WO2020091060A1

WO2020091060A1 - Nonaqueous electrolyte secondary battery

Info

Publication number: WO2020091060A1
Application number: PCT/JP2019/043096
Authority: WO
Inventors: 一郎有瀬; 村上　力
Original assignee: 住友化学株式会社
Priority date: 2018-11-01
Filing date: 2019-11-01
Publication date: 2020-05-07
Also published as: JP2020072041A; KR20210082491A; JP7252735B2

Abstract

The purpose of the present invention is to provide a nonaqueous electrolyte secondary battery that has improved charging capacity after aging. This nonaqueous electrolyte secondary battery is provided with a porous layer that contains an inorganic filler and a resin, a positive electrode plate and a negative electrode plate, wherein (i) the sum of the interface barrier energy of a positive electrode active material of the positive electrode plate and the interface barrier energy of a negative electrode active material of the negative electrode plate, (ii) the aspect ratio of a projected image of the inorganic filler on the surface of the porous layer, and (iii) the degree of orientation of the inorganic filler satisfy specific conditions.

Description

Non-aqueous electrolyte secondary battery

The present invention relates to a non-aqueous electrolyte secondary battery.

Non-aqueous electrolyte secondary batteries, especially lithium secondary batteries, are widely used as batteries for personal computers, mobile phones, personal digital assistants, etc. because of their high energy density, and recently they have been developed as in-vehicle batteries. ing.

As a non-aqueous electrolyte secondary battery, for example, a porous layer containing a plate-like inorganic filler as described in Patent Document 1 and having a porosity of 60 to 90% is provided on at least one surface of a porous substrate. There is known a non-aqueous electrolyte secondary battery including a non-aqueous secondary battery separator that is laminated on.

Japanese Unexamined Patent Publication No. 2010-108753 (Published May 13, 2010)

However, there is room for improvement in the charging capacity after aging in the above-described conventional technology.

One aspect of the present invention has been made in view of the above problems, and an object thereof is to provide a non-aqueous electrolyte secondary battery having an improved charge capacity after aging.

The present invention includes the following configurations:
<1> A porous layer containing an inorganic filler and a resin, a positive electrode plate, and a negative electrode plate are provided,
The interfacial barrier energy of the positive electrode active material when the positive electrode plate and the negative electrode plate are processed into a disk shape having a diameter of 15.5 mm, and immersed in an ethylene carbonate / ethyl methyl carbonate / diethyl carbonate solution of LiPF _{6 having} a concentration of 1 M to measure. And the interfacial barrier energy of the negative electrode active material is 5000 J / mol or more,
The aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is in the range of 1.4 to 4.0,
In the porous layer, I _(hkl) and I _(abc) , which are peak intensities of arbitrary diffraction planes (hkl) and (abc) orthogonal to each other when measured by the wide-angle X-ray diffraction method, are represented by the following formula ( Non-aqueous electrolyte secondary battery satisfying the relationships of 1) and (2):
I _(hkl) > I _(abc)・・・ (1)
The maximum value of 1.5 ≦ (I _(hkl) / I _(abc) ) ≦ 300 (2).
<2> The non-aqueous electrolyte secondary battery according to <1>, wherein the porous layer is laminated on one side or both sides of a polyolefin porous film.
<3> The nonaqueous electrolyte secondary battery according to <1> or <2>, wherein the positive electrode plate contains a transition metal and the negative electrode plate contains graphite.
<4> The resin contained in the porous layer is one or more selected from the group consisting of polyolefin, (meth) acrylate resin, fluorine-containing resin, polyamide resin, polyester resin and water-soluble polymer. The non-aqueous electrolyte secondary battery according to any one of <1> to <3>.
<5> The non-aqueous electrolyte secondary battery according to <4>, wherein the polyamide resin is an aramid resin.

According to one aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery having improved charge capacity after aging.

It is a schematic diagram showing the structure of the said porous layer when the orientation of an inorganic filler is large in the porous layer containing an inorganic filler (left figure), and when the orientation of an inorganic filler is small (right figure). It is a schematic diagram which shows the projected image of the inorganic filler of the surface of the porous layer in one Embodiment of this invention.

An embodiment of the present invention will be described below, but the present invention is not limited to this. The present invention is not limited to each configuration described below, various modifications are possible within the scope shown in the claims, and the technical means disclosed in different embodiments are appropriately combined. The obtained embodiments are also included in the technical scope of the present invention. Unless otherwise specified in the present specification, “A to B” representing a numerical range means “A or more and B or less”.

[1. Non-aqueous electrolyte secondary battery according to one embodiment of the present invention]
A non-aqueous electrolyte secondary battery according to an aspect of the present invention includes a porous layer containing an inorganic filler and a resin, a positive electrode plate, and a negative electrode plate,
The interfacial barrier energy of the positive electrode active material when the positive electrode plate and the negative electrode plate are processed into a disk shape having a diameter of 15.5 mm, and immersed in an ethylene carbonate / ethyl methyl carbonate / diethyl carbonate solution of LiPF _{6 having} a concentration of 1 M to measure. And the interfacial barrier energy of the negative electrode active material is 5000 J / mol or more,
The aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is in the range of 1.4 to 4.0,
Peak strengths of arbitrary diffraction planes (hkl) and (abc) orthogonal to each other, measured by a wide-angle X-ray diffraction method, of the porous layer: I _(hkl) and I _(abc) satisfy the following formula (1). ,
The range of the maximum value of the peak intensity ratio calculated by the following equation (2) is the range of 1.5 to 300:
I _(hkl) > I _(abc)・・・ (1)
I _(hkl) / I _(abc) (2).

According to the combination of the positive electrode plate and the negative electrode plate in which the sum of the interfacial barrier energies is within the above range, migration of ions and charges on the active material surface in the positive electrode active material layer and the negative electrode active material layer during the charge / discharge cycle process. Are made uniform. Therefore, the reactivity of the entire active material becomes appropriate and uniform, and the structural change in the active material layer and the deterioration of the active material itself are suppressed.

The ion permeability is high in the porous layer in which the aspect ratio of the projected image of the inorganic filler and the maximum value of the peak intensity ratio calculated by the formula (2) satisfy the above condition. Therefore, for example, when used as a coating layer of a separator, it is possible to provide a separator having good ion permeability.

By selecting the above members, the non-aqueous electrolyte secondary battery according to an aspect of the present invention has a new effect that the charge capacity after aging is improved. Here, aging means charge and discharge of several cycles that are first performed after assembling the non-aqueous electrolyte secondary battery.

It is considered that the above effect is due to the combination of members having a good ion permeability in the porous layer and a uniform ion distribution in the electrode. That is, as a result of such a combination, the distribution of ions in the active material layer during the aging process is reasonably uniform, and the electrolytic solution further permeates the entire electrode. Therefore, it is estimated that the battery capacity after aging is improved.

Aging conditions can be appropriately set by those skilled in the art. As an example, a method for measuring the charge capacity after aging will be described below. In the following description, "1C" means the current value for discharging the rated capacity with the discharge capacity of 1 hour rate in 1 hour. “CC-CV charging” means a charging method in which charging is performed with a constant current until a predetermined voltage is reached, and then charging is performed while reducing the current so that the predetermined voltage is maintained. The “CC discharge” means a discharge method of discharging a predetermined voltage while maintaining a constant current.

1. (First charge / discharge step) The assembled non-aqueous electrolyte secondary battery was charged with CC-CV at (i) voltage range: 2.7 to 4.1 V and charging current value: 0.2 C (cutoff current). Condition: 0.02C), and then (ii) CC discharge is performed at a discharge current value: 0.2C. This charge / discharge cycle is carried out at 25 ° C.

2. (Gas venting step) From the secondary battery for non-aqueous electrolyte after the initial charge / discharge, a blank part (gas reservoir) where the positive and negative electrode plates do not exist inside the laminate pouch is cut, leaving a resealing point. Then, the inside of the laminate pouch is evacuated with a vacuum sealer to remove the surplus gas components generated by the initial charge and discharge. Further, the laminate pouch is pressure-sealed again.

3. (Aging charge / discharge) CC-CV charging is performed on the non-aqueous electrolyte secondary battery that has undergone the degassing process at (i) voltage range: 2.7 to 4.1 V, charging current value: 0.2 C (stop current Condition: 0.02C), and then (ii) CC discharge is performed at a discharge current value: 0.2C. With the above cycle as one cycle, three cycles of aging charge / discharge are performed. This charge / discharge cycle is carried out at 25 ° C.

4. (Charging capacity after aging) CC-CV charging is performed on the non-aqueous electrolyte secondary battery that has undergone aging charging / discharging at (i) voltage range: 2.7 to 4.1 V, charging current value: 1 C (stop current Condition: 0.02C), and then (ii) CC discharge is performed at a discharge current value: 0.2C. Three cycles of charging and discharging are performed with the above cycle as one cycle. This charge / discharge cycle is carried out at 55 ° C. The charge capacity in the third cycle in this step is referred to as "charge capacity after aging".

The charge capacity after aging of the non-aqueous electrolyte secondary battery according to an aspect of the present invention is preferably 18 mAh or more, and more preferably 18.5 mAh or more.

[2. Positive electrode plate and negative electrode plate]
[Positive plate]
The positive electrode plate in the non-aqueous electrolyte secondary battery according to the exemplary embodiment of the present invention is obtained by processing the positive electrode plate and a negative electrode plate described below into a disk shape having a diameter of 15.5 mm, and a concentration of 1M LiPF ₆ ethylene carbonate / ethyl. There is no particular limitation as long as the sum of the interfacial barrier energies is 5000 J / mol or more as measured by dipping in a methyl carbonate / diethyl carbonate solution. For example, such a positive electrode plate includes a sheet-shaped positive electrode plate in which a positive electrode active material layer, a positive electrode mixture containing a positive electrode active material, a conductive agent, and a binder is carried on a positive electrode current collector. The positive electrode plate may carry the positive electrode mixture on both surfaces of the positive electrode current collector, or may carry the positive electrode mixture on one surface of the positive electrode current collector.

