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; 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 group-containing structural unit, and a sulfonate group-containing structural unit. The cross-linking agent includes an aziridine-based cross-linking agent, and the particle size D100 of the filler is about 1.0 [mu] m or less.

Description

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0182100, filed with the Korean Intellectual Property Office on December 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, electric vehicles, etc.) 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 generally includes a positive electrode and a negative electrode containing an active material capable of intercalating and deintercalating lithium ions, and generates electric energy through oxidation and reduction reactions when lithium ions intercalate and deintercalate between 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 with 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 or shape. 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 safety and life of the battery.

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

[0008] According to an example 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 particle size D100 of the filler is about 1.0 μm or less.

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

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

[0011] Figures 2 to 5 It 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, this description 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. In addition, unless otherwise stated, the term "A or B" may mean "including A, including B, or including both A and B".

[0015] In this specification, "a combination thereof" 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% by volume in a particle size distribution. The particle size distribution can be measured by methods known to those skilled in the art. For example, the particle size distribution can be measured using a particle size analyzer, a transmission electron micrograph, or a scanning electron micrograph. 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 ultrasonic waves of about 28 kHz can be irradiated at an output of 60 W to calculate the particle size D100 based on the 100% particle size distribution in the measuring device.

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

[0018] In the present 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) (wherein R and R' are each independently C1-C20 alkyl), 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), hydrazone 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 (-PO3H) 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 alkylene, for example, cyclohexylene. C6-C20 arylene may be or include, for example, at least one of 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 hereinafter, "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 hereinafter, "alkali metal" means 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 include a tolerance of ±10% around the stated value. When a range is specified, the range includes all values therebetween, such as an increment of 0.1%.

[0026] A separator for a rechargeable lithium battery according to an exemplary embodiment includes a porous substrate and a coating layer disposed 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 particle size D100 of the filler is about 1.0 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 shrinkage rate in an electrolyte. The dry shrinkage rate is measured while the separator is placed at a high temperature, and the shrinkage rate in the electrolyte is measured while the separator is placed at a high temperature in a state impregnated with the 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 the electrolyte can be about 20% or less, for example, about 15% or less, for example, about 10% or less, or for example, about 5% or less.

[0029] According to an exemplary embodiment, a separator for a rechargeable lithium battery exhibits a significantly low shrinkage rate in an electrolyte. The shrinkage rate in the electrolyte is obtained considering the position of the separator in the rechargeable lithium battery. The separator can be impregnated with the electrolyte. The separator having a low shrinkage rate in the electrolyte can improve the stability and lifespan 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 of or including a composition that contains a (meth)acryloyl binder but does not contain an aziridine crosslinker as a crosslinker or contains a crosslinker other than an aziridine crosslinker may not meet the above shrinkage rate range in the electrolyte. According to an exemplary embodiment, the content of the aziridine crosslinker can be about 95 wt% or more of the total crosslinkers in the composition, for example, in the range of about 98 wt% to about 100 wt%, or for example, about 100 wt%.

[0031] A separator formed of or including a composition that contains a (meth)acryloyl binder but does not include a filler having a particle size D100 of about 1.0 μm or less or includes a filler having a particle size D100 greater than about 1.0 μm may not meet the above shrinkage rate range in the electrolyte.

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

[0033] According to an exemplary embodiment, the coating layer can include a composition containing a crosslinked product of a (meth)acryloyl binder and an aziridine crosslinker and a filler having a particle size D100 of about 1.0 μm or less. According to an exemplary embodiment, the crosslinked product can be or include a thermally crosslinked product.

[0034] According to an exemplary embodiment, the coating layer can be formed of or include a composition including a (meth)acryloyl binder, an aziridine crosslinker, and a filler having a particle size D100 of about 1.0 μm or less.

[0035] Coating layer The coating layer can be or include a heat-resistant coating layer.

[0036] The binder includes (meth)acryloyl binders, and the (meth)acryloyl binders contain structural units derived from (meth)acrylate or (meth)acrylic acid, cyano-containing structural units, and sulfonate group-containing structural units.

[0037] The (meth)acryloyl binder is a water-based heat-resistant binder or includes a water-based heat-resistant binder, and can be configured to fix the filler on the porous substrate, provide an adhesive strength such that the coating layer adheres to the porous substrate and the electrode, and helps to improve the heat resistance, air permeability, and antioxidant properties of the separator.

[0038] In the structural units derived from (meth)acrylate or (meth)acrylic acid, the (meth)acrylate can be or include at least one of the conjugate base of (meth)acrylic acid, (meth)acrylate salts, and their derivatives. The structural units derived from (meth)acrylate or (meth)acrylic acid can 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 an alkali metal.

