Separator for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

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 layer includes a binder, the binder including a copolymer, the copolymer including: a first structural unit including a unit derived from an aromatic unsaturated monomer; a second structural unit derived from a (meth) acrylic monomer containing an alkyl group having 4 or more carbon atoms in the main chain of the ester moiety; and the third structural unit is derived from a sulfonic acid group-containing monomer. The first structural unit is included in an amount in a range of about 5 mol% to about 80 mol%, the second structural unit is included in an amount in a range of about 10 mol% to about 40 mol%, and the third structural unit is included in an amount in a range of about 5 mol% to about 80 mol%, based on 100 mol% of the copolymer.

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0157089, filed on November 7, 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 lithium battery and a rechargeable lithium battery including the separator. Background Technology

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

[0004] Rechargeable lithium batteries typically include a positive electrode and a negative electrode containing active materials capable of inserting and deintercalating lithium ions, and generate electrical energy through redox reactions that occur when lithium ions are deintercalated from the positive electrode and inserted into the negative electrode or deintercalated from the negative electrode and inserted into the positive electrode. Summary of the Invention

[0005] This disclosure describes a separator for rechargeable lithium batteries that improves the capacity of rechargeable lithium batteries due to its low membrane resistance.

[0006] This disclosure also describes a separator for rechargeable lithium batteries that improves the safety and lifespan of rechargeable lithium batteries due to its high adhesion.

[0007] This disclosure also describes a separator for rechargeable lithium batteries that improves resistance due to its high electrolyte wettability and improved flexibility.

[0008] This disclosure also describes a separator for rechargeable lithium batteries that exhibits high capacity retention and low DC-IR variation at both room temperature and high temperature.

[0009] This disclosure also describes a rechargeable lithium battery including the separator described above for a rechargeable lithium battery.

[0010] According to an aspect of this disclosure, a separator for a rechargeable lithium battery is described.

[0011] A separator for a rechargeable lithium-ion battery includes a porous substrate and a coating layer on at least one surface of the porous substrate. The coating layer includes a binder comprising a copolymer comprising: a first structural unit including a unit derived from an aromatic unsaturated monomer; a second structural unit derived from a (meth)acrylic acid monomer having an alkyl group having four or more carbon atoms in the main chain of the ester moiety; and a third structural unit derived from a sulfonic acid-containing monomer. Based on 100 mol% of the copolymer, the first structural unit is included in an amount ranging from about 5 mol% to about 80 mol%, the second structural unit is included in an amount ranging from about 10 mol% to about 40 mol%, and the third structural unit is included in an amount ranging from about 5 mol% to about 80 mol%.

[0012] According to another aspect of this disclosure, a rechargeable lithium battery is described.

[0013] A rechargeable lithium battery includes a positive electrode, a negative electrode, and a separator for the rechargeable lithium battery disposed between the positive electrode and the negative electrode. Attached Figure Description

[0014] 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.

[0015] Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment of the present disclosure.

[0016] Figure 5 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment. Detailed Implementation

[0017] Example embodiments of the present disclosure are described in detail below. However, these embodiments are presented by way of example, and the present disclosure is not limited thereto, but is defined only by the scope of the appended claims.

[0018] Unless otherwise stated herein, when a component such as a layer, membrane, region, plate, etc., is described as being disposed "on" another component, it includes not only the case where the component is "directly on" another component, but also the case where other components are present therein.

[0019] Unless otherwise stated herein, the singular may also include the plural. Furthermore, unless otherwise stated, the term "A or B" may mean "including A, including B, or including both A and B".

[0020] In this specification, “combination of them” can mean a mixture, stack, complex, copolymer, alloy, blend or reaction product of the components.

[0021] Unless otherwise defined herein, “particle size D100” refers to the diameter of particles that constitute 100% of the total volume in a particle size distribution. Particle size D100 can be measured by methods known to those skilled in the art, such as using a particle size analyzer, transmission electron microscopy (TEM) images, or scanning electron microscopy (SEM) images. Alternatively, particle size D100 can be obtained by measuring particle size using a measuring device that utilizes dynamic light scattering, performing data analysis to count the number of particles in each particle size range, and then calculating the particle size D100 from the data. Optionally, particle size D100 can be measured using laser diffraction. When measuring particle size by laser diffraction, for example, the particle size D100 can be calculated based on 100% of the particle size distribution in the measuring device by dispersing the particles to be measured in a dispersion medium, introducing the dispersion medium into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and irradiating the device with ultrasound at an output of approximately 28 kHz at 60 W.

[0022] Unless otherwise defined herein, “particle size D50” can be the average particle size D50, which refers to the diameter of particles that constitute 50% of the cumulative volume in the particle size distribution. The particle size distribution can be obtained using the methods described above for particle size D100.

[0023] If the particles are spherical (when the particles are spherical), size can mean diameter.

[0024] In this specification, "(meth)acrylic acid" refers to acrylic acid and / or methacrylic acid.

[0025] In the following text, unless otherwise defined, “substitution” means that hydrogen in a compound is replaced 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), cyano (-CN), amino (-NRR') (here, 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 -(where n is a natural number from 1 to 10) (where R and R' are both independently C1 to C20 alkyl), azide (-N3), amidine (-C(=NH)NH2), hydrazine (-NHNH2), hydrazone (=N(NH2)), carbamoyl (-C(O)NH2), thiol (-SH), acyl (-C(=O)R, where R represents 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 at least one combination thereof.

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

[0027] 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).

[0028] In addition, in chemical formulas, symbols It refers to the part that is connected to the same or different atoms, groups or structural units.

[0029] Unless otherwise specified in the chemical formulas described herein, hydrogen can be considered to be incorporated into the structure of the chemical formulas.

[0030] 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.

[0031] In this specification, when describing a range of values, “X to Y” means “X or greater and Y or less (greater than or equal to X and less than or equal to Y)”.

[0032] 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%.

[0033] According to an example embodiment of this disclosure, a separator for a rechargeable lithium-ion battery includes a porous substrate and a coating layer located on at least one surface of the porous substrate, wherein the coating layer includes an adhesive, the adhesive including a copolymer, the copolymer comprising: a first structural unit including a unit derived from an aromatic unsaturated monomer; a second structural unit derived from a (meth)acrylic acid monomer having an alkyl group having four or more carbon atoms in the main chain of the ester moiety; and a third structural unit derived from a sulfonic acid-containing monomer. Based on 100 mol% of the copolymer, the first structural unit is included in an amount ranging from about 5 mol% to about 80 mol%, the second structural unit is included in an amount ranging from about 10 mol% to about 40 mol%, and the third structural unit is included in an amount ranging from about 5 mol% to about 80 mol%.

