CA1076203A - Flexible cells and batteries formed therefrom - Google Patents
Flexible cells and batteries formed therefromInfo
- Publication number
- CA1076203A CA1076203A CA281,268A CA281268A CA1076203A CA 1076203 A CA1076203 A CA 1076203A CA 281268 A CA281268 A CA 281268A CA 1076203 A CA1076203 A CA 1076203A
- Authority
- CA
- Canada
- Prior art keywords
- cell
- flexible
- anode
- current collector
- metal
- 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
Links
Classifications
-
- 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
- H01M4/06—Electrodes for primary cells
-
- 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
- H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
- H01M50/172—Arrangements of electric connectors penetrating the casing
- H01M50/174—Arrangements of electric connectors penetrating the casing adapted for the shape of the cells
- H01M50/178—Arrangements of electric connectors penetrating the casing adapted for the shape of the cells for pouch or flexible bag cells
-
- 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
- H01M50/50—Current conducting connections for cells or batteries
- H01M50/543—Terminals
- H01M50/562—Terminals characterised by the material
-
- 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
- H01M6/16—Cells with non-aqueous electrolyte with organic 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
- H01M50/50—Current conducting connections for cells or batteries
- H01M50/543—Terminals
- H01M50/564—Terminals characterised by their manufacturing process
- H01M50/566—Terminals characterised by their manufacturing process by welding, soldering or brazing
Abstract
FLEXIBLE CELLS AND BATTERIES
FORMED THEREFROM
ABSTRACT
A high energy density cell or battery capable of undergoing flexular stress with little effect on its discharge properties sither during or after subjection to stress.
FORMED THEREFROM
ABSTRACT
A high energy density cell or battery capable of undergoing flexular stress with little effect on its discharge properties sither during or after subjection to stress.
Description
, ~7~3 This invention relates to high energy density cells or batteries which are subjected to and can withstand repeated stress conditions and abuse in the form of repaated flexing and more particularly to such cells or batteries formed there-from wherein there is employed an active cathodic elementincluding a ~ibrous, conductive material, the cathodic element being sealed in a plastic en~elope.
High enexgy organic electrolyte cells such as those utilizing active components such as lithium anodes and volatile organi.c electrolytes such as tetrahydrofuran must be isolated from ambient atmospheric conditions. Heretofore, such isolation has usually been accomplished by the use of hermetically sealed containers of some bulk and rigidity for protection against abuse and possible rupture. However, truly hermetically sealed packages which have a degree o~ f~exibility have been gen-erally confined to thin film or solid state cells with a minimum of corrosive electrolyte. ~enerally ~hose cells which axe referred to as being ~lexible and which do not contain rigid electrode elements contain, ~or the most park, less corrosive alkaline cell components. These cells are constructed to be adaptable to fit into odd shaped spaces or to be wrapped around electrical componentry. However, they cannot withstand repeated abuse or flexing without deterioration of the electro-chemical and structural properties of the cells. This deterioration includes electrolyte leakage and contamination of cell elements resulting f.rom rupture or opening of the cell package, separation of electrode materials rom current collectors : ~ .
. ~
1)3 and electrical tab contacts, fatigue of metal electrodes if used without supporting current collectors and generally the crumbling and disintegration of electrodes, especially of the pressed powder type, resulting in reduced cell capacity and internal shorting~
It is therefore an o~ject of the present invention to provide high energy density cells which can undergo flexing stresses while maintaining electrical and structural integrity for substantially the entire electrical life of the cell battery.
It is another object to provide a cell, in which each of the individual component elements, as well as the cell as a whole, has the ability to withstand repetitive flexural stress abuse both structurally and electrically.
Generally, the present invention involves both ~he composition and the ~orm of an electrochemical cell. In the case o~ cells having highly active or volatile components the cell container must have the features of substantial hermeticity even under ~lexural strain and abuse and the container material must also be impermeable to the volatile solvent vapors. A
container having such qualities is one composed of a heat sealable ~oil laminate in which the layer facing the interior of the cell is a heat sealable non-conductive plastic which is inert to the ~ volatile or~anic solvent but permeable to the solvent vapors, and : 25 a metal foil outer layer placed upon the inner layer. The metal ~foil lS impermeable to the solvent vapors, but it should not be placed in direct contact with the solvent since it is subject to , ,. .
76Z~3 being corroded by direct contact with the solvent. Direct contact is also undesirable because o~ the electrically conductive nature of metals which might lead to shorting of the cell. The metal foil is supported hy the inner plastic layer. For additional protection a third layer, of plastic, is desirably placed upnn the outside of the foil layer there-by totally enclosing and protectiny the metal layer from abuse.
The third layer is also useful for providing electrical insulation between two or more connected cells as well as for providing additional heat sealing characteristics in individual cells and cells in heat sealed combinations.
A limiting factor on the flexibility of cells is the degree of flexibility o~ the electrodes. Metal electrodes have a degree of ~lexibility, especially when the metal electrode is used in the form of thin sheets. However in the case o~ metals such as lithium, repeated flexing of the electrode tends to work harden the metal anq thereby cause it to become brittle~ r~hus, though lithium sheets can normally be used with o~ without a backing it i~ highly deqirable to ~ provide a flexible, metallic mesh, current collect~ backing for the active material so that the structure will be able to withstand repeated flexural stresses.
As a further refinement which results in increased flexibility the electrode active material can be segmented.
This permitæ most of the flexural stress to be concentrated at the points o~ the current collector between the active segments.
Since the current collector does not become embrittled to the same .;
~L~7~3 extent as would lithium, increased resistance to the normally deleterious effects of flexural stress can be obtained.
Additionally, with segmen~ation of the active material on the current collector, dislodyement o~ the active material from the current collector is minimized.
Heretofore, electrodes have been formed on an expanded metal current collector from cathode activ~ powder~e.g. AgzCrO4~, binders such as polytetrahaloethylene, and a conductive powdered material. Such electrodes, however, have a high degree of rigidity whereby flexing of a cell containing such a cathode results in crumbling or cracking of the electrode structure with the high probability of internal shorting and loss of capacity.
In accordance with the present inven~ion it has been discoverea that ~. f., in addition to or even in place of some or all of the graphite powder, (included in the electrode structure for conductivity3 chopped graphite fibers can be homogeneously dispersed in the electrode to eliminate the rigidity of the electrode whereby to attain a high degree of resiliency as well as structural integrity when subjected to flexural stress.
The amount of graphite fibers necessary can be as low as about 0.1%, which minimal amount will not significantly afect the capacity of the cathode.
~ he present invention also contemplates the use of a pouch in which the cathodic material is enclosed. The pouch will advantageously be formed from a fl0xible material (e.g.
polyolefins such as polypropylene) which is sufficiently porous to permit electrolyte ion flow while inhibiting the movement of ~ 6Z~3 M-3308/3333 the solid electrode materials therethrough. The flexi~le material must be compatible with all oE the cell components such as the lithium, sil-ver chromate and electrolytes such as lithiunl perchlorate in tetrahy-drofuran and propylene carbonate which are used in one embodiment of the high energy density~ fle~ible, cells of the invention. Addition-ally? the flexible separator which surrounds the pressed powder elec- ~-trode for structural integrity during flexation will advantageously be closed on all sides to prevent any loose particles of the pressed powder electro~e which may form from shorting the cell. This is accom-plished by heat sealing the pouch after insertion of the cathodic element, leaving only the terminal tab extending therethrough.
