Separator for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

Examples of the present disclosure include a separator for a rechargeable lithium battery and a rechargeable lithium battery including the same. A separator for a rechargeable lithium battery includes a porous substrate and a coating layer on at least one surface of the porous substrate. The coating comprises: a heat-resistant layer comprising a binder and a filler; and an adhesive layer on the heat resistant layer and including an adhesive binder. The binder includes a (meth) acryloyl-based binder including a first structural unit derived from (meth) acrylic acid, (meth) acrylate, or a salt thereof, a second structural unit derived from hydroxyalkyl (meth) acrylate, and a third structural unit derived from (meth) acrylamide sulfonic acid or a salt thereof. The filler includes a cubic filler having a particle size D50 in the range of about 50 nm to about 250 nm. The adhesive binder includes a fluorine-based adhesive binder having a carboxyl group or a hydroxyl group.

Description

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0057500, filed on April 30, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

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

[0003] With the increasing use of batteries in electronic devices (such as mobile phones, laptops, and electric vehicles), the demand for rechargeable batteries with high energy density and high capacity has increased. Therefore, improving the performance of rechargeable lithium batteries can be beneficial.

[0004] Rechargeable lithium batteries typically include positive and negative electrodes containing active materials that allow lithium ions to be inserted into and extracted from the electrodes, as well as an electrolyte, and generate electrical energy through redox reactions that occur when lithium ions are inserted into and extracted from the positive and negative electrodes.

[0005] Rechargeable lithium batteries may also include a separator between the positive and negative electrodes. Advantageously, the separator may have low membrane resistance and high heat resistance, resulting in low thermal shrinkage. Summary of the Invention

[0006] One example embodiment includes a separator for a rechargeable lithium battery having low membrane resistance, thereby improving the capacity of the rechargeable lithium battery.

[0007] Another example embodiment includes a separator for a rechargeable lithium battery that has a significantly low thermal shrinkage rate, thereby improving the safety and lifespan of the rechargeable lithium battery.

[0008] Another example embodiment includes a rechargeable lithium battery that includes the separator for the rechargeable lithium battery.

[0009] An example embodiment is or includes a separator for a rechargeable lithium battery.

[0010] The separator for a rechargeable lithium-ion battery comprises a porous substrate and a coating on at least one surface of the porous substrate. The coating comprises: a heat-resistant layer including an adhesive and a filler; and an adhesive layer positioned on the heat-resistant layer and comprising an adhesive binder. The adhesive comprises a (meth)acryloyl-based 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 (meth)acrylate, and a third structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof. The filler comprises a generally cubic filler with a particle size D50 in the range of about 50 nm to about 250 nm. The adhesive binder comprises a fluorinated adhesive binder having a carboxyl (-COOH) or hydroxyl group.

[0011] Another example embodiment is or includes a rechargeable lithium battery.

[0012] A rechargeable lithium battery includes a positive electrode, a negative electrode, and a separator between the positive and negative electrodes for rechargeable lithium batteries. Attached Figure Description

[0013] Figure 1 SEM results of a coating comprising cubic fillers with a particle size D50 of approximately 200 nm, according to an example embodiment, are shown.

[0014] Figure 2 SEM results of a coating comprising a plate-shaped filler with a particle size D50 of approximately 300 nm, according to an example embodiment, are shown.

[0015] Figure 3 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment.

[0016] Figures 4 to 7 This is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment.

[0017] Figure 8A and Figure 8B The SEM results of the coating in the diaphragm of Example 1 are shown. Figure 8A This is the result magnified 10 times. Figure 8B This is the result magnified 20 times.

[0018] Figure 9A and Figure 9B The SEM results of the coating in the diaphragm of Comparative Example 4 are shown. Figure 9A This is the result magnified 10 times. Figure 9B This is the result magnified 20 times. Detailed Implementation

[0019] Hereinafter, exemplary embodiments of the present disclosure are described in detail. However, the embodiments are presented by way of example, and the present disclosure is not limited thereto, and is limited only by the scope of the appended claims.

[0020] Unless otherwise stated herein, when a part such as a layer, membrane, region, plate, etc., is described as being disposed "on" another part, it includes not only the case where the part is "directly" on the other part, but also the case where there are other parts in between.

[0021] Unless otherwise stated herein, the singular may also include the plural. Additionally, unless otherwise stated, the term "A or B" may indicate "including A, including B, or including both A and B".

[0022] In this specification, "combination thereof" may refer to a mixture, stack, complex, copolymer, alloy, blend, or reaction product of the components.

[0023] Unless otherwise defined herein, particle size can refer to average particle size. Alternatively, particle size refers to average particle size D50, which is the size of particles representing 50% of the cumulative volume in a particle size distribution. Average particle size D50 can be measured by methods known to those skilled in the art, and can be measured, for example, using a particle size analyzer, transmission electron microscopy (TEM) images, or scanning electron microscopy (SEM) images. Alternatively, average particle size D50 can be obtained by measuring particle size using a dynamic light scattering measuring device, performing data analysis to count the number of particles in each particle size range, and then calculating the average particle size D50 from that data. Optionally, average particle size D50 can be measured using laser diffraction. When average particle size is measured by laser diffraction, for example, it can be calculated based on a 50% particle size distribution in the measuring device by dispersing the particles to be measured in a dispersion medium, introducing the dispersion medium into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and irradiating the device with ultrasound at approximately 28 kHz output at 60 W.

[0024] In this specification, "(meth)acryloyl" refers to acryloyl and / or methacryloyl.

[0025] In the following text, unless otherwise defined, “substitution” indicates that hydrogen in a compound is substituted by a substituent, such as or including C1 to C30 alkyl, C2 to C30 alkenyl, C2 to C30 alkynyl, C6 to C30 aryl, C7 to C30 alkylaryl, C1 to C30 alkoxy, C1 to C30 heteroalkyl, C3 to C30 heteroalkylaryl, C3 to C30 cycloalkyl, C3 to C15 cycloalkenyl, C6 to C30 cycloalkynyl, C2 to C30 heterocycloalkyl, halogen (F, Cl, Br or I), hydroxyl (-OH), nitro (-NO2), amino (-NRR') (here, R and R' are both independently hydrogen or C1 to C6 alkyl), thiobetaine (-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 - (where n is a natural number from 1 to 10) (where R and R' are both independently C1 to C20 alkyl), at least one of the following: azide (-N3), amidine (-C(=NH)NH2), hydrazine (-NHNH2), hydrazone (=N(NH2)), carbamoyl (-C(O)NH2), thiol (-SH), acyl (-C(=O)R, where R represents hydrogen, C1 to C6 alkyl, C1 to C6 alkoxy or C6 to C12 aryl), carboxyl (-COOH) or a salt thereof (-C(=O)OM, where M represents an organic or inorganic cation), sulfonic acid (-SO3H) or a salt thereof (-SO3M, where M represents an organic or inorganic cation), phosphate (-PO3H2) or a salt thereof (-PO3MH or -PO3M2, where M represents an organic or inorganic cation), and combinations thereof.

[0026] In the following description, C1 to C3 alkyl groups may be or include at least one of methyl, ethyl, and propyl. C1 to C10 alkylene groups may be or include at least one of, for example, C1 to C6 alkylene groups, C1 to C5 alkylene groups, and C1 to C3 alkylene groups, and may be or include at least one of, for example, methylene, ethylene, and propylene. C3 to C20 cycloalkylene groups may be or include at least one of, for example, C3 to C10 cycloalkylene groups and C5 to C10 cycloalkylene groups, for example, cyclohexylene. C6 to C20 arylene groups may be or include, for example, C6 to C10 arylene groups, for example, phenylene. C3 to C20 heterocyclic groups may be or include, for example, C3 to C10 heterocyclic groups, for example, pyridyl.

