Negative electrode for rechargeable lithium battery and rechargeable lithium battery comprising the same

Abstract

Provided are a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same. The negative electrode for a rechargeable lithium battery includes a current collector and a negative electrode active material layer on the current collector. The current collector includes a carbon nanotube film. Silicon particles and carbon particles are disposed on the carbon nanotube film.

Description

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2025-0057220, filed on April 30, 2025, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] The present invention relates to a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode. Background Technology

[0003] With the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for rechargeable batteries with high energy density and high capacity is increasing rapidly. Therefore, research and development efforts have been undertaken to improve the performance of rechargeable lithium-ion batteries.

[0004] A rechargeable lithium battery includes a positive electrode and a negative electrode containing active materials capable of inserting and deintercalating lithium ions. Rechargeable lithium batteries generate electrical energy through oxidation and reduction reactions as lithium ions are deintercalated from the positive electrode and inserted into the negative electrode, or vice versa. Summary of the Invention

[0005] This disclosure relates to providing a negative electrode for a rechargeable lithium battery that provides improved battery capacity and flexibility.

[0006] This disclosure also relates to providing a negative electrode for a rechargeable lithium battery with a reduced expansion rate.

[0007] One aspect of this disclosure provides a negative electrode for a rechargeable lithium battery, the negative electrode comprising a current collector and a negative electrode active material layer disposed on the current collector, wherein the current collector comprises a carbon nanotube film, and silicon particles and carbon particles are disposed in the carbon nanotube film.

[0008] This disclosure also relates to providing a rechargeable lithium battery including a positive electrode and a negative electrode for a rechargeable lithium battery.

[0009] The negative electrode for a rechargeable lithium battery according to an embodiment can have improved battery capacity and flexibility, thereby making the battery more useful. The negative electrode for a rechargeable lithium battery according to an embodiment can have a reduced rate of expansion, which results in a long battery life. Attached Figure Description

[0010] The above and other objects, features and advantages of this disclosure will become more apparent to those skilled in the art by referring to the accompanying drawings and describing in detail the exemplary embodiments thereof.

[0011] Figure 1This is a cross-sectional view of the negative electrode for a rechargeable lithium battery according to an embodiment.

[0012] Figure 2 This is a perspective view of the negative electrode for a rechargeable lithium battery according to an embodiment.

[0013] Figures 3 to 6 This is a schematic diagram of a rechargeable lithium battery according to an embodiment. Detailed Implementation

[0014] Embodiments of the present invention will be described in detail below. However, the embodiments are provided by way of example, and this disclosure is not limited to the disclosed embodiments.

[0015] Unless otherwise stated herein, when a component such as a layer, film, region, plate, etc., is described as being “on” another component, it includes not only the case where the component is “directly on” the other component, but also the case where there is another component between them.

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

[0017] As used herein, the term "combination of them" may mean mixtures, laminates, complexes, copolymers, alloys, blends, and reaction products of the components.

[0018] Here, the term "particle size D50" refers to the average particle size representing the diameter of particles that constitute 50% of the cumulative volume in a particle size distribution. Particle size distribution can be measured using methods known to those skilled in the art. For example, particle size distribution can be measured using a particle size analyzer, transmission electron microscopy, or scanning electron microscopy. In another method, the D50 value can be obtained by measuring the particle size using a measuring device that utilizes dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating the particle size from that data. Alternatively, D50 can be measured using laser diffraction. More specifically, when measured by laser diffraction, after dispersing the particles to be measured in a dispersion medium, the particles can be introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound at approximately 28 kHz at an output of 60 W, and the D50 can be calculated based on 100% of the particle size distribution in the measuring device.

[0019] Particle size can be measured using a particle size analyzer (Beckman Coulter; LS 13 320 XR), but this disclosure is not limited thereto.

[0020] According to an embodiment, the negative electrode used in a rechargeable lithium battery can improve battery capacity and flexibility.

