WO2024262634A1 - 二次電池 - Google Patents

二次電池 Download PDF

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Publication number
WO2024262634A1
WO2024262634A1 PCT/JP2024/022688 JP2024022688W WO2024262634A1 WO 2024262634 A1 WO2024262634 A1 WO 2024262634A1 JP 2024022688 W JP2024022688 W JP 2024022688W WO 2024262634 A1 WO2024262634 A1 WO 2024262634A1
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WIPO (PCT)
Prior art keywords
secondary battery
solvent
positive electrode
electrolyte
orthocarbonate
Prior art date
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PCT/JP2024/022688
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English (en)
French (fr)
Japanese (ja)
Inventor
記功 山口
泰之 増田
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Murata Manufacturing Co Ltd
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Murata Manufacturing Co Ltd
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Priority to JP2025528155A priority Critical patent/JPWO2024262634A1/ja
Priority to CN202480036438.7A priority patent/CN121263894A/zh
Publication of WO2024262634A1 publication Critical patent/WO2024262634A1/ja
Priority to US19/336,919 priority patent/US20260018674A1/en
Anticipated expiration legal-status Critical
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    • 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
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • 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

  • This technology relates to secondary batteries.
  • secondary batteries are being developed as a power source that is small, lightweight, and has a high energy density. These secondary batteries contain a positive electrode, a negative electrode, and an electrolyte, and various studies are being conducted on the configuration of these secondary batteries.
  • the positive electrode active material contains manganese oxide
  • the negative electrode active material contains lithium metal
  • the solvent of the electrolyte contains a chain tetraether
  • the content of the chain tetraether in the solvent is 1% by volume to 20% by volume
  • the non-aqueous electrolyte contains an orthocarbonate ester, and the content of the orthocarbonate ester in the non-aqueous electrolyte is 0.001 mmol/g to 0.18 mmol/g (see, for example, Patent Document 2).
  • the secondary battery according to one embodiment of the present technology includes a positive electrode, a negative electrode containing lithium metal, and an electrolyte solution containing a solvent.
  • the solvent contains an orthocarbonate ester compound represented by formula (1), and the content of the orthocarbonate ester compound in the solvent is 40% by weight or more.
  • the negative electrode contains lithium metal
  • the solvent of the electrolyte contains the orthocarbonate ester compound shown in formula (1)
  • the content of the orthocarbonate ester compound in the solvent is 40% by weight or more, so that excellent battery characteristics can be obtained.
  • FIG. 1 is a perspective view illustrating a configuration of a secondary battery according to an embodiment of the present technology.
  • FIG. 2 is an enlarged cross-sectional view showing the configuration of the battery element shown in FIG.
  • FIG. 3 is a block diagram showing a configuration of an application example of a secondary battery.
  • Secondary battery 1-1 Overall configuration 1-2. Detailed configuration of electrolyte 1-3. Operation 1-4. Manufacturing method 1-5. Actions and effects 2. Modifications 3. Uses of secondary battery
  • the secondary battery described here is a so-called lithium metal secondary battery, since it obtains battery capacity by utilizing the precipitation and dissolution of lithium.
  • Fig. 1 shows a perspective view of a secondary battery
  • Fig. 2 shows an enlarged cross-sectional view of a battery element 20 shown in Fig. 1.
  • FIG. 1 shows a state in which the exterior film 10 and the battery element 20 are separated from each other. Also, in FIG. 1, a cross section of the battery element 20 along the XZ plane is shown by a dashed line. In FIG. 2, only a portion of the battery element 20 is shown.
  • this secondary battery includes an exterior film 10, a battery element 20, a positive electrode lead 31, a negative electrode lead 32, and sealing films 41 and 42.
  • the secondary battery described here uses a flexible or pliable exterior film 10 as an exterior member for housing the battery element 20. Therefore, the secondary battery shown in Figures 1 and 2 is a so-called laminate film type secondary battery.
  • the exterior film 10 has a bag-like structure that is sealed when the battery element 20 is housed therein. As a result, the exterior film 10 houses a positive electrode 21, a negative electrode 22, and a separator 23, which will be described later.
  • the exterior film 10 is a single film-like member that is folded in the folding direction F.
