WO2024048136A1 - リチウム二次電池および複合部材 - Google Patents

リチウム二次電池および複合部材 Download PDF

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Publication number
WO2024048136A1
WO2024048136A1 PCT/JP2023/027200 JP2023027200W WO2024048136A1 WO 2024048136 A1 WO2024048136 A1 WO 2024048136A1 JP 2023027200 W JP2023027200 W JP 2023027200W WO 2024048136 A1 WO2024048136 A1 WO 2024048136A1
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Prior art keywords
spacer
negative electrode
material layer
lithium
separator
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PCT/JP2023/027200
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English (en)
French (fr)
Japanese (ja)
Inventor
真一郎 近藤
亮平 宮前
聡 蚊野
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Intellectual Property Management Co Ltd
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Priority to CN202380062359.9A priority Critical patent/CN119790516A/zh
Priority to EP23859905.4A priority patent/EP4583224A4/en
Priority to JP2024544027A priority patent/JPWO2024048136A1/ja
Publication of WO2024048136A1 publication Critical patent/WO2024048136A1/ja
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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • 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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/443—Particulate material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/471—Spacing elements inside cells other than separators, membranes or diaphragms; Manufacturing processes thereof
    • H01M50/474—Spacing elements inside cells other than separators, membranes or diaphragms; Manufacturing processes thereof characterised by their position inside the cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/471—Spacing elements inside cells other than separators, membranes or diaphragms; Manufacturing processes thereof
    • H01M50/477—Spacing elements inside cells other than separators, membranes or diaphragms; Manufacturing processes thereof characterised by their shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present disclosure relates to a lithium secondary battery and a composite member.
  • Non-aqueous electrolyte secondary batteries are used for ICT applications such as personal computers and smartphones, in-vehicle applications, and for power storage. In such applications, non-aqueous electrolyte secondary batteries are required to have even higher capacity.
  • Lithium ion batteries are known as high capacity non-aqueous electrolyte secondary batteries.
  • a high capacity of a lithium ion battery can be achieved by, for example, using graphite in combination with an alloy active material such as a silicon compound as a negative electrode active material.
  • an alloy active material such as a silicon compound as a negative electrode active material.
  • increasing the capacity of lithium-ion batteries is reaching its limits.
  • Lithium secondary batteries are promising as nonaqueous electrolyte secondary batteries with higher capacity than lithium ion batteries.
  • lithium metal is deposited on the negative electrode during charging, and this lithium metal is dissolved in the nonaqueous electrolyte during discharge.
  • Various proposals have been made regarding lithium secondary batteries.
  • Patent Document 1 International Publication No. 2020/066254 describes "a positive electrode including a positive electrode current collector and a positive electrode composite layer including a positive electrode active material; and a negative electrode including a negative electrode current collector facing the positive electrode.
  • a composite oxide comprising a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte having lithium ion conductivity, wherein the positive electrode active material includes lithium and a metal M other than lithium.
  • the metal M includes at least a transition metal, lithium metal is deposited on the negative electrode during charging, the lithium metal is dissolved from the negative electrode during discharging, and the metal M includes at least a transition metal.
  • the length is smaller than a second length in a second direction D2 intersecting the first direction, and the positive electrode and the separator are arranged so that a space for accommodating the lithium metal is formed between the positive electrode and the negative electrode.
  • One of the objects of the present disclosure is to provide a lithium secondary battery in which the expansion of the electrode group during charging (for example, expansion near the negative electrode) is small and the cycle characteristics are good.
  • the lithium secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, a spacer, and a nonaqueous electrolyte having lithium ion conductivity, and the negative electrode is
  • the electrode is an electrode in which lithium metal is deposited during discharge, and the lithium metal is dissolved during discharge, and the spacer is formed on one main surface of one of the positive electrode, the negative electrode, and the separator, and
  • the spacer includes a linear first protrusion that forms a periodically repeated pattern, and a plurality of second protrusions that are not in contact with the first protrusion, and the first protrusion is , including a plurality of annular parts connected to each other, and the second convex part is arranged inside the annular part.
  • the composite member includes a separator having a base material layer and a spacer, and the spacer includes a linear first convex portion forming a periodically repeated pattern and a plurality of linear convex portions that are not in contact with the first convex portion.
  • the first protrusion includes a plurality of annular parts connected to each other, and the second protrusion is disposed inside the annular part.
  • a lithium secondary battery can be obtained in which the expansion of the electrode group during charging (for example, expansion near the negative electrode) is small and the cycle characteristics are good.
  • FIG. 1 is a vertical cross-sectional view schematically showing an example of a lithium secondary battery according to an embodiment of the present disclosure.
  • 2 is a cross-sectional view schematically showing a part of the lithium secondary battery shown in FIG. 1.
  • FIG. FIG. 3 is a top view showing an example of a spacer pattern. 4 is a partially enlarged view of FIG. 3.
  • FIG. 7 is a top view showing another example of a spacer pattern.
  • FIG. 7 is a top view showing another example of a spacer pattern.
  • a lithium secondary battery (hereinafter sometimes referred to as a "lithium secondary battery (L)") according to an embodiment of the present disclosure includes a positive electrode, a negative electrode, and a battery disposed between the positive electrode and the negative electrode. It includes a separator, a spacer, and a nonaqueous electrolyte having lithium ion conductivity.
  • the negative electrode is an electrode in which lithium metal precipitates during charging and dissolves during discharge.
  • the spacer is formed on one main surface of one of the positive electrode, negative electrode, and separator.
  • the spacer includes a linear first convex portion forming a periodically repeated pattern and a plurality of second convex portions that are not in contact with the first convex portion.
  • the first convex portion includes a plurality of annular portions that are connected to each other.
  • the second convex portion is arranged inside the annular portion.
  • the positive electrode, negative electrode, and separator may be collectively referred to as an "electrode group.”
  • electrode group In a lithium secondary battery (L), a space between a positive electrode and a negative electrode is secured by a spacer. Therefore, when charging and discharging are repeated, expansion of the electrode group can be suppressed.
  • the spacer of the lithium secondary battery (L) includes first protrusions arranged in the above pattern. Therefore, when the electrode group is laminated or wound, it is possible to prevent the spacer from being misaligned and causing the electrode plate to bend in an undesirable manner. Therefore, according to the lithium secondary battery (L), a space in which lithium metal is deposited can be appropriately formed by the spacer.
  • the inventors of the present application found that by arranging the second convex portion inside the annular portion, it is possible to achieve both suppression of expansion of the electrode group and good cycle characteristics.
  • the present disclosure is based on this new finding.
  • the reason why high effects can be obtained by using the first and second convex portions is not clear at present.
  • the use of the first convex portion secures a wide space in which the electrolytic solution flows, it is considered that the space is likely to be collapsed because the space is wide.
  • the use of the second convex portion prevents the space from collapsing.
