CA1245279A - Electrochemical cell - Google Patents
Electrochemical cellInfo
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- CA1245279A CA1245279A CA000482100A CA482100A CA1245279A CA 1245279 A CA1245279 A CA 1245279A CA 000482100 A CA000482100 A CA 000482100A CA 482100 A CA482100 A CA 482100A CA 1245279 A CA1245279 A CA 1245279A
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- liquid electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
- H01M10/39—Accumulators not provided for in groups H01M10/05-H01M10/34 working at high temperature
-
- 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
- Y02E60/10—Energy storage using batteries
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- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Inorganic Chemistry (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
ABSTRACT
The invention relates to a rechargeable high temperature electrochemical cell having a molten sodium anode, a molten halide salt liquid electrolyte, a compatible cathode in contact with the liquid electrolyte, and a beta-alumina solid electrolyte between the anode and liquid electrolyte and isolating them from each other. The liquid electrolyte is non-acidic and contains sodium cations as its only alkali metal cations, aluminium cations and chloride anions and is doped with fluoride anions to combat progressively increasing internal resistance of the cell associated with cyclic charging and discharging thereof.
The invention relates to a rechargeable high temperature electrochemical cell having a molten sodium anode, a molten halide salt liquid electrolyte, a compatible cathode in contact with the liquid electrolyte, and a beta-alumina solid electrolyte between the anode and liquid electrolyte and isolating them from each other. The liquid electrolyte is non-acidic and contains sodium cations as its only alkali metal cations, aluminium cations and chloride anions and is doped with fluoride anions to combat progressively increasing internal resistance of the cell associated with cyclic charging and discharging thereof.
Description
THIS INVENTION relates to an e1ectrochemical cell. In particular the inventior, relates to a high temperature rechargeable electrochemical cel1 and to a method of resisting a progressive increase in the internal resistance in an electrochemical cell as it is cyclically charged and discharyed.
According to the invention there is provided a rechargeable high temperature electrochemical cell which comprises a sodium anode which is molten at the operating temperature of the cell, a molten halide salt liquid electrolyte which is also molten at the operating temperature of the cell, a compatible cathode which is in contact with the liquid electrolyte and, between the anode and the liquid electrolyte and isolating the anode from the liquid electrolyte, a beta-alumina solid electrolyte, the molten salt electrolyte comprising sodium cations as the only alkali metal cations therein, aluminium cations, chloride anions and fluoride anions, the liquid electrolyte with the cell in its fully charged state being capable of representation as a mixture containing AlC13, NaCl and NaF in which the molar proportion of AlC13 is no greater than the molar proportion of sodium halide.
~, ~
According to the invention there is provided a rechargeable high temperature electrochemical cell which comprises a sodium anode which is molten at the operating temperature of the cell, a molten halide salt liquid electrolyte which is also molten at the operating temperature of the cell, a compatible cathode which is in contact with the liquid electrolyte and, between the anode and the liquid electrolyte and isolating the anode from the liquid electrolyte, a beta-alumina solid electrolyte, the molten salt electrolyte comprising sodium cations as the only alkali metal cations therein, aluminium cations, chloride anions and fluoride anions, the liquid electrolyte with the cell in its fully charged state being capable of representation as a mixture containing AlC13, NaCl and NaF in which the molar proportion of AlC13 is no greater than the molar proportion of sodium halide.
~, ~
2~
In this specification beta-alumina is used broadly, to include all phases of sodium-ion conductiny beta-alumina such as beta" alumina.
During discharge of the cell, sodium halide is formed at the cathode. This means that, if the abovedescribed constraints for the composition of the li4uid electrolyte are observed, the liquid electrolyte will at no staye of the charye/discharge cycle become on average AlC13-rich, ie the molar proportion of AlC13 in the liquid electrolyte will never exceed that of the sodium halide. This means that at no stage in the cell cycle should there in principle be any free AlC13 in the liquid electrolyte.
The proportion of NaF in the liquid electrolyte may be between 2~ and 25% on a molar basis, preferably between 10% and 20% on a molar basis, and typically 10 - 15%.
In one embodiment of the invention the ratio between the AlC13 and the sodium halide on a molar basis in the liquid electrolyte may be 1:1 when the cell is fully charyed, the molar proportion of chloride ions in the liquid electrolyte being yreater than the molar proportion of fluoride ions therein.
In another embodiment of the invention the ratio between the AlC13 and NaCl on a molar basis in the liquid electrolyte may be 1:1 when the cell is fully charged.
~4~79 The active cathode material in the fully charged cell may be a transition metal halide selected from the group comprising FeC12, NiC12, CoC12, CrCl~, ~lnC12 and mixtures thereof. Of these, FeC12, NiC12 and mixtures thereof are preferred, particularly FeC12.
Instead, the active cathode material in the fully charged cell may comprise a chlorinated intermediate refractory hard metal compound, the intermediate refractory hard metal compound being selected from the group comprising the carbides, nitrides, phosphides, borides and silicides, or mixtures thereof, of the group of transition metals comprising iron, nickel, cobalt, chromium, manganese and mixtures thereof. Cathodes of this type, particularly those comprising Fe3c are described in substantial detail in the Applicant's United States patent No. 4 288 506. Carbides oF alloys of iron and nickel have also been found by the Applicant to be effective.
Typically the molten salt electrolyte will be a sodium aluminium chloride electrolyte, doped with a proportion of sodium fluoride, which is less, on a molar basis, than the proportion of sodium chloride in the electrolyte. The Applicant has found that the prime and unexpected advantage of the present invention is that, when compared with the same cell with substantially the same liquid electrolyte, except that the electrolyte is not doped with sodium fluoride, but comprises only sodium aluminium 5 ~ Z~279 chloride made up of a mixture of AlC13 and NaCl, eg in a 1 1 mole ratio when the cell is fully charged so that it can be expressed as NaAlC14, tnere is a substantially reduced rate of increase in the internal resistance of the cell when it is put throush a number of charge/discharge cycles.
The invention accordinsly extends, in a rechargeable high temperature electrochemical cell comprising a sodium anode which is molten at the operating temperature of the cell, a molten salt liquid electrolyte which is also liquid at the operatiny temperature of the cell, a compatible cathode which is in contact with the liquid electrolyte and~ between the anode and the liquid electrolyte and isolating the anode from the liquid electrolyte, a beta-alumina solid electrolyte, the liquid electrolyte comprising sodium cations as the only alkali metal cations therein, aluminium cations and chloride anions, to the method of resisting a progressive increase in the internal resistance in the cell as it is cyclically charged and discharged, which comprises doping the liquid electrolyte with a proportion of sodium fluoride so that the liquid electrolyte, with the cell in its fully charged condition, can be represented as a mixture containiny AlC13, NaCl and NaF in which ~he molar proportion of AlC13 is no greater than the molar proportion of sodium halide.
