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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
• • 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
  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
  • H01M10/0563—Liquid materials, e.g. for Li-SOCl2 cells
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/665—Composites
  • H01M4/667—Composites in the form of layers, e.g. coatings
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/002—Inorganic electrolyte
  • H01M2300/0022—Room temperature molten salts
• • 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
• • 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
  • H01M4/36—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
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/661—Metal or alloys, e.g. alloy coatings
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
• • 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
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/664—Ceramic materials
• • 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
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49002—Electrical device making
  • Y10T29/49108—Electric battery cell making

Definitions

• the present invention relates to a battery containing an electrolyte, and a method of manufacturing the battery.
• Secondary batteries in which charging and discharging are carried out through cations such as lithium ions passing between a positive electrode and a negative electrode are known.
• a typical example of such a battery is a lithium ion secondary battery.
• an electrolyte in which a supporting electrolyte such as LiPF 6 is dissolved in a nonaqueous solvent such as ethylene carbonate is often used.
• molten salts that are able to be liquid in a temperature range in which a battery is used are known. Studies are being carried out into using an electrolyte having a composition containing such a molten salt as an electrolyte for a secondary battery as described above.
• the electrolyte may be, for example, a molten salt electrolyte or organic electrolyte.
• One invention disclosed here relates to a battery.
• This battery comprises an electrolyte, for example, an electolyte containing a molten salt, and a positive electrode having an active material and an electron conducting material.
• This electron conducting material is used as an additive to give electrical conductivity to the active material.
• the electron conducting material has a barrier layer at least on the surface thereof.
• This barrier layer is substantially constituted from at least one material (barrier material) selected from (a) oxides having at least one element in group 2 to 14 and the third or subsequent period of the periodic table as a constituent element thereof, (b) carbides having at least one element in group 2 to 14 and the third or subsequent period of the periodic table as a constituent element thereof, (c) nitrides having at least one element in group 2 to 14 and the third or subsequent period of the periodic table as a constituent element thereof, and (d) tungsten.
• barrier material selected from (a) oxides having at least one element in group 2 to 14 and the third or subsequent period of the periodic table as a constituent element thereof, (b) carbides having at least one element in group 2 to 14 and the third or subsequent period of the periodic table as a constituent element thereof, (c) nitrides having at least one element in group 2 to 14 and the third or subsequent period of the periodic table as a constituent element thereof, and (d) tungsten.
• 'molten salt' in the invention disclosed here refers to a salt at least part of which is able to be liquid in the ordinary state of use of a battery.
• the temperature of the battery (temperature of use) is in a range from approximately -50°C (more commonly -30°C) to approximately 100°C (more commonly 80°C).
• a salt at least part of which exhibits a liquid form in at least part of such a temperature range is included in the concept of 'molten salt' here.
• the barrier layer contains an oxide of at least one metal in group 4 to 14 of the periodic table.
• the barrier layer may contain an oxide of at least one metal in group 4 to 6 of the periodic table.
• a preferable example of such a metal oxide is a titanium oxide (e.g. TiO 2 or TLtO 7 ).
• the barrier layer may contain an oxide of at least one metal in group 13 or 14.
• a preferable example of such a metal oxide is an indium-tin oxide (ITO).
• ITO indium-tin oxide
• An electron conducting material having a barrier layer substantially constituted from at least one such oxide is preferable.
• the barrier layer contains a carbide of at least one metal in group 4 to 14 of the periodic table.
• the barrier layer may contain a carbide of at least one metal in group 4 to 6 of the periodic table.
• a metal carbide are a titanium carbide (e.g.
• the material constituting the barrier layer has a lower activity than at least carbon to oxidative decomposition of the molten salt. That is, at least the surface of the electron conducting material used in the positive electrode is constituted from a material having a lower activity than carbon to oxidative decomposition of the molten salt.
• a material constituting the barrier layer is preferably an electrically conductive material.
• 'electrically conductive' typically refers to the electrical conductivity (electron conductivity) of the material being at least lxl0 2 S/cm (more preferably at least lxlO 3 S/cm) in the ordinary state of use (at the temperature of use) of the battery.
• a material having an electrical conductivity at 25°C in the above range is preferable.
• the surface and the interior of the electron conducting material may be substantially constituted from the same material (barrier material).
• a preferable example of such an electron conducting material is particles consisting of any of the barrier materials described above.
• the surface and the interior of the electron conducting material may be constituted from different materials.
• the electron conducting material may be one having a barrier layer substantially constituted from any of the barrier materials described above on the surface thereof, with the interior of the electron conducting material being constituted from a material other than a barrier material.
• the electron conducting material may have a barrier layer substantially constituted from any of the barrier materials described above on the surface thereof, with the interior of the electron conducting material being constituted from a barrier material different to that on the surface.
• a material having good electrical conductivity is preferably selected as the material constituting the interior of the electron conducting material.
• Examples of such an interior-constituting material include electrically conductive carbon such as carbon black, metals having a high electrical conductivity such as platinum (Pt), tungsten (W), aluminum ⁇ M), copper (Cu) and silver (Ag), metal oxides such as Tl 2 O 3 , WO 2 and TL t O 7 , and metal carbides such as WC, TiC and TaC.
