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 examples of the present disclosure include a separator for a rechargeable lithium battery including a porous substrate and a coating layer on at least one surface of the porous substrate. The coating layer includes a crosslinking product of a binder, a crosslinking agent and a carboxyalkyl cellulose or a salt thereof, and a filler. The adhesive comprises a (methyl) acryloyl adhesive, and the (methyl) acryloyl adhesive comprises a structural unit derived from (methyl) acrylate or (methyl) acrylic acid, a structural unit containing cyano groups and a structural unit containing sulfonate groups. The cross-linking agent comprises one or more of an aziridine cross-linking agent and a carbodiimide cross-linking agent.

Description

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0049785 filed on April 15, 2024, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] The present disclosure relates to a separator for a rechargeable lithium battery and a rechargeable lithium battery including the separator. Background Art

[0003] As the presence of electronic devices using batteries increases, such as mobile phones, notebook computers, electric vehicles, etc., the demand for secondary batteries with high energy density and high capacity is increasing. Therefore, improving the performance of rechargeable lithium batteries may be advantageous.

[0004] A rechargeable lithium battery is a battery that generally includes a positive electrode and a negative electrode, the positive electrode and the negative electrode contain an active material capable of intercalating and deintercalating lithium ions, and generates electric energy through oxidation reactions and reduction reactions when lithium ions are intercalated into and deintercalated from the positive electrode and the negative electrode.

[0005] The rechargeable lithium battery may further include a separator between the positive electrode and the negative electrode. The separator may have low film resistance and high heat resistance, which results in low thermal shrinkage. Summary of the Invention

[0006] One example embodiment includes a separator for a rechargeable lithium battery that increases battery stability by having low drying shrinkage and low shrinkage in an electrolyte.

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

[0008] Example embodiments include a separator for a rechargeable lithium battery, the separator comprising: a porous substrate; and a coating layer located on at least one surface of the porous substrate, wherein the coating layer comprises a binder, a cross-linking agent, and a cross-linked product of carboxyalkyl cellulose or a salt thereof, and a filler, the binder comprising a (meth)acryloyl-based binder, the (meth)acryloyl-based binder comprising 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, and the cross-linking agent comprising one or more of an aziridine-based cross-linking agent and a carbodiimide-based cross-linking agent.

[0009] The coating layer is formed of or includes a composition comprising a (meth)acryloyl-based binder, a crosslinking agent, carboxyalkyl cellulose or a salt thereof, and a filler.

[0010] The carboxyalkyl cellulose or its salt includes carboxymethyl cellulose or its salt.

[0011] The carboxyalkyl cellulose or its salt is included in an amount ranging from about 20 wt % to about 70 wt % of the total amount of the (meth)acryloyl-based binder, the crosslinking agent, and the carboxyalkyl cellulose or its salt.

[0012] Aziridine crosslinking agents include one or more of N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-(methylenedi-p-phenylene)bis(aziridine-1-carboxamide), triethylene melamine, 1,1-isophthaloylbis(2-methylaziridine), tris(1-aziridinyl)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).

[0013] The carbodiimide crosslinking agent includes one or more of a monocarbodiimide compound and a polycarbodiimide compound.

[0014] The filler includes a filler having a particle size D100 of about 1.0 μm or less.

[0015] The filler is generally spherical, generally plate-like, generally cubic, or amorphous.

[0016] The (meth)acryl-based binder and the filler are included in a mass ratio of about 1:10 to about 1:50.

[0017] Among the total amount of the (meth)acryloyl-based binder, the cross-linking agent and the carboxyalkyl cellulose or its salt, the (meth)acryloyl-based binder is included in an amount ranging from about 25 wt % to about 75 wt %, the cross-linking agent is included in an amount ranging from about 5 wt % to about 30 wt %, and the carboxyalkyl cellulose or its salt is included in an amount ranging from about 20 wt % to about 70 wt %.

[0018] The structural unit derived from (meth)acrylate or (meth)acrylic acid is represented by at least one of the following Chemical Formula 1, Chemical Formula 2, and Chemical Formula 3, or a combination thereof:

[0019] Chemical formula 1:

[0020]

[0021] Chemical formula 2:

[0022]

[0023] Chemical formula 3:

[0024]

[0025] In Chemical Formulas 1 to 3,

[0026] R 1 to R 6 are independently hydrogen or methyl, and

[0027] In Chemical Formula 2,

[0028] M is or includes an alkali metal,

[0029] The cyano group-containing structural unit is represented by the following chemical formula 4:

[0030] Chemical formula 4:

[0031]

[0032] In Chemical Formula 4,

[0033] R 7 and R 8 are independently hydrogen or C1 to C3 alkyl,

[0034] L 1 is or includes -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-,

[0035] x is an integer in the range of 0 to 2,

[0036] L 2 is or 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 heterocyclyl group, and

[0037] y is an integer in the range of 0 to 2, and

[0038] The structural unit containing a sulfonate group is represented by at least one of the following Chemical Formula 5, Chemical Formula 6, and Chemical Formula 7, or a combination thereof:

[0039] Chemical formula 5:

[0040]

[0041] Chemical formula 6:

[0042]

[0043] Chemical formula 7:

[0044]

[0045] In Chemical Formulas 5 to 7,

[0046] R 9 to R 14 are independently hydrogen or C1 to C3 alkyl,

[0047] L 3 , L 5 and L 7 are independently or include -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-,

[0048] L 4 , L 6 and L 8 are independently or include substituted or unsubstituted C1 to C10 alkylene, substituted or unsubstituted C3 to C20 cycloalkylene, substituted or unsubstituted C6 to C20 arylene or substituted or unsubstituted C3 to C20 heterocyclyl,

[0049] a, b, c, d, e, and f are each independently an integer in the range of 0 to 2, and

[0050] In Chemical Formula 6,

[0051] M is or includes an alkali metal.

[0052] Structural units derived from (meth)acrylate or (meth)acrylic acid in an amount ranging from about 10 mol % to about 70 mol %, structural units containing a cyano group in an amount ranging from about 20 mol % to about 85 mol %, and structural units containing a sulfonate group in an amount ranging from about 0.1 mol % to about 20 mol % are included in the (meth)acryloyl-based binder.

[0053] The coating layer has a thickness in a range of about 1 μm to about 4 μm.

[0054] According to another example embodiment, a rechargeable lithium battery includes a positive electrode, a negative electrode, and a separator for a rechargeable lithium battery between the positive electrode and the negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is a cross-sectional view illustrating a separator for a rechargeable lithium battery according to one example embodiment.

[0056] Figures 2 to 5 is a schematic cross-sectional view illustrating a rechargeable lithium battery according to one example embodiment. DETAILED DESCRIPTION

[0057] 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 limited only by the scope of the appended claims.

[0058] Unless stated otherwise herein, when a component such as a layer, film, region, plate, etc. is described as being disposed “on” another component, it not only includes the case where the component is “directly on” the other component but also includes the case where other components exist therebetween.

