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 includes a crosslinking product of a binder and a crosslinking agent, and a filler. The binder includes a (meth) acrylic binder including 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) acrylamide sulfonic acid or a salt thereof. The cross-linking agent comprises an aziridine cross-linking agent, 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. 10-2024-0163678, 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 has grown. Therefore, improving the performance of rechargeable lithium batteries can be beneficial.

[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 a redox reaction when lithium ions are deintercalated from the positive electrode and inserted into the negative electrode / deintercalated from the negative electrode and inserted into the positive electrode.

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

[0006] One example embodiment includes a separator for rechargeable batteries that exhibits low thermal shrinkage, high rate capability during charging and discharging, low film resistance, and high adhesion to electrode plates.

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

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

[0009] The separator for a rechargeable lithium battery includes a porous substrate, a first coating layer and a first adhesive layer located on (e.g., sequentially located on) a first surface of the porous substrate, and a second coating layer and a second adhesive layer located on (e.g., sequentially located on) a second surface of the porous substrate. Both the first and second coating layers include a crosslinking product of an adhesive and a crosslinking agent, and a filler. The adhesive includes a (meth)acrylic acid adhesive, comprising a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or their salts, a second structural unit derived from (meth)acrylic acid hydroxyalkyl esters, and a third structural unit derived from (meth)acrylamide sulfonic acid or its salts. 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 first adhesive layer includes a (meth)acrylic acid adhesive, and the second adhesive layer includes a fluorinated adhesive having a carbonyl group (C=O).

[0010] Another example embodiment provides 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 diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure. Detailed Implementation

[0013] Hereinafter, exemplary embodiments of the present disclosure are described in detail. However, these embodiments are provided as examples, 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 “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 in between.

[0015] Unless otherwise stated in this specification, anything indicated 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”.

[0016] As used herein, the term "combination of them" may mean mixtures, laminates, complexes, copolymers, alloys, blends, and reaction products of the components.

[0017] Here, the term "particle size D50" refers to the average particle size representing 50% by volume of the particle size distribution. Particle size distribution can be measured using methods known to those skilled in the art. For example, particle size distribution can be measured using a particle size analyzer, transmission electron microscopy, or scanning electron microscopy. In another method, particle size can be measured using a measuring device that utilizes dynamic light scattering, data analysis can be performed to count the number of particles in each particle size range, and the particle size can then be calculated to obtain the D50 value. Alternatively, D50 can be measured using laser diffraction. For example, when measured by laser diffraction, after dispersing the particles to be measured in a dispersion medium, the particles can be introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound at approximately 28 kHz at an output of 60 W, and the D50 can be calculated based on 50% of the particle size distribution in the measuring device.

[0018] When the particles are spherical, size can mean diameter.

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

[0020] Unless otherwise defined herein, “substitution” means that hydrogen in a compound is replaced by a substituent, such as or including at least one of the following: 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 - (where n is a natural number from 1 to 10) (where R and R' are both independently C1 to C20 alkyl groups), carboxybenzene group (-RR'N) + (CH2) n COO -The following groups are used for the following purposes: 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 a C1 to C6 alkyl, C1 to C6 alkoxy, or C6 to C12 aryl), carboxyl (-COOH) or its salt (-C(=O)OM, where M is an organic or inorganic cation), sulfonic acid (-SO3H) or its salt (-SO3M, where M is an organic or inorganic cation), phosphate (-PO3H2) or its salt (-PO3MH or -PO3M2, where M is an organic or inorganic cation) and combinations thereof.

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

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

[0023] In chemical formulas, Symbols indicate parts that are 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.

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

[0025] When describing numerical ranges in this specification, “X to Y” means “X or greater and Y or less (greater than or equal to X and less than or equal to Y)”.

[0026] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical values ​​include a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​in increments such as 0.1%.

[0027] The following describes in detail the separator for a rechargeable battery and the rechargeable battery including the separator.

[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, a first coating layer and a first adhesive layer located on (e.g., sequentially located) a first surface of the porous substrate, and a second coating layer and a second adhesive layer located on (e.g., sequentially located) a second surface of the porous substrate. Both the first and second coating layers include 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 salts thereof, a second structural unit derived from a hydroxyalkyl ester of (meth)acrylic acid, 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 fibrous filler. The first adhesive layer includes a (meth)acrylic acid adhesive, and the second adhesive layer includes a fluorinated adhesive having a carbonyl group (C=O).

[0030] According to one example embodiment, a first adhesive layer may be bonded to the negative electrode of the battery, and a second adhesive layer may be bonded to the positive electrode of the battery.

[0031] According to one example embodiment, the crosslinking product may be or include a thermally crosslinked product.

[0032] According to one example embodiment, both the first coating layer and the second coating layer may be formed from a composition for coating layers comprising a (meth)acrylic binder, an aziridine crosslinking agent, and a filler.

[0033] The diaphragm can provide low thermal shrinkage and high adhesion to the electrode plates.

[0034] In one example embodiment, the membrane may have a dry heat shrinkage rate of about 5% or less in the longitudinal direction (MD) and transverse direction (TD), a wet heat shrinkage rate of about 10% or less in the longitudinal direction (MD) and transverse direction (TD), and a membrane resistance of about 0.7 Ω or less. Here, MD and TD are substantially the same as the MD and TD of the porous substrate, respectively.

[0035] In one example embodiment, the diaphragm may have an adhesion force of about 1.1 gf / mm or greater to the positive electrode and an adhesion force of about 0.7 gf / mm or greater to the negative electrode.

