Thin-walled anode can for a metal-air electrochemical cell

Abstract: An alkaline electrochemical cell (10), typically to a metal-air cell of the button-type has elements thinner than corresponding non-reactive elements of prior art cells. The cell (10) has an anode can (24) made from a three-layer metal strip structure (120) having a high steel content, a cathod can (44) and a seal (60) disposed between the anode can and the cathode can. The first or outer layer (126) of the anode can (24) is nickel, the second or core layer (122) is stainless steel and the third or inner layer (124) is copper, the core layer (122) amounting to 77 to 91% by weight of the can (24), and the thickness of the anode can is from 0.144 to 0.127 mm; the cathode can (44) can have a thickness of 0.100 to 0.155mm.

Description: FIELD OF THE INVENTION This invention relates to alkaline electrochemical cells, typically to such cells which have metal-containing anode materials and air cathodes, commonly known as metal-air cells. More particularly, this invention relates to the structure of the several components from which the cell is assembled, and to the overall structure of the cell itself, addressing the efficient use of the three-dimensional volume to be occupied by such cells in electrical appliances. The invention addresses efficient use of non-reactive e.g. structural materials in preserving as much space as possible for use by the electrochemically reactive anode material used by the cell for generating electrical energy, providing an increase in the fraction of the overall volume of the cell which can be allocated to/occupied by the electrochemically reactive anode material. BACKGROUND OF THE INVENTION The growth in use of small electrically-powered devices has increased the demand for very small metal-air electrochemical cells. Metal-air cells have gained significant popularity because only the anode reaction material need be packaged in the cell, while the cathode reaction material is oxygen, which is drawn from the surrounding environment. Such small cells are usually disc-like or pellet-like in appearance, and are about the size of garment buttons. These cells generally have diameters ranging from less than 6.4 millimeters to about 25 millimeters, and height ranging from less than 2.1 millimeters up to about 15 millimeters. The small size and the limited amount of electrochemically reactive material which can be contained in such small metal-air cells result in considerable attention being directed to improving the efficiency and completeness of the electrochemical reactions, which are used in such cells for generating electrical energy. Metal-air cells take in atmospheric oxygen, and convert the oxygen to hydroxyl ions in the air cathode. The hydroxyl ions then migrate to the anode, where they cause the metal contained in the anode to oxidize. Usually the active anode material in such cells comprises zinc. More particularly, the desired reaction in a metal-air cell air cathode involves the reduction of oxygen, the consumption of electrons, and the production of hydroxyl ions, the hydroxyl ions being able to migrate through the electrolyte toward the anode, where oxidation may occur, forming zinc oxide. In most metal-air cells, air enters the cell through a port in the bottom of the cathode can. The port extends through the bottom the cathode can, and may be immediately adjacent the cathode assembly, or may be separated from the cathode assembly by an air reservoir or an air diffusion member. In any of such arrangements, the port facilitates the movement of air through the bottom of the cathode can and to the cathode assembly. At the cathode assembly, the oxygen in the air reacts with water as a chemically reactive participant in the electrochemical reaction of the cell, and thereby forms the hydroxyl ions. Since the overall electrochemical capacity of any electrochemical cell is to some extent determined by the quantity of electrochemically reactive materials which can be loaded into the cell, it is important to maximize the size of the cavity, in the cell, which is devoted to containing the reactive materials. In the case of a metal-air cell, contained reactive material is limited to the anode material. The improvements recited herein could, however, be applied to a variety of other electrochemical cells, and need not be, indeed are not, limited to metal-air cells. In general, the size of any given cell is limited by the inside dimensions of the space provided in the article, or appliance, in which the cell will operate. For example, the size of a hearing aid cell is limited to the internal dimensions of the space, provided for the cell, in the hearing aid appliance. The internal dimensions of the space are determined by the hearing aid manufacturer, not the power cell manufacturer. Thus, any given appliance includes a limited amount of gross space/volume allotted to occupancy by the electrochemical cell which powers the appliance. That gross space may ultimately be divided according to four competing functions. A first and minimal portion of the space is used to provide clearance between the interior elements of the space and the exterior elements of the electrochemical cell. A second portion of the space is occupied by the structural and otherwise non-reactive elements of the electrochemical cell. The third portion of the space is occupied by the electrochemically reactive materials of the electrochemical cell, and especially the anode material. Finally, a fourth portion of the space, if used, can sometimes be described as "wasted" space, because it serves none of the above first through third portions. Such "wasted" space is typically found outside the cell, e.g. at corner locations, where the corner of the cell is less "square" than is structurally feasible, thereby wasting volume that potentially might be occupied, either directly or indirectly, by electrochemically reactive material. Such "wasted" space might also be considered to be included in the space allocated to "clearance" because such space is typically located outside the cell. Any increase in the third portion of the space, namely the cavity in the anode can which cavity is allocated to the anode material, is necessarily gained at the expense of one or more of the other three portions of the fixed volume allocated for occupation by the cell, namely the first clearance portion, the second portion devoted to the non-reactive elements of the cell, or any fourth waste portion. Thus, it is important to identify the first, second, and fourth portions of the overall space, and to reduce the absolute amount of the space devoted to such uses. To the extent such uses can be reduced, the space so recovered can, in general, be allocated for use to hold additional amounts of electrochemically reactive anode material, thereby increasing the potential overall capacity of the cell to generate electrical energy. Of the first, second, and fourth portions of the cell, the first portion, devoted to clearance, appears to hold the least potential for providing much if any significant opportunities for reduction in volume, and the total volume of the "clearance" space is typically relatively small. Namely, overall cell height and width dimensions are specified by the International Electrochemical Commission (IEC). While some manufacturers may employ designs which utilize readily definable wasted space on the outside of the cell, especially at lower corners of the cell, other manufacturers appear to more fully utilize the allocated space. Accordingly, while some small amount of volume may be recovered from "wasted" space, or by reducing the "clearance" space, applicants have concluded that the greatest potential for recovering space for use in holding anode material, and thus to increase "volume efficiency" of