Binder, separator, and rechargeable lithium battery including separator

Abstract

Exemplary embodiments include a binder, a separator comprising the binder, and a rechargeable lithium battery comprising the separator, the binder comprising: a first structural unit derived from (meth) acrylic acid, (meth) acrylate, or a salt thereof; a second structural unit derived from hydroxyalkyl (meth) acrylate; and a third structural unit derived from (meth) acrylamidosulfonic acid or a salt thereof.

Description

Technical Field

[0001] Disclosed are a binder, a separator including the binder, and a rechargeable lithium battery including the separator. Background Art

[0002] With the rapid popularization of electronic devices using batteries, such as, for example, mobile phones, laptop computers, and electric vehicles, the demand for rechargeable batteries with high energy density and high capacity has increased rapidly. Therefore, corresponding research and development are currently being conducted to improve the performance of rechargeable lithium batteries.

[0003] Rechargeable lithium batteries generally include positive and negative electrodes containing active materials capable of inserting and extracting lithium ions, and an electrolyte solution. When lithium ions are inserted / extracted from the positive and negative electrodes, electrical energy is generally generated through oxidation and reduction reactions.

[0004] The separator is an intermediate membrane that substantially separates the positive electrode from the negative electrode in a rechargeable lithium battery and substantially continuously maintains ionic conductivity, thereby enabling the rechargeable lithium battery to be charged and discharged. When the rechargeable lithium battery is exposed to a high temperature environment due to abnormal behavior, the separator may mechanically shrink or be damaged due to the melting characteristics at low temperatures. Here, the positive electrode and the negative electrode contact each other and may cause the battery to explode. To overcome this challenge, it may be advantageous to provide a technology that reduces or inhibits separator shrinkage and ensures or improves the stability of the rechargeable lithium battery.

[0005] For example, a method of increasing the heat resistance of a separator by coating the separator with a mixture of inorganic particles with high heat resistance and an organic binder with adhesion is generally known. However, this method may not be sufficient to ensure the desired bonding strength, and it is challenging to reduce the resistance. Summary of the invention

[0006] Some example embodiments include an adhesive for a rechargeable lithium battery having high heat resistance and low electrical resistance.

[0007] Some exemplary embodiments include a separator for a rechargeable lithium battery including the binder.

[0008] Some exemplary embodiments include a rechargeable lithium battery including the separator.

[0009] Some exemplary embodiments include a binder for a rechargeable lithium battery, the binder comprising at least one of: a first structural unit derived from (meth)acrylic acid, a (meth)acrylic acid ester, or a salt thereof; a second structural unit derived from a hydroxyalkyl (meth)acrylate; and a third structural unit derived from a (meth)acrylamide sulfonic acid or a salt thereof.

[0010] Some exemplary embodiments include a separator for a rechargeable lithium battery, the separator comprising a porous substrate and a coating, the coating being located on at least one surface of the porous substrate and comprising a binder and inorganic particles, wherein the binder comprises at least one of: a first structural unit derived from (meth)acrylic acid, a (meth)acrylic ester, or a salt thereof; a second structural unit derived from a hydroxyalkyl (meth)acrylate; and a third structural unit derived from a (meth)acrylamide sulfonic acid or a salt thereof.

[0011] Some example embodiments include a rechargeable lithium battery including a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

[0012] The binder for a rechargeable lithium battery according to some exemplary embodiments exhibits high heat resistance and low resistance. Therefore, by applying the binder for a rechargeable lithium battery according to some exemplary embodiments to the coating layer of the separator, a rechargeable lithium battery having a desired, favorable or improved cycle life characteristic at room temperature and / or high temperature can be implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figures 1 to 4 is an exploded perspective view of a rechargeable lithium battery according to some example embodiments.

[0014] [Explanation of Symbols]

[0015] 10: positive electrode;

[0016] 11: positive lead lug;

[0017] 12: Positive terminal;

[0018] 20: negative electrode;

[0019] 21: Negative lead lug;

[0020] 22: Negative terminal;

[0021] 30: diaphragm;

[0022] 40: electrode assembly;

[0023] 50: housing;

[0024] 60: sealing member;

[0025] 70: electrode terminal piece;

[0026] 71: positive electrode terminal;

[0027] 72: negative electrode terminal;

[0028] 100: Rechargeable lithium battery. DETAILED DESCRIPTION

[0029] Hereinafter, exemplary embodiments of the present invention will be described in detail. However, these embodiments are examples, and the present invention is not limited thereto and the present invention is defined by the scope of the claims.

[0030] As used herein, when specific definitions are not provided otherwise, it will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present.

[0031] As used herein, when no specific definition is otherwise provided, the singular may also include the plural. In addition, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0032] As used herein, "combinations thereof" may refer to mixtures, stacks, composites, copolymers, alloys, blends, and reaction products of the constituent parts.

[0033] As used herein, when no definition is otherwise provided, particle size may be an average particle size. The average particle size refers to the average particle size (D) as the diameter of particles having a cumulative volume of 50% by volume in a particle size distribution. 50 The average particle size (D) can be measured by methods well known to those skilled in the art (e.g., by measuring using a particle size analyzer, a transmission electron microscope, or a scanning electron microscope). 50 Alternatively, the data analysis is performed using a dynamic light scattering measurement device and the number of particles in each particle size range is counted. Thus, the average particle size (D 50 ) value. A laser diffraction method may also be used. When measuring by laser diffraction, more specifically, particles to be measured are dispersed in a dispersion medium, and then these particles are introduced into a commercially available laser diffraction particle size measuring device (e.g., MT 3000 available from Microtrac, Ltd.) using ultrasonic waves of about 28 kHz, and after irradiation at an output of 60 W, the average particle size (D ) based on 50% of the particle size distribution in the measuring device can be calculated. 50 ).

