Negative electrode for rechargeable lithium battery, rechargeable lithium battery including same, and method of preparing negative electrode active material layer

Abstract

A negative electrode for a rechargeable lithium battery, a rechargeable lithium battery including the same, and a method of preparing a negative electrode active material layer are provided. The negative electrode includes: a current collector; and a negative electrode active material layer including a negative electrode active material and a polymer whose volume or length decreases at a set or predetermined temperature.

Description

TECHNICAL FIELD

[0001] According to one or more embodiments, the present disclosure relates to a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode. BACKGROUND ART

[0002] Recently, the rapid growth in the use of electronic devices using batteries (such as mobile phones, laptop computers, and / or electric vehicles, etc.) has caused a surprisingly large increase in the demand or expectation for rechargeable batteries with relatively high energy density and high capacity. Therefore, in-depth research has been actively conducted or pursued to improve the performance of rechargeable lithium batteries.

[0003] A rechargeable lithium battery includes a positive electrode and a negative electrode, and each of the positive electrode and the negative electrode includes an active material capable of intercalating and deintercalating lithium ions. The rechargeable lithium battery also includes an electrolyte, and electric energy is generated due to oxidation reactions and reduction reactions that occur when lithium ions are respectively intercalated into and deintercalated from the positive electrode and the negative electrode (for example, when lithium ions are respectively intercalated into and deintercalated from the positive electrode and the negative electrode). SUMMARY OF THE INVENTION

[0004] One or more aspects relate to a negative electrode for a rechargeable lithium battery that exhibits excellent or desired fast charging characteristics.

[0005] One or more aspects relate to a rechargeable lithium battery including the negative electrode.

[0006] Additional aspects will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the presented embodiments of the disclosure.

[0007] One or more embodiments provide a negative electrode for a rechargeable lithium battery, the negative electrode including: a current collector; and a negative electrode active material layer on the current collector and including a polymer whose volume or length decreases at a set or predetermined temperature (i.e., a polymer having a volume or length configured to decrease) and a negative electrode active material.

[0008] Another embodiment provides a rechargeable lithium battery including: the negative electrode; a positive electrode; and an electrolyte.

[0009] The negative electrode according to one or more embodiments may exhibit excellent or desired fast or rapid charging characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figures 1 to 4 are schematic views each showing a rechargeable lithium battery according to one or more embodiments. DETAILED DESCRIPTION

[0011] In the following, embodiments are described in more detail. However, these embodiments are merely examples, and the present disclosure is not limited thereto, and the present disclosure is defined by the scope of the claims.

[0012] As used herein, if no definition is otherwise provided (e.g., when no other definition is provided), it will be understood that if an element such as a layer, film, region, or substrate is referred to as "on" another element (e.g., when an element such as a layer, film, region, or substrate is referred to as "on" another element), it can be directly on the other element or there can also be intervening elements.

[0013] Unless otherwise specified in the specification, singular expressions include plural expressions. Unless otherwise specified, "A or B" can mean "including A, including B, or including both A and B".

[0014] As used herein, the term "a combination thereof" can include mixtures, laminates, composites, copolymers, alloys, blends, and reactants of components.

[0015] As used herein, if no definition is otherwise provided (e.g., when no other definition is provided), the particle size can be an average particle size. Such a particle size represents the average particle size (D50) at which the cumulative volume in the particle size distribution is about 50% by volume. The average particle size (D50) can be measured by methods well-suited to those skilled in the art (e.g., by a particle size analyzer or by transmission electron microscope images or scanning electron microscope images). In one or more embodiments, data analysis is performed using a dynamic light scattering measurement device, and the number of particles is counted for each particle size range, whereby the average particle size (D50) value can be easily obtained by calculation. The particle size can be measured by a laser diffraction method. By dispersing the particles to be measured in a dispersion solvent and introducing it into a commercially available laser diffraction particle measurement device (e.g., MT 3000 available from Microtrac Co., Ltd.), irradiating ultrasonic waves of about 28 kHz with a power of about 60 W, and calculating the average particle size (D50) in the 50% standard of the particle distribution in the measurement device, the average particle size (D50) can be obtained.

