CA1315843C - Separator for electrochemical cells - Google Patents
Separator for electrochemical cellsInfo
- Publication number
- CA1315843C CA1315843C CA000572210A CA572210A CA1315843C CA 1315843 C CA1315843 C CA 1315843C CA 000572210 A CA000572210 A CA 000572210A CA 572210 A CA572210 A CA 572210A CA 1315843 C CA1315843 C CA 1315843C
- Authority
- CA
- Canada
- Prior art keywords
- separator
- cells
- anode
- cathode
- cell
- 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 - Fee Related
Links
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Inorganic materials O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims abstract description 21
- -1 polypropylene Polymers 0.000 claims abstract description 15
- 239000004743 Polypropylene Substances 0.000 claims abstract description 14
- 229920001155 polypropylene Polymers 0.000 claims abstract description 14
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910052744 lithium Inorganic materials 0.000 claims description 3
- 239000011255 nonaqueous electrolyte Substances 0.000 claims description 3
- 239000011888 foil Substances 0.000 claims description 2
- 235000015110 jellies Nutrition 0.000 claims 1
- 239000008274 jelly Substances 0.000 claims 1
- 229910001947 lithium oxide Inorganic materials 0.000 abstract description 8
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 239000003792 electrolyte Substances 0.000 description 10
- 238000004519 manufacturing process Methods 0.000 description 4
- 230000002411 adverse Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910000552 LiCF3SO3 Inorganic materials 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/02—Details
-
- 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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/381—Alkaline or alkaline earth metals elements
- H01M4/382—Lithium
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
-
- 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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
-
- 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
- H01M50/463—Separators, membranes or diaphragms characterised by their shape
-
- 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
- H01M50/491—Porosity
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Cell Separators (AREA)
- Primary Cells (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Apparatuses For Bulk Treatment Of Fruits And Vegetables And Apparatuses For Preparing Feeds (AREA)
- Preparation Of Fruits And Vegetables (AREA)
Abstract
ABSTRACT
This invention relates to a separator for non-aqueous electrochemical cells and in particular lithium/manganese dioxide cells. It has been discovered that a polypropylene microporous film having a thickness greater than one mil and voids greater than 50% by volume, has beneficial properties without the concomitant problems generally associated with separators having open structures.
This invention relates to a separator for non-aqueous electrochemical cells and in particular lithium/manganese dioxide cells. It has been discovered that a polypropylene microporous film having a thickness greater than one mil and voids greater than 50% by volume, has beneficial properties without the concomitant problems generally associated with separators having open structures.
Description
~3~5~3 SEPARATOR FOR ELECTROCHEMICAL CELLS
This invention relates to a separator for non-aqueous electrochemical cells and in particular lithium/manganese dioxide cells. It has been discovered that a polypropylene microporous film having a thickness greater than one mil and voids greater than 50X by volume, has beneficial properties without the concomitant problems generally associated with separators having open structuresO
Separators are critical to an electrochemical cell because they provide a physical barrier which prevents short circuits between the electrodes. At the same time a separator must have some porosity in order that electrolyte can occupy the pores to provide a reservoir of electrolyte between the electrodes.
The thickness of the separator determines the distance between the electrodes, which in turn determines the resistivity of the electrolyte therebetween.Therefore, in order to minimize the electrolyte resistance it is normallyconsidered desirable to use a thin separator. A thinner separator also permits more actiYe material to be used in the cell.
~ on-aqueous electrolytes are generally much less conductive than aqueous electrolytes. Therefore non-aqueous cells must use thinner separators than can be tolerated in aqueous cells in order to minimize the electrolyte resistance.
Further, a separator useful in an alkaline cell may not be compatible with the chemicals in a non-aqueous cell. As a result, a separator which has utility in an aqueous cell is generally not useful in a non-aqueous cell.
The porosity of a separator is important in that it must be high enough to provide sufficient electrolyte between the electrodes. However, if the porosity is too high the mechanical integrity of the separator decreases and it becGmes l _ ~3~5~
subject to tearing or breaking during manufacture. One example of a widely used commercially available separator is Celgard 2400 (Questar Corp.). This is a one mil microporous polypropylene film having 38% porosity~ Another commercially available separator is Celgard 2500 which is a one mil microporous polypropylene film having 45X porosity. It is believed that the Celgard 2500 has the highest porosity of all commercially avai1able microporous polypropylene separators.
