WO2019225078A1 - Couche d'isolation, feuille de cellule de batterie et batterie secondaire - Google Patents

Couche d'isolation, feuille de cellule de batterie et batterie secondaire Download PDF

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Publication number
WO2019225078A1
WO2019225078A1 PCT/JP2019/005556 JP2019005556W WO2019225078A1 WO 2019225078 A1 WO2019225078 A1 WO 2019225078A1 JP 2019005556 W JP2019005556 W JP 2019005556W WO 2019225078 A1 WO2019225078 A1 WO 2019225078A1
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self
layer
insulating layer
healing
positive electrode
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PCT/JP2019/005556
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English (en)
Japanese (ja)
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西村　悦子
誠之 廣岡
栄二 關
阿部　誠
祐介 加賀
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株式会社日立製作所
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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
    • 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 invention relates to an insulating layer, a battery cell sheet, and a secondary battery.
  • Patent Document 1 discloses the following contents as a separator having excellent heat resistance. According to at least certain embodiments, new or improved water-soluble or aqueous polyvinylidene fluoride (PVDF) or polyvinylidene difluoride (PVDF) homopolymer or hexafluoropropylene (HFP or [-CF (CF 3 ) -CF 2- ]), copolymers of PVDF with ethylene chloride trifluoride (CTFE), vinylidene fluoride (VF2-HFP), tetrafluoroethylene (TFE), and / or the like, blends thereof .
  • PVDF polyvinylidene fluoride
  • PVDF polyvinylidene difluoride
  • HFP hexafluoropropylene
  • CTFE ethylene chloride trifluoride
  • VF2-HFP vinylidene fluoride
  • TFE tetrafluoroethylene
  • Patent Document 1 when the temperature of the portion short-circuited in the secondary battery instantaneously and locally exceeds the melting point of the separator material, the separator is melted by heat, the positive electrode and the negative electrode are in direct contact, and the short-circuit region is There is a possibility that the discharge capacity of the secondary battery is reduced.
  • An object of this invention is to improve the discharge capacity of a secondary battery.
  • the separator having a readily soluble polymer, the self-healing layer having self-healing layer particles and a self-healing layer binder, and a readily soluble polymer calculated from a Hansen solubility parameter;
  • An insulating layer whose relative energy difference from the self-healing layer binder is less than 1 MPa 0.5 .
  • the discharge capacity of the secondary battery can be improved by the present invention. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.
  • Sectional drawing of a secondary battery Sectional drawing of an electrode body. Relative energy difference calculated from Hansen solubility parameter. The structure and result of an Example and a comparative example.
  • ⁇ Described in this specification is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
  • the upper limit value or lower limit value described in one numerical range may be replaced with the upper limit value or lower limit value described in another stepwise manner.
  • the upper limit value or lower limit value of the numerical ranges described in the present specification may be replaced with the values shown in the examples.
  • a lithium ion secondary battery is an electrochemical device that can store or use electrical energy by occluding / releasing lithium ions to and from an electrode in an electrolyte. This is called by another name of a lithium ion battery, a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery, and any battery is a subject of the present invention.
  • the technical idea of the present invention can also be applied to sodium ion secondary batteries, magnesium ion secondary batteries, calcium ion secondary batteries, zinc secondary batteries, aluminum ion secondary batteries, and the like.
  • FIG. 1 is a cross-sectional view of a secondary battery according to an embodiment of the present invention.
  • FIG. 1 shows a stacked secondary battery.
  • the secondary battery 1000 includes a positive electrode 100, a negative electrode 200, an outer package 500, and an insulating layer 300.
  • the outer package 500 houses the insulating layer 300, the positive electrode 100, and the negative electrode 200.
  • the material of the outer package 500 can be selected from materials that are corrosion resistant to non-aqueous electrolytes, such as aluminum, stainless steel, and nickel-plated steel.
  • the present invention can also be applied to a wound secondary battery.
  • an electrode body 400 composed of a positive electrode 100, an insulating layer 300, and a negative electrode 200 is laminated.
  • the positive electrode 100 or the negative electrode 200 may be referred to as an electrode or a secondary battery electrode.
  • the positive electrode 100, the negative electrode 200, or the insulating layer 300 may be referred to as a secondary battery sheet.
  • a structure in which the insulating layer 300 and the positive electrode 100 or the negative electrode 200 are integrated is sometimes referred to as a battery cell sheet.
  • the positive electrode 100 includes a positive electrode current collector 120 and a positive electrode mixture layer 110.
  • a positive electrode mixture layer 110 is formed on both surfaces of the positive electrode current collector 120.
  • the negative electrode 200 includes a negative electrode current collector 220 and a negative electrode mixture layer 210. Negative electrode mixture layers 210 are formed on both surfaces of the negative electrode current collector 220.
