Separator for rechargeable battery and rechargeable battery including the same

Abstract

The present disclosure relates to a separator for a rechargeable battery and a rechargeable battery including the same. A separator for a rechargeable battery includes a porous substrate and a coating layer on at least one surface of the porous substrate. The coating layer comprises a crosslinking product of a binder and a crosslinking agent, and a filler, and the binder comprises a (meth) acrylic acid binder; the (methyl) acrylic acid binder comprises a first structural unit derived from (methyl) acrylic acid, (methyl) acrylate or a salt thereof, a second structural unit derived from (methyl) hydroxyalkyl acrylate and a third structural unit derived from (methyl) acrylamide sulfonic acid or a salt thereof, and the cross-linking agent comprises an aziridine cross-linking agent. And the filler comprises a mixture of a first filler and a second filler. The first filler is an inorganic filler, and the second filler is a metal-organic framework structure.

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0163676, filed on November 16, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] This disclosure relates to a separator for a rechargeable battery and a rechargeable battery including the separator. Background Technology

[0003] With the increasing prevalence of battery-powered electronic devices (such as mobile phones, laptops, and electric vehicles), the demand for rechargeable batteries with high energy density and high capacity is growing. Therefore, improving the performance of rechargeable lithium batteries could be advantageous.

[0004] A rechargeable lithium battery includes a positive electrode and a negative electrode containing active materials capable of inserting and deintercalating lithium ions, and generates electrical energy through oxidation and reduction reactions as lithium ions deintercalate from the positive electrode and insert into the negative electrode, and deintercalate from the negative electrode and insert into the positive electrode.

[0005] A rechargeable lithium battery may include a separator between the positive and negative electrodes. The separator is impregnated with an electrolyte and is bonded to either the positive or negative electrode. Summary of the Invention

[0006] One example embodiment includes a separator for a rechargeable battery that provides low thermal shrinkage, high rate capability during charging and discharging, and low membrane resistance.

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

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

[0009] The separator for a rechargeable battery includes a porous substrate and a coating layer on at least one surface of the porous substrate. The coating layer includes a binder and a crosslinking product of a crosslinking agent, as well as a filler. The binder includes a (meth)acrylic acid binder comprising a first structural unit derived from (meth)acrylic acid, a (meth)acrylate, or a salt thereof, a second structural unit derived from a hydroxyalkyl (meth)acrylate, and a third structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof. The crosslinking agent includes an aziridine crosslinking agent, and the filler includes a mixture of a first filler and a second filler, wherein the first filler is an inorganic filler and the second filler has a metal-organic framework structure.

[0010] Another example embodiment includes a rechargeable battery.

[0011] A rechargeable battery includes a positive electrode, a negative electrode, and the aforementioned separator for a rechargeable battery located between the positive and negative electrodes. Attached Figure Description

[0012] The above and other objects, features, and advantages of this disclosure will become more apparent to those skilled in the art from the detailed description of exemplary embodiments with reference to the accompanying drawings, in which: Figure 1 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment; and Figures 2 to 5 This is a schematic cross-sectional view of a rechargeable lithium battery according to an example embodiment. Detailed Implementation

[0013] Hereinafter, exemplary embodiments of the present disclosure are described in detail. However, these embodiments are given by way of example, and the present disclosure is not limited thereto, and is limited only by the scope of the appended claims.

[0014] Unless otherwise stated herein, when a component such as a layer, film, region, plate, etc., is described as being disposed "on" another component, it includes not only the case where the component is "directly" on the other component, but also the case where there are one or more other components between them.

[0015] Unless otherwise stated herein, the singular may also include the plural. Additionally, unless otherwise stated, the term "A or B" may mean "including A, including B, or including both A and B".

[0016] In this specification, “combination of them” may mean a mixture, stack, complex, copolymer, alloy, blend or reaction product of the components.

[0017] Unless otherwise defined herein, “particle size D50” can refer to the size of particles that constitute 50% of the cumulative volume in a particle size distribution. Particle size distribution can be measured by methods known to those skilled in the art. For example, particle size distribution can be measured using a particle size analyzer, transmission electron microscopy (TEM) images, or scanning electron microscopy (SEM) images. Alternatively, particle size distribution can be obtained by measuring particle size using a measuring device that utilizes dynamic light scattering, performing data analysis to count the number of particles in each particle size range, and then calculating the particle size D50 from that data. Optionally, particle size distribution can be measured using laser diffraction. When measuring particle size distribution by laser diffraction, for example, the particle size D50 can be calculated based on 50% of the particle size distribution in the measuring device by dispersing the particles to be measured in a dispersion medium, introducing the dispersion medium into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT3000), and irradiating the device with ultrasound at an output of 60W at approximately 28kHz.

[0018] If the particles are spherical, then particle size can refer to the diameter of the particles.

[0019] In this specification, "(meth)acrylic acid" refers to acrylic acid and / or methacrylic acid.

[0020] In the following text, unless otherwise defined, “substitution” means that the hydrogen in a compound is substituted by a group (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 both independently hydrogen or C1 to C6 alkyl), sulfobetaine (-RR'N) + (CH2) n SO3 - (n is a natural number from 1 to 10), carboxybenzene base (-RR'N) + (CH2) n COO -(where n is a natural number from 1 to 10) (where R and R' are both independently C1 to C20 alkyl groups), azido (-N3), amido (-C(=NH)NH2), hydrazine (-NHNH2), hydrazone (=N(NH2)), carbamoyl (-C(O)NH2), thiol (-SH), acyl (-C(=O)R, where R represents hydrogen, C1 to C6 alkyl, C1 to C6 alkoxy, or C6 to C12 aryl), carboxyl (-COOH) or its salt (-C(=O)OM, where M represents an organic or inorganic cation), sulfonic acid (-SO3H) or its salt (-SO3M, where M represents an organic or inorganic cation), phosphate (-PO3H2) or its salt (-PO3MH or -PO3M2, where M represents an organic or inorganic cation) and combinations thereof) substitutions.

[0021] In the following text, C1 to C3 alkyl groups may be or include methyl, ethyl, or propyl. C1 to C10 alkylene groups may be or include, for example, C1 to C6 alkylene groups, C1 to C5 alkylene groups, or C1 to C3 alkylene groups, and may be or include, for example, methylene, ethylene, or propylene. C3 to C20 cycloalkylene groups may be or include, for example, C3 to C10 cycloalkylene groups or C5 to C10 cycloalkylene groups, such as cyclohexylene. C6 to C20 arylene groups may be or include, for example, C6 to C10 arylene groups, such as phenylene. C3 to C20 heterocyclic groups may be or include, for example, C3 to C10 heterocyclic groups, such as pyridyl.

