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
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
• • 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
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• • 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
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• • 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
  • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• • 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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • 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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • 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
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
  • H01M4/623—Binders being polymers fluorinated polymers
• • 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
  • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
• • 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

Definitions

• the present invention relates to enhancement of discharge capacity, recycling capability and high temperature storage stability of electrochemical cells and particularly of rechargeable lithium ion polymer cells and batteries.
• Lithium ion cells generally utilize two different insertion compounds as host cathode and anode materials, i.e., intercalation materials, for the reversible insertion of guest ions (e.g. lithium ions, or other alkaline metal ions) in providing the electrochemical reactions for generation of an electrical current.
• guest ions e.g. lithium ions, or other alkaline metal ions
• lithium ions are extracted from the lithium ion containing anode material and are ionically transported through the electrolyte/separator into the cathode, with generation of an external electrical current .
• the reverse process occurs on charging of the cell with reversal of ion flow.
• Lithium ion cells may either be conventional liquid electrolyte based cells, i.e., with free liquids, generally of a non-aqueous organic nature, or can be "solid state” cells having a polymeric porous matrix in which the electrolyte is immobilized.
• the polymeric matrix comprises a porous separator between anode and cathode to permit the requisite ionic transport between anode and cathode.
• lithium or other electrochemically active metal
• the present invention comprises improving the cycle life, discharge capability, and high temperature storage stability of rechargeable non-aqueous and "solid state" (defined herein as referring to cells with immobilized non-aqueous electrolytes) lithium ion cells, by addition of substantial amounts of substantially insoluble or sparingly soluble lithium compounds (solubility of less than 1CT 2 gm/1, in the electrolyte solvents).
• substantially insoluble lithium compounds include lithium salts, lithium oxides and lithium compounds containing oxygen and third elements.
• the substantially insoluble lithium-containing compounds of the present invention are those compounds which are comprised of lithium and one or more non- metallic elements (i.e., no metallic elements other than lithium) .
• the substantially insoluble lithium compounds are added to the cell cathode and optionally to the anode and separator, where there appears to be an interaction between the substantially insoluble lithium compound and the materials of the cathode, in- si tu or ex si tu through the anode and separator.
• the substantially insoluble lithium compounds of the present invention are not electrochemically active or capable of functioning as ion host materials. Accordingly, their volume presence actually reduces the amount of reaction sites and/or active material in the cell.
• cell discharge capability is measurably enhanced, cycle life is significantly improved at both room and elevated temperatures, and high temperature storage stability is also enhanced.
• the substantially insoluble lithium compounds are generally dispersed throughout the cathode (and optionally in either or both of the separator and anode) and are not concentrated at the electrode-separator interface, as would normally be the case with ionic conductivity enhancers.
• the lithium compounds are accordingly comminuted to an extent whereby they are readily dispersible within the cathode and anode as well as the separator with the substantially insoluble lithium compounds generally being mixed together with the other component materials of the cathode, anode and separator.
• the substantially insoluble lithium compound improves the stability and reduces solubility of the intercalating cathode material. This appears to stabilize the secondary cell characteristics but also beneficially, without significant concomitant detrimental reduction of primary cell performance and capacity, which would otherwise have been expected.
• the present invention relates to the incorporation of the substantially insoluble lithium-containing compound into the cathode material, and into either or both the anode and separator materials of rechargeable lithium ion-containing cell. Since there is reversible material transfer in the rechargeable cells, the substantially insoluble lithium compounds appear to stabilize the solid electrolyte interphase of the anode.
• the stabilizing effect of addition of the substantially insoluble lithium containing compound is however primarily with respect to the primary cathode materials. Inclusion of the substantially insoluble compounds in the electrolyte solution itself is impractical because of their defined insolubility (they would only precipitate from a suspension in the electrolyte solution) . However, the substantially insoluble compounds may be added to the separator if they are thereby trapped in a position where they are exposed to the pathway of transportation and/or are directly juxtaposed with the anode and cathode materials. Again, the inclusion of the substantially insoluble lithium compounds in the separator is secondary in effect relative to the same inclusions in the cathode and is generally in a form therein of a stabilizing material supply site.
