JP2020068178A - Separator having fine pattern, wound body, and nonaqueous electrolyte battery - Google Patents

Abstract

To provide a separator capable of improving liquid transferability in a nonaqueous electrolyte battery and suppressing a dendrite formation, and provide a wound body or the nonaqueous electrolyte battery, including them.SOLUTION: In a cross-sectional view in a direction Z where an outermost part is a pattern top part, an innermost part is a non-pattern bottom part in a separator for a nonaqueous electrolyte battery having a pattern, and the pattern top part and the non-pattern bottom part are passed, when a virtual plane defined so as to be contacted to the non-pattern bottom part and be orthogonal to the direction Z is a surface B1, a virtual plane defined so as to be contacted to the outermost surface side of a surface of the separator in a non-pattern region and to be parallel with the surface B1 is a surface F1, a virtual plane defined so as to be contacted to the outermost surface side from a back surface of the separator in a pattern region and to be parallel with the surface B1 is a surface B2, and a virtual plane defined so as to be contacted to the pattern top part and to be parallel with the surface B1 is a surface F2, the surface F2 is positioned onto the surface side beyond the surface F1, and the surface B2 is positioned onto the surface side beyond the surface B1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a separator used in a non-aqueous electrolyte battery, a wound body or a non-aqueous electrolyte battery including the separator, and the like.

  With the recent development of electronic technology and increasing interest in environmental technology, various electrochemical devices have been used. In particular, expectations for non-aqueous electrolyte secondary batteries that can contribute to the demand for energy savings are increasing. BACKGROUND ART A lithium-ion secondary battery, which is a typical example of a non-aqueous electrolyte secondary battery, is used as a power source for various small devices, and in recent years, has been attracting attention as a power source for hybrid vehicles or a power source for electric vehicles.

  The non-aqueous electrolyte secondary battery usually has a configuration in which a non-aqueous electrolyte and a laminated body including a positive electrode, a separator and a negative electrode or a wound body thereof are housed in a case. The separator is a microporous membrane and has a function of preventing direct contact between the positive and negative electrodes and a function of allowing ions to permeate through the nonaqueous electrolyte retained in the microporous membrane. Therefore, as the microporous membrane, a membrane exhibiting ion permeability due to its porous structure, for example, a polyolefin microporous membrane is used.

Conventionally, it has been proposed to provide a pattern on at least one surface of a separator for the purpose of improving the performance of the separator for a non-aqueous electrolyte secondary battery.
Patent Document 1 discloses that a long porous film is provided with a long porous film for the purpose of facilitating the injection of the nonaqueous electrolytic solution into the battery container in which the wound product including the separator and the electrode sheet is housed. A plurality of non-porous linear regions continuously extending in the width direction from one side surface to the other side surface of the porous film are formed, and at least one surface of the non-porous linear area forms a concave portion or a convex portion. Describe the battery separator that is installed.

  Patent Document 2 maintains a battery characteristic, secures an electrode distance, prevents an internal short circuit, and improves the productivity by increasing the impregnation speed of an electrolytic solution. Therefore, in a non-aqueous electrolytic solution battery, a separator is used. It is described to use a microporous membrane whose surface is processed to have irregularities.

  Patent Document 3 aims to provide a uniaxially-stretched separator that is inexpensive and is resistant to tearing when assembling an electricity storage device, and at least one surface of the uniaxially-stretched separator is provided with a recess or a protrusion in a direction intersecting the stretching direction. Enter.

  Patent Document 4 describes that, in order to suppress the composition deterioration of the electrolytic solution, in a porous film having a large number of pores, an electrolytic solution diffusion hole larger than the pores is present on the membrane surface of the porous film. To do.

Patent Document 5 discloses a method of manufacturing or using a non-aqueous electrolyte battery using an alloy-based negative electrode, for the purpose of improving cycle characteristics at low cost, having a thickness of 1 to 100 μm and a pore diameter of 0.01 to 1 μm. , A microporous polyolefin membrane having protrusions having a height of 0.5 to 100 μm provided on at least one surface by embossing. Further, in Patent Document 6, in the relationship between roughening of a polyethylene resin porous film and physical properties of a battery separator, air permeability is 10 to 1000 seconds / 100 cc, pin puncture strength is 300 gf / 25 μm or more, surface roughness. Describes an embossed polyethylene resin porous film having a maximum height R _max of 3 μm or more.

Patent No. 4529903 JP-A-5-151951 JP, 2016-184710, A JP, 2013-211192, A International Publication No. 2008/053898 JP, 11-106532, A

  Due to the continuous demand for downsizing of non-aqueous electrolyte secondary batteries, in addition to thinning of the laminated body composed of the positive electrode, the separator and the negative electrode or its wound body, the non-aqueous electrolyte secondary battery has a The movement behavior of the non-aqueous electrolyte (hereinafter, also referred to as “liquid surrounding”) is also required. As a method of ensuring liquid flow through a limited flow path in the battery case, for example, a method of forming a concave portion or a convex portion as non-porous as described in Patent Document 1 and Patent Document 2 As described, a method of obtaining a concavo-convex separator (a method of laminating a porous film on the surface of a flat film, a method of corrugating a microporous film, etc.) can be considered.

  However, in the non-aqueous electrolyte secondary battery including the conventional separator, the uneven distribution of the lithium ions flowing from the positive electrode side to the negative electrode side during charging is due to the promotion of the formation of dendritic (dendritic) lithium and the non-aqueous electrolyte. This causes inconvenience such as deterioration acceleration (FIG. 1 (a)). When a battery including separators having different film thicknesses (x and y in FIG. 1A) or porosities as described in Patent Documents 1 and 2 is charged and discharged, the separators are formed. Since the resistance of the film to ions (hereinafter, also referred to as “film resistance”) becomes non-uniform, there is a problem that dendrites are likely to be generated due to uneven distribution of ions in a region where the film resistance is relatively low.

  Similarly, in Patent Document 3, as a method for forming a convex portion, a slurry for forming a convex portion is applied to one surface or both surfaces of a uniaxially stretched separator, and as a method for forming a concave portion, a part of the uniaxially stretched separator is melted. Patent Document 4 exemplifies a mortar shape as the shape of the electrolyte diffusion hole, and Patent Document 5 exemplifies embossing as a method of forming the protrusions. 6 illustrates the embossing roll temperature and the surface roughness after embossing. The techniques described in Patent Documents 3 to 6 also have a problem that the lithium ions are locally unevenly distributed because a part of the separator is provided with a site having a configuration that is significantly different from the others.

  In view of the above circumstances, the present invention has an object to provide a separator capable of improving liquid circulation and suppressing dendrite formation in a non-aqueous electrolyte battery, and a wound body or a non-aqueous electrolyte battery including the separator. To do.

