Binder for rechargeable lithium battery, electrode including same, separator and rechargeable lithium battery

Abstract

Disclosed are a binder for a rechargeable lithium battery, an electrode including the binder, a separator, and a rechargeable lithium battery. In some examples, the binder for a rechargeable lithium battery includes: a first structural unit derived from a (meth) acrylic monomer; the second structural unit is derived from a C1-C10 alkylene glycol monomer; and a third structural unit derived from a zwitterionic vinyl monomer or a zwitterionic (meth) acryloyl monomer. Some example binders for rechargeable lithium batteries have high adhesive strength and low resistance, and thus may contribute to improving the performance of rechargeable lithium batteries.

Description

Technical Field

[0001] A binder for rechargeable lithium batteries, as well as an electrode including the binder and a rechargeable lithium battery, are disclosed. Background Technology

[0002] With the increasing prevalence of battery-powered electronic devices (such as mobile phones, laptops, and electric vehicles), the demand for small, lightweight, and relatively high-capacity rechargeable batteries is growing. Specifically, rechargeable lithium batteries are attractive as a power source for portable devices due to their lightweight design and high energy density.

[0003] Rechargeable lithium batteries typically include positive and negative electrodes containing active materials capable of inserting and deintercalating lithium ions, as well as an electrolyte solution, and generate electrical energy through oxidation and reduction reactions when lithium ions are inserted and deintercalated from the positive and negative electrodes.

[0004] Adhesives are included in the various components of these rechargeable lithium batteries. Adhesives can have high adhesive strength, but adhesives with high adhesive strength often have the disadvantage of high resistance. Summary of the Invention

[0005] Some example embodiments include an adhesive for rechargeable lithium batteries that has high adhesive strength and low resistance.

[0006] In some example embodiments, the binder for rechargeable lithium batteries includes: a first structural unit derived from (meth)acrylic acid monomers; a second structural unit derived from C1-C10 alkylene glycol monomers; and a third structural unit derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers.

[0007] In some example embodiments, the electrode for a rechargeable lithium battery includes: a binder for the rechargeable lithium battery; and an electrode active material.

[0008] In some example embodiments, the separator for a rechargeable lithium battery includes a porous substrate and a coating layer on one or both surfaces of the porous substrate, wherein the coating layer includes an adhesive.

[0009] In some example embodiments, a rechargeable lithium battery includes: a negative electrode; a positive electrode; a separator between the negative electrode and the positive electrode; and an electrolyte; wherein at least one of the negative electrode, the positive electrode, and the separator includes a binder for the rechargeable lithium battery.

[0010] Some example embodiments of the adhesive for rechargeable lithium batteries have high adhesive strength and low resistance, and therefore can help improve the performance of rechargeable lithium batteries. Attached Figure Description

[0011] Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Detailed Implementation

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

[0013] As used herein, unless otherwise specifically defined, it is understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, the element may be “directly on” the other element, or there may be an intervening element.

[0014] As used herein, the singular may also include the plural unless otherwise specifically defined. Additionally, unless otherwise stated, “A or B” may mean “including A, including B, or including both A and B”.

[0015] As used herein, “combination of them” can mean a mixture, stack, complex, copolymer, alloy, blend or reaction product of the components.

[0016] As used herein, unless otherwise defined, particle size can be the average particle size. This average particle size represents the average particle size (D50) as the diameter of particles having a cumulative volume of 50% of the particle size distribution. The average particle size (D50) can be measured by methods known to those skilled in the art (e.g., by measurement with a particle size analyzer, transmission electron microscope, or scanning electron microscope). Optionally, a dynamic light scattering measurement device is used to perform data analysis, and the number of particles is counted for each particle size range. Thus, the average particle size (D50) value can be readily obtained by calculation. Laser diffraction can also be used. When measured by laser diffraction, for example, the particles to be measured are dispersed in a dispersion medium and then introduced into a commercially available laser diffraction particle size measurement device (e.g., the MT3000 available from Microtrac), using ultrasound at approximately 28 kHz, and after irradiation with an output of 60 W, the average particle size (D50) based on 50% of the particle size distribution in the measurement device can be calculated.

[0017] As used herein, unless otherwise specifically defined, “alkyl” means C1 to C20 alkyl, “alken” means C2 to C20 alken, “cycloalken” means C3 to C20 cycloalken, “heterocyclic alken” means C3 to C20 heterocyclic alken, “aryl” means C6 to C20 aryl, “arylalkyl” means C6 to C20 arylalkyl, “alkylene” means C1 to C20 alkylene, “arylene” means C6 to C20 arylene, “alkylarylene” means C6 to C20 alkylarylene, “heteroarylene” means C3 to C20 heteroarylene, and “alkoxide” means C1 to C20 alkoxide.

[0018] As used herein, unless otherwise specifically defined, “substituted” means the substitution of at least one hydrogen atom by a substituent such as or including at least one of the following: halogen atom (F, Cl, Br or I), hydroxyl, C1 to C20 alkoxy, nitro, cyano, amino (or amino), imino, azide, amido, hydrazine, hydrazone, carbonyl, carbamoyl, thiol, ester, ether, carboxyl or a salt thereof, sulfonic acid or a salt thereof, phosphate or a salt thereof, C1 to C20 alkyl, C2 to C20 alkenyl, C2 to C20 alkynyl, C6 to C20 aryl, C3 to C20 cycloalkyl, C3 to C20 cycloalkenyl, C3 to C20 cycloalkynyl, C2 to C20 heterocyclic alkyl, C2 to C20 heterocyclic alkenyl, C2 to C20 heterocyclic alkynyl, C3 to C20 heterocyclic aryl, and combinations thereof.

[0019] Additionally, as used herein, unless otherwise specifically defined, “heterogeneous” means a chemical formula containing at least one heteroatom of at least one of N, O, S, and P.

[0020] Additionally, as used herein, unless otherwise specifically defined, “(meth)acrylate” means both “acrylate” and “methacrylate”, and “(meth)acrylic acid” means both “acrylic acid” and “methacrylic acid”.

[0021] As used herein, unless otherwise specifically defined, “combination” means blend or copolymerization.