[0036] In one example embodiment, the diaphragm may have a surface roughness of about 0.6 μm or less.

[0037] Here, "surface roughness" is obtained by measuring the diaphragm surface using an Olympus microscope, calculating the arithmetic mean roughness (Ra) value by the arithmetic mean of the absolute vertical coordinates within the sampling length, and calculating the Ra value of each of the first and second coating layers of the diaphragm to calculate the average value.

[0038] A first coating layer or a second coating layer that only includes the first filler or the second filler may present the challenge of increased wet heat shrinkage.

[0039] A first and second coating layer consisting solely of fillers (i.e., a mixture of a first and a second filler) may present the challenge of increased dry heat shrinkage. A diaphragm having a first and a second coating layer comprising fillers, as well as a crosslinked product of a (meth)acrylic acid binder and an aziridine crosslinking agent, can provide the effect of increasing adhesion to the electrode plate while satisfying both dry heat shrinkage and wet heat shrinkage.

[0040] A separator having a coating layer formed from a composition for coating that includes a (meth)acrylic acid binder but does not include an aziridine crosslinking agent as a crosslinking agent, or includes crosslinking agents other than aziridine crosslinking agents, may exhibit lower battery reliability due to the increased wet heat shrinkage rate described above. According to an example embodiment, an aziridine crosslinking agent may be included in an amount of about 95 wt% or more (e.g., in the range of about 98 wt% to 100 wt%, or 100 wt%) of the total crosslinking agent in the composition for coating.

[0041] Membranes with coatings formed from compositions comprising aziridine crosslinkers but excluding (meth)acrylic binders, or containing binders other than (meth)acrylic binders, exhibit high thermal shrinkage, high membrane resistance, and high permeability, which can pose challenges to battery capacity, lifespan, and safety. According to one example embodiment, (meth)acrylic binders may be included in an amount of about 95 wt% or more (e.g., in the range of about 98 wt% to 100 wt%, or 100 wt%) of the total binder in the composition for coating.

[0042] The filler includes a mixture of a first filler and a second filler. A separator formed from a composition for coating that includes only the first filler may have poor rate performance during battery charging and discharging. A separator formed from a composition for coating that includes only the second filler may have poor battery reliability due to increased hygrothermal shrinkage. According to one example embodiment, a 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.

[0043] The first adhesive layer comprises a (meth)acrylic adhesive, and the second adhesive layer comprises a fluorinated adhesive with carbonyl groups. The diaphragm having the first and second adhesive layers can provide high adhesion to both the positive and negative electrodes and can advantageously provide a significantly low rate of hygrothermal shrinkage.

[0044] First coating layer The first coating layer may be or may include a heat-resistant layer.

[0045] The adhesive includes a (meth)acrylic adhesive, which comprises a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or salts thereof, a second structural unit derived from (meth)acrylic acid hydroxyalkyl ester, and a third structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0046] According to one example embodiment, the (meth)acrylic adhesive may be or include a non-adhesive adhesive.

[0047] According to one example embodiment, the (meth)acrylic acid binder can be or includes a salt binder, such as an alkali metal salt binder. Here, the alkali metal can 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.

[0048] The (meth)acrylic binder can fix the filler to the porous substrate, enabling the first coating layer to adhere to the porous substrate and helping to improve the membrane's heat resistance, permeability, and oxidation resistance. Additionally, 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 increasing the dispersibility of the filler within the first coating layer. Furthermore, the (meth)acrylic binder in the first coating layer, including the filler described below, can provide a membrane with low membrane resistance, low dry heat shrinkage, and low wet heat shrinkage.

[0049] 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., in the range of about 95 mol% to about 100 mol%, for example, 100 mol%). Within this range, the aforementioned membrane effect can be easily achieved.

[0050] The first structural unit is derived from (meth)acrylic acid, (meth)acrylate, or their salts, and can fix the filler on the porous substrate while providing adhesion, allowing the first coating layer to adhere to the porous substrate and contributing to improved heat resistance and permeability of the membrane. Additionally, the first structural unit can improve the dispersibility of the first coating composition by having a carboxyl functional group (-C(=O)O-) within the structural unit.

[0051] The first structural unit can be represented by any one of the following chemical formulas 1 to 3 and combinations thereof: Chemical Formula 1: Chemical Formula 2: Chemical Formula 3: ; ; .

[0052] Based on 100 mol% of (meth)acrylic acid binder for rechargeable lithium batteries, it can be produced 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%). The first structural unit is comprised in amounts ranging from 1%, 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%, and amounts from 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 ranges, the membrane can exhibit low membrane resistance, desired or improved adhesion to porous substrates, and desired or improved heat resistance, permeability, and oxidation resistance.

[0053] 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. In this case, 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.

[0054] According to another example embodiment, the first structural unit may consist only of structural units represented by chemical formula 2 or chemical formula 3.

[0055] The second structural unit is derived from hydroxyalkyl (meth)acrylate and can fix the filler onto the porous substrate while providing adhesion, allowing the first coating layer to adhere to the porous substrate. Furthermore, the second structural unit can improve the dispersibility of the first coating layer composition by having a carboxyl functional group (-C(=O)O-) within the structural unit.

[0056] The second structural unit can be represented by the following chemical formula 4: Chemical formula 4: .

[0057] Based on 100 mol% of a (meth)acrylic acid 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 this range, it is possible to increase the adhesion of the first coating layer to the porous substrate.

