Electrode for rechargeable lithium battery, method for manufacturing the same, and rechargeable lithium battery comprising the same

Abstract

Provided are an electrode for a rechargeable lithium battery, a method for manufacturing an electrode for a rechargeable lithium battery, and a rechargeable lithium battery, the electrode comprising: a current collector; and an electrode active material layer disposed on the current collector and comprising an electrode active material, cellulose nanofiber, and polytetrafluoroethylene.

Description

Technical Field

[0001] An electrode for a rechargeable lithium battery, a method for manufacturing the electrode, and a rechargeable lithium battery including the electrode 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 rechargeable batteries with high energy density and high capacity is growing. Therefore, improving the performance of rechargeable lithium batteries can be advantageous.

[0003] A rechargeable lithium battery includes electrodes (positive and negative electrodes) containing active materials capable of inserting and deintercalating lithium ions and an electrolyte, and generates electrical energy through redox reactions as lithium ions are inserted and deintercalated between the positive and negative electrodes.

[0004] Typically, electrodes are manufactured using a wet process, which includes a drying process to remove the solvent. During the drying process, the composition within the electrode can become inhomogeneous as the solvent evaporates, making the fabrication of thick-film electrodes challenging.

[0005] There exists a process for manufacturing electrodes using a dry process that does not use solvents to address these drawbacks. Electrodes manufactured using this dry process are economical because they can be easily thickened, and the costs associated with solvent recycling and solvent drying processes can be reduced. Summary of the Invention

[0006] Some example embodiments include an electrode for a rechargeable lithium battery that has improved electrolyte impregnation properties and adhesion strength, and has a thick film.

[0007] Some example embodiments include rechargeable lithium batteries including the electrode that have increased capacity, improved charge / discharge efficiency, high rate capability, and cycle life characteristics.

[0008] An electrode for a rechargeable lithium battery according to some example embodiments includes: a current collector; and an electrode active material layer disposed on the current collector and comprising the electrode active material, cellulose nanofibers, and polytetrafluoroethylene.

[0009] According to some example embodiments, a method for manufacturing an electrode for a rechargeable lithium battery includes: freeze-drying a cellulose nanofiber suspension to prepare cellulose nanofibers; dry-blending the prepared cellulose nanofibers and polytetrafluoroethylene to prepare a mixed binder; dry-blending the mixed binder, an electrode active material, and a conductive material to prepare an electrode mixture; forming the electrode mixture into a sheet to prepare a film; and laminating the film onto a current collector to manufacture the electrode.

[0010] A rechargeable lithium battery according to some example embodiments includes electrodes and an electrolyte.

[0011] The electrode for rechargeable lithium batteries according to some example embodiments improves the impregnation properties and adhesion strength of the electrolyte and promotes thickening, and the rechargeable lithium battery including the electrode exhibits increased capacity, improved charge / discharge efficiency, high rate performance and cycle life characteristics. Attached Figure Description

[0012] Figures 1 to 4 This is a schematic view of a rechargeable lithium battery according to some example embodiments.

[0013] Figure 5 This is a flowchart illustrating a method for manufacturing electrodes for a rechargeable lithium battery according to some example embodiments. Detailed Implementation

[0014] Example embodiments are described in detail below. However, these embodiments are presented by way of example, and this disclosure is not limited thereto, and is defined by the scope of the appended claims.

[0015] 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 between them.

[0016] Unless otherwise stated in this specification, a singular expression may also include a plural expression. Furthermore, unless otherwise stated, “A or B” may mean “including A, including B, or including both A and B”.

[0017] As used here, “the combination of them” refers to mixtures, laminates, complexes, copolymers, alloys, blends, reaction products, etc. of the components.

[0018] As used here, unless otherwise defined, particle size can be the average particle size. Furthermore, particle size can refer to the average particle size (D...). 50 The average particle size (D) refers to the diameter of particles that constitute 50% of the total volume in the particle size distribution. 50 The particle size can be measured using methods known to those skilled in the art, for example, by a particle size analyzer, or by transmission electron microscopy (TEM) or scanning electron microscopy (SEM) images. Optionally, data analysis can be performed using a dynamic light scattering measurement device, and the number of particles in each particle size range can be counted. Thus, the average particle size (D) can be readily obtained by calculation. 50 ) value. Optionally, average particle size (D 50The particle size distribution (Dsize) can be measured using laser diffraction. 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 measuring device (e.g., Microtrac MT 3000), and irradiated with ultrasound at approximately 28 kHz and an output of 60 W to calculate the average particle size (Dsize) based on 50% of the particle size distribution in the measuring device. 50 ).

[0019] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical value includes a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within that range, such as increments of 0.1%.

[0020] Electrodes for rechargeable lithium batteries An electrode for a rechargeable lithium battery according to some example embodiments includes a current collector and an electrode active material layer on the current collector. The electrode active material layer includes an electrode active material, cellulose nanofibers (CNF), and polytetrafluoroethylene (PTFE). The electrode active material layer may be disposed on one or both surfaces of the current collector.

[0021] The dry binders used in existing dry electrode manufacturing processes are mainly hydrophobic, resulting in poor electrolyte impregnation properties, which makes electrode thickening challenging and may degrade the electrochemical performance of the battery.

[0022] The advantage of the electrode according to some example embodiments is that the impregnation properties of the electrolyte are improved by including a mixed binder in which cellulose nanofibers having amphiphilic properties are mixed with polytetrafluoroethylene as a dry binder, and the electrode can be easily formed into a thick film.

[0023] Cellulose nanofibers (CNFs) can act as binders. Because of their amphiphilic nature, cellulose nanofibers can be used in conjunction with hydrophobic polytetrafluoroethylene (PTFE) to improve the electrolyte impregnation properties of dry electrodes. Furthermore, while cellulose nanofibers may exhibit insufficient dispersibility when used alone, when combined with hydrophobic PTFE, they can be dispersed substantially uniformly within the electrode mixture during dry electrode fabrication. Moreover, the durability of dry electrodes incorporating cellulose nanofibers can be improved due to their desired or enhanced mechanical strength and flexibility.

