CA1158302A

CA1158302A - Resistant glass in glass-metal seal and cell terminal structure for lithium electrochemical cells

Info

Publication number: CA1158302A
Application number: CA000353264A
Authority: CA
Inventors: Alwyn H. Taylor; Michael L. Cook; Wayne L. Lees
Original assignee: Duracell International Inc
Current assignee: Duracell Inc USA
Priority date: 1979-07-03
Filing date: 1980-06-03
Publication date: 1983-12-06
Also published as: CH647358A5; DE3023859A1; FR2461363A1; FR2461363B1; BE884121A; SE450438B; IL60102A0; GB2056753B; AU5959780A; DE3023859C2; JPS5613663A; SE8004732L; IT8023201A0; DK285880A; GB2056753A; IT1131892B; NL8003521A

Abstract

ABSTRACT
A lithium-containing electrochemical cell with a glass-metal seal and cell terminal structure thereon with said glass comprising a glass loaded with alumina or other stable metal oxide or an aluminosilicate glass with or without such alumina or stable metal oxide loading.

Description

The present invention relates to glass-metal seal and cell ter-minal structures for electrochemical cells and particularly to those cells containing lithium anodes and corrosive materials.
In the past, the preferred glasses for the construction of glass-metal seals in electrochemical cells and capacitors requiring stringent hermeticity, such as those described in U.S. Patent No. 4,053,692 and U.S.
Patent No. 3,646,405 were those referred to as "borosilicate glasses".
Such glasses include Corning 7052 and Fusite GC (glass designations of the Corning Glass Co. and Fusite Glass Co., respectively) and have the general composition:
Oxide ~ Approximate Si2 70-75 Na2O 4-7 BaO ~-2 Suitable borosilicate glasses have been and are used extenslvely in the const~uction of glass--metal seals becuase of their relati~ely low work-ing temperatures and the good glass-metal seals made therewith. Accordingly such glasses are utilized in a wide variety of glass-metal seal applications.
It has ~een discovered, however, that though such glass-metal seals are considered adequate in sealing cell containers, in certain instances, particularly when used as cell terminals in cells containing lithium anodes, such as glass-metal seals are sub~ect to deterioration with resultant loss of hermeticity and, possibly, electrical insulation, especially under high temperature storage conditions. Such glasses are especially susceptible to deterioration when used in the glass-metal seals of cells containing lithium anodes and9 particularly, corrosive fluid depolarizer electrolytes such as thionyl chloride and sulEur dio~ide. Glass-metal seals in elec-trochemical cells have the typical configuration of outer and inner metal ~ ~5~3~2 member~ separ~ted by alld sealed to the gl~ therebetween by fusl~n at ~-3405/9 3 ~ ~

the glass-~etel ~nterf~ce. Seal~ Df thi6 type ~re de6cribed l~ greater detail in ~.S. Pa~ent ~o. 49053,6~2 ~ssi~ned ~o t~e sa~e assignee ~s the present inven-tion. Typic~lly the metsl members fu~ction as Dppo6ing te~minal~ cf the ~ell with electrical c~nnec~ion to the electrodes withi~ the cell. The glass member therebetween thus fumctions a5 both sn hermetic 6eal and ~n electrical insulator.
In llthi~m cells, the ~etal member u~llized ~s ~he-conductor from the l~thium anode, and the lmmediately ~elghboring glass, attract lithium ions from the electrolyte solution. The attracted lithium has been found to enter the ~eighborin~ glass, making it an electrical conductor. The conducting glass then becomes part ~f the ~node conductor, which thus extend6 into the glass, pro-gresslvely redu~ing the insulator width. The llthium,permeated glass also occupies ~reater volume than the initial glas6, thereby inducing fracture of the glass and, in ~ome ~er~inal conf~gurations, 6epara~ion of the glsss from the ad~oining metal. This ~echanical damage degrades the glass-metal seal directly and affects the rate ~t which insulation is lost through the ~ubst-ltutlon of conductive glsss. As the lithium permeation of the glass increases and spreads across the glass toward the OppDsite cathode conductor, a conducting bridge across the i~itially i~sulating gla~s may be formed ~ith resultant reduction of cell capacity through 6elf-discharge.
It i6 an obJect of the present invention to provlde improved glass-metal 6eal~ for ise in lithium electrochemical cell6, with the glass of ~he seal6 having improved re6i6tance to deterioration even under abuslve conditions.
Generally the pre3ent lnvention compri6es an electrochemical cell (partlcularly one haviug a lithium anode), having A metal-gla6s-metal assembly thereon with the metal member~ o~ said a6se~bly being ter~inal conductor6 for said cell and wherein sait glas6 electrically insulate6 ~aid metal members from each other snd i6 h~rme~ically sealed to esch of said me~l ~e~bers by glass-metal bo~ds. The gl~ss i~6ulator of the pre6ent invention i~ either ~ glas6 loaded with pareicles of a}uminum oxide or alu~in~ tAl203) ~r other ~table metal ~ides or ~n alumino6ilicste or ~imilar gla~ with or wlthout ~uch disper6ed particles the~ei~.

