Patent Description:
Battery manufacturers have made great strides to improve the capacity of the cells to improve the length of time that electrical devices can be powered, while at the same time complying with the applicable dimensional standards for each cell size. As the shape and size of the batteries are often fixed, battery manufacturers must modify cell characteristics to provide increased performance. For example, battery manufacturers generally seek to maximize the total amount of active material, including both the positive electrode (cathode) material and negative electrode (anode) material.

Due to consumers' increasing need for high-capacity electrochemical cells offering maximal run-time, there is a constant need for improved electrochemical cell constructions offering improved discharge performance.

To provide increased electrochemical cell discharge performance, various embodiments are directed to electrochemical cell constructions comprising a hollow container housing a tubular cathode ring surrounding an interior of the hollow container. An electrochemical cell separator is positioned within the hollow interior of the cathode, and is compressed against the interior wall of the cathode to minimize the number of creases within the separator itself and/or to minimize the number of voids between the separator and the cathode. The invention is as defined in independent claims <NUM> and <NUM>. Preferred embodiments are as defined in the dependent claims. The separator according to the present invention is steamed in situ to further decrease the number of creases within the separator. The electrochemical cell according to claim <NUM> is heat-sealed to prevent the positive and negative active materials from coming in direct contact.

The invention is also a a method for forming a separator within an electrochemical cell according to independent claim <NUM>.

In various embodiments, the separator comprises at least two adjacent plies, and wherein the method further comprises heating at least a portion of the separator to bond at least a portion of the adjacent plies together. Moreover, the separator may comprise sidewalls pressed against the interior walls of the active material ring, and a closed bottom end, and wherein the method may further comprise heating at least a portion of the sidewalls of the separator to heat seal adjacent plies of the sidewalls together.

The method may additionally comprise steps for forming a convolute separator by winding a separator sheet around a die; and wherein pressing the separator into the opening comprises pressing the convolute separator into the opening. In certain embodiments, the convolute separator has a tubular sidewall and a closed bottom end, and the tubular sidewall comprises at least one overlapping portion comprising at least two adjacent layers of the separator sheet; and the method further comprising steps for heating at least a part of the overlapping portion to heat seal the adjacent layers of the separator sheet. Moreover, the method may further comprise steps for heating at least a portion of the closed bottom end to heat seal the closed bottom end. The separator sheet of certain embodiments may be a nonwoven fibrous separator sheet comprising thermoplastic fibers, and heating the at least a part of the overlapping portion may melt at least a portion of the thermoplastic fibers. In certain embodiments, heating at least a part of the overlapping portion comprises applying an at least substantially uniform heat to the interior surface of the separator.

The method according to the present invention comprises steaming the separator after pressing the separator into the opening. In various embodiments, pressing the separator into the opening comprises pressing the separator into the opening with a separator insertion tool; and expanding the separator comprises inflating an expandable bladder defining an exterior surface of the separator insertion tool to apply radial pressure the separator. In certain embodiments, inflating the expandable bladder comprises providing a heated fluid to an interior portion of the expandable bladder to apply heat to the separator.

The electrochemical cell according to the present invention comprises a container; a ring-shaped cathode disposed within the container wherein the cathode defines an exterior surface in contact with the container and an interior surface surrounding a hollow interior; an anode disposed within the hollow interior of the cathode; and a separator positioned between the cathode and the anode, wherein the separator has a tubular sidewall and a closed bottom end, wherein the tubular sidewall has at least one overlapping portion defined by at least two layers of a separator sheet being positioned between the cathode and the anode, and wherein at least part of the overlapping portions is heat sealed such that the at least two layers are bonded relative to one another and wherein the separator (<NUM>) is steamed while in place against the interior surface of the ring-shaped cathode (<NUM>).

In various embodiments, the separator is a nonwoven fibrous separator. Moreover, the nonwoven fibrous separator may comprise thermoplastic fibers and wherein portions of the thermoplastic fibers positioned within at least part of the overlapping portions may be melt-bonded relative to one another. Moreover, the separator sheet may be ion permeable and/or the overlapping portions of the separator sheet may be ion permeable.

In certain embodiments, the separator is a convolute separator comprising a spirally wound separator sheet having a first end and a second end, and wherein the first end overlaps the second end to form the heat-sealed overlapping portion. Moreover, at least a portion of the closed bottom end may be heat sealed. In certain embodiments, the separator has an open top end opposite the closed bottom end, and wherein the heat sealed portion extends between the open top end and the closed bottom end.

Certain embodiments are directed to a separator insertion tool for inserting a separator into a cylindrical electrochemical cell, the separator insertion tool comprising: a body portion for pressing the separator into the cylindrical electrochemical cell; and an expansion member for selectably expanding the body portion to apply expansive forces onto an interior surface of the separator.