The expanded metal current collectors used as a backing for the active cathode material should have the requisite flexibility and should be compatible with the electrode and electrolyte materials. Such materials include expanded titanium, tantalum, molybdenum, zirconium, niobium, vanadium, chromium, tungsten, and stainless steel. The tab materials for external electrical connection can be made of the same materials as the current collectors with tantalum being the preferred ~aterial for such tabs~
~enerally, the cathodic structure for the flexible electro-chemical cPll of the present invention comprises a compressed mixture of a powdered cathode actlve mat&rial, chopped graphite fibers, and a binder; said mixture being affixed to a flexible metall:Lc current col-lector; a metal tab aEfixed to said col].ector; and said compressed ~ix-tllre and said current collector being sealed within a plastic pouch w~th said metallic tab extending therethrough; the plastic of said pouch having sufficient porosity to permit ionic flow therethrough, and the pores khereof being suf~iciently small that solid particles will not ~-pass therethrough.
It is highly desirable for the flexible cell, if it is to op-erate satisfactorily, that the electrochemical system be neither pres-surized nor gassing in nature since internal pressure (above a minimal ,:
.. .. . . . .
amount) could result in puf:Elng o:E the cell container which could result ~:
in deterioration oE the hermetic seal. . .
-5A~
: ' ~, ';
`S " '~
:..' .
, ...
~ M-3308/3333 ~'76;~3 Active components for flexible cells include, as preferred anode material, those metals above hydrogen in the EMF scale such as the above-mentioned lithium and the other metals in Groups IA & IIA of the Periodic Table. In some circumstances, if ~he cell so formed is not subjec~ to any ~ significant amount of gassing, zinc, cadmium, aluminum and ; like anodes can also be used.
Active cathode materials include materials such as metal chromates and dichromates, permanganates, vanada~es, oxides and the like which ca~ be made into pressed powder structures.
Other objects, advantages, and ~eatures o~ the invention will be discerned from a further description of the ; invention as well as from the drawings in which:
Figura 1 is an isometric view of the internal cell components ' prior to sealing, with sections cut away for clarity.
Figure 2 is an isometric view of the outer cell casing.
Figure 3 is a top view of ,a; completed cell.
Figure~4 is a schematic view of one type o~ apparatus which can be used for testing the ~lexibility of the cells.
Figure 5 is a discharge curve showing the voltage of a cell of the invention which is being discharged while it is being 1exed.
Figures 6 and 7 show alternative, useful embodiments of multi-cell batteries.
Referring now to the drawings, Figure 1 shows the cell components wherein a~anode 10 is folded about a cathode 11.
A porous separator 12 separates the anode 10 and the cathade 11 ` ~ and extends beyond the perimeter of the ca~hode material. The separator 12 may be any suitable mieroporous thermoplastic : : ~
:~76~03 material which is capable of being heat sealed to enclose the cathode 11. Suitable materials lnclude polyolefin ~ilms such as those described in U.S. Patent No. 3,351,~95. Surrounding the anode 10 is a sheet 13 composed of the same type of sealable material as the separator. The sheet 13 ~xtends beyond the perimeter of the anode and is heat sealed to enclose both the anode 10 and the cathode 11. The latter enclosure 13 serves to hold the anode and cathode together during flexural stress. The anode 10 can be made by pressing an active metal sheet onto an expanded metal current collector 14. The active metal can be segmented at intervals in order to increase the pliability and ruggedness of the anode. The size oE the active metal segments can be varied, with increasing segment sizes (i.e. less spaces) resulting in greater capacity at the cost of pliabllity; while decreasing the size of the segments or enlarging the space between segments results in more unused space which will reduce capacity but increase pliability. The anode terminal is made via a metal tab 15 which is spot welded to ~he expanded metal current collector 14.
The cathode 11 is fabricated by blending powdered active material wlth a binder, graphite flbers9 and? depending on the conductivity of the active cathode material and the intended use of the cell, a powdered conductlve material.
' ~.
., .. . .. . .. . . . ... :
~,7~6~D3 The conductive material can be added in amounts of about 1 to 50 percent; preferably, as when the active cathodic material is silver chromate, the amount of conductive powder will be up to 10 percent. The conductive fibers will be present in an amount of at least 0.1% by weight. PreEerably, the fibers are graphite and are present in an amount of between about 0.1 and 10 percent~ The binder is used in amounts of about 2 to 30 percent; preferably about 10 percent ginder is used. ~t lea~t 50 percent preferably 70% material should be used.
Polytetrafluoroethylene is a preferred binder, but other binders, such as polytrifluoroethylene, polytrifluoro-chloroethylene, polyethylene? and polypropylene can also be used. The balance of the compositions will generally be the preferred active cathode material. The graphite fibers wlll ~`
advantageously be homogeneously dispersed throughout the cathode structure where they provide the flexibility and structural integrlty necessary for the cathode to operate satisfactorily under fIexural stress. The admixture o~
materials forming the cathode is mixed with any suitable liquid in a mamler known in the art (see, for example, U.S. Patent No.
3,655,585; also Canadian Patent No. 998,098) and blended until it has a conslstency o;E dough. It is then rolled onto expanded current collector 24 and dr~ed under vaccum. External electrical connection to the cathode is made by spot welding metal tab 25 to the cathode current collector 24.
: ' ,.
~ ::
1~-33~/3333 ~1762~3 The anode and cathode tabs 15 and 2S are coated with a heat sealable material (16 and 26 respectively) to permit the formation of a durable seal with the outer cell casing 30.
After the anode 10 and cathode 11 have been heat sealed in their respective casings 13 and 12, the entire assembly 20 is placed in ~oil laminate bag 30, shown in Figure
High enexgy organic electrolyte cells such as those utilizing active components such as lithium anodes and volatile organi.c electrolytes such as tetrahydrofuran must be isolated from ambient atmospheric conditions. Heretofore, such isolation has usually been accomplished by the use of hermetically sealed containers of some bulk and rigidity for protection against abuse and possible rupture. However, truly hermetically sealed packages which have a degree o~ f~exibility have been gen-erally confined to thin film or solid state cells with a minimum of corrosive electrolyte. ~enerally ~hose cells which axe referred to as being ~lexible and which do not contain rigid electrode elements contain, ~or the most park, less corrosive alkaline cell components. These cells are constructed to be adaptable to fit into odd shaped spaces or to be wrapped around electrical componentry. However, they cannot withstand repeated abuse or flexing without deterioration of the electro-chemical and structural properties of the cells. This deterioration includes electrolyte leakage and contamination of cell elements resulting f.rom rupture or opening of the cell package, separation of electrode materials rom current collectors : ~ .