the cell, lies in the second portion of the cell, namely the structural and otherwise non-reactive elements of the cell. These elements generally comprise the cathode can, the anode can, the seal, and the cathode assembly, these typically being all of the major structural elements of the cell except for the reactive anode material. Thus, to get more space for holding the reactive anode material, that space must generally be taken away from the anode can, the cathode can, the cathode assembly, or the seal, or some combination of these. It is an object of this invention to provide electrochemical cells having increased fractions of the cell-receiving space devoted to containing electrochemically reactive anode material. It is another object to provide metal-air electrochemical cells wherein one or more of the anode can, the cathode can, the cathode assembly, or the seal have reduced thicknesses, e.g. which have been reduced to thicknesses never before achievable for an electrochemical cell. The invention aims to provide such cells herein the structural integrity of the cell, to abuse from forces outside the cell, is maintained. According to the present invention, there is provided an anode can for use in an electrochemical cell, said anode can having a first, outer surface to be disposed outwardly on such electrochemical cell when said anode can is assembled thereinto and a second, inner surface to be disposed inwardly in such electrochemical cell when said anode can is assembled thereinto, said anode can having a first layer comprising nickel, a second layer comprising copper, and a third layer comprising stainless steel between said first and second layers, characterised by said third layer amounting to 80 percent by weight to 91 percent by weight of said anode can, and the combination of said first and second layers being 9 percent by weight to 20 percent by weight of said anode can. The invention also comprehends an electrochemical cell having an anode, a cathode and a barrier between the anode and cathode, the anode comprising an anode can as defined in the last preceding paragraph. According to the invention the anode can has a first, outer surface to be disposed outwardly on the electrochemical cell when the anode can is assembled thereinto and a second inner surface which is disposed inwardly in the electrochemical cell, and the anode can has a first layer comprising nickel, a second layer comprising copper, and a third layer comprising stainless steel between the first and second layers. The third layer amounts to 80 percent to 91 percent by weight of the anode can. The combination of the first and second layers amounts to 9 percent to 20 percent by weight of the anode can. Preferably, the third layer is 83 percent to 91 percent by weight of the anode can, and the combination of the first and second layers is 9 percent to 17 percent by weight of the anode can. More preferably, the third layer is 87 percent to 91 percent by weight of the anode can, and the combination of said first and second layers is 9 percent to 13 percent by weight of the anode can. Still more preferably, the third layer is 91 percent by weight of the anode can, and the combination of the first and second layers is 9 percent of the anode can. Preferably, the first layer amounts to 2 percent to 7 percent by weight of the anode can, and the second layer amounts to 7 percent to 16 percent by weight of the anode can. More preferably, the first layer is 2 percent to 6 percent by weight of the anode can, and the second layer is 7 percent to 11 percent by weight of the anode can. Even more preferably, the first layer is 2 percent by weight of the anode can, and the second layer is 7 percent by weight of the anode can. In embodiments of this invention, the anode can has a thickness, between the inner and outer surfaces, between .110 millimeter and .145 millimeter. Preferably, the thickness is between .114 millimeter and .140 millimeter. More preferably, the thickness is .127 millimeter. The electrochemical cell according to the invention includes a cathode can joined with the anode can, and a seal between the anode can and the cathode can. The cathode can has an outer surface disposed outwardly on the electrochemical cell and an inner surface disposed inwardly in the electrochemical cell. The cathode can has a thickness between the inner and outer surfaces of .110 millimeter to .145 millimeter. Preferably, the thickness is .114 millimeter to .140 millimeter. More preferably, the thickness is .119 millimeter to .127 millimeter. In an electrochemical cell according to the invention the anode can and the cathode can, in combination, define a cavity, a top and a bottom of the electrochemical cell, and an overall height between the top and the bottom, the cathode can having a side wall defining a maximum diameter of the electrochemical cell. The height and the maximum diameter, in combination, define a right cylinder and an overall volume of the electrochemical cell, which is .06 cm 3 to .60 cm 3 . In some embodiments, the overall volume of the electrochemical cell is between .06 cm 3 and .12 cm 3 and the ratio of the volume of the cavity in the anode can to the overall volume of the electrochemical cell is at least 0.43/1. In other embodiments, the overall volume of the electrochemical cell is between .12 cm 3 and .20 cm 3 and the ratio of the volume of the cavity in the anode can to the overall volume of the electrochemical cell is at least 0.46/1. In still other embodiments, the overall volume of the electrochemical cell is between .20 cm 3 and .30 cm 3 and the ratio of the volume of the cavity in the anode can to the overall volume of the electrochemical cell is at least 0.53/1. In yet further embodiments, the overall volume of the electrochemical cell is between .50 cm 3 and .60 cm 3 and the ratio of the volume of the cavity in the anode can to the overall volume of the electrochemical cell is at least 0.59/1. In an electrochemical cell embodying the anode can of the invention, the anode can has a top wall, and a circumferential side wall extending downwardly from the top wall to a first distal edge thereof. The overall thickness of the side wall between the first outer surface and the second inner surface is defined by a metal strip extending downwardly from the top wall and terminating at a second distal edge of the metal strip coincident with the first distal edge of the side wall. Preferably, the anode can and the cathode can, in combination, define the top and bottom of the electrochemical cell, and hence an overall height between the top and the bottom. The cathode can has a sidewall defining a maximum diameter of the electrochemical cell, and the ratio for the overall height to the maximum diameter is between 0.44/1 and 0.68/1. In some embodiments, the electrochemical cell comprises an anode can of the invention, the anode can having a top wall, and a first circumferential side wall extending downwardly from the top wall to a first distal edge thereof, the cathode can having a bottom wall and a second circumferential side wall extending upwardly from the bottom wall and terminating at a second distal edge thereof. The first side wall is arranged and configured in the electrochemical cell such that, when a closing force is applied to thereby crimp the second side wall of the cathode can inwardly at cell closing, the first side wall bears a force along a top-to-bottom height thereof opposing the closing force. The present invention will now be described in more detail by way of example with reference to the accompanying drawings in which: FIGURE 1 shows a cross-section of a prior art metal-air electrochemical cell in an appliance, inside the space allocated for the cell. FIGURE 2 shows a cross-section of a metal-air electrochemical cell of the invention