KR20070116045A - Method of manufacturing nickel zinc batteries - Google Patents

Abstract

Methods of manufacturing a rechargeable power cell are described. Methods include providing a slurry, paste, or dry mixture of negative electrode materials having low toxicity and including dispersants to prevent the agglomeration of particles that may adversely affect the performance of power cells. The methods utilize semi-permeable sheets to separate the electrodes and minimize formation of dendrites; and further provide electrode specific electrolyte to achieve efficient electrochemistry and to further discourage dendritic growth in the cell. The negative electrode materials may be comprised of zinc and zinc compounds. Zinc and zinc compounds are notably less toxic than the cadmium used in nickel cadmium batteries. The described methods may utilize some production techniques employed in existing NiCad production lines. Thus, the methods described will find particular use in an already well-defined and mature manufacturing base.

Description

How to make nickel zinc batteries {METHOD OF MANUFACTURING NICKEL ZINC BATTERIES}

The present invention relates to rechargeable battery technology, and more particularly to the manufacture of nickel zinc rechargeable battery cells.

The advent of portable communication and computing devices that allow for a variety of mobile connections has fueled growth and innovation in the field of rechargeable batteries. The increased capacity and power has enabled the introduction of rechargeable power sources in a variety of applications, including power tool systems. Because power tools typically have large current demands, rechargeable power sources have evolved to necessarily accommodate fast discharge characteristics. It will also be found that the invention will find use in applications other than power tools such as uninterruptible power supplies (UPS), electric vehicles, and high demand consumer electronics, all of which require high carrying capacity and current charging capability. I can understand. Of course, the present invention also applies to relatively low discharge rate applications such as many mainstream consumer electronics applications.

Rechargeable power supplies have a variety of advantages over non-rechargeable sources. For example, the use of non-rechargeable power sources increases the environmental concern for the disposal and improvement of hazardous waste. In view of the proliferation of portable devices, the number of non-rechargeable power sources required to use such devices is decreasing. Rechargeable power sources allow repeated use of battery cells, thus reducing the introduction of hazardous waste into the environment. Rechargeable power supplies also conserve metal and chemical resources that would have been consumed in non-rechargeable power supplies. Finally, the use of rechargeable power sources helps and extends the ongoing conservation efforts needed to accommodate a growing population.

Although there are many advantages of rechargeable power sources, the benefits are not achieved without cost. In particular, materials included in rechargeable power sources often have significant potential risks to the environment. Local recycling agencies, such as the Northeast Recycling Association (NERC), are actively raising the issue of the disposal of rechargeable power sources. In a recent report by NERC, nine out of ten countries prohibit disposal of lead acid batteries, six out of ten prohibit disposal of nickel / cadmium batteries, and four out of ten Disposal of mercury oxide batteries is prohibited (http: www.nerc.org/documents/recyclingrules0901.html). EPA is also one of a number of products that pose a potential risk to the environment if the NiCad batteries commonly used in industrial and household appliances such as cordless phones, power tools and laptop computers are potentially hazardous. And cadmium, both of which can lead to health problems if not disposed of properly. These are all heavy metals, and the entire industry for disposal of NiCad batteries, stating that they can adversely affect the environment during regeneration and disposal (http://epa.nsw.gov.au/media/0403/eprbatteries.htm). Has pushed the practice of and recently closed feedback on the practice.

Because of the hazardous nature of some of the materials commonly used in conventional reusable power supplies, it would be desirable to manufacture rechargeable power supplies that reduce the amount of any potentially hazardous materials. In particular, it would be desirable to find a substitute for a widely used nickel cadmium battery cell.

It has been found that rechargeable nickel zinc cells can provide power-to-weight and power-to-volume ratios exceeding nickel cadmium cells and lithium ion cells at a reasonable cost. However, nickel zinc battery technology has not been widely developed for at least two reasons. First, it was found to have a relatively limited lifetime. That is, certain nickel zinc cells can only charge and discharge during a portion of the life typically achieved by similar nickel cadmium cells. This is due to zinc distribution and dendrite formation. Second, there is no suitable high volume manufacturing process developed for nickel zinc batteries.

Rather than requiring an entirely new manufacturing infrastructure, it is desirable to use existing manufacturing techniques to the extent possible to create an environmentally safer rechargeable power source to borrow existing manufacturing infrastructure.

The present invention provides the advantages described above by using a nickel-cadmium type manufacturing process with some significant modifications that allows the replacement of cadmium negative electrodes with less harmful negative electrodes such as electrodes made of zinc or zinc compounds such as zinc oxide or calcium zincate. To achieve. Various methods of manufacturing cadmium free power cells are described herein. The method uses high volume lines for nickel and zinc electrode production. As part of the manufacturing process, slurries, pastes, or dry powders of negative and positive electrode materials are continuously coated onto the carrier sheet.

The positive electrode material preferably has a composition similar to that used to make nickel electrodes in conventional nickel-cadmium batteries, although there may be some important optimizations for nickel zinc battery systems. The negative electrode preferably uses zinc oxide and zinc metal or alloys thereof as the electrochemically active material. In some embodiments, the negative electrode includes other materials such as bismuth oxide, indium oxide, and / or aluminum oxide. The carrier for the negative electrode (which serves as a current collector) must be electrochemically compatible with the negative electrode material. For example, for zinc electrodes, the carrier material is preferably copper or an alloy of copper in the form of perforated sheets or elongated metals.

In one embodiment using a wet process, it has been found that agglomerates adversely affect the performance of nickel zinc cells, so that the negative electrode material includes a dispersant to minimize the agglomeration of the zinc oxide particles. In an additional embodiment, the method uses multiple sheets of separator material to separate the electrodes and minimize the formation of zinc dendrites. Examples of suitable separator materials include nylon sheets and microporous polyolefin sheets. In addition, the production method of the present invention preferably uses a high conductivity electrolyte that prevents dendritic growth in the zinc electrode.

Importantly, this manufacturing method produces cells with zinc negative electrodes, but uses some manufacturing technique so far specified for other cell types. In particular, existing nickel cadmium production lines can be used with minor modifications to accommodate the methods described herein. In one example, the method includes the following sequence: coating the positive and negative electrode current collector sheets with a paste or slurry of positive and negative electrode materials; Drying and compressing the electrode sheet of the generator, cutting and cleaning the sheet, and forming a “jelly roll” cell assembly from the cut electrode sheet and the interleaved microporous separator sheet. . The method described will in particular be used particularly in all ready, well-defined and developed manufacturing bases.

Additionally, methods and cell designs are disclosed for increasing the efficiency of rechargeable power cells by inverting the polarity of the cells to invert the terminals as compared to conventional manufacturing methods.

Some embodiments may use a dry process in which a relatively dried powder or granular mixture of electrode components is used instead of a slurry or paste. The electrode composition used in this dry process does not need to include dispersants or other additives conventionally provided to improve the concentration of the slurry or paste.

Certain dry processing methods for manufacturing rechargeable power cells include the following sequence of operations: (a) applying a zinc negative electrode material to a first conductive carrier to form a first electrode sheet; (b) applying a substantially dry nickel positive electrode material to the second conductive carrier to form a second electrode sheet; (c) disposing one or more separators between the first electrode sheet and the second electrode sheet to stack the first electrode sheet, the second electrode sheet, and the one or more separator sheets to form a cell assembly; And (d) winding or folding (ie, winding or folding) the cell assembly to form a three dimensional structure having a form factor generally corresponding to the form factor of the rechargeable power cell. Can be. In some embodiments, the negative electrode material may be applied to the first conductive carrier in a substantially dry state. Alternatively, the negative electrode can be applied as a paste or slurry. Rechargeable power cells can have any form factor, including cylindrical or prismatic cells.