[0021] Negative electrode for rechargeable lithium batteries According to embodiments of this disclosure, the negative electrode for a rechargeable lithium battery includes a current collector and a negative electrode active material layer disposed on the current collector. The current collector includes a carbon nanotube film, wherein silicon particles and carbon particles are disposed on the carbon nanotube film.

[0022] The negative electrode active material layer can be disposed on one or both surfaces of the current collector.

[0023] carbon nanotube membrane In the carbon nanotube membrane according to this disclosure, carbon nanotubes are entangled in a network. Since the long axis length is significantly greater than the short axis length, carbon nanotubes can be entangled in a network to form a membrane. The carbon nanotube membrane can be prepared by the method described below or purchased as a commercially available product. Although not limited, the carbon nanotube membrane can be formed as a void-free sheet or a porous fabric or felt.

[0024] Carbon nanotube films can be more flexible and thinner than conventional metal current collectors. Therefore, carbon nanotube films can be used to improve both the flexibility and capacity of batteries. Here, conventional metal current collectors can be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, and polymer substrates coated with conductive metals and / or combinations thereof.

[0025] In the embodiments, the thickness of the carbon nanotube film can be 10% or less of the thickness of the negative electrode active material layer (e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, greater than 0% and 10% or less, or 2% to 10%). Within such a range, the carbon nanotube film can be used as a current collector for the negative electrode active material layer; therefore, the carbon nanotube film can be beneficial in improving the flexibility and capacity of the negative electrode.

[0026] The thickness of carbon nanotube films can be 10 μm or less (e.g., 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, greater than 0 μm and 5 μm or less, or 1 μm to 10 μm). Within these ranges, carbon nanotube films can be used in batteries. The thickness of the carbon nanotube film can be adjusted by regulating the deposition thickness of the carbon nanotubes during the preparation of the film.

[0027] Carbon nanotube films can include carbon nanotubes and can be porous films with voids or in a void-free form. Specifically, carbon nanotube films can have voids located between multiple carbon nanotubes, and the carbon nanotubes can include voids formed within or between the carbon nanotubes. Voids can increase the flexibility of the carbon nanotube film. However, voids can also reduce the mechanical strength of the carbon nanotube film. In addition, voids can reduce battery capacity compared to a carbon nanotube film with the same area but no voids. In view of this, carbon nanotube films according to some embodiments of the present disclosure include a silicon layer and a carbon layer. Therefore, carbon nanotube films can further improve battery capacity. Such a construction will be described in detail below.

[0028] The carbon nanotubes in the carbon nanotube film can be one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes. The carbon nanotubes can have an average major axis length of 30 μm or less (e.g., greater than 0 μm and 30 μm or less). The carbon nanotubes can have an average minor axis length of 30 nm or less (e.g., greater than 0 nm and 20 nm or less).

[0029] In some embodiments, carbon nanotube films can be formed by chemical vapor deposition. Chemical vapor deposition can be used to prepare thin carbon nanotube films. Chemical vapor deposition can be performed according to conventional methods known to those skilled in the art.

[0030] Carbon nanotube films can be prepared by injecting a mixture of carbon source and catalyst into a chemical vapor deposition furnace, heating the chemical vapor deposition furnace to a predetermined temperature to form carbon nanotube aerogel, spin-coating the carbon nanotube aerogel onto a substrate, and then removing the substrate.

[0031] The carbon source can be oxidized by a catalyst to provide carbon nanotubes. The carbon source can be one or more of alkanes having one to five carbon atoms, alkenes having two to five carbon atoms, and alkynes having two to five carbon atoms. For example, the carbon source can be one or more of methane (CH4), ethylene (C2H4), and acetylene (C2H2). However, this disclosure is not limited to these examples.

[0032] A catalyst can oxidize a carbon source. The catalyst can be a metal catalyst. For example, a catalyst can include iron (Fe) or cobalt (Co). However, this disclosure is not limited to these examples.

