Separator for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

Examples of the present disclosure relate to a separator for a rechargeable lithium battery and a rechargeable lithium battery including the same. The separator for a rechargeable lithium battery includes: a porous substrate; and a coating layer on at least one surface of the porous substrate. The coating includes a crosslinking product of a filler and a composition including a binder and a crosslinking agent, the binder including a (meth) acryloyl-based binder including a first structural unit derived from (meth) acrylamide and a second structural unit derived from (meth) acrylamide, the second structural unit includes at least one of a structural unit derived from (meth) acrylic acid, a structural unit derived from (meth) acrylate, and a structural unit derived from (meth) acrylamidosulfonic acid. The cross-linking agent includes an aziridine-based cross-linking agent in an amount ranging from about 5 wt% to about 50 wt% with respect to an amount of the (meth) acryloyl-based binder, and a particle diameter D100 of the filler is about 0.7 [mu] m or less.

Description

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0156517 filed on November 13, 2023 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. Technical Field

[0002] The present disclosure relates to a separator for a rechargeable lithium battery and a rechargeable lithium battery including the separator. Background Art

[0003] With the widespread use of electronic devices using batteries, such as mobile phones, notebook computers, and electric vehicles, the demand for secondary batteries with high energy density and high capacity is increasing. Therefore, it may be advantageous to improve the performance of rechargeable lithium batteries.

[0004] A rechargeable lithium battery is a battery including positive and negative electrodes containing an active material capable of inserting and extracting lithium ions, and generates electric energy through redox reactions when lithium ions are inserted into and extracted from the positive and negative electrodes.

[0005] A rechargeable lithium battery may include a separator between a positive electrode and a negative electrode. The separator is immersed in an electrolyte. When the separator does not experience thermal shrinkage in the electrolyte and maintains its original form, it can be expected to ensure the safety of the battery. Summary of the invention

[0006] One example embodiment includes a separator for a rechargeable lithium battery, the separator having a low drying shrinkage rate and a low shrinkage rate in an electrolyte, thereby increasing the safety of the battery.

[0007] Another example embodiment includes a rechargeable lithium battery including the separator for a rechargeable lithium battery.

[0008] According to one aspect of the present disclosure, a separator for a rechargeable lithium battery includes: a porous substrate; and a coating layer located on at least one surface of the porous substrate. The coating layer includes a cross-linked product of a binder and a cross-linking agent and a filler, the binder includes a (meth)acryl-based binder including a first structural unit and a second structural unit, the first structural unit is derived from (meth)acrylamide, the second structural unit includes at least one of a structural unit derived from (meth)acrylic acid, a (meth)acrylic ester or a salt thereof, and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof, the cross-linking agent includes an aziridine-based cross-linking agent, the aziridine-based cross-linking agent is included in an amount ranging from about 5 wt % to about 50 wt % relative to the amount of the (meth)acryl-based binder, and the particle size D100 of the filler is about 0.7 μm or less.

[0009] According to another aspect of the present disclosure, a rechargeable lithium battery includes the separator for a rechargeable lithium battery, a positive electrode, and a negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a cross-sectional view showing a separator for a rechargeable lithium battery according to one example embodiment.

[0011] Figures 2 to 5 is a diagram schematically illustrating a rechargeable lithium battery according to an example embodiment. DETAILED DESCRIPTION

[0012] Hereinafter, exemplary embodiments of the present disclosure are described in detail. However, the embodiments are presented as examples, the present disclosure is not limited thereto, and the present disclosure is limited only by the scope of the appended claims.

[0013] Unless otherwise stated herein, when a component such as a layer, film, region, plate, etc. is described as being disposed “on” another component, it not only includes the case where the component is “directly on” the other component but also includes the case where other components exist therebetween.

[0014] Unless otherwise stated herein, the singular may also include the plural. In addition, unless otherwise stated, the term "A or B" may mean "including A, including B, or including A and B".

[0015] In this specification, "a combination thereof" may refer to a mixture, a stack, a composite, a copolymer, an alloy, a blend or a reactant of components.

[0016] Unless otherwise defined herein, "particle size D100" may refer to the diameter of particles with a cumulative volume of 100% by volume in a particle size distribution. Particle size distribution may be measured by methods known to those skilled in the art. For example, particle size distribution may be measured using a particle size analyzer, a transmission electron microscope photograph, or a scanning electron microscope photograph. As another method, particle size distribution may be obtained by measuring the particle size using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles in each particle size range, and then calculating the particle size D100 therefrom. Alternatively, particle size distribution may be measured using a laser diffraction method. For example, when particle size distribution is measured by a laser diffraction method, the particles to be measured may be dispersed in a dispersion medium, and then the dispersion medium may be introduced into a commercially available laser diffraction particle size measuring device (e.g., MT 3000 of Microtrac), and an ultrasonic wave of about 28kHz may be radiated with an output power of 60W to calculate the particle size D100 based on 100% particle size distribution in the measuring device.

[0017] Unless otherwise defined herein, "particle size D50" may refer to the diameter of particles having a cumulative volume of 50% by volume in a particle size distribution. The particle size distribution may be obtained by the method described in particle size D100.

[0018] In the present specification, "(meth)acryloyl" means an acryloyl group and / or a methacryloyl group.

[0019] Hereinafter, unless otherwise defined, "substituted" means that hydrogen in a compound is replaced by a substituent such as or including at least one of the following substituents: 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 each independently hydrogen or C1 to C6 alkyl), thiobetainyl (-RR'NRR') or thiobetainyl (-RR'NRR'). + (CH2) n SO3 - , n is a natural number of 1 to 10) (wherein, R and R' are each independently a C1 to C20 alkyl group), a carboxybetaine group (-RR'N + (CH2) n COO - , n is a natural number from 1 to 10) (here, R and R' are each independently a C1 to C20 alkyl group), an azido group (-N3), a carbamimido group (-C(=NH)NH2), a hydrazine group (-NHNH2), a hydrazine group (-N(NH2)-), a carbamoyl group (-C(O)NH2), a thiol group (-SH), an acyl group (-C(=O)R, where R represents a C1 to C6 alkyl group, a C1 to C6 alkoxy group or a C6 to C12 aryl group), a carboxyl group (-COOH) or a salt thereof (-C(=O)OM, where M represents an organic or inorganic cation), a sulfonic acid group (-SO3H) or a salt thereof (-SO3M, where M represents an organic or inorganic cation), a phosphate group (-PO3H2) or a salt thereof (-PO3MH or -PO3M2, where M represents an organic or inorganic cation) and combinations thereof.

[0020] Hereinafter, C1 to C3 alkyl may be or include at least one of methyl, ethyl or propyl. C1 to C10 alkylene may be or include, for example, C1 to C6 alkylene, C1 to C5 alkylene or C1 to C3 alkylene and may be or include, for example, methylene, ethylene or propylene. C3 to C20 cycloalkylene may be or include, for example, C3 to C10 cycloalkylene or C5 to C10 cycloalkylene, for example, cyclohexylene. C6 to C20 arylene may be or include, for example, C6 to C10 arylene, for example, phenylene. C3 to C20 heterocyclic radical may be or include, for example, C3 to C10 heterocyclic radical, for example, pyridyl.

