Separator for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

The present disclosure relates to a separator for a rechargeable lithium battery and a rechargeable lithium battery including the same. The separator includes: a porous substrate; a first coating layer on the first surface of the porous substrate; and a second coating layer on the second surface of the porous substrate. The first coating layer and the second coating layer comprise a binder and a filler, the binder of the first coating layer comprises the first binder, and the binder of the second coating layer comprises the second binder. The first binder and the second binder each include a copolymer of a monomer mixture, the copolymer of the monomer mixture including: a first structural unit including a unit derived from an aromatic unsaturated monomer; a second structural unit derived from a (meth) acrylic monomer; and the third structural unit is derived from a sulfonic acid group-containing monomer.

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0157092, 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 prevalence of battery-powered electronic devices (such as mobile phones, laptops, and electric vehicles), the demand for rechargeable lithium batteries with high energy density and high capacity continues to grow. Therefore, improving the performance of rechargeable lithium batteries can be beneficial.

[0004] A rechargeable lithium battery includes a positive electrode and a negative electrode containing active materials capable of inserting and deintercalating lithium ions, and generates electrical energy through redox reactions when lithium ions are inserted into the positive electrode / deintercalated from the negative electrode and inserted into the negative electrode / deintercalated from the positive electrode. Summary of the Invention

[0005] This disclosure aims to provide a separator for rechargeable lithium batteries that exhibits low membrane resistance when impregnated with an electrolyte.

[0006] This disclosure also aims to provide a separator for rechargeable lithium batteries that exhibits high electrolyte wettability, desired or improved permeability, and high adhesion to electrode plates.

[0007] This disclosure also aims to provide a separator for rechargeable lithium batteries that exhibits desired or improved heat resistance.

[0008] This disclosure also aims to provide a separator for rechargeable lithium batteries that exhibits high capacity retention and low rate of change of DC internal resistance (DC-IR) at both room temperature and high temperature.

[0009] This disclosure also aims to provide a rechargeable lithium battery including the above-described separator for a rechargeable lithium battery.

[0010] One aspect of this disclosure includes a separator for rechargeable lithium batteries.

[0011] A separator for a rechargeable lithium-ion battery comprises: a porous substrate; a first coating on a first surface of the porous substrate; and a second coating on a second surface of the porous substrate. The first coating comprises a binder and a filler, and the second coating comprises a binder and a filler. The binder of the first coating comprises a first binder, and the binder of the second coating comprises a second binder. Both the first and second binders comprise copolymers, said copolymers 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 contains an alkyl group having four or more carbon atoms in the ester moiety; and a third structural unit derived from a sulfonic acid-containing monomer. Relative to 100 mol% of the copolymer, it comprises about 5 mol% to about 80 mol% of the first structural unit, about 10 mol% to about 40 mol% of the second structural unit, and about 5 mol% to about 80 mol% of the third structural unit. The filler of the first coating comprises a first filler, the filler of the second coating comprises a second filler, and the first and second fillers satisfy the following expression 1: Expression 1: (Average particle size D50 of the second packing) / (Average particle size D50 of the first packing) ≥ 3.

[0012] Another aspect of this disclosure includes a rechargeable lithium battery.

[0013] A rechargeable lithium battery includes a positive electrode, a negative electrode, and the aforementioned separator 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, in which: Figure 1 These are scanning electron microscope (SEM) images of amorphous fillers; Figure 2 This is a SEM image of the cubic packing material; Figure 3 This is a schematic cross-sectional view of a separator for a rechargeable lithium battery according to an example embodiment; and Figures 4 to 7 This is a schematic diagram of a rechargeable lithium battery according to an example embodiment. Detailed Implementation

[0015] 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, and is limited only by the scope of the appended claims.

[0016] Unless otherwise stated herein, when a component such as a layer, film, region, plate, etc., is described as being disposed "on" another component, the component includes not only the case where the component is "directly" on the other component, but also the case where other components are present in between.

[0017] 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".

[0018] In this specification, “combination of them” may mean a mixture, stack, complex, copolymer, alloy, blend or reaction product of the components.

[0019] Unless otherwise defined herein, “particle size D100” refers to the size of particles that constitute 100% of the cumulative volume in a particle size distribution. Particle size D100 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, 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 this data. Alternatively, particle size D100 can be measured using laser diffraction. When measuring particle size by laser diffraction, for example, the particle size to be measured can be calculated based on a particle size distribution of 100% 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 radiating ultrasound at an output of 60 W at approximately 28 kHz.

[0020] Unless otherwise defined herein, “particle size D50” can be the average particle size D50, which refers to the size of particles that constitute 50% of the cumulative volume in the particle size distribution. The particle size distribution can be obtained using the method described above for particle size D100.

[0021] If the particles are spherical, then the size can refer to the diameter.

[0022] In this specification, "(meth)acryloyl" refers to acryloyl and / or methacryloyl.

[0023] In the following text, unless otherwise defined, “substitution” means 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), cyano (-CN), amino (-NRR') (wherein R and R' are both independently hydrogen or C1 to C6 alkyl), sulfobetaine (-RR'N) + (CH2) n SO3 - (where n is a natural number from 1 to 10) (where R and R' are both independently C1 to C20 alkyl groups), carboxybenzene group (-RR'N) + (CH2) n COO - (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 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.

[0024] 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 (e.g., cyclohexylene). C6 to C20 arylene groups may be or include, for example, C6 to C10 arylene groups (e.g., phenylene). C3 to C20 heterocyclic groups may be or include, for example, C3 to C10 heterocyclic groups (e.g., pyridyl).

[0025] In the following text, “heterogeneous” means including one or more heteroatoms, such as or including at least one of N, O, S, Si and P.

[0026] Furthermore, in chemical formulas, symbols It refers to the part that is connected to the same or different atoms, groups or structural units.

[0027] Unless otherwise specified in the chemical formula described herein, hydrogen may be considered to be bonded to the structure of the chemical formula.

[0028] In the following text, "alkali metals" refers to elements belonging to Group 1 of the periodic table, such as lithium, sodium, potassium, rubidium, cesium, or francium, which can exist in either a cation or a neutral state.

[0029] 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)”.

[0030] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it means 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%.

[0031] The separator for a rechargeable lithium battery according to the example embodiment exhibits low membrane resistance when impregnated with an electrolyte. This low membrane resistance can improve the capacity and lifespan of the rechargeable lithium battery.

