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. The separator includes a porous substrate, a first coating layer on a first surface of the porous substrate, and a second coating layer on a second surface of the porous substrate. The first coating layer and the second coating layer include a crosslinking product of a binder and a crosslinking agent, a filler, and an adhesive binder. Binders in the first coating layer and the second coating layer comprise (methyl) acrylic acid binders; the (meth) acrylic binder includes 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 a (meth) acrylamidosulfonic acid or a salt thereof. 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 fibrous filler.

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0163680, 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-ion batteries can 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 immersed in an electrolyte. Summary of the Invention

[0006] One example includes a separator for rechargeable batteries that provides low thermal shrinkage, low membrane resistance, high adhesion to electrode plates, low surface roughness, and high ionic conductivity.

[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. The separator for the rechargeable battery includes a porous substrate, a first coating layer on a first surface of the porous substrate, and a second coating layer on a second surface of the porous substrate. The first coating layer includes a crosslinking product of an adhesive and a crosslinking agent, a filler, and an adhesive binder. The second coating layer includes a crosslinking product of an adhesive and a crosslinking agent, a filler, and an adhesive binder. Both the adhesive in the first and second coating layers include 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 a hydroxyalkyl ester of (meth)acrylic acid, and a third structural unit derived from (meth)acrylamidosulfonic 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 fibrous filler. The adhesive binder in the first coating layer is a (meth)acrylic acid adhesive binder, and the adhesive binder in the second coating layer is a fluorinated adhesive binder having a carbonyl group (C=O).

[0009] Another example embodiment includes a rechargeable battery. The rechargeable battery includes a positive electrode, a negative electrode, and the aforementioned separator for the rechargeable battery located between the positive and negative electrodes. Attached Figure Description

[0010] 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

[0011] Hereinafter, exemplary embodiments of the present disclosure are described in detail. However, these embodiments are provided by way of example, and the present disclosure is not limited thereto, and is limited only by the scope of the claims.

[0012] Unless otherwise stated herein, when a component such as a layer, film, region, plate, etc., is described as being “on” another component, it includes not only the case where the component is “directly on” the other component, but also the case where there is another component between them.

[0013] Unless otherwise stated in this specification, anything expressed in the singular may also include the plural. Furthermore, unless otherwise stated, “A or B” may mean “including A, including B, or including both A and B”.

[0014] As used herein, the term "combination of them" may mean a mixture of components, a laminate, a complex, a copolymer, an alloy, a blend, and a reaction product.

[0015] Here, the term "particle size D50" refers to the average particle size, which means the size of particles that constitute 50% of the cumulative volume in the particle size distribution. The particle size distribution can be measured by methods known to those skilled in the art. For example, the particle size distribution can be measured using a particle size analyzer, transmission electron microscopy, or scanning electron microscopy. In another method, the D50 value can be obtained by measuring the 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 from it. Alternatively, D50 can be measured using laser diffraction. For example, when measured by laser diffraction, after the particles to be measured are dispersed in a dispersion medium, the particles can be introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT3000) and irradiated with ultrasound at approximately 28 kHz at a 60 W output, and the D50 can be calculated based on the 50% particle size distribution in the measuring device.

[0016] When the particles are spherical, particle size can refer to the diameter of the particles.

[0017] In this specification, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0018] Unless otherwise defined herein, “substitution” means that hydrogen in a compound is replaced by a substituent, which is, or includes, 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') (wherein 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), azide (-N3), amidine (-C(=NH)NH2), hydrazine (-NHNH2), hydrazone (=N(NH2)), carbamoyl (-C(O)NH2), thiol (-SH), acyl (-C(=O)R, where R is hydrogen, C1 to C6 alkyl, C1 to C6 alkoxy or C6 to C12 aryl), carboxyl (-COOH) or a salt thereof (-C(=O)OM, where M is an organic or inorganic cation), sulfonic acid (-SO3H) or a salt thereof (-SO3M, where M is an organic or inorganic cation), phosphate (-PO3H2) or a salt thereof (-PO3MH or -PO3M2, where M is an organic or inorganic cation) and at least one combination thereof.

[0019] In the following text, C1 to C3 alkyl means methyl, ethyl, or propyl. C1 to C10 alkylene may be or include at least one of, for example, C1 to C6 alkylene, C1 to C5 alkylene, and C1 to C3 alkylene (such as methylene, ethylene, or propylene). C3 to C20 cycloalkylene may be or include, for example, C3 to C10 cycloalkylene or C5 to C10 cycloalkylene (such as cyclohexylene). C6 to C20 arylene may be or include, for example, C6 to C10 arylene (such as phenylene). C3 to C20 heterocyclic group may be or include, for example, C3 to C10 heterocyclic group (such as pyridyl).

[0020] 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).

[0021] In chemical formulas, the asterisk (*) indicates a portion attached to the same or different atoms, groups, or structural units. Unless otherwise specified in the chemical formulas described herein, it can be assumed that hydrogen is bonded to the structure of the chemical formula.

[0022] 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.

[0023] When describing numerical ranges in this specification, “X to Y” means “X or greater and Y or less (X ≤ and ≤ Y)”.

[0024] 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%.

[0025] The following describes in detail the separator for a rechargeable battery and the rechargeable battery including the separator.

[0026] 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.