• electrically conductive carbon such as carbon black
• metals having a high electrical conductivity such as platinum (Pt), tungsten (W), aluminum ⁇ M), copper (Cu) and silver (Ag)
• metal oxides such as Tl 2 O 3 , WO 2 and TL t O 7
• metal carbides such as WC, TiC and TaC.
• an electron conducting material in which the surface and the interior are constituted from different materials include an electron conducting material having a barrier layer as described above on the surface of carbon particles, an electron conducting material having a barrier layer as described above on the surface of metal particles, and an electron conducting material having a barrier layer as described above on the surface of particles consisting of an electrically conductive metal oxide or metal carbide.
• the active material of the positive electrode is substantially constituted from a composite oxide having lithium and a transition metal as constituent elements thereof.
• a preferable example of such a composite oxide is a composite oxide having lithium, nickel and manganese as constituent elements thereof.
• the positive electrode has an active material able to make the electric potential of the positive electrode at least 4.5 V higher than the potential of metallic lithium.
• a preferable example of such an active material is an active material substantially constituted from a composite oxide having lithium, nickel and manganese as constituent elements thereof.
• the molten salt contained in the electrolyte may be one that exhibits a liquid state in at least part of a temperature range between 10 and 40°C. A molten salt able to maintain a liquid state in a temperature range at least from 10 to 40°C is preferable.
• the cation in the molten salt may be, for example, at least one cation selected from an imidazolium ion, an ammonium ion and a sulfonium ion.
• a molten salt that is constituted from such a cation and a counter ion and exhibits a liquid state in a temperature range as above is preferable.
• the principal component of the electrolyte is a molten salt as described above.
• Such an electrolyte may contain a supporting electrolyte. As the supporting electrolyte, one able to appropriately supply the cation that migrates to charge and discharge the battery may be selected, this being in accordance with the type of this cation.
• any of various lithium salts can be preferably selected as the supporting electrolyte.
• the battery disclosed here may have a negative electrode having an active material able to absorb and release lithium ions.
• this negative electrode has an active material able to maintain the potential of the negative electrode at 1 V or more higher than the potential of metallic lithium.
• a preferable example of such an active material is an active material substantially constituted from a lithium titanate represented by Li 4 Ti 5 ⁇ ] 2 .
• Another invention disclosed here relates to a method of manufacturing a battery. In this method, an electron conducting material having a barrier layer at least on a surface thereof is prepared.
• This barrier layer is substantially constituted from at least one material (barrier material) selected from (a) oxides of at least one element in group 2 to 14 of the periodic table (excluding boron and carbon), (b) carbides of at least one element in group 2 to 14 of the periodic table (excluding boron and carbon), and (c) nitrides having at least one element in group 2 to 14 and the third or subsequent period of the periodic table as a constituent element thereof, and (d) tungsten.
• a positive electrode is manufactured using this electron conducting material and a positive electrode active material.
• the battery can be constructed using this positive electrode, an electrolyte containing a molten salt, and a negative electrode.
• an electron conducting material used in this method one in which the surface and the interior thereof are substantially constituted from the same material may be selected.
• an electron conducting material in which the surface and the interior thereof are constituted from different materials may be used.
• Such an electron conducting material can, for example, be obtained by attaching fine particles (e.g. nanoparticles) consisting of said barrier material onto the surface of particles consisting of another material (e.g. carbon particles and/or metal particles). That is, the barrier layer can be formed on the surface of these particles through the fine particles of the barrier material.
• FIGURE 1 is a graph showing results of cyclic voltammetry measurements for cells manufactured using an appropriate electrolyte and several electrodes on which different materials are held;
• FIGURE 2 is a graph showing the voltage profile obtained upon charging and discharging for batteries constructed using an appropriate electrolyte and several positive electrodes having different electron conducting materials;
• FIGURE 3 is a graph showing results of cyclic voltammetry measurements for cells manufactured using an appropriate electrolyte and several electrodes on which different materials are held;
• FIGURE 4 is a graph showing the voltage profile obtained upon charging and discharging for batteries constructed using an appropriate electrolyte and several positive electrodes having different electron conducting materials;
• FIGURE 5 is a graph showing the voltage profile obtained upon charging and discharging for batteries constructed using an appropriate positive electrode and several electrolytes of different types; and
• FIGURE 6 is a graph showing voltage profiles obtained upon charging and discharging of batteries having an organic electrolyte.
• the electron conducting material of the positive electrode has a barrier layer substantially constituted from a prescribed material (barrier material) at least on the surface of the electron conducting material.
• the barrier layer may contain (a) an oxide having at least one element selected from group 2 to 14 in the third or subsequent period of the periodic table as a constituent element thereof.
• an element in the oxide are elements in groups 4 to 6 of the periodic table (Ti, Zr, Hf, N Nb, Ta, Cr, Mo, W).
• other preferable examples are elements in groups 12 to 14 of the periodic table (Zn, Al, In, TI, Si, Sn, etc.).
• Specific preferable examples of an oxide constituting the barrier layer include
• the barrier layer may contain (b) a carbide having at least one element selected from group 2 to 14 in the third or subsequent period of the periodic table as a constituent element thereof.
• an element in such a carbide are elements in groups 4 to 6 of the periodic table (Ti, Zr, Hf, V, Nb, Ta, Cr,
• a carbide constituting the barrier layer are transition metal carbides that can adopt an interstitial-type structure in which the carbon atoms are in the gaps in the close-packed structure of the metal atoms.