[0022] In the chemical formulas of this specification, unless otherwise specifically defined, hydrogen is bonded at the position where a chemical bond is not drawn.

[0023] In this specification, the weight-average molecular weight (Mw) can be a value measured using gel permeation chromatography (GPC).

[0024] When the terms “about” or “basically” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical value include a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within it, such as increments of 0.1%.

[0025] adhesive In some example embodiments, the binder for rechargeable lithium batteries includes: a first structural unit derived from (meth)acrylic acid monomers; a second structural unit derived from C1-C10 alkylene glycol monomers; and a third structural unit derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers.

[0026] Binders containing only the first and second structural units can increase the adhesion strength of the active material layer to the current collector, but may not be sufficient to improve the resistivity of the active material layer. Furthermore, binders containing only the first and third structural units are essentially insoluble in water, making the fabrication of the active material layer challenging, and their viscosity is too low to easily manufacture the target active material layer. Therefore, binders that include a third structural unit in addition to the first and second structural units can improve resistivity and provide the desired adhesion strength by increasing the degree of lithium-ion transfer.

[0027] Each structural unit is described in detail below.

[0028] The first structural unit derived from (meth)acrylic acid monomers can be represented by chemical formula 1-1 or chemical formula 1-2: Chemical formula 1-1:

[0029] Chemical formula 1-2: .

[0030] In chemical formulas 1-1 and 1-2, R 1 They may be the same or different, and may each independently be or include hydrogen atoms or C1 to C20 alkyl groups, and M1 may be or include alkali metals.

[0031] For example, the first structural unit can be derived from acrylic acid, R 1 The groups can be all hydrogen atoms, and M1 can be derived from metal ions (e.g., lithium ions) in an electrolyte solution.

[0032] In some example embodiments, the first structural unit may be included in amounts ranging from about 50 wt% to about 98 wt%, about 60 wt% to about 90 wt%, or about 70 wt% to about 80 wt%, based on 100 wt% of the first, second, and third structural units. Within these ranges, the binder has a desired viscosity, which facilitates the fabrication of the active material layer and improves adhesive strength.

[0033] The second structural unit derived from C1-C10 alkylene glycol monomers can be represented by chemical formula 2-1 or chemical formula 2-2: Chemical formula 2-1:

[0034] Chemical formula 2-2: .

[0035] In chemical formulas 2-1 and 2-2, M2 can be or includes an alkali metal, and n can be an integer in the range of 1 to 100.

[0036] For example, the second structural unit can be derived from ethylene glycol, in which case n can be in the range of 5 to 20 or 5 to 10, and M2 can be derived from metal ions (e.g., lithium ions) in the electrolyte solution.

[0037] In some example embodiments, based on 100 wt% of the first, second, and third structural units, the second structural unit may be included in amounts ranging from about 1 wt% to about 25 wt%, about 5 wt% to about 20 wt%, or about 10 wt% to about 15 wt%. Within these ranges, the binder may help to further reduce resistance by increasing ionic conductivity.

[0038] The third structural unit derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers has both cationic and anionic functional groups in the molecule, and may have at least one of vinyl and (meth)acryloyl groups for polymerization with other structural units.

[0039] The cationic functional group can be or includes functional groups that exhibit monovalent or polyvalent positive charges in aqueous solvents, and can be or include, for example, substituted or unsubstituted ammonium cations (NH4+). + It may contain, but is not limited to, at least one of the following: imidazolium cation, pyrazolium cation, pyridinium cation, piperidinium cation, piperazineium cation, sulfide cation, naphthium cation, and guanidineium cation. For example, the cationic functional group may be or include substituted or unsubstituted ammonium cations or imidazolium cations.

[0040] The anionic functional group can be or includes functional groups that exhibit monovalent or polyvalent negative charges in aqueous solvents, and can be or include functional groups having at least one of sulfur (S), nitrogen (N), carbon (C), phosphorus (P), and oxygen (O). For example, the anionic functional group can be or includes -SO3. - -CO2 - -O - -and-NR - At least one of them. Here, R can be or include substituted or unsubstituted alkyl groups having 1 to 10 carbon atoms or haloalkyl groups having 1 to 10 carbon atoms.

[0041] The third structural unit derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers can be represented by chemical formula 3-1 or chemical formula 3-2.

[0042] Chemical formula 3-1:

[0043] Chemical formula 3-2: .

[0044] In chemical formulas 3-1 and 3-2, R 2 They may be the same or different, and each may independently be or include hydrogen atoms or C1 to C20 alkyl groups; R 3 They may be the same or different, and may each independently be or include hydrogen atoms or C1 to C20 alkyl groups; L 1 It can be or include *-(C=O)-NR 3 -CH2-* or *-(C=O)-O-*; and L 2 To L 4 Each may be independently or include a single bond or a C1 to C20 alkylene group.

[0045] The third structural unit derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers may be derived from at least one of sulfobetaine monomers, phosphate betaine monomers, carboxybetaine monomers, and imidazolonium monomers, and for example, may be derived from sulfobetaine monomers or vinylimidazolonium sulfonate monomers.

[0046] When the third structural unit can be derived from sulfobetaine (SB) and can be represented by chemical formula 3-1, R 2 It may include or contain methyl groups; L 1 They can be the same or different, and can all be or include *-(C=O)-NR independently. 3 -CH2-* or *-(C=O)-O-*; and L 2 and L 3Both can be or include ethylene.

[0047] When the third structural unit is derived from vinylimidazolium sulfonate (IMS) and represented by chemical formula 3-2, R 2 It may include or contain hydrogen atoms; and L 4 It can be or includes butylene.

[0048] In some example embodiments, based on 100 wt% of the first, second, and third structural units, the third structural unit may be included in amounts ranging from about 1 wt% to about 25 wt%, about 5 wt% to about 20 wt%, or about 10 wt% to about 15 wt%. Within these ranges, the adhesive strength of the active material layer to the current collector can be increased, and the resistance can be reduced.

[0049] The weight ratio of the second structural unit to the third structural unit in the adhesive can be in the range of about 1:2 to about 3:1 (e.g., about 1:1 to about 3:1, about 1:1 to about 2:1, or about 1:1 to about 1.5:1). When the second and third structural units are included in the above weight ratio, the adhesive can increase the bonding strength of the active material layer to the current collector and can also reduce the resistance.

