CA1293221C - Electrodeposition of metal from solution in rotating cell with parallel spaced electrodes - Google Patents

Abstract

ABSTRACT
Process and apparatus for separating metal from a solution in which the metal has been dissolved by use of an electrochemical cell having a cathode electrode with a metal-collecting face. A substantial centrifugal force is applied to the metal-collecting face, the centrifugal force having a substantial component in a direction perpendicular to an outward from said face, whereby metal is deposited on said face as nodules of substantially uniform shape and size. The above may be utilized in a continuous electrowinning process where the nodules are permitted to grow until they reach a size where, under the action of the centrifugal force, they break off from the metal-collecting face and are removed from the cell. The above may also be utilized in the charging of a storage battery with the nodules being maintained at a size well below the size at which they would break off.

Description

~ov 1~,85 16:24 Hale and Dorr, E~oston; ~617) 742-9100 __ _ P,02 "RAFT OF SPECIFICA~IO~S FOR ~,T~-~

Thi~ lnvention relate~ to ~ method An~ apparatus for ~epar~ nd depo~i~ing me~al~ ~r~m a solu~ion containing lon~
o~ ~uch metal ~nd more p~r~l~ularl~ ~o ~ metal separ~tion method an~ ~ppa~atu~ tltll~zin~ cen~rif~gal for~e to control ~he me~al depositio~l and ~uita~le ~or u~ wi~h a ~char~eable ba~tery~

There are many appll~a~ion~ where a me~al i~ dls~o~ved in a 8ollltion dur~ng an ind~str~ ~1 proce~ and i~ ~ deslred elther for re~ m~t~ol~ or cther pur~?o~e~ to ~eparate th~ met~:l from th~
~ol~lt~on~ Ex~mples of such applicati4n~ include the ele~trowinnlng o~e metAls from ~olutions in which ~u~h metal~ have be~ome d~posi~ed ~uring ~ri~ indus~ 1 proce~ an~ ~he redepo~ ny o~ Ine~ rom ~h~ ~lectrolyte of a battsr~ during the char~in~ o~ the battery~
~ p~lem in th~ depo~ on o~ m~t~ rom a sol u'cion ~ n an elec~och~mical ~ell i~ tha~ the dendrl~i~ or m.O8s~t ~rowth of the metal layer re~ult~ in a poro~ nd urle~en depc: sit which ~an ~pan ~he ~Lnterelectrode gap and shor~ c~r~uit ~he cell if ~h~ cell i~
elther run or any ~u~tanl~ial period o~ e or afte~ a rel~tiv~ly ~hort n~llnber of ~har~e-di~ch~rge cycle~ o~ a ~torage battery~ ~;o~d r~ult~3 in overcoming thi~ pxo~lem ~r~d in ~h~evin~
den~e ~nd homo~eneouæ depo~i~s h~ve been a~h~i~ed by ~ltill~ng varlous t~hni~ueæ ~o increase ~he r~lative mo~ment ~e~we~n the ne~ti~e ele~trodes and the electrol~e and~vr ~o in~ease the m~ of meta~ ~rom the elec~rolyte ~olu~lon in the imm~ te ~rea ~ ~32~
Nov 15,~5 16:~5 Hale and Dorr, E~oston; (617) 742-9100 P.03 ...

the ~egat~ve elec~rode. ~he~e obje~tive~; h~ve been obt~ ed in ~r example U~S. Paten~ ~o. 3,7~,110 fi~ued January 1, lg74 ~o Io Ahmad and entltled ~Pro~e~ for ~lectrodepo~itlon o~ Metals Under the Influen~e o~ a c~ntrifugal F~r~e E~l~ldn) by cr:e~clng a ~ery hlgh ~entrifugz~ orc~e which 1~ di~e~ted ~oward~ and ~ub~t~ntially perpendic~lar to the met~l-coll~ctlng face of the ne~at:i~e electrode~ U.S Patent No, 3/5~1,4615 (i~suled 3uly 6, 1~71 to S. Heim~n and entitl~d "Composlte stl~ua~ure Pro~ tionn) utllize~ a slmilar ~echhi~ue tD produ~e compo~i~e m~erl~l~ and Pat~nt No, 4 ,S~l, 4~7 ~ is~ued Jun~ 4, ~g~5 to P. ~ramminen and entl~led "Electr~chemiaal ~ener~tors ~nd ~ethod for the Oper~tion ~hereof") uti1ize~ ~ high aentrifug~l force ~pp11ed to ~he me~
co11ect1n~ f~e of the ne~fltiv~ e1~c~rode d~ring charging of an el~ctro~h~mical generAto~ to retard dendrite grow~h. Whi1e the ~e~hniq~le~ indic~ed al~ove are ~uitable if A~ 1 ~h~t 1~ ~eql~ired i~
homogeneo~ and ~n~e m~1 d~po~it,, th~y are no~ re~dily ~d~pted to the aontinu~u~ e1e~trow1n~ing o~ met~1 ~rom ~ ~olu~lon.