[0032] The membrane includes a porous substrate, a first coating on a first surface of the porous substrate, and a second coating on a second surface of the porous substrate. The first coating includes a binder and a filler, and the second coating includes a binder and a filler, the binder of the first coating including a first binder, and the binder of the second coating including a second binder. Both the first and second binders include copolymers, the copolymers including a first structural unit, a second structural unit, and a third structural unit, the first structural unit including a unit derived from an aromatic unsaturated monomer, the second structural unit derived from a (meth)acrylic acid monomer whose main chain contains an alkyl group having four or more carbon atoms in the ester moiety, and the third structural unit derived from a sulfonic acid-containing monomer. Relative to 100 mol% of the copolymer, it includes about 5 mol% to about 80 mol% of the first structural unit, about 10 mol% to about 40 mol% of the second structural unit, and about 5 mol% to about 80 mol% of the third structural unit.

[0033] By including the aforementioned copolymer in the first and second coatings, the diaphragm can provide low membrane resistance when impregnated with electrolyte.

[0034] In the example, when the diaphragm is impregnated with an electrolyte, the diaphragm can have a membrane resistance of about 0.7 Ω or less.

[0035] The first coating comprises a first filler, the second coating comprises a second filler, and the first filler and the second filler satisfy the following expression 1: Expression 1: (Average particle size D50 of the second packing) / (Average particle size D50 of the first packing) ≥ 3.

[0036] By including a first filler and a second filler satisfying Expression 1, the diaphragm can exhibit high electrolyte wettability, desired or improved permeability, high heat resistance, and high adhesion to the electrode plates. For example, Expression 1 enables a diaphragm having a coating including the aforementioned binder to exhibit desired or improved heat resistance and low membrane resistance. It is believed that by providing fillers with different average particle sizes D50 on both sides of a porous substrate, the permeability, electrolyte wettability, and heat resistance of the diaphragm are complementary, but this disclosure is not limited thereto. Moreover, when Expression 1 is satisfied, the diaphragm can reduce or prevent an increase in membrane resistance when impregnated with an electrolyte.

[0037] In the example, when the separator is applied to the battery, the first coating can be laminated to the positive electrode and the second coating can be laminated to the negative electrode.

[0038] In the example, the value of Expression 1 (i.e., the ratio of the average particle size D50 of the second packing to the average particle size D50 of the first packing) can be in the range of about 3 to about 6, and can be about 3, about 4, about 5, or about 6.

[0039] In the example, the diaphragm may have an electrolyte wettability of about 140 wt% or more.

[0040] In the example, the diaphragm may have an air permeability of approximately 150 seconds / 100cc or less. In this case, air permeability refers to the time (in seconds) it takes for 100cc of air to pass through a unit thickness of the diaphragm. Air permeability per unit thickness can be determined by measuring the air permeability for the total thickness of the diaphragm and dividing the result by the thickness. Air permeability can be determined by measuring the time (in seconds) it takes for 100cc of air to pass through using an air permeability measuring device (EG01-55-1MR, commercially available from ASAHI SEIKO GmbH).

[0041] In the example, the diaphragm may have an average thermal shrinkage rate of about 5% or less in both the longitudinal (MD) and transverse (TD) directions.

[0042] In the example, the diaphragm may have an adhesion to the counter electrode plate of about 0.9 N or greater.

[0043] The membrane resistance, electrolyte wettability, air permeability, heat resistance, and adhesion to the electrode plate when impregnated with electrolytes can be measured by the methods described below.

[0044] The diaphragm can have approximately 85% or greater capacity retention at room temperature and approximately 70% or greater capacity retention at high temperatures. The diaphragm can have approximately 220% or less DC-IR change rate after 200 cycles at room temperature and approximately 330% or less DC-IR change rate after 200 cycles at high temperatures.

[0045] The diaphragm according to an exemplary embodiment of the present disclosure is described in further detail below.

[0046] The diaphragm includes a first coating and a second coating.

[0047] First coating The first coating includes an adhesive and a filler, wherein the adhesive includes a first adhesive and the filler includes a first filler. The first filler and the first adhesive may be dispersed in the first coating.

[0048] In the example, the first binder may be included in the first coating in an amount of about 95 wt% or more of the total binder (e.g., about 95 wt% to about 100 wt%, or about 100 wt%). Within the above range, the aforementioned effects of the diaphragm can be readily achieved.

[0049] In the example, the first filler may be included in the first coating in an amount of about 95 wt% or more of the total filler (e.g., about 95 wt% to about 100 wt%, or about 100 wt%). Within the above range, the aforementioned effects of the diaphragm can be readily achieved.

[0050] First adhesive The first binder may comprise the first structural unit, the second structural unit, and the third structural unit in a total amount of about 95 mol% or more (e.g., about 95 mol% to about 100 mol%, or about 100 mol%). Within the above range, the aforementioned effects of the diaphragm can be readily achieved.

[0051] According to an example embodiment, the first binder may be or include a particulate binder. For example, the first binder 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, 7000 nm). Within the above range, the adhesion of the diaphragm can be increased.

[0052] According to an example embodiment, the first adhesive can constitute an adhesive to ensure the adhesion between the diaphragm and the electrode. There is a trade-off between membrane resistance and adhesion. The copolymer can reduce the membrane resistance of the diaphragm and increase adhesion.

[0053] First structural unit: The first structural unit includes units derived from aromatic unsaturated monomers. These units may include units derived from aromatic vinyl monomers. The units derived from aromatic unsaturated monomers can provide adhesion, allowing the first coating to adhere to the porous substrate and electrodes as needed, and improving the permeability of the membrane.

[0054] The unit derived from aromatic unsaturated monomers is represented by the following chemical formula 1, and the copolymer may include one or more units represented by the following chemical formula 1: Chemical Formula 1: .

[0055] 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.

[0056] 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, anthraceneyl, pyrene, etc.

[0057] 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: .

[0058] 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, and m is an integer in the range of 0 to 5.

[0059] For 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 equal to 0 or 1.

[0060] For example, aromatic unsaturated monomers may include one or more of styrene, α-methylstyrene, 4-butylstyrene (such as 4-n-butylstyrene, 4-isobutylstyrene, 4-tert-butylstyrene, etc.), butoxystyrene including 4-butoxystyrene (such as 4-n-butoxystyrene, 4-isobutoxystyrene, 4-tert-butoxystyrene, etc.), halostyrene (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.).

[0061] 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 about 1 to 3 carbon atoms in the ester moiety. Units derived from (meth)acrylic acid monomers whose main chain contains an alkyl group having about 1 to 3 carbon atoms in the ester moiety can provide additional adhesion improvement.

[0062] Units derived from (meth)acrylic acid monomers whose main chain contains an alkyl group having about 1 to 3 carbon atoms in 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: .

[0063] 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.

[0064] In the example, the (meth)acrylic monomer containing an alkyl group having about 1 to 3 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.

[0065] For example, homopolymers of (meth)acrylic acid monomers whose main chain in the ester moiety contains an alkyl group having about 1 to 3 carbon atoms can have a glass transition temperature of about 50°C or higher (e.g., about 50°C to about 150°C). Within the above range, the glass transition temperature of the first binder described below can be readily achieved. For example, the (meth)acrylic acid monomers whose main chain in the ester moiety contains an alkyl group having about 1 to 3 carbon atoms can be or include methyl methacrylate, ethyl methacrylate, etc.