[0021] Hereinafter, “hetero” means including one or more heteroatoms such as or including at least one of N, O, S, Si, and P.

[0022] In addition, in chemical formulas, the symbol It refers to the parts connected to the same or different atoms, groups or structural units.

[0023] Hereinafter, "alkali metal" refers to an element belonging to Group 1 of the periodic table, such as lithium, sodium, potassium, rubidium, cesium, or francium, and may exist in a cationic or neutral state.

[0024] In the present specification, when describing a numerical range, “X to Y” means “X or more and Y or less (greater than or equal to X and less than or equal to Y)”.

[0025] When the term "about" or "substantially" is used in conjunction with a numerical value in this specification, it is intended that the relevant numerical value includes a tolerance of ±10% around the stated numerical value. In addition, when percentages are mentioned in this specification, it is intended that these percentages are based on weight, i.e., weight percentages. The expression "up to" includes an amount from zero to the indicated upper limit and all values ​​therebetween. When a range is specified, the range includes all values ​​therebetween, such as in increments of 0.1%.

[0026] A separator for a rechargeable lithium battery according to an example embodiment includes: a porous substrate; and a coating layer located on at least one surface of the porous substrate, wherein the coating layer includes a cross-linked product of a binder and a cross-linking agent and a filler, the binder includes a (meth)acryl-based binder including a first structural unit and a second structural unit, the first structural unit being derived from (meth)acrylamide, the second structural unit including at least one of a structural unit derived from (meth)acrylic acid, a (meth)acrylic ester or a salt thereof, and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof, the cross-linking agent includes an aziridine-based cross-linking agent, the aziridine-based cross-linking agent is included in an amount ranging from 5 wt % to 50 wt % relative to the amount of the (meth)acryl-based binder, and a particle size D100 of the filler is about 0.7 μm or less.

[0027] The coating layer includes a cross-linked product of a (meth)acryl-based binder and a given content of an aziridine-based cross-linking agent, and a filler. Therefore, the separator for a rechargeable lithium battery can have a significantly low dry shrinkage rate and a shrinkage rate in an electrolyte. According to an example embodiment, the dry shrinkage rate of the separator for a rechargeable lithium battery can be about 5% or less, and the shrinkage rate in the electrolyte can be about 15% or less, for example, about 10% or less, or for example, about 5% or less.

[0028] According to an example embodiment, a separator for a rechargeable lithium battery shows a significantly low shrinkage rate in an electrolyte. The shrinkage rate in the electrolyte is obtained in consideration of the application position of the separator in the rechargeable lithium battery. The separator may be impregnated with the electrolyte. When the separator is impregnated with the electrolyte, the separator having a low shrinkage rate in the electrolyte can increase the stability of the battery by maintaining heat resistance without weakening the mechanical properties of the (meth)acryl-based binder.

[0029] The separator formed of a composition including a (meth)acryl-based binder but not including an aziridine-based crosslinking agent as a crosslinking agent or including a crosslinking agent other than the aziridine-based crosslinking agent (or including a composition including a (meth)acryl-based binder but not including an aziridine-based crosslinking agent as a crosslinking agent or including a crosslinking agent other than the aziridine-based crosslinking agent) may not satisfy the above-mentioned range of shrinkage rate in the electrolyte. According to an example embodiment, the aziridine-based crosslinking agent may be included in an amount of about 95 wt % or more of the total crosslinking agent in the composition, for example, in a range of about 98 wt % to about 100 wt %, or for example, about 100 wt %.

[0030] The aziridine crosslinking agent is included as a crosslinking agent, and the aziridine crosslinking agent may be included in an amount ranging from about 5 wt % to about 50 wt % relative to the content of the (meth)acryl-based binder. Within the above range, crosslinking of the (meth)acryl-based binder and reduction of shrinkage in the electrolyte may be achieved.

[0031] A separator formed of a composition comprising a (meth)acrylic binder but not including a filler having a particle size D100 of about 0.7 μm or less or including a filler having a particle size D100 greater than about 0.7 μm (or comprising a composition comprising a (meth)acrylic binder but not including a filler having a particle size D100 of about 0.7 μm or less or including a filler having a particle size D100 greater than about 0.7 μm) may not meet the above-mentioned shrinkage rate range in the electrolyte.

[0032] A separator formed of a composition including an aziridine crosslinker and a filler but not including a (meth)acryl-based binder or including a binder other than a (meth)acryl-based binder (i.e., not including any of the first structural unit or the second structural unit of the (meth)acryl-based binder or a binder replaced by another structural unit) (or including a composition including an aziridine crosslinker and a filler but not including a (meth)acryl-based binder or including a binder other than a (meth)acryl-based binder (i.e., not including any of the first structural unit or the second structural unit of the (meth)acryl-based binder or a binder replaced by another structural unit) may not satisfy the above-mentioned ranges of dry shrinkage and shrinkage in the electrolyte. According to an example embodiment, the acryl-based binder may be included in an amount of about 95 wt % or more of the total binder in the composition, for example, in a range of about 98 wt % to about 100 wt %, or for example, about 100 wt % (meth)acryl-based binder.

[0033] According to an example embodiment, the coating may include: a crosslinked product of a composition including a (meth)acryl-based binder and an aziridine-based crosslinking agent; and a filler having a particle size D100 of about 0.7 μm or less. According to an example embodiment, the crosslinked product may be or include a thermal crosslinked product.

[0034] According to one example embodiment, the coating layer may be formed of a composition including a (meth)acryl-based binder and an aziridine-based cross-linking agent, and a filler having a particle size D100 of about 0.7 μm or less.

[0035] coating The binder includes a (meth)acryl-based binder, which includes: a first structural unit derived from (meth)acrylamide; and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylic ester or a salt thereof and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0036] The (meth)acryloyl-based binder is a water-based heat-resistant binder and can fix the filler on the porous substrate, provide bonding strength, allow the coating to adhere to the porous substrate and the electrode, and help increase the heat resistance, air permeability and oxidation resistance of the separator.

[0037] The first structural unit derived from (meth)acrylamide has an amide functional group (-(C=O)-NH2) in the structural unit. The -(C=O)-NH2 functional group can increase the adhesion properties with the porous substrate and the electrode and more firmly fix the inorganic filler in the coating layer by forming a hydrogen bond with the -OH functional group of the filler, thereby enhancing the heat resistance of the separator.

[0038] The structural unit derived from (meth) acrylic acid, (meth) acrylic acid ester or its salt contained in the second structural unit can be configured to fix the filler on the porous substrate, and also provide bonding strength so that the coating is bonded to the porous substrate and the electrode, and helps to increase the heat resistance and air permeability of the separator. In addition, the structural unit derived from (meth) acrylic acid, (meth) acrylic acid ester or its salt can contain a carboxyl functional group (-C(=O)O-) in the structural unit, thereby helping to improve the dispersibility of the slurry used for the coating.

[0039] The structural unit derived from (meth)acrylamidesulfonic acid or a salt thereof included in the second structural unit may include a bulky functional group, thereby reducing mobility of a binder including the same and enhancing heat resistance of the separator.

