CA1307026C - Battery element and battery incorporating doped tin oxide coated substrate - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A battery element useful as at least a portion of the positive plates of a lead-acid battery comprises an acid resistant glass substrate coated with electrically conductive doped tin oxide. This battery element may also be used In the bipolar plates of a lead-acid battery.

Description

BATTERY ELEMENT AND BATTERY INCORPORATING
DOPED TIN OXI~E COATED SUBSTRATE

TFCHNICAL FIELD

The present Inventlon relates to battery elements useful In lead-acld batterles. More partlcularly, the Inventlon relates to battery elements for use In lead-acld batterles, whlch elements Include a substrate havlng a conductlve coatlng.

BACKGROUND

The conventlonal lead-acld battery Is a multl-cell structure. Each cell comprlses a set of vertIcal posltIve and negatlve plates formed of lead-acld alloy grlds contalnlng layers of electrochemlcally actlve pastes. The paste on the posltlve plate when charged comprlses lead dloxlde, whlch Is the posltlve actln3 materlal, and the negatlve plate contalns a negatlve actlve materlal such as sponge lead. An acld electrolyte, based on sulfurlc acld, Is Interposed between the posltlve and negatlve plates.
Hlgher voltages are provlded In a blpolar battery Includlng blpolar plates capable of through-plate conductlon to serlally connected electrodes or cells. ~he blpolar plates must be Impervlous to electrolyte and be electrlcally conductlve to provlde a serial connectlon between electrodes.
U.S. Patents 4,275,130; 4,353,969; 4,405,697;
4,539,268; 4,507,372; 4,542,082; 4,510,219; and 4,547,443 relate to varlous aspects of lead-acld batterles. Certaln of these patents dlscuss varlous asPeCtS of blpolar plates.

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1~)7C)~6 Attempts have been made to Improve the conductlvlty and strength of blpolar plates. Such attemPts Include the use of conductlve carbon partlcles or fllaments such as carbon, graphlte or metal In a resln blnder. However, carbonaceous materlals are oxldlzed In the aggresslve electrochemlcal envlronment of the posltlve plates In the lead-acld cell to acetlc acld, whlch In turn reacts wlth the lead lon to form lead acetate, whlch Is so I ub I e In sul f urlc acl d . Thus, the actlve materlal Is gradually depleted f rom the paste and tles up the lead as a salt wh I ch does not contrlbute to the productlon or storage of electriclty.
The metals f are no better; most metals are not capable of wlthstandlng the hlgh potentlal and strong acl d envlronment present at the posltlve plates of a lead-acld battery. Whlle some metals, such as platlnum, are electrochem~cally stable, thelr prohlbltlve cost prevents thelr use In hlgh volume commerclal applicatlons of the lead-acld battery.