• Fig. 1 is a graph of the discharge capabilities of polymer lithium ion cells having a substantially insoluble lithium compound (Li 2 C0 3 ) dispersed in the anode, separator and cathode, after two room temperature storage periods of two weeks each. Data of 72 groups (about 40 cells per group) for standard cells (without substantially insoluble lithium compound inclusions) is also shown for comparison purposes.
• Fig. 2 is a graph of the discharge capabilities of polymer lithium ion cells having a substantially insoluble lithium compound (Li 2 C0 3 ) dispersed in the anode, separator and cathode, after two 45°C storage periods of two weeks each. Data of 72 groups (about 40 cells per group) for standard cells (without substantially insoluble lithium compound inclusion) is also shown for comparison purposes.
• Fig. 3 is a graph of the impedance growth of polymer lithium ion cells having a substantially insoluble lithium compound (Li 2 C0 3 ) dispersed in the anode, separator and cathode after two room temperature and 45°C storage periods of two weeks each. Data of 72 groups (about 40 cells per group) for standard cells (without substantially insoluble lithium compound inclusion) is also shown for comparison purposes.
• Li 2 C0 3 substantially insoluble lithium compound
• Fig. 4 is a graph of the discharge capacity versus cycle number of a Li 2 C0 3 -containing polymer lithium ion cell. Data is obtained from C-rate with continuous cycling at room temperature with C/5 cycle every twelve C-rate cycles in order to observe any loss in rate capability. (C-rate is the discharge or charge current in amperes, expressed as a multiple of the rated capacity in ampere-hours) .
• Fig. 5 is a graph of the comparative retained discharge capacity versus storage time at room temperature for cells with Li 2 C0 3 inclusions in various cell components. (See Table 2 notation) .
• Fig. 6 is a graph of the comparative impedance at 1kHz versus storage time at room temperature for cells with Li 2 C0 3 inclusions in various cell components.
• Fig. 7 is a graph of the retained discharge capacity versus storage time at 45°C for cells with Li 2 C0 3 inclusion in various cell components.
• Fig. 8 is a graph of the impedance at 1kHz versus storage time at 45°C for cells with Li 2 C0 3 inclusion in various cell components.
• Fig. 9 is a graph of the percent (%) theoretical discharge capacity of cells after each 45°C storage period versus various Li 2 C0 3 inclusion levels.
• Fig. 10 is a graph of the impedance at 1 kHz of cells after each 45°C storage period versus various Li 2 C0 3 inclusion levels.
• Figs, lla-d are graphs showing comparative values (capacity and impedance) of cells having amounts of the substantially insoluble lithium compounds of Li 2 C0 3 , Li 2 B 4 0 7 , Li 3 P0 4/ and LiF (in the separators thereof) under discharge conditions after room and high temperature storage (Figs. 11a and lib) and with 1kHz impedance after room and high temperature storage (lie and lid) respectively.
• Figure 12 is a comparative graph showing discharge capacity initially and after high temperature storage (45°C) of 7 and 14 days, for standard lithium ion cells and cells with Li 2 B 4 0 7 inclusions in the cathodes.
• substantially insoluble lithium compounds comprised of lithium and nonmetallic elements and particularly compounds containing oxygen and third component non-metallic elements, such as lithium carbonate (Li 2 C0 3 )
• lithium carbonate Li 2 C0 3
• substantially insoluble lithium compounds refers to non- electrode active (neither as host or discharge materials) lithium-containing compounds without other metals (e.g., salts, oxides and oxygen containing compounds) which are insoluble or substantially insoluble in non-aqueous electrolyte solvents used in the cell, such as those including acetone, alcohol, and various carbonate solvents, etc.
• Substantial insolubility is defined herein as being less than 10 "2 gm/1.
• Solid state lithium ion polymer cells are well-known in the prior art. See for example, U.S. Patent Nos .
• One particularly preferred type of prior art polymer electrolyte cell utilizes a plasticized thermoplastic polymer as a binder for each of the anode, cathode and separator.
• the individual layers are each produced from a slurry comprised of a mixture of the substituent (anode, cathode or separator) component comminuted into a powder and one or more organic solvents.