[0050] In some example embodiments, the binder for rechargeable lithium batteries may also include a fourth structural unit derived from (meth)acrylamide monomers.

[0051] (Methacrylamide) monomers may include amide or nitrile groups. For example, the fourth structural unit may be derived from acrylonitrile.

[0052] The fourth structural unit derived from (meth)acrylyl monomers can be represented by chemical formula 4.

[0053] Chemical formula 4: .

[0054] In chemical formula 4, R 4 It may include or contain hydrogen atoms or C1 to C20 alkyl groups.

[0055] The fourth structural unit can be derived from, for example, acrylonitrile. For example, R 4 It can be or includes hydrogen atoms.

[0056] In some example embodiments, based on 100 wt% of the first, second, third, and fourth structural units, the first structural unit may be included in an amount ranging from about 30 wt% to about 70 wt%, the second structural unit may be included in an amount ranging from about 1 wt% to about 15 wt%, the third structural unit may be included in an amount ranging from about 1 wt% to about 15 wt%, and the fourth structural unit may be included in an amount ranging from about 20 wt% to about 50 wt%. For example, based on 100 wt% of the first, second, third, and fourth structural units, the first structural unit may be included in an amount ranging from about 40 wt% to about 60 wt%, the second structural unit may be included in an amount ranging from about 2 wt% to about 10 wt%, the third structural unit may be included in an amount ranging from about 2 wt% to about 10 wt%, and the fourth structural unit may be included in an amount ranging from about 25 wt% to about 45 wt%. As another example, the first structural unit may be included in an amount ranging from about 45 wt% to about 55 wt%, the second structural unit may be included in an amount ranging from about 5 wt% to about 10 wt%, the third structural unit may be included in an amount ranging from about 5 wt% to about 10 wt%, and the fourth structural unit may be included in an amount ranging from about 30 wt% to about 40 wt%. In any of the above ranges, the binder has a desired viscosity, which facilitates the fabrication of the active material layer and improves adhesive strength.

[0057] The binder according to some example embodiments may also include a lithium salt, in which case better lithium-ion conductivity can be achieved within the electrode, thereby improving the electrochemical performance of the battery. The binder may form chemical bonds (such as ionic bonds) with the cations and / or anions of the lithium salt, or the binder and lithium salt may be mixed. The lithium salt may be or include any common lithium salt contained in rechargeable lithium batteries without limitation, and may be or include at least one of, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, LiC4F9SO3, LiFSI, LiTFSI, LiOTf, LiDFOB, LiBOB, and combinations thereof.

[0058] The adhesive according to some example embodiments may have a viscosity in an aqueous solution at about 25°C ranging from about 450 cps to about 6500 cps, and a solids content ranging from about 8.5 wt% to about 10 wt%.

[0059] Methods for preparing adhesives Binders according to some example embodiments can be prepared by polymerizing mixtures of monomers using conventional methods known to those skilled in the art. Polymerization can be, or includes, emulsion polymerization, suspension polymerization, solution polymerization, etc.

[0060] Emulsifiers may be or include at least one or combinations thereof of higher fatty acid alkali metal salts, N-acryloyl amino acid salts, alkyl ether carbonates, acylated peptides, alkyl sulfonates, alkylbenzene sulfonates, alkyl amino acid salts, alkylnaphthalene sulfonates, sulfosuccinates, sulfonated oils, alkyl sulfates, alkyl ether sulfates, alkyl aryl ether sulfates, alkylamide sulfates, alkyl phosphates, alkyl ethoxy phosphates, and alkyl aryl ether phosphates. An example of an emulsifier may be sodium dodecylbenzene sulfonate. The alkyl group may be an alkyl group having 1 to 20 carbon atoms.

[0061] Based on the total content of 100 parts by weight of the monomer mixture, the emulsifier content can be in the range of about 0.1 parts by weight to about 3 parts by weight or about 0.1 parts by weight to about 2 parts by weight. When the emulsifier content is within the above range, the adhesive strength can be further improved, and an adhesive with the desired size can be obtained, resulting in the desired dispersion.

[0062] The initiator may be or include at least one of azo compound initiators, such as azobisisobutyronitrile, ammonium persulfate, potassium persulfate, hydrogen peroxide, tert-butyl hydroperoxide, and combinations thereof.

[0063] Based on the total content of 100 parts by weight of the monomer mixture, the content of the initiator may be in the range of about 0.1 parts by weight to about 3 parts by weight, or it may be about 0.1 parts by weight to about 2 parts by weight.

[0064] The binder may have a weight-average molecular weight (Mw) in the range of about 20,000 g / mol to about 1,500,000 g / mol (e.g., about 50,000 g / mol to about 2,500,000 g / mol). Within this range, the binder may be included in the active material layer. Here, "weight-average molecular weight" can be a value calculated using gel permeation chromatography with polystyrene as the conversion base.

[0065] The binder may include at least one of a binder for the positive electrode of a rechargeable lithium battery and a binder for the negative electrode of a rechargeable lithium battery.

[0066] Rechargeable lithium batteries Based on their shape, rechargeable lithium batteries can be classified as cylindrical batteries, prismatic batteries, pouch batteries, or button batteries, etc. Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments, wherein, Figure 1It is a cylindrical battery. Figure 2 It is a prismatic battery. Figure 3 and Figure 4 It is a pouch battery. (See reference) Figures 1 to 4 The rechargeable lithium battery 100 includes an electrode assembly 40 and a housing 50. The electrode assembly 40 has a separator 30 disposed between a positive electrode 10 and a negative electrode 20. The electrode assembly 40 is housed within the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte solution (not shown). Figure 1 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. Additionally, in Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 includes, as Figure 4 The electrode terminals 70 shown or as Figure 3 The positive electrode terminal 71 and negative electrode terminal 72 shown herein form an electrical path for guiding the current generated in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0067] electrode Some example embodiments include electrodes for rechargeable lithium batteries comprising the aforementioned binder and electrode active material according to some example embodiments.

