CA1195377A - Bifunctional gas diffusion electrode - Google Patents
Bifunctional gas diffusion electrodeInfo
- Publication number
- CA1195377A CA1195377A CA000416239A CA416239A CA1195377A CA 1195377 A CA1195377 A CA 1195377A CA 000416239 A CA000416239 A CA 000416239A CA 416239 A CA416239 A CA 416239A CA 1195377 A CA1195377 A CA 1195377A
- Authority
- CA
- Canada
- Prior art keywords
- gas
- layer
- side layer
- electrode
- electrolyte
- 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
Links
- 230000001588 bifunctional effect Effects 0.000 title claims abstract description 27
- 238000009792 diffusion process Methods 0.000 title claims abstract description 21
- 239000004065 semiconductor Substances 0.000 claims abstract description 20
- 230000004888 barrier function Effects 0.000 claims abstract description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 21
- 229910052751 metal Inorganic materials 0.000 claims description 15
- 239000002184 metal Substances 0.000 claims description 15
- 239000003792 electrolyte Substances 0.000 claims description 10
- 230000002209 hydrophobic effect Effects 0.000 claims description 10
- 229910052759 nickel Inorganic materials 0.000 claims description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 claims description 6
- 239000002131 composite material Substances 0.000 claims description 5
- 239000003054 catalyst Substances 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 3
- 238000010276 construction Methods 0.000 claims description 2
- 230000003647 oxidation Effects 0.000 claims description 2
- 238000007254 oxidation reaction Methods 0.000 claims description 2
- 239000010410 layer Substances 0.000 description 62
- 239000007789 gas Substances 0.000 description 52
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 229910052732 germanium Inorganic materials 0.000 description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- ODPOAESBSUKMHD-UHFFFAOYSA-L 6,7-dihydrodipyrido[1,2-b:1',2'-e]pyrazine-5,8-diium;dibromide Chemical compound [Br-].[Br-].C1=CC=[N+]2CC[N+]3=CC=CC=C3C2=C1 ODPOAESBSUKMHD-UHFFFAOYSA-L 0.000 description 1
- 229910001316 Ag alloy Inorganic materials 0.000 description 1
- 229910002899 Bi2Te3 Inorganic materials 0.000 description 1
- 229910004608 CdSnAs2 Inorganic materials 0.000 description 1
- 239000005630 Diquat Substances 0.000 description 1
- 229910005542 GaSb Inorganic materials 0.000 description 1
- 229910005900 GeTe Inorganic materials 0.000 description 1
- 229910000673 Indium arsenide Inorganic materials 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- 229910018289 SbBi Inorganic materials 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910001854 alkali hydroxide Inorganic materials 0.000 description 1
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- CXKCTMHTOKXKQT-UHFFFAOYSA-N cadmium oxide Inorganic materials [Cd]=O CXKCTMHTOKXKQT-UHFFFAOYSA-N 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 239000012777 electrically insulating material Substances 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- WPYVAWXEWQSOGY-UHFFFAOYSA-N indium antimonide Chemical compound [Sb]#[In] WPYVAWXEWQSOGY-UHFFFAOYSA-N 0.000 description 1
- RPQDHPTXJYYUPQ-UHFFFAOYSA-N indium arsenide Chemical compound [In]#[As] RPQDHPTXJYYUPQ-UHFFFAOYSA-N 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910000480 nickel oxide Inorganic materials 0.000 description 1
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052566 spinel group Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- XLOMVQKBTHCTTD-UHFFFAOYSA-N zinc oxide Inorganic materials [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 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
- H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
- H01M4/8605—Porous electrodes
- H01M4/8615—Bifunctional electrodes for rechargeable cells
-
- 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
- H01M12/00—Hybrid cells; Manufacture thereof
- H01M12/08—Hybrid cells; Manufacture thereof composed of a half-cell of a fuel-cell type and a half-cell of the secondary-cell type
-
- 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)
- Inert Electrodes (AREA)
- Hybrid Cells (AREA)
- Electrodes Of Semiconductors (AREA)
Abstract
BIFUNCTIONAL GAS DIFFUSION ELECTRODE
Abstract A bifunctional gas-diffusion electrode operative alternately for gas consumption and gas evolution comprises a gas-side layer in which gas consumption takes place, an electrolyte-side layer where gas evolution takes place and an intermediate rectifying layer of semi-conducting material arranged between the gas-side layer and the electrolyte-side layer so as to prevent unwanted gas evolution in the gas-side layer. The rectifying layer may be a p-n junction or may form part of a Schottky barrier junction.