[0027] In the following text, “heterogeneous” indicates that it includes one or more heteroatoms, such as or including at least one of N, O, S, Si and P.

[0028] Additionally, in chemical formulas, the symbol * indicates a part that is attached to the same or different atoms, groups, or structural units.

[0029] In the following text, "alkali metal" refers to an element belonging to Group 1 of the periodic table, such as or including at least one of lithium, sodium, potassium, rubidium, cesium and francium, and which may exist in a cation or neutral state.

[0030] In this specification, when describing a range of values, “X to Y” indicates “X or greater and Y or less (greater than or equal to X and less than or equal to Y)”.

[0031] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, they mean 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 that range, such as increments of 0.1%.

[0032] A separator for a rechargeable lithium-ion battery according to an example embodiment includes a porous substrate and a coating positioned on at least one surface of the porous substrate. The coating includes a heat-resistant layer and an adhesive layer. The heat-resistant layer includes an adhesive and a filler. The adhesive layer is positioned on the heat-resistant layer and includes an adhesive binder. The adhesive includes a (meth)acryloyl-based binder, comprising a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof, a second structural unit derived from a hydroxyalkyl (meth)acrylate, and a third structural unit derived from (meth)acrylamide sulfonic acid, or a salt thereof. The filler includes a generally cubic filler with a particle size D50 in the range of about 50 nm to about 250 nm. The adhesive binder includes a fluorinated adhesive binder having a carboxyl (-COOH) or hydroxyl group.

[0033] According to one example embodiment, the heat-resistant layer may be formed of or comprise a composition comprising a (meth)acryloyl-based binder and a generally cubic filler with a particle size D50 ranging from about 50 nm to about 250 nm.

[0034] The coating exhibits significantly low film resistance and low thermal shrinkage, thus providing a separator for rechargeable lithium batteries with high heat resistance and low resistance. Therefore, the lifespan and safety of rechargeable lithium batteries can be improved. The coating includes the aforementioned adhesive binder to increase the positive electrode adhesion strength, and simultaneously or concurrently includes the aforementioned (meth)acryloyl binder and the aforementioned filler, thereby providing low film resistance and permeability within the desired range, as well as the aforementioned low thermal shrinkage.

[0035] According to one example embodiment, the diaphragm may have a membrane resistance of about 1 Ω or less.

[0036] According to one example embodiment, after placing the diaphragm at about 200°C for about 1 hour, the thermal shrinkage rate of the diaphragm in each of the longitudinal direction (MD) and transverse direction (TD) can be about 5% or less.

[0037] According to one example embodiment, the diaphragm may have a positive electrode adhesion strength of about 0.75 gf / mm or greater.

[0038] According to one example embodiment, the diaphragm may have an air permeability of less than about 200 sec / 100 cc.

[0039] Membrane resistance, thermal shrinkage rate, positive electrode adhesion strength, and air permeability can be measured according to the methods described below.

[0040] coating The coating may be or may include a heat-resistant adhesive layer. The coating includes a heat-resistant layer and an adhesive layer positioned on the heat-resistant layer.

[0041] The coating includes an adhesive, and in the adhesive, the (meth)acryloyl adhesive described below may be included in an amount of about 95 wt% or more, for example, in an amount in the range of 95 wt% to 100 wt%, in the range of 99 wt% to 100 wt%, or in an amount of 100 wt%.

[0042] (Methacrylamide)-based binders can anchor fillers to porous substrates, ensuring coating adhesion to both the substrate and electrodes, and contributing to improved membrane heat resistance, permeability, and oxidation resistance. For example, (methacrylamide)-based binders can promote lithium-ion movement to reduce membrane resistance and improve ion conductivity, increase coating adhesion to both the substrate and electrodes, and enhance filler dispersion within the coating. In another example, (methacrylamide)-based binders can provide low membrane resistance to the membrane in coatings comprising fillers described below.

[0043] Compared to 100 mol% of (meth)acryloyl-based binders, the sum of the first, second, and third structural units can be about 95 mol% or more, for example, in the range of 95 mol% to 100 mol%, for example, 100 mol%. Within this range, the aforementioned effects of the diaphragm can be easily achieved.

[0044] The first structural unit is derived from at least one of (meth)acrylic acid, (meth)acrylate, or a salt thereof, and can be configured to anchor the filler to a porous matrix, provide adhesive strength to bond the coating to the porous matrix and the electrode, and contribute to improving the heat resistance and permeability of the diaphragm. For example, by having a carboxyl functional group (-C(=O)O-) in the structural unit, the first structural unit can increase the dispersibility of the coating slurry.

[0045] 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: .

[0046] The content of the first structural unit relative to 100 mol% of the binder for rechargeable lithium batteries can range from about 25 mol% to about 65 mol%, for example, from 30 mol% to 65 mol%, 30 mol% to 60 mol%, or 40 mol% to 65 mol%. The content of the first structural unit can be 25 mol%, 26 mol%, 27 mol%, 28 mol%, 29 mol%, 30 mol%, 31 mol%, 32 mol%, 33 mol%, 34 mol%, 35 mol%, 36 mol%, 37 mol%, 38 mol%, 39 mol%, 40 mol%, 41 mol%, 42 mol%, 43 mol%, 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, or 65 mol%. When the included first structural unit is within the above range, the diaphragm can exhibit low membrane resistance, desired or improved adhesion to porous substrates and electrodes, heat resistance, air permeability, and oxidation resistance.

[0047] According to an example embodiment, the first structural unit may include structural units represented by chemical formula 2 above and structural units represented by chemical formula 3 above, and in this case, the structural units represented by chemical formula 2 above and structural units represented by chemical formula 3 above 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.

[0048] According to another example embodiment, the first structural unit may consist only of structural units represented by the above chemical formula 2.

[0049] The second structural unit is derived from hydroxyalkyl (meth)acrylates and can be configured to anchor the filler to a porous matrix and provide adhesive strength, allowing the coating to bond to both the porous matrix and the electrode. For example, by having a carboxyl functional group (-C(=O)O-) in the structural unit, the second structural unit can increase the dispersibility of the coating slurry.

[0050] The second structural unit can be represented by the following chemical formula 4: Chemical formula 4: .

[0051] Compared to 100 mol% of the binder for rechargeable lithium batteries, the content of the second structural unit can range from about 1 mol% to about 20 mol% or from 5 mol% to 15 mol%. For example, the content of the second structural unit can be 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%, or 20 mol%. When the included second structural unit is within the above range, it is possible to increase the adhesion of the coating to the porous substrate and the electrode.

[0052] For example, the second structural unit may be or include structural units derived from hydroxyalkyl (meth)acrylates. Here, alkyl may be or include at least one of C1 to C20 alkyl, C1 to C10 alkyl, and C1 to C6 alkyl.

[0053] For example, hydroxyalkyl (meth)acrylates may include one or more of hydroxymethyl (meth)acrylates, 2-hydroxyethyl (meth)acrylates, 2-hydroxypropyl (meth)acrylates, 2-hydroxybutyl (meth)acrylates, 4-hydroxybutyl (meth)acrylates, and 6-hydroxyhexyl (meth)acrylates.

[0054] The third structural unit derived from (meth)acrylamide sulfonic acid or its salt can increase the likelihood of lithium ions moving in the presence of the first and second structural units, thereby reducing the membrane resistance of the separator.

[0055] By including bulk functional groups derived from (meth)acrylamide sulfonic acid or its salts, the third structural unit can enhance the heat resistance of the membrane by increasing the glass transition temperature. For example, when the third structural unit includes functional groups derived from salts of (meth)acrylamide sulfonic acid, the metal (M) can move through the third structural unit due to the substitution of the metal (M) by the sulfonic acid functional groups, thus reducing the membrane resistance.

