CA1284355C - Process for preventing electrical storage cell capacity loss - Google Patents
Process for preventing electrical storage cell capacity lossInfo
- Publication number
- CA1284355C CA1284355C CA000528776A CA528776A CA1284355C CA 1284355 C CA1284355 C CA 1284355C CA 000528776 A CA000528776 A CA 000528776A CA 528776 A CA528776 A CA 528776A CA 1284355 C CA1284355 C CA 1284355C
- Authority
- CA
- Canada
- Prior art keywords
- cell
- pressure
- psia
- hydrogen
- charge
- 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 - Fee Related
Links
Classifications
-
- 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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-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
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
- H01M10/445—Methods for charging or discharging in response to gas pressure
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
- H02J7/90—Regulation of charging or discharging current or voltage
- H02J7/971—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters
- H02J7/973—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters in response to degree of gas development in the battery
-
- 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
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Power Engineering (AREA)
- Hybrid Cells (AREA)
- Secondary Cells (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
PROCESS FOR PREVENTING ELECTRICAL STORAGE
CELL CAPACITY LOSS
ABSTRACT OF THE DISCLOSURE
A process for preventing electrical capacity loss during storage of a pressurized nickel-hydrogen electrical storage cell. An electrical precharge is applied to the positive electrode of the cell, so that discharge of the cell is negative electrode limited. In one approach, the cell is charged, while sealed, to a state of charge corres-ponding to a first gas pressure, and then the hydrogen pressure is reduced to a lower value, preferably about atmospheric. In another approach, a current is passed through the cell while the cell is unsealed and maintained at atmospheric gas pressure, until the cell reaches the desired state of charge.
CELL CAPACITY LOSS
ABSTRACT OF THE DISCLOSURE
A process for preventing electrical capacity loss during storage of a pressurized nickel-hydrogen electrical storage cell. An electrical precharge is applied to the positive electrode of the cell, so that discharge of the cell is negative electrode limited. In one approach, the cell is charged, while sealed, to a state of charge corres-ponding to a first gas pressure, and then the hydrogen pressure is reduced to a lower value, preferably about atmospheric. In another approach, a current is passed through the cell while the cell is unsealed and maintained at atmospheric gas pressure, until the cell reaches the desired state of charge.
Description
35~i PROCESS FOR PREVENTING ELECTRICAL STORAGE
BACKGROUND OF~THE INVENTION
This invention relates generally to pressurized gas-metal cells ~uch as nickel-hydrogen cells and, more par~icularly, to a proc~ss ~or reducing the open-circuit capacity loss during storage o such cellsO
Rechargeable cel ~ 8 or batteries are electro-chemical devices for storing and retaininy an electrical charge and later delivermg that charge as a useful current. A fa~iliar exa~ple of the rechargeable cell is the lead-acid cell used in automob~les. Another type o~
cell having a greater storage capacity per unit weight is the pressurized gas metal CQll, an i~portant typ~ o~ which is the nickel-hydrogell cell used in spacecraft appli-cation~. A nickel-hydrogen cell used in a satellite is periodically charged by electrical curren~ produced by solar panels on the spacecraft, and then later discharged to supply electrical power, as when the spacecraft is m shadow or peak electrical power is demanded.
The primary requirements of cells to be used in spacecraft are high energy storage capacity per unit weight o~ cell, reli~ility, and the ability to be recycled through many cycles of charging and discharging. A newly assembled nicXel; hydrogen cell has a high ensrgy storage capacity as measured ~n ampere-hours. However, it is observed by ~any users that, after the cell has been stored in an open circul~ or ~hort circult, discharge~ condition for a period of time, the maximum storage capacity upon attempting to fully charge the cell is reduced, as compared with the value that is attaLnable with a newly assembled cell. The loss of full-charge energy capacity that is experienced while the cell is stored gradually inGreases s with increasing storage time, and can be as great as 20% of capacity aftsr a storage time of one ~onth. Once the cell capacity is lost in this manner, it ls dif~icult or impossible to restore the cell fully to its initial high lPvel of capacity.
This reduction of the electrical capacity o~ the cell during open-circuit storage pr~sents a serious problem for the manufacturer and the user of the cell. It is usually most efficient to manufacture and assemble the cell at a site different from that of its installation into the spacecraft. The cell must therefor~ be transported after assembly. Moreover, installa~ion o~ the cell into the spacecraft may occur several days or weeks prior to the actual launching of the spacecrafk and ch~xging of the cell by the solar panels, because of the need to check the spacecraft with the cells in place and also because of possible delays in the launching of the spacecraft. The time betwaen the final assembly of the cell and the actual first operation of the cell in space is often as much as one year, with the result that the electrical storage capacity o~ the nickel-hydrogen cell may be substantially reduced. Moreover, it i~ usually desirable to manu~acture a number o~ calls at one time, ~o that the actual storage time may be even longer, with a corresponding greater decrease in the capacity c~ the cell when it is ~inally placed into se~ice.
It is not practical to delay the final assembly and activation of the cells until ~ust before khe launch of the spacecra~t, because this procedure would b~ ineffi-cient, cumbersome, and would signi~icantly interfere with the smooth scheduling o~ the launrh procedure o~ the spacecraft. I~ is also not practical to e~hip ~he cells partially charged, due to the hazards arising ~rom the presence of pressurized hydrogen. For ~he6e reasons, the various approaches to reducing or eli~inating the reduction in cell capacity durlng cell storaga either have not been successful or aro excessively c08tly-A need therefore exi~ts ~or an approach for reducing or eliminating comple~ely the loss ~n electrical charge capaclty of nickel-hydroyen cells. The approach should be fully capakible with existing cell components and handlm g procedures, and should not necessi~ate signiXicant mod;fication~ to spacecra~t launching procedures. The approach should not require ~pecialized, complex or expensive equipment that would be used in con~unction with the launching of the spacecra~t, ince ~uGh additional equipment would complicate the launch procedures and possibly create difficulties because o~ the support e~uipment~ The approach ~hould also not signi~icantly mcrease the weight of tha cell or decrease its charge capacity, charging and discharging characteristics, or abiiity to be charged and discharged thousands of times during the operating li~e of the Gpac2craft. The present invention fulfills thi~ need, and further provides related ad~antages.
The pre~ent invention reside~ in a method and apparatus for reducm g and eli~inating ~he open-circuit and short-circuit capacity loss during ~torage o~ nickel-hydrogen cells. The process does not require any modifi-cation either to the cell de~ign, or to th~ assembly proce-dure, except ~n the final assembly and packaging stage. No specialized apparatuæ i8 required, either a~ the factory or at the spacecraft launch ~it~. By u~ing the approach o~
the invsn~ion~ ~he cell ~ay be a~sembled many months prior to the launch o~ the 6pacecra~t and ~irs~ operational use of thQ cell, without ~ub~tantial 1088 in the capacity o~
the cell re6ult~ng fro~ the ~torage.
ïn accordance with the in~en'cion, a proces for reducing 1:he open-circui~ c~pacity 10~38 during storage of a pressurized nickel-hydrog~n cel 1, co~nprises precharging the cell prior ~o storage so tha~ discharge of the cell is negative electrode limited, whereby an ele~rlcal charge remains on the nickel positiva electrode when the hydrogen partial pressure o~ the cell ~alls to about 3 psia. This approach is applicable to the fam$1iar nickel-hydrogen cell, and is expscted to be applicable to other cells experiencm~ capacity loss by a comparable m~chanism.