o 0 o
Abstract A bifunctional gas-diffusion electrode operative alternately for gas consumption and gas evolution comprises a gas-side layer in which gas consumption takes place, an electrolyte-side layer where gas evolution takes place and an intermediate rectifying layer of semi-conducting material arranged between the gas-side layer and the electrolyte-side layer so as to prevent unwanted gas evolution in the gas-side layer. The rectifying layer may be a p-n junction or may form part of a Schottky barrier junction.
o 0 o
Description
( - l -3~
BI~UNCTIONAL GAS DIFFUSION E~ECTRODE
, Technical Field The invention relates to bifunctional gas diffusion electrodes operative alternately for gas consumption and gas evolution, and to secondary metal-gas batteries incorporating such electrodes.
Background Art By gas diffusion electrode is understood a porous catalytic electrode in which a gas reactant and an aqueous electrolyte are brought into contact to react electrochemically. Gas diffusion electrodes are used extensively in electrochemical power sources such as metal-air and metal-hydrogen batteries or fuel cells. In all of these, the gas diffusion electrode is one one side in contact with an electrolyte and on the other side in contact with a gas. In the metal-air battery, the gas is air.
Attempts have already been made to provide gas diffusion electrodes which operate alternately for gas consumption and gas evolution. These electrodes, which combine cathodic and anodic functions, are known as bi-functional gas diffusion electrodes. A typical application of these bifunctional electrodes is in secondary metal-gas batteries such as iron-air, zinc-air and nickel-hydrogen batteries ~hich consume gas during ;2 Q~ ~ ~ 7~ ~ ~ ~
BI~UNCTIONAL GAS DIFFUSION E~ECTRODE
, Technical Field The invention relates to bifunctional gas diffusion electrodes operative alternately for gas consumption and gas evolution, and to secondary metal-gas batteries incorporating such electrodes.
Background Art By gas diffusion electrode is understood a porous catalytic electrode in which a gas reactant and an aqueous electrolyte are brought into contact to react electrochemically. Gas diffusion electrodes are used extensively in electrochemical power sources such as metal-air and metal-hydrogen batteries or fuel cells. In all of these, the gas diffusion electrode is one one side in contact with an electrolyte and on the other side in contact with a gas. In the metal-air battery, the gas is air.
Attempts have already been made to provide gas diffusion electrodes which operate alternately for gas consumption and gas evolution. These electrodes, which combine cathodic and anodic functions, are known as bi-functional gas diffusion electrodes. A typical application of these bifunctional electrodes is in secondary metal-gas batteries such as iron-air, zinc-air and nickel-hydrogen batteries ~hich consume gas during ;2 Q~ ~ ~ 7~ ~ ~ ~
-2~
Canadian Patent 957,015 describes a rechargeable metal-air battery with a bifunctiona1 gas diffusion electrode compris-ing two electrode layers bonded to each other: a hydrophilic electrolyte-side layer made of porous nickel and a hydrophobic gas-side layer made of carbon, a PTFE binder and preferably impregnated with an oxygen-reducing catalyst. The hydrophilic porous nickel layer has a dual fun-ction, as a current collector and as an active layer for oxygen evolution during charge. The gas-side hydrophobic layer is an active area of the electrode during the gas consumption phase or discharge cycle of the battery. Thus, the two active zones of the electrode during charge and discharge were theoretically kept apart, but some unwanted oxygen evolution took place in the hydrophobic gas-side layer during charge and, despite attempts to prevent this by an increase of pressure on the gas-side of the electrode, was the cause of corrosion, deactivation of the catalyst and a reduced lifetime.
Efforts to improve these bifunctional electrodes, in particular to obtain an acceptable lifetime, have not been successful to date with the result that metal-gas batteries stlll have a relatively limited use.