. ~
1)3 and electrical tab contacts, fatigue of metal electrodes if used without supporting current collectors and generally the crumbling and disintegration of electrodes, especially of the pressed powder type, resulting in reduced cell capacity and internal shorting~
It is therefore an o~ject of the present invention to provide high energy density cells which can undergo flexing stresses while maintaining electrical and structural integrity for substantially the entire electrical life of the cell battery.
It is another object to provide a cell, in which each of the individual component elements, as well as the cell as a whole, has the ability to withstand repetitive flexural stress abuse both structurally and electrically.
Generally, the present invention involves both ~he composition and the ~orm of an electrochemical cell. In the case o~ cells having highly active or volatile components the cell container must have the features of substantial hermeticity even under ~lexural strain and abuse and the container material must also be impermeable to the volatile solvent vapors. A
container having such qualities is one composed of a heat sealable ~oil laminate in which the layer facing the interior of the cell is a heat sealable non-conductive plastic which is inert to the ~ volatile or~anic solvent but permeable to the solvent vapors, and : 25 a metal foil outer layer placed upon the inner layer. The metal ~foil lS impermeable to the solvent vapors, but it should not be placed in direct contact with the solvent since it is subject to , ,. .
76Z~3 being corroded by direct contact with the solvent. Direct contact is also undesirable because o~ the electrically conductive nature of metals which might lead to shorting of the cell. The metal foil is supported hy the inner plastic layer. For additional protection a third layer, of plastic, is desirably placed upnn the outside of the foil layer there-by totally enclosing and protectiny the metal layer from abuse.
The third layer is also useful for providing electrical insulation between two or more connected cells as well as for providing additional heat sealing characteristics in individual cells and cells in heat sealed combinations.
A limiting factor on the flexibility of cells is the degree of flexibility o~ the electrodes. Metal electrodes have a degree of ~lexibility, especially when the metal electrode is used in the form of thin sheets. However in the case o~ metals such as lithium, repeated flexing of the electrode tends to work harden the metal anq thereby cause it to become brittle~ r~hus, though lithium sheets can normally be used with o~ without a backing it i~ highly deqirable to ~ provide a flexible, metallic mesh, current collect~ backing for the active material so that the structure will be able to withstand repeated flexural stresses.
As a further refinement which results in increased flexibility the electrode active material can be segmented.
This permitæ most of the flexural stress to be concentrated at the points o~ the current collector between the active segments.
Since the current collector does not become embrittled to the same .;
~L~7~3 extent as would lithium, increased resistance to the normally deleterious effects of flexural stress can be obtained.
Additionally, with segmen~ation of the active material on the current collector, dislodyement o~ the active material from the current collector is minimized.
Heretofore, electrodes have been formed on an expanded metal current collector from cathode activ~ powder~e.g. AgzCrO4~, binders such as polytetrahaloethylene, and a conductive powdered material. Such electrodes, however, have a high degree of rigidity whereby flexing of a cell containing such a cathode results in crumbling or cracking of the electrode structure with the high probability of internal shorting and loss of capacity.
In accordance with the present inven~ion it has been discoverea that ~. f., in addition to or even in place of some or all of the graphite powder, (included in the electrode structure for conductivity3 chopped graphite fibers can be homogeneously dispersed in the electrode to eliminate the rigidity of the electrode whereby to attain a high degree of resiliency as well as structural integrity when subjected to flexural stress.
The amount of graphite fibers necessary can be as low as about 0.1%, which minimal amount will not significantly afect the capacity of the cathode.
~ he present invention also contemplates the use of a pouch in which the cathodic material is enclosed. The pouch will advantageously be formed from a fl0xible material (e.g.
polyolefins such as polypropylene) which is sufficiently porous to permit electrolyte ion flow while inhibiting the movement of ~ 6Z~3 M-3308/3333 the solid electrode materials therethrough. The flexi~le material must be compatible with all oE the cell components such as the lithium, sil-ver chromate and electrolytes such as lithiunl perchlorate in tetrahy-drofuran and propylene carbonate which are used in one embodiment of the high energy density~ fle~ible, cells of the invention. Addition-ally? the flexible separator which surrounds the pressed powder elec- ~-trode for structural integrity during flexation will advantageously be closed on all sides to prevent any loose particles of the pressed powder electro~e which may form from shorting the cell. This is accom-plished by heat sealing the pouch after insertion of the cathodic element, leaving only the terminal tab extending therethrough.
The expanded metal current collectors used as a backing for the active cathode material should have the requisite flexibility and should be compatible with the electrode and electrolyte materials. Such materials include expanded titanium, tantalum, molybdenum, zirconium, niobium, vanadium, chromium, tungsten, and stainless steel. The tab materials for external electrical connection can be made of the same materials as the current collectors with tantalum being the preferred ~aterial for such tabs~
~enerally, the cathodic structure for the flexible electro-chemical cPll of the present invention comprises a compressed mixture of a powdered cathode actlve mat&rial, chopped graphite fibers, and a binder; said mixture being affixed to a flexible metall:Lc current col-lector; a metal tab aEfixed to said col].ector; and said compressed ~ix-tllre and said current collector being sealed within a plastic pouch w~th said metallic tab extending therethrough; the plastic of said pouch having sufficient porosity to permit ionic flow therethrough, and the pores khereof being suf~iciently small that solid particles will not ~-pass therethrough.
It is highly desirable for the flexible cell, if it is to op-erate satisfactorily, that the electrochemical system be neither pres-surized nor gassing in nature since internal pressure (above a minimal ,:
.. .. . . . .
amount) could result in puf:Elng o:E the cell container which could result ~:
in deterioration oE the hermetic seal. . .
-5A~
: ' ~, ';
`S " '~
:..' .
, ...
~ M-3308/3333 ~'76;~3 Active components for flexible cells include, as preferred anode material, those metals above hydrogen in the EMF scale such as the above-mentioned lithium and the other metals in Groups IA & IIA of the Periodic Table. In some circumstances, if ~he cell so formed is not subjec~ to any ~ significant amount of gassing, zinc, cadmium, aluminum and ; like anodes can also be used.
Active cathode materials include materials such as metal chromates and dichromates, permanganates, vanada~es, oxides and the like which ca~ be made into pressed powder structures.
Other objects, advantages, and ~eatures o~ the invention will be discerned from a further description of the ; invention as well as from the drawings in which:
Figura 1 is an isometric view of the internal cell components ' prior to sealing, with sections cut away for clarity.
Figure 2 is an isometric view of the outer cell casing.
Figure 3 is a top view of ,a; completed cell.
Figure~4 is a schematic view of one type o~ apparatus which can be used for testing the ~lexibility of the cells.
Figure 5 is a discharge curve showing the voltage of a cell of the invention which is being discharged while it is being 1exed.
Figures 6 and 7 show alternative, useful embodiments of multi-cell batteries.
Referring now to the drawings, Figure 1 shows the cell components wherein a~anode 10 is folded about a cathode 11.
