CA1302489C - Electrochemical cell - Google Patents
Electrochemical cellInfo
- Publication number
- CA1302489C CA1302489C CA000572899A CA572899A CA1302489C CA 1302489 C CA1302489 C CA 1302489C CA 000572899 A CA000572899 A CA 000572899A CA 572899 A CA572899 A CA 572899A CA 1302489 C CA1302489 C CA 1302489C
- Authority
- CA
- Canada
- Prior art keywords
- electrode
- cell
- substrate
- impregnated
- electrochemically active
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 229910052751 metal Inorganic materials 0.000 claims abstract description 25
- 239000002184 metal Substances 0.000 claims abstract description 25
- 239000000758 substrate Substances 0.000 claims abstract description 23
- 239000011262 electrochemically active material Substances 0.000 claims abstract description 21
- 239000001257 hydrogen Substances 0.000 claims abstract description 10
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 10
- 229910000765 intermetallic Inorganic materials 0.000 claims abstract description 10
- 150000004678 hydrides Chemical class 0.000 claims abstract description 8
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims abstract 3
- 239000000463 material Substances 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 7
- 239000007789 gas Substances 0.000 abstract description 14
- 238000006243 chemical reaction Methods 0.000 abstract description 6
- 239000011148 porous material Substances 0.000 abstract description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 17
- 238000005215 recombination Methods 0.000 description 10
- 230000006798 recombination Effects 0.000 description 10
- 239000003792 electrolyte Substances 0.000 description 8
- 229910052759 nickel Inorganic materials 0.000 description 8
- 239000011888 foil Substances 0.000 description 7
- 238000007599 discharging Methods 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 239000004372 Polyvinyl alcohol Substances 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 4
- 239000004020 conductor Substances 0.000 description 4
- BFDHFSHZJLFAMC-UHFFFAOYSA-L nickel(ii) hydroxide Chemical compound [OH-].[OH-].[Ni+2] BFDHFSHZJLFAMC-UHFFFAOYSA-L 0.000 description 4
- 229920002451 polyvinyl alcohol Polymers 0.000 description 4
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 4
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 229920003002 synthetic resin Polymers 0.000 description 3
- 239000000057 synthetic resin Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 239000004952 Polyamide Substances 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- -1 hydride-~orming compounds Chemical class 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 230000002209 hydrophobic effect Effects 0.000 description 2
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910052987 metal hydride Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229920002647 polyamide Polymers 0.000 description 2
- 229920000915 polyvinyl chloride Polymers 0.000 description 2
- 239000004800 polyvinyl chloride Substances 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- NDVLTYZPCACLMA-UHFFFAOYSA-N silver oxide Chemical compound [O-2].[Ag+].[Ag+] NDVLTYZPCACLMA-UHFFFAOYSA-N 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 1
- 239000002390 adhesive tape Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- OJIJEKBXJYRIBZ-UHFFFAOYSA-N cadmium nickel Chemical compound [Ni].[Cd] OJIJEKBXJYRIBZ-UHFFFAOYSA-N 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 239000012777 electrically insulating material Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000011244 liquid electrolyte Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 150000004692 metal hydroxides Chemical class 0.000 description 1
- 229920000609 methyl cellulose Polymers 0.000 description 1
- 239000001923 methylcellulose Substances 0.000 description 1
- 235000010981 methylcellulose Nutrition 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 229920005596 polymer binder Polymers 0.000 description 1
- 239000002491 polymer binding agent Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 229910001923 silver oxide Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
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
- H01M4/24—Electrodes for alkaline accumulators
- H01M4/242—Hydrogen storage electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/34—Gastight accumulators
- H01M10/345—Gastight metal hydride accumulators
-
- 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
- H01M4/64—Carriers or collectors
- H01M4/70—Carriers or collectors characterised by shape or form
- H01M4/80—Porous plates, e.g. sintered carriers
- H01M4/808—Foamed, spongy materials
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
ABSTRACT
Electrochemical cell comprising a negative electrode consisting of a substrate made of porous material which is impregnated with an electrochemically active material, the electrochemically active material being an intermetallic compound which forms a hydride with hydrogen, highly efficient and high-speed gas reactions occurring at the electrode because of the fact that the substrate is impregnated in accordance with a pattern such that a portion of substrate surfaces contains free metal.
Relevant Figure: Figure 3.
Electrochemical cell comprising a negative electrode consisting of a substrate made of porous material which is impregnated with an electrochemically active material, the electrochemically active material being an intermetallic compound which forms a hydride with hydrogen, highly efficient and high-speed gas reactions occurring at the electrode because of the fact that the substrate is impregnated in accordance with a pattern such that a portion of substrate surfaces contains free metal.
Relevant Figure: Figure 3.
Description
~3C~
PHN 12205 1 20.06.1988 ~Electrochemical cell"
rhe invention relates to an electrochemical cell comprising a negative electrode consisting of a substrate made of porous metal which is impregnated with an electrochemically active material, the electrochemically ~ctive material being an intermetallic compound which forms a hydride with hydrogen.