130~7026 SUMMARY OF THE INVENT ! ON

An Improved battery element useful In a lead-acld battery has been dlscovered. In one broad embodIment, the battery element Is useful as at least a portlon of the posltlve plates of the bat~ery and comprlses an acld reslstant glass substrate coated wlth electrlcally conductlve doped tln oxlde, provlded that the glass has Incresed acld reslstance relatlve to E-glass.
In an addltlonal embodlment, the battery element further comprlses a fluld Impervlous matrlx layer havlng mutually opposlng flrst and second surfaces sltuated such that at least a portlon of the coated substrate Is embedded In the matrlx layer to form a fluld Impervlous conductIve composlte. In another embodlment, the battery element further comprlses a posltlve actlve electrode materlal sltuated such that at least a portlon of the coated substrate contacts the electrode materlal. In one embodlment, the posltlve actlve electrode materlal Is In the form of a layer located adJacent to, and In electrlcal communlcatlon wlth, the fIrst surface of the matrlx layer of the above-noted composlte. In a further embodlment, the battery element last descrlbed above further comprlses a fluld-lmpervlous conductlve Iayer that Is adJacent to, and In electrlcal communlcatlon wlth, the second surface of the matrlx layer. In yet another embodlment, the element last descrlbed above further comprlses a negatlve actlve electrode layer located adJacent to, and In electrlcal communlcatlon wlth the fluld Impervlous conductlve layer. An Improved process for coatlng the substrate of the present battery elements wlth doped tln oxlde has also been dlscovered.
The present battery element comprlslng a acld reslstant, glass substrate coated wlth electrlcally conductlve doped tln oxlde Is useful to provlde Improved performance In both conventlonal lead-acld batterles and In blpolar plate lead-acld batterles. For example, the doplng of the tln oxlde (stannlc 13~7~)26 dloxlde) coatlng greatly enhances the electrlcal conductlvlty (reduces the reslstlvlty) of the present battery ele~ent.
As noted prevlously, In conventlonal lead-acld batterles, lead dloxlde Is used as the posltlve actlve electrode materlal and the electrolyte Is sulfurlc acld or a sulfurlc acld based materlal. Electrlcal conductlvlty through the posltlve actlve electrode materlal Is requlred for proper functlonlng of the battery. However, as the battery discharges, lead sulfate, an electrlcal Insulator Is formed from the lead dloxlde, an electrlcal conductor. The present acld reslstant glass substrate coated wlth doped tln oxlde may be placed so that at least a portlon of the coated substrate contacts the posltlve actlve electrode materlal. Even when some of thls posltlve act~ve materlal Is converted to an electrlcal Insulator, e.g., lead sulfate, the present substrate coated wlth doped tln oxlde provldes for electrlcal conductlvlty through the posltlve actlve materlal-lrlsulator composltlon, and thereby Improves the performance of the battery, e.g., a conventlonal lead-acld battery.
The comblnatlon of an acld reslstant glass substrate coated wlth doped tln oxlde has substantlal electrlcal, chemlcal, physlcal and mechanlcal propertles maklng It useful as a lead-acld battery element. For example, the element has substantlal stablllty In the presence of, and Is Impervlous to, the sulfurlc acld or the sulfurlc acld-based electrolyte. The doped tln oxlde coatlng on the acld reslstant glass substrate provldes for Increased electrochemlcal stablllty and reduced corroslon In the terrlbly aggresslve, oxldatlve-acldlc condltlons present on the posltlve slde lead-acld batterles.
Any sultable dopant may be used to dope the tln oxlde coatlng. The dopant or comblnatlon of dopants should be such as to be effectlve to Improve the electrlc conductlvlty (reduce the reslstlvlty) of the tln oxlde coatlng on the substrate. The preferred dopant for the tln oxlde coatlng Is selected from the group conslstlng of fluorlde lon, antlmony lon and mlxtures ~3C~7~ 6 thereof. Fluorlde lon Is partlcularly preferred slnce It Is especlally tolerant of the aggresslve envlronment In a lead-acld battery. The amount of dopant present In the tln oxlde coatlng may vary wldely, provlded that the amount present Is effectlve to Improve the electrlcal conductlvlty of the coatlng, e.g., relatlve to the conductlvlty of the coatlng wlth no dopant present. If fluorlde lon Is to be used as a dopant, It Is preferred that the fluorlde lon be present In the tln oxlde coatlng In an amount In the range of about 0.01 mo I e % to about mo~e %, based on the entlre doped tln oxlde coatlng, preferably from about 1 mole % to about 10 mole %.
The doped tln oxlde coatlng on the acld reslstant glass substrate Is typlcally such that satlsfactory electrlcal conductlvlty Is achleved. Thls coatlng may also act to physlcally protect the substrate from the battery envlronment. The thlckness of the coatlng may vary wldely and depends, for example, on the electrlc conductlvlty deslred, and on the type and amount of acld reslstant substrate. The thIckness of the coatlng may be as llttle as a molecular mono-layer. ~referably, the doped tln oxlde coatlng has an average thlckness In the range of about 0.01 mlcron to about 10 mlcrons, partlcularly when the substrate Is In the form of glass fIbers havlng an average dlameter In the range of about 1 mlcron to about 20 mlcrons and the average length to dlameter ratlo of the glass fIbers Is In the range of about 100,000 to about 2,000,000.
Any sultable process may be employed to apply the doped tln oxlde coatlng onto the glass substrate. The prlmary crlterlon for such processlng Is that an effectlve coatlng results. Where, as Is preferred, the acld reslstant glass substrate Is In the form of partlcles or fIbers, the doped tln oxlde coatlng Is preferably applled uslng spray pyrolysls or a new chemlcal vapor envlronment deposltlon process.
The spray pyrolysls process, whlch Is partlcularlY
preferred, comprlses spraylng a composltlon comprlslng a tln component, a dopant-contalnlng materlal and a solvent onto the i ~; : ..

13~)'7()26 glass substrate whlch Is malntalned at elevated temperatures, preferably temperatures effectlve to evaPorate at least a maJor portlon of the solvent from the substrate; and subJectlng the sprayed substrate to condltlons, preferably oxldatlon condltlons at elevated temperatures, effectlve to form the doPed tln oxlde coatlng on the sprayed substrate. The tln component and the dopant-contalnlng materlal are preferably soluble In the solvent.
In a preferred embodlment, the tln comPonent Is a hydrolyzable tln component, such as tln alkoklde, tln hallde, tln nltrate, mlxtures thereof and the llke. The solvent comPrlses a hydroxyl group contalnlng-solvent, such as water, methanol, ethanol, Isopropanol, butanol, other alcohols, glycols, mlxtures thereof and the llke and the tln comPonent forms, at least partlally, a tln oxygen bond wlth one or more groups derlved from the solvent.
The use of an Inorganlc tln ,.component and a hydroxyl group-contalnlng solvent provldes a coatlng wlth outstandlng electrlcal conductlvlty and ablllty to wlthstand the aggresslve envlronment In a lead-acld battery.
Another technlque useful to apply the doped tln oxlde coatlng on the substrate Is generally referred to as the chemlcal vapor envlronment deposltlon (CVD) process. Thls process comprlses (1) contactlng a vaporous composltlon comprlslng a tln component and a dopant-contalnlng materlal wlth the glass substrate; and (2) contactlng the contacted substrate wlth an oxygen-containlng vaporous medlum at condltlons effectlve to form the doped tln oxlde coatlng on the substrate. The CVD process Is conventlonal and well known In the art for coatlng a slngle flat surface whlch Is malntalned In a flxed posltlon durlng stePS (1) and (2). However, In a preferred embodlment, the present glass substrate Is In the form of partlcles, fIbers and the llke. It has been found that the CVD process technology can be used to apply the doped tln oxlde coatlng to these and other substrates provlded that the substrate Is malntalned In substantlally constant three dlmenslonal motlon durlng steps (1) and (2). By "three dlmenslonal motlon" Is meant that the substrate, e.g., ,, .