[0034] Coatings can improve the lifespan and safety of rechargeable lithium-ion batteries by significantly reducing the membrane resistance of the separator. Coatings can also improve the safety of rechargeable lithium-ion batteries by providing high adhesion. Coatings can exhibit high electrolyte wettability and improved flexibility, thus providing rechargeable lithium-ion batteries with improved resistance. Coatings can also increase the reliability of rechargeable lithium-ion batteries by exhibiting high capacity retention and low DC-IR variation rates at both room temperature (e.g., in the range of about 20°C to about 30°C) and high temperatures (e.g., in the range of about 40°C to about 50°C).

[0035] According to example embodiments of this disclosure, the diaphragm may have an electrolyte wettability of about 130 wt% or greater.

[0036] According to an example embodiment of this disclosure, the diaphragm may have an adhesive force to the positive electrode of about 0.90 N or greater.

[0037] According to an example embodiment of this disclosure, when impregnated with an electrolyte, the diaphragm may have a membrane resistance of about 0.65 Ω or less.

[0038] According to exemplary embodiments of this disclosure, the diaphragm can have a capacity retention of about 85% or higher at room temperature and about 70% or higher at high temperatures.

[0039] According to exemplary embodiments of this disclosure, the diaphragm may have a DC-IR change rate of about 220% or less after 200 cycles at room temperature and about 330% or less after 200 cycles at high temperature.

[0040] Electrolyte wettability, adhesion to the positive electrode, membrane resistance when immersed in electrolyte, capacity retention at room temperature and high temperature, and DC-IR (direct current-internal resistance) change rate at room temperature and high temperature can be measured by the methods described below.

[0041] According to exemplary embodiments of this disclosure, the copolymer constitutes an adhesive (or the copolymer is an adhesive) to ensure adhesion between the diaphragm and the electrode. There is a trade-off between membrane resistance and adhesive strength. The copolymer can reduce the membrane resistance of the diaphragm while increasing the adhesive strength.

[0042] According to exemplary embodiments of this disclosure, the adhesive is a particulate adhesive and may have an average particle size D50 in the range of about 500 nm to about 700 nm (e.g., 500 nm, 510 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, 650 nm, 660 nm, 670 nm, 680 nm, 690 nm, 700 nm). Within this range, the adhesive strength can be increased.

[0043] When an adhesive has a glass transition temperature, the glass transition temperature can be in the range of about 60°C to about 80°C. Within this range, not only is adhesion to the electrodes desired or improved, but ionic conductivity can also be good or desirable. The glass transition temperature of the adhesive can be measured by conventional methods known to those skilled in the art, such as thermomechanical analysis (TMA).

[0044] For example, the glass transition temperature can be measured as follows.

[0045] 1. Cut the copolymer or binder to be analyzed into 0.5mm × 8mm size to prepare the sample, attach it to the holder, and place it on the sample probe of the TMA device.

[0046] 2. Set the mechanical load to 0.0150 N and the heating rate to 5 °C / min, and measure the change in sample length with temperature.

[0047] 3. The temperature at which the slope of the curve obtained from the TMA device changes is designated as the glass transition temperature.

[0048] Based on the total amount of the coating, the binder can be included in an amount ranging from about 1 wt% to about 100 wt%, or from about 1 wt% to about 90 wt% (e.g., about 5 wt% to about 80 wt%, or about 10 wt% to about 80 wt%). Within this range, adhesion to the electrodes can be exhibited, and the cell resistance does not increase, thus there are no limitations on the capacity achieved.

[0049] Coating layer The coating is or includes an adhesive layer. The coating includes an adhesive, and the copolymer of the monomer mixture described below and the alkali metal may be included in the adhesive in an amount of about 95 wt% or more (e.g., in the range of about 95 wt% to about 100 wt%, or about 100 wt%).

[0050] For the copolymer, the sum of the contents of the first, second, and third structural units can be about 95 mol% or more (e.g., in the range of about 95 to about 100 mol%, or about 100 mol%). Within this range, the aforementioned effects of the membrane can be achieved more easily.

[0051] First structural unit: The first structural unit includes units derived from aromatic unsaturated monomers. Aromatic unsaturated monomers may include aromatic vinyl monomers. Units derived from aromatic unsaturated monomers can provide adhesive force, allowing the coating to adhere to the porous substrate and electrodes, and improving the permeability of the membrane.

[0052] Units derived from aromatic unsaturated monomers are represented by the following chemical formula 1, and copolymers may include one or more units represented by the following chemical formula 1: Chemical Formula 1: .

[0053] In chemical formula 1, R 1 and R 2 Each is independently composed of or includes hydrogen or substituted or unsubstituted C1 to C5 alkyl groups, and Ar is or includes substituted or unsubstituted monocyclic or polycyclic C6 to C20 aryl groups.

[0054] In the example, Ar in Formula 1 is or includes monocyclic or polycyclic C6 to C20 aryl groups, and may be or include, for example, phenyl, naphthyl, anthracene, pyrene, etc.

[0055] In the example, the unit derived from the aromatic unsaturated monomer is represented by the following chemical formula 2, and the copolymer may include one or more units represented by the following chemical formula 2: Chemical formula 2: .

[0056] In chemical formula 2, R 3 and R 4 Each is independently composed of or includes hydrogen or substituted or unsubstituted C1 to C5 alkyl groups. R is or includes one or more of substituted or unsubstituted C1 to C20 alkyl, substituted or unsubstituted C3 to C20 cycloalkyl, substituted or unsubstituted C1 to C20 alkoxy, and substituted or unsubstituted C3 to C20 aryl. m is an integer in the range of 0 to 5.

[0057] In the example, R in Formula 2 can be or include substituted or unsubstituted C1 to C20 alkyl or substituted or unsubstituted C1 to C20 alkoxy groups. In the example, m in Formula 2 can be 0 or 1.

[0058] For example, aromatic unsaturated monomers including aromatic vinyl monomers may include one or more of styrene, α-methylstyrene, 4-butylstyrene (such as 4-n-butylstyrene, 4-isobutylstyrene, 4-tert-butylstyrene, etc.), butoxystyrene containing 4-butoxystyrene (such as 4-n-butoxystyrene, 4-isobutoxystyrene, 4-tert-butoxystyrene, etc.), halogenated styrene (such as chlorostyrene, bromostyrene, fluorostyrene, etc.), vinyltoluene (such as 4-vinyltoluene, 3-vinyltoluene, 2-vinyltoluene, etc.), and vinylnaphthalene (such as 1-vinylnaphthalene, 2-vinylnaphthalene, etc.).