[0016] As used herein, the term "and / or" includes any combination and all combinations of one or more of the associated listed items. Expressions such as "at least one of...", "one of...", and "selected from..." modify the entire list of elements (components) if after / before a list of elements (components) (e.g., when after / before a list of elements (components)), rather than modifying individual elements (components) in the list. For example, the expressions "at least one of a to c", "at least one of a, b, or c", and "at least one of a, b, and / or c" can represent only a, only b, only c, (e.g., simultaneously) both a and b, (e.g., simultaneously) both a and c, (e.g., simultaneously) both b and c, all of a, b, and c, or variants thereof.

[0017] Negative electrode A negative electrode for a rechargeable lithium battery according to one or more embodiments includes: a current collector; and a negative electrode active material layer including a polymer whose volume or length decreases at a set or predetermined temperature (i.e., a polymer having a volume or length configured to decrease at a set or predetermined temperature) and a negative electrode active material.

[0018] The polymer can have a physical property of decreasing in volume or length at a set or predetermined temperature (e.g., from about 120 °C to about 200 °C). For example, the polymer decreases in volume or length at a set or predetermined temperature, and thus can form spaces in the negative electrode active material of the final negative electrode. For example, during vacuum drying after coating, drying, and pressing a composition of the negative electrode active material layer including the polymer on the current collector, the volume and / or length can decrease, making some regions occupied by the polymer in the negative electrode active material layer become empty spaces, such that spaces can exist in the final negative electrode active material layer. In some embodiments, if vacuum drying is performed at a set or predetermined temperature, the polymer can be partially removed, thereby reducing the volume and / or length.

[0019] Lithium ions can pass through such empty spaces that can act as channels for lithium ions, thereby improving fast or rapid charging characteristics.

[0020] The set or predetermined temperature at which the volume or length of the polymer decreases can be from about 120 °C to about 200 °C, from about 120 °C to about 180 °C, or from about 120 °C to about 160 °C.

[0021] A polymer according to one or more embodiments can have a reduction rate of about 70% to about 99%, about 80% to about 99%, or about 90% to about 99% represented by Equation 1, which is the ratio of the volume (e.g., the volume of the polymer) at about 120 °C to about 200 °C to the volume at room temperature.

[0022] In the specification, the room temperature can be from about 20°C to about 25°C.

[0023] Equation 1 Volume reduction rate (%) = [(Volume at room temperature - Volume at about 120°C to about 200°C) / Volume at room temperature] × 100.

[0024] The polymer according to one or more embodiments can have a reduction rate of about 70% to about 99%, about 80% to about 99%, or about 90% to about 99% represented by Equation 2, which is the ratio of the length (e.g., the length of the polymer) at about 120°C to about 200°C to the length at room temperature.

[0025] Equation 2 Length reduction rate (%) = [(Length at room temperature - Length at about 120°C to about 200°C) / Length at room temperature] × 100.

[0026] The polymer according to one or more embodiments is not affected by heat treatment at a temperature of about 100°C or lower, and can be partially burned at a temperature above about 100°C, such as about 120°C or higher, to remove at least some of the polymer. The partial removal of the polymer can cause a reduction in volume and / or length at the temperatures described herein.

[0027] In one or more embodiments, the polymer can have a shape such as linear or thread-like (chain-type or chain-like), dendritic or dendritic-like, branched or branched-like, non-woven fabric-type or non-woven fabric-like, etc.

