Separator for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

Examples of the present disclosure relate to a separator for a rechargeable lithium battery and a rechargeable lithium battery including the same, and the separator includes a porous substrate and a coating layer on at least one surface of the porous substrate. The coating layer includes: a crosslinked product of a binder and a crosslinking agent; the binder comprises a (methyl) acryloyl binder, the (methyl) acryloyl binder comprises a structural unit derived from (methyl) acrylate or (methyl) acrylic acid, a cyano group-containing structural unit and a sulfonate group-containing structural unit, and the crosslinking agent comprises an aziridine crosslinking agent. And the filler is surface-modified and has a particle size D100 of about 1.5 [mu] m or less.

Description

[0001] This application claims the benefit of priority of Korean Patent Application No. 10-2023-0182101, filed with the Korean Intellectual Property Office on Dec. 14, 2023, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] Examples of the present disclosure relate to a separator for a rechargeable lithium battery and a rechargeable lithium battery including the separator. Background Art

[0003] As the use of electronic devices using batteries (such as mobile phones, laptop computers, and electric vehicles as examples) increases, the demand for secondary batteries with high energy density and high capacity is increasing. Therefore, it may be advantageous to improve the performance of rechargeable lithium batteries.

[0004] A rechargeable lithium battery is generally a battery that includes a positive electrode and a negative electrode containing an active material capable of intercalating and deintercalating lithium ions and generates electrical energy through oxidation and reduction reactions when lithium ions intercalate into and deintercalate from the positive electrode and the negative electrode.

[0005] A rechargeable lithium battery may include a separator between the positive electrode and the negative electrode. The separator is impregnated in an electrolyte. It may be desirable to ensure the safety of the battery, that is, the separator does not undergo thermal shrinkage in the electrolyte and maintains its original form. Summary of the Invention

[0006] One example embodiment includes a separator for a rechargeable lithium battery having a low dry shrinkage rate and a low shrinkage rate in an electrolyte, thereby improving the stability and lifespan of the battery.

[0007] Another example embodiment includes a rechargeable lithium battery including the separator for the rechargeable lithium battery.

[0008] According to an aspect of the present disclosure, a separator for a rechargeable lithium battery includes a porous substrate and a coating layer located on at least one surface of the porous substrate. The coating layer includes a crosslinked product of a binder and a crosslinking agent and a filler. The binder includes a (meth)acryloyl binder, and the (meth)acryloyl binder includes a structural unit derived from (meth)acrylate or (meth)acrylic acid, a cyano-containing structural unit, and a sulfonate group-containing structural unit. The crosslinking agent includes an aziridine crosslinking agent, and the filler is surface-modified and has a particle size D100 of about 1.5 μm or less.

[0009] According to another aspect of the present disclosure, a rechargeable lithium battery includes the separator for the rechargeable lithium battery, a positive electrode, and a negative electrode. Brief Description of the Drawings

[0010] Figure 1 is a cross-sectional view showing a separator for a rechargeable lithium battery according to an exemplary embodiment.

[0011] Figures 2 to 5 is a cross-sectional view schematically showing a rechargeable lithium battery according to an exemplary embodiment. Detailed Description

[0012] Hereinafter, exemplary embodiments of the present disclosure are described in detail. However, the embodiments are presented as examples, and the present disclosure is not limited thereto, and the present disclosure is only defined by the scope of the appended claims.

[0013] Unless otherwise stated herein, when a part such as a layer, film, region, plate, etc. is described as being disposed "on" another part, it includes not only the case where the part is "directly on" the other part, but also the case where there are other parts between them.

[0014] Unless otherwise stated herein, the singular may also include the plural. Further, unless otherwise stated, the term "A or B" may mean "including A, including B, or including A and B".

[0015] In this specification, "its combination" may mean a mixture, stack, composite, copolymer, alloy, blend, or reaction product of components.

[0016] Unless otherwise defined herein, "particle size D100" may refer to the diameter of particles having a cumulative volume of 100 volume % in a particle size distribution. The particle size distribution can be measured by methods known to those skilled in the art. For example, a particle size analyzer, a transmission electron micrograph, or a scanning electron micrograph can be used to measure the particle size distribution. As another method, the particle size distribution can be obtained by measuring the particle size using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles in each particle size range, and then calculating the particle size D100 therefrom. Alternatively, the particle size distribution can be measured using the laser diffraction method. When measuring the particle size distribution by the laser diffraction method, for example, the particles to be measured can be dispersed in a dispersion medium, and then the dispersion medium can be introduced into a commercially available laser diffraction particle size measuring device (e.g., MT 3000 of Microtrac), and the particle size D100 based on the 100% particle size distribution in the measuring device can be calculated by irradiating ultrasonic waves of about 28 kHz with an output of 60W.

[0017] Unless otherwise defined herein, "particle size D50" may refer to the diameter of particles having a cumulative volume of 50 volume % in a particle size distribution. The particle size distribution can be obtained by the method described for particle size D100.

[0018] In this specification, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0019] Hereinafter, unless otherwise defined, "substituted" means that a hydrogen in a compound is substituted with a substituent, and the substituent is such as or includes C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C6-C30 aryl, C7-C30 alkylaryl, C1-C30 alkoxy, C1-C30 heteroalkyl, C3-C30 heteroalkylaryl, C3-C30 cycloalkyl, C3-C15 cycloalkenyl, C6-C30 cycloalkynyl, C2-C30 heterocycloalkyl, halogen (F, Cl, Br or I), hydroxy (-OH), nitro (-NO2), cyano (-CN), amino (-NRR') (wherein R and R' are each independently hydrogen or C1-C6 alkyl), 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 C1-C20 alkyl), azide group (-N3), amidino group (-C(=NH)NH2), hydrazino group (-NHNH2), hydrazono group (=N(NH2)), carbamoyl group (-C(O)NH2), mercapto group (-SH), acyl group (-C(=O)R, where R represents hydrogen, C1-C6 alkyl, C1-C6 alkoxy or C6-C12 aryl), carboxyl group (-COOH) or its salt (-C(=O)OM, where M represents an organic or inorganic cation), sulfonic acid group (-SO3H) or its salt (-SO3M, where M represents an organic or inorganic cation), phosphoric acid group (-PO3H2) or its salt (-PO3MH or -PO3M2, where M represents an organic or inorganic cation), and at least one of their combinations.

[0020] Hereinafter, C1-C3 alkyl may be or include at least one of methyl, ethyl and propyl. C1-C10 alkylene may be or include, for example, at least one of C1-C6 alkylene, C1-C5 alkylene and C1-C3 alkylene, and may be or include, for example, at least one of methylene, ethylene and propylene. C3-C20 cycloalkylene may be or include, for example, at least one of C3-C10 cycloalkylene and C5-C10 cycloalkylene, for example, cyclohexylene. C6-C20 arylene may be or include, for example, C6-C10 arylene, for example, phenylene. C3-C20 heterocyclic group may be or include, for example, C3-C10 heterocyclic group, for example, pyridyl.

[0021] As used herein, "hetero" means including one or more heteroatoms (such as or including at least one of N, O, S, Si, and P).

[0022] In addition, in chemical formulas, the symbol refers to a moiety that is connected to the same or different atoms, groups, or structural units.

