Negative electrode and secondary battery containing the same

Abstract

The present invention relates to a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, the negative electrode active material including a first negative electrode active material and a second negative electrode active material, the first negative electrode active material being coated artificial graphite particles including primary artificial graphite particles and an amorphous carbon coating layer disposed on the primary artificial graphite particles, the second negative electrode active material being uncoated artificial graphite particles in a secondary particle form in which two or more primary artificial graphite particles are granulated, and the average particle diameter (D 50 ) to the average particle size (D 50 ) for the negative electrode is 1.2 to 4.7.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2021-0174644 dated December 8, 2021, and all content disclosed in the said Korean Patent Application is incorporated herein by reference.

[0002] This invention relates to a negative electrode and a secondary battery including the same. [Background technology]

[0003] With the rapid increase in the use of fossil fuels, the need for alternative and clean energy sources is growing, and one of the most actively researched areas in this field is power generation and energy storage using electrochemical reactions.

[0004] Currently, a typical example of an electrochemical element that uses electrochemical energy is the secondary battery, and its range of applications is gradually expanding. Recently, with the increase in technological development and demand for portable devices such as mobile computers, mobile phones, and cameras, the demand for secondary batteries as an energy source has been rapidly increasing. Furthermore, in order to improve the convenience of using secondary batteries, there is a need to shorten charging times, and consequently, there is a demand for excellent rapid charging performance.

[0005] Generally, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode contains a negative electrode active material that inserts and removes lithium ions that have escaped from the positive electrode.

[0006] Generally, graphite-based active materials, such as natural graphite or synthetic graphite, are used as the negative electrode active material. However, while conventionally used natural graphite is advantageous in that it is inexpensive and offers high cost performance, its irregular structure causes problems such as significant irreversible reactions due to electrolyte penetration and decomposition when applied to batteries. Conventionally used synthetic graphite is advantageous in that it has excellent initial charge-discharge efficiency, but it has the problem of lower discharge capacity than natural graphite, resulting in reduced battery capacity and energy density.

[0007] To solve these problems, conventional methods have used negative electrode active materials that are a mixture of ordinary natural graphite and artificial graphite, or negative electrode active materials in which an amorphous carbon coating layer is formed on ordinary natural graphite or artificial graphite. However, in such cases, the electrode is not rolled sufficiently, making it impossible to reduce the thickness of the electrode and the cell, resulting in a problem of reduced energy density.

[0008] Japanese Patent Publication No. 2019-179687 discloses an artificial graphite-based negative electrode material and a negative electrode for a non-aqueous secondary battery containing the same, but it has not been able to present an alternative to the above-mentioned problems. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2019-179687 [Overview of the project] [Problems that the invention aims to solve]

[0010] One objective of the present invention is to provide a negative electrode that has high energy density and excellent rapid charging performance and output performance.

[0011] Another object of the present invention is to provide a secondary battery including the negative electrode described above. [Means for solving the problem]

[0012] The present invention comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises a first negative electrode active material and a second negative electrode active material, the first negative electrode active material is coated-artificial graphite particles comprising primary artificial graphite particles and an amorphous carbon coating layer located on the primary artificial graphite particles, the second negative electrode active material is uncoated-artificial graphite particles in the form of secondary particles obtained by granulating two or more primary artificial graphite particles, and the average particle size (D 50 ) with respect to the average particle size (D 50 The ratio of the negative electrode is 1.2 to 4.7.

[0013] Furthermore, the present invention provides a secondary battery comprising the above-mentioned negative electrode, a positive electrode facing the negative electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte. [Effects of the Invention]

[0014] The anode of the present invention comprises a first anode active material which is coated artificial graphite particles including primary artificial graphite particles and an amorphous carbon coating layer, and a second anode active material which is uncoated artificial graphite particles in the form of secondary particles formed from granulated primary artificial graphite particles, wherein the average particle size (D) of the first anode active material and the second anode active material 50 The ratio of the first negative electrode active material is adjusted to a specific range. According to the negative electrode of the present invention, the first negative electrode active material can be placed in the empty space between the second negative electrode active material and packed, the rollability is improved by the relatively soft second negative electrode active material, the energy density of the negative electrode can be improved, and the first negative electrode active material, which is in the form of an amorphous carbon coating layer formed on primary artificial graphite particles, can be placed between the second negative electrode active material, which can contribute to reducing the resistance of the negative electrode and improving the rapid charging performance, making it possible to realize a negative electrode and secondary battery with high energy density and excellent output characteristics and rapid charging performance. [Modes for carrying out the invention]

[0015] The present invention will be described in more detail below to facilitate understanding of it.

[0016] The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0017] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0018] In this specification, terms such as “include,” “equip,” or “have” indicate the presence of implemented features, figures, steps, components, or combinations thereof, and should be understood not to preclude the existence or possibility of adding one or more different features, figures, steps, components, or combinations thereof.

[0019] In this specification, D 50 Each of these can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve (graph curve of particle size distribution). 50 This can be measured, for example, using the laser diffraction method. The laser diffraction method can generally measure particle sizes from the submicron region to several millimeters in size, and can obtain highly reproducible and high-resolution results.

