Composite separator and secondary battery using the same

Abstract

To provide a composite separator having an adhesive layer and a secondary battery including the same.SOLUTION: An adhesive layer includes a particulate organic binder having a glass transition temperature of 60 to 80°C, and when the adhesive layers are brought into contact with each other and pressurized at 50°C and a pressure of 1.7 MPa for 2 hours, and then peeled off at 180 degrees at a speed of 300 mm / min, no blocking occurs between the adhesive layers and the adhesive strength to the positive electrode is 5 gf / cm or more. The composite separator according to the present disclosure has excellent adhesive strength to the electrode and can improve the blocking phenomenon that occurs during winding.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a composite separator and a secondary battery including the same.

Background Art

[0002] Separators, porous substrates, and high heat-resistant separators having a porous ceramic layer (or inorganic particle layer) on one or both surfaces of the porous substrate, which are manufactured from conventional porous substrates, have insufficient adhesiveness with electrodes, and the separator and the electrode are separated during the cell assembly process, often resulting in twisting and deformation of the electrode assembly. In particular, when the separator having the porous ceramic layer has insufficient adhesiveness to the electrode, a misalignment problem occurs between the electrode and the separator within the jelly roll during cell stacking.

[0003] As described above, when driving a stack cell battery in which misalignment has occurred, local resistance due to misalignment occurs, or a short circuit occurs between electrodes due to physical damage caused by repeated use, posing safety problems such as fire.

[0004] Furthermore, in recent years, secondary batteries have been increased in capacity and size for application to electric vehicles and the like. In the case of a separator (Ceramic Coated Separator, CCS) having a porous ceramic layer (inorganic particle layer) formed on one or both surfaces of a porous substrate, the thickness is large, and since it is used in automotive batteries that are high-capacity and high heat-resistant batteries, solving the above problems is even more important.

[0005] As one method of improving the adhesiveness between the separator and the electrode, there is a method of providing a separator in which a solution made of an adhesive organic substance is applied to the surface of the separator and dried to form an adhesive layer on the upper part of the separator. However, the air permeability deteriorates due to the adhesive organic substance layer, and it is difficult to make the film thinner, and the electrode adhesiveness is still poor.

[0006] Therefore, when the separator is wound, a blocking phenomenon often occurs in which the adhesive organic matter layer is transferred to the opposite surface and peels off. As problems including this, there are still problems that must be solved, such as a decrease in the ion conductivity of the separator or / and a deviation in thickness occurring during the alignment of the electrode assembly, which inhibits the performance of the battery.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] According to one aspect of the present disclosure, by providing a composite separator in which an adhesive layer containing a particulate organic binder having specific physical properties is formed on one or both surfaces of a porous separator, a composite separator is provided that has excellent electrode adhesiveness and improves the occurrence of a blocking phenomenon during winding of the separator. The porous separator may be a porous separator made of a porous substrate or a porous separator having a porous ceramic layer formed on one or both surfaces of the porous substrate.

[0009] In addition, after winding the composite separator and then unwinding and using it as a separator, a composite separator is provided that can maintain the initial adhesive force without a decrease in adhesive force, does not cause blocking, and has excellent heat resistance.

[0010] In addition, in the process of transporting and storing the wound separator, not only at room temperature around 25°C, but also when stored at a high temperature of 50 to 70°C, no blocking occurs between the adhesive layers of the wound roll, between the adhesive layer and the ceramic layer, or between the adhesive layer and the porous substrate, and a composite separator with excellent anti-blocking properties is provided.

[0011] In addition, it is found that when the separators of the present disclosure have their adhesive layers in contact with each other, are pressed at 50°C under a pressure of 1.7 MPa for 2 hours, and then peeled at a speed of 300 mm / min at 180 degrees without blocking occurring, the above-mentioned conventional problems can be solved, and a composite separator that meets this requirement is provided.

[0012] In addition, a composite separator having uniform lithium ion conductivity over the entire area of the separator is provided.

[0013] The composite separator of the present disclosure and the secondary battery including the same are widely applicable in green technology fields such as electric vehicles, battery charging stations, and solar power generation and wind power generation that use other batteries.

[0014] In addition, the composite separator of the present disclosure and the secondary battery including the same can be used in eco-friendly electric vehicles (EVs), hybrid vehicles, etc. that suppress air pollution and greenhouse gas emissions and prevent climate change.

Means for Solving the Problems

[0015] As a result of intensive research to provide a separator that has excellent adhesiveness to electrodes, does not cause blocking during storage and transportation after being wound into a roll, and can maintain good alignment during battery assembly, the inventors have found that when it contains a particulate organic binder, the adhesive force to the positive electrode satisfies a specific range, and when evaluating the adhesive force between the adhesive layers, no blocking occurs under specific conditions, all of the above objects can be achieved.

[0016] One aspect of the present disclosure is a composite separator including an adhesive layer on the outermost layer of at least one side of a porous separator, wherein the adhesive layer includes a particulate organic binder, and when the adhesive layers are brought into contact with each other and pressed at 50 °C under a pressure of 1.7 MPa for 2 hours and then peeled at a speed of 300 mm / min by 180 degrees, blocking does not occur between the adhesive layers, and the adhesive force to the positive electrode is 5 gf / cm or more.

[0017] As one aspect, the content of the particulate organic binder in the adhesive layer may be 0.1 to 0.5 g / m 2 and is not limited thereto.

[0018] As one aspect, the particulate organic binder may have an average particle diameter of 400 to 600 nm and is not limited thereto.

[0019] As one aspect, the porous separator may have a porous ceramic layer containing inorganic particles formed on one or both sides of a porous base material or a porous base material and is not limited thereto.

[0020] As one aspect, the particulate organic binder may be a core-shell particulate organic binder. The core-shell particulate organic binder may have a glass transition temperature of the whole core-shell particles measured for the whole core-shell particles higher than the glass transition temperature of the core.

[0021] As one aspect, the core-shell particulate organic binder may have a glass transition temperature of the core of 50 to 75 °C, the core-shell particulate organic binder may have a glass transition temperature of the whole core-shell particles of 60 to 80 °C, and the glass transition temperature of the whole core-shell particles may be higher than the glass transition temperature of the core.

[0022] In one aspect, the core-shell particle type organic binder is an acrylic organic particle, and the shell may include a structure derived from an aromatic vinyl monomer.

[0023] In one aspect, the composite separator is obtained by cutting an electrode into a size of 4 cm in width and 6 cm in length, stacking 4 cut positive electrodes and 4 cut negative electrodes on the surface of the composite separator in a cross pattern, and then bonding them at 80 °C under a pressure of 10 kgf / cm 2 for 30 seconds. When it is unfolded, not all of the electrodes need to be detached.

