Separator for lithium secondary battery, and lithium secondary battery comprising same

Abstract

This separator for a battery comprises a porous substrate and a coating layer placed on at least one surface of the porous substrate, wherein the coating layer includes: a binder; a cross-linking agent; a cross-linked product of a carboxyalkyl cellulose or a salt thereof; a filler; and an adhesive binder, the binder including a (meth)acrylic binder that comprises a first structural unit derived from (meth)acrylamide and a second structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof, the cross-linking agent including an aziridine-based cross-linking agent, the carboxyalkyl cellulose or a salt thereof being included in an amount of 20-50 wt% on the basis of the total amount of the (meth)acrylic binder, the cross-linking agent and the carboxyalkyl cellulose or a salt thereof, and the adhesive binder including a swellable adhesive binder, wherein the swellable adhesive binder comprises a first structural unit derived from a vinyl aromatic monomer, a second structural unit derived from an alkyl (meth)acrylate and a third structural unit derived from a phosphonate-based monomer.

Description

Separator for lithium secondary battery and lithium secondary battery including same

[0001] The present invention relates to a separator for a lithium secondary battery and a lithium secondary battery including the same.

[0002] The recent rapid proliferation of battery-powered electronic devices, such as mobile phones, laptops, and electric vehicles, has led to a rapid increase in demand for high-energy density and high-capacity secondary batteries. Accordingly, active research and development is underway to improve the performance of lithium secondary batteries.

[0003] A lithium secondary battery is a battery that includes a positive electrode and a negative electrode that contain active materials capable of intercalating and deintercalating lithium ions, and an electrolyte, and produces electrical energy through oxidation and reduction reactions when lithium ions are intercalated and deintercalated from the positive electrode and the negative electrode.

[0004] Lithium secondary batteries may include a separator between the positive and negative electrodes. The separator is impregnated within the electrolyte. It may be desirable for the separator to maintain its original shape without undergoing thermal shrinkage within the electrolyte, ensuring battery safety.

[0005] One embodiment provides a separator for a lithium secondary battery that reduces salt precipitation and lowers resistance when applied to the battery.

[0006] Another embodiment provides a separator for a lithium secondary battery having low shrinkage in an electrolyte.

[0007] Another embodiment provides a lithium secondary battery including the above-described separator for a lithium secondary battery.

[0008] According to one embodiment, a separator for a lithium secondary battery is provided.

[0009] The above lithium secondary battery separator comprises a porous substrate; a coating layer positioned on at least one surface of the porous substrate, the coating layer comprising a binder; a crosslinking agent; and a crosslinked product of carboxyalkyl cellulose or a salt thereof; a filler; and an adhesive binder, wherein the binder comprises a (meth)acrylic binder including a first structural unit derived from (meth)acryl amide and a second structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof, the crosslinking agent comprises an aziridine crosslinking agent, and the carboxyalkyl cellulose or a salt thereof comprises the (meth)acrylic binder; the crosslinking agent; And the total amount of the carboxyalkyl cellulose or its salt is included in an amount of 20 to 50 wt%, wherein the adhesive binder comprises a swellable adhesive binder, and the swellable adhesive binder comprises a first structural unit derived from a vinyl aromatic monomer, a second structural unit derived from an alkyl (meth)acrylate, and a third structural unit derived from a phosphonate monomer.

[0010] According to another embodiment, a lithium secondary battery is provided.

[0011] The above lithium secondary battery includes a positive electrode, a negative electrode, and a separator for the lithium secondary battery positioned between the positive electrode and the negative electrode.

[0012] A separator for a lithium secondary battery according to one embodiment can improve the capacity of a battery by reducing salt precipitation and lowering resistance when applied to the battery. In addition, the separator for a lithium secondary battery can improve the safety and reliability of the battery by lowering the shrinkage rate in the electrolyte.

[0013] Figure 1 is a cross-sectional view showing a separator for a lithium secondary battery according to one embodiment.

[0014] Figures 2 to 5 are cross-sectional views schematically showing a lithium secondary battery according to one embodiment.

[0015] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention. The present invention is defined solely by the scope of the claims set forth below.

[0016] Unless otherwise specified herein, when a part such as a layer, film, region, plate, etc. is said to be “on top of” another part, this includes not only cases where it is “directly on top of” the other part, but also cases where there is another part in between.

[0017] Unless otherwise specified herein, the singular may also include the plural. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0018] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0019] In this specification, 'particle diameter D100' means the diameter of particles whose cumulative volume is 100% by volume in the particle size distribution. The particle size distribution can be measured by a method widely known to those skilled in the art. For example, the particle size distribution can be measured by a particle size analyzer, or by a transmission electron microscope photograph or a scanning electron microscope photograph. Alternatively, the particle size distribution can be measured using a measuring device that utilizes dynamic light-scattering, and the data can be analyzed to count the number of particles for each particle size range, and then the D100 value can be obtained by calculating from the counted number. Alternatively, the particle size can be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and then D100 based on 100% of the particle size distribution in the measuring device can be calculated.

[0020] In this specification, 'particle diameter D50' refers to the particle diameter of a particle having a cumulative volume of 50% by volume in a particle size distribution. The particle size distribution can be obtained by referring to the method described in the 'particle diameter D100' above.

[0021] In this specification, ‘particle diameter D100’ may mean ‘size 100’.

[0022] In this specification, ‘particle diameter D50’ may mean ‘size 50’.

[0023] In this specification, '(meth)acrylic' means acrylic and / or methacrylic.

[0024] Unless otherwise defined below, "substitution" means that hydrogen in a compound is substituted with a C1 to C30 alkyl group, a C2 to C30 alkenyl group, a C2 to C30 alkynyl group, a C6 to C30 aryl group, a C7 to C30 alkylaryl group, a C1 to C30 alkoxy group, a C1 to C30 heteroalkyl group, a C3 to C30 heteroalkylaryl group, a C3 to C30 cycloalkyl group, a C3 to C15 cycloalkenyl group, a C6 to C30 cycloalkynyl group, a C2 to C30 heterocycloalkyl group, a halogen (F, Cl, Br or I), a hydroxy group (-OH), a nitro group (-NO2), a cyano group (-CN), an amino group (-NRR') (wherein R and R' are each independently hydrogen or a C1 to C6 alkyl group), a sulfobetaine group (-RR'N + (CH2) n SO3 - , n is a natural number from 1 to 10), carboxybetaine group (-RR'N + (CH2) n COO - , n is a natural number from 1 to 10) (wherein, R and R' are each independently a C1 to C20 alkyl group), azido group (-N3), amidino group (-C(=NH)NH2), hydrazino group (-NHNH2), hydrazono group (=N(NH2), carbamoyl group (-C(O)NH2), thiol group (-SH), acyl group (-C(=O)R, where R is hydrogen, a C1 to C6 alkyl group, a C1 to C6 alkoxy group, or a C6 to C12 aryl group), carboxyl group (-COOH) or a salt thereof (-C(=O)OM, where M is an organic or inorganic cation), sulfonic acid group (-SO3H) or a salt thereof (-SO3M, where M is an organic or inorganic cation), phosphoric acid group (-PO3H2) or a salt thereof (-PO3MH or -PO3M2, where M is an organic or inorganic cation) and combinations thereof.

[0025] Hereinafter, a C1 to C3 alkyl group means a methyl group, an ethyl group, or a propyl group. A C1 to C10 alkylene group can be, for example, a C1 to C6 alkylene group, a C1 to C5 alkylene group, a C1 to C3 alkylene group, and can be, for example, a methylene group, an ethylene group, or a propylene group. A C3 to C20 cycloalkylene group can be, for example, a C3 to C10 cycloalkylene group, or a C5 to C10 cycloalkylene group, and can be, for example, a cyclohexylene group. A C6 to C20 arylene group can be, for example, a C6 to C10 arylene group, and can be, for example, a phenylene group. A C3 to C20 heterocyclic group can be, for example, a C3 to C10 heterocyclic group, and can be, for example, a pyridine group.

[0026] Hereinafter, “hetero” means containing one or more heteroatoms selected from N, O, S, Si, and P.

[0027] In the chemical formulas described herein, the * symbol indicates a part that is connected to the same or different atoms, groups, or structural units.

[0028] Unless otherwise specifically stated in the chemical formulas described herein, hydrogen may be considered to be bonded in the structure of the chemical formula.