_ _ . _ , . .. . _ _ . ... ... _ .. ... . . .. _ . . . _ _ _ _ _ _ _ .. _ 3 ~3 ~

Aecording to a further broad aspect of the present invention there is provided a non-aqueous electrochemical cell having an anode comprised of a member of the group consisting of alkali metals, alkaline earth metals, and aluminum. The cell is ' hermetically sealed with a metal-glass-metal seal wherein the glass consists essentially of a member of the group consisting of aluminosilicate glass and glass ~onsisting essentially of alumina and oxides more stable than alumina.
According to a further broad aspect of the present invention there is provided an electrochemical cell eomprising a lithium anode and a cathode depolarizer seleeted from the group consisting of sulfur dioxide and thionyl chloride with the cell being hermetically sealed with a metal-glass-metal seal wherein the glass is comprised of an aluminosilicate glass having included therein at least 10% by weight particles of alumina~ , Aecording to a still further broad aspect of the present invention there is provided an electrochemical cell eomprising a lithium anode and a cathode depolarizer selected from the group eonsisting of sulfur dioxide and thionyl chloride with the cell being hermetieally sealed with a metal-glass-metal seal wherein the ylass is eomprised of a borosilieate glass having included therein at least 10% by weight particles of alumina.

~ ;~S8302 AluminosiLicate glasses conta-ln relatively large amounts (about 15~-35% b~ weight~ of dissolved aluminum oxide or a:Lumina (~1203). The alumina within the aluminosilicate galsses comprises part of the molecular structure of the galss, incorporated into and modifying the galssy structu~e of pure SiO2. Typical aluminosilicate glasses include Corning 1720 and 1723, (:glass designations of the Corning Glass Co.) which have the following general composi-tions:

SiO2 57 60

2 3 MgO 7 7-8 CaO 10 7-8 BaO 6 2~a20 Aluminosilicate glasses have been found to be more resistant to lithium ion invasion, and therefore provide more stable glass-metal seals, than the borosilicate glasses described above. Aluminosilicate glasses, however, have not been commonly utili~ed in the construction of glass-metal seals for use in electrochemical cel:Ls, in part because of the high temper-ature (typically about 1200C~ required in working or softening the glass.
The prevailing maximum temperature for equipment used in continuous manu-facture of glass-metal seals is about 1100C. Becuase of their high so:Eten-ing temperatures, low thermal expansion, and suitabilit~ for matched seal.s to tLmgsten (W~ and milybdenum (Mo), aluminosilicate glasses have been used mainly for high-temperature applications including projection lamps, high-temperature thermometers, combustion tubes and household cooking ware for use directly over flames or other heating ~m-lts.

`~,.......................... .

M-34~5~9 Gla~ses comprising ~nly oxide6 ~uch a6 aluni~a ~nd o~ides more stable than Qlu~in~ ~hsvin~ ~e~ ene~gles of ~orr.a~ion more ne~ati~e than about -125 Rcal/gm-atom of oxygenj s~ch as a calcium aluminste glsss ~ And which meet the thermal contraction, wvrking snd m~al b~ndi~ requirements for glas~-to-metal geals generally are si~ilarly expected to resist lithium attack and to serve as durable terminal insulator glasses and are included wlt~in the scope of the present lnvention.
The deterioration resista~t charac~eriseics of aluminosilicate and ~table o~ide glasses may be further e~hanced by the mechanlcal inclusion or loading therein, by mlxture therewith, of cpecific metal oxide additives, particularly alnminum oxide (alumina) in amounts suf~icient ~o inhibit detri-mental cracking7 typically at least 10% by weight. The incl-lslon of metal oxides such as alumina in the ~xisting boros~licate gl~6ses used in glass-metal 6eals has slso been found to substantially reduce the deterioration of ~uch glasses in glass-metal seals utilized in lithium cell environments.
The di6persion of hard particles of metal oxides such as al~mina within a glass can impede the propagatlon of cracks through the glass struc-ture. It is postulated that, should included particles more contractile than the glass remain bonded thereto during contraction, compressive stresses w$thin the glass ~urrounding each particle will oppose the crack-propagating tension at the tip of an approaching crack. Should the glass 6urrounding the particle 6eparate from the particle during contraction, a cavity is formed therebetween. l'he resuleant cav$ty ~erves to stop a spreading crack by re-distributing ~train in the glas6. Metal oxlde particles that contract the ~ame ~s the glass~if weakly bond2d to the 6urrounding gl8~S, ~111 6imilarly provide ~uch cav~ty inhibition of crack propagation where~6~1f strongly bonded to the glas6, they will inhibit crsck propagation only if they Are ~ore mechan-ically resistant to cr~cking than the ~la6s itself.