[0059] 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 A and B."

[0060] In this specification, "a combination thereof" may refer to a mixture, stack, composite, copolymer, alloy, blend or reaction product of the components.

[0061] Unless otherwise defined herein, "particle size D100" refers to the diameter of the particles whose cumulative volume is 100% by volume in the particle size distribution. The particle size D100 can be measured by methods known to those skilled in the art, for example, it can be measured using a particle size analyzer, a transmission electron microscope photograph, or a scanning electron microscope photograph. As another method, the particle size D100 can be obtained by measuring the particle size using a measuring device using 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 D100 can be measured using a laser diffraction method. When the particle size is measured 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., Microtrac's MT 3000), and an ultrasonic wave 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.

[0062] Unless otherwise defined herein, "particle size D50" may be an average particle size D50, which refers to the diameter of particles having a cumulative volume of 50% by volume in a particle size distribution. The particle size distribution may be obtained by the above method in particle size D100.

[0063] In this specification, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0064] Hereinafter, unless otherwise defined, “substituted” means that hydrogen in a compound is replaced by a substituent, such as or including a C1 to C30 alkyl group, a C2 to C30 alkenyl group, a C2 to C30 alkynyl group, a C6 to C30 aryl group, a C7 to C30 alkylaryl group, a C1 to C30 alkoxy group, a C1 to C30 heteroalkyl group, a C3 to C30 heteroalkylaryl group, a C3 to C30 cycloalkyl group, a C3 to C15 cycloalkenyl group, a C6 to C30 cycloalkynyl group, a C2 to C30 heterocycloalkyl group, a halogen (F, Cl, Br or I), a hydroxyl group (—OH), a nitro group (—NO2), a cyano group (—CN), an amino group (—NRR′) (wherein R and R′ are independently hydrogen or a C1 to C6 alkyl group), a sulfobetaine group (—RR′N + (CH2) n SO3-, n is a natural number of 1 to 10) (wherein, R and R' are independently C1 to C20 alkyl), carboxybetaine group (-RR'N + (CH2) n COO-, n is a natural number from 1 to 10) (here, R and R' are independently C1 to C20 alkyl), azido (-N3), amidine (-C(=NH)NH2), hydrazine (-NHNH2), hydrazone (=N(NH2)), carbamoyl (-C(O)NH2), thiol (-SH), acyl (-C(=O)R, where R represents a C1 to C6 alkyl, a C1 to C6 alkoxy or a C6 to C12 aryl), carboxyl (-COOH) or a salt thereof (-C(=O)OM, where M represents an organic or inorganic cation), sulfonic acid (-SO3H) or a salt thereof (-SO3M, where M represents an organic or inorganic cation), phosphate (-PO3H2) or a salt thereof (-PO3MH or -PO3M2, where M represents an organic or inorganic cation) and at least one of a combination thereof.

[0065] Hereinafter, a C1 to C3 alkyl group may be or include at least one of a methyl group, an ethyl group, and a propyl group. A C1 to C10 alkylene group may be or include, for example, at least one of a C1 to C6 alkylene group, a C1 to C5 alkylene group, and a C1 to C3 alkylene group, and may be or include, for example, at least one of a methylene group, an ethylene group, and a propylene group. A C3 to C20 cycloalkylene group may be or include, for example, at least one of a C3 to C10 cycloalkylene group and a C5 to C10 cycloalkylene group, for example, a cyclohexylene group. A C6 to C20 arylene group may be or include, for example, a C6 to C10 arylene group, for example, a phenylene group. A C3 to C20 heterocyclic group may be or include, for example, a C3 to C10 heterocyclic group, for example, a pyridyl group.

[0066] Hereinafter, “hetero” means including one or more heteroatoms, such as or including at least one of N, O, S, Si and P.

[0067] Additionally, in a chemical formula, the symbol * refers to moieties that are connected to the same or different atoms, groups or structural units.

[0068] Hereinafter, "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.

[0069] In this specification, when describing a numerical range, “X to Y” means “X or more and Y or less (greater than or equal to X and less than or equal to Y)”.

[0070] When the term "about" or "substantially" is 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%.

[0071] A separator for a rechargeable lithium battery according to one 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 binder, a crosslinking agent, and a crosslinked product of carboxyalkyl cellulose or a salt thereof; and a filler. The binder includes a (meth)acryloyl-based binder containing 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 crosslinking agent includes one or more of an aziridine-based crosslinking agent and a carbodiimide-based crosslinking agent.

[0072] Because the coating layer includes a (meth)acryloyl-based binder, a crosslinking agent, and a crosslinked product of carboxyalkyl cellulose or a salt thereof, and a filler, the separator for a rechargeable lithium battery can have significantly low drying shrinkage and shrinkage in an electrolyte.

[0073] According to an example embodiment, the coating layer may be formed of a composition including one or more of an aziridine-type cross-linking agent and a carbodiimide-type cross-linking agent, a (meth)acryl-type binder, carboxyalkyl cellulose or a salt thereof, and a filler, or a composition including one or more of an aziridine-type cross-linking agent and a carbodiimide-type cross-linking agent, a (meth)acryl-type binder, carboxyalkyl cellulose or a salt thereof, and a filler.

[0074] According to an example embodiment, the cross-linked product may be or include a thermal cross-linked product.

[0075] According to one example embodiment, the separator for a rechargeable lithium battery may have a drying shrinkage rate of about 5% or less in each of the longitudinal direction (MD) and the transverse direction (TD), and a shrinkage rate in the electrolyte in each of the MD and TD may be about 20% or less, for example, 15% or less, for example, 10% or less, or for example, 5% or less.

[0076] According to one exemplary embodiment, a separator for a rechargeable lithium battery exhibits significantly low shrinkage in an electrolyte. The shrinkage in the electrolyte is determined by considering the application location of the separator in the rechargeable lithium battery. The separator can be impregnated with the electrolyte. The separator having low shrinkage in the electrolyte can increase the stability of the battery by maintaining heat resistance when the separator is impregnated with the electrolyte without weakening the mechanical properties of the (meth)acrylic binder.

[0077] A separator formed of or including a composition including a (meth)acryl-based binder but not including an aziridine-based crosslinker and a carbodiimide-based crosslinker as a crosslinker, or including a crosslinker other than an aziridine-based crosslinker and a carbodiimide-based crosslinker, may not exhibit the above shrinkage rate range in the electrolyte. According to one example embodiment, one or more of the aziridine-based crosslinker and the carbodiimide-based crosslinker may be included in an amount of about 95 wt % or more (e.g., in a range of 98 wt % to 100 wt %, or, for example, 100 wt %) of the total crosslinker in the composition.