[0028] The porosity of the negative electrode active material layer according to one or more embodiments can be from about 20% to about 30% or from about 25% to about 30%. If the porosity of the negative electrode active material layer is within the described range (e.g., when the porosity of the negative electrode active material layer is within the described range), the transfer of lithium ions can be more promoted, thereby better improving the fast or rapid charging characteristics. If the negative electrode active material layer has a porosity within the described range and includes a polymer whose volume and / or length decreases at a set or predetermined temperature (e.g., when the negative electrode active material layer has a porosity within the described range and includes a polymer whose volume and / or length decreases at a set or predetermined temperature), the resistance can be further reduced, the cycle life characteristics can be further improved, and the fast or rapid charging characteristics can be further improved.

[0029] The polymer can include polyvinyl chloride. For example, the polymer can be polyvinyl chloride.

[0030] In one or more embodiments, based on 100 wt% of the negative electrode active material layer, the amount of the polymer can be from about 0.1 wt% to about 1.0 wt% or from about 0.5 wt% to about 1.0 wt%. If the amount of the polymer is within the described range (e.g., when the amount of the polymer is within the described range), the capacity of the battery can be increased.

[0031] In some embodiments, the weight ratio of the negative electrode active material to the polymer can be a weight ratio of about 99.9:0.1 to about 99.0:1.0 or a weight ratio of about 99.5:0.5 to about 99.0:1.0. If the weight ratio of the negative electrode active material to the polymer is within the described range (e.g., when the weight ratio of the polymer to the negative electrode active material is within the described range), the dispersion of the polymer can be improved or enhanced.

[0032] The negative electrode active material can include a carbon-based negative electrode active material, a Si-based negative electrode active material, and / or a combination thereof (e.g., any suitable combination).

[0033] The carbon-based negative electrode active material can include crystalline carbon, amorphous carbon, and / or a combination thereof (e.g., any suitable combination). The crystalline carbon can be graphite, such as natural graphite or artificial graphite having an indefinite shape, flaky, lamellar, spherical, or fibrous shape, and the amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonization product, and / or calcined coke, etc.

[0034] The Si-based negative electrode active material can include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is selected from 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 / or a combination thereof (e.g., any suitable combination)), and / or a combination thereof (e.g., any suitable combination).

[0035] The silicon-carbon composite can be a composite of silicon and amorphous carbon. According to one or more embodiments, the silicon-carbon composite can be in the form of silicon particles (e.g., primary silicon particles) and amorphous carbon coated on the surface of the silicon particles (e.g., primary silicon particles). For example, the silicon-carbon composite can include secondary particles (cores) aggregated with primary silicon particles and an amorphous carbon coating layer (shell) on the surface of the secondary particles. The amorphous carbon can also be between the primary silicon particles. For example, the primary silicon particles can be coated with amorphous carbon. The secondary particles can be dispersed in an amorphous carbon matrix.

[0036] The silicon-carbon composite can also include crystalline carbon. For example, the silicon-carbon composite can include a core containing crystalline carbon and silicon particles (e.g., primary silicon particles) and an amorphous carbon coating layer on the surface of the core.

[0037] The silicon particles (e.g., primary silicon particles) can be silicon nanoparticles.

[0038] The particle size of the silicon nanoparticles can be from about 10 nanometers (nm) to about 1,000 nm, and in one or more embodiments, can be from about 10 nm to about 200 nm or from about 20 nm to about 150 nm. If the average particle size of the silicon nanoparticles is within the described range (e.g., when the average particle size of the silicon nanoparticles is within the described range), the (e.g., extreme) volume expansion caused during charging and discharging can be suppressed or reduced, and the breakage of the conduction path due to the fragmentation of the particles can be prevented or reduced.

[0039] In the negative electrode active material according to one or more embodiments, the silicon-carbon composite used as the core can include silicon nanoparticles and an amorphous carbon coating layer on the surface of the silicon nanoparticles. The silicon-carbon composite can include an aggregation product (e.g., secondary particle) in which at least one silicon nanoparticle is aggregated and an amorphous carbon coating layer on the surface of the aggregation product (e.g., secondary particle).