A porous separator 12 separates the anode 10 and the cathade 11 ` ~ and extends beyond the perimeter of the ca~hode material. The separator 12 may be any suitable mieroporous thermoplastic : : ~
:~76~03 material which is capable of being heat sealed to enclose the cathode 11. Suitable materials lnclude polyolefin ~ilms such as those described in U.S. Patent No. 3,351,~95. Surrounding the anode 10 is a sheet 13 composed of the same type of sealable material as the separator. The sheet 13 ~xtends beyond the perimeter of the anode and is heat sealed to enclose both the anode 10 and the cathode 11. The latter enclosure 13 serves to hold the anode and cathode together during flexural stress. The anode 10 can be made by pressing an active metal sheet onto an expanded metal current collector 14. The active metal can be segmented at intervals in order to increase the pliability and ruggedness of the anode. The size oE the active metal segments can be varied, with increasing segment sizes (i.e. less spaces) resulting in greater capacity at the cost of pliabllity; while decreasing the size of the segments or enlarging the space between segments results in more unused space which will reduce capacity but increase pliability. The anode terminal is made via a metal tab 15 which is spot welded to ~he expanded metal current collector 14.
The cathode 11 is fabricated by blending powdered active material wlth a binder, graphite flbers9 and? depending on the conductivity of the active cathode material and the intended use of the cell, a powdered conductlve material.
' ~.
., .. . .. . .. . . . ... :
~,7~6~D3 The conductive material can be added in amounts of about 1 to 50 percent; preferably, as when the active cathodic material is silver chromate, the amount of conductive powder will be up to 10 percent. The conductive fibers will be present in an amount of at least 0.1% by weight. PreEerably, the fibers are graphite and are present in an amount of between about 0.1 and 10 percent~ The binder is used in amounts of about 2 to 30 percent; preferably about 10 percent ginder is used. ~t lea~t 50 percent preferably 70% material should be used.
Polytetrafluoroethylene is a preferred binder, but other binders, such as polytrifluoroethylene, polytrifluoro-chloroethylene, polyethylene? and polypropylene can also be used. The balance of the compositions will generally be the preferred active cathode material. The graphite fibers wlll ~`
advantageously be homogeneously dispersed throughout the cathode structure where they provide the flexibility and structural integrlty necessary for the cathode to operate satisfactorily under fIexural stress. The admixture o~
materials forming the cathode is mixed with any suitable liquid in a mamler known in the art (see, for example, U.S. Patent No.
3,655,585; also Canadian Patent No. 998,098) and blended until it has a conslstency o;E dough. It is then rolled onto expanded current collector 24 and dr~ed under vaccum. External electrical connection to the cathode is made by spot welding metal tab 25 to the cathode current collector 24.
: ' ,.
~ ::
1~-33~/3333 ~1762~3 The anode and cathode tabs 15 and 2S are coated with a heat sealable material (16 and 26 respectively) to permit the formation of a durable seal with the outer cell casing 30.
After the anode 10 and cathode 11 have been heat sealed in their respective casings 13 and 12, the entire assembly 20 is placed in ~oil laminate bag 30, shown in Figure
2. The foil laminate bag 30 is formed by ~olding a planar sheet o a compo~site plastic~metal material, such as one having an aluminum foil layer 36~- sandwiched between two polyethylene layers 35 and 37, and heat sealing the ends of the folded sheet as shown. The heat seals which form bag or pouch 30 are shown in Pigure 2 as 31 and 32. The planar sheet of plastic-metal ~oil laminate material is folded ovex onto itself as show~ and heat sealed; first down the center 31 where the edges of the sheet overlap, and then at one end 32, thereby forming an open ended bag 30~ The cell assem~ly 20 of Figure 1 is inserted through the open end 34 of the bag 30, and the cell i~ filled with electrolyte~ ~herea~ter, the bag 30 is sealed, by heat seal 32 (Fig. 3) along the open end 34 to hermetically enclose the call contents. For hermaticity, the tabs 15, 25 leading ~rom the anode and cathode are coated with a heat sealable material at the point at which they are contacted by the final heat seal~ Tabs 15 and 25 protrude from the cell casing for electrica1 connection. Cells in accordance wîth the invention will have a maximum thickness of about 100 mils, preferab1y about 20 to about 70 milsO
Figure 4 depicks a testing device which is useful to determine the effect of repeti~ve flexing upon a cell. The device comprises three pairs of 1 inch diameter cylindrical rods 1, la, 2, 2a, and 3, 3a of which the two outer pai~ 1, la and
Figure 4 depicks a testing device which is useful to determine the effect of repeti~ve flexing upon a cell. The device comprises three pairs of 1 inch diameter cylindrical rods 1, la, 2, 2a, and 3, 3a of which the two outer pai~ 1, la and
3, 3a are stationary and the middle pair 2, 2a is mounted on plate 4 which is slida~l~ mounted in guide 5 end driven by camshaft arrangement 6 so that the pair of rods 2, 2a move back and forth. A cell 7 is placed in the cell holder 8 which comprises two layers o~ flexible polyester sheets held tightly in place by means of two springs 9a and 9b. The arrows indicate operational motion. One ~lexural cycle is defined as including one flex of a cell in each direction.
Figure S is a discharge curve showing the discharge voltage of one cell (that of Example 1 below), th`e ~; 15 voltage being measured as the cell was being subjected to repetitive flexing cycles on the apparatus of Figure 4, said cel} being subjected to flexing at the rate of 100 cycles per minute.
Another testing device which i9 useful ~or determining the properties of cells formed in accordance with the present in~ention i~ one (not shown) which accurately measures the pliability. Such device includes a 1 inch diameter horizontally dispo3ed, stationary rod. A cell is placed on the rod and covered with a thin poIypropylene foil which is connected by means of strings to a pan which~hangs below the horizontal rod.
stationary metal;plate is located 1/2" below a metal po~nter attached on the bottom o~ the pan. The pliability o~ the cell is .
. . ~ .
~7~Z~3 determined by adding tiny pellets to the pan until the pointer touches the stationary metal plate.~ ht b~lb and a battery are operatively connected to the pointer and to the metal plate to indicate wh~n the electrical circuit is completed.
The weight of the metal pellets in the pan is taken as a measure of the inverse pliability of the cells. That is, the lower the weight reguired to bend the cell, ~he greater is the pliability. Meaningful comparisons between the pliability of two dif~erent structures can be obtained, but only when they have the same width and length.
Examples of multicell, flexible batteries are schematically shown in Figures 6 and 7. Figure 6 shows a band type battery 65 having a constant width and a variable length as additional cells such as those described are added to lengthen the structure. The cells in this embodiment are shown to be connected in parallel for greater current capacity.
Figure 7 shows a planar arrangement of cells formed into a square battery 75 and the electrical connections thera-between.
In both Figures 6 and 7 the cells are preferrably electrically interconnected by long insulatively coated tabs 66, 67 and 76,77 respectively, for simple parallal connections.