Porosity of separators has been found to have an impact on cell safety.
When a cell is abused (i.e. short circuited) it generates internal heat. As the internal temperature approaches the melting point of the polyolefin themicropores begin to close as the separator begins to melt. This results in a partial shut down of the short circuit current of the cell, which slows down the generation of heat so that the cell is less likely to vent. It is generally believed that if separators having a more porous structure than those now in common use were used the shut down characteristics would be adversely effected.
This is because it has been believed that the pores would not be closed and also because some films woul~ tend to shrink as they melt or soften. This would enable the electrodes to physically contact each other thereby increasing the short circuit problems of the cell. Rather than shutting down the flow of current and ameliorating the resulting heating, it was believed that cells using such separators would continue to heat and cause the cell to vent.
Microporous films made from polymers which exhibit significantly different densities between their crystalline and amorphous phases, such as polyethylene, are generally believed to be prone to the shrinkage problem regardless of the porosity. Films made from polymers which do not have a significant difference *l!rade-Mark : --2--.
' ' .
~ 5~3 .
between the densities o~ the crystalline and amorphous phases, such aspolypropylene, appear to exhibit less of a shrinkage problem.
US patent 4,335,193 discloses filled microporous films having porosities as high as 75% for use in aqueous eleGtrochemical systems sucn as the lead acid type. In practice, with respect to non-aqueous systems, it has been found that filled microporous films do not shut down when a cell is short circuited. It is believed that this is due to the structural support imparted to the separator by the filler. Accordingly, these films are considered highly undesirable for use in non-aqueous cells. Therefore, a separator such as Celgard 2400 has been widely used in non-aqueous cells because its porosity is about as high as is commercially available for unfilled microporous films. Its 38% porosity has been adopted as a standard for the lithium/manganese dioxide and other cell types and has been considered heretofore to be the preferred separator in terms of cell performance, while ensuring partial shut down without shrinkage during short circuit abuse.
Unfilled separators having higher porosities than those of the film types discussed above are available with non-woven fibrous separators. Non-wovenfibrous separators can have porosities in the range of 60-~0%. However, these materials are generally not useful for many cell environnents, especially when the electrodes with separator therebetween are tightly wound together e.g.
lithium/manganese dioxide, because their open structure permits short circuits between the electrodes. To minimize the short circuit problem these separators have to be used in thicknesses of at least 6 mils. The increased separator thickness increases the resistance of electrolyte between the electrodes and takes up space which could otherwise be filled with active material whe~eupon the energy density would be impaired.
~3~-8~
Microporous films of the type discussed above are used most frequently in the non-aqueous elec~rochemical systems. Typical of these is lithium/ manganese dioxide. Within the past few years the production of lithium/manganese dioxide has increased dramatically. As production levels have increased, it has been found that in a small percentage of cells "soft shorts" occur.
A soft short is a high resistance short as distinguished from a direct short circuit. It occurs when there is a high resistance contact between the electrodes. Apparently, a particle of manganese dioxide can partially penetrate through the thin one mil Celgard 2400 separator permitting electrical contact with the anode. Since manganeie dioxide is a semi-conductor, this is not a zero resistance short circuit. The effect of a soft short is to slowly drain the cell until it is totally discharged. The use of thicker separators would reduce the occurrence of soft shorts but thicker separators would also cause an undesirable increase in the internal resistance of the cell.
At Applicant`s request an experimental microporous polypropylene film which is 1.5 mil thick and has 33~ voids was made by a commercial supplier.
Applicant tried this separator in experimental cells and found that the room temperature performance was comparable to cells with a one mil separator having 38% voids. However, it was not until Applicant tested cells at low temperature e.g. -20C that it was discovered that performance was adversely affected.
This was attributed to the increased electrolyte resistance because of the greater thickness. This suggests that the trade off for improved cell reliability by using a thicker separator will be a decrease in low temperature performance.