[0058] The second structural unit can be, for example, a structural unit derived from (meth)acrylate hydroxyalkyl esters. Here, the alkyl group can be or includes C1 to C20 alkyl, C1 to C10 alkyl, or C1 to C6 alkyl.

[0059] 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.

[0060] 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 migration in the presence of the first and second structural units.

[0061] The third structural unit can enhance the heat resistance of the membrane by including a large-volume functional group derived from (meth)acrylamide sulfonic acid or its salt, thereby increasing the glass transition temperature. 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 the effect of reducing membrane resistance.

[0062] The third structural unit can be represented by at least one of chemical formulas 5, 6, 7, and combinations thereof: Chemical formula 5: Chemical formula 6: Chemical formula 7: ; ; .

[0063] 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.

[0064] The third structural unit may be or include, for example, a structural unit derived from (meth)acrylamidoalkyl sulfonic acid or a salt thereof. Here, the alkane may be or include C1 to C20 alkanes, C1 to C10 alkanes, or C1 to C6 alkanes, and the alkyl may be or include C1 to C20 alkyl, C1 to C10 alkyl, or C1 to C6 alkyl. A salt means a salt consisting of or including the aforementioned sulfonic acid and the desired ion. The ion may be or include, for example, an alkali metal ion; in this case, the salt may be or include an alkali metal salt of a sulfonic acid.

[0065] For example, (meth)acrylamidoalkane sulfonic acid can be 2-(meth)acrylamido-2-methylpropanesulfonic acid.

[0066] 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%). The amounts of (meth)acrylic acid binder (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%) are included in the (meth)acrylic acid binder. When the third structural unit is included within the above ranges, the (meth)acrylic acid binder and the diaphragm including the (meth)acrylic acid binder can exhibit significantly low membrane resistance.

[0067] The descriptions of chemical formulas 1 to 7 are as follows.

[0068] R 1 To R 14 Each can be independently hydrogen or include C1 to C10 alkyl groups. For example, R 1 To R 7 and R 9 To R 14 It may be all or include hydrogen or methyl; and R 8 It can be or include methyl groups.

[0069] L 1 To L 4 Each of these can 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 heterocyclic groups. For example, L 1 It may be or include methylene or ethylene, and L 2 To L 4 Each can be independently or include -C(CH3)2-CH2- .

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

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

[0072] A representative example of a (meth)acrylic adhesive according to an exemplary embodiment is shown in the following chemical formula 8: Chemical formula 8: .

[0073] The description of chemical formula 8 above is as follows.

[0074] R 15 To R 20 Each can be independently hydrogen or include C1 to C10 alkyl groups. For example, R 15 To R 17 R 19 and R 20 It may be all or include hydrogen or methyl; and R 18 It can be or include methyl groups.

[0075] L 5 and L 6 Each of these can 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 heterocyclic groups. For example, L 5 It may be or include methylene or ethylene, and L 6 Can be or include -C(CH3)2-CH2- .

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

[0077] 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.

[0078] l, m, and n can be the molar ratio 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; for example, 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.

[0079] (Meth)acrylic binders may include alkali metals. Alkali metals (e.g., lithium, sodium, potassium, rubidium, or cesium) may exist in cationic form. For example, alkali metals may exist as salts bound to the (meth)acrylic binder. Alkali metals can facilitate the synthesis of (meth)acrylic binders in aqueous solvents, improve the adhesion of the first coating layer, and improve the heat resistance, permeability, and oxidation resistance of the membrane.

[0080] Based on the total content of the (meth)acrylic binder, 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%).

[0081] Based on the total content of the (meth)acrylic adhesive, alkali metals may be included in an amount ranging from 0.1 mol% to 1.0 mol%. When alkali metals are included within the above range, the first coating layer may have desired or improved adhesion, and the diaphragm including the first coating layer may exhibit desired or improved heat resistance, air permeability, and oxidation resistance.

[0082] (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.

[0083] The weight-average molecular weight of (meth)acrylic acid adhesives can range from about 100,000 g / mol to 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 electrical resistance. The weight-average molecular weight can be the average molecular weight converted from polystyrene using, for example, gel permeation chromatography.

[0084] (Meth)acrylic acid binders can be prepared by solution polymerization.

[0085] According to one example embodiment, the (meth)acrylic adhesive may be included in the first coating layer of the diaphragm in the form of a film.

[0086] Crosslinking agents include aziridine crosslinking agents.

[0087] 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 porous substrates.

[0088] 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.

[0089] 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), tris(1-aziridine)phosphine oxide, N,N-hexamethylene-bis(aziridinecarboxamide), trimethylolpropane tris(2-methyl-1-aziridine propionate), trimethylolpropane tris(β-N-aziridine) propionate, and pentaerythritol tris(3-(1-aziridine) propionate).

[0090] In contrast to the adhesive (e.g., (meth)acrylic acid adhesive), a crosslinking agent (e.g., aziridine crosslinking agent) may be included in a desired amount. According to an example embodiment, based on 100 parts by weight of the (meth)acrylic acid adhesive, the amount may range 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 (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, 5 to 30 parts by weight, 5 to 25 parts by weight, or 5 to 20 parts by weight) include crosslinking agents. Within the above ranges, the thermal shrinkage rate and membrane resistance of the membrane in the electrolyte can be significantly reduced.

[0091] The packing material includes a mixture of a first packing material and a second packing material, wherein the first packing material is or includes inorganic packing material, and the second packing material is or includes fiber packing material.

[0092] In one example embodiment, the inorganic filler may be or include non-fibrous fillers, rather than or include fibrous fillers.

