Separator for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

The present disclosure relates to a separator for a rechargeable lithium battery and a rechargeable lithium battery, the separator comprising: a porous substrate; and a coating layer on at least one surface of the porous substrate and including a binder and a filler. The binder includes a (meth) acryloyl-based binder including a first structural unit derived from (meth) acrylic acid, (meth) acrylate, or a salt thereof, a second structural unit derived from hydroxyalkyl (meth) acrylate, and a third structural unit derived from (meth) acrylamidosulfonic acid or a salt thereof. The filler comprises an organic filler and an inorganic filler. The organic filler includes a cross-linked polymer filler. The inorganic filler includes one or more of a first inorganic filler having an average particle size of 50 nm to 250 nm and being cubic and a second inorganic filler having an average particle size of 100 nm to 350 nm and being amorphous.

Description

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0052035, filed on April 18, 2024, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. TECHNICAL FIELD

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

[0003] As the presence of electronic devices using batteries, such as mobile phones, notebook computers, electric vehicles, and the like, increases, the demand for rechargeable lithium batteries having high energy density and high capacity is increasing. Accordingly, it can be advantageous to improve the performance of rechargeable lithium batteries.

[0004] A rechargeable lithium battery generally includes a positive electrode and a negative electrode including an active material capable of intercalating and deintercalating lithium ions, and generates electric energy through an oxidation-reduction reaction when lithium ions intercalate into and deintercalate from the positive electrode and the negative electrode. SUMMARY

[0005] One example embodiment includes a separator for a rechargeable lithium battery having a low film resistance to increase the capacity of the rechargeable lithium battery.

[0006] Another example embodiment includes a separator for a rechargeable lithium battery having a low thermal shrinkage to increase the stability and life of the rechargeable lithium battery.

[0007] Still another example embodiment includes a rechargeable lithium battery including the separator.

[0008] An example embodiment includes a separator for a rechargeable lithium battery.

[0009] 1. A separator for a rechargeable lithium battery includes a porous substrate and a coating layer on at least one surface of the porous substrate and including a binder and a filler. The binder includes a (meth)acryl-based binder including a first structural unit derived from a (meth)acrylic acid, a (meth)acrylate, or a salt thereof, a second structural unit derived from a (meth)acrylhydroxyalkyl ester, and a third structural unit derived from a (meth)acrylamidosulfonic acid or a salt thereof. The filler includes an organic filler and an inorganic filler. The organic filler includes a crosslinked polymer filler, and the inorganic filler includes one or more of a first inorganic filler having an average particle size of about 50 nm to about 250 nm and being cubic, and a second inorganic filler having an average particle size of about 100 nm to about 350 nm and being amorphous.

[0010] 2. In 1, wherein, with respect to 100 mol% of the (meth)acrylic binder: the content of the first structural unit ranges from about 30 mol% to about 65 mol%, the content of the second structural unit ranges from about 1 mol% to about 20 mol%, and the content of the third structural unit ranges from about 20 mol% to about 65 mol%.

[0011] 3. In 1 to 2, wherein the first structural unit is represented by any one or more of the following Chemical Formulae 1 to 3, the second structural unit is represented by the following Chemical Formula 4, and the third structural unit is represented by any one or more of the following Chemical Formulae 5 to 7: Chemical Formula 1: Chemical Formula 2: Chemical Formula 3: Chemical Formula 4:

[0012] Chemical Formula 5: Chemical Formula 6: Chemical Formula 7: .

[0013] In Chemical Formulae 1 to 7, R 1 to R 14 each independently is or includes hydrogen or a C1 to C10 alkyl group, L 1 to L 4 each independently 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 heterocyclic group, a, b, c, and d each independently are an integer in the range of 0 to 2, and M is or includes an alkali metal.

[0014] 4. In 1 to 3, wherein the (meth)acrylic binder is included with an organic filler in a mass ratio of about 1:1 to about 1:10.

[0015] 5. In 1 to 4, wherein the organic filler includes a crosslinked polymethyl methacrylate filler.

[0016] 6. In 1 to 5, wherein the (meth)acrylic binder is included with one or more of a first inorganic filler and a second inorganic filler in a mass ratio of about 1:10 to about 1:50.

[0017] 7. In 1 to 6, wherein one or more of the first inorganic filler and the second inorganic filler comprises at least one of AI2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0018] 8. In 1 to 7, wherein the organic filler and one or more of the first inorganic filler and the second inorganic filler are included in the coating in amounts of about 10 parts by weight to about 80 parts by weight : about 20 parts by weight to about 90 parts by weight, among 100 parts by weight of the organic filler and one or more of the first inorganic filler and the second inorganic filler.

[0019] 9. In 1 to 8, wherein the coating further comprises an adhesive binder.

[0020] 10. In 1 to 9, wherein the adhesive binder comprises one or more of another (meth)acrylic binder and a fluoro-based binder.

[0021] 11. In 1 to 10, wherein the another (meth)acrylic binder is a particle having a core-shell structure, the core comprising a (meth)acrylic binder including structural units derived from a (meth)acrylic acid or a (meth)acrylate, and the shell comprising a binder having structural units derived from a monomer including a polymerizable unsaturated group.

[0022] 12. In 1 to 11, wherein the fluoro-based binder includes a vinylidene fluoride-derived unit and one or more of units derived from chlorotrifluoroethylene, trifluoroethylene, hexafluoropropylene, tetrafluoroethylene, and ethylene monomers.

[0023] 13. In 1 to 12, wherein in the coating, the (meth)acrylic binder and the adhesive binder are included in a weight ratio of about 1 :0.1 to about 1 :3.

[0024] 14. In 1 to 13, wherein the coating has a thickness in a range of about 0.5 pm to about 2 pm.

[0025] Another example embodiment includes a rechargeable lithium battery.

[0026] The rechargeable lithium battery includes a positive electrode, a negative electrode, and a separator for the rechargeable lithium battery located between the positive electrode and the negative electrode. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a magnified cross-sectional view of a first inorganic filler that is a cube.

[0028] Figure 2 is a magnified cross-sectional view of a second inorganic filler which is amorphous.

[0029] Figure 3 is a conceptual diagram of a separator for a rechargeable lithium battery according to one example embodiment.

[0030] Figure 4 is a conceptual diagram of a separator for a rechargeable lithium battery according to another example embodiment.

[0031] Figures 5 to 8 is a cross-sectional view schematically illustrating a rechargeable lithium battery according to an example embodiment. DETAILED DESCRIPTION

[0032] Hereinafter, example embodiments of the disclosure are described in detail. However, the embodiments are presented as examples, the disclosure is not limited thereto, and the disclosure is limited only by the scope of the appended claims.

[0033] Unless otherwise stated herein, when a portion such as a layer, a film, a region, a plate, etc. is described as being disposed "on" another portion, not only a case in which the portion is "directly on" the other portion is included, but also a case in which there is another portion therebetween is included.

[0034] Unless otherwise stated herein, the singular can also include the plural. Also, unless otherwise stated, the term "A or B" can mean "including A, including B, or including A and B".

[0035] In the present specification, "a combination thereof can mean a mixture, a stack, a composite, a copolymer, an alloy, a blend, or a reaction product of components.

[0036] Unless otherwise defined herein, the particle size (particle diameter) can be the average particle size (average particle diameter). In addition, the particle size refers to the average particle size (average particle diameter) D50, which refers to the diameter of the particles of which the cumulative volume is 50% by volume in the particle size distribution. The average particle size D50 can be measured by a method known to those skilled in the art, and for example, can be measured using a particle size analyzer, a transmission electron micrograph, or a scanning electron micrograph. As another method, the average particle size D50 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 for each particle size range, and then calculating the average particle size D50 therefrom. Alternatively, the average particle size D50 can be measured using a laser diffraction method. When the average particle size is measured by the laser diffraction method, for example, the average particle size D50 based on the 50% particle size distribution in the measuring device can be calculated by dispersing the particles to be measured in a dispersion medium, then introducing the dispersion medium into a commercially available laser diffraction particle size measuring device (for example, MT 3000 of Microtrac), and irradiating ultrasonic waves of about 28 kHz at an output of 60 W.

[0037] In the present specification, "(meth)acryl" means acryl and / or methacryl.