[0040] In an exemplary embodiment, the (meth)acryl-based binder may be or include a binary copolymer including a first structural unit derived from (meth)acrylamide and a second structural unit derived from (meth)acrylic acid, (meth)acrylic ester, or a salt thereof, a binary copolymer including a first structural unit derived from (meth)acrylamide and a second structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof, or a terpolymer including a first structural unit derived from (meth)acrylamide and a structural unit derived from (meth)acrylic acid, (meth)acrylic ester, or a salt thereof and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0041] The content of the first structural unit may be in the range of 55 mol % to 95 mol % (e.g., 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 %, 81 mol %, 82 mol %, 83 mol %, 84 mol %, 85 mol %, 86 mol %, 87 mol %, 88 mol %, 89 mol %, 90 mol %, 91 mol %, 92 mol %, 93 mol %, 94 mol %, 95 mol %). ), and the content of the second structural unit can be in the range of 5mol% to 45mol% (for example, 5mol%, 6mol%, 7mol%, 8mol%, 9mol%, 10mol%, 11mol%, 12mol%, 13mol%, 14mol%, 15mol%, 16mol%, 17mol%, 18mol%, 19mol%, 20mol%, 21mol%, 22mol%, 23mol%, 24mol%, 25mol%, 26mol%, 27mol%, 28mol%, 29mol%, 30mol%, 31mol%, 32mol%, 33mol%, 34mol%, 35mol%, 36mol%, 37mol%, 38mol%, 39mol%, 40mol%, 41mol%, 42mol%, 43mol%, 44mol%, 45mol%) relative to 100mol% of the (meth)acryl-based binder. Within the above range, the (meth)acryl-based binder can be easily prepared, and the above-mentioned effects of the coating can be easily provided.

[0042] In an exemplary embodiment, the content of the first structural unit may be in the range of 75 mol % to 95 mol % (e.g., in the range of 80 mol % to 95 mol % or in the range of 80 mol % to 90 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 %, 81 mol %, 82 mol %, 83 mol %, 84 mol %, 85 mol %, 86 mol %, 87 mol %, 88 mol %, 89 mol %, 90 mol %, 91 mol %, 92 mol %, 93 mol %, 94 mol %, 95 mol %) relative to 100 mol % of the (meth)acryl-based binder.

[0043] The content of the structural unit derived from (meth)acrylic acid, (meth)acrylic acid ester or its salt in the second structural unit may be in the range of 0 mol % to 40 mol % (e.g., in the range of more than 0 mol % to 40 mol % or less, in the range of 1 mol % to 40 mol %, or in the range of 1 mol % to 10 mol %) (e.g., 0 mol %, 1 mol %, 2 mol %, 3 mol %, 4 mol %, 5 mol %, 6 mol %, 7 mol %, 8 mol %, 9 mol %, 10 mol %, 11 mol %, 12 mol %, 13 mol %, 14 mol %, 15 mol %, 16 mol %, 17 mol %, 18 mol %, 19 mol %, 20 mol %, 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 %, 2mol%, 23mol%, 24mol%, 25mol%, 26mol%, 27mol%, 28mol%, 29mol%, 30mol%, 31mol%, 32mol%, 33mol%, 34mol%, 35mol%, 36mol%, 37mol%, 38mol%, 39mol%, 40mol%), and the content of the structural unit derived from (meth)acrylamidesulfonic acid or its salt can be in the range of 0mol% to 10mol% (in the range of greater than 0mol% to 10mol% or less, or in the range of 1mol% to 10mol%) (for example, 0mol%, 1mol%, 2mol%, 3mol%, 4mol%, 5mol%, 6mol%, 7mol%, 8mol%, 9mol%, 10mol%).

[0044] The first structural unit derived from (meth)acrylamide may be included in an amount in the range of 80 mol % to 90 mol % relative to 100 mol % of the (meth)acryl-based binder, the structural unit derived from (meth)acrylic acid or (meth)acrylic ester may be included in an amount in the range of 0 mol % to 40 mol % (for example, in the range of greater than 0 mol % to 40 mol % or less, or in the range of 1 mol % to 10 mol %) relative to 100 mol % of the (meth)acryl-based binder, and the structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof may be included in an amount in the range of 0 mol % to 10 mol % (for example, in the range of greater than 0 mol % to 10 mol % or less, or in the range of 1 mol % to 10 mol %) relative to 100 mol % of the (meth)acryl-based binder.

[0045] When the content of each structural unit is within the above range, the heat resistance and adhesive strength of the separator may be further increased.

[0046] The first structural unit derived from (meth)acrylamide may be represented by the following Chemical Formula 1: Chemical formula 1:

[0047] (In Chemical Formula 1, R 1 is hydrogen or methyl).

[0048] The structural unit derived from (meth)acrylic acid, (meth)acrylic acid ester or a salt thereof may be represented, for example, by any one of the following Chemical Formula 2, Chemical Formula 3, Chemical Formula 4 and a combination thereof: Chemical formula 2:

[0049] Chemical formula 3:

[0050] Chemical formula 4:

[0051] (In Chemical Formula 2, Chemical Formula 3 and Chemical Formula 4, R 2 and R 3 are each independently hydrogen or methyl, R 7 is a substituted or unsubstituted C1 to C20 alkyl group, and M is an alkali metal).

[0052] The alkali metal may be or include, for example, at least one of lithium, sodium, potassium, rubidium, or cesium.

[0053] The structural unit derived from (meth)acrylate may be derived from alkyl (meth)acrylate, perfluoroalkyl (meth)acrylate, and (meth)acrylate having a functional group in a side chain, and, for example, may be derived from alkyl (meth)acrylate. In addition, the carbon number of the alkyl group or perfluoroalkyl group bonded to the non-carbonyl oxygen atom of the alkyl (meth)acrylate or perfluoroalkyl (meth)acrylate may be in the range of 1 to 20, for example, in the range of 1 to 10, and, for example, in the range of 1 to 5.

[0054] Examples of alkyl (meth)acrylates in which the alkyl group or perfluoroalkyl group bonded to the non-carbonyl oxygen atom has 1 to 5 carbon atoms may include: alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, or tert-butyl acrylate; 2-(perfluoroalkyl)ethyl acrylates such as 2-(perfluorobutyl)ethyl acrylate or 2-(perfluoropentyl)ethyl acrylate; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and tert-butyl methacrylate; and 2-(perfluoroalkyl)ethyl methacrylates such as 2-(perfluorobutyl)ethyl methacrylate or 2-(perfluoropentyl)ethyl methacrylate.

[0055] Examples of other alkyl (meth)acrylates may include: alkyl acrylates having 6 to 18 carbon atoms in the alkyl group bonded to the non-carbonyl oxygen atom, such as n-hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, or isobornyl acrylate; alkyl methacrylates having 6 to 18 carbon atoms in the alkyl group bonded to the non-carbonyl oxygen atom, such as n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, or cyclohexyl methacrylate; 2-(perfluoroalkyl)ethyl acrylates having 6 to 18 carbon atoms in the perfluoroalkyl group bonded to the non-carbonyl oxygen atom, such as 2-(perfluorohexyl)ethyl acrylate, 2-(perfluorooctyl)ethyl acrylate, 2-(perfluoronitrile)ethyl acrylate, 2-(perfluorodecyl)ethyl acrylate, 2-(perfluorotetradecyl)ethyl acrylate or 2-(perfluorohexadecyl)ethyl acrylate; and 2-(perfluoroalkyl)ethyl methacrylate having 6 to 18 carbon atoms in the perfluoroalkyl group bonded to the non-carbonyl oxygen atom, such as 2-(perfluorohexyl)ethyl methacrylate, 2-(perfluorooctyl)ethyl methacrylate, 2-(perfluorononyl)ethyl methacrylate, 2-(perfluorodecyl)ethyl methacrylate, 2-(perfluorododecyl)ethyl methacrylate, 2-(perfluorotetradecyl)ethyl methacrylate or 2-(perfluorohexadecyl)ethyl methacrylate.