  • This exterior film 10 is provided with a recessed portion 10U (a so-called deep drawn portion) for accommodating the battery element 20.
  • the exterior film 10 is a three-layer laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside, and when the exterior film 10 is folded, the outer peripheral edges of the opposing fusion layers are fused to each other.
  • the fusion layer contains a polymer compound such as polypropylene.
  • the metal layer contains a metallic material such as aluminum.
  • the surface protection layer contains a polymer compound such as nylon.
  • the number of layers in the exterior film 10 is not particularly limited, so it may be one or two layers, or four or more layers.
  • the battery element 20 is housed in an exterior film 10.
  • the battery element 20 is a so-called power generating element, and includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown), as shown in Figures 1 and 2 .
  • the battery element 20 is a so-called wound electrode body, so that the positive electrode 21 and the negative electrode 22 are wound around the winding axis P while facing each other via the separator 23.
  • This winding axis P is a virtual axis extending in the Y-axis direction, as shown in FIG. 1.
  • the three-dimensional shape of the battery element 20 is not particularly limited.
  • the battery element 20 has a flat three-dimensional shape, so that the shape of the cross section (cross section along the XZ plane) of the battery element 20 intersecting the winding axis P is a flat shape defined by the major axis J1 and the minor axis J2.
  • the long axis J1 is an imaginary axis extending in the X-axis direction and has a length greater than that of the short axis J2.
  • the short axis J2 is an imaginary axis extending in the Z-axis direction intersecting the X-axis direction and has a length less than that of the long axis J1.
  • the three-dimensional shape of the battery element 20 is a flattened cylinder, and therefore the cross-sectional shape of the battery element 20 is a flattened, approximately elliptical shape.
  • the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B.
  • the positive electrode current collector 21A may be omitted.
  • the positive electrode collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided.
  • This positive electrode collector 21A contains a conductive material such as a metal material, and a specific example of the conductive material is aluminum.
  • the positive electrode active material layer 21B contains one or more types of positive electrode active materials that absorb and release lithium. However, the positive electrode active material layer 21B may further contain one or more types of other materials such as a positive electrode binder and a positive electrode conductor.
  • the method of forming the positive electrode active material layer 21B is not particularly limited, but specifically includes a coating method.
  • the positive electrode active material layer 21B is provided on both sides of the positive electrode collector 21A.
  • the positive electrode active material layer 21B may be provided on only one side of the positive electrode collector 21A on the side where the positive electrode 21 faces the negative electrode 22.
  • the type of positive electrode active material is not particularly limited, but specifically includes lithium-containing compounds.
  • This lithium-containing compound is a compound that contains one or more transition metal elements as constituent elements along with lithium, and may further contain one or more other elements as constituent elements.
  • the type of other element is not particularly limited, so long as it is an element other than lithium and transition metal elements, but specifically includes elements belonging to groups 2 to 15 of the long period periodic table.
  • the type of lithium-containing compound is not particularly limited, but specifically includes oxides, phosphate compounds, silicate compounds, and borate compounds.
  • oxides include LiNiO2 , LiCoO2 , LiCo0.98Al0.01Mg0.01O2 , LiNi0.5Co0.2Mn0.3O2 , LiNi0.8Co0.15Al0.05O2 , LiNi0.33Co0.33Mn0.33O2 , Li1.2Mn0.52Co0.175Ni0.1O2 , Li1.15 ( Mn0.65Ni0.22Co0.13 ) O2 , and LiMn2O4 .
  • phosphate compounds include LiFePO4 , LiMnPO4 , LiFe0.5Mn0.5PO4 , and LiFe0.3Mn0.7PO4 .
  • the positive electrode binder contains one or more of the following materials: synthetic rubber, polymeric compound, etc.
  • synthetic rubber include styrene butadiene rubber, fluororubber, and ethylene propylene diene.
  • polymeric compounds include polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.
  • the positive electrode conductive agent contains one or more conductive materials such as carbon materials, metal materials, and conductive polymer compounds.
  • conductive materials such as carbon materials, metal materials, and conductive polymer compounds.
  • Specific examples of carbon materials include graphite, carbon black, acetylene black, and ketjen black.