One advantage of dry processing is that nickel positive electrode materials can be prepared substantially without dispersants or organic pasting aids. In addition, in some embodiments, the nickel positive electrode material may comprise a binder, such as a fluorinated polyolipine. In some embodiments, the binder is present in the nickel positive electrode material at a level between about 0.1 and 5 weight percent. In certain instances, the positive electrode material includes nickel hydroxide and / or oxyhydroxide, zinc oxide, cobalt oxide, and a binder. In some embodiments, the negative electrode material consists of zinc oxide, zinc or zinc alloy, bismuth oxide, aluminum oxide. In some cases, the negative electrode also includes a dispersant and / or binder that reduces the aggregation of the particles. Preferably, the negative electrode has a low carbonate content; For example, the negative electrode uses zinc oxide having up to about 1% by weight carbonate. The carbonate is also driven off by heating the negative electrode to a temperature of at least about 200 ° C. Such heating can have other beneficial effects.

In some embodiments, the first conductive carrier is made of copper or a copper alloy. In some examples, the first conductive carrier may comprise perforated copper or copper alloy or elongated copper or copper alloy. In some embodiments, the second conductive carrier is made of nickel, such as a sheet of nickel foam.

In some embodiments, the method also includes the following operations: (e) attaching a first inner terminal to the first end of the cell assembly such that only a negative electrode is electrically connected with the first inner electrode; (f) attaching a second internal terminal to the second end of the cell assembly such that only a positive electrode is electrically connected to the second internal terminal; (g) inserting the cell assembly into a retaining vessel; (h) filling the holding vessel containing the cell assembly with an electrolyte; And (i) sealing the holding vessel such that the electrolyte and cell assembly are substantially isolated from the environment. A variation or kind of this method involves attaching a cell cap terminal to the first inner terminal, inserting the cell assembly into the holding vessel and attaching a second inner terminal to the holding vessel, such that the cell is attached to the negative cap. To have it. The method also includes: initially charging a rechargeable power cell according to a defined charging curve; And individually inspecting the rechargeable power cells so that the rechargeable power cells are grouped by charge / discharge similarity.

Another aspect of the invention provides the following operations: (a) applying a zinc negative electrode material to a first conductive carrier to form a first electrode sheet; (b) applying a nickel positive electrode material to the second conductive carrier to form a second electrode sheet; (c) disposing one or more separator sheets between the first electrode sheet and the second electrode sheet to stack the first electrode sheet, the second electrode sheet and one or more separator sheets to form a cell assembly; (d) winding or folding the cell assembly to form a three dimensional structure having a form factor generally corresponding to the form factor of the rechargeable power cell; And (e) compression bonding a first inner terminal to the first end of the cell assembly such that only the negative electrode is electrically connected to the first inner terminal. The bonding can also be accomplished by soldering a first inner terminal to the first end of the cell assembly such that only the negative electrode is electrically connected to the first inner terminal. In this method, prior to soldering, the first internal terminals may be provided with a solder coating.

Regardless of what type of junction is used, various additional features can be associated with the method. These include everything described above for dry processing procedures. The method may also use internal terminals that take the form of perforated discs, slotted discs, or H-shaped structures. In some embodiments, the first internal terminal remains compressed with the first end of the cell assembly by the downward force provided by the cell cap in the fully assembled rechargeable power cell. Such force can be provided by an elastomeric member interposed between the cell cap and the inner terminal.

The invention will be more fully understood by reference to the following description taken in conjunction with the accompanying drawings.

1 is a schematic diagram of a process flow of an embodiment of the present invention;

2 is an additional schematic diagram of the process flow of an embodiment of the present invention;

3 is a graphical cross sectional view of the cathode and anode before winding;

4A is a graphical representation of an inverse polarity power cell subassembly embodiment.

4B is a graphical sectional view of an opposite polarity power cell subassembly embodiment.

The present invention relates generally to techniques for manufacturing nickel-zinc rechargeable battery cells using techniques similar to the manufacturing techniques generally accepted for nickel-cadmium rechargeable power cells.

Embodiments of this aspect of the invention are discussed below with reference to FIGS. 1-4B. However, those skilled in the art will understand that the detailed description provided herein with reference to these drawings is for illustration only, because the present invention extends beyond these limited embodiments.

First, referring to FIG. 1, FIG. 1 provides a schematic diagram of a manufacturing process for an embodiment of the present invention. Initially, the process comprises two separate paths, one for producing the negative electrode sheet and the other for producing the positive electrode sheet. Ultimately, in the described process, these two paths converge when separate negative and positive electrodes are assembled into a single cell. Typically, these two path process steps are performed in parallel in one factory, so that the electrodes can be continuously formed as sheets that are continuously joined in the process of forming nickel zinc cells in accordance with the present invention.

Blocks 101 and 121 show exemplary starting materials for the positive and negative electrodes. These blocks indicate that the manufacturing process should begin by providing the necessary starting material for producing the electrodes. In addition to the electrode forming raw material, the process also includes an electrode carrier sheet (made of a conductive material that serves as a current collector in the ultimately assembled cell), as well as a separate sheet that separates the positive and negative electrodes from the assembled cell, in the process When used, it requires electrolyte and water to form electrode pastes or slurries, and cell packaging materials (eg, disk terminals, cell cans, etc.).

Considering the negative electrode first, the manufacturing process begins by providing the negative electrode material 101 needed to form the negative electrode. In the exemplary embodiment shown in FIG. 1, the negative electrode material 101 includes zinc metal, ZnO, Bi ₂ O ₃ , Al ₂ O ₃ , HEC, and a dispersant. In some embodiments, indium oxide is also included. Various other formulations are possible, including using other forms of zinc, such as calcium zincate or precursors thereof (eg calcium oxide or zinc oxide). Other electrode formulations include inorganic fluorides, inorganic fibers such as alumina-silica fibers, organic fibers such as curtain flocs, and the like. Another formulation does not use HECs, dispersants or other organic materials.

As mentioned above, the present invention generally relates to a method of making a nickel zinc battery. As such, the negative electrode material is based on zinc and zinc compounds which are significantly less harmful than the more commonly used cadmium compounds. EPA has classified zinc and zinc compounds as Group D, which shows insufficient evidence regarding the potential for carcinogenesis (U.S. EPA, 1995a). In addition, the International Cancer Institute (IARC) did not classify zinc for possible carcinogenicity (IARC, 1987a). In contrast, epidemiological evidence strongly supports the relationship between cadmium exposure and tumor formation, including respiratory and renal cancer (ARB, 1986c). In addition, EPA has classified cadmium as a substance capable of causing cancer in humans based on group B1: human and animal studies indicating an increase in lung cancer (U.S. EPA, 1994a). In addition, IARC classified cadmium and cadmium compounds as Group 1 causing cancers in humans based on epidemiological evidence of carcinogens in humans and carcinogenic effects observed in animals (IARC, 1993b).

As described herein, zinc oxide is an electrochemically active material suitable for use in negative electrodes. In addition, other zinc compounds may also be used. In particular, in another exemplary embodiment, calcium zincate (CaZn (OH) ₄ ) may be used instead of ZnO as starting material. It can be appreciated that producing calcium zincate can include potentially harmful exothermic reactions. The reaction may also be difficult to control while strongly dehydrating water and producing slurry or paste for making negative electrodes. Therefore, when calcium zincate should be used, the calcium zincate should be pre-molded at least in part in place. Thereafter, only this calcium zincate should be added to the mixture of negative electrode materials. The general procedure for using calcium zincate in this manner is described in PCT Patent Application No. CA02 / 00352, filed by inventor J. Phillips on March 15, 2002, which is incorporated herein by reference in its entirety.