[0029] Hereinafter, “alkali metal” refers to an element belonging to Group 1 of the periodic table, such as lithium, sodium, potassium, rubidium, cesium, or francium, which can exist in a cationic or neutral state.

[0030] When describing a numerical range in this specification, 'X to Y' means 'X or more and Y or less (X ≤ and ≤ Y).

[0031] According to one embodiment, a separator for a lithium secondary battery comprises: a porous substrate; a coating layer positioned on at least one surface of the porous substrate, wherein the coating layer comprises: a binder; a crosslinking agent; and a crosslinked product of carboxyalkyl cellulose or a salt thereof; a filler; and an adhesive binder, wherein the binder comprises a (meth)acrylic binder including a first structural unit derived from (meth)acrylamide and a second structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof, wherein the crosslinking agent comprises an aziridine crosslinking agent, and the adhesive binder comprises a swellable adhesive binder, wherein the swellable adhesive binder comprises a first structural unit derived from a vinyl aromatic monomer, a second structural unit derived from an alkyl (meth)acrylate, and a third structural unit derived from a phosphonate monomer.

[0032] According to one embodiment, the coating layer may be formed of a composition for a coating layer comprising the (meth)acrylic binder; the aziridine crosslinking agent; the carboxyalkyl cellulose or a salt thereof; the filler; and the adhesive binder.

[0033] According to one embodiment, the crosslinking agent may be a thermal crosslinking agent.

[0034] The above separator can improve the capacity of a battery by reducing salt precipitation and lowering resistance when applied to a battery by including a coating layer formed from the composition for the coating layer. The precipitated salt can cause a side reaction with the electrolyte, causing a short circuit in the secondary battery, thereby affecting the lifespan of the secondary battery and causing cell volume expansion, which can pose a safety issue.

[0035] In addition, the separator includes a coating layer formed of the composition for the coating layer, thereby reducing shrinkage in the electrolyte solution, thereby improving the safety and reliability of the battery.

[0036] According to one embodiment, the shrinkage rate of the separator in the electrolyte may be 20% or less, for example, 10% or less, and 5% or less in the machine direction (MD) and transverse direction (TD), respectively. Here, 'MD' and 'TD' are the same direction as the MD and TD of the porous substrate, respectively.

[0037] The above separator may have a bonding strength of the coating layer to the porous substrate of 2 gf / mm or more.

[0038] According to one embodiment, the separator may have a wet adhesion of 0.1 gf / mm or more.

[0039] A separator having a coating layer formed with a composition for a coating layer that includes the above (meth)acrylic binder but does not include an aziridine-based crosslinking agent as a crosslinking agent or contains a crosslinking agent other than an aziridine-based crosslinking agent may have increased salt precipitation and increased resistance when applied to a battery.

[0040] According to one embodiment, the aziridine-based crosslinking agent may be included in an amount of 95 wt% or more, for example, 98 to 100 wt%, or 100 wt%, of the total crosslinking agent in the composition for the coating layer.

[0041] A separator having a coating layer formed with a composition for a coating layer that includes the above aziridine-based crosslinking agent and the above filler, but does not include the above (meth)acrylic-based binder or contains a binder other than the above (meth)acrylic-based binder may not reach the shrinkage range in the electrolyte. According to one embodiment, the (meth)acrylic-based binder may be included in an amount of 95 wt% or more, for example, 98 to 100 wt%, or 100 wt%, of the total binder in the composition for a coating layer.

[0042] A separator having a coating layer formed of a composition for a coating layer that does not include carboxyalkyl cellulose or a salt thereof does not reach the shrinkage range in the electrolyte, and when applied to a battery, salt precipitation may increase and resistance may increase.

[0043] A separator having a coating layer formed with a composition for a coating layer having an adhesive binder other than the above-described adhesive binder as an adhesive binder may not reach the above-described substrate bonding strength and / or wet adhesive strength, or may have increased salt precipitation and increased resistance.

[0044] coating layer

[0045] The above coating layer is a heat-resistant adhesive layer.

[0046] The above binder comprises a (meth)acrylic binder comprising a first structural unit derived from (meth)acrylamide and a second structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0047] According to one embodiment, with respect to 100 mol% of the (meth)acrylic binder, the total of the first structural unit and the second structural unit may be included at 95 mol% or more, for example, 95 to 100 mol%, or 100 mol%.

[0048] The above (meth)acrylic binder may further include a third structural unit derived from (meth)acrylic acid or (meth)acrylate.

[0049] According to one embodiment, with respect to 100 mol% of the (meth)acrylic binder, the total of the first structural unit, the second structural unit, and the third structural unit may be included at 95 mol% or more, for example, 95 to 100 mol%, or 100 mol%.

[0050] The above (meth)acrylic binder is a water-based heat-resistant binder that can fix the filler on a porous substrate and provide adhesive strength so that the coating layer adheres well to the porous substrate and electrode, and can contribute to improving the heat resistance, air permeability, and oxidation resistance of the separator.

[0051] The first structural unit derived from the above (meth)acrylamide has an amide functional group (-(C=O)-NH2) within the structural unit. The -(C=O)-NH2 functional group can improve adhesive properties with a porous substrate and an electrode, and can more firmly fix inorganic particles within a coating layer by forming a hydrogen bond with the -OH functional group of the filler, thereby enhancing the heat resistance of the separator.

[0052] The second structural unit derived from the above (meth)acrylamidosulfonic acid or its salt can reduce the mobility of a binder including the bulky functional group and thereby enhance the heat resistance of the separation membrane.

[0053] The third structural unit derived from the above (meth)acrylic acid or (meth)acrylate can serve to fix the filler onto the porous substrate, while providing adhesiveness so that the coating layer adheres well to the porous substrate and the electrode, and can contribute to improving the heat resistance and air permeability of the separator. In addition, the structural unit derived from the above (meth)acrylic acid or (meth)acrylate can contribute to improving the dispersibility of the composition for the coating layer by including a carboxyl functional group (-C(=O)O-) within the structural unit.

[0054] The first structural unit is included in an amount of 55 mol% to 95 mol% based on 100 mol% of the (meth)acrylic binder, and may be included in an amount of, for example, 70 mol% to 95 mol%, 75 mol% to 95 mol%, 80 mol% to 95 mol%, or 80 mol% to 90 mol%.

[0055] The total of the second structural unit and the third structural unit may be included in an amount of 5 mol% to 45 mol%, for example, 5 mol% to 30 mol%, 5 mol% to 25 mol%, 5 mol% to 20 mol%, or 10 to 20 mol%, based on 100 mol% of the (meth)acrylic binder.

[0056] The second structural unit may be included in an amount of 0.1 to 45 mol%, for example, 5 to 45 mol%, 0.1 to 30 mol%, 0.1 to 20 mol%, for example, 0.1 to 10 mol%, 1 to 10 mol%, based on 100 mol% of the (meth)acrylic binder.

[0057] The third structural unit may be included in an amount of 0 to 30 mol%, 1 to 30 mol%, for example, 1 to 20 mol%, 1 to 10 mol%, 5 to 15 mol%, or 5 to 20 mol%, based on 100 mol% of the (meth)acrylic binder.

[0058] When the content of each structural unit is within the above range, the heat resistance and adhesive strength of the separator can be further improved.

[0059] The first structural unit derived from the above (meth)acrylamide can be represented by the following chemical formula 1.

[0060] [Chemical Formula 1]

[0061]

[0062] (In the above chemical formula 1,

[0063] R 1 and R 2 are each independently hydrogen or methyl group.)

[0064] The second structural unit derived from the above (meth)acrylamidosulfonic acid or a salt thereof may be a structural unit derived from (meth)acrylamidosulfonic acid or (meth)acrylamidosulfonate, and the (meth)acrylamidosulfonate may be a conjugate base of (meth)acrylamidosulfonic acid, a (meth)acrylamidosulfonate, or a derivative thereof. The structural unit derived from the above (meth)acrylamidosulfonic acid or (meth)acrylamidosulfonate may be represented by, for example, any one of the following chemical formulas 2, 3, 4, and combinations thereof.