  • a lithium secondary battery (L) is also called a lithium metal secondary battery.
  • Li lithium metal
  • the negative electrode At the negative electrode of this type of battery, lithium metal precipitates during charging and dissolves during discharge.
  • the negative electrode has at least a negative electrode current collector, and lithium metal is deposited on the negative electrode current collector.
  • a lithium secondary battery (L) for example, 70% or more of the rated capacity is developed by precipitation and dissolution of lithium metal.
  • the movement of electrons in the negative electrode during charging and discharging is mainly due to the precipitation and dissolution of lithium metal in the negative electrode.
  • 70 to 100% (for example, 80 to 100% or 90 to 100%) of the movement of electrons (current from another point of view) in the negative electrode during charging and discharging is due to precipitation and dissolution of lithium metal.
  • the negative electrode of the lithium secondary battery (L) differs from the negative electrode in that electron movement in the negative electrode during charging and discharging is mainly caused by intercalation and desorption of lithium ions by a negative electrode active material (such as graphite).
  • a negative electrode active material such as graphite
  • the negative electrode does not include a negative electrode active material (such as graphite) that inserts and releases lithium ions.
  • the positive electrode, negative electrode, and separator may be wound so that the separator is disposed between the positive electrode and the negative electrode.
  • a strip-shaped positive electrode, a strip-shaped negative electrode, and a strip-shaped separator are used.
  • the positive electrode, negative electrode, and separator may be laminated.
  • a flat positive electrode, a flat negative electrode, and a flat separator may be stacked. That is, the electrode group may be a wound type electrode group or a laminated type electrode group.
  • the maximum height H2 of the second protrusion may be greater than the maximum height H1 of the first protrusion. Particularly high effects can be obtained by making the maximum height H2 larger than the maximum height H1.
  • the ratio H2/H1 between the maximum height H2 and the maximum height H1 may be 1 or may be greater than 1.
  • H2/H1 may be 0.5 or more, 1 or more, 2 or more, or 3 or more, or less than 10, or 5 or less.
  • the maximum height H1 of the first convex portion may be 15 ⁇ m or more or 30 ⁇ m or more, and may be 150 ⁇ m or less or 100 ⁇ m or less.
  • the height of the first convex portion is selected in consideration of the design capacity of the lithium secondary battery (L), etc.
  • the second convex portion may be island-shaped (dot-shaped).
  • the number of second protrusions arranged inside one annular portion may be two or more, but is typically one.
  • the second convex portion is located at the center of the annular portion.
  • the spacer may be formed on the positive electrode or the negative electrode. Alternatively, the spacer may be formed on the separator. When a spacer is placed on the positive electrode, the spacer covers the surface of the positive electrode, so that the exchange of lithium ions by the positive electrode active material is partially inhibited. As a result, battery capacity may decrease. By forming the spacer on the separator, the above-mentioned decrease in battery capacity can be avoided.
  • the separator has a first main surface facing the negative electrode and a second main surface facing the positive electrode.
  • the spacer may be formed on the first main surface. By arranging the spacer so as to face the negative electrode, the effect of the heat-resistant layer can be better maintained without covering the heat-resistant layer arranged on the surface of the separator facing the positive electrode. Note that the spacer may be formed on the second main surface of the separator.
  • the separator may include a base material layer and a composite material layer formed on the base material layer.
  • the composite material layer may contain a polymer and inorganic particles.
  • the spacer may be formed on the composite material layer. Alternatively, the spacer may be formed on the base layer.
  • the composite material layer can suppress shrinkage of the base material layer when the temperature of the electrode group increases excessively.
  • the base material layer contracts, the positive electrode and the negative electrode are likely to be short-circuited, and the temperature of the electrode group is further likely to rise.
  • shrinkage of the base material layer can be suppressed, so that further temperature rise in the electrode group can be suppressed.
  • the first protrusions may be arranged in a mesh pattern.
  • the mesh pattern may be honeycomb-like. An example of the mesh pattern will be described later.
  • the mesh pattern may have a defective portion connecting the inner regions of two adjacent annular portions. According to this configuration, the fluidity of the electrolytic solution can be further improved.
  • the interval (pitch P) between the centers of adjacent annular parts may be in the range of 1 mm to 15 mm (for example, in the range of 2.25 to 9.5 mm).
  • the separator has a base material layer.
  • the separator may be composed of only a base material layer, or may include a base material layer and a composite material layer.
  • Base material layer A porous sheet having ion permeability and insulation properties is used for the base material layer.
  • porous sheets include porous membranes, woven fabrics, nonwoven fabrics, and the like.
  • the material of the separator is not particularly limited, but may be a polymer material.
  • polymeric materials include polyolefin resins, polyamide resins, cellulose, and the like.
  • polyolefin resins include polyethylene, polypropylene, copolymers of ethylene and propylene, and the like.
  • the base material layer may contain additives as necessary. Examples of additives include inorganic fillers.
  • the base material layer may be a sheet used as a separator for lithium secondary batteries.
  • the composite material layer is a porous layer.
  • the method for forming the porous composite material layer is not particularly limited, and any known method may be used.
  • a porous composite material layer may be formed by printing the raw material for the composite material layer as ink on the base material layer.
  • the composite material layer may be formed on the main surface on the positive electrode side of the two main surfaces of the base material layer, may be formed on the main surface on the negative electrode side, or may be formed on the main surface on the negative electrode side, or on the main surface on the negative electrode side of the two main surfaces of the base material layer. may be formed on each of the above.
  • the spacer may be formed on the composite material layer, or may be formed on the base material layer without interposing the composite material layer.
  • the separator may have a configuration of base material layer/composite material layer/spacer, composite material layer/base material layer/spacer, or composite material layer/base material layer/composite material layer/spacer. In these configurations, by forming the spacer on the composite material layer, the effect of suppressing thermal shrinkage of the base material layer becomes particularly high.
  • the composite material layer includes a polymer (hereinafter sometimes referred to as "polymer (PL)”) and inorganic particles.
  • the inorganic particles may include first particles and/or second particles.
  • the first particles are lithium-containing phosphate particles.
  • the second particles are particles other than the first particles.
  • the composite material layer is a layer that allows lithium ions to pass through.
  • the arrangement of the positive electrode, negative electrode, base material layer, composite material layer, separator, and spacer is not particularly limited, except that the separator and spacer are arranged between the positive electrode and the negative electrode.
  • the separator may be arranged such that the composite material layer faces the positive electrode, or may be arranged such that the composite material layer faces the negative electrode.
  • the phosphate constituting the first particles is selected from the group consisting of lithium phosphate (Li 3 PO 4 ), dilithium hydrogen phosphate (Li 2 HPO 4 ), and lithium dihydrogen phosphate (LiH 2 PO 4 ). It may be at least one selected. Among these, lithium phosphate is preferred because it is highly effective in suppressing heat generation in the battery during abnormal conditions.