[0038] Hereinafter, unless otherwise defined, "substituted" means that hydrogen in a compound is substituted with a substituent such as or including C1 to C30 alkyl, C2 to C30 alkenyl, C2 to C30 alkynyl, C6 to C30 aryl, C7 to C30 alkylaryl, C1 to C30 alkoxy, C1 to C30 heteroalkyl, C3 to C30 heteroalkylaryl, C3 to C30 cycloalkyl, C3 to C15 cycloalkenyl, C6 to C30 cycloalkynyl, C2 to C30 heterocycloalkyl, halogen (F, Cl, Br, or I), hydroxyl (-OH), nitro (-NO2), cyano (-CN), amino (-NRR') (here, R and R' are each independently hydrogen or C1 to C6 alkyl), sulfobetaine group (-RR'N + (CH2) n SO3 - , n is a natural number of 1 to 10), carboxybetaine group (-RR'N + (CH2) n COO -, n is a natural number of 1 to 10) (herein, R and R' are each independently a C1 to C20 alkyl group), an azido group (-N3), an amidine group (-C(=NH)NH2), a hydrazine group (-NHNH2), a hydrazone group (=N(NH2)), a carbamoyl group (-C(O)NH2), a thiol group (-SH), an acyl group (-C(=O)R, here, R represents hydrogen, a C1 to C6 alkyl group, a C1 to C6 alkoxy group or a C6 to C12 aryl group), a carboxyl group (-COOH) or a salt thereof (-C(=O)OM, here, M represents an organic or inorganic cation), a sulfonic acid group (-SO3H) or a salt thereof (-SO3M, here, M represents an organic or inorganic cation), a phosphate group (-PO3H2) or a salt thereof (-PO3MH or -PO3M2, here, M represents an organic or inorganic cation), and at least one of a combination thereof.

[0039] 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, a C3 to C10 cycloalkylene group or 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.

[0040] Hereinafter, “hetero” means including one or more heteroatoms (such as or including at least one of N, O, S, Si, and P).

[0041] In a chemical formula, the symbol It refers to the site where the same or different atoms, groups or structural units are connected.

[0042] In this specification, the weight average molecular weight (Mw) may be a value measured using gel permeation chromatography (GPC).

[0043] 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.

[0044] 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)”.

[0045] 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%.

[0046] A separator for a rechargeable lithium battery according to one example embodiment can exhibit low film resistance and low thermal shrinkage in electrolyte, thereby improving capacity, stability, and life of the battery.

[0047] 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 and including a binder and a filler. The binder includes a (meth)acryl-based binder including a first structural unit derived from a (meth)acrylic acid, a (meth)acrylate, or a salt thereof, a second structural unit derived from a (meth)acrylhydroxyalkyl ester, and a third structural unit derived from a (meth)acrylamidosulfonic acid or a salt thereof. The filler includes an organic filler and an inorganic filler. The organic filler includes a crosslinked polymer filler, and the inorganic filler includes one or more of a first inorganic filler having an average particle size of about 50 nm to about 250 nm and being cubic, and a second inorganic filler having an average particle size of about 100 nm to about 350 nm and being amorphous.

[0048] A separator for a rechargeable lithium battery can include a (meth)acryl-based binder to provide low film resistance. According to one example embodiment, the separator can have a film resistance of about 0.6 Ω or less.

[0049] A separator for a rechargeable lithium battery can include a (meth)acryl-based binder, an inorganic filler, and an organic filler, thereby improving packing density of the coating layer and reducing thermal shrinkage, so that heat resistance of the separator can be improved. According to one example embodiment, a mechanical direction (MD) shrinkage and a transverse direction (TD) shrinkage of the separator can each be in a range of about 3% or less, for example, 2% or less or 1.5% or less, after being left at 150°C for 1 hour. The thermal shrinkage can be low even when the battery is left at high temperature for a long time, within the above range, thereby improving stability and life of the battery.

[0050] According to one example embodiment, the coating layer can be formed from or include a composition including a binder and a filler, the binder including a (meth)acryl-based binder, the filler including an inorganic filler and an organic filler.

[0051] According to one example embodiment, the coating layer can be or include a dry product or a cured product of the composition.

[0052] The coating layer includes the binder and the filler described below.

[0053] Binder The binder can include the (meth)acryl-based binder to be described below, and the amount of the (meth)acryl-based binder can be in the range of about 95 wt% or more, for example, in the range of 95 wt% to 100 wt% or 100 wt%. Within the above range, the above-mentioned effects of the separator can be easily achieved.

[0054] The binder can include the (meth)acryl-based binder including a first structural unit derived from a (meth)acrylic acid, a (meth)acrylate, or a salt thereof, a second structural unit derived from a (meth)acrylhydroxyalkyl ester, and a third structural unit derived from a (meth)acrylamido sulfonic acid or a salt thereof.

[0055] The (meth)acryl-based binder exhibits high heat resistance and low film resistance. Accordingly, when the (meth)acryl-based binder is applied to the coating layer of the separator, a rechargeable lithium battery having a desired or improved lifespan characteristic at room temperature and / or at high temperature can be achieved.

[0056] The (meth)acryl-based binder is described as follows.

[0057] Among 100 mol% of the (meth)acryl-based binder, the content of the first structural unit can be in the range of about 30 mol% to about 65 mol%, or 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%, 40 mol% to 65 mol%, or 30 mol% to 60 mol%. Within the above range, dispersibility of the binder in the coating layer can be improved and heat resistance can be easily increased.

[0058] The first structural unit can be derived from a (meth)acrylic acid, a (meth)acrylate, or a salt thereof, to fix inorganic particles on the porous substrate, and can provide adhesion strength so that the coating layer is adhered to the porous substrate and the electrode. In addition, the first structural unit can help to improve heat resistance and air permeability of the separator. In addition, the first structural unit can include a carboxyl functional group (-C(=O)O-) in the structural unit, thereby helping to improve dispersibility of the coating slurry.

[0059] The first structural unit can be represented by any one or more of the following Chemical Formula 1 to Chemical Formula 3: Chemical Formula 1: Chemical Formula 2: Chemical Formula 3: .

[0060] The content of the second structural unit can be in the range of about 1 mol% to about 20 mol%, or in the range of 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%, 5 mol% to 15 mol%, relative to 100 mol% of the (meth)acryl-based binder. Within the above range, the adhesion of the coating layer to the porous substrate can be improved.

[0061] The second structural unit can be derived from a (meth)acrylic acid hydroxyalkyl ester to fix the inorganic particles on the porous substrate, and can provide an adhesion strength such that the coating layer is adhered to the porous substrate and the electrode. In addition, the second structural unit can include a carboxyl functional group (-C(=O)O-) in the structural unit, thereby helping to improve the dispersibility of the coating slurry.

[0062] The second structural unit can be represented by the following Chemical Formula 4: Chemical Formula 4: .

[0063] According to one example embodiment, the third structural unit can be included in a higher mole number than the mole numbers of the first structural unit and the second structural unit, relative to 100 mol% of the (meth)acryl-based binder. This can improve the mobility of lithium ions in the coating layer, thereby enabling a low film resistance to be provided.

[0064] According to one example embodiment, the content of the third structural unit can be in a range of about 20 mol% to about 65 mol%, or 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%, or in a range of 30 mol% to 60 mol%, relative to 100 mol% of the (meth)acrylic binder. Within the above range, the coating layer can reduce the film resistance by increasing the mobility of lithium ions.

[0065] The third structural unit can include a bulky functional group derived from a (meth)acrylamidosulfonic acid or a salt thereof, thereby increasing the heat resistance of the separator by increasing the glass transition temperature. Additionally, when the third structural unit includes a functional group derived from a salt of a (meth)acrylamidosulfonic acid, the metal (M) or the cation of the metal (M) can move through the third structural unit through the sulfonic acid functional group on which the metal (M) is substituted, thereby reducing the film resistance.

[0066] The third structural unit can be represented by any one or more of the following Chemical Formula 5 to Chemical Formula 7: Chemical Formula 5: Chemical Formula 6: Chemical Formula 7: .

[0067] Chemical Formula 1 to Chemical Formula 7 are described as follows.

[0068] R 1 to R 14 may each independently be or include hydrogen or a C1 to C10 alkyl, for example, a methyl group. For example, R 1 to R 7 and R 9 to R 14 may each be or include hydrogen, and R 8 may be a methyl group.

[0069] L1 to L 4 each independently is or includes a substituted or unsubstituted C1to C10alkylene, a substituted or unsubstituted C3to C20cycloalkylene, a substituted or unsubstituted C6to C20arylene, or a substituted or unsubstituted C3to C20heterocyclylene. For example, L 1 may be methylene or ethylene, and L 2 to L 4 may each independently be -C(CH3)2-CH2- .