[0059] In addition to units derived from aromatic unsaturated monomers, the first structural unit may also include units derived from (meth)acrylic acid monomers whose main chain contains an alkyl group having one to three carbon atoms. Units derived from (meth)acrylic acid monomers whose main chain contains an alkyl group having one to three carbon atoms can provide additional adhesive strength improvement.

[0060] Units derived from (meth)acrylic acid monomers containing alkyl groups having one to three carbon atoms in the main chain of the ester moiety are represented by the following chemical formula 3, and copolymers may include one or more units represented by the following chemical formula 3: Chemical formula 3: .

[0061] In chemical formula 3, R 5 and R 6 Each is independently hydrogen or includes methyl, and L 1 It may include or include substituted or unsubstituted straight-chain or branched C1 to C3 alkyl groups.

[0062] In the example, the (meth)acrylic monomer containing an alkyl group having one to three carbon atoms in the main chain of the ester moiety may include one or more of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and isopropyl (meth)acrylate.

[0063] For example, homopolymers of (meth)acrylic acid monomers containing alkyl groups having one to three carbon atoms in the main chain of the ester moiety can have a glass transition temperature of about 50°C or higher (e.g., in the range of about 50°C to about 150°C). Within this range, the glass transition temperature of the aforementioned copolymer can be readily achieved. For example, the (meth)acrylic acid monomer containing alkyl groups having one to three carbon atoms in the main chain of the ester moiety can be methyl methacrylate, ethyl methacrylate, etc.

[0064] The first structural unit is included in an amount ranging from about 5 mol% to about 80 mol% relative to 100 mol% of the copolymer. When the first structural unit is included in an amount of about 5 mol% or more, electrolyte wettability can be improved, and capacity retention at room temperature and high temperature can be high. When the first structural unit is included in an amount of about 80 mol% or less, membrane resistance does not increase, and capacity retention at room temperature and high temperature can be high. For example, relative to 100 mol% of the copolymer, it can be expressed as 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%, 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%, 4 The first structural unit comprises amounts ranging from about 10 mol% to about 70 mol% or from about 30 mol% to about 60 mol%. When the first structural unit is included in the above range, the membrane can exhibit low membrane resistance, desired or improved adhesion to porous substrates and electrodes, air permeability, and oxidation resistance.

[0065] Relative to 100 mol% of the copolymer, it can be in the range of about 5 mol% to about 80 mol% (e.g., about 10 mol% to about 70 mol%, about 10 mol% to about 60 mol%, about 10 mol% to about 35 mol%, about 15 mol% to about 30 mol%, or about 5 mol% to about 35 mol%) (e.g., 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%, 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%). The amounts of 36 mol%, 37 mol%, 38 mol%, 39 mol%, 40 mol%, 41 mol%, 42 mol%, 43 mol%, 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, 76 mol%, 77 mol%, 78 mol%, 79 mol%, and 80 mol%) include units derived from aromatic unsaturated monomers. Within the above range, the aforementioned effects of the diaphragm can be easily achieved.

[0066] Relative to 100 mol% of the copolymer, it can be in the range of about 5 mol% to about 80 mol% (e.g., about 10 mol% to about 70 mol%, about 10 mol% to about 60 mol%, about 10 mol% to about 35 mol%, about 15 mol% to about 30 mol%, or about 5 mol% to about 35 mol%) (e.g., 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%, 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%). The amounts of (1%, 38mol%, 39mol%, 40mol%, 41mol%, 42mol%, 43mol%, 44mol%, 45mol%, 46mol%, 47mol%, 48mol%, 49mol%, 50mol%, 51mol%, 52mol%, 53mol%, 54mol%, 55mol%, 56mol%, 57mol%, 58mol%, 59mol%, 60mol%, 61mol%, 62mol%, 63mol%, 64mol%, 65mol%, 66mol%, 67mol%, 68mol%, 69mol%, 70mol%, 71mol%, 72mol%, 73mol%, 74mol%, 75mol%, 76mol%, 77mol%, 78mol%, 79mol%, 80mol%) include units derived from (meth)acrylic acid monomers containing alkyl groups having 1 to 3 carbon atoms in the main chain of the ester moiety. Within the above ranges, the aforementioned effects of the diaphragm can be easily achieved.

[0067] According to example embodiments, the molar ratio of units derived from aromatic unsaturated monomers and units derived from (meth)acrylic acid monomers having alkyl groups having one to three carbon atoms in the main chain of the ester moiety relative to 100 mol% of the copolymer can be in the range of about 1:0.5 to about 1:2 (e.g., about 1:1 to about 1:2), for example, it can be about 1:0.5, about 1:0.6, about 1:0.7, about 1:0.8, about 1:0.9, about 1:1, about 1:1.1, about 1:1.2, about 1:1.3, about 1:1.4, about 1:1.5, about 1:1.6, about 1:1.7, about 1:1.8, about 1:1.9, about 1:2, or about 1:1. Within the above range, the above-described effects of the diaphragm can be readily achieved.

[0068] Second structural unit: The second structural unit is derived from a (meth)acrylic acid monomer containing an alkyl group having four or more carbon atoms in the main chain of the ester moiety. The second structural unit can improve the dispersibility of the coating slurry and also improve the electrolyte wettability and flexibility of the coating.

[0069] The second structural unit derived from the ester moiety containing an alkyl group having four or more carbon atoms in the main chain of a (meth)acrylic acid monomer is represented by the following chemical formula 4, and the copolymer may include one or more structural units represented by the following chemical formula 4: Chemical formula 4: .

[0070] In chemical formula 4, R 7 and R 8 Each is independently hydrogen or includes methyl, and L 2 It may include or include substituted or unsubstituted straight-chain or branched C4 to C30 alkyl groups.

[0071] In this case, C4 to C30 alkyl can be or include C4 to C20 alkyl, C4 to C10 alkyl or C4 to C8 alkyl.

[0072] According to example embodiments, (meth)acrylate monomers containing alkyl groups having four or more carbon atoms in the main chain of the ester moiety may include one or more of the following: 2-ethylhexyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, and isodecyl (meth)acrylate.

[0073] The second structural unit is included in an amount ranging from about 10 mol% to about 40 mol% relative to 100 mol% of the copolymer. When the second structural unit is included in an amount of about 10 mol% or more, the membrane resistance can be reduced upon impregnation with the electrolyte, and the capacity retention at room temperature and high temperature can be high. When the second structural unit is included in an amount of about 40 mol% or less, the permeability can be improved, and the capacity retention at room temperature and high temperature can be high.