• Metals able to form a carbide having such a structure are metals having an atomic radius of at least approximately 1.4A and vanadium.
• Specific examples of such a carbide are carbides represented by the formula MC (M is selected from Ti, Zr, Hf, V, Nb, Ta, Mo and W) and carbides represented by the formula M 2 C (M is selected from V, Ta, Mo and W).
• the barrier layer may contain (c) a nitride having at least one element selected from group 2 to 14 in the third or subsequent period of the periodic table as a constituent element thereof, preferable examples of an element in such a nitride being elements in groups 4 to 6 of the periodic table (Ti, Zr, Hf, V, Nb, Ta, Cr,
• the electron conducting material that gives electrical conductivity to the active material.
• the present inventors have discovered that oxidative decomposition of a molten salt is promoted by the presence of such an electron conducting material made of carbon.
• a barrier layer consisting of at least one selected from (a) oxides, (b) carbides, (c) nitrides, and (d) metallic tungsten as described above, the activity of the electron conducting material disclosed herein to oxidative decomposition of the electrolyte may be lower than that of at least carbon.
• the degree of activity to oxidative decomposition of the electrolyte can be ascertained by, for example, constructing an electrochemical cell using an electrode having the material (barrier material) constituting the barrier layer and an electrolyte, and applying a voltage between the electrode as a positive electrode and a counter electrode (typically cyclic voltammetry (CV) measurements are carried out). If the electrolyte undergoes oxidative decomposition, then an irreversible current (oxidative decomposition current) will be detected in the cell.
• CV cyclic voltammetry
• a material has a lower activity to oxidative decomposition of the electrolyte than carbon if the material satisfies at least one of the following: compared with the case of using an electrode having carbon as the positive electrode, an oxidative decomposition current is not detected until a higher voltage, or the voltage at which an oxidative decomposition current of at least a certain value starts to flow is higher, or the oxidative decomposition current detected at a given voltage is lower.
• an electron conducting material having such a barrier material at least on the surface thereof is used as a constituent material of the positive electrode in a battery containing an electrolyte, oxidative decomposition of the electrolyte will be less prone to being brought about than with carbon.
• a preferable example of the barrier material is one exhibiting the following property. That is, a barrier material exhibiting the property that in the case of constructing an electrochemical cell as described above using an electrode having the barrier material, and carrying out cyclic voltammetry measurements with a sweep rate of 100 mV/sec at room temperature, the current that flows through the cell when the applied voltage reaches 5 V (versus Li) is lower than the current that flows under the same conditions through an electrochemical cell in which an electrode having carbon is used. More preferable is a barrier material for which the current at an applied voltage of 5 V (versus Li) is approximately 1/2 or less, yet more preferably approximately 1/10 or less, particularly preferably approximately 1/100 or less, of that for a cell in which an electrode having carbon is used.
• the electron conducting material disclosed here may be such that at least the surface thereof is substantially constituted from a barrier material as described above.
• the surface and the interior of the electron conducting material are (i.e. the whole of the electron conducting material is) substantially constituted from a substantially homogeneous barrier material.
• the barrier layer constitutes the surface and the interior of the electron conducting material in continuous fashion.
• the electron conducting material disclosed here may be such that the constituent materials of the surface and the interior are different.
• the electron conducting material may have a structure in which a barrier layer substantially constituted from a barrier material of a certain composition is provided on the surface of particles consisting of a barrier material of a different composition.
• the electron conducting material may have a structure in which a barrier layer substantially constituted from a barrier material of a certain composition is provided on the surface of particles consisting of a material other than a barrier material.
• barrier layer-constituting materials for example, oxides such as SnO 2 , Ti 4 O 7 , In 2 O 3 /SnO 2 (ITO), Ta 2 O 5 , WO 2 , W ⁇ 8 O 49 , CrO 2 and Tl 2 O 3 , carbides represented by the formula MC, carbides represented by the formula M 2 C, metal nitrides, and metallic tungsten are electrically conductive.
• the material constituting part the surface, the interior, etc.
• Particles substantially constituted from at least one of these materials are a preferable example of the electron conducting material disclosed here.
• particles having a surface substantially constituted from at least one of these materials and an interior constituted from a material having a higher electrical conductivity are another preferable example of the electron conducting material disclosed here.
• an example of the material constituting the interior of this type of electron conducting material is carbon known as an electron conducting material in common conventional positive electrodes (so-called electrically conductive carbon, e.g. carbon black).
• the material constituting the interior of the electron conducting material are metals having a high electrical conductivity such as platinum (Pt), tungsten (W), aluminum (Al) copper (Cu) and silver (Ag), metal oxides such as Tl 2 O 3 , WO 2 and Ti 4 ⁇ 7 , and metal carbides such as WC, TiC andTaC.
• metals having a high electrical conductivity such as platinum (Pt), tungsten (W), aluminum (Al) copper (Cu) and silver (Ag)
• metal oxides such as Tl 2 O 3 , WO 2 and Ti 4 ⁇ 7
• metal carbides such as WC, TiC andTaC.
• barrier layer-constituting materials for example oxides such as MgO, BaTiO 3 , TiO 2 , ZrO 2 , Al 2 O 3 , and SiO 2 are substantially insulating.
