EP1992028A2 - Pile électrochimique basse température - Google Patents

Pile électrochimique basse température

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Publication number
EP1992028A2
EP1992028A2 EP07757061A EP07757061A EP1992028A2 EP 1992028 A2 EP1992028 A2 EP 1992028A2 EP 07757061 A EP07757061 A EP 07757061A EP 07757061 A EP07757061 A EP 07757061A EP 1992028 A2 EP1992028 A2 EP 1992028A2
Authority
EP
European Patent Office
Prior art keywords
electrochemical cell
carbon
discharge
lithium
anion receptor
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.)
Withdrawn
Application number
EP07757061A
Other languages
German (de)
English (en)
Other versions
EP1992028A4 (fr
Inventor
Jay F. Whitacre
Rachid Yazami
Ratnakumar V. Bugga
Surya G. Prakash
Marshall C. Smart
William C. West
André HAMWI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Centre National de la Recherche Scientifique CNRS
Universite Blaise Pascal Clermont Ferrand II
California Institute of Technology CalTech
Original Assignee
Centre National de la Recherche Scientifique CNRS
Universite Blaise Pascal Clermont Ferrand II
California Institute of Technology CalTech
Priority date (The priority date 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 date listed.)
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Publication date
Application filed by Centre National de la Recherche Scientifique CNRS, Universite Blaise Pascal Clermont Ferrand II, California Institute of Technology CalTech filed Critical Centre National de la Recherche Scientifique CNRS
Priority claimed from PCT/US2007/062243 external-priority patent/WO2007098369A2/fr
Publication of EP1992028A2 publication Critical patent/EP1992028A2/fr
Publication of EP1992028A4 publication Critical patent/EP1992028A4/fr
Withdrawn legal-status Critical Current

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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
    • H01M6/14—Cells with non-aqueous electrolyte
    • H01M6/16—Cells with non-aqueous electrolyte with organic electrolyte
    • H01M6/162—Cells with non-aqueous electrolyte with organic electrolyte characterised by the 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M6/00—Primary cells; Manufacture thereof
    • H01M6/14—Cells with non-aqueous electrolyte
    • H01M6/16—Cells with non-aqueous electrolyte with organic electrolyte
    • H01M6/162—Cells with non-aqueous electrolyte with organic electrolyte characterised by the electrolyte
    • H01M6/168—Cells with non-aqueous electrolyte with organic electrolyte characterised by the electrolyte by additives
    • 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

  • Lithium battery technology for example, continues to rapidly develop, at least in part, due to the discovery of novel electrode and electrolyte materials for these systems.
  • intercalation cathode materials such as fluohnated carbon materials and nanostructured transition metal oxides
  • novel materials strategies for lithium battery systems have revolutionized their design and performance capabilities.
  • lithium battery technology is positioned to be the preferred technology for the next generation of high-power, portable electronic systems. Accordingly, the identification and performance evaluation of novel electrode and/or electrolyte materials is currently a research priority in the development of new and improved lithium based electrochemical energy storage and conversion systems.
  • lithium metal negative electrode for generating lithium ions which during discharge are transported through a liquid phase or solid phase electrolyte and undergo intercalation reaction at a positive electrode comprising an intercalation host material.
  • the element lithium has a unique combination of properties that make it highly attractive for use in an electrochemical cell. First, it is the lightest metal in the periodic table having an atomic mass of 6.94 AMU. Second, lithium has a very high electrochemical reduction potential (i.e., 3.045 V). This unique combination of properties enables lithium based electrochemical cells to have very high specific capacities.
  • Useful intercalation cathode materials for lithium batteries include layered transition metal oxides ⁇ e.g., MnO2, NiO2, COO2), spinel transition metal oxides ⁇ e.g., Mn 2 ⁇ 2, Ti 2 O 2 ), transition metal sulfides (e.g. FeS 2 ) and fluohnated carbon materials (e.g., CF 1 ).
  • Useful nonaqueous electrolytes for lithium batteries include solutions of lithium salts in polar organic or inorganic liquids, ionically conducting polymers and fused lithium salts.
  • electrochemical cells capable of providing useful device performance including: (i) high cell voltages (e.g. up to about 3 V), (ii) substantially constant (e.g., flat) discharge profiles, (iii) long shelf-life (e.g., up to 10 years), and (iv) compatibility with a range of operating temperatures (e.g., -20 to 60 degrees Celsius).
  • high cell voltages e.g. up to about 3 V
  • substantially constant (e.g., flat) discharge profiles e.g., flat) discharge profiles
  • long shelf-life e.g., up to 10 years
  • compatibility with a range of operating temperatures e.g., -20 to 60 degrees Celsius.
  • primary lithium ion batteries are widely used as power sources in a range of portable electronic devices and in other important device applications including, biomedical engineering, sensing, military communications, and lighting. Dual intercalation lithium ion secondary batteries have also been developed.
  • lithium metal is replaced with an intercalation host material for the negative electrode, such as carbons (e.g., graphite, cokes etc.), metal oxides, metal nitrides and metal phosphides.
  • carbons e.g., graphite, cokes etc.
  • metal oxides e.g., metal oxides
  • metal nitrides e.g., metal nitrides
  • metal phosphides e.g., graphite, cokes etc.
  • State of the art lithium ion secondary batteries provide excellent charge-discharge characteristics, and thus, have also been widely adopted as power sources in portable electronic devices, such as cellular telephones and portable computers.
  • Li/CF X batteries using active cathode materials consisting of fluohnated carbonaceous materials, such as coke or graphite comprise a potentially attractive system for low temperature energy source applications. Many of these systems utilize nonaqueous electrolyte solutions having low freezing points that are compatible with low temperature operation. Further, Li/CF X battery systems are know to be capable of delivery of up to 700 Wh/kg, 1000 Wh/I, at room temperature, and at a rate of C/100 (i.e., a battery current of a 1/100 th that of the capacity of the battery per hour). (See, e.g., Bruce, G. Development of a CFx D Cell for Man Portable Applications, in Joint Service Power Expo. 2005; and Gabano, J.
  • Cathodes in these systems typically have carbon - fluoride stoichiometries typically ranging from CFi 05 to CFi 1.
  • This cathode material is known to be discharge rate limited, and currents lower than C/50 (battery current 1/50 th that of the capacity of the battery divided by 1 hour) are often necessary to avoid cell polarization and large capacity loss.
  • Low electronic conductivity of CFx is a potential cause of the observed discharge rate limitations, as there is a strong correlation between cathode thickness and performance; thicker cathodes tend to be more rate-limited. (See, e.g., Gunther, R. G. in Fifth Power Sources Conference. Pages 713 - 728, 1975).
  • a similar CFx spirally-wound electrode design exhibited a bulk cathode impedance of 0.0002 ohms/mm 2 and was able to deliver over 500 mAh/g active cathode material at a C/20 rate at -30°C.
  • Substantial self heating under some discharge conditions has also been reported for the Li-CFx positive electrode system, which could also enhance low temperature operation of these electrochemical cells.
  • Rohde, D., M.J. Root, and D. Fostor. Li/CFx Cell and Material Development for High Rate Applications in 37th Power Sources Conference. 1996
  • electrochemical storage and conversion devices capable of satisfying the demanding device performance requirements inherent to many important aerospace applications.
  • electrochemical cells are needed that are capable of providing useful specific capacities under large discharge rate conditions and at low temperatures (e.g., less than about -30 degrees Celsius).
  • the present invention provides electrochemical cells providing good electronic performance, particularly at low temperatures. Electrochemical cells of the present invention include lithium batteries with useful specific capacities under significant discharge rates for a wide range of temperatures, including temperatures as low as about -60 degrees Celsius. The present invention also provides methods for making electrochemical cells including a room temperature predischarge step that enhances the performance of batteries having subfluorinated carbonaceous positive electrode active materials at low temperatures.
  • Electrochemical cells of the present invention combine specially selected electrode and electrolyte materials, compositions and form factors to provide higher specific capacities than conventional state of the art electrochemical cells for substantial discharge rates (e.g., greater than or equal to about C/20) over a wide range of temperatures, including temperatures less than or equal to about -20 degrees Celsius.
  • Electrochemical cells of the present invention include lithium batteries having a positive electrode comprising a multiphase, subfluohnated carbonaceous active material that are capable of providing high specific capacities (e.g., specific capacity greater than or equal to about 625 mAh g "1 ) for high current density discharge conditions over a wide range of temperatures.