13~ 6 partlcles, fIbers and the llke, Is In motlon about Its x axls, Its y axls and Its z axls. Wlth the substrate belng In substant I ally constant three dImenslonal motlon, each polnt on the substrate Is exposed to substantially the same condltlons durlng steps (1) and (2). Thls, In turn, leads to a substant1ally unlform doped tln oxlde coatlng on the substrate.
The substantlally constant three dlmensional motlon of the glass substrate may be provlded by mechanlcal means such as agltators and mlxers. However, It Is preferred that the motlon occur In response to the vaporous composltlon and vaporous medlum contactlng the substrate. In other words, It Is preferred that the force of the vaporous composltlon and the vaporous medlum be suffIclent so that the substrate Is put into substantially constant three dImenslonal motlon.
Steps (1) and (2) may occur sequentlally, e.g., In a batch system In a slngle vessel wlth step (1) precedlng s~ep (2).
Alternately, steps (1) and (2) may oc~ur substantlally slmultaneously In at least one fluldlzed bed reactlon zone. In thls latter system, the glass substrate Is caused to move from one end of the zone to the other end of the zone and to be contacted flrst as In step (1) and then to be contacted as In step (2). In thls manner, a contlnuous coatlng operatlon Is provlded. More than one fluldlzed bed reactlon zone may be employed.
The tln component and dopant-contalnlng materlal useful In the present CVD process Include any such component and materlal useful to provlde the deslred doped tln oxlde coatlng on the glass substrate. Tln components whlch are conventlonally used to coat flat surfaces by the CVD process may be employed. It Is preferred to use the solutlon referred to under spray pyrolysls and that the tln component be other than tln oxlde. Hydrogen fluorlde and certaln fluorlde lon-formlng materlals are useful as the dopant-contalnlng materlal In the present CVD process. Of course, If the dopant Is to be other than fluorlde lon, the dopant-contalnlng materlal Is to be changed accordlngly.

13~)70;~6 The present three dlmenslonal motlon CVD process has appllcablllty beyond provldlng doped tln oxlde coatlngs on glass substrates useful In lead-acld batterles. Any sultable substrate can be at least partlally coated wlth any sultable metal-contalnlng materlal, e.g., tln oxlde, tltanlum nltrlde- and others, uslng the present process Improvement. In the event the coatlng Is to be metal-contalnlng materlal other than an oxlde, step (2) comprlses contactlng the contacted substrate wlth a vaporous medlum at condltlons effectlve to form the deslred metal-contalnlng materlal coatlng on the substrate.
As noted above, the acld reslstant glass substrate Is preferably In the form of partIcles or fIbers. Because of avallablllty, cost and performance conslderatlons, It Is preferred that the substrate be In the form of fIbers. The presently useful f I bers preferably are In a form se I ected from the group conslstlng of fIber rovlngs, chopped fIbers, slngle fIbers, woven fIbers and the I Ike. In order to provlde Improved polnt-to-polnt contactlng In the flbrous substrate, whlch Is hlghly deslrable for Improved conductlvlty and electrlcal effectlveness of the lead-acld battery, the glass substrate more preferably Is In the form of a body of woven flbers, stlll more preferably, a body of woven flbers havlng a poroslty In the range of about 60% to about 95%. Poroslty Is defIned as the percent or fractlon of vold space wlthln a body of woven fIbers. The above-noted porosltles are calculated based on the woven flbers Includlng the deslred doped tln oxlde coatlng.
The glass substrate Is more acld reslstant than E-glass, I.e., has Increased acld reslstance relatlve to E-glass.
That Is, the glass substrate exhlblts Increased reslstance relatlve to E-glass to corroslon, eroslon and/or other forms of deterloratlon at the condltlons present, e.g., at or near the posltlve plate, or posltlve slde of the blpolar plates, In a lead-acld battery. Preferably, the acld reslstant glass substrate Is at least as reslstant as Is C-glass to the condltlons present In a lead-acld battery.

-702~

Typlcal composltlons of E-glass and C-glass are as follows:
Welght Percent E-glass C-glass Slllca 54 65 Alumlna 14 4 Calcla 18 14 Magnesla 5 3 Soda + Potasslum Oxlde 0.5 9 Borla 8 5 Tltanla + Iron Oxlde 0.5 Preferably the glass contalns more than about 60% by welght of sillca and less than about 35~ by welght of alumlna, and alkall and alkallne earth metal oxldes.
The posltlve actlve electrode materlal is sltuated so that at least a portlon of the electrlcally conductlve doped tln oxlde coated glass substrate contacts the electrode materlal. Any sultable posltlve actlve electrode materlal or comblnatlon of materlals useful In lead-acld batterles may be employed In the present Inventlon. One partlcularly useful posltlve actlve electrode materlal comprlses electrochemlcally actlve lead oxlde, e.g., lead dloxlde, materlal. A paste of thls materlal Is often used. If a paste Is used In the present Inventlon, It Is applled so that there Is approprlate contactlng between the coated substrate and paste.
Any sultable matrlx materlal may be used to embed at least a portlon of the doped tln oxlde coated substrate. The matrlx materlal should be at least Inltlally fluld Impervlous to be useful In the present battery elements and batterles.
Preferably, the matrlx materlal comprlses a polymerlc materlal, e.g., one or more synthetlc polymers. The polymerlc materlal may be elther thermoplastlc or a thermoset materlal. Thermoplastlc materlals are those whlch can be softened wlth heat and whlle soft can be molded, cast, or extruded under pressure.
Thermosettlng materlals are those whlch are changed chem~callY by ,. .

