Silicone dispersion crosslinked separator

Abstract

A separator for a nonaqueous secondary battery containing a silicon (Si) molecule, wherein, in a Voronoi polygon obtained by Voronoi partitioning of a Si-containing image detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) of the separator for a nonaqueous secondary battery, a maximum frequency Voronoi area (mu) is in a range of 1.0 μm 2 ~ 17.5 μm 2 or 6.0 μm 2 ~ 12.0 μm 2 , and a breadth (sigma) of a Voronoi area frequency distribution of the Si-containing image detected by TOF-SIMS is in a range of 0.5 μm 2 ~ 8.5 μm 2 .

Description

Technical Field

[0001] This invention relates to a separator for non-aqueous secondary batteries and a method for manufacturing the same, or a non-aqueous secondary battery comprising the separator. Background Technology

[0002] Microporous membranes are widely used as separation or selective permeation membranes for various substances, as well as as separators. Examples of their applications include microfiltration membranes, separators for fuel cells and capacitors, master materials for functional membranes that incorporate functional materials into their pores to achieve new functions, and separators for batteries. Among these, polyolefin microporous membranes are suitable for use as separators in lithium-ion batteries, which are widely used in electric vehicles, laptop computers, mobile phones, and digital cameras.

[0003] To ensure battery safety, battery separators must balance the activation of the shutdown function with the increase in membrane rupture temperature.

[0004] In addition, to ensure battery safety and cycle characteristics, battery separators require improved mechanical strength, activation of the shutdown function, and increased membrane rupture temperature. From the perspective of imbuing battery separators with functionality, this study investigated the inclusion of modified polyolefins in microporous membranes, the crystal structure of the resin constituting the microporous membrane, and the coating of the microporous membrane with resin or inorganic slurry.

[0005] For example, a technique has been proposed to contain inorganic particles and polyolefin resin in a polyolefin microporous membrane that can be used as a separator for lithium-ion batteries (Patent Document 1).

[0006] In addition, from the viewpoint of improving safety by introducing advanced structures such as silane crosslinking structures into polyolefin microporous membranes, a battery separator that initiates a silane crosslinking reaction within the battery (Patent Document 2) or a polyolefin microporous membrane with an island structure obtained by blending silane into medium molecular weight polyethylene (Patent Document 3) has been proposed.

[0007] In addition, Patent Document 2 describes a method of making a polyolefin microporous membrane containing silane-modified polyolefin, etc., and configuring an inorganic porous layer containing inorganic particles and a resin binder on at least one side of the polyolefin microporous membrane.

[0008] For example, in the manufacturing process of the separator made of silane crosslinked polyolefin described in Patent Document 4, the carbon number of the branches of the repeating unit from ethylene, the repeating unit from olefins other than ethylene, and the repeating unit from olefins other than ethylene in the silane-modified polyolefin was studied.

[0009] For example, polyolefin microporous membranes containing silane-modified polyolefins were studied, and the crystallinity of polyethylene, the size of polyethylene crystallites, and the cross-sectional crystal orientation of the polyolefin microporous membranes were measured by X-ray diffraction (XRD) (Patent Document 5). Furthermore, the crystallization long period measured by small-angle X-ray scattering (SAXS) was also studied for polyolefin microporous membranes (Patent Document 6) and stretched polypropylene films (Patent Document 7).

[0010] Patent document 8 studies the film thickness of stretched polyethylene film and the area ratio R = I(110) / (I(110)+I(200)) expressed as the area of ​​the diffraction peak of the (110) plane when X-rays are irradiated from the film thickness direction. It also describes coating the stretched polyethylene film with aromatic amide resin, etc.

[0011] Furthermore, Non-Patent Literature 1 investigated, for example, a synthetic route from tetracoordinate allylsilane to pentacoordinate allyl silicate. Non-Patent Literature 1 describes how low molecular weight organosilicon compounds form higher coordination complexes in the presence of alkali metal fluorides. Si not only exhibits Lewis acid-like properties but also, due to its high affinity for oxygen, can take non-covalent electron pairs from oxygen compounds to form a structure that is thermodynamically stable due to stereoregularity, thereby promoting electron addition reactions at the β-position of the higher coordination complex.

[0012] Non-patent document 2 describes that in a battery using a Si-containing negative electrode active material, as lithium ions charge and discharge to the Si-containing particles, the volume of the Si-containing negative electrode active material will expand or contract significantly.

[0013] Existing technical documents

[0014] Patent documents

[0015] Patent Document 1: International Publication No. 2008 / 035674

[0016] Patent Document 2: International Publication No. 2020 / 075866

[0017] Patent Document 3: International Publication No. 2020 / 040389

[0018] Patent Document 4: Korean Patent Publication No. 10-2020-0078407

[0019] Patent Document 5: International Publication No. 2020 / 067161

[0020] Patent Document 6: International Publication No. 2014 / 175252

[0021] Patent Document 7: International Publication No. 2015 / 012324

[0022] Patent Document 8: Japanese Patent No. 6012839

[0023] Non-patent literature

[0024] Non-patent literature 1: "Special issue on silicone polymer organic silicon chemistry", Journal of Japan Rubber Industry Association, Vol. 62, No. 12 (1989)

[0025] Non-patent document 2: "Volume Expansion during Lithiation of Amorphous SiliconThin Film Electrodes Studied by In-Operando Neutron Reflectometry" J.Phys.Chem.C2014, 118, 9395-9399

[0026] Non-patent document 3: "Near-Shore Aggregation Mechanism of ElectrolyteDecomposition Products to Explain Solid Electrolyte Interphase Formation" J. Electrochem. Soc. C2015, 162, 2670-2678

[0027] Non-patent document 4: "Coupled LiPF6 Decomposition and CarbonateDehydrogenation Enhanced by Highly Covalent Metal Oxides in High-Energy Li-Ion Batteries" J.Phys.Chem.C2018, 122, 48, 27368-27382 Summary of the Invention

[0028] The problem the invention aims to solve

[0029] In recent years, the demand for high-output and high-energy-density lithium-ion secondary batteries for mobile devices and vehicles has been continuously increasing, leading to requirements for battery cell miniaturization, stable cycle performance over long-term use, and improved productivity. Consequently, the required battery safety levels are also more stringent than in previous products. Therefore, the battery separators described in Patent Documents 1-4 have room for improvement in ensuring battery safety and achieving longer battery life. The battery separators described in Patent Documents 2, 5-8 have room for improvement in ensuring productivity, improving battery safety, extending battery life, and / or achieving a balance between these aspects.

[0030] It is known that SFCs (SEI film components), which typically form on the surface of the positive electrode material, aggregate and accumulate on the surface of the negative electrode material to form a solid electrolyte interface (SEI) layer by coating the surface of the negative electrode material (Non-Patent Document 3). The SEI layer, on the one hand, hinders electrolyte decomposition on the electrode surface and inhibits battery degradation, and on the other hand, inhibits lithium ion (Li) ion exchange. + The movement of SFCs increases internal resistance. Furthermore, SFC formation is temperature-dependent; higher temperatures result in a thicker SEI layer. For example, when increasing battery energy density or output by enlarging the battery, the temperature tends to be higher in the center compared to the outer side due to the difference in heat dissipation capacity, leading to more significant SFC formation near the center. Insufficient SFC dispersion results in an uneven SEI layer, where Li ions are trapped, leading to a decrease in cycle performance capacity retention. Methods for increasing battery size include increasing the diameter and length; the use of 4680-type cylindrical batteries to replace the widely used 18650-type cylindrical batteries is being considered. Additionally, batteries using cathode materials containing nickel oxide can increase energy density by increasing the nickel (Ni) content, and as described in Non-Patent Document 4, the lower oxidation potential promotes SFC formation. Therefore, insufficient SFC diffusion tends to easily form an uneven SEI layer.

[0031] Furthermore, lithium-ion rechargeable batteries experience electrode volume changes and internal temperature increases during charging and discharging. Electrode volume changes create uneven stress distribution within the battery. When the internal temperature rises under this uneven stress, the resin, under stress at high temperatures, gradually deforms (thermal creep), causing uneven deformation of the separator and uneven damage to its microporous structure. Consequently, during charging and discharging, lithium-ion flow is partially obstructed, leading to a decrease in cycle performance. Furthermore, uneven lithium-ion movement at the negative electrode and lithium dendrite growth further worsen cycle performance and crush test pass rates. This is especially true for cylindrical and prismatic batteries, where the winding process and the tightening caused by changes over time can easily lead to uneven stress distribution within the battery, resulting in poorer cycle performance and crush test pass rates.

[0032] Furthermore, as mentioned above, while the SEI layer inhibits electrolyte decomposition and battery degradation, excessive formation can increase the battery's internal resistance and cause Li ion accumulation in the electrolyte, leading to poor cycle performance. Therefore, it is preferable to form an SEI layer of suitable thickness uniformly. Uneven deformation of the separator and uneven disruption of its microporous structure can also obstruct the flow of electrolyte decomposition products. This results in uneven formation of the SEI layer, causing a decrease in cycle performance. In particular, when batteries are enlarged, although higher output and energy density can be achieved, the stress difference generated within the battery also increases, making it easier for the separator to deform unevenly. Furthermore, the larger the battery, the greater the temperature difference between the center and the outer periphery due to differences in heat dissipation capacity. This can easily lead to thermal deformation of the electrodes, thermal shrinkage of the separator, and thermal creep, further increasing the stress difference within the battery. Consequently, the above mechanisms can easily cause poor cycle performance and decreased safety during crush tests. Examples of large batteries include the 4680 cylindrical battery and large square batteries.

[0033] Furthermore, while batteries using silicon-containing anode materials can improve energy density, the large expansion rate of the anode material during charging and discharging easily causes uneven deformation of the separator, and the microporous structure of the separator is easily damaged unevenly. This mechanism, in turn, leads to poor cycle performance and decreased safety during crush tests. Conversely, batteries using nickel oxide-containing cathode materials can improve energy density, but on the other hand, electrolyte decomposition easily occurs on the electrode surface, leading to uneven formation of SFCs. If SFCs reach the anode surface in an insufficiently diffused state, they easily form an uneven SEI layer, resulting in poor cycle performance. Examples of nickel oxide-containing cathode materials include NMC111, NMC611, and NMC811.

[0034] In view of the above problems, the object of the present invention is to provide a separator for non-aqueous secondary batteries that can take into account both safety and long life of non-aqueous secondary batteries, and a method for manufacturing the same, or a non-aqueous secondary battery having the separator for non-aqueous secondary batteries.

[0035] Solution for solving the problem

[0036] The inventors conducted repeated and in-depth research to solve the above-mentioned problems. As a result, they discovered that the above-mentioned problems can be solved by using a separator for a non-aqueous secondary battery having the following configuration and a method for manufacturing the same, or by using a non-aqueous secondary battery containing the separator, thereby completing the present invention. An example of the present invention is as follows.

[0037] (1) A separator for a non-aqueous secondary battery, comprising silicon (Si) molecules,

[0038] In the Voronoi polygons obtained by segmenting the Si-containing images detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) of the aforementioned non-aqueous secondary battery separators, the Voronoi area (mu) with the highest frequency is 1.0 μm. 2 ~17.5μm 2 Within the range, and

[0039] The extent (σ) of the Voronoi area frequency distribution in the Si-containing images detected by TOF-SIMS is within 0.5 μm. 2 ~8.5μm 2 Within the range.

[0040] (2) The separator for non-aqueous secondary batteries according to Project 1, wherein the ratio (σ / mu) of the breadth (σ) of the aforementioned Voronoi area frequency distribution to the aforementioned Voronoi area (mu) with the highest frequency is 0.06 to 0.70.

[0041] (3) A separator for a non-aqueous secondary battery, comprising silicon (Si) molecules,

[0042] In the Voronoi polygons obtained by segmenting the Si-containing images detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) of the aforementioned non-aqueous secondary battery separator, the Voronoi area (mu) with the highest frequency is 6.0 μm. 2 ~12.0μm 2 Within the range.

[0043] (4) The separator for non-aqueous secondary batteries as described in Project 3, wherein the extent (σ) of the Voronoi area frequency distribution of the Si-containing image detected by TOF-SIMS is within 2.0 μm. 2 ~4.0μm 2 Within the range.

[0044] (5) The separator for non-aqueous secondary batteries according to item 3 or 4, wherein the ratio (σ / mu) of the breadth (σ) of the aforementioned Voronoi area frequency distribution to the aforementioned Voronoi area (mu) with the highest frequency is 0.20 to 0.40.

[0045] (6) A separator for a non-aqueous secondary battery according to any one of items 1 to 5, wherein the aforementioned Si-containing molecules are dispersed in a non-island structure in the aforementioned separator for a non-aqueous secondary battery.

[0046] (7) A separator for a non-aqueous secondary battery according to any one of items 1 to 6, wherein the aforementioned separator for a non-aqueous secondary battery is a microporous membrane made of polyethylene, and

[0047] The change ratio of air permeability (air permeability Sh after compression / air permeability Sj before compression) when the thickness is compressed by 30% is 1.1 to 7.0 times.

[0048] (8) A separator for a non-aqueous secondary battery, comprising a microporous membrane made of polyethylene.

[0049] The change ratio of air permeability (air permeability Sh after compression / air permeability Sj before compression) when the thickness is compressed by 30% is 1.1 to 7.0 times.

[0050] (9) The separator for non-aqueous secondary batteries according to Item 8 comprises silane-modified polyethylene and polyolefins other than the aforementioned silane-modified polyethylene.

[0051] (10) A separator for a non-aqueous secondary battery, comprising a silane-modified polyolefin, wherein the long period of the polyethylene crystallization, as determined by small-angle X-ray scattering, is 20–50 nm, and the crystallinity, as determined by wide-angle X-ray scattering, is 60%–80%, and the crystallite size (110), as determined by wide-angle X-ray scattering, is 10–50 nm.

[0052] (11) The separator for non-aqueous secondary batteries according to Item 10, wherein the thickness of the amorphous portion is 3 to 23 nm, and the thickness of the amorphous portion is calculated by the following formula based on the crystallization long period of polyethylene detected by small-angle X-ray scattering and the crystallinity detected by wide-angle X-ray scattering.

[0053] Formula: Amorphous part thickness [nm] = (crystallization period [nm]) × (1 - crystallinity [%) / 100).

[0054] (12) The separator for non-aqueous secondary batteries according to item 10 or 11, wherein the cross-sectional crystal orientation degree of polyethylene measured from the MD direction by wide-angle X-ray scattering is 0.70 to 0.99, and the cross-sectional crystal orientation degree of polyethylene measured from the TD direction is 0.70 to 0.99.

[0055] (13) A separator for a non-aqueous secondary battery according to any one of items 10 to 12, wherein the ratio of the cross-sectional crystal orientation degree of polyethylene measured from the MD direction to the cross-sectional crystal orientation degree of polyethylene measured from the TD direction, MD / TD, is 0.5 to 1.2.

[0056] (14) A separator for a non-aqueous secondary battery according to any one of items 10 to 13, wherein the ratio (110) / (200) of the crystallite size (110) of polyethylene to the crystallite size (200) of polyethylene, as determined by wide-angle X-ray scattering, is 0.9 to 2.0.

[0057] (15) A separator for a non-aqueous secondary battery according to any one of items 10 to 14, wherein the aforementioned silane-modified polyolefin is silane-modified polyethylene.

[0058] (16) A separator for a non-aqueous secondary battery according to any one of items 10 to 15, wherein the number of methylene (CH2) groups constituting the connection portion with the organic part of the main chain in the aforementioned silane-modified polyolefin containing silicon (Si) functional groups is 2 to 10.

[0059] (17) A separator for a non-aqueous secondary battery according to any one of items 10 to 16, comprising a polyolefin microporous membrane as a substrate and an inorganic porous layer comprising inorganic particles and a resin binder stacked on at least one side of the aforementioned polyolefin microporous membrane.

[0060] (18) The separator for non-aqueous secondary batteries according to Item 17, wherein, based on the total mass of the aforementioned inorganic porous layer, the content of the aforementioned inorganic particles contained in the aforementioned inorganic porous layer is 5% to 99% by mass.

[0061] (19) The separator for non-aqueous secondary batteries according to item 17 or 18, wherein the aforementioned inorganic particles are selected from at least one of the following groups: alumina, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, cerium oxide, yttrium oxide, zinc oxide, iron oxide, silicon nitride, titanium nitride, boron nitride, silicon carbide, aluminum hydroxide, talc, kaolinite, dickite, perlite, halloysite, pyrophyllite, montmorillonite, sericite, mica, magnesia chlorite, bentonite, asbestos, zeolite, diatomite, silica sand and glass fiber.

[0062] (20) A separator for a non-aqueous secondary battery according to any one of items 10 to 16, comprising a polyolefin microporous membrane as a substrate and a thermoplastic polymer layer formed on at least one side of the aforementioned polyolefin microporous membrane, wherein the thermoplastic polymer contained in the aforementioned thermoplastic polymer layer comprises at least one of the following: (meth)acrylate and / or (meth)acrylic acid polymer units; polyvinylidene fluoride (PVDF); polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP); and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE).

[0063] (21) A separator for a non-aqueous secondary battery according to any one of items 10 to 16, comprising a polyolefin microporous membrane as a substrate and an active layer disposed on at least one side of the aforementioned polyolefin microporous membrane, the aforementioned active layer containing at least one fluorinated polyvinyl chloride compound selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE) and inorganic particles.

[0064] (22) A separator for a non-aqueous secondary battery according to any one of items 10 to 16, comprising a polyolefin microporous membrane as a substrate and a heat-resistant resin layer comprising a heat-resistant resin laminated on at least one side of the aforementioned polyolefin microporous membrane, wherein the aforementioned heat-resistant resin comprises at least one selected from the group consisting of fully aromatic polyamide, polyimide, polyamide-imide, polysulfone, polyketone, polyether, polyetherketone, polyetherimide and cellulose.

[0065] (23) The separator for non-aqueous secondary batteries according to item 22, wherein the aforementioned heat-resistant resin layer contains 30% to 90% by mass of inorganic filler with an average particle size of 0.2 μm to 0.9 μm.

[0066] (24) A separator for a non-aqueous secondary battery according to any one of items 10 to 23, wherein the separator further comprises a polyolefin other than the aforementioned silane-modified polyolefin.

[0067] (25) A separator for a non-aqueous secondary battery according to any one of items 10 to 24, wherein the Voronoi polygon obtained by Voronoi segmentation of the Si-containing image detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) of the aforementioned separator for a non-aqueous secondary battery has a Voronoi area (mu) with the highest frequency of occurrence of 6.00 μm. 2 ~12.00μm 2 The range.

[0068] (26) The separator for non-aqueous secondary batteries according to Item 25, wherein the extent (σ) of the Voronoi area frequency distribution of the Si-containing image detected by TOF-SIMS is 2.00 μm. 2 ~4.00μm 2 Within the range.

[0069] (27) The separator for non-aqueous secondary batteries according to item 25 or 26, wherein the ratio (σ / mu) of the breadth (σ) of the aforementioned Voronoi area frequency distribution to the aforementioned Voronoi area (mu) with the highest frequency is 0.20 to 0.40.

[0070] (28) A non-aqueous secondary battery comprising a positive electrode, a negative electrode, a separator for a non-aqueous secondary battery as described in any one of items 1 to 27, and a non-aqueous electrolyte.

[0071] (29) The non-aqueous secondary battery according to Item 28, wherein the aforementioned positive electrode contains the formula: Li-Ni x -Mn y -Co z The lithium (Li)-nickel (Ni)-manganese (Mn)-cobalt (Co) composite oxide shown is given by the formula where x represents the Ni ratio, y represents the Mn ratio, z represents the Co ratio, and x+y+z=1, and the Ni ratio x in the aforementioned formula is 5~9.

[0072] (30) The non-aqueous secondary battery according to item 28 or 29, wherein the aforementioned negative electrode contains a negative electrode active material, and the Si content in the aforementioned negative electrode active material is 5% to 90% by weight.

[0073] (31) The non-aqueous secondary battery according to any one of items 28 to 30, wherein the aforementioned non-aqueous electrolyte contains lithium salt in a concentration ranging from 1.2 mol / L to 10 mol / L.

[0074] (32) The non-aqueous secondary battery according to any one of items 28 to 31, wherein the aforementioned non-aqueous electrolyte contains ethyl methyl carbonate (EMC) and / or acetonitrile (AcN), and the total content of EMC and AcN in the aforementioned non-aqueous electrolyte is in the range of 50% by mass to 90% by mass.

[0075] (33) A method for manufacturing a separator for a non-aqueous secondary battery according to any one of items 17 to 19, comprising the following steps:

[0076] (1) Sheet forming process: The aforementioned silane-modified polyolefin, polyethylene and plasticizer are extruded into sheet form using an extruder and cooled and solidified to form a sheet-shaped molded body;

[0077] (2) Stretching process: The aforementioned sheet-shaped molded body is biaxially stretched at a magnification ratio of 20 times or more and 250 times or less to form the stretched material.

[0078] (3) Porous body forming process: extracting the plasticizer from the aforementioned stretched material to form a porous body;

[0079] (4) Heat treatment process: The aforementioned porous body is subjected to heat treatment, and stretched and relaxed along the width direction to obtain a heat-treated porous body.

[0080] (5A) Coating process, wherein a coating liquid containing the aforementioned inorganic particles and the aforementioned resin binder and containing a surfactant, and having a pH of 6.7 or less or 7.5 or more, is applied to at least one surface of the aforementioned heat-treated porous body, thereby forming the aforementioned inorganic porous layer on at least one surface of the aforementioned heat-treated porous body.

[0081] (6) Drying process, drying to remove the solvent from the aforementioned inorganic porous layer; and

[0082] (7) Assembly process: The electrode and the aforementioned non-aqueous secondary battery separator laminate or its winding, as well as the non-aqueous electrolyte, are housed in the outer casing.

[0083] Furthermore, the aforementioned silane-modified polyolefin is cross-linked in at least one of the aforementioned steps (5A), (6) and (7).

[0084] (34) The manufacturing method of the separator for non-aqueous secondary batteries according to item 20 includes the following steps:

[0085] (1) Sheet forming process: The aforementioned silane-modified polyolefin, polyethylene and plasticizer are extruded into sheet form using an extruder and cooled and solidified to form a sheet-shaped molded body;

[0086] (2) Stretching process: The aforementioned sheet-shaped molded body is biaxially stretched at a magnification ratio of 20 times or more and 250 times or less to form the stretched material.

[0087] (3) Porous body forming process: extracting the plasticizer from the aforementioned stretched material to form a porous body;

[0088] (4) Heat treatment process: The aforementioned porous body is subjected to heat treatment, and stretched and relaxed along the width direction to obtain a heat-treated porous body.

[0089] (5B) Coating process: A coating liquid containing the aforementioned thermoplastic polymer and surfactant, and having a pH of 6.7 or less or 7.5 or more, is applied to at least one surface of the aforementioned heat-treated porous body, thereby forming the aforementioned thermoplastic polymer layer on at least one surface of the aforementioned heat-treated porous body.

[0090] (6) Drying process, drying to remove the solvent from the aforementioned thermoplastic polymer layer; and

[0091] (7) Assembly process: The electrode and the aforementioned non-aqueous secondary battery separator laminate or its winding, as well as the non-aqueous electrolyte, are housed in the outer casing.

[0092] Furthermore, in at least one of the aforementioned steps (5B), (6) and (7), the aforementioned silane-modified polyolefin is made to form a cross-linked structure.

[0093] (35) The method for manufacturing a separator for a non-aqueous secondary battery according to item 21 includes the following steps:

[0094] (1) Sheet forming process: The aforementioned silane-modified polyolefin, polyethylene and plasticizer are extruded into sheet form using an extruder and cooled and solidified to form a sheet-shaped molded body;

[0095] (2) Stretching process: The aforementioned sheet-shaped molded body is biaxially stretched at a magnification ratio of 20 times or more and 250 times or less to form the stretched material.

[0096] (3) Porous body forming process: extracting the plasticizer from the aforementioned stretched material to form a porous body;

[0097] (4) Heat treatment process: The aforementioned porous body is subjected to heat treatment, and stretched and relaxed along the width direction to obtain a heat-treated porous body.

[0098] (5C) Coating process, in which a coating liquid containing the aforementioned fluorinated polyvinyl group compound, the aforementioned inorganic particles and organic solvent are applied to at least one surface of the aforementioned heat-treated porous body, thereby forming the aforementioned active layer on at least one surface of the aforementioned heat-treated porous body.

[0099] (6) Drying process, drying to remove the solvent from the aforementioned active layer; and

[0100] (7) Assembly process: The electrode and the aforementioned non-aqueous secondary battery separator laminate or its winding, as well as the non-aqueous electrolyte, are housed in the outer casing.

[0101] Furthermore, the aforementioned silane-modified polyolefin is cross-linked in at least one of the aforementioned steps (5C), (6) and (7).

[0102] (36) The method for manufacturing a separator for a non-aqueous secondary battery according to item 35, wherein the following step is included between the aforementioned coating step (5C) and the aforementioned drying step (6):

[0103] (5.5C) Water washing process, in which the organic solvent in the aforementioned active layer is replaced with a water-based solvent.

[0104] Furthermore, in the aforementioned (5.5C) process, the aforementioned silane-modified polyolefin is cross-linked.

[0105] (37) The method for manufacturing a separator for a non-aqueous secondary battery according to item 22 or 23 includes the following steps:

[0106] (1) Sheet forming process: The aforementioned silane-modified polyolefin, polyethylene and plasticizer are extruded into sheet form using an extruder and cooled and solidified to form a sheet-shaped molded body;

[0107] (2) Stretching process: The aforementioned sheet-shaped molded body is biaxially stretched at a magnification ratio of 20 times or more and 250 times or less to form the stretched material.

[0108] (3) Porous body forming process: extracting the plasticizer from the aforementioned stretched material to form a porous body;

[0109] (4) Heat treatment process: The aforementioned porous body is subjected to heat treatment, and stretched and relaxed along the width direction to obtain a heat-treated porous body.

[0110] (5D) Coating process, applying a coating liquid containing the aforementioned heat-resistant resin and organic solvent to at least one surface of the aforementioned heat-treated porous body, thereby forming the aforementioned heat-resistant resin layer on at least one surface of the aforementioned heat-treated porous body.

[0111] (6) Drying process, drying to remove the solvent from the aforementioned heat-resistant resin layer; and

[0112] (7) Assembly process: The electrode and the aforementioned non-aqueous secondary battery separator laminate or its winding, as well as the non-aqueous electrolyte, are housed in the outer casing.

[0113] Furthermore, the aforementioned silane-modified polyolefin is cross-linked in at least one of the aforementioned steps (5D), (6), and (7).

[0114] (38) The method for manufacturing a separator for a non-aqueous secondary battery according to item 37, wherein the following steps are included between the aforementioned coating step (5D) and the aforementioned drying step (6):

[0115] (5.5D) The water washing process replaces the organic solvent in the aforementioned heat-resistant resin layer with a water-based solvent.

[0116] Furthermore, in the aforementioned (5.5D) process, the aforementioned silane-modified polyolefin is cross-linked.

[0117] The effects of the invention

[0118] According to the present invention, it is possible to achieve both safety and long lifespan of non-aqueous secondary batteries with separators for non-aqueous secondary batteries. More specifically, it is possible to improve safety in nail penetration and hotbox tests, cycling characteristics including low-temperature cycling characteristics and high-temperature cycling characteristics, and productivity. Attached Figure Description

[0119] Figure 1 This is an image showing the TOF-SIMS analysis results of the separator in Example 1.

[0120] Figure 2 This is an example of a three-dimensional image of a filter in the image processing of the TOF-SIMS spectrum in Example 1.

[0121] Figure 3 This is an example of a two-dimensional image of a filter in the image processing of the TOF-SIMS spectrum in Example 1.

[0122] Figure 4 This is an example of the state after image processing (1) to (2) of the TOF-SIMS spectrum of Example 1.

[0123] Figure 5 This is an example of the state after image processing (1) to (6) of the TOF-SIMS spectrum of Example 1.

[0124] Figure 6 An example of the Voronoi region obtained by Voronoi segmentation of the TOF-SIMS spectrum of Example 1 is shown.

[0125] Figure 7 An example of a Voronoi area that was determined to be valid based on the results of Example 1 is shown.

[0126] Figure 8 This is a histogram of the Voronoi area from Example 1.

[0127] Figure 9 This is a histogram after converting the area of ​​Voronoi in Example 1 into the actual area.

[0128] Figure 10 This is an example of the fitting results for the Voronoi area in Example 1.

[0129] Figure 11 This is an image showing the TOF-SIMS analysis results of the separator in Comparative Example 1.

[0130] Figure 12 This is an example of the state after image processing (1) to (2) of the TOF-SIMS spectrum of Comparative Example 1.

[0131] Figure 13 This is an example of the state after image processing (1) to (6) of the TOF-SIMS spectrum of Comparative Example 1.

[0132] Figure 14 This is an example of the Voronoi region obtained by Voronoi segmentation of the TOF-SIMS spectrum of Comparative Example 1.

[0133] Figure 15 This example shows a Voronoi area that was determined to be valid based on the results of Comparative Example 1.

[0134] Figure 16 Histogram of the area of ​​Voronoi for Comparative Example 1.

[0135] Figure 17 This is a histogram showing the area of ​​Voronoi in Comparative Example 1 converted to its actual area.

[0136] Figure 18 This is an example showing the fitting results for the Voronoi area of ​​Comparative Example 1.

[0137] Figure 19 This is a schematic diagram and a partially enlarged view illustrating the repeating periodic structure of crystalline and amorphous portions in a separator made of crystalline resins such as polyethylene. Detailed Implementation

[0138] The following describes in detail the methods for implementing the present invention (hereinafter referred to as "implementation methods"). The present invention is not limited to the following embodiments, and various modifications can be made without departing from its spirit. The numerical ranges recorded using "~" in this specification include the values ​​recorded before and after them. The abbreviation "MD" refers to the machine direction, which is the direction along the long side of the battery winding body during continuous film forming of the separator. The abbreviation "TD" refers to the direction that crosses MD at a 90° angle (hereinafter also referred to as the width direction), which is the transverse direction. The various measurement methods and evaluation methods shown below are performed according to the methods described in the examples, unless otherwise stated.

[0139] <Separator for non-aqueous secondary batteries>

[0140] Separators for non-aqueous secondary batteries (hereinafter also referred to as "separators") require insulation and ion permeability, and are therefore typically formed from paper, nonwoven fabrics made of polyolefins, or microporous membranes made of resins that have a porous structure and are insulating materials. In particular, as a separator substrate used in non-aqueous secondary batteries with positive and negative electrodes capable of absorbing / releasing lithium and a non-aqueous electrolyte dissolved in a non-aqueous solvent, polyolefin microporous membranes with redox resistance and the ability to form a dense and uniform porous structure are excellent. Therefore, separators for non-aqueous secondary batteries may include polyolefin microporous membranes. It is desirable that separators for non-aqueous secondary batteries may include layers formed on one or both sides of the polyolefin microporous membrane, such as thermoplastic polymer layers, active layers, inorganic porous layers, heat-resistant resin layers, etc.

[0141] <Implementation Method 1: Silicon-containing Structure of Separator and Voronoi Segmentation (1)>

[0142] The separator in Embodiment 1 contains silicon (Si) molecules. In the Voronoi polygons obtained by Voronoi segmentation of the Si-containing image detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS), the Voronoi area (μm) with the highest frequency is 1.0 μm. 2 ~17.5μm 2 Within the range, and the breadth (σ) of the Voronoi area frequency distribution of Si-containing images detected by TOF-SIMS measurement is within 0.5 μm. 2 ~8.5μm 2 Within the range.

[0143] For the separator in Embodiment 1, when TOF-SIMS measurement is performed with a square area of ​​100 μm, at least one silicon-containing structure can be detected, preferably with Si molecules dispersed in the separator in a non-island structure state. It should be noted that an island structure refers to a structure in which a solid material generally contains two types of structures, and the other type (like an island) is discontinuously mixed in one of the relatively continuous types (like a sea).

[0144] In Implementation Method 1, the various values ​​obtained through Voronoi segmentation are values ​​measured when the separator is a polyolefin microporous membrane, and can serve as indicators of the deviation level of Si-containing molecules on the separator surface. The TOF-SIMS measurement of the separator can be referenced... Figures 1-6 and Figures 11-14 As described in the embodiments, the Voronoi segmentation of the TOF-SIMS image can be performed with reference to... Figures 7-10and Figures 15-18 Perform as described in the embodiments.

[0145] Among the Voronoi polygons obtained by the above Voronoi segmentation, the Voronoi area (mu) with the highest frequency is 1.0 μm. 2 ~17.5μm 2 Within a certain range, the tendency for Si molecules to disperse in the separator in a non-island structure is stronger. For example, in a non-aqueous secondary battery, specifically a lithium-ion secondary battery, when a separator with uniformly dispersed Si coexists with a lithium (Li) complex solvated by an electrolyte containing non-covalent electron pairs such as oxygen atoms, it is believed that the battery's product life in cycle characteristic tests is extended through the following phenomena (i) and (ii):

[0146] (i) Li complexes exhibit a high affinity for Si atoms and thus exist with a high probability around dispersed Si atoms. For this phenomenon to be effective, the non-donated electron pairs in the electrolyte's molecular structure coordinate with Si atoms. As mentioned in Non-Patent Document 1, Si atoms have a large atomic radius, enabling coordination with more than four atoms, and possess unique properties such as the ability to have a 4-electron 3-center bond and utilize d-orbitals. This results in a path for the uniform flow of Li ions across the entire surface of the separator. Therefore, secondary batteries, for example, containing NMC cathodes with lithium (Li)-nickel (Ni)-manganese (Mn)-cobalt (Co) composite oxides, tend to exhibit uniform charging and discharging, thereby suppressing crystal damage; and

[0147] (ii) In addition, for example, when the negative electrode is a Si-containing negative electrode, the Si element in the negative electrode can be charged and discharged uniformly, and the deformation inside the secondary battery can be suppressed by making the Si-containing negative electrode expand uniformly.

[0148] Regarding the phenomena described in (i) and (ii) above, while we do not wish to be bound by theory, it is believed that this is because, in non-aqueous secondary batteries, a complex is uniformly formed on the separator as shown in route 1 below, thereby increasing the Li content of the separator. + The flow of ions also becomes uniform, thus causing this to occur.

[0149]

[0150] In the formula, Sol represents the non-aqueous solvent in the electrolyte, and X... - The term "represents the counterion of lithium salt as an electrolyte" and, as an example of a non-aqueous solvent, includes ethylene carbonate (EC); as an example of the resin constituting the separator in Embodiment 1, includes silane-modified polyethylene; and R represents, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc., or a siloxane bond crosslinked with a nearby silanol.

[0151] Furthermore, in non-aqueous secondary battery systems containing lithium hexafluorophosphate (LiPF6) as the electrolyte, due to the Young's-Taylor effect of phosphorus atoms, they exist in the system as dissociated F anions or lithium fluoride (LiF) at a certain concentration. Therefore, LiF exhibits a stronger Lewis acid effect in the state of addition with Si than in the state before addition, thus making the phenomena mentioned above (i) and (ii) more significant, and further demonstrating good low-temperature cycling characteristics. This was discovered by the present invention and is believed to be due to: as shown in route 2 below,

[0152]

[0153] {In the formula, Sol represents a non-aqueous solvent in the electrolyte, an example of which is ethylene carbonate (EC), an example of which is LiPF6, an example of which is the resin constituting the separator in Embodiment 1, which is silane-modified polyethylene, and R represents, for example, H, Me, Et, Bu, etc., or a siloxane bond formed by crosslinking with a nearby silanol.}

[0154] Physically solvated Li + The Si atoms of the Si-containing molecules in the polymer constituting the separator are stably coordinated, resulting in a coordination complex with a high probability. This method is unique to the amorphous structure obtained by film formation using a polymer composition of resin A and resin B or resin C described later, and is different from the Lewis acid properties of Si in the coordination complexes of low molecular weight allyl silane compounds as described in Non-Patent Document 1.

[0155] Furthermore, most Si-containing molecules possess cross-linking properties. For example, when they possess silane cross-linking properties, it is believed that the silane cross-linking of Si-containing molecules dispersed in non-aqueous secondary batteries can be ensured, thereby ensuring the stability of siloxane bonds and maintaining the cross-linked structure of the separator over a long period. This ensures safety in safety tests such as nail penetration tests. It is known that during the charging and discharging of lithium-ion batteries, if the flow of lithium ions is uneven and the movement is slower than the rate of insertion reaction into the electrode, lithium ions will accumulate in the electrical stagnation zone and form dendrites. Especially when the battery operates at low temperatures, the electrolyte viscosity increases, making it difficult for ions to move within the system, thus tending to form dendrites. As a result, the safety of the battery after low-temperature cycling may decrease significantly. This phenomenon is a serious problem when mobile device power supplies, battery cars, etc., are used in seasons and regions with large temperature differences. In Implementation 1, by designing a separator containing Si atoms dispersed in a non-island structure (non-matrix structure), the uniformity of lithium ion flow can be improved and the problem can be solved.

[0156] From the viewpoint of further improving the safety of the separator and the non-aqueous secondary battery containing it, the separator preferably contains silane-modified polyethylene as a Si-containing molecule, and more preferably, the silane-modified polyethylene undergoes a silane crosslinking reaction when the separator comes into contact with the electrolyte.

[0157] From the perspective of balancing the long lifespan and safety of non-aqueous secondary batteries in terms of cycle characteristics, and / or achieving a balance between them, the Voronoi area (mu) with the highest frequency in the Voronoi polygons obtained by the above-mentioned Voronoi segmentation is preferably 1.5 μm. 2 ~17.0μm 2 Within the range, more preferably within 4.0 μm 2 ~16.0μm 2 Within the range, it is further preferred to be within 6.0 μm. 2 ~13.0μm 2 Within the range. From the same perspective, the breadth (σ) of the Voronoi area frequency distribution of Si-containing images detected by TOF-SIMS is within 0.5 μm. 2 ~8.5μm 2 Within the range of 1.7 to 6.3, it is more preferably within the range of 1.8 μm. 2 ~4.2μm 2 Within the range.

[0158] The Voronoi partitioning refers to the process of dividing a region into its constituent parts by considering multiple points (parent points) located at arbitrary points in space at a certain distance, and identifying which parent point is closest to other points in the same space. The resulting map containing these regions is called a Voronoi map. Typically, in a Voronoi map, the boundaries of the regions become part of the bisecting lines of each parent point, and the regions form polygons (Voronoi polygons).

[0159] It should be noted that when performing Voronoi segmentation within the field of view, non-closed regions are excluded from the Voronoi segmentation. Examples of non-closed regions include areas obtained by Voronoi segmentation of an object that exists at the boundary of the field of view and cannot be observed in its entirety. Therefore, it is preferable to confirm whether the entire object can be observed in an image located at the end of the image obtained by photographing at least a portion of the surface of the segmenter.

[0160] For Si-containing images detected by TOF-SIMS, the ratio (σ / mu) of the breadth (σ) of the Voronoi area frequency distribution to the Voronoi area (mu) with the highest frequency preferably satisfies the following relationship.

[0161] 0.06≤σ / mu≤0.70

[0162] In Embodiment 1, the ratio (σ / mu) in the Voronoi fractionation can be considered as an indicator of whether Si-containing molecules are uniformly dispersed on the surface of the separator. When the ratio (σ / mu) is in the range of 0.06 to 0.70, the Si-containing molecules are uniformly dispersed on the surface of the separator. In non-aqueous secondary batteries, this greatly facilitates the coexistence of Li complexes derived from the electrolyte with the separator, the silane crosslinking reaction of the separator, etc., and can extend the cycle life of the battery. Although it is not desirable to be bound by theory, the concentration of intermediates formed by the coordination of Li complexes within the separator surface, or the equilibrium state life of the intermediates, are important. In Embodiment 1, experiments have shown that the specified ratio (σ / mu) in the Voronoi fractionation can help to make the intercalation reaction to the electrode uniform. From the viewpoint of further extending the cycle life of the battery, the ratio (σ / mu) is preferably in the range of 0.07 to 0.57, and more preferably in the range of 0.19 to 0.38.

[0163] The values ​​of the separator obtained by Voronoi splitting in Embodiment 1 can be adjusted to the range described above, for example, by controlling the structure containing Si molecules, the molecular weight or molecular weight distribution of the raw materials constituting the separator, and the mixing range of the raw materials constituting the separator.

[0164] <Implementation Method 2: Silicon-containing Structure of Separator and Voronoi Segmentation (2)>

[0165] The separator in Embodiment 2 contains silicon (Si) molecules. In the Voronoi polygons obtained by Voronoi segmentation of the Si-containing image detected by TOF-SIMS measurement, the area (μm) of the Voronoi polygon with the highest frequency is 6.0 μm. 2 ~12.0μm 2 Within the range.

[0166] When performing TOF-SIMS measurement on the separator of Embodiment 2 with a square area of ​​100 mm, at least one silicon-containing structure can be detected, and preferably, Si-containing molecules are detected dispersed in the separator in a non-island structure state.

[0167] In Implementation Method 2, the various values ​​obtained by Voronoi segmentation are values ​​measured when the separator is a polyolefin microporous membrane, and can be used as an indicator of the deviation level of Si-containing molecules on the surface of the separator.

[0168] In the Voronoi polygons, the Voronoi area (mu) with the highest frequency is 6.0 μm. 2 ~12.0μm 2Within the specified range, similar to Embodiment 1, the Si molecules in the separator tend to disperse in a non-island structure, which can simultaneously ensure the safety of non-aqueous secondary batteries with separators and extend their cycle life. This can be achieved through Li... + The homogenization of ion flow, the Lewis acid effect, or the crosslinking of Si molecules ensure low-temperature cycling characteristics and safety in nail penetration tests. Based on this, in Embodiment 2, when a spacer with uniformly dispersed Si elements coexists with oligomers (SFCs: SEI film components) generated through a chemical reaction on the surface of the cathode material via the electrolyte, as shown in Route 3 below, the non-covalent electrons of oxygen in the SFC molecular structure can coordinate with Si atoms. SFCs exhibit affinity for Si atoms, thus improving the diffusivity of SFCs.

[0169]

[0170] In the formula, Sol represents the non-aqueous solvent in the electrolyte, and X... - This indicates the counter anion of the lithium salt as the electrolyte. As an example, the right side shows a case where the non-aqueous solvent is ethylene carbonate (EC), SFC is an oligomer formed by the reduction polymerization of EC2 molecules, and the resin constituting the separator contains silane-modified polyethylene. Furthermore, R represents, for example, a siloxane bond formed by methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc., or crosslinked with a nearby silanol.

[0171] In embodiment 2, the Voronoi area (mu) of the separator is 6.0 μm. 2 ~12.0μm 2 Within a certain range, it is assumed that the Si molecules are finely and uniformly dispersed in the separator. Therefore, as shown in Route 3, the SFC is uniformly dispersed throughout the separator, forming a uniformly thick SEI layer on the negative electrode that inhibits electrolyte decomposition, thereby improving the cycle test capacity retention. When the vorono area of ​​the separator is too large (i.e., the distance between Si molecules is too large), the SFC diffusion is insufficient, easily forming an uneven SEI layer, which in turn worsens the cycle test capacity retention. On the other hand, when the vorono area is too small (i.e., the distance between Si atoms is too small), the SFC coordinated with Si atoms is dense in a narrow range, and the movement of SFC is inhibited due to steric hindrance, resulting in insufficient SFC diffusion and also worsening the cycle test capacity retention.

[0172] From the viewpoint of further improving the safety of the separator and the non-aqueous secondary battery containing it, the separator of Embodiment 2 preferably contains silane-modified polyethylene as a Si-containing molecule, and more preferably, the silane-modified polyethylene undergoes a silane crosslinking reaction when the separator comes into contact with the electrolyte.

[0173] From the viewpoint of uniformly distributing SFCs throughout the separator, taking into account the cycle characteristics and safety of non-aqueous secondary batteries, and / or achieving a balance between the two, for the separator in Embodiment 2, the Voronoi polygon obtained by the Voronoi segmentation described above preferably has a Voronoi area (mu) with the highest frequency of occurrence of 6.5 μm. 2 ~11.5μm 2 Within the range, more preferably within 7.0 μm 2 ~11.0μm 2 Within the range, it is further preferred to be within 7.5μm. 2 ~10.5μm 2 Within this range. From the same perspective, the breadth (σ) of the Voronoi area frequency distribution in Si-containing images detected by TOF-SIMS is preferably within 2.0 μm. 2 ~4.0μm 2 Within the range, more preferably within 2.2 μm 2 ~3.8μm 2 Within the range, it is further preferred to be within 2.5μm. 2 ~3.5μm 2 Within the range.

[0174] For Si-containing images detected by TOF-SIMS, the ratio (σ / mu) of the breadth (σ) of the Voronoi area frequency distribution to the Voronoi area (mu) with the highest frequency preferably satisfies the following relationship.

[0175] 0.20≤σ / mu≤0.40

[0176] In Embodiment 2, the ratio (σ / mu) in the Voronoi fractionation can be considered as an indicator of whether Si-containing molecules are uniformly dispersed on the surface of the separator. When the ratio (σ / mu) in Embodiment 2 is in the range of 0.20 to 0.40, similar to Embodiment 1, the uniform dispersion of Si-containing molecules on the surface of the separator is highly beneficial in non-aqueous secondary batteries, facilitating the coexistence of Li complexes from the electrolyte with the separator and the silane crosslinking reaction of the separator, thereby extending the battery's cycle characteristics. Furthermore, in Embodiment 2, by improving the dispersion of the SFC and promoting the uniform formation of the SEI layer, the battery's cycle characteristics can be improved. From the viewpoint of further extending the cycle life of the battery, the ratio (σ / mu) in Embodiment 2 is more preferably in the range of 0.22 to 0.38, and even more preferably in the range of 0.25 to 0.35.

[0177] The values ​​of the separator obtained by Voronoi splitting in Embodiment 2 can be adjusted to the range described above, for example, by controlling the structure containing Si molecules, the molecular weight or molecular weight distribution of the raw materials constituting the separator, and the mixing range of the raw materials constituting the separator.

[0178] <Implementation Method 3: Changes in air permeability of the separator before and after compression>

[0179] The separator in Embodiment 3 comprises a microporous membrane made of polyethylene, and the change in air permeability (air permeability Sh after compression / air permeability Sj before compression) when the thickness is compressed by 30% is in the range of 1.1 to 7.0 times.

[0180] In embodiment 3, when the permeability change ratio (permeability Sh / permeability Sj) is in the range of 1.1 to 7.0 times, ion permeability can be maintained even when the non-aqueous secondary battery containing the separator is compressed along the thickness direction of the separator, and there is a tendency to ensure safety and low-temperature cycling characteristics in the battery's nail penetration test. This tendency is more pronounced when the negative electrode of the battery contains an easily expandable negative electrode such as a Si negative electrode. From this point of view, the permeability change ratio (permeability Sh / permeability Sj) is preferably 1.3 to 6.9 times.

[0181] The change ratio of air permeability (air permeability Sh / air permeability Sj) was measured when the separator was a polyolefin microporous membrane, and the measurement could be performed by the method described in the examples.

[0182] <Implementation Method 4: Containment and Crystal Structure of Silane-Modified Polyolefins>

[0183] The separator in Embodiment 4 comprises a silane-modified polyolefin, the long period of which the polyethylene crystallization, as measured by small-angle X-ray scattering (SAXS), is 20 to 50 nm, the crystallinity, as measured by wide-angle X-ray scattering (WAXS), is 60% to 80%, and the crystallite size (110), as measured by wide-angle X-ray scattering (WAXS), is 10 to 50 nm.

[0184] Typically, in separators using crystalline resins such as polyethylene, the separators contain a repeating periodic structure of crystalline and amorphous portions. Figure 19 Long crystallization period (f) c ) refers to: the average length of one cycle of the repeating cycle of the crystalline and amorphous parts, and the thickness of the crystalline part (t) c (t) refers to the average thickness of the crystalline portion and the average thickness of the amorphous portion during the repeating cycle of the crystalline and amorphous portions. a( ) refers to: the average thickness of the amorphous portion during the repetition cycle of the crystalline and amorphous portions; crystallite size refers to the average size of each crystallite; crystallinity refers to: the proportion of the crystalline portion in the whole; and crystal orientation (a c The crystal structure refers to the degree of orientation of the crystals along a certain direction. For example, the crystallite size (110) refers to the average size of each polyethylene crystallite in the (110) direction, the crystallite size (200) refers to the average size of each polyethylene crystallite in the (200) direction, and the crystal orientation degree of the MD section refers to the degree to which the (110) planes of the polyethylene crystals are arranged parallel to the MD-TD plane in the cross-section (MD section) obtained by cutting the separator along a plane perpendicular to MD. In addition, the crystal orientation degree of the TD section refers to the degree to which the (110) planes of the polyethylene crystals are arranged parallel to the MD-TD plane in the cross-section (TD section) obtained by cutting the separator along a plane perpendicular to TD. The crystal structure of the separator can be determined using an X-ray structure evaluation device.

[0185] In Embodiment 4, SAXS and WAXS measurements are performed on the separator that serves as the substrate. Therefore, when the separator is in the form of a multilayer film or a laminated film, the layers other than the polyolefin microporous film are removed before the SAXS and WAXS measurements are performed.

[0186] In Implementation 4, in the specific combination of SAXS and WAXS X-ray structural analysis, when the crystallization period is in the range of 20 nm to 50 nm, the crystallinity is in the range of 60% to 80%, and the crystallite size (110) of polyethylene is in the range of 10 to 50 nm, the heat creep resistance of the separator is improved and the distance between the silane modified units is optimal. When in contact with the coating liquid during the coating process, the crosslinking reaction is promoted. Therefore, even without the addition of a crosslinking process, the battery's crush test pass rate, cycle test capacity retention rate, and high temperature cycle life can be improved.

[0187] After coating the separators, and following assembly, finishing (charge / discharge, degassing), and inspection processes, non-aqueous secondary batteries can be manufactured within 1 to 5 days after coating, if all goes smoothly. From the perspective of ensuring the cross-linking reaction proceeds fully before this point, it is important that the cross-linking process is easy to complete (fast reaction).

[0188] It is known that the crosslinking reaction rate depends on environmental factors such as solvent liquidity and temperature. However, the influence of structural factors such as inter-functional group distance and steric hindrance has not been fully studied. In this invention, the inventors, through a combination of specific X-ray structural analysis (SAXS and WAXS) and specific functional group dispersion analysis (TOF-SIMS) based on the desired application, discovered conditions under which the crosslinking reaction of the separator is easily carried out. Furthermore, considering thermal creep resistance, they discovered conditions optimal for separators used in non-aqueous secondary batteries. While not wishing to be bound by theory, according to this invention, by designing in a manner that specifies a crystal structure, the number of banded molecules in the amorphous layer increases, thermal creep resistance is improved, and even when uneven stress is generated within the battery, uneven deformation of the separator can be suppressed. This also suppresses localized obstruction of the flow of Li ions and electrolyte decomposition products, which is believed to improve high-temperature cycle life.

[0189] Furthermore, by designing the structure with numerical values ​​related to the crystal structure and specifying the dispersion state of the silicon (Si) functional groups, the diffusion of the Li ion complex is improved due to the interaction with the Si element in the silicon (Si) functional groups, thereby suppressing the local growth of Li dendrites and improving cycle performance. Additionally, by designing the structure with numerical values ​​related to the crystal structure and specifying the dispersion state of the silicon (Si) functional groups, the silicon (Si) functional groups are closer together, facilitating crosslinking reactions and enabling crosslinking reactions to occur during the coating process in the manufacturing process of the separator. Furthermore, by designing the structure with numerical values ​​related to the crystal structure and specifying the dispersion state of the silicon (Si) functional groups, the number of crosslinks increases and the resin fluidity at high temperatures decreases, thereby improving safety during crush tests. By using a coating liquid with high polyolefin penetration in the coating process, the thermal vibration of the aforementioned silicon (Si) functional groups is promoted through the solvent penetrating between the polyolefin molecular chains, thereby further promoting the crosslinking reaction. By using a coating liquid containing polar molecules, the polar molecules and / or hydrogen ions and / or hydroxide ions in the coating liquid act as catalysts, further promoting the crosslinking reaction between the aforementioned silicon (Si) functional groups. Through these methods, the high-temperature fluidity of the separator can be reduced, thereby improving the high-temperature cycle life and crush-damage safety of non-aqueous secondary batteries.

[0190] From the viewpoint of facilitating crosslinking of the separator and improving the battery's crush test pass rate, cycle test capacity retention rate, high-temperature cycle life, and / or achieving a balance between them, it is preferable to analyze the crystal structure of polyolefins, and more preferably to analyze the crystal structure of polyethylene, in the SAXS and WAXS measurements of the separator. The silane-modified polyolefin of Embodiment 4 can be contained at any location in the separator. For example, in the case of a single-layer separator containing only a microporous membrane made of polyolefin, it can exist in or on the surface of the microporous membrane. In the case of a multi-layer separator containing layers formed on one or both sides of the microporous membrane, it can exist in or on the surface of the microporous membrane, or in or on the formed layers. From the same viewpoint, it is preferable to exist in or on the surface of the microporous membrane made of polyolefin as the substrate. The WAXS measurement can be performed by transmission method or reflection method (XRD). From the viewpoint of analyzing not only the surface of the separator but also the internal crystal structure, the WAXS measurement of the separator is preferably performed by transmission method.

[0191] Regarding the crystallization period obtained from SAXS testing, from the same viewpoint, it is preferably greater than 20 nm and less than 49 nm, more preferably greater than 22 nm and less than 47 nm. From the same viewpoint, the crystallinity obtained from WAXS testing is preferably greater than 60% and less than 80%, more preferably greater than 62% and less than 78%. From the viewpoint of improving the battery's crush test pass rate, cycle test capacity retention rate, high-temperature cycle life, and / or achieving a balance between them, the crystallite size (110 facets) of polyethylene containing silane-modified polyolefin separators detected in WAXS testing is preferably in the range of 10 nm to 50 nm, more preferably in the range of 12 nm to 47 nm.

[0192] When the crystallization period is too long, the crystal melting temperature rises due to the Gibbs-Thomson effect, resulting in a higher shut-off temperature. Furthermore, an excessively long crystallization period reduces the number of ligand molecules, thus decreasing heat creep resistance. This leads to a decrease in the crush test pass rate and a reduction in high-temperature cycle life. Additionally, increasing the deformation during the stretching process to extend the crystallization period worsens the thermal shrinkage properties of the separator.

[0193] On the other hand, when the crystallization cycle is too short, the distance between the silane-modified units in the amorphous region becomes excessively small, resulting in decreased solvent permeability and / or steric hindrance between the silane-modified groups, leading to decreased crosslinking. Consequently, the viscoelasticity during melting decreases, and the melting point drops. This, in turn, causes a decrease in the crush test pass rate and a decrease in high-temperature cycle life. Furthermore, to reduce the crystallization cycle, the stretching amount needs to be reduced in the stretching process, resulting in a decrease in the pore size and number of pores in the separator, which worsens permeability. This, in turn, causes a decrease in the crush test pass rate, a decrease in the cycle test capacity retention rate, and a decrease in high-temperature cycle life.

[0194] Similarly, excessive crystallinity leads to an increase in the crystal melting temperature due to the Gibbs-Thomson effect, a higher closing temperature of the separators, and a decrease in the number of banded molecules, thus reducing heat creep resistance. Between opposing crystal planes, the distance between silane-modified units decreases, reducing solvent penetration and steric hindrance of the branches, resulting in decreased crosslinking. This leads to a decrease in viscoelasticity and melting point during melting. Consequently, this causes a decrease in the crush test pass rate and a reduction in high-temperature cycle life.

[0195] On the other hand, when crystallinity is too low, the film-forming properties of the separators are limited, resulting in poor thermal shrinkage. Furthermore, the number of banded molecules decreases, thus reducing heat creep resistance. Additionally, the distance between silane-modified units increases between opposing crystal planes, reducing cross-linking and lowering viscoelasticity and melting point. Consequently, this leads to a decrease in crush test pass rate and high-temperature cycle life.

[0196] When the crystallite size is too large, the crystal melting temperature and shut-off temperature rise due to the Gibbs-Thomson effect. Furthermore, the number of ligand molecules decreases, thus reducing heat creep resistance. This, in turn, leads to a decrease in the crush test pass rate and a reduction in high-temperature cycle life.

[0197] On the other hand, reducing the crystallite size requires stretching and heat treatment at low temperature and high tensile force after sheet forming. This can easily leave residual stress in the separator, leading to poor thermal shrinkage. Consequently, this results in a decrease in the crush test pass rate and a reduction in high-temperature cycle life.

[0198] From the viewpoint of facilitating cross-linking of the separator and improving the battery's crush test pass rate, cycle test capacity retention rate, high temperature cycle life, and / or achieving a balance between them, the crystallite size (110) of polyethylene in the separator, as determined by XRD, is preferably 14.2 to 40.0 nm, and / or the crystallinity, as determined by XRD, is preferably 80 to 99%.

[0199] Regarding the separator containing silane-modified polyolefin, the ratio (110) / (200) of the crystallite size in the direction perpendicular to the (110) plane to the crystallite size in the direction perpendicular to the (200) plane, as detected in WAXS measurements, is preferably 0.9 to 2.0, more preferably in the range of 1.0 to 1.7, from the viewpoint of improving the battery's crush test pass rate, cycle test capacity retention rate, high temperature cycle life, etc., and / or achieving a balance between them.

[0200] Starting from the same point of view as above, the thickness (length) of the amorphous portion of the separator containing silane-modified polyolefin is calculated by the following formula based on the crystallization long period of polyethylene detected by small-angle X-ray scattering and the crystallinity detected by wide-angle X-ray scattering.

[0201] Formula: Amorphous region thickness [nm] = (crystallization period [nm]) × (1 - crystallinity [%) / 100)

[0202] Preferably, the amorphous portion is in the range of 3nm to 23nm, more preferably in the range of 5nm to 15nm, and even more preferably in the range of 8nm to 13nm. When the amorphous portion thickness (amorphous portion length) is too large, the entanglement of molecular chains within the amorphous portion increases, thus strengthening the intercrystalline constraint and increasing the shut-off temperature. Furthermore, the distance between silane-modified units between opposing crystal planes increases, reducing crosslinking and decreasing the viscoelasticity and melting point during melting. This, in turn, leads to a decrease in the crush test pass rate and a decrease in high-temperature cycle life. On the other hand, when the amorphous portion length is too small, the entanglement of molecular chains decreases, resulting in a decrease in heat creep resistance. Additionally, the distance between silane-modified units between opposing crystal planes decreases, leading to a decrease in crosslinking due to reduced solvent penetration and steric hindrance of branches, resulting in a decrease in viscoelasticity and melting point during melting. This, in turn, leads to a decrease in the crush test pass rate and a decrease in high-temperature cycle life.

[0203] Regarding the thickness of the crystalline portion of the separator containing silane-modified polyolefin, from the same viewpoint as above, it is preferably in the range of 15 nm to 36 nm, and more preferably in the range of 17 nm to 34 nm. When the crystalline portion thickness (crystal length) is too large, the crystal melting temperature and shut-off temperature increase due to the Gibbs-Thomson effect. Furthermore, the number of banded molecules decreases, thus reducing heat creep resistance. This, in turn, leads to a decrease in the crush test pass rate and a decrease in high-temperature cycle life. On the other hand, reducing the crystal length requires stretching and heat treatment at low temperature and high tensile force after sheet forming, which easily leaves residual stress in the separator, resulting in poor thermal shrinkage. This, in turn, leads to a decrease in the crush test pass rate and a decrease in high-temperature cycle life.

[0204] From the same perspective as above, in the WAXS measurement of separators containing silane-modified polyolefins, it is preferable that the cross-sectional crystal orientation degree of polyethylene in the separator, measured from the MD direction, is in the range of 0.70 to 0.99, and the cross-sectional crystal orientation degree of polyethylene in the TD direction, measured from the TD direction, is in the range of 0.70 to 0.99. When the cross-sectional crystal orientation degree measured from the MD and TD directions is 0.70 or higher, it is easy to ensure the strength of the separator; on the other hand, when it is 0.99 or lower, it is easy to form a film from the separator. From the viewpoint of the strength and film-forming properties of the separator, it is more preferable that the cross-sectional crystal orientation degree of polyethylene in the separator, measured from the MD direction, is in the range of 0.76 to 0.98, and / or that the cross-sectional crystal orientation degree of polyethylene in the separator, measured from the TD direction, is in the range of 0.74 to 0.93.

[0205] When the cross-sectional crystal orientation is too large, the deformation along the orientation direction during melting increases, resulting in poor thermal shrinkage. Consequently, the crush test pass rate and high-temperature cycle life decrease. Conversely, when the cross-sectional crystal orientation is too small, it also leads to a decrease in the crush test pass rate and high-temperature cycle life. It is known that, generally, when stress is applied to resin materials, the fewer the telomeres oriented along the stress direction, the lower the heat creep resistance. When the cross-sectional crystal orientation is too small, uneven stress is generated within the cell, causing uneven deformation of the separator, uneven flow of the SFC, and the formation of an uneven SEI layer, which in turn leads to a decrease in the crush test pass rate and high-temperature cycle life.

[0206] From the viewpoint of improving the mechanical strength of the separator, the pass rate of the battery crush test, the capacity retention rate of the cycle test, the high temperature cycle life, and / or achieving a balance between them, the cross-sectional crystal orientation degree of polyethylene in the MD direction of the separator, as measured by XRD, is preferably 0.85 to 0.99, and / or the cross-sectional crystal orientation degree of polyethylene in the TD direction is preferably 0.85 to 0.99.

[0207] Based on the same viewpoint as above, the ratio of the cross-sectional crystal orientation degree of polyethylene measured from the MD direction to that measured from the TD direction, MD / TD, of the separator is preferably in the range of 0.45 to 1.35 or 0.5 to 1.2, more preferably in the range of 0.50 to 1.20 or 0.60 to 1.25, and even more preferably in the range of 0.80 to 1.15. By ensuring that the ratio of the cross-sectional crystal orientation degree of polyethylene measured from the MD direction to that measured from the TD direction, MD / TD, of the separator is within the above range, the mechanical strength of the separator increases, and it is less prone to creep deformation under complex stresses generated unevenly within the battery. Consequently, the battery's crush test pass rate, cycle test capacity retention rate, and high-temperature cycle life are improved.

[0208] The values ​​of the separators detected by SAXS and / or WAXS measurements can be adjusted to the range described above, for example, during the manufacturing process of the separators, by quantifying or selecting the Si modification rate, C3 / C4 molecular structure, number-average molecular weight (Mn), weight-average molecular weight (Mw), dispersity (Mn / Mw), etc., for the silane-modified polyolefins used to prepare uniform Si molecular structures, and / or by quantifying or selecting the polyolefin resins other than silane-modified polyolefins by Mn, Mw, Mn / Mw, etc., and / or by quantifying the mixing ratio of silane-modified polyolefins and polyolefin resins other than silane-modified polyolefins.

[0209] In the Voronoi polygons obtained by Voronoi segmentation of Si-containing images detected by TOF-SIMS measurement of separators containing silane-modified polyolefins, the Voronoi area (mu) with the highest frequency is preferably 6.00 m. 2 ~12.00μm 2 Within this range. The Voronoi area (mu) with the highest frequency is 6.00 μm. 2 ~12.00μm 2 Within this context, there is a tendency to easily improve the battery's crush test pass rate, cycle test capacity retention rate, high-temperature cycle life, and / or to easily achieve a balance between them. More specifically, in the Voronoi polygons obtained by the above Voronoi segmentation, the Voronoi area (mu) with the highest frequency is 6.00 μm. 2 ~12.00μm 2 Within a certain range, there is a strong tendency for Si molecules to be dispersed in the separator in a non-island structure. For example, when the non-aqueous secondary battery is a lithium-ion secondary battery, when a separator with uniformly dispersed Si elements coexists with a lithium (Li) complex solvated by an electrolyte containing non-covalent electron pairs such as oxygen atoms, it is believed that the battery's product life in cycle characteristic tests is extended due to the phenomena described in items (i) and (ii) above in Embodiment 1.

[0210] Furthermore, most Si-containing molecules have cross-linking properties. For example, when they have silane cross-linking properties, it is believed that the silane cross-linking properties of Si-containing molecules dispersed in non-aqueous secondary batteries can be ensured, thereby ensuring the stability of siloxane bonds and maintaining the cross-linking structure of the separator for a long time. Thus, safety can be ensured in safety tests such as crush tests.

[0211] For the separator in Embodiment 4, when TOF-SIMS measurement is performed with a 100 μm tetragonal area, at least one silicon-containing structure can be detected, and preferably, Si-containing molecules are detected dispersed in the separator in a non-island structure state.

[0212] From the viewpoint of further improving the safety of the separator and the non-aqueous secondary battery containing it, the separator of Embodiment 4 preferably contains silane-modified polyethylene as a Si-containing molecule, and more preferably, the separator undergoes a silane crosslinking reaction of the silane-modified polyethylene when in contact with the coating liquid or electrolyte.

[0213] From the viewpoint of improving the battery's pass rate in crush tests, capacity retention in cycle tests, high-temperature cycle life, and / or achieving a balance between them, the Voronoi polygon obtained by the aforementioned Voronoi segmentation preferably has a Voronoi area (mu) with the highest frequency of 6.20 μm. 2 ~11.80μm 2 Within the range.

[0214] The extent (σ) of the Voronoi area frequency distribution in the Si-containing image detected by TOF-SIMS measurement is more preferably 2.00 μm. 2 ~4.00μm 2 Within the range. The σ of the separator is 2.00 μm. 2 At the above levels, it is easy to fabricate a film on the separator; on the other hand, the thickness is 4.00 μm. 2 The following parameters can improve the battery's crush test pass rate, cycle test capacity retention rate, and high-temperature cycle life. From this perspective, the σ of the separator is more preferably 2.30 μm. 2 ~3.60μm 2 Within the range.

[0215] For Si-containing images detected by TOF-SIMS, the ratio (σ / mu) of the breadth (σ) of the voronoie area frequency distribution to the voronoie area (mu) with the highest frequency preferably satisfies the following relationship.

[0216] 0.20≤σ / mu≤0.40

[0217] The ratio (σ / mu) in the Voronoi separator can be considered an indicator of whether Si-containing molecules are uniformly dispersed on the surface of the separator. When the ratio (σ / mu) is in the range of 0.20 to 0.40, the Si-containing molecules are uniformly dispersed on the surface of the separator. In non-aqueous secondary batteries, this is conducive to the coexistence of Li complexes from the electrolyte with the separator and the silane crosslinking reaction of the separator, and can take into account the film-forming properties of the separator containing silane-modified polyolefins and the cycle characteristics of non-aqueous secondary batteries. Although it is not desirable to be bound by theory, the concentration of intermediates formed by the coordination of Li complexes in the separator surface and the equilibrium state lifetime of the intermediates are important. In Embodiment 4, experiments showed that the ratio (σ / mu) within the above-mentioned numerical range can help to make the intercalation reaction to the electrode uniform. From the viewpoint of ensuring the film-forming properties of the separator and further extending the cycle life of the battery, the ratio (σ / mu) is more preferably 0.22 or more and 0.38 or less.

[0218] The values ​​of the separator obtained by Voronoi splitting in Embodiment 4 can be adjusted to the range described above, for example, by controlling the structure containing Si molecules, the molecular weight or molecular weight distribution of the raw materials constituting the separator, and the mixing range of the raw materials constituting the separator.

[0219] As is desired, the separator in embodiment 4 can have a multi-layer structure and can be provided in the form of a non-aqueous secondary battery with the separator.

[0220] <Implementation Method 5: Structure of the separator containing silane-modified polyolefin, Voronoi segmentation, and changes in air permeability and crystal structure before and after compression>

[0221] Embodiment 5 provides a separator for a non-aqueous secondary battery that combines the configurations of Embodiments 1 to 4.

[0222] In Embodiment 5, the separator for the non-aqueous secondary battery is a polyolefin microporous membrane containing silane-modified polyolefin. The Voronoi polygons obtained by Voronoi segmentation of the Si-containing image detected by TOF-SIMS measurement of the separator have a Voronoi area (mu) with the highest frequency of occurrence within 1.0 μm. 2 ~17.5μm 2 Or 6.0μm 2 ~12.0μm 2 Within the range, and the breadth (σ) of the Voronoi area frequency distribution of Si-containing images detected by TOF-SIMS measurement is within 0.5 μm. 2 ~8.5μm 2Within the range, and the change ratio of air permeability (air permeability Sh after compression / air permeability Sj before compression) when the thickness of the separator is compressed by 30% is in the range of 1.1 to 7.0 times, and the crystallization period of polyethylene detected by SAXS is 20 to 50 nm, the crystallinity detected by WAXS is 60% to 80%, and / or the crystallite size (110) of polyethylene detected by WAXS is 10 to 50 nm.

[0223] The constituent elements of the separator in embodiments 1 to 5 will be described below.

[0224] <Polyolefins>

[0225] The polyolefin is not particularly limited, and examples include homopolymers of ethylene or propylene, or copolymers formed from at least two monomers selected from the group consisting of ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, norbornene, and modified polyolefins. From the viewpoint of not clogging pores and being able to undergo heat setting at higher temperatures (sometimes abbreviated as "HS"), high-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene (UHMWPE), or modified polyolefins are preferred, with high-density polyethylene, UHMWPE, or modified polyolefins being more preferred. Typically, the weight-average molecular weight of UHMWPE is known to be 1,000,000 or higher. It should be noted that a single polyolefin or a combination of two or more can be used.

[0226] From the viewpoint of imparting to the separator the properties obtained by the Voronoi split as described above, the properties obtained by SAXS and / or WAXS, modified polyolefins are preferred as polyolefins, and silane-modified polyethylene (hereinafter referred to as Resin A) is more preferred.

[0227] From the perspective of seeking a balance between the long lifespan and safety of non-aqueous secondary batteries in terms of cycle characteristics, and from the perspective of uniformly configuring the Si-containing molecular structure, optimizing the various values ​​described above regarding SAXS and / or WAXS measurements and Voronoi segmentation, facilitating cross-linking of the separator, and improving the battery's crush test pass rate, cycle test capacity retention rate, high-temperature cycle life, and / or achieving a balance between them, it is preferable to use at least one polyolefin other than silane-modified polyethylene in addition to resin A. As a polyolefin other than silane-modified polyethylene, it is more preferable to use UHMWPE (hereinafter referred to as resin B) with a viscosity-average molecular weight (Mv) of 1,800,000 or more. It is even more preferable to use not only resin B but also polyethylene with an Mv of less than 1,800,000 (hereinafter referred to as resin C).

[0228] (Silicon-containing structure of separators and Voronoi partition)

[0229] In the silane-modified polyolefin of the separator, the number of methylene (CH2) groups constituting the linking portion with the main chain is preferably 2 to 10. The number of methylene (CH2) groups constituting the linking portion with the main chain refers to the number of (CH2) groups connecting the main chain of the silane-modified polyolefin and the Si atoms, for example, the value of n in the following formula (I).

[0230]

[0231] {In the formula, R can be represented by methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc., and n is the number of methylene (CH2) groups that constitute the linking portion to the main chain as described above.}

[0232] For example, for silane-modified polyolefins containing Si functional groups, if the number of CH2 groups constituting the linking portion with the polyolefin backbone containing polyethylene or similar main components is in the range of 2 to 10, it is easy to construct a higher-order structure that readily undergoes silane crosslinking reaction. From the viewpoint of ensuring the ease of crosslinking of the separator and improving the battery's crush test pass rate, cycle test capacity retention rate, high-temperature cycle life, and / or achieving a balance between them, the number of CH2 groups is more preferably in the range of 2 to 6.

[0233] <Resin A: Silane-modified polyethylene>

[0234] The separator containing silane-modified polyethylene (resin A) preferably undergoes a silane crosslinking reaction of the silane-modified polyethylene when in contact with a coating liquid or electrolyte. Examples of silane-modified polyethylene include, for instance, silane-grafted modified polyethylene. It is believed that the functional groups contained in the polyolefin constituting the separator do not enter the crystalline portion of the polyolefin but instead undergo crosslinking in the amorphous portion. Therefore, when the separators of Embodiments 1 to 5 come into contact with the electrolyte, a crosslinked structure is formed using the chemical substances in the electrolyte, thereby suppressing the increase of internal stress or the deformation of the manufactured battery, and improving safety in tests such as nail puncture.

[0235] In addition, the separators in embodiments 1 to 5 can react with H in the coating liquid. + Crosslinking reactions occur through ionic or -OH group reactions, thereby suppressing the increase of internal stress or deformation of the manufactured battery, and improving safety in tests such as crush tests. While it is undesirable to be bound by theory, it is believed that when the aqueous coating solution is acidic, the activity energy of the reaction system decreases, and the crosslinking reaction of the separator becomes easier. When the aqueous coating solution is alkaline, it is believed that the presence of OH- promotes the silane crosslinking reaction of the separator. In the case of non-aqueous coating solutions, the organic solvent of the coating solution enters the amorphous portion of the polyethylene in the separator and promotes molecular motion, which is believed to promote the silane crosslinking reaction.

[0236] In the separator, a silane cross-linked structure (gel-like structure) is constructed by modifying polyethylene with silane, thereby exhibiting high-temperature rupture resistance and improved safety in crush tests. This is presumably because the polyethylene dispersed in the mixed resin is suitably linked to each other, and / or to polyolefins other than polyethylene, through the silane cross-linked structure. That is, by changing the overall morphology of the separator containing the polyolefin microporous membrane, an increase in tensile elongation is also achieved, thereby potentially reducing the likelihood of separator breakage when the battery deforms under external forces.

[0237] Silane-modified polyolefins are structures in which the main chain is a polyolefin and alkoxysilane groups are grafted onto the main chain. Silane-modified polyolefins can be obtained, for example, by grafting alkoxysilane groups onto the main chain of a polyolefin. Examples of unmodified silane polyolefins include polyethylene, polypropylene, and copolymers of ethylene and propylene. Examples of silane-modified polyethylene include graft copolymers obtained by grafting unsaturated silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltriacetoxysilane onto polyethylene such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, as well as ethylene-olefin unsaturated silane compound copolymers.

[0238] It is speculated that the alkoxysilyl group of silane-modified polyethylene is converted into a silanol group through a water-based hydrolysis reaction and undergoes a cross-linking reaction to form a siloxane bond (refer to the hydrolysis reaction, condensation reaction, and dehydration condensation reaction shown in the following formula; the ratio of T0 structure to T1, T2, or T3 structure is arbitrary, and the following formula describes the case where the number n of methylene (CH2) constituting the linking part with the main chain described in the above formula (I) is 2, but n can also be 3 to 10). There are no particular limitations on the alkoxysilyl group replaced by the alkoxy group, and examples include methoxy compounds, ethoxy compounds, butoxy compounds, etc. For example, in the following formula, R can include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, etc.

[0239]

[0240] In silane-modified polyethylene, the main chain and the graft are connected by covalent bonds. There are no particular limitations on the structures forming these covalent bonds; examples include alkyl groups, ethers, glycols, and esters.

[0241] From the perspective of uniformly configuring the equilibrium state lifetime of Si-containing molecular structures and Li complex coordination, and also from the perspective of optimizing the various values ​​of SAXS and / or WAXS measurements and Voronoi fractionation as described above, facilitating crosslinking of the separator, and improving the battery's crush test pass rate, cycle test capacity retention rate, high-temperature cycle life, and / or achieving their balance, in the stage before the crosslinking reaction of resin A, resin A preferably contains 0.03 to 1.0 mol% silanol units (i.e., silanol unit modification rate of 0.03 to 1.0 mol%), more preferably 0.05 to 0.35 mol%, further preferably 0.07 to 0.32 mol%, particularly preferably 0.08 to 0.30 mol%, and most preferably 0.12 to 0.28 mol%. In embodiments 1 to 5, the silane-modified units exist only in the amorphous portion of the separator. Furthermore, considering the distance between the silane-modified units and their thermal vibrational motion at -10°C to 80°C, molecular structures that facilitate cross-linking reactions are designed. In the above formulas, structures T0, T1, T2, and T3 can all construct coordination intermediates with the Li complex. However, considering that the Li complex randomly coordinates, decoordinates, and recoordinates between Si atoms in the amorphous portion, the effect is maximized by adjusting the amount of silanol unit modification in resin A.

[0242] Based on the same viewpoint as above, resin A is preferably modified by 0.01 to 2.0 mol% of propylene (C3) units, 0.01 to 2.0 mol% of butene (C4) units, or a total of 0.01 to 2.0 mol% of C3 and C4 units.

[0243] From the same point of view as above, the C3 unit modification rate of resin A is more preferably 0.01 to 1.2 mol%, more preferably 0.01 to 0.75 mol%, particularly preferably 0.02 to 0.60 mol%, and most preferably 0.05 to 0.30 mol%.

[0244] Based on the cycle characteristics and safety of non-aqueous secondary batteries, and from the viewpoint of the FUSE function of the separator, the C4 unit modification rate of resin A is more preferably 0.01 to 1.0 mol%, more preferably 0.30 to 0.70 mol%, and particularly preferably 0.48 to 0.65 mol% during the stage before the crosslinking reaction of resin A. On the other hand, during the heat setting (HS) process of the separator film, the C4 unit modification rate of resin A is preferably 0.43 mol% or less, more preferably 0.40 mol% or less, and even more preferably 0.1 mol% or less.

[0245] From the perspective of not only the cycle characteristics and safety of non-aqueous secondary batteries, but also from the perspective of optimizing the SAXS and / or WAXS measurements and Voronoi segmentation of the separator and the various values ​​described above, improving the crush test pass rate, cycle test capacity retention rate, high temperature cycle life and / or achieving a balance between them, the total modification rate of C3 and C4 units of resin A is more preferably 1.5 mol% or less, further preferably 1.0 mol% or less, particularly preferably 0.6 mol% or less, and most preferably 0.3 mol% or less.

[0246] Regarding the number-average molecular weight (Mn) of resin A, from the viewpoint of the cycle characteristics and safety of non-aqueous secondary batteries, it is preferably 10,000 to 20,000, more preferably 16,000 or less, and even more preferably 15,000 or less.

[0247] From the same point of view as above, the weight-average molecular weight (Mw) of resin A is preferably 45,000 to 200,000, more preferably 140,000 or less, even more preferably 129,000 or less, particularly preferably 100,000 or less, and most preferably 72,000 or less.

[0248] Based on the same viewpoint as above, the Mw / Mn ratio of resin A is preferably 3.0 to 12, more preferably 4.0 to 9.0, and even more preferably 4.1 to 8.0.

[0249] From the same point of view as above, the crystallinity of resin A is preferably 40-70%, more preferably 50-68%, and even more preferably 60-65%.

[0250] From the same point of view as above, the crystallite size (110) of resin A is preferably 15-30 nm, more preferably 17-28 nm, and even more preferably 20-25 nm.

[0251] Based on the same viewpoint as above, the crystallization period of resin A is preferably 15-30 nm, more preferably 17-27 nm, and even more preferably 20-25 nm.

[0252] For resin A, there are no limitations; its viscosity-average molecular weight (Mv) can be, for example, 20,000 to 150,000, and its density can be, for example, 0.90 to 0.97 g / cm³. 3 Its melt mass flow rate (MFR) at 190°C can be, for example, 0.1 to 15 g / min.

[0253] The polyethylene constituting silane-modified polyethylene can be composed of a single type of ethylene or two or more types of ethylene. It is also possible to use a combination of two or more silane-modified polyethylenes composed of different types of ethylene.

[0254] <Resin B: UHMWPE with an Mv of 1,800,000 or higher>

[0255] Resin B is a UHMWPE with an Mv of 1,800,000 or higher, and is preferably used in combination with resin A. It can also be used in combination with resin C as desired.

[0256] Regarding the Mn content of resin B, from the viewpoint of the cycle characteristics and safety of non-aqueous secondary batteries, and also from the viewpoint of optimizing the various values ​​described above for the SAXS and / or WAXS measurements and Voronoi segmentation of the separator, improving the crush test pass rate, cycle test capacity retention rate, high temperature cycle life, etc., and / or achieving a balance among them, it is preferably 200,000 to 1,400,000, more preferably 210,000 to 1,200,000, and even more preferably 250,000 to 1,000,000.

[0257] Based on the same viewpoint as above, the Mw of resin B is preferably 1,500,000 to 8,800,000, more preferably 1,600,000 to 7,100,000, and even more preferably 1,700,000 to 6,200,000.

[0258] From the same point of view as above, the ratio of Mw to Mn (Mw / Mn) of resin B is preferably 3.0 to 12, more preferably 4.0 to 9.0, and even more preferably 6.0 to 8.8.

[0259] From the same point of view as above, the Mv of resin B is preferably greater than 1,800,000 and less than 10,000,000, more preferably 1,850,000 to 8,500,000, even more preferably 1,950,000 to 7,800,000, and particularly preferably 2,000,000 to 6,500,000.

[0260] <Resin C: Polyethylene with a molecular weight (Mv) of less than 1,800,000>

[0261] Resin C is polyethylene with an Mv of less than 1,800,000, and is preferably used in combination with resin A, but may be used in combination with resin B as desired.

[0262] Regarding the Mn content of resin C, from the viewpoint of the cycle characteristics and safety of non-aqueous secondary batteries, and also from the viewpoint of optimizing the various values ​​described above for SAXS and / or WAXS measurements and Voronoi segmentation of the separator, improving the crush test pass rate, cycle test capacity retention rate, high temperature cycle life, and / or achieving a balance among them, it is preferably 20,000 to 250,000, more preferably 30,000 to 200,000, further preferably 32,000 to 150,000, and particularly preferably 40,000 to 110,000.

[0263] From the same point of view as above, the Mw of resin C is preferably 230,000 to 1,500,000, more preferably 280,000 to 1,300,000, even more preferably 320,000 to 1,200,000, and particularly preferably 400,000 to 1,000,000.

[0264] From the same point of view as above, the ratio of Mw to Mn (Mw / Mn) of resin C is preferably 3.0 to 12, more preferably 4.0 to 9.0, and even more preferably 6.0 to 8.8.

[0265] From the same point of view as above, the Mv of resin C is preferably 250,000 or more and less than 1,800,000, more preferably 300,000 or more and less than 1,600,000, even more preferably 320,000 or more and less than 1,100,000, and particularly preferably 450,000 to 800,000.

[0266] <Any ingredient>

[0267] As any component that may be included in the separator, examples include components that are different from all resins A to C, such as polymers or additives that are different from all resins A to C. Any component is not limited to a single one. The separator may include multiple polymers that are different from all resins A to C, and may include multiple additives. Alternatively, the separator may include both the polymer and the additive. Examples of any polymer component include, for example, polypropylene (PP), polystyrene (PS), polyacrylate, polymethacrylate, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyester, polycarbonate (PC), polysulfone (PSU), polyethersulfone (PES), polyphenylene ether (PPO), polyarylene ether polymers, polyphenylene sulfide (PPS), polyphenylene sulfide sulfone, polyphenylene oxide (PPP), polyarylene polymers, polyarylene ketones, polyether ketones (PEK), and polyarylene... Homopolymers and copolymers of at least one of the following: phosphine oxide, polyether phosphine oxide, polybenzoxazole (PBO), polybenzothiazole (PBT), polybenzimidazole (PBI), polyamide (PA), polyimide (PI), polyetherimide (PEI), and polyimide sulfone (PIS). Examples of additives include antioxidants such as phenolic compounds, phosphorus compounds, and sulfur compounds; metal soaps such as calcium stearate and zinc stearate; ultraviolet absorbers; light stabilizers; antistatic agents; antifogging agents; and coloring pigments. When the separator contains multiple arbitrary components, the total content of these multiple arbitrary components may be less than 20% by mass.

[0268] The separator may contain not only the additives exemplified above, but also known additives such as plasticizers, but preferably no catalysts containing organometallic substances (dehydration condensation catalysts).

[0269] (Dehydration condensation catalyst)

[0270] Alkoxysilyl groups form siloxane bonds via water-based hydrolysis. However, the reaction is slow, so organometallic catalysts are often used to accelerate the condensation reaction. The metal in organometallic catalysts is, for example, at least one selected from the group consisting of scandium, vanadium, copper, zinc, zirconium, palladium, gallium, tin, titanium, iron, nickel, and lead. Examples of organometallic catalysts include dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin dioctanoate, which are known to significantly accelerate the reaction rate through the reaction mechanism proposed by Wei et al. (FW van de r. Wei”: Macromol. Chem., 181, 2541, 1980.). However, in recent years, to avoid the environmental and human health hazards of organotin compounds, it is known that the Lewis function of copper or titanium chelate complexes, combined with organic bases, can accelerate the formation of siloxane bonds between alkoxysilyl groups in a similar manner to organotin complexes.

[0271] It is known that catalysts containing organometallic compounds (dehydration condensation catalysts) also act as catalysts for the siloxane bond formation reaction of alkoxysilyl-containing resins. In this specification, the resin containing organometallic compounds (or dehydration condensation catalysts) prepared by pre-adding such catalysts to a resin containing silane-modified polyethylene before the sheet forming process (e.g., during a mixing process as required) is referred to as masterbatch resin.

[0272] The separator is preferably free of catalysts (dehydration condensation catalysts) containing organometallic substances and masterbatch resins containing them.

[0273] <Separator Characteristics>

[0274] The following separator characteristics apply to polyolefin microporous flat membranes or monolayer membranes. When the microporous membrane is in the form of a laminated membrane, the following characteristics can be measured after removing the layers other than the polyolefin microporous membrane from the laminated membrane.

[0275] The porosity of the separator is preferably 20% or more, more preferably 30% or more, and even more preferably 32% or more or 35% or more. By making the porosity 20% or more, there is a tendency to further improve the puncture strength of the separator and its ability to follow the rapid movement of lithium ions. On the other hand, the porosity of the separator is preferably 90% or less, more preferably 80% or less, and even more preferably 50% or less. By making the porosity 90% or less, there is a tendency to further improve the film strength, further suppress self-discharge, and / or optimize the permeability. The porosity of the separator can be determined by the method described in the examples.

[0276] The air permeability of the separator, in the state before or before compression testing, is preferably 1 second or more, more preferably 30 seconds or more, further preferably 50 seconds or more, even more preferably 55 seconds or more, particularly preferably 70 seconds or more, and most preferably 75 seconds or more. By making the air permeability 1 second or more, there is a tendency to improve the balance between film thickness, porosity, and pore size, or to improve puncture strength. Furthermore, the air permeability of the separator is preferably 400 seconds or less, more preferably 300 seconds or less, and even more preferably 270 seconds or less. By making the air permeability 400 seconds or less, there is a tendency to further improve ion permeability. The air permeability of the separator can be measured by the method described in the examples.

[0277] The tensile strength of the separator is preferably 1000 kgf / cm in both the MD and TD directions. 2 The above, more preferably 1050 kgf / cm 2 The above is further optimized to 1100 kgf / cm². 2 The above. By achieving a tensile strength of 1000 kgf / cm. 2 The above measures aim to further suppress breakage during slitting, lamination, or winding with electrodes, or to further suppress short circuits caused by foreign objects within the battery. On the other hand, the tensile strength of the separator is preferably 5000 kgf / cm². 2 The following is more preferably 4500 kgf / cm² 2 The following is a further preferred value: 4000 kgf / cm² 2 The following is an example of achieving a tensile strength of 5000 kgf / cm. 2 The following results show that the separators quickly loosen and the contraction force weakens during the heating test, indicating a tendency for improved safety.

[0278] The tensile modulus of the separator is preferably 120 N / cm or less in both the MD and TD directions, more preferably 100 N / cm or less, and even more preferably 90 N / cm or less. A tensile modulus of 120 N / cm or less indicates that the separator has very little orientation for use in non-aqueous secondary batteries. In heating tests, for example, when a plugging agent such as polyethylene melts and shrinks, the polyethylene or the like quickly undergoes stress relaxation, thereby suppressing the shrinkage of the separator within the battery. This makes it easier to prevent short circuits between electrodes (i.e., it improves the safety of the separator during heating). A separator with such a low tensile modulus can be achieved by including polyethylene with a weight-average molecular weight of 500,000 or less in the polyolefin that forms the microporous membrane made of polyolefin, which serves as the substrate for the separator. On the other hand, there is no particular limitation on the lower limit of the tensile modulus of the separator, but it is preferably 10 N / cm or more, more preferably 30 N / cm or more, and even more preferably 50 N / cm or more. The tensile modulus can be appropriately adjusted by adjusting the degree of stretching or by relaxing it after stretching as needed.

[0279] The membrane thickness of the separator is preferably 1.0 μm or more, more preferably 2.0 μm or more, and even more preferably 3.0 μm or more or 4.0 μm or more. By making the membrane thickness 1.0 μm or more, there is a tendency to further improve the membrane strength. Furthermore, the membrane thickness of the separator is preferably 24 μm or less, more preferably 22 μm or less, and even more preferably 20 μm or less or 18 μm or less. By making the membrane thickness 24 μm or less, there is a tendency to further improve ion permeability. The membrane thickness of the separator can be measured by the method described in the examples.

[0280] In the polyethylene crystal structure of the separator, the preferred crystallinity of polyethylene, as determined by X-ray diffraction (XRD), is 60–99%, the preferred (110) crystallite size is 14.2–50.0 nm, the preferred cross-sectional orientation is 0.65–0.99, the preferred layer thickness is 15–40 nm, and the preferred crystallization period is 25–55 nm. The separator exhibits excellent crystal structure as determined by X-ray structural analysis due to its high compressive elastic recovery rate and resistance to creep deformation under external forces.

[0281] Regarding the puncture strength of the separator, from the viewpoints of ensuring handleability, safety in the HotBox test, and stabilization of heat shrinkage rate, a range of 200 gf to 600 gf is preferred, and a range of 210 gf to 390 gf is more preferred. From the same viewpoint, the puncture strength is calculated based on the unit area weight of the separator (puncture strength of the separator (gf) / unit area weight of the separator (g / m²)). 2 Preferred concentration is 50 gf / m 2 / g~100gf / m 2 Within the range of / g, more preferably within 60gf / m2 / g~90gf / m 2 Within the range of / g.

[0282] <Layer Composition>

[0283] The separator can have either a single-layer or multi-layer structure. From the viewpoint of having redox resistance and a dense and uniform porous structure, it is preferable to include at least one type of polyolefin microporous membrane. The polyolefin microporous membrane can be a single-layer membrane composed of a single layer of polyolefin-containing microporous layer, a multi-layer membrane composed of multiple polyolefin-containing microporous layers, or a multi-layer membrane with a polyolefin resin layer and a resin containing other resins as the main components, such as a thermoplastic polymer layer, an active layer, a heat-resistant resin layer, or an inorganic porous layer.

[0284] When the membrane is a bilayer formed from two microporous layers containing polyolefins, the polyolefin compositions of the two layers can be different. Furthermore, when the membrane is a multilayer formed from three or more microporous layers containing polyolefins, the polyolefin compositions of the outermost and innermost layers can be different; for example, it can be a three-layer membrane.

[0285] (Preferred multi-layer structure 1)

[0286] The separator having the preferred multilayer structure 1 preferably comprises: a polyolefin microporous membrane as a substrate and an inorganic porous layer, comprising inorganic particles and a resin binder, laminated on at least one side of the polyolefin microporous membrane. From the viewpoint of suppressing thermal shrinkage, improving the pass rate of crush tests, the capacity retention rate of cycle tests, the high-temperature cycle life, and / or achieving a balance among these, the content of inorganic particles contained in the inorganic porous layer is preferably 5% to 99% by mass based on the total mass of the inorganic porous layer, more preferably 10% by mass or more and less than 99% by mass.

[0287] (Another preferred multilayer structure 2-4)

[0288] It is also preferable to have a partition having the multi-layer structure 2 to 4 as illustrated below. In addition, any combination of multi-layer structures 1 to 4 is also preferred.

[0289] The separator having a multilayer structure 2 comprises: a polyolefin microporous membrane as a substrate and a thermoplastic polymer layer formed on at least one side of the polyolefin microporous membrane. The thermoplastic polymer contained in the thermoplastic polymer layer is preferably a polymeric unit comprising (meth)acrylate and / or (meth)acrylic acid, or a polyvinyl chloride compound containing at least one fluorinated atom selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE). By including the thermoplastic polymer layer, the adhesion between the electrode and the separator is improved, thus improving the processability during battery manufacturing.

[0290] The separator having a multilayer structure 3 comprises: a polyolefin microporous membrane as a substrate and an active layer disposed on at least one side of the polyolefin microporous membrane. The active layer is preferably at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE), PVDF homopolymer, a mixture of PVDF and tetrafluoroethylene-ethylene copolymer (ETFE), or a terpolymer of vinylidene fluoride-tetrafluoroethylene-ethylene, more preferably at least one selected from the group consisting of PVDF-HFP and PVDF-CTFE. By copolymerizing HFP or CTFE with vinylidene fluoride, the crystallinity of the fluorinated resin can be controlled within a suitable range, thus suppressing the flow of the active layer during the bonding process with the electrode. Furthermore, during the bonding process with the electrode, the adhesive strength is improved, thus reducing interfacial slippage when used as a separator for secondary batteries, thereby increasing the pass rate in the crush test.

[0291] Specific examples of PVDF are Arkema's Kynar Flex (registered trademark) series, such as LBG and LBG8200; and SOLVAY's Solef (registered trademark) series, such as Grade 1015 and 6020.

[0292] Specific examples of high-polymer PVDF-HFP are the Solef (registered trademark) series from SOLVAY, such as grades 21216 and 21510 (both soluble in acetone). Specific examples of high-polymer PVDF-CTFE are also the Solef (registered trademark) series from SOLVAY, such as grade 31508 (soluble in acetone).

[0293] The separator having a multilayer structure 4 comprises: a polyolefin microporous membrane as a substrate and a heat-resistant resin layer, comprising a heat-resistant resin, laminated on at least one side of the polyolefin microporous membrane. The heat-resistant resin preferably comprises at least one selected from the group consisting of fully aromatic polyamides (also known as aromatic amides), polyimides, polyamide-imides, polysulfones, polyketides, polyethers, polyetherketides, polyether-imides, and cellulose. From the viewpoint of durability, fully aromatic polyamides are preferred, and para-aromatic polyamides and / or meta-aromatic polyamides are more preferred. Furthermore, from the viewpoint of porous layer formation and redox resistance, meta-aromatic polyamides are preferred. Examples of meta-type polyamides include poly(m-phenylene isophthalamide). Furthermore, examples of para-type polyamides include copolymers (3,4'-oxydiphenylene terephthalamide) and poly(p-phenylene terephthalamide). Additionally, the heat-resistant resin layer preferably contains 30% to 90% by mass of inorganic materials with an average particle size of 0.2 μm to 0.9 μm. By incorporating a heat-resistant resin layer, thermal deformation of the separator is suppressed even in the event of a localized short circuit within the battery, thus improving the pass rate of the crush test.

[0294] The inorganic particles of multilayer structure 1 and / or 3, and the inorganic filler of multilayer structure 4, can be inorganic materials used in the manufacturing method of the separator for non-aqueous secondary batteries described later. Preferably, they are selected from at least one of the following groups: alumina, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, cerium oxide, yttrium oxide, zinc oxide, iron oxide, silicon nitride, titanium nitride, boron nitride, silicon carbide, aluminum hydroxide, talc, kaolinite, dickite, perlite, halloysite, pyrophyllite, montmorillonite, sericite, mica, magnesia chlorite, bentonite, asbestos, zeolite, diatomite, silica sand, and glass fiber.

[0295] <Manufacturing Method of Separators for Non-Aqueous Secondary Batteries>

[0296] (Manufacturing method of polyolefin microporous membrane)

[0297] As a method for manufacturing a separator for non-aqueous secondary batteries, the following description focuses on the case where the polyolefin microporous membrane is a single-layer membrane (flat membrane), but this is not intended to exclude methods other than flat membranes. The manufacturing methods of the microporous membranes in Embodiments 1 to 5 include the following steps:

[0298] (1) Sheet forming process;

[0299] (2) Stretching process;

[0300] (3) Porous body forming process; and

[0301] (4) Heat treatment process.

[0302] The manufacturing method of the microporous membrane in embodiments 1 to 5 may, as desired, include: a resin modification process or a mixing process before the sheet forming process (1); and / or, a winding / slitting process after the heat treatment process (3). From the viewpoint of maintaining the crosslinking property of the microporous membrane until it is housed in the battery, it is preferable not to include a crosslinking structure formation process or a contact process with a crosslinking promoting catalyst.

[0303] The cross-linking structure formation process includes: (1) a secondary step of causing the multiple functional groups contained in the microporous membrane to undergo a condensation reaction with each other; (2) a secondary step of causing the functional groups contained in the microporous membrane to react with chemical substances inside the battery; or (3) a secondary step of causing the functional groups contained in the microporous membrane to react with other functional groups. The cross-linking promoting catalyst is any catalyst capable of promoting cross-linking reactions, such as (I) condensation reactions of multiple identical functional groups, (II) reactions between multiple dissimilar functional groups, (III) chain condensation reactions of functional groups with the electrolyte, and (IV) chain condensation reactions of functional groups with additives. The cross-linking promoting catalyst may, for example, be a catalyst containing an organometallic substance.

[0304] (Manufacturing method of multilayer film)

[0305] The manufacturing method for a separator used in non-aqueous secondary batteries will be described below, particularly for the case of a multilayer film. The manufacturing method for a multilayer film includes the following steps:

[0306] (1) Sheet forming process;

[0307] (2) Stretching process;

[0308] (3) Porous body formation process;

[0309] (4) Heat treatment process;

[0310] (5) Coating process;

[0311] (6) Drying process; and

[0312] (7) Assembly process,

[0313] The process between process (5) and process (6) may include the water washing process of process (5.5).

[0314] In the method for manufacturing a multilayer membrane, a polyolefin microporous membrane is formed by performing steps (1) to (4) in the same manner as in the method for manufacturing a single-layer membrane. A coating step (5) is performed to coat at least one surface of the obtained polyolefin microporous membrane or a heat-treated porous body obtained by the heat treatment step (4). A drying step (6) is performed to remove the coating liquid. An assembly step (7) is performed to house the laminate of electrodes and separators or its winding with a non-aqueous electrolyte in a housing. Between steps (5) and (6), a water washing step (5.5) may be included to replace the solvent component in the coating liquid with another solvent component. Furthermore, the method for manufacturing a multilayer membrane is characterized by forming a cross-linked structure of the silane-modified polyolefin contained in the multilayer membrane in at least one of the coating step (5), the water washing step (5.5), the drying step (6), and the assembly step (7). Preferably, the cross-linked structure of the silane-modified polyolefin is formed in the coating step (5) and the assembly step (7).

[0315] The following describes the various steps involved in the manufacturing methods of single-layer and multilayer films.

[0316] In the mixing process, a mixing machine can be used to mix, for example, polyolefins, other desired resins, plasticizers, or inorganic materials. From the viewpoint of suppressing the formation of resin aggregates during the manufacturing process and maintaining the crosslinking properties of the microporous membrane until it is housed in the battery, it is preferable not to add masterbatch resin containing crosslinking promoting catalysts to the mixture.

[0317] The polyolefin supplied for the mixing or sheet forming process (1) is not limited to olefin homopolymers, but can also be a polyolefin obtained by copolymerizing monomers with functional groups, or a functional group-modified polyolefin. This functional group is one that can participate in the formation of a cross-linked structure, such as the alkoxysilyl group described above. By preparing silane-modified polyethylene (resin A) as a raw material, the resin modification process can be omitted.

[0318] On the other hand, when the polyolefin raw material lacks functional groups capable of participating in the formation of a cross-linking structure, or when the molar percentage of such functional groups is lower than a specified proportion, the polyolefin raw material can be supplied to a resin modification process to introduce functional groups into the resin backbone or increase the molar percentage of functional groups, thereby obtaining a functional group-modified polyolefin. The resin modification process can be carried out by known methods. For example, the polyolefin raw material can be contacted with the reaction reagent in a manner that allows cross-linking functional groups to be introduced into the polyolefin backbone through liquid spraying, gas spraying, dry mixing, impregnation, coating, etc.

[0319] From the viewpoint of imparting the properties to the separator obtained by the change rate of air permeability before and after vorono segmentation or compression as described above, and from the viewpoint of optimizing the crystal structure containing Si molecules as described above, as well as the various values ​​described above regarding SAXS and / or WAXS measurements and vorono segmentation, it is preferable to prepare silane-modified polyethylene (resin A) as a polyolefin raw material, and more preferably, not only resin A, but also resin B and / or resin C as described above.

[0320] From the perspectives of the lifetime of the equilibrium state of the coordination intermediate of the Li complex with uniformly configured Si molecular structures, uniform extrusion / blending, optimizing the crystal structure of the Si molecules as described above, and considering the various values ​​explained above regarding SAXS and / or WAXS measurements and Voronoi fractionation, specific molecular designs or blends can be performed on resin A and resins B and C. As mentioned above, Si molecules exist only in the amorphous portion of the polyolefin resin. By integrally introducing the siloxane units and C3 / C4 units of resin A into the design, the lifetime of the equilibrium state of the coordination intermediate of the Li complex can be controlled. On the other hand, by blending resin A with resins B and C, from the perspective of constructing suitable amorphous winding structures, developing reaction selectivity based on molecular orbitals as described in Non-Patent Document 1, and controlling the thermal vibrations of molecules—that is, from a thermodynamic perspective—the lifetime of the equilibrium state of the coordination intermediate of the Li complex can be controlled.

[0321] Regarding the content of resin A in the polyolefin raw material supplied for the sheet forming process (1), from the viewpoint of imparting the characteristics obtained by Voronoi splitting as described above to the separator, and from the viewpoint of optimizing the crystal structure containing Si molecules as described above and the various values ​​described above regarding SAXS and / or WAXS determination and Voronoi splitting, based on the total mass of the solid components of the polyolefin raw material, it is preferably 3 to 70% by mass, more preferably 5 to 60% by mass, and even more preferably 10 to 50% by mass.

[0322] Based on the same viewpoint as above, the content of resin B in the polyolefin raw material is preferably 3 to 70% by mass, more preferably 5 to 60% by mass, and even more preferably 5 to 40% by mass, based on the total mass of the solid components of the polyolefin raw material.

[0323] Based on the same viewpoint as above, the content of resin C in the polyolefin raw material is preferably 1 to 90% by mass, more preferably 5 to 60% by mass, and even more preferably 5 to 50% by mass, based on the total mass of the solid components of the polyolefin raw material.

[0324] From the same point of view as above, the mass ratio (A / B) of resin A to resin B supplied in the sheet forming process (1) is preferably 0.07 to 12.00, more preferably 0.10 to 11.00, and even more preferably 0.50 to 10.00.

[0325] From the same point of view as above, the mass ratio (A / C) of resin A to resin C supplied in the sheet forming process (1) is preferably 0.07 to 12.00, more preferably 0.10 to 11.00, and even more preferably 0.20 to 10.00.

[0326] From the same point of view as above, the mass ratio (B / C) of resin B to resin C supplied in the sheet forming process (1) is preferably 0.06 to 7.00, more preferably 0.10 to 7.00, and even more preferably 0.12 to 6.90.

[0327] From the same point of view as above, the molecular weights Mn, Mw, Mv or Mw / Mn of the resins A to C supplied for the sheet forming process (1) are preferably the same as those described above regarding the constituent elements of the separator.

[0328] By appropriately controlling the molecular weight, molecular weight distribution, and mixing ratio of the raw materials supplied to the sheet forming process (1) as described above, the relevant characteristics of the Voronoi splitting of the separators in Embodiments 1 to 5 can be easily achieved.

[0329] From the viewpoint of improving safety by providing low-temperature cycling performance and high-temperature film rupture resistance, and suppressing thermal runaway during battery failure, resin A in the sheet forming process is preferably not a masterbatch resin containing a catalyst that promotes the crosslinking reaction of alkoxysilanes before the sheet forming process.

[0330] The plasticizer used in the sheet forming process (1) is not particularly limited, and examples include organic compounds that can form a homogeneous solution with polyolefins at temperatures below their boiling points. More specifically, examples include: decahydronaphthalene, xylene, dioctyl phthalate, dibutyl phthalate, stearyl alcohol, oleyl alcohol, decanol, nonanol, diphenyl ether, n-decane, n-dodecane, paraffin oil, etc. Among these, paraffin oil and dioctyl phthalate are preferred. One type of plasticizer may be used alone, or two or more may be used in combination. The proportion of plasticizer is not particularly limited, but from the viewpoint of the porosity of the resulting microporous membrane, the polyolefin and the silane-grafted modified polyolefin are preferably 20% by mass or more relative to the total mass, and from the viewpoint of the viscosity during melt mixing, preferably 90% by mass or less.

[0331] The sheet forming process (1) is a process in which the obtained compound, or a mixture of polyolefin and plasticizer, is extruded using an extruder, cooled and solidified, and then formed into a sheet to obtain a sheet. There are no particular limitations on the sheet forming method; for example, methods that solidify the molten compound and extruded material through compression cooling or deformation cooling can be listed. As for cooling methods, examples include: methods that allow the molten material to directly contact cooling media such as cold air or cooling water; methods that allow the molten material to contact rollers or presses cooled by refrigerant, etc. The method of contacting rollers or presses cooled by refrigerant offers excellent film thickness control and is preferred.

[0332] The stretching process (2) involves extracting plasticizers or inorganic materials from the obtained sheet as needed, and then stretching the sheet in at least one axial direction. Examples of sheet stretching methods include MD uniaxial stretching based on a roll stretching machine, TD uniaxial stretching based on a spreading machine, successive biaxial stretching based on a combination of a roll stretching machine and a spreading machine or a spreading machine and a spreading machine, and simultaneous biaxial stretching based on a simultaneous biaxial spreading machine or blow molding. From the viewpoint of obtaining a more uniform film, simultaneous biaxial stretching is preferred. From the viewpoint of film thickness uniformity, elongation, porosity, and average pore size balance, the total aspect ratio is preferably 8 times or more, more preferably 15 times or more, and even more preferably 20 times or more or 30 times or more. By making the total aspect ratio 8 times or more, it is easier to obtain a film with high strength and good thickness distribution. Furthermore, from the viewpoint of preventing breakage, the aspect ratio can be 250 times or less.

[0333] The porous body forming process (3) is a process of extracting plasticizer from the stretched material after the stretching process and making the stretched material porous. There are no particular limitations on the extraction method for the plasticizer, but examples include: immersing the stretched material in an extraction solvent, spraying the stretched material with the extraction solvent, etc. There are no particular limitations on the extraction solvent, but preferably a solvent that is a poor solvent for polyolefins and a good solvent for plasticizers or inorganic materials, with a boiling point lower than the melting point of polyolefins. There are no particular limitations on such extraction solvents, but examples include: hydrocarbons such as n-hexane or cyclohexane; halogenated hydrocarbons such as dichloromethane or 1,1,1-trichloroethane, and fluorocarbons; alcohols such as ethanol or isopropanol; ketones such as acetone or 2-butanone; and alkaline water. One extraction solvent can be used alone, or two or more can be used in combination.

[0334] The heat treatment step (4) is a step after the stretching step whereby the plasticizer is extracted from the sheet as needed and further heat-treated to obtain a microporous membrane. There are no particular limitations on the heat treatment method; examples include heat setting methods such as stretching and relaxation operations using a spreader or a roll stretching machine. The relaxation operation refers to a shrinkage operation performed along the mechanical direction (MD) and / or width direction (TD) of the membrane at a specified temperature and relaxation rate. The relaxation rate is the value obtained by dividing the MD dimension of the membrane after the relaxation operation by the MD dimension of the membrane before the operation; or by dividing the TD dimension of the membrane after the relaxation operation by the TD dimension of the membrane before the operation; or, in the case of relaxation of both MD and TD, it is the value obtained by multiplying the relaxation rate of MD by the relaxation rate of TD. The stretching and relaxation operations in the heat treatment step (4) are preferably performed at least along the TD.

[0335] In the coating step (5), a coating liquid is applied to at least one surface of the polyolefin microporous membrane obtained above, or to at least one surface of the heat-treated porous body obtained by the heat treatment step (4). As the coating step (5), known coating methods can be used, such as methods of coating the coating liquid onto a substrate, a microporous membrane, or a heat-treated porous body; methods of laminating or extruding the raw materials of the microporous membrane with the raw materials of other layers by co-extrusion; methods of bonding two layers together after they have been made separately, etc.

[0336] More specifically, the coating process (5) can be any or any combination of the following processes (5A) to (5D):

[0337] (5A) Coating process, wherein a coating liquid containing inorganic particles, resin binder and surfactant and having a pH of 6.7 or less or 7.5 or more is applied to at least one surface of a polyolefin microporous monolayer membrane or a heat-treated porous body, thereby forming an inorganic porous layer on at least one surface of the polyolefin microporous monolayer membrane or the heat-treated porous body.

[0338] (5B) Coating process, wherein a coating liquid containing a thermoplastic polymer and a surfactant and having a pH of less than 6.7 or greater than 7.5 is applied to at least one surface of a microporous monolayer membrane or a heat-treated porous body made of polyolefin, thereby forming a thermoplastic polymer layer on at least one surface of a microporous monolayer membrane or a heat-treated porous body made of polyolefin.

[0339] (5C) A coating process in which a coating liquid containing a fluorinated polyethylene-based compound, inorganic particles, and an organic solvent is applied to at least one surface of a polyolefin microporous monolayer membrane or a heat-treated porous body, thereby forming an active layer on at least one surface of the polyolefin microporous monolayer membrane or heat-treated porous body; and

[0340] (5D) Coating process, in which a coating liquid containing heat-resistant resin and organic solvent is applied to at least one surface of a polyolefin microporous monolayer or a heat-treated porous body, thereby forming a heat-resistant resin layer on at least one surface of the polyolefin microporous monolayer or the heat-treated porous body.

[0341] Through the coating process (5A), a multilayer membrane can be formed having a polyolefin microporous membrane and an inorganic porous layer of the preferred multilayer structure 1 described above.

[0342] Through the coating process (5B), a multilayer film containing a thermoplastic polymer layer can be formed, which has a polyolefin microporous membrane and the preferred multilayer structure 2 described above.

[0343] Through the coating process (5C), a multilayer membrane can be formed having an active layer comprising a polyolefin microporous membrane and the preferred multilayer structure 3 described above.

[0344] Through the coating process (5D), a multilayer film can be formed having a polyolefin microporous membrane and a heat-resistant resin layer of the preferred multilayer structure 4 described above.

[0345] In coating processes (5A) and (5B), when the pH of the aqueous or non-aqueous coating solution is below 6.7, the activity energy of the reaction system of the silane-modified polyolefin in contact with the coating solution decreases, making it easier for a silane crosslinking reaction to occur. On the other hand, when the pH of the aqueous or non-aqueous coating solution is above 7.5, the presence of OH- can promote the silane crosslinking reaction of the silane-modified polyolefin.

[0346] In the coating processes (5C) and (5D), the organic solvent contained in the non-aqueous coating solution can promote the silane crosslinking reaction of silane-modified polyolefins by entering the amorphous part of the polyolefin microporous monolayer membrane or heat-treated porous body.

[0347] The coating liquid used to form a thermoplastic polymer layer preferably contains a thermoplastic polymer, and the thermoplastic polymer comprises at least one selected from the group consisting of polymeric units selected from (meth)acrylate and / or (meth)acrylic acid, polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE).

[0348] The coating solution used to form the active layer preferably contains a fluorinated polyethylene-based compound, and the fluorinated polyethylene-based compound is at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and polyvinylidene fluoride-chlorotrifluoroethylene (PVDF-CTFE).

[0349] The coating solution may contain, as desired, resin binders, inorganic particles or fillers, dispersants, surfactants, solvents, etc. Coating solutions used to form inorganic porous layers contain inorganic particles and resin binders.

[0350] Examples of resin adhesives include:

[0351] Polyolefin resins such as polyethylene, polypropylene, and α-polyolefin;

[0352] Fluoropolymers such as polyvinylidene fluoride and polytetrafluoroethylene, or copolymers containing these;

[0353] Diene polymers containing conjugated dienes such as butadiene and isoprene as monomer units, or copolymers containing these, or their hydrides;

[0354] Acrylic polymers containing (meth)acrylate, (meth)acrylic acid, etc. as monomer units and without polyalkylene glycol units; acrylic polymers containing (meth)acrylate, (meth)acrylic acid, etc. as monomer units and with one or two polyalkylene glycol units; copolymers containing these; or hydrogenated forms thereof.

[0355] Rubber products such as ethylene propylene rubber, polyvinyl alcohol, and polyvinyl acetate;

[0356] Polyalkylene glycols such as polyethylene glycol and polypropylene glycol do not have polymerizable functional groups;

[0357] Resins such as polyphenylene ether, polyphenylene sulfide, and polyester;

[0358] A copolymer of olefinically unsaturated monomers having alkylene glycol units repeating in a number of 3 or more, as copolymer units; and,

[0359] They can be combined, or the aforementioned thermoplastic polymers can be used.

[0360] From the viewpoint of improving the safety of batteries with separators in puncture tests, the resin binder preferably contains polymeric units of (meth)acrylate and / or (meth)acrylic acid.

[0361] The resin binder described above can be manufactured using the corresponding monomer or comonomer and employing known polymerization methods. Suitable polymerization methods include, for example, solution polymerization, emulsion polymerization, and bulk polymerization.

[0362] Regarding resin adhesives, it is preferable to form particulate adhesive polymers through emulsion polymerization and use the resulting polymer emulsions as aqueous latexes.

[0363] The coating solution used to form inorganic porous layers, active layers, or heat-resistant resin layers contains inorganic particles or inorganic fillers. There are no particular limitations on the inorganic particles or fillers used; examples include oxide-based ceramics such as alumina, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, cerium oxide, yttrium oxide, zinc oxide, and iron oxide; nitride-based ceramics such as silicon nitride, titanium nitride, and boron nitride; ceramics such as silicon carbide, calcium carbonate, magnesium sulfate, aluminum sulfate, aluminum hydroxide, aluminum hydroxide, potassium titanate, talc, kaolinite, dickite, perlite, halloysite, pyrophyllite, montmorillonite, sericite, mica, magnesia chlorite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; and glass fibers. These can be used individually or in combination.

[0364] From the viewpoint of improving electrochemical stability and the heat resistance of the separator, at least one of the following is preferred: alumina, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, cerium oxide, yttrium oxide, zinc oxide, iron oxide, silicon nitride, titanium nitride, boron nitride, silicon carbide, aluminum hydroxide, talc, kaolinite, dickite, perlite, halloysite, pyrophyllite, montmorillonite, sericite, mica, magnesia chlorite, bentonite, asbestos, zeolite, diatomite, silica sand, and glass fiber. Alumina compounds such as alumina and aluminum hydroxide are more preferred. Alumina compounds such as kaolinite, dickite, perlite, halloysite, and pyrophyllite that do not have ion exchange function are also preferred.

[0365] It should be noted that alumina exists in various crystalline forms, including α-alumina, β-alumina, γ-alumina, and θ-alumina, and any of these is preferred. Among these, α-alumina is preferred due to its thermal and chemical stability.

[0366] Alumina hydroxide (AlO(OH)) is particularly preferred as the alumina compound. From the viewpoint of preventing internal short circuits caused by lithium dendrite formation, boehmite is more preferred as the alumina hydroxide. For example, by using boehmite-based particles as the inorganic filler constituting the heat-resistant resin layer, there is a tendency to achieve a porous layer that maintains high permeability and is very lightweight, and even with a thinner porous layer, it suppresses thermal shrinkage of the microporous membrane at high temperatures, exhibiting excellent heat resistance. Synthetic boehmite that can reduce ionic impurities that adversely affect the characteristics of electrochemical devices is further preferred.

[0367] Regarding the content of inorganic particles in the coating liquid used to form the inorganic porous layer, based on the total mass of the solid components of the coating liquid, it is preferably 5% to 99% by mass, more preferably 10% by mass or more and less than 99% by mass.

[0368] The inorganic filler contained in the coating solution used to form the heat-resistant resin layer preferably has an average particle size of 0.2 μm to 0.9 μm, and / or the content of the inorganic filler in the coating solution is preferably 30% to 90% by mass based on the total mass of the solid components of the coating solution.

[0369] Examples of dispersants contained in the coating solution include, for example, aqueous solutions of ammonium polycarboxylate. Examples of surfactants contained in the coating solution include, for example, emulsifiers and soaps.

[0370] Examples of solvents used in coating solutions include water (e.g., deionized water, pure water), aqueous solvents (e.g., mixtures of water and alcohol), and organic solvents. Organic solvents that can be used include, for example, alcohols, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), ethanol, toluene, hot xylene, dichloromethane, and hexane.

[0371] Methods for preparing coating liquids containing inorganic particles or inorganic fillers include, for example, mechanical stirring methods based on ball mills, bead mills, planetary ball mills, vibratory ball mills, sand mills, colloid mills, grinding mills, roller mills, high-speed impeller dispersers, dispersers, homogenizers, high-speed impact mills, ultrasonic dispersers, stirring blades, etc.

[0372] Examples of coating methods for coating liquids containing inorganic particles or inorganic fillers include photogravure coating, small-diameter photogravure coating, reverse roller coating, transfer roller coating, mating coating, dip coating, doctor blade coating, air knife coating, blade coating, bar coating, extrusion coating, cast coating, die coating, screen printing, and spray coating.

[0373] The coating process (5D) may include steps such as introducing the coating film into an atmosphere with a humidity of 50% or higher or blowing steam onto the coated surface after the coating film has been formed. By maintaining the humidity of the coated surface, the precipitation of the aromatic amide resin can be promoted.

[0374] In the drying step (6), the solvent is removed from the coating film formed in the coating step (5). Methods for removing the solvent include drying at a temperature below the melting point of the material constituting the microporous membrane; drying under reduced pressure at low temperature; and drying after replacing the solvent in the coating solution with another solvent. Alternatively, a small amount of solvent may remain, as long as it does not significantly affect the characteristics of the non-aqueous secondary battery. Methods for replacing the solvent in the coating solution with another solvent include immersing the membrane in the other solvents described above; and blowing the membrane with the other solvents described above.

[0375] In the water washing step (5.5), the solvent in the coating film formed in the coating step (5) can be replaced with other solvents. Examples of solvents before replacement include DMF, DMA, NMP, and DMSO, and examples of solvents after replacement include water and alcohol.

[0376] The manufacturing method of the separator may include a winding / slitting process as desired. The winding / slitting process is the process of slitting the obtained microporous membrane into a specified core as needed.

[0377] In assembly step (7), the laminate of electrodes and separators or its winding, along with the non-aqueous electrolyte, is housed in the housing. Step (7) can be performed in the same manner as the manufacturing of the non-aqueous secondary battery described later, and the electrodes, non-aqueous electrolyte, and housing used in step (7) can be the same as those described for the non-aqueous secondary battery.

[0378] In the coating process (5) and / or the washing process (5.5) and / or the drying process (6) and / or the assembly process (7), it is preferable that the silane-modified polyolefin contained in the separator forms a cross-linked structure in the coating process (5), the washing process (5.5), the drying process (6) and the assembly process (7).

[0379] The separator obtained by the method including the various processes described above can be used in a non-aqueous secondary battery having a positive electrode and a negative electrode capable of absorbing / releasing lithium, and a non-aqueous electrolyte formed by dissolving an electrolyte in a non-aqueous solvent. It is preferably used in a lithium secondary battery or a lithium-ion secondary battery.

[0380] <Non-aqueous secondary batteries>

[0381] Non-aqueous secondary batteries are constructed by housing the positive electrode, negative electrode, separator, and non-aqueous electrolyte in any battery casing.

[0382] The positive electrode is connected to the positive electrode lead in the non-aqueous secondary battery and the negative electrode is connected to the negative electrode lead in the non-aqueous secondary battery. One end of the positive electrode lead and the negative electrode lead are respectively led out to the outside of the battery casing in a way that can be connected to external devices, etc., and their ionomer portions are thermally fused together with one edge of the battery casing.

[0383] The positive electrode consists of a positive current collector and a positive active material layer. The negative electrode consists of a negative current collector and a negative active material layer. The positive active material layer contains positive active material, and the negative active material layer contains negative active material. The positive and negative electrodes are arranged opposite each other with the positive and negative active material layers separated by a separator.

[0384] As the positive electrode, known battery positive electrodes can be used. From the viewpoint of the effect of the present invention, a positive electrode that is prone to thermal decomposition or releases O2 can also be used. In addition, a composite positive electrode active material of lithium and other metals can be used, or a composite positive electrode of lithium with at least one metal selected from the group consisting of nickel, manganese and cobalt can be used, such as LNO positive electrode, NCA positive electrode, LCO positive electrode, positive electrode containing a lithium (Li)-nickel (Ni)-manganese (Mn)-cobalt (Co) composite oxide as the positive electrode active material (NMC positive electrode), etc.

[0385] From the viewpoint of the effectiveness of the present invention, an NMC cathode is preferred, more preferably an NMC cathode with a relatively high nickel content, and particularly preferably the molar ratio of nickel (Ni) to the total amount of nickel, manganese, and cobalt in the cathode is 3-9, 5-9, 6-9, 5-8, or 6-8, especially preferably 5-9. Specifically, for the inclusion formula: Li-Ni x -Mn y -Co z The cathode of the lithium (Li)-nickel (Ni)-manganese (Mn)-cobalt (Co) composite oxide shown in the formula {where x represents the Ni ratio, y represents the Mn ratio, z represents the Co ratio, and x+y+z=1} is preferably 5 to 9 in the Ni ratio x.

[0386] The positive current collector can be made of metal foils such as aluminum foil, nickel foil, and stainless steel foil.

[0387] Examples of anode active materials that constitute the negative electrode include: carbon materials such as hard carbon, graphite, pyrolytic carbon, coke, glassy carbon, calcined organic polymers, mesophase carbon microspheres, carbon fibers, activated carbon, carbon colloids, and carbon black; as well as metallic lithium, metal oxides, metal nitrides, lithium alloys, tin alloys, silicon (Si)-containing materials, intermetallic compounds, organic compounds, inorganic compounds, metal complexes, and organic polymers. Anode active materials can be used alone or in combination of two or more.

[0388] From the viewpoint of the effectiveness of this invention, Si-containing materials are preferred as the negative electrode active material, such as silicon, Si alloys, and Si oxides. Similarly, the Si content in the negative electrode active material is preferably 5 to 90 mol%.

[0389] The lithium-ion storage capacity of Si-containing anode active materials is significantly higher than that of carbon-based anode materials. Furthermore, it is known that during the charging and discharging of lithium ions into Si-containing particles, the volume of the Si-containing anode active material expands and contracts significantly, as shown in Non-Patent Document 2. At this time, the battery internal volume remains constant, and the separator is significantly compressed or deformed in the thickness direction due to the presence of the Si-containing anode active material. This invention discovers that by adjusting the type and blending of resin raw materials, optimizing the SAXS and / or WAXS measurements of the separator, and optimizing the various values ​​of the Voronoi fractionation described above, permeability can be maintained even when the separator is compressed or deformed in the thickness direction in non-aqueous secondary batteries. This allows for an excellent balance between strength and ion diffusion, improving the crush test pass rate, cycle test capacity retention rate, high-temperature cycle life, and / or achieving a balance between them in non-aqueous secondary batteries.

[0390] Furthermore, the separator with a structure in which Si atoms are dispersed in a non-island structure, as discovered in this invention, uniformly performs an intercalation reaction into the Si-containing negative electrode active material as described above. This allows the Si-containing negative electrode active material to expand and contract uniformly inside the battery, suppressing slippage of the winding structure inside the battery and improving battery cycle performance and battery safety.

[0391] The negative current collector can be made of metal foils such as copper foil, nickel foil, or stainless steel foil.

[0392] Non-aqueous electrolytes

[0393] In this specification, a non-aqueous electrolyte refers to an electrolyte containing an electrolyte in a non-aqueous solvent, and the amount of water is less than 1% by mass based on the total mass. The non-aqueous electrolyte is preferably as water-free as possible, but may contain trace amounts of water. Such water content relative to the total amount of the non-aqueous electrolyte is preferably less than 300 ppm by mass, more preferably less than 200 ppm by mass.

[0394] The electrolyte in a battery may contain water, and the water contained in the battery system after manufacturing may be water contained in the electrolyte or water introduced by components such as electrodes or separators. The electrolyte may contain non-aqueous solvents. Examples of non-aqueous solvents include alcohols such as methanol and ethanol, and aprotic solvents. Among these, aprotic solvents are preferred as non-aqueous solvents.

[0395] Examples of aprotic solvents include: cyclic carbonates, fluoroethylene carbonates, lactones, organic compounds containing sulfur atoms, chain fluorinated carbonates, cyclic ethers, mononitriles, alkoxy-substituted nitriles, dinitriles, cyclic nitriles, short-chain fatty acid esters, chain ethers, fluorinated ethers, ketones, and compounds in which some or all of the H atoms of the above aprotic solvents are replaced by halogen atoms.

[0396] Examples of cyclic carbonates include: ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentene carbonate, trans-2,3-pentene carbonate, cis-2,3-pentene carbonate, vinylene carbonate, 4,5-dimethylethyleneene carbonate, and vinyl ethyleneene carbonate.

[0397] Examples of fluoroethylene carbonates include: 4-fluoro-1,3-dioxolane-2-one, 4,4-difluoro-1,3-dioxolane-2-one, cis-4,5-difluoro-1,3-dioxolane-2-one, trans-4,5-difluoro-1,3-dioxolane-2-one, 4,4,5-trifluoro-1,3-dioxolane-2-one, 4,4,5,5-tetrafluoro-1,3-dioxolane-2-one, and 4,4,5-trifluoro-5-methyl-1,3-dioxolane-2-one.

[0398] Examples of lactones include γ-butyrolactone, α-methyl-γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone.

[0399] Examples of organic compounds containing sulfur atoms include: ethylene sulfite, propylene sulfite, butyl sulfite, pentene sulfite, sulfolane sulfonate, sulfolane cyclobutane, 3-cyclobutene sulfonate, 3-methyl sulfolane sulfonate, 1,3-propane sulpholactone, 1,4-butane sulpholactone, 1-propene 1,3-sulpholactone, dimethyl sulfoxide, tetramethylene sulfoxide, and ethylene glycol sulfite.

[0400] Examples of chain carbonates include: methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, etc.

[0401] Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, and 1,3-dioxane.

[0402] Examples of mononitriles include acetonitrile, propionitrile, butyronitrile, valerate, benzonitrile, and acrylonitrile.

[0403] Examples of alkoxy-substituted nitriles include methoxyacetonitrile and 3-methoxypropionitrile.

[0404] Examples of dinitrile include: malononitrile, succinate, methylsuccinate, glutaronitrile, dimethylglutaronitrile, adiponitrile, 1,4-dicyanoheptane, 1,5-dicyanopentane, 1,6-dicyanhexane, 1,7-dicyanoheptane, 2,6-dicyanoheptane, 1,8-dicyanoctane, 2,7-dicyanoctane, 1,9-dicyanonane, 2,8-dicyanonane, 1,10-dicyandecane, 1,6-dicyandecane, and 2,4-dimethylglutaronitrile, ethylene glycol bis(propionitrile) ether, etc.

[0405] Examples of cyclic nitriles include benzonitrile.

[0406] Examples of short-chain fatty acid esters include: methyl acetate, methyl propionate, methyl isobutyrate, methyl butyrate, methyl isovalerate, methyl valerate, methyl neovalerate, methyl angelic acid ester, methyl hexanoate, ethyl acetate, ethyl propionate, ethyl isobutyrate, ethyl butyrate, ethyl isovalerate, ethyl valerate, ethyl neovalerate, ethyl angelic acid ester, ethyl hexanoate, propyl acetate, propyl propionate, propyl isobutyrate, propyl isovalerate, propyl valerate, propyl neovalerate, propyl angelic acid ester, propyl hexanoate, isopropyl acetate, isopropyl propionate, isopropyl isobutyrate, isopropyl butyrate, isopropyl isovalerate. Isopropyl valerate, isopropyl neovalerate, hydrogenated angelic acid isopropyl ester, isopropyl hexanoate, butyl acetate, butyl propionate, butyl isobutyrate, butyl butyrate, butyl isovalerate, butyl valerate, butyl neovalerate, hydrogenated angelic acid ester, butyl hexanoate, isobutyl acetate, isobutyl propionate, isobutyl isobutyrate, isobutyl butyrate, isobutyl isovalerate, isobutyl valerate, isobutyl neovalerate, hydrogenated angelic acid isobutyl ester, isobutyl hexanoate, tert-butyl acetate, tert-butyl propionate, tert-butyl isobutyrate, tert-butyl butyrate, tert-butyl isovalerate, tert-butyl valerate, tert-butyl neovalerate, hydrogenated angelic acid ester, and tert-butyl hexanoate, etc.

[0407] Examples of chain ethers include: dimethoxyethane, diethyl ether, 1,3-dioxolane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

[0408] Examples of fluorinated ethers include those with the general formula Rf. aa -OR bb (where Rf) aa It is an alkyl group containing a fluorine atom, and R bb Compounds, etc., that contain organic groups that may contain fluorine atoms.

[0409] Examples of ketones include acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[0410] Compounds in which some or all of the H atoms of the aforementioned aprotic solvent are replaced by halogen atoms include compounds in which the halogen atom is fluorine.

[0411] Examples of fluorinated chain carbonates include, for instance, methyl trifluoroethyl carbonate, trifluorodimethyl carbonate, trifluorodiethyl carbonate, trifluoroethyl methyl carbonate, methyl 2,2-difluoroethyl carbonate, methyl 2,2,2-trifluoroethyl carbonate, and methyl 2,2,3,3-tetrafluoropropyl carbonate. These fluorinated chain carbonates can be represented by the following general formula:

[0412] R cc -OC(O)OR dd

[0413] In the formula, R cc and R dd The free radicals CH3, CH2CH3, CH2CH2CH3, CH(CH3)2 and CH2Rf are selected. ee (where Rf) ee It consists of at least one group from the group consisting of an alkyl group having 1 to 3 carbon atoms, formed by replacing a hydrogen atom with at least one fluorine atom, and R cc and / or R dd It contains at least one fluorine atom.

[0414] In addition, examples of fluorinated short-chain fatty acid esters include fluorinated short-chain fatty acid esters such as 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, and 2,2,3,3-tetrafluoropropyl acetate. Fluorinated short-chain fatty acid esters can be represented by the following general formula:

[0415] R ff -C(O)OR gg

[0416] In the formula, R ff The free radicals are CH3, CH2CH3, CH2CH2CH3, CH(CH3)2, CF3CF2H, CFH2, CF2H, and CF2Rf. hh CFHRf hh and CH2Rf ii At least one of the groups, R gg The free radicals CH3, CH2CH3, CH2CH2CH3, CH(CH3)2, and CH2Rf are selected. ii At least one of the groups, Rf hh Rf is an alkyl group having 1 to 3 carbon atoms, in which at least one hydrogen atom is optionally replaced by a fluorine atom. ii It is an alkyl group with 1 to 3 carbon atoms formed by replacing a hydrogen atom with at least one fluorine atom, and R ff and / or R gg Contains at least one fluorine atom, in R ff In the case of CF2H, R ggNot CH3}.

[0417] From the viewpoint of the effects of the present invention, the non-aqueous solvent used as the non-aqueous electrolyte preferably contains ethyl methyl carbonate (EMC) and / or acetonitrile (AcN), and / or preferably the total content of EMC and AcN in the non-aqueous electrolyte is in the range of 50% to 90% by mass.

[0418] Lithium salts are preferred as electrolytes, and fluorinated lithium salts that can generate hydrogen fluoride (HF) are further preferred from the viewpoint of promoting silane crosslinking reactions. Examples of fluorinated lithium salts include lithium hexafluorophosphate (LiPF6), lithium fluorosulfonate (LiFSO3), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiN(SO2F)2), lithium fluoroborate (LiBF4), and lithium bis(oxalatoborate) (LiBC4O8). Although not limited by theory, for example, when the electrolyte contains LiPF6, LiPF6 reacts with trace amounts of moisture contained in the energy storage device (e.g., moisture contained in components such as electrodes, separators, and electrolyte) to generate hydrogen fluoride (HF) or fluorinated organic compounds derived from HF. It can be considered that these HF or fluorinated organic compounds derived from HF dissolve in the electrolyte, swell and diffuse into the amorphous portions of the polyolefin having crosslinkable silanes, thereby catalyzing the silane crosslinking reaction.

[0419] From the viewpoint of the effectiveness of the present invention, a relatively higher lithium salt concentration in the non-aqueous electrolyte is preferred, more preferably a concentration in the range of 1.2 mol / L to 10 mol / L, and even more preferably a lithium salt concentration of 1.5 mol / L or higher, particularly preferably 3.0 mol / L or higher. Specifically, in a non-aqueous secondary battery system containing lithium hexafluorophosphate (LiPF6) as the electrolyte, due to the Young's-Taylor effect of phosphorus atoms, it exists in the system as a certain concentration of dissociated F anions or lithium fluoride (LiF). It is generally known that dissociated F anions lead to phenomena such as electrode corrosion and decreased battery life; however, LiF, in its Si-addition state, exhibits a stronger Lewis acid effect than in its unaddition state, thus making the phenomena described in (i) and (ii) above more pronounced, and further exhibiting good low-temperature cycling characteristics. It should be noted that the combination of electrolyte and electrolyte is preferably selected such that the lithium salt concentration does not exceed the saturation dissolution concentration.

[0420] In non-aqueous electrolytes, substances that catalyze the silane crosslinking reaction, in addition to those mentioned above, may include substances (acid sources) that react with the non-aqueous electrolyte and / or trace amounts of water contained in it to generate hydrogen ions, such as inorganic or organic acids; and substances (alkali sources) that react with the non-aqueous electrolyte and / or trace amounts of water contained in it to generate hydroxide ions. Examples of alkali sources include alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkali metal phosphates, ammonia, and amine compounds. From the viewpoint of the safety of the energy storage device and the crosslinking properties of silanes, alkali metal hydroxides or alkaline earth metal hydroxides are preferred, alkali metal hydroxides are more preferred, and sodium hydroxide is even more preferred.

[0421] The battery casing for a non-aqueous secondary battery can be constructed using known methods. For example, a battery canister or a laminated film casing can be used as the battery casing.

[0422] Non-aqueous secondary batteries can be shaped in various ways, such as square, rectangular, cylindrical, oval, button-shaped, coin-shaped, flat, and laminated.

[0423] Non-aqueous secondary batteries, except for using the aforementioned non-aqueous electrolyte, positive electrode, negative electrode, separator, and battery casing, can be manufactured in the same manner as known manufacturing methods.

[0424] Example

[0425] The present invention will be further described in detail below through examples, but the present invention is not limited to these examples. It should be noted that the physical properties in the examples were determined by the following methods. For substrate weight per unit area, substrate film thickness, substrate porosity, substrate air permeability, substrate puncture strength, SAXS, WAXS, NMR, and TOF-SIMS, measurements were performed after removing the coating layer when one was present on the substrate. For crush test pass rate, cycle test capacity retention rate, and cycle life test, measurements were performed without removing the coating layer when one was present on the substrate. Battery evaluation tests (crush test, cycle capacity retention rate, high-temperature cycle life) were all performed 4 days after the coating solution was applied to the separator.

[0426] <Detection Method for Silane-Modified Polyolefins in Separators>

[0427] When the silane-modified polyolefin contained in the separator is cross-linked, it is insoluble or has insufficient solubility in organic solvents, making it sometimes difficult to directly determine the content of silane-modified polyolefin from the separator. In such cases, as a sample pretreatment, methyl orthoformate, which does not cause side reactions, is used to decompose the siloxane bonds into methoxysilane alcohols, followed by solution NMR determination. This allows the detection of the silane-modified polyolefin contained in the separator, or it can be determined by GPC. The pretreatment experiment can be performed according to Japanese Patent No. 3529854 and Japanese Patent No. 3529858. It should be noted that thermal analysis such as TMA and DMA can also be performed after the polymerization reaction.

[0428] Specifically, the detection method for silane-modified polyolefins contained in the separator can effectively utilize the silane-modified polyolefins used as raw materials in the manufacture of the separator. 1 H or 13 NMR identification of C. The following is... 1 H and 13 An example of a method for determining C by NMR will be explained.

[0429] ( 1 (NMR determination of H)

[0430] The sample was dissolved in o-dichlorobenzene-d4 at 140 °C to obtain a proton resonance frequency of 600 MHz. 1 H-NMR spectrum. 1 The determination conditions for H-NMR are as follows.

[0431] Device: AVANCE NEO 600 manufactured by Bruker

[0432] Sample tube diameter:

[0433] Solvent: o-dichlorobenzene-d4

[0434] Measurement temperature: 130℃

[0435] Pulse angle: 30°

[0436] Pulse wait time: 1 sec

[0437] Total number of times: 1000 or more

[0438] Sample concentration: 1 wt / vol%

[0439] ( 13 (NMR determination of C)

[0440] The sample was dissolved in o-dichlorobenzene-d4 at 140 °C to obtain 13 C-NMR spectra. 13The C-NMR measurement conditions are as follows.

[0441] Device: AVANCE NEO 600 manufactured by Bruker

[0442] Sample tube diameter:

[0443] Solvent: o-dichlorobenzene-d4

[0444] Measurement temperature: 130℃

[0445] Pulse angle: 30°

[0446] Pulse wait time: 5 seconds

[0447] Total number of times: 10,000 or more

[0448] Sample concentration: 10 wt / vol%

[0449] pass 1 H and / or 13 NMR determination of C can confirm the amount of silane unit modification, the amount of alkyl modification, the C4 unit modification rate (mol%), and the number of methylene (CH2) in the silane grafting junction in polyolefin raw materials. Furthermore, it can identify the content of silane-modified polyolefin in the separator.

[0450] It should be noted that the amount of silanol unit modification in resin A can be quantitatively determined by the NMR chemical shift and integral value of the methylene group next to the Si atom (-CH2-Si: 1 H, 0.69ppm, t; 13 C, 6.11 ppm, s). Propylene modification (C3) can be quantified by the NMR chemical shift and integral value of the terminal methyl group (-CH3: 13 C, 19.42 ppm, s). Butene modification (C4) can be quantitatively determined by the NMR chemical shift and integral value of the terminal methyl group (-CH3: 13 C, 10.63 ppm, s).

[0451] <Weight-average molecular weight and number-average molecular weight>

[0452] Using a Waters ALC / GPC 150C (trademark) chromatogram, standard polystyrene was measured under the following conditions to create a calibration curve. Additionally, for the following polymers, chromatograms were measured under the same conditions, and the weight-average molecular weight of each polymer was calculated based on the calibration curve using the following method.

[0453] Chromatographic columns: 2 Tosoh GMH6-HT (trademark) columns + 2 GMH6-HTL (trademark) columns

[0454] Mobile phase: o-dichlorobenzene

[0455] Detector: Differential refractometer

[0456] Flow rate: 1.0 ml / min

[0457] Column temperature: 140℃

[0458] Sample concentration: 0.1 wt%

[0459] (Weight-average molecular weight and number-average molecular weight of polyethylene, polypropylene and silane-modified polyolefins)

[0460] By multiplying each molecular weight component in the obtained calibration curve by 0.43 (Q factor of polyethylene / Q factor of polystyrene = 17.7 / 41.3) or 0.64 (Q factor of polypropylene / Q factor of polystyrene = 26.4 / 41.3), the molecular weight distribution curves for polyethylene or polypropylene are obtained, and the weight-average molecular weight and number-average molecular weight are calculated. It should be noted that the same Q factor is used for silane-modified polyethylene as for polyethylene, and the same Q factor is used for silane-modified polypropylene as for polypropylene.

[0461] (Weight-average molecular weight of the resin composition)

[0462] The Q factor value of the polyolefin with the largest mass fraction is used, and the weight-average molecular weight is calculated in the same manner as for polyethylene.

[0463] <Viscosity-average molecular weight (Mv)>

[0464] Based on ASTM-D4020, determine the intrinsic viscosity [η] at 135°C in decahydronaphthalene solvent. Calculate the Mv of polyethylene and silane-modified polyethylene using the following formula.

[0465] [η] = 6.77 × 10 -4 Mv 0.67

[0466] The Mv of polypropylene is calculated as follows.

[0467] [η] = 1.10 × 10 -4 Mv 0.80

[0468] <Mel mass flow rate (MFR) (g / 10min)>

[0469] For polyethylene and silane-modified polyethylene, the MFR value was determined by measuring the weight of the resin extruded for 10 minutes at 190°C and a load of 2.16 kg using a melt flow rate tester (MELT INDEXER F-F01) manufactured by Toyo Seiki. For polypropylene and silane-modified polypropylene, the MFR was measured at 230°C.

[0470] <Film thickness (μm)>

[0471] The thickness of the microporous membrane was measured using a miniature thickness gauge manufactured by Toyo Seiki and a KBM (trademark) at room temperature of 23±2℃ and relative humidity of 60%. Specifically, the membrane thickness was measured at almost equal intervals along the entire TD direction, and their average value was obtained.

[0472] It should be noted that the coating thickness is calculated by observing the cross-section or side surface using SEM at any magnification.

[0473] <Porosity (%) and substrate porosity (%)>

[0474] A 10cm × 10cm square sample is cut from a microporous membrane. Calculate its volume (cm³). 3 ) and mass (g), derived from these and density (g / cm³) 3 The porosity is calculated using the following formula. It should be noted that the density of the mixture is calculated using the density of each of the raw materials used and the mixing ratio.

[0475] Porosity (%) = (Volume - Mass / Density of the mixture) / Volume × 100

[0476] < Breathability (sec / 100cm) 3 ) and substrate air permeability (sec / 100cm) 3 >

[0477] The air permeability of the samples was determined according to JIS P-8117 (2009) using the Oken-type air permeability and smoothness testing machine manufactured by Asahi Seiko Co., Ltd., EGO1-55-1MR (trademark).

[0478] <Puncture strength (gf) and substrate puncture strength (gf)>

[0479] Using a handheld deformation tester "KES-G5" (manufactured by kato-tech, trademark), a puncture test was conducted with a needle tip curvature radius of 0.5 mm and a puncture speed of 2 mm / s to determine the puncture strength of the microporous membrane.

[0480] <SAXS (Transmission Method) Determination and Crystallization Long Period (nm)>

[0481] Small-angle X-ray scattering (SAXS) based on transmission method was measured for polyolefin microporous membranes used as separator substrates under the following conditions.

[0482] (Measurement)

[0483] Small-angle X-ray scattering (SAXS) measurements were performed using a Nano-Viewer manufactured by RIGAKU Corporation. The substrate, serving as a separator, was irradiated with CuKα rays (with the X-ray incident direction parallel to the film thickness direction of the sample), and scattering was detected using a DECTRIS PILATUS 100K detector. Measurements were performed at a sample-detector distance of 841.5 mm, an output power of 60 kV, and 45 mA. The optical system used point focusing, with slit diameters of 1st slit: ψ = 0.4 mm, 2nd slit: ψ = 0.2 mm, and guard slit: = 0.8 mm. As a pretreatment for the measurement, to reduce scattering from particle size, a slurry was prepared by mixing the sample and propylene glycol at a weight ratio of 1:1 and then measured.

[0484] (Analysis: Crystallization long period (nm))

[0485] The obtained peaks were subjected to long-term crystallization analysis using the following method.

[0486] For the X-ray scattering pattern obtained from the imaging plate, blank element scattering correction is performed, and a one-dimensional SAXS spectrum I(q) is obtained by annular averaging. It should be noted that q is the absolute value of the scattering vector. To calculate the long period d of crystallization, the scattering from the long period of crystallization is emphasized by multiplying the SAXS spectrum by the square of the absolute value of the scattering vector. Then, the logarithm of the SAXS spectrum multiplied by the square of the absolute value of the scattering vector and the absolute value of the scattering vector, respectively, are plotted as the vertical and horizontal axes. The horizontal axis represents logarithm. 10 q, the vertical axis represents log. 10 (I(q)×q2).

[0487] For the plotted data, perform the following operations: Draw tangent lines from the peak positions of the lamellae, tangent to one point on both the small-angle and wide-angle sides, and subtract these tangent lines from the data. Next, determine the horizontal axis position Xm that yields the maximum value between the two tangent points. Finally, calculate the crystallization period d using the following formula.

[0488] qm = 10 Xm d = 2π / qm

[0489] <WAXS (Reflection Method) and MD, TD Section Crystal Orientation (%)>

[0490] Wide-angle X-ray scattering (WAXS) based on reflection method was performed on microporous membranes made of polyolefin as the separator substrate under the following conditions.

[0491] (Measurement)

[0492] Wide-angle X-ray scattering measurements based on the reflection method were performed using the NANO-Viewer X-ray structure evaluation system manufactured by RIGAKU. The sample was irradiated with CuKα rays, and the scattering was detected through an imaging plate. Wide-angle X-ray scattering measurements were conducted under conditions of a sample-detector distance of 95.2 mm, an output power of 60 kV, and 45 mA. The optical system employed point focusing with a slit diameter of 1st slit. and 2nd slit: The measurements were performed under the specified conditions. It should be noted that the sample was positioned at a 10.5° angle between its cross-section and the X-ray incident direction. Inaccurate measurements cannot be obtained with thin microporous membranes; therefore, overlapping was performed as needed, and measurements were conducted after obtaining a sufficiently thick membrane with adequate strength.

[0493] (Analysis: Crystal orientation degree (%) of MD and TD sections)

[0494] The direction in which the upstream direction of the sample surface's normal is projected onto the detector surface is set as the azimuth angle. Define the azimuth angle on the detector surface in a clockwise direction. to Next, the X-ray scattering pattern obtained from the imaging plate is subjected to detector background correction and blank cell scattering correction. Then, relative to the azimuth angle... In azimuth Plot the azimuth angles within the range The cumulative intensity of the (110) plane diffraction peak of lower polyethylene in the range of 19.5° < 2θ < 21.3°. When the molecular chains are oriented in a direction parallel to the film plane in the cross-section Become The curve is a single peak centered on the Gaussian function. The curve is fitted by adding the constant shown in Equation 2 and the Gaussian function, and the orientation degree f' of the cross section is calculated from the half-value width of the Gaussian function of the fitted result according to Equation 3.

[0495]

[0496] Explanation of symbols in Equation 2

[0497] A certain azimuth angle after background correction and blank cell scattering correction Cumulative intensity in the range of 19.5° < 2θ < 21.3°

[0498] Azimuth (rad)

[0499] f'=1-FWHM / 180 Equation 3

[0500] Explanation of symbols in Equation 3

[0501] f: Cross-sectional orientation

[0502] FWHM: Half-width (°) of the Gaussian function obtained from the fitting results.

[0503] <WAXS (transmission method) determination of crystallinity (%), crystallite size (110) (nm), crystallite size (200) (nm), and crystal orientation degree in the film thickness direction (%)>

[0504] Wide-angle X-ray scattering (WAXS) based on transmission method was performed on microporous membranes made of polyolefins as separator substrates under the following conditions.

[0505] (Measurement)

[0506] Wide-angle X-ray scattering measurements based on transmission method were performed using the NANO-Viewer X-ray structure evaluation system manufactured by RIGAKU. The sample was irradiated with CuKα rays, and scattering was detected using an imaging plate. Wide-angle X-ray scattering measurements were performed under conditions of a sample-detector distance of 95.2 mm, an output power of 60 kV, and 45 mA. The optical system used point focusing with a 1st slit diameter. and 2nd slit: The measurements were performed under the specified conditions. It should be noted that the sample was positioned at a 10.5° angle between the sample surface and the X-ray incident direction. Inaccurate measurements cannot be obtained when the microporous membrane is too thin; therefore, overlapping is performed as needed, and measurements are conducted after a sufficiently thick membrane with adequate strength is achieved.

[0507] (Analysis: crystallite size (110) (nm), crystallite size (200) (nm) and crystallinity %)

[0508] The X-ray scattering pattern obtained from the imaging plate, ranging from 2θ = 9.7° to 2θ = 29.0°, was separated into three peaks: an orthorhombic (110) diffraction peak, an orthorhombic (200) diffraction peak, and an amorphous peak. The crystallite size was calculated using the Scherer formula (Equation 1) based on the half-width at half-maximum (WWM) of the (110) diffraction peak. The (110) and (200) diffraction peaks were approximated using the VOOIT function, while the amorphous peak was approximated using the Gauss function. It should be noted that peak separation was performed with the amorphous peak position fixed at 2θ = 19.6° and the WWM fixed at 6.3°, while the peak position and WWM of the crystalline peak were not particularly fixed. The crystallite size was calculated using the Scherer formula (Equation 1) based on the WWM of the (110) diffraction peak obtained through peak separation.

[0509] D(110 or 200)=Kλ / (βcosθ) Equation 1

[0510] Explanation of symbols in Equation 1

[0511] D (110 or 200): Crystalline size (nm)

[0512] K: 0.9 (constant)

[0513] λ: Wavelength of X-rays (nm)

[0514] β: (β1) 2 -β2 2 0.5

[0515] β1: Half-width (rad) of the (hkl) peak calculated from the peak separation results.

[0516] β2: Half-width of incident beam spread (rad)

[0517] θ: Angle Bragg

[0518] In addition, the crystallinity (X) is calculated using the following formula.

[0519] Crystallinity X={I(110)+I(200)} / {I(110)+I(200)+Iamr}×100

[0520] Iamr: Area of ​​the amorphous peak

[0521] In addition, the crystallite size ratio (110) / (200) is calculated using the crystallite size obtained by Equation 1, and is then calculated by the following formula.

[0522] Crystallite size ratio (110) / (200) = (crystallet size (110) [nm]) / (crystallet size (200) [nm])

[0523] <Thickness of amorphous portion (nm) and thickness of crystalline portion (nm)>

[0524] Using the crystallization period of SAXS and the crystallinity of WAXS determined by the above method, the thickness of the amorphous part (nm) and the thickness of the crystalline part (nm) are calculated according to the following formula.

[0525] Amorphous portion thickness [nm] = (crystallization period [nm]) × (1 - crystallinity [%) / 100)

[0526] <Substrate separator TOF-SIMS analysis / image processing>

[0527] (I) TOF-SIMS analysis of the separator

[0528] For the separators obtained in the examples and comparative examples, TOF-SIMS analysis was performed. A nano-TOF mass spectrometer manufactured by ULVAC-PHI, INCORPORATED, was used as the TOF-SIMS mass spectrometer. The analytical conditions are described below.

[0529] (Image measurement conditions)

[0530] Primary ion: Bismuth (Bi)

[0531] Accelerating voltage: 30kV

[0532] Ion current: approximately 0.5 nA (DC).

[0533] Analysis area: 100μm × 100μm

[0534] Analysis time: 90 minutes

[0535] Detected ions: Positive ions (m / z = 28)

[0536] Neutralization: Electron gun + Ar monomer ions

[0537] Vacuum level: Approximately 5.0 × 10⁻⁶ -5 Pa (Oxygen is introduced to improve the detection intensity of Si)

[0538] (Depth-direction measurement conditions)

[0539] Analysis Conditions

[0540] Primary ion: Bismuth (Bi)

[0541] Accelerating voltage: 30kV

[0542] Ion current: Approximately 1.2 nA (DC).

[0543] Analysis area: 100μm × 100μm

[0544] Analysis time: 5 frames / loop

[0545] Detected ions: Positive ions (m / z = 28)

[0546] Neutralization: Electron gun + Ar monomer ions

[0547] Vacuum level: Approximately 5.0 × 10⁻⁶ -5 Pa (Oxygen is introduced to improve the detection intensity of Si)

[0548] Splashing Conditions

[0549] Sputtered ions: GCIB(Ar 2500 + )

[0550] Accelerating voltage: 20kV

[0551] Ion current: approximately 5 nA

[0552] Sputtering area: 400μm × 400μm

[0553] Splash time: 30 seconds / cycle

[0554] Neutralization: Electron gun + Ar monomer ions

[0555] Under the above conditions, the spectra of Si ions (equivalent to positive ions with m / z = 28) were detected. As an example, the TOF-SIMS analysis results of the separator from Example 1 are shown below. Figure 1 The TOF-SIMS analysis results of the separator in Comparative Example 1 are shown below. Figure 11 It should be noted that, Figure 1 The units for the vertical and horizontal axes are pixels. Figure 11 The units for the vertical and horizontal axes are pixels.

[0556] (II) Image Processing

[0557] For the image data of the TOF-SIMS spectrum obtained above, perform image processing according to the following steps.

[0558] (1) Fabricate a filter that matches the beam shape (2 μm diameter, 0.39 μm pixel resolution). Show a 3D image of the filter... Figure 2 Displaying a two-dimensional image Figure 3 Additionally, the filter value h1 is shown in Table 1 below. It should be noted that... Figure 2 The units for the vertical and horizontal axes are pixels. Figure 3 The unit for each axis is pixels.

[0559] [Table 1]

[0560]

[0561] (Method for calculating filter values)

[0562] The calculation was performed using the `fspecial` function from the Image Processing Toolbox of MATLAB (a registered trademark), a numerical computation software developed by Mathworks.

[0563] fspecia("gaussian", [13 13], 1.69865)

[0564] (2) Use the created filter for two-dimensional data.

[0565] (3) Calculate the mean and standard deviation of the two-dimensional data after applying the filter.

[0566] (4) Use the mean + standard deviation × 3 as the threshold for binarization.

[0567] (In the case of a normal distribution, 99.74% of the values ​​fall within the range of mean + standard deviation × 3, therefore the intention is to extract the numerically unique parts.)

[0568] (5) Perform 7-pixel dilation and contraction to connect the nearby extraction areas.

[0569] (6) Remove areas with small size (less than 50 pixels).

[0570] (7) Calculate the parameters for the remaining regions.

[0571] Extract area (pixels) and centroid position (x0, y0).

[0572] The maximum value in the region, the average value of the region, and the weighted center position (xm, ym).

[0573] (8) Calculate the distance between the center positions of each weighted position.

[0574] The calculation was performed using the WeightedCentroid option of the regionprops function in the Image Processing Toolbox of MATLAB, a numerical computation software manufactured by Mathworks.

[0575] regionprops(cc,I,'WeightedCentroid')

[0576] Here, cc is a variable representing the extracted region, and I is a variable containing the two-dimensional data after the filter has been applied.

[0577] As an example, the results obtained by performing the image processing described in (1) to (2) above on the TOF-SIMS analysis results of the separator are shown below. Figure 4(Example 1) and Figure 12 (Comparative Example 1) shows the results obtained by performing the image processing steps (1) to (6) above. Figure 5 (Example 1) and Figure 13 (Comparative Example 1). It should be noted that, Figure 4 The units for the vertical and horizontal axes are pixels. Figure 12 The units for the vertical and horizontal axes are pixels. Figure 5 The units for the vertical and horizontal axes are pixels. Figure 13 The units for the vertical and horizontal axes are pixels.

[0578] (III) Voronoi Split

[0579] Based on the previously calculated weighted center position (xm, ym), the Voronoi region was segmented to obtain its area. The numerical computation software MATLAB from Mathworks was used for the calculations.

[0580] Figure 6 (Example 1) or Figure 14 The Voronoi region map shown in (Comparative Example 1) can be obtained through the following calculation steps. It should be noted that... Figure 6 The units for the vertical and horizontal axes are pixels. Figure 14 The units for the vertical and horizontal axes are pixels. VXB and VYB are temporary variables used in the calculation.

[0581] [VXB, VYB] = voronoi (xm, ym);

[0582] plot(VXB, VYB, '-b', xm, ym, '.r');

[0583] The calculation of the region obtained from the Voronoi partition and its area are performed through the steps shown below. First, the following calculation steps are performed.

[0584] DTB=delaunayTriangulation([xm, ym]);

[0585] [VB, rB]=voronoiDaigram(DTB);

[0586] DTB is a temporary variable used in the calculation process. delaunayTriangulation(xm, ym) is the function that creates the elements of this temporary variable, namely the Delaunay triangulation. VB is a row and column variable that contains a list representing the positions of the endpoints of the triangles that make up the Voronoi section. rB is a column that shows which endpoints in the list contained in VB were used for each Voronoi region obtained by performing the Voronoi section.

[0587] Next, for each Voronoi region shown in each column rB, the following calculations are performed in the order of the columns. In the calculations, the columns of the list shown in rB are calculated sequentially from 1 to the end. The calculation for the list in its k-th column is performed as described below.

[0588] (1) If the endpoints of VB shown in the k-th list rB{k} of rB contain points corresponding to the outside of the image region, then that region is considered a non-closed region and excluded from the computation. This is because regions connected to the edges of the image contain boundaries called edges of the image that do not represent the island structure of the Voronoi segment, and therefore are considered to lack the area representing the original island structure features. The list shown in k that does not contain the points excluded here is determined to represent valid Voronoi regions.

[0589] (2) For the Voronoi region k that can be determined to be valid through the previous determination, its area A is calculated as follows.

[0590] rBK = rB{k};

[0591] XPB = VB(rBK, 1);

[0592] YPB = VB(rBK, 2);

[0593] A(i) = polyarea(XPB, YPB);

[0594] i is a sequential number assigned to the regions deemed valid, starting from 1 and incrementing by 1 each time it is substituted in the above calculations. rBK, XPB, and YPB are temporary variables used in the calculations.

[0595] For these calculations (1) and (2), k is incremented sequentially from 1 until the end of the list of rB, and only the area of ​​the region that is judged to be valid as the Voronoi region is brought into A.

[0596] For example Figure 7 (Example 1) and Figure 15 (Comparative Example 1) shows the Voronoi region, whose area was determined to be valid and calculated, as the result of this calculation. It should be noted that... Figure 7 The units for the vertical and horizontal axes are pixels. Figure 15 The units for the vertical and horizontal axes are pixels.

[0597] As an example of the area calculation results, the histogram of the separator is shown in... Figure 8 (Example 1) and Figure 16 (Comparative Example 1)

[0598] The area of ​​the Voronoi diagram is calculated based on the image and is therefore expressed in pixels. However, it can be converted to the actual area depending on the shooting conditions when the image was captured. Depending on the shooting conditions, if the length of one side of a pixel is lp (μm), then the area equivalent to one pixel is lp. 2 (μm 2 The actual area can be obtained by multiplying the area of ​​the Voronoi region (represented by the number of pixels) by the area of ​​a single pixel. For example, when photographing a 100μm square area using a 256×256 pixel image, the length of one side of a pixel is 0.39μm, and the area of ​​one pixel is 0.153μm. 2 For example, the actual area of ​​the Voronoi region, calculated to be 100 pixels, is 153 μm. 2 Therefore, the area obtained from an image in pixels can be easily converted to the actual area. An example of the converted histogram is shown below. Figure 9 (Example 1) and Figure 17 (Comparative Example 1). Furthermore, if the length of one side of a pixel is lp (μm), then the corresponding area of ​​one pixel is lp. 2 (μm 2 In addition, by converting the actual area of ​​the Voronoi region in the same way as above, a converted histogram can be obtained.

[0599] Next, a method for calculating parameters representing the distribution characteristics of the area of ​​the Voronoi region from this histogram is shown. This calculation is performed by fitting the area distribution to a probability distribution function as shown below.

[0600]

[0601] Here, x represents the input data. The fitting parameters are three: shape parameter k, location parameter μ representing the maximum value, and scale parameter σ representing the deviation.

[0602] The calculations were performed using the `fitdist` function with the `GeneralizedExtremeValueDistribution` option from the Statistics and Machine Learning Toolbox of MATLAB, a numerical computing software developed by MathWorks. During runtime, the previously calculated area A was used as x, as follows.

[0603] pd=fitdist(A,'GeneralizedExtremeValueDistribution');

[0604] The output `pd` is a structure containing the fitting results and retains the aforementioned values ​​of `k`, `μ`, and `σ`. Each data point can be accessed using the formats `pd.k`, `pd.mu`, and `pd.sigma`, respectively. An example of the fitting results is shown below. Figure 10 (Example 1) and Figure 18 (Comparative Example 1). In this case, the peak positions and σ, representing the deviation, are used from the distribution parameters obtained through this fitting. σ / mu can also be calculated using the obtained mu and σ.

[0605] <Compression Resistance Test>

[0606] Two separator pieces were cut into 10cm x 10cm pieces, overlapped, and their air permeability Sj was measured. Then, the thickness was measured at any nine points within an 8cm x 8cm area, with the intersection of the diagonals as the reference point when viewed from above, and their average value was calculated. Two 10cm x 10cm PET films were then placed over this layer to form a laminate. The laminate was then clamped between two 5mm thick 10cm x 10cm rubber sheets, and pressure was applied while heating using a small testing press (model: MP-WCH) manufactured by TOYOSEIKI. It should be noted that the PET film and rubber sheets were applied with uniform pressure across the entire surface, and this uniformity was confirmed using a pressure sensor. The upper and lower heaters of the press were set to 90°C, and a uniform pressure of 8 MPa was applied to the 10cm x 10cm sample for 3 minutes. After the heating and compression operation, the air permeability Sh of the separator formed by the two overlapping pieces was measured. Next, measure the thickness of the separator formed by overlapping the two pieces at any 9 points within an 8cm × 8cm area, using the intersection of the diagonals as a reference, and calculate their average value. The change in thickness before and after the quantitative compression operation is taken as the thickness reduction rate (%), and the change in air permeability after quantitative compression is taken as the air permeability change ratio.

[0607] Thickness reduction rate (%) = ((thickness after compression (μm) - thickness before compression (μm)) / thickness before compression (μm)) × 100

[0608] Change in air permeability (%) = ((Air permeability after compression Sh (sec) - Air permeability before compression Sj (sec)) / Air permeability before compression Sj (sec)) × 100

[0609] <Contact angle of coating liquid (°)>

[0610] Using a contact angle meter (CA-V) (model name) manufactured by Kyowa Interface Science Co., Ltd., 2 μl of each coating solution was dropped onto the clean surface of the separator substrate, and the contact angle was measured after 40 seconds. Measurements were taken three times on both the MD and TD surfaces, and the average value was used as the contact angle. Furthermore, this measurement method was performed on both the front and back surfaces of the microporous membrane used as the separator substrate; the value from the side with the larger value was used.

[0611] <Confirmation of crosslinking reaction during coating process>

[0612] The TMA fracture temperature was measured before and after coating the polyolefin microporous membrane, which served as the separator substrate, with the coating solution applied. The comparison of the two temperatures confirmed the progress of the crosslinking reaction during the coating process. The progress of the crosslinking reaction was evaluated for the TMA fracture temperature according to the following criteria.

[0613] (Coating with inorganic porous layers or thermoplastic polymer layers)

[0614] 〇 (Good): Above 190℃

[0615] Δ (Acceptable): 170℃~190℃

[0616] × (Poor): Below 170℃

[0617] (Coating of an active layer or a heat-resistant resin layer)

[0618] 〇 (Good): Above 200℃

[0619] Δ (Acceptable): 180℃~200℃

[0620] × (Poor): Below 180℃

[0621] <Battery Evaluation I: Cyclic Test, Hot Box Test, and Nail Puncture Test>

[0622] To manufacture a laminated battery or a 4680 cylindrical battery, follow these steps: perform a cycle test (1), a hot box test, and a nail puncture test on the laminated battery, and perform a cycle test (2) on the 4680 cylindrical battery.

[0623] (The fabrication of the batteries used in the safety tests)

[0624] a. Production of the positive electrode

[0625] LiNi will be used as the positive electrode active material 0.8 Mn 0.1 Co 0.1O2, carbon black as a conductive additive, and polyvinylidene fluoride solution as a binder were mixed at a solid content mass ratio of 91:5:4. N-methyl-2-pyrrolidone was added as a dispersing solvent to bring the solid content to 68% by mass, and then the mixture was further mixed to prepare a slurry solution. This slurry solution was coated onto both sides of a 15 μm thick aluminum foil, with a portion of the foil exposed, and then dried to remove the solvent. The density of the positive electrode mixture was then determined to be 2.8 g / cm³. 3 The cathode is obtained by rolling using a roller press. It is then cut to include the exposed aluminum foil portion.

[0626] b. Negative electrode fabrication

[0627] Artificial graphite (as the negative electrode active material), styrene-butadiene rubber (as the binder), and carboxymethyl cellulose aqueous solution were mixed at a solid content mass ratio of 96.4:1.9:1.7. Water was added as a dispersion solvent to bring the solid content to 50% by mass, and the mixture was then stirred to prepare a slurry solution. This slurry solution was coated onto a portion of a 10 μm thick copper foil, which was then dried to remove the solvent. The density of the negative electrode mixture was then determined to be 1.45 g / cm³. 3 The cathode is obtained by rolling using a roller press. It is then cut to include the exposed copper foil portion.

[0628] c. Preparation of non-aqueous electrolytes

[0629] The electrolyte and electrolyte solution are mixed as shown in Tables 18 and 19, thereby preparing a non-aqueous electrolyte solution.

[0630] d-1. Assembly of laminated batteries

[0631] A 55mm wide strip separator was repeatedly folded to create a laminate containing 15 double-sided negative electrodes and 14 double-sided positive electrodes, with the active materials of the positive and negative electrodes facing each other and sandwiched between them. The heat-resistant B layer of sample 1 was then positioned opposite the positive electrode. Aluminum leads with sealant were welded to the exposed portions of the 14 positive electrode aluminum foils, and nickel leads with sealant were welded to the exposed portions of the 15 negative electrode copper foils. These were then inserted into an aluminum laminated casing, and the exposed edges of the positive / negative electrode leads and two other edges were laminated and sealed. The aforementioned non-aqueous electrolyte was then injected into the casing, and the opening was sealed, producing 28 opposing laminated batteries. After the obtained battery was left at room temperature for one day, it was charged for the first time for a total of 8 hours at 25°C with a constant current of 330mA (0.3C) to a battery voltage of 4.2V, and then charged with a constant voltage to maintain the 4.2V. Then, the battery was discharged with a current of 330mA (0.3C) to a battery voltage of 3.0V.

[0632] d-2. Battery assembly of cylindrical batteries

[0633] Using the aforementioned positive electrode, negative electrode, and electrolyte, a cylindrical (4680 type) lithium secondary battery (battery dimensions: diameter 46mm, height 80mm) was fabricated using a long strip separator with the active materials of the positive and negative electrodes facing each other and sandwiched between them. Regarding the length of the positive and negative electrodes during battery fabrication, the electrodes were sealed with the maximum length that could be inserted into the battery container. At this time, the coating layer of the separator was positioned opposite the positive electrode. After the resulting battery was left at room temperature for one day, it underwent its first charge for a total of 8 hours at 25°C by charging it with a constant current of 5A (0.3C) to a battery voltage of 4.2V, and then maintaining the 4.2V voltage with a constant voltage charge. Next, the battery was discharged at a current of 5A (0.3C) to a battery voltage of 3.0V.

[0634] (Cyclic test (1): at 5°C and 50°C)

[0635] For the batteries obtained in "d-1. Battery Assembly of Laminated Batteries" above, 1000 charge-discharge cycles were performed each at 5°C and 50°C. Regarding charging, the batteries were charged for a total of 3 hours using a constant current of 1A (1.0C) to a battery voltage of 4.2V, followed by constant voltage charging to maintain 4.2V. Regarding discharging, the batteries were discharged to a battery voltage of 3.0V using a current of 1A (1.0C). The capacity retention rate was calculated from the discharge capacity of the 1000th cycle and the discharge capacity of the 1st cycle. A high capacity retention rate is considered to indicate good cycle characteristics.

[0636] (Hot Box Test)

[0637] The battery obtained by the above "d-1. Battery assembly of laminated battery" was subjected to 300 charge-discharge cycles at 5°C and then stored in a high-temperature chamber set at 136°C for 1 hour. The battery status was observed during and after storage.

[0638] When the microporous membrane, which serves as a separator within the battery, undergoes thermal shrinkage due to high-temperature storage, an internal short circuit occurs between the two electrodes of the battery, namely the positive and negative terminals, sometimes resulting in fire or explosion. Batteries exhibiting such fire or explosion are evaluated as defective. Batteries without observed fire or explosion are evaluated as acceptable.

[0639] For the same separator, the hot box test was performed on 100 batteries and the pass rate (%) was calculated.

[0640] (Prick test)

[0641] The following experiment was conducted: A diameter [missing information] was inserted into a battery charged to 4.2V and obtained through the above-described "d-1. Laminated Battery Assembly" process. A nail is inserted and pierced through the battery, causing an internal short circuit. In this experiment, the phenomena of an internal short circuit are elucidated by measuring the time-varying behavior of the battery voltage drop and the rise in battery surface temperature caused by the internal short circuit. Furthermore, during an internal short circuit, sometimes due to insufficient sealing function of the separator or membrane rupture at low temperatures, the battery may rapidly exothermize, leading to electrolyte ignition, battery smoke, and / or explosion.

[0642] To determine whether the batteries that underwent the nail puncture test as described above are qualified, the nail puncture test was performed on 100 batteries for the same separator, and the number of batteries that did not catch fire / smoke / explode, X, was calculated as the qualified ratio (X / 100), as shown in Tables 2 to 17.

[0643] (Cyclic Experiment (2))

[0644] The battery obtained in "d-2. Battery Assembly of Cylindrical Batteries" above was subjected to 500 charge-discharge cycles at 40°C. For charging, the battery was charged for a total of 3 hours using a constant current of 17.5A (1.0C) to a battery voltage of 4.2V, followed by constant voltage charging to maintain 4.2V. For discharging, the battery was discharged to a battery voltage of 3.0V using a current of 17.5A (1.0C). The capacity retention rate was calculated from the discharge capacity of the 1000th cycle and the discharge capacity of the 1st cycle. A high capacity retention rate indicates good cycle characteristics.

[0645] <Battery Evaluation II>

[0646] (Battery making)

[0647] In battery evaluation, non-aqueous secondary batteries containing sample cells were fabricated and evaluated according to the following steps. For crush tests, cycle test capacity retention, and cycle life tests, 4680-type cylindrical batteries were fabricated, and measurements were taken 4 days after the separators were coated.

[0648] a. Production of the positive electrode

[0649] LiNi will be used as the positive electrode active material 0.6 Mn 0.2 Co 0.2O2, carbon black as a conductive additive, and polyvinylidene fluoride solution as a binder were mixed at a solid content mass ratio of 91:5:4. N-methyl-2-pyrrolidone was added as a dispersing solvent to bring the solid content to 68% by mass, and then the mixture was further mixed to prepare a slurry solution. This slurry solution was coated onto both sides of a 15 μm thick aluminum foil, with a portion of the foil exposed, and then dried to remove the solvent. The density of the positive electrode mixture was then determined to be 2.8 g / cm³. 3 The cathode is obtained by rolling using a roller press. It is then cut to include the exposed aluminum foil portion.

[0650] b. Negative electrode fabrication

[0651] Carbon-coated silicon powder (as the negative electrode active material), lithium-doped carbon-coated silicon oxide powder, graphite powder, styrene-butadiene rubber (as a binder), and carboxymethyl cellulose aqueous solution were mixed at a solid content mass ratio of 3:27:66.4:1.9:1.7. Water was added as a dispersion solvent to bring the solid content to 50% by mass, and the mixture was then stirred to prepare a slurry solution. This slurry solution was coated onto both sides of a 10 μm thick copper foil with a portion of the foil exposed, and then dried to remove the solvent. The density of the negative electrode mixture was 1.45 g / cm³. 3 The cathode is obtained by rolling using a roller press. It is then cut to include the exposed copper foil portion.

[0652] c: Electrolyte preparation

[0653] A non-aqueous electrolyte was prepared by dissolving LiPF6 as a solute in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a ratio of 1:2 (volume ratio).

[0654] d. Battery assembly

[0655] A cylindrical (4580 type) lithium secondary battery (battery size: diameter 46mm, height 80mm) was manufactured using the above-described positive electrode, negative electrode, and electrolyte, with the active materials of the positive and negative electrodes facing each other and sandwiched between them, using a long strip separator. Regarding the length of the positive and negative electrodes during battery manufacturing, the electrodes were sealed with the maximum length that could be inserted into the battery container. At this time, the coating layer configured as the separator was positioned opposite the positive electrode. After the resulting battery was placed at room temperature for 1 day, it was first charged for a total of 8 hours at a constant current of 1A (0.06C) to a battery voltage of 4.2V in a 25°C atmosphere, followed by constant voltage charging to maintain 4.2V. Then, the battery was discharged to a battery voltage of 3.0V using a current of 1A (0.06C).

[0656] (Bar impact test (crush test))

[0657] The following test was conducted using a specified number of batteries: Batteries obtained in "d. Battery Assembly" of Battery Evaluation II were used, with a diameter perpendicular to the length of the batteries. After applying the SUS bar, a 9.1 kg weight was dropped freely from a height of 61 cm and subjected to impact to confirm the battery's temperature rise and fire status. Batteries that released heat above 80°C after the impact were evaluated as non-conforming products, and the pass rate (%) based on the total number of batteries was calculated.

[0658] (Cyclic test capacity retention rate (%))

[0659] For the batteries obtained in "d. Battery Assembly" of Battery Evaluation II above, 500 charge-discharge cycles were performed at 55°C. Regarding charging, the batteries were charged for a total of 3 hours using a constant current of 8.7A (0.5C) to a battery voltage of 4.2V, followed by a constant voltage charge to maintain 4.2V. Regarding discharging, the batteries were discharged to a battery voltage of 3.0V using a current of 8.7A (0.5C). The capacity retention rate was calculated from the discharge capacity of the 1000th cycle and the discharge capacity of the 1st cycle. A high capacity retention rate indicates good cycle characteristics.

[0660] (Cyclic life test)

[0661] The batteries obtained in "d. Battery Assembly" of Battery Evaluation II above were repeatedly charged and discharged at 65°C until the capacity retention rate was below 50%. For charging, the batteries were charged for a total of 3 hours using a constant current of 8.7A (0.5C) to a battery voltage of 4.2V, followed by constant voltage charging to maintain 4.2V. For discharging, the batteries were discharged to a battery voltage of 3.0V using a current of 8.7A (0.5C). The number of cycles in which the capacity retention rate was below 50% was recorded as the cycle life. A high cycle life was considered an indicator of good cycle characteristics.

[0662] [Preparation of Silane-Modified Polyolefins]

[0663] The raw material polyolefin used in silane-modified polyolefins only needs to have a viscosity-average molecular weight (Mv) of 10,000 or more and 1,000,000 or less, a weight-average molecular weight (Mw) of 30,000 or more and 920,000 or less, and a number-average molecular weight of 10,000 or more and 150,000 or less. It can be an α-olefin copolymerized with propylene or butene. While the raw material polyethylene is melt-blended using an extruder, an organic peroxide (di-tert-butyl peroxide) is added. After free radicals are generated in the α-olefin polymer chain, trimethoxyalkoxy compounds are injected to replace vinyl silanes. Through an addition reaction, alkoxysilyl groups are introduced into the α-olefin polymer to form a silane graft structure. In addition, an appropriate amount of antioxidant (pentaerythritol tetratetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) is added to simultaneously regulate the free radical concentration in the system and inhibit the chain reaction (gelation) in the α-olefin. The obtained silane-grafted polyolefin molten resin was cooled in water, granulated, and then dried at 80°C for 2 days to remove moisture or unreacted trimethoxyalkoxylated vinylsilane. It should be noted that the residual concentration of unreacted trimethoxyalkoxylated vinylsilane in the granules is below 3000 ppm. Furthermore, by using octenyltrialkoxysilane instead of trimethoxyalkoxylated vinylsilane, a silane-modified polyolefin with 8 methylene (CH2) groups forming the linking portion of the aforementioned main chain can be manufactured; and by using dodecyltrialkoxysilane instead of trimethoxyalkoxylated vinylsilane, a silane-modified polyolefin with 12 methylene (CH2) groups forming the linking portion of the aforementioned main chain can be manufactured.

[0664] [Preparation methods for polyolefins other than silane-modified polyolefins]

[0665] The preferred polyolefin used in the preparation of polyolefins other than silane-modified polyolefins is not limited, and can be produced by the following method: Hexane, ethylene, α-olefins such as 1-pentene or 1-butene, hydrogen, catalyst components such as Ziegler-Natta catalysts or metallocene catalysts, co-catalyst components such as triisobutylaluminum and diisobutylaluminum hydride, and an antistatic agent are continuously fed into a Bessel-type polymerization reactor equipped with a stirrer to obtain a polyethylene polymerization slurry. At this time, the polymerization temperature is kept constant by jacket cooling, and the polymerization slurry is continuously discharged into a flash drum with a constant temperature to keep the level of the polymerization reactor constant, separating unreacted ethylene and hydrogen. The solvent is then separated using a centrifuge, and dried by a nitrogen gas stream to obtain polyethylene powder. For the obtained polyethylene powder, aliphatic saturated alcohols such as methanol and calcium stearate are added, and the mixture is mixed evenly using a Henschel mixer. Then, substances that cannot pass through the sieve are removed using a sieve with a suitable mesh size, thereby obtaining a polyolefin other than silane-modified polyolefins.

[0666] [Preparation of Resin Raw Materials]

[0667] (Preparation of resin raw material A1)

[0668] Resin raw material A1 was granulated by mixing 1.4 parts by weight of vinyltrimethoxysilane, 0.025 parts by weight of di-tert-butyl peroxide as an organic peroxide, and 0.15 parts by weight of polyolefin with a viscosity average molecular weight of 150,000 with 100 parts by weight of vinyltrimethoxysilane, 0.025 parts by weight of di-tert-butyl peroxide as an organic peroxide, and 0.15 parts by weight of calcium stearate with 100 parts by weight of vinyltrimethoxysilane. The mixture was then melt-blended at 220°C using a TEX-44 twin-screw extruder (44 mm screw diameter, L / D = 35) manufactured by Nippon Steel Works Co., Ltd.

[0669] (Preparation of resin raw material B1)

[0670] On one hand, hexane is used at a flow rate of 55 L / h, with Mg6(C4H9) as a catalyst component. 12 A 0.5 g / h Ziegler-Natta catalyst of Al(C2H5)3 and titanium tetrachloride, and a 9 mmol / h mixture of triisobutylaluminum and diisobutylaluminum hydride (a co-catalyst component) were fed into a Bessel-type 300L polymerization reactor maintained at 53°C via jacket cooling. Ethylene was continuously supplied to maintain a polymerization pressure of 0.3 MPa, thereby carrying out the polymerization reaction to obtain a polyethylene polymerization slurry. At this time, STATSAFE3000 as an antistatic agent was added at a concentration of 15 ppm relative to the polyethylene powder. Additionally, 1-butene as an α-olefin was continuously added at a concentration of 6.9 mol% relative to the gaseous ethylene concentration. To maintain a constant level in the polymerization reactor, the polyethylene polymerization slurry was continuously discharged into a flash drum at a pressure of 0.05 MPa to separate unreacted ethylene. Solvent separation was then performed by centrifugation, and drying was carried out using a rotary drum dryer adjusted to 80°C in the jacket and 80 ppm oxygen concentration under a nitrogen flow to obtain polyethylene powder. Methanol was added to the obtained polyethylene powder at a concentration of 150 ppb, and calcium stearate was added at a concentration of 1000 ppm (wet preparation method). Substances that could not pass through the sieve were removed using a sieve with a mesh size of 425 μm to obtain resin raw material B1.

[0671] (Preparation of resin raw material C2)

[0672] The flow rate of hexane will be adjusted to 40 L / h at 3°C, with Mg6(C4H9) as the catalyst component. 12A 0.2 g / h Ziegler-Natta catalyst of Al(C2H5)3 and titanium tetrachloride, and a 10 mmol / h mixture of triisobutylaluminum and diisobutylaluminum hydride (9:1 mixture) as co-catalyst components are fed into a Bessel-type 300L polymerization reactor maintained at 80°C by jacket cooling. Ethylene is continuously supplied to maintain a polymerization pressure of 0.5 MPa, thereby carrying out the polymerization reaction to obtain a polyethylene polymerization slurry. At this time, STATSAFE3000 as an antistatic agent is added at a concentration of 15 ppm relative to the polyethylene powder. Additionally, 1-butene as an α-olefin is continuously added at a concentration of 5 mol% relative to the gaseous ethylene. Hydrogen is supplied at a concentration of 5.5 mol% relative to the gaseous ethylene. To maintain a constant level in the polymerization reactor, the polyethylene polymerization slurry is continuously discharged into a flash drum at a pressure of 0.05 MPa to separate unreacted ethylene. Solvent separation was then performed by centrifugation, followed by drying in a rotary drum dryer with a jacket temperature of 80°C and an oxygen concentration of 80 ppm under a nitrogen flow to obtain polyethylene powder. Methanol was added to the obtained polyethylene powder at 150 ppb, and calcium stearate was added at a concentration of 1000 ppm (wet preparation method). Substances that could not pass through the sieve were removed using a 425 μm mesh sieve to obtain resin raw material C2.

[0673] (Preparation of other resin raw materials)

[0674] By changing the molecular weight and copolymer concentration of the polyolefin, the amount of trimethoxyalkoxy compound substituted for vinylsilane, and the mixing conditions, the process is carried out in the same manner as the preparation of resin raw material A1, thereby producing resin raw materials A2-A12 and resin raw materials D1-D14 as shown in Tables 20-25. Specifically, in the preparation of resin raw material D13, octenyloctenyltrialkoxysilane is used instead of trimethoxyalkoxy compound substituted for vinylsilane; in the preparation of D14, dodecyltrialkoxysilane is used instead of trimethoxyalkoxy compound substituted for vinylsilane. By changing the amount of raw materials, the polymerization reactor temperature, and the polymerization pressure, the process is carried out in the same manner as the preparation of resin raw material B1, thereby producing resin raw materials B2-B6 and E1-E5 as shown in Tables 20-25. By changing the amount of raw materials, the polymerization reactor temperature, and the polymerization pressure, the process is carried out in the same manner as the preparation of resin raw material C2, thereby producing resin raw materials C1, C3-C5, and F1-F4 as shown in Tables 20-25.

[0675] [Example 1] Fabrication and evaluation of the separator

[0676] (Fabrication of microporous membranes made of polyolefin as separators)

[0677] A mixture was obtained by dry mixing a mixed resin composition of 30 wt% resin A1, 30 wt% resin B1, and 40 wt% resin C2 with 1000 ppm pentaerythritol-tetra-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] as an antioxidant, using a drum mixer. The resulting mixture was then fed into a twin-screw extruder under a nitrogen atmosphere. Separately, liquid paraffin (with a kinematic viscosity of 7.59 × 10⁻⁶ at 37.78°C) was also added. -5 m 2 / s) is injected into the extruder drum via a plunger pump.

[0678] The mixture and liquid paraffin were melt-blended in an extruder. The feeder and pump were adjusted so that the liquid paraffin accounted for 75% by mass in the extruded polyolefin composition (i.e., the polymer concentration was 25% by mass). The melt-blending conditions were set at a temperature of 230°C, a screw speed of 100 rpm, and a discharge rate of 80 kg / h.

[0679] Next, the molten compound is extruded through a T-die onto a cooling roller with a surface temperature controlled at 25°C and then cast to obtain a gel sheet (sheet-shaped molded body) with a blank film thickness of 1250 μm.

[0680] Next, the sheet-shaped material was guided to a biaxial stretching machine for biaxial stretching to obtain a stretched product. The stretching conditions were set as follows: MD ratio 7.0, TD ratio 6.4 (i.e., 7 × 6.4), and biaxial stretching temperature 125°C. The stretched gel sheet was then guided to a dichloromethane bath for thorough impregnation in dichloromethane to extract and remove liquid paraffin. After drying to remove the dichloromethane, a porous body was obtained. Subsequently, the porous body was guided to a TD stretching machine for heat setting (HS). HS was performed at a heat setting temperature of 133°C and a stretching ratio of 1.8 based on the sheet width at the TD stretching machine inlet. A relaxation operation was then performed until the TD ratio reached 1.6 based on the sheet width at the TD stretching machine inlet, thus obtaining a microporous membrane. Finally, the ends of the obtained microporous membrane were cut off, and it was wound into a master roll with a width of 1100 mm and a length of 5000 m.

[0681] <Coating of Inorganic Coating Layers>

[0682] (Preparation method of acrylic latex)

[0683] Acrylic latex used as a resin binder is manufactured by the following method: 70.4 parts by mass of ion-exchanged water, 0.5 parts by mass of "AquaronKH1025" (a registered trademark, a 25% aqueous solution manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), and 0.5 parts by mass of "ADEKAREASOAP SR1025" (a registered trademark, a 25% aqueous solution manufactured by ADEKA Co., Ltd.) as emulsifiers are added to a reaction vessel equipped with a stirrer, a reflux condenser, a dropping tank, and a thermometer. Next, the temperature inside the reaction vessel is raised to 80°C, and while maintaining this temperature, 7.5 parts by mass of a 2% aqueous solution of ammonium persulfate is added to obtain an initial mixture. The addition of the ammonium persulfate aqueous solution is then stopped. After 5 minutes, the emulsion is added dropwise from the dropping tank to the reaction vessel over a period of 150 minutes. It should be noted that the above emulsion was prepared by mixing the following substances for 5 minutes using a homogenizer: 70 parts by weight of butyl acrylate; 29 parts by weight of methyl methacrylate; 1 part by weight of methacrylic acid; 3 parts by weight of "Aquaron KH1025" (registered trademark, 25% aqueous solution manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) and 3 parts by weight of "ADEKA REASOAP SR1025" (registered trademark, 25% aqueous solution manufactured by ADEKA Co., Ltd.) as emulsifiers; 7.5 parts by weight of 2% aqueous solution of ammonium persulfate; and 52 parts by weight of deionized water.

[0684] After the emulsion was added dropwise, the temperature inside the reaction vessel was maintained at 80°C for 90 minutes, and then cooled to room temperature. The resulting emulsion was adjusted to pH 8.0 with a 25% ammonium hydroxide aqueous solution, and a small amount of water was added to obtain an acrylic latex with a solid content of 40%. The number average particle size of the obtained acrylic latex was 145 nm, and the glass transition temperature was -23°C.

[0685] (Formation of inorganic porous layers)

[0686] A dispersion was prepared by uniformly dispersing 95 parts by weight of aluminum hydroxide (average particle size 1.4 μm) as inorganic particles and 0.4 parts by weight (solids content conversion) of an aqueous solution of ammonium polycarboxylate (SNDispersant 5468 manufactured by SAN NOPCO LIMITED, 40% solids content) as an ionic dispersant in 100 parts by weight of water. The resulting dispersion was then subjected to a bead mill (tank volume 200 cc, zirconia bead diameter 0.1 mm, filling rate 80%) to adjust the particle size distribution of the inorganic particles to D50 = 1.0 μm. 4.6 parts by weight (solids content conversion) of an acrylic latex (40% solids content, average particle size 145 nm, glass transition temperature -23 °C, monomers: butyl acrylate, methyl methacrylate, methacrylic acid) as a resin binder was added to the particle size-adjusted dispersion to prepare a slurry containing inorganic particles.

[0687] Subsequently, the microporous membrane is continuously unwound from the aforementioned microporous membrane master roll, and a slurry containing inorganic particles is coated on one side of the microporous membrane using a photogravure reverse coating machine. Then, it is dried in a 60°C dryer to remove water, and wound up to obtain the master roll of the separator.

[0688] During evaluation, the separators released from the master roll are cut as needed and used as evaluation separators.

[0689] The thickness, air permeability, porosity, puncture strength, and change in air permeability before and after a 30% compression test of the obtained polyolefin microporous membrane were measured and are shown in Table 2. For the evaluation separator and the battery containing it, various evaluations were performed according to the above evaluation methods, and the evaluation results are shown in Table 2.

[0690] [Examples 2-33, Comparative Examples 4 and 7] Fabrication and Evaluation of Separators

[0691] As shown in Tables 2-8, the molecular weight mixture, manufacturing conditions, and composite composition conditions of the polyolefin microporous membrane were changed, and the same operation as in Example 1 was performed to obtain the separators shown in Tables 2-8. Various evaluations were performed on the obtained separators and the batteries containing them according to the evaluation methods described above, and the evaluation results are also shown in Tables 2-8.

[0692] It should be noted that the silane-modified PP described in Examples 28 and 30 is manufactured and used in the same manner as the method described in the [Preparation Method of Silane-Modified Polyolefin] section above, using polypropylene (E-100GV) manufactured by Prime Polymer Co., Ltd. The PP uses polypropylene (E-100GV) manufactured by Prime Polymer Co., Ltd.

[0693] The PP-PE described in Example 28 uses a block polymer (DYNARON 6201B) of olefin crystallization / ethylene butene / olefin crystallization manufactured by JSR Corporation.

[0694] [Comparative Example 1] Fabrication and Evaluation of Separators

[0695] Resin B1 and Resin C2 were used in a 50:50 (mass ratio), and the fabrication conditions for the polyolefin microporous membrane and the composite composition conditions were changed as shown in Table 7. Otherwise, the same operation as in Example 1 was performed to obtain the separator shown in Table 7. Various evaluations were performed on the obtained separator and the battery containing it according to the evaluation methods described above, and the evaluation results are also shown in Table 7.

[0696] [Comparative Example 2] Fabrication and Evaluation of Separators

[0697] In an extruder, 24 kg / h of unmodified silane polyethylene (VH035, manufactured by Daehan Oil & Chemical Industry Co., Ltd.) with a weight-average molecular weight of 350,000 and a melting point of 136.2℃, 24 kg / h of resin raw material A1, and liquid paraffin (kinematic viscosity of 7.59 × 10⁻⁶ at 37.78℃) were mixed. -5 m 2 / s)112kg / h. At this time, the weight ratio of unmodified silane polyethylene: modified silane polyethylene: liquid paraffin is 15:15:70. Then, based on a total of 100 parts by weight of unmodified silane polyethylene, modified silane polyethylene, and liquid paraffin, 0.5 parts by weight of vinyltriethoxysilane (an alkoxysilane compound containing carbon-carbon double bonds), 2 parts by weight of dibutyltin dilaurate (a crosslinking catalyst) based on 100 parts by weight of the alkoxysilane compound containing carbon-carbon double bonds, and 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane (DHBP) (an initiator) based on 100 parts by weight of the alkoxysilane compound containing carbon-carbon double bonds) are introduced into an extruder and mixed. Then, extrusion is performed at 200°C to obtain a silane-modified polyethylene composition. The obtained silane-modified polyethylene composition was formed into sheets using a T-die and cooling casting rollers, and then biaxially stretched using a spreader-type successive stretching machine, first by MD stretching and then by TD stretching. The MD stretching ratio was 5.5 times, and the TD stretching ratio was 5.0 times. The stretching temperatures were 105°C for MD and 125°C for TD. Liquid paraffin was extracted from the stretched sheets using dichloromethane, and heat-set at 126°C to change the stretching ratio from 1.3 times to 1.1 times, thereby producing a porous membrane. This porous membrane was subjected to aqueous crosslinking at 85°C and 85% relative humidity for 48 hours to obtain the separators shown in Table 7. The obtained separators and the batteries containing them were evaluated according to the above evaluation methods, and the evaluation results are also shown in Table 7.

[0698] [Comparative Example 3] Fabrication and Evaluation of Separators

[0699] A modified polyolefin H3-1 (VH035H manufactured by Korea Petrochemical Industry) containing an average of 7.7 alkylene groups of 3 carbon atoms as short-chain branches (SCBs) based on a carbon number of 1000 was prepared. This modified polyolefin had a weight-average molecular weight of 380,000 and a melting point of 129.1°C. At this point, the modified polyolefin was a polyolefin containing repeating units derived from ethylene and repeating units derived from α-olefins, the repeating units derived from 1-pentene. The modified polyolefin H3-1 prepared as input was prepared at a rate of 7.5 kg / h, along with 7.5 kg / h of unmodified silane polyethylene (VH035 manufactured by Korea Petrochemical Industry) with a weight-average molecular weight of 300,000 and a melting point of 135°C, and liquid paraffin as a plasticizer (kinematic viscosity at 37.78°C: 7.59 × 10⁻⁶). -5 m 2A total of 35 kg / h of alkoxysilanes containing carbon-carbon double bond groups, including 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane (DHBP) as an initiator, vinyltrimethoxysilane (VTMS) as a crosslinking agent, and dibutyltin dilaurate (DBTDL) as a catalyst, are added to the extruder and mixed. At this point, the weight ratio of modified polyolefin H3-1 to silane-unmodified polyolefin is 50:50. When the alkyl group from the repeating unit of the α-olefin has 3 carbon atoms, the carbon number of the main polyolefin chain is 1000. The weight ratio of the added polyolefin to the plasticizer is 30:70. The content of alkoxyvinylsilane containing carbon-carbon double bonds was 0.3 parts by weight based on a total of 100 parts by weight of polyolefin and plasticizer added; the content of initiator was 1.7 parts by weight based on 100 parts by weight of alkoxysilane containing carbon-carbon double bonds; and the content of crosslinking catalyst was 6.7 parts by weight based on 100 parts by weight of alkoxysilane containing carbon-carbon double bonds. The mixture was then extruded using an extruder, and the resulting mixture was extruded at 190°C to obtain silane-modified polyolefin composition H3-2. The obtained silane-modified polyolefin composition H3-2 was formed into sheets using a T-die and cooling casting rolls, and then biaxially stretched using a successive stretching machine that performs MD stretching followed by TD stretching. Both the MD stretching ratio and the TD stretching ratio were 7.0 times. The stretching temperatures were 103°C for MD and 118°C for TD. Considering the melt temperature of the modified polyolefin, stretching was performed at a temperature lower than that used for the composition of typical polyolefins. Liquid paraffin was extracted from the stretched sheet using dichloromethane and heat-set at 124°C to prepare a porous membrane. This porous membrane was then subjected to aqueous crosslinking at 85°C and 85% relative humidity for 24 hours to obtain the separators shown in Table 7. The obtained separators and the batteries containing them were evaluated using the methods described above, and the results are also shown in Table 7.

[0700] [Comparative Example 5] Fabrication and Evaluation of Separators

[0701] The mixture was premixed using a super mixer with 18 parts by weight of high-density polyethylene "SH800" (trademark, manufactured by Asahi Kasei Chemicals Co., Ltd.) with a viscosity-average molecular weight (Mv) of 270,000, 12 parts by weight of ultra-high molecular weight polyethylene "UH850" (trademark, manufactured by Asahi Kasei Chemicals Co., Ltd.) with an Mv of 2 million, 20 parts by weight of silica "DM10C" (trademark, manufactured by Tokuyama Co., Ltd., treated with dimethyl dichlorosilane for hydrophobicity) with an average primary particle size of 15 nm, 30 parts by weight of liquid paraffin "Smoil P-350P" (trademark, manufactured by Matsumura Petroleum Research Institute Co., Ltd.) as a plasticizer, and 0.3 parts by weight of pentaerythritol-tetra-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] as an antioxidant. The resulting mixture was fed into the feed port of a twin-screw extruder. In addition, liquid paraffin was side-fed into the twin-screw extruder drum at a ratio of 50 parts by mass in the total mixture (100 parts by mass) of melt-blended and extruded material. The melt-blending conditions in the extruder were set at a temperature of 200°C, a screw speed of 180 rpm, and a discharge rate of 12 kg / h. Next, the melt-blended material was extruded through a gear pump, conduit, and T-die at a temperature of 220°C into a cooling roller chamber with a surface temperature controlled at 25°C, yielding a sheet-like polyolefin composition. This sheet-like polyolefin composition was then continuously guided to a simultaneous biaxial stretcher for simultaneous biaxial stretching of 7 times longitudinally and 7 times transversely. The set temperature of the simultaneous biaxial stretcher was 123°C. The sheet-like polyolefin composition was then guided to a dichloromethane bath for thorough immersion in dichloromethane to extract and remove the liquid paraffin. Finally, the material was dried in dichloromethane. Next, the sheet-like polyolefin composition was guided to a transverse stretching machine, stretched 1.4 times laterally, relaxed to 1.2 times at the final exit, and then wound up to obtain the separator shown in Table 7. The set temperature for the transverse stretching section was 132°C, and the set temperature for the relaxation section was 137°C. Various evaluations were performed on the obtained separator and the battery containing it according to the evaluation method described above, and the evaluation results are also shown in Table 8.

[0702] [Comparative Example 6] Fabrication and Evaluation of Separators

[0703] 25 parts by weight of high-density polyethylene (HDPE) with a weight-average molecular weight (Mw) of 380,000 and a molecular weight distribution (Mw / Mn) of 5, 0.5 parts by weight of resin raw material A1 with a kinematic viscosity of 40°C, and 70 parts by weight of paraffin oil were mixed and fed into a twin-screw extruder (inner diameter 58 mm, L / D = 56). The mixture was extruded from the twin-screw extruder into a 300 mm wide T-die at 200°C and a screw speed of 40 rpm. The extrudate was then passed through casting rolls at 40°C to produce a substrate sheet with a thickness of 800 μm. The substrate sheet was stretched longitudinally 6 times using a roller stretcher at 110°C and transversely 7 times using a spreading stretcher at 125°C to produce a stretched film. The stretched film was then immersed in a dichloromethane leaching bath at 25°C for 1 minute to remove the paraffin oil, thus producing a porous membrane. After drying the porous membrane at 50°C, it was heated to 125°C using a stretching machine to heat-set it so that the transverse (TD) was 1.25 times greater than before stretching. The porous membrane was then crosslinked in a constant temperature and humidity bath at 85°C and 85% for 72 hours to obtain the separators shown in Table 8. Various evaluations were performed on the obtained separators and the batteries containing them according to the evaluation methods described above, and the evaluation results are also shown in Table 8.

[0704] [Comparative Example 8] Fabrication and Evaluation of Separators

[0705] In an extruder, 22.4 kg / h of unmodified silane polyethylene with a weight-average molecular weight of 900,000 and a melting point of 135℃, 22.4 kg / h of resin raw material A1, and liquid paraffin (kinematic viscosity at 37.78℃ is 7.59 × 10⁻⁶) were added. -5 m 2The mixture was prepared at a rate of 115.2 kg / h. At this point, the weight ratio of unmodified silane polyethylene to modified silane polyethylene to liquid paraffin was 14:14:72. Next, 0.5 parts by mass of vinyltriethoxysilane (an alkoxysilane compound containing carbon-carbon double bonds), 2 parts by mass of dibutyltin dilaurate (a crosslinking catalyst), and 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane (an initiator), were introduced into an extruder and mixed. The mixture was then extruded at 200°C to obtain the silane-modified polyethylene composition. The obtained silane-modified polyethylene composition was formed into sheets using a T-die and cooling casting rollers, and then biaxially stretched using a spreader-type successive stretching machine, first by MD stretching and then by TD stretching. The MD stretching ratio was 5.5 times, and the TD stretching ratio was 5.0 times. The stretching temperatures were 105°C for MD and 125°C for TD. Liquid paraffin was extracted from the stretched sheets using dichloromethane, and heat-set at 126°C to change the stretching ratio from 1.3 times to 1.1 times, thereby producing a porous membrane. This porous membrane was subjected to aqueous crosslinking at 85°C and 85% relative humidity for 48 hours to obtain the separators shown in Table 8. The obtained separators and the batteries containing them were evaluated according to the above evaluation methods, and the evaluation results are also shown in Table 8.

[0706] [Examples 1, 34-39, Comparative Examples 1, 4, 7, 9, 10]

[0707] As shown in Tables 2, 7, 9-14, the separators obtained in Examples 1, 34-39 and Comparative Examples 1, 4, 7, 9, 10 were arranged in order of the change in air permeability when compressed by 30% in the thickness direction, and their effects on the first battery configuration (Tables 9 and 10), the second battery configuration (Tables 11 and 12), and the third battery configuration (Tables 13 and 14) were tested respectively.

[0708] [Relationship between the separator in Example 1 and various battery configurations: Examples 1A to 1Q]

[0709] For the separator obtained in Example 1, batteries manufactured by changing the battery configuration as shown in Tables 15 to 17 were evaluated. The sub-numbers of Examples 1A to 1Q are labeled accordingly with respect to the battery configuration, and the battery evaluation results are also shown in Tables 15 to 17.

[0710] [Electrolyte mixing conditions, electrolyte blending conditions, resin raw material composition]

[0711] Table 18 shows the electrolyte mixing conditions used in the manufacture of batteries and separators and in various evaluations, Table 19 shows the electrolyte mixing conditions, and Tables 20-22 show the composition of resin raw materials.

[0712] [Table 2]

[0713]

[0714] [Table 3]

[0715]

[0716] [Table 4]

[0717]

[0718] [Table 5]

[0719]

[0720] [Table 6]

[0721]

[0722] [Table 7]

[0723]

[0724] [Table 8]

[0725]

[0726] [Table 9]

[0727]

[0728] [Table 10]

[0729]

[0730] [Table 11]

[0731]

[0732] [Table 12]

[0733]

[0734] [Table 13]

[0735]

[0736] [Table 14]

[0737]

[0738] [Table 15]

[0739]

[0740] [Table 16]

[0741]

[0742] [Table 17]

[0743]

[0744] [Table 18]

[0745] Electrolyte formulation P1 P2 P3 P4 P5 P6 EC / wt% 50 15 50 20 0 0 EMC / wt% 50 85 45 20 100 0 AcH / wt% 0 0 5 60 0 100

[0746] [Table 19]

[0747] Electrolyte formulation S1 S2 S3 S4 S5 S6 <![CDATA[LiPF6]]> 100 - - - 98 2 <![CDATA[LiBF4]]> - 100 - - - - LiTFSI - - 100 - - - LiFSI - - - 100 2 98

[0748] [Table 20]

[0749]

[0750] [Table 21]

[0751]

[0752] [Table 22]

[0753]

[0754] <Evaluation of multi-layered separators and batteries containing them>

[0755] [Table 23-1]

[0756]

[0757] [Table 23-2]

[0758] Resin D D8 D9 D10 D11 D12 013 D14 Mn 47500 15200 15600 15700 15600 16700 17000 Mw 311000 138100 135100 132200 118200 82000 85000 Mw / Mn 6.55 9.09 8.66 8.42 7.58 8.20 8.29 Mv 370000 165100 161000 158000 139200 90000 95100 C3 0.14 0 0.03 1.5 0 0.16 0.13 C4 0.03 0.03 0 0 1.2 0.55 0.53 Vin-Si 0.1 0.1 0.1 0.1 0.1 0.13 0.14 Crystallinity of resin D 63 62 69 67 65 56 55 Microcrystal size of resin D 24 19 27 26 24 21 19 <![CDATA[CH2 number]]> 2 2 2 2 2 8 12

[0759] [Table 24]

[0760] Resin E E1 E2 E3 E4 E5 Mn 400,100 520,100 510,100 650,200 200,000 Mw 3,700,000 4,800,000 4,900,100 6,100,000 1,867,000 Mw / Mn 9.2 9.2 9.6 9.4 9.3 Mv 4,500,000 6,000,100 6,100,100 7,500,100 2,300,000 C3 0.03 0 0.04 0 0 C4 0.06 0.03 0 0 0 Vin-Si 0 0 0 0 0

[0761] [Table 25]

[0762] Resin F F1 F2 F3 F4 Mn 63,000 64,100 65,100 63,000 Mw 690,100 700,100 720,100 580,000 Mw / Mn 11.0 10.9 11.1 9.2 Mv 790,100 810,100 780,200 750,200 C3 0 0.03 0 0 C4 0 0 0.06 0 Vin-Si 0 0 0 0

[0763] (Preparation method of acrylic latex)

[0764] Acrylic latex, used as a binder for thermoplastic polymers or resins, is manufactured by the following method: 70.4 parts by weight of ion-exchanged water, 0.5 parts by weight of "Aquaron KH1025" (a registered trademark, a 25% aqueous solution manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), and 0.5 parts by weight of "ADEKA REASOAP SR1025" (a registered trademark, a 25% aqueous solution manufactured by ADEKA Co., Ltd.) as emulsifiers are added to a reaction vessel equipped with a stirrer, reflux condenser, dropping tank, and thermometer. Next, the temperature inside the reaction vessel is raised to 80°C, and while maintaining this temperature, 7.5 parts by weight of a 2% aqueous solution of ammonium persulfate is added to obtain an initial mixture. The addition of the ammonium persulfate aqueous solution is then stopped. After 5 minutes, the emulsion is added dropwise from the dropping tank to the reaction vessel over a period of 150 minutes. It should be noted that the above emulsion was prepared by mixing the following substances for 5 minutes using a homogenizer: 70 parts by weight of butyl acrylate; 29 parts by weight of methyl methacrylate; 1 part by weight of methacrylic acid; 3 parts by weight of "Aquaron KH1025" (registered trademark, 25% aqueous solution manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) and 3 parts by weight of "ADEKA REASOAP SR1025" (registered trademark, 25% aqueous solution manufactured by ADEKA Co., Ltd.) as emulsifiers; 7.5 parts by weight of 2% aqueous solution of ammonium persulfate; and 52 parts by weight of deionized water.

[0765] After the emulsion was added dropwise, the temperature inside the reaction vessel was maintained at 80°C for 90 minutes, and then cooled to room temperature. The resulting emulsion was adjusted to pH 8.0 with a 25% ammonium hydroxide aqueous solution, and a small amount of water was added to obtain an acrylic latex with a solid content of 40%. The number average particle size of the obtained acrylic latex was 145 nm, and the glass transition temperature was -23°C.

[0766] (Other resins)

[0767] Prepare commercially available PVDF latex and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). Additionally, prepare an aqueous mixture of PVDF and acrylic resins using the aforementioned acrylic latex and PVDF latex (mixing ratios are shown in the table below). Furthermore, form an acrylic resin through core-shell polymerization to prepare a PVDF / acrylic resin (core-shell polymerization) mixture.

[0768] <Confirmation that crosslinking is achieved by coating an inorganic porous layer on the separator substrate>

[0769] [Example 40-1: Fabrication and Evaluation of Separators and Crosslinking Confirmation in Coating Process]

[0770] (Fabrication of microporous membranes made of polyolefin as a separator substrate)

[0771] A mixture was obtained by dry mixing a mixed resin composition consisting of 30.0 wt% of resin D2 (with 2 CH2 silane grafted joints), 30.0 wt% of resin E3, and 40.0 wt% of resin F3, with 1000 ppm of pentaerythritol-tetra-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] added relative to the total amount as an antioxidant using a drum mixer. The resulting mixture was then fed into a twin-screw extruder under a nitrogen atmosphere. Separately, liquid paraffin (with a kinematic viscosity of 7.59 × 10⁻⁶ at 37.78°C) was also added. -5 m 2 / s) is injected into the extruder drum via a plunger pump.

[0772] The mixture and liquid paraffin were melt-blended in an extruder. The feeder and pump were adjusted so that the liquid paraffin accounted for 75% by mass of the extruded polyolefin composition (i.e., the polymer concentration was 25% by mass). The melt-blending conditions were set at a temperature of 230°C, a screw speed of 100 rpm, and a discharge rate of 80 kg / h. The melt-blended material was then extruded through a T-die onto a cooling roller with a surface temperature controlled at 25°C and cast to obtain a gel sheet (sheet-shaped molded body) with a preform thickness of 1250 μm.

[0773] Next, the sheet-shaped material is guided to a biaxial stretching machine for biaxial stretching to obtain a stretched product. The stretching conditions are set as follows: MD ratio 7.0, TD ratio 6.4 (i.e., 7 × 6.4), and biaxial stretching temperature 125°C. The stretched gel sheet is then guided to a dichloromethane bath for thorough impregnation in dichloromethane to extract and remove liquid paraffin. After drying to remove the dichloromethane, a porous body is obtained. Subsequently, the porous body is guided to a TD stretching machine for heat setting (HS) at a temperature of 133°C and a stretching ratio of 1.8. A relaxation operation is then performed until the sheet width at the TD stretching machine inlet is 1.6 times the TD ratio, thus obtaining a microporous membrane. Finally, the ends of the obtained microporous membrane are cut off and wound into a master roll 1100 mm wide and 5000 m long.

[0774] The obtained polyolefin microporous membrane was used as a separator substrate, and was measured and evaluated according to the above method. The evaluation results are shown in Table 26.

[0775] (Confirmation of coating and crosslinking of inorganic porous layers)

[0776] Subsequently, boehmite was selected as the inorganic particle, as shown in Table 26.

[0777] Next, inorganic particles and an aqueous solution of ammonium polycarboxylate (SN Dispersant 5468 manufactured by SAN NOPCO LIMITED, 40% solids concentration) as an ionic dispersant were uniformly dispersed in 100 parts by weight of water in a specified ratio to prepare a dispersion. The resulting dispersion was crushed using a bead mill (tank volume 200cc, zirconia bead diameter 0.1mm, filling amount 80%) to adjust the particle size distribution of the inorganic particles to D50 = 1.0μm. For the dispersion with adjusted particle size distribution, the aforementioned acrylic latex (40% solids concentration, average particle size 145nm, glass transition temperature -23°C, constituent monomers: butyl acrylate, methyl methacrylate, methacrylic acid) as a resin binder was added in the manner shown in Table 26 as the weight ratio of inorganic particles, thereby producing a slurry containing inorganic particles.

[0778] The pH of the slurry containing inorganic particles and the contact angle of the coating liquid relative to the clean surface of the separator substrate were also determined according to the above method.

[0779] Microporous membranes are continuously unwound from the aforementioned microporous membrane master roll. A slurry containing inorganic particles is coated on one side of the microporous membrane using a photogravure reverse coating machine. The membrane is then dried in a 60°C dryer to remove water, and wound up to obtain a master roll of multilayer separators with the coating thickness shown in Table 26. Furthermore, the crosslinking reaction during the coating process is confirmed by comparing the TMA fracture temperatures before and after coating.

[0780] During evaluation, the multi-layered separators released from the master roll are cut as needed and used as evaluation separators.

[0781] The evaluation partitions were evaluated using the methods described above, and the results are shown in Table 26.

[0782] (Including tests on batteries with multilayer separators coated with inorganic porous layers)

[0783] In Example 40-1, a separator substrate formed from a polyolefin microporous membrane and a multilayer separator coated with an inorganic porous layer were obtained. Furthermore, a non-aqueous secondary battery was fabricated using the multilayer separator according to the battery fabrication method described above, and the battery was evaluated. The battery evaluation results are shown in Table 26.

[0784] [Examples 40-2 to 40-53, Comparative Examples 11-1 to 11-7]

[0785] As shown in Table 26, the resin composition and molecular weight mixture of the polyolefin microporous membrane, manufacturing conditions, substrate characteristics, type and ratio of inorganic particles, and composition and properties of the coating liquid were modified. Otherwise, the same procedures as in Example 40-1 were performed to obtain a separator substrate formed from the polyolefin microporous membrane and a multilayer separator coated with an inorganic porous layer. The obtained separator substrate and multilayer separator were evaluated using the evaluation methods described above, and the evaluation results are also shown in Table 26. Furthermore, a non-aqueous secondary battery was obtained using the multilayer separator coated with an inorganic porous layer. The obtained battery was evaluated using the evaluation methods described above, and the evaluation results are also shown in Table 26.

[0786] [Table 26-1]

[0787]

[0788] [Table 26-2]

[0789]

[0790] [Table 26-3]

[0791]

[0792] [Table 26-4]

[0793]

[0794] [Table 26-5]

[0795]

[0796] [Table 26-6]

[0797]

[0798] [Table 26-7]

[0799]

[0800] <Confirmation of crosslinking achieved by coating the separator substrate with a thermoplastic polymer layer>

[0801] [Example 41-1]

[0802] As shown in Table 27, the manufacturing conditions of the polyolefin microporous membrane were changed, and the same operation as in Example 40-1 was performed to obtain a separator substrate formed from the polyolefin microporous membrane.

[0803] Subsequently, as shown in Table 27, the type of resin and the concentration of organic solvent were adjusted to obtain a coating liquid containing thermoplastic polymer. The pH of the coating liquid and the contact angle of the coating liquid relative to the clean surface of the separator substrate were also measured according to the above method.

[0804] Furthermore, similar to Example 40-1, a photogravure reverse coating machine was used to coat the separator substrate with a coating liquid to obtain a multilayer separator with coating film thicknesses as shown in Table 27. Additionally, the crosslinking reaction in the coating process was confirmed by comparing the TMA fracture temperatures before and after coating. Various evaluations were performed on the obtained multilayer separators according to the evaluation methods described above, and the evaluation results are also shown in Table 27.

[0805] Furthermore, using multi-layer separators, non-aqueous secondary batteries were manufactured according to the battery manufacturing method described above, and the batteries were evaluated. The battery evaluation results are also shown in Table 27.

[0806] [Examples 41-2 to 41-49, Comparative Examples 12-1 to 12-7]

[0807] As shown in Table 27, the resin composition and molecular weight mixture of the polyolefin microporous membrane, the manufacturing conditions, the substrate characteristics, the type of thermoplastic resin, and the composition and properties of the coating liquid were changed. Otherwise, the same procedures as in Example 41-1 were performed to obtain a separator substrate formed from a polyolefin microporous membrane and a multilayer separator coated with a thermoplastic polymer layer. The obtained separator substrate and multilayer separator were evaluated according to the evaluation methods described above, and the evaluation results are also shown in Table 27.

[0808] Furthermore, a non-aqueous secondary battery was obtained using a multilayer separator coated with a thermoplastic polymer layer. The obtained battery was evaluated using the aforementioned evaluation methods, and the results are shown in Table 27.

[0809] [Table 27-1]

[0810]

[0811] [Table 27-2]

[0812]

[0813] [Table 27-3]

[0814]

[0815] [Table 27-4]

[0816]

[0817] [Table 27-5]

[0818]

[0819] [Table 27-6]

[0820]

[0821] <Confirmation that crosslinking is achieved by coating an active layer onto the separator substrate>

[0822] [Example 42-1]

[0823] As shown in Table 28, the manufacturing conditions of the polyolefin microporous membrane were changed, and the same operation as in Example 40-1 was performed to obtain a separator substrate formed from the polyolefin microporous membrane.

[0824] Next, as shown in Table 28, commercially available PVDF-HFP was prepared as a fluorinated resin. Furthermore, a coating solution was prepared having 95 parts by weight of aluminum hydroxide (average particle size 1.4 μm) as inorganic particles, PVDF-HFP, and N-methyl-2-pyrrolidone (NMP) as an organic solvent, and having the organic solvent concentrations shown in Table 28.

[0825] Furthermore, similar to Example 40-1, a photogravure reverse coating machine was used to coat the separator substrate with a coating liquid, followed by washing and drying to obtain a multilayer separator with the coating film thickness shown in Table 28. Additionally, the crosslinking reaction during the coating process was confirmed by comparing the TMA fracture temperature before and after coating. Various evaluations were performed on the obtained multilayer separators according to the evaluation methods described above, and the evaluation results are also shown in Table 28.

[0826] Furthermore, a non-aqueous secondary battery was fabricated using a multi-layer separator according to the battery manufacturing method described above, and the battery was evaluated. The battery evaluation results are also shown in Table 28.

[0827] [Examples 42-2 to 42-43, Comparative Examples 13-1 to 13-7]

[0828] As shown in Table 28, the resin composition and molecular weight mixture of the polyolefin microporous membrane, the manufacturing conditions, the substrate characteristics, the type of fluorinated resin, and the composition and properties of the coating solution were changed. Otherwise, the same procedures as in Example 42-1 were performed to obtain a separator substrate formed from the polyolefin microporous membrane and a multilayer separator coated with an active layer. The obtained separator substrate and multilayer separator were evaluated according to the evaluation methods described above, and the evaluation results are also shown in Table 28.

[0829] Furthermore, a non-aqueous secondary battery was obtained using a multilayer separator coated with an active layer. The obtained battery was then evaluated using the methods described above, and the results are shown in Table 28.

[0830] [Table 28-1]

[0831]

[0832] [Table 28-2]

[0833]

[0834] [Table 28-3]

[0835]

[0836] [Table 28-4]

[0837]

[0838] [Table 28-5]

[0839]

[0840] [Table 28-6]

[0841]

[0842] <Confirmation that crosslinking is achieved by coating a heat-resistant resin layer onto the separator substrate>

[0843] [Example 43-1]

[0844] As shown in Table 29, the manufacturing conditions of the polyolefin microporous membrane were changed, and the same operation as in Example 40-1 was performed to obtain a separator substrate formed from the polyolefin microporous membrane.

[0845] Subsequently, inorganic fillers with specified inorganic particle sizes are prepared as shown in Table 29 and mixed in a coating solution containing para-aromatic amides or meta-aromatic amides in a manner that achieves a specified inorganic particle weight ratio and organic solvent concentration.

[0846] (In the case of para-aromatic amides)

[0847] 150 parts by mass of p-phenylenediamine were added to 5000 parts by mass of an N-methyl-2-pyrrolidone (NMP) / calcium chloride solution (calcium chloride concentration = 7.1% by mass). The solution was dissolved and stirred under a N2 atmosphere. Then, 273.94 parts by mass of terephthalic acid dichloride were added and stirred, allowing the reaction to proceed for 1 hour to obtain a poly(p-phenylene terephthalamide) polymer solution. 1000 parts by mass of the polymer solution, 3000 parts by mass of NMP, and a specified amount of alumina (Al2O3) particles (with particle sizes shown in Table 29) were stirred and mixed, and dispersed using a homogenizer to obtain a coating solution. Using a drum-mounted rod coater, the coating solution was coated onto one side of a polyolefin microporous membrane under conditions of a clearance of 20 μm to 30 μm and a coating film thickness shown in Table 29. The membrane was dried at approximately 70°C to obtain a multilayer separator.

[0848] (The case of meta-aromatic amides)

[0849] 100 parts by mass of meta-aromatic polyamide and a specified amount of boehmite (with particle sizes shown in Table 29) were mixed. This mixture was then combined with a mixed solvent of dimethylacetamide (DMAc) and tripropylene glycol (TPG) (mass ratio = 1:1) at a meta-aromatic polyamide concentration of 3% by mass to obtain a coating solution. The coating solution was applied to one side of a polyolefin microporous membrane using a wire rod coater at a gap of 20 μm to 30 μm and a coating film thickness shown in Table 29 to obtain a coated separator. The coated separator was immersed in a coagulation solution at a mass ratio of water:DMAc:TPG = 2:1:1 and a temperature of 35°C, followed by washing and drying to obtain a multilayer separator.

[0850] For multilayer separators coated with a heat-resistant resin layer containing para- or meta-aromatic amides and inorganic fillers, the crosslinking reaction during the coating process was confirmed by comparing the TMA fracture temperatures before and after coating. Various evaluations were performed on the obtained multilayer separators according to the above evaluation methods, and the evaluation results are shown in Table 29.

[0851] (Including testing of batteries with multilayer separators coated with heat-resistant resin layers)

[0852] In Example 43-1, a non-aqueous secondary battery was further fabricated using a multi-layer separator according to the battery fabrication method described above, and the battery was evaluated. The battery evaluation results are also shown in Table 29.

[0853] [Examples 43-2 to 43-50, Comparative Examples 14-1 to 14-7]

[0854] As shown in Table 29, the resin composition and molecular weight mixture of the polyolefin microporous membrane, the manufacturing conditions, the substrate characteristics, the type, particle size and ratio of the inorganic filler, the type of aromatic amide resin, and the composition and properties of the coating liquid were changed. Otherwise, the same procedures as in Example 43-1 were performed to obtain a separator substrate formed from the polyolefin microporous membrane and a multilayer separator coated with a heat-resistant resin layer. The obtained separator substrate and multilayer separator were evaluated according to the evaluation methods described above, and the evaluation results are also shown in Table 29.

[0855] Furthermore, a non-aqueous secondary battery was obtained using a multilayer separator coated with a heat-resistant resin layer. The obtained battery was evaluated using the aforementioned evaluation methods, and the results are shown in Table 29.

[0856] [Table 29-1]

[0857]

[0858] [Table 29-2]

[0859]

[0860] [Table 29-3]

[0861]

[0862] [Table 29-4]

[0863]

[0864] [Table 29-5]

[0865]

[0866] [Table 29-6]

[0867]

[0868] Explanation of reference numerals in the attached figures

[0869] t c Thickness of crystallization

[0870] t a Amorphous portion thickness

[0871] f c Long crystallization cycle

[0872] a c Crystal Orientation

Claims

1. A separator for a non-aqueous secondary battery, comprising silicon-containing Si molecules, The Voronoi polygons obtained by Voronoi segmentation of the Si-containing image detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) for the separator of the non-aqueous secondary battery have a Voronoi area (mu) with the highest frequency of occurrence at 6.0 μm. 2 ~13.0μm 2 Within the range, and The breadth σ of the Voronoi area frequency distribution in the Si-containing image detected by TOF-SIMS measurement is 2.0 μm. 2 ~3.8μm 2 Within the range, in, The separator for the non-aqueous secondary battery comprises silane-modified polyethylene and at least one polyolefin other than silane-modified polyethylene. The polyolefin other than silane-modified polyethylene includes ultra-high molecular weight polyethylene with a viscosity-average molecular weight (Mv) of 1,800,000 or higher, or polyethylene with a viscosity-average molecular weight (Mv) of less than 1,800,000. The silane-modified polyethylene contains 0.03 to 1.0 mol% silanol units, and the butene C4 unit modification rate of the silane-modified polyethylene is 0.01 to 1.0 mol%. The silane-modified polyethylene has a number-average molecular weight (Mn) of 10,000–20,000, a weight-average molecular weight (Mw) of 45,000–200,000, an Mw / Mn ratio of 3.0–12, and a viscosity-average molecular weight (Mv) of 20,000–150,000. In the silane-modified polyethylene, the number of methylene CH2 groups constituting the linker with the main chain is 2 to 6.

2. The separator for non-aqueous secondary batteries according to claim 1, wherein, The highest frequency Voronoi area (mu) is 6.2 μm. 2 ~11.8μm 2 Within the range.

3. The separator for non-aqueous secondary batteries according to claim 1, wherein, The ratio of the breadth σ of the frequency distribution of the Voronoi area to the area mu of the Voronoi with the highest frequency, σ / mu, is 0.06 to 0.

70.

4. The separator for non-aqueous secondary batteries according to claim 3, wherein, The ratio σ / mu is 0.07~0.

57.

5. The separator for non-aqueous secondary batteries according to claim 3, wherein, The ratio σ / mu is 0.19~0.

38.

6. A separator for a non-aqueous secondary battery, comprising silicon-containing Si molecules, The Voronoi polygons obtained by segmenting the Si-containing images detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) of the separator used in the non-aqueous secondary battery have a Voronoi area (mu) with the highest frequency of occurrence at 6.2 μm. 2 ~11.8μm 2 Within the range, the breadth σ of the Voronoi area frequency distribution of Si-containing images detected by the TOF-SIMS measurement is within 2.3 μm. 2 ~3.6μm 2 Within the range, in, The separator for the non-aqueous secondary battery comprises silane-modified polyethylene and at least one polyolefin other than silane-modified polyethylene. The polyolefin other than silane-modified polyethylene includes ultra-high molecular weight polyethylene with a viscosity-average molecular weight (Mv) of 1,800,000 or more, a number-average molecular weight (Mn) of 200,000 to 1,400,000, a weight-average molecular weight (Mw) of 1,500,000 to 8,800,000, and an Mw / Mn ratio of 3.0 to 12; or polyethylene with a viscosity-average molecular weight (Mv) less than 1,800,000, a number-average molecular weight (Mn) of 20,000 to 250,000, a weight-average molecular weight (Mw) of 230,000 to 1,500,000, and an Mw / Mn ratio of 3.0 to 12. The silane-modified polyethylene contains 0.03 to 1.0 mol% silanol units, and the butene C4 unit modification rate of the silane-modified polyethylene is 0.01 to 1.0 mol%. The silane-modified polyethylene has a number-average molecular weight (Mn) of 10,000–20,000, a weight-average molecular weight (Mw) of 45,000–200,000, an Mw / Mn ratio of 3.0–12, and a viscosity-average molecular weight (Mv) of 20,000–150,000. In the silane-modified polyethylene, the number of methylene CH2 groups constituting the linker with the main chain is 2 to 6.

7. The separator for non-aqueous secondary batteries according to claim 6, wherein, The highest frequency Voronoi area (μm) is 6.5 μm. 2 ~11.5μm 2 Within the range.

8. The separator for non-aqueous secondary batteries according to claim 6, wherein, The highest frequency Voronoi area (μm) is 7.0 μm. 2 ~11.0μm 2 Within the range.

9. The separator for non-aqueous secondary batteries according to claim 6, wherein, The highest frequency Voronoi area (μm) is 7.5 μm. 2 ~10.5μm 2 Within the range.

10. The separator for non-aqueous secondary batteries according to claim 6, wherein, The breadth σ of the Voronoi area frequency distribution is 2.5 μm. 2 ~3.5μm 2 Within the range.

11. The separator for a non-aqueous secondary battery according to any one of claims 6 to 10, wherein, The ratio of the breadth σ of the frequency distribution of the Voronoi area to the area mu of the Voronoi with the highest frequency, σ / mu, is 0.20 to 0.

40.

12. The separator for a non-aqueous secondary battery according to claim 11, wherein, The ratio σ / mu is 0.22~0.

38.

13. The separator for a non-aqueous secondary battery according to claim 11, wherein, The ratio σ / mu is 0.25~0.

35.

14. The separator for a non-aqueous secondary battery according to any one of claims 1-10, 12-13, wherein, In the separator for the non-aqueous secondary battery, the Si-containing molecules are dispersed in a non-island structure.

15. The separator for a non-aqueous secondary battery according to any one of claims 1-10, 12-13, wherein, The separator for the non-aqueous secondary battery is a microporous membrane made of polyethylene, and The change ratio of air permeability when the thickness is compressed by 30%, that is, the air permeability Sh after compression / the air permeability Sj before compression, is 1.1 to 7.0 times.

16. The separator for a non-aqueous secondary battery according to claim 15, wherein, The air permeability change ratio, i.e., the air permeability Sh after compression / the air permeability Sj before compression, is 1.3 to 6.9 times.

17. A non-aqueous secondary battery comprising a positive electrode, a negative electrode, a separator for a non-aqueous secondary battery as described in any one of claims 1 to 16, and a non-aqueous electrolyte.

18. The non-aqueous secondary battery according to claim 17, wherein, The negative electrode contains a negative electrode active material, and the Si content in the negative electrode active material is 5% to 90% by weight.

19. The non-aqueous secondary battery according to claim 17 or 18, wherein, The non-aqueous electrolyte contains lithium salts at a concentration ranging from 1.2 mol / L to 10 mol / L.

20. The non-aqueous secondary battery according to claim 19, wherein, The non-aqueous electrolyte contains lithium salts at a concentration ranging from 1.5 mol / L to 10 mol / L.

21. The non-aqueous secondary battery according to claim 19, wherein, The non-aqueous electrolyte contains lithium salts at a concentration ranging from 3.0 mol / L to 10 mol / L.

22. The non-aqueous secondary battery according to claim 19, wherein, The lithium salt is a fluorinated lithium salt that can produce hydrogen fluoride.

23. The non-aqueous secondary battery according to claim 17 or 18, wherein, The non-aqueous electrolyte contains ethyl methyl carbonate (EMC) and / or acetonitrile (AcN), and the total content of EMC and AcN in the non-aqueous electrolyte is in the range of 50% to 90% by mass.

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