Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/06—Electrodes for primary cells
  • H01M4/08—Processes of manufacture
  • H01M4/12—Processes of manufacture of consumable metal or alloy electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
  • H01M50/183—Sealing members
  • H01M50/186—Sealing members characterised by the disposition of the sealing members
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M12/00—Hybrid cells; Manufacture thereof
  • H01M12/02—Details
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
  • H01M50/183—Sealing members
  • H01M50/19—Sealing members characterised by the material
  • H01M50/191—Inorganic material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
  • H01M50/183—Sealing members
  • H01M50/19—Sealing members characterised by the material
  • H01M50/193—Organic material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
  • H01M50/183—Sealing members
  • H01M50/19—Sealing members characterised by the material
  • H01M50/195—Composite material consisting of a mixture of organic and inorganic materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
  • H01M50/183—Sealing members
  • H01M50/19—Sealing members characterised by the material
  • H01M50/198—Sealing members characterised by the material characterised by physical properties, e.g. adhesiveness or hardness
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0025—Organic electrolyte
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• This invention relates generally to electrode structures useful in electrochemical cells and, more particularly, this invention relates to a perimeter seal for consumable reactive metal anodes and a method of forming the same. Description of the Prior Art
• Electrochemical cells utilizing consumable, reactive metal anodes are well known.
• the anode comprises an alkali metal, such as lithium, in elemental, compound or complex form, in conjunction with a cathode and an aqueous or non-aqueous electrolyte.
• the anode is lithium
• the electrolyte comprises an aqueous solution of lithium hydroxide.
• the anode typically is in the form of a disc, plate, or other structure having at least one surface which contacts the electrolyte during operation, and another surface or edge which perimetrically surrounds at least a portion of the electrolyte-contacting surface of the anode.
• a seal for a perimetric surface of a reactive metal anode comprises a hydrophobic, chemically inert polymer having selected flexural modulus, flexural strength, Izod and elongation properties which result in effective sealing of the perimetric surface, and breaking off of portions of the seal as the electrolyte-contacting face of the anode is consumed during use.
• the polymer is selected to have physical characteristics wherein the ratio of flexural modulus to flexural strength is at least about 25, the Izod impact value is less than or equal to about 2.0 ft.-lb./in. and the elongation property is less than or equal to about 20%.
• Useful polymers include selected paraffins, polyolefins, polyacrylates, polystyrenes and polyethers, and may be filled or unfilled.
• the polymer is preferably applied to the perimetric surface of the anode in an atmosphere in which the anodic metal does not react to form a reaction product, such as oxides or hydroxides.
• Fig. 1 is an exploded perspective view of a typical bipolar cell construction used in a reactive metal electrochemical cell
• Fig. 2 is an elevation of a typical electrochemical cell utilizing a reactive metal anode; and, Fig. 3 is an elevation of a portion of a power module assembly of monopolar electrochemical cells, with a portion of one cell shown in section.
• reactive metal electrochemical cells generally comprise an anode of a reactive metal, a cathode, and an aqueous or non-aqueous electrolyte which contacts at least a portion of the anode and the cathode during operation of the cell.
• Each of the anode and the cathode are connected to a terminal, and the respective terminals are connected to a load during operation.
• the anode is typically of an alkali metal, such as sodium, for example, and is preferably of lithium.
• the anodic metal may be present is elemental, compound or complex form, as is well known in the art.
• the cathode may be of any suitable metal, such as iron or silver oxide (AgO) , for example, or may be a gas-consuming cathode, such as an air cathode, for ex- ample.
• the anode and the cathode are spaced from each other, either by a mechanical separator, which may be a catalyst, or merely by the metallic hydroxide film which invariably forms on the anode by exposure to humid air.
• a mechanical separator which may be a catalyst
• metallic hydroxide film which invariably forms on the anode by exposure to humid air.
• Fig. 1 illustrates a bipolar cell construction, generally designated 10, which comprises an anode 12, a cathode 14, a cell separator 16 disposed between the anode 12 and the cathode 14, and a bipolar wall 20 disposed adjacent the cathode 14.