2~
Without being bound by theory, the Applicant belie~/es that the increase in internal resistance upon being put through a number of charge/discharge cycles sufferred by similar cells containiny no sodium fluoride dopant, can arise from the presence in the 1i4uid electrolyte of free or excess AlC13, possibly dissolved therein. Furthermore, when the cathode contains iron, there is a possibility of free or dissolved FeC13 or FeC12 in the liquid electrolyte. This free AlCl~, possibly reinforced by species such as free FeC12 or FeC13, or possible other analoyous transition metal chlorides, can attack the surface of the heta-alumina at the solid electrolyte/1i4uid electrolyte interface. If these dissolved species are reyarded as Lewis acids and the beta-alumina surface is regarded as a Lewis base, reaction between said acids and said base can lead to reaction products which block the free passage of sodium ions through the beta-alumina solid electrolyte surface at the solid electrolyle/1i4uid electrolyte interface, thereby increasing the cell's internal resistance.
It is believed by the Applicant, without being bound by theory, that the sodium fluoride dopant may reduce the quantity of any free AlC13 in the liquid electrolyte, and when the cathode contains iron, the sodium fluoride dopant may also suppress the activity of species such as AlC13, FeC12 and/or FeC13 in the li~uid electrolyte, either by varyiny the solubility thereof or by forming highly stable comp1exes therewith. Such complexes may ~2~5279 by their nature have a relatively reduced tendency to poison the beta-alumina surface. It i5 for this reason that a 1:1 mole ratio between AlC13 and sodium halide in the liquid electrolyte forms one of the preferred embodiments of the invention, because at this mole ratio the solubility of FeC12 therein is at a minimum.
The Applicant believes that similar considerations rnay apply when other transition metals such as those mentioned above are present in the cathode.
It is possible that the presence of fluoride ions in the liquid electrolyte may act to reduce the presence of any free AlC13 or other related acidic species, and of species such as FeC13 or the like transition metal chlorides, if transition metals are present in the cathode. This may be because the corresponding fluorides of the dissolved species, such as AlF3, FeF3 or the like may be less soluble than the chlorides in the melt and can tend to precipitate out, eg as AlF3, FeF3 or the like, or as partially exchanyed species such as AlClF2, FeClF2 or the like, which also have reduced solubility compared with the chlorides.
The invention will now be described in more detail with reference to the following illustrative Examples, Examples 1 and 2, in which, in Example 2:
Z4~279 The single Figure of the drawing shows a plot of cell resistance in Ohm cm2 against charge/discharge cycles through which the cells of Example 2 were taken.
: EXAMPLE 1 , To test the practicability of the invention, experiments were carried out adding increasing proportions of NaF to equ.imolar mixtures of NaCl and AlC13, and the melting points `
: were measured, the results being set out in the following table:
.
:
:
:
.
TABLE
ConstitUe~ Melting Point (C) AlCl3 NaCl NaF
~5 10 155 From the above table it appears that doping an equimo1ar AlCl3/NaCl mixture with NaF causes no unacceptable change in melting point.
In a comparative experiment, two substantially identical secondary or rechargeable electrochemical high temperature power storage cells were assembled according to the followiny configurations:
l. Na/beta-alumina/NaAlCl4/FeCl2 (on carbon) 2. Na/beta-alumina/NaAlX4/FeCl2 (on carbon) . .
` 1G ~a24~ 27~3 In cell No. 2, X comprised Cl ar,d F anions, the molar ratio of Cl :F being 32:1, the molar ratio of AlC13:NaCl:NaF in the 1i~uid electrolyte being 8:8:1 (ie expressed in mole % about 47:47:6). In both cells the sodium cations were the only alkali metal cations in the liquid electrolyte.
These two cells were charged and discharged up to about 140 cycles under identical conditions and values for cycle life against internal resistance are shown on the accompanyins drawing, which is a plot of internal resistance in Ohm cm2 during discharge against cycle life.
From the plot it can be seen that the internal resistance oF
cell No. 2 in accordance with the invention remained substantially constant over the first 140 cycles, and indeed continued constant up to about 230 cycles. In the case of cell no. 1 (the prior art control) the internal resistance rose progressively so that after about 140 cycles its internal resistance was approaching double that of the cell in accordance with the invention. Furthermore, the cell in accordance with the invention had, at all times, a lower internal resistance than that of the control.
It will be noted with regard to the Table in Example 1 above, that the sodium fluoride was in each case doped or added 2~9 into a mixture of AlC13 and NaCl having a 50:50 mole ratio, ie so that it can be expressed as NaAlC14. This procedure was dictated by practical considerations.
Thus, the Applicant has found that, to make a melt consisting of NaCl and AlC13 which is adequately pure and homogeneous for use as a liquid electrolyte in electrochemical cells of the type in question, the best way of proceeding is to mix AlC13 and NaCl starting materials together with the NaCl making up slishtly more than 50% on a molar basis, and to heat this mixture up to a temperature above 200C, eg in the region of 500C. There are several reasons for this.
First, it should be noted that, while it is in principle possible to have mixes of AlC13 and NaCl which are AlC13-rich, ie which contain more than 50 mole % AlC13~ the reverse is not true.
At the ternperatures in ~uestion, say below 500C, additional NaCl added to a mixture of AlC13 and NaCl which comprises a 50:50 mole ratio, does not lead to the melt's becoming NaCl-rich, the NaCl merely being insoluble therein. This means that any starting mixture of NaCl and AlC13 which contains more than 50 rnole % NaCl will result in a melt which has a 50:50 mole ratio between AlC13 and NaCl, the excess NaCl merely existing in solid form as a precipitate or the like which settles out from the melt.
~2~279 On the other hand, problems arise in fcrming a melt from a starting material which contains more than 50 mole % AlC13. The reason for this is that AlC13 sublimes at about 200C, and losses of AlC13 and vapour pressure problems can accordinyly arise with AlC13-rich starting mixtures, unless the melting takes place in an autoclave. The AlC13-rich melt obtained is furthermore acidic from a Lewis-acid point of view.
It follows that, to make a melt comprising a mixture of AlC13 and NaCl without employiny an autoclave and without any problems which can arise from AlC13 vapour pressure or acidity, it is easiest and most practical to start with a neutral 50:50 molar mix of AlC13 and NaCl. Indeed, to ensure that this mix is neutral and that the melt cbtained will have the desired 50:50 molar proportions, a slight excess of NaCl is conveniently employed, which will settle out from the supernatant melt.
