JP2018125272A - Lithium ion battery separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion battery separator which can be fabricated without using a complicated process, which is superior in the property of absorbing an electrolyte solution, and which can increase the efficiency of liquid injection when using the separator to fabricate a battery.SOLUTION: A lithium ion battery separator has grooves in its surface and comprises a nonwoven fabric base material, and an inorganic particle layer deposited on the nonwoven fabric base material. The inorganic particle layer has grooves in the surface thereof. It is preferable that the angle between the grooves and a liquid injection direction when injecting an electrolyte solution into a lithium ion battery assembled by use of the lithium ion battery separator is -70° to +70°.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lithium ion battery separator.

  Lithium ion batteries (hereinafter sometimes abbreviated as “batteries”) use lithium ion battery separators (hereinafter sometimes abbreviated as “separators”) in order to prevent contact between the electrodes.

  Lithium-ion batteries have an assembly of a wound body in which a positive electrode / negative electrode and a separator are stacked and a laminated body in which a positive electrode / negative electrode and a separator are laminated, inserted into an exterior material, and the opening of the exterior material is closed and electrolysis is performed. Manufactured by a procedure of filling the liquid from the liquid inlet and sealing the liquid inlet.

  In the injection of the electrolytic solution, the electrolytic solution must penetrate the entire assembly including the positive electrode / negative electrode and the separator. However, the gap between the positive electrode / negative electrode and the separator is very narrow, and it takes time to sufficiently infiltrate.

  In order to solve this problem, there are other methods for filling the electrolyte solution, such as a solution injection method that uses natural fall, and a solution injection method that shortens the solution injection time using centrifugal force, reduced pressure, or vacuum. Efficiency is required.

  In Patent Document 1, the separator surface is roughened to improve the permeability of the electrolytic solution. However, the roughening of the separator surface is performed by a rubbing process, and there is a problem that the process becomes complicated. It was.

JP-A-6-333550

  An object of the present invention relates to a lithium ion battery separator, which can be manufactured without using complicated processes, has excellent liquid absorption of an electrolytic solution, and has a liquid injection property when manufacturing a battery using the separator. The object is to provide a separator capable of increasing efficiency.

  The above problems have been solved by the following means.

(1) A lithium ion battery separator having grooves on the surface, wherein the separator includes a nonwoven fabric substrate and an inorganic particle layer applied to the nonwoven fabric substrate, and has grooves on the surface of the inorganic particle layer. Lithium ion battery separator.

(2) The lithium ion according to (1) above, wherein the angle between the injection direction and the groove when injecting the electrolyte into the lithium ion battery assembled using the lithium ion battery separator is -70 ° to + 70 ° Battery separator.

(3) The lithium ion battery separator according to (1) or (2), wherein the inorganic particle layer is provided only on one side of the nonwoven fabric substrate.

(4) The lithium ion battery separator according to (1) or (2), wherein the inorganic particle layer is provided on both surfaces of the nonwoven fabric substrate.

(5) The lithium ion battery separator according to any one of (1) to (4), wherein the inorganic particle layer includes inorganic particles having an average particle size of 0.5 μm or more and 4.0 μm or less.

(6) The lithium ion battery separator according to any one of (1) to (4), wherein the inorganic particle layer includes inorganic particles having an average particle diameter of 0.5 μm or more and less than 3.0 μm.

(7) Inorganic particle layer A in which the inorganic particle layer contains inorganic particles having an average particle size of 2.0 μm or more and 4.0 μm or less, and inorganic particle layer B containing inorganic particles having an average particle size of 0.5 μm or more and less than 2.0 μm The lithium ion battery separator according to any one of the above (1) to (4).

(8) The lithium ion battery separator according to (7), wherein the inorganic particle layer A and the inorganic particle layer B are laminated in this order on one surface of the nonwoven fabric substrate.

(9) The lithium ion battery separator according to the above (7), which has an inorganic particle layer A provided on one side of the nonwoven fabric base and an inorganic particle layer B provided on the other side.

(10) The lithium ion battery separator according to any one of (1) to (9), wherein the inorganic particle layer includes one or more inorganic particles selected from the group consisting of an aluminum compound and a magnesium compound.

(11) The lithium ion battery separator according to any one of (1) to (9), wherein the inorganic particle layer includes a magnesium compound.

(12) The lithium ion battery separator according to (10) or (11), wherein the magnesium compound is magnesium hydroxide.

(13) The lithium ion battery separator according to any one of (1) to (12), wherein the nonwoven fabric substrate includes fibrillated heat-resistant fibers.

(14) The lithium ion battery separator according to (13), wherein the modified freeness of the fibrillated heat resistant fiber is 300 ml or less.
Modified freeness: A value measured in accordance with JIS P8121-2 except that an 80-mesh wire mesh having a wire diameter of 0.14 mm and an aperture of 0.18 mm was used as a sieve plate, and the sample concentration was 0.1%.

(15) The lithium ion battery separator according to (13) or (14), wherein the fibrillated heat-resistant fiber is a fibrillated wholly aromatic polyamide fiber.

  Advantageous Effects of Invention According to the present invention, a separator having excellent electrolyte absorbability can be obtained without using a complicated process, and the efficiency of liquid injection can be improved when a battery is manufactured using the separator. Is obtained.

It is the schematic for demonstrating the angle of the liquid injection direction in a separator, and a groove | channel. It is a schematic sectional drawing which shows an example of the separator which has a groove | channel on the surface of an inorganic particle layer.

  The separator of the present invention includes a nonwoven fabric substrate and an inorganic particle layer formed on the nonwoven fabric substrate, and has a groove on the surface of the inorganic particle layer.

  The inorganic particle layer applied to the nonwoven fabric substrate is obtained by applying a liquid containing inorganic particles (hereinafter sometimes referred to as “coating solution”) to the surface of the nonwoven fabric substrate and drying it. The inorganic particle layer may be provided only on one side of the nonwoven fabric base material, or may be provided on both surfaces of the nonwoven fabric base material. The inorganic particle layer may be a single layer or a multilayer. In the case of a multilayer, the inorganic particles contained in each layer may be the same, or the type, average particle diameter, shape, and the like may be different.