[0065] [Chemical Formula 2]

[0066]

[0067] [Chemical Formula 3]

[0068]

[0069] [Chemical Formula 4]

[0070]

[0071] In the above chemical formulas 2 to 4,

[0072] R 10 , R 11 , R 12 , R 13 , R 14 , R 15 are each independently hydrogen or methyl group,

[0073] L 1 , L 2 , and L 3 are each independently a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group,

[0074] a, b and c are each independently an integer from 0 to 2, M is an alkali metal, and the alkali metal may be, for example, lithium, sodium, potassium, rubidium, or cesium.

[0075] For example, in the chemical formulas 2 to 4, L 1 , L 2 , and L 3 are each independently a substituted or unsubstituted C1 to C10 alkylene group, and a, b and c can each be 1.

[0076] The structural unit derived from the above (meth)acrylamidosulfonic acid or its salt may include a structural unit represented by the above chemical formula 2, a structural unit represented by the above chemical formula 3, and a structural unit represented by the above chemical formula 4, or may include two or more types thereof together. As an example, the structural unit represented by the above chemical formula 2 may be included, and as another example, the structural unit represented by the above chemical formula 2 and the structural unit represented by the above chemical formula 3 may be included together.

[0077] When the structural unit represented by the above chemical formula 2 and the structural unit represented by the above chemical formula 3 are included together, the structural unit represented by the above chemical formula 2 and the structural unit represented by the above chemical formula 3 may be included in a molar ratio of 10:1 to 1:2, preferably 5:1 to 1:1, and more preferably 3:1 to 1:1.

[0078] The sulfonate group in the structural unit derived from the above (meth)acrylamidosulfonic acid or a salt thereof may be, for example, a functional group derived from vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, anethole sulfonic acid, acrylamidoalkane sulfonic acid, sulfoalkyl (meth)acrylate, or a salt thereof. Here, the alkane may be a C1 to C20 alkane, a C1 to C10 alkane, or a C1 to C6 alkane, and the alkyl may be a C1 to C20 alkyl, a C1 to C10 alkyl, or a C1 to C6 alkyl. The salt refers to a salt composed of the above-mentioned sulfonic acid and an appropriate ion. The ion may be, for example, an alkali metal ion, in which case the salt may be a sulfonic acid alkali metal salt.

[0079] The above acrylamidoalkane sulfonic acid may be, for example, 2-acrylamido-2-methylpropane sulfonic acid.

[0080] The third structural unit derived from the above (meth)acrylic acid or (meth)acrylate can be represented by any one of the following chemical formulas 5, 6, 7, and combinations thereof.

[0081] [Chemical Formula 5]

[0082]

[0083] [Chemical Formula 6]

[0084]

[0085] [Chemical Formula 7]

[0086]

[0087] (In the above chemical formulas 5 to 7,

[0088] R 3 , R 4 , R 6 , R 7 , R 8 and R 9 are each independently hydrogen or methyl group,

[0089] R 5 is a substituted or unsubstituted C1 to C20 alkyl group,

[0090] M is an alkali metal).

[0091] The structural unit derived from the above (meth)acrylate may be derived from (meth)acrylic acid alkyl ester, (meth)acrylic acid perfluoroalkyl ester, and (meth)acrylate having a functional group in the side chain, and may be derived from (meth)acrylic acid alkyl ester, for example. In addition, the carbon number of the alkyl group or perfluoroalkyl group bonded to the noncarbonyl oxygen atom of the (meth)acrylic acid alkyl ester or (meth)acrylic acid perfluoroalkyl ester may be specifically 1 to 20, more specifically 1 to 10, and for example 1 to 5.

[0092] Specific examples of (meth)acrylic acid alkyl esters having 1 to 5 carbon atoms in the alkyl group or perfluoroalkyl group bonded to the non-carbonyl oxygen atom include acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, and t-butyl acrylate; 2-(perfluoroalkyl) ethyl acrylate such as 2-(perfluorobutyl) ethyl acrylate, and 2-(perfluoropentyl) ethyl acrylate; methacrylic acid alkyl esters such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and t-butyl methacrylate; And methacrylic acid-2-(perfluoroalkyl) ethyl, such as methacrylic acid-2-(perfluorobutyl) ethyl, methacrylic acid-2-(perfluoropentyl) ethyl, methacrylic acid-2-(perfluoroalkyl) ethyl, etc.

[0093] Other (meth)acrylic acid alkyl esters include acrylic acid alkyl esters having 6 to 18 carbon atoms in the alkyl group bonded to the noncarbonyl oxygen atom, such as n-hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, and isobornyl acrylate; methacrylic acid alkyl esters having 6 to 18 carbon atoms in the alkyl group bonded to the noncarbonyl oxygen atom, such as n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, and cyclohexyl methacrylate; 2-(perfluoroalkyl) ethyl acrylate having 6 to 18 carbon atoms in the perfluoroalkyl group bonded to a noncarbonyl oxygen atom, such as 2-(perfluorohexyl) ethyl acrylate, 2-(perfluorooctyl) ethyl acrylate, 2-(perfluorononyl) ethyl acrylate, 2-(perfluorodecyl) ethyl acrylate, 2-(perfluorododecyl) ethyl acrylate, 2-(perfluorotetradecyl) ethyl acrylate, and 2-(perfluorohexadecyl) ethyl acrylate; Examples of methacrylic acid-2-(perfluoroalkyl) ethyl compounds having 6 to 18 carbon atoms in the perfluoroalkyl group bonded to a non-carbonyl oxygen atom include methacrylic acid-2-(perfluorohexyl) ethyl compounds, methacrylic acid-2-(perfluorooctyl) ethyl compounds, methacrylic acid-2-(perfluorononyl) ethyl compounds, methacrylic acid-2-(perfluorodecyl) ethyl compounds, methacrylic acid-2-(perfluorododecyl) ethyl compounds, methacrylic acid-2-(perfluorotetradecyl) ethyl compounds, and methacrylic acid-2-(perfluorohexadecyl) ethyl compounds.

[0094] The structural unit derived from the above (meth)acrylic acid or (meth)acrylate or a salt thereof may each include a structural unit represented by the chemical formula 5, a structural unit represented by the chemical formula 6 and a structural unit represented by the chemical formula 7, or may include them together, and when included together, the structural unit represented by the chemical formula 5; and the structural unit represented by the chemical formula 6 and the structural unit represented by the chemical formula 7 may be included in a molar ratio of 10:1 to 1:1, preferably 6:1 to 1:1, and more preferably 3:1 to 1:1.

[0095] The above (meth)acrylic binder can be represented by, for example, the following chemical formula 8.

[0096] [Chemical Formula 8]

[0097]

[0098] In the above chemical formula 8,

[0099] R 1 , R 2 , R 12 , R 13 , R 16 , R 17 are each independently hydrogen or methyl group,

[0100] R 18 is OR or O - M + , R is hydrogen or a C1 to C6 alkyl group, M is an alkali metal,

[0101] L 2 is a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group,

[0102] b is an integer between 0 and 2,

[0103] M is an alkali metal,

[0104] l, m and n represent the molar ratio of each unit.

[0105] The alkali metal may be lithium, sodium, potassium, rubidium, or cesium.

[0106] For example, in the chemical formula 8, l+m+n=1. Also, as an example, 0.05≤(l+n)≤0.45, 0.55≤m≤0.95, and specifically 0 <l≤0.4, 및 0<n≤0.1일 수 있으며, 예를 들어 0.8≤m≤0.9, 0<l≤0.1, 및 0<n≤0.1, 예를 들어 0.8≤m≤0.9, 0.01≤l≤0.1, 및 0.01≤n≤0.1일 수 있다.

[0107] For example, in the chemical formula 8, L 2 is a substituted or unsubstituted C1 to C10 alkylene group, and b may be 1.

[0108] In the above (meth)acrylic binder, an alkali metal (M + ) may be present in an amount of 50 to 100 mol%, for example, 60 to 90 mol% or 70 to 90 mol%, based on 100 mol% of the total amount of (meth)acrylamidosulfonic acid structural units. When the above range is satisfied, the (meth)acrylic binder and the separator including the same may exhibit excellent adhesive strength, heat resistance, and oxidation resistance.

[0109] The (meth)acrylic binder may further include other units in addition to the aforementioned units. For example, the (meth)acrylic binder may further include a unit derived from an alkyl (meth)acrylate, a unit derived from a diene, a unit derived from a styrene, an ester group-containing unit, a carbonate group-containing unit, or a combination thereof.

