Separation membrane for electrochemical device and electrochemical device including the same

Abstract

The present invention relates to a separation membrane for an electrochemical element and an electrochemical element including the same. The present invention relates to a separation membrane for an electrochemical element and an electrochemical element including the same, in which a polymer resin contained in a porous polymer substrate is selected from specific types, and the polydispersity index, weight average molecular weight, content of an elution fraction at a specific temperature, and indentation depth of a polymer eluted at a high temperature are adjusted to improve the compression resistance and breakdown voltage of the separation membrane.

Description

Technical Field

[0001] This application claims priority based on Korean Patent Application Nos. 10-2023-0051176, 10-2023-0055916, and 10-2023-0065754, which were filed with the Korean Intellectual Property Office on April 19, 2023, April 28, 2023, and May 22, 2023, respectively, the contents of which are hereby incorporated by reference in their entirety into this application.

[0002] The present invention relates to a separation membrane for an electrochemical device and an electrochemical device including the same.

Background Art

[0003] Among the components of an electrochemical device, the separation membrane includes a polymer substrate having a porous structure located between a positive electrode and a negative electrode, separates the positive electrode and the negative electrode, serves to prevent an electrical short circuit between the two electrodes, and allows an electrolyte and ions to pass through. Although the separation membrane itself is not involved in an electrochemical reaction, physical properties such as wettability with respect to an electrolyte solution, degree of porosity, and thermal shrinkage rate affect the performance and safety of the electrochemical device.

[0004] Therefore, various methods have been attempted to add a coating layer to the porous polymer substrate to enhance the physical properties of the separation membrane and add various substances to the coating layer to change the physical properties of the coating layer. As an example, an inorganic substance may be added to the coating layer to improve the mechanical strength of the separation membrane, or an inorganic substance or hydrate may be added to the coating layer to improve the flame retardancy and heat resistance of the polymer substrate.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technical problem to be solved by the present invention is to provide a separation membrane for an electrochemical element and an electrochemical element including the same, which can improve the dielectric breakdown voltage of the separation membrane by preventing deformation of the separation membrane and damage to pores caused by the pressure applied in the lamination process for adhering the separation membrane and the electrode.

[0006] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

Means for Solving the Problems

[0007] One embodiment of the present invention provides a separation membrane for an electrochemical element, which includes a porous polymer substrate, the porous polymer substrate includes an amorphous polymer resin and a crystalline polymer resin, and the weight average molecular weight (Mw) of the eluate eluted from the porous polymer substrate by the temperature rising elution fractionation method (TREF) is about 100,000 or more.

[0008] According to one embodiment of the present invention, the porous polymer substrate may contain about 40% by weight or less of the fraction eluted at a temperature of 35°C or lower by the temperature rising elution fractionation method.

[0009] According to one embodiment of the present invention, the content of the amorphous polymer resin in the porous polymer substrate may be about 40% by weight or less.

[0010] According to one embodiment of the present invention, the content of the crystalline polymer resin in the porous polymer substrate may be about 60% by weight or more.

[0011] According to one embodiment of the present invention, the weight ratio of the amorphous polymer resin to the crystalline polymer resin in the porous polymer substrate may be about 1:1 to 10:1.

[0012] According to one embodiment of the present invention, the deviation of the indentation depth in the porous polymer substrate may be about -5 nm or more and 5 nm or less.

[0013] According to one embodiment of the present invention, the porous polymer substrate contains a polyolefin resin, the amorphous polymer resin is an amorphous polyolefin resin, and the crystalline polymer resin can be a crystalline polyolefin resin.

[0014] According to one embodiment of the present invention, the polyolefin resin can be one selected from the group consisting of polyethylene; polypropylene; polybutylene; polypentene; polyhexene; polyoctene; a copolymer of one or more of ethylene, propylene, butene, pentene, 4-methylpentene, hexene or octene; and combinations thereof.

[0015] According to one embodiment of the present invention, the polyolefin resin can have an average short-chain branch (SCB) of about 500 or less per 1000 total carbon atoms.

[0016] According to one embodiment of the present invention, the polyolefin resin can have a melt index (ASTM D1238, 190 °C, 2.16 kg) of about 0.1 g / 10 min to 0.3 g / 10 min.

[0017] According to one embodiment of the present invention, the weight average molecular weight (Mw) of the porous polymer substrate can be about 500,000 or more and 1,000,000 or less.

[0018] According to one embodiment of the present invention, the polydispersity index (PDI) of the eluate can be about 5 or more.

[0019] According to one embodiment of the present invention, when a pressure of 8 MPa is applied at 70 °C, any one or more of the following (i) to (iii) can be satisfied.

[0020] (i) The thickness reduction rate of the porous polymer substrate defined by the following Mathematical Formula 1 is about 10% or less:

[0021] [Mathematical Formula 1] Thickness reduction rate (%) = (Thickness of the porous polymer substrate before applying pressure - Thickness of the porous polymer substrate after applying pressure) / Thickness of the porous polymer substrate before applying pressure X 100

[0022] (ii) The air permeability increase rate of the porous polymer substrate defined by the following Mathematical Formula 2 is about 185% or less:

[0023] [Mathematical Formula 2] Air permeability increase rate (%) = (Air permeability after compression - Air permeability before compression) / (Air permeability before compression) X 100

[0024] (iii) The breakdown voltage of the porous polymer substrate is about 1,000 V or more.

[0025] According to an embodiment of the present invention, the porous polymer substrate may have a thickness of about 1 μm or more and 30 μm or less.

[0026] An embodiment of the present invention provides an electrochemical element including a positive electrode; a negative electrode; and the separator interposed between the positive electrode and the negative electrode.

Advantages of the Invention

[0027] The separator for an electrochemical element according to an embodiment of the present invention can improve the weight average molecular weight and polydispersity index of the eluate eluted at high temperature, minimize the deformation due to the pressure applied in the lamination process, and improve the breakdown voltage.

[0028] The electrochemical element according to an embodiment of the present invention can prevent high-potential (Hi-Pot) defects and low-voltage defects and improve battery performance.

Brief Description of the Drawings

[0029]

Figure 1

[0030] In some of the accompanying drawings, corresponding components are given the same reference numerals. Those skilled in the art will understand that this drawing shows the elements simply and clearly, and is not necessarily drawn to scale. For example, for the purpose of assisting the understanding of various embodiments, the dimensions of some of the elements shown in the drawing may be exaggerated compared to other elements. Also, elements of known technology that are useful or essential in commercially practicable embodiments are often not depicted so as not to impede the gist of various embodiments of the present invention.

Best Mode for Carrying Out the Invention

[0031] As used herein, when a part states that a certain component "comprises", this means that, unless otherwise stated to the contrary, it does not exclude other components, but may further include other components.

[0032] As used herein, "A and / or B" means "A and B, or A or B".

[0033] As used herein, when it is stated that a certain component is "provided on" another component, this means that, unless otherwise stated to the contrary, it does not exclude the possibility that other components are disposed therebetween, but other components may be further disposed.

[0034] As used herein, "about", "approximately", "substantially" are used in the context of the inherent manufacturing and material tolerances, in the scope of that numerical value or degree or a similar meaning, and are used to prevent infringers from improperly using the disclosure that mentions an exact numerical value or an absolute numerical value provided to assist the understanding of the present invention.

[0035] As used herein, the property of "having pores" means that the object contains a plurality of pores, and a fluid in a gas phase and / or a liquid phase can pass from one side to the other side of the object through a structure in which the pores are interconnected with each other.

[0036] In this specification, the separator has a porous property including a large number of pores, and serves as a porous ion-conducting barrier that allows ions to pass through while blocking electrical contact between the negative electrode and the positive electrode in an electrochemical device.

[0037] Hereinafter, the present invention will be described in more detail.

[0038] In a secondary battery electrode assembly, the separator can be adhered to the electrode through a lamination process, and a polymer binder can be added to the coating layer composition of the separator to ensure the adhesion between the electrode and the separator.

[0039] On the other hand, when increasing the process speed to improve the yield in the lamination process, there is a problem that the time for heat application decreases and the adhesion force decreases. In order to improve the adhesion force, the problem has been solved by increasing the pressure in the lamination process. However, the high pressure applied to the separator causes deformation such as a decrease in the thickness of the separator, and the breakdown voltage of the separator decreases due to damage to the pores, resulting in problems such as Hi-pot failure and low voltage failure.

[0040] The present invention provides a separator capable of preventing a decrease in the thickness of the separator by adjusting the polymer resin contained in the porous polymer base material and improving the breakdown voltage.

[0041] In the case of polyethylene applied to the porous base material of the separator, crystals and non-crystals are mixed, and the content of crystals is relatively high. The narrower the molecular weight distribution at this time, the better the compression resistance, which has an excellent effect on the degree of deformation of the thickness of the raw roll after compression. On the other hand, when propylene is added in the polyethylene polymerization process to improve the processability during the production of the polyethylene film, the content of non-crystals increases. Therefore, in the invention of the present application according to one embodiment, by not adding propylene or adding a small amount below the reference value in the polyethylene polymerization process, the content of crystals in the produced porous base material is increased or adjusted, thereby improving various properties of the separator such as compression resistance.