Examples of the positive electrode active material include materials that can be doped with lithium ions and dedoped. A transition metal oxide is preferable as the material. Examples of the transition metal oxide include a lithium composite oxide containing at least one transition metal such as V, Mn, Fe, Co, and Ni. Among the above-mentioned lithium composite oxides, a lithium composite oxide having an α-NaFeO ₂ type structure, such as lithium nickel oxide and lithium cobalt oxide, and a lithium complex having a spinel structure, such as lithium manganese spinel, because they have a high average discharge potential. Oxides are more preferred. The lithium composite oxide may contain various metal elements, and composite lithium nickel oxide is more preferable.

Furthermore, the number of moles of at least one metal element selected from the group consisting of Ti, Zr, Ce, Y, V, Cr, Mn, Fe, Co, Cu, Ag, Mg, Al, Ga, In and Sn, and When the composite lithium nickelate containing the metal element is used such that the ratio of the at least one metal element is 0.1 to 20 mol% with respect to the sum of the number of moles of Ni in lithium nickelate, It is even more preferable because it has excellent cycle characteristics when used in a high capacity. Above all, an active material containing Al or Mn and having a Ni ratio of 85% or more, and more preferably 90% or more is used in a high capacity non-aqueous electrolyte secondary battery including a positive electrode plate containing the active material. Is particularly preferable because it has excellent cycle characteristics.

Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and organic polymer compound fired bodies. Only one type of the conductive agent may be used, or two or more types may be used in combination, for example, artificial graphite and carbon black may be mixed and used.

Examples of the binder include polyvinylidene fluoride, vinylidene fluoride copolymer, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. Thermoplastics such as ethylene-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, thermoplastic polyimide, polyethylene and polypropylene Examples include resins, acrylic resins, and styrene-butadiene rubber. The binder also has a function as a thickener.

As a method for obtaining the positive electrode mixture, for example, a method of pressurizing a positive electrode active material, a conductive agent and a binder on a positive electrode current collector to obtain a positive electrode mixture; a positive electrode active material using a suitable organic solvent, a conductive material A method of forming a positive electrode mixture by forming the paste and the binder into a paste; and the like.

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 easily processed into a thin film and is inexpensive.

As a method for producing a sheet-shaped positive electrode plate, that is, a method of supporting a positive electrode mixture on a positive electrode current collector, for example, a positive electrode active material serving as a positive electrode mixture, a conductive agent, and a binder are provided on the positive electrode current collector. Pressure molding method: A positive electrode active material, a conductive agent and a binder are made into a paste using an appropriate organic solvent to obtain a positive electrode mixture, and then the positive electrode mixture is applied to a positive electrode current collector, A method of applying pressure to the sheet-shaped positive electrode mixture obtained by drying and fixing it to the positive electrode current collector;

The particle size of the positive electrode active material is represented by, for example, the average particle size per volume (D50). The average particle size per volume of the positive electrode active material is usually about 0.1 to 30 μm. The average particle diameter (D50) per volume of the positive electrode active material can be measured using a laser diffraction particle size distribution meter (manufactured by Shimadzu Corporation, trade name: SALD2200).

The aspect ratio (major axis diameter / minor axis diameter) of the positive electrode active material is usually a value of about 1 to 100. The aspect ratio of the positive electrode active material is the length of the minor axis (minor axis) of 100 particles that do not overlap in the thickness direction in a SEM image observed from above the placement surface in a state where the inorganic filler is placed on a plane. It can be measured by a method represented as an average value of the ratio of the diameter) to the length of the major axis (major axis diameter).

The porosity of the positive electrode active material layer is usually about 10 to 80%. The porosity (ε) of the positive electrode active material layer is the density ρ (g / m ³ ) of the positive electrode active material layer, and each of the substances (eg, positive electrode active material, conductive agent, binder, etc.) constituting the positive electrode active material layer. Based on the following formula, from the mass composition (wt%) b ¹ , b ² , ... B ^{n of} the substance and the true density (g / m ³ ) c ¹ , c ² , ... C ⁿ of each of the substances. Can be calculated by Here, as the true density of the substance, a literature value may be used, or a value measured using a pycnometer method may be used.
^{ε = 1- {ρ × (b} 1/100) / c 1 + ρ × (b 2/100) / c 2 + ··· ρ × (b n / 100) / c n} × 100.

The proportion of the positive electrode active material in the positive electrode active material layer is usually 70% by weight or more.

The coating line speed for applying the positive electrode mixture containing the positive electrode active material on the current collector is in the range of 10 to 200 m / min. The coating line speed during coating can be adjusted by appropriately setting the device for coating the positive electrode active material.

[Negative electrode plate]
The negative electrode plate in the non-aqueous electrolyte secondary battery according to the exemplary embodiment of the present invention is obtained by processing the positive electrode plate and the negative electrode plate into a disk shape having a diameter of 15.5 mm, and a concentration of 1 M of LiPF ₆ ethylene carbonate / ethyl methyl. There is no particular limitation as long as the sum of interface barrier energies is 5000 J / mol or more when measured by immersing in a carbonate / diethyl carbonate solution. For example, such a negative electrode plate includes a sheet-shaped negative electrode plate in which a negative electrode active material layer, a negative electrode mixture containing a negative electrode active material, a conductive agent, and a binder is carried on a negative electrode current collector. The negative electrode plate may carry the negative electrode mixture on both surfaces of the negative electrode current collector, or may carry the negative electrode mixture on one surface of the negative electrode current collector.

The sheet-shaped negative electrode plate preferably contains the conductive agent and the binder.

Examples of the negative electrode active material include materials that can be doped / dedoped with lithium ions, lithium metal, lithium alloys, and the like. Specific examples of the material include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and organic polymer compound fired bodies; potential lower than that of the positive electrode plate Chalcogen compounds such as oxides and sulfides for doping and dedoping lithium ions with Al; Al, Pb, Sn, Bi, Si and other metals alloying with them, and cubic crystals capable of intercalating alkali metals Examples thereof include system intermetallic compounds (AlSb, Mg ₂ Si, NiSi ₂ ), lithium nitrogen compounds (Li _{3 −x} M _x N (M: transition metal)), and the like. Among the negative electrode active materials, those having graphite are preferable because they have high potential flatness and can obtain a large energy density when combined with the positive electrode plate because of low average discharge potential, and thus, those containing graphite are preferable, such as natural graphite and artificial graphite. The carbonaceous material containing the graphite material as a main component is more preferable. The negative electrode active material may be a mixture of graphite and silicon, and the negative electrode active material having a ratio of Si to C constituting the graphite of 5% or more is preferable, and the negative electrode active material having 10% or more is preferable. More preferable.

As a method of obtaining the negative electrode mixture, for example, a method of pressing the negative electrode active material on the negative electrode current collector to obtain the negative electrode mixture; making the negative electrode active material into a paste using an appropriate organic solvent to form the negative electrode mixture. And the like.

Examples of the negative electrode current collector include Cu, Ni, and stainless steel. Particularly, in a lithium ion secondary battery, Cu is more preferable because it is difficult to form an alloy with lithium and is easily processed into a thin film.

As a method for producing a sheet-shaped negative electrode plate, that is, a method of supporting a negative electrode mixture on a negative electrode current collector, for example, a method of press-molding a negative electrode active material to be a negative electrode mixture on the negative electrode current collector; A negative electrode active material is made into a paste using a different organic solvent to obtain a negative electrode mixture, and then the negative electrode mixture is applied to a negative electrode current collector, and the sheet-shaped negative electrode mixture obtained by drying is added. A method of applying pressure to fix to the negative electrode current collector; and the like. The paste preferably contains the conductive agent and the binder.

The average particle size (D50) per volume of the negative electrode active material is usually about 0.1 to 30 μm.

The aspect ratio (major axis diameter / minor axis diameter) of the negative electrode active material is usually a value of about 1 to 10.

The porosity of the negative electrode active material layer is usually about 10 to 60%.

The proportion of the active material in the negative electrode active material layer is usually 70% by weight or more, preferably 80% or more, more preferably 90% or more.

The coating line speed for coating the negative electrode mixture containing the negative electrode active material on the current collector is in the range of 10 to 200 m / min. The coating line speed during coating can be adjusted by appropriately setting the device for coating the negative electrode active material.

The method for determining the particle size, aspect ratio, porosity, proportion occupied in the negative electrode active material layer, and coating roll speed of the negative electrode active material is the same as the method described in [Positive electrode plate].

[Sum of interface barrier energy]
An interfacial barrier when a positive electrode plate and a negative electrode plate according to an embodiment of the present invention are processed into a disk shape having a diameter of 15.5 mm and immersed in an ethylene carbonate / ethyl methyl carbonate / diethyl carbonate solution of LiPF _{6 having} a concentration of 1 M for measurement. The sum of energy is 5000 J / mol or more. The sum of the interface barrier energies is preferably 5100 J / mol or more, more preferably 5200 J / mol or more.

By setting the sum of interface barrier energies to 5000 J / mol or more, the movement of ions and charges on the surface of the active material in the active material layer is made uniform, and as a result, the reactivity of the entire active material layer is appropriate, and Be uniform. It is considered that this suppresses structural changes in the active material layer and deterioration of the active material itself.

On the other hand, when the sum of the interfacial barrier energies is less than 5000 J / mol, the reactivity in the active material layer becomes non-uniform, which causes a local structural change in the active material layer or a partial active material It is considered to cause deterioration (generation of gas, etc.).