[0066] 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%, 45 mol%, 4 The first structural unit may be included in amounts of 6 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%, or may be included in amounts ranging from about 10 mol% to about 70 mol%, or from 30 mol% to 60 mol%. When the first structural unit is included in the above ranges, the membrane may exhibit low membrane resistance, desired or improved adhesion to porous substrates and electrodes, air permeability, and oxidation resistance.

[0067] Relative to 100 mol% of the copolymer, it can be in the range of about 5 mol% to about 80 mol% (e.g., 10 mol% to 70 mol%, 10 mol% to 60 mol%, 10 mol% to 35 mol%, 15 mol% to 30 mol%, or 5 mol% to 35 mol%) (5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, 17 mol%, 18 mol%, 19 mol%, 20 mol%, 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%). The amounts of 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.

[0068] Relative to 100 mol% of the copolymer, it can be in the range of about 5 mol% to about 80 mol% (e.g., 10 mol% to 70 mol%, 10 mol% to 60 mol%, 10 mol% to 35 mol%, 15 mol% to 30 mol%, or 5 mol% to 35 mol%) (5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, 17 mol%, 18 mol%, 19 mol%, 20 mol%, 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%, 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%, 80 mol%) include units derived from (meth)acrylic acid monomers whose main chain contains an alkyl group having about 1 to 3 carbon atoms. Within the above range, the aforementioned effects of the diaphragm can be readily achieved.

[0069] According to example embodiments, units derived from aromatic unsaturated monomers and units derived from (meth)acrylic acid monomers whose main chain contains an alkyl group having about 1 to 3 carbon atoms can be included in a molar ratio from about 1:0.5 to about 1:2 (e.g., 1:1 to 1:2) (1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2). A 1:1 molar ratio can also be included. Within the above ranges, the aforementioned effects of the diaphragm can be readily achieved.

[0070] Second structural unit: The second structural unit is derived from a (meth)acrylic acid monomer whose main chain contains an alkyl group having four or more carbon atoms. The second structural unit can improve the dispersibility of the first coating slurry and also improve the electrolyte wettability and flexibility of the first coating.

[0071] The second structural unit derived from the main chain of a (meth)acrylic acid monomer containing an alkyl group having four or more carbon atoms in the ester moiety 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: .

[0072] In chemical formula 4, R 7 and R 8 Each is independently hydrogen or includes methyl, and L 2 It is or includes substituted or unsubstituted straight-chain or branched C4 to C30 alkyl groups.

[0073] In this case, C4 to C30 alkyl can be or include C4 to C20 alkyl, C4 to C10 alkyl or C4 to C8 alkyl.

[0074] According to example embodiments, a (meth)acrylate monomer whose main chain in the ester moiety contains an alkyl group having four or more carbon atoms 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.

[0075] 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 during impregnation with the electrolyte can be reduced, 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, air permeability can be improved, and the capacity retention at room temperature and high temperature can be high.

[0076] For example, relative to 100 mol% of the copolymer, the second structural unit can be included in amounts of 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%, or 40 mol%, or in amounts ranging from about 15 mol% to about 35 mol% (e.g., 20 mol% to 30 mol%). Within these ranges, adhesion to the porous substrate and the electrode, as well as the flexibility of the first coating, can be increased.

[0077] Third structural unit: The third structural unit is derived from a sulfonic acid-containing monomer. In the presence of the first and second structural units, this third structural unit can reduce the membrane resistance by increasing the likelihood of lithium-ion migration.

[0078] According to an example embodiment, the third structural unit increases the glass transition temperature of the first binder 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.

[0079] 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, chemical formula 6, and chemical formula 7: Chemical formula 5: .

[0080] Chemical formula 6: .

[0081] Chemical Formula 7: .

[0082] In chemical formulas 5 to 7 R 9 R 10 R 11 R 12 R 13 and 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.

[0083] In the example, in chemical formulas 5 to 7, L 3 L 5 and L 7They can all be independently -C(=O)NH-, L 4 L 6 and L 8 They may each be independently alkylene groups or include C1 to C10 alkylene groups, and a, b, c, d, e, and f can all equal 1.

[0084] The third structural unit derived from the sulfonic acid-containing monomer may include only one, two, or more of the structural units represented by chemical formulas 5 to 7. In one example, the third structural unit derived from the sulfonic acid-containing monomer may include the structural unit represented by chemical formula 6, and in another example, the third structural unit derived from the sulfonic acid-containing monomer may include both the structural units represented by chemical formula 6 and the structural units represented by chemical formula 7.

[0085] 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.

[0086] Here, alkanes can be or include C1 to C20 alkanes, C1 to C10 alkanes, or C1 to C6 alkanes, and alkyl groups can be or include C1 to C20 alkyl groups, C1 to C10 alkyl groups, or C1 to C6 alkyl groups. A salt refers to a salt composed of the aforementioned sulfonic acid and suitable ions. Ions can be or include, for example, alkali metal ions, and in this case, the salt can be or include an alkali metal sulfonate salt.

[0087] (Methacrylamidoalkane sulfonic acid may be or include, for example, 2-(meth)acrylamido-2-methylpropane sulfonic acid, and (meth)acrylate sulfonyl ester may be or include at least one of, for example, (meth)acrylate 2-sulfoethyl ester, (meth)acrylate 3-sulfopropyl ester, etc.

[0088] 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 DC-IR change rate 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 DC-IR change rate at room temperature and high temperature can be reduced.

[0089] 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%. The third structural unit may be included in amounts ranging from about 10 mol% to about 60 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%. When the third structural unit is included in the above range, the membrane resistance of the first binder and the separator including the first 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.

[0090] The first binder may include an alkali metal. The alkali metal may be present in cationic form and may be, or include, at least one of, for example, lithium, sodium, potassium, rubidium, or cesium. For example, the alkali metal may exist in the form of a salt by combining with a copolymer. The alkali metal can help synthesize the monomer mixture into a copolymer in an aqueous solvent and improve the adhesion of the first coating, the permeability of the membrane, oxidation resistance, etc.

[0091] The first adhesive may have a glass transition temperature in the range of about 60°C to about 80°C. In examples, the glass transition temperature may 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, or 80°C, and the glass transition temperature may be from 62°C to 78°C (e.g., from 64°C to 75°C). Within the above range, the first coating may have desired or improved adhesion, and the membrane including the first coating may exhibit desired or improved permeability and oxidation resistance. The glass transition temperature of the first adhesive can be measured by typical methods known to those skilled in the art (such as thermomechanical analysis (TMA)). For example, the glass transition temperature may be measured as follows: 1. Cut the copolymer or adhesive 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; 2. Set the mechanical load to 0.0150 N, the heating rate to 5 °C / min, and measure the change in sample length with temperature; 3. The temperature at which the slope of the curve obtained by the TMA device changes is called the glass transition temperature.

