EP1716607A2 - Pile alcaline dotee d'un boitier plat - Google Patents
Pile alcaline dotee d'un boitier platInfo
- Publication number
- EP1716607A2 EP1716607A2 EP04820021A EP04820021A EP1716607A2 EP 1716607 A2 EP1716607 A2 EP 1716607A2 EP 04820021 A EP04820021 A EP 04820021A EP 04820021 A EP04820021 A EP 04820021A EP 1716607 A2 EP1716607 A2 EP 1716607A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- cell
- housing
- metal cover
- cathode
- anode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the invention relates to an alkaline battery having a substantially flat outer housing.
- the invention relates to alkaline battery having an anode comprising zinc, a cathode comprising manganese dioxide, and an electrolyte comprising aqueous potassium hydroxide.
- Conventional alkaline electrochemical cells have an anode comprising zinc and a cathode comprising manganese dioxide.
- the cell is typically formed of a cylindrical outer housing.
- the fresh cell has an open circuit voltage (EMF) of about 1.5 volt and typical average running voltage of between about 1.0 to 1.2 Volt in medium drain service
- the cylindrical housing is initially formed with an enlarged open end and opposing closed end. After the cell contents are supplied, an end cap assembly with insulating grommet and negative terminal end cap is inserted into the housing open end. The open end is closed by crimping the housing edge over an edge of the insulating plug and radially compressing the housing around the insulating plug to provide a tight seal.
- the insulating grommet electrically insulates the negative end cap from the cell housing. A portion of the cell housing at the opposing closed end forms the positive terminal.
- Electrochemical cells particularly alkaline cells
- Electrochemical cells are conventionally provided with rupturable diaphragms or rupturable membranes within the end cap assembly.
- the rupturable diaphragm or membrane may be formed within a plastic insulating member as described, for example, in U.S. Patent 3,617,386.
- the prior art discloses rupturable vent membranes, which are integrally formed as thinned areas within the insulating disk included within the end cap assembly.
- vent membranes can be oriented such that they lie in a plane perpendicular to the cell's longitudinal axis, for example, as shown in U.S. Patent 5,589,293, or they may be oriented so that they are slanted in relation to the cell's longitudinal axis as shown in U.S.
- U.S. Patent 6,127,062 discloses an insulating sealing disk and an integrally formed rupturable membrane, which is oriented vertically, that is, parallel to the cell's central longitudinal axis. When the gas pressure within the cell rises to a predetermined level the membrane ruptures thereby releasing the gas pressure to the external environment through apertures in the end cap.
- Other types of vents are disclosed in the art for relieving gas pressure within an electrochemical cell.
- One such vent is a reseatable rubber plug, which has been used effectively in connection with small flat rectangular shaped nickel metal hydride rechargeable cells.
- One such rechargeable battery with the reseatable rubber plug vent is a 7/5-F6 size nickel metal hydride rechargeable battery available commercially as battery model GP14M145 manufactured by Gold Peak Batteries, Hong Kong.
- the rubber plug is physically compressed to sit tightly within a beveled aperture within a cavity or seat in the cell's end cap assembly. When the cell's internal gas pressure reaches a predetermined level, the plug lifts off its seat thereby letting gas to escape through the underlying aperture. The plug reseats itself when the gas pressure within the cell returns to normal.
- Primary alkaline electrochemical cells typically include a zinc anode active material, an alkaline electrolyte, a manganese dioxide cathode active material, and an electrolyte permeable separator film, typically of cellulose or cellulosic and polyvinylalcohol fibers.
- the anode active material can include for example, zinc particles admixed with conventional gelling agents, such as sodium carboxymethyl cellulose or the sodium salt of an acrylic acid copolymer, and an electrolyte.
- the gelling agent serves to suspend the zinc particles and to maintain them in contact with one another.
- a conductive metal nail inserted into the anode active material serves as the anode current collector, which is electrically connected to the negative terminal end cap.
- the electrolyte can be an aqueous solution of an alkali metal hydroxide for example, potassium hydroxide, sodium hydroxide or lithium hydroxide.
- the cathode typically includes particulate manganese dioxide as the electrochemically active material admixed with an electrically conductive additive, typically graphite material, to enhance electrical conductivity.
- an electrically conductive additive typically graphite material
- small amount of polymeric binders, for example polyethylene binder and other additives, such as titanium-containing compounds can be added to the cathode.
- the manganese dioxide used in the cathode is preferably electrolytic manganese dioxide (EMD) which is made by direct electrolysis of a bath of manganese sulfate and sulfuric acid. The EMD is desirable, since it has a high density and high purity.
- the electrical conductivity (resistivity) of EMD is fairly low.
- An electrically conductive material is added to the cathode mixture to improve the electric conductivity between individual manganese dioxide particles.
- Such electrically conductive additive also improves electric conductivity between the manganese dioxide particles and the cell housing, which also serves as cathode current collector in conventional cylindrical alkaline cells.
- Suitable electrically conductive additives can include, for example, graphite, graphitic material, conductive carbon powders, such as carbon blacks, including acetylene blacks.
- the conductive material comprises flaky crystalline natural graphite, or flaky crystalline synthetic graphite, including expanded or exfoliated graphite or graphitic carbon nanofibers and mixtures thereof.
- the F6 size has a thickness of 6.0 mm, width of 17.0 mm and length of 35.7 mm (without label). There is a version of the F6 size wherein the length can be as great as about 48.0 mm.
- the 7/5-F6 size has thickness of 6.0 mm, width of 17.0 mm, and length of 67.3 mm. According to the IEC standard, allowed deviation for the 7/5-F6 size in thickness is +0 mm, -0.7 mm, in width is +0 mm, -1 mm, and in length is +0, -1.5 mm.
- the average running voltage of the F6 or 7/5F6 NiMH rechargeable batteries when used to power miniature digital audio players is between about 1.1 and 1.4 volt typically about 1.12 volt.
- mini disk (MD) player the battery is drained at a rate of between about 200 and 250 milliAmp.
- digital audio MP3 player the battery is drained typically at a rate of about 100 milliAmp.
- a small flat alkaline battery of the same size and shape as small size cuboid shaped (rectangular parallelepiped) nickel metal hydride batteries, so that the small alkaline size battery can be used interchangeably with the nickel metal hydride battery to power small electronic devices such as mini disk or MP3 players.
- a primary (nonrechargeble) alkaline battery preferably a zinc/MnO 2 alkaline battery as a replacement for small rectangular shaped rechargeable batteries, particularly small size nickel metal hydride rechargeable battery.
- a particular problem associated with the design of rectangular (cuboid) shaped primary Zn/MnO 2 alkaline battery is that of the tendency of the electrodes to swell during cell discharge.
- housing wall thickness can result in significant decrease in available volume for anode and cathode materials for rectangular cells having small overall thickness, e.g. under about 10 mm.
- the added wall thickness adds to the cost of manufacture of the cell.
- a small flat (nonrechargeable) alkaline cell such as an F6 or 7/5 -F6 size cell having a rectangular (cuboid) shaped housing, but yet with small housing wall thickness, wherein the housing does not significantly bulge or swell during normal cell usage.
- a principal aspect of the invention is directed to a primary (nonrechargeable) alkaline cell which generates hydrogen gas upon discharge, wherein said cell has an outer casing (housing), an end cap assembly which includes a vent mechanism which allows the hydrogen gas to escape from the cell when gas pressure reaches a predetermined level.
- the casing has at least a pair of opposing flat walls running along the cell's length. An end cap assembly is inserted into the casing open end and sealed by crimping or welding to close the casing.
- the casing edge at the open end may be crimped over an insulating seal member, typically of nylon or polypropylene, inserted into the open end, but it is preferred to laser weld a metal cover to the casing to close the open end thereof.
- the alkaline cell may be in the shape of a parallelepiped, but is desirably in the shape of a cuboid (rectangular parallelepiped).
- the casing is thus preferably of cuboid shape, which does not have any integral cylindrical sections.
- the alkaline cell desirably has an anode comprising zinc, and an aqueous alkaline electrolyte, preferably aqueous solution of potassium hydroxide.
- An end cap assembly includes a venting mechanism and preferably a rectangular shaped metallic cover.
- the cover is used to close the open end of the casing after the cell contents are inserted into the casing.
- the metallic cover can form the cell's negative terminal if insulation or an insulating seal member is inserted between the edge of the said cover and the casing edge and the casing edge crimped over the insulation.
- the cover can be welded directly to the casing edge. If the cover is welded to the casing edge, a separate end cap insulated from the cover can be employed in electrical communication with the anode to function as the cell's negative terminal.
- the casing is positive and forms the cell's positive terminal.
- the metal cover is welded directly to the casing edge to close the casing open end, and a plastic extender seal is stacked on top of the metal cover and a negative end plate in turn is stacked onto the plastic extender.
- a paper washer can be used instead of the plastic extender.
- the cathode comprising MnO 2 is inserted, preferably in the form of a plurality of compacted slabs or disks.
- the cathode slabs or disks are preferably rectangular shaped, each having a central hollow core running through the slab's thickness.
- the slabs are inserted so that they are stacked one on top of another.
- the slabs are aligned along the cell's length, so that their outside surface is in contact with the inside surface of the casing.
- the stacked cathode slabs form a central hollow core running along the cell's longitudinal axis.
- the central hollow core within the stacked cathode slabs forms the anode cavity.
- the inside surface of each cathode slab, which defines the central hollow core (anode cavity) within the slab is preferably a curved surface. Such curved inside surface improves the mechanical strength of the slab during transfer and handling and also provides more uniform contact between the electrolyte permeable separator and the cathode.
- the separator is inserted into the cell's central hollow core (anode cavity) so that the outside surface of the separator abuts and closely contacts the inside surface of the cathode.
- An anode slurry comprising zinc particles is inserted into the anode cavity with the separator providing the interface between anode and cathode.
- the end cap assembly has an elongated anode current collector, which is inserted into the anode slurry and in electrical communication with the cell's negative terminal.
- the end cap assembly has an insulating sealing member, which insulates such anode current collector from the cell's outer casing.
- the anode cavity preferably has an elongated or oblong configuration when the anode cavity is viewed in plan view upon taking a cross section of a cathode slab along a plane perpendicular to the cell's longitudinal axis.
- the outer casing (housing) is desirably of steel, preferably of nickel-plated steel.
- the casing wall thickness is desirably between about 0.30 and 0.50 mm, typically between about 0.30 and 0.45 mm, preferably between about 0.30 and 0.40 mm, more desirably between about 0.35 and 0.40.
- a reusable or reactivatable vent preferably, a reseatable plug vent mechanism may be employed as a primary vent mechanism.
- the reseatable plug is preferably designed to activate when the cell's internal gas pressure reaches a threshold level pressure PI of between about 100 and 300 psig (689.5 x 10 3 and 2069 x 10 3 pascal gage), desirably between about 100 and 200 psig (689.5 x 10 3 and 1379 x 10 3 pascal gage).
- PI threshold level pressure
- one more spaced apart groove vents preferably a single continuous groove vent (coined vent) comprising at least one stamped or scored region on the casing surface may be used as the primary venting mechanism.
- the groove vent can be stamped, cut or scored into the casing surface so that the underlying thinned region ruptures at pressure PI between about 250 and 800 psig (1724 x 10 3 and 5515 x 10 3 pascal gage). In such design the reseatable plug may be eliminated.
- the groove vent is located in proximity to the closed end of the casing in proximity to the positive terminal.
- the groove boundary may be closed or open.
- the groove can be a straight or substantially straight, preferably parallel to a casing edge.
- the groove width is typically small, for example, under about 1 mm.
- groove or "groove vent” as used herein is not intended to be restricted to any particular width or shape, but rather encompasses any depression on the cell's casing resulting in a thinned underlying material region expected to crack or rupture when gas pressure within the cell reaches a target threshold level.
- a groove vent located on the casing wide face and parallel to a wide edge, preferably in proximity to the casing closed end.