[0042] One embodiment of the present invention includes a porous polymer substrate manufactured by the above method. The porous polymer substrate contains an amorphous polymer resin and a crystalline polymer resin. As a result of analyzing the porous polymer substrate by temperature rising elution fractionation (TREF), the weight average molecular weight (Mw) of the eluted eluate is about 100,000 or more, and a separation membrane for an electrochemical device is provided.

[0043] In the production of the separation membrane for an electrochemical device according to one embodiment of the present invention, as described above, by not adding propylene or adding a small amount of propylene during the polyethylene polymerization process, the crystal content is increased or adjusted, and the weight average molecular weight and polydispersity index of the eluate eluted at a high temperature are improved, and the deformation due to the pressure applied in the lamination process can be minimized to improve the breakdown voltage.

[0044] One embodiment of the present invention relates to a separation membrane for an electrochemical device to which the separation membrane itself or the separation membrane can be applied as a component. Therefore, according to one embodiment of the present invention, on at least one surface of the porous polymer substrate, other layers can be further arranged from the aspects of materials and functions as needed. For example, in one embodiment of the present invention, the separation membrane may have a coating layer containing inorganic particles and / or a polymer binder, for example, an organic / inorganic composite coating layer, formed on at least one side or both sides of the porous polymer substrate.

[0045] According to one embodiment of the present invention, the separation membrane for an electrochemical device includes a porous polymer substrate. As described above, since the separation membrane for an electrochemical device includes a porous polymer substrate, it is possible to block the electrical contact between the positive electrode and the negative electrode while allowing lithium ions to pass through, and to implement a shutdown function at an appropriate temperature. In this specification, the "shutdown function" may mean that the pores of the porous polymer substrate are blocked under abnormal high temperature conditions so that lithium ions cannot pass through the separation membrane.

[0046] According to an embodiment of the present invention, the porous polymer substrate includes an amorphous polymer resin and a crystalline polymer resin. For example, the polymer resin contained in the porous polymer substrate may simultaneously include a crystalline one and an amorphous one, and the amorphous polymer resin and the crystalline polymer resin may be uniformly mixed and contained, or may contain an amorphous structure and a crystalline structure simultaneously within one molecule. As described above, by including the amorphous polymer resin and the crystalline polymer resin in the porous polymer substrate, the uniformity of the porous polymer substrate can be improved and the compression resistance can be increased.

[0047] According to one embodiment of the present invention, the porous polymer substrate of the invention of the present application adjusts the presence or absence of addition of propylene during the polyethylene polymerization process, so that the polymer resin contained in the porous polymer substrate includes both crystalline and amorphous ones. When the porous polymer substrate is analyzed by temperature rising elution fractionation (TREF), the weight average molecular weight (Mw) of the eluted eluate is about 100,000 or more. For example, when the porous polymer substrate is eluted by temperature rising elution fractionation (TREF), the weight average molecular weight (Mw) of the eluted eluate is about 100,000 or more and 10,000,000 or less, 200,000 or more and 9,000,000 or less, 300,000 or more and 8,000,000 or less, 400,000 or more and 7,000,000 or less, 500,000 or more and 6,000,000 or less, 600,000 or more and 5,000,000 or less, 700,000 or more and 4,000,000 or less, 800,000 or more and 3,000,000 or less, 900,000 or more and 2,000,000 or less, or 900,000 or more and 1,000,000 or less. When the porous polymer substrate is eluted by temperature rising elution fractionation (TREF) within the above-mentioned range, by adjusting the weight average molecular weight (Mw) of the eluate within the range, the uniformity of the porous polymer substrate can be improved and the compression resistance can be increased.

[0048] According to one embodiment of the present invention, the eluate may be eluted by temperature rising elution fractionation (TREF) at a temperature of about 90°C or higher and 110°C or lower. For example, the eluate may be eluted by temperature rising elution fractionation (TREF) at a temperature of about 90°C or higher and 110°C or lower, 91°C or higher and 109°C or lower, 92°C or higher and 108°C or lower, 93°C or higher and 107°C or lower, 94°C or higher and 106°C or lower, 95°C or higher and 105°C or lower, 96°C or higher and 104°C or lower, 97°C or higher and 103°C or lower, 98°C or higher and 102°C or lower, 99°C or higher and 101°C or lower. The porous polymer substrate of the present invention adjusts the presence or absence of propylene addition during the polyethylene polymerization process, and simultaneously contains a crystalline polymer resin and an amorphous polymer resin in the porous polymer substrate. As described above, by adjusting the temperature at which the eluate of the porous polymer substrate is eluted by temperature rising elution fractionation (TREF) within the above range, the uniformity of the porous polymer substrate can be improved, and the compression resistance can be increased. Furthermore, the mechanical properties of the porous polymer substrate can be improved.

[0049] In this specification, the "Temperature Rising Elution Fractionation (TREF)" analysis can be measured using a PolymerChar TREF machine. That is, the temperature rising elution fractionation method can dissolve the sample and inject it into the column at a high temperature, then gradually lower the temperature to induce crystallization of the sample. Once the sample has precipitated in the column, it can be to measure the molecular weight of the sample eluted while raising the temperature. For example, after dissolving 40 mg of a polymer sample in 20 mL of trichlorobenzene solvent at 150 °C for 120 minutes, it is stabilized at 100 °C for 45 minutes. After introducing this into a TREF column, it is cooled to 35 °C at a temperature drop rate of 0.5 °C per minute and maintained for 15 minutes. Then, while heating from 35 °C to 80 °C at a temperature increase rate of 20 °C per minute, it is maintained in 5 °C increments for 20 minutes each. While heating from 80 °C to 120 °C at a temperature increase rate of 20 °C per minute, it is maintained in 2 °C increments for 20 minutes each to measure the weight average molecular weight of the polymer sample eluted, and it can be meant to derive a TREF analysis graph through the results of such concentration measurements.

[0050] According to an embodiment of the present invention, the porous polymer substrate may contain about 40% by weight or less of a fraction eluted at a temperature of 35 °C or lower by the temperature rising elution fractionation method. For example, the porous polymer substrate may include a first fraction eluted at a temperature of 35 °C or lower and a second fraction eluted at a temperature exceeding 35 °C when analyzed by the temperature rising elution fractionation method. The first fraction may contain an amorphous polymer resin. The second fraction is one in which the porous polymer substrate is eluted at a temperature exceeding 35 °C by the temperature rising elution fractionation method and may contain a crystalline polymer resin. For example, the second fraction may be eluted at a temperature exceeding 35 °C and 100 °C or lower, 40 °C or higher and 90 °C or lower, 50 °C or higher and 80 °C or lower, or 60 °C or higher and 70 °C or lower. Alternatively, the second fraction may be eluted at a temperature of 98 °C or higher.

[0051] According to one embodiment of the present invention, the content of the amorphous polymer resin in the porous polymer substrate can be about 40% by weight or less. For example, the content of the amorphous polymer resin in the porous polymer substrate is more than about 0% by weight and 40% by weight or less, 2% by weight or more and 38% by weight or less, 4% by weight or more and 36% by weight or less, 6% by weight or more and 34% by weight or less, 8% by weight or more and 32% by weight or less, 10% by weight or more and 30% by weight or less, 12% by weight or more and 28% by weight or less, 14% by weight or more and 26% by weight or less, 16% by weight or more and 24% by weight or less, or 18% by weight or more and 22% by weight or less. By adjusting the content of the amorphous polymer resin in the porous polymer substrate within the above-described range, the uniformity of the porous polymer substrate can be improved, and the compression resistance can be increased. Furthermore, the mechanical properties of the porous polymer substrate can be improved.

[0052] According to one embodiment of the present invention, the content of the crystalline polymer resin in the porous polymer substrate may be about 60% by weight or more. For example, the content of the crystalline polymer resin in the porous polymer substrate is about 60% by weight or more and less than 100% by weight, 62% by weight or more and 98% by weight or less, 64% by weight or more and 96% by weight or less, 66% by weight or more and 94% by weight or less, 68% by weight or more and 92% by weight or less, 70% by weight or more and 90% by weight or less, 72% by weight or more and 88% by weight or less, 74% by weight or more and 86% by weight or less, 76% by weight or more and 84% by weight or less, or 78% by weight or more and 82% by weight or less. Alternatively, the content of the crystalline polymer resin in the porous polymer substrate may be about 70% by weight or more and 85% by weight or less. By adjusting the content of the crystalline polymer resin in the porous polymer substrate within the above-described range, the uniformity of the porous polymer substrate can be improved, and the compression resistance can be increased. Furthermore, the mechanical properties of the porous polymer substrate can be improved.