Other suitable electrochemically active materials for use in negative electrodes are zinc metals and zinc alloys. Preferably, the zinc metal or alloy particles are relatively small in size, for example less than about 50 micron average diameter; More preferably less than about 45 micron average diameter; Even more preferably smaller than about 40 micron average diameter. In certain embodiments, the zinc material has a particle size distribution wherein 92 weight percent of the material has a particle size smaller than 45 microns and 8 weight percent of the material has a particle size larger than 45 microns. Various alloying elements can be used in zinc alloys. Examples are indium and bismuth, and lead and iron are also suitable in some cases. Preferably, the indium and / or bismuth concentration does not exceed 1% of the total alloy mass. In some embodiments, the alloy contains up to about 500 ppm indium and up to about 500 ppm bismuth. In some embodiments, the alloy may contain up to about 25 ppm lead and up to about 5 ppm iron.

High temperature "burn out" procedures can improve the high rate performance of the zinc electrode obtained. In a typical method, zinc oxide is between about 200 and 400 ° C., preferably between about 300 ° C. and in a period of between about 0.5 and 2 hours in an inert atmosphere or under vacuum (to limit oxidation of the underlying copper current collector) Heated to a temperature between 380 ° C. (eg, about 320 ° C.). The burnout procedure may remove dispersing agents and other organic materials that are believed to have a deleterious effect on the high rate discharge of the zinc electrode. Alternatively, or in addition, the burnout procedure may remove carbonates that may interfere with high rate discharges. The burnout procedure may reduce the conductivity of the electrolyte, possibly by depleting hydroxide from the electrolyte and / or reducing the transport capacity of the electrolyte. Unfortunately, zinc oxide readily reacts with the surrounding carbon dioxide to form zinc carbonate. Therefore, the surface of the zinc oxide particles exposed to the atmosphere may gradually increase in the amount of carbonate. Many commercial sources of zinc oxide have significant carbonate content. In order to alleviate this problem, it may be desirable to heat the zinc oxide and to expel carbon dioxide prior to electrode manufacture. In a preferred embodiment, the zinc oxide used to prepare the negative electrode contains a weight percent no greater than about 1 of the carbonate. It has been found that the zinc metal component can withstand oxidation during the burnout procedure. Only a relatively small percentage of zinc is converted to oxide during burnout during exposure to the atmosphere.

In some embodiments, the zinc electrode is formed from a slurry or paste of zinc oxide and other electrode materials. In another embodiment, the zinc electrode is formed by a dry process in which the electrode components are provided as a mixture of powders that are compressed on a current collector or other carrier. As explained more fully below, the dry process does not require dispersants or other organic materials that may adversely affect performance.

In addition to zinc oxide or other electrochemically active zinc sources, negative electrode mixtures may include other materials that facilitate any process within the electrode, such as ion transport, electron transport, wetting, porosity, structural integrity, active material solubility, and the like. Can be. In the wet process, other additives control the concentration for the flow and other-related properties of the slurry or paste itself. In certain embodiments, the negative electrode slurry comprises zinc alloy, bismuth oxide, aluminum oxide hydroxyethyl cellulose (HEC), and a dispersant.

Hydroethyl cellulose (HEC) can be used to control the concentration of slurry or paste of negative electrode material. HECs are nonionic, water soluble polymers that can thicken, float, bind, emulsify, form films, stabilize, disperse, retain water, and provide protective colloidal behavior. HEC can be easily dissolved in hot or cold water and can be used to prepare solutions with a wide range of viscosities. In addition, HEC has excellent resistance to dissolved electrolytes. Thus, HEC or other materials with related properties are used to keep the negative electrode material (in the form of paste) retaining water.

In one method of forming the negative electrode slurry, two separate mixtures are produced and then combined to form the slurry. The first mixture comprises water and HEC (or other suitable material), and the second mixture comprises water and a pre-sieved solid (eg zinc metal or zinc alloy, ZnO, Al ₂ O ₃ , Bi ₂ O ₃ , and dispersants).

Other negative electrode compositions are described in the following documents, each of which is incorporated herein by reference: International Patent Publication No. 2002/39517 (J, Phillips), International Publication No. 2002/039520 (J. Phillips), International Patent Publication No. 2002 / 39521, International Patent Publication No. 2002/039534 to J. Phillips and US Patent Application No. 10 / 098,195 filed March 15, 2002. Among the negative electrode additives described in these references are silica and fluorides of various alkaline earth metals, transition metals, heavy metals, and precious metals.

As described herein, the manufacturing process preferably uses low carbonate zinc oxide. Unfortunately, it was found that low carbonate zinc oxide agglomerated in suspension much more easily than typical higher carbonate oxides. Therefore, since zinc oxide tends to form agglomerates, it has been found that it is difficult to produce negative electrodes with components that are well mixed and uniformly dispersed in the wet composition. To address this problem, some embodiments use dispersants to minimize aggregation of low carbonate zinc oxide particles. In general, dispersants alter the surface properties of the particles to facilitate dispersion throughout the slurry or other suspension. Many dispersants are conventional surfactants or variations thereof tailored to the surface properties of the particular particles to be dispersed. Since zinc oxide is widely used in the paint industry, various dispersants for oxides have been developed. One such dispersant is commercially available as NOPCOSPERSE 44 from San Nopco, Kyoto, Japan. In sufficient amounts, the dispersant was found to coat the surface of the zinc oxide particles to remove zinc oxide particle agglomerates in the manufacturing process of the present invention.

Returning to FIG. 1, the negative electrode material 101 is bonded as described above to form a water-based slurry 103 and is continuously applied to the conductive carrier sheet 151 with a slurry coating 105. Those skilled in the art will recognize that the material can also be made of a paste and continuously applied through the paste head as in step 125 for the formation of a negative electrode. In a particular example, the paste head applies the negative electrode paste mixture at a pressure of about 3 psi (pounds per square inch) to both sides of the carrier sheet. If slurry coating is used, a conventional slurry coating apparatus can be used. In such an apparatus, a continuous supply of slurry is provided to the chamber through which the carrier sheet passes.

It should be noted that a conventional zinc electrode is formed by a vacuum technique that draws a paste or slurry onto the carrier of a negative electrode. In some cases where calcium oxide and zinc oxide are used as active materials, petroleum-based additives are used to promote fibrillation of Teflon, which facilitates the production of electrode sheets that can be pressed onto a carrier.

In some embodiments, the zinc electrode component is provided as a dry mixture. That is, this embodiment does not use slurries, pastes or other wet compositions. In the dry mixture, the electrode component is provided as a powder or granular mixture, relatively free of water or other liquid media. Thus, the electrode mixture will not flow in the manner of a paste or slurry and therefore will not be delivered through the paste head or related mechanisms.

Dry processing follows electrode mixtures using metal additives such as zinc or zinc alloys that can foam in the paste or slurry and adversely affect the concentration of the paste or slurry. In addition, dry processing does not require the use of any organic materials such as dispersants or paste concentration additives, for example HEC. As mentioned above, such additives can adversely affect the performance of nickel-zinc cells.

In one example, the zinc electrode mixture used in the dry process comprises an oxide such as aluminum oxide, bismuth oxide, and / or indium oxide and a source of electrochemically active zinc. Other additives may include various inorganic fluorides, inorganic fibers such as alumina-silica fibers, and organic fibers such as curtain flocs and the like. The source of electrochemically active zinc can be zinc oxide, zinc metal, alloys of zinc metal, calcium zincate or precursors thereof (calcium oxide and zinc oxide), partially oxidized zinc metal and combinations thereof. For zinc alloys, examples of alloying elements include indium and bismuth. One particular embodiment uses zinc metal or zinc metal alloy powder that has been partially oxidized to zinc oxide. The resulting partially oxidized metal is combined with an oxide and a suitable binder such as dry polytetrafluoroethylene (P.T.F.E.) powder as described above and applied to the negative electrode carrier material.

The dry powder zinc process feeds a controlled proportion of powder into a compression roller with a three-dimensional electrochemically compatible substrate, such as meshed copper foam or elongated copper metal, to ensure that the powder is maintained in proper porosity and compacted. It includes.