It should also noted that AlC13, particularly that which is commercially available for large scale use, typically contains impurities, and can have impurities generated therein by polymerization-type changes to the AlC13 which can form complexes which in the context of melts for liquid electrolytes in electrochemical cells can be regarded as impurities. A starting mix comprising AlC13 containing such irr,purities and NaCl, with NaCl forming slightly more than half of the mix on a molar basis, is accordinyly heated to eg 500C, to obtain a relatively pure 24~2~
supernatant melt consistiny of AlC13 and NaCl in a 50:50 mole ratio. The excess NaCl and the impurities contained in or forrr,ed frolr, the AlC13 settle out. The relatively pure supernatant melt can then be used for the desired molten electrolyte in an electrochemical cell.
It should be noted, with regard to this melt, that additional NaCl added thereto will be insoluble therein and will merely settle out therefrom, but that additional AlC13 added thereto will dissolve and will result in AlC13-rich acldic melt.
As mentioned above, following this procedure avoids vapour pressure problems arising from sublirnation of AlC13 in the starting material, and the melt produced is neutral from a Lewis-acid point of view and is accordingly relatively easy to handle. In this regard it is to be noted that the heating, typically to about 500C, is always to a temperature of above 200C, so that vapour pressure problems can in principle arise when excess AlC13 is present.
For the abovP various reasons, it is accordingly most convenient to dope the NaF in accordance with the invention into a melt which comprises AlC13 and NaCl in a 50:50 mole ratio. This is the reason why the Table in Example 1 comprises equimolar amounts of AlC13 and NaCl, into which NaF is doped.
, 14 ~ 9 Starting with a 50:50 molar melt of AlC13 and l~aCl, initial doping with NaF results in precipitation of an at least roughly equivalent amount OT NaCl on a molar basis, the 50:50 mole ration being maintained, between aluminium halide on the one hand and sodium halide on the other. The volume of the sodium fluoride doped into the melt is approximately equal to the volume of the sodium chloride which precipitates out of the melt, so little volulne change takes place in the melt.
As increasing proportions of sodium fluoride are doped into a 50:50 molar AlC13/NaCl melt, more complex precipitates form and settle out, containing sodium and/or aluminium cations, and chloride and/or fluoride anions. The melt itself maintains its 50:50 ratio on a molar basis between aluminium halide and sodium halide, and it is possible to increase the molar proportion of sodium fluoride in the doped melt up to 20 to 30% on a molar basis or more. Ever-increasing proportions of the starting materials are lost in the precipitate which can be discarded if desired, or if retained in the liquid electrolyte in an electrochemical cell, it can in fact form part of the active cathode material. Thus for example, when a cell is loaded in its discharged sta~e, this can be done by forming an appropriate dry cathode powder mix of iron and sodium chloride and by then saturating this powder mix with molten salt electrolyte. ~hen sodium fluoride doping is employed, the sodium fluoride can form part of the dry powder mix, undoped 50:50 molar NaAlC14 being used to saturate the powder. In this case the ~ 2~79 sodium fluoride will dissolve in the 1i4uid electrolyte and the precipitate resulting therefrom, which will be predominantly sodium chloride, will form in the saturated powder mix in dispersed form.
The sodium chloride in the precipitate, which will be roughly equivalent on a molar basis to the sodium fluoride dopant employed, can then form part of the discharged active iron/sodium chloride mix, the amount of precipitate expected being taken into account in calculating the proportions or iron and sodium chloride in the initial dry powder mix.
Furthermore, as the abovementioned more complex precipitates containing aluminium cations are formed, the volume of precipitate formed starts materially to exceed the volume of sodium fluoride dopant added, so that the volume of melt remaining starts to become appreciably reduced.
While, in principle, any doping of sodium fluoride can reduce the rate of increase in in~ernal resistance of the cell in accordance with the invention, the applicant has found in tests that an effective mirlin1um proportion for the sodium fluoride, to improve cell life, is in the region of 2 - 3% on a molar basis. As far as the upper limit for doping the sodium fluoride is concerned, an excessive amount of sodium fluoride dopant will, for the above reasons, lead to the precipitation, which can become excessive, of the aforementioned insoluble species.
It is convenient simply to dope the 50:50 molar melt of AlC13/NaCl with NaF, and to charge the doped melt immediately into the cell. In this way the precipitates can form in the cell, and while in relatively low ~uantities these precipitates are harmless and amount at most to slight dead weight, excessive quantities of such precipitates can adversely affect the performance of the cell, both from the point of view of excessive dead weight and from the point of vierw of relatively reduced charging and discharginy rates obtainable.
Froln a practical point of view, balancing the various considerations mentioned above, and bearing in mind that excessive proportions of fluoride ions may increase the proportion of high melting point solids in the electrolyte to an unacceptable deyree, it appears that the most desirable proportion of sodium ~luoride dopant to be added, to provide a liquid electrolyte which can immediately be chargecl into a cell and will not contain excessive insoluble species, is in the region of 10 - 15% on a molar basis.
In other words, to a 50:50 molar AlC13/NaCl melt, 10 - 15% on a molar basis NaF will be added. A roughly equivalent molar amount of NaCl will become insoluble and precipitate therefrom, possibly containing some aluminium cations and fluoride anions, but the doped melt as a whole can be used in the electrochemical cell of the type in question, without the necessity for decanting the supernatant melt for use in the cell.
17 ~2~279 It should be noted in this reyard that, furthermore, following this procedure results in the presence of sodium chloride precipitate in insoluble forrn in the 1i4uid electrolyte melt in the cell, and this excess NaCl acts as a safety feature, so that when the cell is in its fully charged state there is always some sodium chloride in solid form present, thereby ensuring that the proportion of aluminium chloride in the molten salt electrolyte can never exceed 50% on a molar basis, so that the melt can never become acidic.
It should also be noted that, while there will yenerally be more chloride anions in the melt than ~luoride anions, possible situations can exist in accordance with the invention where the proportion of fluoride anions on a molar basis is greater than that of the chloride anions. Furthermore, dependiny on other considerations such as the desirability Gf obtainins a high proportion of fluoride anions in the solution, there may be situations where cations other than sodium and aluminium are present in the 1i4uid electrolyte (althouyh yenerally alkali metal cations other than sodium will be avoided as these will lower the conductivity of the beta-alumina), and the invention accordingly also contemplates this possibility.