in a corresponding appliance as in FIGURE 1, also inside the space allocated for the cell. FIGURE 3 shows a pictorial view of a cathode assembly used in cells of the invention. FIGURE 4 shows a cross-section of the cathode assembly, taken at 4-4 of FIGURE 3. FIGURE 5 shows a cross section of an electrochemical cell of the invention. FIGURE 6 illustrates the die arrangement, and the final stage of the method used to bring together the anode, the cathode, and the seal, to thereby close and crimp the respective elements in assembly of the cell. FIGURE 7 shows a fragmentary cross-section of metal strip used to make cathode cans of the invention. FIGURES 8A-8C show cross-sections of cathode can pre-forms, illustrating stages of fabrication of cathode cans of the invention. FIGURE 9 shows a fragmentary cross-section of metal strip used to make anode cans of the invention. FIGURE 10 shows a split-half, side-by-side cross-section comparison of two halves of a metal air cell, illustrating the volume gains achieved using the invention. DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Referring now by characters of reference to the drawings, a comparison of FIGURES 1 and 2 illustrates the general concept of the invention. Referring first to FIGURE 2, the cell 10 is disposed inside the space 12 allocated for occupation by the cell, in an appliance 14. As illustrated in FIGURE 2, the space 12 is generally bounded by a bottom wall 16 of the appliance, a top wall 18 of the appliance, and side walls 20. Referring, now, specifically to the cell 10, the negative electrode 22, also referred to as the anode 22, includes an anode can 24 and electrochemically reactive anode material 26 contained therein. The anode can 24 has a top wall 28, and circumferential downwardly-depending side wall 30. Top wall 28 and side wall 30 have, in combination, an inner surface 32 and an outer surface 34. Side walls 30 terminate in a circumferential can foot 36. The top wall 28 and side walls 30 generally define a cavity 38 within the anode can, which cavity 38 contains the anode material 26. The positive electrode 40, also referred to as the cathode 40, includes a cathode assembly 42, contained within the cathode can 44. Cathode can 44 has a bottom 46, and a circumferential upstanding side wall 47. Bottom 46 has a generally flat inner surface 48, a generally flat outer surface 50, and an outer perimeter 52 defined on the flat outer surface 50. A plurality of small ports 54 extend through the bottom 46 of the cathode can, providing avenues for transport of oxygen into the cell adjacent cathode assembly 42. An air reservoir 55 spaces the cathode assembly 42 from bottom 46 and the corresponding ports 54. A porous diffusion layer 57 fills the air reservoir 55. Side wall 47 of the cathode can has an inner surface 56 and an outer surface 58. The anode 22 is electrically insulated from the cathode 40 by a seal 60. Seal 60 includes a circumferential side wall 62 disposed between the upstanding side wall 47 of the cathode can and the downwardly-depending side wall 30 of the anode can, a seal foot 64 disposed generally between the can foot 36 of the anode can and the cathode assembly 42, and a seal top 66 where the side wall 62 of seal 60 extends from between the side walls 30 and 47 adjacent the top of the cell. The outer surface 68 of the cell 10 is thus defined by portions of the outer surface 34 of the top of the anode can, outer surface 58 of the side wall 47 of the cathode can, outer surface 50 of the bottom of the cathode can, and the top 66 of the seal 60. In general, this invention addresses the materials and structures which affect the degree of efficiency with which the cell 10 fills the space 12 with electrochemically reactive material. Accordingly, the invention addresses materials, structures, and methods for improving the efficiency with which the design of the cell 10 fills the space 12 with electrochemically reactive material. To the extent feasible within other constraints on making and using the cell, the cell should have a flat top and a flat bottom. The side wall 47 should meet the bottom 46 at a generally perpendicular angle. The top corner of the cell, adjacent the top 66 of the seal 62 should be as close as possible to the corresponding upper corner of the space 12. Returning again to the prior art, the cell of FIGURE 1 is derived from United States Patent Re. 31,143. A comparison of the cell of the prior art shown in FIGURE 1 to the cell 10 of the invention illustrated in FIGURE 2 suggests the significance of the configuration of the outer walls of the cell to the efficiency with which the cell fills the space 12. First addressing the "clearance" portion of the space 12, the ratio "W1/H1" of the width "W1" of the prior art cell in FIGURE 1 to the height "H1" of the cell is less than the ratio "W2/H2" of the width "W2" of the cell of the invention in FIGURE 2 to the height "H2" of the cell. The affect of such difference in the W/H ratio's is that the volume defined between the outer surface of the cathode can of the prior art cell of FIGURE 1 and the side walls 20 of the space 12 is greater than the volume defined between the outer surface 58 of the cathode can of the invention and the side walls 20 of the space 12. Accordingly, the cell 10 of the invention, as can be seen visually from the comparison of FIGURES 1 and 2, illustrates better use of the first "clearance" portion of the space 12. Further examination of FIGURE 1 illustrates the principle of the fourth portion of the space 12, namely the "wasted" portion of the space. As seen there, the bottom wall of the cathode can is convex, whereby the outer bottom corners of the space are not occupied by the cell but are, rather, vacant and "wasted," as suggested by the designation "WA" therein. The areas designated "WA" also illustrate a second indicator of waste in the in-cut corners "IC" between the convex portion of the bottom and the downwardly inclined portion of the cell which is disposed outwardly thereof but inwardly of the upstanding side wall of the cathode can. The cell 10 of the invention, on the other hand, efficiently uses the outer bottom corners 70 of the space 12, as illustrated in FIGURE 2. Having thus described conceptually the desire to efficiently fill as much as possible of the space 12 with the cell 10, the methods of so filling the space, and of maximizing the fraction of the volume of the cell 10 which is occupied by electrochemically reactive material, will be discussed following. THE SEAL Seal 60 performs at least two primary functions. First, the seal serves as a closure for the cell, to prevent anode material and/or electrolyte from leaking from the cell between the outer surface 34 of the side wall 30 of the anode can and the inner surface 56 of the side wall 47 of the cathode can. Thus, the seal must possess adequate liquid sealing properties to prevent such leakage. Generally, such properties are available in a variety of resiliently deformable thermoplastic polymeric materials. Second, the seal provides electrical insulation, preventing all effective direct electrical contact between the anode can 24 and the cathode can 44. Accordingly, the side wall 62 of the seal must circumscribe, and provide electrical insulation properties about, the entirety of the circumference of the cell between outer surface 34 and inner surface 56, generally from the top of side wall 47 to the bottom of side wall 30. Similarly, the foot 64 of the seal must circumscribe, and provide electrical insulation properties about, the entirety of the circumference of the cell between foot 36 of side wall 30, the lower portion of side wall 47, and the outer perimeter portion of the cathode assembly 42. The combination of good liquid sealing properties and good electrical insulation properties is typically