WO2023054149A1 - リチウム二次電池 - Google Patents

リチウム二次電池 Download PDF

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Publication number
WO2023054149A1
WO2023054149A1 PCT/JP2022/035300 JP2022035300W WO2023054149A1 WO 2023054149 A1 WO2023054149 A1 WO 2023054149A1 JP 2022035300 W JP2022035300 W JP 2022035300W WO 2023054149 A1 WO2023054149 A1 WO 2023054149A1
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Prior art keywords
secondary battery
negative electrode
spacer
heat
lithium
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PCT/JP2022/035300
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English (en)
French (fr)
Japanese (ja)
Inventor
亮平 宮前
聡 蚊野
真一郎 近藤
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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 CN202280064894.3A priority Critical patent/CN117999685A/zh
Priority to US18/696,465 priority patent/US20240387861A1/en
Priority to JP2023551404A priority patent/JPWO2023054149A1/ja
Priority to EP22876016.1A priority patent/EP4411914A4/en
Publication of WO2023054149A1 publication Critical patent/WO2023054149A1/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
    • 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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • 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
    • H01M50/431—Inorganic 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
    • H01M50/443—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
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • 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
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic 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
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • 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
    • H01M50/463—Separators, membranes or diaphragms 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
    • 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
    • H01M50/491—Porosity
    • 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 disclosure relates to lithium secondary batteries.
  • Non-aqueous electrolyte secondary batteries are used for applications such as ICT such as personal computers and smartphones, vehicles, and power storage. In such applications, the non-aqueous electrolyte secondary battery is required to have a higher capacity.
  • Lithium ion batteries are known as high-capacity non-aqueous electrolyte secondary batteries.
  • a high capacity lithium ion battery can be achieved by using, for example, graphite and an alloy active material such as a silicon compound together as a negative electrode active material.
  • increasing the capacity of lithium-ion batteries is reaching its limit.
  • a lithium secondary battery (lithium metal secondary battery) is promising as a high-capacity non-aqueous electrolyte secondary battery that exceeds that of lithium-ion batteries.
  • lithium metal is deposited on the negative electrode during charging, and this lithium metal dissolves in the non-aqueous electrolyte during discharging.
  • Various proposals have been made for lithium secondary batteries.
  • Patent Literature 1 International Publication No. 2020/066254 discloses that "a positive electrode including a positive electrode current collector and a positive electrode mixture layer containing a positive electrode active material, and a negative electrode including a negative electrode current collector facing the positive electrode. , 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 is a composite oxide containing 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 first The length is smaller than a second length in a second direction D2 that intersects with the first direction, and the space between the positive electrode and the separator is formed such that a space for accommodating the lithium metal is formed between the positive electrode and the negative electrode.
  • a lithium secondary battery, wherein spacers are provided therebetween, and a straight line SL can be drawn along the first direction D1 so as to pass through the spacers at three or more locations. ” is disclosed.
  • One object of the present disclosure is to provide a lithium secondary battery with higher characteristics (eg, safety).
  • the lithium secondary battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte having lithium ion conductivity, wherein the negative electrode is charged with lithium metal.
  • the spacers are formed on the main surface, and the spacers are arranged closer to the negative electrode than the substrate and the heat-resistant layer, and the average height of the spacers is equal to the average thickness of the substrate and the thickness of the heat-resistant layer. Greater than the sum of the average thickness.
  • FIG. 1 is a longitudinal sectional view schematically showing an example of a lithium secondary battery according to an embodiment of the present disclosure
  • FIG. FIG. 2 is a cross-sectional view schematically showing part of the lithium secondary battery shown in FIG. 1
  • FIG. 4 is a top view showing an example of a pattern of spacers
  • 4 is a partially enlarged view of FIG. 3
  • FIG. 10 is a top view showing another example of a pattern of spacers
  • a lithium secondary battery according to an embodiment of the present disclosure (hereinafter sometimes referred to as “lithium secondary battery (L)”) includes a positive electrode, a negative electrode, and a It includes a separator and a non-aqueous electrolyte having lithium ion conductivity.
  • the negative electrode is an electrode in which lithium metal deposits during charging and lithium metal dissolves during discharging.
  • a separator includes a substrate, a heat-resistant layer, and a spacer.
  • the heat-resistant layer is formed on at least one main surface selected from two main surfaces of the substrate.
  • the spacer is arranged closer to the negative electrode than the substrate and the heat-resistant layer.
  • the average height of the spacers is greater than the sum of the average thickness of the substrate and the average thickness of the heat-resistant layer.
  • the form in which the element B is formed on the element A includes the form in which the element B is directly formed on the element A, and the form in which the element B is formed directly on the element A Forms in which B is formed are included.
  • a lithium secondary battery (L) is also called a lithium metal secondary battery.
  • the negative electrode of this type of battery lithium metal deposits during charging and dissolves during discharging.
  • 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 for example, 70% or more of the rated capacity is expressed by deposition and dissolution of lithium metal. Electron movement at the negative electrode during charge and discharge is primarily due to deposition and dissolution of lithium metal at the negative electrode. Specifically, 70-100% (eg, 80-100% or 90-100%) of the electron transfer (or current in another aspect) at the negative electrode during charging and discharging is due to the deposition and dissolution of lithium metal. That is, the negative electrode according to the present disclosure differs from a negative electrode in which electron movement in the negative electrode during charge and discharge is mainly due to lithium ion absorption and release by the negative electrode active material (such as graphite).
  • the negative electrode active material such as graphite
  • the positive electrode, the negative electrode, and the separator may be collectively referred to as an "electrode group".
  • the positive electrode, the negative electrode, and the separator may be wound such that the separator is positioned 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, the negative electrode and the 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 electrode group or a laminated electrode group.