- the thinned material underlying the groove vent can be designed to rupture when gas pressure within the cell reaches a design burst pressure PI of between about 250 and 800 psig (1724 x 10 3 and 5515 x 10 3 pascal gage).
- a design burst pressure PI of between about 250 and 800 psig (1724 x 10 3 and 5515 x 10 3 pascal gage).
- the thinned material underlying groove may have a thickness between about 0.04 and 0.15 mm.
- the thinned material underlying the groove vent can be designed to rupture when gas pressure within the cell reaches a design burst pressure of between about 400 and 800 psig (2758 x 10 3 and 5515 x 10 3 pascal gage), desirably between about 400 and 600 psig (2758 x 10 3 and 4136 x 10 3 pascal gage).
- the thinned material underlying the groove may have a thickness between about 0.07 and 0.15 mm.
- the groove vent may be made by stamping the casing surface with a die, preferably a die having a cutting knife edge.
- a mandrel is held against the inside surface of the casing as the stamping die punches into the casing outside surface.
- the groove can be conveniently cut in a V shape having equal length sides or in the V shape having unequal length sides.
- the sides forming the V shaped groove desirably form an acute angle of about 40 degrees and in the latter case they form an angle preferably between about 10 to 30 degrees.
- a supplemental venting system comprising one or more laser welds securing the metal cover to the casing.
- Such welds may be comprise one or both a weak laser weld and a strong laser weld which may be designed to rupture at pressures higher than the rupture pressure PI of the thinned region underlying the groove vent.
- Such laser welds are preferably made using a Nd:Yag laser.
- there may be just one laser weld namely, a strong weld securing the entire circumferential edge of metal cover to the casing.
- the strong weld can function as the supplemental venting system designed to rupture under catastrophic conditions, for example, if the cell were inadvertently subjected to recharging under extremely high current or under extremely abusive conditions causing gas generation within the cell to rise abruptly to levels between about 800 psig and 2500 psig (5515 x 10 3 and 17235 x 10 3 pascal gage).
- the single groove vent functions may function as the cell's primary venting mechanism wherein the thinned material underlying the groove is designed to rupture if gas within the cell rises to a level between about 250 and 800 psig (1724 x 10 and 5515 x 10 pascal gage), more typically between about 400 and 800 psig (2758 x 10 3 and 5515 x 10 3 pascal gage).
- a supplemental venting system comprising a strong laser weld securing the edges of a metal cover to the casing.
- Such strong laser weld is designed to crack or rupture in the event of a catastrophic situation wherein gas within the cell rises abruptly to levels between about 800 psig and 2500 psig (5515 x 10 3 and 17235 x 10 3 pascal gage). In such case gas within the cell will quickly escape through the rupture and the cell's internal pressure will immediately return to nominal levels.
- the cell is balanced so that the cathode is in excess.
- the cell is balanced so that the ratio of theoretical capacity of the MnO 2 (based on a theoretical specific value of 370 mAmp-hr per gram MnO 2 ) divided by the mAmp-hr capacity of zinc (based on a theoretical specific value of 820 mAmp-hr per gram zinc) is between about 1.15 and 2.0, desirably between about 1.2 and 2.0, preferably between about 1.4 and 1.8. It has been determined that design of the flat alkaline cell herein at higher ratio of theoretical capacity of MnO 2 to theoretical capacity of zinc reduces the amount of overall swelling.
- the above ratio of theoretical capacity of MnO 2 to theoretical capacity of zinc can feasibly be as high as about 2.5 or even up to about 3.0 in order to reduce overall swelling, but cell design at such higher ratios above about 2.0 more significantly reduces cell capacity and thus becomes less desirable from that standpoint. It is not known with certainty why this occurs. It may be in part due to the fact the most all of the zinc gets discharged. In such case there is little if any zinc hydroxide intermediates left in the anode, which can cause swelling.
- the ratio of anode thickness to the casing outside thickness is desirably between about 0.30 and 0.40.
- the alkaline cell has the overall shape of a small cuboid (rectangular parallelepiped), typically having an outside thickness between about 5 and 10 mm, particularly a thickness between about 5 and 7 mm.
- the outside thickness is measured by the distance between the outside surface of opposing sides of the housing defining the short dimension of the cell.
- nonrechargeable alkaline cell of the invention can be used, for example, as a replacement for small size flat rechargeable cells.
- primary alkaline cell can be used as a replacement for same sized rechargeable nickel metal hydride cells, for example, the 7/5-F6 size rectangular rechargeable nickel metal hydride cell.
- a separator can be fabricated into a bag shape having an open end and opposing closed end. Such separator can readily be formed by wrapping a single sheet of separator material and closing one end with adhesive or by heat sealing. After the cathode disks are inserted into the cell casing, the wrapped separator is then inserted so that the separator surface faces the exposed cathode surface.
- the separator width is somewhat less than the width of the total anode cavity. This results in a gap between one short side of the separator and cathode disks.
- the gap is between about 2 and 4 mm, preferably between about 2 and 3 mm.
- Anode material can then be filled into the anode cavity through the separator open end. This results in a casing filled with anode material, cathode material, and separator therebetween, wherein there is a gap (void space) between one short side of the separator and the cathode. Additional alkaline electrolyte solution can now be added to the cell interior by pouring it into the gap.
- additional electrolyte solution may be added in small increments to said gap between separator and cathode, desirably with a short time interval between incremental electrolyte dispenses.
- a portion of the additional electrolyte may be added to the gap after the cathode is in place but before anode material is inserted into the anode cavity. Then anode material is inserted into the cell's anode cavity and thereafter additional electrolyte may be added to the gap.
- alkaline electrolyte After the final amounts of alkaline electrolyte is added to said gap between separator and cathode, the anode swells to push the separator surface flush against the cathode, thus causing the gap to disappear.
- the additional electrolyte solution can help to improve anode utilization and overall cell performance. It can also be a factor tending to retard cell swelling. If additional electrolyte is added to said gap, it is preferably added in dispense increments with sufficient time delay between dispenses, for example between about 1 to 4 minutes, to allow for absorption of the electrolyte.
- Fig. 1 is perspective view of the flat alkaline cell of the invention showing the cell's negative terminal end.
- Fig. 1 A is a perspective view of the flat alkaline cell of Fig. 1 showing the cell's positive terminal end.
- Fig. 2 is a cross sectional view of the cell shown in Fig. 1A taken along view lines 2-2.
- Fig. 2A is a cross sectional view of the cell shown in Fig.
- Fig. 3 is a cross sectional view of the cell shown in Fig. 1 A taken along view lines 3-3.
- Fig. 3 A is a cross sectional view of the cell shown in Fig. 1A taken along view lines 3-3 and showing a modified plug design.
- Fig. 4 is an exploded view of the components comprising the end cap assembly for the flat alkaline cell.
- Fig. 4 A is a perspective view of the modified plug shown in Figs. 2 A and
- Fig. 4B is a plan view of a cross section of the cell taken in a plane perpendicular to the cell's longitudinal axis along sight lines 4B-4B of Fig. 1A to show an elongated anode cavity.
- Fig. 4C is a plan view of a cross section of the cell to show another embodiment of the elongated anode cavity.
- Fig. 4D is a plan view of a cross section to show a third embodiment of the elongated anode cavity.
- Fig. 5 is an exploded view showing installation of the cell contents and end cap assembly into the cell casing (housing).
- FIG. 6 is a plan view of a metal cover plate shown laser welded along its edge with a strong weld and a weak weld to the inside surface of the cell's casing.
- Fig. 6A is a plan view of a metal cover plate shown laser welded along its edge with a strong weld and a weak weld to the crimped edge of the cell's casing.
- Fig. 7 is a view of the cell casing body showing an embodiment of strong and weak welds therein.
- Fig. 7 A is a view of the cell casing body showing an embodiment of curved strong and weak welds therein.
- Fig. 8 is a side view of the cell showing a groove within the casing body forming an underlying region of thinned material.
- FIG. 8 A is a side view of the cell showing a plurality of grooves within the casing body wherein each groove forms an underlying region of thinned material.
- Fig. 9 is a cross sectional view of a representative groove shown in Figs. 8 and 8A.
- Fig. 10 is a top plan view of the metal cover laser welded to the cell casing shown in Fig. 10 A.
- Fig. 10A is a side view of an embodiment of the flat alkaline cell showing a single grooved vent on a wide side of the casing.
- Fig. 11 is cross sectional view along the wide side of the cell shown in Fig.
- Fig. 12 is cross sectional view along the short side of the cell shown in Fig. 10A.
- FIG. 13 is an exploded view of the components comprising the end cap assembly for the flat cell shown in Fig. 10A.
- Fig. 14 shows fabrication of the separator for the cell of Fig. 10A from a single sheet of separator material.
- Fig. 14A shows the process of forming a wrapped separator sheet.
- Fig. 14B shows the finished wrapped separator having an open end and opposing closed end.
- Fig. 15 shows an alternative type of V shaped groove cut fro the grooved vent.
- Fig. 16 shows an embodiment wherein there is a gap between a short side of the separator and the cathode.
- Fig. 17 shows an alternative embodiment similar to the cell of Fig. 11 except that a paper washer is stacked over the welded metal cover instead of a plastic extender.
- FIG. 1-5 A specific embodiment of the flat alkaline cell 10 of the invention is shown in Figs. 1-5.
- Cell 10 has at least two flat opposing sides, which are parallel to the cell's longitudinal axis.
- Cell 10 is preferably of rectangular shape, that is, a cuboid, as shown best in Figs. 1 and 1A.
- the term "cuboid” as used herein shall mean the geometrical definition, which is a rectangular parallelepiped. However, cell 10 can also be a parallelepiped.
- Outer casing 100 as shown in the figures preferably is of cuboid shape, thus without having any integral cylindrical sections.
- Cell 10 typically has a thickness smaller than its width and a width smaller than its length.
- the cell 10 preferably comprises a cuboid shaped casing (housing) 100, preferably of nickel plated steel.
- the inside surface of casing 100 is preferably coated with a layer of solvent based carbon coating, for example, available under the trade designation TIMREX E-LB carbon coating.
- casing (housing) is preferably of solvent based carbon coating, for example, available under the trade designation TIMREX E-LB carbon coating.
- Casing 100 is bounded by a pair of opposing large flat walls 106a and 106b; a pair of opposing small flat walls 107a and 107b; a closed end 104; and opposing open end 102.
- the cell's thickness is defined by the distance between the outside surfaces of walls 106a and 106b.
- the cell's width is defined by the distance between the outside surface of walls 107a and 107b.
- Casing 100 is desirably coated on its inside surface with a layer of carbon or indium to improve conductivity.
- Cell contents comprising a anode 150, cathode 110 and separator 140 therebetween are supplied through the open end 102.
- the anode 150 comprises particulate zinc
- the cathode 110 comprises MnO2.
- the cathode 110 may be in the form of a plurality of slabs 110a having a hollow central core 110b through its thickness, shown best in Fig. 5.
- the cathode slabs 110a preferably are of overall rectangular shape.
- the cathode slabs 110a are inserted into casing 100 and stacked vertically one on top of the other along the cell's length as shown in Figs. 2, 3 and 5.
- Each cathode slab 110a may be recompacted after it is inserted into casing 100. Such recompaction assures that the outside surface of each cathode slab 110a is in intimate contact with the inside surface of casing 100.
- the hollow central cores 110b within cathode slabs 110a are aligned to form one continuous central core along the cell's longitudinal axis 190, for receiving anode slurry 150.
- the cathode slab 110a closest to the closed end 104 of casing 100 can have a bottom surface which abuts and covers the inside surface of closed end 104.
- Cathode slabs 110a can be die cast or compression molded.
- cathode 110 can be formed of cathode material which is extruded through a nozzle to form a single continuous cathode 110 having a hollow core.
- Cathode 1 10 can also be formed of a plurality of slabs 110a with hollow core 110b, wherein each slab is extruded into casing 100. After cathode 110 is inserted, an electrolyte permeable separator 140 is then positioned within central core 110b of each slab 110a so that the outside surface separator 140 abuts the inside surface of the cathode as shown in Figs. 2, 3, and 5.