[0034] As used herein, when a specific definition is not otherwise provided, “alkyl” refers to a C1 to C20 alkyl group, “alkenyl” refers to a C2 to C20 alkenyl group, “cycloalkenyl” refers to a C3 to C20 cycloalkenyl group, “heterocycloalkenyl” refers to a C3 to C20 heterocycloalkenyl group, “aryl” refers to a C6 to C20 aryl group, “arylalkyl” refers to a C7 to C20 arylalkyl group, “alkylene” refers to a C1 to C20 alkylene group, “arylene” refers to a C6 to C20 arylene group, “alkylarylene” refers to a C7 to C20 alkylarylene group, “heteroarylene” refers to a C3 to C20 heteroarylene group, and “alkyleneoxy” refers to a C1 to C20 alkyleneoxy group.

[0035] As used herein, when a specific definition is not otherwise provided, “substituted” means that at least one hydrogen atom is replaced by a substituent such as, for example, a halogen atom (F, Cl, Br or I), a hydroxyl group, a C1 to C20 alkoxy group, a nitro group, a cyano group, an amino group, an imino group, an azido group, a carbamimido group, a hydrazine group, a hydrazone group, a carbonyl group, a carbamoyl group, a thiol group, an ester group, an ether group, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C1 to C20 alkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 to C20 aryl group, a C3 to C20 cycloalkyl group, a C3 to C20 cycloalkenyl group, a C3 to C20 cycloalkynyl group, a C2 to C20 heterocycloalkyl group, a C2 to C20 heterocycloalkenyl group, a C2 to C20 heterocycloalkynyl group, a C3 to C20 heteroaryl group, or a combination thereof.

[0036] In addition, when a specific definition is not otherwise provided, "hetero" means that at least one hetero atom among N, O, S and P is included in a chemical formula.

[0037] Furthermore, when a specific definition is not otherwise provided, “(meth)acrylate” refers to both “acrylate” and “methacrylate”, “(meth)acrylic acid” refers to both “acrylic acid” and “methacrylic acid”, and “(meth)acrylamidesulfonic acid” refers to both “acrylamidesulfonic acid” and “methacrylamidesulfonic acid”.

[0038] In the chemical formulae of the present specification, unless a specific definition is otherwise provided, when a chemical bond is not drawn where it should be given, hydrogen bonds to the position.

[0039] As used herein, the weight average molecular weight (Mw) may be a value measured by gel permeation chromatography (GPC).

[0040] 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 numerical value. In addition, when percentages are mentioned in this specification, it is intended that those percentages are based on weight, i.e., weight percentages. The expression "up to" includes an amount from zero to the stated upper limit and all values ​​between zero and the stated upper limit. When a range is specified, the range includes all values ​​between the range, for example, in increments of 0.1%.

[0041] Adhesives

[0042] Some exemplary embodiments provide an adhesive for a rechargeable lithium battery, the adhesive comprising: a first structural unit derived from (meth)acrylic acid, a (meth)acrylic acid ester, or a salt thereof; a second structural unit derived from a hydroxyalkyl (meth)acrylate; and a third structural unit derived from a (meth)acrylamide sulfonic acid or a salt thereof.

[0043] The binder for a rechargeable lithium battery according to some exemplary embodiments exhibits high heat resistance and low resistance. Therefore, by applying the binder for a rechargeable lithium battery according to some exemplary embodiments to the coating layer of the separator, a rechargeable lithium battery having a desired, favorable or improved cycle life characteristic at room temperature and / or high temperature can be implemented.

[0044] A description of an adhesive for a rechargeable lithium battery according to some exemplary embodiments is as follows.

[0045] The first structural unit may be included in an amount of about 20 mol % to about 75 mol %, or about 25 mol % to about 70 mol %, or about 30 mol % to about 65 mol % based on 100 mol % of the binder for a rechargeable lithium battery according to some example embodiments.

[0046] The first structural unit is derived from (meth) acrylic acid, (meth) acrylic acid ester or its salt, and is configured to fix the inorganic particles on the porous substrate, and also provides adhesion so that the coating is fully adhered to the porous substrate and the electrode, and can help improve the heat resistance and air permeability of the separator. In addition, the first structural unit can help improve the dispersibility of the coating slurry by including a carboxyl functional group (-C(=O)O-) in the structural unit.

[0047] The first structural unit may be represented by any one of Chemical Formula 1 to Chemical Formula 3:

[0048] [Chemical formula 1] [Chemical formula 2] [Chemical formula 3]

[0049]

[0050] The second structural unit may be included in an amount of about 1 mol % to about 20 mol %, about 2 mol % to about 15 mol %, or about 5 mol % to about 15 mol % based on 100 mol % of the binder for a rechargeable lithium battery according to one exemplary embodiment.

[0051] The second structural unit is derived from a hydroxyalkyl (meth)acrylate and is configured to fix the inorganic particles to the porous substrate while providing adhesion so that the coating is fully adhered to the porous substrate and the electrode. In addition, the second structural unit can help improve the dispersibility of the coating slurry by including a hydroxyl functional group (-OH) in the structural unit.

[0052] The second structural unit can be represented by Chemical Formula 4:

[0053] [Chemical formula 4]

[0054]

[0055] The third structural unit may be included in an amount of about 20 mol % to about 75 mol %, about 25 mol % to about 70 mol %, or about 30 mol % to about 65 mol %.

[0056] The third structural unit includes a bulky functional group derived from (meth)acrylamide sulfonic acid or a salt thereof, thereby increasing its glass transition temperature and thus enhancing the heat resistance of the separator. In addition, 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 due to the replacement of the sulfonic acid functional group by the metal (M), which can have the effect of reducing the resistance.

[0057] The third structural unit may be represented by any one of Chemical Formula 5 to Chemical Formula 7:

[0058] [Chemical formula 5] [Chemical formula 6] [Chemical formula 7]

[0059]

[0060] The explanations of Chemical Formula 1 to Chemical Formula 7 are as follows.

[0061] R 1 To R 8 can be independently hydrogen or C1 to C10 alkyl. 1 To R 4 and R 6 To R 8 may each be hydrogen or methyl; and R 5 It may be methyl.