[0042] The alkali metal can 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 about 10 mol% to about 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%, 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 any of the above ranges, the separator containing 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, and 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 substituted 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 C2-C20 olefins, C2-C10 olefins and C2-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. 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%, 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 any of the above ranges, 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 adhesion strength, heat resistance, and air permeability.

[0050] The sulfonate group-containing structural unit can be or include a structural unit containing at least one of a conjugate base of a sulfonate, a sulfonate salt, a sulfonic acid, and its derivatives. 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.

[0051] Chemical Formula 5:

[0052] Chemical Formula 6:

[0053] Chemical Formula 7: .

[0054] In Chemical Formulas 5 to 7, R 9 、R 10 、R 11, R 12 , R 13 and R 14 are each independently hydrogen or a C1-C3 alkyl group, L 3 , L 5 and L 7 are each independently -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, L 4 , L 6 and L 8 are each independently 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, 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 is or includes an alkali metal.

[0055] For example, in Chemical Formulas 5 to 7, L 3 , L 5 and L 7 are each independently -C(=O)NH-, L 4 , L 6 and L 8 are each independently a C1-C10 alkylene group, and a, b, c, d, e and f can each be an integer equal to 1.

[0056] The sulfonate group-containing structural unit may include only one or two 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.

[0057] The sulfonate group-containing structural unit may be or include at least one of structural units derived from, for example, vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, anetholesulfonic acid, (meth)acrylamidoalkanesulfonic acid, (meth)acrylic acid sulfonoalkyl ester and its salts.

[0058] 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 composed of the above-mentioned sulfonic acid and the 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 sulfonic acid.

[0059] The (meth)acrylamidoalkanesulfonic acid can be or include, for example, 2-(meth)acrylamido-2-methylpropanesulfonic acid, and the (meth)acrylic acid sulfalkyl ester can be or include at least one of, for example, 2-sulfoethyl (meth)acrylate, 3-sulfopropyl (meth)acrylate, etc.

[0060] The content of the structural unit containing a sulfonate group in the (meth)acryloyl binder can be in the range of about 0.1 mol% to about 20 mol%, 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 structural unit containing a sulfonate group is within any of the above ranges, 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.

[0061] As described above, the (meth)acryloyl 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 binder and exist in the form of a salt. The alkali metal can contribute to the synthesis of the (meth)acryloyl binder in an aqueous solvent, improve the adhesion strength of the coating layer, and improve the heat resistance, air permeability, antioxidant properties, etc. of the separator.

[0062] 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 99:1 to 60:40, a weight ratio of 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.

[0063] 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 oxidation resistance.

[0064] The (meth)acryloyl binder can be represented, for example, by the following Chemical Formula 8: Chemical Formula 8: .

[0065] 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-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-C10 alkylene group, a substituted or unsubstituted C3-C20 cycloalkylene group, a substituted or unsubstituted C6-C20 arylene group, or a substituted or substituted C3-C20 heterocyclic group, x, y, c, and d are each independently integers in the range of 0 to 2, M is or includes an alkali metal, such as 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.

[0066] 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 example, 0.1 ≤ k ≤ 0.5 and 0 ≤ l ≤ 0.25.

[0067] 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.

[0068] 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 any of the above ranges, the (meth)acryloyl binder and the separator including the (meth)acryloyl binder can exhibit desired or improved adhesion strength, heat resistance, and antioxidant properties.

[0069] The (meth)acryloyl binder can be in various forms, such as an alternating polymer with alternating units, a random polymer with randomly distributed units, or a graft polymer with some structural units grafted.

[0070] 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 any of the above ranges, 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 or include the polystyrene-equivalent average molecular weight measured by gel permeation chromatography.

[0071] 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 any of the above ranges, 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 a value measured by, for example, differential scanning calorimetry.

[0072] The (meth)acryloyl binder can be prepared by solution polymerization.

[0073] 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.

[0074] The crosslinking agent includes aziridine crosslinking agents. The aziridine crosslinking agents can crosslink the (meth)acryloyl binder and also enable the separator to easily meet the above dry shrinkage rate range and shrinkage rate range in the electrolyte.

[0075] 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 present in the molecule. According to an exemplary embodiment, the aziridine crosslinking agents may be or include at least one of bifunctional and trifunctional aziridine crosslinking agents.

[0076] For example, the aziridine crosslinking agents may include one or more of N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-(methylenedi-p-phenylene)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).