The invention has the desirable effect that it obtains a substantial decrease in the rate at which the internal resistance of the cell rises when put through a substantial number of 1~ ~2~279 charge/discharge cycles. Furthermore, doping a sodium aluminium chloride molten salt electrolyte made up of an equimolar mixture of NaCl and AlC13 with sodium fluoride, while keeping the molar proportion of AlC13 in the mix no greater than the proportion of sodium halide and indeed no yreater than the proportion of NaCl, provides the unexpected feature that there is no unacceptable increase in melting point, at least until the NaF forms more than at least 20~ - 30% on a molar basis of the mix.
It is known that certain fluoride compounds of the metals in question such as cryolite (Na3AlF6) have a much higher melting point (about 1000C) than the corresponding chloride compounds (Na3AlC16 melts at 150C). Similarly AlF3 has a much hiyher rnelting point (about 990C) than AlC13. It should thus be expected that the addition of NaF, in the proportions demonstrated in the above table, to an equimolar NaCl/AlC13 melt, should cause substantial "~apid and ur,acceptable increase in melting point of the melt. On the contrary~ the additions of substantial proportions of NaF were found to be possible without raising the melting point to an unacceptable level, while in no substantial way adversely affecting cell performance while desirably reducing the rate of internal resistance increase, as described above.
19 ~ 2~7~
Finally, it should be emphasised that it is important that alkali metal cations other than sodium cations ey lithium or potassium cations, are not desirable in the li~uid electrolyte, as these alkali nletal cations ~/ill penetrate the beta-alumina at the beta-alumina/liquid electrolyte interface, leading to a rapid and unacceptable build-up of the internal resistance, and permanent and irreversible deterioration of the cell.
In this specification beta-alumina is used broadly, to include all phases of sodium-ion conductiny beta-alumina such as beta" alumina.
During discharge of the cell, sodium halide is formed at the cathode. This means that, if the abovedescribed constraints for the composition of the li4uid electrolyte are observed, the liquid electrolyte will at no staye of the charye/discharge cycle become on average AlC13-rich, ie the molar proportion of AlC13 in the liquid electrolyte will never exceed that of the sodium halide. This means that at no stage in the cell cycle should there in principle be any free AlC13 in the liquid electrolyte.
The proportion of NaF in the liquid electrolyte may be between 2~ and 25% on a molar basis, preferably between 10% and 20% on a molar basis, and typically 10 - 15%.
In one embodiment of the invention the ratio between the AlC13 and the sodium halide on a molar basis in the liquid electrolyte may be 1:1 when the cell is fully charyed, the molar proportion of chloride ions in the liquid electrolyte being yreater than the molar proportion of fluoride ions therein.
In another embodiment of the invention the ratio between the AlC13 and NaCl on a molar basis in the liquid electrolyte may be 1:1 when the cell is fully charged.
~4~79 The active cathode material in the fully charged cell may be a transition metal halide selected from the group comprising FeC12, NiC12, CoC12, CrCl~, ~lnC12 and mixtures thereof. Of these, FeC12, NiC12 and mixtures thereof are preferred, particularly FeC12.
Instead, the active cathode material in the fully charged cell may comprise a chlorinated intermediate refractory hard metal compound, the intermediate refractory hard metal compound being selected from the group comprising the carbides, nitrides, phosphides, borides and silicides, or mixtures thereof, of the group of transition metals comprising iron, nickel, cobalt, chromium, manganese and mixtures thereof. Cathodes of this type, particularly those comprising Fe3c are described in substantial detail in the Applicant's United States patent No. 4 288 506. Carbides oF alloys of iron and nickel have also been found by the Applicant to be effective.
Typically the molten salt electrolyte will be a sodium aluminium chloride electrolyte, doped with a proportion of sodium fluoride, which is less, on a molar basis, than the proportion of sodium chloride in the electrolyte. The Applicant has found that the prime and unexpected advantage of the present invention is that, when compared with the same cell with substantially the same liquid electrolyte, except that the electrolyte is not doped with sodium fluoride, but comprises only sodium aluminium 5 ~ Z~279 chloride made up of a mixture of AlC13 and NaCl, eg in a 1 1 mole ratio when the cell is fully charged so that it can be expressed as NaAlC14, tnere is a substantially reduced rate of increase in the internal resistance of the cell when it is put throush a number of charge/discharge cycles.
The invention accordinsly extends, in a rechargeable high temperature electrochemical cell comprising a sodium anode which is molten at the operating temperature of the cell, a molten salt liquid electrolyte which is also liquid at the operatiny temperature of the cell, a compatible cathode which is in contact with the liquid electrolyte and~ between the anode and the liquid electrolyte and isolating the anode from the liquid electrolyte, a beta-alumina solid electrolyte, the liquid electrolyte comprising sodium cations as the only alkali metal cations therein, aluminium cations and chloride anions, to the method of resisting a progressive increase in the internal resistance in the cell as it is cyclically charged and discharged, which comprises doping the liquid electrolyte with a proportion of sodium fluoride so that the liquid electrolyte, with the cell in its fully charged condition, can be represented as a mixture containiny AlC13, NaCl and NaF in which ~he molar proportion of AlC13 is no greater than the molar proportion of sodium halide.
2~
Without being bound by theory, the Applicant belie~/es that the increase in internal resistance upon being put through a number of charge/discharge cycles sufferred by similar cells containiny no sodium fluoride dopant, can arise from the presence in the 1i4uid electrolyte of free or excess AlC13, possibly dissolved therein. Furthermore, when the cathode contains iron, there is a possibility of free or dissolved FeC13 or FeC12 in the liquid electrolyte. This free AlCl~, possibly reinforced by species such as free FeC12 or FeC13, or possible other analoyous transition metal chlorides, can attack the surface of the heta-alumina at the solid electrolyte/1i4uid electrolyte interface. If these dissolved species are reyarded as Lewis acids and the beta-alumina surface is regarded as a Lewis base, reaction between said acids and said base can lead to reaction products which block the free passage of sodium ions through the beta-alumina solid electrolyte surface at the solid electrolyle/1i4uid electrolyte interface, thereby increasing the cell's internal resistance.
It is believed by the Applicant, without being bound by theory, that the sodium fluoride dopant may reduce the quantity of any free AlC13 in the liquid electrolyte, and when the cathode contains iron, the sodium fluoride dopant may also suppress the activity of species such as AlC13, FeC12 and/or FeC13 in the li~uid electrolyte, either by varyiny the solubility thereof or by forming highly stable comp1exes therewith. Such complexes may ~2~5279 by their nature have a relatively reduced tendency to poison the beta-alumina surface. It i5 for this reason that a 1:1 mole ratio between AlC13 and sodium halide in the liquid electrolyte forms one of the preferred embodiments of the invention, because at this mole ratio the solubility of FeC12 therein is at a minimum.