[0020] <Negative electrode> This invention relates to a negative electrode, specifically a negative electrode for a lithium secondary battery.

[0021] The negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises a first negative electrode active material and a second negative electrode active material, the first negative electrode active material is coated-artificial graphite particles comprising primary artificial graphite particles and an amorphous carbon coating layer located on the primary artificial graphite particles, the second negative electrode active material is uncoated-artificial graphite particles in the form of secondary particles obtained by granulating two or more primary artificial graphite particles, and the average particle size (D 50 ) with respect to the average particle size (D 50 The ratio of ) is characterized by being between 1.2 and 4.7.

[0022] The anode of the present invention comprises a first anode active material which is coated artificial graphite particles including primary artificial graphite particles and an amorphous carbon coating layer, and a second anode active material which is uncoated artificial graphite particles in the form of secondary particles formed from granulated primary artificial graphite particles, wherein the average particle size (D) of the first anode active material and the second anode active material 50 The ratio of the first negative electrode active material is adjusted to a specific range. According to the negative electrode of the present invention, the first negative electrode active material can be placed in the empty space between the second negative electrode active material and packed, the rollability is improved by the relatively soft second negative electrode active material, the energy density of the negative electrode can be improved, and the first negative electrode active material, which is in the form of an amorphous carbon coating layer formed on primary artificial graphite particles, can be placed between the second negative electrode active material, which can contribute to reducing the resistance of the negative electrode and improving the rapid charging performance, making it possible to realize a negative electrode and secondary battery with high energy density and excellent output characteristics and rapid charging performance.

[0023] The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.

[0024] The negative electrode current collector only needs to be conductive without causing chemical changes to the battery, and is not particularly limited. For example, as the negative electrode current collector, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface treatment of the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used. Specifically, transition metals that adsorb carbon well, such as copper and nickel, can be used as the negative electrode current collector. The thickness of the negative electrode current collector can be 6 μm to 20 μm, but the thickness of the current collector is not limited thereto.

[0025] The negative electrode active material layer is disposed on at least one surface of the negative electrode current collector. Specifically, the negative electrode active material layer can be disposed on one surface or both surfaces of the negative electrode current collector.

[0026] The negative electrode active material layer contains a negative electrode active material. The negative electrode active material contains a first negative electrode active material and a second negative electrode active material. Here, the ratio of the average particle size (D 50 ) of the second negative electrode active material to the average particle size (D 50 ) of the first negative electrode active material is 1.2 to 4.7.

[0027] According to the present invention, the first negative electrode active material is coated-artificial graphite particles in which an amorphous carbon coating layer is formed on primary artificial graphite particles, the second negative electrode active material is uncoated-artificial graphite particles in the form of secondary particles, and the first negative electrode active material and the second negative electrode active material are included in the negative electrode active material layer at a ratio of appropriate average particle sizes (D 50 ). Since the second negative electrode active material has a secondary particle form, it can not only exhibit excellent rapid charging performance but also have excellent rolling performance. Further, the first negative electrode active material has an average particle size (D 50Because it has the properties described above, when placed between the second negative electrode active materials, the packing properties of the negative electrode active material layer can be improved. Furthermore, the first negative electrode active material includes an amorphous carbon coating layer placed on its surface, and when the first negative electrode active material is placed between the second negative electrode active materials, it can contribute to improved charge mobility and reduced resistance. The negative electrode according to the present invention can improve energy density due to its excellent rollability, as well as improve rapid charging performance and output performance.

[0028] For example, the average particle size (D) of the first negative electrode active material. 50 ) with respect to the average particle size (D 50 If the ratio of the first negative electrode active material to the second negative electrode active material is less than 1.2, the first negative electrode active material layer may not be packed to a desirable level between the second negative electrode active material, which may lead to a decrease in energy density, and the small particle size of the first negative electrode active material may clog the voids, potentially reducing the rapid charging performance and output performance. On the other hand, if the average particle size of the first negative electrode active material is less than 1.2, 50 ) with respect to the average particle size (D 50 If the ratio exceeds 4.7, the differential generated by particle cracking during rolling may reduce the rapid charging performance and output performance.

[0029] Specifically, the average particle size (D) of the first negative electrode active material 50 ) with respect to the average particle size (D 50 The ratio can be 2.0 to 3.5, in which case the aforementioned energy density, fast charging performance, and output performance can be further improved.

[0030] The first negative electrode active material is coated artificial graphite particles, which include primary artificial graphite particles and an amorphous carbon coating layer located on the primary artificial graphite particles.

[0031] The term "primary artificial graphite particles" may refer to artificial graphite particles in single-particle form and is used to distinguish them from "secondary artificial graphite particles," which are aggregates formed when two or more primary artificial graphite particles are aggregated by an intentional granulation or bonding process.