• the mixtures may include plasticizer fillers and volatile solvents to remove the plasticizer for imparting porosity to the particular component.
• a single cell assembly is made simply by applying heat and pressure to fuse the juxtaposed component layers together (anode and cathode layers with separator therebetween) .
• the plasticizer is solvent extracted from the cell to create microporous matrices into which an ionically conductive non-aqueous liquid electrolyte is backfilled.
• the entire cell pack may be encapsulated in an insulated package with appropriate exposed terminal connections.
• the cells are stacked and connected either in series or parallel to form batteries of desired voltages and discharge capability.
• the binding polymer used in the electrodes and separator elements is preferably a thermoplastic polymer and may be any suitable copolymer, but is preferably and commonly, in commercial cells, a copolymer of poly (vinylidene fluoride) - hexafluoropropylene (or PVdF-HFP) . Since no free electrolyte exists in the solid state polymer lithium ion cell system, it is considered to be safer than its liquid electrolyte analog.
• Polymer Cell construction and components In a polymer type cell the cathode and anode are applied to opposite sides of the solid polymer electrolyte separator and respective electrically conductive current collectors are placed adjacent the anodes and cathodes.
• the anode, cathode, current collectors and separator together comprise the individual cell assembly which is placed into a metallized plastic laminate which is sealed under heat and pressure to form a completed sealed cell, with the respective current collectors remaining electrically externally accessible.
• the cell anode, cathode and separator are each preferably comprised of a combination of a poly (vinylidene fluoride) copolymer matrix and a compatible organic plasticizer which maintains a homogeneous composition in the form of a self- supporting film.
• the separator copolymer composition comprises from about 75 to about 92% by weight poly (vinylidene fluoride) (PVdF) and about 8 to about 25% by weight hexafluoropropylene (HFP) , (both commercially available from Elf AtoChem North America as Kynar FLEX t ) , and an organic plasticizer.
• the copolymer composition is also used as binder material in the manufacture of the respective electrodes to insure a compatible interface with the separator.
• Particularly preferred are the higher-boiling point plasticizers such as dibutyl phthalate, dimethyl phthalate, diethyl phthalate and tris butoxyethyl phosphate.
• inorganic fillers may be added to enhance the physical strength and melt viscosity of the separator membrane, and to increase the electrolyte solution absorption level.
• Preferred fillers include fumed alumina and silanized fumed silica. Any common procedure for casting or forming films or membranes of polymer compositions may be used to make the separator. A readily evaporated casting solvent may be added to obtain desired viscosity during casting.
• the preferred anodes of the present invention are made by preparing a slurry of PVDF- HFP and acetone along with the dibutylphthalate (DBP) .
• DBP dibutylphthalate
• the ion intercalation or host material generally of a carbon material such as a pitch coke, or graphitic composition, most preferably mesocarbon micro beads (MCMB, Osaka Gas, Osaka, Japan) , with carbon black being added to further facilitate electrical conductivity.
• MCMB mesocarbon micro beads
• the cathode preferably is prepared in a fashion similar to the anode. However, an amount of lithium manganese oxide is added to the mix in place of the graphite as the host intercalation material for the lithium ions.
• the anode, cathode and separator are made porous by solvent extraction of the plasticizer material such as DBP, which, after the extraction, leaves matrices or pores in the electrodes and separator.
• the porous electrodes are dipped into the electrolyte, in order to load the electrolyte into the cell.
• the current collectors which are assembled to be in intimate electrical contact with the cathode and the anode are preferably made from aluminum and copper, respectively, and may be foil or grid-like in configuration.
• the electrolyte comprises a solution of a soluble lithium salt in one or more organic solvents such as ethylene carbonate and dimethyl carbonate (EC-DMC) .
• organic solvents such as ethylene carbonate and dimethyl carbonate (EC-DMC) .
• EC-DMC ethylene carbonate and dimethyl carbonate
• Other commonly utilized non- aqueous solvents include ⁇ -butyrolactone ( ⁇ -BL) , tetrahydrofuran (THF) , 1, 2 -dimethoxyethane (1,2-DME), propylene carbonate (PC), diethyl carbonate (DEC) , methyl ethyl carbonate (MEC) , diethoxyethane (DEE) , dioxolane (DOL) and methyl formate (MF) .