[0027] According to one example embodiment, a separator for a rechargeable lithium-ion battery includes a porous substrate, a first coating layer on a first surface of the porous substrate, and a second coating layer on a second surface of the porous substrate. The first coating layer includes a crosslinking product of an adhesive and a crosslinking agent, a filler, and an adhesive binder. The second coating layer includes a crosslinking product of an adhesive and a crosslinking agent, a filler, and an adhesive binder. Both the adhesive in the first and second coating layers include 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 a hydroxyalkyl ester of (meth)acrylic acid, and a third structural unit derived from (meth)acrylamidosulfonic 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 fibrous filler. The adhesive binder in the first coating layer is a (meth)acrylic acid adhesive binder, and the adhesive binder in the second coating layer is a fluorinated adhesive binder having a carbonyl group (C=O).

[0028] According to one example embodiment, the first coating layer may be positioned close to the negative electrode of the battery, and the second coating layer may be positioned close to the positive electrode of the battery.

[0029] According to one example embodiment, the inorganic filler may be a non-fibrous filler instead of a fibrous filler.

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

[0031] According to one example embodiment, the first coating layer may be formed of a composition comprising a (meth)acrylic adhesive, an aziridine crosslinking agent, a filler, and a (meth)acrylic adhesive, or a composition comprising a (meth)acrylic adhesive, an aziridine crosslinking agent, a filler, and a (meth)acrylic adhesive. According to one example embodiment, the second coating layer may be formed of a composition comprising a (meth)acrylic adhesive, an aziridine crosslinking agent, a filler, and a carbonyl-based fluorinated adhesive, or a composition comprising a (meth)acrylic adhesive, an aziridine crosslinking agent, a filler, and a carbonyl-based fluorinated adhesive.

[0032] The diaphragm can provide low thermal shrinkage, low membrane resistance, low surface roughness, high ionic conductivity and high adhesion to the electrode plate.

[0033] In one example embodiment, the membrane may have a dry heat shrinkage rate of about 12% or less in the longitudinal direction (MD) and about 5% or less in the transverse direction (TD), and a membrane resistance of about 0.65 Ω or less. Here, MD and TD are substantially the same orientation as the MD and TD of the porous substrate, respectively.

[0034] In one example embodiment, the diaphragm may have an adhesion of 1.1 gf / mm or greater to the positive electrode and an adhesion of about 0.85 gf / mm or greater to the negative electrode.

[0035] In one example embodiment, the membrane may have an ionic conductivity of about 0.6 mS / cm or greater.

[0036] In one example embodiment, the diaphragm may have a surface roughness of about 0.5 μm or less. Within the aforementioned range, the diaphragm can be advantageous in achieving high adhesion and high ionic conductivity to the electrode plates.

[0037] When a first coating layer comprising a mixture of fillers (i.e., a first filler and a second filler) is used, the diaphragm is advantageous in achieving ionic conductivity.

[0038] A diaphragm having a first coating layer and a second coating layer comprising fillers, (meth)acrylic acid binders, and aziridine crosslinking agents can provide the aforementioned range of ionic conductivity and the aforementioned range of membrane resistance.

[0039] A membrane having a coating layer formed from a composition for the coating layer may struggle to achieve the aforementioned ionic conductivity. This composition includes a (meth)acrylic binder but excludes aziridine crosslinking agents as crosslinking agents, or includes crosslinking agents other than aziridine crosslinking agents. According to one example embodiment, aziridine crosslinking agents 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 100 wt%) of the total crosslinking agents in the composition for the coating layer.

[0040] A membrane having a coating layer formed from a composition for the coating layer may present challenges of increased membrane resistance and reduced ionic conductivity. This composition for the coating layer may include an aziridine crosslinking agent but not a (meth)acrylic binder, or may include 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 100 wt%) of the total binder in the composition for the coating layer.

[0041] The filler includes a mixture of a first filler and a second filler. Membranes formed from or comprising compositions for coating layers that include only the first filler may present challenges in reducing heat resistance. Membranes formed from or comprising compositions for coating layers that include only the second filler may struggle to achieve the aforementioned ionic conductivity. According to one example embodiment, the mixture of the first and second fillers 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 100 wt%) of the total filler in the composition for coating layers.

[0042] First 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.

[0043] According to one example embodiment, the (meth)acrylic adhesive may be or include a non-adhesive adhesive.

[0044] 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.

[0045] The (meth)acrylic binder can fix the filler onto the porous substrate, enabling the first coating layer to adhere to both the porous substrate and the electrode, and contributing to improved heat resistance, permeability, and oxidation resistance of the membrane. Furthermore, the (meth)acrylic binder can promote lithium-ion movement, thereby reducing membrane resistance and improving ionic conductivity, increasing the adhesion of the first coating layer to the porous substrate and electrode, and increasing the dispersion of the filler within the coating layer. Additionally, the (meth)acrylic binder in the first coating layer, including the filler described below, can provide a membrane with low membrane resistance and low dry heat shrinkage.

[0046] Based on 100 mol% (meth)acrylic acid binder, the sum of the contents of the first, second, and third structural units can be about 95 mol% or greater (e.g., about 95 mol% to about 100 mol%, for example, 100 mol%). Within the above range, the above-mentioned membrane effect can be easily achieved.

[0047] The first structural unit is derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof, and can fix the filler on a porous substrate while providing adhesion, 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 composition used for the coating by having a carboxyl functional group (-C(=O)O-) within the structural unit.

[0048] 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: ; ; .