The Applicant believes that similar considerations rnay apply when other transition metals such as those mentioned above are present in the cathode.
It is possible that the presence of fluoride ions in the liquid electrolyte may act to reduce the presence of any free AlC13 or other related acidic species, and of species such as FeC13 or the like transition metal chlorides, if transition metals are present in the cathode. This may be because the corresponding fluorides of the dissolved species, such as AlF3, FeF3 or the like may be less soluble than the chlorides in the melt and can tend to precipitate out, eg as AlF3, FeF3 or the like, or as partially exchanyed species such as AlClF2, FeClF2 or the like, which also have reduced solubility compared with the chlorides.
The invention will now be described in more detail with reference to the following illustrative Examples, Examples 1 and 2, in which, in Example 2:
Z4~279 The single Figure of the drawing shows a plot of cell resistance in Ohm cm2 against charge/discharge cycles through which the cells of Example 2 were taken.
: EXAMPLE 1 , To test the practicability of the invention, experiments were carried out adding increasing proportions of NaF to equ.imolar mixtures of NaCl and AlC13, and the melting points `
: were measured, the results being set out in the following table:
.
:
:
:
.
TABLE
ConstitUe~ Melting Point (C) AlCl3 NaCl NaF
~5 10 155 From the above table it appears that doping an equimo1ar AlCl3/NaCl mixture with NaF causes no unacceptable change in melting point.
In a comparative experiment, two substantially identical secondary or rechargeable electrochemical high temperature power storage cells were assembled according to the followiny configurations:
l. Na/beta-alumina/NaAlCl4/FeCl2 (on carbon) 2. Na/beta-alumina/NaAlX4/FeCl2 (on carbon) . .
` 1G ~a24~ 27~3 In cell No. 2, X comprised Cl ar,d F anions, the molar ratio of Cl :F being 32:1, the molar ratio of AlC13:NaCl:NaF in the 1i~uid electrolyte being 8:8:1 (ie expressed in mole % about 47:47:6). In both cells the sodium cations were the only alkali metal cations in the liquid electrolyte.
These two cells were charged and discharged up to about 140 cycles under identical conditions and values for cycle life against internal resistance are shown on the accompanyins drawing, which is a plot of internal resistance in Ohm cm2 during discharge against cycle life.
From the plot it can be seen that the internal resistance oF
cell No. 2 in accordance with the invention remained substantially constant over the first 140 cycles, and indeed continued constant up to about 230 cycles. In the case of cell no. 1 (the prior art control) the internal resistance rose progressively so that after about 140 cycles its internal resistance was approaching double that of the cell in accordance with the invention. Furthermore, the cell in accordance with the invention had, at all times, a lower internal resistance than that of the control.
It will be noted with regard to the Table in Example 1 above, that the sodium fluoride was in each case doped or added 2~9 into a mixture of AlC13 and NaCl having a 50:50 mole ratio, ie so that it can be expressed as NaAlC14. This procedure was dictated by practical considerations.
Thus, the Applicant has found that, to make a melt consisting of NaCl and AlC13 which is adequately pure and homogeneous for use as a liquid electrolyte in electrochemical cells of the type in question, the best way of proceeding is to mix AlC13 and NaCl starting materials together with the NaCl making up slishtly more than 50% on a molar basis, and to heat this mixture up to a temperature above 200C, eg in the region of 500C. There are several reasons for this.
First, it should be noted that, while it is in principle possible to have mixes of AlC13 and NaCl which are AlC13-rich, ie which contain more than 50 mole % AlC13~ the reverse is not true.
At the ternperatures in ~uestion, say below 500C, additional NaCl added to a mixture of AlC13 and NaCl which comprises a 50:50 mole ratio, does not lead to the melt's becoming NaCl-rich, the NaCl merely being insoluble therein. This means that any starting mixture of NaCl and AlC13 which contains more than 50 rnole % NaCl will result in a melt which has a 50:50 mole ratio between AlC13 and NaCl, the excess NaCl merely existing in solid form as a precipitate or the like which settles out from the melt.
~2~279 On the other hand, problems arise in fcrming a melt from a starting material which contains more than 50 mole % AlC13. The reason for this is that AlC13 sublimes at about 200C, and losses of AlC13 and vapour pressure problems can accordinyly arise with AlC13-rich starting mixtures, unless the melting takes place in an autoclave. The AlC13-rich melt obtained is furthermore acidic from a Lewis-acid point of view.
It follows that, to make a melt comprising a mixture of AlC13 and NaCl without employiny an autoclave and without any problems which can arise from AlC13 vapour pressure or acidity, it is easiest and most practical to start with a neutral 50:50 molar mix of AlC13 and NaCl. Indeed, to ensure that this mix is neutral and that the melt cbtained will have the desired 50:50 molar proportions, a slight excess of NaCl is conveniently employed, which will settle out from the supernatant melt.
It should also noted that AlC13, particularly that which is commercially available for large scale use, typically contains impurities, and can have impurities generated therein by polymerization-type changes to the AlC13 which can form complexes which in the context of melts for liquid electrolytes in electrochemical cells can be regarded as impurities. A starting mix comprising AlC13 containing such irr,purities and NaCl, with NaCl forming slightly more than half of the mix on a molar basis, is accordinyly heated to eg 500C, to obtain a relatively pure 24~2~
supernatant melt consistiny of AlC13 and NaCl in a 50:50 mole ratio. The excess NaCl and the impurities contained in or forrr,ed frolr, the AlC13 settle out. The relatively pure supernatant melt can then be used for the desired molten electrolyte in an electrochemical cell.
It should be noted, with regard to this melt, that additional NaCl added thereto will be insoluble therein and will merely settle out therefrom, but that additional AlC13 added thereto will dissolve and will result in AlC13-rich acldic melt.
As mentioned above, following this procedure avoids vapour pressure problems arising from sublirnation of AlC13 in the starting material, and the melt produced is neutral from a Lewis-acid point of view and is accordingly relatively easy to handle. In this regard it is to be noted that the heating, typically to about 500C, is always to a temperature of above 200C, so that vapour pressure problems can in principle arise when excess AlC13 is present.
For the abovP various reasons, it is accordingly most convenient to dope the NaF in accordance with the invention into a melt which comprises AlC13 and NaCl in a 50:50 mole ratio. This is the reason why the Table in Example 1 comprises equimolar amounts of AlC13 and NaCl, into which NaF is doped.
