CA2097301A1 - Ionic conductors for solid oxide fuel cells - Google Patents
Ionic conductors for solid oxide fuel cellsInfo
- Publication number
- CA2097301A1 CA2097301A1 CA002097301A CA2097301A CA2097301A1 CA 2097301 A1 CA2097301 A1 CA 2097301A1 CA 002097301 A CA002097301 A CA 002097301A CA 2097301 A CA2097301 A CA 2097301A CA 2097301 A1 CA2097301 A1 CA 2097301A1
- Authority
- CA
- Canada
- Prior art keywords
- framework structure
- molecular framework
- substituted
- ionic conductor
- recited
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/14—Cells with non-aqueous electrolyte
- H01M6/18—Cells with non-aqueous electrolyte with solid electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
- H01M8/124—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
IONIC CONDUCTORS FOR SOLID OXIDE FUEL CELLS
Abstract of the Disclosure An electrolyte that operates at temperatures rang-ing from 600°C to 800°C is provided. The electrolyte con-ducts charge ionically as well as electronically. The ionic conductors include molecular framework structures having planes or channels large enough to transport oxides or hy-drated protons and having net-positive or net-negative charges. Representative molecular framework structures in-clude substituted aluminum phosphates, orthosilicates, silicoaluminates, cordierites, apatites, sodalites, and hollandites.
Abstract of the Disclosure An electrolyte that operates at temperatures rang-ing from 600°C to 800°C is provided. The electrolyte con-ducts charge ionically as well as electronically. The ionic conductors include molecular framework structures having planes or channels large enough to transport oxides or hy-drated protons and having net-positive or net-negative charges. Representative molecular framework structures in-clude substituted aluminum phosphates, orthosilicates, silicoaluminates, cordierites, apatites, sodalites, and hollandites.
Description
2~3973~i IONIC CONDUCTORS FOR SOLID OXIDE FUEL CELLS
CONTRACTUAL ORIGIN OF THE INVENTION
The United States has rights in this invention pursuant to contract No. W-31-109-ENG-38 between the United States Government and Argonne National Laboratory.
BACXGROUND OF_THE INVENTION
1. Field of__he InventiQn This invention relates to high-temperature ionic conductors for solid oxide fuel cells and more particularly to a class of ionic conductors stable at temperatures in the order of 600-800C and which are based on framewor~ struc-tures with net positive or negative charges along channels, tunnels or planes that are large enough to transport an oxide ion or a hydrated proton.
2. Background~of t~e_Invention Solid oxide fuel cells (SOFC's) can become one of the most durable and economical fuel systems for utility and transportation applications. Using solid electrolytes vir-tually eliminates corrosion reactions and alectrolyte losses that are common in liquid electrolyte fuel cells. Further-more, fuel processing for SOFC's is simpler and less expen-sive than other types of fuel cells.
Presently, SOFC's operate at temperatures of ap-proximately 1000C. The requirement of high-operating tem-peratures to attain adequate conductivity levels limits the -. " ` . ~ . . .
. ~ : .., .... . . . .~ ~ .. . .
. ~., . ~ ~ -2~973~1 number of materials available for SoFC fabrication as most materials become compromised thermally, chemically and me-chanically under these high temperature conditions. For ex-ample, the conductivity of the commonly used yttrium-stabilized zirconium oxide is lo~1 ohm~1 cm~1 at lO00 oc.
This conductivity decreases to 4 x 10-2 ohm~l cm~1 at 8000C.
Examples of yttria-stabilized zirconia electrolyte use at high temperatures can be found in U.S. Patent Nos.
4,476,1~6; 4,476,197 and 4,476,198, wherein the electrolytes facilitate ion transfer in electrochemical fuel cells operating in temperatures exceeding 1000C. As with the above-mentioned teachings, most fuel cells incorporating yttria-stabilized zirconia also rely on standard materials, such as zirconium-based cermet as constituents for the accompanying electrodes.
Presently known high-temperature electrolytes are oxide ion conductors that transport oxide ions by the va-cancy migration mechanism. In the yttrium-stabilized zirconium oxide system, a positive charge deficiency is created by substituting some trivalent yttrium ions for the tetravalent zirconium ions in the cation sublattice. To compensate for the positive charge deficiency, oxide ion vacancies are formed in the oxide sublattice. These vacancies provide the stopping-off points for hopping oxide ions. Aside from zirconium oxid~e, other presently known oxide ion conductors include CeO2, ThO2, HfO2, and Bi2o3~
A11 of these host oxides contain various types of dopants to enhance conductivity. When these materials crystallize in thP fluorite structure, oxygen ion vacancies can be found in the oxygen sublattice. These vacancies facilitate the mechanism for the hopping of oxides across the electrolyte thereby serving as the conduit for oxide ions through the t~ electrolyte.
- . , . ::,, ., ,,, ::
- . , , ::: .:.:;,:~: : ^: . - : : ~ :: :-:
., ; ,, ::
:-: . .
2Q~73 ~v~1 I
Operating a SOFC at more moderate temperatures, ' such as 600-800C, would allow much greater flexibility in engineering the fuel stack because ~etals could be used as interconnect and gasket materials. This would ultimately reduce the cost and open up new applications. With the pre-sent technology, it is not possible to lower the operating temperature of the fuel cell because the electrical resis-tance of the electrolyte increases exponentially as tempera-ture decreases. To decrease the operating temperature, a new electrolyte is required.
New electrolytes have been discovered to conduct - by a different mechanism; i.e. by transport of interst,itial ions instead of by vacancy migration. These oxides do not crystallize in the fluorite structure. They have framework structures which feature channels or planes that are large enough to transport an oxide ion or a hydrated proton through them. By creating net positive or negative charges on the framewor~, interstitial oxide ions (such as~ o2-) or hydrated protons (such as H30+) are able to pass through the channels and/or planas at a high rate.
SUMMARY OF THE INVENTION
It is an object of the present invention to pro-vide a class of electrolytes that overcomes many of the dis-advantages of prior art arrangements.
It is another object of the present invention to provide a class of electrolytes for transporting ions for use in utility and transportation applications. A feature of the present class of electrolytes is their use at temper-atures of between approximately 600-800OC. An advantage of the present invention is the ability to now incorporate a wider range of materials in the fabrication of solid oxide fuel cells.
. ;. . -: ` , :
.. `: . - `.
: . '. :: ' `-- ,,,' - ', ::
,. , - :. , . , ~
`. '' "` -' ,`' ' ~ ~ ~:
,: :,:: ` :` : ~.
:: : :::, .. ` . .~
2t~73 J~
Still another object of the pr~sent invention is to provide a highly conductive electrolyte at temperatures below 1000C. A feature of the invention is the incorpora-tion of a new class of ionic conductors consisting of molec-ular framework structures having channels or planes large enough to accommodate rapid transport of io~s. An advantage of the prasent invention is a high level of ion conductance at relatively low temperatures.
Yet another object of the present invention is its use as electrolytes in fuel cells, sensors or batteries. A
feature of the present invention is substituting some of the atoms on the molecular framework structure of the elec-trolytes with relatively high- or low-valent elements to create a net positive or net negative charge on the lattice.
