CA1041620A - Cathode electrode for an electrical device and method - Google Patents
Cathode electrode for an electrical device and methodInfo
- Publication number
- CA1041620A CA1041620A CA232,809A CA232809A CA1041620A CA 1041620 A CA1041620 A CA 1041620A CA 232809 A CA232809 A CA 232809A CA 1041620 A CA1041620 A CA 1041620A
- Authority
- CA
- Canada
- Prior art keywords
- cathode electrode
- copper
- capacitor
- electrolyte
- anode
- 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
- 238000000034 method Methods 0.000 title claims description 15
- 239000003990 capacitor Substances 0.000 claims abstract description 50
- 239000010949 copper Substances 0.000 claims abstract description 43
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 38
- 229910052802 copper Inorganic materials 0.000 claims abstract description 38
- 150000001875 compounds Chemical class 0.000 claims abstract description 20
- XSOKHXFFCGXDJZ-UHFFFAOYSA-N telluride(2-) Chemical compound [Te-2] XSOKHXFFCGXDJZ-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000000463 material Substances 0.000 claims abstract description 12
- OMZSGWSJDCOLKM-UHFFFAOYSA-N copper(II) sulfide Chemical compound [S-2].[Cu+2] OMZSGWSJDCOLKM-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052711 selenium Inorganic materials 0.000 claims abstract 2
- 229910052717 sulfur Inorganic materials 0.000 claims abstract 2
- 229910052714 tellurium Inorganic materials 0.000 claims abstract 2
- 239000003792 electrolyte Substances 0.000 claims description 36
- 229910052751 metal Inorganic materials 0.000 claims description 18
- 239000002184 metal Substances 0.000 claims description 18
- 239000000243 solution Substances 0.000 claims description 13
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 12
- IRPLSAGFWHCJIQ-UHFFFAOYSA-N selanylidenecopper Chemical compound [Se]=[Cu] IRPLSAGFWHCJIQ-UHFFFAOYSA-N 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 7
- 229910052709 silver Inorganic materials 0.000 claims description 7
- 239000007864 aqueous solution Substances 0.000 claims description 6
- 150000003839 salts Chemical class 0.000 claims description 6
- 229910052715 tantalum Inorganic materials 0.000 claims description 5
- 229910045601 alloy Inorganic materials 0.000 claims description 4
- 239000000956 alloy Substances 0.000 claims description 4
- 235000011149 sulphuric acid Nutrition 0.000 claims description 4
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 claims description 3
- 229910000366 copper(II) sulfate Inorganic materials 0.000 claims description 3
- 239000000470 constituent Substances 0.000 claims description 2
- 235000011167 hydrochloric acid Nutrition 0.000 claims description 2
- 239000011244 liquid electrolyte Substances 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 claims description 2
- 235000011007 phosphoric acid Nutrition 0.000 claims description 2
- LAJZODKXOMJMPK-UHFFFAOYSA-N tellurium dioxide Chemical compound O=[Te]=O LAJZODKXOMJMPK-UHFFFAOYSA-N 0.000 claims description 2
- 229910017770 Cu—Ag Inorganic materials 0.000 claims 2
- 229910003069 TeO2 Inorganic materials 0.000 claims 1
- 150000003016 phosphoric acids Chemical class 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 9
- -1 copper sele-nide Chemical class 0.000 abstract description 3
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 abstract 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 abstract 1
- 238000004519 manufacturing process Methods 0.000 abstract 1
- 229920000136 polysorbate Polymers 0.000 abstract 1
- 239000011669 selenium Substances 0.000 abstract 1
- 239000011593 sulfur Substances 0.000 abstract 1
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 abstract 1
- 239000011248 coating agent Substances 0.000 description 16
- 238000000576 coating method Methods 0.000 description 16
- 239000002253 acid Substances 0.000 description 10
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 6
- 239000004332 silver Substances 0.000 description 6
- 238000013461 design Methods 0.000 description 5
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 5
- 229910000881 Cu alloy Inorganic materials 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 4
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 238000011049 filling Methods 0.000 description 3
- 238000007747 plating Methods 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- SITVSCPRJNYAGV-UHFFFAOYSA-N tellurous acid Chemical compound O[Te](O)=O SITVSCPRJNYAGV-UHFFFAOYSA-N 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 238000013459 approach Methods 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 239000003599 detergent Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 230000000873 masking effect Effects 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- JPJALAQPGMAKDF-UHFFFAOYSA-N selenium dioxide Chemical compound O=[Se]=O JPJALAQPGMAKDF-UHFFFAOYSA-N 0.000 description 2
- 229910001316 Ag alloy Inorganic materials 0.000 description 1
- ZLSWBLPERHFHIS-UHFFFAOYSA-N Fenoprop Chemical compound OC(=O)C(C)OC1=CC(Cl)=C(Cl)C=C1Cl ZLSWBLPERHFHIS-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910018162 SeO2 Inorganic materials 0.000 description 1
- NEIHULKJZQTQKJ-UHFFFAOYSA-N [Cu].[Ag] Chemical compound [Cu].[Ag] NEIHULKJZQTQKJ-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 238000002048 anodisation reaction Methods 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229960000443 hydrochloric acid Drugs 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 229920001021 polysulfide Polymers 0.000 description 1
- 239000005077 polysulfide Substances 0.000 description 1
- 150000008117 polysulfides Polymers 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 150000003346 selenoethers Chemical class 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/04—Electrodes or formation of dielectric layers thereon
- H01G9/042—Electrodes or formation of dielectric layers thereon characterised by the material
- H01G9/0425—Electrodes or formation of dielectric layers thereon characterised by the material specially adapted for cathode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/04—Electrodes or formation of dielectric layers thereon
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
- Chemically Coating (AREA)
- Electroplating Methods And Accessories (AREA)
Abstract
CATHODE ELECTRODE FOR AN ELECTRICAL DEVICE
AND METHOD OF MAKING SAME
Abstract of the Disclosure A cathode electrode of copper-based material adapted for use in an electrical device is provided with a layer com-posed of at least one compound from the group of copper sele-nide, copper telluride and copper sulfide by the reaction be-tween the copper-based cathode electrode and an appropriate reactive compound of selenium, tellurium or sulfur. When utilized in an electrolytic capacitor, the layer on the cathode electrode helps to depolarize the capacitor and helps to increase the capacitance of the cathode electrode.