[0022] In the following text, “heterogeneous” means including one or more heteroatoms (such as or including at least one of N, O, S, Si and P).

[0023] Additionally, in chemical formulas, the symbol * indicates a portion attached to the same or different atoms, groups, or structural units. Unless otherwise specified in the chemical formulas shown here, it can be assumed that hydrogen is bonded to the structure of the chemical formula.

[0024] In the following text, "alkali metals" refers to elements belonging to Group 1 of the periodic table (such as lithium, sodium, potassium, rubidium, cesium, or francium) and which can exist in either a cation or a neutral state.

[0025] In this specification, when describing a range of values, “X to Y” means “X or greater and Y or less (≥X and ≤Y)”.

[0026] The following describes in detail a separator for a rechargeable battery and a rechargeable battery including the separator according to the present disclosure.

[0027] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical value includes a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within it, such as increments of 0.1%.

[0028] In the following description, only rechargeable lithium batteries are described. However, in addition to rechargeable lithium batteries, this disclosure can also be applied to rechargeable batteries with different metal ions.

[0029] According to one example embodiment, a separator for a rechargeable lithium-ion battery includes 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 and a crosslinking agent, and a filler. The binder includes a (meth)acrylic acid binder comprising a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof, a second structural unit derived from a hydroxyalkyl methacrylate, and a third structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof. The crosslinking agent includes an aziridine crosslinking agent. The filler includes a mixture of a first filler and a second filler, wherein the first filler is an inorganic filler and the second filler is a metal-organic framework (MOF) structure.

[0030] In one example embodiment, the crosslinking product may be or include a thermally crosslinked product.

[0031] According to one example embodiment, the coating layer may be formed by or include a composition for the coating layer, the composition for the coating layer including (meth)acrylic binder, aziridine crosslinking agent and filler.

[0032] The diaphragm can provide low thermal shrinkage, high rate capability during charging and discharging, and low membrane resistance.

[0033] In one example embodiment, the membrane may have a dry heat shrinkage rate of about 5% or less in each of the longitudinal (MD) and transverse (TD) directions, a wet heat shrinkage rate of about 5% or less in each of the MD and TD directions, and a membrane resistance of about 0.5 Ω or less. Here, MD and TD are substantially the same as the MD and TD of the porous substrate, respectively.

[0034] A coating layer comprising only fillers (e.g., a mixture of a first filler and a second filler) cannot provide a diaphragm having the aforementioned dry heat shrinkage and wet heat shrinkage ranges. A diaphragm having a coating layer comprising fillers and a crosslinked product of a (meth)acrylic acid binder and an aziridine crosslinking agent can have the aforementioned dry heat shrinkage and wet heat shrinkage ranges, as well as the membrane resistance range.

[0035] A separator having a coating formed from or comprising a composition for coating may reduce battery reliability due to an increase in one or more of the aforementioned dry heat shrinkage and wet heat shrinkage rates. The composition for coating comprises a (meth)acrylic acid binder but excludes aziridine crosslinking agents as crosslinking agents, or comprises crosslinking agents other than aziridine crosslinking agents. According to an example embodiment, aziridine crosslinking agents may be included in an amount of about 95 wt% or more (e.g., the range from about 98 wt% to about 100 wt% or about 100 wt%) of the total crosslinking agents in the composition for coating.

[0036] A separator having a coating formed from a composition for coating can exhibit high thermal shrinkage, high membrane resistance, and high permeability, which may cause issues with battery capacity, lifespan, and safety. The composition for coating includes an aziridine crosslinking agent but excludes a (meth)acrylic binder, or includes a binder other than a (meth)acrylic binder. According to one example embodiment, the (meth)acrylic binder may be included in an amount of about 95 wt% or more (e.g., in the range of about 98 wt% to about 100 wt% or about 100 wt%) of the total binder in the composition for coating.

[0037] The filler includes a mixture of a first filler and a second filler. A separator formed from or comprising a composition for a coating layer that includes only the first filler may have poor rate performance during battery charging and discharging. A separator formed from or comprising a composition for a coating layer that includes only the second filler may have poor battery reliability due to increased dry heat shrinkage and / or wet heat shrinkage. According to one example embodiment, the mixture of the first filler and the second filler may be included in an amount of about 95 wt% or more (e.g., in the range of about 98 wt% to about 100 wt% or about 100 wt%) of the total filler in the composition for the coating layer.

[0038] Coating layer The adhesive includes a (meth)acrylic adhesive, which comprises a first structural unit derived from (meth)acrylic acid, (meth)acrylate or a salt thereof, a second structural unit derived from (meth)acrylic acid hydroxyalkyl ester or a third structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0039] In one example embodiment, the (meth)acrylic adhesive may be or may include a non-adhesive adhesive.

[0040] According to one example embodiment, the (meth)acrylic acid binder may be or includes a salt binder, such as an alkali metal salt binder. Here, the alkali metal may be or includes at least one of lithium, sodium, potassium, rubidium, and cesium. In this case, it is possible to reduce the membrane resistance of the diaphragm.

[0041] (Meth)acrylic acid binders can fix fillers onto porous substrates, enabling coatings to adhere to both the substrate and electrodes, and contributing to improved membrane heat resistance, permeability, and oxidation resistance. Furthermore, (meth)acrylic acid binders can promote lithium-ion movement, thereby reducing membrane resistance and improving ionic conductivity, increasing the adhesion of the coating to the porous substrate and electrodes, and enhancing filler dispersion within the coating. Additionally, (meth)acrylic acid binders can provide membranes with low membrane resistance, low dry heat shrinkage, and low wet heat shrinkage in coatings including the fillers described below.

[0042] Based on 100 mol% (meth)acrylic acid binder, the sum of the contents of the first structural unit, the second structural unit, and the third structural unit can be about 95 mol% or more, for example, in the range of about 95 mol% to about 100 mol%, for example, about 100 mol%. Within the above range, the above-mentioned membrane effect can be easily achieved.

[0043] The first structural unit is derived from (meth)acrylic acid, (meth)acrylate, or their salts, and can fix the filler to a porous substrate while providing adhesive strength, allowing the coating to adhere to the porous substrate and the electrode, and can help improve the heat resistance and permeability of the diaphragm. Additionally, the first structural unit can improve the dispersibility of the coating composition by having a carboxyl functional group (-C(=O)O-) within the structural unit.