For the above reason, by using the combination of the positive electrode plate and the negative electrode plate having a total interface barrier energy of 5000 J / mol or more, the non-aqueous electrolyte secondary battery according to the embodiment of the present invention can be charged after aging. The capacity is improved.

The upper limit of the sum of interface barrier energy is not particularly limited. However, an excessively high sum of interfacial barrier energies is not preferable because it inhibits the movement of ions and charges on the surface of the active material, and as a result, the redox reaction of the active material due to charging and discharging is less likely to occur. As an example, the upper limit of the sum of interface barrier energies is about 15,000 J / mol.

The sum of the interface barrier energies described above is measured and calculated as the sum of the interface barrier energies of the positive electrode active material and the negative electrode active material according to the following procedure.
(1) A positive electrode plate and a negative electrode plate are cut into a disk shape having a diameter of 15 mm. At the same time, the polyolefin porous film is cut into a disk shape having a diameter of 17 mm, which is used as a separator.
(2) Prepare a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) in a volume ratio of 3/5/2. LiPF ₆ is dissolved in the mixed solvent so as to be 1 mol / L to prepare an electrolytic solution.
(3) A negative electrode plate, a separator, a positive electrode plate, a SUS plate (diameter: 15.5 mm, thickness: 0.5 mm) and a wave washer are laminated in this order from the bottom side in a CR2032 type battery case. After that, an electrolytic solution is injected, the lid is closed, and a coin battery is manufactured.
(4) The coin battery thus prepared is placed in a constant temperature bath. A Nyquist plot is measured under the conditions of frequency: 1 MHz to 0.1 Hz and voltage amplitude: 10 mV using an AC impedance device (FRA 1255B, manufactured by Solartron) and a cell test system (1470E). The temperature of the constant temperature bath is 50 ° C, 25 ° C, 5 ° C or -10 ° C.
(5) From the diameter of the semicircular arc (or the arc of a flat circle) of the obtained Nyquist plot, the resistance r ₁ + r ₂ on the interface of the electrode active material of the positive electrode plate and the negative electrode plate at each temperature is obtained. Here, the resistance r ₁ + r ₂ is the sum of the resistance associated with the ion movement of the positive electrode and the negative electrode and the resistance associated with the charge transfer of the positive electrode and the negative electrode. This semi-circular arc may be completely divided into two circular arcs, or may be a flat circle in which two circles overlap each other. The sum of the interface barrier energy of the positive electrode active material and the interface barrier energy of the negative electrode active material is calculated according to the following equations (3) and (4).

k = 1 / (r ₁ + r ₂ ) = Aexp (−Ea / RT) Equation (3)
ln (k) = ln {1 / (r ₁ + r ₂ )} = ln (A) −Ea / RT Formula (4) Ea: Sum of interface barrier energy between the positive electrode active material and the negative electrode active material (J / Mol)
k: transfer constant r ₁ + r ₂ : resistance (Ω)
A: Frequency factor R: Gas constant = 8.314 J / mol / K
T: Temperature of constant temperature bath (K).

Here, the expression (4) is an expression obtained by taking the natural logarithm of both sides of the expression (3). In Expression (4), ln {1 / (r ₁ + r ₂ )} is a linear function of 1 / T. Therefore, Ea / R is obtained from the slope of the approximate straight line obtained by plotting the values of the resistances at the respective temperatures in the equation (4) and obtaining the least squares method from the plot. By substituting the gas constant R into this value, the sum Ea of interface barrier energies can be calculated.

The frequency factor A is a unique value that does not change due to temperature changes. This value is determined depending on the molar concentration of lithium ions in the electrolytic solution bulk and the like. According to the equation (4), the frequency factor A is a value of ln (1 / r ₀ ) when (1 / T) = 0, and can be calculated based on the approximate straight line.

The sum of interface barrier energies can be controlled by, for example, the particle size ratio of the positive electrode active material and the negative electrode active material. The value of the particle size ratio between the positive electrode active material and the negative electrode active material (particle size of the negative electrode active material / particle size of the positive electrode active material) is preferably 6.0 or less. If the value of the particle size ratio of the positive electrode active material and the negative electrode active material is too large, the sum of the interface barrier energies tends to be too small.

[3. Porous layer)
The porous layer in one embodiment of the present invention is a porous layer containing an inorganic filler and a resin, and is an inorganic material on the surface of the porous layer (hereinafter, may be referred to as “porous layer surface”). The aspect ratio of the projected image of the filler is in the range of 1.4 to 4.0, and arbitrary diffraction planes (hkl), (abc) of the porous layer, which are measured by a wide-angle X-ray diffraction method and are orthogonal to each other. Peak intensity: I _(hkl) and I _(abc) satisfy the following equation (1), and the maximum value of the peak intensity ratio calculated by the following equation (2) is in the range of 1.5 to 300. Characterize things.
I _(hkl) > I _(abc) ... (1),
I _(hkl) / I _(abc) (2).

In one embodiment of the present invention, the porous layer may be disposed between the polyolefin porous film and at least one of the positive electrode plate and the negative electrode plate as a member constituting the non-aqueous electrolyte secondary battery. The porous layer may be formed on one side or both sides of the polyolefin porous film. Alternatively, the porous layer may be formed on the active material layer of at least one of the positive electrode plate and the negative electrode plate. Alternatively, the porous layer may be arranged between the polyolefin porous film and at least one of the positive electrode plate and the negative electrode plate so as to be in contact with them. The porous layer disposed between the polyolefin porous film and at least one of the positive electrode plate and the negative electrode plate may be one layer or two or more layers. The porous layer is preferably an insulating porous layer containing a resin.

When the porous layer is laminated on one side of the polyolefin porous film, the porous layer is preferably laminated on the surface of the polyolefin porous film facing the positive electrode plate. More preferably, the porous layer is laminated on the surface in contact with the positive electrode plate.

The above-mentioned “aspect ratio of the projected image of the inorganic filler on the surface of the porous layer” and the above-mentioned “maximum value of the peak intensity ratio calculated by the formula (2)” are both the orientation of the inorganic filler in the porous layer. Is an index representing. Here, FIG. 1 shows a schematic diagram of the state of the inorganic filler in the porous layer when the orientation is high and when the orientation is low. The left diagram of FIG. 1 is a schematic diagram showing the structure of the porous layer containing an inorganic filler when the orientation of the filler is large and the anisotropy is high, and the right diagram of FIG. 1 is the inorganic layer. It is a schematic diagram showing the structure of the said porous layer in case the orientation of a filler is small and anisotropy is low.

The porous layer in one embodiment of the present invention contains an inorganic filler and a resin. The porous layer has a large number of pores inside and has a structure in which these pores are connected, and is a layer through which gas or liquid can pass from one surface to the other surface. Further, when the porous layer in one embodiment of the present invention is used as a member constituting a laminated separator for a non-aqueous electrolyte secondary battery described later, the porous layer is for the non-aqueous electrolyte secondary battery. The outermost layer of the laminated separator can be a layer in contact with the electrode.

The resin used for the porous layer in one embodiment of the present invention is preferably insoluble in the electrolytic solution of the battery and electrochemically stable in the range of use of the battery.

Examples of the resin used for the porous layer include polyolefin; (meth) acrylate resin; fluorine-containing resin; polyamide resin; polyimide resin; polyester resin; rubbers; melting point or glass transition temperature of 180 ° C. or higher. Resins; water-soluble polymers; polycarbonates, polyacetals, polyether ether ketones and the like.

Among the above resins, polyolefin, (meth) acrylate resin, fluorine-containing resin, polyamide resin, polyester resin and water-soluble polymer are preferable.

As the polyolefin, polyethylene, polypropylene, polybutene, ethylene-propylene copolymer and the like are preferable.

Examples of the fluorine-containing resin include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer Coalescence, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trichloroethylene copolymer, vinylidene fluoride-vinyl fluoride copolymer, vinylidene fluoride-hexafluoro Examples thereof include propylene-tetrafluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer and the like, and fluorine-containing rubber having a glass transition temperature of 23 ° C. or lower among the fluorine-containing resins. .

As the polyamide resin, aramid resins such as aromatic polyamide and wholly aromatic polyamide are preferable.

Specific examples of the aramid resin include poly (paraphenylene terephthalamide), poly (metaphenylene isophthalamide), poly (parabenzamide), poly (metabenzamide), poly (4,4′-benzanilide terephthalate). Amide), poly (paraphenylene-4,4′-biphenylenedicarboxylic acid amide), poly (metaphenylene-4,4′-biphenylenedicarboxylic acid amide), poly (paraphenylene-2,6-naphthalenedicarboxylic acid amide), Poly (metaphenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloroparaphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer, metaphenylene terephthalamide / 2 , 6-diclosure Paraphenylene terephthalamide copolymer and the like. Of these, poly (paraphenylene terephthalamide) is more preferable.

As the polyester resin, aromatic polyester such as polyarylate and liquid crystal polyester are preferable.

Examples of rubbers include styrene-butadiene copolymer and its hydride, methacrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, ethylene propylene rubber, polyvinyl acetate and the like. Can be mentioned.

Examples of the resin having a melting point or glass transition temperature of 180 ° C. or higher include polyphenylene ether, polysulfone, polyether sulfone, polyphenylene sulfide, polyetherimide, polyamideimide, and polyetheramide.

Examples of water-soluble polymers include polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, polyacrylamide, polymethacrylic acid and the like.

As the resin used for the porous layer, only one kind may be used, or two or more kinds may be used in combination.

Among the resins, when the porous layer is arranged to face the positive electrode plate, various performances such as rate characteristics and resistance characteristics of the non-aqueous electrolyte secondary battery can be obtained even if oxidative deterioration occurs during battery operation. A fluorine-containing resin is preferable because it can be easily maintained.