[0056] The third structural unit can be represented by at least one of the following chemical formulas 5, 6 and 7, or a combination thereof.

[0057] Chemical formula 5: Chemical formula 6: Chemical formula 7: .

[0058] The third structural unit may include only one of the structural units represented by chemical formula 5, chemical formula 6, and chemical formula 7 above, or may include two or more of them. In one example, the third structural unit may include the structural unit represented by chemical formula 6 above, and in another example, the third structural unit may include the structural units represented by chemical formula 6 and chemical formula 7 above.

[0059] The third structural unit may be or includes, for example, a structural unit derived from (meth)acrylamide alkane sulfonic acid or a salt thereof. Here, the alkane may be or include at least one of C1 to C20 alkanes, C1 to C10 alkanes, and C1 to C6 alkanes, and the alkyl group may be or include at least one of C1 to C20 alkyl groups, C1 to C10 alkyl groups, and C1 to C6 alkyl groups. The salt refers to a salt composed of the aforementioned sulfonic acid and a desired ion. The ion may be or include, for example, an alkali metal ion, and in this case, the salt may be or include an alkali metal salt of the sulfonic acid.

[0060] For example, (meth)acrylamide alkane sulfonic acid can be or include 2-(meth)acrylamide-2-methylpropane sulfonic acid.

[0061] The third structural unit may be included in the (meth)acryloyl-based binder in an amount ranging from about 20 mol% to about 65 mol% (e.g., 30 mol% to 60 mol%), wherein the third structural unit may be in the form of 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%. The amounts of 39 mol%, 40 mol%, 41 mol%, 42 mol%, 43 mol%, 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, and 65 mol% are included in (meth)acryloyl binders. When the included third structural unit is within the above range, (meth)acryloyl binders and membranes including (meth)acryloyl binders can exhibit significantly low membrane resistance.

[0062] The descriptions of chemical formulas 1 to 7 are as follows.

[0063] R 1 To R 14 All can be independently hydrogen or include C1 to C10 alkyl groups. For example, R 1 To R 7 and R 9 To R 14 Both can be or include hydrogen or methyl; and R 8 It can be or include methyl groups.

[0064] L 1 To L 4 All 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 include or contain methylene or ethylene; and L 2 To L 4 All can be independently *-C(CH3)2-CH2-*.

[0065] 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.

[0066] 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.

[0067] A representative example of a binder for a rechargeable lithium battery according to an example embodiment is shown by the following chemical formula 8: Chemical formula 8: .

[0068] The description of chemical formula 8 above is as follows.

[0069] R 15 To R 20 All can be independently hydrogen or include C1 to C10 alkyl groups. For example, R 15 To R 17 R 19 and R 20 Both can be or include hydrogen or methyl; and R 18 It can be or include methyl.

[0070] L 5 and L 6All 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 include or contain methylene or ethylene; and L 6 It can be or include *-C(CH3)2-CH2-*.

[0071] 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.

[0072] 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.

[0073] l, m, and n can be the molar ratio of each unit, and l+m+n can be 1. For example, 0.2≤l≤0.65, 0.01≤m≤0.2 and 0.2≤n≤0.65; or 0.3≤l≤0.65, 0.01≤m≤0.2 and 0.2≤n≤0.65; or 0.3≤l≤0.6, 0.05≤m≤0.15 and 0.3≤n≤0.6.

[0074] (Methacryl)acryloyl binders may include alkali metals. Alkali metals may exist in cationic form and may be, for example, at least one of lithium, sodium, potassium, rubidium, and cesium. For example, alkali metals may be bonded to (meth)acryloyl binders and exist in the form of salts. Alkali metals can facilitate the synthesis of (meth)acryloyl binders in aqueous solvents, increase the adhesive strength of the coating, and enhance the heat resistance, permeability, and oxidation resistance of the membrane.

[0075] Alkali metals may be included in an amount ranging from about 1 wt% to about 40 wt% (e.g., 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 10 wt% to 20 wt%) of the alkali metal and (meth)acryloyl binder. For example, the (meth)acryloyl binder and alkali metal may be included in a weight ratio ranging from about 99:1 to about 60:40, from 99:1 to 70:30, from 99:1 to 80:20, or from 90:10 to 80:20.

[0076] Alkali metals may be included in an amount ranging from about 0.1 mol% to about 1.0 mol% relative to the total content of alkali metals and (meth)acryloyl-based binders. When the included alkali metals are within the above range, the coating may have desired or improved adhesive strength, and the diaphragm including the coating may exhibit desired or improved heat resistance, air permeability, and oxidation resistance.

[0077] (Methacrylamide) 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.

[0078] The weight-average molecular weight of (meth)acryloyl-based 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, 100,000 g / mol to 130,000 g / mol, or 300,000 g / mol to 900,000 g / mol. When the weight-average molecular weight of (meth)acryloyl-based adhesives meets the above ranges, they can exhibit desired or improved adhesive strength and low electrical resistance. The weight-average molecular weight can be the average molecular weight measured using gel permeation chromatography and calibrated with polystyrene.

[0079] (Methacrylamide) adhesives can be manufactured by solution polymerization.

[0080] According to one example embodiment, (meth)acryloyl-based adhesives may be included in the coating of a diaphragm in the form of a film.

[0081] The filler particle size D50 is in the range of about 50 nm to about 250 nm and includes generally cubic fillers. Fillers with the above particle size D50 range and shape can increase the bulk density in the coating and, due to their low specific surface area and low moisture content, can help reduce the thermal shrinkage rate. By including fillers, although the diaphragm includes a coating of thin thickness, the diaphragm can provide a low thermal shrinkage rate due to its high heat resistance, increase the breakdown voltage (BDV) characteristics of the diaphragm, and provide permeability within the above range.

[0082] According to one example embodiment, after placing the diaphragm at approximately 200°C for approximately 1 hour, both the MD shrinkage rate and TD shrinkage rate can be approximately 5% or less. Here, the total thickness of the coating in the diaphragm can be in the range of approximately 0.01 μm to approximately 5 μm, 0.1 μm to 3 μm, or 0.1 μm to 1.5 μm.

[0083] Figure 1 SEM results of a coating comprising approximately cubic fillers with a particle size D50 of about 200 nm, according to an example embodiment, are shown. (Refer to...) Figure 1As can be seen, by having a roughly cubic shape, the filler can be densely included in the coating, with virtually no empty spaces between them. Therefore, roughly cubic fillers with a particle size D50 of approximately 200 nm can provide a high packing density in the coating. Here, "cubic" indicates that the outer surfaces constituting the filler all have a roughly rectangular, roughly square, or a variation thereof roughly cubic shape, such as... Figure 1 As shown in the image.

[0084] on the other hand, Figure 2 SEM results are shown for a coating comprising plate-like fillers with a particle size D50 of approximately 300 nm. (Refer to...) Figure 2 It can be seen that, with Figure 1 Compared to roughly cubic fillers with a particle size D50 of about 200 nm, the fillers have relatively more empty spaces and a lower packing density in the coating.

[0085] For example, the filler may have a particle size D50 in the range of about 100 nm to about 250 nm, or 150 nm to 240 nm. For example, the filler may have a particle size D50 of 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, 205 nm, 210 nm, 215 nm, 220 nm, 225 nm, 230 nm, 235 nm, 240 nm, 245 nm, and 250 nm.

[0086] According to one example embodiment, a generally cubic filler with a particle size D50 in the range of about 50 nm to about 250 nm may be included in an amount of about 95 wt% or more (e.g., an amount in the range of 95 wt% to 100 wt%, an amount in the range of 98 wt% to 100 wt%, or an amount of 100 wt%).