[0077] 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%. The shrinkage rate in the electrolyte can be controlled within any of the above ranges.

[0078] The filler has a particle size D100 of about 1.0 μm or less. In any of the above ranges, 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, 0.5 μm to 0.8 μm, for example, 0.5 μm to 0.7 μm. According to an exemplary embodiment, the coating layer includes small particles having a particle size D100 of about 1.0 μm or less as the filler, and by using the (meth)acryloyl binder and the aziridine crosslinking agent, both the dry shrinkage rate and the shrinkage rate in the electrolyte can be reduced.

[0079] According to an exemplary embodiment, the particle size D50 of the filler can be about 0.4 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, for example, 0.35 μm or less. In any of the above ranges, the shrinkage rate in the electrolyte can be reduced.

[0080] The filler can be or include at least one of, for example, inorganic fillers, organic fillers, organic-inorganic composite fillers, and combinations thereof. The inorganic filler can be or include a ceramic material that can improve heat resistance. The inorganic filler can include at least one of, for example, metal oxides, metalloid oxides, metal fluorides, metal hydroxides, and combinations thereof. The inorganic filler can 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 can include at least one of acrylic compounds, imide compounds, amide compounds, and combinations thereof, but is not limited thereto. The organic filler can have a core-shell structure, but is not limited thereto.

[0081] The filler can be substantially spherical, substantially plate-shaped, substantially cubic, or amorphous. For example, the filler can be plate-shaped.

[0082] With respect to the 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 any of the above ranges, the shrinkage rate in the electrolyte can be reduced.

[0083] 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 any of the above ranges, the separator can exhibit desired or improved heat resistance, durability, oxidation resistance, and stability.

[0084] The coating layer can have a thickness of about 0.01 μm to about 20 μm, and within any of the above ranges, the coating layer can have a thickness of 1 μm to 10 μm, 1 μm to 5 μm, or 1 μm to 3 μm.

[0085] 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, such as, 0.05 to 0.4, 0.05 to 0.3, or 0.1 to 0.2. Within any of the above ranges, the separator can exhibit desired or improved gas permeability, heat resistance, adhesion strength, etc. Here, the "thickness of the coating layer" refers to 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.

[0086] Porous substrate A porous substrate can be or include a substrate that has a plurality of pores and is generally included 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, polyetheretherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, fiberglass, Teflon (polytetrafluoroethylene), and at least one of copolymers or mixtures of two or more of these types.

[0087] The porous substrate can be or include, for example, a polyolefin-based substrate containing polyolefins, and the polyolefin-based substrate can have a desired or improved shut-off function, thus contributing to improving the safety of the battery. The polyolefin-based substrate 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. Additionally, the polyolefin-based resin can also include a non-olefin-based resin other than the olefin-based resin or a copolymer including an olefin monomer and a non-olefin monomer.

[0088] 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.

[0089] 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 about 0.05 gf / mm to about 0.1 gf / mm, for example, in the range of about 0.05 gf / mm to about 0.2 gf / mm. The adhesion strength can be measured by the following method.

[0090] The separator for 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 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 jig, and the negative electrode plate is fixed to the lower jig so that the gap between the jigs is 20 mm, and then peeled by pulling in the 180° direction. After starting peeling 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 of the measured values.

[0091] The separator for a rechargeable lithium battery according to an exemplary embodiment can exhibit a desired or improved air permeability, and has 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 can have an air permeability value of less than 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.).

[0092] The separator for a rechargeable lithium battery according to an exemplary embodiment can be formed by coating a composition for forming a coating layer on one or both surfaces of a porous substrate, drying, and then curing the coating layer. Curing can be performed using conventional methods known to those skilled in the art.

[0093] 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 crosslinked product 4, and the crosslinked product 4 includes a (meth)acryloyl binder and a crosslinking agent.

[0094] Rechargeable lithium battery According to an exemplary embodiment, a rechargeable lithium battery includes a separator for a rechargeable lithium battery, a positive electrode, and a negative electrode.

[0095] The separator for a rechargeable lithium battery is as described above. The separator for a rechargeable lithium battery can be located between the positive electrode and the negative electrode.

[0096] Positive electrode The positive electrode for a rechargeable lithium battery can include a current collector and a positive electrode active material layer on the current collector. The positive electrode active material layer can include a positive electrode active material and can also include a binder and / or a conductive material. For example, the positive electrode can also include an additive that can form a sacrificial positive electrode.

[0097] Positive electrode active material The positive electrode active material can include a compound capable of intercalating and deintercalating lithium (lithiated 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 can be used.

