CA1208283A - Electrochemical cell - Google Patents
Electrochemical cellInfo
- Publication number
- CA1208283A CA1208283A CA000439310A CA439310A CA1208283A CA 1208283 A CA1208283 A CA 1208283A CA 000439310 A CA000439310 A CA 000439310A CA 439310 A CA439310 A CA 439310A CA 1208283 A CA1208283 A CA 1208283A
- Authority
- CA
- Canada
- Prior art keywords
- cell
- components
- contact
- operating temperature
- porous material
- 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.)
- Expired
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Classifications
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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
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/443—Particulate material
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
-
- 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
- H01M6/20—Cells with non-aqueous electrolyte with solid electrolyte 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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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Secondary Cells (AREA)
Abstract
ABSTRACT
An electrochemical cell and a method of reducing potential hazard in electrochemical cells are provided. The cell has as reactive components molten sodium and molten sodium aluminium chloride and according to the invention a macroporous material such as a fibrous felt material is impregnated by one of said reactive components in a zone where they can react upon damage to the cell, to reinforce the reaction products produced and to enhance the ability of the reaction product to separate the reactive components from each other, to reduce undesirable consequences of the damage.
An electrochemical cell and a method of reducing potential hazard in electrochemical cells are provided. The cell has as reactive components molten sodium and molten sodium aluminium chloride and according to the invention a macroporous material such as a fibrous felt material is impregnated by one of said reactive components in a zone where they can react upon damage to the cell, to reinforce the reaction products produced and to enhance the ability of the reaction product to separate the reactive components from each other, to reduce undesirable consequences of the damage.
Description
t32B~
THIS INVENTION relates to an electrochemical cell. In particular, it relates to an electro~
chemical cell of the type having two or more reactive components at least one of which is liquid at the operating temperature of the cell, the components being separated from one another and being capable of reacting together with potentially un-desirable consequences; and the invention relates also to a method of reducing the potential hazard constituted thereby.
Accordlng to one aspect there is provided an electrochemical cell which comprises at least two reactive components which are liquid in the operating temperature of the cell, the components being sepa-rated from one another and being capable of reactingtogether with potentially undesirable consequences to form at least one reaction product which is solid at the operating temperature of the cell and to which they are inert, at least one of the said reactive components being separa-ted from the cathode of the cell and being impregnated into a macroporous material in at least one zone where contact between the reactive components can take place, thereby to enhance the ability of any such reaction product formed in said zone to separate said components from one another.
~L~ 3 The potential hazard which the invention is intended to guard against would arise from failure and particularly damage to a cell, which can arise for example from an accident, such as a motor accident when the cell forms part of the propulsion system of a motor vehicle~ Reactive components in an electochemical cell, when they come into contact with one another, form reaction products to which the components are inherently inert. Such reaction products will tend to separate the reactive components from one another, and the purpose of providing the macroporous material in the cell is to strengthen and/or trap said reaction products, in order, as mentioned above, to enhance the ability of the reaction products to separate the reactive components from one another, to reduce the potentially undesirable consequences arising from the reaction of the reactive components with one another, as the result of failure or accidental damage to the cell.
The porous materiàl may be particulate, ie fibrous or granular, eg so as to provide a body, 3;Z83 layer or bed of particles which is macroporous.
Macroporous in this context means that the material will be impregnated by a liquid cell component in the sense of impregnation by capillary action or the like, as contrasted with microporous materials such as atomic sieves provided by zeolites or the like, which are porous at the atomic or molecular level, and are impregnated by mechanisms other than ordinary capillary reaction.
The particles may be loose or unconnected to one another, and capable of movement relative to one anothex. In this case the porous material may have a different density from that of the reactive component with which it is in contact, occupying part of the space occupied by said component, so that the porous material forms a layer in the component at the operating temperature of the cell.
Thus, for example, if contact between the components is anticipated at a high elevation or level in one of the components, the particles of the porous component may have a lower density than said component so that they form a floating bed in it at said high level. On the othex hand, if contact is anticipated at a low elevation or level, the porous material may have particles of a greater density ~z~ 3 than that of the component, so that they settle to form a bed or layer at the bottom of the component.
On the other hand, the particles, while separate from one another, may be held in contact with one another, by being forced together in a compacted mass which is held together by compression and is impregnated by said component. In this case the porous material may occupy substantially the whole of the space occupied by the reactive cell component with which it is impregnated.
Instead~ the porous material may be in the form of an artifact, eg an artifact which comprises woven or felted fibrous material.Instead, th~ porous artifact may be one having a sponge-like structure, such as one made by a sintered bed of particles.
The artifact may thus be a sintered artifact.
As mentioned above, the component of the cell which is impregnated into or surrounds and saturates the porous material will be a liquid, at least at the operating temperature of the cell. The porosity of the porous material is thus preferably such as to provide for unrestricted diffusion 8~Z83 therethrough of the component with which it is in contact at the operating temperature of the cell.
