Separator for electrochemical device, method for manufacturing same, and electrochemical device comprising same

Abstract

A separator for an electrochemical device according to one embodiment of the present invention comprises a porous polymer substrate, wherein the total pore volume span value of the porous polymer substrate is 0.65 or greater.

Description

Separator for an electrochemical device, method for manufacturing the same, and electrochemical device including the same

[0001] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0150855 filed on October 30, 2024 and Korean Patent Application No. 10-2025-0159649 filed on October 29, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of the specification.

[0002] The present invention relates to a separator for an electrochemical device, a method for manufacturing the same, and an electrochemical device including the same.

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions. Recently, lithium-ion batteries, which are a type of electrochemical device characterized by high energy density and voltage, long cycle life, and applicability in various fields, are being widely used.

[0004] A lithium secondary battery may include an electrode assembly manufactured by combining a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and the electrode assembly may be manufactured by housing it in a case together with an electrolyte.

[0005] The present invention provides a separator for an electrochemical device capable of lowering resistance by controlling the Total Pore Volume Span value of a porous polymer substrate.

[0006] However, the present invention is not limited to the features mentioned above, and other unmentioned features will be clearly understood by those skilled in the art from the following description.

[0007] One embodiment of the present invention provides a separator for an electrochemical device comprising a porous polymer substrate, wherein the total pore volume span of the porous polymer substrate is about 0.65 or higher.

[0008] According to one embodiment of the present invention, the porosity of the porous polymer substrate may be greater than about 45%.

[0009] According to one embodiment of the present invention, the electrical resistance (ER) of the porous polymer substrate may be about 0.37 ohm or less.

[0010] According to one embodiment of the present invention, the pore size D10 of the porous polymer substrate may be about 0.037 μm or less.

[0011] According to one embodiment of the present invention, the pore size D90 of the porous polymer substrate may be about 0.075 μm or larger.

[0012] According to one embodiment of the present invention, the difference in pore size (D90-D10) of the porous polymer substrate may be about 40 nm or more.

[0013] According to one embodiment of the present invention, the air permeability of the porous polymer substrate before compression may be about 75 s / 100cc or less.

[0014] According to one embodiment of the present invention, the air permeability of the porous polymer substrate after compression may be about 120 s / 100cc or less.

[0015] According to one embodiment of the present invention, the resistance increase rate of the separator for the electrochemical device may be about 40% or less.

[0016] One embodiment of the present invention provides a method for manufacturing a separator for an electrochemical device, comprising the step of forming a porous polymer substrate by stirring the polymer resin and the pore-forming agent, and adding the pore-forming agent two or more times.

[0017] According to one embodiment of the present invention, the stirring speed of the polymer resin and the pore-forming agent may be such that the stirring speed when the pore-forming agent is added once is greater than the stirring speed when the pore-forming agent is added twice.

[0018] According to one embodiment of the present invention, the stirring speed of the polymer resin and the pore-forming agent may be such that the stirring speed when the pore-forming agent is added once is about 1.5 times or more and 3 times or less the stirring speed when the pore-forming agent is added twice.

[0019] According to one embodiment of the present invention, the stirring speed of the polymer resin and the pore-forming agent may be about 100 RPM or more and 300 RPM or less when the pore-forming agent is added once, and about 50 RPM or more and 150 RPM or less when the pore-forming agent is added twice.

[0020] According to one embodiment of the present invention, the stirring speed of the polymer resin and the pore-forming agent may be about 20 RPM or more and 80 RPM or less when the pore-forming agent is added three times.

[0021] One embodiment of the present invention provides an electrochemical device comprising: an anode; a cathode; and a separator interposed between the anode and the cathode and any one of the aforementioned separators.

[0022] A separator for an electrochemical device according to one embodiment of the present invention improves air permeability and resistance by controlling the Total Pore Volume Span value of a porous polymer substrate.

[0023] A method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention improves the air permeability and resistance of the separator by controlling the number of times a pore-forming agent is added and the stirring speed.

[0024] An electrochemical device according to one embodiment of the present invention improves resistance and enhances the performance of the electrochemical device by controlling the Total Pore Volume Span value of the porous polymer substrate included in the separator.

[0025] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0026] Figure 1 shows a graph of the total pore volume span of a porous polymer substrate according to one embodiment of the present invention.

[0027] In parts of the attached drawings, corresponding components are given the same reference numerals. Those skilled in the art understand that the drawings are intended to illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to aid in understanding various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated compared to others. Additionally, elements of known technology that are useful or essential in commercially viable embodiments may often be omitted so as not to hinder the spirit of the various embodiments of the present invention.

[0028] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0029] In this specification, "A and / or B" means "A and B, or A or B".

[0030] In this specification, “about,” “approximately,” and “substantially” are used to mean a range of numerical or degree or an approximation thereof, taking into account inherent manufacturing and material tolerances (e.g., ± 5%), and are used to prevent an infringer from unfairly using the disclosure in which precise or absolute figures provided to aid in understanding the invention are mentioned.

[0031] In this specification, when a component is described as being "on" one component, this means that, unless specifically stated otherwise, other components may be placed in between, without excluding the placement of other components.