  As a result of intensive studies, the present inventors have shown that in a separator having a pattern region and a non-pattern region, the separator outermost portion is the pattern top portion, the separator outermost portion is the non-pattern bottom portion, and the direction passing through the pattern top portion and the non-pattern bottom portion. In a cross-sectional view of, the non-pattern bottom, the separator surface of the non-pattern area, the separator back surface of the pattern area, found that it is possible to solve the above problems by controlling the positional relationship between the pattern top, and completed the present invention. Let

That is, the present invention includes the following aspects.
[1]
A separator used in a non-aqueous electrolyte battery,
The separator is in the form of a film having front and back surfaces, and has a pattern region in which a pattern is formed, and a non-pattern region in which the pattern is not formed,
The outermost portion of the separator surface is a pattern top portion, the outermost portion of the separator back surface is a non-pattern bottom portion, and in a cross-sectional view in the direction Z passing through the pattern top portion and the non-pattern bottom portion of the separator,
An imaginary plane that is in contact with the non-pattern bottom and is defined to be orthogonal to the direction Z is a plane B1,
An imaginary plane defined so as to be in contact with the most front side of the separator surface in the non-pattern region and to be parallel to the surface B1 is a surface F1,
An imaginary plane defined so as to be in contact with the most front side of the back surface of the separator in the pattern region and parallel to the surface B1 is a surface B2,
When a virtual plane defined by being in contact with the top of the pattern and parallel to the surface B1 is a surface F2, the surface F2 is located on the front side of the surface F1 and the surface B2 is the surface B1. A separator characterized by being located on the front side.
[2]
The distance L (F1-F2) between the surface F1 and the surface F2 is 1 μm or more and 100 μm or less, and / or the distance L (B1-B2) between the surface B1 and the surface B2 is 1 μm or more and 100 μm or less. The separator according to item 1, wherein
[3]
In the cross-sectional view of the separator in the direction Z, the region of 20% or more and 100% or less of the total cross-sectional area of the separator has the shortest distance L (min) between the front surface of the separator and the back surface of the separator is equal to item 1 or 2. The described separator.
[4]
When the shortest distance L2 (min) between the separator surface and the separator back surface in the pattern area is thickness X, and the shortest distance L1 (min) between the separator surface and the separator back surface in the non-pattern area is thickness Y The separator according to any one of Items 1 to 3, wherein the thickness X is 0.4 times or more and 1.4 times or less of the thickness Y.
[5]
Item 5. The separator according to Item 4, wherein the thickness X is more than 0.4 times and less than 1.0 times the thickness Y.
[6]
When the longest distance L2 (max) between the front surface of the separator and the back surface of the separator in the pattern area is defined as the thickness X (max), the average thickness T (ave of the separator) with respect to the thickness X (max). ) Is in the range of 0.4X (max) to 1.4X (max), The separator according to any one of Items 1 to 5.
[7]
Item 7. The separator according to Item 6, which satisfies 0.4X (max) <T (ave) <1.0X (max).
[8]
The distance L (F1-B1) between the surface F1 and the surface B1 and the distance L (F2-B2) between the surface F2 and the surface B2 are expressed by the following formula (1) or (2): 0.9 ≦ {L (F1-B1) / L (F2-B2)} ≦ 1.1 (1)
| L (F1-B1) -L (F2-B2) | <3 μm (2)
Item 9. The separator according to any one of Items 1 to 7, which satisfies the relationship.
[9]
9. The separator according to any one of Items 1 to 8, wherein the pattern has an aspect ratio of a major axis and a minor axis of 10 or less.
[10]
10. The separator according to any one of Items 1 to 9, wherein one or both of the separator front surface and the separator back surface is formed of an organic or inorganic coating layer.
[11]
Item 11. The separator according to any one of Items 1 to 10, wherein the separator is wound.
[12]
A non-aqueous electrolyte battery comprising the separator according to any one of Items 1 to 11.
[13]
13. The non-aqueous electrolyte battery according to item 12, which is a secondary battery.

  According to one aspect of the present invention, in a non-aqueous electrolyte battery including a separator, it is possible to improve the liquid flow of the non-aqueous electrolytic solution and suppress dendrite generation.

In a non-aqueous lithium ion battery comprising a separator (a) related to the prior art or a separator (b) according to one aspect of the present invention, and a non-aqueous electrolyte, a schematic for explaining the relationship between the form of the separator and the ionic behavior. It is a figure. It is a schematic cross section of the separator concerning a first embodiment of the present invention. It is a schematic cross section of the separator concerning a second embodiment of the present invention. It is a schematic cross section of the separator concerning a third embodiment of the present invention. It is a bottom view which shows the pattern shape (a)-(g) of the separator which concerns on this invention.

  Hereinafter, modes for carrying out the present invention (hereinafter, simply referred to as “embodiments”) will be described, but the present invention is not limited to the following embodiments. In addition, unless otherwise specified, the term "to" in the present specification means that the numerical values before and after the "to" are included as the upper limit value and the lower limit value. The distance is the shortest distance unless otherwise specified. Further, the configurations shown in the drawings, such as the scale, the shape, the angle, and the length, may be exaggerated or schematically shown for the purpose of describing the invention in detail.

<Separator>
One embodiment of the present invention is a separator used for a non-aqueous electrolyte battery. In one aspect, the separator is in the form of a film having front and back sides, and has a pattern region R1 in which a pattern is formed and a non-pattern region R2 in which no pattern is formed, and the outermost surface of the separator surface. Is defined as the pattern top portion T, and the outermost portion of the back surface of the separator is defined as the non-pattern bottom portion N. The separator according to one aspect of the present invention has a cross-sectional view in a direction Z passing through a pattern top portion T and a non-pattern bottom portion N:
An imaginary plane defined by the non-pattern bottom N so as to be orthogonal to the direction Z is a plane B1;
Of the separator surface F of the non-pattern region R2, an imaginary plane defined so as to be in contact with the most front side and parallel to the surface B1 is a surface F1;
An imaginary plane defined by being in contact with the most front side of the pattern region R1 so as to be in contact with the most front side and parallel to the plane B1; and an imaginary plane defined in contact with the pattern top portion T and being parallel to the plane B1. Plane F2;
Then, the surface F2 is located on the front side of the surface F1, and the surface B2 is located on the front side of the surface B1.

  FIG. 1B is a schematic diagram for explaining the relationship between the form of the separator and the ionic behavior in the non-aqueous electrolyte battery including the separator and the non-aqueous electrolytic solution according to one embodiment of the present invention. Features of one embodiment of the present invention will be described with reference to FIG. When the surface F2 is located on the front side with respect to the surface F1 and the surface B2 is located on the front side with respect to the surface B1, a flow path of the electrolytic solution is secured not only on the positive electrode side but also on the negative electrode side in the non-aqueous electrolyte battery including the separator 100. As a result, not only the liquid flow is improved, but also the membrane resistance of the separator is uniform or almost uniform, so that the generation of dendrites derived from ions tends to be suppressed.

  In the present disclosure, which of the two main surfaces of the separator 100 is the front surface and which is the back surface is defined by whether or not the conditions of the present disclosure regarding the surfaces F1, F2, B1 and B2 are satisfied. The front surface and the back surface may be the same or different from each other in elements other than the pattern shape (eg, material, porous structure, etc.).

  The positions of the surfaces B1, F1, B2, and F2 can be confirmed using a microscope image of a cross section in the thickness direction of the separator (direction orthogonal to the surface defined by the machine direction and the width direction of the separator). A scanning electron microscope or the like can be used as the microscope. The cross-section observation sample can be prepared, for example, by placing a separator on a horizontal surface (the back surface of the separator is opposed to the horizontal surface) and cutting the separator so as to pass through the pattern top portion T in the vertical direction. The size of the observation region (that is, the size of the separator in the in-plane direction) is appropriately selected so as to include the pattern to be observed and reflect the shape of the entire separator. In a separator used for non-aqueous electrolyte battery applications, an observation region that reflects the properties of the entire separator has a size of, for example, 10 mm × 10 mm. A plurality of cross-section observation samples are prepared by arbitrarily selecting three locations from the observation area. In addition, each of the plurality of cross-section observation samples is prepared so that a plurality of patterns (more specifically, for example, 2 to 100) are included. The plurality of obtained cross-section observation samples are subjected to cross-section observation to obtain a plurality of cross-section images (hereinafter, also referred to as “evaluation cross-section images”). The surfaces B1, F1, B2, and F2 are defined for each of the plurality of evaluation cross-sectional images.