In general, while frequently the entire body or mass of the component in question will be impregnated into the porous material so as to surround and/or saturate it, the invention will often be applied by providing the porous material only in a zone or 7.ones in the cell, where contact between reactive components is expected or anticipated, in the event of certain anticipated types of damage to the cell.
.
When reactive cell components come into contact with each other in a gentle or orderly fashion, it can happen that a layer of reaction products is created between them, effectively sepaxating them from each other and preventing or reducing any ~urther reaction between the components. However, in a more or less catastrophic or violent accident, causing substantial damage to the cell, the components can become more or less thoroughly intermixed, particularly when they are both liquid, thus leading to a violent, uncontrollable and possible catastrophic reaction.
In such case, even if a layer of reaction products lZ(~8~83 between the components has been created, the layer can be destroyed, possibly repeatedly, if the accident or damage to the cell is sufficiently violent, making possible further contact between the components, and aggravating the undesirable consequences.
~ owever, in accordance with the present invention, the presence of particles such as fibres in a zone where contact between the components takes place and reaction products are formed, can act to reinforce the layer of reaction products and render it less liable to subsequent mechanical failure; or the porous material can entrap and immobilise the reaction products (as with granular particles or porous sponge-like artifacts) thereby enhancing the ability of the reaction products to separate the components. Depending on the porous material used, such reinorcement a~nd entrapment can both be present.
Two of the reactive cell components may be liquid at the operating temperature of the cell, being separated from one another by a separator wlth which they are both in contact, a layer of the porous material being provided on at least one side of the separator, at the interface between the . . .
~ZC)~ 33 separator and the component on that side of the separato.r.
The separator may be a solid electrolyte, the components on opposite sides thereof comprising anode material and liquid electrolyte material respectively. The layer may be provided at the interface between the liquid electrolyte and solid electrolyte, and the anode material-may comprise an alkali metal and/or an alkaline earth metal, the liquid electrolyte being a molten salt electrolyte comprising one or more alkali metal and/or alkaline earth metal halide salts, and the layer of porous material comprising non-conductive fibrous material.
As examples of this type of cell to which the invention can be applied, there are cells having an anode and a cathode, a solid electrolyte separating the anode from the cathode, and a liquid electrolyte in the cathode department which acts as ionic conductor without otherwise taking part in the cell reaction but which is capable of reacting violently with the active anode material. In such a case, the active anode material may for example be liquid sodium, the solid electrolyte being beta alumina (beta-A1203), and the electrolyte being 8~
molten sodium aluminium chloride (NaAlC14), surrounding the cathode material which may be in the form of a solid, porous, active matrix. The beta alumina electrolyte acts effectively as a separator which separates the sodium aluminium chloride from the sodium anode material, this liquid electrolyte/anode combination comprising two substances which are extremely reactive with each other, and which, upon accidental contact in the event of damage, can react dangerously with each other, depending on the degree of intermixing therebetween.
In accordance with the invention, a layer of porous material as described above, for example in the form of a fibrous structure may be provided in zones in the cell, where the liquid electrolyte is able or is anticipated, in the event of damage, to react with the anode material, for example in the event of fracture of the solid electrolyte. The inert reaction products formed by such reaction would tend to be reinforced by the fibrous structure, to form a fibre-reinforced barrier resistant to penetration by either the liquid electrolyte or the active anode material, one or 32~3 both of which will be liquid at the operating temperature of the cell.
Although the fibrous structure can be disposed at the interface between the solid electrolyte and the liquid electrolyte as described above, it can equally easily be disposed throughout the space in the cathode compartment which contains the liquid electrolyte. Further such fibrous material may also be provided in the anode compartment, eg throughout the anode compartment or at the solid electrolyte/anode material interface.
For cells of this type, the fibrous structure is preferably non-conductive, as described above, and may comprise ceramic material, alumina, glass fibres, or the like.
For cells which have a cathode which is intended to be of the type comprising an artifact, eg a sintered artifact, which is porous to liquid electrolyte, fibrous material can also in accordance with the invention be incorporated into the cathode material prior to formation of the artifact, thereby aiding the sintering process, and binding of the cathode material.
,.
1~2V8Z1~3 A method of reducing the potential hazard constituted by contact between at least two reactive components in an electrochemical cell which are liquid at the operating temperature of the cell, the compo-nents being separated from one another and beingcapable of reacting together with potentially un-desirable consequences to form at least one reaction product which is solid at the operating temperature of the cell and to which they are inert, the method comprising providing in at least one zone in the cell where contact between the reactive components can take place ~ macroporous material which is impregnated with at least one of the reactive components which is separated from the cathode of the cell, thereby to enchance the ability of the reaction product to separate said components from one another.
This invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which Figure 1 shows a sectional slde elevation of a vessel containing cell components tested by the Applicant;
~ZO~Z~3 Figure 2 shows a sectional side elevation of a cell in accordance with the present invention; and Figure 3 shows a sectional side elevation of a further cell in accordance with the present invention.
In Figure l, reference numeral lO
generally designates a suitable heated vessel into which liquid sodium, designated by reference numeral 12 was charged at 250C, and after and on top of which liquid sodium aluminium chloride, designated 14, was also charged at 250C. These components were added at a gentle and controlled rate, and separated into layers, as shown in Figure l.
The addition was carried out under argon, with the vessel 10 held at a temperature o~ 250C.
The sodium and sodium aluminium chloride were found to react rapidly at this temperature/ and exothermically, to glve solid reaction products forming the layer 16, in accordance with the reaction:
NaAlC14 ~ 3Na ~ ~ 4 NaCl + Al.
With gentle addition of the components, the layer 16 was found to form in a fashion such that it effectively separated the components from one lZ(~8;~83 another, without an unacceptable temperature increase. The solid barrier formed by the reaction product served to slow down reaction between the components rapidly, and the temperature increase was found to be limited to less than 50C.
It was further found that when the barrier 16 was badly ruptured, eg by stirring, a violent reaction took place with a rapid rise in temperature of up to 1000C, demonstrating the danger inherent in violent damage to cells containing the sodium and sodium aluminium chloride, in a fashion that extensive and rapid mixing between these components takes place.
With reference to Figure 2, re~erence numeral 18 generally designates an electrochemical cell in accordance with the invention. The cell comprises a housing 20 within which is located molten sodium 22. A cup-shaped beta-alumina solid electrolyte separator 24 is partially immersed in the sodium 22, within which is located a solid active cathode matrix 26 in turn immersed in the cup
THIS INVENTION relates to an electrochemical cell. In particular, it relates to an electro~
chemical cell of the type having two or more reactive components at least one of which is liquid at the operating temperature of the cell, the components being separated from one another and being capable of reacting together with potentially un-desirable consequences; and the invention relates also to a method of reducing the potential hazard constituted thereby.
Accordlng to one aspect there is provided an electrochemical cell which comprises at least two reactive components which are liquid in the operating temperature of the cell, the components being sepa-rated from one another and being capable of reactingtogether with potentially undesirable consequences to form at least one reaction product which is solid at the operating temperature of the cell and to which they are inert, at least one of the said reactive components being separa-ted from the cathode of the cell and being impregnated into a macroporous material in at least one zone where contact between the reactive components can take place, thereby to enhance the ability of any such reaction product formed in said zone to separate said components from one another.
~L~ 3 The potential hazard which the invention is intended to guard against would arise from failure and particularly damage to a cell, which can arise for example from an accident, such as a motor accident when the cell forms part of the propulsion system of a motor vehicle~ Reactive components in an electochemical cell, when they come into contact with one another, form reaction products to which the components are inherently inert. Such reaction products will tend to separate the reactive components from one another, and the purpose of providing the macroporous material in the cell is to strengthen and/or trap said reaction products, in order, as mentioned above, to enhance the ability of the reaction products to separate the reactive components from one another, to reduce the potentially undesirable consequences arising from the reaction of the reactive components with one another, as the result of failure or accidental damage to the cell.
The porous materiàl may be particulate, ie fibrous or granular, eg so as to provide a body, 3;Z83 layer or bed of particles which is macroporous.
Macroporous in this context means that the material will be impregnated by a liquid cell component in the sense of impregnation by capillary action or the like, as contrasted with microporous materials such as atomic sieves provided by zeolites or the like, which are porous at the atomic or molecular level, and are impregnated by mechanisms other than ordinary capillary reaction.
The particles may be loose or unconnected to one another, and capable of movement relative to one anothex. In this case the porous material may have a different density from that of the reactive component with which it is in contact, occupying part of the space occupied by said component, so that the porous material forms a layer in the component at the operating temperature of the cell.
Thus, for example, if contact between the components is anticipated at a high elevation or level in one of the components, the particles of the porous component may have a lower density than said component so that they form a floating bed in it at said high level. On the othex hand, if contact is anticipated at a low elevation or level, the porous material may have particles of a greater density ~z~ 3 than that of the component, so that they settle to form a bed or layer at the bottom of the component.
On the other hand, the particles, while separate from one another, may be held in contact with one another, by being forced together in a compacted mass which is held together by compression and is impregnated by said component. In this case the porous material may occupy substantially the whole of the space occupied by the reactive cell component with which it is impregnated.
Instead~ the porous material may be in the form of an artifact, eg an artifact which comprises woven or felted fibrous material.Instead, th~ porous artifact may be one having a sponge-like structure, such as one made by a sintered bed of particles.