  • the positive electrode mixture layer 110 or the negative electrode mixture layer 210 may be referred to as an electrode mixture layer, and the positive electrode current collector 120 or the negative electrode current collector 220 may be referred to as an electrode current collector.
  • the positive electrode current collector 120 has a positive electrode tab portion 130.
  • the negative electrode current collector 220 has a negative electrode tab portion 230.
  • the positive electrode tab portion 130 or the negative electrode tab portion 230 may be referred to as an electrode tab portion.
  • An electrode mixture layer is not formed on the electrode tab portion. However, an electrode mixture layer may be formed on the electrode tab portion as long as the performance of the secondary battery 1000 is not adversely affected.
  • the positive electrode tab portion 130 and the negative electrode tab portion 230 protrude to the outside of the outer package 500, and the plurality of protruding positive electrode tab portions 130 and the plurality of negative electrode tab portions 230 are bonded together by, for example, ultrasonic bonding. Thus, a parallel connection is formed in the secondary battery 1000.
  • the present invention can also be applied to a bipolar secondary battery in which an electrical series connection is configured in the secondary battery 1000.
  • the positive electrode mixture layer 110 includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.
  • the negative electrode mixture layer 210 includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.
  • the non-aqueous electrolyte positive electrode active material or negative electrode active material may be referred to as an electrode active material, the positive electrode conductive agent or negative electrode conductive agent as an electrode conductive agent, and the positive electrode binder or the negative electrode binder as an electrode binder.
  • the electrode conductive agent improves the conductivity of the electrode mixture layer.
  • Examples of the electrode conductive agent include, but are not limited to, ketjen black, acetylene black, and graphite. These materials may be used alone or in combination.
  • the electrode conductive agent may have only these materials, or may have other materials.
  • the electrode binder binds an electrode active material or an electrode conductive agent in the electrode.
  • the electrode binder include, but are not limited to, styrene-butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride (PVDF), and polyvinylidene fluoride-hexafluoropropylene copolymer (P (VdF-HFP)). Absent. These materials may be used alone or in combination.
  • the electrode binder may include only these materials, and may further include other materials.
  • ⁇ Positive electrode active material> In the positive electrode active material exhibiting a noble potential, lithium ions are desorbed in the charging process, and lithium ions desorbed from the negative electrode active material are inserted in the discharging process.
  • As the positive electrode active material a lithium composite oxide having a transition metal is desirable.
  • part of oxygen in these materials may be substituted with other elements such as fluorine.
  • chalcogenides such as sulfur, TiS 2 , MoS 2 , Mo 6 S 8 , TiSe 2 , vanadium oxides such as V 2 O 5 , halides such as FeF 3 , Fe (MoO 4 ) 3 constituting polyanions, Examples include, but are not limited to, quinone organic crystals such as Fe 2 (SO 4 ) 3 and Li 3 Fe 2 (PO 4 ) 3 .
  • the element ratio may deviate from the above stoichiometric composition.
  • the positive electrode active material may include only these materials, and may further include other materials.
  • the positive electrode current collector 120 may include only these materials, or may include other materials.
  • ⁇ Negative electrode active material> In the negative electrode active material exhibiting a base potential, lithium ions are desorbed in the discharging process, and lithium ions desorbed from the positive electrode active material in the positive electrode mixture layer 110 are inserted in the charging process.
  • a negative electrode active material carbon-based materials (graphite, graphitizable carbon materials, amorphous carbon materials, organic crystals, activated carbon, etc.), conductive polymer materials (polyacene, polyparaphenylene, polyaniline, polyacetylene, etc.), lithium composites Oxides (lithium titanate: Li 4 Ti 5 O 12 and Li 2 TiO 4 etc.), metal lithium, metals alloyed with lithium (having at least one kind of aluminum, silicon, tin, etc.) and oxides thereof
  • the negative electrode active material may have only these materials, and may further include other materials.
  • the negative electrode current collector may have only these materials, or may have other materials.
  • An electrode mixture layer is prepared by adhering an electrode slurry in which an electrode active material, an electrode conductive agent, an electrode binder, and an organic solvent are mixed to an electrode current collector by a coating method such as a doctor blade method, a dipping method, or a spray method. Is done. Then, in order to remove an organic solvent, an electrode mixture layer is dried, and an electrode is produced by pressure-molding an electrode mixture layer with a roll press.
  • the nonaqueous electrolyte is injected into the secondary battery 1000 from the vacant side or the injection hole of the outer package 500, and the pores of the electrode mixture layer are filled with the nonaqueous electrolyte. You may let them. This eliminates the need for supported particles contained in the semi-solid electrolyte, and the particles such as electrode active material and electrode conductive agent in the electrode mixture layer function as supported particles, and these particles hold the non-aqueous electrolyte. To do.
  • a slurry in which a non-aqueous electrolyte, an electrode active material, an electrode conductive agent, and an electrode binder are mixed is prepared, and the prepared slurry is collected into an electrode current collector.