Disclosure of Invention The invention is directed to novel composite bifunctional gas diffusion electrodes and to secondary metal-gas batteries incorporating such electrodes, as set out in the claims, in which the problem of ~5~
unwanted gas evolution in the gas-side layer is greatly reduced by provid-ing an intermediate rectifying layer of semi-conducting material. This semiconducting layer may be a p-n junction diode or may contact a layer of metal to form a Shottky barrier junction. This rectifier is always arranged in such a way that the gas-side layer is practically electrically inactive during the gas-evolution phase which corresponds to the charging cycle of the battery, so that substantially no undesired gas evolution can take place in this layer. Electron flow into or out of the gas-side layer of the electrode is thus allowed freely during the gas consumption phase which corresponds to discharge of the battery, but is strongly inhibited during charging.
The arrangement of the rectifying layer to provide the desired direction of electron flow depends on the nature of the gas reactant used, i.e. whether the gas is reduced or is oxidised during the consumption phase. When the supplied gas is reduced, electrons must be able to flow into the gas-side layer and when the supplied gas is oxidised, electrons must be able to flow out of the gas-side layer. To illustrate this, in the case of a p-n junction used in a metal~air battery (i.e. where gas reduction takes place), the p-type conducting zone will face the gas-side layer and the n-type conducting zone will face the electrolyte-side layer. Conversely, jn the case of gas oxidation (as in metal-hydrogen batteries), the relative position of the two zones will be reversed, the n-type semi-conducting zone facing the gas-side and the p-type semi-conducting zone facing the electrolyte-side of the bi-Functional electrode.
53~7 In one embodiment of the invention, the rectifying semi-conducting layer is a porous electrolyte permeable layer formed, for example, of appropriately doped materials such as Te, SbBi, Sb, Si, GeTe, Ge, Bi, InAs, InSb, CdSnAs2, GaSb and Bi2Te3.
In a preferred embodiment, the current collection means is a for-aminate metal current collector of sandwich construction in which the semi-conducting layer is encapsulated, and hence protected from the electrolyte. For example, the semi-conducting layer is sandwiched between two foraminous sheets of nickel foil. The outer part of this current col'lector can constitute the gas-evolving part of the electrolyte-side layer of the bifunctional electrode.
It is desirable but no essential for the rectifying layer to occupy the entire surface of the electrode. ConYeniently, and especially for large electrode, an array of small rectifying layers can be placed between the gas-side layer and the electrolyte-side layer.
Although the invention is described with specific reference to use of the electrodes in batteries, especially metal-gas batteries, the bi'functional gas-diffusion electrode of the invention is usefu'l in other systems involving alternate gas evolut:ion and consumption~ for example as oxygen cathodes in chlor-alkali electrolysis where gas evolution within the gas-diffusion electrode structure must be avoided. Such unwanted gas evolution can happen when the cells are short-circuited for maintenance.
(~
Canadian Patent 957,015 describes a rechargeable metal-air battery with a bifunctiona1 gas diffusion electrode compris-ing two electrode layers bonded to each other: a hydrophilic electrolyte-side layer made of porous nickel and a hydrophobic gas-side layer made of carbon, a PTFE binder and preferably impregnated with an oxygen-reducing catalyst. The hydrophilic porous nickel layer has a dual fun-ction, as a current collector and as an active layer for oxygen evolution during charge. The gas-side hydrophobic layer is an active area of the electrode during the gas consumption phase or discharge cycle of the battery. Thus, the two active zones of the electrode during charge and discharge were theoretically kept apart, but some unwanted oxygen evolution took place in the hydrophobic gas-side layer during charge and, despite attempts to prevent this by an increase of pressure on the gas-side of the electrode, was the cause of corrosion, deactivation of the catalyst and a reduced lifetime.
Efforts to improve these bifunctional electrodes, in particular to obtain an acceptable lifetime, have not been successful to date with the result that metal-gas batteries stlll have a relatively limited use.
Disclosure of Invention The invention is directed to novel composite bifunctional gas diffusion electrodes and to secondary metal-gas batteries incorporating such electrodes, as set out in the claims, in which the problem of ~5~
unwanted gas evolution in the gas-side layer is greatly reduced by provid-ing an intermediate rectifying layer of semi-conducting material. This semiconducting layer may be a p-n junction diode or may contact a layer of metal to form a Shottky barrier junction. This rectifier is always arranged in such a way that the gas-side layer is practically electrically inactive during the gas-evolution phase which corresponds to the charging cycle of the battery, so that substantially no undesired gas evolution can take place in this layer. Electron flow into or out of the gas-side layer of the electrode is thus allowed freely during the gas consumption phase which corresponds to discharge of the battery, but is strongly inhibited during charging.
