Abstract: The present invention provides a nonaqueous electrolyte secondary cell having a construction wherein a flat spiral-shaped electrode assembly, in which positive and negative electrodes capable of intercalating and deintercalating lithium ions are wound with a separator disposed therebetween, is enclosed in a casing which changes shape with a slight increase in the internal pressure of the cell, a gel polymer containing a nonaqueous liquid electrolyte exists between the positive electrode and the separator, bonding the positive electrode and the separator, and the adhesive strength between the separator and the positive electrode is 0.02 N/10 mm or higher. In the above construction of a nonaqueous electrolyte secondary cell, even when the cell is overcharged and gas is generated in the cell, explosion caused by detachment of the bonded portion of the positive electrode and the separator is prevented.

Abstract: A closure assembly for sealed batteries in which explosion-proof features are incorporated. A metal plate (8) having a hole (81), an insulating resin sheet (9), a metal thin sheet (6b), an insulating sheet (4) having an air hole (41), a metal guide plate (3) having a hole (31), and a metal cap (1b) are laid upon one another within an insulating gasket (5b). Metal plate (8) and metal guide plate (3) are in contact with each other and electrically connected. Upon a build-up of pressure within the battery, the insulating-resin sheet (9) expands and ruptures, whereby a narrow part (69) provided in the metal thin sheet (6b) positioned above the insulating resin sheet (9) breaks, thus cutting supply of electric current.

Abstract: A gastight-sealed alkaline nickel/metal hydride storage battery in the form of a button cell having positive and negative electrodes which are arranged in the cell case and separated by a separator. Both electrodes have a support and conductor framework, which consists of a porous metal foam or metal felt, the positive electrode having a metallic region which is free of active material on the side bearing against the cell case.

Abstract: Cracking or the like is prevented from being formed in an outer wall of a container of a closed battery module whose internal space is divided by partitions. Each partition dividing the internal space of the container of the closed battery module is provided with a deformable portion that deforms before a stress greater than an allowable value is caused in a container outer wall by load applied to the container. When a load is applied to the module container, the partitions dividing the container internal space restrict deformation of the container outer walls, so that great stress is likely to occur in the outer walls. However, as the deformable portion of a partition deforms due to such load, the stress caused in the container outer walls decreases, so that formation of a crack or the like in the container outer walls becomes less likely.

Abstract: In order to be able to produce prismatic, unsealed nickel-cadmium batteries without limiting the amount of electrolyte, employing fiber-structure electrodes which, while retaining the above-described advantages over conventional nicad batteries in terms of the charging voltages, are compatible with these conventional products by not requiring higher charging voltages yet involve less maintenance in connection with water consumption, the invention proposes the manufacture of an electrode system for nicad batteries under at least partial utilization of fiber-structure electrodes, for which purpose positive and negative lamellar electrodes are produced and, with separator material interlayered, stacked in alternating fashion in a defined number to form an electrode assembly, with the respective equidirectional electrodes mutually connected by means of connecting straps; the said electrode assembly is pressed and positionally locked between mechanical clamping elements into a unitized, coplanar, undeformable bloc

Abstract: A fuel cell assembly includes a stack assembly having fuel cell plates and a frame having a bottom section and at least two side sections integrally formed with the bottom section. The stack assembly is placed on the frame bottom section, and one or more fasteners are used to attach the frame to an upper portion of the stack assembly to apply a compressive force on the stack assembly.

Abstract: A plastic battery container for a recombinant sealed lead-acid battery having reduced end wall deflection, the end wall comprising a base portion from which extends a series of integrally molded ribs disposed at approximately +/−45° to the horizontal, substantially all intersection points of the ribs with the base portion having a rounded character to enhance processing characteristics.

Abstract: This invention relates to a battery cell housing for valve-regulated, lead-acid batteries. The housing includes a tray base, vertical side walls attached to the base so that the tray base and vertical side walls define a single battery compartment. A top wall is secured to the side walls and has at least one opening. A compression member is positioned in the battery compartment beneath the top wall for movement between the side walls so as to compress a stack of battery cells stacked in a horizontal position in the battery compartment. At least one internally threaded member is included with the top wall and is aligned with at least one opening. At least one compression bolt extends through the top wall opening and contacts the compression member while threadedly engaging at least one internally threaded member.