  • the negative electrode 22 faces the positive electrode 21 with a separator 23 interposed therebetween, and contains lithium metal.
  • lithium metal is what is known as an elemental lithium. However, the purity of lithium metal is not necessarily limited to 100%. For this reason, lithium metal may unintentionally contain any amount of impurities, or may intentionally contain any amount of additives.
  • the separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22.
  • the separator 23 allows lithium to pass through in an ionic state while preventing the occurrence of a short circuit due to contact between the positive electrode 21 and the negative electrode 22.
  • the separator 23 contains one or more types of insulating polymer compounds, and a specific example of the insulating polymer compound is polyethylene.
  • the electrolyte is a liquid electrolyte, and is impregnated into each of the positive electrode 21 and the separator 23.
  • the electrolyte contains a solvent and an electrolyte salt, and the solvent contains an orthocarbonate compound. The detailed composition of the electrolyte will be described later.
  • the positive electrode lead 31 is a positive electrode wiring connected to the positive electrode current collector 21A of the positive electrode 21, and is led out of the exterior film 10.
  • the positive electrode lead 31 contains one or more kinds of conductive materials such as metal materials, and a specific example of the conductive material is aluminum, etc.
  • the shape of the positive electrode lead 31 is a thin plate shape, a mesh shape, etc.
  • the negative electrode lead 32 is a negative electrode wiring connected to the negative electrode 22, and is led out of the exterior film 10.
  • the lead-out direction of the negative electrode lead 32 is the same as the lead-out direction of the positive electrode lead 31.
  • This negative electrode lead 32 contains one or more kinds of conductive materials such as metal materials, and a specific example of the conductive material is copper. Details regarding the shape of the negative electrode lead 32 are the same as the details regarding the shape of the positive electrode lead 31.
  • sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31. Also, as shown in Fig. 1, the sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32. However, one or both of the sealing films 41 and 42 may be omitted.
  • the sealing film 41 is a sealing member that prevents outside air from entering the interior of the exterior film 10.
  • This sealing film 41 contains a polymer compound such as polyolefin that has adhesion to the positive electrode lead 31, and a specific example of the polymer compound is polypropylene.
  • the configuration of the sealing film 42 is the same as that of the sealing film 41, except that the sealing film 42 is a sealing member that has adhesion to the negative electrode lead 32.
  • the sealing film 42 contains a polymer compound such as polyolefin that has adhesion to the negative electrode lead 32.
  • the electrolyte contains a solvent, which is a medium for dissolving and ionizing the electrolyte salt.
  • the solvent contains one or more of the orthocarbonate ester compounds represented by formula (1). Therefore, an electrolyte containing an orthocarbonate ester compound as a non-aqueous solvent is a so-called non-aqueous electrolyte.
  • this orthocarbonate compound is a compound in which four oxygen-containing groups (-OR1, -OR2, -OR3, and -OR4) are bonded to a carbon atom.
  • each of R1 to R4 is a hydrocarbon group, and the types of R1 to R4 may be the same as or different from one another. Of course, any two types of R1 to R4 may be the same as one another, or any three types of R1 to R4 may be the same as one another.
  • Hydrocarbon group is a general term for groups that contain carbon and hydrogen as constituent elements, and the number of carbon atoms in the hydrocarbon group is not particularly limited.
  • This hydrocarbon group may be a chain group, a cyclic group, or a group in which the chain group and the cyclic group are bonded to each other.
  • the chain group may be linear or branched with one or more side chains.
  • hydrocarbon groups include alkyl groups, alkenyl groups, alkynyl groups, aryl groups, cycloalkyl groups, and linking groups. Details of linking groups will be described later.
  • alkyl groups include methyl, ethyl, propyl, and butyl groups.
  • alkenyl groups include vinyl and allyl groups.
  • alkynyl groups include ethynyl groups.
  • aryl groups include phenyl and naphthyl groups.
  • cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl groups.
  • the linking group is a general term for a monovalent group in which two or more of the following groups are bonded to each other: alkyl groups, alkenyl groups, alkynyl groups, aryl groups, and cycloalkyl groups.
  • a specific example of a linking group is the benzyl group, which is a monovalent group in which an aryl group (phenyl group) and an alkyl group (methyl group) are bonded to each other.