[0024] In one aspect, the inorganic particles of the porous ceramic layer may have an average particle size of 50 nm to 2 μm, but are not limited thereto.

[0025] In one aspect, the inorganic particles of the porous ceramic layer may include first inorganic particles having an average particle size of 50 to 500 nm and second inorganic particles having an average particle size of 500 nm to 2000 nm, but are not limited thereto.

[0026] In one aspect, in the porous ceramic layer, the inorganic particles may be connected by a binder, and pores may be formed between the inorganic particles.

[0027] In one aspect, the porous substrate may be a polyolefin-based porous film, but is not limited thereto.

[0028] In one aspect, the composite separator may have a heat shrinkage rate of 3% or less in both the machine direction and the width direction at 150 °C.

[0029] Another aspect of the present disclosure provides a lithium secondary battery including the composite separator of the above aspect.

[0030] As one aspect, when performing cycle evaluation to measure the discharge capacity after charging and discharging the lithium secondary battery 300 times at a discharge rate of 1C and measuring the degree of decrease with respect to the initial capacity, the ratio of the discharge capacity calculated by the following formula may be 90% or more. Ratio of discharge capacity = (Battery measured capacity after 300 cycles) / Initial battery capacity

[0031] Still another aspect of the present disclosure is a composite separator including an adhesive layer on at least the outermost layer of at least one surface of a porous separator, wherein the adhesive layer includes a particulate organic binder, the content of the particulate organic binder in the adhesive layer is 0.1 to 0.5 g / m 2 and the particulate organic binder has an average particle diameter of 400 to 600 nm, the particulate organic binder includes a core-shell particulate organic binder, and the core-shell particulate organic binder provides a composite separator in which the glass transition temperature of the entire core-shell particles is higher than the glass transition temperature of the core.

Advantages of the Invention

[0032] The composite separator according to one aspect of the present disclosure has excellent adhesion to the electrode and can improve the blocking phenomenon that occurs during winding.

[0033] Another aspect of the present disclosure can provide a composite separator in which the peeling phenomenon of the coating layer does not occur due to the blocking phenomenon even when exposed to high temperature during the process of storing and transporting the wound separator.

[0034] Specifically, during the process of transporting and storing the wound separator, not only at room temperature around 25°C, but also when stored at a high temperature of 50 to 70°C, between the adhesive layers of the wound roll, between the adhesive layer and the ceramic layer, or between the adhesive layer and the porous substrate, a composite separator excellent in antiblocking property in which blocking does not occur can be provided.

[0035] Further, a composite separator that does not cause blocking can be provided when the adhesive layers of the separators of the present disclosure are brought into contact with each other, pressurized at 50° C. under a pressure of 1.7 MPa for 2 hours, and then peeled at 180 degrees at a speed of 300 mm / min.

[0036] Further, a composite separator with little heat shrinkage and excellent battery safety can be provided.

[0037] Further, after winding and when unwinding and using, a composite separator with little change in adhesive force and excellent adhesive force to the electrode can be provided.

[0038] Further, during cell stacking, excellent alignment can be achieved between the electrode and the separator, the occurrence of misalignment during the process can be suppressed, and a battery with a uniform thickness deviation can be provided.

[0039] Further, a uniform lithium ion conductivity can be provided with respect to the entire area of the separator, and a battery can be provided in which the capacity retention rate after 300 cycles is maintained at 90% or more, or 95% or more with respect to the initial capacity.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0041] The following will describe the present disclosure in detail. However, this is merely exemplary and the present disclosure is not limited to the specific embodiments described by way of example.

[0042] Also, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. The terms used in the description of the present disclosure are for the purpose of effectively describing specific examples only and are not intended to limit the present disclosure.

[0043] Also, the singular forms used in the specification and the appended claims can be intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0044] Also, when a part is described as "including" a certain component, this means that it can further include other components, rather than excluding other components, unless there is a special description to the contrary.

[0045] Also, unless otherwise defined, when a layer or a member is described as being "on" another layer or member, this includes not only the case where a layer or a member is in contact with another layer or member, but also the case where there is still another layer or still another member between the two layers or the two members.

[0046] Also, terms such as "about" and "substantially" are used in the sense of that numerical value or close to that numerical value when the manufacturing and material tolerances inherent in the recited meaning are presented, and are used to prevent unscrupulous infringers from improperly using the disclosed content where an exact or absolute numerical value is recited for the purpose of facilitating the understanding of the present disclosure.

[0047] In the present disclosure, "average particle size" means "D50", and "D50" means the particle size of inorganic particles and particulate organic binders corresponding to 50% in terms of the volume-based integrated fraction. The average particle size can be derived from the results of the particle size distribution obtained by sampling a sample in accordance with the ISO 13320-1 standard for the inorganic particles and / or particulate organic binders to be measured and analyzing it using S3500 manufactured by MICROTRAC.

[0048] In the present disclosure, "glass-transition temperature (Tg)" means the temperature range in which glass transition occurs, and means the value measured using a dilatometer or a differential scanning calorimeter (DSC).

[0049] In the present disclosure, "composite separator" means a form having an adhesive layer formed on one or both sides of a porous separator, and the "porous separator" may be in the form of the porous substrate itself, or may be one having a porous ceramic layer (a porous inorganic particle layer can be used in the same meaning) formed on one or both sides of the porous substrate. The porous ceramic layer may be one in which inorganic particles are connected and fixed by a binder and pores are formed between the inorganic particles.

[0050] In the present disclosure, "blocking" means that the adhesive layers of the composite separator are measured with two sheets in contact with each other. Here, "no blocking" means that when observing five randomly selected 50×50 μm regions with a scanning electron microscope (SEM), it includes both the absence of peeling of the coating layer and the peeling being shown in less than 2% of the coating layer area. That is, when the adhesive layer is formed only on one side of the composite separator, it means that two composite separators are prepared, stacked with the adhesive layers of the composite separators facing each other in contact, then pressed at 50 °C under a pressure of 1.7 MPa for 2 hours, and then peeled at a speed of 300 mm / min by 180 degrees to evaluate the blocking. Also, when the adhesive layer is formed on both sides of the composite separator, it means that two composite separators are prepared, one side of either side is selected, stacked with the adhesive layers facing each other in contact, then pressed at 50 °C under a pressure of 1.7 MPa for 2 hours, and then peeled at a speed of 300 mm / min by 180 degrees to evaluate the blocking. Here, the adhesive layers formed on both sides may have the same composition as each other.

[0051] Hereinafter, one aspect of the present disclosure will be described.