The porous layer in one embodiment of the present invention contains an inorganic filler. The lower limit of the content is preferably 50% by weight or more and 70% by weight or more based on the total weight of the filler and the resin constituting the porous layer in the embodiment of the present invention. More preferably, it is more preferably 90% by weight or more. On the other hand, the upper limit of the content of the inorganic filler in the porous layer in the embodiment of the present invention is preferably 99% by weight or less, and more preferably 98% by weight or less. The content of the filler is preferably 50% by weight or more from the viewpoint of heat resistance, and the content of the filler is preferably 99% by weight or less from the viewpoint of adhesion between the fillers. By containing the inorganic filler, the slipperiness and heat resistance of the separator including the porous layer can be improved. The inorganic filler is not particularly limited as long as it is a filler that is stable in a non-aqueous electrolytic solution and is electrochemically stable. From the viewpoint of ensuring the safety of the battery, a filler having a heat resistant temperature of 150 ° C. or higher is preferable.

The inorganic filler is not particularly limited, but is usually an insulating filler. The inorganic filler is preferably an inorganic material containing at least one element selected from the group consisting of aluminum element, zinc element, calcium element, zirconium element, silicon element, magnesium element, barium element, and boron element, and preferably Is an inorganic substance containing an aluminum element. The inorganic filler preferably contains an oxide of the above element.

Specifically, as the inorganic filler, titanium oxide, alumina (Al ₂ O ₃ ), zinc oxide (ZnO), calcium oxide (CaO), zirconia oxide (ZrO ₂ ), silica, magnesia, barium oxide, boron oxide, Examples thereof include mica, wollastonite, attapulgite, and boehmite (alumina monohydrate). As the inorganic filler, one kind of filler may be used alone, or two or more kinds of filler may be used in combination.

The inorganic filler in the porous layer in one embodiment of the present invention preferably contains alumina and a plate-like filler. Examples of the plate-like filler include one or more fillers selected from the group consisting of zinc oxide (ZnO), mica, and boehmite among oxides of the above-mentioned elements.

The volume average particle size of the inorganic filler is preferably in the range of 0.01 μm to 10 μm from the viewpoint of ensuring good adhesiveness and slipperiness, and moldability of the laminate. The lower limit value is more preferably 0.05 μm or more, further preferably 0.1 μm or more. The upper limit value is more preferably 5 μm or less, further preferably 1 μm or less.

The shape of the inorganic filler is arbitrary and is not particularly limited. The shape of the inorganic filler may be a particle shape, for example, a spherical shape; an elliptical shape; a plate shape; a rod shape; an indefinite shape; a fibrous shape; a spherical or columnar single particle such as a peanut shape and / or a tetrapot shape. The shape may be any of the above. From the viewpoint of preventing a short circuit in the battery, the inorganic filler is preferably plate-like particles and / or non-aggregated primary particles. Further, from the viewpoint of ion permeation, the shape of the inorganic filler is such that the particles in the porous material are difficult to be most closely packed, voids are easily formed between the particles, bumps, dents, constrictions, ridges or bulges, and dendritic It is preferable that a single particle is heat-fused such as an indeterminate shape such as a shape, a coral shape, or a tuft shape; a fibrous shape; a peanut shape and / or a tetrapot shape. The shape of the inorganic filler is particularly preferably a shape in which spherical or columnar single particles such as peanut-shaped and / or tetrapot-shaped particles are heat-sealed.

The filler can improve the slipperiness by forming fine irregularities on the surface of the porous layer, but when the filler is plate-like particles and / or primary particles which are not aggregated, the filler is As a result, the unevenness formed on the surface of the porous layer becomes finer, and the adhesiveness between the porous layer and the electrode becomes better.

In the embodiment of the present invention, the oxygen atom mass percentage of the oxide of the element forming the inorganic filler contained in the porous layer is preferably 10% to 50%, and preferably 20% to 50%. Is more preferable. In the present specification, “oxygen atom mass percentage” means a ratio of the mass of oxygen atoms in the oxide to the total mass of the oxide of the element, which is expressed as a percentage. For example, in the case of zinc oxide, since the atomic weight of zinc is 65.4 and the atomic weight of oxygen is 16.0, the molecular weight of zinc oxide (ZnO) is 65.4 + 16.0 = 81.4. The atomic mass percentage is 16.0 / 81.4 × 100 = 20 (%).

If the oxygen atomic mass percentage of the oxide of the element is in the above range, the affinity between the solvent or the dispersion medium in the coating liquid used in the method for producing a porous layer described later and the inorganic filler is preferable. It is possible to maintain a proper distance between the inorganic fillers. As a result, the dispersibility of the coating liquid can be improved, and as a result, the "aspect ratio of the projected image of the inorganic filler on the surface of the porous layer" and the "orientation degree of the porous layer" can be set within appropriate specified ranges. Can be controlled.

The aspect ratio of the inorganic filler itself contained in the porous layer in the embodiment of the present invention is such that, in a state where the inorganic filler is arranged on a plane, in the SEM image observed from vertically above the arrangement surface, the aspect ratio overlaps in the thickness direction. It is expressed as the average value of the ratio of the length of the minor axis (minor axis diameter) to the length of the major axis (minor axis diameter) of 100 particles that are not present. The aspect ratio of the inorganic filler itself is preferably 1 to 10, more preferably 1.1 to 8, and even more preferably 1.2 to 5. By the aspect ratio of the inorganic filler itself is in the above range, when the porous layer in one embodiment of the present invention is formed by the method described below, in the resulting porous layer, the orientation of the filler, The uniformity of the distribution of the filler on the surface of the porous layer can be controlled within a preferable range.

The porous layer in one embodiment of the present invention may contain other components than the above-mentioned inorganic filler and resin. Examples of the other components include surfactants, waxes and binder resins. The content of the other components is preferably 0% by weight to 50% by weight based on the weight of the entire porous layer.

The average film thickness of the porous layer in one embodiment of the present invention is preferably in the range of 0.5 μm to 10 μm per one layer of the porous layer from the viewpoint of ensuring adhesiveness to the electrode and high energy density. More preferably, it is in the range of 1 μm to 5 μm.

The basis weight per unit area of the porous layer can be appropriately determined in consideration of the strength, film thickness, weight and handling property of the porous layer. The basis weight per unit area of the porous layer is preferably 0.5 to 20 g / m ² and more preferably 0.5 to 10 g / m ² per porous layer.

By setting the basis weight per unit area of the porous layer within these numerical ranges, the weight energy density and volume energy density of the non-aqueous electrolyte secondary battery can be increased. When the basis weight of the porous layer exceeds the above range, the non-aqueous electrolyte secondary battery tends to be heavy.

The porosity of the porous layer is preferably 20 to 90% by volume, and more preferably 30 to 80% by volume so that sufficient ion permeability can be obtained. The pore size of the pores of the porous layer is preferably 1.0 μm or less, more preferably 0.5 μm or less. By setting the pore diameters to these sizes, the non-aqueous electrolyte secondary battery can obtain sufficient ion permeability.

[Aspect ratio of projected image of inorganic filler on porous layer surface]
In the porous layer according to the embodiment of the present invention, the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is in the range of 1.4 to 4.0 and is 1.5 to 2.3. It is preferably in the range. Here, for the aspect ratio, a scanning electron microscope (SEM) is used to take an SEM image, which is an electron micrograph of the surface, immediately above the porous layer, that is, from above the vertical direction. It is a value obtained by creating a projected image of the filler and calculating the ratio of the major axis length / minor axis length of the projected image of the inorganic filler. The length of the major axis is also referred to as the major axis diameter, and the length of the minor axis is also referred to as the minor axis diameter. That is, the aspect ratio refers to the shape of the inorganic filler observed when the inorganic filler on the surface of the porous layer is observed from directly above the porous layer.

Note that FIG. 2 shows a schematic diagram of a projected image of the inorganic filler created from the SEM image of the surface of the porous layer described above.

As a specific measuring method of the aspect ratio, for example, a method including the following steps (1) to (4) can be mentioned. The “surface” of the porous layer means the surface of the porous layer that can be observed by SEM from directly above the porous layer.
(1) In a laminated body in which a porous layer is laminated on a substrate, an SEM at an accelerating voltage of 5 kV is used from directly above the porous side of the laminated body by using a field emission scanning electron microscope JSM-7600F manufactured by JEOL Ltd. A step of observing the surface (reflected electron image) to obtain an SEM image.
(2) An OHP film is placed on the SEM image obtained in the step (1), a projection image laid along the contour of the particles of the inorganic filler shown in the SEM image is created, and the projection image is obtained. The process of shooting with a digital still camera.
(3) The photographic data obtained in the step (2) is loaded into a computer, and the filler particles 100 are filled with the image analysis free software IMAGEJ issued by the National Institutes of Health (NIH). Calculating the aspect ratio of each of the pieces. Here, each of the filler particles is approximated to an ellipse one by one, the major axis diameter and the minor axis diameter are calculated, and the value obtained by dividing the major axis diameter by the minor axis diameter is defined as an aspect ratio.
(4) A step of calculating the average value of the aspect ratios of the projected images of the respective particles obtained in the step (3), and using that value as the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer.

The aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is an index showing the uniformity of the distribution of the inorganic filler on the porous layer, especially on the surface thereof. When the aspect ratio is close to 1, the shape and distribution of the constituent material on the surface of the porous layer are uniform, and it is easy to be densely packed. On the other hand, when the aspect ratio is large, the arrangement of the constituent components in the surface structure of the porous layer becomes non-uniform, and as a result, the uniformity of the shape and distribution of the openings of the surface of the porous layer deteriorates.