The invention also relates to a method of producing such an electrochemical cell.
Examples of the use of electrochemical cells comprising such an electrode are fuel cells and sealed rechargeable cells.
United States Patent US 4217939 discloses an electrode made of a porous metal tfoam metal or sponge metal) having interlinked pores, which are filled with an electrochemically active material in paste form. The electrode which is made of foam nickel filled with a nickel hydroxide-containing paste is suitable for use as the positive electrode in a rechargeable cell. The electrode is uniformly impregnated with the active material, the paste being provided, for example, at one side of the foam metal and is thereafter pressed therethrough. The porous ~etal is entirely filled with electrochemically active material and there is no free metal at the surface.
In several types of electrochemical cells reactions occur at the interface of a solid electrode, a liquid electrolyte and a gas present. This is, for example, the case in several types of fuel cells, but also in sealed rechargeable cells. In a gas-tight rechargeable nickel-cadmium cell or nickel-metal hydride cell oxygen recombination ; occurs at the negative electrode during excessive charging of the cell. In a nickel-metal hydride cell hydrogen recombination occurs at the positive electrode during excessive discharging of the cell. It is desirable for these reactions to proceed as rapidly as possible, for 3~ a fuel cell, because of the cell efficiency and for rechargeable cells because of their operating life, expressed in charging and discharging cycles. When in a rechargeable cell the recombination rate on charging ~3~
PHN 12205 1 20.06.1988 ~Electrochemical cell"
rhe invention relates to an electrochemical cell comprising a negative electrode consisting of a substrate made of porous metal which is impregnated with an electrochemically active material, the electrochemically ~ctive material being an intermetallic compound which forms a hydride with hydrogen.
The invention also relates to a method of producing such an electrochemical cell.
Examples of the use of electrochemical cells comprising such an electrode are fuel cells and sealed rechargeable cells.
United States Patent US 4217939 discloses an electrode made of a porous metal tfoam metal or sponge metal) having interlinked pores, which are filled with an electrochemically active material in paste form. The electrode which is made of foam nickel filled with a nickel hydroxide-containing paste is suitable for use as the positive electrode in a rechargeable cell. The electrode is uniformly impregnated with the active material, the paste being provided, for example, at one side of the foam metal and is thereafter pressed therethrough. The porous ~etal is entirely filled with electrochemically active material and there is no free metal at the surface.
In several types of electrochemical cells reactions occur at the interface of a solid electrode, a liquid electrolyte and a gas present. This is, for example, the case in several types of fuel cells, but also in sealed rechargeable cells. In a gas-tight rechargeable nickel-cadmium cell or nickel-metal hydride cell oxygen recombination ; occurs at the negative electrode during excessive charging of the cell. In a nickel-metal hydride cell hydrogen recombination occurs at the positive electrode during excessive discharging of the cell. It is desirable for these reactions to proceed as rapidly as possible, for 3~ a fuel cell, because of the cell efficiency and for rechargeable cells because of their operating life, expressed in charging and discharging cycles. When in a rechargeable cell the recombination rate on charging ~3~
-2- 2010~-7800 or discharging is insufficient, the pressure in the cell increases. This may cause gas (possibly with electrolyte) to escape via a safety qalve, which reduces the operating life and the capacity of the cell.
The invention has its object to provide an electrode for an electrochemical cell, and also a method of producing such a cell, in which gas reactions occur at the electrode with high efficiency and at a high rate. The invention has more speci-fically for its object to provide a rechargeable cell with a long operating life which may however not be obtained at the cost of the initial capacity and the loadability.
Accordingly, the present invention provides an electrochemical cell comprising a positive electrode and a neg-ative electrode, the negative electrode consisting of a substrate made of porous metal which is impregnated with an electrochem-ically active metal, the electrochemically active material being an intermetallic compound which forms a hydride with hydrogen, characterized in that the substrate is impregnated in accordance with a pattern such that a portion of the surfaces of the substrate contains free metal.
The invention further provides a method of producing an electrochemical cell comprising a positive electrode and a negative electrode, the negative electrode consisting of a sub-strate made of porous metal which is impregnated with an electrochemically active material, the electrochemically active material being an intermetallic compound which forms a hydride with hydrogen, characterized in that the electrode is produced by partly enveloping the substrate with a non-porous tape ~3~
~2a- 2010~-7800 material, whereafter the electrochemically active material in paste form is pressed into the porous substrate, whereafter the tape material is removed.
In a suitable embodiment of the electrochemical cell according to the invention the substrate of the electrode is designed as a flat plate which is impregnated at one side. The expression "flat" is used to indicate that the plate has no texture, for example a mesh structure. In use, the plate may be bent or rolled in any desired shape.