[0062] L 1 To L 4and L may each independently be 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. 1 can be methylene or ethylene; and L 2 To L 4 Each may independently be *-C(CH3)2-CH2-*.

[0063] a, b, c, and d may each independently be one of integers in the range of 0 to 2. For example, a, b, c, and d may all be equal to 1.

[0064] M may be an alkali metal, and the alkali metal may be at least one of lithium, sodium, potassium, rubidium, or cesium. For example, M may be lithium or sodium.

[0065] Representative examples of adhesives for rechargeable lithium batteries according to some exemplary embodiments are as follows:

[0066] [Chemical formula 8]

[0067]

[0068] The explanation of Chemical Formula 8 is as follows.

[0069] R 9 To R 12 can be each independently hydrogen or C1 to C10 alkyl. 9 , R 10 and R 12 may each be hydrogen or methyl; and R 11 It may be methyl.

[0070] L 5 and L 6 and L may each independently be 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. 5 can be methylene or ethylene; and L 6 It can be *-C(CH3)2-CH2-*.

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

[0072] l, m and n are the molar ratios of each unit, and l+m+n=1. For example, 0.2≤l≤0.75, 0.01≤m≤0.2 and 0.2≤n≤0.75; or 0.25≤l≤0.7, 0.02≤m≤0.15 and 0.25≤n≤0.7; or 0.3≤l≤0.65, 0.05≤m≤0.15 and 0.3≤n≤0.65.

[0073] The binder may have a weight average molecular weight of about 100,000 to about 1,000,000 g / mol, about 200,000 to about 950,000 g / mol, or about 300,000 to about 900,000 g / mol as measured by gel permeation chromatography (GPC).

[0074] When the above range is satisfied, the separator including the binder for a rechargeable lithium battery according to some exemplary embodiments may exhibit desirable, favorable, or improved adhesion and low resistance.

[0075] Diaphragm

[0076] In some exemplary embodiments, a separator for a rechargeable lithium battery includes: a porous substrate; and a coating disposed on at least one surface of the porous substrate and comprising a binder and inorganic particles, wherein the binder comprises: a first structural unit derived from (meth)acrylic acid, a (meth)acrylic ester or a salt thereof; a second structural unit derived from a hydroxyalkyl (meth)acrylate; and a third structural unit derived from a (meth)acrylamide sulfonic acid or a salt thereof.

[0077] The adhesive may be the adhesive for a rechargeable lithium battery according to the aforementioned exemplary embodiment.

[0078] The adhesive for rechargeable lithium batteries according to the aforementioned exemplary embodiments exhibits high heat resistance and low resistance. Therefore, by applying the adhesive for rechargeable lithium batteries according to the aforementioned embodiments to the coating layer of the separator, a rechargeable lithium battery having a desired, favorable or improved cycle life characteristic at room temperature and / or high temperature can be implemented.

[0079] Hereinafter, excluding the description overlapping with the above, a description of a separator for a rechargeable lithium battery according to some exemplary embodiments is as follows.

[0080] Inorganic particles

[0081] The inorganic particles can hinder or prevent the diaphragm from shrinking or deforming rapidly due to the increase in temperature. The inorganic particles can be a ceramic material capable of improving heat resistance, for example, the inorganic particles can be at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite and combinations thereof, but are not limited thereto.

[0082] The inorganic particles may be at least one of spherical, plate-shaped, cubic, or irregular shapes.

[0083] The average particle size of the inorganic particles may be about 0.2 μm to about 1 μm, about 0.25 μm to about 0.7 μm, or about 0.25 μm to about 0.5 μm.

[0084] The average particle size of the inorganic particles may be the particle size at 50 volume % in the cumulative size distribution curve (D 50 ). By using inorganic particles having an average particle size within the above range, appropriate strength can be provided to the coating layer, thereby improving the heat resistance, durability and stability of the separator.

[0085] Meanwhile, the weight ratio of the binder:inorganic particles in the coating layer may be in the range of about 1:5 to about 1:40, desirably in the range of about 1:10 to about 1:35, and more desirably in the range of about 1:15 to about 1:30. When included within the above range, the separator may exhibit desirable, advantageous or improved heat resistance and low electrical resistance.

[0086] coating

[0087] The coating may have a thickness of about 0.2 μm to about 5 μm, for example, about 0.5 μm to about 3 μm.

[0088] Within the above range, high heat resistance and low resistance can be achieved simultaneously or at the same time, thereby improving the safety and reliability of the battery.

[0089] The coating layer may be provided on one or both surfaces of the porous substrate. In the case where the coating layer is provided on both surfaces of the porous substrate, it may be advantageous to achieve high heat resistance and low electrical resistance of the separator.

[0090] Porous substrate

[0091] The porous substrate may have a plurality of pores and may generally be or include a substrate used in an electrochemical device. Non-limiting examples of the porous substrate may be or include a polymer film formed from a copolymer or mixture of two or more of the following: polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetals, polyamides, polyimides, polycarbonates, polyetheretherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfides, polyethylene naphthalate, fiberglass, Teflon, and polytetrafluoroethylene.

[0092] The porous substrate may be or include a polyolefin-based substrate including polyolefins, and the polyolefin-based substrate may have a desired, advantageous or improved shutdown function, which may help improve the safety of the battery. The polyolefin-based substrate may be, for example, one of a polyethylene monolayer film, a polypropylene monolayer film, a polyethylene / polypropylene double-layer film, a polypropylene / polyethylene / polypropylene three-layer film, and a polyethylene / polypropylene / polyethylene three-layer film. In addition, the polyolefin-based resin may include a non-olefin resin in addition to an olefin resin, or may include a copolymer of an olefin and a non-olefin monomer.

[0093] The porous substrate may have a thickness in a range of about 1 μm to about 40 μm, for example about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 2 μm to about 15 μm, or about 5 μm to about 10 μm.

