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  Dry-particle based adhesive and dry film and methods of making sameRelated Patent Categories: Chemistry: Electrical Current Producing Apparatus, Product, And Process, Current Producing Cell, Elements, Subcombinations And Compositions For Use Therewith And Adjuncts, Electrode, Having Active Material With Organic Component, Organic Component Is A BinderThe Patent Description & Claims data below is from USPTO Patent Application 20070122698. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] The present Application is a Continuation-In-Part of and claims priority from commonly assigned copending U.S. patent application Ser. No. 11/116,882, filed Apr. 27, 2005, Attorney Docket M109US-GENIII-v.3; which is a Continuation-In-Part of U.S. patent application Ser. No. 10/817,702, filed Apr. 2, 2004, Attorney Docket Number M109US-GEN.5. FIELD OF THE INVENTION [0002] The present invention relates generally to the field energy storage devices. More particularly, the present invention relates to structures and methods for making dry particle based adhesives and films for capacitor products. BACKGROUND INFORMATION [0003] Energy storage devices are used throughout modern society to provide energy. Inclusive of such energy storage devices are batteries, fuel cells, and capacitors. With each type of device are associated positive and negative characteristics. Based on these characteristics, decisions are made as to which device is more suitable for use in a particular application. Overall cost of an energy storage device is an important characteristic that can make or break a decision as to whether a particular type of energy storage device is used. [0004] Double-layer capacitors, also referred to as ultracapacitors and super-capacitors, are energy storage devices that are able to store more energy per unit weight and unit volume than capacitors made with traditional technology, for example, electrolytic capacitors. [0005] Double-layer capacitors store electrostatic energy in a polarized electrode/electrolyte interface layer. Double-layer capacitors include two electrodes, which are separated from contact by a porous separator. The separator prevents an electronic (as opposed to an ionic) current from shorting the two electrodes. Both the electrodes and the porous separator are immersed in an electrolyte, which allows flow of the ionic current between the electrodes and through the separator. At the electrode/electrolyte interface, a first layer of solvent dipole and a second layer of charged species is formed (hence, the name "double-layer" capacitor). [0006] Although, double-layer capacitors can theoretically be operated at voltages as high as 4.0 volts, and possibly higher, current double-layer capacitor manufacturing technologies limit nominal operating voltages of double-layer capacitors to about 2.5 to 2.7 volts. Higher operating voltages are possible, but at such voltages undesirable destructive breakdown begins to occur, which in part may be due to interactions with impurities and residues that can be introduced into and/or attach themselves to electrodes during manufacture. For example, undesirable destructive breakdown of double-layer capacitors is seen to appear at voltages between about 2.7 to 3.0 volts. [0007] Known capacitor electrode fabrication techniques utilize processing additive based coating and/or extrusion processes. Both processes utilize binders, which typically comprise polymers or resins that provide cohesion between structures used to make the capacitor. Known double-layer capacitors utilize electrode film and adhesive/binder layer formulations that have in common the use of one or more added processing additive (hereafter referred throughout as "additive"), variations of which are known to those skilled in the arts as solvents, lubricants, liquids, plasticizers, and the like. When such additives are utilized in the manufacture of a capacitor product, the operating lifetime, as well maximum operating voltage, of a final capacitor product may become reduced, typically because of undesirable chemical interactions that can occur between residues of the additive(s) and a subsequently used capacitor electrolyte. [0008] In a coating process, an additive (typically organic, aqueous, or blends of aqueous and organic solvents) is used to dissolve binders within a resulting wet slurry. The wet slurry is coated onto a collector through a doctor blade or a slot die. The slurry is subsequently dried to remove the solvent. With prior art coating based processes, as layer thickness is increased above a certain thickness or decreased below a certain thickness, it becomes increasingly more difficult to achieve an even homogeneous layer, for example, wherein a uniform above 25 micron thick coating of an adhesive/binder layer is desired, or a coating of less than 5 microns is desired. The process of coating also entails high-cost and complicated processes. Furthermore, coating processes require large capital investments, as well as high quality control to achieve a desired thickness, uniformity, top to bottom registration, and the like. [0009] In the prior art, a first wet slurry layer is coated onto a current collector to provide the current collector with adhesive/binder layer functionality. A second slurry layer, with properties that provide functionality of a conductive electrode layer, may be coated onto the first coated layer. In another prior art example, an extruded layer can be applied