- the inside surface of each cathode slab 110a, which defines said hollow central core 110b, is preferably a curved surface. Such curved inside surface improves the mechanical strength of the slab during transfer and handling and also provides more uniform contact between the separator 140 and the cathode 110.
- the central core 110b of slabs 110a are aligned to form one continuous core as above described.
- the continuous core forms the anode cavity 155 for housing anode material 150.
- the anode cavity is within the central core of cathode slab 110a which is devoid of cathode material.
- the anode cavity 155 has an elongated or oblong shape when viewed in plan view (Fig. 4B) upon taking a cross section of a cathode slab 110a along a plane perpendicular to the cell's longitudinal axis 190.
- the cross section of the anode cavity 155 defined by boundary perimeter 156 may be elliptical or substantially elliptical.
- Cavity 155 has a long dimension Dl which is greater than its short dimension D2. Cavity 155 thus can have a diameter (or width), Dl, which is greater along the path of a plane parallel to the wide side (106a or 106b) of the cell than its diameter (or width), D2, in the direction of a plane parallel to a narrow side (107a or 107b) of the cell.
- anode cavity 155 may take the shape of an ellipse or appear to be substantially elliptical when viewed in cross section along a plane perpendicular to the central longitudinal axis 190.
- the opposing long boundary edges 158a and 158b of the anode cavity when viewed in cross section Fig.
- the cavity 155 has an elongated or oblong shape when viewed in cross section (Fig. 4B, 4C and 4D) obtained by cutting a cathode slab 110a by a plane perpendicular to the cell's central longitudinal axis 190.
- elongated shape can be an elongated polygon or a rectangular shape as shown in Fig. 4C.
- the axes defining the long dimension D 1 and short dimension D2 of cavity 155 defined by boundary perimeter 156 may be skewed as shown in Fig. 4D.
- the cavity 155 when viewed in cross section (Fig. 4B) obtained by cutting a cathode slab 110a by a plane perpendicular to the cell's central longitudinal axis 190 (Fig. 1A) has at least a portion of its boundary perimeter 156 which is curved.
- Cavity 155 is desirably of an oblong configuration.
- substantially all of the boundary perimeter 156 defining cavity 155 is curved.
- at least the opposing surfaces 157a and 157b of cavity 155 closest to the opposing narrow sides 107a and 107b of the cell are curved as shown best in Fig. 4B.
- substantially all of the perimeter 156 of cavity 155 when viewed in cross section as above described is curved.
- the opposing long edges 158a and 158b are preferably outwardly curved (convex) when viewed from outside casing 100 as shown in Fig. 4B.
- long edges 158a and 158b may be flat or substantially flat.
- long edges 158a and 158b may be slightly inwardly curved (concave) or lightly outwardly curved (convex) or may be of convoluted curvature, for example having alternating convex and concave surfaces.
- short edges 157a and 157b may be slightly inwardly curved (concave) or lightly outwardly curved (convex) or may be of convoluted curvature, for example, having alternating convex and concave surfaces.
- the long diameter (Dl) will normally be in the direction along a plane parallel to a wide side (106a or 106b) of the cell and the small diameter (D2) is in the direction along a plane parallel to a narrow side (107a or 107b) of the cell as shown in Fig. 4B.
- Cavity 155 when viewed in cross section as above described has at least some curvature and is characterized in that the ratio of D1/D2 is greater than 1.0 reflecting that it is of elongated or oblong configuration.
- the shape of the cavity 155 when viewed in a cross section taken along a plane perpendicular to longitudinal axis 190 desirably has a symmetrical oblong configuration having a ratio of D1/D2 greater than 1.0.
- the dimensions Dl and D2 are perpendicular to each other as shown in Fig. 4B.
- the shape of cavity 155 in when viewed in such cross section is of oblong shape and may be elliptical or substantially elliptical.
- Anode 150 is preferably in the form of a gelled zinc slurry comprising zinc particles and aqueous alkaline electrolyte. The anode slurry 150 is poured into the central core 155 of the cell along the cell's longitudinal axis 190. Anode 150 is thus separated from direct contact with cathode 110 by separator 140 therebetween. After the cell contents are supplied, the cell assembly 12 (Fig.
- the closed end 104 of the casing can function as the cell's positive terminal.
- the closed end 104 can be drawn or stamped to provide a protruding positive pip or else a separate end plate 184 having a protruding pip 180 can be welded to the closed end 104 of the casing as shown in Fig. 1 A.
- the components comprising a specific embodiment of the end cap assembly 12 are shown best in Fig. 4.
- End cap assembly 12 comprises an elongated anode current collector 160; an insulating sealing member 220; a metal cover 230 which lies over sealing member 220; a metal rivet 240 which penetrates partially through insulating sealing member 220; a plastic spacer 250, which insulates rivet 240 from metal cover 230; a rubber vent plug 260 seated within a cavity 248 in rivet 240; a vent pip cap 270 over rubber plug 260; a plastic extender seal 280; and a negative terminal plate 290 over plastic extender 280.
- the cell 10 is a small size flat cell, for example a cuboid shaped cell having an overall thickness between about 5 and 10 mm, an edge of flange 161 will, therefore, terminate close to an inside surface of casing 100.
- Applicants have modified the subassembly comprising current collector
- the insulating sealing skirt 226 surrounds the widest part, namely flange 1 1 of anode current collector 160. Insulating skirt 161 thus provides a barrier between the edge of current collector flange 161 and the inside surface of casing 100.
- the insulating skirt 161 has been determined to reduce the production of corrosive chemicals, typically metal containing complexes or compounds, in the space between flange 161 and the inside surface of casing 100 during cell discharge. Such corrosive chemicals, if produced in quantity, can interfere with cell performance and promote cell gassing.
- the widest part of the anode current collector 160 namely, flange 161 is between about 0.5 and 2 mm, preferably between about 0.5 and 1.5 mm from the housing inside surface.
- Such modified design of the invention in turn made the reseatable rubber vent plug assembly suitable as a viable vent mechanism for the flat primary alkaline cell herein described.
- the anode current collector 160 comprises an elongated shaft or wire 162 terminating at its bottom end in tip 163 and terminating at its top end in an outwardly extending integral flange 161, which is preferably at right angles to shaft 162.
- the edge of outwardly extending flange 161 can be closer to the inside surface of casing 100 than shaft 162.
- Insulating sealing member 220 has a top panel 227 and opposing open bottom 228. Insulating sealing member 220 is preferably of nylon 66 or nylon 612, which is durable, resistant to alkaline, and permeable to hydrogen.
- insulating sealing member 220 may be composed of polypropylene, talc filled polypropylene, sulfonated polyethylene or other polyamide (nylon) grades, which are durable and hydrogen permeable. Insulating member 220 is preferably rectangular so that it can fit snugly within the open end 102 of casing 100.
- the opposing side walls 226a and opposing end wall 226b extending from top end 227 of insulating member 220 forms a downwardly extending skirt 226 around top panel 227. Skirt 226 defines the bounds of open bottom 228 of said insulating sealing member 220.
- a metal cover 230 which can be a metal plate having an aperture 234 therethrough.
- Rivet 240 can be of nickel plated steel or stainless steel. Rivet 240 has a cavity 248 within head 247. Cavity 248 passes completely through rivet head 247 and the rivet shaft 245.
- the flange 161 of current collector 160 is inserted into the open bottom 228 of insulating sealing member 220 so that the flange 161 of the current collector 160 is surrounded and protected by insulating skirt 226 of said sealing member 220. As shown in Fig. 4, flange portion 161 of current collector 160 has an aperture 164 therethrough. The base 246 of rivet 240 can be passed through said aperture 164 and riveted to said flange 161 to keep the current collector 160 in electrical contact with said rivet.
- insulating skirt 226 provides a barrier between flange 161 of the current collector and the inside surface of the cell's casing 100. It has been determined that narrow gaps, for example, less than about 0.5 mm, between any surface of the anode current collector 160 and the cell's casing 100 inside surface can provide regions in which corrosive by-products can occur during alkaline cell discharge. This in turn can passivate neighboring regions of the anode current collector 160 and promote gassing.
- the downward extending skirt 226 of insulating sealing member 220 is intended to suixound outwardly extending portions of the current collector 160 such as integral flange 161, thereby providing a barrier between the widest portions of the current collector 160 and casing 100.
- the metal cover 230 is positioned over the top panel 227 of the insulating sealing member 220 so that aperture 234 through metal cover 230 is aligned with aperture 224.
- a plastic spacer disk 250 is inserted over metal cover 230 so that the aperture 252 through spacer disk 250 is aligned with aperture
- the base 246 of rivet 240 is passed through aperture 252 of plastic spacer 250 and also through aperture 234 of metal cover 230.
- Base 246 of rivet 240 is also passed through aperture 224 of insulating sealing member 220 and aperture 164 of current collector flange 161.
- Plastic spacer 250 insulates rivet 240 from metal cover 230.
- the base 246 of rivet shaft 245 extends through aperture
- Plug 260 is preferably of a compressible, resilient material which is resistant to alkaline electrolyte.
- a preferred material for plug 260 is a rubber, preferably a neoprene or EPDM (ethylene-propylene diene terpolymer) rubber or other alkaline resistant compressible rubber.
- the surface of the plug 240 is preferably coated with a nonwetting agent such as Teflon (polytetrafluoroethylene), asphalt or a polyamide.
- a metal vent pip cap 270 is then inserted over plug 260. The vent pip cap 270 is pressed onto plug 260 with force sufficient to compress the plug by about 0.55 mm.
- Plug 260 compression can be adjusted so that the seal can withstand internal pressures typically between about 100 and 300 psig (6.895 x 10 5 and 20.69 x 10 5 pascal gage), desirably between about 100 and 200 psig (6.895 x 10 5 and 13.79 x 10 s pascal gage). Higher degree of compression of plug 260 is also possible, if desired, to enable the seal to withstand higher pressures, that is, higher than 300 psig (20.69 x 10 5 pascal gage).
- vent pip cap 270 can have several downwardly extending segments which fit into indentations or crevices 253 within the top surface of plastic spacer 250 as vent cap 270 is pressed onto plug 260. This is shown best in Fig. 5. After vent pip cap 270 is inserted over plug 260, thereby compressing said plug within rivet head cavity 248, vent cap 270 is welded to rivet head 247. Plug 260 is thereby maintained compressed within rivet head cavity 248. The plastic extender member 280 is placed over the vent cap head 271. The vent cap head
- Terminal end plate 290 (negative terminal), is then welded to vent cap head 271. Vent cap 270 is thus welded to both end plate 290 and rivet 240.
- Terminal end plate 290 is constructed of a conductive metal having good mechanical strength and corrosion resistance such as nickel plated cold rolled steel or stainless steel, preferably, nickel plated low carbon steel.
- a completed end cap assembly 12 is formed with terminal end plate 290 in permanent electrical contact with current collector 163.
- the completed end cap assembly 12 is then inserted into the open end 102 of casing 100.
- the current collector shaft 162 penetrates into anode slurry 150.
- the edge of metal cover 230 is welded, preferably by laser welding, to the top peripheral edge 104 of the casing.
- End terminal plate 290 is in electrical contact with current collector 160 and anode 150, and thus forms the cell's negative terminal for the zinc/MnO2 alkaline cell embodiment described herein. It will be appreciated that the negative terminal plate 290 is electrically insulated from casing 100 by plastic extender 280. Rivet 240 and anode current collector 160 is electrically insulated from casing 100 by plastic spacer 250 and insulating sealing member 220. As shown in Figs. 1A, 2 and 3, pip 180 at the opposing closed end of casing 100 forms the cell's positive terminal.
- the pip 180 can be integrally formed from the closed end 104 of the casing or may be a formed of a separate plate 184, which is separately welded to the closed end as shown in Fig. 1 A.