  • the thickness of the electrode mixture layer is desirably equal to or greater than the average particle diameter of the electrode active material. If the thickness of the electrode mixture layer is small, the electron conductivity between adjacent electrode active materials may deteriorate. If the electrode active material powder has coarse particles having an average particle size equal to or greater than the thickness of the electrode mixture layer, the coarse particles are removed in advance by sieving classification, wind flow classification, etc., and particles having a thickness of the electrode mixture layer or less. Is desirable.
  • FIG. 2 is a cross-sectional view of the electrode body.
  • the insulating layer 300 has a self-healing layer 310 and a separator 320.
  • the self-healing layer 310 is formed on the electrode, and the electrode and the self-healing layer 310 are integrated.
  • the self-healing layer 310 serves as a medium for transmitting ions between the positive electrode 100 (the positive electrode mixture layer 110 in FIG. 2) and the negative electrode 200.
  • the self-healing layer 310 also functions as an electronic insulator and prevents a short circuit between the positive electrode 100 and the negative electrode 200.
  • the self-healing layer 310 may be formed on both surfaces of the positive electrode 100 and the negative electrode 200 as shown in FIG.
  • the self-healing layer 310 may be formed on the surface of the separator 320, and the separator 320 and the self-healing layer 310 may be integrated.
  • the thickness of the self-healing layer 310 is preferably 5 to 50 ⁇ m, 10 to 30 ⁇ m, and 15 to 25 ⁇ m. If the self-healing layer 310 is too thin, it is difficult to obtain electrical insulation between the positive electrode 100 and the negative electrode 200. If the thickness of the self-healing layer 310 is too large, the diffusion resistance of lithium ions increases, and the performance of the secondary battery 1000 may deteriorate.
  • the self-healing layer 310 has a self-healing layer binder and self-healing layer particles.
  • the self-healing layer binder is desirably a polymer that melts at a temperature lower than the thermal runaway temperature (300 ° C.) of the secondary battery 1000.
  • P (VdF-HFP) is suitable as the self-healing layer binder.
  • P (VdF-HFP) retains the electrolyte and allows Li ions to permeate.
  • P (VdF-HFP) is softened and melted by heat when a short circuit occurs inside the secondary battery 1000, covers the short circuit part of the secondary battery 1000, and is mixed with the self-healing layer particles 310. Play.
  • the function of regenerating the self-healing layer 310 is called self-healing.
  • oxide particles as self-healing layer particles.
  • oxide particles SiO 2 , Al 2 O 3 , AlOOH, ZrO 2 , CeO, MgO, BaTiO 3 or the like can be applied. These materials may be used alone or in combination.
  • the self-healing layer particles may include only these materials, and may further include other materials.
  • SiO 2 , Al 2 O 3 , and AlOOH have excellent affinity with non-aqueous electrolytes. Therefore, the non-aqueous electrolyte quickly penetrates into the self-healing layer 310 having these, and the diffusion resistance of Li ions Decrease.
  • the composition of the oxide particles is desirably 10 to 98% by mass or less with respect to the mass of the self-healing layer 310. If the content of the oxide particles is small, the insulating property of the self-healing layer 310 may be deteriorated. When the content of the oxide particles is large, the composition of the self-healing layer binder is decreased, and the mechanical strength of the self-healing layer 310 may be reduced.
  • the self-healing layer 310 may be mixed or compounded with a readily soluble polymer in addition to P (VdF-HFP).
  • the easily soluble polymer is excellent in solubility with P (VdF-HFP), and it is desirable that the easily soluble polymer becomes a uniform polymer when mixed with P (VdF-HFP).
  • an acrylic resin such as PVdF or polymethyl methacrylate (PMMA) can be applied.
  • the easily soluble polymer may contain only these materials, and may further contain other materials.
  • FIG. 3 shows the relative energy difference RED calculated based on the Hansen solubility parameters (dD, dP, dH). It suggests that P (VdF-HFP) and soluble polymer are easy to dissolve when RED is smaller than 1 MPa 0.5 .
  • the readily soluble polymers having a RED of less than 1 based on P (VdF-HFP) were cellulose, PMMA, and PVDF. These polymers can be mixed uniformly with P (VdF-HFP).
  • PMMA Li ions coordinate to many polar functional groups (carboxyl groups) in the molecule, and Li ions easily diffuse along the polymer chain. Can be increased.
  • poorly soluble polymers such as polyethylene terephthalate (PET) and polyethylene (PE) have a RED of more than 1 based on P (VdF-HFP).
  • the separator 320 preferably has an easily soluble polymer such as cellulose fiber or PMMA fiber in which the relative energy difference in FIG.
  • a secondary battery 1000 can be manufactured.