[0032] The first negative electrode active material (coated artificial graphite particles) according to the present invention contains a hard amorphous carbon coating layer compared to graphite. Therefore, when the first negative electrode active material is placed between the second negative electrode active materials, its shape can be maintained even by rolling. This can contribute to improving the overall charge transfer performance of the negative electrode, reducing resistance, and improving rapid charging performance. Furthermore, the first negative electrode active material has a smaller average particle size (D) compared to the second negative electrode active material, which is preferable. 50 Because it has the properties of ), the packing properties of the negative electrode active material layer are improved, and the energy density of the negative electrode can be increased. If the first negative electrode active material does not contain an amorphous carbon coating layer, the conductivity will decrease, which may affect the structure of the voids after rolling, and may reduce the rapid charging performance and output performance.

[0033] The amorphous carbon coating layer can be included in the first negative electrode active material in an amount of 1% to 10% by weight, specifically 3% to 5% by weight.

[0034] The amorphous carbon coating layer can be formed by providing a carbon precursor to the primary artificial graphite particles and then heat-treating them. The carbon precursor can be, but is not limited to, polymer resins such as sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, polyacrylonitrile resin, polyamide resin, furan resin, cellulose resin, styrene resin, polyimide resin, epoxy resin, vinyl chloride resin, and polyvinyl chloride; or pitches such as coal-based pitch, petroleum-based pitch, and mesophase pitch. The heat treatment temperature can be 1,000°C to 1,800°C.

[0035] The average particle size (D) of the first negative electrode active material 50 The specific surface area of ​​the first negative electrode active material can be 4 μm to 13 μm, specifically 7 μm to 10 μm. When it is within this range, the specific surface area of ​​the first negative electrode active material can be reduced to a desirable level, which not only contributes to improving the capacity of the negative electrode but also allows for dense filling of the empty space formed between the second negative electrode active material, which will be described later, thereby improving the rolling performance.

[0036] The BET specific surface area of ​​the first negative electrode active material is 0.1 m². 2 / g~3.0m 2 / g, specifically 0.5m 2 / g~2.0m 2 The BET specific surface area can be as follows: it can be as / g, and when it is within the aforementioned range, it is preferable in that side reactions of the electrolyte are minimized and high-temperature output performance can be improved. The BET specific surface area can be measured using a BEL Sorption instrument (manufactured by BEL Japan).

[0037] The second negative electrode active material is uncoated artificial graphite particles in a secondary particle form, formed by granulating two or more primary artificial graphite particles. As artificial graphite particles in a secondary particle form, the second negative electrode active material not only has excellent rapid charging performance but also excellent rolling performance due to the voids formed between the primary artificial graphite particles present inside.

[0038] The aforementioned uncoated artificial graphite particles may mean artificial graphite particles in which the artificial graphite is completely exposed on the surface, as they are not coated. More specifically, the aforementioned uncoated artificial graphite particles may consist of uncoated artificial graphite particles or may not include another coating layer (such as an amorphous carbon coating layer). For example, when secondary artificial graphite particles with an amorphous carbon coating layer are used as the second negative electrode active material, the negative electrode active material layer is not sufficiently compressed by rolling, energy density is not secured, particle cracking occurs, and problems arise in which rapid charging performance and output performance are reduced due to an increase in specific surface area, worsening of electrolyte side reactions, and clogging of voids.

[0039] The uncoated artificial graphite particles can be produced by mixing coke and binder pitch, then performing high-temperature heat treatment to produce primary artificial graphite particles, mixing the primary artificial graphite particles with binder pitch, and then performing high-temperature heat treatment, specifically at a temperature of 2,500°C to 3,200°C. This high-temperature heat treatment graphitizes the binder pitch, making it possible to produce uncoated artificial graphite particles that do not contain coating materials such as amorphous carbon. The high-temperature heat treatment preferably has a total heat treatment time (considering heating, maintaining the heat treatment temperature, and temperature decrease) of 1 to 3 weeks, and the heat treatment temperature maintenance time is preferably 48 to 70 hours, in order to ensure sufficient graphitization. The coke may be needle coke and / or isotropic coke, the coke and the binder pitch may be mixed in a weight ratio of 80:20 to 95:5, and the primary particles and the binder pitch may be mixed in a weight ratio of 80:20 to 95:5.

[0040] The aforementioned uncoated artificial graphite particles have an average particle size (D 50 The particle size can be granulated from two or more primary artificial graphite particles having a particle size of 7 μm to 10 μm. When the average particle size of the primary artificial graphite particles contained in the uncoated artificial graphite particles is within the above range, the volume is adjusted to a preferred level, and the average particle size of the primary artificial graphite particles (D 50 A decrease in rapid charging performance due to an excessively large ) can be prevented. More specifically, in the uncoated artificial graphite particles, the average particle size (D) of the primary artificial graphite particles can be prevented. 50 Specifically, the particle size can be 8 μm to 9 μm. When the average particle size of the primary artificial graphite particles is within the above range, the development capacity can be sufficiently maintained while also maintaining high charging characteristics such as rapid charging.