In one appr~ach, the step of precharging includes ~he step~ of applying a charge to the positive electrode o~
the cell wi~h the cell unvented, to an electrical charge correspondm g to a f$rst pressure, and reducing th~
pressure withLn the cell to a second pr~ssure. The first pressure is desirably about 65 psia (pounds per square $nch, absolute), and the ~econd pressure is desirably about 15 psia, or atmospheric pressure. In another approach, the step of pracharging includes the step of applying a charge to the positive electrode of the cell while the pressure within khe cell is ma$ntained at a reduced level, prefer-ably about 15 psia. In this second approach, the charge applied to the positive alectrode preferably corresponds to a sealed cell gas pressure o~ about 65 psiaO
In another embodiment, a process ~or precharging a pressurized gas-metal cell comprises the ~teps of dis~
charging the cell to about O volts at a hydrogen partial pressure of about 15 psia, electrically charging the cell while sealed to a charge corresponding to a first hydrogen pressure~ and reducing the hydrogen pressure within the cell to about 15 psia. Th~ ~irst gas pressure is preferably about 65 psia.
In accordanc~ wi~h another embo~imen~ of ~he invention, a process for prech rging a pressurized nickel-hydrogen cell comprise~ passing a current through ~he cell while the cell is unsealed and maintained al: a gas pressure of about 15 psia, unt~ 1 the cell reaches a charge state corresponding to a ~irst ~ealed hydrogen partial pressure.
The first sealed hydrogen partial sealed gas pressure is preferably about 65 psiaO
Each of these approaches results in retention of a partial chargP on the positive electrode when the hydrogen partial pressure i5 reduced to zero. Complete discharging of the positlve elec~rode during ~torage therefore cannot occur. It is thought that this avoidance o2 the complete discharging of the positive electrode $s critical to reducing or avoiding the incidenc~ of cell capacity loss during storage.
It will now be appreciated that through the use of the precharging process of the in~entlon, a nickel-hydrogen cell can be prechaxged during manufacturing to reduce or avoid the loss of cell capacity during ~ubsequent storage.
The xeduction or avoidance of ths capacity loss allows the cell to be economically manufactured at one location, shipped to the spacecraft l~unch site, assembled and tested in th2 spacecra~t, maintained in a ready condition unt~
the spacecraft is launched, and then placed into operational service after launch of the spacecraftt all of ~hese activities occupying a period of weeks or months, without sign; ficant loss of the electrical storage capaci~y of the cell. The process requires only a minimal change to the manufacturing procedures, does not lncrease the cost or weight of the cell, and allows its full potential to be realized. Other features and advantages of the present in~ention will become apparent ~rom the following more detailed description, taken in con~unction wi~h the accom-panying drawings, which ~lustrate, by way of example, ~he principles of the invention.
C:9 E 1 ~ e~ios~ v~tional Yi~W e~:t a ~light-type nlck~l ~ hydrog~n call:
FIGURE 2 i;3 a d~tail og FIGURE 1, taken g~nerally on line 2-2, illustratlng 'cha pl~te ~et~; and FIG~TRE 3 $~ a sche~na~ic graph o~ px~s~ura as a runction oi~ ele~ric~l char~ orQd in a nlG~ hydrogen cell during charging.
Th~ px~s~nt ~v0ntion i~ u~d ln con~unctlon with a nick~l-hydrog~n ~tor~g~ c~ll 10, ~ illustrak0d in FIGU~ES 1 and 2, o~ pr~surizod g~ tal cQll ~ype.
Such a cs11 lU ~yp~eally ao~apris~ a p~urality of indiv~du~l platQ ~Qt~ .12. ~aeh E~ t 12 in turn ::o~pri~ n anod~ or l?o~i~iYv~ ctrQd~ athod~ or nagati~ro al~etrod~ n~ an ~l~ctroly~-eon~aining 6epara~0r 18, whieh ~hy~ie~lly ~a~t~ ctrod~ l~
and 16, an~ ~180 I~U~pp~ th~ ctroly~ modlum through whieh ion~ a an~ ctron t~an~or oe~r4 C~rging and diseharging o~ tho ~l~ctrod~6 ~4 ~nd 16 ar~ ae~o~pli hed t~rough r~ ctr~eal l~d~ 2 0.
V~riou~ con~tructlon~ o~ n~X~ hyd~og~h ~ and comonent~. ar~ d~clo~d ln th~ ~cllowin~ U~S. P~nt~:
BACKGROUND OF~THE INVENTION
This invention relates generally to pressurized gas-metal cells ~uch as nickel-hydrogen cells and, more par~icularly, to a proc~ss ~or reducing the open-circuit capacity loss during storage o such cellsO
Rechargeable cel ~ 8 or batteries are electro-chemical devices for storing and retaininy an electrical charge and later delivermg that charge as a useful current. A fa~iliar exa~ple of the rechargeable cell is the lead-acid cell used in automob~les. Another type o~
cell having a greater storage capacity per unit weight is the pressurized gas metal CQll, an i~portant typ~ o~ which is the nickel-hydrogell cell used in spacecraft appli-cation~. A nickel-hydrogen cell used in a satellite is periodically charged by electrical curren~ produced by solar panels on the spacecraft, and then later discharged to supply electrical power, as when the spacecraft is m shadow or peak electrical power is demanded.
The primary requirements of cells to be used in spacecraft are high energy storage capacity per unit weight o~ cell, reli~ility, and the ability to be recycled through many cycles of charging and discharging. A newly assembled nicXel; hydrogen cell has a high ensrgy storage capacity as measured ~n ampere-hours. However, it is observed by ~any users that, after the cell has been stored in an open circul~ or ~hort circult, discharge~ condition for a period of time, the maximum storage capacity upon attempting to fully charge the cell is reduced, as compared with the value that is attaLnable with a newly assembled cell. The loss of full-charge energy capacity that is experienced while the cell is stored gradually inGreases s with increasing storage time, and can be as great as 20% of capacity aftsr a storage time of one ~onth. Once the cell capacity is lost in this manner, it ls dif~icult or impossible to restore the cell fully to its initial high lPvel of capacity.
This reduction of the electrical capacity o~ the cell during open-circuit storage pr~sents a serious problem for the manufacturer and the user of the cell. It is usually most efficient to manufacture and assemble the cell at a site different from that of its installation into the spacecraft. The cell must therefor~ be transported after assembly. Moreover, installa~ion o~ the cell into the spacecraft may occur several days or weeks prior to the actual launching of the spacecrafk and ch~xging of the cell by the solar panels, because of the need to check the spacecraft with the cells in place and also because of possible delays in the launching of the spacecraft. The time betwaen the final assembly of the cell and the actual first operation of the cell in space is often as much as one year, with the result that the electrical storage capacity o~ the nickel-hydrogen cell may be substantially reduced. Moreover, it i~ usually desirable to manu~acture a number o~ calls at one time, ~o that the actual storage time may be even longer, with a corresponding greater decrease in the capacity c~ the cell when it is ~inally placed into se~ice.