Tn ~c~ord~nce w1th thi~ în~ention, ît ha~ been dî~overe~
that new and unexpected re~ul~ which, ~nong othe~ th~n~ permi~
the con~inuou~ e1e~trow1nning of metal ~rom ~ so1ution, c~n be achieved by h~in~ rong ~n~rifug~ ~orce ~pp1ied to ~he meta1-ço11e~tlng ar~e of ~he negat;Lve e1e~trod~ oP an electrocheml~al cell which $orce h~ a 8ub~;~an~i~1 component perpendic~ r ~o ~uch f~ce ~nd in ~ directilsn aw~y from th~ face.
Thus/ ~hls invention lltill~e~ a ~entri~2ga1 forc~ ~ur~ng ~n ~3;~

electrowinning process which :Eorce is directed in the opposite direction from the direction in which such force has been directed in all known prior art applications.
In one aspect, the invention provides a process for depositing a metal from a solution containing said metal onto a metal-collecting face of a cathode electrode, said cathode elec-trode and an anode electrode, mounted with a face substantially parallel to said metal~collecting face, forming part of an ~lectrochemical cell, comprising the steps of: providing said solution to said cell at least in the area thereof between said electrodes; applying a substantial centrifugal force to said metal-collecting face, said force having a substantial component in a direction perpendicular to and outward from the face; and applying an electric current to said electrode.
In a further aspect, the invention provides apparatus for depositing a metal from an electrolyte solution containing ions of the metal comprising: a cell rotatable about an axis;
at least one cathode electrode having a metal-collecting face;
at least one anode electrode having an inner face; means for moun-ting said electrodes in said ~ell with said metal-collecting face of said cathode and said inner face of said anode substantially parallel to each other and spaced by a predetermined distance r ~aid cathode being mounted closer to said cell axis than said anode and said electrodes being oriented in the cell such that, when said cell is rotated, the resulting centrifugal force has a substantial component in a direction perpendicular to said faces : 3 -, 1~3~2~L

and outward from the cell axis; means for providing said elec-trolyte solutions to said cell at least in the area between said electrodes; means for rotating said eell about its axis, said electrodes and electrolyte being rotated with said cell; and means for applying an eleetrie eurrent to said electrodes.
Another aspect of the invention provides a reehargeable battery comprising: at least one positive eleetrode having an outer face; at least one negative electrode formed at least in part of a metal and having a metal-collecting faee; at least one eharg-ing electrode having an inner faee; a rotatable eell having an axis of rotation; means for mounting said electrodes in said cell in a manner sueh that (a) said positive eleetrode is elosest to said axis of rotation, said charging electrode is furthest from said axis of rotation and said negative electrode is positioned between said posit.ive eleetrdoe and said eharging eleetrodes, (b) said faees are substantially parallel to eaeh other; (e) said positive eleetrode is spaced from said negative electrode by a first predetermined distance and said negative electrode is spaeed from said charging electrode by a seeond predetermined distance, (d) said electrodes are oriented in said cell relative to said axis of rotation such that, when -the eell is rotated, the resultant centrifugal foree applied to the eleetrode faees has a substantial eomponent in a direetion perpendicular to said faees, and (e) said metal-collecting face is facing said inner face whereby the perpendicular eomponent of the centrifugal force applied to said metal-eolleeting face is in a direction outward and away from said - 3a -face; an electrolyte in said cell at least in the area thereof between said electrodes, ions of the metal of said metal elec-trode being dis~olved into sald electrolyte during discharge of said battery and being deposited from said electrolyte onto said metal-collecting face during charging of said battery; means for rotating said cell about its rotation axis at least during charg-ing of said battery, said lectrodes and electrolyte being rotated with sa~d cell; and m~ans for applying an electric current to said negative electrode and said charging electrode during charging of said battery.
With respect to the aspect of the,'invention relating to a process for depositing metal ~rom an electrolyte solution which contains ions of the metal, the first step in this process is to mount at least one cathode electrode having a metal collectiny face and at least one anode electrode ha~ing an inner face in a rotatable cell. The electrodes are mounted (a) wlth their faces su~stan-tially parallel to each other and spaced from each other by a predetermined distance, ~b) oriented in the cell relative to the axis of rotation of the cell such that when the cell is rotated, the resulting centrifugal force applied to the electrode face~ has a substantial component in a direction perpendicular to said faces and (c) with the cathode electrode closer to the axis of rotation of the cell than the anode electrode so that the perpendicular component of th~ centrifugal forc2 applied ~o the me~al collecting face of the cathode electrode is in a direction away from said face. The electrolyte solution is provided to the cell in at ~ 3b -~3Z2~ 64371-23 least the space between the electrodes. The cell, and th~ls the electrodes and the electrolyte solution therein, is rotated about the cell's axis of rotation to generate the centrifugal force and an electric current is applied to the electrodes, resulting in the deposition of the metal on the metal-collecting face of the cathode electrode in the form of nodules of substantially uniform size and shape.

- 3~ -' Nov 15,85 16:~6 Hale ~nd l~orr, ~oston;(617) 74~-glOO P.O~
:~2~2~

Pig. 1 i~ ~ schem~ti~ aross-~ec~iona~ vi~7 of ~ppar~'clu~ which may be us~d ln accordAn~e with ~he te~hing oP the invention to ~eparate met~l f~om ~ ~olu~ion.
Fl~ n enlar~ed v~e~ of a p~ti on o~ the ele~trode~ of th~ appa~atu~ shown in Flg. 1 ~lu~trat~ng ~he manner in which ~he met~l is depo~ited.
Fi~. 3 ~ a E;chema~ic cro~s~ea~$onal view o~ ~ portion of an alte~native embodiment o~ appar~tus ~uitflbl~ for practiain~ the ~e~h~n~ of thi~ invention.
Fi~. 4 i~ a ~hem~tic perspecti~re vlew o~ ~he el~trode stru~tur~ for ~n alternatlve emodi.ment of ~he inv~n~lon~
5 i~ ~ ~chema~ic ~ra~-sec~ional view o~ a portion of a ~torage ba~tery which op~te~ in ac~ordane wi~h the teachings o~
th~s in~enSion, ; Re~erxin~ to Fig~ 1, appar~tus or practicing the teachlngs of ~hi~ lnventlon includes ~ hou~ng 1~ which m~y be of ~etal, pl~t~ or other ~ui~ble m~eri~l. A ~otor 1~ which ls o~ -conYention~l de~i~n and ~he ~ontrol o~ whi~h ~oes not form par~ of th~ pre~ent in~entlon, i~ mount~d to the ~ottom ~ housin~ 10 at the cen~er ~her~o and oper~te~ ~o ro~e ~ ~haPt 14 whic~
proje~ts from the top thereofO ~hile ~h~t 14 may be rot~ted in elther direction, for purpo~e~ of ~hi~ dl~cu~s~on, it will b~
a~sumed ~o rot~te in the dire~tion o~ arr~ . Shaft 14 proje~t~
through the top of hou~lng 10 ~nd ~ journal~d in the top of the houslng ~0 by bearing 18 ~nd near mo~or 12 by bearin~ 19 1~

