JP2019121508A - Separator for secondary battery, laminate for secondary battery, including the same, manufacturing method thereof, wound body, secondary battery, and coating resin composition - Google Patents

Abstract

To provide a separator for a secondary battery, which is high in adhesion with a microporous base material and an adhesive layer, which has a high adhesion strength with a positive electrode and a negative electrode, and which is low in degree of air permeation resistance and small in electrical resistance.SOLUTION: A separator for a secondary battery comprises: a laminate having a microporous base material (A) and a filler layer (B) disposed so as to be adjacent to one face of the microporous base material (A); and an adhesive layer (C) arranged so as to cover at least part of one or each face of the laminate. The adhesive layer (C) contains a water-soluble resin and a water-insoluble resin. The mass proportion of the water-insoluble resin and the water-soluble resin is 99.99/0.01 to 98/2. The quantity of the water-insoluble resin to a total mass of the adhesive layer (C) is 65 mass% or more and 99.99 mass % or less. The thickness proportion of the filler layer (B) and the adhesive layer (C) is 4/1 to 30/1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a separator for a secondary battery, a laminate for a secondary battery including the same, a method of manufacturing the same, a wound body, a secondary battery, and a resin composition for coating.

  Conventionally, development of secondary batteries centering on lithium ion secondary batteries has been actively conducted. In a general secondary battery, a separator having fine pores and made of polyolefin or the like is disposed between a positive electrode and a negative electrode. Such a separator has a function of preventing direct contact between the positive electrode and the negative electrode and transmitting ions through the electrolytic solution or the like held in the micropores. Therefore, the separator is required to have electrolytic solution resistance and oxidation resistance. Furthermore, safety such as the characteristic that the battery reaction is rapidly stopped when abnormal heating is performed, and the performance that maintains the shape even at high temperature and prevents the dangerous situation in which the positive electrode material and the negative electrode material directly react with each other. Performance is required. In addition to them, recently, the separator is also required to improve the adhesion to the electrode from the viewpoint of uniforming the charge and discharge current and suppressing lithium dendrite. By improving the closeness between the separator and the battery electrode, uneven charging / discharging current is less likely to occur, and lithium dendrite is less likely to be deposited. As a result, charge / discharge cycle life and safety are improved.

  For example, Patent Documents 1 and 2 disclose a separator having a polyolefin microporous substrate and an adhesive layer formed on the microporous film.

JP, 2015-28842, A International Publication No. 2014/017651

  In the separator having the configuration as described in Patent Document 1, the micropores of the polyolefin micropore base material are easily filled with the resin constituting the adhesive layer. Therefore, there is a problem that the air resistance is easily increased and the resistance is easily increased. Also, although an adhesive containing a particulate polymer having a core-shell structure is used, it is necessary to go through a complicated manufacturing process in order to control the pore distribution while maintaining the adhesiveness. Therefore, considering mass production, it can not be said that it is advantageous in terms of production efficiency and product cost.

  In patent document 2, it is set as the structure (sea-island structure) which distribute | arranged the thermoplastic polymer which is an adhesive material partially to the base-material surface in patent document 2 for the said subject improvement. According to the method of Patent Document 2, the air permeability of the separator is improved, and it is possible to suppress to some extent the increase in in-cell resistance derived from the adhesive. However, the adhesive resin melts and spreads on the separator surface, and the micropores on the substrate surface are easily blocked. Therefore, as compared with the separator not having the adhesive layer, there is still an increase in the in-cell resistance, and the load characteristics are degraded. Therefore, further resistance reduction is required.

  The present invention has been made in view of the above problems. That is, the present invention provides a separator for a secondary battery, which has high adhesiveness between the microporous substrate and the adhesive layer, high adhesive strength to the positive electrode and the negative electrode, low air resistance and low electrical resistance. With the goal.

The first of the present invention is the following secondary battery separator.
[1] A laminate having a micropore substrate (A) and a filler layer (B) disposed adjacent to one surface of the micropore substrate (A), and one side or both sides of the laminate An adhesive layer (C) arranged to cover at least a part, and the adhesive layer (C) contains a water-soluble resin and a water-insoluble resin, and the water-insoluble resin and the water-soluble resin The mass ratio with the resin is 99.99 / 0.01 to 98/2, and the amount of the water-insoluble resin is 65% by mass or more and 99.99% by mass or less based on the total mass of the adhesive layer (C). The separator for a secondary battery, wherein the thickness ratio of the filler layer (B) to the adhesive layers (C) is 4/1 to 30/1.

[2] The separator for a secondary battery according to [1], wherein the water-soluble resin in the adhesive layer (C) is a nonionic resin.
[3] The separator for a secondary battery according to [1] or [2], wherein the water-soluble resin in the adhesive layer (C) contains a vinyl alcohol group.
[4] The glass transition temperature (Tg) of the water-insoluble resin in the adhesive layer (C) by differential scanning calorimetry (DSC) is not detected below 20 ° C., and is detected in the range of 20 ° C. to 80 ° C. The separator for a secondary battery according to any one of [1] to [3].
[5] For the secondary battery according to any one of [1] to [4], wherein each adhesive layer (C) has a mass per unit area of 0.1 g / m ² or more and less than 1 g / m ² Separator.
[6] The adhesive layer (C) may be in the form of a sea-island, wherein the adhesive area containing the water-soluble resin and the water-insoluble resin, and the non-adhesive area containing neither the water-soluble resin nor the water-insoluble resin. The separator for a secondary battery according to any one of [1] to [5], wherein the adhesion region is disposed in a dot shape.

A second aspect of the present invention is the following laminate for a secondary battery, a wound body, or a secondary battery.
[7] A laminate for a secondary battery, in which the positive electrode, the separator for a secondary battery according to any one of the above [1] to [6], and the negative electrode are laminated in this order, the separator for a secondary battery The laminated body for secondary batteries in which the said contact bonding layer (C), and the said positive electrode and / or negative electrode were couple | bonded.
[8] A wound body obtained by winding the laminate for a secondary battery according to the above [7].
[9] A secondary battery comprising the laminate for a secondary battery according to the above [7], or the wound body according to [8].

The third of the present invention is a method of manufacturing a laminate for a secondary battery as follows.
[10] The method for producing a laminate for a secondary battery according to the above [7], wherein the positive electrode, the separator for a secondary battery, and the negative electrode are stacked in this order, and the adhesive layer (C) The manufacturing method of the laminated body for secondary batteries including the process of heat-pressing at the temperature in the glass transition temperature (Tg) by differential scanning calorimeter (DSC) of water-insoluble resin which contains.

The fourth of the present invention is the following coating composition.
[11] A coating composition comprising at least a water-soluble resin having a hydroxyl group, water-insoluble resin particles having an average particle size of 1 μm or less, and water, wherein the water-soluble resin and the water-insoluble resin The resin composition for coating whose ratio of the said water soluble resin is 0.01 mass% or more and 2 mass% or less with respect to the total mass of particle | grains.

  According to the present invention, the adhesive strength between the microporous substrate and the adhesive layer in the secondary battery separator can be sufficiently high. Further, the adhesive layer of the secondary battery separator has high adhesive strength to the positive electrode and the negative electrode. Furthermore, since the separator for secondary batteries has a sufficiently low air resistance, it is possible to obtain a secondary battery with a small electric resistance.

FIG. 1 is a schematic cross-sectional view showing an example of the secondary battery separator of the present invention. It is a schematic sectional drawing which shows an example of the laminated body for secondary batteries of this invention.

1. Separator for Secondary Battery In the separator 10 for a secondary battery of the present invention, as shown in FIG. 1, a microporous substrate (A) 11 and a filler layer (B) disposed adjacent to one surface of the microporous substrate (A) 13 and an adhesive layer (C) 12 a, 12 b disposed on one side or both sides of the laminated body 15. In addition, the secondary battery separator 10 may include other layers as necessary.

  As described above, in the adhesive layer of the secondary battery separator, high adhesive strength to the electrode and adhesive strength to the microporous substrate are required. However, when one of the adhesive strength to the electrode and the adhesive strength to the microporous substrate was increased, the other was likely to decrease. This relates to the amount of the water-soluble resin which is a component of the adhesive layer. The addition of a water-soluble resin to the adhesive layer can enhance the adhesion to the microporous substrate. However, a water-soluble resin generally has a high glass transition temperature, and for example, when heat pressing is performed at a temperature of less than 100 ° C. so that the micropores of the substrate are not clogged, the water-soluble resin is hard to soften by heat. Thus, the adhesion between the electrode and the adhesive layer is reduced. In addition, when a large amount of water-soluble resin is included to enhance the adhesion to the microporous substrate, the material fills the pores of the microporous substrate, and the air resistance of the secondary battery separator is increased, and electricity is used. There was a problem that resistance became large. That is, in the conventional secondary battery separator, it is difficult to increase the adhesive strength between the adhesive layer and the micropore base while enhancing the adhesive strength between the adhesive layer and the electrode, and furthermore, the low permeability of the secondary battery separator It was difficult to realize the degree of resistance (low electrical resistance).