[0053] According to one embodiment of the present invention, the weight ratio of the amorphous polymer resin to the crystalline polymer resin in the porous polymer substrate may be about 1:1 to 10:1. For example, the weight ratio of the amorphous polymer resin to the crystalline polymer resin in the porous polymer substrate may be about 1.5:1 to 9.5:1, 2.0:1 to 9.0:1, 2.5:1 to 8.5:1, 3.0:1 to 8.0:1, 3.5:1 to 7.5:1, 4.0:1 to 7.0:1, 4.5:1 to 6.5:1, 5.0:1 to 6.0:1. By adjusting the weight ratio of the amorphous polymer resin to the crystalline polymer resin in the porous polymer substrate within the above-described range, the uniformity of the porous polymer substrate can be improved, and the compression resistance can be increased. Furthermore, the mechanical properties of the porous polymer substrate can be improved.

[0054] According to one embodiment of the present invention, the content of the crystalline polymer resin in the porous polymer substrate may be about 70% by weight or more and 85% by weight or less based on 100% by weight of the porous polymer substrate. By adjusting the content of the crystalline polymer resin in the porous polymer substrate within the above-described range, the indentation depth of the porous polymer substrate can be made low, the deviation of the indentation depth can be minimized, and the dielectric breakdown voltage can be improved.

[0055] According to one embodiment of the present invention, the indentation depth of the porous polymer substrate may be about 20 nm or less. For example, the indentation depth of the porous polymer substrate may be about 0 nm or more and 20 nm or less, more than 0 nm and 19 nm or less, 1 nm or more and 18 nm or less, 2 nm or more and 17 nm or less, 3 nm or more and 16 nm or less, 4 nm or more and 15 nm or less, 5 nm or more and 14 nm or less, 6 nm or more and 13 nm or less, 7 nm or more and 12 nm or less, 8 nm or more and 11 nm or less, or 9 nm or more and 10 nm or less. By adjusting the indentation depth of the porous polymer substrate within the above-described range, the compression resistance of the porous polymer substrate can be improved, the uniformity of the thickness of the porous polymer substrate after lamination can be improved, and the deformation of the thickness can be minimized.

[0056] In this specification, "indentation" is one of the analysis methods for the mechanical properties of materials. It is an experimental method in which diamond indenters of various shapes are pressed into a material, and then the indentation mark and the load during indentation are compared and analyzed. Such an indentation test is not only a method for measuring the fracture toughness and hardness of materials, but recently, a lot of research has been conducted in various other directions, and it is also used as a research method for analyzing the elastic-plastic behavior of materials, the residual stress state, the adhesion test of thin films, fracture characteristics, phase transformation analysis, etc. For example, when performing indentation on a fine material such as a separation membrane as in the present invention, nano-indentation applying a load of a unit of N (Newton) or less using a indenter can be applied.

[0057] FIG. 1 is a drawing schematically explaining a method for measuring the indentation depth. In this specification, the "indentation depth" is measured by an atomic force microscope (AFM, Atomic Force Microscope, OSTESPA-R3, Bruker, f = 300 kHz, k = 26 N / m) after setting the Dimension Icon (Bruker) under the following conditions and then moving the tip relative to the surface of the sample as shown in FIG. 1 while measuring the peak tapping force, and it can be the depth of the tip penetrated into the surface of the sample when the peak tapping force is measured. - Mode: Tapping (Peak Force QNM)

[0058] - Scan speed (0.3 Hz)

[0059]

[0060] ​- Peak Force setpoint: 100 nN, amplitude: 300 nm

[0061] - Scan angle: 90°

[0062] According to one embodiment of the present invention, the deviation with respect to the indentation depth in the porous polymer substrate may be about -5 nm or more and 5 nm or less. For example, the deviation with respect to the indentation depth in the porous polymer substrate may be about -4 nm or more and 4 nm or less, -3 nm or more and 3 nm or less, -2 nm or more and 2 nm or less, -1 nm or more and 1 nm or less, -0.5 nm or more and 0.5 nm or less, or -0.1 nm or more and 0.1 nm or less. As used herein, "deviation" means the difference in the variable with respect to the average, and may mean the difference in the indentation depth at a specific position of the porous polymer substrate with respect to the average indentation depth of the porous polymer substrate. By adjusting the deviation with respect to the indentation depth in the porous polymer substrate within the above-described range, the breakdown voltage of the porous polymer substrate can be improved.

[0063] According to one embodiment of the present invention, the porous polymer substrate may contain a polyolefin resin. As described above, by including a polyolefin resin in the porous polymer substrate, the separation membrane for the electrochemical element can be easily formed, and a shutdown function can be realized when high temperature occurs during the operation of the battery.

[0064] According to one embodiment of the present invention, the amorphous polymer resin can be an amorphous polyolefin resin. As used herein, "amorphous" may mean that the molecules are arranged without order. As described above, by selecting an amorphous polyolefin resin as the amorphous polymer resin, a shutdown function can be realized when high temperature occurs during the operation of the battery.

[0065] According to one embodiment of the present invention, the crystalline polymer resin may be a crystalline polyolefin resin. In this specification, "crystalline" may mean that the molecules are regularly arranged. As described above, by selecting the crystalline polymer resin to be a crystalline polyolefin resin, the mechanical properties of the porous polymer resin can be improved and the compression resistance can be improved.

[0066] In this specification, "degree of crystallinity" may mean the content of crystals eluted at about 98 °C or higher during TREF measurement.

[0067] According to one embodiment of the present invention, the polyolefin resin may be selected from the group consisting of polyethylene; polypropylene; polybutylene; polypentene; polyhexene; polyoctene; a copolymer of one or more of ethylene, propylene, butene, pentene, 4-methylpentene, hexene or octene; and combinations thereof. For example, the polyolefin resin may be polyethylene. By selecting the polyolefin resin from the above-mentioned ones, the porous polymer substrate can be made to contain a crystalline polymer resin and an amorphous polymer resin, and through this, the mechanical properties and compression resistance of the porous polymer can be improved.

[0068] According to one embodiment of the present invention, the polyolefin resin may have an average short chain branch (SCB) of about 500 or less per 1000 total carbon atoms of the polyolefin contained therein. The short chain branch may be the number of methyl groups per 1000 total carbon atoms (CH3 / 1000TC). The short chain branch may prevent the formation of a crystal structure during the crystallization process of the polymer and may affect the physical properties of the base material. By adjusting the type and content of the monomers contained in the polyolefin base material, the number of the short chain branches can be adjusted. For example, by adjusting the polymerization process of the polymer resin used for the polyolefin base material and / or the type and content of the polyolefin-based polymer resin used in the film forming process using the polymer resin, the number of short chain branches contained in the polyolefin base material can be adjusted. For example, when polymerizing a polyolefin-based polymer resin, the content of propylene, butylene, etc. can be increased, or polypropylene, etc. can be added in the film forming process to increase the number of short chain branches. The number of the short chain branches can be confirmed by comparing the resins contained in the fractions eluted at different temperatures during the analysis according to the temperature rising elution fractionation method. For example, the number of CH3 per about 1000 carbon atoms can be confirmed using an IR detector and CH, CH2, CH3 filters used when performing the temperature rising elution fractionation method. For example, the polyolefin base material may have an average short chain branch of about 100 or more and 500 or less, 150 or more and 450 or less, 200 or more and 400 or less, or 250 or more and 350 or less per 1000 total carbon atoms. Alternatively, the polyolefin base material may have an average short chain branch of 400 or less per 1000 total carbon atoms. When the number of the average short chain branches exceeds the above-described range, it is disadvantageous for the orientation of the polyolefin-based polymer resin contained in the polyolefin base material. By adjusting the number of the average short chain branches within the above-described range, the orientation of the crystalline polyolefin-based polymer resin can be achieved, and a polyolefin base material having compression resistance for the lamination process can be provided.

[0069] According to one embodiment of the present invention, the polyolefin resin may have a melt index of about 0.1 / 10 min to 0.3 g / 10 min. The melt index can be measured according to ASTM D1238. After introducing a sample into a cylinder, it is heated to about 190 °C, or a piston applying a load of about 2.16 kg is arranged with the heated sample in the cylinder, and the weight of the resin discharged through an orifice (inner diameter: 2.09 mm, length: 8 mm) located on the opposite side of the piston is measured and converted to the throughput for 10 minutes to obtain the melt index. By adjusting the melt index of the polyolefin within the above-described range, the rigidity of the porous polymer substrate containing the polyolefin resin can be determined, and a porous polymer substrate having compression resistance in the lamination process can be provided.

[0070] According to one embodiment of the present invention, the weight average molecular weight (Mw) of the porous polymer substrate may be about 500,000 or more and 3,000,000 or less. For example, the weight average molecular weight (Mw) of the porous polymer substrate may be about 500,000 or more and 2,500,000 or less, or 1,000,000 or more and 2,000,000 or less. By adjusting the weight average molecular weight (Mw) of the porous polymer substrate within the above-described range, the mechanical properties and compression resistance of the porous polymer substrate can be improved. Further, when mixing and using different polyolefin resins or forming a separation membrane with a multilayer structure composed of different polyolefin resins, the weight average molecular weight of the polyolefin resin can be calculated by adding the weight average molecular weights corresponding to the content ratios of the respective polyolefin resins.