to the first coated layer to provide conductive electrode layer functionality. [0010] In the prior art process of forming an extruded conductive electrode layer, binder and carbon particles are blended together with one or more processing additive. The resulting material has dough-like properties that allow the material to be introduced into an extruder apparatus. The extruder apparatus fibrillates the binder and provides an extruded film, which is subsequently dried to remove most, but as discussed below, typically not all of the additive(s). When fibrillated, the binder acts to support the carbon particles as a matrix. The extruded film may be calendered many times to produce an electrode film of desired thickness and density. [0011] Known methods for attaching additive/solvent based extruded electrode films and/or coated slurries to a current collector include the aforementioned precoating of a slurry of adhesive/binder. Pre-coated slurry layers of adhesive/binder are used in the capacitor prior arts to promote electrical and physical contact with current collectors, and the current collectors themselves provide a physical electrical contact point. [0012] Impurities can be introduced or attach themselves during the aforementioned coating and/or extrusion processes, as well as during prior and subsequent steps. Just as with processing additives, the residues of impurities can reduce a capacitor's operating lifetime and maximum operating voltage. In order to reduce the amount of additive and impurity in a final capacitor product, one or more of the various prior art capacitor structures described above are processed through a dryer. In the prior art, the need to provide adequate throughput requires that the drying time be limited to on the order of hours, or less. However, with such short drying times, sufficient removal of additive and impurity is difficult to achieve. Even with a long drying time (on the order of days) the amounts of remaining additive and impurity is still measurable, especially if the additives or impurities have a high heat of absorption. Long dwell times limit production throughput and increase production and process equipment costs. Residues of the additives and impurities remain in commercially available capacitor products and can be measured to be on the order of many parts-per-million. [0013] Binder particles used in prior art additive based fibrillization steps include polymers. Polymers and similar ultra-high molecular weight substances capable of fibrillization are commonly referred to as "fibrillizable binders" or "fibril-forming binders." Fibril-forming binders find use with other powder like materials. In one prior art process, fibrillizable binder and powder materials are mixed with solvent, lubricant, or the like, and the resulting wet mixture is subjected to high-shear forces to fibrillize the binder particles. Fibrillization of the binder particles produces fibrils that eventually allow formation of a matrix or lattice for supporting a resulting composition of matter. In the prior art, solvents, liquids, and processing aides are added so that subsequent shear forces applied to a resulting mixture are sufficient to fibrillize the particles. During prior art extrusion and/or coating and/or subsequent calendering stages, although fibrillization is known to occur, such processes also cause a large number of the fibrillized binder particles to re/coalesce and be formed into agglomerates. As seen in FIG. 13, such agglomeration is seen and evidenced by the large smeared and individual globular structures present in a final film product. The large number of such re/coalesced binder particles results in a reduced final film integrity and performance. [0014] In the prior art, the resulting additive based extruded product can be subsequently processed in a high-pressure compactor, dried to remove the additive, shaped into a needed form, and otherwise processed to obtain an end-product for a needed application. For purposes of handling, processing, and durability, desirable properties of the end product typically depend on the consistency and homogeneity of the composition of matter from which the product is made, with good consistency and homogeneity being important requirements. Such desirable properties depend on the degree of fibrillization of the polymer. Tensile strength commonly depends on both the degree of fibrillization of the fibrillizable binder, and the consistency of the fibril lattice formed by the binder within the material. When used as an electrode film, internal resistance of an end product is also important. Internal resistance may depend on bulk resistivity--volume resistivity on large scale--of the material from which the electrode film is fabricated. Bulk resistivity of the material is a function of the material's homogeneity; the better the dispersal of the conductive carbon particles or other conductive filler within the material, the lower the resistivity of the material. When electrode films are used in capacitors, such as double-layer capacitors, capacitance per unit volume is yet another important characteristic. In double layer capacitors, capacitance increases with the specific surface area of the electrode film used to make a capacitor electrode. Specific surface area is defined as the ratio of (1) the surface area of electrode film exposed to an electrolytic solution when the electrode material is immersed in the solution, and (2) the volume of the electrode film. An electrode