, 14 ~ 9 Starting with a 50:50 molar melt of AlC13 and l~aCl, initial doping with NaF results in precipitation of an at least roughly equivalent amount OT NaCl on a molar basis, the 50:50 mole ration being maintained, between aluminium halide on the one hand and sodium halide on the other. The volume of the sodium fluoride doped into the melt is approximately equal to the volume of the sodium chloride which precipitates out of the melt, so little volulne change takes place in the melt.
As increasing proportions of sodium fluoride are doped into a 50:50 molar AlC13/NaCl melt, more complex precipitates form and settle out, containing sodium and/or aluminium cations, and chloride and/or fluoride anions. The melt itself maintains its 50:50 ratio on a molar basis between aluminium halide and sodium halide, and it is possible to increase the molar proportion of sodium fluoride in the doped melt up to 20 to 30% on a molar basis or more. Ever-increasing proportions of the starting materials are lost in the precipitate which can be discarded if desired, or if retained in the liquid electrolyte in an electrochemical cell, it can in fact form part of the active cathode material. Thus for example, when a cell is loaded in its discharged sta~e, this can be done by forming an appropriate dry cathode powder mix of iron and sodium chloride and by then saturating this powder mix with molten salt electrolyte. ~hen sodium fluoride doping is employed, the sodium fluoride can form part of the dry powder mix, undoped 50:50 molar NaAlC14 being used to saturate the powder. In this case the ~ 2~79 sodium fluoride will dissolve in the 1i4uid electrolyte and the precipitate resulting therefrom, which will be predominantly sodium chloride, will form in the saturated powder mix in dispersed form.
The sodium chloride in the precipitate, which will be roughly equivalent on a molar basis to the sodium fluoride dopant employed, can then form part of the discharged active iron/sodium chloride mix, the amount of precipitate expected being taken into account in calculating the proportions or iron and sodium chloride in the initial dry powder mix.
Furthermore, as the abovementioned more complex precipitates containing aluminium cations are formed, the volume of precipitate formed starts materially to exceed the volume of sodium fluoride dopant added, so that the volume of melt remaining starts to become appreciably reduced.
While, in principle, any doping of sodium fluoride can reduce the rate of increase in in~ernal resistance of the cell in accordance with the invention, the applicant has found in tests that an effective mirlin1um proportion for the sodium fluoride, to improve cell life, is in the region of 2 - 3% on a molar basis. As far as the upper limit for doping the sodium fluoride is concerned, an excessive amount of sodium fluoride dopant will, for the above reasons, lead to the precipitation, which can become excessive, of the aforementioned insoluble species.
It is convenient simply to dope the 50:50 molar melt of AlC13/NaCl with NaF, and to charge the doped melt immediately into the cell. In this way the precipitates can form in the cell, and while in relatively low ~uantities these precipitates are harmless and amount at most to slight dead weight, excessive quantities of such precipitates can adversely affect the performance of the cell, both from the point of view of excessive dead weight and from the point of vierw of relatively reduced charging and discharginy rates obtainable.
Froln a practical point of view, balancing the various considerations mentioned above, and bearing in mind that excessive proportions of fluoride ions may increase the proportion of high melting point solids in the electrolyte to an unacceptable deyree, it appears that the most desirable proportion of sodium ~luoride dopant to be added, to provide a liquid electrolyte which can immediately be chargecl into a cell and will not contain excessive insoluble species, is in the region of 10 - 15% on a molar basis.
In other words, to a 50:50 molar AlC13/NaCl melt, 10 - 15% on a molar basis NaF will be added. A roughly equivalent molar amount of NaCl will become insoluble and precipitate therefrom, possibly containing some aluminium cations and fluoride anions, but the doped melt as a whole can be used in the electrochemical cell of the type in question, without the necessity for decanting the supernatant melt for use in the cell.
17 ~2~279 It should be noted in this reyard that, furthermore, following this procedure results in the presence of sodium chloride precipitate in insoluble forrn in the 1i4uid electrolyte melt in the cell, and this excess NaCl acts as a safety feature, so that when the cell is in its fully charged state there is always some sodium chloride in solid form present, thereby ensuring that the proportion of aluminium chloride in the molten salt electrolyte can never exceed 50% on a molar basis, so that the melt can never become acidic.
It should also be noted that, while there will yenerally be more chloride anions in the melt than ~luoride anions, possible situations can exist in accordance with the invention where the proportion of fluoride anions on a molar basis is greater than that of the chloride anions. Furthermore, dependiny on other considerations such as the desirability Gf obtainins a high proportion of fluoride anions in the solution, there may be situations where cations other than sodium and aluminium are present in the 1i4uid electrolyte (althouyh yenerally alkali metal cations other than sodium will be avoided as these will lower the conductivity of the beta-alumina), and the invention accordingly also contemplates this possibility.
The invention has the desirable effect that it obtains a substantial decrease in the rate at which the internal resistance of the cell rises when put through a substantial number of 1~ ~2~279 charge/discharge cycles. Furthermore, doping a sodium aluminium chloride molten salt electrolyte made up of an equimolar mixture of NaCl and AlC13 with sodium fluoride, while keeping the molar proportion of AlC13 in the mix no greater than the proportion of sodium halide and indeed no yreater than the proportion of NaCl, provides the unexpected feature that there is no unacceptable increase in melting point, at least until the NaF forms more than at least 20~ - 30% on a molar basis of the mix.
It is known that certain fluoride compounds of the metals in question such as cryolite (Na3AlF6) have a much higher melting point (about 1000C) than the corresponding chloride compounds (Na3AlC16 melts at 150C). Similarly AlF3 has a much hiyher rnelting point (about 990C) than AlC13. It should thus be expected that the addition of NaF, in the proportions demonstrated in the above table, to an equimolar NaCl/AlC13 melt, should cause substantial "~apid and ur,acceptable increase in melting point of the melt. On the contrary~ the additions of substantial proportions of NaF were found to be possible without raising the melting point to an unacceptable level, while in no substantial way adversely affecting cell performance while desirably reducing the rate of internal resistance increase, as described above.
19 ~ 2~7~
Finally, it should be emphasised that it is important that alkali metal cations other than sodium cations ey lithium or potassium cations, are not desirable in the li~uid electrolyte, as these alkali nletal cations ~/ill penetrate the beta-alumina at the beta-alumina/liquid electrolyte interface, leading to a rapid and unacceptable build-up of the internal resistance, and permanent and irreversible deterioration of the cell.