It has now been discovered that lithium/manganese dioxide cells using as separator material a microporous polypropylene film havlng a thlckness between 1.1 and 4 mil, and preferably 1.5 to 3 mils, but with at least 45%, and preferably 50-80%, and more preferably 55-70~ voids performs in all respects, including low temperature discharge, at least as well as the comrnercially available one mil polypropylene separator with 38~ voids.
The features and advantages of the present invention are evident upon consideration of the following examples.
Example 1 The test cell for this and the following examples is a 2/3A size Li/MnO2 cell. The cell uses a lithium foil anode, and an MnO2 cathode having 10% by weight carbon as a conductive agent and 5~ PTFE as binder. The electrodes are spirally wound with the separator interposed therebetween. The spirally wound electrodes and separator are inserted into an open ended can. The cell is filled with a non-aqueous electrolyte comprised of I M LiCF3S03 in anapproximately 1:1 ratio of propylene carbonateldioxolane. An electrically isolated cover is sealed on the open end of the cell. The electrodes are connected to the eell can and cover respectively.
Five identical cells are built as described above, except that the separator in three cells is a polypropylene microporous film that is 1.5 mil thick and has a porosity of 33g while the other two use a microporouspolypropylene film that is one mil thick and has a porosity of 38%(Celgard 2400). All five cells are tested using a low temperature(-20C) pulse regime of 1.2 amps for 3 seconds followed by 7 seconds off. All three cells having the thicker separator deliver an average of 33% fewer pulses to a one volt cutoff ~31~
than cells having the Celgard 2400 separator. As both separatorS have roughly the same porosity this example demonstrates the adverse impact on low temperature performance of separators thicker than one mil.
Example 2 Two cells are ~uilt using a separator comprised of Celgard 2400 and three cells are built using a separator comprising a polypropy1ene microporous film that is 1.8 mil thick and has a porosity of 62%. The three cells us;ng the thicker separator give an average of 39~ more pulses to a one volt cutoff than the three cells using the thinner separator. This example demonstrates unexpected beneficial performance characteristics of cells using thicker separators with a higher porosity.
Example 3 Two cells are built using Celgard 2400 and three cells are built using a polypropylene microporous film 1.3 mil thick and 60X porosity. The cells using the thicker separator perform as well as the cells using Celgard 2400 under the low temperature pulse test.
Example 4 Two cells are built using a polypropylene microporous separator that is 2.5 mil thick and 55X porous. These cells deliver over 300 pulses to a one volt cut-off under the low temperature pulse test.
The previous examples clearly demonstrate the performance benefits of cells using microporous polypropylene separators having a thickness between 1.1 and 3 milS and a porosity of between 50% and 80. While a microporous separator with these voids but with a thickness of 4 mil or greater would be operable, such thicknesses are not preferred because the separator would take up too much space.
Because of the greater thickness over Celgard 2400, the separators of the present invention are expected to reduce the scrap rate of cells due to soft shorts without detrimentally affecting the low temperature performance. The separators encompassed by the present invention offer a significant advancement in the manufacture of spirally wound lithium/manganese dioxide cells.
This invention relates to a separator for non-aqueous electrochemical cells and in particular lithium/manganese dioxide cells. It has been discovered that a polypropylene microporous film having a thickness greater than one mil and voids greater than 50X by volume, has beneficial properties without the concomitant problems generally associated with separators having open structuresO
Separators are critical to an electrochemical cell because they provide a physical barrier which prevents short circuits between the electrodes. At the same time a separator must have some porosity in order that electrolyte can occupy the pores to provide a reservoir of electrolyte between the electrodes.
The thickness of the separator determines the distance between the electrodes, which in turn determines the resistivity of the electrolyte therebetween.Therefore, in order to minimize the electrolyte resistance it is normallyconsidered desirable to use a thin separator. A thinner separator also permits more actiYe material to be used in the cell.
~ on-aqueous electrolytes are generally much less conductive than aqueous electrolytes. Therefore non-aqueous cells must use thinner separators than can be tolerated in aqueous cells in order to minimize the electrolyte resistance.
Further, a separator useful in an alkaline cell may not be compatible with the chemicals in a non-aqueous cell. As a result, a separator which has utility in an aqueous cell is generally not useful in a non-aqueous cell.