[0093] The first filler can be spherical, plate-shaped, cubic, or amorphous. For example, the first filler can be cubic, and in the case of a cubic shape, the aforementioned heat shrinkage rate can be significantly reduced.

[0094] 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), for example, the first filler may have an average particle size D50 of 150 nm. Within the above range, when the first filler is combined with the second filler described below, the above-mentioned wet heat shrinkage rate can be achieved.

[0095] 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 inorganic filler may be boehmite.

[0096] The second filler is or includes a fiber filler. The fiber filler has a fibrous form and can fill the space between the first fillers, thereby reducing the thermal shrinkage rate in the electrolyte, and can have the effect of reducing the surface roughness of each of the first and second coating layers, thereby increasing the adhesion to the porous substrate by means of a particulate adhesive.

[0097] In one example embodiment, the fiber filler can have an aspect ratio in the range of about 5 or greater (e.g., in the range of about 5 to about 500). Here, the aspect ratio refers to the ratio of the length of the fiber filler to its dimension (or diameter). The size of the fiber filler can be in the range of about 10 nm to about 200 nm (e.g., it can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 10 nm to 100 nm), and the length can be 100 nm or greater (e.g., in the range of 100 nm to 1000 nm). Within the above range, the aspect ratio can be readily achieved.

[0098] The fiber filler may include at least one of boehmite, carbon nanotubes, silver nanowires, boron carbide nanowires, cellulose nanofibers, copper hydroxide nanowires, silicon monoxide nanowires, hydroxyapatite nanowires, Al2O3, TiO2, SiO2, and combinations thereof.

[0099] 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. Within this range, the weight ratio can be beneficial in reducing dry heat shrinkage and wet heat shrinkage. For example, the weight ratio can be 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, 90:10, 95:5, 55:45 to 95:5, 60:40 to 90:10, or 60:40 to 50:50, and within this range, the rate characteristics can be further improved.

[0100] The mass ratio of (meth)acrylic binder to filler (i.e., mixture) can be 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, 1:10 to 1:40 or 1:20 to 1:30). Within this range, an effect of improving the heat resistance within the electrolyte can be achieved.

[0101] Fillers (e.g., mixtures) may be included in an amount ranging from about 50 wt% to about 99 wt% of the total amount of the first coating layer (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 fillers within the above range are included, desired or improved heat resistance, durability, oxidation resistance, and stability may be exhibited.

[0102] The first coating layer may have a thickness in the range of about 0.01 μm to about 20 μm, and within this range, 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.

[0103] 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 this range, the membrane can exhibit desired or improved permeability, heat resistance, and adhesion.

[0104] First adhesive layer The first adhesive layer comprises a (meth)acrylic adhesive. The (meth)acrylic adhesive can increase the adhesion to the negative electrode. The (meth)acrylic adhesive can be granular and cross-linked.

[0105] (Meth)acrylic adhesives may include (meth)acrylate polymers or copolymers. According to one example embodiment, a (meth)acrylic adhesive may be or include crosslinked (meth)acrylate polymers or copolymers. For example, a (meth)acrylic adhesive may include crosslinked polymethyl methacrylate (PMMA).

[0106] To prepare crosslinked (meth)acrylate polymers, a crosslinking agent can be further added during the polymerization step. The (meth)acrylate adhesive can 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 improved adhesion to the electrode desired, but also improved ionic conductivity. The glass transition temperature can be measured using differential scanning calorimetry (DSC). For example, after placing 2 mg of the polymer in a pressure-resistant pan for DSC measurement, the temperature range is set to 25°C to 200°C, the heating rate is set to 10°C / min, and the glass transition temperature is obtained under a controlled atmosphere.

[0107] The (meth)acrylic adhesive may be included in the first adhesive layer in an amount of about 95 wt% or more (e.g., in the range of about 95 wt% to 100 wt%, or 100 wt%).

[0108] The first adhesive layer may have a thickness in the range of about 0.01 μm to about 20 μm, and within this range, it may have a thickness of 0.01 μm to 7 μm, 0.1 μm to 5 μm, or 0.1 μm to 3 μm. For example, the first adhesive layer may have a thickness of 0.1 μm to 2 μm.

[0109] Second coating layer The second coating layer may be or may include a heat-resistant layer.

[0110] The adhesive includes a (meth)acrylic adhesive, which comprises a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or salts thereof, a second structural unit derived from (meth)acrylic acid hydroxyalkyl ester, and a third structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0111] Details regarding the (meth)acrylic adhesive are omitted because they are substantially the same as those for the (meth)acrylic adhesive in the first coating layer. The specific composition of the (meth)acrylic adhesive in the first coating layer may be substantially the same as that in the (meth)acrylic adhesive in the second coating layer.

[0112] The crosslinking agent includes aziridine crosslinking agents, and the filler includes a mixture of a first filler and a second filler. The specific components of the aziridine crosslinking agent, the first filler, and the second filler may be substantially the same as those described in the first coating layer.

[0113] Second adhesive layer The second adhesive layer comprises a fluorinated adhesive with carbonyl groups (C=O). Fluorinated adhesives can help provide high adhesion to the positive electrode.

[0114] Fluorinated adhesive binders comprise mixtures of fluorinated homopolymers and interpenetrating polymer network (IPN) binders of fluorinated cross-linked polymers and acrylate cross-linked polymers (hereinafter also referred to as IPN binders). This mixture can be included in a second adhesive layer to advantageously increase adhesion to the positive electrode.