The cells 80; arranged are sealed within flexible casing 65,75 sL~ilar to the construction of the unit cell casings of Figure 2.
The multicell cvnstxuction has the advantage of lower resistance to bending and an increased capability of .~
-~ M-3308/3333 ~762~?3 withstanding flexural cycles. A disadvantage as compared with the unitary flexible cells is a possible reduction of energy density resulting from unused spacing between the cells.
Other arrangements of the cells in multicell batteries as well as the ~ariations in the individual sizes of the unit cells and other modifications of the same ilk are contemplated to be within the ambit of the present invention.
--:L;2--~L~7~3 :
The following Examples are given to further illustrate the invention. In the examples, as throughout the speciflcation, all parts or percentages given are by weight unless otherwise specified.
EXAMPLE I
A flexible cell is made in accordance with the principles of the present i~vention and as shown in Flgures 1-3. The cell is made using a lithium anode 10 folded about a silver chromate ~Ag2CrO~) cathode 11. A "Celgard"
(a trademark of the Celanese Corp. ~or porous polypropylene) separator 12 (.001" thick~ separates the anode and the cathode and extend~ beyond the perimeter of the cathode material. The polypropylene of separator 12 is a thermoplastic, microporous material which is heat sealed to enclose the cathode 11 with only tab 25 extending therethrough. Surroundin~ the lithium anode 10 is a second sheet 13 of polypropylene. Sheet 13 extends beyond the perimeter of ~he lithium anode and is heat sealed to enclose both the lithium anode 10 and the pouch containing the silver chromate cathode 11 leaving tabs 15 and 25 extending therethrough. The lithium anode 10 ls segmented 7 and is made by pressing lithium strips having a thickness o~ 0.01 lnch and a wldth of 0.25 inch onto expanded tltanlum current collector 14, the lithium strips being spaced at about 1/16" intervals. The anode terminal is made vla a tantalum tab 15 which is spot welded to the expanded current collector 14.
The cathode 11 is abricated from 85 percent ;
, powdered Ag2CrO4 with 4.5 percent powdered graphite, ~ ' .- , .
~ M~3308/3333 ~76Z~3 10 percent colloidal polytetra~luoroethylene binder and 0.5 percent graphite fibers. The formation of the cathode includes the steps of treating ~ibrous graphite (l/4"-fine, Basic Carbon Corp.-GY2-30)` in a Waring blender for lS
seconds at medium speed, mixing silver chromate with the graphite powder and fibars; thoroughly milling the mix~ure:
pelletizing the ground mixture; grinding the pellets;
passing the resulting powder-fiber mixture through a 100 mesh U.S. sieve; adding the polytetrafluoroethylene binder with sufficient isopropyl alcohol to form a slurry thereof; mixing the resulting admixture till it becomes rubbery; rolling the mixture into a sheet; pressing the sheet onto an expanded titanium current collector which is thoroughly dried under vacuum. The cathode structure has dimensions of about 2" x .6"
x 0.012". The graphite fibers are homogeneously dispersed throughout the cathode structure whera they provide the ~lexibility and structural integrity necessary ~or the cathode to operate satisfactorily under ~lexural strees. External electrical connect.ion to the cathode is made by spot welding a tantalum tab to the titanium cathode current collector.
The anode and cathode tabs are coated with a heat sealable material (polyeth~lene strips 16 and 26 respectively) to permit the formation o~ a durable seal with the outer cell casing 30.
A foil laminate bag is ormed by folding a planar sheet 33 o~ material having an aluMinum foil layer 36 sandwiched between two polyethylene layers 35 and 37 (a single sheet of sai~ material having a total thickness of 0.003 inches) and heat sealing the ends of the folded sheet.
M~3308/3333 31L~76~03 The heat seals forming bag or pouch 30 are shown in Figure 2 as 31 and 32. The planar sheet of plastic-foil laminate material is folded over onto itself as shown and heat sealed down the center 31 where the edges of the sheet overlap and at one end thereby forming an open ended bag 30.
The cell assembly is inserted through the open end 34 of the bag 30, and the cell is filled with electrolyte in the form of lM lithium perchlorate dissolved in a mixture of equal parts of propylene carbonate and tetrahydrofuran and the excess squeezed out. A~ter the cell is ~illed with the electrolyte the bag is heat sealed along the open end to hermetically enclose the cell contents. For hermeticity~
the tabs 15,25 leading ~-rom the anode and cathode are coated with a heat sealable material a~ the point at which they are contacted by the final heat seal. Tabs 15 and 25 protrude from the cell casing for electrical connection.
The above cell has a total thickness of about .055 inch and measures 0.75 inch by 2.0 inches (not including the tab length) and i9 subjected to flexural stress on the testing device depicted in Figure 4 and described above.
The cell was electrically discharged while being 1exed, and Figure 5 is a discharge curve showlng the cell voltage as a function of time. The cell is discharged at 5 mA ..
while being flexed at 100 cycles per minute and it lasted ~5 63,859 cycles before failure. Failure is defined in the instant case as an amplitude of voltage fluctuation caused by the flexing conditions so large that meaningful cell operati~n becomes impossible. Ihe cell accordingly lasted `~ for about 10 hours to 1.0 volt.
EX~MPLE II
Flexural Characteristics: The flexural characteristies of ~lexible cells (0.75" x 2.0") made in accordance with the procedure herein are evaluated by first flexing the cells for a large number of flexural cycles at frequencies of 10, 50 and 100 cycles/minute~
The cells are then discharged at a constant current of 5 mA
and the calls ~are tested electrochemieally for ef~ieieney by discharging them and determining the cell capacity to a cut-off voltage of 2.0 and 1.0 volt. The result9 are shown in Tables 1 and 2. Two cells (14 and 15) were discharg~d while they were being flexed at frequeneies o~ 50 and 100 cycles/minute. The eells are cathode limiting and therefore the performance of the eells is also expressed in terms of the utilization effieiency of the eathode in Table 1.
~Thereis no degradation of cell performance a~ter 1000 ~lexural cycles at cy~ling fregueneies o~ 10 or 100 CPM (eyeles/minu~e).
The data in Table 2 indicates that though there is some degradation of eell performanee after 2000 and 4000 flexural eyeles at 100 CPM, when the eells were diseharge~ while being flexed~ the eells were ablè to withstand even larger nu~ers of flexural eyeles before failure. Cell 15 (Table 2) is deseribed in Example I and, as nvted, lasted 63,859 eyeles prior to failure. I was flexed at 100 CPM while being diseharged at 5 mA.
.
~7~i2~ 3 OD --I ~ 00 ~ ~ --I
~ . . . ~ . . . .
Figure S is a discharge curve showing the discharge voltage of one cell (that of Example 1 below), th`e ~; 15 voltage being measured as the cell was being subjected to repetitive flexing cycles on the apparatus of Figure 4, said cel} being subjected to flexing at the rate of 100 cycles per minute.