It is not practical to delay the final assembly and activation of the cells until ~ust before khe launch of the spacecra~t, because this procedure would b~ ineffi-cient, cumbersome, and would signi~icantly interfere with the smooth scheduling o~ the launrh procedure o~ the spacecraft. I~ is also not practical to e~hip ~he cells partially charged, due to the hazards arising ~rom the presence of pressurized hydrogen. For ~he6e reasons, the various approaches to reducing or eli~inating the reduction in cell capacity durlng cell storaga either have not been successful or aro excessively c08tly-A need therefore exi~ts ~or an approach for reducing or eliminating comple~ely the loss ~n electrical charge capaclty of nickel-hydroyen cells. The approach should be fully capakible with existing cell components and handlm g procedures, and should not necessi~ate signiXicant mod;fication~ to spacecra~t launching procedures. The approach should not require ~pecialized, complex or expensive equipment that would be used in con~unction with the launching of the spacecra~t, ince ~uGh additional equipment would complicate the launch procedures and possibly create difficulties because o~ the support e~uipment~ The approach ~hould also not signi~icantly mcrease the weight of tha cell or decrease its charge capacity, charging and discharging characteristics, or abiiity to be charged and discharged thousands of times during the operating li~e of the Gpac2craft. The present invention fulfills thi~ need, and further provides related ad~antages.
The pre~ent invention reside~ in a method and apparatus for reducm g and eli~inating ~he open-circuit and short-circuit capacity loss during ~torage o~ nickel-hydrogen cells. The process does not require any modifi-cation either to the cell de~ign, or to th~ assembly proce-dure, except ~n the final assembly and packaging stage. No specialized apparatuæ i8 required, either a~ the factory or at the spacecraft launch ~it~. By u~ing the approach o~
the invsn~ion~ ~he cell ~ay be a~sembled many months prior to the launch o~ the 6pacecra~t and ~irs~ operational use of thQ cell, without ~ub~tantial 1088 in the capacity o~
the cell re6ult~ng fro~ the ~torage.
ïn accordance with the in~en'cion, a proces for reducing 1:he open-circui~ c~pacity 10~38 during storage of a pressurized nickel-hydrog~n cel 1, co~nprises precharging the cell prior ~o storage so tha~ discharge of the cell is negative electrode limited, whereby an ele~rlcal charge remains on the nickel positiva electrode when the hydrogen partial pressure o~ the cell ~alls to about 3 psia. This approach is applicable to the fam$1iar nickel-hydrogen cell, and is expscted to be applicable to other cells experiencm~ capacity loss by a comparable m~chanism.
In one appr~ach, the step of precharging includes ~he step~ of applying a charge to the positive electrode o~
the cell wi~h the cell unvented, to an electrical charge correspondm g to a f$rst pressure, and reducing th~
pressure withLn the cell to a second pr~ssure. The first pressure is desirably about 65 psia (pounds per square $nch, absolute), and the ~econd pressure is desirably about 15 psia, or atmospheric pressure. In another approach, the step of pracharging includes the step of applying a charge to the positive electrode of the cell while the pressure within khe cell is ma$ntained at a reduced level, prefer-ably about 15 psia. In this second approach, the charge applied to the positive alectrode preferably corresponds to a sealed cell gas pressure o~ about 65 psiaO
In another embodiment, a process ~or precharging a pressurized gas-metal cell comprises the ~teps of dis~
charging the cell to about O volts at a hydrogen partial pressure of about 15 psia, electrically charging the cell while sealed to a charge corresponding to a first hydrogen pressure~ and reducing the hydrogen pressure within the cell to about 15 psia. Th~ ~irst gas pressure is preferably about 65 psia.
In accordanc~ wi~h another embo~imen~ of ~he invention, a process for prech rging a pressurized nickel-hydrogen cell comprise~ passing a current through ~he cell while the cell is unsealed and maintained al: a gas pressure of about 15 psia, unt~ 1 the cell reaches a charge state corresponding to a ~irst ~ealed hydrogen partial pressure.
The first sealed hydrogen partial sealed gas pressure is preferably about 65 psiaO
Each of these approaches results in retention of a partial chargP on the positive electrode when the hydrogen partial pressure i5 reduced to zero. Complete discharging of the positlve elec~rode during ~torage therefore cannot occur. It is thought that this avoidance o2 the complete discharging of the positive electrode $s critical to reducing or avoiding the incidenc~ of cell capacity loss during storage.
It will now be appreciated that through the use of the precharging process of the in~entlon, a nickel-hydrogen cell can be prechaxged during manufacturing to reduce or avoid the loss of cell capacity during ~ubsequent storage.
The xeduction or avoidance of ths capacity loss allows the cell to be economically manufactured at one location, shipped to the spacecraft l~unch site, assembled and tested in th2 spacecra~t, maintained in a ready condition unt~
the spacecraft is launched, and then placed into operational service after launch of the spacecraftt all of ~hese activities occupying a period of weeks or months, without sign; ficant loss of the electrical storage capaci~y of the cell. The process requires only a minimal change to the manufacturing procedures, does not lncrease the cost or weight of the cell, and allows its full potential to be realized. Other features and advantages of the present in~ention will become apparent ~rom the following more detailed description, taken in con~unction wi~h the accom-panying drawings, which ~lustrate, by way of example, ~he principles of the invention.
C:9 E 1 ~ e~ios~ v~tional Yi~W e~:t a ~light-type nlck~l ~ hydrog~n call:
FIGURE 2 i;3 a d~tail og FIGURE 1, taken g~nerally on line 2-2, illustratlng 'cha pl~te ~et~; and FIG~TRE 3 $~ a sche~na~ic graph o~ px~s~ura as a runction oi~ ele~ric~l char~ orQd in a nlG~ hydrogen cell during charging.
Th~ px~s~nt ~v0ntion i~ u~d ln con~unctlon with a nick~l-hydrog~n ~tor~g~ c~ll 10, ~ illustrak0d in FIGU~ES 1 and 2, o~ pr~surizod g~ tal cQll ~ype.
Such a cs11 lU ~yp~eally ao~apris~ a p~urality of indiv~du~l platQ ~Qt~ .12. ~aeh E~ t 12 in turn ::o~pri~ n anod~ or l?o~i~iYv~ ctrQd~ athod~ or nagati~ro al~etrod~ n~ an ~l~ctroly~-eon~aining 6epara~0r 18, whieh ~hy~ie~lly ~a~t~ ctrod~ l~
and 16, an~ ~180 I~U~pp~ th~ ctroly~ modlum through whieh ion~ a an~ ctron t~an~or oe~r4 C~rging and diseharging o~ tho ~l~ctrod~6 ~4 ~nd 16 ar~ ae~o~pli hed t~rough r~ ctr~eal l~d~ 2 0.
V~riou~ con~tructlon~ o~ n~X~ hyd~og~h ~ and comonent~. ar~ d~clo~d ln th~ ~cllowin~ U~S. P~nt~:
4,369,212; 4,283,844t ~,262~0611 4,2~,235~ ~,400,350j and 3,6~9,744.
Th~ po~itlv~ 14 ~ ~orma~ ~y i~pr~g-nating nlc~csl hyd20xi~0 into porou~ or~d nlc~c~l tha~ is suppQrt~d on ~n ~t~h2d nlck~ ro~ ~ub~trat~. The n~gativ~ ~lQctro~o 16 i~ coat~d on on~ ~ld~ lay ~ ntered :
Th~ po~itlv~ 14 ~ ~orma~ ~y i~pr~g-nating nlc~csl hyd20xi~0 into porou~ or~d nlc~c~l tha~ is suppQrt~d on ~n ~t~h2d nlck~ ro~ ~ub~trat~. The n~gativ~ ~lQctro~o 16 i~ coat~d on on~ ~ld~ lay ~ ntered :
5 ~
~ixturQ o~ platinu~ blacX and polytetra~luoroethylene and on ~hQ other ~id~ wlt~a ~ porou~ l~y~r c~ polyt~tra~luoro~
ethylene 19. Th~e layQr~ ar~ applled to ~ nlck@l sub-~trate in the ~orm o~ etch~d ~h~et or ~ woven me h, to ~orm the nega~ive ele~rode 16. 2~any di~g~ren~ ~ype~ o~ ~epa rators 18 have b~n usQd, including, for example, asbestos, nylon, and a cloth o~ zirconium ox~de-y~crium oxide con taininy polysul~one. Th~ elect:rolyte, pre~errably potas sium hydroxi~e, i~ impregna~d into ~he separator la.
