Negative electrode for rechargeable lithium battery and rechargeable lithium battery including same

Abstract

The present disclosure includes a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same. A negative electrode for a rechargeable lithium battery includes a current collector and a negative electrode active material layer including a negative electrode active material on the current collector, in which a PCR (plane angle change rate) value is about 5.0 or less.

Description

Technical Field

[0001] The example embodiment relates to a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode. Background Technology

[0002] With the increasing use of battery-powered electronic devices (such as mobile phones, laptops, and electric vehicles), the demand for smaller, lighter, and relatively high-capacity rechargeable lithium batteries is growing. Improving the performance of rechargeable lithium batteries would be beneficial.

[0003] Rechargeable lithium batteries typically include an electrolyte, and positive and negative electrodes with active materials capable of inserting and deintercalating lithium ions, and generate electrical energy through oxidation and reduction reactions during the insertion / deintercalation of lithium ions at the positive and negative electrodes. Summary of the Invention

[0004] One or more exemplary embodiments include a negative electrode for a rechargeable lithium battery that exhibits desired or improved battery characteristics.

[0005] Another example embodiment includes a rechargeable lithium battery that includes the negative electrode.

[0006] One or more example embodiments include a negative electrode for a rechargeable lithium battery, the negative electrode comprising a current collector and a layer of negative electrode active material containing negative electrode active material on the current collector, wherein the PCR (rate of change of plane angle) value defined by Equation 1 below is about 5.0 or less.

[0007] [Equation 1] PCR = Peak intensity of 2H(002) plane / [Peak intensity of 3R(101) plane and peak intensity of Cu(111) plane] In Equation 1, the peak intensity is a value obtained by X-ray diffraction measurement using CuKα rays.

[0008] Another example embodiment includes a rechargeable lithium battery comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte.

[0009] The negative electrode used in rechargeable lithium batteries can exhibit desired or improved battery characteristics. Attached Figure Description

[0010] Figures 1 to 4 This is a schematic cross-sectional view of a rechargeable lithium battery according to some example embodiments.

[0011] Figure 5The graph shows the X-ray diffraction analysis of the current collector and negative electrode active material layer after measuring the cycle life characteristics of the batteries according to Example 1 and Comparative Example 1.

[0012] Figure 6 and Figure 7 It is shown Figure 5 Enlarged views of some parts. Detailed Implementation

[0013] Example embodiments are described in detail below. However, these embodiments are exemplary, and this disclosure is not limited thereto; rather, this disclosure is defined by the scope of the claims.

[0014] As used herein, unless otherwise specified, it will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it may be directly on said other element or there may be an intervening element.

[0015] Unless otherwise stated herein, singular expressions include plural expressions. Unless otherwise stated, "A or B" may indicate "including A, including B, or including both A and B".

[0016] As used herein, the term "combination thereof" may include mixtures, laminates, complexes, copolymers, alloys, blends, and reactants of components.

[0017] As used herein, unless otherwise defined, particle size can be the average particle size. Such a particle size represents the average particle size (D50) when the cumulative volume in the particle size distribution is about 50% by volume. The average particle size (D50) can be measured by methods well known to those skilled in the art (e.g., by a particle size analyzer, or by transmission electron microscopy images or scanning electron microscopy images). In some embodiments, data analysis is performed using a dynamic light scattering measurement device, and the number of particles for each particle size range is counted, thereby easily obtaining the average particle size (D50) value by calculation. Particle size can be measured by laser diffraction methods. Laser diffraction can be obtained by distributing the particles to be measured in a distribution solvent and introducing the distribution solvent into a commercially available laser diffraction particle measurement device (e.g., the MT3000 available from Microtrac), irradiating with ultrasound at a power of about 60 W at about 28 kHz, and calculating the average particle diameter (D50) of a 50% standard particle distribution in the measurement device.

[0018] In some embodiments, the average particle size can be measured by various techniques, and for example by a particle analyzer.

[0019] In some embodiments, thickness can be measured by SEM or TEM images of the cross-section, but is not limited thereto, and thickness can be measured by any technique, as long as that technique can measure thickness in the relevant field. Thickness can be average thickness.

[0020] As used herein, soft carbon refers to a graphitizable carbon material that is readily graphitized by heat treatment at high temperatures (e.g., about 2800°C), and hard carbon refers to a non-graphitizable carbon material that is substantially ungraphitized or only slightly graphitized by heat treatment. The terms “soft carbon” and “hard carbon” may be well known in the relevant fields.