  The separator according to one aspect of the present invention has a cross section in the direction Z that passes through the pattern top portion T and the non-pattern bottom portion N as long as the face F2 is located on the front side of the face F1 and the face B2 is located on the front side of the face B1. Visually, it may have any cross-sectional shape, for example, the cross-sectional shape described in the first, second or third embodiments below. Further, the thickness z of the separator is arbitrary, and it is preferable that the thickness z is not biased from the viewpoint of achieving both good liquid flow and suppression of dendrite formation.

  FIG. 2 is a schematic cross-sectional view of the separator according to the first embodiment of the present invention. The cross-sectional structure according to the first embodiment can be called, for example, an embossed structure, a double-sided concavo-convex structure, or the like. In the separator 200 shown in FIG. 2, the face F2 is located on the front side of the face F1, the face B2 is located on the front side of the face B1, and the faces F2, F1, B2, and B1 from the front side to the back side along the direction Z. They are arranged in order. Whether the separator 200 is observed from the front side or the back side, the pattern region R1 has a planar dimension with respect to the non-pattern region R2, so that embossed or uneven patterns can be observed on both the front surface and the back surface. . In FIG. 2, when the shortest distance L2 (min) between the separator surface and the back surface of the pattern region R1 is the thickness X and the longest distance L2 (max) is the thickness X (max), the separator surface and the back surface are separated. The shortest distance L (min) is equal to or substantially equal to X, and the distance L (F1-B1) between the surfaces F1 and B1 is equal to the distance L (F2-B2) between the surfaces F2 and B2, Or almost equal. However, the separator 200 may be of equal thickness or not as long as the embossed or uneven pattern can be observed on both the front surface and the back surface thereof.

  FIG. 3 is a schematic cross-sectional view of the separator according to the second embodiment of the present invention. The sectional structure according to the second embodiment can be called, for example, a jagged structure, an accordion structure, a zigzag structure, or the like. In the separator 300 shown in FIG. 3, the face F2 is located on the front side with respect to the face F1, the face B2 is located on the front side with respect to the face B1, and the faces F2, B2, F1, and B1 from the front side to the back side along the direction Z. They are arranged in order. When observing the separator 300 from either the front side or the back side, the non-pattern region R2 has a one-dimensional or two-dimensional dimension with respect to the pattern region R1, and the cross-sectional view in the direction Z of the separator 300 indicates the surface B1. Since the included angle with the back surface of the separator is almost constant, lines, points, cones or polygonal pyramidal patterns can be observed on both the front surface and the back surface of the separator. In FIG. 3, the shortest distance L2 (min) between the front and back surfaces of the separator in the pattern area R1 is the thickness X, the longest distance L2 (max) is the thickness X (max), and the separator thickness of the non-pattern area R2 is When Y is set, the shortest distance L (min) between the front surface and the back surface of the separator is equal to or approximately equal to X, and the distance L (F1-B1) between the face F1 and the face B1 and the face F2 and the face B2. The distance L (F2-B2) and the thickness Y are substantially equal. However, the separator 300 may be of equal thickness as long as lines, points, cones, or polygonal pyramidal patterns can be observed on both the front surface and the back surface thereof.

  FIG. 4 is a schematic cross-sectional view of the separator according to the third embodiment of the present invention. The sectional structure according to the third embodiment can be called a wavy structure, a continuous wavy structure, or the like. In the separator 400 shown in FIG. 4, the face F2 is located on the front side of the face F1, the face B2 is located on the front side of the face B1, and the faces F2, B2, F1, and B1 are arranged from the front side to the back side along the direction Z. They are arranged in order. When observing the separator 400 from either the front side or the back side, the non-pattern region R2 has a one-dimensional or two-dimensional dimension with respect to the pattern region R1. Since the included angle with the back surface B varies, embossed, caldera or crater patterns can be observed on both the front surface F and the back surface B. In FIG. 4, the shortest distance between the separator surface F and the back surface B is L (min), the shortest distance L2 (min) between the separator surface F and the back surface B of the pattern region R1 is the thickness X, and the separator thickness of the non-pattern region R2 is L. When the thickness is Y, the shortest distance L (min), the thickness X and the thickness Y are substantially equal. However, the separator 400 may or may not have the same thickness as long as embossed, caldera or crater patterns can be observed on both the front surface and the back surface thereof.

  The cross-sectional structures according to the first, second and third embodiments can be arbitrarily combined in one separator. A preferred configuration of the separator according to the first, second and third embodiments will be described below.

  With reference to FIGS. 2 to 4, in a cross-sectional view in the direction Z of the separator, a region where the shortest distance L (min) between the separator front surface and the separator back surface is equal is from the viewpoint of suppressing dendrite generation during charge / discharge of the nonaqueous electrolyte battery. The total cross-sectional area of the separator is preferably 20% or more and 100% or less, 22% or more and 98% or less, or 25% or more and 95% or less.

  With reference to FIGS. 2 to 4, the distance L (F1-F2) between the surface F1 and the surface F2 and / or the distance L (B1-B2) between the surface B1 and the surface B2 allows the nonaqueous electrolyte to satisfactorily flow. From the viewpoint of forming a flow path, preferably 1 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, from the viewpoint of forming a pattern region that is difficult to deform or from the viewpoint of ion permeability, preferably 100 μm or less, It is preferably 90 μm or less, more preferably 80 μm or less.

  2 to 4, the shortest distance L2 (min) between the separator surface and the back surface of the pattern area R1 is the thickness X, and the shortest distance L1 (min) between the separator surface and the back surface of the non-pattern area R2 is the thickness Y. At this time, the thickness X is preferably 0.4 times or more and 1.4 times or less the thickness Y from the viewpoint of suppressing dendrite generation, separator mechanical strength and ion permeability, and the thickness X is the thickness. More preferably, it is more than 0.4 times and less than 1.0 times Y.

With reference to FIGS. 2 to 4, when the longest distance L2 (max) between the front surface and the back surface of the separator in the pattern region R1 is set to the thickness X (max), uneven distribution of lithium ions and good mechanical strength of the separator (particularly, From the viewpoint of prevention of separator damage due to dendrite formation), the average thickness T (ave) of the separator is within the range of 0.4X (max) to 1.4X (max) with respect to the thickness X (max). It is preferable that there is, and it is more preferable that 0.4X (max) <T (ave) <1.0X (max) is satisfied. From the same viewpoint, the distance L (F1-B1) between the surface F1 and the surface B1 and the distance L (F2-B2) between the surface F2 and the surface B2 are expressed by the following formula (1) or (2):
0.9 ≦ {L (F1-B1) / L (F2-B2)} ≦ 1.1 (1)
| L (F1-B1) -L (F2-B2) | <3 μm (2)
It is preferable to satisfy the relationship of.

  In one aspect, the thickness of the separator, the thickness of each region of the separator, and the distance between the plurality of surfaces are the pattern region R1, the non-pattern region R2, and the plane F1 in the plurality of evaluation cross-sectional images described above. , F2, B1, and B2 can be measured. In one aspect, the average thickness T (ave) of the separator is calculated by calculating the shortest distance between the front surface and the back surface of the separator at each of 10 points in each of the plurality of evaluation cross-sectional images, and calculating the total number of those values. Use the average value.