In various embodiments, the body portion comprises a rigid cylindrical rod. Moreover, the expansion member comprises an inflatable bladder surrounding the rigid cylindrical rod. In certain embodiments, the separator insertion tool further comprises a fluid conduit extending at least partially through the body portion, and the separator insertion tool may be configured to selectably expand the inflatable bladder by directing fluid through the fluid conduit and into the interior of the inflatable bladder. Moreover, the separator insertion tool may further comprise a heating element configured to heat seal at least a portion of the separator and/or at least one steam vent configured to emit steam into the separator.

Referring now to <FIG>, a bobbin-style electrochemical cell <NUM> is shown according to one embodiment of the present invention. In the illustrated embodiment of <FIG>, the electrochemical cell is an alkaline cell having a manganese dioxide cathode active material and a zinc anode active material. However, it should be understood that the electrochemical cell may have any of a number of active material chemistries.

The alkaline electrochemical cell <NUM> shown in the exemplary embodiment and described herein is a cylindrical primary (non-rechargeable) battery cell of size LR6 (AA). However, it should be appreciated that the teachings of the present invention may be applicable to other alkaline electrochemical cells of other shapes and sizes, including LR03 (AAA), LR14 (C) and LR20 (D) size cylindrical battery cells, as examples. Moreover, although the following specifically discusses cylindrical electrochemical cells, it should be understood that various embodiments are applicable for other cell shapes, such as rectangular electrochemical cells, and/or the like. Additionally, the electrochemical cell <NUM> may be employed as a single cell battery or may be employed in a multiple cell battery.

The electrochemical cell <NUM> comprises a cylindrical container <NUM> that may be embodied as a metallic (e.g., steel) can, having a closed end <NUM>, an open opposite end <NUM>, and a cylindrical side wall extending between the opposite ends. The cylindrical container <NUM> is made of a suitable electrically conductive metal that may be formed into a desired shape and is adapted to seal the internal contents within the cell <NUM>. In the embodiment shown, the cylindrical container <NUM> also functions as the cathode current collector, and therefore exhibits good electrical conductivity. In one embodiment, the cylindrical container <NUM> may be plated with nickel and cobalt, such as may be achieved in an annealing process. The interior surface of the cylindrical container <NUM> may be coated with a graphite, if desired. In one example of an LR6 size cell, the cylindrical container <NUM> has a wall thickness of about <NUM> inch (<NUM> mils or <NUM>) and the cylindrical wall has an outside diameter of about <NUM> inch (<NUM>).

A positive contact terminal <NUM> comprising a plated steel or other conductive metal material is welded or otherwise secured onto the closed end <NUM> of the cylindrical container <NUM> in the illustrated embodiment of <FIG>. However, in certain embodiments, the positive contact terminal <NUM> may be integrally formed as a portion of the cylindrical container <NUM>. The positive contact terminal <NUM> has a protruding nubbin (i.e., protrusion), at its center which serves as the positive contact terminal of the cell <NUM>. Assembled onto the opposite open end <NUM> of the cylindrical container <NUM> is a collector and seal assembly made up of an anode current collector <NUM> (e.g., nail), a polymeric (e.g., nylon) seal <NUM> and a negative contact terminal <NUM>. The open end <NUM> of container <NUM> is crimped onto the seal <NUM> which abuts bead <NUM> to seal closed the open end <NUM> of container <NUM>. The negative contact terminal <NUM> forms a negative contact terminal of the cell <NUM>. Positive and negative contact terminals <NUM> and <NUM> are made of electrically conductive metal and serve as the respective positive and negative electrical terminals. Additionally, a jacket <NUM> may be formed about the exterior surface of the cylindrical container <NUM>, and may include an adhesive layer, such as a metalized, plastic film layer.

Disposed within the sealed volume of cylindrical container <NUM> is a positive electrode, referred to as the cathode ring <NUM>, generally positioned adjacent the interior surface of the cylindrical container <NUM>. The cathode has an exterior shape corresponding to the shape of the container (e.g., the cathode positioned within cylindrical container <NUM> has a generally cylindrical shape) with an interior surface defining an interior cavity therein. For example, the interior cavity may have a generally cylindrical shape, having an inside diameter ID. However, it should be understood that the interior cavity may have any of a variety of shapes. As other examples, the interior cavity may have a star-shape, an elliptical shape, a "gear" shape (having a plurality of interconnected cavities extending around a central hub, thus providing the general shape of a gear), and/or the like. A separator <NUM> is disposed in the interior cavity and contacts the interior surface of the cathode ring <NUM>. A negative electrode, referred to as the anode <NUM>, is disposed within the interior cavity inside the separator <NUM>. Additionally, an alkaline electrolyte solution, including water, is disposed within the sealed volume of the container <NUM> in contact with both the anode <NUM> and the cathode ring <NUM>.