  • a spacer secures a space between the positive electrode and the negative electrode.
  • the spacer is arranged on the negative electrode side of the separator and forms a space on the surface of the negative electrode.
  • lithium metal is deposited on the surface of the negative electrode. Lithium metal can be deposited in the spaces formed by the spacers. Therefore, expansion of the electrode group can be suppressed when charging and discharging are repeated.
  • the separator of the lithium secondary battery (L) includes a heat-resistant layer formed on the surface of the substrate.
  • This heat-resistant layer can suppress shrinkage of the base material when the temperature of the electrode group rises excessively.
  • the base material shrinks, short-circuiting between the positive electrode and the negative electrode is more likely to occur, and the temperature of the electrode group is more likely to rise.
  • the shrinkage of the base material can be suppressed, so that the further temperature rise of the electrode group can be suppressed.
  • the separator includes a spacer.
  • the spacer not only secures a space between the electrode plates, but also dramatically increases the effect of suppressing an excessive temperature rise of the electrode group by combining it with a heat-resistant layer. Found it. This disclosure is based on this new finding.
  • the spacer when a spacer is arranged on the positive electrode, the spacer covers the surface of the positive electrode, so that the transfer of lithium ions by the positive electrode active material is partially inhibited. As a result, the cell capacity may decrease.
  • the spacer in the lithium secondary battery (L), the spacer is formed on the separator, so the above problem can be avoided. That is, according to the lithium secondary battery (L), it is possible to simultaneously suppress the expansion of the electrode group and maintain a high cell capacity, and furthermore, it is possible to suppress the temperature rise of the battery in the event of an abnormality.
  • the separator includes at least one heat-resistant layer.
  • the heat-resistant layer may be formed on the main surface on the positive electrode side of the two main surfaces of the substrate, may be formed on the main surface on the negative electrode side, or may be formed on each of the two main surfaces. may be formed on the
  • the spacer may be formed on the heat-resistant layer, or may be formed on the substrate without the heat-resistant layer interposed therebetween.
  • the separator may have a configuration of base material/heat-resistant layer/spacer, heat-resistant layer/base material/spacer, or heat-resistant layer/base material/heat-resistant layer/spacer. In these configurations, the spacer is placed on the negative electrode side. That is, the separator is arranged such that the spacer faces the negative electrode.
  • the heat-resistant layer is formed on the negative electrode-side main surface of the two main surfaces of the substrate, and the spacer is formed on the heat-resistant layer.
  • the spacer is formed on the heat-resistant layer.
  • a porous sheet having ion permeability and insulation is used as the base material.
  • porous sheets include porous membranes, woven fabrics, non-woven 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 and copolymers of ethylene and propylene.
  • the base material may contain additives as needed. An inorganic filler etc. are mentioned as an additive.
  • a sheet used as a separator for a lithium secondary battery may be used as the base material.
  • the spacer may contain resin (for example, insulating resin) or may contain resin and particles.
  • the spacer may be composed only of resin, or may be composed of resin and particles.
  • the ratio of the resin in the spacer may be 10% by volume or more, 30% by volume or more, or 50% by volume or more, and may be 100% by volume or less, or 80% by volume or less.
  • the particle content in the spacer may be lower than the particle content in the heat-resistant layer.
  • the particle content in the spacer may be lower than the particle content in the heat-resistant layer.
  • resin materials include fluorine-containing resins such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene, fluorine-containing rubbers such as vinylidene fluoride-tetrafluoroethylene copolymers and ethylene-tetrafluoroethylene copolymers, and styrene.
  • PVdF polyvinylidene fluoride
  • fluorine-containing rubbers such as vinylidene fluoride-tetrafluoroethylene copolymers and ethylene-tetrafluoroethylene copolymers
  • styrene styrene
  • Non-porous spacers having a certain height or more made of these resin materials are layers impermeable to lithium ions.
  • the average height of the spacers may be 3 times or more, 5 times or more, or 10 times or more the average thickness of the heat-resistant layer, and may be 100 times or less, 30 times or less, or 20 times or less.
  • 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, silicon oxide (silica), and the like.
  • Aluminum hydroxide etc. can be mentioned as a metal hydroxide.
  • metal nitrides include silicon nitride, aluminum nitride, boron nitride, and titanium nitride.
  • metal carbides include silicon carbide and boron carbide. Barium sulfate etc.
  • a metal sulfide can be mentioned as a metal sulfide.
  • Minerals such as aluminosilicate, layered silicate, barium titanate, and strontium titanate may also be used. Among them, it is preferable to use alumina, silica, titania, or the like.
  • the average particle size of the particles is not particularly limited, but may be 0.1 ⁇ m or more or 0.5 ⁇ m or more, or may be 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 with an electron microscope to obtain an image of the cross section. Next, image processing such as binarization is performed on the image to identify the particle portion. Next, the diameter of a circle having the same area as the cross-sectional area of each particle (equivalent circle diameter) is determined, and the arithmetic mean of the determined equivalent circle diameters can be used as the average particle diameter. Arithmetic averages can be determined, for example, from 100 or more particles. The average particle size of other particles contained in the electrode plate and separator 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 spacers is greater than the total Tw of the average thickness Tb of the substrate and the average thickness Tt of the heat-resistant layer.
  • the ratio Hs/Tw between the average height Hs and the total Tw may be greater than 1, greater than or equal to 1.5, greater than or equal to 2, or greater than or equal to 3.
  • the ratio Hs/Tw may be 10 or less, 8 or less, 5 or less, or 4 or less.
  • 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 with an electron microscope to obtain an image of the cross section. Next, in the image, 20 arbitrary locations of the spacer are selected, and the height of the spacer at that location is measured. Next, the heights measured at 20 points are arithmetically averaged, and the obtained average value is defined as the average height Hs.