[0087] According to one example embodiment, the packing material can have approximately 30m³. 2 Specific surface area per g or less, for example, in 5m³. 2 / g to 16m 2 Specific surface area within the range of / g. Within this range, the moisture content of the filler decreases, thus enabling the provision of low thermal shrinkage even at thin thicknesses. Here, "specific surface area" may refer to the Brunauer-Emmett-Teller (BET) specific surface area.

[0088] The filler may be or includes, for example, inorganic fillers, organic fillers, organic-inorganic composite fillers, or combinations thereof. Inorganic fillers may be or include ceramic materials that can increase heat resistance. Inorganic fillers may include, for example, at least one of metal oxides, quasi-metal oxides, metal fluorides, metal hydroxides, and combinations thereof. Inorganic fillers may include, for example, at least one of Al₂O₃, SiO₂, TiO₂, SnO₂, CeO₂, MgO, NiO, CaO, GaO, ZnO, ZrO₂, Y₂O₃, SrTiO₃, BaTiO₃, Mg(OH)₂, boehmite, and combinations thereof, but are not limited thereto. Organic fillers may include, but are not limited to, at least one of acrylic compounds, imide compounds, amide compounds, and combinations thereof. Organic fillers may have a core-shell structure, but are not limited thereto. For example, the filler may be or include inorganic fillers, such as ceramics (e.g., boehmite).

[0089] The filler can be included in a desired amount relative to the binder (e.g., a (meth)acryloyl binder). According to one example embodiment, the (meth)acryloyl binder and filler can be included in a mass ratio ((meth)acryloyl binder:filler) in the range of about 1:10 to about 1:50 (e.g., in the range of 1:20 to 1:30). Within these ranges, coatings with desired or improved heat resistance and low air permeability can be obtained.

[0090] The filler 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%, or 95 wt% to 99 wt%). When the included filler is within the above range, the diaphragm may exhibit desired or improved heat resistance, durability, oxidation resistance, and stability.

[0091] Due to the adhesive binder, the separator can maintain heat resistance and adhesive strength, and when the adhesive binder is included in the battery, it can improve the battery's stability and lifespan, and also improve the battery's resistance.

[0092] Adhesive adhesives are or include organic adhesives, and include fluorinated adhesive adhesives having carboxyl or hydroxyl groups. Fluorinated adhesive adhesives having carboxyl or hydroxyl groups can increase the wet bond strength of the diaphragm. The wet bond strength is described below.

[0093] According to one example embodiment, fluorinated adhesives having carboxyl or hydroxyl groups can be or include poly(vinylidene fluoride) (PVDF) adhesives having carboxyl or hydroxyl groups.

[0094] For example, PVDF adhesives include at least one structural unit derived from vinylidene fluoride and a structural unit derived from a monomer having at least one carboxyl or hydroxyl group. The structural unit derived from the monomer having at least one carboxyl or hydroxyl group can provide improved wet bond strength, durability, and breathability. The monomer having at least one carboxyl or hydroxyl group can be or include one or more of (meth)acrylic acid, itaconic acid or derivatives thereof, maleic acid or derivatives thereof, and hydroxyalkyl allyl ethers.

[0095] PVDF adhesives can also be derived from structural units of monomers that can be copolymerized with vinylidene fluoride. Copolymerizable monomers can be one or more of trichloroethylene monomers, trifluorochloroethylene monomers, trifluoroethylene monomers, hexafluoropropylene monomers, tetrafluoroethylene monomers, and ethylene monomers.

[0096] According to one example embodiment, the PVDF-based adhesive is or includes at least one of vinylidene fluoride, a monomer having a carboxyl or hydroxyl group, and a copolymer of hexafluoropropylene, and may include at least one of structural units derived from vinylidene fluoride, structural units derived from a monomer having a carboxyl or hydroxyl group, and structural units derived from hexafluoropropylene.

[0097] PVDF-based adhesives containing carboxyl or hydroxyl groups can have a glass transition temperature (Tg) in the range of about -70°C to about -20°C, and a weight-average molecular weight in the range of about 200,000 g / mol to about 3,000,000 g / mol, 200,000 g / mol to 2,000,000 g / mol, or 300,000 g / mol to 1,500,000 g / mol. When the glass transition temperature (Tg) and weight-average molecular weight are within the above ranges, the membrane can have the desired or improved adhesive strength.

[0098] According to one example embodiment, the PVDF-based adhesive may include structural units derived from vinylidene fluoride in an amount ranging from about 80 mol% to about 99 mol%, structural units derived from hexafluoropropylene in an amount ranging from about 0.5 mol% to about 10 mol%, and structural units derived from monomers having carboxyl or hydroxyl groups in an amount ranging from about 0.5 mol% to about 10 mol%.

[0099] PVDF-based adhesives can take various forms, such as or include 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. Furthermore, PVDF-based adhesives can be or include linear polymers, branched polymers, or mixtures thereof.

[0100] In PVDF-based adhesives, structural units derived from vinylidene fluoride can be included in amounts ranging from about 90 mol% to about 99.5 mol%, 93 mol% to 99 mol%, or 95 mol% to 99 mol%, and structural units derived from hexafluoropropylene can be included in amounts greater than about 0 mol% and less than or equal to about 10 mol%, for example, in amounts ranging from 0.5 mol% to 10 mol%, 1 mol% to 10 mol%, 1 mol% to 9 mol%, 2 mol% to 7 mol%, or 4 mol% to 6 mol%. Within these ranges, PVDF-based adhesives can exhibit chemical stability and desired or improved adhesion, while also exhibiting desired or improved solubility in low-boiling-point solvents. Therefore, adhesive layers can be formed using low-boiling-point solvents without any additional processing, and the reduction in permeability that may inevitably occur due to the use of high-boiling-point solvents can be reduced or prevented. The low-boiling-point solvent may be, for example, a solvent with a boiling point of about 80°C or lower, and may include, for example, at least one of acetone, methyl ethyl ketone, ethyl isobutyl ketone, tetrahydrofuran, dimethylformaldehyde, cyclohexane and mixtures thereof, but is not limited thereto.

[0101] PVDF adhesives containing carboxyl or hydroxyl groups can have a crystallinity of about 40% to about 65%, for example, 45% to 60%, or 50% to 55%. In this case, the adhesive can exhibit the desired or improved bond strength. The crystallinity of PVDF adhesives containing carboxyl or hydroxyl groups can be higher than that of PVDF adhesives without carboxyl and hydroxyl groups, as described below.

[0102] PVDF-based adhesives with carboxyl or hydroxyl groups can have melting points of about 150°C or higher, for example, in the range of 150°C to 200°C.

[0103] Adhesive adhesives are or include organic adhesives, and may also include fluorinated adhesives (e.g., PVDF-based) that do not have carboxyl and hydroxyl groups. Fluorinated adhesives that do not have carboxyl and hydroxyl groups can increase the dry bond strength of the adhesive layer. The dry bond strength is described below.

[0104] Fluorinated adhesives that do not have carboxyl and hydroxyl groups may include structural units derived from vinylidene fluoride and structural units derived from copolymerizable monomers. Copolymerizable monomers may be one or more of trichloroethylene monomers, trifluorochloroethylene monomers, trifluoroethylene monomers, hexafluoropropylene monomers, tetrafluoroethylene monomers, and ethylene monomers.

[0105] Fluorine-based adhesives without carboxyl and hydroxyl groups can take various forms, such as alternating polymers, random polymers, or grafted polymers. Fluorine-based adhesives without carboxyl and hydroxyl groups are or include linear polymers, branched polymers, or mixtures thereof, and can be or include polymers with more branches than fluorine-based adhesives with carboxyl or hydroxyl groups.

[0106] Fluorine adhesives that do not have carboxyl and hydroxyl groups may include structural units derived from vinylidene fluoride and structural units derived from hexafluoropropylene.