  • the hydrocarbon group contains an alkyl group and that the number of carbon atoms in the alkyl group is 3 or less. This is because it improves the solubility and compatibility of the orthocarbonate ester compound and makes it easier to synthesize the orthocarbonate ester compound.
  • the content of the orthocarbonate ester compound in the solvent is set to a predetermined amount. Specifically, the content of the orthocarbonate ester compound in the solvent is 40% by weight or more.
  • the solvent contains an orthocarbonate ester compound, and the content of the orthocarbonate ester compound in the solvent is 40% by weight or more, because this suppresses the decomposition reaction of the electrolyte on the surface of the negative electrode 22 during charging and discharging, even if the negative electrode 22 contains lithium metal.
  • orthocarbonate ester compounds have the property of being able to sufficiently dissolve and ionize electrolyte salts even when used alone, making them excellent solvents for use in electrolytes. This allows the electrolyte to function effectively even when only orthocarbonate ester compounds are used as the solvent.
  • orthocarbonate compounds have a high lowest unoccupied energy mass (LUMO) and therefore have excellent resistance to reduction. Therefore, the orthocarbonate compounds contained in the solvent are not easily decomposed during charging and discharging, and the electrolyte salt and other compounds described later are more likely to decompose preferentially than the orthocarbonate compounds. As a result, a coating derived from the electrolyte salt and other solvents is easily formed on the surface of the negative electrode 22, and the surface of the negative electrode 22 is electrochemically protected by using the coating.
  • LUMO lowest unoccupied energy mass
  • the decomposition reaction of the electrolyte on the surface of the negative electrode 22 during charging and discharging is suppressed.
  • the content of the orthocarbonate ester compound in the solvent is particularly optimized, so that the protective function of the orthocarbonate ester compound that protects the surface of the negative electrode 22 is fully exerted.
  • the surface of the negative electrode 22 is sufficiently and stably protected by the coating derived from the electrolyte salt and other solvents, and the decomposition reaction of the electrolyte is also sufficiently and stably suppressed.
  • the content of the orthocarbonate ester compound in the solvent is preferably 60% by weight or more, and more preferably 80% by weight or more. This is because the protective function of the orthocarbonate ester compound is more effectively exerted, and the decomposition reaction of the electrolyte is more effectively suppressed.
  • the orthocarbonate ester compound contains tetramethyl orthocarbonate. This is because the protective function of the orthocarbonate ester compound is fully exerted, and the decomposition reaction of the electrolyte is also sufficiently suppressed.
  • the electrolyte is analyzed to confirm that the solvent contains an orthocarbonate ester compound and to measure the amount of the orthocarbonate ester compound contained in the solvent.
  • the method for analyzing the electrolyte is not particularly limited, but may be one or more of the following: inductively coupled plasma (ICP) optical emission spectroscopy, nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectrometry (GC-MS).
  • the secondary battery When analyzing the electrolyte, the secondary battery is disassembled to recover the electrolyte, which is then analyzed. This identifies the type of component (orthocarbonate ester compound) contained in the electrolyte, as well as the amount of that component.
  • the solvent may further contain one or more of the other compounds.
  • the solvent may contain other compounds in addition to the orthocarbonate compound.
  • the other compounds are non-aqueous solvents (organic solvents).
  • organic solvents organic solvents.
  • orthocarbonate compounds mentioned above are excluded from the other compounds described here.
  • Non-aqueous solvents include esters and ethers, and more specifically, carbonate ester compounds, carboxylate ester compounds, and lactone compounds. This is because they improve the dissociation of the electrolyte salt and also the mobility of ions.
  • Carbonate compounds include cyclic carbonates and chain carbonates. Specific examples of cyclic carbonates include ethylene carbonate and propylene carbonate, while specific examples of chain carbonates include dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.
  • Carboxylic acid ester compounds include chain carboxylates.
  • chain carboxylates include ethyl acetate, ethyl propionate, propyl propionate, and ethyl trimethylacetate.
  • Lactone compounds include lactones. Specific examples of lactones include gamma-butyrolactone and gamma-valerolactone.
  • the ethers may be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, etc.