[0023] As used herein, "alkali metal" refers to an element belonging to Group 1 of the periodic table, such as lithium, sodium, potassium, rubidium, cesium, or francium, and may exist in a cationic or neutral state.

[0024] In this specification, when describing a numerical range, "X to Y" means "X or greater and Y or less (greater than or equal to X and less than or equal to Y)".

[0025] When the terms "about" or "substantially" are used in conjunction with a numerical value in this specification, it is intended that the relevant numerical value includes a tolerance of ±10% around the stated numerical value. When a range is specified, the range includes all values therebetween, such as increments of 0.1%.

[0026] The separator for a rechargeable lithium battery according to an exemplary embodiment includes a porous substrate and a coating layer located on at least one surface of the porous substrate. The coating layer includes a crosslinked product of a binder and a crosslinking agent and a filler. The binder includes a (meth)acryloyl binder, and the (meth)acryloyl binder includes a structural unit derived from (meth)acrylate or (meth)acrylic acid, a cyano-containing structural unit, and a sulfonate group-containing structural unit. The crosslinking agent includes an aziridine crosslinking agent, and the filler is surface-modified and has a particle size D100 of about 1.5 μm or less.

[0027] Because the coating layer includes a crosslinked product of a (meth)acryloyl binder and an aziridine crosslinking agent and a filler, the separator for a rechargeable lithium battery can have a significantly low dry shrinkage rate and a significantly low shrinkage rate in an electrolyte.

[0028] According to an exemplary embodiment, the dry shrinkage rate of the separator for a rechargeable lithium battery can be about 5% or less, and the shrinkage rate in an electrolyte can be about 15% or less, for example, about 10% or less, or for example, about 5% or less.

[0029] According to an exemplary embodiment, the separator for a rechargeable lithium battery exhibits a significantly low shrinkage rate in an electrolyte. The shrinkage rate in an electrolyte is obtained in consideration of the application position of the separator in a rechargeable lithium battery. The separator can be impregnated with an electrolyte. A separator having a low shrinkage rate in an electrolyte can improve the stability of the battery by maintaining heat-resistant properties without weakening the mechanical properties of the (meth)acryloyl binder when the separator is impregnated with the electrolyte.

[0030] A separator formed from a composition comprising a (meth)acryloyl binder but not comprising an aziridine crosslinker as a crosslinker or comprising a crosslinker other than an aziridine crosslinker, or a separator comprising such a composition, may not satisfy the above shrinkage rate range in the electrolyte. According to an exemplary embodiment, the content of the aziridine crosslinker may be about 95 wt% or more of the total crosslinker in the composition, for example, in the range of 98 wt% to 100 wt%, or for example, 100 wt%.

[0031] A separator formed from a composition comprising a (meth)acryloyl binder but not comprising a surface-modified filler having a particle size D100 of about 1.5 μm or less or comprising a surface-modified filler having a particle size D100 greater than 1.5 μm, or a separator comprising such a composition, may not satisfy the above shrinkage rate range in the electrolyte.

[0032] A separator formed from a composition comprising an aziridine crosslinker and a filler but not comprising a (meth)acryloyl binder or comprising a binder other than a (meth)acryloyl binder, or a separator comprising such a composition, may not satisfy the above dry shrinkage rate range and the shrinkage rate range in the electrolyte. According to an exemplary embodiment, the content of the (meth)acryloyl binder may be about 95 wt% or more of the total binder in the composition, for example, in the range of 98 wt% to 100 wt%, or for example, 100 wt%.

[0033] According to an exemplary embodiment, the coating layer may comprise a composition comprising a crosslinked product of a (meth)acryloyl binder and an aziridine crosslinker and a surface-modified filler having a particle size D100 of about 1.5 μm or less. According to an exemplary embodiment, the crosslinked product may be or comprise a thermally crosslinked product.

[0034] According to an exemplary embodiment, the coating layer may be formed from or comprise a composition comprising a (meth)acryloyl binder, an aziridine crosslinker, and a surface-modified filler having a particle size D100 of about 1.5 μm or less.

[0035] Coating layer The coating layer may be or comprise at least one heat-resistant coating layer.

[0036] The binder comprises a (meth)acryloyl binder, and the (meth)acryloyl binder comprises a structural unit derived from (meth)acrylate or (meth)acrylic acid, a cyano-containing structural unit, and a sulfonate group-containing structural unit.

[0037] The (meth)acryloyl binder is a water-based heat-resistant binder or includes a water-based heat-resistant binder, and can fix a filler to a porous substrate, providing an adhesive strength such that a coating layer adheres to the porous substrate and an electrode, and contributing to improving the heat resistance, air permeability, and oxidation resistance of a separator.

[0038] In a structural unit derived from (meth)acrylate or (meth)acrylic acid, the (meth)acrylate may be or include at least one of a conjugate base of (meth)acrylic acid, a (meth)acrylate salt, and its derivatives. The structural unit derived from (meth)acrylate or (meth)acrylic acid may be represented, for example, by the following Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, or a combination thereof: Chemical Formula 1:

[0039] Chemical Formula 2:

[0040] Chemical Formula 3:

[0041] In Chemical Formulas 1 to 3, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 are each independently hydrogen or methyl, and in Chemical Formula 2, M is or includes an alkali metal.

[0042] The alkali metal may be or include at least one of, for example, lithium, sodium, potassium, rubidium, and cesium.

[0043] The content of the structural unit derived from (meth)acrylate or (meth)acrylic acid in the (meth)acryloyl binder can be in the range of 10 mol% to 70 mol%, for example, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, 17 mol%, 18 mol%, 19 mol%, 20 mol%, 21 mol%, 22 mol%, 23 mol%, 24 mol%, 25 mol%, 26 mol%, 27 mol%, 28 mol%, 29 mol%, 30 mol%, 31 mol%, 32 mol%, 33 mol%, 34 mol%, 35 mol%, 36 mol%, 37 mol%, 38 mol%, 39 mol%, 40 mol%, 41 mol%, 42 mol%, 43 mol%, 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, for example, 20 mol% to 60 mol%, for example, 30 mol% to 60 mol%, for example, 40 mol% to 55 mol%, or for example, 10 mol% to 50 mol%. When the content of the structural unit derived from (meth)acrylate or (meth)acrylic acid is within the above range, the separator including the (meth)acryloyl binder can exhibit desired or improved adhesive strength, heat resistance, air permeability, and antioxidant properties.

[0044] For example, the structural unit derived from (meth)acrylate or (meth)acrylic acid can include the structural unit represented by Chemical Formula 2 and the structural unit represented by Chemical Formula 3. In this case, the molar ratio of the structural unit represented by Chemical Formula 2 to the structural unit represented by Chemical Formula 3 can be in the range of about 10:1 to about 1:2, 10:1 to 1:1, or 5:1 to 1:1.

[0045] The cyano-containing structural unit can be represented, for example, by the following Chemical Formula 4: Chemical Formula 4:

[0046] In Chemical Formula 4, R 7 and R 8 are each independently or include hydrogen or a C1 to C3 alkyl group, L1 is or includes -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, X is an integer in the range of 0 to 2, L 2 is or includes a substituted or unsubstituted C1-C10 alkylene group, a substituted or unsubstituted C3-C20 cycloalkylene group, a substituted or unsubstituted C6-C20 arylene group or a substituted or unsubstituted C3-C20 heterocyclic group, and y is an integer in the range of 0 to 2.