[0052] As illustrated in FIGS. 1 and 2, one aspect of the present disclosure is a composite separator 100 including an adhesive layer 120 formed on one or both sides of a porous separator 110 having a porous ceramic layer (a porous inorganic particle layer can also be used in the same meaning) in which a porous substrate or inorganic particles formed on one or both sides of the porous substrate are connected and fixed by a binder and pores are formed between the inorganic particles, wherein the adhesive layer includes a particulate organic binder, and when the adhesive layers are brought into contact with each other, pressed at 50 °C under a pressure of 1.7 MPa for 2 hours, and then peeled at 300 mm / min by 180 degrees, a composite separator in which no blocking occurs between the adhesive layers can be provided.

[0053] Also, the composite separator can provide a composite separator in which the adhesive force of the adhesive layer to the positive electrode is 5 gf / cm or more.

[0054] One aspect of the present disclosure is a composite separator including an adhesive layer on at least the outermost layer of at least one surface of a porous separator, wherein the adhesive layer includes a particulate organic binder, and when the adhesive layers are brought into contact with each other and pressed at 50 °C under a pressure of 1.7 MPa for 2 hours and then peeled at 300 mm / min at 180 degrees, blocking does not occur between the adhesive layers, and the adhesive force of the adhesive layer to the positive electrode is 5 gf / cm or more. By simultaneously satisfying the physical properties, it is possible to prevent blocking from occurring during the process of winding and storing and transporting the composite separator on a roll, and also, during the assembly of the secondary battery, alignment is well maintained, and the effect of improving the capacity retention rate of the battery can be achieved simultaneously.

[0055] As one aspect, the adhesive layer may be an adhesive layer having only the particulate organic binder.

[0056] As one aspect, the adhesive layer may be laminated to face the negative electrode and the positive electrode of the lithium secondary battery. That is, during the assembly of the lithium secondary battery, the adhesive layer is laminated on the negative electrode or the positive electrode and can exhibit adhesiveness.

[0057] As one aspect, the porous substrate, the porous ceramic layer, and the adhesive layer may have substantially the same area or may be different from each other. For example, the porous ceramic layer may be formed over the entire surface of the porous substrate with the same area or may be formed with an area smaller than that of the porous substrate. Also, the adhesive layer may be formed over the entire surface with the same area as the porous substrate or the porous ceramic layer, or may be formed with an area smaller than that of the porous substrate or the porous ceramic layer.

[0058] For example, the area where the adhesive layer is formed may be formed in an area of 10 to 100% with respect to the total area of the porous ceramic layer or the porous substrate, and may have an area of 99% or less, 95% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or more, 20% or more, 50% or more, or an area between the numerical values. For example, it may be formed in an area of 10 to 90% or 20 to 80%, but is not limited as long as the object of the present disclosure can be achieved. Preferably, it may be formed in an area of 80% to 100%.

[0059] In one aspect, the porous ceramic layer may be formed with a thickness of 1 to 50%, 1 to 45%, 1 to 40%, or 1 to 35% with respect to the thickness of the entire composite separator. As an example, the thickness may be 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, or 1 to 5 μm, or any range between the numerical values, and is not limited thereto.

[0060] In one aspect, the adhesive layer has a coating amount of 0.05 to 1.0 g / m 2 、0.1 to 0.8 g / m 2 、0.1 to 0.5 g / m 2 or 0.1 to 0.3 g / m 2 and may be, or may be in any range between the numerical values, and is not limited thereto.

[0061] As one aspect, the composite separator of the present disclosure has the following property: when the adhesive layers are brought into contact with each other, pressurized at 50 °C under a pressure of 1.7 MPa for 2 hours, and then peeled at a speed of 300 mm / min at 180 degrees, no blocking occurs between the adhesive layers. When evaluating the presence or absence of blocking between the adhesive layers by the above method, it was found that when no blocking occurs, even under severe conditions that occur during storage and transportation after the composite separator is wound up, blocking can be prevented, and thus the invention of the present disclosure was completed. For example, it can be confirmed that no blocking occurs even when the wound roll is stored at 50 to 70 °C for 7 days. The presence or absence of the above blocking means that it was evaluated by the method described in the measurement method to be described later.

[0062] As one aspect, the adhesive force of the adhesive layer to the positive electrode may be 5 gf / cm or more, 6 gf / cm or more, 7 gf / cm or more, 8 gf / cm or more, 9 gf / cm or more, 10 gf / cm or more, 20 gf / cm or less, or any range between the above numerical values. For example, it may be 5 to 20 gf / cm, 5 to 15 gf / cm, 5 to 12 gf / cm, or 5.2 to 10.2 gf / cm. The higher the adhesive force, the more preferable it is. However, from the perspective of preventing blocking from occurring after winding and facilitating alignment during battery assembly, the adhesive force to the positive electrode may be 5 to 15 gf / cm. When the above range is satisfied, it may be more advantageous for providing the effect that no blocking occurs not only at room temperature but also at 50 to 70 °C.

[0063] The positive electrode is not limited, but may be formed from a positive electrode slurry produced by adding lithium cobalt composite oxide (LiCoO2) as a cathode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder to N-methyl-2-pyrrolidone (NMP) as a solvent.

[0064] As one aspect, the adhesive layer may have an adhesive force to the negative electrode of 2 gf / cm or more, 3 gf / cm or more, 4 gf / cm or more, 5 gf / cm or more, 6 gf / cm or more, 7 gf / cm or more, 15 gf / cm or less, or any range between the above numerical values, and is not limited thereto.

[0065] The negative electrode is not limited, but may be formed from a negative electrode slurry produced by adding artificial graphite, an acrylic latex as a binder, and carboxymethyl cellulose as a thickener to water as a solvent.

[0066] The composite separator according to one aspect of the present disclosure may have a heat shrinkage rate of 3% or less, 2% or less, 1.5% or less, 1% or less, or 0.5% or less after being left at 150 °C for 1 hour. By having the above low heat shrinkage rate, it is possible to prevent ignition and rupture due to abnormal phenomena such as a rapid temperature rise in the lithium secondary battery.

[0067] Further, a lithium secondary battery including the composite separator according to one aspect of the present disclosure, based on an initial cell capacity of 1800 mAh, after charging and discharging the lithium secondary battery 300 times at a discharge rate of 1C, measuring the discharge capacity, and measuring the degree of decrease with respect to the initial capacity, at the time of cycle evaluation, it is possible to provide a battery in which the ratio of the discharge capacity calculated by the following formula is 90% or more, 95% or more, or 97% or more. For example, it is possible to provide a battery having a ratio of 90 to 99% or 92 to 97%.

[0068] Discharge capacity ratio = (measured battery capacity after 300 cycles) / initial battery capacity

[0069] Further, the composite separator according to one aspect of the present disclosure cuts the electrodes into 4 cm in width and 6 cm in length, stacks 4 cut positive electrodes and 4 negative electrodes on the surface of the composite separator so as to intersect, and then at a temperature atmosphere of 80 °C, 10 kgf / cm 2 It is possible to provide a composite separator in which there are substantially no electrodes that fall when lifted vertically after heating and pressing at 30 seconds.