[0049] Based on a 100 mol% (meth)acrylic acid binder, 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 9 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%, 25 mol% to 70 mol%, 30 mol% to 65 mol%, 30 mol% to 60 mol%, or 40 mol% to 65 mol%. When the first structural unit is included within the above range, the diaphragm can exhibit low membrane resistance and desired or improved adhesion to porous substrates and electrodes, heat resistance, permeability, and oxidation resistance.

[0050] 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, 10:1 to 1:1 or 5:1 to 1:1.

[0051] According to another example embodiment, the first structural unit may consist only of structural units represented by chemical formula 2 or chemical formula 3.

[0052] The second structural unit is derived from hydroxyalkyl (meth)acrylate and can immobilize 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 composition used for the coating by having a carboxyl functional group (-C(=O)O-) within the structural unit.

[0053] The second structural unit can be represented by the following chemical formula 4: Chemical formula 4: .

[0054] Based on 100 mol% (meth)acrylic acid binder, 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 layer to the porous substrate and the electrode.

[0055] 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.

[0056] 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.

[0057] The third structural unit derived from (meth)acrylamide sulfonic acid or its salt can reduce the membrane resistance of the separator by increasing the likelihood of lithium ion movement in the presence of the first and second structural units.

[0058] The third structural unit can enhance the heat resistance of the membrane by including a bulky functional group derived from (meth)acrylamide sulfonate or its salt, thereby increasing the glass transition temperature. When the third structural unit includes a functional group derived from (meth)acrylamide sulfonate, the metal (M) can move through the third structural unit by substituting the sulfonic acid functional group containing the metal (M), thereby exhibiting the effect of reducing membrane resistance.

[0059] The third structural unit can be represented by chemical formula 5, chemical formula 6, chemical formula 7, or a combination thereof: Chemical formula 5: Chemical formula 6: Chemical formula 7: ; ; .

[0060] The third structural unit may include only one, two, 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. As another example, the third structural unit may include the structural units represented by chemical formula 6 and chemical formula 7.

[0061] 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. A salt is defined as a salt consisting of or including the aforementioned sulfonic acid and a 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.

[0062] For example, (meth)acrylamidoalkylsulfonic acid can be 2-(meth)acrylamido-2-methylpropanesulfonic acid.

[0063] In (meth)acrylic acid binders, the third structural unit may be present in an amount from 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%). The amounts included are within the range of 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%, 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 membrane including the (meth)acrylic acid binder can exhibit significantly low membrane resistance.

[0064] The descriptions of chemical formulas 1 to 7 are as follows.

[0065] 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; R 8 It can be or include methyl.

[0066] 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-* .

[0067] 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.

[0068] 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.

[0069] A representative example of a (meth)acrylic adhesive according to an exemplary embodiment is shown in the following chemical formula 8: Chemical formula 8: .

[0070] The description of the above chemical formula 8 is as follows.

[0071] 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 R 19 and R 20 It may consist entirely of or include hydrogen or methyl; R 18 It can be or include methyl.

[0072] L 5 and L 6 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 5 It may include or contain methylene or ethylene, L 6 It may include or can include * -C(CH3)2-CH2- * .

[0073] 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.

[0074] l, m, and n can be the molar ratio of each unit, 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.

[0075] Both e and f can be independent integers in the range of 0 to 2. For example, e and f can both be equal to 1.

[0076] (Meth)acrylic binders may include alkali metals. Alkali metals can exist in cationic form, such as lithium, sodium, potassium, rubidium, or cesium. For example, alkali metals can exist as salts bound to (meth)acrylic binders. Alkali metals can assist in the synthesis of (meth)acrylic binders in aqueous solvents, improve the adhesion of the coating, and improve the heat resistance, permeability, and oxidation resistance of the membrane.

[0077] Based on the total content of alkali metal and (meth)acrylic binder, alkali metal may be included in an amount ranging from about 1 wt% to about 40 wt% (e.g., 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 10 wt% to 20 wt%). For example, (meth)acrylic binder and alkali metal may be included in a weight ratio ranging from about 99:1 to about 60:40, or a weight ratio of 99:1 to 70:30 (e.g., 99:1 to 80:20, or 90:10 to 80:20).

[0078] 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.

[0079] (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.

[0080] 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 adhesion and low resistance. The weight-average molecular weight can be the average molecular weight converted from polystyrene measured using gel permeation chromatography.

[0081] (Meth)acrylic acid binders can be prepared by solution polymerization.

[0082] 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.

[0083] Crosslinking agents include aziridine crosslinking agents.

[0084] Aziridine crosslinking agents can crosslink (meth)acrylic acid binders to promote the membrane to achieve the aforementioned thermal shrinkage rate range in the electrolyte. Additionally, aziridine crosslinking agents can crosslink (meth)acrylic acid binders to significantly reduce the membrane resistance. Furthermore, aziridine crosslinking agents can crosslink (meth)acrylic acid binders to increase adhesion to the electrodes.

[0085] 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.

[0086] 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).

[0087] Crosslinking agents (e.g., aziridine crosslinking agents) may be included in a desired amount relative to the adhesive (e.g., (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.

[0088] 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 a fiber packing material.

[0089] According to one example embodiment, the inorganic filler may be a non-fibrous filler instead of a fibrous filler.

[0090] The first filler can be spherical, plate-shaped, cubic, or amorphous. Preferably, the first filler can be cubic, in which case the aforementioned heat shrinkage rate can be significantly reduced.