[0044] The first structural unit can be represented by any one of the following chemical formulas 1 to 3: Chemical Formula 1: Chemical Formula 2: Chemical Formula 3: .

[0045] Based on a 100 mol% binder for rechargeable lithium batteries, the first structural unit can be in the form of about 20 mol% to about 75 mol% (e.g., 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%). The amounts included are within the range of 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, from 25 mol% to 70 mol%, from 30 mol% to 65 mol%, from 30 mol% to 60 mol%, or from 40 mol% to 65 mol%. When the first structural unit is included within the above range, the diaphragm can exhibit low membrane resistance, desired or improved adhesion to porous substrates and electrodes, heat resistance, permeability, and oxidation resistance.

[0046] According to an example embodiment, the first structural unit may include structural units represented by chemical formula 2 and structural units represented by chemical formula 3, wherein the structural units represented by chemical formula 2 and structural units represented by chemical formula 3 may be included in a molar ratio in the range of about 10:1 to about 1:2, about 10:1 to about 1:1, or about 5:1 to about 1:1.

[0047] According to another example embodiment, the first structural unit may consist only of structural units represented by chemical formula 2 or chemical formula 3.

[0048] The second structural unit is derived from hydroxyalkyl (meth)acrylate and can fix the filler onto the porous substrate while providing adhesion, allowing the coating to adhere to both the porous substrate and the electrode. Furthermore, the second structural unit can improve the dispersibility of the coating composition by having a carboxyl functional group (-C(=O)O-) within the structural unit.

[0049] The second structural unit can be represented by the following chemical formula 4: Chemical formula 4: .

[0050] Based on 100 mol% of the binder for rechargeable lithium batteries, the second structural unit can be included in an amount ranging from about 1 mol% to about 20 mol% (e.g., 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%, 2 mol% to 15 mol%, 5 mol% to 15 mol%, or 5 mol% to 10 mol%). Within the above range, it is possible to increase the adhesion of the coating to the porous substrate and the electrode.

[0051] The second structural unit may be or include, for example, structural units derived from (meth)acrylate hydroxyalkyl esters. Here, alkyl may be or include C1 to C20 alkyl, C1 to C10 alkyl, or C1 to C6 alkyl.

[0052] Hydroxyalkyl methacrylates may include at least one of, for example, methyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, and 6-hydroxyhexyl methacrylate.

[0053] The third structural unit derived from (meth)acrylamide sulfonic acid or its salt can reduce the membrane resistance of the separator by increasing the possibility of lithium ion migration in the presence of the first and second structural units.

[0054] The third structural unit can enhance the membrane's heat resistance due to the increased glass transition temperature by including a large-volume functional group derived from (meth)acrylamide sulfonic acid or its salt. When the third structural unit includes a functional group derived from a salt of (meth)acrylamide sulfonic acid, the metal (M) can move through the third structural unit by substituting the sulfonic acid functional group containing the metal (M), thereby exhibiting a reduction in membrane resistance.

[0055] The third structural unit can be represented by at least one of the following chemical formulas 5, 6, 7, and combinations thereof.

[0056] Chemical formula 5: Chemical formula 6: Chemical formula 7: .

[0057] The third structural unit may include only one or more of the structural units represented by chemical formula 5, chemical formula 6, and chemical formula 7. For example, the third structural unit may include the structural unit represented by chemical formula 6, and as another example, the third structural unit may include the structural units represented by chemical formula 6 and chemical formula 7.

[0058] The third structural unit may be or includes, for example, a structural unit derived from (meth)acrylamidoalkylsulfonic acid or a salt thereof. Here, the alkane may be or includes C1 to C20 alkanes, C1 to C10 alkanes, or C1 to C6 alkanes, and the alkyl group may be or includes C1 to C20 alkyl groups, C1 to C10 alkyl groups, or C1 to C6 alkyl groups. The salt consists of or includes the aforementioned sulfonic acid and the desired ion. The ion may be, for example, an alkali metal ion, in which case the salt may be or includes an alkali metal salt of a sulfonic acid.

[0059] For example, (meth)acrylamidoalkylsulfonic acid can be 2-(meth)acrylamido-2-methylpropanesulfonic acid.

[0060] The third structural unit can be in the range of about 20 mol% to about 75 mol% (e.g., 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%). The amounts of (meth)acrylic acid binder included in the form of 1 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, 25 mol% to 70 mol%, 20 mol% to 65 mol%, 30 mol% to 65 mol%, or 30 mol% to 60 mol% are 25 mol% to 70 mol%, 20 mol% to 65 mol%, 30 mol% to 65 mol%, or 30 mol% to 60 mol%. When the third structural unit is included within the above range, the (meth)acrylic acid binder and the diaphragm including the (meth)acrylic acid binder can exhibit significantly low membrane resistance.

[0061] The descriptions of chemical formulas 1 to 7 are as follows.

[0062] R 1 To R 14 They can all be or include hydrogen or C1 to C10 alkyl groups independently. For example, R 1 To R 7 and R 9 To R 14 It may consist entirely of or include hydrogen or methyl; and R 8 It can be or include methyl.

[0063] L 1 To L 4 Each of these groups may independently be or include substituted or unsubstituted C1 to C10 alkylene groups, substituted or unsubstituted C3 to C20 cycloalkylene groups, substituted or unsubstituted C6 to C20 arylene groups, or substituted or unsubstituted C3 to C20 divalent heterocyclic groups. For example, L 1 It may include or contain methylene or ethylene; and L 2 To L 4 They can all be or include independently. * -C(CH3)2-CH2- * .

[0064] a, b, c, and d can each be an integer in the range of 0 to 2. For example, a, b, c, and d can all be equal to 1.

[0065] M can be or includes an alkali metal, which can be or includes lithium, sodium, potassium, rubidium, or cesium. For example, M can be lithium or sodium.

[0066] A representative example of a (meth)acrylic adhesive according to an exemplary embodiment is shown in the following chemical formula 8: Chemical formula 8: .

[0067] The description of the above chemical formula 8 is as follows.

[0068] R 15 To R 20 They can all be or include hydrogen or C1 to C10 alkyl groups independently. For example, R 15 To R 17 and R 19 and R 20 It may consist entirely of or include hydrogen or methyl; and R 18 It can be or include methyl.

[0069] L 5 and L 6Each of these groups may independently be or include substituted or unsubstituted C1 to C10 alkylene groups, substituted or unsubstituted C3 to C20 cycloalkylene groups, substituted or unsubstituted C6 to C20 arylene groups, or substituted or unsubstituted C3 to C20 divalent heterocyclic groups. For example, L 5 It may include or contain methylene or ethylene; L 6 It may include or can include * -C(CH3)2-CH2- * .