[0070] In addition, after winding up the composite separator having the porous separator and the adhesive layer for 1000 m or more, and storing it in an oven at 50°C and 70°C for 12 hours respectively, when the wound composite separator is unwound, it is possible to provide a composite separator in which there is no adhesion between the surfaces of the facing adhesive layers and there is no detachment of the ceramic layer.

[0071] Hereinafter, each configuration of the composite separator according to one aspect of the present disclosure will be described with examples.

[0072] [Porous separator] As one aspect of the present disclosure, the porous separator may be made of a porous base material, or a porous ceramic layer containing inorganic particles may be formed on one or both surfaces of the porous base material.

[0073] The porous base material may be a film, a sheet, etc. made of a polyolefin-based resin, and any microporous membrane adopted in the technical field can be used without limitation. Furthermore, as long as it has pores such as containing inorganic particles inside the pores or on the surface of non-woven fabric, paper, and these microporous membranes, and is a porous membrane applicable to a battery, it is not particularly limited.

[0074] The polyolefin-based resin may be a single or a mixture of polyolefin-based resins. As specific examples, it may be any one or a mixture of two or more selected from polyethylene, polypropylene, and copolymers thereof. Further, the porous base material may be made of a single polyolefin-based resin or a polyolefin-based resin as a main component, and further containing inorganic particles or organic particles. Further, the porous base material can be used in a laminated form. For example, the polyolefin-based resin may be composed of multiple layers. When the porous base material is composed of multiple layers, any one layer or all layers may contain inorganic particles and organic particles in the polyolefin-based resin.

[0075] The thickness of the porous substrate is not particularly limited, but it may be 5 to 30 μm. As the porous substrate, a porous substrate mainly produced by stretching can be employed, but it is not limited thereto.

[0076] The porous ceramic layer may be one in which inorganic particles are connected by a binder and pores are formed between the inorganic particles.

[0077] The binder may be contained in an amount of 0.1 to 20 parts by weight, 0.1 to 10 parts by weight, or 1 to 5 parts by weight based on 100 parts by weight of the inorganic particles. Usually, any binder used in this field can be used without limitation. As described above, by using the binder in a significantly smaller amount than the inorganic particles, a structure in which the inorganic particles are connected to each other is obtained, and pores are formed where the inorganic particles are in surface contact, thereby ensuring porosity.

[0078] Examples of the binder include various water-soluble and water-insoluble resins such as polymethyl methacrylate and its copolymers or acrylic resins such as polyacrylamide, ester resins, polyamides, polyimides, fluorine-based resins, polyacrylonitrile, polyethylene oxide, cellulose-based resins, polyvinyl alcohol-based resins, polyvinyl pyrrolidone, ethylene vinyl acetate copolymers, and cyanoethyl furan, and mixtures thereof. It may be dissolved in a solvent or used in particle form, and this is not limited.

[0079] The inorganic particles of the porous ceramic layer can generally be used without limitation as long as they are those used in the art. For example, any one or more inorganic particles selected from alumina, boehmite, aluminum hydroxide, titanium oxide, barium titanium oxide, magnesium oxide, magnesium hydroxide, silica, clay, and glass powder may be used, but the present invention is not limited thereto.

[0080] The inorganic particles can be contained in an amount of 70% by weight or more and 99.5% by weight or less based on 100% by weight of the total weight of the porous ceramic layer. For example, it may be contained in an amount of 70% by weight or more and 99% by weight or less, 70% by weight or more and 98% by weight or less, 80% by weight or more and 98% by weight or less, 85% by weight or more and 98% by weight or less, or 90% by weight or more and 98% by weight or less, but the present invention is not limited thereto. When the porous ceramic layer contains a binder and inorganic particles in the above content, the pores of the porous ceramic layer can be ensured, and the adhesiveness between the porous substrate and the porous ceramic layer or between the inorganic particles can be ensured.

[0081] The average particle diameter (D50) of the inorganic particles is not limited and may be, for example, 50 nm to 2 μm or 50 to 1000 nm.

[0082] In one aspect, the inorganic particles may be used in combination of two or more kinds of inorganic particles having different average particle diameters. Taking the two kinds of inorganic particles having different average particle diameters as an example, the first inorganic particle may be 50 to 500 nm, or 100 to 400 nm, and the second inorganic particle may be 500 nm to 2000 nm, or 600 to 1000 nm.

[0083] As one aspect, the porous ceramic layer may have a thickness of 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, or may be in the range of 1 to 5 μm, or may be any range between the above values, and is not limited thereto.

[0084] [Adhesive layer] The adhesive layer of the present disclosure may be formed on the outermost layer of at least one surface of the porous separator.

[0085] The adhesive layer of the present disclosure contains a particulate organic binder, and when the adhesive layers are brought into contact with each other, pressurized at 50 °C under a pressure of 1.7 MPa for 2 hours, and then peeled at 300 mm / min and 180 degrees, no blocking occurs between the adhesive layers, and the adhesive strength of the adhesive layer to the positive electrode is 5 gf / cm or more, the object of the present disclosure can be more easily achieved. The non-occurrence of blocking means that no blocking occurs in the evaluation method described in <Evaluation Method for Blocking Property> among the following physical property evaluation methods.

[0086] The composite separator having the adhesive layer according to the present disclosure can achieve the effect that no blocking occurs between the adhesive layers even at high temperatures, no alignment defects occur during battery assembly, and can impart excellent characteristics of battery capacity retention rate.

[0087] The reason for the particulate organic binder to exhibit blocking characteristics is not limited, and the particulate organic binder can be used without limitation as long as it satisfies the adhesive strength and blocking characteristics. For example, it may be a core-shell particulate organic binder, and the glass transition temperature of the whole core-shell particle may be higher than the glass transition temperature of the core part. In addition, the size and particle distribution of the core-shell particles, the degree of crosslinking, the type and content of comonomers, etc. can affect the above physical properties, and there is no particular limitation as long as the blocking characteristics are exhibited under the above conditions.

[0088] The core-shell particle type organic binder means one composed of a core in particle form and a shell wrapping its surface.

[0089] As an example, the glass transition temperature measured for the entire core-shell particle type organic binder can be 60 °C or higher and 80 °C or lower, or any value between the said numerical values. For example, the glass transition temperature can be 60 to 80 °C, 65 to 80 °C, 69 to 78 °C or 70 to 78 °C. The core-shell particle type binder may be an acrylic particle type binder, or may be a particle type binder having the said glass transition temperature and manufactured by adjusting the degree of crosslinking within a specific range, or may be a particle type acrylic organic binder manufactured by modifying the surface of organic binder particles using a specific modifier, etc., but any organic particle type binder satisfying the physical properties of the present disclosure is not limited thereto.