• the interior of the electron conducting material is thus preferably constituted from an electrically conductive material.
• the material constituting the interior of this type of electron conducting material for example at least one out of electrically conductive barrier materials (e.g. T O ), electrically conductive carbon, and metals may be selected.
• the form of the electron conducting material disclosed here is typically particulate.
• the shape of the particles is, broadly speaking, preferably spherical, fiber-like or flake-like.
• the average particle diameter of the particles may be, for example, approximately 10 nm to 10 ⁇ m.
• the average particle diameter of the particles is preferably approximately 10 nm to 5 ⁇ m, more preferably approximately 10 nm to 1 ⁇ m.
• the average thickness of the barrier layer is preferably at least approximately 1 nm, more preferably at least approximately 5 nm.
• the thickness of the barrier layer is preferably made to be, for example, approximately 100 nm or less.
• the thickness of the barrier layer is preferably made to be not more than approximately 100 nm, more preferably not more than approximately 30 nm.
• Such an electron conducting material may, for example, be one in which nanoparticles of an insulating barrier material are held on the surface of particles consisting of an electrically conductive material (which may be an electrically conductive barrier material).
• Nanoparticles are particles having a particle diameter of nanometer order, typically particles with an average particle diameter in a range of approximately 5 to 100 nm.
• An electron conducting material in which the constituent materials of the surface and the interior are different can be manufactured, for example, applying, on the surface of particles consisting of a material for constituting the interior (core particles), particles having a smaller diameter than the core particles and consisting of a material for constituting the surface (surface-forming particles).
• An example of a preferable manufacturing method is a method in which a mixture of these particles is mixed (kneaded) while applying pressure.
• a so-called mechanochemical method can be adopted.
• the mechanochemical method may be either a dry or wet method.
• the average particle diameter of the core particles used is, for example, preferably in a range of approximately 50 nm to 5 ⁇ m, more preferably in a range of approximately 50 nm to 3 ⁇ m.
• the average particle diameter of the surface-forming particles used is preferably not more than 1/5 (typically approximately 1/5 to 1/300), more preferably not more than 1/10 (typically approximately 1/10 to 1/100), of the average particle diameter of the core particles.
• An electron conducting material obtained using such nanoparticles will have a dense, uniform barrier layer on the surface of the core particles.
• Another method of manufacturing an electron conducting material in which the constituent materials of the surface and the interior are different is a method in which a slurry in which the core particles and the surface-forming particles are dispersed in an appropriate solvent is dried. As the method of drying the slurry, a spray drying method can be preferably used. As a result, particles in which the surface-forming particles are coated on the surface of the core particles can be obtained.
• the particles may be further heated or baked.
• a battery comprising a positive electrode having an electron conducting material as described above and an electrolyte containing a molten salt
• an effect of suppressing oxidative decomposition of the molten salt can be produced regardless of the type of the cation that passes between the positive electrode and the negative electrode (i.e. the cation involved in charging and discharging).
• the art disclosed here can thus be applied to batteries that are charged and discharged through the passage of any of various cations.
• alkali metal ions such as lithium ions, sodium ions, potassium ions and cesium ions
• alkaline earth metal ions such as calcium ions and barium ions
• other metal ions such as magnesium ions, aluminum ions, silver ions and zinc ions
• ammonium ions such as tetrabutylammonium ions, tetraethylammonium ions, tetramethylammonium ions, triethyhnethylammonium ions and triethylammonium ions
• imidazolium ions such as imidazolium ions and ethylmethylimidazolium ions
• pyridinium ions hydrogen ions, tetraethylphosphonium ions, tetramethylphosphonium ions, tetraphenylphosphonium ions, triphenylsulfonium ions, and triethylsulfonium ions.
• preferable cations are alkali metal ions, with lithium ions being particularly preferable.
• a battery comprising a positive electrode having an electron conducting material as described above and an electrolyte containing organic solvents, an effect of suppressing oxidative decomposition of the organic solvent can be produced regardless of the type of the cation that passes between the positive electrode and the negative electrode (i.e. the cation involved in charging and discharging).
• the art disclosed here can thus be applied to batteries that are charged and discharged through the passage of any of various cations.
• the organic type electrolyte may include an organic solvent and an Li-salt, where the organic solvent may include one or mixture of the following organic chemicals, ethylene carbonate, propylene carbonate, butylene carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydorofuran, 1,3-dioxolane, 4-methyl- 1,3-dioxolane, methyl formate, methyl acetate, methyl propionate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate, and a lithium salt which may include one or more of the following salts: LiPF 6 , LiAsF 6 , LiSbF 6 , LiBF 4 , LiClO 4 , LiCF 3 SO 3 , Li(CF 3 SO 2 ) 2 N, Li(C 2 F 5 SO 2 ) 2 N, LiC 4 F 9 SO 3 , Li(CF 3 SO 2 ) 3
• the active material of the positive electrode a material for which absorption and release (e.g. insertion and extraction) of the above cations can take place can be selected, this being in accordance with the type of the cations. It is preferable to use an active material having a constitution including the cations.
• an active material having a constitution including the cations for example, in a battery that is charged and discharged through the migration of lithium ions (typically a lithium ion secondary battery), any of various lithium composite oxides containing lithium and a transition metal as constituent elements thereof can be preferably used. Examples of such composite oxides include Li-Ni-containing oxides (LiNiO 2 etc.), Li-Mn-containing oxides (e.g. LiMnO 2 , LiNio. 5 Mn ⁇ .