[0098] The composite oxide can be or include a lithium transition metal composite oxide. Examples of the composite oxide can 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.

[0099] As an example, the following compounds represented by any of the following chemical formulas can 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 Coc 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); and Li a FePO4 (0.90 ≤ a ≤ 1.8).

[0100] 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.

[0101] The positive electrode active material may 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 may be capable of exhibiting a high capacity and may be applied to a high-capacity, high-density rechargeable lithium battery.

[0102] Based on 100 wt% of the positive electrode active material layer, the amount of the positive electrode active material can be in the range of 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 in the range of about 0.5 wt% to about 5 wt% respectively.

[0103] The binder is configured to attach the positive electrode active material particles to each other and also 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, polymers 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.

[0104] The conductive material can be configured 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 included in 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 at least one of copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0105] Al can be included as the current collector, but is not limited thereto.

[0106] 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).

[0107] For example, the negative electrode active material layer can include about 90 wt% to about 99 wt% of the negative electrode active material, about 0.5 wt% to about 5 wt% of the binder, and about 0 wt% to about 5 wt% of the conductive material.

[0108] 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.

[0109] Materials capable of reversibly embedding / desorbing 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 graphite, such as at least one of natural graphite and artificial graphite that is non-shaped, flaky, lamellar, spherical, or fibrous. The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0110] 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.

[0111] 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 composite, SiO x (0 < x < 2), at least one of 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.

[0112] 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, or may include 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 aggregated, 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.

[0113] 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.

[0114] 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.

[0115] 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 at least one of non-aqueous binders, aqueous binders, dry binders, and combinations thereof.

[0116] 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.

[0117] The aqueous binder may be or include at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin polymer, 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.

[0118] 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.

[0119] 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.

[0120] The conductive material may be configured 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 may be included 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; metal-based 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.

[0121] 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.

[0122] The rechargeable lithium battery may further include an electrolyte.

[0123] Electrolyte The electrolyte for the rechargeable lithium battery may include a non-aqueous organic solvent and a lithium salt.

[0124] Non-aqueous organic solvents can form a medium for transporting ions participating in the electrochemical reaction of the battery.

[0125] 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.

[0126] 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.

[0127] The ester solvents can include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc.

[0128] 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: 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, etc.

[0129] The non-aqueous organic solvent can be included alone or in combination with two or more solvents.

[0130] In addition, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio in the range of about 1:1 to about 1:9.

[0131] 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 y F2y+1 SO2) (where x and y are integers in the range of 1 to 20), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), lithium difluorobis(oxalate)borate (LiDFBOB), and lithium bis(oxalate)borate (LiBOB).

[0132] Rechargeable lithium batteries can be classified into cylindrical batteries, prismatic batteries, pouch-type batteries, coin-type batteries, etc. according to their shapes.

[0133] 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 disposed 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 . The electrode tab 70 may be, for example, the positive electrode tab 71 and the negative electrode tab 72 shown in

[0134] . The electrode tabs 70, 71, and 72 form a circuit path for guiding the current formed in the electrode assembly 40 to the outside.

[0135] The following examples and comparative examples are provided to highlight one or more characteristics of the exemplary embodiments, but it is understood that the examples and comparative examples will not be construed as limiting the scope of the exemplary embodiments, and the comparative examples will not be construed as being outside the scope of the exemplary embodiments. Furthermore, it is understood that the exemplary embodiments are not limited to the specific details described in the embodiments and comparative examples.

[0136] 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, 0.02 mol), and a 20% aqueous sodium 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. This step was repeated three times, and acrylonitrile (AN) (31.31 g, 0.59 mol) was added.

[0137] 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 a 25% aqueous ammonia solution.

[0138] Thus, poly(acrylic acid-co-sodium acrylate-co-acrylonitrile-co-sodium 2-acrylamido-2-methylpropanesulfonate) as an acrylate binder was prepared. The molar ratio of acrylic acid + sodium acrylate, acrylonitrile, and sodium 2-acrylamido-2-methylpropanesulfonate 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%).

[0139] Preparation Example 2 An acrylate 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 + sodium acrylate to acrylonitrile was 42:58. The non-volatile components of the reaction solution were 9.0 wt% (theoretical value: 10%).

[0140] Preparation Example 3 An acrylate 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 + sodium acrylate to sodium 2-acrylamido-2-methylpropanesulfonate was 74:26. The non-volatile components of the reaction solution were 9.0 wt% (theoretical value: 10%).

[0141] Preparation Example 4 The 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 sodium 2-acrylamido-2-methylpropanesulfonate was 74:26. The non-volatile component of the reaction solution was 9.0 wt% (theoretical value: 10%).