An advantage of the present invention is the electrolyte's ability to attract and shuttle through the molecular frame-work structure ions such as oxides and hydrated protons.
In brief, the objects and advantages of the pre-sent invention are achieved by a solid oxide elèctrolyte.
An ionic conductor comprising molecular framework structures having net positive or net negative charges, or oxide-ion vacancies is utilized. These structures have channels or planes running through them that are large enough to transport ions such as o~ide ions or hydrated protons.
These molecular framework structures can be selected from, but are not limited to, the group consisting of substituted aluminum phosphates, orthosilicates, silicoaluminates, cancrinites, cordierites, apatites, sodalites, and hollandites.
BRIEF DESCRIPTION OF THE DRAWING
The present invention together with the above and other objects and advantages may best be understood from the I
-., ,, : :: :: : .: .: ~: : :
following detailed description of the embodiment of the in~ention illustrated in the drawings, wherein-FIG. 1 is a crystal structure plot ofAnthophyllite, which i5 a molecular framework structure utilized in the present invention;
FIG. 2 is a crystal structure plot of Apatite, which is a molecular framework structure utilized in the present invention;
FIG. 3 is a crystal structure plot of Cordierite, which is a molecular framework structure utilized in the present invention;
FIG. 4 is a crystal structure plot of Dumortierite, which is a molecular framework structure utilized in the present invention;
FIG. 5 is a crystal structure plot of Garnet, which is a molecular framework structure utilized in the present invention;
FIG. 6 is a crystal structure plot of LaP04 (monoclinic), which is a molecular framework structure utilized in the present invention:
FIG. 7 is a crystal structure plot of LaP04 (hexagonal), which is a molecular framework structure utilized in the present invention;
FIG. 8 is a crystal structure plot of Nepheline, whic:h is a molecular framework structure utilized in the present invention; and ..~ . , .~ ~ .
.
.
':
- . : .
: .
~9~3~ 1 -5a-FIG. 9 is a crystal structure plot of Sodalite, which is a molecular framework structure utili2ed in the present in~ention.
DETAILED DESC~IPTION OF THE INVENTION
The new electrolyt:es of the present invention described herein operate at temperatures ranging from 600- 800C to display conductivities higher than presently used ,;~- i l 20~73~1 solid oxide electrolytes operating at similar temperatures.
The invented class of ionic conduckors have molecular frame-work structures featuring channels or planes that are large enough to transport an oxide ion or a hydrated proton through them. When these structures have net positive or net negative charqes associated with them, by for example, substituting some atoms on the structures with relatively higher- or lower-valent elements, i.e., doping the material with aliovalent ions, these structures easily accommodate the shuttling of ions through the channels and/or planes.
Conductivity of the partially substituted elec-trolytes can be measured by ac impedance spectroscopy in ei-ther air or in a humidified hydrogen/oxygen cell, the latter serving to mimic fuel cell stack conditions. Also, by ~easuring the electromotive force between the two electrodes in humidified hydrogen/oxygen and comparing the experimental to the theoretical values, the ionic transference number can be determined as additional assurance that the conductivity occurring is ionic and not electronic as is the case with the "hopping" oxide ion phenomenon found in the prior art.
Unity is the theoretical value depicting a one-to-one ion transfer through the electrolyte.
Molecular Framework Material Tvpes A myriad of materials can be used as molecular framework structures which contain channels or pores in the crystal structure that are large enough to accommodate ions.
Structures associated with apatite [Ca5F(PO4)3], cordierite (Mg2A14Si5O18), berlinite (AlP04), cristobalite (sio2-AlPO4), and tridymite (SiO2-AlPO~) are representative of the framework structures.
A characteristic of framework materials is open channels or planes running parallel to a crystallographic :. : ,-,.,: : : : .:
. ::, . .~
. :: ~ : : . . .
- :, . - :: .,: . ~ ~:
20~73~
axis that are amenable to rapid ion migration. A crucial - element in choosing a molecular framework structure is the "openness" of the channels. Generally, such channels and planes having diameters of about 3 Angstroms (A) are accept-able. The openness of the channels and planes can be fur-ther quantified by counting the number of oxygen atoms in a 1000 cubic A volume. Table 1 lists the names of exemplary framework structures together with their openness character-istics and with reference to a corresponding FIGURE of the drawing.
Table 1. Structural Types and Openness of Electrolyte Materials Structural Formula of O enness~ FIG.
Type Parent Mineral 0~ ,1000A3 No.
Anthophyllite (HO)2Mg7Si8022 54.18 20 Apatite ca5F(PO4)3 4S.87a 2 Berlinite AlPO4 Cordierite Mg2A14sisOl8 46.36 3 Cristobalite (Si2~AlPo4) Dumortierite (Al,Fe)703(B03)(Sio4)3 64.29 4 Garnet Ca3A12(siO4)3 57.62 5 Framework L LaPO4 53.88 6 (hexagonal) Framswork L LaPO4 42.73 7 (monoclinic) 30 Nepheline KNa3(AlSiO4)4 43.66 8 Sodalite Na4Al3si3ol2cl 36.76a 9 Tridymite (Sio2-Alpo4) Olivineb Mg2Sio4 54.59 Hollandite 8aA12TiOl6 48.81 aHalide ion is included in oxide ion count.
bIncluded for the sake of co~parison. Olivine representS a close approximation to cubic close~packinq.
.
:: : .... : : :, .: .-:
. .:: ,.... . . :. :
2~973~3 ~
The openness listed in Table 1 for the various electrolyte materials is greater than that of ZrO2. Fur-thermore, most of the materials tested by the inventors and included in Table 1 are more open than the two well-known types of molecular packing, namely hexagonal and cubic close-packing. Cubic close-packing is represented by olivine in Table 1. The openness desirability is inversely proportional to the openness numbers found in Table 1 so that those compounds which have low numbers in the openness column are more desirable from an ion transport capability standpoint.
Al~0~. An example of a molecular framework having channels to accommodate ion flow-through i5 aluminum phos-phate (AlP04). AlP04 is isomorphous with sio2 and has simi-lar phases and structures as silica. In three of these structures, berlinite, cristobalite and tridymite, there is a central channel of abo~t three Angstroms (~) in diameter which is large enough to accommodate either an 0~ or H30+
ion. In native AlP04, the channel is unoccupied and the conductivity of aluminum phosphate is very low. Substitut-ing some of the aluminum or phosphorus with a higher-valent element, such as silicon or titanium, leads to either the formation of interstitial oxide ions or free ions. These same effects would be seen when substituting some of the phosphorous with hexavalent sulfur (as sulfate ion) or heptavalent chlorine (as perchlorate ion). Generally, with such substitutions, a net positive charge is put on the framework. This positive charge can be compensated by oxide ions in the channel.
Similarly, by substituting a lower-valent element, such as magnesium or zinc for the aluminum or silicon for the phosphorus, a net negative charge is created on the framework that can be compensated by the formation of ;. . , .: : :.
20973~1 vacancies or by positive ions in the channel. The formation of vacancies is a manifestation of the principle of le Chatelier wherein the equivale!nt of oxide ions leave the lattice structure of the oxide molecule to balance any negative charge resulting from substitution by lower-valance cations.