An electrode with locally very advantageous recombin-ation properties is obtained when the substrate is a flat plate wherein portions are present which at both sides are not impreg-nated, this being maintained during further processing operations on the electrodes, for example on rolling or further steps in which the electrodes are given their appropriate shapes.
A suitable, simple method of producing an electro-chemical cell according to the invention, is characterized in that the electrode is produced by partly wrapping a non-porous material in the form of tape around the substrate, whereafter the electrochemically active material in paste form is pressed into the porous substrate, whereafter the tape material is removed.
The rate at which the above-mentioned interface reactions proceed depends inter alla on the size of the c~talytic surface area present, i.e. the free metal surface of an electrode contacted by the gas. The quantity of active material which is decisive for the capacity of the cell must consequently not be too large. In ~" . \
:~3~
PHN 12205 3 20.06.1988 addition there is the fact that, when a cell contains an excessive quantity of electrolyte or when the electrolyte is preferably bound by the electrode, the free metal surface is covered with liquid as a result of which the gas recombination rate is significantly reduced. On designing a, for example, gas-tight rechargeable cell, com~romises must be made between a high gas recombination rate, a high loadability and a large capacity.
This constitutes a problem, more specifically for cells having a nickel/nickel hydroxyde electrode as its positive electrode and a hydride-forming intermetallic compound as its negative electrode, since in such a cell no water transport takes place during the charging and discharging cycle. As a result thereof a mechanism which might ensure that the electrolyte periodically disappears from the electrodes is missing.
According to the invention, this problem is solved by producing an electrode having both hydrophilic and hydrophobic regions.
Gas recombination requires pores in which gas, electrolyte and metal contact each other, and that is optimally the case on a surface having a transition from a hydrophilic to a hydrophobic character. Thus, the water produced during hydrogen recombination will, for example, not cover the free, active surface but will be conveyed to a more hydrophilic region.
The invention is based on constructing an electrode which is locally very suitable for gas recombination reactions and in other places behaves as a suitable electrode for a rechargeable cell. ~y separating these functions, better properties are obtained then with an electrode which evidences the sa~e compromise properties over the entire surface area. In addition, any changes in the hydrophilic character of the electrode during the operating life of a rechargeable cell will have no or a much lower influence on the gas recombination rate.
The invention and its advantages will now be described in greater detail with reference to embodiments and an accompanying drawing, in which Figure 1 is a partially cross sectional and partly elevational view of a sealed rechargeable electrochemical cell according to the invention, Figures 2a and b are schematically an elevational view ~3~
PHN 12205 4 20.06.1988 and a cross-sectional view of an electrode for use in such a cell, and wherein Figure 3 is a schematic elevational view of a specific construction of an electrode for use in a cell according to the invention.
ExamDle of a recharaeable cell structure The cell which is shown in Figure 1 and which is sealed from the air is made from a suitable housing 1 made of metal, for example stainless steel and provided with a cover 2 having apertures for the conductors 3 and 4. By means of synthetic resin material rings 5 the conductors are insulated from the metal housing t1,2). At the outside the housing may have, for example, a diameter of 22 mm and a height of 41 mm. A wound section consisting of a negative electrode 6, a separator 7 and a positive electrode 8 is provided within the housing, whilst the whole assembly i9 enveloped by an electrically insulating plastic film 9 of, for example, polyvinyl chloride and bears on a disc 10 made of an electrically insulating material, for example polyvinyl chloride.
The negative electrode 6 comprises a hydride-forming intermetallic compound and is connected to the conductor 3. The hydride-formin~ compound has, for example, the composition LaO 8Ndo 2Ni2 5C2 4Sio 1 Further suitable hydride-~orming compounds are described in, for example, United States Patent US 4487817. The negative electrode 6 is produced by fusing appropriate quantities of the relevant elements and pulverizing the intermetallic compound thus ob~ained and by applying it to a nickel substrate, Eor example with the aid of a polymer binder material such as polyvinylalcohol. The paste is, for example, composed of 75% by weight of the intermetallic compound, 24.5% by weight of water and 0.5~ by ~eight of polyvinyl alcohol.
The positive electrode 8 is a nickel hydroxide electrode of the conventional sintered type, and is connected to the conductor 4.
An aqueous 6 N potassium hydroxide solution is used as the electrolyte. The electrolyte is absorbed in the separator 7 and is so contacted with the electrochemically active material of the two electrodes that it is wetted thereby. The separator is in the form of a non-woven sheet of polyamide fi~res.
~L 3 ~ -D ~
PHN 12205 5 2~.Q6.1988 The free gas space ~n the cell is approximately 5 cm3.
A sealed cell of this type has an EMF of between 1.2 and 1.4 V. The cells in accordance with the invention can be assembled in a conventional manner to form batteries comprising, for example, a plurality of series-arranged cells.
It is possible to use the electrode improved in accordance with the invention in electrochemical cells other than the cells described in the foregoing. The cell may be in open connection with the at~osphere or ~ay be sealed from the atmosphere. A cell sealed from the atmosphere may include a valve of such a dimension that it is made operative at a predetermined pressure.