  • Average thickness Tb and average thickness Tt can also be measured by the same procedure.
  • the average thickness Tb of the base material 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 heat-resistant layer may be 1 ⁇ m or more or 2 ⁇ m or more, or may be 5 ⁇ m or less or 3 ⁇ m or less.
  • the average height Hs of the spacers may be 10 ⁇ m or more, or 20 ⁇ m or more, and may be 100 ⁇ m or less, 50 ⁇ m or less, 40 ⁇ m or less, or 30 ⁇ m or less. These heights and thicknesses may vary depending on the configurations of the positive and negative electrodes, and may take values outside the ranges exemplified here. In order to keep the distance between the electrode plates formed by the spacers as constant as possible, the spacers are usually formed so that their heights are as constant as possible.
  • the spacer preferably includes a non-porous structure impermeable to lithium ions.
  • Such spacers can be realized by forming the spacers under conditions that do not make them porous.
  • the phrase "lithium ions do not permeate" means that an amount that affects the characteristics and shape of the battery does not permeate. Including when moving within.
  • the area S1 of the spacer may be 30% or less of the area S0 of the separator. According to this range, it is possible to secure a sufficient space for deposition of lithium metal.
  • the area S1 and the area S0 are respective areas of the separator when viewed from the spacer side.
  • the ratio S1/S0 between 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 spacer may include linear projections and/or dot-shaped projections.
  • a linear convex part is a ridge-shaped convex part from one viewpoint.
  • the spacer preferably includes a linear projection, and may be composed only of a linear projection.
  • the width of the linear projections may be 100 ⁇ m or more or 200 ⁇ m or more, and may be 2000 ⁇ m or less or 1000 ⁇ m or less.
  • the linear protrusions may be mesh-like protrusions. Since the effect of suppressing shrinkage of the base material is enhanced by forming the mesh, the effect of suppressing excessive temperature rise of the electrode group can be enhanced.
  • the spacer may include a plurality of linear projections arranged in stripes.
  • the planar shape of the linear protrusion may be a shape combining polygons.
  • An example of a mesh shape includes a shape in which polygons are combined so as to share sides. Polygons include triangles, quadrilaterals, hexagons, and the like. Different types of polygons may be combined.
  • the planar shape of the linear protrusion may be a honeycomb shape. According to the honeycomb-shaped protrusions, as described for the mesh-shaped protrusions, the effect of suppressing an excessive temperature rise of the electrode group can be enhanced.
  • a preferred example of the spacer satisfies at least one, preferably two or all of the following conditions (1) to (3). When the following conditions are satisfied, it is possible to achieve a good balance between securing a space for depositing lithium metal and suppressing an excessive temperature rise of the electrode assembly.
  • the ratio S1/S0 between the area S1 and the area S0 is 0.30 or less. The ratio S1/S0 may be in the range described above.
  • the spacer includes a linear protrusion, and the width of the linear protrusion is 2000 ⁇ m or less. The width of the protrusion may be within the range described above.
  • the spacer includes linear protrusions, and the linear protrusions are repeatedly formed in a predetermined pattern in the region between the positive electrode and the negative electrode. The pattern may be a mesh pattern (for example, a honeycomb pattern).
  • the first resin forming the spacer preferably has higher heat resistance than the second resin forming the base material.
  • 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.
  • each of the first resin and the second resin may contain a plurality of types of resins.
  • the heat-resistant layer may contain a polymer (hereinafter sometimes referred to as "polymer (PL)”) and inorganic particles.
  • the inorganic particles may include first particles of phosphate containing lithium, and may further include second particles other than phosphate.
  • the heat-resistant layer is a layer permeable to lithium ions.
  • 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 ). At least one may be selected. Among these, lithium phosphate is preferable because it is highly effective in suppressing heat generation of the battery in the event of an abnormality.
  • the average particle diameter of the first particles is in the range of 0.1 ⁇ m to 1.0 ⁇ m (for example, the range of 0.1 ⁇ m to 0.5 ⁇ m, the range of 0.1 ⁇ m to 0.2 ⁇ m, or the range of 0.1 ⁇ m to 0.19 ⁇ m ).
  • the average particle size of the first particles may be 0.1 ⁇ m or greater, or 0.15 ⁇ m or greater.
  • 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 permeation of the electrolytic solution can be secured. Setting the average particle diameter to 1.0 ⁇ m or less is preferable from the viewpoint of forming a high-density layer of the first particles.
  • the polymer (PL) a polymer having higher heat resistance than the main component of the base material of the separator can be used.
  • the polymer (PL) preferably contains at least one selected from the group consisting of aromatic polyamides, aromatic polyimides, and aromatic polyamideimides. These are known as polymers (otherwise macromolecules or resins) with high heat resistance. From the viewpoint of heat resistance, aramids, that is, meta-aramids (meta-based wholly aromatic polyamides) and para-aramids (para-based wholly aromatic polyamides) are preferred.
  • One preferred example polymer (PL) is a meta-aramid.
  • Known aromatic polyamides, aromatic polyimides, and aromatic polyamideimides may be used for the polymer (PL).
  • aromatic polyamides examples include polymers formed by condensation polymerization of monomers having aromatic skeletons and containing amide bonds in repeating units.
  • aromatic polyamides examples include meta aromatic polyamides (eg meta wholly aromatic polyamides) and para aromatic polyamides (eg para wholly aromatic polyamides).
  • Wholly aromatic polyamides are also called aramids.
  • a preferred example of the second particles is a particle composed of an insulating inorganic compound that does not melt or decompose when the battery abnormally heats up.