Nov 15,~5 16:~7 Hale and Dorr, Eoston; (617) 742-glOO P.06 ~.Z~32~L

A cell 20, con~ru~ted o~ s~nle~ ~teel or o~her makerla:l of ~uitable strength which ~oul~ no~ be corroded by the ele~trQlyte, 1~ a~ he~ ~o ~ha~ 14 by ~ ~uitable mountln~
el~m~nt ~ and ro~es wi~h sh~t 14, Mo~nted in cell 20 are ~t le~t one ~tho~e ele~rode ~4 and at le~ one anode electrode 26~ While a pl~rali~y of ~ee~p~ir~ of elec~rode~ 24 ahd ~6 m~y ~e mo~nte~ in cell Z0, the elec~rode~ are p~eferab~ y in the ~orln of ~ncentKic wire ~ylinder~. ~he cylindric~al electrode~ may be wire net~ or me~hes a~; ~hown in Fi~s ~ 1 ~nd 2, ~q~11 rrel-cage ~orligu~tion~ o~ parallel wire~ a~ illustrated ln ~ig, 4 or other ~ui~le conf igur~tions~ The electrodes are formed of a ~uit~ble con~u~tin~ nlatexi~l such ~ stainles~ steel or nlckel-pl~t~d ~opper. Fo~ a preferre~ e~odiment o~ the lnvention, both ele~tro~e~ ~re me~hes o~ ~tainle~ s~eel wi~e, the wire~ b~ing 0.3mm thi~k ~nd being ~paced ~om each other by ~.6mm. The ele~trode~ ~e ~pport~d in cell ~n by sep~rator~ 28 of pl~tic or other ~uita~le non-condu~ing material, th`e separat:ors being ~ttached to ~ha~t 14 and to the side wall~ o ~ell ~0. ~he spa~ing betwe~n the ele~rode~ i~ maintained ~ epar~tor~ 28., The ex~ent o~ 'chis ~pacin~ w~ ry dependin~ on th~ me~al belng ~epara~ed and on ~he o~er~ll dlmension~ of the app~r~tu~, For ~n embodiment ~h~re the m~al bein~ deposi~ed ~7as zinc, ~ spacing o 3mm between the electrod~s wa~ ~ound to be suit~ble, ~ leetric curr~n~, from a ~ult~e con~entiorlal ~o~r~e which doçs not folcm p~rt of the p~e~erlt invention, i~ ~pplied to wlres 30 ~nd 3~ ~egati~te current ~rom w~re ~0 is ~pplied ~hro~lgh bru~h 34 to sl~p ring ~6 on shaf~ 14 and khrough ~lip ~ing ~6 to wire 3~

Nov 15,85 16:~ Hale and Dorr, Boston; (617) 74:~-9100 P.07 3Z~

wh~ch e:Rtends ~hrou~h sha~t 14 and conne~t~ ~o cathode ele~trode 24. Similarly, po~i~lve current ICrom wire ~ appl ied throu~h ~ush 40 and slip r1n~ 4~ to wire ~ whi~h ex~nd~ throLIgh ~haft 14 to anode elec~r~de ~. Th~ current ~pplled t~ wire~ 30 ~nd 32 w~ 1 vary with the metal l~eing ~eparated ~nd ~th other f~tor~O
In ~ preEerred embodim~nt wi~h zin~ being deposited, ~ ~urren~ o 117mAJcm2 ~a~ ~ound to be ~ita~le.
An ele~trolyte solu~:lon 45 c~nlt~ining the metal to be deposited ~ ore~ re~ervoir ~6~ The eleal~roly~e ~low~, ei~her under l:he in~luen~e o~ ~ravity or by u~e of a ~ultabl~ p-lmp ~not ~h~wn), throu~h tu~ 4~ uitable ~low con~crol ~e~rice S0 , and tllbe 52 ~o r~t~t~ng d~Rtrlbution pla~e 5~ m~unted ln cell 20 on sh~t 14. From plAte 54, ~he electrolyte flow~ t~ncier the ln~ enc~ of centrifugal ~orce Itoward the ~id~ ~lls o~ ah~ber ~0. Pl~te S4 a~su~e~ a ~ub~tantial.ly uniform distril~tion ~ the Rlectrolyte solution ~rounci the p~iph~ry of ~ell 2~. Ele~tro~yte ~olukion 45 ~low~ 1;hrough cell ~0 under the lnflu~n~e o~ ~ravity ~Yith the he~v ~er~ met~l-rioh, ~ol-ltion being ~or~ed to ~he o~lter wall oE ~ell ~0 by th~ ~ntrlfug~l f~rce resultlny ro~n the rotation of the ~ell Rnd the li~ht~r m~tal~poor ~lect~olyt&
~olution ~ro~n which me~al $ons have be~n depo~ted b~ing ~lo~e~t to the c~nter (~.e., rc:~a~on a~i~) of the çell. ~h~ met~l-po{)r ele~rolyte ~rom the ~enter vf ~he ~ell i~ removed frorn the c~ll thro~gh p~rt~ 56 and i~ collec~d ln ~h~m~er S~ of ho~ ng 10.
Cham~er $8 i~ ~ound~a ~y w~ 0 ~nd ~y lowe~ w~ll 62~ From ~haTn~e~ 58, the ele~trolyte le~OtYB th~ough openin~ ~4 ~n wAll 6~
to ayllndrlcal çha~nb~r 66 formed in hou~ng 10 and 1B removed from the ~pp~r~ rom ~hi~ chambe~ through tul~ 6~. If the desired Nov 15,85 16:28 H~le and ~orr, Boston; (~17) 74~-glOO ...n~ P 0~