[0056] The structural unit derived from (meth)acrylic acid, (meth)acrylic acid ester or a salt thereof may include one or two or more of the structural unit represented by Chemical Formula 2 and the structural units represented by Chemical Formula 3 and Chemical Formula 4. When two or more structural units are included at the same time, a molar ratio of the structural unit represented by Chemical Formula 2 to the structural units represented by Chemical Formula 3 and Chemical Formula 4 may be in the range of 10:1 to 1:1, as an example, in the range of 6:1 to 1:1, and as another example, in the range of 3:1 to 1:1.

[0057] The structural unit derived from (meth)acrylamide sulfonic acid or its salt may be or include a structural unit derived from (meth)acrylamide sulfonic acid or (meth)acrylamide sulfonic acid salt, and the (meth)acrylamide sulfonic acid salt may be or include a conjugate base of (meth)acrylamide sulfonic acid, (meth)acrylamide sulfonic acid ester or a derivative thereof. The structural unit derived from (meth)acrylamide sulfonic acid or (meth)acrylamide sulfonic acid salt may be represented by any one of the following Chemical Formula 5, Chemical Formula 6, Chemical Formula 7 and combinations thereof, for example: Chemical formula 5:

[0058] Chemical formula 6:

[0059] Chemical formula 7:

[0060] (In Chemical Formulae 5 to 7, R 4 , R 5 and R 6 are each independently hydrogen or methyl, L 1 , L 2 and L 3 each is independently 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 heterocyclyl group, a, b and c are each independently an integer from 0 to 2, and M is an alkali metal).

[0061] The alkali metal may be or include, for example, at least one of lithium, sodium, potassium, rubidium, or cesium.

[0062] As an example, in Chemical Formula 5 to Chemical Formula 7, L 1 , L 2 and L 3 may each independently be a substituted or unsubstituted C1 to C10 alkylene group, and a, b, and c may each be 1.

[0063] The structural unit derived from (meth)acrylamidesulfonic acid or a salt thereof may include each or two or more of the structural unit represented by Chemical Formula 5, the structural unit represented by Chemical Formula 6, and the structural unit represented by Chemical Formula 7. As an example, the structural unit may include the structural unit represented by Chemical Formula 6, and as another example, include both the structural unit represented by Chemical Formula 6 and the structural unit represented by Chemical Formula 7.

[0064] When the structural unit represented by Chemical Formula 6 and the structural unit represented by Chemical Formula 7 are simultaneously included, the molar ratio of the structural unit represented by Chemical Formula 6 to the structural unit represented by Chemical Formula 7 may be in the range of 10:1 to 1:2, as an example, in the range of 5:1 to 1:1, or as another example, in the range of 3:1 to 1:1.

[0065] The sulfonic acid group in the structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof may be or include, for example, at least one of vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, anetholesulfonic acid, (meth)acrylamidoalkanesulfonic acid, sulfoalkyl(meth)acrylate, or a functional group derived from a salt thereof.

[0066] Here, the alkane may be or include a C1 to C20 alkane, a C1 to C10 alkane or a C1 to C6 alkane, and the alkyl may be or include a C1 to C20 alkyl, a C1 to C10 alkyl or a C1 to C6 alkyl. The salt refers to a salt composed of the above-mentioned sulfonic acid and a desired ion. The ion may be or include, for example, at least one of an alkali metal ion, and in this case, the salt may be or include a sulfonic acid alkali metal salt.

[0067] The (meth)acrylamidoalkanesulfonic acid may be or include, for example, 2-(meth)acrylamido-2-methylpropanesulfonic acid, and the sulfoalkyl(meth)acrylate may be or include, for example, 2-sulfoethyl(meth)acrylate, 3-sulfopropyl(meth)acrylate, and the like.

[0068] The (meth)acryl-based adhesive may be represented by the following Chemical Formula 8, for example: Chemical formula 8:

[0069] (In Chemical Formula 8, R 8 To R 10 each independently is or includes hydrogen or methyl, R 11 is or includes OR 12 or OM + , R 12 is or includes hydrogen or C1 to C6 alkyl, M is or includes an alkali metal, L 2is or includes 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 heterocyclyl group, b is an integer in the range of 0 to 2, M is or includes an alkali metal, and l, m and n refer to the molar ratio of the respective units).

[0070] The alkali metal may be or include, for example, at least one of lithium, sodium, potassium, rubidium, or cesium.

[0071] As an example, in Chemical Formula 8, l+m+n=1. As an example, 0.05≤(l+n)≤0.45 and 0.55≤m≤0.95 (e.g., 0≤l≤0.4 and 0≤n≤0.1), for example, 0.8≤m≤0.9, 0≤l≤0.1 and 0≤n≤0.1, or for example, 0.8≤m≤0.9, 0.01≤l≤0.1 and 0.01≤n≤0.1.

[0072] As an example, in Chemical Formula 8, L 2 may be or include a substituted or unsubstituted C1 to C10 alkylene group, and b may be equal to 1.

[0073] In the (meth)acryl-based binder, relative to 100 mol% of the total amount of (meth)acrylamide sulfonic acid structural units, substituted with alkali metal (M + ) may be present in an amount ranging from about 50 mol % to about 100 mol % (e.g., ranging from about 60 mol % to about 90 mol %, or ranging from about 70 mol % to about 90 mol %). When any of the above ranges is satisfied, the (meth)acryl-based binder and the separator including the (meth)acryl-based binder may exhibit desired or improved adhesive strength, heat resistance, and oxidation resistance.

[0074] In addition to the above-mentioned units, the (meth)acryl-based adhesive may further include other units. For example, the (meth)acryl-based adhesive may further include at least one of a unit derived from an alkyl (meth)acrylate, a unit derived from a diene-based adhesive, a unit derived from a styrene-based adhesive, an ester-containing unit, a carbonate-containing unit, or a combination thereof.

[0075] The (meth)acryl-based binder may be in various forms such as an alternating polymer in which units are alternately distributed, a random polymer in which units are randomly distributed, or a graft polymer in which some structural units are grafted.

[0076] The weight average molecular weight of the (meth)acryl-based binder may be in the range of about 350,000 g / mol to about 970,000 g / mol, for example, about 450,000 g / mol to about 970,000 g / mol or about 450,000 g / mol to about 700,000 g / mol. When the weight average molecular weight of the (meth)acryl-based binder satisfies any of the above ranges, the (meth)acryl-based binder and the diaphragm including the (meth)acryl-based binder may exhibit desired or improved bonding strength, heat resistance and air permeability. The weight average molecular weight may be or include a polystyrene-converted average molecular weight measured using gel permeation chromatography.