[0107] The structural units derived from vinylidene fluoride, relative to the adhesive, can be included in an amount ranging from about 90 mol% to about 99.5 mol%, 93 mol% to 99 mol%, or 95 mol% to 99 mol%. When the included structural units derived from vinylidene fluoride are within the above ranges, the adhesive can ensure desired or improved adhesive strength, electrolyte impregnation, etc.

[0108] The structural units derived from hexafluoropropylene, relative to the binder, can be included in an amount greater than about 0 mol% and less than or equal to about 10 mol%, for example, in the range of 0.5 mol% to 10 mol%, 1 mol% to 9 mol%, 2 mol% to 8 mol%, 3 mol% to 7 mol%, or 4 mol% to 6 mol%. When the included structural units derived from hexafluoropropylene are within the above ranges, the binder can exhibit chemical stability and desired or improved adhesion, while also exhibiting desired or improved solubility in low-boiling-point solvents. Therefore, the adhesive layer can be formed using low-boiling-point solvents without substantially any additional processing, and the reduction in permeability that may inevitably occur due to the use of high-boiling-point solvents can be reduced or prevented.

[0109] Fluorinated adhesives lacking carboxyl and hydroxyl groups can have a glass transition temperature (Tg) in the range of about -70°C to about 20°C, and a weight-average molecular weight in the range of about 800,000 g / mol to about 2,000,000 g / mol or 800,000 g / mol to 1,900,000 g / mol. When a fluorinated adhesive lacking carboxyl and hydroxyl groups has a weight-average molecular weight within the above ranges, the adhesive layer including this fluorinated adhesive can exhibit improved wet and dry bond strength. The weight-average molecular weight can be an average molecular weight measured using gel permeation chromatography and calibrated for polystyrene.

[0110] Fluorine-based adhesives without carboxyl and hydroxyl groups have a crystallinity in the range of about 35% to about 45% (e.g., 35% to 40%). When fluorine-based adhesives without carboxyl and hydroxyl groups have a crystallinity within the above range, adhesive layers containing fluorine-based adhesives without carboxyl and hydroxyl groups exhibit desired or improved dry bond strength. The crystallinity of fluorine-based adhesives without carboxyl and hydroxyl groups may be lower than that of fluorine-based adhesives with hydroxyl or carboxyl groups.

[0111] Fluorine-based adhesives (e.g., PVDF-based) that do not have carboxyl and hydroxyl groups may have a melting point of about 150°C or higher, for example, in the range of about 150°C to 200°C.

[0112] Both types of fluorinated adhesives can be prepared by various known methods, such as emulsion polymerization, suspension polymerization, bulk polymerization, or solution polymerization. For example, both types of fluorinated adhesives can be prepared by emulsion polymerization.

[0113] Wet bond strength and dry bond strength are measured using the following method: The battery is manufactured using the following method, and the wet bond strength and dry bond strength are measured.

[0114] Battery manufacturing Manufacturing of the negative electrode: A negative electrode active material slurry was prepared by mixing 97 wt% graphite particles with an average particle size of 25 μm, 1.5 wt% styrene-butadiene rubber (SBR) binder, and 1.5 wt% carboxymethyl cellulose (CMC), then adding distilled water and stirring with a mechanical stirrer for 60 minutes. The slurry was then coated onto a 10 μm thick copper current collector using a doctor blade, dried in a 100°C hot air dryer for 0.5 hours, and then dried again under vacuum and 120°C for 4 hours. Finally, the mixture was rolled to fabricate the negative electrode.

[0115] Manufacturing of the positive electrode: A slurry for the positive electrode active material was prepared by mixing 97 wt% LiCoO2, 1.5 wt% carbon black powder as a conductive additive, and 1.5 wt% PVDF, adding the mixture to an N-methyl-2-pyrrolidone solvent, and then stirring the mixture for 30 minutes using a mechanical stirrer. The slurry was then coated onto a 20 μm thick aluminum current collector using a doctor blade, dried in a 100°C hot air dryer for 0.5 hours, dried again under vacuum and 120°C for 4 hours, and then rolled to fabricate the positive electrode.

[0116] Electrode assembly core: The electrode core was prepared by inserting a diaphragm between the positive and negative electrodes manufactured above and winding the diaphragm. The electrode core was inserted into a bag, an electrolyte was injected into it, and the bag was vacuum-sealed. As the electrolyte, a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (volume ratio 3:5:2) containing 1.3 M LiPF6 was prepared.

[0117] By applying 11.7 kgf / cm 2 The rechargeable lithium battery is manufactured by pressing the electrode core inserted into the bag under pressure at a temperature of 80°C for 3 minutes.

[0118] Wet bond strength: Wet adhesion strength is the electrode adhesion strength (flexural strength) of the separator in a lithium battery, measured using the three-point bending method. Lithium batteries are constructed by immersing the battery assembly, including the positive electrode, negative electrode, and separator, in an electrolyte solution, and the wet adhesion strength is measured at 10 kgf / cm². 2 Up to 20 kgf / cm 2 It is obtained by extruding the battery assembly under pressure, temperature of 70°C to 90°C and time of 1 to 5 minutes.

[0119] As the electrolyte, 1.3 M LiPF6 was dissolved in a mixed solvent of EC / EMC / DEC (volume ratio 3 / 5 / 2). At 80 °C, the electrolyte was prepared at 11.7 kgf / cm³. 2 The pressure squeezes the battery assembly, which is in the core state and inserted into the bag, for 180 seconds.

[0120] Dry bond strength: Dry bond strength is the electrode bond strength (flexural strength) of the separator in a lithium battery, measured using the three-point bending method. Lithium batteries achieve a dry bond strength of 10 kgf / cm. 2 Up to 20 kgf / cm 2 It is obtained by extruding a battery assembly, including a positive electrode, a negative electrode, and a separator, under conditions of pressure, temperature of 70°C to 90°C, and time of 5 to 20 seconds.

[0121] A battery assembly in a core state is prepared by inserting a separator between the positive and negative electrodes manufactured as described above, and then winding the separator. The battery assembly is inserted into a bag, electrolyte is injected into it, and the bag is vacuum-sealed.

[0122] At a temperature of 85℃, using 11.7 kgf / cm 2 The pressure was applied to the battery assembly inserted into the bag for 10 seconds, and the dry bond strength was evaluated using the electrode adhesion strength (bending strength) of the separator obtained using the 3-point bending method.

[0123] The electrode adhesion strength (flexural strength) of the separator was measured using the 3-point bending (INSTRON) method to determine the adhesion strength between the active material layer of the positive electrode and the separator. A pouch cell that had undergone 0.1C charge / discharge was compressed using a fixture at a speed of 5 mm / min, and the maximum bending strength (N, MPa) from zero to 5 mm was measured. The evaluation conditions for the 3-point bending (INSTRON) method are as follows.

[0124] Lower span width: 27mm, lower span dimension: 5mm Upper clamp size: 5mm, load sensor: 1000N The adhesive binder can be included in the range of about 1 wt% to about 20 wt% (e.g., 5 wt% to 20 wt%, or 5 wt% to 15 wt%) of the total coating amount. Within this range, because a strong bond with the electrode is achieved and the battery resistance does not increase, there is no limitation on the capacity.

[0125] The coating may have a total thickness in the range of about 0.01 μm to about 20 μm, and may have a thickness in the range of 0.01 μm to 5 μm, 0.1 μm to 3 μm or 0.1 μm to 1.5 μm.

[0126] According to one example embodiment, the total thickness of the heat-resistant layer can be in the range of about 0.8 μm to about 2.5 μm (e.g., 0.9 μm to 2.2 μm or 1.0 μm to 2.0 μm).