The porosity of a separator is important in that it must be high enough to provide sufficient electrolyte between the electrodes. However, if the porosity is too high the mechanical integrity of the separator decreases and it becGmes l _ ~3~5~
subject to tearing or breaking during manufacture. One example of a widely used commercially available separator is Celgard 2400 (Questar Corp.). This is a one mil microporous polypropylene film having 38% porosity~ Another commercially available separator is Celgard 2500 which is a one mil microporous polypropylene film having 45X porosity. It is believed that the Celgard 2500 has the highest porosity of all commercially avai1able microporous polypropylene separators.
Porosity of separators has been found to have an impact on cell safety.
When a cell is abused (i.e. short circuited) it generates internal heat. As the internal temperature approaches the melting point of the polyolefin themicropores begin to close as the separator begins to melt. This results in a partial shut down of the short circuit current of the cell, which slows down the generation of heat so that the cell is less likely to vent. It is generally believed that if separators having a more porous structure than those now in common use were used the shut down characteristics would be adversely effected.
This is because it has been believed that the pores would not be closed and also because some films woul~ tend to shrink as they melt or soften. This would enable the electrodes to physically contact each other thereby increasing the short circuit problems of the cell. Rather than shutting down the flow of current and ameliorating the resulting heating, it was believed that cells using such separators would continue to heat and cause the cell to vent.
Microporous films made from polymers which exhibit significantly different densities between their crystalline and amorphous phases, such as polyethylene, are generally believed to be prone to the shrinkage problem regardless of the porosity. Films made from polymers which do not have a significant difference *l!rade-Mark : --2--.
' ' .
~ 5~3 .
between the densities o~ the crystalline and amorphous phases, such aspolypropylene, appear to exhibit less of a shrinkage problem.
US patent 4,335,193 discloses filled microporous films having porosities as high as 75% for use in aqueous eleGtrochemical systems sucn as the lead acid type. In practice, with respect to non-aqueous systems, it has been found that filled microporous films do not shut down when a cell is short circuited. It is believed that this is due to the structural support imparted to the separator by the filler. Accordingly, these films are considered highly undesirable for use in non-aqueous cells. Therefore, a separator such as Celgard 2400 has been widely used in non-aqueous cells because its porosity is about as high as is commercially available for unfilled microporous films. Its 38% porosity has been adopted as a standard for the lithium/manganese dioxide and other cell types and has been considered heretofore to be the preferred separator in terms of cell performance, while ensuring partial shut down without shrinkage during short circuit abuse.
Unfilled separators having higher porosities than those of the film types discussed above are available with non-woven fibrous separators. Non-wovenfibrous separators can have porosities in the range of 60-~0%. However, these materials are generally not useful for many cell environnents, especially when the electrodes with separator therebetween are tightly wound together e.g.
lithium/manganese dioxide, because their open structure permits short circuits between the electrodes. To minimize the short circuit problem these separators have to be used in thicknesses of at least 6 mils. The increased separator thickness increases the resistance of electrolyte between the electrodes and takes up space which could otherwise be filled with active material whe~eupon the energy density would be impaired.
~3~-8~
Microporous films of the type discussed above are used most frequently in the non-aqueous elec~rochemical systems. Typical of these is lithium/ manganese dioxide. Within the past few years the production of lithium/manganese dioxide has increased dramatically. As production levels have increased, it has been found that in a small percentage of cells "soft shorts" occur.
A soft short is a high resistance short as distinguished from a direct short circuit. It occurs when there is a high resistance contact between the electrodes. Apparently, a particle of manganese dioxide can partially penetrate through the thin one mil Celgard 2400 separator permitting electrical contact with the anode. Since manganeie dioxide is a semi-conductor, this is not a zero resistance short circuit. The effect of a soft short is to slowly drain the cell until it is totally discharged. The use of thicker separators would reduce the occurrence of soft shorts but thicker separators would also cause an undesirable increase in the internal resistance of the cell.
At Applicant`s request an experimental microporous polypropylene film which is 1.5 mil thick and has 33~ voids was made by a commercial supplier.
Applicant tried this separator in experimental cells and found that the room temperature performance was comparable to cells with a one mil separator having 38% voids. However, it was not until Applicant tested cells at low temperature e.g. -20C that it was discovered that performance was adversely affected.