  • the average particle size of the first particles is in the range of 0.1 ⁇ m to 1.0 ⁇ m (for example, in the range of 0.1 ⁇ m to 0.5 ⁇ m, in the range of 0.1 ⁇ m to 0.2 ⁇ m, or in the range of 0.1 ⁇ m to 0.19 ⁇ m). ).
  • the average particle size of the first particles may be 0.1 ⁇ m or more or 0.15 ⁇ m or more.
  • the average particle size of the first particles may be 1.0 ⁇ m or less, 0.5 ⁇ m or less, 0.3 ⁇ m or less, or 0.2 ⁇ m or less. By setting the average particle size to 0.1 ⁇ m or more, sufficient pores necessary for penetration of the electrolytic solution can be ensured. It is preferable to set the average particle size to 1.0 ⁇ m or less from the viewpoint of forming a high-density layer of first particles.
  • the polymer (PL) a polymer having higher heat resistance than the main component of the base layer of the separator can be used.
  • the polymer (PL) preferably contains at least one selected from the group consisting of aromatic polyamide, aromatic polyimide, and aromatic polyamide-imide. These are known as polymers (otherwise known as polymers or resins) with high heat resistance. From the viewpoint of heat resistance, aramids, ie, meta-aramids (meta-based wholly aromatic polyamides) and para-based aramids (para-based wholly aromatic polyamides) are preferred. A preferred example of the polymer (PL) is meta-aramid. As the polymer (PL), known aromatic polyamides, aromatic polyimides, and aromatic polyamideimides may be used.
  • aromatic polyamides include polymers formed by condensation polymerization of monomers having an aromatic skeleton and containing amide bonds in repeating units.
  • aromatic polyamides e.g., fully aromatic polyamides
  • meta-aromatic polyamides e.g., fully aromatic meta-polyamides
  • para-aromatic polyamides e.g., fully aromatic para-polyamides
  • Fully aromatic polyamides are also called aramids.
  • a preferred example of the second particles is particles made of an insulating inorganic compound that does not melt or decompose during abnormal heat generation of the battery.
  • the second particles may be inorganic particles that are generally used as inorganic fillers.
  • Examples of the material of the second particles include oxides, oxide hydrates, hydroxides, nitrides, carbides, sulfides, etc., and these may contain metal elements.
  • the average particle diameter of the second particles may be 0.2 ⁇ m or more and 2 ⁇ m or less.
  • oxides and oxide hydrates include aluminum oxide, boehmite, magnesium oxide, titanium oxide, zirconium oxide, silicon oxide, yttrium oxide, zinc oxide, and the like.
  • nitrides include silicon nitride, aluminum nitride, boron nitride, titanium nitride, and the like.
  • carbides include silicon carbide, boron carbide, and the like.
  • sulfides include barium sulfate and the like.
  • hydroxides include aluminum hydroxide.
  • the material of the second particles may be a porous aluminosilicate such as zeolite, a layered silicate such as talc, barium titanate (BaTiO 3 ), strontium titanate (SrTiO 3 ), or the like. From the viewpoint of insulation and heat resistance, at least one member selected from the group consisting of aluminum oxide, boehmite, talc, titanium oxide, and magnesium oxide may be used as the material for the second particles.
  • the average particle size of the second particles may be within the range exemplified for the average particle size of the first particles.
  • the inorganic particles may include the first particles and second particles other than phosphate.
  • the composite material layer may include a first layer containing first particles and a second layer containing second particles. According to this configuration, the effect of suppressing excessive temperature rise of the electrode group can be particularly enhanced. Note that the composite material layer may be composed of only the first layer or only the second layer.
  • the first layer and the second layer may be laminated on the main surface on the positive electrode side of the two main surfaces of the base material layer, may be laminated on the main surface on the negative electrode side, or may be laminated on the main surface on the negative electrode side, or It may be laminated on the surface.
  • the separator and spacer are base material layer/first layer/second layer/spacer, base material layer/second layer/first layer/spacer, first layer/second layer/ It may have a laminated structure of base layer/spacer or second layer/first layer/base layer/spacer.
  • the first layer and the second layer may be arranged on different main surfaces of the base layer.
  • the separator and spacer may have a laminated structure of first layer/base layer/second layer/spacer or second layer/base layer/first layer/spacer. .
  • the first layer may contain first particles as a main component.
  • the content of the first particles in the first layer may be in the range of 50% by mass to 99% by mass, may be in the range of 85% by mass to 99% by mass, or may be in the range of 90% by mass to It may be in the range of 98% by mass.
  • the content may be 50% by mass or more, 70% by mass or more, 85% by mass or more, or 90% by mass or more.
  • the content may be 99% by mass or less, 98% by mass or less, or 95% by mass or less.
  • the first particles have a sufficient surface area and it is easy to inactivate lithium at high temperatures.
  • the first layer may contain solid components other than the first particles.
  • the first layer may include a binder, an inorganic material other than the first particles (eg, inorganic particles), a polymer (PL), and the like.
  • the content of the binder in the first layer may be in the range of 1% by mass to 15% by mass, and may be in the range of 2% by mass to 10% by mass. There may be.
  • the content of the binder in the first layer may be 1% by mass or more or 2% by mass or more.
  • the content of the binder in the first layer may be 15% by mass or less or 10% by mass or less.
  • the binder contained in the first layer is not particularly limited, and includes polyolefins (polyethylene, polypropylene, copolymers of ethylene and ⁇ -olefin, etc.), fluorine-containing resins (polyvinylidene fluoride, polytetrafluoroethylene, polyfluorinated vinyl, etc.), fluorine-containing rubber (vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, etc.), styrene-butadiene copolymer and its hydride, acrylonitrile-butadiene copolymer These include acrylonitrile-butadiene-styrene copolymer and its hydride, and N-vinylacetamide.
  • polyolefins polyethylene, polypropylene, copolymers of ethylene and ⁇ -olefin, etc.
  • the second layer includes second particles other than the first particles (phosphate particles). Note that the second layer may or may not contain the first particles.
  • the second layer preferably contains a polymer (PL).
  • the content of the polymer (PL) in the second layer may be in the range of 50% by mass to 100% by mass (for example, in the range of 80% to 100% by mass or 90% to 100% by mass).
  • the second layer may consist only of polymer (PL).
  • the second layer may contain second particles as a main component.
  • the content of the second particles in the second layer may be in the range of 50% to 99% by weight (for example in the range of 85% to 99% by weight).
  • the second layer may include a binding material.
  • the binding material the binding materials exemplified in the description of the first layer can be used.
  • the content of the second particles in the second layer may be 50% by mass or more, 70% by mass or more, 85% by mass or more, or 90% by mass or more.
  • the content may be 99% by mass or less, 98% by mass or less, or 95% by mass or less.
  • the composite material layer contains the first particles, it is possible to particularly suppress the rise in temperature of the battery during abnormal conditions.