[0127] According to one example embodiment, the total thickness of the adhesive layer can be in the range of about 0.5 μm to about 2.0 μm (e.g., 0.5 μm to 1.5 μm).

[0128] The ratio of coating thickness to the thickness of the porous substrate can range from about 0.05 to about 0.5 (e.g., 0.05 to 0.4, 0.05 to 0.3, or 0.1 to 0.2). Within this range, the diaphragm can exhibit desired or improved permeability, heat resistance, adhesive strength, etc. Here, when the coating is formed on only one surface of the porous substrate, "coating thickness" refers to the thickness of one coating, and when the coating is formed on both surfaces of the porous substrate, "coating thickness" refers to the total thickness of the two coatings.

[0129] Porous matrix A porous matrix can be or includes a matrix having multiple pores and is typically included in electrochemical devices. A porous matrix can be or includes a polymer membrane formed from or containing any polymer, such as or including at least one of polyolefins (such as polyethylene or polypropylene), polyesters (such as polyethylene terephthalate or polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and Teflon (polytetrafluoroethylene), or copolymers or mixtures of two or more of these polymers.

[0130] The porous matrix can be or includes, for example, a polyolefin matrix comprising polyolefins, and the polyolefin matrix can have desired or improved shut-off functionality, thereby contributing to improved battery safety. The polyolefin matrix can be or includes at least one of, for example, polyethylene monolayers, polypropylene monolayers, polyethylene / polypropylene bilayers, polypropylene / polypropylene / polypropylene trilayers, and polyethylene / polypropylene / polypropylene trilayers. Furthermore, in addition to olefin resins, polyolefin resins can also include non-olefin resins, or copolymers comprising olefin monomers and non-olefin monomers.

[0131] The porous matrix 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).

[0132] A separator for a rechargeable lithium battery according to an example embodiment can exhibit desired or improved air permeability and can have an air permeability value, for example, less than about 200 sec / 100cc (e.g., 190 sec / 100cc or less, or 180 sec / 100cc or less). For example, the separator can have an air permeability value of less than 40 sec / 100cc·1μm per unit thickness (e.g., 30 sec / 100cc·1μm or less, or 25 sec / 100cc·1μm or less). Here, air permeability refers to the time (in seconds) it takes for 100cc of air to pass through a unit thickness of the separator. The air permeability per unit thickness can be obtained by measuring the air permeability of the total thickness of the separator and dividing the air permeability by the thickness. The air permeability can be obtained by measuring the time (in seconds) it takes for 100cc of air to pass through the separator using an air permeability measuring device (EG01-55-1MR, Asahi Seiko Co., Ltd.).

[0133] A separator for a rechargeable battery according to an example embodiment can be formed by the following steps: applying a composition for forming a heat-resistant layer to one or both surfaces of a porous substrate, drying the composition to form a heat-resistant layer, applying an adhesive to one surface of the heat-resistant layer, and drying the adhesive to form an adhesive layer. Drying can be performed using conventional methods known to those skilled in the art.

[0134] Figure 3 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment.

[0135] Reference Figure 3 An example separator for a rechargeable lithium battery includes a porous substrate 1 and coatings 2 on two surfaces of the porous substrate 1. Coating 2 may include a heat-resistant layer 5 comprising a (meth)acryloyl-based binder 4 and a filler 3, and an adhesive layer 7 on the heat-resistant layer 5 comprising an adhesive binder 6.

[0136] 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.

[0137] 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.

[0138] 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 a positive electrode active material and may further include a binder and / or a conductive material.

[0139] For example, the positive electrode may further include additives that can be configured as a sacrificial positive electrode.

[0140] Positive electrode active material The positive electrode active material may include compounds capable of intercalating and deintercalating lithium (lithiation intercalation compounds). For example, at least one of the composite oxides of lithium and metals such as or including at least one of cobalt, manganese, nickel and combinations thereof may be used.

[0141] 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.

[0142] As an example, the following compounds, represented by any of the following chemical formulas, can be used: Li a A1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni b Co c L 1 d G e O2 (0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8, and 0.001≤b≤0.1); Li a CoG 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).

[0143] 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 is or includes at least one of Mn, Al and combinations thereof.

[0144] 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 nickel content of the high-nickel positive electrode active material is 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 exhibit high capacity and can be used in high-capacity, high-density rechargeable lithium batteries.

[0145] 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%.

[0146] The binder is configured to adhere the positive electrode active material particles to each other and to adhere the positive electrode active material to the current collector. As a non-limiting example, examples of the binder may include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, 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.

[0147] Conductive materials may be included to impart conductivity (e.g., electrical conductivity) to the electrodes. The battery may include any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons. 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, 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.

[0148] It may include Al as a current collector, but is not limited thereto.

[0149] 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 also include a binder and / or a conductive material (e.g., an electrically conductive material).

[0150] For example, the negative electrode active material layer may include from about 90 wt% to about 99 wt% of a negative electrode active material, from about 0.5 wt% to about 5 wt% of a binder, and from about 0 wt% to about 5 wt% of a conductive material.

[0151] Negative electrode active material The negative electrode active material may include at least one of a material that reversibly embeds / extracts lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, and a transition metal oxide.

[0152] The material that reversibly embeds / extracts lithium ions may include a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof as an example. The crystalline carbon may be or include graphite, such as natural graphite or artificial graphite that is non-shaped, substantially flaky, lamellar, substantially spherical, or fibrous. The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0153] 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.

[0154] The material capable of doping / dedoping lithium may be or include at least one of a Si-based negative electrode active material and a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (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.

[0155] 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 may include secondary particles (cores) in which primary silicon particles aggregate and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon may also be present between the primary silicon particles, and, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed within an amorphous carbon matrix.

[0156] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core and an amorphous carbon coating on the surface of the core, the core comprising crystalline carbon and silicon particles.

[0157] Si-type or Sn-type negative electrode active materials can be included together with carbon-type negative electrode active materials.

[0158] The binder can be configured to adhere the negative electrode active material particles to each other and to adhere the negative electrode active material to the current collector. The binder may include non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0159] 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.

[0160] The waterborne adhesive may be or include at least one of the following: 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.

[0161] When an aqueous binder is included as a 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 methylcellulose, methylcellulose, and their alkali metal salts. The alkali metal may include at least one of Na, K, and Li.

[0162] Dry adhesives can be or include fibrous polymeric materials. For example, dry adhesives can be or include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0163] Conductive materials may be included to impart conductivity (e.g., electrical conductivity) to the electrodes. The battery may include any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons. 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, 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.

[0164] 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 conductive metal, and combinations thereof.

[0165] Rechargeable lithium batteries may also include an electrolyte.

[0166] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0167] Non-aqueous organic solvents can be constructed as media for transporting ions that participate in the electrochemical reactions of a battery.

[0168] 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.

[0169] 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 (EMC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC).

[0170] 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.

[0171] 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 at least one of ethanol, isopropanol, etc., and aprotic solvents may include: 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.

[0172] Non-aqueous organic solvents may be included alone or in combination of two or more solvents.

[0173] For example, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0174] Lithium salts dissolved in organic solvents are configured to supply lithium ions in batteries to enable basic operation of rechargeable lithium batteries and improve 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 SO2 (where x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), lithium difluorobis(oxalate)borate (LiDFBOB), and lithium bis(oxalate)borate (LiBOB).

[0175] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch, or coin-shaped batteries.

[0176] Figures 4 to 7 This is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment. Figure 4 A cylindrical battery is shown. Figure 5 A prismatic battery is shown. Figure 6 and Figure 7 A pouch-type battery is shown. (See reference) Figures 4 to 7The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50 therein, the electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The rechargeable lithium battery 100 may include a sealing member 60 for sealing the housing 50, such as... Figure 4 As shown. In Figure 5 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 6 and Figure 7 As shown, the rechargeable lithium battery 100 may include Figure 7 The electrode terminal 70 shown (or for example) Figure 6 The positive electrode terminal 71 and negative electrode terminal 72 shown (electrode terminals 70 / 71 / 72) form an electrical path for guiding the current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0177] 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 electrical devices.