As discussed herein, the illustrated cathode ring <NUM> of <FIG> includes manganese dioxide (MnO<NUM>) as the electrochemically active material of the positive electrode. Cathode ring <NUM> is generally formed of a mixture of manganese dioxide, graphite, barium sulfate, and aqueous alkaline electrolyte solution. According to an impact molding embodiment, the cathode <NUM> may be formed by disposing a quantity of the cathode mixture into the open ended container <NUM> and, with use of an impact molding ram, molding the mixture into a solid tubular (e.g., cylindrical) configuration that defines a cavity generally concentric with the side wall of the container <NUM>. Alternately, according to a ring molding embodiment, the cathode ring <NUM> may be formed by preforming a plurality of rings (e.g., three or four rings) from the cathode mixture and then inserting the preformed rings into the container <NUM> to form the tubular shaped cathode ring <NUM>. In certain embodiments, the interior surface of the cathode ring <NUM> (whether formed via impact molding or ring molding) may have a generally circular cross-section, a generally elliptical cross-section, a generally "star"-shaped cross-section, and/or the like.

The anode <NUM>, also referred to herein as the negative electrode, may include a homogeneous mixture of an aqueous alkaline electrolyte, a zinc powder and a gelling agent, such as cross-linked polyacrylic acid. The zinc powder is the electrochemically active material of the anode <NUM>. The aqueous alkaline electrolyte may include an alkaline metal hydroxide, such as potassium hydroxide (KOH), sodium hydroxide or mixtures thereof. A gelling agent suitable for use in the anode <NUM> may include a cross-linked polyacrylic acid, such as Carbopol <NUM>®, which is commercially available from Noveon, Inc. , of Cleveland, Ohio. Examples of other gelling agents that may be suitable for use in the cell <NUM> may include Carboxymethyylcellulose, polyacrylamide and sodium polyacrylate. The zinc powder may include pure zinc or zinc alloy. Additional optional components of the anode <NUM> may include gassing inhibitors, organic or inorganic anti-corrosive agents, binders or surfactants that may be added to the ingredients listed above. Examples of suitable gassing inhibitors or anti-corrosive agents include indium salts (such as indium hydroxide), perfluoroalkyl ammonium salts, alkali metal sulfides, etc. Examples of suitable surfactants include polyethylene oxide, polyethylene, alkylethers, perfluoroalkyl compounds and the like. The anode <NUM> may be manufactured by combining the ingredients into a ribbon blender or drum mixer and then working the anode mixture into a wet slurry.

In addition to the aqueous alkaline electrolyte absorbed by the gelling agent during the anode manufacturing process, an additional quantity of aqueous solution containing a solution of potassium hydroxide and water, also referred to herein as free electrolyte, is added to the electrochemical cell <NUM> during the manufacturing process. The free electrolyte may be incorporated into the cell <NUM> by disposing it into the cavity defined by the cathode ring <NUM> after the separator <NUM> is inserted and may also be injected after the anode <NUM> is disposed into the cell. According to one embodiment, the aqueous solution contains approximately thirty-seven percent (<NUM>%) by weight KOH, and sixty-three percent (<NUM>%) deionized water.

In the bobbin-type zinc/manganese dioxide alkaline cell <NUM> shown and described herein, the separator <NUM> may be provided as a layered ion permeable, non-woven fibrous fabric which separates the cathode ring <NUM> from the anode <NUM>. The separator <NUM> maintains a physical dielectric separation of the cathode electrochemically active material (manganese dioxide) and the anode electrochemically active material (zinc) and allows for the transport of ions between the positive and negative electrode materials. Additionally, the separator <NUM> acts as a wicking medium for the aqueous electrolyte solution and as a collar that prevents fragmented portions of the anode <NUM> from contacting the top of the cathode ring <NUM>. The separator <NUM> may include a conventional non-woven separator typically made of two or more layers of paper in the shape of a basket having a cylindrical wall and a closed bottom end.

The separator <NUM> comprises an ion permeable material having a high electrical resistance (i.e., low electrical conductivity), such as a thin nonwoven fabric. The separator may be a single-ply or multi-ply (e.g., two-ply) construction to provide a desired porosity to achieve the desired electrical resistance and ion-permeability while maintaining a low overall volume within an electrochemical cell. As mentioned above, because the overall volume of electrochemical cells are generally fixed, minimizing the overall volume of non-active materials (such as the separator) within an electrochemical cell provides additional volume within the cell that may be occupied by electrochemical materials such as the cathode and/or anode.