Th~ indi~ridual plat~ ~ets 1~ are ~ss¢mbled onto a central core ~2 to ~or~ a ~tacked arr y 2~. In ~orming the s~acked array 24, a ~ono~ilament polypropyl~n~ ~creen 26 is placed ~Qtween each plat~ ~Qt ï2, ~o t:hat oxyg~n l~erated during overcharging ~t ~ach po5it:lvla electrode 14 can diffu~ away ~ro~ the el~rodQ 14 ~nd to tha negative elec~rodQ 16 to com~ine with hydrog~n. Th~ ~tacXed array 24 is placed under a long~:udinal pres~ure o~, ~or example, about 19 pounds per squar~ inch, ~y tlghtening comprPssion plates 28 against ~ach ~nd o~ s~acked array 24. The tigh~ening o~ th~ co~pr~s~ion plat~ 2g i~ prer~rably accomplished by ~o~px~g . ing ~he array 24 and th~n ti~hten-ing . nut 30 on tr~ad~ on th~ corel 22, th~reby compr~ss~ng a B~11QV~ wash~r ~ 32 ag~ t ~ co~pr~sion plate 28 to hold th~ ~aek~d ~rr y 24 ln placa ThQ ~tack~d array 2 4 i~ s~ d wi~hin a pr~s,~re vessal 34, ~anuSactur~d o~ ~ mat~rial such as Inconel 718 nictc~l-based ~lloy which carl wi~h . tand lnt~nal pressures on th~ ord~r ol~ 1,000 p~ia, wi~hout d~ g~ by hyd:~og2n em-brittlemQnt or coxro~ion by thQ~ ctrolyt~. ~ gas tube 3 5 allows ga~ cont~n~ an~ prelB~lUS~3 wil:h~n th~ p~essure vessel 34 to bQ controll~d. Th~ pr~ surQ v~el 34 is typio~lly cozlstruc~d ln tho ~orall o~ ~ cyl~ndrical l:ube having domed Qnds~ By way o~ ratlon, th~ cell 10 hav~g th~ pre~surel v~8~1 34 oi~ ~xt:@rnal dimension~ 3-1/2 inche~ di~e~o~ and 13 inch~ long can contain abou~ 4 0 individual pl~to 6~t~ 12, wlt~ a resul~g ~l~ctrical ~torag~ capa~ty o~ the c211 oi! about 50 amplære-hours.
r~
The cell 10 ~ay be charged and discharged through thou-sand~ of cycles without apparent damage, if the charging and discharging are accomplished properly. A number of cells 10 can be combined in ~eries or parallel ~o produce a battary.
Charging is accomplished by impressing a voltage through the leads 20 across each plate set 12 so that electrons flow ~rom thP electrode 16 to the elsctrode 14.
Electrical energy is thereby stored in each plate set in the form of chemical reactants, for subsequent discharying to produce a usable current. ~ nickel-hydrogen cell of the type described previously may be fully charged by a solar cell array to a capacity of, for example, about 50 ampere hours, using a current o~ ~bou~ 5 amperes at 1.5 volts through a charging period of about 14 hours from a dis-charged state. The voltage and charging time vary, depend-ing upon the power ava; 1 able from the solar cell and the cycle dictat~d by the orbi~ of the spacecrart.
When the gas f~ tube 35 is sealed at 15 psia (atmospheric pressure) and charging commenced fro~ a fully discharged ~tate, the gas pressure within the cell 10 initially increases in a generally linear fashlon proport-ional to the charge etored within the cell 10. FIGURE 3 schematically ;llu~trates this initial increase in gas pressure as a function of charge, and the correspondence of a particular charye and pressure value.
A.fter the cell is manufactured but before it is placed into ~ervice, the cell may be stored for a period of time in an "open circuit" condition, wherein no further charging or discharging of the cell is accomplished.
During that period of open circui~ storage, in addition to self dischargm g to a fully discharg~d sta~e, the cell apparently physically change~ in ~ome manner ~o that i~s maximum electrical capaci~y, to which it may subsequently be charged, gradually fallsO For exa~ple, and as xeported in greater dQtail in Tables I and II, a cell having an ~rlitial maximum capaci~y o~ 53.5 ampere-hours experiences a reduction of maximum capacity to 44.6 ampere~hours after 32 days of open circuit discharged ~torage. Similarly, a cell having an initial capacity o~ 28.1 ampere-hours experiences a reduction in capaci~y to 27.3 ampere-hour~ after 32 days of storage, and to 23.1 amperQ-hours ater 128 days of storage. The precise reason for this lo~s o2 maximum electrical capacity during storage i~. not known with cer-tainty, and Applicants do not wish to be bound by any parti-cular explanation of this phenomenon. However, it is believed that during storage with a hydxogen gas partial pressure within the cell, an insulating material is pro-duced at the positive electrode 14. Discharging results in a continuous bu~ld-up of the insulating material, with the consequent result that the areas of active material on the positive electrode become isolated. At a later time when the cell is charged, the isolated active areas remaLn isolated because of the presence o~ the discharged insu-lating ~aterial, thereby reducing the useful reactive capacity of the positive electrode, and thence the cell.
In accordance with ~he presen~ invention, i~ has been found that the gradual loss of maximum cPll capacity during storage can be reduced or avoided ~ntirely ~hrough a precharging procedure applied to the cell after assembly, but prior to the beginning of the period during which the cell is stored in an open-circuit condition. To accomplish the precharging procedure, the cell is manu~actured m the usual ~anner as described previously, except ~or a PLnal step in which the positi~e electrode of the cell is charged and the hydrogen precharging pressure is set to a value less than that defined by the characteristic line ~llus-trated in Figure 3, and pre*erably to 15 psia.
Discharging oî a sealed nickel-hydrogen cell is ordinarlly positive~elactrode limi~d. AB khe cell dls-charges, hydxog~n i~ con6ume~ by reac~ion with l:he active material of the po itive or nickel electrode. The reactants availabl~ at the pos~tive 01ectrode are exhausted be~ore 11 of the hydrogen is consumed. The precharging process of the present lnvention results in re~uced hydroyen avail-ab;lity during discharging, w~th the result that discharg-lng becomes ne~ative-electrode limited. That ls, upon dis-charging of a c~11 that has been precharged by the present invention, an electrical charge remains on the positive electrode wh~n the hydrogen partlal pressure of the sealed cell is reduced to about O psia. It is believed that this negative-electrode limitatlon durlng discharge is instru-mental in reducing or avolding subsequent loss o~ capacity during storage.
This precharg m g procedure ~ay be accomplished in any of several different ways. In the prasently most pre-~erred approach, the cell 10 is discharged to zero volts and the internal pressur~ is ~quilibrated to a partial pressure of 1 atmosphere of hydrogen, or 15 psia. The fill tube 35 is then ealed, and the pos~tive electrode of the cell ~ s charged t~ a positive charge level, pre~erably a charge level corresponding to a pressure of about 65 psia.