[0074] For example, relative to 100 mol% of the copolymer, the second structural unit can be included in amounts ranging from about 15 mol% to about 35 mol% (e.g., about 20 mol% to about 30 mol%). Within this range, the adhesion to the porous substrate and the electrode, as well as the flexibility of the coating, can be readily increased.

[0075] Third structural unit: The third structural unit is derived from a sulfonic acid-containing monomer. This third structural unit, derived from the sulfonic acid-containing monomer, can reduce the membrane resistance by increasing the likelihood of lithium-ion migration in the presence of the first and second structural units.

[0076] According to an example embodiment, the third structural unit increases the glass transition temperature of the copolymer by including a bulky functional group derived from (meth)acrylamide sulfonic acid or a salt thereof, and thus provides structural safety. Furthermore, 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 metal-containing sulfonic acid functional group, and therefore the membrane resistance of the diaphragm can be significantly reduced.

[0077] The third structural unit may be represented by the following chemical formula 5, chemical formula 6, or chemical formula 7. The copolymer may include one or more structural units represented by the following chemical formulas 5, 6, and 7: Chemical formula 5: .

[0078] Chemical formula 6: .

[0079] Chemical Formula 7: .

[0080] In chemical formulas 5 to 7 R 9 R 10 R 11 R 12 R 13and R 14 Each is independently hydrogen or includes C1 to C3 alkyl groups. L 3 L 5 and L 7 Each of these can be independently -C(=O)-, -C(=O)O-, -OC(=O)-, -O-, or -C(=O)NH-. L 4 L 6 and L 8 Each is independently or comprises or includes substituted or unsubstituted C1 to C10 alkylene, substituted or unsubstituted C3 to C20 cycloalkylene, substituted or unsubstituted C6 to C20 arylene, or substituted or unsubstituted C3 to C20 heterocyclic groups, and a, b, c, d, e, and f are all independent integers in the range of 0 to 2, and In chemical formula 6, M is or includes alkali metals.

[0081] In the example, in chemical formulas 5 to 7, L 3 L 5 and L 7 They can all be independently -C(=O)NH-, L 4 L 6 and L 8 They can all be independently C1 to C10 alkylene groups, and a, b, c, d, e, and f can all equal 1.

[0082] The third structural unit derived from the sulfonic acid-containing monomer may include only one of the structural units represented by chemical formulas 5 to 7, or two or more of them. In one example, the third structural unit derived from the sulfonic acid-containing monomer may include a structural unit represented by chemical formula 6; in another example, the third structural unit derived from the sulfonic acid-containing monomer may include both structural units represented by chemical formula 6 and structural units represented by chemical formula 7.

[0083] The third structural unit derived from a sulfonic acid monomer can be or include, for example, structural units derived from vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, anethole sulfonic acid, (meth)acrylamidoalkyl sulfonic acid, (meth)acrylic acid sulfonyl ester, or their salts.

[0084] Here, the alkane may be or include C1 to C20 alkanes, C1 to C10 alkanes, or C1 to C6 alkanes, and the alkyl group may be or include C1 to C20 alkyl groups, C1 to C10 alkyl groups, or C1 to C6 alkyl groups. The salt refers to a salt composed of the aforementioned sulfonic acid and a suitable 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.

[0085] (Methacrylamidoalkane sulfonic acid may be or include, for example, 2-(meth)acrylamido-2-methylpropanesulfonic acid, and (meth)acrylic acid sulfonyl ester may be or include, for example, (meth)acrylic acid 2-sulfoethyl ester, (meth)acrylic acid 3-sulfopropyl ester, etc.

[0086] The third structural unit is included in an amount ranging from about 5 mol% to about 80 mol% relative to 100 mol% of the copolymer. When the third structural unit is included in an amount of about 5 mol% or more, the membrane resistance of the separator can be reduced, and the rate of change of DC-IR at room temperature and high temperature can be reduced. When the third structural unit is included in an amount of about 80 mol% or less, the capacity retention of the battery at room temperature and high temperature can be increased, and the rate of change of DC-IR at room temperature and high temperature can be reduced.

[0087] For example, relative to 100 mol% of the copolymer, it can be expressed as 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%, 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%. The third structural unit may be included in amounts ranging from about 10 mol% to about 60 mol%, with a concentration of 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, 76 mol%, 77 mol%, 78 mol%, 79 mol%, and 80 mol%. For example, relative to 100 mol% of the copolymer, the third structural unit may be included in amounts ranging from about 20 mol% to about 60 mol% or from about 30 mol% to about 60 mol%. When the third structural unit is included in the above range, the membrane resistance of the binder and the separator including the binder can be significantly reduced, the capacity retention rate of the battery at room temperature and high temperature can be increased, and the DC-IR change rate at room temperature and high temperature can be reduced.

[0088] The binder may include alkali metals. Alkali metals may be present in cationic form and may be, or include, at least one of, for example, lithium, sodium, potassium, rubidium, and cesium. For example, alkali metals may exist in the form of salts by combining with copolymers. Alkali metals can facilitate the synthesis of copolymers from monomer mixtures in aqueous solvents and improve the adhesion of coatings, the permeability of membranes, oxidation resistance, etc.

[0089] The adhesive can have a glass transition temperature in the range of about 60°C to about 80°C. In examples, the glass transition temperature can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, or in the range of about 62°C to about 78°C (e.g., about 64°C to about 75°C). Within these ranges, the coating can have desired or improved adhesion, and the diaphragm including the coating can exhibit desired or improved permeability and oxidation resistance. The glass transition temperature of the adhesive can be measured using typical methods known to those skilled in the art, such as thermomechanical analysis (TMA).

[0090] For example, the glass transition temperature can be measured as follows.

[0091] 1. Cut the copolymer to be analyzed into 0.5mm × 8mm pieces to prepare the sample, attach it to the support, and place it on the sample probe of the TMA device.

[0092] 2. Set the mechanical load to 0.0150 N and the heating rate to 5 °C / min, and measure the change in sample length with temperature.

[0093] 3. The temperature at which the slope of the curve obtained from the TMA device changes is designated as the glass transition temperature.

[0094] In binders comprising alkali metals and copolymers, alkali metals may be included in an amount ranging from about 1 wt% to about 40 wt% (e.g., about 1 wt% to about 30 wt%, about 1 wt% to about 20 wt%, or about 10 wt% to about 20 wt%) (e.g., 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%). For example, copolymers and alkali metals may be included in a weight ratio ranging from about 99:1 to about 60:40 or from about 99:1 to about 70:30 (e.g., a weight ratio ranging from about 99:1 to about 80:20 or from about 90:10 to about 80:20).