The nonwoven fabric of the separator <NUM> may be embodied as a fiber paper comprising natural, artificial, and/or synthetic fibers. For example, the fiber paper may comprise a blend of synthetic and artificial fibers, a blend of synthetic fibers and natural materials (e.g., wood pulp), and/or the like. As a specific example, the fiber paper may comprise fibrillated cellulose fibers and synthetic fibers. In certain embodiments, the synthetic fibers may comprise a thermoplastic material, such as polyvinyl alcohol fibers having a melting point of at least about <NUM>, phenylboronic acid fibers (PBA fibers), and/or the like. In certain embodiments, the synthetic fibers may comprise first synthetic fibers that are soluble in water at a temperature of at least <NUM> and second synthetic fibers that are insoluble in water. Moreover, the fiber paper may comprise solvent spun cellulose fibers subject to fibrillation in well-known refinement and digestion processes in paper manufacturing.

The combination of the cellulose fibers and the synthetic fibers provide a porous, non-woven fabric that may be rolled/coiled to form a tubular and/or convolute shape before or after being inserted into an electrochemical cell <NUM>. Moreover, the bottom end of the tubular separator <NUM> may be folded to form a closed bottom end having a "cup" shape that may be inserted into an electrochemical cell. As yet another example, the separator <NUM> may comprise a cross-strip separator construction comprising two separator paper/fabric strips the centers of which are overlapped and the strips are disposed at right angles such that the overlapped strips collectively have <NUM> at least substantially equal-sized portions extending at right angles relative to one another from a central hub portion. When inserted, each of the <NUM> portions is folded upward toward the central portion to form an at least substantially cylindrical shape with the hub portion defining the base of the formed cylinder. Such an embodiment may form <NUM> overlapping portions as discussed in greater detail herein.

Once inserted into the electrochemical cell, the resulting separator <NUM> defines an exterior surface surrounding the outside of the resulting separator. The exterior of the sidewalls are in contact with an interior surface of the cathode, and the exterior bottom surface of the separator is in contact with a portion of the can. As shown in the exploded view of <FIG>, the inserted convolute separator <NUM> defines one or more overlapping portions <NUM> in which at least two layers of separator paper are aligned to overlap one another within the electrochemical cell <NUM>. In embodiments in which the separator <NUM> is defined as an at least substantially continuous flat sheet of paper that is rolled to form the convolute separator, the overlapping portions are located adjacent opposite ends of the continuous sheet of separator paper, and have a length (measured along the coiled length of the separator paper) equal to the portion of overlapping paper. Thus, the overall size of the overlapping portions <NUM> are equal to the area of the thickest portion (measured in terms of greatest number of separator sheet layers) of the separator <NUM>. Moreover, the flat bottom end of the separator <NUM> comprises overlapping portions to define a closed bottom end of the separator <NUM>.

In certain embodiments, one or more overlapping portions of the separator <NUM> sidewalls and/or bottom end are heat sealed to at least partially secure overlapping portions of the separator relative to one another. As discussed in greater detail herein, the overlapping portions of the separator <NUM> are heat sealed by applying a heat source (e.g., a steam filled chamber, a resistance heater, and/or the like) to at least the overlapping portions of the separator <NUM>. The applied heat causes at least a portion of the synthetic fibers within the separator paper to melt and bond with portions of an overlapping portion of separator <NUM>, thereby mechanically bonding the overlapping portions of the separator <NUM>. For example, a portion (e.g., a linear portion) of the separator <NUM> sidewalls extending between an open upper end of the separator <NUM> and a closed bottom end of the separator <NUM> may be heat sealed.

The resulting heat sealed separator <NUM> defines an at least substantially continuous separator having a shape corresponding to the interior surface of the cathode ring <NUM> (e.g., a cylindrical separator shape corresponding to a cylindrical cathode ring <NUM>) without gaps between overlapping portions of the separator <NUM>. The heat sealed separator <NUM> thus prevents undesirable movement of anode or cathode material between sheets of the separator material that may cause internal short circuits within the electrochemical cell.

Moreover, in certain embodiments the separator <NUM> may be applied directly onto the interior surface of the cathode ring <NUM> once inserted into the electrochemical cell <NUM>. The separator <NUM> may thus be applied to minimize the number and/or size of gaps between the interior surface of the cathode ring <NUM> and the exterior surface of the separator <NUM>. Because each of those gaps occupy interior volume within the electrochemical cell <NUM> that may otherwise be filled with active material, minimizing the number and/or volume of gaps between the cathode ring <NUM> and the separator <NUM> may provide an increased usable portion of the interior volume that may be utilized for active material within the electrochemical cell <NUM>.

In certain embodiments, radial pressure is applied to the separator <NUM> utilizing an expandable insertion tool <NUM> as discussed in greater detail herein. The expandable insertion tool <NUM> may be configured to press (e.g., radially press) the separator <NUM> against the interior surface of the cathode ring <NUM>. Moreover, the expandable insertion tool <NUM> may be configured to apply steam to the separator <NUM> once inserted into the electrochemical cell <NUM> to remove and/or minimize one or more creases within the separator material.