[0047] The cyano-containing structural unit may be or include, for example, at least one of structural units derived from (meth)acrylonitrile, olefin nitrile, (meth)acrylic acid cyanoalkyl ester, and 2-(vinyloxy)alkanenitrile. Herein, the olefin may be or include at least one of C1-C20 olefins, C1-C10 olefins, and C1-C6 olefins, the alkyl group may be or include at least one of C1-C20 alkyl groups, C1-C10 alkyl groups, and C1-C6 alkyl groups, and the alkane may be or include at least one of C1-C20 alkanes, C1-C10 alkanes, and C1-C6 alkanes.

[0048] The olefin nitrile may be or include, for example, at least one of allyl cyanide, 4-pentenenitrile, 3-pentenenitrile, 2-pentenenitrile, 5-hexenenitrile, etc. The (meth)acrylic acid cyanoalkyl ester may be or include, for example, at least one of (meth)acrylic acid cyanomethyl ester, (meth)acrylic acid cyanoethyl ester, (meth)acrylic acid cyanopropyl ester, (meth)acrylic acid cyanooctyl ester, etc. The 2-(vinyloxy)alkanenitrile may be or include, for example, at least one of 2-(vinyloxy)acetonitrile, 2-(vinyloxy)propanenitrile, etc.

[0049] The content of the cyano-containing structural unit in the (meth)acryloyl binder can be in the range of about 30 mol% to about 85 mol%, for example, 30 mol%, 31 mol%, 32 mol%, 33 mol%, 34 mol%, 35 mol%, 36 mol%, 37 mol%, 38 mol%, 39 mol%, 40 mol%, 41 mol%, 42 mol%, 43 mol%, 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, 76 mol%, 77 mol%, 78 mol%, 79 mol%, 80 mol%, 81 mol%, 82 mol%, 83 mol%, 84 mol%, 85 mol%, for example, 40 mol% to 85 mol%, for example, 30 mol% to 70 mol%, for example, 30 mol% to 60 mol%, for example, 35 mol% to 60 mol%, or for example, 35 mol% to 55 mol%. When the content of the cyano-containing structural unit is within the above range, the (meth)acryloyl binder and the separator including the (meth)acryloyl binder can ensure the desired or improved antioxidant property, and exhibit the desired or improved adhesive strength, heat resistance and air permeability.

[0050] The sulfonate group-containing structural unit can be or include a structural unit containing a conjugate base of a sulfonate, a sulfonate salt, a sulfonic acid or a derivative thereof. For example, the sulfonate group-containing structural unit can be represented by the following Chemical Formula 5, Chemical Formula 6, Chemical Formula 7 or a combination thereof: Chemical Formula 5:

[0051] Chemical Formula 6:

[0052] Chemical Formula 7: 。

[0053] In Chemical Formulas 5 to 7, R 9 、R 10 、R 11 、R 12 、R13 and R 14 each independently is or includes hydrogen or C1-C3 alkyl, L 3 、L 5 and L 7 each independently is or includes -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, L 4 、L 6 and L 8 each independently is or includes substituted or unsubstituted C1-C10 alkylene, substituted or unsubstituted C3-C20 cycloalkylene, substituted or unsubstituted C6-C20 arylene or substituted or unsubstituted C3-C20 heterocyclic group, a, b, c, d, e and f are each independently integers in the range of 0 to 2, and in Chemical Formula 6, M is or includes an alkali metal.

[0054] For example, in Chemical Formulas 5 to 7, L 3 、L 5 and L 7 each independently is or includes -C(=O)NH-, L 4 、L 6 and L 8 each independently is or includes C1-C10 alkylene, and a, b, c, d, e and f can each be an integer equal to 1.

[0055] The sulfonate group-containing structural unit may include only one or more of the structural units represented by Chemical Formula 5, the structural unit represented by Chemical Formula 6, and the structural unit represented by Chemical Formula 7. As an example, the sulfonate group-containing structural unit may include the structural unit represented by Chemical Formula 6, and as another example, the sulfonate group-containing structural unit may include the structural unit represented by Chemical Formula 6 and the structural unit represented by Chemical Formula 7.

[0056] The sulfonate group-containing structural unit may be or include, for example, a structural unit derived from at least one of vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, anetholesulfonic acid, (meth)acrylamidoalkanesulfonic acid, (meth)acrylic acid sulfonoalkyl ester and its salts.

[0057] Here, the alkane can be or include at least one of C1 - C20 alkanes, C1 - C10 alkanes, and C1 - C6 alkanes, and the alkyl group can be or include at least one of C1 - C20 alkyl groups, C1 - C10 alkyl groups, and C1 - C6 alkyl groups. The salt refers to a salt compound composed of or including the above - mentioned sulfonic acid and a desired ion. The ion can be or include, for example, an alkali metal ion, and in this case, the salt can be or include an alkali metal salt of the sulfonic acid.

[0058] The (meth)acrylamidoalkanesulfonic acid can be or include, for example, 2 - (meth)acrylamido - 2 - methylpropane sulfonic acid, and the sulfalkyl (meth)acrylate can be or include at least one of, for example, 2 - sulfoethyl (meth)acrylate, 3 - sulfopropyl (meth)acrylate, etc.

[0059] The content of the sulfonate - group - containing structural unit in the (meth)acryloyl - type binder can be in the range of about 0.1 mol% to about 20 mol%, for example, 0.1 mol%, 0.5 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, 17 mol%, 18 mol%, 19 mol%, 20 mol%, for example, 0.1 mol% to 10 mol%, for example, 1 mol% to 20 mol%, or for example, 1 mol% to 10 mol%. When the content of the sulfonate - group - containing structural unit is within the above range, the (meth)acryloyl - type binder and the separator including the (meth)acryloyl - type binder can exhibit desired or improved adhesive strength, heat resistance, air permeability, and antioxidant properties.

[0060] As described above, the (meth)acryloyl - type binder can include an alkali metal. The alkali metal can exist in the form of a cation and can be or include, for example, at least one of lithium, sodium, potassium, rubidium, and cesium. For example, the alkali metal can be combined with the (meth)acryloyl - type binder and can exist in the form of a salt. The alkali metal can contribute to the synthesis of the (meth)acryloyl - type binder in an aqueous solvent, improve the adhesive strength of the coating layer, and improve the heat resistance, air permeability, antioxidant properties, etc. of the separator.

[0061] The content range of the alkali metal can be about 1 wt% to about 40 wt% of the alkali metal and (meth)acryloyl binder. For example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 10 wt% to 20 wt%. For example, the (meth)acryloyl binder and the alkali metal can be included in a weight ratio of about 99:1 to 60:40, 99:1 to 70:30. For example, a weight ratio of 99:1 to 80:20, or for example, a weight ratio of 90:10 to 80:20.