Abstract: An electrochemical cell has a silver vanadium oxide cathode material formed into a pellet shape which expands as the cell is discharged. A cathode current collector circumferentially surrounds the cathode pellet and is in contact with the peripheral edge of the cathode pellet to prevent peripheral cathode expansion. The peripheral cathode current collector maintains a stable cell impedance during cell discharge. The cell has a D-shaped housing in which the cathode is disposed adjacent to a first interior surface, and a lithium anode is disposed adjacent to a second interior surface.

Abstract: An improved electrochemical generator is disclosed. The electrochemical generator includes a thin-film electrochemical cell which is maintained in a state of compression through use of an internal or an external pressure apparatus. A thermal conductor, which is connected to at least one of the positive or negative contacts of the cell, conducts current into and out of the cell and also conducts thermal energy between the cell and thermally conductive, electrically resistive material disposed on a vessel wall adjacent the conductor. The thermally conductive, electrically resistive material may include an anodized coating or a thin sheet of a plastic, mineral-based material or conductive polymer material. The thermal conductor is fabricated to include a resilient portion which expands and contracts to maintain mechanical contact between the cell and the thermally conductive material in the presence of relative movement between the cell and the wall structure.

Abstract: A thermal conductor for use with an electrochemical energy storage device is disclosed. The thermal conductor is attached to one or both of the anode and cathode contacts of an electrochemical cell. A resilient portion of the conductor varies in height or position to maintain contact between the conductor and an adjacent wall structure of a containment vessel in response to relative movement between the conductor and the wall structure. The thermal conductor conducts current into and out of the electrochemical cell and conducts thermal energy between the electrochemical cell and thermally conductive and electrically resistive material disposed between the conductor and the wall structure. The thermal conductor may be fabricated to include a resilient portion having one of a substantially C-shaped, double C-shaped, Z-shaped, V-shaped, O-shaped, S-shaped, or finger-shaped cross-section.

Abstract: The invention concerns a lead-acid battery having all the surfaces of all the electrodes under high pressure and their circumferences kept unchanged by support from mechanically rigid cell walls such that only the thickness of the electrodes is allowed to expand under strong resilient load during the discharge and return during charge. The pressure is 0.49-10.sup.5 -9.81-10.sup.5 Pa (0.5-10 kp/cm.sup.2), and may be obtained by separators or by springs applied to the outer sides of the cell container and may be changed for increased or decreased capacity. The construction of the tubular battery design, prevents material losses due to sludging and a long working life is obtained, since also a totally corroded lead conductor under high pressure may function as a current conductor. The rigid outer containers also allow high liquid pressure and thus a high oxygen solubility and oxygen recombination for sealed cells.

Abstract: An improved electrochemical energy storing device includes a number of thin-film electrochemical cells which are maintained in a state of compression through use of an internal or an external pressure apparatus. A thermal conductor, which is connected to at least one of the positive or negative contacts of each electrochemical cell, conducts current into and out of the electrochemical cells and also conducts thermal energy between the electrochemical cells and thermally conductive material disposed on a wall structure adjacent the conductors. The wall structure includes electrically resistive material, such as an anodized coating or a thin film of plastic. The thermal conductors are fabricated to include a spring mechanism which expands and contacts to maintain mechanical contact between the electrochemical cells and the thermally conductive material in the presence of relative movement between the electrochemical cells and the wall structure.

Abstract: The subject invention discloses apparatus and methods to provide compression of an electrochemical cell independent of atmospheric pressure. One aspect of this invention is directed towards a lithium ion cell assembly which is surrounded by a layer of material under tension, so that the material applies pressure which compresses the cell to enhance contact between the anode, separator, and cathode layers. Specifically, a heat shrink material (material which reduces in size, or contracts in at least one dimension of a three-dimensional conformation, due to the application of heat) is provided about a laminar battery and shrunk in situ to provide a battery package. Another embodiment of this invention is directed towards a lithium ion cell asembly in which a sealed package contains both the battery and a spring element. The spring element within the package applies pressure to the battery to compress it and improve contact between the anode, separator, and cathode layers.