achieved by molding known battery-grade nylon polymeric material in the desired configuration. To meet the electrical insulation requirements, the seal must have good dielectric insulation properties, must have a minimum thickness about side wall 62, and must be free of any pinholes or other imperfections that might permit transmission of electric current between side walls 30 and 47. Thickness for seal side wall 62 of .200 to .250 millimeter is common in conventional electrochemical cells. Thickness as low as .160 millimeter is known. Applicants have surprisingly discovered that seals thinner than .160 millimeter, as thin as .100 millimeter, made from the same resiliently deformable thermoplastic nylon material as the thicker .160 millimeter seals, exhibit acceptable properties, both liquid seal properties and electrical insulation properties. Depending on the structure of the cell to which the seal is to be applied, intermediate thicknesses such as .150 millimeter, .140 millimeter or .127 millimeter, may be selected for some cells. However, where cell volume efficiency is a driving consideration, preferred thicknesses are less, for example .120 millimeter or .110 millimeter to as thin as .100 millimeter. Thus, the range of thicknesses for seals 60 preferred for use in cells 10 of the invention has a lower end of .100 millimeter and an upper end of .150 millimeter. All thicknesses between the lower and upper ends of the range are operable, and thus are included for use in the cells of the invention. Suitable such nylon seals are available from Suratco Products Company, Poynette, Wisconsin USA. THE CATHODE ASSEMBLY FIGURE 3 shows a perspective view of the cathode assembly 42 used in cells representative of the present invention. Active layer 72 of the cathode assembly is interposed between barrier layer 74 and air diffusion layer 57. Active layer 72 ranges preferably between .050 millimeter and 1.25 millimeter thick, and facilitates the reaction between the hydroxyl in the electrolyte and the cathodic oxygen of the air. Barrier layer 74 is a micro-porous plastic membrane about .025 millimeter thick, typically polypropylene, having the primary function of preventing anodic zinc particles from coming into physical contact with the remaining elements of the cathode assembly 42. Barrier layer 74 however, does permit passage of hydroxyl ions and water therethrough. Air diffusion layer 57 is preferably a micro-porous hydrophobic polymeric material such as a polytetrafluoroethylene (PTFE) membrane .025 to .050 millimeter thick, which permits passage of air therethrough and which is generally impervious to battery electrolyte. The air diffusion layer 57, alone or in combination with the small ports 54, may be used to limit the current density produced by the cell to a desired maximum. FIGURE 4 is an enlarged perspective view of the cathode assembly 42. Active layer 72 is further comprised of connecting substratum capable of being connected, as a current collector, to electrical circuitry, namely conductive woven nickel wire layer 76. Carbon, indicated at 78, preferably forms a matrix surrounding the conductive layer 76 of nickel wire. Nickel is preferred for layer 76 because nickel exhibits little or no corrosion in the alkaline environment of the zinc-air cell, and also because nickel is an excellent electrical conductor. In addressing a primary objective of the invention, the thickness of the cathode assembly between the barrier layer 74 and the diffusion layer 57 should desirably be as small as possible. A cathode assembly preferred for use in electrochemical cells of the invention may be made as follows. Place e.g. 1000 milliliters of distilled water in a non-reactive container, and add 19 grams of KMnO 4 thereto. Mix this solution for ten minutes. Then slowly add 204 grams of PWA activated carbon having the appropriate particle sizes to the central mix vortex. PWA activated carbon has the following characteristics: surface area between 1000 and 1,150 m 2 /g., apparent density of about 0.51 g/cc., real density of about 2.1 g/cc., pore volume of about 0.90 g/cc., specific heat at 100 degrees C. of about 0.25, and 65% by weight to 75% by weight of such material will pass through a wet 44 µm (-325 U.S. mesh screen). After 10 minutes of mixing, slowly and uniformly, and without interruption, add 51 grams of Teflon® T-30 dispersant to the edge of the mix vortex, and continue mixing for yet another ten minutes at the speed required to maintain a vortex in the mix after the Teflon dispersant is added. Filter the resulting solution through Whatman #1 or equivalent filter paper, and heat to between 100 degrees C. and 140 degrees C., in a mechanical convection drying oven for at least 16 hours, or until dry, to yield a suitable cake of cathode material. Combine the resulting cathode material with Black Pearls 2000 carbon black and mix for 30 minutes, or until the mix becomes free flowing. Roll the resulting cathode mix between conventional stainless steel roller mills to obtain the active layer 72. Further details for making such preferred cathode assemblies 42 for use in cells 10 of the invention, including methods for incorporating conductive layer 76 of nickel wire into the cathode assembly, are disclosed in United States Patent 5,308,711. THE CATHODE CAN FIGURES 6 generally represents a cross-section of the metal-air cell 10, preferably a zinc-air cell, of the invention, previously discussed generally with respect to FIGURE 2. The anode 22 is electrically insulated from the cathode 40 by the nylon or similar seal 60. Cathode 40 is generally comprised of the cathode assembly 42, contained within cathode can 44. Cathode can 44 has a bottom 46, and circumferential upstanding side wall 47 extending upwardly from the bottom. The bottom 46 has an outer surface 50. Preferably, the entirety of the outer surface 50 is flat. Bottom 46 further has a generally flat inner surface 48, disposed opposite outer surface 50. Similarly, the side wall 47 has inner surface 56 and outer surface 58, the inner and outer surfaces 56, 58 extending about the circumference of the can, and defining the side wall 47 therebetween. FIGURE 6 illustrates the die arrangement, and the final stage of the process of bringing together the anode, the cathode, and the intervening seal, to close the cell and crimp the distal edges of the cathode side wall about the anode. Referring now specifically to FIGURE 6, a closing punch 100 exerts an upwardly directed force 102, indicated by the double headed arrows, against the bottom 46 of the cathode can 44. An opposing ejector punch 104 exerts an opposing downwardly directed force 106 of lesser magnitude, indicated by the double headed arrows, against the top wall 28 of the anode can 24. Split closing die 108 generally surrounds the cavity in which the cell is closed and crimped. As the closing punch 100 exerts the upwardly-directed force 102 indicated by arrows, thus urging the cathode can against the anode can and the seal, the cathode can is moved into the closing die 108 and against the transverse crimping lands 110 of the die. At the same time, the ejector punch 104 exerts its downwardly-directed opposing force 106 against the anode can. In order for the closing punch 100 to force the cathode can closed, it must exert sufficient force to form the crimp on the distal edges 112 of the side wall 47, thus gripping anode can 24 and seal 60 in closure of the cell, as well as sufficient force to overcome the resistance of the downwardly-directed opposing force 106 on the anode can. The force 106 on the anode can helps stabilize the anode can while the cell is being closed. To the extent the thickness of the material is reduced, e.g. to correspondingly increase usable interior volume, the contribution of the metal thickness to resisting