  • the second particles may be inorganic particles that are commonly used as inorganic fillers. Examples of materials for the second particles include oxides, oxide hydrates, hydroxides, nitrides, carbides, sulfides, etc., which may contain metallic elements.
  • the average particle size 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, and zinc oxide.
  • 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 and the like.
  • the material of the second particles may be porous aluminosilicate such as zeolite, layered silicate such as talc, barium titanate (BaTiO 3 ), strontium titanate (SrTiO 3 ), or the like. At least one selected from the group consisting of aluminum oxide, boehmite, talc, titanium oxide, and magnesium oxide may be used as the material of the second particles from the viewpoint of insulation and heat resistance.
  • 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 heat-resistant layer may include a first layer containing the first particles and a second layer containing the second particles. According to this configuration, it is possible to particularly enhance the effect of suppressing an excessive temperature rise of the electrode group.
  • the heat-resistant 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, may be laminated on the main surface on the negative electrode side, or may be laminated on different main surfaces.
  • the separator can be: substrate/first layer/second layer/spacer, substrate/second layer/first layer/spacer, first layer/second layer/substrate/spacer, Alternatively, it may have a laminated structure of second layer/first layer/base material/spacer. Alternatively, the first layer and the second layer may be disposed on different major surfaces of the substrate.
  • the separator may have a laminated structure of first layer/substrate/second layer/spacer or second layer/substrate/first layer/spacer. The separator is arranged such that the spacer faces the negative electrode. That is, the spacer is arranged closer to the negative electrode than the substrate and the heat-resistant layer.
  • the first layer may contain the 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 weight.
  • 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 deactivate lithium at high temperatures.
  • the first layer may contain solid components other than the first particles.
  • the first layer may contain a binder, an inorganic material other than the first particles (for example, 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 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 binder content 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 may be polyolefin (polyethylene, polypropylene, copolymer of ethylene and ⁇ -olefin, etc.), fluorine-containing resin (polyvinylidene fluoride, polytetrafluoroethylene, polyfluoride vinyl, etc.), fluorine-containing rubber (vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, etc.), styrene-butadiene copolymer and its hydride, acrylonitrile-butadiene copolymer Included are coalescences and their hydrides, acrylonitrile-butadiene-styrene copolymers and their hydrides, N-vinylacetamide.
  • the second layer includes second particles other than the first particles (phosphate particles).
  • the second layer may or may not contain the first particles.
  • the second layer preferably contains a polymer (PL).
  • the polymer (PL) content in the second layer may be in the range of 50% to 100% by weight (eg 80% to 100% by weight or 90% to 100% by weight).
  • the second layer may consist of polymer (PL) only.
  • 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 (eg, in the range of 85% to 99% by weight).
  • the second layer may also contain a binder.
  • 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 thickness of the first and second layers may independently be in the range of 0.2 ⁇ m to 10 ⁇ m (eg, in the range of 1 ⁇ m to 8 ⁇ m, or in the range of 2 ⁇ m to 4 ⁇ m, or in the range of 4 ⁇ m to 10 ⁇ m).
  • the thickness of the first layer may range from 0.2 ⁇ m to 10 ⁇ m and the thickness of the second layer may range from 0.2 ⁇ m to 10 ⁇ m.
  • the thickness of the first layer may be 0.2 ⁇ m or more, 0.3 ⁇ m or more, or 0.5 ⁇ m or more, preferably 1 ⁇ m or more, more preferably 2 ⁇ m or more, 3 ⁇ m or more is more preferable, and 4 ⁇ m or more is even more preferable.
  • the thickness of the first layer may be 10 ⁇ m or less, 8 ⁇ m or less, or 7 ⁇ m or less, 5 ⁇ m or less.
  • the thickness of the second layer may be 0.2 ⁇ m or more, 0.3 ⁇ m or more, or 0.5 ⁇ m or more, preferably 1 ⁇ m or more, more preferably 2 ⁇ m or more, 3 ⁇ m or more is more preferable, and 4 ⁇ m or more is even more preferable.
  • the thickness of the second layer may be 10 ⁇ m or less, 8 ⁇ m or less, or 7 ⁇ m or less, 5 ⁇ m or less.
  • the first layer and the second layer has a thickness of 0.2 ⁇ m or more, it is advantageous in suppressing an increase in battery temperature in the event of an abnormality.
  • the first layer and the second layer has a thickness of 10 ⁇ m or less, it is advantageous in terms of the electrical characteristics of the battery.
  • the heat-resistant layer contains the first particles, it is possible to particularly suppress the temperature rise of the battery in the event of an abnormality.
  • the mechanism is not clear at present.
  • One possibility is that the first particles react with the lithium metal of the negative electrode when the battery temperature rises abnormally, reducing the reactivity of the surface of the lithium metal.
  • a preferable example of the separator may satisfy the following condition (K1) and further satisfy the following conditions (K2) and/or (K3). Excessive temperature rise of the electrode group can be particularly suppressed by satisfying the following conditions.
  • the spacer contains at least one resin selected from the group consisting of polyvinylidene fluoride, acrylonitrile-acrylate copolymer, and polyimide.
  • the heat-resistant layer contains at least one resin selected from the group consisting of wholly aromatic polyamide, polyvinylidene fluoride, and N-vinylacetamide. In that case, the heat-resistant layer preferably contains phosphate particles.
  • the base material contains polyolefin (polyethylene, polypropylene, etc.) as a main component (content: 50% by mass or more).
  • the method for producing the separator is not particularly limited, and the separator may be produced by the following method. First, a base material is prepared. A commercially available substrate may be used. Next, a heat-resistant layer is formed on the substrate.