[0071] In this specification, the weight average molecular weight (Mw) and the polydispersity index can be measured by gel permeation chromatography (GPC: gel permeation chromatography, PL GPC220, Agilent Technologies), and the measurement conditions can be set as follows.

[0072] - Column: PL Olexis (Polymer Laboratories)

[0073] - Solvent: Trichlorobenzene (TCB)

[0074] - Flow rate: 1.0 ml / min

[0075] - Sample concentration: 1.0 mg / ml

[0076] - Injection volume: 200 μl

[0077] - Column temperature: 160 °C

[0078] - Detector: Agilent High Temperature Refractive Index Detector (RI detector)

[0079] - Standard: Polystyrene (corrected with a cubic function)

[0080] According to one embodiment of the present invention, in addition to the polyolefin resin, other resin components can be further mixed as necessary, and for example, filler particles can be included in addition to the resin components. The filler particles can be introduced for the purpose of a pressure barrier so that the thickness, pore size, and porosity of the separation membrane substrate do not decrease excessively with respect to the high pressure applied in the lamination process described later. The filler particles can include organic fillers or inorganic fillers having a predetermined particle size, and are not limited to specific components as long as they have a strength higher than that of the polyolefin resin.

[0081] According to one embodiment of the present invention, the porous polymer substrate may be manufactured by a method (wet method) in which a polyolefin resin is kneaded with a diluent at a high temperature to form a single phase, the polymer material and the diluent are phase-separated during the cooling process, the diluent is then extracted to form pores, and then stretching and heat setting treatments are performed.

[0082] According to an embodiment of the present invention, the average size and the maximum size of the pores of the separation membrane can be easily manufactured by adjusting the mixing ratio of the plasticizer, the draw ratio, the temperature of the heat setting treatment, etc., so that those skilled in the art can meet the scope of the present invention.

[0083] According to an embodiment of the present invention, the size of the pores can be calculated from the pore size distribution measured by the Capillary flow Porometer method. For example, first, after wetting the separation membrane to be measured with a wetting agent such as a galwick solution, the air pressure on one side of the substrate is gradually increased. At this time, when the applied air pressure becomes greater than the capillary attraction of the wetting agent present in the pores, the wetting agent blocking the pores is pushed out, and the size and distribution of the pores are measured by the pressure and flow rate at the moment of extrusion, from which the average pore size and the maximum size can be confirmed.

[0084] The porous polymer substrate may include pores having an average diameter of about 0.01 μm or more and 1 μm or less. For example, the size of the pores contained in the porous polymer substrate may be about 0.01 μm or more and 0.09 μm or less, 0.02 μm or more and 0.08 μm or less, 0.03 μm or more and 0.07 μm or less, or 0.04 μm or more and 0.06 μm or less. By adjusting the pore size of the porous polymer substrate within the above-described range, the air permeability and the ionic conductivity of the entire manufactured separation membrane can be adjusted.

[0085] According to one embodiment of the present invention, the polydispersity index (PDI) of the eluate may be about 5 or more. For example, the polydispersity index (PDI) of the eluate may be about 6 or more and 19 or less, 7 or more and 18 or less, 8 or more and 17 or less, 9 or more and 16 or less, 10 or more and 15 or less, 11 or more and 14 or less, or 12 or more and 13 or less. By adjusting the polydispersity index of the eluate within the above-described range, the uniformity of the crystalline polymer resin can be improved, and the compression resistance can be improved.

[0086] According to one embodiment of the present invention, when a pressure of 8 MPa is applied at about 70 °C, the separation membrane may satisfy any one or more of the following (i) to (iii).

[0087] (i) The thickness reduction rate of the porous polymer substrate defined by the following Mathematical Formula 1 may be about 10% or less.

[0088] [Mathematical Formula 1]

[0089] Thickness reduction rate (%) = (Thickness of the porous polymer substrate before applying pressure - Thickness of the porous polymer substrate after applying pressure) / Thickness of the porous polymer substrate before applying pressure X 100

[0090] For example, when a pressure of 8 MPa is applied at about 70 °C, the thickness reduction rate of the porous polymer substrate defined by the following Mathematical Formula 1 may be about 0% or more and 10% or less, 1% or more and 9% or less, 2% or more and 8% or less, 3% or more and 7% or less, or 4% or more and 6% or less. By realizing the thickness reduction rate of the porous polymer substrate within the above-described range, the compression resistance of the separation membrane can be improved.

[0091] (ii) The increased ventilation rate of the porous polymer substrate after compression defined by the following Mathematical Formula 2 may be about 185% or less.

[0092] [Mathematical Formula 2]

[0093] Air permeability increase rate (%) = (Air permeability after compression - Air permeability before compression) / (Air permeability before compression) X 100

[0094] Whether the porous polymer substrate has compression resistance can be determined by the change rate of air permeability of the substrate before and after compression. The porous polymer substrate before compression can have an air permeability of about 10 s / 100 cc or more and 100 s / 100 cc or less. For example, the air permeability of the porous polymer substrate can be 10 s / 100 cc or more and 90 s / 100 cc or less, 20 s / 100 cc or more and 80 s / 100 cc or less, 30 s / 100 cc or more and 70 s / 100 cc or less, or 40 s / 100 cc or more and 60 s / 100 cc or less. Alternatively, the air permeability of the porous polymer substrate can be about 50 s / 100 cc or more and 80 s / 100 cc or less. When the air permeability of the porous polymer substrate is within the above-mentioned range, the air permeability of the produced separation membrane can be provided within a range suitable for ensuring the output and cycle characteristics of the electrochemical element.

[0095] Also, when the porous polymer substrate is compressed at 70 °C under a pressure of 8 MPa for about 10 seconds, the air permeability increase rate after compression can be about 0% or more and 180% or less, 20% or more and 160% or less, 40% or more and 140% or less, 60% or more and 120% or less, or 80% or more and 100% or less. Alternatively, the porous polymer substrate after compression can have an air permeability of about 200 s / 100 cc or less. A porous polymer substrate that satisfies the air permeability increase rate within the above-mentioned range can reduce the occurrence of defects associated with the deformation of its shape even in the lamination process. When a substrate with an air permeability after compression exceeding about 200 s / 100 cc under the above conditions is used, the output and cycle characteristics of the electrochemical element may deteriorate.

[0096] The air permeability (s / 100cc) means the time (seconds) it takes for about 100 cc of air to pass through a porous polymer substrate or a separation membrane with a predetermined area under a constant pressure. The air permeability can be measured using a Gurley densometer in accordance with ASTM D 726-58, ASTM D726-94, or JIS-P8117. For example, using a 4110N device from Gurley, the time it takes for about 100 cc of air to pass through a sample of about 1 square inch (or 6.54 cm 2 ) under the pressure of air at about 0.304 kPa or water at about 1.215 kN / m 2 can be measured. For example, using an EG01-55-1MR device from Asahi Seiko, the time it takes for about 100 cc of air to pass through a sample of about 1 square inch under a constant pressure of 4.8 inches of water at room temperature can be measured.

[0097] (iii) The breakdown voltage of the porous polymer substrate can be about 1,000 V or more.

[0098] For example, when applying a pressure of 8 MPa at about 70°C, the breakdown voltage of the porous polymer substrate may be about 1,000 V or more and 2,000 V or less, 1,100 V or more and 1,900 V or less, 1,200 V or more and 1,800 V or less, 1,300 V or more and 1,700 V or less, or 1,400 V or more and 1,600 V or less. By adjusting the breakdown voltage of the porous polymer substrate within the above-described range, the insulation property of the porous polymer substrate can be improved.

[0099] In this specification, the breakdown voltage may also mean the voltage when the voltage is increased at a rate of about 100 mV / s for a test piece with a thickness of about 12 μm and when it exceeds about 0.5 mA and 3 seconds.

[0100] According to one embodiment of the present invention, the porous polymer substrate may have a thickness of about 1 μm or more and 30 μm or less. For example, the thickness of the porous polymer substrate may be about 2 μm or more and 29 μm or less, 3 μm or more and 28 μm or less, 4 μm or more and 27 μm or less, 5 μm or more and 26 μm or less, 6 μm or more and 25 μm or less, 7 μm or more and 24 μm or less, 8 μm or more and 23 μm or less, 9 μm or more and 22 μm or less, 10 μm or more and 21 μm or less, 11 μm or more and 20 μm or less, 12 μm or more and 19 μm or less, 13 μm or more and 18 μm or less, 14 μm or more and 17 μm or less, or 15 μm or more and 16 μm or less. By adjusting the thickness of the porous polymer substrate within the above-described range, the energy density of the separation membrane for the electrochemical device can be improved.

[0101] A method for manufacturing a porous polymer substrate according to one embodiment of the present invention includes kneading and extruding a composition for a porous polymer substrate containing a polymer resin; cooling the extruded composition for a porous polymer substrate to produce a sheet; stretching the sheet; and forming pores in the stretched sheet; and heat-fixing the sheet having the pores formed therein to produce a porous polymer substrate. By manufacturing a porous polymer substrate by the above-described method, a porous polymer substrate containing uniform pores can be manufactured.