AND METHOD OF MAKING SAME
Abstract of the Disclosure A cathode electrode of copper-based material adapted for use in an electrical device is provided with a layer com-posed of at least one compound from the group of copper sele-nide, copper telluride and copper sulfide by the reaction be-tween the copper-based cathode electrode and an appropriate reactive compound of selenium, tellurium or sulfur. When utilized in an electrolytic capacitor, the layer on the cathode electrode helps to depolarize the capacitor and helps to increase the capacitance of the cathode electrode.
Description
2(~ :
The present invention re`lates to elec~rical devices, and more particularly, to cathode electrodes adapted for use -in electrolytic, dielectric oxide film-forming metal anode capacitors and the like.
While the present invention will be discussed hereinafter with reference to use in electrolytic capacitors, it is to be understood that the invention may be utilized in a variety of other ~ ;
electrical devices where a cathode electrode is required.
Electrolytic capac;tors of the sintered dielectric oxide film-forming metal anode type generally consist of a cathode electrode, an electrically conductive electrolyte and a porous anode ~;
with a dielectric oxide film formed thereon. Typically, the cathode electrode is composed of silver, an alloy of silver, copper, or an alloy of copper to impart high electrical conductivity and corrosion resistance, the electrolyte is an aqueous solution of an inorganic acid, and the anode is composed of a film-forming metal such as tantalum, aluminum, or niobium, preferably tantalum. Certain inorganic salts may be added to the electrolyte, for example see U.S. Patent 2,616,953 issued to J. M. Booe on November 4, 1952, to act as a depolarizer and to thereby help prevent the formation of potentially damaging gaseous products and films on the cathode electrode surface.
In most situations, the cathode electrode also functions as the case or housing for the electrolytic capacitor by surrounding and retaining both the anode and the electrolyte. Present practice is to -utilize silver as a main constituent of the cathode electrode because of the desirable electrical and chemical properties of silver. Due to the relatively high cost of silver, it would be advantageous to use copper or ' " '' ,' , ''' ~,, :
.
~v~z~ :
copper alloys for tha cathode electrode while still retaining the performance characteristics of silvex-based cathode elec-trodes.
The anode in this type of electrolytic capacitor is generally formed by pressing powders of the particular ~ilm-forming metal into the desired shape and then sintering the press-ed powder. The resultant sintered anode is characterized as having a myriad of interconnecting void areas and therefore has a very large surface area per unit of volume which contributes greatly to the capacitance of the device in which it is utilized.
A dielectric oxide film of the metal is then formed over ;
the anode, typically by an electrolytic anodization process.
While the anode exhibits a relatively large capaci-tance, the interface between the cathode electrode and the electrolyte has an inherent charge separation due to polar-ization and thus exhibits a cathodic capacitance. This cathodic capacitance due to polarization may result from the formation of an asymmetric conductive film on the cathode electrode surface or from electrochemically developed insoluble insulat-ing films or gas polarization films on the cathode electrodesurface.
Since both the anode and cathode electrode possess `~
inherent asymmetric conducting properties, the two electrodes are series-opposed with respect to their arrangement in the capacitor structure. When under the influence of an applied pulsating voltage, the electrodes charge and discharge alter-nately; that is, one electrode discharges as the other charges. ~ -As a consequence, the electrolyte between the electrodes re-mains at a negative potential toward the external electrodes throughout an alternating cycle. This differs from the charge-discharge function of two ordinary electrostatic capa-,. .- . . .
:,. , ~.,., , ~ ,, .
~4~L~20 citors connected in series, however, the law governing the admittance of the circuit remains the same: l/C (device) =
l/C (anode) + l/C (cathode) where C is capacitance. This relationship results in the condition that the charge trans-fer is limited by the smaller of the two capacitances in either arrangement.
In the design of electrolytic capacitors, par-ticularly relating to capacitor rating, the design is established invariably from the design parameters of the anode. Therefore the cathode capacitance should be made several orders of magnitude higher than the anode capacitance by suitable arrangement or treatment so as to be compatible with the anode design. Thus, the term l/C (cathode) in -the above relation would become small relative to the other terms and the device capacitance would become essentially equal to the anode capacitance. Ideally, the operating characteristics of the capacitor approach optimum stability as the cathode capacitance approaches infinity. This condition, of course, can be attained only approximately in practical design of capacitors.
Several methods are known to increase the capaci-tance of the cathode electrode in electrolytic, film-forming metal capacitors and they include;
(1) applying to the surface of the cathode elec-trode a layer of finely divided, substantially inert conduc-tive material such as carbon or certain of the platinum metals or gold; when properly applied, these materials provide a very high cathode surface area necessary for cathode capaci-tance, or (2) providing certain metal ions in the electro-
The present invention re`lates to elec~rical devices, and more particularly, to cathode electrodes adapted for use -in electrolytic, dielectric oxide film-forming metal anode capacitors and the like.
While the present invention will be discussed hereinafter with reference to use in electrolytic capacitors, it is to be understood that the invention may be utilized in a variety of other ~ ;
electrical devices where a cathode electrode is required.