[0032] In this specification, the characteristic of having pores means that a gaseous and / or liquid fluid can pass from one side to the other side of the object through a structure in which the object includes a plurality of pores and said pores are interconnected.

[0033] In this specification, the separator has porous characteristics including a plurality of pores and acts as a porous ion-conducting barrier that blocks electrical contact between the cathode and the anode in an electrochemical device while allowing ions to pass through.

[0034] Among the components of an electrochemical device, the separator may comprise a polymer substrate having a porous structure located between the anode and the cathode. The separator isolates the anode and the cathode to prevent an electrical short circuit between the two electrodes, while simultaneously allowing the electrolyte and ions to pass through. Although the separator itself does not participate in electrochemical reactions, its physical properties, such as wettability to the electrolyte, porosity, and thermal shrinkage rate, can affect the performance and safety of the electrochemical device.

[0035] The porous polymer substrate included in the separator uses a polyolefin (polyethylene, polypropylene, etc.) film. Such a separator can be manufactured through a wet manufacturing method in which pores are formed using a pore-forming agent, or through a dry manufacturing method in which a polymer material is melted, manufactured into a membrane form, and then stretched to form pores.

[0036] The present invention improves the air permeability and resistance of a porous polymer substrate by controlling the size and distribution of pores formed in the porous polymer substrate.

[0037] The present invention will be described in more detail below.

[0038] An electrochemical device according to one embodiment of the present invention comprises an anode and a cathode, and a separator interposed between the anode and the cathode. The separator comprises a porous polymer substrate; and a coating layer provided on at least one surface of the porous polymer substrate and comprising inorganic particles. The electrochemical device according to one embodiment of the present invention may further comprise an electrolyte and a case, etc.

[0039] One embodiment of the present invention comprises a separator for an electrochemical device comprising a porous polymer substrate, wherein the total pore volume span of the porous polymer substrate is about 0.65 or higher.

[0040] A separator for an electrochemical device according to one embodiment of the present invention improves air permeability and resistance by controlling the Total Pore Volume Span value of a porous polymer substrate.

[0041] The separator for the electrochemical device described above includes a porous polymer substrate. As described above, by including a porous polymer substrate, the separator for the electrochemical device allows lithium ions to pass through while blocking electrical contact, and enables a shutdown function at an appropriate temperature.

[0042] According to one embodiment of the present invention, the porous polymer substrate may be manufactured using a polyolefin-based resin as a base resin. Examples of polyolefin-based resins include polyethylene, polypropylene, and polypentene, and may include one or more of these. A porous separator, for example having a plurality of pores, manufactured using such a polyolefin-based resin as a base resin, can provide a shutdown function at an appropriate temperature. The shutdown function is a function that prevents thermal runaway by blocking the current flow through the separator blocking the pores when the battery overheats; it is a function in which, when the internal temperature of the battery rises above a certain temperature, the separator melts and blocks the pores, thereby blocking contact between the positive and negative electrodes and stopping the current flow.

[0043] According to one embodiment of the present invention, the weight-average molecular weight of the polyolefin resin may be approximately 500,000 to 1,500,000. By controlling the weight-average molecular weight of the polyolefin resin within the above-described range, the compression resistance of the separator can be improved. Furthermore, when using a mixture of different types of polyolefin resins or forming a separator with a multilayer structure made of different types of polyolefin resins, the weight-average molecular weight of the polyolefin resin can be calculated by adding the weight-average molecular weights according to the content ratio of each polyolefin resin.

[0044] In the present specification, the weight-average molecular weight (Mw) can be measured by gel permeation chromatography (GPC: gel permeation chromatography, PL GPC220, Agilent Technologies), and the measurement conditions can be set as follows.

[0045] - Column: PL Olexis (Polymer Laboratories)

[0046] - Solvent: TCB (Trichlorobenzene)

[0047] - Flow rate: 1.0 ml / min

[0048] - Sample concentration: 1.0 mg / ml

[0049] - Injection volume: 200 µl

[0050] - Column temperature: 160 ℃

[0051] - Detector: Agilent High Temperature RI detector

[0052] - Standard: Polystyrene (corrected by a cubic function)

[0053] According to one embodiment of the present invention, the Total Pore Volume Span value of the porous polymer substrate is about 0.65 or higher. For example, the Total Pore Volume Span value of the porous polymer substrate may be about 0.65 or higher and 0.90 or lower, 0.66 or higher and 0.89 or lower, 0.67 or higher and 0.88 or lower, 0.68 or higher and 0.87 or lower, 0.69 or higher and 0.86 or lower, 0.70 or higher and 0.85 or lower, 0.71 or higher and 0.84 or lower, or 0.72 or higher and 0.84 or lower. In the pore size distribution of the above-described range, pores of relatively large size increase, and as a result, air permeability and resistance characteristics are improved. In addition, by controlling the Total Pore Volume Span value of the porous polymer substrate within the aforementioned range, the pore size distribution is widened, so that a pore size of at least a certain size can be maintained even when compressed during the manufacturing process, thereby suppressing an increase in air passage time and resistance. Furthermore, in the case of an electrochemical device using this, by controlling the Total Pore Volume Span value of the porous polymer substrate, the decrease in pore size due to an increase in internal pressure can be suppressed even as the cycle proceeds, thereby minimizing the increase in resistance.