[0110] The above (meth)acrylic binder may have various forms, such as an alternating polymer in which the units are alternately distributed, a random polymer in which the units are randomly distributed, or a graft polymer in which some structural units are grafted.

[0111] The weight average molecular weight of the (meth)acrylic binder may be 350,000 to 970,000, for example, 450,000 to 970,000, or 450,000 to 700,000. When the weight average molecular weight of the (meth)acrylic binder satisfies the above range, the (meth)acrylic binder and the separator including the same may exhibit excellent adhesive strength, heat resistance, and air permeability. The 'weight average molecular weight' may be a polystyrene-converted average molecular weight measured using gel permeation chromatography.

[0112] The above (meth)acrylic binder can be manufactured by various known methods such as emulsion polymerization, suspension polymerization, bulk polymerization, solution polymerization, or bulk polymerization.

[0113] The above (meth)acrylic binder can be manufactured by a solution polymerization method.

[0114] According to one embodiment, the (meth)acrylic binder may be included in the coating layer of the separator in the form of a film.

[0115] The (meth)acrylic binder may be included in an amount of 30 to 70 wt%, for example, 30 to 65 wt%, 40 to 65 wt%, of the total of the (meth)acrylic binder; the crosslinking agent; and the carboxyalkyl cellulose or its salt. Within the above range, the heat resistance characteristics in the electrolyte may be improved.

[0116] The above cross-linking agent includes an aziridine-based cross-linking agent.

[0117] The above aziridine-based crosslinking agent can crosslink the (meth)acrylic binder and at the same time facilitate the separator to reach the dry shrinkage rate and shrinkage rate in the electrolyte solution range.

[0118] The above aziridine cross-linking agent may be a bifunctional or higher aziridine cross-linking agent. Here, "bifunctional or higher" means that two or more aziridine groups are present in the molecule. According to one embodiment, the aziridine cross-linking agent may be a bifunctional or trifunctional aziridine cross-linking agent.

[0119] For example, the aziridine-based crosslinking agent may include at least one of N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-(methylenedi-p-phenylene)bis(aziridine-1-carboxamide), triethylenemelamine, 1,1-isophthaloyl bis(2-methylaziridine), tris(1-aziridinyl)phosphine oxide, N,N-hexamethylene-bis(aziridinecarboxamide), trimethylolpropane tris(2-methyl-1-aziridinepropionate), trimethylolpropane tris(beta-N-aziridinyl)propionate, and pentaerythritol tris(3-(1-aziridinyl)propionate).

[0120] The above crosslinking agent, for example, the aziridine-based crosslinking agent, should be included in an appropriate amount with respect to the binder, for example, the (meth)acrylic-based binder and the carboxyalkyl cellulose or its salt.

[0121] According to one embodiment, the crosslinking agent may be included in an amount of 5 to 30 wt%, for example, 10 to 30 wt%, 10 to 20 wt%, of the total of the (meth)acrylic binder; the crosslinking agent; and the carboxyalkyl cellulose or its salt. Within this range, the heat resistance in the electrolyte may be improved.

[0122] The crosslinking agent, for example, the aziridine-based crosslinking agent, should be included in an appropriate amount relative to the binder, for example, the (meth)acrylic binder. For example, the crosslinking agent may be included in an amount of 5 to 50 wt%, for example, 10 to 50 wt%, 20 to 50 wt%, or 10 to 40 wt% relative to the (meth)acrylic binder. Within the above range, the heat resistance effect may be improved.

[0123] The above carboxyalkyl cellulose or its salt has a cyclic structure within the molecule and a carboxyl group within the molecule. It can react with the crosslinking agent, thereby increasing the modulus of the coating layer and facilitating further reduction of the dry shrinkage rate and shrinkage rate in the electrolyte solution.

[0124] The above carboxyalkyl cellulose may be, for example, carboxymethyl cellulose.

[0125] The salt of the above carboxyalkyl cellulose may be a salt of carboxyalkyl cellulose, for example, a carboxyalkyl cellulose monovalent metal salt, for example, a carboxyalkyl cellulose sodium salt, etc.

[0126] The above carboxyalkyl cellulose or its salt should be included in an appropriate amount with respect to the binder, for example, the (meth)acrylic binder, and the crosslinking agent.

[0127] According to one embodiment, the carboxyalkyl cellulose or its salt may be included in an amount of 20 to 70 wt%, for example, 20 to 65 wt%, 20 to 50 wt%, or 25 to 50 wt%, of the total of the (meth)acrylic binder; the crosslinking agent; and the carboxyalkyl cellulose or its salt. Within this range, the heat resistance characteristics in the electrolyte may be improved.

[0128] The above filler may include a filler having a particle size D100 of 0.7 μm or less. Within the above range, when combined with the (meth)acrylic binder, the crosslinking agent, and the carboxyalkyl cellulose or its salt, it may be easy to achieve the dry shrinkage ratio and the shrinkage ratio in the electrolyte. For example, the filler may have a particle size D100 of 0.1 to 0.7 μm, or 0.5 to 0.7 μm.

[0129] According to one embodiment, the filler may have a particle size D50 of 0.4 μm or less, for example, 0.35 μm or less, 0.3 μm or less, or 0.1 to 0.3 μm. Within this range, the heat resistance characteristics may be improved.

[0130] According to one embodiment, the filler having a particle size D100 of 0.7 μm or less may be included in an amount of 95 wt% or more, for example, 95 to 100 wt%, 98 to 100 wt%, or 100 wt%, of the total filler in the coating layer. Within the above range, the effect of the present separation membrane may be easily realized.

[0131] In one embodiment, the filler may be surface-modified, but may not be surface-modified. Preferably, the filler may be surface-modified.

[0132] The filler may be, for example, an inorganic filler, an organic filler, an organic-inorganic composite filler, or a combination thereof. The inorganic filler may be a ceramic material capable of improving heat resistance. The inorganic filler may include, for example, a metal oxide, a metalloid oxide, a metal fluoride, a metal hydroxide, or a combination thereof. The inorganic filler may include, but is not limited to, Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, or a combination thereof. The organic filler may include, but is not limited to, an acrylic compound, an imide compound, an amide compound, or a combination thereof. The organic filler may have a core-shell structure, but is not limited thereto. For example, the filler may be preferably boehmite.

[0133] The above filler may be spherical, plate-shaped, cubic, or amorphous. Preferably, the filler may be cubic, and the cubic filler may have a significantly lower shrinkage rate as described above.

[0134] The above filler should be included in an appropriate amount relative to the binder, for example, the (meth)acrylic binder. According to one embodiment, the (meth)acrylic binder: the filler may be included in a mass ratio of 1:10 to 1:50, for example, a mass ratio of 1:20 to 1:30. Within the above range, the heat resistance characteristics in the electrolyte may be improved.

[0135] The filler may be included in an amount of 50 wt% to 99 wt% of the total weight of the coating layer, for example, 70 wt% to 99 wt%, for example, 75 wt% to 99 wt%, for example, 80 wt% to 99 wt%, for example, 85 wt% to 99 wt%, for example, 90 wt% to 99 wt%, for example, 95 wt% to 99 wt%. When the filler is included in the above range, excellent heat resistance, durability, oxidation resistance, and stability may be exhibited.

[0136] The above coating layers may each have a thickness of 0.01 μm to 20 μm, and within the above range may have a thickness of 1 μm to 10 μm, or 1 μm to 5 μm, or 1 μm to 3 μm.

[0137] The ratio of the thickness of the coating layer to the thickness of the porous substrate may be 0.05 to 0.5, for example, 0.05 to 0.4, or 0.05 to 0.3, or 0.1 to 0.2. In the above range, the separator may exhibit excellent air permeability, heat resistance, and adhesive strength. Here, the 'thickness of the coating layer' means the thickness of one coating layer when the coating layer is formed on only one side of the porous substrate, and means the thickness of the entire two coating layers when the coating layers are formed on both sides of the porous substrate.

[0138] The above adhesive binder is a swellable adhesive binder. Since the above swellable adhesive binder is a binder with excellent heat resistance and adhesive strength, the coating layer can harmoniously exhibit heat resistance and adhesive strength with a single layer.

[0139] Within the above coating layer, the swellable adhesive binder may be distributed relatively more in the upper portion of the coating layer, and the crosslinked product of the (meth)acrylic binder, filler, and aziridine-based crosslinking agent may be distributed relatively more in the lower portion. This is due to the difference in particle size D50 of the swellable adhesive binder and the density of the swellable adhesive binder and the filler.