32;~L

amo~lht o~ metal h~ be~n renlove~ ~rom ~he electrolyte ~ol~tion 45, then the ~olut$on removed ~rough tube 6~ may flow to a ~ui~ e ~e~e~vo~r ~Or ~eu~e or d~po~al~ I it i~ de~ired ~o remove ~dditlonal met~l f~on~ th~ ~;olution, the electroly~e ~olu~ion ex1ting l~hrough t~l~e 6~ m~y be pumped ~ac~ ln~o re~er~oir 4~ ~or ~ec~l in~ h0 ele~roly~ may ~ be pumped ~hrough ~ !~ed o oxe or u~ed in ano~h~;e indu~rl~l p~oce~ be~ore being recycled.
C~ll 20 al~o has a plur~lity ~f openin~ 70 ~ormed in 1~s outer wall in the area the~eof adja~nt the wide~t portion of ~:he c~ll. The~e are prePera~ly ~o-~r to ~ix openin~ 70 even~y spaced around the p~rlph~ry of ce'~ 1 20~ Each open~ng 70 i~ normally se~led by a conical pl~sg 72 whi~h i~ ~pring-br~ed ~n the clo~ed po~ltion by a corre~pond~og r~d 74 whi&h ~x~end into ~ box 76 mo~lnted on ~ha~t 14~ I~ b~x 7~ ch rod ter~nina~es ~n a ~onica~
tlp 77~ a ~prin~ po~it~oned betwe~n tip 77 an~ the w~ll of box 7~ pe~formlng ~he brasln~ ~unc~:ion. A ro~ 7~ ~'civa~e~ by a s~lenoi~ 80 extends through ~haft 14 in~o box 7~ and i8 pro~t~ded wi~h A coni&~l tip ~1. When ~olenoid ~0 i8 p~rioc~l~ally activ~ted from a ~uil~able 50ur&~ of ele~tri~ energy (în a conventlonal manner t~rhich doeP not form p~rt of the pre~en~c invention), rod 7 is lowered, aau~lng tip 81 to b~ wedg~d between ~ips 77~ p~lshing tip~ 77 ~nd the rods 74 ~onnected ~h~re~o ou~waxd~ ~her~y moving plugs ~2 o~tward to open op~n~ng 70O A~ will dl~ ed la~er, in accor~ance with the teachln~ his iLntrent~on, rne~l nodule~ 82 break ~ff rom ~he metal-~ollea~clng ~ace o~ c~thode elec~rode 24 and, un~er th~ influence of the cent~ gal ~rce ~enerated wi~h~n ~3~ 64371-23 cell 20, Elow toward openings 70. Solenoid 80 is periodically pulsed to unplug openings 70, permitting metal nodules 82 adjacent thereto to be thrown in-to housing 10 where they are accumulated in area 84 of the housing. The metal nodules or granules may be continuously removed from housing 10 through opening 86 formed in the wall of the housing and tuhe 88. To the extent any electro-lyte solution 45 is thrown out through openings 70 with the me-tal nodules 82, such electrolyte solution passes through openings 90 in separator wall 62 to chamber 66.
In operation, the apparatus of Figure 1 will be assumed for purposes of illustration to have no electrolyte 45 therein initially and it will be assumed that solenoid 80 is initially deactivated so that plugs 72 are sealing openings 70. The first steps in the operation are to apply energy to motor 12 to cause cell 20 to start rotating and to operate control 50 to cause electrolyte solution 45 to flow from reservoir 46 into cell 20.
When electrolyte solution 45 has subs-tantially covered electrodes 24 and 26, electric current may be applied to the electrodes through lines 30 and 32 and their related, previously described, circuitry. The negative charge applied to electrode 24 and the positive charge applied to electrode 26 cause metal in the electrolyte solution to be separated from the solution and deposited on the outer, metal-collecting face ~2 of cathode electrode Z4. In accordance with the teachings of this invention, it has been found that when cell 20 is rotated at a rate suffic-ient to cause a substantial centrifugal force (in the order of several hundred times the Eorce Nov 15,~5 1~:30 Hale an~ Dorr, ~oston; (~17) 742-9100 32~:L