Some of the substituted aluminum phosphates that were used for testing were first made by dissolving aluminum ni-trate, the substitute metal nitrate, and ammonium phosphate in water and then precipitating the aluminum phosphate at a controlled pH of 5 to 1. The precipitate was then washed, dried and calcined. Finally, the resulting powder was pressed into pellets that were sintered to be~te~ than 90%
density at temperatures of 900-1600C.
Sulfate ion was incorporated into AlPO4 by dis-solving stoichiometric amounts of aluminum nitrate, aluminum sulfate and monobasic ammonium phosphate in water, drying and calcining at 800C overnight. A similar procedure was used to incorporate perchlorate ion.
Some of the AlPO4 compositions produced are listed in Table 2 below in isoelectronic formalism. This formalism is based on an analogy of AlP04 with SiO2. In illustrating the isoelectronic formalism, SiO2 is rewritten as ~SiO2][Sio2]. Replacing the first Si4+ with a lower-valent Al3+ and keeping the total oxygen content constant would - necessitate a negative charge on the fragment to maintain charge balance. This intermediate species is represented as [AlO2]-[SiO2]. Analogously, replacing the remaining 5i4+
atom with P5~~ would produce a fragment with a positive charge on it and would yield [AlO2]-[P02]+ for AlP04.
-; ~: - . .
:. ;.
I20~73 ~ ~
!Table 2. Doped AlP04 Compositionsl [A12] 0.g4[sio2]l.68~po2]2-52[oi ]0.84 [A12] 0.s4[Mgo2] 0.16~P2]~0 84[C102]3+o 32[i"]0 32 [A102]-[PO2]+o.g4[clo2]3 0.48[i ]0.64 -: [A102]-[P02]+o 84[so2]2+o 24[oi ]0.16 1 i represents interstitial oxide ion.
In accordance with a feature of the present inven-tion, AlP04 doped with silicon on the aluminum site and sul-fur on the phosphorus site has conductivities that are sev-eral orders of magnitude higher than those of native AlP04.
Separately, AlP04 that was doped with 12 Mg mole percent ex-hibited conductivities as high as 3 x 10-2 ohm~1cm~1.
Cordierite. These compounds have a general for-mula (Mg,Fe)2A14Si5018. Three aluminum atoms are in six-co-ordination and the fourth substitutes for one Si in a ring structure. Together, they produce an AlSi5018 group. There are channels within the ring structure in which water and other ions could be accommodated. Two compounds containing interstitial oxygen ions were synthesized, and are repre-sented by the following formulae:
Mg2A14Si4.5P0.518.25 and Mg2A13.6si5.40l8.2o The cordierite compounds were made by reacting stoichiometric amounts of the respective oxides and monoba-sic ammonium phosphate at 8630C for 10 hours. Pellets of the compounds were pressed and then sintered at 1200C for 18 hours.
.. I .
:: : :; ; : : :: :, , : .:
-: , , ... , ::.: :~ .. , . .. , .: . :
: : . : . : . .: :, : :: : , . . ..
-., ~.~ :::: ~ ,: - . .:
2 ~ ~ 7 3 ~
Aluminosilicophosphates. Aluminosilicophosphates ; represent another framework material type that may contain interstitial oxide ions. A formula for this type of com-pound is AlSi2P3Ol3. It is hexagonal in structure. This compound was made by solgel processing whereby 0.1 moles of aluminum nitrate and 0.1 moles of monobasic ammonium phos-phate were dissolved in a minimum amount of water (approximately 0.8 moles). 0.2 moles of tetraethoxysilane was then added to the mixture, along with a minimum amount of ethanol to make the mixture homogeneous. The reaction mixture was gently heated to make it a gel. The gel was dried at 130~C and ground into a paste with 0.1 moles of P2O5 in methylenechloride as the grinding medium. The dried paste was then calcined at 1000C for six days. X-ray diffraction analysis indicated that the calcined material contained about 80% of the desired compound.
Impedance measurements on this compound were con-ducted in a humidified H2lO2 cell, so as to mimic actual use conditions, and also as direct current measure~ents can yield inaccurate conductance values due to electrical polar-ization. Measurements in H2/O2 yielded a value of 10-6 ohm~
lcm~l for conductivity and 0.4 as the ionic transference number.
Apatites. Given the general structural apatite formula of [Ca5F(PO4)3~, solid solution apatite structures containing lone oxygen atoms have been produced depicted by the general formula SrS 5La4 s(P4)1.5(si4)4 5 oxygen atom sits in a central channel along the crystallo-graphic c-axis, free to migrate. The conductivity and ionic transference numbers for this material were measured in a humidified H2/O2 cell (water on both sides), and the results are depicted in Table 3, below:
~. ~
% ~ ~ r~
Table 3. Conductivity and Ionic Transference Data from Sr5 5La4 5(Po4)l.s(sio4)4~so TemperatureConductivity Transference Cohm~1cm~1 Number 8102.08 x 10-80.84 7062 . 27 X 10-7 0 . 83 6097.58 x lO-90.67 -Another strontium-containing apatite, having the formula Sr5~0H)(PO4)3, yielded even higher conductivity values. These values are listed in Table 4, below:
Table 4-. Conductivity data from Sr5(OH)~P04)3 Temperature Conductivlty Transference ocohm-lcm-l Number 4959.26 x 10-60.32 5782.78 x 10-50.42 68~7.52 ~ 10-50.47 7812.58 x 10-4o.Ss Framework L. Framework L has the following, gen-eralized, nonsubstituted formula LaPO4. When framework L is doped with 10~ E3i, it retains its hexagonal-to-monoclinic transition at low tPmperatures, with the relatively higher-valent Bismuth introducing vacancies into the lattice.
These materials exhibited conductivities of 1 x 10-3 ohm~l cm~l and an ionic transference number of 0.96 at 8000C in an H2/air cell.
Another way to stabilize the hexagonal form of framework L is to use a template around which L can crystal-lize. The si~plest te~plate for this use may be an oxide ion. As such, a pellet of L containing 5~ excess L-metal .. !
` ` : : : . ' . `~
2~7~
was made. The conduct:ivity and ionic transference data of this pellet was measured in a humidified, oxygen-gradiPnt cell, and is depicted in Table 5.
Table 5. Conductivity and Ionic Transference Data for 5%~
excess L-metal1 in Framework L
TemperatureConductlvity Transference C ohm~lcm-l Number 510 7.33 x 10-6 0.17 609 1.68 x 10-5 0.57 713 4.12 x 10-5 0.58 814 8.39 x 10-5 0.72 1 This material was found to be monoclinic by x-ray diffraction analysis.
In summary, the invented ionic conductors de-scribed in the foregoing detailed description can be used as electrolytes in solid oxide fuel cells, sensors or~batteries at temperatures ranging from 600C to 800C. For example, the exemplary molecular framewor~ structure compounds repre-sented by substituted aluminum phosphates can be used as proton or oxide ion conductors. Substituted alu~inum phos-phates can also be used as sodium or lithium conductors in batteries. Such substituted aluminum phosphates include the material commonly known as NASICON, which has the following general formula:
Al+XD2_X/3sixp3-xol2-2x/3 wherein A is an alkali metal, and D is a quadrivalent ion of group IV of the periodic table. A more complete description of NASICON can be found in U.S. Patent No.