  As inorganic particles, silica; alumina such as α-alumina, β-alumina and γ-alumina; alumina hydrate such as boehmite; aluminum hydroxide; magnesium compound such as magnesium hydroxide and magnesium oxide; calcium oxide and the like are used. be able to. Among these, one or more inorganic particles selected from the group consisting of aluminum compounds such as alumina, hydrated alumina, aluminum hydroxide, and magnesium compounds are high in stability to the electrolyte used in the lithium ion battery. It is preferable. Moreover, a magnesium compound is more preferable at the point which can suppress reaction with electrolyte solution, and liquid absorption property also becomes efficient, and magnesium hydroxide is still more preferable.

  In order to obtain the effect of improving the liquid absorbency of the electrolytic solution by capillarity, the inorganic particle layer preferably contains inorganic particles having an average particle size of 0.5 μm or more and 4.0 μm or less. When the average particle diameter of the inorganic particles is 0.5 μm or more and 4.0 μm or less, the liquid absorbency is easily improved. The average particle diameter of the inorganic particles is more preferably 3.7 μm or less, further preferably 3.5 μm or less, and particularly preferably less than 3.0 μm.

  The inorganic particle layer includes an inorganic particle layer A containing inorganic particles having an average particle size of 2.0 μm or more and 4.0 μm or less, and an inorganic particle layer B containing inorganic particles having an average particle size of 0.5 μm or more and less than 2.0 μm. It is more preferable to have. As a separator having the inorganic particle layer A and the inorganic particle layer B, a separator (8) having a configuration in which the inorganic particle layer A and the inorganic particle layer B are laminated in this order on one surface of the nonwoven fabric substrate, A separator having a configuration in which an inorganic particle layer B and an inorganic particle layer A are laminated in this order on one side of the substrate, an inorganic particle layer A provided on one side of a nonwoven fabric substrate, and provided on the other side And a separator (9) having an inorganic particle layer B. Among these, separators (8) and (9) are more preferable.

  In order to obtain the effect of improving the liquid absorbency of the electrolytic solution by capillary action, the average particle size of the inorganic particles in the inorganic particle layer A is more preferably 2.2 μm or more and 3.7 μm or less, and still more preferably It is 2.5 μm or more and 3.5 μm or less. The average particle diameter of the inorganic particles in the inorganic particle layer B is more preferably 0.5 μm or more and 1.5 μm or less, further preferably 0.5 μm or more and 1.3 μm or less, and particularly preferably 0.5 μm or more. 1.0 μm or less.

  The inorganic particle layer and the coating liquid can contain a binder resin in addition to the inorganic particles. As the binder resin, various synthetic resins such as styrene-butadiene copolymer resin, acrylic ester resin, methacrylic ester resin, and fluororesin such as polyvinylidene fluoride can be used.

  The average particle diameter in the present invention is a volume-based median diameter (D50) obtained from a particle size distribution measurement by a laser diffraction method.

  In addition to the inorganic particles and the binder resin, the inorganic particle layer and the coating liquid include a dispersant such as polyacrylic acid and sodium carboxymethyl cellulose; a thickener such as hydroxyethyl cellulose, sodium carboxymethyl cellulose, and polyethylene oxide; a wetting agent. An additive such as an antiseptic and an antifoaming agent can be blended as necessary.

In the present invention, the absolute dry coating amount of the inorganic particle layer is preferably 5 g / m ² or more and 30 g / m ² or less, more preferably 10 g / m ² or more and 20 g / m ² or less. When the absolute dry coating amount is 5 g / m ² or more, the surface of the nonwoven fabric substrate is easily covered with the inorganic particle layer, and internal short circuit is easily prevented. Moreover, when the absolute dry coating amount is 30 g / m ² or less, an increase in internal resistance can be suppressed.

The absolute dry coating amount of the inorganic particle layer A in the separator having the inorganic particle layer A and the inorganic particle layer B is preferably 2.0 g / m ² or more and 10.0 g / m ² or less, more preferably 2. It is 5 g / m ² or more and 8.0 g / m ² or less, and more preferably 3.0 g / m ² or more and 6.0 g / m ² or less. The absolute dry coating amount of the inorganic particle layer B in the separator having the inorganic particle layer A and the inorganic particle layer B is preferably 2.5 g / m ² or more and 10.0 g / m ² or less, more preferably 3. It is 0 g / m ² or more and 8.5 g / m ² or less, and more preferably 3.5 g / m ² or more and 7.0 g / m ² or less. When the dry coating amount of the inorganic particle layer A is 2.0 g / m ² or more and the dry coating amount of the inorganic particle layer B is 2.5 g / m ² or more, the surface of the nonwoven fabric base material is inorganic particles. It becomes easy to be sufficiently covered with the layer, and it becomes easy to prevent internal short circuit. Moreover, the raise of internal resistance can be suppressed because the absolute dry coating amount of the inorganic particle layer A and the inorganic particle layer B is 10.0 g / m < ² > or less.

  The coating amount of the inorganic particle layer A is preferably the same as or less than the coating amount of the inorganic particle layer B. When the coating amount of the inorganic particle layer A is larger than the coating amount of the inorganic particle layer B, the content of the inorganic particles having a relatively large average particle diameter is increased, so that the thickness of the separator may be increased. .

  The ratio of the coating amount of the inorganic particle layer A and the inorganic particle layer B (= the coating amount of the inorganic particle layer A / the coating amount of the inorganic particle layer B) is preferably 0.23 or more and 1.00 or less. 0.33 or more and less than 0.95 is more preferable, and 0.43 or more and less than 0.90 is more preferable. When the ratio of the coating amount of the inorganic particle layer A and the inorganic particle layer B is 0.23 or more and 1.00 or less, the separator may not be too thick and pinholes may not easily occur.

  In the present invention, the fibers forming the nonwoven fabric substrate include polyolefins such as polypropylene and polyethylene; polyesters such as polyethylene terephthalate, polyethylene isophthalate and polyethylene naphthalate; acrylics such as polyacrylonitrile; 6,6 nylon and 6 nylon. The synthetic resin short fiber which consists of various synthetic resins, such as polyamide, and is not fibrillated is illustrated. Among these, at least polyester or polypropylene is preferably used as the fiber for reasons such as heat resistance and low hygroscopicity. In addition to the synthetic resin short fibers, it is more preferable to include fibrillated heat resistant fibers. By including the fibrillated heat-resistant fiber, excessive penetration of the coating liquid into the nonwoven fabric base material can be suppressed, and the groove can be easily formed. Further, the fibrillated heat resistant fiber can impart higher heat resistance to the separator. Moreover, the nonwoven fabric substrate may contain various cellulose pulps such as wood pulp, hemp pulp, and cotton pulp; and cellulose-based regenerated fibers such as rayon and lyocell.