[0033] Chemical vapor deposition furnaces can be heated to temperatures at which carbon nanotube aerogels are formed. For example, the furnace can be heated to 800°C or higher (e.g., 800°C to 1200°C). However, this disclosure is not limited to heating to these temperatures.

[0034] Carbon nanotube films can be prepared by spin-coating carbon nanotube aerogel onto a substrate using a nozzle equipped with a chemical vapor deposition furnace. The thickness and porosity of the carbon nanotube film can be adjusted by regulating the spin-coating speed, the distance between the nozzle and the substrate, and / or the environmental conditions during spin-coating.

[0035] The furnace used to prepare carbon nanotube films can be a vertical chemical vapor deposition furnace, thus it can be used for the reaction between the carbon source and the catalyst and for spin coating. That is, the carbon source and catalyst can be added to the upper inlet of the vertical chemical vapor deposition furnace, the reaction can take place in the furnace, and carbon nanotube aerogel can be spin-coated through the lower inlet to prepare a carbon nanotube film.

[0036] Because carbon nanotube membranes contain both silicon and carbon particles, the capacity and flexibility of batteries incorporating carbon nanotube membranes are improved.

[0037] Carbon nanotube films can include both silicon particles and carbon particles.

[0038] In carbon nanotube films containing only silicon particles, the silicon particles may over-expand during battery charging and discharging, potentially leading to reduced battery reliability. Furthermore, in carbon nanotube films containing only silicon particles, the volume of the silicon particles may change significantly due to direct contact with the electrolyte, and the silicon particles may be damaged by the electrolyte. Therefore, the battery may have a reduced capacity.

[0039] Carbon nanotube films containing only carbon particles may not be able to completely fill the gaps between carbon nanotubes, which could reduce the strength of the carbon nanotube film. In addition, carbon nanotube films containing only carbon particles may not significantly improve battery capacity.

[0040] Silicon particles can be present on the surface of the carbon nanotube film. For example, in one embodiment, the silicon particles can be included as a silicon layer on the surface of the carbon nanotube film. Here, "silicon layer" can refer to a continuous layer containing silicon particles. In some embodiments, the silicon layer can cover the surface of the carbon nanotube film. The silicon layer on the surface of the carbon nanotubes can be used as a negative electrode active material to improve battery capacity.

[0041] In another embodiment, silicon particles may be located in the voids between carbon nanotubes and / or in the voids within the carbon nanotubes of the carbon nanotube film, thereby increasing the mechanical strength of the carbon nanotube film.

[0042] The silicon particles may include silicon nanoparticles that do not reduce the flexibility of the carbon nanotube film. Furthermore, the silicon nanoparticles can be readily accommodated within the voids of the carbon nanotubes. The silicon nanoparticles may have an average particle size (D50) of 40 nm or smaller (e.g., 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, greater than 0 nm and 40 nm or smaller, or 1 nm to 40 nm). The silicon nanoparticles may have a spherical shape, but this disclosure is not limited in this respect.

[0043] In some embodiments, silicon particles can be formed by deposition of silane (SiH4) gas. Silane gas can decompose to form silicon particles. The reaction for forming silicon particles from silane gas can be carried out according to Scheme 1 below: [Option 1] SiH4(g)→Si(s)+2H2(g) The reaction that forms silicon particles from silane gas can be carried out using conventional methods known to those skilled in the art. Specifically, silicon nanoparticles can be readily prepared from silane gas.

[0044] In this embodiment, the reaction may include chemical vapor deposition. Specifically, a silane gas may be injected into a furnace for chemical vapor deposition and decomposed at a temperature of 420°C or higher (e.g., 500°C or higher). The reaction may be carried out in an inert atmosphere.

[0045] When silicon particles are used as the active material for the negative electrode, carbon particles can reduce the degree of expansion during battery charging and discharging.

[0046] In some embodiments, the carbon particles may be present on the silicon particles. In some embodiments, the carbon particles may be present on the silicon layer.