It is to be understood that any one of a number of carrier materials may be used to form a positive electrode, including but not limited to nickel, nickel plated steel, silver, and the like. Those skilled in the art will appreciate that the carrier sheet serves as a current collector for the negative electrode in the finished nickel zinc cell. Copper and copper alloys are particularly preferred materials for carrier sheets, provided the copper's resistivity is low, relatively inexpensive, and electrochemically compatible with zinc electrodes. In particular, nickel plated steel is the selected carrier for cadmium electrodes in commercial nickel cadmium cells.

The carrier sheet can be provided in a variety of structural foams, including perforated metal sheets, elongated metals, and metal foams. Among the criteria used to select a particular structural form are cost, ease of coating, and the ability to facilitate electron transport between the electrochemically active electrode material and the current collector. In a preferred embodiment, the thickness of the carrier may be between about 2 and 5 mils for the perforated sheet but between 2 and 20 mils for the drawn metal. The metal foam substrate may be between 15 and 60 mils.

Once the negative electrode is coated, the negative electrode is dried 107 in the case of a wet process to dislodge excess water used as the delivery medium for the electrode material. For this purpose, a heat dryer can be used, which is used to flow air or nitrogen.

Thereafter, the resulting negative electrode is compressed 109 using a roller or other suitable compression mechanism. As will be appreciated by those skilled in the art, compression may allow the electrodes to have a uniform thickness, thus maintaining manufacturing tolerances. Compression also allows the negative electrode to reach the desired porosity. It can be appreciated that porosity controls the transport properties of ions between the electrolyte and the electrode. Porosity also represents the active surface area, thus representing the current density of the negative electrode. In a typical example, the post-compression thickness of the negative electrode is between about 10 to 40 mils and the porosity is between about 40 to 65%.

After the electrode sheet is compressed to an appropriate degree, it is cut and cleaned in step 111. The carrier sheet typically has a significantly larger width than is required for a single battery cell; For example, it should be noted that the width may be on the order of one yard. Thus, the negative electrode is cut into widths (eg about 1.25 inches for sub C size cells) according to the end-product specific tolerance. Some of the cut negative electrodes may be "cleaned" prior to further assembly. In particular, the strip of negative electrode material along the edge length of the negative electrode is removed. The cleaned strip facilitates attachment of the terminal to the negative electrode current collector in an additional step 203 by exposing the underlying current collector metal. While other terminal attachment methods can be achieved, cleaning leaves a surface particularly well suited for soldering, spot welding, or any other type of electrically-conductive bonding known in the art. As will be appreciated by those skilled in the art, cleaning the electrodes can be performed in any of the following ways: scraping, scoring, grinding, washing, and wiping. Can be achieved by This is typically accomplished with vacuum clean up to remove certain material.

In the same manner as described above for the negative electrode, the positive electrode can be formed. Beginning at initial step 121, a positive electrode material is provided to form a positive electrode. In an exemplary embodiment used in the wet process, and as shown in FIG. 1, nickel hydroxide (Ni (OH) ₂ ), zinc oxide, cobalt oxide (coO), nickel metal, optionally, carboxymethyl cellulose ( Positive electrode material 121 is provided that includes a flow regulator, such as CMC. In a preferred embodiment, at least some of the zinc oxide and cobalt oxide are provided with nickel hydroxide in the chemical mixture such that the individual particles contain nickel hydroxide, zinc oxide, and cobalt oxide. Such premixed materials may be prepared by co-precipitation of the individual components and obtained in a commercially available manner from conventionally known vendors such as International Nickel Company and Tanaka. have. Such materials prevent leaching by locking the oxides into the insoluble nickel matrix. Coprecipitation also clearly assists charge transfer efficiency by creating conductive channels through the positive electrode material. In a preferred embodiment, zinc oxide and cobalt oxide are each present in the co-precipitated material at a concentration of about 2 to 3 wt% with respect to zinc and about 2 to 6 wt% with respect to cobalt oxide. In addition, the positive electrode material may further comprise chemically pure cobalt and nickel metal.

When cobalt metal is used in the positive electrode, the cobalt metal is preferably present at a concentration between about 1 to 10% by weight. This concentration range is suitable for a wide range of discharge rates (eg 0.001 to 0.4 Amperes / cm ² of zinc electrode surface area). In typical high ratio applications (eg, discharge is done at 0.01 to 0.4 Amperes / cm ² of zinc electrode surface area), the concentration of cobalt metal is between about 4-10 weight putts at the positive electrode. In typical low ratio applications, the concentration of cobalt metal is between about 1-5 weight percent and the discharge is done at about 0.001 to 0.01 Amperes / cm ² of zinc electrode surface area.

In alternative embodiments, cobalt oxide may be added to the material to increase conductivity in operation 121. However, it is generally preferred that the starting materials contain little or no additional cobalt oxide. It should be noted that in commercial nickel cadmium cells, cobalt oxide is not commonly used in positive electrode mixtures.

In one method, the positive electrode paste comprises two separate mixtures; It is formed from one comprising CMC (carboxymethylcellulose) and water and another comprising water and co-precipitated nickel hydroxide-cobalt oxide-zinc oxide, nickel metal, and relatively pure cobalt oxide. Thereafter, these two mixtures are combined to form a positive electrode paste. It should be noted that CMC is included to improve the flow characteristics for the paste obtained in step 123.

Several positive electrode compositions are each referenced herein: PCT Publication No. WO 02.039534 (J. Phillips) (precipitated Ni (OH) ₂ , CoO and finely divided cobalt metal) and 2002 2002 US patent application Ser. No. 10 / 198,194 filed on May 15 (Fluoride Additives).

At block 125, the paste is continuously applied to the positive electrode carrier sheet through the paste head. Any of a number of carrier metals can be used to form negative electrodes as long as they meet appropriate design criteria such as low cost, high conductivity, electrochemical compatibility with positive electrodes, and good contact with electrochemically active materials. It can be recognized. Examples include, but are not limited to nickel and nickel-plated stainless steels. The carrier metal may have one of a variety of structural forms, including perforated metal, elongated metal, sintered metal, metal foam, and metal-coated polymeric material. In a preferred embodiment, the carrier is, for example, a nickel metal foam formed by pyrolysing urethane foam where nickel is electrochemically deposited. The thickness of the foam positive electrode carrier after undergoing a quadrupole to ensure thickness uniformity is, for example, between about 15 and 60 mils.

As with the negative electrode, the positive electrode can be prepared using a dry process. In this method, CMC and any other organics are not used. It should be noted that in some embodiments, it is not possible to burn-off organics from the positive electrode mixture. Thus, a relatively organic free dry process offers significant advantages, particularly in the context of nickel-zinc cells using electrolytes having relatively low hydroxide concentrations. In certain embodiments, the positive electrode composition for the dry process includes nickel hydroxide, zinc oxide, cobalt oxide (CoO), nickel metal, and optionally cobalt metal, wherein the zinc oxide and cobalt oxide are at least partially of nickel hydroxide. Present in the chemical mixture. In addition, finely divided binders such as dry P.T.F.E. This material provides the adhesion necessary for the structural integrity of the electrolyte in the absence of CMC and aqueous media. The dry mixed material is metered into a compression roll with a three-dimensional carrier. As the powder fills the voids, the powder is compressed to the appropriate porosity.

In some embodiments, the composition of the positive electrode used in the dry mixing procedure is very similar to that used in the wet process described above. However, CMC binders are not used and apparently much less water is used because no pastes and slurries are produced. In certain embodiments, the dry positive electrode component is electrochemically active nickel (nickel hydroxide (Ni (OH) ₂ ), nickel oxide and / or nickel hydroxide), zinc oxide, cobalt oxide, and cobalt metal. Note that since the binder is introduced later in this embodiment, the binder is not included here. Mixing of the components can be accomplished using a mixing device suitable for mixing the powder and granule compositions. As one example, the mixer apparatus may use blades, impingement wheels, rollers, ribbons, inner screws, vibrating elements, and the like, to perform even mixing. In an alternative embodiment, mixing is accomplished manually, for example using a spatula.