• the cell separator 16 illustratively comprises a layer 22 of reticulated foam and a screen 24 of Vexar® plastic.
• Each of the anode 12, cathode 14 and components of the cell separator 16 comprises a flat plate having concave indentations 26 at opposed sides thereof.
• the bipolar wall 20 comprises a generally oval plate having inlet and outlet inserts 30 and 32 at opposed sides thereof.
• the inserts 30 and 32 are congruent with the indentations 26, and have electrolyte inlet and outlet ports 33 and 34, respectively.
• an electrolyte flows into the inlet port 33, between the cathode 14 and anode 12 through the cell separator 16, and out the outlet port 34.
• a face 35 of the anode 12 is exposed to the electrolyte.
• a perimetric edge surface 36 is defined around the anode surface 35. In operation, if an effective seal is not present, the edge surface 36 is subject to corrosion by reaction with the electrolyte.
• Fig. 2 illustrates a cell 40 comprising an anode 42, a cathode 44 spaced from the anode 42 by a catalyst-plated screen 46, and a pair of support plates and current collectors 50 and 52 adjacent the anode 42 and cathode 44, respectively.
• the cell 40 of Fig. 2 is especially useful with a hydrogen peroxide-containing electrolyte, which flows between the anode 42 and cathode 44 through the screen 46, in contact with an anode surface 54.
• the cell 40 is subject to compression in the direction of the arrows 55 as the surface 54 is consumed.
• a perimetric surface 56 defined on the anode 42 surrounds the surface 54.
• Fig. 3 illustrates a portion of a power module assembly of monopolar electrochemical cells, as described in detail in Klootwyk U.S. Patent No. 4,188,462 (February 12, 1980) .
• Mounted in a cell frame (not shown) is a pair of anode support guides 60 in the form of generally rectangular cross-section bars.
• a consumable anode 62 is positioned -between the guides 60.
• Each guide 60 is provided with electrolyte flow distribution and shunt suppression manifold 64.
• a screen 66 extends between the manifolds 64 and defines a portion of the cathode. The screen 66 contacts an adjacent face 70 of the anode, with electrolyte circulating between the contacting surfaces of the anode and cathode.
• a circumferential recess 72 is defined about the anode 62 to provide space for a protective seal on the perimeter anode surface 74.
• anode 62 As the anode 62 is consumed during use, it is compressed, as by a bag 76, in order to maintain contact between the anode 62 and the screen 66.
• the edge coating on the anode surface 74 in the recess 72 serves to lubricate the anode, in addition to its other functions.
• edge surfaces 36 (Fig. 1) , 56 (Fig. 2) and 74 (Fig. 3) are subject to parasitic attack by the electrolyte, resulting in uneven wear and decreas ⁇ ed battery power and energy output, and an increase in heat output and hydrogen gas production rates.
• a perimetric surface which at least partially surrounds an electrolyte-contacting surface of the anode is coated with an edge seal in order to prevent contact of the electrolyte with the edge surface.
• the edge seal material is a hydrophobic polymer which is chemically inert with respect to both the electrolyte and to the material of the anode. Also, the polymer must be a brittle, as opposed to rubbery, solid under conditions of use of the cell, and it must have a long shelf life.
• the polymer is qualitatively characterized as "brittle" in order to assure that the portions of the seal directly adjacent the electrolyte-contacting anode surface break off and thus do not interfere with electrolyte flow as the anode surface is consumed.
• the polymer must have physical characteristics which simultaneously satisfy the following three conditions: 1.
• the (unitless) ratio of flexural modulus to flexural strength (both as determined by ASTM D790) must be equal to or exceed about 25;
• the Izod impact value (as determined by ASTM D256A) must be equal to or less than about 2.0 ft.-lb./in.; and,
• the preferred materials have a "Gordon Mechanical Index” (GMI) of greater than or equal to 1.0.