• ⁇ -BL ⁇ -butyrolactone
• THF tetrahydrofuran
• 1, 2 -dimethoxyethane 1, 2 -dimeth
• the soluble electrolyte is present in about 1 to 2 molar solutions and with preferred and common soluble electrolyte lithium salts being LiPF 6 , LiAsF 6 , LiBF 4 , LiC10 4 , LiCF 3 S0 3/ LiN(CF 3 S0 2 ) 3 , and LiN (C2F5SO2) 3 , with LiPF 6 being particularly preferred.
• the absolute amount of electyrolyte salt in the cell is, of course, generally dependent on the cell size, type and desired discharge capability.
• organic solvents are characterized as generally containing water impurities which tend to react, albeit in small amounts with the electrolyte salts (and particularly halogen containing salts) to form acids such as HF, as may occur with use of fluorine containing salts such as LiPF 6 .
• scavenging material added to the electrolyte i.e., in excess of the amount of the actual electrolyte salt which is the source of a component of the acid production
• the scavenging material is located in the cells in a site specific manner, in order to facilitate the effect of such scavenging process, i.e., in the electrolyte or separator containing the electrolyte or in the anode, to control the interface between the anode and separator, where the detrimental effects of HF are greatest.
• the substantially insoluble lithium compounds of the present invention are present in the electrodes and separator in amounts (by weight or total moles) on the order of or greater than that of the cell electrolyte salt (the source of the HF) there is no discernible function of the substantially insoluble lithium compounds in such greater amounts.
• the lithium compounds of the present invention are substantially insoluble (by definition) they do not function as ionically conducting salts and absent the present invention would be considered to be a waste of volumetric capacity.
• one or more substantially insoluble lithium-containing compounds e.g., lithium salts, oxides, and oxygen containing compounds with third non-metallic elements, are added to and dispersed in the cell cathode and optionally also dispersed into the anode and/or separator. Because of such placement, primarily in the cell cathode, there is minimal scavenger effect as described in the prior art with use of substantially insoluble lithium compounds such as Li 2 C0 3 and thus, absent the present invention, no perceived utility in the art for inclusion of substantially insoluble, non electrode active lithium compounds in the cell electrodes and separator.
• substantially insoluble lithium-containing compounds e.g., lithium salts, oxides, and oxygen containing compounds with third non-metallic elements
• the preferred substantially insoluble lithium-containing compounds with non-metallic elements, of the present invention include Li 2 C0 3 , Li 2 B 4 0 7 , and Li 3 P0 4 .
• substantially insoluble lithium compounds include Li 2 C 2 0 4 , LiB 3 0 5 , LiB 8 0 13 , LiB0 2 , Li 4 B 2 0 5 , Li 3 B0 3 , Li 2 B 2 0 4 , Li 2 B 6 O ⁇ o, LiP0 3 , Li 4 P 2 0 7 , LiP, Li 3 P, Li 3 N, Li 2 0, LiSi0 3 , Li 4 Si0 4 , Li 2 Si 3 0 7 , Li 2 Si 2 0 5 , Li 13 Si 4 , Li 2 ⁇ Si 8 , Li 2 Se0 4 , Li 2 Se, Li 2 S0 3 , Li 2 S0 4 , Li 2 S 2 0 6 , Li 2 S 2 0 and the halides of LiF, LiBr, LiCl and Lil.
• the most preferred substantially insoluble lithium compound is Li 2 C0 3 . It is understood that these lithium compounds specifically do not include intercalation materials such as carbonaceous materials (e.g. LiC 6 ) , or lithium with metallic elements such as the Li ⁇ +x Mn 2 0 4 , which is used as a common host cathode material in lithium ion polymer cells.
• intercalation materials such as carbonaceous materials (e.g. LiC 6 ) , or lithium with metallic elements such as the Li ⁇ +x Mn 2 0 4 , which is used as a common host cathode material in lithium ion polymer cells.
• Other lithium intercalation compounds used as cathode materials include manganese oxide compounds such as LiMn 2 0 4 , Li n0 2 , as well as various cobalt and nickel compounds.