The arrangement of the rectifying layer to provide the desired direction of electron flow depends on the nature of the gas reactant used, i.e. whether the gas is reduced or is oxidised during the consumption phase. When the supplied gas is reduced, electrons must be able to flow into the gas-side layer and when the supplied gas is oxidised, electrons must be able to flow out of the gas-side layer. To illustrate this, in the case of a p-n junction used in a metal~air battery (i.e. where gas reduction takes place), the p-type conducting zone will face the gas-side layer and the n-type conducting zone will face the electrolyte-side layer. Conversely, jn the case of gas oxidation (as in metal-hydrogen batteries), the relative position of the two zones will be reversed, the n-type semi-conducting zone facing the gas-side and the p-type semi-conducting zone facing the electrolyte-side of the bi-Functional electrode.
53~7 In one embodiment of the invention, the rectifying semi-conducting layer is a porous electrolyte permeable layer formed, for example, of appropriately doped materials such as Te, SbBi, Sb, Si, GeTe, Ge, Bi, InAs, InSb, CdSnAs2, GaSb and Bi2Te3.
In a preferred embodiment, the current collection means is a for-aminate metal current collector of sandwich construction in which the semi-conducting layer is encapsulated, and hence protected from the electrolyte. For example, the semi-conducting layer is sandwiched between two foraminous sheets of nickel foil. The outer part of this current col'lector can constitute the gas-evolving part of the electrolyte-side layer of the bifunctional electrode.
It is desirable but no essential for the rectifying layer to occupy the entire surface of the electrode. ConYeniently, and especially for large electrode, an array of small rectifying layers can be placed between the gas-side layer and the electrolyte-side layer.
Although the invention is described with specific reference to use of the electrodes in batteries, especially metal-gas batteries, the bi'functional gas-diffusion electrode of the invention is usefu'l in other systems involving alternate gas evolut:ion and consumption~ for example as oxygen cathodes in chlor-alkali electrolysis where gas evolution within the gas-diffusion electrode structure must be avoided. Such unwanted gas evolution can happen when the cells are short-circuited for maintenance.
(~
3~7 Brief Description of the Drawings Figure 1 is a schematic cross section of one metal-gas battery module with a bifunctional gas diffusion electrode according to this invention.
Figure 2 is a schematic cross-section of another bifunctional gas diffusion electrode with a composite current collector of the present invention, Figure 2A shows a detail of the composite current collector of Figure 2.
Best Modes for Carrying out the Invention As shown in Fig~ 1~ a metal-gas battery comprises a metal electrode 1, using iron, zinc, cadmium or nickel oxide as active material; an electrolyte compartment 2, containing an alkali hydroxide electrolyte, preferably KOH; and a bifunctional gas diffusion electrode 3. The bi-functional electrode 3 of the present invention comprises a porous carbon hydrophilic electrolyte side layer 4 and a hydrophobic gas side layer 6, separated by a porous semi~conducting layer 7. The hydrophilic porous electrolyte-side layer 4 contains a pressed-in current collector 5, prefer-able a foraminous nickel plate or mesh. The hydrophobic gas-side layer 6 has a catalytically-active gas reaction zone 6a made of pressed carbon particles impregnated with silver, platinum or another cata1yst and a binder preferably PTFE, and a hydrophobic backing 6b directly exposed to a reacting gas, e.g air/oxygen. The part of zone 6a adjacent the semi~conducting layer 7 is /~ ( 5;3~
sufficiently hydrophilic to be impregnated with electrolyte penetrating via layer 7 to set up a 3-phase reaction boundary within the generally hydrophobic reaction zone 6a.
The semi-conducting layer 7 is made of a semi-conductor such as germanium or silicon, doped by conventional techniques to provide a p-n junction diode. As shown, this diode is arranged to allow electron flow from layer 4 to layer 6 but not in the reverse direction. For example, the layer 7 consists of a wafer of n-type germanium doped with indium to form a p-type conducting zone on its face adjacent the gas-side layer 6.