<Pattern>
5A to 5G are bottom views showing the pattern shape according to one embodiment of the present invention. 5A to 5D can correspond to the separator according to the first or third embodiment. 5E to 5G can correspond to the separator according to the second embodiment. The shape of the pattern when the separator is viewed from the bottom (that is, the plan view from the back surface side of the separator) is circular as shown in FIGS. 5A and 5B, oval as shown in FIG. An S-shape as shown in (d), a waveform as shown in FIGS. 5 (e) and (f), a stripe as shown in FIG. 5 (g), a polygon not shown (for example, a rectangle, a pentagon, a hexagon). Etc.) and the like. The bottom view shape of the pattern may be a closed figure as shown in FIGS. 5A to 5D or may be an open figure as shown in FIGS. 5E to 5G. Further, the non-pattern region R2 may have a substantially linear shape as shown in FIG. 5 (f) or (g), or a substantially dot (dot) shape (not shown). In a typical embodiment, the separator has a plurality of patterns arranged regularly or randomly. In one aspect, it is preferable that the patterns are arranged in a grid pattern (that is, a grid pattern) from the viewpoint of achieving good physical property uniformity over the entire separator while obtaining the advantages of the pattern formation. In the present disclosure, the lattice-like array means an array at predetermined intervals along two intersecting directions. Therefore, the grid-like array includes a hexagonal array (FIG. 5A), a tetragonal array (FIG. 5B), a three-way array (not shown), and the like. The arrangement of the plurality of patterns may be one type or a combination of two or more types among those exemplified above.

  With reference to FIGS. 5A to 5G, in one aspect, the aspect ratio L / D between the major axis L and the minor axis D of the bottom view shape of the pattern region is 1 or more, for example, 2 or more, or It may be 3 or more, or 5 or more, and is preferably 10 or less, more preferably 9 or less, and further preferably 8 or less from the viewpoint of good formation of the flow path of the non-aqueous electrolyte. In the present disclosure, the major axis L and the minor axis D are respectively defined as the long side and the short side of the circumscribing rectangle in a bottom view shape.

  The major axis L and the minor axis D can be measured by the following method. That is, the back surface of the separator is observed with a microscope. The observation region is selected so as to reflect the properties of the entire separator and has, for example, the size of 10 mm × 10 mm described above. The outer edge of the pattern area is determined on the obtained back surface image. When the outer edge is a closed figure, the circumscribed rectangle of the closed figure is determined, and the long side of the circumscribed rectangle is the major axis L and the short side is the minor axis D. On the other hand, when the outer edges are open figures, the shortest distance between the outer edges in each pattern area is the minor axis D, and the major axis L has no value.

  In one aspect, the major axis L is preferably 150 μm or more, more preferably 200 μm or more, still more preferably 300 μm or more, from the viewpoint of forming a pattern region that is difficult to deform, and forms a flow path in which the non-aqueous electrolyte can satisfactorily flow. From this viewpoint, the thickness is preferably 1800 μm or less, more preferably 1500 μm or less, still more preferably 1200 μm or less.

  In one aspect, the minor axis D is preferably 100 μm or more, more preferably 120 μm or more, from the viewpoint of forming a pattern region that is difficult to deform, and from the viewpoint of forming a flow path in which the nonaqueous electrolyte can satisfactorily flow. Is 1500 μm or less, more preferably 1200 μm or less, still more preferably 1000 μm or less.

  With reference to FIGS. 5A to 5G, it is preferable that the bottom view shape of the pattern region has a regular array having a constant pitch P. In the present disclosure, the pitch P means the shortest distance between adjacent pattern regions. The pitch P is preferably 170 μm or more, more preferably 220 μm or more, still more preferably 320 μm or more from the viewpoint of forming a flow path through which the nonaqueous electrolyte can satisfactorily flow, and from the above viewpoint, preferably 1820 μm or less, more preferably Is 1520 μm or less, more preferably 1220 μm or less. In one aspect, the pitch P is measured for all the patterns in the back surface image, and the number average value thereof is set as the value of the pitch P.

  The separator for a non-aqueous electrolyte secondary battery can be used as a laminate of a positive electrode and a negative electrode and a separator, or a wound body thereof. Due to the presence of the pattern region R1, there is a space that functions well as a flow path for the non-aqueous electrolyte in the laminate or the wound body thereof, particularly on the surface F side of the separator. This space contributes to the improvement of liquid flow at the time of charging and / or discharging of the non-aqueous electrolyte battery, and also contributes to suppression of electrode material deterioration, suppression of electrolyte deterioration and dendrite formation by uniform diffusion of the non-aqueous electrolyte when the battery is used. To do.

  Further, when the separator is formed of a microporous film, the pattern region R1 also retains a porous structure (that is, retains the function as a separator), so that, for example, a convex portion or a concave portion is different from the microporous membrane. It has an advantage that the effective area is large as compared with the case where it is formed of a material.

[Separator material]
The separator of the present embodiment can be manufactured by forming a pattern of a desired shape on the base material by embossing or the like. Hereinafter, a suitable example of the material of the separator will be described.

As the base material, a material having high ion permeability and having a function of electrically isolating the positive electrode and the negative electrode, for example, a known microporous membrane used in a non-aqueous electrolyte secondary battery can be used.
Specifically, such as polyolefins (polyethylene (PE), polypropylene (PP), etc.), polyesters, polyimides, polyamides, polyurethanes, etc., are stable to the non-aqueous electrolyte in the battery and are electrochemically stable. A microporous membrane or a non-woven fabric made of a stable material can be used as the substrate.
In addition, as a substrate, at a temperature of preferably 80 ° C. or higher (more preferably 100 ° C. or higher), and preferably 180 ° C. or lower (more preferably 150 ° C. or lower), the function of closing its pores (that is, shutdown function) ) Are preferred. Therefore, the base material has a melting temperature, that is, a melting temperature range measured using a differential scanning calorimeter (DSC) according to JIS K 7121, preferably 80 ° C. or higher (more preferably 100 ° C. or higher). ), And it is more preferable to use a microporous membrane or nonwoven fabric containing a polyolefin having a temperature of 180 ° C or lower (more preferably 150 ° C or lower). In this case, the microporous membrane or the non-woven fabric as the base material may be composed of PE alone, PP alone, or may contain two or more kinds of materials.
The base material is not limited to a single material, and may include a plurality of layers. Therefore, the base material is a laminated body of a microporous membrane made of PE and a microporous membrane made of PP (PP / PE / PP three-layer laminated body, etc.), a microporous membrane made of PE and a microporous membrane made of polyimide. It may be a laminated body or the like.
As a typical example of the substrate, a microporous polyolefin membrane or the like can be mentioned.

(Polyolefin microporous membrane)
The polyolefin microporous film is configured to include a polyolefin resin. The polyolefin resin is not particularly limited, and examples thereof include homopolymers of ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and the like, and copolymers thereof, multistage polymers and the like. Can be used. More specifically, but not limited to, low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, isotactic polypropylene, atactic polypropylene, ethylene-propylene random copolymer, polybutene. , And ethylene propylene rubber.
Among them, when the application to a non-aqueous electrolyte secondary battery is assumed, a resin having a low melting point and high strength and having high density polyethylene as a main component is preferable as the polyolefin resin.

  It is more preferable to use polypropylene and a polyolefin resin other than polypropylene in combination. The use of such a polyolefin resin tends to further improve the heat resistance of the separator. The three-dimensional structure of polypropylene is not particularly limited, but examples thereof include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene.

  As content of polypropylene, 1-35 mass% is preferable with respect to 100 mass% of polyolefin resin, 3-20 mass% is more preferable, 4-10 mass% is still more preferable. When the content of polypropylene is within the above range, higher heat resistance and a better shutdown function tend to be compatible.

The polyolefin resin other than polypropylene is not particularly limited, but examples thereof include those mentioned above, and among them, polyethylene, polybutene, ethylene-propylene random copolymer and the like are preferable. In particular, low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, and ultrahigh molecular weight polyethylene are more preferable from the viewpoint of shutdown characteristics. From the viewpoint of strength, polyethylene having a density measured according to JIS K 7112 of 0.93 g / cm ³ or more is also preferable.
The polyolefin resins may be used alone or in combination of two or more.