[0047] Carbon particles can be included as a carbon layer on the surface of a silicon layer. Here, "carbon layer" can refer to a continuous layer containing carbon particles. For example, a carbon layer can cover the surface of a silicon layer. The carbon layer on the surface of the silicon layer can reduce the volume change of the silicon particles during charging and discharging.

[0048] In some embodiments, the carbon layer can cover the carbon nanotubes in the carbon nanotube membrane. Therefore, the carbon layer can fill the voids in the carbon nanotube membrane, thereby increasing the strength of the carbon nanotube membrane.

[0049] The carbon particles may include amorphous carbon. Amorphous carbon can prevent the volume expansion of silicon particles and can be easily stacked on the carbon nanotubes of the carbon nanotube film. Amorphous carbon may be included in the carbon layer at 95 wt% or more (e.g., 95 wt% to 100 wt%, or 100 wt%) relative to 100 wt% carbon layer.

[0050] The thickness of the carbon layer can be 10 nm or less (e.g., 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, greater than 0 nm and 10 nm or less, or 1 nm to 10 nm). Within these ranges, the carbon layer can be used in batteries.

[0051] Carbon particles can be formed by chemical vapor deposition. Chemical vapor deposition can uniformly form carbon particles (preferably, a carbon layer) on carbon nanotube films or silicon particles.

[0052] Carbon particles can be prepared by injecting a carbon source into a chemical vapor deposition furnace, separating the carbon from the carbon source by heating the chemical vapor deposition furnace to a predetermined temperature, and coating the surface of a substrate (e.g., carbon nanotubes coated with silicon nanoparticles) with carbon.

[0053] The carbon source can be one or more of alkanes having one to five carbon atoms, alkenes having two to five carbon atoms, and alkynes having two to five carbon atoms. For example, the carbon source can be one or more of methane (CH4), ethylene (C2H4), and acetylene (C2H2). However, this disclosure is not limited to these examples.

[0054] Chemical vapor deposition furnaces can be heated to temperatures at which carbon is separated from a carbon source. For example, the furnace can be heated to 800°C or higher (e.g., 800°C to 1200°C). However, this disclosure is not limited to these temperatures.

[0055] Carbon separated from a carbon source is formed in a chemical vapor deposition furnace. The thickness of the carbon layer can be adjusted by regulating the carbon source supply rate and supply time, as well as the environmental conditions used for coating.

[0056] The furnace used for carbon coating is a vertical or horizontal chemical vapor deposition furnace. Using such a furnace, carbon separated from a carbon source can readily react with the substrate surface. In other words, a carbon-coated substrate can be prepared by injecting a carbon source into the gas inlet of the chemical vapor deposition furnace, separating carbon within the furnace, and then coating the substrate surface with the carbon.

[0057] The thickness of the current collector can be 10 μm or less (e.g., 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, greater than 0 nm and 10 μm or less, or 1 μm to 10 μm). Within these ranges, the current collector can be used in the battery.

[0058] Negative electrode active material layer The negative electrode active material layer can be disposed on at least one surface of the carbon nanotube membrane.

[0059] The negative electrode active material layer prevents the silicon particles from expanding in volume during battery charging and discharging. Furthermore, it prevents drastic volume changes caused by direct contact between the silicon particles and the electrolyte. The negative electrode active material layer completely prevents silicon particles from contacting the electrolyte.

[0060] The negative electrode active material layer may contain a negative electrode active material. The negative electrode active material layer may also include a conductive material and / or a binder.

[0061] The amount of negative electrode active material can be from 90 wt% to 99.5 wt% relative to 100 wt% of the negative electrode active material layer. The amounts of binder and conductive material can both be from 0.5 wt% to 5 wt% relative to 100 wt% of the negative electrode active material layer.