  • the affinity between polymers is important between the self-healing layer 310 and the separator 320, and it is desirable that the relative energy difference be less than one. If the relative energy difference is 0.8 or less, the two types of polymers begin to dissolve.
  • the weight ratio of the first polymer to the second polymer is one polymer, such as 1/19 to 1/4 or 4/1 to 19/1. It dissolves when its composition is large. Further, when the relative energy difference is 0.6 or less, the two kinds of polymers come to be dissolved in any mixed composition, which is more preferable.
  • the intermolecular force at the micro level works between the polymer (mainly containing P (VdF-HFP)) on the surface of the self-healing layer 310 and the polymer contained in the separator 320, and the self-healing layer 310 and the separator 320 adhere to each other. It is considered that the polymers are easily mixed by increasing the force. Therefore, the gap between self-healing layer 310 and separator 320 is reduced, the movement of lithium ions is promoted, and the performance of secondary battery 1000 is improved.
  • the short circuit between the positive electrode 100 and the negative electrode 200 can be prevented by making the separator 320 larger than the positive electrode 100 or the negative electrode 200.
  • the fiber diameter of the cellulose fibers is preferably 1 nm to 500 ⁇ m and 1 nm to 10 ⁇ m.
  • the fiber length of the cellulose fiber is preferably 1 to 500 ⁇ m.
  • the aspect ratio is preferably 10 to 10,000 and 100 to 10,000. If the fiber length of the cellulose fiber is too large, it may be difficult to produce a smooth self-healing layer 310.
  • the cellulose material may be a fiber derived from natural pulp, or cellulose, a modified cellulose (such as carboxymethyl cellulose (CMC) or hydroxypropyl cellulose (HPC)), cellulose acetate, ethyl cellulose, or the like. These materials may be used alone or in combination. Cellulose may have only these materials, and may also have other materials.
  • CMC carboxymethyl cellulose
  • HPC hydroxypropyl cellulose
  • the non-aqueous electrolyte is injected into the secondary battery 1000 from the vacant side or the liquid injection hole of the outer package 500, so that the non-aqueous electrolyte is not contained in the insulating layer 300. Filled with water electrolyte.
  • a semi-solid electrolyte layer may be used as the self-healing layer 310.
  • the semi-solid electrolyte layer has a semi-solid electrolyte binder and a semi-solid electrolyte.
  • the semi-solid electrolyte has supported particles and a non-aqueous electrolyte.
  • the semi-solid electrolyte has pores formed by aggregates of supported particles, and a non-aqueous electrolyte is held therein. By holding the non-aqueous electrolyte in the semi-solid electrolyte, the semi-solid electrolyte permeates lithium ions.
  • the nonaqueous electrolytic solution may be injected into the secondary battery 1000 from the vacant side or the liquid injection hole of the outer package 500.
  • a method for producing the semi-solid electrolyte layer a method of compressing a semi-solid electrolyte powder into a pellet shape with a molding die or the like, a method of adding and mixing a semi-solid electrolyte binder to the semi-solid electrolyte powder, and forming a sheet, There is a method of mixing a water electrolyte solution and supported particles at a predetermined ratio, then adding and mixing a semisolid electrolyte binder, and pressing to obtain a sheet.
  • a semi-solid electrolyte binder powder By adding and mixing a semi-solid electrolyte binder powder to the semi-solid electrolyte, a highly flexible sheet-like semi-solid electrolyte layer can be produced.
  • a semi-solid electrolyte layer may be produced by adding and mixing a solution of a binder in which a semi-solid electrolyte binder is dissolved in a dispersion solvent to the semi-solid electrolyte, and distilling off the dispersion solvent. You may produce a semi-solid electrolyte layer by apply
  • the supported particles are the same as the self-healing layer particles included in the self-healing layer 310.
  • a solid electrolyte may be used as the support particles.
  • the solid electrolyte include particles of an inorganic solid electrolyte such as an oxide solid electrolyte such as Li—La—Zr—O and a sulfide solid electrolyte such as Li 10 Ge 2 PS 12 .
  • the average primary particle size of the supported particles is preferably 1 nm to 10 ⁇ m. If the average particle size of the primary particles of the supported particles is large, the supported particles may not properly hold a sufficient amount of the non-aqueous electrolyte, and it may be difficult to form a semi-solid electrolyte. In addition, if the average particle size of the primary particles of the supported particles is small, the inter-surface force between the supported particles becomes large and the supported particles tend to aggregate with each other, which may make it difficult to form a semi-solid electrolyte.
  • the average particle size of the primary particles of the supported particles is more preferably 1 to 50 nm, and further preferably 1 to 10 nm.
  • the average particle size of the primary particles of the supported particles can be measured using a transmission electron microscope (TEM).
  • the non-aqueous electrolyte has a non-aqueous solvent.