- the completed cell is shown in the perspective views of Figs. 1 and 1A and in cross sectional views of Figs. 2 and 3.
- plug 260 becomes unseated within rivet head cavity 248. This will allow gas to escape from within the cell interior through rivet head cavity 248, then through vent aperture 272 of vent cap 270 and to the external environment. As pressure within the cell is reduced, plug 260 becomes reseated within rivet head cavity 248.
- the cell can be provided with a second venting device which functions to supplement the reseatable plug vent 260.
- the supplemental vent may be designed to activate in a catastrophic situation, for example, if the user inadvertently attempts to recharge primary cell 10 for long periods of time using battery chargers designed for flat rechargeable cells.
- the cell 10 of the invention is designed to be a primary (nonrechargeable cell). Despite ample written notice on the cell label that the cell should not be recharged, it is always possible that the user will inadvertently attempt to recharge the cell in a conventional flat battery charger, for example, one designed for recharging a flat nickel metal hydride cell.
- plug vent 260 will unseat thereby releasing pressure as the internal gas pressure reaches the design threshold, desirably a pressure between about 100 and 300 psig (6.895 x 10 5 and 20.69 x 10 5 pascal gage). Plug 260 will unseat again should the pressure again build up upon continued charging for long periods of time. Such process of plug unseating and reseating can be repeated many times resulting in a pulsed release of gas pressure from the cell interior.
- the venting system of the invention may include primary and supplemental venting mechanisms.
- the primary venting mechanism is activated when gas pressure within the cell builds up to a design pressure threshold level, PI. It is desirable to have a supplemental venting mechanism which activates at a higher pressure level, P2, in the event that the primary vent mechanism fails to operate properly or if the cell is subjected to an abusive situation resulting in a rapid build up of gas pressure.
- a reseatable plug 240 is employed as a primary venting mechanism, which activates at a design threshold pressure PI, between about 100 and 300 psig.
- a supplemental venting mechanism can be a weak laser weld anywhere within a cut out portion of the casing body 100 or end cap assembly 12. The weak laser weld is designed to rupture when gas pressure within the cell reaches a higher pressure P2, desirably between about 400 and 800 psig. There may be a strong weld, preferably contiguous with the weak weld.
- the strong weld is designed to rupture at yet a higher pressure P3, desirably between about 800 and 2500 psig.
- the supplemental venting system can be provided by forming a weak laser weld along a portion of the laser welded interface between the metal cover 230 and inside surface of casing 100. (Metal cover 230 is used to close the open end 102 of casing 100.)
- a weak laser weld 310a can be applied between a major portion of one of the metal cover long edges 230a and casing edge 108a as shown in Fig.6.
- the weak laser weld 310a can be applied so that the weld thickness is such that it will crack or rupture desirably as gas within the cell builds up to a pressure of between about 400 and 800 psig (2748 x 10 3 and 5515 x 10 3 pascal).
- the depth of penetration of the weak weld can be adjusted to achieve the desired rupture pressure.
- a rupture pressure between about 400 and 800 psig (2748 x 10 3 and 5515 x 10 3 pascal gage) can be achieved with a depth of penetration of the laser weld between about 2 and 4 mil (0.0508 and 0.102 mm).
- the weak weld may desirably run along a major portion of at least one of the long edges 230a of metal cover 230.
- the weak weld begins at a point 312a which is at least about 1 mm from the corner intersecting short edge 108c and long edge 108a of casing 100.
- the length of the weak weld may be at least about 10 mm, typically about 13 mm.
- the remainder of the perimeter interface between the edge of metal cover 230 and the casing edge (casing edges 107c, 107d, and 106d) (Fig.
- a strong laser weld 310b designed to rupture at a higher pressure level, for example, a gas pressure between about 800 and 2500 psig (5515 x 10 3 and 17235 x 10 3 pascal gage), typically between about 800 and 1600 psig (5515 x 10 3 and 11030 x 10 3 pascal gage).
- the depth of penetration of the strong weld can be adjusted to achieve the desired rupture pressure.
- a rupture pressure between about 800 and 2500 psig (5515 x 10 3 and 17235 x 10 3 pascal gage) can be achieved with a depth of penetration of the laser weld between about 5 and 7 mil (0.127 and 0.178 mm).
- the depth of penetration of the strong weld can be more finely adjusted allowing the weld to rupture at a desired pressure level, for example, between about 1300 and 1600 psig (8962 x 10 3 and 11030 x 10 3 pascal gage).
- a desired pressure level for example, between about 1300 and 1600 psig (8962 x 10 3 and 11030 x 10 3 pascal gage).
- the casing edge 108 defined by opposing long edges 108a and 108b and opposing short edges 108c and 108d are crimped so that such edges lie in about the same plane as metal plate 230.
- the edges 230a and 230b of metal plate 230 can be laser welded directly to the crimped casing edge 180.
- a strong laser weld 310b can be applied between plate edge 230b and casing edges 108b, 108c, and 108d; a weak laser weld 310a can be applied between plate edge 230a and casing edge 108a.
- the cut out portion may be polygonal (Fig. 7) or may have at least a portion of its boundary curved (Fig. 7A).
- a metal plate e.g. plate 400 (Fig. 7) or plate 500 (Fig. 7A) may by inserted into such cut out portions.
- the edges of metal plate 400 (Fig. 7) or metal plate 500 (Fig. 7A) may be laser welded to the casing to close the cut out portion.
- the welds may desirably be in the form of a strong laser weld 410b and a contiguous weak laser weld 410a as shown in the embodiment of Fig. 7.
- the welds may in the form of a strong laser weld 510b and preferably a contiguous weak laser weld 510a as shown in the embodiment of Fig. 7 A.
- the strong and weak welds can be achieved using different types of lasers operating within a range of peak power output.
- the following are nonlimiting examples of a weak and strong welds produced using a Nd:Yag laser.
- the weak weld as above described will crack or rupture as above described when gas pressure within the cell reaches a threshold pressure of between about 400 and 800 psig (2758 x 10 3 and 5515 x 10 3 pascal gage).
- the strong weld will rupture when the gas pressure within the cell reaches a threshold pressure of between about 800 and 2500 psig (5515 x 10 3 and 17235 x 10 3 pascal gage), typically between about 800 and 1600 psig (5515 x 10 3 and 11030 x 10 3 pascal gage).
- the weak weld in particular provides a supplemental venting system allowing gas to escape from within the cell should the cell be abused as above described.
- the supplemental venting mechanism may be in the form of a grooved vent, that is, one or more grooves on the surface of casing 100 which results in an underlying thinned material region.
- the depth of the groove and thickness of the underlying thinned material region can be adjusted so that the thinned region ruptures when gas pressure within the cell rises to a pressure P2 greater than PI .
- the reseatable plug can be eliminated and a laser weld can be used as the primary vent mechanism activating at a pressure PI .
- the supplemental venting mechanism may be a thinned material region underlying a groove on the casing surface. The thinned material may be designed to rupture at a higher pressure level P2.
- One groove may have underlying thinned regions of small thickness allowing it to rupture as gas within the cell builds up to the design pressure level, P
- a second groove on the casing surface which may be contiguous with or spaced apart from the first groove, may have an underlying thinned region designed to rupture if gas pressure within the cell builds up to a higher pressure, P2.
- a groove such as groove 600a (Fig. 8) can be formed on the casing surface so that the thinned material underlying the groove will rupture when gas pressure within the cell reaches a pressure of between about 400 and 800 psig (2758 x 10 3 and 5515 x 10 3 pascal gage).
- the non grooved portions of the casing wall may typically have an average wall thickness of between about 0.3 and 0.50 mm, desirably between about 0.3 and 0.45 mm.
- the groove is formed so that the underlying thimied material has a thickness typically of between about 0.07 and 0.08 mm.
- the groove is formed so that the underlying thinned material has a thickness of about 0.074 mm, such underlying material will rupture when the gas pressure within the cell reaches a level of about 435 psig (2999 x 10 3 pascal gage).
- a groove 600 which may, for example, be in the form of a groove 600a or 600b (Figs. 8-8A) on the casing surface may be made by stamping the surface of the casing with a die, preferably a die having a cutting knife edge. A mandrel is held against the inside surface of the casing as the stamping die punches into the casing outside surface.
- the thickness of the underlying thinned region 610 (Fig. 9) primarily determines the pressure at which the thinned region will rupture.
- the groove cut may desirably be V-shaped (Fig. 9), which is obtained preferably with a stamping die having a knife edge.
- the V shaped groove desirably has an acute angle, ,.of about 40 degrees.
- the groove 600 can be made by other methods, for example, by chemical etching.
- the thinned material underlying groove 600 is preferably the same as the casing material, typically of nickel plated cold rolled steel.
- the groove 600 may have boundaries which are straight or curved or may have a combination of straight and curved portions.
- the groove 600 may have boundaries which are rectangular, polygonal or oblong.
- the groove may have at least a portion of their boundaries which are convoluted, that is partially convex and partially concave.
- the groove boundary may be closed or open.
- the groove can be a straight or substantially straight, preferably parallel to a wide edge 108a of the casing (Fig.
- the groove 600a (Figs. 8 and 8A) can desirably be located parallel to casing wide edge 108a and about 10 mm therefrom and may have a length of about 8 mm.
- the second groove 600b may be parallel to groove 600a and about 10 mm form the positive terminal 180 (closed end).
- Groove 600b may have a length of about 8 mm.
- the underlying material thickness of each groove 600a and 600b may be different so that the underlying material in each ruptures when gas pressure within the cell reaches different pressure levels.
- the thinned material underlying groove a 600a can be designed to rupture when gas pressure within the cell reaches a design burst pressure of between about 250 and 800 psig.
- a design burst pressure of between about 250 and 800 psig (1724 x 10 3 and 5515 x 10 3 pascal gage)
- the thinned material underlying groove 600a has a thickness between about 0.04 and 0.15 mm.
- the thinned material underlying groove 600a can be designed to rupture when gas pressure within the cell reaches a design burst pressure of between about 400 and 800 psig (2758 x 10 3 and 5515 x 10 3 pascal gage).
- the thinned material underlying the groove 600a has a thickness between about 0.07 and 0.15 mm.
- the thinned material underlying second groove 600b can be designed to rupture when gas pressure within the cell ruptures in a catastrophic situation in the event that the cell be misused and gas pressure within the cell rapidly rises to a level of between about 800 and 1600 psig (5515 x 10 3 and 11030 x 10 3 pascal gage).
- the thinned material 610 underlying groove 600b typically has a thickness of between about 0.15 and 0.35 mm.
- Example 1 (Weak Weld using Nd:Yag Laser)
- the weak weld used to weld metal cover 230 to casing 100 along casing edge 106c can be produced by employing an Nd:Yag laser.
- the laser is operated at a frequency of about 100 Hertz.
- the peak power output per pulse is about 35 Watts.
- the average power output is 0.5 Killiwatts.
- the pulse width (cycle time between peak power) is about 0.7 millisecond.
- the laser feed rate (rate of movement of the laser along weld path) is about 3 inches per minute.
- a uniform weld along long edge 106c of the casing is produced thereby welding abutting long edge 230a of metal cover 230 thereto.
- the weld had a unifo ⁇ n depth of penetration between about of 2 and 4 mils (0.0508 and 0.102 mm), typically about 3 mil (0.0762 mm).
- the weld cracks when pressure within the cell reaches a level of between about 400 and 800 psig (2757 x 10 3 and 5515 x 10 3 pascal gage) and thereby functions as a supplemental vent should the operation of primary vent (plug 260) become compromised.
- Example 2 (Strong Weld using Nd:Yag Laser
- the strong weld used to weld metal cover 230 to casing 100 along casing edges 106d, 107c and 107d (Fig. 6 or 6A) can be produced by employing an Nd:Yag laser.
- the strong weld used to weld metal cover 230 to casing 100 along casing edge 106d, 107c and 107d can be produced by employing an Nd:Yag laser.
- the laser is operated at a frequency of about 12 Hertz.