[0024] For example, the average diameter of cellulose nanofibers can be in the range of about 0.1 nm to about 200 nm, for example, about 1 nm to about 100 nm, about 3 nm to about 50 nm, or about 5 nm to about 20 nm.

[0025] The diameter of a cellulose nanofiber can refer to the widest diameter among the fiber diameters measured based on the cross-section of each nanofiber, and can be measured in a direction perpendicular to the longitudinal direction of the nanofiber.

[0026] The average diameter of cellulose nanofibers can be calculated by randomly measuring the cross-sectional diameter of approximately 20 fibers in a scanning electron microscope image of the surface of the electrode active material layer and calculating their arithmetic mean.

[0027] When this numerical range is met, dry electrodes with desired or improved durability can be manufactured because the dispersion within the electrode mixture is improved.

[0028] For example, the average length of cellulose nanofibers can be in the range of about 1 μm to about 20 μm, for example, about 5 μm to about 20 μm, about 5 μm to about 15 μm, about 5 μm to about 10 μm, or about 10 μm to about 15 μm.

[0029] The average length of cellulose nanofibers can be calculated by randomly measuring the lengths of approximately 20 fibers in a scanning electron microscope image of the surface of the electrode active material layer and calculating their arithmetic mean.

[0030] When the above-mentioned ranges for average diameter and average length are met, the bonding force between the electrode active material, conductive material and current collector is substantially desired or improved during the manufacture of the dry electrode, thereby enabling the manufacture of a dry electrode with desired or improved durability.

[0031] For example, based on a 100 wt% electrode active material layer, cellulose nanofibers may be included in an amount ranging from about 0.01 wt% to about 5 wt%, for example, from about 0.01 wt% to about 2.5 wt%, from about 0.01 wt% to about 1 wt%, or from about 0.5 wt% to about 1 wt%. When cellulose nanofibers are included in an amount less than about 0.01 wt% based on a 100 wt% electrode active material layer, it may be challenging to adequately improve the electrolyte impregnation properties of the dry electrode, and when cellulose nanofibers are included in an amount greater than about 5 wt%, the electrode resistance may increase, leading to a decrease in battery performance.

[0032] For example, cellulose nanofibers can be prepared by freeze-drying.

[0033] Cellulose nanofibers prepared by freeze-drying can be dried into powder form while maintaining their fibrous form, allowing the cellulose nanofibers to be essentially uniformly fibrillated, thereby improving the mechanical properties of electrodes containing cellulose nanofibers.

[0034] The freeze-drying process is described in detail in the manufacturing method below.

[0035] Polytetrafluoroethylene (PTFE) may be or include dry binders that are not impregnated, dissolved or dispersed in process solvents during the dry electrode manufacturing process, and may be or include binders that do not include process solvents or do not come into contact with process solvents during the dry electrode manufacturing process.

[0036] For example, in a process of manufacturing an electrode film by sheeting an electrode mixture, part or all of the dry binder in particulate form can be fibrillated to form an electrode active material layer including the dry binder.

[0037] Polytetrafluoroethylene (PTFE) has the desired or improved heat resistance, flexibility, and mechanical strength, and therefore, when used as a dry binder, it is possible to manufacture dry electrodes with the desired or improved mechanical strength.

[0038] For example, based on a 100 wt% electrode active material layer, polytetrafluoroethylene may be included in an amount ranging from about 0.01 wt% to about 5 wt%, for example, from about 0.5 wt% to about 5 wt%, from about 0.5 wt% to about 2.5 wt%, from about 1 wt% to about 2.5 wt%, or from about 1 wt% to about 2 wt%.

[0039] When polytetrafluoroethylene (PTFE) is included in an amount of less than about 0.01 wt% of a 100 wt% electrode active material layer, the adhesion and durability of the dry electrode may be low, and when PTFE is included in an amount of more than about 5 wt%, the electrode resistance may increase, leading to a decrease in battery performance.

[0040] For example, the weight ratio of cellulose nanofibers to polytetrafluoroethylene (PTFE) can be in the range of about 2:8 to about 8:2, for example, a weight ratio of about 2.5:7.5 to about 8:2, or a weight ratio of about 2.5:7.5 to about 5:5. When the above-mentioned cellulose nanofibers and PTFE are included in the electrode active material layer in the above-mentioned weight ratio, the mechanical strength is desired or improved, and the impregnation properties of the electrolyte are improved, making it easy to use cellulose nanofibers in thick film electrodes.

[0041] The electrode active material layer may also include other dry binders.

[0042] Other dry binders may include at least one of the following: vinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer, polyethylene oxide, polyvinyl alcohol, polyacrylonitrile, starch, hydroxypropyl cellulose, cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluorinated elastomers, copolymers thereof, and combinations thereof.

[0043] For example, the electrode active material layer may also include a conductive material.

[0044] The conductive material may be a dry conductive material or may include a dry conductive material, and the dry conductive material may be or include, for example, a conductive material that is not impregnated, dissolved or dispersed in the process solvent during the manufacturing process of the dry electrode mixture and the dry electrode film, and may be or include a conductive material that does not include the process solvent or is not in contact with the process solvent.

[0045] For example, conductive materials may include carbon-based conductive materials, and carbon-based conductive materials may include at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, and combinations thereof.

[0046] For example, carbon-based conductive materials may include at least one of fibrous carbon materials having an aspect ratio greater than or equal to about 10, particulate carbon materials having an aspect ratio less than about 10, and combinations thereof.

[0047] Conductive materials may also include at least one of the following: metallic materials in the form of metal powder or metal fibers containing at least one of copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; and combinations thereof.

[0048] Based on a 100wt% electrode active material layer, conductive material may be included in an amount ranging from about 0.01wt% to about 5wt%, for example, from about 0.05wt% to about 5wt% or from about 0.1wt% to about 5wt%. When the above numerical ranges are met, a thick-film electrode with desired or improved lithium-ion conductivity can be formed.

[0049] For example, the electrode active material layer may also include an inorganic solid electrolyte.

[0050] For example, inorganic solid electrolytes may include at least one of sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, and combinations thereof. As an example, inorganic solid electrolytes may include sulfide solid electrolytes.