  • the non-aqueous solvent has an organic solvent, an ionic liquid, or a mixture (complex) of an ether solvent and a solvated electrolyte salt exhibiting properties similar to those of the ionic liquid.
  • a non-volatile solvent such as an ionic liquid or an ether solvent
  • volatilization of the non-aqueous electrolyte from the semi-solid electrolyte layer can be suppressed.
  • An organic solvent, an ionic liquid, or an ether solvent may be referred to as a main solvent.
  • An ionic liquid is a compound that dissociates into a cation and an anion at room temperature, and maintains a liquid state.
  • the ionic liquid may be referred to as an ionic liquid, a low melting point molten salt or a room temperature molten salt.
  • the non-aqueous solvent is desirably low volatility, specifically, having a vapor pressure of 150 Pa or less at room temperature, from the viewpoint of stability in the air and heat resistance in the secondary battery, but is not limited thereto. Absent.
  • the content of the non-aqueous electrolyte in the semi-solid electrolyte layer is not particularly limited, but is preferably 40 to 90 vol%.
  • the content of the non-aqueous electrolyte is small, the interface resistance between the electrode and the semisolid electrolyte layer may increase.
  • content of a non-aqueous electrolyte is large, a non-aqueous electrolyte may leak from a semi-solid electrolyte layer.
  • the content of the non-aqueous electrolyte in the semi-solid electrolyte layer is preferably 50 to 80 vol%, more preferably 60 to 80 vol%.
  • a semi-solid electrolyte layer is formed by applying a mixture of a semi-solid electrolyte and a solution in which a semi-solid electrolyte binder is dissolved in a dispersion solvent on an electrode, the content of the non-aqueous electrolyte in the semi-solid electrolyte layer is 40-60 vol% is desirable.
  • the weight ratio of the main solvent in the non-aqueous electrolyte is not particularly limited, but the weight ratio of the main solvent in the total amount of the solvent in the non-aqueous electrolyte is 30 to 70 wt%, particularly from the viewpoint of battery stability and fast charge / discharge. It is desirable that the content be 40 to 60 wt%, and further 45 to 55 wt%.
  • Organic solvent As organic solvents, carbonates such as ethylene carbonate (EC), butylene carbonate (BC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ⁇ -butyrolactone (GBL) ), Formamide, dimethylformamide, trimethyl phosphate (TMP), triethyl phosphate (TEP), tris (2,2,2-trifluoroethyl) phosphite (TFP), dimethyl methylphosphonate (DMMP), etc. . These nonaqueous solvents may be used alone or in combination.
  • EC ethylene carbonate
  • BC butylene carbonate
  • PC propylene carbonate
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • MEC methyl ethyl carbonate
  • GBL ⁇ -butyrolactone
  • TMP trimethyl phosphate
  • TMP trimethyl phosphate
  • DMMP di
  • the ionic liquid or an ether solvent that exhibits similar properties to the ionic liquid has a low viscosity organic solvent.
  • the low-viscosity organic solvent lowers the viscosity of the nonaqueous electrolytic solution and improves the ionic conductivity. Since the internal resistance of the nonaqueous electrolytic solution is large, the internal resistance of the nonaqueous electrolytic solution can be lowered by adding a low viscosity organic solvent to increase the ionic conductivity of the nonaqueous electrolytic solution.
  • the low-viscosity organic solvent is desirably a solvent having a viscosity lower than 140 Pa ⁇ s at 25 ° C.
  • low viscosity organic solvent examples include, but are not limited to, PC, EC, TMP, TEP, TFP, GBL, DMMP and the like. These low-viscosity organic solvents may be used alone or in combination.
  • the ionic liquid is composed of a cation and an anion. Ionic liquids are classified into imidazolium, ammonium, pyrrolidinium, piperidinium, pyridinium, morpholinium, phosphonium, sulfonium, and the like depending on the cation species. Examples of the cation constituting the imidazolium-based ionic liquid include alkyl imidazolium cations such as 1-butyl-3-methylimidazorium (BMI).
  • BMI 1-butyl-3-methylimidazorium
  • Examples of the cation constituting the ammonium-based ionic liquid include, in addition to tetraamylammonium, alkylammonium cations such as N, N, N-trimethyl-N-propylammonium.
  • Examples of the cation constituting the pyrrolidinium-based ionic liquid include alkylpyrrolidinium cations such as N-methyl-N-propylpyrrolidinium (Py13) and 1-butyl-1-methylpyrrolidinium.
  • Examples of the cation constituting the piperidinium-based ionic liquid include alkylpiperidinium cations such as N-methyl-N-propylpiperidinium (PP13) and 1-butyl-1-methylpiperidinium.
  • Examples of the cation constituting the pyridinium-based ionic liquid include alkylpyridinium cations such as 1-butylpyridinium and 1-butyl-4-methylpyridinium.
  • Examples of the cation constituting the morpholinium-based ionic liquid include alkylmorpholinium such as 4-ethyl-4-methylmorpholinium.
  • Examples of the cation constituting the phosphonium-based ionic liquid include alkylphosphonium cations such as tetrabutylphosphonium and tributylmethylphosphonium.
  • Examples of the cation constituting the sulfonium-based ionic liquid include alkylsulfonium cations such as trimethylsulfonium and tributhylsulfonium.
  • anions that are paired with these cations include bis (trifluoromethanesulfonyl) imide (TFSI), bis (fluorosulfonyl) imide, tetrafluoroborate (BF 4 ), hexafluorophosphate (PF 6 ), bis (pentafluoroethanesulfonyl) imide (BETI), and trifluoromethanesulfonate (BETI).
  • Triflate acetate, dimethyl phosphate, dicyanamide, trifluoro (trifluoromethyl) borate and the like. These ionic liquids may be used alone or in combination.
  • the non-aqueous electrolyte has an electrolyte salt.
  • the electrolyte salt is preferably one that can be uniformly dispersed in the main solvent.
  • Lithium cation and those consisting of the above anions can be used as lithium salts, such as lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium bis (pentafluoroethane) Examples include, but are not limited to, sulfonyl) imide (LiBETI), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluorophosphate (LiPF 6 ), and lithium triflate. These materials may be used alone or in combination.
  • the ether solvent constitutes a solvated electrolyte salt and a solvated ionic liquid.
  • a symmetric glycol diglyceride represented by a known glyme (RO (CH 2 CH 2 O) n-R ′ (R and R ′ are saturated hydrocarbons, n is an integer)) showing properties similar to ionic liquids.
  • the generic name of ether can be used.
  • tetraglyme tetraethylene dimethyl glycol, G4
  • triglyme triethylene glycol dimethyl ether, G3
  • pentag lime pentag lime
  • pentag lime pentag lime
  • pentag lime pentag lime
  • pentag lime pentag lime
  • lithium salts such as LiFSI, LiTFSI, LiBETI, LiBF 4 , and LiPF 6 can be used, but are not limited thereto.
  • non-aqueous solvent a mixture of an ether solvent and a solvated electrolyte salt may be used alone or in combination.
  • the non-aqueous electrolyte may have a negative electrode interface stabilizer.
  • a stable coating SEI
  • SEI stable coating
  • the addition amount of the negative electrode interface stabilizer is preferably 30 wt% or less, particularly preferably 10 wt% or less, based on the weight of the non-aqueous electrolyte. If it is 30 wt% or more, the ion conductivity may be inhibited, or the resistance may increase due to reaction with the electrode.
  • the negative electrode interface stabilizer include vinylene carbonate (VC) and fluoroethylene carbonate (FEC), but are not limited thereto. These negative electrode interface stabilizers may be used alone or in combination.
  • the non-aqueous electrolyte may have a corrosion inhibitor.
  • the corrosion inhibitor forms a film in which the metal is difficult to elute even when the positive electrode current collector 120 is exposed to a high electrochemical potential.
  • a material containing an anionic species such as PF 6 or BF 4 and a material containing a cationic species having a strong chemical bond for forming a stable compound in the atmosphere containing moisture is desirable.
  • water solubility and presence / absence of hydrolysis can be mentioned.
  • the solubility in water is desirably less than 1%.
  • the presence or absence of hydrolysis can be evaluated by molecular structure analysis of the sample after mixing with water.
  • no hydrolysis means that the corrosion inhibitor is hygroscopic or mixed with water and then heated at 100 ° C. or higher to remove moisture and 95% of the residue shows the same molecular structure as the additive. Means that.
  • the corrosion inhibitor is represented by (M ⁇ R) + An ⁇ , and the cation of (M ⁇ R) + An ⁇ is (M ⁇ R) +, where M is nitrogen (N), boron (B), phosphorus It consists of either (P) or sulfur (S), and R is composed of a hydrocarbon group.
  • the anion of (M ⁇ R) + An ⁇ is An ⁇ , and BF 4 ⁇ and PF 6 ⁇ are preferably used.
  • corrosion inhibitors examples include tetrabutylammonium hexafluorophosphate (NBu 4 PF 6 ), quaternary ammonium salt of tetrabutylammonium tetrafluoroborate (NBu 4 BF 4 ), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF 4 ), 1-ethyl-3-methylimidazolium hexafluorophosphate (EMI-PF 6 ), 1-butyl-3-methylimidazolium tetrafluoroborate (BMI-BF 4 ), 1-butyl- Examples include imidazolium salts such as 3-methylimidazolium hexafluorophosphate (BMI-PF 6 ). In particular, if the anion is PF 6 , elution of the positive electrode current collector 120 can be suppressed. These materials may be used alone or in combination.
  • the content of the corrosion inhibitor is preferably 0.5 to 20 wt%, more preferably 1 to 10 wt%, based on the total weight of the non-aqueous electrolyte.