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13~7~26 the appllcatlon of heat to become hard, dense, Insoluble, and Infuslble substances. Among the polymers partlcularly useful In the present Inventlon are polymers derlved from a monomer component comprlslng a maJor amount by welght of at least one substantlally hydrocarbonaceous compound, more preferably selected from the group conslstlng of oleflns and dloleflns (both alIphatlc and aromatlc) havlng 2 to about 12 car~on atoms per molecule and a mlnor amount by welght of at least one addltlonal monomer effectlve to Increase the polarlty of the polymer. If the polymerlc matrlx materlal Is to be a thermoplastlc polymer, It Is preferred that the matrlx be substantlally hydrocarbon-based and Include one or more groups effectlve to Increase the po-larlty of the polymer relatlve to polypropylene. Addltlve or addltlonal monomers, such as malelc anhydrlde, vlnyl acetate, acryllc acld, and the ll~e and mlxtures thereof, may be Included prlor to polymerlzat I on to glve the substantlally hydrocarbon-based polymer Increased polarlty. Hydroxyl groups may also be Included In a llmlted amount, uslng conventlonal technlques, to Increase the polarlty of the fInal substantlally hydrocarbon-based polymer.
By "substantlally hydrocarbonaceous" and "substantlally hydrocarbon-based" Is meant those compounds and polymers, respectlvely, whlch comprlse malnly car~on and hydrogen atoms.
These compounds and polymers may Include mlnor amounts of one or more non-hydrocarbon groups, e.g., to provlde the presently deslred Increased polarlty, provlded that such non-hydrocarbon groups do not substantlally Interfere wlth the functlonlng of the present battery elements and batterles. Among the non-hydrocarbon groups whlch may be Included are those groups whlch contaln halogens, sulfur, nltrogen, oxygen, phosphorous and the llke.
Among the preferred thermoplastlc polymer matrlx materlals Include co-polymers of addltlonal monomers and oleflns such as ethylene, propylene, butylenes, pentenes, hexanes, styrene and mlxtures thereof. Other preferred thermoplastlc 1307~26 polymers Include polyvlnyldene dlfluorlde, comblnatlons of polyphenylene oxlde and polystyrene and mlxtures thereof.
Because of welght and strength conslderatlons, If the polymerlc matrlx materlal Is to be a thermoplastlc polymer, It Is preferred that the matrlx be a polypropylene-based polymer whl Ch Includes one or more groups effectlve to Increase the polarlty.
The preferred addltlonal monomer Is malelc anhydrlde, more preferably present In the polymer In an amount In the range of about o.1% to about 1o% by welght, more preferably about 1% to about 5% by we I ght.
Thermoset polymers, whlch have Increased polarlty relatlve to polypropy I ene and are stable at the condltlons present In a lead-acld battery, are more preferred for use In the present polymerlc matrlx materlals. The vlscoslty propertles and flexlblllty of certaln of these thermoset polymers provlde for ease of manufacturlng the coated acld reslstant substrate-matrlx materlal composlte of the present battery elements. For example, the coated substrate may be at least partlally embedded In the thermoset polymer or polymer precursor prlor to the flnal polymerlzatlon of the thermoset polymer. More effectlve bondlng of the coated substrate wlth thermoset polymerlc matrlx materlals Is achleved. Thls bondlng Is Important to provlde Increased protectlon for the coated substrate at the aggresslve condltlons present In lead-acld batterles.
The thermoset polymers useful In the present Inventlon are selected from the group conslstlng of epoxles, phenol-formaldehyde polymers, polyesters, polyvlnyl esters, polyurethanes, melamlne-formaldehyde polymers and urea-formaldehyde polymers. Each of these classes of polymers represents many Indlvldual polymers, the composltlon of whlch can be varled by selectln~ dlfferent monomers and/or adJustlng the ratlo or ratlos of the monomers used to produce the thermoset polymer. These thermoset polymers may be produced uslng conventlonal technlques, well ~nown In the art. Therefore, no further dlscusslon of such technlques Is presented here. More preferably, the thermoset polymers are selected from the group conslstlng of epoxles, phenol-formaldehyde polymers, polyesters and polyvlnyl esters.
In order to provlde enhanced bondlng between the doped tln oxlde coated substrate and the matrlx materlal, It Is preferred that the matrlx materlai have an Increased polarlty, as Indlcated by an Increased dlpole moment, relatlve to the polarlty of polypropylene. Because of welght and strength conslderatlons, If the matrlx materlal Is to be a thermoplastlc polymer, It Is preferred that the matrlx be a polypropylene-based polymer whlch Includes one or more groups effectlve to Increase the polarlty of the polymer relatlve to polypropylene. Addltlve or addltlonal monomers, such as malelc anhydrlde, vlnyl acetate, acryllc acld, and the llke and mlxtures thereof, may be Included prlor to propylene polymerlza.tlon to glve the product propylene-based polymer Increased polarlty. Hydroxyl groups may also be Included In a llmlted amount, uslng conventlonal technlnues, to Increase the polarlty of the flnal propylene-based polymer.
Thermoset polymers whlch have Increased polarlty relatlve to polypropylene, are more preferred for use In the present matrlx materlal. Partlcularly preferred thermoset polymers Include epoxles. phenol-formaldehyde polymers, polyesters, and polyvlnyl esters.
Varlous technlques, such as castlng, moldlng and the e, may be used to at least partlally embed the doped tln oxlde coated substrate Into the matrlx materlal. The cholce of technlque may depend, for.example, on the type of matrlx materlal u8ed~ the type and form of the substrate used and t.he speclflc applIcatlon Involved. Certaln of these technlques are presented In ~.S. Patent 4,547,443 One partlcular embodlment Involves pre-lmpregnatlng (or comblnlng) that portlon of the doped tln oxlde coated substrate to be embedded In the matrlx materlal wlth a relatlvely polar (Increased polarlty relatlve to polypropylene) thermoplastlc polymer, such as .~:

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polyvlnylldene dlfluorlde, prlor to the coated substrate belng embedded In the matrlx materlal. Thls embodIment Is partlcularly useful when the matrlx materlal Is Itself a thermoplastlc polymer, such as polypropylene, and has been found to provlde Improved bondlng between the doped tln oxlde coated substrate and the matrlx materlal. -The bondlng between the matrlx materlal and the dopedtln oxlde coated, acld-reslstant substrate Is Important to provlde effectlve battery operatlon. In order to provlde for Improved bondlng of the doped tln oxlde coatlng (on the substrate) wlth the matrlx materlal, It Is preferred to at least partlally, more preferably substantlally totally, coat the doped tln oxlde coated substrate wlth a coupllng agent whlch acts to Improve the bondlng of the doped tln o%lde coatlng wlth the matrlx. Thls Is partlcularly useful when the substrate comprlses acld reslstant glass flbers. Any sultable coupllng agent may be employed. Such agents preferably comprlse molecules whlch have both a polar portlon and a non-polar portlon. Certaln materlals generally In use as slzlngs for glass fIbers may be used here as a "slze" for the doped tln oxlde coated glass fIbers. The amount of coupllng agent used to coat the doped tln oxlde coated glass fIbers should be effectlve to provlde the Improved bondlng noted above and, preferably, Is substantlally the same as Is used to slze bare glass flbers. Preferably, the coupllng agent Is selected from the group conslstlng of sllanes, sllane derlvatlves, tltanates, tltanate derlvatlves and mlxtures thereof. U.S. Patent 4,154,638 dlscloses one sllane-based coupllng agent adapted for use wlth tln oxlde surfaces.
In the embodlment In whlch the present battery element Is at least a portlon of a blpolar plate In a lead-acld battery, It Is preferred that the element further comprlses a fluld-lmpervlous conductlve layer that Is reslstant to reductlon adJacent to, and preferably In-electrlcal communlcatlon wlth, the , ,~.
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`` ~307~Z6 second surface of the matrlx materlal. The conductlve layer Is preferably selected from metal, more preferably lead, and substantlally non-conductlve polymers, more preferably synthetlc polymers, contalnlng conductlve materlal. The non-conductlve polymers may be chosen from the polymers dlscussed prevlousJy as matrlx materlals. One partlcular embodIment Involves uslng the same polymer In the matrlx materlal and In the conductlve layer at a thIckness from about 1 to about 20 mlls. The electrIcally conductlve materlal contalned In the non-conductlve layer preferably Is selected from the group conslstlng of graphlte, lead and mlxtures thereof.
In the blpolar plate conflguratlon, the present battery element further comprlses a negatlve actlve electrode layer located to, and preferably In electrlc communlcatlon wlth the fluld Impervlous conductlve layer. Any sultable negatlve actlve electrode materlal useful In lead-acld batterles may be employed In the present Inventlon. One partlcularly useful negatlve actlve electrode materlal comprlses lead, e.g., sponge lead. Lead paste Is often used.

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~0~26 BRIEF DESCRIPTION OF THE DRAWINGS

Flgure 1 Is a schematlc dlagram of the serles-parallel electrlcal connectlon of blpolar and monopolar plates; and Flgure 2 Is a c.oss-sectlon of a blpolar plate for a lead-acld battery Incorporatlng doped tln oxlde coated acld reslstant glass substrate.

DETAILED DESCRIPTION OF PREFERRED EMBODlMi_NTS

Referrlng now to Flgure 1 a schematic representatlon of a blpolar battery 10 Is shown, comprlslng a positlve termlnal 12 and a negatlve termlnal 14. Battery 10 Includes a monopolar grld or plate stack havlng two posltlve monopolar plates 16 and 18 and two negatlve monopolar plates 20 and 22.
Monopolar plates 16, 18, 20, 22 are stacked vertlcally wlth sultable electrolyte layers tnot shown) provlded. Posltlve monopolar plates 16 and 18 are connected ~n parallel by a bus bar, shown schematlcally at 24, to posltlve termlnal 12 to provlde an electrlc potentlal of about elght volts. The amount of current Is determlned by the slze of posltlve monopolar plates 16 and 18. Negatlve monopolar plates 20 and 22 are connected by a bus bar, shown schematlcally at 26, to negatlve termlnal 14 to also provlde a voltage potentlal of about elght volts and a current varylng dependlng upon the slze of negatlve monopolar plates 20 and 22.
As Is known In blpolar battery technology, blpolar plate grouplngs 28, 30, 32 are Inserted between the monopolar plates 16, 18, 20, 22. Blpolar plate grouplngs 28, 30, 32 are posltloned so that thelr uppermost and lowermost posltlve sldes are adJacent to one of negatlve monopolar plates 20 and 22 and thelr uppermost and lowermost negatlve sldes are adJacent to one of posltlve monopolar plates 16 and 18. Blpolar plate grouplngs 1 307i~)26 28, 30, 32 Include a serles of vertlcally stacked blpolar plates 34. Blpolar plates 34 are stacked vertlcally wlth sultable electrolyte layers (not shown) provlded between blpolar plates 34 to provlde a blpolar plate grouplng havlng varlable voltage dependlng upon the number of blpolar plates 34 present In a glven grouplng. It wlll be appreclated that the blpolar plate grouplng Is not connected to bus bars 24 and 26, but rather Is secured wlthln the battery stacic by suitable non-conductive means (not shown).
Referrlng now to Flgure 2, a unltary, blpolar battery plate 34 Is Illustrated. Plate 34 comprlses a body 36 of woven fIberglass wlth the glass belng C-glass (wlth a composltlon substantlally as Indlcated prevlously), the strands 38 of whlch contaln a coatlng of electrlcally conductlve fluorlde lon doped tln oxlde. Body 36 has a poroslty of about 75%. The average dlameter of the IndIvldual fIbers or strands 38 In body 36 is about 5 mlcrons. The average thlckness of the doped tln oxlde coatlng Is about 1 mlcron and about 2 mole % of the coatlng is fluorlde lon.
The lower portlon of flberglass body 36 Is embedded In a layer 40 of synthetlc, epoxy-type thermoset polymer formlng a fluld-Impervlous, through-conductlve substrate.
The lower portlon of body 36 may be embedded In thermoset layer 40 uslng varlous technlques. It Is preferred that the lower portlon of body 36 be contacted wlth the materlal maklng up thermoset layer 40 before the thermoset polymer Is fully cured. One of the advantages of uslng thermoset polymers, such as epoxles, for layer 40 Is that the vlscoslty of the monomers or pre-polymers Is sufflclently low to allow the doped tIn oxlde coated substrate, e.g., fIberglass body 36, to be contacted wlth the monomers or pre-polymers wlth no substantlal undue breai<age of the substrate, e.g., Indlvldual glass flber strands wlthln body 36. Thls low vlscoslty of the thermoset's monomers or pre-polymers provldes for Improved control over the manufacture of the doped tln oxlde coated substrate-matrlx i6 ....