Electrolytic capac;tors of the sintered dielectric oxide film-forming metal anode type generally consist of a cathode electrode, an electrically conductive electrolyte and a porous anode ~;
with a dielectric oxide film formed thereon. Typically, the cathode electrode is composed of silver, an alloy of silver, copper, or an alloy of copper to impart high electrical conductivity and corrosion resistance, the electrolyte is an aqueous solution of an inorganic acid, and the anode is composed of a film-forming metal such as tantalum, aluminum, or niobium, preferably tantalum. Certain inorganic salts may be added to the electrolyte, for example see U.S. Patent 2,616,953 issued to J. M. Booe on November 4, 1952, to act as a depolarizer and to thereby help prevent the formation of potentially damaging gaseous products and films on the cathode electrode surface.
In most situations, the cathode electrode also functions as the case or housing for the electrolytic capacitor by surrounding and retaining both the anode and the electrolyte. Present practice is to -utilize silver as a main constituent of the cathode electrode because of the desirable electrical and chemical properties of silver. Due to the relatively high cost of silver, it would be advantageous to use copper or ' " '' ,' , ''' ~,, :
.
~v~z~ :
copper alloys for tha cathode electrode while still retaining the performance characteristics of silvex-based cathode elec-trodes.
The anode in this type of electrolytic capacitor is generally formed by pressing powders of the particular ~ilm-forming metal into the desired shape and then sintering the press-ed powder. The resultant sintered anode is characterized as having a myriad of interconnecting void areas and therefore has a very large surface area per unit of volume which contributes greatly to the capacitance of the device in which it is utilized.
A dielectric oxide film of the metal is then formed over ;
the anode, typically by an electrolytic anodization process.
While the anode exhibits a relatively large capaci-tance, the interface between the cathode electrode and the electrolyte has an inherent charge separation due to polar-ization and thus exhibits a cathodic capacitance. This cathodic capacitance due to polarization may result from the formation of an asymmetric conductive film on the cathode electrode surface or from electrochemically developed insoluble insulat-ing films or gas polarization films on the cathode electrodesurface.
Since both the anode and cathode electrode possess `~
inherent asymmetric conducting properties, the two electrodes are series-opposed with respect to their arrangement in the capacitor structure. When under the influence of an applied pulsating voltage, the electrodes charge and discharge alter-nately; that is, one electrode discharges as the other charges. ~ -As a consequence, the electrolyte between the electrodes re-mains at a negative potential toward the external electrodes throughout an alternating cycle. This differs from the charge-discharge function of two ordinary electrostatic capa-,. .- . . .
:,. , ~.,., , ~ ,, .
~4~L~20 citors connected in series, however, the law governing the admittance of the circuit remains the same: l/C (device) =
l/C (anode) + l/C (cathode) where C is capacitance. This relationship results in the condition that the charge trans-fer is limited by the smaller of the two capacitances in either arrangement.
In the design of electrolytic capacitors, par-ticularly relating to capacitor rating, the design is established invariably from the design parameters of the anode. Therefore the cathode capacitance should be made several orders of magnitude higher than the anode capacitance by suitable arrangement or treatment so as to be compatible with the anode design. Thus, the term l/C (cathode) in -the above relation would become small relative to the other terms and the device capacitance would become essentially equal to the anode capacitance. Ideally, the operating characteristics of the capacitor approach optimum stability as the cathode capacitance approaches infinity. This condition, of course, can be attained only approximately in practical design of capacitors.
Several methods are known to increase the capaci-tance of the cathode electrode in electrolytic, film-forming metal capacitors and they include;
(1) applying to the surface of the cathode elec-trode a layer of finely divided, substantially inert conduc-tive material such as carbon or certain of the platinum metals or gold; when properly applied, these materials provide a very high cathode surface area necessary for cathode capaci-tance, or (2) providing certain metal ions in the electro-
-3-~L~4~
lyte which are capable of being electro-deposited on a cathode electrode of a suitable metal and dissolved therefrom in sub-stantially the exact proportion of the current flowing back and forth across the cathode-electrolyte interface.
In system (1) it is thought that the current tra-versing the electrolyte-cathode junction discharges hydrogen ~ -or hydroxyl ions which are absorbed on the surface of the metal to yield a dielectric film. In system (2), it is be-lieved the electrochemical discharge and disso]ution of metal ions creates an ionic double layer in the electrolyte at the cathode electrode surface, and the space charge across this layer exhibits a high capacitance.
Since film-forming metal anode type capacitors are usually made as small as possible and the anode capacitance is therefore very high per device volume, the usual practice is to employ both methods of increasing the capacitance of the cathode electrode. However, applying the layer of finely divid-ed conductive material to the surface of the cathode electrode is genexally tedious and costly, especially when gold or plati-num are utilized. The method generally involves the steps ofcleaning the cathode, applying a coat of masking material over a portion of the cathode electrode surface, etching the surface with an acid, rinsing, filling with plating solution, electroplating with a platinum anode, removing the anode and plating solution, rinsing, drying and removing the mask material.
It is therefore a feature of the present invention to provide a copper-based cathode electrode for an electrical device with a layer or coating thereon to help increase the capacitance of the cathode by increasing the effective surface area of the cathode electrode. Another feature of the pres-ent invention is that the layer applied to the cathode electrode _4 ~3L62C~
contains at least one compound selected from copper selenide, copper telluride and copper sulfide. Yet another feature of the present invention is that the method of applying the layer includes relatively few process steps and is therefore comparatively inexpensive. Another feature is that a copper-based cathode electrode with a layer according to this invention is substantially non-film forming, is non-gassing, offers mini-mal internal series resistance, stabilizes electrical character-istics of the capacitor and is substantially inert to corrosive chemical attack by an operating electrolyte. Yet another fea-ture of the present invention is that the electrolyte with which the copper-based cathode electrode is in contact is de-aerated so as to reduce the possibility of corrosion of the cathode electrode by oxidizing substances in the electrolyte.
These and various other features of this invention as well as many specific advantages will become more fully apparent from a detailed consideration of the remainder of this disclosure including the examples and the appended claims in conjunction with the accompanying drawing, in which the figure is a cross-sectional view of a typical electrolytic, film-forming metal anode capacitor.