  In this invention, it is preferable that the fiber diameter of a synthetic resin short fiber exists in the range of 1 micrometer or more and 8 micrometers or less. By being 1 μm or more, it becomes easy to suppress an increase in internal resistance. Moreover, it becomes difficult for the provided coating liquid to fall off from a nonwoven fabric base material because it is 8 micrometers or less.

  The synthetic resin short fiber may be a fiber (single fiber) made of a single resin, or may be a composite fiber made of two or more kinds of resins. Moreover, the synthetic resin short fiber contained in the nonwoven fabric base material of the present invention may be used alone or in combination of two or more. Examples of the composite fiber include a core-sheath type, an eccentric type, a side-by-side type, a sea-island type, an orange type, and a multiple bimetal type.

  The fiber length of the synthetic resin short fiber is preferably 1 mm or more and 10 mm or less, and more preferably 1 mm or more and 5 mm or less. If the fiber length exceeds 10 mm, formation may be poor. On the other hand, when the fiber length is less than 1 mm, the mechanical strength of the nonwoven fabric substrate is lowered, and the nonwoven fabric substrate may be damaged when forming the inorganic particle layer.

  In the present invention, the fibrillated heat-resistant fiber includes wholly aromatic polyamide, wholly aromatic polyester, polyimide, polyamideimide, polyether ether ketone, polyphenylene sulfide, polybenzimidazole, poly-p-phenylenebenzobisthiazole, poly- A fibrillated fiber made of a heat-resistant resin such as p-phenylenebenzobisoxazole or polytetrafluoroethylene is used. Among these, wholly aromatic polyamides are preferred because of their high affinity with the electrolyte and easy fibrillation.

  The modified freeness of the fibrillated heat-resistant fiber in the present invention is 0 to 300 ml, preferably 0 to 200 ml, more preferably 0 to 100 ml. When the modified freeness exceeds 300 ml, the fiber width of the fibrillated heat-resistant fiber trunk fiber is large, and it may be difficult to reduce the thickness of the nonwoven fabric substrate. Furthermore, since the point of adhesion with other fibers such as binder fibers is reduced, it may be difficult to reduce the strength of the nonwoven fabric substrate or to suppress excessive penetration of the coating liquid into the nonwoven fabric substrate.

  In the present invention, the modified freeness is defined by JIS P8121-2 except that an 80 mesh wire net having a wire diameter of 0.14 mm and an aperture of 0.18 mm is used as a sieve plate, and the sample concentration is 0.1% by mass. It is a value measured in compliance.

  The mass weighted average fiber length of the fibrillated heat resistant fiber is preferably 0.02 mm or more and 1.00 mm or less. The length-weighted average fiber length of the fibrillated heat resistant fiber is preferably 0.02 mm or more and 0.50 mm or less. When the average fiber length is shorter than the preferred range, the fibrillated heat resistant fiber may fall off from the nonwoven fabric substrate. If the average fiber length is longer than the preferred range, it may be difficult to reduce the thickness of the nonwoven fabric substrate.

  When the fibrillated heat resistant fiber has the above-mentioned mass weighted average fiber length and length weighted average fiber length, even when the content of the fibrillated heat resistant fiber contained in the nonwoven fabric substrate is small, Between the fibrillated heat-resistant fiber and the synthetic resin short fiber, a dense network structure is formed by the fiber, the strength is high, the thickness can be reduced, and excessive penetration of the coating liquid into the nonwoven fabric substrate It becomes easy to obtain the nonwoven fabric base material which can suppress easily.

  In the present invention, the mass-weighted average fiber length and length-weighted average fiber length of the fibrillated heat-resistant fiber are mass weights measured in the projected fiber length (Proj) mode using Kajaani Fiber Lab V3.5 (manufactured by Metso Automation). An average fiber length (L (w)) and a length weighted average fiber length (L (l)).

  The average fiber width of the fibrillated heat resistant fiber is preferably from 0.5 μm to 20.0 μm, more preferably from 3.0 μm to 16.0 μm, and even more preferably from 5.0 μm to 15.0 μm. When the average fiber width exceeds 20.0 μm, it may be difficult to reduce the thickness of the nonwoven fabric substrate. When the average fiber width is less than 0.5 μm, the nonwoven fabric substrate may fall off.

  In the present invention, the average fiber width of the fibrillated heat-resistant fiber is a fiber width (Fiber Width) measured using Kajaani Fiber Lab V3.5 (manufactured by Metso Automation).

  Fibrilized heat-resistant fiber consists of refiner, beater, mill, grinding device, rotary homogenizer that gives shearing force by high-speed rotary blade, high-speed rotating cylindrical inner blade and fixed outer blade Double cylindrical high-speed homogenizer that generates shearing force between them, ultrasonic crusher that is refined by ultrasonic impact, and a high-speed by passing a small-diameter orifice by applying a pressure difference of at least 20 MPa to the fiber suspension Then, it can be obtained by processing using a high-pressure homogenizer or the like that applies a shearing force or cutting force to the fiber by colliding with this and rapidly decelerating.

  When the non-woven fabric substrate contains fibrillated heat-resistant fibers, the content of the fibrillated heat-resistant fibers is 1.0% by mass or more and less than 5.0% by mass with respect to all the fiber components contained in the non-woven fabric substrate. Preferably there is. 2.0 mass% or more is more preferable, and 3.0 mass% or more is further more preferable. Moreover, less than 4.5 mass% is more preferable. When the content of the fibrillated heat-resistant fiber is 5.0% by mass or more, it may be difficult to crush the nonwoven fabric substrate or the tensile strength may be deteriorated in order to reduce the thickness of the nonwoven fabric substrate. . On the other hand, when the content rate of the fibrillated heat resistant fiber is less than 1.0% by mass, the easiness of forming the groove is not changed as compared with the nonwoven fabric base material not including the fibrillated heat resistant fiber.