[0102] According to one embodiment of the present invention, the method for manufacturing the porous polymer substrate may include kneading and extruding a composition for a porous polymer substrate containing a polymer resin. By including the kneading and extruding steps as described above, a uniform composition for a porous polymer substrate can be manufactured, and a porous polymer substrate having a uniform pore size can be manufactured.

[0103] According to one embodiment of the present invention, the composition for a porous polymer substrate may further contain a plasticizer. For example, the plasticizer may be liquid paraffin oil. By containing a plasticizer as described above, the plasticizer can be easily removed from the sheet, and denaturation of the polymer resin can be prevented.

[0104] According to one embodiment of the present invention, the liquid paraffin oil may have a kinematic viscosity at 40 °C of about 30 cSt or more and 50 cSt or less. By manufacturing the kinematic viscosity of the liquid paraffin oil within the above-described range, the concentration of the plasticizer in the composition for the porous polymer substrate can be uniformly adjusted.

[0105] According to one embodiment of the present invention, the weight ratio of the polymer resin to the plasticizer in the composition for the porous polymer substrate may be about 2:8 to 5:5. By adjusting the weight ratio of the polymer resin to the plasticizer in the composition for the porous polymer substrate within the above-described range, the porosity of the porous polymer substrate can be adjusted.

[0106] According to one embodiment of the present invention, the extrusion may be performed through a T-die using a twin-screw extruder. By performing the extrusion as described above, the thickness of the sheet can be easily adjusted, and the cooling efficiency can be improved.

[0107] According to one embodiment of the present invention, the method for manufacturing the porous polymer substrate may include a step of cooling the extruded composition for the porous polymer substrate to produce a sheet.

[0108] According to one embodiment of the present invention, the temperature for cooling the sheet may be about 40 °C or more and 80 °C or less. For example, the temperature for casting through the T-die onto a roll may be about 40 °C or more and 80 °C or less. By adjusting the temperature for cooling the sheet within the above-described range, the polymer resin can be made crystalline, and the content of the crystalline polymer resin and the non-crystalline polymer resin in the porous polymer resin can be adjusted to reduce the indentation depth and at the same time minimize the standard deviation of the indentation depth.

[0109] According to one embodiment of the present invention, the method for manufacturing the porous polymer substrate may include a step of stretching the sheet. By including the step of stretching the sheet as described above, the thickness of the porous polymer substrate can be adjusted, and thinning can be realized.

[0110] According to one embodiment of the present invention, the stretching step may be biaxial stretching using a tenter-type simultaneous stretching machine. For example, after stretching in the MD (machine direction), it may be stretched in the TD (transverse direction). By performing the stretching step as described above, the sheet can be manufactured into a large-area porous polymer substrate.

[0111] According to one embodiment of the present invention, the method for manufacturing the porous polymer substrate may include a step of forming pores in the stretched sheet. For example, the step of forming pores in the stretched sheet may be a step of removing a plasticizer contained in the porous polymer substrate using a solvent. The solvent may be methylene chloride. By including the step of forming pores in the stretched sheet as described above, a porous polymer substrate can be manufactured, and the remaining plasticizer can be minimized.

[0112] One embodiment of the present invention may include a step of heat-fixing the sheet having the pores formed therein to manufacture a porous polymer substrate. For example, the temperature of the heat-fixing step may be about 100°C or higher and 150°C or lower. By heat-fixing the sheet as described above, the heat resistance of the separation membrane can be improved.

[0113] According to one embodiment of the present invention, the separation membrane for an electrochemical element may further include a coating layer formed on at least one surface of the porous polymer substrate.

[0114] According to one embodiment of the present invention, the coating layer includes a polymer binder and inorganic particles and has porous characteristics.

[0115] According to one embodiment of the present invention, the coating layer may be a porous coating layer including a plurality of pores. For example, the coating layer may be a porous coating layer including a plurality of pores inside. As described above, since the coating layer includes a plurality of pores, lithium ions can pass through while physically blocking the negative electrode and the positive electrode so that an electric current can flow.

[0116] According to one embodiment of the present invention, the polymer binder and the inorganic particles in the coating layer may be included in a ratio of about 1:99 to 30:70 by weight. The ratio can be appropriately adjusted within the above-described range, and the polymer binder can be about 1 wt% or more, 5 wt% or more, or 10 wt% or more based on 100 wt% in total of the polymer binder and the inorganic particles, and the inorganic particles can be about 80 wt% or more, 85 wt% or more, 90 wt% or more, or 95 wt% or more.

[0117] According to one embodiment of the present invention, the coating layer may be formed by inorganic particles being bound by a polymer binder and accumulated in the layer. The pores inside the coating layer may be caused by the interstitial volume, which is the empty space between the inorganic particles.

[0118] In one embodiment of the present invention, the porosity of the coating layer may be about 30% by volume to 70% by volume. When the porosity of the coating layer is about 70% by volume or less, mechanical properties that can withstand the pressing process of adhering to the electrode can be ensured, and the surface aperture ratio does not become too high, which is suitable for ensuring the adhesive force. On the other hand, when the porosity is about 30% by volume or more, it is advantageous from the viewpoint of ion permeability.

[0119] In this specification, the porosity of the coating layer means the ratio of the volume occupied by pores to the total volume of the coating layer, and volume% is used as its unit, and it can be used interchangeably with terms such as void ratio and porosity.

[0120] In this specification, the porosity corresponds to the value obtained by subtracting the volume converted from the weight and density of each component of the porous polymer substrate and the coating layer from the volume calculated in terms of thickness, width, and length of the porous polymer substrate and the coating layer.

[0121] For example, the porous polymer substrate can have a porosity of about 10 vol% or more and 60 vol% or less. In one embodiment, the porosity of the porous polymer substrate can be about 15 vol% or more and 55 vol% or less, 20 vol% or more and 50 vol% or less, 25 vol% or more and 45 vol% or less, or 30 vol% or more and 40 vol% or less. When the porosity of the porous polymer substrate is within the above-described range, the ionic conductivity of the produced separation membrane can be provided within a range suitable for ensuring the output and cycle characteristics of the electrochemical device.

[0122] In one embodiment of the present invention, the porosity and pore size of the porous polymer substrate and the coating layer can be measured by the BET six-point method by the nitrogen gas adsorption flow method using a scanning electron microscope (SEM) image, a mercury porosimeter, a capillary flow porometer, or a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini). At this time, it may be advantageous to use a capillary flow porometer.

[0123] According to one embodiment of the present invention, the thickness of the coating layer can be formed to be about 1 μm to 20 μm with respect to any one of the porous polymer substrates, but is not particularly limited thereto. The thickness can be adjusted by those skilled in the art within an appropriate range from the viewpoints of heat resistance and electrical resistance.

[0124] According to an embodiment of the present invention, the thickness of the porous polymer substrate and / or the coating layer can be measured by applying a contact thickness measuring instrument. For example, VL-50S-B of Mitutoyo can be used as the contact thickness measuring instrument.

[0125] According to an embodiment of the present invention, the polymer binder that can be used in the coating layer may be any one polymer resin selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or a mixture of two or more of these. However, it is not particularly limited thereto.

[0126] In one embodiment of the present invention, the inorganic particles that can be used for the coating layer are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in one embodiment of the present invention are not particularly limited as long as oxidation and / or reduction reactions do not occur within the operating voltage range of the applied electrochemical device (e.g., 0 V to 5 V based on Li / Li + ).

[0127] According to one embodiment of the present invention, non-limiting examples of the inorganic particles include BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT, 0 < x < 1, 0 < y < 1), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, Al(OH)3, TiO2, aluminum peroxide, zinc stannate hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), antimony pentoxide (Sb2O5), etc., and may include one or more of these.

[0128] According to one embodiment of the present invention, the average diameter (D 50 ) of the inorganic particles is not particularly limited, but is preferably in the range of about 0.3 μm or more and 1 μm or less for forming a coating layer with a uniform thickness and an appropriate porosity. For example, if it is less than about 0.3 μm, the dispersibility of the inorganic particles in the slurry prepared for coating layer production may decrease, and if it exceeds about 1 μm, the thickness of the formed coating layer may increase.

[0129] In this specification, "D50 particle size" means the particle size at about 50% of the cumulative distribution of the number of particles according to the particle size. The particle size can be measured using the laser diffraction method. For example, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500). When the particles pass through the laser beam, the difference in the diffraction pattern according to the particle size is measured to calculate the particle size distribution. The D50 particle size can be measured by calculating the particle diameter at the point where the cumulative distribution of the number of particles according to the particle size in the measuring device reaches 50%.

[0130] According to one embodiment of the present invention, the method for forming the coating layer is, for example, as follows. First, a polymer binder is dissolved in a suitable organic solvent to produce a polymer solution, or the polymer binder is dispersed in a suitable dispersion medium to produce a polymer emulsion. As the organic solvent or dispersion medium that can be used at this time, it is preferable that the solubility index is similar to the polymer binder to be used and the boiling point is low. This is to facilitate uniform mixing and subsequent removal of the solvent or dispersion medium. Non-limiting examples of solvents that can be used include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof.