The artifact may thus be a sintered artifact.
As mentioned above, the component of the cell which is impregnated into or surrounds and saturates the porous material will be a liquid, at least at the operating temperature of the cell. The porosity of the porous material is thus preferably such as to provide for unrestricted diffusion 8~Z83 therethrough of the component with which it is in contact at the operating temperature of the cell.
In general, while frequently the entire body or mass of the component in question will be impregnated into the porous material so as to surround and/or saturate it, the invention will often be applied by providing the porous material only in a zone or 7.ones in the cell, where contact between reactive components is expected or anticipated, in the event of certain anticipated types of damage to the cell.
.
When reactive cell components come into contact with each other in a gentle or orderly fashion, it can happen that a layer of reaction products is created between them, effectively sepaxating them from each other and preventing or reducing any ~urther reaction between the components. However, in a more or less catastrophic or violent accident, causing substantial damage to the cell, the components can become more or less thoroughly intermixed, particularly when they are both liquid, thus leading to a violent, uncontrollable and possible catastrophic reaction.
In such case, even if a layer of reaction products lZ(~8~83 between the components has been created, the layer can be destroyed, possibly repeatedly, if the accident or damage to the cell is sufficiently violent, making possible further contact between the components, and aggravating the undesirable consequences.
~ owever, in accordance with the present invention, the presence of particles such as fibres in a zone where contact between the components takes place and reaction products are formed, can act to reinforce the layer of reaction products and render it less liable to subsequent mechanical failure; or the porous material can entrap and immobilise the reaction products (as with granular particles or porous sponge-like artifacts) thereby enhancing the ability of the reaction products to separate the components. Depending on the porous material used, such reinorcement a~nd entrapment can both be present.
Two of the reactive cell components may be liquid at the operating temperature of the cell, being separated from one another by a separator wlth which they are both in contact, a layer of the porous material being provided on at least one side of the separator, at the interface between the . . .
~ZC)~ 33 separator and the component on that side of the separato.r.
The separator may be a solid electrolyte, the components on opposite sides thereof comprising anode material and liquid electrolyte material respectively. The layer may be provided at the interface between the liquid electrolyte and solid electrolyte, and the anode material-may comprise an alkali metal and/or an alkaline earth metal, the liquid electrolyte being a molten salt electrolyte comprising one or more alkali metal and/or alkaline earth metal halide salts, and the layer of porous material comprising non-conductive fibrous material.
As examples of this type of cell to which the invention can be applied, there are cells having an anode and a cathode, a solid electrolyte separating the anode from the cathode, and a liquid electrolyte in the cathode department which acts as ionic conductor without otherwise taking part in the cell reaction but which is capable of reacting violently with the active anode material. In such a case, the active anode material may for example be liquid sodium, the solid electrolyte being beta alumina (beta-A1203), and the electrolyte being 8~
molten sodium aluminium chloride (NaAlC14), surrounding the cathode material which may be in the form of a solid, porous, active matrix. The beta alumina electrolyte acts effectively as a separator which separates the sodium aluminium chloride from the sodium anode material, this liquid electrolyte/anode combination comprising two substances which are extremely reactive with each other, and which, upon accidental contact in the event of damage, can react dangerously with each other, depending on the degree of intermixing therebetween.
In accordance with the invention, a layer of porous material as described above, for example in the form of a fibrous structure may be provided in zones in the cell, where the liquid electrolyte is able or is anticipated, in the event of damage, to react with the anode material, for example in the event of fracture of the solid electrolyte. The inert reaction products formed by such reaction would tend to be reinforced by the fibrous structure, to form a fibre-reinforced barrier resistant to penetration by either the liquid electrolyte or the active anode material, one or 32~3 both of which will be liquid at the operating temperature of the cell.
Although the fibrous structure can be disposed at the interface between the solid electrolyte and the liquid electrolyte as described above, it can equally easily be disposed throughout the space in the cathode compartment which contains the liquid electrolyte. Further such fibrous material may also be provided in the anode compartment, eg throughout the anode compartment or at the solid electrolyte/anode material interface.
For cells of this type, the fibrous structure is preferably non-conductive, as described above, and may comprise ceramic material, alumina, glass fibres, or the like.
For cells which have a cathode which is intended to be of the type comprising an artifact, eg a sintered artifact, which is porous to liquid electrolyte, fibrous material can also in accordance with the invention be incorporated into the cathode material prior to formation of the artifact, thereby aiding the sintering process, and binding of the cathode material.
,.
1~2V8Z1~3 A method of reducing the potential hazard constituted by contact between at least two reactive components in an electrochemical cell which are liquid at the operating temperature of the cell, the compo-nents being separated from one another and beingcapable of reacting together with potentially un-desirable consequences to form at least one reaction product which is solid at the operating temperature of the cell and to which they are inert, the method comprising providing in at least one zone in the cell where contact between the reactive components can take place ~ macroporous material which is impregnated with at least one of the reactive components which is separated from the cathode of the cell, thereby to enchance the ability of the reaction product to separate said components from one another.
This invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which Figure 1 shows a sectional slde elevation of a vessel containing cell components tested by the Applicant;
~ZO~Z~3 Figure 2 shows a sectional side elevation of a cell in accordance with the present invention; and Figure 3 shows a sectional side elevation of a further cell in accordance with the present invention.
In Figure l, reference numeral lO
generally designates a suitable heated vessel into which liquid sodium, designated by reference numeral 12 was charged at 250C, and after and on top of which liquid sodium aluminium chloride, designated 14, was also charged at 250C. These components were added at a gentle and controlled rate, and separated into layers, as shown in Figure l.
The addition was carried out under argon, with the vessel 10 held at a temperature o~ 250C.
The sodium and sodium aluminium chloride were found to react rapidly at this temperature/ and exothermically, to glve solid reaction products forming the layer 16, in accordance with the reaction:
NaAlC14 ~ 3Na ~ ~ 4 NaCl + Al.
With gentle addition of the components, the layer 16 was found to form in a fashion such that it effectively separated the components from one lZ(~8;~83 another, without an unacceptable temperature increase. The solid barrier formed by the reaction product served to slow down reaction between the components rapidly, and the temperature increase was found to be limited to less than 50C.
It was further found that when the barrier 16 was badly ruptured, eg by stirring, a violent reaction took place with a rapid rise in temperature of up to 1000C, demonstrating the danger inherent in violent damage to cells containing the sodium and sodium aluminium chloride, in a fashion that extensive and rapid mixing between these components takes place.
With reference to Figure 2, re~erence numeral 18 generally designates an electrochemical cell in accordance with the invention. The cell comprises a housing 20 within which is located molten sodium 22. A cup-shaped beta-alumina solid electrolyte separator 24 is partially immersed in the sodium 22, within which is located a solid active cathode matrix 26 in turn immersed in the cup
2~ in molten sodium aluminium chloride liquid electrolyte 28. The housing 20 acts as an anode current collector, and a cathode current collector ' :
~2~ l33 30 is provided, embedded in and extending upwardly away from the matrix 26, and out of the electrolyte 28 and housing 20, from which it is insulated at 32.
In accordance with the invention, graphite felt (not shown) has been used to line the inner surface of the cup 24, where it is saturated by the liquid electrolyte 28. In the event of rupture or breakage of the cup 24, sodium 22 penetrating into the cathode compartment constituted by said cup 24, reacts with the liquid electrolyte in the felt lining, according to the reaction given above, to provide sodium chloride and aluminium as reaction products in a layer which is reinforced by the fibres of the carbon felt. It has been found that this carbon fibre reinforced layer of reaction products is much more robust and difficult to rupture than a corresponding layer of unreinforced reaction products without the carbon fibres, eg during subsequent vibration or impacts to which the cell may be subjected.
The Applicant further contemplates, in addition, the possibility of entirely filling the space of the cakhode compartment occupied by the liquid electrolyte- with such felt. However, if it t3 is found that there is a danger of premature over-discharge, particularly in the zone in the liquid electrolyte 28 above the cathode matrix 26, it would be preferable to use fibres which are electrically insulating, such as ceramic fibres, alumina fibres, or glass fibres, the fibres naturally being selected to be stable with regard to reaction with the liquid electrolyte. If a mat or wool of such fibres is employed, they can act partially to immobilize the melt 28, thereby enhancing safety, although the Applicant believes that, from this point of view, the use of particles instead of fibres, as in a powder saturated by the liquid electrolyte, may be a better immobilizer.
Similarly, a layer of suitable fibrous material, inert to sodium at the temperature in question, can be used to line the outer suxface of the cup 24, to guard against penetration of liquid electrolyte 28 into the sodium 22 of the anode, by forming a fibre reinforced layer of reaction products on the outside of the cup; or such fibrous material can fill the whole of the anode space.
In Figure 3, a similar cell is shown, and unless otherwise specified, the same reference 2~3 numerals refer to the same parts. In this case, the matrix 26 is omitted, and the cathode compartment is filled with molten sodium aluminium chloride with, as active species dissolved therein, SbCl5. In this case, too, the invention can be applied analogously, in the same fashion as described above for Figure 2.