Generally, the present invention comprehends a ca-thode electrode for an electrical device wherein the cathode electrode is composed of a copper based material and has a layer or coating over the cathode electrode surface of a com-pound selected from the group consistin~ of copper telluride, copper selenide, copper sulfide and mixtures thereof. The invention also comprehends a method for applying the layer to the cathode electrode surface. The invention is particularly adapted for use in electrolytic, film-forming metal anode - ;
.. ..
: ' ' .
capacitors where a high cathodic capacitance and stable electrical characteristics are desired.
In particular, the invention pertains to a capacitor comprising an anode electrode, a cathode electrode, and dielectric means between the anode electrode and the cathode electrode, the cathode electrode in-cluding a surface containing Cu contacted by at least semi-liquid elec-trolyte, and a composition on the cathode electrode surface containing at least one compound selected from the group of copper selenide, copper telluride and copper sulfide.
As indicated previouslya the present invention can be utilized in various electrical devices but will be discussed hereinafter with reference to its application in electrolytic capacitors although not limited thereto. The main advantages realized by the utilization of a copper-based cathode electrode are a significant reduction in the final cost of the completed capacitor without a reduction in performance capa-bility as compared to capacitors having platinized silver-based cathode electrodes, and the ease of forming the layer over the cathode electrode surface. ~-The invention can be more clearly understood with reference to the drawing. The figure ~s a cross-sectional view of an electrolytic capacitor 10 containing a dieleotri~ oxide film-~orm;ng metal anode 11 with anode riser 19. The anode 11 has a dielectric oxide film or layer (not shown) over its surface. In combination with anode 11 is cathode electrode 12 which also serves as the housing or case for capacitor 10.
The anode 11 ;s retained within the cathode housing 12 by means of the insulative bottom spacer 13 and end seal assembly 14. End seal assembly 14 is shown as a glass-to-metal seal 15 in conjunction with a resiliant washer 16, but the end seal assembly forms no part of the present in-Yention and, as is known in the art9 a wide variety of different types of structures may be employed to close the open end of the housing 12.
-' - ., : : ~ . . . -Z~
Electrolyte 17 contacts the anode 11 and the interior surface coating :~
18 of the cathode electrode 12. External electrical termination for ;
the cathode electrode is provided by cathode lead 20. ~ ~
: i.. '' ~: ~`
,. , ~
,~ .. ~.,;
,: : : :
C~
~, . ,.,.. . ~, . .. ...
,' ,'' ''' '',' ' ~ '" ,; ~,''; : ` ' ', ' " ''''', '''''' ' ' ',.': ";'' ''i ' '. , , ~`
: , ,:,., , ; , ,. . :. . . . ... . .. .. ..
~L~34~6;~ i The operating electrolyte 17 for the capacitor is typically a dilute, non-oxidizing aqueous solution of an inorganic acid such as sulfuric acid, phosphoric acid, hydro-chloric acid, and the like. The presently preferred electro-lyte is a 39 wt.% solution of sulfuric acid. To help prevent cor-rosion of the interior surfaces of the cathode electrode 12 by the electrolyte 17, preferably the electrolyte is de-aerated by means such as refluxing in a closed system before being added to the capacitor 10.
According to the present invention, the cathode elec-trode 12 is composed of a copper-based material, that is, a material containing at least 50 wt.~ copper. Preferably, the copper-based material contai~s at least 90% copper. One particularly advantageous material is argentiferous copper, CDA #116, which is a copper based alloy containing about 25 troy ounces of silver per ton of copper, or about 0.1 wt.
silverO This copper alloy has desirable mechanical proper-ties such as ductility, retention of work-hardenad temper over the operating temperature range of a typical capacitor, and good corrosion resistance.
As mentioned previously, the surface area of the case or housing acting as a cathode electrode 12 in the capaci~
tor 10 should be signi~icantly increased so as to take full advantage of the capacitance of the anode 11. Conventional methods of accomplishing this end include platinization by electrochemical means and application of an artificial graphite coating by means of a liquid dispersion or paint.
While conventional methods may be ade~uate for some purposes, it has been found that treatment of the interior of the cathode electrode 12 can be accomplished in fewer , .. .. , : , . .. .....
: ,;, , , . . . -, . ,, , :
1~4~ 0 steps, and therefore generally at a lower cost, by forming a coating 18 of copp~r selenide, copper telluride or copper sulfide by reaction of a solution of the appropriate acid or other reactive compound with the copper-based cathode electrode 12. Thus, for example, a reaction of seleneous acid with the copper-based cathode electrode 12 would produce a coating 18 of copper selenide, tellurous acid would yield copper telluride and a polysulfide would produce copper sulfide.
The presently pre~erred compound for the coating 18 over the cathode electrode 12 is copper telluride. Generally, the quantity of acid or compound required to form the coating 18 is in the range of about 0.2 to 1.0 milligrams per square centimeter of cathode electrode surface.
The coating 18 formed by the reaction product of the reactive acids or compounds with the cathode electrode 12 may be applied at several different stages of the capacitor assem-bly. The appropriate compound may be added to the fill electro-lyte 17 and thus the reaction takes place in the completed capacitor 10. Alternatively, the porous anode 11 may be dipped in an aqueous solution of the appropriate compound and then dried. The reaction will commence when the anode 11 is insert-ed into the electrolyte 17 and any unreacted compound will thereby remain in the capacitor 10. In another method, an a~ueous solution of the compound is placed in a dry housing 12 and the reaction with the cathode surface 12 allowed to take place. Then the remaining solution is removed and the housing 12 drained. The electrolyte 17 is added in a subsequent step and the capacitor assembly is then completed.