[0041] The average particle size of the second negative electrode active material (D 50 The particle size can be 15 μm to 25 μm, specifically 17 μm to 22 μm. When it is within this range, a decrease in rapid charging performance due to excessive particle size is prevented, and the specific surface area of ​​the active material is adjusted to a favorable level, which is advantageous for improving high-temperature performance.

[0042] The BET specific surface area of ​​the second negative electrode active material is 0.1 m². 2 / g~3.0m 2 / g, specifically 0.5m 2 / g~2.0m 2 The BET specific surface area can be as follows: it can be as / g, and when it is within the aforementioned range, it is preferable in that side reactions of the electrolyte can be minimized and high-temperature output performance can be improved. The BET specific surface area can be measured using a BEL Sorption instrument (manufactured by BEL Japan).

[0043] The first negative electrode active material and the second negative electrode active material can independently have at least one shape selected from the group consisting of plate-like, needle-like, and polygonal shapes. In this case, the negative electrode active materials can be densely arranged on the negative electrode, improving packing properties and advantageously contributing to an improvement in the energy density of the negative electrode.

[0044] The first negative electrode active material and the second negative electrode active material can be included in the negative electrode active material layer in a weight ratio of 10:90 to 80:20, specifically 25:75 to 50:50. This range is preferable because it allows for good maintenance of the void structure even in high-energy-density electrodes.

[0045] The tap density of the negative electrode active material can be 1.00 g / cc to 1.20 g / cc, specifically 1.03 g / cc to 1.05 g / cc. When the tap density of the negative electrode active material is within this range, the tap density is sufficiently high, allowing for a thin coating during electrode coating.

[0046] The tap density refers to the mass per unit volume of a powder composed of particles, and means the density obtained by filling the gaps between particles by tapping or vibrating them at a constant rate. Factors that affect the tap density include particle size distribution, moisture content, particle shape, and cohesiveness. The tap density can be used to predict the fluidity and compressibility of a substance. The tap density can be measured in accordance with ASTM D4781 and can be calculated using the formula TD = W / V (TD: tap density, W: weight of the sample (g), V: volume of the sample after tapping).

[0047] The BET specific surface area of ​​the negative electrode active material is 0.1 m². 2 / g~3.0m 2 / g, specifically 0.5m 2 / g~2.0m 2 / g, more specifically 1.3m 2 / g~1.5m 2 The BET specific surface area can be as follows: it can be as / g, and when it is within the aforementioned range, it is preferable in that side reactions of the electrolyte can be minimized and high-temperature output performance can be improved. The BET specific surface area can be measured using a BEL Sorption instrument (manufactured by BEL Japan).

[0048] The average particle size (D) of the negative electrode active material 50 The particle size can be 12 μm to 20 μm, specifically 14 μm to 18 μm.

[0049] During XRD analysis (X-ray Diffraction analysis) of the negative electrode active material, the crystal size La(100) in the a-axis direction can be 200 nm to 300 nm, and the crystal size Lc(002) in the c-axis direction can be 50 nm to 100 nm. When the crystal size is within this range, the crystallinity of the particles is adjusted to a sufficient degree, which is preferable in terms of capacity development and improvement of rapid charging performance.

[0050] In this specification, La(100) means the width of the crystallite in the a-axis direction calculated based on the diffraction lines of the (100) crystal plane during XRD analysis of the particles, and means the crystal size in the (100) plane in the a-axis direction, and Lc(002) means the width of the crystallite in the c-axis direction calculated based on the diffraction lines of the (002) crystal plane during XRD analysis of the particles, and means the crystal size in the (002) plane in the c-axis direction of the uncoated artificial graphite particles.

[0051] During XRD analysis (X-ray Diffraction analysis) of the negative electrode active material, the crystal size La(100) in the a-axis direction can be specifically 210 nm to 290 nm, and more specifically 230 nm to 270 nm. Furthermore, during XRD analysis (X-ray Diffraction analysis) of the coated artificial graphite particles, the crystal size Lc(002) in the c-axis direction can be 60 nm to 90 nm, and more specifically 65 nm to 85 nm.

[0052] In this specification, La(100) and Lc(002) can be measured by XRD analysis. Specifically, XRD analysis can be performed using a Bruker AXS D4 Endeavor XRD (voltage: 40kV, current: 40mA) under Cu-Ka radiation conditions (wavelength: 1.54Å) and at a scanning speed of 87.5 seconds for every 0.02° from 2-Theta 10° to 90°. From the measurement results, the full width at half maximum (FWHM) of the (002) crystal peak shown around 20° to 30° and the full width at half maximum of the (100) crystal peak shown around 38° to 50° can be measured, and the Lc(002) and La(100) values ​​can be obtained by calculation using Scherrer's formula.

[0053] The negative electrode active material can be contained in the negative electrode active material layer in an amount of 80% to 99% by weight, preferably 88% to 98% by weight.

[0054] The negative electrode active material layer may further include, in addition to the negative electrode active material described above, a binder, a conductive material, and / or a thickening agent.