After the dry ingredients are mixed, a binder such as PTFE (polytetrafluoroethylene) may be added at a level between about 0.1 and 5% by weight of the total dry mixture of positive electrode components. As a binder, such materials "bind" other components of the electrode, thereby keeping these components in place and minimizing the possibility of flaking or separating from the current collector. In some embodiments, the selected binder material is inert to the electrochemical environment of the positive electrode. That is, the binder material does not decompose, melt, or diffuse from the positive electrode during manufacture or during normal operation. In some embodiments, such materials interfere with oxidation or other chemical degradation. Preferably, this material will not produce carbon dioxide or carbonates. An example of a grade of material having a member that can serve as a useful electrode binder in accordance with an embodiment of the present invention is a fluorinated polyolefin.

The binder can be added, for example, in a dry state or as an emulsion. In certain embodiments, when the binder is a fluorinated polyolefin, the binder is provided as an emulsion comprising about 60% by weight of the binder. The binder is combined with the rest of the ingredients manually or by any suitable mixing device (as described above) to produce an evenly dispersed mixture which is subsequently heated to remove moisture. In a manual process, the person responsible for mixing can use a snow blower or similar tool to perform the mixing. In some embodiments, the binder and the remaining components of the positive electrode are combined in a single step as opposed to the two-step procedure described above.

The binder or other component of the positive electrode is bonded in a well-mixed state and then deposited in a dry state on a current collector or other carrier or substrate. In one embodiment, a foam or elongated metal current collector, for example a nickel foam having a density between about 300 and 600 gm / m ² , and more preferably between 450 and 500 gm / m ² , serves this purpose. Used for.

The positive electrode mixture is applied to the substrate, for example, by brushing, pressing, or the like in a continuous manner. In an alternative embodiment, the application is achieved in a batch fashion, or semi-continuous manner, such that the mixture is applied to a “flaque” of the substrate sufficient to form, for example, 8-10 cells. . Flags with the applied positive electrode material are cut, scored and processed to create individual stripes of electrodes for assembly in the final cell.

Brushing can be accomplished by manually brushing in the electrode mixture with the brush and periodically checking to ensure that the correct amount of positive electrode material is incorporated into the current collector foam or other substrate material. Because of this, the substrate and integrated electrode material may sometimes be weighted until the set end point is reached. Brushing can be automated, for example, using a device having two or more brushes located on both sides of the substrate containing the supplied electrode metal. As the substrate passes between the brushes, the electrode material is drawn into the substrate.

Then, in accordance with an embodiment of the present invention, the electrode material is compressed onto the substrate by a suitable technique such as calendaring. In certain embodiments, the electrode and carrier are passed vertically through a calendering roller to produce a compressed electrode sheet of appropriate dimensions. In certain embodiments, the resulting electrode has a thickness between about 10 and 50 mils, or between about 20 and 30 mils.

After the metal is applied, the outer coating can be applied. This step is suitable when the electrode is susceptible to flaking, peeling, or easy separation of the active electrode material from the current collector or carrier. The coating serves to encapsulate the electrode material or reduce the likelihood that at least the metal will separate from the carrier. In one embodiment, the coating comprises PTFE or a physically similar material. In certain embodiments, the electrode is immersed into or sprayed into an emulsion of coating material (eg, an emulsion of about 60 wt% PTFE).

In some embodiments, the resulting electrode and carrier assembly (with or without coating) is subjected to "micorcracking". This is the process of bending an electrode sheet while tension is being applied to make the electrode more flexible by introducing a "microcracks". One apparatus for introducing microcracks uses an offset roller in which the electrode sheet is pulled under tension.

In some embodiments that use continuous supply of carriers and deposition of electrode materials, the carrier / electrode sheets must be cut periodically. In another embodiment, the carrier is sized to support positive electrodes for one or a predetermined number of cells. If the carrier supports electrodes for a set number of cells (eg eight cells), the carrier is called a flag. After the electrode material is incorporated into the flag, the flag is cut into a number of individual electrode strips. In certain embodiments, one or more such cuts are made longitudinally along the flag such that the cuts define the top of one electrode strip and the bottom of another electrode strip, the top and bottom names being positions within the assembled cell. Related to.

Once the carrier sheet is coated with the positive electrode material, the resulting sheet is dried if necessary (127), dehydrated excess water and then compressed (129). This process operation can be performed in much the same way as operations 107 and 109 for negative electrodes. As will be appreciated by those skilled in the art, compression allows the electrodes to have a uniform desired thickness and porosity as described above for the negative electrode path. Preferably, the resulting positive electrode sheet has a thickness of between about 15 and 40 mils (eg, about 25 mils) and has a porosity between about 30 and 45%.

A similar process as described above for the positive electrode can be applied to the negative electrode. Although the electroactive materials and components are different, the use and basic process of the binder will follow the procedure described above.

After preparing the positive electrode as described above, the positive electrode is tabbing and slitting as shown in step 131. Slitting the electrode to a certain width can be done before or after tabbing, but in most automated lines, electrode stock is slit after the inline tabbing process. Tabbing of the coined edges facilitates final welding of the current collector array after the winding of the jelly-roll. As described herein, the current collector (substrate) can be a nickel foam or other material having a void fraction. To ensure that the current collector is in proper electrical contact with the collector disk, the process includes applying a metal tab (eg, a thin nickel sheet about 0.08 to 0.15 inches wide) along one longitudinal edge of the current collector. It may include. After rolling the tacked positive electrode into the jellyroll, the tab is in contact with the collector disc, for example by soldering, welding, or pressing contact. The tab may be secured to the edge of the current collector (without applying a wet or dry electrode mixture) at various stages of the process, for example by a seam welding process, a resistance welding process, or an ultrasonic welding process. have.

In some embodiments, even when using a high void volume current collector, such as nickel foam, no tab is used. In such cases, the coined unpasted areas can be folded, creating a flat or generally flat surface that is more easily bonded to the current collector disk. In some embodiments, the coined region may be cut off to facilitate bending. For example, the section may be cut to leave many small tacked sections. After bending, contact with the current collector plate or disk can be made by either resistance welding or pressure contact. In this embodiment, the positive electrode jellyroll foam is in integrated contact with the collector dex and no intermediate features such as tabs are used. The application of this design or negative cap design in “opposite polarity” is described elsewhere herein.

At this point in the process, the two paths (negative electrode fabrication and positive electrode fabrication) converge and provide the remaining stacked array of sheets to the cell for completion. At the point of convergence, multiple sheets of material arrive together and are wound or assembled into a cell structure (indicated by “A” in FIG. 1). In a particular example, four sheets of separate material (shown as sources 113 and 133) are interleaved with the positive electrode sheet and the negative electrode sheet. Thus, once the electrode is manufactured, the electrode is sandwiched between the semi-osmotic separator sheets 113 and 133.

In an exemplary embodiment, the separator for the positive electrode 113 is a plurality of sheets of porous polyolefins commonly available as SOLUPORE products from the CELGARD® line alc Solutech of the separator from Celgard (Charlotville, NC). It includes. The separator serves to mechanically isolate the positive and negative electrodes while allowing ion exchange to occur between the electrode and the electrolyte. Therefore, it is desirable that the osmoticity to the electrolyte is good. In an exemplary embodiment, the separator 133 for negative electrode comprises a nylon sheet. Other separator materials known in the art can be used. As described herein, nylon-based materials and porous polyolefins (eg, polyethylene and polypropylene) are suitable.