If the aspect ratio is greater than 4.0, the uniformity of the shape and distribution of the porous layer, especially the surface openings thereof, is excessively reduced, so that a non-aqueous electrolyte secondary electrode incorporating the porous layer is used. It is considered that in the battery, a portion where the capacity of the porous layer to receive the electrolyte solution during the operation of the battery is reduced, and as a result, the rate characteristic of the non-aqueous electrolyte secondary battery is reduced. On the other hand, when the aspect ratio is less than 1.4, the porous layer, in particular, the distribution of the inorganic filler on the surface thereof has an excessively uniform structure, and as a result, the surface opening area of the porous layer is small. In the non-aqueous electrolyte secondary battery incorporating the porous layer, the electrolyte receiving capacity of the porous layer during the operation of the battery decreases, and as a result, the battery rate of the non-aqueous electrolyte secondary battery decreases. It is considered that the characteristics are degraded.

[Orientation of porous layer]
The porous layer according to one embodiment of the present invention has a peak intensity of arbitrary diffraction planes (hkl), (abc) orthogonal to each other in the porous layer measured by a wide-angle X-ray diffraction method: I _(hkl) and I It is preferable that _(abc) satisfies the following formula (1) and the maximum value of the peak intensity ratio calculated by the following formula (2) is in the range of 1.5 to 300, preferably 1.5 to 300. The range of 250 is more preferable.
I _(hkl) > I _(abc) ... (1),
I _(hkl) / I _(abc) (2).

Hereinafter, in this specification, the maximum value of the peak intensity ratio calculated by the above formula (2) is also referred to as “the orientation degree of the porous layer”.

The method for measuring the peak intensities I _(hkl) and I _(abc) and the peak intensity ratio I _(hkl) / I _(abc) is not particularly limited. For example, the following (1) to (3) are used. A method comprising the steps shown can be mentioned.
(1) A step of preparing a measurement sample by cutting a 2 cm square laminate (laminated porous film) obtained by laminating a porous layer on a substrate.
(2) The measurement sample obtained in step (1) is mounted on an Al holder with the porous layer side of the sample as the measurement surface, and an X-ray profile is obtained by a wide-angle X-ray diffraction method (2θ-θ scan method). Measuring step. The device for measuring the X-ray profile and the measurement conditions are not particularly limited. For example, RU-200R (rotating anticathode type) manufactured by Rigaku Denki Co., Ltd. is used as the device, and CuKα rays are used as the X-ray source. The output may be measured at 50 KV-200 mA and a scanning speed of 2 ° / min.
(3) Based on the X-ray profile obtained in step (2), peak intensity I _{(hkl) of} arbitrary diffraction planes (hkl) and (abc) orthogonal to each other in wide-angle X-ray diffraction measurement of the porous layer And I _(abc) satisfy the equation (1), the peak intensity ratio calculated by the equation (2) is calculated, and the maximum value of the peak intensity ratio, that is, the degree of orientation of the porous layer is calculated. Process.

In the calculation of the degree of orientation of the porous layer, it is important to determine both the orientation in the horizontal direction and the orientation in the normal direction with respect to the substrate surface by using the diffractive surfaces orthogonal to each other. is there.

The maximum value of the peak intensity ratio shown by the above formula (2) is an index showing the degree of orientation inside the porous layer. A small peak intensity ratio represented by the formula (2) means that the degree of orientation in the internal structure of the porous layer is low, and a large peak intensity ratio represented by the formula (2) means that It shows that the internal structure of the texture layer has a high degree of orientation.

When the maximum value of the peak intensity ratio represented by the formula (2) is larger than 300, the anisotropy of the internal structure of the porous layer becomes excessively high, and the ion permeation flow channel length inside the porous layer is increased. Therefore, as a result, in the non-aqueous electrolyte secondary battery incorporating the porous layer, the ion permeation resistance of the porous layer increases, and the charge capacity after aging of the non-aqueous electrolyte secondary battery decreases. It is thought that.

On the other hand, when the maximum value of the peak intensity ratio represented by the above formula (2) is less than 1.5, compared to the case where the porous layer having the peak intensity ratio of 1.5 or more is used, In a non-aqueous electrolyte secondary battery incorporating a porous layer, the ions supplied from the electrodes are permeated at high speed. Therefore, the supply of ions from the electrode becomes rate-determining (that is, the ions are depleted on the electrode surface), and the limiting current, which is the battery operating current value condition, becomes small. As a result, it is considered that the battery rate characteristics of the non-aqueous electrolyte secondary battery are deteriorated.

[Method for producing porous layer]
The method for producing the porous layer according to the embodiment of the present invention is not particularly limited, but for example, one of the following steps (1) to (3) may be used on the substrate, A method of forming a porous layer containing the inorganic filler and the resin can be mentioned. In the case of the step (2) and the step (3) shown below, the porous layer can be produced by depositing the resin and then drying it to remove the solvent. The coating liquid in steps (1) to (3) may be in a state in which the inorganic filler is dispersed and the resin is dissolved. The solvent can be said to be a solvent for dissolving the resin and a dispersion medium for dispersing the resin or the inorganic filler.

(1) A step of forming a porous layer by applying a coating liquid containing the inorganic filler and the resin onto a substrate and drying and removing the solvent in the coating liquid.

(2) After applying a coating liquid containing the inorganic filler and the resin on the surface of the base material, the base material is immersed in a deposition solvent that is a poor solvent for the resin, A step of depositing a resin to form a porous layer.

(3) After coating a coating liquid containing the inorganic filler and the resin on the surface of the base material, the liquid property of the coating liquid is made acidic by using a low-boiling organic acid, A step of depositing a resin to form a porous layer.

In addition to the polyolefin porous film described below, other films, a positive electrode plate, a negative electrode plate, and the like can be used as the base material.

Preferably, the solvent does not adversely affect the base material, dissolves the resin uniformly and stably, and disperses the inorganic filler uniformly and stably. Examples of the solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, acetone and water.

As the deposition solvent, for example, isopropyl alcohol or t-butyl alcohol is preferably used.

In the step (3), as the low boiling point organic acid, for example, paratoluenesulfonic acid, acetic acid, etc. can be used.

In addition, as a method of controlling the orientation of the porous layer in one embodiment of the present invention, that is, the “aspect ratio of the projected image of the inorganic filler on the surface of the porous layer” and the “degree of orientation of the porous layer”, As shown, used in the production of the porous layer, the solid content concentration of the coating liquid containing the inorganic filler and the resin, and the coating shear rate when coating the coating liquid on the substrate The adjustment can be mentioned.

A suitable solid content concentration of the coating liquid may vary depending on the type of filler, etc., but generally it is preferably more than 20% by weight and 40% by weight or less. That the solid content concentration is in the above range, the viscosity of the coating liquid is appropriately maintained, and as a result, the “aspect ratio of the projected image of the inorganic filler on the surface of the porous layer” and the “degree of orientation of the porous layer”. Is preferable because it can be controlled within the above-mentioned preferable range.

The coating shear rate at the time of coating the coating liquid on the base material may vary depending on the kind of the filler and the like, but in general, it is preferably 2s ^-1 or more, and 4s ^-1 to 50s ^-1. Is more preferable.

Here, for example, as the inorganic filler, a shape in which spherical or columnar single particles such as peanut-shaped and / or tetrapot-shaped are heat-fused, spherical-shaped, elliptical-shaped, plate-shaped, rod-shaped, or irregular-shaped. When an inorganic filler having the above-mentioned shape is used, if the coating shear rate is increased, a high shearing force is applied to the inorganic filler, so that the anisotropy tends to increase. On the other hand, when the coating shear rate is reduced, the shearing force is not applied to the inorganic filler, so that the inorganic filler tends to be oriented isotropically.

On the other hand, when the inorganic filler is a long fiber diameter inorganic filler such as long wollastonite having a large fiber diameter, when the coating shear rate is increased, the long fibers are entangled with each other, or the long blades of the doctor blade are long fibers. Tend to be in a disoriented orientation due to the trapping of the, and anisotropy tends to be low. On the other hand, when the coating shear rate is reduced, the long fibers do not become entangled with each other and do not get caught on the blade of the doctor blade, so that they tend to be oriented and the anisotropy tends to increase.

[4. Polyolefin porous film]
The non-aqueous electrolyte secondary battery in one embodiment of the present invention may include a polyolefin porous film. Below, a polyolefin porous film may only be called a "porous film." The porous film contains a polyolefin-based resin as a main component and has a large number of pores connected to the inside thereof, so that a gas and a liquid can pass from one surface to the other surface. The porous film alone can serve as a separator for a non-aqueous electrolyte secondary battery. It can also serve as a porous base material in the laminated separator for a non-aqueous electrolyte secondary battery in which the above-mentioned porous layer is laminated.

On at least one surface of the polyolefin porous film, a laminate in which the porous layer is laminated, in the present specification, also referred to as "non-aqueous electrolyte secondary battery laminated separator" or "laminated separator" .. Further, the separator for a non-aqueous electrolyte secondary battery in one embodiment of the present invention may further include other layers such as an adhesive layer, a heat resistant layer, and a protective layer, in addition to the polyolefin porous film.

The proportion of polyolefin in the porous film is 50% by volume or more of the entire porous film, more preferably 90% by volume or more, and further preferably 95% by volume or more. Further, it is more preferable that the polyolefin contains a high molecular weight component having a weight average molecular weight of 5 × 10 ⁵ to 15 × 10 ⁶ . In particular, when the polyolefin contains a high molecular weight component having a weight average molecular weight of 1,000,000 or more, the strength of the separator for a non-aqueous electrolyte secondary battery is improved, which is more preferable.

The polyolefin, which is a thermoplastic resin, is specifically a homopolymer obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene and 1-hexene. Alternatively, a copolymer may be used. Examples of the homopolymer include polyethylene, polypropylene and polybutene. Examples of the copolymer include ethylene-propylene copolymer.

Among these, polyethylene is more preferable because it can block excessive current from flowing at lower temperatures. Note that blocking the flow of this excessive current is also referred to as shutdown. Examples of the polyethylene include low density polyethylene, high density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), and ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more. Among these, ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is more preferable.