  • the present invention also provides electrolyte compositions for lithium batteries providing high ionic conductivities, good chemical stability and useful positive electrode wetting an conditioning characteristics during low temperature operation
  • the present invention provides novel materials strategies for enhancing the performance of lithium batteries.
  • the present invention provides complementary subfluohnated carbonaceous positive electrode active materials and electrolyte compositions that provide synergistic performance enhancements important for improving the electronic performance of lithium batteries at low temperatures and/or for accessing advantageous electrode form factors, including thicker positive electrode configurations.
  • the present invention provides subfluorinated carbonaceous positive electrode active materials comprising nanoscale intermixed fluohnated and unfluorinated domains providing enhanced cathode performance at low temperatures compared to conventional CFi positive electrode active materials.
  • the present invention also provides electrolyte compositions for lithium ion batteriess, including anion receptor additives, lithium salt concentrations, and nonaqueous solvent compositions, providing physical and chemical properties that extend the range of useful operating temperatures of electrochemical cells having subfluorinated carbonaceous positive electrode active materials.
  • the combination of subfluorinated positive electrode active materials and electrolyte compositions of the present invention enhance the kinetics and charge transfer properties of the positive electrode and the ion conductivity of the electrolyte, thereby enabling lithium batteries exhibiting superior low temperature performance compared to state of the art lithium battery systems and enabling electrochemical cells having advantageous positive electrode form factors and configurations.
  • an electrochemical cell capable of low temperature operation having a positive electrode comprising a multiphase subfluorinated carbonaceous active material.
  • an electrochemical cell of this aspect comprises a positive electrode comprising a subfluorinated carbonaceous material having an average stoichiometry CFx, wherein x is the average atomic ratio of fluorine atoms to carbon atoms and is selected from the range of about 0.3 to about 1.0.
  • the subfluorinated carbonaceous material comprising the positive electrode of this aspect of the present invention is a multiphase material having an unfluohnated carbon component and at least one fluorinated carbon component.
  • An electrochemical cell of this embodiment further comprises a negative electrode; and a nonaqueous electrolyte that is provided between the positive and negative electrodes.
  • Useful negative electrodes in electrochemical cells of this aspect of the present invention comprise a source of metal cations, such as lithium ions.
  • Nonaqueous electrolytes are preferably provided such that ions in the electrolyte can efficiently interact with positive and negative electrodes of the electrochemical cell.
  • the electrolyte of this aspect comprises a high performance low temperature electrolyte having a composition selected to provide ionic conductivities and reaction kinetics at the subfluorinated carbonaceous positive electrode for enhanced low temperature performance.
  • subfluorinated carbonaceous material refers to a multiphase carbonaceous material having an unfluorinated carbonaceous component.
  • an "unfluorinated carbonaceous component” includes unfluorinated carbon compositions and/or phases, such as graphite, coke, multiwalled carbon nanotubes, carbon nanofibers, carbon nanowhiskers, multi-layered carbon nanoparticles, carbon nanowhiskers, and carbon nanorods, and also includes slightly fluorinated carbon compositions and/or phases.
  • Multiphase subfluorinated carbonaceous materials may comprises a mixture of carbonaceous phases including, one or more unfluorinated carbonaceous phases, and one or more fluorinated phase (e.g., poly(carbon monoflouride (CFi); poly(dicarbon monofluohde) etc.).
  • Subfluorinated carbonaceous materials include carbonaceous materials exposed to a fluorine source under conditions resulting in incomplete or partial fluorination of a carbonaceous starting material.
  • Selection of the fluorine atom to carbon atom stoichiometry of the subfluorinated carbonaceous positive electrode active material in this aspect of the invention determines, at least in part, the specific capacity and discharge rate characteristics of the electrochemical cell, wherein a larger extent of fluorination (e.g. a larger value of x) provides for larger specific capacities.
  • a larger extent of fluorination e.g. a larger value of x
  • selection of a large average atomic ratio (x) of fluorine atoms to carbon atoms is useful for providing electrochemical cells capable of exhibiting specific capacities greater than about 500 mAh g "1 for discharge at about 2 V, and in some embodiments greater than about 625 mAh g "1 for discharge at about 2.1 V.
  • the fluorine atom to carbon atom stoichiometry also, at least in part, determines the extent of the unfluorinated component of the subfluorinated carbonaceous positive electrode active material.
  • the unfluorinated carbon component is between about 5% to about 70% by mass of the subfluorinated carbonaceous material comprising the positive electrode active material, and preferably for some embodiments the unfluorinated carbon component is between about 10% to about 20% by mass of the subfluorinated carbonaceous material comprising the positive electrode active material.
  • Use of subfluorinated carbonaceous positive electrode active materials having an unfluorinated carbon component of at least about 5% by mass is beneficial for providing electrodes having useful conductivities in some embodiments.
  • a range of carbonaceous materials are useful for subfluorinated active materials in positive electrodes of the present invention including graphite, coke, and carbonaceous nanomatehals, such as multiwalled carbon nanotubes, carbon nanofibers, multi-layered carbon nanoparticles, carbon nanowhiskers and carbon nanorods.
  • the subfluorinated carbonaceous material comprises a plurality of nanostructured particles; wherein each of the nanostructured particles comprise a plurality of fluorinated domains and a plurality of unfluorinated domains.
  • a “domain” is a structural component of a material having a characteristic composition (e.g., unfluorinated or fluorinated), phase (e.g., amorphous, crystalline, C 2 F, CFi, graphite, coke, carbon fiber, carbon nanomatehals such as multiwalled carbon nanotube, carbon whisker, carbon fiber etc.), and/or morphology.
  • a characteristic composition e.g., unfluorinated or fluorinated
  • phase e.g., amorphous, crystalline, C 2 F, CFi, graphite, coke, carbon fiber, carbon nanomatehals such as multiwalled carbon nanotube, carbon whisker, carbon fiber etc.
  • Useful subfluorinated carbonaceous materials for positive electrode active materials comprise a plurality of different domains.
  • Individual fluorinated and unfluorinated domains preferably for some applications have at least one physical dimension (e.g., lengths, depths, cross sectional dimensions etc.) less than about 50 nanometers, and more preferably for some applications at least one physical dimension less than about 10 nanometers.
  • Positive electrode active materials particularly useful for electrochemical cells providing high performance at low temperatures include nanostructured particles having fluorinated domains and unfluorinated domains that are distributed throughout each nanostructured particle of the active material, and in some embodiments substantially uniformly distributed throughout each nanostructured particle of the active material.
  • fluorinated domains of particles of the positive electrode active material comprise a subfluorinated carbonaceous material having an average stoichiometry CFy, wherein y is the average atomic ratio of fluorine atoms to carbon atoms and is selected from the range of about 0.8 to about 0.9, and the unfluorinated domains of the particles of the positive electrode active material comprise a unfluorinated carbonaceous phase, such as graphite, coke, multiwalled carbon nanotubes, multi-layered carbon nanofibers, multi-layered carbon nanoparticles, carbon nanowhiskers and carbon nanorods.
  • nanostructured subfluorinated carbonaceous particles as positive electrode active materials provides a number of benefits in electrochemical cells of the present invention.
  • nanoscale intermixing of fluorinated and unfluorinated domains in these particles results in high interfacial surface areas between the fluorinated and unfluorinated domains. This attribute provides good electronic and interface properties between these domains facilitating electron transfer, particularly at low temperatures.
  • the presence of an appreciable unfluorinated component in these particles enhances net electrode conductivity by providing nanoscale electrically conducting pathways in the electrode active material.
  • nanoscale fluorinated domains in these materials provides an appreciable density of fluorinated domains having high fluorine ion loading exposed to the electrolyte, thereby resulting in a high interfacial surface area of fluorinated structural domains exposed to the electrolyte further enhancing the kinetics at the positive electrode.
  • Positive electrodes of the present electrochemical cell may further comprises a conductive diluent, such as acetylene black, carbon black, powdered graphite, coke, carbon fiber, and metallic powder, and/or may further comprises a binder, such polymer binder.
  • a conductive diluent such as acetylene black, carbon black, powdered graphite, coke, carbon fiber, and metallic powder
  • binder such polymer binder.
  • Useful binders for positive electrodes in some embodiments comprise a fluoropolymer such as polyvinylidene fluoride (PVDF).