bending forces is similarly reduced. Further, the lever arm between the anode can side wall and the cathode can side wall is also reduced when can wall thickness is reduced. In order for the opposing force 106 to remain effective in stabilizing the bottom 46 as the cell is closed, the magnitude of the force 106 can, in principle, be increased to offset any reduced contributions of the lever arm and the bottom thickness. But as the thickness of the side wall 30 of the anode can is reduced, the capacity of the side wall 30 to tolerate the downward force 106 is reduced. Indeed, the 227 kilograms of force conventionally used with an anode can side wall thickness of .203mm can cause the anode can to collapse during the closing process where the thickness of the side wall is reduced to less than .203mm. The ability to reduce the thickness of the cathode can between its inner and outer surfaces, whether at side wall 47 or at bottom 46, is improved by making the cathode can from a modified metal strip material. For making conventional button-type cells, it is known to use a three-layer metal strip 114, illustrated in FIGURE 7, including a core layer 116 of AISI 1008, Aluminum Killed, Battery Grade cold rolled steel, plated on opposing surfaces with layers 118 of nickel, each of the layers 118 being .00165 mm to .00215 mm thick. The plated three-layer structure 114 is diffusion annealed such that the nickel layers 118 are diffusion bonded to the core layer 116. The diffusion annealed three-layer strip 114 is then temper rolled to specified thickness. However, conventionally-known such three layer structures have limited ability to withstand the closing forces 102, 106 as the thickness of the three-layer metal strip 114 is reduced. The inventors herein have surprisingly discovered that the thickness of the metal strip 114 can be further reduced where the physical properties of the metal strip 114 are modified. Table 1 sets forth comparable properties for a metal strip used in the invention, as Invention Example #1, and Comparative Example #1 for a prior art metal strip. As referred to in TABLE 1, and elsewhere herein, the nomenclature used for the Temper of the metal strip 114 is adapted from the Special Temper designation suggested by supplier, Thomas Steel Strip Corporation, Warren, Ohio, from whom the metal strip 114 used in the invention can be obtained. Such metal strip can also be obtained from Hille & Muller, Dusseldorf, Germany. Accordingly, the Temper designations "Temper 4" for the Comparative Prior Art Strip, and "Temper 3.5" for the metal strip 114 used in cathode cans used in the invention represent the combination of physical properties illustrated in TABLE 1. In the temper designation system incorporated into TABLE 1, a lower Temper number generally represents a harder, less ductile material, while a higher Temper number generally represents a softer, more ductile material. Property Inv. Ex #1 C Ex 1 Temper Number 3.5 4 Grain Size, ASTM E112-88 7-12 9-12 Yield Strength 310-358 N/mm 2 (45-52 ksi) 220-310 N/mm 2 (32-45 ksi) Elongation, Min, 80-100 mm width 25% 35% Hardness 76-82 77-82 Erichsen Ductility ASTM E643-84 ≥7.5 mm ≥9.5 mm As seen from the properties illustrated in TABLE 1, metal strip 114 used for cathode cans used in cells of the invention has a higher yield strength, less elongation, and is less ductile than conventional metal strips of e.g. Comparative Example 1. Grain size is also reduced to a degree. The physical properties in TABLE 1 suggest that the metal strip 114 is harder and less formable than conventional battery grade metal strip. Yet battery-forming experiments by the inventors herein show that the modified metal strip 114 is suitable for making batteries using the methods disclosed herein. The hardness and formability of the strip represent compromises between the need to be able to form the strip in making the cathode can 44, and to crimp the distal edges of the side wall 47 in closing the cell at final assembly, and the desire to obtain as much strength as possible in a minimum thickness. Applicants have discovered that by reducing the thickness of the strip 114, and by also somewhat reducing the formability of the strip 114 as represented by reduced elongation and ductility values, the ability to form the strip is surprisingly preserved, and the strength of the cathode cans formed from the strip is surprisingly preserved at a sufficiently high level that the cans tolerate normal conditions of cell assembly and usage. Accordingly, metal strip, tempered as above, and suitable for forming cathode cans of the invention for use in metal-air cells, may be preferably .110 mm to .145 mm thick, more preferably .114 mm to .140 mm, most preferably .119 mm to .127 mm thick. EXAMPLE OF CATHODE CAN CORNER STRUCTURE Nickel plated steel is obtained from Hille & Muller, Dusseldorf, Germany. The metal is fabricated into cathode cans using a press having three draw stations. Prior to fabrication in the press, the metal is lubricated with forming lubricant. At Draw Station No. 1, a cup representing a rough approximation of the finished can is stamped in the metal strip. At Draw Station No. 2, the cup is further worked, to more closely approach the dimensions of the finished can. At Draw Station No. 3, the final can dimensions are generated. After Draw Station No. 3, the workpiece/cup is separated from the metal strip and trimmed, to complete fabrication of the cathode can. FIGURES 8A-8C illustrate the progressive formation of the workpiece at the three draw stations. Following Table 2 illustrates the conditions of the workpiece at the conclusion of operation at each draw station. "O/Dia" means outside diameter of the workpiece. "I/Dia" means inside diameter of the workpiece. "Depth" refers to the inside depth of the workpiece. "Radius" refers to the radius described by the inner surface of the can between the side wall and the bottom wall at the respective draw stations. Station No. O/Dia I/Dia Depth Radius 1 (FIG 8A) 9.80mm 9.49mm 3.76mm .800mm 2 (FIG 8B) 8.54mm 8.23mm 4.82mm .400mm 3 (FIG 8C) 7.75mm 7.44mm 5.43mm Sharp A suitable cathode assembly 42 is placed in the cathode can. A suitable anode, including anode can and anode material are selected. The anode, a suitable seal 60, and the cathode are placed in juxtaposed position with respect to each other and the anode and seal are urged part-way into the cathode can, to thus partially close the cell, and prepare it for final closure and sealing. The partially closed cell is then placed in a closing assembly including a closing punch 100, closing die 108, and ejector punch 104, all as illustrated in FIGURE 6. Closing punch 100 then applies closing force 102 against the outer surface 50 of the bottom 46 of the cathode can while ejector punch 104 applies opposing force 106 of lesser magnitude. Under the influence of forces 102 and 106, the cathode, the anode, and the seal move together into the closing die 108 and the cathode is fully seated over the anode. As the cathode, the anode, and the seal move into the closing die, the distal edge 112 of cathode side wall 47 is engaged by the crimping lands 110 of the split closing die 108, crimping the edge 112 inwardly against seal 60 and anode can 24, and thus closing and sealing the cell 10. By the time the cell has been so closed, the force 102 applied by the closing punch 100 reaches about 445 kilograms, and the opposing force 106 reaches about 32 kilograms. The resulting cell is structurally sound, and all components meet desired dimension specifications. Optionally, the cathode can may be formed entirely of a metal or alloy having a hydrogen overvoltage similar to that of the electrode (as opposed to plating or cladding the can) so long as sufficient strength and ductility are available from the material selected. In addition