  • the method of forming the heat-resistant layer is not particularly limited, and may be formed by the following method. First, a slurry (or coating liquid) is formed by mixing components of the heat-resistant layer and a liquid component (dispersion medium). Next, the slurry (or coating liquid) is applied to a substrate to form a coating film, and then the coating film is dried. Thus, a heat-resistant layer can be formed.
  • a slurry or coating liquid
  • the slurry (or coating liquid) is applied to a substrate to form a coating film, and then the coating film is dried.
  • a heat-resistant layer can be formed.
  • each layer may be formed by the method described above.
  • each step in forming the heat-resistant layer there is no particular limitation on each step in forming the heat-resistant layer, 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.
  • drying may be performed by a known method such as drying by heating or natural drying.
  • the spacer is formed on the heat-resistant layer or base material.
  • a method for forming the spacer is not particularly limited, and the spacer may be formed by the following method. First, a slurry or coating solution is prepared by mixing spacer components and liquid components. Next, the slurry or the coating liquid is applied to the portions where the spacers are to be formed, and then dried. Spacers can be formed in this way. Examples of liquid components include N-methyl-2-pyrrolidone and the like. Application of the slurry or coating liquid may be performed using a dispenser or the like, or may be performed using a known printing method such as gravure printing, inkjet printing, or screen printing. Moreover, drying may be performed by a known method such as drying by heating or natural drying. A separator is obtained as described above.
  • each component of the lithium secondary battery (L) will be specifically described below. Note that the constituent elements described below are examples, and the constituent elements of the lithium secondary battery (L) of the present embodiment are not limited to the following constituent elements. You may use a well-known component for components other than the part characteristic of this embodiment. Since the separator has been described above, redundant description will be omitted.
  • the negative electrode includes a negative electrode current collector.
  • lithium metal is deposited on the negative electrode current collector by charging. More specifically, lithium ions contained in the non-aqueous electrolyte receive electrons on the negative electrode current collector during charging to become lithium metal, which is deposited on the negative electrode current collector. Lithium metal deposited on the negative electrode current collector dissolves as lithium ions in the non-aqueous electrolyte due to discharge.
  • the lithium ions contained in the non-aqueous electrolyte may be derived from the lithium salt added to the non-aqueous electrolyte, or may be supplied from the positive electrode active material during charging. There may be.
  • a conductive sheet can be used for the negative electrode current collector.
  • a strip-shaped conductive sheet is used.
  • Examples of conductive sheets include conductive films, metal foils, and the like.
  • the surface of the conductive sheet may be smooth. This facilitates uniform deposition of lithium metal derived from the positive electrode 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 metallic material such as a metal, an alloy, or the like.
  • the conductive material is preferably a material that does not react with lithium. More specifically, materials that form neither alloys nor intermetallic compounds with lithium are preferred.
  • Such conductive materials include, for example, copper (Cu), nickel (Ni), iron (Fe), alloys containing these metal elements, or graphite in which the basal plane is preferentially exposed.
  • alloys include copper alloys and stainless steel (SUS). Copper and/or copper alloys are preferred because of their 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 mixture layer (not shown) may be formed on the surface of the negative electrode current collector.
  • the negative electrode mixture layer is formed, for example, by applying a paste containing a negative electrode active material such as graphite to at least part of the surface of the negative electrode current collector.
  • the thickness of the negative electrode mixture layer is set 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-like lithium metal or lithium alloy placed on the negative electrode current collector. That is, the negative electrode current collector may be provided in advance with a base layer containing lithium metal (lithium metal or lithium alloy layer). Lithium alloys may contain elements other than lithium, such as aluminum, magnesium, indium, and zinc. By providing the underlying layer in advance and depositing lithium metal thereon during charging, dendrite-like deposition can be more effectively suppressed.
  • the thickness of the underlayer 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 mixture layer supported by the positive electrode current collector.
  • the positive electrode mixture layer includes, for example, a positive electrode active material, a conductive material, and a binder.
  • the positive electrode mixture layer may be formed only on 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 mixture slurry containing a positive electrode active material, a conductive material, and a binder on both sides of a positive electrode current collector, drying the coating film, and then rolling.
  • a positive electrode active material is a material that absorbs and releases lithium ions.
  • positive electrode active materials include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanions, and transition metal sulfides. Among them, lithium-containing transition metal oxides are preferable in terms of low production cost and high average discharge voltage.
  • the transition metal elements contained in the lithium-containing transition metal oxide include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, W, and the like.
  • the lithium-containing transition metal oxide may contain one or more transition metal elements.
  • the transition metal elements may be Co, Ni and/or Mn.
  • the lithium-containing transition metal oxide may contain one or more main group elements as needed. Typical elements include Mg, Al, Ca, Zn, Ga, Ge, Sn, Sb, Pb, and Bi. A 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 optionally containing Al, and having a layered structure and a rock salt type crystal structure are highly This is preferable in terms of obtaining capacity.
  • the molar ratio of the total amount mLi of lithium possessed by the positive electrode and the negative electrode to the amount mM of the metal M other than lithium possessed by the positive electrode: mLi/mM is set to, for example, 1.1 or less.
  • the conductive material is, for example, a carbon material.
  • carbon materials include carbon black, acetylene black, ketjen black, carbon nanotubes, and graphite.
  • binders include fluorine resins, polyacrylonitrile, polyimide resins, acrylic resins, polyolefin resins, and rubber-like polymers.
  • fluororesins include polytetrafluoroethylene and polyvinylidene fluoride.
  • the positive electrode current collector may be a conductive sheet.
  • a foil, a film, or the like is used as the conductive sheet.
  • a carbon material may be applied to the surface of the positive electrode current collector.
  • Examples of materials for 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, or the like.
  • 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 liquid or gel.
  • 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 the non-aqueous solvent.