  • PVDF polyvinylidene fluoride
  • Positive electrodes of the present invention may be provided in a range of useful configurations and form factors as known in the art of electrochemistry and battery science, including thin electrode designs, such as thin film electrode configurations.
  • the positive electrode comprises a thin composite film comprising a subfluohnated carbonaceous active material provided on metallic current collector, wherein the thickness of the thin composite film is selected from the range of about 20 microns to 120 microns. Electrode active materials and electrolytes of the present invention enable lithium batteries capable of providing useful discharge rates with electrode form factors having thicknesses greater than or equal to about 90 microns. In an embodiment, a positive electrode comprising a subfluorinated carbonaceous active material is provided in a spirally-wound electrode configuration.
  • Negative electrodes of the present invention comprise a source of ions of a metal selected from Groups 1 , 2, and 3 of the Periodic Table of Elements.
  • the negative electrode comprises a source of lithium ions, such as lithium metal, a lithium alloy, a carbon-lithium material and lithium metal oxide intercalation compounds.
  • Useful carbon-lithium materials include carbonaceous materials, such as graphite or coke, intercalated with lithium ions.
  • electrochemical cells of the present invention have a nonaqueous electrolyte comprising a high performance low temperature electrolyte.
  • high performance low temperature electrolyte refers to electrolyte compositions having a low freezing point and one or more of the following properties at temperatures less than about -20 degrees Celsius: (i) ionic conductivity of greater than or equal to 0.0001 S cm "1 , greater than or equal to 0.001 S cm “1 , or greater than or equal to 0.005 S cm “1 ; (ii) good positive electrode conditioning and wetting properties for subfluorinated carbonaceous electrode active materials; and (iii) high chemical and electrochemical stability, particularly with respect to decomposition on positive and negative electrode surfaces.
  • a high performance low temperature nonaqueous electrolyte comprises a solution of a lithium salt and a solvent.
  • Useful lithium salts for this aspect of the present invention include, but are not limited to, LiBF 4 , LiF, LiCIO 4 , LiAsF 6 , LiSbF 6 and LiPF 6 .
  • the concentration of lithium salt in the nonaqueous electrolyte solution is an important parameter which is selected in some embodiments to enhance low temperature performance.
  • the lithium salt such as LiBF 4
  • the lithium salt has a concentration in the nonaqueous electrolyte solution that is preferably less than 1.0 M for some applications, and more preferably less than 0.5 M for some applications.
  • Useful lithium salt concentrations for some electrochemical cells of the present invention are selected from the range of about 0.75 M to about 0.25 M, for example when LiBF 4 is the selected lithium salt.
  • Solvent composition is also selected in embodiments of the present invention to enhance low temperature electrochemical cell performance.
  • Solvents useful in nonaqueous electrolytes of the present invention include, but are not limited to, propylene carbonate, 1 ,2-dimethoxy ethane, trifluoroethyl ether, diethyl ether, diethoxyethane, 1-3 dioxolane, tetrahydrofuran, 2-methyl tetrahydrofuran, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ⁇ -butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, gamma-butyrolactone, diethoxyethane, acetonitrile, and methylacetate.
  • Nonaqueous electrolytes of the present invention also include fluorine analogs of the solvents provided above.
  • fluorine analogs include: (i) fully fluorinated analogs wherein each hydrogen atom of the solvent molecule is replaced by a fluorine atom, and (ii) partially fluorinated analogs wherein at least one hydrogen atom of the solvent molecule is replaced by a fluorine atom.
  • Use of solvents containing fluorine analogs is preferred in some embodiments as these materials comprise a fluorous phase that can associatively interact with the positive electrode given the inherent fluorophilicity of subfluorinated and fully fluorinated carbonaceous electrode active materials.
  • fluorophilic subflourinated CFx active material undergo enhance wetting and conditioning at the positive electrode, thereby enabling high discharge rate performance, particularly at low temperatures.
  • a solvent comprising a mixture of mixture of propylene carbonate (or alternatively ethylene carbonate) and 1 ,2-dimethoxy ethane provides a nonaqueous electrolyte solution exhibiting useful physical and chemical properties in the present invention.
  • the relative proportions of propylene carbonate and 1 ,2-dimethoxy ethane in these solvent blends is selected to provide sufficient propylene carbonate to achieve a high dielectric constant so as to prevent significant self discharge, thereby enhancing battery stability.
  • sufficient 1 ,2-dimethoxy ethane is provided in the electrolyte to achieve low viscosity and good coordinating properties with the lithium salt so as to provide useful ionic conductivities.
  • propylene carbonate should be provided in sufficient proportion so as to impart effective passivation of the negative electrode.
  • the solvent has a volume to volume ratio of propylene carbonate to 1 ,2-dimethoxy ethane is selected from the range of about 0.25 to about 1. In an embodiment, for example, the solvent has a volume to volume ratio of propylene carbonate to 1 ,2-dimethoxy ethane that is less than about 0.50.
  • Another strategy for enhancing the low temperature performance of nonaqueous electrolytes in electrochemical cells of the present invention includes use of solvents containing an ether having at least one fluroalkyl group, such as trifluoroethyl ether (TEE).
  • Ethers having fluoroalkyl groups impart beneficial physical properties to electrolyte solutions of the present invention due to the low melting points, low viscosity and good solvating properties of these compounds.
  • addition of hydrofluorocarbon ethers to the electrolyte solution enhances the wetting of active electrode materials comprising subfluohnated carbonaceous materials.
  • the invention provides a nonaqueous electrolyte solution comprising an ether having at least one fluroalkyl group, such as trifluoroethyl ether, having a percent by volume of the solvent selected from the range of about 10% to about 40%.
  • an ether having at least one fluroalkyl group such as trifluoroethyl ether
  • a percent by volume of the solvent selected from the range of about 10% to about 40%.
  • the present invention provides high performance nonaqueous electrolyte solutions comprising an anion receptor.
  • High performance nonaqueous electrolytes of the present invention are particularly beneficial for enhancing low temperature performance of lithium batteries having a fluorinated carbonaceous positive electrode active material, such as a subfluorinated carbonaceous material or fully fluohnate carbonaceous material.
  • Incorporation of anion receptors that do not use hydrogen bonding to tie up the anion, such as a Lewis acid anion receptor increases the solubility of the lithium salt so as to enhance the net ionic conductivity of the electrolyte solutions of the present invention, particularly at low temperatures.
  • anion receptors of the present invention are capable of dissolving discharge reactants that can buildup on the positive electrode surface upon discharge of the electrochemical cell. Dissolution of such discharge reactants is beneficial as buildup can reduce kinetic performance at the electrode, particularly at the positive electrode. Dissolution of discharge reactants by anion receptors in nonaqueous electroytes of electrochemical cells of the present invention enables the practical thickness of the active material positive electrode to be increased while still preserving useful discharge rate performance, (e.g., high discharge rate capability, no significant voltage delay or severe polarization effects).
  • a high performance nonaqueous electrolyte of the present invention further comprises an anion receptor capable of coordinating fluoride ions.
  • Use of a fluoride ion anion receptor in these aspects of the present invention is useful for reducing or eliminating unwanted LiF buildup on the positive electrode interface.
  • LiF commonly precipitates on the surface of carbonaceous positive electrode active materials. LiF is virtually insoluble in many nonaqueous electrolytes and is also electrochemically inactive. Therefore, build up on an electrode surface impedes ionic and/or electronic conductivity at the positive electrode. Further, the equilibrium constant (K sp ) for the LiF precipitation reaction is small;
  • Li soln + F soln ⁇ LiFpptJ thereby strongly favoring the formation of the solid precipitate LiF ppt at the surface of the positive electrode.
  • LiF ppt grain growth via Ostwald ripening is exceeding slow resulting in tiny grains that do not grow effectively, but rather agglomerate, thereby resulting in a dense fine coating at the cathode capable of degrading electron and ion conductivity.
  • Addition of a fluoride ion anion receptor in the electrolytes of the present invention is useful for initiating the dissolution of LiF ppt via a fluoride ion complex reactions.
  • the high performance low temperature electrolytes of the present invention enhance electronic conductivity by improving electrolyte access to the carbonaceous positive electrode active material.
  • grain growth of the LiFppt is much more favored, resulting in less conformal coating of the positive electrode.