- the peak power output per pulse is about 46 Watts.
- the average power output is 0.65 Killiwatts.
- the pulse width (cycle time between peak power) is about 5.9 millisecond.
- the laser feed rate rate (rate of movement of the laser along weld path) is about 2 inches per minute.
- a uniform weld along long edges 106d, 107c, and 107d of the casing is produced thereby welding abutting edges of metal cover 230 thereto as shown in Fig. 6.
- the weld had a uniform depth of penetration of between about 5 and 7 mils (0.127 and 0.178 mm), typically about 6 mil 0.152 mm).
- the weld cracks when pressure within the cell reaches a level of between about 800 and 2500 psig (5515 x 10 3 and 17235 x 10 3 pascal gage), typically between about 800 and 1600 psig (5515 x 10 3 and 11030 x lO 3 pascal).
- Yag laser could be operated at higher peak power of about 125 Watts to produce the weak weld and a peak power of about 150 Watts to produce the strong weld. Such operation at higher peak power allows the laser to be moved along the weld path (feed rate) at higher speed.
- the plug 260 may be modified so that it occupies less space within the cavity in rivet head 247 housing plug 260.
- a specific embodiment of such improved design is shown as plug 260 in Figs. 2A, 3A, and 4A.
- plug 260 occupies less space within rivet head cavity 248 than the frustum design for the plug shown in Figs. 2, 3 and 4.
- the amount of free space within cavity 248 housing said plug is greater than about 10 percent, desirably between about 10 and 40 percent.
- the amount of free space within the rivet cavity of plug 260 shown in the frustum embodiment shown in Figs. 2, 3, and 4 is typically less than about 10 percent. It has been determined that the greater amount of free space, typically between about 10 and 40 percent within rivet head cavity 248, which is achieved with the modified plug design (Fig. 4A) assures more effective operation of the plug in an abuse situation, for example, if the cell is inadvertently subjected to charging as above described.
- Such modified plug 260 desirably unseats as gas pressure within the cell reaches the design threshold level, e.g. between about 100 and 300 psig.
- the greater amount of free space within rivet head cavity 248 accommodates any gradual KOH crystalline buildup therein, which may occur if the cell is abused by inadvertent charging. There is nevertheless enough free space remaining within rivet head cavity 248 to allow the plug
- plug 260 to operate effectively in unseating itself to allow gas pressure to release as pressure within the cell builds up to the design threshold level.
- the shape of plug 260 can be altered as shown in Fig. 4 A to achieve the greater amount of free space within rivet head cavity 248.
- plug 260 has a cylindrical base 262 and integrally formed cylindrical body 261 of smaller diameter extending therefrom.
- the ratio of diameter of body 261 to the diameter of base 262 can be adjusted as required to achieve the desired greater amount of free space within rivet head cavity 248, typically between about 10 and 40 percent, after modified plug 260 (Fig. 4A) has been compressed within the cavity.
- the cylindrical shape of body 261 withstands well the pressure of compressing plug 260 within rivet head cavity 248.
- Modified plug 260 (Fig.
- plug 4A is compressed within rivet head cavity 248 by applying a force to the top surface 263 of the plug and then welding vent cap 270 to the rivet head 247.
- the body 261 of plug 260 assumes a bulbous configuration as shown in Figs. 1 A and 2A.
- gas pressure within the cell builds up to a threshold level, desirably between about 100 and 300 psig, the plug unseats itself thereby letting gas from within the cell to escape through vent apertures 272 within vent cap 270.
- a threshold level desirably between about 100 and 300 psig
- the plug unseats itself thereby letting gas from within the cell to escape through vent apertures 272 within vent cap 270.
- Plug 260 is desirably of an elastomeric, preferably rubber material which is sufficiently compressible and resilient, yet resists chemical attack or physical degradation upon contact with alkaline electrolyte.
- a preferred rubber material for plug 260 is vulcanized EPDM rubber, desirably having a Durometer hardness between about 80 and 85.
- the modified configuration for plug 260 as shown in Fig. 4A is preferred, it will be appreciated that other shapes of the plug can help achieve the desired increase in free space within rivet head cavity 248 which houses the plug.
- the body 261 of the plug could be slightly sloped instead of cylindrical as shown in Fig. 4A.
- the width of rivet head cavity can be enlarged in the direction of wide side of the cell (Fig. 2A). In such case the rivet head cavity 248 will be elongated along one axis, that is, in the direction of the wide side of the cell (Fig. 2A).
- the alkaline cell 100 can be is a small sized rectangular (cuboid), typically having a thickness between about 5 and 10 mm, particularly a thickness between about 5 and 7 mm as measured by the outside* surface of the casing in the direction of the cell thickness.
- the cell width may typically be between about 12 and 30 mm and the cell length may typically be between about 40 and 80 mm.
- the alkaline cell 10 of the invention can be used as a replacement for same sized rechargeable nickel metal hydride cells, for example, standard 7/5-F6 size rectangular cells.
- the 7/5-F6 size cell has thickness of 6.1 mm, width of 17.3 mm, and length of about
- anode 150 comprises manganese dioxide
- an anode 150 comprises zinc and electrolyte.
- the aqueous electrolyte comprises a conventional mixture of KOH, zinc oxide, and gelling agent.
- the anode material 150 can be in the form of a gelled mixture containing mercury free (zero-added mercury) zinc alloy powder. That is, the cell has a total mercury content less than about 100 parts per million parts (ppm) of zinc by weight, preferably less than 50 parts mercury per million parts of zinc by weight.
- the cell also preferably does not contain any added amounts of lead and thus is essentially lead-free, that is, the total lead content is less than 30 ppm, desirably less than 15 ppm of the total zinc in the anode.
- Such mixtures can typically contain aqueous KOH electrolyte solution, a gelling agent (e.g., an acrylic acid copolymer available under the tradename CARBOPOL C940 from B.F. Goodrich), and surfactants (e.g., organic phosphate ester-based surfactants available under the tradename GAP AC RA600 from Rhone Poulenc).
- a gelling agent e.g., an acrylic acid copolymer available under the tradename CARBOPOL C940 from B.F. Goodrich
- surfactants e.g., organic phosphate ester-based surfactants available under the tradename GAP AC RA600 from Rhone Poulenc.
- the cathode 110 desirably has the following composition: 87-93 wt% of electrolytic manganese dioxide (e.g., Trona D from Kerr-McGee), 2-6 wt% (total) of graphite, 5-7 wt% of a 7-10 Normal aqueous KOH solution having a KOH concentration of about 30-40 wt%; and 0.1 to 0.5 wt% of an optional polyethylene binder.
- the electrolytic manganese dioxide typically has an average particle size between about 1 and 100 micron, desirably between about 20 and 60 micron.
- the graphite is typically in the fonn of natural, or expanded graphite or mixtures thereof.
- the graphite can also comprise graphitic carbon nanofibers alone or in admixture with natural or expanded graphite.
- Such cathode mixtures are intended to be illustrative and are not intended to restrict this invention.
- the anode material 150 comprises: Zinc alloy powder 62 to 69 wt% (99.9 wt% zinc containing indium containing 200 to 500 ppm indium as alloy and plated material), an aqueous KOH solution comprising 38 wt% KOH and about 2 wt% ZnO; a cross-linked acrylic acid polymer gelling agent available commercially under the tradename "CARBOPOL C940" from B.F.
- the term zinc as used herein shall be understood to include zinc alloy powder which comprises a very high concentration of zinc, for example, at least 99.9 percent by weight zinc. Such zinc alloy material functions electrochemically essentially as pure zinc.
- the zinc powder mean average particle size is desirably between about 1 and 350 micron, desirably between about 1 and 250 micron, preferably between about 20 and 250 micron.
- the zinc powder may have a mean average particle size of about 150 micron.
- the zinc particles in anode 150 can be of acicular or spherical shape. The spherical shaped zinc particles are preferred, since they dispense better from dispensing nozzles used to fill the relatively small anode cavity of the cell with zinc slurry.
- the bulk density of the zinc in the anode is between about 1.75 and 2.2 grams zinc per cubic centimeter of anode.
- the percent by volume of the aqueous electrolyte solution in the anode is preferably between about 69.2 and 75.5 percent by volume of the anode.
- the cell 10 can be balanced in the conventional manner so that the mAmp- hr capacity of MnO 2 (based on 370 mAmp-hr per gram MnO 2 ) divided by the mAmp-hr capacity of zinc (based on 820 mAmp-hr. per gram zinc) is about 1. However, it is preferred to balance the cell so that the cathode is in significant excess.
- cell 10 is balanced so that the total theoretical capacity of the MnO divided by the total theoretical capacity of the zinc is between about 1.15 and 2.0, desirably between about 1.2 and 2.0, preferably between about 1.4 and l! ⁇ , more preferably between about 1.5 and 1.7.
- Cell balance with such cathode excess has been determined to reduce the amount of cathode expansion because there is a smaller percentage conversion of MnO 2 to MnOOH on discharge based on total cell weight. This in turn reduces the amount of swelling of the cell casing.
- the above ratio of theoretical capacity of MnO 2 to theoretical capacity of zinc can feasibly be as high as about 2.5 or even up to about 3.0 in order to reduce overall swelling, but cell design at such higher ratios above about 2.0 more significantly reduces cell capacity and thus becomes less desirable from that standpoint. It has been determined desirable to have the casing 100 wall thickness between about 0.30 and 0.50 mm, typically between about 0.30 and 0.45 mm, preferably between about 0.30 and 0.40 mm, more desirably between about 0.35 and 0.40.
- Cell 10 is preferably of cuboid shape (Figs. 1 and 2) having an overall thickness desirably between about 5 and 10 mm. In combination therewith the cell is balanced so that the cathode is in excess.
- the cell is balanced so that the ratio of theoretical capacity of the MnO 2 (based on 370 mAmp-hr per gram MnO 2 ) divided by the mAmp-hr capacity of zinc (based on 820 mAmp-hr. per gram zinc) is between about 1.15 and 2.0, desirably between about 1.2 and 2.0, preferably between about 1.4 and 1.8.
- the ratio of anode thickness to the casing outside thickness is desirably between about 0.30 and 0.40.
- the separator 140 can be a conventional ion porous separator consisting of an inner layer of a nonwoven material of cellulosic and polyvinylalcohol fibers and an outer layer of cellophane. Such a material is only illustrative and is not intended to restrict this invention.
- Casing 100 is preferably of nickel plated steel. Casing 100 is desirably coated on its inside surface with a carbon coating, preferably a graphitic carbon coating.
- Such graphitic coatings can, for example, be in the form of aqueous based graphite dispersion, which can be applied to the casing inside surface and subsequently dried under ambient conditions.
- the graphitic carbon improves conductivity and can indirectly reduce cell gassing by reducing the chance of surface corrosion occurring on the casing inside surface.
- the metallic cover 230, negative terminal plate 290 and positive terminal plates 180 are also preferably of nickel plated steel.
- Current collector 160 can be selected from a variety of known electrically conductive metals found to be useful as current collector materials, for example, brass, tin plated brass, bronze, copper or indium plated brass.
- Insulating sealing member 220 is preferably of nylon 66 or nylon 612. The following a specific examples showing comparative performance using same size rectangular cell with different cell balance.
- the fresh cell in each case had a thickness of 5.6 mm, a width of 17 mm, and length of 67 mm. (All dimensions are outside dimensions without a label around the casing, unless otherwise specified.)
- the casing 100 wall thickness was the same at 0.38 mm for each of the cells tested.
- the casing 100 for each cell was nickel plated steel coated on its inside surface with graphitic carbon.
- the cell configuration was the same in each case, as depicted in the drawings (Figs. 1-5).
- the edge of the wide portion (flange 161) of the anode current collector 160 was about 0.5 mm from the inside surface of casing 100.
- Circumventing skirt 226 of insulating sealing member 220 surrounded said wide portion (flange 161) of current collector 160, thereby providing a barrier between it and the inside wall surface of casing 100.