Claims (11)
1. A rechargeable high temperature electrochemical cell which comprises a sodium anode which is molten at the operating temperature of the cell, a molten halide salt liquid electrolyte which is also molten at the operating temperature of the cell, a compatible cathode which is in contact with the liquid electrolyte and, between the anode and the liquid electrolyte and isolating the anode from the liquid electrolyte, a beta-alumina solid electrolyte, the molten salt electrolyte comprising sodium cations as the only alkali metal cations therein, aluminium cations, chloride anions and fluoride anions, the liquid electrolyte with the cell in its fully charged state being capable of representation as a mixture containing AlCl3, NaCl and NaF in which the molar proportion of AlCl3 is no greater than the molar proportion of sodium halide.
2. A cell as claimed in claim 1, in which the proportion of NaF in the liquid electrolyte is between 2% and 25% on a molar basis.
3. A cell as claimed in claim 2, in which the proportion of NaF in the liquid electrolyte is between 10% and 20% on a molar basis.
4. A cell as claimed in claim 1, in which the ratio between the AlCl3 and the sodium halide on a molar basis in the liquid electrolyte is 1:1 when the cell is fully charged, the molar proportion of chloride ions in the liquid electrolyte being greater than the molar proportion of fluoride ions therein.
5. A cell as claimed in claim 1, in which the ratio between the AlCl3 and NaCl on a molar basis in the liquid electrolyte is 1:1 when the cell is fully charged.
6. A cell as claimed in claim 1, in which the active cathode material in the fully charged cell is a transition metal halide selected from the group comprising FeCl2, NiCl2, CoCl2, CrCl2, MnCl2 and mixtures thereof.
7. A cell as claimed in claim 6, in which the active cathode material is selected from the group comprising FeCl2, NiCl2 and mixtures thereof.
8. A cell as claimed in claim 7, in which the active cathode material comprises FeCl2.
9. A cell as claimed in claim 1, in which the active cathode material comprises a chlorinated intermediate refractory hard metal compound, the interemediate refractory hard metal compound being selected from the group comprising the carbides, nitrides, phosphides, borides and silicides, or mixtures thereof, of the group of transition metals comprising iron, nickel, cobalt, chromium, manganese and mixtures thereof.
10. A cell as claimed in claim 9, in which the refractory hard metal compound is selected from the group comprising Fe3C and carbides of alloys of iron and nickel.
11. In a rechargeable high temperature electrochemical cell comprising a sodium anode which is molten at the operating temperature of the cell, a molten salt liquid electrolyte which is also liquid at the operating temperature of the cell, a compatible cathode which is in contact with the liquid electrolyte and, between the anode and the liquid electrolyte and isolating the anode from the liquid electrolyte, a beta-alumina solid electrolyte, the liquid electrolyte comprising sodium cations as the only alkali metal cations therein, aluminium cations and chloride anions, the method of resisting a progressive increase in the internal resistance in the cell as it is cyclically charged and discharged, which comprises doping the liquid electrolyte with a proportion of sodium fluoride so that the liquid electrolyte, with the cell in its fully charged condition, can be represented as a mixture containing AlCl3, NaCl and NaF in which the molar proportion of AlCl3 is no greater than the molar proportion of sodium halide.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA84/4040 | 1984-05-28 | ||
| ZA844040 | 1984-05-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1245279A true CA1245279A (en) | 1988-11-22 |
Family
ID=25577331
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000482100A Expired CA1245279A (en) | 1984-05-28 | 1985-05-22 | Electrochemical cell |
Country Status (9)
| Country | Link |
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| US (1) | US4592969A (en) |
| JP (1) | JPS60262366A (en) |
| AU (1) | AU566856B2 (en) |
| CA (1) | CA1245279A (en) |
| DE (1) | DE3518859C2 (en) |
| FR (1) | FR2565034B1 (en) |
| GB (1) | GB2159661B (en) |
| IT (1) | IT1186711B (en) |
| SE (1) | SE465544B (en) |
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| GB8319749D0 (en) * | 1983-07-22 | 1983-08-24 | Ind Distributors Shannon Ltd | Electrochemical cell |
| GB8613800D0 (en) * | 1986-06-06 | 1986-07-09 | Lilliwyte Sa | Electrochemical cell |
| GB8613799D0 (en) * | 1986-06-06 | 1986-07-09 | Lilliwyte Sa | Electrochemical cell |
| GB8613796D0 (en) * | 1986-06-06 | 1986-07-09 | Lilliwyte Sa | Electrochemical cell |
| GB8812586D0 (en) * | 1988-05-27 | 1988-06-29 | Lilliwyte Sa | Electrochemical cell |
| GB8828229D0 (en) * | 1988-12-02 | 1989-01-05 | Lilliwyte Sa | Electrochemical cell |
| GB8828230D0 (en) * | 1988-12-02 | 1989-01-05 | Lilliwyte Sa | Electrochemical cell |
| GB8828829D0 (en) * | 1988-12-09 | 1989-01-18 | Lilliwyte Sa | Electrochemical cell |
| GB8829948D0 (en) * | 1988-12-22 | 1989-02-15 | Lilliwyte Sa | Electrochemical cells |
| GB8829949D0 (en) * | 1988-12-22 | 1989-02-15 | Lilliwyte Sa | Electrochemical cell |
| US4975344A (en) * | 1989-12-01 | 1990-12-04 | Lilliwyte Societe Anonyme | Electrochemical cell |
| GB9005485D0 (en) * | 1990-03-12 | 1990-05-09 | Aabh Patent Holdings | Electrochemical cell |
| GB9005484D0 (en) * | 1990-03-12 | 1990-05-09 | Lilliwyte Sa | Electrochemical cell |
| GB9007998D0 (en) * | 1990-04-09 | 1990-06-06 | Aabh Patent Holdings | Electrochemical cell |
| GB9011035D0 (en) * | 1990-05-16 | 1990-07-04 | Programme 3 Patent Holdings | Electrochemical cell |
| CA2042322A1 (en) * | 1990-05-16 | 1991-11-17 | Roger J. Bones | Electrochemical cells |
| US5194343A (en) * | 1990-10-09 | 1993-03-16 | The United States Of America As Represented By The United States Department Of Energy | Method of electrode fabrication and an electrode for metal chloride battery |