[0070] a, b, c, and d can each independently be an integer in the range of 0 to 2. For example, a, b, c, and d can all equal 1.

[0071] M can be or include an alkali metal, and the alkali metal can be or include at least one of lithium, sodium, potassium, rubidium, and cesium. For example, M can be or include lithium or sodium.

[0072] Representative examples of (meth)acrylic binders according to one example embodiment are as follows: Chemical Formula 8: .

[0073] Chemical Formula 8 is described as follows.

[0074] R 15 to R 20 may each independently be or include hydrogen or a C1to C10alkyl, for example, methyl. For example, R 15 to R 17 , R 19 , and R 20 may each be or include hydrogen, and R 18 may be or include methyl.

[0075] L 5 and L 6 each independently is or includes a substituted or unsubstituted C1to C10alkylene, a substituted or unsubstituted C3to C20cycloalkylene, a substituted or unsubstituted C6to C20arylene, or a substituted or unsubstituted C3to C20heterocyclylene. For example, L 5 may be or include methylene or ethylene, and L 6 may be or include -C(CH3)2-CH2- .

[0076] M can be or include an alkali metal, and the alkali metal can be or include at least one of lithium, sodium, potassium, rubidium, and cesium. For example, M can be or include lithium or sodium.

[0077] e and f can each independently be an integer in the range of 0 to 2. For example, e and f can both equal 1.

[0078] l, m, and n are molar ratios of respective units, and can satisfy l+m+n=1. For example, l, m, and n can satisfy 0.3≤l≤0.65, 0.01≤m≤0.2, and 0.2≤n≤0.65, or can be 0.3≤l≤0.6, 0.05≤m≤0.15, and 0.3≤n≤0.6.

[0079] The (meth)acryl-based binder can have a weight average molecular weight in the range of about 100,000 g / mol to about 1,000,000 g / mol, 100,000 g / mol to 500,000 g / mol, 100,000 g / mol to 150,000 g / mol, 200,000 g / mol to 130,000 g / mol, or 300,000 g / mol to 900,000 g / mol. When satisfying the above range, the separator for a rechargeable lithium battery including the binder according to one example embodiment can exhibit a desired or improved adhesion strength and a low film resistance.

[0080] The (meth)acryl-based binder can include an alkali metal. The alkali metal can exist in the form of a cation, and for example, can be or include at least one of lithium, sodium, potassium, rubidium, and cesium. For example, the alkali metal can be combined with the (meth)acryl-based binder, and can exist in the form of a salt. The alkali metal can help synthesis of the (meth)acryl-based binder in an aqueous solvent, increase the adhesion strength of the coating layer, and increase the heat resistance, air permeability, oxidation resistance, etc. of the separator.

[0081] The content of the alkali metal can be in the range of about 1 wt% to about 40 wt% of the alkali metal and the (meth)acryl-based binder, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 10 wt% to 20 wt%. For example, the (meth)acryl-based binder and the alkali metal can be included in the range of a weight ratio of about 99:1 to about 60:40, 99:1 to 70:30, for example, 99:1 to 80:20, or for example, 90:10 to 80:20.

[0082] The alkali metal can be included in the range of about 0.1 mol% to about 1.0 mol% of 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 can have a desired or improved adhesion strength, and the separator including the coating layer can exhibit a desired or improved heat resistance, air permeability, and oxidation resistance.

[0083] The (meth)acryl-based binder can 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.

[0084] According to one example embodiment, the (meth)acryl-based binder can be prepared by a solution polymerization method.

[0085] Filler The filler includes an organic filler and an inorganic filler, the inorganic filler including one or more of a first inorganic filler having an average particle size D50 in a range of about 50 nm to about 250 nm and being cubic, and a second inorganic filler having an average particle size D50 in a range of about 100 nm to about 350 nm and being amorphous.

[0086] The organic filler includes a cross-linked polymer filler. The cross-linked polymer filler can reduce a water content, thereby further reducing a heat shrinkage rate of the separator and improving an insulation property. The cross-linked polymer filler can be included in a combination of the (meth)acryl-based binder and the inorganic filler, thereby enabling a reduction in the heat shrinkage rate of the separator.

[0087] According to one example embodiment, a content of the cross-linked polymer filler can be in a range of about 95 wt% or more of the organic filler, for example, in a range of about 95 wt% to about 100 wt% or 100 wt%. Within the above range, the above-described effects of the separator can be easily achieved.

[0088] The organic filler can be highly cross-linked, thereby improving heat resistance and reducing or inhibiting a heat shrinkage rate of the porous substrate at a high temperature. According to one example embodiment, the organic filler can include at least one of an acrylate compound or a derivative thereof, a diallyl phthalate compound or a derivative thereof, a polyimide compound or a derivative thereof, and a polyurethane compound or a derivative thereof. For example, the organic filler can be or include cross-linked polymethyl methacrylate particles. The organic filler can be prepared by a conventional method known to one of ordinary skill in the art. The cross-linked polymer filler can be prepared by adding a cross-linking agent during polymerization of a monomer.

[0089] The organic filler can have an average particle size D50 in a range of about 0.1 µm to about 0.35 µm, for example, 0.1 µm to 0.2 µm. Within the above range, a thickness of the separator can be reduced by forming a coating layer having a uniform thickness.

[0090] The organic filler can be included at a desired content with respect to the binder (e.g., (meth)acryl-based binder). According to one example embodiment, the (meth)acryl-based binder and the organic filler can be included at a mass ratio of about 1:1 to about 1:10, for example, 1:1 to 1:5. Within the above range, heat resistance, durability, and low film resistance effects can be achieved.

[0091] The inorganic filler includes one or more of a first inorganic filler and a second inorganic filler.

[0092] According to one example embodiment, the content of one or more of the first inorganic filler and the second inorganic filler can be in a range of about 95 wt% or more of the inorganic filler, for example, in a range of 95 wt% to 100 wt% or 100 wt%. Within the above range, the above effects of the separator can be easily achieved.

[0093] Figure 1 is a magnified sectional view of the first inorganic filler which is a cube. Referring to Figure 1 The cubic inorganic filler can have a three-dimensional shape in which each substantially entire surface of the inorganic filler has a rectangular or square shape.

[0094] Figure 2 is a magnified sectional view of the second inorganic filler which is amorphous. Referring to Figure 2 The amorphous inorganic filler has an uneven and irregular surface which forms the filler.

[0095] The first inorganic filler and the organic filler can improve the coating density by ensuring that there is substantially no uncoated portion when coating the porous substrate with the composition including the binder. In addition, since the first inorganic filler has a small average particle size and a small specific surface area, the moisture content is low. Thus, it can be advantageous in reducing the heat shrinkage of the separator. The first inorganic filler can be advantageous in improving the coating density when the average particle size D50 is about 50 nm or more, and the first inorganic filler can improve the coating density and reduce the heat shrinkage when the average particle size D50 is about 250 nm or less. For example, the average particle size D50 of the first inorganic filler can be in a range of about 100 nm to about 250 nm, for example, in a range of 150 nm to 250 nm or 200 nm.

[0096] The second inorganic filler and the organic filler can improve the coating density by ensuring that there is substantially no uncoated portion when coating the porous substrate with the composition including the binder. Thus, it can be advantageous in terms of reducing the heat shrinkage of the separator. The second inorganic filler can be advantageous in improving the coating density when the average particle size D50 is in the range of about 100 nm or more, and can improve the coating density and reduce the heat shrinkage when the average particle size D50 is in the range of about 300 nm or less. For example, the average particle size D50 of the second inorganic filler can be in the range of about 150 nm to about 350 nm, for example, in the range of 200 nm to 350 nm or 300 nm.

[0097] For example, the coating layer can include a combination of the organic filler and the first inorganic filler, in which case the heat shrinkage can be further reduced.

[0098] According to one example embodiment, the (meth)acryl-based binder and one or more of the first inorganic filler and the second inorganic filler can be included in a mass ratio of about 1:10 to about 1:50, for example, 1:20 to 1:30. Within the above range, the effects of heat resistance, durability, and low film resistance can be achieved.

[0099] According to one example embodiment, the specific surface area of each of the organic filler and the inorganic filler can be in the range of about 30 m 2 / g or less, for example, can be in the range of 1 m 2 / g to 30 m 2 / g. Here, the "specific surface area" is the Brunauer-Emmett-Teller (BET) specific surface area.