[0051] Because the electrode is manufactured in a dry manner, the electrode active material layer contains little or no solvent. Therefore, even if the electrode active material layer also includes inorganic solid electrolyte, it will not cause side reactions with the solvent.

[0052] Sulfide solid electrolytes may include, for example, Li₂S-P₂S₅, Li₂S-P₂S₅-LiX (where X is or includes a halogen element, such as I or Cl), Li₂S-P₂S₅-Li₂O, Li₂S-P₂S₅-Li₂O-LiI, Li₂S-SiS₂, Li₂S-SiS₂-LiI, Li₂S-SiS₂-LiBr, Li₂S-SiS₂-LiCl, Li₂S-SiS₂-B₂S₃-LiI, Li₂S-SiS₂-P₂S₅-LiI, Li₂S-B₂S₃, and Li₂S-P₂S₅-Z. m S n (Where m and n are integers, and Z is or includes Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (where p and q are integers, and M is or includes P, Si, Ge, B, Al, Ga, or In) and at least one of their combinations.

[0053] For example, sulfide-based solid electrolyte particles can include argentite-germanium sulfides. Argentite-germanium sulfides can be, for example, composed of the chemical formula Li... a M b P c S d A e (Where a, b, c, d, and e are all in the range of approximately 0 and less than or equal to approximately 12, M is or includes a metal other than Li or a combination of multiple metals other than Li, and A is F, Cl, Br, or I) and, as an example, sulfide of the silver-germanium sulfide type can be represented by the chemical formula Li 7-x PS 6-x A x (Where x is greater than or equal to about 0.2 and less than or equal to about 1.8, and A is F, Cl, Br, or I). Australite-type sulfides can be, for example, Li3PS4, Li7P3S 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 Li 6.2 PS 5.2 Br 0.8 wait.

[0054] Oxide-based inorganic solid electrolytes include, for example, Li 1+x Ti 2-x Al(PO4)3 (LTAP) (0≤x≤4), Li 1+x+ y Alx Ti 2-x Si y P 3-y O 12 (0 < x < 2, 0 ≤ y < 3), BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT) (0 ≤ x < 1, 0 ≤ y < 1), Pb(Mg3Nb 2 / 3 )O3 - PbTiO3 (PMN - PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), Li2O, LiAlO2, Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2 - type ceramics, garnet - type ceramics Li 3+ x La3M2O 12 (M = Te, Nb or Zr; x is an integer in the range from 1 to 10) and at least one of their combinations.

[0055] Halide - type solid electrolytes may include Li element, M element (M is or includes a metal other than Li), and X element (X is or includes a halogen). Examples of X may include F, Cl, Br, and I. In particular, halide - type solid electrolytes in which X is or includes at least one of Br and Cl may be suitable. In addition, M may be or include, for example, metal elements such as at least one of Sc, Y, B, Al, Ga, and In.

[0056] The composition of halide - type solid electrolytes is not particularly limited, but may be composed of Li 6-3a M a Br b Cl cis represented by (where M is or includes a metal other than Li, 0 < a < 2, 0 ≤ b ≤ 6, 0 ≤ c ≤ 6 and b + c = 6). Here, "a" can be equal to or greater than about 0.75, or equal to or greater than about 1, and can be less than or equal to about 1.5. "b" can be equal to or greater than about 1, and can be equal to or greater than about 2. Additionally, "c" can be equal to or greater than about 3, or equal to or greater than about 4. Examples of the halide-based solid electrolyte can include at least one of Li3YBr6, Li3YCl6, and Li3YBr2Cl4.

[0057] For example, the electrode can be manufactured in a dry manufacturing process. Thus, the electrode active material layer can also include a solvent, which includes an organic solvent or an aqueous solvent, but based on 100 wt% of the electrode active material layer, the solvent can be included in an amount less than about 0.01 wt%, and as an example, the solvent may not be included.

[0058] Since the electrode active material layer hardly includes a solvent (the solvent is less than about 0.01 wt%), the electrode can be referred to as being manufactured by a dry process. The dry manufacturing process of these electrodes is described below.

[0059] For example, when the electrode active material layer is a positive electrode active material layer, it can also include an organic solvent, and based on 100 wt% of the positive electrode active material layer, the organic solvent can be included in an amount less than about 0.01 wt%. Any type of organic solvent used in the manufacture of the positive electrode active material layer slurry can be used without limitation, and can include, for example, N-methyl-2-pyrrolidone (NMP).

[0060] For example, when the electrode active material layer is a negative electrode active material layer, it can also include an aqueous solvent, and based on 100 wt% of the negative electrode active material layer, the aqueous solvent can be included in an amount less than about 0.01 wt%. For the type of aqueous solvent, any aqueous solvent used in the manufacture of the negative electrode active material layer slurry can be used without limitation, and can include, for example, water.

[0061] The electrode active material layer can be formed into a thick film with a sufficient thickness by including both the above-mentioned cellulose nanofibers and polytetrafluoroethylene, so that the impregnation property of the electrolyte can be improved. For example, the thickness of the electrode active material layer can be greater than or equal to about 150 μm, for example, greater than or equal to about 200 μm or greater than or equal to about 250 μm. For example, the thickness of the electrode active material layer can be in the range of about 150 μm to about 500 μm, about 150 μm to about 400 μm, about 200 μm to about 400 μm, or about 200 μm to about 300 μm.

[0062] For example, based on a 100 wt% electrode active material layer, the electrode active material may be included in an amount ranging from about 90 wt% to about 99.5 wt%, for example, from about 90 wt% to about 99 wt%.

[0063] For example, the electrode active material may include a positive electrode active material, in which case the electrode may be or include a positive electrode.

[0064] The positive electrode for a rechargeable lithium battery may include a current collector and a layer of positive electrode active material formed on the current collector. The positive electrode active material layer includes positive electrode active material and may optionally include additives capable of constituting a sacrificial positive electrode.

[0065] For example, the positive electrode active material may be or includes compounds capable of intercalating and deintercalating lithium (lithiation compounds). For example, at least one composite oxide of lithium with a metal such as or including at least one of cobalt, manganese, nickel and combinations thereof may be used.