. . .

)7~2:6 composlte. Prlor to belng partlally embedded In layer 40, body 36 (Includlng the doped tln oxlde coatlng) Is coated wlth a sllane derlved coupllng agent as descrlbed In U.S. Patent 4,154,638 to Improve the bondlng of body 36 wlth layer 40.
The upper portlon of body 36 contalns lead dloxlde formlng a posltlve actlve electrode layer 42. The partlcles 44 Of lead dloxlde are In contact wlth strands 38 whlch form conductlon paths from top surface 45 to bottom surface 46 of layer 42.
The thlckness of the resln layer 40 Is preferably In the range of about 1 to about 20 mlls, more preferably about 4 to about 10 mlls.
Posltlve actlve electrode layer 42 Is prepared accordlng to methods well establIshed In the art. The lead dloxlde partlcles 44 can be dlspersed In water to form a paste and Impregnated Into the upper portlon of body 36 and drled, or a precursor paste of lead sulfate and lltharge (PbO) such as one contalnlng 75% lead sulfate and 25% lltharge In water can be worked Into the pores of the upper portlon of body 36 and drled and cured. The paste Is converted to lead dloxlde by applylng a charglng potentlal to the paste.
A layer 50, whlch Is conductlve and stable under reduclng condltlons, Is adhered to plate 34 by a conductlve adheslve such as a fllm 52 of graphlte-fllled epoxy adheslve.
Layer 50 can be a thln fllm or foll of lead preferably havlng a thlckness In the range of 0.5 to about 10 mlls, more preferably about 1 to about 5 mlls. The fabrIcatlon of the blpolar plate Is completed by deposltlng a layer 54 of negatlve actlve materlal such as lead paste onto layer 50 supPorted by a sheet 56 of glass scrlm.
Battery 10 Is placed In servlce and performs well In both the charge and dlscharge modes. The doped tln oxlde coatlng on body 36 provldes adequate conductlvlty. Importantly, thls performance contlnues after a perlod of tlme In charge./dlscharge cycllc operatlon. Thls performance stablllty Is vltal In many lead-acld battery appllcatlons. Thus, the doped tln oxlde coated, .

. , ~31~7026 acid reslstant glass flbers of body 36 have substantlal stablllty at the aggresslve, acldlc/oxldatlve condltlons present on the posltlve slde of blpolar plates 34. In addltlon, the present system provldes for outstandlng bondlng between the coated substrate and the matrlx materlal. Weakness In thls bondlng has been one prlmary cause of fallurè In prlor art ~Ipolar plates.
Improved bondlng between the doped tln oxlde coated substrate and the matrlx materlal at condltlons present In the lead-acld battery Is one of ~he prImary advantages of the present Inventlon.

' ~3~7~26 A serles of slx (6) materlals were prepared for stablllty testlng In 30 wt.% sulfurlc acld, whlch slmulates the electro I yte In a typlcal lead-ac I d battery. These slx (6) materlals were as follows: -Composltlon 1- A glass mat composed of both ~-glass and E-glass, typlcal composltlons of whlch are as set forth prevlously. The mat or woven body was prepared from C-glass fIber bundles tled together (cross stltched) wlth E-glass strands. C-glass Is more ac I d reslstant than E-glass. The glass mat contalned 33% by welght of E-glass and was coated, uslng conventlonal technlques wlth stannlc oxlde.
Composltlon 2- E-glass flbers coated wlth stannlc oxlde were composlted wlth polypropylene by compresslon moldlng polypropylene fllm sheets In a lamlnated mode to avold undue breaklng of the relatlvely fraglle flbers.
Composltlon 3- A stannlc oxlde coated glass mat as In Composltlon 1 was Impregnated wlth polyvlnylldene dlfluorlde (PVDF) so that the fInal composlte contalned about 30% by welght of PVDF.
Composltlon 4- Flbers of C-glass as used In Composltlon 1.
Composltlon 5- Flbers of E-glass as used In Composltlon 1 coated wlth stannlc oxlde.
Composltlon 6- Flbers of C-glass as used In Composltlon 1 coated wlth stannlc oxlde.
Dlstllled, delonlzed water used to prepare the 30 wt.%
sulfurlc acld electrolyte. ~elatlve amounts of the electrolyte and composltlon were scaled to provlde sufflclent analyte for analytlcal purposes. The tests were conducted for perlods of tlme as shown In the table below at amblent temperature condltlons.
Perlodlc samples of electrolyte were taken and analyzed for calclum and tln.