[0100] According to one example embodiment, among the total of 100 parts by weight of the organic filler and the inorganic filler in the coating layer, the organic filler and the inorganic filler can be included in an amount of about 10 parts by weight to about 80 parts by weight: about 20 parts by weight to about 90 parts by weight, for example, in an amount of 10 parts by weight to 40 parts by weight: 60 parts by weight to 90 parts by weight, or 10 parts by weight to 30 parts by weight: 70 parts by weight to 90 parts by weight. Within the above range, the ratio can be advantageous in terms of reducing the film resistance and the heat shrinkage.

[0101] The first inorganic filler and the second inorganic filler can each be or include a ceramic material.

[0102] According to one example embodiment, the first inorganic filler and the second inorganic filler can each include at least one of, for example, a metal oxide, a metalloid oxide, a metal fluoride, a metal hydroxide, and combinations thereof. The first inorganic filler and the second 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 are not limited thereto. For example, the first inorganic filler and the second inorganic filler can be or include the same ceramic, such as, for example, boehmite.

[0103] The filler (i.e., the first inorganic filler alone, the second inorganic filler alone, or the sum of the first inorganic filler and the second inorganic filler) can be included in an amount ranging from about 50 wt% to about 99 wt%, for example, 70 wt% to 99 wt%, for example, 75 wt% to 99 wt%, for example, 80 wt% to 99 wt%, for example, 85 wt% to 99 wt%, for example, 90 wt% to 99 wt%, for example, 95 wt% to 99 wt%, of the total amount of the coating. When the filler is included in the above range, the separator can exhibit desirable or improved heat resistance, durability, oxidation resistance, and stability.

[0104] Each coating can have a thickness ranging from about 0.01 µm to about 20 µm, for example, a thickness ranging from 0.1 µm to 10 µm, 0.1 µm to 5 µm, or 0.5 µm to 2 µm.

[0105] The ratio of the thickness of the coating to the thickness of the porous substrate can range from about 0.05 to about 0.5 (for example, 0.05 to 0.4, 0.05 to 0.3, or 0.1 to 0.2). Within the above range, the separator can exhibit desirable or improved air permeability, heat resistance, adhesive strength, etc. Here, the “thickness of the coating” refers to the thickness of one coating when the coating is formed on only one surface of the porous substrate, and refers to the thickness of two coatings when the coating is formed on both surfaces of the porous substrate.

[0106] Porous substrate The porous substrate may be a substrate having a plurality of pores and generally included in an electrochemical device. The porous substrate may be or include a polymer film formed of any polymer such as or including at least one of the following polymers: polyolefins (such as or including at least one of polyethylene and polypropylene), polyesters (such as polyethylene terephthalate or polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyetheretherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, Teflon, and polytetrafluoroethylene, or copolymers or mixtures of two or more thereof.

[0107] The porous substrate may be or include, for example, a polyolefin-based substrate comprising a polyolefin-based resin, 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. For example, the polyolefin-based resin may include a non-olefin resin other than an olefin resin, or may include a copolymer of an olefin monomer and a non-olefin monomer.

[0108] The porous substrate may have a thickness in a range of about 1 μm to about 40 μm (eg, 1 μm to 30 μm, 1 μm to 20 μm, or 5 μm to 15 μm).

[0109] A separator for a rechargeable lithium battery according to an example embodiment may exhibit desirable or improved air permeability and may have an air permeability value within a range of, for example, less than about 200 sec / 100 cc, for example, about 190 sec / 100 cc or less or 180 sec / 100 cc or less. For example, the separator may have an air permeability value per unit thickness within a range of less than about 40 sec / 100 cc·1 μm, for example, 30 sec / 100 cc·1 μm or less or 25 sec / 100 cc·1 μm or less. Here, the air permeability value refers to the time (in seconds) required for 100 cc of air to pass through a unit thickness of the separator. The air permeability value per unit thickness can be obtained by measuring the air permeability value of the total thickness of the separator and dividing the air permeability value by the thickness. The air permeability value can be obtained by measuring the time required for 100 cc of air to pass through the diaphragm using an air permeability measuring device (EG01-55-1MR, Asahi Seiko Co., Ltd.).

[0110] The separator for a rechargeable lithium battery according to one example embodiment can be formed by the following steps: applying a composition for forming a coating layer on one surface or both surfaces of a porous substrate, drying it, and then curing the composition. The drying can be performed using, for example, typical methods known to those skilled in the art.

[0111] Figure 3 is a cross-sectional view illustrating a separator for a rechargeable lithium battery according to one example embodiment.

[0112] Referring to Figure 3 , the separator for a rechargeable lithium battery includes a porous substrate 1 and a coating layer 2 on both surfaces of the porous substrate 1. The coating layer 2 can include an inorganic filler 3, an organic filler 4, and a (meth)acryl-based binder 5.

[0113] The coating layer can further include an adhesive binder.

[0114] Adhesive binder The adhesive binder is configured to achieve the adhesion strength between the separator and the electrode. The adhesive binder can maintain the heat resistance and adhesion strength of the separator, improve the stability and life of the battery when included in a subsequent battery, and reduce the film resistance of the battery.

[0115] The adhesive binder can include one or more of a (meth)acryl-based binder and a fluorine-based binder.

[0116] According to one example embodiment, the adhesive binder can include a (meth)acryl-based binder including a structural unit derived from a (meth)acrylic acid or a (meth)acrylate. In addition to the (meth)acryl-based binder, the adhesive binder can include a binder having a structural unit derived from a monomer including a polymerizable unsaturated group.

[0117] According to one example embodiment, the adhesive binder is a particle having a core-shell structure, in which the core can include a (meth)acryl-based binder including a structural unit derived from a (meth)acrylic acid or a (meth)acrylate, and the shell can include a binder having a structural unit derived from a monomer including a polymerizable unsaturated group.

[0118] The structural unit derived from a (meth)acrylic acid or a (meth)acrylate can be or include at least one of the following Chemical Formula 9, Chemical Formula 10, and combinations thereof: Chemical Formula 9:

[0119] Chemical Formula 10: .

[0120] In Chemical Formula 9 and Chemical Formula 10, R 21 to R 24 may each independently be or include hydrogen or a C1 to C10 alkyl group, for example, a methyl group. For example, R 21 and R 23 may each be or include hydrogen, and R 22 and R 24 may each be or include hydrogen or a methyl group.

[0121] R 25 may be or include a C1 to C20 alkyl group, for example, a C1 to C10 alkyl group, for example, a methyl group.

[0122] The (meth)acrylic acid or (meth)acrylate can include at least one of an alkyl (meth)acrylate, a perfluoroalkyl (meth)acrylate, and a (meth)acrylate having a functional group in a side chain, for example, can be or include an alkyl (meth)acrylate. In the alkyl (meth)acrylate, the perfluoroalkyl (meth)acrylate, or the (meth)acrylate having a functional group in a side chain, the number of carbons of an alkyl group present in the ester moiety is in a range of about 1 to about 20, for example, in a range of 1 to 10 or 1 to 5.

[0123] The monomer including a polymerizable unsaturated group can include one or more of a styrene-based monomer, an acid monomer, and combinations thereof.

[0124] The styrene-based monomer can include at least one aromatic vinyl-based monomer represented by the following Chemical Formula 11: Chemical Formula 11: .

[0125] In Chemical Formula 11, R 26 and R 27 are each independently hydrogen or a C1 to C6 alkyl group, R a to R e are each independently hydrogen, a C1 to C6 alkyl group, or a halogen, L 7 is or includes a substituted or unsubstituted C1 to C10 alkylene, a substituted or unsubstituted C3 to C20 cycloalkylene, a substituted or unsubstituted C6 to C20 arylene, or a substituted or unsubstituted C3 to C20 heterocyclyl, and e is an integer of 0 to 2, and is a connection point.

[0126] For example, the styrene-based monomer can be or include styrene, and can be or include at least one of methylstyrene, bromostyrene, chlorostyrene, and combinations thereof.

[0127] The acid-derived monomer includes a substituent corresponding to -COOH, and can be or include at least one of itaconic acid, (meth)acrylic acid, and combinations thereof.

[0128] The adhesive binder can be cross-linked and non-cross-linked. To prepare the cross-linked (meth)acryl-based polymer, a cross-linking agent can be further added during the polymerization process.

[0129] According to another example embodiment, the adhesive binder can be or include a fluorine-based binder.

[0130] The fluorine-based binder can include a vinylidene fluoride-derived unit. The fluorine-based binder can include a vinylidene fluoride-derived unit and other monomer-derived units. For example, the fluorine-based binder can include at least one of a polyvinylidene fluoride homopolymer, a polyvinylidene fluoride-hexafluoropropylene copolymer, and combinations thereof.