[0115] In one example embodiment, the fluorinated adhesive may be a water-based adhesive.

[0116] According to one example embodiment, the mixture may be included in an amount of about 95 wt% or more (e.g., in the range of about 95 wt% to about 100 wt%, or 100 wt%) of the fluorinated adhesive.

[0117] Fluorinated homopolymers can include polyvinylidene fluoride homopolymers.

[0118] Fluorinated homopolymers are materials with high melting points (Tm) in the range of about 100°C to about 200°C, and they retain their particulate shape even after hot compression processes, thus helping to ensure the permeability of the membrane after hot compression. Fluorinated homopolymers can have melting points of about 100°C or higher, 120°C or higher, or 130°C or higher and about 200°C or lower, 180°C or lower, or 170°C or lower.

[0119] Fluorinated homopolymers can be located within the network structure of IPN adhesives to enhance air permeability. Additionally, fluorinated homopolymers can provide desired or improved adhesion.

[0120] Fluorinated homopolymers can have a particle size D50 in the range of about 50 nm to about 1000 nm. Within this range, desired or improved permeability can be provided for separators used in rechargeable lithium batteries. For example, the particle size D50 can be about 50 nm or larger, 100 nm or larger, 150 nm or larger, 200 nm or larger and about 1000 nm or smaller, 800 nm or smaller, 600 nm or smaller, 400 nm or smaller, or 300 nm or smaller.

[0121] Fluorinated homopolymers can have a weight-average molecular weight in the range of about 100,000 g / mol or greater, 200,000 g / mol or greater, or 300,000 g / mol or greater and about 1,500,000 g / mol or less.

[0122] According to one example embodiment, the fluorinated homopolymer may have a carbonyl (C=O) functional group. When the fluorinated homopolymer is coated onto a second adhesive layer, the carbonyl (C=O) functional group can enhance the adhesive function. The method for introducing the carbonyl functional group into the fluorinated homopolymer can be a conventional method known to those skilled in the art.

[0123] IPN binders can be or include particulate binders in which fluorinated crosslinked polymers and acrylate crosslinked polymers form an interpenetrating polymer network. The two crosslinked polymers forming the interpenetrating polymer network can impart desired or improved adhesion to the separator for a rechargeable lithium battery of an example embodiment.

[0124] For example, both acrylate crosslinked polymers and fluorinated crosslinked polymers have network structures and can be entangled in a network form.

[0125] The acrylate crosslinking polymer can be or includes at least one of the following: polymethyl methacrylate, polymethyl methacrylate, polyethyl methacrylate, polyacrylate, polybutyl acrylate, etc.

[0126] Fluorine-based crosslinked polymers can be or include crosslinked polymers such as homopolymers containing only structural units derived from vinylidene fluoride monomers, copolymers containing structural units derived from vinylidene fluoride monomers and structural units derived from another monomer, etc.

[0127] The copolymer may include, but is not limited to, structural units derived from vinylidene fluoride monomers and one or more structural units derived from trifluoroethylene chloromonopolymer, trifluoroethylene monomer, hexafluoropropylene monomer, tetrafluoroethylene monomer, and ethylene monomer. For example, the copolymer may be or include a vinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer, which includes structural units derived from vinylidene fluoride monomers and structural units derived from hexafluoropropylene monomers.

[0128] According to one example embodiment, the fluorinated adhesive can be an aqueous particulate adhesive.

[0129] In one example embodiment, based on the total molar amount of 100 mol of vinylidene fluoride and hexafluoropropylene, the copolymer 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 groups.

[0130] The weight ratio of acrylate crosslinking polymers to fluorinated crosslinking polymers can range from about 8:2 to about 1:9. Within this range, the desired or improved adhesion can be maintained even after thermal compression of the separator for rechargeable lithium batteries according to the example embodiment. For example, the weight ratio can range from 8:2 to 1:9, 7:3 to 2:8, 6:4 to 2:8, or 5:5 to 3:7.

[0131] The weight-average molecular weight of the IPN binder can be about 100,000 g / mol or greater. Within this range, the desired or improved adhesion can be maintained even after thermal compression of the separator used in rechargeable lithium batteries. For example, the weight-average molecular weight of the IPN binder can be about 200,000 g / mol or greater, or about 300,000 g / mol or greater and about 1,500,000 g / mol or less.

[0132] In the second adhesive layer, based on a total of 100 wt%, an IPN adhesive comprising fluorinated homopolymers and fluorinated crosslinked polymers and acrylate crosslinked polymers may be included in a weight ratio ranging from about 95:5 to about 15:85. Within this range, synergistic effects may exist in providing desired or improved adhesion and enhanced air permeability. For example, the weight ratio may be 95:5 to 15:85, 85:15 to 15:85, or 80:20 to 20:80.

[0133] On each side of the porous substrate, the loading of a fluorinated adhesive (e.g., a mixture) can be approximately 0.1 g / m². 2 To approximately 1.0 g / m 2 Within the above range, desired or improved adhesion, thermal stability, and structural stability can be enhanced.

[0134] Based on the total amount of the second coating layer, a fluorinated adhesive binder (e.g., a mixture) may be included in an amount ranging from about 1 wt% to about 20 wt% (e.g., 5 wt% to 20 wt%, or 5 wt% to 15 wt%). Within this range, adhesion to the electrodes is observed and the battery resistance does not increase, thus there are no limitations in terms of capacity achievement.

[0135] The second adhesive layer may have a thickness in the range of about 0.01 μm to about 20 μm, and within the above range, the thickness may be 0.01 μm to 5 μm, 0.1 μm to 3 μm or 0.1 μm to 1.5 μm.