  • the mechanism is currently not clear.
  • One possibility is that the first particles and the lithium metal of the negative electrode react with each other when the battery temperature rises abnormally, reducing the reactivity of the surface of the lithium metal.
  • the spacer may contain resin (for example, insulating resin), or may contain resin and particles.
  • the spacer may be made of only resin, or may be made of resin and particles.
  • the proportion of the resin in the spacer may be 10 volume% or more, 30 volume% or more, or 50 volume% or more, and may be 100 volume% or less, or 80 volume% or less.
  • the content of particles in the spacer may be lower than the content of particles in the composite layer.
  • resin materials include fluorine-containing resins such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene, fluorine-containing rubbers such as vinylidene fluoride-tetrafluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers, and styrene.
  • PVdF polyvinylidene fluoride
  • fluorine-containing rubbers such as vinylidene fluoride-tetrafluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers, and styrene.
  • polyimide polyvinylidene fluoride, acrylonitrile-acrylic acid ester copolymer, and the like are preferable as materials that do not allow lithium ions to pass therethrough, and polyimide may also be used.
  • a non-porous spacer of a certain height or more formed of these resin materials is a layer through which lithium ions do not permeate.
  • the particles may be inorganic particles or organic particles.
  • inorganic particles such as insulating metal oxides, metal hydroxides, metal nitrides, metal carbides, and metal sulfides can be mentioned.
  • Preferred metal oxides include aluminum oxide (alumina and boehmite), magnesium oxide, titanium oxide (titania), zirconium oxide, and silicon oxide (silica).
  • Examples of the metal hydroxide include aluminum hydroxide.
  • metal nitrides include silicon nitride, aluminum nitride, boron nitride, titanium nitride, and the like.
  • metal carbides include silicon carbide and boron carbide.
  • metal sulfides include barium sulfate. Additionally, minerals such as aluminosilicate, layered silicate, barium titanate, and strontium titanate may be used. Among them, it is preferable to use alumina, silica, titania, etc.
  • the average particle size of the particles is not particularly limited, but may be 0.1 ⁇ m or more, 0.5 ⁇ m or more, and 10 ⁇ m or less, 5 ⁇ m or less, or 2 ⁇ m or less.
  • the average particle size can be measured by the following method. First, a cross section of the spacer in the thickness direction of the separator is photographed using an electron microscope to obtain an image of the cross section. Next, image processing such as binarization is performed on the image to identify particle portions. Next, the diameter of a circle (equivalent circle diameter) having the same area as the area of the cross section of each particle is determined, and the arithmetic mean of the determined equivalent circle diameters can be taken as the average particle diameter. The arithmetic mean can be determined from, for example, 100 or more particles. Note that the average particle diameters of other particles contained in the electrode plates and separators can also be determined in a similar manner.
  • the content of particles in the spacer is preferably 50% by volume or less. This makes it easier to ensure sufficient strength of the spacer.
  • the average height Hs of the spacer may be larger than the sum Tw of the average thickness Tb of the base material layer and the average thickness Tt of the composite material layer.
  • the ratio Hs/Tw of the average height Hs to the total Tw may be greater than 1, and may be 1.5 or more, 2 or more, or 3 or more.
  • the ratio Hs/Tw may be 10 or less, 8 or less, 5 or less, or 4 or less. By setting this ratio to 1.5 or more, expansion of the electrode group can be particularly suppressed.
  • the average height Hs can be measured by the following method. First, a cross section of the separator in the thickness direction of the separator is photographed using an electron microscope to obtain an image of the cross section. Next, in the image, 20 arbitrary locations of the spacers are selected, and the height of the spacer at that location is measured. Next, the measured heights at 20 locations are arithmetic averaged, and the resulting average value is defined as the average height Hs.
  • the average thickness Tb and the average thickness Tt can also be measured using the same procedure.
  • the cross-sectional shape of the linear protrusion in the direction perpendicular to the direction in which the linear first protrusion extends is not limited, and may be rectangular or tapered.
  • the cross-sectional shape may be a trapezoid whose width becomes narrower as the distance from the separator increases.
  • the cross-sectional shape of the second convex portion is not limited, and may be rectangular or tapered (for example, trapezoidal).
  • the planar shape of the second convex portion is not particularly limited, and may be circular (perfect circle or ellipse), polygonal (triangular, quadrangular, etc.), or the like.
  • the maximum diameter of the second convex portion may be 0.1 mm or more or 0.01 mm or more, and may be 1 mm or less or 5 mm or less.
  • the maximum diameter of the second convex portion is in a range of 0.01 to 0.5 times (for example, a range of 0.01 to 0.1 times) the distance (pitch P) between the center portions of adjacent annular portions. It's okay.
  • the width W of the linear first convex portion is not particularly limited. The width W may be 0.01 mm or more.
  • the average thickness Tb of the base material layer may be 5 ⁇ m or more, or 10 ⁇ m or more, and may be 30 ⁇ m or less, or 20 ⁇ m or less.
  • the average thickness Tt of the composite material layer may be 1 ⁇ m or more or 2 ⁇ m or more, and may be 5 ⁇ m or less or 3 ⁇ m or less.
  • the average height Hs of the spacer may be 10 ⁇ m or more, 20 ⁇ m or more, 100 ⁇ m or less, 50 ⁇ m or less, 40 ⁇ m or less, or 30 ⁇ m or less. These heights and thicknesses vary depending on the configuration of the positive electrode and negative electrode, and may take values outside the ranges illustrated here. Note that the first convex portion and the second convex portion are each normally formed so that the height thereof is as constant as possible so that the distance between the electrode plates formed by the spacer is as constant as possible.
  • the spacer may include a non-porous structure that does not allow lithium ions to pass through.
  • a spacer can be realized by forming the spacer under conditions that do not make it porous.
  • the method for forming a spacer having a non-porous structure is not particularly limited, and any known method may be used.
  • a spacer having a non-porous structure may be formed by printing the constituent material of the spacer as ink on a separator.
  • "lithium ions do not pass through” means that the amount that affects the characteristics and shape of the battery does not pass through the spacer. Including when moving within.
  • the spacer allows lithium ions to pass through, the lithium ions will pass through the spacer during charging.
  • the lithium ions that have passed through the spacer are deposited between the negative electrode and the base material layer where the spacer is formed. As a result, the thickness of the electrode group in the stacking direction increases. Therefore, it is preferable that the spacer does not allow lithium ions to pass therethrough.
  • the lamination direction means the radial direction of the wound type electrode group.
  • the area S1 of the spacer may be 30% or less of the area S0 of the separator. According to this range, a sufficient space for lithium metal to precipitate can be secured.
  • the area S1 and the area S0 are respective areas when the separator is viewed from the spacer side.
  • the ratio S1/S0 of the area S1 and the area S0 may be 0.20 or less (20% or less) or 0.10 or less, and may be 0.03 or more (3% or more) or 0.05 or more. Good too. By setting this ratio to 0.05 or more (5% or more), the effect of suppressing excessive temperature rise of the electrode group can be enhanced.