c>~ ~r~it~) to ~ç applied in a direc:tio~ ~way rom met~l aollectlny ~ace g~ he me~al 1~ depo~ed ~ an 3rray of ~ub~t~nti~lly idRntical colnpac~ nodule~ o~ sub~t~ntially uniorm lens~h~ Fig~ ~ 18 a pi~t~r~l repre~en~tion of zinc nodules formed ~rom ~ 37.6~ po~as~ium hydroxi~e~w~ter ~ol~ion having ~%
zin~ oxidç d~solv~d therein. Th~ dimen~ n~ o~ thq elec'cr~de~ ~n thi~ 2xper~ment ~re z~ pre~ou~ tated ~nd the ~en~rl~lgal fo~c¢
B applied aw~y froT~ f~ce 9~ wa~ ~50 g~ ~h~ nodule l~ng~h~ (i.e~, ~he ~h~kne~ o~ the ~ne~al deposi~) ls ro~ghly half the spacing betw~en th~ electrodes ~suring th~r~ Will not ~e a ~hort ~iraui~ing of the electrode~.
The ~hape o~ the nodules ~ormed during d~po~ition on fa~e 9~
depend~ prima~ily on the ~onf ~guration of electr~e ~4 and on ~he m~ter~ om which this elect:~ode ~8 fo~med~ If ~ fo~ ~xample, ~he ~quir~el-ca~e flrran~ement o~ . 4 l~ utili~ed inst:~ad of ~ire me~h, the Inet~l nod~lles wlll be produced in the form of rod~
or small ~ti~k~ ~inc~e di~er~nt m~teri~l~ have di~eren~
physic~1 and ele~tri~a~ propertie~, ~nclll~ln~ ~dherence, ~he use of a nlaterial o~her than s~ainle~ st~el tthe ma~erial used for the ele~trode~ wlkh ~he no~ule~ ~hown in F~. 2) for electrode 24 ~u~h a~ fox ~x~mple nick~l-pl~ted copper ~hi~h has ~ higher condll~tivi~y and le~ ~ur~ace ~h~rence, will also cause ~he shape of th~ nod-lleR l:o~v~ryv When ~ep~ra~ion and depo~ on of metal i~ continued, the nodules grow bigger unt~ they re~ch a ~ize, ~he length of whi~h i~ les~ than the dis~ance between th~ electrodes, where ~he ce~rifugal force break~ or tear~ them of~ metal-coilecting face Nov 1~,' 16:30 Hale and Dorr, Boston; (617) 742-9100 P.11 ~3~

~2. The openlng~ in anod~ electrode 26 are ~elected to be large enouyh ~o th~t the brok~n-o~ nodule~ ms~ through ~ht~
ele~rode to the ~ide ~11 o~ cell 20 ~n the are~ o openin~ 70.
~inc~ ~olenold 80 i~ ln~t~lly not actiYated, ~he o~n:lngs 70 ar~
plug~ed ~au~inq the m~t~l nodule~ 82 to ac~umulate ad~ac~ o t;he~o open~n~. Beaau~e o~ ~heir ~re~tor welght, ~-he centrl~ugal force c~u~es the nodule~ 82 to ill the ~p~e ln cell 20 in the a~e~ of opening 7QO ~lect~olyt~ ~olutlon 45 1~ thu~ e~eentlall~
Ik~pt ou~ o~ thl~ a~e~. ~olenold ~0 1 ~ E~rlodlc~lly puls~d ~o remo~re plugs 7~ fro~ opening~ 70 to por~it nodul~ 82 t~ be thro~an ~om cell ~0 lnto hou~inq 10 andy in pArti~ula~, ~nto the area 84 ~he~eo~ ~jaae~st n~dule r~rao~ral openlng ~6~ B~ de~n~rgi~lng solenold 80 and c~usin~ o~nings 70 to be replu~g~d be~ore all o th~ nodule~ 82 have b~n ~mov~d, the amount o~ a~roly~e which ~a~ through ope~ln~s 70 wl~h the nodule~ durirl~ each nodul~
r~mova~ ~yc~ n be ~inim~æed. To th~ ~xtent a~ e:Le~trol~t~
doe~ ~c~e with th~ no~ule~, it pa~ e~3 through op~n~ng~ ~0 into ayl~ndri~l ¢heun~ 6 Por ~c~clill~ or dli8pO~ The nodul~
r~lnov~d th~ou~h t~ b~3 ~8 ~ y be m~lt~d down fo~ r~u~ ~r o~h~rwl~e u3~d ~or ~ a~s~red pUJ~pO~.
~ h~ el~trolyt~ 1 or m~ ~ horizonta] ~e~th of electrolyte 801~ut~0n ~n a~l 20 ~ ~ndl3~t¢d by dot~:~d 1 ~n~ 94 ~n~ i8 d~t~rmined by th~ pl~c~oe3lt o~ ~lec~roly~ r~ov~l por~ 5S.
S~nce, a~ ha~ b~en pr~3vi~u~ly lnda~ted, th~ electrolyt~ ~olut~n aon'cainlng the met~l-lon~ i~ h~a~r ~n ~he IDe~al-poor ele~trolyte ~olution ro~ whlch met~l ha~ be~n d~posite~ on ~ace ~2. the ~le~troly~ 10w~ un~er bo~ ~h~ influerlc~ of l:h~ el~ric 1~
~ .