  • a gel-like non-aqueous electrolyte contains a lithium salt and a matrix polymer, or a lithium salt, a non-aqueous solvent and a matrix polymer.
  • the matrix polymer for example, a polymer material that gels by absorbing a non-aqueous solvent is used. Examples of polymer materials include fluorine resins, acrylic resins, polyether resins, and the like.
  • lithium salt or anion known ones used for 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 ⁇ , anions of imides, and anions of oxalate complexes.
  • the anion of the oxalate complex may contain boron and/or phosphorus.
  • the anion of the oxalate complex includes bisoxalate borate anion, 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 these anions singly or in combination of two or more.
  • the non-aqueous electrolyte preferably contains at least an anion of an oxalate complex. Due to the interaction between the anion of the oxalate complex and lithium, the lithium metal is easily precipitated uniformly in the form of fine particles. Therefore, it becomes easier to suppress local deposition of lithium metal. You may combine the anion of an oxalate complex with another anion. Other anions may be PF 6 - and/or imide class anions.
  • the non-aqueous electrolyte may contain LiBF 2 (C 2 O 4 ) (lithium difluorooxalatoborate) as a solute (lithium salt).
  • non-aqueous solvents examples include esters, ethers, nitriles, amides, and halogen-substituted products thereof.
  • the non-aqueous electrolyte may contain one of these non-aqueous solvents, or two or more of them. Fluoride etc. are mentioned as a halogen substitution body.
  • esters include carbonic acid esters and carboxylic acid esters.
  • Cyclic carbonates include ethylene carbonate, propylene carbonate, fluoroethylene carbonate (FEC), and the like.
  • Chain carbonic acid esters include dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate and the like.
  • Cyclic carboxylic acid esters include ⁇ -butyrolactone, ⁇ -valerolactone and the like. Examples of chain carboxylic acid esters include ethyl acetate, methyl propionate, and methyl fluoropropionate.
  • Ethers include cyclic ethers and chain ethers.
  • Cyclic ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran and the like.
  • Chain ethers 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 non-aqueous electrolyte is, for example, 0.5 mol/L or more and 3.5 mol/L or less.
  • the anion concentration 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 non-aqueous electrolyte may be 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. Formation of the film derived from the additive on the negative electrode facilitates suppression of the formation of dendrites. Examples of such additives include vinylene carbonate, FEC, vinyl ethyl carbonate (VEC), and the like.
  • lithium secondary battery (L) of the present embodiment will be specifically described below with reference to the drawings.
  • the components described above can be applied to the components of the example lithium secondary battery described below.
  • the components of the example described below can be modified based on the above description.
  • the matters described below may be applied to the above embodiments.
  • components that are not essential for the lithium secondary battery according to the present disclosure may be omitted. It should be noted that in the following figures, the scale of the constituent elements has been changed to facilitate understanding.
  • FIG. 1 is a longitudinal sectional view schematically showing an example of a lithium secondary battery according to Embodiment 1.
  • FIG. A cylindrical lithium secondary battery 10 shown in FIG. 1 includes a cylindrical battery case, and 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 which is a bottomed cylindrical metal container, and a sealing member 16 which seals the opening of the case body 15 .
  • a gasket 27 is arranged between the case main body 15 and the sealing member 16 . 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 in the case main body 15 .
  • 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 stepped portion 21 may be annularly formed on the side wall of the case body 15 along the circumferential direction of the case body 15 .
  • the sealing member 16 is supported by the surface of the stepped portion 21 on the opening side.
  • 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. In the sealing member 16, these members are laminated in this order.
  • the sealing member 16 is attached to the opening of the case body 15 so that the cap 26 is positioned outside the case body 15 and the filter 22 is positioned inside the case body 15 .
  • Each of the members constituting the sealing member 16 is, for example, disk-shaped or ring-shaped.
  • 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 edge portions.
  • 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 ventilation hole (not shown) is formed in the lower valve body 23 . Therefore, when the internal pressure of the battery case rises due to abnormal heat generation or the like, the upper valve body 25 swells toward the cap 26 side and separates from the lower valve body 23 . Thereby, 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 is broken, and gas is discharged from an opening (not shown) formed in the cap 26 .
  • FIG. 2 is an enlarged view of part of the electrode group 14.
  • FIG. FIG. 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 has a positive electrode 11 , a negative electrode 12 and a separator 50 .
  • the positive electrode 11, the negative electrode 12, and the separator 50 are all belt-shaped.
  • the strip-shaped positive electrode 11 and negative electrode 12 are spirally wound with a separator 50 interposed therebetween such that the width direction of the strip-shaped positive electrode 11 and negative electrode 12 is parallel to the winding axis.
  • the positive electrode 11 and the negative electrode 12 are alternately laminated in the radial direction of the electrode group 14 with the separator 50 interposed therebetween. . That is, the longitudinal direction of each electrode is the winding direction, and the width direction of each electrode is the axial direction.
  • the positive electrode 11 includes a positive electrode current collector 11a and a positive electrode mixture layer 11b.
  • the positive current collector 11a is electrically connected via a positive lead 19 to a cap 26 functioning as a positive terminal.
  • a negative electrode negative electrode current collector
  • the negative electrode 12 is electrically connected via a negative lead 20 to a case body 15 functioning as a negative terminal.
  • the separator 50 includes a base material 51, a heat-resistant layer 52, and spacers 53.
  • the heat-resistant layer 52 is formed on the main surface 51b of the two main surfaces 51a and 51b of the base material 51 on the negative electrode 12 side.
  • the heat-resistant layer 52 is preferably formed so as to cover at least a region sandwiched between the positive electrode 11 and the negative electrode 12 on at least one main surface of the base material 51 .