[0062] In addition, relative to the total content of the alkali metal and the (meth)acryloyl binder, the content of the alkali metal can be in the range of about 0.1 mol% to about 1.0 mol%. When the alkali metal is included within the above range, the coating layer can have a desired or improved adhesion strength, and the separator including the coating layer can exhibit desired or improved heat resistance, air permeability, and antioxidant properties.

[0063] The (meth)acryloyl binder can be represented, for example, by the following Chemical Formula 8: Chemical Formula 8: .

[0064] In Chemical Formula 8, R 15 , R 16 , R 17 and R 18 are each independently hydrogen or methyl, R 19 , R 20 , R 21 and R 22 are each independently hydrogen or a C1 to C3 alkyl group, L 1 and L 5 are each independently -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, L 2 and L 6 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, x, y, c, and d are each independently integers within the range of 0 to 2, M is or includes an alkali metal, such as or including at least one of lithium, sodium, potassium, rubidium, and cesium, and k, l, m, and n refer to the molar ratio of each structural unit.

[0065] As an example, in Chemical Formula 8, k + l + m + n = 1. Additionally, as an example, 0.1 ≤ (k + l) ≤ 0.5, 0.4 ≤ m ≤ 0.85, and 0.001 ≤ n ≤ 0.2. For instance, 0.1 ≤ k ≤ 0.5 and 0 ≤ l ≤ 0.25.

[0066] For example, in Chemical Formula 8, x = y = 0, L 5 is or includes -C(=O)NH-, L 6 is or includes a C1 to C10 alkylene group, and c = d = 1.

[0067] The degree of substitution of an alkali metal (M + ) in the (meth)acryloyl binder can be in the range of about 0.5 to about 1.0 relative to (k + n). For example, 0.6 to 0.9 or 0.7 to 0.9. When the degree of substitution of the alkali metal satisfies the above range, the (meth)acryloyl binder and the separator including the (meth)acryloyl binder can exhibit desired or improved adhesion strength, heat resistance, and antioxidant properties.

[0068] The (meth)acryloyl binder can be in various forms, such as an alternating polymer with units distributed alternately, a random polymer with units distributed randomly, or a graft polymer with some structural units grafted.

[0069] The weight-average molecular weight (Mw) of the (meth)acryloyl binder can be in the range of about 200,000 g / mol to about 700,000 g / mol. For example, 200,000 g / mol to 600,000 g / mol, or for example, 300,000 g / mol to 600,000 g / mol. When the weight-average molecular weight of the (meth)acryloyl binder satisfies the above range, the (meth)acryloyl binder and the separator including the (meth)acryloyl binder can exhibit desired or improved adhesion strength, heat resistance, air permeability, and antioxidant properties. The weight-average molecular weight can be the polystyrene-equivalent average molecular weight measured by gel permeation chromatography.

[0070] The glass transition temperature of the (meth)acryloyl binder can be in the range of about 200 °C to about 280 °C. For example, 210 °C to 270 °C, or for example, 210 °C to 260 °C. When the glass transition temperature of the (meth)acryloyl binder satisfies the above range, the (meth)acryloyl binder and the separator including the (meth)acryloyl binder can exhibit desired or improved adhesion strength, heat resistance, air permeability, and antioxidant properties. The glass transition temperature can be the value measured by differential scanning calorimetry.

[0071] The (meth)acryloyl binder can be prepared by solution polymerization.

[0072] According to an exemplary embodiment, the (meth)acryloyl binder may be included in the coating layer of the separator in the form of a film.

[0073] The crosslinking agent includes aziridine crosslinking agents. The aziridine crosslinking agents can crosslink the (meth)acryloyl binder and enable the separator to easily meet the above dry shrinkage rate range and shrinkage rate range in the electrolyte.

[0074] The aziridine crosslinking agents may be or include bifunctional or higher-functional aziridine crosslinking agents. Here, "bifunctional or higher-functional" means that there are two or more aziridine groups in the molecule. According to an exemplary embodiment, the aziridine crosslinking agents may be or include bifunctional or trifunctional aziridine crosslinking agents.

[0075] For example, the aziridine crosslinking agents may include one or more of N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-(methylenediphenylene)bis(aziridine-1-carboxamide), triethylenetrlamine, 1,1-isophthaloyl bis(2-methylaziridine), tris(1-aziridinyl)phosphine oxide, N,N-hexamethylene-bis(aziridinecarboxamide), trimethylolpropane tris(2-methyl-1-aziridinepropionate), trimethylolpropane tris(β-N-aziridinyl)propionate, and pentaerythritol tris(3-(1-aziridinyl)propionate).

[0076] The crosslinking agent (e.g., aziridine crosslinking agent) may be included in a desired amount relative to the binder (e.g., (meth)acryloyl binder). According to an exemplary embodiment, the content of the aziridine crosslinking agent may be in the range of about 5 wt% to about 50 wt% relative to the content of the (meth)acryloyl binder, for example, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, for example, 10 wt% to 40 wt%, or for example, 10 wt% to 20 wt%. Within the above range, the shrinkage rate in the electrolyte can be reduced.

[0077] The filler has a particle size D100 of about 1.5 μm or less. Within the above range, when the (meth)acryloyl binder is combined with the aziridine crosslinking agent, the separator can easily meet the dry shrinkage rate and the shrinkage rate in the electrolyte. For example, the particle size D100 of the filler can be 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1.0 μm, 1.05 μm, 1.1 μm, 1.15 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, about 1.5 μm, about 0.5 μm to about 1.0 μm, about 0.85 μm or less, 0.5 μm to 0.8 μm, or 0.55 μm to 0.7 μm.

[0078] According to an exemplary embodiment, the particle size D50 of the filler can be about 0.5 μm or less. For example, 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm. For example, 0.4 μm or less, or for example, 0.35 μm or less. Within the above range, the shrinkage rate in the electrolyte can be reduced.

[0079] The filler is surface-modified. The surface modification may include modifying the surface of the filler to have an amino group. Here, the "amino group" may represent N(R 1 )(R 2 ). (Here, R 1 and R 2 are each independently hydrogen or a substituted or unsubstituted C1 to C10 alkyl group), and preferably represents an -NH2 group. Compared with the case of using an un-surface-modified filler, this surface modification can expand the particle size range of the filler that can provide the dry shrinkage rate and the shrinkage rate in the electrolyte.

[0080] According to an exemplary embodiment, the surface modification may include surface-treating the un-surface-modified filler with an amino-silane compound. The amino-silane compound may include a silane compound having one or more nitrogens (for example, 1 to 6 nitrogens).

[0081] In an exemplary embodiment, the amino-silane compound may include, but is not limited to, one or more compounds of the following Chemical Formula 9, Chemical Formula 10, and Chemical Formula 11: Chemical Formula 9:

[0082] Chemical formula 10:

[0083] Chemical formula 11: .