[0140] However, the relative distribution of the swellable adhesive binder and the filler within the coating layer is different, and they do not completely phase separate. Accordingly, the coating layer is distinguished from a coating layer having a multilayer structure of two or more layers.

[0141] Commonly known adhesive binders can only develop wet adhesion under high temperature and high pressure conditions.

[0142] However, square lithium secondary batteries are manufactured by inserting a jelly roll containing a stack of positive electrode / separator / negative electrodes into a square can and then injecting an electrolyte. High temperature and high pressure conditions cannot be applied during and / or after the manufacturing process. Therefore, when commonly known binders are applied to square lithium secondary batteries, wet adhesive strength is not ensured.

[0143] On the other hand, the above-mentioned swellable adhesive binder can exhibit wet adhesive strength even under low temperature and low pressure conditions, as it includes a first structural unit derived from a vinyl aromatic monomer; a second structural unit derived from an alkyl (meth)acrylate; and a third structural unit derived from a phosphonate monomer.

[0144] According to one embodiment, the separator can secure a wet adhesion between the separator and the negative electrode of 0.05 gf / mm or more, for example, 0.05 to 0.5 gf / mm, after undergoing a low-temperature and low-pressure process. Through this, the separator can improve the high-temperature charge / discharge and / or storage characteristics of a lithium secondary battery.

[0145] Accordingly, a separator according to one embodiment can secure wet adhesion even under low temperature and low pressure conditions during a manufacturing process (e.g., a formation process) of a square lithium secondary battery.

[0146] The first structural unit derived from the above vinyl aromatic monomer can be represented by the following chemical formula 9.

[0147] The second structural unit derived from the above alkyl (meth)acrylate can be represented by the following chemical formula 10.

[0148] The third structural unit derived from the above phosphonate monomer can be represented by the following chemical formula 11.

[0149] [Chemical Formula 9]

[0150]

[0151] [Chemical Formula 10]

[0152]

[0153] [Chemical Formula 11]

[0154]

[0155] The description of the above chemical formulas 9 to 11 is as follows:

[0156] R 19 , R 20 , R 22 , R 23 , R 25 and R 26 Each independently may be hydrogen or a C1 to C6 alkyl group. For example, R 19 , R 20 , R 22 , R 23 , R 25 and R 26 can be hydrogen or methyl group.

[0157] R 21It may be a fluorine, a substituted or unsubstituted C1 to C6 alkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C1 to C6 alkenyl group.

[0158] R 24 may be a substituted or unsubstituted C1 to C20 alkyl group. For example, R 24 is a branched-chain substituted or unsubstituted C1 to C20 alkyl group, which may be an ethylhexyl group.

[0159] L 1 It may be a substituted or unsubstituted C1 to C6 alkylene group, a substituted or unsubstituted C3 to C10 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a combination thereof.

[0160] L 2 may be a carboxyl group (-C(=O)O-), a carbonyl group (-C(=O)-), an ether group (-O-), a substituted or unsubstituted C1 to C6 alkylene group, a substituted or unsubstituted C3 to C10 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a combination thereof. For example, L 2 may be a carboxyl group (-C(=O)O-).

[0161] L 3 It can be a carboxyl group (-C(=O)O-), a carbonyl group (-C(=O)-), an ether group (-O-), a substituted or unsubstituted C1 to C6 alkylene group, a substituted or unsubstituted C3 to C10 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a combination thereof. For example, L 3 may be a substituted or unsubstituted C1 to C6 alkylene group or methylene group.

[0162] R 27 , R 28 Each of R may independently be a substituted or unsubstituted C1 to C10 alkoxy group, or a substituted or unsubstituted C6 to C20 aryloxy group. For example, R27 , R 28 All of them can be substituted or unsubstituted C1 to C10 alkoxy groups or methoxy groups.

[0163] a, c, and d can each independently be an integer from 0 to 2, and b can be an integer from 0 to 5. For example, a can be 0, b can be 0, c can be 1, and d can be 1.

[0164] The above-mentioned swellable adhesive binder is in particle form and can maintain the particle form without dissolving in an aqueous solvent.

[0165] For example, the swellable adhesive binder may be a particle having a core-shell structure. The particle having a core-shell structure may be advantageous in securing an appropriate particle diameter D50 and swelling degree.

[0166] The components of the core are not particularly limited and may be, for example, (meth)acrylic polymers, diene polymers, or mixtures or copolymers thereof. For example, the core may be a copolymer of one or more of alkyl (meth)acrylates and vinyl aromatic monomers.

[0167] The shell may include a first structural unit derived from the vinyl aromatic monomer; a second structural unit derived from an alkyl (meth)acrylate; and a third structural unit derived from a phosphonate monomer.

[0168] According to one embodiment, with respect to 100 wt% of the shell, the first structural unit may be included in an amount of 40 to 90 wt%, or 50 to 80 wt%, the second structural unit in an amount of 5 to 40 wt%, or 10 to 30 wt%, and the third structural unit in an amount of 0.1 to 20 wt%, or 5 to 20 wt%. In the above range, the coating layer may implement excellent adhesive strength even with a thin thickness without lowering the heat resistance of the separator.

[0169] The particle size D50 of the above-mentioned swellable adhesive binder may be 0.1 µm to 1 µm, 0.2 µm to 0.9 µm, 0.2 µm to 0.8 µm, or 0.2 µm to 0.7 µm. Within the above range, the coating layer can achieve excellent adhesive strength even with a thin thickness without lowering the heat resistance of the separator.

[0170] The glass transition temperature of the above-mentioned swellable adhesive binder may be 60°C to 120°C, 60°C to 90°C, or 60°C to 75°C. In the above range, the swellable adhesive binder is advantageous in exhibiting wet adhesive strength even under low temperature and low pressure conditions, and the coating layer can exhibit excellent adhesive strength even with a thin thickness without lowering the heat resistance of the separator.

[0171] The above-mentioned swellable adhesive binder can expand 2 to 1000 times, 3 to 1000 times, or 6 to 1000 times compared to its initial volume after being left at 60°C for 72 hours. In the above range, the swellable adhesive binder is advantageous in exhibiting wet adhesive strength even under low temperature and low pressure conditions, and the coating layer can implement excellent adhesive strength even with a thin thickness without lowering the heat resistance and air permeability of the separator. The electrolyte composition is according to the embodiment.

[0172] The weight average molecular weight of the above swellable adhesive binder may be 100,000 g / mol to 800,000 g / mol, or 300,000 g / mol to 500,000 g / mol.

[0173] The above-mentioned swelling adhesive binder should be included in an appropriate amount with respect to the above-mentioned binder, for example, the above-mentioned (meth)acrylic binder.

[0174] According to one embodiment, the swellable adhesive binder may be included in an amount of 5 to 50 wt%, for example 10 to 40 wt%, for example 10 to 30 wt% or 10 to 20 wt%, based on the content of the (meth)acrylic binder. Within this range, there may be an effect of improving the yield in the electrolyte.

[0175] porous substrate

[0176] The porous substrate may be a substrate having a plurality of pores and typically used in electrochemical devices. The porous substrate may be, but is not limited to, a polymer selected from the group consisting of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon, and polytetrafluoroethylene, or a polymer film formed of a copolymer or mixture of two or more thereof.

[0177] The porous substrate may be, for example, a polyolefin-based substrate including polyolefin, and the polyolefin-based substrate may have an excellent shutdown function, thereby contributing to improved battery safety. The polyolefin-based substrate may be selected from, for example, a polyethylene single film, a polypropylene single film, a polyethylene / polypropylene bilayer film, a polypropylene / polyethylene / polypropylene triple film, and a polyethylene / polypropylene / polyethylene triple film. In addition, the polyolefin-based resin may include a non-olefin resin in addition to an olefin resin, or may include a copolymer of an olefin and a non-olefin monomer.

[0178] The porous substrate may have a thickness of 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, or 5 μm to 15 μm.