[0094] Method for manufacturing diaphragm

[0095] The separators of some exemplary embodiments may be manufactured by various known methods. For example, a separator for a rechargeable lithium battery may be formed by applying a composition for forming a coating layer to one or both surfaces of a porous substrate and then drying it.

[0096] Rechargeable lithium battery

[0097] Some example embodiments include a rechargeable lithium battery including a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

[0098] Positive electrode active material

[0099] The positive electrode active material may be or include a compound capable of intercalating and deintercalating lithium (lithiated intercalation compound). For example, a composite oxide of lithium and one or more types of metals, such as cobalt, manganese, nickel, and combinations thereof, may be used.

[0100] The composite oxide may be a lithium transition metal composite oxide, and examples may include at least one of, for example, lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free lithium nickel manganese-based oxides, and combinations thereof.

[0101] As an example, a compound represented by any one of the following chemical formulae may be used. a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 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, 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, 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, 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, 0≤e≤0.1); Li a NeG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3(0≤f≤2); and Li a FePO4(0.90≤a≤1.8).

[0102] In the above chemical formula, A is Ni, Co, Mn or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; and L 1 It is Mn, Al or a combination thereof.

[0103] The positive electrode active material may be or include, for example, a lithium nickel-based oxide represented by Chemical Formula 11, a lithium cobalt-based oxide represented by Chemical Formula 12, a lithium iron phosphate-based compound represented by Chemical Formula 13, and a cobalt-free lithium nickel manganese-based oxide represented by Chemical Formula 14, or a combination thereof.

[0104] [Chemical formula 11]

[0105] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0106] In Chemical Formula 11, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1 and 0≤b1≤0.1, M 1 and M 2 Each is independently one or more of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W and Zr, and X is one or more of F, P and S.

[0107] In Chemical Formula 11, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0108] [Chemical formula 12]

[0109] Li a2 Co x2 M 3 y2 O 2-b2 Xb2

[0110] In Chemical Formula 12, 0.9 ≤ a2 ≤ 1.8, 0.7 ≤ x2 ≤ 1, 0 ≤ y2 ≤ 0.3, 0.9 ≤ x2 + y2 ≤ 1.1 and 0 ≤ b2 ≤ 0.1, M 3 is one or more of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more of F, P, and S.

[0111] [Chemical Formula 13]

[0112] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0113] In Chemical Formula 13, 0.9 ≤ a3 ≤ 1.8, 0.6 ≤ x3 ≤ 1, 0 ≤ y3 ≤ 0.4 and 0 ≤ b3 ≤ 0.1, M 4 is one or more of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more of F, P, and S.

[0114] [Chemical Formula 14]

[0115] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0116] In Chemical Formula 14, 0.9 ≤ a2 ≤ 1.8, 0.8 ≤ x4 < 1, 0 < y4 ≤ 0.2, 0 ≤ z4 ≤ 0.2, 0.9 ≤ x4 + y4 + z4 ≤ 1.1 and 0 ≤ b4 ≤ 0.1, M 5 is one or more of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more of F, P, and S.

[0117] As an example, the positive electrode active material may be or include a high nickel-based positive electrode active material 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%, based on 100 mol% of metals excluding lithium in the lithium transition metal composite oxide. The high nickel-based positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0118] Positive electrode

[0119] A 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.

[0120] For example, the positive electrode may further include additives configured to operate as a sacrificial positive electrode.

[0121] The positive electrode active material may be contained in an amount of about 90 wt % to about 99.5 wt %, and the binder and the conductive material may be contained in an amount of about 0.5 wt % to about 5 wt % based on 100 wt % of the positive electrode active material layer, respectively.

[0122] The binder is configured to sufficiently attach the positive electrode active material particles to each other and also sufficiently attach the positive electrode active material to the current collector. Examples of the binder may include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing 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., but are not limited thereto.

[0123] Conductive materials can be used to impart conductivity (e.g., electrical conductivity) to the electrodes. Any material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used in the battery. Examples of conductive materials may include: carbon-based materials such as, for example, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metal-based materials including, for example, copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fibers; conductive polymers such as, for example, polyphenylene derivatives; or mixtures thereof.

[0124] The current collector may be or include Al, but is not limited thereto.

[0125] Negative electrode active material

[0126] The negative electrode active material may be or include at least one of a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0127] The material that reversibly intercalates / deintercalates lithium ions may include a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be or include graphite, such as natural graphite or artificial graphite that is irregular, flaky, lamellar, spherical, or fibrous. The amorphous carbon may be or include soft carbon, hard carbon, a mesophase pitch carbonization product, a calcined coke, etc.

[0128] The lithium metal alloy may include lithium and a metal, where the metal is at least one of, for example (by way of example), Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0129] The material capable of doping / dedoping lithium may be or include a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (0 < x < 2), a Si-Q alloy (where Q is 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). The Sn-based negative electrode active material may include, for example, Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0130] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to some exemplary embodiments, the silicon-carbon composite may be in the form of silicon particles and an amorphous carbon coating on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) that aggregate primary silicon particles, and an amorphous carbon coating (shells) on the surface of the secondary particles. The amorphous carbon may also be between the primary silicon particles, and, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0131] The silicon-carbon composite may also include crystalline carbon. For example, the silicon-carbon composite may include a core that includes crystalline carbon and silicon particles, and an amorphous carbon coating on the surface of the core.

[0132] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in combination with the carbon-based negative electrode active material.

[0133] Negative electrode

[0134] A negative electrode for a rechargeable lithium battery includes a current collector and a negative electrode active material layer on the current collector. The negative electrode active material layer contains a negative electrode active material and may further contain a binder and / or a conductive material.

[0135] 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 0.5 wt % to about 5 wt % of the conductive material.

[0136] The binder may be configured to sufficiently attach the negative electrode active material particles to each other and also sufficiently attach the negative electrode active material to the current collector. The binder may include at least one of a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0137] 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.

[0138] The water 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.

[0139] When a water binder is used as the negative electrode binder, the water binder may further include a cellulose compound capable of imparting viscosity. The cellulose compound includes one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be or include Na, K, or Li.