4,465,744, which is incorporated herein by reference.
While the invention has been described with ref-erence to details of the illustrated embodiments, these de-. ,: , : , 2~73~
tails are not intended to limit the scope of the invention as defined in the appended claims.
'`'" :' 1 :-. ~
,.~ -, , . : :
:. ,
CONTRACTUAL ORIGIN OF THE INVENTION
The United States has rights in this invention pursuant to contract No. W-31-109-ENG-38 between the United States Government and Argonne National Laboratory.
BACXGROUND OF_THE INVENTION
1. Field of__he InventiQn This invention relates to high-temperature ionic conductors for solid oxide fuel cells and more particularly to a class of ionic conductors stable at temperatures in the order of 600-800C and which are based on framewor~ struc-tures with net positive or negative charges along channels, tunnels or planes that are large enough to transport an oxide ion or a hydrated proton.
2. Background~of t~e_Invention Solid oxide fuel cells (SOFC's) can become one of the most durable and economical fuel systems for utility and transportation applications. Using solid electrolytes vir-tually eliminates corrosion reactions and alectrolyte losses that are common in liquid electrolyte fuel cells. Further-more, fuel processing for SOFC's is simpler and less expen-sive than other types of fuel cells.
Presently, SOFC's operate at temperatures of ap-proximately 1000C. The requirement of high-operating tem-peratures to attain adequate conductivity levels limits the -. " ` . ~ . . .
. ~ : .., .... . . . .~ ~ .. . .
. ~., . ~ ~ -2~973~1 number of materials available for SoFC fabrication as most materials become compromised thermally, chemically and me-chanically under these high temperature conditions. For ex-ample, the conductivity of the commonly used yttrium-stabilized zirconium oxide is lo~1 ohm~1 cm~1 at lO00 oc.
This conductivity decreases to 4 x 10-2 ohm~l cm~1 at 8000C.
Examples of yttria-stabilized zirconia electrolyte use at high temperatures can be found in U.S. Patent Nos.
4,476,1~6; 4,476,197 and 4,476,198, wherein the electrolytes facilitate ion transfer in electrochemical fuel cells operating in temperatures exceeding 1000C. As with the above-mentioned teachings, most fuel cells incorporating yttria-stabilized zirconia also rely on standard materials, such as zirconium-based cermet as constituents for the accompanying electrodes.
Presently known high-temperature electrolytes are oxide ion conductors that transport oxide ions by the va-cancy migration mechanism. In the yttrium-stabilized zirconium oxide system, a positive charge deficiency is created by substituting some trivalent yttrium ions for the tetravalent zirconium ions in the cation sublattice. To compensate for the positive charge deficiency, oxide ion vacancies are formed in the oxide sublattice. These vacancies provide the stopping-off points for hopping oxide ions. Aside from zirconium oxid~e, other presently known oxide ion conductors include CeO2, ThO2, HfO2, and Bi2o3~
A11 of these host oxides contain various types of dopants to enhance conductivity. When these materials crystallize in thP fluorite structure, oxygen ion vacancies can be found in the oxygen sublattice. These vacancies facilitate the mechanism for the hopping of oxides across the electrolyte thereby serving as the conduit for oxide ions through the t~ electrolyte.
- . , . ::,, ., ,,, ::
- . , , ::: .:.:;,:~: : ^: . - : : ~ :: :-:
., ; ,, ::
:-: . .
2Q~73 ~v~1 I
Operating a SOFC at more moderate temperatures, ' such as 600-800C, would allow much greater flexibility in engineering the fuel stack because ~etals could be used as interconnect and gasket materials. This would ultimately reduce the cost and open up new applications. With the pre-sent technology, it is not possible to lower the operating temperature of the fuel cell because the electrical resis-tance of the electrolyte increases exponentially as tempera-ture decreases. To decrease the operating temperature, a new electrolyte is required.
New electrolytes have been discovered to conduct - by a different mechanism; i.e. by transport of interst,itial ions instead of by vacancy migration. These oxides do not crystallize in the fluorite structure. They have framework structures which feature channels or planes that are large enough to transport an oxide ion or a hydrated proton through them. By creating net positive or negative charges on the framewor~, interstitial oxide ions (such as~ o2-) or hydrated protons (such as H30+) are able to pass through the channels and/or planas at a high rate.
SUMMARY OF THE INVENTION
It is an object of the present invention to pro-vide a class of electrolytes that overcomes many of the dis-advantages of prior art arrangements.
It is another object of the present invention to provide a class of electrolytes for transporting ions for use in utility and transportation applications. A feature of the present class of electrolytes is their use at temper-atures of between approximately 600-800OC. An advantage of the present invention is the ability to now incorporate a wider range of materials in the fabrication of solid oxide fuel cells.
. ;. . -: ` , :
.. `: . - `.
: . '. :: ' `-- ,,,' - ', ::
,. , - :. , . , ~
`. '' "` -' ,`' ' ~ ~ ~:
,: :,:: ` :` : ~.
:: : :::, .. ` . .~
2t~73 J~
Still another object of the pr~sent invention is to provide a highly conductive electrolyte at temperatures below 1000C. A feature of the invention is the incorpora-tion of a new class of ionic conductors consisting of molec-ular framework structures having channels or planes large enough to accommodate rapid transport of io~s. An advantage of the prasent invention is a high level of ion conductance at relatively low temperatures.
Yet another object of the present invention is its use as electrolytes in fuel cells, sensors or batteries. A
feature of the present invention is substituting some of the atoms on the molecular framework structure of the elec-trolytes with relatively high- or low-valent elements to create a net positive or net negative charge on the lattice.
An advantage of the present invention is the electrolyte's ability to attract and shuttle through the molecular frame-work structure ions such as oxides and hydrated protons.
In brief, the objects and advantages of the pre-sent invention are achieved by a solid oxide elèctrolyte.
An ionic conductor comprising molecular framework structures having net positive or net negative charges, or oxide-ion vacancies is utilized. These structures have channels or planes running through them that are large enough to transport ions such as o~ide ions or hydrated protons.
These molecular framework structures can be selected from, but are not limited to, the group consisting of substituted aluminum phosphates, orthosilicates, silicoaluminates, cancrinites, cordierites, apatites, sodalites, and hollandites.
BRIEF DESCRIPTION OF THE DRAWING
The present invention together with the above and other objects and advantages may best be understood from the I
-., ,, : :: :: : .: .: ~: : :
following detailed description of the embodiment of the in~ention illustrated in the drawings, wherein-FIG. 1 is a crystal structure plot ofAnthophyllite, which i5 a molecular framework structure utilized in the present invention;
FIG. 2 is a crystal structure plot of Apatite, which is a molecular framework structure utilized in the present invention;
FIG. 3 is a crystal structure plot of Cordierite, which is a molecular framework structure utilized in the present invention;
FIG. 4 is a crystal structure plot of Dumortierite, which is a molecular framework structure utilized in the present invention;
FIG. 5 is a crystal structure plot of Garnet, which is a molecular framework structure utilized in the present invention;
FIG. 6 is a crystal structure plot of LaP04 (monoclinic), which is a molecular framework structure utilized in the present invention:
FIG. 7 is a crystal structure plot of LaP04 (hexagonal), which is a molecular framework structure utilized in the present invention;
FIG. 8 is a crystal structure plot of Nepheline, whic:h is a molecular framework structure utilized in the present invention; and ..~ . , .~ ~ .