  When the non-woven fabric substrate contains fibrillated heat-resistant fibers, the content of the synthetic resin short fibers is preferably 90.0% by mass or more, and 92.0% by mass or more with respect to the total fiber components contained in the non-woven fabric substrate. Is more preferably 94.0% by mass or more, particularly preferably more than 95.0% by mass. Moreover, 99.0 mass% or less is preferable, 98.0 mass% or less is more preferable, and 96.0 mass% or less is further more preferable. When the synthetic resin short fiber is more than 99.0% by mass, the easiness of forming the groove is not changed as compared with the nonwoven fabric base material not containing the fibrillated heat resistant fiber. On the other hand, when the synthetic resin short fiber is less than 90.0% by mass, when the basis weight of the nonwoven fabric substrate is lowered, the nonwoven fabric substrate may be damaged when the inorganic particle layer is formed due to low mechanical strength. is there.

In the present invention, the basis weight of the nonwoven substrate is preferably from 5 to 30 g / ^{m 2,} more preferably from 6~20g / ^{m 2.} When the basis weight is 5 g / m ² or more, it becomes easy to obtain the uniformity of the nonwoven fabric substrate, and when it is 30 g / m ² or less, a thickness suitable for the lithium ion battery separator is easily obtained. In addition, it is preferable that the thickness of a nonwoven fabric base material is 7-45 micrometers, and if it is this range, the thickness suitable for a lithium ion battery separator will be easy to be obtained after coating.

  Examples of methods for producing the nonwoven fabric substrate include various production methods such as a spunbond method, a melt blow method, an electrostatic spinning method, and a wet method. Among these, a wet method is preferable because a thin and dense structure can be obtained. Examples of methods for bonding fibers include various methods such as a chemical bond method and a heat fusion method. Among these, the heat fusion method is preferable because a nonwoven fabric substrate having a smooth surface can be obtained.

  In the present invention, as a method for forming grooves on the surface of the inorganic particle layer, gravure coating is exemplified, and the grooves can be easily formed as compared with rubbing treatment or the like. Specifically, the shape of the gravure roll used for the gravure coating is not particularly limited as long as the groove can be formed in the inorganic particle layer, but preferably has a slanted groove. A groove is formed on the surface of the inorganic particle layer by applying the applied coating liquid to the nonwoven fabric substrate and drying it. The material of the gravure roll is not particularly limited. However, since the gravure roll has high wear resistance, the surface of the gravure roll is preferably surface-treated with hard chromium plating or metal oxide spraying such as chromium oxide.

  In order to form grooves on the surface of the inorganic particle layer, the B-type viscosity of the coating liquid is preferably 500 mPa · s or more. When the B-type viscosity is 500 mPa · s or more, the separator of the present invention can be easily obtained. If the B-type viscosity of the coating liquid is lower than 500 mPa · s, the grooves are leveled between the time the coating liquid is applied to the nonwoven fabric substrate and the drying, and the grooves are lost. I can't get it. The B type viscosity was 25 ° C., spindle no. It is a value measured based on JIS K 7117; 1999 using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd., model BL) at 2 and 12 rpm. The B-type viscosity of the coating liquid is preferably 600 mPa · s or more, more preferably 700 mPa · s or more, and the leveling of the coating liquid is further suppressed, and the formation of grooves is facilitated. When the B-type viscosity of the coating liquid exceeds 3000 mPa · s, it is difficult to apply the coating itself.

  In this invention, it is preferable that the angle of the liquid injection direction and groove | channel at the time of inject | pouring electrolyte solution into the lithium ion battery assembled using the lithium ion battery separator is -70 degree-+70 degree. If it is this range, it will become easy to achieve the effect of the efficiency improvement of liquid injection property. FIG. 1 is a schematic diagram for explaining the angle between the liquid injection direction and the groove and the distance between the tops of the separator 1. The angles 4 and 5 between the injection direction and the groove are obtained by measuring the angle between the injection direction 3 and the continuous line of the top 2 of the groove. The angle between the liquid injection direction and the groove includes a sign 4 (acute angle: ± 90 ° to 0 °) and a sign 5 (obtuse angle: ± 90 ° to 180 °). The angle is 4 (acute angle). That is, the angle between the liquid injection direction and the groove in the present invention is expressed as ± 90 ° to 0 °. In addition, “−” means that the angle is on the right side with respect to the liquid injection direction, and “+” means that the angle is on the left side with respect to the liquid injection direction. For example, the angle 4 in FIG. 1 is “+”. FIG. 2 is a schematic cross-sectional view showing an example of a separator having grooves 11 on the surface of the inorganic particle layer 12. The height 14 of the groove is preferably 0.1% or more and 99.0% or less of the height 15 of the inorganic particle layer. By setting it to 0.1% or more, the liquid absorbency of the electrolytic solution is improved as compared with the separator without the groove 11. When it is larger than 99.0%, the covering property of the nonwoven fabric base material 13 with the inorganic particle layer 12 may not be sufficiently obtained at the bottom of the groove 11. By the way, when the coating liquid is given to the nonwoven fabric base material 13 and the inorganic particle layer 12 is formed, a part of the inorganic particle layer 12 penetrates into the nonwoven fabric base material 13. Here, the “height of the inorganic particle layer” is the height of the inorganic particle layer 12 that does not include a portion that has penetrated into the nonwoven fabric substrate 13. The interval between the grooves and the number of grooves are not particularly limited. In addition, the angle between the liquid injection direction and the groove, the height of the groove, the interval between the grooves, the number of grooves, etc., the shape of the gravure roll, the coating speed, the rotation speed of the gravure roll, the B-type viscosity of the coating liquid, etc. It can be adjusted by changing. A lithium ion battery is manufactured by incorporating an electrode group including a positive electrode, a separator, and a negative electrode into a battery cell, injecting an electrolyte into the cell, and then sealing the inlet of the electrolyte. As the structure of the electrode group, two types, a stacked structure and a wound structure, are mainstream. In either structure, the end face of the electrode is often exposed on the end face side in the machine direction (Machine Direction; MD, flow direction, longitudinal direction, longitudinal direction) of the separator 1, and the electrolyte is injected from this face. By doing so, the injection speed can be made relatively high. Therefore, it is common that the end face side in the machine direction of the separator 1 faces the injection port, and the liquid injection direction 3 is the cross direction (CD, lateral direction) of the separator 1.