[0070] M can be or includes an alkali metal, which can be or includes lithium, sodium, potassium, rubidium, or cesium. For example, M can be lithium or sodium.

[0071] Both e and f can be independent integers from 0 to 2. For example, both e and f can be equal to 1.

[0072] l, m, and n can be the molar ratios of the individual units, and l + m + n = 1. For example, 0.20 ≤ l ≤ 0.75, 0.01 ≤ m ≤ 0.2, and 0.2 ≤ n ≤ 0.75; or 0.25 ≤ l ≤ 0.70, 0.01 ≤ m ≤ 0.15, and 0.25 ≤ n ≤ 0.75; or 0.3 ≤ l ≤ 0.65, 0.05 ≤ m ≤ 0.15, and 0.3 ≤ n ≤ 0.65.

[0073] (Meth)acrylic binders may include alkali metals. Alkali metals may exist in the form of cations (e.g., lithium, sodium, potassium, rubidium, or cesium). For example, alkali metals may exist as salts bound to the (meth)acrylic binder. Alkali metals can assist in the synthesis of (meth)acrylic binders in aqueous solvents, improve the adhesion of the coating, and enhance the heat resistance, permeability, and oxidation resistance of the membrane.

[0074] Alkali metals 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 alkali metals and (meth)acrylic binder. For example, (meth)acrylic binder and alkali metals may be included in a weight ratio ranging from about 99:1 to about 60:40, from about 99:1 to about 70:30, from about 99:1 to about 80:20, or from about 90:10 to about 80:20.

[0075] Based on the total content of alkali metal and (meth)acrylic binder, the alkali metal may be included in an amount ranging from about 0.1 mol% to about 1.0 mol%. When the alkali metal is included within the above range, the coating may have desired or improved adhesion, and the diaphragm including the coating may exhibit desired or improved heat resistance, air permeability, and oxidation resistance.

[0076] (Meth)acrylic adhesives can take various forms, such as alternating polymers in which structural units are distributed alternately, random polymers in which structural units are distributed randomly, or grafted polymers in which some of the structural units are grafted.

[0077] The weight-average molecular weight of (meth)acrylic acid adhesives can range from 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, 130,000 g / mol to 200,000 g / mol, or 300,000 g / mol to 900,000 g / mol. When the weight-average molecular weight of the (meth)acrylic acid adhesive meets the above ranges, the (meth)acrylic acid adhesive can exhibit desired or improved adhesive strength and low electrical resistance. The weight-average molecular weight can be or includes the average molecular weight converted from polystyrene using, for example, gel permeation chromatography.

[0078] (Meth)acrylic acid binders can be prepared, for example, by solution polymerization.

[0079] According to one example embodiment, the (meth)acrylic adhesive may be included in the coating layer of the diaphragm in the form of a film.

[0080] Crosslinking agents include aziridine crosslinking agents.

[0081] Aziridine crosslinking agents can crosslink (meth)acrylic acid binders to promote the membrane to achieve the aforementioned range of thermal shrinkage in the electrolyte. Additionally, aziridine crosslinking agents can crosslink (meth)acrylic acid binders to significantly reduce the membrane resistance of the membrane. Furthermore, aziridine crosslinking agents can crosslink (meth)acrylic acid binders to increase adhesion to the electrodes.

[0082] Aziridine crosslinking agents can be or include aziridine crosslinking agents with bifunctional or more functional groups. Here, "bifunctional or more functional groups" means that there are two or more aziridine groups within the molecule. According to an example embodiment, aziridine crosslinking agents can be or include aziridine crosslinking agents with bifunctional or trifunctional groups.

[0083] For example, aziridine crosslinking agents may include at least one 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), tri(1-aziridine)phosphine oxide, N,N-hexamethylene-bis(aziridinecarboxamide), trimethylolpropane tris(2-methyl-1-aziridine propionate), trimethylolpropane tris(β-N-aziridine) propionate, and pentaerythritol tris(3-(1-aziridine) propionate).

[0084] The crosslinking agent (e.g., an aziridine crosslinking agent) may be included in a desired amount relative to the adhesive (e.g., a (meth)acrylic acid adhesive). According to an example embodiment, based on 100 parts by weight of the (meth)acrylic acid adhesive, the crosslinking agent may be included in amounts from about 5 parts by weight to about 50 parts by weight (e.g., 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, etc.). The amounts are included in the range of 28 parts by weight, 29 parts by weight, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 36 parts by weight, 37 parts by weight, 38 parts by weight, 39 parts by weight, 40 parts by weight, 41 parts by weight, 42 parts by weight, 43 parts by weight, 44 parts by weight, 45 parts by weight, 46 parts by weight, 47 parts by weight, 48 parts by weight, 49 parts by weight, 50 parts by weight, 5 to 30 parts by weight, 5 to 25 parts by weight, or 5 to 20 parts by weight. Within the above ranges, the thermal shrinkage rate and membrane resistance of the diaphragm in the electrolyte can be significantly reduced.

[0085] The packing material includes a mixture of a first packing material and a second packing material, wherein the first packing material is an inorganic packing material and the second packing material is an MOF structure.

[0086] The first filler may have an average particle size D50 in the range of about 100 nm to about 200 nm (e.g., 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 nm, 185 nm, 190 nm, 195 nm, 200 nm, 120 nm to 180 nm or 150 nm). Within the above range, when the first filler is combined with the MOF described below, the above-mentioned dry heat shrinkage rate and wet heat shrinkage rate can be achieved.

[0087] The first filler may be or include a ceramic material as an inorganic filler. The inorganic filler may include at least one of metal oxides, quasi-metal oxides, metal fluorides, metal hydroxides, and combinations thereof. The inorganic filler may include at least one of Al₂O₃, SiO₂, TiO₂, SnO₂, CeO₂, MgO, NiO, CaO, GaO, ZnO, ZrO₂, Y₂O₃, SrTiO₃, BaTiO₃, Mg(OH)₂, boehmite, and combinations thereof, but is not limited thereto. For example, the filler may preferably be or include boehmite.

[0088] The first filler can be spherical, plate-shaped, cubic, or without a fixed shape. For example, the first filler can be cubic, and cubic types can have a significantly lower rate of thermal shrinkage as described above.

[0089] The second filler may include a compound in which a metal cation and a linking ligand are coordinated and bonded. For example, the second filler may be or include a microporous crystal consisting of a metal or metal cluster and a linking ligand that links the metal or metal cluster by coordination bonds, or may include a metal or metal cluster and a linking ligand that links the metal or metal cluster by coordination bonds.