[0040] In the amorphous carbon coating layer, the amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonized product, and / or calcined coke, etc. The thickness of the amorphous carbon coating layer can be from about 1 nm to about 2 μm, from about 1 nm to about 500 nm, from about 10 nm to about 300 nm, or from about 20 nm to about 200 nm. If the thickness of the amorphous carbon coating layer is within the described range (e.g., when the thickness of the amorphous carbon coating layer is within the described range), the volume expansion of silicon during charging and discharging can be effectively suppressed or reduced.

[0041] The crystalline carbon can be graphite, such as natural graphite or artificial graphite without a definite shape, flaky, lamellar, spherical, or fibrous.

[0042] If the silicon-carbon composite includes silicon nanoparticles and an amorphous carbon coating layer (e.g., when the silicon-carbon composite includes silicon nanoparticles and an amorphous carbon coating layer), based on the total 100 wt% of the silicon-carbon composite, the amount of the silicon nanoparticles can be from about 30 wt% to about 70 wt% or from about 40 wt% to about 65 wt%. Based on the total 100 wt% of the silicon-carbon composite material, the amount of the amorphous carbon coating layer can be from about 30 wt% to about 70 wt% or from about 35 wt% to about 60 wt%.

[0043] If (e.g., when) the silicon-carbon composite further includes crystalline carbon, based on 100 wt% of the total silicon-carbon composite, the amount of silicon nanoparticles can be about 20 wt% to about 70 wt% or about 25 wt% to about 65 wt%. Based on 100 wt% of the total silicon-carbon composite, the amount of amorphous carbon can be about 25 wt% to about 70 wt% or about 25 wt% to about 60 wt%, and the amount of crystalline carbon can be about 1 wt% to about 20 wt% or about 5 wt% to about 15 wt%.

[0044] In the negative electrode active material layer, based on 100 wt% of the total negative electrode active material layer, the amount of the negative electrode active material can be about 95 wt% to about 98 wt%.

[0045] The negative electrode active material layer may include a binder and may also include a conductive material. Based on 100 wt% of the total negative electrode active material layer, the amount of the binder can be about 1 wt% to about 4 wt%. Based on 100 wt% of the total negative electrode active material layer, the amount of the conductive material can be about 0.05 wt% to about 1.0 wt%.

[0046] The binder can be used to make the negative electrode active material particles adhere well to each other and can also be used to make the negative electrode active material adhere well to the current collector. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, and / or a combination thereof (e.g., any suitable combination).

[0047] The non-aqueous binder can include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and / or a combination thereof (e.g., any suitable combination).

[0048] The aqueous binder can be selected from styrene-butadiene rubber, (meth)acrylate-modified styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin rubber, polyphosphazene, poly(meth)acrylonitrile, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and / or a combination thereof (e.g., any suitable combination).

[0049] The negative electrode binder can be a cellulose-based compound. In one or more embodiments, the cellulose-based compound can be used together with an aqueous binder. The cellulose-based compound can include one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and its alkali metal salts. The alkali metal can be Na, K, or Li. The cellulose-based compound can be used as a binder and can be used as a thickener for imparting viscosity. The cellulose-based compound can be used in an appropriate amount in the amount of the binder. For example, based on 100 parts by weight of the negative electrode active material, it can be used in an amount of about 0.1 part by weight to 3 parts by weight.

[0050] The dry binder can be a polymeric material capable of being fibrous. For example, the dry binder can be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and / or a combination thereof (e.g., any suitable combination).

[0051] The conductive material can be used to impart conductivity (e.g., electrical conductivity) to the electrode. Any material that does not cause a chemical change (e.g., does not cause an undesirable chemical change in a rechargeable lithium battery) and conducts electrons can be used in the battery. Non-limiting examples of such materials can include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials including copper, nickel, aluminum, and / or silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; and / or a mixture thereof (e.g., any suitable mixture).

[0052] The current collector can include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and / or a combination thereof (e.g., any suitable combination).

[0053] Preparation of the Negative Electrode The negative electrode and the negative electrode active material layer according to one or more embodiments can be prepared by the following steps.