The forward voltage bias or conduction of the layer is preferably no greater than about 0.1 V.
Multiples of the module shown in Figure 1 constitute a metal-gas battery of any desired capacity.
The battery is charged by an external charger 9 and discharged via external load ~. To charge the battery a potential difference is applied between the metal electrode 1 and current collector 5 by means of charger 9 so that electrons flow from electrolyte-side layer 4 of the gas diffusion electrode through the charger 9 to metal electrode 1. During charging, gas evolut;on takes place on the electrolyte-side 4 of the gas diffusion electrode which acts as anode; however, virtually no gas evolution can take place within the gas-side layer 6 because of the rectifying effect of the semi-conducting layer 7. Conversely, when discharging the battery, electrons flow from the metal electrode 1 through the load 8 and current collector 5 and through the semi-conductor layer 7 into the gas side 6 of the bi-functional electrode where a reduction reaction with a supplied gas takes place in zone 6a.
To minimize the forward bias voltage of the rectifying semi-conducting layer 7, the battery may conveniently be operated above room temperature.
Figure 2 shows a bifunctional electrode 20 comprising a composite current collector 21, a gas-side layer 22, e.g. of porous carbon im-pregnated with a catalyst, and a hydrophobic backing layer 23. The current collector 21 comprises two foraminous sheets 24, 25 of corrosion-resistant metal, preferably nickel or a nickel/silver alloy, between which a semi-conductor layer 26 is sandwiched with a protective layer of electrically insulating material 27 applied over the exposed edges so that the semi-conductor layer 26 is encapsulated. The semi-conductor material is thus protected from chemical attack when the electrode is in its operating environment with an electrolyte such as KOH on the side of the current collector 21 and a gas supplied to the gas-side layer 22 via the backing 23. The outer sheet 24 of the current collector thus forms the operative gas-evolving face of the bifunctional electrode. If desired, to reduce energy requirements during charging of the battery, sheet 24 can be coated with an electrocatalytic gas-evolution coating such as one or more platinum-group metal oxides, mixed platinum-group metal oxide valve metal oxides, or other mixed oxides such as spinels and perovskites. Also, if desired, the surface of sheet 25 ~acing the gas-side layer can be coated with silver or another coating which reduces corrosion contact between the current collector and the carbon of layer 22.
The outer sheet 24 is connected to a metal electrode of a battery via an external charger or a load and thus effectively acts as current collector whereas the rear sheet 25 simply acts as a backing and to conduct current into or out of the gas-side layer during discharge of the battery.
As before, the semi-conducting layer 26 acts as a rectifier to prevent the flow of current into or out of layer 22 during charging of the battery thereby preventing unwanted gas evolution therein. The layer 26 may be formed of any of the aforementioned semi-conducting materials.
The rectifying effect may be produced either by making the layer 26 form a p-n junction diode, or by making the layer 26 of p or n-type semi-conducting material which forms a Schottky barrier junction with one of the metal sheets 24 or 25 and an ohmic contact with the other one. In the case of a p-n junction, the layer 26 should have a low contact resistance with the nickel or other sheets 24, 25 and thls can be ensured by vapour deposition of a thin metal layer on the semi-conductor prior to lamination of the sandwich assembly. A Schottky barrier junction can conveniently be formed with two nickel sheets 24, 25 in contact with an n-doped layer having one surface heavily doped n+, a rectifying Schottky junction being formed at the inter face of the n-doped region and one nickel sheet, and a non-rectifying ohmic contact being formed at the interface of the n doped reglon and other nickel sheet.
Figure 2 is a schematic cross-section of another bifunctional gas diffusion electrode with a composite current collector of the present invention, Figure 2A shows a detail of the composite current collector of Figure 2.