[0068] Some example embodiments include electrode compositions for rechargeable lithium batteries comprising the aforementioned binder, electrode active material, and solvent. The binder-containing electrode can be manufactured by applying the electrode composition to a current collector, drying, and pressing.

[0069] The electrode can be or includes a negative electrode or a positive electrode. Even when the binder is included in the negative electrode, which undergoes large volume changes due to the charging and discharging of the rechargeable lithium battery, the binder has high adhesive strength and low resistance, and therefore can help improve the performance of the rechargeable lithium battery.

[0070] The following describes electrodes for rechargeable lithium batteries according to some example embodiments.

[0071] negative electrode The negative electrode includes a current collector and a layer of negative electrode active material on the current collector. The negative electrode active material layer includes a negative electrode active material and may also include a binder and / or a conductive material. The binder may be the binder of the foregoing example embodiments.

[0072] For example, the negative electrode active material layer may include from about 90 wt% to about 99 wt% or from about 90 wt% to about 99.5 wt% of a negative electrode active material, from about 0.5 wt% to about 5 wt% of a binder, and from about 0 wt% to about 5 wt% of a conductive material.

[0073] The negative electrode active material may include at least one of a material that can reversibly intercalate / deintercalate lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / de-doping lithium, and a transition metal oxide.

[0074] The material that can reversibly intercalate / deintercalate lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof as a carbon-based negative electrode active material. The crystalline carbon may be irregular or natural graphite or artificial graphite in the form of flakes, platelets, spheres, or fibers. The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0075] The lithium metal alloy includes an alloy of lithium and a metal (such as or including at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn).

[0076] The material capable of doping / de-doping 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 (where 0 < x ≤ 2), a Si-Q alloy (where Q is or includes at least one element such as an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and a combination thereof), and a combination thereof. The Sn-based negative electrode active material may be or include at least one of Sn, SnO2, a Sn-based alloy, and a combination thereof.

[0077] The silicon-carbon composite may be or include a composite of silicon and amorphous carbon. According to some example 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) in which silicon primary particles are assembled and an amorphous carbon coating layer (shells) on the surface of the secondary particles. Amorphous carbon may also be present 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.

[0078] The silicon-carbon composite may also include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating layer on the surface of the core.

[0079] Si-based or Sn-based negative electrode active materials can be mixed with carbon-based negative electrode active materials.

[0080] The binder is configured to adhere the negative electrode active material particles to each other and to adhere the negative electrode active material to the current collector. The binder may be or include at least one of non-aqueous binders, aqueous binders, dry binders, and combinations thereof.

[0081] Non-aqueous adhesives may include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, and combinations thereof.

[0082] Waterborne adhesives may include at least one of the following: styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxygenated alcohol, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0083] In addition to the adhesive according to the foregoing example embodiments, other adhesives may be included or added as negative electrode adhesives. When an aqueous adhesive is included as the negative electrode adhesive, a cellulosic compound capable of imparting viscosity may be further included. As a cellulosic compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts may be mixed. The alkali metal may be or include at least one of Na, K, and Li.

[0084] The dry binder may be or include a polymeric material capable of being turned into fibers, and may be or include at least one of, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0085] Conductive materials may be included to provide electrode conductivity, and any electrically conductive material may be included as a conductive material unless it causes a chemical change in the battery. Examples of conductive materials include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metallic materials such as metal powders or metal fibers, including at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0086] The negative electrode current collector may include at least one of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and combinations thereof.

[0087] positive electrode The positive electrode may include a current collector and a layer of positive electrode active material formed on the current collector. The positive electrode active material layer may include a positive electrode active material, and may also include a binder and / or a conductive material. The binder may be or include the binder described in the example embodiments.

[0088] Based on a 100wt% positive electrode active material layer, the content of the positive electrode active material can be in the range of about 90wt% to about 99wt% or about 90wt% to about 99.5wt%, and based on the 100wt% positive electrode active material layer, the respective contents of the binder and the conductive material can be in the range of about 0.5wt% to about 5wt%.

[0089] The positive electrode active material can be or includes compounds capable of intercalating and deintercalating lithium (lithiation intercalation compounds). For example, it can include one or more types of composite oxides of lithium and metals (such as or including at least one of cobalt, manganese, nickel and combinations thereof).

[0090] The composite oxide can be or includes lithium transition metal composite oxides, and examples of such composite oxides can include at least one of lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, and combinations thereof.

[0091] As an example, it may include compounds represented by any of the following chemical formulas. Li 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 bX 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 NiG 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 Mn2G b O4 (0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-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).

[0092] In the above chemical formulas, A is or includes at least one of Ni, Co, Mn, and combinations thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is or includes at least one of O, F, S, P, and combinations thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; and L 1 It is or includes at least one of Mn, Al and combinations thereof.

[0093] The positive electrode active material may be or include at least one of the following: lithium nickel oxide represented by chemical formula 11, lithium cobalt oxide represented by chemical formula 12, lithium iron phosphate compound represented by chemical formula 13, cobalt-free lithium nickel manganese oxide represented by chemical formula 14, and combinations thereof.

[0094] Chemical Formula 11: Li a1 Nix1 M 1 y1 M 2 z1 O 2-b1 X b1 .

[0095] 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 of them independently consists of or includes 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 or includes one or more of F, P, and S.

[0096] 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.

[0097] Chemical formula 12: Li a2 Co x2 M 3 y2 O 2-b2 X b2 .

[0098] 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 X is or includes 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 or includes one or more of F, P, and S.

[0099] Chemical formula 13: Li a3 Fe x3 M 4 y3 PO 4-b3 X b3 .

[0100] In chemical formula 13, 0.9 ≤ a³ ≤ 1.8, 0.6 ≤ x³ ≤ 1, 0 ≤ y³ ≤ 0.4, and 0 ≤ b³ ≤ 0.1, M 4is or includes 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 or includes one or more of F, P, and S.

[0101] Chemical Formula 14: Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4 .

[0102] In Chemical Formula 14, 0.9 ≤ a4 ≤ 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 or includes 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 or includes one or more of F, P, and S.