Nov 15,P5 16:31 Hale and Dorr, Boston;(617) 74~-9100 P.l~

3~2~

f ield and of cen~r ~ ~ugal orce f rom the ou~e~ p~rlphe~y ~ d the ~en~er o~ cell 2Q, as w~ flowln~, under ~:be ~n1~1~n~e o gr~vi~, fxom the top of the ~ell ~a the 13o~tom~ Th~, the e~trolyte removed thro~gh por~ 5~, whlc:h i~ 'çhe portion of 'the elec~ lo~e~lt to t~e axi~ o~ ro~ion of cQ~l 20, 1~
Qctroly~e ~rom w~ich mGst or ~11 of.the meta~. ions ha~e been ~emo~d ti.e.., me~cal~poor ~lectroly~). The electr~ly~:e leaving cell 20t ~h~ough por~ $~ pas~e~, 'chro~lgh ch~m1~er 5~, opening~ 64, in w~ll 6~, cham~r ~ ~nd ~u~e 6~ ~o l~e eitber ~i~po~ed of or rec~rcul~tetl ~o ~es~rvolr 4 Slnce ~he ~odule~ ~reak o~f ~nd ~re removed ~n A oontinuou~
ba~i~, the apparatu~ ~hown ln Fig. ~ may opera~e ~ontinuou~ly ~or extended per iod~ o~ tlme a~ lon~ a~ Pre~h ~le~trolyte ~ol~tion containlng the met~l to ~e ~p~ra~ed i~ suppl1ed ~o ~e~ervoir 4~.
~hu~ th~ nQW and unexpected ~e~ult~ ~chieved by u~e o~ the t~2~hing~ of thi~ inven~ion make ~o~ible ~ con~inuou~ mode o~
electr~winnin~ ~nd o~ el~trod~po~i~ion wh~ch w~s not previou~ly po~ble.
Fig. 3 i~ A ~chem~ repre~entation of ~n ~ltern~tive e~nbodiment ~o~ the aell 20 illus~rat~ng s~ver~l modified feat~lres.
~lr~t~ in~te~d of h~v~ng a ~ing~e ~onaen~ri~ palr o anod~-catho~e trode~, the ~mbodlmen~ o ~ ba~ ~wo p~ of such ~oncen~rlc elec~ode~ t~4' ~ t ~hichr ~or pu~po~e~ o~
iLllu~ tion~ ~e ill~r~ted as be;ng o~ the ~;q~l~ rrel cage cc~n ~gur~ n of ~ig. 4 r~th~r ~h~n the n~esh con~ ~u~ation of Flg~ 1 and 2~ ~h~ two Plectrode pairs are sep~ated ~ an Nov 15,85 1~:3~ Hale and Dorr, Boston; (617) 7~-9100 P,13 .

2:~

~n~ ing member 9~ of plagtic: or other n~n-~onductlng mat~r~ al .
The ~our elec~rode~ and ~he ~n~ulat~.n~ member are ~upported by non-cond!la~ing ~ep~rator~ ~4.
The e~t~ode~ of ~ 3 Al~o differ ~rom ~ho~e in Fi~ n that th~y Are ir~ ~he ~h21pe of trunc~te~ ~one~ r~ther 'ch~n cyl~nder~. Thl~ ~onfigur~tion h~s been ~ound adv~n~geous in pr~cti~ q th~ t~ch~ n~ o thi~ lnv~ltion in that the centriug~1 Po~ce di~ted ~ an ~ngle to th~ me~-al-~olle~tin~ ac~ g~ of the Ga~hod~ elect~ode~ ~ mor~ e~f~tive ~n breaking ~f~ the metal nod~le~ when the n~dule~ ~e~h ~he de~ixed sl~e. I~ i~ important, how~ver, in ord~r tn ac!hieve the nodule~orlning ~ap~bîlitie~ o~
thle invent~orl, tha~ ~he ~en~ri~ug~l ~orae ha~re ~ ~ubs~an~ al aomponen~: ~n a ~ e~ion perl~ndiaul~r to th~ metal ~ollect~ng f~ce of the ~athode e~trode~ and ~way th~re~r~m. An angle o~
approx~mately 45 de~ree~ for the el~ct~ode~ has b~en ~ound to be a suitable ~n~le~
With ~he ~onf iguratiorl ~hown in Fiçt. ~ ~ when ~.he meta nodule~ ~ break off, they ~rl~t, under th~ influen~e o~ the o~ntrl~u~al force, down the ~loping ele~rode~ ~nd sol~d ~lopin~
in~ul~tin~ member 9~ ~ w~ drifting down the ~l~nting ~de w~ll o~ ~el~ ~I~ and ~lltim~ely accumulate ~ ce~nt openlng~ 70 ' at the bottom s)~ the ~de wAll. Soleno~d 80' i~ perlo~icall~
pul~d to remove pl~g~ 7~ ' froln open~n~ 70 ' ~nd pern~lt the ~coumulated metal nodt~ to e~cape :ln ~he m~nner pr~v;ou~y d~ ~cr lbed ~, 3~22~

Referring now to Figure 5, an embodiment of the invention is shown which is suitable for use as a rechargeable storage battery. Batteries to which this invention may be applied include zinc-nickel and zinc-air batteries, with the embodiment shown in Figure 5 being, for purposes of illustration, a zinc-air battery. In Figure 5, the cell housing 120 has mounted therein three concentric cylindrical electrodes, a positive air electrode 122, a zinc electrode 124 which is the battery cathode, and a positive charging electrode 126 which is used during recharging of the battery. The cell is rotated about its axis at least during charging of the cell. Electrolyte 125 is applied through tube 128 to cell 120, flows through the cell in the manner previously in-dicated, and is removed from the cell through tube 130. Tube 130 connects to tube 128 to recirculate the electrolyte during both charge and discharge to prevent the loss of the zinc from elec-trode 124, the zinc being depo~ited in the electrolyte during discharge of the battery. During charging of the battery, an electric current is applied, in the manner previously indicated, between electrodes 124 and 126 and the electrolyte solution having zinc ions deposited therein is recirculated through tubes 128 and 130 until substantially all of the zinc in the electrolyte solution has been deposited on metal collecting face 132 of zinc electrode 124 in the form of substantially uniform nodules of the type shown in Figure 2. The quantity of zinc in the electrolyte and the charging time are not sufficient to permit the zinc nodules to reach a size which would cause them to break off. Any electrolyte which is lost through evaporation or otherwise may be replaced either ~ ~3;2;2~

manually or automatically at some point in the recirculation cycle of the electrolyte, either prior to or during charge, discharge or both.
While the preferred embodiments described above have utilized zinc as the metal to be deposited from the electrolyte solution, it is apparent that the teachings of this invention could be utilized to separate and deposit most metals, including any metal which can be dissolved in an electrolyte solution as ions. Further; while several configurations for the electrodes have been shown and described, it is apparent that numerous other configurations are possible while still practicing the -teachings of this invention and that other materials, in addition to stain-less steel and nickel~plated copper may be used for such elect-rodes. The applications to which the metal separation method and apparatus of this invention may be applied also are not limited to those speciEically disclosed. Thus, while the invention has been particularly shown and described with reEerence to various pre-ferred embodiments, it is to be understood that the foreyoing and other changes in Eorm and detail may be made therein by one skill-ed in the art without departing from the spirit and scope of theinvention.