Best Modes for Carrying out the Invention As shown in Fig~ 1~ a metal-gas battery comprises a metal electrode 1, using iron, zinc, cadmium or nickel oxide as active material; an electrolyte compartment 2, containing an alkali hydroxide electrolyte, preferably KOH; and a bifunctional gas diffusion electrode 3. The bi-functional electrode 3 of the present invention comprises a porous carbon hydrophilic electrolyte side layer 4 and a hydrophobic gas side layer 6, separated by a porous semi~conducting layer 7. The hydrophilic porous electrolyte-side layer 4 contains a pressed-in current collector 5, prefer-able a foraminous nickel plate or mesh. The hydrophobic gas-side layer 6 has a catalytically-active gas reaction zone 6a made of pressed carbon particles impregnated with silver, platinum or another cata1yst and a binder preferably PTFE, and a hydrophobic backing 6b directly exposed to a reacting gas, e.g air/oxygen. The part of zone 6a adjacent the semi~conducting layer 7 is /~ ( 5;3~
sufficiently hydrophilic to be impregnated with electrolyte penetrating via layer 7 to set up a 3-phase reaction boundary within the generally hydrophobic reaction zone 6a.
The semi-conducting layer 7 is made of a semi-conductor such as germanium or silicon, doped by conventional techniques to provide a p-n junction diode. As shown, this diode is arranged to allow electron flow from layer 4 to layer 6 but not in the reverse direction. For example, the layer 7 consists of a wafer of n-type germanium doped with indium to form a p-type conducting zone on its face adjacent the gas-side layer 6.
The forward voltage bias or conduction of the layer is preferably no greater than about 0.1 V.
Multiples of the module shown in Figure 1 constitute a metal-gas battery of any desired capacity.
The battery is charged by an external charger 9 and discharged via external load ~. To charge the battery a potential difference is applied between the metal electrode 1 and current collector 5 by means of charger 9 so that electrons flow from electrolyte-side layer 4 of the gas diffusion electrode through the charger 9 to metal electrode 1. During charging, gas evolut;on takes place on the electrolyte-side 4 of the gas diffusion electrode which acts as anode; however, virtually no gas evolution can take place within the gas-side layer 6 because of the rectifying effect of the semi-conducting layer 7. Conversely, when discharging the battery, electrons flow from the metal electrode 1 through the load 8 and current collector 5 and through the semi-conductor layer 7 into the gas side 6 of the bi-functional electrode where a reduction reaction with a supplied gas takes place in zone 6a.
To minimize the forward bias voltage of the rectifying semi-conducting layer 7, the battery may conveniently be operated above room temperature.
Figure 2 shows a bifunctional electrode 20 comprising a composite current collector 21, a gas-side layer 22, e.g. of porous carbon im-pregnated with a catalyst, and a hydrophobic backing layer 23. The current collector 21 comprises two foraminous sheets 24, 25 of corrosion-resistant metal, preferably nickel or a nickel/silver alloy, between which a semi-conductor layer 26 is sandwiched with a protective layer of electrically insulating material 27 applied over the exposed edges so that the semi-conductor layer 26 is encapsulated. The semi-conductor material is thus protected from chemical attack when the electrode is in its operating environment with an electrolyte such as KOH on the side of the current collector 21 and a gas supplied to the gas-side layer 22 via the backing 23. The outer sheet 24 of the current collector thus forms the operative gas-evolving face of the bifunctional electrode. If desired, to reduce energy requirements during charging of the battery, sheet 24 can be coated with an electrocatalytic gas-evolution coating such as one or more platinum-group metal oxides, mixed platinum-group metal oxide valve metal oxides, or other mixed oxides such as spinels and perovskites. Also, if desired, the surface of sheet 25 ~acing the gas-side layer can be coated with silver or another coating which reduces corrosion contact between the current collector and the carbon of layer 22.
The outer sheet 24 is connected to a metal electrode of a battery via an external charger or a load and thus effectively acts as current collector whereas the rear sheet 25 simply acts as a backing and to conduct current into or out of the gas-side layer during discharge of the battery.
As before, the semi-conducting layer 26 acts as a rectifier to prevent the flow of current into or out of layer 22 during charging of the battery thereby preventing unwanted gas evolution therein. The layer 26 may be formed of any of the aforementioned semi-conducting materials.
The rectifying effect may be produced either by making the layer 26 form a p-n junction diode, or by making the layer 26 of p or n-type semi-conducting material which forms a Schottky barrier junction with one of the metal sheets 24 or 25 and an ohmic contact with the other one. In the case of a p-n junction, the layer 26 should have a low contact resistance with the nickel or other sheets 24, 25 and thls can be ensured by vapour deposition of a thin metal layer on the semi-conductor prior to lamination of the sandwich assembly. A Schottky barrier junction can conveniently be formed with two nickel sheets 24, 25 in contact with an n-doped layer having one surface heavily doped n+, a rectifying Schottky junction being formed at the inter face of the n-doped region and one nickel sheet, and a non-rectifying ohmic contact being formed at the interface of the n doped reglon and other nickel sheet.