In various embodiments, the insertion tool <NUM> may be configured to expand and steam the separator paper prior to applying heat to heat seal portions of the sidewalls of the separator <NUM> to minimize gaps and/or creases between the separator <NUM> and the cathode ring <NUM> before heat sealing the separator <NUM>. However, in certain embodiments the insertion tool <NUM> may be configured to concurrently expand and press the separator <NUM> against the interior surface of the cathode ring <NUM> and to apply heat (e.g., dry heat or moist heat) to heat seal the overlapping portions of the separator <NUM>. In certain embodiments, the insertion tool <NUM> is configured to emit steam at a temperature sufficient to simultaneously remove creases within the separator <NUM> and to heat seal overlapping portions <NUM> of the separator <NUM> relative to one another.

Various embodiments are directed to an insertion tool <NUM> configured for inserting a separator <NUM> (e.g., a convolute separator, a cross-strip separator, and/or the like) into an electrochemical cell <NUM> and for smoothing the separator <NUM> along the interior wall of a cathode ring <NUM> within an electrochemical cell <NUM>. The insertion tool <NUM> may be embodied as an at least substantially cylindrical component that may be used to engage and insert an at least substantially cylindrical separator <NUM> into an at least substantially cylindrical electrochemical cell <NUM>. In certain embodiments, the insertion tool <NUM> is configured for inserting a separator <NUM> into an irregular or otherwise non-cylindrical cavity within a cathode ring <NUM>. Accordingly, the insertion tool <NUM> may have any of a variety of cross-sectional shapes, such as a shape corresponding to a shape of the cathode ring <NUM> interior cavity.

<FIG> schematically illustrate one embodiment of a separator insertion tool <NUM>. As shown in <FIG>, the separator insertion tool <NUM> may comprise an expansion component configured to expand a diameter D of the separator insertion tool <NUM> to provide radial forces onto the interior surface of the separator <NUM>. The expansion component may comprise an inflatable bladder <NUM> that may be selectively filled with a fluid (e.g., air, heated air, steam, inert gas, heated inert gas, water, heated water, oil, heated oil, and/or the like) to expand the diameter D of the inflatable bladder <NUM>.

The inflatable bladder <NUM> may surround a rigid insertion rod <NUM> configured to press the separator <NUM> into the interior of the electrochemical cell <NUM>. The rigid insertion rod <NUM> may comprise a metal material (e.g., aluminum, steel, stainless steel, titanium, and/or the like), a plastic material (e.g., a high-heat resistant plastic, a thermoplastic, a thermoset plastic, and/or the like), a composite material, a ceramic material, and/or the like. In certain embodiments, rigid insertion rod <NUM> may comprise one or more fluid vents <NUM>, valves, and/or the like configured to selectively enable fluid to be added to the interior of the inflatable bladder <NUM>. For example, the one or more fluid vents <NUM> may extend into an interior of the rigid insertion rod <NUM> into fluid communication with a fluid conduit <NUM> extending through an interior portion of the rigid insertion rod <NUM> to a fluid source (e.g., a pump, a compressed fluid storage container, and/or the like). As yet another example, the rigid insertion rod <NUM> may be embodied as a porous rigid rod (e.g., comprising a plurality of sintered particles collectively forming a rigid, porous rod that fluid may flow through) defining a fluid conduit <NUM> through a central portion of the rigid rod <NUM>.