[0095] Alkali metals may be included in an amount ranging from about 0.1 mol% to about 1.0 mol% relative to the total amount of the copolymer of alkali metals and monomer mixtures. When alkali metals are included in the above range, the coating may have desired or improved adhesion, and the diaphragm including the coating may exhibit desired or improved air permeability and oxidation resistance.

[0096] Binders that include copolymers of monomer mixtures can take various forms (such as alternating polymers in which structural units are distributed alternately, random polymers in which structural units are distributed randomly, and grafted polymers in which some of the structural units are grafted, etc.).

[0097] Binders comprising copolymers of monomer mixtures may have a weight-average molecular weight in the range of about 100,000 g / mol to about 1,000,000 g / mol, about 100,000 g / mol to about 500,000 g / mol, about 100,000 g / mol to about 150,000 g / mol, about 200,000 g / mol to about 300,000 g / mol, or about 300,000 g / mol to about 900,000 g / mol. When the weight-average molecular weight of the binder comprising copolymers of monomer mixtures meets the above ranges, it can exhibit desired or improved adhesive strength and low electrical resistance. The weight-average molecular weight may be or include the average molecular weight converted from polystyrene using, for example, gel permeation chromatography.

[0098] Binders comprising copolymers of monomer mixtures can be prepared by solution polymerization.

[0099] According to an example embodiment, the binder, which comprises a copolymer of monomer mixtures, may be included in the coating layer of the diaphragm in the form of a film.

[0100] The coating layer can have a thickness ranging from about 0.01 μm to about 20 μm. Within this range, the thickness can be from about 0.01 μm to about 5 μm, from about 0.1 μm to about 3 μm, or from about 0.1 μm to about 1.5 μm. Within this range, the coating layer can be used for a diaphragm.

[0101] The ratio of the coating thickness to the porous substrate thickness can be in the range of about 0.1 to about 0.8 (e.g., about 0.1 to about 0.7 or about 0.15 to about 0.6). Within this range, the diaphragm can exhibit desired or improved permeability, heat resistance, and adhesion.

[0102] Porous substrate Porous substrates can be or include substrates having a plurality of pores and are typically used in electrochemical devices. Porous substrates can be, or include, polymer membranes formed from any polymer, such as or including polyolefins (e.g., polyethylene, polypropylene, etc.), polyesters (e.g., polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyacetals, polyamides, polyimides, polycarbonates, polyetheretherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cyclic olefin copolymers, polyphenylene sulfide, glass fibers, and polytetrafluoroethylene (e.g., Teflon). ® At least one of the following, or copolymers or mixtures of two or more of them.

[0103] The porous substrate can be or includes, for example, a polyolefin-based substrate containing polyolefins, and the polyolefin-based substrate can contribute to improved battery safety due to its desired or improved shut-off function. 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. Furthermore, the polyolefin resin can include non-olefin resins other than olefin resins, or copolymers comprising olefin monomers and non-olefin monomers.

[0104] The porous substrate may have a thickness ranging from about 1 μm to about 40 μm (e.g., about 1 μm to about 30 μm, about 1 μm to about 20 μm, or about 5 μm to about 15 μm).

[0105] According to one example embodiment, the separator for a rechargeable lithium battery can exhibit desired or improved permeability and can have a permeability value, for example, less than about 250 sec / 100cc (e.g., about 230 sec / 100cc or less, or about 200 sec / 100cc or less). That is, the separator can have a permeability value of about 40 sec / 100cc·1μm (per unit thickness) or less (e.g., about 30 sec / 100cc·1μm or less, or about 25 sec / 100cc·1μm or less). Here, permeability refers to the time (in seconds) it takes for 100cc of air to permeate a unit thickness of the separator. The permeability per unit thickness can be obtained by measuring the permeability over the entire thickness of the separator and then dividing the permeability by the thickness. The permeability can be measured using a permeability measuring device (Asahi Seiko, EG01-55-1MR) according to the time (in seconds) it takes for 100cc of air to permeate.

[0106] A rechargeable lithium battery separator according to an example embodiment can be manufactured by coating one or both sides of a porous substrate with a composition for forming a coating layer, and then drying the composition.

[0107] A method for manufacturing a rechargeable lithium-ion battery separator includes coating at least one side of a porous substrate with a separator coating composition comprising an adhesive, and drying the porous substrate coated with the separator coating composition to form a coating layer.

[0108] Figure 5 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment. (Refer to...) Figure 5 The separator for a rechargeable lithium battery includes a porous substrate 1 and a coating layer 2 located on two surfaces of the porous substrate 1. The coating layer 2 may include an adhesive (not shown).

[0109] 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.

[0110] 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.

[0111] 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 also include a binder and / or a conductive material.

[0112] For example, the positive electrode may also include additives that can constitute a sacrificial positive electrode.

[0113] 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 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.

[0114] 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.

[0115] As an example, a compound represented by any of the following chemical formulas can be used: Li a A 1-b X b O 2-c Dc (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 FePO 4（ 0.90≤a≤1.8).

[0116] 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.

[0117] 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.

[0118] 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%.

[0119] 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.

[0120] 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.

[0121] Al can be used as a current collector, but the current collector is not limited thereto.

[0122] 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).

[0123] 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.

[0124] 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.

[0125] The material that reversibly embeds / extracts lithium ions may include a carbon-based negative electrode active material (such as exemplified by crystalline carbon, amorphous carbon, or a combination thereof). The crystalline carbon may be or include graphite (such as non-shaped, flaky, lamellar, spherical, or fibrous natural graphite or artificial graphite). The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization product, calcined coke, etc.

[0126] The lithium metal alloy includes an alloy of lithium and a metal (such as at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn).

[0127] 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 (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.

[0128] 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.

[0129] 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.

[0130] Si-based or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0131] 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 at least one of non-aqueous binders, aqueous binders, dry binders, and combinations thereof.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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 the battery. 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.

[0137] 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.

[0138] Rechargeable lithium batteries may also include an electrolyte.

[0139] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0140] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0141] 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.

[0142] 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).

[0143] 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.

[0144] 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 includes double bonds, aromatic rings, or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0145] Non-aqueous organic solvents can be used alone or in combination of two or more solvents.

[0146] 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.

[0147] 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).

[0148] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch, or coin-shaped batteries.

[0149] Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment. Figure 1 A cylindrical battery is shown. Figure 2 A prismatic battery is shown. Figure 3 and Figure 4 A pouch-type battery is shown. (See reference) Figures 1 to 4The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50 therein housing the electrode assembly 40. The electrode assembly 40 includes 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). Figure 1 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. Figure 2 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 3 and Figure 4 As shown, the rechargeable lithium battery 100 may include Figure 4 The electrode terminal 70 shown, or for example Figure 3 The positive electrode terminal 71 and negative electrode terminal 72 shown herein form an electrical path for guiding the current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0150] 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.