[0055] The binder can typically be included in the negative electrode active material layer in an amount of 1% to 30% by weight, preferably 1% to 10% by weight, as a component that facilitates bonding between the active material and / or the current collector.

[0056] The binder may include at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber, preferably at least one selected from polyvinylidene fluoride and styrene-butadiene rubber.

[0057] As the aforementioned thickening agent, all thickening agents conventionally used in lithium secondary batteries can be used, one example being carboxymethylcellulose (CMC).

[0058] The conductive material can be included in the negative electrode active material layer in an amount of 1% to 30% by weight, preferably 1% to 10% by weight, as a component to further improve the conductivity of the negative electrode active material.

[0059] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. Examples of such materials include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. Specific examples of commercially available conductive materials include acetylene black (products from Chevron Chemical Company and Denka Black (manufactured by Denka Singapore Private Limited)), Gulf Oil Company, Ketjenblack, EC (manufactured by Armak Company), Vulcan XC-72 (manufactured by Cabot Company), and Super P (manufactured by Timcal).

[0060] The thickness of the negative electrode active material layer can be 10 μm to 150 μm, specifically 50 μm to 100 μm, but is not limited to this.

[0061] The rolling density of the negative electrode can be 1.5 g / cc to 2.0 g / cc, specifically 1.6 g / cc to 1.8 g / cc. According to the present invention, two types of artificial graphite particles have a preferred average particle size (D 50 By being included in the negative electrode according to the ratio of ), it is possible to realize a negative electrode that has excellent energy density, and in particular, has improved rapid charging performance even at the aforementioned rolling density.

[0062] The negative electrode active material layer can be manufactured by mixing the above-mentioned negative electrode active material with at least one selected from a binder, a conductive material, and a thickener in a solvent to produce a negative electrode slurry, and then applying the negative electrode slurry to the negative electrode current collector, rolling it, and drying it.

[0063] The solvent may include water or an organic solvent such as NMP (N-methyl-2-pyrrolidone), and can be used in an amount that results in a desirable viscosity when the negative electrode active material and, selectively, a binder and a conductive material are included. For example, the solvent may be included such that the concentration of solids, which includes the negative electrode active material and at least one selected selectively from the binder, thickener and conductive material, is 50% to 95% by weight, preferably 70% to 90% by weight.

[0064] <Secondary battery> Furthermore, the present invention provides a secondary battery including the above-described negative electrode, more specifically a lithium secondary battery.

[0065] The secondary battery may include the negative electrode, the positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte.

[0066] The positive electrode can face the negative electrode.

[0067] The positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.

[0068] The positive electrode current collector can be any negative electrode current collector commonly used in the art, and is not particularly limited as long as it does not cause chemical changes in the secondary battery and has high conductivity. For example, the positive electrode current collector may include at least one selected from copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and aluminum-cadmium alloys, preferably aluminum.

[0069] The positive electrode current collector can also have fine irregularities formed on its surface to strengthen the bonding force of the positive electrode active material, and can be used in various forms such as films, sheets, foils, meshes, porous materials, foams, and nonwoven fabrics.

[0070] The positive electrode current collector can generally have a thickness of 3 μm to 500 μm.

[0071] The positive electrode active material layer can contain a positive electrode active material.

[0072] The positive electrode active material can include a compound capable of reversible intercalation and deintercalation of lithium, specifically, a lithium composite metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium. More specifically, the lithium composite metal oxide includes lithium-manganese-based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (e.g., LiCoO2, etc.), lithium-nickel-based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese-based oxides (e.g., LiNi 1-Y Mn Y O2 (where 0 < Y < 1), LiMn 2-z Ni z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (where 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where 0 < Y2 < 1), LiMn 2-z1 Co z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co q Mn r1 )O2 (where 0 < p < 1, 0 < q < 1, 0 < r1 < 1, p + q + r1 = 1) or Li(Ni<000005 (4)Co q1 Mn r2 )O4 (where 0 < p1 < 2, 0 < q1 < 2, 0 < r2 < 2, p1 + q1 + r2 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni p2 Co q2 Mn r3 M S2)O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are, as the atomic fractions of independent elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc.), and one or more of these compounds can be included. Among them, in terms of being able to enhance the capacity characteristics and stability of the battery, the lithium composite metal oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (for example, Li(Ni 0.8 Mn 0.15 Co 0.05 [[ID=Z24]])O2, etc.), etc. can be used. Considering the remarkable improvement effect by controlling the types and content ratios of the constituent elements forming the lithium composite metal oxide, the lithium composite metal oxide is Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 ?)O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni ? 0.8 Mn 0.1 Co 0.1 )O2, etc. can be used, and one or more mixtures of these can be used. <00,00373>

[0073] The positive electrode active material can be contained in the positive electrode active material layer at 80% to 99% by weight.

[0074] It should be noted that there seem to be some unclear or potentially incorrect tags in the original text (such as the "?" in the translated text), which may need to be further verified in the original source to ensure accurate translation.The positive electrode active material layer may further include, together with the positive electrode active material, at least one selected from the group consisting of a binder and a conductive material.