This was attributed to the increased electrolyte resistance because of the greater thickness. This suggests that the trade off for improved cell reliability by using a thicker separator will be a decrease in low temperature performance.
It has now been discovered that lithium/manganese dioxide cells using as separator material a microporous polypropylene film havlng a thlckness between 1.1 and 4 mil, and preferably 1.5 to 3 mils, but with at least 45%, and preferably 50-80%, and more preferably 55-70~ voids performs in all respects, including low temperature discharge, at least as well as the comrnercially available one mil polypropylene separator with 38~ voids.
The features and advantages of the present invention are evident upon consideration of the following examples.
Example 1 The test cell for this and the following examples is a 2/3A size Li/MnO2 cell. The cell uses a lithium foil anode, and an MnO2 cathode having 10% by weight carbon as a conductive agent and 5~ PTFE as binder. The electrodes are spirally wound with the separator interposed therebetween. The spirally wound electrodes and separator are inserted into an open ended can. The cell is filled with a non-aqueous electrolyte comprised of I M LiCF3S03 in anapproximately 1:1 ratio of propylene carbonateldioxolane. An electrically isolated cover is sealed on the open end of the cell. The electrodes are connected to the eell can and cover respectively.
Five identical cells are built as described above, except that the separator in three cells is a polypropylene microporous film that is 1.5 mil thick and has a porosity of 33g while the other two use a microporouspolypropylene film that is one mil thick and has a porosity of 38%(Celgard 2400). All five cells are tested using a low temperature(-20C) pulse regime of 1.2 amps for 3 seconds followed by 7 seconds off. All three cells having the thicker separator deliver an average of 33% fewer pulses to a one volt cutoff ~31~
than cells having the Celgard 2400 separator. As both separatorS have roughly the same porosity this example demonstrates the adverse impact on low temperature performance of separators thicker than one mil.
Example 2 Two cells are ~uilt using a separator comprised of Celgard 2400 and three cells are built using a separator comprising a polypropy1ene microporous film that is 1.8 mil thick and has a porosity of 62%. The three cells us;ng the thicker separator give an average of 39~ more pulses to a one volt cutoff than the three cells using the thinner separator. This example demonstrates unexpected beneficial performance characteristics of cells using thicker separators with a higher porosity.
Example 3 Two cells are built using Celgard 2400 and three cells are built using a polypropylene microporous film 1.3 mil thick and 60X porosity. The cells using the thicker separator perform as well as the cells using Celgard 2400 under the low temperature pulse test.
Example 4 Two cells are built using a polypropylene microporous separator that is 2.5 mil thick and 55X porous. These cells deliver over 300 pulses to a one volt cut-off under the low temperature pulse test.
The previous examples clearly demonstrate the performance benefits of cells using microporous polypropylene separators having a thickness between 1.1 and 3 milS and a porosity of between 50% and 80. While a microporous separator with these voids but with a thickness of 4 mil or greater would be operable, such thicknesses are not preferred because the separator would take up too much space.
Because of the greater thickness over Celgard 2400, the separators of the present invention are expected to reduce the scrap rate of cells due to soft shorts without detrimentally affecting the low temperature performance. The separators encompassed by the present invention offer a significant advancement in the manufacture of spirally wound lithium/manganese dioxide cells.
Claims (5)
1) An electrochemical cell comprising a sealed casing; an anode, a cathode, a separator positioned between said anode and said cathode, and a non-aqueous electrolyte sealed in said casing; a pair of electrical terminals on said casing; means for electrically isolating the electrical terminals from each other; and means for electrically connecting the anode to one terminal and the cathode to the other terminal; wherein the anode is comprised of lithium foil, the cathode is comprised of manganese dioxide, and said separator consists essentially of a microporous polypropylene film having a thickness of about 1.5 mils and internal voids of about 60% by volume; wherein said anode, cathode, and separator are spirally wound together in a jelly roll configuration.
2) An electrochemical cell comprising an anode comprised of lithium; a cathode comprised of manganese dioxide; and a non aqueous electrolyte; wherein said separator is comprised of a microporous polypropylene film having a thickness between 1.1 and 4.0 mils and internal voids of between 50% and 80% by volume.
