Abstract: An alkaline electrochemical cell having a cathode comprising manganese dioxide and conductive graphitized mesophase pitch-based carbon fibers having an increased BET surface area of between about 10 and 60 m2/g, desirably between about 10 and 50 m2/g, preferably between about 30 and 50 m2/g by heat treatment between 800 and 1200° C. with potassium hydroxide. The treated graphitized mesophase pitch-based carbon fibers can comprise between about 1 and 100 percent by weight of the total graphite material in the cathode, typically between about 5 and 50 percent by weight of the total graphite. The total graphite in the cathode desirably comprises between about 4 and 10 percent by weight of the cathode. The graphite can be the mixtures of the graphitized mesophase pitch-based carbon fibers with flaky crystalline graphites including expanded graphites. The graphitized mesophase pitch-based carbon fibers have a mean average diameter typically between about 1 and 10 micron.

Abstract: A process for manufacture of manganese dioxide comprising subjecting an aqueous bath comprising manganese sulfate (MnSO4) and sulfuric acid (H2SO4) to electrolysis in a closed cell wherein the electrolysis bath is maintained at an elevated temperature above 110° C., preferably above 115° C. and at superatmospheric pressure. Desirably the bath can be maintained at an elevated temperature between about 115° C. and 155° C. The electrolysis is carried out preferably at elevated current density of between about 12.5 and 37 Amp/sq. ft (135 and 400 Amp/sq. meter) which allows for smaller or fewer electrolysis units. An MnO2 product having a specific surface area (SSA) within desired range of between 18-45 m2/g can be obtained. A doping agent, preferably a soluble titanium dopant is employed to help obtain the desired specific surface area (SSA) of the MnO2 product. The manganese dioxide product in zinc/MnO2 alkaline cells gives excellent service life, particularly in high power application.

Abstract: The invention relates to electrochemical cells having a metal current collector, particularly zinc/MnO2 primary alkaline cells wherein the cathode metal current collector is the cell's steel casing. The present invention is directed to a coating on the current collector, such as the inside surface of the steel casing of an alkaline cell, to improve the cell's performance, particularly when it is used for high power applications. In accordance with the invention the current collector or inside surface of the steel casing for the cell, is preferably preplated with nickel, then plated with a layer of cobalt or cobalt alloy, and subsequently coated with a layer of carbon over the cobalt layer. The carbon may be applied from a carbon/solvent coating mixture which is dried to evaporate the solvent carrier. The service life of the cell is improved, particularly during high power applications.

Abstract: A casing for cylindrical electrochemical cells, for example, alkaline cells or lithium cells. The casing is characterized by having a non-uniform wall thickness. The casing comprises a cylindrical body surface, an open end and an integrally formed closed bottom. A portion of the casing body forms the peripheral edge of the casing at the open end thereof. The casing body surface has a wall thickness which is less than the wall thickness of the casing bottom. The casing has a peripheral edge which has a wall thickness which is greater than the wall thickness of the body surface. The peripheral edge wall thickness is desirably about the same or greater than the wall thickness of the casing bottom. The casing is formed by subjecting a sheet of metal to a series of discrete punching steps. A partially formed cup is punched through a die cavity in each step thereby progressively drawing the cup to a progressively reduced diameter and increased length.

Abstract: An electrochemical separator is formed insitu on an electrode surface within an electrochemical cell, preferably an alkaline cell cathode surface. The alkaline cell comprises a zinc anode, a and potassium hydroxide electrolyte. The cathode may comprise a cathode comprising manganese dioxide. The separator may be formed by coating an electrode surface preferably with a low molecular weight copolymer of polyvinyalcohol and polyvinylacetate. The film can be coagulated to form a permeable separator uniformly conforming to and covering the electrode surface irrespective of the shape and contour of the electrode. A separate protector disk can be inserted onto the top surface of the cathode to protect the cathode from shorting in the event that imperfections in the separator surface develop. The protector disk can have a protruding lip which surrounds and protects the inside corner edge of the cathode.

Abstract: An end seal assembly for small sized cylindrical alkaline cells. The seal assembly eliminates the need for a separate end cap and also eliminates the need for an insulating washer which is normally included between the end cap and housing at the cell's open end in order to insulate the end cap from the housing. The seal assembly includes an insulating sealing disk which fits into the open end of the cell housing. The peripheral edge of the cell housing is crimped over the edge of the sealing disk to seal the cell. The sealing disk comprises an integral raised central boss which protrudes from the housing open end. An elongated current collector penetrates into the cell's interior through an aperture in the central boss. The head of the current collector is thus exposed to the external environment and forms an end (negative) terminal for the cell. The boss is wider than normal in order to prevent interlocking with heads from other like cells.

Abstract: An alkaline cell having an anode comprising zinc and a cathode comprising manganese dioxide wherein the cathode is located annularly along the inside surface of the cell housing and has a plurality of indentations on the inside of its surface facing the cell interior. Each indentation has a wall defining a channel with an opening thereto running preferably in the direction of the cell's length. The channel and opening facing the cell interior filled with anode material. The cell can have an anode current collector, typically of metal, with at least a portion of its surface extending into the cathode indentation channel. The anode current collector can have a portion of its surface extending from a point within the anode and into the cathode indentation channel through said opening. The cell can include a cathode current collector comprising a sheet of conductive material such as a sheet of metal or graphite placed within the cathode, particularly within thick regions of the cathode.