[0075] The binder is typically added in an amount of 1 to 30% by weight relative to the total weight of the positive electrode mixture, as a component that facilitates the bonding of the active material to the conductive material and to the current collector. Examples of such binders include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, and fluororubber.

[0076] The binder can be contained in the positive electrode active material layer in an amount of 1% to 30% by weight.

[0077] The conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive. Examples of such materials include graphite; carbon-based materials such as carbon black, acetylene black, Ketjenblack, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. Specific examples of commercially available conductive materials include acetylene black-based materials (products from Chevron Chemical Company and Denka Black (manufactured by Denka Singapore Private Limited)), products from Gulf Oil Company, Ketjenblack, EC-based materials (manufactured by Armak Company), Vulcan XC-72 (manufactured by Cabot Company), and Super P (manufactured by Timcal).

[0078] The conductive material can be added to the positive electrode active material layer in an amount of 1% to 30% by weight.

[0079] The separator separates the negative and positive electrodes and provides a passage for lithium ions to move. Generally, any separator used in lithium secondary batteries can be used without particular limitations, but those with low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity are particularly preferred. Specifically, porous polymer films, such as polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof, can be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, coated separators containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength, and can be selectively used in single-layer or multi-layer structures.

[0080] Furthermore, the electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0081] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0082] The aforementioned organic solvent can be used without particular limitations, as long as it serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvents that can be used include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes. Among these, carbonate-based solvents are preferred, and more preferably, a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant, which can improve the charge and discharge performance of the battery, and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate). In this case, by mixing the cyclic carbonate and the linear carbonate in a volume ratio of about 1:1 to about 1:9, the electrolyte can exhibit excellent performance.

[0083] The lithium salt can be any compound capable of providing lithium ions for use in lithium secondary batteries, without any particular limitations. Specifically, examples of lithium salts that can be used include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably within the range of 0.1 to 2.0 M. When the concentration of the lithium salt falls within this range, the electrolyte exhibits excellent electrolyte performance due to having appropriate conductivity and viscosity, and lithium ions can move effectively.

[0084] As described above, the lithium secondary battery according to the present invention exhibits excellent discharge capacity, rapid charging characteristics, and stable capacity retention, making it useful in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs). In particular, it can be preferably used as a component battery in medium- and large-sized battery modules. Therefore, the present invention also provides a medium- and large-sized battery module that includes the secondary battery described above as a unit battery.

[0085] Such medium- and large-sized battery modules can be preferably applied as power sources requiring high output and large capacity, such as electric vehicles, hybrid electric vehicles, and power storage devices.

[0086] Hereinafter, embodiments of the present invention will be described in detail so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in a variety of different forms and is not limited to the embodiments described herein.

[0087] Examples and Comparative Examples Example 1: Manufacturing of the negative electrode 1. Manufacturing of the first negative electrode active material Single-particle primary artificial graphite particles (average particle diameter (D 50 ): 8 μm) were prepared. After mixing the primary artificial graphite particles with pitch, heat treatment was performed at 1,300 °C for 12 hours to produce coated-artificial graphite particles in which an amorphous carbon coating layer was located on the primary artificial graphite particles.

[0088] The amorphous carbon coating layer was formed at 4% by weight on the coated-artificial graphite particles.

[0089] The average particle diameter (D 50 ) of the coated-artificial graphite particles was 8 μm.

[0090] 2. Production of the second negative electrode active material Uncoated-artificial graphite particles in the form of secondary particles (average particle diameter (D 50 ): 8 μm) in which a plurality of primary artificial graphite particles (average particle diameter (D 50 ): 20 μm) were aggregated were prepared.

[0091] Specifically, the uncoated-artificial graphite particles were obtained by pulverizing a coke raw material into coke having an average particle diameter (D 50 ) of 8 μm, then mixing the pulverized coke with pitch to produce an intermediate granulated into the form of secondary particles, gradually raising the temperature to 3,000 °C, maintaining 3,000 °C for 60 hours, and gradually lowering the temperature to room temperature for heat treatment to graphitize and form secondary particles, and adjusting the average particle diameter (D 50 ) of the secondary particles to 20 μm for production. Here, the total heat treatment time of the intermediate was 2 weeks.

[0092] The first negative electrode active material and the second negative electrode active material produced as described above were mixed at a weight ratio of 30:70 to produce the negative electrode active material of Example 1.

[0093] The average particle diameter (D 50 ) of the negative electrode active material was 17 μm, the BET specific surface area was 1.4 m 2 / g, and the tap density was 1.04 g / cc.

[0094] In addition, La(100), which is the crystal size in the a-axis direction measured by X-ray diffraction analysis of the negative electrode active material, was 242.5 nm, and Lc(002), which is the crystal size in the c-axis direction, was 72.5 nm.

[0095] Example 2: Production of negative electrode active material Average particle size (D 50 ) Coated artificial graphite particles were produced in the same manner as in Example 1, except that single-particle-form primary artificial graphite particles with an average particle size of 12 μm were used. The average particle size (D 50 ) of the coated artificial graphite particles was 12 μm.