.
.
':
- . : .
: .
~9~3~ 1 -5a-FIG. 9 is a crystal structure plot of Sodalite, which is a molecular framework structure utili2ed in the present in~ention.
DETAILED DESC~IPTION OF THE INVENTION
The new electrolyt:es of the present invention described herein operate at temperatures ranging from 600- 800C to display conductivities higher than presently used ,;~- i l 20~73~1 solid oxide electrolytes operating at similar temperatures.
The invented class of ionic conduckors have molecular frame-work structures featuring channels or planes that are large enough to transport an oxide ion or a hydrated proton through them. When these structures have net positive or net negative charqes associated with them, by for example, substituting some atoms on the structures with relatively higher- or lower-valent elements, i.e., doping the material with aliovalent ions, these structures easily accommodate the shuttling of ions through the channels and/or planes.
Conductivity of the partially substituted elec-trolytes can be measured by ac impedance spectroscopy in ei-ther air or in a humidified hydrogen/oxygen cell, the latter serving to mimic fuel cell stack conditions. Also, by ~easuring the electromotive force between the two electrodes in humidified hydrogen/oxygen and comparing the experimental to the theoretical values, the ionic transference number can be determined as additional assurance that the conductivity occurring is ionic and not electronic as is the case with the "hopping" oxide ion phenomenon found in the prior art.
Unity is the theoretical value depicting a one-to-one ion transfer through the electrolyte.
Molecular Framework Material Tvpes A myriad of materials can be used as molecular framework structures which contain channels or pores in the crystal structure that are large enough to accommodate ions.
Structures associated with apatite [Ca5F(PO4)3], cordierite (Mg2A14Si5O18), berlinite (AlP04), cristobalite (sio2-AlPO4), and tridymite (SiO2-AlPO~) are representative of the framework structures.
A characteristic of framework materials is open channels or planes running parallel to a crystallographic :. : ,-,.,: : : : .:
. ::, . .~
. :: ~ : : . . .
- :, . - :: .,: . ~ ~:
20~73~
axis that are amenable to rapid ion migration. A crucial - element in choosing a molecular framework structure is the "openness" of the channels. Generally, such channels and planes having diameters of about 3 Angstroms (A) are accept-able. The openness of the channels and planes can be fur-ther quantified by counting the number of oxygen atoms in a 1000 cubic A volume. Table 1 lists the names of exemplary framework structures together with their openness character-istics and with reference to a corresponding FIGURE of the drawing.
Table 1. Structural Types and Openness of Electrolyte Materials Structural Formula of O enness~ FIG.
Type Parent Mineral 0~ ,1000A3 No.
Anthophyllite (HO)2Mg7Si8022 54.18 20 Apatite ca5F(PO4)3 4S.87a 2 Berlinite AlPO4 Cordierite Mg2A14sisOl8 46.36 3 Cristobalite (Si2~AlPo4) Dumortierite (Al,Fe)703(B03)(Sio4)3 64.29 4 Garnet Ca3A12(siO4)3 57.62 5 Framework L LaPO4 53.88 6 (hexagonal) Framswork L LaPO4 42.73 7 (monoclinic) 30 Nepheline KNa3(AlSiO4)4 43.66 8 Sodalite Na4Al3si3ol2cl 36.76a 9 Tridymite (Sio2-Alpo4) Olivineb Mg2Sio4 54.59 Hollandite 8aA12TiOl6 48.81 aHalide ion is included in oxide ion count.
bIncluded for the sake of co~parison. Olivine representS a close approximation to cubic close~packinq.
.
:: : .... : : :, .: .-:
. .:: ,.... . . :. :
2~973~3 ~
The openness listed in Table 1 for the various electrolyte materials is greater than that of ZrO2. Fur-thermore, most of the materials tested by the inventors and included in Table 1 are more open than the two well-known types of molecular packing, namely hexagonal and cubic close-packing. Cubic close-packing is represented by olivine in Table 1. The openness desirability is inversely proportional to the openness numbers found in Table 1 so that those compounds which have low numbers in the openness column are more desirable from an ion transport capability standpoint.
Al~0~. An example of a molecular framework having channels to accommodate ion flow-through i5 aluminum phos-phate (AlP04). AlP04 is isomorphous with sio2 and has simi-lar phases and structures as silica. In three of these structures, berlinite, cristobalite and tridymite, there is a central channel of abo~t three Angstroms (~) in diameter which is large enough to accommodate either an 0~ or H30+
ion. In native AlP04, the channel is unoccupied and the conductivity of aluminum phosphate is very low. Substitut-ing some of the aluminum or phosphorus with a higher-valent element, such as silicon or titanium, leads to either the formation of interstitial oxide ions or free ions. These same effects would be seen when substituting some of the phosphorous with hexavalent sulfur (as sulfate ion) or heptavalent chlorine (as perchlorate ion). Generally, with such substitutions, a net positive charge is put on the framework. This positive charge can be compensated by oxide ions in the channel.
Similarly, by substituting a lower-valent element, such as magnesium or zinc for the aluminum or silicon for the phosphorus, a net negative charge is created on the framework that can be compensated by the formation of ;. . , .: : :.
20973~1 vacancies or by positive ions in the channel. The formation of vacancies is a manifestation of the principle of le Chatelier wherein the equivale!nt of oxide ions leave the lattice structure of the oxide molecule to balance any negative charge resulting from substitution by lower-valance cations.
Some of the substituted aluminum phosphates that were used for testing were first made by dissolving aluminum ni-trate, the substitute metal nitrate, and ammonium phosphate in water and then precipitating the aluminum phosphate at a controlled pH of 5 to 1. The precipitate was then washed, dried and calcined. Finally, the resulting powder was pressed into pellets that were sintered to be~te~ than 90%
density at temperatures of 900-1600C.
Sulfate ion was incorporated into AlPO4 by dis-solving stoichiometric amounts of aluminum nitrate, aluminum sulfate and monobasic ammonium phosphate in water, drying and calcining at 800C overnight. A similar procedure was used to incorporate perchlorate ion.
Some of the AlPO4 compositions produced are listed in Table 2 below in isoelectronic formalism. This formalism is based on an analogy of AlP04 with SiO2. In illustrating the isoelectronic formalism, SiO2 is rewritten as ~SiO2][Sio2]. Replacing the first Si4+ with a lower-valent Al3+ and keeping the total oxygen content constant would - necessitate a negative charge on the fragment to maintain charge balance. This intermediate species is represented as [AlO2]-[SiO2]. Analogously, replacing the remaining 5i4+
atom with P5~~ would produce a fragment with a positive charge on it and would yield [AlO2]-[P02]+ for AlP04.
-; ~: - . .
:. ;.
I20~73 ~ ~
!Table 2. Doped AlP04 Compositionsl [A12] 0.g4[sio2]l.68~po2]2-52[oi ]0.84 [A12] 0.s4[Mgo2] 0.16~P2]~0 84[C102]3+o 32[i"]0 32 [A102]-[PO2]+o.g4[clo2]3 0.48[i ]0.64 -: [A102]-[P02]+o 84[so2]2+o 24[oi ]0.16 1 i represents interstitial oxide ion.