In the present invention, the basis weight of the separator is preferably 10 to 60 g / ^{m 2,} more preferably from 16~40g / ^{m 2.} When the basis weight is 10 g / m ² or more, it is easy to obtain uniformity and to prevent internal short circuit. Moreover, the thickness suitable for a lithium ion battery separator is easy to be obtained because it is 60 g / m < ² > or less. In addition, it is preferable that the thickness of a separator is 10-60 micrometers.

The lithium ion battery in the present invention means a lithium ion secondary battery or a lithium ion polymer secondary battery. The negative electrode active material of the lithium ion battery is not limited in any way, but it is preferable to use a negative electrode active material having an equilibrium potential of 1 V (vs Li + / Li) or less for inserting and extracting lithium ions. By using such a negative electrode active material, a battery having a large potential difference between the positive and negative electrodes, that is, a large amount of energy that can be stored can be obtained. As the negative electrode active material satisfying this condition, for example, a carbon material such as graphite, hard carbon, low crystalline carbon, graphite coated with amorphous carbon, carbon nanotube, or a mixture thereof can be used. Further, not only a carbon-based material but also a negative electrode material containing Si, Sn, N, or the like can be used. The positive electrode active material is not particularly limited as long as it can reversibly occlude and release lithium ions. For example, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), spinel-type lithium manganate (LiMn ₂ O ₄ ), and a general formula: LiNi _x Co _y Mn _z O ₂ (x + y + z = 1) And composite metal oxides such as lithium vanadium compound (LiV ₂ O ₅ ) and olivine-type LiMPO ₄ (wherein M represents Co, Ni, Mn or Fe).

  Lithium-ion battery is a state in which a separator is disposed between a positive electrode and a negative electrode, and an assembly such as a wound body in which the positive electrode, the negative electrode, and the separator are stacked and laminated, and a laminated body laminated in multiple layers are inserted into an exterior material, It is manufactured by a procedure of closing the opening of the exterior material, filling the electrolytic solution from the injection port, and sealing the injection port. Using the separator of the present invention having grooves on the surface of the inorganic particle layer applied to the nonwoven fabric substrate, preferably the assembly so that the angle 4 between the liquid injection direction and the grooves is ± 70 ° to 0 °. By making it, the time required for injecting the electrolyte can be shortened.

The electrolyte of a lithium ion battery usually contains an electrolyte lithium salt, a main solvent carbonate ester as essential components, and if necessary, an auxiliary solvent such as a fatty acid ester, an additive for improving battery characteristics, etc. 0-20 mass% is further included. The lithium salt that is an electrolyte is most commonly lithium hexafluorophosphate (LiPF ₆ ), but lithium tetrafluoroborate (LiBF ₄ ) or the like may be used. As the carbonate which is the main solvent, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate are mainly used. When an auxiliary solvent is used, fatty acid esters such as ethyl acetate, propyl acetate, and ethyl propionate are generally used. As the additive, vinylene carbonate, propane sultone or the like is used. Carbonate, the main solvent, has similar solubility in various substances, and most of the substances that dissolve in one type of carbonate are also soluble in other carbonates and their mixed solvents. To do. Moreover, the electrolytic solution may further contain polyethylene glycol or a derivative thereof, a polymethacrylic acid derivative, polysiloxane or a derivative thereof, polyvinylidene fluoride, or the like, and may be in a gel form.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In Examples,% and part are all based on mass unless otherwise specified. The coating amount is an absolutely dry coating amount. In this example, the liquid injection direction was CD of the separator.

Production of Non-woven Fabric Base A Fineness 0.06 dtex (average fiber diameter 2.4 μm), oriented crystallized polyethylene terephthalate (PET) short fiber 40 mass parts with fiber length 3 mm and fineness 0.1 dtex (average fiber diameter 3.0 μm) , 20 mass parts of oriented crystallized PET short fibers with a fiber length of 3 mm, fineness of 0.2 dtex (average fiber diameter 4.3 μm), single component binder PET short fibers with a fiber length of 3 mm (softening point 120 ° C., melting point) (230 ° C.) 40 parts by mass was dispersed in water with a pulper to prepare a uniform papermaking slurry having a concentration of 1% by mass. This slurry for paper making is made by a wet method on an inclined paper machine, and a PET short fiber for a binder is adhered by a cylinder dryer at 135 ° C. to develop a nonwoven fabric strength. A nonwoven fabric having a basis weight of 12 g / m ² . It was. Furthermore, this nonwoven fabric was subjected to conditions of a hot roll temperature of 200 ° C., a linear pressure of 100 kN / m, and a processing speed of 30 m / min, using a 1-nip thermal calender consisting of a dielectric heating jacket roll (metal hot roll) and an elastic roll. To produce a nonwoven fabric substrate A having a thickness of 18 μm.

Production of Non-woven Fabric Base B Fineness 0.06 dtex (average fiber diameter 2.4 μm), oriented crystallized polyethylene terephthalate (PET) short fiber 37 parts by mass and fiber length 3 mm and fineness 0.1 dtex (average fiber diameter 3.0 μm) , 20 mass parts of oriented crystallized PET short fibers with a fiber length of 3 mm, fineness of 0.2 dtex (average fiber diameter 4.3 μm), single component binder PET short fibers with a fiber length of 3 mm (softening point 120 ° C., melting point) 230 ° C) 40 parts by mass and a high-pressure homogenizer, a fibrillated heat resistance obtained by fibrillating a wholly aromatic polyamide fiber pulp (average fiber length 1.7 mm, average fiber diameter 10 µm) to a modified freeness of 50 ml 3 parts by mass of fiber was dispersed in water by a pulper to prepare a uniform papermaking slurry having a concentration of 1% by mass. This slurry for paper making is made by a wet method on an inclined paper machine, and a PET short fiber for a binder is adhered by a cylinder dryer at 135 ° C. to develop a nonwoven fabric strength. A nonwoven fabric having a basis weight of 12 g / m ² . It was. Furthermore, this nonwoven fabric was subjected to conditions of a hot roll temperature of 200 ° C., a linear pressure of 100 kN / m, and a processing speed of 30 m / min, using a 1-nip thermal calender consisting of a dielectric heating jacket roll (metal hot roll) and an elastic roll. To produce a nonwoven fabric substrate B having a thickness of 18 μm.