[0096] The negative electrode active material of Example 2 was produced in the same manner as in Example 1, except that the coated artificial graphite particles produced as described above were used as the first negative electrode active material.

[0097] The average particle size (D 50 ) of the negative electrode active material was 18 μm, the BET specific surface area was 1.2 m 2 / g, and the tap density was 1.07 g / cc.

[0098] In addition, La(100), which is the crystal size in the a-axis direction measured by X-ray diffraction analysis of the negative electrode active material, was 241.5 nm, and Lc(002), which is the crystal size in the c-axis direction, was 71.8 nm.

[0099] Example 3: Production of negative electrode active material Average particle size (D 50 ) Coated artificial graphite particles were produced in the same manner as in Example 1, except that single-particle-form primary artificial graphite particles with an average particle size of 5 μm were used. The average particle size (D 50 ) of the coated artificial graphite particles was 5 μm.

[0100] The negative electrode active material of Example 3 was produced in the same manner as in Example 1, except that the coated artificial graphite particles produced as described above were used as the first negative electrode active material.

[0101] The average particle size (D 50 ) of the negative electrode active material was 15 μm, and the BET specific surface area was 1.6 m2 The value was / g, and the tap density was 1.06 g / cc.

[0102] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 240.5 nm, and the crystal size Lc(002) in the c-axis direction was 71.5 nm.

[0103] Example 4: Production of negative electrode active material The same first and second negative electrode active materials as those produced in Example 1 were prepared, and the first and second negative electrode active materials were mixed in a weight ratio of 70:30 to produce the negative electrode active material of Example 4.

[0104] The average particle size (D) of the negative electrode active material 50 The surface area is 13 μm, and the BET specific surface area is 1.8 m². 2 The value was / g, and the tap density was 1.11g / cc.

[0105] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 242.1 nm, and the crystal size Lc(002) in the c-axis direction was 71.4 nm.

[0106] Example 5: Production of negative electrode active material The same first and second negative electrode active materials as those produced in Example 1 were prepared, and the first and second negative electrode active materials were mixed in a weight ratio of 15:85 to produce the negative electrode active material of Example 5.

[0107] The average particle size (D) of the negative electrode active material 50 The surface area is 19 μm, and the BET specific surface area is 1.0 m². 2 The value was / g, and the tap density was 1.01 g / cc.

[0108] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 243.0 nm, and the crystal size Lc(002) in the c-axis direction was 71.9 nm.

[0109] Comparative Example 1: Manufacturing of Negative Electrode Active Material Single-particle form primary artificial graphite particles (average particle size (D 50 A material with a thickness of 8 μm was used as the first negative electrode active material. No amorphous carbon coating layer was formed on the first negative electrode active material.

[0110] The negative electrode active material of Comparative Example 1 was manufactured in the same manner as in Example 1, except that the first negative electrode active material was used.

[0111] The average particle size (D) of the negative electrode active material 50 The surface area is 17 μm, and the BET specific surface area is 1.8 m². 2 The value was / g, and the tap density was 0.99 g / cc.

[0112] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 241.3 nm, and the crystal size Lc(002) in the c-axis direction was 71.3 nm.

[0113] Comparative Example 2: Manufacturing of Negative Electrode Active Material 1. Manufacturing of the first negative electrode active material Single-particle form primary artificial graphite particles (average particle size (D 50 A material with a thickness of 6 μm was used as the first negative electrode active material. No amorphous carbon coating layer was formed on the first negative electrode active material.

[0114] 2. Manufacturing of the second negative electrode active material Average particle size of secondary particles (D 50 The second negative electrode active material was prepared in the same manner as in Example 1, except that the 20 μm was adjusted to 22 μm.

[0115] As described above, the first and second anode active materials were mixed in a weight ratio of 30:70 to produce the anode active material of Comparative Example 2.

[0116] The average particle size (D) of the negative electrode active material 50 The surface area is 15 μm, and the BET specific surface area is 2.1 m². 2The value was / g, and the tap density was 1.01 g / cc.

[0117] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 242.5 nm, and the crystal size Lc(002) in the c-axis direction was 71.6 nm.

[0118] Comparative Example 3: Production of Negative Electrode Active Material In Comparative Example 3, only the second negative electrode active material from Example 1 was used as the negative electrode active material.

[0119] The average particle size (D) of the negative electrode active material 50 The surface area is 20 μm, and the BET specific surface area is 1.2 m². 2 The value was / g, and the tap density was 0.97g / cc.

[0120] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 242.2 nm, and the crystal size Lc(002) in the c-axis direction was 71.5 nm.

[0121] Comparative Example 4: Production of Negative Electrode Active Material Uncoated artificial graphite particles, as used in Example 1, were prepared. After mixing the uncoated artificial graphite particles with pitch, the mixture was heat-treated at 1,300°C for 12 hours to form an amorphous carbon coating layer on the uncoated artificial graphite particles, which was used as the negative electrode active material for Comparative Example 4.