[0084] In Chemical formulas 9 to 11, X 1 、X 2 and X 3 are each independently or include hydrogen, a hydroxyl group, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C6-C20 aryl group, a substituted or unsubstituted C3-C20 cycloalkyl group, a substituted or unsubstituted C7-C20 aralkyl group, a substituted or unsubstituted C1-C20 alkoxy group, or a substituted or unsubstituted C6-C20 aryloxy group, X 1 、X 2 and X 3 at least one of which is or includes a hydroxyl group, a substituted or unsubstituted C1-C20 alkoxy group, or a substituted or unsubstituted C6-C20 aryloxy group, Y 1 、Y 2 、Y 3 、Y 4 、Y 5 and Y 6 are each independently or include a divalent C1-C20 aliphatic hydrocarbon group, a divalent C5-C20 alicyclic hydrocarbon group, or a divalent C6-C20 aromatic hydrocarbon group, and R 15 、R 16 、R 17 、R 18 、R 19 、R 20 、R 21 、R 22 and R 23 are each independently or include hydrogen, a hydroxyl group, a substituted or unsubstituted monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, a substituted or unsubstituted monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0085] For example, the aminosilane compound may include one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropyltriethoxysilane, aminoethylaminopropylmethyldimethoxysilane, aminoethylaminopropylmethyldiethoxysilane, aminoethylaminomethyltriethoxysilane, aminoethylaminomethylmethyldiethoxysilane, diethylenetriaminopropyltrimethoxysilane, diethylenetriaminopropyltriethoxysilane, diethylenetriaminopropylmethyldimethoxysilane, diethylenetriaminopropylmethyldiethoxysilane, and diethylenetriaminomethylmethyldiethoxysilane, but is not limited thereto.

[0086] According to an exemplary embodiment, the surface modification may be performed using an aminosilane compound by a typical method.

[0087] The filler may be or include at least one of, for example, an inorganic filler, an organic filler, an organic-inorganic composite filler, and combinations thereof. The inorganic filler may be or include a ceramic material that can improve heat resistance. The inorganic filler may include at least one of, for example, metal oxides, metalloid oxides, metal fluorides, metal hydroxides, and combinations thereof. The inorganic filler may include at least one of, for example, Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof, but is not limited thereto. The organic filler may include at least one of acrylic compounds, imide compounds, amide compounds, and combinations thereof, but is not limited thereto. The organic filler may have a core-shell structure, but is not limited thereto.

[0088] The filler may be substantially spherical, substantially plate-like, substantially cubic, or amorphous. For example, the filler may be plate-like.

[0089] Relative to a binder (e.g., (meth)acryloyl binder), the filler can be included in a desired amount. According to an exemplary embodiment, the mass ratio of the binder to the filler can be in the range of about 1:10 to about 1:50, such as 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40, 1:41, 1:42, 1:43, 1:44, 1:45, 1:46, 1:47, 1:48, 1:49, 1:50, 1:10 to 1:40, or 1:20 to 1:30. Within the above range, the shrinkage rate in the electrolyte can be reduced.

[0090] The content range of the filler can be about 50 wt% to about 99 wt% of the total amount of the coating layer, such as 70 wt% to 99 wt%, such as 75 wt% to 99 wt%, such as 80 wt% to 99 wt%, such as 85 wt% to 99 wt%, such as 90 wt% to 99 wt%, or such as 95 wt% to 99 wt%. When the filler is included within the above range, the separator can exhibit desired or improved heat resistance, durability, oxidation resistance, and stability.

[0091] The coating layer can have a thickness of 0.01 μm to 20 μm, and within the above range, the coating layer can have a thickness of 1 μm to 10 μm, 1 μm to 5 μm, or 1 μm to 3 μm.

[0092] The ratio of the thickness of the coating layer to the thickness of the porous substrate can be in the range of about 0.05 to about 0.5, for example, 0.05 to 0.4, 0.05 to 0.3, or 0.1 to 0.2. Within the above range, the separator can exhibit desired or improved gas permeability, heat resistance, adhesion strength, etc. Here, the "thickness of the coating layer" means the thickness of one coating layer when the coating layer is formed only on one surface of the porous substrate, and the thickness of two coating layers when the coating layer is formed on both surfaces of the porous substrate.

[0093] Porous substrate The porous substrate can be or include a substrate having a plurality of pores and typically used in an electrochemical device. The porous substrate can be or include a polymer film formed of or including any one polymer, such as or including polyolefins (such as polyethylene or polypropylene), polyesters (such as polyethylene terephthalate or polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ether ketones, polyaryl ether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, Teflon, and polytetrafluoroethylene, and at least one of copolymers or mixtures of two or more types thereof.

[0094] The porous substrate can be or include, for example, a polyolefin matrix containing polyolefins, and the polyolefin matrix can have a desired or improved shut-off function, thereby contributing to improving the safety of the battery. The polyolefin matrix can be or include, for example, at least one of a polyethylene single film, a polypropylene single film, a polyethylene / polypropylene double film, a polypropylene / polyethylene / polypropylene triple film, and a polyethylene / polypropylene / polyethylene triple film. In addition, the polyolefin resin can also include a non-olefin resin other than the olefin resin or a copolymer including an olefin monomer and a non-olefin monomer.

[0095] The thickness range of the porous substrate can be from about 1 μm to about 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, or 5 μm to 15 μm.

[0096] The separator for a rechargeable lithium battery according to an exemplary embodiment can have a desired or improved adhesion strength. For example, the adhesion strength of the separator for a rechargeable lithium battery can be about 0.05 gf / mm or greater, for example, in the range of 0.05 gf / mm to 0.1 gf / mm, for example, in the range of 0.05 gf / mm to 0.2 gf / mm. The adhesion strength can be measured by the following method.

[0097] The separator used in a rechargeable lithium battery is located between the positive electrode and the negative electrode, and the separator is bonded to the positive electrode and the negative electrode by passing it between rollers having a pressure of 250 kgf at a speed of 150 mm / sec in an 80°C chamber. Samples are made by cutting the separator bonded to the positive electrode and the negative electrode into a width of 25 mm and a length of 50 mm. A universal testing machine (UTM) is used as the bonding strength measuring device. In the above sample, the separator is separated from the negative electrode plate by about 10 mm to 20 mm, then the separator is fixed to the upper fixture, and the negative electrode plate is fixed to the lower fixture so that the gap between the fixtures is 20 mm, and then peeled by pulling in the 180° direction. After starting to peel at a peeling speed of 20 mm / minute, the average value is obtained by measuring the force required to peel 40 mm three times. The average value is calculated as the average value of the measured values.

[0098] The separator for a rechargeable lithium battery according to an exemplary embodiment may exhibit a desired or improved air permeability, and have an air permeability value of, for example, less than about 200 sec / 100 cc, such as 190 sec / 100 cc or less, or 180 sec / 100 cc or less. That is, the separator may have an air permeability value of less than about 40 sec / 100 cc·1μm per unit thickness, such as 30 sec / 100 cc·1μm or less, or 25 sec / 100 cc·1μm or less. Here, the air permeability refers to the time (seconds) it takes for 100 cc of air to pass through a separator of unit thickness. The air permeability per unit thickness can be obtained by measuring the air permeability of the separator for the total thickness and dividing the air permeability by the thickness. The air permeability can be obtained by measuring the time it takes for 100 cc of air to pass through the separator using an air permeability measuring device (EG01-55-1MR, Asahi Seiko Co., Ltd.).

[0099] The separator for a rechargeable lithium battery according to an exemplary embodiment can be formed by applying a composition for forming a coating layer on one or both surfaces of a porous substrate, drying, and curing the applied coating layer. Curing can be performed using conventional methods known to those skilled in the art.