• Li-Co-containing oxides LiCoO 2 etc.
• 'Li-Ni-containing oxides' has a meaning encompassing not only oxides having Li and Ni as constituent elements thereof, but also composite oxides containing at least one other metallic element in addition to Li and Ni (i.e. at least one selected from transition metal elements and representative metal elements other than Li and Ni).
• These metallic elements may be one or two or more selected from the group consisting of Co, Al, Mn, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La and Ce.
• 'Li-Mn-containing oxides' has a meaning encompassing composite oxides containing at least one other metallic element in addition to Li and Mn (e.g. at least one metallic element selected from the group consisting of Co, Al, Ni, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La and Ce).
• the positive electrode of the battery disclosed here preferably has an active material able to make the positive electrode be at a high potential, within a range such that oxidative decomposition of the molten salt in the electrolyte of the battery is not brought about excessively.
• the positive electrode has an active material able to make the potential of the positive electrode at least approximately 4.5 V (versus Li).
• the positive electrode has an active material able to make the potential of the positive electrode at least approximately 5 V (versus Li).
• an active material able to make the positive electrode be at such a potential upon charging can be preferably used.
• a positive electrode potential of at least 4 V (versus Li), or at least 4.5 V (versus Li), or even at least 5 V (versus Li) oxidative decomposition of the molten salt in the electrolyte can be suppressed.
• the effects of applying the art disclosed here are particularly well exhibited for an embodiment with a positive electrode having such a high-potential active material.
• a preferable specific example of the positive electrode active material is a lithium composite oxide represented by LiNi x Mn 2 _ x O .
• x is a number satisfying 0.3 ⁇ x ⁇ 0.7, more preferably a number satisfying 0.45 ⁇ x ⁇ 0.55.
• the positive electrode active material include active materials consisting of LiMe a 0 . 5 Mn ⁇ . 5 O 4 (Me a is Co and/or Ni), LiMe b PO 4 (Me b is at least one selected from the group consisting of Cr, Co and Cu), Li 3 V 2 (PO ) 3 , Li 2 CoPO 4 F, LiNio. 33 Mno. 33 Coo. 33 O 2 or the like, and active materials in which a metal oxide such as ZrO 2 , ZnO or Al 2 O 3 is coated with LiCoO 2 .
• the positive electrode of the battery disclosed here may be made to have a constitution in which a mixture containing an electron conducting material and an active material as described above is held on an electrically conductive member consisting of a metal or the like.
• an electrically conductive member consisting of a metal or the like.
• the electrically conductive member collector
• a rod-like body, plate-like body, foil-like body, mesh-like body or the like consisting of a metal such as Al, Ni or Ti may be used.
• a constitution in which a layer of a mixture containing the electron conducting material and the active material (active material-containing layer) is provided on the surface of a sheet-like electrically conductive member e.g. Al foil
• the active material-containing layer may as required contain one or two or more kinds of other materials commonly used in positive electrodes.
• binders are examples of such materials.
• PVDF polyvinylidene fluoride
• PTFE polytetrafluoroethylene
• PVDF-HFP poly(vinylidene fluoride-hexafluoropropylene) copolymers
• the amount used of the electron conducting material relative to 100 parts by mass of the active material may, for example, be made to be in a range of 1 to 15 parts by mass.
• a positive electrode having such a constitution can, for example, be manufactured as follows. That is, a slurry in which the active material, the electron conducting material and a binder are dispersed in a prescribed ratio (mass ratio) in an appropriate solvent is prepared. This slurry is applied onto the surface of an electrically conductive member (e.g. Al foil).
• an electrically conductive member e.g. Al foil.
• a coating method using a roll coater, a bar coater, a doctor blade or the like, a screen printing method, a transfer method or the like can be adopted as appropriate. So that the applying on of the slurry can be carried out more appropriately, thickeners
• pH adjusters e.g. carboxymethyl cellulose
• pH adjusters e.g. carboxymethyl cellulose
• a positive electrode having an active material-containing layer on the surface of an electrically conductive member can be obtained.
• Another embodiment of the positive electrode of the battery disclosed here is a positive electrode obtained by mixing the active material, the electron conducting material, a binder and so on together and compression-molding into a prescribed shape (e.g. a disk shape).
• a prescribed shape e.g. a disk shape.
• the binder one as described earlier or the like can be used.
• the battery disclosed here contains an electrolyte, for example containing a molten salt.
• a molten salt having an aromatic cation such as an imidazolium salt or a pyridinium salt, an aliphatic quaternary ammonium salt, or a sulfonium salt
• imidazolium salts are ones having an imidazolium cation such as: a dialkylimidazolium ion such as a dimethylimidazolium ion, an ethylmethylimidazolium ion, a propylmethylimidazolium ion, a butylmethylimidazolium ion, a hexylmethylimidazolium ion or an octylmethylimidazolium ion; or a trialkylimidazolium ion such as a 1,2,3-trimethylimidazolium ion, a l-ethyl-2,3-dimethylimidazolium ion, a l-butyl-2,3 -dimethylimidazolium ion or a l-hexyl-2,3-dimethylimidazolium ion.