One particular advantage in utilizing a coating 18 of copper selenide, copper telluride or copper sulfide as oppo~ed to conventional methods of increasing the cathode 1~416~0 electrode surface area such as platinization ~nd graphite coating is that many processing steps in the assembly of an electrolytic capacitor can ba eliminated. For example, platinization of the interior surface of the cathode electrode requires the steps of masking, etching, rinsing, plating, rinsing and drying as set forth previously. The layers or coat-ing 18 of the present invention may be provided simply by add-ing a small amount of an appropriate compound, for example, tellurous acid, to the fill electrolyte. This particular acid can be formed in acid electrolytes by adding the oxide of the element, fox example, tellurium oxide (TeO2), to the acid -electrolyte such as sulfuric acid.
In the presently preferre~ method, the coating or layer over the cathode electrode is formed prior to the introduc-tion of the fill electrolyte. In this method, the reactive compound is formed in an aqueous media, usually an agueous solution of an acid such as H2S04, and brought into contact with the cathode electrode surface 12. The reaction between the reactive compound and the copper component of the cathode -;
~0 electrode is allowed to take place to form the layer of copper telluride, copper selenide, or copper sulfide. In most situa-tions, the optimum reaction time is between about five and twelve minutes. The presently preferred reaction time is eight minutes plus or minus two minutes. After the reaction, the solution is removed and the surface allowed to drain. Subse-~uently, the fill electrolyte is dispensed, the anode inserted, and the device sealed.
Thus, the method for providing the coating over the cathode electrode surface according to this invention is greatly simplified in comparison to the conventional methods such as platinization of the cathode electrode surface.
.. . . ; ." ::
, 6ZC~
It is also advantageous to add certain soluble inorganic salts as depolarizers to the operating electrolyte of capacitors according to this invention as as to minimize leakage current effects present during capacitor operation.
Such salts help to prevent the formation of gaseous products which are liberated due to leakage current between the electrodes. -One particular salt that can be used advantageously with a capacitor according to this invention is CuSO4, prefera~ly in its hydrated form and with sulfuric acid electrolytes.
The amount of salt needed is typically from about 0.1 wt.
to about 5 wt.% of the electrolyte.
Several capacitors made according to this invention and performance data for these capacitors are presented in the following examples. It should be understood that the examples are given for the purpose of illustration only and the examples do not limit the invention as has theretofore been described.
EXAMPLE I
A 450 uf capacitor of 6 volt rating is prepared according to the present invention.
A copper-based cathode housing composed of CDA #116 silver-copper, tough pitch, is fabricated with a length of about 0.677 inches and a diameter of about 0.187 inches. The interior of the housing is cleaned with a warm detergent solu-tion and rinsed with de-ionized water and then the excess water drained. An electrolyte of de-aerated 39 wt.% H2SO4 with the addition of 0.4 wt.% SeO2 is then poured into the housing. A
sintered tantalum anode with a dielectric oxide coating and a length of about 0.503 inches is placed in the electrolyte and the open end of the housing sealed with an appropriate seal .
" ~ ~ ' ! ', .
: :' ' ,, ~L~)41~;Z~
assembly .
The SeO2 forms an acid in the electrolyte and reacts during and after filling with the copper of the interior sur~
face of the cathode housiny to produce an adherent layer of copper selenide. The finished capacitor exhibits good per-formance data on a foward life test at 85C and on shock-vibration tests.
EXAMPLE II
A 78 uf capacitor of 50 volt rating is prepared according to the present invention.
The housing is the same size as the housing utilized in EXAMPLE I. Again the housing is cleansed by warm deter-gent solution and then rinsed with de-ionized water and drained.
A treating solution of about one gram of TeO2 in about 100 grams of 39 wt.% H2SO~ solution is dispensed into the housing, filling the housing to about 1/32 inch from the top of the housing. Reaction between the copper of the housing and the tellurous acid is allowed to take place to form the layer of copper telluride and then the housing is flushed with de-ionized water and dried at about 85C.
After the housing is dry, electrolyte consisting of a de-aerated aqueous solution of about 39 w~.~ H2SO4 with about 3 wt.~ CuSO4 ~ 5H2O is dispensed into the housing. A sintered tantalum anode with a dielectric oxide film thereon is in-serted into the electrolyte and the open end of the housing is closed by a seal assembly.
Two finished capacitors made by the above procedure are tested and are found to have the following electrical proper- ~-ties at various temperatures.
: ' , , , ,, "; ' ~4~2C~
Capacitance Change (~C) +25C -35C -55C ~85~ +25C
Unit 1 80~4 uf -12 -24 -0.37 -3.6 3.6%DF
Unit 2 81.2 uf -12 -20 -0.74 -3.8 3.7%DF
Acceptable ~40 tlO i5 Limits ,: ~
As can be noted from the above table, the performance of both capacitors is well within acceptable limits for temper-ature stability.
Forward life tests at 85C indicate that the abovetype capacitor is also within acceptable limits in terms of performance even after 1000 hours of testing. Percentage change in capacitance is less than 2~ and usually less than 1%, D.C. leakage is well below the initial value and percentage change in dissipation factor i5 less than 10~, usually less than 5%, well within acceptable limits.
Thus the invention as has been described comprehends the use of a copper-based~cathode electrode in an electrical device wherein a surface of the cathode electrode has an ad-herent layer or coating of a material selected from the group of copper selenide, copper telluride, copper sulfide or mix-tures thereof. The layer is relatively easy and inexpensive to apply to the cathode electrode surface and permits the efficient utilization of copper-based materials as cathode electrodes for electrical devices, especially electrolytic aapacitors.
While the present invention has been described with ~`
reference to particular embodiments thereof, it will be under-stood that numerous modifications may be made by those skilled in the art without actually departing from the spirit and scope of the invention as defined in the appended claims.
:; . ' ~ ~ , -: ....................... , . ' :", ' '' , ~' , .
. . . . .. ..
lyte which are capable of being electro-deposited on a cathode electrode of a suitable metal and dissolved therefrom in sub-stantially the exact proportion of the current flowing back and forth across the cathode-electrolyte interface.