[0078] A separator formed of or including a composition including an aziridine-based crosslinking agent or a carbodiimide-based crosslinking agent and a filler but not including a (meth)acryl-based binder or including a binder other than a (meth)acryl-based binder may not exhibit the above drying shrinkage range and shrinkage range in the electrolyte. According to one exemplary embodiment, the (meth)acryl-based binder may be included in an amount of about 95 wt % or more (e.g., in the range of 98 wt % to 100 wt %, or, for example, 100 wt %) of the total binder in the composition.

[0079] A separator formed of or including a composition not including carboxyalkyl cellulose or a salt thereof may not exhibit the above range of drying shrinkage and shrinkage in an electrolyte.

[0080] coating

[0081] The coating layer may be or include a heat-resistant layer, and the adhesive may be or include a heat-resistant adhesive.

[0082] The adhesive includes a (meth)acryloyl-based adhesive containing 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.

[0083] According to one example embodiment, the total amount of structural units derived from (meth)acrylate or (meth)acrylic acid, structural units containing a cyano group, and structural units containing a sulfonate group in the binder may be about 95 mol% or more, for example, may be in the range of 99 mol% to 100 mol%, or may be 100 mol%.

[0084] The (meth)acryloyl-based binder is a water-based heat-resistant binder and can fix the filler to the porous substrate, provide bonding strength so that the coating layer is bonded to the porous substrate and the electrode, and contribute to increasing the heat resistance, air permeability, and oxidation resistance of the separator.

[0085] In the structural unit derived from (meth)acrylate or (meth)acrylic acid, the (meth)acrylate may be or include a conjugate base of (meth)acrylic acid, a (meth)acrylate salt, or a derivative thereof. The structural unit derived from (meth)acrylate or (meth)acrylic acid may be, for example, represented by at least one of the following Chemical Formulas 1, 2, and 3, or a combination thereof:

[0086] Chemical formula 1:

[0087]

[0088] Chemical formula 2:

[0089]

[0090] Chemical formula 3:

[0091]

[0092] In Chemical Formulas 1 to 3,

[0093] R 1 to R 6 are independently hydrogen or methyl, and

[0094] In Chemical Formula 2,

[0095] M is or includes an alkali metal.

[0096] The alkali metal may be or include, for example, at least one of lithium, sodium, potassium, rubidium, and cesium.

[0097] The structural unit derived from (meth)acrylate or (meth)acrylic acid may be included in the (meth)acryloyl-based binder in an amount ranging from about 10 mol% to about 70 mol% (e.g., 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, in a range of 10 mol% to 50 mol%, in a range of 20 mol% to 60 mol%, or in a range of 30 mol% to 60 mol%). When the structural unit derived from (meth)acrylate or (meth)acrylic acid is included in the above range, the separator including the (meth)acryloyl-based binder may exhibit desired or improved bonding strength, heat resistance, air permeability, and oxidation resistance.

[0098] For example, the structural unit derived from (meth)acrylate or (meth)acrylic acid may include the structural unit represented by Chemical Formula 2 and the structural unit represented by Chemical Formula 3, and in this case, the structural unit represented by Chemical Formula 2 and the structural unit represented by Chemical Formula 3 may be included in a molar ratio of about 10:1 to about 1:2, 10:1 to 1:1, or 5:1 to 1:1.

[0099] The cyano group-containing structural unit can be represented, for example, by the following Chemical Formula 4:

[0100] Chemical formula 4:

[0101]

[0102] In Chemical Formula 4,

[0103] R 7 and R 8 are independently hydrogen or C1 to C3 alkyl,

[0104] L 1 is or includes -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-,

[0105] x is an integer in the range of 0 to 2,

[0106] L 2 is or 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 heterocyclyl group, and

[0107] y is an integer in the range of 0 to 2.

[0108] The cyano group-containing structural unit may be or include, for example, a structural unit derived from at least one of (meth) acrylonitrile, olefin nitrile, (meth) cyanoalkyl acrylate, and 2-(vinyloxy)alkanenitrile. Here, the olefin may be or include at least one of a C2 to C20 olefin, a C2 to C10 olefin, and a C2 to C6 olefin, the alkyl may be or include at least one of a C1 to C20 alkyl, a C1 to C10 alkyl, and a C1 to C6 alkyl, and the alkane may be or include at least one of a C1 to C20 alkane, a C1 to C10 alkane, and a C1 to C6 alkane.

[0109] 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 cyanoalkyl (meth)acrylate may be or include, for example, at least one of cyanomethyl (meth)acrylate, cyanoethyl (meth)acrylate, cyanopropyl (meth)acrylate, cyanooctyl (meth)acrylate, etc. The 2-(vinyloxy)alkanenitrile may be or include, for example, at least one of 2-(vinyloxy)acetonitrile, 2-(vinyloxy)propionitrile, etc.

[0110] The cyano group-containing structural unit may be included in the (meth)acryl-based adhesive in an amount ranging from about 20 mol% to about 85 mol% (e.g., 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, in a range of 30 mol% to 85 mol%, in a range of 40 mol% to 85 mol%, in a range of 30 mol% to 70 mol%, or in a range of 30 mol% to 60 mol%). When the cyano group-containing structural unit is included within the above range, the (meth)acryl-based adhesive and the separator including the (meth)acryl-based adhesive may exhibit desired or improved oxidation resistance and easily exhibit desired or improved bonding strength, heat resistance, and air permeability.

[0111] The structural unit containing a sulfonate group may be or include a structural unit containing a conjugate base of a sulfonic acid, a sulfonate salt, a sulfonic acid, or a derivative thereof. For example, the structural unit containing a sulfonate group may be represented by at least one of the following Chemical Formula 5, Chemical Formula 6, and Chemical Formula 7, or a combination thereof:

[0112] Chemical formula 5:

[0113]

[0114] Chemical formula 6:

[0115]

[0116] Chemical formula 7:

[0117]

[0118] In Chemical Formulas 5 to 7,

[0119] R 9 to R 14 are independently hydrogen or C1 to C3 alkyl,

[0120] L 3 , L 5 and L 7 are independently or include -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-,

[0121] L 4 , L 6 and L 8 are independently or include substituted or unsubstituted C1 to C10 alkylene, substituted or unsubstituted C3 to C20 cycloalkylene, substituted or unsubstituted C6 to C20 arylene or substituted or unsubstituted C3 to C20 heterocyclyl,

[0122] a, b, c, d, e, and f are each independently an integer in the range of 0 to 2, and

[0123] In Chemical Formula 6,

[0124] M is or includes an alkali metal.

[0125] For example, in Chemical Formulas 5 to 7,

[0126] L 3 , L 5 and L 7 are independently or include -C(=O)NH-,

[0127] L 4 , L 6 and L 8 are independently or include C1 to C10 alkylene, and

[0128] a, b, c, d, e, and f may all be integers equal to 1.

[0129] The sulfonate group-containing structural unit may include only one or two or more of the structural unit 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.

[0130] 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, sulfoalkyl(meth)acrylate, or salts thereof.