In a rechargeable cell of the sealed type the electrochemical active portion of the positive electrode is made of, for example, nickel hydroxide, silver oxide or manganese oxide, nicke:L
hydroxide generally being preferred for practical reasons.
The electrolyte used in the cell generally consists of a solution of one or more alkaline metal hydroxides, such as lithium hydroxide, sodium hydroxide and potassium hydroxide, having a pH
exceeding 7.
In addition, the cell may include a separator ~hich electrically insulates the electrodes, but permits ion and gas transport. The separator may consist of (woven or non-wo~en) synthetic ; resin material fibres, for example polyamide fibres or polypropylene fibres, and preferably has a hydrophylic character.
The improvement of an electrode according to the invention may both relate to the positive and to the ne~ative electrode. An improvement of the negative electrode will be described in the following embodiments.
Embodi ent 1.
An electrochemically active material for the negative electrode of the composition LaO 8Ndo 2Ni2 5C2 4C2 4Sio 1 is prepared by mixing, fusing and pulverizing by means of repeated hydrogen adsorption and desorption of the required quantities of the different compounds. Thereafter the resultant material which with hydrogen is capable of forming a hydride is mixed with a binder, for example polyvinyl alcohol, which results in a paste. It i5 possible to substitute, for example, methyl cellulose for polyvinyl alcohol.
PHN 12205 6 20.06.1988 A porous nickel metal ~oil 11 having, for example, a thickness of 1.0 mm is thereafter impregnated at one side 12 with the paste, such that the other side of the foil 13 remains free o:E
electrochemically active material and consequentl~ has a free metal surface, see Figures 2a and b. This can be effected in a si~ple manner by, for example, applying the paste to one side of the foil and to press it into the foil.
The foil is subsequently built into an electrochemical cell, for example as described in the foregoing.
Embodiment 2.
Figure 3 shows an alternative eMbodiment of a negative electrode for use in an electrochemical cell in accordance with the in~ention. A synthetic resin tape, having, for example, a ~idth of 3 mm is helically wound around a plate or foil of porous nickel metal. Normal commercially available adhesive tape is suitable for this purpose.
Thereafter both sides of the nickel foil are impregnated with the pastes described for the preceding embodiment, by applying the paste to the foil and by subsequent rolling of the assembly to, for example, a thic~ness of 0.5 mm. This results in the foil having regions 15 which are impregnated on both sides with electrochemically active material, but also regions 14 which are not impregnated at all. Between these regions there are regions 16 which contain electrochemically active material at one side. Thexeafter the synthetic resin tape is removed a~d the electrode is ready for building into an electrochemical cell.
For the production of electrodes impregnated in accordance with a pattern, different suitable masking techniques or silk screening techniques may alternatively be used. A speckled pattern ~ay be chosen for this purpose. It is alternatively possible to choose a striped pattern, for example horizontal or vertical stripes, to promote gas transport in a desired direction.
At a cell produced in accordance with this example it was measured after 25 charging and discharging cycles that the pressure in the cell amounts to 0.15 MPa after 24 hours charging, both at a charging rate of 10% and at a charging rate of 20% of the capacity of the cell per hour.
ComParative_example. not in acc~r~a~c~ ~ith the invention.
A cell is produced in the manner as described ~o~ the
The invention has its object to provide an electrode for an electrochemical cell, and also a method of producing such a cell, in which gas reactions occur at the electrode with high efficiency and at a high rate. The invention has more speci-fically for its object to provide a rechargeable cell with a long operating life which may however not be obtained at the cost of the initial capacity and the loadability.
Accordingly, the present invention provides an electrochemical cell comprising a positive electrode and a neg-ative electrode, the negative electrode consisting of a substrate made of porous metal which is impregnated with an electrochem-ically active metal, the electrochemically active material being an intermetallic compound which forms a hydride with hydrogen, characterized in that the substrate is impregnated in accordance with a pattern such that a portion of the surfaces of the substrate contains free metal.
The invention further provides a method of producing an electrochemical cell comprising a positive electrode and a negative electrode, the negative electrode consisting of a sub-strate made of porous metal which is impregnated with an electrochemically active material, the electrochemically active material being an intermetallic compound which forms a hydride with hydrogen, characterized in that the electrode is produced by partly enveloping the substrate with a non-porous tape ~3~
~2a- 2010~-7800 material, whereafter the electrochemically active material in paste form is pressed into the porous substrate, whereafter the tape material is removed.
In a suitable embodiment of the electrochemical cell according to the invention the substrate of the electrode is designed as a flat plate which is impregnated at one side. The expression "flat" is used to indicate that the plate has no texture, for example a mesh structure. In use, the plate may be bent or rolled in any desired shape.
An electrode with locally very advantageous recombin-ation properties is obtained when the substrate is a flat plate wherein portions are present which at both sides are not impreg-nated, this being maintained during further processing operations on the electrodes, for example on rolling or further steps in which the electrodes are given their appropriate shapes.