In system (1) it is thought that the current tra-versing the electrolyte-cathode junction discharges hydrogen ~ -or hydroxyl ions which are absorbed on the surface of the metal to yield a dielectric film. In system (2), it is be-lieved the electrochemical discharge and disso]ution of metal ions creates an ionic double layer in the electrolyte at the cathode electrode surface, and the space charge across this layer exhibits a high capacitance.
Since film-forming metal anode type capacitors are usually made as small as possible and the anode capacitance is therefore very high per device volume, the usual practice is to employ both methods of increasing the capacitance of the cathode electrode. However, applying the layer of finely divid-ed conductive material to the surface of the cathode electrode is genexally tedious and costly, especially when gold or plati-num are utilized. The method generally involves the steps ofcleaning the cathode, applying a coat of masking material over a portion of the cathode electrode surface, etching the surface with an acid, rinsing, filling with plating solution, electroplating with a platinum anode, removing the anode and plating solution, rinsing, drying and removing the mask material.
It is therefore a feature of the present invention to provide a copper-based cathode electrode for an electrical device with a layer or coating thereon to help increase the capacitance of the cathode by increasing the effective surface area of the cathode electrode. Another feature of the pres-ent invention is that the layer applied to the cathode electrode _4 ~3L62C~
contains at least one compound selected from copper selenide, copper telluride and copper sulfide. Yet another feature of the present invention is that the method of applying the layer includes relatively few process steps and is therefore comparatively inexpensive. Another feature is that a copper-based cathode electrode with a layer according to this invention is substantially non-film forming, is non-gassing, offers mini-mal internal series resistance, stabilizes electrical character-istics of the capacitor and is substantially inert to corrosive chemical attack by an operating electrolyte. Yet another fea-ture of the present invention is that the electrolyte with which the copper-based cathode electrode is in contact is de-aerated so as to reduce the possibility of corrosion of the cathode electrode by oxidizing substances in the electrolyte.
These and various other features of this invention as well as many specific advantages will become more fully apparent from a detailed consideration of the remainder of this disclosure including the examples and the appended claims in conjunction with the accompanying drawing, in which the figure is a cross-sectional view of a typical electrolytic, film-forming metal anode capacitor.
Generally, the present invention comprehends a ca-thode electrode for an electrical device wherein the cathode electrode is composed of a copper based material and has a layer or coating over the cathode electrode surface of a com-pound selected from the group consistin~ of copper telluride, copper selenide, copper sulfide and mixtures thereof. The invention also comprehends a method for applying the layer to the cathode electrode surface. The invention is particularly adapted for use in electrolytic, film-forming metal anode - ;
.. ..
: ' ' .
capacitors where a high cathodic capacitance and stable electrical characteristics are desired.
In particular, the invention pertains to a capacitor comprising an anode electrode, a cathode electrode, and dielectric means between the anode electrode and the cathode electrode, the cathode electrode in-cluding a surface containing Cu contacted by at least semi-liquid elec-trolyte, and a composition on the cathode electrode surface containing at least one compound selected from the group of copper selenide, copper telluride and copper sulfide.
As indicated previouslya the present invention can be utilized in various electrical devices but will be discussed hereinafter with reference to its application in electrolytic capacitors although not limited thereto. The main advantages realized by the utilization of a copper-based cathode electrode are a significant reduction in the final cost of the completed capacitor without a reduction in performance capa-bility as compared to capacitors having platinized silver-based cathode electrodes, and the ease of forming the layer over the cathode electrode surface. ~-The invention can be more clearly understood with reference to the drawing. The figure ~s a cross-sectional view of an electrolytic capacitor 10 containing a dieleotri~ oxide film-~orm;ng metal anode 11 with anode riser 19. The anode 11 has a dielectric oxide film or layer (not shown) over its surface. In combination with anode 11 is cathode electrode 12 which also serves as the housing or case for capacitor 10.
The anode 11 ;s retained within the cathode housing 12 by means of the insulative bottom spacer 13 and end seal assembly 14. End seal assembly 14 is shown as a glass-to-metal seal 15 in conjunction with a resiliant washer 16, but the end seal assembly forms no part of the present in-Yention and, as is known in the art9 a wide variety of different types of structures may be employed to close the open end of the housing 12.
-' - ., : : ~ . . . -Z~
Electrolyte 17 contacts the anode 11 and the interior surface coating :~
18 of the cathode electrode 12. External electrical termination for ;
the cathode electrode is provided by cathode lead 20. ~ ~
: i.. '' ~: ~`
,. , ~
,~ .. ~.,;
,: : : :
C~
~, . ,.,.. . ~, . .. ...
,' ,'' ''' '',' ' ~ '" ,; ~,''; : ` ' ', ' " ''''', '''''' ' ' ',.': ";'' ''i ' '. , , ~`
: , ,:,., , ; , ,. . :. . . . ... . .. .. ..
~L~34~6;~ i The operating electrolyte 17 for the capacitor is typically a dilute, non-oxidizing aqueous solution of an inorganic acid such as sulfuric acid, phosphoric acid, hydro-chloric acid, and the like. The presently preferred electro-lyte is a 39 wt.% solution of sulfuric acid. To help prevent cor-rosion of the interior surfaces of the cathode electrode 12 by the electrolyte 17, preferably the electrolyte is de-aerated by means such as refluxing in a closed system before being added to the capacitor 10.
According to the present invention, the cathode elec-trode 12 is composed of a copper-based material, that is, a material containing at least 50 wt.~ copper. Preferably, the copper-based material contai~s at least 90% copper. One particularly advantageous material is argentiferous copper, CDA #116, which is a copper based alloy containing about 25 troy ounces of silver per ton of copper, or about 0.1 wt.
silverO This copper alloy has desirable mechanical proper-ties such as ductility, retention of work-hardenad temper over the operating temperature range of a typical capacitor, and good corrosion resistance.