A further aspect contemplated by the invention is reduction of the danger of an undesirable reaction (with xeference particularly to Figure 2) between the liquid sodium anode material and liquid electrolyte, such as sodium aluminium chloride, when the electrolyte is impregnated into the porous cathode matrix. The degree of impregnation of the liquid electrolyte into the matrix presently attained is insufficient to lead to a violent reaction between the liquid electrolyte impregnated into the matrix material and the sodium, but if increased available porosity is developed for the matrix, the sodium aluminium chloride impregnated therein may increase to a level where reaction thereof with the sodium, in the event of breakage to the matrix and contact thereof with the sodium, could become a problem. To guard against this, similar fibres could be incorporated in the pores of the matrix to reduce the danger. Such ~2Vl3~83 fibres would be added during the manufacturing stage, being mixed for example with powders from which the matrix is formed, prior to fabrication and sintering. The presence of such fibres can also aid in the control of the sintering, and help bind the cathode matrix together during subsequent operation.
Furthermore, if a porous artifact such as a mineral sponge impregnated by capillary action, or a bed (possibly sintered) of particles, is used in a fashion similar to the fibres described above, e.g.
as an inner and/or outer lining to the cup 24, or filling the whole of the anode or cathode compartments, then should rupture of the cup lead to penetration of the anode compartment by liquid electrolyte or penetration of the cathode compartment by anode material, reaction products would be trapped in a layer in the artifact or bed, at the interface with-the cup. This will serve to immobilize and strengthen the layer of reaction products formed, enhacing its ability to separate the liquid electrolyte and anode material, and if the artifact or bed contains fibres, fibre reinforcement of the layer can be obtained as well.
~Z~ 3 Although electrochemical cells according to the invention have been described with reference to cells of cylindrical shape in the drawings, it will naturally be appreciated that cells of other shapes, eg flat cells, can easily be made in accordance with the invention.
~2~ l33 30 is provided, embedded in and extending upwardly away from the matrix 26, and out of the electrolyte 28 and housing 20, from which it is insulated at 32.
In accordance with the invention, graphite felt (not shown) has been used to line the inner surface of the cup 24, where it is saturated by the liquid electrolyte 28. In the event of rupture or breakage of the cup 24, sodium 22 penetrating into the cathode compartment constituted by said cup 24, reacts with the liquid electrolyte in the felt lining, according to the reaction given above, to provide sodium chloride and aluminium as reaction products in a layer which is reinforced by the fibres of the carbon felt. It has been found that this carbon fibre reinforced layer of reaction products is much more robust and difficult to rupture than a corresponding layer of unreinforced reaction products without the carbon fibres, eg during subsequent vibration or impacts to which the cell may be subjected.
The Applicant further contemplates, in addition, the possibility of entirely filling the space of the cakhode compartment occupied by the liquid electrolyte- with such felt. However, if it t3 is found that there is a danger of premature over-discharge, particularly in the zone in the liquid electrolyte 28 above the cathode matrix 26, it would be preferable to use fibres which are electrically insulating, such as ceramic fibres, alumina fibres, or glass fibres, the fibres naturally being selected to be stable with regard to reaction with the liquid electrolyte. If a mat or wool of such fibres is employed, they can act partially to immobilize the melt 28, thereby enhancing safety, although the Applicant believes that, from this point of view, the use of particles instead of fibres, as in a powder saturated by the liquid electrolyte, may be a better immobilizer.
Similarly, a layer of suitable fibrous material, inert to sodium at the temperature in question, can be used to line the outer suxface of the cup 24, to guard against penetration of liquid electrolyte 28 into the sodium 22 of the anode, by forming a fibre reinforced layer of reaction products on the outside of the cup; or such fibrous material can fill the whole of the anode space.
In Figure 3, a similar cell is shown, and unless otherwise specified, the same reference 2~3 numerals refer to the same parts. In this case, the matrix 26 is omitted, and the cathode compartment is filled with molten sodium aluminium chloride with, as active species dissolved therein, SbCl5. In this case, too, the invention can be applied analogously, in the same fashion as described above for Figure 2.
A further aspect contemplated by the invention is reduction of the danger of an undesirable reaction (with xeference particularly to Figure 2) between the liquid sodium anode material and liquid electrolyte, such as sodium aluminium chloride, when the electrolyte is impregnated into the porous cathode matrix. The degree of impregnation of the liquid electrolyte into the matrix presently attained is insufficient to lead to a violent reaction between the liquid electrolyte impregnated into the matrix material and the sodium, but if increased available porosity is developed for the matrix, the sodium aluminium chloride impregnated therein may increase to a level where reaction thereof with the sodium, in the event of breakage to the matrix and contact thereof with the sodium, could become a problem. To guard against this, similar fibres could be incorporated in the pores of the matrix to reduce the danger. Such ~2Vl3~83 fibres would be added during the manufacturing stage, being mixed for example with powders from which the matrix is formed, prior to fabrication and sintering. The presence of such fibres can also aid in the control of the sintering, and help bind the cathode matrix together during subsequent operation.