  The content of the polyolefin resin is preferably 50% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, and further preferably 70% by mass or more and 100% by mass or less with respect to 100% by mass of the base material. preferable. When the content of the polyolefin resin is within the above range, the shutdown performance tends to be further improved when the polyolefin resin is used as a separator for a non-aqueous electrolyte secondary battery.

  The viscosity average molecular weight of the polyolefin resin is preferably from 30,000 to 12,000,000, more preferably from 50,000 to 2,000,000, still more preferably from 100,000 to 1,000,000. When the viscosity average molecular weight is 30,000 or more, the melt tension at the time of melt molding becomes large, the moldability of the base material becomes good, and the base material tends to have higher strength due to the entanglement of the polymers. On the other hand, when the viscosity average molecular weight is 12,000,000 or less, it becomes easy to uniformly melt and knead, and the moldability of the sheet, particularly the thickness stability tends to be excellent. Furthermore, when the viscosity average molecular weight is 1,000,000 or less, pores are likely to be clogged when the temperature rises, and a good shutdown function tends to be obtained. Note that, for example, instead of using a polyolefin having a viscosity average molecular weight of less than 1,000,000 alone, it is a mixture of a polyolefin having a viscosity average molecular weight of 2 million and a polyolefin having a viscosity average molecular weight of 270,000, and the viscosity average molecular weight is less than 1 million. A polyolefin resin mixture may be used.

  The substrate can contain any additive. The additives are not particularly limited, but include, for example, polymers other than polyolefin resin; inorganic particles; resin fine particles; antioxidants such as phenol-based, phosphorus-based, and sulfur-based; metal soaps such as calcium stearate and zinc stearate; Examples include UV absorbers, light stabilizers, antistatic agents, antifogging agents, and coloring pigments.

  When the substrate contains inorganic particles and / or resin fine particles, the polyolefin microporous film may contain inorganic particles and / or resin fine particles.

The inorganic particles are preferably sodium oxide, potassium oxide, magnesium oxide, calcium oxide, barium oxide, lanthanum oxide, cerium oxide, strontium oxide, vanadium oxide, SiO ₂ —MgO (magnesium silicate), SiO ₂ —CaO ( Calcium silicate), hydrotalcite, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, lanthanum carbonate, cerium carbonate, basic titanate, basic silicotitanate, basic copper acetate, basic sulfuric acid Lead, layered double hydroxide (Mg-Al type, Mg-Fe type, Ni-Fe type, Li-Al type), layered double hydroxide-alumina silica gel composite, boehmite, alumina, zinc oxide, lead oxide, Iron oxide, iron oxyhydroxide, hematite, bismuth oxide, Anions such as tin oxide, titanium oxide, zirconium oxide, zirconium phosphate, titanium phosphate, apatite, non-basic titanate, niobate, cation adsorbents such as niobium titanate, zeolite, Carbonates such as calcium sulfate, magnesium sulfate, aluminum sulfate, gypsum and barium sulfate, and sulfates, alumina trihydrate (ATH), fumed silica, precipitated silica, zirconia, oxide ceramics such as yttria, nitriding Nitride-based ceramics such as silicon, titanium nitride, and boron nitride, layered silicates such as silicon carbide, kaolinite, talc, dickite, nacrite, halloysite, pyrophyllite, montmorillonite, sericite, amethite, bentonite, asbestos, and silicate. Algae earth, glass fiber, go Layered silicates, e.g., be selected mica or fluoro mica, and from the group consisting of zinc borate. These may be used alone or in combination of two or more.

  The resin fine particles have heat resistance and electrical insulation, are stable to non-aqueous electrolytes, and are not easily redox-reduced in the operating voltage range of non-aqueous electrolyte secondary batteries, and are electrochemically stable resins. It is preferable that As a resin for forming such resin fine particles, styrene resin (polystyrene etc.), styrene-butadiene rubber, acrylic resin (polymethylmethacrylate etc.), polyalkylene oxide (polyethylene oxide etc.), fluororesin (polyvinylidene fluoride). Etc.) and a cross-linked product of at least one resin selected from the group consisting of derivatives thereof, urea resins, polyurethanes and the like. As the resin fine particles, the resins exemplified above may be used alone or in combination of two or more. Further, the resin fine particles may contain a known additive that can be added to the resin, such as an antioxidant, if necessary.

  The form of the inorganic particles or resin fine particles may be any of plate-like, scale-like, needle-like, columnar, spherical, polyhedral, and lump-like forms. The inorganic particles or resin particles having the above-mentioned form may be used alone or in combination of two or more. From the viewpoint of improving the transparency, a polyhedral shape having a plurality of surfaces is preferable.

  The average particle diameter (D50) of the inorganic particles or resin fine particles is preferably 0.1 μm to 4.0 μm, more preferably 0.2 μm to 3.5 μm, and 0.4 μm. More preferably, it is about 3.0 μm. By adjusting the average particle size within such a range, heat shrinkage at high temperature tends to be further suppressed.

  The total content of these additives is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the base material. The lower limit of the total content is not particularly limited, and can be, for example, more than 0 parts by mass with respect to 100 parts by mass of the base material.

(Coating layer)
In one aspect, the front surface, the back surface, or both of the separators are each formed of an inorganic or organic coating layer. Such a separator can be manufactured by forming a coating layer on one surface or both surfaces of a base material. The coating layer may be present in the patterned area, the non-patterned area, or both. The inorganic coating layer is preferable from the viewpoint of heat resistance, dimensional stability, strength and the like. The organic coating layer is preferable from the viewpoint of strength, thermoplasticity, adhesiveness to electrodes, prevention of press-back or roll-back of the wound body, and the like.

The inorganic layer is not particularly limited, but examples thereof include those containing an inorganic filler and a resin binder.
Among these, as the inorganic filler, those exemplified above as the inorganic particles can be preferably used. Among them, aluminum oxide compounds such as alumina and boehmite, or ion exchange capacities of kaolinite, dikite, nacrite, halloysite, pyrophyllite, etc., from the viewpoint of improving electrochemical stability and heat resistance of the microporous membrane. Aluminum silicate compounds which do not have are preferred. Aluminum hydroxide oxide is preferable as the aluminum oxide compound. As the aluminum silicate compound having no ion-exchange ability, kaolin mainly composed of kaolin minerals is preferable because it is inexpensive and easily available. Kaolin includes wet kaolin and calcined kaolin obtained by calcining it. Calcined kaolin releases impurities in addition to water of crystallization during the calcining process, and therefore has a significant electrochemical stability. Is particularly preferable.

  The shape of the inorganic filler is not particularly limited, and examples thereof include a plate shape, a scale shape, a needle shape, a columnar shape, a spherical shape, a polyhedral shape, and a lump shape, and a plurality of kinds of inorganic fillers having the above shapes are used in combination. Good. Among them, a polyhedron shape having a plurality of surfaces, a columnar shape, and a spindle shape are preferable. By using such an inorganic filler, the permeability tends to be further improved.

  As content of an inorganic filler, with respect to 100 mass% of inorganic layers, 50 mass% or more and less than 100 mass% are preferable, 70 mass% or more and 99.99 mass% or less are more preferable, 80 mass% or more and 99.9 mass%. % Or less is more preferable, and 90% by mass or more and 99% by mass or less is particularly preferable. When the content of the inorganic filler is within the above range, the binding property of the inorganic filler, the heat resistance, and the permeability in the case of a multilayer microporous film tend to be further improved.

