The present invention glass as the transition to the separation membrane temperature comprises another binder, in particular comprising a first coating layer and second coating layer is a binder different types of coated on the separator base material, the first coating layer has a glass transition temperature that includes less than 30 ℃ binder, wherein the second coating layer is for a secondary battery separator that includes a binder glass transition temperature is less than 30 ℃.
BACKGROUND
[2]
In recent years, portable computers, portable telephones, has a technology development and the increase in demand and rapidly increasing, and such secondary batteries of high energy density and operating potential demand for secondary batteries as an energy source, as on portable devices such as a camera cycle life the long self-discharge rate is a number of studies been performed for low lithium secondary batteries, are also commercially available and widely used.
[3]
The study, depending on the interest in environmental issues grows like a gasoline car, electricity that can replace vehicles that use fossil fuels, such as diesel vehicles, hybrid electric cars of the main causes of air pollution is going much, and Li secondary batteries are also used as a power source, such as such an electric car, a hybrid electric vehicle.
[4]
Accordingly, they are to continue trying to improve the safety of the lithium secondary battery of high energy density.
[5]
In general, the separation membrane is composed of a coating layer coated on the separator substrate and the separator substrate, the physical properties of the separation membrane may be determined in accordance with configuration of the coating layer.
[6]
Specifically, there is a coating layer composed of a single layer on the separator base material can be formed, or may be a coating layer made of a multi-layer structure is formed, in the case that the multi-layered coating layer, the layer adjacent to the membrane base material to the separator to increase the peel strength of the coating layer, the layer facing the electrode is to improve the adhesion between the electrode material mixture layer.
[7]
When the electrodes and the adhesive force between the separator weaker has a short circuit between the electrodes in advance of the membrane and the electrode during charging and discharging of the battery can take place, at this time it can cause the problem that the heating battery ignite or explode in due to excessive currents locally flow to the. If the adhesive force between the electrodes is weak increase in the interface resistance between the electrodes by the flaring and bar electrode can be bent, this is due to safety issues therefrom.
[8]
Patent Document 1 has a glass transition temperature (T g ) is 30 ℃ than the first polymeric binder and the glass transition temperature (T g for) the 30 ℃ less than the second power storage a porous layer containing a resin binder formed on the porous substrate layer device It discloses a separator.
[9]
However, the separation membrane of Patent Document 1 is a heat-shrinkable than the separator large problem of low adhesion strength of the structure formed on the separator base material structure of bars formed on the porous layer made of a single layer, a plurality of the membrane coating base.
[10]
Patent Document 2 discloses that to improve the adhesive strength by controlling the content of inorganic particles and binder polymer as an active component formed on a part of the surface study group and / or the base material of the polyolefin-based separator substrate.
[11]
However, Patent Document 2, but discloses the effectiveness of such a heat-shrinkable, short stability of the membrane, techniques to improve the peel strength and adhesive strength of the separation membrane is does not provide.
[12]
In this way, it improves the peel strength between the membrane base and the membrane coating the coating layer is prevented from being separated from the membrane base material and improve the bonding strength between the coating layer and the electrode of the separator a short circuit occurs between the electrodes due to a jungle to excitation of the membrane effective solution to which can prevent the technology has not yet given up.
[13]
(Prior art document)
[14]
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2016-072117 No.
[15]
Patent Document 2: Republic of Korea Patent Application Publication No. 2006-0072065 No.
Detailed Description of the Invention
SUMMARY
[16]
The present invention serves to solve the above problems, a coating layer of a multi-layer structure coated on the separator base material, the first coating layer has a glass transition temperature comprises a binder is less than 30 ℃, and the second coating layer has a glass transition temperature is by including a binder at least 30 ℃, improves the peel strength of the separator base material, and an object thereof is to provide an improved secondary battery separator adhesive force between the electrode material mixture layer.
Problem solving means
[17]
Secondary battery separator, a separator substrate made of a polymer resin, a porous structure, is coated on the separator substrate a first coating layer and the first coating layer including a first inorganic material and a first binder according to the present invention for achieving this purpose is coated on the second inorganic material and a second binder claim comprising a second coating, the first coating layer has a glass transition temperature (T containing g , and a third binder is less than) the 30 ℃, the second coating layer has a glass transition temperature (T g a) may be made of a structure comprising a fourth binder less than 30 ℃.
[18]
Secondary battery separator according to the present invention is a bar, as compared to the separation membrane formed two days coating layer on the separator base material, does not occur good thermal contraction, excellent in adhesion between the electrode advantages including a coating layer consisting of a first coating layer and second coating layer have.
[19]
The first coating layer affects the peel strength of the separation membrane as a layer coated on the separator base material, the second coating layer is influenced in adhesion with an electrode as a layer to be coated on the first coating layer.