As mentioned previously, the surface area of the case or housing acting as a cathode electrode 12 in the capaci~
tor 10 should be signi~icantly increased so as to take full advantage of the capacitance of the anode 11. Conventional methods of accomplishing this end include platinization by electrochemical means and application of an artificial graphite coating by means of a liquid dispersion or paint.
While conventional methods may be ade~uate for some purposes, it has been found that treatment of the interior of the cathode electrode 12 can be accomplished in fewer , .. .. , : , . .. .....
: ,;, , , . . . -, . ,, , :
1~4~ 0 steps, and therefore generally at a lower cost, by forming a coating 18 of copp~r selenide, copper telluride or copper sulfide by reaction of a solution of the appropriate acid or other reactive compound with the copper-based cathode electrode 12. Thus, for example, a reaction of seleneous acid with the copper-based cathode electrode 12 would produce a coating 18 of copper selenide, tellurous acid would yield copper telluride and a polysulfide would produce copper sulfide.
The presently pre~erred compound for the coating 18 over the cathode electrode 12 is copper telluride. Generally, the quantity of acid or compound required to form the coating 18 is in the range of about 0.2 to 1.0 milligrams per square centimeter of cathode electrode surface.
The coating 18 formed by the reaction product of the reactive acids or compounds with the cathode electrode 12 may be applied at several different stages of the capacitor assem-bly. The appropriate compound may be added to the fill electro-lyte 17 and thus the reaction takes place in the completed capacitor 10. Alternatively, the porous anode 11 may be dipped in an aqueous solution of the appropriate compound and then dried. The reaction will commence when the anode 11 is insert-ed into the electrolyte 17 and any unreacted compound will thereby remain in the capacitor 10. In another method, an a~ueous solution of the compound is placed in a dry housing 12 and the reaction with the cathode surface 12 allowed to take place. Then the remaining solution is removed and the housing 12 drained. The electrolyte 17 is added in a subsequent step and the capacitor assembly is then completed.
One particular advantage in utilizing a coating 18 of copper selenide, copper telluride or copper sulfide as oppo~ed to conventional methods of increasing the cathode 1~416~0 electrode surface area such as platinization ~nd graphite coating is that many processing steps in the assembly of an electrolytic capacitor can ba eliminated. For example, platinization of the interior surface of the cathode electrode requires the steps of masking, etching, rinsing, plating, rinsing and drying as set forth previously. The layers or coat-ing 18 of the present invention may be provided simply by add-ing a small amount of an appropriate compound, for example, tellurous acid, to the fill electrolyte. This particular acid can be formed in acid electrolytes by adding the oxide of the element, fox example, tellurium oxide (TeO2), to the acid -electrolyte such as sulfuric acid.
In the presently preferre~ method, the coating or layer over the cathode electrode is formed prior to the introduc-tion of the fill electrolyte. In this method, the reactive compound is formed in an aqueous media, usually an agueous solution of an acid such as H2S04, and brought into contact with the cathode electrode surface 12. The reaction between the reactive compound and the copper component of the cathode -;
~0 electrode is allowed to take place to form the layer of copper telluride, copper selenide, or copper sulfide. In most situa-tions, the optimum reaction time is between about five and twelve minutes. The presently preferred reaction time is eight minutes plus or minus two minutes. After the reaction, the solution is removed and the surface allowed to drain. Subse-~uently, the fill electrolyte is dispensed, the anode inserted, and the device sealed.
Thus, the method for providing the coating over the cathode electrode surface according to this invention is greatly simplified in comparison to the conventional methods such as platinization of the cathode electrode surface.
.. . . ; ." ::
, 6ZC~
It is also advantageous to add certain soluble inorganic salts as depolarizers to the operating electrolyte of capacitors according to this invention as as to minimize leakage current effects present during capacitor operation.
Such salts help to prevent the formation of gaseous products which are liberated due to leakage current between the electrodes. -One particular salt that can be used advantageously with a capacitor according to this invention is CuSO4, prefera~ly in its hydrated form and with sulfuric acid electrolytes.
The amount of salt needed is typically from about 0.1 wt.
to about 5 wt.% of the electrolyte.
Several capacitors made according to this invention and performance data for these capacitors are presented in the following examples. It should be understood that the examples are given for the purpose of illustration only and the examples do not limit the invention as has theretofore been described.
EXAMPLE I
A 450 uf capacitor of 6 volt rating is prepared according to the present invention.
A copper-based cathode housing composed of CDA #116 silver-copper, tough pitch, is fabricated with a length of about 0.677 inches and a diameter of about 0.187 inches. The interior of the housing is cleaned with a warm detergent solu-tion and rinsed with de-ionized water and then the excess water drained. An electrolyte of de-aerated 39 wt.% H2SO4 with the addition of 0.4 wt.% SeO2 is then poured into the housing. A
sintered tantalum anode with a dielectric oxide coating and a length of about 0.503 inches is placed in the electrolyte and the open end of the housing sealed with an appropriate seal .
" ~ ~ ' ! ', .
: :' ' ,, ~L~)41~;Z~
assembly .
The SeO2 forms an acid in the electrolyte and reacts during and after filling with the copper of the interior sur~
face of the cathode housiny to produce an adherent layer of copper selenide. The finished capacitor exhibits good per-formance data on a foward life test at 85C and on shock-vibration tests.
EXAMPLE II
A 78 uf capacitor of 50 volt rating is prepared according to the present invention.
The housing is the same size as the housing utilized in EXAMPLE I. Again the housing is cleansed by warm deter-gent solution and then rinsed with de-ionized water and drained.
A treating solution of about one gram of TeO2 in about 100 grams of 39 wt.% H2SO~ solution is dispensed into the housing, filling the housing to about 1/32 inch from the top of the housing. Reaction between the copper of the housing and the tellurous acid is allowed to take place to form the layer of copper telluride and then the housing is flushed with de-ionized water and dried at about 85C.