[0131] Next, inorganic particles are added and dispersed in the produced polymer solution and / or polymer dispersion medium to produce a slurry for the coating layer. According to one embodiment of the present invention, the content ratio of the inorganic particles to the polymer binder is as described above, and is appropriately adjusted in consideration of the thickness, pore size, and porosity of the coating layer of the present invention finally produced.

[0132] Next, the slurry for the coating layer produced above is applied to at least one side surface of the prepared porous polymer substrate and dried. The method of applying the slurry to the surface of the porous polymer substrate is not particularly limited to any one method, and ordinary methods known in the art can be used. For example, various methods such as dip coating, die coating, roll coating, comma coating, or a mixed method thereof can be used.

[0133] In the drying step, the conditions of temperature and time are appropriately set in order to minimize the generation of surface defects of the coating layer. For the drying, drying auxiliary devices such as a drying oven or hot air can be used within an appropriate range.

[0134] When the separation membrane includes a coating layer, damage caused by pressing inorganic particles on the surface of the porous polymer substrate facing the coating layer during the lamination process can be reduced.

[0135] According to an embodiment of the present invention, the separation membrane is interposed between a negative electrode and a positive electrode and is manufactured as an electrochemical element by a lamination process in which heat and / or pressure is applied for binding. In an embodiment of the present invention, the lamination process can be performed by a roll press device including a pair of pressure rollers. That is, the negative electrode, the separation membrane, and the positive electrode are sequentially laminated, and this is put between the pressure rollers to achieve interlayer binding. At this time, the lamination process can be performed by a method of hot pressing.

[0136] An embodiment of the present invention provides an electrochemical element including a positive electrode; a negative electrode; and a separation membrane interposed between the positive electrode and the negative electrode.

[0137] The electrochemical element according to an embodiment of the present invention can prevent high-potential (Hi-Pot) defects and low-voltage defects and improve battery performance.

[0138] In the present invention, the electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and includes a primary battery and a secondary battery (Secondary Battery). In this specification, the secondary battery means a rechargeable and dischargeable lithium secondary battery, nickel-cadmium battery, nickel-metal hydride battery, etc. The lithium secondary battery includes, but is not limited to, a non-aqueous electrolyte secondary battery containing a liquid electrolyte in which lithium ions are used as an ion conductor, an all-solid battery containing a solid electrolyte, a lithium polymer battery containing a gel polymer electrolyte, a lithium metal battery using lithium metal as a negative electrode, and the like.

[0139] According to an embodiment of the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The positive electrode active material includes layered compounds such as lithium manganese composite oxides (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x O4 (where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3) represented by Ni-site type lithium nickel oxide; chemical formula LiMn 1-x M xA lithium manganese composite oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a part of Li in the chemical formula is substituted with an alkaline earth metal ion; a disulfide compound; It may contain one or a mixture of two or more of Fe2(MoO4)3.

[0140] According to one embodiment of the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. As the negative electrode active material, the negative electrode includes carbon such as lithium metal oxide, graphitized carbon, and graphite-based carbon; LixFe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) and other metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; It may contain one or a mixture of two or more selected from titanium oxides.

[0141] According to one embodiment of the present invention, the conductive material may be any one selected from the group consisting of, for example, graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whisker, conductive metal oxide, activated carbon, and polyphenylene derivative, or a mixture of two or more of these conductive materials. Alternatively, it may be one selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more of these conductive materials.

[0142] According to one embodiment of the present invention, the current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, stainless steel, copper, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used.

[0143] According to one embodiment of the present invention, as the binder resin, a polymer that is usually used for electrodes in the art can be used. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, etc., and is not limited thereto.

[0144] In one embodiment of the present invention, the positive electrode slurry for manufacturing the positive electrode active material layer may contain a dispersant, and the dispersant may be a pyrrolidone-based compound. For example, it may be N-methylpyrrolidone (N-methylpyrrolidone, ADC-01, LG Chem).

[0145] According to one embodiment of the present invention, the content of the dispersant contained in the positive electrode slurry may be more than about 0 parts by weight and 0.5 parts by weight or less with respect to 100 parts by weight of the positive electrode slurry. For example, the content of the dispersant contained in the positive electrode slurry may be more than about 0.05 parts by weight and 0.4 parts by weight or less with respect to 100 parts by weight of the positive electrode slurry.

[0146] According to one embodiment of the present invention, the negative electrode slurry for manufacturing the negative electrode active material layer may contain a dispersant, and the dispersant may be a polypyrrolidone-based compound. For example, the dispersant may be polyvinylpyrrolidone (Polyvinylpyrrolidone, Junsei).

[0147] According to one embodiment of the present invention, the content of the dispersant contained in the negative electrode slurry may be more than about 0 parts by weight and 0.5 parts by weight or less with respect to 100 parts by weight of the negative electrode slurry. For example, the content of the dispersant contained in the negative electrode slurry may be more than about 0.05 parts by weight and 0.4 parts by weight or less with respect to 100 parts by weight of the negative electrode slurry.

[0148] According to one embodiment of the present invention, the electrochemical element prepared as described above can be housed in an appropriate case and an electrolytic solution can be injected to manufacture a battery.

[0149] According to one embodiment of the present invention, the electrolytic solution is a salt having a structure such as A + B - where A + is an alkali metal cation such as Li + , Na + , K + or an ion composed of a combination thereof, and B - is PF6 - or BF4- 、 Cl - 、 Br - 、 I - 、 ClO4 - 、 AsF6 - 、 CH3CO2 - 、 CF3SO3 - 、 N(CF3SO2)2 - 、 C(CF2SO2)3 - Salts containing anions such as these, or ions composed of combinations thereof, are dissolved or dissociated in an organic solvent composed of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (γ-butyrolactone), or mixtures thereof, but are not limited thereto.

[0150] One embodiment of the present invention provides a battery module including the electrochemical element as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Examples of the device include power tools powered by a battery motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheel vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; power storage systems, etc., but are not limited thereto.

[0151] Hereinafter, examples will be given for a detailed description of the present invention for illustrative purposes. However, the examples according to the present invention can be changed into various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those with average knowledge in the industry.

[0152] <Example 1> 30 parts by weight of a polymer resin (polyethylene resin, Mw: 800,000) with a log (Log) Mw of 5.5 and 70 parts by weight of liquid paraffin oil (kinematic viscosity at 40 °C: 40 cSt) were put into a twin-screw extruder and kneaded, and then extruded. After extrusion, it was formed into a sheet via a T-die and a cooling casting roll, and then biaxially stretched by a tenter-type simultaneous stretching machine with MD stretching followed by TD stretching. The liquid paraffin oil, which is a diluent, was extracted from the stretched sheet with methylene chloride, and heat-fixed at about 128 °C to produce a porous polymer base material. That is, in the production of the polyethylene film of Example 1, propylene was not added in the polymerization process in order to increase the crystal content and improve the compression resistance.

[0153] For the porous polymer base material, the weight-average molecular weight of the eluate was determined using a PolymerChar TREF machine. For example, 40 mg of a sample was prepared for the porous polymer base material, dissolved in 20 mL of trichlorobenzene solvent at 150 °C for 120 minutes, and then stabilized at 100 °C for 45 minutes. Then, after introducing this into a TREF column, it was cooled to 35 °C at a temperature decrease rate of 0.5 °C / min and maintained for 15 minutes. Then, while heating from 35 °C to 80 °C at a temperature decrease rate of 20 °C / min, it was maintained for 20 minutes in 5 °C units, and while heating from 80 °C to 120 °C at a temperature decrease rate of 20 °C / min, it was maintained for 20 minutes in 2 °C units. The weight-average molecular weight of the polymer sample eluted at 98 °C was measured while flowing trichlorobenzene, which is the solvent, through the column at a flow rate of 0.5 mL / min.

[0154] Furthermore, the weight-average molecular weight measured for the porous polymer substrate and the number-average molecular weight derived through gel permeation chromatography (GPC) analysis were determined, and the polydispersity index was calculated using the following Equation 3.

[0155] [Equation 3] Polydispersity index (PDI) = (weight-average molecular weight) / (number-average molecular weight)

[0156] The log (log) value (log Mw) of the weight-average molecular weight of the eluate of the porous polymer substrate was 5.5, and the polydispersity index (PDI) of the eluate of the porous polymer substrate was 6.0.

[0157] <Example 2> In Example 1, a porous polymer substrate was produced in the same manner as in Example 1, except that the log (Log) Mw of the polymer resin was 6.2.

[0158] <Example 3> In Example 1, a porous polymer substrate was produced in the same manner as in Example 1, except that the log (Log) Mw of the polymer resin was 5.1 and the polydispersity index (PDI) was 5.2.

[0159] <Example 4> In Example 1, a porous polymer substrate was produced in the same manner as in Example 1, except that the log (Log) Mw of the polymer resin was 5.1 and the polydispersity index (PDI) was 9.9.