[0062] The negative electrode active material layer may contain graphite as the negative electrode active material. When the negative electrode active material layer contains graphite as the negative electrode active material, it can prevent contact between silicon particles and the electrolyte and can increase the battery capacity. For example, the negative electrode active material layer may contain 90 wt% or more (e.g., 90 wt% to 99 wt% or 95 wt% to 100 wt%) of graphite.

[0063] Graphite can include one or more types of natural graphite and synthetic graphite.

[0064] Graphite can have an average particle size (D50) of 20 μm or smaller (e.g., 5 μm to 7 μm, 5 μm to 20 μm, 13 μm to 18 μm, or 15 μm to 20 μm). Within these ranges, the specific surface area can be kept relatively constant, thereby preventing an increase in side reactions with the electrolyte and avoiding degradation of fast-charging performance.

[0065] The average particle size (D50) of the artificial graphite can be from 10 μm to 20 μm (e.g., 13 μm to 18 μm, or 15 μm to 20 μm). Within these ranges, the specific surface area can be kept relatively constant, thereby preventing an increase in side reactions with the electrolyte and avoiding degradation of fast-charging performance.

[0066] Artificial graphite can have a maximum particle size of 30 μm to 40 μm. The shape of artificial graphite is not limited, but it can be spherical.

[0067] Artificial graphite can be one or more of the following types: single particles, primary particles, secondary particles as assemblies of primary particles, and tertiary particles as assemblies of secondary particles.

[0068] In one embodiment, a coating containing amorphous carbon may be included on the surface of secondary particles in an assembly of primary particles.

[0069] The negative electrode active material layer may also include one or more of a binder and a conductive material.

[0070] Adhesives may include non-aqueous adhesives, aqueous adhesives, dry adhesives, or combinations thereof.

[0071] Non-aqueous adhesives may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0072] Waterborne adhesives may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic 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.

[0073] When using an aqueous binder as the negative electrode binder, it may also include a cellulose-based compound that imparts viscosity. One or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, and their alkali metal salts may be used as the cellulose-based compound. Na, K, or Li may be used as the alkali metal.

[0074] The dry binder is a fiber-forming polymer material, such as polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof. In other words, the negative electrode can be a dry negative electrode plate.

[0075] The active material layer of the negative electrode may include conductive material in a proportion greater than 0 wt% and 5 wt% or less.

[0076] Conductive materials are used to impart conductivity to electrodes, and in batteries that include conductive materials, any electrically conductive material that does not cause undesirable chemical changes can be used as the conductive material. Specific examples can be: carbon-based materials, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, or carbon nanotubes; metallic substances, including copper, nickel, aluminum, or silver, in the form of metal powder or metal fibers; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0077] Figure 1 This is a cross-sectional view of the negative electrode for a rechargeable lithium battery according to an embodiment of the present disclosure.

[0078] Reference Figure 1 The negative electrode for a rechargeable lithium battery may include a carbon nanotube membrane 1 having silicon particles and a carbon layer, and a negative electrode active material layer 2 and / or 3 located on one or both surfaces of the carbon nanotube membrane 1.

[0079] Carbon nanotube membranes can have exposed carbon nanotube tabs (see...) Figure 2 Carbon nanotube tabs can be connected to the current collector of a battery. During the fabrication of the carbon nanotube membrane, the carbon nanotube tabs can be formed by partially protruding from the carbon nanotube membrane.

[0080] Figure 2 This is a perspective view of the negative electrode for a rechargeable lithium battery according to one embodiment. (Refer to...) Figure 2 The negative electrode for a rechargeable lithium battery may include a carbon nanotube membrane 1 having silicon particles and a carbon layer, and a negative electrode active material layer 2 and / or 3 located on one or both surfaces of the carbon nanotube membrane 1. The carbon nanotube membrane 1 may have exposed carbon nanotube tabs 4.

[0081] Rechargeable lithium batteries According to embodiments of this disclosure, a rechargeable lithium battery includes a positive electrode and a negative electrode. Here, the negative electrode is as described above.