3) The electrochemical cell of claim 2 wherein the thickness of the separator is between 1.5 and 3 mils.
4) The electrochemical cell of claim 3 wherein the internal voids are between 55% and 70% by volume.
5) The electrochemical cell of claim 4 wherein the anode, the cathode, and the separator are spirally wound together with the separator between the anode and cathode.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/074,590 US4794057A (en) | 1987-07-17 | 1987-07-17 | Separator for electrochemical cells |
| US74,590 | 1987-07-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1315843C true CA1315843C (en) | 1993-04-06 |
Family
ID=22120402
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000572210A Expired - Fee Related CA1315843C (en) | 1987-07-17 | 1988-07-15 | Separator for electrochemical cells |
Country Status (21)
| Country | Link |
|---|---|
| US (1) | US4794057A (en) |
| JP (1) | JPS6435872A (en) |
| KR (1) | KR890003055A (en) |
| AR (1) | AR240212A1 (en) |
| AU (1) | AU1470788A (en) |
| BE (1) | BE1001677A3 (en) |
| BR (1) | BR8802351A (en) |
| CA (1) | CA1315843C (en) |
| CH (1) | CH675794A5 (en) |
| DE (1) | DE3824101C2 (en) |
| DK (1) | DK395988A (en) |
| ES (1) | ES2007232A6 (en) |
| FR (2) | FR2618259B1 (en) |
| GB (1) | GB2206990B (en) |
| HK (1) | HK19294A (en) |
| IL (1) | IL86034A0 (en) |
| IT (1) | IT1219386B (en) |
| NL (1) | NL8801216A (en) |
| NO (1) | NO883153L (en) |
| SE (1) | SE8802633L (en) |
| ZA (1) | ZA882785B (en) |
Families Citing this family (25)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5176968A (en) * | 1990-12-27 | 1993-01-05 | Duracell Inc. | Electrochemical cell |
| US5290414A (en) * | 1992-05-15 | 1994-03-01 | Eveready Battery Company, Inc. | Separator/electrolyte combination for a nonaqueous cell |
| US5368958A (en) * | 1992-08-20 | 1994-11-29 | Advanced Energy Technologies Incorporated | Lithium anode with conductive for and anode tab for rechargeable lithium battery |
| US5700600A (en) * | 1996-01-12 | 1997-12-23 | Danko; Thomas | Long life battery separator |
| US5700599A (en) * | 1996-01-12 | 1997-12-23 | Danko; Thomas | High absorption rate battery separator |
| KR100189809B1 (en) * | 1996-06-11 | 1999-06-01 | 손욱 | Winding pole plate group |
| KR100210502B1 (en) * | 1996-06-19 | 1999-07-15 | 손욱 | Winding electrode plate military separator |
| US5962162A (en) * | 1997-10-10 | 1999-10-05 | Ultralife Batteries Inc. | Lithium ion polymer cell separator |
| US5958088A (en) * | 1998-03-04 | 1999-09-28 | Duracell, Inc. | Prismatic cell construction |
| US6670074B2 (en) * | 2001-04-23 | 2003-12-30 | Wilson Greatbatch Ltd. | Glass to metal seal |
| US6849360B2 (en) | 2002-06-05 | 2005-02-01 | Eveready Battery Company, Inc. | Nonaqueous electrochemical cell with improved energy density |
| US8465860B2 (en) * | 2008-01-23 | 2013-06-18 | The Gillette Company | Lithium cell |
| US8273483B2 (en) * | 2008-02-14 | 2012-09-25 | The Gillette Company | Lithium cell |
| US20090214950A1 (en) * | 2008-02-22 | 2009-08-27 | Bowden William L | Lithium cell |
| US8076028B2 (en) * | 2008-04-16 | 2011-12-13 | The Gillette Company | Lithium cell with cathode including iron disulfide and iron sulfide |
| US8859145B2 (en) * | 2008-05-23 | 2014-10-14 | The Gillette Company | Method of preparing cathode containing iron disulfide for a lithium cell |