In certain embodiments, the inflatable bladder <NUM> may comprise an elastic material having an at least substantially smooth surface. For example, the inflatable bladder <NUM> may comprise an elastic plastic material configured to expand and stretch upon introduction of a fluid (e.g., a high-pressure fluid) within the interior of the inflatable bladder <NUM>. In certain embodiments, the inflatable bladder <NUM> comprises an elastic sack enclosing the one or more fluid vents <NUM>, valves, and/or the like of the rigid insertion rod <NUM>, and the elastic sack may have a closed end <NUM> and an open end <NUM>. The open end <NUM> is secured with an airtight seal relative to a portion of the insertion tool at a seal member <NUM>. The closed end <NUM> may extend around a rigid bottom portion of the rigid insertion rod <NUM>. When in the unexpanded configuration, the inflatable bladder <NUM> may be form-fit around the rigid insertion rod <NUM> of the separator insertion tool <NUM>, such that the rigid insertion rod <NUM> of the separator insertion tool <NUM> may be utilized to form the cylindrical separator <NUM> (e.g., by wrapping planar separator paper around the rigid insertion rod <NUM>) and to initially guide the separator <NUM> into the electrochemical cell <NUM>. Once the separator <NUM> is placed within the electrochemical cell <NUM>, the inflatable bladder <NUM> may be inflated such that the bladder expands away from the rigid insertion rod <NUM> in the separator <NUM> to apply radial pressure onto the separator <NUM> to press the separator against the interior walls of the cathode ring <NUM>. The inflatable bladder <NUM> may expand and contour to the interior surface of the cathode ring <NUM>, thereby forming the separator <NUM> against the cathode ring <NUM>. Thus, if the cathode ring <NUM> has an irregular interior surface, the inflatable bladder <NUM> may press the separator <NUM> against the irregular interior surface to conform the separator <NUM> to the shape of the cathode ring <NUM>. As a specific example, the separator <NUM> and the inflatable bladder <NUM> may expand within an interior opening of the cathode ring <NUM> having a gear-shaped cross-section (as described herein) such that the separator <NUM> is pressed into the plurality of interconnected cavities such that the separator <NUM> takes on a gear shaped cross-section conforming to the shape of the interior surface of the cathode ring <NUM>. For example, a pump mechanism in fluid communication with the interior of the inflatable bladder <NUM> via the fluid conduit <NUM> and one or more fluid vents <NUM> may be configured to pump fluid into the interior of the inflatable bladder <NUM> until the bladder reaches a defined pressure to press a separator <NUM> formed around the rigid insertion rod <NUM> against the interior walls of a cathode ring <NUM>. Moreover, the pump may be reversible in certain embodiments, to deflate the inflatable bladder <NUM> such that the separator insertion tool <NUM> may be easily removed from the interior of the electrochemical cell after the separator <NUM> is positioned against the interior walls of the cathode ring <NUM>. In certain embodiments, the inflatable bladder <NUM> may comprise one or more vents, holes, valves, and/or the like to allow fluid (e.g., air, steam, and/or the like) to exit through the inflatable bladder <NUM> into the electrochemical cell <NUM>.

In certain embodiments, the inflatable bladder <NUM> may expand laterally, with the bottom portion (e.g., closed end <NUM>) of the inflatable bladder <NUM> secured relative to the rigid insertion rod <NUM> of the insertion tool <NUM> to press the sidewall of the separator <NUM> against the interior sidewall of the cathode ring <NUM>. However in certain embodiments the closed bottom portion <NUM> of the inflatable bladder <NUM> may be configured to expand away from the rigid insertion rod <NUM> of the insertion tool <NUM> to depress the closed bottom end of the convolute separator <NUM> against the closed bottom end of the electrochemical cell <NUM>.

In various embodiments, the inflatable bladder <NUM> may comprise an elastic plastic material having a high melting point, such that high temperature fluids may be utilized to inflate the inflatable bladder <NUM>. In such embodiments, the elastic material of the inflatable bladder <NUM> may also be a heat conductive material (or an inefficient heat insulator) such that heat from the heated fluid may be transferred (e.g., via conductive and/or convective heat transfer) from the inflatable bladder <NUM> to the separator <NUM>. As discussed herein, the insertion tool <NUM> may be configured to apply sufficient heat to the separator material to heat-seal overlapping portions of the separator <NUM>. Accordingly, the fluid within the inflatable bladder <NUM> may be sufficiently hot that the inflatable bladder <NUM> may heat seal the separator <NUM> upon compressing the inflatable bladder <NUM> against the interior surface of the separator <NUM>. In embodiments in which the fluid utilized to expand the inflatable bladder <NUM> is utilized to heat seal the separator <NUM>, the separator insertion tool <NUM> may be configured to apply an at least substantially uniform heat across at least substantially the entirety of the interior surface of the separator <NUM> sidewall.

In certain embodiments, the expansion mechanism may be embodied as one or more panels <NUM> that may expand outward from a rigid portion <NUM> of the insertion tool <NUM>. Each of the panels <NUM> may be at least partially rigid, and each may be configured to expand outward via a mechanical mechanism (e.g., a hydraulic or pneumatic mechanism, a mechanical linkage, and/or the like) to apply an outward, radial pressure onto the separator <NUM> to press the separator <NUM> against the interior surface of the cathode ring <NUM>. In certain embodiments, the insertion tool <NUM> may comprise a plurality of expandable panels <NUM> (e.g., <NUM> panels, <NUM> panels, <NUM> panels, <NUM> panels, <NUM> panels, and/or the like) to provide a generally uniform pressure onto the separator <NUM>.