  The resin binder is not particularly limited, but it is preferable to use one that is insoluble in the non-aqueous electrolyte and is electrochemically stable in the range of use of the lithium ion secondary battery. The resin binder is not particularly limited, but examples thereof include polyolefins such as polyethylene and polypropylene; fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene; vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymerization Fluorine-containing rubber such as polymer, ethylene-tetrafluoroethylene copolymer; styrene-butadiene copolymer, and its hydride, acrylonitrile-butadiene copolymer, and its hydride, acrylonitrile-butadiene-styrene copolymer, and Its hydride, methacrylic acid ester-acrylic acid ester copolymer, styrene-acrylic acid ester copolymer, acrylonitrile-acrylic acid ester copolymer, ethylene propylene rubber, polyvinyl alcohol, poly Rubbers such as vinyl acetate; cellulose derivatives such as ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose; melting points of polyphenylene ether, polysulfone, polyether sulfone, polyphenylene sulfide, polyetherimide, polyamideimide, polyamide, polyester, and / or the like. Examples thereof include resins having a glass transition temperature of 180 ° C. or higher.

  When polyvinyl alcohol is used as the resin binder, the saponification degree is preferably 85% or more and 100% or less, more preferably 90% or more and 100% or less, further preferably 95% or more and 100% or less, and 99% or more 100%. The following are particularly preferred. When the saponification degree of PVA is 85% or more, the temperature at which the separator short-circuits (short-circuit temperature) is improved, and better safety performance tends to be obtained.

  The polymerization degree of polyvinyl alcohol is preferably 200 or more and 5,000 or less, more preferably 300 or more and 4,000 or less, and further preferably 500 or more and 3,500 or less. When the polymerization degree is 200 or more, a small amount of polyvinyl alcohol can firmly bind the inorganic filler such as calcined kaolin to the inorganic layer, and suppress the increase in air permeability of the base material while maintaining the mechanical strength of the inorganic layer. Tend to be able to. Further, when the degree of polymerization is 5,000 or less, gelation or the like tends to be prevented when the coating liquid is prepared.

  As the resin binder, a resin latex binder is preferable. By using the resin-made latex binder, the ion permeability is less likely to decrease and high output characteristics tend to be easily obtained. In addition, even when the temperature rises rapidly during abnormal heat generation, smooth shutdown characteristics are exhibited, and high safety tends to be easily obtained.

  The resin latex binder is not particularly limited, but for example, from the viewpoint of improving electrochemical stability and binding property, an aliphatic conjugated diene monomer, an unsaturated carboxylic acid monomer, and an aliphatic binder. Emulsifying a conjugated diene-based monomer, and / or an unsaturated carboxylic acid monomer, and an aliphatic conjugated diene-based monomer, and / or another monomer copolymerizable with the unsaturated carboxylic acid monomer Those obtained by polymerization are preferred. The emulsion polymerization method is not particularly limited, and a known method can be used. The addition method of the monomer and other components is not particularly limited, and any one of a batch addition method, a divided addition method, and a continuous addition method can be adopted, and one-step polymerization, two-step polymerization or Any of multi-step polymerization and the like can be adopted.

  The aliphatic conjugated diene-based monomer is not particularly limited, but examples thereof include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3 butadiene, and 2-chloro-1. , 3-butadiene, substituted linear conjugated pentadienes, substituted, and side chain conjugated hexadienes. These may be used alone or in combination of two or more. Among the above, 1,3-butadiene is particularly preferable.

  The unsaturated carboxylic acid monomer is not particularly limited, and examples thereof include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid. These may be used alone or in combination of two or more. Among the above, acrylic acid and methacrylic acid are particularly preferable.

Other monomers copolymerizable with the aliphatic conjugated diene monomer and / or the unsaturated carboxylic acid monomer are not particularly limited, but include, for example, aromatic vinyl monomers and vinyl cyanide. Examples thereof include system monomers, unsaturated carboxylic acid alkyl ester monomers, hydroxyalkyl group-containing unsaturated monomers and unsaturated carboxylic acid amide monomers. These may be used alone or in combination of two or more.
Of these, unsaturated carboxylic acid alkyl ester monomers are particularly preferable. The unsaturated carboxylic acid alkyl ester monomer is not particularly limited, and examples thereof include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl. Examples thereof include maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, and 2-ethylhexyl acrylate. These may be used alone or in combination of two or more. Among the above, methyl methacrylate is particularly preferable.
In addition to these monomers, in order to improve various quality and physical properties, monomer components other than the above may be further used.

  The average particle size of the resin binder is preferably 50 to 800 nm, more preferably 60 to 700 nm, and even more preferably 80 to 500 nm. When the average particle diameter of the resin binder is 50 nm or more, when the inorganic layer is laminated on at least one side of the polyolefin microporous film, the ion permeability is unlikely to decrease and high output characteristics tend to be easily obtained. In addition, even when the temperature rises rapidly during abnormal heat generation, smooth shutdown characteristics are exhibited, and high safety tends to be easily obtained. When the average particle diameter of the resin binder is 800 nm or less, good binding properties are exhibited, and when a multilayer microporous film is formed, heat shrinkage becomes good and safety tends to be excellent. The average particle size of the resin binder can be controlled by adjusting the polymerization time, the polymerization temperature, the raw material composition ratio, the raw material feeding order, the pH and the like.

  The layer thickness of the inorganic layer is preferably 1 to 50 μm, more preferably 1.5 to 20 μm, further preferably 2 to 10 μm, further preferably 3 to 10 μm, and particularly preferably 3 to 7 μm. When the layer thickness of the inorganic layer is 1 μm or more, the heat resistance and insulating property of the base material tend to be further improved. Moreover, when the layer thickness of the inorganic layer is 50 μm or less, the battery capacity and the permeability tend to be further improved.

The layer density of the inorganic layer is preferably ^{0.5~2.0g / cm 3, 0.7~1.5g / cm} 3 is more preferable. When the layer density of the inorganic layer is 0.5 g / cm ³ or more, the heat shrinkage rate at high temperature tends to be good. Further, when the layer density of the inorganic layer is 2.0 g / cm ³ or less, the air permeability tends to be further reduced.

  An example of the organic coating layer is an adhesive layer. The adhesive layer comprises a thermoplastic polymer. The position of the adhesive layer on the separator is not particularly limited. For example, a separator having an adhesive layer disposed on at least one surface thereof, a separator having the above-mentioned inorganic layer disposed on at least one surface of the above microporous membrane, and an adhesive layer provided on at least one surface thereof may be mentioned. The adhesive layer may be arranged on all of at least one surface of the separator, or may be arranged on only a part thereof. In the adhesive layer, the portion containing the thermoplastic polymer and the portion not containing the thermoplastic polymer may exist in a sea-island shape. In a preferred embodiment, the adhesive layer is preferably formed on the back surface of the separator, which can reduce the contact area between the pattern and the adhesive layer.

[Characteristics of separator]
The separator is configured to include the above base material. The porosity of the separator is preferably 30% or more, and preferably 40% or more, in a dry state of the separator, in order to secure a holding amount of the non-aqueous electrolyte and improve ion permeability. More preferable. On the other hand, from the viewpoint of ensuring the strength of the separator and preventing an internal short circuit, the porosity of the separator is preferably 80% or less, and more preferably 70% or less in the dried state of the separator. The porosity Po (%) of the separator is calculated from the thickness of the separator including the pattern height (that is, the distance between the plane B1 and the plane F2), the mass per area, and the density of the constituents as follows. formula:
Po = {1- (m / t) / (Σa _i · ρ _i )} × 100
{In the formula, a _i is the ratio of the component i when the total mass is 1, ρ _i is the density (g / cm ³ ) of the component i, and m is the unit area of the separator. It is a mass (g / cm ² ), and t is a thickness (cm) including the pattern height of the separator. }
Can be calculated by calculating the total sum for each component i.