Abstract: Rechargeable generator consisting of an anode of an alkali metal or a malleable alkali alloy, at least one polymer electrolyte which is conductive with respect to alkali cations and acts as separator, as well as at least one cathode which is reversible to cations of alkali metal and its current collector. The anode comprises a thin metallic sheet, which includes at the surface thereof a passivation film SEI capable of limiting reaction between the metal and the polymer electrolyte and to exchange lithium ions. The polymer electrolyte comprises a homogeneous separator which is capable of transmitting a pressure on the anode to resist against the dendridic strain of the metal of the anode by undergoing a rate of deformation lower than 35% of its thickness.

Abstract: A cell contains a device for inserting a stack of electrodes and holding it in place. This device enables a stack of electrodes to be inserted and held in place in a container having a base and receiving a lid, the stack having two opposite plane faces and the container having two opposite plane walls. The device comprises two tapes connected by a central blade and is disposed between the plane faces of the stack and the plane walls of the container. The two tapes form elastic cylindrical sectors, advantageously parabolic in shape, with the concave side facing outwards when fitted.

Abstract: This invention pertains to electrode cans and metal air electrochemical cells made with the electrode cans. The invention provides improved structure, and methods for making the outer edge of the closed end of the can at the joinder of the closed end of the can with an side wall extending from the closed end. A substantially flat portion of the outer surface of the closed end of the can extends outwardly of the inner surface of the side wall. The electrochemical cells are assembled using improved assembly methods. Button-type electrochemical cells made using the invention are free of the inward dishing common to especially cathode cans in such button cells.

Abstract: An improved bipolar lead-acid battery including a novel "cup" design of a bipolar plate, a resilient sliding rim seal for each battery cell, spring conductors for achieving both high compression and current collection, unique current collecting plates, and a self-sealing venting port on the external container.

Abstract: A rechargeable lithium battery comprising at least a cathode, a separator, an anode, and an electrolyte or electrolyte solution integrated in a battery housing, characterized in that said rechargeable lithium battery is provided with a pressure means comprising a polymer gel for pressing said anode and cathode.

Abstract: A coin-shaped lithium battery is disclosed. The coin-shaped lithium battery comprises a battery can containing therein an anode pellet composed of lithium or lithium alloy and a cathode pellet which are arranged to face each other with a separator provided between the pellets. At least one of the anode pellet and the cathode pellet has its central part swollen to form a curved surface. The battery can is elastically deformed to be aligned with the curved surface. In the coin-shaped lithium battery, total height of the anode pellet and the cathode pellet in outer rim part is smaller than total height in central part by 4 to 12%.

Abstract: An electrochemical cell has a cathode material formed into a pellet shape which expands as the cell is discharged. A cathode current collector circumferentially surrounds the cathode pellet and is in contact with the peripheral edge of the cathode pellet to prevent peripheral cathode expansion. The peripheral cathode current collector maintains a stable cell impedance during cell discharge.

Abstract: Sealed lead-acid cells and batteries include an expandable cover capable of accommodating the grid growth which occurs in service, the expandable cover comprises a first region which expands outwardly toward a second region and a flange which defines the terminal opening, and the cells or batteries include a terminal cover sealing assembly comprising inner-and outer-cell sealing members which together form an annulus in which the flange is seated and retain one or both include resilient seals such as an O-ring that provide a terminal-cover seal.

Abstract: A thin profile battery includes: a) an anode, b) a cathode positioned adjacent to the anode; c) a separator and electrolyte between the anode and the cathode; d) a conductive first terminal housing member in electrical contact with one of the anode or the cathode, the first terminal housing member having a surrounding periphery and a concave central portion intermediate of its surrounding periphery; e) a conductive second terminal housing member in electrical contact with the other of the anode or the cathode, the second terminal housing member having a surrounding periphery and a concave central portion intermediate of its surrounding periphery which is opposingly concave to the concave central portion of the first terminal housing member; and f) the first and second terminal housing members being insulatingly joined and sealed at their respective peripheries to form an enclosed housing which retains and protects the anode, cathode, separator and electrolyte, with the concave central portions of the first an

Abstract: A metal-air battery assembly having plurality of free standing metal-air cells forming a cell group within a battery case assembly. Each free standing cell has flexible, compressible walls capable of containing electrolyte, the walls comprising air cathodes including cathode current distributors. Each cell has a split anode assembly and current. The anode assembly has one or more reactive anode fuel plates and an anode current collector. Each of the cells is free standing and easily replaced. The battery case assembly has a mechanism for compressing the cells when the lid is closed and releasing the cell group for servicing when the lid is open.