[0103] For example, the positive electrode active material may be or include a high-nickel positive electrode active material. Based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide, the nickel content in the 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%. The high-nickel positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0104] In addition to the binder according to some exemplary embodiments, other binders may be included or added as the positive electrode binder. The binder improves the adhesion properties between the positive electrode active material particles and between the positive electrode active material particles and 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, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylic esterified styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon, but are not limited thereto.

[0105] The conductive material is included to provide electrode conductivity, and may include any electrically conductive material as the conductive material unless the electrically conductive material causes a chemical change. Examples of conductive materials may include: carbon-based materials, such as or including at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metallic materials such as metal powders or metal fibers, including at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0106] The current collector may include, but is not limited to, Al.

[0107] electrolytes The electrolyte used in rechargeable lithium batteries can be or include, for example, an electrolyte solution that may contain a non-aqueous organic solvent and a lithium salt.

[0108] Non-aqueous organic solvents can be configured as media for transporting ions that participate in the electrochemical reactions of a battery. Non-aqueous organic solvents can be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0109] Carbonate solvents may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC). Ester solvents may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, caprolactone, etc. Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include at least one of ethanol, isopropanol, etc., and aprotic solvents may include at least one of the following: nitriles, such as R-CN (where R is a C2-C20 straight-chain, branched or cyclic hydrocarbon group, and may include double bonds, aromatic rings or ether groups, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0110] Non-aqueous organic solvents may be included alone or in combination of two or more solvents. When the combination includes two or more types, the mixing ratio can be adjusted as needed to determine the desired battery performance, as is widely understood by those skilled in the art.

[0111] When using carbonate solvents, cyclic carbonates and chain carbonates can be mixed, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio ranging from about 1:1 to about 1:9.

[0112] Non-aqueous organic solvents may also include aromatic hydrocarbon organic solvents. For example, carbonate solvents and aromatic hydrocarbon organic solvents can be mixed in a volume ratio ranging from about 1:1 to about 30:1.

[0113] The electrolyte solution may also include at least one of vinyl ethyl carbonate, vinylene carbonate, and ethylene carbonate compounds to improve battery cycle life.

[0114] Representative examples of ethylene carbonate compounds may include at least one of fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0115] Lithium salts dissolved in organic solvents supply lithium ions in batteries, are configured to enable basic operation of rechargeable lithium batteries, and improve lithium ion transport between the positive and negative electrodes. 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+1 At least one of the following: (SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0116] The concentration of lithium salt can be in the range of about 0.1 M to about 2.0 M. When the concentration of lithium salt is within the above range, the electrolyte solution has the desired ionic conductivity and viscosity, thus achieving the desired or improved performance and allowing lithium ions to move efficiently.

[0117] diaphragm Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, multilayer films of the same two or more layers, and hybrid multilayer films (such as polyethylene / polypropylene bilayer separators, polyethylene / polypropylene / polypropylene trilayer separators, polypropylene / polypropylene / polypropylene trilayer separators, etc.).

[0118] The membrane may include a porous substrate and a coating layer on one or both surfaces of the porous substrate, the coating layer comprising an organic material, an inorganic material, or a combination thereof.

[0119] The porous substrate may be or include a polymer membrane formed of or comprising any polymer, wherein any polymer is at least one of polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, TEFLON and polytetrafluoroethylene, or a copolymer or mixture of two or more thereof.

[0120] The porous substrate may have a thickness ranging from about 1 μm to about 40 μm (e.g., about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 10 μm to about 15 μm).

[0121] In one example, the organic material of the coating may include the aforementioned binder according to some example embodiments. In some example embodiments, the separator for a rechargeable lithium battery includes a porous substrate and a coating on one or both surfaces of the porous substrate, wherein the coating includes the aforementioned binder. In the coating, the binder may be included together with the inorganic material in an amount ranging from about 1 wt% to about 100 wt%, for example, in amounts such as about 1 wt% to about 10 wt%, about 1 wt% to about 5 wt%, or about 80 wt% to about 100 wt%, about 90 wt% to about 100 wt%, or about 91 wt% to about 99 wt%. A separator including the aforementioned binder in the coating can achieve desired or improved heat resistance and mechanical strength.

[0122] Organic materials may include (meth)acrylic acid copolymers comprising a first structural unit and a second structural unit, wherein the first structural unit is derived from (meth)acrylamide and the second structural unit comprises at least one of structural units derived from (meth)acrylic acid or (meth)acrylate and structural units derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0123] Inorganic materials may include, but are not limited to, inorganic particles (such as or including 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). The average particle size (D) of the inorganic particles... 50 It can be in the range of about 1nm to about 2000nm (e.g., about 100nm to about 1000nm or about 100nm to about 700nm).

[0124] Organic and inorganic materials can be mixed in a single coating layer, or coating layers comprising organic materials and coating layers comprising inorganic materials can be stacked.

[0125] The thickness of the coating can be in the range of about 0.5 μm to about 20 μm (e.g., about 1 μm to about 10 μm or about 1 μm to about 5 μm).

[0126] Examples and comparative examples of this disclosure are described below. However, the following examples are merely examples of this disclosure, and this disclosure is not limited to these examples.

[0127] Preparation Example 1 Based on 100 parts by weight of a monomer mixture comprising 50 wt% acrylic acid (AA), 35 wt% acrylonitrile (AN), 8 wt% sulfobetaine (SB), and 7 wt% ethylene glycol (EG), an azo compound initiator and water are mixed therewith. Based on 100 parts by weight of the monomer mixture, the initiator is used in an amount of 0.2 parts by weight.

[0128] Subsequently, a solution comprising a binder is prepared, the binder comprising a copolymer obtained by emulsion polymerization of the obtained mixture. The prepared binder comprises a first structural unit derived from acrylic acid, a second structural unit derived from ethylene glycol, a third structural unit derived from sulfobetaine, and a fourth structural unit derived from acrylonitrile.

[0129] Preparation Example 2 The adhesive was prepared in essentially the same manner as in Preparation Example 1, except that propylene glycol (PG) was used instead of ethylene glycol (EG).

[0130] Preparation Example 3 The binder was prepared in essentially the same manner as in Preparation Example 1, except that vinylimidazolium sulfonate (IMS) was used instead of sulfobetaine (SB).