| DE4134986A1 (en) * | 1990-10-24 | 1992-04-30 | Aabh Patent Holdings | ELECTROCHEMICAL CELL |
| USH1334H (en) | 1991-06-10 | 1994-07-05 | The United States Of America As Represented By The Secretary Of The Army | Method of making a teflon bonded cathode for use in a high temperature cell and high temperature cell including said cathode |
| US5283135A (en) * | 1991-10-10 | 1994-02-01 | University Of Chicago | Electrochemical cell |
| US5340668A (en) * | 1991-10-10 | 1994-08-23 | The University Of Chicago | Electrochemical cell |
| US5536593A (en) * | 1991-10-10 | 1996-07-16 | Redey; Laszlo I. | Electrochemical cell |
| IT1269906B (en) * | 1993-04-02 | 1997-04-16 | Programme 3 Patent Holding | Electrochemical cell |
| AU686091B2 (en) * | 1994-06-08 | 1998-01-29 | Programme 3 Patent Holdings | Electrochemical cell |
| GB9512971D0 (en) * | 1995-06-26 | 1995-08-30 | Programme 3 Patent Holdings | Electrochemical cell |
| US5972533A (en) * | 1996-02-29 | 1999-10-26 | Electro Chemical Holdings Societe Anonyme | Electrochemical cell comprising a molten salt electrolyte containing sodium iodide |
| DE69805719T2 (en) * | 1997-02-06 | 2002-11-28 | Aabh Patent Holdings S.A., Luxemburg/Luxembourg | ELECTROCHEMICAL CELL |
| RU2340982C1 (en) * | 2007-07-25 | 2008-12-10 | Государственное образовательное учреждение высшего профессионального образования Самарский государственный технический университет | Electrolyte for chemical source of current |
| US7993768B2 (en) | 2007-12-20 | 2011-08-09 | General Electric Company | Energy storage device and method |
| US10320033B2 (en) | 2008-01-30 | 2019-06-11 | Enlighten Innovations Inc. | Alkali metal ion battery using alkali metal conductive ceramic separator |
| US8178231B2 (en) * | 2009-09-24 | 2012-05-15 | General Electric Company | Composition and energy storage device |
| US8343661B2 (en) * | 2009-11-04 | 2013-01-01 | General Electric Company | Cathode compositions comprising Zn and chalcogenide and energy storage cell comprising same |
| RU2410799C1 (en) * | 2009-11-30 | 2011-01-27 | Государственное образовательное учреждение высшего профессионального образования Самарский государственный технический университет | Electrolyte for chemical source of current |
| US8329336B2 (en) | 2010-09-29 | 2012-12-11 | General Electric Company | Composition and energy storage device |
| US8697279B2 (en) | 2011-01-14 | 2014-04-15 | General Electric Company | Composition and energy storage device |
| US10224577B2 (en) | 2011-11-07 | 2019-03-05 | Field Upgrading Usa, Inc. | Battery charge transfer mechanisms |
| US10854929B2 (en) | 2012-09-06 | 2020-12-01 | Field Upgrading Usa, Inc. | Sodium-halogen secondary cell |
| EP2901517B8 (en) * | 2012-09-28 | 2017-12-27 | Field Upgrading USA, Inc. | Battery charge transfer mechanisms |
| US20150044549A1 (en) * | 2013-03-15 | 2015-02-12 | H&D Electric, LLC | Advances in electric car technology |
| JP6682427B2 (en) * | 2013-09-25 | 2020-04-15 | フィールド アップグレーディング ユーエスエー・インク | Medium temperature sodium-metal halide battery |
| US10615407B2 (en) * | 2014-08-14 | 2020-04-07 | Battelle Memorial Institute | Na—FeCl2 ZEBRA type battery |
| ES2957614T3 (en) * | 2018-12-14 | 2024-01-23 | Geyser Batteries Oy | Electrochemical device to store energy |
| US12166187B1 (en) | 2024-04-08 | 2024-12-10 | Inlyte Energy, Inc. | Method for improving performance of metal conversion batteries and metal conversion batteries formed therefrom preliminary class |
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|---|---|---|---|---|
| US4058795A (en) * | 1972-10-03 | 1977-11-15 | International Business Machines Corporation | Method and apparatus for context-aided recognition |
| US3877984A (en) * | 1974-04-24 | 1975-04-15 | Esb Inc | Alkali metal-metal chloride battery |
| US3988163A (en) * | 1975-06-09 | 1976-10-26 | Esb Incorporated | Sodium-mixture of metal halides, sulfur battery |
| ZA785392B (en) * | 1978-09-22 | 1980-05-28 | South African Inventions | Cathode for an electrochemical cell,and an electrochemical cell |
| US4288506A (en) * | 1978-09-22 | 1981-09-08 | South African Inventions Development Corp. | Cathode for an electrochemical cell and an electrochemical cell |
| CA1149865A (en) * | 1979-08-22 | 1983-07-12 | Margaretha J. Nolte | Electrolyte for an electrochemical cell, and an electrochemical cell including the electrolyte |
| US4452777A (en) * | 1981-06-26 | 1984-06-05 | Eic Laboratories, Inc. | Electrochemical cells |
| ZA828603B (en) * | 1981-12-10 | 1983-09-28 | South African Inventions | Electrochemical cell |
-
1985
- 1985-05-16 AU AU42544/85A patent/AU566856B2/en not_active Ceased
- 1985-05-17 GB GB08512513A patent/GB2159661B/en not_active Expired
- 1985-05-22 CA CA000482100A patent/CA1245279A/en not_active Expired
- 1985-05-24 DE DE3518859A patent/DE3518859C2/en not_active Expired - Fee Related
- 1985-05-24 SE SE8502585A patent/SE465544B/en not_active IP Right Cessation
- 1985-05-24 FR FR8507883A patent/FR2565034B1/en not_active Expired - Fee Related
- 1985-05-24 US US06/737,442 patent/US4592969A/en not_active Expired - Lifetime
- 1985-05-27 JP JP60113955A patent/JPS60262366A/en active Granted
- 1985-05-28 IT IT20924/85A patent/IT1186711B/en active
Also Published As
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| IT8520924A1 (en) | 1986-11-28 |
| IT1186711B (en) | 1987-12-16 |
| GB2159661B (en) | 1987-05-07 |
| GB8512513D0 (en) | 1985-06-19 |
| AU4254485A (en) | 1985-12-05 |
| JPH0582029B2 (en) | 1993-11-17 |
| JPS60262366A (en) | 1985-12-25 |
| GB2159661A (en) | 1985-12-04 |
| US4592969A (en) | 1986-06-03 |
| DE3518859A1 (en) | 1985-11-28 |
| DE3518859C2 (en) | 1994-12-22 |
| SE8502585D0 (en) | 1985-05-24 |
| SE465544B (en) | 1991-09-23 |
| FR2565034B1 (en) | 1992-12-24 |
| IT8520924A0 (en) | 1985-05-28 |
| SE8502585L (en) | 1985-11-29 |
| AU566856B2 (en) | 1987-10-29 |
| FR2565034A1 (en) | 1985-11-29 |
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