  • a beneficial result provided by the addition of fluoride ion anion receptors of the present invention is to modify the composition and/or morphology of the solid electrolyte interface (SEI) film so as to decrease interfacial resistance at the subfluorinated carbonaceous positive electrode.
  • SEI solid electrolyte interface
  • Useful anion receptors in the present high performance nonaqueous electrolyte solutions include fluorinated boron-based anion receptors, such as boranes, boronates and borates having electron withdrawing ligands.
  • Useful anion receptors in the electrochemical cells of the present invention include, but are not limited to, fluorinated borate-based compounds, phenyl boron-based compounds and aza-ether boron-based compounds.
  • Anion receptor-containing nonaqueous electrolyte solutions of some aspects of the present invention have a concentration of anion receptor less than about 2M, preferably for some embodiments a concentration of anion receptor less than about 1 M, and more preferably for some embodiments a concentration of anion receptor less than about 0.5 M.
  • anion receptors of the present invention are capable of facilitating dissolution of low solubility lithium salts, such as LiF, in a non aqueous solvent.
  • Anion receptors of the present invention are capable of increasing the specific capacity of subfluorinated carbonaceous positive electrodes.
  • Anion receptors of the present invention are capable of increasing the conductivity of nonaqueous electrolyte solutions of the present invention, for example, to a value greater than or equal to about 0.001 S cm "1 for some embodiments or, a value greater than or equal to about 0.01 S cm "1 for some embodiments.
  • a high performance low temperature nonaqueous electrolyte solution of the present invention further comprises an anion receptor having the chemical structure AR1 :
  • R 3 wherein R 1 , R 2 and R 3 are independently selected from the group consisting of alkyl, aromatic, ether, thioether, heterocyclic, aryl or heteroaryl groups which are optionally substituted with one or more halogens, including F, alkyl, alkoxide, thiol, thioalkoxide, aromatic, ether or thioether.
  • the present invention provides a high performance low temperature nonaqueous electrolyte solution comprising a borate- based anion receptor compound having the chemical structure AR2:
  • R 4 , R 5 and R 6 are selected from the group consisting of alkyl, aromatic, heterocyclic, aryl or heteroaryl groups which are optionally substituted with one or more halogens, including F, alkyl, alkoxide, thiol, thioalkoxide, aromatic, ether or thioether.
  • R 4 , R 5 and R 6 are identical.
  • each of R 4 , R 5 and R 6 are F-beahng moieties.
  • the present invention provides a high performance low temperature nonaqueous electrolyte solution comprising a phenyl boron-based anion receptor compound having the chemical structure AR3:
  • R 7 and R 8 are selected from the group consisting of alkyl, aromatic, heterocyclic, aryl or heteroaryl groups which are optionally substituted with one or more halogens, including F, alkyl, alkoxide, thiol, thioalkoxide, aromatic, ether or thioether.
  • R 7 and R 8 are identical.
  • each of R 7 and R 8 are F- bearing moieties.
  • R 7 and R 8 together from an aromatic, including a phenyl that is optionally substituted, including substituents that are F and substituents that are themselves F-bearing moieties, as shown by chemical formula AR4:
  • a high performance low temperature nonaqueous electrolyte solution of the present invention further comprises a Tris (hexafluoroisopropyl) borate (THFIB; MW 511.9 AMU) anion receptor having the chemical structure AR5:
  • BHFIPFPB Bis (1 ,1 ,3,3,3-hexafluoroisopropyl) pentafluorophenyl boronate
  • Anion receptors useful in electrolytes of present invention include those having the formula selected from the group consisting of: (CH 3 O) 3 B, (CF 3 CH 2 O) 3 B, (C 3 F 7 CH 2 O) 3 B, [(CFs) 2 CHO] 3 B, [(CFs) 2 C(C 6 H 5 )O] 3 B, ((CF 3 )CO) 3 B, (C 6 H 5 O) 3 B, (FC 6 H 4 O) 3 B, (F 2 C 6 H 3 O) 3 B, (F 4 C 6 HO) 3 B 1 (C 6 F 5 O) 3 B, (CF 3 C 6 H 4 O) 3 B, [(CFs) 2 C 6 H 3 O] 3 B and (C 6 Fs) 3 B.
  • the present invention provides lithium batteries capable of enhanced operation, particularly at low temperatures.
  • a primary lithium battery of the present invention is capable of providing discharge rates equal to or greater than C/5 at temperatures lower than or equal to -40 degrees Celsius; wherein C is the capacity of the electrochemical cell.
  • a primary lithium battery of the present invention is capable of providing a specific capacity equal to or greater than 500 mAh g "1 at a discharge rate of C/5 and with a discharge voltage greater than or equal to about 2.5 V at a temperature equal to -40 degrees Celsius.
  • a primary lithium battery of the present invention is capable of providing a specific capacity of 625 mAh/g for discharge at C/40 at -40C at 2.3V.
  • a primary lithium battery of the present invention is capable of providing an energy density greater than or equal to about 1700 Wh kg "1 , at a discharge rate equal to or greater than about C/40 and at -40 degrees Celsius.
  • the present invention provides a method of generating an electrical current at a temperature less than or equal to -40 degrees Celsius comprising the steps of: (i) providing an electrochemical cell comprising: a positive electrode comprising a subfluohnated carbonaceous material having an average stoichiometry CF x , wherein x is the average atomic ratio of fluorine atoms to carbon atoms and is selected from the range of about 0.3 to about 1.0; the subfluohnated carbonaceous material being a multiphase material having an unfluorinated carbon component; a negative electrode; and a nonaqueous electrolyte provided between the positive and negative electrodes; and (ii) discharging the electrochemical cell at a temperature less than or equal to -40 degrees Celsius.
  • the method of this aspect of the invention further comprising the step of discharging a portion of the capacity of the electrochemical cell at a temperature equal to about 20 to about 30 degrees Celsius prior to the step of discharging the electrochemical cell at a temperature less than or equal to -40 degrees Celsius.
  • a portion of the capacity of the electrochemical cell at a temperature equal to about 20 to about 30 degrees Celsius prior to the step of discharging the electrochemical cell at a temperature less than or equal to -40 degrees Celsius.
  • the present invention provides a method of making an electrochemical cell capable of low temperature operation comprising the steps of: (i) providing an electrochemical cell comprising: a positive electrode comprising a subfluorinated carbonaceous material having an average stoichiometry CF x , wherein x is the average atomic ratio of fluorine atoms to carbon atoms and is selected from the range of about 0.3 to about 1.0; the subfluorinated carbonaceous material being a multiphase material having an unfluorinated carbon component; a negative electrode; and a nonaqueous electrolyte provided between the positive and negative electrodes; and discharging a portion of the capacity of the electrochemical cell at a temperature equal to about 20 to about 30 degrees Celsius.
  • between about 0.5 % to about 10% of the capacity of the electrochemical cell is discharged at a temperature equal to about 20 to about 30 degrees Celsius prior to the step of discharging the electrochemical cell at a temperature less than or equal to - 40 degrees Celsius.
  • room temperature predischarge conditioning results in formation of a fluorine-free carbonaceous layer at the positive electrode - electrolyte interface that enhances wetability and conductivity of the electrode.
  • Room temperature predischarge conditioning provides a useful means, therefore, of preparing the positive electrode interfacial regions to accommodate high performance low temperature discharge.
  • Figure 4 Line scan x-ray energy dispersive data showing the relative normalized intensities of the kp x-rays excited as a function of position (as indicated by line on SEM image).
  • FIG. 7 Room-temperature data from a Li-CF 065 test cell.
  • the cathodes were about 1.5 mils thick.
  • Discharge rates were C/5 and 2C.
  • FIG. 8 Performance of the cathodes based on commercial CFi 08 material mixed with 30 wt% carbon black.
  • the electrolyte solvent was 20/80 wt% PC/DME, the discharge temperature was -40°C, the active material mass was 6.08, 4.64 mg for the C/20, C/40 cells (respectively), and the cathode thickness: ⁇ 1 millimeter.
  • Figure 9 Discharge data from similar Li-CF 065 test cells at -40°C with and without a room-temperature pre-discharge of 3% the total capacity of the cell.
  • Figure 10 Discharge data from test cells at -40°C as discharged at different rates, (a) CF 0 65 test cell discharged at a C/20 rate followed by a C/40 rate, (b) CF 065 test cell discharged at a C/10 rate Followed by a C/20 rate, (c) Li-CF 054 test cell at a C/10 rate followed by a C/20 rate at -40°C.