Another testing device which i9 useful ~or determining the properties of cells formed in accordance with the present in~ention i~ one (not shown) which accurately measures the pliability. Such device includes a 1 inch diameter horizontally dispo3ed, stationary rod. A cell is placed on the rod and covered with a thin poIypropylene foil which is connected by means of strings to a pan which~hangs below the horizontal rod.
stationary metal;plate is located 1/2" below a metal po~nter attached on the bottom o~ the pan. The pliability o~ the cell is .
. . ~ .
~7~Z~3 determined by adding tiny pellets to the pan until the pointer touches the stationary metal plate.~ ht b~lb and a battery are operatively connected to the pointer and to the metal plate to indicate wh~n the electrical circuit is completed.
The weight of the metal pellets in the pan is taken as a measure of the inverse pliability of the cells. That is, the lower the weight reguired to bend the cell, ~he greater is the pliability. Meaningful comparisons between the pliability of two dif~erent structures can be obtained, but only when they have the same width and length.
Examples of multicell, flexible batteries are schematically shown in Figures 6 and 7. Figure 6 shows a band type battery 65 having a constant width and a variable length as additional cells such as those described are added to lengthen the structure. The cells in this embodiment are shown to be connected in parallel for greater current capacity.
Figure 7 shows a planar arrangement of cells formed into a square battery 75 and the electrical connections thera-between.
In both Figures 6 and 7 the cells are preferrably electrically interconnected by long insulatively coated tabs 66, 67 and 76,77 respectively, for simple parallal connections.
The cells 80; arranged are sealed within flexible casing 65,75 sL~ilar to the construction of the unit cell casings of Figure 2.
The multicell cvnstxuction has the advantage of lower resistance to bending and an increased capability of .~
-~ M-3308/3333 ~762~?3 withstanding flexural cycles. A disadvantage as compared with the unitary flexible cells is a possible reduction of energy density resulting from unused spacing between the cells.
Other arrangements of the cells in multicell batteries as well as the ~ariations in the individual sizes of the unit cells and other modifications of the same ilk are contemplated to be within the ambit of the present invention.
--:L;2--~L~7~3 :
The following Examples are given to further illustrate the invention. In the examples, as throughout the speciflcation, all parts or percentages given are by weight unless otherwise specified.
EXAMPLE I
A flexible cell is made in accordance with the principles of the present i~vention and as shown in Flgures 1-3. The cell is made using a lithium anode 10 folded about a silver chromate ~Ag2CrO~) cathode 11. A "Celgard"
(a trademark of the Celanese Corp. ~or porous polypropylene) separator 12 (.001" thick~ separates the anode and the cathode and extend~ beyond the perimeter of the cathode material. The polypropylene of separator 12 is a thermoplastic, microporous material which is heat sealed to enclose the cathode 11 with only tab 25 extending therethrough. Surroundin~ the lithium anode 10 is a second sheet 13 of polypropylene. Sheet 13 extends beyond the perimeter of ~he lithium anode and is heat sealed to enclose both the lithium anode 10 and the pouch containing the silver chromate cathode 11 leaving tabs 15 and 25 extending therethrough. The lithium anode 10 ls segmented 7 and is made by pressing lithium strips having a thickness o~ 0.01 lnch and a wldth of 0.25 inch onto expanded tltanlum current collector 14, the lithium strips being spaced at about 1/16" intervals. The anode terminal is made vla a tantalum tab 15 which is spot welded to the expanded current collector 14.
The cathode 11 is abricated from 85 percent ;
, powdered Ag2CrO4 with 4.5 percent powdered graphite, ~ ' .- , .
~ M~3308/3333 ~76Z~3 10 percent colloidal polytetra~luoroethylene binder and 0.5 percent graphite fibers. The formation of the cathode includes the steps of treating ~ibrous graphite (l/4"-fine, Basic Carbon Corp.-GY2-30)` in a Waring blender for lS
seconds at medium speed, mixing silver chromate with the graphite powder and fibars; thoroughly milling the mix~ure:
pelletizing the ground mixture; grinding the pellets;
passing the resulting powder-fiber mixture through a 100 mesh U.S. sieve; adding the polytetrafluoroethylene binder with sufficient isopropyl alcohol to form a slurry thereof; mixing the resulting admixture till it becomes rubbery; rolling the mixture into a sheet; pressing the sheet onto an expanded titanium current collector which is thoroughly dried under vacuum. The cathode structure has dimensions of about 2" x .6"
x 0.012". The graphite fibers are homogeneously dispersed throughout the cathode structure whera they provide the ~lexibility and structural integrity necessary ~or the cathode to operate satisfactorily under ~lexural strees. External electrical connect.ion to the cathode is made by spot welding a tantalum tab to the titanium cathode current collector.
The anode and cathode tabs are coated with a heat sealable material (polyeth~lene strips 16 and 26 respectively) to permit the formation o~ a durable seal with the outer cell casing 30.
A foil laminate bag is ormed by folding a planar sheet 33 o~ material having an aluMinum foil layer 36 sandwiched between two polyethylene layers 35 and 37 (a single sheet of sai~ material having a total thickness of 0.003 inches) and heat sealing the ends of the folded sheet.
M~3308/3333 31L~76~03 The heat seals forming bag or pouch 30 are shown in Figure 2 as 31 and 32. The planar sheet of plastic-foil laminate material is folded over onto itself as shown and heat sealed down the center 31 where the edges of the sheet overlap and at one end thereby forming an open ended bag 30.
The cell assembly is inserted through the open end 34 of the bag 30, and the cell is filled with electrolyte in the form of lM lithium perchlorate dissolved in a mixture of equal parts of propylene carbonate and tetrahydrofuran and the excess squeezed out. A~ter the cell is ~illed with the electrolyte the bag is heat sealed along the open end to hermetically enclose the cell contents. For hermeticity~
the tabs 15,25 leading ~-rom the anode and cathode are coated with a heat sealable material a~ the point at which they are contacted by the final heat seal. Tabs 15 and 25 protrude from the cell casing for electrical connection.
The above cell has a total thickness of about .055 inch and measures 0.75 inch by 2.0 inches (not including the tab length) and i9 subjected to flexural stress on the testing device depicted in Figure 4 and described above.
The cell was electrically discharged while being 1exed, and Figure 5 is a discharge curve showlng the cell voltage as a function of time. The cell is discharged at 5 mA ..
while being flexed at 100 cycles per minute and it lasted ~5 63,859 cycles before failure. Failure is defined in the instant case as an amplitude of voltage fluctuation caused by the flexing conditions so large that meaningful cell operati~n becomes impossible. Ihe cell accordingly lasted `~ for about 10 hours to 1.0 volt.
EX~MPLE II
Flexural Characteristics: The flexural characteristies of ~lexible cells (0.75" x 2.0") made in accordance with the procedure herein are evaluated by first flexing the cells for a large number of flexural cycles at frequencies of 10, 50 and 100 cycles/minute~
The cells are then discharged at a constant current of 5 mA
and the calls ~are tested electrochemieally for ef~ieieney by discharging them and determining the cell capacity to a cut-off voltage of 2.0 and 1.0 volt. The result9 are shown in Tables 1 and 2. Two cells (14 and 15) were discharg~d while they were being flexed at frequeneies o~ 50 and 100 cycles/minute. The eells are cathode limiting and therefore the performance of the eells is also expressed in terms of the utilization effieiency of the eathode in Table 1.