[0140] The dry binder may be or include a polymer material configured to be fiberized, and may be or include, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0141] The conductive material is included to provide the electrode conductivity, and any electrically conductive material can be used as the conductive material unless the electrically conductive material causes a chemical change. Examples of the conductive material may be, for example, at least one of the following: a carbon-based material such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; a metal-based material such as copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; a conductive polymer such as a polyphenylene derivative; or a mixture thereof.

[0142] 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, and combinations thereof, but is not limited thereto.

[0143] Electrolyte solution

[0144] The electrolyte solution for a rechargeable lithium battery includes a non-aqueous organic solvent and a lithium salt.

[0145] The non-aqueous organic solvent is configured as a medium for transferring ions participating in the electrochemical reaction of the battery.

[0146] The non-aqueous organic solvent may be or include at least one of a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0147] The carbonate solvent may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. 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, mevalonate lactone, valerolactone, caprolactone, etc. The ether solvent may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. The ketone solvent may include, for example, cyclohexanone. The alcohol solvent may include at least one of ethanol, isopropanol, etc., and the aprotic solvent may include nitriles such as R-CN (wherein R is a C2 to C20 straight chain, branched or cyclic hydrocarbon group, a double bond, an aromatic ring, or an ether group), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane or 1,4-dioxolane, cyclopentane, etc.

[0148] The nonaqueous organic solvents may be used alone or in combination of two or more.

[0149] In addition, when a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed in a volume ratio of about 1:1 to about 1:9.

[0150] Lithium salts dissolved in organic solvents supply lithium ions in the battery, enable basic operation of rechargeable lithium batteries, and improve the transport of lithium ions between the positive electrode and the negative electrode. Examples of lithium salts may 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 F 2y+1SO2) (x and y are integers from 1 to 20), one or more of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate, lithium difluoro(oxalato)borate (LiDFOB) and lithium bis(oxalato)borate (LiBOB).

[0151] Rechargeable lithium battery

[0152] The rechargeable lithium battery may be classified into, for example, a cylindrical battery, a prismatic battery, a pouch battery, a coin-type battery, or the like, depending on the shape of the rechargeable lithium battery. Figures 1 to 4 is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment. Figure 1 A cylindrical battery is shown, Figure 2 A prismatic cell is shown, and Figure 3 and Figure 4 Pouch cell battery shown. Figures 2 to 4 , the rechargeable lithium battery 100 includes an electrode assembly 40 and a case 50 including the electrode assembly 40, and the electrode assembly 40 includes a separator 30 located between a positive electrode 10 and a negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte solution (not shown). Figure 1 As shown, the rechargeable lithium battery 100 may include a sealing member 60 for sealing the housing 50. Figure 2 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 3 As shown, the rechargeable lithium battery 100 includes a positive electrode tab 71 and a negative electrode tab 72, which serve as an electrical path for introducing the current formed in the electrode assembly 40 to the outside. Figure 4 As shown, the rechargeable lithium battery 100 includes an electrode terminal tab 70, and the electrode terminal tab 70 includes Figure 3 The positive electrode tab 71 and the negative electrode tab 72 shown in FIG. 4 are used as an electrical path for introducing the current formed in the electrode assembly 40 to the outside.

[0153] Rechargeable lithium batteries according to some exemplary embodiments may be used in or applied to, for example, automobiles, mobile phones, and / or various types of electrical devices, but the present invention is not limited thereto.

[0154] Hereinafter, examples and comparative examples of the present invention are described. However, these examples should not be interpreted as limiting the scope of the present invention in any sense.

[0155] Synthesis Example and Comparative Synthesis Example: Preparation of Adhesive

[0156] Synthesis Example 1: Poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt (30:10:60)

[0157] After distilled water (1249.72 g), 20% lithium hydroxide aqueous solution (203.69 g), acrylic acid (21.6 g, 0.3 mol), hydroxyethyl methacrylate (13 g, 0.1 mol), 2-acrylamido-2-methylpropanesulfonic acid (124.3 g, 0.6 mol) and ammonium persulfate (0.2 g, 0.001 mol) were added to a 3-liter four-necked separable flask equipped with a stirrer, a thermometer and a cooling tube, the internal pressure of the flask was repeatedly reduced three times to 10 mmHg using a diaphragm pump, and the internal pressure was returned to normal pressure using nitrogen gas.

[0158] The reaction solution was reacted by heating while its reaction temperature was controlled to be stable between about 65° C. and about 70° C. for 12 hours.

[0159] After the reaction solution was cooled to room temperature, about 10 ml of the reaction solution was taken to measure the non-volatile component (NV), which was 9.8% (theoretical value: 10%). In addition, in the obtained poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt, the first structural unit derived from acrylic acid, the second structural unit derived from hydroxyethyl methacrylate and the third structural unit derived from 2-acrylamide-2-methylpropanesulfonic acid had a molar ratio of 30:10:60.

[0160] Synthesis Example 2: Poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt (40:10:50)

[0161] An acrylic copolymer was prepared in the same manner as in Synthesis Example 1 except that acrylic acid (28.8 g, 0.4 mol), hydroxyethyl methacrylate (13 g, 0.1 mol) and 2-acrylamido-2-methylpropanesulfonic acid (103.6 g, 0.5 mol) were used.

[0162] The reaction solution had a non-volatile component of 9.7% (theoretical value: 10%). In addition, in the obtained poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt, the first structural unit derived from acrylic acid, the second structural unit derived from hydroxyethyl methacrylate and the third structural unit derived from 2-acrylamide-2-methylpropanesulfonic acid had a molar ratio of 40:10:50.

[0163] Synthesis Example 3: Poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt (60:10:30)

[0164] An acrylic copolymer was prepared in the same manner as in Synthesis Example 1 except that acrylic acid (43.2 g, 0.6 mol), hydroxyethyl methacrylate (13 g, 0.1 mol) and 2-acrylamido-2-methylpropanesulfonic acid (62.2 g, 0.3 mol) were used.

