Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1997-10-10
2001-01-09
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S232000
Reexamination Certificate
active
06171723
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to batteries and polymeric electrodes.
BACKGROUND OF THE INVENTION
In an increasingly mobile and technologically advanced society, batteries are playing an ever more important role. The importance of rechargeable, i.e., secondary, batteries is growing especially quickly due to the use of cellular phones, portable computers and the like. Along with the increased use of batteries, demand is growing for batteries with improved performance capability such as longer use on a single charge. Since batteries are typically used for mobile uses, size and weight considerations are significant.
SUMMARY OF THE INVENTION
In a first aspect, the invention features an article for use in a battery including a laminate, the laminate including:
(a) a porous, polymeric separator disposed between a first polymeric electrode and a second polymeric electrode, at least one of the electrodes comprising a porous polymer matrix, where at least one of the electrodes has a resistivity from about 200 ohm-cm to about 0.1 ohm-cm; and
(b) a lithium salt electrolyte.
Both the first polymeric electrode and the second polymeric electrode can comprise porous polymer matrices. The porous polymer matrix can comprise polypropylene, polyethylene or polyvinylidene fluoride. The porous polymer matrix can comprise a thermoplastic polymer, electrically conductive particles and redox active particles, where the redox active particles and the electrically conductive particles are chemically distinct. The porous polymer matrix can comprise a polyolefin. The electrolyte can includes a liquid composition or a gel composition.
Generally, one of the electrodes includes a cathode active material and the other of the electrodes includes an anode active material. At least one of the polymeric electrodes preferably includes between about 2 percent and about 12 percent by weight electrically conductive particles. At least one of the electrodes preferably comprises a porous polymer having a distribution of pore sizes between about 0.01&mgr; and about 5&mgr; when measured by mercury porosimetry. The article can further include a pair of current collectors with one of the current collectors in electrical contact with each of the electrodes.
In another aspect the invention features a method of producing a battery component comprising laminating together a pair of polymer electrodes and a polymer separator such that the polymer separator is disposed between the electrodes, at least one element of the polymer electrodes comprising a porous polymer matrix. The polymer separator can comprise a porous polymer element. One of the electrodes preferably includes a lithium ion-cathode active material and the other of the electrodes preferably includes a lithium ion-anode active material. The electrodes can include a polyolefin. The lamination can involve heat lamination, pressure lamination, coextrusion, solvent lamination and mixtures thereof.
In another aspect the invention features a porous, polymer electrode including a polymeric compound and from about 2 percent to about 15 percent by weight of conducting particles, the electrode having a void volume from about 20 percent to about 60 percent, and a maximum pore size of 5 microns. The porous, polymer electrode can include a lithium ion-active material. The porous, polymer electrode can include greater than about 60 percent lithium ion-cathode active material or greater than about 60 percent lithium ion-anode active material. The porous, polymer electrode can further include a conductive current collector embedded in the porous, polymer composition.
In another aspect the invention features a porous, polymer cathode including:
(a) a polymeric compound;
(b) between about 60 percent and about 94 percent by weight electrically insulating or semiconducting particles, which comprise a cathode-active material; and
(c) between about 1 percent and about 15 percent by weight electrically conductive particles.
The electrically conductive particles can include electrically conductive carbon. The porous, polymer cathode can include between about 5 percent and about 12 percent by weight electrically conductive particles.
In another aspect, the invention features an isolated porous, polymer anode including:
(a) a polymeric compound;
(b) between about 60 percent and about 94 percent by weight particles, which comprise an anode active material; and
(c) greater than about 1 percent by weight electrically conductive particles, chemically distinct from the anode active material.
The electrically conductive particles can include nongraphitic carbon. The anode active material can include graphite.
In another aspect, the invention features a method of producing a porous, polymer electrode comprising cooling a composition that comprises a melt blend of a polymer, redox active particles, electrically conductive particles chemically distinct from the redox active particles and a solubilizing amount of a diluent to induce a phase transition, the polymer comprising polyethylene, polypropylene, poly(tetrafluoroethylene-co-perfluoro-(propyl vinyl ether)) or polyvinylidine fluoride. The electrically conductive particles include electrically conductive carbon. The method can further include the step of removing the diluent.
In the method, the porous, polymer electrode upon removing the diluent can include between about 1 percent by weight and about 12 percent by weight electrically conductive particles. Similarly, the porous, polymer electrode upon removing the diluent can include between about 60 percent and 94 percent by weight redox active particles. The cooling step can be performed in the presence of a conductive current collector such that the current collector is embedded in the porous, polymer electrode.
In another aspect, the invention features a method of producing a porous, polymer article comprising heating a porous, polymer film to a temperature within about 20° C. of the melting point of the polymer for a time sufficient to increase the bubble point without substantially altering structural integrity of the film, where the film includes at least about 25 percent by volume particles such as carbonaceous or silicaceous material. The method can further including calendering the porous, polymer film to reduce void volume.
In another aspect the invention features a method of producing a porous polymer electrode including the steps of:
a) forming a blend of lubricant, a swellable-fibril-forming polymer and redox active particles, the blend having a cohesive consistency and the lubricant being present in an amount exceeding the adsorptive and absorptive capacity of particulates by at least 3 weight percent;
b) intensively mixing the blend at a temperature and for a time sufficient to cause initial fibrillation of the polymer; and
c) biaxially calendering the mass between gaps in calendering rolls maintained at a temperature and for a time to cause additional fibrillation of the polymer, the calendering step being repeated to form a self-supporting tear resistant sheet.
In another aspect, the invention features a conductive adhesive comprising a polyethylene latex and carbon particles.
Preferred porous electrodes are capable of handling a high current density, a high conductivity and a high loading of active material while maintaining good mechanical strength. Preferred batteries are produced using preferred electrodes laminated on either side of a polymer separator. Batteries produced from preferred porous electrodes are capable of producing a high current. Preferred batteries also have a high capacity for a given size and weight with respect to total current produced by the battery on a single charge. Rechargeable batteries can be produced from the preferred electrodes by incorporating appropriate active materials into the battery.
REFERENCES:
patent: 3314820 (1967-04-01), Smith
patent: 3508967 (1970-04-01), Lyall et al.
patent: 4153661 (1979-05-01), Ree et al.
patent: 4206980 (1980-06-01), Krueger et al.
patent: 4465533 (1984-08-01), Covitch
patent: 4518665 (1985-05-01
Fredericksen Brian D.
Larson James M.
Loch Robert B.
3M Innovative Properties Company
Kalafut Stephen
Pastirik Daniel R.
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