After the housing is dry, electrolyte consisting of a de-aerated aqueous solution of about 39 w~.~ H2SO4 with about 3 wt.~ CuSO4 ~ 5H2O is dispensed into the housing. A sintered tantalum anode with a dielectric oxide film thereon is in-serted into the electrolyte and the open end of the housing is closed by a seal assembly.
Two finished capacitors made by the above procedure are tested and are found to have the following electrical proper- ~-ties at various temperatures.
: ' , , , ,, "; ' ~4~2C~
Capacitance Change (~C) +25C -35C -55C ~85~ +25C
Unit 1 80~4 uf -12 -24 -0.37 -3.6 3.6%DF
Unit 2 81.2 uf -12 -20 -0.74 -3.8 3.7%DF
Acceptable ~40 tlO i5 Limits ,: ~
As can be noted from the above table, the performance of both capacitors is well within acceptable limits for temper-ature stability.
Forward life tests at 85C indicate that the abovetype capacitor is also within acceptable limits in terms of performance even after 1000 hours of testing. Percentage change in capacitance is less than 2~ and usually less than 1%, D.C. leakage is well below the initial value and percentage change in dissipation factor i5 less than 10~, usually less than 5%, well within acceptable limits.
Thus the invention as has been described comprehends the use of a copper-based~cathode electrode in an electrical device wherein a surface of the cathode electrode has an ad-herent layer or coating of a material selected from the group of copper selenide, copper telluride, copper sulfide or mix-tures thereof. The layer is relatively easy and inexpensive to apply to the cathode electrode surface and permits the efficient utilization of copper-based materials as cathode electrodes for electrical devices, especially electrolytic aapacitors.
While the present invention has been described with ~`
reference to particular embodiments thereof, it will be under-stood that numerous modifications may be made by those skilled in the art without actually departing from the spirit and scope of the invention as defined in the appended claims.
:; . ' ~ ~ , -: ....................... , . ' :", ' '' , ~' , .
. . . . .. ..
Claims (11)
IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A capacitor comprising an anode electrode, a cathode electrode, and dielectric means between the anode electrode and the cathode electrode, the cathode electrode including a surface containing Cu contacted by at least semi-liquid electrolyte, and a composition on the cathode electrode surface containing at least one compound selected from the group of copper selenide, copper telluride and copper sulfide.
2. The capacitor of claim 1 wherein the cathode electrode sur-face contains as a major constituent Cu.
3. The capacitor of claim 2 wherein the cathode electrode sur-face consists essentially of a Cu-Ag alloy.
4. The capacitor of claim 3, wherein the cathode electrode surface consists of an alloy of about 0.10 wt.% to about 10 wt.% Ag, the remainder essentially Cu.
5. The capacitor of claim 1 and an electrolyte contacting the anode electrode and the cathode electrode surface.
6. The capacitor of claim 1, wherein the anode electrode com-prises a film-forming metal and has a dielectric oxide film of the film-forming metal contacting the anode electrode, and electrolyte contacting the dielectric oxide film of the anode electrode and the composition on cathode electrode surface.
7. The capacitor of claim 6 wherein the electrolyte contains at least one material selected from the group including sulfuric, hydrochloric and phosphoric acids, and metal salts thereof, and wherein the film-forming metal of the anode electrode is selected from the group consisting of Ta and Nb.
8. The capacitor of claim 7 wherein the cathode electrode surface is essentially an alloy of Cu-Ag.
9. The capacitor of claim 8 wherein the electrolyte is an aqueous solution containing H2SO4 and CuSO4 and the composition on the cathode electrode surface is essentially copper telluride.
10. A method of providing the composition on the cathode electrode surface of claim 1 comprising contacting the cathode electrode surface with a solution containing at least one compound reactive with copper, the compound containing an element selected from Se, Te, and S.
11. The method of claim 10 wherein the compound is TeO2 in an aqueous solution of H2SO4.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US49557074A | 1974-08-08 | 1974-08-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1041620A true CA1041620A (en) | 1978-10-31 |
Family
ID=23969146
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA232,809A Expired CA1041620A (en) | 1974-08-08 | 1975-08-05 | Cathode electrode for an electrical device and method |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5141856A (en) |
| CA (1) | CA1041620A (en) |
| DE (1) | DE2534997C3 (en) |
| FR (1) | FR2281637A1 (en) |
| GB (1) | GB1503795A (en) |
| NL (1) | NL7509505A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52132414U (en) * | 1976-04-05 | 1977-10-07 | ||
| JPS569899Y2 (en) * | 1976-04-05 | 1981-03-05 | ||
| US8883339B2 (en) | 2010-07-22 | 2014-11-11 | University Of Central Florida Research Foundation, Inc. | Alkali metal-cathode solution battery |
| WO2012012743A1 (en) * | 2010-07-22 | 2012-01-26 | University Of Central Florida Research Foundation, Inc. | Alkali metal-copper storage battery |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3845364A (en) * | 1973-10-15 | 1974-10-29 | Mallory & Co Inc P R | Cathode electrode for operation under conditions of reverse polarity voltage |
-
1975
- 1975-07-29 GB GB3169975A patent/GB1503795A/en not_active Expired
- 1975-08-05 DE DE19752534997 patent/DE2534997C3/en not_active Expired
- 1975-08-05 CA CA232,809A patent/CA1041620A/en not_active Expired
- 1975-08-07 FR FR7524696A patent/FR2281637A1/en active Granted
- 1975-08-08 JP JP50096576A patent/JPS5141856A/en active Pending
- 1975-08-08 NL NL7509505A patent/NL7509505A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2281637B1 (en) | 1979-05-18 |
| JPS5141856A (en) | 1976-04-08 |
| DE2534997A1 (en) | 1976-02-26 |
| DE2534997C3 (en) | 1979-07-26 |
| NL7509505A (en) | 1976-02-10 |
| FR2281637A1 (en) | 1976-03-05 |
| GB1503795A (en) | 1978-03-15 |
| DE2534997B2 (en) | 1978-11-16 |
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