In accordance with a feature of the present inven-tion, AlP04 doped with silicon on the aluminum site and sul-fur on the phosphorus site has conductivities that are sev-eral orders of magnitude higher than those of native AlP04.
Separately, AlP04 that was doped with 12 Mg mole percent ex-hibited conductivities as high as 3 x 10-2 ohm~1cm~1.
Cordierite. These compounds have a general for-mula (Mg,Fe)2A14Si5018. Three aluminum atoms are in six-co-ordination and the fourth substitutes for one Si in a ring structure. Together, they produce an AlSi5018 group. There are channels within the ring structure in which water and other ions could be accommodated. Two compounds containing interstitial oxygen ions were synthesized, and are repre-sented by the following formulae:
Mg2A14Si4.5P0.518.25 and Mg2A13.6si5.40l8.2o The cordierite compounds were made by reacting stoichiometric amounts of the respective oxides and monoba-sic ammonium phosphate at 8630C for 10 hours. Pellets of the compounds were pressed and then sintered at 1200C for 18 hours.
.. I .
:: : :; ; : : :: :, , : .:
-: , , ... , ::.: :~ .. , . .. , .: . :
: : . : . : . .: :, : :: : , . . ..
-., ~.~ :::: ~ ,: - . .:
2 ~ ~ 7 3 ~
Aluminosilicophosphates. Aluminosilicophosphates ; represent another framework material type that may contain interstitial oxide ions. A formula for this type of com-pound is AlSi2P3Ol3. It is hexagonal in structure. This compound was made by solgel processing whereby 0.1 moles of aluminum nitrate and 0.1 moles of monobasic ammonium phos-phate were dissolved in a minimum amount of water (approximately 0.8 moles). 0.2 moles of tetraethoxysilane was then added to the mixture, along with a minimum amount of ethanol to make the mixture homogeneous. The reaction mixture was gently heated to make it a gel. The gel was dried at 130~C and ground into a paste with 0.1 moles of P2O5 in methylenechloride as the grinding medium. The dried paste was then calcined at 1000C for six days. X-ray diffraction analysis indicated that the calcined material contained about 80% of the desired compound.
Impedance measurements on this compound were con-ducted in a humidified H2lO2 cell, so as to mimic actual use conditions, and also as direct current measure~ents can yield inaccurate conductance values due to electrical polar-ization. Measurements in H2/O2 yielded a value of 10-6 ohm~
lcm~l for conductivity and 0.4 as the ionic transference number.
Apatites. Given the general structural apatite formula of [Ca5F(PO4)3~, solid solution apatite structures containing lone oxygen atoms have been produced depicted by the general formula SrS 5La4 s(P4)1.5(si4)4 5 oxygen atom sits in a central channel along the crystallo-graphic c-axis, free to migrate. The conductivity and ionic transference numbers for this material were measured in a humidified H2/O2 cell (water on both sides), and the results are depicted in Table 3, below:
~. ~
% ~ ~ r~
Table 3. Conductivity and Ionic Transference Data from Sr5 5La4 5(Po4)l.s(sio4)4~so TemperatureConductivity Transference Cohm~1cm~1 Number 8102.08 x 10-80.84 7062 . 27 X 10-7 0 . 83 6097.58 x lO-90.67 -Another strontium-containing apatite, having the formula Sr5~0H)(PO4)3, yielded even higher conductivity values. These values are listed in Table 4, below:
Table 4-. Conductivity data from Sr5(OH)~P04)3 Temperature Conductivlty Transference ocohm-lcm-l Number 4959.26 x 10-60.32 5782.78 x 10-50.42 68~7.52 ~ 10-50.47 7812.58 x 10-4o.Ss Framework L. Framework L has the following, gen-eralized, nonsubstituted formula LaPO4. When framework L is doped with 10~ E3i, it retains its hexagonal-to-monoclinic transition at low tPmperatures, with the relatively higher-valent Bismuth introducing vacancies into the lattice.
These materials exhibited conductivities of 1 x 10-3 ohm~l cm~l and an ionic transference number of 0.96 at 8000C in an H2/air cell.
Another way to stabilize the hexagonal form of framework L is to use a template around which L can crystal-lize. The si~plest te~plate for this use may be an oxide ion. As such, a pellet of L containing 5~ excess L-metal .. !
` ` : : : . ' . `~
2~7~
was made. The conduct:ivity and ionic transference data of this pellet was measured in a humidified, oxygen-gradiPnt cell, and is depicted in Table 5.
Table 5. Conductivity and Ionic Transference Data for 5%~
excess L-metal1 in Framework L
TemperatureConductlvity Transference C ohm~lcm-l Number 510 7.33 x 10-6 0.17 609 1.68 x 10-5 0.57 713 4.12 x 10-5 0.58 814 8.39 x 10-5 0.72 1 This material was found to be monoclinic by x-ray diffraction analysis.
In summary, the invented ionic conductors de-scribed in the foregoing detailed description can be used as electrolytes in solid oxide fuel cells, sensors or~batteries at temperatures ranging from 600C to 800C. For example, the exemplary molecular framewor~ structure compounds repre-sented by substituted aluminum phosphates can be used as proton or oxide ion conductors. Substituted alu~inum phos-phates can also be used as sodium or lithium conductors in batteries. Such substituted aluminum phosphates include the material commonly known as NASICON, which has the following general formula:
Al+XD2_X/3sixp3-xol2-2x/3 wherein A is an alkali metal, and D is a quadrivalent ion of group IV of the periodic table. A more complete description of NASICON can be found in U.S. Patent No.
4,465,744, which is incorporated herein by reference.
While the invention has been described with ref-erence to details of the illustrated embodiments, these de-. ,: , : , 2~73~
tails are not intended to limit the scope of the invention as defined in the appended claims.
'`'" :' 1 :-. ~
,.~ -, , . : :
:. ,
Claims (18)
1. An ionic conductor of oxide ions or hydrated protons comprising:
a) a molecular framework structure having a net positive charge or a net negative charge or oxide-ion vacancies; and b) said molecular framework structure having channels large enough to transport said oxide ions or hydrated protons;
wherein the molecular framework structure is selected from the group consisting of substituted aluminum phosphates, substituted orthosilicates, substituted silicoaluminates, substituted apatites having the general formula Ca5F(PO4)3, substituted sodalites having the general formula Na4Al3Si3O12Cl, and combinations thereof.
a) a molecular framework structure having a net positive charge or a net negative charge or oxide-ion vacancies; and b) said molecular framework structure having channels large enough to transport said oxide ions or hydrated protons;
wherein the molecular framework structure is selected from the group consisting of substituted aluminum phosphates, substituted orthosilicates, substituted silicoaluminates, substituted apatites having the general formula Ca5F(PO4)3, substituted sodalites having the general formula Na4Al3Si3O12Cl, and combinations thereof.
2. An ionic conductor as recited in claim 1 wherein the channels in the molecular framework structure are about 3.ANG. in diameter or greater.