  Furthermore, in recent years, in order to improve the heat resistance of a separator, the case where the laminated body of a microporous substrate (A) and a filler layer (B) is used is increasing. The filler layer (B) has a high porosity. Therefore, when the resin composition that constitutes the adhesive layer is applied on the filler layer (B), the water-soluble resin and the non-water-soluble resin in the adhesive layer enter the lower filler layer (B) to form pores. Shut up. Therefore, there is a problem that load characteristics are likely to be degraded.

In contrast, the adhesive layer (C) of the secondary battery separator 10 of the present invention contains a water-soluble resin and a water-insoluble resin. And mass ratio of these water-soluble resin and non-water-soluble resin is 99.99 / 0.01-98 / 2, and content of non-water-soluble resin is 65 mass to the total mass of adhesion layer (C) % Or more and 99.99% by mass or less. The microporous substrate of the adhesive layer (C) having an amount of the water-soluble resin of 0.01 parts by mass or more based on 100 parts by mass of the total amount of the water-soluble resin and the water-insoluble resin contained in the adhesive layer (C) Adhesive strength to A) and heat resistance increase dramatically. One of the reasons is that the water-soluble resin has high affinity to both the microporous substrate (A) and the water-insoluble resin, and has high adhesiveness to both. In particular, the above effects can be easily obtained in a nonionic water-soluble resin, particularly a water-soluble resin having an ethylene chain in the main chain and a hydrophilic functional group in the side chain, such as a polymer having a vinyl alcohol group. On the other hand, when the amount of the water-soluble resin is 2 parts by mass or less with respect to 100 parts by mass of the total amount of the water-soluble resin and the water-insoluble resin contained in the adhesive layer (C), the adhesive layer (C) and the electrode The adhesion strength is easily increased. For example, even if the area of the adhesion layer (C) is reduced, the adhesion layer (C) can exhibit sufficient adhesion strength to the electrode. The reason is that when the ratio of the water-soluble resin is lowered, the adhesive layer (C) is easily softened even at less than 100 ° C., and the resin is easily intruded into the irregularities of the electrode. When the non-water-soluble resin occupying much of the volume of the adhesive layer (C) is in the form of particles, when it is bonded to an electrode or the like, the microporous substrate (A) and the filler layer (B) It is difficult to completely cover the micropores, and in particular, it is difficult to increase the air resistance (electrical resistance).
Hereafter, each layer which comprises the separator for secondary batteries of this invention is demonstrated in detail.

1-1. Laminate The laminate may be such that a filler layer (B) described later is disposed on one side of the microporous substrate (A), and the filler layer (B) is disposed on the entire side of one side. It may be arranged in only a part of the area. In the present invention, the filler layer (B) may be disposed on both sides of the microporous substrate (A).

・ Microporous substrate (A)
The microporous substrate (A) is a substrate having a large number of fine pores, at least a part of which are connected, and a group through which gas or liquid can pass from one side to the other side. It is sufficient if it is a material. The microporous substrate (A) may be formed of only one layer, or two or more layers may be laminated.

  Here, the average pore diameter of the microporous substrate (A) is preferably 0.01 to 1.0 μm, and more preferably 0.05 to 0.5 μm. When the average pore diameter of the microporous substrate (A) is in the above range, the air resistance of the separator is reduced, that is, the electrical resistance tends to be reduced.

  The porosity of the microporous substrate (A) is preferably 30 to 80% by volume, and more preferably 40 to 70% by volume. If the porosity is less than 30% by volume, the amount of electrolyte retained may be insufficient. On the other hand, when an abnormal temperature rise occurs in the secondary battery, at least a part of the separator is melted to block the micropores of the micropore base material (A) to cut off the current (hereinafter also referred to as "shutdown") However, when the porosity is more than 80% by volume, the above-mentioned shutdown function may not be sufficiently exhibited.

  The microporous substrate (A) is not particularly limited as long as it has an electrical insulating property and is made of a material stable to the non-aqueous electrolyte of the secondary battery, and is a substrate made of an inorganic material. It may be a substrate made of an organic material. Examples of organic materials include polyolefin, Teflon (registered trademark), polyamide, polyvinyl chloride, polyvinylidene fluoride, polyaniline, polyimide, polyethylene terephthalate, polystyrene cellulose and the like. However, from the viewpoint of easily exhibiting the above-mentioned shutdown function, the material of the microporous substrate (A) is preferably a thermoplastic resin, more preferably a thermoplastic resin having a melting point of less than 200 ° C. In particular, polyolefin is preferred.

  Examples of the polyolefin include polyethylene, ethylene / α-olefin copolymer, polypropylene, propylene / α-olefin copolymer and the like. Among these, from the viewpoint of easily obtaining the above-mentioned shutdown function, polyolefins having a structure derived from ethylene are preferable, and polyolefins having a content of ethylene of 95% by mass or more are particularly preferable. The polyolefin may contain, in addition to ethylene, an α-olefin such as propylene, 1-butene, 4-methyl-1-pentene or 1-hexene. Among these, propylene is particularly preferable.

Moreover, it is preferable that the weight average molecular weights (polyethylene conversion) measured by the gel permeation chromatography (GPC) of polyolefin are 2 * 10 < ⁵ > -15 * 10 < ⁶ >. When the weight average molecular weight of the polyolefin is 2 × 10 ⁵ or more, the strength of the secondary battery separator is likely to be increased. On the other hand, when the weight average molecular weight is 15 × 10 ⁶ or less, the shutdown function is easily obtained.

  Here, the thickness of the microporous substrate (A) is preferably 5 to 30 μm, and more preferably 5 to 20 μm. When the thickness of the microporous substrate (A) is less than 5 μm, the strength of the secondary battery separator is low, so the membrane may be easily broken, and the above-mentioned shutdown function may be insufficient. On the other hand, when the thickness of the microporous substrate (A) exceeds 30 μm, the electric capacity when the secondary battery separator is applied to a secondary battery tends to be small.

· Filler layer (B)
The filler layer (B) is responsible for, for example, the heat resistance of the separator and the function of enhancing the dimensional stability. The filler layer (B) contains, for example, inorganic particles and a binder resin for binding the same. The filler layer (B) may contain other components (various additives and the like) as long as the purpose and effect of the present invention are not impaired.

  The inorganic particles contained in the filler layer (B) are not particularly limited as long as they are particles that are stable to the non-aqueous electrolyte of the secondary battery and are electrochemically stable inorganic materials. The said inorganic particle can be made to be the same as that of the inorganic particle contained, for example in the below-mentioned adhesion layer (C). The shape of the inorganic particles is not particularly limited, and may be spherical or flat.

  The average particle size of the inorganic particles is not particularly limited, but is preferably 0.1 to 3 μm, and more preferably 0.2 to 1.5 μm. The average particle size is an average value when particle sizes of arbitrary 10 inorganic particles are measured by observing a cross section of the secondary battery separator by observation with a scanning electron microscope (SEM).

  The amount of the inorganic particles relative to the total mass of the filler layer (B) is preferably more than 85% by mass and 99.97% by mass or less, more preferably 90 to 99% by mass, and 95 to 98% by mass Is more preferred. When the amount of the inorganic particles is in the above range, the dimensional stability of the secondary battery separator is likely to be enhanced, and furthermore, the electrical resistance of the secondary battery separator is less likely to be enhanced.

  On the other hand, the binder resin contained in the filler layer (B) is not particularly limited as long as it does not impair the purpose and effects of the present invention, and is the same as the resin used in the filler layer of the conventional secondary battery separator be able to. On the other hand, you may use resin similar to water-soluble resin contained in the below-mentioned adhesive layer (C) as binder resin.

  When the water-soluble resin is contained in the filler layer (B), the amount of the water-soluble resin is preferably 0.03% by mass or more and less than 3% by mass with respect to the total mass of the filler layer (B). It is more preferable that it is 05-2.5 mass%, and it is further more preferable that it is 0.1-2 mass%. When the amount of the water-soluble resin is in the above range, the heat resistance of the secondary battery separator can be enhanced and heat shrinkage can be suppressed without increasing the electrical resistance of the secondary battery separator.

  The filler layer (B) may contain components other than the inorganic particles and the binder resin, and may contain the same resin as the water-insoluble resin contained in the adhesive layer (C) described later. Good.