The air permeability of the separator is preferably 10 seconds / 100 cm ³ or more and 500 seconds / 100 cm ³ or less, more preferably 20 seconds / 100 cm ³ or more and 450 seconds / 100 cm ³ or less, and further preferably 30 seconds. / 100 cm ³ or more and 450 seconds / 100 cm ³ or less. When the air permeability is 10 seconds / 100 cm ³ or more, self-discharge tends to be less when the separator is used in a non-aqueous electrolyte secondary battery. Further, when the air permeability is 500 seconds / 100 cm ³ or less, better charge / discharge characteristics tend to be obtained.

[Method of manufacturing separator]
(Method of manufacturing base material)
The method for producing the base material is not particularly limited, but, for example, a known production method can be adopted. As a known manufacturing method, for example, after a composition containing a polyolefin resin or the like (hereinafter, also referred to as “resin composition”) and a plasticizer are melt-kneaded to form a sheet, and optionally stretched, Method of making porous by extracting plasticizer; Method of making resin composition melt-kneaded and extruding at a high draw ratio, and then making it porous by peeling the resin crystal interface by heat treatment and stretching; Resin composition and inorganic A method of forming a sheet by melt-kneading a filler and forming a sheet, and then making the interface porous by peeling the interface between the resin and the inorganic filler; after the resin composition is dissolved, the resin is immersed in a poor solvent for the resin. Examples of the method include a method of solidifying the solution and a method of making it porous by removing the solvent at the same time.

  Here, the method of forming the pattern is not particularly limited, and examples thereof include a method of passing a sheet of the resin composition between both rolls of a predetermined embossing roll and a predetermined elastic backup roll. . The processing conditions such as the linear pressure between both rolls and the outer diameter and surface temperature of each roll can be adjusted appropriately. The elastic backup roll preferably has a rubber hardness according to JIS K6253 Durometer Type A of 50 ° or less. By satisfying this hardness, it is possible to prevent the holes of the separator from being blocked. The rubber hardness of the elastic backup roll according to JIS K6253 Durometer Type A is more preferably 40 ° or less, 30 ° or less, or 20 ° or less. Silicon rubber and its foam are preferably used as the material of the elastic backup roll.

  For example, when the separator has an inorganic layer, the method of forming the inorganic layer is not particularly limited, for example, at least one surface of the microporous film, inorganic by applying a coating liquid containing an inorganic filler and a resin binder. The method of forming a layer can be mentioned.

  The method of dispersing the inorganic filler and the resin binder in the solvent of the coating solution is not particularly limited, for example, ball mill, bead mill, planetary ball mill, vibrating ball mill, sand mill, colloid mill, attritor, roll mill, high-speed impeller dispersion. , A disperser, a homogenizer, a high-speed impact mill, ultrasonic dispersion, mechanical stirring with a stirring blade, and the like.

  The method of applying the coating liquid to the substrate is not particularly limited, for example, gravure coater method, small diameter gravure coater method, reverse roll coater method, transfer roll coater method, kiss coater method, dip coater method, knife coater method, air The doctor coater method, the blade coater method, the rod coater method, the squeeze coater method, the cast coater method, the die coater method, the screen printing method, the spray coating method and the like can be mentioned.

  The method of removing the solvent from the coating film after coating is not particularly limited as long as it does not adversely affect the microporous film, for example, a method of drying at a temperature below its melting point while fixing the microporous film or Examples include a method of drying under reduced pressure at a low temperature. From the viewpoint of controlling the shrinkage stress in the flow direction (MD direction) of the microporous membrane, it is preferable to appropriately adjust the drying temperature, the winding tension, and the like.

  The method of dispersing the inorganic filler and the resin binder in the solvent of the coating solution is not particularly limited, for example, ball mill, bead mill, planetary ball mill, vibrating ball mill, sand mill, colloid mill, attritor, roll mill, high-speed impeller dispersion. , A disperser, a homogenizer, a high-speed impact mill, ultrasonic dispersion, mechanical stirring with a stirring blade, and the like.

  The method of applying the coating liquid to the substrate is not particularly limited, for example, gravure coater method, small diameter gravure coater method, reverse roll coater method, transfer roll coater method, kiss coater method, die coater method, screen printing method, spray Examples include a coating method and a transfer method. More specifically, a fine pattern can be formed by coating a base material with a roll and drying.

[Use mode of separator]
The separator of the present embodiment can be applied to a laminated or wound type non-aqueous electrolyte secondary battery. One preferable embodiment is a wound body formed by winding a separator (separator wound body). The diameter of the tube (core) around which the separator is wound is not particularly limited as long as it is a diameter used as a product, but is preferably 2 inches (about 5.08 cm) or more, more preferably 3 inches or more, and further preferably Is 6 inches or more. From the standpoint of roll productivity, the tube diameter can be 10 inches or less.

  The material of the tube around the separator is not particularly limited. It may include any of paper, ABS resin, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, and vinyl chloride resin. Of these, a resin is preferable, and the resin may include any of ABS resin, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, and vinyl chloride resin.

  Although the winding length of the separator is not particularly limited, it is preferably 300 m or more, more preferably 400 m or more, and further preferably 500 m or more, from the viewpoint of productivity in producing a battery. The winding length of the separator may be 5000 m or less from the viewpoint of roll productivity.

[Secondary battery]
One embodiment of the present invention is a secondary battery including an electrolyte and a stacked body in which a positive electrode, the separator described above, and a negative electrode are stacked or a wound body of the stacked body (a rolled product). Further, one embodiment of the present invention includes a positive electrode, a separator described above, and a laminated body in which the negative electrode is laminated or a wound body of the laminated body (rolled material), and a non-aqueous electrolyte. It is an electrolyte secondary battery.

  Examples of the form of the non-aqueous electrolyte secondary battery include a tubular shape (for example, a square tubular shape, a cylindrical shape, etc.) using a steel can, an aluminum can, or the like as an outer can. In addition, a non-aqueous electrolyte secondary battery can be constructed by using a laminated film having a metal deposited thereon as an exterior body. A lithium ion secondary battery is a typical example of the non-aqueous electrolyte secondary battery.

[Positive electrode]
The positive electrode preferably includes a positive electrode active material, a conductive material, a binder, and a current collector. As the positive electrode active material that can be contained in the positive electrode, a known material that can occlude and release lithium ions electrochemically can be used. Above all, a material containing lithium is preferable as the positive electrode active material. Note that conductive materials, binders, and current collectors known in the art may be used to form the positive electrode.

[Negative electrode]
The negative electrode preferably contains a negative electrode active material, a binder, and a current collector. As the negative electrode active material that can be included in the negative electrode, a known substance that can electrochemically store and release lithium ions can be used. The negative electrode active material is not particularly limited, but carbon materials such as graphite powder, mesophase carbon fibers, and mesophase spherules; and metals, alloys, oxides, and nitrides are preferable. These may be used alone or in combination of two or more. Note that a binder and a collector known in the art may be used to form the negative electrode.

[Non-aqueous electrolyte]
As the non-aqueous electrolyte, for example, a solution (non-aqueous electrolytic solution) in which a lithium salt is dissolved in an organic solvent is used. The lithium salt is not particularly limited, and known ones can be used. Such a lithium salt is not particularly limited, but for example, LiPF ₆ (lithium hexafluorophosphate), LiClO ₄ , LiBF ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F _{2k + 1} [formula In the formula, k is an integer of 1 to 8], LiN (SO ₂ C _k F _{2k + 1} ) ₂ [wherein, k is an integer of 1 to 8], LiPF _n (C _k F _{2k + 1} ) _6-n [in the formula, n is an integer of 1 to 5 and k is an integer of 1 to 8], LiPF ₄ (C ₂ O ₄ ), and LiPF ₂ (C ₂ O ₄ ) ₂ To be Of these, LiPF ₆ is preferable. By using LiPF ₆ , the battery characteristics and safety tend to be superior even at high temperatures. These lithium salts may be used alone or in combination of two or more.
The non-aqueous solvent used for the non-aqueous electrolyte is not particularly limited, and known ones can be used. Examples of the non-aqueous solvent include aprotic polar solvents.