Abstract: An alkaline cell having an anode comprising zinc and a cathode comprising manganese dioxide wherein the cathode is located annularly along the inside surface of the cell housing and has a plurality of indentations on the inside of its surface facing the cell interior. Each indentation has a wall defining a channel with an opening thereto running preferably in the direction of the cell's length. The channel and opening facing the cell interior filled with anode material. The cell can have an anode current collector, typically of metal, with at least a portion of its surface extending into the cathode indentation channel. The anode current collector can have a portion of its surface extending from a point within the anode and into the cathode indentation channel through said opening. The cell can include a cathode current collector comprising a sheet of conductive material such as a sheet of metal or graphite placed within the cathode, particularly within thick regions of the cathode.

Abstract: A process for heat treating an anode casing of a zinc/air depolarized cell after the casing has been formed but before anode material comprising zinc is inserted therein. The anode casing has a layer of copper on its inside surface. The process comprises heat treating the anode casing by passing a gas at a temperature between about 200° C. and 700° C., preferably between about 300° C. and 600° C. in contact therewith to form a heat treated anode casing and then cooling said heat treated anode casing to ambient temperature. The heat treated anode casing is stored away from atmospheric air until anode active material is inserted therein during cell assembly. The heat treating process significantly reduces gassing during cell discharge and storage and eliminates the need to add mercury to the anode material.

Abstract: A primary lithium cell having a wound electrode assembly. The electrode assembly comprises an anode comprising lithium, a cathode comprising a manganese dioxide and an electrolyte permeable separator therebetween. The electrode assembly comprises a cathode sheet, an anode sheet and electrolyte permeable separator sheet therebetween. The sheets are wound into a spiral roll. An exposed edge of each revolution of the separator sheet is then heat treated, for example, by applying a heated platen thereto to mold said exposed edge into a continuous separator membrane. The continuous separator membrane, so formed, covers and seals off said edge of adjacent revolutions of the cathode sheet and thus provides electrical insulation therefor. The electrode assembly can then be inserted into the cell casing so that the continuous separator membrane abuts a surface of the casing and provides electrical insulation between the casing and the wound cathode sheet.

Abstract: A zinc/air button cell having an adhesive sealant applied to a portion of the inside surface of the cell's cathode casing. The adhesive sealant can be applied to the inside surface of a recessed annular step surrounding the cell's positive terminal on the cathode casing. The adhesive is preferably applied in a pattern which conforms to the shape of the annular recessed step. An electrolyte barrier sheet, preferably of Teflon, can be applied to the adhesive pattern on the inside surface of said recessed step, preferably so that the adhesive bonds the edge of the barrier sheet to the step. The adhesive prevents electrolyte from leaking from the cell. The adhesive is applied preferably by preparing a plate having a desired pattern etched thereon, filling the etching in the plate with an adhesive mixture, applying a silicon pad to the etching to transfer the adhesive pattern to the pad, then applying the pad to the inside surface of the cathode casing step to transfer the adhesive pattern thereto.

Abstract: The invention relates to an improved method for preparing a lithiated manganese dioxide having a stabilized &ggr;-MnO2-type crystal structure whereby an essentially dry mixture of manganese dioxide and a lithium salt is subjected to a mechanical activation process in the presence of milling media. The mechanical activation process serves to promote partial ion-exchange of protons present in the manganese dioxide crystal lattice and on the surface of the manganese dioxide particles by lithium cations. The formed lithium ion-exchanged intermediate product is heat-treated to form a lithiated manganese dioxide product having a &ggr;-MnO2-type crystal structure that can be advantageously included in the cathode of a lithium primary electrochemical cell.

Abstract: A removable tab for metal/air cell, particularly miniature zinc/air button cells which have a principal use as hearing aid batteries. The tab covers air holes in the surface of the cell. The tab has a stiff elongated member that has an extended portion which forms a handle for removing the tab from the cell in order to activate the cell. The tab also comprises a resilient material, preferably a polymeric foam. A portion of the resilient material is adhered to at least a portion of one side of the stiff elongated member and another portion of the resilient material is adhered to cover air holes in the cell surface. A polymeric film can be inserted between the foam and cell surface. The resilient material conforms better to the cell surface which can typically have curved, grooved or depressed regions in addition to the air holes. The resilient material provides more uniform adhesion of the tab to the cell surface with releasable pressure sensitive adhesives.

Abstract: An anode composition for zinc/air cells comprises a metal binder added to particulate zinc. The metal binder in contact with the particulate zinc is heated to above its melting point. Upon cooling the metal binder solidifies and adheres to the zinc particle surfaces to form agglomerates wherein individual zinc particles are held bound to each other by the metal binder. Gelling agent and electrolyte can then be added to form an anode mixture. The metal binder has a melting point desirably above about 35° C. and below the melting point of zinc. A preferred metal binder for the particulate zinc is an alloy of indium and bismuth (In/Bi). Other desirable metal binders, for example, can be an alloy of indium, bismuth and tin (In/Bi/Sn) or alloy of indium and tin (In/Sn) as well as indium metal. Use of the metal binder in the anode mixture improves conductivity of the zinc particles and replaces the need to add mercury to the anode composition.