[0082] positive electrode The positive electrode for a rechargeable lithium battery may include a current collector and a layer of positive electrode active material on the current collector. The positive electrode active material layer may include positive electrode active material and may also include a binder and / or conductive material. For example, the positive electrode may also include additives that can be used as a sacrificial positive electrode.

[0083] Positive electrode active material The positive electrode active material may include compounds capable of intercalating and deintercalating lithium (lithium-intercalating compounds). Specifically, at least one of the composite oxides of lithium and metals selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0084] The composite oxide can be a lithium transition metal composite oxide. Specific examples of composite oxides include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, or combinations thereof.

[0085] In some examples, the following compounds, represented by any of the following chemical formulas, may be used: Li a A 1- b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, and 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, and 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, and 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, and 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, and 0≤e≤0.1); Li a NiG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a CoG b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-b G b O2 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn2G bO4 (0.90≤a≤1.8 and 0.001≤b≤0.1); Li a Mn 1-g G g PO4 (0.90≤a≤1.8 and 0≤g≤0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); or Li a FePO4 (0.90≤a≤1.8). In these chemical formulas, A is Ni, Co, Mn or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof; D is O, F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; and L 1 It is Mn, Al, or a combination thereof.

[0086] The positive electrode active material can be, for example, a high-nickel positive electrode active material. Based on 100 mol% of metals other than lithium in the lithium transition metal complex oxide, the positive electrode active material can have a nickel content of greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. High-nickel positive electrode active materials can provide high capacity and can be used in high-capacity, high-density rechargeable lithium batteries.

[0087] 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%. Based on the 100wt% positive electrode active material layer, the amounts of binder and conductive material can be from about 0.5wt% to about 5wt%, respectively.

[0088] The binder is used to adhere the positive electrode active material particles to each other, and also to adhere the positive electrode active material to the current collector. As a non-limiting example, examples of binders include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, nylon, etc.

[0089] Conductive materials can be used to impart conductivity (e.g., electrical conductivity) to electrodes. Any material that does not cause undesirable chemical changes in a rechargeable lithium-ion battery and conducts electrons can be used in the battery. Examples of conductive materials include: carbon-based materials such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials, including copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0090] Aluminum can be used as a current collector, but this disclosure is not limited thereto.

[0091] electrolyte Rechargeable lithium batteries may also include an electrolyte. The electrolyte used in rechargeable lithium batteries may include non-aqueous organic solvents and lithium salts.

[0092] Non-aqueous organic solvents can be used as media for transporting ions that participate in the electrochemical reactions of a battery.

[0093] Non-aqueous organic solvents can be carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0094] Carbonate solvents can include 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), butyl carbonate (BC), etc.

[0095] Ester solvents can include methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, caprolactone, etc.

[0096] Ether solvents can include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents can include cyclohexanone, etc. Alcohol solvents can include ethanol, isopropanol, etc. Aprotic solvents can 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.

[0097] Non-aqueous organic solvents can be used alone or in combination of two or more.

[0098] When using carbonate solvents, cyclic carbonates and chain carbonates can be mixed and used, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0099] Lithium salts dissolved in organic solvents supply lithium ions in batteries, enabling rechargeable lithium batteries to operate fundamentally and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include those selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO2C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 At least one of the following: (SO2) (where x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0100] Depending on the type of rechargeable battery, a separator may be present between the positive and negative electrodes.

[0101] diaphragm The membrane may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer membranes of two or more layers thereof (e.g., mixed multilayer membranes such as polyethylene / polypropylene double membranes, polyethylene / polypropylene / polyethylene triple membranes, polypropylene / polyethylene / polypropylene triple membranes, etc.).

[0102] 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.

[0103] The porous substrate can be a polymer membrane, which is formed from polymers or copolymers or mixtures of two or more of the following polymers: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., TEFLON). ® ).

[0104] Organic materials may include polyvinylidene fluoride polymers or (meth)acrylic acid polymers.

[0105] Inorganic materials may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. However, this disclosure is not limited to these examples.

[0106] Organic and inorganic materials can be mixed in a single coating layer. In other embodiments, coating layers comprising organic materials and coating layers comprising inorganic materials can be stacked.

[0107] Rechargeable lithium batteries can be cylindrical, prismatic, pouch-shaped, or coin-shaped, depending on their shape.

[0108] Figures 3 to 6 A rechargeable lithium battery according to an embodiment of the present disclosure is shown. Figure 3 A cylindrical battery is shown. Figure 4 A prismatic battery is shown. Figure 5 and Figure 6 A pouch-type battery is shown. (See reference) Figures 3 to 6 The rechargeable lithium battery 100 may include an electrode assembly 40 and a housing 50. The electrode assembly 40 includes a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40 is housed within the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 3 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. (As illustrated...) Figure 4 As shown, the rechargeable lithium battery 100 may include a positive lead terminal 11, a positive terminal 12, a negative lead terminal 21, and a negative terminal 22. Figure 5 and Figure 6 As shown, the rechargeable lithium battery 100 may include electrode terminals 70 forming an electrical path for guiding current formed in the electrode assembly 40 to the outside of the rechargeable lithium battery 100. The electrode terminals 70 may be, for example, a positive electrode terminal 71 and a negative electrode terminal 72.

[0109] As a non-limiting example, the rechargeable lithium battery according to the embodiments can be used in automobiles, mobile phones and / or various types of electronic devices.

[0110] Examples and comparative examples of this disclosure will be described below. However, the examples provided below are for illustrative purposes only, and this disclosure is not limited to the examples below.

[0111] Example 1 Carbon nanotube aerogels were prepared by injecting a mixture of CH4 as a carbon source and Fe as a catalyst into a vertically extended chemical vapor deposition furnace. The mixture was heated to 800°C to 1200°C, and carbon nanotube films were prepared by spin-coating the carbon nanotube aerogels through the furnace outlet.

[0112] The prepared carbon nanotube film was placed in a horizontally positioned chemical vapor deposition furnace, and SiH4 gas and hydrogen were injected. The furnace was then heated to 500°C to coat the carbon nanotube film with silicon nanoparticles.

[0113] A carbon nanotube membrane with silicon nanoparticles and a carbon layer is prepared by placing a carbon nanotube membrane coated with silicon nanoparticles into a chemical vapor deposition furnace, adding CH4 as a carbon source, separating carbon from the carbon source by heating the furnace to 800°C to 1200°C, and forming a carbon layer on the carbon nanotube membrane.

[0114] A slurry for the active material layer of the negative electrode was prepared by mixing 97.4 wt% artificial graphite, 1.0 wt% carboxymethyl cellulose, 1.5 wt% styrene-butadiene rubber and 0.1 wt% carbon nanotubes as conductive materials, and adding distilled water to the mixture.

[0115] A negative electrode consisting of three layers—a negative electrode active material layer, a carbon nanotube membrane, and a negative electrode active material layer—is prepared by coating two surfaces of a carbon nanotube membrane with a slurry for the negative electrode active material layer, and then drying and rolling the coated membrane.

[0116] A positive electrode paste was prepared by mixing 97 wt% lithium-cobalt-nickel-aluminum oxide as the positive electrode active material, 1.5 wt% carbon nanotubes as the conductive material, and 1.5 wt% polyvinylidene fluoride, and adding N-methyl-2-pyrrolidone. The positive electrode was then prepared by coating the prepared positive electrode paste onto an aluminum foil, drying it, and rolling the foil.

[0117] A three-layer positive electrode-separator-negative electrode laminate is formed by placing a separator between the positive and negative electrodes, and then the laminate is placed in a bag. 2.5g of electrolyte (ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate dissolved in 1.5M LiPF6 (volume ratio 30:50:20)) is injected into the bag to manufacture the battery.