  • the areas S0 and S1 are areas in plan view. In other words, the areas S0 and S1 are the areas of the separator and spacer, respectively, when viewed from above.
  • the linear protrusion is a ridge-like protrusion.
  • the linear protrusions may be mesh-like protrusions. By forming the mesh, the effect of suppressing shrinkage of the base material layer is enhanced, and therefore the effect of suppressing excessive temperature rise of the electrode group can be enhanced.
  • the planar shape of the linear convex portion may be a combination of polygons.
  • An example of a mesh shape includes a shape in which polygons are combined so that they share sides. That is, the annular portion may be polygonal. Polygons include triangles, quadrilaterals, hexagons, etc. Different types of polygons may be combined.
  • the planar shape of the linear convex portion may be honeycomb-shaped. According to the honeycomb-shaped convex portion, as described for the mesh-like convex portion, the effect of suppressing excessive temperature rise of the electrode group can be enhanced.
  • the first resin forming the spacer has higher heat resistance than the second resin forming the base layer.
  • high heat resistance means that the decomposition temperature or melting point of the first resin is higher than the decomposition temperature or melting point of the second resin.
  • the first resin and the second resin may each contain multiple types of resins.
  • the separator includes a base material layer and a composite material layer
  • it may be produced by the following method. First, a base material layer is prepared. A commercially available material may be used for the base material layer. Next, a composite material layer is formed on the base material layer.
  • the method for forming the composite material layer is not particularly limited, and may be formed by the following method. First, a slurry (or coating liquid) is formed by mixing the components of the composite material layer and a liquid component (dispersion medium). Next, the slurry (or coating liquid) is applied to the base layer to form a coating film, and then the coating film is dried. In this way, a composite material layer can be formed.
  • a slurry or coating liquid
  • each step in forming the composite material layer is not particularly limited, and known methods can be applied.
  • the slurry (or coating liquid) may be applied by a known method such as a method using a bar coater.
  • the drying may be performed by a known method such as drying by heating or natural drying.
  • the spacer is formed on the composite material layer or the base material layer.
  • the spacer may be formed by the following method. First, a slurry or coating liquid is prepared by mixing spacer components and liquid components. Next, the slurry or coating liquid is applied to the area where the spacer will be formed, and then dried. In this way, spacers can be formed. Examples of liquid components include N-methyl-2-pyrrolidone and the like.
  • the slurry or coating liquid may be applied using a dispenser or the like, or may be applied using known printing methods such as gravure printing, inkjet printing, and screen printing. Further, the drying may be performed by a known method such as drying by heating or natural drying. A separator is obtained in the above manner.
  • the negative electrode includes a negative electrode current collector.
  • lithium metal is deposited on the negative electrode current collector by charging. More specifically, upon charging, lithium ions contained in the nonaqueous electrolyte receive electrons on the negative electrode current collector to become lithium metal, which is deposited on the negative electrode current collector. Lithium metal deposited on the negative electrode current collector is dissolved into the nonaqueous electrolyte as lithium ions by discharge. Note that the lithium ions contained in the non-aqueous electrolyte may be derived from a lithium salt added to the non-aqueous electrolyte, or may be supplied from the positive electrode active material by charging, and both of these may be There may be.
  • a conductive sheet can be used for the negative electrode current collector.
  • the electrode group is of a wound type, a strip-shaped conductive sheet is used.
  • conductive sheets include conductive films, metal foils, and the like.
  • the surface of the conductive sheet may be smooth. This makes it easier for lithium metal derived from the positive electrode to be deposited evenly on the conductive sheet during charging. Smooth means that the maximum height roughness Rz of the conductive sheet is 20 ⁇ m or less. The maximum height roughness Rz of the conductive sheet may be 10 ⁇ m or less. The maximum height roughness Rz is measured according to JIS (Japanese Industrial Standard) B 0601:2013.
  • the material of the negative electrode current collector may be any conductive material other than lithium metal and lithium alloy.
  • the conductive material may be a metal material such as a metal or an alloy.
  • the conductive material is preferably a material that does not react with lithium. More specifically, a material that forms neither an alloy nor an intermetallic compound with lithium is preferable. Examples of such conductive materials include copper (Cu), nickel (Ni), iron (Fe), alloys containing these metal elements, or graphite whose basal surface is preferentially exposed. .
  • Examples of the alloy include copper alloy and stainless steel (SUS). Copper and/or copper alloys are preferred because they have high electrical conductivity.
  • the thickness of the negative electrode current collector is not particularly limited, and may be in the range of 5 to 300 ⁇ m.
  • a negative electrode composite material layer may be formed on the surface of the negative electrode current collector.
  • the negative electrode composite material layer is formed, for example, by applying a paste containing a negative electrode active material such as graphite to at least a portion of the surface of the negative electrode current collector.
  • the thickness of the negative electrode composite layer is set to be sufficiently thin so that lithium metal can be deposited on the negative electrode.
  • the negative electrode may include a negative electrode current collector and a sheet of lithium metal or lithium alloy disposed on the negative electrode current collector. That is, a base layer containing lithium metal (a layer of lithium metal or lithium alloy) may be provided in advance on the negative electrode current collector. In addition to lithium, the lithium alloy may contain elements such as aluminum, magnesium, indium, and zinc. By providing the base layer in advance and depositing lithium metal thereon during charging, dendrite-like precipitation can be more effectively suppressed.
  • the thickness of the base layer is not particularly limited, but may be in the range of 5 ⁇ m to 25 ⁇ m, for example.
  • the positive electrode includes, for example, a positive electrode current collector and a positive electrode composite material layer supported by the positive electrode current collector.
  • the positive electrode composite material layer includes, for example, a positive electrode active material, a conductive material, and a binder.
  • the positive electrode composite material layer may be formed on only one side of the positive electrode current collector, or may be formed on both sides.
  • the positive electrode is obtained, for example, by applying a positive electrode composite slurry containing a positive electrode active material, a conductive material, and a binder to both sides of a positive electrode current collector, drying the coating film, and then rolling the slurry.
  • the positive electrode active material is a material that absorbs and releases lithium ions.
  • the positive electrode active material include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, transition metal sulfides, and the like. Among these, lithium-containing transition metal oxides are preferred because of their low manufacturing cost and high average discharge voltage.
  • transition metal elements contained in the lithium-containing transition metal oxide include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, and W.
  • the lithium-containing transition metal oxide may contain one type of transition metal element, or may contain two or more types of transition metal elements.
  • the transition metal element may be Co, Ni and/or Mn.
  • the lithium-containing transition metal oxide may contain one or more typical elements as necessary. Typical elements include Mg, Al, Ca, Zn, Ga, Ge, Sn, Sb, Pb, Bi, and the like.
  • the typical element may be Al or the like.