[0165] The reaction solution had a non-volatile component of 9.7% (theoretical value: 10%). In addition, in the obtained poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt, the first structural unit derived from acrylic acid, the second structural unit derived from hydroxyethyl methacrylate, and the third structural unit derived from 2-acrylamide-2-methylpropanesulfonic acid had a molar ratio of 60:10:30.

[0166] Synthesis Example 4: Poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt (40:5:55)

[0167] An acrylic copolymer was prepared in the same manner as in Synthesis Example 1 except that acrylic acid (28.8 g, 0.4 mol), hydroxyethyl methacrylate (6.5 g, 0.05 mol) and 2-acrylamido-2-methylpropanesulfonic acid (114 g, 0.55 mol) were used.

[0168] The reaction solution had a non-volatile component of 9.8% (theoretical value: 10%). In addition, in the obtained poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt, the first structural unit derived from acrylic acid, the second structural unit derived from hydroxyethyl methacrylate and the third structural unit derived from 2-acrylamide-2-methylpropanesulfonic acid had a molar ratio of 40:5:55.

[0169] Synthesis Example 5: Poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt (40:15:45)

[0170] An acrylic copolymer was prepared in the same manner as in Synthesis Example 1 except that acrylic acid (28.8 g, 0.4 mol), hydroxyethyl methacrylate (19.5 g, 0.15 mol) and 2-acrylamido-2-methylpropanesulfonic acid (93.3 g, 0.45 mol) were used.

[0171] The reaction solution had a non-volatile component of 9.8% (theoretical value: 10%). In addition, in the obtained poly(acrylic acid-co-hydroxyethyl methacrylate-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt, the first structural unit derived from acrylic acid, the second structural unit derived from hydroxyethyl methacrylate, and the third structural unit derived from 2-acrylamide-2-methylpropanesulfonic acid had a molar ratio of 40:15:45.

[0172] Comparative Synthesis Example 1: Poly(acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt (35:65)

[0173] An acrylic copolymer was prepared in the same manner as in Synthesis Example 1, except that acrylic acid (25.2 g, 0.35 mol) and 2-acrylamido-2-methylpropanesulfonic acid (134.7 g, 0.65 mol) were used.

[0174] The reaction solution had a non-volatile component of 9.7% (theoretical value: 10%). In addition, in the obtained poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt, the first structural unit derived from acrylic acid and the third structural unit derived from 2-acrylamide-2-methylpropanesulfonic acid had a molar ratio of 35:65.

[0175] Comparative Synthesis Example 2: Poly(acrylic acid-co-acrylonitrile-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt (45:50:5)

[0176] Distilled water (968 g), a 20% lithium hydroxide aqueous solution (102 g), acrylic acid (54 g, 0.62 mol), ammonium persulfate (0.65 g, 2.85 mmol) and 2-methylpropanesulfonic acid (6 g, 0.02 mol) were added to a 3-liter four-necked separable flask equipped with a stirrer, a thermometer and a cooling tube, and after the internal pressure of the flask was repeatedly reduced three times to 10 mmHg using a diaphragm pump and the flask was restored to normal pressure using nitrogen, acrylonitrile (60 g, 0.94 mol) was added thereto.

[0177] The reaction solution was reacted by heating while controlling its reaction temperature to be stable between 65°C and 70°C for 18 hours, and ammonium persulfate (0.22 g, 0.95 mmol) was added thereto twice, and then it was heated to 80°C and reacted again for 4 hours.

[0178] After the reaction solution was cooled to room temperature, the reaction solution was treated with a 25% ammonia solution to adjust the potential of hydrogen (pH) to 7 to 8. About 10 ml of the reaction solution was taken to measure the non-volatile component (NV), which was 9.8% (theoretical value: 10%). In addition, in the obtained poly (acrylic acid-co-acrylonitrile-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt, the structural unit derived from acrylic acid, the structural unit derived from acrylonitrile and the structural unit derived from 2-acrylamide-2-methylpropanesulfonic acid had a molar ratio of 45:50:5.

[0179] Comparative Synthesis Example 3: Poly(acrylic acid-co-acrylamide-co-2-acrylamide-2-methylpropanesulfonic acid) lithium salt (0 / 95 / 5)

[0180] After distilled water (6,361 g), acrylamide (675.3 g, 9.5 mol), potassium persulfate (2.7 g, 0.01 mol), 2-acrylamido-2-methylpropanesulfonic acid (103.6 g, 0.5 mol) and 5N lithium hydroxide aqueous solution (1.05 equivalents based on the total amount of 2-acrylamido-2-methylpropanesulfonic acid) were added to a 3-liter four-necked separable flask equipped with a stirrer, a thermometer and a cooling tube, the internal pressure of the flask was repeatedly reduced three times to 10 mmHg using a diaphragm pump, and the internal pressure was returned to normal pressure using nitrogen gas.

[0181] The reaction solution was reacted by heating while the reaction temperature thereof was controlled to be stable between 65° C. and 70° C. for 12 hours. After the reaction solution was cooled to room temperature, the reaction solution was treated with a 25% ammonia solution to adjust the pH to 7 to 8.

[0182] About 10 ml of the reaction solution (reaction product) was taken to measure the non-volatile components, which were 9.5% (theoretical value: 10%). In addition, in the obtained poly(acrylic acid-co-acrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt, the structural unit derived from acrylic acid, the structural unit derived from acrylamide, and the structural unit derived from 2-acrylamido-2-methylpropanesulfonic acid had a molar ratio of 0:95:5. In fact, it can be said that it is poly(acrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) lithium salt.