A suitable, simple method of producing an electro-chemical cell according to the invention, is characterized in that the electrode is produced by partly wrapping a non-porous material in the form of tape around the substrate, whereafter the electrochemically active material in paste form is pressed into the porous substrate, whereafter the tape material is removed.
The rate at which the above-mentioned interface reactions proceed depends inter alla on the size of the c~talytic surface area present, i.e. the free metal surface of an electrode contacted by the gas. The quantity of active material which is decisive for the capacity of the cell must consequently not be too large. In ~" . \
:~3~
PHN 12205 3 20.06.1988 addition there is the fact that, when a cell contains an excessive quantity of electrolyte or when the electrolyte is preferably bound by the electrode, the free metal surface is covered with liquid as a result of which the gas recombination rate is significantly reduced. On designing a, for example, gas-tight rechargeable cell, com~romises must be made between a high gas recombination rate, a high loadability and a large capacity.
This constitutes a problem, more specifically for cells having a nickel/nickel hydroxyde electrode as its positive electrode and a hydride-forming intermetallic compound as its negative electrode, since in such a cell no water transport takes place during the charging and discharging cycle. As a result thereof a mechanism which might ensure that the electrolyte periodically disappears from the electrodes is missing.
According to the invention, this problem is solved by producing an electrode having both hydrophilic and hydrophobic regions.
Gas recombination requires pores in which gas, electrolyte and metal contact each other, and that is optimally the case on a surface having a transition from a hydrophilic to a hydrophobic character. Thus, the water produced during hydrogen recombination will, for example, not cover the free, active surface but will be conveyed to a more hydrophilic region.
The invention is based on constructing an electrode which is locally very suitable for gas recombination reactions and in other places behaves as a suitable electrode for a rechargeable cell. ~y separating these functions, better properties are obtained then with an electrode which evidences the sa~e compromise properties over the entire surface area. In addition, any changes in the hydrophilic character of the electrode during the operating life of a rechargeable cell will have no or a much lower influence on the gas recombination rate.
The invention and its advantages will now be described in greater detail with reference to embodiments and an accompanying drawing, in which Figure 1 is a partially cross sectional and partly elevational view of a sealed rechargeable electrochemical cell according to the invention, Figures 2a and b are schematically an elevational view ~3~
PHN 12205 4 20.06.1988 and a cross-sectional view of an electrode for use in such a cell, and wherein Figure 3 is a schematic elevational view of a specific construction of an electrode for use in a cell according to the invention.
ExamDle of a recharaeable cell structure The cell which is shown in Figure 1 and which is sealed from the air is made from a suitable housing 1 made of metal, for example stainless steel and provided with a cover 2 having apertures for the conductors 3 and 4. By means of synthetic resin material rings 5 the conductors are insulated from the metal housing t1,2). At the outside the housing may have, for example, a diameter of 22 mm and a height of 41 mm. A wound section consisting of a negative electrode 6, a separator 7 and a positive electrode 8 is provided within the housing, whilst the whole assembly i9 enveloped by an electrically insulating plastic film 9 of, for example, polyvinyl chloride and bears on a disc 10 made of an electrically insulating material, for example polyvinyl chloride.
The negative electrode 6 comprises a hydride-forming intermetallic compound and is connected to the conductor 3. The hydride-formin~ compound has, for example, the composition LaO 8Ndo 2Ni2 5C2 4Sio 1 Further suitable hydride-~orming compounds are described in, for example, United States Patent US 4487817. The negative electrode 6 is produced by fusing appropriate quantities of the relevant elements and pulverizing the intermetallic compound thus ob~ained and by applying it to a nickel substrate, Eor example with the aid of a polymer binder material such as polyvinylalcohol. The paste is, for example, composed of 75% by weight of the intermetallic compound, 24.5% by weight of water and 0.5~ by ~eight of polyvinyl alcohol.
The positive electrode 8 is a nickel hydroxide electrode of the conventional sintered type, and is connected to the conductor 4.
An aqueous 6 N potassium hydroxide solution is used as the electrolyte. The electrolyte is absorbed in the separator 7 and is so contacted with the electrochemically active material of the two electrodes that it is wetted thereby. The separator is in the form of a non-woven sheet of polyamide fi~res.
~L 3 ~ -D ~
PHN 12205 5 2~.Q6.1988 The free gas space ~n the cell is approximately 5 cm3.
A sealed cell of this type has an EMF of between 1.2 and 1.4 V. The cells in accordance with the invention can be assembled in a conventional manner to form batteries comprising, for example, a plurality of series-arranged cells.
It is possible to use the electrode improved in accordance with the invention in electrochemical cells other than the cells described in the foregoing. The cell may be in open connection with the at~osphere or ~ay be sealed from the atmosphere. A cell sealed from the atmosphere may include a valve of such a dimension that it is made operative at a predetermined pressure.