to nickel, stainless steel, palladium, silver, platinum, and gold may be suitable plating, cladding, or can materials. Steel strip plated or clad with nickel and nickel alloy is generally used because the cost is low, and because pre-plated or pre-clad steel strip, which generally requires no post-plating or post-cladding processes, is commercially available. The metal in the can must be ductile enough to withstand the drawing process, and strong enough to withstand the cell crimping and closure process. Cathode cans, for example, may be made of cold-rolled steel plated with nickel. Steel strip pre-plated with nickel can also be used. Cathode cans may also be formed from cold-rolled mild steel, with at least the inside portions of the cans being subsequently post plated with nickel. Other examples of materials for cathode cans include nickel-clad stainless steel; nickel-plated stainless steel; INCONEL (INCO alloy of nickel, a non-magnetic alloy); pure nickel with minor alloying elements (NICKEL 200 and related family of NICKEL 200 alloys such as NICKEL 201, etc.), all available from Huntington Alloys, a division of INCO, Huntington, West Virginia. Some noble metals may also find use as plating, cladding, or can metals, including steel strip plated with nickel, and mild steel strip subsequently plated with nickel after forming the can. In order to obtain the advantages of the Temper 3.5 metal strip, one, of course, must select appropriate materials and utilize proper metal processing steps, as illustrated above, to obtain the balance of properties of hardness and ductility which provide sufficient strength for the thinner can wall while tolerating the forming steps wherein the can is formed from the metal strip, and wherein the cathode can is crimped about the seal 60 and the anode can. Given the above teaching of Temper and related properties, those skilled in the art can now apply the principles taught therein to a variety of the above related metals and structures. The process described above for forming cathode cans from metal strip, to obtain the improved corner structure, and intermediate element 80, is also useful for making anode cans having related improvements in physical properties. Such making of anode cans is, of course, practiced using metal structures compatible with the polarity of the anode. THE ANODE CAN The anode can is plated with copper on its inner surface. Copper has a hydrogen overvoltage similar to that of zinc. An anode can is readily formed of stainless steel wherein the inner surface 32 is plated with copper, and the outer surface 34 is plated with nickel. As illustrated in FIGURE 9, typical anode cans comprise a metal strip 120 having a three-layer structure including a core layer 122 of e.g. 304 stainless steel, plated on opposing surfaces with outer layers 124 and 126 of copper and nickel, respectively. As with other aspects of this invention, the thickness of the metal strip 120 used to form the anode can is desirably reduced to a value less than thicknesses for conventionally known such elements. In conventional metal strip material used to make anode cans, about 76 percent by weight of the metal is contained in the core layer 122 of stainless steel, about 16 percent by weight is contained in the inner copper layer 124, and about 8 percent by weight is contained in the outer nickel layer 126. Accordingly, with all expressions being percent by weight represented by the respective layer, the structure can be expressed, layer for layer, as /16% Cu/76% SS/8% Ni/. The strength of the above metal strip structure is provided by a combination of (a) thickness of the structure, and (b) the combined strengths of the materials in the individual layers. Regarding materials, the stainless steel provides proportionately more strength than the copper or the nickel. The inventors have surprisingly discovered that the fraction of the metal strip comprising the stainless steel layer can be increased, thus providing greater strength per unit of thickness, while maintaining suitable forming properties for forming anode cans and reducing the overall thickness of the three-layer metal strip. Thus, a three-layer structure of the above nature, having the combination of suitable forming properties along with sufficient strength, stiffness, and crush resistance in the anode can, can be made into anode cans when the relative amounts of the layers 122, 124, and 126 are revised to increase the relative amount of the stainless steel layer 122. The following structures illustrate that the amount of stainless steel can be increased by up to about 20% over the conventional structures, from 80% stainless steel to about 91% stainless steel. "Cu" is copper. "SS" is stainless steel. "Ni" is nickel. All expressions are percent by weight. Exemplary such structures are: /16% Cu/82% SS/2% Ni/ / 7% Cu/91% SS/2% Ni/ The above two structures of metal strip 120, for making anode cans of the invention, are merely illustrative of the full range of structures that can be made wherein the common feature is the increase in the amount of stainless steel relative to the amount of copper and/or nickel. Accordingly, the weight of the copper layer can range from about 7% to about 16% of the weight of the three-layer metal strip, and the weight of the nickel layer can range from about 2% to about 7% by weight of the three-layer metal strip. So long as the stainless steel content is increased above the conventionally known level of about 76%, and amounts to 80 to 91%, the strength of the metal strip 120, for any given thickness, is improved. Thus, the metal strip 120 used in the invention allows for reduction in thickness while maintaining the strength of the anode can. Preferred steps in the development of structures having increasing amounts of the stainless steel layer, and thus higher strength/thickness ratio, produce anode cans having progressively, 80% stainless steel, 82% stainless steel, 83% stainless steel, 87% stainless steel, and 91% stainless steel, with corresponding 20%, 18%, 17%, 13%, and 9% as the corresponding combined amounts of the copper and nickel layers 124 and 126. Preferred steps in development of structures for metal strip 120 having decreasing amounts of the copper layer 124 are 15% copper, 11% copper, and 7% copper. Preferred steps in development of structures having decreasing amounts of the nickel layer 126 are 7% nickel, 6% nickel, 3% nickel, and 2% nickel. The full range of the structures sDecified can be obtained from Sumitomo Metals Company, Japan, the most preferred such structure having the designation "high strength CSTN-12," as annealed and work-hardened product. It is contemplated that the operation and functions of the invention have become fully apparent from the foregoing description of elements, but for completeness of disclosure the overall scope of the invention will be briefly described. VOLUME EFFICIENCIES The volume efficiencies of cells of the invention are obtained as a result of the combination of numerous reductions in space usage for various of the non-reactive elements of the cell, primarily structural elements inside the cell related to the second portion of the space 12. FIGURE 10 shows a cross-section of a cell wherein the left half of the cell uses conventional thicker materials of construction while the right half of the cell uses the thinner materials of construction disclosed herein, illustrating the greater volume which can be gained for use in containing additional electrochemically reactive anode material 26 e.g. anodic zinc paste. As illustrated in FIGURE 10, in cells of the invention, thicknesses have been reduced at least in one or more, preferably all of the following - anode can 24, cathode can 44, cathode assembly 42, and seal 60. Table 3 gives data regarding various non-reactive elements