[0054] Total Pore Volume Span refers to the size and distribution of pores present in a material (e.g., a membrane), and is represented by a curve or data indicating the pore size and the relative proportion of pores having that size, according to one embodiment. Total Pore Volume Span is directly related to the physical and chemical properties of the membrane, such as permeability, strength, adsorption capacity, reactivity, and storage capacity.

[0055] According to one embodiment of the present invention, the total pore volume span value can be calculated using the following Equation 1.

[0056] [Equation 1]

[0057]

[0058] At this time, D10, D50, and D90 represent the average pore size corresponding to the lower 10%, median, and upper 90% of the pore size distribution of the porous polymer substrate, and the total pore size distribution (Total Pore Volume Span) is measured using an aqua pore measuring device.

[0059] According to one embodiment of the present invention, “D10, D50, D90” refers to the average particle size at the 10%, 50%, and 90% points of the cumulative number distribution according to particle size.

[0060] The above particle size can be measured using the laser diffraction method. Specifically, after dispersing the target of measurement in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) to measure the difference in diffraction patterns according to particle size as the particles pass through the laser beam, thereby calculating the particle size distribution. Particle sizes D10, D50, and D90 can be measured by calculating the average particle diameter at the points where the cumulative distribution of the number of particles according to particle size in the measuring device reaches 10%, 50%, and 90%. In addition, the total pore volume span can be measured by various methods, such as mercury intrusion porosimetry (MIP), which analyzes the size and distribution of pores by injecting high-pressure mercury, or nitrogen adsorption methods (BET, BJH), which analyze nano-sized pores through the adsorption and desorption of nitrogen.

[0061] According to one embodiment of the present invention, the porosity of the porous polymer substrate may be greater than 45%. For example, the porosity of the porous polymer substrate may be greater than about 45% and less than 70%, greater than 46% and less than 68%, greater than 46% and less than 66%, greater than 46% and less than 64%, greater than 46% and less than 62%, greater than 46% and less than 60%, greater than 46% and less than 58%, greater than 46% and less than 56%, greater than 46% and less than 55%, greater than 46% and less than 54%, greater than 46% and less than 53%, or greater than 47% and less than 52%. At the porosity of the above-described range, an increase in the resistance of the separator and an increase in the resistance of the electrochemical device can be prevented, and a decrease in the mechanical strength of the separator can be prevented or suppressed.

[0062] According to one embodiment of the present invention, the porosity refers to the ratio of the volume occupied by pores to the volume of the separation membrane, and the porosity can be measured according to ASTM D-2873.

[0063] According to one embodiment of the present invention, the electrical resistance (ER) of the porous polymer substrate may be about 0.37 ohms or less. For example, the electrical resistance (ER) of the porous polymer substrate may be about 0.1 ohms or more and 0.37 ohms or less, 0.15 ohms or more and 0.37 ohms or less, 0.2 ohms or more and 0.37 ohms or less, 0.25 ohms or more and 0.37 ohms or less, 0.3 ohms or more and 0.37 ohms or less, or 0.35 ohms or more and 0.37 ohms or less. By controlling the value of the electrical resistance (ER) of the porous polymer substrate within the above-described range, the performance of the separator can be improved. For example, the electrical resistance (ER) of the porous polymer substrate may be controlled by the Total Pore Volume Span value of the porous polymer substrate. The larger the Total Pore Volume Span value of the porous polymer substrate, the wider the pore size distribution of the porous polymer substrate, and by having a pore size larger than a certain size, the increase in resistance can be minimized even if deformation of the pore size occurs as compression and cycling proceed.

[0064] According to one embodiment of the present invention, the electrical resistance (ER) can be measured by manufacturing each coin cell by interposing a separator according to one embodiment of the present invention between each SUS, injecting an electrolyte containing 1M LiPF6 and mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:2 into the coin cell, and using a VMP3 from BioLogic Science Instrument to measure the resistance of the coin cells, the electrical resistance can be measured through the results of electrochemical impedance spectroscopic analysis at 25°C under conditions of Amplitude 10 mV and Scan range 0.1 Hz to 1 MHz.

[0065] According to one embodiment of the present invention, the pore size D10 of the porous polymer substrate may be about 0.037 μm or less. For example, the pore size D10 of the porous polymer substrate may be about 0.01 μm or more and 0.037 μm or less, 0.015 μm or more and 0.037 μm or less, 0.02 μm or more and 0.037 μm or less, 0.025 μm or more and 0.037 μm or less, 0.027 μm or more and 0.037 μm or less, or 0.03 μm or more and 0.036 μm or less. At the pore size (D10) of the above-described range, the Total Pore Volume Span value of the porous polymer substrate is not reduced, and the increase in air passage time and resistance can be minimized. As described above, by controlling the pore size D10 of the porous polymer substrate within the aforementioned range, the Total Pore Volume Span of the porous polymer substrate can be increased, thereby minimizing the increase in air circulation time and resistance.