In a rechargeable cell of the sealed type the electrochemical active portion of the positive electrode is made of, for example, nickel hydroxide, silver oxide or manganese oxide, nicke:L
hydroxide generally being preferred for practical reasons.
The electrolyte used in the cell generally consists of a solution of one or more alkaline metal hydroxides, such as lithium hydroxide, sodium hydroxide and potassium hydroxide, having a pH
exceeding 7.
In addition, the cell may include a separator ~hich electrically insulates the electrodes, but permits ion and gas transport. The separator may consist of (woven or non-wo~en) synthetic ; resin material fibres, for example polyamide fibres or polypropylene fibres, and preferably has a hydrophylic character.
The improvement of an electrode according to the invention may both relate to the positive and to the ne~ative electrode. An improvement of the negative electrode will be described in the following embodiments.
Embodi ent 1.
An electrochemically active material for the negative electrode of the composition LaO 8Ndo 2Ni2 5C2 4C2 4Sio 1 is prepared by mixing, fusing and pulverizing by means of repeated hydrogen adsorption and desorption of the required quantities of the different compounds. Thereafter the resultant material which with hydrogen is capable of forming a hydride is mixed with a binder, for example polyvinyl alcohol, which results in a paste. It i5 possible to substitute, for example, methyl cellulose for polyvinyl alcohol.
PHN 12205 6 20.06.1988 A porous nickel metal ~oil 11 having, for example, a thickness of 1.0 mm is thereafter impregnated at one side 12 with the paste, such that the other side of the foil 13 remains free o:E
electrochemically active material and consequentl~ has a free metal surface, see Figures 2a and b. This can be effected in a si~ple manner by, for example, applying the paste to one side of the foil and to press it into the foil.
The foil is subsequently built into an electrochemical cell, for example as described in the foregoing.
Embodiment 2.
Figure 3 shows an alternative eMbodiment of a negative electrode for use in an electrochemical cell in accordance with the in~ention. A synthetic resin tape, having, for example, a ~idth of 3 mm is helically wound around a plate or foil of porous nickel metal. Normal commercially available adhesive tape is suitable for this purpose.
Thereafter both sides of the nickel foil are impregnated with the pastes described for the preceding embodiment, by applying the paste to the foil and by subsequent rolling of the assembly to, for example, a thic~ness of 0.5 mm. This results in the foil having regions 15 which are impregnated on both sides with electrochemically active material, but also regions 14 which are not impregnated at all. Between these regions there are regions 16 which contain electrochemically active material at one side. Thexeafter the synthetic resin tape is removed a~d the electrode is ready for building into an electrochemical cell.
For the production of electrodes impregnated in accordance with a pattern, different suitable masking techniques or silk screening techniques may alternatively be used. A speckled pattern ~ay be chosen for this purpose. It is alternatively possible to choose a striped pattern, for example horizontal or vertical stripes, to promote gas transport in a desired direction.
At a cell produced in accordance with this example it was measured after 25 charging and discharging cycles that the pressure in the cell amounts to 0.15 MPa after 24 hours charging, both at a charging rate of 10% and at a charging rate of 20% of the capacity of the cell per hour.
ComParative_example. not in acc~r~a~c~ ~ith the invention.
A cell is produced in the manner as described ~o~ the
3~3~2f~
PHN 12205 7 20.06.19~8 embodiment 2, the difference being that during impregnation no tape was wound around the porous nickel metal. The electrode is fully impregnated and has no free metal surface.
Measurements on this cell which was not produced in accordance with the invention showed that after 25 charging and discharging cycles the pressure in the cell is 0.50 and 0.80 MPa after 24 of hours of charging, at charging rates of 10~O and 20%, respectively, of the capacity of the cell per hour.
The electrochemical cells according to the invention have a high capacity and loadability and a long operating life, that is to say they can be charged and discharged a large number of ti~es, without a reduction in their serviceability. More specifically, the operating life is hardly negatively affected by overcharging or overdischarging at .
high rates.
The examples specifically refer to electrochemical cells where hydride forming materials are employed as electrochemically active material for one of the electrodes. However, the invention can also be applied with other electrochemically active materials, for example for nickel electrodes covered with a nickelhydroxide-containing paste.
PHN 12205 7 20.06.19~8 embodiment 2, the difference being that during impregnation no tape was wound around the porous nickel metal. The electrode is fully impregnated and has no free metal surface.
Measurements on this cell which was not produced in accordance with the invention showed that after 25 charging and discharging cycles the pressure in the cell is 0.50 and 0.80 MPa after 24 of hours of charging, at charging rates of 10~O and 20%, respectively, of the capacity of the cell per hour.
The electrochemical cells according to the invention have a high capacity and loadability and a long operating life, that is to say they can be charged and discharged a large number of ti~es, without a reduction in their serviceability. More specifically, the operating life is hardly negatively affected by overcharging or overdischarging at .
high rates.