[0131] According to one example embodiment, the adhesive binder can have an average particle size D50 in the range of about 0.1 µm to about 0.6 µm, for example, an average particle size D50 in the range of 0.2 µm to 0.5 µm. Within the above range, the adhesive binder can be included in the coating layer.

[0132] According to one example embodiment, the (meth)acryl-based binder and the adhesive binder can be included in the coating layer at a weight ratio of about 1:0.1 to about 1:3. Within the above range, the adhesion strength can be improved.

[0133] Figure 4 is a cross-sectional view illustrating a separator for a rechargeable lithium battery according to another example embodiment. Referring to Figure 4 The separator for a rechargeable lithium battery includes a porous substrate 1 and a coating layer 2 on both surfaces of the porous substrate 1. The coating layer 2 can include an inorganic filler 3, an organic filler 4, a (meth)acryl-based binder 5, and an adhesive binder 6.

[0134] Rechargeable lithium battery According to one example embodiment, the rechargeable lithium battery includes a separator for a rechargeable lithium battery, a positive electrode, and a negative electrode.

[0135] The separator for a rechargeable lithium battery refers to the above-described description. The separator for a rechargeable lithium battery can be located between the positive electrode and the negative electrode.

[0136] Positive electrode A 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 further include a binder and / or a conductive material.

[0137] For example, the positive electrode can further include an additive that can be configured as a sacrificial positive electrode.

[0138] 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 a metal such as or including at least one of cobalt, manganese, nickel, and combinations thereof can be included.

[0139] The composite oxide can be or include a lithium transition metal composite oxide. Examples of the composite oxide can include at least one of a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free lithium nickel manganese-based oxide, and combinations thereof.

[0140] As an example, the following compounds represented by any one of the following chemical formulas can 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 Ge O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5 and 0≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn2G b O4 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90≤a≤1.8 and 0≤g≤0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); or Li a FePO4 (0.90≤a≤1.8).

[0141] 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 is or includes at least one of Mn, Al, and combinations thereof.

[0142] The positive electrode active material can be or include, for example, a high-nickel-based positive electrode active material, the high-nickel-based positive electrode active material having a nickel content 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 a lithium-transition metal composite oxide. The high-nickel-based positive electrode active material can enable high capacity, and can be applied to a high-capacity, high-density rechargeable lithium battery.

[0143] 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, based on 100 wt% of the positive electrode active material layer.

[0144] The binder is configured to adhere the positive electrode active material particles to each other, and to adhere the positive electrode active material to the current collector. As non-limiting examples, examples of the binder can include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer including an oxirane, polyvinylpyrrolidone, 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.

[0145] A conductive material can be included to impart electrical conductivity (e.g., electronic conductivity) to the electrode. Any material that does not cause a chemical change (e.g., does not cause an undesirable chemical change in the rechargeable lithium battery) and conducts electrons can be included in the battery. Examples of the conductive material can include: a carbon-based material, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; a metal-based material including at least one of copper, nickel, aluminum, silver, and the like, in the form of a metal powder or a metal fiber; a conductive polymer, such as a polyphenylene derivative; or a mixture thereof.

[0146] Al can be included as the current collector, but is not limited thereto.

[0147] Negative electrode A 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 further include a binder and / or a conductive material (e.g., an electronic conductive material).

[0148] 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.

[0149] Negative electrode active material The negative electrode active material can include at least one of a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / de-doping lithium, and a transition metal oxide.

[0150] The material that reversibly intercalates / deintercalates lithium ions can include a carbon-based negative electrode active material, such as exemplified by crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon can be graphite, such as at least one of natural graphite and artificial graphite that is not fixed in shape, flaky, flake-like, spherical, or fibrous. The amorphous carbon can be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, and the like.

[0151] Lithium metal alloys include alloys 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.

[0152] The material capable of doping / dedoping lithium can be or include at least one of a Si-based negative electrode active material and a Sn-based negative electrode active material. The Si-based negative electrode active material can include silicon, a silicon-carbon composite, SiO x (0 < x < 2), a Si-Q alloy (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof). The Sn-based negative electrode active material can include at least one of Sn, SnO2, a Sn-based alloy, and combinations thereof.

[0153] The silicon-carbon composite can be or include a composite of silicon and amorphous carbon. According to an example 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 assembled, and an amorphous carbon coating (shell) on the surface of the secondary particles. The 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.

[0154] The silicon-carbon composite can also include crystalline carbon. For example, the silicon-carbon composite can include a core including crystalline carbon and silicon particles, and an amorphous carbon coating on the surface of the core.

[0155] The Si-based negative electrode active material or the Sn-based negative electrode active material can be combined with a carbon-based negative electrode active material.

[0156] The binder can be configured to adhere the negative electrode active material particles to each other, and to adhere the negative electrode active material to the current collector. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, or combinations thereof.

[0157] The non-aqueous binder can include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide imide, polyimide, and combinations thereof.

[0158] The aqueous binder can be or include at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoro rubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0159] When the aqueous binder is included as the negative electrode binder, a cellulose-based compound capable of imparting adhesiveness can also be included. The cellulose-based compound can include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof. The alkali metal can include at least one of Na, K, and Li.

[0160] The dry binder can be or include a polymeric material capable of being in a fibrous form. For example, the dry binder can be or include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0161] An electrically conductive material can be included to impart electrical conductivity (e.g., electronic conductivity) to the electrode. Any material that does not cause a chemical change (e.g., does not cause an undesirable chemical change in the rechargeable lithium battery) and conducts electrons can be included in the battery. Non-limiting examples of the electrically conductive material can include: a carbon-based material, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; a metal-based material including at least one of copper, nickel, aluminum, silver, and the like, in the form of a metal powder or a metal fiber; an electrically conductive polymer, such as a polyphenylene derivative; or a mixture thereof.

[0162] The negative electrode current collector can include at least one of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with an electrically conductive metal, and combinations thereof.

[0163] The rechargeable lithium battery can further include an electrolyte.

[0164] Electrolyte The electrolyte for the rechargeable lithium battery can include a non-aqueous organic solvent and a lithium salt.

[0165] The non-aqueous organic solvent can be configured as a medium for transporting ions participating in an electrochemical reaction of the battery.

[0166] The non-aqueous organic solvent can be or include at least one of a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, an aprotic solvent, and combinations thereof.

[0167] 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.

[0168] 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.

[0169] Ether solvents may include at least one of dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, and the like. Furthermore, ketone solvents may include cyclohexanone, and the like. Alcohol solvents may include at least one of ethanol and isopropanol, and aprotic solvents may include at least one of the following: nitriles, 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); amides, such as dimethylformamide; dioxolanes, such as 1,3-dioxolane and 1,4-dioxolane; sulfolane; and the like.

[0170] The nonaqueous organic solvent may be included alone or in combination of two or more.

[0171] In addition, when the carbonate-based solvent is used, the cyclic carbonate and the chain carbonate may be mixed, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of about 1:1 to about 1:9.

[0172] Lithium salts dissolved in organic solvents are configured to supply lithium ions in the battery to enable basic operation of the rechargeable lithium battery and to 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 F 2y+1 SO2) (wherein, x and y are integers of 1 to 20), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOBP), lithium difluorobis(oxalato)borate (LiDFBOB) and lithium bis(oxalato)borate (LiBOB).

[0173] The rechargeable lithium battery can be classified into a cylindrical battery, a prismatic battery, a pouch-type battery, or a coin-type battery, etc. according to its shape.

[0174] Figures 5 to 8 is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment. Figure 5 is illustrated a cylindrical battery, Figure 6 is illustrated a prismatic battery, and Figure 7 is illustrated a pouch-type battery. Referring to Figure 8 , the rechargeable lithium battery 100 can include an electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is accommodated. The positive electrode 10, the negative electrode 20, and the separator 30 can be impregnated with an electrolyte (not shown). As shown in Figures 5 to 8 , the rechargeable lithium battery 100 can include a sealing member 60 sealing the case 50. In Figure 5 , the rechargeable lithium battery 100 can 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 shown in Figure 6 and Figure 7 , the rechargeable lithium battery 100 can include Figure 8 , as shown in Figure 8 , an electrode tab 70 shown in Figure 7 , or, for example, a positive electrode tab 71 and a negative electrode tab 72 shown in , the electrode tab 70 / 71 / 72 forms an electrical path for guiding an electric current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0175] As a non-limiting example, the rechargeable lithium battery according to an example embodiment can be applied to, for example, an automobile, a mobile phone, and / or various types of electrical devices.