Abstract: A coin-shaped lithium battery is disclosed. The coin-shaped lithium battery comprises a battery can containing therein an anode pellet composed of lithium or lithium alloy and a cathode pellet which are arranged to face each other with a separator provided between the pellets. At least one of the anode pellet and the cathode pellet has its central part swollen to form a curved surface. The battery can is elastically deformed to be aligned with the curved surface. In the coin-shaped lithium battery, total height of the anode pellet and the cathode pellet in outer rim part is smaller than total height in central part by 4 to 12%.

Abstract: The Bipolar Battery Construction disclosed and claimed above solves the problem of constructing a bipolar battery (11,12) with a desired, uniform, constant, pressure between each bipolar plate (20) and separator (30) in the battery cell stack (48). The provision of such a pressure dramatically increases battery life, and increases the power of the cell stack (48). Compressive force is provided by spring-loaded clamping internal to the battery (11,12). A sealed battery case (52) provides common confinement of gases and vapors from all cells (58), minimizing battery sealing requirements. An inhibitor device (80,81) is provided for minimizing or eliminating leakage current between adjacent battery cells (58) through electrolyte (32), avoiding self-discharge of the cells (58). Insulation (54) minimize temperature gradients in the cell stack (48) which assures uniform and stable performance.

Abstract: A method and apparatus for increasing charging and discharging efficiency of a battery. A battery is provided having electrodes and an electrolyte. The electrodes are connected to a charging or discharging circuit and at least one electrode is mechanically manipulated during the charging or discharging.

Abstract: A button-type battery includes: a) an anode; b) a cathode positioned adjacent to the anode; c) a separator and electrolyte between the anode and the cathode; d) a conductive first terminal housing member in electrical contact with one of the anode or the cathode, the first terminal housing member having a surrounding periphery and a concave central portion intermediate of its surrounding periphery; e) a conductive second terminal housing member in electrical contact with the other of the anode or the cathode, the second terminal housing member having a surrounding periphery and a concave central portion intermediate of its surrounding periphery which is opposingly concave to the concave central portion of the first terminal housing member; and f) the first and second terminal housing members being insulatingly joined and sealed at their respective peripheries to form an enclosed housing which retains and protects the anode, cathode, separator and electrolyte, with the concave central portions of the first and

Abstract: The present invention provides a unit battery of sealed alkaline storage battery comprising a plurality of cells each of which comprises a container in which are inserted an alkali electrolyte and an electrode group comprising a plurality of positive plates and a plurality of negative plates with separators provided between the adjacent plates and which is sealed by a cap provided with a safety valve, the adjacent cells being electrically connected, wherein at least a part of the outermost portion of the electrode group in the cell contacts with the container, the adjacent cells contact with each other at at least a part of their container and a space through which air can pass in at least one direction is provided between the adjacent cells, the unit battery being constrained by holders at a part or the whole surface of both ends in the direction of arranging of the cells.

Abstract: The state of charge of electrochemical batteries of different kinds is determined by measuring the incremental change in the total volume of the reactive masses in the battery. The invention is based on the principle that all electrochemical batteries, either primary or secondary (rechargeable), produce electricity through a chemical reaction with at least one electrode, and the chemical reactions produce certain changes in the composition and density of the electrode. The reactive masses of the electrodes, the electrolyte, and any separator or spacers are usually contained inside a battery casing of a certain volume. As the battery is used, or recharged, the specific volume of at least one of the electrode masses will change and, since the masses of the materials do not change considerably, the total volume occupied by at least one of the electrodes will change. These volume changes may be measured in many different ways and related to the state of charge in the battery.

Abstract: A flexible spacer for positioning a cell element in a cell compartment of a container of a storage battery includes a sheet member folded over on itself to a U-shaped configuration with the space between opposing surfaces of the sheet member defining a compartment for receiving the cell element, enabling the cell element and the spacer to be inserted as a unit into the cell compartment, the opposing surfaces of the sheet member each including a ribbed section that flexes upon insertion of the spacer and element into the cell, automatically adjusting for differences in cell element thickness.