[0077] The (meth)acryl-based binder can be prepared by various known methods such as, for example, emulsion polymerization, suspension polymerization, bulk polymerization or solution polymerization.

[0078] The (meth)acryl-based binder can be prepared by, for example, a solution polymerization method.

[0079] According to one example embodiment, the (meth)acryl-based binder may be included in the coating layer of the separator in the form of a film.

[0080] The crosslinking agent includes an aziridine-based crosslinking agent. The aziridine-based crosslinking agent can be configured to crosslink the (meth)acryl-based binder, and also allows the separator to easily meet the above-mentioned dry shrinkage rate and shrinkage rate range in the electrolyte. According to an example embodiment, the aziridine-based crosslinking agent can be crosslinked by reacting with an amide group in the binder.

[0081] The aziridine crosslinking agent may be or include at least one of a bifunctional or higher functional aziridine crosslinking agent. Here, "bifunctional or higher functional" means that there are two or more aziridine groups in one molecule. According to an example embodiment, the aziridine crosslinking agent may be or include a bifunctional or trifunctional aziridine crosslinking agent, for example, a trifunctional aziridine crosslinking agent.

[0082] For example, the aziridine crosslinking agent may include one or more of N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-(methylene diphenylene)bis(aziridine-1-carboxamide), triethylene melamine, 1,1-isophthaloylbis(2-methylaziridine), tris(1-aziridine)phosphine oxide, N,N-hexamethylene-bis(aziridinecarboxamide), trimethylolpropane tris(2-methyl-1-aziridine propionate), trimethylolpropane tris(β-N-aziridine) propionate, and pentaerythritol tris(3-(1-aziridine) propionate).

[0083] Relative to the binder (e.g., (meth)acrylic binder), a crosslinking agent (e.g., aziridine crosslinking agent) may be included in a desired amount. Relative to the content of the (meth)acrylic binder, the content of the aziridine crosslinking agent is in the range of about 5 wt % to about 50 wt %. Within the above range, crosslinking of the (meth)acrylic binder and reduction of the shrinkage rate of the separator in the electrolyte can be achieved. For example, the content of the aziridine crosslinking agent may be in the range of about 10 wt % to about 40 wt % (e.g., in the range of about 10 wt % to about 30 wt %, in the range of 10 wt % to 20 wt %) (about 5 mol, about 6 mol, about 7 mol, about 8 mol, about 9 mol, about 10 mol, about 11 mol, about 12 mol, about 13 mol, about 14 mol, about 15 mol, about 16 mol, about 17 mol, about 18 mol, about 19 mol, about 20 mol, about 21 mol, about 22 mol, about 23 mol 1 mol%, about 24 mol%, about 25 mol%, about 26 mol%, about 27 mol%, about 28 mol%, about 29 mol%, about 30 mol%, about 31 mol%, about 32 mol%, about 33 mol%, about 34 mol%, about 35 mol%, about 36 mol%, about 37 mol%, about 38 mol%, about 39 mol%, about 40 mol%, about 41 mol%, about 42 mol%, about 43 mol%, about 44 mol%, about 45 mol%, about 46 mol%, about 47 mol%, about 48 mol%, about 49 mol%, about 50 mol%).

[0084] The aziridine-based cross-linking agent may be included in an amount of about 95 wt % or more (eg, in a range of about 95 wt % to about 100 wt %) of the total cross-linking agent of the composition.

[0085] The particle size D100 of the filler is about 0.7 μm or less. Within the above range, when the (meth)acryl-based binder is combined with the aziridine-based crosslinking agent, the separator can easily meet the dry shrinkage rate and the shrinkage rate in the electrolyte. For example, the particle size D100 of the filler can be about 0.3 μm to about 0.7 μm (about 0.05 μm, about 0.1 μm, about 0.15 μm, about 0.2 μm, about 0.25 μm, about 0.3 μm, about 0.35 μm, about 0.4 μm, about 0.45 μm, about 0.5 μm, about 0.55 μm, about 0.6 μm, about 0.65 μm, about 0.7 μm).

[0086] According to an example embodiment, the particle size D50 of the filler may be about 0.4 μm or less (e.g., about 0.35 μm or less, about 0.25 μm or less, or in the range of about 0.1 μm to about 0.35 μm) (about 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm). Within any of the above ranges, the heat resistance of the separator can be increased.

[0087] The filler may be or include at least one of, for example, an inorganic filler, an organic filler, an organic-inorganic composite filler, or a combination thereof. The inorganic filler may be or include a ceramic material capable of increasing heat resistance. The inorganic filler may include, for example, at least one of a metal oxide, a metalloid oxide, a metal fluoride, a metal hydroxide, or a combination thereof. The inorganic filler may include, for example, Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, or a combination thereof, but is not limited thereto. The organic filler may include at least one of an acrylic compound, an imide compound, an amide compound, or a combination thereof, but is not limited thereto. The organic filler may have a core-shell structure, but is not limited thereto.

[0088] The filler may be spherical, plate-like, cubic or amorphous. For example, the filler may be plate-like.

[0089] The filler may be included in a desired amount relative to the binder (e.g., (meth)acrylic binder). According to an example embodiment, the (meth)acrylic binder and the filler may be included in a mass ratio in a range of about 1:10 to about 1:50 (e.g., in a range of about 1:15 to about 1:40, or in a range of about 1:20 to about 1:30) (1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40, 1:41, 1:42, 1:43, 1:44, 1:45, 1:46, 1:47, 1:48, 1:49, 1:50, 1:51 1:47, 1:48, 1:49, 1:50). Within any of the above ranges, the heat resistance can be increased.

[0090] The filler may be included in an amount ranging from about 50 wt % to about 99 wt % (e.g., ranging from about 70 wt % to about 99 wt %, such as ranging from about 75 wt % to about 99 wt %, such as ranging from about 80 wt % to about 99 wt %, such as ranging from about 85 wt % to about 99 wt %, such as ranging from about 90 wt % to about 99 wt %, or such as ranging from about 95 wt % to about 99 wt %) of the total amount of the coating. When a filler within any of the above ranges is included, the separator may exhibit desired or improved heat resistance, durability, oxidation resistance, and stability.

[0091] The coating may have a thickness in the range of about 0.01 μm to about 20 μm, and within the above range, the coating may have a thickness in the range of about 1 μm to about 10 μm, in the range of about 1 μm to about 5 μm, or in the range of about 1 μm to about 3 μm.

[0092] The ratio of the thickness of the coating layer to the thickness of the porous substrate may be in the range of about 0.05 to about 0.5, for example, in the range of about 0.05 to about 0.4 or in the range of about 0.1 to about 0.4. Within any of the above ranges, the separator may exhibit desired or improved air permeability, heat resistance, adhesive strength, etc. Here, the "thickness of the coating layer" refers to the thickness of one coating layer when the coating layer is formed only on one surface of the porous substrate, and refers to the thickness of two coating layers when the coating layer is formed on both surfaces of the porous substrate.

[0093] Porous substrate The porous substrate may be or include a substrate having a plurality of pores and generally included in an electrochemical device. The porous substrate may be or include a polymer film formed of (or including) any polymer such as or including at least one of the following polymers: polyolefins (such as polyethylene or polypropylene), polyesters (such as polyethylene terephthalate or polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyetheretherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, Teflon, and polytetrafluoroethylene or copolymers or mixtures of two or more types thereof.