[0131] Preparation Example 4 The binder was prepared in essentially the same manner as in Preparation Example 2, except that vinylimidazolium sulfonate (IMS) was used instead of sulfobetaine (SB).

[0132] Preparation Example 5 Based on 100 parts by weight of a monomer mixture comprising 55 wt% acrylic acid (AA) and 45 wt% acrylonitrile (AN), an azo compound initiator and water are mixed therewith. Based on 100 parts by weight of the monomer mixture, the initiator is used in an amount of 0.2 parts by weight.

[0133] Subsequently, a solution comprising a binder is prepared, the binder comprising a copolymer obtained by emulsion polymerization of the obtained mixture.

[0134] Preparation Example 6 The adhesive is manufactured in essentially the same manner as in Preparation Example 5, except that acrylamide (AM) is used instead of acrylonitrile (AN).

[0135] Preparation Example 7 Based on a monomer mixture comprising 50 wt% acrylic acid (AA) and 50 wt% sulfobetaine (SB) in 100 parts by weight, an azo compound initiator and water are mixed therewith. Based on 100 parts by weight of the monomer mixture, the initiator is included in an amount of 0.2 parts by weight.

[0136] Subsequently, a solution comprising a binder is prepared, the binder comprising a copolymer obtained by emulsion polymerization of the obtained mixture.

[0137] Preparation Example 8 The adhesive was prepared in essentially the same manner as in Preparation Example 7, except that acrylonitrile (AN) was used instead of acrylic acid (AA).

[0138] Preparation Example 9 The binder was prepared in essentially the same manner as in Preparation Example 7, except that vinylimidazolium sulfonate (IMS) was used instead of sulfobetaine (SB).

[0139] Preparation Example 10 The adhesive was prepared in essentially the same manner as in Preparation Example 9, except that acrylonitrile (AN) was used instead of acrylic acid (AA).

[0140] Preparation Example 11 Based on a monomer mixture comprising 45 wt% acrylic acid (AA), 40 wt% acrylonitrile (AN), and 15 wt% sulfobetaine (SB), an azo compound initiator and water are mixed therewith. Based on 100 parts by weight of monomer mixture, an initiator is used in an amount of 0.2 parts by weight.

[0141] Subsequently, a solution comprising a binder is prepared, the binder comprising substantially a copolymer obtained by reacting the obtained mixture with the obtained copolymer.

[0142] Preparation Example 12 The adhesive is manufactured in essentially the same manner as in Preparation Example 11, except that acrylamide (AM) is used instead of acrylonitrile (AN).

[0143] Preparation Example 13 The binder was manufactured in essentially the same manner as in Preparation Example 11, except that vinylimidazolium sulfonate (IMS) was used instead of sulfobetaine (SB).

[0144] Preparation Example 14 The binder was manufactured in essentially the same manner as in Preparation Example 12, except that vinylimidazolium sulfonate (IMS) was used instead of sulfobetaine (SB).

[0145] The types and contents of monomers included in the binders according to the preparation examples are shown in Table 1 below.

[0146] Table 1:

[0147] For the adhesives, the respective contents of acrylic acid (AA), acrylonitrile (AN), acrylamide (AM), sulfobetaine (SB), vinylimidazolium sulfonate (IMS), ethylene glycol (EG), and propylene glycol (PG) are expressed as a weight percentage (wt%) based on a total of 100 wt% of each adhesive.

[0148] 1. Evaluation of the usability of the adhesive's negative electrode Example 1 (1) Manufacturing of the negative electrode A negative electrode active material slurry was prepared by mixing 93.4 wt% of graphite negative electrode active material, 4 wt% of silicon-carbon composite negative electrode active material, 1.0 wt% of binder according to Preparation Example 1, 1.5 wt% of styrene-butadiene (SBR), and 0.1 wt% of conductive material in an aqueous solvent. The negative electrode active material slurry was coated onto a copper foil current collector, then dried and pressed to fabricate a negative electrode.

[0149] (2) Manufacturing of the positive electrode 97.0wt% (LiNi) 0.88 Co 0.105 Al 0.015 O2) positive electrode active material, 1.5 wt% polyvinylidene fluoride binder and 1.5 wt% carbon nanotube conductive material are mixed to prepare positive electrode active material layer slurry, and the positive electrode active material layer slurry is coated on aluminum foil current collector, then dried and pressed to manufacture positive electrode.

[0150] (3) Preparation of electrolyte solution Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 2:4:4 to prepare an organic solvent. LiPF6 lithium salt was then mixed with the organic solvent at a concentration of 1.15 M to obtain an electrolyte solution.

[0151] (4) Manufacturing of rechargeable lithium battery cells The positive and negative electrodes are assembled with a polyethylene separator coated with an acrylamide functional layer to obtain an electrode assembly, and after the electrode assembly is housed in a prismatic housing, an electrolyte solution is injected therein to form a rechargeable lithium battery cell.

[0152] Examples 2 to 4 Each rechargeable lithium battery cell was manufactured in essentially the same manner as in Example 1, except that the binder used to prepare Example 2 was used in Example 2, the binder used to prepare Example 3 was used in Example 3, and the binder used to prepare Example 4 was used in Example 4 instead of the binder used to prepare Example 1 when manufacturing the negative electrode.

[0153] Comparison Examples 1 to 10 Each rechargeable lithium battery cell was manufactured in essentially the same manner as in Example 1, except that the binder used in Preparation Example 5 was used in Comparative Example 1, the binder used in Preparation Example 6 was used in Comparative Example 2, the binder used in Preparation Example 7 was used in Comparative Example 3, the binder used in Preparation Example 8 was used in Comparative Example 4, the binder used in Preparation Example 9 was used in Comparative Example 5, the binder used in Preparation Example 10 was used in Comparative Example 6, the binder used in Preparation Example 11 was used in Comparative Example 7, the binder used in Preparation Example 12 was used in Comparative Example 8, the binder used in Preparation Example 13 was used in Comparative Example 9, and the binder used in Preparation Example 14 was used in Comparative Example 10 instead of the binder used in Preparation Example 1.

[0154] Evaluation Example 1: Slurry Viscosity The viscosity of one gram (g) of each slurry according to Examples 1 to 4 and Comparative Examples 1 to 10 at 25°C was measured using a rheometer (Anton Paar GmbH) by the flow viscosity measurement method. The results are shown in Table 2 below.