3. An ionic conductor as recited in claim 1 wherein the aluminum phosphates are selected from the group consisting of berlinites, tridymites, cristobalites, and combinations thereof.
4. An ionic conductor as recited in claim 1 wherein the orthosilicates are selected from the group consisting of:
Anthophyllite having the formula (HO)2Mg7Si8O22;
Dumortierite having the formula (Al,Fe)7O3(BO3) (SiO4)3;
Olivine having the formula Mg2SiO4; and Framework L having the general formula LaPO4.
Anthophyllite having the formula (HO)2Mg7Si8O22;
Dumortierite having the formula (Al,Fe)7O3(BO3) (SiO4)3;
Olivine having the formula Mg2SiO4; and Framework L having the general formula LaPO4.
5. An ionic conductor as recited in claim 1 wherein the silicoaluminates are selected from the group consisting of:
Nepheline having the formula KNa3(AlSiO4)4;
Garnet having the formula Ca3Al2(SiO4)3;
Cordierite having the formula Mg2Al4Si55O18; and Sodalite having the formula Na4Al3Si3O12Cl.
Nepheline having the formula KNa3(AlSiO4)4;
Garnet having the formula Ca3Al2(SiO4)3;
Cordierite having the formula Mg2Al4Si55O18; and Sodalite having the formula Na4Al3Si3O12Cl.
6. An ionic conductor as recited in claim 1 wherein the net positive charge on the molecular framework structure is provided by substituting some of the atoms of the molecular framework structure with relatively higher-valent elements.
7. An ionic conductor as recited in claim 6 wherein the higher-valent elements are selected from the group consisting of silicon, titanium, sulfur, chlorine, and combinations thereof.
8. An ionic conductor as recited in claim 1 wherein the net positive charge on said molecular framework structure is provided by substituting some of the aluminum of an aluminum phosphate of the molecular framework structure with a relatively higher-valent element selected from the group consisting of silicon, titanium and combinations thereof.
9. An ionic conductor as recited in claim 1 wherein the net positive charge on said molecular framework structure is provided by substituting some of the phosphorus of an aluminum phosphate molecular framework structure with a higher-valent element selected from the group consisting of aluminum, silicon and combinations thereof.
10. An ionic conductor as recited in claim 1 wherein the net negative charge on the molecular framework structure is provided by substituting some of the atoms of the molecular framework structure with relatively lower-valent elements.
11. An ionic conductor as recited in claim 10 wherein the lower-valent elements are selected from the group consisting of magnesium, zinc, silicon or combinations thereof.
12. An ionic conductor as recited in claim 1 wherein the net negative charge on said molecular framework structure is provided by substituting some of the aluminum of an aluminum phosphate molecular framework structure with a lower-valent element selected from the group consisting of magnesium, zinc, and combinations thereof.
13. An ionic conductor as recited in claim 1 wherein the net negative charge on said molecular framework structure is provided by substituting some of the phosphorus of an aluminum phosphate molecular framework structure with silicon.
14. An ionic conductor as recited in claim 1 wherein the ionic conductor is used as an electrolyte in fuel cells, sensors, or batteries.
15. An ionic conductor as recited in claim 1 wherein the substituted aluminum phosphates are used as a proton, vacancy or oxide ion conductor.
16. An electrolyte for an electrochemical fuel cell comprising:
a molecular framework structure having a net positive charge or a net negative charge;
said molecular framework structure having channels large enough to transport oxide ions or hydrated protons; and said molecular framework structure being thermodynamically stable at fuel cell operating temperatures of less than 800°C; and said molecular framework structure is selected from the group consisting of substituted aluminum phosphates, substituted orthosilicates, substituted silicoaluminates, substituted apatites having the general formula Ca5F(PO4)3, substituted sodalites having the general formula Na4Al3Si3O12Cl, cancrinites, cordierites and combinations thereof.
a molecular framework structure having a net positive charge or a net negative charge;
said molecular framework structure having channels large enough to transport oxide ions or hydrated protons; and said molecular framework structure being thermodynamically stable at fuel cell operating temperatures of less than 800°C; and said molecular framework structure is selected from the group consisting of substituted aluminum phosphates, substituted orthosilicates, substituted silicoaluminates, substituted apatites having the general formula Ca5F(PO4)3, substituted sodalites having the general formula Na4Al3Si3O12Cl, cancrinites, cordierites and combinations thereof.
17. An electrolyte as recited in claim 16 wherein the net positive charge or net negative charge on the molecular framework structure is provided by substituting some of the atoms of the molecular framework structure with relatively higher-valent or lower-valent elements.
18. A fuel cell having an anode and a cathode separated by a solid, ionic conductor of oxide ions or hydrated protons, said solid ionic conductor comprising a molecular framework structure having a net positive charge, a net negative charge or oxide ion vacancies;
-19a-said molecular framework structure having channels large enough to transport said oxide ions or hydrated protons, wherein said molecular framework structure is selected from the group consisting of substituted aluminum phosphates, substituted orthosilicates, substituted silicoaluminates, substituted apatites having the general formula Ca5F(PO4)3, substituted sodalites having the general formula Na4Al3Si3O12Cl, and combinations thereof.
