CA1259371A

CA1259371A - Cell corrosion reduction

Info

Publication number: CA1259371A
Application number: CA000485736A
Authority: CA
Inventors: Purush Chalilpoyil; Frank E. Parsen; Chih-Chung Wang; Jesse R. Rea
Original assignee: Duracell International Inc
Current assignee: Duracell Inc USA
Priority date: 1984-07-09
Filing date: 1985-06-27
Publication date: 1989-09-12
Also published as: FR2567327A1; BE902827A; BR8503252A; GB2161645A; FR2567327B1; PH21168A; ZA854961B; AU4467085A; AU567857B2; MX157252A; GB2161645B; IT8521475A0; IT1187685B; DK311785A; JPS6164076A; ES8604659A1; IN163914B; NL8501874A; GB8517353D0; KR860001496A

Abstract

CELL CORROSION REDUCTION

ABSTRACT

Corrosion is reduced in aqueous electrochemical cells having zinc anodes by utilizing single crystal zinc particles to which small amounts of one or more of indium, thallium, gallium, bismuth, cadmium, tin and lead have been added and amalgamated with mercury. A synergistically lowered rate of corrosion and cell gassing is obtained even with reduction of mercury content.

Description

~5~371 This invention relstes to 1nethods ntilized in the reduction of corrosion nnd gns3ing in aqueous electrochemical cells particularly in slkaline type cells haviug zinc anodes.
~ problem in nqueous electrochemical cells bss been the evolntion of hydrogen gas in the sealed cell container. Such g&ssing hns resulted in corrosion, lesknge of the electrolyte $rom the cell, cell container deformation and rupture, and a possible hazard ~hen the cell is disposed of in a fire. Vsrious e~cpedients hsve been ntilized in preventing, minimi~ing llud controlling snch hydrogen 8a8 evolntion and its conseqnences, Such espedients have included mechanical mesua snch a8 vents snd sdditional volume for storing the hydrogen without ~ceDsive pressnre build up. Chemical e~cpedients hsve inclnded: corrosion and gallsing inhibitors such as lesd, indinm, tin, cadmium, bismuth, thallium, and gallinm; hydrogen getters such as rare raetala ~lupported ou o~idos ~uch a8 plstimm snpported on alnminum oxide or palladinm or finely di~p2rsed nickel mixed with pol~tetrsflnoroethylene and manganeae dioxide, and hydrides l~nch a8 Lalli'd; hydrogen recombination with oxygen particulsrly ntilized in nickel cadmium cells; and removsl of chemicsls 3uch as chlorides fro~ the snrface of the nnode metal vhich tend to accelerate torrosion. The st conmlon, ~o~t effective snd the oldest e~pedient (particnlnrly in slkaline electrolyte cells) hss been the utili~ation of ~ercnry to 3malgsmate the anode metal such as zinc to increase the norrdally high h~drogen overpotentisl and to psovide for a nniform equipotentisl surface on the anode metal. B.ecently, ~ith the incresse of environmental concerna, rednction or elimination~of rdercnrv without ~ubstantial concomitant incresse in cell corrosion or ga~sing hns been vigorously pursued.

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~L2~937~

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It is en object of the pre~ent inveDtion to provide ~eaD~ for reduction or eli~iu-tion of mercurg in cell uodec vithout lo~- of corrosiou protection Ird ircre-ee in cell g-s-iDg.
Thi- and other object~, feature~ aDd advautage- of the pre~ent inveDtiou vill beco~e Dore evideDt fro~ th~ follo~iDg ti~CU~3ioD.
GeDerllly the pre~ent invention eo~pri~e~ ~ethod for ou~iDg an electrocherqical cell eubject to reduced ga--iDg by me-ua of utiliz-tion of ~pecific o teri-lo iD apecific ~t-tee; ~uch ~gteri~ nd the cell it~elf.
~he method i~ pgrticulorly epplic-ble to ~ cell hnviDg n anode comprieed of a r~ercury a2alg~0ated povdered ~etal ~ueh a- rinc. In tbe oethod of the pre~eDt~iDvention the po~dered ~et-l ia oubet-nti~ formed into individu-1 siDgle cry~t~19 erd a a~11 amouDt of or~e or Dore of indiu~, c-drqiur~, g-llium, tballiurq, biuruth, tin, nd le-d ia added to the anodic terial i e. the povdered ~et~l (amalgar~ted or un~ulgss~ed) or to ~ercury vhich i~ then ~ulga~eted vith the po~dered r~etal. The mercur~ Dd the additive, in thi~ latter procedure, geuerally form a ~urace allag OD
each of the particles Though the u~ of ~ingle cry~e~1 aDOde ~uterial r~t tbe u-e of a~
iudiu~ snd/or other adtiti~e~ have aep-rately been ~no~n to effec~ivelg per2it 70~e redUCtioD of ~ercury content in the auode vithout aetri~eDtal incres~e iu ga~iDg, the effect of the ~o~biD~tioD h~- uDe~p~ctedl7 ~e~u discovered to be coD-iderehl~ ~ore teun ~dditive. Thu~, in cell~ h-vin~
~alga~ated 3ingle cry~tal riDc ~node~ the ~ount of nercury in the : .
ar~algsm csn be effeceively reduced frorq bout 6-72 to about 42. Similarly the utili~stion oS aD intiu~ additiv~ vith polycr~t-lliDe ~iDC a~algaD