[0066] According to one embodiment of the present invention, the pore size D90 of the porous polymer substrate may be about 0.075 μm or more. For example, the pore size D90 of the porous polymer substrate may be about 0.075 μm or more and 0.1 μm or less, 0.075 μm or more and 0.095 μm or less, 0.075 μm or more and 0.09 μm or less, 0.075 μm or more and 0.085 μm or less, 0.076 μm or more and 0.084 μm or less, 0.077 μm or more and 0.083 μm or less, 0.078 μm or more and 0.082 μm or less, 0.078 μm or more and 0.081 μm or less, or 0.078 μm or more and 0.08 μm or less. At the pore size D90 of the aforementioned range, the Total Pore Volume Span of the porous polymer substrate is not significantly reduced, and the increase in airflow time and resistance can be minimized. In this way, by controlling the pore size D90 of the porous polymer substrate within the aforementioned range, the Total Pore Volume Span of the porous polymer substrate can be increased, thereby minimizing the increase in airflow time and resistance.

[0067] According to one embodiment of the present invention, the difference in pore size (D90-D10) of the porous polymer substrate may be about 40 nm or more. For example, the difference in pore size (D90-D10) of the porous polymer substrate may be about 40 nm or more and 100 nm or less, 40 nm or more and 90 nm or less, 40 nm or more and 80 nm or less, 40 nm or more and 70 nm or less, 40 nm or more and 60 nm or less, or 40 nm or more and 50 nm or less. By controlling the difference in pore size (D90-D10) of the porous polymer substrate within the above-described range, the Total Pore Volume Span value of the porous polymer substrate can be increased, thereby minimizing the increase in air passage time and resistance.

[0068] According to one embodiment of the present invention, the air permeability of the porous polymer substrate before compression may be about 75 s / 100cc or less. For example, the air permeability of the porous polymer substrate before compression may be about 50 s / 100cc or more and 75 s / 100cc or less, 52 s / 100cc or more and 75 s / 100cc or less, 54 s / 100cc or more and 75 s / 100cc or less, 55 s / 100cc or more and 75 s / 100cc or less, 56 s / 100cc or more and 75 s / 100cc or less, or 57 s / 100cc or more and 75 s / 100cc or less. The increase in resistance of the separator can be minimized at the air permeability before compression in the above-described range.

[0069] According to one embodiment of the present invention, the air permeability of the porous polymer substrate after compression may be about 120 s / 100cc or less. For example, the air permeability of the porous polymer substrate after compression may be about 80 s / 100cc or more and 120 s / 100cc or less, 85 s / 100cc or more and 120 s / 100cc or less, 90 s / 100cc or more and 120 s / 100cc or less, 95 s / 100cc or more and 120 s / 100cc or less, 97 s / 100cc or more and 120 s / 100cc or less, 97 s / 100cc or more and 115 s / 100cc or less, or 97 s / 100cc or more and 110 s / 100cc or less. The increase in resistance of the separator can be minimized at the air permeability after compression within the above-described range.

[0070] According to one embodiment of the present invention, the air permeability can be measured by the ASTM D726-94 method as the air permeability (air time, Gurley) of a porous polymer substrate according to one embodiment of the present invention, and the Gurley, as resistance to air flow, can be measured by a Gurley Densometer. The air permeability value described herein is when 100 cc of air flows under a pressure of 12.2 in H2O, and a separator 1 in 2The time taken to pass through the cross-section (in seconds), for example, can be expressed as the air time, and the air permeability can be measured as the air permeability before and after compression, respectively.

[0071] According to one embodiment of the present invention, the thickness of the porous polymer substrate may be about 5 μm or more and 20 μm or less. For example, the thickness of the porous polymer substrate may be about 6 μm or more and 18 μm or less, 6 μm or more and 17 μm or less, 6 μm or more and 16 μm or less, 6 μm or more and 15 μm or less, 6 μm or more and 14 μm or less, 6 μm or more and 13 μm or less, 7 μm or more and 12 μm or less, 8 μm or more and 11 μm or less, or 9 μm or more and 11 μm or less. At thicknesses within the above-described ranges, the deterioration of the function as a separator can be prevented or suppressed, and the increase in resistance and the increase in air passage time can be suppressed. By controlling the thickness of the porous polymer substrate within the above-described ranges in this way, the energy density of the battery can be improved.

[0072] According to one embodiment of the present invention, the thickness of the porous polymer substrate can be measured by a contact measurement method using a thickness gauge (Mitutoyo, VL-50S-B).

[0073] According to one embodiment of the present invention, the resistance increase rate of the separator for an electrochemical device may be about 40% or less. For example, the resistance increase rate of the separator for an electrochemical device may be about 1% or more and 40% or less, 5% or more and 40% or less, 10% or more and 40% or less, 15% or more and 35% or less, 15% or more and 30% or less, 15% or more and 25% or less, or 17% or more and 24% or less. By controlling the resistance increase rate of the separator for an electrochemical device within the above-described range, the performance of the separator can be improved. For example, the resistance increase rate of the separator for an electrochemical device may be controlled by the Total Pore Volume Span value of the porous polymer substrate. The larger the Total Pore Volume Span value of the porous polymer substrate, the wider the pore size distribution of the porous polymer substrate, and by having a pore size larger than a certain size, the increase in resistance can be minimized even if deformation of the pore size occurs as compression and cycling proceed.