~ 3405/9 ~ ~5~3~2 ~ e~al Dx~de~ ~ther tha~ alu~ns which ~e ~uitable for lnclusion within ~he gla~ses of ~lsss-to-metal seals utillzed in lithium electrochemucal cells to decrease deteriorati~n thereof, ~nclude CaO, BeO, MgO~ SrO, BaO, CeO2, Sc2O3, Ce203, ZrO2, T102, Ti203 ~nd ~he like which ha~e high thermo-ynamic stability e~en ~hen utilized in corrosive lithiumrcell environments.negati~e Sultable ~etal oxides generally h~ve a ~ore ~ free energy ~f ~rmati~n than ~hat of alumina (about ~125 Kcal/gm-atom of oxygen) and therefore are thermo-dynamically ~re 6table than slumina. For si~plicity of ~2nufacturing9 it is preferred that the amount of ~etal oxide inclusions not lDcrease ehe glass working temperature above 1100C.
The alumina or other s~able particle inclusions are ~enerally effected by mechanically mlx-lng appropriate amounts of tried powdered glass and alumina, presslng the mixture into a friable compact of desired configu~a-tion, and heating to eoalesce the gl ss particles by local flow among the still-rigid par~icles Df alumina. It is p~eferred that, prior to fusion ineo a terminal ~sembly, the glass compact be slntered (typically from about 800C
to 1000C for the alumina-aluminosilicate glas6 and from about 600C to ~00C
for the alumina-borosilicste glass) for 8 6hort period of tlme to reduce ics porosity and to minimize the flow requiret for ~ealtng. It $s also preferred that after the fusing, the gla66 mixture be annealed to provide greater mechani-cal strength for the ~lass and to relieve 6tresses in the glass when used in the glas6-metal seal. In the formation of the ~etal-glass metal seal the gla6s preform structure is placed between two metal members and heated to a high te~perature ~ufficient to eoften the gla6s, with A met~l glass-metal seal being thereby effected ln sccordance ~ith known glass-metal seal technology.
The temperature used in forming the gla6s-metal seals 16 generally dependent upon the amount of undisc01ved ~lum~na ~nclusion, with ~reater percentages of alumina requiring l~wer glass ViECo6ity and #o ~omewhat higher working te~r peratures. To facilitate relative mo~lon of the alumina particles when the glass flows, the alumlna par~ cl~s are preferably as $ree of asperi.ties a6 ls practic~bie. The preferred partlcle Bi7es range ~n dia~e~er between 1 and 30 microD~s .

~-~405/9 1 ~ 58302 m e gl~6~-~etal 6Pals of the pre~ent i~vention encompass both ~atched-expansi~n 6eals ~nd ~pre~sl~n ~al6. In a ~atched-e~pa~sion ~eal the selected slumino6i-licate gl~ss o~ the alu~ina (or other ~table partlcle) loa~ed ~.lass is utilized with 8 pure m~tal, or ~lloy o~ ~tals, having a ~ubstantially ~i~ilar coefficient of thermal expansion while ~he glass $6 rigld. '~he ~etal utilized ln the matched-expansion 6eal u~ual~y ls glven, before assemb-ly, A surface coating of lts oxlde whereby an inti~ate and hermetic bond betueen the oxlde glass and the metal or ~et~l alloy ~ith its cxide ~ay be effected. Generally an outer compre6sion 6eal comprise6 glass 6urrounded by an outer metal ~ember havin~ a coefflcient of expa~slon suff$ciently grea~er than that of the glass to compres6 the glass, as co~ g continues after the glass be~om~s slgid, but ~ot large enough ~o cause inela6tic RtraiD or glass crscking. An inner com-pression seal compri~es a less expan6i~e ~etal ~urrounded by glass.
The 6eals of the pre6ent invention are particulsrly useful in cells contalning lithium anode~. In addition to lithium, other anode materials for use in non-aqueous electrolyte cells include ~he alkali and fllkaline earth metals, 6uch as soaiu~n, potassium, ~a~nesi~n and calcium; and slumlnum.
Cathode~ u6ed i~ lithium cell6 include cathode ~ctiYe materials such as silver chromate or carbon fluoride (CFX)n Dr 8 carbon2ceous 6ubstrate for fioluble active cathode ~3terials ~uch as fluid o~yhalides, non-metallic oxides, or non-metallic hal~de6. Such soluble active cathode materials include 6ulfur dioxide ~SO~) and ~hionyl chloride (SOC12) a~ well as phosphorous oxychloride (POC13), ~elenium oxychloride (SeOC12), 6ulfur trioxlde ~SO3) 9 vanadium oxy-trlchloride tVOC13). chromylchloride (CrO2C12), sulfuric oxychloride (S02C12), nitryl chloride (NO2CI), ~itro6yl chloride (NOCl), ~itrogen dioxide (NO2), ~ulfur ~onochloride (S2C12), sulfur monobromide (S2Br~), ~nd mlxture5 thereof.
Other active cathod~ ~aterials include MnOx (with x being approximately 2), ~gCrO4, ~gO, and generally metal halites~ oxides, chro~ate~ ~nd dichromates, permanganstes, periodates, ~olybdates, vanada~es~ chalcogenides, a~d mixtures thereof.