[0136] Porous substrate Porous substrates have a large number of pores and can be, or include, substrates commonly used in electrochemical devices. Porous substrates can be, or include, polymer films formed from one or more of the following polymers, or copolymers or mixtures thereof: polymers such as or including polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyetheretherketones, polyaryletherketones, polyetherimides, polyamide-imides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., Teflon). ® At least one of the following.

[0137] The porous substrate can be or includes, for example, a polyolefin-based substrate containing polyolefins, and the polyolefin-based substrate has the desired or improved shut-off function, thus contributing to improved battery safety. The polyolefin-based 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. Additionally, the polyolefin-based substrate may include non-olefin resins in addition to olefin resins, or may include copolymers of olefin monomers and non-olefin monomers.

[0138] 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).

[0139] Porous substrates can have an air permeability of 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 this range, porous substrates can be used for membranes.

[0140] A separator for a rechargeable battery according to an example embodiment can be formed by coating one or both sides of a porous substrate with a composition for forming a coating layer, then drying the composition to form a coating layer; and coating the coating layer with a composition for forming an adhesive layer, then drying the composition to form an adhesive layer. Drying can be performed using conventional methods known to those skilled in the art.

[0141] Figure 1 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment.

[0142] Reference Figure 1The separator for a rechargeable lithium battery may include a porous substrate 1, a first coating layer 2a and a first adhesive layer 2b located on a first surface of the porous substrate 1 (e.g., sequentially located), and a second coating layer 3a and a second adhesive layer 3b located on a second surface of the porous substrate 1 (e.g., sequentially located). The first coating layer 2a may include a crosslinking product 3 of a (meth)acrylic binder and an aziridine crosslinking agent, a first filler 4, and a second filler 5. The first adhesive layer 2b may include a (meth)acrylic adhesive 6. The second coating layer 3a may include a crosslinking product 3 of a (meth)acrylic binder and an aziridine crosslinking agent, the first filler 4, and the second filler 5. The second adhesive layer 3b may include a fluorinated adhesive 7.

[0143] 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.

[0144] The separator used in rechargeable lithium batteries is described above. The separator for rechargeable lithium batteries can be located between the positive and negative electrodes.

[0145] 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.

[0146] Positive electrode active material The positive electrode active material may include compounds capable of intercalating 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.

[0147] 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.

[0148] 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 Xb O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni b Co c L 1 d G e O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a CoG 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).

[0149] In the above chemical formulas, A is or includes at least one of Ni, Co, Mn, and combinations thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is or includes at least one of O, F, S, P, and combinations thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; and L 1 It may include at least one of Mn, Al, and combinations thereof.

[0150] 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 of greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. High-nickel positive electrode active materials can achieve high capacity and can be used in high-capacity, high-density rechargeable lithium batteries.

[0151] 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 amounts of binder and conductive material can each range from about 0.5 wt% to about 5 wt%.

[0152] 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.

[0153] Conductive materials can impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in rechargeable lithium batteries) and conducts electrons can be used in batteries. 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, 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.

[0154] Al can be used as the current collector, but the current collector is not limited thereto.

[0155] negative electrode The negative electrode for a rechargeable lithium battery may include a current collector and a negative electrode active material layer on the current collector. The negative electrode active material layer may include a negative electrode active material, and may further include a binder and / or a conductive material (e.g., an electrically conductive material).

[0156] For example, the negative electrode active material layer may include from about 90 wt% to about 99 wt% of the negative electrode active material, from about 0.5 wt% to about 5 wt% of the binder, and from about 0 wt% to about 5 wt% of the conductive material.

[0157] 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 capable of doping / dedoping lithium, and a transition metal oxide.

[0158] The material that can reversibly intercalate / deintercalate lithium ions may include a carbonaceous negative electrode active material (such as, for example, crystalline carbon, amorphous carbon, or a combination thereof). Crystalline carbon may be graphite (such as natural graphite or artificial graphite that is non-shaped, flaky, lamellar, spherical, or fibrous). Amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0159] The lithium metal alloy includes an alloy of lithium and a metal (such as, for example, 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).

[0160] The material capable of doping / dedoping 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 (where 0 < x ≤ 2), a Si-Q alloy (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and 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.

[0161] Silicon-carbon composites can be or include composites of silicon and amorphous carbon. According to example embodiments, the silicon-carbon composite can be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite can include secondary particles (cores) in which primary silicon particles are assembled, and an amorphous carbon coating layer (shell) on the surface of the secondary particles. Amorphous carbon can also be present between the primary silicon particles; for example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed within an amorphous carbon matrix.

[0162] Silicon-carbon composites may also include crystalline carbon. For example, a silicon-carbon composite may include a core comprising crystalline carbon and silicon particles, and an amorphous carbon coating layer on the surface of the core.

[0163] Si-based or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] When using an aqueous binder as the negative electrode binder, it may also 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.

[0168] 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.

[0169] Conductive materials can impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in rechargeable lithium batteries) and conducts electrons can be used in batteries. Non-limiting examples of conductive materials may include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; 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.

[0170] 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.

[0171] Rechargeable lithium batteries may also include an electrolyte.

[0172] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0173] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0174] 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.

[0175] 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).

[0176] 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.

[0177] 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.

[0178] Non-aqueous organic solvents can be used alone or in combination of two or more solvents.

[0179] 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.

[0180] 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 trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0181] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch, or coin-shaped batteries.