  • Figure 11 Potential vs. time plots for room temperature and -40°C galvanostatic testing on Li/Cu half cells. The current used, 0.23 mA, was a typical discharge rate for the Li-CF x cells.
  • Figure 12 Three-electrode measurements using a Li reference electrode on a Li-CFi 08 glass test cell. The scale for the anode potential is on the right.
  • FIG. 14 Discharge data from Li-CF 0 65 test cells at -40°C at a C/10 rate. Five different electrolytes are compared here. The two cells that offered very little capacity at this discharge rate were then discharged at a C/40 rate and subsequently yielded full capacity.
  • Figure 15 EIS data collected from Li-CFO.65 cells before and after full discharge at -40°C with 8/2 v/v% DME/PC electrolyte solvent using (a) 1 M LiBF 4 and (b) 0.5 M LiBF 4 .
  • the frequency range was 100,000 Hz to 50 mHz.
  • FIG. 16 Discharge data from various Li-CF x test cells at -40°C at a C/5 rate.
  • the cells containing SFCF x yielded significantly more capacity at higher discharge potentials than that for the cell containing commercially available CF 1 O ⁇ -
  • the Highest capacity material was CF 0 82 (MWNT precursor), which delivered over 650 mAh/g above 1.5V.
  • FIG. 1 Discharge behavior at a C/5 rate, -40 degrees C as a function of composite cathode thickness, for CF 0 65-based test cells.
  • the 0.5 M LiBF 4 with 8/2 v/v% DME/PC electrolyte was used in all cases, and the TTFEB anion acceptor was added in thick electrode case (115 ⁇ m thick).
  • Fig. 20 Discharge data from test cells at -40°C as discharged at different rates, (a) CF 0 65 test cell discharged at a C/20 rate followed by a C/40 rate, (b) CF 0 65 test cell discharged at a C/10 rate Followed by a C/20 rate, (c) Li-CF 0 S 4 test cell at a C/10 rate followed by a C/20 rate at -40°C.
  • Fig. 21 CF 065 and CF 1 08 cathode materials as discharged under C/10 and C/5 rates.
  • the CFi 0 8 baseline material yielded a specific capacity less than 30% of the CF 0 65 material.
  • Fig. 22 Specific capacity as a function of fluorination level in the sub- fluorinated CFx materials as discharged at a C/10 rate at -40 degrees C.
  • Fig. 23 Discharge behavior at a C/5 rate, -40 degrees C as a function of composite cathode thickness, for CF 0 65 - based test cells.
  • Fig. 25 The performance of CFi 0 8 - based cathodes under identical conditions (C/2.5 rate, -40°C) using the same electrolyte + anion receptor. Nearly an order of magnitude less specific capacity was realized. Cell B discharge was stopped after 30 mAh/g and a lower rate discharge was attempted.
  • Fig. 26 Li-CF 0 65 test cells with the anion receptor additive at -40, -50, and -60 degrees C at a C/5 discharge rate. Even at -60 C, a specific capacity of nearly 300 mAh/g was realized.
  • FIG. 27 A thick electrode CF 0 6 S discharge with anion receptor additive: a functional, high rate (C/5) cathode 115 microns thick was created and offered nearly 600 mAh/g.
  • Fig. 28A provides plots of the imaginary impedance (Ohms) versus real impedance (Ohms) for a propylene carbonate solution having a varying lithium salt and anion receptor composition.
  • Fig. 28B shows these plots on an expanded scale for the circled region indicated in figure 28A.
  • Fig. 29 provides plots showing the results of cyclic voltammetry experiments which show the reductive stability of a tris (hexafluoroisopropyl) borate anion receptor in a propylene carbonate solvent.
  • Electrochemical cell refers to devices and/or device components that convert chemical energy into electrical energy or electrical energy into chemical energy. Electrochemical cells typical have two or more electrodes (e.g., positive and negative electrodes) wherein electrode reactions occurring at the electrode surfaces result in charge transfer processes. Electrochemical cells include, but are not limited to, primary batteries, secondary batteries, lithium batteries and lithium ion batteries. General cell and/or battery construction is known in the art, see e.g., U.S. Pat. Nos. 6,489,055, 4,052,539, 6,306,540, Seel and Dahn J. Electrochem. Soc. 147(3) 892-898 (2000).
  • Capacity is a characteristic of an electrochemical cell that refers to the total amount of electrical charge an electrochemical cell, such as a battery, is able to hold. Capacity is typically expressed in units of ampere-hours.
  • specific capacity refers to the capacity output of an electrochemical cell, such as a battery, per unit weight. Specific capacity is typically expressed in units of ampere-hours kg “1 .
  • discharge rate refers to the current at which an electrochemical cell is discharged.
  • Discharge current can be expressed in units of ampere-hours.
  • discharge current can be normalized to the rated capacity of the electrochemical cell, and expressed as C/(X t), wherein C is the capacity of the electrochemical cell, X is a variable and t is a specified unit of time, as used herein, equal to 1 hour.
  • nanostructured refers materials and/or structures have a plurality of discrete structural domains with at least one physical dimension (e.g., height, width, length, cross sectional dimension) that is less than about 1 micron.
  • structural domains refer to features, components or portions of a material or structure having a characteristic composition, morphology and/or phase.
  • Nanostructured materials useful as positive electrode active materials include nanostructured composite particles having a plurality of fluohnated carbon domains and unfluohnated carbon domains.
  • nanostructured materials of the present invention comprise a plurality of structural domains having different compositions, morphologies and/or phase intermixed on a very fine scale (e.g., at least smaller than 10's of nanometers).
  • Active material refers to the material in an electrode that takes part in electrochemical reactions which store and/or delivery energy in an electrochemical cell.
  • the present invention provides electrochemical cells having a positive electrode with a subfluorinated carbonaceous active material.
  • a carbon nanomaterial has at least one dimension that is between one nanometer and one micron. In an embodiment, at least one dimension of the nanomaterial is between 2 nm and 1000 nm. For carbon nanotubes, nanofibers, nanowhiskers or nanorods the diameter of the tube, fiber, nanowhiskers or nanorod falls within this size range. For carbon nanoparticles, the diameter of the nanoparticle falls within this size range.
  • Carbon nanomaterials suitable for use with the invention include materials which have total impurity levels less than 10% and carbon materials doped with elements such as boron, nitrogen, silicon, tin and phosphorous.
  • nanotube refers to a tube-shaped discrete fibril typically characterized by a diameter of typically about 1 nm to about 20 nm. In addition, the nanotube typically exhibits a length greater than about 10 times the diameter, preferably greater than about 100 times the diameter.
  • multi-wall as used to describe nanotubes refers to nanotubes having a layered structure, so that the nanotube comprises an outer region of multiple continuous layers of ordered atoms and a distinct inner core region or lumen. The layers are disposed substantially concentrically about the longitudinal axis of the fibril. For carbon nanotubes, the layers are graphene layers.
  • Carbon nanotubes have been synthesized in different forms as Single-, Double- and Multi-Walled Carbon Nanotubes noted SWCNT, DWCNT and MWCNT respectively.
  • the diameter size ranges between about 2 nm in SWCNTs and DWCNTs to about 20 nm in MWCNTs.
  • the MWNT used in the invention have a diameter greater than 5 nm, greater than 10 nm, between 10 and 20 nm, or about 20 nm.
  • Electrodes are manufactured as disclosed herein and as known in the art, including as disclosed in, for example, U.S. Pat. Nos. 4,052,539, 6,306,540, 6,852,446. Briefly, the electrode is typically fabricated by depositing a slurry of the electrode material, an electrically conductive inert material, the binder, and a liquid carrier on the electrode current collector, and then evaporating the carrier to leave a coherent mass in electrical contact with the current collector.
  • Root temperature refers to a temperature selected over the range of about 293 to 303 degrees Celsius.
  • Example 1 Low Operational Temperature Li-CFx Batteries Using Cathodes Containing Sub-Fluorinated Graphitic materials Overview
  • Electrochemical tests showed that these materials are able to deliver specific capacity values up to 5 times greater than commercial CFi 0 8 powder inserted into identically fabricated test cells tested at -40°C. Testing also indicated that a room-temperature pre- discharge step was necessary to condition the electrode materials before exposure to the low-temperature test environment.