[0155] Evaluation Example 2: Electrode Plate Adhesion Strength The adhesive strength between the current collector and the active material layer of the negative electrode according to Examples 1 to 4 and Comparative Examples 1 to 10 was measured using a Universal Testing Machine (UTM) tensile strength tester. Samples were prepared by attaching a glass slide (length × width = 7 cm × 2.5 cm) to one side of double-sided adhesive tape (length × width = 4 cm × 2.5 cm) and attaching each of the negative electrodes (length × width = 7 cm × 2.5 cm) to the other side of the double-sided adhesive tape. The samples were mounted on the UTM tensile strength tester, and the adhesive strength was subsequently measured by peeling the negative electrode from the glass slide at a peel angle of 180°, a peel temperature of 25°C, and a peel speed of 100 mm / min. The results are shown in Table 2 below.

[0156] Table 2:

[0157] Referring to Table 2, compared with the slurry and negative electrode of the comparative example, the slurry and negative electrode of the example exhibit the desired slurry viscosity and the desired or improved adhesion strength to the negative electrode current collector.

[0158] Evaluation Example 3: Evaluation of Battery Cell Characteristics 1. Charging rate The battery cells of Examples 1 to 4 and Comparative Examples 1 to 10 were evaluated by charging them to a cutoff voltage of 4.25V at a constant current of 1.0C at 25°C. In the corresponding charging method, the percentage (%) of "maximum charging capacity / total battery capacity" was calculated using the maximum charging capacity of the battery cell when it reached 4.25V, which is shown as the charging rate in Table 3 below.

[0159] 2. DC-IR (DC internal resistance) The battery cells of Examples 1 to 4 and Comparative Examples 1 to 10, each with a capacity of 75 mAh, were charged at a constant current / constant voltage under conditions of 0.2C, 4.25V, and 0.05C cutoff, paused for 10 minutes, discharged at a constant current of 0.33C under conditions of 2.80V cutoff, and paused for 10 minutes at 25°C to perform the first charge and discharge. The voltage drop (V) that occurred when a 1C current passed through for 10 seconds was then measured at SOC50 (based on the state where 100% of the total charge capacity was charged to 50% of the charge capacity, which also represents the state where it was discharged to 50% during discharge). Subsequently, the DC internal resistance (DC-IR) was measured using this voltage drop, and the results are shown in Table 3 below.

[0160] 3. Life retention rate after 200 cycles The battery cells of Examples 1 to 4 and Comparative Examples 1 to 10 were charged at a constant current of 0.5C to a voltage of 4.2V, and then cut off at a constant voltage mode of 0.025C at 25°C. Subsequently, the battery cells were discharged at a rate of 0.5C to 2.5V, and this charge-discharge cycle was repeated 200 times to evaluate the capacity retention rate, i.e., the cycle life retention rate, based on the number of cycles. The results are shown in Table 3 below.

[0161] Table 3:

[0162] Referring to Table 3 above, compared with the rechargeable lithium battery cell according to the comparative example, the rechargeable lithium battery cell according to the example exhibits the same or expected or improved cycle life retention, as well as improved charge rate and reduced DC-IR.

[0163] 2. Evaluation of the usability of the positive electrode of the binder Example 5 (1) Manufacturing of the positive electrode 95.8 wt% of LFP (lithium iron phosphate active material) as positive electrode active material, 2.0 wt% of carbon nanotubes as conductive material and 2.2 wt% of the binder of Preparation Example 1 were mixed and water was added to prepare a positive electrode slurry. The positive electrode slurry was then coated on an aluminum foil current collector and dried and pressed to manufacture a positive electrode.

[0164] (2) Manufacturing of the negative electrode A negative electrode active material slurry was prepared by mixing 97.4 wt% graphite negative electrode active material, 1.0 wt% carboxymethyl cellulose, 1.5 wt% styrene-butadiene rubber and 0.1 wt% carbon nanotubes as conductive material. The negative electrode active material slurry was then coated onto a copper foil current collector, dried and pressed to manufacture a negative electrode.

[0165] (3) Preparation of electrolyte solution Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 2:4:4 to prepare an organic solvent, and lithium LiPF6 salt was added to it at a concentration of 1.15 M to obtain an electrolyte solution.

[0166] (4) Manufacturing of rechargeable lithium battery cells The positive and negative electrodes are assembled with a polyethylene separator coated with an acrylamide functional layer to obtain an electrode assembly, and after the electrode assembly is housed in a prismatic housing, an electrolyte solution is injected therein to manufacture a rechargeable lithium battery cell.

[0167] Examples 6 to 8 Each rechargeable lithium battery cell was manufactured in essentially the same manner as in Example 5, except that the binder used in Example 2 was used in Example 6, the binder used in Example 3 was used in Example 7, and the binder used in Example 4 was used in Example 8 instead of the binder used in Example 1 when manufacturing the positive electrode.

[0168] Comparative Examples 11 to 16 Each rechargeable lithium battery cell was manufactured in essentially the same manner as in Example 5, except that the binder used in Comparative Example 11 was used in Comparative Example 12, the binder used in Comparative Example 11 was used in Comparative Example 13, the binder used in Comparative Example 14 was used in Comparative Example 15, the binder used in Comparative Example 13 was used in Comparative Example 16, and the binder used in Comparative Example 14 was used instead of the binder used in Comparative Example 1.

[0169] Evaluation Example 4: Slurry Viscosity The viscosity of the slurries of Examples 5 to 8 and Comparative Examples 11 to 16 was measured in essentially the same manner as in Evaluation 1, and the results are shown in Table 4 below.

[0170] Evaluation Example 5: Electrode Plate Adhesion Strength The adhesion strength between the current collector and the positive electrode active material layer of the positive electrodes according to Examples 5 to 8 and Comparative Examples 11 to 16 was evaluated in essentially the same manner as in Evaluation Example 2, and the results are shown in Table 4 below.

[0171] Table 4:

[0172] Referring to Table 4, compared with the slurry and positive electrode of the comparative example, the slurry and positive electrode of the example exhibit the desired slurry viscosity and the desired or improved adhesion strength to the positive electrode current collector.