  Here, the thickness of the filler layer (B) is preferably 2.5 μm or more and 5 μm or less, and more preferably 3 to 5 μm. When the thickness of the filler layer (B) is in the above range, dimensional stability and heat resistance of the secondary battery separator are likely to be increased. On the other hand, if the thickness of the filler layer (B) is excessively thick, the electrical resistance of the secondary battery separator tends to increase, but if it is in the above range, the electrical resistance can be sufficiently lowered.

The filler layer (B) can be produced, for example, as follows. However, the method for forming the filler layer (B) is not limited to the following method.
First, a composition for forming a filler layer is prepared, which contains the above-described inorganic particles, a binder resin, a solvent for dissolving or dispersing these, and, if necessary, other components. The type of solvent is not particularly limited, and may be, for example, water; alcohols such as ethyl alcohol and butyl alcohol; Moreover, the mixing method in particular of these is not restrict | limited, What is necessary is just to stir by a well-known stirrer etc.

  After preparation of the composition for forming a filler layer, the composition for forming a filler layer is applied to at least one surface of the microporous substrate (A) described above and dried. The method of applying the composition for forming the filler layer is not particularly limited, and examples thereof include roll coating, gravure coating such as reverse gravure coating, kiss coating, dip coating, spray coating, air knife coating, Mayer bar coating The method includes pipe method, blade coating method, die coating method and the like.

  Moreover, the method to dry a coating film after coating | coating of the composition for filler layer formation is not restrict | limited in particular, You may make it dry at room temperature, and you may make it dry, heating with oven etc.

1-2. Adhesive layer (C)
The adhesive layer (C) is disposed to cover one side or both sides of the above-mentioned laminate. That is, it may be arrange | positioned so that the filler layer (B) of a laminated body may be covered, and you may be arrange | positioned so that a microporous substrate (A) may be covered. In addition, when the adhesive layer (C) is arrange | positioned on both surfaces of a laminated body, these may be the same and may differ.

  In addition, an adhesion region (adhesion layer (C)) containing a water-soluble resin and a water-insoluble resin may be disposed so as to cover the entire surface of one side or both sides of the laminate, so as to cover only a partial area. It may be arranged. However, from the viewpoint of increasing the air permeation resistance of the secondary battery separator, the adhesive layer (C) may be any one of an adhesion region containing a water-soluble resin and a water-insoluble resin, a water-soluble resin and a water-insoluble resin. It is preferable to have the non-adhesion area | region which does not also contain. The non-adhesive area can be, for example, an air gap.

  When the adhesive layer (C) has an adhesive area and a non-adhesive area, they are preferably arranged substantially uniformly on the laminate, and the adhesive area and the non-adhesive area are arranged in a sea island manner Is preferred. The shape of the adhesion region and the shape of the non-adhesion region are not particularly limited, and may be any shape such as linear, dot, grid, stripe, and turtle shell pattern. Further, the adhesion region may be disposed in an island shape, and the non-adhesion region may be disposed in an island shape.

  In the separator for a secondary battery according to the present invention, in particular, the adhesion regions are preferably arranged in a dot shape (circular island shape), and the distance between the adhesion regions is preferably 5 μm to 500 μm, and 50 μm to 500 μm It is more preferable that If the distance between the adhesion regions is 500 μm or less, the adhesion between the adhesion layer (C) and the electrode tends to be good. Furthermore, when the distance between the adhesion regions is in the above range, the area of the non-adhesion region is relatively large relatively, and the air resistance of the secondary battery separator tends to be low (the electric resistance is low).

  Furthermore, the area ratio of the bonded area to the non-bonded area is preferably 1:99 to 50:50, and more preferably 1:90 to 30:70. When the area ratio of the adhesion area to the non-adhesion area is within the above range, the adhesion strength between the adhesion layer (C) and the electrode tends to be good. The distance between the adhesion regions, the area ratio between the adhesion region and the non-adhesion region, and the like can be identified by analyzing the image of the adhesion layer observed with a scanning microscope (SEM).

Here, the mass per unit area of each adhesive layer (C) is preferably less than 0.1 g / ^{m 2} or more ^{1g / m 2, 0.1g / m} 2 or more 0.7 g / ^{m 2} or less And more preferably 0.1 g / m ² or more and 0.5 g / m ² or less. When the mass per unit area of the adhesive layer (C) is in the above range, the adhesion to the electrode becomes good, and furthermore, the air resistance becomes sufficiently low. In addition, the obtained secondary battery exhibits good load characteristics.

  The average thickness of each layer of the adhesive layer (C) (adhesive region), that is, the adhesive layer (C) disposed on one surface of the laminate is preferably 0.3 μm or more and 1 μm or less, and 0.3 It is more preferable that it is -0.8 micrometer. When the average thickness of each adhesive layer (C) is in the above range, the adhesiveness between the adhesive layer (C) and the electrode, and between the adhesive layer (C) and the microporous substrate (A) or the filler layer (B) Adhesiveness tends to be good. The thickness of the adhesive layer (C) is, for example, an average value when the cross-section of the adhesive layer (C) is observed by scanning microscope (SEM) observation and the thickness of any ten points in the adhesive region is measured.

  The thickness ratio of the filler layer (B) to each adhesive layer (C) in the above-mentioned laminate is 4/1 to 30/1, preferably 6/1 to 30/1, 8/1. It is more preferable that it is -25/1. The filler layer (B) described above has a high porosity, and when a resin composition constituting the adhesive layer (C) is applied, the non-water-soluble resin and the water-soluble resin enter the filler layer (B). May clog the pores and the load characteristics may deteriorate. On the other hand, by setting the thickness ratio of the filler layer (B) to each adhesive layer (C) to 4/1 or more, the non-water-soluble resin and the water-soluble resin contained in the adhesive layer (C) It is possible to suppress a decrease in load characteristics due to infiltration into (B). Moreover, the favorable adhesiveness of an adhesive layer (C) and an electrode is hold | maintained by setting it as 30/1 or less.

  The adhesive layer (C) contains at least a water-soluble resin and a water-insoluble resin as described above. The adhesive layer (C) may contain other components as needed. In the present specification, the term "water-soluble resin" refers to a resin that is soluble in 5 g or more in 100 g of water. The water-soluble resin can be, for example, a compound having a hydroxyl group. Examples of the water-soluble resin contained in the adhesive layer (C) include polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, cellulose, cellulose ether, sodium alginate, polyacrylic acid, polymethacrylic acid, polyacrylamide and the like. Examples of cellulose ethers include carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), carboxyethylcellulose, methylcellulose, ethylcellulose, cyanoethylcellulose, oxyethylcellulose and the like. In the adhesive layer (C), only one kind of water-soluble resin may be contained, or two or more kinds may be contained. Among these, the water-soluble resin is preferably a resin having a vinyl alcohol group, or a nonionic resin such as hydroxyethyl cellulose (HEC) or polyacrylamide, and more preferably a resin having a vinyl alcohol group. Particularly preferred is polyvinyl alcohol.

  The weight average molecular weight (in terms of polystyrene) measured by GPC of the water-soluble resin is preferably 10,000 to 2,000,000, and more preferably 50,000 to 1,000,000. When the weight average molecular weight of the water-soluble resin is at least 10,000, the heat resistance of the secondary battery separator is likely to be increased. On the other hand, when the weight average molecular weight of the water-soluble resin is 2,000,000 or less, the viscosity of the coating resin composition for forming the adhesive layer (C) is in a suitable range, and coating becomes easy.

  When the water-soluble resin is polyvinyl alcohol, the degree of polymerization thereof is preferably 100 to 20,000, and more preferably 300 to 2,000. In the present specification, "polyvinyl alcohol" also includes resins obtained by saponifying vinyl polycarboxylate, poly (alkyl vinyl carbonate) and the like. The degree of saponification in these saponified products is not particularly limited, but is preferably 60 mol% or more, more preferably 75 mol% or more, from the viewpoint of enhancing the heat resistance of adhesion.

  Further, as described above, the content of the water-soluble resin is 0.01 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the total amount of the water-insoluble resin and the water-soluble resin. The content is more preferably 0.01 to 1 part by mass, and still more preferably 0.1 to 0.7 parts by mass. When the amount of the water-soluble resin is in the above range, the adhesive strength between the adhesive layer (C) and the electrode, and in each layer between the adhesive layer (C) and the microporous substrate (A) or the filler layer (B) are good. Show good adhesion.