nodes permie- the retuction of ~ercury from ~bout 6-72 to ~bout 3.5Y.
~o~ever, in accordance ~ith the pre-ent invention, a corqbiD~tioD of the t~o, i e ~ siDgle cry~t~l zinc er~ lg~ h an indiun ~ddi~ive u~e2pectedly pernit~ ~he effective reduction of tbe w rcury to gbout 1.52.
Aa a nstter of course, conbinstion of cher~ical gas reduction e~pedients does oot usually provide an 9dditiv~ effect nor doe~ e~ceB~i~o utili~stion of addit ives .

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~5~ 3~

The single crystnls of zinc are preferably prepsred 88 described in copending application llo. 448,306 . Such procedure involves the formstion of a thin ~kin crucible on esch of the zinc particles by oxidation in air at a temperature just below the melting point (419~C) of the zinc, heating of the skin encloJsd zinc particles in an inert atmosphere sbove the melting point of tbe zinc snd 810~ cooling thereafter with removal of the oxide skins. Zinc particle sizes generally range between 80 and 600 microns for ntility in electroches~ical cells and such ~ethod provideD an effective means for makiug single crystal particles of such smsll dinensions.
Generally the amounts of indium or other additive added to the snode metal amslgAm may range between ~5-5000 ppm and preferably bet~een lOO-lOOO ppm. 8uch ~terial may be directlg added to the marcury itself.
For e~a~ple indium is highly solnble in mercury snd can be directly ~Idded tbereto in the form of powder or grsnules. ~lternatively, the additive mav oe plated on the ~urface of the anode metal from ~alts of the ~Idditive prior to amalgamation with mercury. Such balts include the halides, particularly chlorides, o~l:ides and acetates of the ~aterials Dnch as indinm. It has been discovered that the addit*e~ ~uch a~ indium whether by addition to the mercury or by platiog on the single crystsl anode 1Detsl particles do not in fact disrupt the ~ingle crystsl nsture thereof to any detrimental extent ss msy have been expected.
The ~Dount of mercury in the anode llmalgam may range from O - 4%
depending upon the cell utilizstion snd the degree of gas~ing to be tolerated.
The amalgamated single crystal ~etal particles with sdditives ~uch as indium are then formed into anodes for electrochemical cells particulsrly slkaline electrochemical cells. Such cells generally have snodes of zinc and cathode~ of materisls ~uch as msngauese dioxide, oilver oxide, nercuric oxide and the li!ce. Electrolytes in such cells sre generally alkaline and u~ually comprise hydroxide solutions such as of sodius~ or potassium hydroxide. Other anode metals capable of being formed into ' -~;~593~71 single crystal po~ders and vhich are u~eful in electrochcmicsl cells .include Al, Cd, Ca, Cu, Pb,.~g, Ni, and Sn. It is uuderstood that with ~nodes of these metals th additive is not the ~sme as the nnode act *e r~aterial but is less-electrochemically-nctive.
.Tbe effects of the present ineention csn be ~ore clesrly evidenced by consideration:of co~psrative gas~ing rates and dischArge-capRcities-ss -sho7n in the follo~iug e~ples. It is understood that ~uch 2~a~ples are for illustrstive purpo~es And re not to be con~trued a8 a limitstion OD
the present invention. In the e~mples a8 vell as throughout this discus~ion all pArts are pArts by ~eight-unless other~ise indicated.
.~3A~PLE 1 Zinc po~der.dmalg~ms contaiDing.1.5Z mercury-are ~ade ~ith :polycrystalline ZiDC alone, polycrystalline zinc:~ith O.lZ.indium as aD
additi~e element-with the ~ercury, single crystAl:zinc,:and single crystAl zinc with O.lZ indium a8 an additive ele~ent with the ~ercury. LquAl AmOUUts of.the amalgAm po~dera arz theu plac~d.in equal a~ounts of 37Z XO'd ~lkaline colution (typical electrolyte.oolutiou of alk~line cells) and tested for ga~sing st 8 te~perature of 71~C. The amouut of gassing, meAsured in-microliters/gram-per day tuL¦g-day) and the rste reduction fActors (~ith the polvcrystAlline zinc:control beiug 1) are szt:forth iu Table 1:
T~BL~ 1 ~NODE ~AT~BI~LGA5SING B~TERATE B3D~CTION F~CTOR
PolycrystalliDe zinc, 1.5%.~g 295 PolycrgstAlline riDc, 1.5Z ~g 105 .2.8 O.lZ indium Single crystal zinc, 1.5~ 'dS 140 2.1 Siugle crystnl zinc, 1.5% ~g 30 9.8 0.1% indium ~ rate reduction factoT (if auy~ ~ould at ~ost ba~e b~en e~ected to be ~bout 5.9 (2.8 x 2.1~ for 8 co~bined utilizatioo of ~Lngle cry~tal zinc :and indiu~ vith a gas~ing rate reduction to about 50 uL/g-day. Tbe ` ~5~37~