[0179] According to one embodiment, a separator for a lithium secondary battery may exhibit excellent air permeability, and may have an air permeability value of, for example, less than 200 sec / 100cc, for example, less than 190 sec / 100cc, or less than 180 sec / 100cc. That is, it may have an air permeability value of less than 40 sec / 100cc·1㎛ per unit thickness, for example, less than 30 sec / 100cc·1㎛ or less, or less than 25 sec / 100cc·1㎛. Here, air permeability refers to the time (in seconds) it takes for 100cc of air to permeate the unit thickness of the separator. The air permeability per unit thickness can be obtained by measuring the air permeability for the entire thickness of the separator and then dividing by the thickness. The air permeability can be measured by measuring the time (in seconds) it takes for 100cc of air to permeate using an air permeability measuring device (Asahi Seiko, EG01-55-1MR).

[0180] A secondary battery separator according to one embodiment can be formed by applying a composition for forming a coating layer to one or both sides of a porous substrate, drying the composition, and then curing the composition. The curing can be performed using a conventional method known to those skilled in the art.

[0181] Figure 1 is a cross-sectional view showing a separator for a lithium secondary battery according to one embodiment.

[0182] Referring to FIG. 1, a separator for a lithium secondary battery includes a porous substrate 1 and a coating layer 2 positioned on both sides of the porous substrate 1. The coating layer 2 may include a filler 3; a (meth)acrylic binder, a crosslinked product 4 of carboxyalkyl cellulose or a salt thereof and a crosslinking agent; and an adhesive binder 6.

[0183] lithium secondary battery

[0184] Another embodiment provides a lithium secondary battery comprising a separator for a lithium secondary battery according to one embodiment; a positive electrode; and a negative electrode. The separator for a lithium secondary battery refers to the content described above. The separator for a lithium secondary battery can be positioned between the positive electrode and the negative electrode.

[0185] A positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer includes a positive electrode active material and may further include a binder and / or a conductive material. For example, the positive electrode may further include an additive that can function as a sacrificial positive electrode.

[0186] A compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used as a cathode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0187] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxide, lithium cobalt-based oxide, lithium manganese-based oxide, lithium iron phosphate-based compound, cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0188] As an example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-αD α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8).

[0189] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0190] For example, the cathode active material may be a high-nickel cathode active material in which the nickel content is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more and 99 mol% or less, based on 100 mol% of metals excluding lithium in the lithium transition metal composite oxide. The high-nickel cathode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0191] The content of the positive electrode active material may be 90 wt% to 99.5 wt% of 100 wt% of the positive electrode active material layer, and the contents of the binder and conductive material may be 0.5 wt% to 5 wt%, respectively, with respect to 100 wt% of the positive electrode active material layer.

[0192] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0193] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc. and in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0194] Al may be used as the above current collector, but is not limited thereto.

[0195] A negative electrode for a lithium secondary battery includes a current collector and a negative electrode active material layer positioned on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0196] For example, the negative electrode active material layer may include 90 to 99 wt% of the negative electrode active material, 0.5 to 5 wt% of the binder, and 0 to 5 wt% of the conductive material.

[0197] The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0198] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0199] As the above lithium metal alloy, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0200] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), a Si-Q alloy (wherein Q is selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0201] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the composite may include secondary particles (cores) in which silicon primary particles are assembled and an amorphous carbon coating layer (shell) positioned on the surface of the secondary particles. The amorphous carbon may also be positioned between the silicon primary particles, such that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed and present in an amorphous carbon matrix.

[0202] The silicon-carbon composite may further comprise crystalline carbon. For example, the silicon-carbon composite may comprise a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core.

[0203] The above Si-based negative electrode active material or Sn-based negative electrode active material can be used in a mixture with a carbon-based negative electrode active material.

[0204] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0205] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0206] The above-mentioned aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0207] When using an aqueous binder as the above-mentioned negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li.

[0208] The above dry binder is a polymeric material capable of being fiberized, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0209] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials in the form of metal powder or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0210] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0211] Lithium secondary batteries may further contain electrolyte.

[0212] An electrolyte for a lithium secondary battery may include a non-aqueous organic solvent and a lithium salt.

[0213] The above non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0214] The above non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0215] As the above carbonate solvent, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be used.

[0216] Ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone.

[0217] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. In addition, examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol, and examples of aprotic solvents that can be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0218] The above non-aqueous organic solvents can be used alone or in combination of two or more.

[0219] In addition, when using a carbonate solvent, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0220] The above lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), lithium bis(oxalato)borate (LiBOB).

[0221] Lithium secondary batteries can be classified into cylindrical, square, pouch, coin, etc. types according to their shapes. FIGS. 2 to 5 are schematic diagrams illustrating lithium secondary batteries according to one embodiment. FIG. 2 can be said to be a cylindrical battery type, FIG. 3 a square battery type, and FIGS. 4 and 5 a pouch-type battery type. Referring to FIGS. 2 to 5, a lithium secondary battery (100) may include an electrode assembly (40) having a separator (30) interposed between a positive electrode (10) and a negative electrode (20), and a case (50) in which the electrode assembly (40) is built. The positive electrode (10), the negative electrode (20), and the separator (30) may be impregnated with an electrolyte (not shown). The lithium secondary battery (100) may include a sealing member (60) that seals the case (50) as shown in FIG. 1. In addition, in FIG. 3, the lithium secondary battery (100) may include a positive lead tab (11), a positive terminal (12), a negative lead tab (21), and a negative terminal (22). As in FIGS. 4 and 5, the lithium secondary battery (100) may include electrode tabs (70), i.e., a positive tab (71) and a negative tab (72), which serve as electrical paths for inducing current formed in the electrode assembly (40) to the outside.

[0222] A lithium secondary battery according to one embodiment of the present invention can be applied to automobiles, mobile phones, and / or various types of electrical devices, but the present invention is not limited thereto.

[0223]

[0224] Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0225]

[0226] Manufacturing Example 1

[0227] In a 10 L four-necked flask equipped with a stirrer, thermometer and condenser, distilled water (6361 g), acrylic acid (1.0 mol), acrylamide (8.5 mol), potassium persulfate (2.7 g, 0.01 mol), 2-acrylamido-2-methylpropanesulfonic acid (0.5 mol) and 5 N lithium hydroxide aqueous solution (1.05 equivalents based on the total amount of 2-acrylamido-2-methylpropanesulfonic acid) are added, and then the internal pressure is reduced to 10 mmHg using a diaphragm pump, and the operation of returning the internal pressure to atmospheric pressure with nitrogen is repeated three times.

[0228] The reaction is carried out for 12 hours while the temperature of the reaction solution is controlled to stabilize between 65°C and 70°C. After cooling to room temperature, the pH of the reaction solution is adjusted to 7 to 8 using a 25% ammonia aqueous solution.

[0229] Poly(acrylic acid-co-acrylic acid lithium salt-co-acrylamide-co-2-acrylamido-2-methylpropanesulfonic acid lithium salt) was prepared in this manner. The molar ratio of acrylic acid + acrylic acid lithium salt, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid lithium salt was 10:85:5. About 10 mL of the reaction solution (reaction product) was taken, and the nonvolatile component was measured, and it was 9.5 wt% (theoretical value: 10 wt%).

[0230] Manufacturing Example 2

[0231] An acrylic binder was prepared in the same manner as in Preparation Example 1, except that acrylamide and 2-acrylamido-2-methylpropanesulfonic acid were used, and acrylic acid was not used. The molar ratio of acrylamide and acrylamido-2-methylpropanesulfonic acid was 74:26. ​​The nonvolatile component of the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0232] Example 1

[0233] (1) Manufacture of adhesive binder

[0234] A core-shell swellable adhesive binder having a D50 particle size of 0.5 μm, a glass transition temperature of 65°C, and a swelling ratio of 8 is prepared. In the swellable adhesive binder, the core comprises a copolymer of alkyl acrylate and divinylbenzene, and the shell comprises a core-shell copolymer of 70 wt% of styrene, 20 wt% of 2-ethylhexyl methacrylate, and 10 wt% of dimethyl[(acryloyloxy)methyl]phosphonate.

[0235] The above swelling degree refers to the degree of expansion compared to the initial volume after leaving the swellable adhesive binder in an electrolyte at 60°C for 72 hours. The electrolyte is a mixed solution of ethyl carbonate: ethyl methyl carbonate: diethyl carbonate containing LiPF6 at a concentration of 1.3 M.