• Cathode compositions preferably comprise from about 5 to about 80 weight % of dry PVdF-HFP, more preferably about 10 to about 60 weight %, and most preferably about 10 to about 35 weight % PVdF-HFP.
• the substantially insoluble lithium compound present in the cell is preferably at least on the order of the amount of the soluble electrolyte salt and is at least preferably present in an amount of from about 1 to about 80 dry weight % of the PVdF- MFP in the cathode, more preferably from about 1 to about 50 weight percent, and most preferably in significant amounts from about 10 to about 35 dry weight % of the active cathode material .
• the following comparative examples serve to illustrate the efficacy of the substantially insoluble lithium compound additions in the cells of the present invention. The examples should not however be construed as limiting the invention. The following examples relate to testing of cells in which the cathode and either or both the anode and polymeric separator have been formed with addition of the substantially insoluble lithium compounds therein.
• Example 1 Effect of Li 2 C0 3 inclusions in full cell (cathode, anode and separator) -Fabrication of Li 2 C0 3 containing polymer lithium ion cells:
• Cells were prepared with the following relative percentages of components with the substantially insoluble lithium carbonate being added to both electrodes and the separator, as given in Table 1.
• Fig. 3 shows a comparison of impedance in substantially insoluble compound containing lithium cells and and the cells without inclusions, at both room temperature and 45°C.
• Polymer lithium ion cells without lithium compound inclusion failed after about 200 continuous C-rate (charge or discharge the cell within 1 hour) cycling at room temperature.
• the cells with Li 2 C0 3 inclusion in anode, separator and cathode (full cell inclusion) showed about 3 -fold improvement in terms of cycle life.
• Fig. 4 shows that a cell completed more than 600 cycles at C-rate (with a C/5 rate cycle every 12 cycles) before a reduction of rate capability below 70% of rated capacity appeared.
• Example 5 Li 2 C0 3 cross inclusion formulations: Li 2 C0 3 was selectively included in the various cell components of anode, cathode, and separator and these components were assembled into solid state polymer cells in a variety of combinations as shown in the following table. The relative inclusion amounts (when present) were the same as for the cells described in Example 1.
• Formulation 7 X X 0 A+S 0 means no lithium compound inclusion in that cell component .
• X means compound inclusion present in the cell component .
• the cells with substantially insoluble lithium compound-containing cathodes showed enhanced storage characteristics.
• impedance increase at room temperature storage was not significant for all the cells after a two month storage .
• Li 2 C0 3 inclusion Various levels (0, 5, 10, 25, 50, 80%) of Li 2 C0 3 inclusion were attempted in the solid state polymer cells using Formulation 4 (A+C) of Example 5. The percentages of Li 2 C0 3 inclusion levels in cell components were calculated against the dry weight of PVdF-HFP copolymer.
• Example 7 - Inclusion of Li 2 B 4 0 7 in cell cathode Lithium ion polymer cells with similar component inclusions of other non-soluble lithium compounds of Li 2 B 4 0 7 , Li 3 P0 4 and LiF respectively in the separator alone were compared to that of Li 2 C0 3 , as shown in Figures lla-d with somewhat comparable results, particularly for the former two compounds, and such compounds if included to the cathodes of cells tend to exhibit improvement in high temperature storage, recycling capability and discharge capability as compared to cells without such inclusions.
• lithium ion cells with Li 2 B 4 0 7 included in the cathode material were compared to standard cells, without such inclusion, under storage conditions of 45°C.
• All the compared cells contained cathodes with 158.4 gm of active manganese oxide material, 30 grams of PVdF-HFP polymer, 12.2 gms of carbon black and 39.4 grams of DBP filler material.
• One set of cells additionally contained 5 gm of contained Li 2 B0 7 in the cathodes thereof.
• Initial discharge capacities were about the same. However, after seven days there was about a 20% improvement in % theoretical discharge capacity with use of the additive and after 14 days this improvement increased to about a 25% improvement, as shown in Figure 12. It is accordingly expected that other substantially insoluble lithium compounds and particularly oxygen containing compounds will provide the cycling and high temperature improvements when added in substantial amounts to the cathodes of lithium ion cells.

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