[0021] In some embodiments, crystalline carbon and amorphous carbon can be distinguished by XRD measurements. Crystalline carbon includes natural graphite and synthetic graphite. Natural graphite can refer to graphite that can be naturally generated by separation from minerals, and when measured by XRD, the interplanar spacing (d002) of the (002) plane can be from about 3.350 Å to about 3.360 Å. Synthetic graphite can refer to graphite manufactured by graphitization, and if measured by XRD (e.g., when measured by XRD), the interplanar spacing (d002) of the (002) plane can be from about 3.355 Å to about 3.365 Å. Meanwhile, amorphous carbon can have an interplanar spacing (d002) of the (002) plane of about 3.34 Å or less when measured by XRD. XRD can be performed using CuKα rays as the target line, with an X-ray diffractometer (e.g., product name: X'Pert, manufacturer: Malvern Panalytical), and by removing the monochromator to improve peak density resolution. Measurement conditions can be 2θ = 10° to 80°, scanning speed (° / s) from 0.044 to 0.089, and step size (° / step) from 0.013 to 0.039.

[0022] 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 ​​in increments such as 0.1%.

[0023] The negative electrode for a rechargeable lithium battery according to one or more example embodiments includes a current collector and a layer of negative electrode active material containing negative electrode active material on the current collector, wherein the PCR (Plane angle Change Ratio) value defined by Equation 1 is about 5.0 or less.

[0024] [Equation 1] PCR = Peak intensity of 2H(002) plane / [Peak intensity of 3R(101) plane and peak intensity of Cu(111) plane] In Equation 1, the peak intensity is a value obtained by measuring X-ray diffraction using CuKα rays.

[0025] The peak intensities of the 2H(002) plane and the 3R(101) plane can be the peak intensities of the negative electrode active material layer, and the peak intensities of the Cu(111) plane can be the peak intensities of the current collector.

[0026] R-face represents the rhombohedral hexahedral structure.

[0027] Peak intensity can be the height or area of ​​a peak (e.g., the integral area of ​​a peak). According to one or more exemplary embodiments, peak intensity can be the integral area of ​​a peak.

[0028] In one or more example embodiments, the PCR value defined by Equation 1 is about 5.0 or less, or about 4.0 or less, and about 0.1 or more, or about 1.0 or more. If the PCR value is about 5.0 or less, a battery exhibiting desired or improved battery characteristics (e.g., improved cycle life characteristics, high rate characteristics, and efficiency) can be provided.

[0029] In one or more exemplary embodiments, if X-ray diffraction is measured using CuKα rays, the current collector may be a Cu current collector exhibiting a peak on the (111) plane. In another example embodiment, the current collector may be the ratio (I111) of the peak intensity of the (111) plane to the peak intensity of the (200) plane, as measured by X-ray diffraction using CuKα rays. 111 / I 200 The Cu current collector has a peak intensity of approximately 1.0 to approximately 80.0. The ratio of the peak intensity of the Cu current collector (I) 111 / I 200 () can be from about 5.0 to about 50.0, or from about 10.0 to about 30.0.

[0030] The Cu current collector can be or includes Cu foil or Cu foam.

[0031] If X-ray diffraction is measured using CuKα, the appearance of peaks on the (111) plane in a Cu current collector indicates a current collector with sufficient surface roughness on both sides. This surface roughness can improve the adhesion between the active material layer and the current collector and reduce the interfacial resistance, thereby exhibiting desired or improved cycle life characteristics and high rate performance. In some example embodiments, if the ratio of the peak intensities of the Cu current collector (I...) 111 / I 200 A strength of approximately 5.0 to approximately 50.0 ensures sufficient strength to withstand the stresses applied to the current collector during the expansion / contraction of the negative electrode during charging and discharging, thereby achieving long cycle life characteristics.

[0032] If the current collector does not have a peak on the (111) surface, then even if the current collector is a Cu current collector, the surface roughness is insufficient, resulting in insufficient adhesion between the active material layer and the current collector.

[0033] In one or more example embodiments, X-ray diffraction is measured using CuKα rays as target rays, and by removing the monochromator to improve peak intensity resolution. Here, the measurement conditions are 2θ = 10° to 80°, the scan rate (° / s) is 0.044 to 0.089, and the step size (° / step) is 0.013 to 0.039.

[0034] In one or more example embodiments, the negative electrode active material may be or include a carbon-based active material, or a mixture of a carbon-based active material and an active material containing Si.

[0035] The carbon-based active material may be or includes crystalline carbon, and the crystalline carbon may be or includes natural graphite, artificial graphite, or a combination thereof. Artificial or natural graphite may have unspecified shapes, sheet shapes, flake shapes, spherical shapes, fibrous shapes, or combinations thereof, but is not limited to these shapes. If artificial and natural graphite are mixed, the mixing ratio may be from about 70 wt%:30 wt% to about 95 wt%:5 wt%.

[0036] The carbon-based active material may be or includes a graphite composite. In one or more example embodiments, the graphite composite may include aggregates of natural graphite particles, amorphous carbon on the surface of the particles, and a coating layer including amorphous carbon surrounding the aggregates. The particle size of the natural graphite particles may be from about 5 μm to about 15 μm, for example, from about 5 μm to about 13 μm, from about 5 μm to about 12 μm, or from about 5.5 μm to about 11.5 μm, and the particle size of the aggregates may be from about 8 μm to 24 μm, for example, from about 10 μm to about 24 μm, from about 11 μm to about 24 μm, from about 12 μm to about 24 μm, from about 13 μm to about 24 μm, from about 13 μm to about 23 μm, or from about 13 μm to about 20 μm.

[0037] The thickness of the coating can be from about 5 nm to about 50 nm, for example, from about 10 nm to about 50 nm, or from about 20 nm to about 50 nm.

[0038] Amorphous carbon can be or include at least one of soft carbon, hard carbon, mesophase pitch carbide, sintered coke and mixtures thereof.

[0039] In another exemplary embodiment, the graphite composite may include secondary particles in which natural graphite is crushed to prepare primary particles with small particle sizes and then the primary particles are aggregated and spheroidized, tertiary particles formed by aggregation of the secondary particles, and artificial graphite located on the surfaces of the primary particles and the secondary particles. The primary particles, secondary particles, and tertiary particles may include natural graphite.

[0040] The particle size of the primary particles may be from about 4 μm to about 8 μm. The particle size of the primary particles may be, for example, from about 5 μm to about 8 μm, from about 6 μm to about 8 μm, or from about 6 μm to about 7 μm.

[0041] The particle size of the secondary particles may be from about 5 μm to about 10 μm. The particle size of the secondary particles may be, for example, from about 6 μm to about 10 μm, from about 6 μm to about 8 μm, or from about 7 μm to about 8 μm.

[0042] The particle size of the tertiary particles may be from about 9 μm to about 15 μm. For example, the particle size of the tertiary particles may be from about 9.2 μm to about 15 μm, or from about 9.5 μm to about 15 μm.

[0043] The graphite composite according to another exemplary embodiment may include an amorphous carbon coating layer surrounding the tertiary particles. The thickness of the coating layer may be from about 5 nm to about 50 nm, for example, from about 10 nm to about 50 nm, or from about 20 nm to about 50 nm. The amorphous carbon may be or include at least one of soft carbon, hard carbon, mesophase pitch carbide, sintered coke, and mixtures thereof.

[0044] In one or more exemplary embodiments, the natural graphite may be or include flaky natural graphite, and this enables lithium intercalation to occur more actively. According to one or more exemplary embodiments, the flaky natural graphite may be fine (small particle) flaky natural graphite. If the natural graphite is fine natural graphite, the sites for lithium ion intercalation and deintercalation in the same area increase, and the path through which lithium ions can transfer becomes shorter, making the path more suitable for fast (high rate) charging and discharging.

[0045] The negative electrode active material containing Si may be or include silicon, Si-C composite, SiO x (0 < x ≤ 2), Si-Q alloy (where Q is an element including 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), or a combination thereof.

[0046] In one or more example embodiments, the Si-C composite may be or include silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the Si-C composite may include secondary particles (cores) of aggregated primary silicon particles and an amorphous carbon coating (shell) on the surface of the secondary particles. The amorphous carbon may be between the primary silicon particles, for example, it may be coated on the primary silicon particles. The silicon-carbon composite may also include a core in which silicon particles are distributed in an amorphous carbon matrix and an amorphous carbon coating on the surface of the core.

[0047] The secondary particles are located at the center of the Si-C composite; therefore, they can be referred to as the core or central portion. The amorphous carbon coating can be referred to as the outer portion or shell.

[0048] The silicon particles can be or include nano-silicon particles. The particle size of the nano-silicon particles can be from about 10 nm to about 1000 nm, or, according to another example embodiment, from about 20 nm to about 900 nm, from about 20 nm to about 800 nm, from about 20 nm to about 500 nm, from about 20 nm to about 300 nm, or from about 20 nm to about 150 nm. If the particle size of the nano-silicon particles is within any of the above ranges, significant or extreme volume expansion during charging and discharging can be reduced or suppressed, and damage to conductive paths due to particle breakage can be prevented or hindered.

[0049] The mixing ratio of nano-silicon and amorphous carbon can be from about 20:80 to about 70:30 by weight.

[0050] In one or more example embodiments, the secondary particles or core may further comprise crystalline carbon. If the silicon-carbon composite also comprises crystalline carbon, the silicon-carbon composite may comprise primary silicon particles and secondary particles of aggregated crystalline carbon, as well as an amorphous carbon coating layer on the surface of the secondary particles.

[0051] If the Si-C comprises silicon particles, crystalline carbon, and amorphous carbon, then based on 100 wt% of the total Si-C composite, the amount of amorphous carbon can be from about 30 wt% to about 70 wt%, and based on 100 wt% of the total Si-C composite, the amount of crystalline carbon can be from about 1 wt% to about 20 wt%. Based on 100 wt% of the total Si-C composite, the amount of silicon particles can be from about 20 wt% to about 69 wt%, or, according to one or more example embodiments, from about 30 wt% to about 60 wt%.

[0052] The particle size of the Si-C composite can be appropriately adjusted, and is not limited thereto.

[0053] If amorphous carbon is surrounded by secondary particles on its surface, its thickness can be appropriately adjusted, but for example, it can be from about 5 nm to about 100 nm.

[0054] In one or more example embodiments, the negative electrode for a rechargeable lithium battery may include a coated region comprising a layer of negative electrode active material formed on a current collector, and an uncoated region where the negative electrode active material is not formed on the current collector. The uncoated region refers to the region where no layer of negative electrode active material is formed; therefore, it refers to the region where only the current collector exists.

[0055] According to one or more example embodiments, the negative electrode includes an uncoated area, so the X-ray diffraction of the current collector can be easily measured, and after charging and discharging, the X-ray diffraction measurement results of the uncoated area can be used to account for the X-ray diffraction measurement of the current collector.

[0056] The PCR values ​​defined by Equation 1 according to one or more example embodiments can be obtained from such a negative electrode, and can also be obtained from X-ray diffraction of the negative electrode after charging and discharging the battery including the negative electrode and separating the negative electrode from the battery. Thus, the PCR values ​​can have substantially the same value before and after charging and discharging. A substantially the same value can mean a difference of ±0.01.

[0057] The negative electrode active material layer may further include a binder and / or a conductive material.

[0058] For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% of negative electrode active material and about 1 wt% to about 10 wt% of binder, or may include about 90 wt% to about 99 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder and about 0.5 wt% to about 5 wt% of conductive material.

[0059] The binder improves the adhesion properties between the active material particles of the negative electrode and between the active material particles of the negative electrode and the current collector. The binder can be or includes non-aqueous binders, aqueous binders, or combinations thereof.

[0060] The non-aqueous adhesive may be or 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.

[0061] Waterborne adhesives may include at least one of 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.

[0062] Aqueous binders may be or include cellulose compounds, or may be or include cellulose compounds together with aqueous binders. Cellulose compounds are referred to herein as thickeners because they can impart viscosity or constitute a binder, and therefore can be called binders. Cellulose compounds may be used in appropriate amounts within the scope of binders, and are not limited thereto. Cellulose compounds include one or more of carboxymethyl cellulose, hydroxypropyl methylcellulose, methylcellulose, and their alkali metal salts. Alkali metals may be or include Na, K, or Li.

[0063] This includes conductive materials to provide electrode conductivity. Any conductive material can be conductive unless it causes a chemical change. Examples of conductive materials can be: carbonaceous 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, including at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0064] The negative electrode according to one or more example embodiments can be prepared by applying a magnetic field. The preparation of the negative electrode will be described in more detail below.

[0065] A current collector is positioned on and / or below a magnet, and subsequently coated thereon with a negative electrode active material layer composition comprising a negative electrode active material. This process allows a magnetic field to be applied via the magnet.

[0066] The current collector can be or includes a Cu current collector that exhibits a peak on the (111) plane when X-ray diffraction is measured using CuKα rays. In another example embodiment, the current collector can be or includes the ratio (I111) of the peak intensity of the (111) plane to the peak intensity of the (200) plane when X-ray diffraction is measured using CuKα rays. 111 / I 200 The Cu current collector is approximately 1.0 to approximately 80.0.

[0067] The magnetic field strength can be approximately 1,000 Gauss to approximately 10,000 Gauss, approximately 2,000 Gauss to approximately 8,000 Gauss, or approximately 4,000 Gauss to approximately 7,000 Gauss.

[0068] The duration of applying the magnetic field (e.g., the duration of exposing the current collector to the magnetic field) can be from about 7 seconds to about 30 seconds, or from about 8 seconds to about 25 seconds.

[0069] If the magnetic field strength or the duration of exposure to the magnetic field exceeds this range, it may not be possible to prepare a negative electrode with a PCR value of approximately 5.0 or less as defined by Equation 1.

[0070] In one or more example embodiments, if the negative electrode is prepared by applying the above-described magnetic field to a current collector having the above-described X-ray diffraction characteristics, a negative electrode with the desired PCR value can be prepared. If the current collector does not have the above-described X-ray diffraction characteristics (e.g., if the current collector is a Cu current collector that does not show a peak on the (111) plane), the desired PCR value will not be obtained even if a magnetic field of the above-described intensity is applied.

[0071] In one or more example embodiments, coating can also be performed while the current collector is being moved.

[0072] The negative electrode active material layer composition may also include a binder and / or a conductive material. The negative electrode active material, binder, and conductive material may be as described above.

[0073] The negative electrode active material layer composition includes a solvent, and the solvent may be or include water or an organic solvent such as N-methylpyrrolidone. For example, when the binder is or includes an aqueous binder, the solvent may be water.

[0074] Subsequently, the current collector coated with the negative electrode active material layer composition is dried and pressurized to prepare the negative electrode.

[0075] Rechargeable lithium batteries Another example embodiment includes a rechargeable lithium battery comprising a negative electrode, a positive electrode, and an electrolyte.

[0076] positive electrode The positive electrode may include a current collector and a layer of positive electrode active material on the current collector. The layer of positive electrode active material includes a positive electrode active material and may also include a binder and / or a conductive material.

[0077] For example, the positive electrode may further include additives that can constitute a sacrificial positive electrode.

[0078] Based on a 100wt% positive electrode active material layer, the amount of positive electrode active material can be from about 90wt% to about 99.5wt%, and based on a 100wt% positive electrode active material layer, the amounts of binder and conductive material can be from 0.5wt% to 5wt%, respectively.

[0079] The positive electrode active material may include compounds capable of intercalating and deintercalating lithium (lithiation intercalation compounds). In some example embodiments, at least one of lithium and a composite oxide of a metal including at least one of cobalt, manganese, nickel, and combinations thereof may be used.

[0080] 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.

[0081] For 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 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); Lia 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); Li a FePO4 (0.90≤a≤1.8).

[0082] In the above 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 may include or include Mn, Al or combinations thereof.

[0083] For example, the positive electrode active material can be or includes a high-nickel positive electrode active material, based on 100 mol% of the metals other than lithium in a lithium transition metal composite oxide, wherein 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.

[0084] The binder improves the adhesion properties between the positive electrode active material particles and between the positive electrode active material particles and the current collector. Examples of binders may include, but are not limited to, at least one of the following: 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)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, nylon, etc.

[0085] The conductive material is included to provide electrode conductivity, and any conductive material can be used as a conductive material unless the conductive material causes a chemical change. Examples of conductive materials may include: carbonaceous materials, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials including at least one of copper, nickel, aluminum, silver, etc.; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0086] The current collector may include, but is not limited to, Al.

[0087] electrolytes Electrolytes used in rechargeable lithium batteries include non-aqueous organic solvents and lithium salts.

[0088] Non-aqueous organic solvents can serve as media for transporting ions that participate in the electrochemical reactions of a battery.

[0089] Non-aqueous organic solvents may include at least one of carbonate aprotic solvents, ester aprotic solvents, ether aprotic solvents, ketone aprotic solvents, alcohol aprotic solvents, and aprotic solvents.

[0090] Carbonate solvents may include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC). Ester solvents may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, caprolactone, etc. Ether solvents may include at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include: nitriles, such as R-CN (where 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.

[0091] Non-aqueous organic solvents may be used alone or in mixtures of two or more of the compounds mentioned above.

[0092] If carbonate solvents are used, cyclic carbonates and chain carbonates can be used together, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0093] Lithium salts dissolved in organic solvents supply lithium ions to the battery, essentially operating a rechargeable lithium battery and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include those from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 The supporting electrolyte salts are one or more 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).

[0094] diaphragm Depending on the type of rechargeable lithium battery, a separator can be disposed between the positive electrode and the negative electrode. The separator may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, and multilayers having two or more layers, and may be a mixed multilayer, such as a polyethylene / polypropylene double-layer separator, a polyethylene / polypropylene / polyethylene triple-layer separator, a polypropylene / polypropylene / polypropylene triple-layer separator, etc.

[0095] The membrane may include a porous substrate and a coating layer on one or both surfaces of the porous substrate, comprising organic materials, inorganic materials or combinations thereof.

[0096] The porous substrate may be or include polymer films formed from any one or more copolymers or mixtures of 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 Teflon (polytetrafluoroethylene).

[0097] Organic materials may include polyvinylidene fluoride polymers or (meth)acrylamide polymers.

[0098] Inorganic materials may be or include inorganic particles, which include, but are not limited to, 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.

[0099] Organic and inorganic materials can be mixed in a coating layer, or coating layers including inorganic materials and coating layers including organic materials can be stacked.

[0100] Rechargeable lithium batteries can be classified according to their shape as cylindrical batteries, prismatic batteries, pouch batteries, or coin-shaped batteries, etc. Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to an example embodiment, and Figure 1 A cylindrical battery is shown. Figure 2 A prismatic battery is shown, and 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 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). The rechargeable lithium battery 100 may also include a sealing member 60 that seals the housing 50, such as... Figure 1 As shown. In Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11 and a positive electrode terminal 12, and a negative electrode lead connector 21 and a negative electrode terminal 22. For example... Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 may include an electrical path that can be used to guide current formed in the electrode assembly 40 to the outside. Figure 4 The electrode terminal block 70 shown, for example, Figure 3 The positive electrode terminal 71 and the negative electrode terminal 72 are shown.

[0101] As a non-limiting example, the rechargeable lithium battery according to the example embodiment can be used in, for example, automobiles, mobile phones and / or various types of electrical devices.

[0102] The following examples and comparative examples are provided to highlight the characteristics of one or more exemplary embodiments; however, it will be understood that the examples and comparative examples should not be construed as limiting the scope of the exemplary embodiments, nor should the comparative examples be construed as being outside the scope of the exemplary embodiments. Furthermore, it will be understood that the exemplary embodiments are not limited to the specific details described in the examples and comparative examples.

[0103] Example 1 In X-ray diffraction measurements using CuKα rays as the target rays, a Cu foil current collector exhibiting peaks on the (111) plane was prepared. X-ray diffraction was measured using an X'Pert XRD apparatus (available from PANalytical BV), but the monochromator was removed to improve peak intensity resolution. Measurements were performed at 2θ = 10° to 80°, a scan rate (° / s) = 0.06436, and a step size of 0.026° / step.

[0104] A negative electrode active material slurry was prepared by mixing artificial graphite and Si-C composite negative electrode active material (92 wt% artificial graphite, 5 wt% Si-C composite), 2 wt% styrene-butadiene rubber and 1 wt% carboxymethyl cellulose in an aqueous solvent.

[0105] As a Si-C composite, a composite comprising a secondary particle core in which silicon nanoparticles and natural graphite are aggregated, and a soft carbon layer on the core, is used. Based on a 100 wt% Si-C composite, the amount of silicon nanoparticles is 40 wt%, the amount of natural graphite is 20 wt%, and the amount of soft carbon is 40 wt%. The average particle size (D50) of the silicon nanoparticles is 20 nm, and the average thickness of the soft carbon layer is 100 nm.

[0106] A Cu foil current collector was positioned on a magnet with a magnetic field of 3000 Gauss. A negative electrode active material layer slurry was coated onto some areas of the Cu foil current collector while the Cu foil current collector was moved to expose it to the magnetic field for 9 seconds. The resulting product was then dried and pressurized to prepare a negative electrode comprising coated areas where a negative electrode active material layer was formed and uncoated areas where no negative electrode active material layer was formed.

[0107] A slurry for the positive electrode active material layer was prepared by mixing 96 wt% LiCoO2 positive electrode active material, 2 wt% carbon black conductive agent, and 2 wt% polyvinylidene fluoride binder in N-methylpyrrolidone solvent. The prepared slurry was coated onto an Al substrate and dried, and then pressurized to prepare the positive electrode.

[0108] A rechargeable lithium battery is manufactured using a negative electrode, a positive electrode, and an electrolyte. As the electrolyte, 1M LiPF6 dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate (50:50 volume ratio) is used.

[0109] Example 2 The rechargeable lithium battery is manufactured using the same steps as in Example 1, except that a magnet with a magnetic field of 4000 gauss is used.

[0110] Example 3 The rechargeable lithium battery is manufactured using the same steps as in Example 1, except that the Cu foil current collector of Example 1 is positioned on a magnet with a magnetic field strength of 5000 Gauss, the negative electrode active material layer slurry of Example 1 is partially coated on it, and the Cu foil current collector is moved and then exposed to the magnetic field for 20 seconds.

[0111] Example 4 The rechargeable lithium battery is manufactured using the same steps as in Example 1, except that the Cu foil current collector of Example 1 is positioned on a magnet with a magnetic field strength of 4000 Gauss, the negative electrode active material layer slurry of Example 1 is partially coated on it, the Cu foil current collector is moved, and then exposed to the magnetic field for 15 seconds.

[0112] Comparison Example 1 The rechargeable lithium battery is manufactured using the same steps as in Example 1, except that a Cu foil current collector with peaks not shown on the (111) facet is used.

[0113] Comparison Example 2 The rechargeable lithium battery is manufactured using the same steps as in Example 1, except that the Cu foil current collector of Example 1 is positioned on a magnet, the negative electrode active material layer slurry of Example 1 is partially coated onto it, the Cu foil current collector is moved, and then exposed to a magnetic field for 5 seconds.

[0114] Experimental Example 1): Evaluation of X-ray diffraction characteristics The batteries according to Examples 1 to 4, as well as Comparative Examples 1 and 2, were charged and discharged twice at 0.1C, and then fully discharged to 2.75V at 0.1C. The fully discharged battery cells were disassembled to obtain the negative electrode. In the obtained negative electrode, X-ray diffraction was measured for both the active material layer and the uncoated area using an X'Pert XRD apparatus (available from PANalytical BV) with CuKα rays as the target ray and the monochromator removed to improve peak intensity resolution. Measurements were performed at 2θ = 10° to 80°, a scan rate (° / s) = 0.06436, and a step size of 0.026° / step.

[0115] Single-peak fitting was performed using the measured peak intensities of the 2H(002) plane, the 3R(101) plane, and the Cu(111) plane, and then PCR was calculated using the WinPlotR program published by the Institute Laue-Langevin. The results are shown in Table 1.

[0116] Equation 1 PCR = Peak intensity of 2H(002) plane / [Peak intensity of 3R(101) plane and peak intensity of Cu(111) plane] Regarding the negative electrode active material layer and Cu foil current collector of Example 1 and Comparative Example 1, the X-ray diffraction measurement curves are illustrated in the figure below. Figure 5 In. Figure 5 In the graph shown, the results displayed between 2θ = 40° and 67° are magnified (enlarged) and Figure 6 The results shown are magnified (enlarged) and presented at 2θ = 41° to 46°. Figure 7 As shown in the image.

[0117] like Figures 5 to 7 As shown, the Cu foil current collector of Example 1 shows a peak corresponding to the (111) plane, but the Cu foil current collector of Comparative Example 1 does not show a peak corresponding to the (111) plane.

[0118] The peak intensities of the (002) and (101) planes of the negative electrode active material layer, as well as the peak intensities at the uncoated areas of the current collector (e.g., the (111) plane), are shown in Table 1.

[0119] Based on these results, the PCR values ​​calculated according to Equation 1 are shown in Table 1.

[0120] Equation 1 PCR = Peak intensity of 2H(002) plane / [Peak intensity of 3R(101) plane and peak intensity of Cu(111) plane] In Equation 1, the peak intensity is a value obtained from X-ray diffraction measurements using CuKα rays.

[0121] Experimental Example 2): Evaluation of Cycle Life Characteristics Batteries from Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to constant current / constant voltage charging at 1.8C constant current (CC) and 4.25V cutoff, and constant voltage charging at 4.25V and 0.025C cutoff, with a 10-minute pause. They were then subjected to constant current discharging at 1.0C and 3.0V cutoff, with a 10-minute pause. This process constituted one charge-discharge cycle, and the cycle was repeated a total of 200 times. The capacity retention rate of the charge-discharge cycle was obtained by comparing the discharge capacity of each cycle with the discharge capacity of the first cycle. The results are shown in Table 1.

[0122] Experiment Example 3): Evaluation of High-Rate Charging The half-cells according to Examples 1 to 4 and Comparative Examples 1 to 2 will be tested at 0.01V to 1.5V (vs. Li / Li) under the following conditions. +Charge and discharge within the voltage range of ) One 1C charge / 0.5C discharge cycle; One 2C charge / 0.5C discharge cycle; One 3C charge / 0.5C discharge cycle; One 4C charge / 0.5C discharge cycle; One 5C charge / 0.5C discharge cycle; One 6C charge / 0.5C discharge cycle; One 2C charge / 0.2C discharge cycle.

[0123] The ratio of the final charging capacity at 2C to that at 0.2C was calculated. The results are shown in Table 1 as the high-rate charging speed.

[0124] Table 1

[0125] As shown in Table 1, the batteries of Examples 1 to 4 with a PCR value of 5.0 or less as defined by Equation 1 exhibited the desired or improved capacity retention and high-rate charging.

[0126] However, Comparative Example 1 and Comparative Example 2, with PCR values ​​greater than 5, exhibited degraded capacity retention and high-rate charging speeds. Among these, the battery of Comparative Example 2, to which a magnetic field was applied for a short time, exhibited a sudden degraded capacity retention and high-rate charging speed. Therefore, this result shows that insufficient application of a magnetic field leads to significant performance degradation compared to batteries with a magnetic field application time ranging from approximately 7 to approximately 30 seconds.

[0127] While this disclosure has been described in conjunction with what are now considered to be exemplary embodiments, it will be understood that the disclosure is not limited to the disclosed exemplary embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A negative electrode for a rechargeable lithium battery, the negative electrode comprising: A current collector and a negative electrode active material layer on the current collector, the negative electrode active material layer comprising a negative electrode active material. Among them, the plane angle change rate PCR value defined by Equation 1 is 5.0 or less; Equation 1 PCR = peak intensity of 2H(002) plane / [peak intensity of 3R(101) plane and peak intensity of Cu(111) plane]; and The peak intensity is a value obtained by X-ray diffraction using CuKα rays.

2. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The peak intensities of the 2H(002) plane and the 3R(101) plane correspond to the peak intensities of the negative electrode active material layer, and the peak intensities of the Cu(111) plane correspond to the peak intensities of the current collector.

3. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, PCR value of 4.0 or lower.

4. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, PCR value of 0.1 or higher.

5. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, PCR value of 1.0 or higher.

6. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The current collector includes a Cu current collector with a peak appearing on the (111) surface.

7. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The current collector includes a Cu current collector, wherein the ratio I of the peak intensity of the (111) plane to the peak intensity of the (200) plane, as measured by X-ray diffraction of CuKα rays, is... 111 / I 200 The range is from 1.0 to 80.

0.

8. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The peak intensity is the integral area of ​​the peak.

9. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The negative electrode active material includes a mixture of carbon-based active materials and active materials containing Si, and one of the carbon-based active materials.

10. The negative electrode for a rechargeable lithium battery according to claim 9, wherein, The carbon-based active substances include crystalline carbon.

11. The negative electrode for a rechargeable lithium battery according to claim 10, wherein, The crystalline carbon includes at least one of natural graphite and artificial graphite.

12. The negative electrode for a rechargeable lithium battery according to claim 9, wherein, The active material containing Si includes a complex of Si and carbon.

13. The negative electrode for a rechargeable lithium battery according to claim 9, wherein, The negative electrode for the rechargeable lithium battery includes a coated region and an uncoated region. The coated region includes a layer of negative electrode active material on the current collector, and the uncoated region does not have the negative electrode active material layer formed on the current collector.

14. The negative electrode for a rechargeable lithium battery according to claim 1, wherein, The negative electrode is prepared by applying a magnetic field.

15. The negative electrode for a rechargeable lithium battery according to claim 14, wherein, Applying a magnetic field includes positioning the current collector at at least one of the magnet and below the magnet.

16. The negative electrode for a rechargeable lithium battery according to claim 14, wherein, The magnetic field has a strength of 1000 Gauss to 10000 Gauss.

17. A rechargeable lithium battery, said rechargeable lithium battery comprising: The negative electrode according to any one of claims 1 to 16; Positive electrode; and Non-aqueous electrolyte.

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