  On the other hand, the term "non-water soluble resin" as used herein refers to a resin having a dissolution amount of less than 5 g at 20 ° C. in 100 g of water. The water-insoluble resin may be any resin that can adhere to the electrode by heat pressing etc. However, the glass transition temperature (Tg) by differential scanning calorimeter (DSC) is not detected at less than 20 ° C. It is preferable that it is resin detected in the range below ° C. The glass transition temperature (Tg) is more preferably 65 ° C. or less. By not observing the glass transition temperature below 20 ° C., it becomes difficult for the particles to fuse together when the non-water-soluble resin is in the form of particles at ordinary temperature, etc., and the rise in air permeability resistance is easily suppressed. On the other hand, when the glass transition temperature is 80 ° C. or less, the adhesive layer (C) sufficiently adheres to the electrode or the like by heat pressing. The glass transition temperature (Tg) can be measured, for example, using a Shimadzu automatic differential scanning calorimeter DSC-60. More specifically, an appropriate amount of non-water soluble resin is put in an aluminum pan and dried with a hot air dryer at 130 ° C. for 30 minutes. About 10 mg of the dried film after drying is packed in an aluminum container for measurement, and a DSC curve can be obtained by measuring at a temperature rising rate of 20 ° C./min and a measurement temperature range of −10 to 200 ° C. The glass transition temperature (Tg) can be identified from the curve.

  Examples of water-insoluble resins include polyolefin resins such as polyethylene, polypropylene and α-polyolefins; fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene and copolymers containing these; conjugated dienes such as butadiene and isoprene as monomer units Diene polymers, copolymers containing these, and hydrides thereof; acrylic acid ester, methacrylic acid ester, styrene, acrylic acid, methacrylic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, etc. as monomer units Acrylic polymers, copolymers containing these, and hydrides thereof; Ethylene propylene rubber, polyvinyl alcohol, polyvinyl acetate and other rubbers; Ethyl cellulose, methyl cellulose Polyphenylene ether; polysulfones; polyethersulfones; polyphenylene sulfide; hydroxyethyl cellulose, cellulose derivatives such as carboxymethyl cellulose polyetherimides, polyamides imides; include polyester and the like; polyamides.

  Among the above, from the viewpoint of excellent adhesion with the electrode and flexibility, polyolefin resins, diene polymers, acrylic polymers or fluorine polymers are preferable.

  The diene polymer can be a polymer obtained by polymerizing a conjugated diene monomer having conjugated double bonds such as butadiene and isoprene. The diene polymer may be one obtained by polymerizing only one conjugated diene monomer, or may be one obtained by polymerizing two or more kinds. Examples of conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1, Included are 3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene and the like.

  The diene-based polymer may contain other copolymerizable components. In this case, the proportion of the conjugated diene monomer is preferably 40% by mass or more, more preferably 50% by mass or more, and more preferably 60% by mass or more, based on all the monomer components constituting the diene polymer. More preferable.

  Examples of components (monomers) copolymerizable with the conjugated diene monomer include α, β-unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid and fumaric acid Styrene, styrene-based monomers such as styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, methylvinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene, α-methylstyrene, divinylbenzene, etc .; ethylene, propylene Olefins such as, for example, halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; methyl vinyl ether, ethyl vinyl ether, butylbiether ether, etc. Vinyl ethers; Vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, isopropenyl vinyl ketone; Heterocyclic ring-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine, vinyl imidazole; methyl acrylate, methyl Acrylic acid esters such as methacrylate and / or methacrylic acid ester compounds; hydroxyalkyl group-containing compounds such as β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate; acrylamide, N-methylol acrylamide, acrylamido-2-methylpropane sulfonic acid, etc. An amide type monomer etc. are contained. Only one of these may be copolymerized with the conjugated diene monomer, or two or more may be copolymerized with the conjugated diene monomer.

  Moreover, the said acryl-type polymer can be used as the polymer which superposed | polymerized the (meth) acrylate monomer. The acrylic polymer may be one obtained by polymerizing only one (meth) acrylate monomer, or one obtained by copolymerizing two or more kinds. In the present specification, "(meth) acrylate" represents acrylate and / or methacrylate.

  Examples of (meth) acrylate monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) Acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) Alkyl (meth) acrylates such as acrylate, n-tetradecyl (meth) acrylate and stearyl (meth) acrylate; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxy Le (meth) hydroxy group-containing acrylate such as (meth) acrylate; an amino group such as aminoethyl (meth) acrylate containing (meth) acrylate; containing epoxy groups such as glycidyl (meth) acrylate (meth) acrylate; includes.

  The acrylic polymer may contain a copolymer component other than the (meth) acrylate monomer. In this case, of all the monomer components constituting the acrylic polymer, the proportion of (meth) acrylate monomer is preferably 40% by mass or more, more preferably 50% by mass or more, and 60% by mass or more Is more preferred. Examples of the component copolymerized with (meth) acrylate include the same components as the component (monomer) copolymerizable with the above-mentioned conjugated diene monomer.

  The fluorine-based polymer can be a homopolymer of vinylidene fluoride monomer, a copolymer of vinylidene fluoride and another copolymer component (monomer), or the like. When the fluorine-based polymer contains another copolymerization component, the proportion of the vinylidene fluoride monomer is preferably 40% by mass or more, and more preferably 50% by mass or more, based on all the monomer components constituting the fluorine-based polymer. More preferably, it is 60 mass% or more.

  Examples of components (monomers) copolymerizable with vinylidene fluoride include vinyl fluoride, tetrafluoroethylene, trifluorochloroethylene, hexafluoropropylene, hexafluoroisobutylene, perfluoroacrylic acid, perfluoromethacrylic acid, acrylic acid Or fluorine-containing ethylenically unsaturated compounds such as fluoroalkyl esters of methacrylic acid; fluorine-free ethylenically unsaturated compounds such as cyclohexyl vinyl ether and hydroxyethyl vinyl ether; fluorine-free diene compounds such as butadiene, isoprene and chloroprene .

  The fluorine-based polymer is preferably a homopolymer of vinylidene fluoride, a vinylidene fluoride / tetrafluoroethylene copolymer, a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer, etc., and a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer Is particularly preferred.

  In addition, when preparing a diene polymer, an acrylic polymer or a fluorine polymer, a monomer containing a hydroxyl group other than the above, a monomer containing a sulfonic acid group, a monomer containing a carboxyl group, an amide group A monomer or a monomer having a cyano group can also be used.

  When the water-insoluble resin contained in the adhesive layer is in the form of particles, the average particle diameter of the particles is preferably 1 μm or less, more preferably 0.7 μm or less, and still more preferably 0.5 μm or less Preferably, 0.3 μm or less is particularly preferable. When the average particle diameter of the particles made of the water-insoluble resin is 1 μm or less, the electrical resistance of the secondary battery separator is difficult to increase. The average particle size is obtained by observing the cross section of the adhesive layer (C) of the separator for a secondary battery by observation with a scanning electron microscope (SEM) and measuring the particle size of particles composed of 10 arbitrary water-insoluble resins It is an average value.

  Also, as described above, the content of the water-insoluble resin is 65% by mass to 99.99% by mass with respect to the mass of the adhesive layer (C), but the content of the water-insoluble resin is more Preferably it is 90-99.99 mass%, More preferably, it is 97-99.99 mass%. The adhesive strength between the adhesive layer (C) and the electrode, and the adhesive strength between the adhesive layer (C) and the microporous substrate (A) or the filler layer (B), when the amount of the water-insoluble resin is in the relevant range. Balance is good.

  Examples of components other than the water-soluble resin and the water-insoluble resin contained in the adhesive layer (C) include inorganic particles. When inorganic particles are contained in the adhesive layer (C), the adhesive layer is less likely to be crushed by heat pressing, and an increase in resistance in the battery can be suppressed.

  The inorganic particles contained in the adhesive layer are not particularly limited as long as they are particles that are stable to the non-aqueous electrolyte of the secondary battery and are electrochemically stable inorganic materials. Examples of inorganic particles include calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomaceous earth, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, aluminum hydroxide oxide (boehmite) And magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, aluminum oxide, mica, zeolite, glass and the like. The adhesive layer (C) may contain only one type of inorganic particles, or may contain two or more types. Among the above, the inorganic particles are preferably aluminum hydroxide oxide (boehmite), aluminum hydroxide, aluminum oxide, magnesium oxide, or magnesium hydroxide from the viewpoint of being hard to react with the electrolytic solution.

  Here, the shape of the inorganic particles is not particularly limited, and may be spherical or flat.

  The average particle size of the inorganic particles is not particularly limited, but is preferably 0.1 to 3 μm, and more preferably 0.2 to 1.5 μm. The average particle size is an average value when particle sizes of arbitrary ten inorganic particles are measured by observing a cross section of the adhesive layer (C) of the separator for a secondary battery by observation with a scanning electron microscope (SEM).