  • Non-aqueous solvents include unsaturated cyclic carbonates, fluorinated cyclic carbonates, sulfonates, phosphates, acid anhydrides, nitrile compounds, and isocyanate compounds. The use of these compounds can improve the electrochemical stability of the electrolyte.
  • unsaturated cyclic carbonates include vinylene carbonate, vinylethylene carbonate, and methyleneethylene carbonate.
  • fluorinated cyclic carbonates include monofluoroethylene carbonate and difluoroethylene carbonate.
  • sulfonic acid esters include propane sultone and propene sultone.
  • phosphate esters include trimethyl phosphate and triethyl phosphate.
  • acid anhydrides include succinic anhydride, 1,2-ethanedisulfonic anhydride, and 2-sulfobenzoic anhydride.
  • nitrile compounds include succinonitrile.
  • isocyanate compounds include hexamethylene diisocyanate.
  • the electrolyte salt contains one or more kinds of light metal salts such as lithium salts.
  • lithium salt examples include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium trifluoromethanesulfonate (LiCF 3 SO 3 ), lithium bis(fluorosulfonyl)imide (LiN(FSO 2 ) 2 ), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3 SO 2 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF 3 SO 2 ) 3 ), lithium bis(oxalato)borate (LiB(C 2 O 4 ) 2 ), lithium monofluorophosphate (Li 2 PFO 3 ), and lithium difluorophosphate (LiPF 2 O 2 ). With this content, high ionic conductivity can be obtained.
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the amount of electrolyte salt contained is not particularly limited, but is typically 0.3 mol/kg to 5.0 mol/kg relative to the solvent. This is because high ionic conductivity is obtained.
  • This secondary battery operates in the battery element 20 as follows.
  • lithium When charging, lithium is released in an ionic state from the positive electrode 21. This causes the lithium to move through the electrolyte to the negative electrode 22, causing lithium metal to precipitate on the surface of the negative electrode 22.
  • lithium metal dissolves from the negative electrode 22. This causes the lithium to move in an ionic state through the electrolyte to the positive electrode 21, where it is absorbed.
  • the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent are mixed together to prepare a positive electrode mixture.
  • the positive electrode mixture is put into a solvent to prepare a paste-like positive electrode mixture slurry.
  • This solvent may be an aqueous solvent or an organic solvent.
  • the positive electrode mixture slurry is applied to both sides of the positive electrode current collector 21A to form the positive electrode active material layer 21B.
  • the positive electrode active material layer 21B may be compression molded using a compression device such as a roll press. In this case, the positive electrode active material layer 21B may be heated, or the compression molding may be repeated multiple times. As a result, the positive electrode active material layer 21B is formed on both sides of the positive electrode current collector 21A, and the positive electrode 21 is produced.
  • the negative electrode 22 containing lithium metal as the negative electrode active material is prepared.
  • the negative electrode 22 may be produced by attaching a lithium metal foil or the like to a negative electrode current collector.
  • electrolyte solution The electrolyte salt is added to a solvent containing an orthocarbonate compound, and the solvent is then stirred. In this case, the amount of the orthocarbonate compound added is adjusted so that the content of the orthocarbonate compound in the solvent falls within the above-mentioned range. This causes the electrolyte salt to dissolve in the solvent, and an electrolytic solution is prepared.
  • the positive electrode lead 31 is connected to the positive electrode current collector 21A of the positive electrode 21 by using a joining method such as welding.
  • the negative electrode lead 32 is connected to the negative electrode 22 by using a joining method such as welding.
  • the positive electrode 21 and the negative electrode 22 are stacked on top of each other with the separator 23 interposed therebetween to form a laminate (not shown).
  • the laminate is then wound to produce a wound body (not shown), which is then pressed using a compression device such as a press to form the wound body into a flat shape.
  • the wound body after this formation has a configuration similar to that of the battery element 20, except that the positive electrode 21 and the separator 23 are not impregnated with electrolyte.
  • the exterior film 10 (adhesive layer/metal layer/surface protection layer) is folded so that the exterior films 10 face each other.
  • the outer edges of two of the opposing adhesive layers are joined to each other using an adhesive method such as heat fusion, thereby housing the roll in the bag-shaped exterior film 10.