[20]
The first coating layer, and a third bar binder having a glass transition temperature less than 30 ℃, the glass transition temperature of the third binder may be up to preferably 10 ℃, preferably - it can be not more than 5 ℃.
[21]
In this way, the first coating layer is because a third binder is less than the glass transition temperature of 30 ℃ the binder particles at a low temperature does not maintain a circular and form an informal take place are here filming phenomenon can have fluidity. Thus, the first coating layer can be obtained an effect that the bar is increased binding affinity to the separation membrane fabric, increase the peel strength.
[22]
The second coating layer has a glass transition temperature be at least 4 bar binder, the glass transition temperature of said fourth binder is preferably from 45 ℃ containing not less than 30 ℃, it may be greater than or equal to 60 ℃ more preferably.
[23]
In this way, the second coating layer is a filming phenomenon does not occur easily because a fourth binder glass transition temperature is less than 30 ℃. Thus, by using the fourth binder to the second coating layer, it is possible to prevent the conventional problems was the pores of the separator base material makhimyeonseo increase the resistance of the membrane.
[24]
In one specific example, the first coating layer and said first inorganic substance as a main component, wherein the second coating layer may be made of a structure wherein the second binder is a main component.
[25]
That is, a kind of spacer with the first coating layer is to maintain the role and the physical form of inorganic material in bar, the inorganic particles contained as a main component is to enable an empty space (interstitial volume) between the inorganic particles forming the fine pores than the binder (spacer) is gyeomhage roles. Further, the inorganic particles because generally has a characteristic that does not change even if the physical properties at high temperature more than 200 ℃, will have the organic / inorganic composite porous film have excellent heat resistance is formed.
[26]
The inorganic particles, just electrochemically stable is not particularly limited. That is, as long as the inorganic particles that can be used in the present invention, the operating voltage range (for example, Li / Li + reference to 0 ~ 5V) oxidation and / or reduction reaction in the cell is not induced to be applied is not particularly limited. In particular, in the case of using the inorganic particles in the ion conductivity can be improved performance, increasing the ion conductivity in the electrochemical device, it is preferable that the ionic conductivity as high as possible. Further, when the inorganic particles have a high density because it is also a problem of weight increase during battery production, as well as there is a difficulty in dispersion during coating, it is preferred that the smallest possible density. In the case where the high dielectric constant inorganic material may contribute to the salt within the liquid electrolyte is an electrolyte, such as increased dissociation of lithium salts to increase the ionic conductivity of the electrolyte.
[27]
The first can be used is of the same material will first inorganic material and the second inorganic material, or may be used ones of a different material, (a) a dielectric constant of 5 or more inorganic particles, (b) inorganic particles and having piezoelectricity (piezoelectricity) (c) it may be at least one member selected from the group consisting of inorganic particles having lithium ion conductivity.
[28]
The first inorganic material and the second inorganic material is a bar, which may be a dielectric constant of 5 or more, preferably 10 or more high dielectric constant inorganic particles, for example, SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , TiO 2 may be or SiC.
[29]
Piezoelectric (piezoelectricity) material is in the atmospheric pressure applied to the non-conductive and, as a by the internal structure change when a predetermined pressure is applied to mean a material having a physical property electricity through, constant pressure as well as the dielectric constant exhibit 100 or more high-k characteristics to one side and electric charges are generated when the tension or compression in the amount, the other side is the inorganic particles having the function of a potential difference occurs between both sides, each being charged negatively.
[30]
Inorganic particles having the piezoelectricity is to be the potential difference is formed due to the positive charge and negative charge are generated between the both surfaces of the particles upon application of a predetermined pressure, BaTiO 3 , Pb (Zr, Ti) O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), Pb (Mg 1/3 Nb 2/3 ) O 3 -PbTiO 3 (PMN-PT), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2O 3 , TiO 2 , SiC, or may be at least one member selected from the group consisting of mixtures thereof.
[31]
Inorganic particles having lithium ion conductivity is, but containing a lithium element nor not store lithium inorganic particles having a function for moving the lithium ions as referring in the present invention, inorganic particles having lithium ion conductivity is within the particle structure since due to the presence type of defect (defect) to be delivered and moving lithium ions, and improve lithium ion conductivity within the cell, which results the performance of the battery can be improved.
[32]
Inorganic particles having the lithium ion conductivity is intended to, but containing a lithium element and move lithium ions without storing lithium, lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , 0
[55]
Acrylic polymer binder (with a Tg of -5 ℃ binder) 5 g, as an inorganic Al 2 O 3 is dispersed to be 95 g to prepare a slurry for the first coating layer.
[56]
It was dispersed 100 g of acrylic polymer binder (the binder Tg is 60 ℃) Prepare the slurry for the second coating layer.
[57]
Porous poly in the first coat the coating slurry, and coating the second slurry for the second coating layer in one hour drying the phase forming the first coating layer, the first coating layer to a 25 ℃ and 25 ℃ on the separator base material of the propylene material 1 hours and dried to form a second coating layer.
[58]
[59]