[0160] <Comparative Example 1> Compared with Example 1 in which propylene was not added during the polymerization process of the polyethylene resin, in Comparative Example 1, 7 parts by weight of propylene was added to 100 parts by weight of ethylene during the polymerization process of the polyethylene resin to produce a polymer resin (Mw: 800,000), and a porous polymer substrate was produced in the same manner as in Example 1, except that the log (Log) Mw of the polymer resin was 2.9.

[0161] <Comparative Example 2> Compared with Example 1 where no propylene was added during the polymerization process of the polyethylene resin, in Comparative Example 2, 5.5 parts by weight of propylene was added to 100 parts by weight of ethylene during the polymerization process of the polyethylene resin to produce a polymer resin (Mw: 800,000). A porous polymer substrate was produced in the same manner as in Example 1 except that the log (Log) Mw of the polymer resin was 4.4.

[0162] <Comparative Example 3> Compared with Example 1 where no propylene was added during the polymerization process of the polyethylene resin, in Comparative Example 3, 3 parts by weight of propylene was added to 100 parts by weight of ethylene during the polymerization process of the polyethylene resin to produce a polymer resin (Mw: 800,000). A porous polymer substrate was produced in the same manner as in Example 1 except that the log (Log) Mw of the polymer resin was 5.1 and the polydispersity index (PDI) was 2.3.

[0163] <Comparative Example 4> Compared with Example 1 where no propylene was added during the polymerization process of the polyethylene resin, in Comparative Example 4, 1.5 parts by weight of propylene was added to 100 parts by weight of ethylene during the polymerization process of the polyethylene resin to produce a polymer resin (Mw: 800,000). A porous polymer substrate was produced in the same manner as in Example 1 except that the log (Log) Mw of the polymer resin was 5.1 and the polydispersity index (PDI) was 3.9.

[0164] <Experimental Example 1: Measurement of Thickness Reduction Rate> Using a contact thickness gauge (Mitutoyo, VL-50S-B), the thickness before applying pressure and the thickness after applying a pressure of 8 MPa at 70 °C were measured for the porous polymer substrates of Examples 1 to 4 and Comparative Examples 1 to 4, and the thickness reduction rate of the porous polymer substrate was measured according to the following formula 1. The measurement was carried out by punching out the porous substrate at 5 × 5 cm, and then measuring 5 points: 4 points at a position 1 cm away from the corner and 1 point at the center. Then, samples at the left / middle / right positions along the TD direction were taken 3 times, and the arithmetic mean was taken as the thickness of the porous polymer substrate.

[0165] [Formula 1] Reduction rate of thickness (%) = (Thickness of the porous polymer substrate before applying pressure - Thickness of the porous polymer substrate after applying pressure) / Thickness of the porous polymer substrate before applying pressure × 100

[0166]

Table 1

[0167] Referring to Table 1 above, it was confirmed that in Comparative Examples 1 and 2, the weight average molecular weight was low and the reduction rate of the thickness of the porous polymer substrate increased, while in Examples 1 and 2, the reduction rate of the thickness of the porous polymer substrate decreased as the weight average molecular weight increased.

[0168] Furthermore, in Comparative Examples 3 and 4, when the weight average molecular weight was the same, the polydispersity index was low and the reduction rate of the thickness of the porous polymer substrate increased, while in Examples 3 and 4, it was confirmed that the reduction rate of the thickness of the porous polymer substrate decreased as the polydispersity index increased.

[0169] According to one embodiment of the present invention, by adjusting the weight average molecular weight and polydispersity index of the crystalline polymer resin contained in the porous polymer substrate, the compression resistance can be improved and the thickness change rate can be reduced.

[0170] <Example 5> A polyolefin resin (a copolymer containing ethylene and propylene in a weight ratio of 96:4, weight average molecular weight: 800,000) and a liquid paraffin oil (kinematic viscosity at 40°C: 40 cSt) were mixed at a weight ratio of 3:7, and 5% by weight of polypropylene was further added based on the total weight of the polyolefin resin. The mixture was charged into a twin-screw extruder and kneaded and extruded. After extrusion, it was formed into a sheet shape by passing through a T-die and a cooling casting roll, and biaxially stretched using a tenter-type sequential stretching machine that performs TD stretching after MD stretching. The liquid paraffin oil was extracted from the stretched sheet with methylene chloride and heat-fixed at about 128°C to produce a polyolefin substrate (thickness 9 μm).

[0171] <Example 6> A polyolefin resin (a copolymer containing ethylene and propylene in a weight ratio of 93:7) and liquid paraffin oil were mixed at a weight ratio of 3:7, and 5% by weight of polypropylene was further added based on the total weight of the polyolefin resin. A polyolefin substrate (thickness: 9 μm) was produced in the same manner as in Example 5 except for the above.

[0172] <Example 7> A polyolefin resin (a copolymer containing ethylene and propylene in a weight ratio of 85:15) and liquid paraffin oil were mixed at a weight ratio of 3:7, and 2% by weight of polypropylene was further added based on the total weight of the polyolefin resin. A polyolefin substrate (thickness: 9 μm) was produced in the same manner as in Example 5 except for the above.

[0173] <Example 8> A polyolefin resin (a copolymer containing ethylene and propylene in a weight ratio of 85:15) and liquid paraffin oil were mixed at a weight ratio of 3:7, and 3.5% by weight of polypropylene was further added based on the total weight of the polyolefin resin. A polyolefin substrate (thickness: 9 μm) was produced in the same manner as in Example 5 except for the above.

[0174] <Comparative Example 5> A polyolefin resin (a copolymer containing ethylene and propylene in a weight ratio of 70:30) and liquid paraffin oil were mixed at a weight ratio of 3:7, and 5% by weight of polypropylene was further added based on the total weight of the polyolefin resin. A polyolefin substrate (thickness: 9 μm) was produced in the same manner as in Example 5 except for the above.

[0175] <Comparative Example 6> A polyolefin resin (a copolymer containing ethylene and propylene in a weight ratio of 85:15) and liquid paraffin oil were mixed at a weight ratio of 3:7, and 7% by weight of polypropylene was further added based on the total weight of the polyolefin resin. A polyolefin substrate (thickness: 9 μm) was produced in the same manner as in Example 5 except for the above.

[0176] <Experimental Example 2: Confirmation of the Content of Amorphous Polymer Resin Contained in Polyolefin Substrate> In the examples and comparative examples, the content of the amorphous polyolefin polymer resin contained in the polyolefin substrate was confirmed using the TREF machine of PolymerChar. For example, 40 mg of the polyolefin substrate was dissolved in 20 mL of trichlorobenzene solvent at 150 °C for 120 minutes, and then stabilized at 100 °C for 45 minutes. After introducing this into the TREF column, it was cooled to 35 °C at a temperature drop rate of 0.5 °C / min and maintained for 15 minutes. Then, while heating from 35 °C to 80 °C at a temperature drop rate of 20 °C / min, it was maintained for 20 minutes in 5 °C units, and while heating from 80 °C to 120 °C at a temperature drop rate of 20 °C / min, it was maintained for 20 minutes in 2 °C units. Then, while flowing trichlorobenzene, which is the solvent, through the column at a flow rate of 0.5 mL / min, the weight of the fraction eluted at 35 °C was measured and shown in Tables 2 and 3 below.

[0177] At the same time, using the IR detector included in the machine, the average number of CH3 per 1000 carbon atoms was confirmed and shown in Tables 2 and 3 below.

[0178] <Experimental Example 3: Confirmation of Compression Resistance According to the Content of Amorphous Polymer Resin Contained in Polyolefin Substrate> The polyolefin substrates of Example 5, Example 6, and Comparative Example 5 were measured using the EG01-55-1MR device of Asahi Seiko at room temperature under a constant pressure of 4.8 inches of water to confirm the air permeability before compression by measuring the time it takes for 100 cc of air to pass through a 1 square inch sample.

[0179] Each of the polyolefin substrates was attached to a pressing device and pressed at 70 °C under a pressure of 8 MPa for 10 seconds, and then the air permeability after compression was confirmed by measuring in the same manner using the device.

[0180] Based on the air permeability of the original fabric before and after compression, the air permeability increase rate was calculated according to the above formula 1 and shown in Table 2 below.

[0181]

Table 2

[0182] As can be seen from Table 2 above, in the case of Comparative Example 5, the increase rate of air permeability is 364%, while in the case of Examples 5 and 6, the increase rates of air permeability are 30% and 68% respectively.

[0183] <Experimental Example 4: Confirmation of Compression Resistance According to the Average Short Chain Branching of Polyolefin Substrate> Using the polyolefin substrates of Examples 7, 8 and Comparative Example 6, the air permeability before and after compression was measured in the same manner as in Experimental Example 3.

[0184] Based on the air permeability of the original fabric before and after compression, the increase rate of air permeability was calculated according to the above formula (2) and shown in Table 3 below.