  • lithium-containing transition metal oxides composite oxides containing Co, Ni, and/or Mn as transition metal elements, and Al as an optional component, and having a rock salt crystal structure with a layered structure, are highly This is preferable in terms of obtaining capacity.
  • the molar ratio of the total amount of lithium (mLi) in the positive electrode and the negative electrode to the amount (mM) of metal M other than lithium in the positive electrode is set to, for example, 1.1 or less. may be done.
  • the conductive material is, for example, a carbon material.
  • the carbon material include carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphite.
  • binder examples include fluororesin, polyacrylonitrile, polyimide resin, acrylic resin, polyolefin resin, rubber-like polymer, and the like.
  • fluororesin examples include polytetrafluoroethylene and polyvinylidene fluoride.
  • the positive electrode current collector may be any conductive sheet. Foil, film, etc. are used as the conductive sheet. A carbon material may be applied to the surface of the positive electrode current collector.
  • Examples of the material of the positive electrode current collector include metal materials containing Al, Ti, Fe, and the like.
  • the metal material may be Al, Al alloy, Ti, Ti alloy, Fe alloy, etc.
  • the Fe alloy may be stainless steel (SUS).
  • the thickness of the positive electrode current collector is not particularly limited, and may be in the range of 5 to 300 ⁇ m.
  • a non-aqueous electrolyte having lithium ion conductivity includes, for example, a non-aqueous solvent, and lithium ions and anions dissolved in the non-aqueous solvent.
  • the non-aqueous electrolyte may be in liquid form or gel form.
  • a liquid non-aqueous electrolyte is prepared by dissolving a lithium salt in a non-aqueous solvent. Lithium ions and anions are generated by dissolving the lithium salt in a nonaqueous solvent.
  • the gel-like nonaqueous electrolyte includes a lithium salt and a matrix polymer, or a lithium salt, a nonaqueous solvent, and a matrix polymer.
  • a matrix polymer for example, a polymer material that absorbs a non-aqueous solvent and gels is used. Examples of polymer materials include fluororesins, acrylic resins, polyether resins, and the like.
  • lithium salt or anion known salts used in non-aqueous electrolytes of lithium secondary batteries can be used. Specific examples include BF 4 ⁇ , ClO 4 ⁇ , PF 6 ⁇ , CF 3 SO 3 ⁇ , CF 3 CO 2 ⁇ , imide anions, oxalate complex anions, and the like.
  • the anion of the oxalate complex may contain boron and/or phosphorus.
  • Examples of the anion of the oxalate complex include bisoxalate borate anions, BF 2 (C 2 O 4 ) - , PF 4 (C 2 O 4 ) - , PF 2 (C 2 O 4 ) 2 - , and the like.
  • the non-aqueous electrolyte may contain one or more of these anions.
  • the nonaqueous electrolyte preferably contains at least an anion of an oxalate complex.
  • the interaction between the anion of the oxalate complex and lithium makes it easier for lithium metal to precipitate uniformly in the form of fine particles. Therefore, local precipitation of lithium metal can be easily suppressed.
  • the anion of the oxalate complex and other anions may be combined.
  • Other anions may be PF 6 - and/or imide anions.
  • the nonaqueous electrolyte may include LiBF 2 (C 2 O 4 ) (lithium difluorooxalatoborate) as a solute (lithium salt).
  • nonaqueous solvent examples include esters, ethers, nitriles, amides, and halogen-substituted products thereof.
  • the non-aqueous electrolyte may contain one or more of these non-aqueous solvents.
  • halogen-substituted substances include fluorides and the like.
  • esters include carbonate esters and carboxylic acid esters.
  • examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, fluoroethylene carbonate (FEC), and the like.
  • Examples of chain carbonate esters include dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate, and the like.
  • Examples of the cyclic carboxylic acid ester include ⁇ -butyrolactone and ⁇ -valerolactone.
  • chain carboxylic acid esters include ethyl acetate, methyl propionate, methyl fluoropropionate, and the like.
  • Ethers include cyclic ethers and chain ethers.
  • the cyclic ether include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran.
  • the chain ether include 1,2-dimethoxyethane, diethyl ether, ethyl vinyl ether, methylphenyl ether, benzyl ethyl ether, diphenyl ether, dibenzyl ether, 1,2-diethoxyethane, diethylene glycol dimethyl ether, and the like.
  • the concentration of the lithium salt in the nonaqueous electrolyte is, for example, 0.5 mol/L or more and 3.5 mol/L or less.
  • the concentration of anions in the non-aqueous electrolyte may be 0.5 mol/L or more and 3.5 mol/L or less.
  • the concentration of the anion of the oxalate complex in the nonaqueous electrolyte may be set to 0.05 mol/L or more and 1 mol/L or less.
  • the non-aqueous electrolyte may contain additives.
  • the additive may form a film on the negative electrode. By forming a film derived from the additive on the negative electrode, the generation of dendrites is easily suppressed.
  • examples of such additives include vinylene carbonate, fluoroethylene carbonate (FEC), vinyl ethyl carbonate (VEC), and the like.
  • the exterior body houses a positive electrode, a negative electrode, a separator, a spacer disposed on the separator, and a nonaqueous electrolyte.
  • the exterior body is not particularly limited, and any exterior body used in known lithium secondary batteries may be used.
  • the present disclosure further discloses a composite member (C) used in a battery.
  • the composite member (C) includes the separator and spacer described as constituent elements of the lithium secondary battery (L). That is, the composite member (C) includes the above-described separator and a spacer formed on the separator. Since the separator and spacer have been described above, redundant explanation will be omitted.
  • the composite member (C) can be used as a separator for lithium secondary batteries.
  • the composite member (C) includes a separator having a base layer and a spacer. Spacers can be formed directly or indirectly on the base layer. A composite material layer may be arranged between the spacer and the base layer.
  • the composite member (C) includes a first protrusion including a plurality of annular parts connected to each other, and a second protrusion disposed inside the annular part. Therefore, the shrinkage of the convex portions during drying when forming the spacer is made uniform, and it is possible to suppress the formation of wrinkles in the base material layer.
  • lithium secondary battery (L) of this embodiment will be specifically described with reference to the drawings.
  • the above-mentioned components can be applied to the components of an example of a lithium secondary battery described below. Further, the constituent elements of the example described below can be changed based on the above description. Further, the matters described below may be applied to the above embodiments. Furthermore, in the lithium secondary battery described below, components that are not essential to the lithium secondary battery according to the present disclosure may be omitted. Note that in the figures below, the scale of the components has been changed to facilitate understanding.
  • FIG. 1 is a vertical cross-sectional view schematically showing an example of a lithium secondary battery according to a first embodiment. Note that, in FIG. 1, illustration of the spacer and the space formed by the spacer is omitted.