[60]
Acrylic polymer binder (with a Tg of -5 ℃ binder) 5 g, as an inorganic Al 2 O 3 is dispersed to be 95 g to prepare a slurry for the first coating layer.
[61]
It was dispersed 100 g of acrylic polymer binder (the binder Tg of -5 ℃) Prepare the slurry for the second coating layer.
[62]
Porous poly in the first coat the coating slurry, and coating the second slurry for the second coating layer in one hour drying the phase forming the first coating layer, the first coating layer to a 25 ℃ and 25 ℃ on the separator base material of the propylene material 1 hours and dried to form a second coating layer.
[63]
[64]

[65]
Acrylic polymer binder (with a Tg of 60 ℃ binder) 5 g, as an inorganic Al 2 O 3 is dispersed to be 95 g to prepare a slurry for the first coating layer.
[66]
It is dispersed 100 g of an acrylic polymeric binder (the binder Tg is 60 ℃) Prepare the slurry for the second coating layer.
[67]
Porous poly in the first coat the coating slurry, and coating the second slurry for the second coating layer in one hour drying the phase forming the first coating layer, the first coating layer to a 25 ℃ and 25 ℃ on the separator base material of the propylene material 1 hours and dried to form a second coating layer.
[68]
[69]

[70]
Acrylic polymer binder (with a Tg of 60 ℃ binder) 5 g, as an inorganic Al 2 O 3 is dispersed to be 95 g to prepare a slurry for the first coating layer.
[71]
It was dispersed 100 g of acrylic polymer binder (the binder Tg of -5 ℃) Prepare the slurry for the second coating layer.
[72]
Porous poly in the first coat the coating slurry, and coating the second slurry for the second coating layer in one hour drying the phase forming the first coating layer, the first coating layer to a 25 ℃ and 25 ℃ on the separator base material of the propylene material 1 hours and dried to form a second coating layer.
[73]
[74]

[75]
Performed to produce a slurry and the first coating layer a second coating slurry for the Example 1 in the same manner.
[76]
The porous polyester by coating the composition for first coating a slurry on the separator base material of the polypropylene material, and coating the composition for two coating slurry in the slurry phase for the first coating and dried for 1 hour in 25 ℃ to prepare the separation membranes.
[77]
[78]
The peel strength measurement
[79]
Example 1 and Comparative Example 1 to Comparative Example to measure the peel strength of the resulting separation membrane 4, the double-sided pressure-sensitive adhesive on a slide glass tape, one side of the separation membrane in fixing the one attached to the prepared membrane sequence then, the slide glass state the end by pulling at 180 DEG was used as a method for measuring the force.
[80]
The measured peel strength is shown in Table 1 below.
[81]
[82]
Adhesion measurement electrode
[83]
To Example 1 and Comparative Example 1 to compare to measure the peel strength of the resulting membrane in Example 4, the cathode and the membrane was given a load of 8.5MPa to flat press at 90 ℃ to prepare a measurement sample electrode adhesion. After attaching the double-sided adhesive tape, the adhesive force measurement samples in order to slide glass by pulling one end of the membrane to 180 DEG was used as a method for measuring the force.
[84]
To the measured electrode adhesion it is shown in Table 1 below.
[85]
[86]
TABLE 1
The peel strength (gf / 15mm) Electrode adhesion (gf / 15mm)
Example 1 50 12
Comparative Example 1 40 7
Comparative Example 2 2 0
Comparative Example 3 5 1
Comparative Example 4 10 19