Furthermore, if a porous artifact such as a mineral sponge impregnated by capillary action, or a bed (possibly sintered) of particles, is used in a fashion similar to the fibres described above, e.g.
as an inner and/or outer lining to the cup 24, or filling the whole of the anode or cathode compartments, then should rupture of the cup lead to penetration of the anode compartment by liquid electrolyte or penetration of the cathode compartment by anode material, reaction products would be trapped in a layer in the artifact or bed, at the interface with-the cup. This will serve to immobilize and strengthen the layer of reaction products formed, enhacing its ability to separate the liquid electrolyte and anode material, and if the artifact or bed contains fibres, fibre reinforcement of the layer can be obtained as well.
~Z~ 3 Although electrochemical cells according to the invention have been described with reference to cells of cylindrical shape in the drawings, it will naturally be appreciated that cells of other shapes, eg flat cells, can easily be made in accordance with the invention.
Claims (13)
1. An electrochemical cell which comprises at least two reactive components which are liquid in the operating temperature of the cell, the components being separated from one another and being capable of reacting together with potentially undesirable consequences to form at least one reaction product which is solid at the operating temperature of the cell and to which they are inert, at least one of the said reactive components being separated from the cathode of the cell and being impregnated into a macroporous material in at least one zone where contact between the reactive components can take place, thereby to enhance the ability of any such reaction product formed in said zone to separate said components from one another.
2. A cell as claimed in claim 1, in which the porous material is particulate.
3. A cell as claimed in claim 2, in which the porous material has a different density from that of the reactive component with which it is in contact and occupies part of the space occupied by said component, so that the porous material forms a layer in the component at the operating temperature of the cell.
4. A cell as claimed in claim 2, in which the particles of the porous material are held in contact with one another.
5. A cell as claimed in claim 1, in which the porous material is in the form of an artifact.
6. A cell as claimed in claim 5, in which the artifact comprises woven or felted fibrous material.
7. A cell as claimed in claim 5, in which the artifact is a sintered artifact.
8. A cell as claimed in claim 1, in which the porosity of the porous material is such as to provide for unrestricted diffusion therethrough of the component with which it is in contact at the operating temperature of the cell.
9. A cell as claimed in claim 1, in which two of the reactive cell components are liquid at the operating temperature of the cell and are separated from each other by a separator with which they are both in contact, a layer of the porous material being provided on at least one side of the separator, at the interface between the separator and the component on that side of the separator.
10. A cell as claimed in claim 9, in which the separator is a solid electrolyte, the components on opposite sides thereof comprising anode material and liquid electrolyte material respectively.
11. A cell as claimed in claim 10, in which the layer is provided at the interface between the liquid electrolyte and solid electrolyte.
12. A cell as claimed in claim 10, in which the anode material comprises an alkali metal and/or an alkaline earth metal, and the liquid electrolyte is a molten salt electrolyte comprising one or more alkali metal and/or alkaline earth metal halide salts, the layer comprising non-conductive fibrous material.
13. A method of reducing the potential hazard constituted by contact between at least two reactive components in an electrochemical cell which are liquid at the operating temperature of the cell, the components being separated from one another and being capable of reacting together with potentially undesirable consequences to form at least one reaction product which is solid at the operating temperature of the cell and to which they are inert, the method comprising providing in at least one zone in the cell where contact between the reactive components can take place a macroporous material which is impregnated with at least one of the reactive components which is separated from the cathode of the cell, thereby to enhance the ability of the reaction product to separate said components from one another.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8229944 | 1982-10-20 | ||
| GB8229944 | 1982-10-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1208283A true CA1208283A (en) | 1986-07-22 |
Family
ID=10533716