[0151] Examples and comparative examples of this disclosure are described below. These examples are given for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0152] Preparation Example 1 Distilled water (1249.72 g), 20% lithium hydroxide aqueous solution (203.69 g), styrene (SM, 36.45 g, 0.35 mol), methyl methacrylate (MMA, 35.04 g, 0.35 mol), 2-ethylhexyl acrylate (EHA, 36.83 g, 0.20 mol), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS, 20.73 g, 0.10 mol) were added to a 3 L four-necked separable flask equipped with a stirrer, thermometer, and condenser. Sodium dodecylbenzenesulfonate (16.02 g, 0.05 mol) was then added. The process was repeated three times using a diaphragm pump to reduce the pressure inside the flask to 10 mmHg and then restoring the pressure to atmospheric pressure using nitrogen.

[0153] The reaction was carried out for 12 hours while heating was controlled to keep the temperature of the reaction solution stable at 65°C to 70°C.

[0154] After cooling to room temperature, approximately 10 mL of the reaction solution was taken, and the non-volatile (NV) component was measured. As a result, a particulate binder with an NV component content of 9.8 wt% (theoretical value: 10 wt%) was obtained. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS) salt), the molar ratio of the first structural unit derived from SM and MMA, the second structural unit derived from EHA, and the third structural unit derived from AMPS was 70:20:10, the average particle size was 500 nm, and the glass transition temperature (Tg) of the binder was 65.1 °C.

[0155] Preparation Example 2 The binder was prepared in the same manner as in Preparation Example 1, except that SM (30.20 g, 0.29 mol), MMA (29.04 g, 0.29 mol), EHA (40.52 g, 0.22 mol), and AMPS (41.45 g, 0.20 mol) were used, and the glass transition temperature of the binder was 65.0 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, MMA-derived units, EHA-derived second structural units, and AMPS-derived third structural units was 29:29:22:20. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0156] Preparation Example 3 The binder was prepared in the same manner as in Preparation Example 1, except that SM (23.95 g, 0.23 mol), MMA (23.03 g, 0.23 mol), EHA (44.20 g, 0.24 mol), and AMPS (62.18 g, 0.30 mol) were used, and the glass transition temperature of the binder was 64.0 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, the MMA-derived units, the EHA-derived second structural units, and the AMPS-derived third structural units was 23:23:24:30. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0157] Preparation Example 4 The binder was prepared in the same manner as in Preparation Example 1, except that SM (17.71 g, 0.17 mol), MMA (35.04 g, 0.17 mol), EHA (47.88 g, 0.26 mol), and AMPS (82.9 g, 0.40 mol) were used, and the glass transition temperature (Tg) of the binder was 64.8 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, MMA-derived units, EHA-derived second structural units, and AMPS-derived third structural units was 17:17:26:40. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0158] Preparation Example 5 The binder was prepared in the same manner as in Preparation Example 1, except that SM (11.46 g, 0.11 mol), MMA (11.01 g, 0.11 mol), EHA (51.56 g, 0.28 mol), and AMPS (103.63 g, 0.50 mol) were used, and the glass transition temperature (Tg) of the binder was 64.7 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, MMA-derived units, EHA-derived second structural units, and AMPS-derived third structural units was 11:11:28:50. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0159] Preparation Example 6 The binder was prepared in the same manner as in Preparation Example 1, except that SM (5.21 g, 0.05 mol), MMA (5.01 g, 0.05 mol), EHA (55.25 g, 0.30 mol), and AMPS (124.35 g, 0.60 mol) were used, and the glass transition temperature (Tg) of the binder was 64.6 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, MMA-derived units, EHA-derived second structural units, and AMPS-derived third structural units was 5:5:30:60. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0160] Preparation Example 7 The binder was prepared in the same manner as in Preparation Example 1, except that SM (20.83 g, 0.20 mol), EHA (55.28 g, 0.30 mol), and AMPS (103.63 g, 0.50 mol) were used instead of MMA, and the glass transition temperature (Tg) of the binder was 60.0 °C. In the case of the obtained binder (lithium poly(SM-co-EHA-co-AMPS) salt), the molar ratio of the SM-derived unit, the EHA-derived second structural unit, and the AMPS-derived third structural unit was 20:30:50. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0161] Comparative preparation example 1 The binder was prepared in the same manner as in Preparation Example 1, except that SM (2.08 g, 0.02 mol), MMA (2 g, 0.02 mol), EHA (55.28 g, 0.30 mol), and AMPS (136.785 g, 0.66 mol) were used, and the glass transition temperature (Tg) of the binder was 67.1 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, the MMA-derived units, the EHA-derived second structural units, and the AMPS-derived third structural units was 2:2:30:66. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0162] Comparative preparation example 2 The binder was prepared in the same manner as in Preparation Example 1, except that SM (44.26 g, 0.425 mol), MMA (42.55 g, 0.425 mol), EHA (18.43 g, 0.10 mol), and AMPS (10.36 g, 0.05 mol) were used, and the glass transition temperature (Tg) of the binder was 85.5 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, MMA-derived units, EHA-derived second structural units, and AMPS-derived third structural units was 42.5:42.5:10:5. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0163] Comparative preparation example 3 The binder was prepared in the same manner as in Preparation Example 1, except that SM (41.66 g, 0.40 mol), MMA (40.05 g, 0.40 mol), EHA (9.21 g, 0.05 mol), and AMPS (31.09 g, 0.15 mol) were used, and the glass transition temperature (Tg) of the binder was 102.9 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, MMA-derived units, EHA-derived second structural units, and AMPS-derived third structural units was 40:40:5:15. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0164] Comparative preparation example 4 The binder was prepared in the same manner as in Preparation Example 1, except that SM (20.83 g, 0.20 mol), MMA (20.02 g, 0.20 mol), EHA (82.93 g, 0.45 mol), and AMPS (31.09 g, 0.15 mol) were used, and the glass transition temperature (Tg) of the binder was 20.7 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, MMA-derived units, EHA-derived second structural units, and AMPS-derived third structural units was 20:20:45:15. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0165] Comparative preparation example 5 The binder was prepared in the same manner as in Preparation Example 1, except that SM (41.66 g, 0.40 mol), MMA (40.05 g, 0.40 mol), EHA (32.25 g, 0.175 mol), and AMPS (5.18 g, 0.025 mol) were used, and the glass transition temperature (Tg) of the binder was 67.3 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, MMA-derived units, EHA-derived second structural units, and AMPS-derived third structural units was 40:40:17.5:2.5. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0166] Comparative preparation example 6 The binder was prepared in the same manner as in Preparation Example 1, except that SM (2.6 g, 0.025 mol), MMA (2.5 g, 0.025 mol), EHA (18.43 g, 0.10 mol), and AMPS (176.16 g, 0.85 mol) were used, and the glass transition temperature (Tg) of the binder was 127.3 °C. In the case of the obtained binder (lithium poly(SM-co-MMA-co-EHA-co-AMPS)), the molar ratio of the SM-derived units, the MMA-derived units, the EHA-derived second structural units, and the AMPS-derived third structural units was 2.5:2.5:10:85. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0167] Table 1 below shows the molar ratios of monomers in the binders prepared in Preparation Examples 1 to 7 and Comparative Preparation Examples 1 to 6.