[0091] 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 second filler described below, the above-mentioned dry heat shrinkage rate and wet heat shrinkage rate can be achieved.

[0092] The first filler may be or include ceramic materials as inorganic fillers. Inorganic fillers may include at least one of metal oxides, quasi-metal oxides, metal fluorides, metal hydroxides, and combinations thereof. Inorganic fillers 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 are not limited thereto. For example, the filler may be boehmite.

[0093] The second filler can be spherical, plate-shaped, cubic, or amorphous. For example, the second filler can be cubic, in which case the aforementioned heat shrinkage rate can be significantly reduced.

[0094] The second filler is a fiber filler. The fiber filler is in the form of fibers and fills the spaces between the first fillers, thereby improving the rate performance during charging and discharging.

[0095] In one example embodiment, the fiber filler may have an aspect ratio of about 5 or greater (e.g., in the range of about 5 to about 500). Here, aspect ratio refers to the ratio of the length to the diameter of the fiber filler. The diameter of the fiber filler can range from about 10 nm to about 200 nm (e.g., 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 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, 10 nm to 100 nm), and the length can be 100 nm or greater (e.g., 100 nm to 1000 nm). Within the above range, the aspect ratio can be easily achieved.

[0096] The fiber filler may include at least one of boehmite, carbon nanotubes, silver nanowires, boron carbide nanowires, cellulose nanofibers, copper hydroxide nanowires, silica nanowires, hydroxyapatite nanowires, Al2O3, TiO2, SiO2, and combinations thereof. For example, boehmite may be used.

[0097] 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 about 50:50 to about 95:5. Weight ratios within this range can advantageously 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, 50:50 to 90:10, or in the range of 80:20 to 90:10, and within this range, membrane resistance and ionic conductivity can be further improved.

[0098] 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 about 1:10 to about 1:50 (e.g., 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, in the range of 1:10 to 1:40 or in the range of 1:20 to 1:30). Within the above range, it can have the effect of improving the heat resistance within the electrolyte.

[0099] 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.

[0100] The adhesive is a (meth)acrylic adhesive. (Meth)acrylic adhesives can increase adhesion to the negative electrode. The adhesive can be granular and cross-linked.

[0101] (Meth)acrylate adhesives may include (meth)acrylate polymers or copolymers. According to one example embodiment, the adhesive may be or include crosslinked (meth)acrylate polymers or copolymers. For example, the adhesive may include crosslinked polymethyl methacrylate (PMMA) polymers.

[0102] To prepare the crosslinked (meth)acrylic acid polymer, a crosslinking agent may be further added during the polymerization step. The (meth)acrylic acid adhesive may have a glass transition temperature in the range of about 50°C to about 110°C (e.g., 50°C to 70°C). Within this range, not only is electrode adhesion desirable or improved, but also ionic conductivity is desired. The glass transition temperature can be measured by differential scanning calorimetry (DSC), but is not limited to this method. The glass transition temperature is measured by placing 2 mg of the polymer in a pressure-resistant pan for DSC measurement and then heating the polymer to a temperature range of 25°C to 200°C at a heating rate of 10°C / min. The above experiments were performed in a controlled environment.

[0103] Based on 100 parts by weight of (meth)acrylic acid adhesive, the (meth)acrylic acid adhesive can be used in quantities from about 1 part by weight to about 100 parts by weight (e.g., 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 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). Servings, 23 servings, 24 servings, 25 servings, 26 servings, 27 servings, 28 servings, 29 servings, 30 servings, 31 servings, 32 servings, 33 servings, 34 servings, 35 servings, 36 servings, 37 servings, 38 servings, 39 servings, 40 servings, 41 servings, 42 servings, 43 servings, 44 servings, 45 servings, 46 servings, 47 servings, 48 ​​servings, 49 servings, 50 servings, 51 servings 52 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight. The quantities included are within the range of 81 parts by weight, 82 parts by weight, 83 parts by weight, 84 parts by weight, 85 parts by weight, 86 parts by weight, 87 parts by weight, 88 parts by weight, 89 parts by weight, 90 parts by weight, 91 parts by weight, 92 parts by weight, 93 parts by weight, 94 parts by weight, 95 parts by weight, 96 parts by weight, 97 parts by weight, 98 parts by weight, 99 parts by weight, 100 parts by weight, 1 to 50 parts by weight, 1 to 30 parts by weight, 5 to 30 parts by weight, or 5 to 20 parts by weight.

[0104] The first coating layer may have a thickness in the range of about 0.01 μm to about 20 μm, within which the thickness may be 0.01 μm to 7 μm, 0.1 μm to 5 μm, or 0.1 μm to 3 μm. For example, the first coating layer may have a thickness of 0.1 μm to 2 μm.

[0105] The ratio of the thickness of the first coating layer to the thickness of the porous substrate can be in the range of 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 the above range, the diaphragm can exhibit desired or improved permeability, heat resistance, and adhesion.

[0106] Second coating layer The second coating layer may be formed from a composition comprising (meth)acrylic adhesive, aziridine crosslinking agent, filler and adhesive.

[0107] The detailed composition of each of the (meth)acrylic binder, aziridine crosslinking agent, and filler is substantially the same as that described in the first coating layer. Therefore, their detailed description is omitted here.

[0108] Adhesive binders are or include fluorinated adhesive binders having a carbonyl group (C=O). Fluorinated adhesive binders can be advantageous in providing high adhesion to the positive electrode.