| US20090317725A1 (en) * | 2008-06-23 | 2009-12-24 | Zhiping Jiang | Lithium cell with cathode containing iron disulfide |
| US8153296B2 (en) * | 2008-08-27 | 2012-04-10 | The Gillette Company | Lithium cell with cathode containing metal doped iron sulfide |
| US8076029B2 (en) * | 2009-01-20 | 2011-12-13 | The Gillette Company | Lithium cell with iron disulfide cathode and improved electrolyte |
| US20100203370A1 (en) * | 2009-02-12 | 2010-08-12 | Michael Pozin | Lithium cell with iron disulfide cathode |
| US8048562B2 (en) * | 2009-03-27 | 2011-11-01 | The Gillette Company | Lithium cell with improved iron disulfide cathode |
| US20130183568A1 (en) * | 2009-11-18 | 2013-07-18 | Susan J. Babinec | Composite separator for electrochemical cell and method for its manufacture |
| US9383593B2 (en) * | 2014-08-21 | 2016-07-05 | Johnson & Johnson Vision Care, Inc. | Methods to form biocompatible energization elements for biomedical devices comprising laminates and placed separators |
| JP6974641B1 (en) * | 2021-03-31 | 2021-12-01 | 日本たばこ産業株式会社 | Induction heating device, its control unit, and its operation method |
| JP6967169B1 (en) | 2021-03-31 | 2021-11-17 | 日本たばこ産業株式会社 | Induction heating device and its operation method |
Family Cites Families (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2227794A (en) * | 1939-02-24 | 1941-01-07 | Jr Benjamin F Phillips | Canning apparatus |
| US2785434A (en) * | 1955-09-08 | 1957-03-19 | Chick Nova Corp | Meat boning machine |
| FR2010184A1 (en) * | 1968-06-05 | 1970-02-13 | Tomelleri Giordano | Shaping artichoke bottoms within the actual artichoke |
| US3684580A (en) * | 1970-08-19 | 1972-08-15 | Michael J Lysaght | Battery separator materials |
| US3947537A (en) * | 1971-07-16 | 1976-03-30 | Exxon Research & Engineering Co. | Battery separator manufacturing process |
| FR2191851A1 (en) * | 1972-07-12 | 1974-02-08 | Aubert & Cie Ets | Artichoke cutting machine - removes the bottom from leaves and fibrous portions |
| JPS5819689B2 (en) * | 1975-06-18 | 1983-04-19 | 旭化成株式会社 | Takoumaku |
| US4221123A (en) * | 1978-09-26 | 1980-09-09 | Gould Inc. | Separator materials for secondary alkaline battery systems and method of analytically determining the suitability of such materials |
| FR2418672A1 (en) * | 1978-03-03 | 1979-09-28 | So Ve Mar Co Europ | Knife for food shredder-mixer - has blades pivoted to hub and returned to vertical position when at rest by springs |
| US4259417A (en) * | 1980-03-10 | 1981-03-31 | Exxon Research And Engineering Co. | Ionic barrier |
| US4327157A (en) * | 1981-02-20 | 1982-04-27 | The United States Of America As Represented By The Secretary Of The Navy | Stabilized nickel-zinc battery |
| US4333994A (en) * | 1981-03-27 | 1982-06-08 | Union Carbide Corporation | Cell employing a coiled electrode assembly |
| JPS5937292A (en) * | 1982-08-25 | 1984-02-29 | Matsushita Electric Ind Co Ltd | Rotary compressor |
| JPS5987753A (en) * | 1982-11-10 | 1984-05-21 | Sanyo Electric Co Ltd | Organic electrolytic battery |
| JPS6023954A (en) * | 1983-07-18 | 1985-02-06 | Sanyo Electric Co Ltd | Nonaqueous electrolyte battery |
| JPS6095859A (en) * | 1983-09-30 | 1985-05-29 | エバレディ−、バッテリ−、カンパニ−、インコ−ポレ−テッド | Coiled electrode asembly for battery and method of producing same |