• a dialkylimidazolium ion such
• Examples of anions able to form a molten salt together with such an imidazolium ion (cation) include BF 4 ⁇ , PF ⁇ f , CF 3 SO 3 ⁇ , (CF 3 SO 2 ) 2 N ⁇ , (C 2 F 5 SO 2 ) 2 N ⁇ , CF andBr " .
• imidazolium salts include ethyhnethylimidazolium tetrafluoroborate (EMI-BF ), ethyhnethylimidazolium trifluoromethanesulfonylimide (EMI-TFSI), propylmethylimidazolium tetrafluoroborate, l,2-diethyl-3-methylimidazolium trifluoromethanesulfonylimide (DEMI-TFSI), and l,2,4-triethyl-3-methylimidazolium trifluoromethanesulfonylimide (TEMI-TFSI).
• EMI-BF ethyhnethylimidazolium tetrafluoroborate
• EMI-TFSI ethyhnethylimidazolium trifluoromethanesulfonylimide
• DEMI-TFSI dimethylimidazolium tetrafluoroborate
• pyridinium salts are ones having an alkyl pyridinium ion such as a 1-ethylpyridinium ion, a 1-butylpyridinium ion or a 1-hexylpyridinium ion.
• a salt between such a pyridinium ion (cation) and an anion as described above can be used.
• Specific examples of pyridinium salts include 1-ethylpyridinium tetrafluoroborate and 1 -ethylpyridinium trifluoromethanesulfonylimide.
• ammonium salts include trimethylpropylammonium trifluoromethanesulfonylimide (TMPA-TFSI), diethylmethylpropylammonium trifluoromethanesulfonylimide, and 1 -butyl- 1-methylpyrrolidinium trifluoromethanesulfonylimide.
• sulfonium salts include triethylsulfonium trifluoromethanesulfonylimide (TES-TFSI).
• the electrolyte may be made to have a composition substantially constituted from at least one molten salt as described above.
• a molten salt constituting the electrolyte for example, one at least part (preferably the whole) of which exhibits a liquid state in at least part of a temperature range from -50 to 100°C can be selected. In general it is preferable to select one that exhibits a liquid state in at least part of a temperature range from -30 to 80°C.
• An example of a preferable molten salt is one able to maintain a liquid state in a temperature range of at least from 10 to 40°C.
• a more preferable molten salt is one able to maintain a liquid state in a temperature range of at least from 0 to 60°C (more preferably from -10 to 60°C, particularly preferably from -30 to 60°C).
• the electrolyte contains two or more kinds of molten salts
• the electrolyte further contains a supporting electrolyte as a cation source.
• a compound able to supply lithium ions to the electrolyte (a lithium source) can be selected.
• a lithium salt that will dissolve in the molten salt can be preferably used.
• a salt between a lithium ion and an anion such as BF 4 ⁇ , PF 6 ⁇ , CF 3 SO 3 ⁇ , (CF 3 SO 2 ) 2 N ⁇ , or(C 2 F 5 SO 2 ) 2 N ⁇ can be used.
• a salt between a lithium ion and an anion of the same type is preferable to use as the anion in the molten salt.
• concentration of the supporting electrolyte contained in the electrolyte there are no particular limitations on the concentration of the supporting electrolyte contained in the electrolyte.
• a composition containing 0.1 to 5 mol of the supporting electrolyte (lithium salt etc.) per 1 liter of the electrolyte may be used. It is generally preferable to make this concentration be such that the supporting electrolyte can dissolve stably (i.e. without precipitation or the like being observed) at least in a temperature range of 10°C and above (preferably 0°C and above).
• the electrolyte may be made to have a composition substantially constituted from the at least one molten salt and a supporting electrolyte (e.g. lithium salt) as described above.
• a supporting electrolyte e.g. lithium salt
• An electrolyte that has such a composition and exhibits a liquid state in a temperature range as mentioned earlier is preferable.
• An electrolyte able to maintain a liquid state in a temperature range at least from 10 to 40°C is particularly preferable.
• the electrolyte may contain general solvents (typically organic solvents). As such solvents, it is generally appropriate to select aprotic solvents.
• the electrolyte may be made to contain one or two or more kinds of solvents selected from aprotic solvents used as constituent components of general lithium ion secondary battery electrolytes such as propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, ⁇ -butyrolactone, tetrahydrofuran, 1,3-dioxolane, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.
• aprotic solvents used as constituent components of general lithium ion secondary battery electrolytes
• the solvent content is preferably made to be not more than the molten salt content.
• the solvent content relative to 50 parts by mass of the molten salt in the electrolyte may be made to be not more than 50 parts by mass. Moreover, the solvent content relative to 50 parts by mass of the molten salt in the electrolyte may be made to be not more than 15 parts by mass, or not more than 5 parts by mass, or even not more than 1 part by mass.
• An electrolyte in which the molten salt is made to be the principal component in this way is a preferable example of the electrolyte in the battery disclosed here.
• the battery disclosed here may have a negative electrode having an active material for which absorption and release (e.g. insertion and extraction) of the cation described earlier can take place, this being in accordance with the type of the cation.
• a carbon material having an amorphous structure and/or a graphite structure can be used.