• GMI Gordon Mechanical Index
• the coating material material may be a homopolymer, a copolymer, or a more complex material, and may be filled or unfilled.
• useful materials include solid hydrocarbons such as paraffins, polyolefins, polystyrenes, poly ⁇ acrylates (especially polymethacrylates) and polyethers.
• Table I below, lists a number of candidate materials along with their respective ratios of flexural modulus to flexural strength, Izod impact values and percent elongation. Some of the materials listed in Table I are seen to be unsuitable.
• a suitable coating material may be selected based on its chemical viability in the cell, and the material can then be modified by the addition of a filler to satisfy the required mechanical parameters.
• a film or coating of the selected material protects the anodic edge surface until the anodic face has been electrochemically consumed, leaving a very thin exposed ridge of the coating. At this time, ' the exposed brittle film breaks off to the level of the anode face, and the cycle is repeated.
• the coating is applied by any suitable method, preferably in the presence of an atmosphere which does not react with the anodic material. Suitable application techniques include abrasion coating, solution coating, aerosol spraying, or pressure application. In the case of pressure application, the coating may include a thin film of material which is slightly reactive with the anodic metal to enhance bonding such as, for example, a polymer containing a small concentration of a halogen.
• a non-reactive atmosphere prevents the formation on the anode of a hydrophilic film of a reaction product of the anodic metal.
• the absence of such a film greatly enhances the strength and integ ⁇ rity of the bond between the polymeric coating and the anode, thus greatly improving the resistance of the anode to corrosion and wear. This in turn greatly increases the useful life and efficiency of the anode.
• Suitable non-reactive atmospheres include those of the Noble gases, such as argon and helium, for example.
• the atmospheric gas need not be an inert gas per se, but may comprise a normally reactive gas such as air, oxygen, nitrogen or carbon dioxide if maintained rigorously free of moisture, which catalyzes reactions between alkali metals and non-Noble gases.
• One secondary advantage of the invention is that the polymeric coating acts as a lubricant to improve the motion of the anode in multiple anode power modules, such as described in Klootwyk U.S. Pat. No. 4,188,462.
• Example 1 A strip of elemental lithium (1" x 0.25" x
• Example 2 demonstrates the efficacy of a paraffin material in protecting a lithium surface from corrosive attack by water.
• a series of four lithium anodes was tested for corrosion with and without various edge seals, as follows: A first anode (.41 cm thick) without an edge seal was exposed to an aqueous electrolyte for 20 minutes at 40°C. Severe corrosion about the peripheral edges was noted. An identical anode was coated about its peripheral edges with a commercial rubber-like plating material (Microflex®) and was exposed to an aqueous electrolyte at 40°C for 35 minutes. Although some improvement was noted, edge corrosion was still severe. A third electrode (0.81 cm thick) was coated about its peripheral edge with polymethylmethacrylate in methylene chloride and exposed to an aqueous electrolyte at 35°C for 100 minutes. Very little edge corrosion was noted.
• anode was coated with the PMMA/methylene chloride solution in an inert atmosphere and exposed to a 55°C aqueous electrolyte for 90 minutes. Almost no corrosion was detected, and it was determined that the inert atmosphere application technique eliminates the thin, hydrophilic solid lithium hydroxide layer which may otherwise be present between the anode and the PMMA film.

Applications Claiming Priority (4)

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• 1985
  • 1985-09-09 WO PCT/US1985/001710 patent/WO1986002494A1/fr not_active Application Discontinuation
  • 1985-09-09 BR BR8507020A patent/BR8507020A/pt unknown
  • 1985-09-09 AU AU48024/85A patent/AU572695B2/en not_active Ceased
  • 1985-09-09 EP EP19850904560 patent/EP0197954A4/fr not_active Withdrawn
  • 1985-10-02 ES ES547519A patent/ES8609504A1/es not_active Expired
• 1986
  • 1986-06-06 NO NO862255A patent/NO862255L/no unknown

Non-Patent Citations (1)

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