[0182] 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 5The rechargeable lithium battery 100 may include an electrode assembly 40 comprising a separator 30 between a positive electrode 10 and a negative electrode 20, and a housing 50 therein housing the electrode assembly 40. The positive electrode 10, negative electrode 20, and 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 electrode terminal 12 connected to the positive electrode lead connector 11, a negative electrode lead connector 21, and a negative electrode 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 form an electrical path for guiding the current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0183] 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.

[0184] 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.

[0185] 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 3 L 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 proceeded for 12 hours, with heating controlled to stabilize the reaction solution temperature between 65 °C and 70 °C. After cooling to room temperature, approximately 10 mL of the reaction solution was taken and the non-volatile (NV) component content was measured to be 9.8 wt% (theoretical value: 10 wt%). In addition, in the obtained poly(lithium acrylate-co-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate), 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 is 30:10:60.

[0186] Preparation Example 2 The contents of each monomer in Preparation Example 1 were varied to prepare poly(lithium acrylate-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate). 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 was 40:10:50. Approximately 10 mL of the reaction solution (reaction product) was taken and the content of the nonvolatile component was measured. The nonvolatile component content was 9.0 wt% (theoretical value: 10 wt%).

[0187] Preparation Example 3 The contents of each monomer in Preparation Example 1 were varied to prepare poly(lithium acrylate-co-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate). 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 was 65:5:30. Approximately 10 mL of the reaction solution (reaction product) was taken and the content of the nonvolatile component was measured to be 9.0 wt% (theoretical value: 10 wt%).

[0188] Preparation Example 4 The contents of each monomer in Preparation Example 1 were varied to prepare poly(lithium acrylate-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate). 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 was 40:5:55. Approximately 10 mL of the reaction solution (reaction product) was taken and the content of the nonvolatile component was measured to be 9.0 wt% (theoretical value: 10 wt%).

[0189] Preparation Example 5 The (meth)acrylic acid binder 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 second structural unit derived from 2-hydroxyethyl methacrylate to the third structural unit derived from lithium 2-acrylamido-2-methylpropanesulfonic acid was 74:26. ​​The content of non-volatile components in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0190] Preparation Example 6 The (meth)acrylic acid binder 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 first structural unit derived from lithium acrylate and the third structural unit derived from lithium 2-acrylamido-2-methylpropanesulfonic acid was 74:26. ​​The content of non-volatile components in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0191] Preparation Example 7 The (meth)acrylic acid binder 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 first structural unit derived from lithium acrylate and the second structural unit derived from 2-hydroxyethyl methacrylate was 42:58. The content of the nonvolatile component in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0192] Example 1 (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 nanofibers (boehmite, length: 100 nm to 500 nm, diameter: 10 nm to 50 nm) as the second filler were mixed in a weight ratio of 50:50 to prepare a mixture.

[0193] The (meth)acrylic binder prepared in Preparation Example 1 (containing 10 wt% in distilled water) 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.

[0194] 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% to prepare compositions for forming a first coating layer and compositions for forming a second 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.

[0195] (2) The composition for forming the first coating layer prepared as described above is applied to the first surface of a polyethylene-based membrane (thickness: 5.5 μm, CZMZ, air permeability: 110 sec / 100 cc, puncture strength: 340 kgf) as a porous substrate using a molding method, and the composition for forming the second coating layer prepared as described above is applied to the second surface using a molding method, and the membrane is dried and aged in an oven at 70°C for 16 hours to form the first coating layer and the second coating layer.

[0196] (3) The composition comprising cross-linked polymethyl methacrylate (i.e., (meth)acrylic adhesive) (Tg: 50°C) is applied onto the first coating layer prepared above using a molding method, and then dried and aged to form the first adhesive layer.

[0197] (4) A mixture of a fluorinated homopolymer with carbonyl (C=O) functional groups used as an aqueous adhesive and an IPN adhesive with vinylidene fluoride crosslinking polymer and acrylate crosslinking polymer is diluted to a solid content of 2 wt% to prepare a composition for a second adhesive layer.

[0198] (5) The composition for the second adhesive layer prepared as described above is coated onto the second coating layer prepared as described above using a molding method, dried and aged to form the second adhesive layer, thereby manufacturing a diaphragm having a first coating layer (thickness: 0.7 μm), a first adhesive layer (thickness: 0.5 μm), a second coating layer (thickness: 0.7 μm) and a second adhesive layer (thickness: 0.5 μm).

[0199] Example 2 Except that the weight ratio between the fillers in Example 1 is changed to 60:40, the diaphragm is manufactured in the same manner as in Example 1.

[0200] Examples 3 to 5 Except for changing the type of binder (i.e., the molar ratio of the first structural unit, the second structural unit, and the third structural unit) as shown in Table 1 below and using the binder instead of the binder used in Example 1, the membrane is manufactured in the same manner as in Example 1.

[0201] Comparison Example 1 The diaphragm is manufactured in the same manner as in Example 1, except that the second filler in Example 1 is not used and cross-linked PMMA is used as the adhesive binder in the second adhesive layer.

[0202] Comparison Example 2 The diaphragm is manufactured in the same manner as in Example 1, except that the second filler in Example 1 is not used.

[0203] Comparison Example 3 The diaphragm is manufactured in the same manner as in Example 1, except that the weight ratio of the filler in Example 1 is changed and the adhesive used for the second adhesive layer is used as the adhesive used for the first adhesive layer.