  • Li/CF X batteries can deliver up to 700 Wh/kg, 1000 Wh/I, (at room temperature, C/100 rate) and typically use active cathode materials consisting of fluohnated carbonaceous materials such as coke or graphite. These cathodes have compositions typically ranging from CFi 05 to CFi 1 that can deliver specific capacities in excess of 800 mAh/g at 2.5 Volts under low-rate conditions at room temperature. This cathode material, however, is known to be discharge rate limited, and currents lower than C/50 (battery current 1 /50th that of the capacity of the battery divided by 1 hour) are often necessary to avoid cell polarization and large capacity loss.
  • the present Example describes the performance of Li-CF x test cells based on SFCF x active cathode materials and electrolytes designed to function well at low-temperatures. A series of test cells based on commercially-supplied CF 1 08 powders were tested in parallel in identical test cells.
  • Electrochemical Analyses [089] Spray-deposited cathodes were fabricated using SFCF x powders that were prepared using a mix consisting of 80 wt%, 10 wt% carbon black in a NMP solution solvating 10 wt% PVDF (pre-stirred solution). As a control, a commercial CFi 0 8-based cathode mixture was also produced which had a similar overall fluorine mass fraction as in the CF 0 S4 mix (and so therefore had a higher carbon-diluent-to "active material” ratio). Specifically, these baseline cathodes contained 30 wt% C black, 60 wt% CFi 08 and 10 wt% PVDF.
  • the fully intermixed slurry (as mechanically stirred for at least 12 hours) was spray-deposited in multiple layers onto a roughened 1 -mil thick Al foil current collector.
  • the resulting physically robust cathode structures 1 to 3 mils in thickness, were vacuum-furnace dried for 24 to 48 hours at ⁇ 105°C.
  • 2032 size coin cell test cells were then fabricated using 16 mm diameter cathode disks, a single layer of Tonen separator, and a 16 mm diameter Li foil anode.
  • the electrolytes contained 1 M LiBF 4 salt solvated in a mix of either propylene carbonate (PC) + 1 ,2,-dimethoxy ethane (DME) in a 20/80 or 50/50 v/v % ratio. Since these electrodes were so thin, the variation in wettability between these two solvent compositions was not found to have a significant effect on cell performance. A series of electrolytes made using various solvent additives has also been performed, and will be reported on elsewhere in detail.
  • Electrochemical testing consisted of galvanostatic discharges at room temperature and -40°C under currents consistent with rates ranging from 2C to C/40. These rate values were calculated using the nominal room-temperature specific capacities that have been previously published for these SFCF x materials. A room- temperature pre-discharge step of 3% of the total estimated cathode capacity at a C/33 rate was employed in most cases. Electrochemical impedance spectroscopy (EIS) in the potentiostatic mode (5 mV signal amplitude, 10 ⁇ 2 to 10 5 Hz frequency range) was carried out to examine the effect of this pre-discharge on the cathode an anode.
  • EIS Electrochemical impedance spectroscopy
  • Figure 9 shows the -40°C performance of Li-CF 0 6 s cells (using 20/80 PC/DME electrolyte solution) with and without the room temperature pre-discharge step.
  • a capacity of 600 mAh/g was extracted from the cathode that had undergone the pre- discharge. This experiment was repeated several times using different electrolytes and cathode materials and the results were similar: the pre-discharge was useful for enhancing the performance of the cells at low temperatures. For this reason, this conditioning step was adopted and used for most experiments in this Example.
  • Figure 10 shows discharge curves from CF 0 65 and CF 0 54 cells at -40°C, using multiple discharge rates in succession.
  • a CF 0 65 and cell was first discharged at a C/20 rate (to 0.5 V) followed by a discharge at a C/40 rate, while in (b) the respective rates were C/10 and C/20 on a CF 0 65 cell.
  • the total capacity delivered under a C/20 discharge current was greatly enhanced if preceded by a C/10 discharge.
  • Table 1 contains a partial list of test cells, composition, test conditions, and resulting capacities.
  • Table 1 Partial List of test cells, discharge conditions, and specific capacity/energy values (as calculated based on cathode active material mass content).
  • Microstructure The characterization data indicate that the SFCF x materials were comprised of pristine un-fluorinated graphite mixed intimately with fluorinated C, and are consistent with data reported previously.
  • the SEM/XEDS analyses indicate that the C and F are intermixed at a very fine scale (at least smaller than 10's of nm), while the XRD data show that the graphitic material that has undergone fluorination is likely fluorinated to the same degree regardless of the total fluorination of the sample (i.e. x in CF x ). There is also no evidence of graphitic gallery staging at the various levels of fluohnation.
  • microstructure of this material is a collection of nano-dimensional graphite and CF y domains, where y is approximately 0.8 to 0.9.
  • the small scale of these compositionally variant regions dictates that the material have a very high graphite-to-CF y surface area and subsequently will posses excellent electronic/interface transport properties at all temperatures.
  • the fluorination of graphite is kinetically unfavorable as it requires the following: i) separation of the graphene layers to allow for fluorine diffusion, ii) change in the carbon hybridization from stable sp 2 to less stable sp 3 , and iii) dissociation of the F 2 molecule.
  • the practical end point is reached after 17-hours reaction. Both samples show unreacted graphite.
  • the CFi 0 8 yielded significantly lower capacities at lower discharge potentials than the SFCF x materials, even though the latter were in a slightly thicker electrode form factor, as summarized in table 1.
  • the CFi O ⁇ - based cathodes typically delivered one-third the capacity of the CF 0 65 material under identical conditions. The result is more pronounced when considering the fact that the baseline material cathodes also polarized to a greater degree, thereby offering a energy density.
  • FIG. 12 shows the anode, cathode and full cell potential (vs. Li reference electrode) as a function of time during a 2 hour pre-discharge of a thick CFi 0 8-based cathode.
  • the anode polarizes approximately 5 mV, while the cathode potential varies though a range of nearly 1 V.
  • EIS analyses on the cathode of this cell before and after the pre-discharge are conclusive (figure 13): the cathode interfacial resistance decreased to about 20% its pre-discharge value.
  • FIG 10 Another relationship is indicated in figure 10, where it is shown that high-rate discharges at -40°C can improve subsequent performance in lower rate discharging at the same temperature.
  • Figure 10(a) shows that an initial C/20 rate discharge yields about 150 mAh/g of capacity in a Li/CF 0 647 cell.
  • Figure 10(b) indicates that if a very short C/10 rate discharge preceded a C/20 discharge, over 500 mAh/g was extracted for this similar cell. There is a voltage recovery event early on in this C/20 discharge, which may also be indicative of a variety of possible electrode conditioning effects. In other cases, significantly more capacity was extracted at a C/10 rate at -40°C, as in figure 10(c).
  • This Example shows that the nano-scale intermixing of graphitic domains and CFy found in sub-fluohnated CF x (SFCF x ) materials greatly benefited the specific capacity of these materials when discharged at low temperatures using aggressive current densities.
  • the performance of SFCF x materials was compared to industry- standard, fully-fluorinated CFi 0 8 powders inserted in otherwise identical test cells.
  • the SFCF x and CFi 0 8 active material yielded nearly the same specific capacity values at room temperature at rates as high as 2C. However the SFCF x gave a 3 times (or greater) capacity value at -40°C using rates up to C/10.
  • Example 2 Enhanced Low-Temperature Performance of Li-Cf x Batteries Overview
  • the focus of the present Example is to further improve low-temperature functionality by matching the highest capacity sub-fluorinated cathode active material with the proper electrolyte blend and electrode form factor.
  • three different electrolytes were tested at low temperatures with a standard Li-CF 0 65 cell. The best electrolyte was then used to test several variations of sub-fluorinated CF x cathode material. These results were compared to those obtained from cathodes produced using commercially available CFi O ⁇ - In some cells, a solvating anion receptor additive was also inserted into the electrolyte with the intention of reducing cathode surface Li-F passivation, thereby increasing the electrode functionality. The most promising test cells were able to support substantial discharge currents at temperatures colder than - 40°C, with composite cathode thicknesses exceeding 110 ⁇ m.
  • a standard test vehicle was adopted that consisted of a spray-deposited cathode layer containing 10% PVDF binder, 10% carbon black, and 80% active material on a 1 -mil thick Al current collector foil (and spray-deposited onto the heated Al current collector). These composite cathodes ranged in thickness from 10 ⁇ m to 120 ⁇ m, with the most commonly tested thickness being about 40 ⁇ m +/- 5 ⁇ m. The relationship between electrode mass and thickness was determined using a precision caliper on the thicker samples (>50 ⁇ m).