[0092] The copolymer can be included in an amount ranging from about 1 wt% to about 90 wt% (e.g., 5 wt% to 80 wt%, or 10 wt% to 80 wt%) relative to the total amount of the first coating. Within the above range, adhesion to the electrode can be exhibited, and therefore the battery resistance is not increased, so there is no limitation on the capacity achieved.

[0093] In a first binder comprising alkali metals and copolymers, 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%) (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 99:1 to 70:30 (e.g., from 99:1 to 80:20, or from 90:10 to 80:20).

[0094] 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 (or copolymer and alkali metal) of the monomer mixture. When alkali metals are included in the above range, the first coating may have desired or improved adhesion, and the diaphragm including the first coating may exhibit desired or improved permeability and oxidation resistance.

[0095] The first binder of the copolymer, which includes a mixture of monomers, can be in 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.

[0096] The first binder of the copolymer comprising a monomer mixture may have a weight-average molecular weight in the range of about 100,000 g / mol to about 1,000,000 g / mol, 100,000 g / mol to 500,000 g / mol, 100,000 g / mol to 150,000 g / mol, 130,000 g / mol to 200,000 g / mol, or 300,000 g / mol to 900,000 g / mol. When the weight-average molecular weight of the first binder of the copolymer comprising the monomer mixture meets the above ranges, it can exhibit desired or improved adhesion and low membrane resistance. The weight-average molecular weight may be or may include the average molecular weight converted from polystyrene as measured by gel permeation chromatography.

[0097] The first binder, which is a copolymer of monomer mixtures, can be prepared by solution polymerization.

[0098] According to an example embodiment, a first binder comprising a copolymer of monomer mixtures may be included in a first coating of a diaphragm in the form of a membrane.

[0099] First packing The first filler may have an average particle size D50 greater than 0 nm and less than about 100 nm (e.g., in the range of about 10 nm to about 90 nm, 10 nm to 80 nm, 20 nm to 60 nm, or 50 nm). The first filler may have an average particle size D50 of 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, or 99 nm. Within the above ranges, Expression 1 can be readily satisfied.

[0100] In the example, the first packing material can have approximately 50m. 2 / g or greater (e.g., at approximately 60m) 2 / g to approximately 200m 2 / g, or 60m 2 / g to 150m 2 The specific surface area (within the range of / g) of the first packing can be 50m². 2 / g、55m 2 / g、60m 2 / g、65m 2 / g、70m 2 / g、75m 2 / g、80m 2 / g、85m 2 / g、90m 2 / g、95m 2 / g, 100m 2 / g, 105m 2 / g、110m 2 / g、115m 2 / g、120m 2 / g、125m 2 / g、130m 2 / g、135m 2 / g, 140m 2 / g、145m 2 / g, 150m 2 / g、155m 2 / g、160m 2 / g、165m 2 / g、170m 2 / g、175m2 / g、180m 2 / g、185m 2 / g、190m 2 / g、195m 2 / g、200m 2 The specific surface area is / g. Within the above range, the above-mentioned effects of the diaphragm can be easily achieved. In this specification, "specific surface area" may refer to the Brunauer-Emmett-Teller (BET) specific surface area and can be measured by typical methods known to those skilled in the art.

[0101] In the example, the first packing material can have a pH of about 7 or higher (e.g., a pH in the range of about 7 to about 9 (7, 7.5, 8, 8.5, 9)). Within this range, the aforementioned effects of the diaphragm can be easily achieved. In this specification, the pH of the packing material can be measured using a pH meter.

[0102] For example, the pH of a solution obtained by dissolving the packing material in pure water can be measured using a pH meter. Similarly, the pH of a solution obtained by adding 10g of packing material to 100mL of pure water, allowing the mixture to stand at room temperature for 30 days, and then removing the packing material can be measured using a pH meter. The pH meter can be used according to typical methods known to those skilled in the art.

[0103] In the example, the first filler may be amorphous. The amorphous filler may preferably include boehmite (particle size D50: 50 nm).

[0104] Figure 1 This is a scanning electron microscope (SEM) image of an amorphous filler. (See reference...) Figure 1 Amorphous fillers can have irregular shapes, rather than constant or uniform shapes.

[0105] The first filler may be or include, for example, inorganic fillers, organic fillers, organic / inorganic composite fillers, or combinations thereof. The inorganic filler may be or include ceramic materials capable of improving heat resistance. The inorganic filler may include, for example, at least one of metal oxides, quasi-metal oxides, metal fluorides, metal hydroxides, or combinations thereof. The inorganic filler 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, or combinations thereof, but this disclosure is not limited thereto. The organic filler may include at least one of acrylic compounds, imide compounds, amide compounds, or combinations thereof, but this disclosure is not limited thereto. The organic filler may have a core-shell structure, but this disclosure is not limited thereto.

[0106] For example, the first filler may be or include boehmite.

[0107] The first filler may be included in an appropriate amount relative to the first binder (e.g., a copolymer). According to example embodiments, the first binder and the first filler may be included in a mass ratio in the range of about 1:10 to about 1:50 (e.g., 1:20 to 1:30) (1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50). Within the above range, an effect of improved heat resistance in the electrolyte can be achieved.

[0108] The first filler may be included in an amount ranging from about 50 wt% to about 99 wt% (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%) relative to the total amount of the first coating. When the first filler is included in the above range, desired or improved heat resistance, durability, oxidation resistance, and stability may be exhibited.

[0109] The first coating may have a thickness ranging from about 0.01 μm to about 20 μm. Within this range, the thickness may be from about 0.01 μm to about 5 μm, from 0.1 μm to 3 μm, or from 0.1 μm to 1.5 μm. Within this range, the first coating may be used in a diaphragm.

[0110] The ratio of the thickness of the first coating to the thickness of the porous substrate can be in the range of about 0.1 to about 0.8 (e.g., 0.1 to 0.7 or 0.15 to 0.6). Within the above range, the diaphragm can exhibit desired or improved permeability, heat resistance, and adhesion.

[0111] Second coating The second coating includes an adhesive and a filler, wherein the adhesive includes a second adhesive and the filler includes a second filler. The second filler and the second adhesive may be dispersed in the second coating.

[0112] In the example, the second binder can be included in the second coating in an amount of about 95 wt% or more of the total binder (e.g., in the range of about 95 wt% to about 100 wt% or 100 wt%). Within the above range, the above-described effects of the diaphragm can be easily achieved.

[0113] In the example, the second filler can be included in the second coating in an amount of about 95 wt% or more of the total filler (e.g., in the range of about 95 wt% to about 100 wt% or 100 wt%). Within the above range, the above-described effects of the diaphragm can be easily achieved.