  • the cylindrical lithium secondary battery 10 shown in FIG. 1 includes a cylindrical battery case, a wound electrode group 14, and a non-aqueous electrolyte (not shown) housed in the battery case.
  • the battery case includes a case body 15 that is a cylindrical metal container with a bottom, and a sealing body 16 that seals the opening of the case body 15.
  • a gasket 27 is arranged between the case body 15 and the sealing body 16. The gasket 27 ensures hermeticity of the battery case.
  • insulating plates 17 and 18 are arranged at both ends of the electrode group 14 in the winding axis direction, respectively.
  • the case body 15 has, for example, a stepped portion 21 formed by partially pressing the side wall of the case body 15 from the outside.
  • the step portion 21 may be formed in a ring shape on the side wall of the case body 15 along the circumferential direction of the case body 15.
  • the sealing body 16 is supported by the opening side surface of the stepped portion 21.
  • the sealing body 16 includes a filter 22 , a lower valve body 23 , an insulating member 24 , an upper valve body 25 , and a cap 26 .
  • these members are laminated in this order.
  • the sealing body 16 is attached to the opening of the case body 15 such that the cap 26 is located on the outside of the case body 15 and the filter 22 is located on the inside of the case body 15.
  • Each of the above-mentioned members constituting the sealing body 16 has, for example, a disk shape or a ring shape.
  • the lower valve body 23 and the upper valve body 25 are connected to each other at their central portions, and an insulating member 24 is interposed between their peripheral edges.
  • the filter 22 and the lower valve body 23 are connected to each other at their central portions.
  • the upper valve body 25 and the cap 26 are connected to each other at their central portions. That is, each member except the insulating member 24 is electrically connected to each other.
  • a vent hole (not shown) is formed in the lower valve body 23. Therefore, when the internal pressure of the battery case increases due to abnormal heat generation or the like, the upper valve body 25 swells toward the cap 26 and separates from the lower valve body 23. As a result, the electrical connection between the lower valve body 23 and the upper valve body 25 is cut off. When the internal pressure further increases, the upper valve body 25 breaks and gas is discharged from an opening (not shown) formed in the cap 26.
  • FIG. 2 is an enlarged view of a part of the electrode group 14. 2 includes a portion near the positive electrode surrounded by region II in FIG. 1 and a portion near the negative electrode surrounded by region III in FIG.
  • the electrode group 14 includes a positive electrode 11, a negative electrode 12, a separator 50, and a spacer 53.
  • the positive electrode 11, the negative electrode 12, and the separator 50 are all band-shaped. Spacer 53 is formed on separator 50 (composite material layer 52).
  • the electrode group 14 is formed by winding the positive electrode 11, the negative electrode 12, and the separator 50 such that the separator 50 is disposed between the positive electrode and the negative electrode 12.
  • the positive electrode 11 includes a positive electrode current collector 11a and a positive electrode composite layer 11b.
  • the positive electrode current collector 11a is electrically connected via the positive electrode lead 19 to a cap 26 that functions as a positive electrode terminal.
  • a negative electrode negative electrode current collector
  • the negative electrode 12 is electrically connected to the case body 15, which functions as a negative electrode terminal, via a negative electrode lead 20.
  • the separator 50 includes a base layer 51 and a composite material layer 52. Separator 50 has a first main surface 50a facing negative electrode 12 and a second main surface 50b facing positive electrode 11. In the example shown in FIG. 2, the spacer 53 is formed on the first main surface 50a.
  • the composite member (C) described above includes a separator 50 and a spacer 53.
  • the composite material layer 52 is formed on the main surface on the negative electrode 12 side, of the two main surfaces of the base layer 51.
  • the spacer 53 is formed on the composite material layer 52 and is in contact with the negative electrode 12.
  • a space 14s is formed between the positive electrode 11 and the negative electrode 12 (between the negative electrode 12 and the separator 50) by the spacer 53.
  • FIG. 2 shows the height h of the spacer 53.
  • lithium metal is deposited on the negative electrode 12 during charging. Since the space 14s exists between the positive electrode 11 and the negative electrode 12, the volume change of the electrode group 14 due to the precipitation of lithium metal is reduced, and the cycle characteristics are improved.
  • FIG. 3 An example of the planar shape of the spacer 53 is shown in FIG. 3, and a partially enlarged view of FIG. 3 is shown in FIG.
  • the example spacer 53 in FIG. 3 includes linear first protrusions 53a arranged in a honeycomb shape and dot-shaped second protrusions 53b.
  • the second convex portion 53b is arranged at the center of the hexagonal annular portion. Adjacent annular portions share a side.
  • the area where the spacer 53 is not formed constitutes a space 14s.
  • FIG. 4 shows the width W of the linear first convex portion 53a.
  • FIGS. 5 and 6 Another example of the planar shape of the spacer 53 is shown in FIGS. 5 and 6.
  • the spacer 53 in FIG. 5 has a defective portion 53x that connects the inner regions of two adjacent annular portions.
  • the spacer 53 in FIG. 6 includes first convex portions 53a arranged in a grid pattern.
  • the annular portion is a quadrilateral (diamond).
  • Embodiment 1 a cylindrical lithium secondary battery including a wound electrode group was described.
  • the lithium secondary battery of this embodiment is not limited to the form of Embodiment 1, and can be applied to other forms as well.
  • the shape of the lithium secondary battery can be appropriately selected from various shapes such as a cylindrical shape, a coin shape, a square shape, a sheet shape, and a flat shape, depending on its use.
  • the form of the electrode group is not particularly limited either, and may be a stacked type.
  • a lithium secondary battery A positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, a spacer, and a non-aqueous electrolyte having lithium ion conductivity
  • the negative electrode is an electrode in which lithium metal is deposited during charging and the lithium metal is dissolved during discharge
  • the spacer is formed on one main surface of one of the positive electrode, the negative electrode, and the separator,
  • the spacer includes a linear first convex portion forming a periodically repeated pattern, and a plurality of second convex portions that are not in contact with the first convex portion,
  • the first convex portion includes a plurality of annular portions that are connected to each other,
  • the second convex portion is disposed inside the annular portion.
  • (Technology 2) The lithium secondary battery according to technique 1, wherein the maximum height of the second protrusion is greater than the maximum height of the first protrusion.
  • (Technology 3) The lithium secondary battery according to technology 1 or 2, wherein the second convex portion is island-shaped.
  • (Technology 4) The lithium secondary battery according to any one of techniques 1 to 3, wherein the spacer is formed on the separator.
  • (Technique 5) The separator has a first main surface facing the negative electrode and a second main surface facing the positive electrode, The lithium secondary battery according to technique 4, wherein the spacer is formed on the first main surface.
  • the separator includes a base layer and a composite material layer formed on the base layer, The composite material layer contains a polymer and inorganic particles, The lithium secondary battery according to any one of techniques 1 to 5, wherein the spacer is formed on the composite material layer.