of cells of the invention, illustrating the Volume Efficiencies obtained thereby. The volume efficiencies obtained in the invention readily translate into corresponding increases in the overall potential milliampere-hour capacities of the corresponding cells. Sizes referred to in Table 3 represent designations of the IEC. For Examples 2 and 3, along with Comparative Examples 4-8, the cell Overall Volume is about .55 cm 3 . For Examples 9 and 10, along with Comparative Examples 11-15, the cell Overall Volume is about .25 cm 3 . For Examples 16 and 17, along with Comparative Examples 18-22, the cell Overall Volume is about .16 cm 3 . For Examples 23 and 24, along with Comparative Examples 25-26, the cell Overall Volume is about .090 cm 3 . Overall Volume for both the Examples of the invention and the Comparative Examples is calculated using average height and diameter for the respective size, based on IEC standards, and assuming a cylindrical configuration. The term "Volume Efficiency" means the fraction of the overall volume, generally referred to as a decimal fraction, which is defined by the cavity 38. Thus, the larger the cavity 38, the higher is the Volume Efficiency of the cell. Volume Efficiency is expressed as a fraction of the Overall Volume of the cell, Volume Efficiency being measured as the composite of thin horizontal slices of the cell, top to bottom, where each slice is e.g. 0.5 millimeter thick. SIZE PR44 Data Measured Ex. 2 Ex. 3 C Ex4 C Ex5 C Ex6 C Ex7 C Ex8 Overall Height .2070 .2070 .2070 .2070 .2070 .2070 .2070 Overall Dia .4550 .4550 .4550 .4550 .4550 .4550 .4550 Overall Vol .5515 .5515 .5515 .5515 .5515 .5515 .5515 Anode Top .0050 .0075 .0100 .0102 .0075 .0100 .0088 AnodeSidewall .0050 .0075 .0100 .0100 .0093 .0235 .0088 Seal Sidewall .0040 .0100 .0105 .0108 .0085 .0092 .0121 Cathode Can .0047 .0065 .0080 .0100 .0070 .0087 .0104 Seal Foot .0270 .0287 .0305 .0383 .0285 .0429 .0376 Cathode .0100 .0126 .0142 .0152 .0171 .0169 .0264 To 1st Radius .1395 .1373 .1395 .1238 .0965 .1529 .1277 Anode Top .2870 .2851 .2780 .3005 .2812 .2774 .3070 Anode Volume .3915 .3456 .3177 .3039 .3102 .3106 .2875 Vol Efficiency 71% 63% 58% 55% 56% 56% 52% SIZE PR48 Data Measured Ex 9 Ex 10 C Ex11 C Ex12 C Ex13 C Ex14 C Ex15 Overall Height .2070 .2070 .2070 .2070 .2070 .2070 .2070 Overall Dia .3050 .3050 .3050 .3050 .3050 .3050 .3050 Overall Vol .2478 .2478 .2478 .2478 .2478 .2478 .2478 Anode Top .0050 .0060 .0080 .0097 .0069 .0073 .0061 AnodeSidewall .0050 .0060 .0080 .0107 .0082 .0134 .0126 Seal Sidewall .0040 .0078 .0090 .0062 .0082 .0081 .0129 Cathode Can .0047 .0080 .0080 .0094 .0068 .0077 .0076 Seal Foot .0240 .0263 .0291 .0317 .0289 .0376 .0238 Cathode .0100 .0142 .0157 .0264 .0247 .0219 .0230 To 1st Radius .1273 .1221 .1273 .1292 .1146 .1462 .1499 Anode Top .1740 .1740 .1608 .1782 .1560 .1798 .1826 Anode Volume .1586 .1344 .1235 .1157 .1180 .1278 .1239 Vol Efficiency 64% 54% 50% 47% 48% 52% 50% SIZE PR41 Data Measured Ex 16 Ex 17 C Ex18 C Ex19 C Ex20 CEx21 C Ex22 Overall Height .1350 .1350 .1350 .1350 .1350 .1350 .1350 Overall Dia .3050 .3050 .3050 .3050 .3050 .3050 .3050 Overall Vol .1616 .1616 .1616 .1616 .1616 .1616 .1616 Anode Top .0050 .0061 .0080 .0076 .0068 .0058 .0058 AnodeSidewall .0050 .0061 .0080 .0173 .0143 .0108 .0129 Seal Sidewall .0040 .0067 .0093 .0083 .0085 .0079 .0095 Cathode Can .0047 .0080 .0080 .0099 .0065 .0075 .0081 Seal Foot .0233 .0209 .0227 .0379 .0312 .0294 .0217 Cathode .0100 .0118 .0123 .0258 .0233 .0221 .0250 To 1st Radius .0597 .0597 .0542 .0791 .0663 .0804 .0818 Anode Top .1700 .1746 .4738 .1717 .1582 .1763 .1548 Anode Volume .0887 .0785 .0718 .0611 .0647 .0721 .0680 Vol Efficiency 55% 49% 44% 38% 40% 45% 42% SIZE PR70 Data Measured Ex 23 Ex 24 C Ex25 C Ex26 Overall Height .1350 .1350 .1350 .1350 Overall Dia .2880 .2880 .2880 .2880 Overall Vol .0903 .0903 .0903 .0903 Anode Top .0050 .0060 .0060 .0080 AnodeSidewall .0050 .0060 .0060 .0080 Seal Sidewall .0040 .0063 .0113 .0101 Cathode Can .0047 .0060 .0080 .0083 Seal Foot .0233 .0246 .0266 .0264 Cathode .0100 .0100 .0100 .0258 To 1st Radius .0723 .0752 .0752 .0641 Anode Top .1250 .1151 .1151 .1186 Anode Volume .0506 .0436 .0377 .0331 Vol Efficiency 56% 48% 42% 37% TABLE 3A repeats TABLE 3, but gives the Diameter, Thickness and Height dimensions converted into millimetres. SIZE PR44 Data Measured Ex 2 Ex 3 C Ex C Ex5 C Ex6 C Ex7 C Ex8 Overall Height 5.26 5.26 5.26 5.26 5.26 5.26 5.26 Overall Dia 11.56 11.56 11.56 11.56 11.56 11.56 11.56 Overall Vol .5515 .5515 .5515 .5515 .5515 .5515 .5515 Anode Top 0.13 0.19 0.25 0.26 0.19 0.25 0.22 AnodeSidewall 0.13 0.19 0.25 0.25 0.24 0.60 0.22 Seal Sidewall 0.10 0.25 0.27 0.27 0.22 0.23 0.31 Cathode Can 0.12 0.16 0.20 0.25 0.18 0.22 0.26 Seal Foot 0.69 0.73 0.77 0.98 0.72 1.09 0.96 Cathode 0.25 0.32 0.36 0.39 0.43 0.43 0.67 To 1st Radius 3.54 3.49 3.54 3.14 2.45 3.97 3.24 Anode Top 7.29 7.24 7.06 7.63 7.14 7.04 7.80 Anode Volume .3915 .3456 .3177 .3039 .3102 .3106 .2875 Vol Efficiency 71% 63% 58% 55% 56% 56% 52% SIZE PR48 Data Measured Ex 9 EX10 C Ex11 C Ex12 C Ex13 CEx14 C Ex15 Overall Height 5.26 5.26 5.26 5.26 5.26 5.26 5.26 Overall Dia 7.75 7.75 7.75 7.75 7.75 7.75 7.75 Overall Vol .2478 .2478 .2478 .2478 .2478 .2478 .2478 Anode Top 0.13 0.15 0.20 0.25 0.18 0.19 0.15 AnodeSidewall 0.13 0.15 0.20 0.27 0.21 0.34 0.32 Seal Sidewall 0.10 0.20 0.23 0.16 0.21 0.21 0.33 Cathode Can 0.12 0.20 0.20 0.24 0.17 0.20 0.19 Seal Foot 0.61 0.67 0.74 0.80 0.73 0.96 0.60 Cathode 0.25 0.36 0.40 0.67 0.63 0.56 0.58 To 1st Radius 3.23 3.10 3.23 3.28 2.91 3.71 3.81 Anode Top 4.42 4.42 4.08 4.53 3.96 4.57 4.64 Anode Volume .1586 .1344 .1235 .1157 .1180 .1278 .1239 Vol Efficiency 64% 54% 50% 47% 48% 52% 50% SIZE PR41 Data Measured Ex 16 Ex 17 C Ex18 C Ex19 C Ex20 CEx21 C Ex22 Overall Height 3.43 3.43 3.43 3.43 3.43 3.43 3.43 Overall Dia 7.75 7.75 7.75 7.75 7.75 7.75 7.75 Overall Vol .1616 .1616 .1616 .1616 .1616 .1616 .1616 Anode Top 0.13 0.15 0.20 0.19 0.17 0.15 0.15 AnodeSidewall 0.13 0.15 0.20 0.44 0.36 0.27 0.33 Seal Sidewall 0.10 0.17 0.24 0.21 0.22 0.20 0.24 Cathode Can 0.12 0.20 0.20 0.25 0.17 0.19 0.21 Seal Foot 0.59 0.53 0.58 0.96 0.79 0.75 0.55 Cathode 0.25 0.30 0.31 0.66 0.59 0.56 0.64 To 1st Radius 1.52 1.52 1.38 2.01 1.68 2.04 2.08 Anode Top 4.32 4.43 12.03 4.36 4.02 4.48 3.93 Anode Volume .0887 .0785 .0718 .0611 .0647 .0721 .0680 Vol Efficiency 55% 49% 44% 38% 40% 45% 42% SIZE PR70 Data Measured Ex 23 Ex 24 C Ex25 C Ex26 Overall Height 3.43 3.43 3.43 3.43 Overall Dia 7.32 7.32 7.32 7.32 Overall Vol .0903 .0903 .0903 .0903 Anode Top 0.13 0.15 0.15 0.20 AnodeSidewall 0.13 0.15 0.15 0.20 Seal Sidewall 0.10 0.16 0.29 0.26 Cathode Can 0.12 0.15 0.20 0.21 Seal Foot 0.59 0.62 0.67 0.67 Cathode 0.25 0.25 0.25 0.66 To 1st Radius 1.84 1.91 1.91 1.63 Anode Top 3.17 2.92 2.92 3.01 Anode Volume .0506 .0436 .0377 .0331 Vol Efficiency 56% 48% 42% 37%