[0114] Second adhesive The second binder may comprise the first structural unit, the second structural unit, and the third structural unit in a total amount of about 95 mol% or more (e.g., in the range of about 95 mol% to about 100 mol%, or 100 mol%). Within the above range, the aforementioned effects of the diaphragm can be readily achieved.

[0115] The first, second, and third structural units are substantially the same as those described above regarding the first adhesive. Therefore, the description of the first adhesive can also be applied to the second adhesive.

[0116] In the example, the content of the first structural unit of the second adhesive may be the same as or different from the content of the first structural unit of the first adhesive. In the example, the content of the second structural unit of the second adhesive may be the same as or different from the content of the second structural unit of the first adhesive. In the example, the content of the third structural unit of the second adhesive may be the same as or different from the content of the third structural unit of the first adhesive.

[0117] In the example, the first structural unit type of the second adhesive may be the same as or different from the first structural unit type of the first adhesive. In the example, the second structural unit type of the second adhesive may be the same as or different from the second structural unit type of the first adhesive. In the example, the third structural unit type of the second adhesive may be the same as or different from the third structural unit type of the first adhesive.

[0118] Second packing The second filler may have an average particle size D50 of about 100 nm or larger and about 300 nm or smaller (e.g., in the range of about 180 nm to about 220 nm, 130 nm to 160 nm, or 150 nm). The second filler may have an average particle size D50 of 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, or 300 nm. Within the above ranges, Expression 1 above can be readily satisfied.

[0119] In the example, the second packing material can have approximately 50m. 2 / g or less (e.g., in about 10m) 2 / g to approximately 50m 2 / g or 10m 2 / g to 30m 2The second filler can have a specific surface area within the range of / g, and the second filler can have a specific surface area of ​​5m². 2 / g, 10m 2 / g, 15m 2 / g、20m 2 / g、25m 2 / g、30m 2 / g、35m 2 / g、40m 2 / g、45m 2 / g, 50m 2 The specific surface area is / g. Within the above range, the above-mentioned effects of the diaphragm can be easily achieved.

[0120] In the example, the second packing material may have a pH of about 7 or higher (e.g., a pH in the range of about 7 to about 9 (7, 7.5, 8, 8.5, 9)).

[0121] In the example, the second packing material can be cubic. The cubic packing material may preferably include boehmite (particle size D50: 150 nm).

[0122] Figure 2 This is a SEM image of the cubic packing material. (Reference) Figure 2 Cubic fillers can have shapes with angled corners and opposing quadrilateral (such as rectangular or square) faces.

[0123] The second filler may be or include, for example, inorganic fillers, organic fillers, organic / inorganic composite fillers, or combinations thereof. Inorganic fillers may be or include ceramic materials capable of improving heat resistance. Inorganic fillers may include, for example, at least one of metal oxides, quasi-metal oxides, metal fluorides, metal hydroxides, or 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, or combinations thereof, but this disclosure is not limited thereto. Organic fillers may include at least one of acrylic compounds, imide compounds, amide compounds, or combinations thereof, but this disclosure is not limited thereto. Organic fillers may have a core-shell structure, but this disclosure is not limited thereto.

[0124] For example, the second filler may be or include boehmite.

[0125] The second filler may be included in an appropriate amount relative to the second binder (e.g., a copolymer). According to example embodiments, the second binder and the second filler may be included in a mass ratio within the range of about 1:10 to about 1:50 (e.g., 1:20 to 1:30) (1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50). Within the above range, an effect of improved heat resistance in the electrolyte can be achieved.

[0126] The second filler may be included in an amount ranging from about 50 wt% to about 99 wt% (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%) relative to the total amount of the second coating. When the second filler is included in the above range, desired or improved heat resistance, durability, oxidation resistance, and stability may be exhibited.

[0127] The second coating may have a thickness ranging from about 0.01 μm to about 20 μm. Within this range, the thickness may be from 0.01 μm to 5 μm, from 0.1 μm to 3 μm, or from 0.1 μm to 1.5 μm. Within this range, the second coating may be used in a diaphragm.

[0128] The ratio of the thickness of the second coating to the thickness of the porous substrate can be in the range of about 0.1 to about 0.8 (e.g., 0.1 to 0.7 or 0.15 to 0.6). Within the above range, the diaphragm can exhibit desired or improved permeability, heat resistance, and adhesion.

[0129] Porous substrate Porous substrates can be or include substrates having a plurality of pores and are commonly used in electrochemical devices. Porous substrates can be, or include, polymeric membranes formed from or comprising any one or two or more copolymers or mixtures of: polyolefins, such as polyethylene, polypropylene, etc.; polyesters, such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.; polyacetal; polyamide; polyimide; polycarbonate; polyetheretherketone; polyaryletherketone; polyetherimide; polyamideimide; polybenzimidazole; polyethersulfone; polyphenylene ether; cyclic olefin copolymers; polyphenylene sulfide; glass fiber; and polytetrafluoroethylene (e.g., Teflon).

[0130] The porous substrate can be or includes, for example, a polyolefin substrate comprising polyolefins, and the polyolefin substrate contributes to improved battery safety due to its desired or improved shut-off function. The polyolefin substrate can be or includes at least one of, for example, polyethylene monolayer membranes, polypropylene monolayer membranes, polyethylene / polypropylene bilayer membranes, polypropylene / polypropylene / polypropylene trilayer membranes, and polyethylene / polypropylene / polypropylene trilayer membranes. Furthermore, in addition to olefin resins, polyolefin resins can also include non-olefin resins, or copolymers comprising olefin monomers and non-olefin monomers.

[0131] Porous substrates can have a thickness ranging from about 1 μm to about 40 μm (e.g., 1 μm to 30 μm, 1 μm to 20 μm, or 5 μm to 15 μm).

[0132] Figure 3 This is a cross-sectional view of a separator for a rechargeable lithium battery according to an exemplary embodiment of this disclosure. (Refer to...) Figure 3 The diaphragm includes a porous substrate 1, a first coating 2 located on a first surface of the porous substrate 1, and a second coating 3 located on a second surface of the porous substrate 1. The first coating 2 may include a first filler 4 and a first binder 5. The second coating 3 may include a second filler 6 and a second binder 7.

[0133] Diaphragm manufacturing method A separator for a rechargeable lithium battery can be manufactured by coating a first surface of a porous substrate with a composition for a first coating to form a coating film for a first coating, coating a second surface of the porous substrate with a composition for a second coating to form a coating film for a second coating, and drying the two coating films.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] For example, the positive electrode may also include additives that can form a sacrificial positive electrode.

[0138] 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.

[0139] 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, or combinations thereof.