[87]
Referring to Table 1, the Example 1 and Comparative Example 1, the peel strength of the fabric is high in the case of using the binder Tg is from -5 ℃ first coating layer. For comparison with the binder 60 ℃ Example 2 and Comparative Example 3 is very low in peel strength compared to Example 1 and Comparative Example 1. In addition, while the second coating layer from the electrode than the adhesive force of Comparative Example 1 used the higher the binder is a -5 ℃ in Example 1 using a binder with a Tg of 60 ℃ in Comparative Example 2 and Comparative Example 3, the peeling strength Fig was lower electrode adhesion is low. simultaneous coating in the case of a 4 compared to form a single layer, electrode adhesion but small increase, the measured peel strength is very low.
[88]
Thus, the first coating layer and it can be seen that the effect appears to be the Tg is included, and the second coating layer has a Tg of, peel strength and adhesive strength is improved in both the electrode if it contains a binder at least 30 ℃ the binder is less than 30 ℃.
[89]
Those of ordinary skill in the art that the present invention it will be possible to perform a variety of applications and modifications within the scope of the present invention in the accompanying claims.
Industrial Applicability
[90]
As described above, the secondary battery separator according to the present invention, the first coating layer and second and second coating layer is formed, the first coating layer has a glass transition temperature (T on the separator base g and include the binder is less than 30 ℃), the second coating layer is prevented by using a secondary battery separator glass transition temperature having a bar, of the multi-layered coating layer which comprises a binder at least 30 ℃, by providing the peeling strength for the separator base material enhanced the coating layer a coating layer is eliminated or deultteuneun can do.
[91]
Further, by effectively preventing a short circuit between the electrodes of the membrane electrode and the bars, the charge and discharge are improved adhesion between the effect of the battery cell safety is further improved.

WE Claims

[Claim 1]
A separator base material made of a polymer resin of the porous structure; The membrane is coated on a substrate a first coating layer comprising a first inorganic material and a first binder; And it is coated on the first coating layer a second coating layer comprising a second inorganic material and a second binder; A and wherein the first coating layer has a glass transition temperature (T g and the second coating layer, and a third binder) is less than 30 ℃ is the glass transition temperature (T g second to a fourth binder or higher) is 30 ℃ cell membrane.
[Claim 2]
The method of claim 1, wherein the first coating layer and said first inorganic substance as a main component, wherein the second coating layer has a secondary battery separator wherein the second binder is a main component.
[Claim 3]
The method of claim 1, wherein the first inorganic material and the second inorganic material is a secondary battery separator same material.
[Claim 4]
The method of claim 1, wherein the first inorganic material and the second inorganic material may be the same or different from each other, (a) a dielectric constant of 5 or more inorganic particles, (b) a piezoelectric inorganic particles and (c) lithium with (piezoelectricity) at least one member selected from the group consisting of a secondary battery separator inorganic particles having ion conductivity.
[Claim 5]
The method of claim 4, wherein the dielectric constant inorganic particles more than the constant is 5 (a) is a SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , TiO 2 or SiC, and; Inorganic particles (b) having the piezoelectric due to the positive charge and negative charge are generated between the both sides at the time of the particles is a constant pressure to be a potential difference is formed, BaTiO 3 , Pb (Zr, Ti) O 3 (PZT), Pb 1 -x La x Zr 1-y Ti y O 3 (PLZT), Pb (Mg 1/3 Nb 2/3) O 3 -PbTiO 3 (PMN-PT), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , TiO 2 , SiC or is at least one selected from the group consisting of mixtures thereof, and that of the inorganic particles (c) having the lithium ion conductivity is, but containing a lithium element and move lithium ions without storing lithium, lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3, 0