Abstract: An anode for use in an electrochemical cell comprising a current collector layer having a thickness less than about 10 mils, and desirably less than about 4 mils, and a rigid support extending adjacent one side of the current collector layer so that the current collector layer is sandwiched between the anodic layer of the anode and the rigid support. The rigid support maintains the current collector layer in the original configuration of the current collector layer during discharge and recharge cycles of the cell. A cell containing the anode is also disclosed. The rigid support for the anode current collector can be mounted in the electrochemical cell case so as to allow for the release from the cell of gas produced at the anode.

Abstract: A galvanic cell employing an anode electrode that is disposed within the cathode electrode, and that extends up to at least 80 percent of the height of the cathode electrode.

Abstract: A button-type battery includes: a) an anode; b) a cathode positioned adjacent to the anode.

Abstract: An electrochemical cell including a housing containing a cathode electrode, an anode electrode, electrode terminals, and a liquid electrolyte; characterized in that the electrodes are in the form of unbonded granules located in separate compartments within the housing and separated by a separator; the granules filling their respective compartments and being subjected to a compressive force to produce good electrical contact between their outer surfaces; the electrolyte filling the interstitial spaces between the granules.

Abstract: A non-aqueous electrochemical cell comprising an active metal anode, an organic electrolyte and a cathode comprising a minor amount of a desiccant which is insoluble in the organic electrolyte and non-reactive during cell discharge. The resulting cell has been found to be resistant to internal gas generation. Such a desiccant is particularly useful in lithium/manganese dioxide cells.

Abstract: Accumulated dimensional variations in fuel cells and electrolysis cell assemblies can reduce the efficiency of the assembly and provide leakage paths for fuel and oxidant. A metal compression pad comprised of a metal having an elastic strain of about 3% to about 40% at about 2,500 psig can compensate for component dimensional variations and improve inter-cell conductivity at pressures up to and exceeding about 10,000 psig.

Abstract: A novel battery construction which incorporates a disconnect safety device which is hydraulically activated by an increase in solid volume upon abusive overcharge of the battery to disconnect the cathode or anode. A rechargeable battery which comprises: (a) a Li.sub.x MO.sub.2 cathode wherein x, is equal to or less than 1.1, and M is Ni, Co, Mn or combinations thereof; (b) a carbonaceous anode; (c) an electrolyte of one or more lithium salts dissolved in one or more non-aqueous organic solvents; and (d) an internal disconnect device which activates by hydraulic means on overcharge.

Abstract: The subject invention provides for a prismatic zinc-air cell comprising a prismatic container, an air cathode, and an anode assembly. The prismatic container has one or more oxygen access openings, and the air cathode is disposed in the container in gaseous communication with the oxygen access openings. The anode assembly comprises a rectangular anode frame having peripheral members, a separator mounted proximate to one end of the anode frame and extending substantially continuously between the anode frame peripheral members. The anode frame and separator thereby define a trough. The anode assembly also comprises a zinc anode which comprises zinc, an aqueous electrolyte, and a gelling agent. The zinc anode is disposed in the trough in electrolytic contact with a first side of the separator, and the anode assembly is disposed in the containers such that a second side of the separator is in electrolytic contact with the air cathode.

Abstract: A device for compressing the cell stack disposed within the battery case of a multicell battery and providing a gas-tight, electrically isolated seal for one of the battery terminals. The device comprising an expandable unit disposed between the cell stack and a surface of the battery case. The unit having a cavity disposed therein and a sealable port through which a pressurized fluid may be provided to the cavity thereby expanding the unit. The unit is preferably comprised of two concentric annular metal bellows.

Abstract: An electrochemical battery made of stacked cells which are separated by separator plates comprising a good heat conductive material, e.g. nickel, stainless steel, copper. The separator plates extend beyond the edge of the stacked cells and outside the enclosure of the battery. The separator plates directly conduct heat, which is generated by the electrochemical process, from the battery cells to the ambient environment. Sealing of the enclosure between the separator plates is provided by an O-ring or, alternatively, by a bellows sealed to adjacent separator plates by O-rings. Sealing is possible for hydrogen at low pressure which is presented in batteries utilizing a metal-hydride hydrogen storage capacity.

Abstract: This invention relates to method and apparatus for compressing an assembly of plates inside a valve regulated lead-acid battery thereby allowing the battery case to expand without causing slippage or partial loss of contact between the battery plates.