[0066] The composite oxide can be or includes lithium transition metal composite oxides, and examples 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.

[0067] As an example, a compound represented by any of the following chemical formulas can be used. Li a A 1-b X b O 2-c 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 Nib 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).

[0068] In the chemical formula, 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.

[0069] For example, the positive electrode active material can be or includes a high-nickel positive electrode active material, based on 100 mol% of metal other than lithium in a lithium transition metal composite oxide. The nickel content of the high-nickel positive electrode active material is greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol%, and less than or equal to about 99 mol%. High-nickel positive electrode active materials can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0070] For example, the positive electrode active material may include lithium-nickel composite oxides and may include, for example, compounds represented by chemical formula 1 below.

[0071] Chemical Formula 1: Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 .

[0072] In Chemical Formula 1, 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 are different elements and each independently is or includes at least one of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zn and Zr, and X is or includes at least one of F, P and S.

[0073] In Chemical Formula 1, 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; or 0.9 ≤ x1 < 1, 0 < y1 ≤ 0.1 and 0 ≤ z1 ≤ 0.1.

[0074] As an example, the positive electrode active material may include a lithium nickel cobalt composite oxide represented by the following Chemical Formula 2.

[0075] Chemical Formula 2: Li a2 Ni x2 Co y2 M 3 z2 O 2-b2 X b2 .

[0076] In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.8, 0.3 ≤ x2 < 1, 0 < y2 ≤ 0.7, 0 ≤ z2 ≤ 0.7, 0.9 ≤ x2 + y2 + z2 ≤ 1.1 and 0 ≤ b2 ≤ 0.1, M 3 is or includes one or more of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is or includes one or more of F, P and S.

[0077] In Chemical Formula 2, for example, 0.7 ≤ x2 < 1, 0 < y2 ≤ 0.3, 0 ≤ z2 ≤ 0.3; 0.8 ≤ x2 < 1, 0 < y2 ≤ 0.2, 0 ≤ z2 ≤ 0.2; or 0.9 ≤ x2 < 1, 0 < y2 ≤ 0.1, 0 ≤ z2 ≤ 0.1.

[0078] As another example, the positive electrode active material may include at least one of a lithium nickel cobalt manganese composite oxide, a lithium nickel cobalt aluminum composite oxide, and a lithium nickel cobalt aluminum manganese composite oxide represented by the following Chemical Formula 3.

[0079] Chemical Formula 3: Li a3 Ni x3 Co y3 M 4 z3 M 5 w3 O 2-b3 X b3 .

[0080] In Chemical Formula 3, 0.9 ≤ a3 ≤ 1.8, 0.3 ≤ x3 ≤ 0.98, 0.01 ≤ y3 ≤ 0.69, 0.01 ≤ z3 ≤ 0.69, 0 ≤ w3 ≤ 0.69, 0.9 ≤ x3 + y3 + z3 + w3 ≤ 1.1 and 0 ≤ b3 ≤ 0.1, M 4 is or includes at least one of Al, Mn, and their combinations, M 5 is or includes one or more of B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is or includes one or more of F, P, and S.

[0081] When the electrode active material layer is a positive electrode active material layer, the current collector may include Al, but is not limited thereto.

[0082] As another example, the electrode active material may include a negative electrode active material, in which case the electrode may be or include a negative electrode.

[0083] The negative electrode for a rechargeable lithium battery includes a current collector and a negative electrode active material layer on the current collector.

[0084] For example, the negative electrode active material may include at least one of a material that reversibly intercalates / deintercalates lithium ions, lithium metal, a lithium metal alloy, a material that can dope / de-dope lithium, and a transition metal oxide.

[0085] Materials capable of reversibly inserting / extracting lithium ions may include carbon-based negative electrode active materials, for example, crystalline carbon, amorphous carbon, or a combination thereof. Crystalline carbon may be or include graphite, such as natural graphite or artificial graphite in amorphous, flaky, lamellar, spherical, or fibrous forms, and amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0086] Lithium metal alloys include alloys of lithium with metals such as or including at least one of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0087] Materials capable of doping / dedoping lithium may be or include Si-based negative electrode active materials or Sn-based negative electrode active materials. Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (0 < x ≤ 2), Si-Q alloys (where Q is or includes at least one of alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), and combinations of at least one of them. Sn-based negative electrode active materials may include at least one of Sn, SnO2, Sn-based alloys, and combinations thereof.

[0088] 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 amorphous carbon coated 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 (shell) on the surface of the secondary particles. Amorphous carbon may also be between the silicon primary particles, and for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0089] 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 on the surface of the core.

[0090] Si-based negative electrode active materials or Sn-based negative electrode active materials may be used in combination with carbon-based negative electrode active materials.

[0091] When the electrode active material layer is a negative electrode active material layer, the current collector may be or 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.

[0092] Some example embodiments include a rechargeable lithium battery including the aforementioned electrodes and electrolyte.

[0093] For example, a rechargeable lithium battery may include a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte.

[0094] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch-shaped, and coin-shaped. Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Figure 1 A cylindrical battery is shown. Figure 2 A prismatic battery is shown. Figure 3 and Figure 4 A pouch-type battery is shown. (See reference) Figures 1 to 4 The rechargeable lithium battery 100 includes: an electrode assembly 40, with a separator 30 between a positive electrode 10 and a negative electrode 20; and a housing 50 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 1 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12 connected to the positive electrode lead connector 11, a negative electrode lead connector 21, and a negative electrode terminal 22 connected to the negative electrode lead connector 21. For example... Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 includes Figure 4 The electrode terminals 70 shown in the figure or Figure 3 The positive electrode terminal 71 and negative electrode terminal 72 shown in the figure form an electrical path for guiding the current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100.

[0095] Electrolytes used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0096] Non-aqueous organic solvents constitute the medium for transporting ions that participate in the electrochemical reactions of rechargeable lithium batteries.

[0097] Non-aqueous organic solvents may be or include at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0098] 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). Esters may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, and caprolactone. Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Ketone solvents may include cyclohexanone. Alcohol solvents may include at least one of ethanol and isopropanol. Aprotic solvents may include at least one of the following: nitriles, such as R-CN (wherein R is a C2 to C20 straight-chain, branched or cyclic hydrocarbon group, and may include double bonds, aromatic rings or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane; etc.

[0099] Non-aqueous organic solvents can be used alone or in mixtures of two or more types of solvents.

[0100] 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.

[0101] Lithium salts dissolved in organic solvents supply lithium ions in rechargeable lithium batteries, enabling the operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. For example, 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) (x and y are integers in the range of 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), lithium difluoro(oxalate)borate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0102] 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, and multilayer films of the same two or more layers (e.g., hybrid multilayer films such as polyethylene / polypropylene bilayer separators, polyethylene / polypropylene / polyethylene trilayer separators, polypropylene / polypropylene / polypropylene trilayer separators, etc.)).

[0103] The membrane may include a porous substrate and a coating on one or both surfaces of the porous substrate, comprising organic materials, inorganic materials, or combinations thereof.

[0104] The porous substrate may be or include a polymer membrane, which is formed from or includes any one or more polymers, including polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., TEFLON). ® ( ) or a copolymer or mixture of two or more of them.

[0105] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0106] Inorganic materials may include, but are not limited to, inorganic particles containing 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.

[0107] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked together.

[0108] As another example, a rechargeable lithium battery may be or include an all-solid-state rechargeable battery, which includes a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive and negative electrodes.

[0109] The solid electrolyte layer may include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, etc., and the inorganic solid electrolytes are as described above.

[0110] Method for manufacturing electrodes for rechargeable lithium batteries Some example embodiments include a method for manufacturing an electrode for a rechargeable lithium battery, the method comprising: freeze-drying a cellulose nanofiber suspension to prepare cellulose nanofibers; dry-blending the prepared cellulose nanofibers with polytetrafluoroethylene to prepare a mixed binder; dry-blending the mixed binder, an electrode active material, and a conductive material to prepare an electrode mixture; forming the electrode mixture into a sheet to prepare a film; and laminating the film onto a current collector to manufacture the electrode.

[0111] Each of the above operations is described in detail below.

[0112] First, a cellulose nanofiber suspension is prepared. The cellulose nanofiber suspension can be or includes a liquid prepared by dispersing cellulose nanofibers in an aqueous solvent.

[0113] As an example, a method for manufacturing electrodes may also include wet milling of the cellulose nanofiber suspension prior to a freeze-drying step. The wet milling step may involve mechanically pulverizing the cellulose nanofibers into nanounits and can be performed by a grinding process or an ultrasonic treatment process. The grinding process can be performed using commonly used grinding techniques, such as an in-line grinding apparatus or a disc grinding apparatus.

[0114] The wet milling process can control the average diameter or average length of cellulose nanofibers within the desired range.

[0115] Following a wet milling step, the cellulose nanofiber suspension is freeze-dried to prepare cellulose nanofibers. The freeze-drying process may include dehydrating the cellulose nanofiber suspension to dry the cellulose nanofibers in the suspension into powder or granular form while retaining their fibrous form.

[0116] Using conventional drying processes instead of freeze-drying to prepare cellulose nanofibers may result in the nanofibers not being uniformly fiberized and having the desired particle size and length, which in turn degrades the mechanical properties of electrodes containing cellulose nanofibers.

[0117] For example, freeze drying can be performed under a vacuum ranging from about 0.01 mbar to about 1 mbar, for example, from about 0.01 mbar to about 0.5 mbar, from about 0.01 mbar to about 0.25 mbar, from about 0.05 mbar to about 0.25 mbar, or from about 0.1 mbar to about 0.25 mbar.

[0118] For example, freeze drying can be performed at temperatures ranging from about -80°C to about -40°C, for example, from about -60°C to about -40°C or from about -50°C to about -40°C.

[0119] For example, freeze drying can be performed for a duration ranging from about 24 hours to about 72 hours, for example, from about 24 hours to about 60 hours, or from about 36 hours to about 60 hours.

[0120] When freeze-drying is performed under the above conditions, cellulose nanofibers in powder form with the desired diameter or length can be obtained while maintaining the desired fibrous form. Furthermore, the cellulose nanofibers prepared by freeze-drying under these conditions can be brittle, thus allowing them to be easily pulverized in a subsequent powder-forming step.

[0121] For example, a method for manufacturing an electrode may also include a powder-forming step of pulverizing the freeze-dried cellulose nanofibers after a freeze-drying step. The powder-forming step may include pulverizing the entangled cellulose nanofibers into powder after freeze-drying.

[0122] Through a powder forming step, cellulose nanofibers can be prepared to have substantially uniform length and particle size. The prepared cellulose nanofibers can then be substantially uniformly dry-mixed with electrode active materials, polytetrafluoroethylene (PTFE), and conductive materials in a subsequent step of preparing a mixed binder to improve processability. Furthermore, the mechanical properties of electrodes incorporating the prepared cellulose nanofibers can be improved.

[0123] Subsequently, a method for manufacturing electrodes according to some example embodiments includes preparing a mixed binder by dry mixing the prepared cellulose nanofibers and polytetrafluoroethylene.

[0124] Polytetrafluoroethylene (PTFE) is a hydrophobic material, resulting in poor electrolyte impregnation properties, and thickening the dry electrode can be challenging when PTFE is used alone as a binder. Therefore, some example embodiments involve blending cellulose nanofibers (an amphiphilic material) with PTFE to improve electrolyte impregnation properties and enhance electrode thickness.

[0125] For example, the prepared cellulose nanofibers and polytetrafluoroethylene can be mixed in a weight ratio ranging from about 2:8 to about 8:2, for example, from about 2.5:7.5 to about 8:2 or from about 2.5:7.5 to about 5:5.

[0126] The dry-mixed binder at this weight ratio has the advantages of forming a dry binder and improving the impregnation properties of the electrolyte, and is therefore used in thick film electrodes.

[0127] Next, a method for manufacturing an electrode according to some example embodiments includes dry mixing a binder, an electrode active material, and a conductive material to prepare an electrode mixture, and forming the electrode mixture into a sheet to manufacture a film.

[0128] Dry mixing refers to mixing without the use of process solvents. Process solvents are, for example, solvents used in electrode slurries. Process solvents can be, or include, for example, water, NMP, etc., but are not limited to these, and can include any process solvent used to prepare electrode slurries.

[0129] Dry mixing can be performed, for example, by using a mixer.

[0130] Dry mixing using a mixer can be performed, for example, at temperatures ranging from about 25°C to about 85°C, for example, from about 25°C to about 70°C, from about 25°C to about 50°C, or from about 25°C to about 30°C.

[0131] Dry mixing using a stirrer can be performed, for example, at rotational speeds ranging from about 500 rpm to about 2000 rpm, for example, from about 500 rpm to about 1500 rpm, from about 750 rpm to about 1250 rpm, or from about 900 rpm to about 1100 rpm.

[0132] Dry mixing using a mixer can be performed for a duration ranging from about 5 minutes to about 30 minutes, for example, from about 5 minutes to about 20 minutes, from about 5 minutes to about 15 minutes, from about 5 minutes to about 10 minutes, or from about 10 minutes to about 15 minutes.

[0133] Dry mixing can be performed, for example, once, twice, or more.

[0134] When dry mixing is performed under the above conditions, a fully fibrillated dry binder is produced, thereby improving the impregnation properties of the electrolyte and the adhesion strength of the electrodes including the dry binder.

[0135] Electrode mixtures, including fibrillated dry-mixed binders, can be obtained by drying. For example, shear force can be applied to the electrode mixture during the step of processing the electrode mixture into a film using a rolling device, thereby fibrillating the binder.

[0136] For example, a mixer can include a kneader.

[0137] For example, a stirrer may include: a chamber; one or more rotating shafts disposed inside the chamber; and blades rotatably coupled to the rotating shafts and arranged in the longitudinal direction of the rotating shafts. The blades may be, for example, one or more blades, such as at least one of ribbon blades, sigma blades, jet (Z) blades, dispersing blades, and helical blades. The blades can facilitate the preparation of dough-like mixtures by efficiently mixing electrode active materials, dry-mix binders, and conductive materials without solvents.

[0138] For example, based on a 100 wt% electrode mixture, a mixed binder may be included in an amount ranging from about 0.01 wt% to about 10 wt%. When the mixed binder is used in the above amounts, desired or improved electrolyte impregnation properties can be achieved, thereby facilitating the fabrication of thick-film electrodes.

[0139] For example, based on a 100 wt% electrode mixture, the electrode active material may be included in an amount ranging from about 90 wt% to about 99.5 wt%.

[0140] For example, based on 100 wt% of the electrode mixture, conductive material may be included in an amount ranging from about 0.01 wt% to about 5 wt%. When the amounts of electrode active material and conductive material within the above range are met, a thick-film electrode having a desired or improved lithium-ion conductivity can be manufactured.

[0141] In addition, the electrode mixture may also include the aforementioned inorganic solid electrolyte. The inorganic solid electrolyte may be the same as described above.

[0142] The subsequent step of forming the electrode mixture into a sheet to prepare a membrane includes molding the electrode mixture into a membrane.

[0143] For example, this step can be performed by feeding a dry-manufactured electrode mixture into an extrusion apparatus and extruding the electrode mixture into sheet or film form. Extrusion can be performed using a rolling process, for example, at a pressure in the range of about 4 MPa to about 100 MPa. Within this pressure range, the materials in the electrode mixture can be readily assembled and formed substantially uniformly into sheets without damaging the materials. In the step of processing the electrode mixture into a film, the electrode mixture can be subjected to shear forces to fibrillate the binder, thereby forming a strong fiber network and enhancing the mechanical stability of the electrode.

[0144] Subsequently, a method for manufacturing an electrode according to some example embodiments includes pressing the manufactured film layer onto a current collector to manufacture the electrode.

[0145] For example, this step may be or include laminating the manufactured film onto a current collector such as aluminum or copper foil, and compressing the laminate using a process such as roll forming. Additionally, optionally, a hot pressing process may be performed to enhance the adhesive strength between the dry adhesive and the current collector.

[0146] Figure 5 This is a flowchart illustrating a method for manufacturing electrodes for a rechargeable lithium battery according to some example embodiments. Figure 5In method 500, steps 510, 520, 530, 540, and 550 are included. Step 510 includes freeze-drying a cellulose nanofiber suspension to prepare cellulose nanofibers. For example, freeze-drying is performed for about 24 hours to about 72 hours under a vacuum ranging from about 0.01 mbar to about 1 mbar and at a temperature ranging from about -80°C to about -40°C. Step 520 includes dry-blending the prepared cellulose nanofibers and polytetrafluoroethylene to prepare a mixed binder. For example, in the preparation of the mixed binder, the prepared cellulose nanofibers and polytetrafluoroethylene are mixed in a weight ratio ranging from about 2:8 to about 8:2. In another example, the mixed binder includes fibrillating the dry-blended binder. Step 530 includes dry-blending the mixed binder, an electrode active material, and a conductive material to prepare an electrode mixture. Step 540 includes forming the electrode mixture into a sheet to manufacture a film. For example, in the fabrication of the membrane, a mixed binder is included in an amount ranging from about 0.01 wt% to about 10 wt% of the electrode mixture, an electrode active material is included in an amount ranging from about 90 wt% to about 99.5 wt%, and a conductive material is included in an amount ranging from about 0.01 wt% to about 5 wt%. Operation 550 includes laminating the membrane onto the current collector to fabricate the electrode.

[0147] In the example, method 500 also includes a powder forming process for preparing cellulose nanofibers by pulverizing the freeze-dried cellulose nanofiber suspension after freeze-drying the cellulose nanofiber suspension.

[0148] 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.

[0149] Example: Example 1 First, a cellulose nanofiber suspension was prepared and freeze-dried at a vacuum of 0.1 mbar and a temperature of -45°C for 48 hours to prepare cellulose nanofibers (average diameter: 5 nm, average length: 10 μm).

[0150] Cellulose nanofibers and polytetrafluoroethylene were mixed in a weight ratio of 2.5:7.5 to prepare a hybrid binder.

[0151] Subsequently, 2 wt% of the mixed binder, 97 wt% of artificial graphite and 1 wt% of carbon black (SUPER-P) as a conductive material were added to the blade mixer, and then dry-mixed at 1000 rpm for 10 minutes at 25°C to produce the electrode mixture.

[0152] The manufactured electrode mixture is fed into an extruder and extruded to prepare a self-supporting membrane in sheet form.

[0153] A self-standing film is laminated onto a copper foil to create a dry negative electrode.

[0154] Here, the negative electrode active material layer disposed on the copper foil current collector has a thickness of 200 μm. In addition, the 100 wt% negative electrode active material layer includes 0.5 wt% cellulose nanofibers (CNF), 1.5 wt% polytetrafluoroethylene (PTFE), 97 wt% artificial graphite, and 1 wt% conductive material.

[0155] Example 2 and Comparative Examples 1-1 to 1-4 and Comparative Examples 2-1 to 2-4 Each dry negative electrode was manufactured in the same manner as in Example 1, except that the mixed binder was changed to have the composition and wt% as shown in Table 1.

[0156] Example 3 2 wt% of the mixed binder according to Example 1 and 96.5 wt% of LiNi as the positive electrode active material. 0.91 Co 0.05 Al 0.04 O2, 1 wt% carbon black (SUPER-P) as a conductive material, and 0.5 wt% Li2S-P2S5 as a sulfide solid electrolyte are added to a blade mixer and then dry-mixed at 1000 rpm for 10 minutes at 25°C to produce an electrode mixture.

[0157] The manufactured electrode mixture is added to an extruder and then extruded to prepare a self-supporting membrane in sheet form.

[0158] A self-standing film is laminated onto an aluminum foil to create a dry positive electrode.

[0159] Here, the positive electrode active material layer disposed on the aluminum foil current collector has a thickness of 200 μm. Furthermore, the 100 wt% positive electrode active material layer includes 0.5 wt% cellulose nanofibers, 1.5 wt% polytetrafluoroethylene, and 96.5 wt% LiNi. 0.91 Co 0.05 Al 0.04 O2, 1 wt% conductive material and 0.5 wt% Li2S-P2S5.

[0160] Example 4 and Comparative Examples 3-1 to 3-4 and 4-1 to 4-4 The dry positive electrode was manufactured in the same manner as in Example 3, except that the mixed binder was changed to have the composition and wt% as shown in Table 2.

[0161] Evaluation example: Evaluation Example 1: Bond Strength Evaluation The adhesion strength between the negative electrode active material layer and the copper foil current collector of the dry negative electrodes in Examples 1 and 2, and Comparative Examples 1-1 to 2-4, was evaluated. Specifically, after attaching 3M Scotch tape to the surface of each negative electrode active material layer and rolling the 3M Scotch tape once with a metal roller to adhere it thereto, the tape was peeled off from the negative electrode active material layer to check the degree of separation between the negative electrode active material layer and the negative electrode current collector.

[0162] If the separation between the negative electrode active material layer and the negative electrode current collector is less than or equal to 5% based on the area of ​​the negative electrode active material layer, then “○ (Excellent)” is given; if the separation is greater than 5% and less than or equal to 20%, then “△ (Medium)” is given; and if the separation is greater than 20%, then “X (Insufficient)” is given, as provided in Table 1 below.

[0163] In addition, the adhesion strength between the positive electrode active material layer and the aluminum foil current collector of the dry positive electrodes of Examples 3 and 4, and Comparative Examples 3-1 to 4-4, was evaluated. Specifically, after attaching 3M fiber tape to the surface of each positive electrode active material layer and rolling the 3M fiber tape once with a metal roller to adhere the 3M fiber tape thereto, the tape was peeled off from the positive electrode active material layer to check the degree of separation between the positive electrode active material layer and the positive electrode current collector.

[0164] If the separation between the positive electrode active material layer and the positive electrode current collector is less than or equal to 5% based on the area of ​​the positive electrode active material layer, then “○ (Excellent)” is given; if the separation is greater than 5% and less than or equal to 20%, then “△ (Medium)” is given; and if the separation is greater than 20%, then “X (Insufficient)” is given, as provided in Table 1 below.

[0165] Evaluation Example 2: Evaluation of the Impregnation Properties of the Electrolyte The electrolyte impregnation properties of the negative and positive electrodes of the example and comparative examples were measured by cutting each electrode to prepare an electrode sample with a width and length of 20 mm, and then dropping 20 μL of electrolyte onto the surface of the sample to measure the time until the electrolyte was completely penetrated, thereby checking the degree of electrolyte impregnation / immersion.

[0166] If the immersion / soaking time is less than or equal to 25 seconds, a "○ (Excellent)" is given; if it is greater than 25 seconds but less than or equal to 50 seconds, a "△ (Medium)" is given; and if it is greater than 50 seconds, an "X (Inadequate)" is given, as shown in Tables 1 and 2 below.

[0167] In Tables 1 and 2, PVDF is polyvinylidene fluoride adhesive, CMC is carboxymethyl cellulose adhesive, and SBR is styrene-butadiene rubber adhesive.

[0168] Table 1:

[0169] Referring to Table 1, it was confirmed that the negative electrodes (Example 1 and Example 2) manufactured by dry processes including CNF and PTFE exhibited the desired or improved adhesive strength and electrolyte impregnation properties.

[0170] Comparative Example 1-1, which includes CNF but not PTFE, showed worse adhesive strength than Examples 1 and 2.

[0171] In Comparative Examples 1-2 to 1-4, which use PVDF, CMC, and SBR combined with CNF (which are difficult to use as dry binders, as they must be dissolved in solvents and are difficult to use in dry processes), it is difficult to manufacture the dry electrode itself, resulting in insufficient electrode adhesion strength. Comparative Examples 1-2 to 1-4, which include CNF, exhibit average electrolyte impregnation properties that are still worse than those of Examples 1 and 2.

[0172] In addition, the electrode of Comparative Example 2-1, which includes PTFE (dry binder) alone, exhibits the desired or improved adhesive strength, but is not included in combination with CNF and exhibits insufficient electrolyte impregnation properties.