[0109] Fluorinated adhesive binders are particulate organic binders and may include at least one fluorinated adhesive binder having a carbonyl group (C=O) and a hydroxyl group (OH), such as polyvinylidene fluoride (PVDF) adhesive binders having both carbonyl and hydroxyl groups. Fluorinated adhesive binders having carbonyl and hydroxyl groups can be advantageous in increasing adhesion to the positive electrode.

[0110] Polyvinylidene fluoride (PVDF) adhesives may include structural units derived from PVDF and structural units derived from monomers having at least one carbonyl and one hydroxyl group. Structural units derived from monomers having at least one carbonyl and one hydroxyl group can provide improved adhesion, durability, and breathability. Monomers having at least one carbonyl and one hydroxyl group may be or include at least one of (meth)acrylic acid, itaconic acid or derivatives thereof, maleic acid or derivatives thereof, and hydroxyalkyl allyl ethers.

[0111] Polyvinylidene fluoride (PVDF) adhesives may also include structural units derived from monomers that are copolymerizable with PVDF. The copolymerizable monomers may be, or include, at least one of trichloroethylene, chlorotrifluoroethylene, trifluoroethylene, hexafluoropropylene, tetrafluoroethylene, and ethylene monomers.

[0112] According to one example embodiment, a polyvinylidene fluoride-based adhesive is or includes a copolymer of vinylidene fluoride, a monomer having carbonyl and hydroxyl groups, and hexafluoropropylene, and may include structural units derived from vinylidene fluoride, structural units derived from monomers having carbonyl and hydroxyl groups, and structural units derived from hexafluoropropylene.

[0113] According to one example embodiment, polyvinylidene fluoride-based adhesives may be or include water-based particulate adhesives.

[0114] According to one example embodiment, a polyvinylidene fluoride-based adhesive may include about 65 mol% to about 99 mol% (e.g., 80 mol% to 99 mol% or 65 mol% to 85 mol%) of polyvinylidene fluoride repeating units, about 10 mol% to about 25 mol% of hexafluoropropylene repeating units, and about 0.5 mol% to about 10 mol% of repeating units derived from monomers having carbonyl and hydroxyl groups.

[0115] According to one example embodiment, based on a total of 100 moles of vinylidene fluoride and hexafluoropropylene, a polyvinylidene fluoride-based adhesive comprises about 75 mol% to about 90 mol% of repeating units derived from vinylidene fluoride and about 10 mol% to about 25 mol% of repeating units derived from hexafluoropropylene, and may also include repeating units derived from monomers having carbonyl and hydroxyl groups. Polyvinylidene fluoride-based adhesives can take various forms, such as alternating polymers in which structural units are alternately distributed, random polymers in which repeating units are randomly distributed, or grafted polymers in which some of the repeating units are grafted. Additionally, polyvinylidene fluoride-based adhesives can be linear polymers, branched polymers, or mixtures thereof.

[0116] The crystallinity of fluorinated adhesives can range from about 35% to about 65% (e.g., 40% to 60% or 40% to 55%). In this range, the adhesive can exhibit desired or improved adhesion. The crystallinity described above can be measured using DSC as follows: 2 mg of the fluorinated adhesive is added to a pressure-resistant pan used for DSC measurement, and then heated to a temperature range of 25°C to 200°C at a heating rate of 10°C / min. The above experiment is performed in a controlled environment.

[0117] Fluorine-based adhesives can have melting points of about 150°C or higher, for example, in the range of about 150°C to about 200°C. In this case, the adhesive can exhibit desired or improved adhesion.

[0118] Fluorinated adhesives can have a weight-average molecular weight in the range of about 100,000 g / mol to about 1,500,000 g / mol (e.g., 200,000 g / mol to 800,000 g / mol). The weight-average molecular weight can be obtained, for example, by gel permeation chromatography as a polystyrene equivalent.

[0119] Fluorine-based adhesives can have a swelling ratio of approximately 70% or greater. Within this range, they can reduce or prevent deformation of the electrode assembly. The swelling ratio is the percentage increase in volume obtained by measuring the volume of the adhesive before immersion in the electrolyte and comparing it to the volume after immersion. For example, a swelling ratio of 100% means that the adhesive has expanded to twice its volume before immersion in the electrolyte.

[0120] Fluorine-based adhesive binders can be prepared by various known methods, such as emulsion polymerization, suspension polymerization, bulk polymerization, or solution polymerization, and for example, by emulsion polymerization.

[0121] Based on 100 parts by weight of (meth)acrylic acid adhesive, fluorinated adhesives can be used in quantities from about 1 part by weight to about 100 parts by weight (e.g., 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 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, 2...). 3 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 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, 51 parts by weight, 5 2 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, 8 The quantities included are within the range of 1 part by weight, 82 parts by weight, 83 parts by weight, 84 parts by weight, 85 parts by weight, 86 parts by weight, 87 parts by weight, 88 parts by weight, 89 parts by weight, 90 parts by weight, 91 parts by weight, 92 parts by weight, 93 parts by weight, 94 parts by weight, 95 parts by weight, 96 parts by weight, 97 parts by weight, 98 parts by weight, 99 parts by weight, 100 parts by weight, 1 to 50 parts by weight, 1 to 30 parts by weight, 5 to 30 parts by weight, or 5 to 20 parts by weight.

[0122] Porous substrate Porous substrates have a large number of pores and may be or include substrates commonly used in electrochemical devices. Porous substrates may be, but are not limited to, polymer membranes formed of or comprising a polymer, such as or including at least one of polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, glass fiber, and polytetrafluoroethylene (such as Teflon) or copolymers or mixtures of two or more of these.

[0123] The porous substrate can be or includes, for example, a polyolefin substrate comprising polyolefins, and the polyolefin substrate can have desired or improved shut-off functionality, and thus can contribute to improved battery safety. The polyolefin substrate 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. In addition to olefin resins, polyolefin resins can also include non-olefin resins, or can include copolymers of olefin and non-olefin monomers.

[0124] 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).

[0125] Porous substrates can have a permeability value of less than about 200 seconds / 100cc (e.g., about 190 seconds / 100cc or less, or about 180 seconds / 100cc or less). Within the above range, porous substrates can be used in diaphragms.

[0126] 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 sides of a porous substrate and then drying the composition. Drying can be performed using conventional methods known to those skilled in the art.

[0127] Figure 1 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment.

[0128] Reference Figure 1 The separator for a rechargeable lithium battery includes a porous substrate 1, a first coating layer 2a located on a first surface of the porous substrate 1, and a second coating layer 2b located on a second surface of the porous substrate 1. The first coating layer 2a may include a crosslinking product 3 of a (meth)acrylic acid binder and an aziridine crosslinking agent, a first filler 4, a second filler 5, and a first adhesive binder 6. The second coating layer 2b may include a crosslinking product 3 of a (meth)acrylic acid binder and an aziridine crosslinking agent, a first filler 4, a second filler 5, and a second adhesive binder 7.

[0129] Rechargeable lithium batteries According to one example embodiment, a rechargeable lithium battery includes a separator, a positive electrode, and a negative electrode for the rechargeable lithium battery.

[0130] The separator used in rechargeable lithium batteries refers to the one described above. The separator used in rechargeable lithium batteries can be located between the positive and negative electrodes.

[0131] 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.

[0132] Positive electrode active material The positive electrode active material may include compounds capable of inserting and deintercalating lithium (lithium-intercalating compounds). 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) may be used.

[0133] 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.

[0134] As an example, the following compounds, represented by any of the following chemical formulas, can be used. Li a A 1- b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni b Co c L 1 d G eO2 (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).

[0135] 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.

[0136] 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.

[0137] 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%.

[0138] 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 including 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.

[0139] Conductive materials can impart electrical conductivity (e.g., electronic 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.

[0140] Al can be used as a current collector, but current collectors are not limited to this.

[0141] 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 electronically conductive material).

[0142] For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder, and about 0 wt% to about 5 wt% of conductive material.

[0143] Negative electrode active material The negative electrode active material may include at least one of the following: materials capable of reversibly inserting / deintercalating lithium ions, lithium metal, lithium metal alloys, materials capable of doping / dedoping lithium, and transition metal oxides.

[0144] Materials that can reversibly intercalate / deintercalate lithium ions may include carbonaceous negative electrode active materials, such as at least one of crystalline carbon, amorphous carbon, and combinations thereof. The crystalline carbon may be graphite, such as natural graphite or artificial graphite that is amorphous, flaky, lamellar, spherical, or fibrous. The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0145] 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).

[0146] Materials capable of doping / de-doping lithium may be or include Si-based negative electrode active materials or Sn-based negative electrode active materials. The Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (0 < x ≤ 2), at least one of Si-Q alloys (where Q is or includes at least one of alkali metals, alkaline earth metals, group 13 elements, group 14 elements (except Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof). The Sn-based negative electrode active materials may include at least one of Sn, SnO2, Sn-based alloys, and combinations thereof.

[0147] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are assembled and an amorphous carbon coating layer (shell) on the surface of the secondary particles. The amorphous carbon may also be between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0148] 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.

[0149] The Si-based negative electrode active materials or the Sn-based negative electrode active materials may be used in combination with the carbonaceous negative electrode active materials.

[0150] The binder can attach the negative electrode active material particles to each other and can attach the negative electrode active material to the current collector. The binder may include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] Conductive materials can impart electrical conductivity (e.g., electronic 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.

[0156] 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.

[0157] Rechargeable lithium batteries may also include an electrolyte.

[0158] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0159] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0160] 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.

[0161] 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).

[0162] 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.

[0163] 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.

[0164] Non-aqueous organic solvents can be used alone or in combination of two or more solvents.

[0165] 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.

[0166] 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 F2y+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).

[0167] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch, or coin-shaped batteries.

[0168] 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.

[0169] 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.

[0170] Examples and comparative examples of this disclosure are described below. However, the following examples are provided only as examples of this disclosure, and this disclosure is not limited to the following examples.

[0171] 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 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, approximately 10 mL of the reaction solution was taken and the content of non-volatile (NV) components was measured, which was 9.8 wt% (theoretical value: 10 wt%). In addition, in the obtained poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) 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 lithium 2-acrylamido-2-methylpropanesulfonic acid is 30:10:60.

[0172] Preparation Example 2 In Preparation Example 1, the content of each monomer was varied to prepare a poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt. The molar ratio of the structural units derived from lithium acrylate, 2-hydroxyethyl methacrylate, and lithium 2-acrylamido-2-methylpropanesulfonic acid, respectively, 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%).