Claims (11)
1. A composite bifunctional porous gas-diffusion electrode operative alternately for gas consumption and gas evolution, comprising a gas-side layer operative for gas consumption, an electrolyte-side layer operative for gas evolution and current-collection means associated with the electrolyte-side layer, characterized in that it comprises an intermediate rectifying layer of semi-conducting material between the gas-side layer and the electrolyte-side layer.
2. The bifunctional electrode of Claim 1, wherein the rectifying layer of semi-conducting material is a p-n junction diode.
3. The bifunctional electrode of Claim 2, wherein the gas-side layer is operative for gas reduction, and the layer of semi-conducting material has a p-type conduction zone facing the gas-side layer and an n-type conduction zone facing the electro-lyte-side layer.
4. The bifunctional electrode of Claim 2, wherein the gas-side layer is operative for gas oxidation, and the layer of semi-conducting material has an n-type conduction zone facing the gas-side layer and a p-type conduction zone facing the electro-lyte-side layer.
5. The bifunctional electrode of Claim 1, wherein the layer of semi-conducting material contacts a layer of metal to form a Schottky barrier junction.
6. The bifunctional electrode of Claim 1, wherein the layer of semi-conducting material is porous and electrolyte-permeable.
7. The bifunctional electrode of Claim 1, wherein the current-collection means is a foraminate metal current collector of sandwich construction in which the layer of semi-conducting material is encapsulated.
8. The bifunctional electrode of Claim 7, wherein the layer of semi-conducting material is sandwiched between two foraminate sheets of nickel.
9. The bifunctional electrode of Claim 1, wherein the gas-side layer comprises a hydrophobic body having a hydrophilic part in contact with the layer of semi-conducting material.
10. The bifunctional electrode of Claim 9, wherein the gas-side layer comprises carbon, hydrophobic material and a catalyst.
11. A secondary metal-gas battery comprising a metal electrode, a porous gas-diffusion bifunctional electrode having a gas-side layer operative during discharge for gas consumption, an electrolyte-side layer operative during charging for gas evolution and current-collection means associated with the electrolyte-side layer, electrolyte between the metal electrode and the electrolyte-side of the bifunctional electrode, and means for supplying gas to the gas-side layer of the bifunctional electrode, characterized in that the bifunctional electrode comprises an intermediate rectifying layer of semiconducting material between the gas-side layer and the electrolyte-side layer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US332,519 | 1981-12-21 | ||
| US06/332,519 US4409301A (en) | 1981-12-21 | 1981-12-21 | Bifunctional gas diffusion electrode |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1195377A true CA1195377A (en) | 1985-10-15 |
Family
ID=23298585
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000416239A Expired CA1195377A (en) | 1981-12-21 | 1982-11-24 | Bifunctional gas diffusion electrode |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4409301A (en) |
| EP (1) | EP0082553B1 (en) |
| JP (1) | JPS58111269A (en) |
| AT (1) | ATE29089T1 (en) |
| CA (1) | CA1195377A (en) |
| DE (1) | DE3277049D1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE461820B (en) * | 1987-08-10 | 1990-03-26 | Ts Lab Elektrochimicheski Izto | DEVICE AND ACID RECOVERY IN LEAD BATTERIES |
| US5306579A (en) * | 1992-10-30 | 1994-04-26 | Aer Energy Resources, Inc. | Bifunctional metal-air electrode |
| US5318862A (en) * | 1993-09-22 | 1994-06-07 | Westinghouse Electric Corp. | Bifunctional gas diffusion electrodes employing wettable, non-wettable layered structure using the mud-caking concept |