After the cell is charged with the fill tube 35 sealed, the fil 1 tube 35 is then unsealed by venting the tube 35, and the internal pressure wikhin the cell is reduced to a lesser value, preferably 15 psia, with the charging lead~
disconnected but the cell remainlng in the partially charged condition. The tube 35 is sealed, and the pre-charging procedure is complete. The cell may then be stored for extended periods of time substantially without loss o~ maximum charging capacity during ~he s~orage period.
Tables I and II ~llustrate the ef~ect of various precharge~ upon the loss o~ ~aximum electrical capacity of several cells. The cells whose rasult3 are reporked in Table I are construct~d to have initial electrical capa-cities of about 50 ampere-hours, whil~ those whose results are reported in Table II axe construct2d to have initial capacities of about 25 a~per~-hours. Cells 288 (Table I), 202 and 1~8 tTable II) were not precharged with the approach o~ the invçntion but ~n~tead w~r~ ~ealed at 15 psia. ~hey were then stored in an open circuit condition for the indicated number~ o~ day~:. After the indicated period of 6torage of the cell in the open circult con-di~ion, the maximum electrical charge capac~:~y waF- deter-mined. As may b~ ~een, the maximum charge capacity o~ cell No. 288 fell from 53.5 to ~4.6 ampere~hours after 32 days.
Cells 202 and 188 experienced ~imilar re~uctions.
~.ECE I
Capacity ~o ~.OV f~Hcurs) Cell~ha~eInlt~l No. o~ Days In Open C~. (Dis~harqed~
No.I~vel ~1) Capa- 0 1 4 8 16 32 ci1~y 2926 ~H 53.2 53.9 55.5 5~.954.2 5S.2 53.7 3016 AH 52 . 353 . 855 . 5 54 . B 54 .155 . 052 ~ 9 28815 psia 53.5 48c7 51.9 50.950.6 48.9 44.6 42565 psi~ 51.1 45.3 48.~ 48.348.3 47.5 42.9 44865 psi 51.8 48.3 51.2 5~.249.9 48.0 42.5 ~ II
_ _ C~pacity ~o l. a~r (P~Hours) Cell E~ha~ge Init'l No. of_DaYs in Op2n C~rcuit (Dis~harqecl2 No.If ~vel (1) Capa- 0 1 4 8 16 32 64 128 ci~y 1695 A~I 28.5 2g.5 2~.2 29.629.2 2~.1 29.1 27.8 28.4 20215 psia 25.4 27.6 28.3 28.628.4 28.0 26.9 23.3 21.5 18815 psia 28.1 28.6 28.6 28.928.8 28.5 27.3 23.~ 23.1 20765 psia 24.8 27.~ 28.3 28.828.S 27~8 26.3 23.2 19.5 __ _ _ _. _._ _ ___ -- - __ . __ _ -- -- T_ _ _ . .~
(1) ~e p~ha~e level is E~pecified in rela~i~ to ~e ~ of pre-~ -~harge. For positive-electrode limited di~rg~ t within the in-a~h~ (~).
i Cells 29~ and 301 ~Table I) and 169 (Table II) were given an initial precharge in accordance wlth the present inventio~, using the method previously described. ~n each case, the maximum electrlcal storage cap~city o~ the cell after extended periods of storag~ was ~ssentially unchanged.
This unchanged maximum electrical storage capac$ty is highly desirable so that the cell can be ~tored for extended periods of ti~e befora use.
Cells 425 and 448 (Table I~ and 207 (Ta~le II) were given a positive initial hydrogen gas partial pressure, which leav~s them positive-electrode limited upon discharge, a procedure not in accordance with the invention and perform~d for c:omparison. That is, the cells were pressurized above their norm~l hydrogen gas pressure during charg~ng. In eac:h case, there was a significant loss o~ maximum electrical storage capacity after the battery was stored for a period of days.
It is possible within the scope of the mvention to reduce the gas pressure to a level below the characteristic gas pressure depicted schematically in FIGURE 3, but not to atmospheric, durm g the precharging treatment. That is, for example, the positive electrode oould ba charged to a charge state corresponding to 65 psia, and then the gas pressure reduced to a valua less than 65 psia but greatar than atmos pheric. Such an approach would create a negative-electrode l~mited discharge and thenc~ provide the benefits o~ the invention, and would reduce the loss o~ capaci~y during storage. However~ this approach is not preferred, s~nc:e it would require the cell to be ~hipped with an ~nternal hydro-gen pressure.
Table III illustrates a further benefit obtained from the present precharg~ng approach. Cells are observed to undergo a self discharge when stored under charge. That is, when the cell is ch~rged and ~tored, a portion Or the charge is lost upon etorage. ~This pheno~enon i8 distlnguished from the loss o~ capaci~y wh~n ~torQd ~n the discharged or open circuit 6tate, described previously.) In these tests, cell F005 was precharged to a value o~ 65 psia using a hydrogen tank, a procedure not in accordance wi~h the present invention~ Cel 1 F006 wa3 prechargad by applying a precharge correcponding to 65 p~;ia hydrogen to ~he positive electrode (approximately 5 AH), and then charged and reducing the hydrogen prassure to 15 ps$a, a procedure in accordance with the pxesent inventionO Each cell was then allowed $o stand at laboratory ambient temperature ~approximately 2 0 C) for 72 hours- The charge OI the cell before and after the storaga period was mea~ured, and the ratio taken. As may be seen, cell F006 ~uf~ered less discharge during the storage test, retaining 78% o~ its charge as compared to 68% for cell F005. It is believed that this reduced spontaneous di~charge ~s related to the lower pressure during storage within the cell precharged ln accordance with the present invention.
TABLE XII
Cell No.
Test F005 F006 Initial capacity, ampere hours 39.7 53.2 Charge a~ter ~tanding 72 hours, ampere hours 27.2 42 Ratio, standing to initlal, percent 68 78 Other techniques for achieving the negatiYe-electrode limited discharge state gas precharge may also be utilized. In one such an alternative approach, the cell is manufactured in a cordance with the usual procedures. In ~he precharging procedure, tha :~111 tube 35 is le~t open during precharging 60 that the hydrogen pres~ure wi~hin tha cell is essentially atmospheric or 15 psia during charging. ~n electrical cuxrent that is equivalent to ~ positive gas pressure i5 then pa~d into the Ge~l to oharge the cell, but becau~e the ~iU tub~ 35 r~main~ op~n, th~ hydrogen partial pressure within the cell doQ~ not Rubstant1ally increase.
After the cell is partially sharged, the fill tube 35 is 6ealed and khe precharging ls comple'ce. This precharge procedure produces ~ubstantially 'che same result as the previously described pxecharging procedurQ wherein the prassure ~ s reduced to 15 psia.
As has now been demonstrated, the precharglng procedure of the present invantion allows a pressurized nickel-hydrogen cell to be precharged in a manner such that the cell may be E;tored for extended periods of time in the open-circuit condition, without 10s8 of the maximum energy torage capaci~y after such extended periods. The procedure is fully compati~le with the existing design of such cells, and may be readily implemented. Such a precharged cell also suffers less 6pontaneous discharging durlng ~torage in the charged ~tate, as may occur wherl the cell ls placed into operation on board a spacecraft.
Although a particular embodiment of the invention has been described in detail for purpo5es of illustration, various modifications ~ay be made without departing from the spirit and ~cope o~ the inventlon. Accordingly, the invention is not to be lim~ed except as by the appended claims.