  • a sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31, and a sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32.
  • the wound body is impregnated with the electrolyte and is enclosed in a bag-shaped exterior film 10, thus assembling a secondary battery.
  • Stabilization treatment of secondary battery after assembly The assembled secondary battery is charged and discharged. Stabilization conditions such as the environmental temperature, the number of charge/discharge cycles (number of charge/discharge conditions), and the like can be set arbitrarily.
  • a coating is formed on the surface of each of the positive electrode 21 and the negative electrode 22.
  • a coating derived from the electrolyte salt and other compounds is formed on the surface of the negative electrode 22.
  • the state of the battery element 20 becomes electrochemically stable, and the secondary battery is completed.
  • the negative electrode 22 contains lithium metal
  • the solvent of the electrolyte contains an orthocarbonate compound
  • the content of the orthocarbonate compound in the solvent is 40% by weight or more.
  • the properties of the orthocarbonate ester compound are utilized to improve the solubility of the electrolyte salt in the solvent, and a good coating derived from the electrolyte salt and other compounds is easily formed on the surface of the negative electrode 22 during charging and discharging.
  • the surface of the negative electrode 22 is electrochemically protected using the coating, so that even if the negative electrode 22 contains highly reactive lithium metal, the decomposition reaction of the electrolyte on the surface of the negative electrode 22 during charging and discharging is suppressed. Therefore, excellent battery characteristics can be obtained.
  • the decomposition reaction of the electrolyte is further suppressed by utilizing the protective function of the orthocarbonate ester compound, so that a higher effect can be obtained.
  • the content of the orthocarbonate ester compound in the solvent is 80% by weight or more, the decomposition reaction of the electrolyte is further suppressed, so that an even higher effect can be obtained.
  • the hydrocarbon group in formula (1) for the orthocarbonate ester compound contains an alkyl group and the number of carbon atoms in the alkyl group is 3 or less, the solubility and compatibility of the orthocarbonate ester compound are improved, and a greater effect can be obtained.
  • the orthocarbonate ester compound contains tetramethyl orthocarbonate, the protective function of the orthocarbonate ester compound is fully exerted. Therefore, the decomposition reaction of the electrolyte is also sufficiently suppressed, and a higher effect can be obtained.
  • a porous membrane separator 23 was used. However, although not specifically shown here, a laminated separator including a polymer compound layer may also be used.
  • the laminated separator includes a porous membrane having a pair of surfaces, and a polymer compound layer provided on one or both surfaces of the porous membrane.
  • the polymer compound layer includes polyvinylidene fluoride, etc. This is because polyvinylidene fluoride has excellent physical strength and is electrochemically stable.
  • one or both of the porous film and the polymer compound layer may contain one or more types of insulating particles. This is because the insulating particles dissipate heat when the secondary battery generates heat, improving the safety (heat resistance) of the secondary battery.
  • the insulating particles contain one or more types of insulating materials such as inorganic materials and resin materials. Specific examples of inorganic materials include aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials include acrylic resin and styrene resin.
  • a precursor solution containing a polymer compound and an organic solvent is prepared, and then the precursor solution is applied to one or both sides of a porous film.
  • the precursor solution may contain multiple insulating particles.
  • the lithium can move in an ionic state between the positive electrode 21 and the negative electrode 22, so the same effect can be obtained.
  • swelling of the secondary battery is further suppressed, so a greater effect can be obtained.
  • the positive electrode 21 and the negative electrode 22 are wound facing each other with the separator 23 and the electrolyte layer interposed between them.
  • the electrolyte layer is interposed between the positive electrode 21 and the separator 23, and also between the negative electrode 22 and the separator 23.
  • the electrolyte layer contains a polymer compound together with an electrolyte solution, and the electrolyte solution is held by the polymer compound. This is because leakage of the electrolyte solution is prevented.
  • the composition of the electrolyte solution is as described above.
  • the polymer compound contains polyvinylidene fluoride and the like.
  • the lithium ions can move between the positive electrode 21 and the negative electrode 22 via the electrolyte layer, so the same effect can be obtained.
  • leakage of the electrolyte is particularly prevented as described above, so a greater effect can be obtained.