Moreover, the insertion tool may comprise one or more heat seal mechanisms <NUM>, such as a resistance heater wire, that may be configured to apply (e.g., conduct) heat directly to the separator <NUM> to heat seal the separator <NUM>. The heat seal mechanism <NUM> may be provided on insertion tools <NUM> with or without one or more expansion mechanisms, such that the heat seal mechanism <NUM> is configured to heat seal the separator <NUM> once the separator <NUM> is in its final position within the electrochemical cell <NUM>. The heat seal mechanism <NUM> may be configured for near-instantaneous heat sealing, gradual heat sealing, and/or the like. The heat seal mechanism <NUM> may be further configured to seal at least a portion of the tubular sidewall of the separator and/or at least a portion of the closed bottom end of the separator <NUM>.

The heat seal mechanism <NUM> may extend along at least a portion of the length of the separator insertion tool <NUM> to heat seal at least a portion of the separator <NUM> sidewall. For example, the heat seal mechanism <NUM> may extend at least substantially linearly along at least a portion of the length of the separator insertion tool <NUM> to form a heat seal along at least substantially the entire height of the separator <NUM>, extending between an open upper end of the separator <NUM> to the closed bottom end of the separator <NUM>.

The insertion tool <NUM> may additionally comprise one or more steam nozzles <NUM> configured to apply steam to the separator <NUM> to at least partially heat and moisten the separator <NUM> to promote bonding between overlapping portions of the separator <NUM> when positioned within the electrochemical cell <NUM>. In certain embodiments, the steam nozzles <NUM> may be configured to apply steam to the separator <NUM> prior to applying heat and pressure to press the separator <NUM> against the cathode ring <NUM>. The combination of heat and moisture applied to the separator <NUM> may cause the one or more synthetic materials within the separator <NUM> to dissolve and, upon drying, plasticize to heat seal adjacent portions of the separator <NUM>.

Manufacturing of an electrochemical cell <NUM> according to various embodiments begins by providing a cylindrical container <NUM> having an open top end and a closed bottom end. In certain embodiments, the closed bottom end may define a protrusion (e.g., in the form of a plate welded onto the closed bottom end or a protrusion integrally formed with the cylindrical container <NUM> itself. Active materials are then added to the interior of the cylindrical container <NUM> through the open top end. Cathode material is first added to the cylindrical container <NUM> to form a cathode ring <NUM> adjacent the outer wall of the cylindrical container <NUM>. As noted above, the cathode material may be premolded into cathode rings, and one or more cathode rings may be added into the interior of the cylindrical container <NUM>. Alternatively, granular cathode material may be added to the interior of the cylindrical container <NUM>, and a molding ram may be inserted into the interior of the cylindrical container <NUM> to impact mold the cathode material into a continuous cathode ring <NUM>.

Once the cathode ring is positioned within the interior of the cylindrical container <NUM>, the cathode ring <NUM> has an exterior surface adjacent the interior surface of the cylindrical container <NUM> wall and an interior surface defining an opening (e.g., a cylindrical opening) at least substantially within the center of the cylindrical container <NUM>. The separator <NUM> may then be placed within the opening within the interior of the cathode ring <NUM>. In certain embodiments, the separator <NUM> may be formed of an at least substantially continuous rectangular paper sheet that is coiled around an at least substantially cylindrical insertion tool <NUM> to form a convolute separator <NUM>. The coiled paper sheet may form a single-layer ring having a short overlapping portion where portions proximate opposing ends of the paper sheet overlap to form an overlapping portion <NUM> comprising a two-layer portion. In certain embodiments, the coiled paper sheet may form a multi-layer ring (e.g., at least two layers) having an overlapping portion where portions proximate opposing ends of the paper sheet overlap to form an overlapping portion <NUM> comprising at least one additional layer (e.g., at least three layers where the convolute separator <NUM> comprises at least two layers). A bottom end of the resulting convolute separator <NUM> is folded inward over an end of the insertion tool to form a closed bottom end of the convolute separator <NUM>.

It should be understood that the separator <NUM> may be formed by folding and/or rolling paper in a variety of ways to provide a separator <NUM> having a closed bottom end. In certain embodiments, the separator <NUM> may comprise a plurality of overlapping portions. For example, a separator may be a cross-strip separator comprising one or more separator paper sheets folded over an end of an insertion tool <NUM> (e.g., in a "U" shape), and the portions of the separator paper sheet located on opposite sides of the insertion tool <NUM> may be folded toward one another, around the cylindrical insertion tool <NUM> to form a cylindrical separator <NUM>. In such an embodiment, the cylindrical separator <NUM> has two overlapping portions <NUM> on opposite sides of the resulting cylindrical separator <NUM>.