- All cell components were the same as above described and each cell tested had a vent end cap assembly 12 as shown in the figures. The only difference was in cell balance and anode composition.
- the comparative cell (Comparative Example) was balanced so that the balance ratio, namely, theoretical capacity of the MnO2 (based on 370 mAmp-l r per gram MnO 2 ) divided by the mAmp-hr capacity of zinc (based on 820 mAmp- hr per gram zinc) was 1.1.
- test cell of Test Example 1 was balanced so that the balance ratio, namely, theoretical capacity of the MnO 2 divided by the theoretical capacity of the zinc was 1.25.
- the test cells of Test Examples 2 and 3 were balanced so that the theoretical capacity of the MnO 2 divided by the theoretical capacity of the zinc was 1.6 and 2.0, respectively.
- the comparative and test cells in the following examples were discharged intermittently at cycles of 90 milliWatts power on followed by three hours power off, until a cutoff voltage of 0.9 Volts was reached. (Such intermittent discharge simulates typical usage of portable solid state digital audio players, which are typically capable of using the MP3 audio format.) The actual service hours total was then recorded and the amount of swelling of the cell casing was evaluated and recorded.
- Comparative Example (Comparative Cell) A comparative test cell 10 of rectangular (cuboid) configuration and end cap assembly shown in the drawings was prepared.
- the cell as defined by the casing 100 outside dimensions had a length of about 67 mm and a width of about 17 and a thickness (before discharge) of about 5.6 mm.
- the anode 150 and cathode 110 had the following composition.
- Anode Composition Wt.% Zinc 70.0 Surfactant 2 0.088 (RA 600) Electrolyte 3 (9 Normal KOH) 29.91 100.00 Notes: 1.
- the zinc particles had a mean average particle size of about 150 micron and were alloyed and plated with indium to yield a total indium content of about 200 ppm. 2.
- Organic phosphate ester-based surfactant solution RA600 from Rhone Poulenc. 3.
- the electrolyte solution contained gelling agents Waterlock A221 and Carbopol C940 comprising in total about 1.5 wt.% of the electrolyte solution.
- Cathode Composition Wt.% MnO 2 (EMD) (Trona D from Kerr McGee) 87.5 Graphite 1 (NdG 15 natural graphite) 7.4 Electrolyte (9 Normal KOH) 5.1 100.0
- Graphite NdG15 is natural graphite from Nacional De Grafite.
- the casing 100 wall thickness for the cell was 0.38 mm.
- the fresh cell 10 had a length of 67 mm, thickness of 5.6 mm and a width of 17 mm.
- the cell's anode 150 and cathode 110 was balanced so that the theoretical capacity of the MnO 2 (based on 370 mAmp-hr per gram MnO ) divided by the mAmp-hr capacity of zinc (based on 820 mAmp- hr per gram zinc) was 1.1.
- the anode had 2.8 grams zinc.
- the cathode had 6.89 grams MnO 2 .
- the anode 150, cathode 110 and separator 140 comprised about 66 percent of the external volume of casing 100 of configuration shown in Figs. 1 and 1A.
- the ratio of anode thickness to the casing outside thickness was about 0.35.
- the thicknesses are measured along a plane perpendicular to the longitudinal axis 190, across the outside thickness (small dimension) of the cell.
- the cell was discharged intermittently at cycles of 90 milliWatts with "power on” followed by three hours "power off, until a cutoff voltage of 0.9 Volts was reached.
- the actual service life was 24.5 hours.
- Test Cell Example 1 A test cell 10 of rectangular configuration and of same size as in the comparative example was prepared.
- the anode 150 and cathode 110 had the following composition.
- Graphite NdGl 5 is natural graphite from Nacional De Grafite.
- the casing 100 wall thickness for the test cell was 0.38 mm.
- the fresh cell 10 had a length of 67 mm, thickness of 5.6 mm and a width of 17 mm.
- the cell's anode 150 and cathode 110 was balanced so that the theoretical capacity of the MnO 2 (based on
- the anode had 2.56 grams of zinc.
- the cathode had 7.11 grams MnO 2 .
- the anode, cathode, electrolyte and separator comprised about 66 percent of the external volume of casing 100, that is, as measured between its closed end 104 and open end 102.
- the ratio of anode thickness to the casing outside thickness was about 0.35. The thicknesses are measured along a plane pe ⁇ endicular to the longitudinal axis 190, across the outside thickness (small dimension) of the cell.
- Test Cell Example 2 A test cell 10 of rectangular configuration and of same size as in the comparative example was prepared.
- the anode 150 and cathode 110 had the following composition.
- the zinc particles had a mean average particle size of about 150 micron and were alloyed and plated with indium to yield a total indium content of about 200 ppm.
- Organic phosphate ester-based surfactant solution RA600 from Rhone Poulenc 3.
- the electrolyte solution contained gelling agents Waterlock A221 and Carbopol
- Cathode Composition Wt.% MnO 2 (EMD) (Trona D from ⁇ Kerr McGee) 87.5 Graphite 1 (NdGl 5 natural graphite) 7.4 Electrolyte (9 Normal KOH) 5.1 100.0 Notes: 1. Graphite NdGl 5 is natural graphite from Nacional De Grafite. The casing 100 wall thickness for the test cell was 0.38 mm. The fresh cell 10 had a length of 67 mm, thickness of 5.6 mm and a width of 17 mm.
- the cell's anode 150 and cathode 110 was balanced so that the theoretical capacity of the MnO 2 (based on 370 mAmp-hr per gram MnO 2 ) divided by the mAmp-hr capacity of zinc (based on 820 mAmp-hr per gram zinc) was 1.6.
- the anode had 2.01 grams of zinc.
- the cathode had 7.13 grams MnO 2 .
- the anode, cathode and separator comprised about 66 percent of the external volume of casing 100.
- the ratio of anode thickness to the casing outside thickness was about 0.35. The thicknesses are measured along a plane pe ⁇ endicular to the longitudinal axis 190, across the outside thickness (small dimension) of the cell.
- Test Cell Example 3 A test cell 10 of rectangular configuration and of same size as in the comparative example was prepared.
- the anode 150 and cathode 110 had the following composition. ⁇ Anode Composition: Wt.% Zinc 1 52.0 Surfactant 2 0.083 (RA 600) El eeccttrroollyyttee 33 47.92 (9 Normal KOH) 100.00
- the zinc particles had a mean average particle size of about 150 micron and were alloyed and plated with indium to yield a total indium content of about 200 ppm.
- the electrolyte solution contained gelling agents Waterlock A221 and Carbopol C940 comprising in total about 1.5 wt.% of the electrolyte solution.
- Cathode Composition Wt.% MnO 2 (EMD) (Trona D from Kerr McGee) 87.5 Graphite 1 (NdGl 5 natural graphite) 7.4 Electrolyte (9 Normal KOH) 5.1 100.0
- the casing 100 wall thickness for the test cell was 0.38 mm.
- the fresh cell 10 had a length of 68 mm, thickness of 5.6 mm and a width of 17 mm.
- the anode had 1.61 grams of zinc.
- the cathode had 7.13 grams MnO 2 .
- the anode, cathode and separator comprised about 66 percent of the external volume of casing 100.
- the ratio of anode thickness to the casing outside thickness was about 0.35. The thicknesses are measured along a plane pe ⁇ endicular to the longitudinal axis 190, across the outside thickness (small dimension) of the cell.
- the cell was discharged intermittently at cycles of 90 milliWatt with "power on” followed by three hours “power off, until a cutoff voltage of 0.9 Volts was reached.
- the actual service life was 18.5 hours.
- the casing had swelled from a thickness of 5.6 mm to a thickness of 5.87 mm. (Thickness measured between outside surface of side walls 106a and 106b shown in Fig. 1A).
- the edge of the wide portion (flange 161) of the anode current collector 160 was about 0.5 mm from the inside surface of casing 100 and was surrounded by insulating barrier 226.
- the balance ratios have been defined as the theoretical capacity of the MnO 2 (based on 370 mAmp-hr per gram MnO 2 ) divided by the mAmp-hr capacity of zinc (based on 820 mAmp-hr per gram zinc).
- swelling of the flat test cell increases significantly from an overall thickness of 5.6 mm to 6.13 mm when the cell's balance ratio (theoretical capacity of MnO 2 to theoretical capacity of zinc) is about 1.1.
- test Example 1 balance ratio of 1.25
- the cell swells less, namely from 5.6 mm to 6.03 mm.
- test Example 2 (balance ratio of 1.6) the cell swells from 5.6 mm to 5.95 mm.
- test Example 3 (balance ratio of 2.0) the cell swells even less from 5.6 mm to 5.87 mm.
- the cell service life becomes moderately less (from 24.5 hours to 20.9 hours) as balance ratios increase between 1.1 and 1.6 and more significantly less (18.5 hours) at the highest balance ratio of 2.0.
- a reusable or reactivatable vent mechanism such as reseatable plug 260 is desirable, it can be eliminated as in the embodiment shown in Figs. 10-17.
- reseatable plug 260 can be eliminated and a weak laser weld can be used as a primary vent mechanism which cracks or ruptures at the activation pressure of the reseatable plug, namely a pressure PI preferably between about 100 to 300 psig (689 x 10 3 and 2068 x 10 3 pascal).
- the supplemental venting mechanism may be a thinned material region underlying a groove (groove 600a or 600b), on the casing surface. The thinned material may be designed to rupture at a higher pressure level P2.
- one or more groove vents preferably a single groove vent 600a or 600b can be used as the primary venting mechanism.
- the single groove vent such as 600a or 600b can be cut or scored into the casing surface so that the underlying thinned region ruptures at pressure PI .
- the single groove vent 600b is located in proximity to the closed end of the casing in proximity to positive terminal 180 as shown in Fig. 10A.
- the groove boundary may be closed or open.
- the groove can be a straight or substantially straight, preferably parallel to a wide edge 108a of the casing (Fig. 8-8A).
- groove vent 600b located on the casing wide face 106a (Fig. 10A).
- groove vent 600b comprises the only groove vent on the casing surface.
- groove 600b may be a straight groove parallel to the closed end of the cell (Fig. 10A)
- the ends of straight groove 600b may be equidistant from the narrow sides of the casing.
- groove 600b may be about 8 mm in length and about 5 to 10 mm from the closed end 104 of the casing as shown in Fig. 10A.
- the straight groove 600b is desirable, it is not intended to limit such groove to such configuration.
- the groove vent 600b may have other configurations, such as curvilinear shape or partially straight and partially curvilinear and may form an open or closed boundary pattern.
- the thinned material underlying groove 600b (Fig. 10A) can be designed to rupture when gas pressure within the cell reaches a design burst pressure of between about 250 and 800 psig (1724 x 10 3 and 5515 x 10 3 pascal gage). To achieve such range in burst pressure between about 250 and 800 psig (1724 x 10 and 5515 x 10 pascal gage), the thinned material underlying groove 600b has a thickness between about 0.04 and 0.15 mm.
- the thinned material underlying groove 600b can be designed to rupture when gas pressure within the cell reaches a design burst pressure of between about 400 and 800 psig (2758 x 10 3 and 5515 x 10 3 pascal gage).
- a design burst pressure of between about 400 and 800 psig (2758 x 10 3 and 5515 x 10 3 pascal gage).
- the thinned material underlying the groove 600b has a thickness between about 0.07 and 0.15 mm.
- the width of groove 600b (Fig. 10A) at its base (adjacent thinned area 610) may typically be between about 0.1 and 1 mm, more typically between about 0.1 and 0.5 mm.
- Groove 600b may be made by stamping the surface of casing 100 with a die, preferably a die having a cutting knife edge. A mandrel is held against the inside surface of the casing as the stamping die punches into the casing outside surface. Groove 600b can be cut in a V shape having equal length sides shown in Fig. 9 or in the V shape having unequal length sides as shown in Fig. 15. In the former case (Fig.
- the sides forming the V shaped groove desirably has an acute angle, a, of about 40 degrees and in the latter case (Fig. 15) it has an angle preferably between about 10 to 30 degrees.