[0131] Here, the alkane may be or include at least one of a C1 to C20 alkane, a C1 to C10 alkane, and a C1 to C6 alkane, and the alkyl group may be or include at least one of a C1 to C20 alkyl group, a C1 to C10 alkyl group, and a C1 to C6 alkyl group. The salt is composed of or includes the above-mentioned sulfonic acid and a suitable ion. The ion may be or include, for example, an alkali metal ion, and in this case, the salt may be or include an alkali metal salt of the sulfonic acid.

[0132] The (meth)acrylamidoalkanesulfonic acid may be or include, for example, 2-(meth)acrylamido-2-methylpropanesulfonic acid, and the (meth)acrylic acid sulfoalkyl ester may be or include, for example, at least one of 2-sulfoethyl (meth)acrylate, 3-sulfopropyl (meth)acrylate, and the like.

[0133] The sulfonate-containing structural unit may be included in an amount of about 0.1 mol% to about 20 mol% (e.g., 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%, in the range of 0.1 mol% to 10 mol%, in the range of 1 mol% to 20 mol%, or in the range of 1 mol% to 10 mol%) in the (meth) acryl-based adhesive. When the sulfonate-containing structural unit is included within the above range, the (meth) acryl-based adhesive and the separator including the (meth) acryl-based adhesive may exhibit desired or improved bonding strength, heat resistance, air permeability, and oxidation resistance.

[0134] As described above, the (meth)acryl binder may include an alkali metal. The alkali metal may exist in the form of a cation and, for example, may be or include at least one of lithium, sodium, potassium, rubidium, and cesium. For example, the alkali metal may be combined with the (meth)acryl binder and may exist in the form of a salt. The alkali metal may facilitate the synthesis of the (meth)acryl binder in an aqueous solvent, increase the bonding strength of the coating layer, and increase the heat resistance, air permeability, oxidation resistance, etc. of the diaphragm.

[0135] The alkali metal may be included in an amount ranging from about 1 wt % to about 40 wt % (e.g., 1 wt % to 30 wt %, 1 wt % to 20 wt %, or 10 wt % to 20 wt %) of the total amount of the alkali metal and the (meth)acryl-based binder. For example, the (meth)acryl-based binder and the alkali metal may be included in a weight ratio of about 99:1 to about 60:40, a weight ratio of 99:1 to 70:30 (e.g., a weight ratio of 99:1 to 80:20, or, for example, a weight ratio of 90:10 to 80:20).

[0136] In addition, the alkali metal may be included in an amount ranging from about 0.1 mol% to about 1.0 mol% relative to the total content of the alkali metal and the (meth)acryl-based binder. When the alkali metal is included in the above range, the coating layer may have desired or improved bonding strength, and the separator including the coating layer may exhibit desired or improved heat resistance, air permeability, and oxidation resistance.

[0137] The (meth)acryl-based adhesive may be represented by the following Chemical Formula 8, for example:

[0138] Chemical formula 8:

[0139]

[0140] In Chemical Formula 8,

[0141] R 15 to R 18 are independently hydrogen or methyl,

[0142] R 19 to R 22 are independently hydrogen or C1 to C3 alkyl,

[0143] L 1 and L 5 are independently or include -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-,

[0144] L 2 and L 6 are independently or include substituted or unsubstituted C1 to C10 alkylene, substituted or unsubstituted C3 to C20 cycloalkylene, substituted or unsubstituted C6 to C20 arylene or substituted or unsubstituted C3 to C20 heterocyclyl,

[0145] x, y, c and d are each independently an integer in the range of 0 to 2,

[0146] M is or includes an alkali metal such as lithium, sodium, potassium, rubidium or cesium, and

[0147] k, l, m and n refer to the molar ratios of the respective structural units.

[0148] As an example, in Chemical Formula 8, k+l+m+n=1. Also, as an example, 0.1≤(k+l)≤0.5, 0.3≤m≤0.85, and 0.001≤n≤0.2, for example, 0.1≤k≤0.5 and 0≤l≤0.25.

[0149] 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.

[0150] Alkali metals (M + The degree of substitution of the alkali metal with respect to (k+n) may be in the range of about 0.5 to about 1.0, for example, in the range of 0.6 to 0.9 or in the range of 0.7 to 0.9. When the degree of substitution of the alkali metal satisfies the above range, the (meth)acryl-based binder and the separator including the (meth)acryl-based binder may exhibit desired or improved bonding strength, heat resistance, and oxidation resistance.

[0151] The (meth)acryloyl-based binder may be in various forms such as an alternating polymer in which units are alternately distributed, a random polymer in which units are randomly distributed, or a graft polymer in which some structural units are grafted.

[0152] The weight average molecular weight (Mw) of the (meth)acryl-based binder may be in the range of about 200,000 g / mol to about 700,000 g / mol (e.g., 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)acryl-based binder satisfies the above range, the (meth)acryl-based binder and the diaphragm including the (meth)acryl-based binder may exhibit desired or improved bonding strength, heat resistance, air permeability, and oxidation resistance. The weight average molecular weight may be an average molecular weight measured using gel permeation chromatography in terms of polystyrene.

[0153] The glass transition temperature of the (meth)acryl-based adhesive may be in the range of about 200°C to about 280°C, for example, in the range of 210°C to 280°C. When the glass transition temperature of the (meth)acryl-based adhesive satisfies the above range, the (meth)acryl-based adhesive and the separator including the (meth)acryl-based adhesive may exhibit desired or improved bonding strength, heat resistance, air permeability, and oxidation resistance. The glass transition temperature may be a value measured by, for example, differential scanning calorimetry.

[0154] The (meth)acryl-based adhesive can be prepared by, for example, a solution polymerization method.

[0155] According to one example embodiment, the (meth)acryl-based adhesive may be included in the coating layer of the separator in the form of a film.

[0156] %, 48 wt%, 49 wt%, 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 100 wt%, 101 wt%, 102 wt%, 103 wt%, 104 %, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%), 30wt% to 70wt% or 30wt% to 60wt% of the (meth)acryl-based binder. Within the above range, the above shrinkage rate of the separator can be easily achieved.

[0157] The crosslinking agent includes one or more of an aziridine crosslinking agent and a carbodiimide crosslinking agent. The aziridine crosslinking agent and the carbodiimide crosslinking agent can crosslink the (meth)acryl binder and make the separator easily meet the above dry shrinkage range and the shrinkage range in the electrolyte.

[0158] For example, the cross-linking agent may be or include an aziridine cross-linking agent. Compared with carbodiimide cross-linking agents, aziridine cross-linking agents can further reduce the drying shrinkage and the shrinkage in electrolyte.

[0159] The aziridine crosslinking agent may be or include a bifunctional or higher functional aziridine crosslinking agent. 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 agent may be or include a bifunctional or trifunctional aziridine crosslinking agent.