[0100] Figure 1 is a cross-sectional view showing a separator for a rechargeable lithium battery according to an exemplary embodiment. Referring to Figure 1 , the separator for a rechargeable lithium battery includes a porous substrate 1 and coating layers 2 located on both surfaces of the porous substrate 1. The coating layer 2 includes a filler 3 and a cross-linked product 4 of a (meth)acryloyl binder and a cross-linking agent.

[0101] Rechargeable lithium battery According to an exemplary embodiment, a rechargeable lithium battery includes a separator, a positive electrode, and a negative electrode for the rechargeable lithium battery.

[0102] The separator for the rechargeable lithium battery is as described above. The separator for the rechargeable lithium battery may be located between the positive electrode and the negative electrode.

[0103] Positive electrode The positive electrode for the rechargeable lithium battery may include a current collector and a positive electrode active material layer on the current collector. The positive electrode active material layer may include a positive electrode active material and may also include a binder and / or a conductive material. For example, the positive electrode may further include an additive that can form a sacrificial positive electrode.

[0104] Positive electrode active material The positive electrode active material may include a compound capable of intercalating and deintercalating lithium (lithiation intercalation compound). For example, at least one of a composite oxide of lithium and at least one metal such as or including cobalt, manganese, nickel, and combinations thereof may be used.

[0105] The composite oxide may be or include a lithium transition metal composite oxide. Examples of the composite oxide may include at least one of lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free lithium nickel manganese-based oxides, and combinations thereof.

[0106] As an example, the following compounds represented by any 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 and 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 and 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5 and 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 and 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 and 0 ≤ e ≤ 0.1); Li a NiG b O2 (0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a Mn 1-b G b O2 (0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a Mn 1-g G g PO4 (0.90 ≤ a ≤ 1.8 and 0 ≤ g ≤ 0.5); Li (3-f) Fe2(PO4)3 (0 ≤ f ≤ 2); or Li a FePO4 (0.90 ≤ a ≤ 1.8).

[0107] In the above chemical formulas, A is or includes at least one of Ni, Co, Mn and combinations thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and combinations thereof; D is or includes at least one of O, F, S, P and combinations thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V and combinations thereof; and L 1 is or includes at least one of Mn, Al and combinations thereof.

[0108] The positive electrode active material can be or include, for example, a high-nickel type positive electrode active material. Based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide, the nickel content of the high-nickel type positive electrode active material is greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol% or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. The high-nickel type positive electrode active material can exhibit high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0109] Based on 100 wt% of the positive electrode active material layer, the amount of the positive electrode active material can be from about 90 wt% to about 99.5 wt%. Based on 100 wt% of the positive electrode active material layer, the amounts of the binder and the conductive material can be from about 0.5 wt% to about 5 wt% respectively.

[0110] The binder is configured to attach the positive electrode active material particles to each other and also to attach the positive electrode active material to the current collector. As non-limiting examples, examples of the binder can include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0111] A conductive material can be included to impart conductivity (e.g., electrical conductivity) to the electrode. Any material that does not cause a chemical change (e.g., does not cause an undesirable chemical change in a rechargeable lithium battery) and conducts electrons can be used for the battery. Examples of the conductive material can include: carbon-based materials such as or including at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials including copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or a mixture thereof.

[0112] Al can be included as the current collector, but is not limited thereto.

[0113] Negative electrode The negative electrode for a rechargeable lithium battery can include a current collector and a negative electrode active material layer on the current collector. The negative electrode active material layer can include a negative electrode active material and can also include a binder and / or a conductive material (e.g., an electrically conductive material).

[0114] For example, the negative electrode active material layer can include from about 90 wt% to about 99 wt% of the negative electrode active material, from about 0.5 wt% to about 5 wt% of the binder, and from about 0 wt% to about 5 wt% of the conductive material.

[0115] Negative electrode active material The negative electrode active material can include at least one of a material that can reversibly intercalate / deintercalate lithium ions, lithium metal, a lithium metal alloy, a material that can dope / de-dope lithium, and a transition metal oxide.

[0116] Materials that can reversibly embed / desorb lithium ions may include carbonaceous negative electrode active materials, such as crystalline carbon, amorphous carbon, or a combination thereof as examples. The crystalline carbon may be or include graphite, such as natural graphite and artificial graphite in an amorphous shape, flaky, lamellar, spherical, or fibrous form. The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0117] The lithium metal alloy includes an alloy of lithium and a metal such as or including at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0118] Materials capable of doping / undoping lithium may be or include at least one of Si-based negative electrode active materials and Sn-based negative electrode active materials. The Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (0 < x < 2), Si-Q alloys (where Q is or includes at least one of 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). The Sn-based negative electrode active materials may include at least one of Sn, SnO2, Sn-based alloys, and combinations thereof.

[0119] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to an exemplary 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 silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are assembled, and an amorphous carbon coating layer (shell) on the surface of the secondary particles. The amorphous carbon may also be between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0120] The silicon-carbon composite may also include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer on the surface of the core.

[0121] The Si-based negative electrode active material or the Sn-based negative electrode active material may be combined with the carbonaceous negative electrode active material.

[0122] The binder may be configured to attach the negative electrode active material particles to each other and attach the negative electrode active material to the current collector. The binder may include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0123] The non-aqueous binder may include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and combinations thereof.

[0124] The aqueous binder may be or include at least one of styrene-butadiene rubber, (meth)acrylate esterified styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin rubber, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0125] When including an aqueous binder as the negative electrode binder, a cellulose-based compound capable of imparting adhesiveness may also be included. The cellulose-based compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include at least one of Na, K, and Li.

[0126] The dry binder may be or include a polymeric material capable of being fibrous. For example, the dry binder may be or include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0127] A conductive material may be included to impart conductivity (e.g., electrical conductivity) to the electrode. Any material that does not cause a chemical change (e.g., does not cause an undesired chemical change in a rechargeable lithium battery) and conducts electrons can be used in the battery. Non-limiting examples of the conductive material may include: carbon-based materials, such as or including at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metallic materials in the form of metal powder or metal fiber, including at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0128] The negative electrode current collector may include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0129] The rechargeable lithium battery may further include an electrolyte.

[0130] Electrolyte The electrolyte for the rechargeable lithium battery may include a non-aqueous organic solvent and a lithium salt.

[0131] A non-aqueous organic solvent can form a medium for transporting ions participating in the electrochemical reaction of the battery.

[0132] The non-aqueous organic solvent can be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0133] The carbonate solvents can include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc.

[0134] The ester solvents can include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, caprolactone, mevalonolactone, valerolactone, caprolactone, etc.

[0135] The ether solvents can include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In addition, the ketone solvents can include cyclohexanone, etc. The alcohol solvents can include at least one of ethanol, isopropanol, etc., and the aprotic solvents can include at least one of the following: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched-chain or cyclic hydrocarbon group and includes double bonds, aromatic rings or ether bonds, etc.); amides, such as dimethylformamide; dioxolanes, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane; and so on.

[0136] The non-aqueous organic solvent can be included alone or in combination of two or more solvents.

[0137] In an example, when using carbonate solvents, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed at a volume ratio of about 1:1 to about 1:9.