[0090] As an example, the glass transition temperature of the core of the core-shell particle type organic binder can be 50 °C or higher and 75 °C or lower, or any value between the said numerical values. For example, it can be 50 to 75 °C, 55 to 70 °C, 60 to 70 °C, 62 to 70 °C, 65 to 70 °C, and it may be an acrylic particle type organic binder in which the glass transition temperature of the entire core-shell particle type organic binder is 60 to 80 °C and the glass transition temperature of the whole particles is in a higher range compared to the core. In this way, by making the glass transition temperature of the whole particles including the core-shell higher than that of the core, the target anti-blocking property and adhesiveness can be exhibited, and an excellent effect on the battery capacity retention rate can be provided.

[0091] As one aspect, the ratio of the content of the core and the shell of the core-shell particle type organic binder may be 60 to 99:40 to 1 wt%, 60 to 90:40 to 10 wt%, and although not limited thereto, within the said range, the effect of having more excellent electrode adhesiveness and anti-blocking can be provided.

[0092] As one mode, the core-shell particle type organic binder is polymer particles that can be produced by emulsion polymerization or suspension polymerization, and may be uncrosslinked or crosslinked particles.

[0093] The core-shell particle type organic binder can be acrylic organic particles, and the shell may include a structure derived from an aromatic vinyl monomer.

[0094] The acrylic organic particles may be composed of an acrylic polymer. Examples of the acrylic polymer include (meth)acrylonitrile such as C1-C10 alkyl (meth)acrylate, (meth)acrylate, acrylonitrile, and methacrylonitrile, and aromatic vinyl monomers such as styrene, α-methylstyrene, styrenesulfonic acid, butoxystyrene, and vinylnaphthalene, and maleimide derivatives such as maleimide and phenylmaleimide. It may be a polymer obtained by polymerizing any one or more monomers selected from the above. Without being limited thereto, it can be produced by mixing various monomers so that the glass transition temperature is 60 to 80°C.

[0095] For example, in the case of a core-shell particle type organic binder, the core may be an acrylic copolymer obtained by copolymerizing C1-C10 alkyl (meth)acrylate, (meth)acrylate, and (meth)acrylonitrile, and the glass transition temperature can be lowered by adjusting the content of C1-C10 alkyl (meth)acrylate. The (meth)acrylate means acrylate or methacrylate. Specifically, for example, it may be methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, etc., and is not limited thereto. The shell may be an acrylic copolymer copolymerized using a monomer mixture containing an aromatic vinyl monomer such as styrene and (meth)acrylate, and the glass transition temperature can be increased by adjusting the content of the aromatic vinyl monomer. The (meth)acrylate means acrylate or methacrylate.

[0096] In one aspect, when the particulate organic binder is also impregnated with the electrolyte, the swelling ratio according to the following formula 1 may be 300-500% or 320-490%. Within this range, it is more preferable although not limited thereto because it is advantageous for achieving the object required in the present disclosure.

[0097] [Formula 1] Swelling ratio = W2 / W1 × 100

[0098] The W2 is the weight measured after impregnation with the electrolyte, and W1 is the weight measured before impregnation with the electrolyte.

[0099] Here, the swelling ratio may be measured according to the measurement method of the examples described later. The electrolyte may be a mixture of ethylene carbonate:ethyl methyl carbonate:dimethyl carbonate in a volume ratio of 3:5:2.

[0100] The adhesive layer has the particulate organic binder at 0.05-1.0 g / m 2, 0.1 to 0.8 g / m 2 , 0.1 to 0.5 g / m 2 , 0.1 to 0.4 g / m 2 or 0.1 to 0.3 g / m 2 It may be applied in a content amount that is not limited thereto, but is not limited thereto.

[0101] The size of the particulate organic binder may be such that the average particle size of D50 is 300 nm or more and 700 nm or less, or a value between the numerical values. For example, it may be 300 to 700 nm, 400 to 600 nm, 450 to 550 nm, or 450 to 520 nm, and may also be a value between the numerical values. However, within the above range, it is possible to prevent the pores of the porous separator from being blocked, and it is possible to more easily exhibit the electrode adhesion force, which is preferable.

[0102] Although the particulate organic binder has been described by way of example, as long as it satisfies the glass transition temperature and no blocking occurs when evaluated by the method described in the evaluation method of the present disclosure, its type is not limited. For example, in addition to acrylic polymers, fluorine-based polymers or copolymers thereof can be used, and this is not restricted.

[0103] [Method for manufacturing a composite separator] Hereinafter, a method for manufacturing the composite separator of the present disclosure will be described.

[0104] A method for manufacturing a composite separator for a secondary battery according to one aspect of the present disclosure includes a step of applying an aqueous dispersion containing a particulate organic binder on one or both surfaces of a porous separator and drying to form an adhesive layer.

[0105] Also, a method for manufacturing a composite separator for a secondary battery according to an aspect of the present disclosure includes: a) applying a slurry containing inorganic particles and a binder onto one or both surfaces of a porous substrate, and drying to form a porous ceramic layer; and b) applying an aqueous dispersion containing a particulate organic binder onto one or both surfaces of a ceramic coated separator on which the porous ceramic layer is formed, and drying to form an adhesive layer.

[0106] Each of the above configurations is as described above.

[0107] The slurry for forming the porous ceramic layer may be an aqueous slurry using water as a dispersion medium.

[0108] Water may be used as a dispersion medium for the dispersion for forming the adhesive layer. The particulate organic binder may be provided in a particulate form dispersed in water by emulsion or suspension polymerization.

[0109] Any of the commonly known methods in the art can be applied without limitation to the coating method. By way of non-limiting example, roll coating, spin coating, dip coating, bar coating, die coating, slit coating, inkjet printing, and combinations thereof may be applied.

[0110] The drying step is not particularly limited, but the drying temperature may be 100°C or lower, for example, 30 - 100°C, or 40 - 100°C. When drying is performed at the above temperature, the physical properties of the porous substrate are not affected, and the coating layer can be uniformly dried to prevent coating defects.

[0111] Also, after the drying, a step of winding around a roll for storage and transfer may be included.

[0112] [Lithium secondary battery] One aspect of the present disclosure provides a lithium secondary battery including the above-described composite separator for a secondary battery. The lithium secondary battery may be manufactured to include the composite separator for a secondary battery according to one aspect of the present invention, a positive electrode, a negative electrode, and a non-aqueous electrolyte.

[0113] As one aspect, since the lithium secondary battery is formed by arranging and assembling a negative electrode, a composite separator, and a positive electrode and then injecting an electrolyte, which is a general manufacturing method, it will not be described in more detail here.