film's specific surface area and capacitance per unit volume are believed to improve with improvement in consistency and homogeneity. [0015] A need thus exists for new methods of producing low cost capacitor electrode materials with one or more of the following qualities: improved consistency and homogeneity of distribution of binder and active particles on microscopic and macroscopic scales; improved tensile strength of electrode film produced from the materials; decreased resistivity; and increased specific surface area. Yet another need exists for capacitor electrodes fabricated from materials with these qualities. A further need is to provide capacitors and capacitor electrode materials without the use of processing additives. SUMMARY [0016] The present invention provides a high yield method for making durable, highly reliable, and inexpensive structures. The present invention eliminates or substantially reduces use of water, additives, and solvents, and eliminates or substantially reduces impurities, and associated drying steps and apparatus. The invention utilizes a dry fibrillization technique, where a matrix formed thereby is used to support or hold one or more types of particles for use in further processing steps. [0017] In one embodiment, a particle packaging process includes the steps of supplying articles; supplying binder; mixing the particles and binder; and dry fibrillizing the binder to create a matrix that supports the particles. The step of dry fibrillizing may comprise application of a high-shear. The high-shear may be applied in a jet-mill. The shear may be applied by a calender mill. The application of high-shear may effectuated by application of a pressure. The pressure may be applied by a calender roll. The pressure may be applied as a pressurized gas. The gas may comprise oxygen. The pressure may be greater than or equal to about 10 PSI. After and/or during a pass though a compacting apparatus the matrix may be formed into a dry self supporting film. The dry self supporting film may be formed without the use of processing additives. The dry self supporting film may be formed without the use of liquid. The binder may comprise a fibrillizable fluoropolymer. The matrix may comprise between about 1% to 30% fluoropolymer particles by weight. In one embodiment, a film manufacturing method may include the steps of: dry fibrillizing particles and binder; and forming a product from the fibrillized mix without the use of any processing additives. The fibrillized mix may be fibrillized by application of a pressure. The pressure may be applied as a pressurized gas. [0018] In one embodiment, a product may include dry particles supported by a matrix of dry binder The product may comprise a compacted sheet. The compacted sheet may be coupled to a substrate. The sheet is preferably substantially free of processing additives. The processing additives that are not used include hydrocarbons, high boiling point solvents, antifoaming agents, surfactants, dispersion aids, water, pyrrolidone mineral spirits, ketones, naphtha, acetates, alcohols, glycols, toluene, xylene, Isopars.sup.tm, and others used by those skilled in the art. The substrate may comprise a collector. In one embodiment, dry binder may also be fibrillized by application of a positive or negative pressure to the particles, for example as by a pressurized gas or a vacuum. [0019] In one embodiment, a product is formed of a structure, the structure comprising a plurality of particles, wherein the structure is substantially free of processing additives. In one embodiment, the processing additive that are not used include hydrocarbons, high boiling point solvents, antifoaming agents, surfactants, dispersion aids, water, pyrrolidone mineral spirits, ketones, naphtha, acetates, alcohols, glycols, toluene, xylene, and/or Isopars.sup.tm. The structure may comprise a capacitor structure. The structure may comprise a battery structure. The structure may comprise a fuel-cell structure. In one embodiment, at least some of the particles may comprise carbon. In one embodiment, at least some of the particles may comprise conductive carbon. In one embodiment, at least some of the particles may comprise activated carbon. In one embodiment, at least some of the particles may comprise activated carbon and conductive carbon. In one embodiment, at least some of the particles may comprise manganese dioxide. In one embodiment, at least some of the particles may comprise a metal oxide. In one embodiment, at least some of the particles may comprise a fibrillizable fluoropolymer. In one embodiment, at least some of the particles may comprise thermoplastic. In one embodiment, at least some of the particles may comprise catalyst impregnated carbon. In one embodiment, at least some of the particles may comprise graphite. In one embodiment, at least some of the particles may comprise manganese dioxide. In one embodiment, at least some of the particles may comprise a metal. In one embodiment, at least some of the particles may comprise intercalated carbon. In one embodiment, at least some of the particles may comprise intercalated carbon. In one embodiment, the structure is in the form of a sheet. [0020] In one embodiment, a solvent free method used for manufacture of a product device electrode includes steps of: providing particles; providing binder; and forming the particles and binder into a product without the use of any solvent. Continue reading... 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