[0054] In one or more embodiments, the method for preparing the negative electrode active material layer includes: coating a negative electrode active material layer composition on a current collector, the negative electrode active material layer composition including a polymer whose volume or length decreases at a set (e.g., predetermined) temperature, a negative electrode active material, and a solvent; and drying it (e.g., the current collector having the negative electrode active material layer composite). The solvent can be an organic solvent such as N-methylpyrrolidone and / or water.

[0055] The drying can be carried out at about 20°C to about 100°C, but is not limited thereto.

[0056] Pressurize the dried product to provide a pressurized product.

[0057] Thereafter, the pressurized product is dried under vacuum. The vacuum drying can be carried out at a temperature of about 120 °C to about 200 °C, or can be carried out at about 150 °C to about 200 °C or about 180 °C to about 200 °C. The vacuum drying can be carried out for about 8 hours to about 14 hours. The vacuum drying can cause some polymers to be removed, thereby forming (e.g., providing) empty spaces within the negative electrode active material layer.

[0058] Rechargeable lithium battery Another embodiment provides a rechargeable lithium battery including a negative electrode, a positive electrode, and an electrolyte. The negative electrode can be a negative electrode according to one or more embodiments.

[0059] Positive electrode The positive electrode can include a current collector and a positive electrode active material layer on the current collector.

[0060] The positive electrode active material layer can include a positive electrode active material and can also include a binder and / or a conductive material (e.g., an electrically conductive material). For example, the positive electrode can also include an additive that can be used as a sacrificial positive electrode.

[0061] The positive electrode active material can include a compound capable of intercalating and deintercalating lithium (a lithiated intercalation compound). In one or more embodiments, at least one of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used.

[0062] The composite oxide can be a lithium transition metal composite oxide, and examples of the composite oxide can include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free nickel manganese-based oxides, and / or combinations thereof (e.g., any suitable combination).

[0063] As an example, the following compounds represented by any one 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); Li a CoG b O2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-b G b O2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-g G g PO4 (0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5); Li (3-f) Fe2(PO4)3 (0 ≤ f ≤ 2); Li a FePO4 (0.90 ≤ a ≤ 1.8).

[0064] In the foregoing chemical formulas, A is Ni, Co, Mn, and / or a combination thereof (e.g., any suitable combination); X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and / or a combination thereof (e.g., any suitable combination); D is O, F, S, P, and / or a combination thereof (e.g., any suitable combination); G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and / or a combination thereof (e.g., any suitable combination); and L 1 is Mn, Al, and / or a combination thereof (e.g., any suitable combination).

[0065] For example, based on 100 mol% of the metal other than lithium in the lithium transition metal composite oxide, the positive electrode active material can be a high-nickel type positive electrode active material having a nickel content (e.g., amount) 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%. The high-nickel type positive electrode active material can be capable of achieving a high capacity and can be applied to a high-capacity, high-density rechargeable lithium battery.

[0066] Based on 100 wt% of the positive electrode active material layer, the amount of the positive electrode active material can be from about 90 wt% to about 98 wt%. Based on 100 wt% of the positive electrode active material layer, the amounts of the binder and the conductive material can be from about 1 wt% to about 5 wt% respectively.

[0067] The binder is used to make the positive electrode active material particles adhere well to each other and is also used to make the positive electrode active material adhere well to the current collector. As non-limiting examples, examples of the binder can include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate esterified styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and / or nylon, etc.

[0068] The conductive material can be used to impart conductivity (e.g., electrical conductivity) to the electrode, and any material that does not cause a chemical change (e.g., does not cause an undesired chemical change in a rechargeable lithium battery) and conducts electrons can be used in the battery. Examples of the conductive material can include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; and / or their (e.g., any suitable) mixtures.

[0069] Al can be used as the current collector, but the present disclosure is not limited thereto.

[0070] Electrolyte The electrolyte includes a non-aqueous organic solvent and a lithium salt.