Claims: An anode can (24) for use in an electrochemical cell (10), said anode can having a first, outer surface (34) to be disposed outwardly on such electrochemical cell (10) when said anode can (24) is assembled thereinto and a second, inner surface (32) to be disposed inwardly in such electrochemical cell when said anode can is assembled thereinto, said anode can (24) having a first layer (126) comprising nickel, a second layer (124) comprising copper, and a third layer (122) comprising stainless steel between said first and second layers, characterised by said third layer (122) amounting to 80 percent by weight to 91 percent by weight of said anode can, and the combination of said first and second layers (126, 124) being 9 percent by weight to 20 percent by weight of said anode can. An anode can according to claim 1, wherein said third layer (122) is 83 percent by weight 91 percent by weight of said anode can, the combination of said first and second layers (126, 124) being 9 percent by weight to 17 percent by weight of said anode can. An anode can according to claim 1, wherein said third layer (122) is 87 percent by weight to 91 percent by weight of said anode can (24), the combination of said first and second layers (126, 124) being 9 percent by weight to 13 percent by weight of said anode can. An anode can according to claim 1, wherein said third layer (122) is comprising 91 percent by weight of said anode can (24), the combination of said first and second layers (126, 124) being 9 percent by weight of said anode can. An anode can according to any of claims 1 to 4, wherein said first layer (126) amounts to 2 percent by weight to 7 percent by weight of said anode can (24), said second layer (124) amounting to 7 percent by weight to 16 percent by weight of said anode can. An anode can according to any of claims 1 to 4, wherein said first layer (126) is 2 percent by weight to 6 percent by weight of said anode can (24), said second layer being 7 percent by weight to 11 percent by weight of said anode can. An anode can according to any of claims 1 to 4, wherein said first layer (126) is 2 percent by weight of said anode can (24), said second layer being 7 percent by weight of said anode can. An anode can according to any of claims 1 to 7, wherein said anode can (24) has a thickness between said inner and outer surfaces (32, 34) of between .110 millimeter and .145 millimeter. An anode can according to any of claims 1 to 7, wherein said anode can (24) has a thickness between said inner and outer surfaces (32 and 34) of between .114 millimeter and .140 millimeter. An anode can according to any of claims 1 to 7, wherein said anode can (24) has a thickness between said inner and outer surfaces (32, 34) of .127 millimeter. An electrochemical cell having an anode, a cathode, and a barrier layer between said anode and said cathode, said anode having an anode can (24) according to any of the preceding claims. An electrochemical cell according to claim 11, including a cathode can (44) assembled with said anode can (24), and a seal (60) between said anode can and said cathode can, said cathode can (44) having an outer surface disposed outwardly on said electrochemical cell and an inner surface disposed inwardly in said electrochemical cell, said cathode can having a thickness between said inner and outer surfaces of .110 millimeter to .140 millimeter. An electrochemical cell according to claim 12, wherein the said thickness is .114 millimeter to .140 millimeter. An electrochemical cell according to claim 12, wherein the said thickness is .119 millimeter to .127 millimeter. An electrochemical cell according to any of claims 11 to 14, wherein said anode can (24) and said cathode can (44), in combination define a top and a bottom of said electrochemical cell, and hence an overall height between the top and the bottom, said cathode can (44) having a side wall defining the maximum diameter of said electrochemical cell (10), the height and the maximum diameter, in combination, defining a right cylinder and the overall volume of said electrochemical cell, which is .06 cm 3 to .60 cm 3 . An electrochemical cell according to any of claims 11 to 15, said anode can (24) having a top wall (28), and a circumferential side wall (30) extending downwardly from said top wall to a first distal edge (36) thereof, the overall thickness of said side wall (30) between the first, outer surface (34) and the second, inner surface (32) being defined by a metal strip extending downwardly from said top wall and terminating at a second distal edge of the metal strip coincident with the first distal edge (36) of said side wall (30). An electrochemical cell according to any of claims 11 to 16, wherein said anode can (24) and said cathode can (44), in combination, define a top (28) and a bottom (46) of said electrochemical cell (10), and hence an overall height between the top and the bottom, said cathode can (44) having a side wall defining a maximum diameter of said electrochemical cell, and the ratio of the overall height to the maximum diameter being 0.44/1 to 0.68/1. An electrochemical cell according to any of claims 11 to 17, wherein said anode can (24) has a top wall (28), and a circumferential side wall (30) extending downwardly from said top wall to a distal edge (36) thereof, said cathode can (44) having a bottom wall (46) and a circumferential side wall (47) extending upwardly from said bottom wall (46) and terminating at a distal edge thereof, said anode side wall (30) being arranged and configured in said electrochemical cell (10) such that, when a closing force is applied to thereby crimp said side wall (47) of said cathode can (44) inwardly at cell closing, said anode side wall (30) bears a force along a top-to-bottom height thereof opposing the closing force. An electrochemical cell according to any of claims 11 to 18, wherein said anode can (24) and said cathode can (44), in combination, defining a top (28) and a bottom (46) of said electrochemical cell (10), and hence a height between the top and the bottom, a maximum diameter of said electrochemical cell (10) being defined by a side wall (47) of said cathode can (44), the height and the maximum diameter, in combination, defining a right cylinder and representing an overall volume of said electrochemical cell (10), said overall volume being .06 cm 3 to .12 cm 3 , and the ratio of the volume of a cavity (38) defined by said anode can (24) to the overall volume of said electrochemical cell (10) being at least 0.43/1. An electrochemical cell according to any of claims 11-18, said anode can (24) and said cathode can (44), in combination, defining a top (28) and a bottom (46) of said electrochemical cell (10), and hence a height between the top and the bottom, a maximum diameter of said electrochemical cell (10) being defined by a side wall (47) of said cathode can (44), the height and the maximum diameter, in combination, defining a right cylinder and representing an overall volume of said electrochemical cell (10), said overall volume being .12 cm 3 to .20 cm 3 , and the ratio of the volume of a cavity (38) defined by said anode can (24) to the overall volume of said electrochemical cell (10) being at least 0.46/1. An electrochemical cell according to any of claims 11 to 18, said anode can (24) and said cathode can (44), in combination, defining a top (28) and a bottom (46) of said electrochemical cell (10), and hence a height between the top and the bottom, a maximum diameter of said electrochemical cell (10) being defined by a side wall (47) of said cathode can (44), the height and the maximum diameter, in combination, defining a right cylinder and representing an overall volume of said electrochemical cell (10), said overall volume being .20 cm 3 to .30 cm 3 , and the ratio of the volume of a cavity (38) defined by said anode can (24) to the overall volume of said electrochemical cell (10), being at least 0.53/1. An electrochemical cell according to any of claims 11 to 18, said anode can (24) and said cathode can (44), in combination, defining a top (28) and a bottom (46) of said electrochemical cell (10), and hence a height between the top and the bottom, a maximum diameter of said electrochemical cell (10) being defined by a side wall of said cathode can (44), the height and the maximum diameter, in combination, defining a right cylinder and representing an overall volume of said electrochemical cell (10) said overall volume being .50 cm 3 to .60 cm 3 , and the ratio of the volume of a cavity (38) defined by said anode can (24) to the overall volume of said electrochemical cell (10) being at least 0.59/1.

Inventors: OLTMAN JOHN EDWARD, OLTMAN, JOHN EDWARD
Applicants: RAY O VAC CORP, RAYOVAC CORPORATION
Application year: 1996
Main classification: H01M6
IPC codes: H01M2, H01M4, H01M12