Claims (42)

1. A process for depositing a metal from a solution containing said metal onto a metal-collecting face of a cathode electrode, said cathode electrode and an anode electrode, mounted with a face substantially parallel to said metal-collecting face, forming part of an electrochemical cell, comprising the steps of:
providing said solution to said cell at least in the area thereof between said electrodes;
applying a substantial centriugal force to said metal-collecting face, said force having a substantial component in a direction perpendicular to and outward from the face; and applying an electric current to said electrodes.

2. A process as claimed in Claim 1 wherein said solution is an electrolyte solution containing ions of the metal;
wherein said cell is a rotatable cell;
wherein said electrodes are mounted in said cell (a) with said faces substantially parallel to each other and spaced from each other by a predetermined distance, (b) oriented in said cell relative to the axis of rotation of the cell such that when the cell is rotated, the resulting centrifugal force applied to said electrode faces has a substantial component in a direction perpendicular to said faces and (c) with the cathode electrode closer to said axis of rotation than said anode electrode so that the perpendicular component of the centrifugal force applied to the metal-collecting face of said cathode electrode is in a direction away from said face; and including the step of rotating said cell, and thus said electrodes and the electrolyte solution therebetween, about said axis of rotation, whereby said centrifugal force is generated.

3. A process as claimed in Claim 2 wherein said providing step includes causing said electrolyte solution to continuously flow through said cell at a controllable rate.

4. A process as claimed in Claim 3 wherein the metal is deposited from said electrolyte onto said metal collecting face;
and wherein, as a result of the centrifugal forces exerted on the electrolyte, the metal-poor electrolyte from which the metal ions have been removed is moved toward the rotation axis of said cell;
and including the step of removing the metal-poor, inner most electrolyte from the cell.

5. A process as claimed in Claim 2 wherein, as a result of the charge applied to said electrodes and of the centrifugal force applied thereto, metal is deposited from said electrolyte solution onto said metal collecting face in the form of nodules of substantially uniform configuration.

6. A process as claimed in Claim 5 wherein said cathode electrode has a predetermined configuration, permitting nodules of a predetermined shape to be obtained.

7. A process as claimed in Claim 6 wherein said cathode electrode is in the form of a wire mesh.

8. A process as claimed in Claim 6 wherein said cathode electrode is in the form of an array of parallel wires.

9. A process as claimed in Claim 5 wherein the shape of said nodules is determined at least in part by the material from which said cathode electrode is constructed.

10. A process as claimed in Claim 9 wherein said cathode electrode is formed of stainless steel.

11. A process as claimed in Claim 9 wherein said cathode electrode is formed of nickel-plated copper.

12. A process as claimed in Claim 5 wherein, when said metal nodules reach a size which is less than the predetermined distance between said electrodes, they break off from said metal collecting face; and including the step of removing the broken off nodules from said cell.

13. A process as claimed in Claim 12 wherein said removing step includes utilizing the centrifugal force to move the broken off metal nodules to the periphery of said cell and through a nodule removing opening in said periphery.

14. A process as claimed in Claim 2 wherein said electrodes are oriented in said cell substantially parallel to the axis of rotation of the cell.

15. A process as claimed in Claim 2 wherein said electrodes are oriented in said cell with said faces at an angle to the axis of rotation of said cell.

16. A process as claimed in claim 15 wherein, under the influence of said electric current applied to the electrodes and the centrifugal force applied to the electrodes, metal is deposited from said electrolyte solution onto said metal collecting face in the form of nodules having a predetermined shape;
wherein, when said nodules have grown to a size which size is less than the spacing between said faces of the electrodes, said nodules break off from said metal collecting face; and including the step of utilizing said angled electrodes and said centrifugal force to guide said broken off nodules to a nodule removal opening at the periphery of said cell.

17. A process as claimed in claim 2 wherein when said electrodes are in the form of concentric cylinders, their axes are said axis of rotation.

18. A process as claimed in claim 2 wherein said electrodes are in the form of concentric truncated cones the axes of which are the axis of rotation of said cell.

19. A process as claimed in claim 18 wherein there are a plurality of pairs of said cathode and anode electrodes, each cathode anode pair of electrodes being separated from the adjacent pair by a conical member of a non-conducting material.

20. A process as claimed in claim 1 wherein there are a plurality of pairs of cathode and anode electrodes.
19a

21. A process as claimed in Claim 2 wherein said cell is part a rechargeable battery;
wherein said deposition of metal occurs during charging of said battery, said cathode electrode being the negative electrode of the battery and said anode electrode being a charging electrode; and wherein the electrolyte solution is the battery electrolyte in which ions of the metal of the negative electrode have dissolved during discharge of the battery.

22. A process as claimed in Claim 1 wherein said cathode electrode is a zinc electrode and wherein the metal being deposition on the metal collecting face is zinc.