[0094] The porous substrate may be or include, for example, a polyolefin-based substrate including polyolefins, and the polyolefin-based substrate may have a desired or improved shutdown function, thereby contributing to increasing the safety of the battery. The polyolefin-based substrate may be or include, for example, at least one of a polyethylene monofilm, a polypropylene monofilm, a polyethylene / polypropylene double film, a polypropylene / polyethylene / polypropylene trifilm, and a polyethylene / polypropylene / polyethylene trifilm. In addition, in addition to the olefin resin, the polyolefin-based resin may also include a non-olefin resin, or the polyolefin-based resin may include a copolymer of an olefin monomer and a non-olefin monomer.

[0095] The thickness of the porous substrate may be in the range of about 1 μm to about 40 μm, for example, in the range of about 1 μm to about 30 μm, in the range of about 1 μm to about 20 μm, or in the range of about 5 μm to about 15 μm.

[0096] The separator for a rechargeable lithium battery according to an example embodiment may exhibit desired or improved air permeability, and for example, the air permeability value is less than about 200 sec / 100 cc, for example, about 180 sec / 100 cc or less, or about 160 sec / 100 cc or less. For example, the air permeability value per unit thickness of the separator may be less than about 40 sec / 100 cc 1 μm, for example, about 30 sec / 100 cc 1 μm or less or about 25 sec / 100 cc 1 μm or less. Here, air permeability refers to the time (seconds) required for 100 cc of air to pass through a separator of unit thickness. The air permeability per unit thickness can be obtained by measuring the air permeability of the total thickness of the separator and dividing the air permeability by the thickness. The air permeability can be obtained by measuring the time required for 100 cc of air to pass through the separator using an air permeability measuring device (EG01-55-1MR, Asahi Seiko Co., Ltd.).

[0097] The separator for a rechargeable lithium battery according to an exemplary embodiment can be formed by applying a composition for forming a coating layer on one or both surfaces of a porous substrate, drying it, and then curing the coating layer. Crosslinking and curing can be performed by heat treatment and by using a typical method known to those skilled in the art.

[0098] Figure 1 is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment. Figure 1 , a separator for a rechargeable lithium battery includes a porous substrate 1 and a coating layer 2 located on both surfaces of the porous substrate 1. The coating layer 2 includes a filler 3 and a cross-linked product 4 of a (meth)acryl-based binder and a cross-linking agent.

[0099] Rechargeable lithium battery According to one example embodiment, a rechargeable lithium battery includes a separator for a rechargeable lithium battery, a positive electrode, and a negative electrode.

[0100] The separator for a rechargeable lithium battery is referred to the above description. The separator for a rechargeable lithium battery may be positioned between the positive electrode and the negative electrode.

[0101] Positive electrode The positive electrode for a rechargeable lithium battery may include a current collector and a positive electrode active material layer on the current collector. The positive electrode active material layer may include a positive electrode active material and may further include a binder and / or a conductive material. For example, the positive electrode may also include an additive that may constitute a sacrificial positive electrode.

[0102] Positive electrode active material The positive electrode active material may include a compound capable of intercalating and deintercalating lithium (lithiated intercalation compound). 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 a combination thereof may be used.

[0103] The composite oxide may be or include a lithium transition metal composite oxide. Examples of the composite oxide 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.

[0104] As an example, the following compounds represented by any one of the following chemical formulas can be used. 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 NeG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 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).

[0105] In the above chemical formula, 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, a rare earth element 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 a combination thereof.

[0106] For example, the positive electrode active material may be or include a high nickel positive electrode active material, and the nickel content of the high nickel positive electrode active material is greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%, based on 100 mol% of metals other than lithium in the lithium transition metal composite oxide. The high nickel positive electrode active material can achieve high capacity and can be applied to high capacity, high density rechargeable lithium batteries.

[0107] The amount of the positive electrode active material may be in the range of about 90 wt % to about 99.5 wt % based on 100 wt % of the positive electrode active material layer, and the amount of the binder and the conductive material may be in the range of about 0.5 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer.

[0108] The binder is configured to attach the positive electrode active material particles to each other and also to attach the positive electrode active material to the current collector. As a non-limiting example, examples of the binder may include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers including ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth) acrylated styrene-butadiene rubber, epoxy resin, (meth) acrylic resin, polyester resin, nylon, etc. At least one of the above.

[0109] The conductive material may be configured to impart conductivity (e.g., electrical conductivity) to the electrode. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons may be included in the battery. Examples of the conductive material may include: a carbon-based material such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; a metal-based material containing at least one of copper, nickel, aluminum, silver, etc. and in the form of a metal powder or metal fiber; a conductive polymer such as a polyphenylene derivative; or a mixture thereof.

[0110] As the current collector, Al may be included, but is not limited thereto.

[0111] Negative electrode The negative electrode for a rechargeable lithium battery may include a current collector and a negative electrode active material layer on the current collector. The negative electrode active material layer may include a negative electrode active material, and may also include a binder and / or a conductive material (eg, an electrically conductive material).

[0112] For example, the negative electrode active material layer may include about 90 wt % to about 99 wt % of the negative electrode active material, about 0.5 wt % to about 5 wt % of the binder, and about 0 wt % to about 5 wt % of the conductive material.

[0113] Negative electrode active material The negative electrode active material may include at least one of a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / dedoping lithium, or a transition metal oxide.

[0114] Materials capable of reversibly inserting / extracting lithium ions may include carbonaceous negative electrode active materials, such as, for example, crystalline carbon, amorphous carbon, or a combination thereof. Crystalline carbon may be graphite, such as natural graphite or artificial graphite that is amorphous, flaky, lamellar, spherical, or fibrous. Amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0115] Lithium metal alloys include alloys of lithium and a metal such as or including at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0116] Materials capable of doping / dedoping lithium may be or include Si-based negative electrode active materials or Sn-based negative electrode active materials. Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (0 < x < 2) and at least one of Si-Q alloys (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof). Sn-based negative electrode active materials may include at least one of Sn, SnO2, Sn-based alloys, or combinations thereof.

[0117] Silicon-carbon composites may be or include composites 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) assembled from silicon primary particles and an amorphous carbon coating (shell) located on the surface of the secondary particles. Amorphous carbon may also be located between the silicon primary particles. For example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0118] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating located on the surface of the core.

[0119] Si-based negative electrode active materials or Sn-based negative electrode active materials may be included in combination with carbonaceous negative electrode active materials.

[0120] The binder may be configured to attach the negative electrode active material particles to each other and is also used to 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.

[0121] 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 a combination thereof.

[0122] The aqueous binder may be or include at least one of styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0123] When an aqueous binder is included as a negative electrode binder, a cellulose compound capable of imparting viscosity may be further included. The cellulose compound may include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose or an alkali metal salt thereof. The alkali metal may include at least one of Na, K or Li.

[0124] The dry binder may be or include a polymer material capable of becoming a fiber. For example, the dry binder may be or include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0125] The conductive material may be configured to impart conductivity (e.g., electrical conductivity) to the electrode. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons may be included in the battery. Non-limiting examples of conductive materials may include: carbon-based materials such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials including at least one of copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0126] The negative electrode current collector may include at least one of a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0127] The rechargeable lithium battery may further include an electrolyte.