| EP0143562A1 (en) * | 1983-11-02 | 1985-06-05 | Raychem Limited | Electrode article |
| US4550064A (en) * | 1983-12-08 | 1985-10-29 | California Institute Of Technology | High cycle life secondary lithium battery |
| US4565751A (en) * | 1984-06-18 | 1986-01-21 | Eastman Kodak Company | Cathode for high current density and high power density electrochemical cells |
| JPS618852A (en) * | 1984-06-22 | 1986-01-16 | Sanyo Electric Co Ltd | non-aqueous electrolyte battery |
| US4761352A (en) * | 1985-05-17 | 1988-08-02 | Eastman Kodak Company | Accordian folded electrode assembly |
| JPS62139253A (en) * | 1985-12-12 | 1987-06-22 | Matsushita Electric Ind Co Ltd | Cylindrical lithium battery |
-
1987
- 1987-07-17 US US07/074,590 patent/US4794057A/en not_active Expired - Lifetime
-
1988
- 1988-04-11 IL IL86034A patent/IL86034A0/en unknown
- 1988-04-14 GB GB8808823A patent/GB2206990B/en not_active Expired - Lifetime
- 1988-04-15 BE BE8800427A patent/BE1001677A3/en not_active IP Right Cessation
- 1988-04-18 AU AU14707/88A patent/AU1470788A/en not_active Abandoned
- 1988-04-20 ZA ZA882785A patent/ZA882785B/en unknown
- 1988-05-09 NL NL8801216A patent/NL8801216A/en not_active Application Discontinuation
- 1988-05-16 BR BR8802351A patent/BR8802351A/en unknown
- 1988-05-18 KR KR1019880005816A patent/KR890003055A/en not_active Withdrawn
- 1988-05-20 CH CH1925/88A patent/CH675794A5/de not_active IP Right Cessation
- 1988-05-30 ES ES8801702A patent/ES2007232A6/en not_active Expired
- 1988-06-08 JP JP63141954A patent/JPS6435872A/en active Pending
- 1988-06-13 FR FR888807835A patent/FR2618259B1/en not_active Expired - Lifetime
- 1988-06-14 FR FR888807935A patent/FR2618057B1/en not_active Expired - Fee Related
- 1988-06-17 IT IT67574/88A patent/IT1219386B/en active
- 1988-07-14 SE SE8802633A patent/SE8802633L/en not_active Application Discontinuation
- 1988-07-15 CA CA000572210A patent/CA1315843C/en not_active Expired - Fee Related
- 1988-07-15 DK DK395988A patent/DK395988A/en not_active Application Discontinuation
- 1988-07-15 DE DE3824101A patent/DE3824101C2/en not_active Expired - Lifetime
- 1988-07-15 NO NO88883153A patent/NO883153L/en unknown
- 1988-07-15 AR AR311420A patent/AR240212A1/en active
-
1994
- 1994-03-10 HK HK192/94A patent/HK19294A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| NL8801216A (en) | 1989-02-16 |
| GB2206990A (en) | 1989-01-18 |
| HK19294A (en) | 1994-03-18 |
| SE8802633D0 (en) | 1988-07-14 |
| NO883153L (en) | 1989-01-18 |
| DK395988D0 (en) | 1988-07-15 |
| DE3824101C2 (en) | 1998-01-15 |
| ZA882785B (en) | 1989-12-27 |
| BE1001677A3 (en) | 1990-02-06 |
| JPS6435872A (en) | 1989-02-06 |
| FR2618259B1 (en) | 1990-08-24 |
| KR890003055A (en) | 1989-04-12 |
| IT1219386B (en) | 1990-05-11 |
| GB2206990B (en) | 1990-11-28 |
| FR2618057B1 (en) | 1992-03-06 |
| GB8808823D0 (en) | 1988-05-18 |
| ES2007232A6 (en) | 1989-06-01 |
| AR240212A1 (en) | 1990-02-28 |
| IT8867574A0 (en) | 1988-06-17 |
| FR2618259A1 (en) | 1989-01-20 |
| BR8802351A (en) | 1989-02-08 |
| FR2618057A1 (en) | 1989-01-20 |
| DK395988A (en) | 1989-01-18 |
| IL86034A0 (en) | 1988-09-30 |
| NO883153D0 (en) | 1988-07-15 |
| AU1470788A (en) | 1989-01-19 |
| DE3824101A1 (en) | 1989-01-26 |
| CH675794A5 (en) | 1990-10-31 |
| US4794057A (en) | 1988-12-27 |
| SE8802633L (en) | 1989-01-18 |
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