[0140] As an example, the following compounds, represented by any of the following chemical formulas, can be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05), Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05), Li a Ni 1-b-c Co b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2), Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, and 0<α<2); Li a Ni b Co c L 1 d G 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 bO2 (0.90≤a≤1.8, and 0.001≤b≤0.1), Li a Mn2G b O4 (0.90≤a≤1.8, and 0.001≤b≤0.1), Li a Mn 1-g G g PO4 (0.90≤a≤1.8, and 0≤g≤0.5), Li (3-f) Fe2(PO4)3 (0≤f≤2) or Li a FePO4 (0.90≤a≤1.8).

[0141] In the above chemical formulas, A is or includes at least one of Ni, Co, Mn, or a combination thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is or includes at least one of O, F, S, P, or a combination thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 It is or includes at least one of Mn, Al, or combinations thereof.

[0142] 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, having 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.

[0143] 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%.

[0144] 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, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, nylon, etc.

[0145] 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, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0146] Al can be used as a current collector, but current collectors are not limited to this.

[0147] negative electrode The negative electrode for a rechargeable lithium battery may include a current collector and a layer of negative electrode active material on the current collector. The negative electrode active material layer may include a negative electrode active material and may also include a binder and / or a conductive material (e.g., an electrically conductive material).

[0148] For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder, and about 0 wt% to about 5 wt% of conductive material.

[0149] Negative electrode active material The negative electrode active material may include at least one of the following: materials that can reversibly insert / deintercalate lithium ions, lithium metal, lithium metal alloys, materials capable of doping / dedoping lithium, or transition metal oxides.

[0150] Materials capable of reversibly inserting / deintercalating lithium ions can include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. Crystalline carbon can be or includes graphite such as amorphous, flake, sheet, spherical, or fibrous natural or artificial graphite. Amorphous carbon can be or includes at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0151] Lithium metal alloys include alloys of lithium and metals (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).

[0152] Materials capable of doping / dedoping lithium can be, or include, Si-based or Sn-based negative electrode active materials. Si-based negative electrode active materials can include silicon, silicon-carbon composites, and SiO₂. x(0 < x ≤ 2), at least one of Si-Q alloys (where Q is or includes at least one of alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof). The Sn-based negative electrode active material may include at least one of Sn, SnO2, Sn-based alloys, or combinations thereof.

[0153] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are combined and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon may also be present between the primary silicon particles. For example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0154] 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, and the core includes crystalline carbon and silicon particles.

[0155] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0156] The binder may attach the negative electrode active material particles to each other and may attach the negative electrode active material to the current collector. The binder may include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0157] The non-aqueous binder may include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0158] The aqueous binder may be or include at least one of styrene-butadiene rubber, (meth)acrylic esterified styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, poly(ethylene oxide), polyvinylpyrrolidone, poly(epichlorohydrin), polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or combinations thereof.

[0159] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity may be further included. The cellulose-based compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may include at least one of Na, K, or Li.

[0160] Dry adhesives can be or include polymeric materials that can be fibers. For example, dry adhesives can be or include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0161] Conductive materials can impart electrical conductivity (e.g., electroconductivity) 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 may include: carbon-based materials, such as or including at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0162] The negative electrode current collector may include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0163] Rechargeable lithium batteries may also include an electrolyte.

[0164] electrolyte Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0165] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0166] Non-aqueous organic solvents may be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0167] 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 butylene carbonate (BC).

[0168] 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.

[0169] Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc. Aprotic solvents may include at least one of the following: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0170] Non-aqueous organic solvents can be used alone or in combination of two or more solvents.

[0171] Furthermore, 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.

[0172] Lithium salts dissolved in organic solvents supply lithium ions in batteries to enable the 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 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).

[0173] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch-shaped, or coin-shaped batteries.

[0174] 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-shaped battery is shown. (See reference) Figures 4 to 7The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40 is housed within the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 4 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. Figure 5 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 6 and Figure 7 As shown, the rechargeable lithium battery 100 may include Figure 7 The electrode terminals 70 shown in the figure, or for example Figure 6 The positive electrode terminal 71 and negative electrode terminal 72 shown in the figure form an electrical path for guiding the current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0175] 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.

[0176] 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.

[0177] <Reference Example> 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 pressure inside the flask was then reduced to 10 mmHg using a diaphragm pump and the pressure was restored to atmospheric pressure using nitrogen. This process was repeated three times.

[0178] 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.

[0179] 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)), 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 particle size was 500 nm, and the glass transition temperature (Tg) of the binder was 65.1 °C.

[0180] 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 (Tg) 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, the MMA-derived units, the EHA-derived second structural units, and the 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%).

[0181] 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 (Tg) 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%).

[0182] 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 (poly(SM-co-MMA-co-EHA-co-AMPS) lithium salt), 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 17:17:26:40. The NV component content in the reaction solution was 9.0 wt% (theoretical value: 10 wt%).

[0183] 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, the MMA-derived units, the EHA-derived second structural units, and the 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%).

[0184] 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, the MMA-derived units, the EHA-derived second structural units, and the 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%).

[0185] 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 (poly(SM-co-EHA-co-AMPS) lithium 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%).

[0186] 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%).

[0187] 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, the MMA-derived units, the EHA-derived second structural units, and the 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%).

[0188] 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, the MMA-derived units, the EHA-derived second structural units, and the 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%).

[0189] 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, the MMA-derived units, the EHA-derived second structural units, and the 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%).

[0190] 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, the MMA-derived units, the EHA-derived second structural units, and the 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%).

[0191] 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%).

[0192] 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.

[0193] Table 1:

[0194] Refer to Example 1 Ten parts by weight of the adhesive of Preparation Example 1 and 90 parts by weight of distilled water were mixed to prepare a coating composition.

[0195] The prepared coating composition was applied to both sides of a polyethylene-based membrane (commercially available from CZMZ, thickness: 5.5 μm, air permeability: 110 s / 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 a coating with a total thickness of 1.4 μm, thereby manufacturing a separator for rechargeable lithium batteries.

[0196] Refer to Examples 2 to 7 The separator for rechargeable lithium batteries is manufactured in the same manner as in Reference Example 1, except that the type of binder is changed.

[0197] Compare with reference examples 1 to 6 The separator for rechargeable lithium batteries is manufactured in the same manner as in Reference Example 1, except that the type of binder is changed.

[0198] Battery manufacturing Manufacturing of the negative electrode: A slurry of negative electrode active material 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) as the negative electrode active material. The mixture was then added to distilled water and stirred with a mechanical stirrer for 60 minutes. The slurry was coated onto a 10 μm thick copper current collector using a doctor blade, dried in a hot air dryer set at 100 °C for 0.5 hours, and then further dried under vacuum at 120 °C for 4 hours. The mixture was then rolled to fabricate the negative electrode.