[0173] Preparation Example 3 In Preparation Example 1, the content of each monomer was varied to prepare a poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt. The molar ratio of the structural units derived from lithium acrylate, 2-hydroxyethyl methacrylate, and lithium 2-acrylamido-2-methylpropanesulfonic acid, respectively, 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%).

[0174] Preparation Example 4 In Preparation Example 1, the content of each monomer was varied to prepare a poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt. The molar ratio of the structural units derived from lithium acrylate, 2-hydroxyethyl methacrylate, and lithium 2-acrylamido-2-methylpropanesulfonic acid, respectively, 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%).

[0175] 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 was 74:26. ​​The content of the non-volatile component in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0176] 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%).

[0177] 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%).

[0178] Example 1 (1) Based on a total of 100 parts by weight, boehmite (particle size D50: 150 nm, KB-01S, cubic of DAEJOO KC Ltd.) as the first filler and nanofibers (boehmite, length: 100 nm to 500 nm, diameter: 10 nm to 50 nm) as the second filler were mixed at a weight ratio of 90:10 to prepare a mixture.

[0179] 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 ground and dispersed at 25°C for 30 minutes using a bead mill to prepare a dispersion.

[0180] Trimethylolpropane tris(2-methyl-1-aziridine propionate), a trifunctional aziridine crosslinking agent, was added to the dispersion, and water was added to make the total solids content 20 wt%. At this point, the aziridine crosslinking agent was included in an amount of 10 parts by weight based on 100 parts by weight of methacrylic acid binder.

[0181] Ten parts by weight of crosslinked polymethyl methacrylate (Tg: 60°C) as an adhesive binder, based on 100 parts by weight of methacrylic acid binder, were added to the resulting dispersion to prepare a composition for the first coating layer.

[0182] (2) Prepare a dispersion comprising the mixture of methacrylic acid binder, filler, and aziridine crosslinker prepared in Preparation Example 1 in the same manner as in (1). Add 10 parts by weight of polyvinylidene fluoride adhesive (75130, comprising a copolymer of vinylidene fluoride and hexafluoropropylene in a molar ratio of 90:10 and also comprising acrylic acid as a monomer, melting point: 154°C, crystallinity: 53%) based on 100 parts by weight of methacrylic acid binder to the above dispersion to prepare a composition for the second coating layer.

[0183] (3) The composition for the first coating layer is applied to the first surface of a polyethylene membrane (thickness: 5.5 μm, CZMZ, air permeability: 110 seconds / 100 cc, puncture strength: 340 kgf) as a porous substrate using a molding method, and the composition for the second coating layer is applied to the second surface of the membrane using a molding method. The membrane is then dried and aged in an oven at 70°C for 16 hours to form the first coating layer (thickness: 1 μm) and the second coating layer (thickness: 1 μm), thereby manufacturing a separator for a rechargeable lithium battery.

[0184] Example 2 The diaphragm was prepared in the same manner as in Example 1, except that the weight ratio between the fillers in Example 1 was changed to 80:20.

[0185] Example 3 The diaphragm was prepared in the same manner as in Example 1, except that the weight ratio between the fillers in Example 1 was changed to 50:50.

[0186] Examples 4 to 6 Except for the type of binder as shown in Table 1 below, which is changed and used in place of the binder in Preparation Example 1, the membrane is prepared in the same manner as in Example 1.

[0187] Comparison Example 1 The diaphragm is prepared in the same manner as in Example 1, except that the first filler is not used in Example 1.

[0188] Comparison Example 2 The membrane was prepared in the same manner as in Example 1, except that a second filler was not used in Example 1.

[0189] Comparison Example 3 The membrane was prepared in the same manner as in Example 1, except that no aziridine crosslinking agent was used in Example 1.

[0190] Compare Example 4 Except that a polyvinylidene fluoride-based adhesive is used as the adhesive in the first coating layer in Example 1, the diaphragm is prepared in the same manner as in Example 1.

[0191] Compare Example 5 The diaphragm was prepared in the same manner as in Example 1, except that cross-linked polymethyl methacrylate was used as the adhesive binder in the second coating layer in Example 1.

[0192] Comparison Examples 6 to 8 Except for the type of binder as shown in Table 1 below, which is changed and used in place of the binder in Preparation Example 1, the membrane is prepared in the same manner as in Example 1.

[0193] Compare Example 9 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.

[0194] Compare Example 10 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.

[0195] Battery manufacturing Manufacturing of the negative electrode: The negative electrode is manufactured according to the following process.

[0196] 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.

[0197] Manufacturing of the positive electrode: The positive electrode is manufactured according to the following process.

[0198] A mixture of 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) was added to an N-methyl-2-pyrrolidone solvent and stirred for 30 minutes using a mechanical stirrer to prepare a slurry for the positive electrode active material. The slurry was then 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 under vacuum at 120°C for 4 hours. Finally, it was rolled to manufacture the positive electrode.

[0199] Electrode assembly core: Each diaphragm obtained according to the example and comparative example was placed between the positive and negative electrodes fabricated above, and then wound to prepare the electrode assembly core. The core was inserted into a bag, electrolyte was injected, and the bag was vacuum-sealed. As the electrolyte, 1.3M LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 3:5:2.

[0200] The electrode core inserted into the bag was pressed at 80°C for 3 minutes while being subjected to an application of 11.7 kgf / cm². 2 The pressure is to manufacture rechargeable lithium batteries.