The thickness of the porous film is preferably 4 to 40 μm, more preferably 5 to 30 μm, and further preferably 6 to 15 μm.

The basis weight per unit area of the porous film can be appropriately determined in consideration of strength, film thickness, weight and handleability. However, the basis weight is preferably 4 to 20 g / m ² , and preferably 4 to 12 g / m ² so that the weight energy density and the volume energy density of the non-aqueous electrolyte secondary battery can be increased. More preferably, it is more preferably 5 to 10 g / m ² .

The air permeability of the porous film is preferably 30 to 500 sec / 100 mL in Gurley value, and more preferably 50 to 300 sec / 100 mL. When the porous film has the above-mentioned air permeability, sufficient ion permeability can be obtained. The air permeability of the laminated separator for a non-aqueous electrolyte secondary battery in which the above-mentioned porous layer is laminated on the porous film is preferably 30 to 1000 sec / 100 mL in terms of Gurley value, and is 50 to 800 sec / 100 mL. Is more preferable. Since the laminated separator for a non-aqueous electrolyte secondary battery has the above-mentioned air permeability, it is possible to obtain sufficient ion permeability in the non-aqueous electrolyte secondary battery.

The porosity of the porous film is preferably 20 to 80% by volume so as to increase the holding amount of the electrolytic solution and to surely prevent the flow of an excessive current at a lower temperature. It is more preferably 30 to 75% by volume. The pore size of the pores of the porous film is 0.3 μm or less so that sufficient ion permeability can be obtained and particles can be prevented from entering the positive electrode plate and the negative electrode plate. Is preferably 0.14 μm or less, and more preferably 0.14 μm or less.

[Method for producing polyolefin porous film]
The method for producing the polyolefin porous film is not particularly limited. For example, a sheet-shaped polyolefin resin composition is prepared by kneading a polyolefin resin, a pore-forming agent such as an inorganic filler and a plasticizer, and optionally an antioxidant and the like and then extruding the kneaded product. After removing the pore-forming agent from the sheet-shaped polyolefin resin composition with an appropriate solvent, the polyolefin resin composition from which the pore-forming agent has been removed may be stretched to produce a polyolefin porous film. it can.

The above-mentioned inorganic filler is not particularly limited, and examples thereof include inorganic fillers, specifically calcium carbonate and the like. The plasticizer is not particularly limited, and examples thereof include low molecular weight hydrocarbons such as liquid paraffin.

Specifically, a method including the following steps can be mentioned.
(A) a step of kneading an ultrahigh molecular weight polyethylene, a low molecular weight polyethylene having a weight average molecular weight of 10,000 or less, a pore forming agent such as calcium carbonate or a plasticizer, and an antioxidant to obtain a polyolefin resin composition,
(B) a step of rolling the obtained polyolefin resin composition with a pair of rolling rollers and gradually cooling it while pulling it with a take-up roller having a different speed ratio to form a sheet,
(C) a step of removing the pore forming agent from the obtained sheet with a suitable solvent,
(D) A step of stretching the sheet from which the pore forming agent has been removed at an appropriate stretching ratio.

[Method for producing laminated separator for non-aqueous electrolyte secondary battery]
Examples of the method for producing a laminated separator for a non-aqueous electrolyte secondary battery in one embodiment of the present invention include, for example, in the above-mentioned “method for producing a porous layer”, as the base material to which the coating liquid is applied, The method of using a polyolefin porous film can be mentioned.

[5. Non-aqueous electrolyte)
The non-aqueous electrolyte that can be included in the non-aqueous electrolyte secondary battery according to the embodiment of the present invention is not particularly limited as long as it is a non-aqueous electrolyte that is generally used in non-aqueous electrolyte secondary batteries. As the non-aqueous electrolyte, 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 , lower aliphatic carboxylic acid lithium salt, LiAlCl _{4 and the} like. The lithium salt may be used alone or in combination of two or more kinds.

Examples of the organic solvent that constitutes the non-aqueous electrolytic solution include carbonates, ethers, esters, nitriles, amides, carbamates and sulfur-containing compounds, and fluorine-containing compounds introduced into these organic solvents. Fluorine organic solvents and the like can be mentioned. The organic solvent may be used alone or in combination of two or more.

[6. Method for manufacturing non-aqueous electrolyte secondary battery]
Examples of the method for producing the non-aqueous electrolyte secondary battery according to the embodiment of the present invention include the following methods. First, the positive electrode plate, the non-aqueous electrolyte secondary battery laminated separator, and the negative electrode plate are arranged in this order to form a non-aqueous electrolyte secondary battery member. After that, the member for a non-aqueous electrolyte secondary battery is put in a container that will be the casing of the non-aqueous electrolyte secondary battery, and then the inside of the container is filled with the non-aqueous electrolyte solution and then sealed while depressurizing. Thereby, the non-aqueous electrolyte secondary battery according to the embodiment of the present invention can be manufactured.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

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.

[Methods for measuring various physical properties]
Various physical properties of the non-aqueous electrolyte secondary batteries according to the following Production Examples and Comparative Examples were measured by the following methods.

(1) Film thickness (unit: μm)
The thickness of the polyolefin porous film and the porous layer was measured using a high precision digital length measuring machine (VL-50) manufactured by Mitutoyo Corporation. The film thickness of the porous layer was a value obtained by subtracting the film thickness of the part where the porous layer was not formed from the film thickness of the part where the porous layer was formed in each laminate.

(2) Measurement of Aspect Ratio of Projection Image of Inorganic Filler on Surface of Porous Layer From the porous layer side of the laminate comprising the polyolefin porous film and the porous layer produced in Examples and Comparative Examples, from Japan An electron microscope photograph (SEM image) was obtained by observing the SEM surface (backscattered electron image) with an electron emission field emission scanning electron microscope JSM-7600F at an accelerating voltage of 5 kV.

An OHP film was placed on the obtained SEM image to create a projected image laid out along the contours of the particles of the inorganic filler, and the projected image was taken by a digital still camera. The obtained photograph data is imported into a computer, and the aspect ratio of each of 100 particles is calculated using the free image analysis software IMAGEJ issued by the National Institutes of Health (NIH). The average was defined as the aspect ratio of the projected image of the inorganic filler on the surface of the porous layer in the porous layer (hereinafter also referred to as the surface filler aspect ratio). Here, each filler particle was approximated to an ellipse, the major axis diameter and the minor axis diameter were calculated, and the value obtained by dividing the major axis diameter by the minor axis diameter was taken as the aspect ratio per filler.

(3) Measurement of maximum value of peak intensity ratio (I _(hkl) / I _(abc) ) (measurement of orientation degree of porous layer)
A laminate composed of the polyolefin porous film and the porous layer produced in Examples and Comparative Examples was cut into a 2 cm square to obtain a measurement sample. The obtained measurement sample was attached to an Al holder using the porous layer of the sample as a measurement surface, and the X-ray profile was measured by the wide-angle X-ray diffraction method (2θ-θ scan method). RU-200R (rotating anticathode type) manufactured by Rigaku Denki Co., Ltd. was used as an apparatus, CuKα rays were used as an X-ray source, and the output was measured at 50 KV-200 mA and a scan speed of 2 ° / min. Based on the obtained X-ray profile, the peak intensities I _(hkl) and I _{(abc) of} arbitrary diffraction planes (hkl) and (abc) orthogonal to each other in the wide-angle X-ray diffraction measurement of the porous layer are represented by the following formula (1 _). The peak intensity ratio calculated by I _(hkl) / I _(abc) in the case of satisfying ₍₁₎ is calculated, and the maximum value of the peak intensity ratio is calculated.
I _(hkl) > I _(abc) ... (1).

(4) Sum of interface barrier energies The sum of interface barrier energies was measured based on the method described in the item of [sum of interface barrier energies] in [2].

(5) Charge capacity after aging The charge capacity after aging was measured based on the method described in [1].

[Example 1]
[Preparation of porous layer and laminated separator for non-aqueous electrolyte secondary battery]
(Production of polyolefin porous film)
A polyolefin porous film was produced using polyethylene as the polyolefin. Specifically, 70 parts by weight of ultra high molecular weight polyethylene powder (340M, manufactured by Mitsui Chemicals, Inc.) and 30 parts by weight of polyethylene wax having a weight average molecular weight of 1000 (FNP-0115, manufactured by Nippon Seiro Co., Ltd.) are mixed. To obtain mixed polyethylene. With respect to 100 parts by weight of the obtained mixed polyethylene, 0.4 parts by weight of an antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals Co., Ltd.), and an antioxidant (P168, manufactured by Ciba Specialty Chemicals Co., Ltd.) 0. 1 part by weight and 1.3 parts by weight of sodium stearate were added, and further, calcium carbonate having an average particle size of 0.1 μm (manufactured by Maruo Calcium Co., Ltd.) was added so that the ratio of the total volume was 38% by volume. It was This composition as a powder was mixed with a Henschel mixer and then melt-kneaded with a biaxial kneader to obtain a polyethylene resin composition. Then, this polyethylene resin composition was rolled by a pair of rollers whose surface temperature was set to 150 ° C. to prepare a sheet. This sheet was immersed in an aqueous hydrochloric acid solution prepared by mixing 0.5 mol% of a nonionic surfactant in 4 mol / L hydrochloric acid to dissolve and remove calcium carbonate. Subsequently, the polyolefin porous film 1 made of polyethylene was produced by stretching the sheet 6 times at 105 ° C. The polyolefin porous film 1 had a porosity of 53%, a basis weight of 7 g / m ² , and a film thickness of 16 μm.