The examples specifically refer to electrochemical cells where hydride forming materials are employed as electrochemically active material for one of the electrodes. However, the invention can also be applied with other electrochemically active materials, for example for nickel electrodes covered with a nickelhydroxide-containing paste.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electrochemical cell comprising a positive electrode and a negative electrode, the negative electrode con-sisting of a substrate made of porous metal which is impregnated with an electrochemically active metal, the electrochemically active material being an intermetallic compound which forms a hydride with hydrogen, characterized in that the substrate is impregnated in accordance with a pattern such that a portion of the surfaces of the substrate contains free metal.
2. An electrochemical cell as claimed in Claim 1, the substrate being designed as a flat plate which is impregnated at one side.
3. An electrochemical cell as claimed in Claim 1, the substrate being a flat plate wherein portions are present which are non-impregnated on both sides.
4. A method of producing an electrochemical cell com-prising a positive electrode and a negative electrode, the negative electrode consisting of a substrate made of porous metal which is impregnated with an electrochemically active material, the electrochemically active material being an intermetallic compound which forms a hydride with hydrogen, characterized in that the electrode is produced by partly enveloping the sub-strate with a non-porous tape material, whereafter the electrochemically active material in paste form is pressed into the porous substrate, whereafter the tape material is removed.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8701778A NL8701778A (en) | 1987-07-28 | 1987-07-28 | ELECTROCHEMICAL CELL. |
| NL8701778 | 1987-07-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1302489C true CA1302489C (en) | 1992-06-02 |
Family
ID=19850383
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000572899A Expired - Lifetime CA1302489C (en) | 1987-07-28 | 1988-07-25 | Electrochemical cell |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4783384A (en) |
| EP (1) | EP0301647B1 (en) |
| JP (1) | JP2512019B2 (en) |
| CA (1) | CA1302489C (en) |
| DE (1) | DE3852795T2 (en) |
| DK (1) | DK172626B1 (en) |
| ES (1) | ES2069544T3 (en) |
| NL (1) | NL8701778A (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5017442A (en) * | 1988-03-19 | 1991-05-21 | Hitachi Maxell, Ltd. | Coiled lithium battery |
| FR2679072B1 (en) * | 1991-07-09 | 1993-09-24 | Accumulateurs Fixes | ACTIVE MASS FOR ELECTROCHEMICAL GENERATOR ELECTRODE WITH THREE - DIMENSIONAL POROUS SUPPORT. |
| DE4316990C1 (en) * | 1993-05-21 | 1994-11-17 | Deutsche Automobilgesellsch | Gastight maintenance-free cell or battery |
| FR2712733B1 (en) * | 1993-11-16 | 1996-02-09 | Bollore Technologies | Method of manufacturing a multilayer electrochemical assembly comprising an electrolyte between two electrodes and assembly thus produced. |
| DE69606349T2 (en) * | 1995-05-09 | 2000-10-19 | Matsushita Electric Ind Co Ltd | Battery electrodes and manufacturing method |
| JP2976863B2 (en) * | 1995-10-09 | 1999-11-10 | 松下電器産業株式会社 | Manufacturing method of battery electrode |
| US5981108A (en) * | 1995-10-09 | 1999-11-09 | Matsushita Electric Industrial Co, Ltd. | Electrodes for battery and method of fabricating the same |
| US6162264A (en) * | 1996-06-17 | 2000-12-19 | Dai Nippon Printing Co., Ltd. | Process for producing porous coating layer electrode plate for secondary battery with nonaqueous electrolyte process for producing same and sheet for peeling active material layer |
| US6027835A (en) * | 1996-12-11 | 2000-02-22 | Fuji Film Celltec Co., Ltd. | Cell electrode sheet with displaced electrode depolarizing mixes |
| JP3191752B2 (en) * | 1996-12-26 | 2001-07-23 | 松下電器産業株式会社 | Nickel-hydrogen secondary battery and method for manufacturing electrode thereof |
| DE10146274A1 (en) * | 2001-09-19 | 2003-04-10 | Bosch Gmbh Robert | Metallic surface of a body, method for producing a structured metallic surface of a body and its use |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE546290C (en) * | 1930-07-20 | 1932-03-11 | Ig Farbenindustrie Ag | Process for increasing the durability of electrodes for alkaline collectors made by sintering iron powder |