[0199] Manufacturing of the positive electrode: A slurry of positive electrode active material 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). The mixture was then added to an N-methyl-2-pyrrolidone solvent and stirred mechanically for 30 minutes. The slurry was coated onto a 20 μm thick aluminum current collector using a doctor blade, dried in a hot air dryer at 100°C for 0.5 hours, and then further dried under vacuum at 120°C for 4 hours. Finally, the mixture was rolled to fabricate the positive electrode.

[0200] Electrode assembly core: Each diaphragm obtained from the reference example and comparative reference example was placed between the fabricated positive and negative electrodes and then wound to fabricate the electrode assembly core. The core was inserted into a bag, electrolyte was injected, and the bag was vacuum-sealed. The electrolyte used was prepared by dissolving 1.3 M LiPF6 in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 3:5:2 (based on a total of 10). The core inserted into the bag was pressed at 80°C for 3 minutes while applying 11.7 kgf / cm². 2 The pressure is used to manufacture rechargeable lithium batteries.

[0201] Capacity retention after 200 cycles (in %) For batteries manufactured using each separator from the reference example and comparative reference example, 200 cycles were repeated, in which constant current charging was performed at 0.5C rate until the voltage reached 4.2V at 25°C and 45°C, followed by cutoff at 0.025C rate in constant voltage mode, and then the battery was discharged at 0.5C rate until the voltage reached 2.5V. The capacity retention rate (i.e., lifetime characteristics) based on the number of cycles was evaluated, and the results were obtained.

[0202] DC internal resistance (DC-IR, unit: mΩ) Batteries with a capacity of 75 mAh, manufactured using separators from the reference example and comparative reference example, were charged at 25°C and 45°C with a constant current of 0.2C and a constant voltage of 4.25V under a 0.05C cutoff condition. After resting for 10 minutes, the batteries 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 (100%), or equivalently discharged to 50%) by applying a current of 1C for 10 seconds and measuring the resulting voltage drop (V).

[0203] The DC-IR change rate is the ratio of the DC-IR after 200 cycles to the initial DC-IR, expressed as a percentage.

[0204] Table 2:

[0205] Table 3:

[0206] As shown in Table 2, it can be seen that, by including the binder described above in this disclosure, the membrane of the reference example is able to exhibit high capacity retention at room temperature and high temperature, and low DC-IR change rate after 200 cycles at room temperature and high temperature.

[0207] On the other hand, as shown in Table 3, it can be seen that, by excluding the binder described above in this disclosure, the diaphragm of the comparative reference example exhibits a relatively low capacity retention or a high DC-IR change rate.

[0208] Example 1 The binder of Example 7 was prepared and boehmite (particle size D50: 50 nm, amorphous, pH: 7.71, BET specific surface area: 90.4 m²) was used as a filler. 2 (g) Based on the solid content, binder:filler are mixed at a mass ratio of 1:20, and the mixture is added to an aqueous solvent and ground and dispersed using a bead mill at 25°C for 30 minutes to prepare a dispersion for the first coating.

[0209] The binder of Example 7 was prepared along with boehmite (particle size D50: 150 nm, cubic, pH: 7.22, BET specific surface area: 22.1 m²) as a filler. 2 (g) Based on the solid content, binder:filler are mixed at a mass ratio of 1:20, and the mixture is added to an aqueous solvent and ground and dispersed at 25°C for 30 minutes using a bead mill to prepare a dispersion for the second coating.

[0210] The dispersion for the first coating was applied to one surface of a polyethylene-based membrane (commercially available from CZMZ, thickness: 5.5 μm, air permeability: 110 seconds / 100 cc, puncture strength: 360 kgf) serving as a porous substrate using a die-coating method. The dispersion for the second coating was then applied to the other surface of the membrane using the same die-coating method, at a concentration of 14 g / m³. 3 The dispersion is dried at an absolute water vapor content (average value) to form a first coating (thickness: 1 μm) and a second coating (thickness: 1 μm), thereby manufacturing a separator for rechargeable lithium batteries.

[0211] Example 2 The diaphragm was manufactured in the same manner as in Example 1, except that the adhesive used in Preparation Example 3 was used instead of the adhesive used in Preparation Example 7.

[0212] Example 3 The diaphragm was manufactured in the same manner as in Example 1, except that the adhesive used in Preparation Example 6 was used instead of the adhesive used in Preparation Example 7.

[0213] Example 4 The diaphragm is manufactured in the same manner as in Example 2, except that the particle size D50 of the boehmite in the first and second coatings is changed as shown in Table 4.

[0214] Comparison Example 1 The diaphragm is manufactured in the same manner as in Example 2, except that fillers are not included in the first and second coatings.

[0215] Comparison Example 2 The diaphragm is manufactured in the same manner as in Example 2, except that no filler is included in the second coating.

[0216] Compare Example 3 The membrane was manufactured in the same manner as in Example 2, except that the first coating included boehmite (particle size D50: 150 nm, cubic, pH: 7.22, BET specific surface area: 22.1 m²). 2 / g) is used as filler, and filler is not included in the second coating.

[0217] Compare Example 4 The membrane was manufactured in the same manner as in Example 2, except that boehmite (particle size D50: 150 nm, cubic, pH: 7.22, BET specific surface area: 22.1 m²) was included in both the first and second coatings. 2 / g) as filler.

[0218] Compare Example 5 The membrane was manufactured in the same manner as in Example 2, except that boehmite (particle size D50: 50 nm, amorphous, pH: 7.71, BET specific surface area: 90.4 m²) was included in both the first and second coatings. 2 / g) as filler.

[0219] The battery is manufactured using the same method described above, using the manufactured separator.

[0220] Breathability (unit: seconds / 100cc) The permeability of the manufactured diaphragm is determined by measuring the time (in seconds) it takes for 100cc of air to pass through the diaphragm using a measuring device (EG01-55-1MR, available from ASAHI SEIKO GmbH).

[0221] Air permeability measurement device settings: Measured pressure: 0.5 kg / cm² 2 Cylinder pressure: 2.5 kg / cm² 2 And set the time: 10 seconds.

[0222] Electrolyte wettability (unit: wt%) The prepared adhesive was dried in an oven set at 120°C for 12 hours to obtain a film (thickness: 20 μm, weight before impregnation (W1)). The film was placed in a manufactured bag and impregnated with an electrolyte, and the bag was vacuum sealed. After allowing the sealed bag to stand in an oven set at 60°C for 72 hours, the film was immediately removed and weighed to obtain the weight (W2). The wettability was calculated by W2 / W1×100.