[0173] Evaluation Example 6: Evaluation of Battery Cell Characteristics The characteristics of the battery cells of Examples 5 to 8 and Comparative Examples 11 to 16 were evaluated in essentially the same manner as in Evaluation Example 3, and the results are shown in Table 5 below.

[0174] Table 5:

[0175] Referring to Table 5, compared with the rechargeable lithium battery cell of the comparative example, the rechargeable lithium battery cell of the example exhibits the same or expected or improved cycle life retention, as well as improved charge rate and reduced DC-IR.

[0176] While this disclosure has been described in conjunction with what are now considered to be practical exemplary embodiments, it will be understood that the disclosure is not limited to the disclosed embodiments. Rather, the disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0177] Explanation of reference numerals in the attached figures: 100: Rechargeable lithium battery; 10: Positive electrode 11: Positive electrode lead connector 12: Positive electrode terminal 20: Negative electrode 21: Negative electrode lead connector 22: Negative electrode terminal; 30: Diaphragm 40: Electrode assembly; 50: Housing 60: Sealing component; 70: Electrode terminal piece 71: Positive electrode connector; 72: Negative electrode connector.

Claims

1. An adhesive for a rechargeable lithium battery, the adhesive comprising: The first structural unit is derived from (meth)acrylic acid monomers; The second structural unit is derived from C1-C10 alkylene glycol monomers; as well as The third structural unit is derived from zwitterionic vinyl monomers or zwitterionic (meth)acryloyl monomers.

2. The adhesive according to claim 1, wherein, The first structural unit is represented by chemical formula 1-1 or chemical formula 1-2, and The second structural unit is represented by chemical formula 2-1 or chemical formula 2-2: Chemical formula 1-1: Chemical formula 1-2: Among them, in chemical formula 1-1 and chemical formula 1-2, Each R 1 Independently includes hydrogen atoms or C1 to C20 alkyl groups; and M1 includes alkali metals. Chemical formula 2-1: Chemical formula 2-2: Among them, in chemical formula 2-1 and chemical formula 2-2, M2 includes alkali metals, and n is an integer in the range between 1 and 100.

3. The adhesive according to claim 1, wherein: The zwitterionic vinyl monomer or the zwitterionic (meth)acryloyl monomer has at least one cationic functional group, the at least one cationic functional group including at least one of substituted or unsubstituted ammonium cation, imidazolium cation, pyrazolium cation, pyridinium cation, piperidinium cation, piperazineium cation, sulfide cation, naphthium cation and guanidineium cation.

4. The adhesive according to claim 1, wherein: The zwitterionic vinyl monomer or the zwitterionic (meth)acryloyl monomer has at least one anionic functional group, the at least one anionic functional group including -SO3. - -CO2 - -O - -and-NR - At least one of them, and R includes substituted or unsubstituted C1 to C10 alkyl or C1 to C10 haloalkyl.

5. The adhesive according to claim 1, wherein, The zwitterionic vinyl monomers or the zwitterionic (meth)acryloyl monomers include at least one of sulfobetaine monomers, phosphate betaine monomers, carboxybetaine monomers, and imidazoline monomers.

6. The adhesive according to claim 1, wherein, The third structural unit is represented by chemical formula 3-1 or chemical formula 3-2: Chemical formula 3-1: Chemical formula 3-2: Among them, in chemical formulas 3-1 and 3-2, Each R 2 Independently includes hydrogen atoms or C1 to C20 alkyl groups; Each R 3 Independently includes hydrogen atoms or C1 to C20 alkyl groups; L 1 Including *-(C=O)-NR 3 -CH2-* or *-(C=O)-O-*; and L 2 To L 4 Each independently includes a single bond or a C1 to C20 alkylene group.

7. The adhesive according to claim 1, wherein, Based on 100wt% of the first structural unit, the second structural unit, and the third structural unit: The first structural unit is included in an amount ranging from 50 wt% to 98 wt%. The second structural unit is included in an amount ranging from 1 wt% to 25 wt%, and The third structural unit is included in amounts ranging from 1 wt% to 25 wt%.

8. The adhesive according to claim 1, wherein the adhesive further comprises a fourth structural unit derived from (meth)acrylyl monomers.

9. The adhesive according to claim 8, wherein, The (meth)acrylamide monomers include one of an amide group and a nitrile group.

10. The adhesive according to claim 8, wherein, The fourth structural unit is represented by chemical formula 4: Chemical formula 4: In chemical formula 4, R 4 Includes hydrogen atoms or C1 to C20 alkyl groups.

11. The adhesive according to claim 8, wherein, Based on 100wt% of the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit: The fourth structural unit is included in amounts ranging from 20 wt% to 50 wt%.

12. The adhesive according to claim 11, wherein, Based on 100wt% of the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit: The first structural unit is included in an amount ranging from 30 wt% to 70 wt%. The second structural unit is included in an amount ranging from 1 wt% to 15 wt%, and The third structural unit is included in an amount ranging from 1 wt% to 15 wt%.

13. The adhesive according to claim 1, wherein the adhesive further comprises a lithium salt.

14. The adhesive according to claim 1, wherein, The adhesive has a viscosity in the range of 450 cps to 6500 cps in an aqueous solution at 25°C and a solid content in the range of 8.5 wt% to 10 wt%.

15. An electrode for a rechargeable lithium battery, said electrode include: The adhesive according to claim 1; and Electrode active material.

16. The electrode according to claim 15, wherein, The electrode includes a negative electrode.

17. The electrode according to claim 16, wherein, The negative electrode includes a negative electrode active material, which includes at least one of carbon-based negative electrode active materials and silicon-based negative electrode active materials.

18. A separator for a rechargeable lithium battery, the separator comprising: Porous substrate and coating layer on one or both surfaces of the porous substrate, The coating layer includes the adhesive according to claim 1.

19. A rechargeable lithium battery, said rechargeable lithium battery comprising: negative electrode; Positive electrode; A diaphragm is located between the negative electrode and the positive electrode; as well as Electrolytes; Wherein, at least one of the negative electrode, the positive electrode and the diaphragm includes the adhesive according to claim 1.

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