Production of Non-woven Fabric Substrate C Fineness 0.06 dtex (average fiber diameter 2.4 μm), oriented crystallized polyethylene terephthalate (PET) short fiber 37 parts by mass and fiber length 3 mm and fineness 0.1 dtex (average fiber diameter 3.0 μm) , 20 mass parts of oriented crystallized PET short fibers with a fiber length of 3 mm, fineness of 0.2 dtex (average fiber diameter 4.3 μm), single component binder PET short fibers with a fiber length of 3 mm (softening point 120 ° C., melting point) 230 ° C.) 40 parts by mass and a high-pressure homogenizer, a fibrillated heat resistance obtained by fibrillating a wholly aromatic polyamide fiber pulp (average fiber length 1.7 mm, average fiber diameter 10 μm) to a modified freeness of 250 ml Non-woven fabric in the same manner as non-woven fabric substrate B, except that 3 parts by mass of fiber was dispersed in water with a pulper to prepare a uniform papermaking slurry having a concentration of 1% by mass. To prepare a wood C.

Fabrication of Non-woven Fabric Substrate D Fineness 0.06 dtex (average fiber diameter 2.4 μm), oriented crystallized polyethylene terephthalate (PET) short fiber 37 parts by mass and fiber length 3 mm and fineness 0.1 dtex (average fiber diameter 3.0 μm) , 20 mass parts of oriented crystallized PET short fibers with a fiber length of 3 mm, fineness of 0.2 dtex (average fiber diameter 4.3 μm), single component binder PET short fibers with a fiber length of 3 mm (softening point 120 ° C., melting point) 230 ° C.) 40 parts by mass and a high pressure homogenizer, fibrillated heat resistance obtained by fibrillating fully aromatic polyamide fiber pulp (average fiber length 1.7 mm, average fiber diameter 10 μm) to a modified freeness of 320 ml Non-woven fabric in the same manner as non-woven fabric substrate B, except that 3 parts by mass of fiber was dispersed in water with a pulper to prepare a uniform papermaking slurry having a concentration of 1% by mass. To prepare a wood D.

Preparation of Coating Liquid A As inorganic particles, 100 parts of boehmite secondary particles having an average particle diameter of 2.3 μm formed by aggregation of primary particles having a particle diameter of 0.7 μm were used. A boehmite dispersion was prepared by dispersing in 120 parts of a 0.3% aqueous solution of carboxymethylcellulose sodium salt at 200 mPa · s and stirring well. Next, 200 parts of a 0.5% aqueous solution of carboxymethylcellulose sodium salt having a viscosity of 7000 mPa · s at 25 ° C. in a 1% by mass aqueous solution was mixed and stirred, and further 45% styrene-butadiene copolymer as an adhesive (binder resin). 15 parts of latex polymer of the combined resin was mixed and stirred to prepare a coating solution. The B type viscosity of the coating liquid A was 1000 mPa · s.

Preparation of coating liquid B Coating was performed in the same manner as coating liquid A, except that 200 parts of a 0.5% by weight aqueous solution of carboxymethylcellulose sodium salt having a viscosity of 7000 mPa · s at 25 ° C. in a 1% by weight aqueous solution was changed to 120 parts. Liquid B was prepared. The B-type viscosity of the coating liquid B was 400 mPa · s. Since the coating liquid B has a lower viscosity than the coating liquid A, no groove is formed.

Preparation of Coating Solution C Coating Solution C was prepared in the same manner as Coating Solution A, except that 100 parts of magnesium hydroxide having an average particle size of 0.1 μm was used as the inorganic particles. In addition, the B type viscosity of the coating liquid C was 1000 mPa · s.

Preparation of coating liquid D A coating liquid D was prepared in the same manner as the coating liquid A, except that 100 parts of magnesium hydroxide having an average particle diameter of 0.5 μm was used as the inorganic particles. In addition, the B type viscosity of the coating liquid D was 1000 mPa · s.

Preparation of coating solution E Coating solution E was prepared in the same manner as coating solution A, except that 100 parts of magnesium hydroxide having an average particle size of 2.0 μm was used as the inorganic particles. In addition, the B type viscosity of the coating liquid E was 1000 mPa · s.

Preparation of coating solution F Coating solution F was prepared in the same manner as coating solution A, except that 100 parts of magnesium hydroxide having an average particle size of 3.0 μm was used as the inorganic particles. In addition, the B type viscosity of the coating liquid F was 1000 mPa · s.

Example 1
On one side of the non-woven fabric substrate A, the coating liquid A is applied with a Kiss Reverse gravure coater (KRG) so that the absolute dry coating amount is 16 g / m ^2. -It dried and produced the separator of thickness 36 micrometers. The angle 4 between the injection direction and the groove was + 40 °.

Example 2
On one side of the nonwoven fabric substrate A, the coating liquid A is applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 16 g / m ² , thereby producing a separator having a thickness of 36 μm. did. The angle 4 between the injection direction and the groove was + 70 °.

Example 3
On one side of the nonwoven fabric substrate A, the coating liquid A is applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 16 g / m ² , thereby producing a separator having a thickness of 36 μm. did. The angle 4 between the injection direction and the groove was + 15 °.

Example 4
On one side of the nonwoven fabric substrate A, the coating liquid A is applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 16 g / m ² , thereby producing a separator having a thickness of 36 μm. did. The angle 4 between the injection direction and the groove was + 80 °.

Comparative Example 1
On one side of the non-woven fabric substrate A, coating liquid B is applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 16 g / m ² , thereby producing a separator having a thickness of 36 μm. did. The viscosity of the coating liquid B was low, and no grooves were formed.

Comparative Example 2
On one side of the nonwoven fabric substrate A, the coating liquid A was applied and dried with a die coater so that the absolutely dry coating amount was 16 g / m ² to prepare a separator having a thickness of 36 μm. No groove was formed.

Example 5
On one side of the nonwoven fabric base material B, the coating liquid A was coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 16 g / m ² , thereby producing a separator having a thickness of 36 μm. . The angle 4 between the injection direction and the groove was + 15 °.

Example 6
On one side of the nonwoven fabric base material B, the coating liquid D was applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 16 g / m ² , thereby producing a separator having a thickness of 34 μm. . The angle 4 between the injection direction and the groove was + 15 °.