• active materials commonly used in lithium ion secondary battery negative electrodes such as natural graphite, mesocarbon microbeads (MCMBs), highly ordered pyrolytic graphite (HOPG), hard carbon and soft carbon can be preferably used, although there is no limitation thereto.
• the negative electrode of the battery disclosed here preferably has an active material able to make the negative electrode be at a low electric potential, within a range such that decomposition (e.g. reductive decomposition) of the molten salt in the electrolyte of the battery is not brought about excessively.
• the negative electrode has an active material able to make the potential of the negative electrode at least approximately 1 V (versus Li).
• the negative electrode has an active material able to make the potential of the negative electrode at least approximately 1.2 V (versus Li).
• the negative electrode has an active material able to make the potential of the negative electrode at least approximately 1.5 V (versus Li).
• An active material able to realize such a negative electrode potential can be preferably used.
• an active material able to maintain the negative electrode potential at at least a potential as above when the state of charge (SOC) is approximately 60% can be preferably selected.
• An active material able to maintain the negative electrode potential at at least a potential as above when the SOC is approximately 100% is more preferable.
• a specific example of a material that can be preferably used as the negative electrode active material is a lithium titanate represented by LLTisO ⁇ .
• the negative electrode of the battery disclosed here may be made to have a constitution in which such an active material is held on an electrically conductive member consisting of a metal or the like.
• the electrically conductive member (collector).
• a constitution in which a layer of the active material (an active material-containing layer) is provided on the surface of a sheet-like electrically conductive member (e.g. Cu foil) may be used.
• the active material-containing layer may as required contain one or two or more kinds of other materials commonly used in negative electrodes. Examples of such materials are binders.
• a binder as for the active material-containing layer of the positive electrode may be used.
• the amount used of the binder relative to 100 parts by mass of the active material may, for example, be made to be in a range of approximately 1 to 10 parts by mass.
• a negative electrode having such a constitution can, for example, be manufactured using the same method as for the positive electrode.
• the battery disclosed here may be made to have a constitution in which an electrolyte as described earlier is disposed between such a positive electrode and a negative electrode.
• the battery may be made to have a constitution in which a separator is disposed between the positive electrode and the negative electrode, and the electrolyte is soaked into the separator.
• a porous film consisting of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) may be used.
• a woven cloth or nonwoven cloth consisting of polypropylene, polyethylene terephthalate (PET), methyl cellulose (MC) or the like may be used.
• the battery disclosed here may be suitable as a secondary battery used such that the electric potential of the positive electrode is, for example, in a range of approximately 3 to 4.5 V (versus Li) (in a more preferable embodiment, approximately 3 to 5 V (versus Li)).
• the battery may be suitable as a secondary battery used such that the battery voltage (inter-electrode voltage) is approximately 1.5 V or above.
• the battery may be suitable as a lithium ion secondary battery used under such conditions.
• EXAMPLES Experimental example 1 Study into electrode-constituting materials> The present experimental example is an example in which a study was carried out into the effect of the type of the material constituting an electrode on the electrochemical stability of a molten salt.
• Manufacture of cell 1 TiO 2 nanoparticles (average particle diameter: 20 nm) and polyvinylidene fluoride (PVDF) were mixed together in N-methylpyrrolidone (NMP).
• NMP N-methylpyrrolidone
• TiO 2 :PVDF mass ratio in the mixture was approximately 7:1.
• the mixture was applied onto Al foil and then dried.
• As the PVDF 'KF Polymer #1120' (trademark), a product of Kureha Chemical Industry Co., Ltd. was used.
• a solution of 1.25 mol/L of lithium trifluorosulfonylimide (LiTFSI) as a supporting electrolyte in l-ethyl-3-methylimidazolium trifluorosulfonylimide (EMI-TFSI) as an electrolyte a 3-electrode electrochemical cell (cell 1) was constructed. Pt was used as the counter electrode of the cell.
• LiTFSI lithium trifluorosulfonylimide
• EMI-TFSI l-ethyl-3-methylimidazolium trifluorosulfonylimide
• Experimental example 2 Manufacture of batteries> The present experimental example is an example in which batteries were manufactured using various electron conducting materials. (Manufacture of battery 1) A positive electrode was manufactured as follows. That is, the TiO 2 nanoparticles used in experimental example 1 and the carbon particles used in experimental example 1 were mixed together in a mass ratio of approximately 1:10, and mechanochemical treatment (1300 rpm, 120 minutes) was carried out in a nitrogen atmosphere.
• particles (particles 1) in which TiO 2 nanoparticles were held on the surface of carbon particles were obtained.
• LiNio. 5 Mn ⁇ . 5 O 4 as an active material, the particles 1 as an electron conducting material, and PVDF as a binder were mixed together with NMP.
• the mixture contained the LiNio.sMn ⁇ .sO 4 , the particles 1 and the PVDF in a mass ratio of approximately 85:10:5.
• the mixture was applied onto one surface of Al foil (a positive electrode collector) of thickness approximately 15 ⁇ m.
• the applied material was dried at 80°C, and then pressing was carried out in the thickness direction, thus manufacturing a sheet in which approximately 6 mg/cm 2 of an active material-containing layer was formed on one surface of the collector.