[0176] Hereinafter, examples and comparative examples of the present disclosure are described. However, the following examples are only embodiments of the present disclosure, and the present disclosure is not limited to the following examples.

[0177] Synthetic Example 1: Poly(acrylic acid-co-methyl acrylate 2-hydroxyethyl ester-co-2-acrylamido-2-methylpropane sulfonic acid) lithium salt (30:10:60) In a 3L four-necked flask equipped with a stirrer, a thermometer, and a cooling tube, distilled water (1249.72 g), 20% aqueous lithium hydroxide solution (113.4 g, 1.05 equivalents of the total amount of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid), acrylic acid (21.60 g, 0.30 mol), 2-hydroxyethyl methacrylate (13.00 g, 0.10 mol), 2-acrylamido-2-methylpropanesulfonic acid (124.30 g, 0.6 mol), and ammonium persulfate (0.2 g, 0.001 mol) were added, and then the internal pressure was reduced to 10 mmHg three times using a diaphragm pump, and the internal pressure was restored to the normal pressure using nitrogen gas.

[0178] The reaction was performed while the temperature of the reaction solution was controlled to be stabilized between 65°C and 70°C for 12 hours.

[0179] After cooling to room temperature, the non-volatile component (NV) in about 10 mL of the reaction solution was measured, and the measurement result was 9.8 wt% (theoretical value: 10 wt%). In addition, in the poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt obtained here, the molar ratio of the first structural unit derived from acrylic acid, the second structural unit derived from 2-hydroxyethyl methacrylate, and the third structural unit derived from 2-acrylamido-2-methylpropanesulfonic acid was 30:10:60.

[0180] Synthesis Example 2: Poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt (40:10:50) A (meth)acryl-based binder was prepared in the same manner as in the method in Synthesis Example 1, except that acrylic acid (28.80 g, 0.40 mol), 2-hydroxyethyl methacrylate (13.00 g, 0.10 mol), and 2-acrylamido-2-methylpropanesulfonic acid (103.60 g, 0.5 mol) were used.

[0181] The non-volatile component of the reaction solution was 9.7 wt% (theoretical value: 10 wt%). In addition, in the poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt obtained here, the molar ratio of the first structural unit derived from acrylic acid, the second structural unit derived from 2-hydroxyethyl methacrylate, and the third structural unit derived from 2-acrylamido-2-methylpropanesulfonic acid was 40:10:50.

[0182] Synthesis Example 3: Poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt (60:10:30) A (meth)acryl-based binder was prepared in the same manner as in Synthesis Example 1, except that acrylic acid (43.20 g, 0.60 mol), 2-hydroxyethyl methacrylate (13.00 g, 0.10 mol), and 2-acrylamido-2-methylpropanesulfonic acid (62.20 g, 0.30 mol) were used.

[0183] The nonvolatile component of the reaction solution was 9.7 wt% (theoretical value: 10 wt%). Also, in the poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt obtained here, the molar ratio of the first structural unit derived from acrylic acid, the second structural unit derived from 2-hydroxyethyl methacrylate, and the third structural unit derived from 2-acrylamido-2-methylpropanesulfonic acid was 60:10:30.

[0184] Synthesis Example 4: Poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2- acrylamido-2-methylpropanesulfonic acid) lithium salt (40:5:55) A (meth)acryl-based binder was prepared in the same manner as in Synthesis Example 1, except that acrylic acid (28.80 g, 0.40 mol), 2-hydroxyethyl methacrylate (6.500 g, 0.05 mol), and 2-acrylamido-2-methylpropanesulfonic acid (114.00 g, 0.55 mol) were used.

[0185] The nonvolatile component of the reaction solution was 9.8 wt% (theoretical value: 10 wt%). Also, in the poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt obtained here, the molar ratio of the first structural unit derived from acrylic acid, the second structural unit derived from 2-hydroxyethyl methacrylate, and the third structural unit derived from 2-acrylamido-2-methylpropanesulfonic acid was 40:5:55.

[0186] Synthesis Example 5: Poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2- acrylamido-2-methylpropanesulfonic acid) lithium salt (40:15:45) A (meth)acryl-based binder was prepared in the same manner as in Synthesis Example 1, except that acrylic acid (28.80 g, 0.40 mol), 2-hydroxyethyl methacrylate (19.50 g, 0.15 mol), and 2-acrylamido-2-methylpropanesulfonic acid (93.30 g, 0.45 mol) were used.

[0187] The nonvolatile component of the reaction solution was 9.8% by weight (theoretical value: 10% by weight). In addition, in the poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt obtained here, the molar ratio of the first structural unit derived from acrylic acid, the second structural unit derived from 2-hydroxyethyl methacrylate, and the third structural unit derived from 2-acrylamido-2-methylpropanesulfonic acid was 40:15:45.

[0188] Comparative Synthesis Example 1: Poly(acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt (35:65) A (meth)acryl-based binder was prepared in the same manner as in Synthesis Example 1, except that acrylic acid (25.20 g, 0.35 mol) and 2-acrylamido-2-methylpropanesulfonic acid (134.70 g, 0.65 mol) were used.

[0189] The nonvolatile component of the reaction solution was 9.7% by weight (theoretical value: 10% by weight). In addition, in the poly(acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt obtained here, the molar ratio of the first structural unit derived from acrylic acid and the third structural unit derived from 2-acrylamido-2-methylpropanesulfonic acid was 35:65.

[0190] Comparative Synthesis Example 2: Poly(acrylic acid-co-acrylonitrile-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt (45:50:5) In a 3L four-necked flask equipped with a stirrer, a thermometer, and a cooling tube, distilled water (968 g), 20% aqueous lithium hydroxide solution (78.72 g, 0.8 equivalents of the total amount of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid), acrylic acid (54.00 g, 0.75 mol), ammonium persulfate (0.65 g, 2.85 mmol), and 2-acrylamido-2-methylpropanesulfonic acid (6.00 g, 0.07 mol) were added, and then the process of reducing the internal pressure to 10 mmHg using a diaphragm pump three times and restoring the internal pressure to normal pressure using nitrogen was repeated, and then acrylonitrile (60.00 g, 1.13 mol) was added.

[0191] The reaction was carried out while controlling the temperature of the reaction solution to be stabilized between 65°C and 70°C for 18 hours, and after the second addition of ammonium persulfate (0.22 g, 0.95 mmol), the temperature was raised to 80°C and the reaction was further carried out for 4 hours.

[0192] After cooling to room temperature, the pH of the reaction solution was adjusted to 7 to 8 using a 25% aqueous ammonia solution. The non-volatile content (NV) in approximately 10 mL of the reaction solution was measured and found to be 9.8 wt% (theoretical value: 10 wt%). Furthermore, in the poly(acrylic acid-co-acrylonitrile-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt obtained here, the molar ratio of the structural units derived from acrylic acid, the structural units derived from acrylonitrile, and the structural units derived from 2-acrylamido-2-methylpropanesulfonic acid was 45:50:5.

[0193] Comparative Synthesis Example 3: Poly(acrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt (95:5) In a 10 L four-necked flask equipped with a stirrer, a thermometer, and a cooling tube, distilled water (6361 g), acrylamide (675.3 g, 9.5 mol), potassium persulfate (2.7 g, 0.01 mol), 2-acrylamido-2-methylpropanesulfonic acid (103.6 g, 0.5 mol), and a 5N aqueous lithium hydroxide solution (1.05 equivalents based on the total amount of 2-acrylamido-2-methylpropanesulfonic acid) were added, and then a process of reducing the internal pressure to 10 mmHg using a diaphragm pump and returning the internal pressure to normal pressure using nitrogen was repeated three times.

[0194] The reaction was performed for 12 hours while the temperature of the reaction solution was controlled to be stable between 65° C. and 70° C. After cooling to room temperature, the pH of the reaction solution was adjusted to 7 to 8 using a 25% aqueous ammonia solution.

[0195] The non-volatile content of approximately 10 mL of the reaction solution (reaction product) was measured and found to be 9.5 wt% (theoretical value: 10 wt%). Furthermore, the molar ratio of structural units derived from acrylamide to structural units derived from 2-acrylamido-2-methylpropanesulfonic acid in the poly(acrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt obtained here was 95:5.