| NL7600029A (en) * | 1976-01-05 | 1977-07-07 | Philips Nv | ELECTRODE, THE ELECTROCHEMICALLY ACTIVE PART OF WHICH CONSISTS OF A HYDRIDE FORMING INTERMETALLIC CONNECTION AND FACING BATTERY AND FUEL CELL WITH SUCH ELECTRODE. |
| US4142025A (en) * | 1976-09-17 | 1979-02-27 | Trw Inc. | Sealed nickel cadmium battery capable of withstanding high rate overdischarge |
| US4082875A (en) * | 1976-09-23 | 1978-04-04 | Samuel Citron | Tape having a longitudinal strip of adhesive which is useful as a means for framing sheets |
| US4033803A (en) * | 1976-11-02 | 1977-07-05 | Coder Glen L | Double adhesive masking tape |
| GB2006514B (en) * | 1977-10-21 | 1982-05-06 | Atomic Energy Authority Uk | Electric cells |
| NL8303630A (en) * | 1983-10-21 | 1985-05-17 | Philips Nv | ELECTROCHEMICAL CELL WITH STABLE HYDRIDE-FORMING MATERIALS. |
| JPS60130053A (en) * | 1983-12-15 | 1985-07-11 | Toshiba Corp | Sealed secondary battery having a negative electrode consisting of hydrogen-absorbing alloy electrode |
| US4605603A (en) * | 1983-12-26 | 1986-08-12 | Kabushiki Kaisha Toshiba | Hermetically sealed metallic oxide-hydrogen battery using hydrogen storage alloy |
| US4622277A (en) * | 1985-09-30 | 1986-11-11 | Duracell Inc. | Electrochemical cells |
| US4664989A (en) * | 1985-10-03 | 1987-05-12 | Union Carbide Corporation | Liquid cathode cell system employing a coiled electrode assembly |
| JP2639939B2 (en) * | 1987-07-20 | 1997-08-13 | 三洋電機株式会社 | Cathode for alkaline storage battery |
-
1987
- 1987-07-28 NL NL8701778A patent/NL8701778A/en not_active Application Discontinuation
- 1987-10-07 US US07/106,309 patent/US4783384A/en not_active Expired - Lifetime
- 1987-10-12 JP JP62254832A patent/JP2512019B2/en not_active Expired - Lifetime
-
1988
- 1988-07-18 DE DE3852795T patent/DE3852795T2/en not_active Expired - Lifetime
- 1988-07-18 ES ES88201552T patent/ES2069544T3/en not_active Expired - Lifetime
- 1988-07-18 EP EP88201552A patent/EP0301647B1/en not_active Expired - Lifetime
- 1988-07-25 CA CA000572899A patent/CA1302489C/en not_active Expired - Lifetime
- 1988-07-25 DK DK198804163A patent/DK172626B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| US4783384A (en) | 1988-11-08 |
| DK416388D0 (en) | 1988-07-25 |
| JP2512019B2 (en) | 1996-07-03 |
| NL8701778A (en) | 1989-02-16 |
| EP0301647A1 (en) | 1989-02-01 |
| DE3852795T2 (en) | 1995-08-24 |
| DK172626B1 (en) | 1999-03-15 |
| EP0301647B1 (en) | 1995-01-18 |
| DK416388A (en) | 1989-01-29 |
| DE3852795D1 (en) | 1995-03-02 |
| ES2069544T3 (en) | 1995-05-16 |
| JPS6441164A (en) | 1989-02-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0697746B1 (en) | Sealed zinc secondary battery and zinc electrode therefor | |
| RU2126193C1 (en) | Rechargeable electrochemical cell | |
| US7006346B2 (en) | Positive electrode of an electric double layer capacitor | |
| US5611823A (en) | Method for fabricating a battery electrode | |
| US6800399B2 (en) | Non-sintered thin electrode for battery, battery using same and process for same | |
| Jindra | Progress in sealed Ni-Zn cells, 1991–1995 | |
| CA1101053A (en) | Rechargeable galvanic cell | |
| US5637416A (en) | Cylindrical battery | |
| CA1302489C (en) | Electrochemical cell | |
| US3463669A (en) | Manganese dioxide-zinc alkaline secondary cell | |
| EP0384945B1 (en) | Sealed alkaline storage battery and method of producing negative electrode thereof | |
| US5460899A (en) | Sealed zinc secondary battery and zinc electrode therefor | |
| JPH07254431A (en) | Secondary battery containing electrolytic aqueous solution of which maintenance is unnecessary | |
| EP1958278B1 (en) | Rechargeable alkaline manganese cell having reduced capacity fade and improved cycle life | |
| EP1215741B1 (en) | Method for manufacturing a positive electrode plate | |
| EP1039566B1 (en) | Alkaline storage battery with two separators | |
| CN1310490A (en) | Button cell type air seal alkaline accumulator | |
| EP0800221B1 (en) | Alkaline storage battery and method for manufacturing positive electrode plate therefor | |
| US12206095B2 (en) | Electrode for rechargeable energy storage device | |
| US3347707A (en) | Charged secondary cell | |
| EP0834940B1 (en) | Sealed alkaline storage battery | |
| US5837396A (en) | Negative electrode construction for a secondary battery | |
| EP0520990B1 (en) | Manganese dioxide cathode for a rechargeable cell, and cell containing the same | |
| CA2173330C (en) | Bipolar electrochemical battery of stacked wafer cells | |
| JP3504303B2 (en) | Cylindrical alkaline secondary battery |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |