Separator-integrated electrode, method for manufacturing same, electrode assembly including same, and rechargeable lithium battery

Abstract

Disclosed are a separator-integrated electrode, a method of manufacturing the same, and an electrode assembly and a rechargeable lithium battery including the same. The separator-integrated electrode includes an electrode and a polymer fiber layer on the electrode. The polymer fiber layer comprises polyacrylic acid. The polymer fiber layer has a tensile strength in the MD direction of greater than or equal to about 120 kgf / cm2. The polymeric fiber layer has an air permeability of less than or equal to about 500 sec / 100 cc.

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0131059, filed on September 26, 2024, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0002] An integrated separator electrode, a method for manufacturing the integrated separator electrode, an electrode assembly including the integrated separator electrode, and a rechargeable lithium battery are disclosed. Background Technology

[0003] The separator in a rechargeable lithium battery is a type of component typically included in rechargeable lithium batteries. The separator isolates the positive and negative electrodes from each other while maintaining ion conductivity, thereby enabling the battery to charge and discharge.

[0004] Since battery stability is advantageous, the role of the separator in reducing or preventing short circuits between electrodes is crucial. Commonly used polyolefin fabrics exhibit poor physical durability and severe thermal shrinkage at high temperatures. Therefore, when problems arise in the battery and internal temperatures rise, the separator is likely to deform, and in severe cases, may explode. Thus, improving heat resistance and shrinkage resistance, which are related to high-temperature stability, is a key factor in separator development. Regarding improving the heat resistance of separators, nonwoven separators manufactured by processing heat-resistant polymers into fibers, ceramic separators manufactured by connecting inorganic particles using a small amount of binder, and coated separators (Korean Patent No. 10-0775310) have been developed.

[0005] However, in the case of nonwoven diaphragms manufactured by processing them into known fiber shapes, there are problems such as weak bonding between fibers, low tensile strength, low air permeability, and almost no adhesive strength between electrodes.

[0006] Furthermore, the diaphragm is typically manufactured separately from the electrodes, and a separate process is required to bond the diaphragm to the electrodes. Simplifying the process to reduce costs and increasing bonding between fibers could be advantageous. Summary of the Invention

[0007] Some example embodiments include a membrane-integrated electrode having a polymer fiber layer that can replace a conventional separator and is integral with the electrode active material layer, thereby reducing or eliminating the need for separate processes for combining the separator and electrode active material layers, thus simplifying the process, reducing costs, improving bonding between fibers, and exhibiting low thermal shrinkage, desired or improved tensile strength, desired air permeability, and desired or improved adhesion strength to the electrode. Other example embodiments include methods for manufacturing separators, as well as electrode assemblies including separators and rechargeable lithium batteries.

[0008] Some example embodiments include a diaphragm-integrated electrode comprising an electrode and a polymer fiber layer on the electrode, wherein the polymer fiber layer comprises polyacrylic acid. The tensile strength of the polymer fiber layer in the mechanical direction (“MD direction”) is greater than or equal to about 120 kgf / cm². 2 Furthermore, the air permeability of the polymer fiber layer is less than or equal to approximately 500 sec / 100cc.

[0009] In some example embodiments, a method for manufacturing a membrane-integrated electrode includes the steps of: manufacturing a polymer fiber layer comprising polyacrylic acid on the electrode; dissolving a portion of the polyacrylic acid by spraying microdroplets onto the polymer fiber layer; and physically bonding and chemically imidizing the dissolved polyacrylic acid by hot pressing.

[0010] In some example embodiments, an electrode assembly including an integrated diaphragm electrode is provided.

[0011] In some example embodiments, a rechargeable lithium battery including an electrode assembly is provided.

[0012] According to some example embodiments, the diaphragm-integrated electrode includes a polymer fiber layer that can replace the existing diaphragm and is integral with the electrode, eliminating the need for a separate process for bonding the diaphragm and the electrode, thereby simplifying the process, reducing costs, and improving the bonding between the fibers. Simultaneously, the electrode can have a low rate of thermal shrinkage, desired or improved tensile strength, desired air permeability, and desired or improved adhesion strength to the electrode. Attached Figure Description

[0013] Figures 1 to 4 This is a schematic cross-sectional view of a rechargeable lithium battery according to some example embodiments.

[0014] Figure 5 This is a flowchart illustrating a method for manufacturing a diaphragm-integrated electrode according to an example embodiment. Detailed Implementation

[0015] The following describes exemplary embodiments in detail, enabling those skilled in the art to readily implement them. However, this disclosure may be embodied in many different forms and is not to be construed as limited to the exemplary embodiments set forth herein.

[0016] The terminology used herein is for describing exemplary embodiments only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, singular expressions include plural expressions.

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

[0018] It should be understood here that terms such as “including,” “comprising,” or “having” are intended to indicate the presence of the features, quantities, steps, elements, or combinations thereof embodied, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, elements, or combinations thereof.

[0019] In the accompanying drawings, for clarity, the thickness of layers, films, panels, regions, etc., may be exaggerated, and the same reference numerals denote the same elements throughout the specification. 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" said other element, or an intervening element may be present between them. Conversely, when an element is referred to as being "directly on" another element, an intervening element may not be present.

[0020] In addition, the term "layer" here includes not only shapes that form across the entire surface when viewed from a plan view, but also shapes that form on a portion of the surface.

[0021] The average particle size can be measured by 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. Alternatively, the average particle size value can be obtained by performing data analysis using dynamic light scattering, counting the number of particles in each particle size range, and calculating the average particle size value. Unless otherwise defined, the average particle size can be represented as the diameter (D) of particles that constitute 50% of the total volume in the particle size distribution. 50 As used herein, unless otherwise defined, the average particle size represents the diameter of 50% of the total volume of particles in a particle size distribution obtained by randomly measuring the size (diameter or major axis length) of approximately 20 particles in a scanning electron microscope (SEM) image. 50 ).

[0022] Here, "or" will not be interpreted as having an exclusive meaning; for example, "A or B" is interpreted as including A, B, A+B, etc.

[0023] The term "metal" is interpreted as encompassing common metals, transition metals, and metalloids (semi-metals).

[0024] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical values ​​include 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%.

[0025] Diaphragm integrated electrode Some example embodiments include a membrane-integrated electrode, which includes an electrode and a polymer fiber layer on the electrode. Here, a membrane-integrated electrode means an electrode in which the membrane and the electrode are physically bonded or chemically bonded simultaneously to form, for example, an integral electrode.

[0026] polymer fiber layer The polymer fiber layer comprises polyacrylic acid (PAA). Polyacrylic acid is a polymer composed of or including acrylic acid units and includes carboxyl groups (-COOH). As a result, according to the manufacturing method described below, an imidization process occurs along with physical bonding, enabling chemical bonding, increasing the molecular chain strength, and also increasing the strength of the fibers within the polymer fiber layer.

[0027] Here, the polymer fiber layer can be disposed between the electrodes like a conventional diaphragm to reduce or prevent short circuits. According to some example embodiments, the diaphragm-integrated electrode can simplify the process by reducing costs and increasing productivity, eliminating the need for separate processes (such as lamination) for attaching the electrodes and diaphragm together.

[0028] Nonwoven separators, manufactured by processing known fibers, present a challenge: the adhesion between fibers is typically weak, resulting in low tensile strength, insufficient air permeability, and virtually no adhesion strength to the electrodes. This can cause delamination during battery assembly and short circuits during battery operation.

[0029] However, the polymer fiber layer in the diaphragm-integrated electrode according to an example embodiment may have desired or improved tensile strength, desired air permeability, and desired or improved adhesion strength to the electrode.

[0030] The polymer fiber layer of the diaphragm-integrated electrode has a tensile strength in the MD direction greater than or equal to approximately 120 kgf / cm. 2 The tensile strength of the polymer fiber layer can be greater than or equal to approximately 130 kgf / cm². 2 ≥150 kgf / cm 2 Greater than or equal to approximately 170 kgf / cm2 Greater than or equal to approximately 180 kgf / cm 2 Greater than or equal to approximately 190 kgf / cm 2 Or greater than or equal to approximately 200 kgf / cm² 2 Furthermore, the higher the tensile strength of the polymer fiber layer, the better; therefore, there is no upper limit to the tensile strength. The tensile strength in the MD direction of the polymer fiber layer can be measured using a universal testing machine (UTM). For example, the tensile strength in the MD direction can be obtained by separating the polymer fiber layer from the diaphragm-integrated electrode, applying a tensile force at a constant speed using a UTM, and measuring the force required per unit area until the polymer fiber layer breaks.

[0031] The permeability of the polymer fiber layer in the above-mentioned integrated separator electrode is less than or equal to approximately 500 sec / 100cc. The permeability of the polymer fiber layer can be less than or equal to approximately 450 sec / 100cc, less than or equal to approximately 400 sec / 100cc, less than or equal to approximately 350 sec / 100cc, less than or equal to approximately 300 sec / 100cc, less than or equal to approximately 250 sec / 100cc, less than or equal to approximately 200 sec / 100cc, less than or equal to approximately 150 sec / 100cc, or less than or equal to approximately 130 sec / 100cc, and greater than or equal to approximately 50 sec / 100cc, greater than or equal to 60 sec / 100cc, greater than or equal to 70 sec / 100cc, greater than or equal to 80 sec / 100cc, or greater than or equal to 90 sec / 100cc. When the permeability of the polymer fiber layer meets the above ranges, the battery can operate because the electrolyte and ions can move smoothly while reducing or preventing short circuits. The air permeability of a polymer fiber layer is the time it takes for 100cc of air to pass through a predetermined area when a predetermined pressure is applied. Air permeability can be measured using an air permeability measuring device, such as the EG01-55-1MR device from Asahi Seiko.

[0032] In addition to polyacrylic acid (PAA), the polymer fiber layer may also include a first polymer. Besides PAA, the polymer fiber layer can further improve adhesion, heat resistance, and spinning properties by further including the first polymer.

[0033] The first polymer may include at least one of polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and mixtures thereof.

[0034] The first polymer may be or include a polyvinylidene fluoride (PVDF) polymer. PVDF polymers may include homopolymers or copolymers, such as polyvinylidene fluoride (PVdF) or polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP). In some example embodiments, the first polymer may be or include polyvinylidene fluoride.

[0035] The weight ratio of polyacrylic acid to the first polymer in the polymer fiber layer can be in the range of about 1:9 to about 9:1, about 5:5 to about 9:1, or about 6:4 to about 8:2. When the polyacrylic acid and the first polymer in the polymer fiber layer meet the above ranges, the dimensional stability is further improved, making it possible to manufacture batteries with high-efficiency charge / discharge characteristics.

[0036] The polymer fiber layer can take the form of a nonwoven fabric in which multiple polymer fibers are integrated.

[0037] The diameter of the fibers within the polymer fiber layer can range from about 10 nm to about 1000 nm, about 50 nm to about 500 nm, about 50 nm to about 200 nm, or about 50 nm to about 150 nm. The diameter of the fibers within the polymer fiber layer can be measured using transmission electron microscopy (TEM) or scanning electron microscopy (SEM) images, and the fiber diameter can be, for example, an average diameter. The average diameter of the fibers can be the average of the diameters of the individual fibers measured in TEM or SEM images. When the fiber diameters in the polymer fiber layer meet the above ranges, a highly porous structure can be formed, which can improve the mobility of lithium ions.

[0038] The diaphragm-integrated electrode can meet the above-mentioned tensile strength and air permeability, while improving the heat shrinkage rate and having the desired or improved adhesion strength to the electrode.

[0039] For example, the thermal shrinkage rate of the polymer fiber layer in an integrated separator electrode can be less than or equal to about 1%, such as less than or equal to about 0.95%, less than or equal to about 0.9%, less than or equal to about 0.85%, or less than or equal to about 0.81%. Since a lower limit indicates better thermal shrinkage, there is no specific restriction on the lower limit; it can be greater than or equal to 0%, greater than or equal to about 0.01%, greater than or equal to about 0.02%, greater than or equal to about 0.03%, greater than or equal to about 0.04%, or greater than or equal to about 0.05%. When the thermal shrinkage rate of the polymer fiber layer meets the above range, the thermal stability of the battery can be significantly improved. Typically, the separator is constructed to physically separate the positive and negative electrodes; however, when the separator shrinks due to heat, the positive and negative electrodes may come into contact with each other, leading to a short circuit in the battery. The thermal shrinkage rate is an important factor that can improve the thermal stability of the battery. A lower thermal shrinkage rate indicates less shrinkage due to heat, and therefore, a lower thermal shrinkage rate indicates improved battery thermal stability. The thermal shrinkage rate of the polymer fiber layer can be calculated by measuring the length in the TD or MD direction before shrinkage and the length in the TD or MD direction after shrinkage after the diaphragm-integrated electrode has been placed in an oven at a temperature of about 150°C for about 1 hour, and then substituting the results into Equation 1 to calculate the average value.

[0040] Equation 1: Heat shrinkage rate (%) = (A) i -A f ) / Ai×100 In equation 1 above, A i It is the length in the TD or MD direction before contraction, A f It is the length in the TD or MD direction after contraction.

[0041] The thickness of the polymer fiber layer can range from about 5 μm to about 40 μm. For example, the thickness can be from about 7 μm to about 20 μm, or from about 8 μm to about 16 μm. The thickness of the polymer fiber layer can be measured by taking a cross-section of the diaphragm-integrated electrode using a scanning electron microscope (SEM) and measuring only the thickness of the polymer fiber layer excluding the electrode, or by using a micrometer.

[0042] The polymer fiber layer may also include inorganic materials within the polymer fiber layer. The inorganic materials may be dispersed in the pores within the polymer fiber layer.

[0043] Inorganic materials may include, but are not limited to, inorganic particles of 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.

[0044] electrode The electrode described above may include an electrode current collector and an electrode active material layer on the electrode current collector. Here, the membrane-integrated electrode may have a structure in which the electrode current collector-electrode active material layer-polymer fiber layer are laminated (e.g., sequentially laminated).

[0045] An electrode can be either a positive electrode or a negative electrode.

[0046] The following sections will explain the cases where the electrode is a positive electrode and the cases where the electrode is a negative electrode.

[0047] When the electrode is a positive electrode, the electrode current collector can be a positive electrode current collector, and the electrode active material layer can be a positive electrode active material layer.

[0048] There are no particular limitations on the positive electrode current collector, as long as it is conductive and does not cause adverse chemical changes in the rechargeable lithium battery. In some example embodiments, the positive electrode current collector may be aluminum foil or include aluminum foil.

[0049] The positive electrode active material layer may include a positive electrode active material and may optionally include a first binder, a first conductive material, or a combination thereof.

[0050] The positive electrode active material can be or includes compounds capable of intercalating and deintercalating lithium (lithium-intercalating 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).

[0051] 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.

[0052] 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 Xb The 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 The 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 The 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).

[0053] 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.

[0054] The positive electrode active material can be, for example, 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, or a combination thereof.

[0055] Chemical Formula 11: Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 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 is independently at least one of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, Zr and combinations thereof, and X is or includes one or more of F, P and S.

[0056] 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.

[0057] Chemical formula 12: Li a2 Co x2 M 3 y2 O 2-b2 X b2 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 3One or more of, or including, Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, Zr, and combinations thereof, and X is at least one of, or including, F, P, S, and combinations thereof.

[0058] Chemical Formula 13 Li a3 Fe x3 M 4 y3 PO 4-b3 X b3 In Chemical Formula 13, 0.9 ≤ a3 ≤ 1.8, 0.6 ≤ x3 ≤ 1, 0 ≤ y3 ≤ 0.4, and 0 ≤ b3 ≤ 0.1, M 4 is or includes one or more of, or including, Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, Zr, and combinations thereof, and X is at least one of, or including, F, P, S, and combinations thereof.

[0059] Chemical Formula 14: Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4 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 Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, Zr, or combinations thereof, and X is one or more of, or including, F, P, and S.

[0060] As an example, the electrode active material can be or include a high-nickel type positive electrode active material. Based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide, the high-nickel type positive electrode active material has a nickel content of greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, greater than or equal to about 94 mol%, or greater than or equal to 99 mol%. The high-nickel type positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0061] The first adhesive is configured to adhere the positive electrode active material to each other and to the positive electrode active material to the electrode current collector. Examples of the first adhesive may include at least one of, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acryloyl styrene-butadiene rubber, epoxy resin, (meth)acryloyl resin, polyester resin, nylon, etc.

[0062] The first conductive material is included to provide electrode conductivity and can include any material that does not cause chemical changes and is electronically conductive in the battery to be formed. Examples of such a first conductive material may include: a conductive material comprising a carbon-based material, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; a metallic material, including at least one of copper, nickel, aluminum, silver, etc., and in the form of a metal powder or metal fiber; a conductive polymer, such as a polyphenylene derivative; or a mixture thereof.

[0063] When the electrode is a negative electrode, the electrode current collector can be a negative electrode current collector, and the electrode active material layer can be a negative electrode active material layer.

[0064] There are no particular limitations on the negative electrode current collector, as long as it is conductive and does not cause adverse chemical changes in the rechargeable lithium battery. The negative electrode current collector can be or includes 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.

[0065] The negative electrode active material layer may include a negative electrode active material, and may optionally further include a second binder, a second conductive material, or a combination thereof.

[0066] The negative electrode active material includes at least one of the following: materials capable of reversibly inserting / deintercalating lithium ions, lithium metal, alloys of lithium metal, materials capable of doping and dedoping lithium, and transition metal oxides.

[0067] Materials capable of reversibly inserting / deintercalating lithium ions can be or include carbon-based negative electrode active materials. In some example embodiments, the negative electrode active material may include a carbon-based negative electrode active material.

[0068] The carbonaceous negative electrode active material may include crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be irregular, or may be 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. Soft carbon refers to a carbon material that can be graphitized and is a material that can be easily graphitized by heat treatment at a high temperature such as about 2800 °C. Hard carbon is a carbon material that cannot be graphitized or is only slightly graphitized by heat treatment.

[0069] In addition to the carbonaceous negative electrode active material, the negative electrode active material layer may further include other types of negative electrode active materials, and may also include at least one of, for example, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, etc.

[0070] 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, Sn, and combinations thereof.

[0071] The material capable of doping / undoping lithium may be or include a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2) and at least one of Si-Q alloys (where Q is or includes at least one of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, but does not include Si); and the Sn-based negative electrode active material may include at least one of Sn, SnO2, Sn-R alloys (where R is or includes at least one of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, but does not include Sn). At least one of the above materials may be mixed with SiO2. The elements Q and R may be or include at least one of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0072] For example, the negative electrode active material may include silicon-carbon composite particles. The average particle size (D 50 ) may be, for example, in the range of about 0.5 μm to about 20 μm. The average particle size (D 50)(Measured by a particle size analyzer and refers to the diameter of the particles with a cumulative volume of 50% by volume in the particle size distribution. Based on 100 wt% of the silicon-carbon composite particles, the amount of silicon included can be in the range of about 10 wt% to about 60 wt%, and the amount of carbon included can be in the range of about 40 wt% to about 90 wt%. For example, the silicon-carbon composite particles can include a core containing silicon particles and a carbon coating on the surface of the core. In the core, the average particle size (D 50 ) can be in the range of about 10 nm to about 1 μm, or about 10 nm to about 200 nm. The silicon particles can exist as elemental silicon, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon can be represented by SiO x (0 < x ≤ 2). Additionally, the thickness of the carbon coating can be in the range of about 5 nm to about 100 nm.

[0073] As an example, the silicon-carbon composite particles can include a core containing silicon particles and crystalline carbon, and a carbon coating provided on the surface of the core and including amorphous carbon. For example, in the silicon-carbon composite particles, amorphous carbon may not exist in the core but only in the carbon coating. The crystalline carbon can be artificial graphite, natural graphite, or a combination thereof, and the amorphous carbon can be at least one of coal tar pitch, mesophase pitch, petroleum pitch, coal oil, heavy petroleum, and polymer resins (phenolic resin, furan resin, polyimide, etc.). Among them, based on 100 wt% of the silicon-carbon composite particles, the content of crystalline carbon can be in the range of about 10 wt% to about 70 wt%, and the content of amorphous carbon can be in the range of about 20 wt% to about 40 wt%.

[0074] In the silicon-carbon composite particles, the core can include voids in the center. The radius of the voids can be in the range of about 30% to about 50% of the radius of the silicon-carbon composite particles by length.

[0075] The aforementioned silicon-carbon composite particles effectively reduce or suppress problems caused by charging and discharging (such as volume expansion, structural collapse, or particle fragmentation), reduce or prevent the disconnection of the conductive path, achieve high capacity and high efficiency, and are conducive to use under high voltage or high-speed charging conditions.

[0076] Si-based negative electrode active materials or Sn-based negative electrode active materials can be included by mixing with carbon-based negative electrode active materials. When using a mixture of Si-based negative electrode active materials or Sn-based negative electrode active materials and carbon-based negative electrode active materials, the mixing ratio can be in the range of about 1:99 to about 9:1 by weight.

[0077] The second 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 second binder may be or include at least one of non-aqueous binders, aqueous binders, dry binders, and combinations thereof.

[0078] 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.

[0079] Waterborne adhesives may include at least one of the following: styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acryloyl rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, 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.

[0080] When an aqueous binder is included as a second binder, it may also include a cellulose compound capable of imparting viscosity. As a cellulose 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.

[0081] Dry adhesives may be or include polymeric materials capable of being fibrous, and may be or include at least one of, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0082] A second conductive material is included to provide electrode conductivity, and may include any electrically conductive material as the conductive material unless such electrically conductive material causes an adverse chemical change in the battery. Examples of conductive materials may include: carbon-based materials, such as at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, 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.

[0083] Based on 100 wt% of the electrode active material layer (positive electrode active material layer or negative electrode active material layer), the amount of the included electrode active material (positive electrode active material or negative electrode active material) can be in the range of about 90 wt% to about 99.8 wt%, or about 94 wt% to about 99 wt%. Based on 100 wt% of the electrode active material layer, the amount of the included binder (first binder or second binder) can be in the range of about 0.1 wt% to about 5 wt%, or about 0.5 wt% to about 3 wt%. Based on 100 wt% of the electrode active material layer, the amount of the included conductive material (first conductive material or second conductive material) can be in the range of about 0.1 wt% to about 5 wt%, or about 0.5 wt% to about 3 wt%.

[0084] Method for manufacturing diaphragm-integrated electrodes In some example embodiments, a method for manufacturing a membrane-integrated electrode includes: fabricating a polymer fiber layer comprising polyacrylic acid on the electrode; dissolving a portion of the polyacrylic acid by spraying microdroplets onto the polymer fiber layer; and chemically imidizing the dissolved polyacrylic acid by hot pressing.

[0085] The diaphragm-integrated electrode manufactured by this method can meet the tensile strength, air permeability, and adhesive strength between the electrode and the polymer fiber layer as described above by simultaneously or concurrently chemically imidizing the fibers within the polymer fiber layer through physical bonding of the fibers.

[0086] First, a polymer fiber layer comprising polyacrylic acid is fabricated on the electrode. The polymer fiber layer comprises polyacrylic acid containing carboxyl groups for physical bonding and chemical bonding via imidization, as described below.

[0087] As described above, for example, a polymer fiber layer can be fabricated on the electrode active material layer of the electrode.

[0088] The manufacture of polymer fiber layers is unrestricted, as long as a method for manufacturing polymer fiber layers is applicable. For example, polymer fiber layers can be manufactured by electrospinning. For instance, the steps of manufacturing a polymer fiber layer include preparing a spinning solution comprising polyacrylic acid, injecting the spinning solution into an electrospinning nozzle, and performing electrospinning while an electric field is formed between the electrospinning nozzle and an electrode (e.g., an electrode active material layer), thereby forming a polymer fiber layer on the electrode (e.g., the electrode active material layer).

[0089] The spinning solution may include polyacrylic acid. The spinning solution may also include a first polymer together with the polyacrylic acid, and the type of the first polymer and the weight ratio of the polyacrylic acid to the first polymer are as described above.

[0090] The spinning solution may also include a first solvent for dissolving polyacrylic acid and the first polymer. There are no particular limitations on the type of the first solvent, as long as it can dissolve both the polyacrylic acid and the first polymer. For example, the first solvent may include at least one of dimethylacetamide, dimethyl acetate, dimethylformamide, dimethylformaldehyde, dimethyl sulfoxide, N-methylpyrrolidone, ethanol, methanol, chloroform, acetone, water, and combinations thereof.

[0091] Electrospinning can be performed at voltages ranging from about 1 kV to about 120 kV, about 40 kV to about 90 kV, or about 70 kV to about 80 kV. The resulting solution can then be spun from an electrospinning nozzle through which a high voltage is applied to form a nanofiber coating on the electrode.

[0092] The polymer fiber layer can be manufactured by further drying after electrospinning to remove the first solvent. Depending on the drying process, most of the first solvent can be removed immediately or shortly after electrospinning, but it is also possible to completely remove the first solvent using a separate drying device.

[0093] Next, microdroplets are sprayed onto the polymer fiber layer to dissolve some of the polyacrylic acid. When the polymer fiber layer also includes a first polymer in addition to polyacrylic acid, a portion of both the polyacrylic acid and the first polymer can be dissolved by spraying microdroplets. The microdroplets can be formed by spraying a solution containing an imidizing agent into a second solvent capable of dissolving the polymer (e.g., polyacrylic acid and the first polymer) of the manufactured polymer fiber layer, or by spraying the second solvent. That is, the microdroplets may include a second solvent, an imidizing agent, or a combination thereof.

[0094] The second solvent may include a polar organic solvent, such as or including at least one of dimethylacetamide, N-methylpyrrolidone, dimethyl phthalate, dimethyl sulfoxide, pyridine, m-cresol, and combinations thereof.

[0095] The imidizing agent may include an anhydride, or a mixture of an anhydride and an imidizing catalyst. By further including the imidizing agent in the second solvent, the tensile strength is improved due to the chemical bonds induced by the imidizing agent forming together with the physical bonds of the polyacrylic acid dissolved by hot pressing as described below. At the same time, a membrane-integrated electrode exhibiting the desired permeability and low thermal shrinkage can be provided that can form a diaphragm.

[0096] As described above, the acid anhydride may include organic carboxylic acid anhydrides, and examples may include at least one of acetic anhydride, propionic anhydride, butyric anhydride, benzoic anhydride, and combinations thereof.

[0097] The imidization catalyst may include at least one of isoquinoline, pyridine, trialkylamine, methylpyridine, dimethylpyridine, N-methylmorpholine, and combinations thereof.

[0098] Based on 100 parts by weight of microdroplets, the amount of imidizing agent included can range from about 5 to about 20 parts by weight. When the imidizing agent is a mixture of acid anhydride and imidizing catalyst, the weight ratio of acid anhydride to imidizing catalyst can range from about 1:0.5 to about 1:5. When the imidizing agent in the microdroplets is included within the above range, chemical bonds can be formed in addition to the physical bonding through hot pressing as described below to further improve tensile strength and thermal shrinkage.

[0099] The spraying is not limited, as long as it is a method capable of forming droplets of a second solvent or a solution containing a second solvent. As an example, spraying can be performed via electro-spraying. For instance, during electro-spraying, a layer of polymer fibers can be disposed between a nozzle and a collector, such that the second solvent to be electro-sprayed or a solution containing a second solvent can be sprayed onto the polymer fiber layer. Electro-spraying can be performed by spraying the second solvent or a solution containing a second solvent through a nozzle at an injection rate in the range of about 0.1 mL / min to about 20 mL / min, about 0.3 mL / h to about 10 mL / h, or about 0.5 mL / h to about 5 mL / h, and applying a voltage in the range of about 10 kV to about 100 kV, about 30 kV to about 80 kV, or about 50 kV to about 60 kV.

[0100] In the portion where a second solvent or a solution including the second solvent is sprayed onto the polymer fiber layer, a portion of the polyacrylic acid in the polymer fiber layer can dissolve due to the second solvent.

[0101] Next, the polyacrylic acid dissolved in the polymer fiber layer is chemically imidized by hot pressing to combine the physical bonds.

[0102] Hot pressing can be performed using heated rollers. For example, hot pressing can be performed at a temperature ranging from about 50°C to about 110°C and a pressure ranging from about 0.05 MPa to about 2 MPa, at a speed ranging from about 1 cm / min to about 1 m / min.

[0103] Hot pressing can physically bond the molten polymer within the polymer fiber layer, and the hot pressing of the laminated polymer fiber layer and the electrode can physically bond the interface between the polymer fiber layer and the electrode.

[0104] Polyacrylic acid dissolved by hot pressing can form some chemical bonds while physically bonding, and when the second solvent sprayed also includes an imidizing agent, chemical bonds can also be formed due to imidization, thereby improving tensile strength. This allows for the provision of membrane-integrated electrodes that can form a diaphragm while or simultaneously exhibiting the desired permeability and low thermal shrinkage without separate processes (such as lamination), thus simplifying the process, reducing costs and improving productivity.

[0105] Electrode components and rechargeable lithium batteries Electrode assembly In some example embodiments, an electrode assembly including an integrated membrane electrode is provided. For example, the electrode assembly may include a positive electrode and a negative electrode, and the positive or negative electrode may be or include the aforementioned integrated membrane electrode. Because the polymer fiber layer in the aforementioned integrated membrane electrode constitutes a membrane, the electrode assembly according to some example embodiments may not include a separate membrane.

[0106] The contents of the aforementioned diaphragm-integrated electrode are as described above.

[0107] When the aforementioned membrane-integrated electrode is a positive electrode, the electrode assembly may include a membrane-integrated electrode and a negative electrode. In this case, the electrode assembly may have a membrane-integrated electrode-negative electrode structure, and for example, it may have a structure in which the negative electrode (e.g., a negative electrode active material layer) is attached to a surface of a polymer fiber layer in the membrane-integrated electrode that is not attached to the positive electrode.

[0108] When the membrane-integrated electrode is the negative electrode, the electrode assembly may include a membrane-integrated electrode and a positive electrode. In this case, the electrode assembly may have a membrane-integrated electrode-positive electrode structure, for example, it may have a structure in which the positive electrode (e.g., a positive electrode active material layer) is attached to a surface of a polymer fiber layer in the membrane-integrated electrode that is not attached to the negative electrode.

[0109] For example, the electrode assembly can be a single, integrated electrode assembly.

[0110] In some example embodiments, in the method for manufacturing an integrated diaphragm electrode, after a portion of the polyacrylic acid is dissolved by jetting microdroplets and before the polyacrylic acid is physically bonded and chemically imidized by hot pressing, an electrode other than the integrated diaphragm electrode is disposed on a polymer fiber layer, and then hot pressing is performed to manufacture an integrated electrode assembly. When the integrated diaphragm electrode is a negative electrode, a positive electrode can be disposed on the surface of the polymer fiber layer where no negative electrode active material layer is disposed, and then hot pressing can be performed. Through hot pressing, the negative electrode active material layer is physically bonded and chemically imidized with the polymer fiber layer, the polymer fibers within the polymer fiber layer, and the polymer fiber layer and the positive electrode active material layer to provide an integrated electrode assembly. In the above-described method for manufacturing an integrated electrode assembly, except for the placement of the positive electrode, the integrated diaphragm electrode assembly can be manufactured in the same manner as described in the method for manufacturing an integrated diaphragm electrode.

[0111] Integrated diaphragm electrode assemblies can simplify the manufacturing process of known electrode assemblies, thereby reducing costs and increasing productivity, while also ensuring the adhesion strength between the integrated diaphragm electrode and another electrode.

[0112] For example, the adhesion strength of the polymer fiber layer within the diaphragm-integrated electrode to an electrode not included in the diaphragm-integrated electrode can be greater than or equal to about 0.1 gf / mm. There is no particular upper limit to the adhesion strength between the electrode and the polymer fiber layer, as higher adhesion strength reduces or prevents thermal shrinkage of the polymer fiber layer and allows bonding of the electrode to the polymer fiber layer without a separate lamination process, thus simplifying the process, reducing costs, and increasing productivity. The adhesion strength of the polymer fiber layer within the diaphragm-integrated electrode to an electrode not included in the diaphragm-integrated electrode can be measured using UTM. For example, in an electrode assembly including the diaphragm-integrated electrode, the electrode other than the diaphragm-integrated electrode is fixed to the upper handle, and the diaphragm-integrated electrode is fixed to the lower handle. The peel force is then measured by pulling using UTM, and the adhesion force can be measured by dividing the measured peel force by the area of ​​the electrode assembly.

[0113] Rechargeable lithium batteries A rechargeable lithium battery may include the aforementioned electrode assembly, and the electrode assembly may be impregnated with an electrolyte.

[0114] The electrolyte can be or include, for example, an electrolyte that can include a non-aqueous organic solvent and a lithium salt.

[0115] Non-aqueous organic solvents are constructed as media for transporting ions that participate in the electrochemical reactions of the battery.

[0116] Non-aqueous organic solvents can be at least one of carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, and combinations thereof.

[0117] 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, 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. Additionally, 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 groups, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0118] Non-aqueous organic solvents may be included alone or as a mixture of two or more types of solvents.

[0119] 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.

[0120] Lithium salts dissolved in organic solvents are configured to supply lithium ions in batteries to enable the operation of rechargeable lithium batteries and improve lithium ion transport between the positive and negative electrodes. Examples of lithium salts 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 F2 y+1 At least one of the following: (SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0121] Rechargeable lithium batteries can be classified according to their shape, such as cylindrical, prismatic, pouch, or coin-shaped batteries. 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 may include an electrode assembly 40 and a housing 50 therein housing the electrode assembly 40. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 1 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the 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 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 connector 70 shown is or Figure 3 The positive electrode terminal 71 and negative electrode terminal 72 shown form an electrical path for guiding current in the electrode assembly 40 to the outside of the battery 100.

[0122] Unlike traditional rechargeable lithium batteries, rechargeable lithium batteries according to some example embodiments do not include a separate separator and can be replaced by a separator-integrated electrode. For example, in Figure 1 In this battery, the negative electrode 20 can be an integrated electrode where the negative electrode and the separator are integrated, and the battery 100 can be the same as a conventional rechargeable lithium battery, except that the battery 100 includes the aforementioned integrated electrode.

[0123] Figure 5 This is a flowchart illustrating a method for manufacturing a membrane-integrated electrode according to an example embodiment. In the example, method 500 includes operations 510, 520, and 530.

[0124] Operation 510 includes fabricating a polymer fiber layer comprising polyacrylic acid on an electrode. For example, the step of fabricating the polymer fiber layer includes preparing a spinning solution comprising polyacrylic acid, injecting the spinning solution into an electrospinning nozzle, and performing electrospinning while an electric field is formed between the electrospinning nozzle and the electrode. In an example, the spinning solution further includes a first polymer and a first solvent, the first solvent comprising at least one of dimethylacetamide, dimethyl acetate, dimethylformamide, dimethylformaldehyde, dimethyl sulfoxide, N-methylpyrrolidone, ethanol, methanol, chloroform, acetone, and water.

[0125] Operation 520 involves dissolving a portion of the polyacrylic acid by spraying microdroplets onto a layer of polymer fibers. For example, the microdroplets comprise at least one of a second solvent and an imidizing agent. In another example, the second solvent comprises at least one of dimethylacetamide, N-methylpyrrolidone, dimethyl phthalate, dimethyl sulfoxide, pyridine, and m-cresol. In yet another example, the imidizing agent comprises an anhydride or a mixture of an anhydride and an imidizing catalyst, the anhydride comprising at least one of acetic anhydride, propionic anhydride, butyric anhydride, and benzoic anhydride, and the imidizing catalyst comprising at least one of isoquinoline, pyridine, trialkylamine, methylpyridine, dimethylpyridine, and N-methylmorpholine.

[0126] Operation 530 includes physically bonding and chemically imidizing the molten polyacrylic acid by hot pressing. For example, hot pressing is carried out using heated rollers and at a speed ranging from about 1 cm / min to about 1 m / min at a temperature ranging from about 50°C to about 110°C and a pressure ranging from about 0.05 MPa to about 2 MPa.

[0127] Examples and comparative examples of this disclosure are described below. However, these examples should not be construed in any way as limiting the scope of this disclosure.

[0128] Manufacturing of diaphragm-integrated negative electrode Example 1 (1) Manufacturing of polymer fiber layers A negative electrode active material prepared by mixing artificial graphite and silicon particles in a weight ratio of 93.5:6.5, and a binder prepared by mixing styrene-butadiene rubber and carboxymethyl cellulose in a ratio of 1:2, were mixed in a weight ratio of 97:3 and then dispersed in distilled water to prepare a negative electrode slurry. The negative electrode slurry was coated onto copper foil to a thickness of 10 μm, then dried and compressed to manufacture the negative electrode.

[0129] The spinning solution was prepared by mixing polyacrylic acid and polyvinylidene fluoride in a weight ratio of 7:3 and then dispersing the mixture in dimethylacetamide as the first solvent.

[0130] The spinning solution was electrospun onto the prepared negative electrode (the active material layer of the negative electrode), and then dried with hot air at 90°C to remove the first solvent. Here, the spinning solution was injected into the nozzle by positioning a nozzle assembly consisting of a tip with an orifice size of 25G and a roller at a distance of 15cm, and electrospinning was performed by applying a voltage of about 70kV at 20°C and 0.01% relative humidity to create an integral electrode with a polymer fiber layer formed on the negative electrode.

[0131] (2) Electro-injection On the polymer fiber layer, dimethylacetamide, acting as a second solvent, is electrospinned to form microdroplets, thereby dissolving some of the polyacrylic acid in the polymer fiber layer. Electrospinning is performed by positioning a nozzle assembly consisting of a tip with an orifice size of 25G and a roller at a distance of 15 cm, injecting dimethylacetamide as a second solvent into the tip at a rate of 1 mL / min, and applying a voltage of approximately 50 kV. Here, electrospinning is carried out under the same temperature and humidity conditions as in electrospinning.

[0132] (3) Hot pressing Polyacrylic acid dissolved in a second solvent is physically bonded by hot pressing after being electro-sprayed onto the polymer fiber layer. Here, the hot pressing process is performed using heated rollers. The hot pressing process is carried out at a temperature of 85°C, a pressure of 0.2 MPa, and a speed of 5 cm / min.

[0133] Example 2 The membrane was manufactured in the same manner as in Example 1, except that in the preparation of the polymer fiber layer (1) of Example 1, only polyacrylic acid was used instead of the mixture of polyacrylic acid and polyvinylidene fluoride in a ratio of 7:3. Here, some of the polyacrylic acid dissolved in it when the microdroplets were dispersed.

[0134] Example 3 The membrane is manufactured in the same manner as in Example 1, except that, during the electro-spraying of Example 1 (2), a mixed solvent of dimethylacetamide as the second solvent and a mixture of acetic anhydride (as an acid anhydride) and isoquinoline (as an imidization catalyst) is used instead of dimethylacetamide as the second solvent.

[0135] Here, based on 100 parts by weight of dimethylacetamide, the imidizing agent included in the mixed solvent is used in an amount of 14 parts by weight, and the weight ratio of the acid anhydride and the imidizing catalyst in the imidizing agent is 1:1.

[0136] Example 4 The membrane was manufactured in the same manner as in Example 3, except that in the preparation of the polymer fiber layer in Example 3 (1), only polyacrylic acid was used instead of the mixture of polyacrylic acid and polyvinylidene fluoride in a ratio of 7:3. Here, some of the polyacrylic acid dissolved when the microdroplets were dispersed.

[0137] Comparison Example 1 The diaphragm was manufactured in the same manner as in Example 1, except that (1) the preparation of the polymer fiber layer of Example 1 was performed, but (2) electro-spraying and (3) hot pressing of Example 1 were not performed.

[0138] Comparison Example 2 The diaphragm was manufactured in the same manner as in Example 2, except that (1) the preparation of the polymer fiber layer of Example 2 was performed, but (2) electro-spraying and (3) hot pressing of Example 2 were not performed.

[0139] Compare Example 3 The diaphragm is manufactured in the same manner as in Example 1, except that distilled water is used instead of dimethylacetamide as the solvent for (2) electro-spraying in Example 1. Here, polyacrylic acid and polyvinylidene fluoride do not dissolve in the droplets containing distilled water.

[0140] Compare Example 4 The diaphragm is manufactured in the same manner as in Example 1, except that the (2) electro-injection of Example 1 is not performed.

[0141] Compare Example 5 The membrane was manufactured in the same manner as in Comparative Example 1, except that during the preparation of the (1) polymer fiber layer in Comparative Example 1, polyacrylonitrile was used instead of polyacrylic acid to mix with polyvinylidene fluoride at a ratio of 7:3.

[0142] Refer to Example 1 After electrospraying in Example 3 (2) but before hot pressing in Example 3 (3), a positive electrode is placed on the surface of the polymer fiber layer sprayed with solvent and then hot pressing is performed to manufacture an integrated electrode assembly in which the diaphragm-integrated electrode (negative electrode-polymer fiber layer) and the positive electrode are stacked sequentially.

[0143] By using LiNi as the positive electrode active material in a weight ratio of 92:4:4 0.91 Co 0.05 Al 0.04 A mixture of O2, polyvinylidene fluoride (PVDF) as the first binder, and carbon as the second conductive material is dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode paste. The positive electrode paste is coated onto an aluminum foil, and then the positive electrode paste is dried and compressed to manufacture a positive electrode.

[0144] Refer to Example 2 After electrospraying in Example 4 (2) but before hot pressing in Example 4 (3), the positive electrode is placed on the surface of the polymer fiber layer sprayed with solvent and then hot pressing is performed to manufacture an integrated electrode assembly in which the diaphragm-integrated electrode (negative electrode-polymer fiber layer) and the positive electrode are stacked sequentially.

[0145] The positive electrode is the same as the positive electrode in Reference Example 1.

[0146] Evaluation Example The thermal shrinkage rate, air permeability, and tensile strength of each polymer fiber layer of the diaphragm-integrated negative electrode according to Examples 1 to 4 and Comparative Examples 1 to 5 were measured using the following methods, and the results are shown in Table 1 below. Additionally, the thermal shrinkage rate of each polymer fiber layer and the adhesion force to each positive electrode of the electrode assembly according to Reference Examples 1 to 2 were measured using the following methods, and the results are shown in Table 1 below.

[0147] In the electrode assemblies of Examples 1 to 4 and Comparative Examples 1 to 5, in which the positive electrode is not adhered to the respective polymer fiber layers of the diaphragm-integrated negative electrode, it is not possible to measure the adhesion force of the positive electrode. In the electrode assemblies of Reference Examples 1 to 2, in which the diaphragm-integrated negative electrode is bonded to the positive electrode, it is not possible to measure the air permeability and tensile strength of the polymer fiber layers.

[0148] 1. Heat shrinkage rate The diaphragm-integrated negative electrode according to Examples 1 to 4 and Comparative Examples 1 to 5, and the electrode assembly according to Reference Examples 1 to 2, were each cut into 5 pieces with a width of about 10 cm (in the longitudinal direction (machine direction, MD)) × a length of about 10 cm (in the transverse direction (TD)). The pieces were stored in a chamber at 150°C for 1 hour to measure the length of the polymer fiber layer in the TD and MD directions before and after shrinkage, respectively. The heat shrinkage rate was calculated according to Equation 1, and the average value of a total of ten measurements was also calculated.

[0149] Equation 1: Heat shrinkage rate (%) = (A) i -A f ) / A i ×100 In equation 1, A i It is the length in the TD or MD direction before contraction, and A f It is the length in the TD or MD direction after contraction.

[0150] 2. Breathability The time it took for 100cc of air to pass through each of the diaphragm-integrated negative electrodes in Examples 1 to 4 and Comparative Examples 1 to 5 was measured using an air permeability measuring device (EG01-55-1MR, Asahi Seiko Co., Ltd.). Five different times were measured to calculate the average value, which was used as the air permeability evaluation.

[0151] 3. Tensile strength Five pieces of the diaphragm-integrated negative electrode according to Examples 1 to 4 and Comparative Examples 1 to 5 were cut, each piece having a rectangular shape with a width (MD) of 10 mm and a length (TD) of 25 mm. Each of the samples was mounted on a UTM (Universal Tensile Testing Machine) and each diaphragm-integrated negative electrode was fixed so that the measurement length was 40 mm. Each diaphragm-integrated negative electrode was pulled in the MD direction to measure the average tensile strength.

[0152] 4. Adhesion strength to the positive electrode The diaphragm-integrated negative electrode according to Reference Examples 1 and 2 was cut into a width of 25 mm and a length of 80 mm. Then, the positive electrode was fixed to the upper fixture, while the diaphragm-integrated negative electrode was fixed to the lower fixture. It was then stretched and peeled using UTM. Here, the speed was 100 mm / min, and the measurement was repeated three times to calculate the average value.

[0153] Table 1:

[0154] Summarize Referring to Table 1, compared to Comparative Examples 1 to 5, Examples 1 to 4 exhibited lower thermal shrinkage, desired permeability, and desired or significantly improved tensile strength. This confirms that the improved mechanical and thermal strength of Examples 1 to 4 is achieved through physical bonding and chemical imidization between fibers in the polymer fiber layer comprising polyacrylic acid and between the electrode and the polymer fiber layer. The membrane-integrated electrodes of Comparative Examples 1 to 5, unlike the example membrane-integrated electrodes, exhibited relatively high thermal shrinkage and considerably low permeability, which could lead to short circuits and, when permeability is relatively high, may result in difficulties in cell operation and low tensile strength.

[0155] Furthermore, according to Reference Examples 1 to 2, compared with the diaphragm-integrated electrodes of Examples 1 to 4, the diaphragm-integrated electrode assembly manufactured by adhering the positive electrode before hot pressing exhibits a much lower thermal shrinkage rate. This may be due to the adhesion of the polymer fiber layer to both the positive and negative electrodes in the diaphragm-integrated electrode. In addition, the positive electrode and the diaphragm-integrated negative electrode have an adhesion strength of 0.1 gf / mm or greater, which means that it may be possible to manufacture the integrated electrode assembly itself without a separate process.

[0156] 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 exemplary embodiments. Rather, the disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0157] 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. A separator-integrated electrode comprising: an electrode; and a polymer fiber layer on the electrode, wherein the polymer fiber layer comprises polyacrylic acid, The tensile strength of the polymer fiber layer in the MD direction is greater than or equal to 120 kgf / cm 2 and the polymer fiber layer has an air permeability of less than or equal to 500 sec / 100 cc. 2.The separator-integrated electrode of claim 1, wherein: the polymer fiber layer further comprises a first polymer, and the first polymer comprises at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, and polyacrylonitrile.

3. The separator-integrated electrode according to claim 2, wherein a weight ratio of the polyacrylic acid to the first polymer in the polymer fiber layer is in a range of 1:9 to 9:

1.

4. The separator-integrated electrode according to claim 1, wherein a diameter of a fiber within the polymer fiber layer is in a range of 10 nm to 1000 nm. 5.The separator-integrated electrode of claim 1, wherein: a thermal shrinkage of the polymer fiber layer is less than or equal to 1%, the thermal shrinkage being calculated by measuring a length in a TD direction or an MD direction before shrinkage and a length in the TD direction or the MD direction after shrinkage after the separator-integrated electrode is left at a temperature of 150℃ for 1 hour, and then calculating an average value by substituting the results into Equation 1: Equation 1: Heat shrinkage (%) = (A i -A f ) / A i x 100 wherein in Equation 1, A i is the length in the TD direction or the MD direction before shrinkage, A f is the length in the TD direction or the MD direction after shrinkage.

6. The separator-integrated electrode according to claim 1, wherein the polymer fiber layer has a thickness in a range of 5 μm to 40 μm. 7.A method for manufacturing a separator-integrated electrode, the method comprising the steps of: manufacturing a polymer fiber layer comprising polyacrylic acid on an electrode; dissolving a portion of the polyacrylic acid by spraying droplets onto the polymer fiber layer; and physically bonding and chemically imidizing the dissolved polyacrylic acid by thermal pressing.

8. The method of claim 7, wherein, the step of manufacturing the polymer fiber layer comprises: preparing a spinning solution comprising polyacrylic acid; injecting the spinning solution into an electrospinning nozzle; and performing electrospinning while forming an electric field between the electrospinning nozzle and an electrode. 9.The method of claim 8, wherein: the spinning solution further comprises a first polymer and a first solvent, and the first solvent comprises at least one of dimethylacetamide, dimethylacetate, dimethylformamide, dimethylformaldehyde, dimethylsulfoxide, N-methylpyrrolidone, ethanol, methanol, chloroform, acetone, and water.

10. The method of claim 7, wherein, the droplets comprise at least one of a second solvent and an imidization agent.

11. The method of claim 10, wherein, the second solvent comprises at least one of dimethylacetamide, N-methylpyrrolidone, dimethylphthalate, dimethylsulfoxide, pyridine, and m-cresol. 12.The method of claim 10, wherein: the imidization agent comprises an acid anhydride or a mixture of an acid anhydride and an imidization catalyst, the acid anhydride comprises at least one of acetic anhydride, propionic anhydride, butyric anhydride, and benzoic anhydride, and the imidization catalyst comprises at least one of isoquinoline, pyridine, trialkyl amine, methylpyridine, dimethylpyridine, and N-methylmorpholine. 13.The method of claim 7, wherein: the thermal pressing is performed using a heating roller, and The hot-pressing is performed at a temperature in the range of 50°C to 110°C, at a pressure in the range of 0.05 MPa to 2 MPa, and at a speed in the range of 1 cm / min to 1 m / min.

14. An electrode assembly comprising the separator-integrated electrode according to any one of claims 1 to 13.

15. A rechargeable lithium battery comprising the electrode assembly according to claim 14.

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