(Preparation of coating liquid)
As the inorganic filler 1, hexagonal plate-shaped zinc oxide having a mass percentage of oxygen atoms of 20% (manufactured by Sakai Chemical Industry Co., Ltd., trade name: XZ-100F) was used. The particle size of the inorganic filler 1 was D10 = 0.2 μm, D50 = 0.4 μm, and D90 = 2.1 μm. The BET specific surface area per unit area of the inorganic filler 1 was 7.3 m ² / g.

The volume-based particle size distribution of the inorganic filler was calculated by measuring D10, D50, and D90 using a laser diffraction particle size distribution analyzer SALD2200 manufactured by Shimadzu Corporation. D50, D10, and D90 are the particle diameter at which the cumulative distribution by volume is 50%, the particle diameter at 10%, and the particle diameter at 90%, respectively. The specific surface area of the inorganic filler was calculated from the BET method by measuring the adsorption-desorption isotherm with nitrogen using a constant volume method. Specifically, in Examples and Comparative Examples, the BET specific surface area per unit area was measured using BELSORP-mini (manufactured by Microtrac Bell Co., Ltd.). The adsorption-desorption isotherm by nitrogen of the filler that had been vacuum dried at a pretreatment temperature of 80 ° C. for 8 hours was measured by the constant volume method, and calculated by the BET method. Various conditions in the constant volume method are as follows: adsorption temperature; 77 K, adsorbate; nitrogen, saturated vapor pressure; measured value, adsorbate cross section; 0.162 nm ² , equilibrium waiting time (adsorption equilibrium state (adsorption Waiting time after the pressure change during desorption reaches a value below a predetermined value)): 500 sec. The pore volume was calculated by the MP method and the BJH method, and the pretreatment device used was BELPREP-vacII (manufactured by Microtrac Bell Co., Ltd.).

As a binder, a vinylidene fluoride-hexafluoropropylene copolymer (manufactured by Arkema Ltd .; trade name “KYNAR2801”) was used.

Inorganic filler 1, vinylidene fluoride-hexafluoropropylene copolymer and solvent (N-methyl-2-pyrrolidinone manufactured by Kanto Chemical Co., Inc.) were mixed in the following proportions. That is, 10 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer was mixed with 90 parts by weight of inorganic filler, and the solid content (inorganic filler 1 and vinylidene fluoride-hexafluoropropylene copolymer weight) in the resulting mixed liquid was mixed. Solvents were mixed so that the concentration of (combined) was 37% by weight. The obtained mixed liquid was stirred and mixed with a thin film swivel type high speed mixer (Filmiku (registered trademark) manufactured by Primix Co., Ltd.) to obtain a uniform coating liquid 1.

(Preparation of porous layer and laminated separator for non-aqueous electrolyte secondary battery)
The obtained coating liquid 1 was applied to one surface of the polyolefin porous film 1 by a doctor blade method at a coating shear rate of 3.9 s ⁻¹ to form a coating film. Then, the coating film was dried at 65 ° C. for 20 minutes to form a porous layer. In this way, a laminated separator 1 for non-aqueous electrolyte secondary battery was obtained. The basis weight of the porous layer was 7 g / m ² and the thickness was 4 μm. The surface filler aspect ratio of the non-aqueous electrolyte secondary battery multilayer separator 1 was 1.43, and the degree of orientation of the porous layer was 1.6 (I (002) / I (110)).

[Preparation of non-aqueous electrolyte secondary battery]
(Positive plate)
The positive electrode mixture (LiNi _0.5 Mn _0.3 Co _0.2 O ₂ / conductive agent / PVDF (weight ratio: 92/5/3)) was laminated on one surface of the positive electrode current collector (aluminum foil). A positive electrode plate was obtained. The volume-based average particle diameter (D50) of LiNi _0.5 Mn _0.3 Co _0.2 O ₂ was 5 μm. The positive electrode plate is cut so that the size of the portion where the positive electrode active material layer is laminated is 45 mm × 30 mm, and the outer periphery thereof has a width of 13 mm where the positive electrode active material layer is not laminated. Got 1. The thickness of the positive electrode active material layer of the positive electrode plate 1 was 38 μm.

(Negative electrode plate)
A negative electrode plate in which a negative electrode mixture (natural graphite / styrene-1,3-butadiene copolymer / sodium carboxymethyl cellulose (weight ratio 98/1/1)) is laminated on one side of a negative electrode current collector (copper foil) Obtained. The volume-based average particle diameter (D50) of the natural graphite was 15 μm. The negative electrode plate is cut so that the size of the portion where the negative electrode active material layer is laminated is 50 mm × 35 mm, and the outer periphery thereof has a width of 13 mm where the negative electrode active material layer is not laminated. Got 1. The thickness of the negative electrode active material layer of the negative electrode plate 1 was 38 μm.

(Assembly of non-aqueous electrolyte secondary battery)
Using the positive electrode plate 1, the negative electrode plate 1 and the non-aqueous electrolyte secondary battery laminated separator 1, a non-aqueous electrolyte secondary battery was manufactured by the following method.

In the laminate pouch, the positive electrode plate 1, the non-aqueous electrolyte secondary battery laminated separator 1 and the negative electrode plate 1 were laminated in this order to obtain a non-aqueous electrolyte secondary battery member 1. At this time, the positive electrode plate 1 and the negative electrode plate 1 were arranged such that the entire main surface of the positive electrode active material layer of the positive electrode plate 1 was included in the range of the main surface of the negative electrode active material layer of the negative electrode plate 1. That is, the positive electrode plate 1 and the negative electrode plate 1 were arranged so that the entire main surface of the positive electrode active material layer of the positive electrode plate 1 overlaps the main surface of the negative electrode active material layer of the negative electrode plate 1. The surface of the non-aqueous electrolyte secondary battery laminated separator 1 on the side of the porous layer was opposed to the positive electrode active material layer of the positive electrode plate 1.

Then, the non-aqueous electrolyte secondary battery member 1 was placed in a previously prepared bag in which an aluminum layer and a heat seal layer were laminated, and 0.23 mL of the non-aqueous electrolyte solution was further placed in this bag. Injected. The non-aqueous electrolyte is prepared by dissolving LiPF _{6 in a} mixed solvent prepared by mixing ethylene carbonate, ethylmethyl carbonate and diethyl carbonate in a volume ratio of 3: 5: 2 so as to have a concentration of 1 mol / L. Prepared. Then, the inside of the bag was depressurized and the bag was heat-sealed to manufacture the non-aqueous electrolyte secondary battery 1.

After that, the battery characteristics of the non-aqueous electrolyte secondary battery 1 were measured by the method described above. The results are shown in Table 1.

[Example 2]
[Preparation of non-aqueous electrolyte secondary battery]
A laminated separator 2 for a non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 1 except for the following changes.
As the raw material of the inorganic filler 2, spherical alumina (Sumitomo Chemical Co., Ltd., trade name AA03) and mica (Wako Pure Chemical Industries, Ltd., trade name: non-swelling synthetic mica, tabular particles) were used. Inorganic filler 2 was prepared by mixing 50 parts by weight of each of these raw materials in a mortar (oxygen atom mass percentage 45%). The particle size of the inorganic filler 2 was D10 = 0.5 μm, D50 = 4.2 μm, and D90 = 11.5 μm. The BET specific surface area per unit area of the inorganic filler 2 was 4.5 m ² / g.
10 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer was mixed with 90 parts by weight of inorganic filler 2, and the solid content (inorganic filler 2 and vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed liquid was mixed. Coating solution 2 was prepared by mixing the solvents so that the concentration of (combined) was 30% by weight.
The coating liquid 2 was applied to one side of the polyolefin porous film 1 at a coating shear rate of 7.9 s ^-1 .

The surface filler aspect ratio of the non-aqueous electrolyte secondary battery laminated separator 2 was 1.45, and the degree of orientation of the porous layer was 224 (I (002) / I (040)).

A non-aqueous electrolyte secondary battery 2 was produced in the same manner as in Example 1, using the non-aqueous electrolyte secondary battery laminated separator 2 instead of the non-aqueous electrolyte secondary battery laminated separator 1. Then, the battery characteristics of the non-aqueous electrolyte secondary battery 2 were measured by the method described above. The results are shown in Table 1.

[Example 3]
[Preparation of non-aqueous electrolyte secondary battery]
A laminated separator 3 for a non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 1 except for the following changes.
As the inorganic filler 3, wollastonite (Hayashi Kasei Co., Ltd., trade name: Wollastonite VM-8N, fibrous particles) having an oxygen atomic mass percentage of 42% was used. The particle size of the inorganic filler 3 was D10 = 2.4 μm, D50 = 10.6 μm, and D90 = 25.3 μm. The BET specific surface area per unit area of the inorganic filler 3 was 1.3 m ² / g.
10 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer are mixed with 90 parts by weight of inorganic filler 3, and the solid content (inorganic filler 3 and vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed liquid is mixed. The coating liquid 3 was prepared by mixing the solvents so that the concentration of the (combined) was 40% by weight.
The coating liquid 3 was applied to one surface of the polyolefin porous film 1 at a coating shear rate of 7.9 s ^-1 .

The surface filler aspect ratio of the non-aqueous electrolyte secondary battery laminated separator 3 was 2.48, and the degree of orientation of the porous layer was 99 (I (202) / I (040)).

A non-aqueous electrolyte secondary battery 3 was produced in the same manner as in Example 1 using the non-aqueous electrolyte secondary battery laminated separator 3 instead of the non-aqueous electrolyte secondary battery laminated separator 1. After that, the battery characteristics of the non-aqueous electrolyte secondary battery 3 were measured by the method described above. The results are shown in Table 1.