[0074] According to one embodiment of the present invention, the resistance increase rate of the separator for the electrochemical device can be calculated by charging and discharging the electrochemical device according to one embodiment of the present invention once at 0.1 C in a voltage range of 3.0 V to 4.35 V in a 25 ℃ chamber, repeating the 1 C charging and 1 C discharging for 300 cycles, and measuring the resistance before and after the 300 cycles.

[0075] One embodiment of the present invention includes a method for manufacturing a separator for an electrochemical device, comprising the step of forming a porous polymer substrate by stirring the polymer resin and the pore-forming agent, and wherein the pore-forming agent is added two or more times.

[0076] A method for manufacturing a separator for an electrochemical device according to one embodiment of the present invention can improve the air permeability and resistance of the separator by controlling the number of times a pore-forming agent is added and the stirring speed.

[0077] According to one embodiment of the present invention, the polymer resin may be manufactured using a polyolefin-based resin as a base resin. Examples of polyolefin-based resins include polyethylene, polypropylene, polypentene, etc., and may include one or more of these. A porous separator, for example having a plurality of pores, manufactured using such a polyolefin-based resin as a base resin, can provide a shutdown function at an appropriate temperature. According to one embodiment, the polymer resin may be a polyethylene resin.

[0078] According to one embodiment of the present invention, the pore-forming agent may be a material that is dispersed within the polymer resin, exhibits heterogeneity in the substrate manufactured through extrusion, stretching, etc., and is subsequently removed from the substrate. Accordingly, the portion of the polymer of the substrate where the pore-forming agent is located may remain in the form of pores. The pore-forming agent may be a material that is, for example, liquid during the extrusion process but maintains a solid state.

[0079] According to one embodiment of the present invention, the pore-forming agent may be an aliphatic hydrocarbon solvent such as solution-type paraffin, paraffin oil, mineral oil, or paraffin wax; vegetable oil such as soybean oil, sunflower oil, rapeseed oil, palm oil, coconut oil, corn oil, grapeseed oil, cottonseed oil, etc.; or a plasticizer such as a dialkyl phthalate. In particular, the plasticizer may be di-2-ethylhexyl phthalate (DOP), di-butyl phthalate (DBP), di-isononyl phthalate (DINP), di-isodecyl phthalate (DIDP), butyl benzyl phthalate (BBP), etc. For example, the pore-forming agent may be solution-type paraffin. By selecting the pore-forming agent within the range described above, the Total Pore Volume Span value of the porous polymer substrate can be controlled.

[0080] According to one embodiment of the present invention, the content ratio of the polymer resin and the pore-forming agent may be about 1:2 to 1:9, and according to one embodiment, may be 3:7.

[0081] According to one embodiment of the present invention, the method includes the step of forming a porous polymer substrate by stirring the polymer resin and the pore-forming agent. As described above, a porous polymer substrate with formed pores can be formed by including the step of stirring the polymer resin and the pore-forming agent.

[0082] According to one embodiment of the present invention, the pore-forming agent may be characterized by being added two or more times. By being characterized by adding the pore-forming agent two or more times as described above, the narrowing of the pore size distribution during pore formation regardless of the stirring speed is suppressed, and the Total Pore Volume Span value of the porous polymer substrate is reduced, thereby preventing or suppressing the increase in resistance and air passage time of the separation membrane.

[0083] According to one embodiment of the present invention, the pore-forming agent may be characterized by being added three or more times. By being characterized by adding the pore-forming agent three or more times as described above, the narrowing of the pore size distribution during pore formation regardless of the stirring speed is suppressed, and the Total Pore Volume Span value of the porous polymer substrate is reduced, thereby preventing or suppressing the increase in resistance and air passage time of the separation membrane.

[0084] According to one embodiment of the present invention, the stirring speed of the polymer resin and the pore-forming agent may be such that the stirring speed when the pore-forming agent is added once is greater than the stirring speed when the pore-forming agent is added twice. As described above, by adjusting the stirring speed of the polymer resin and the pore-forming agent so that the stirring speed when the pore-forming agent is added once is greater than the stirring speed when the pore-forming agent is added twice, the Total Pore Volume Span value of the porous polymer substrate can be increased.

[0085] According to one embodiment of the present invention, the stirring speed of the polymer resin and the pore-forming agent may be such that the stirring speed when the pore-forming agent is added once is about 1.5 times or more and 3 times or less the stirring speed when the pore-forming agent is added twice. For example, the stirring speed when the pore-forming agent is added once may be twice the stirring speed when the pore-forming agent is added twice. By adjusting the stirring speed when the pore-forming agent is added once and the stirring speed when the pore-forming agent is added twice within the above-described range, the Total Pore Volume Span value of the porous polymer substrate can be increased.

[0086] According to one embodiment of the present invention, the stirring speed of the polymer resin and the pore-forming agent may be about 100 RPM or more and 300 RPM or less when the pore-forming agent is added once, and about 50 RPM or more and 150 RPM or less when the pore-forming agent is added twice. For example, it may be about 150 RPM or more and 250 RPM or less when the pore-forming agent is added once, and about 75 RPM or more and 125 RPM or less when the pore-forming agent is added twice. Alternatively, it may be about 180 RPM or more and 220 RPM or less when the pore-forming agent is added once, and about 90 RPM or more and 110 RPM or less when the pore-forming agent is added twice. By controlling the stirring speed when the pore-forming agent is added once and twice within the range described above, the total pore volume span of the porous polymer substrate can be increased.