  The amount of the inorganic particles relative to the total mass of the adhesive layer (C) is preferably less than 34.99% by mass, more preferably less than 30% by mass, and still more preferably less than 20% by mass. When the amount of the inorganic particles is in the above range, it is possible to suppress the collapse of the adhesive layer by the heat press and the increase in the resistance in the battery due to this.

Although the formation method in particular of adhesion layer (C) is not restricted, for example, it can produce as follows. However, it is not limited to the following method.
First, a resin composition for an adhesive layer (in the present specification, “coating,” including the above-mentioned water-soluble resin, non-water-soluble resin, inorganic particles as required, and a solvent for dissolving or dispersing these Resin composition (also referred to as “resin composition”). The type of solvent contained in the adhesive layer resin composition is not particularly limited, and may be, for example, water; alcohols such as ethyl alcohol and butyl alcohol, and the like. Moreover, the mixing method in particular of these is not restrict | limited, What is necessary is just to stir by a well-known stirrer etc.

  After preparation of the resin composition for adhesive layer, the resin composition for adhesive layer is applied on the above-mentioned laminate and dried. The coating method of the resin composition for adhesive layer is not particularly limited, and roll coating, gravure coating such as reverse gravure coating, kiss coating, dip coating, spray coating, air knife coating, Mayer bar coating, pipe doctor, Methods such as blade coating, die coating, flexographic printing, offset printing, ink jet printing, and the like.

  In addition, the method for drying the coating film is not particularly limited after the application of the resin composition for adhesive layer, and may be dried at room temperature or may be dried while heating in an oven or the like.

1-3. Layer Configuration of Secondary Battery Separator As described above, the secondary battery separator of the present invention only needs to include at least the laminate and the adhesive layer (C). For example, one surface of the laminate is The adhesive layer (C) described above may be disposed, and the second adhesive layer (C ′) including the above-described water-insoluble resin and the like may be disposed on the other surface.

  Further, in view of the adhesiveness between the adhesive layer (C) and the electrode (positive electrode and negative electrode) and the adhesiveness between the adhesive layer (C) and the laminate, the secondary battery separator is described above on both sides of the laminate. More preferably, the adhesive layer (C) is disposed.

1-4. Physical Properties of Secondary Battery Separator The thickness of the entire secondary battery separator described above is preferably 5 to 25 μm, and more preferably 8 to 20 μm. When the thickness of the secondary battery separator is 5 μm or more, the mechanical strength of the secondary battery separator tends to be sufficiently increased. On the other hand, when the thickness of the secondary battery separator is 25 μm or less, the electrical resistance of the secondary battery separator does not easily increase.

  Furthermore, in particular, the heat shrinkage ratio at 130 ° C. of the secondary battery separator is preferably 5% or less, and more preferably 4% or less. When the thermal contraction rate of the secondary battery separator is 5% or less, short circuit and the like do not occur at the time of use of the secondary battery, and stable use can be achieved. The heat shrinkage ratio is determined by holding the sample (separator) cut into a predetermined size in a thermostat controlled at 130 ° C. for 1 hour, taking out the sample and allowing it to cool to room temperature, and then holding it in the thermostat It is a value measured by comparing the size of the previous sample and the size of the sample after holding. When the sample has directionality, the length before heating and after heating is measured in the longitudinal (MD) direction to calculate the thermal contraction rate, and this is taken as the thermal contraction rate of the secondary battery separator .

2. Laminate for Secondary Battery, and Secondary Battery Using the Same 2-1. 2. Laminated Body for Secondary Battery The laminated body 20 for secondary battery of the present invention has a structure in which a positive electrode 21, the above-mentioned secondary battery separator 10, and a negative electrode 22 are laminated as shown in FIG. For example, one adhesive layer (C) 12a of the secondary battery separator 10 and the positive electrode 21 are bonded, and the other adhesive layer (C) 12b and the negative electrode 22 are bonded. it can. In addition, although the laminated body for secondary batteries in which the positive electrode 21, the separator 10 for secondary batteries, and the negative electrode 22 are contained one by one is shown in FIG. 2, these may be further laminated | stacked. In that case, an arbitrary number of layers, etc. can be laminated in the order of positive electrode / secondary battery separator / negative electrode / secondary battery separator / positive electrode / secondary battery separator / negative electrode.

  Hereinafter, the positive electrode and the negative electrode included in the laminate for a secondary battery will be described using the positive electrode and the negative electrode of a lithium ion secondary battery as an example. However, the positive electrode and the negative electrode to be laminated with the secondary battery separator are not limited to these, and the type thereof is appropriately selected according to the type of the desired secondary battery.

The positive electrode can have a structure including a positive electrode current collector and a positive electrode active material layer formed thereon. Examples of the positive electrode current collector include aluminum foil, stainless steel foil, titanium foil and the like. The thickness of the positive electrode current collector can be about 5 μm to 20 μm.

The positive electrode active material layer generally contains a positive electrode active material and a binder, and may further contain a conductive aid. Examples of the positive electrode active material include lithium-containing transition metal oxides and the like, and specific examples thereof include lithium-manganese complex oxides (LiMn ₂ O ₄ etc.), lithium-nickel complex oxides (LiNiO ₂ etc.) , Lithium-cobalt complex oxide (LiCoO ₂ etc.), lithium-iron complex oxide (LiFeO ₂ etc.), lithium-nickel-manganese complex oxide (LiNi _0.5 Mn _0.5 O ₂ etc.), lithium-nickel Cobalt complex oxide (LiNi _0.8 Co _0.2 O ₂ etc.), lithium-nickel-cobalt-manganese complex oxide, lithium-transition metal phosphate compound (LiFePO ₄ etc.), and lithium-transition metal sulfate compound (Li _x Fe ₂ (SO ₄ ) ₃ ) and the like are included. The positive electrode active material layer may contain only one type of positive electrode active material, or may contain two or more types.

  The amount of the positive electrode active material contained in the positive electrode active material layer is preferably 10% by mass or more, more preferably 30% by mass or more, and still more preferably 50% by mass or more. Moreover, it is preferable that it is 99.9 mass% or less, and it is more preferable that it is 99 mass% or less.

  Further, examples of the binder contained in the positive electrode active material layer include polyvinylidene fluoride resins, styrene-butadiene rubber and the like. The amount of the binder contained in the positive electrode active material layer is preferably 0.1% by mass to 80% by mass, more preferably 1% by mass to 40% by mass, and 5% by mass to 10% by mass. Is more preferred. When the content of the binder in the positive electrode active material layer is a certain amount or more, the positive electrode active material is easily retained, and battery performance such as cycle characteristics is less likely to be impaired. In addition, when the ratio of the binder is less than or equal to a certain amount, it is easy to suppress a decrease in battery capacity and conductivity.

  Furthermore, carbon materials such as acetylene black, ketjen black, and graphite powder are included in the example of the conductive support agent contained in the positive electrode active material layer.

Here, the thickness of the positive electrode active material layer can be usually about 10 to 200 μm.
Such a positive electrode is prepared by applying a positive electrode mixture paste prepared by dispersing the above-mentioned positive electrode active material, a binder, and optionally, a conductive auxiliary agent and the like in a solvent on a positive electrode current collector, followed by heating and curing. It can be obtained by using a material layer.

-Negative electrode A negative electrode can be set as the structure containing a negative electrode collector and the negative electrode active material layer provided on it. Examples of the negative electrode current collector include copper foil, nickel foil, stainless steel foil and the like. The thickness of the negative electrode current collector can be about 5 μm to 20 μm.

The negative electrode active material layer generally contains a negative electrode active material and a binder, and may further contain a conductive aid. Specific examples of the negative electrode active material include a carbon material, a material containing silicon (Si, Si alloy, Si nitride, carbide or oxide), a material containing tin (Sn alloy, Sn carbide or oxide), and germanium The material which contains (Ge oxide, carbide or nitride) is included. Examples of materials containing silicon include SiC, Si ₃ N ₄ , SiO _x (0 <x ≦ 2). Examples of the material containing tin include SnO _w (0 <w ≦ 2), SnSiO ₃ , Mg ₂ Sn and the like. The negative electrode active material may contain only one type of negative electrode active material, or may contain two or more types.

  The amount of the negative electrode active material contained in the negative electrode active material layer is preferably 10% by mass to 99.9% by mass, more preferably 30% by mass to 99% by mass, and 50% by mass to 99% by mass It is further preferred that

  Further, the types and amounts of the binder and the conductive additive contained in the negative electrode active material layer can be the same as the amounts of the binder and the conductive additive and the amount contained in the positive electrode active material layer. The thickness of the negative electrode active material layer can be usually about 5 to 200 μm, and more preferably about 10 to 100 μm.