Referring briefly to FIG. 3, FIG. 3 is a cross sectional view of the positive and negative electrodes prior to welding. In the example shown, the separators 301, 305 are initially folded over the electrodes 303, 307 along the planar surface of the electrodes before being drawn out to the electrode sheet and fed to the winding device 309. In this method, two separator sources are used. In an alternative embodiment, each electrode sheet is drawn irregularly by two separate sources of separator sheets, so four separator sources rather than two are used. Thus, initially, the separator sheet is not folded over the leading edge of the electrode. However, the laminated structure obtained is the same. Both methods produce a structure in which two separator layers separate each electrode layer from an adjacent next electrode layer. This is generally the case with nickel cadmium cells that use a single separator layer between adjacent electrode layers. Additional layers used in nickel zinc cells help to prevent short circuits that can result from zinc dendrites formation.

Dendrites are crystal structures with a backbone or tree-like growth pattern (“dendritic growth”) in metal deposition. Indeed, dendrites are formed in the conductive medium of a power cell during the life of the cell, and actually bridge the negative and positive electrodes, resulting in short circuits and subsequent battery loss.

It should be noted that the separator sheet does not generally cover the entire width of the electrode sheet. In particular, one edge of each electrode sheet remains exposed to attach the terminal at step 203. This is the clean edge obtained by cleaning the electrode material in steps 111 and 131. In addition, and for the same reason, the electrodes are laterally offset by the width of the above-described cleaned strip. This provides one lateral edge with only the exposed negative current collector and an opposing lateral edge with only the exposed positive current collector to facilitate terminal attachment at step 203.

The winding device draws multiple sheets simultaneously and rolls them into a jellyroll-like structure. After a cylinder of sufficient thickness has been produced, the device cuts the layers of electrodes and separators to produce a finished cell assembly.

Referring to FIG. 2, the process flow of FIG. 1 is shown continuously. The process of FIG. 2 begins at cell assembly 201 due to the assembly operation (“A”). For cylindrical cells, this assembly is a jellyroll-like structure. In an alternative embodiment, this assembly is a rectangular or prismatic stacked structure. Those skilled in the art will recognize that the form factor of the cell assembly is user dependent and may take any of a number of forms well known in the art. When using prismatic shapes, it may be desirable to pre-wrapp the positive and negative electrode sheets in their separators prior to assembly.

Once winding and other assembly of the electrode layer and the interleaved separator layer are completed, individual internal terminals are conductively attached to each of the negative electrode and the positive electrode. In particular, the positive terminal is conductively attached to the positive current collector exposed at one axial end of the cell assembly, and the negative terminal is conductively attached to the negative current collector exposed at the other axial end of the cell assembly. Attachment of the internal terminals may be by any method well known in the art, such as spot welding, ultrasonic welding, laser welding, solder, pressure contact, or any other type of electrically-conductive bonding suitable for terminal and current collector materials. Can be achieved. Specific methods of attaching copper internal terminals are described below.

In one embodiment of the invention, the inner terminal comprises a disk which can be perforated or slotted or cannot be perforated or slotted. In yet another embodiment, the inner terminal comprises an H-type structure. Regardless of their actual structure, the inner terminal can be conductively attached to the electrode without the tab present on the electrode to which it can be attached.

After the inner terminal is attached, the cell assembly is inserted into a holding vessel 205, such as a can in the case of a cylindrical cell assembly. The can or other container serves as the outer housing or casing of the final cell. By means of the cell assembly in the can, in step 207 the terminal disk (or other internal terminal) may be conductively attached to the can and lead or other external terminal of the cell.

External terminals provide direct electrical access to power cells for powered devices. As such, in some embodiments the external terminals are preferably plated with a non-corrosive metal, such as a nickel plate. The external terminal can also function to isolate the electrode from mechanical shock. Due to the portable nature of electronic devices, the likelihood of mechanical shock is quite high. If the external terminal is attached directly to the electrode current collector, the welded joint may be significantly damaged or the electrode may be directly damaged.

In the next step 209, a suitable electrolyte is provided. In particular with respect to the present invention, the electrolyte must possess a composition that limits dendrite formation and other forms of material redistribution in the zinc electrode. Such electrolytes are generally not recognized in the art. However, what appears to meet the criteria is described in US Pat. No. 5,215,836 to M. Eisenberg, dated June 1, 1993, which is incorporated herein by reference. Particularly preferred electrolytes are (1) alkali or alkaline earth hydroxides present in an amount to produce a stoichiometrically excess hydroxide for acids in the range of 2.5 to 11.0 equivalents / liter, (2) 0.01 to 1.0 equivalents per liter of total solution Soluble alkali or alkaline earth fluorides in an amount corresponding to the concentration range of and (3) borate, arsenate and / or phosphate (preferably potassium borate, potassium metaborate, sodium borate and / or metaborate) Sodium). In one specific embodiment, the electrolyte comprises 4.5 to 10 equivalents per liter of potassium hydroxide, 2.0 to 0.6 equivalents per liter of boric acid or sodium metaborate sodium metaborate from 0.01 to 1.00 equivalents of potassium fluoride. Current preferred electrolytes for high ratio applications include 8 equivalents per liter of hydroxide, 4.5 equivalents of boric acid and 0.2 equivalents of potassium fluoride.

The invention is not limited to the electrolyte composition provided in the Eisenberg patent. In general, an electrolyte composition that meets the criteria specific to the application of interest will be sufficient. Assuming high power applications are desired, the electrolyte should have very good conductivity. Assuming a long life is desired, the electrolyte should interfere with dendrite formation. In the present invention, fluoride and / or borate salts containing KOH electrolyte along appropriate separator layers are used to reduce the formation of dendrites, resulting in a more robust and long-lasting power cell.

In certain embodiments, the electrolyte composition comprises more than about 3-5 equivalents / liter of hydroxide (eg, KOH), NaOH, LiOH. For calcium zincate negative electrodes, alternative electrolyte formulations may be suitable. In one example, a suitable electrolyte for calcium zincate has the following composition: about 15 to 25 weight percent KOH, about 0.5 to 5.0 weight percent LiOH.

Various techniques can be used to fill the container with electrolyte. In one example, the electrolyte is introduced through an injection process, where the electrolyte enters the cell through the charging port. In other cases, the electrolyte can be added before lid application and the cell is rotated to disperse the liquid.

After the can or other containment vessel is filled with the electrolyte, the vessel is sealed to isolate the electrode and electrolyte from the environment. See block 211. As will be appreciated by those skilled in the art, any one of a number of sealing methods can be used, including but not limited to crimping, welding, stamping, or gluing. In the cylindrical cell, it should be noted that the leads are fixed on the gaskets that are typically on the circumferential bead on the top of the can. Then, in order to seal, the top edge of the can is crimped down towards the lid without making electrical contact.

Although the cell is generally sealed from the environment, in some embodiments, the cell may be able to exhaust the gas from the battery generated during charging and discharging. A typical nickel cadmium cell exhausts the gas at about 200 PSI. In some embodiments, nickel zinc cells are designed to operate at this or higher pressures (eg, up to 300 PSI) without requiring exhaust. This may promote the recombination of any oxygen and hydrogen generated in the cell. Preferably, the cell is configured to maintain no greater than about 600 PSI of internal pressure and more preferably no greater than about 450 PSI. In another embodiment, the nickel zinc cell is designed to exhaust the gas at a relatively lower pressure. This may be suitable for releasing hydrogen and / or oxygen gas rather than promoting recombination of hydrogen and oxygen in the nickel zinc cell. The exhaust mechanism is preferably designed to allow gas emissions, but not to allow passage of electrolytes that may interfere with the renewable function of the exhaust. The use of hydrophobic membranes is efficient for this purpose (e.g., US Patent Application No. 10 / 098,193, "Leak Proof Pressure, filed March 15, 2002 by J. Phillps, which is incorporated herein by reference for all purposes). Relief Valve for Secondary Batteries), which can be used alone or in combination with a curved gas exhaust route. Many other battery exhaust mechanisms are known in the art and are suitable for use with the present invention.