[0168] Table 1:

[0169] Example 1 A composition for an adhesive layer was prepared by mixing 10 parts by weight of the adhesive of Preparation Example 1 with 90 parts by weight of distilled water.

[0170] The prepared composition for the adhesive layer was applied to both sides of a polyethylene-based membrane (thickness: 5.5 μm, CZMZ, air permeability: 110 sec / 100 cc, puncture strength: 360 kgf) serving as a porous substrate using a die-coating method at a speed of 80 m / min, and then coated with a 14 g / m 3 The material is dried at 60°C with an absolute water vapor content (average value) to form an adhesive layer with a total thickness of 1.4 μm, thereby manufacturing a separator for rechargeable lithium batteries.

[0171] Examples 2 to 7 The separator for the rechargeable lithium battery is manufactured in the same manner as in Example 1, except that the type of adhesive used in Example 1 is changed.

[0172] Comparison Examples 1 to 6 The separator for the rechargeable lithium battery is manufactured in the same manner as in Example 1, except that the type of adhesive used in Example 1 is changed.

[0173] Battery manufacturing Manufacturing of the negative electrode: A slurry for the negative electrode active material was prepared by mixing 97 wt% graphite particles with an average particle size of 25 μm as the negative electrode active material, 1.5 wt% styrene-butadiene rubber (SBR) binder, and 1.5 wt% carboxymethyl cellulose (CMC), adding the mixture to distilled water, and stirring with a mechanical stirrer for 60 minutes. After coating the slurry onto a 10 μm thick copper current collector using a doctor blade, the slurry was dried in a hot air dryer at 100°C for 0.5 hours, and then further dried at 120°C under vacuum for 4 hours. Finally, it was rolled to fabricate the negative electrode.

[0174] Manufacturing of the positive electrode: A slurry for the positive electrode was prepared by mixing 97 wt% LiCoO2 as the positive electrode active material, 1.5 wt% carbon black powder as the conductive material, and 1.5 wt% polyvinylidene fluoride (PVdF). This mixture was then added to an N-methyl-2-pyrrolidone solvent and stirred for 30 minutes using a mechanical stirrer. After coating the slurry onto a 20 μm thick aluminum current collector using a doctor blade, the slurry was dried in a hot air dryer at 100°C for 0.5 hours, followed by further drying at 120°C under vacuum for 4 hours. Finally, it was rolled to fabricate the positive electrode.

[0175] Electrode assembly core: Each of the diaphragms obtained according to the examples and comparative examples was placed between the positive and negative electrodes fabricated above, and then wound to prepare the electrode assembly core. After inserting the core into the bag, electrolyte was injected, and then the bag was vacuum sealed. The electrolyte used was 1.3 M LiPF6 dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 3:5:2. The core inserted into the bag was pressed at 80°C for 3 minutes while applying 11.7 kgf / cm². 2 The pressure is to manufacture rechargeable lithium batteries.

[0176] Breathability (unit: sec / 100cc) The air permeability of a manufactured diaphragm is measured using a measuring device (EG01-55-1MR, Asahi Seiko Co., Ltd.) by measuring the time (in seconds) required for 100cc of air to pass through the diaphragm.

[0177] Air permeability measuring device settings: Measurement pressure: 0.5 kg / cm 2 Cylinder pressure: 2.5 kg / cm² 2 Time setting: 10 seconds Electrolyte wettability (unit: wt%) The prepared binder was dried in an oven at 120°C for 12 hours to obtain a film (thickness: 20 μm, initial weight W1 measured before impregnation). The film was placed in a manufactured bag and impregnated with the electrolyte, and the bag was vacuum sealed. After placing the sealed bag in an oven at 60°C for 72 hours, the film was immediately removed, and the weight W2 of the film was measured. The electrolyte wettability was calculated as W2 / W1×100.

[0178] Adhesive force to the positive electrode (unit: N) The separator was attached to the positive electrode (manufactured in the same manner as described in "Battery Manufacturing") and inserted into the bag. Then, the electrolyte (1.3 M LiPF6 dissolved in a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) at a volume ratio of 3 / 5 / 2) was injected and left to stand for 12 hours. The assembly was then subjected to a temperature of 10 kgf / cm². 2 Up to 20 kgf / cm 2 The electrode was pressed for 5 to 20 seconds under pressure and a temperature of 70°C to 90°C, and then disassembled. After removing the diaphragm and positive electrode from the bag, the positive electrode and diaphragm were unfolded 180° and the force required to separate the positive electrode from the diaphragm was measured using a tensile testing machine (HT400, Tinius Olsen).

[0179] Membrane resistance (unit: Ω) The membrane resistance was evaluated as electrochemical impedance spectroscopy (EIS) resistance. Each of the separators fabricated in the example and comparative examples was impregnated with an electrolyte of 1.5 M LiPF6 dissolved in a mixed solvent of ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate (volume ratio 3 / 5 / 2). These membranes were then mounted onto aluminum foil electrodes with leaded terminals and sealed in an aluminum cask to fabricate a test cell. The resistance (Ω) of this test cell was measured at 20 °C using AC impedance spectroscopy (measurement frequency 100 kHz).

[0180] Capacity retention after 200 cycles (in %) For batteries manufactured using the separators of the example and comparative examples, constant current charging was performed at 0.5C at 25°C and 45°C until the voltage reached 4.2V, followed by cutoff at 0.025C in constant voltage mode. Afterwards, discharge was performed at 0.5C until the voltage reached 2.5V, and this cycle was repeated 200 times. The capacity retention rate (i.e., lifetime characteristics) based on the number of cycles was evaluated, and the results were obtained.