[0223] Adhesion to the positive electrode (unit: N) The separator was attached to the positive electrode (in the same manner as described in "Battery Manufacturing"), then inserted into a bag, and an electrolyte (1.3 M LiPF6 dissolved in a mixed solvent of EC, EMC, and DEC in a volume ratio of 3:5:2) was injected. The resulting assembly was then allowed to stand for 12 hours at 10 kgf / cm². 2 Up to 20 kgf / cm 2 Press the membrane and positive electrode under pressure and at a temperature of 70°C to 90°C for 5 to 20 seconds, then disassemble. Remove the diaphragm and positive electrode from the bag, unfold the positive electrode and diaphragm 180°, and use a tensile tester (HT400, available from Tinius Olsen) to measure the force required to separate the positive electrode from the diaphragm.

[0224] Membrane resistance during electrolyte impregnation (unit: Ω) The membrane resistance was evaluated using electrochemical impedance spectroscopy (EIS). Each membrane fabricated in the example and comparative examples was impregnated with an electrolyte prepared by dissolving 1.5 M LiPF6 in a mixed solvent of EC, EMC, and dimethyl carbonate (DMC) in a volume ratio of 3:5:2. The membrane was then mounted onto an aluminum foil electrode with leaded terminals and sealed in an aluminum cask to fabricate a test cell. The resistance (Ω) of the test cell was measured at 20 °C using alternating current (AC) impedance spectroscopy (measurement frequency: 100 kHz).

[0225] Heat resistance (unit: %) Heat resistance is evaluated by the shrinkage rate in the electrolyte.

[0226] Samples were prepared by cutting the separator for rechargeable lithium batteries, based on the example and comparative examples, into 8cm × 8cm dimensions. A 5cm × 5cm square was drawn on the surface of each sample.

[0227] A slurry of positive electrode active material (LiCoNiAl), a slurry of carbon nanotubes (carbon nanotubes), and a slurry of polyvinylidene fluoride (PVDF) was prepared by mixing 97 wt% of LiCoNiAl as the positive electrode active material, 1.5 wt% of carbon nanotubes as the conductive material, and 1.5 wt% of polyvinylidene fluoride (PVDF) and adding water. The prepared positive electrode active material slurry was coated onto aluminum foil, dried, and rolled to manufacture the positive electrode.

[0228] A negative electrode active material slurry was prepared by mixing 97.4 wt% of a negative electrode active material, 1.0 wt% of carboxymethyl cellulose, 1.5 wt% of styrene-butadiene rubber, and 0.1 wt% of carbon nanotubes as a conductive material. A silicon-based negative electrode active material was used. The prepared negative electrode active material slurry was coated onto a copper foil, dried, and rolled to fabricate the negative electrode.

[0229] Three sets of positive electrode-sample-negative electrode laminates were prepared by placing a sample between the positive and negative electrodes and inserting the laminates into a bag. 2 g of electrolyte (1.5 M LiPF6 dissolved in a mixed solvent of EC, EMC, and DMC in a volume ratio of 30:50:20) was injected to completely saturate the laminates. The bag was sealed and allowed to stand at 25°C for 12 hours. Then, the resulting laminates were placed in an oven at 150°C for 1 hour. The samples were removed, and the dimensions of the sides of a drawn square were measured to calculate the shrinkage rates in the longitudinal (MD) and transverse (TD) directions. The shrinkage rate was calculated using Equation 1 below. The MD and TD shrinkage rates were measured, and their average values ​​were obtained.

[0230] Equation 1: Shrinkage rate = (L0-L1) / L0×100.

[0231] L0 is the initial length of the diaphragm, and L1 is the length of the diaphragm after it has been left to stand at 150°C for 1 hour.

[0232] Table 4:

[0233] In Table 4, thickness It is the thickness of the first coating / the thickness of the second coating.

[0234] As shown in Table 4, the example diaphragms are able to exhibit high electrolyte wettability, desired or improved permeability, and high adhesion to the electrode plates.

[0235] The separator for rechargeable lithium batteries according to the example embodiments can improve the capacity of rechargeable lithium batteries, and can also improve the safety and lifespan of rechargeable lithium batteries.

[0236] Example embodiments of this disclosure have been described, but the disclosure is not limited thereto. Various modifications can be made within the scope of the claims, the detailed description of this disclosure, and the accompanying drawings, and such modifications are also included within the scope of this disclosure.

Claims

1. A separator for a rechargeable lithium battery, the separator comprising: Porous substrate; A first coating is applied to a first surface of the porous substrate; as well as The second coating is applied to the second surface of the porous substrate. The first coating comprises a first adhesive and a first filler, and the second coating comprises a second adhesive and a second filler. Both the first and second adhesives comprise copolymers, the copolymers 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 contains an alkyl group having four or more carbon atoms in the ester moiety; and a third structural unit derived from a sulfonic acid-containing monomer. The copolymer, relative to 100 mol%, comprises 5 mol% to 80 mol% of the first structural unit, 10 mol% to 40 mol% of the second structural unit, and 5 mol% to 80 mol% of the third structural unit. The first packing and the second packing satisfy the following expression 1: Expression 1: (Average particle size D50 of the second packing) / (Average particle size D50 of the first packing) ≥ 3.

2. The diaphragm according to claim 1, wherein, The first filler has an average particle size D50 greater than 0 nm and less than 100 nm, and the second filler has an average particle size D50 of 100 nm or greater and 300 nm or less.

3. The diaphragm according to claim 1, wherein, The first filler is amorphous, and the second filler is cubic.

4. The diaphragm according to claim 1, wherein, The first packing material and the second packing material have a pH of 7 or higher.

5. The diaphragm according to claim 1, wherein, Both the first filler and the second filler include at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

6. The diaphragm according to claim 1, wherein, Both the first adhesive and the second adhesive have a glass transition temperature in the range of 60°C to 80°C.

7. The diaphragm according to claim 1, wherein, It includes the first adhesive and the first filler in a mass ratio ranging from 1:10 to 1:50, and includes the second adhesive and the second filler in a mass ratio ranging from 1:10 to 1:

50.

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: ； 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, 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 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 whose main chain contains an alkyl group having one to three carbon atoms in the ester moiety.

10. The diaphragm according to claim 9, wherein, The unit of the (meth)acrylic acid monomer, whose main chain contains an alkyl group having 1 to 3 carbon atoms, derived from 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 whose main chain contains alkyl groups having 1 to 3 carbon atoms, in a range of 1:0.5 to 1:

2.

12. The diaphragm according to claim 9, wherein, The copolymer comprises, relative to 100 mol%, 5 mol% to 35 mol% of the units derived from aromatic unsaturated monomers, 5 mol% to 35 mol% of the units derived from (meth)acrylic acid monomers whose main chain contains alkyl groups having 1 to 3 carbon atoms, 20 mol% to 30 mol% of the second structural units, and 10 mol% to 60 mol% of the third structural units.

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 isodecyl (meth)acrylate. 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, Both the first coating and the second coating have 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 diaphragm according to any one of claims 1 to 14 is placed between the positive electrode and the negative electrode.

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