[0071] The non-aqueous organic solvent can be used as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0072] The non-aqueous organic solvent can be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, and / or their (e.g., any suitable) combination.

[0073] Carbonate solvents may 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), and / or butylene carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and / or caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and / or tetrahydrofuran, etc. Ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol and / or isopropanol, etc. Aprotic solvents may include nitriles (such as R-CN (wherein, R is a C2 to C20 straight-chain, branched-chain or cyclic hydrocarbon group, and may include double bonds, aromatic rings, and / or ether bonds, etc.)); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane and / or 1,4-dioxolane, etc.); and / or sulfolane, etc.

[0074] The non-aqueous organic solvents may be used alone or in combination of two or more.

[0075] If a carbonate solvent is used (for example, when a carbonate solvent is used), a cyclic carbonate and a chain carbonate may be mixed and used, and the cyclic carbonate and the chain carbonate may be mixed at a volume ratio of about 1:1 to about 1:9.

[0076] The lithium salt dissolved in the organic solvent supplies lithium ions in the battery, enabling the rechargeable lithium battery to operate substantially, and improving the transport of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt include at least one selected from LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide, LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2) (wherein, x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroether sulfonate, lithium difluoro bis(oxalate) phosphate (LiDFOP), and lithium bis(oxalate) borate (LiBOB).

[0077] Separator Depending on the type or kind of rechargeable lithium battery, a separator may be present between the positive electrode and the negative electrode. The separator may include polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, as well as a hybrid multilayer film, such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, and / or a polypropylene / polyethylene / polypropylene three-layer separator, etc.

[0078] The separator may include a porous substrate and a coating layer including an organic material, an inorganic material, and / or a combination thereof (e.g., any suitable combination) on the surface of the porous substrate (e.g., one or two surfaces (e.g., opposite surfaces)).

[0079] The porous substrate may be a polymer film formed of any one selected from the following polymers: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyarylether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, polytetrafluoroethylene (e.g., Teflon), or a copolymer or mixture of two or more thereof.

[0080] The organic material may include polyvinylidene fluoride-based polymers or (meth)acrylic polymers.

[0081] The inorganic material may include inorganic particles selected from among Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and / or a combination thereof (e.g., any suitable combination), but the present disclosure is not limited thereto.

[0082] The organic material and the inorganic material may be mixed in one coating layer, or a coating layer including the organic material and a coating layer including the inorganic material may be stacked.

[0083] The rechargeable lithium battery may be classified into a cylindrical battery, a prismatic battery, a pouch battery, a coin-type (or coin-like) battery, etc., according to its shape. Figures 1 to 4 are schematic diagrams each showing a rechargeable lithium battery according to one or more embodiments. Figure 1 shows a cylindrical battery, Figure 2 shows a prismatic battery, Figure 3 and Figure 4 shows a pouch or pouch-like battery. Refer to Figures 1 to 4, a 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 included in the housing 50. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. As Figure 1 shown, the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. In Figure 2 , the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As Figure 3 shown, the rechargeable lithium battery 100 may include electrode tabs, and the electrode tabs may be, for example, a positive electrode tab 71 and a negative electrode tab 72 that serve as a circuit path for guiding the current formed in the electrode assembly 40 to the outside. As Figure 4 shown, the rechargeable lithium battery 100 may include an electrode tab 70 that serves as a circuit path for guiding the current formed in the electrode assembly 40 to the outside.

[0084] As a non-limiting example, a rechargeable lithium battery according to one or more embodiments may be applied to an automobile, a mobile phone, and / or one or more suitable types of electrical devices.

[0085] Terms such as “substantially,” “about,” and “approximately” are used as relative terms and not as terms of degree, and are intended to account for the inherent deviations of measured or calculated values that would be recognized by a person of ordinary skill in the art. They may include the stated value and an acceptable range of deviations as determined by a person of ordinary skill in the art, taking into account the limitations and errors associated with the measurement of that quantity. For example, “about” may refer to one or more standard deviations, or within ±30%, ±20%, ±10%, ±5% of the stated value.