[0236] (2) Manufacturing of membrane

[0237] The acrylic binder (10 wt% in distilled water) manufactured in Manufacturing Example 1 and boehmite (particle size D100: 0.5 ㎛, particle size D50: 0.2 ㎛, cubic type) as a filler were mixed at a mass ratio of acrylic binder:filler = 1:20 based on solid content, and then added to a water solvent, milled and dispersed using a bead mill at 25°C for 30 minutes to prepare a dispersion.

[0238] To the above dispersion, trimethylolpropane tris(2-methyl-1-aziridinepropionate) (a trifunctional aziridine crosslinking agent), carboxymethylcellulose (CMC), and a crosslinked polymethylmethacrylate polymer (crosslinked PMMA, particle size D50: 0.5 μm) as an adhesive binder were added, and water was added so that the total solid content became 20 wt%, thereby preparing a composition for a coating layer. At this time, the acrylic binder: carboxymethylcellulose: and the aziridine crosslinking agent were included in the amount of 45 parts by weight: 45 parts by weight: 10 parts by weight out of a total of 100 parts by weight. At this time, the loading amount of the adhesive binder was calculated as the weight of the swellable adhesive binder included per unit area with respect to the surface of the electrode plate (the surface of the coating layer) and was 0.05 g / m 2This was included to make it happen.

[0239] The composition for forming the coating layer was coated on both sides of a polyethylene film (thickness: 8 ㎛, SK, air permeability: 120 sec / 100 cc, puncture strength: 480 kgf) as a porous substrate to a thickness of 1.5 ㎛ by die-coating, and then dried and aged in an oven at 80°C for 16 hours to form a coating layer, thereby manufacturing a separator for a lithium secondary battery in which a coating layer was formed on each side of the porous substrate.

[0240]

[0241] Examples 2 to 6

[0242] A separator was manufactured in the same manner as in Example 1, except that the composition for the coating layer and the loading amount of the adhesive layer were changed as in Table 1 below.

[0243]

[0244] Example 7

[0245] A separator was manufactured in the same manner as in Example 1, except that the binder of Manufacturing Example 2 was used instead of the acrylic binder of Manufacturing Example 1.

[0246]

[0247] Comparative Examples 1 to 5

[0248] A separator was manufactured in the same manner as in Example 1, except that the composition for the coating layer was changed as in Table 1 below.

[0249]

[0250] Bonding force (unit: gf / mm)

[0251] The test was conducted according to Korean Industrial Standard KS-A-01107 (Testing Methods for Adhesive Tapes and Adhesive Sheets). Each of the separators manufactured in the above Examples and Comparative Examples was cut to a width of 25 mm and a length of 250 mm, and tape (nitto 31B) was attached to both sides to make a specimen. Then, the specimen was compressed by reciprocating once at a speed of 300 mm / min using a compression roller with a load of 2 kg. After 30 minutes of compression, the specimen was flipped 180°, and approximately 25 mm was peeled off. The separator and the tape attached to one side of the separator were fixed to the upper clip of a tensile strength tester (Instron Series 1X / s Automated Materials Tester-3343, Instron). The tape attached to the other side of the separator was fixed to the lower clip, and then pulled at a tensile speed of 60 mm / min to measure the pressure when the porous adhesive layer was peeled off from the porous substrate.

[0252] Wet adhesion (unit: gf / mm)

[0253] The separator for lithium secondary batteries of the examples and comparative examples is cut into a size of 3 cm × 8 cm to prepare a sample.

[0254] A cathode slurry was prepared by mixing 97 wt% LiCoNiAl as a cathode active material, 1.5 wt% carbon nanotubes as a conductive material, and 1.5 wt% polyvinylidene fluoride as a binder, and adding water. The prepared cathode slurry was applied to aluminum foil, dried, and rolled to prepare a cathode.

[0255] A slurry of negative active material was prepared by mixing 97.4 wt% of negative active material, 1.0 wt% of carboxymethyl cellulose, 1.5 wt% of styrene-butadiene rubber as a binder, and 0.1 wt% of carbon nanotubes as a conductive material. A silicon-based negative active material was used as the negative active material. The prepared negative electrode slurry was applied to copper foil, dried, and rolled to prepare a negative electrode.

[0256] One sheet of the above sample was placed between the positive and negative electrodes, and the stack of positive electrode-sample-negative electrode was placed in a pouch. 2.5 g of electrolyte (ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio) containing 1.5 M LiPF6 dissolved therein) was injected, sealed, and left at 25°C for 12 hours. Then, it was left to stand for 2 hours in an environment with a pressure of 200 kgf in a 50°C chamber. After separating the separator from the negative electrode plate by about 10 to 20 mm in the above sample, the separator was fixed to the upper grip, and the negative electrode plate was fixed to the lower grip with a gap of 20 mm between the grips, and then peeled by pulling in the 180° direction. The peeling speed was 20 mm / min, and the force required to peel 40 mm after the start of peeling was measured three times and the average value was obtained. The average of the measured values ​​was used for calculation.

[0257] Shrinkage in electrolyte (unit: %)

[0258] A sample is prepared by cutting the separator for a lithium secondary battery of the examples and comparative examples into a size of 8 cm × 8 cm. A square of size 5 cm × 5 cm is drawn on the surface of the sample.

[0259] A cathode slurry was prepared by mixing 97 wt% LiCoNiAl as a cathode active material, 1.5 wt% carbon nanotubes as a conductive material, and 1.5 wt% polyvinylidene fluoride as a binder, and adding water.

[0260] The manufactured positive electrode slurry was applied to aluminum foil, dried, and rolled to manufacture a positive electrode.

[0261] A slurry of negative active material was prepared by mixing 97.4 wt% of negative active material, 1.0 wt% of carboxymethyl cellulose, 1.5 wt% of styrene-butadiene rubber as a binder, and 0.1 wt% of carbon nanotubes as a conductive material. A silicon-based negative active material was used as the negative active material. The prepared negative electrode slurry was applied to copper foil, dried, and rolled to prepare a negative electrode.

[0262] One sheet of the sample was placed between the positive and negative electrodes, and three sets of positive electrode-sample-negative electrode laminates were made, which were then placed in a pouch. 3 g of electrolyte (1.5 M LiPF6 dissolved in ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (volume ratio 30:50:20)) was injected to completely saturate the laminate with the electrolyte, seal it, and leave it at 25°C for 12 hours. Then, after leaving it in an oven at 150°C for 1 hour, the sample was taken out, and the dimensions of the sides of the drawn rectangle were measured to calculate the shrinkage ratio in the mechanical direction (MD) and the vertical direction (transverse direction, TD). The shrinkage ratio is calculated according to the following mathematical equation 1.

[0263] [Mathematical Formula 1]

[0264] Shrinkage = (L0 - L1) / L0 x 100

[0265] (L0 is the initial length of the membrane, L1 is the length of the membrane after leaving it at 150℃ for 1 hour)

[0266] Cell characteristics

[0267] Salt deposition measurement (unit: %): Jelly rolls are assembled using the separators of the examples and comparative examples, and the anode and cathode described above. After n cycles, the jelly rolls are disassembled. Photographs of the disassembled plates are taken, and the salt deposition area ratio (the ratio of the area of ​​the deposited salt to the unit area of ​​the plate) confirmed in the photographs is calculated using a computer program.

[0268] Resistance measurement (DC-IR, unit: Ω): Assemble the coin cell using the separator. The assembly order is bottom-separator-gasket-spacer-spring-cap. The electrolyte is 1.15M LiPF6EC / EMC / DMC=2 / 4 / 4 VCR-01 (1%), VC (1.5%), VEC (0.5%) or 1.5M LiPF6EC / EMC / DMC=2 / 1 / 7 FEC(12.5%) LiBF4(0.2%) LiBOB(1.0%) AB43(1.0%) SN(0.25%) OA-1300(0.5%), and inject 2.5g. Let it sit for 24 hours to ensure that the separator is sufficiently saturated with the electrolyte. Measure the impedance using the manufactured coin cell and calculate the resistance of one separator.