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000439310A Expired CA1208283A (en) | 1982-10-20 | 1983-10-19 | Electrochemical cell |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS59132575A (en) |
| CA (1) | CA1208283A (en) |
| DE (1) | DE3337991A1 (en) |
| FR (1) | FR2535118A1 (en) |
| GB (1) | GB2132003B (en) |
| ZA (1) | ZA837601B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3425859A1 (en) * | 1984-07-13 | 1986-01-16 | Brown, Boveri & Cie Ag, 6800 Mannheim | METHOD FOR PRODUCING A STORAGE CELL |
| GB8728394D0 (en) * | 1987-12-04 | 1988-01-13 | Lilliwyte Sa | Electrochemical cell |
| GB8730136D0 (en) * | 1987-12-24 | 1988-02-03 | Lilliwyte Sa | Electrochemical cell |
| GB9005483D0 (en) * | 1990-03-12 | 1990-05-09 | Aabh Patent Holdings | Electrochemical cell |
| EP0766073B1 (en) | 1995-09-28 | 2002-01-02 | Endress + Hauser GmbH + Co. | Electronic casing |
| DE59507485D1 (en) * | 1995-09-28 | 2000-01-27 | Endress Hauser Gmbh Co | Electronics housing |
Family Cites Families (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2115522A5 (en) * | 1970-11-23 | 1972-07-07 | Accumulateurs Fixes | Sodium-sodium halide cell - using aluminium chloride-sodium halide complexes |
| GB1456073A (en) * | 1974-02-18 | 1976-11-17 | Nat Res Dev | Electrolytic cells |
| US3980496A (en) * | 1975-01-29 | 1976-09-14 | Ford Motor Company | Energy conversion devices with improved electrode shapes |
| US3933520A (en) * | 1975-04-03 | 1976-01-20 | The United States Of America As Represented By The United States Energy Research And Development Administration | Method of preparing electrodes with porous current collector structures and solid reactants for secondary electrochemical cells |
| US3969138A (en) * | 1975-06-09 | 1976-07-13 | Esb Incorporated | Sodium-aluminum halide, sulfur battery |
| US3992222A (en) * | 1975-07-15 | 1976-11-16 | The United States Of America As Represented By The United States Energy Research And Development Administration | Metallic sulfide additives for positive electrode material within a secondary electrochemical cell |
| US3985575A (en) * | 1976-01-30 | 1976-10-12 | Ford Motor Company | Secondary battery or cell with dual electrode |
| IT1066389B (en) * | 1976-01-30 | 1985-03-04 | Ford Motor Co | SECONDARY ELECTRIC CELL OR BATTERY WITH WET POLYSULPHIDE ELECTRODE |
| GB1528672A (en) * | 1976-02-18 | 1978-10-18 | Chloride Silent Power Ltd | Sodium sulphur cells |
| DE2616593C2 (en) * | 1976-04-14 | 1985-07-11 | Robert Bosch Gmbh, 7000 Stuttgart | System for switching between two color television signals |
| US4069372A (en) * | 1976-11-30 | 1978-01-17 | Battelle Development Corporation | Electric accumulator with a solid electrolyte |
| FR2381396A1 (en) * | 1977-02-17 | 1978-09-15 | Comp Generale Electricite | Electrochemical cell using chalcogenide(s) as positive material - to provide lower working temp. for beta-alumina type cells |
| CA1093150A (en) * | 1977-03-09 | 1981-01-06 | Johan Coetzer | Cathode, the formation of a cathode, and a cell incorporating such a cathode |
| GB1595765A (en) * | 1977-11-30 | 1981-08-19 | Chloride Silent Power Ltd | Sodium-sulphur cells |
| GB2042243B (en) * | 1979-02-13 | 1983-02-16 | Chloride Silent Power Ltd | Sodium sulphur cells |
| GB2048557A (en) * | 1979-04-23 | 1980-12-10 | Chloride Silent Power Ltd | Sodium-sulphur cell |
| FR2455367A1 (en) * | 1979-04-26 | 1980-11-21 | Proge | MOLTEN SALT COMPOSITION FOR USE AS ANODIC ELECTROLYTE IN ALKALINE ALUMINUM BATTERIES AND NEGATIVE ALKALINE METAL ELECTRODE |
| GB2052460B (en) * | 1979-05-24 | 1983-01-12 | Chloride Silent Power Ltd | Carbon fibre cathode |
| FR2466107A1 (en) * | 1979-08-08 | 1981-03-27 | Comp Generale Electricite | Sodium-sulphur cell - with negative active material comprising a rigid porous material impregnated with liq. sodium |
| SE8008330L (en) * | 1979-12-05 | 1981-06-06 | Western Electric Co | ELECTROLYTIC CELL |
| DE3022449A1 (en) * | 1980-06-14 | 1982-01-07 | Brown, Boveri & Cie Ag, 6800 Mannheim | ELECTROCHEMICAL STORAGE CELL |
| DE3028836C2 (en) * | 1980-07-30 | 1986-04-17 | Brown, Boveri & Cie Ag, 6800 Mannheim | Electrochemical storage cell |
| ZA828603B (en) * | 1981-12-10 | 1983-09-28 | South African Inventions | Electrochemical cell |
-
1983
- 1983-10-12 ZA ZA837601A patent/ZA837601B/en unknown
- 1983-10-18 GB GB08327829A patent/GB2132003B/en not_active Expired
- 1983-10-19 DE DE3337991A patent/DE3337991A1/en not_active Withdrawn
- 1983-10-19 JP JP58195913A patent/JPS59132575A/en active Pending
- 1983-10-19 FR FR8316638A patent/FR2535118A1/en active Pending
- 1983-10-19 CA CA000439310A patent/CA1208283A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| ZA837601B (en) | 1984-06-27 |
| FR2535118A1 (en) | 1984-04-27 |
| GB2132003A (en) | 1984-06-27 |
| GB2132003B (en) | 1986-05-08 |
| GB8327829D0 (en) | 1983-11-16 |
| DE3337991A1 (en) | 1984-04-26 |
| JPS59132575A (en) | 1984-07-30 |
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