  • a secondary battery used as a power source may be a main power source or an auxiliary power source in electronic devices and electric vehicles.
  • a main power source is a power source that is used preferentially regardless of the presence or absence of other power sources.
  • An auxiliary power source may be a power source used in place of the main power source or a power source that can be switched from the main power source.
  • secondary batteries are as follows: Electronic devices such as video cameras, digital still cameras, mobile phones, notebook computers, headphone stereos, portable radios, and portable information terminals. Storage devices such as backup power sources and memory cards. Power tools such as electric drills and power saws. Battery packs installed in electronic devices. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles such as electric cars (including hybrid cars). Power storage systems such as home or industrial battery systems that store power in preparation for emergencies. In these applications, one secondary battery may be used, or multiple secondary batteries may be used.
  • the battery pack may include a single cell or a battery pack.
  • the electric vehicle is a vehicle that runs on a secondary battery as a driving power source, and may be a hybrid vehicle that also includes a driving source other than the secondary battery.
  • a home power storage system it is possible to use home electrical appliances and the like by utilizing the power stored in the secondary battery, which is a power storage source.
  • FIG. 3 shows the block diagram of a battery pack, which is an example of an application of a secondary battery.
  • the battery pack described here is a battery pack (a so-called soft pack) that uses one secondary battery, and is installed in electronic devices such as smartphones.
  • this battery pack includes a power source 51 and a circuit board 52.
  • This circuit board 52 is connected to the power source 51 and includes a positive terminal 53, a negative terminal 54, and a temperature detection terminal 55.
  • the power source 51 includes one secondary battery.
  • the positive electrode lead is connected to the positive electrode terminal 53
  • the negative electrode lead is connected to the negative electrode terminal 54.
  • This power source 51 is connected to the outside via the positive electrode terminal 53 and the negative electrode terminal 54, and is therefore capable of charging and discharging.
  • the circuit board 52 includes a control unit 56, a switch 57, a PTC element 58 which is a thermosensitive resistor, and a temperature detection unit 59. However, the PTC element 58 may be omitted.
  • the control unit 56 includes a central processing unit (CPU) and memory, and controls the operation of the entire battery pack. This control unit 56 detects and controls the usage status of the power source 51.
  • CPU central processing unit
  • the control unit 56 turns off the switch 57 to prevent charging current from flowing through the current path of the power source 51.
  • the overcharge detection voltage is not particularly limited, but is specifically 4.20V ⁇ 0.05V, and the overdischarge detection voltage is not particularly limited, but is specifically 2.40V ⁇ 0.10V.
  • Switch 57 includes a charge control switch, a discharge control switch, a charge diode, and a discharge diode, and switches between the presence and absence of a connection between power source 51 and an external device in response to an instruction from control unit 56.
  • Switch 57 includes a field effect transistor (MOSFET) that uses a metal oxide semiconductor, and the charge current and discharge current are each detected based on the ON resistance of switch 57.
  • MOSFET field effect transistor
  • the temperature detection unit 59 includes a temperature detection element such as a thermistor. This temperature detection unit 59 measures the temperature of the power supply 51 using the temperature detection terminal 55, and outputs the temperature measurement result to the control unit 56. The temperature measurement result measured by the temperature detection unit 59 is used when the control unit 56 performs charge/discharge control in the event of abnormal heat generation, and when the control unit 56 performs correction processing when calculating the remaining capacity.
  • test secondary battery was fabricated according to the following procedure: This test secondary battery was a simplified lithium metal secondary battery.
  • the electrolyte salt lithium bis(trifluoromethanesulfonyl)imide
  • the solvent was then stirred to prepare the electrolyte solution.
  • the solvent used was tetramethyl orthocarbonate (OTTM), an orthocarbonate ester compound, and 1,2-dimethoxyethane (DME), another compound.
  • OTTM tetramethyl orthocarbonate
  • DME 1,2-dimethoxyethane
  • the content (wt%) of the orthocarbonate compound in the solvent and the content (wt%) of other compounds in the solvent are as shown in Table 1.
  • test electrode and counter electrode were then laminated together with a separator impregnated with electrolyte interposed between them. This resulted in the test electrode and counter electrode facing each other with the separator impregnated with electrolyte interposed between them, completing a test secondary battery.