[0178] Examples and comparative examples of this disclosure are described below. However, the following examples are merely exemplary embodiments of this disclosure, and this disclosure is not limited to these examples.

[0179] Preparation Example 1 In a 3L four-necked separable flask equipped with a stirrer, thermometer, and cooling tube, 1249.72g of distilled water, 113.4g of a 20% lithium hydroxide aqueous solution (equivalent to 1.05 equivalences of acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid), acrylic acid (AA, 0.40 mol), 2-hydroxyethyl methacrylate (HEMA, 0.10 mol), 2-acrylamide-2-methylpropanesulfonic acid (AMPS, 0.5 mol), and ammonium persulfate (0.001 mol) were added. The following process was repeated three times: the internal pressure was reduced to 10 cmHg using a diaphragm pump, and then restored to atmospheric pressure using nitrogen. 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, the non-volatile (NV) component in approximately 10 mL of the reaction solution was measured, and the result was 9.8 wt% (theoretical value: 10 wt%). Furthermore, in the poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt obtained here, 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-acrylamide-2-methylpropanesulfonic acid is 40:10:50.

[0180] Preparation Example 2 Lithium poly(acrylate-co-2-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) was prepared by varying the content of each monomer in Preparation Example 1. The molar ratio of lithium acrylate, 2-hydroxyethyl methacrylate, and lithium 2-acrylamide-2-methylpropanesulfonic acid was 30:10:60. The non-volatile component in approximately 10 mL of the reaction solution (reaction product) was measured, and the result was 9.0 wt% (theoretical value: 10 wt%).

[0181] Preparation Example 3 (Methacrylamide)-based adhesives were prepared in the same manner as in Preparation Example 1, except that acrylic acid and 2-hydroxyethyl methacrylate (HEMA) were used, and 2-acrylamido-2-methylpropanesulfonic acid was not used. The molar ratio of lithium acrylate to 2-hydroxyethyl methacrylate was 42:58. The non-volatile component in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0182] Preparation Example 4 (Methacryl)acryloyl-based adhesives were 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 lithium acrylate to lithium 2-acrylamido-2-methylpropanesulfonic acid was 74:26. ​​The non-volatile component in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0183] Preparation Example 5 (Methacrylamide)-based adhesives were 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 2-hydroxyethyl methacrylate to lithium 2-acrylamido-2-methylpropanesulfonic acid was 74:26. ​​The non-volatile component in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0184] Table 1 below shows the molar ratios of the monomers in the (meth)acryloyl binders prepared in Preparation Examples 1 to 5.

[0185] Table 1:

[0186] Example 1 The dispersion was prepared by the following steps: The (meth)acryloyl binder (10 wt%, in distilled water) prepared in Preparation Example 1 and boehmite (particle size D50: 200 nm, cubic, Eston Ltd. BG200) as filler were mixed at a mass ratio of 1:20 based on solids content ((meth)acryloyl binder: filler = 1 part by weight: 20 parts by weight). This mixture was added to an aqueous solvent, and then the mixture was milled at 25°C for 30 minutes using a bead mill to disperse it. A composition for forming a heat-resistant layer was prepared by adding water to the dispersion to bring the total solids content to 20 wt%.

[0187] The heat-resistant layer is formed by the following steps: using a molding method, the composition for forming the heat-resistant layer is applied to both surfaces of a polyethylene film (thickness: 5.5 μm, CZMZ, air permeability: 110 sec / 100 cc, puncture strength: 360 kgf) serving as a porous substrate with a total thickness of 1 μm, and the composition is dried in an oven at 70°C for 10 minutes.

[0188] The first adhesive solution was prepared by the following steps: 8 wt% of a carboxyl-containing PVDF-hexafluoropropylene adhesive 75130 (weight average molecular weight 1,300,000 g / mol, PVDF:hexafluoropropylene molar ratio 98:2, including acrylic acid as a monomer, glass transition temperature -30°C, melting point 154°C, crystallinity 53%) was added to acetone as an adhesive and stirred at 40°C for 3 hours. The second adhesive solution was prepared by the following steps: 8 wt% of a carboxyl-free PVDF-hexafluoropropylene adhesive LBG (weight average molecular weight 1,300,000 g / mol, PVDF:hexafluoropropylene molar ratio 98:2, excluding acrylic acid as a monomer, glass transition temperature -30°C, melting point 151°C, crystallinity 40%) was added to acetone as an adhesive and stirred at 40°C for 3 hours. A composition for an adhesive layer was prepared by mixing a first adhesive solution and a second adhesive solution in a weight ratio of 5:5.

[0189] The heat-resistant layer was directly coated on both surfaces at a speed of 80 mm / min using the prepared composition for the adhesive layer, and then the absolute water vapor content (average) was 14 g / m. 3 The membrane is dried at 60°C in the presence of [a substance] to form an adhesive layer with a total thickness of 0.7 μm, thereby manufacturing a separator for rechargeable lithium batteries.

[0190] Examples 2 to 5 The separator for rechargeable lithium batteries is manufactured in the same manner as in Example 1, except that boehmite is included as a filler, as shown in Table 2 below, but the particle size D50 is changed, the type of (meth)acryloyl binder is changed, or the thickness of the heat-resistant layer is changed.

[0191] Comparison Examples 1 to 6 The separator for rechargeable lithium batteries is manufactured in the same manner as in Example 1, except that boehmite is included as a filler, as shown in Table 2 below, but the particle size D50 or the type of (meth)acryloyl binder is changed.

[0192] In Comparative Example 4, boehmite (particle size D50: 300 nm, cubic shape) was included as a filler. In Comparative Example 5, boehmite (particle size D50: 30 nm, cubic shape) was included as a filler. In Comparative Example 6, an acrylic adhesive was included as the adhesive.

[0193] Battery manufacturing Manufacturing of the negative electrode: The negative electrode active material slurry was prepared by the following steps: 97 wt% of graphite particles with an average particle size of 25 μm, used as the negative electrode active material, 1.5 wt% of SBR (styrene-butadiene rubber) binder, and 1.5 wt% of CMC (carboxymethyl cellulose) were mixed, then distilled water was added, and the mixture was stirred using a mechanical stirrer for 60 minutes. The slurry was then 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 and at 120°C for 4 hours. Finally, the mixture was rolled to fabricate the negative electrode.

[0194] Manufacturing of the positive electrode: The positive electrode active material slurry was prepared by the following steps: 97 wt% of LiCoO2 as the positive electrode active material, 1.5 wt% of carbon black powder as a conductive additive, and 1.5 wt% of PVDF were mixed. The mixture was then added to an N-methyl-2-pyrrolidone solvent, and stirred for 30 minutes using a mechanical stirrer. The slurry was coated onto a 20 μm thick aluminum current collector using a doctor blade, dried in a 100°C hot air dryer for 0.5 hours, and then dried again under vacuum and 120°C for 4 hours. Finally, it was rolled to fabricate the positive electrode.

[0195] Manufacturing of the electrode assembly core: The electrode assembly core was prepared by inserting a diaphragm obtained according to the example and comparative example between the positive and negative electrodes manufactured as described above, and then winding the diaphragm. The core was inserted into a bag, an electrolyte was injected into it, and the bag was vacuum-sealed. As the electrolyte, a mixed solvent of EC, EMC, and DEC (volume ratio 3:5:2) containing 1.3 M LiPF6 was used. The electrolyte was prepared by applying 11.7 kgf / cm³ of electrolyte. 2 The rechargeable lithium battery is manufactured by pressing the electrode core inserted into the bag under pressure at a temperature of 80°C for 3 minutes.