[0142] Table 1 below shows the molar ratio, weight-average molecular weight, and glass transition temperature of each monomer of the (meth)acrylate binders prepared in Preparation Examples 1 to 4.

[0143] Table 1:

[0144] Example 1 A dispersion was prepared by mixing the acrylate binder prepared in Preparation Example 1 (10 wt% in distilled water) and boehmite as a filler (particle size D100: 0.5 μm, particle size D50: 0.2 μm, plate-like) at a mass ratio of acrylate binder: filler = 1 part by weight: 30 parts by weight based on the solid content, adding the mixture to an aqueous solvent, and grinding and dispersing it at 25°C for 30 minutes using a bead mill.

[0145] 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%.

[0146] The composition for forming a coating layer was respectively coated on both sides of a polyethylene film (thickness: 8 μm, SK Co., 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.

[0147] Examples 2 to 8 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 D50 and D100 were changed, the mass ratio of acrylate binder: filler was changed, and the content of the aziridine crosslinking agent was changed.

[0148] Comparative Examples 1 to 6 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 crosslinking agent, the content of the crosslinking agent, the mass ratio of (meth)acryloyl binder: filler, the type of adhesive binder, etc. were changed.

[0149] PVA is a homopolymer of polyvinyl alcohol. The epoxy crosslinking agent is ethylene glycol diglycidyl ether.

[0150] Dry shrinkage rate (unit: %) Samples were manufactured 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, then placing the sample between paper or alumina powder, placing the sample in an oven at 150 °C for 1 hour, taking out the sample, and measuring the side dimensions of the drawn square, the shrinkage rate in each of the longitudinal (mechanical direction, MD) and transverse (transverse direction, TD) directions was calculated. The shrinkage rate was calculated according to Equation 1 below.

[0151] 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.

[0152] Shrinkage rate in the electrolyte (unit: %) Samples were manufactured 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.

[0153] A positive electrode paste was prepared by mixing 97 wt% LiCoNiAl as the positive electrode active material, 1.5 wt% carbon nanotubes as the conductive material, and 1.5 wt% polyvinylidene fluoride as the binder, and adding water thereto. The positive electrode was manufactured by coating the prepared positive electrode paste on an aluminum foil and drying and rolling it.

[0154] A negative electrode active material paste was prepared by mixing 97.4 wt% of the negative electrode active material, 1.0 wt% of carboxymethyl cellulose, 1.5 wt% of styrene-butadiene-based rubber, and 0.1 wt% of carbon nanotubes as the conductive agent. Artificial graphite was used as the negative electrode active material. The negative electrode was manufactured by coating the prepared negative electrode paste on a copper foil and drying and rolling it.

[0155] A sample was placed between a positive electrode and a negative electrode to form three sets of positive electrode - sample - negative electrode laminates, which were then placed in 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 so that the laminate was completely soaked with the electrolyte solution, sealed, and left at 25 °C for 12 hours. Then, the laminate was placed in an oven at 150 °C for 1 hour, and then the sample was taken out, and the shrinkage rate in each of the longitudinal (MD) and transverse (TD) directions was calculated by measuring the side dimensions of the drawn square. The shrinkage rate was calculated according to Equation 1 above.

[0156] Presence or absence of crosslinking Samples were prepared by cutting the separators for rechargeable lithium batteries of the example and comparative example into a size of 8 cm × 8 cm. When the samples were sufficiently impregnated in deionized water at 25 °C and left for 25 hours, it was visually determined 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.

[0157] Table 2:

[0158] As shown in Table 2 above, the separators for rechargeable lithium batteries according to the examples exhibited significantly low dry shrinkage rates and shrinkage rates in the electrolyte. Therefore, although not shown in Table 2, it was expected that the separators of the examples improved the stability and lifespan of the battery.

[0159] However, the separators of the comparative examples exhibited higher dry shrinkage rates and / or shrinkage rates in the electrolyte than those of the examples. In addition, although not shown in Table 2 above, the binder prepared in Preparation Example 4 did not undergo a crosslinking reaction.

[0160] 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, thereby improving the stability and lifespan of the battery.

[0161] Although the 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 any modification also falls 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 has a particle size D100 of 1.0 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 1.0 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 0.4 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 structural unit derived from (meth)acrylate or (meth)acrylic acid is represented by one or more 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 the following 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 substituted 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 the following Chemical Formula 5, Chemical Formula 6, Chemical Formula 7 or a combination thereof: 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 substituted 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.

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

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

Images