[0090] In one example embodiment, the second filler may include a metal ion (such as a zinc ion or a cobalt ion) linked by a coordination bond and an imidazole compound (or a derivative of an imidazole compound) as a linking ligand. The imidazole compound may be or include one or more of imidazole, methylimidazolium containing 2-methylimidazolium, and benzimidazole. The nitrogen atom of the imidazole compound may form a coordination bond with at least one of the metal ions.

[0091] The second filler may include zeolite imidazole ester skeleton (ZIF) compounds, such as ZIF-8.

[0092] The second filler may have an average particle size D50 in the range of about 100 nm to 200 nm (e.g., 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm, 160 nm, 165 nm, 170 nm, 175 nm, 180 nm, 185 nm, 190 nm, 195 nm, 200 nm, 120 nm to 180 nm or 150 nm). Within the above range, when the second filler is combined with the first filler, the above-mentioned dry heat shrinkage rate and wet heat shrinkage rate can be achieved.

[0093] Based on 100 parts by weight of the mixture, the first filler and the second filler can be included in a weight ratio ranging from 50:50 to 95:5. Within this range, it is beneficial to reduce dry heat shrinkage and wet heat shrinkage. For example, the weight ratio can be in the range of 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, 90:10, 95:5, 60:40 to 95:5, or 70:30 to 90:10, and within this range, the rate characteristics can be further improved.

[0094] The filler (i.e., the mixture) and (meth)acrylic binder can be included in a (meth)acrylic binder:mixture mass ratio in the range of 1:10 to 1:40 (e.g., 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:10 to 1:30, or 1:20 to 1:30). Within the above range, it can have the effect of improving heat resistance in the electrolyte.

[0095] The filler (i.e., the mixture) may be included in an amount ranging from about 50 wt% to about 99 wt% of the total amount of the coating (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%, 95 wt% to 99 wt%). When the filler is included within the above range, desired or improved heat resistance, durability, oxidation resistance, and stability may be exhibited.

[0096] Each of the coating layers may have a thickness ranging from about 0.01 μm to about 20 μm, and within the aforementioned range, the thickness may be from 0.01 μm to 7 μm, from 0.1 μm to 5 μm, or from 0.1 μm to 3 μm. For example, the coating layer may have a thickness ranging from about 0.1 μm to about 2 μm.

[0097] The ratio of the coating thickness to the porous substrate thickness can range from about 0.01 to about 0.7 (e.g., 0.01 to 0.5, 0.01 to 0.4, or 0.01 to 0.3). Within this range, the diaphragm can exhibit desired or improved permeability, heat resistance, and adhesive strength. Here, the term "coating thickness" refers to the thickness of a single coating when it is formed only on one side of the porous substrate, and to the total thickness of two coatings when they are formed on both sides of the porous substrate.

[0098] Porous substrate Porous substrates can be or include a matrix having multiple pores and are typically used in electrochemical devices. Porous substrates can be or include polymer membranes formed from or comprising any polymer, such as or including at least one or more copolymers or mixtures of polyolefins (such as polyethylene or polypropylene), polyesters (such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyetheretherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cyclic olefin copolymers, polyphenylene sulfide, glass fibers, and polytetrafluoroethylene (such as Teflon).

[0099] The porous substrate can be or includes, for example, a polyolefin matrix comprising polyolefins, and the polyolefin matrix can have desired or improved shut-off functionality, thereby contributing to improved battery safety. The polyolefin matrix can be or includes at least one of, for example, polyethylene monolayer membranes, polypropylene monolayer membranes, polyethylene / polypropylene bilayer membranes, polypropylene / polyethylene / polypropylene trilayer membranes, and polyethylene / polypropylene / polyethylene trilayer membranes. Furthermore, in addition to olefin resins, polyolefin resins can also include non-olefin resins, or copolymers comprising olefin and non-olefin monomers.

[0100] Porous substrates can have a thickness ranging from about 1 μm to about 40 μm (e.g., 1 μm to 30 μm, 1 μm to 20 μm, or 5 μm to 15 μm).

[0101] Porous substrates can exhibit desired or improved permeability and have permeability values, for example, less than about 200 sec / 100 cc (e.g., about 190 sec / 100 cc or less, or about 180 sec / 100 cc or less). Within the above range, porous substrates can be used in membranes.

[0102] A separator for a rechargeable lithium battery according to an example embodiment can be formed by applying a composition for forming a coating layer to one or both surfaces of a porous substrate and drying the porous substrate. Drying can be performed using, for example, conventional methods known to those skilled in the art.

[0103] Figure 1 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment.

[0104] Reference Figure 1 The separator for a rechargeable lithium battery includes a porous substrate 1 and a coating layer 2 located on each side of the porous substrate 1. The coating layer 2 may include a crosslinking product 3 of a (meth)acrylic acid binder and an aziridine crosslinking agent, a first filler 4, and a second filler 5.

[0105] Rechargeable lithium batteries Another example embodiment includes a rechargeable lithium battery, which includes a separator, a positive electrode, and a negative electrode according to an example embodiment.

[0106] The separator used in rechargeable lithium batteries refers to the above-mentioned components. The separator used in rechargeable lithium batteries can be located between the positive and negative electrodes.

[0107] positive electrode The positive electrode for a rechargeable lithium battery may include a current collector and a layer of positive electrode active material on the current collector. The positive electrode active material layer may include positive electrode active material and may also include a binder and / or conductive material. For example, the positive electrode may also include additives that can constitute a sacrificial positive electrode.

[0108] Positive electrode active material The positive electrode active material may include compounds capable of intercalating and deintercalating lithium (lithiation intercalation compounds). For example, at least one of lithium and a composite oxide of a metal (such as or including at least one of cobalt, manganese, nickel and combinations thereof) may be used.

[0109] The composite oxide can be or includes lithium transition metal composite oxides. Examples of composite oxides 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.

[0110] As an example, the following compounds, represented by any of the following chemical formulas, can be used. Li a A 1- b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni 1-b-c Mnb X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni b Co c L 1 d G e O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8, and 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8, and 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8, and 0.001≤b≤0.1); Li a Mn2G b O4 (0.90≤a≤1.8, and 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90 ≤ a ≤ 1.8, and 0 ≤ g ≤ 0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); and Li a FePO4 (0.90≤a≤1.8).

[0111] 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.