- Such welds may be comprise one or both a weak laser weld and a strong laser weld which may be designed to rupture at pressures higher than the rupture pressure of the thinned region underlying groove 600b. As earlier described such laser welds may be made using an Nd: Yag laser.
- weld 310a and 310b contiguous weak and strong laser welds, for example, weld 310a and 310b, used to secure metal cover 230 to casing 100 have been shown and described with reference to Figs. 6 and 6 A.
- there may be just one laser weld namely, a strong weld 310b securing the entire circumferential edge of metal cover 230 to casing 100 as shown in Fig. 10.
- the strong weld 310 may be designed to rupture under catastrophic conditions for example, if the cell were inadvertently subjected to recharging under extremely high current or under extremely abusive conditions causing gas generation within the cell to rise abruptly to levels between about 800 psig and 2500 psig (5515 x 10 3 and 17235 x 10 3 pascal gage).
- the single groove 600b functions as the cell's primary venting mechanism wherein the thinned material 610 (Figs.
- underlying groove 600b is designed to rupture if gas within the cell rises to a level between about 250 and 800 psig (1724 x 10 3 and 5515 x 10 3 pascal gage), more typically between about 400 and 800 psig (2758 x 10 and 5515 x 10 pascal gage).
- the strong laser weld 310b securing the edges of metal cover 230 to casing 100 is designed to function as the cell's supplemental venting system.
- Such strong laser weld 310b is designed to crack or rupture in the event of a catastrophic situation when gas pressure within the cell rises abruptly to levels between about 800 psig and 2500 psig.
- the rupture of laser weld 310b under such catastrophic situations will allow gas to escape therethrough quickly reducing gas pressure within the cell to nominal levels.
- the cell shown in Figs. 10 and 10A is shown in the cross section view of Fig. 11 taken through a plane parallel to large side 106a and in cross section view of Fig. 12 taken through a plane parallel to narrow side 107a.
- the reseatable plug 260 inco ⁇ orated the previous specific embodiment (Fig. 2 and Fig.4) has been eliminated. It was also possible to eliminate related components forming the cell's end cap assembly 12, namely, the elimination of vent pip cap 270 and plastic spacer disk 250 shown in earlier embodiments (Figs. 2 and 4).
- rivet 240 can be welded directly to the negative terminal plate 290 as shown best in Figs. 11 and 12. Welding of the rivet 240 to the negative terminal plate 290 can be efficiently performed by electrical resistance welding.
- Rivet 240 is preferably of brass, desirably brass plated with a layer of tin typically between about 1 to 3 micron thick.
- the negative terminal plate 290 is preferably of nickel plated cold rolled steel.
- terminal plate 290 It has been determined that the welding can be most efficiently performed and a uniform weld readily achieved when the thickness of the terminal plate 290 at the weld site is about 4 mil (0.102 mm). It is desirable that the remaining portion of terminal plate 290 be thicker, preferably about 8 mil (0.204 mm) for overall strength. Since 8 mil thick cold roll steel plate is commercially available, it was determined that the central portion 290a (Fig. 13) of terminal plate 290, that is, the weld area can be readily be stamped with a mandrel to reduce its thickness of the plate at the weld site to about 4 mil (0.102 mm). The stamping is preferably done from the top side of terminal plate 290 (Fig. 13) to form stamped area 290a.
- the central portion 290a (Fig. 13) of terminal plate 290 can be stamped in various configurations, for example, rectangular, circular or oval.
- the long dimension of the stamped area 290a in the direction of wide side of the casing
- the rivet head 247 diameter to allow for placement of the welding electrodes (not shown).
- the long dimension of the stamped area 209a may be about 4 mm and the short dimension of the stamped area 290a may be between about 3 to 4 mm.
- anode material 150 comprising zinc and cathode material comprising MnO 2 with separator 140 therebetween is inserted into the cell casing 100 through open end 102.
- the end cap assembly 12 (Fig. 13) is formed by inserting metal cover 230 over insulating seal member 220 so that the protruding head 221 of the seal member is inserted into aperture 234 of the metal cover 230.
- the rivet shaft 240 is then inserted through aperture 234 in metal cover plate 230 (Fig. 13).
- the rivet shaft 240 is insulated from metal cover 230 by protruding head 221 of the insulating seal member 220.
- the top flange portion 161 of anode current collector 160 preferably of brass, is pushed up against the bottom surface of sealing member 220 and fastened to the lower portion of rivet 240, preferably of brass or tin plated brass by conventional riveting technique, thus electrically connecting current collector 160 to rivet 240.
- the upper portion 249b of rivet 240 is desirably solid as shown in Figs.
- metal cover 230 is welded by a strong laser weld (rupture pressure preferably 800 to 2500 psig) to the inside surface of casing 100.
- the central portion of metal cover 230 is indented or depressed forming well region
- KORITE asphalt sealant is a nonhardening asphalt comprising a mixture of about 55 to 70 wt.% asphalt and 30 to 45% asphalt.
- the viscosity of the sealant can be adjusted by adjusting the asphalt/solvent ratio and temperature of the sealant as it is being applied.
- the well region 235 within cover plate 230 and rivet head 247 are heated before the asphalt sealant is poured into the well region 235.
- the asphalt sealant is at a viscosity of about 1000 centipoise as it is being poured into well region 235.
- the asphalt fills depressed region 235 and provides additional sealing protection between rivet 240 and sealing member 220.
- the subassembly comprising metal cover 230 rivet 240 and insulating seal member 220 is then inserted into the open end 102 of the casing so that the current collector shaft 162 penetrates into the anode material 150 (Figs. 11 and 12).
- a plastic extender seal 280 (Fig. 13) can be inserted over rivet 240. This is done by inserting rivet head 247 through aperture 282 of the plastic extender 280.
- a flat negative metal plate 290 is then placed onto the top surface of plastic extender 280 so that it contacts the protruding rivet head 247.
- the negative plate 290 is then welded to rivet heat 247 to complete construction of end cap assembly 12.
- the completed end cap assembly 12 in cell 10 is shown in Figs. 11 and 12.
- a heat conductive medium desirably a liquid or metal to metal cover 230.
- the heat conductive medium is preferably a liquid which can be conveniently placed within the well or trough region 235 on the surface of metal cover 230. Such heat conductive medium can absorbs a substantial portion of the heat generated during the laser welding.
- the metal cover can be precooled to a temperature less than ambient room temperature (21°C), preferably to a temperature approaching the freezing point of water and even lower. Such precooling can also help to keep metal cover
- metal cover 230 from exceeding 100°C during the welding operation. Additionally, the metal cover 230 can be precooled and heat conductive medium also applied to the metal cover 230. Plastic extender seal 280 is press fitted into casing 100 above metal cover 230. If the metal cover 230 is not kept sufficiently cool during laser welding, seal 280 could possibly overheat to a point adversely affecting its physical properties. This could result in a loss in radial compression, that is, a loosing of the tight fit between seal 280 and casing 100, in turn providing a path to the casing exterior for electrolyte which may have leaked into the region between metal cover 230 and metal cover 280.
- metal cover 230 it is recommended to keep metal cover 230 sufficiently cool, or apply a heat conductive medium to the metal cover to assure that sufficient heat is absorbed during the laser welding operation.
- a convenient way of accomplishing this is to simply add a small amount of cool deionized water, e.g at about 5 to 10°C, to the trough region 235 of metal cover 230. This keeps the temperature of metal cover 230 below about 100°C, in turn allowing seal 280 (Figs. 11 and 12) to stay within a favorable working temperature.
- sealant e.g. asphalt sealant
- a metal block (optionally precooled) can be applied in contact with metal cover 230.
- the metal block typically of steel, can absorb sufficient heat during the welding operation to assure that the metal cover 230 does not reach temperatures above about 100°C.
- water can be added to well area 235 to keep metal cover 230 cool during the laser operation, it will be appreciated that other suitable coolants can be used.
- a cool aqueous solution of polyvinylalcohol and potassium hydroxide may be used instead of pure water.
- the polyvinylalcohol will coat out on the top surface of metal cover 230 thereby providing additional sealing protection between metal cover 230 and seal 280.
- Such solution can also be applied directly to the underside of plastic seal 280
- a gelling agent can be added to the aqueous cooling solution supplied to well 235.
- the term gelling agent is intended to include conventional gelling agents as well as superabsorbents.
- Such gelling agents include polyacrylic acid, polyacrylates, the sodium salt of an acrylic acid copolymer, carboxymethyl cellulose, sodium carboxymethyl cellulose, starch graft copolymers and the like.
- the gelling agent will coat the surface of metal cover 230 to provide additional sealing protection between metal cover 230 and seal 280.
- the gelling agent can be applied as a powder to the underside of plastic seal 280 using compression rollers and the like (Figs.
- the paper washer can be pre saturated with an aqueous solution comprising a gelling agent or with an aqueous solution of polyvinylalcohol and potassium hydroxide.
- Such prewetting of paper washer 295 provides additional sealing protection should electrolyte leak into the region between metal cover 230 and terminal plate 290 (Fig. 17.
- a separate layer comprising gelling agent powder can be pressed onto the underside of washer 295, using compression rollers and the like or dispersed within the fibrous network comprising washer 295, as described in U.S. Patent 4,999,264.
- a separate protruding metal member 180 can be welded to opposing closed end 104 of the cell.
- metal member 180 is in electrical contact with the cell casing and thus forms the cell's positive terminal.
- End plate 290 is in electrical contact with rivet 240 which in turn in electrical contact with anode current collector 160 and thus forms the cell's negative terminal.
- the current collector 160 (Figs. 4 and 13) is shown as an elongated member in the shape of a nail terminating at its top end in a horizontally extending flange 161 with an aperture 164 therethrough.
- the current collector shaft 162 is shown as a straight nail in the embodiment of Fig. 4 and as straight nail having a curved surface in the embodiment shown in Fig. 13.
- rivet 240 may be a solid member having a head portion 247 (Fig. 11) with an integrally formed elongated shaft portion (not shown) in the shape of a nail extending downwardly from head 247 and at least partially penetrating into anode 150.
- the current collector shaft can be oriented so that it is centrally located along the cell's central longitudinal axis 190.
- the head portion 247 of such rivet can still be welded to the terminal end plate 290 in the manner above described.
- Another specific embodiment of the flat cell of the invention is shown in Fig. 17.
- a paper washer 295 for example of Kraft paper, can be employed between metal cover 290 and the negative terminal plate 290 instead of plastic extender 280.
- the Kraft washer is durable and provides the necessary electrical insulation between metal cover 230 and terminal plate 290.
- Such design reduces the height of rivet head 247 thereby compacting the total height of the end cap assembly 12. It also has the advantage of eliminating the need to mold a plastic extender 280. This in turn results in more available volume for anode/cathode active material within the cell interior.
- the other components of the cell shown in Fig. 17 are essentially the same as those shown and described with respect to the cell shown in Figs. 10-12). It will be appreciated that the rivet 240 shown in Fig.
- each of the cell embodiments are intended to have a conventional film label wrapped around the cell casing. Suitable plastic film for such label are known in the art and typically comprise polyvmylchloride. The label can be imprinted with desired design or indicia. Such labels may be adhesive coated, typically at the edges and applied by wrapping around the casing surface.
- the label can be applied in the form of a sleeve and heat shrunk onto the casing surface.
- a typical label 12 is shown in Fig. 17.
- Separator Fabrication In the cell embodiment shown in Figs. 10-13 the separator 140 can be conveniently formed from separator material conventionally employed in alkaline cells. For example, typically of cellulose or cellulosic and polyvinylalcohol fibers.
- Cell 10 (Figs. 10-13) may typically be of cuboid configuration having an overall thickness of about 6 mm, a width of about 17 mm and a length of between about 35 and 67 mm.
- separator 140 is inserted so that the separator faces the exposed cathode surface.
- Separator 140 for use in the above described flat cell (Figs. 10-13) is conveniently made by rolling a flat separator sheet as shown in Figs. 14-14B.