[0160] For example, the aziridine crosslinking agent may include one or more of N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-(methylenedi-p-phenylene)bis(aziridine-1-carboxamide), triethylene melamine, 1,1-isophthaloylbis(2-methylaziridine), tris(1-aziridinyl)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).

[0161] According to one example embodiment, the carbodiimide-based cross-linking agent may include one or more of a monocarbodiimide-based compound and a polycarbodiimide-based compound.

[0162] According to one example embodiment, the carbodiimide-based crosslinking agent may be or include a monocarbodiimide-based compound having the chemical formula RN=C=N-R' (R and R' are each independently or include a substituted or unsubstituted C1 to C5 alkyl group or a substituted or unsubstituted C5 to C10 cycloalkyl group).

[0163] According to another exemplary embodiment, the carbodiimide-based cross-linking agent may be or include a polycarbodiimide-based compound prepared by subjecting diisocyanate to a decarboxylation condensation reaction in the presence of a carbodiimide catalyst.

[0164] The diisocyanate included in the decarboxylation condensation reaction may include, for example, at least one of 4,4′-diphenylmethane diisocyanate, 3,3′-dimethoxy-4,4′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, 4,4′-diphenylether diisocyanate, 3,3′-dimethyl-4,4′-diphenylether diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, and tetramethylxylene diisocyanate.

[0165] Examples of the carbodiimide catalyst that can be included in the decarboxylation condensation reaction can include phosphorene oxides, such as 1-phenyl-2-phosphene-1-oxide, 3-methyl-2-phosphene-1-oxide, 1-ethyl-3-methyl-2-phosphene-1-oxide, 1-ethyl-2-phosphene-1-oxide, or 3-phosphene isomers thereof.

[0166] One or more crosslinking agents (e.g., aziridine crosslinking agents and carbodiimide crosslinking agents) may be included in appropriate amounts relative to the binder (e.g., (meth)acryl binder), crosslinking agent, and carboxyalkyl cellulose or its salt. According to one exemplary embodiment, the crosslinking agent may be included in an amount ranging from about 5 wt % to about 30 wt % (e.g., 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt %, 20 wt %, 21 wt %, 22 wt %, 23 wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt %, 30 wt %), 10 wt % to 30 wt %, or 10 wt % to 20 wt % of the total amount of the (meth)acryl binder, crosslinking agent, and carboxyalkyl cellulose or its salt. Within the above ranges, binder crosslinking may be present or included.

[0167] Carboxyalkyl cellulose or its salt can react with a crosslinking agent by having a cyclic structure and a carboxyl group in the molecule, so that the modulus of the coating layer can be increased and the drying shrinkage and the shrinkage in the electrolyte can be further reduced.

[0168] The carboxyalkyl cellulose can be or include, for example, carboxymethyl cellulose.

[0169] The salt of carboxyalkyl cellulose may be or include, for example, a monovalent metal salt of carboxyalkyl cellulose, for example, a sodium salt of carboxyalkyl cellulose.

[0170] The carboxyalkyl cellulose or its salt may be included in an appropriate amount relative to the binder (e.g., (meth)acryloyl binder) and the cross-linking agent. According to an exemplary embodiment, the carboxyalkyl cellulose or its salt may be included in an amount of about 20 wt % to about 70 wt % (20 wt %, 21 wt %, 22 wt %, 23 wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt %, 30 wt %, 31 wt %, 32 wt %, 33 wt %, 34 wt %, 35 wt %, 36 wt %, 37 wt %, 38 wt %, 39 wt %, 40 wt %, 41 wt %, 42 wt %, 43 wt %, 44 wt %) of the total amount of the (meth)acryloyl binder, the cross-linking agent and the carboxyalkyl cellulose or its salt. %, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, 70wt%), for example, 30wt% to 70wt%, or for example, 30wt% to 60wt% includes the carboxyalkyl cellulose or its salt. Within the above range, it is possible to further reduce the drying shrinkage and the shrinkage in the electrolyte by increasing the modulus of the coating layer.

[0171] The filler can include a filler having a particle size D100 of about 1.0 μm or less. Within the above range, when the (meth)acryl binder is combined with the aziridine crosslinking agent, the dry shrinkage rate and the shrinkage rate in the electrolyte can be met. For example, the filler can have a particle size D100 of 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, 0.8 μm or less, 0.7 μm or less, or in the range of 0.3 μm to 0.7 μm.

[0172] According to an example embodiment, the filler having a particle size D100 of about 1.0 μm or less may be included in an amount of about 95 wt % or more (e.g., in a range of 95 wt % to 100 wt %, in a range of 98 wt % to 100 wt %, or 100 wt %) of the total filler in the coating layer.

[0173] According to an exemplary embodiment, the filler may have a particle size D50 of about 0.4 μm or less (eg, 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm), or 0.35 μm or less. Within the above range, heat resistance can be increased.

[0174] The filler can be or include, for example, an inorganic filler, an organic filler, an organic-inorganic composite filler, or a combination thereof. The inorganic filler can be or include a ceramic material that can increase heat resistance. The inorganic filler can include, for example, at least one of a metal oxide, a metalloid oxide, a metal fluoride, a metal hydroxide, and a combination thereof. The inorganic filler can include, for example, at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and a combination thereof, but is not limited thereto. The organic filler can include, but is not limited to, an acrylic compound, an imide compound, an amide compound, and a combination thereof. The organic filler can have a core-shell structure, but is not limited thereto.

[0175] The filler can be generally spherical, generally plate-like, cubic, or amorphous. For example, the filler can be plate-like or cubic, and in another example, can be cubic. The generally cubic shape can have the significantly low shrinkage rate mentioned above.

[0176] The filler can be included in an appropriate amount relative to the binder (e.g., a (meth)acrylic binder). According to one exemplary embodiment, the (meth)acrylic binder and filler can be included in a mass ratio ranging from about 1:10 to about 1:50 (e.g., 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50), or 1:20 to 1:30. Within this range, heat resistance can be increased.

[0177] The filler may be included in an amount ranging from about 50 wt % to about 99 wt % (e.g., 70 wt % to 99 wt %, 75 wt % to 99 wt %, 80 wt % to 99 wt %, 85 wt % to 99 wt %, 90 wt % to 99 wt %, or 95 wt % to 99 wt %) of the total amount of the coating layer. When the filler is included within the above range, the separator may exhibit desired or improved heat resistance, durability, oxidation resistance, and stability.

[0178] The coating layer may have a thickness in the range of about 0.01 μm to about 20 μm, and within the above range, may have a thickness in the range of 1 μm to 10 μm, 1 μm to 5 μm, 1 μm to 4 μm, or 1 μm to 3 μm.

[0179] 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, in the range of 0.05 to 0.4 or in the range of 0.1 to 0.4. Within the above range, the separator can exhibit desired or improved air permeability, heat resistance, bonding 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 refers to the thickness of two coating layers when the coating layer is formed on both surfaces of the porous substrate.