[0196] Figure 8A and Figure 8B The SEM results of the coating in the diaphragm of Example 1 are shown. Figure 8A This is the result magnified 10 times. Figure 8B This is the result magnified 20 times. Figure 9A and Figure 9B The SEM results of the coating in the diaphragm of Comparative Example 4 are shown. Figure 9A This is the result magnified 10 times. Figure 9B This is the result magnified 20 times. It can be seen that... Figure 9A and Figure 9B There are uncoated areas, however, in Figure 8A and Figure 8B There are no uncoated areas.

[0197] Thermal shrinkage rate (%) after being placed at 200℃ for 1 hour. Samples were prepared by cutting the separators for rechargeable lithium batteries of the example and comparative examples into 8cm × 8cm dimensions. A 5cm × 5cm square was drawn on the surface of the sample, and the sample was placed between pieces of paper or alumina powder. The sample was then placed in an oven at 200°C for 1 hour. After removing the sample, the side dimensions of the drawn square were measured, and the shrinkage rate in each of the mechanical direction (MD) and transverse direction (TD) was calculated. The shrinkage rate was calculated according to Equation 1 below.

[0198] Equation 1: Shrinkage rate (%) = (L0-L1) / L0×100.

[0199] L0 represents the initial length of the diaphragm, and L1 represents the length of the diaphragm after being placed at 200°C for 1 hour.

[0200] Coating density (unit: g / cm³) 3 ) The thickness (a) and unit weight (b) of the porous substrate were measured before coating with the composition used to form the heat-resistant layer. The porous substrate was then coated with the composition for forming the heat-resistant layer and an adhesive binder, and dried in an oven at 70°C for 10 minutes. The total thickness (c) and unit weight (d) were then measured, and the coating thickness (e) and coating weight (f) were calculated. The coating density was calculated by dividing the coating weight by the coating thickness.

[0201] Coating thickness (e) = ca Coating weight (f) = db Coating density = f / e Breathability (unit: sec / 100cc) Air permeability is measured by measuring the time (in seconds) it takes for 100cc of air to pass through the diaphragm using a measuring device (EG01-55-1MR, Asahi Seiko Co., Ltd.).

[0202] Air permeability measuring device setting conditions: Measured pressure: 0.5 kg / cm 2 Cylinder pressure: 2.5 kg / cm² 2 Time setting: 10 seconds Positive electrode adhesion strength (unit: gf / mm) The separators of the example and comparative examples were cut to a width of 25 mm and a length of 80 mm, and the polyethylene nonwoven fabric was also cut to the same dimensions. The manufactured electrodes were cut to a width of 30 mm and a length of 80 mm. The cell was manufactured by placing the electrodes on one surface of each separator and placing the polyethylene nonwoven fabric and electrodes on the other surface of each separator.

[0203] The electrolyte (a mixed solvent containing 1.3 M LiPF6 in EC / EMC / DEC (volume ratio 3 / 5 / 2)) was injected into a 10cm × 10cm bag, and the diaphragm and positive electrode were immersed for 12 hours. Afterward, the bag was removed and subjected to a 300 kgf / cm² electrolyte concentration. 2 Under the conditions of bonding at 80°C for 1 hour. After removing the diaphragm and positive electrode from the bag, the positive electrode and diaphragm were unfolded to 180°, and the force required to peel the positive electrode from the diaphragm was measured using a tension measuring device (HT400, Tinius Olsen Ltd.).

[0204] Membrane resistance (unit: Ω) The membrane resistance was evaluated using electrochemical impedance spectroscopy (EIS). Membranes fabricated in the example and comparative examples were impregnated with an electrolyte (a mixed solvent containing 1.5 M LiPF6 in ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 2 / 1 / 7)), assembled onto aluminum foil electrodes with attached lead terminals, and sealed in an aluminum cask to create test cells. The resistance (Ω) of the test cells was measured at 20°C using alternating current impedance spectroscopy (measurement frequency 100 kHz).

[0205] Table 2:

[0206] As shown in Table 2 above, the example separator for rechargeable lithium batteries exhibits low membrane resistance and low thermal shrinkage, and provides high adhesive strength and low air permeability.

[0207] According to one example embodiment, the separator for a rechargeable lithium battery can have low film resistance and low thermal shrinkage, thereby improving the battery's capacity, safety, and lifespan.

[0208] Although exemplary embodiments of the present disclosure have been described above, the present disclosure is not limited thereto, and modifications may be made in any form within the scope of the claims, the detailed description of the present disclosure, and the accompanying drawings, and such modifications also fall within the scope of the present disclosure.

Claims

1. A separator for a rechargeable lithium battery, the separator comprising: Porous matrix; as well as A coating is applied to at least one surface of the porous substrate. The coating comprises: a heat-resistant layer including an adhesive and a filler; and an adhesive layer on the heat-resistant layer, including an adhesive binder. The adhesive comprises a (meth)acryloyl-based adhesive, which includes a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or their salts, a second structural unit derived from a hydroxyalkyl (meth)acrylate, and a third structural unit derived from (meth)acrylamide sulfonic acid or its salts. The packing material comprises cubic packing material with a particle size D50 in the range of 50 nm to 250 nm, and The adhesive includes fluorinated adhesives having carboxyl or hydroxyl groups.

2. The diaphragm according to claim 1, wherein, The mass ratio of the (meth)acryloyl-based binder to the filler is in the range of 1:10 to 1:

50.

3. The diaphragm according to claim 1, wherein, The packing has a 30m 2 / g or smaller specific surface area.

4. The diaphragm according to claim 1, wherein, The filler includes boehmite.

5. The diaphragm according to claim 1, wherein: The first structural unit is represented by at least one of chemical formula 1, chemical formula 2, and chemical formula 3: Chemical Formula 1: Chemical Formula 2: Chemical Formula 3: ； The second structural unit is represented by chemical formula 4: Chemical formula 4: ； The third structural unit is represented by at least one of chemical formulas 5, 6, and 7: Chemical formula 5: Chemical formula 6: Chemical formula 7: ； and In chemical formulas 1 to 7 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.

6. The diaphragm according to claim 1, wherein, Relative to 100 mol% of the (meth)acryloyl-based binder: The content of the first structural unit is in the range of 25 mol% to 65 mol%. The content of the second structural unit is in the range of 1 mol% to 20 mol%, and The content of the third structural unit is in the range of 20 mol% to 65 mol%.

7. The diaphragm according to claim 1, wherein, The (meth)acryloyl-based adhesive is represented by chemical formula 8: Chemical formula 8: ,and 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 heterocyclic group. Both e and f are independent integers in the range of 0 to 2. M includes alkali metals, and l, m, and n are the molar ratios of each structural unit, where l + m + n = 1.

8. The diaphragm according to claim 1, wherein, The adhesive includes poly(vinylidene fluoride) adhesives, which include structural units derived from vinylidene fluoride and structural units derived from monomers having at least one carboxyl or hydroxyl group.

9. The diaphragm according to claim 8, wherein, The poly(vinylidene fluoride) adhesives also include structural units derived from one or more of the following: trichloroethylene monomer, trifluorochloroethylene monomer, trifluoroethylene monomer, hexafluoropropylene monomer, tetrafluoroethylene monomer, and ethylene monomer.

10. The diaphragm according to claim 1, wherein, The total thickness of the coating is in the range of 0.01 μm to 20 μm.

11. A rechargeable lithium battery, said rechargeable lithium battery comprising: Positive electrode; negative electrode; as well as The separator for a rechargeable lithium battery according to any one of claims 1 to 10, between the positive electrode and the negative electrode.

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