[0204] Compare Example 4 Except that polyvinyl alcohol is used as a binder, the diaphragm is manufactured in the same manner as in Example 1.

[0205] Compare Example 5 The membrane is manufactured in the same manner as in Example 1, except that the aziridine crosslinking agent used in Example 1 is not used.

[0206] Comparison Examples 6 to 8 Except for changing the type of binder (i.e., the molar ratio of the first structural unit, the second structural unit, and the third structural unit) as shown in Table 2 below and using the binder instead of the binder used in Preparation Example 1 of Example 1, the membrane is manufactured in the same manner as in Example 1.

[0207] Compare Example 9 The membrane was manufactured in the same manner as in Example 1, except that ethylene glycol diglycidyl ether (an epoxy crosslinking agent) was used instead of the aziridine crosslinking agent in Example 1.

[0208] Compare Example 10 The membrane was manufactured in the same manner as in Example 1, except that CARBODILITE V-50 (Nisshinbo Chemicals) was used as a carbodiimide (CDI) crosslinking agent instead of the aziridine crosslinking agent in Example 1.

[0209] Thermal shrinkage rate of electrolyte (wet heat shrinkage rate, unit: %) Manufacturing of the negative electrode: A slurry of graphite particles with an average particle size of 25 μm, used as the negative electrode active material, was prepared by mixing 97 wt% of graphite particles as the negative electrode active material, 1.5 wt% of styrene-butadiene rubber (SBR) binder, and 1.5 wt% of carboxymethyl cellulose (CMC). The mixture was then added to distilled water and stirred using a mechanical stirrer for 60 minutes. The slurry was coated onto 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, the mixture was rolled to fabricate the negative electrode.

[0210] Manufacturing of the positive electrode: 97 wt% of LiCoO2 as the positive electrode active material, 1.5 wt% of carbon black powder as the conductive material, and 1.5 wt% of 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 coated onto 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.

[0211] 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, methyl ethyl 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. Afterward, the sample was placed in an oven at 150°C for 1 hour, removed, and cooled. The dimensions of the sample's edges were then measured to calculate the shrinkage rate. The shrinkage rate can be calculated using the following mathematical formula 1.

[0212] Mathematical formula 1: Shrinkage rate = (L0-L1) / L0×100.

[0213] L0 is the initial length of the diaphragm, and L1 is the length of the diaphragm after standing at 150°C for 1 hour.

[0214] Adhesion force to the positive electrode (unit: gf / mm) The separator is attached to the positive electrode (manufactured in the same manner as in the battery manufacturing described above), with the second coating layer of the separator facing the positive electrode, and inserted into a bag. An electrolyte (1.3 M LiPF6 in a 3 / 5 / 2 (volume ratio) mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC)) is injected, and the resulting assembly is allowed to stand for 12 hours at 10 kgf / cm². 2 Up to 20 kgf / cm2 The electrode is pressed under pressure, at a temperature of 70°C to 90°C, and for a duration of 5 to 20 seconds, and then disassembled. After removing the diaphragm and positive electrode from the bag, the positive electrode and diaphragm are unfolded 180°, and the force required to separate the positive electrode from the diaphragm is measured using a tensile testing machine (Tinius Olsen, HT400).

[0215] Adhesion force to the negative electrode (unit: gf / mm) The separator is attached to the negative electrode (manufactured in the same manner as in the battery manufacturing described 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, and the resulting assembly is allowed to stand for 12 hours at 10 kgf / cm². 2 Up to 20 kgf / cm 2 The electrode 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 separate the negative electrode from the diaphragm was measured using a tensile testing machine (Tinius Olsen, HT400).

[0216] 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 test cells. The resistance (Ω) of the test cells was measured at 20°C using AC impedance spectroscopy (measurement frequency: 100 kHz).

[0217] Table 1:

[0218] Table 2:

[0219] (Table 2 continued)

[0220] As shown in Table 1 above, the example separator for rechargeable lithium batteries can provide low wet heat shrinkage, high rate performance during charging and discharging, low film resistance, and high adhesion to the electrode plates, thereby improving battery reliability.

[0221] According to one example embodiment, a separator for a rechargeable battery can improve battery capacity, safety, and lifespan by providing low wet heat shrinkage, high rate capability during charging and discharging, low film resistance, and high adhesion to the electrode plates.

[0222] 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 and a first adhesive layer are located on the first surface of the porous substrate; as well as The second coating layer and the second adhesive layer are located on the second surface of the porous substrate. Both the first and second coating layers comprise crosslinking products of an adhesive and a crosslinking agent, as well as fillers. The adhesive includes a (meth)acrylic acid adhesive, which comprises a first structural unit derived from (meth)acrylic acid, (meth)acrylates, or their salts, a second structural unit derived from (meth)acrylate hydroxyalkyl esters, and a third structural unit derived from (meth)acrylamide sulfonic acid or its salts. The crosslinking agent comprises an aziridine crosslinking agent. 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. The first adhesive layer comprises a (meth)acrylic adhesive, and The second adhesive layer comprises a fluorinated adhesive having carbonyl groups.

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

3. The diaphragm according to claim 1, wherein, The mixture, based on 100 parts by weight, comprises the first filler and the second filler in a weight ratio ranging from 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 contained 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, The crosslinking agent is included in an amount ranging from 5 to 50 parts by weight, based on 100 parts by weight of the (meth)acrylic adhesive.

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 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: 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 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 acid binder, 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 homopolymers with carbonyl functional groups and IPN adhesives of fluorinated crosslinked polymers and acrylate crosslinked polymers.

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

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