~ixturQ o~ platinu~ blacX and polytetra~luoroethylene and on ~hQ other ~id~ wlt~a ~ porou~ l~y~r c~ polyt~tra~luoro~
ethylene 19. Th~e layQr~ ar~ applled to ~ nlck@l sub-~trate in the ~orm o~ etch~d ~h~et or ~ woven me h, to ~orm the nega~ive ele~rode 16. 2~any di~g~ren~ ~ype~ o~ ~epa rators 18 have b~n usQd, including, for example, asbestos, nylon, and a cloth o~ zirconium ox~de-y~crium oxide con taininy polysul~one. Th~ elect:rolyte, pre~errably potas sium hydroxi~e, i~ impregna~d into ~he separator la.
Th~ indi~ridual plat~ ~ets 1~ are ~ss¢mbled onto a central core ~2 to ~or~ a ~tacked arr y 2~. In ~orming the s~acked array 24, a ~ono~ilament polypropyl~n~ ~creen 26 is placed ~Qtween each plat~ ~Qt ï2, ~o t:hat oxyg~n l~erated during overcharging ~t ~ach po5it:lvla electrode 14 can diffu~ away ~ro~ the el~rodQ 14 ~nd to tha negative elec~rodQ 16 to com~ine with hydrog~n. Th~ ~tacXed array 24 is placed under a long~:udinal pres~ure o~, ~or example, about 19 pounds per squar~ inch, ~y tlghtening comprPssion plates 28 against ~ach ~nd o~ s~acked array 24. The tigh~ening o~ th~ co~pr~s~ion plat~ 2g i~ prer~rably accomplished by ~o~px~g . ing ~he array 24 and th~n ti~hten-ing . nut 30 on tr~ad~ on th~ corel 22, th~reby compr~ss~ng a B~11QV~ wash~r ~ 32 ag~ t ~ co~pr~sion plate 28 to hold th~ ~aek~d ~rr y 24 ln placa ThQ ~tack~d array 2 4 i~ s~ d wi~hin a pr~s,~re vessal 34, ~anuSactur~d o~ ~ mat~rial such as Inconel 718 nictc~l-based ~lloy which carl wi~h . tand lnt~nal pressures on th~ ord~r ol~ 1,000 p~ia, wi~hout d~ g~ by hyd:~og2n em-brittlemQnt or coxro~ion by thQ~ ctrolyt~. ~ gas tube 3 5 allows ga~ cont~n~ an~ prelB~lUS~3 wil:h~n th~ p~essure vessel 34 to bQ controll~d. Th~ pr~ surQ v~el 34 is typio~lly cozlstruc~d ln tho ~orall o~ ~ cyl~ndrical l:ube having domed Qnds~ By way o~ ratlon, th~ cell 10 hav~g th~ pre~surel v~8~1 34 oi~ ~xt:@rnal dimension~ 3-1/2 inche~ di~e~o~ and 13 inch~ long can contain abou~ 4 0 individual pl~to 6~t~ 12, wlt~ a resul~g ~l~ctrical ~torag~ capa~ty o~ the c211 oi! about 50 amplære-hours.
r~
The cell 10 ~ay be charged and discharged through thou-sand~ of cycles without apparent damage, if the charging and discharging are accomplished properly. A number of cells 10 can be combined in ~eries or parallel ~o produce a battary.
Charging is accomplished by impressing a voltage through the leads 20 across each plate set 12 so that electrons flow ~rom thP electrode 16 to the elsctrode 14.
Electrical energy is thereby stored in each plate set in the form of chemical reactants, for subsequent discharying to produce a usable current. ~ nickel-hydrogen cell of the type described previously may be fully charged by a solar cell array to a capacity of, for example, about 50 ampere hours, using a current o~ ~bou~ 5 amperes at 1.5 volts through a charging period of about 14 hours from a dis-charged state. The voltage and charging time vary, depend-ing upon the power ava; 1 able from the solar cell and the cycle dictat~d by the orbi~ of the spacecrart.
When the gas f~ tube 35 is sealed at 15 psia (atmospheric pressure) and charging commenced fro~ a fully discharged ~tate, the gas pressure within the cell 10 initially increases in a generally linear fashlon proport-ional to the charge etored within the cell 10. FIGURE 3 schematically ;llu~trates this initial increase in gas pressure as a function of charge, and the correspondence of a particular charye and pressure value.
A.fter the cell is manufactured but before it is placed into ~ervice, the cell may be stored for a period of time in an "open circuit" condition, wherein no further charging or discharging of the cell is accomplished.
During that period of open circui~ storage, in addition to self dischargm g to a fully discharg~d sta~e, the cell apparently physically change~ in ~ome manner ~o that i~s maximum electrical capaci~y, to which it may subsequently be charged, gradually fallsO For exa~ple, and as xeported in greater dQtail in Tables I and II, a cell having an ~rlitial maximum capaci~y o~ 53.5 ampere-hours experiences a reduction of maximum capacity to 44.6 ampere~hours after 32 days of open circuit discharged ~torage. Similarly, a cell having an initial capacity o~ 28.1 ampere-hours experiences a reduction in capaci~y to 27.3 ampere-hour~ after 32 days of storage, and to 23.1 amperQ-hours ater 128 days of storage. The precise reason for this lo~s o2 maximum electrical capacity during storage i~. not known with cer-tainty, and Applicants do not wish to be bound by any parti-cular explanation of this phenomenon. However, it is believed that during storage with a hydxogen gas partial pressure within the cell, an insulating material is pro-duced at the positive electrode 14. Discharging results in a continuous bu~ld-up of the insulating material, with the consequent result that the areas of active material on the positive electrode become isolated. At a later time when the cell is charged, the isolated active areas remaLn isolated because of the presence o~ the discharged insu-lating ~aterial, thereby reducing the useful reactive capacity of the positive electrode, and thence the cell.
In accordance with ~he presen~ invention, i~ has been found that the gradual loss of maximum cPll capacity during storage can be reduced or avoided ~ntirely ~hrough a precharging procedure applied to the cell after assembly, but prior to the beginning of the period during which the cell is stored in an open-circuit condition. To accomplish the precharging procedure, the cell is manu~actured m the usual ~anner as described previously, except ~or a PLnal step in which the positi~e electrode of the cell is charged and the hydrogen precharging pressure is set to a value less than that defined by the characteristic line ~llus-trated in Figure 3, and pre*erably to 15 psia.
Discharging oî a sealed nickel-hydrogen cell is ordinarlly positive~elactrode limi~d. AB khe cell dls-charges, hydxog~n i~ con6ume~ by reac~ion with l:he active material of the po itive or nickel electrode. The reactants availabl~ at the pos~tive 01ectrode are exhausted be~ore 11 of the hydrogen is consumed. The precharging process of the present lnvention results in re~uced hydroyen avail-ab;lity during discharging, w~th the result that discharg-lng becomes ne~ative-electrode limited. That ls, upon dis-charging of a c~11 that has been precharged by the present invention, an electrical charge remains on the positive electrode wh~n the hydrogen partlal pressure of the sealed cell is reduced to about O psia. It is believed that this negative-electrode limitatlon durlng discharge is instru-mental in reducing or avolding subsequent loss o~ capacity during storage.
This precharg m g procedure ~ay be accomplished in any of several different ways. In the prasently most pre-~erred approach, the cell 10 is discharged to zero volts and the internal pressur~ is ~quilibrated to a partial pressure of 1 atmosphere of hydrogen, or 15 psia. The fill tube 35 is then ealed, and the pos~tive electrode of the cell ~ s charged t~ a positive charge level, pre~erably a charge level corresponding to a pressure of about 65 psia.