[0183] Example and Comparative Example: Separator for Rechargeable Lithium Battery and Production of Rechargeable Lithium Battery Cell

[0184] Example 1

[0185] The binder of Synthesis Example 1 (10 wt % in distilled water) and boehmite (amorphous, D 50 =0.3 micron) was dispersed in water, and then ground using a bead mill at 25°C for 30 minutes to prepare an inorganic dispersion. Subsequently, water was added thereto so that the total solid content was 20% by weight, thereby preparing a composition for coating. The prepared composition for coating was die-coated to a thickness of 1 micron on a single surface of a 5.5 micron thick polyethylene porous substrate (air permeability: 110 seconds / 100 cubic centimeters, puncture strength: 360 kgf, CZMZ company), and then dried at 70°C for 10 minutes, thereby manufacturing a separator.

[0186] By using LiNi as the positive electrode active material 0.75 Mn 0.23 Al 0.02 O2, polyvinylidene fluoride as a binder, and acetylene black as a conductive material were mixed in a weight ratio of 96:3:1 and the mixture was dispersed in N-methylpyrrolidone to prepare a positive electrode active material slurry.

[0187] The positive electrode active material slurry was coated on a 15 μm thick Al foil, dried at 100° C., and pressed to manufacture a positive electrode.

[0188] A negative electrode active material slurry was prepared by mixing artificial graphite and Si-C composite in a weight ratio of 93:7 to prepare a negative electrode active material, mixing the negative electrode active material, styrene-butadiene rubber binder and carboxymethyl cellulose in a ratio of 98:1:1, and dispersing the mixture in distilled water.

[0189] The Si-C composite has a core containing artificial graphite and silicon particles and a coal-based pitch coated on the core.

[0190] The negative electrode active material slurry was coated on a 10 μm thick Cu foil, dried at 100° C., and pressed to manufacture a negative electrode.

[0191] The positive electrode and the negative electrode are assembled with a separator to manufacture an electrode assembly, and an electrolyte solution is injected into the electrode assembly to manufacture a rechargeable lithium battery cell. Here, the electrolyte solution is prepared by mixing ethylene carbonate (EC) and ethylmethyl carbonate (EMC) in a volume ratio of 3:7 and dissolving 1M LiPF6 in the mixed non-aqueous organic solvent.

[0192] Example 2

[0193] A separator for a rechargeable lithium battery and a rechargeable lithium battery cell were manufactured in the same manner as in Example 1, except that the binder of Synthesis Example 2 was used instead of the binder of Synthesis Example 1.

[0194] Example 3

[0195] A separator for a rechargeable lithium battery and a rechargeable lithium battery cell were manufactured in the same manner as in Example 1, except that the binder of Synthesis Example 3 was used instead of the binder of Synthesis Example 1.

[0196] Example 4

[0197] A separator for a rechargeable lithium battery and a rechargeable lithium battery cell were manufactured in the same manner as in Example 1, except that the binder of Synthesis Example 4 was used instead of the binder of Synthesis Example 1.

[0198] Example 5

[0199] A separator for a rechargeable lithium battery and a rechargeable lithium battery cell were manufactured in the same manner as in Example 1, except that the binder of Synthesis Example 5 was used instead of the binder of Synthesis Example 1.

[0200] Comparative Example 1

[0201] A separator for a rechargeable lithium battery and a rechargeable lithium battery cell were manufactured in the same manner as in Example 1, except that the binder of Comparative Synthesis Example 1 was used instead of the binder of Synthesis Example 1.

[0202] Comparative Example 2

[0203] A separator for a rechargeable lithium battery and a rechargeable lithium battery cell were manufactured in the same manner as in Example 1, except that the binder of Comparative Synthesis Example 2 was used instead of the binder of Synthesis Example 1.

[0204] Comparative Example 3

[0205] A separator for a rechargeable lithium battery and a rechargeable lithium battery cell were manufactured in the same manner as in Example 1, except that the binder of Comparative Synthesis Example 3 was used instead of the binder of Synthesis Example 1.

[0206] Each thickness and composition of the coatings according to Examples and Comparative Examples are provided in Table 1.

[0207] [Table 1]

[0208]

[0209] Assessment 1: Diaphragm Assessment

[0210] Each of the separators according to Examples 1 to 5 and Comparative Examples 1 to 3 was evaluated according to the following method, and the results are shown in Table 2.

[0211] (1) Thermal shrinkage

[0212] After each of the separators was cut into a size of 10 cm (machine direction (MD)) × 10 cm (transverse direction (TD)) to prepare a sample and a quadrilateral with a size of 8 cm × 8 cm was drawn on the sample, the sample was inserted between paper or alumina powder and then allowed to stand in an oven at 150°C for 60 minutes.

[0213] Then, the sample was taken out and compared with a pre-drawn quadrilateral having a size of 8 cm (machine direction, MD)×8 cm (transverse direction, TD) to calculate each heat shrinkage rate in the machine direction (MD) and the transverse direction (TD) according to Equation 1.

[0214] [Equation 1] Heat shrinkage rate = [(initial length - length after heat shrinkage treatment) / (initial length)]

[0215] (2) Resistance when immersed in electrolyte solution

[0216] Each of the separators was cut into a size of 10 cm×10 cm to prepare a sample, and the sample was immersed in the electrolyte solution of Example 1 to measure resistance at 25° C. by an alternating current method.

[0217] (3) Breathability

[0218] After the membrane was cut to have a cross section of 1 square inch to prepare a sample, the time (seconds) taken for 100 cubic centimeters of air to pass through the sample was measured by a densitometer according to the ASTM D726-94 test method.

[0219] (4) Adhesion strength

[0220] After the coating of the separator was brought into contact with the negative electrode active material layer of Example 1, the separator was bonded to the negative electrode using a laminator in a chamber at 60° C. Therefore, the bonded laminate of the separator and the negative electrode was cut into a predetermined size (width: 25 mm, length: 50 mm) to prepare a sample, and the force required for peeling in a 180° direction was measured using a tensiometer (TA-XT, Stable Micro Systems).

[0221] [Table 2]

[0222]

[0223] Referring to Table 2, each of the separators of Examples 1 to 5 exhibited enhanced adhesive strength compared to the separator of Comparative Example 1.