~307~26 The results of the stablllty testIng were as follows:
COMPOSITION HOURS Ca/Sn* HOURS CaJSn* HOURS Ca/Sn*
1 48 6.1/2.8 : 143 20.3/6.7 : 268 258/2.7 2 48 2.7/1.6 : 143 9.4/2.6 : 268 14.7/0.5 3 48 4.7/1.9 : 143 13.9/1.3 : 268 20/0.4 4 4S 1.6/- : 1432/- : 268 2.5/~
100 61/1.6 6 100 0.5/1.6 : - -- : - --*The concentratlon of soluble calclum and tln In the electrolyte Is expressed as welght parts per mllllon (ppm) In the electrolyte sample The calclum levels are Inltlally relatlvely hlgh and/or Increase wlth tlme whenever E-glass Is present (Composltlons 1, 2, 3 and 5). In compos I tlons contaln I ng only C-glass (Composltlons 2 and 6), the calclum levels are Inltlally relatlvely low and are substantlally malntalned at thls low level wlth tlme.
These results clearly show that C-glass Is superlor to E-glass as a substrate materlal In the present Inventlon.
Deterloratlon of the substrate materlal can result In reduced conductlvlty or even complete battery fallure.
Although the doped tln oxlde coatlng does protect the substrate somewhat from acld attack, the comblnatlon of doped tln oxlde coatlng on a glass substrate havlng Increased Inherent acld reslstance relatlve to E-glass has been found not only to more effectlvely thwart electrolyte attac~, but also to provlde Improved overall lead-acld battery performance. Preferably, addltlonal means are employed to protect the substrate from attack In the aggresslve envlronment of the lead-acld battery.
The preferred use of certaln forms of acld reslstant glass substrates, coupllng agents, doped tln oxlde coatlng technlques, and/or polymerlc matrlx materlals provlde the present battery elements and batterles wlth Improved electrochemlcal,.physlcal and/or mechanlcal performance and/or performance stablllty.

~0 ~ ..
:
~ ~ .

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~307~)26 While the Inventlon has been descrlbed wlth respect to varlous speclflc embodlments and examples, It Is to be understood that the Inventlon Is not llmlted thereto and that It can be varlously practlced wlthln the scope of the followlng clalms~

Claims (74)

1. A battery element useful as at least a portion of the positive plates in a lead-acid battery comprising an acid resistant inorganic substrate coated with electrically conductive doped tin oxide, said inorganic substrate having increased acid resistance relative to E-glass.

2. The element of claim 1 which further comprises a fluid impervious matrix layer having mutually opposing first and second surfaces situated such that at least a portion of said coated inorganic substrate is embedded in said matrix layer to form a fluid impervious, conductive composite.

3. The element of claim 1 wherein said tin oxide is doped with a dopant selected from the group consisting of fluoride ion, antimony ion and mixtures thereof.

4. The element of claim 1 wherein said tin oxide is doped with fluoride ion and said inorganic substrate is glass.

5. The element of claim 1 which further comprises a positive active electrode material, provided that at least a portion of said coated inorganic substrate contacts said electrode material.

6. The element of claim 1 wherein said tin oxide is doped with fluoride ion.

7. The element of claim 2 which further comprises a positive active electrode material layer located adjacent to said first surface of said matrix layer, provided that a portion of said coated inorganic substrate contacts said electrode layer.

8. The element of claim 7 which further comprises a fluid-impervious conductive layer that is resistant to reduction adjacent to said second surface of said matrix layer.

9. The element of claim 8 wherein said conductive layer is selected from metal and substantially non-conductive polymers containing conductive material.

10. The element of claim 8 which further comprises a negative active electrode layer located adjacent to said fluid-impervious conductive layer.

11. In a lead-acid battery having a plurality of positive plates and a plurality of negative plates, the improvement which comprises using battery elements in accordance with claim 1 as at least a part of said positive plates.

12. In a lead-acid battery having a plurality of positive plates and a plurality of negative plates, the improvement which comprises using battery elements in accordance with claim 4 as at least a part of said positive plates.

13. In a lead-acid battery having a plurality of positive plates and a plurality of negative plates, the improvement which comprises using battery element in accordance with claim 5 as at least a part of said positive plates.

14. In a lead-acid battery having a plurality of positive plates and a plurality of negative plates, the improvement which comprises using battery elements in accordance with claim 6 as at least a part of said positive plates.

15. In a lead-acid battery having a plurality of bipolar plates, the improvement which comprises using battery elements in accordance with claim 10 as said bipolar plates.

16. The element of claim 1 wherein said acid resistant inorganic substrate is in the form of particles or fibers.

17. The element of claim 4 wherein said acid resistant glass is in the form of particles or fibers.

18. The element of claim 17 wherein said fibers are in a form selected from the group consisting of fiber rovings, chopped fibers, single fibers, woven fibers and mixtures-thereof.

19. The element of claim 1 wherein said acid resistant inorganic substrate is at least as resistant as C-glass to the conditions present in said lead-acid battery.

20. The element of claim 17 wherein said fibers are in the form of a body of woven fibers having a porosity of about 60% to about 95%.

21. The element of claim 2 wherein said doped tin oxide coated inorganic substrate is at least partially coated with a coupling agent acting to improve the bonding of said doped tin oxide coating with said matrix.

22. The element of claim 2 wherein said matrix is a polymeric material having a polarity which is increased relative to polypropylene.

23. The element of claim 22 wherein said polymeric matrix material is a thermoset polymer.

24. The element of claim 6 wherein said fluoride ion is present in said coating in an amount in the range of about 0.01 mole% to about 20 mole%.

25. The element of claim 4 wherein said glass is coated with said doped tin oxide by a process comprising spraying a composition comprising a tin component, a dopant containing material and a solvent onto said glass which is maintained at slevated temperatures; and subjecting said sprayed glass to conditions effective to form said doped tin oxide coating on said sprayed glass.

26. The element of claim 25 wherein said glass is in the form of glass fibers, and said tin component comprises an inorganic tin component and said solvent comprises a hydroxyl group-containing solvent.