After the cell is charged with the fill tube 35 sealed, the fil 1 tube 35 is then unsealed by venting the tube 35, and the internal pressure wikhin the cell is reduced to a lesser value, preferably 15 psia, with the charging lead~
disconnected but the cell remainlng in the partially charged condition. The tube 35 is sealed, and the pre-charging procedure is complete. The cell may then be stored for extended periods of time substantially without loss o~ maximum charging capacity during ~he s~orage period.
Tables I and II ~llustrate the ef~ect of various precharge~ upon the loss o~ ~aximum electrical capacity of several cells. The cells whose rasult3 are reporked in Table I are construct~d to have initial electrical capa-cities of about 50 ampere-hours, whil~ those whose results are reported in Table II axe construct2d to have initial capacities of about 25 a~per~-hours. Cells 288 (Table I), 202 and 1~8 tTable II) were not precharged with the approach o~ the invçntion but ~n~tead w~r~ ~ealed at 15 psia. ~hey were then stored in an open circuit condition for the indicated number~ o~ day~:. After the indicated period of 6torage of the cell in the open circult con-di~ion, the maximum electrical charge capac~:~y waF- deter-mined. As may b~ ~een, the maximum charge capacity o~ cell No. 288 fell from 53.5 to ~4.6 ampere~hours after 32 days.
Cells 202 and 188 experienced ~imilar re~uctions.
~.ECE I
Capacity ~o ~.OV f~Hcurs) Cell~ha~eInlt~l No. o~ Days In Open C~. (Dis~harqed~
No.I~vel ~1) Capa- 0 1 4 8 16 32 ci1~y 2926 ~H 53.2 53.9 55.5 5~.954.2 5S.2 53.7 3016 AH 52 . 353 . 855 . 5 54 . B 54 .155 . 052 ~ 9 28815 psia 53.5 48c7 51.9 50.950.6 48.9 44.6 42565 psi~ 51.1 45.3 48.~ 48.348.3 47.5 42.9 44865 psi 51.8 48.3 51.2 5~.249.9 48.0 42.5 ~ II
_ _ C~pacity ~o l. a~r (P~Hours) Cell E~ha~ge Init'l No. of_DaYs in Op2n C~rcuit (Dis~harqecl2 No.If ~vel (1) Capa- 0 1 4 8 16 32 64 128 ci~y 1695 A~I 28.5 2g.5 2~.2 29.629.2 2~.1 29.1 27.8 28.4 20215 psia 25.4 27.6 28.3 28.628.4 28.0 26.9 23.3 21.5 18815 psia 28.1 28.6 28.6 28.928.8 28.5 27.3 23.~ 23.1 20765 psia 24.8 27.~ 28.3 28.828.S 27~8 26.3 23.2 19.5 __ _ _ _. _._ _ ___ -- - __ . __ _ -- -- T_ _ _ . .~
(1) ~e p~ha~e level is E~pecified in rela~i~ to ~e ~ of pre-~ -~harge. For positive-electrode limited di~rg~ t within the in-a~h~ (~).
i Cells 29~ and 301 ~Table I) and 169 (Table II) were given an initial precharge in accordance wlth the present inventio~, using the method previously described. ~n each case, the maximum electrlcal storage cap~city o~ the cell after extended periods of storag~ was ~ssentially unchanged.
This unchanged maximum electrical storage capac$ty is highly desirable so that the cell can be ~tored for extended periods of ti~e befora use.
Cells 425 and 448 (Table I~ and 207 (Ta~le II) were given a positive initial hydrogen gas partial pressure, which leav~s them positive-electrode limited upon discharge, a procedure not in accordance with the invention and perform~d for c:omparison. That is, the cells were pressurized above their norm~l hydrogen gas pressure during charg~ng. In eac:h case, there was a significant loss o~ maximum electrical storage capacity after the battery was stored for a period of days.
It is possible within the scope of the mvention to reduce the gas pressure to a level below the characteristic gas pressure depicted schematically in FIGURE 3, but not to atmospheric, durm g the precharging treatment. That is, for example, the positive electrode oould ba charged to a charge state corresponding to 65 psia, and then the gas pressure reduced to a valua less than 65 psia but greatar than atmos pheric. Such an approach would create a negative-electrode l~mited discharge and thenc~ provide the benefits o~ the invention, and would reduce the loss o~ capaci~y during storage. However~ this approach is not preferred, s~nc:e it would require the cell to be ~hipped with an ~nternal hydro-gen pressure.
Table III illustrates a further benefit obtained from the present precharg~ng approach. Cells are observed to undergo a self discharge when stored under charge. That is, when the cell is ch~rged and ~tored, a portion Or the charge is lost upon etorage. ~This pheno~enon i8 distlnguished from the loss o~ capaci~y wh~n ~torQd ~n the discharged or open circuit 6tate, described previously.) In these tests, cell F005 was precharged to a value o~ 65 psia using a hydrogen tank, a procedure not in accordance wi~h the present invention~ Cel 1 F006 wa3 prechargad by applying a precharge correcponding to 65 p~;ia hydrogen to ~he positive electrode (approximately 5 AH), and then charged and reducing the hydrogen prassure to 15 ps$a, a procedure in accordance with the pxesent inventionO Each cell was then allowed $o stand at laboratory ambient temperature ~approximately 2 0 C) for 72 hours- The charge OI the cell before and after the storaga period was mea~ured, and the ratio taken. As may be seen, cell F006 ~uf~ered less discharge during the storage test, retaining 78% o~ its charge as compared to 68% for cell F005. It is believed that this reduced spontaneous di~charge ~s related to the lower pressure during storage within the cell precharged ln accordance with the present invention.
TABLE XII
Cell No.
Test F005 F006 Initial capacity, ampere hours 39.7 53.2 Charge a~ter ~tanding 72 hours, ampere hours 27.2 42 Ratio, standing to initlal, percent 68 78 Other techniques for achieving the negatiYe-electrode limited discharge state gas precharge may also be utilized. In one such an alternative approach, the cell is manufactured in a cordance with the usual procedures. In ~he precharging procedure, tha :~111 tube 35 is le~t open during precharging 60 that the hydrogen pres~ure wi~hin tha cell is essentially atmospheric or 15 psia during charging. ~n electrical cuxrent that is equivalent to ~ positive gas pressure i5 then pa~d into the Ge~l to oharge the cell, but becau~e the ~iU tub~ 35 r~main~ op~n, th~ hydrogen partial pressure within the cell doQ~ not Rubstant1ally increase.
After the cell is partially sharged, the fill tube 35 is 6ealed and khe precharging ls comple'ce. This precharge procedure produces ~ubstantially 'che same result as the previously described pxecharging procedurQ wherein the prassure ~ s reduced to 15 psia.
As has now been demonstrated, the precharglng procedure of the present invantion allows a pressurized nickel-hydrogen cell to be precharged in a manner such that the cell may be E;tored for extended periods of time in the open-circuit condition, without 10s8 of the maximum energy torage capaci~y after such extended periods. The procedure is fully compati~le with the existing design of such cells, and may be readily implemented. Such a precharged cell also suffers less 6pontaneous discharging durlng ~torage in the charged ~tate, as may occur wherl the cell ls placed into operation on board a spacecraft.
Although a particular embodiment of the invention has been described in detail for purpo5es of illustration, various modifications ~ay be made without departing from the spirit and ~cope o~ the inventlon. Accordingly, the invention is not to be lim~ed except as by the appended claims.