[0173] Furthermore, the negative electrodes of Comparative Examples 2-2 to 2-4, which individually include PVDF, CMC, and SBR, which are difficult to use as dry binders, were difficult to manufacture as dry electrodes and were found to exhibit insufficient adhesive strength and electrolyte impregnation properties.

[0174] Table 2:

[0175] Referring to Table 2, the positive electrodes (Examples 3 and 4) manufactured by dry methods, including both CNF and PTFE, all exhibited the desired or improved adhesive strength and electrolyte impregnation properties.

[0176] Comparative Example 3-1, which includes CNF but not PTFE, showed worse adhesive strength than Examples 3 and 4.

[0177] In Comparative Examples 3-2 to 3-4, which use PVDF, CMC, and SBR combined with CNF that are difficult to use as dry binders (they must be dissolved in a solvent and are difficult to use in dry processes), the fabrication of dry electrodes is inherently challenging, resulting in insufficient electrode bond strength. Comparative Examples 3-2 to 3-4, which include CNF, exhibit worse average electrolyte impregnation properties than Examples 3 and 4.

[0178] In addition, Comparative Example 4-1, which includes PTFE (dry binder) alone, exhibits the desired or improved electrode bond strength, but without combination with CNF, it exhibits insufficient electrolyte impregnation properties.

[0179] Furthermore, the negative electrodes of Comparative Examples 4-2 to 4-4, which were manufactured by individually including PVDF, CMC, and SBR, which are difficult to use as dry binders, were difficult to manufacture as dry electrodes, thus demonstrating insufficient adhesive strength and electrolyte impregnation properties.

[0180] While this disclosure has been described in conjunction with exemplary embodiments now considered to be practical, 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.

[0181] 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: Casing 60: Sealing component 70: Electrode connector 71: Positive electrode connector 72: Negative electrode connector.

Claims

1. An electrode for a rechargeable lithium battery, the electrode comprising: current collector; as well as An electrode active material layer is disposed on the current collector and includes an electrode active material, cellulose nanofibers, and polytetrafluoroethylene.

2. The electrode according to claim 1, wherein: The average diameter of the cellulose nanofibers is in the range of 0.1 nm to 200 nm, and The average length of the cellulose nanofibers is in the range of 1 μm to 20 μm.

3. The electrode according to claim 1, wherein, The cellulose nanofibers are included in an amount ranging from 0.01 wt% to 5 wt% of the electrode active material layer, which is based on 100 wt% of the electrode active material layer.

4. The electrode according to claim 1, wherein, The cellulose nanofibers were prepared by freeze-drying.

5. The electrode according to claim 1, wherein, The polytetrafluoroethylene is included in an amount ranging from 0.01 wt% to 5 wt% of the 100 wt% electrode active material layer.

6. The electrode according to claim 1, wherein, The weight ratio of the cellulose nanofibers to the polytetrafluoroethylene is in the range of 2:8 to 8:

2.

7. The electrode according to claim 1, wherein: The electrode active material layer also includes a conductive material, and The conductive material includes carbon-based conductive materials.

8. The electrode according to claim 1, wherein: The electrode active material layer also includes an inorganic solid electrolyte, and The inorganic solid electrolytes include sulfide solid electrolytes.

9. The electrode according to claim 1, wherein, The electrode is manufactured using a dry process.

10. The electrode according to claim 1, wherein: The electrode active material layer further includes a solvent, which includes one of an organic solvent and an aqueous solvent. The solvent is included in an amount of less than 0.01 wt% of the 100 wt% electrode active material layer.

11. The electrode according to claim 1, wherein, The thickness of the electrode active material layer is in the range of 150 μm to 500 μm.

12. The electrode according to claim 1, wherein: The electrode active material includes a positive electrode active material, and The positive electrode active material includes a lithium-nickel composite oxide represented by chemical formula 1: Chemical Formula 1: Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 ; In chemical formula 1, 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 They are different elements, and each independently includes at least one of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Zn, and Zr. X includes at least one of F, P, and S.

13. The electrode according to claim 1, wherein: The electrode active material includes a negative electrode active material; and The negative electrode active material includes at least one of carbon-based negative electrode active materials, Si-based negative electrode active materials, Sn-based negative electrode active materials, and combinations thereof.

14. A method for manufacturing an electrode for a rechargeable lithium battery, the method comprising the steps of: Cellulose nanofibers were prepared by freeze-drying a cellulose nanofiber suspension. The prepared cellulose nanofibers and polytetrafluoroethylene are dry-mixed to prepare a mixed binder; The mixed binder, electrode active material and conductive material are dry-mixed to prepare an electrode mixture; The electrode mixture is formed into a sheet to manufacture a film; and The film is pressed onto the current collector to manufacture an electrode.

15. The method according to claim 14, wherein, The freeze-drying is performed for 24 to 72 hours under a vacuum ranging from 0.01 mbar to 1 mbar and at a temperature ranging from -80°C to -40°C.

16. The method of claim 14, wherein, The method further includes: Following the step of freeze-drying the cellulose nanofiber suspension to prepare cellulose nanofibers, a powder-forming process is performed by pulverizing the freeze-dried cellulose nanofibers.

17. The method of claim 14, wherein, In the step of preparing the mixed binder: The prepared cellulose nanofibers and polytetrafluoroethylene are mixed in a weight ratio ranging from 2:8 to 8:

2.

18. The method according to claim 14, wherein, The hybrid adhesive includes a fibrillated dry hybrid adhesive.

19. The method of claim 14, wherein, In the step of manufacturing the membrane: Based on 100 wt% of the electrode mixture, The mixed adhesive is included in an amount ranging from 0.01 wt% to 10 wt%. The electrode active material is included in an amount ranging from 90 wt% to 99.5 wt%. and The conductive material is included in amounts ranging from 0.01 wt% to 5 wt%.

20. A rechargeable lithium battery, comprising: The electrode according to any one of claims 1 to 13 or the electrode manufactured by the method according to any one of claims 14 to 19; as well as Electrolytes.

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