27. The element of claim 4 wherein said glass is coated with said doped tin oxide by a process comprising (1) contacting a vaporous composition comprising said tin component and a dopant-containing material with said glass; and (2) contacting said contacted glass with an oxygen-containing vaporous medium at conditions effective to form said doped tin oxide coating on said glass, provided that said glass is maintained in substantially constant three dimensional motion during steps (1) and (2).

28. A process for at least partially coating fibers with an electrically conductive, fluorine doped, tin-containing coating comprising (1) contacting a vaporous composition comprising at least one component of tin component and at least one fluorine-containing component with said fibers; and (2) contacting said contacted fibers with an oxygen-containing vaporous medium at conditions effective to form said electrically conductive fluorine doped, tin-containing coating on said fibers provided that said fibers are maintained in substantially constant three dimensional motion during steps (1) and (2).

29. The process of claim 28 wherein said fibers are glass fibers.

30. An article comprising an acid resistant inorganic substrate, other than electrically conductive doped tin oxide, in the form of fibers or particles coated with electrically conductive doped tin oxide, provided said acid resistant inorganic substrate has an increased acid resistance relative to E-glass.

31. The article of claim 30 which further comprises said coated substrate embedded in a matrix material.

32. The article of claim 31 wherein said matrix material is a polymeric material.

33. The article of claim 30 wherein said electrically conductive doped tin oxide is doped with fluoride ion.

34. The article of claim 33 wherein said acid resistant inorganic substrate is in the form of fibers.

35. The article of claim 33 wherein said acid resistant inorganic substrate in the form of particles.

36. The article of claim 34 wherein said fibers are in a form selected from the group consisting of fiber rovings, chopped fibers, single fibers, and woven fibers.

37. The article of claim 36 wherein said fibers comprise acid resistant glass.

38. The article of claim 30 wherein said acid resistant inorganic substrate is glass.

39. The article of claim 38 wherein said glass is at least as acid resistant as C-glass.

40. The article of claim 33 wherein the average thickness of said doped tin oxide coating on said fibers is in the range of about 10 microns or less.

41. The article of claim 36 wherein the average thickness of said doped tin oxide coating on said fibers is in the range of about 10 microns or less.

42. The article of claim 38 wherein the average thickness of said doped tin oxide coating on said fibers is in the range of about 10 microns or less.

43. The article of claim 33 wherein said fluoride ion is present in said coating in an amount effective to increase the electrical conductivity of said coating.

44. The article of claim 36 wherein said fluoride ion is present in said coating in an amount effective to increase the electrical conductivity of said coating.

45. The article of claim 37 wherein said fluoride ion is present in said coating in an amount effective to increase the electrical conductivity of said coating.

46. The article of claim 38 wherein said fluoride ion is present in said coating in an amount effective to increase the electrical conductivity of said coating.

47. The article of claim 33 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.

48. The article of claim 36 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.

49. The article of claim 38 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.

50. The article of claim 40 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.

51. The article of claim 42 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.

52. The article of claim 44 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.

53. The article of claim 47 wherein said polymeric matrix material is selected from the group consisting of polyolefins, poly vinyl polymers, epoxy-based polymers, phenol-formaldehyde polymers, polyesters and polyvinyl esters.

54. The article of claim 49 wherein said polymeric matrix material is selected from the group consisting of polyolefins, poly vinyl polymers, epoxy-based polymers, phenol-formaldehyde polymers, polyesters and polyvinyl esters.

55. The article of claim 47 wherein said coated substrate embedded in said polymeric matrix material is a fluid impervious conductive composite.

56. The article of claim 49 wherein said coated substrate embedded in said polymeric matrix material is a fluid impervious conductive composite.

57. The article of claim 47 wherein said polymeric matrix material has polarity which is larger than the polarity of polypropylene.

58. The article of claim 49 wherein said polymeric matrix material has polarity which is larger than the polarity of polypropylene.

59. The article of claim 47 wherein said polymeric matrix material is selected from the group consisting of polyethylene, polypropylene, polymethylpentane and mixtures thereof.

60. The article of claim 49 wherein said polymeric matrix material is selected from the group consisting of polyethylene, polypropylene, polymethylpentane and mixtures thereof.

61. The article of claim 35 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.

62. The article of claim 61 wherein said polymeric matrix material is selected from the group consisting of polyolefins, poly vinyl polymers, epoxy-based polymers, phenol-formaldehyde polymers, polyesters and polyvinyl esters.

63. The article of claim 61 wherein said polymeric matrix material has polarity which is larger than the polarity of polypropylene.

64. The article of claim 32 wherein said polymeric matrix material is selected from the group consisting of polyethylene, polypropylene, polymethylpentane and mixtures thereof.

65. An article consisting essentially of an acid resistant inorganic substrate, other than electrically conductive fluoride ion doped tin oxide, in the form of particles or fibers coated with electrically conductive, fluoride ion doped tin oxide, provided that said acid resistant inorganic substrate has an increased acid resistance relative to E-glass.

66. The article of claim 65 wherein said acid resistant inorganic substrate is in the form of particles.

67. The article of claim 65 wherein said acid resistant inorganic substrate is in the form of fibers.

68. The article of claim 65 wherein said acid resistant inorganic substrate is at least an acid resistant as C-glass.

69. The article of claim 35 wherein said particles comprise acid resistant glass.

70. The article of claim 35 wherein said particles comprise acid resistant glass at least as acid resistant as C-glass.

71. The article of claim 35 wherein the average thickness of said doped tin oxide coating on said particles is in the range of about 10 microns or less.

72. The article of claim 69 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.

73. The article of claim 70 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.

74. The article of claim 71 which further comprises said coated substrate at least partially embedded in a polymeric matrix material.