co~bination ho~vcr ryDer~i~ticallJ rhducr- tbe gae-isg ~o about double tbe ~xp~ct2d reduction E~PL~ 2 FifeeeD ~ ~u of aingle cry~eal ~inc particlce ~ith ~rioue co2bin-tion~ of atditi~r ~ter h le of indiu~, tb~lliuA~ g-lliu~ ~nd lc-d ~re prep~rad 1st t-ot d for cDrroeion. Th- ~dtiti~c r~teri lJ rc pl~ed on tb- ~inc plrticl-- frn~ ~-lta tboroof. All eh~ a~ulga~ cont-i~ 1 5~ by veigbt of ~rcury rb- aoounta of ~c~ of tbo tditiv~ r~terial~
(deri~n~t~d bg ~Jaud ~-~ if not pr-- nt) aro 0 12 in~iu~ t~n~ 0.0lg t~alliu~ ~TI~0.005X ~-lliu~ (C ), ~n~ 0.042 lc d (~o). T~o ~r~DJ of c~cb of tho 2alg~rt~ re pl~ced in 372 ~O~ trolyt- aolution ~it~ g~-~ing t tbe nt of 24 and 48 bourr b-in~ ~q~ur d at 90-C ~ ~ein~
r~pre~entativ2 of corro~ion ~J controls t~o ~ lg~-u re ~ d- Yitb one cont~ining no Idditiv~ ~rerial but vith 1.5~ u-rcur~ ~nd th~ otb~r ~ont~iing pol~er~et~lline rinc ~itb 77 ~rcury cimilar to tb~t co D only u-~d in ~lk~lin~ typ- c-llo. ~eault~ of Juch t~cta re ~iv~n in T~ble 2.
I~nL~ 2 ADDITIVE BLE~E~T VOL~E OP C~S (2L), 90 C
In Tl G- Pb 24 aour~ 48 3Our~