• a negative electrode was manufactured as follows. That is, a lithium titanate (Li Ti 5 O ⁇ 2 ) as an active material, carbon black (CB) as an electron conducting material, and PVDF as a binder were mixed together with NMP. The mixture contained the Li 4 Ti 5 O ⁇ 2 , the CB and the PVDF in a mass ratio of approximately 85: 10:5. As the a product of Japan Pure Chemical Co., Ltd. was used. As the CB and the PVDF, the same ones as those used in the manufacture of the positive electrode were used. The mixture was applied onto one surface of Al foil (a negative electrode collector) of thickness approximately 15 ⁇ m.
• Al foil a negative electrode collector
• the applied material was dried at 80°C, and then pressing was carried out in the thickness direction, thus manufacturing a sheet in which approximately 8 mg/cm 2 of an active material-containing layer was formed on one surface of the collector.
• This sheet was cut to 4 cm x 5 cm, thus obtaining a negative electrode.
• a battery was constructed using the positive electrode and negative electrode obtained in this way.
• As a separator a porous polyethylene film cut to 4 cm x 5 cm was used.
• an electrolyte one obtained by adding LiTFSI to EMI-TFSI in a proportion of 1.25 mol/L and then mixing by stirring of was used.
• the positive electrode and the negative electrode were disposed with the separator therebetween such that the active material-containing layers were facing one another.
• the mixture contained the LiNi 0 .5Mn ⁇ . 5 O 4 , the T ⁇ O ? particles and the PVDF in a mass ratio of approximately 85: 10:5.
• a positive electrode was manufactured as for battery 1 using this mixture.
• a battery 2 was then manufactured as for battery 1, except that this positive electrode was used.
• the same TiC particles as those held on the electrode in cell 3 were used as the electron conducting material of the positive electrode instead of the Ti 4 O 7 particles.
• a battery 3 was manufactured as for battery 2.
• Manufacture of battery 4 The same carbon particles as those held on the electrode in cell 4 were used as the electron conducting material of the positive electrode instead of the Ti O 7 particles.
• a battery 4 was manufactured as for battery 2.
• the current density of 1/5 C is approximately 3.2 mA.
• the voltage profiles of the batteries upon ca ⁇ ying out charging and discharging in this way are shown in Figure 2. Note that the vertical axis in Figure 2 shows the potential of the positive electrode relative to the negative electrode (the inter-electrode voltage). As shown in Figure 2, in the voltage profile for battery 4 in which carbon was used as the electron conducting material of the positive electrode, an irreversible plateau appeared in the vicinity of an inter-electrode voltage of 3.4 V (co ⁇ esponding to approximately 4.9 V versus Li), and the inter-electrode voltage did not readily rise upon continuing charging beyond this. This suggests that the charging current supplied to the battery was being consumed by oxidative decomposition of the molten salt.
• the present experimental example is another example in which a study was carried out into the effect of the type of the material constituting an electrode on the electrochemical stability of a molten salt.
• (Manufacture of cell 5) TaC particles (average particle diameter: 5 ⁇ m) were used instead of the TiO 2 nanoparticles held on the electrode in cell 1.
• the same procedure as for cell 1 was carried out, thus manufacturing a working electrode in which TaC is held on the surface of Al foil.
• An electrochemical cell (cell 5) having the same constitution as for cell 1 was constructed using this working electrode.
• the present inventors also carried out similar experiments using cells in which SnO 2 or ZrO 2 is held on the working electrode. As a result, it was found that for these materials as well, the effect of promoting oxidative decomposition of the molten salt (EMI-TFSI) is less than that of carbon.
• Experimental example 5 Manufacture of batteries> The present experimental example is an example in which batteries were manufactured using various electron conducting materials. (Manufacture of battery 5) The same TaC particles as those held on the electrode in cell 5 were used as the electron conducting material of the positive electrode instead of the Ti 4 O 7 particles used in battery 2. Other than this, a battery 5 was manufactured as for battery 2.
• the charge time for each of the batteries was approximately 4.5 to 6 hours, and the discharge time for each was approximately 4 to 5 hours. In this way, for each of the batteries, the coulomb efficiency was good. Particularly good results were obtained for battery 5 and battery 7. Note that the average battery voltage (inter-electrode voltage) for each of these batteries was approximately 3.1 to 3.2 V.
• Experimental example 7 Manufacture of batteries> The present experimental example is an example in which batteries were manufactured using a positive electrode having TiC as the electron conducting material, and several electrolytes having different compositions.
• a positive electrode the same as that used in battery 3 (having TiC particles as the electron conducting material) was used.
• a battery 8 was manufactured as for battery 3.
• a solution of 1.25 mol/L of LiTFSI as a supporting electrolyte in triethylsulfonium trifluorosulfonylimide (TES-TFSI) was used as an electrolyte.
• TES-TFSI triethylsulfonium trifluorosulfonylimide
• the electrolyte was 1 M LiPF 6 dissolved in a mixture of ethylene carbonate/dimethyl carbonate/ethyl methyl carbonate (EC/DMC/EMC).
• EC/DMC/EMC ethylene carbonate/dimethyl carbonate/ethyl methyl carbonate
• GC graphitic carbon
• oxidative decomposition of the electrolyte in a second battery was greatly reduced by using titanium carbide (TiC) as the electron conductive material, as indicated by the much lower oxidative decomposition current.
• TiC titanium carbide
• Other electron conductive materials, such as those described herein, can also be used in a battery according to the present invention having an organic electrolyte.

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