[0086] The numerical ranges disclosed herein include and are intended to disclose all sub-ranges having the same numerical precision. For example, the range “1.0 to 10.0” includes all sub-ranges having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, by way of example, 2.4 to 7.6. Accordingly, the applicant reserves the right to amend the specification and claims to expressly recite any sub-ranges that are included within the ranges expressly recited herein.

[0087] Hereinafter, exemplary and comparative examples of the present disclosure are described. However, these examples are not to be construed as limiting the scope of the present disclosure in any sense.

[0088] Examples Example 1 0.5 wt% of polyvinyl chloride polymer, 5 wt% of silicon-carbon composite negative electrode active material, 92 wt% of negative electrode active material, 1.5 wt% of carboxymethyl cellulose, and 1 wt% of styrene-butadiene rubber are mixed in an aqueous solvent to prepare a slurry for the negative electrode active material layer.

[0089] The polyvinyl chloride polymer has a shrinkage rate of 80% at 180 °C relative to the volume at room temperature (25 °C), which is represented by Equation 1, and has a shrinkage rate of 90% at 180 °C relative to the length at room temperature (25 °C), which is represented by Equation 2.

[0090] Equation 1 Shrinkage rate of volume (%) = [(Volume at room temperature (25 °C) - Volume at 180 °C) / Volume at room temperature (25 °C)] × 100.

[0091] Equation 2 Shrinkage rate of length (%) = [(Length at room temperature (25 °C) - Length at 180 °C) / Length at room temperature (25 °C)] × 100.

[0092] The silicon-carbon composite includes an aggregation product of secondary particles that are aggregates of silicon nanoparticles with an average particle size of 100 nanometers (nm), and a soft carbon coating layer on the surface of the aggregation product (e.g., secondary particles). Based on 100 wt% of the silicon-carbon composite, the amount of silicon nanoparticles is 60 wt%, and the amount of soft carbon (amorphous carbon) is 40 wt%. The soft carbon coating layer has a thickness of 100 nm.

[0093] The slurry for the negative electrode active material layer is coated on a Cu foil current collector, dried, pressed, and vacuum dried at 180 °C for 8 hours to prepare a negative electrode in which the negative electrode active material layer is on the current collector.

[0094] According to the general procedure, a half-cell is fabricated using the negative electrode, a lithium metal counter electrode, and an electrolyte. The electrolyte is used by dissolving 1 M LiPF6 in a mixed solvent of ethylene carbonate and dimethyl carbonate (volume ratio 3:7).

[0095] In the context of this application and unless otherwise defined, the term "use" and its variants can be considered to be synonymous with the term "utilize" and its variants, respectively. In addition, the use of "may" when describing embodiments of the present invention refers to "one or more embodiments of the present invention".

[0096] A battery management system (BMS) device and / or any other related device or component according to embodiments of the present disclosure described herein can be implemented using any suitable hardware, firmware (e.g., application specific integrated circuit), software, or a combination of software, firmware, and hardware. For example, the components of the device can be formed on one integrated circuit (IC) chip or separate IC chips. Additionally, the components of the device can be implemented on a flexible printed circuit membrane, tape carrier package (TCP), printed circuit board (PCB), or formed on a substrate. Further, the components of the device can be processes or threads that run on one or more processors in one or more computing devices, execute computer program instructions, and interact with other system components to perform the functions described herein. The computer program instructions are stored in a memory, which can be implemented in a computing device using a standard memory device (such as random access memory (RAM) for example). The computer program instructions can also be stored in other non-transitory computer-readable media such as, for example, CD-ROMs, flash drives, etc. Additionally, those skilled in the art will recognize that, without departing from the scope of the present disclosure, the functions of a computing device can be combined or integrated into a single computing device, or the functions of a particular computing device can be distributed across one or more other computing devices.

[0097] Although the present disclosure has been described in connection with what are presently considered to be practical example embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments, but on the contrary, is intended to cover one or more suitable modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents.