Once the cylindrical separator <NUM> is formed around the insertion tool <NUM>, the insertion tool <NUM> pushes the separator into the interior of cathode ring <NUM>. Upon initial insertion, the combination of the insertion tool <NUM> and the separator <NUM> have a diameter smaller than the internal diameter of the cathode ring <NUM>, such that the separator <NUM> may be inserted into the cylindrical cell <NUM> without substantially disturbing the cathode ring <NUM>. Once the separator <NUM> is at least partially inserted into the cell <NUM>, the insertion tool <NUM> may expand to press the separator <NUM> against the interior walls of the cathode ring <NUM> to conform the separator <NUM> to the shape of the interior surface of the cathode ring <NUM>. As noted herein, the insertion tool <NUM> may comprise an expansion mechanism such as an inflatable bladder <NUM> surrounding an exterior of the insertion tool <NUM> that may be inflated to apply a radial pressure to push the separator <NUM> against the interior walls of the cathode ring <NUM>. The inflatable bladder <NUM> may be inflated with a fluid, such as a gaseous composition (e.g., air, heated air, steam, inert gas, a vapor, and/or the like) or a liquid composition (e.g., water, heated water, oil, heated oil, and/or the like). In other embodiments, the insertion tool <NUM> may comprise one or more mechanically actuated expansion panels <NUM> that may be actuated via pistons, mechanical linkages, and/or the like within the interior of the insertion tool <NUM>.

The expansion mechanism is configured to press the separator <NUM> against the interior walls of the cathode ring <NUM> to minimize and/or eliminate voids existing between the cathode ring <NUM> and the separator <NUM>. Moreover, the insertion tool <NUM> may comprise one or more heating mechanisms <NUM> and/or steam mechanisms to eliminate creases and/or other imperfections within the separator <NUM> while positioned within the cathode ring <NUM>. In various embodiments, the insertion tool <NUM> comprises one or more steam nozzles <NUM> configured to apply steam to the separator <NUM> while positioned within the cathode ring <NUM>. The application of steam directly to the separator <NUM> causes the removal of one or more creases, wrinkles, and/or the like within the separator <NUM> to provide an at least substantially smooth separator <NUM> having an at least substantially smooth shape corresponding to the shape of the interior surface of the cathode ring <NUM>.

Moreover, the insertion tool <NUM> may be configured to apply heat to at least a portion of the separator <NUM> to heat seal at least the overlapping portions of the separator <NUM>. As noted above, the insertion tool <NUM> may comprise an inflatable bladder <NUM> that may be filled with a heated fluid, such as steam, heated water, and/or heated oil. The heated fluid within the inflatable bladder <NUM> may apply heat to the separator <NUM> sufficient to melt at least a portion of the synthetic fibers within the separator paper to heat seal layers of the separator <NUM> relative to one another. However, it should be noted that the insertion tool <NUM> may comprise separate heating elements <NUM> (e.g., resistance heaters) configured to directly apply heat to the overlapping portions of the separator <NUM> (e.g., overlapping portions within the walls of the separator and/or overlapping portions in the closed bottom end of the separator).

Once the separator <NUM> is placed within the cathode ring <NUM>, the insertion tool <NUM> may be removed from the cathode ring <NUM>, leaving the separator <NUM> behind. Particularly in those embodiments in which the insertion tool <NUM> comprises one or more expansion configurations, the insertion tool <NUM> may reduce its diameter (e.g., by reducing the diameter of the expansion configuration) such that the outer diameter D of the insertion tool <NUM> is not in direct contact with the interior surface of the convolute separator <NUM>. The insertion tool <NUM> may then be removed from the electrochemical cell <NUM>, leaving an interior portion of the separator <NUM> open for the placement of anode material therein.

After removal of the insertion tool <NUM>, anode material may be added to the remaining opening within the interior of the separator <NUM>, and free electrolyte may be added to the interior of the electrochemical cell <NUM>. Because the separator insertion tool <NUM> caused removal of substantially all wrinkles and/or creases within the separator <NUM>, the added anode material forms an anode component <NUM> having a sidewall shape corresponding to the shape of the interior surface of the separator <NUM> (and corresponding to the interior shape of the cathode ring <NUM>). The anode material may be a gelled anode material that may be extruded or otherwise added to the interior of the separator <NUM>. Thereafter, the anode <NUM>, current collector <NUM>, and seal arrangement <NUM> are put in place to seal the open end of the container <NUM> and to form a complete electrochemical cell <NUM>. Again, because the separator <NUM> is provided substantially free of creases and/or wrinkles, the useful volume occupied by active material, including both cathode and anode material, is maximized within the interior of the electrochemical cell <NUM>.

Claim 1:
A method for forming a separator (<NUM>) within an electrochemical cell (<NUM>), the method comprising:
providing a cylindrical electrochemical cell can (<NUM>) having an active material ring (<NUM>) disposed proximate an interior surface of the cell can (<NUM>);
pressing a separator (<NUM>) into an opening within the active material ring (<NUM>);
applying steam to the separator; and
applying radial pressure to press the separator (<NUM>) against interior walls of the active material ring (<NUM>).