  • the heat-resistant layer 52 may be formed so as to entirely cover one side of the substrate 51 , or may be formed so as to entirely cover both surfaces of the substrate 51 .
  • a spacer 53 is formed on the heat-resistant layer 52 .
  • spacer 53 is in contact with negative electrode 12 .
  • a space 14 s is formed by the spacer 53 on the surface of the negative electrode 12 (between the heat-resistant layer 52 and the negative electrode 12 ).
  • FIG. 2 shows the height h of the spacer 53. As shown in FIG.
  • lithium metal is deposited on the negative electrode 12 during charging. Since spaces 14s exist on the surface of the negative electrode 12, lithium metal can be deposited in the spaces 14s. Since the lithium metal deposited on the surface of the negative electrode 12 is accommodated in the space 14s, the volume change of the electrode group 14 due to the deposition of the lithium metal is reduced, and the cycle characteristics are improved. The deposited lithium metal dissolves in the non-aqueous electrolyte during discharge.
  • the spacer 53 When the spacer 53 is permeable to lithium ions, the lithium ions pass through the spacer 53 during charging. Lithium ions that have passed through the spacer 53 are deposited between the spacer 53 and the negative electrode 12 . As a result, the thickness of the electrode group 14 in the stacking direction (radial direction of the wound electrode group) increases. Therefore, the spacers 53 are preferably impermeable to lithium ions.
  • 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 spacer 53 is composed of a linear protrusion 53a.
  • the linear protrusions 53a are arranged in a mesh pattern, and more specifically, are uniformly formed in a honeycomb pattern.
  • a honeycomb pattern is a pattern in which a plurality of hexagons are arranged so as to share sides with each other.
  • a region in which the linear convex portion 53a is not formed constitutes a space 14s.
  • FIG. 4 shows the width W of the linear protrusion 53a.
  • FIG. 5 Another example of the planar shape of the spacer 53 is shown in FIG.
  • the spacer 53 of FIG. 5 includes a plurality of linear projections 53a spaced apart from each other. A gap P exists between the linear protrusions 53a. A region in which the linear convex portion 53a is not formed constitutes a space 14s.
  • Embodiment 1 a cylindrical lithium secondary battery with a wound electrode group has been described.
  • the lithium secondary battery of this embodiment is not limited to the form of Embodiment 1, and can be applied to other forms.
  • the shape of the lithium secondary battery can be appropriately selected from various shapes such as cylindrical, coin-shaped, rectangular, sheet-shaped, flat-shaped, etc., according to its use.
  • the form of the electrode group is also not particularly limited, and may be a laminated type.
  • NMP N-methyl-2-pyrrolidone
  • the resulting positive electrode mixture slurry was applied to both sides of a strip-shaped Al foil (positive electrode current collector), and then dried to form a coating film of the positive electrode mixture.
  • the coating film of the positive electrode mixture was rolled using a roller.
  • the obtained laminate of the positive electrode current collector and the positive electrode mixture was cut into a predetermined electrode size to prepare a positive electrode having positive electrode mixture layers on both sides of the positive electrode current collector.
  • a band-shaped porous polyethylene film (average thickness: 10 ⁇ m) was prepared as a base material.
  • a heat-resistant layer (having an average thickness of 2 ⁇ m) was formed on one side of the substrate. The heat-resistant layer was formed by forming the second layer and the first layer in this order on the substrate.
  • 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. The mixture was heated to about 80° C. to completely dissolve the calcium chloride. Then, this solution was returned to room temperature, and 2200 g of the solution was sampled, and then 0.6 mol of paraphenylenediamine (PPD) was added and dissolved completely. While this solution was kept at about 20° C., 0.6 mol of terephthaloyl dichloride (TPC) was added little by little. The resulting solution was aged at about 20° C. for 1 hour to obtain a polymerization solution.
  • NMP N-methyl-2-pyrrolidone
  • PPD paraphenylenediamine
  • TPC terephthaloyl dichloride
  • the coating liquid was applied onto the substrate by a slot die method to form a coating film.
  • the base material on which the coating film was formed was left in an atmosphere of 25° C. and 70% relative humidity 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 poly-N-vinylacetamide (PNVA) were mixed at a mass ratio of 100:8 to obtain a mixture. Lithium phosphate particles having a volume-based median diameter of 0.19 ⁇ m were used. Water (ion-exchanged water) was added to the resulting mixture and stirred to prepare a slurry (coating liquid) having a solid content concentration of 12% by mass. The slurry was then coated onto the second layer by microgravure coating to form a coating. Next, the coating film was dried in a drying oven attached to the coating machine. Thus, a first layer was formed. Thus, a heat-resistant layer was formed.
  • Li 3 PO 4 lithium phosphate
  • PNVA poly-N-vinylacetamide
  • a coating liquid containing polyvinylidene fluoride and alumina particles (inorganic filler) was discharged onto the heat-resistant layer in the pattern shown in FIG. After that, the coating liquid was vacuum-dried. Thus, the honeycomb-shaped non-porous spacer shown in FIG. 3 was formed.
  • the mesh shape of the spacer was a regular hexagon.
  • the height of the linear projections was set to 30 ⁇ m (average height: 30 ⁇ m).
  • the distance between the two opposing sides was about 2.25 mm.
  • the width of the linear protrusion was 0.25 mm.
  • the spacer area S1 was 21% of the separator area S0.
  • LiPF 6 and LiBF 2 (C 2 O 4 ) were dissolved in the resulting mixed solvent so that the concentration was 1 mol/L and the concentration of LiBF 2 (C 2 O 4 ) was 0.1 mol/L, thereby forming a liquid non-aqueous electrolyte. was prepared.