[0224] In addition, compared to the separators of Comparative Examples 2 and 3, the separators of Examples 1 to 5 may exhibit reduced resistance when impregnated with an electrolyte solution.

[0225] Assessment 2: Evaluation of Rechargeable Lithium Cells

[0226] (1) Room temperature charge / discharge cycle evaluation

[0227] The rechargeable lithium battery cells of Examples 1 to 5 and Comparative Examples 1 to 3 were respectively charged and discharged to evaluate cycle characteristics, and the results are shown in Table 3.

[0228] After charging and discharging the monomer for 200 cycles at 25°C under the conditions of 0.33C charge (CC / CV, 4.45V, 0.025C cut-off) / 1.0C discharge (CC, 2.5V cut-off), the capacity retention rate and the change of direct current internal resistance (DC-IR) were measured.

[0229] The capacity retention rate was calculated according to Equation 2, and the DC-IR change rate was calculated according to Equation 3 based on the voltage changed when discharging for 30 seconds by applying a current of SOC 50C.

[0230] [Equation 2]

[0231] Capacity retention rate = (discharge capacity after 200 cycles / discharge capacity after 1 cycle)*100 (%)

[0232] [Equation 3]

[0233] DC internal resistance change rate = {(DC-IR after 200 cycles) - (DC-IR after 1 cycle) / (DC-IR after 1 cycle)} * 100 (%)

[0234] [Table 3]

[0235]

[0236] Referring to Table 3, the rechargeable lithium battery cells of Examples 1 to 5 exhibited a reduced DC-IR change rate at room temperature compared to the rechargeable lithium battery cell of Comparative Example 1. In addition, compared to the separators of Comparative Examples 2 and 3, the rechargeable lithium battery cells of Examples 1 to 5 exhibited reduced initial resistance and improved capacity retention at room temperature.

[0237] (2) Evaluation of high temperature (45°C) charge and discharge cycle characteristics

[0238] The rechargeable lithium battery cells of Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated in terms of cycle characteristics after charging and discharging under the following conditions, and the results are shown in Table 4.

[0239] After charging and discharging the monomer for 200 cycles at 45°C under the conditions of 0.33C charge (CC / CV, 4.45V, 0.025C cutoff) / 1.0C discharge (CC, 2.5V cutoff), the capacity retention and the change of DC internal resistance (DC-IR) were measured.

[0240] The capacity retention rate and the DC internal resistance (DC-IR) change rate were calculated according to Equation 2 and Equation 3, respectively.

[0241] [Table 4]

[0242]

[0243] Referring to Table 4, the rechargeable lithium battery cells of Examples 1 to 5 exhibited a reduced DC-IR change rate at high temperatures compared to the rechargeable lithium battery cell of Comparative Example 1. In addition, compared to the separators of Comparative Examples 2 and 3, the rechargeable lithium battery cells of Examples 1 to 5 exhibited reduced initial resistance and improved capacity retention at high temperatures.

[0244] Summarize

[0245] In summary, the separator of the example includes a binder containing a specific structural unit and has high heat resistance and low electrical resistance. When such a binder is applied to the coating of the separator, a rechargeable lithium battery having a desired, favorable or improved cycle life characteristic at room temperature and / or high temperature can be achieved.

[0246] While the present disclosure has been described in conjunction with what are presently considered to be practical example embodiments, it is to be understood that the invention is not limited to the disclosed example embodiments, but on the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. An adhesive for a rechargeable lithium battery, the adhesive comprising: A first structural unit derived from at least one of (meth)acrylic acid, (meth)acrylic acid ester and a salt thereof; A second structural unit derived from hydroxyalkyl (meth)acrylate; as well as The third structural unit is derived from at least one of (meth)acrylamide sulfonic acid and a salt thereof.

2. The adhesive according to claim 1, wherein based on 100 mol % of the adhesive, at least one of the following is satisfied: The first structural unit is contained in an amount of 20 mol% to 75 mol%, The second structural unit is contained in an amount of 1 mol% to 20 mol%, and The third structural unit is included in an amount of 20 mol % to 75 mol %.

3. The adhesive according to claim 1, wherein at least one of the following is satisfied: The first structural unit is represented by any one of Chemical Formula 1 to Chemical Formula 3, The second structural unit is represented by Chemical Formula 4, and The third structural unit is represented by any one of Chemical Formula 5 to Chemical Formula 7: [Chemical formula 4] In Chemical Formulae 1 to 7, R 1 To R 8 each independently comprises hydrogen or a C1 to C10 alkyl group, L 1 To L 4 each independently includes at least one of 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, and a substituted or unsubstituted C3 to C20 heterocyclyl group, a, b, c and d are each independently an integer ranging from 0 to 2, and M includes alkali metals. 4 . The adhesive according to claim 1 , wherein the adhesive has a weight average molecular weight of 100,000 g / mol to 1,000,000 g / mol.

5. A separator for a rechargeable lithium battery, the separator comprising: porous substrate; as well as a coating layer located on at least one surface of the porous substrate and comprising a binder and inorganic particles, The adhesive comprises: A first structural unit derived from (meth)acrylic acid, (meth)acrylic acid ester or a salt thereof; A second structural unit derived from a hydroxyalkyl (meth)acrylate; and The third structural unit is derived from (meth)acrylamide sulfonic acid or a salt thereof.

6. The separator according to claim 5, wherein the inorganic particles include at least one of Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite or a combination thereof. 7 . The separator according to claim 5 , wherein an average particle size of the inorganic particles is in the range of 0.2 μm to 1 μm. 8 . The separator according to claim 5 , wherein a weight ratio of the binder to the inorganic particles is in a range of 1:5 to 1:

40. 9 . The separator according to claim 5 , wherein a thickness of the coating layer is in the range of 0.2 μm to 5 μm.

10. A rechargeable lithium battery comprising: A positive electrode, a negative electrode, and the separator for a rechargeable lithium battery according to claim 5 located between the positive electrode and the negative electrode.

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