-19a-said molecular framework structure having channels large enough to transport said oxide ions or hydrated protons, wherein said molecular framework structure is selected from the group consisting of substituted aluminum phosphates, substituted orthosilicates, substituted silicoaluminates, substituted apatites having the general formula Ca5F(PO4)3, substituted sodalites having the general formula Na4Al3Si3O12Cl, and combinations thereof.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/777,955 US5232794A (en) | 1991-10-17 | 1991-10-17 | Ionic conductors for solid oxide fuel cells |
| US777,955 | 1991-10-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2097301A1 true CA2097301A1 (en) | 1993-04-18 |
Family
ID=25111819
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002097301A Abandoned CA2097301A1 (en) | 1991-10-17 | 1992-09-30 | Ionic conductors for solid oxide fuel cells |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5232794A (en) |
| EP (1) | EP0567640A4 (en) |
| JP (1) | JPH06503918A (en) |
| CA (1) | CA2097301A1 (en) |
| WO (1) | WO1993008613A1 (en) |
Families Citing this family (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0763864A1 (en) * | 1995-09-13 | 1997-03-19 | Kabushiki Kaisha Meidensha | High temperature solid electrolyte fuel cell |
| US6203946B1 (en) * | 1998-12-03 | 2001-03-20 | Valence Technology, Inc. | Lithium-containing phosphates, method of preparation, and uses thereof |
| US5871866A (en) * | 1996-09-23 | 1999-02-16 | Valence Technology, Inc. | Lithium-containing phosphates, method of preparation, and use thereof |
| US20020192137A1 (en) * | 2001-04-30 | 2002-12-19 | Benjamin Chaloner-Gill | Phosphate powder compositions and methods for forming particles with complex anions |
| US6030718A (en) * | 1997-11-20 | 2000-02-29 | Avista Corporation | Proton exchange membrane fuel cell power system |
| US6096449A (en) * | 1997-11-20 | 2000-08-01 | Avista Labs | Fuel cell and method for controlling same |
| US6153333A (en) | 1999-03-23 | 2000-11-28 | Valence Technology, Inc. | Lithium-containing phosphate active materials |
| US7001690B2 (en) | 2000-01-18 | 2006-02-21 | Valence Technology, Inc. | Lithium-based active materials and preparation thereof |
| US6528033B1 (en) | 2000-01-18 | 2003-03-04 | Valence Technology, Inc. | Method of making lithium-containing materials |
| US6387568B1 (en) | 2000-04-27 | 2002-05-14 | Valence Technology, Inc. | Lithium metal fluorophosphate materials and preparation thereof |
| US8057769B2 (en) * | 2000-04-27 | 2011-11-15 | Valence Technology, Inc. | Method for making phosphate-based electrode active materials |
| US6777132B2 (en) * | 2000-04-27 | 2004-08-17 | Valence Technology, Inc. | Alkali/transition metal halo—and hydroxy-phosphates and related electrode active materials |
| US7524584B2 (en) * | 2000-04-27 | 2009-04-28 | Valence Technology, Inc. | Electrode active material for a secondary electrochemical cell |
| US6964827B2 (en) * | 2000-04-27 | 2005-11-15 | Valence Technology, Inc. | Alkali/transition metal halo- and hydroxy-phosphates and related electrode active materials |
| US7326480B2 (en) * | 2000-05-17 | 2008-02-05 | Relion, Inc. | Fuel cell power system and method of controlling a fuel cell power system |
| US6468682B1 (en) | 2000-05-17 | 2002-10-22 | Avista Laboratories, Inc. | Ion exchange membrane fuel cell |
| US6645452B1 (en) * | 2000-11-28 | 2003-11-11 | Valence Technology, Inc. | Methods of making lithium metal cathode active materials |
| KR100666820B1 (en) * | 2002-10-22 | 2007-01-09 | 주식회사 엘지화학 | Mea consisting of solid electrolyte membrane made of one or plural kinds of layered silicate minerals or intercalation compounds of the layered silicate minerals, fuel cell and electrochemical cell including the same, and method of preparing solid electrolyte membrane for fuel cell by using one or plural kinds of layered silicate minerals or intercalation compounds of the layered silicate minerals |
| US20070026285A1 (en) * | 2005-07-28 | 2007-02-01 | Wang Da Y | Proton conducting solid oxide electrolytes, electrochemical cells utilizing the proton conducting materials and methods of making the same |
| JP5949124B2 (en) * | 2012-05-11 | 2016-07-06 | 富士通株式会社 | Ionic conductor and secondary battery |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL294315A (en) * | 1962-06-27 | 1900-01-01 | ||
| US4477541A (en) * | 1982-12-22 | 1984-10-16 | The United States Of America As Represented By The United States Department Of Energy | Solid electrolyte structure |
| US4462891A (en) * | 1983-02-07 | 1984-07-31 | Lawless William N | Oxygen sensor and high temperature fuel cells |
| US4476196A (en) * | 1983-10-12 | 1984-10-09 | The United States Of America As Represented By The United States Department Of Energy | Solid oxide fuel cell having monolithic cross flow core and manifolding |
| US4476198A (en) * | 1983-10-12 | 1984-10-09 | The United States Of America As Represented By The United States Department Of Energy | Solid oxide fuel cell having monolithic core |
| US4476197A (en) * | 1983-10-12 | 1984-10-09 | The United States Of America As Represented By The United States Department Of Energy | Integral manifolding structure for fuel cell core having parallel gas flow |
| DE3583150D1 (en) * | 1984-10-23 | 1991-07-11 | Mitsubishi Heavy Ind Ltd | SOLID ELECTROLYTE FUEL CELL AND METHOD FOR THE PRODUCTION THEREOF. |
| US4702971A (en) * | 1986-05-28 | 1987-10-27 | Westinghouse Electric Corp. | Sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells |
| DE3837814C1 (en) * | 1988-11-08 | 1989-11-23 | Mtu Friedrichshafen Gmbh |
-
1991
- 1991-10-17 US US07/777,955 patent/US5232794A/en not_active Expired - Fee Related
-
1992
- 1992-09-30 WO PCT/US1992/008167 patent/WO1993008613A1/en not_active Application Discontinuation
- 1992-09-30 CA CA002097301A patent/CA2097301A1/en not_active Abandoned
- 1992-09-30 JP JP5507685A patent/JPH06503918A/en active Pending
- 1992-09-30 EP EP19930908774 patent/EP0567640A4/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| WO1993008613A1 (en) | 1993-04-29 |
| US5232794A (en) | 1993-08-03 |
| JPH06503918A (en) | 1994-04-28 |
| EP0567640A1 (en) | 1993-11-03 |
| EP0567640A4 (en) | 1994-11-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2097301A1 (en) | Ionic conductors for solid oxide fuel cells | |
| Adachi et al. | Fast Li⊕ conducting ceramic electrolytes | |
| Nomura et al. | Electrical conduction behavior in (La0. 9Sr0. 1) MIIIO3− δ (MIII= Al, Ga, Sc, In, and Lu) perovskites | |
| Iwahara et al. | Effect of ionic radii of dopants on mixed ionic conduction (H++ O2−) in BaCeO3-based electrolytes | |
| EP2900594B1 (en) | High conductivity nasicon electrolyte for room temperature solid- state sodium ion batteries | |
| Huang et al. | Protonic conduction in the single crystals of Y-doped SrZrO3 | |
| Guggilla et al. | Crystal chemical characterization of the mixed conductor Sr (Fe, Co) 1.5 O y exhibiting unusually high oxygen permeability | |
| JP6448020B2 (en) | Electrical conductor | |
| JP2001307546A (en) | Ionic conductor | |
| US5213911A (en) | Solid-oxide fuel cell electrolyte | |
| Bloom et al. | Oxide-ion conductivity of bismuth aluminates | |
| Collongues et al. | Superionic conducting oxides | |
| Esaka et al. | Oxide ion and electron mixed conduction in the fluorite-type cubic solid solution in the system Bi2O3-Tb2O3. 5 | |
| JP2864928B2 (en) | Mixed ionic conductor | |
| Idemoto et al. | Determination of thermodynamic data of Ln1. 85Ce0. 15CuO4 and Ln2CuO4 (Ln= Nd, Sm, Eu) by the EMF method | |
| CA2516809C (en) | Mixed ionic conductor | |
| US7125622B2 (en) | Method of producing oxide ion conductor | |
| Ruiz‐Bustos et al. | On the stability of Sr‐doped La2CuO4 against different electrolytes for IT‐SOFCs | |
| Krumpelt et al. | Ionic conductors for solid oxide fuel cells | |
| Tsuji et al. | Electrical conduction in BaThO3 doped with Y2O3 | |
| JP3877809B2 (en) | Proton conductive ceramics | |
| Tsai et al. | Stability of Bi2O3-based ionic conductor and its application on composite cathode | |
| Li et al. | Influences of ZrO2 content on microstructural and ionic conductivity of Li1. 4Al0. 4Ti1. 6 (PO4) 3 solid-state electrolytes | |
| Porras-Vázquez et al. | A new family of oxide ion conductors based on tricalcium oxy-silicate | |
| Noviyanti et al. | Conductivity of Lanthanum Silicate Apatite Derived from Rice Husk |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |