Separator for non-aqueous electrolyte secondary battery, member for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery

Abstract

To provide a non-aqueous electrolyte secondary battery separator having excellent impact resistance.SOLUTION: A non-aqueous electrolyte secondary battery separator includes a polyolefin porous film, and a peak area ratio R of a (200) plane calculated from a diffraction intensity profile obtained by wide-angle X-ray diffraction performed by irradiating a surface with X-rays from the vertical direction=the peak area of the diffraction peak of the (200) plane: the peak area of the diffraction peak on the I(200) / (110) plane: I(110) is 0.15 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a separator for a non-aqueous electrolyte secondary battery, a member for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery.

Background Art

[0002] Non-aqueous electrolyte secondary batteries such as lithium secondary batteries are currently widely used as batteries for devices such as personal computers, mobile phones, and portable information terminals, or as in-vehicle batteries.

[0003] Examples of the separator in such a non-aqueous electrolyte secondary battery include a separator made of a porous film mainly composed of polyolefin described in Patent Document 1, and a laminate including the porous film and a heat-resistant resin layer laminated on at least one side of the porous film.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, there is room for improvement in the impact resistance of the conventional separators described above.

[0006] Therefore, an aspect of the present invention aims to provide a separator for a non-aqueous electrolyte secondary battery having excellent impact resistance. More specifically, the object is to provide a separator for a non-aqueous electrolyte secondary battery that can prevent ignition of the non-aqueous electrolyte secondary battery caused by external impact and improve the safety of the non-aqueous electrolyte secondary battery due to excellent impact resistance.

Means for Solving the Problems

[0007] As a result of intensive research, the present inventors have found that a separator for a non-aqueous electrolyte secondary battery containing polyolefin crystals with the orientation suppressed within a specific range is excellent in impact resistance, and have arrived at the present invention.

[0008] One aspect of the present invention includes the inventions shown in the following [1] to [7].

[0009] [1] A separator for a non-aqueous electrolyte secondary battery including a polyolefin porous film, A separator for a non-aqueous electrolyte secondary battery, wherein the peak area ratio R of the (200) plane calculated by the following formula (1) is 0.15 or more from the diffraction intensity profile obtained by measurement of wide-angle X-ray diffraction (WAXD).

[0010] Peak area ratio R of (200) plane = I(200) / I(110) ··· (1) (Here, the WAXD is performed by irradiating X-rays from the vertical direction to the surface of the separator for the non-aqueous electrolyte secondary battery, I(110) is the peak area of the diffraction peak of the (110) plane in the diffraction intensity profile, and I(200) is the peak area of the diffraction peak of the (200) plane in the diffraction intensity profile.) [2] Further including a porous layer containing a resin, The separator for a non-aqueous electrolyte secondary battery according to [1], wherein the porous layer is laminated on one or both sides of the polyolefin porous film.

[0011] [3] The separator for a non-aqueous electrolyte secondary battery according to [2], wherein the resin is selected from one or more of the group consisting of polyolefin, (meth)acrylate resin, fluorine-containing resin, polyamide resin, polyester resin, and water-soluble polymer.

[0012] [4] The separator for a non-aqueous electrolyte secondary battery according to [2] or [3], wherein the resin is an aramid resin.

[0013] [5] The separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [4], wherein the piercing strength of the polyolefin porous film is 5.0 N or more.

[0014] [6] A member for a non-aqueous electrolyte secondary battery, in which a positive electrode, a separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [5], and a negative electrode are arranged in this order.

[0015] [7] A non-aqueous electrolyte secondary battery including the separator for a non-aqueous electrolyte secondary battery according to any one of [1] to [5]

Advantages of the Invention

[0016] The separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention has excellent impact resistance, can prevent ignition of the non-aqueous electrolyte secondary battery caused by external impact, and has the effect of improving the safety of the non-aqueous electrolyte secondary battery.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0018] The following describes one embodiment of the present invention, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Unless otherwise specified in this specification, "A~B" representing a numerical range means "A or more and B or less".

[0019] In this specification, the MD direction (Machine Direction) means the direction in which the sheet-like polyolefin resin composition, the primary sheet, the secondary sheet, and the porous film are conveyed in the method for producing the porous film described later. The TD direction (Transverse Direction) means a direction parallel to the surface of the sheet-like polyolefin resin composition, the primary sheet, the secondary sheet, and the porous film and perpendicular to the MD direction.

[0020] [Embodiment 1: Separator for Non-aqueous Electrolyte Secondary Battery] 1. Separator for Non-aqueous Electrolyte Secondary Battery A separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention is a separator for a non-aqueous electrolyte secondary battery including a polyolefin porous film, and from the diffraction intensity profile obtained by measurement of wide-angle X-ray diffraction (WAXD), the peak area ratio R of the (200) plane calculated by the following formula (1) is 0.15 or more.

[0021] Peak area ratio R of (200) plane = I(200) / I(110) ··· (1) (Here, the WAXD is performed by irradiating X-rays from the vertical direction to the surface of the separator for the non-aqueous electrolyte secondary battery, I(110) is the peak area of the diffraction peak of the (110) plane in the diffraction intensity profile, and I(200) is the diffraction peak of the (200) plane in the diffraction intensity profile. Peak area.) The separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention includes a polyolefin porous film. Hereinafter, the polyolefin porous film is also simply referred to as a "porous film".

[0022] The separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention can be a separator for a non-aqueous electrolyte secondary battery made of the porous film. Further, the separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention can be a separator for a non-aqueous electrolyte secondary battery that is a laminate including the porous film and a porous layer described later.

[0023] Note that the separator for a non-aqueous electrolyte secondary battery that is the laminate described later is also hereinafter referred to as a "laminated separator for a non-aqueous electrolyte secondary battery".

[0024] Furthermore, the separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention may, if necessary, include known porous layers such as a heat-resistant layer, an adhesive layer, and a protective layer described later as another porous layer in addition to the porous film and the porous layer.

[0025] The porous film contains a polyolefin resin and is generally a porous film mainly composed of a polyolefin resin. Further, "mainly composed of a polyolefin resin" means that the proportion of the polyolefin resin in the porous film is 50% by volume or more, preferably 90% by volume or more, and more preferably 95% by volume or more of the entire material constituting the porous film.

[0026] The porous film has a large number of pores connected inside thereof, and it is possible to allow gas or liquid to pass from one surface to the other surface.

[0027] The peak area ratio R of the (200) surface of the separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention is 0.15 or more.

[0028] The peak area ratio R of the (200) plane is a parameter representing the orientation of the crystals of the polyolefin, which is the main component of the polyolefin porous film. A large value of the peak area ratio R of the (200) plane means that the orientation of the crystals of the polyolefin decreases, and the manifestation of the anisotropy of the crystals of the polyolefin is suppressed.

[0029] For the separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention, since the peak area ratio R of the (200) plane is 0.15 or more, the orientation is low. Here, when the orientation is low, the crystal structure of the polyolefin has high flexibility with respect to changes due to external forces or the like. Therefore, when an external impact is applied, the polyolefin porous film in an embodiment of the present invention easily retains the crystal structure of the polyolefin and is difficult to break. Therefore, the separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention is excellent in impact resistance.

[0030] For the separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention, the larger the peak area ratio R of the (200) plane is, the more preferable it is because of excellent impact resistance. Specifically, the peak area ratio R of the (200) plane is preferably 0.15 or more, and more preferably 0.16 or more. Also, the upper limit value of the peak area ratio R of the (200) plane is not particularly limited, but for example, it is 0.20 or less.

[0031] The peak area ratio R of the (200) plane can be obtained based on the diffraction intensity profile obtained by measurement of wide-angle X-ray diffraction (WAXD). The R is measured, for example, by the methods shown in the following (1) to (5).

[0032] (1) Irradiate the surface of the separator for a non-aqueous electrolyte secondary battery with X-rays from the vertical direction to perform wide-angle X-ray diffraction (WAXD) measurement and obtain a WAXD pattern. "Irradiating the surface with X-rays from the vertical direction" means irradiating the X-rays so that the angle formed by the X-rays irradiated from an X-ray irradiation device (for example, NANO-Viewer manufactured by Rigaku Corporation, described later) and the surface (the irradiation angle of the X-rays to the surface) is 90 degrees.

[0033] (2) From the WAXD pattern, with respect to the peak of the (110) plane of the polyolefin, taking the horizontal direction as the azimuth angle β = 0 degrees, calculate the azimuth angle profile.

[0034] (3) Centering on the peak that appears most strongly in the vicinity of β = 0 degrees of the azimuth angle profile, calculate the profile of the diffraction intensity with respect to the diffraction angle 2θ in the range where the azimuth angle is ±5 degrees.

[0035] (4) From the profile of the diffraction intensity, calculate the area I(110) of the peak of the (110) plane of the polyolefin and the area I(200) of the peak of the (200) plane in the polyolefin porous film that is the main component of the separator for a non-aqueous electrolyte secondary battery.

[0036] (5) Using the calculated I(110) and I(200), calculate the peak area ratio R of the (200) plane based on the following formula (1).

[0037] (200) plane peak area ratio R = I(200) / I(110) ··· (1) The positions of the peak of the (110) plane and the peak of the (200) plane vary depending on the type of the polyolefin and the like. For example, when the polyolefin is polyethylene, the peak of the (110) plane is detected at around the diffraction angle 2θ of 21 degrees, and the peak of the (200) plane is detected at around the diffraction angle 2θ of 24.5°.

[0038] Here, in the diffraction intensity profile, peaks derived from the polyolefin, which is the main component of the polyolefin porous film, are observed. On the other hand, for example, peaks derived from the porous layer or the like, which is a member other than the polyolefin porous film, are not observed. That is, the porous layer or the like does not affect the measurement of the peak area ratio R of the (200) plane.

[0039] Therefore, even when the separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention is a laminated separator for a non-aqueous electrolyte secondary battery, the peak area ratio R of the (200) plane becomes a parameter representing the characteristics of the polyolefin porous film.

[0040] Therefore, when the separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention is made of a porous film and when it is a laminated separator for a non-aqueous electrolyte secondary battery, the peak area ratio R of the (200) plane can be measured by the method described above.

[0041] The MD breaking elongation of the porous film is preferably 20% GL (Gauge Length) or more, and more preferably 30% GL or more. The upper limit of the MD breaking elongation is not particularly limited, but it can usually be 300% GL or less. The MD breaking elongation is measured by a method conforming to the JIS K7127 standard.

[0042] Here, the MD breaking elongation is represented by the ratio (%) of the length by which the porous film has elongated in the MD direction when the porous film has broken to the length of the porous film in the MD direction before the operation when a predetermined operation is performed. Note that the predetermined operation is an operation of stretching the porous film in the MD direction.

[0043] The TD breaking elongation of the porous film is preferably 50% GL or more, and more preferably 60% GL or more. The upper limit of the TD breaking elongation is not particularly limited, but it can usually be 300% GL or less. The TD breaking elongation is measured by a method conforming to the JIS K7127 standard.

[0044] The TD breaking elongation of the porous film can be expressed in the same manner as the MD breaking elongation. That is, when an operation of stretching the porous film in the TD direction is performed, it is represented by the ratio (%) of the length by which the porous film has elongated in the TD direction when the porous film breaks to the length of the porous film in the TD direction before the operation is performed.

[0045] On the other hand, in the single-sheet type, that is, in the porous film processed to a predetermined size, it may be difficult to distinguish between the TD direction and the MD direction. In that case, if the single-sheet type porous film is rectangular, the breaking elongation when it is stretched in a direction parallel to a specific side of the rectangle and the breaking elongation when it is stretched in a direction perpendicular to the specific side of the rectangle are measured. Since the porous film usually has a lower strength when stretched in the MD direction, among the two breaking elongations, the smaller value is taken as the "value of the MD breaking elongation", and the larger value is taken as the "value of the TD breaking elongation".

[0046] Also, when the TD direction and the MD direction of the porous film cannot be distinguished and the shape of the porous film is not rectangular, the porous film is stretched in any plurality of directions, and the breaking elongation in each direction when stretched is measured. Then, among the measured breaking elongations, the smallest value is taken as the "value of the MD breaking elongation". Then, the direction perpendicular to the elongation direction in which the "value of the MD breaking elongation" is measured is taken as the "TD direction", and the value of the breaking elongation in that direction is taken as the "value of the TD breaking elongation". Note that in this specification, the shape of the porous film is intended to be the shape of the plane perpendicular to the thickness direction.

[0047] The film thickness of the porous film is 4 to 40 μm, preferably 5 to 20 μm. If the film thickness of the porous film is 4 μm or more, internal short circuit of the battery can be sufficiently prevented. On the other hand, if the film thickness of the porous film is 40 μm or less, enlargement of the non-aqueous electrolyte secondary battery can be prevented.

[0048] When the film thickness of the porous film is excessively thick, for example, when the film thickness exceeds 40 μm, a certain degree of impact resistance can be obtained due to the film thickness. However, with this configuration, it is not possible to meet the recent demand for thinning of the separator for non-aqueous electrolyte secondary batteries.

[0049] On the other hand, the separator for non-aqueous electrolyte secondary batteries according to an embodiment of the present invention has a configuration in which, even when the film thickness is, for example, 4 to 40 μm, the peak area ratio R of the (200) plane is 0.15 or more, so that sufficient impact resistance can be exhibited.

[0050] The polyolefin resin preferably contains a high molecular weight component having a weight average molecular weight of 5×10 5 ~15×10 6 In particular, when the polyolefin resin contains a high molecular weight component having a weight average molecular weight of 1 million or more, the strength of the obtained porous film and the separator for non-aqueous electrolyte secondary batteries containing the porous film is improved, which is more preferable.

[0051] Further, in order to control the peak area ratio R of the (200) plane to 0.15 or more, the main component of the polyolefin resin is preferably a polyolefin having a weight average molecular weight of 500,000 or more. Here, the "main component" means a component that occupies 50% by weight or more based on the total weight of the polyolefin resin.

[0052] The polyolefin resin is not particularly limited, and examples thereof include homopolymers or copolymers obtained by polymerizing one or more monomers selected from monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene.

[0053] Examples of the homopolymer include polyethylene, polypropylene, and polybutene. Examples of the copolymer include an ethylene-propylene copolymer.

[0054] Among these, polyethylene is more preferable because it can prevent an excessive current from flowing through the separator for a non-aqueous electrolyte secondary battery at a lower temperature. Examples of the polyethylene include low-density polyethylene, high-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), and ultra-high molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more. Among these, ultra-high molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is even more preferable.

[0055] The polyolefin resin may contain a polyolefin having a long-chain branching degree of preferably 20 or less, more preferably 10 or less per molecule. Here, the long-chain branching degree is, for example, a value calculated from a conformation plot using GPC-MALS. Here, the conformation plot means a logarithmic plot of the molecular radius and the molecular weight.

[0056] The weight per unit area of the porous film, that is, the weight per unit area, is usually 4 to 20 g / m 2 so as to increase the weight energy density and the volume energy density of the battery, preferably 2 5 to 12 g / m, and more preferably

[0057] From the viewpoint of exhibiting sufficient ion permeability, the air permeability of the porous film is preferably 110 to 200 sec / 100 mL in Gurley value, and more preferably 110 to 190 sec / 100 mL.

[0058] The piercing strength of the porous film is preferably 5.0 N or more, more preferably 5.3 N or more, and even more preferably 5.5 N or more. The fact that the piercing strength is 5.0 N or more means that the strength of the separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention is sufficiently high. Therefore, it is preferable because more excellent impact resistance can be achieved. The piercing strength can be measured by the following method.

[0059] (i) After fixing the porous film to the upper surface of the base with a 12 mm Φ washer, a pin (pin diameter 1 mm Φ, tip 0.5R) is pierced into the porous film under the conditions of piercing speed: 10 mm / sec and piercing depth: 10 mm. Here, the base only needs to have a flat upper surface, and its shape, material, etc. are not limited.

[0060] (ii) Measure the maximum stress (gf) when the pin is pierced into the porous film in (i), and use the measured value as the piercing strength of the film.

[0061] The porosity of the porous film is preferably 20% to 80% by volume, more preferably 30% to 75% by volume, so as to increase the retention amount of the electrolyte and obtain a function of reliably preventing (shutting down) the flow of excessive current at a lower temperature.

[0062] The pore diameter of the pores in the porous film is preferably 0.3 μm or less, more preferably 0.14 μm or less, from the viewpoints of sufficient ion permeability and preventing the intrusion of particles constituting the electrode.

[0063] 2. Method for producing a polyolefin porous film The method for producing a polyolefin porous film in an embodiment of the present invention is not particularly limited, but specifically, for example, a method including the following steps (A) to (D) can be mentioned.

[0064] (A) A polyolefin resin and, optionally, a pore former such as A step of adding an additive to a kneader and melt-kneading to obtain a polyolefin resin composition. (B) A step of extruding the obtained polyolefin resin composition from a T-die of an extruder, stretching it in a first direction while cooling, and forming it into a sheet shape to obtain a primary sheet. (C) A step of stretching the primary sheet in a second direction different from the first direction to obtain a secondary sheet. Step of stretching the secondary sheet in a second direction different from the first direction while shrinking it in the first direction.

[0065] In step (A), the amount of the polyolefin resin used is preferably 6% by weight to 45% by weight, more preferably 9% by weight to 36% by weight, when the weight of the resulting polyolefin resin composition is 100% by weight. Also, the weight average molecular weight of the main component of the polyolefin is preferably 500,000 or more.

[0066] The first direction is preferably the MD direction. Also, the second direction is preferably the TD direction.

[0067] The pore former is not particularly limited, and examples thereof include inorganic fillers and plasticizers. The inorganic filler is not particularly limited, and examples of inorganic fillers include calcium carbonate and the like. The plasticizer is not particularly limited, and examples thereof include low molecular weight hydrocarbons such as liquid paraffin.

[0068] As the additive, in addition to the pore former, known additives can be optionally used within a range that does not impair the effects of the present invention. Examples of the known additives include antioxidants and the like.

[0069] In step (B), the method for obtaining the primary sheet is not particularly limited, and the primary sheet can be produced by a sheet forming method such as inflation processing, calendar processing, T-die extrusion processing, or the skive method.

[0070] For example, the sheet forming temperature in the sheet forming method, such as the T-die extrusion temperature in T-die extrusion processing, is preferably 200°C or higher and 280°C or lower, more preferably 220°C or higher and 260°C or lower.

[0071] As a method for obtaining a primary sheet with higher film thickness accuracy, for example, there is a method of roll forming a polyolefin resin composition using a pair of rotational molding tools adjusted to a surface temperature higher than the melting point of the polyolefin resin contained in the polyolefin resin composition. At this time, the surface temperature of the rotational molding tool is preferably (the melting point of the polyolefin resin + 5) °C or higher. Also, the upper limit of the surface temperature is preferably (the melting point of the polyolefin resin + 30) °C or lower, and more preferably (the melting point of the polyolefin resin + 20) °C or lower.

[0072] Examples of the pair of rotational molding tools include rolls or belts. The peripheral speeds of both rotational molding tools do not necessarily have to be exactly the same, and a difference of within about ±5% is acceptable. Also, a laminate of single-layer sheets obtained by the above sheet forming method may be used as the primary sheet.

[0073] When roll forming the polyolefin resin composition using a pair of rotational molding tools, the polyolefin resin composition extruded in a strand form from an extruder may be directly introduced between the pair of rotational molding tools, or a polyolefin resin composition that has been pelletized once may also be used.

[0074] The draw ratio in step (B) is preferably 1.1 times or more and 1.9 times or less, and more preferably 1.2 times or more and 1.8 times or less. Also, the drawing temperature in step (B) is preferably 120 °C or higher and 160 °C or lower, and more preferably 130 °C or higher and 155 °C or lower.

[0075] For cooling the polyolefin resin composition in step (B), methods such as contacting with a refrigerant such as cold air or cooling water, or contacting with a cooling roll can be used. Preferably, the method of contacting with a cooling roll is used.

[0076] In step (B), the first direction is preferably the MD direction. The fact that the first direction is the MD direction is preferable because, through the relaxation operation described later, the strength against elongation in the MD direction of the porous film can usually be improved to the lowest level, and the strength against elongation of the entire porous film can be efficiently improved.

[0077] When the pore-forming agent is included in the polyolefin resin composition and the primary sheet, a step of washing the stretched sheet with a cleaning liquid to remove the pore-forming agent is included during step (B) and step (C) or after step (C).

[0078] The cleaning liquid is not particularly limited as long as it is a solvent capable of removing the pore-forming agent, and examples thereof include an aqueous hydrochloric acid solution, heptane, dichloromethane, and the like.

[0079] In step (C), the stretching temperature when stretching in the second direction is preferably 80°C or higher and 140°C or lower, more preferably 90°C or higher and 130°C or lower. Also, the stretching ratio when stretching in the second direction is preferably 2 times or more and 12 times or less, more preferably 3 times or more and 10 times or less.

[0080] In step (D), when stretching the secondary sheet in the second direction, the impact resistance of the obtained porous film can be improved by performing an operation of shrinking the secondary sheet in the first direction.

[0081] In step (D), the step of starting the stretching of the secondary sheet in the second direction and the step of shrinking the secondary sheet in the first direction may be carried out simultaneously, or either one may be carried out first and then the other. However, it is preferable to carry out these steps simultaneously or to carry out the step of starting the stretching of the secondary sheet in the second direction first. In this case, by stretching the secondary sheet in the second direction, a shrinking force in the first direction acts on the secondary sheet, so that the secondary sheet can be shrunk without wrinkles.

[0082] In step (D), when shrinking the secondary sheet in the first direction, the stretching temperature is preferably 80°C or higher and 140°C or lower, more preferably 90°C or higher and 130°C or lower. Further, when stretching the secondary sheet in the second direction, the stretching ratio is preferably 1.2 times or more and 2 times or less, more preferably 1.3 times or more and 1.5 times or less. When shrinking the secondary sheet in the first direction, the shrinkage rate is preferably 10% or more and 50% or less, more preferably 20% or more and 40% or less.

[0083] Here, in step (D), by shrinking the secondary sheet in the first direction, the tensile elongation in the first direction of the obtained porous film is improved, and the expression of anisotropy of polyolefin crystals in the porous film can be suppressed.

[0084] Also, in step (D), an embodiment (hereinafter referred to as "embodiment A") in which the stretching ratio of stretching the secondary sheet in the second direction is made as small as possible compared to the stretching ratio of stretching the primary sheet in the second direction in step (C) is preferable. For example, it is preferable to control the stretching ratio in step (D) to a size such that wrinkles do not occur in the obtained porous film. Thereby, the orientation of polyolefin crystals in the porous film can be controlled such that the peak area ratio R of the (200) plane is 0.15 or more.

[0085] Actually, in Examples 1 to 4 described later that satisfy the above embodiment A, the R of the separator for non-aqueous electrolyte secondary batteries is a high value of 0.15 or more, and it has been obtained that the separator for non-aqueous electrolyte secondary batteries is difficult to break through in a simple impact test.

[0086] In addition, when only step (D) is performed without performing step (C), the tensile elongation in the first direction of the obtained porous film is improved, but the anisotropy of polyolefin crystals in the obtained porous film is expressed, and the orientation of the polyolefin crystals is improved.

[0087] For example, in Comparative Example 2 described later, the peak area ratio R of the (200) plane of the separator for a non-aqueous electrolyte secondary battery including a porous film obtained by performing only step (D) without performing step (C) is a low value of less than 0.15. Further, it has been obtained that the separator for a non-aqueous electrolyte secondary battery is liable to break through in a simple impact test.

[0088] 3. Porous layer The separator for a non-aqueous electrolyte secondary battery according to an embodiment of the present invention may be a laminated separator for a non-aqueous electrolyte secondary battery including the polyolefin porous film and a porous layer laminated on one or both surfaces of the polyolefin porous film.

[0089] The porous layer is a resin layer containing a resin, and preferably a heat-resistant layer or an adhesive layer. The resin constituting the porous layer is preferably insoluble in the electrolyte of the battery and electrochemically stable within the operating range of the battery.

[0090] When the porous layer is laminated on the one surface, the porous layer is preferably laminated on the surface of the polyolefin porous film facing the positive electrode when the non-aqueous electrolyte secondary battery is formed, and more preferably laminated on the surface in contact with the positive electrode.

[0091] Examples of the resin include polyolefin; (meth)acrylate resin; fluorine-containing resin; polyamide resin; polyimide resin; polyester resin; rubbers; resins having a melting point or a glass transition temperature of 180°C or higher; water-soluble polymers; polycarbonate, polyacetal, polyetheretherketone, and the like.

[0092] Among the above-mentioned resins, polyolefin, (meth)acrylate resin, fluorine-containing resin, polyamide resin, polyester resin, and water-soluble polymer are preferred.

[0093] Preferred polyolefins include polyethylene, polypropylene, polybutene, ethylene-propylene copolymers, and the like.

[0094] Preferred fluorine-containing resins include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trichloroethylene copolymer, vinylidene fluoride-vinyl fluoride copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, and the like. Among the above-mentioned fluorine-containing resins, fluorine-containing rubbers with a glass transition temperature of 23°C or lower can also be mentioned.

[0095] Preferred polyamide-based resins include aramid resins such as aromatic polyamide and wholly aromatic polyamide.

[0096] Examples of aramid resins include, specifically, poly(p-phenyleneterephthalamide), poly(m-phenyleneisophthalamide), poly(p-benzamide), poly(m-benzamide), poly(4,4'-benzani lideterephthalamide), poly(p-phenylene-4,4'-biphenylenedicarboxamide), poly(m-phenylene-4,4'-biphenylenedicarboxamide), poly(p-phenylene-2,6-naphthalenedicarboxamide), poly(m-phenylene-2,6-naphthalenedicarboxamide), poly(2-chlorop-phenyleneterephthalamide), p-phenyleneterephthalamide / 2,6-dichlorop-phenyleneterephthalamide copolymer, m-phenyleneterephthalamide / 2,6-dichlorop-phenyleneterephthalamide copolymer, poly(4,4'-diphenylsulfonylterephthalamide), p-phenyleneterephthalamide / 4,4'-diphenylsulfonylterephthalamide copolymer, and the like. Among these, poly(p-phenyleneterephthalamide) is more preferred.

[0097] Note that only one type of the resin may be used, or two or more types may be used in combination.

[0098] The porous layer may contain fine particles. The fine particles in this specification generally refer to organic or inorganic fine particles commonly referred to as fillers. The fine particles are preferably insulating fine particles.

[0099] Examples of the organic fine particles include fine particles made of resin. Examples of the inorganic fine particles include fillers composed of inorganic substances such as calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomaceous earth, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, boehmite, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, titanium nitride, alumina (aluminum oxide), aluminum nitride, mica, zeolite, and glass. Only one type of the fine particles may be used, or two or more types may be used in combination.

[0100] The content of the fine particles in the porous layer is preferably 1 to 99% by volume, more preferably 5 to 95% by volume, of the porous layer.

[0101] The thickness of the porous layer per layer is preferably 0.5 to 15 μm, more preferably 2 to 10 μm. If the thickness of the porous layer per layer is 0.5 μm or more, internal short circuits due to breakage of the non-aqueous electrolyte secondary battery or the like can be sufficiently suppressed. Also, the amount of the electrolyte retained in the porous layer becomes sufficient. On the other hand, if the thickness of the porous layer per layer is 15 μm or less, a decrease in rate characteristics or cycle characteristics can be suppressed.

[0102] The weight per unit area of the porous layer, that is, the weight per unit area, is preferably 1 to 20 g / m 2 and more preferably 4 to 10 g / m 2 for each layer.

[0103] The volume of the porous layer constituent components contained per square meter of the porous layer is preferably 0.5 to 20 cm 3 and more preferably 1 to 10 cm 3 for each layer, and even more preferably 2 to 7 cm 3 for each layer.

[0104] The porosity of the porous layer is preferably 20 to 90% by volume, more preferably 30 to 80% by volume, so as to obtain sufficient ion permeability. Also, the pore diameter of the pores in the porous layer is preferably 3 μm or less, more preferably 1 μm or less, so that the laminated separator for non-aqueous electrolyte secondary batteries can obtain sufficient ion permeability.

[0105] The film thickness of the laminated separator for non-aqueous electrolyte secondary batteries is preferably 5.5 μm to 45 μm, more preferably 6 μm to 25 μm.

[0106] The air permeability of the laminated separator for the non-aqueous electrolyte secondary battery is preferably 100 to 350 sec / 100 mL in Gurley value, and more preferably 100 to 300 sec / 100 mL.

[0107] Also, the puncture strength of the laminated separator for the non-aqueous electrolyte secondary battery is preferably 5.0 N or more, more preferably 5.3 N or more, and even more preferably 5.5 N or more. Note that the puncture strength is measured in the same manner as the porous film.

[0108] In addition, the separator for the non-aqueous electrolyte secondary battery in one embodiment of the present invention may optionally include another porous layer other than the porous film and the porous layer, as long as the object of the present invention is not impaired. Examples of the other porous layer include known porous layers such as a heat-resistant layer, an adhesive layer, and a protective layer.

[0109] 4. Method for manufacturing a porous layer and a laminated separator for a non-aqueous electrolyte secondary battery As a method for manufacturing the porous layer in one embodiment of the present invention and the laminated separator for the non-aqueous electrolyte secondary battery according to one embodiment of the present invention, for example, there is a method of applying a coating liquid containing a resin contained in the porous layer to one or both surfaces of the porous film and drying it to deposit the porous layer.

[0110] The coating liquid contains a resin contained in the porous layer. Further, the coating liquid may contain fine particles described later that may be contained in the porous layer. The coating liquid can usually be prepared by dissolving a resin that may be contained in the aforementioned porous layer in a solvent and dispersing the fine particles. Here, the solvent for dissolving the resin is not particularly limited and also serves as a dispersion medium for dispersing the fine particles. Also, the resin may be made into an emulsion with the solvent.

[0111] The coating liquid may be formed by any method as long as it can satisfy conditions such as the resin solid content (resin concentration) and the amount of fine particles necessary to obtain a desired porous layer.

[0112] The method for applying the coating liquid onto the porous film is not particularly limited. As the application method, a conventionally known method can be adopted. Specifically, for example, a gravure coater method, a dip coater method, a bar coater method, a die coater method, etc. can be mentioned.

[0113] [Embodiment 2: Member for non-aqueous electrolyte secondary battery, Embodiment 3: Non-aqueous electrolyte secondary battery] The member for non-aqueous electrolyte secondary battery according to Embodiment 2 of the present invention is formed by arranging a positive electrode, a separator for non-aqueous electrolyte secondary battery according to Embodiment 1 of the present invention, and a negative electrode in this order.

[0114] The non-aqueous electrolyte secondary battery according to Embodiment 3 of the present invention includes a separator for non-aqueous electrolyte secondary battery according to Embodiment 1 of the present invention.

[0115] The non-aqueous electrolyte secondary battery is, for example, a non-aqueous secondary battery that obtains an electromotive force by doping and dedoping of lithium, and may include a non-aqueous electrolyte secondary battery member in which a positive electrode, the separator for non-aqueous electrolyte secondary battery, and a negative electrode are laminated in this order. Note that the components of the non-aqueous electrolyte secondary battery other than the separator for non-aqueous electrolyte secondary battery are not limited to the components described below.

[0116] The non-aqueous electrolyte secondary battery usually has a structure in which a battery element in which a negative electrode and a positive electrode are impregnated with an electrolytic solution in a structure where they face each other via the separator for non-aqueous electrolyte secondary battery is enclosed in an exterior material. The non-aqueous electrolyte secondary battery is preferably a lithium secondary battery in particular. Note that doping means occlusion, loading, adsorption, or insertion, and means a phenomenon in which lithium ions enter the active material of an electrode such as a positive electrode.

[0117] The non-aqueous electrolyte secondary battery member includes the separator for non-aqueous electrolyte secondary battery. Therefore, the non-aqueous electrolyte secondary battery member has the effect that a non-aqueous electrolyte secondary battery excellent in safety, for example, safety against external impact, can be manufactured.

[0118] The non-aqueous electrolyte secondary battery includes the separator for the non-aqueous electrolyte secondary battery. Therefore, the non-aqueous electrolyte secondary battery has an effect of being excellent in safety, for example, safety against external impact.

[0119] 1. Positive electrode The positive electrode in the non-aqueous electrolyte secondary battery member and the non-aqueous electrolyte secondary battery is not particularly limited as long as it is generally used as a positive electrode of a non-aqueous electrolyte secondary battery. For example, a positive electrode sheet having a structure in which an active material layer containing a positive electrode active material and a binder is formed on a current collector can be used. The active material layer may further contain a conductive agent.

[0120] Examples of the positive electrode active material include materials capable of doping and dedoping lithium ions. Specifically, examples of such materials include lithium composite oxides containing at least one kind of transition metal such as V, Mn, Fe, Co, and Ni.

[0121] Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired products of organic polymer compounds. The conductive agent may be used alone or in combination of two or more.

[0122] Examples of the binder include fluorine-based resins such as polyvinylidene fluoride, acrylic resins, and styrene-butadiene rubber. The binder also has a function as a thickener.

[0123] Examples of the positive electrode current collector include conductors such as Al, Ni, and stainless steel. Among them, Al is more preferable because it is easy to process into a thin film and is inexpensive.

[0124] Examples of the method for manufacturing the sheet-like positive electrode include a method of pressure-molding a positive electrode active material, a conductive agent, and a binder on a positive electrode current collector; a method of making a paste of the positive electrode active material, the conductive agent, and the binder using an appropriate organic solvent, applying the paste to the positive electrode current collector, drying it, and then pressing it to adhere it to the positive electrode current collector; and the like.

[0125] 2. Negative electrode The negative electrode in the non-aqueous electrolyte secondary battery member and the non-aqueous electrolyte secondary battery is not particularly limited as long as it is generally used as a negative electrode of a non-aqueous electrolyte secondary battery. For example, a negative electrode sheet having a structure in which an active material layer containing a negative electrode active material and a binder is formed on a current collector can be used. The active material layer may further contain a conductive agent.

[0126] Examples of the negative electrode active material include materials capable of doping and dedoping lithium ions, lithium metal, lithium alloys, and the like. Examples of such materials include carbonaceous materials. Examples of carbonaceous materials include natural graphite, artificial graphite, cokes, carbon black, and pyrolytic carbons.

[0127] Examples of the negative electrode current collector include Cu, Ni, and stainless steel. In particular, in a lithium secondary battery, Cu is more preferable because it is difficult to form an alloy with lithium and is easy to process into a thin film.

[0128] Examples of the method for manufacturing the sheet-like negative electrode include a method of pressure-molding a negative electrode active material on a negative electrode current collector; a method of making a paste of the negative electrode active material using an appropriate organic solvent, applying the paste to the negative electrode current collector, drying it, and then pressing it to adhere it to the negative electrode current collector; and the like. The paste preferably contains the conductive agent and the binder.

[0129] 3. Non-aqueous electrolyte The non-aqueous electrolyte in the non-aqueous electrolyte secondary battery is not particularly limited as long as it is a non-aqueous electrolyte generally used in non-aqueous electrolyte secondary batteries. For example, a non-aqueous electrolyte obtained by dissolving a lithium salt in an organic solvent can be used. Examples of the lithium salt include LiClO 4 , LiPF 6 , LiAsF 6 , LiSbF 6 , LiBF 4 , LiCF 3 SO 3 , LiN(CF 3 SO 2 ), 2 , LiC(CF 3 SO 2 ), 3 , Li 2 B 10 Cl 10 , lithium salts of lower aliphatic carboxylic acids, LiAlCl 4 , and the like. The lithium salt may be used alone or in combination of two or more.

[0130] Examples of the organic solvent constituting the non-aqueous electrolyte include carbonates, ethers, esters, nitriles, amides, carbamates, sulfur-containing compounds, and fluorine-containing organic solvents obtained by introducing a fluorine group into these organic solvents. The organic solvent may be used alone or in combination of two or more.

Examples

[0131] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0132] [Measurement method] The physical properties and the like of the porous film and the laminated separator for non-aqueous electrolyte secondary batteries (hereinafter referred to as "laminated porous film") produced in Examples 1 to 4 and Comparative Examples 1 to 2 were measured using the following methods.

[0133] [Film thickness] The film thicknesses of the porous film and the laminated porous film were measured using a high-precision digital length measuring instrument (VL-50) manufactured by Mitutoyo Corporation.

[0134] [Areal weight] A square with a side length of 8 cm was cut out as a sample from the laminated porous film, and the weight W (g) of the sample was measured. Then, the areal weight of the laminated porous film was calculated according to the following formula (2).

[0135] [Areal weight (g / m 2 ) = W / (0.08 × 0.08) ··· (2) In the same manner, the areal weight of the porous film constituting the laminated porous film was calculated. Then, the areal weight of the para-aramid layer constituting the laminated porous film was calculated by subtracting the areal weight of the porous film from the areal weight of the laminated porous film.

[0136] [Air permeability] The air permeability (Gurley value) of the laminated porous film was measured in accordance with JIS P8117.

[0137] [Puncture strength] The puncture strength of the laminated porous film was measured by the methods shown in the following (i) and (ii).

[0138] (i) After fixing the laminated porous film to the upper surface of the base with a washer of 11.3 mm Φ, a pin (pin diameter 1 mm Φ, tip 0.5R) was punctured into the laminated porous film under the conditions of a puncture speed of 10 mm / sec and a puncture depth of 200 mm.

[0139] (ii) The maximum stress (gf) when the pin was punctured into the laminated porous film in (i) was measured, and the measured value was taken as the puncture strength of the laminated porous film.

[0140] [MD breaking elongation, TD breaking elongation] The MD breaking elongation and TD breaking elongation of the laminated porous film were measured by a method conforming to the JIS K7127 standard. The specific measurement method is shown below.

[0141] The length of the laminated porous film in the MD direction was measured. The measured length is hereinafter referred to as the "MD length before elongation". Thereafter, the laminated porous film was elongated in the MD direction, and the length of the laminated porous film in the MD direction when the laminated porous film broke was measured. The measured length is hereinafter referred to as the "MD length after elongation". The MD breaking elongation was measured using the following formula (3). MD breaking elongation [%GL] = [{(MD length after elongation) - (MD length before elongation)} / (MD length before elongation)]×100 ··(3) Similarly, the length of the laminated porous film in the TD direction was measured. The measured length is hereinafter referred to as the "TD length before elongation". Thereafter, the laminated porous film was elongated in the TD direction, and the length of the laminated porous film in the TD direction when the laminated porous film broke was measured. The measured length is hereinafter referred to as the "TD length after elongation". The TD breaking elongation was measured using the following formula (4). TD breaking elongation [%GL] = [{(TD length after elongation) - (TD length before elongation)} / (TD length before elongation)]×100 ··(4) [Simple impact test] A square with a side length of 5 cm was cut out from the laminated porous film as a sample, and the sample was attached to a polyurethane sheet with a side length of 5 cm and a thickness of 5 mm (manufactured by Daiso Industries, earthquake-resistant mat square). A glass sphere with a diameter of 1.2 cm and a weight of 2.2 g (manufactured by Daiso Industries, g l ass pearl beads) was placed statically at the center of the sample attached to the sheet, and a cylindrical weight with a weight of 148 g and a bottom diameter of 2.2 cm was freely dropped from a height of 35 cm to make the weight collide with the glass sphere. At that time, the presence or absence of breakage of the sample was confirmed, and when it was not broken, it was marked as 〇, and when it was broken, it was marked as ×. The test was carried out a total of 4 times, including the case where the sample was not broken, starting from creating a new sample.

[0142] [Peak area ratio R of (200) plane] First, wide-angle X-ray diffraction (WAXD) measurement of the porous film was performed using a NANO-Viewer manufactured by Rigaku Corporation (X-ray output: Cu target, 40 kV, 20 mA). Based on the area ratio of the crystal peaks of polyethylene obtained, the peak area ratio R of the (200) plane of the polyethylene crystal in the laminated porous film was evaluated.

[0143] Specifically, the R was calculated by the following method. That is, first, with the MD direction of the sample of the laminated porous film as the vertical direction, the sample was attached to the sample holder, and X-rays were irradiated onto the surface of the sample from the vertical direction of the sample to obtain a WAXD pattern.

[0144] Next, regarding the peak of the (110) plane of polyethylene that appears near the diffraction angle 2θ = 21 degrees, with the horizontal direction as the azimuth angle β = 0 degrees, the azimuth angle profile was calculated. Based on the peak that appeared most strongly near β = 0 degrees in the azimuth angle profile, in the range where the azimuth angle is ±5 degrees, the profile of the diffraction intensity with respect to the diffraction angle 2θ was obtained.

[0145] In the obtained diffraction intensity profile, the area I(110) of the peak of the (110) plane of polyethylene and the area I(200) of the peak of the (200) plane, which are detected near the diffraction angles 2θ = 21 degrees and 24.5 degrees, were obtained. Further, the peak area ratio R of the (200) plane was calculated by the following formula (1).

[0146] Peak area ratio R of (200) plane = I(200) / I(110) ··· (1) [Example 1] 70% by weight of ultra-high molecular weight polyethylene powder (intrinsic viscosity: 21 dL / g, viscosity-average molecular weight 3 million, manufactured by Tosoh Corporation) and 30% by weight of polyethylene wax with a weight-average molecular weight of 2000 (Excelex 20700, manufactured by Mitsui Chemicals, Inc.) were prepared. Taking the total of this ultra-high molecular weight polyethylene and polyethylene wax as 100 parts by weight, 0.4 part by weight of an antioxidant (IRGANOX 1010, manufactured by BASF), 0.1 part by weight of an antioxidant (IRGAFOS 168, manufactured by BASF), and 1.3 parts by weight of sodium stearate were added.

[0147] Furthermore, calcium carbonate with an average particle size of 0.1 μm (manufactured by Maruo Calcium Co., Ltd.) was added so as to be 38% by volume with respect to the total volume of the obtained mixture. These were mixed as powders using a Henschel mixer and then melt-kneaded using a twin-screw kneader to obtain a polyolefin resin composition.

[0148] The polyolefin resin composition was stretched at a draw ratio of 1.4 times in the MD direction using a pair of rolls to produce a sheet-like polyolefin resin composition. The obtained sheet-like polyolefin resin composition was immersed in an aqueous hydrochloric acid solution (hydrochloric acid 4 mol / L, nonionic surfactant 0.5% by weight) to remove the calcium carbonate and obtain a primary sheet.

[0149] Subsequently, both ends of the obtained primary sheet in the TD direction were gripped by a plurality of gripping members adjacent in the MD direction. The primary sheet was stretched at a draw ratio of 4.29 times in the TD direction to obtain a secondary sheet.

[0150] Subsequently, both ends of the secondary sheet in the TD direction were gripped by a plurality of gripping members adjacent in the MD direction. Subsequently, while relaxing the secondary sheet in the MD direction by reducing the distance between the gripping members adjacent in the MD direction, the distance between the opposing gripping members in the TD direction was increased, and the sheet was stretched at a draw ratio of 1.63 times in the TD direction at a temperature of 115°C. Subsequently, until the draw ratio became 1.4 times, the secondary sheet was contracted in the TD direction to obtain a porous film with a film thickness of 13.8 μm. The MD relaxation rate at this time was 25%.

[0151] Subsequently, the production of poly(p-phenylene terephthalamide) was carried out using a 3-liter separable flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a powder addition port.

[0152] First, the separable flask was thoroughly dried and charged with 2200 g of N-methyl-2-pyrrolidone (NMP). Next, 151.07 g of calcium chloride powder that had been vacuum-dried at 200°C for 2 hours was added, and the temperature inside the separable flask was raised to 100°C to completely dissolve the calcium chloride powder.

[0153] After returning the temperature to room temperature, 68.23 g of p-phenylenediamine was added and completely dissolved. While maintaining the obtained solution at 20°C ± 2°C, 124.97 g of terephthaloyl chloride was divided into 5 portions and added to the solution at approximately 10-minute intervals. Thereafter, while stirring, the solution was aged for 1 hour while maintaining it at 20°C ± 2°C. The aged solution was filtered using a 1500-mesh stainless steel wire mesh. The concentration of para-aramid in the obtained para-aramid solution was 6% by weight.

[0154] 100 g of the para-aramid solution was weighed into a flask, 158 g of NMP was added, and a solution with a para-aramid concentration of 2.25% by weight was prepared. Subsequently, the solution was stirred for 10 minutes. 6 g of alumina C (manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter 13 nm) and 2.3 g of calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) were mixed into the solution with a para-aramid concentration of 2.25% by weight to obtain a coating solution.

[0155] After applying the obtained coating solution to the porous film, the coating solution was dried to form a para-aramid layer (porous layer) on the porous film. As a result, a laminated porous film having a para-aramid layer formed on the porous film was obtained. The basis weight of the para-aramid layer was 1.9 g / m 2 It was.

[0156] The physical property values, etc. of the obtained laminated porous film (laminated separator for non-aqueous electrolyte secondary battery) were measured by the above-described method. The results are shown in Tables 1 and 2. Further, the diffraction intensity profile of the laminated porous film obtained by the above-described method is shown in FIG. 1.

[0157] Note that the "MD relaxation rate" refers to the reduction rate of the length of the porous film in the MD direction with respect to the length of the secondary sheet in the MD direction before stretching.

[0158] [Example 2] A primary sheet was obtained by the same method as the method for obtaining the primary sheet in Example 1. Thereafter, the obtained primary sheet was stretched at a stretching ratio of 3.57 times in the TD direction by the same method as in Example 1 to obtain a secondary sheet.

[0159] Both ends of the secondary sheet in the TD direction were gripped by a plurality of gripping members adjacent in the MD direction. Subsequently, while relaxing the secondary sheet in the MD direction by reducing the distance between the gripping members adjacent in the MD direction, the distance between the opposing gripping members in the TD direction was increased, and the sheet was stretched at a stretching ratio of 1.4 times in the TD direction at a temperature of 110°C. As a result, a porous film having a thickness of 14.1 μm was obtained. The MD relaxation rate at this time was 25%.

[0160] Using the obtained porous film, a para-aramid layer was formed on the porous film by the same method as the method for obtaining the laminated porous film in Example 1 to obtain a laminated porous film. The basis weight of the para-aramid layer was 1.7 g / m 2 at that time.

[0161] The physical property values, etc. of the obtained laminated porous film (laminated separator for non-aqueous electrolyte secondary battery) were measured by the above-described method. The results are shown in Tables 1 and 2. Further, the diffraction intensity profile of the laminated porous film obtained by the above-described method is shown in FIG. 2.

[0162] [Example 3] The primary sheet in Example 1to The primary sheet was obtained in the same manner as the method for obtaining it. Subsequently, the obtained primary sheet was stretched at a draw ratio of 4.29 times in the TD direction in the same manner as in Example 1 to obtain a secondary sheet.

[0163] Both ends of the secondary sheet in the TD direction were gripped by a plurality of gripping members adjacent in the MD direction. Subsequently, while relaxing the secondary sheet in the MD direction by reducing the distance between the gripping members adjacent in the MD direction, the distance between the opposing gripping members in the TD direction was increased, and it was stretched at a draw ratio of 1.4 times in the TD direction at a temperature of 115°C. As a result, a porous film with a thickness of 14.1 μm was obtained. The MD relaxation rate at this time was 25%.

[0164] Using the obtained porous film, a para-aramid layer was formed on the porous film in the same manner as the method for obtaining the laminated porous film in Example 1 to obtain a laminated porous film. The basis weight of the para-aramid layer was 2.1 g / m 2 was.

[0165] The physical property values, etc. of the obtained laminated porous film (laminated separator for non-aqueous electrolyte secondary battery) were measured by the above-described method. The results are shown in Tables 1 and 2. Also, the diffraction intensity profile of the laminated porous film obtained by the above-described method is shown in FIG. 3.

[0166] [Example 4] The secondary sheet in Example 2 to A secondary sheet was obtained in the same manner as the method for obtaining it. The obtained secondary sheet was stretched in the TD direction while relaxing in the MD direction in the same manner as in Example 2, except that the temperature during stretching was 115°C, to obtain a porous film with a thickness of 14.1 μm.

[0167] Using the obtained porous film, a para-aramid layer was formed on the porous film in the same manner as the method for obtaining the laminated porous film in Example 1 to obtain a laminated porous film. The basis weight of the para-aramid layer was 1.9 g / m2 It was.

[0168] The physical property values and the like of the obtained laminated porous film (laminated separator for non-aqueous electrolyte secondary battery) were measured by the above-described method. The results are shown in Tables 1 and 2. Further, the diffraction intensity profile of the laminated porous film obtained by the above-described method is shown in FIG. 4.

[0169] [Comparative Example 1] 68% by weight of ultra-high molecular weight polyethylene powder (GUR2024, manufactured by Ticona) and 32% by weight of polyethylene wax (FNP-0115, manufactured by Nippon Seiko Co., Ltd.) having a weight average molecular weight of 1000 were prepared. With the total of this ultra-high molecular weight polyethylene and polyethylene wax being 100 parts by weight, 0.4 part by weight of an antioxidant (IRGANOX 1010, manufactured by BASF), 0.1 part by weight of an antioxidant (IRGAFOS 168, manufactured by BASF), and 1.3 parts by weight of sodium stearate were added.

[0170] Furthermore, calcium carbonate having an average particle diameter of 0.1 μm (manufactured by Maruo Calcium Co., Ltd.) was added so as to be 38% by volume with respect to the total volume of the obtained mixture. After mixing these as powders with a Henschel mixer, they were melt-kneaded with a twin-screw kneader to obtain a polyolefin resin composition.

[0171] The polyolefin resin composition was stretched at a draw ratio of 1.4 times in the MD direction with a pair of rolls to produce a sheet-like polyolefin resin composition. The obtained sheet-like polyolefin resin composition was immersed in an aqueous hydrochloric acid solution (4 mol / L hydrochloric acid, 0.5% by weight of a nonionic surfactant) to remove the calcium carbonate, and a primary sheet was obtained.

[0172] Subsequently, both ends of the obtained primary sheet in the TD direction were gripped by a plurality of gripping members adjacent in the MD direction. Subsequently, the primary sheet was stretched at a draw ratio of 7.05 times in the TD direction at 123°C to obtain a porous film having a thickness of 13.5 μm.

[0173] Using the obtained porous film, a para-aramid layer was formed on the porous film by the same method as the method for obtaining the laminated porous film in Example 1, and a laminated porous film was obtained. The basis weight of the para-aramid layer was 3.0 g / m 2 was obtained.

[0174] The physical property values and the like of the obtained laminated porous film (laminated separator for non-aqueous electrolyte secondary battery) were measured by the above-described method. The results are shown in Tables 1 and 2. Also, the diffraction intensity profile of the laminated porous film obtained by the above-described method is shown in FIG. 5.

[0175] [Comparative Example 2] The procedure was the same as in Example 1 until the primary sheet was obtained. Subsequently, both ends of the obtained primary sheet in the TD direction were gripped by a plurality of gripping members adjacent in the MD direction.

[0176] Subsequently, while relaxing the primary sheet in the MD direction by reducing the distance between the gripping members adjacent in the MD direction, the distance between the opposing gripping members in the TD direction was increased to stretch the sheet at a draw ratio of 5 times in the TD direction. As a result, a porous film having a thickness of 14.0 μm was obtained. The MD relaxation rate at this time was 20%.

[0177] Using the obtained porous film, a para-aramid layer was formed on the porous film by the same method as the method for obtaining the laminated porous film in Example 1, and a laminated porous film was obtained. The basis weight of the para-aramid layer was 1.7 g / m 2 was obtained.

[0178] The physical property values and the like of the obtained laminated porous film (laminated separator for non-aqueous electrolyte secondary battery) were measured by the above-described method. The results are shown in Tables 1 and 2. Also, the diffraction intensity profile of the laminated porous film obtained by the above-described method is shown in FIG. 6.

[0179] [Results]

[0180]

Table 1

[0181]

Table 2

[0182] As shown in Table 2, the laminated separators for non-aqueous electrolyte secondary batteries of Examples 1 to 4 had a peak area ratio R of the (200) plane of 0.15 or more, while the laminated separators for non-aqueous electrolyte secondary batteries of Comparative Examples 1 and 2 had a peak area ratio R of the (200) plane of less than 0.15. The laminated separators for non-aqueous electrolyte secondary batteries of Examples 1 to 4 were more difficult to break in the simple impact test than the laminated separators for non-aqueous electrolyte secondary batteries of Comparative Examples 1 and 2.

[0183] Therefore, it was found that the separator for a non-aqueous electrolyte secondary battery according to one embodiment of the present invention is excellent in impact resistance because the peak area ratio R of the (200) plane is 0.15 or more.

Industrial Applicability

[0184] One aspect of the present invention can be suitably used for manufacturing non-aqueous electrolyte secondary batteries.

Claims

1. A separator for a non-aqueous electrolyte secondary battery comprising a polyolefin porous film, wherein the peak area ratio R of the (200) plane calculated by the following formula (1) is 0.15 or more and 0.20 or less from the diffraction intensity profile obtained by wide-angle X-ray diffraction (WAXD): A separator for a non-aqueous electrolyte secondary battery. Peak area ratio R of (200) plane = I(200) / I(110) ··· (1) (Here, the WAXD is performed by irradiating X-rays from the vertical direction onto the surface of the separator for the non-aqueous electrolyte secondary battery, I(110) is the peak area of the diffraction peak of the (110) plane in the diffraction intensity profile, and I(200) is the diffraction intensity profile. Is the peak area of the diffraction peak of the (200) plane.)

2. A separator for a non-aqueous electrolyte secondary battery comprising a polyolefin porous film, wherein the peak area ratio R of the (200) plane calculated by the following formula (1) is 0.15 or more and 0.20 or less from the diffraction intensity profile obtained by wide-angle X-ray diffraction (WAXD); Peak area ratio R of (200) plane = I(200) / I(110) ··· (1) (Here, the WAXD is performed by irradiating X-rays from the vertical direction onto the surface of the separator for the non-aqueous electrolyte secondary battery, I(110) is the peak area of the diffraction peak of the (110) plane in the diffraction intensity profile, and I(200) is the diffraction intensity profile. Is the peak area of the diffraction peak of the (200) plane.) further comprising a porous layer containing a resin, wherein the porous layer is laminated on one or both sides of the polyolefin porous film, and the resin is a resin selected from the group consisting of (meth)acrylate resins, fluorine-containing resins, polyamide resins, polyimide resins, polyester resins, water-soluble polymers, polycarbonates, polyacetals, and polyether ether ketones. Separator for non-aqueous electrolyte secondary battery.

3. The separator for a non-aqueous electrolyte secondary battery according to claim 2, wherein the resin is selected from the group consisting of (meth)acrylate resins, fluorine-containing resins, polyamide resins, polyester resins, and water-soluble polymers.

4. The separator for a non-aqueous electrolyte secondary battery according to claim 2 or 3, wherein the polyamide resin is an aramid resin.

5. The separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the piercing strength of the polyolefin porous film is 5.0 N or more.

6. A member for a non-aqueous electrolyte secondary battery, in which a positive electrode, the separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, and a negative electrode are arranged in this order.

7. A non-aqueous electrolyte secondary battery including the separator for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5.

Images