  The negative electrode is formed by applying a negative electrode material paste prepared by dispersing the above-mentioned negative electrode active material, a binder, and optionally, a conductive auxiliary agent, in a solvent on a negative electrode current collector, and then heat curing to form a negative electrode active material layer It is obtained by doing.

2-2. Method of Manufacturing Laminated Body for Secondary Battery The above-described laminated body for secondary battery can be manufactured by laminating a positive electrode, a separator for a secondary battery, and a negative electrode in this order and heat-pressing them. The temperature at the time of heat pressing is preferably equal to or higher than the glass transition temperature (Tg) of a non-water-soluble resin by differential scanning calorimeter (DSC), and more preferably 70 to 100 ° C. The resin contained in the adhesive layer (C) of the separator for a secondary battery is softened by setting the temperature at the time of heat pressing to a glass transition temperature (Tg) or higher by a differential scanning calorimeter (DSC) of a water-insoluble resin And the positive electrode or the negative electrode. In addition, when the adhesion layer (C) containing different non-water-soluble resin is arrange | positioned on the both sides of the laminated body of the said separator for secondary batteries, the temperature at the time of heat press is made from both glass transition temperature (Tg) Higher temperatures are preferred.

  The heat pressing time is preferably 10 seconds to 300 seconds, and more preferably 10 seconds to 100 seconds. By setting the pressure and time at the time of heat pressing in the above range, the adhesive strength between the secondary battery separator and the electrode (positive electrode and negative electrode) can be sufficiently enhanced.

  The obtained laminate for a secondary battery may be used for the secondary battery in this state (flat plate shape), but if necessary, the wound body may be used for the secondary battery. The winding method is appropriately selected according to the type and the structure of the secondary battery, and can be the same as the winding method in a known secondary battery.

  The separator for a secondary battery of the present invention can reduce the internal resistance and prevent the reaction from being uneven, particularly in the wound type, so that uneven charging / discharging current is less likely to occur and lithium dendrite is also less likely to precipitate. .

2-3. Secondary Battery A secondary battery using the above-described laminate or wound body for a secondary battery may have a structure in which the above-described laminate or wound body for a secondary battery is enclosed in an outer packaging material together with an electrolytic solution. it can.

The electrolytic solution can be, for example, a solution containing an electrolyte and a non-aqueous solvent.
The nonaqueous solvent contained in the electrolytic solution can be the same as the nonaqueous solvent of a general lithium ion secondary battery, but is preferably a cyclic aprotic solvent or a linear aprotic solvent . The non-aqueous solvent may contain only any one of these, or may contain both. From the viewpoint of enhancing the safety of the lithium ion secondary battery, that is, increasing the flash point of the solvent, a cyclic aprotic solvent is more preferable.

  Examples of cyclic aprotic solvents include cyclic carbonates, cyclic carboxylic acid esters, cyclic sulfones, cyclic ethers. The non-aqueous solvent may contain only one of them, or may contain two or more of them.

  When the non-aqueous solvent contains a cyclic aprotic solvent, the content thereof is preferably 10 to 100% by mass, more preferably 20 to 90% by mass, and 30 to 80% by mass. Is more preferred. When the non-aqueous solvent contains the cyclic aprotic solvent in the above range, the conductivity of the electrolytic solution is increased.

  On the other hand, examples of chain-like aprotic solvents include chain-like carbonates, chain-like carboxylic acid esters, chain-like ethers, chain-like phosphoric acid esters and the like. The non-aqueous solvent may contain only one of them, or may contain two or more of them. When the non-aqueous solvent contains a chain-like aprotic solvent, its content is preferably 10 to 100% by mass, more preferably 20 to 90% by mass, and 30 to 80% by mass. Is more preferred.

  From the viewpoint of enhancing the load characteristics of the battery and the low temperature characteristics, it is preferable that the non-aqueous solvent be a mixed solvent of a cyclic aprotic solvent and a chain aprotic solvent. In particular, from the viewpoint of enhancing the electrochemical stability of the electrolytic solution, a mixed solvent of a cyclic carbonate and a linear carbonate is preferable. From the viewpoint of increasing the conductivity of the electrolytic solution, a mixed solvent of cyclic carboxylic acid ester, cyclic carbonate, and / or linear carbonate is also preferable.

On the other hand, the electrolyte of the electrolytic solution preferably contains LiPF _6. Since LiPF ₆ has a high degree of dissociation, the conductivity of the electrolyte is likely to be increased. Further, when the electrolyte contains LiPF _6, easy reductive decomposition reaction of the electrolytic solution on the negative electrode is suppressed. The electrolyte may comprise only LiPF _6, may further include an electrolyte other than LiPF _6.
The concentration of the electrolyte in the electrolytic solution is preferably 0.1 mol / L to 3 mol / L, and more preferably 0.5 mol / L to 2 mol / L.

  In addition, the electrolytic solution is at least one selected from the group consisting of a carbonate compound having a carbon-carbon unsaturated bond, a carbonate compound substituted with a fluorine atom, a fluorophosphoric acid compound, an oxalato compound, and a cyclic sultone compound. Preferably it further comprises an agent.

  Examples of carbonate compounds having a carbon-carbon unsaturated bond include methyl vinyl carbonate, ethyl vinyl carbonate, divinyl carbonate, methyl propynyl carbonate, ethyl propynyl carbonate, dipropynyl carbonate, methyl phenyl carbonate, ethyl phenyl carbonate, diphenyl carbonate and the like Carbonates: vinylene carbonate, methylvinylene carbonate, 4,4-dimethylvinylene carbonate, 4,5-dimethylvinylene carbonate, vinyl ethylene carbonate, 4,4-divinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, ethynyl ethylene carbonate, 4, 4-diethynyl ethylene carbonate, 4, 5-diethynyl ethylene carbonate, propy Le ethylene carbonate, 4,4-propynyl carbonate, cyclic carbonates such as 4,5-di-propynyl carbonate; and the like. Among these, methylphenyl carbonate, ethylphenyl carbonate, diphenyl carbonate, vinylene carbonate, vinyl ethylene carbonate, 4,4-divinyl ethylene carbonate, and 4,5-divinyl ethylene carbonate are preferable, and more preferably vinylene carbonate, It is vinyl ethylene carbonate.

  As a carbonate compound having a fluorine atom, methyl trifluoromethyl carbonate, ethyl trifluoromethyl carbonate, bis (trifluoromethyl) carbonate, methyl (2,2,2-trifluoroethyl) carbonate, ethyl (2,2,2 -Linear carbonates such as -trifluoroethyl) carbonate and bis (2,2,2-trifluoroethyl) carbonate; 4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4 -Cyclic carbonates such as trifluoromethyl ethylene carbonate; and the like. Among these, preferred are 4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate and the like.

  As the fluorophosphoric acid compound, lithium difluorophosphate, lithium monofluorophosphate, difluorophosphoric acid, monofluorophosphoric acid, methyl difluorophosphate, ethyl difluorophosphate, dimethyl fluorophosphate, diethyl fluorophosphate and the like can be mentioned. . Among these, preferred are lithium difluorophosphate and lithium monofluorophosphate.

  Examples of the oxalato compound include lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, lithium tris (oxalato) phosphate, lithium difluoro (oxalato) borate, lithium bisoxalatoborate and the like. Among these, preferred are lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, and lithium bisoxalatoborate.

  Examples of cyclic sultone compounds include 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, 1-methyl-1,3-propene sultone, 2-methyl-1,3-propene sultone, 3- And sultones such as methyl-1,3-propene sultone. Among these, 1,3-propane sultone and 1,3-propene sultone are preferable.

  Particularly preferable compounds among the above-mentioned additives are vinylene carbonate, vinyl ethylene carbonate, 4-fluoroethylene carbonate, 4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, lithium monofluorophosphate, difluorophosphoric acid Lithium, difluorobis (oxalato) lithium phosphate, lithium tetrafluoro (oxalato) phosphate, lithium tris (oxalato) phosphate, lithium difluoro (oxalato) borate, lithium bisoxalatoborate, 1,3-propanesultone, and 1,3-propene sultone is mentioned. The electrolytic solution may contain only one type of the above-mentioned additive, or may contain two or more types.

  When the electrolytic solution contains the above additive, the content (total content in the case of two or more types) is not particularly limited, but 0.001 to 10 mass% with respect to the total amount of the electrolytic solution Is preferably 0.05 to 5% by mass, more preferably 0.1 to 4% by mass, and still more preferably 0.1 to 2% by mass More preferably, 0.1% by mass to 1% by mass is particularly preferable.