  • the standard test cell consisted of 2032 coin cells with a Li metal anode, and a single layer of polypropylene (TonenTM) separator.
  • control electrode based on CF 1 O s as received from a commercial vendor, contained 30 wt% carbon black and 10 wt% PVDF. This resulted in a composite electrode capable of similar room temperature performance (per unit mass of the total composite electrode) as a CFo 55-containing electrodes.
  • the selected electrolyte blends are indicated in Table 2.
  • the lithium tetrafluoroborate used was battery grade and obtained from Mitsubishi Petrochemicals Co. and vacuum dried prior to use.
  • the propylene carbonate (PC) and 1 ,2-dimethoxyethane (DME) were also high purity battery grade and obtained from Mitsubishi Petrochemicals Co. and used as received.
  • the trifluoroethyl ether (TEE) was synthesized by a known method consisting of the acid catalyzed dehydration reaction of 2,2,2-trifluoroethanol.
  • test cells were made and tested using four different cathode active materials; three were SFCF x -based, and the last was the CFi 0 8-based standard.
  • the CF 0 65 electrodes used partially fluorinated Madagascar graphite precursor, while the other two SFCF x variations contained CF 059 or CF 082 material made using multi-wall carbon nano-tube material precursor materials supplied by MER Corporation. Characterization data indicated that all of the SFCF x materials were comprised of pristine un-fluohnated graphite domains mixed intimately with nano-dispersed near-fully fluorinated graphitic regions, and are consistent with data reported previously. The small scale of these regions dictates that the materials had a very high graphite-to-CF surface area and subsequently might possess excellent electron ic/interfacial transport properties.
  • Example 1 Previous work (See, Example 1 ) indicated that a room-temperature pre- discharge step (consisting of a 1 hour, discharge at a C/33 current level) was necessary to prepare the electrode interfacial regions to accommodate low-temperature discharge. This preparation was used here for most test cells, however, the necessity of this pre- discharge was re-examined for the most promising electrode/electrolyte combinations. In all cases, the C rate was calculated based on the expected room-temperature capacity of the cathode if discharged at a C/40 rate. Results
  • Figure 14 shows discharge data from CF 0 64 SFCF x active material cells using a C/10 discharge rate at -40°C with the different electrolytes listed in Table 2.
  • the best (highest power, smoothest discharge curve) result was obtained with 0.5 M LiBF 4 solvated in an 8/2 (v/v %) DME/PC blend.
  • Test cells made with electrolytes that had a higher salt content (1 M), were more rate-limited and had erratic potential variations during discharge at these low temperatures. Repeated testing supports this finding. Those cells that polarized rapidly were still functional and displayed smooth discharge curves and good discharge capacities at lower rates (C/20 or slower) at -40°C.
  • Figure 16 shows a comparison between the -40°C temperature performances of various CF x cathodes (of similar mass/thickness) as discharged at C/5 rate using the 0.5 M LiBF 4 solvated in 8/2 (v/v %) DME/PC electrolyte.
  • the delivered capacities for the SFCF x cathodes were as much as 300% greater with the subfluorinated cathodes than that of the CFi 0 8 baseline cathode under identical discharge conditions. Multiple electrodes were tested for each electrode composition with consistent results.
  • Cathodes as thick as 95 ⁇ m or higher were severely polarized upon discharge under these conditions, but were able to deliver full capacity at reduced discharge rates, for example at C/10 rate for the 95 ⁇ m cathode and a C/40 rate for the 118 ⁇ m thick cathode.
  • FIG. 17 also contains the results from a 115 ⁇ m-thick CF 0 65 cathode discharged at a C/5 rate at -40°C with the anion receptor additive.
  • Figure 18 contains plots of Li-CF 0 65 cells made using TTFEB anion receptor in 0.5 M LiBF 4 , 8/2 PC/DME electrolyte and discharged at progressively lower temperatures at a C/5 rate. Even at -60 °C, smooth discharges were observed and a specific capacity nearly 275 mAh/g was obtained. In all cases, those cells made with the anion receptor additive did not exhibit any noticeable voltage delay effects, even without the execution of a room temperature pre-discharge step. There was, instead, a characteristic positive voltage excursion upon discharge.
  • a decrease in the electrolyte salt content from 1 M to 0.5 M in an 80/20 v/v% DME/PC solution has further enhanced the low temperature performance of the Li/SFCF ⁇ electrochemical couple compared to previously published results.
  • This improvement can be attributed to at least one of several mechanisms, including enhanced low temperature electrolyte conductivity, or a relative decrease in surface precipitation on the active cathode material surfaces.
  • the impedance spectroscopy data indicate, however, that there is not a substantial difference between the electrode impedance as a function of salt content, which indicates that the enhancement mechanism is not directly related to the IR losses associated with an SEI layer.
  • the cathode impedance is substantially reduced after discharge, in solutions with either 0.5 M or 1.0 M salt concentration, with or without the anion receptor additive. Furthermore, previous results on three-electrode cells indicate that much of the change in series resistance occurs on the cathode side of the cell under these conditions. Even though the series resistance, reflected in the x-axis intercept at high frequencies, does not change, the low frequency impedance is significantly reduced. This may be due to inadequate wetting of the interface before discharge, or could be due to the insulating nature of a native film that forms on the cathode before discharge.
  • Electrolyte screening identified that blends consisting of 20/80 v/v% PC/DME with 1 M LiBF 4 offered superior low temperature performance compared to the baseline formulations, based on 1 M LiBF 4 in either 50/50 v/v% or 20/80 v/v% PC/DME.
  • Three variations of SFCF x cathode materials were inserted into similar -40 ⁇ m thick composite electrode structures and tested at -40°C using several different electrolyte blends.
  • the CF 0 65 and CF 0 82 based cells could deliver well over 600 mAh/g above 2 V under a C/5 discharge rate at - 40°C with the proper electrolyte blend.
  • an anion receptor electrolyte additive, TTFEB was evaluated and proved to be effective. With this additive, composite cathode structures 115 ⁇ m thick yielded over 500 mAh/g at a C/5 discharge rate at -40°C.
  • Example 3 Low Temperature Primary Li - CFx Battery Development and Testing CFx Cathode Materials Development
  • a standard test vehicle was adopted that consisted of a spray - deposited cathode layer containing 10% PVDF binder, 10% carbon black conductive diluent, and 80% active material on a 1 -mil thick Al current collector. These composite cathodes ranged in thickness from 10 ⁇ m to 120 ⁇ m, with the most commonly tested thickness being about 35 ⁇ m.
  • the standard test cell consisted of 2032 coin cells with a Li metal anode, and a TonenTM separator.
  • the characterization data indicate that the SFCF x materials were comprised of pristine un-fluohnated graphite mixed intimately with fluohnated C.
  • the SEM/XEDS analyses indicate that the C and F are intermixed at a very fine scale (at least smaller than 10's of nm), while the XRD data show that the graphitic material that has undergone fluohnation is likely fluorinated to the same degree regardless of the total fluohnation of the sample (i.e. x in CF x ). There is also no evidence of graphitic gallery staging at the various levels of fluorination.
  • microstructure of this material is a collection of nano-dimensional graphite and CF y domains, where y is approximately 0.8 to 0.9.
  • the small scale of these compositionally variant regions dictates that the material have a very high graphite-to- CFy surface area and subsequently will posses excellent electronic/interface transport properties at all temperatures.
  • the fluorination of graphite is kinetically unfavorable as it requires the following: i) separation of the graphene layers to allow for fluorine diffusion, ii) change in the carbon hybridization from stable sp 2 to less stable sp 3 , and iii) dissociation of the F 2 molecule.
  • the chemical activity of fluorine decreases with the depth of fluorine penetration within the layers. Consequently, the rate of the fluorination reaction
  • Table 3 has a summary of some early test results taken from cells using the 1 M LiBF 4 salt content electrolytes.
  • FIG. 20 shows a comparison of high rate (C/10) discharges of the generation Il CF 0 65 cathode material using different electrolytes.
  • the 0.5 M LiBF 4 solvated in an 8/2 DME/PC blend had the most stable discharge while delivering over 600 mAh/g at -40°C.