[0114] Here, the positive electrode, the negative electrode, and the non-aqueous electrolyte can be used without limitation as long as they are those usually used in lithium secondary batteries.

[0115] As one aspect, the positive electrode and the negative electrode may be manufactured by mixing and stirring a positive electrode active material and a negative electrode active material with a solvent, and optionally a binder, a conductive material, a dispersant, etc. to produce a composition, then applying this to a current collector made of a metal material, drying, and then pressing.

[0116] The positive electrode active material can be used as long as it is an active material usually used for the positive electrode of a secondary battery. For example, lithium metal oxide particles containing one or more metals selected from the group consisting of Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, B, and combinations thereof may be used.

[0117] The negative electrode active material can be used as long as it is an active material usually used for the negative electrode of a secondary battery. The negative electrode active material of a lithium secondary battery is preferably a material capable of intercalating lithium. As a more limited example, the negative electrode active material is lithium (metallic lithium), easily graphitizable carbon (soft carbon), hardly graphitizable carbon (hard carbon), graphite, silicon, Sn alloy, Si alloy, Sn oxide, Si oxide, Ti oxide, Ni oxide, Fe oxide (FeO), and lithium-titanate (LiTiO2, Li4Ti5O 12It may be one or more substances selected from the group of negative electrode active materials such as

[0118] As the conductive material, ordinary conductive carbon materials can be used without particular limitation.

[0119] The non-aqueous electrolyte contains a lithium salt as an electrolyte and an organic solvent. As the lithium salt, those commonly used in electrolytes for lithium secondary batteries and the like can be used without limitation, and it can be represented by Li + X - It can be represented by

[0120] The anion of the lithium salt is not particularly limited, and any one or more selected from F - , Cl - , Br - , I - , NO 3- , N(CN) 2- , BF 4- , ClO 4- , PF 6- , (CF3)PF 4- , (CF3)3PF 3- , (CF3)4PF 2- , (CF3)5PF - , (CF3)6P - , CF3SO 3- , CF3CF2SO 3- , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO 3- , CH3CO 2- , SCN - and (CF3CF2SO2)2N - Any one or more selected from the like can be used.

[0121] As the organic solvent, any one or a mixture of two or more selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma-butyrolactone, and tetrahydrofuran can be used.

[0122] The non-aqueous electrolyte may be injected into an electrode structure including a positive electrode, a negative electrode, and a composite separator interposed between the positive electrode and the negative electrode.

[0123] The outer shape of the lithium secondary battery is not particularly limited, and may be selected from, for example, a cylindrical shape, a rectangular shape, a pouch shape, or a coin shape using a can.

[0124] As described above, the embodiments of the present invention have been described in detail. However, those having ordinary knowledge in the technical field to which the present invention pertains can implement the present invention in various modified forms without departing from the spirit and scope of the present invention defined in the appended claims. Therefore, future modifications of the embodiments of the present invention cannot deviate from the technology of the present invention.

[0125] Hereinafter, with reference to specific experimental examples, the embodiments of the present disclosure will be further described. The examples and comparative examples included in the experimental examples illustrate the present invention and do not limit the scope of the appended patent claims. It is obvious to those skilled in the art that various changes and modifications regarding the examples can be made within the scope and technical idea of the present invention, and it goes without saying that such modifications and changes belong to the scope of the appended patent claims.

[0126] 1. Adhesion to the positive electrode After laminating so that the adhesive layer of the composite separator faces the surface of the following positive electrode, it was pressure-bonded and adhered at 80 °C and 20 MPa for 30 seconds using a heat press machine. According to ASTM D 903, it was peeled at 180° using a UTM equipment (product name: Instron 3365) manufactured by INSTRON, and the electrode adhesion was measured. When the adhesion of the adhesive layer of the composite separator was too low and it was impossible to peel it using the UTM equipment, it was evaluated as "unmeasurable".

[0127] Manufacture of positive electrode: 94 wt% of lithium cobalt composite oxide (LiCoO2) as the positive electrode active material, 3.5 wt% of carbon black as the conductive material, and 2.5 wt% of polyvinylidene fluoride (PVdF) as the binder were added to N-methyl-2-pyrrolidone (NMP) as the solvent to produce a positive electrode slurry. The produced slurry was applied to an aluminum (Al) thin film with a thickness of 30 μm, dried at a temperature of 120 °C, and then roll-pressed to produce a positive electrode with a thickness of 150.

[0128] 2. Evaluation of electrode adhesion The electrode was cut into a size of 4 cm in width and 6 cm in length. After stacking 4 cut positive electrodes and 4 negative electrodes on the surface of the composite separator in a cross pattern, they were adhered at 80 °C in an atmosphere of 10 kgf / cm 2 for 30 seconds, and then unfolded to evaluate the number of electrodes attached.

[0129] A: 8 pieces, B: 6 - 7 pieces, C: 4 - 5 pieces, D: less than 4 pieces

[0130] The positive electrode and negative electrode used for the evaluation were manufactured as follows.

[0131] Manufacture of the positive electrode: 94% by weight of lithium cobalt composite oxide (LiCoO2) as the positive electrode active material, 3.5% by weight of carbon black as the conductive material, and 2.5% by weight of polyvinylidene fluoride (PVdF) as the binder were added to N-methyl-2-pyrrolidone (NMP) as the solvent to produce a positive electrode slurry. The produced slurry was coated on an aluminum (Al) thin film with a thickness of 30 μm, dried at a temperature of 120 °C, and then roll-pressed to produce a positive electrode with a thickness of 150.

[0132] Manufacture of the negative electrode: Artificial graphite, a binder (acrylic latex with a Tg of -52 °C), and a thickener (CMC carboxymethyl cellulose) were added to water as the solvent at 95% by weight, 3% by weight, and 2% by weight respectively to produce a negative electrode mixture slurry. The produced slurry was coated on a copper (Cu) thin film with a thickness of 20 μm, dried at 120 °C, and roll-pressed and crimped to produce a negative electrode with a thickness of 150 μm.

[0133] 3. Blocking evaluation Two samples were prepared, the adhesive layers were brought into contact with each other, pressurized at 50 °C under a pressure of 1.7 MPa for 2 hours, and then peeled at 180 degrees at a speed of 300 mm / min to evaluate whether delamination of the coating layer between the adhesive layers occurred. When confirmed by visual observation and SEM, it was evaluated whether delamination of the coating layer occurred in a region of 50×50 μm.