Example 7
On one side of the nonwoven fabric substrate C, the coating liquid A was applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 16 g / m ² , thereby producing a separator having a thickness of 36 μm. . The angle 4 between the injection direction and the groove was + 15 °.

Example 8
On one side of the nonwoven fabric substrate D, the coating liquid A was applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 16 g / m ² to prepare a separator having a thickness of 36 μm. . The angle 4 between the injection direction and the groove was + 15 °.

Example 9
On one side of the nonwoven fabric substrate A, the coating liquid C was coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 16 g / m ² to prepare a separator having a thickness of 33 μm. . The angle 4 between the injection direction and the groove was + 15 °.

Example 10
On one side of the nonwoven fabric substrate A, the coating liquid E was applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 16 g / m ² , thereby producing a separator having a thickness of 35 μm. . The angle 4 between the injection direction and the groove was + 15 °.

Example 11
On one side of the nonwoven fabric substrate A, the coating liquid F was coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 16 g / m ² to prepare a separator having a thickness of 37 μm. . The angle 4 between the injection direction and the groove was + 15 °.

Example 12
On one side of the nonwoven fabric substrate A, the coating liquid A is applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 8 g / m ^2, and then the nonwoven fabric substrate A On the other surface, coating solution A was coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 8 g / m ² , thereby producing a separator having a thickness of 35 μm. The angle 4 between the injection direction and the groove was + 15 ° on both sides.

Example 13
On one side of the non-woven fabric substrate A, the coating liquid F is applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount becomes 8 g / m ^2. The working fluid D was coated and dried with a kiss reverse gravure coater so that the dry coating amount was 8 g / m ² , thereby preparing a separator having a thickness of 34 μm. The angle 4 between the injection direction and the groove was + 15 °.

Example 14
On one side of the nonwoven fabric substrate A, the coating liquid D is applied and dried with a kiss reverse gravure coater so that the dry coating amount is 8 g / m ^2. The working fluid F was coated and dried with a kiss reverse gravure coater so that the dry coating amount was 8 g / m ² , thereby producing a separator having a thickness of 34 μm. The angle 4 between the injection direction and the groove was + 15 °.

Example 15
On one side of the nonwoven fabric substrate A, the coating liquid F is coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 8 g / m ^2, and then the nonwoven fabric substrate A On the other surface, the coating liquid D was coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 8 g / m ² , thereby preparing a separator having a thickness of 33 μm. The angle 4 between the injection direction and the groove was + 15 ° on both sides.

Example 16
On one side of the nonwoven fabric substrate A, the coating liquid E is applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 8 g / m ^2. On the other surface, coating liquid E was coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 8 g / m ² , thereby preparing a separator having a thickness of 34 μm. The angle 4 between the injection direction and the groove was + 15 ° on both sides.

Comparative Example 3
On one side of the nonwoven fabric substrate A, the coating liquid A is applied and dried with a die coater so that the dry coating amount is 8 g / m ^2. Next, the other side of the nonwoven fabric substrate A is coated. On the surface, the coating liquid A was coated and dried with a die coater so that the dry coating amount was 8 g / m ² , thereby preparing a separator having a thickness of 35 μm. No groove was formed.

Example 17
On one side of the nonwoven fabric base material B, the coating liquid A is applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 8 g / m ^2. On the other surface, coating solution A was coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 8 g / m ² , thereby producing a separator having a thickness of 35 μm. The angle 4 between the injection direction and the groove was + 15 ° on both sides.

Example 18
On one side of the nonwoven fabric substrate B, the coating solution F is applied and dried with a kiss reverse gravure coater so that the dry coating amount is 8 g / m ^2. The working fluid D was coated and dried with a kiss reverse gravure coater so that the dry coating amount was 8 g / m ² , thereby preparing a separator having a thickness of 34 μm. The angle 4 between the injection direction and the groove was + 15 °.

Example 19
On one side of the nonwoven fabric base material B, the coating liquid F is applied and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 8 g / m ^2. On the other surface, the coating liquid D was coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 8 g / m ² , thereby preparing a separator having a thickness of 33 μm. The angle 4 between the injection direction and the groove was + 15 ° on both sides.

Example 20
On one side of the nonwoven fabric base material B, the coating liquid E is coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount is 8 g / m ^2. On the other surface, coating liquid E was coated and dried with a kiss reverse gravure coater so that the absolutely dry coating amount was 8 g / m ² , thereby preparing a separator having a thickness of 34 μm. The angle 4 between the injection direction and the groove was + 15 ° on both sides.

  The separators produced in Examples 1 to 20 are produced by gravure coating, and are separators having grooves on the surface of the inorganic particle layer, so that no complicated post-processing is required after drying, and uniform grooves are formed. It was. On the other hand, in Comparative Example 1, the viscosity of the coating liquid B was low, and no grooves were formed on the surface of the inorganic particle layer. In Comparative Examples 2 and 3, since a die coater was used in place of the kiss reverse gravure coater, no groove was formed on the surface of the inorganic particle layer.

<Evaluation>
[Liquid injection properties]
A sample of MD50 mm × CD100 mm was cut out from the produced separator using an electrolytic solution that was a 7/3 (volume ratio) mixed solvent solution (1 mol / L) of ethylene carbonate and diethyl carbonate of LiPF ₆ , and a CD100 mm of this sample was cut out. The lower 5 mm was immersed in the electrolytic solution, and the time until the electrolytic solution reached 5 mm from the electrolytic solution surface was measured. It can be said that the shorter this time, the better the liquid injection property.

  From the results of Examples 1 to 4 and Comparative Examples 1 and 2, since the separators of Examples 1 to 4 have grooves on the surface of the inorganic particle layer, the separators of Comparative Examples 1 and 2 having no grooves on the surface of the inorganic particle layer. The liquid injection property was better than that of the separator. In particular, the separators of Examples 1 to 3 exhibited better liquid injection properties because the angle between the liquid injection direction and the groove was −70 ° to + 70 °.

  From the results of Examples 3, 5, 7 and 8, the separators of Examples 5, 7 and 8 in which the nonwoven fabric substrate contains fibrillated heat resistant fibers are examples in which the nonwoven fabric substrate does not contain fibrillated heat resistant fibers. The liquid injection property was better than that of the separator No. 3. In particular, the liquid injection properties of the separators of Examples 5 and 7 in which the modified freeness of the fibrillated heat resistant fiber was 300 ml or less were more excellent.