[0118] Comparison Example 1 A slurry for the negative electrode active material layer was prepared by mixing 97.4 wt% artificial graphite and siloxane particles, 1.0 wt% carboxymethyl cellulose, 1.5 wt% styrene-butadiene rubber, and 0.1 wt% carbon nanotubes as a conductive material, and distilled water was added to the mixture. A three-layer negative electrode was prepared by coating the negative electrode active material layer slurry onto both surfaces of a copper foil, drying, and rolling the resulting foil. This foil consisted of a negative electrode active material layer (with the same thickness as the negative electrode active material layer in Example 1), a copper layer (with the same thickness as the carbon nanotube film in Example 1), and another negative electrode active material layer (with the same thickness as the negative electrode active material layer in Example 1). A battery was manufactured using the prepared negative electrode in the same manner as in Example 1.

[0119] The example and comparative example batteries were charged at 0.1C and discharged at 0.2C once in constant current (CC) and constant voltage (CV) modes, charged at 0.2C and discharged at 0.2C once in both CC and CV modes, and charged at 0.33C and discharged at 0.33C 500 times in both CC and CV modes to calculate the capacity retention and expansion rate of each battery. In the first charging phase, charging was performed in CC mode with a cutoff voltage of 10mV and CV mode with a cutoff time of 15 hours, followed by discharging at a cutoff voltage of 1.5V. Subsequent processes were performed under cutoff conditions of CC mode with a cutoff voltage of 10mV and CV mode at a 1 / 10C rate.

[0120] Capacity retention is calculated as the ratio of discharge capacity after 500 cycles to discharge capacity after the first cycle. Expansion ratio is calculated as the ratio of cell thickness after 500 cycles to cell thickness after the first cycle.

[0121] The results are shown in Table 1.

[0122] Table 1

[0123] As shown in Table 1, compared with Comparative Example 1, the negative electrode of Example 1 for rechargeable lithium batteries exhibits superior charge and discharge characteristics (such as specific capacity, efficiency and C-rate) as well as improved cycle life characteristics and safety.

[0124] Although preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the explicitly disclosed embodiments.

Claims

1. A negative electrode for a rechargeable lithium battery, the negative electrode comprising: current collector; as well as A negative electrode active material layer is disposed on the current collector. The current collector includes a carbon nanotube membrane, and the carbon nanotube membrane includes carbon nanotubes. Silicon particles and carbon particles are disposed on the carbon nanotube film.

2. The negative electrode according to claim 1, wherein, The silicon particles are disposed on the surface of the carbon nanotubes in the carbon nanotube film.

3. The negative electrode according to claim 2, wherein, The silicon particles are disposed in the gaps between the carbon nanotubes.

4. The negative electrode according to claim 2, wherein, The silicon particles are disposed in the voids within the carbon nanotubes.

5. The negative electrode according to claim 2, wherein, The silicon particles are silicon nanoparticles.

6. The negative electrode according to claim 5, wherein, The silicon nanoparticles have an average particle size of 40 nm or smaller.

7. The negative electrode according to claim 1, wherein, The carbon particles cover the silicon particles and the carbon nanotubes.

8. The negative electrode according to claim 1, wherein, The carbon particles include amorphous carbon.

9. The negative electrode according to claim 1, wherein, The carbon particles are included as a carbon layer on the surface of the silicon particles.

10. The negative electrode according to claim 1, wherein, The thickness of the carbon nanotube film is 10% or less of the thickness of the negative electrode active material layer.

11. The negative electrode according to claim 1, wherein, The negative electrode active material layer includes graphite as the negative electrode active material.

12. The negative electrode according to claim 11, wherein, The graphite comprises 90 wt% to 99 wt% of the negative electrode active material.

13. The negative electrode according to claim 1, wherein, The carbon nanotube membrane includes exposed carbon nanotube tabs.

14. A rechargeable lithium battery, said rechargeable lithium battery comprising: The negative electrode for a rechargeable lithium battery according to any one of claims 1 to 13; as well as Positive electrode.

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