[0087] According to one embodiment of the present invention, the stirring speed of the polymer resin and the pore-forming agent may be approximately 20 RPM or more and 80 RPM or less when the pore-forming agent is added three times. For example, it may be approximately 40 RPM or more and 60 RPM or less when the pore-forming agent is added three times. As described above, by controlling the stirring speed when the pore-forming agent is added three times, the Total Pore Volume Span value of the porous polymer substrate can be increased.

[0088] One embodiment of the present invention includes an electrochemical element comprising: an anode; a cathode; and a separator interposed between the anode and the cathode and any one of the aforementioned separators.

[0089] An electrochemical device according to one embodiment of the present invention can improve resistance and enhance the performance of the electrochemical device by controlling the Total Pore Volume Span value of the porous polymer substrate included in the separator.

[0090] According to one embodiment of the present invention, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer comprising 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 is a layered compound such as a lithium manganese complex oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M xNi-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 ~ 0.3); chemical formula LiMn1-xM x It may include a lithium manganese complex 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 part of the Li of the chemical formula is substituted with alkaline earth metal ions; a disulfide compound; and one or more of Fe2(MoO4)3.

[0091] According to one embodiment of the present invention, the cathode comprises a cathode current collector and a cathode active material layer comprising a cathode active material, a conductive material, and a binder resin on at least one surface of the current collector. The cathode comprises, as the cathode active material, carbon such as lithium metal oxide, non-graphitizable carbon, or 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, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물 중 선택된 1종 또는 2종 이상의 혼합물을 포함할 수 있다.

[0092] According to one embodiment of the present invention, the conductive material may be, for example, any one selected from graphite, carbon black, carbon fiber or metal fiber, metal powder, conductive whiskers, 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 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.

[0093] According to one embodiment of the present invention, the current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used.

[0094] According to one embodiment of the present invention, the binder resin may be a polymer commonly used in the industry for electrodes. 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 copolymer, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples include acetatepropionate), cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, but are not limited thereto.

[0095] According to one embodiment of the present invention, the anode slurry for manufacturing the anode active material layer may include a dispersant, and the dispersant may be a pyrrolidone-based compound. Specifically, it may be N-methylpyrrolidone (N-methylpyrrolidone, ADC-01, LG Chem).

[0096] According to one embodiment of the present invention, the electrochemical element may further include an electrolyte (E) containing an electrolyte, and the electrolyte is A + B - As a salt with a structure like that, A + is Li + , Na + , K + It may include alkali metal cations such as or ions composed of a combination thereof. In addition, B - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - A salt comprising an anion such as or a combination thereof may be dissolved or dissociated in an organic solvent comprising 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), ethylmethyl carbonate (EMC), gamma butyrolactone, or a mixture thereof, but is not limited thereto.

[0097] According to one embodiment of the present invention, the electrochemical device may be a cylindrical electrochemical device comprising a separator, an anode, and a cathode according to the above description. In this case, the cylindrical electrochemical device may be manufactured by interposing the aforementioned separator between the anode and the cathode in the order of 'separator-cathode-separator-anode', stacking them in the form of an electrode assembly, and then winding them into a jelly roll shape. Meanwhile, the electrochemical device of the present invention may also be a pouch-type or prismatic electrochemical device depending on the shape of the case housing the electrode assembly.

[0098] Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0099]

[0100] <Comparative Example 1>

[0101] Polyethylene resin (PE, weight-average molecular weight 1 million, Tm: 135 ℃) was prepared as the polymer resin, and solution paraffin was prepared as the pore-forming agent. The content ratio of the polyethylene and solution paraffin is 3:7.

[0102] After adding the solution-type paraffin once to the polyethylene solution, the mixture was stirred at a speed of 200 RPM.

[0103] Subsequently, the above mixture is extruded using an extruder to obtain an extruder, and an extruded sheet is manufactured by passing it through a cooling roll. The extruded sheet is stretched using a twin-axis stretcher at 100°C to achieve a stretching ratio of 400% in the MD direction. Then, it is stretched at 130°C in the TD direction to achieve 400% relative to the initial input width.

[0104] From the stretched sheet above, solution paraffin was removed using the solvent methyl chloride (MC), and heat-treated at a temperature of 120 °C for 1 to 2 minutes to produce a porous polymer substrate (thickness: 10 μm, porosity: 45%, air permeability before compression: 90 s / 100cc, ER: 0.38 ohm).

[0105] At this time, the Total Pore Volume Span value of the porous polymer substrate is 0.55.

[0106]

[0107] <Comparative Example 2>

[0108] In Comparative Example 1 above, a porous polymer substrate (thickness: 10 μm, porosity: 45%, air permeability before compression: 80 s / 100cc, ER: 0.38 ohm) was prepared by the same process as Comparative Example 1, except that the solution-type paraffin was added once and then stirred at a speed of 100 RPM.

[0109] At this time, the Total Pore Volume Span value of the porous polymer substrate is 0.63.