[0181] DC internal resistance (DC-IR, unit: mΩ) To measure DC-IR, 75mAh cells manufactured using the separators from the example and comparative examples were charged at 25°C and 45°C with a constant current of 0.2C / 4.25V under a 0.05C cutoff condition. After resting for 10 minutes, the cells were discharged at a constant current of 0.33C under a 2.80V cutoff condition and allowed to rest for 10 minutes. After one charge-discharge cycle, DC-IR was measured at SOC50 (state of charge 50%, meaning the battery is charged to 50% of its total capacity, or equivalently discharged 50%) by applying a current at 1C for 10 seconds and measuring the resulting voltage drop (V).

[0182] The DC-IR change rate is the ratio of the DC-IR after 200 cycles to the initial DC-IR, expressed as a percentage.

[0183] Table 2:

[0184] Table 3:

[0185] As shown in Table 2 above, the example separator exhibits low membrane resistance, thereby improving battery capacity, safety, and lifespan. Additionally, the example separator for rechargeable lithium batteries exhibits high adhesion to electrodes (such as the positive electrode), thereby increasing reliability.

[0186] As shown in Table 3 above, the diaphragm in the comparison example cannot achieve the same effect as the diaphragm in the example.

[0187] According to exemplary embodiments of this disclosure, separators for rechargeable lithium batteries can improve battery capacity, safety, and lifespan by exhibiting low membrane resistance, high electrolyte wettability, improved flexibility, high adhesion, and high capacity retention and low DC internal resistance change rate at room temperature and high temperature.

[0188] 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 disclosed claims, detailed description and 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 substrate; as well as A coating layer is located on at least one surface of the porous substrate. The coating layer includes an adhesive. The adhesive comprises a copolymer, the copolymer comprising: a first structural unit comprising a unit derived from an aromatic unsaturated monomer; a second structural unit derived from a (meth)acrylic acid monomer whose main chain of the ester moiety contains an alkyl group having four or more carbon atoms; and a third structural unit derived from a sulfonic acid-containing monomer, and Based on 100 mol% of the copolymer, the first structural unit is included in an amount ranging from 5 mol% to 80 mol%, the second structural unit is included in an amount ranging from 10 mol% to 40 mol%, and the third structural unit is included in an amount ranging from 5 mol% to 80 mol%.

2. The diaphragm according to claim 1, wherein, The adhesive is a particulate adhesive.

3. The diaphragm according to claim 1, wherein, The binder has an average particle size D50 in the range of 500 nm to 700 nm.

4. The diaphragm according to claim 1, wherein, The copolymer is an adhesive.

5. The diaphragm according to claim 1, wherein, The adhesive has a glass transition temperature in the range of 60°C to 80°C.

6. The diaphragm according to claim 1, wherein, The adhesive is included in the coating in an amount ranging from 1 wt% to 100 wt%.

7. The diaphragm according to claim 1, wherein, Based on the copolymer, the sum of the contents of the first structural unit, the second structural unit, and the third structural unit is 95 mol% or greater.

8. The diaphragm according to claim 1, wherein, The unit derived from aromatic unsaturated monomers is represented by the following chemical formula 1: Chemical Formula 1: ； In chemical formula 1, R 1 and R 2 Each independently comprises hydrogen or substituted or unsubstituted C1 to C5 alkyl groups, and Ar includes substituted or unsubstituted monocyclic or polycyclic C6 to C20 aryl groups. The second structural unit is represented by the following chemical formula 4: Chemical formula 4: ； In chemical formula 4, R 7 and R 8 Each independently includes either hydrogen or methyl, and L 2 Including substituted or unsubstituted straight-chain or branched C4 to C30 alkyl groups, and The third structural unit is represented by any one of the following chemical formulas 5 to 7: Chemical formula 5: ； Chemical formula 6: ； Chemical Formula 7: ； In chemical formulas 5 to 7 R 9 R 10 R 11 R 12 R 13 and R 14 Each independently includes hydrogen or C1 to C3 alkyl groups. L 3 L 5 and L 7 Each independently includes -C(=O)-, -C(=O)O-, -OC(=O)-, -O-, or -C(=O)NH-. L 4 L 6 and L 8 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, d, e, and f are all independent integers in the range of 0 to 2, and In chemical formula 6, M includes alkali metals.

9. The diaphragm according to claim 1, wherein, The first structural unit also includes a unit derived from a (meth)acrylic acid monomer having an alkyl group having one to three carbon atoms in the main chain of the ester moiety.

10. The diaphragm according to claim 9, wherein, The unit of the (meth)acrylic acid monomer, which comprises an alkyl group having 1 to 3 carbon atoms in the main chain of the ester moiety, is represented by the following chemical formula 3: Chemical formula 3: ； In chemical formula 3, R 5 and R 6 Each independently includes either hydrogen or methyl, and L 1 Includes substituted or unsubstituted straight-chain or branched C1 to C3 alkyl groups.

11. The diaphragm according to claim 9, wherein, The molar ratio comprises the units derived from aromatic unsaturated monomers and the units derived from (meth)acrylic acid monomers having an alkyl group having one to three carbon atoms in the main chain of the ester moiety, in a range of 1:0.5 to 1:

2.

12. The diaphragm according to claim 9, wherein, Based on 100 mol% of the copolymer, the unit derived from the aromatic unsaturated monomer is included in an amount ranging from 5 mol% to 35 mol%, the unit derived from the (meth)acrylic acid monomer whose main chain contains an alkyl group having 1 to 3 carbon atoms is included in an amount ranging from 5 mol% to 35 mol%, the second structural unit is included in an amount ranging from 20 mol% to 30 mol%, and the third structural unit is included in an amount ranging from 10 mol% to 60 mol%.

13. The diaphragm according to claim 9, wherein, The copolymer includes: The unit derived from aromatic unsaturated monomers is derived from one or more of styrene, α-methylstyrene, 4-butylstyrene, 4-butoxystyrene, halostyrene, vinyltoluene, and vinylnaphthalene; The main chain of the ester moiety contains a unit of an alkyl (meth)acrylic acid monomer having one to three carbon atoms, derived from one or more of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate and isopropyl (meth)acrylate. The second structural unit is derived from one or more of the following: 2-ethylhexyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, and isodecanyl (meth)acrylate; and The third structural unit is derived from at least one of vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, anethole sulfonic acid, (meth)acrylamidoalkane sulfonic acid, (meth)acrylic acid sulfonyl ester and their salts.

14. The diaphragm according to claim 1, wherein, The coating layer has a thickness in the range of 0.1 μm to 1.5 μm.

15. 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 claim 1 is disposed between the positive electrode and the negative electrode.

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