Preparing a cell for use typically requires one or more "formation" cycles to alter the electrode structure. In FIG. 2, formation of the cell is accomplished in step 213. The formation cycle follows a specific voltage-current-time curve that takes into account factors such as electrode composition and cell capacity. In a typical case, formation is accomplished using a large power source that simultaneously charges multiple cells over a period of, for example, about 24 to 74 hours.

In a particular example, the formation and related operations may be performed as follows. The cell is vacuum filled with electrolyte and immersed for less than 2 hours (in contrast, nickel cadmium cells are usually immersed for 24 hours but are typically drip fill. Before 2 hours, the cell is pure 100% A theoretical capacity of -150% is placed on the formation charge input over 24-60 hours The formation protocol includes the discharge and charge steps that are believed to help distribute the electrolyte, but this example can be run without this operation. In another example, the intermediate-formation discharge is eliminated, although the cells can be discharged alone or two in succession, in a manufacturing environment it is more useful to charge the cells with a larger series of strings. By monitoring the voltage behavior for the complete formation process and collecting weight loss, impedance values and open circuit voltage It may identify and classify the weak cell.

Once the formation is complete, all cells are discharged during the quality control step 215 to determine the specific capacity of each cell. Cells with similar capacities are grouped for use in the same battery pack. In this way, each cell in the battery pack is fully charged after receiving substantially the same amount of charge. Thus, once charging is complete, the cells in the pack are not significantly under-used and the cells in the pack are not significantly overcharged. Grouping of batteries can be limited to two or more groupings depending on the characteristics and sensitivity of the application.

It should be noted that the operation of FIG. 2 is generally the same or nearly similar to the corresponding operation used in the manufacture of nickel cadmium cells. Thus, the devices used for this operation in nickel cadmium cell manufacture can also be used generally in nickel zinc cell manufacture. However, it should be noted that electrode, current collector, and electrolyte differences may require customized equipment or processing. For example, zinc electrodes may use copper current collectors that cannot be used with cadmium electrodes. Copper has better electronic conductivity than steel, but can be problematic in manufacturing. For example, attaching a current collecting copper disk to a copper sheet may require specific laser welding settings and appropriate jigs to provide continuous pressure during welding.

Nickel zinc cells prepared in accordance with the present invention can have particularly useful properties for power tools and UPS applications. For example, the energy density will exceed about 60 Wh / kg, and the continuous power density typically exceeds about 500 W / kg or even over 1000 W / kg.

In another embodiment of the present invention, the terminal polarity of the cell is reversed compared to conventional cells for consumer electronics. Many of the same manufacturing methods described herein are used to achieve this example with a few variations described herein. In conventional power cell fabrication, the polarity of the cell is set to positive for lead and negative for can and container. That is, the positive electrode of the cell assembly is electrically connected to the lead and the negative electrode of the cell assembly is electrically connected to the can holding the cell assembly. In particular, the leads are electrically insulated from the cans by using flexible gaskets and bituminous sealing agents.

Referring to FIG. 4A, FIG. 4A is a graphical representation of an inverse polarity power cell subassembly embodiment. Cell assembly 407 is manufactured using the techniques provided herein. The negative inner terminal 405 is electrically connected to the negative electrode of the cell assembly. Because of the electrochemical specific properties of nickel / zinc, the negative inner terminal 405 is preferably made of copper. Typically, conventional power cells exhibit an overall impedance of approximately 3 to 5 mΩ (milliohms). Approximately 0.8 mV may belong to a positive current collector and the resistance is welded to the cap. This is due in part to the compositional requirements of the terminals due to the electrochemical nature of conventional power cells. In this embodiment, the use of copper in the manner described above results in a significant impedance reduction of about 0.5 mΩ at the negative terminal, thus achieving a more power efficient cell. Those skilled in the art will be able to construct a somewhat higher impedance cell by coating or plating the inner surface of the holding vessel 411 with copper and then making contact with the negative current collection disk, although this method requires an alternative manufacturing step. It will be appreciated.

Importantly, in this and other embodiments, copper needs special attention when used as internal terminals. In particular, as is well known in the art, copper is particularly efficient in transferring current as well as in conducting heat. As such, electrically attaching negative electrodes and internal terminals requires specific manufacturing techniques. In an exemplary embodiment, the copper inner terminal is perforated and attached at multiple points along the negative electrode, which is attached to the current collector at multiple points along its length. By activating a larger area, the charge and discharge efficiency is further improved. The perforation also serves to position the electrodes and the stack is uniformly passed by the electrolyte during the charging operation of the electrolyte. In another embodiment, the internal terminals are slotted to achieve the named advantage.

In addition, as described above, copper is particularly efficient at conducting heat, which requires novel techniques for attaching negative electrodes and internal terminals to avoid damaging the negative electrodes. In particular, this novel technique is compatible with spot welding, ultrasonic welding, laser welding, non-welding heat bonding (eg solder), pressure bonding, or any other type of electrically-conductive bonding suitable for terminal and current collector materials. The same may be used with other techniques that are well known in the art.

In one preferred embodiment, laser welding is used to form a low impedance connection between the inner terminal and the copper current collector. In a particular method, laser welding is performed in a crossover manner or other tracking method that minimizes the number of weldments, where the laser is moved across the surface of the inner terminal to capture each point. We find that good welding can be achieved using a laser pulse with a 600 micron beam diameter with a power between about 0.2 and 5 kW, a pulse width between about 0.5 and 4 milliseconds, and a pulse frequency between about 1 and 20 Hz. It was. This power level and duty cycle can be achieved with a pulsed Nd: YAG laser such as model number LW70A from Unitek Miyachi. In one method, the wound nickel-zinc jelly roll is inserted into a jig in which a copper current collection disk is pressed onto the exposed copper edge of the negative electrode. The laser beam is then programmed to lap weld the connection as it traverses to the end of the jelly-roll. The power level required depends on the thickness of the copper electrode substrate and the thickness of the current collecting disk. Depending on cell size and current carrying capacity, the former is typically between 0.002-0.005 inches and the latter is between 0.002-0.01 inches.

Yet another embodiment uses solder to join the copper internal terminals to the copper sheet of the jelly-roll. The inner terminals and jelly-rolls are brought into contact at the temperature that generates the solder. In some embodiments, a thin layer of solderable metal is applied to the inner terminals. This layer is applied on one or both sides of the terminal to coat the entire face (s) or only a specific area thereof. The metal is applied by electroplating, electrodeless plating, high temperature contact with the electrodes, and the like. The metal chosen should be electrochemically compatible with the zinc electrode and typically be resistant to corrosion when contacting the electrolyte at the potential experienced during overcharge and overdischarge. In certain instances, the inner electrode is coated on one or more sides with tin or tin alloy having a thickness between about 0.0002 and 0.002 inches.

In another embodiment, the contact is made by compression between the inner electrode and the copper of the jelly-roll. Such compression may be provided by the downward force provided by the cell cap in the fully assembled cell. To couple the cap to the inner terminal, some embodiments use an O-ring or other elastomeric member or metal spring device interposed between the cap and the inner terminal. In certain embodiments, the inner terminal is provided as a single folded member having one wing in contact with the jelly-roll and another wing in contact with the cell cap. An O-ring or other elastomeric member or copper plated stainless steel spring is positioned between the two wings of the inner terminal so that when the cell cap is positioned, the cell cap is from one ring of the terminal to the O-ring and jelly -Transfer the downward force onto the second wing of the terminal in contact with the roll.

Returning to FIG. 4A, the positive internal terminal 409 is electrically connected to the positive electrode using techniques well known in the art. Thereafter, power cell fabrication proceeds using the fabrication techniques described herein. For the sake of explanation, FIG. 4B is provided to clarify the above-described embodiment. In particular, FIG. 4B is a graphical cross-sectional view of an opposite polarity power cell subassembly embodiment. In particular, FIG. 4B shows the location of an insulating gasket 403 that serves to electrically insulate the negative external terminal (eg, lead 401) from the positive external terminal (eg, can 409). . It is contemplated that various materials may be used in this embodiment to achieve electrical isolation.

