingly, a feature and advantage of the preferred embodiment is its ability to effectively prevent dendrite growth.
Another feature and advantage of the preferred embodiment is its ability to provide improved electrical performance and life cycle.
Another feature and advantage of the preferred embodiment is its ability to be simply constructed and economically manufactured.
Still another feature and advantage of the preferred embodiment is its ability to operate at high current levels.
Yet another feature and advantage of the preferred embodiment is its ability to stand for prolonged periods of time in a discharged condition without undue internal pressure build-up.
Yet still another feature and advantage of the preferred embodiment is its long life cycle.
A further feature and advantage of the preferred embodiment is its ability to provide higher discharge capacity than conventional nickel-zinc cells up to one hundred cycles or more.
Yet another feature and advantage of the preferred embodiment is its inclusion of wicking layers on the separator adjacent both positive and negative electrode layers, thereby increasing cell life cycle and cell capacity.
These and other features and advantages of the preferred embodiment will become more apparent to one skilled in the art from the following description and claims when read in light of the accompanying drawings.
The preferred embodiment will be better understood by reading the Detailed Description of the Preferred Embodiments with reference to the accompanying drawing figures, in which like reference numerals denote similar structure and refer to like elements throughout, and in which:
In describing the preferred and selected alternate embodiments of the preferred embodiment, as illustrated in
Referring to
It will be noted that in the prior art configuration of
It will be recognized by those skilled in the art that zinc negative electrode 30 may be made by techniques known in the art. For example, without limitation, a powdered mixture of the desired materials, typically zinc metal and zinc oxide, and a binder may be rolled onto a suitable current collector, such as, for exemplary purposes only, a copper screen. Prior techniques have utilized calcium hydroxide as a further component of the negative electrode mixture. However, it is not necessary to include calcium hydroxide in the preferred embodiment and it is preferred that zinc negative electrode 30 is essentially free of calcium hydroxide. Additionally, it should be recognized by those skilled in the art that a variety of materials for fabricating zinc electrode is known, wherein typically, the binder material utilized is inert in the cell environment and is incorporated in an amount sufficient to hold the mixture together.
Referring now to
Zinc negative electrode 30 is disposed on front surface 55 of separator 20 between longitudinal fold line 80 and second edge 52 of separator 20, wherein first edge 33 of zinc negative electrode 30 is disposed approximately parallel to and proximate longitudinal fold line 80 of separator 20. Separator 20 is folded along longitudinal folding line 80 such that first edge 51 of separator 20 is disposed proximate second edge 52 of separator 20, wherein both front surface 37 and back surface 38 of zinc negative electrode 20 are thus in contact with wicking layer 22a. As best shown in
It will be noted that, contrary to the prior art embodiment discussed herein above, the preferred embodiment results in first edge 33 of zinc negative electrode 30 being completely surrounded by separator 20, wherein first edge 33 can no longer contact a container once the electrodes and separator are wound and placed in a cell. Further, any material that sloughs off first edge 33 of zinc negative electrode 30 will be retained in longitudinal fold line 80 and can no longer provide electrical communication between zinc negative electrode 30 and any container therearound.
The material utilized for separator 20 comprises a membrane having relatively fine, uniformly-sized pore structure to preferably facilitate wicking and electrolyte permeation therethrough, while reducing or eliminating dendrite penetration therethrough. The material employed should possess sufficient flexibility and strength characteristics to endure adequately any shape change and/or electrode expansion, and for the preferred embodiment, a composite membrane is utilized comprising two wicking layers 22a, 22b on either side of microporous layer 21. As one illustrative example, without limitation, microporous layer 21 may comprise commercially available CELGARD polypropylene film, while wicking layers 22a, 22b could comprise non-woven nylon or polypropylene material.
As a further illustrative example, without limitation, it is satisfactory to utilize an aqueous potassium hydroxide solution containing approximately 10% to 30% by weight of potassium hydroxide (KOH), optionally approximately 1% by weight of lithium hydroxide (LiOH), approximately 5% by weight of potassium acetate (KAcet), approximately 5% by weight of cesium carbonate CsCO3, between 8% and 15% by weight of cesium acetate (CsAcet), approximately 150 ppm of potassium stannate (K2SnO3) and approximately between 150 and 200 ppm of indium sulphate In2(SO4)3. It is desirable to utilize initially an electrolyte saturated with zinc oxide (ZnO) so as to suppress initial dissolution of zinc oxide from the electrode into the electrolyte. As is known in the sealed electrochemical cell art, the amount of electrolyte utilized should be restricted sufficiently so that an effective oxygen recombination reaction will be provided at the zinc electrode. In the preferred embodiment, the necessary electrolyte can be added to the open space in the core of the jelly roll wound cell element prior to the sealing of the cell.
Referring now to
Referring now to
As best shown in
Zinc negative electrode 30 is in electrical communication with cover 72 to reduce generation of hydrogen gas, which does not readily combine within the cell, by minimizing the metal surface area which is in electrical communication with zinc negative electrode 30. (If hydrogen gas is generated, having no place to recombine, pressure within the cell will increase, leading to possibly hazardous consequences. Accordingly, the preferred embodiment is in electrical communication to the cover of the positive electrode of the can. Oxygen gas readily combines at the zinc electrode under optimal conditions, thereby reducing the tendency for excess pressure due to oxygen.)
In an alternative embodiment cover 70 could comprise triclad material of nickel on the outside, steel in the middle and copper on the inside of cover 70, wherein the copper can be plated with tin, zinc, indium or combinations thereof, to reduce the microcell effect, which could cause the gassing of zinc electrode 30.
In another alternate embodiment, cover 70 could be coated with polymer resin, including but not limited to, epoxy resin, to further reduce the heterogeneous metal contact in the presence of electrolyte and thereby reduce hydrogen gassing.
The foregoing description and drawings comprise illustrative embodiments of the preferred embodiment. Having thus described exemplary embodiments of the preferred embodiment, it should be noted by those skilled in the art that the within disclosures are exemplary only, and that various other alternatives, adaptations, and modifications may be made within the scope of the preferred embodiment. Merely listing or numbering the steps of a method in a certain order does not constitute any limitation on the order of the steps of that method. Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Accordingly, the preferred embodiment is not limited to the specific embodiments illustrated herein, but is limited only by the following claims.
This application relates to a non-provisional U.S. Patent Application entitled “Non-Toxic Alkaline Electrolyte with Additives for Rechargeable Zinc Cells” by inventor Lin-Feng Li, and to a non-provisional U.S. Patent Application entitled “Polymer Membrane Utilized as a Separator in Rechargeable Zinc Cells” by inventor Lin-Feng Li, both filed concurrently, which applications are incorporated herein in their entirety by reference.