[0185]

Table 3

[0186] As shown in Table 3 above, in the case of Comparative Example 6, the increase rate of air permeability is 201%, while in the case of Examples 7 and 8, the increase rates of air permeability are 27% and 147% respectively.

[0187] <Example 9>

[0188] 30 parts by weight of a polymer resin (polyethylene resin, Mw: 1.5 million) and 70 parts by weight of liquid paraffin oil (kinematic viscosity at 40 °C: 40 cSt) were put into a twin-screw extruder, kneaded and then extruded. After extrusion, it was formed into a sheet through a T-die and a cooling casting roll, and then biaxially stretched by a tenter-type simultaneous stretching machine with MD stretching followed by TD stretching. The liquid paraffin oil as a diluent was extracted from the stretched sheet with methylene chloride and heat-fixed at about 128 °C to produce a porous polymer substrate.

[0189] The weight ratio of the eluate eluted at 98 °C was determined for the porous polymer substrate using PolymerChar's TREF machine. For example, a 40 mg sample was prepared for the porous polymer substrate, dissolved in 20 mL of trichlorobenzene solvent at 150 °C for 120 minutes, and then stabilized at 100 °C for 45 minutes. Thereafter, after introducing this into a TREF column, it was cooled to 35 °C at a temperature decrease rate of 0.5 °C / min and maintained for 15 minutes. Then, while heating from 35 °C to 80 °C at a temperature decrease rate of 20 °C / min, it was maintained for 20 minutes in 5 °C units, and while heating from 80 °C to 120 °C at a temperature decrease rate of 20 °C / min, it was maintained for 20 minutes in 2 °C units. While flowing trichlorobenzene, which is the solvent, through the column at a flow rate of 0.5 mL / min, the weight of the polymer sample eluted at 98 °C was measured. The content of the crystalline polymer resin contained in the porous polymer substrate was 72% by weight.

[0190] <Example 10> In Example 9 above, a porous polymer substrate was produced in the same manner as in Example 9, except that the content of the crystalline polymer resin contained in the porous polymer substrate was 83% by weight.

[0191] <Comparative Example 7> In Example 9 above, 7 parts by weight of polypropylene (Mw: 350,000) was added to 100 parts by weight of polyethylene (Mw: 600,000) to produce a polymer resin (Mw: 580,000). A porous polymer substrate was produced in the same manner as in Example 9, except that the content of the crystalline polymer resin contained in the porous polymer substrate was 66% by weight.

[0192] <Comparative Example 8> In Example 9 above, 0.5 parts by weight of polypropylene (Mw: 350,000) was added to 100 parts by weight of polyethylene (Mw: 600,000) to produce a polymer resin (Mw: 600,000). A porous polymer substrate was produced in the same manner as in Example 9, except that the content of the crystalline polymer resin contained in the porous polymer substrate was 90% by weight.

[0193] <Experimental Example 5: Measurement of Indentation Depth and Standard Deviation> Using a nanoindenter (Fischerscope, HM2000), the porous polymer substrate was indented with a Vickers indenter (the width of the tip of the chip was 0.5 μm) with a force of 100 nN, and then the depth to which the indenter was pushed was measured with an atomic force microscope (AFM, Atomic Force Microscope).

[0194] After setting the Dimension Icon (Bruker) on the surfaces of the porous polymer substrates of Example 9 and 10 and Comparative Examples 7 and 8 under the following conditions, while moving the tip over the surface of the sample as shown in FIG. 1, the peak tapping force was measured, and when the peak tapping force was measured, the depth of the tip that penetrated the surface of the sample was measured with an atomic force microscope (AFM, Atomic Force Microscope, OSTESPA - R3, Bruker, f = 300 kHz, k = 26 N / m).

[0195] - Mode: Tapping (Peak Force QNM)

[0196] - Scan speed: 0.3 Hz

[0197] - Peak Force setpoint: 100 nN, Amplitude: 300 nm

[0198] - Scan angle: 90°

[0199] <Experimental Example 6: Measurement of Dielectric Breakdown Voltage> For Example 9 and 10 and Comparative Examples 7 and 8 having a thickness of 12 μm, after applying a pressure of 8 MPa at 70°C, the voltage when the current exceeded 0.5 mA and 3 seconds was measured while increasing the pressure at a rate of 100 mV / s.

[0200]

Table 4

[0201] Referring to Table 4 above, it was confirmed that in Examples 9 and 10, the crystalline polymer resin was contained in the porous polymer substrate in an appropriate content equal to or higher than the reference value, the indentation depth was relatively low, the standard deviation of the indentation depth decreased, and the dielectric breakdown voltage after compression increased.

[0202] In contrast, in Comparative Example 7, the porous polymer substrate contained only a small amount of 66% by weight of the crystalline polymer resin, the indentation depth increased sharply, the dielectric breakdown voltage after compression increased relatively slightly to 1,000 V or less, and in Comparative Example 8, the porous polymer substrate contained 90% by weight of the crystalline polymer resin in excess, the standard deviation of the indentation depth increased, and it was confirmed that the dielectric breakdown voltage after compression also increased relatively slightly to 1,000 V or less.

[0203] Therefore, the separation membrane for an electrochemical element according to an embodiment of the present invention can adjust the content of the crystalline polymer resin contained in the porous polymer substrate to adjust the indentation depth and its standard deviation, and improve the dielectric breakdown voltage after lamination.

[0204] As described above, the present invention has been described with reference to preferred examples. However, those skilled in the art or those having ordinary knowledge in the technical field can understand that the present invention can be variously modified and changed without departing from the spirit and technical scope of the present invention described in the claims below. Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

Claims

1. comprising a porous polymer substrate, the porous polymer substrate comprising an amorphous polymer resin and a crystalline polymer resin, a separation membrane for an electrochemical device, wherein the weight-average molecular weight (Mw) of the eluate eluted from the porous polymer substrate by temperature rising elution fractionation (TREF) is 100,000 or more.

2. The separation membrane for an electrochemical device according to claim 1, wherein the porous polymer substrate contains 40% by weight or less of a fraction eluted at a temperature of 35°C or lower by temperature rising elution fractionation.

3. The separation membrane for an electrochemical device according to claim 1, wherein the content of the amorphous polymer resin in the porous polymer substrate is 40% by weight or less.

4. The separation membrane for an electrochemical device according to claim 1, wherein the content of the crystalline polymer resin in the porous polymer substrate is 60% by weight or more.

5. The separation membrane for an electrochemical device according to claim 1, wherein the weight ratio of the amorphous polymer resin to the crystalline polymer resin in the porous polymer substrate is 1:1 to 10:

1.

6. The separation membrane for an electrochemical device according to claim 1, wherein the deviation of the indentation depth in the porous polymer substrate is -5 nm or more and 5 nm or less.

7. the porous polymer substrate comprising a polyolefin resin, the amorphous polymer resin being an amorphous polyolefin resin, the crystalline polymer resin being a crystalline polyolefin resin, the separation membrane for an electrochemical device according to claim 1.

8. The separation membrane for an electrochemical device according to claim 7, wherein the polyolefin resin is one selected from the group consisting of polyethylene; polypropylene; polybutylene; polypentene; polyhexene; polyoctene; a copolymer of one or more of ethylene, propylene, butene, pentene, 4-methylpentene, hexene or octene; and combinations thereof.

9. The separation membrane for an electrochemical device according to claim 7, wherein the polyolefin resin has an average short-chain branch (SCB) of 500 or less per 1000 total carbon atoms.

10. The separation membrane for an electrochemical device according to claim 7, wherein the polyolefin resin has a melt index (ASTM D1238, 190°C, 2.16 kg) of 0.1 g / 10 min to 0.3 g / 10 min.

11. The weight average molecular weight (Mw) of the porous polymer substrate is 500,000 or more and 3,000,000 or less. The separation membrane for an electrochemical element according to claim 1.

12. The polydispersity index (PDI) of the eluate is 5 or more. The separation membrane for an electrochemical element according to claim 1.

13. When a pressure of 8 MPa is applied at 70°C, the separation membrane for an electrochemical element according to claim 1 satisfies any one or more of the following (i) to (iii): (i) The thickness reduction rate of the porous polymer substrate defined by the following formula 1 is 10% or less: [Formula 1] Thickness reduction rate (%) = (Thickness of the porous polymer substrate before applying pressure - Thickness of the porous polymer substrate after applying pressure) / Thickness of the porous polymer substrate before applying pressure X 100 (ii) The increased ventilation rate of the porous polymer substrate after compression defined by the following formula 2 is 185% or less: [Formula 2] Increased ventilation rate (%) = (Ventilation rate after compression - Ventilation rate before compression) / (Ventilation rate before compression) X 100 (iii) The dielectric breakdown voltage of the porous polymer substrate is 1,000 V or more.

14. The separation membrane for an electrochemical element according to claim 1 has a thickness of 1 μm or more and 30 μm or less.

15. A positive electrode; a negative electrode; and an electrochemical element including the separation membrane for an electrochemical element according to any one of claims 1 to 14, interposed between the positive electrode and the negative electrode.

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