[0201] Dry heat shrinkage rate (unit: %) Each separator for the example and comparative examples of rechargeable lithium batteries was cut into 8cm × 8cm dimensions to prepare samples. 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 130°C for 1 hour. It was then removed, and the dimensions of the drawn squares were measured. The shrinkage rate in each of the longitudinal (MD) and transverse (TD) directions was calculated. The shrinkage rate was calculated according to Formula 1 below.

[0202] Mathematical formula 1: Shrinkage rate = (L0-L1) / L0×100.

[0203] L0 is the initial length of the diaphragm, and L1 is the length of the diaphragm after standing at 130°C for 1 hour.

[0204] Adhesion to the positive electrode (unit: gf / mm) The separator is attached to the positive electrode (manufactured in the same manner as described in "Battery Manufacturing" above), with the second coating layer of the separator facing the positive electrode, and inserted into a bag. An electrolyte (1.3M LiPF6 in a 3 / 5 / 2 (volume ratio) mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC)) is injected. The resulting assembly is allowed to stand for 12 hours at 10 kgf / cm². 2 Up to 20 kgf / cm 2 It was pressed under pressure, at a temperature of 70°C to 90°C, and for 5 to 20 seconds, and then disassembled. After removing the diaphragm and positive electrode from the bag, the positive electrode and diaphragm were unfolded 180°, and the force required to separate the positive electrode from the diaphragm was measured using a tensile tester (Tinius Olsen, HT400).

[0205] Adhesion to the negative electrode (unit: gf / mm) The separator is attached to the negative electrode (manufactured in the same manner as described in "Battery Manufacturing" above), with the first coating layer of the separator facing the negative electrode, and inserted into a bag. An electrolyte (1.3M LiPF6 in a 3 / 5 / 2 (volume ratio) mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC)) is injected. The resulting assembly is allowed to stand for 12 hours at 10 kgf / cm². 2 Up to 20 kgf / cm 2 It was pressed under pressure, at a temperature of 70°C to 90°C, and for 5 to 20 seconds, and then disassembled. After removing the diaphragm and negative electrode from the bag, the negative electrode and diaphragm were unfolded 180°, and the force required to tear the negative electrode from the diaphragm was measured using a tensile tester (Tinius Olsen, HT400).

[0206] Membrane resistance (unit: Ω) The membrane resistance was evaluated as electrochemical impedance spectroscopy (EIS) resistance. Membranes fabricated in the example and comparative examples were impregnated with an electrolyte (1.5 M LiPF6 dissolved in a mixed solvent of ethylene carbonate, ethyl methyl 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).

[0207] Ionic conductivity (unit: mS / cm): The separators fabricated in the example and comparative examples were impregnated with an electrolyte (1.5M LiPF6 dissolved in a mixed solvent of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate (volume ratio of 2 / 1 / 7), mounted on aluminum foil electrodes with leaded tabs, and sealed in an aluminum cask to fabricate test cell units. The ionic conductivity of the test cell units was measured by AC impedance method (measurement frequency 100kHz).

[0208] Surface roughness (Ra value, unit: μm) The diaphragm surface was measured using an Olympus microscope. The arithmetic mean roughness (Ra) value was obtained from the arithmetic mean of the absolute vertical coordinates within the sampling length. The Ra values ​​of the first and second coating layers of the diaphragm were obtained, and the average value was recorded.

[0209] Table 1:

[0210] Table 2:

[0211] (Table 2 continued)

[0212] As shown in Table 1 above, the example separator for rechargeable lithium batteries can provide low thermal shrinkage, low film resistance, high adhesion to electrode plates, high ionic conductivity and low surface roughness, thereby improving battery reliability.

[0213] According to one example embodiment, a separator for a rechargeable battery can improve battery capacity, safety, and lifespan by providing low thermal shrinkage, low film resistance, high adhesion to electrode plates, low surface roughness, low ionic conductivity, and high rate performance during charging and discharging.

[0214] Although 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 claims, the detailed description of the disclosure, and the drawings, which also fall within the scope of the present disclosure.

Claims

1. A separator for a rechargeable battery, the separator comprising: Porous substrate; A first coating layer is located on the first surface of the porous substrate; as well as The second coating layer is located on the second surface of the porous substrate. The first coating layer comprises: a crosslinking product of an adhesive and a crosslinking agent; a filler; and a (meth)acrylic adhesive. The second coating layer comprises: a crosslinking product of the adhesive and the crosslinking agent; the filler; and a carbonyl-based fluorine-based adhesive. Both the adhesive in the first coating layer and the adhesive in the second coating layer comprise (meth)acrylic acid adhesives, which include a first structural unit derived from (meth)acrylic acid, (meth)acrylates, or salts thereof, a second structural unit derived from (meth)acrylate hydroxyalkyl esters, and a third structural unit derived from (meth)acrylamidosulfonic acid or salts thereof. The crosslinking agent includes aziridine crosslinking agents. 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 fiber packing material.

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 packing has an aspect ratio of 5 or greater.

6. The diaphragm according to claim 1, wherein, The second packing fills the space between the first packing.

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: ； In chemical formula 8, 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 the individual units, 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 1, wherein, The (meth)acrylic adhesive has a glass transition temperature in the range of 50°C to 110°C.

15. The diaphragm according to claim 1, wherein, The fluorinated adhesives include fluorinated adhesives having carbonyl and hydroxyl groups.

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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