  • the battery was charged at a current density of 0.22 mA/cm 2 until the total charging time reached 3 hours.
  • the battery was discharged until the voltage reached 0.1 V.
  • the secondary battery was repeatedly charged and discharged until the total number of cycles reached 25, while calculating the coulombic efficiency for each cycle.
  • the charging and discharging conditions were as described above.
  • the average Coulombic efficiency which is an index for evaluating the charge/discharge characteristics, was calculated by averaging the 16 Coulombic efficiencies calculated for each of the 10th to 25th cycles. This average Coulombic efficiency value was rounded off to one decimal place.
  • the nine coulombic efficiencies calculated during the initial charge/discharge cycles (1st to 9th cycles) are not used to calculate the average coulombic efficiency. This is because the coulombic efficiency is prone to variation during the initial charge/discharge cycles.
  • the coulombic efficiency is less likely to vary. This ensures the calculation accuracy and reproducibility of the average coulombic efficiency.
  • Patent Document 2 JP Patent Publication No. 2002-270222 contains an orthocarbonate ester similar to the orthocarbonate ester compound.
  • the secondary battery disclosed in Patent Document 2 is a lithium ion secondary battery, not a lithium metal secondary battery.
  • the orthocarbonate compound in the non-aqueous electrolyte is 0.001 mmol/g to 0.18 mmol/g, so the content of the orthocarbonate in the non-aqueous electrolyte should be less than 40% by weight when converted into the content of the orthocarbonate compound in the solvent.
  • Patent Document 2 does not disclose the appropriate range of orthocarbonate content required to increase the average coulomb increase rate in a lithium metal secondary battery.
  • the battery structure of the secondary battery has been described as being of a laminate film type.
  • the battery structure of the secondary battery is not particularly limited, and may be of a cylindrical type, a square type, a coin type, a button type, etc.
  • the battery element has been described as having a wound structure.
  • the structure of the battery element is not particularly limited, and may be a stacked type or a zigzag type.
  • the positive and negative electrodes are alternately stacked with a separator between them, while in the zigzag type, the positive and negative electrodes are folded in a zigzag pattern while facing each other with the separator between them.
  • the present technology can also be configured as follows.
  • the solvent contains an orthocarbonate compound represented by formula (1),
  • the content of the orthocarbonate compound in the solvent is 40% by weight or more.
  • Secondary battery. (Each of R1, R2, R3 and R4 is a hydrocarbon group.)
  • the content of the orthocarbonate compound in the solvent is 60% by weight or more.
  • ⁇ 3> The content of the orthocarbonate compound in the solvent is 80% by weight or more.
  • the hydrocarbon group includes an alkyl group.
  • the alkyl group has 3 or less carbon atoms.
  • the orthocarbonate ester compound includes tetramethyl orthocarbonate.

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09199171A (ja) * 1996-01-18 1997-07-31 Sony Corp 非水電解液二次電池
JP2011228535A (ja) * 2010-04-21 2011-11-10 Taiyo Yuden Co Ltd 非水電解液及びこれを用いた電気化学デバイス
JP2012119151A (ja) * 2010-11-30 2012-06-21 Sony Corp 非水電解質二次電池および非水電解質

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09199171A (ja) * 1996-01-18 1997-07-31 Sony Corp 非水電解液二次電池
JP2011228535A (ja) * 2010-04-21 2011-11-10 Taiyo Yuden Co Ltd 非水電解液及びこれを用いた電気化学デバイス
JP2012119151A (ja) * 2010-11-30 2012-06-21 Sony Corp 非水電解質二次電池および非水電解質

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
CADGER T. G. ET AL.,: " Novel solute/solvent combinations for rechargeable lithium cells", PROCEEDINGS OF THE SYMPOSIUM ON PRIMARY AND SECONDARY AMBIENT TEMPERATURE LITHIUM BATTERIES : [... PAPERS PRESENTED AT THE LITHIUM BATTERY SYMPOSIUM IN HONOLULU, HAWAII, ON OCTOBER 18 - 23, 1987], THE ELECTROCHEMICAL SOCIETY, US, 18 October 1987 (1987-10-18), US, pages 699 - 707, XP009559506 *

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