[0180] porous substrate

[0181] The porous substrate can be or include a substrate having 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 polymer, such as or including a polyolefin (such as polyethylene or polypropylene), a polyester (such as polyethylene terephthalate or polybutylene terephthalate), a polyacetal, a polyamide, a polyimide, a polycarbonate, a polyetheretherketone, a polyaryletherketone, a polyetherimide, a polyamideimide, a polybenzimidazole, a polyethersulfone, a polyphenylene oxide, a cyclic olefin copolymer, a polyphenylene sulfide, a polyethylene naphthalate, a glass fiber, Teflon (polytetrafluoroethylene), and at least one of copolymers or mixtures of two or more types thereof.

[0182] The porous substrate may be or include, for example, a polyolefin-based substrate containing polyolefins, and the polyolefin-based substrate may have a desired or improved shutdown function, thereby contributing to increased battery safety. The polyolefin-based substrate may be or include, for example, at least one of a polyethylene monolayer, a polypropylene monolayer, a polyethylene / polypropylene bilayer, a polypropylene / polyethylene / polypropylene trilayer, and a polyethylene / polypropylene / polyethylene trilayer. Furthermore, the polyolefin-based resin may include a non-olefin resin other than an olefin resin, or a copolymer comprising an olefin monomer and a non-olefin monomer.

[0183] The porous substrate may have a thickness in a range of about 1 μm to about 40 μm, for example, in a range of 1 μm to 30 μm, in a range of 1 μm to 20 μm, or in a range of 5 μm to 15 μm.

[0184] The diaphragm for a rechargeable lithium battery according to an example embodiment may exhibit desired or improved air permeability and have, for example, an air permeability value of less than about 200 sec / 100 cc (e.g., 180 sec / 100 cc or less, or 160 sec / 100 cc or less). That is, the diaphragm may have an air permeability value of less than about 40 sec / 100 cc 1 μm (e.g., 30 sec / 100 cc 1 μm or less, or 25 sec / 100 cc 1 μm or less) per unit thickness. Here, air permeability refers to the time (seconds) it takes for 100 cc of air to pass through a diaphragm of unit thickness. The air permeability per unit thickness can be obtained by measuring the air permeability of the diaphragm of 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 diaphragm using an air permeability measuring device (EG01-55-1MR, Asahi Seiko Co., Ltd.).

[0185] The separator 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.

[0186] Figure 1 is a cross-sectional view illustrating a separator for a rechargeable lithium battery according to one example embodiment.

[0187] Reference Figure 1 , a separator for a rechargeable lithium battery includes a porous substrate 1 and a coating layer 2 located on one surface of the porous substrate 1. The coating layer 2 includes a filler 3 and a cross-linked product 4 of a (meth)acrylic binder, a cross-linking agent, and carboxyalkyl cellulose or a salt thereof.

[0188] Rechargeable lithium battery

[0189] According to one example embodiment, a rechargeable lithium battery includes a separator for a rechargeable lithium battery, a positive electrode, and a negative electrode.

[0190] The separator for a rechargeable lithium battery is described above and may be located between the positive electrode and the negative electrode.

[0191] positive electrode

[0192] A positive electrode for a 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 further include a binder and / or a conductive material.

[0193] For example, the positive electrode may further include an additive that may be configured as a sacrificial positive electrode.

[0194] Positive electrode active material

[0195] The positive electrode active material may include a compound capable of intercalating and deintercalating lithium (lithiated intercalation compound), for example, at least one of a composite oxide of lithium and a metal such as or including at least one of cobalt, manganese, nickel, and combinations thereof.

[0196] 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 oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, and combinations thereof.

[0197] As an example, a compound represented by any one of the following chemical formulas may be included: 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 bO2(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).

[0198] In the above chemical formula, 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 It is or includes at least one of Mn, Al and combinations thereof.

[0199] The positive electrode active material may be or include, for example, a high-nickel positive electrode active material having a nickel content of 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%, based on 100 mol% of metals other than lithium in the lithium transition metal composite oxide. The high-nickel positive electrode active material may be capable of achieving high capacity and may be applied to high-capacity, high-density rechargeable lithium batteries.

[0200] The amount of the positive electrode active material may be in the range of about 90 wt % to about 99 wt % based on 100 wt % of the positive electrode active material layer. The amount of the binder and the conductive material may be in the range of about 0.5 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer, respectively.

[0201] 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 may 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, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, and the like.

[0202] Conductive materials may be included to impart electrical conductivity (e.g., electrical conductivity) to the electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons may be included in the battery. Examples of conductive materials may include: carbon-based materials such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials including at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0203] Al may be included as a current collector, but is not limited thereto.

[0204] negative electrode

[0205] The negative electrode for a rechargeable lithium battery may include a current collector and a negative electrode active material layer on the current collector. The negative electrode active material layer may include a negative electrode active material and may also include a binder and / or a conductive material (eg, an electrically conductive material).

[0206] For example, the negative electrode active material layer may 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.

[0207] Negative electrode active material

[0208] The negative electrode active material may include at least one of a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and a transition metal oxide.

[0209] 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. Crystalline carbon can be graphite, such as natural graphite or artificial graphite that is non-shaped, flaky, lamellar, spherical or fibrous. Amorphous carbon can be or include at least one of soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0210] Lithium metal alloys include alloys of lithium with metals 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.

[0211] Materials capable of doping / undoping lithium can be or include at least one of Si-based negative electrode active materials and Sn-based negative electrode active materials. Si-based negative electrode active materials can 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). Sn-based negative electrode active materials can include at least one of Sn, SnO2, Sn-based alloys and combinations thereof.

[0212] The silicon-carbon composite can be or include a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which primary silicon particles are aggregated and an amorphous carbon coating layer (shells) on the surface of the secondary particles. Amorphous carbon can also be between the primary silicon particles. For example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0213] The silicon-carbon composite can also include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core.

[0214] Si-based negative electrode active materials or Sn-based negative electrode active materials can be combined with carbonaceous negative electrode active materials.

[0215] The binder can be configured to attach negative electrode active material particles to each other and to attach the negative electrode active material to the current collector. The binder can include a non-aqueous binder, an aqueous binder, a dry binder or a combination thereof.

[0216] 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.

[0217] 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, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0218] When an aqueous binder is included as the negative electrode binder, a cellulose compound that can impart viscosity may also be included. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and an alkali metal salt thereof. The alkali metal may include at least one of Na, K, and Li.

[0219] The dry binder may be or include a polymer material capable of being in a fibrous form. 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.

[0220] Conductive materials may be included to impart electrical conductivity (e.g., electrical conductivity) to the electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons may be included in the battery. Non-limiting examples of conductive materials may include: carbon-based materials such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials including at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0221] 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.

[0222] Rechargeable lithium batteries may also include an electrolyte.