Z0 + - - - 0.17 0.51 ~ 0.13 0 49 - - ~ - 0 42 1.35 _ _ _ ~ 0.40 1.15 0.13 0.36 _ ~ _ 0 l~ 0 47 ~ ~ + 0.15 0.4~
~ ~ ~ ~ 0.12 0 40 - ~ + 0.12 0 56 ~ + 0 40 1.13 30 ~ ~ ~ - 0.13 0 42 I + - l 0.1l 0.32 - + I ~ 0 15 0.60 0.14 0.44 ~ ~ + + 0 lO 0 28 - - - - (control) 0 41 1 39 Concrol 72 ~g-polycsy~t~llin~ Zn 0.16 0 43 Indiu~ ~nd/or thalliu~ aa ho~n in tbe abovr t-bl~ provide the ~o-~efficaciou- reduction of gA-~ing and ~re thuc pref~rred r~hodir~nr~ of che pre~ent invention aoYever incre-~e ir percen~age of g~lliur or le-d i-~g3~7~ i expected to provide similcr effects Oeh~r materiala imil~r i2 effecc toiDdium such as c-dmiu~ ein ~nd bi~muth m~y be ~imil-rly eIpected to provide the enhsnc~d effe~t of th~ preoeoe inventior E~A~PLE 3 ~ even zinc malgams CODt~iniDg 1 57. ag ~re prep-red ~icb three beiag comprised of Dingle crystal zinc (~dde ~c dercribed bove) ~Dd four bein8 comprised of polycry~talline zinc The armilg~mJ containing ~intle cry~tal ZiDC coQprise tvo h~viug 0 12 i~dium tone dded to the ~ercury prior to amdigamation ~nd the other beiD8 plated on che ZiDc particle urf-ces prior to amalg~r~dtion) dDd ore having DO indiun The polycry~t-lline zinc ~r~ Ig-ms iDclude three vithout lead for direct cor~p-riaon vitb tbe ~ingle crystal zinc whicù cont-iD~ Do le-t Dd on~ polycry~t~lline r~alg~r~ vi~b le-d ~ commooly utilized in electrocbemicel cella Sbe lead free polycrysc-lline ~rJdlg-~s are directly ~r-l~gou~ to tbe tbree ~ingle cryDt~l zinc ~m lg~mD The polycry~tilliDe le-d~d zin~ ~m31~-~ cont-in-0 022 indiun A control of polycry~t-lliDe ZiDC vitb le-d and 77 rDercury ~as commonly utilized in Ik~line c~ o pr~p~red Tvo gram samples of each of the sbove a~algama sre te~t~d for ga~aing t elevDted temperdtures (71 C and 90'C) for varying time ptriod~ vitb total gar volume and 8asaiD8 r~tes ùeirlg cor~par~tively deterriiDed la Cet forth in lable 3 below E~AHPLE 4 Cells are 3~de vith tbe 4mDlgar~ de~crib~d iD ~-r~ple 3 of ~iDgle crystal zirlc vith 0 lY indium ~both typea), polycryatallirle ziuc vith 0 1 indium plated OD th~ zinc p~rticle~ polycry4t-11iDe ZiDC vitbD 0.02~
indium added to the ~ercury, Dd a control of polycry~t~lline ZiDC vitb Do iDdium and 7~ r~ercury ~- typicAl alk-lioe cell) E-cb of tbe cell~ of AA
standdrd size ~oDtaiD~ a 2 7 grdr~ ~Dode ~1 75~ 4t2rch graft copoly~er gelling agene) 2 6 grars of a 37~ 80~ ~lectrolyte Dd a r~Dg~e3e diolide rathode vith the cell beiDg aoode limited Five cellr~ ~re te~ted for gassing for varyiDg periods at 71 C vitbout diDch~rge aod five are similarly tes~cd but after partial disch~rge at 3 9 ohm for ODe bour lo~al gas volu~e aDd gassiog rates are set forth in Table 3 belo~
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12593~7~

lo o~l ~ 1 ~ 1~ ~ c ~ o~ 0 _ C D ,_ ~o ~ ~ ~

O ~ V~ ~_ ~a ~W~ 00 1-OOO 0000 ~1-00 ~'~
OOO.pO~ oo~ 0~i~ O~ 1:~ ~;;
~0 1~~ _ ~
q~ ~

n~ 00 000 0 0000 ~~00 oOO~O~ O Co~oco ~1~ .

Z ~: ~

W
""~ w 1"" ~ 0~O 0~ 1I11 0 1111~ ~0~0 ~ ~C a~z O :~ ?~C~
P
O ~1--00 td 1--OO ~ ~ C _ ooo~ ~3 ~ o V10C~ ~ oo~o ~ _ , O~ Do~ . . ~ ..1~,,. ~W~1~ C ~
a b w ~~ ww~www~ oo ~-ooo oooo ~ oo ~ Zn ~n~ o~o~n\n~JW~I~ 0~00 _~jW~~ o ~ ~C
., n e ~ ~2~3~