[0112] The positive electrode active material can be, or includes, for example, a high-nickel positive electrode active material, based on 100 mol% of metals other than lithium in a lithium transition metal complex oxide. The high-nickel positive electrode active material has 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%. High-nickel positive electrode active materials can achieve high capacity and can be used in high-capacity, high-density rechargeable lithium batteries.

[0113] Based on a 100 wt% positive electrode active material layer, the amount of positive electrode active material can range from about 90 wt% to about 99.5 wt%. Based on a 100 wt% positive electrode active material layer, the amount of each of the binder and conductive material can each independently range from about 0.5 wt% to about 5 wt%.

[0114] The binder causes the positive electrode active material particles to adhere to each other and to adhere the positive electrode active material to the current collector. As a non-limiting example, examples of binders may include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, nylon, etc.

[0115] Conductive materials can impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause chemical changes in the battery (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used. Examples of conductive materials can include: carbon-based materials, such as at least one of natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials, comprising 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.

[0116] Al can be used as a current collector, but current collectors are not limited to this.

[0117] negative electrode The negative electrode for a rechargeable lithium battery may include a current collector and a layer of negative electrode active material 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 (e.g., an electrically conductive material).

[0118] For example, the negative electrode active material layer may include a negative electrode active material in the range of about 90 wt% to about 99 wt%, a binder in the range of about 0.5 wt% to about 5 wt%, and a conductive material in the range of about 0 wt% to about 5 wt%.

[0119] Negative electrode active material The negative electrode active material may include at least one of a material that can reversibly intercalate / deintercalate lithium ions, lithium metal, a lithium metal alloy, a material that can dope / de-dope lithium, and a transition metal oxide.

[0120] The material that can reversibly intercalate / deintercalate lithium ions may include a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Crystalline carbon may be graphite, such as natural graphite or artificial graphite in an amorphous shape, flaky, lamellar, spherical, or fibrous form. Amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0121] The lithium metal alloy includes an alloy of lithium and a metal (such as or including at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn).

[0122] The material that can dope / de-dope lithium may be or include a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may 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 (except Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and a combination thereof). The Sn-based negative electrode active material may include at least one of Sn, SnO2, a Sn-based alloy, and a combination thereof.

[0123] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite may be in the form of silicon particles and an amorphous carbon coating on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are assembled and an amorphous carbon coating layer (shells) on the surface of the secondary particles. Amorphous carbon may also be between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0124] The silicon-carbon composite may also include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core.

[0125] Si-based or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0126] The binder can adhere the negative electrode active material particles to each other and can also adhere the negative electrode active material to the current collector. The binder can include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0127] Non-aqueous adhesives may 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.

[0128] The waterborne adhesive may be or include at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0129] When an aqueous binder is used as the negative electrode binder, it may further include a cellulose compound capable of imparting viscosity. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts. The alkali metal may include at least one of Na, K, and Li.

[0130] Dry adhesives can be or include polymeric materials capable of being fibrous. For example, dry adhesives can be or include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0131] Conductive materials can impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause chemical changes in the battery (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used. Non-limiting examples may include: carbon-based materials, such as at least one of natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic 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.

[0132] The negative electrode current collector may include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and combinations thereof.

[0133] Rechargeable lithium batteries may also include an electrolyte.

[0134] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0135] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0136] Non-aqueous organic solvents may be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0137] Carbonate solvents may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC).

[0138] Ester solvents may include at least one of the following: methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, caprolactone, etc.

[0139] Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc. Aprotic solvents may include at least one of the following: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0140] Non-aqueous organic solvents can be used alone or in combination of two or more solvents.

[0141] In addition, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed together, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0142] Lithium salts dissolved in organic solvents supply lithium ions in batteries, enabling rechargeable lithium batteries to operate and improving lithium ion transport between the positive and negative electrodes. 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, and LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (SO2) (where x and y are integers in the range of 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), lithium difluoro(oxalate)borate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0143] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch, or coin-shaped batteries.

[0144] Figures 2 to 5 This is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment. Figure 2 A cylindrical battery is shown. Figure 3 A prismatic battery is shown. Figure 4 and Figure 5 A pouch-type battery is shown. (See reference) Figures 2 to 5 The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40 is housed within the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 2 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. Figure 3 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive terminal 12 connected to the positive electrode lead connector 11, a negative electrode lead connector 21, and a negative terminal 22 connected to the negative electrode lead connector 21. For example... Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include Figure 5 The electrode terminal 70 shown, or for example Figure 4 The positive electrode terminal 71 and negative electrode terminal 72 shown in the figure form an electrical path for guiding the current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0145] As a non-limiting example, the rechargeable lithium battery according to the example embodiment can be used in, for example, automobiles, mobile phones and / or various types of electronic devices.

[0146] Examples and comparative examples of this disclosure are described below. However, the following examples are merely examples of this disclosure, and this disclosure is not limited to these examples.

[0147] Preparation Example 1 Distilled water (1249.72 g), 20% lithium hydroxide aqueous solution (203.69 g), acrylic acid (AA, 0.3 mol), 2-hydroxyethyl methacrylate (HEMA, 0.10 mol), 2-acrylamido-2-methylpropanesulfonic acid (AMPS, 0.6 mol), and ammonium persulfate (0.001 mol) were added to a 3L four-necked separable flask equipped with a stirrer, thermometer, and condenser. The internal pressure was then reduced to 10 mmHg using a diaphragm pump and restored to atmospheric pressure using nitrogen three (3) times. The reaction was carried out for 12 hours while heating was controlled to stabilize the temperature of the reaction solution between 65°C and 70°C. After cooling to room temperature, about 10 mL of the reaction solution was taken and the content of nonvolatile (NV) components was measured, which was 9.8 wt% (theoretical value: 10 wt%). In addition, in the obtained poly(lithium acrylate-co-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate lithium salt), the molar ratio of the first structural unit derived from lithium acrylate, the second structural unit derived from 2-hydroxyethyl methacrylate, and the third structural unit derived from 2-acrylamido-2-methylpropanesulfonate lithium salt is 30:10:60.

[0148] Preparation Example 2 In Preparation Example 1, the content of each monomer was varied to prepare poly(lithium acrylate-co-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate lithium salt). The molar ratio of the structural units derived from lithium acrylate, 2-hydroxyethyl methacrylate, and 2-acrylamido-2-methylpropanesulfonate lithium salt was 40:10:50. Approximately 10 mL of the reaction solution (reaction product) was taken, and the content of the non-volatile component was measured to be 9.0 wt% (theoretical value: 10 wt%).