- the near edge 140a is first folded inwardly in the direction FI along a bend line 140b which is displaced about 3 to 5 mm from edge 140a.
- a mandrel (not shown) can be placed against the separator surface 140d. Then separator far edge 140c can be wrapped around the mandrel so that edge 140c passes around edge 140a resulting in the partially wrapped configuration shown in Fig. 14A. Far edge 140c is continually wrapped over the separator surface in the direction F2 (Fig. 14A). Edge 140c can be adhesively secured to the separator surface. The bottom separator edge 142 may then be folded inwardly about 3 I mm over the back surface of the separator as shown in Fig. 14B and adhesively secured thereto. The use of adhesive to secure edge 140c and/or bottom separator edge 142 can be eliminated by simply folding bottom separator edge 140c in the direction F3 and then pressing it to form the bag configuration shown in Fig.
- the cathode shape also helps maintain the separator in the bag configuration shown in Fig. 14B.
- the mandrel (not shown) is removed.
- the resulting wrapped separator 140 (Fig. 14B) is in the shape of a bag having a closed boundary surface 148 with an open end 144 and opposing closed end 143.
- the separator boundary surface 148 defines a cavity 155 for insertion of anode material 150 therein.
- the anode cavity 155 preferably has an oblong configuration as shown in Fig. 14B.
- the short dimension of the oblong configuration of cavity 155 may typically be between about 2 and 3 mm for a cell 10 of cuboid configuration and overall thickness of about 6 mm.
- the long dimension of the oblong configuration is somewhat less than the width of the available space within the cell for the total anode cavity 155. This results in a gap 145 between one short side of the separator and cathode disks 110a as shown in Fig. 16.
- Gap 145 is between about 2 and 4 mm, preferably between about 2 and 3 mm.
- Anode material 150 can then be filled into the anode cavity 155 through the separator open end 143 resulting in a casing 100 filled with anode material 150, cathode material ,110, and separator 140 therebetween, wherein there is a gap 145 (void space) between one short side of the separator and the cathode as shown in Fig. 16. It has been determined that if desired, additional alkaline electrolyte solution can now be added to the cell interior by dispensing it directly into gap 145. The additional electrolyte may be dispensed into gap 145 by inserting a dispensing nozzle directly into said gap.
- a small quantity of additional electrolyte solution may be added into gap 145 after the anode 150 and cathode 110 are in place in the cell.
- a portion of the additional electrolyte may be added to gap 145 after the cathode is in place but before anode material is inserted into the anode cavity. Then anode material can be inserted into the cell's anode cavity and thereafter a final quantity of electrolyte may be added into gap 145.
- the additional electrolyte helps to improve anode utilization (percent anode actives discharged) and overall cell performance. It can also be a factor tending to retard cell swelling.
- electrolyte solution to the gap 145 between separator 140 and cathode 110 as above described avoids overflow problems which can occur if electrolyte is added directly to the anode. For example, if there is initially no gap between separator 140 and cathode 110 and additional electrolyte is added to the cell interior there may be an overflow of electrolyte into void space 146 (Fig. 11) above anode 150. Such overflow is undesirable, since it could cause wetting along the underside or edge of metal cover 230 after the metal cover 230 is placed in position covering the cell's open end 102.
- the amount of additional electrolyte solution to be added to gap 145 will be under about 1 gram.
- the electrolyte can be added in about four incremental equal dispenses with a time interval of between about 1 to 4 minutes between dispenses to allow sufficient time for the incremental amounts of electrolyte to be properly absorbed into the anode, cathode and separator.
- the anode 150 swells sufficiently to expand the anode cavity 155 bounded by separator surface 148.
- test Cell Example 4 A test cell 10 of rectangular configuration in the embodiment shown in Figs. 10-13 and of same size as in the comparative example was prepared. The amount of zinc in the anode was 2.01g and the amount of MnO2 was 6.69.
- the anode 150 arid cathode 110 had the following composition.
- the zinc particles had a mean average particle size of about 150 micron and were alloyed and plated with indium to yield a total indium content of about 200 ppm.
- Organic phosphate ester-based surfactant solution RM510 from Rhone Poulenc 3.
- the electrolyte solution contained gelling agents Waterlock A221 and Carbopol
- Cathode Composition Wt.% MnO 2 (EMD) (Trona D from Kerr McGee) 84.0 Graphite 1 (NdGl 5 natural graphite) 10.0 Electrolyte (9 Normal KOH) 6.0 100.0 Notes: 1. Graphite NdGl 5 is natural graphite from Nacional De Grafite. After the anode and cathode were in place in the cell casing an additional total 0.82g of 9N KOH electrolyte was added in four dispense increments (0.205g per increment) to the gap 145 between the separator 140 and the cathode (Fig. 16).
- the time interval between dispense increments was between about 1 and 4 minutes.
- the addition of the total of 0.82g electrolyte does not significantly change the above anode and cathode compositions. A portion of the total added electrolyte becomes absorbed into the anode, another portion becomes absorbed into the cathode and a portion becomes absorbed into the separator.
- the electrolyte added to gap 145 causes the anode to swell and thereby close gap 145. This technique allows additional electrolyte to be added to the anode without causing any overflow of electrolyte into the void space 146 above the anode.
- the casing 100 wall thickness for the test cell was 0.38 mm.
- the fresh cell 10 had a length of 67 mm, thickness of 5.6 mm and a width of 17 mm.
- the cell's anode 150 and cathode 110 was balanced so that the theoretical capacity of the MnO 2 (based on
- the anode had 2.01 grams of zinc.
- the cathode had 6.69 grams MnO 2 .
- the anode, cathode and separator comprised about 66 percent of the external volume of casing 100.
- the ratio of anode thickness to the casing outside thickness was about 0.35. The thicknesses are measured along a plane pe ⁇ endicular to the longitudinal axis 190, across the outside thickness (small dimension) of the cell.
- the cell was discharged intermittently at cycles of 90 milliWatts with "power on” followed by three hours “power off, until a cutoff voltage of 0.9 Volts was reached.
- the actual service life was 20.1 hours.
- the casing had swelled from a thickness of 5.6 mm to a thickness of 5.99 mm. (Thickness measured between outside surface of large side walls 106a and 106b shown in Fig. 1A or Fig. 12).
- swelling of the flat test cell increased significantly from an overall thickness of 5.6 mm to 6.13 mm when the cell's balance ratio (theoretical capacity of MnO 2 to theoretical capacity of zinc) is about 1.1.
- the present invention is intended to extend desirably to an overall battery shape that is flat in that a side of the outer casing along the length of the casing is substantially flat.
- the term "flat" is intended to extend to and include surfaces that are substantially flat in that the degree of curvature of such surface may be slight.
- the concept of the present invention is intended to extend to flat batteries wherein a side of the battery casing surface along the length of the casing has a flat polygonal surface.
- the battery may thus have the overall shape of a polyhedron with all sides of the outer casing being polygonal.
- the invention is also intended to extend to batteries wherein a side of the battery casing along its length has a flat surface, which is a parallelogram and wherein the overall shape of the battery is prismatic.
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- Primary Cells (AREA)
- Sealing Battery Cases Or Jackets (AREA)
- Gas Exhaust Devices For Batteries (AREA)
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Abstract
La présente invention concerne une pile alcaline dotée d'un boîtier plat, de préférence de forme cuboïde. Cette pile peut posséder une anode contenant du zinc et une cathode contenant MnO2. Le boîtier peut posséder une épaisseur globale relativement faible, généralement comprise entre environ 5 mm et 10 mm. Le contenu de la pile peut être délivré par une extrémité ouverte ménagée dans le boîtier et un ensemble capuchon d'extrémité inséré dans celui-ci de manière à sceller la pile. Il peut exister un espace entre le séparateur et la cathode pour l'insertion d'un électrolyte supplémentaire. L'ensemble capuchon d'extrémité comprend un mécanisme de type évent, de préférence un évent rainuré, qui peut être activé, lorsque la pression du gaz à l'intérieur de la pile atteint un niveau seuil généralement compris entre environ 250 et 800 psig (1724 x 103 et 5515 x 103 pour une mesure en pascals). Cette pile peut comporter un mécanisme évent supplémentaire, tel qu'une région soudée par laser sur la surface du boîtier, qui peut être activé à des niveaux de pression supérieurs.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/722,879 US7294429B2 (en) | 2003-01-03 | 2003-11-26 | Alkaline cell with flat housing |
PCT/US2004/037979 WO2005055342A2 (fr) | 2003-01-03 | 2004-11-12 | Pile alcaline dotee d'un boitier plat |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1716607A2 true EP1716607A2 (fr) | 2006-11-02 |
Family
ID=37024898
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP04820021A Withdrawn EP1716607A2 (fr) | 2003-11-26 | 2004-11-12 | Pile alcaline dotee d'un boitier plat |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1716607A2 (fr) |
JP (1) | JP2007512671A (fr) |
CN (1) | CN100466336C (fr) |
BR (1) | BRPI0416841A (fr) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
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CN104979499B (zh) * | 2015-05-20 | 2017-04-12 | 福建南平南孚电池有限公司 | 一次碱性电池的密封结构 |
US10492528B2 (en) * | 2015-08-11 | 2019-12-03 | Altria Client Services Llc | Power supply section configuration for an electronic vaping device and electronic vaping device |
JP6725351B2 (ja) * | 2016-07-14 | 2020-07-15 | 株式会社Gsユアサ | 蓄電素子及び蓄電素子の製造方法 |
WO2022036531A1 (fr) * | 2020-08-17 | 2022-02-24 | 宁德时代新能源科技股份有限公司 | Élément de batterie, batterie et procédé et appareil de préparation d'élément de batterie |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS59154742A (ja) * | 1983-02-23 | 1984-09-03 | Hitachi Maxell Ltd | 密閉型電池 |
JPH08321293A (ja) * | 1995-05-26 | 1996-12-03 | Japan Storage Battery Co Ltd | 非水電解液電池 |
JPH09259842A (ja) * | 1996-03-27 | 1997-10-03 | Sanyo Electric Co Ltd | 密閉型角形電池 |
JP3392656B2 (ja) * | 1996-09-19 | 2003-03-31 | 松下電器産業株式会社 | 防爆型電池缶 |
JPH11185714A (ja) * | 1997-12-25 | 1999-07-09 | At Battery:Kk | 非水電解液二次電池 |
ATE385347T1 (de) * | 1997-12-31 | 2008-02-15 | Duracell Inc | Alkalische elektrochemische zelle mit ausgeglichenem aktivstoffeninhalt |
US6081992A (en) * | 1998-07-02 | 2000-07-04 | Eveready Battery Company, Inc. | Electrochemical cell formed with big mouth open end can |
JP2001185113A (ja) * | 1999-12-28 | 2001-07-06 | Shin Kobe Electric Mach Co Ltd | 密閉型非水電解液二次電池 |
JP3863351B2 (ja) * | 2000-02-18 | 2006-12-27 | 松下電器産業株式会社 | 角形電池および角形電池の安全機構の製造方法 |
JP2003297323A (ja) * | 2002-04-04 | 2003-10-17 | Alps Electric Co Ltd | 二次電池の安全装置 |
-
2004
- 2004-11-12 CN CNB2004800350156A patent/CN100466336C/zh not_active Expired - Fee Related
- 2004-11-12 EP EP04820021A patent/EP1716607A2/fr not_active Withdrawn
- 2004-11-12 JP JP2006541283A patent/JP2007512671A/ja active Pending
- 2004-11-12 BR BRPI0416841-0A patent/BRPI0416841A/pt not_active IP Right Cessation
Non-Patent Citations (1)
Title |
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See references of WO2005055342A2 * |
Also Published As
Publication number | Publication date |
---|---|
CN1886846A (zh) | 2006-12-27 |
JP2007512671A (ja) | 2007-05-17 |
CN100466336C (zh) | 2009-03-04 |
BRPI0416841A (pt) | 2007-02-13 |
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