E~PLF 5 Cells are m~de a6 iD EYa~ple 4 nd re e-ch di~charged to v-riou~
cutoff-volt~ea vith 3 9 oh~ lo-d ~ith ehe capscitiea in ~er~ic~ hours et oreh iD T3ble 4 belov.
IABLE 4 (Diacharge Ch~r-cteri~tic-) (Service ~oura t 3.9 oh~s) SINGLE C8YSTAL ZINC PCLYCRYSTALLIN~ Z~NC
CDT-OFF 0 1~ In 0.1Z In 0 022 In 0 lZ Ia aO In ~OLTAGES 1 5% 'd4 in 1 5Z ~ 1.5Z ~g tl,5Z dc 72 a~ Ctrl 1 2 0 660 0 668 0 533 0 688 0 bZ3 1 1 1 616 1 638 1.457 1.712 1 553 1 0 i 826 2 859 2.480 2.926 2.598 0.8 3 800 3 967 3.498 3.883 3 599 0.65 3 986 4 179 3.594 4.020 3 684 It i~ evident ro~ the bove el~ple- nd table- th~t th~ gle crys~sl ~inc ~ith o~e or ~ore ~dditive~ of tho pre~eot iuvention h ~arkedly effective in permittine larEe'nercury reduction~ vithout increase iD cell g~s-ing uhile at the ~r~ e enhADciDg cell diich-rge characteristics ~hen such cell- ~re co~pared to the current co~rcial alkaline cells having higb r~ercury aw-lga~ content It is understood that the above e~arlples are for illu~tr~tive purpose~
only and detail~ contained therein are not to be conatrued a~ limitatioD6 on tbe preaent in~eDtioD Changea in cell coDctruction, materialc, ratio~
aDd tbe like ~ay iD fact be made vithout departiDg fro~ the ~cope of ~he pre6ent invention a~ defiD~d iD the folloviDg clai~

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Claims

What is claimed is:

1. An electrochemical cell comprising an anode, a cathode and an aqueous electrolyte characterized in that said anode is comprised of single crystal anode metal particles and one or more members of the group consisting of indium, cadmium, gallium, thallium, bismuth, tin and lead.

2. The cell of claim 1 wherein said one or more members are present in said anode in a range of 25-5000 ppm.

3. The cell of claim 2 wherein said range is between 100-1000 ppm.

4. The cell of claim 1 wherein said anode further comprises mercury.

5. The cell of claim 4 wherein said anode is comprised of single crystal anode metal particles and one or more members of the group consisting of indium, thallium, gallium and lead.

6. The cell of claim 5 wherein said anode is comprised of single crystal anode metal particles and indium.

7. The cell of claim 5 wherein said anode metal is zinc.

8. The cell of claim 4 wherein said electrolyte is comprised of an alkaline solution.

9. The cell of claim 4 wherein said mercury is present in said anode in amounts of up to 4% by weight thereof.

10. The cell of claim 9 wherein said mercury is present in said anode in amounts of up to 1.5% by weight thereof.

11. A method for making an aqueous electrochemical cell subject to reduced gassing said method comprising the steps of making single crystal particles of the metal utilized as the active anode of said cell, adding ore or more additives selected from the group consisting of indium, cadmium, gallium, thallium, bismuth, tin and lead to said single crystal particles, and utilizing said single crystal particles with said one or more additives as the anode of said cell.

12. The method of claim 11 wherein said single crystal particles with said one or more additives are amalgamated with mercury.

13. The method of claim 11 wherein said single crystal metal particles are made by forming individual thin oxide coatings on polycrystalline metal particles by oxidation of said polycrystalline metal particles in air at a temperature below the melting point of said metal, heating of said metal particles in an inert atmosphere above the melting point of said metal, alow cooling of the metal particles and removal of said coatings.

14. The method of claim 13 wherein said metal is zinc.

15. The method of claim 16, wherein said single crystal zinc particles with said one or more additives are amalgamated with mercury.

16. The method of claim 15 wherein said one or more additives comprise from 25-5000 ppm of said anode.

17. The method of claim 16 wherein said one or more additives comprise from 100-1000 ppm.

18. The method of claim 17 wherein said single crystal zinc particles are alloyed with one or more additives of the group consisting of indium, thallium, gallium and lead.

19. The method of claim 18 wherein said mercury is present in said snode in amounts of up to 4% by weight thereof.

20. The method of claim 19 wherein said mercury is present in said anode in amounts of up to 1.5% by weight thereof.

21. The method of claim 18 wherein said one or more additives are plated on said single crystal zinc particles prior to amalgamation of said particles with mercury.

22. The method of claim 18 wherein said one or more additives are admixed with said mercury prior to amalgamation of said single crystal zinc particles with said mercury.

23. an electrochemical cell subject to reduced gassing comprising an aqueous alkaline electrolyte, a cathode and an anode comprised of mercury amalgamated single crystal zinc particles and indium with said mercury comprising up to 4% by weight of said anode and said indium comprising from 100 to 1000 ppm of said anode.

24. The cell of claim 23 wherein said mercury comprises up to 1.5% by weight of said anode, said cathode is comprised of manganese dioxide and said aqueous electrolyte is comprised of n potassium hydroxide solution.