[0223] electrolyte

[0224] An electrolyte for a rechargeable lithium battery may include at least a non-aqueous organic solvent and a lithium salt.

[0225] The non-aqueous organic solvent may be configured as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0226] The non-aqueous organic solvent may be or include at least one of a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, and combinations thereof.

[0227] The carbonate solvent may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc.

[0228] The ester solvent may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonolactone, valerolactone, caprolactone, and the like.

[0229] The ether solvent may include at least one of dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In addition, the ketone solvent may include cyclohexanone, etc. The alcohol solvent may include at least one of ethanol, isopropanol, etc., and the aprotic solvent may include at least one of the following: nitrile, such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group and includes a double bond, an aromatic ring, or an ether bond, etc.); amide, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0230] The non-aqueous organic solvent may be included alone or in combination of two or more solvents.

[0231] In addition, when a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0232] Lithium salts dissolved in organic solvents supply lithium ions in batteries to enable basic operation of rechargeable lithium batteries and improve the transport of lithium ions between the positive electrode and the negative electrode. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F2y+1 SO2) (wherein x and y are integers of 1 to 20), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOP), lithium difluorobis(oxalato)borate (LiDFBOB) and lithium bis(oxalato)borate (LiBOB).

[0233] Rechargeable lithium batteries may be classified into cylindrical, prismatic, pouch-type, or coin-type batteries, etc., according to their shapes.

[0234] Figures 2 to 5 is a schematic diagram illustrating a rechargeable lithium battery according to example embodiments. Figure 2 shows a cylindrical battery, Figure 3 A prismatic cell is shown, and Figure 4 and Figure 5 A pouch type battery is shown. Figures 2 to 5 , the rechargeable lithium battery 100 may include an electrode assembly 40 and a case 50 in which the electrode assembly 40 is accommodated, the electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 2 As shown in , the rechargeable lithium battery 100 may include a sealing member 60 that seals the case 50. Figure 3 In the embodiment, 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. Figure 4 and Figure 5 As shown in FIG, the rechargeable lithium battery 100 may include Figure 5 The electrode tab 70 shown in FIG. 1 , or for example Figure 4 The positive electrode tab 71 and the negative electrode tab 72 shown in FIG. 7 , the electrode tabs 70 , 71 , 72 form an electrical path for guiding current formed in the electrode assembly 40 to the outside of the battery 100 .

[0235] As non-limiting examples, rechargeable lithium batteries according to example embodiments may be applied to, for example, automobiles, mobile phones, and / or various types of electronic devices.

[0236] Hereinafter, examples and comparative examples of the present disclosure are described. However, the following examples are merely exemplary embodiments of the present disclosure, and the present disclosure is not limited to the following examples.

[0237] Preparation Example 1

[0238] In a 3 L four-necked flask equipped with a stirrer, a thermometer and a cooling tube, distilled water (968 g), acrylic acid (AA) (54.00 g, 0.75 mol), ammonium persulfate (0.65 g, 2.85 mmol), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) (6.00 g, 0.03 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, and then the internal pressure was reduced to 10 mmHg using a diaphragm pump and returned to normal pressure using nitrogen gas. The above steps were repeated three times, and then acrylonitrile (AN) (60.00 g, 1.13 mol) was added.

[0239] 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., and after adding ammonium persulfate (0.22 g, 0.001 mol) twice, 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.

[0240] Thus, a poly(acrylic acid-co-acrylonitrile-co-2-acrylamido-2-methylpropanesulfonic acid) sodium salt was prepared as an acrylic copolymer (i.e., a (meth)acrylic binder). Acrylic acid, acrylonitrile, and 2-acrylamido-2-methylpropanesulfonic acid were included in a molar ratio of 39:59:2. The non-volatile component in approximately 10 mL of the reaction solution (reaction product) was measured and found to be 9.0 wt % (theoretical value: 10 wt %).

[0241] Preparation Example 2

[0242] An acrylic copolymer was prepared in the same manner as in Preparation Example 1, except that acrylic acid (50 g, 0.69 mol) and acrylonitrile (50 g, 0.94 mol) were used and 2-acrylamido-2-methylpropanesulfonic acid was not used. Acrylic acid and acrylonitrile were included in a molar ratio of 42:58. The non-volatile component of the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0243] Preparation Example 3

[0244] An acrylic copolymer was prepared in the same manner as in Preparation Example 1, except that acrylic acid (50 g, 0.69 mol) and 2-acrylamido-2-methylpropanesulfonic acid (50 g, 0.24 mol) were used and acrylonitrile was not used. Acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid were included in a molar ratio of 74:26. ​​The non-volatile component of the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0245] Table 1 below shows the molar ratio, weight average molecular weight, and glass transition temperature of each monomer in the (meth)acryloyl-based adhesives prepared in Preparation Examples 1 to 3.

[0246] Table 1:

[0247]

[0248] Example 1

[0249] A dispersion was prepared by mixing the acryl copolymer prepared in Preparation Example 1 (in distilled water, 10 wt %) and boehmite (particle size D100: 0.5 μm, particle size D50: 0.2 μm, cubic) as a filler at a mass ratio of 1:30 in parts by weight of the acryl copolymer and the filler, adding the mixture to an aqueous solvent, and then grinding and dispersing it using a bead mill at 25° C. for 30 minutes.

[0250] A composition for forming a coating layer was prepared by adding trimethylolpropane tris (2-methyl-1-aziridine propionate) (a trifunctional aziridine crosslinking agent) and carboxymethyl cellulose (CMC) as an aziridine crosslinking agent and adding water so that the total solid content becomes 20 wt %. In this case, the acryl copolymer, carboxymethyl cellulose, and aziridine crosslinking agent were included in a ratio of 45:45:10 (parts by weight) relative to a total of 100 parts by weight.

[0251] A separator for a rechargeable lithium battery was manufactured by coating one surface of a polyethylene film (thickness: 8 μm, air permeability: 120 sec / 100 cc, puncture strength: 480 kgf) as a porous substrate with the composition for forming a coating layer using a direct metering (DM) coating method, and then drying and aging it in an oven at 80° C. for 16 hours.

[0252] Examples 2 to 7

[0253] A separator for a rechargeable lithium battery was manufactured in the same manner as in Example 1, except that boehmite (cubic) was used as a filler, as shown in Table 2 below, but D50 and D100 were changed, the mass ratio of the acryl copolymer and the filler was changed, and the contents of the acryl copolymer, carboxymethyl cellulose, and aziridine crosslinking agent were changed.

[0254] Example 8

[0255] A separator for a rechargeable lithium battery was manufactured in the same manner as in Example 1, except that a carbodiimide-based crosslinking agent, polycarbodiimide (trifunctional carbodiimide crosslinking agent, Carbodilite SV-02), was used instead of the aziridine-based crosslinking agent.