[0149] Preparation Example 3 In Preparation Example 1, the content of each monomer was varied to prepare poly(lithium acrylate-co-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate lithium salt). The molar ratio of the structural units derived from lithium acrylate, 2-hydroxyethyl methacrylate, and 2-acrylamido-2-methylpropanesulfonate lithium salt was 65:5:30. Approximately 10 mL of the reaction solution (reaction product) was taken, and the content of the non-volatile component was measured to be 9.0 wt% (theoretical value: 10 wt%).

[0150] Preparation Example 4 In Preparation Example 1, the content of each monomer was varied to prepare poly(lithium acrylate-co-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate lithium salt). The molar ratio of the structural units derived from lithium acrylate, 2-hydroxyethyl methacrylate, and 2-acrylamido-2-methylpropanesulfonate lithium salt was 40:5:55. Approximately 10 mL of the reaction solution (reaction product) was taken, and the content of the non-volatile component was measured to be 9.0 wt% (theoretical value: 10 wt%).

[0151] Preparation Example 5 The acrylic copolymer was prepared in the same manner as in Preparation Example 1, except that 2-hydroxyethyl methacrylate and 2-acrylamido-2-methylpropanesulfonic acid were used and acrylic acid was not used. The molar ratio of the structural units derived from 2-hydroxyethyl methacrylate and lithium 2-acrylamido-2-methylpropanesulfonic acid, respectively, was 74:26. ​​The content of the non-volatile component in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0152] Preparation Example 6 The acrylic copolymer was prepared in the same manner as in Preparation Example 1, except that acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid were used and 2-hydroxyethyl methacrylate was not used. The molar ratio of the structural units derived from lithium acrylate and lithium 2-acrylamido-2-methylpropanesulfonic acid salt was 74:26. ​​The content of the nonvolatile component in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0153] Preparation Example 7 The acrylic copolymer was prepared in the same manner as in Preparation Example 1, except that acrylic acid and 2-hydroxyethyl methacrylate were used and 2-acrylamido-2-methylpropanesulfonic acid was not used. The molar ratio of the structural units derived from lithium acrylate and 2-hydroxyethyl methacrylate, respectively, was 42:58. The content of the nonvolatile components in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0154] Example 1 Based on a total of 100 parts by weight, boehmite (particle size D50: 150 nm, KB-01S, cubic, DAEJOO·KC Ltd.) as the first filler and ZIF-8 as MOF (particle size D50: 150 nm) as the second filler were mixed at a weight ratio of 90:10 to prepare a mixture.

[0155] The (meth)acrylic binder (10 wt% in distilled water) prepared in Preparation Example 1 and the mixture prepared above were mixed at a (meth)acrylic binder:filler mass ratio of 1:20, added to an aqueous solvent, and then milled at 25°C for 30 minutes using a bead mill and dispersed to prepare a dispersion.

[0156] Trimethylolpropane tris(2-methyl-1-aziridine propionate), a trifunctional aziridine crosslinking agent, was added to the dispersion, and water was added to bring the total solids content to 20 wt% to prepare a composition for forming a coating layer. In this case, the aziridine crosslinking agent was included in an amount of 10 parts by weight based on 100 parts by weight of (meth)acrylic acid binder.

[0157] The composition for forming the coating layer was applied to each side of a polyethylene membrane (thickness: 5.5 μm, CZMZ, air permeability: 110 sec / 100 cc, puncture strength: 340 kgf) with a total thickness of 2.0 μm as a porous substrate using a die-coating method, and then dried and aged in an oven at 70 °C for 16 hours to form the coating layer, thereby preparing a separator for rechargeable lithium batteries.

[0158] Example 2 The diaphragm is prepared in the same manner as in Example 1, except that the weight ratio between the fillers in Example 1 is changed to 70:30.

[0159] Examples 3 to 5 Except for changing the type of binder to replace the binder in Preparation Example 1 as shown in Table 1 below, the membrane is prepared in the same manner as in Example 1.

[0160] Comparison Example 1 The membrane was prepared in the same manner as in Example 1, except that no aziridine crosslinking agent was used in Example 1.

[0161] Comparison Example 2 The diaphragm is prepared in the same manner as in Example 1, except that the first filler is not used in Example 1.

[0162] Comparison Examples 3 to 5 Except for changing the type of binder to replace the binder in Preparation Example 1 as shown in Table 1 below, the membrane is prepared in the same manner as in Example 1.

[0163] Comparison Example 6 Except that ethylene glycol diglycidyl ether (an epoxy crosslinking agent) is used instead of the aziridine crosslinking agent in Example 1, the membrane is prepared in the same manner as in Example 1.

[0164] Compare Example 7 Except that CARBODILITE V-50 (Nisshinbo Chemical) was used as a carbodiimide (CDI) crosslinking agent instead of the aziridine crosslinking agent in Example 1, the membrane was prepared in the same manner as in Example 1.

[0165] Dry heat shrinkage rate (unit: %) Samples were prepared by cutting the separators for rechargeable lithium batteries of the example and comparative examples into 8cm × 8cm dimensions. After drawing a 5cm × 5cm square on the surface of the sample, the sample was placed between paper or alumina powder and allowed to stand in an oven at 150°C for 1 hour. It was then removed, and the dimensions of the drawn squares were measured. The shrinkage rate was calculated in each of the longitudinal (MD) and transverse (TD) directions. The shrinkage rate was calculated according to Formula 1 below.

[0166] Mathematical formula 1: Shrinkage rate (%) = (L0-L1) / L0×100.

[0167] L0 is the initial length of the diaphragm, and L1 is the length of the diaphragm after standing at 150°C for 1 hour.

[0168] Thermal shrinkage rate of electrolyte (wet heat shrinkage rate, unit: %) Manufacturing of the negative electrode: 97 wt% of graphite particles with an average particle size of 25 μm, used as the negative electrode active material, 1.5 wt% of styrene-butadiene rubber (SBR) binder, and 1.5 wt% of carboxymethyl cellulose (CMC) were mixed. The mixture was then added to distilled water and stirred using a mechanical stirrer for 60 minutes to prepare a negative electrode active material slurry. The slurry was applied to a 10 μm thick copper current collector using a doctor blade, dried in a hot air dryer at 100°C for 0.5 hours, and then dried again under vacuum at 120°C for 4 hours. Finally, it was rolled to manufacture the negative electrode.