[0138] The lithium salt dissolved in the organic solvent is configured to supply lithium ions in the battery to enable the rechargeable lithium battery to perform basic operations and improve the transport of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt 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 yF 2y+1 at least one of lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFBOB), lithium difluoro(oxalato)phosphate (LiDFBOBP), lithium tetrafluoroethanesulfonate, lithium trifluoromethanesulfonate, where x and y are integers from 1 to 20).

[0139] Rechargeable lithium batteries can be classified into cylindrical batteries, prismatic batteries, pouch-type batteries, coin-type batteries, etc. according to their shapes.

[0140] Figures 2 to 5 is a schematic diagram showing a rechargeable lithium battery according to an exemplary embodiment. Figure 2 shows a cylindrical battery, Figure 3 shows a prismatic battery, and Figure 4 and Figure 5 shows a pouch-type battery. Referring to Figures 2 to 5 , the rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40 is included in the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). As Figure 2 shown, the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. In Figure 3 , the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As Figure 4 and Figure 5 shown, the rechargeable lithium battery 100 may include Figure 5 the electrode tab 70 shown in Figure 4 , or for example

[0141] the positive electrode tab 71 and the negative electrode tab 72 shown in

[0142] The electrode tab 70 / 71 / 72 forms a circuit path for guiding the current formed in the electrode assembly 40 to the outside of the battery 100. As a non-limiting example, the rechargeable lithium battery according to the exemplary embodiment may be applicable to, for example, automobiles, mobile phones, and / or various types of electrical devices.

[0143] Preparation Example 1 In a 3 L four-necked flask equipped with a stirrer, a thermometer, and a cooling tube, distilled water (968 g), acrylic acid (AA) (28.00 g, 0.39 mol), ammonium persulfate (0.65 g, 2.85 mmol), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) (4.14 g, 0.02 mol), and 20% aqueous lithium hydroxide solution (0.8 equivalent relative to the total amount of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid) were added. Then, the internal pressure was reduced to 10 mmHg using a diaphragm pump and restored to atmospheric pressure using nitrogen, and this step was repeated three times. Then, acrylonitrile (AN) (31.31 g, 0.59 mol) was added.

[0144] The reaction was carried out for 18 hours while controlling the temperature of the reaction solution to be stable between 65 °C and 70 °C. After the second addition of ammonium persulfate (0.22 g, 0.95 mmol), the temperature was raised to 80 °C, and the reaction was carried out for another 4 hours. After cooling to room temperature, the pH of the reaction solution was adjusted to 7 to 8 using 25% aqueous ammonia solution.

[0145] Thus, poly(acrylic acid-co-lithium acrylate-co-acrylonitrile-co-2-acrylamido-2-methylpropanesulfonic acid lithium) was prepared. The molar ratio of acrylic acid + lithium acrylate, acrylonitrile, and 2-acrylamido-2-methylpropanesulfonic acid lithium was 39:59:2. The non-volatile components in about 10 mL of the reaction solution (reaction product) were measured, and the measurement result was 9.0 wt% (theoretical value: 10 wt%).

[0146] Preparation Example 2 An acryloyl binder was prepared in the same manner as in Preparation Example 1, except that acrylic acid and acrylonitrile were used instead of 2-acrylamido-2-methylpropanesulfonic acid. The molar ratio of acrylic acid + lithium acrylate to acrylonitrile was 42:58. The non-volatile components of the reaction solution were 9.0 wt% (theoretical value: 10 wt%).

[0147] Preparation Example 3 An acryloyl binder was prepared in the same manner as in Preparation Example 1, except that acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid were used instead of acrylonitrile. The molar ratio of acrylic acid + lithium acrylate to 2-acrylamido-2-methylpropanesulfonic acid lithium was 74:26. The non-volatile components of the reaction solution were 9.0 wt% (theoretical value: 10 wt%).

[0148] Preparation Example 4 An acrylate binder was prepared in the same manner as in Preparation Example 1, except that acrylonitrile and 2-acrylamido-2-methylpropanesulfonic acid were used instead of acrylic acid. The molar ratio of acrylonitrile to lithium 2-acrylamido-2-methylpropanesulfonate was 74:26. The non-volatile component of the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0149] Table 1 below shows the molar ratio, weight-average molecular weight, and glass transition temperature of each monomer among the (meth)acrylate binders prepared in Preparation Examples 1 to 4.

[0150] Table 1:

[0151] Example 1 3-Aminopropyltrimethoxysilane corresponding to 1.5 wt% per solid content of boehmite (particle size D100: 0.5 μm, particle size D50: 0.2 μm, plate-like) was added to anhydrous toluene to prepare boehmite (particle size D100: 0.5 μm, particle size D50: 0.2 μm, plate-like) surface-modified with 3-aminopropyltrimethoxysilane. The surface-modified boehmite has an amino group (-NH2) on its outermost surface.

[0152] The acrylate binder prepared in Preparation Example 1 (10 wt% in distilled water) and the prepared amino-surface-modified boehmite as a filler were mixed at a mass ratio of acrylate binder: filler = 1 part by weight: 20 parts by weight based on the solid content. The mixture was added to an aqueous solvent, and then the mixture was ground and dispersed using a bead mill at 25 °C for 30 minutes to prepare a dispersion.

[0153] A composition for forming a coating layer was prepared by adding tris(2-methyl-1-aziridinepropionate) of trimethylolpropane (a trifunctional aziridine crosslinking agent) as an aziridine crosslinking agent in an amount of 0.1 part by weight based on the solid content (content of 10 wt% of the acrylate binder) to the dispersion and adding water so that the total solid content became 20 wt%.

[0154] The composition for forming a coating layer was separately coated on both sides of a polyethylene film (thickness: 8 μm, SK Corporation, air permeability: 120 sec / 100 cc, puncture strength: 480 kgf) as a porous substrate to a thickness of 1.5 μm by die coating. A separator for a rechargeable lithium battery was manufactured by drying and aging in an oven at 80 °C for 16 hours.

[0155] Examples 2 to 5 A separator for a rechargeable lithium battery was manufactured in the same manner as in Example 1, except that, as shown in Table 2 below, boehmite was used as a filler, but the D50 and D100 were changed, the mass ratio of acrylate binder: filler was changed, and the content of aziridine crosslinker was changed.

[0156] Comparative Example 1 to Comparative Example 7 A separator for a rechargeable lithium battery was manufactured in the same manner as in Example 1, except that, as shown in Table 2 below, the D50 and D100 of the filler, the type of crosslinker, the content of the crosslinker, the mass ratio of acrylate binder: filler, etc. were changed. The epoxy crosslinker was ethylene glycol diglycidyl ether.

[0157] Dry shrinkage rate (unit: %) Samples were prepared by cutting the separators for rechargeable lithium batteries of the examples and comparative examples into a size of 8 cm × 8 cm. By drawing a square with a size of 5 cm × 5 cm on the surface of the sample, and then placing the sample between sheets of alumina powder or paper, the sample was placed in an oven at 150 °C for 1 hour, the sample was taken out, and then the side dimensions of the drawn square were measured to calculate the shrinkage rate in each of the longitudinal (mechanical direction, MD) and transverse (transverse direction, TD) directions. The shrinkage rate was calculated according to Equation 1 below.