[0196] Example 1 The binder of Synthesis Example 1, boehmite (cubic, average particle size D50 = 0.2 μm, specific surface area: 16 m 2 / g) and cross-linked polymethyl methacrylate (PMMA) (spherical, average particle size D50 = 0.15 μm, specific surface area: 18 m 2 A binder aqueous solution (10 wt % in distilled water) of 1% (400 μg / g) was dispersed in water, and then the binder aqueous solution was ground and dispersed using a bead mill at 25°C for 30 minutes to prepare a dispersion. A composition for coating was prepared by adding water so that the total solid content was 20 wt %.

[0197] The weight ratio of the binder:boehmite of the composition for the coating layer was 1:20, and the weight ratio of the binder:cross-linked PMMA of the composition for the coating layer was 1:3.

[0198] A separator was manufactured by coating both surfaces of a 5.5 μm thick polyethylene porous substrate (CZMZ Company, air permeability: 110 sec / 100 cc, puncture strength: 360 kgf) with the prepared composition for coating to thicknesses of 0.9 μm and 1.1 μm, and then drying the prepared composition at 70° C. for 10 minutes.

[0199] By using LiNi as the positive electrode active material 0.75 Mn 0.23 Al 0.02 O2, polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed at a weight ratio of 96:3:1 and the mixture was dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0200] The positive electrode was manufactured by coating the positive electrode active material slurry on a 15 μm thick Al foil, drying it, and then roll-pressing the positive electrode active material slurry at 100°C.

[0201] As the negative electrode active material, a mixture of artificial graphite and Si-C composite was used at a weight ratio of 93:7, and a negative electrode active material slurry was prepared by mixing and dispersing the negative electrode active material, styrene-butadiene rubber binder, and carboxymethyl cellulose at a weight ratio of 98:1:1. The Si-C composite used a core including artificial graphite and silicon particles and carbonyl pitch coated on the surface of the core.

[0202] The negative electrode was manufactured by coating the negative electrode active material slurry on a 10 μm thick Cu foil, drying it, and then roll-pressing the negative electrode active material slurry at 100°C.

[0203] The electrode assembly core is fabricated by assembling the positive electrode, negative electrode, and the fabricated separator. The core is inserted into a pouch, injected with electrolyte, and then vacuum-sealed. The electrolyte is 1M LiPF6 dissolved in a non-aqueous organic solvent consisting of a 3:7 volume ratio of ethylene carbonate (EC) and ethyl methyl carbonate (EMC).

[0204] The core inserted into the bag is pre-charged to 50% state of charge (SOC) and a force of 250 kgf / cm is applied to the core. 2 The core was thermally softened at 70°C for 1 hour.

[0205] Subsequently, the gas was removed from the bag (degassing), and the electrode core was charged at a constant current of 0.2C rate at a temperature of 45°C for 1 hour while applying a pressure of 200 kgf / cm 2 2, until the voltage reached 4.3 V, held at 4.3 V, and charged at a constant voltage until the current reached 0.05C. Subsequently, the formation process was performed by repeating the discharge cycle 5 times until the voltage reached 3.0 V at a constant current of 0.2C.

[0206] Example 2 A separator for a rechargeable lithium battery and a rechargeable lithium battery were manufactured in the same manner as in Example 1, except that the binder of Synthesis Example 2 was used instead of the binder of Synthesis Example 1.

[0207] Example 3 A separator for a rechargeable lithium battery and a rechargeable lithium battery were manufactured in the same manner as in Example 1, except that the binder of Synthesis Example 3 was used instead of the binder of Synthesis Example 1.

[0208] Example 4 A separator for a rechargeable lithium battery and a rechargeable lithium battery were manufactured in the same manner as in Example 1, except that the binder of Synthesis Example 4 was used instead of the binder of Synthesis Example 1.

[0209] Example 5 A separator for a rechargeable lithium battery and a rechargeable lithium battery were manufactured in the same manner as in Example 1, except that the binder of Synthesis Example 5 was used instead of the binder of Synthesis Example 1.

[0210] Example 6 A dispersion was prepared by dispersing a binder aqueous solution (10 wt% in distilled water) including the binder of Synthesis Example 1, boehmite (amorphous, average particle size D50 = 0.3 μm, specific surface area: 18 m 2 / g) and cross-linked PMMA (spherical, average particle size D50 = 0.15 μm) in water, and then grinding and dispersing the binder aqueous solution at 25°C for 30 minutes using a bead mill.

[0211] The weight ratio of the binder: boehmite of the dispersion was 1:20, and the weight ratio of the binder: cross-linked PMMA of the dispersion was 1:3.

[0212] A composition for coating was prepared by adding water so that the total solid content was 20 wt%. A separator was manufactured by coating both surfaces of a 5.5 μm-thick polyethylene porous substrate (CZMZ Co., air permeability: 110 sec / 100 cc, puncture strength: 360 kgf) with the prepared composition for coating to a thickness of 0.9 μm and 1.1 μm, and then drying the prepared composition at 70°C for 10 minutes. A rechargeable lithium battery was manufactured in the same manner as in Example 1.

[0213] Example 7 A dispersion was prepared by dispersing a binder aqueous solution (10 wt%, in distilled water) including the (meth)acryl-based binder of Synthetic Example 1, boehmite (cubic, average particle size D50 = 0.2 μm, specific surface area: 16 m 2 / g) and cross-linked PMMA (spherical, average particle size D50 = 0.15 μm, specific surface area: 18 m 2 / g) in water, and then grinding and dispersing the binder aqueous solution at 25°C for 30 minutes using a bead mill.

[0214] The weight ratio of the binder of the dispersion: boehmite was 1:20, and the weight ratio of the binder of the dispersion: cross-linked PMMA was 1:3.

[0215] A composition for coating was prepared by adding an adhesive binder having a core-shell structure (core: polymethyl methacrylate, shell: polystyrene, particle, average particle size D50: 0.35 μm) to the dispersion and adding water so that the total solid content was 20 wt%.

[0216] The weight ratio of the (meth)acryl-based binder of the composition for coating: adhesive binder was 1:0.1.

[0217] A separator was manufactured by coating both surfaces of a 5.5 μm-thick polyethylene porous substrate (CZMZ Co., air permeability: 110 sec / 100 cc, puncture strength: 360 kgf) with the prepared composition for coating to a thickness of 0.9 μm and 1.1 μm, and then drying the prepared composition at 70°C for 10 minutes. A rechargeable lithium battery was manufactured in the same manner as in Example 1.

[0218] Example 8 A dispersion was prepared by dispersing a binder aqueous solution (10 wt%, in distilled water) including the (meth)acryl-based binder of Synthetic Example 1, boehmite (cubic, average particle size D50 = 0.2 μm, specific surface area: 16 m 2 / g) and cross-linked PMMA (spherical, average particle size D50 = 0.15 μm, specific surface area: 18 m 2A dispersion was prepared by dispersing an aqueous solution (10 wt% in distilled water) of a binder (g) in water, and then grinding and dispersing the aqueous binder solution using a bead mill at 25°C for 30 minutes.

[0219] The weight ratio of the binder of the dispersion : boehmite was 1 : 20, and the weight ratio of the binder of the dispersion : crosslinked PMMA was 1 : 3.

[0220] A composition for coating was prepared by adding a polyvinylidene fluoride (PVDF)-based adhesive binder (particles, average particle size D50: 0.3 μm) to the dispersion and adding water so that the total solid content was 20 wt%.

[0221] The weight ratio of the (meth)acryl-based binder : adhesive binder of the composition for coating was 1 : 0.1.

[0222] A separator was manufactured by coating both surfaces of a 5.5 μm-thick polyethylene porous substrate (CZMZ Co., air permeability: 110 sec / 100 cc, puncture strength: 360 kgf) with the prepared composition for coating to a thickness of 0.9 μm and 1.1 μm, and then drying the prepared composition at 70°C for 10 minutes. A rechargeable lithium battery was manufactured in the same manner as in Example 1.

[0223] Comparative Example 1 A separator for a rechargeable lithium battery and a rechargeable lithium battery were manufactured in the same manner as in Example 1, except that the binder of Comparative Synthesis Example 1 was used instead of the binder of Synthesis Example 1.

[0224] Comparative Example 2 A separator for a rechargeable lithium battery and a rechargeable lithium battery were manufactured in the same manner as in Example 1, except that the binder of Comparative Synthesis Example 2 was used instead of the binder of Synthesis Example 1.