  From the results of Examples 5 and 6, the inorganic particles are more inorganic than the separator of Example 5 which is boehmite (aluminum compound) having an average particle diameter of 2.3 μm formed by agglomeration of primary particles having a particle diameter of 0.7 μm. The separator of Example 6 which is magnesium hydroxide (magnesium compound) having an average particle diameter of 0.5 μm showed better liquid injection properties. Further, from the results of Examples 3 and 10, the inorganic particles are more inorganic than the separator of Example 3 which is boehmite (aluminum compound) having an average particle size of 2.3 μm formed by agglomeration of primary particles having a particle size of 0.7 μm. The separator of Example 10 in which the particles were magnesium hydroxide (magnesium compound) having an average particle diameter of 2.0 μm showed better liquid injection properties.

  From the results of Examples 9 to 11 and Comparative Examples 1 and 2, since the separators of Examples 9 to 11 have grooves on the surface of the inorganic particle layer, the separators of Comparative Examples 1 and 2 having no grooves on the surface of the inorganic particle layer. The liquid injection property was better than that of the separator. From the results of Examples 9 to 11, the separator of Example 10 in which the average particle diameter of the inorganic particles is 0.5 μm or more and less than 3.0 μm is the Example in which the average particle diameter of the inorganic particles is less than 0.5 μm. The liquid injection property was better than that of Example 11 in which the separator 9 and the average particle size of the inorganic particles were 3.0 μm or more.

  From the results of Examples 12, 15 and 16 and Comparative Example 3, even in the separator in which the inorganic particle layer is provided on both surfaces of the nonwoven fabric substrate, when the inorganic particle layer has a groove, good liquid injection property is obtained. Indicated.

  From the results of Examples 13 to 15, the inorganic particle layer contains inorganic particles having an average particle size of 2.0 μm or more and 4.0 μm or less, and inorganic particles having an average particle size of 0.5 μm or more and less than 2.0 μm. In the separator having the inorganic particle layer B containing, the separator of Example 13 having a configuration in which the inorganic particle layer A and the inorganic particle layer B are laminated in this order on one side of the nonwoven fabric base, and on the one side of the nonwoven fabric base The separator of Example 15 having the inorganic particle layer A and the inorganic particle layer B on the other surface has an arrangement in which the inorganic particle layer B and the inorganic particle layer A are laminated in this order on one surface of the nonwoven fabric substrate. The liquid injection property was better than that of the separator of Example 14.

  From the results of Example 12 and Example 17, the results of Example 13 and Example 18, the results of Example 15 and Example 19, and the results of Example 16 and Example 20, the nonwoven fabric is a fibrillated heat resistant fiber. The separators of Examples 17 to 20 including the non-woven fabric base material do not contain fibrillated heat-resistant fibers, compared with the corresponding separators of Examples 12, 13, 15 and 16, respectively, with good liquid injection properties. Indicated.

  As an application example of the present invention, a lithium ion battery separator and a lithium ion polymer battery separator are suitable.

1 Lithium ion battery separator 2 Top of groove 3 Injection direction 4 Angle between injection direction and groove (acute angle)
5 Angle between liquid injection direction and groove (obtuse angle)
11 Groove 12 Inorganic Particle Layer 13 Nonwoven Fabric Base Material 14 Groove Height 15 Inorganic Particle Layer Height

Claims (15)

  Lithium ion battery separator having a groove on the surface, wherein the separator includes a non-woven fabric base material and an inorganic particle layer applied to the non-woven fabric base material, and has a groove on the surface of the inorganic particle layer Battery separator.   2. The lithium ion battery separator according to claim 1, wherein an angle between the injection direction and the groove when injecting the electrolyte into the lithium ion battery assembled using the lithium ion battery separator is −70 ° to + 70 °.   The lithium ion battery separator according to claim 1 or 2, wherein the inorganic particle layer is provided only on one side of the nonwoven fabric substrate.   The lithium ion battery separator according to claim 1 or 2, wherein the inorganic particle layer is provided on both surfaces of the nonwoven fabric substrate.   The lithium ion battery separator according to any one of claims 1 to 4, wherein the inorganic particle layer contains inorganic particles having an average particle diameter of 0.5 µm or more and 4.0 µm or less.   The lithium ion battery separator according to any one of claims 1 to 4, wherein the inorganic particle layer contains inorganic particles having an average particle diameter of 0.5 µm or more and less than 3.0 µm.   The inorganic particle layer has an inorganic particle layer A containing inorganic particles having an average particle size of 2.0 μm or more and 4.0 μm or less, and an inorganic particle layer B containing inorganic particles having an average particle size of 0.5 μm or more and less than 2.0 μm. The lithium ion battery separator in any one of Claims 1-4.   The lithium ion battery separator according to claim 7, which has a configuration in which an inorganic particle layer A and an inorganic particle layer B are laminated in this order on one side of a nonwoven fabric substrate.   The lithium ion battery separator according to claim 7, comprising an inorganic particle layer A provided on one side of the nonwoven fabric substrate and an inorganic particle layer B provided on the other side.   The lithium ion battery separator according to any one of claims 1 to 9, wherein the inorganic particle layer includes one or more inorganic particles selected from the group consisting of an aluminum compound and a magnesium compound.   The lithium ion battery separator according to claim 1, wherein the inorganic particle layer contains a magnesium compound.   The lithium ion battery separator according to claim 10 or 11, wherein the magnesium compound is magnesium hydroxide.   The lithium ion battery separator according to any one of claims 1 to 12, wherein the nonwoven fabric substrate contains fibrillated heat-resistant fibers. The lithium ion battery separator according to claim 13, wherein the modified freeness of the fibrillated heat resistant fiber is 300 ml or less.
Modified freeness: A value measured in accordance with JIS P8121-2 except that an 80-mesh wire mesh having a wire diameter of 0.14 mm and an aperture of 0.18 mm was used as a sieve plate, and the sample concentration was 0.1%.   The lithium ion battery separator according to claim 13 or 14, wherein the fibrillated heat-resistant fiber is a fibrillated wholly aromatic polyamide fiber.

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