  • Figure 21 shows the comparative performance of CF 0 65 and CF 1 08 at -40°C at a C/10 and C/5 rate in this electrolyte blend.
  • FIG. 23 shows the behavior of CF 0 65 composite cathodes with thickness varying in thickness from 4 to 118 ⁇ m at a very aggressive C/5 discharge rate.
  • the cells delivered full capacity with some polarization up to a thickness of at least 57 ⁇ m.
  • Cathodes thicker than 95 ⁇ m polarized upon discharge (these cells were able to deliver full capacity at a C/10 rate for the 95 ⁇ m cathode and C/40 for the 120 ⁇ m thick cathode).
  • the commercial CFi 08 baseline and SFCF x cathode materials behaved differently.
  • the CF 1 08 yielded significantly lower capacities at lower discharge potentials than the SFCF x materials, even though the latter were in a slightly thicker electrode form factor, as summarized in Table 3.
  • the CF 1 08 - based cathodes typically delivered one-third the capacity of the CF 0 6 S material under identical conditions. The result is more pronounced when considering the fact that the baseline material cathodes also polarized to a greater degree, thereby offering a energy density.
  • This Example shows that the nano-scale intermixing of graphitic domains and CFy found in sub-fluorinated CF x (SFCF x ) materials greatly benefited the specific capacity of these materials when discharged at low temperatures using aggressive current densities.
  • the performance of SFCF x materials was compared to industry- standard, fully-fluorinated CFi 0 8 powders inserted in otherwise identical test cells.
  • the SFCF x and CFi 0 8 active material yielded nearly the same specific capacity values at room temperature at rates as high as 2C. However the SFCF x gave a 3 times (or greater) capacity value at -40°C using rates up to C/10.
  • the capacity/energy density of a D-sized cell produced using the CF 0 647 cathode material can now be estimated (for a -40 ° C, C/5 discharge condition). It is assumed that the CF 0 647 active material may be inserted into the same cell structure the 15.5 Ah D-size LiCF x battery under development at Eagle Picher. Substituting 600 mAh/g CF 0 647 into this cell format results in a cell with an energy density of about 400 Wh/kg when discharged at a C/5 rate at -40°C.
  • the present invention includes nonaqueous electrolyte compositions having anion receptor additives useful in lithium batteries.
  • Anion receptors in some aspects of the present invention are capable of conditioning the surfaces of subfluohnated and fully fluohnated carbonaceous positive electrode active materials by dissolving discharge products, such as LiF, that can degrade the electrical and ion conductivity at the electrode.
  • discharge products such as LiF
  • Figure 28A provides plots of the imaginary impedance (Ohms) versus real impedance (Ohms) for propylene carbonate solvent having a varying lithium salt and anion receptor composition.
  • Figure 28B shows these plots on an expanded scale for the circled region indicated in figure 28A.
  • circle markers correspond to pure propylene carbonate solvent
  • open square markers correspond to 2.25 M LiF in propylene carbonate solvent
  • dashed line markers correspond to 2.25 M LiF, 1 M tris (hexafluoroisopropyl) borate anion receptor in propylene carbonate solvent.
  • the test setup employed in these experiments was a Pt-Pt conductivity cell at room temperature.
  • Figure 29 provides plots showing the results of cyclic voltammetry experiments which show the reductive stability of a tris (hexafluoroisopropyl) borate anion receptor in a propylene carbonate solvent.
  • Experimental conditions corresponding to Figure 29 are a saturated solution of 1 :1 (molar ratio) LiF : tris (hexafluoroisopropyl) borate (THFIPB) in propylene carbonate.
  • THFIPB hexafluoroisopropyl borate
  • the electrolyte solution was reductively stable to Li, then Li metal should be stripped from the Li counter electrode and plated on the Cu working electrode when the potential of the working electrode falls below OV vs. Li/Li "1" .
  • any plated Li on the Cu working electrode should be stripped and re-plated at the Li counter. If, however, the electrolyte is not stable in contact with Li metal, then the small amount of plated Li metal at the Cu working electrode will react with the electrolyte and will not be stripped from the Cu working electrode. In this manner, it is possible to probe the relative stability of the electrolytes to Li metal.
  • fluoride ion anion receptors of the present invention decrease electrolyte viscosity and improve low temperature conductivity.
  • the present anion receptors complex BF 4 "1 , thereby increase the Li + transport number in electrolyte systems having a LiBF 4 lithium salt.
  • Isotopic variants of a molecule are generally useful as standards in assays for the molecule and in chemical and biological research related to the molecule or its use. Methods for making such isotopic variants are known in the art. Specific names of compounds are intended to be exemplary, as it is known that one of ordinary skill in the art can name the same compounds differently.
  • ionizable groups groups from which a proton can be removed (e.g., -COOH) or added (e.g., amines) or which can be quaternized (e.g., amines)]. All possible ionic forms of such molecules and salts thereof are intended to be included individually in the disclosure herein.
  • salts of the compounds herein one of ordinary skill in the art can select from among a wide variety of available countehons those that are appropriate for preparation of salts of this invention for a given application. In specific applications, the selection of a given anion or cation for preparation of a salt may result in increased or decreased solubility of that salt.

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Abstract

L'invention concerne des piles électrochimiques d'une bonne efficacité électronique à basses températures. Ces piles électrochimiques comportent des accumulateurs au lithium pouvant fournir des capacités spécifiques utiles à des vitesses de décharge importantes à des températures aussi basses que -60°C. L'invention concerne également des procédés de fabrication de piles électrochimiques comportant une étape de décharge préalable à température ambiante précédant le fonctionnement à basse température qui améliore l'efficacité des accumulateurs ayant des matériaux actifs d'électrodes positives carbonées sous-fluorées à basses températures.
EP07757061A 2006-02-16 2007-02-15 Pile électrochimique basse température Withdrawn EP1992028A4 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US77426206P 2006-02-16 2006-02-16
US78496006P 2006-03-20 2006-03-20
US78495706P 2006-03-21 2006-03-21
US79853206P 2006-05-08 2006-05-08
US90040907P 2007-02-09 2007-02-09
PCT/US2007/062243 WO2007098369A2 (fr) 2006-02-16 2007-02-15 Pile électrochimique basse température

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EP1992028A4 EP1992028A4 (fr) 2010-03-17

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US20130236786A1 (en) * 2010-12-22 2013-09-12 Mingjie Zhou Electrode sheet and its preparation method and super capacitor and lithium ion battery
CN102109580B (zh) * 2011-01-30 2013-03-20 白科 一种检测磷酸铁锂电池自放电工艺
JP5742024B2 (ja) * 2011-08-03 2015-07-01 大阪瓦斯株式会社 キャパシタの製造方法およびキャパシタ

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EP0169407A1 (fr) * 1984-06-29 1986-01-29 Daikin Kogyo Co., Ltd. Pile du type lithium-graphite fluoré
US6022643A (en) * 1997-12-08 2000-02-08 Brookhaven Science Associates Boron compounds as anion binding agents for nonaqueous battery electrolytes
US20020106558A1 (en) * 2000-04-25 2002-08-08 Maske Cecilia T. Extended temperature operating range electrochemical cells
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JPS4916131B1 (fr) * 1970-04-20 1974-04-19
JPS58191221A (ja) * 1982-05-01 1983-11-08 Showa Denko Kk フツ化炭素系繊維
JP2003306320A (ja) * 2002-04-11 2003-10-28 Univ Shinshu フッ素化カーボンチューブおよびこれを用いた摺動材
JP4747505B2 (ja) * 2004-03-29 2011-08-17 パナソニック株式会社 非水電解液電池
JP2007087688A (ja) * 2005-09-21 2007-04-05 Matsushita Electric Ind Co Ltd 非水電解液電池用正極、非水電解液電池および非水電解液電池用正極の製造方法

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EP0169407A1 (fr) * 1984-06-29 1986-01-29 Daikin Kogyo Co., Ltd. Pile du type lithium-graphite fluoré
US6022643A (en) * 1997-12-08 2000-02-08 Brookhaven Science Associates Boron compounds as anion binding agents for nonaqueous battery electrolytes
US20020106558A1 (en) * 2000-04-25 2002-08-08 Maske Cecilia T. Extended temperature operating range electrochemical cells
US20050227146A1 (en) * 2003-12-12 2005-10-13 Dania Ghantous Medium rate and high rate batteries

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See also references of WO2007098369A2 *

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