23. Apparatus for depositing a metal from an electrolyte solution containing ions of the metal comprising:
a cell rotatable about an axis;
at least one cathode electrode having a metal-collecting face;
at least one anode electrode having an inner face;
means for mounting said electrodes in said cell with said metal-collecting face of said cathode and said inner face of said anode substantially parallel to each other and spaced by a predetermined distance, said cathode being mounted closer to said cell axis than said anode and said electrodes being oriented in the cell such that, when said cell is rotated, the resulting centrifugal force has a substantial component in a direction perpendicular to said faces and outward from the cell axis;
means for providing said electrolyte solutions to said cell at least in the area between said electrodes;
means for rotating said cell about its axis, said electrodes and electrolyte being rotated with said cell; and means for applying an electric current to said electrodes.

24. Apparatus as claimed in claim 23 wherein, as a result of a charge applied to said electrodes and of the centrifugal force applied thereto, the metal is deposited from the electrolyte onto said metal-collecting face;
wherein, as a result of the centrifugal force exerted on the electrolyte, the metal-poor electrolyte from which the metal ions have been removed is moved toward the rotation axis of said cell;

said apparatus including means for causing the electrolyte solution to continuously flow through said cell at a controllable rate, said means including means for removing the metal-poor, innermost electrolyte from the cell.

25. Apparatus as claimed in claim 23 wherein, as a result of a charge applied to said electrodes and of the centrifugal force applied thereto, metal is deposited from said electrode solution onto said metal-collecting face in the form of nodules of substantially uniform configuration.

26. Apparatus as claimed in claim 25 wherein said cathode electrode has a predetermined configuration, permitting nodules of a predetermined shape to be obtained; and wherein said cathode electrode is in the form of a wire mesh.

27. Apparatus as claimed in claim 25 wherein said cathode electrode has a predetermined configuration, permitting nodules of a predetermined shape to be obtained; and wherein said cathode electrode is in the form of an array of parallel wires.

28. Apparatus as claimed in claim 25 wherein the shape of said nodules is determined at least in part by the material from which said cathode electrode is constructed; and wherein said cathode electrode is formed of stainless steel.

29. Apparatus as claimed in claim 25 wherein the shape of said nodules is determined at least in part by the material from which said cathode electrode is constructed; and wherein said cathode electrode is formed of nickel-plated copper.

30. Apparatus as claimed in claim 25 wherein, when said metal nodules have grown to a size which is less than the predetermined distance between said electrodes, they break off from said metal-collecting face; and including means for removing the broken-off nodules from said cell.

31. Apparatus as claimed in claim 30 wherein said means for removing the broken-off nodules includes at least one nodule removing opening in the periphery of said cell and means for utilizing said centrifugal force to guide the broken-off nodules to said opening.

32. Apparatus as claimed in claim 23 wherein said electrodes are oriented in said cell substantially parallel to the axis of rotation of the cell.

33. Apparatus as claimed in Claim 23 wherein said electrodes are oriented in said cell with said faces at an angel to the axis of rotation of the cell.

34. Apparatus as claimed in Claim 23 wherein said electrodes are in the form of concentric cylinders, the axes of which are said axis of rotation.

35. Apparatus as claimed in Claim 23 wherein said electrodes are in the form of concentric truncated cones, the axes of which are the axis of rotation of said cell.

36. Apparatus as claimed in Claim 35 wherein there are a plurality of pairs of said cathode and anode electrodes; and including a conical member of a non-conducting material separating each of said anode-cathode pairs.

37. Apparatus as claimed in Claim 23 wherein there are a plurality of pairs of cathode and anode electrodes.

38. Apparatus as claimed in Claim 23 wherein said cathode electrode is a zinc electrode; and wherein the metal being deposited on the metal-collecting face is zinc.

39. Apparatus as claimed in Claim 23 wherein said apparatus functions as a rechargeable battery;
said cathode electrode being the negative elec-trode of said battery;
said anode electrode being the charging electrode of the battery;
said electrolyte solution being the battery electrolyte in which ions of the metal of the negative elec-trode have been dissolved during discharge of the battery;
and further including a positive electrode for use during discharge of the battery.

40. A rechargable battery comprising:
at least one positive electrode having an outer face;
at least one negative electrode formed at least in part of a metal and having a metal-collecting face;
at least one charging electrode having an inner face;
a rotatable cell having an axis of rotation;
means for mounting said electrodes in said cell in a manner such that (a) said positive electrode is closest to said axis of rotation, said charging electrode is furthest from said axis of rotation and said negative electrode is positioned between said positive electrode and said charging electrodes, (b) said faces are substantially parallel to each other; (c) said positive electrode is spaced from said negative electrode by a first predetermined distance and said negative electrode is spaced from said charging electrode by a second predetermined distance, (d) said electrodes are oriented in said cell relative to said axis of rotation such that, when the cell is rotated, the resultant centrifugal force applied to the electrode faces has a substantial component in a direction perpendicular to said faces, and (e) said metal-collecting face is facing said inner face whereby the perpendicular component of the centrifugal force applied to said metal-collecting face is in a direction outward and away from said face;

an electrolyte in said cell at least in the area thereof between said electrodes, ions of the metal of said metal electrode being dissolved into said electrolyte during discharge of said battery and being deposited from said electrolyte onto said metal-collecting face during charging of said battery;
means for rotating said cell about its rotation axis at least during charging of said battery, said electrodes and electrolyte being rotated with said cell; and means for applying an electric current to said negative electrodes and said charging electrode during charging of said battery.

41. A rechargeable battery as claimed in Claim 40 wherein said positive electrode is an air electrode; and wherein said negative electrode is a zinc electrode, zinc being the metal which is dissolved in said electrolyte during discharge of the battery and which is deposited onto said metal-collecting face during charging of the battery.

42. A rechargeable battery as claimed in Claim 40 including means for circulating the electrolyte passed said electrode.