[0225] Comparative Example 3 A separator for a rechargeable lithium battery and a rechargeable lithium battery were manufactured in the same manner as in Example 1, except that the binder of Comparative Synthesis Example 3 was used instead of the binder of Synthesis Example 1.

[0226] Comparative Example 4 A separator and a rechargeable lithium battery were manufactured in the same manner as in Example 1, except that crosslinked PMMA was not used as an organic filler.

[0227] Comparative Example 5 A separator and a rechargeable lithium battery were manufactured in the same manner as in Example 6, except that crosslinked PMMA was not used as an organic filler.

[0228] The separators according to the examples and comparative examples were evaluated by the following methods, and the evaluation results are shown in Table 1 below.

[0229] (1) Coating density (unit: g / cm 2 ) The thickness (a) and the unit weight (b) of the textile before coating were measured. The coating thickness and weight were measured by measuring the total thickness (c) and the unit weight (d) after coating. The coating density was measured by dividing the coating weight by the thickness.

[0230] Coating thickness (e) = c - a Coating weight (f) = d - b Coating density = f / e (2) Air permeability (unit: sec / 100cc) A sample was manufactured by cutting the separator so that the cross-sectional area was 1 square inch (inch 2 ), and the time (second) taken for 100cc of air to pass through the sample was measured using a densimeter according to the ASTM D726-94 test method. The difference between the air permeability value of the uncoated polyethylene porous substrate and the coated separator is referred to as Δ air permeability.

[0231] (3) Heat shrinkage rate (unit: %) A sample was manufactured by cutting the separator to a size of 10 cm (longitudinal direction, MD) x 10 cm (transverse direction, TD), and drawing a square having a size of 8 cm x 8 cm on the surface of the sample, then placing the sample between a paper sheet or alumina powder, and placing the sample in an oven at 150°C for 1 hour.

[0232] Then, by taking out the sample and comparing the sample with the square having a size of 10 cm (longitudinal direction, MD) x 10 cm (transverse direction, TD) previously drawn, the heat shrinkage rate on each of MD and TD was calculated according to Equation 1 below.

[0233] Equation 1: Heat shrinkage rate = (initial length - length after heat shrinkage treatment) / (initial length) x 100 (4) Adhesion (unit: gf) The coating layer of the separator was brought into contact with the negative electrode active material layer of Example 1, and the separator and the negative electrode were bonded using a laminating device in a chamber at 60°C. Accordingly, a sample was manufactured by cutting the laminate of the separator and the electrode to a predetermined size (width: 25 mm, length: 50 mm), and then the force required to peel off in the 180° direction was measured using a tensile meter (Stable Micro System, TA-XT).

[0234] (5) Membrane resistance (unit: Ω) when impregnated with electrolyte The membrane resistance was evaluated by electrochemical impedance spectroscopy (EIS) resistance. A sample was manufactured by cutting the separator into a size of 10 cm x 10 cm, impregnating the sample with an electrolyte mixed solution in which 1.5 M LiPF6 was dissolved in ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate (volume ratio 2:1:7), a test battery cell was manufactured by inserting the impregnated sample into an aluminum foil electrode to which a lead tab was attached and sealing the impregnated sample in an aluminum pack, and the membrane resistance (Ω) of the test battery cell was measured at 20°C by an alternating current impedance method (measurement frequency 100 kHz).

[0235] (6) Moisture content (unit: ppm / g) The moisture content was evaluated by taking out the electrode core from the pouch and separating the separator. Here, the moisture content was measured according to the Karl-Fischer method.

[0236] (7) Pressure resistance (unit: kV) For the lithium batteries of the examples and comparative examples, the insulating property (breakdown voltage, BDV) of the separator was evaluated, and the results are shown in Table 1 below. The BDV was measured by placing the separator between stainless steel (SUS) plates and measuring the voltage at the point at which the voltage stopped rising (breakdown, short circuit) while fixing the current to 0.3 mA in an alternating current (AC) mode using TOS5301 of KIKISUI and increasing the voltage to 0.3 kV at a voltage increase rate of 8 seconds.

[0237] Table 1:

[0238] As shown in Table 1, the separator according to the examples can exhibit low membrane resistance and low thermal shrinkage, thereby improving the capacity, stability, and life of the battery.

[0239] The separator for a rechargeable lithium battery according to one example embodiment can exhibit low membrane resistance and low thermal shrinkage in an electrolyte, thereby improving the capacity, stability, and life of the battery. Although example embodiments of the present disclosure have been described above, the present disclosure is not limited thereto, and can be modified in any form within the scope of the claims, the detailed description of the present disclosure, and the drawings, and the modifications also fall within the scope of the present disclosure.

Claims

1. A separator for a rechargeable lithium battery, the separator comprising: a porous substrate; and a coating layer on at least one surface of the porous substrate and including a binder and a filler, wherein the binder includes a (meth)acryl binder including a first structural unit derived from a (meth)acrylic acid, a (meth)acrylate, or a salt thereof, a second structural unit derived from a (meth)acryl hydroxyalkyl ester, and a third structural unit derived from a (meth)acrylamido sulfonic acid or a salt thereof, the filler includes an organic filler and an inorganic filler, the organic filler includes a crosslinked polymeric filler, and the inorganic filler includes one or more of a first inorganic filler having an average particle size D50 in a range of 50 nm to 250 nm and being cubic, and a second inorganic filler having an average particle size D50 in a range of 100 nm to 350 nm and being amorphous. with respect to 100 mol% of the (meth)acryl binder:

2. The septum of claim 1, wherein, a content of the first structural unit ranges from 30 mol% to 65 mol%, a content of the second structural unit ranges from 1 mol% to 20 mol%, and a content of the third structural unit ranges from 20 mol% to 65 mol%. the first structural unit is represented by any one or more of Chemical Formula 1 to Chemical Formula 3, 3. The septum of claim 1, wherein, the second structural unit is represented by Chemical Formula 4, and the third structural unit is represented by any one or more of Chemical Formula 5 to Chemical Formula 7: Chemical Formula 1: Chemical Formula 2: Chemical Formula 3: Chemical Formula 4: Chemical Formula 5: Chemical Formula 6: Chemical Formula 7: in Chemical Formulae 1 to 7, a, b, c, and d are each independently an integer in a range of 0 to 2, and R 1 to R 14 each independently comprises hydrogen or Ci to C10 alkyl, L 1 to L 4 each independently comprises a substituted or unsubstituted C1to C10alkylene, a substituted or unsubstituted C3to C20cycloalkylene, a substituted or unsubstituted C6to C20arylene, or a substituted or unsubstituted C3to C20heterocyclylene, M includes an alkali metal. a mass ratio of the (meth)acryl binder to the organic filler is in a range of 1:1 to 1:

10.

4. The septum of claim 1, wherein, the organic filler includes a crosslinked polymethyl methacrylate filler.

5. The septum of claim 1, wherein, a mass ratio of the (meth)acryl binder to the one or more of the first inorganic filler and the second inorganic filler is in a range of 1:10 to 1:

50.

6. The septum of claim 1, wherein, the one or more of the first inorganic filler and the second inorganic filler includes at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, and boehmite.

7. The septum of claim 1, wherein, of 100 parts by weight of the organic filler and the one or more of the first inorganic filler and the second inorganic filler in the coating layer, a content of the organic filler and the one or more of the first inorganic filler and the second inorganic filler is 10 parts by weight to 80 parts by weight: 20 parts by weight to 90 parts by weight.

8. The septum of claim 1, wherein, the coating layer further includes an adhesive binder.

9. The septum of claim 1, wherein, ​ 10. The septum of claim 9, wherein, The adhesive binder includes one or more of another (meth)acryl-based binder and a fluorine-based binder.

11. The separator according to claim 10, wherein: The other (meth)acryl-based binder includes particles having a core-shell structure, The core includes a (meth)acryl-based binder including structural units derived from a (meth)acrylic acid or a (meth)acrylate, and The shell includes a binder having structural units derived from a monomer including a polymerizable unsaturated group.

12. The septum of claim 10, wherein, The fluorine-based binder includes a vinylidene fluoride-derived unit and one or more of units derived from a chlorotrifluoroethylene, a trifluoroethylene, a hexafluoropropylene, a tetrafluoroethylene, and an ethylene monomer.

13. The septum of claim 10, wherein, In the coating layer, a weight ratio of the (meth)acryl-based binder to the adhesive binder is in a range of 1:0.1 to 1:

3.

14. The septum of claim 1, wherein, The thickness of the coating layer is in a range of 0.5 pm to 2 pm.

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

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