[0128] Electrolyte An electrolyte for a rechargeable lithium battery may include a non-aqueous organic solvent and a lithium salt.

[0129] The non-aqueous organic solvent may constitute a medium for transporting ions participating in the electrochemical reaction of the battery.

[0130] The non-aqueous organic solvent may be or include at least one of a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent or an alcohol solvent, an aprotic solvent or a combination thereof.

[0131] The carbonate-based solvent may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and the like.

[0132] The ester solvent may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonolactone, valerolactone, caprolactone, and the like.

[0133] The ether solvent may include at least one of dibutyl ether, tetraglyme, diglyme, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In addition, the ketone solvent may include cyclohexanone, etc. The alcohol solvent may include at least one of ethanol, isopropanol, etc., and the aprotic solvent may include: nitrile, such as at least one of R-CN (wherein R is a C2 to C20 straight chain, branched or cyclic hydrocarbon group and may include a double bond, an aromatic ring or an ether bond, etc.); amide, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane; etc.

[0134] The non-aqueous organic solvent may be included alone or in combination of two or more solvents.

[0135] In addition, when the carbonate-based solvent is used, the cyclic carbonate and the chain carbonate may be mixed, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio in the range of about 1:1 to about 1:9.

[0136] The lithium salt dissolved in the organic solvent is configured to supply lithium ions in the battery to enable the basic operation of the rechargeable lithium battery and improve the transport of lithium ions between the positive electrode and the negative electrode. 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, LiN(C x F 2x+1 SO2)(C y F2y+1 SO2) (wherein, x and y are integers in the range of 1 to 20), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOP), lithium difluoro(oxalato)borate (LiDFOB) and lithium bis(oxalato)borate (LiBOB).

[0137] Rechargeable lithium batteries may be classified into cylindrical batteries, prismatic batteries, pouch-type batteries, coin-type batteries, etc., according to their shapes.

[0138] Figures 2 to 5 is a schematic diagram illustrating a rechargeable lithium battery according to example embodiments. Figure 2 A cylindrical battery is shown, Figure 3 A prismatic cell is shown, and Figure 4 and Figure 5 A pouch type battery is shown. Figures 2 to 5 , the rechargeable lithium battery 100 may include an electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20 and a case 50 including the electrode assembly 40 therein. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 2 As shown in , the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. Figure 3 In the embodiment, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. Figure 4 and Figure 5 As shown in FIG. 1 , the rechargeable lithium battery 100 may include Figure 5 The electrode tab 70 shown in FIG. 1 and the electrode tab 70 may be, for example, Figure 4 A positive electrode tab 71 and a negative electrode tab 72 are shown in FIG. 1 , and the electrode tabs 70 / 71 / 72 form an electrical path for extracting current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100 .

[0139] As non-limiting examples, rechargeable lithium batteries according to example embodiments may be applied to automobiles, mobile phones, and / or various types of electrical devices.

[0140] The following examples and comparative examples are provided to highlight the features of one or more example embodiments, but it is to be understood that the examples and comparative examples are not to be interpreted as limiting the scope of the example embodiments, nor are they to be interpreted as being outside the scope of the example embodiments. In addition, it is to be understood that the example embodiments are not limited to the specific details described in the examples and comparative examples.

[0141] Preparation Example 1 In a 10 L four-necked flask equipped with a stirrer, a thermometer and a cooling tube, a process of adding distilled water (6361 g), acrylic acid (72.06 g, 1.0 mol), acrylamide (604.1 g, 8.5 mol), potassium persulfate (2.7 g, 0.01 mol), 2-acrylamido-2-methylpropanesulfonic acid (103.6 g, 0.5 mol) and a 5N lithium hydroxide aqueous solution (1.05 equivalents relative to the total amount of 2-acrylamido-2-methylpropanesulfonic acid) was repeated three times, and then the internal pressure was reduced to 10 mmHg using a diaphragm pump and the internal pressure was restored to normal pressure using nitrogen.

[0142] The reaction was performed for 12 hours while the temperature of the reaction solution was controlled to be stable between 65° C. and 70° C. After cooling to room temperature, the pH of the reaction solution was adjusted to 7 to 8 using a 25% ammonia aqueous solution.

[0143] In this way, poly(acrylic acid-co-acrylic acid lithium salt-co-acrylamide-co-2-acrylamide-2-methylpropanesulfonic acid lithium salt) was prepared. The molar ratio of acrylic acid + acrylic acid lithium salt, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid lithium salt was 10:85:5. The non-volatile component in about 10 mL of the reaction solution (reactant) was measured, and the measurement result was 9.5 wt % (theoretical value: 10 wt %).

[0144] Example 1 A dispersion was prepared by mixing the acryl-based binder (10 wt % in distilled water) prepared in Preparation Example 1 and boehmite (particle size D100: 0.5 μm, particle size D50: 0.2 μm, plate-like) as a filler in a mass ratio of acryl-based binder:filler = 1 part by weight:30 parts by weight (based on solid content), adding the mixture to an aqueous solvent, and then grinding and dispersing it using a bead mill at 25° C. for 30 minutes.

[0145] A composition for forming a coating layer was prepared by adding trimethylolpropane tris(2-methyl-1-aziridine propionate) (trifunctional aziridine-based crosslinking agent) as an aziridine-based crosslinking agent in an amount of 0.1 parts by weight (based on the solid content) (content of the acryl-based binder of 10 wt %) to the dispersion and adding water so that the total solid content became 20 wt %.

[0146] A separator for a rechargeable lithium battery was manufactured by coating the composition for forming a coating layer on both surfaces of a polyethylene film (thickness: 8 μm, SK Corporation, air permeability: 120 sec / 100 cc and puncture strength: 480 kgf) as a porous substrate using a die coating method, and then drying and aging it in an oven at 85° C. for 16 hours.

[0147] Examples 2 to 7 A separator for a rechargeable lithium battery was manufactured in the same manner as in Example 1, except that in Example 1, as shown in Table 1 below, boehmite was used as a filler, but D50 and D100 were changed, the mass ratio of the (meth)acryl-based binder and the filler was changed, and the content of the aziridine-based cross-linking agent was changed.

[0148] Comparative Examples 1 to 4 A separator for a rechargeable lithium battery was manufactured in the same manner as in Example 1, except that in Example 1, D50 and D100 of the filler, the type of the cross-linking agent, the content of the cross-linking agent, the mass ratio of the (meth)acryl-based binder and the filler, etc. were changed as shown in the following Table 1. PVA is a homopolymer of polyvinyl alcohol.

[0149] Dry shrinkage (unit: %) The samples were prepared by cutting the separators for rechargeable lithium batteries of the examples and comparative examples into a size of 8 cm × 8 cm. The shrinkage rate in each of the longitudinal direction (MD) and the transverse direction (TD) was calculated by drawing a square of 5 cm × 5 cm on the surface of the sample, placing it between paper sheets or alumina powder sheets, allowing it to stand in an oven at 150°C for 1 hour, taking out the sample, and then measuring the side length of the drawn square. The shrinkage rate was calculated according to the following equation 1.