  • the spacer includes a linear first convex portion forming a periodically repeated pattern, and a plurality of second convex portions that are not in contact with the first convex portion,
  • the first convex portion includes a plurality of annular portions that are connected to each other,
  • the second convex part is a composite member arranged inside the annular part.
  • the composite member according to technique 9 wherein the maximum height of the second convex portion is greater than the maximum height of the first convex portion.
  • the composite member according to technique 9 or 10 wherein the second convex portion is island-shaped.
  • NMP N-methyl-2-pyrrolidone
  • the obtained positive electrode mixture slurry was applied to both sides of a band-shaped Al foil (positive electrode current collector), and then dried to form a coating film of the positive electrode mixture.
  • the coating film was rolled using a roller.
  • the obtained laminate of the positive electrode current collector and positive electrode composite material was cut into a predetermined electrode size to produce a positive electrode having positive electrode composite layers on both sides of the positive electrode current collector.
  • a band-shaped porous membrane made of polyethylene (average thickness 10 ⁇ m) was prepared as a base material layer.
  • a porous composite material layer (average thickness 2 ⁇ m) was formed on one side of the base material layer.
  • the composite material layer was formed by forming the second layer and the first layer in this order on the base material layer.
  • the second layer was formed as follows. First, N-methyl-2-pyrrolidone (NMP) and calcium chloride were mixed at a mass ratio of 94.2:5.8. This mixture was heated to about 80°C to completely dissolve the calcium chloride. Then, this solution was returned to room temperature, 2200 g was collected, and 0.6 mol of para-phenylenediamine (PPD) was added to completely dissolve it. While maintaining this solution at about 20° C., 0.6 mol of terephthalic acid dichloride (TPC) was added little by little. The obtained solution was aged at about 20° C. for 1 hour to obtain a polymerization solution.
  • NMP N-methyl-2-pyrrolidone
  • PPD para-phenylenediamine
  • TPC terephthalic acid dichloride
  • the coating solution was applied onto the base layer using a slot die method to form a coating film.
  • the base material layer on which the coating film was formed was left in an atmosphere at a temperature of 25° C. and a relative humidity of 70% for 1 hour to precipitate the aromatic polyamide.
  • NMP and calcium chloride in the coating film were removed by washing with water.
  • a second layer was then formed by drying the coating at 60° C. for 5 minutes.
  • the first layer was formed as follows. First, particles of lithium phosphate (Li 3 PO 4 ) and polyN-vinylacetamide (PNVA) were mixed at a mass ratio of 100:8 to obtain a mixture. The lithium phosphate particles used had a volume-based median diameter of 0.19 ⁇ m. Water (ion-exchanged water) was added to the resulting mixture and stirred to prepare a slurry (coating liquid) with a solid content concentration of 12% by mass. Next, the slurry was applied onto the second layer by microgravure coating to form a coating film. Next, the coating film was dried in a drying oven attached to the coating machine. In this way, the first layer was formed. In this way, a composite material layer was formed.
  • PNVA polyN-vinylacetamide
  • a coating liquid containing polyvinylidene fluoride and alumina particles (inorganic filler) was discharged onto the composite material layer in a pattern (honeycomb+dots) shown in FIG. 3. Thereafter, the coating liquid was vacuum dried. In this way, spacers arranged in the pattern shown in FIG. 3 were formed. At this time, the distance between two adjacent dots (distance between the centers of two adjacent honeycomb shapes: pitch P) was set to 4.5 mm. The average height of the spacers was 30 ⁇ m. Note that the maximum height H2 of the dots (second protrusions) was the same as the maximum height H1 of the honeycomb pattern (first protrusions).
  • LiPF 6 was dissolved at a concentration of 1 mol/L and LiBF 2 (C 2 O 4 ) was dissolved at a concentration of 0.1 mol/L to form a liquid non-aqueous electrolyte. was prepared.
  • the obtained electrode group was housed in a bag-shaped exterior body formed of a laminate sheet with an Al layer, and the non-aqueous electrolyte was injected into the exterior body housing the electrode group, and then the exterior body was sealed. In this way, a lithium secondary battery A1 was produced.
  • Battery A2 was manufactured using the same method and conditions as battery A1, except that the orientation of the separator was changed. In battery A2, the separator was arranged so that the spacer faced the negative electrode.
  • Battery A3 and batteries C2 to C5 Battery A3 and Battery C2 to C5 were produced. Note that in these batteries, the average height of the spacers was the same as the average height (30 ⁇ m) of the spacers in battery A1.
  • Battery C1 was produced in the same manner and under the same conditions as battery A1, except that no spacer was formed on the separator.
  • Battery A4 was manufactured using the same method and conditions as battery A1, except that the maximum height of the spacer was changed. In the spacer for battery A4, the maximum height H1 of the honeycomb pattern convex portion was 30 ⁇ m, and the maximum height H2 of the dot-like convex portion was 50 ⁇ m.
  • a plurality of batteries produced as described above were evaluated by the following method.
  • (Charge/discharge test) A charge/discharge test was conducted on each of the obtained batteries. In the charge/discharge test, the battery was charged in a constant temperature bath at 25° C. under the following conditions, then paused for 20 minutes, and then discharged under the following conditions.
  • Constant current charging is performed with a current of 2.15 mA per unit area (square centimeter) of the electrode until the battery voltage reaches 4.1 V, and then, with a voltage of 4.1 V, the current value per unit area of the electrode is 0. Constant voltage charging was performed until the voltage reached 54 mA.
  • Discharge capacity maintenance rate 100 ⁇ C(50)/C(1)
  • the thickness was measured at five arbitrary points within the laminate, and the arithmetic average of the five measured values was taken as the average thickness of the laminate.
  • the average thickness X obtained by subtracting the thickness of the two base material layers and the thickness of the two composite material layers from this average thickness was determined.
  • Table 1 shows some of the battery manufacturing conditions and evaluation results. Note that in Table 1, the rhombus is a rhombic pattern similar to the first convex portion 53a in FIG.
  • Batteries A1 to A4 are batteries according to the present disclosure, and batteries C1 to C5 are batteries of comparative examples. Batteries A1 to A4 were able to suppress expansion near the negative electrode and achieved high capacity retention (good cycle characteristics).
  • the present disclosure is applicable to lithium secondary batteries.
  • the lithium secondary battery according to the present disclosure can be used in electronic devices such as mobile phones, smartphones, and tablet terminals, electric vehicles including hybrids and plug-in hybrids, household storage batteries combined with solar cells, and the like.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Cell Separators (AREA)
  • Secondary Cells (AREA)
PCT/JP2023/027200 2022-08-31 2023-07-25 リチウム二次電池および複合部材 Ceased WO2024048136A1 (ja)

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JP2015138770A (ja) * 2014-01-24 2015-07-30 旭化成イーマテリアルズ株式会社 積層体、蓄電デバイス用セパレータ、蓄電デバイス、リチウムイオン二次電池および共重合体
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