[Example 4]
[Preparation of laminated separator for non-aqueous electrolyte secondary battery]
A laminated separator 4 for a non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 1 except for the following changes.
As the raw material for the inorganic filler 4, α-alumina (Sumitomo Chemical Co., Ltd., trade name: AKP3000) and hexagonal plate-shaped zinc oxide (Sakai Chemical Industry Co., Ltd., trade name: XZ-1000F) were used. Then, a mixture (oxygen atom mass percentage 47%) obtained by mixing 99 parts by weight of α-alumina, 1 part by weight of hexagonal plate-shaped zinc oxide in a mortar was used as the inorganic filler 4. The particle diameter of the inorganic filler 4 was D10 = 0.4 μm, D50 = 0.8 μm, and D90 = 2.2 μm. The BET specific surface area per unit area of the inorganic filler 4 was 4.5 m ² / g.
In addition to mixing 90 parts by weight of inorganic filler 4 with 10 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer, the solid content (inorganic filler 4 and vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed liquid is mixed. The coating liquid 4 was prepared by mixing the solvents so that the concentration of the (combined) was 40% by weight.
The coating liquid 4 was applied to one side of the polyolefin porous film 1 at a coating shear rate of 39.4 s ^-1 .

The surface filler aspect ratio of the non-aqueous electrolyte secondary battery laminated separator 4 was 1.73, and the degree of orientation of the porous layer was 4.0 (I (300) / I (006)).

[Preparation of non-aqueous electrolyte secondary battery]
(Positive plate)
A positive electrode plate was obtained in which the positive electrode mixture (LiCoO ₂ / conductive agent / PVDF (weight ratio: 100/5/3)) was laminated on one surface of the positive electrode current collector (aluminum foil). The positive electrode plate is cut so that the size of the portion where the positive electrode active material layer is laminated is 45 mm × 30 mm, and the outer periphery thereof has a width of 13 mm where the positive electrode active material layer is not laminated. Got 2. The thickness of the positive electrode active material layer of the positive electrode plate 2 was 38 μm.

(Assembly of non-aqueous electrolyte secondary battery)
The non-aqueous electrolyte secondary battery laminated separator 4 was used in place of the non-aqueous electrolyte secondary battery laminated separator 1 and the positive electrode plate 2 was used in place of the positive electrode plate 1, and the non-aqueous electrolyte secondary battery laminated separator 1 was prepared in the same manner as in Example 1. A water electrolyte secondary battery 4 was produced. After that, the battery characteristics of the non-aqueous electrolyte secondary battery 4 were measured by the method described above. The results are shown in Table 1.

[Comparative Example 1]
[Preparation of non-aqueous electrolyte secondary battery]
A laminated separator 5 for a non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 1 except for the following changes.
As the inorganic filler 5, attapulgite (manufactured by Hayashi Kasei Co., Ltd., trade name: ATTAGEL # 50) having an oxygen atomic mass percentage of 48% was used. The particle size of the inorganic filler 5 was D10 = 0.4 μm, D50 = 2.0 μm, and D90 = 3.3 μm. The BET specific surface area per unit area of the inorganic filler 5 was 235.0 m ² / g.
10 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer are mixed with 90 parts by weight of inorganic filler 5, and the solid content (inorganic filler 5 and vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed liquid is mixed. Coating solution 5 was prepared by mixing the solvents so that the concentration of the (combined) was 17% by weight.
The coating liquid 5 was applied to one surface of the polyolefin porous film 1 at a coating shear rate of 1.3 s ⁻¹ .

The surface filler aspect ratio of the non-aqueous electrolyte secondary battery laminated separator 5 was 4.27, and the degree of orientation of the porous layer was 2.0 (I (200) / I (040)).

A non-aqueous electrolyte secondary battery 5 was produced in the same manner as in Example 1 using the non-aqueous electrolyte secondary battery laminated separator 5 instead of the non-aqueous electrolyte secondary battery laminated separator 1. After that, the battery characteristics of the non-aqueous electrolyte secondary battery 5 were measured by the method described above. The results are shown in Table 1.

[Comparative Example 2]
[Preparation of non-aqueous electrolyte secondary battery]
A laminated separator 6 for a non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 1 except for the following changes.
As the inorganic filler 6, mica (manufactured by Wako Pure Chemical Industries, trade name: non-swelling mica) having an oxygen atom mass percentage of 44% was used. The particle size of the inorganic filler 6 was D10 = 0.5 μm, D50 = 5.5 μm, and D90 = 12.1 μm. The BET specific surface area per unit area of the inorganic filler 6 was 3.2 m ² / g.
10 parts by weight of vinylidene fluoride-hexafluoropropylene copolymer are mixed with 90 parts by weight of inorganic filler 6, and the solid content (inorganic filler 6 and vinylidene fluoride-hexafluoropropylene copolymer) in the resulting mixed liquid is mixed. A coating liquid 6 was prepared by mixing a solvent so that the concentration of the (combined) was 20% by weight.
The coating liquid 6 was applied to one surface of the polyolefin porous film 1 at a coating shear rate of 0.4 ^-1 .

The surface filler aspect ratio of the non-aqueous electrolyte secondary battery laminated separator 6 was 1.67, and the degree of orientation of the porous layer was 367 (I (002) / I (040)).

A non-aqueous electrolyte secondary battery 6 was produced in the same manner as in Example 1 using the non-aqueous electrolyte secondary battery laminated separator 6 instead of the non-aqueous electrolyte secondary battery laminated separator 1. After that, the battery characteristics of the non-aqueous electrolyte secondary battery 6 were measured by the method described above. The results are shown in Table 1.

[Comparative Example 3]
[Preparation of non-aqueous electrolyte secondary battery]
(Negative electrode plate)
A negative electrode plate was obtained in which a negative electrode mixture (artificial spherulite graphite / conductive agent / PVDF (weight ratio 85/15 / 7.5)) was laminated on one surface of a negative electrode current collector (copper foil). The negative electrode plate is cut so that the size of the portion where the negative electrode active material layer is laminated is 50 mm × 35 mm, and the outer periphery thereof has a width of 13 mm where the negative electrode active material layer is not laminated. Got 2. The thickness of the negative electrode active material layer of the negative electrode plate 2 was 36 μm.

(Assembly of non-aqueous electrolyte secondary battery)
A non-aqueous electrolyte secondary battery laminated separator 4 was used in place of the non-aqueous electrolyte secondary battery laminated separator 1, and a negative electrode plate 2 was used in place of the negative electrode plate 1 in the same manner as in Example 1. A water electrolyte secondary battery 7 was produced. After that, the battery characteristics of the non-aqueous electrolyte secondary battery 7 were measured by the method described above. The results are shown in Table 1.

(result)
From Table 1, a non-aqueous electrolyte secondary satisfying three requirements: (i) surface filler aspect ratio requirement, (ii) porous layer orientation degree requirement, and (iii) interfacial barrier energy sum requirement. In the battery, the charge capacity after aging was improved. On the other hand, in a non-aqueous electrolytic secondary battery that did not satisfy any of the above conditions, no improvement in charge capacity was observed after aging.

[Reference example: Control of interface barrier energy]
A positive electrode plate and a negative electrode plate in which the particle size ratio of the positive electrode active material and the negative electrode active material was adjusted were prepared, and the sum of interface barrier energies was measured. Specifically, a positive electrode plate and a negative electrode plate having the same composition as in Example 1 but with the particle diameter of the active material changed as follows were produced. Table 2 shows the results of measuring the interface barrier energy using the positive electrode plate and the negative electrode plate.

(result)
The positive electrode plate and the negative electrode plate in Example 1 have the same composition as the positive electrode plate and the negative electrode plate in the reference example. However, the particle size ratio of the positive electrode active material and the negative electrode active material ((the value of the particle size of the negative electrode active material / the particle size of the positive electrode active material)) was 3 in Example 1, while in the reference example. It was 24.7. The sum of the interface barrier energies was 9069 J / mol in Example 1, whereas it was only 4228 J / mol in Reference Example.

From these experimental results, it was shown that adjusting the particle size ratio of the positive electrode active material and the negative electrode active material is effective for controlling the sum of the interfacial barrier energies. Of course, the control of the sum of the interface barrier energies can be performed by other methods.

The non-aqueous electrolyte secondary battery according to one aspect of the present invention has improved charge capacity after aging. Therefore, it can be suitably used as a battery used in a personal computer, a mobile phone, a personal digital assistant, and the like, and a vehicle-mounted battery.

Claims

A porous layer containing an inorganic filler and a resin, a positive electrode plate, and a negative electrode plate,
The interfacial barrier energy of the positive electrode active material when the positive electrode plate and the negative electrode plate are processed into a disk shape having a diameter of 15.5 mm, and immersed in an ethylene carbonate / ethyl methyl carbonate / diethyl carbonate solution of LiPF 6 having a concentration of 1 M to measure. And the interfacial barrier energy of the negative electrode active material is 5000 J / mol or more,
The aspect ratio of the projected image of the inorganic filler on the surface of the porous layer is in the range of 1.4 to 4.0,
Peak strengths of arbitrary diffraction planes (hkl) and (abc) orthogonal to each other, measured by a wide-angle X-ray diffraction method, of the porous layer: I (hkl) and I (abc) satisfy the following formula (1). ,
A non-aqueous electrolyte secondary battery in which the maximum value of the peak intensity ratio calculated by the following formula (2) is in the range of 1.5 to 300.
I (hkl) > I (abc)・・・ (1)
I (hkl) / I (abc)・・・ (2)
The non-aqueous electrolyte secondary battery according to claim 1, wherein the porous layer is laminated on one side or both sides of a polyolefin porous film.
The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the positive electrode plate contains a transition metal, and the negative electrode plate contains graphite.
The resin contained in the porous layer is one or more selected from the group consisting of polyolefin, (meth) acrylate resin, fluorine-containing resin, polyamide resin, polyester resin and water-soluble polymer. 4. The non-aqueous electrolyte secondary battery according to any one of 1 to 3.
The non-aqueous electrolyte secondary battery according to claim 4, wherein the polyamide resin is an aramid resin.