| EP1843415A1 (en) * | 2006-04-06 | 2007-10-10 | Vlaamse Instelling Voor Technologisch Onderzoek (Vito) | Bifunctional gas diffusion electrodes |
| CA2824007C (en) * | 2011-02-04 | 2019-02-19 | Afc Energy Plc | Fuel cell electrodes |
| WO2012111101A1 (en) * | 2011-02-16 | 2012-08-23 | 富士通株式会社 | Air secondary battery |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3400305A (en) * | 1964-08-18 | 1968-09-03 | Audrey Dinwiddie Coffman | Alternating current electrodes for electrochemical power cells |
| US3898103A (en) * | 1969-03-21 | 1975-08-05 | Electrochem Inc | Semi-conductor electrode depolarizer |
| FR2085867A1 (en) * | 1970-04-06 | 1971-12-31 | Leesona Corp | Rechargeable metal/air or metal-oxygencells |
| FR2102480A5 (en) * | 1970-08-05 | 1972-04-07 | Comp Generale Electricite | Fuel electrode for metal-air/oxygen cell - having second porous layer for disengaging oxygen |
| DE2057446C3 (en) * | 1970-11-23 | 1981-11-26 | Deutsche Automobilgesellschaft Mbh, 7000 Stuttgart | Reversible air electrode for metal-air elements with a rechargeable negative electrode |
| US4007059A (en) * | 1975-08-20 | 1977-02-08 | General Motors Corporation | Electrochemical cell electrode separator and method of making it and fuel cell containing same |
| US4333993A (en) * | 1980-09-22 | 1982-06-08 | Gould Inc. | Air cathode for air depolarized cells |
| US4341848A (en) * | 1981-03-05 | 1982-07-27 | The United States Of America As Represented By The United States Department Of Energy | Bifunctional air electrodes containing elemental iron powder charging additive |
-
1981
- 1981-12-21 US US06/332,519 patent/US4409301A/en not_active Expired - Fee Related
-
1982
- 1982-11-24 CA CA000416239A patent/CA1195377A/en not_active Expired
- 1982-12-09 DE DE8282201564T patent/DE3277049D1/en not_active Expired
- 1982-12-09 AT AT82201564T patent/ATE29089T1/en not_active IP Right Cessation
- 1982-12-09 EP EP82201564A patent/EP0082553B1/en not_active Expired
- 1982-12-20 JP JP57223636A patent/JPS58111269A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| EP0082553A3 (en) | 1985-07-17 |
| DE3277049D1 (en) | 1987-09-24 |
| US4409301A (en) | 1983-10-11 |
| JPS58111269A (en) | 1983-07-02 |
| EP0082553B1 (en) | 1987-08-19 |
| JPH0139634B2 (en) | 1989-08-22 |
| ATE29089T1 (en) | 1987-09-15 |
| EP0082553A2 (en) | 1983-06-29 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0667041B1 (en) | Bifunctional airelectrode | |
| US5069988A (en) | Metal and metal oxide catalyzed electrodes for electrochemical cells, and methods of making same | |
| US6998184B2 (en) | Hybrid fuel cell | |
| US3432354A (en) | Electrochemical power supply with movable anode material | |
| US3438812A (en) | Rechargeable alkaline cell | |
| US7435492B2 (en) | Hybrid fuel cell | |
| WO2019151063A1 (en) | Negative electrode for metal air cell | |
| JPS61283173A (en) | Power source element | |
| US7220501B2 (en) | Integrated hybrid electrochemical device | |
| CA1195377A (en) | Bifunctional gas diffusion electrode | |
| US6060197A (en) | Zinc based electrochemical cell | |
| EP2001072A2 (en) | Powdered Fuel Cell | |
| EP2909880B1 (en) | Electrochemical cell with doping of metallic anodes | |
| EP0114884A1 (en) | Sealed nickel-zinc battery | |
| EP0533711A1 (en) | Metal and metal oxide catalyzed electrodes for electrochemical cells, and methods of making same | |
| US7906246B2 (en) | Powdered fuel cell | |
| US20220013864A1 (en) | Metal-air battery | |
| JP3196151B2 (en) | Light air secondary battery | |
| Jörissen et al. | Applications of Bifunctional Air Electrodes | |
| JORISSEN et al. | Center for Solar Energy and Hydrogen Research Energy Storage and Energy Conversion Division, Ulm (Germany) | |
| Hine | Batteries | |
| JPH06223888A (en) | Light-air secondary battery |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEC | Expiry (correction) | ||
| MKEX | Expiry |