[0110]

[0111] <Example 1>

[0112] In Comparative Example 1 above, a porous polymer substrate (thickness: 10 μm, porosity: 47%, air permeability before compression: 75 s / 100cc, ER: 0.37 ohm) was prepared by the same process as Comparative Example 1, except that the solution-type paraffin was added once and stirred at a speed of 200 RPM, and then the solution-type paraffin was added twice and stirred at a speed of 100 RPM.

[0113] At this time, the Total Pore Volume Span value of the porous polymer substrate is 0.72.

[0114]

[0115] <Example 2>

[0116] In Comparative Example 1 above, a porous polymer substrate (thickness: 10 μm, porosity: 52%, air permeability before compression: 57 s / 100cc, ER: 0.35 ohm) was prepared by the same process as Comparative Example 1, except that the solution-type paraffin was added once and stirred at a speed of 200 RPM, the solution-type paraffin was added twice and stirred at a speed of 100 RPM, and the solution-type paraffin was added three times and stirred at a speed of 50 RPM.

[0117] At this time, the Total Pore Volume Span value of the porous polymer substrate is 0.84.

[0118]

[0119] Manufacture of Electrochemical Devices

[0120] Electrochemical devices were each manufactured using a separator for an electrochemical device comprising the porous polymer substrate of the above examples and comparative examples.

[0121] 1) Manufacture of the anode

[0122] Cathode active material (LiNi 0.8 Mn 0.1 Co 0.1 O2), a conductive material (carbon black), a dispersant (N-methylpyrrolidone, ADC-01, LG Chem), and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for an anode active material layer with a concentration of 50 wt% of the components excluding water. Next, the slurry was applied to the surface of an aluminum thin film (thickness 10 μm) and dried to manufacture an anode having an anode active material layer (thickness 120 μm).

[0123] 2) Preparation of the cathode

[0124] Graphite (a blend of natural graphite and artificial graphite), a conductive material (carbon black), a dispersant (Polyvinylpyrrolidone, Junsei, Japan), and a binder resin (a mixture of PVDF-HFP and PVDF) were mixed with water in a weight ratio of 97.5:0.7:0.14:1.66 to prepare a slurry for a negative electrode active material layer with a concentration of 50 wt% of the components excluding water. Next, the slurry was applied to the surface of a copper thin film (thickness 10 μm) and dried to manufacture a negative electrode having a negative electrode active material layer (thickness 120 μm).

[0125] 3) Fabrication of cylindrical electrochemical devices

[0126] The separator of the above example and comparative example was interposed between the above-manufactured cathode and anode, and the layers were stacked in the order of separator-cathode-separator-anode.

[0127] A cylindrical electrochemical device was manufactured by binding the above-mentioned stacked electrode assembly to a core, winding it, winding it into a jelly roll shape, and inserting it into a cylindrical can.

[0128]

[0129] <Experimental Example>

[0130] Calculation of Total Pore Volume Span value

[0131] The above Total Pore Volume Span value can be calculated as follows.

[0132]

[0133] At this time, D10, D50, and D90 represent the pore sizes corresponding to the lower 10%, median, and upper 90% of the pore size distribution of a porous polymer substrate, and are measured using an aqua pore measuring device.

[0134]

[0135] Electrical Resistance (ER) Measurement

[0136] Coin cells were manufactured by interposing the separators of the above examples and comparative examples between SUS layers. An electrolyte containing 1M LiPF6 and mixed with ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:2 was injected into the coin cells. To measure the resistance of the coin cells, the resistance was measured using a VMP3 from BioLogic Science Instruments at 25°C under conditions of Amplitude 10 mV and Scan range 0.1 Hz to 1 MHz, and the results of electrochemical impedance spectroscopic analysis were shown in Table 1 below.

[0137]

[0138] Air permeability measurement

[0139] The air permeability (air time, gully) of the porous polymer substrates of the above examples and comparative examples was measured by the ASTM D726-94 method. The gully used herein is the resistance to air flow and is measured by a gully densometer. The air permeability values ​​described herein are for 100 cc of air under a pressure of 12.2 in H2O, with a separator 1 in 2 It is expressed as the time (in seconds) taken to pass through the cross-section, i.e., the airflow time. The above airflow was measured as the airflow before and after compression, respectively, and is shown in Table 1 below.

[0140]

[0141] Measurement of resistance increase rate

[0142] The cylindrical electrochemical elements of the above examples and comparative examples were charged and discharged once at 0.1 C in a 25 ℃ chamber in a voltage range of 3.0 V to 4.35 V, and the 1 C charging and 1 C discharging were repeated for 300 cycles. The resistance before and after the 300 cycles was measured to determine the resistance increase rate (%), which is shown in Table 1 below.

[0143]

[0144] Comparative Example 1 Comparative Example 2 Example 1 Example 2 Number of times pore-forming agent is added (times) 1 1 2 3 Stirring speed (RPM / time) 2 0 1 0 0 200 / 10 200 / 100 / 50 Porous polymer substrate Porosity (%) 4 5 4 5 4 7 5 2 ER (ohm) 0.3 8 0.3 8 0.3 7 0.3 5 Total Pore Volume Span value 0.5 5 0.6 3 0.7 2 0.8 4 Pores Size (μm) D 100.03 7550.038550.0360.03D 500.0539 20.0559 20.0570.059D 900.0670.074490.0780.08 Air Permeability (s / 100cc) Before Compression 90807557 After Compression 15013011097 Resistance Increase Rate (%) 50432417

[0145]

[0146] Figure 1 shows a graph of the total pore volume span of a porous polymer substrate according to one embodiment of the present invention.