[0269] Coating layer Binder 1 Binder 2 Crosslinker Binder 1 / Binder 2 / Crosslinker Adhesive Binder Loading amount Example 1 Manufacturing example 1 CMC Aziridine 45 / 45 / 10 Core shell 0.05 Example 2 Manufacturing example 1 CMC Aziridine 55 / 35 / 10 Core shell 0.05 Example 3 Manufacturing example 1 CMC Aziridine 65 / 25 / 10 Core shell 0.05 Example 4 Manufacturing example 1 CMC Aziridine 45 / 45 / 10 Core shell 0.1 Example 5 Manufacturing example 1 CMC Aziridine 45 / 45 / 10 Core shell 0.2 Example 6 Manufacturing example 1 CMC Aziridine 45 / 45 / 10 Core shell 0.3 Example 7 Manufacturing Example 2 CMC Aziridine 45 / 45 / 10 Core Shell 0.05 Comparative Example 1 Manufacturing Example 1 XX 100 / 0 / 0 Core Shell 0.05 Comparative Example 2 Manufacturing Example 1 X Aziridine 90 / 0 / 10 Core Shell 0.05 Comparative Example 3 Manufacturing Example 1 CMC Aziridine 35 / 55 / 10 Core Shell 0.05 Comparative Example 4 Manufacturing Example 1 CMC Aziridine 25 / 65 / 10 Core Shell 0.05 Comparative Example 5 Manufacturing Example 1 CMC Aziridine 45 / 45 / 10 X-

[0270] *CMC: Carboxymethylcellulose

[0271] Base Bonding StrengthWet AdhesionShrinkage in ElectrolyteCell CharacteristicsMDTD Salt DepositionDC-IRExample 12.230.1550.181.23Example 22.120.1110150.31.28Example 32.270.1118200.351.26Example 42.890.1534.50.211.31Example 54.540.19680.241.29Example 65.650.238110.261.31Example 72.260.11450.211.26Comparative Example 12.140.143470.711.29Comparative Example 22.310.137400.681.34Comparative Example 31.970.151570.881.42Comparative example 41.890.153581.021.38Comparative example 50.7501371.213.21

[0272]

[0273] As shown in Table 2 above, the lithium secondary battery separator of the embodiment can improve the capacity of the battery by reducing salt precipitation and lowering resistance when applied to the battery. In addition, the lithium secondary battery separator can improve the safety and reliability of the battery by providing high substrate bonding strength, high wet adhesion, and low shrinkage in the electrolyte.

[0274]

[0275] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. A porous substrate; comprising a coating layer positioned on at least one surface of the porous substrate; The above coating layer comprises a binder; a crosslinking agent; and a crosslinked product of carboxyalkyl cellulose or its salt; a filler; and an adhesive binder. The above binder comprises a (meth)acrylic binder comprising a first structural unit derived from (meth)acrylamide and a second structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof, The above cross-linking agent includes an aziridine-based cross-linking agent, The above carboxyalkyl cellulose or its salt is included in an amount of 20 to 50 wt% of the total of the (meth)acrylic binder; the crosslinking agent; and the above carboxyalkyl cellulose or its salt. A separator for a lithium secondary battery, wherein the adhesive binder comprises a swellable adhesive binder, and the swellable adhesive binder comprises a first structural unit derived from a vinyl aromatic monomer, a second structural unit derived from an alkyl (meth)acrylate, and a third structural unit derived from a phosphonate monomer.

2. A separator for a lithium secondary battery, wherein the coating layer is formed of a composition comprising the (meth)acrylic binder, the crosslinking agent, the carboxyalkyl cellulose or a salt thereof, the filler, and the adhesive binder.

3. A separator for a lithium secondary battery, wherein the carboxyalkyl cellulose or salt thereof in claim 1 or 2 comprises carboxymethyl cellulose or a salt thereof.

4. A separator for a lithium secondary battery according to any one of claims 1 to 3, wherein the aziridine-based crosslinking agent comprises at least one of N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-(methylenedi-p-phenylene)bis(aziridine-1-carboxamide), triethylenemelamine, 1,1-isophthaloyl bis(2-methylaziridine), tris(1-aziridinyl)phosphine oxide, N,N-hexamethylene-bis(aziridinecarboxamide), trimethylolpropane tris(2-methyl-1-aziridinepropionate), trimethylolpropane tris(beta-N-aziridinyl)propionate, and pentaerythritol tris(3-(1-aziridinyl)propionate).

5. A separator for a lithium secondary battery, wherein the filler comprises a filler having a particle diameter D100 of 0.7 ㎛ or less in any one of claims 1 to 4.

6. A separator for a lithium secondary battery, wherein the filler is spherical, plate-shaped, cubic, or amorphous in any one of paragraphs 1 to 5.

7. A separator for a lithium secondary battery, wherein the (meth)acrylic binder and the filler are included in a mass ratio of 1:10 to 1:50 in any one of claims 1 to 6.

8. A separator for a lithium secondary battery, wherein the (meth)acrylic binder; the crosslinking agent; and the carboxyalkyl cellulose or salt thereof are included in a total amount of 30 to 70 wt%, the crosslinking agent is included in a total amount of 5 to 30 wt%, and the carboxyalkyl cellulose or salt thereof is included in a total amount of 20 to 50 wt% in any one of the preceding claims.

9. In any one of claims 1 to 8, in the (meth)acrylic binder, the first structural unit is represented by the following chemical formula 1: [Chemical Formula 1] (In the above chemical formula 1, R 1 , R 2 are each independently hydrogen or methyl group), A separator for a lithium secondary battery, wherein the second structural unit in the above (meth)acrylic binder is represented by any one of the following chemical formulas 2, 3, 4, and combinations thereof: [Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4] In the above chemical formulas 2 to 4, R 10 , R 11 , R 12 , R 13 , R 14 , R 15 are each independently hydrogen or methyl group, L 1 , L 2 , and L 3 are each independently a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group, a, b, and c are each independently an integer from 0 to 2, and M is an alkali metal.

10. A separator for a lithium secondary battery, wherein the (meth)acrylic binder further comprises a third structural unit derived from (meth)acrylic acid or (meth)acrylate, in any one of claims 1 to 9.

11. In the 10th paragraph, the third structural unit is a separator for a lithium secondary battery represented by any one of the following chemical formulas 5, 6, 7, and combinations thereof: [Chemical Formula 5] [Chemical Formula 6] [Chemical Formula 7] (In the above chemical formulas 5 to 7, R 3 , R 4 , R 6 , R 7 , R 8 and R 9 are each independently hydrogen or methyl group, R 5 is a substituted or unsubstituted C1 to C20 alkyl group, M is an alkali metal).

12. In any one of claims 1 to 11, the first structural unit derived from the vinyl aromatic monomer is represented by the following chemical formula 9: The second structural unit derived from the above alkyl (meth)acrylate is represented by the following chemical formula 10, The third structural unit derived from the above phosphonate monomer is a separator for a lithium secondary battery, represented by the following chemical formula 11: [Chemical Formula 9] [Chemical Formula 10] [Chemical Formula 11] The description of the above chemical formulas 9 to 11 is as follows: R 19 , R 20 , R 22 , R 23 , R 25 and R 26 are each independently hydrogen or a C1 to C6 alkyl group, R 21 is fluorine, a substituted or unsubstituted C1 to C6 alkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C1 to C6 alkenyl group, R 24 is a substituted or unsubstituted C1 to C20 alkyl group, L 1 is a substituted or unsubstituted C1 to C6 alkylene group, a substituted or unsubstituted C3 to C10 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a combination thereof, L 2 is a carboxyl group (-C(=O)O-), a carbonyl group (-C(=O)-), an ether group (-O-), a substituted or unsubstituted C1 to C6 alkylene group, a substituted or unsubstituted C3 to C10 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a combination thereof, L 3 is a carboxyl group (-C(=O)O-), a carbonyl group (-C(=O)-), an ether group (-O-), a substituted or unsubstituted C1 to C6 alkylene group, a substituted or unsubstituted C3 to C10 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a combination thereof, R 27 and R 28 are each independently a substituted or unsubstituted C1 to C10 alkoxy group, or a substituted or unsubstituted C6 to C20 aryloxy group, a, c and d are each independently an integer from 0 to 2, and b is an integer from 0 to 5.

13. A separator for a lithium secondary battery according to any one of claims 1 to 12, wherein the swellable adhesive binder is a particle having a core-shell structure.

14. A separator for a lithium secondary battery, wherein the swellable adhesive binder is included in an amount of 5 to 50 wt% based on the content of the (meth)acrylic binder in any one of claims 1 to 13.

15. A lithium secondary battery comprising a positive electrode, a negative electrode, and a separator for a lithium secondary battery according to any one of claims 1 to 14 positioned between the positive electrode and the negative electrode.

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