[0158] Equation 1: Shrinkage rate (%) = (L0 - L1) / L0 × 100 L0 represents the initial length of the separator, and L1 represents the length of the separator after being placed at 150 °C for 1 hour.

[0159] Shrinkage rate in the electrolyte (unit: %) Samples were prepared by cutting the separators for rechargeable lithium batteries of the examples and comparative examples into a size of 8 cm × 8 cm. A square with a size of 5 cm × 5 cm was drawn on the surface of the sample.

[0160] A positive electrode slurry was prepared by mixing 97 wt% of LiCoNiAl as a positive electrode active material, 1.5 wt% of carbon nanotubes as a conductive material, and 1.5 wt% of polyvinylidene fluoride as a binder, and adding water thereto. A positive electrode was manufactured by applying the prepared positive electrode slurry to an aluminum foil and drying and rolling the prepared positive electrode slurry.

[0161] A negative electrode active material slurry was prepared by mixing 97.4 wt% of negative electrode active material, 1.0 wt% of carboxymethyl cellulose, 1.5 wt% of styrene-butadiene rubber, and 0.1 wt% of carbon nanotubes as a conductive agent. Artificial graphite was used as the negative electrode active material. The negative electrode was fabricated by applying the prepared negative electrode slurry onto a copper foil and drying and rolling the prepared negative electrode slurry.

[0162] A sample was placed between the positive electrode and the negative electrode to form a laminate of three sets of positive electrode-sample-negative electrode, and then it was put into a bag. 2 g of an electrolyte solution (ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 30:50:20) in which 1.5 M LiPF6 was dissolved) was injected to fully soak the laminate with the electrolyte solution, sealed, and left at 25 °C for 12 hours. Then, by placing the laminate in an oven at 150 °C for 1 hour, then taking out the sample, and measuring the side dimensions of the drawn square, the shrinkage rate in each of the longitudinal (MD) and transverse (TD) directions was calculated. The shrinkage rate was calculated according to Equation 1.

[0163] Presence or absence of crosslinking Samples were fabricated by cutting the separators for rechargeable lithium batteries of the examples and comparative examples into a size of 8 cm × 8 cm. When the samples were fully immersed in deionized water at 25 °C and left for 25 hours, visual inspection was performed to check whether the filler peeled off from the coating layer. When the filler did not peel off, it indicated that crosslinking occurred in the coating layer composition, and when the filler peeled off, it indicated that crosslinking did not occur in the coating layer composition.

[0164] Table 2:

[0165] As shown in Table 2, the separators for rechargeable lithium batteries according to the examples exhibited significantly low dry shrinkage rates and significantly low shrinkage rates in the electrolyte solution. Therefore, although not shown in Table 2, it is expected that the separators of the examples improve the stability and lifespan of the battery.

[0166] However, the separators of the comparative examples exhibited higher dry shrinkage rates and / or shrinkage rates in the electrolyte solution than those of the separators of the examples. In addition, although not shown in Table 2, the binder prepared in Preparation Example 4 did not undergo a sufficient crosslinking reaction.

[0167] The separator for a rechargeable lithium battery according to an example embodiment can exhibit significantly low dry shrinkage rates and shrinkage rates in the electrolyte solution, thereby improving the stability and lifespan of the battery.

[0168] Although example embodiments of the present disclosure have been described above, the present disclosure is not limited thereto, and can be modified in any form within the scope of the claims, the detailed description of the present disclosure, and the drawings, and such modifications also fall within the scope of the present disclosure.

Claims

1. A separator for a rechargeable lithium battery, the separator comprising: porous substrate; as well as a coating layer disposed on at least one surface of the porous substrate, Wherein, the coating layer includes a cross-linked product of a binder and a cross-linking agent and a filler, The adhesive comprises a (meth)acryl-based adhesive, wherein the (meth)acryl-based adhesive comprises a structural unit derived from (meth)acrylate or (meth)acrylic acid, a structural unit containing a cyano group, and a structural unit containing a sulfonate group. The cross-linking agent includes an aziridine cross-linking agent, and The filler is surface-modified and has a particle size D100 of 1.5 μm or less.

2. The diaphragm according to claim 1, wherein The coating layer includes a composition including the (meth)acryl-based binder, the aziridine-based cross-linking agent, and the filler having a particle size D100 of 1.5 μm or less.

3. The diaphragm according to claim 1, wherein The aziridine crosslinking agent includes one or more of N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-(methylenediphenylene)bis(aziridine-1-carboxamide), triethylene melamine, 1,1-isophthaloylbis(2-methylaziridine), tris(1-aziridine)phosphine oxide, N,N-hexamethylene-bis(aziridinecarboxamide), trimethylolpropane tris(2-methyl-1-aziridine propionate), trimethylolpropane tris(β-N-aziridine) propionate and pentaerythritol tris(3-(1-aziridine) propionate).

4. The diaphragm according to claim 1, wherein The content of the aziridine crosslinking agent is 5 wt % to 50 wt % relative to the content of the (meth)acryl-based binder.

5. The diaphragm according to claim 1, wherein The mass ratio of the (meth)acryl-based binder to the filler is 1:10 to 1:

50.

6. The diaphragm according to claim 1, wherein The filler has a particle size D50 of 0.5 μm or less.

7. The diaphragm according to claim 1, wherein The filler includes a plate-like inorganic filler.

8. The diaphragm according to claim 1, wherein The filler is surface-modified such that the surface of the filler includes an amino group.

9. The diaphragm according to claim 8, wherein The filler is surface-modified with an aminosilane compound.

10. The diaphragm according to claim 1, wherein The structural unit derived from (meth)acrylate or (meth)acrylic acid is represented by at least one of Chemical Formula 1, Chemical Formula 2 and Chemical Formula 3: Chemical formula 1: Chemical formula 2: Chemical formula 3: ， In Chemical Formulae 1 to 3, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 each independently comprises hydrogen or methyl, and In chemical formula 2, M includes alkali metals, The cyano group-containing structural unit is represented by Chemical Formula 4: Chemical formula 4: ， In chemical formula 4, R 7 and R 8 each independently comprises hydrogen or C1 to C3 alkyl, L 1 including -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, x is an integer in the range of 0 to 2, L 2 includes 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, and y is an integer in the range of 0 to 2, The structural unit containing a sulfonate group is represented by at least one of Chemical Formula 5, Chemical Formula 6 and Chemical Formula 7: Chemical formula 5: Chemical formula 6: Chemical formula 7: ， In Chemical Formulae 5 to 7, R 9 , R 10 , R 11 , R 12 , R 13 and R 14 each independently comprises hydrogen or C1 to C3 alkyl, L 3 , L 5 and L 7 Each independently includes -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, L 4 , L 6 and L 8 Each independently includes 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, c, d, e and f are each independently an integer in the range of 0 to 2, and In Chemical Formula 6, M includes alkali metals.

11. The diaphragm according to claim 1, wherein The coating layer has a thickness in the range of 1 μm to 3 μm.

12. A rechargeable lithium battery, comprising: The separator for a rechargeable lithium battery according to claim 1; a positive electrode; and Negative electrode.

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