  In addition, as an exterior material of the secondary battery, a metal can, for example, a can-like formed body made of iron, stainless steel, aluminum or the like can be used. The packaging material may be a film-like bag in which an extremely thin aluminum is laminated with a resin. The shape of the packaging material may be any shape including cylindrical, square, thin and coin as long as it can accommodate the above-described laminate for a secondary battery or a wound body.

  EXAMPLES The present invention will be specifically described below by examples and comparative examples, but the present invention is not limited to these examples.

1. Materials The following water-soluble resin and inorganic particles were used in Examples and Comparative Examples.
Water-soluble resin PVA (100%): polyvinyl alcohol having a degree of saponification of 100% PVA (75%): polyvinyl alcohol having a degree of saponification of 75% PVB: polyvinyl butyral HEC: hydroxyethyl cellulose PAANa: sodium polyacrylate

Inorganic particles Al ₂ O ₃ particles: aluminum oxide having an average particle diameter (D50) of 0.6 μm

2. Method of Producing Water Dispersion of Non-Water-soluble Resin As the non-water-soluble resin, those produced in the following Production Examples 1 to 3 were used.
・ Production example 1
In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer, 600 g of ion-exchanged water and 1 g of sodium dodecyl diphenyl ether disulfonate were charged, and the temperature was raised to 70 ° C. with nitrogen replacement under stirring. The internal temperature was kept at 70 ° C., and 3 g of potassium persulfate was added as a polymerization initiator and dissolved. Thereafter, an emulsion prepared by adding beforehand 350 g of ion exchange water and 3 g of sodium dodecyl diphenyl ether disulfonate to 600 g of methyl methacrylate, 350 g of n-butyl acrylate, 20 g of methacrylic acid, 20 g of 2-hydroxyethyl methacrylate and 15 g of ethylene glycol dimethacrylate under stirring The substance was dropped into the reaction solution continuously over 3 hours. After completion of the dropwise addition, aging was performed for 3 hours. The obtained aqueous emulsion was cooled to room temperature, and ion-exchanged water and aqueous ammonia were added to adjust the solid content to 50% by mass, pH 8, and an aqueous dispersion of water-insoluble resin A was obtained. The obtained particle size was 0.16 μm. Moreover, the glass transition temperature of water-insoluble resin A was 56 ° C.

・ Production example 2
In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer, 1400 g of ion-exchanged water and 1 g of polyoxyethylene styrenated phenyl ether were charged, and the temperature was raised to 70 ° C. while nitrogen was substituted under stirring. While maintaining the internal temperature at 70 ° C., 10 g of potassium persulfate was added as a polymerization initiator and dissolved. Thereafter, in advance, 600 g of ion exchanged water, 6 g of polyoxyethylene dodecyl ether, 40 g of acrylamide, 1000 g of methyl methacrylate, 700 g of n-butyl acrylate, 40 g of methacrylic acid, 90 g of 2-hydroxyethyl methacrylate and 4 g of dodecyl mercaptan were added under stirring. The emulsion was dropped into the reaction solution continuously over 3 hours. After completion of the dropwise addition, aging was performed for 3 hours. The obtained aqueous emulsion was cooled to room temperature, and ion-exchanged water and aqueous ammonia were added to adjust the solid content to 45% by mass, pH 7, and an aqueous dispersion of water-insoluble resin B was obtained. The obtained particle size was 0.5 μm. Moreover, the glass transition temperature of water-insoluble resin B was 23 ° C.

・ Production example 3
In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer, 1200 g of ion-exchanged water and 5 g of sodium dodecyldiphenyletherdisulfonate were charged, and the temperature was raised to 70 ° C. with nitrogen replacement under stirring. While maintaining the internal temperature at 70 ° C., 6 g of potassium persulfate was added as a polymerization initiator and dissolved. Thereafter, an emulsion is prepared by adding, in advance, 600 g of ion-exchanged water, 6 g of sodium dodecyl diphenyl ether disulfonate, 20 g of acrylamide, 1000 g of methyl methacrylate, 800 g of 2-ethylhexyl acrylate, 60 g of methacrylic acid, and 20 g of polyethylene glycol dimethacrylate under stirring. The reaction solution was dropped continuously over 3 hours. After completion of the dropwise addition, aging was performed for 3 hours. The obtained aqueous emulsion was cooled to room temperature, and ion-exchanged water and aqueous ammonia were added to adjust the solid content to 50% by mass, pH 8, and an aqueous dispersion of water-insoluble resin C was obtained. The obtained particle size was 0.1 μm. Moreover, the glass transition temperature of water-insoluble resin C was 27 ° C.

3. Production of Separator for Secondary Battery (1) Example 1
Method of Forming Laminate (Filler Layer (B)) To 90 parts by mass of ion-exchanged water, 10 parts by mass of a water-soluble resin (PVA (100%)) is added and stirred at 90 ° C. for 1 hour. % Aqueous solution was prepared. In 15 parts by mass of the aqueous solution (1.5 parts by mass of solid content), 98 parts by mass of Al ₂ O ₃ particles (aluminum oxide of (D50) 0.6 μm), 10% aqueous solution of dispersant (sodium polyacrylate) 5 The mass part (0.5 mass part of solid content) and water were added, and it stirred for 30 minutes using the rotation revolution mixer. Thereby, the slurry for filler layers with a solid content concentration of 50 mass% was obtained.
Then, the above-mentioned slurry for the filler layer is applied to one side of a microporous substrate (material: polyethylene, thickness: 12 μm, porosity: 46% by volume, air resistance: 140 s / 100 ml air) by reverse gravure coating. It applied. Then, the said coating film was dried and the filler layer (B) of the thickness shown in Table 1 was obtained.

Preparation of resin composition for adhesive layer (resin composition for coating) 10 parts by mass of water-soluble resin (PVA (100%)) is added to 90 parts by mass of ion-exchanged water, and stirred at 90 ° C. for 1 hour Then, a 10% by mass aqueous solution of PVA was prepared. The said aqueous solution 0.5 mass part (solid content 0.05 mass part), 199.9 mass parts (solid content 99.95 mass part) of the water dispersion of water-insoluble resin A, and water were mixed. The solution was stirred at room temperature for 1 hour to prepare a resin composition for an adhesive layer having a solid content concentration of 10% by mass.

-Formation of adhesive layer (C) The above-mentioned resin composition for adhesive layers was applied to both sides of the layered product which consists of a micropores base material (A) and a filler layer (B) by a reverse gravure coat method, respectively. Then, the said coating film was dried and the 0.5-micrometer-thick contact bonding layer (C) was formed, respectively, and the separator for secondary batteries was obtained. At this time, the mass per unit area of each adhesive layer (C) was 0.4 g / m ² .

(2) Examples 2-14, Comparative Examples 1-5
The composition of the adhesive layer (C) and the film thickness ratio between the filler layer (B) and each adhesive layer (C) were changed as shown in Tables 1 to 3 below, and the secondary was the same as in Example 1 A battery separator was obtained. In addition, the composition of each component shown to Tables 1-3 is a mass part.

3. Evaluation Regarding the obtained secondary battery separator, the adhesiveness of the adhesive layer to the electrode, the adhesiveness of the adhesive layer to the microporous substrate, the air resistance of the secondary battery separator, and the like as follows. The load characteristics were measured. The results are shown in Tables 1 to 3.

(3-1) Electrode Adhesion A positive electrode, a separator (filler layer (B) is disposed on the positive electrode side), and a negative electrode are laminated in this order, and these are thermally pressed at 1 MPa and 80 ° C. for 20 seconds to produce a laminate. The interlayer adhesion (the adhesion between the adhesive layer and the electrode) was confirmed.
○: There is delamination of the laminate ×: No delamination of the laminate

(3-2) Adhesiveness to substrate The tape (made by 3M) having a width of 10 mm and a length of 70 mm was attached to the adhesive layer (C). Peeling force when peeling the tape from the sample at a speed of 30 mm / min, using a 90 ° peel strength tester (JIS C 6471 (Shimadzu Corporation tensile tester EZ-S, adhesive tape peeling tester), peeling Based on the measurement results obtained, the adhesive strength (adhesive strength between the adhesive layer and the microporous substrate) was evaluated according to the following evaluation criteria.
○: Peeling strength 0.1 N / cm or more ×: Peeling strength less than 0.1 N / cm

(3-3) Air resistance The air resistance was measured using a Gurley type densometer.