_7_ !L 15~3~

Electrolyte solvents used in lith~um cells include organic solvents such as tetrahydrofuran, propylene carbonate9 dimethyl sulfate, dimethyl 5ul-foxide, N-nitrosodimethylamine7 ga~ma-butyrolactone, dimethyl carbonate, methyl iormate, butyl formate, dimethoxyethane, acetonitrile and N:N di-methyl formamide. Electrolyte salts for such cells include light metal salts such as perchlorates, tetJachloroaluminates, tetrafluoroborates, halides, hexafluorophosphates~ hexafluoarsenates, and clovoborates.
Examples of specific metals ior use ln such seals and which are com-patible with various components in cells containing lithium anodes include the following:
In appropriate electrolytes, metals suitable for contact with lithium include copper, iron, steel, stainless steel of all types, nickel, titanium, tantalum, molybdenum, vanadium, niobium, tungsten, and metal alloys such 8S
Kovar~ Inconel, and Monel.
Examples of metals and metal alloys which are stable at cathode ptenetial with sulfur dioxide include aluminum, titanium; tantalum, vanadium, tungsten, niobium and molybdenum.
Examples of metals compatible with silver chromate include titanium, tantalum, molybdenum, ~anadium, chromium, tungsten, and stainless steel.
Examples of metals and metal alloys stable at cathode potentials with the highly oxidizing thionyl chloride include titanlum, molybdenum, niobum, tantalum, tungsten, Kovar*(trademark of ~estinghouse Electric Corp. for an expansion alloy), Inconel*(trademark of lnternational Nickel Co. for a nickel chromium alloy), Monel*(trademark of Wllbur D. Driver Co. for a glass sealing alloy), nickel and stainless steel.
The following examples illustrate seals made in accordance with the present invention which are tested in lithium cell environments whereby their stabllity ~ay be more clearly seen. All parts are parts by weight un-less otherwise indlcated. Since the following examples are for illustratlve purposes any details di~closed thereln should not be conslderPd as limita-tions on the present invention.

* ~eglstered Trademark 1 15~302 EXAMPLE I
~ q~ant~ty nf B~ehler "1 micron" alumi~a abrasi~e is heated to transform any ~emaining alumina hydrate to anhydrou~ ~lpha alu~ina. The dried alu~ina is mixed wi~h pGwdered a~d dried Cor~ing 1723 aluminosilicate glass in 6ufficlent quantlty to form a 10% alumina ~ix~ure. ~asher-shaped pellets, or "preforms", are pressed at 33 Kpsi from the mlxture and sintered in air ~r~m 850C to 1050C with temperature increased in progres6ive 50C
steps at lO-minute intervals. A ~etal-tc~glass-to metal ~er~inal i6 assem-bled, with the pellet in the annular space between a cold-rolled-steel (low carbon) outer metal ~ember ~nd an inner molybednum member, which wi:Ll pro-Yide an outer compression and an inner matched seal. The &eals are made ~n an argon atmosphere by fusing for 15 minu~es at 1200C followed by a 15 minute annealing period at 712 C. The completed terminal thereafter is assembled into a "D" size Li/S02 cell with its outer metal ~ember connected to the lithium anode. The cell is filled with an electrolyte comprising a

3/4 molar solution of lithium brDmide in a ~ixture Df 74% by weight sulfur di~xide and 26% by ~eight acetonitrile~ and is stored at 72C in a position with the terminal at the bottom. After 6 mon~hs there is no leakage of electrolyte or det~rioration of the lnsulation.