~Thereis no degradation of cell performance a~ter 1000 ~lexural cycles at cy~ling fregueneies o~ 10 or 100 CPM (eyeles/minu~e).
The data in Table 2 indicates that though there is some degradation of eell performanee after 2000 and 4000 flexural eyeles at 100 CPM, when the eells were diseharge~ while being flexed~ the eells were ablè to withstand even larger nu~ers of flexural eyeles before failure. Cell 15 (Table 2) is deseribed in Example I and, as nvted, lasted 63,859 eyeles prior to failure. I was flexed at 100 CPM while being diseharged at 5 mA.
.
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~"`. M-3308/3333 ~i36'~3 EXP-MPLE III
Pliability Characteristics: The pliability of cells with dimensions of 0.75 inch by 2.0 inch was measured for ~our types of cell constructions. The results are shown in Table 3. Inverse pliability (stiffne~s) is defined as the weight required to bend the flexible cell around a 1 inch diameter rod and is quite reproducible for a particular type of cell constrwction.
The average inverse pliability values for cells with 0.01 inch thick non-segmented and the segmented lithium foil are 335 grams and 132 grams respectivelyO
Thus segmentation resulted in an almost thraefold improve-ment in pliability. The average values for the inverse pliability of cells with 0.002 inch thick lithium foil are 106 gm for the non-segmented type and 85 gm for the segmented t~pe. Reduction of thickness of the lithium foil results~ in a significant improvèment in pliability.
Increased pliability, with its resultant reduced cell component deterioration under stress, lS thus attained by segmentation of elèctrodes and, in this case, speci~ically the lithium anode. Eowe~er, reduced capacity results from both segmentation and reduced thickness. ~ weighing of priorities (pliabili.ty v.capacity) in light of the cells intended use is therefore called for in order to obtain an optimum balance.
.
MEASUREMEN~rS OF PLI~BILITY OF ~HE: FI~T FOIL TYPE CELLS
Anode Construct ion*
Cell Foil Thickness Thickness Inverse Cell No._ tIn.) ~inch) Segmented Pliability**
16 0.069 0.01 No 320 17 0.068 0.01 No 311 18 0.067 0.01 ~ 373.8 Average of cells 16 to 18=335 ~9 0.051 0.01 Yes 129.1 0.050 0.01 Yes 135.5 Average of cells 19 and 20~132 21 0.0260 0.002 Yes 85 22 0.0250 0.002 Ye~ 77 23 . 0.0245 0.002 Yes 85.5 24 0.0265 0.002 ~es 80.2 0.0255 0.002 Yes g6.5 26 0.0255 0.002 Yes 80 27 0.0250 0.002 Yes 91.5 28 0.0260 0.002 Yes 90.9 I Average of cells 21 to 28=85 ; 29 0.0270 0.002 No 109.2 0.0270 0.002 No 93.2 31 0.0270 0.002 M~ 101.5 32: 0.0285 ;0.002 N~ - 118.4 : ~ Average of cells 29 to 32 iO6 * Lithium foil o~ expanded:tita~ium~ current collector.
** Weight in grams re~uired to bend the cell axou~d 1 inch diameter~rod.
:
i3 In the construction of the electrodes for the above described flexible cells the thickness of the electrodes becomes a limiting factor with respect to flexibility. Thus, in the construc~ion of the pr~ssed powder electrodes the maximum thickness which would sti~l retain flexible charac~eristics is about 40 mils. The thickness of-the anode m~tal is likewise limit~d and the thickness can range from about 2 to 20 mils with a preferred thickness range of 10 to 20 milsO
The cell as a whole should not have a total thickness in excess of about 100 mils with a preferred thickness range between 20 and 70 mils.
The cells contemplated within the present invention are those generally utilizing high energy density organic electrolytescomprising an eleckrolyte salt di.ssolved in an organic solven~.
Examples of useful electrolyte salts include perchlorates, tetrachloroaluminates, tetrafluoroborates, halides, hexafluorophosphates and hexafluoroarsenates of metals from Groups IA and IIA of the Periodic Table.
Examples of use~ul, organic solvents include: esters and orthoesters such as propylene carbonate, dimethyl carbonate, alkyl formates such as methyl and butyl formate, alkyl acetates, butyrates, methyl or ethyl orthacetate and orthoformate; ethers such as tetrahydrofuran, methoxyethanes and methoxy methanes, ethers derived frvm ethylene glycol and polyethylene glycol, and cyclic ethers such as dioxana, dioxolane; aldehydes and ketones such as acetaldehyde and acetone; nitriles such as acetonitrile, propionitrile, benæonikrile: and amides such as formamide, `
,~ ,~
~L~76~
N,~ dimethyl formamide, N,N dimethylacetamide and closely related amide like compounds such as N,~ dimethyl m~thyl carbama~e and tetramethyluxea; amines such as ~-nitrosodimethylamine;
as well as other known solvents such as dimethyl sulfite, dimethyl sulfoxide, and gamma-butyrolactone~
While there are shown and described presently contemplated embodiments of the invention, it is to be understood that the invention is not limited thereto, but may be otherwise variously embod.ied and practiced within the scope of the following claims.
. - .- . . . . .. .
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~"`. M-3308/3333 ~i36'~3 EXP-MPLE III
Pliability Characteristics: The pliability of cells with dimensions of 0.75 inch by 2.0 inch was measured for ~our types of cell constructions. The results are shown in Table 3. Inverse pliability (stiffne~s) is defined as the weight required to bend the flexible cell around a 1 inch diameter rod and is quite reproducible for a particular type of cell constrwction.
The average inverse pliability values for cells with 0.01 inch thick non-segmented and the segmented lithium foil are 335 grams and 132 grams respectivelyO
Thus segmentation resulted in an almost thraefold improve-ment in pliability. The average values for the inverse pliability of cells with 0.002 inch thick lithium foil are 106 gm for the non-segmented type and 85 gm for the segmented t~pe. Reduction of thickness of the lithium foil results~ in a significant improvèment in pliability.
Increased pliability, with its resultant reduced cell component deterioration under stress, lS thus attained by segmentation of elèctrodes and, in this case, speci~ically the lithium anode. Eowe~er, reduced capacity results from both segmentation and reduced thickness. ~ weighing of priorities (pliabili.ty v.capacity) in light of the cells intended use is therefore called for in order to obtain an optimum balance.
.