[0147] Referring to Table 1 above, it can be seen that the Total Pore Volume Span values ​​of the porous polymer substrates in Examples 1 and 2 are 0.72 and 0.84, respectively, which is 0.65 or higher. On the other hand, in Comparative Examples 1 and 2, the Total Pore Volume Span values ​​of the porous polymer substrates are 0.55 and 0.63, respectively, which is 0.65 or lower. Additionally, referring to FIG. 1, it can be seen that the pore size distribution of Examples 1 and 2 is more widely spread than that of Comparative Examples 1 and 2.

[0148] Meanwhile, the air permeability of the porous polymer substrate after compression was 110 s / 100cc and 97 s / 100cc, respectively, in the case of Examples 1 and 2, which is 120 s / 100cc or less, and the air permeability after compression was 150 s / 100cc and 130 s / 100cc, respectively, which is greater than 120 s / 100cc.

[0149] In addition, the resistance increase rates of Examples 1 and 2 were 24% and 17%, respectively, which can be seen as a decrease compared to the resistance increase rates of Comparative Examples 1 and 2, which were 50% and 43%. For example, according to Figure 1 and Table 1 and the analysis results above regarding Examples 1 and 2, in which the Total Pore Volume Span value of the porous polymer substrate was adjusted to 0.65 or higher, it can be seen that in Comparative Examples 1 and 2, where the Total Pore Volume Span value of the porous polymer substrate did not reach 0.65, the air permeability after compression of the substrate was 120 s / 100cc or higher, which is relatively larger than that of Examples 1 and 2, and the resistance of the electrochemical device fabricated using this increased relatively significantly compared to the case of Examples 1 and 2.

[0150] Therefore, based on these results, it can be seen that the air permeability of the separator and the resistance characteristics of the electrochemical device are improved by controlling the Total Pore Volume Span value of the porous polymer substrate in the separator according to one embodiment of the present invention.

[0151] Although the foregoing has been described with reference to the embodiments of the present disclosure, a person skilled in the art or having ordinary knowledge in the art will understand that various modifications and changes can be made to the various embodiments of the present disclosure without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

1. A separator for an electrochemical device comprising a porous polymer substrate, A separator for an electrochemical device having a Total Pore Volume Span value of 0.65 or higher of the above-mentioned porous polymer substrate.

2. In Claim 1, A separator for an electrochemical device, wherein the porosity of the above-mentioned porous polymer substrate is greater than 45%.

3. In Claim 1, A separator for an electrochemical device, wherein the electrical resistance (ER) of the porous polymer substrate is 0.37 ohm or less.

4. In Claim 1, A separator for an electrochemical device, wherein the pore size D10 of the porous polymer substrate is 0.037 μm or less.

5. In Claim 1, A separator for an electrochemical device, wherein the pore size D90 of the porous polymer substrate is 0.075 μm or larger.

6. In Claim 1, A separator for an electrochemical device, wherein the difference in pore size (D90-D10) of the above porous polymer substrate is 40 nm or more.

7. In Claim 1, A separator for an electrochemical device, wherein the air permeability of the porous polymer substrate before compression is 75 s / 100cc or less.

8. In Claim 1, A separator for an electrochemical device, wherein the air permeability of the porous polymer substrate after compression is 120 s / 100cc or less.

9. In Claim 1, An electrochemical device separator having a resistance increase rate of 40% or less.

10. A step of forming a porous polymer substrate by stirring a polymer resin and a pore-forming agent; comprising, A method for manufacturing a separator for an electrochemical device, characterized by adding the above-mentioned pore-forming agent two or more times.

11. In Claim 10, The stirring speed of the above polymer resin and pore-forming agent is A method for manufacturing a separator for an electrochemical device, wherein the stirring speed when the pore-forming agent is added once is greater than the stirring speed when the pore-forming agent is added twice.

12. In Claim 10, The stirring speed of the above polymer resin and pore-forming agent is A method for manufacturing a separator for an electrochemical device, wherein the stirring speed when the pore-forming agent is added once is 1.5 times or more and 3 times or less the stirring speed when the pore-forming agent is added twice.

13. In claim 10, The stirring speed of the above polymer resin and pore-forming agent is When the above pore-forming agent is injected once, the speed is 100 RPM or more and 300 RPM or less, and A method for manufacturing a separator for an electrochemical device, wherein the above-mentioned pore-forming agent is 50 RPM or more and 150 RPM or less when added twice.

14. In Claim 13, The stirring speed of the above polymer resin and pore-forming agent is A method for manufacturing a separator for an electrochemical device, wherein the above-mentioned pore-forming agent is 20 RPM or more and 80 RPM or less when added three times.

15. An electrochemical device comprising: an anode; a cathode; and a separator of claim 1 interposed between the anode and the cathode.

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