[0169] Manufacturing of the positive electrode: 97 wt% LiCoO2 as the positive electrode active material, 1.5 wt% carbon black powder as the conductive material, and 1.5 wt% polyvinylidene fluoride (PVdF) were mixed and added to N-methyl-2-pyrrolidone solvent. The mixture was stirred for 30 minutes using a mechanical stirrer to prepare a slurry of the positive electrode active material. The slurry was applied to a 20 μm thick aluminum current collector using a doctor blade, dried in a hot air dryer at 100°C for 0.5 hours, and then dried again at 120°C under vacuum for 4 hours. Finally, it was rolled to manufacture the positive electrode.

[0170] A sample was placed between the positive and negative electrodes to create three sets of positive electrode-sample-negative electrode laminates, which were then placed in a bag. 3g of electrolyte (1.5M LiPF6 dissolved in ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 30:50:20 based on a total volume of 100%)) was injected to completely impregnate the laminate, which was then sealed and allowed to stand at 25°C for 12 hours. After standing in an oven at 150°C for 1 hour, the sample was removed and cooled, and the edge dimensions of the sample were measured to calculate the shrinkage rate. The shrinkage rate can be calculated using Equation 1 above.

[0171] Membrane resistance (unit: Ω) The membrane resistance was evaluated as electrochemical impedance spectroscopy (EIS) resistance. Membranes prepared in the example and comparative examples were impregnated with an electrolyte (1.5 M LiPF6 dissolved in a mixed solvent of ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate (volume ratio 2 / 1 / 7)), mounted onto aluminum foil electrodes with leaded terminals, and sealed in an aluminum cask to fabricate a test cell. The resistance (Ω) of this test cell was measured at 20°C using AC impedance spectroscopy (measurement frequency 100 kHz).

[0172] Ratio characteristics (unit: %) Manufacture a single coin-sized full-cell battery, measure the discharge capacity at 1C, 3C, and 5C, and set the 5C capacity of Example 1 to 100% for relative comparison.

[0173] Table 1:

[0174] (Continued from Table 1)

[0175] According to one example embodiment, a separator for a rechargeable battery can improve battery capacity, safety, and lifespan by providing low thermal shrinkage, high rate capability during charging and discharging, and low membrane resistance.

[0176] While exemplary embodiments of the present disclosure have been described above, the present disclosure is not limited thereto, and various modifications can be made within the scope of the disclosed claims, detailed description and drawings, which also fall within the scope of the present disclosure.

Claims

1. A separator for a rechargeable battery, the separator comprising: Porous substrate; as well as A coating layer is located on at least one surface of the porous substrate; The coating layer includes a crosslinking product of an adhesive and a crosslinking agent, as well as a filler. The adhesive comprises a (meth)acrylic acid adhesive, which includes a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof, a second structural unit derived from (meth)acrylic acid hydroxyalkyl ester, and a third structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof. The crosslinking agent includes aziridine crosslinking agents, and The packing material comprises a mixture of a first packing material and a second packing material, wherein the first packing material is an inorganic packing material and the second packing material is a metal-organic framework structure.

2. The diaphragm according to claim 1, wherein, The (meth)acrylic adhesive includes salt-based adhesives.

3. The diaphragm according to claim 1, wherein, Based on 100 parts by weight of the mixture, the first filler and the second filler are included in a weight ratio in the range of 50:50 to 95:

5.

4. The diaphragm according to claim 1, wherein, The first filler has an average particle size D50 in the range of 100 nm to 200 nm.

5. The diaphragm according to claim 1, wherein, The second filler comprises zinc or cobalt ions linked by coordination bonds with imidazole compounds.

6. The diaphragm according to claim 1, wherein, The second filler has an average particle size D50 in the range of 100 nm to 200 nm.

7. The diaphragm according to claim 1, wherein, The (meth)acrylic adhesive and the mixture are included in a mass ratio ranging from 1:10 to 1:

40.

8. The diaphragm according to claim 1, wherein, The aziridine crosslinking agents include at least one 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), tri(1-aziridine)phosphine oxide, N,N-hexamethylene-bis(aziridinecarboxamide), trimethylolpropane tris(2-methyl-1-aziridine propionate), trimethylolpropane tris(β-N-aziridine) propionate, and pentaerythritol tris(3-(1-aziridine) propionate).

9. The diaphragm according to claim 1, wherein, Based on 100 parts by weight of the (meth)acrylic adhesive, the crosslinking agent is included in an amount ranging from 5 parts by weight to 50 parts by weight.

10. The diaphragm according to claim 1, wherein, The first structural unit is represented by at least one of chemical formula 1, chemical formula 2, chemical formula 3, and combinations thereof: Chemical Formula 1: Chemical Formula 2: Chemical Formula 3: ， ， ， The second structural unit is represented by chemical formula 4: Chemical formula 4: ,and The third structural unit is represented by at least one of chemical formulas 5, 6, 7, and combinations thereof: Chemical formula 5: Chemical formula 6: Chemical formula 7: ， ， ， Among them, R 1 To R 14 Each independently includes hydrogen or C1 to C10 alkyl groups. L 1 To L 4 Each independently comprises 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 divalent heterocyclic group. a, b, c, and d are all independent integers in the range of 0 to 2, and M includes alkali metals.

11. The diaphragm according to claim 1, wherein, The (meth)acrylic adhesive is represented by chemical formula 8: Chemical formula 8: ， Among them, R 15 To R 20 Each independently includes hydrogen or C1 to C10 alkyl groups. L 5 and L 6 Each independently comprises 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 divalent heterocyclic group. M includes alkali metals. Both e and f are independent integers in the range of 0 to 2, and l, m, and n are the molar ratios of each unit, and l + m + n = 1.

12. The diaphragm according to claim 1, wherein: Based on 100 mol% of the (meth)acrylic acid binder, The first structural unit is included in an amount ranging from 20 mol% to 75 mol%. The second structural unit is included in an amount ranging from 1 mol% to 20 mol%; and The third structural unit is included in an amount ranging from 20 mol% to 75 mol%.

13. The diaphragm according to claim 1, wherein, Based on 100 mol% of the (meth)acrylic adhesive, the sum of the contents of the first structural unit, the second structural unit, and the third structural unit is 95 mol% or greater.

14. The diaphragm according to claim 2, wherein, The aziridine crosslinking agent is included in an amount of 95 wt% or greater of the total crosslinking agent in the composition used for the coating layer.

15. The diaphragm according to claim 1, wherein, The coating layer has a thickness in the range of 0.1 μm to 2 μm.

16. A rechargeable battery, said rechargeable battery comprising: Positive electrode; negative electrode; as well as The diaphragm according to any one of claims 1 to 15 is located between the positive electrode and the negative electrode.

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