MEASUREMEN~rS OF PLI~BILITY OF ~HE: FI~T FOIL TYPE CELLS
Anode Construct ion*
Cell Foil Thickness Thickness Inverse Cell No._ tIn.) ~inch) Segmented Pliability**
16 0.069 0.01 No 320 17 0.068 0.01 No 311 18 0.067 0.01 ~ 373.8 Average of cells 16 to 18=335 ~9 0.051 0.01 Yes 129.1 0.050 0.01 Yes 135.5 Average of cells 19 and 20~132 21 0.0260 0.002 Yes 85 22 0.0250 0.002 Ye~ 77 23 . 0.0245 0.002 Yes 85.5 24 0.0265 0.002 ~es 80.2 0.0255 0.002 Yes g6.5 26 0.0255 0.002 Yes 80 27 0.0250 0.002 Yes 91.5 28 0.0260 0.002 Yes 90.9 I Average of cells 21 to 28=85 ; 29 0.0270 0.002 No 109.2 0.0270 0.002 No 93.2 31 0.0270 0.002 M~ 101.5 32: 0.0285 ;0.002 N~ - 118.4 : ~ Average of cells 29 to 32 iO6 * Lithium foil o~ expanded:tita~ium~ current collector.
** Weight in grams re~uired to bend the cell axou~d 1 inch diameter~rod.
:
i3 In the construction of the electrodes for the above described flexible cells the thickness of the electrodes becomes a limiting factor with respect to flexibility. Thus, in the construc~ion of the pr~ssed powder electrodes the maximum thickness which would sti~l retain flexible charac~eristics is about 40 mils. The thickness of-the anode m~tal is likewise limit~d and the thickness can range from about 2 to 20 mils with a preferred thickness range of 10 to 20 milsO
The cell as a whole should not have a total thickness in excess of about 100 mils with a preferred thickness range between 20 and 70 mils.
The cells contemplated within the present invention are those generally utilizing high energy density organic electrolytescomprising an eleckrolyte salt di.ssolved in an organic solven~.
Examples of useful electrolyte salts include perchlorates, tetrachloroaluminates, tetrafluoroborates, halides, hexafluorophosphates and hexafluoroarsenates of metals from Groups IA and IIA of the Periodic Table.
Examples of use~ul, organic solvents include: esters and orthoesters such as propylene carbonate, dimethyl carbonate, alkyl formates such as methyl and butyl formate, alkyl acetates, butyrates, methyl or ethyl orthacetate and orthoformate; ethers such as tetrahydrofuran, methoxyethanes and methoxy methanes, ethers derived frvm ethylene glycol and polyethylene glycol, and cyclic ethers such as dioxana, dioxolane; aldehydes and ketones such as acetaldehyde and acetone; nitriles such as acetonitrile, propionitrile, benæonikrile: and amides such as formamide, `
,~ ,~
~L~76~
N,~ dimethyl formamide, N,N dimethylacetamide and closely related amide like compounds such as N,~ dimethyl m~thyl carbama~e and tetramethyluxea; amines such as ~-nitrosodimethylamine;
as well as other known solvents such as dimethyl sulfite, dimethyl sulfoxide, and gamma-butyrolactone~
While there are shown and described presently contemplated embodiments of the invention, it is to be understood that the invention is not limited thereto, but may be otherwise variously embod.ied and practiced within the scope of the following claims.
. - .- . . . . .. .
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A cathodic structure for a flexible electro-chemical cell comprising a compressed mixture of a powdered cathode active material, chopped graphite fibers, and a binder; said mixture being affixed to a flexible metallic current collector; a metal tab affixed to said collector;
and said compressed mixture and said current collector being sealed within a plastic pouch with said metallic tab extend-ing therethrough, the plastic of said plastic pouch having sufficient porosity to permit ionic flow therethrough, and the pores thereof being sufficiently small that solid par-ticles will not pass therethrough.
and said compressed mixture and said current collector being sealed within a plastic pouch with said metallic tab extend-ing therethrough, the plastic of said plastic pouch having sufficient porosity to permit ionic flow therethrough, and the pores thereof being sufficiently small that solid par-ticles will not pass therethrough.
2. The cathodic structure of claim 1 wherein said mixture contains at least 0.1% graphite fibers by weight.
3. The cathodic structure of claim 1 wherein said cathode active material is silver chromate (Ag2CrO4).
4. The cathodic structure of claim 1 wherein said plastic is a heat sealable, flexible, microporous polymeric material.
5. The cathodic structure of claim 1 wherein said metallic current collector is an expanded metal with the metals of said current collector and said tab being individually selected from the group consisting of stainless steel, tantalum, titanium, molybdenum, zirconium, niobium, vanadium, chromium, and tunsten.
6. A flexible, non-gassing, high energy density electrochemical cell comprising a flexible, active metal anode having an electrically conductive tab operatively associated therewith; an organic electrolyte; a cathodic structure as defined in claim 1; and an outer, flexible, electrolyte impermeable container hermetically sealed around said anode, said electrolyte and said cathodic structure, with said tabs extending through said outer container.
7. A cell as in claim 6 wherein said anode sub-stantially surrounds said cathodic structure, and a plastic pouch is positioned inside said outer container and sealed around both said anode and said cathodic structure.
8. A cell as in claim 6 wherein said anode comprises segmented portions of said active metal in close proximity to one another and arranged in a parallel direction on said current collector and is affixed to a flexible, ex-panded metal, current collector and said tab associated with said anode is affixed to said current collector.
9. A cell as in claim 6 wherein said active metal is lithium.
10. A cell as in claim 6 wherein said cell has a thickness less than about 100 mils.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/706,877 US4092464A (en) | 1976-07-19 | 1976-07-19 | Flexible cells and batteries formed therefrom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1076203A true CA1076203A (en) | 1980-04-22 |
Family
ID=24839440
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA281,268A Expired CA1076203A (en) | 1976-07-19 | 1977-06-23 | Flexible cells and batteries formed therefrom |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4092464A (en) |
| JP (1) | JPS5325831A (en) |
| BE (1) | BE856920A (en) |
| CA (1) | CA1076203A (en) |
| DE (1) | DE2731973A1 (en) |
| FR (1) | FR2359516A1 (en) |
| GB (1) | GB1576285A (en) |
| NL (1) | NL7707970A (en) |
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-
1976
- 1976-07-19 US US05/706,877 patent/US4092464A/en not_active Expired - Lifetime
-
1977
- 1977-06-23 CA CA281,268A patent/CA1076203A/en not_active Expired
- 1977-07-12 GB GB29178/77A patent/GB1576285A/en not_active Expired
- 1977-07-15 DE DE19772731973 patent/DE2731973A1/en not_active Withdrawn
- 1977-07-18 NL NL7707970A patent/NL7707970A/en not_active Application Discontinuation
- 1977-07-19 FR FR7722115A patent/FR2359516A1/en not_active Withdrawn
- 1977-07-19 JP JP8658277A patent/JPS5325831A/en active Pending
- 1977-07-19 BE BE2056090A patent/BE856920A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5325831A (en) | 1978-03-10 |
| GB1576285A (en) | 1980-10-08 |
| US4092464A (en) | 1978-05-30 |
| NL7707970A (en) | 1978-01-23 |
| FR2359516A1 (en) | 1978-02-17 |
| DE2731973A1 (en) | 1978-02-02 |
| BE856920A (en) | 1977-11-14 |
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