The present invention and the presently preferred embodiments of the present invention have been described in detail. It is anticipated that many variations and modifications in the practice of the invention will be made by those skilled in the art. Such modifications and variations are included in the following claims.

The entire specification of all references cited herein is incorporated for all purposes.

Claims (39)

A method of manufacturing a rechargeable power cell, comprising: Applying a zinc negative electrode material to the first conductive carrier to form a first electrode sheet; Applying a substantially dry nickel positive electrode material to the second conductive carrier to form a second electrode sheet; Disposing one or more separators between the first electrode sheet and the second electrode sheet to form a cell assembly by laminating the first electrode sheet, the second electrode sheet, and one or more separator sheets; And Winding or folding the cell assembly to form a three-dimensional structure having a form factor generally corresponding to the form factor of the rechargeable power cell. The method of claim 1, wherein the rechargeable power cell is a cylindrical cell. The method of claim 1, wherein the rechargeable power cell is a prismatic cell. The method of claim 1, wherein the negative electrode material is applied to the first conductive carrier in a substantially dry state. The method of claim 1, wherein the negative electrode material is applied to the first conductive carrier as a face or slurry. The method of claim 1, wherein the nickel positive electrode material is substantially free of dispersant and organic pasting aid. The method of claim 1, wherein the nickel positive electrode material comprises a binder. 8. The method of claim 7, wherein said binder is a fluorinated polyolefin. The method of claim 7, wherein the binder is present in the nickel positive electrode material at a level between about 0.1 wt% and 5 wt%. The method of claim 1, further comprising: attaching a first inner terminal to the first end of the cell assembly such that only a negative electrode is electrically connected to the first inner electrode; Attaching a second internal terminal to the second end of the cell assembly such that only a positive electrode is electrically connected to the second internal terminal; Inserting the cell assembly into a holding vessel; Filling the holding vessel containing the cell assembly with an electrolyte; And Sealing the holding vessel such that the electrolyte and cell assembly are substantially isolated from the environment. The method of claim 10, wherein at least one of the first terminal and the second terminal is attached to the cell assembly by one of a spot welding method, a laser welding method, an acoustic wave welding method, a pressure contact method, and a solder method. The method of claim 1, further comprising: initially charging the rechargeable power cell according to a defined charging curve; Individually inspecting the rechargeable power cells to cause the rechargeable power cells to be grouped by charge / discharge similarity. The method of claim 1, wherein the negative electrode material consists of ZnO, zinc or zinc alloy, bismuth oxide, and aluminum oxide. The method of claim 1, wherein the positive electrode material consists of nickel hydroxide and / or oxyhydroxide, zinc oxide, cobalt oxide, and a binder. The negative electrode material of claim 1, wherein the negative electrode material is composed of calcium zincate or zinc oxide, zinc metal or zinc alloy, bismuth oxide, aluminum oxide, a binder, and a dispersant to reduce agglomeration of particles, and the positive electrode The material consists of nickel hydroxide and / or oxyhydroxide, zinc oxide, cobalt oxide, and a binder. The method of claim 1, wherein the first conductive carrier is made of copper or a copper alloy. 17. The method of claim 16, wherein the first conductive carrier consists of a clarified copper or copper alloy or elongated copper or copper alloy. The method of claim 1, wherein the second conductive carrier is made of nickel. The method of claim 1, further comprising: attaching a first inner terminal to the first end of the cell assembly such that only a negative electrode is electrically connected to the first inner terminal; Attaching a second internal terminal to the second end of the cell assembly such that only a positive electrode is electrically connected to the second internal terminal; Attaching a cell cap terminal to the first internal terminal; And Inserting the cell assembly into a holding vessel and attaching a second internal terminal to the holding vessel such that the cell has a negative cap. The method of claim 1, wherein the at least one separator sheet comprises at least two layers comprising at least one nylon layer and at least one microporous polyolefin layer. The method of claim 1, wherein the negative electrode material comprises zinc oxide having up to 1% by weight of carbonate. The method of claim 1, further comprising heating the negative electrode to a temperature of about 200 ° C. or higher. A method of manufacturing a rechargeable power cell, comprising: Applying a zinc negative electrode material to the first conductive carrier to form a first electrode sheet; Applying a nickel positive electrode material to the second conductive carrier to form a second electrode sheet; Arranging at least one separator sheet between the first electrode sheet and the second electrode sheet to form a cell assembly by laminating the first electrode sheet, the second electrode sheet, and at least one separator sheet; Winding or folding the cell assembly to form a three-dimensional structure having a form factor generally corresponding to the form factor of the rechargeable power cell; And And compression bonding a first internal terminal to the first end of the cell assembly such that only a negative electrode is electrically connected to the first internal terminal. 24. The method of claim 23, further comprising attaching a second internal terminal to the second terminal of the cell assembly such that only a positive electrode is electrically connected to the second internal terminal. 25. The method of claim 24, wherein at least one of the inner terminals comprises a perforated disk, a slotted disk or an H-shaped structure. 24. The method of claim 23, wherein the first internal terminal is kept compressed with the first end of the cell assembly by the downward force provided by the cell cap in the fully assembled rechargeable power cell. 27. The method of claim 26, wherein the compression is maintained by an elastomeric member or a spring device interposed between the cell cap and the inner terminal. 24. The method of claim 23, further comprising: inserting the cell assembly into a holding vessel; Filling the holding vessel containing the cell assembly with an electrolyte; And Sealing the holding vessel such that the electrolyte and cell assembly is substantially isolated from the environment. The method of claim 23, wherein the rechargeable power cell is a cylindrical cell. 24. The method of claim 23, wherein said rechargeable power cell is a prismatic cell. 24. The method of claim 23, wherein the negative electrode material consists of zinc oxide, zinc or zinc alloy, bismuth oxide, and aluminum oxide. 24. The method of claim 23, wherein said positive electrode material is comprised of nickel hydroxide and / or oxyhydroxide, zinc oxide, cobalt oxide, and a binder. 24. The positive electrode material of claim 23, wherein the negative electrode material is comprised of calcium zincate or zinc oxide, zinc metal or zinc alloy, bismuth oxide, aluminum oxide, a binder, and a dispersant to reduce agglomeration of the particles. Is nickel hydroxide and / or oxyhydroxide, zinc oxide, cobalt oxide and a binder. The method of claim 23, wherein the first conductive carrier consists of perforated copper or copper alloy or elongated copper or copper alloy. The method of claim 23, wherein the second conductive carrier is made of nickel. 24. The method of claim 23, further comprising: attaching a second internal terminal to the second end of the cell assembly such that only a positive electrode is electrically connected to the second internal terminal; Attaching a cell cap terminal to the first internal terminal; And The cell assembly further comprises inserting into the holding vessel and attaching a second internal terminal to the holding vessel such that the cell has a negative cap. The method of claim 23, wherein the negative electrode material comprises zinc oxide having up to about 1 weight percent carbonate. The method of claim 23, further comprising heating the negative electrode to a temperature of about 200 ° C. or higher. A method of manufacturing a rechargeable power cell, comprising: Applying a zinc negative electrode material to the first conductive carrier to form a first electrode sheet; Applying a nickel positive electrode material to the second conductive carrier to form a second electrode sheet; Placing at least one separator sheet between the first electrode sheet and the second electrode sheet to form a cell assembly by laminating the first electrode sheet, the second electrode sheet, and at least one separator sheet; Winding or folding the cell assembly to form a three-dimensional structure having a form factor generally corresponding to the form factor of the rechargeable power cell; And Soldering a first inner terminal to the first end of the cell assembly such that only a negative electrode is electrically connected with the first inner terminal, wherein prior to the soldering, the first inner terminal is provided with a solder coating Manufacturing method.

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