Abstract: A galvanic cell, such as an alkaline cell employing an anode that expands during discharge, such as a zinc electrode, in which a gas filled collapsible member is disposed within the anode to accommodate any expansion of the anode during discharge or during storage.

Abstract: A flexible rib plaque is provided for insertion between battery cell elements and the end and/or an interior wall of the battery container. The plaque improves performance by limiting the harmful effects caused by flexing of the container walls due to hydraulic pressure changes of the electrolyte contained within the battery. The ribs of the plaques may be located on one or both sides of the plaque. If ribs extend from only one side, they may contact the cell element or the container wall.

Abstract: A rechargeable battery cell (10) has an integral vibrating means. The cell has a positive electrode (14), a negative electrode (16), and an electrolyte (18) disposed between the two electrodes. The electrolyte contains a piezoelectric material (20) that vibrates when subjected to an alternating electric field. In one embodiment, at least one of the electrodes contains a piezoelectric material that functions as a vibrating means when subjected to an alternating electric field. In another embodiment, a piezoelectric material that functions as a vibrating means when subjected to an alternating electric field is attached as part of a current collector (22) to at least one of the electrodes. The piezoelectric material performs an additional function of being an electronic insulator for the purpose of stacking the cells.

Abstract: Accumulated dimensional variations in fuel cells and electrolysis cell assemblies can reduce the efficiency of the assembly and provide leakage paths for fuel and oxidant. A metal compression pad comprised of a metal having an elastic strain of about 3% to about 40% at about 2,500 psig can compensate for component dimensional variations and improve inter-cell conductivity at pressures up to and exceeding about 10,000 psig.

Abstract: A storage battery cell based on the principle of the oxygen cycle, having a block-shaped, gastightly sealed cell housing in which the rectangular electrode plates of different polarity are stacked. The electrode plates are electrically connected via current collector lugs to positive and negative terminal pillars of corresponding polarity passed through the wall of the same housing side. In order to achieve a longer service life of the cell, the electrode plates are arranged in parallel with the housing wall of the terminal pillars and are enclosed in an equidistant manner on all four peripheral sides of the electrode plates by the walls of the cell housing. All the electrode plates have in each case a central hole on whose inner edge the current collector lugs are mounted, the current collector lugs being routed elastically in the duct formed by the central holes to the terminal pillars of the corresponding polarity.

Abstract: A battery charge indicator is permanently incorporated into a battery to indicate the state of charge. In one embodiment, the indicator includes a compressible chamber which is filled with a viscous gel and which is exposed to the expandable cathode of the battery. As the battery discharges, the cathode expands thus causing the gel within the chamber to be extruded out through an outlet into a viewing channel in an overlying disk. The amount of gel flowing into the viewing channel is proportional to the amount of expansion of the cathode and, thus, indicates the amount of discharge and, conversely, the remaining life of the battery. In a second embodiment, a piston assembly is caused to move with a deformable end wall of the battery and indicia on the side wall of the piston assembly is viewed through a lens as a measure of the remaining amount of expect expansion of the cathode.

Abstract: This invention relates to rechargeable manganese dioxide cells (usually alkaline cells with zinc anodes or cells having non-aqueous electrolyte and lithium anodes), and particularly to the cathodes therefore. In keeping with the present invention, the cathodes are essentially unconstrained--that is, no cage is used in the cell between the cathodes and the anodes. The cathode is restricted from significantly changing its dimensions during discharge of the cell, when it is inclined to swell--as opposed to the tendency of the cathode to contract during a charge cycle. The cathode substantially fills the entire space allotted for it within the cell, with a light accommodation for height-wise or longitudinal expansion or growth of the cathode of bobbin-type cells, or crosswise expansion or growth of button-type cells.

Abstract: This invention relates to rechargeable manganese dioxide cells (usually alkaline cells with zinc anodes or cells having non-aqueous electrolyte and lithium anodes), and particularly to the cathodes therefore. In keeping with the present invention, the cathodes are essentially unconstrained--that is, no cage is used in the cell between the cathodes and the anodes. The cathode is restricted from significantly changing its dimensions during discharge of the cell, when it is inclined to swell--as opposed to the tendency of the cathode to contract during a charge cycle. The cathode substantially fills the entire space allotted for it within the cell, with a light accommodation for height-wise or longitudinal expansion or growth of the cathode of bobbin-type cells, or cross-wise expansion or growth of button-type cells.