  • the obtained electrode group was housed in a bag-shaped exterior body formed of a laminate sheet having an Al layer, and after the non-aqueous electrolyte was injected into the exterior body containing the electrode group, the exterior body was sealed. Thus, a lithium secondary battery A1 was produced.
  • Battery A2 was produced in the same manner and under the same conditions as the method for producing battery A1, except that the spacer pattern was changed. In Battery A2, the spacers were formed in a striped pattern instead of a honeycomb pattern. The height and width of the linear protrusions and the ratio S1/S0 between the area S1 and the area S0 were the same as those of the separator of the battery A1.
  • Battery C1 A battery C1 was produced in the same manner and under the same conditions as the method for producing the battery A1, except that the positive electrode and the separator were changed.
  • separator of battery C the same separator as that of battery A1 was used except that it did not contain a spacer. That is, a separator composed of a base material and a heat-resistant layer was used as the separator of battery C1.
  • the positive electrode of battery C1 the positive electrode in which spacers were formed on both sides of the positive electrode used in battery A1 was used.
  • the spacers were formed by the same method and pattern as the method for forming the spacers of the separator of Battery A1.
  • a battery C1 was produced using this positive electrode and the above separator.
  • Battery C2 A battery C2 was produced in the same manner and under the same conditions as the method for producing the battery A1, except that the negative electrode and the separator were changed.
  • a negative electrode obtained by forming spacers on both sides of the negative electrode (negative electrode current collector) used in battery A1 was used.
  • the spacers were formed by the same method and pattern as the method for forming the spacers of the separator of battery A1.
  • a battery C2 was produced using this negative electrode and the above separator.
  • Battery C3 A battery C3 was produced in the same manner and under the same conditions as the method for producing the battery A1, except that the separator was changed.
  • the same separator as that of battery A1 was used, except that it did not include a heat-resistant layer. That is, in the production of the separator of battery C3, spacers were formed on the substrate. The spacers were formed by the same method and pattern as the method for forming the spacers of the separator of battery A1. A battery C3 was produced using this separator.
  • Battery C4 A battery C3 was produced in the same manner and under the same conditions as the method for producing the battery A1, except that the separator was changed.
  • the separator of battery C4 the same separator as that of battery A1 was used, except that the height of the spacer was changed.
  • the height of the separator of battery C4 was set to 10 ⁇ m (average height: 10 ⁇ m).
  • the spacers were formed by the same method and pattern as the method for forming the spacers of the separator of battery A1.
  • a battery C4 was produced using this separator.
  • the separator was placed so that the spacer faced the negative electrode.
  • Battery C5 A battery C4 was produced in the same manner and under the same conditions as the method for producing the battery A1, except that the separator was changed.
  • the separator of battery C5 the same separator as that of battery A1 was used except that no spacer was formed. A battery C5 was produced using this separator. The separator was arranged so that the heat-resistant layer faced the negative electrode.
  • a plurality of batteries produced as described above were evaluated by the following methods.
  • (Charging and discharging test) A charge/discharge test was performed on each of the obtained batteries. In the charge/discharge test, the battery was charged under the following conditions in a constant temperature bath at 25° C., then rested for 20 minutes, and then discharged under the following conditions.
  • Constant current charging is performed at a current of 2.15 mA per unit area (square centimeter) of the electrode until the battery voltage reaches 4.1 V, and then at a voltage of 4.1 V, the current value per unit area of the electrode is 0.0. Constant voltage charging was performed until the battery reached 54 mA.
  • the thickness was measured at five arbitrary points in the laminate, and the arithmetic mean 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 substrates and the thickness of the two heat-resistant layers from this average thickness was obtained.
  • the ratio (%) of the average thickness X at the second cycle to the average thickness X before charge/discharge was taken as the expansion coefficient of the electrode group. That is, the expansion rate (%) of the electrode group is the ratio of the average thickness X at the second cycle when the average thickness X before charge/discharge is 100%.
  • Table 1 shows some of the battery manufacturing conditions and evaluation results.
  • the initial charge capacity is expressed as a relative value when the initial charge capacity of the battery C1 is set to 100.
  • the gas generation rate is expressed as a relative value when the gas generation rate of battery C3 is set to 100.
  • a high initial charge capacity is preferred.
  • It is preferable that the expansion coefficient of the electrode group is low. A low gassing rate is preferred.
  • Batteries A1 and A2 are batteries according to the present disclosure, and batteries C1 to C5 are batteries of comparative examples. Batteries A1 and A2 had a high initial charge capacity, a low expansion rate of the electrode assembly, and a low gas generation rate. On the other hand, batteries C1 and C2 in which a spacer was formed on the positive electrode or on the negative electrode and battery C3 in which a separator without a heat-resistant layer was used exhibited a high gas generation rate. Battery C4, in which the average spacer height was lower than the sum of the thicknesses of the base material and the heat-resistant layer, and battery C5, in which a spacer-free separator was used, showed an extremely high expansion rate of the electrode group. Battery A1 using a separator with a honeycomb spacer pattern had a lower expansion rate of the electrode group and a lower gas generation rate than battery A2 using a separator with a stripe spacer pattern.
  • the present disclosure can be applied 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. While the invention has been described in terms of presently preferred embodiments, such disclosure is not to be construed in a limiting sense. Various alterations and modifications will no doubt become apparent to those skilled in the art to which the invention pertains after reading the above disclosure. Therefore, the appended claims are to be interpreted as covering all variations and modifications without departing from the true spirit and scope of the invention.

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PCT/JP2022/035300 2021-09-30 2022-09-22 リチウム二次電池 Ceased WO2023054149A1 (ja)

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JP2023551404A JPWO2023054149A1 (https=) 2021-09-30 2022-09-22
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EP4411914A4 (en) 2025-05-21

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