(3-4) Load characteristics <Production of negative electrode>
98 parts by mass of artificial graphite, 1 part by mass of carboxymethylcellulose, and 1 part by mass of SBR (styrene / butadiene latex) were mixed using water as a solvent to prepare a paste-like negative electrode mixture slurry.
Next, this negative electrode mixture slurry was applied to one side of a negative electrode current collector made of a 18 μm-thick strip copper foil and dried. Then, it compressed by roll press and obtained the sheet-like negative electrode which consists of a negative electrode collector and a negative electrode active material layer. The application density of the negative electrode active material layer at this time was 12.7 mg / cm ² , and the packing density was 1.5 g / ml.

<Fabrication of positive electrode>
98 parts by mass of nickel-manganese-cobalt ternary active material (LiNiO ₂ : LiMnO ₂ : LiCoO ₂ (molar ratio) = 5: 3: 2), 1 part by mass of acetylene black, and 1 part by mass of polyvinylidene fluoride The paste was mixed with N-methyl pyrrolidone as a solvent to prepare a paste-like positive electrode mixture slurry.
Next, this positive electrode material mixture slurry was applied to one side of a positive electrode current collector of strip-shaped aluminum foil having a thickness of 20 μm and dried. Then, it compressed by roll press and obtained the sheet-like positive electrode which consists of a positive electrode collector and a positive electrode active material. The coating density of the positive electrode active material layer at this time was 22 mg / cm ² , and the packing density was 3.0 g / ml.

<Preparation of Nonaqueous Electrolyte>
Ethylene carbonate (EC) and methyl ethyl carbonate (EMC) were mixed in a mass ratio of 1: 2 to obtain a non-aqueous solvent. To the nonaqueous solvent, the LiPF ₆ as the electrolyte, eventually electrolyte concentration in the non-aqueous electrolyte solution obtained was dissolved at a 1 mole / liter.

<Installation of current collection tab>
A positive electrode tab made of aluminum foil was attached to the above-described positive electrode, and a negative electrode tab made of stainless steel foil was attached to the above-described negative electrode by ultrasonic welding.

<Fabrication of laminated electrode body>
An electrode body was obtained by laminating one negative electrode attached with the negative electrode tab and one positive electrode attached with the positive electrode tab via the above-mentioned secondary battery separator. Moreover, the positive electrode and the negative electrode were laminated in the direction in which the positive electrode tab and the negative electrode tab were on the same side.

<Fabrication of laminated battery>
The above laminated electrode body was inserted into an outer package made of a laminate film, and the side of the outer package to which the positive electrode tab and the negative electrode tab were attached was heat-sealed. The temperature at this time was higher than the glass transition temperature (Tg) of the non-water-soluble resin contained in the adhesive layer. Furthermore, two sides of the remaining three sides of the outer package were similarly heat-sealed. And the said electrolyte solution was inject | poured in the exterior body from the one side which is not heat-seal | fused. Then, the other side of the outer package was heat-sealed to obtain a laminate type battery. Each measurement was implemented about the obtained lamination type battery (test battery).

[Evaluation method]
The cell is left at 45 ° C. for 10 hours, charged to 4.2 V at a measurement temperature of 25 ° C. and a current value of 0.2 C, and further charged to a current value of 0.05 C at a constant voltage of 4.2 V did. Thereafter, it was discharged to 3 V at 0.2C. Next, the battery was charged to 4.2 V at a current value of 0.2 C, and further charged to a current value of 0.05 C at a constant voltage of 4.2 V. Thereafter, it was discharged to 3 V at 2C. From the obtained discharge capacity, load characteristics were calculated by the following equation.
Discharge capacity at load characteristic = 2C / Discharge capacity at 0.2C

  As shown in the above Tables 1 and 2, the adhesive layer (C) contains a water-soluble resin and a water-insoluble resin, and the mass ratio of the water-insoluble resin to the water-soluble resin is 99.99 / 0. And the amount of the water-insoluble resin relative to the total mass of the adhesive layer (C) is from 65% by mass to 99.99% by mass, and the filler layer (B) and each adhesive layer (C) In the separator for a secondary battery having a thickness ratio of 4/1 to 30/1, both the adhesion between the adhesive layer and the electrode and the adhesion between the adhesive layer and the microporous substrate (A) are good. It became a result. In these examples, the air resistance was also sufficiently low, and the load characteristics were also good (Examples 1 to 14).

  In particular, in the case where the water-soluble resin is a nonionic water-soluble resin (Examples 1 to 6 and 9 to 14), it is easy to achieve both substrate adhesion and electrode adhesion. This is because the water-soluble resin is non-ionic, the dispersibility with the non-water-soluble resin is high, and the substrate adhesion is improved with a small amount. Moreover, since it is a small amount, it is considered that the heat softening property of the adhesive layer (C) was not reduced.

  On the other hand, as shown in Table 3, when the adhesive layer (C) did not contain a water-soluble resin, the adhesiveness to the microporous substrate (A) was low (Comparative Example 1). On the other hand, when the amount of the water-soluble resin was excessively increased, the adhesion between the adhesive layer and the electrode decreased, and the air resistance was also increased (Comparative Examples 2 and 3). Since the water-soluble resin has filled the micropores of the micropore base material (A), it is considered that the air resistance is increased.

  Furthermore, when the thickness ratio of the said filler layer (B) and each said contact bonding layer (C) was less than 4/1, load characteristics fell (comparative example 4). On the other hand, when the said thickness ratio is larger than 30/1, adhesiveness with an electrode was inadequate (comparative example 5).

  The separator for a secondary battery of the present invention has high adhesiveness between the microporous substrate and the adhesive layer. In addition, the adhesive layer contained in the secondary battery separator has high adhesive strength to the positive electrode and the negative electrode. Furthermore, the secondary battery separator has low air resistance and low electrical resistance. Therefore, it is very useful as a separator of various secondary batteries.

10 Separator for Secondary Battery 11 Microporous Substrate (A)
12a, 12b Adhesive layer 13 Filler layer 15 Laminate 20 Laminate for secondary battery 21 Positive electrode 22 Negative electrode

Claims (11)

A laminate having a microporous substrate (A) and a filler layer (B) disposed adjacent to one surface of the microporous substrate (A);
An adhesive layer (C) disposed to cover at least a part of one side or both sides of the laminate;
The adhesive layer (C) contains a water-soluble resin and a water-insoluble resin, and the mass ratio of the water-insoluble resin to the water-soluble resin is 99.99 / 0.01 to 98/2.
The amount of the water-insoluble resin is 65% by mass or more and 99.99% by mass or less based on the total mass of the adhesive layer (C),
The separator for secondary batteries whose thickness ratio of the said filler layer (B) and each said contact bonding layer (C) is 4/1-30/1. The water soluble resin in the adhesive layer (C) is a nonionic resin,
The separator for a secondary battery according to claim 1. The water-soluble resin in the adhesive layer (C) contains a vinyl alcohol group,
A separator for a secondary battery according to claim 1 or 2. The glass transition temperature (Tg) of the water-insoluble resin in the adhesive layer (C) by differential scanning calorimetry (DSC) is not detected below 20 ° C., but is detected in the range of 20 ° C. or more and 80 ° C. or less
The separator for secondary batteries as described in any one of Claims 1-3. The weight per unit area of each of the adhesive layers (C) is 0.1 g / m ² or more and less than 1 g / m ² .
The separator for secondary batteries as described in any one of Claims 1-4. In the adhesion layer (C), an adhesion area containing the water-soluble resin and the water-insoluble resin, and a non-adhesion area containing neither the water-soluble resin nor the water-insoluble resin are present like islands. Layer,
The adhesion areas are arranged in dots.
The separator for secondary batteries as described in any one of Claims 1-5. It is a laminated body for secondary batteries in which the positive electrode, the separator for secondary batteries as described in any one of Claims 1-6, and the negative electrode were laminated | stacked in this order,
The laminated body for secondary batteries in which the said contact bonding layer (C) of the said separator for secondary batteries, and the said positive electrode and / or negative electrode are couple | bonded.   A wound body obtained by winding the laminate for a secondary battery according to claim 7.   A secondary battery comprising the laminate for a secondary battery according to claim 7 or the wound body according to claim 8. It is a manufacturing method of the layered product for secondary batteries according to claim 7,
The positive electrode, the separator for a secondary battery, and the negative electrode are stacked in this order, and the water-insoluble resin contained in the adhesive layer (C) has a glass transition temperature (Tg) or higher by differential scanning calorimetry (DSC) The manufacturing method of the laminated body for secondary batteries including the process of heat-pressing by temperature. A coating composition comprising at least a water-soluble resin having a hydroxyl group, water-insoluble resin particles having an average particle diameter of 1 μm or less, and water,
The ratio of the water-soluble resin to the total mass of the water-soluble resin and the water-insoluble resin particles is 0.01% by mass or more and 2% by mass or less.
Resin composition for coating.

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