[0134] PASS: When visually observing and randomly checking five 50×50 μm regions for the entire area of the SEM sample, if no delamination of the coating layer occurs at all

[0135] OK: When visually observing, no delamination of the coating layer is confirmed, and when randomly checking five 50×50 μm regions for the entire area of the SEM sample, if less than 2% delamination of the coating layer is confirmed

[0136] Fail: When observing visually, peeling of the coating layer is observed, or when randomly checking five 50×50 μm areas out of the entire area of the SEM sample, peeling of the coating layer of 2% or more is confirmed.

[0137] 4. Thermal shrinkage rate After leaving a 10 cm × 10 cm composite separator at 150°C for 1 hour, the reduction rate of the area was measured, and the thermal shrinkage rate was calculated according to the following formula.

[0138] Thermal shrinkage rate (%) = ((Length before heating - Length after heating) / Length before heating) × 100

[0139] 5. Ratio of battery life discharge capacity to the initial value Similar to the above electrode adhesion evaluation, a pouch-type battery was assembled by the stacking method. For each assembled battery, before injecting the electrolyte, at 80°C and 10 kgf / cm 2 , thermal pressure bonding was performed for 30 seconds, and an electrolyte in which 1 M lithium hexafluorophosphate (LiPF6) was dissolved in ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / dimethyl carbonate (DMC) = 3:5:2 (volume ratio) was injected to manufacture a lithium secondary battery.

[0140] After charging and discharging each of the manufactured batteries 300 times at a discharge rate of 1C, the discharge capacity was measured, and a cycle evaluation was performed to measure the degree of decrease with respect to the initial capacity.

[0141] Ratio of discharge capacity = (Measured battery capacity after 300 cycles) / Initial battery capacity (1.8 Ah)

[0142] 6. Method for measuring average particle size In accordance with the ISO 13320-1 standard, the average particle size D50 was measured using the S3500 manufactured by Microtrac, a particle size analyzer.

[0143] 7. Method for measuring glass transition temperature Analysis was performed using a DSC (Differential Scanning Calorimeter, manufactured by Mettler Toledo, DSC-822E). The analysis conditions were as follows: After removing the solvent and solidifying the sample, 5 mg of the solidified sample was heated from -50 °C to 200 °C at a scanning rate of 10 °C / min under nitrogen conditions until the sample was completely melted, then cooled at 10 °C / min until solidified, and then reheated from -50 °C to 200 °C at 10 °C / min to measure the glass transition temperature. The glass transition temperature of the particulate organic binder was measured as follows. For example, the glass transition temperature of the core-shell particulate organic binder was measured as follows. First, after synthesizing the core polymer, the glass transition temperature (Tg) of the core was measured. Then, core-shell particles were produced and the Tg of all the particles was measured.

[0144] 8. Weight change rate (swelling ratio) during electrolyte impregnation An aqueous dispersion containing organic particles for forming an adhesive layer was placed in a Teflon (registered trademark) Petri dish, and after evaporating water at 60 °C for one day to produce a film, 1 g of the film was immersed in an electrolyte in which ethylene carbonate:ethyl methyl carbonate:dimethyl carbonate was mixed at a volume ratio of 3:5:2, left at 50 °C for 48 hours, then the electrolyte was removed, the weight of the film was measured, and the weight change rate was calculated.

[0145] Swelling ratio = W2 / W1 × 100

[0146] Wherein W2 is the weight measured after impregnation with the electrolyte, and W1 is the weight measured before impregnation with the electrolyte. The unit is %.

[0147] 9. Average thickness (μm) The average thickness of the separator was determined by the following method. After stacking 10 separators, the thickness was measured at five arbitrary points in the width direction using a thickness measuring instrument manufactured by Mitutoyo Corporation, and the measurements were summed up. Then, the sum was divided by 5 to derive the average thickness of the 10 - layer separator, and further divided by 10 to derive the overall average thickness of a single separator.

[0148] The average thickness of the porous substrate was determined as follows. After stacking 10 porous substrates only, the thickness was measured at five arbitrary points in the width direction using a thickness measuring instrument manufactured by Mitutoyo Corporation, and the measurements were summed up. Then, the sum was divided by 5 to derive the average thickness of the 10 - layer porous substrate, and further divided by 10 to derive the average thickness of the porous substrate. In the case after forming the inorganic particle layer, the inorganic particle layer was detached, thoroughly dried, and the average thickness of the porous substrate from which the inorganic particle layer was detached was derived by the above - mentioned method.

[0149] 10. Gurley Permeability (sec / 100cc) Using a Densometer manufactured by Toyoseiki, the measurement was carried out in accordance with ASTM D726 standard. The time (in seconds) taken for 100 cc of air to pass through an area of 1 square inch of the separator was recorded and compared.

[0150] [Example 1] 1) Manufacture of Ceramic Coated Separator On both sides of a polyethylene porous substrate (ENPASS, manufactured by SK innovation) with a Gurley permeability of 126 sec / 100cc and a thickness of 9 μm, the following slurry for the inorganic particle layer was bar - coated at a speed of 5 m / min to form a coating layer, and then thoroughly dried at 40°C to form a porous ceramic layer. After drying, the coating thickness of the porous ceramic layers on both sides was 1.5 μm each.

[0151] The slurry for the inorganic particle layer contained, as inorganic particles, 29.1 wt% of boehmite particles with an average particle diameter (D 50 ) of 300 nm, and 29.1 wt% of boehmite particles with an average particle diameter (D 50) 67.9 wt% of boehmite particles of 700 nm and 3 wt% of polyacrylamide resin were mixed, water as a solvent was added and stirred to produce a composition with a solid content concentration of 25 wt%.

[0152] 2) Manufacture of composite separator On both surfaces of the manufactured ceramic-coated separator, the following coating liquid for the adhesive layer was bar-coated at a speed of 5 m / min to form an adhesive layer, and it was sufficiently dried at 40 °C and wound up in a roll form. The thickness of each of the adhesive coating layers on both sides was 0.5 μm, and the coating amount of each was 0.2 g / m 2 It was.

[0153] The coating liquid for the adhesive layer used polymer particle aqueous dispersions (acrylic particles with a core-shell structure manufactured from butyl methacrylate, methyl methacrylate, acrylonitrile, and styrene monomers with D50 of 0.5 μm and Tg of 77.4 °C).

[0154] The physical properties of the manufactured composite separator were evaluated and shown in Table 2 below.

[0155] [Examples 2 to 5] As shown in Table 1 below, it was manufactured in the same manner as in Example 1 except that the physical properties of the core-shell particles were changed.

[0156] The physical properties of the manufactured composite separator were evaluated and shown in Table 2 below.

[0157] [Comparative Examples 1 to 3] As shown in Table 1 below, it was manufactured in the same manner as in Example 1 except that the monomer content was adjusted to change the physical properties of the core-shell particles.

[0158] The physical properties of the manufactured composite separator were evaluated and shown in Table 2 below.