_ _ _ _ _ _ _ . _ .. . . ., .. .. , ., .. _ . . _ . _ _ .. _ . _ . _ .. _ _ _ 9,_ 3~2 EX~UPLE II
-A glass-to-metal 6eal i6 ~ade in accordaDce with the procedure of Example I but with the surroundlng metal member comprlsed of m~lybdenum 60 that a matched seal result6. The 6esl i6 thereafter placed iD 8 sealed glass vial containiug an electrolyte ~olutlon of the above component6 but ~ith 40~
S02, ~ith the metal member of the seal being llthium polarized. The vlals are stored for 5 ~onth6 at 72 C. At the end of 6torage only slight corrosion, iDdicative of only mincr attack, i6 vi6ible. Borosilicate glass seals tested iD a similar manner showed extensive corrosion after only 6 weeks of 6torage.

EXA~LE III
A Fusite borosilicate gla6s losded with 30.8~ alumina by weight is bonded in matched ~lass-to-metal seal6 ~ith Rovar*conductor6. The inner metal member or feedthrough is lithium polarized and the seai i6 exposed to boiling refluxed l molar LiAlC14-thionyl chloride electrolyte 601utlon, for 3~ days.
Only slight blackenlng at the inner aeal i8 evident at such time. A seal of 6imilar construction utill~ing such Fuslte borosilicate gla6s, but with only 5% alumina load, develops extensive ~racture under 61milcr testlng.

The preceeding example6 were pre6ented for illustratlve purposes as demonstrating more clearly the efficacy of the seal6 of the present invention.
It 16 understood that changes and varlations may be made wlthout departing from the scope of the pre6ent lnventlon a6 deflned in the followlng claims.

* Registered Trademark .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A non-aqueous electrochemical cell having an anode comprised of a member of the group consisting of alkali metals, alkaline earth metals, and aluminum, said cell being hermetically sealed with a metal-glass-metal seal wherein said glass consists essentially of a member of the group consisting of aluminosilicate glass and glass consisting essentially of alumina and oxides more stable than alumina.
2. The electrochemical cell of claim 1 wherein said glass containing alumina and oxides more stable than alumina comprises calcium aluminate.
3. The electrochemical cell of claim l wherein said glass in said metal-glass-metal seal contains particles of metal oxides having free energies of formation per gm atom of oxygen at least as negative as that of alumina.
4. The electrochemical cell of claim 3 wherein said particles are comprised of alumina.
5. The electrochemical cell of claim 4 wherein said alumina particles are substantially free of asperities.
6. The electrochemical cell of claim 5 wherein said particles have diameters ranging between l and 30 microns.
7. The electrochemical cell of claim 1 wherein said cell contains a lithium anode.
8. The electrochemical cell of claim 3 wherein said amount particles comprises at least 10% by weight of said glass.
9. The electrochemical cell of claim 7 wherein said cell contains a cathode depolarizer selected from the group consisting of sulfur dioxide and thionyl chloride.
10. The electrochemical of claim 3 wherein said particles are selected from members of the group consist-ing of CaO,BeO, Ba20, MgO, SrO, BaO, CeO2, Sc2O3, Ce2O3, ZrO2, TiO2, and Ti2O3.
11. The electrochemical cell of claim 3 wherein said metal oxide particle inclusions does not increase the glass working temperature above 1100°C.
12. An electrochemical cell comprising a lithium anode and a cathode depolarizer selected from the group consisting of sulfur dioxide and thionyl chloride with said cell being hermetically sealed with a metal-glass-metal seal wherein said glass is comprised of an aluminosilicate glass having included therein at least 10% by weight particles of alumina.
13. An electrochemical cell comprising a lithium anode and a cathode depolarizer selected from the group consisting of sulfur dioxide and thionyl chloride with said cell being hermetically sealed with a metal-glass-metal seal wherein said glass is comprised of a borossilicate glass having included therein at least 10%
by weight particles of alumina.
14. An electrochemical cell having an anode comprised of a member of the group consisting of alkali metals, alkaline earth metals and aluminum, said cell being hermetically sealed with a metal-glass-metal seal wherein said glass has included therein particles of metal oxides which comprise at least 10% by weight of said glass, whereby cracking of said glass with resultant glass-metal separation caused by anode metal ion permea-tion is substantially prevented, with said metal oxides having free energies of formation per gm atom of oxygen at least as negative as that of alumina.
15. The electrochemical cell of claim 14 wherein said glass is a borosilicate glass.