  The aprotic polar solvent is not particularly limited, but for example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate. Cyclic carbonates such as trifluoromethylethylene carbonate, fluoroethylene carbonate, and 4,5-difluoroethylene carbonate; lactones such as γ-ptyrolactone and γ-valerolactone; cyclic sulfones such as sulfolane; cyclic ethers such as tetrahydrofuran and dioxane; ethyl Methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isoprovir carbonate, dipropyl carbonate, methyl butyl carbonate Chain carbonates such as bonates, dibutyl carbonate, ethylpropyl carbonate, and methyltrifluoroethyl carbonate; nitriles such as acetonitrile; chain ethers such as dimethyl ether; chain carboxylic acid esters such as methyl propionate; and chains such as dimethoxyethane Specific ether carbonate compounds may be mentioned. These may be used alone or in combination of two or more.

  The non-aqueous electrolyte may contain other additives as needed. Such additives are not particularly limited, for example, lithium salts other than those exemplified above, unsaturated bond-containing carbonates, halogen atom-containing carbonates, carboxylic acid anhydrides, sulfur atom-containing compounds (for example, sulfides, disulfides , Sulfonic acid esters, sulfites, sulfates, sulfonic acid anhydrides, etc.), nitrile group-containing compounds, and the like.

Specific examples of other additives are as follows:
Lithium salt: For example, lithium monofluorophosphate, lithium difluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium tetrafluoro (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, etc .;
Unsaturated bond-containing carbonate: for example, vinylene carbonate, vinyl ethylene carbonate, etc .;
Halogen atom-containing carbonate: for example, fluoroethylene carbonate, trifluoromethylethylene carbonate, etc .;
Carboxylic anhydrides: for example, acetic anhydride, benzoic anhydride, succinic anhydride, maleic anhydride, etc .;
Sulfur atom-containing compound: For example, ethylene sulfite, 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, ethylene sulfate, vinylene sulfate, etc .;
Nitrile group-containing compound: For example, succinonitrile and the like.

When the non-aqueous electrolyte contains the other additive described above, the cycle characteristics of the battery tend to be further improved.
Among them, at least one selected from the group consisting of lithium difluorophosphate and lithium monofluorophosphate is preferable from the viewpoint of further improving the cycle characteristics of the battery. The content of at least one additive selected from the group consisting of lithium difluorophosphate and lithium monofluorophosphate is preferably 0.001% by mass or more based on 100% by mass of the non-aqueous electrolyte, and is 0.1. 005 mass% or more is more preferable, and 0.02 mass% or more is still more preferable. When the content is 0.001% by mass or more, the cycle life of the lithium ion secondary battery tends to be further improved. Further, this content is preferably 3% by mass or less, more preferably 2% by mass or less, still more preferably 1% by mass or less. When the content is 3% by mass or less, the ionic conductivity of the lithium ion secondary battery tends to be further improved.
The content of other additives in the non-aqueous electrolyte can be confirmed by NMR measurement such as ³¹ P-NMR and ¹⁹ F-NMR.

  The concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.5 mol / L to 6.0 mol / L. From the viewpoint of reducing the viscosity of the non-aqueous electrolyte, the concentration of the lithium salt in the non-aqueous electrolyte is more preferably 0.9 mol / L to 1.25 mol / L. The concentration of the lithium salt in the non-aqueous electrolyte can be selected according to the purpose.

  Although one aspect of the present invention has been described above, the present invention is not limited to the above-described embodiment, and additions, omissions, substitutions, and other modifications of the configuration are possible within the scope of the gist of the present invention. It is possible.

x, y, z, X, Y, X (max) Thickness R1 Pattern area R2 Non-pattern area T Pattern top N Non-pattern bottom Z Direction passing through pattern top and non-pattern bottom B1, F1, B2, F2 surface ( Virtual plane)
Side B (back side of separator)
F side (separator surface)
100, 200, 300, 400 Separator L (min) Shortest distance between separator surface and back surface L1 (min) Shortest distance between separator surface and back surface in non-pattern area L2 (min) Shortest distance between separator surface and back surface in pattern area L2 ( max) longest distance between the front and back surfaces of the separator in the pattern area L (F1-F2) distance between faces F1 and F2 L (B1-B2) distance between faces B1 and B2 L (F1-B1) face F1 and faces B1 distance L (F2-B2) Face F2 and face B2 distance D Minor diameter L Major diameter P Pitch

Claims (13)

A separator used in a non-aqueous electrolyte battery,
The separator is in the form of a film having front and back surfaces, and has a pattern region in which a pattern is formed, and a non-pattern region in which the pattern is not formed,
The outermost portion of the separator surface is a pattern top portion, the outermost portion of the separator back surface is a non-pattern bottom portion, and in a cross-sectional view in the direction Z passing through the pattern top portion and the non-pattern bottom portion of the separator,
An imaginary plane that is in contact with the non-pattern bottom and is defined to be orthogonal to the direction Z is a plane B1,
An imaginary plane defined so as to be in contact with the most front side of the separator surface in the non-pattern region and to be parallel to the surface B1 is a surface F1,
An imaginary plane defined so as to be in contact with the most front side of the back surface of the separator in the pattern region and parallel to the surface B1 is a surface B2,
When a virtual plane defined by being in contact with the top of the pattern and parallel to the surface B1 is a surface F2, the surface F2 is located on the front side of the surface F1 and the surface B2 is the surface B1. A separator characterized by being located on the front side.   The distance L (F1-F2) between the surface F1 and the surface F2 is 1 μm or more and 100 μm or less, and / or the distance L (B1-B2) between the surface B1 and the surface B2 is 1 μm or more and 100 μm or less. The separator according to claim 1, wherein   The shortest distance L (min) between the separator front surface and the separator back surface is equal in a region of 20% or more and 100% or less of the total cross-sectional area of the separator in a cross-sectional view of the separator in the direction Z. Separator described in.   When the shortest distance L2 (min) between the separator surface and the separator back surface in the pattern area is thickness X, and the shortest distance L1 (min) between the separator surface and the separator back surface in the non-pattern area is thickness Y The separator according to any one of claims 1 to 3, wherein the thickness X is 0.4 times or more and 1.4 times or less than the thickness Y.   The separator according to claim 4, wherein the thickness X is more than 0.4 times and less than 1.0 times the thickness Y.   When the longest distance L2 (max) between the front surface of the separator and the back surface of the separator in the pattern area is defined as the thickness X (max), the average thickness T (ave of the separator) with respect to the thickness X (max). ) Is in the range of 0.4X (max) to 1.4X (max), The separator according to any one of claims 1 to 5.   The separator according to claim 6, which satisfies 0.4X (max) <T (ave) <1.0X (max). The distance L (F1-B1) between the surface F1 and the surface B1 and the distance L (F2-B2) between the surface F2 and the surface B2 are expressed by the following formula (1) or (2): 0.9 ≦ {L (F1-B1) / L (F2-B2)} ≦ 1.1 (1)
| L (F1-B1) -L (F2-B2) | <3 μm (2)
The separator according to any one of claims 1 to 7, which satisfies the relationship of.   The separator according to any one of claims 1 to 8, wherein the pattern has an aspect ratio of a major axis and a minor axis of 10 or less.   The separator according to any one of claims 1 to 9, wherein one or both of the separator front surface and the separator back surface is composed of an organic or inorganic coating layer.   The separator according to any one of claims 1 to 10, wherein the separator is wound.   A non-aqueous electrolyte battery comprising the separator according to claim 1.   The non-aqueous electrolyte battery according to claim 12, which is a secondary battery.

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