Claims (10)
1. A process for reducing the open-circuit capacity loss during storage of a pressurized nickel-hydrogen cell comprising:
precharging the cell prior to storage so that discharge of the cell is negative electrode limited, whereby an electrical charge remains on the nickel positive electrode when the hydrogen partial pressure falls to about 0 psia.
precharging the cell prior to storage so that discharge of the cell is negative electrode limited, whereby an electrical charge remains on the nickel positive electrode when the hydrogen partial pressure falls to about 0 psia.
2. The process of claim 1, wherein aid step of precharging includes the steps of applying a charge to the positive electrode of the cell with the cell unvented, to an electrical charge corres-ponding to a first pressure; and reducing the pressure within the cell to a second pressure.
3. The process of claim 2, wherein the second pressure is about 15 psia.
4. The process of claim 2, wherein the first pressure about 65 psia.
5. The process of claim 1, wherein said step of precharging includes the step of:
applying a charge to the positive electrode of the cell while the pressure within the cell is maintained at about 15 psia.
applying a charge to the positive electrode of the cell while the pressure within the cell is maintained at about 15 psia.
6. The process of claim 5, wherein the charge level corresponds to a hydrogen partial pressure of about 65 psia.
7. A process for precharging pressurized nickel-hydrogen cell, comprising the steps of:
discharging the cell to about zero volts at a hydrogen partial pressure of about 15 psia;
electrically charging the cell while sealed to a charge corresponding to a first hydrogen pressure; and reducing the hydrogen pressure to about 15 psia.
discharging the cell to about zero volts at a hydrogen partial pressure of about 15 psia;
electrically charging the cell while sealed to a charge corresponding to a first hydrogen pressure; and reducing the hydrogen pressure to about 15 psia.
8. The process of claim 7, wherein the first gas pressure is about 65 psia.
9. A process for precharging a pressurized nickel-hydrogen cell, comprising:
passing a current through the cell while the cell is unsealed and maintained at a gas pressure of about 15 psia, until the cell reaches a charge state corresponding to a first sealed hydrogen partial pressure.
passing a current through the cell while the cell is unsealed and maintained at a gas pressure of about 15 psia, until the cell reaches a charge state corresponding to a first sealed hydrogen partial pressure.
10. The process of claim 9, wherein the first sealed hydrogen partial pressure is about 65 psia.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/788,593 US4689544A (en) | 1985-10-17 | 1985-10-17 | Control of the charging of pressurized gas-metal electrical storage cells |
| US827,023 | 1986-02-07 | ||
| US06/827,023 US4683178A (en) | 1985-10-17 | 1986-02-07 | Process for preventing electrical storage cell capacity loss |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1284355C true CA1284355C (en) | 1991-05-21 |
Family
ID=39620129
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000520666A Expired CA1257900A (en) | 1985-10-17 | 1986-10-16 | Control of the charging of pressurized gas-metal electrical storage cells |
| CA000528776A Expired - Fee Related CA1284355C (en) | 1985-10-17 | 1987-02-02 | Process for preventing electrical storage cell capacity loss |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000520666A Expired CA1257900A (en) | 1985-10-17 | 1986-10-16 | Control of the charging of pressurized gas-metal electrical storage cells |
Country Status (6)
| Country | Link |
|---|---|
| US (2) | US4689544A (en) |
| EP (2) | EP0241552B1 (en) |
| JP (2) | JPH0793152B2 (en) |
| CA (2) | CA1257900A (en) |
| DE (2) | DE3687655T2 (en) |
| WO (2) | WO1987002515A2 (en) |
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| CN103947027B (en) | 2011-10-13 | 2016-12-21 | 赛昂能源有限公司 | Electrode structure and manufacture method thereof |
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| KR101991149B1 (en) | 2012-12-19 | 2019-06-19 | 시온 파워 코퍼레이션 | Electrode structure and method for making same |
| US12261284B2 (en) | 2013-03-15 | 2025-03-25 | Sion Power Corporation | Protective structures for electrodes |
| KR102622781B1 (en) | 2014-05-01 | 2024-01-08 | 시온 파워 코퍼레이션 | Electrode fabrication methods and associated articles |
| JP6864536B2 (en) * | 2017-04-25 | 2021-04-28 | 株式会社東芝 | Rechargeable battery system, charging method, program, and vehicle |
| US10868306B2 (en) | 2017-05-19 | 2020-12-15 | Sion Power Corporation | Passivating agents for electrochemical cells |
| JP7210475B2 (en) | 2017-05-19 | 2023-01-23 | シオン・パワー・コーポレーション | Electrochemical cell passivator |
| WO2020257414A1 (en) | 2019-06-21 | 2020-12-24 | Sion Power Corporation | Methods, systems, and devices for applying forces to electrochemical devices |
| US11978917B2 (en) | 2019-11-19 | 2024-05-07 | Sion Power Corporation | Batteries with components including carbon fiber, and associated systems and methods |
| US11791511B2 (en) | 2019-11-19 | 2023-10-17 | Sion Power Corporation | Thermally insulating compressible components for battery packs |
| US11824228B2 (en) | 2019-11-19 | 2023-11-21 | Sion Power Corporation | Compression systems for batteries |
| US11984575B2 (en) | 2019-11-19 | 2024-05-14 | Sion Power Corporation | Battery alignment, and associated systems and methods |
| EP4118701A1 (en) | 2020-03-13 | 2023-01-18 | Sion Power Corporation | Application of pressure to electrochemical devices including deformable solids, and related systems |
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-
1985
- 1985-10-17 US US06/788,593 patent/US4689544A/en not_active Expired - Lifetime
-
1986
- 1986-02-07 US US06/827,023 patent/US4683178A/en not_active Expired - Lifetime
- 1986-09-15 DE DE8787900356T patent/DE3687655T2/en not_active Expired - Fee Related
- 1986-09-15 WO PCT/US1986/001900 patent/WO1987002515A2/en not_active Ceased
- 1986-09-15 JP JP62500052A patent/JPH0793152B2/en not_active Expired - Lifetime
- 1986-09-15 EP EP87900356A patent/EP0241552B1/en not_active Expired - Lifetime
- 1986-10-16 CA CA000520666A patent/CA1257900A/en not_active Expired
- 1986-12-29 EP EP87900591A patent/EP0254730B1/en not_active Expired - Lifetime
- 1986-12-29 JP JP62500592A patent/JPH0787103B2/en not_active Expired - Lifetime
- 1986-12-29 WO PCT/US1986/002787 patent/WO1987004863A1/en not_active Ceased
- 1986-12-29 DE DE8787900591T patent/DE3673821D1/en not_active Expired - Fee Related
-
1987
- 1987-02-02 CA CA000528776A patent/CA1284355C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0254730B1 (en) | 1990-08-29 |
| JPS63501111A (en) | 1988-04-21 |
| CA1257900A (en) | 1989-07-25 |
| DE3673821D1 (en) | 1990-10-04 |
| DE3687655D1 (en) | 1993-03-11 |
| EP0254730A1 (en) | 1988-02-03 |
| WO1987002515A2 (en) | 1987-04-23 |
| EP0241552B1 (en) | 1993-01-27 |
| JPS63502310A (en) | 1988-09-01 |
| WO1987004863A1 (en) | 1987-08-13 |
| WO1987002515A3 (en) | 1987-07-16 |
| US4683178A (en) | 1987-07-28 |
| DE3687655T2 (en) | 1993-06-03 |
| JPH0793152B2 (en) | 1995-10-09 |
| US4689544A (en) | 1987-08-25 |
| EP0241552A1 (en) | 1987-10-21 |
| JPH0787103B2 (en) | 1995-09-20 |
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