[0150] Equation 1: Shrinkage rate = (L0-L1) / L0×100% In the above Equation 1, L0 represents the initial length of the separator, and L1 represents the length of the separator after being left to stand at 150° C. for 1 hour.

[0151] Shrinkage in electrolyte (unit: %) Samples were manufactured by cutting the separators for a rechargeable lithium battery of Examples and Comparative Examples into a size of 5 cm×5 cm.

[0152] A positive electrode active material slurry was prepared by mixing 97 wt % of LiCoNiAl as a positive electrode active material, 1.5 wt % of carbon nanotubes, and 1.5 wt % of polyvinyl fluoride as a conductive material and adding water thereto.

[0153] The positive electrode was manufactured by applying the prepared positive electrode active material slurry onto an aluminum foil and drying and rolling it.

[0154] The negative electrode active material slurry was prepared by mixing 97.4wt% of a negative electrode active material, 1.0wt% of carboxymethyl cellulose, 1.5wt% of styrene-butadiene rubber and 0.1wt% of carbon nanotubes as a conductive agent. Artificial graphite was used as the negative electrode active material. The negative electrode was manufactured by applying the prepared negative electrode active material slurry to a copper foil and drying and rolling it.

[0155] One sample was positioned between the positive electrode and the negative electrode to form a stack of three sets of positive electrode-sample-negative electrode, which were then placed in a bag. 2 g of electrolyte (1.5 M LiPF6 dissolved in ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 30:50:20)) was injected so that the stack was completely saturated with the electrolyte, sealed, and left at 25°C for 12 hours. Then, the shrinkage in each of the longitudinal direction (MD) and the transverse direction (TD) was calculated by leaving the stack in an oven at 150°C for 1 hour, then taking out the sample, and measuring the side length of the drawn square. The shrinkage was calculated according to Equation 1.

[0156] Presence or absence of cross-linking The samples were prepared by cutting the separators for rechargeable lithium batteries of the examples and comparative examples into a size of 8 cm×8 cm. When the samples were fully immersed in deionized water at 25° C. and left to stand for 25 hours, it was visually checked whether the filler was detached from the coating. When the filler was not detached, it indicated that the coating composition was crosslinked, and when the filler was detached, it indicated that the coating composition was not crosslinked.

[0157] Table 1:

[0158] As shown in Table 1, the separators of Examples 1 to 7 have significantly low drying shrinkage and shrinkage in the electrolyte, thereby increasing the safety of the battery.

[0159] Therefore, the separator for a rechargeable lithium battery according to example embodiments may have significantly low drying shrinkage and shrinkage in an electrolyte, thereby increasing the stability of the battery.

[0160] Although example embodiments of the present disclosure have been described above, the present disclosure is not limited thereto and may be modified in any form within the scope of the claims, detailed description, and drawings of the present disclosure, and the modifications also fall within the scope of the present disclosure.

Claims

1. A separator for a rechargeable lithium battery, the separator comprising: porous substrate; as well as a coating disposed on at least one surface of the porous substrate, Wherein, the coating comprises a filler and a cross-linked product of a binder and a cross-linking agent, The binder includes a (meth)acryl-based binder including a first structural unit and a second structural unit, wherein the first structural unit is derived from (meth)acrylamide, and the second structural unit includes at least one of a structural unit derived from (meth)acrylic acid, a (meth)acrylic ester or a salt thereof, and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof, The cross-linking agent includes an aziridine cross-linking agent, The aziridine-based crosslinking agent is included in an amount ranging from 5 wt % to 50 wt % relative to the content of the (meth)acryl-based binder, and The particle size D100 of the filler is 0.7 μm or less.

2. The diaphragm according to claim 1, wherein The coating layer is formed by including the (meth)acryl-based binder and the aziridine-based cross-linking agent.

3. The diaphragm according to claim 1, wherein The aziridine cross-linking agent includes a trifunctional aziridine cross-linking agent.

4. The diaphragm according to claim 1, wherein The aziridine crosslinking agent includes one or more of N,N'-toluene-2,4-bis(1-aziridine carboxamide), N,N'-(methylene diphenylene)bis(aziridine-1-carboxamide), triethylene melamine, 1,1-isophthaloylbis(2-methylaziridine), tris(1-aziridine)phosphine oxide, N,N-hexamethylene-bis(aziridine carboxamide), trimethylolpropane tris(2-methyl-1-aziridine propionate), trimethylolpropane tris(β-N-aziridine) propionate and pentaerythritol tris(3-(1-aziridine) propionate).

5. The diaphragm according to claim 1, wherein The mass ratio of the (meth)acrylic binder to the filler is 1:10 to 1:

50.

6. The diaphragm according to claim 1, wherein The filler has a particle size D50 of 0.4 μm or less.

7. The diaphragm according to claim 1, wherein The filler includes a plate-like inorganic filler.

8. The diaphragm according to claim 1, wherein The first structural unit derived from (meth)acrylamide is represented by the following Chemical Formula 1: Chemical formula 1: In Chemical Formula 1, R 1 including hydrogen or methyl, The structural unit derived from (meth)acrylic acid, (meth)acrylic acid ester or a salt thereof is represented by any one or more of the following Chemical Formula 2, Chemical Formula 3 and Chemical Formula 4: Chemical formula 2: Chemical formula 3: Chemical formula 4: In Chemical Formula 2, Chemical Formula 3 and Chemical Formula 4, R 2 and R 3 Each independently includes hydrogen or methyl, R 7 includes a substituted or unsubstituted C1 to C20 alkyl group, and M includes an alkali metal, and The structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof is represented by any one or more of the following Chemical Formula 5, Chemical Formula 6, and Chemical Formula 7: Chemical formula 5: Chemical formula 6: Chemical formula 7: In Chemical Formulae 5 to 7, R 4 , R 5 and R 6 Each independently includes hydrogen or methyl, L 1 , L 2 and L 3 Each independently includes 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 heterocyclyl group, a, b and c are each independently an integer in the range of 0 to 2, and M includes an alkali metal.

9. The diaphragm according to claim 8, wherein: The first structural unit derived from (meth)acrylamide is contained in an amount ranging from 80 mol % to 90 mol %, the structural unit derived from (meth)acrylic acid, (meth)acrylate or a salt thereof is contained in an amount ranging from 0 mol % to 10 mol %, and the structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof is contained in an amount ranging from 0 mol % to 10 mol %, relative to 100 mol % of the (meth)acryl-based binder.

10. The diaphragm according to claim 8, wherein The (meth)acryl-based adhesive is represented by the following chemical formula 8: Chemical formula 8: In Chemical Formula 8, R 8 To R 10 each independently comprises hydrogen or methyl, R 11 Include OR 12 or OM + , R 12 includes hydrogen or C1 to C6 alkyl, M includes an alkali metal, L 2 including 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 group, b is an integer in the range of 0 to 2, M includes an alkali metal, and l, m and n refer to the molar ratios of the corresponding units.

11. The diaphragm according to claim 1, wherein The thickness of the coating is in the range of 1 μm to 3 μm.

12. A rechargeable lithium battery, comprising: The separator for a rechargeable lithium battery according to claim 1; a positive electrode; and Negative electrode.

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