[0159]

Table 1

[0160]

Table 2

[0161] As shown in Table 1 and Table 2 above, when the examples of the present disclosure use an organic particle binder that satisfies the glass transition temperature and also satisfies the swelling ratio, they have excellent electrode adhesion, no blocking occurs in the blocking evaluation, no electrode desorption occurs in the electrode adhesion evaluation, and the capacity retention rate after 300 cycles is 90% or more, 92% or more, indicating very excellent characteristics. Also, after manufacturing the composite separator and winding it up for storage, it was confirmed that not only at room temperature but also when stored at a high temperature of 50 to 70 °C, no blocking occurs between the adhesive layers of the wound roll, between the adhesive layer and the ceramic layer, or between the adhesive layer and the porous substrate, and a composite separator with excellent anti-blocking properties can be provided.

[0162] However, as in Comparative Examples 1 and 2, when using an organic particle type binder that does not satisfy the glass transition temperature of the present invention, it was confirmed that the electrode adhesion is low, electrode desorption occurs in the electrode adhesion evaluation, and blocking occurs in the blocking evaluation.

[0163] Also, as in Comparative Example 3, when the glass transition temperature of the whole particles is lower than that of the core, it was found that the electrode adhesion is satisfied, but blocking occurs severely in the blocking evaluation. Also, it was found that the capacity retention rate is very low.

[0164] Therefore, with the method of predicting electrode adhesion and blocking characteristics only based on the conventional electrode adhesion force, accurate prediction could not be achieved. However, as in the present disclosure, when an organic particle type binder is used and the adhesion force characteristics are simultaneously satisfied while meeting the glass transition temperature characteristics of the organic particle type binder, it was confirmed that all of the blocking characteristics, electrode adhesiveness, and capacitance retention rate can be satisfied. Also, it was confirmed that even if the electrode adhesion force is satisfied without meeting the glass transition temperature characteristics, the blocking characteristics and capacitance cannot be satisfied. From this, it was found that the presence or absence of blocking could not be predicted only by the conventional electrode adhesiveness evaluation, and the effects of the present invention could be well demonstrated.

[0165] The above content is merely an exemplification applying the principle of the present disclosure, and other configurations may be further included without departing from the scope of the present invention.

[0166] As described above, in the present invention, specific matters and limited examples are used for explanation, but this is provided for helping a more general understanding of the present disclosure. The present disclosure is not limited to the above examples, and those with ordinary knowledge in the field to which the present disclosure pertains can make various modifications and deformations from such descriptions.

[0167] Therefore, the idea of the present disclosure should not be defined only by the above examples, and it can be said that not only the claims described later but also all those with equivalent or equivalent deformations to the claims belong to the scope of the idea of the present disclosure.

Explanation of Reference Numerals

[0168] 100 Composite separator 110 Porous separator 120 Adhesive layer

Claims

1. A composite separator including an adhesive layer on at least one outermost layer of a porous separator, The adhesive layer includes a particulate organic binder, and when the adhesive layers are abutted against each other and pressed at 50° C. under a pressure of 1.7 MPa for 2 hours, and then peeled off at a speed of 300 mm / min at a 180° angle, no blocking occurs between the adhesive layers and the adhesive strength to the positive electrode is 5 gf / cm or more.

2. The content of the particulate organic binder in the adhesive layer is 0.1 to 0.5 g / m ２ 2. The composite separator of claim 1 ,

3. The composite separator according to claim 1 , wherein the particulate organic binder has an average particle size of 400 to 600 nm.

4. The composite separator according to claim 1 , wherein the porous separator comprises a porous substrate, or a porous ceramic layer including inorganic particles formed on one or both surfaces of the porous substrate.

5. 2. The composite separator according to claim 1, wherein the particulate organic binder is a core-shell particulate organic binder.

6. 6. The composite separator according to claim 5, wherein the core-shell particle type organic binder has a glass transition temperature of the entire core-shell particle higher than the glass transition temperature of the core.

7. 6. The composite separator according to claim 5, wherein the core of the core-shell particle type organic binder has a glass transition temperature of 50 to 75°C.

8. 6. The composite separator according to claim 5, wherein the core-shell particle type organic binder has a glass transition temperature of 60 to 80° C. for the entire core-shell particle.

9. 6. The composite separator according to claim 5, wherein the core-shell particle type organic binder is an acrylic organic particle, and the shell includes a structure derived from an aromatic vinyl monomer.

10. The electrodes were cut into pieces of 4 cm wide and 6 cm long, and four cut positive electrodes and four cut negative electrodes were stacked on the surface of the composite separator in a cross-stacked manner. Then, the electrodes were subjected to a pressure of 10 kgf / cm in an atmosphere having a temperature of 80° C. ２ 2. The composite separator of claim 1, wherein none of the electrodes detach when deployed after being adhered at 250.degree. C. for 30 seconds.

11. The composite separator of claim 4, wherein the inorganic particles of the porous ceramic layer have an average particle size of 50 nm to 2 μm.

12. 12. The composite separator of claim 11, wherein the inorganic particles of the porous ceramic layer include first inorganic particles having an average particle size of 50 to 500 nm and second inorganic particles having an average particle size of 500 nm to 2000 nm.

13. 5. The composite separator according to claim 4, wherein the porous ceramic layer comprises inorganic particles bound together by a binder, and pores are formed between the inorganic particles.

14. The composite separator according to claim 4 , wherein the porous substrate is a polyolefin-based porous film.

15. 2. The composite separator according to claim 1, which has a heat shrinkage rate at 150°C of 3% or less in both the machine direction and the width direction.

16. A lithium secondary battery comprising the composite separator according to any one of claims 1 to 15.

17. 17. The lithium secondary battery of claim 16, wherein the lithium secondary battery is charged and discharged 300 times at a discharge rate of 1C, and then a discharge capacity is measured. In a cycle evaluation in which a degree of decrease in a capacity relative to an initial capacity is measured, the discharge capacity ratio calculated by the following formula is 90% or more. Discharge capacity ratio=(battery capacity measured after 300 cycles) / initial battery capacity

18. A composite separator including an adhesive layer on at least one outermost layer of a porous separator, The adhesive layer includes a particulate organic binder, The content of the particulate organic binder in the adhesive layer is 0.1 to 0.5 g / m ２ and The particulate organic binder has an average particle size of 400 to 600 nm, The particle-type organic binder includes a core-shell particle-type organic binder, The core-shell particle type organic binder has a glass transition temperature of the entire core-shell particle higher than the glass transition temperature of the core.

19. The composite separator according to claim 18, wherein the core of the core-shell particle type organic binder has a glass transition temperature of 50 to 75°C, and the whole particle has a glass transition temperature of 60 to 80°C.

20. 20. A lithium secondary battery comprising the composite separator of claim 18.

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