[0256] Example 9

[0257] A separator for a rechargeable lithium battery was manufactured in the same manner as in Example 1, except that boehmite (particle size D100: 0.5 μm, particle size D50: 0.2 μm, plate-shaped) was used.

[0258] Comparative Examples 1 to 8

[0259] 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 the acryl copolymer and the filler was changed, and the acryl copolymer, carboxymethyl cellulose, and aziridine-based crosslinking agent and their contents were changed.

[0260] PVA is a homopolymer of polyvinyl alcohol.

[0261] The epoxy crosslinking agent is ethylene glycol diglycidyl ether.

[0262] PVDF is polyvinylidene fluoride.

[0263] SBR is styrene butadiene rubber.

[0264] Drying shrinkage (unit: %)

[0265] Samples were prepared by cutting the separators for rechargeable lithium batteries of Examples and Comparative Examples into 8 cm × 8 cm sizes. The shrinkage rate in each of the machine direction (MD) and transverse direction (TD) was calculated by drawing a 5 cm × 5 cm square on the surface of the sample, placing the sample between paper sheets or aluminum oxide powder, placing the sample in an oven at 150°C for 1 hour, removing the sample, and measuring the side dimensions of the drawn square. The shrinkage rate was calculated according to Equation 1 below.

[0266] Equation 1:

[0267] Shrinkage (%) = (L0-L1) / L0×100

[0268] L0 represents the initial length of the separator, and L1 represents the length of the separator after being left at 150° C. for 1 hour.

[0269] Shrinkage in electrolyte (unit: %)

[0270] Samples were manufactured by cutting the separators for rechargeable lithium batteries of Examples and Comparative Examples into a size of 5 cm×5 cm.

[0271] A positive electrode slurry was prepared by mixing 97 wt % of LiCoNiAl as a positive electrode active material, 1.5 wt % of carbon nanotubes, and 1.5 wt % of polyethylene fluoride as a conductive material and adding water thereto.

[0272] The positive electrode was manufactured by coating the prepared positive electrode slurry on an aluminum foil and drying and rolling the prepared positive electrode slurry.

[0273] A negative electrode active material slurry was prepared by mixing 97.4 wt% of a negative electrode active material (silicon-carbon composite), 1.0 wt% of carboxymethyl cellulose, 1.5 wt% of styrene-butadiene rubber, and 0.1 wt% of carbon nanotubes as a conductive material. A silicon-based negative electrode active material was used as the negative electrode active material. The negative electrode was manufactured by coating the prepared negative electrode slurry on copper foil, drying the prepared negative electrode slurry, and rolling it.

[0274] A sample is positioned between the positive electrode and the negative electrode to form a stack of three groups of positive electrode-sample-negative electrode, which are then placed in a bag. 3 g of electrolyte (ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 30:50:20) dissolved with 1.5 M of LiPF6) is injected to completely saturate the stack with the electrolyte, seal, and place at 25 ° C for 12 hours. Then, the stack is placed in an oven at 150 ° C for 1 hour, the sample is taken out, and the side size of the drawn square is measured to calculate the shrinkage in each direction in MD and TD. Shrinkage is calculated according to Equation 1.

[0275] Table 2:

[0276]

[0277] As shown in Table 2, the example separator may exhibit significantly lower drying shrinkage and shrinkage in the electrolyte than the comparative example, thereby increasing the stability of the battery.

[0278] A separator for a rechargeable lithium battery according to one example embodiment may exhibit significantly low drying shrinkage and shrinkage in an electrolyte, thereby increasing the stability of the battery.

[0279] Although example embodiments of the present disclosure have been described above, the present disclosure is not limited thereto and may be modified in any form within the scope of the claims, detailed description of the present disclosure, and drawings, and the modifications also fall within the scope of the present disclosure.

Claims

1. A separator for a rechargeable lithium battery, comprising: porous substrate; as well as a coating layer disposed on at least one surface of the porous substrate, Wherein, the coating layer comprises a binder, a cross-linking agent, a cross-linked product of carboxyalkyl cellulose or its salt, and a filler. The adhesive comprises a (meth)acryl-based adhesive comprising 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, and The cross-linking agent includes one or more of an aziridine cross-linking agent and a carbodiimide cross-linking agent.

2. The diaphragm according to claim 1, wherein The coating layer includes a composition comprising the (meth)acrylic binder, the cross-linking agent, the carboxyalkyl cellulose or a salt thereof, and the filler.

3. The diaphragm according to claim 1, wherein The carboxyalkyl cellulose or its salt includes carboxymethyl cellulose or its salt. The diaphragm according to claim 1 , wherein: The carboxyalkyl cellulose or its salt is included in an amount ranging from 20 wt % to 70 wt % of the total amount of the (meth)acryl-based binder, the cross-linking agent, and the carboxyalkyl cellulose or its salt.

5. 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'-(methylenedi-p-phenylene)bis(aziridine-1-carboxamide), triethylene melamine, 1,1-isophthaloylbis(2-methylaziridine), tris(1-aziridinyl)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). The diaphragm according to claim 1 , wherein: The carbodiimide cross-linking agent includes one or more of a monocarbodiimide compound and a polycarbodiimide compound.

7. The diaphragm according to claim 1, wherein The filler includes a filler having a particle size D100 of 1.0 μm or less.

8. The diaphragm according to claim 1, wherein The filler is one of approximately spherical, approximately plate-like, approximately cubic, and amorphous.

9. The diaphragm according to claim 1, wherein The (meth)acryl-based binder and the filler are included in a mass ratio ranging from 1:10 to 1:

50.

10. The diaphragm according to claim 1, wherein Among the total amount of the (meth)acryloyl-based binder, the cross-linking agent and the carboxyalkyl cellulose or its salt, the (meth)acryloyl-based binder is included in an amount ranging from 25 wt % to 75 wt %, the cross-linking agent is included in an amount ranging from 5 wt % to 30 wt %, and the carboxyalkyl cellulose or its salt is included in an amount ranging from 20 wt % to 70 wt %.

11. 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 Formulas 1 to 3, R 1 to 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 a C1 to C3 alkyl group, 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 including 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, and The sulfonate group-containing structural unit 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 Formulas 5 to 7, R 9 to R 14 each independently comprises hydrogen or a C1 to C3 alkyl group, 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 an alkali metal.

12. The diaphragm according to claim 1, wherein The (meth)acryl adhesive includes: the structural unit derived from (meth)acrylate or (meth)acrylic acid in an amount ranging from 10 mol% to 70 mol%; an amount of the cyano group-containing structural unit in a range of 20 mol % to 85 mol %; and The sulfonate group-containing structural unit is present in an amount ranging from 0.1 mol% to 20 mol%.

13. The diaphragm according to claim 1, wherein The coating layer has a thickness in the range of 1 μm to 4 μm.

14. A rechargeable lithium battery, comprising: positive electrode; negative electrode; as well as The separator for a rechargeable lithium battery according to claim 1, located between the positive electrode and the negative electrode.

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