Claims

1. A negative electrode, the negative electrode comprising: A current collector; And A negative electrode active material layer on the current collector and comprising: a polymer, the volume or length of the polymer being configured to decrease at a set temperature; and a negative electrode active material, Wherein the negative electrode is for a rechargeable lithium battery.

2. The negative electrode according to claim 1, wherein, The set temperature is 120°C to 200°C.

3. The negative electrode according to claim 1, wherein, The polymer has a reduction rate of 70% to 99% represented by Equation 1, the reduction rate being the ratio of the volume of the polymer at 120°C to 200°C to the volume of the polymer at room temperature: Equation 1 Volume reduction rate = [(Volume at room temperature - Volume at 120°C to 200°C) / Volume at room temperature] × 100%.

4. The negative electrode according to claim 1, wherein, The polymer has a reduction rate of 70% to 99% represented by Equation 2, the reduction rate being the ratio of the length of the polymer at 120°C to 200°C to the length of the polymer at room temperature: Equation 2 Length reduction rate = [(Length at room temperature - Length at 120°C to 200°C) / Length at room temperature] × 100%.

5. The negative electrode according to claim 1, wherein, The polymer comprises polyvinyl chloride.

6. The negative electrode according to claim 1, wherein, Based on 100 wt% of the negative electrode active material layer, the amount of the polymer is 0.1 wt% to 1.0 wt%.

7. The negative electrode according to claim 1, wherein, The weight ratio of the negative electrode active material to the polymer is a weight ratio of 99.9:0.1 to 99.0:1.

0.

8. The negative electrode according to claim 1, wherein, The negative electrode active material layer has a porosity of 20% to 30%.

9. The negative electrode according to claim 1, wherein The negative electrode active material comprises a carbon-based negative electrode active material, a Si-based negative electrode active material, and / or a combination thereof.

10. The negative electrode according to claim 9, wherein, The carbon-based negative electrode active material comprises crystalline carbon, amorphous carbon, and / or a combination thereof.

11. The negative electrode according to claim 9, wherein, The Si-based negative electrode active material comprises: Silicon; Silicon-carbon composite; SiO x , 0 < x ≤ 2; Si-Q alloy, Q comprising an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element other than Si, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and / or a combination thereof; and / or A combination thereof.

12. The negative electrode according to claim 1, wherein, The negative electrode active material layer further comprises a binder.

13. The negative electrode according to claim 1, wherein, The negative electrode active material layer further comprises a conductive material.

14. The negative electrode according to claim 1, wherein, The negative electrode active material layer is prepared by the following steps: Coating a negative electrode active material layer composition on the current collector, the negative electrode active material layer composition comprising: the polymer, the volume or length of the polymer being configured to decrease at the set temperature; the negative electrode active material; and a solvent; Drying the current collector having the negative electrode active material layer composition to provide a dried product; Pressing the dried product to provide a pressed product; and Performing vacuum drying on the pressed product.

15. The negative electrode according to claim 14, wherein, The vacuum drying is performed at 120°C to 200°C.

16. The negative electrode according to claim 1, wherein, The negative electrode active material layer has empty spaces.

17. A method for preparing a negative electrode active material layer, the method comprising: Coating a negative electrode active material layer composition on a current collector, the composition comprising: a polymer, the volume or length of the polymer decreasing at a set temperature; a negative electrode active material; and a solvent; Dry the current collector having the negative electrode active material layer composition to provide a dried product; Pressurize the dried product to provide a pressurized product; and Perform vacuum drying on the pressurized product.

18. The method according to claim 17, wherein, The vacuum drying is carried out at 120 °C to 200 °C.

19. The method according to claim 17, wherein, The vacuum drying provides empty spaces in the negative electrode active material layer.

20. A rechargeable lithium battery, the rechargeable lithium battery comprising: A negative electrode according to any one of claims 1 to 16; A positive electrode; and An electrolyte.

Images