  • the content of the corrosion inhibitor is preferably 0.5 to 20 wt%, more preferably 1 to 10 wt%, based on the total weight of the non-aqueous electrolyte.
  • the semi-solid electrolyte binder is similar to the self-healing layer binder.
  • a semi-solid electrolyte is formed by supporting or holding the non-aqueous electrolyte on the support particles.
  • a method for producing a semi-solid electrolyte a non-aqueous electrolyte and supported particles are mixed at a specific volume ratio, and an organic solvent such as methanol is added and mixed to prepare a semi-solid electrolyte slurry. It is spread on a petri dish and the organic solvent is distilled off to obtain a semi-solid electrolyte powder.
  • Example 1> ⁇ Preparation of positive electrode 100> LiNi 1/3 Co 1/3 Mn 1/3 O 2 was used as the positive electrode active material, carbon black was used as the positive electrode conductive agent, and vinylidene fluoride-hexafluoropropylene copolymer was used as the positive electrode binder.
  • NMP N-methyl-2-pyrrolidone
  • the prepared positive electrode slurry was applied onto the stainless steel foil as the positive electrode current collector 120 so that the solid content was 19 mg / cm 2, and the positive electrode mixture layer 110 was formed on the positive electrode current collector 120.
  • a positive electrode 100 was prepared. Thereafter, the positive electrode 100 was dried in a hot air drying furnace at 100 ° C. for 10 minutes. Next, the positive electrode mixture layer 110 was roll-pressed so that the density of the positive electrode mixture layer 110 was adjusted to 2.8 g / cm 3 .
  • ⁇ Fabrication of insulating layer 300> A slurry in which 20 wt% of P (VdF-HPF) and 80 wt% of SiO 2 powder having an average particle diameter of 1 ⁇ m were added to an NMP solvent and sufficiently dispersed using a planetary mixer was prepared. This was coated on the positive electrode 100 and dried at 100 ° C., so that the self-repair layer 310 was formed on the positive electrode 100. Self-healing layers 310 were provided on both sides of the positive electrode 100. The coating amount was controlled so that the thickness of the self-healing layer 310 was 15 ⁇ m on each side of the positive electrode 100.
  • a separator 320 having a porous sheet having cellulose fibers and P (VdF-HFP) binder as an easily soluble polymer and having a thickness of 25 ⁇ m and a porosity of 65-75% was prepared.
  • the separator 320 was produced as follows. First, an underwater pulp was decomposed by ultrasonic waves until it became loose fibers, and excess water was vaporized to prepare a suspension in which cellulose fibers were concentrated. To this, P (VdF-HFP) and 1-methyl-2-pyrrolidone (NMP) were mixed, applied onto a PET film and dried to form a film, which was used as the separator 320.
  • Natural graphite was used as the negative electrode active material, and vinylidene fluoride-hexafluoropropylene copolymer was used as the negative electrode binder.
  • the negative electrode active material and the negative electrode binder were mixed so that the mass% of the non-aqueous electrolyte was 91 and 9, and further dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a negative electrode slurry.
  • NMP N-methyl-2-pyrrolidone
  • the prepared negative electrode slurry was applied onto the copper foil as the negative electrode current collector 220 so that the solid content was 12 mg / cm 2, and the negative electrode mixture layer 210 was formed on the negative electrode current collector 220.
  • a negative electrode 200 was prepared. Thereafter, the negative electrode 200 was dried in a hot air drying furnace at 100 ° C. for 10 minutes. Next, the negative electrode mixture layer 210 was roll-pressed to adjust the density of the negative electrode mixture layer 210 to 1.6 g / cm 3 .
  • the non-aqueous electrolyte was a liquid in which PC was mixed with LiTFSI / G4 (equal mole), and VC and NBu 4 PF 6 were further added to the battery.
  • the positive electrode 100, the separator 320, and the negative electrode 200 in which the self-healing layer 310 was integrated were laminated to produce a secondary battery 1000 with a rated capacity of 3 Ah.
  • the secondary battery 1000 was initialized at room temperature. As an initialization condition, the battery was charged at a constant current of 0.1 A until it reached 4.2 V at 0.1 A, and then charged at a constant voltage of 4.2 V until the current decayed to 0.01 A. The battery was energized at a constant current of 0.1 A until the battery voltage reached 2.7 V, and the discharge capacity of the secondary battery 1000 was measured. The discharge capacity at this time was 3 Ah.
  • the insulation resistance is an insulation resistance between the positive electrode 100 and the negative electrode 200 in an experiment simulating a nail penetration test. If the insulation resistance is 1 k ⁇ or more, this is a simple test method for determining safety in an actual nail penetration test.
  • the nail penetration test was performed according to the following procedure. First, the positive electrode 100, the separator 320, and the negative electrode 200 in which the self-healing layer 310 is integrated are laminated. From above the laminated surface, the tip of a soldering iron heated to 300 ° C. was pierced, and the resistance at that time was measured. The measurement results are shown in the column of insulation resistance in FIG. A case where the insulation resistance was 1 k ⁇ or more was judged to be acceptable.
  • Examples 2 to 17> A secondary battery 1000 was prepared and evaluated in the same manner as in Example 1 except that the combination of the material in the self-healing layer 310 and the material of the separator 320 was changed as shown in FIG. The coating amount was controlled so that the thickness of the self-healing layer 310 was 15 ⁇ m on each side of the positive electrode 100.
  • the separator 320 used in Example 17 was obtained by suspending PMMA fibers (average fiber diameter 0.5 ⁇ m, fiber length 50-100 ⁇ m) produced by a melt spinning method in an NMP solvent, which is referred to as tetrafluoropolyethylene (hereinafter referred to as PTFE). .) It is applied on a film and dried to form a film.
  • PMMA fibers average fiber diameter 0.5 ⁇ m, fiber length 50-100 ⁇ m
  • NMP solvent which is referred to as tetrafluoropolyethylene (hereinafter referred to as PTFE).
  • a secondary battery 1000 was prepared and evaluated in the same manner as in Example 1 except that the combination of the material in the self-healing layer 310 and the material of the separator 320 was changed as shown in FIG.
  • the PET separators used in Comparative Examples 1 to 3 were obtained by suspending PET fibers (average fiber diameter 0.5 ⁇ m, fiber length 50-100 ⁇ m) prepared by melt spinning in an NMP solvent, applying them on a PTFE film, and drying them. It is a film.
  • Example 1 to 17 The evaluation results of Examples and Comparative Examples are shown in FIG. In Examples 1 to 17, the 1CA capacity was 63% or more. As in Examples 14 to 17, the 1CA capacity increased when PMMA or PVDF was mixed with P (VdF-HFP). Further, when comparing the evaluation results of Example 2 and Examples 14 to 17, the insulation resistance tended to increase as the two types of polymers were used. Comparison of the insulation resistance within each group of Examples 1 to 3, Example 4 to 6, and Examples 7 to 9 revealed that the insulation resistance increased as the oxide composition increased.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Secondary Cells (AREA)
  • Cell Separators (AREA)

Abstract

La présente invention aborde le problème consistant à fournir : une couche d'isolation pour améliorer la capacité de décharge d'une batterie secondaire ; et une feuille de cellule de batterie et une batterie secondaire qui comprennent chacune ladite couche d'isolation. Pour résoudre ce problème, cette couche d'isolation a un séparateur et une couche auto-réparatrice, le séparateur ayant un polymère facilement soluble, et la couche auto-réparatrice ayant des particules de couche auto-réparatrice et un liant de couche auto-réparatrice, et une différence d'énergie relative entre le polymère facilement soluble et le liant de couche auto-réparatrice telle que calculée à partir du paramètre de solubilité de Hansen est inférieure à 1 MPa0.5. De préférence, le liant de couche auto-réparatrice a un copolymère de fluorure de polyvinylidène-hexafluoropropylène, et le rapport pondéral du polymère facilement soluble au liant de couche auto-réparatrice est de 1/19-1/4 ou 4/1-19/1.
PCT/JP2019/005556 2018-05-24 2019-02-15 Couche d'isolation, feuille de cellule de batterie et batterie secondaire WO2019225078A1 (fr)

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CN116454542A (zh) * 2023-06-15 2023-07-18 中材锂膜有限公司 一种电池隔膜及其制备方法以及电池

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JP2015088460A (ja) * 2013-09-26 2015-05-07 三菱製紙株式会社 リチウム二次電池用セパレータ用基材及びリチウム二次電池用セパレータ
JP2017536677A (ja) * 2014-12-05 2017-12-07 セルガード エルエルシー リチウム電池用の改善されたコーティングしたセパレータおよび関連方法
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WO2014148036A1 (fr) * 2013-03-19 2014-09-25 ソニー株式会社 Séparateur, batterie, bloc de batteries, appareil électronique, véhicule électrique, dispositif de stockage d'énergie, et système d'énergie
JP2015088460A (ja) * 2013-09-26 2015-05-07 三菱製紙株式会社 リチウム二次電池用セパレータ用基材及びリチウム二次電池用セパレータ
JP2017536677A (ja) * 2014-12-05 2017-12-07 セルガード エルエルシー リチウム電池用の改善されたコーティングしたセパレータおよび関連方法
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116454542A (zh) * 2023-06-15 2023-07-18 中材锂膜有限公司 一种电池隔膜及其制备方法以及电池
CN116454542B (zh) * 2023-06-15 2023-09-15 中材锂膜有限公司 一种电池隔膜及其制备方法以及电池

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