[0122] The amorphous carbon coating layer was formed at 3% by weight relative to the total weight of the amorphous carbon coating layer and the uncoated artificial graphite particles.

[0123] The average particle size (D) of the negative electrode active material 50 The surface area is 20 μm, and the BET specific surface area is 1.1 m². 2 The value was / g, and the tap density was 0.98 g / cc.

[0124] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 242.6 nm, and the crystal size Lc(002) in the c-axis direction was 71.1 nm.

[0125] Comparative Example 5: Production of Negative Electrode Active Material Only the first negative electrode active material from Example 1 was used as the negative electrode active material for Comparative Example 5.

[0126] The average particle size (D) of the negative electrode active material 50 The surface area is 8 μm, and the BET specific surface area is 2.0 m². 2 The value was / g, and the tap density was 1.07 g / cc.

[0127] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 242.7 nm, and the crystal size Lc(002) in the c-axis direction was 71.8 nm.

[0128] Comparative Example 6: Production of Negative Electrode Active Material 1. Manufacturing of the first negative electrode active material Single-particle form primary artificial graphite particles (average particle size (D 50 A material with a thickness of 8 μm was used as the first negative electrode active material. No amorphous carbon coating layer was formed on the first negative electrode active material.

[0129] 2. Manufacturing of the second negative electrode active material Uncoated artificial graphite particles, as used in Example 1, were prepared. After mixing the uncoated artificial graphite particles with pitch, the mixture was heat-treated at 1,300°C for 12 hours to form an amorphous carbon coating layer on the uncoated artificial graphite particles, which was used as the second negative electrode active material for Comparative Example 6.

[0130] The amorphous carbon coating layer was formed at 3% by weight relative to the total weight of the amorphous carbon coating layer and the uncoated artificial graphite particles.

[0131] The average particle size of the second negative electrode active material (D 50 The diameter was 20 μm.

[0132] As described above, the first and second negative electrode active materials were mixed in a weight ratio of 30:70 to produce the negative electrode active material of Comparative Example 6.

[0133] The average particle size (D) of the negative electrode active material 50 The surface area is 18 μm, and the BET specific surface area is 1.1 m². 2 The value was / g, and the tap density was 1.02 g / cc.

[0134] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 241.6 nm, and the crystal size Lc(002) in the c-axis direction was 71.6 nm.

[0135] Comparative Example 7: Production of Negative Electrode Active Material The anode active material of Comparative Example 7 was manufactured in the same manner as in Example 1, except that the second anode active material manufactured in Comparative Example 6 was used in place of the second anode active material of Example 1.

[0136] The average particle size (D) of the negative electrode active material 50 The surface area is 19 μm, and the BET specific surface area is 1.0 m². 2 The value was / g, and the tap density was 1.06 g / cc.

[0137] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 242.3 nm, and the crystal size Lc(002) in the c-axis direction was 71.4 nm.

[0138] Comparative Example 8: Production of Negative Electrode Active Material Average particle size (D 50 Coated artificial graphite particles were prepared in the same manner as in Example 1, except that 18 μm single-particle primary artificial graphite particles were used.

[0139] The average particle size (D) of the coated artificial graphite particles 50 The diameter was 18 μm.

[0140] The negative electrode active material of Comparative Example 8 was manufactured in the same manner as in Example 1, except that the coated artificial graphite particles manufactured as described above were used as the first negative electrode active material.

[0141] The average particle size (D) of the negative electrode active material 50 The surface area is 21 μm, and the BET specific surface area is 1.1 m². 2 The value was / g, and the tap density was 1.01 g / cc.

[0142] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 242.6 nm, and the crystal size Lc(002) in the c-axis direction was 71.9 nm.

[0143] Comparative Example 9: Production of Negative Electrode Active Material 1. Manufacturing of the first negative electrode active material Average particle size (D 50 Coated artificial graphite particles were manufactured in the same manner as in Example 1, except that primary artificial graphite particles in single particle form with a diameter of 5 μm were used. The average particle size (D) of the coated artificial graphite particles was also used. 50 The thickness was 5 μm.

[0144] 2. Manufacturing of the second negative electrode active material Average particle size of secondary particles (D 50 The second negative electrode active material was prepared in the same manner as in Example 1, except that the 20 μm was adjusted to 27 μm.

[0145] As described above, the first and second anode active materials were mixed in a weight ratio of 30:70 to produce the anode active material of Comparative Example 9.

[0146] The average particle size (D) of the negative electrode active material 50 The surface area is 24 μm, and the BET specific surface area is 1.1 m². 2 The value was / g, and the tap density was 1.08 g / cc.

[0147] Furthermore, the crystal size La(100) in the a-axis direction, measured by X-ray diffraction analysis of the negative electrode active material, was 242.8 nm, and the crystal size Lc(002) in the c-axis direction was 71.3 nm.

[0148] [Table 1]

[0149] [Table 2]

[0150] [Table 3]

[0151] Experimental example <Manufacturing of negative electrodes> 1. Manufacturing of the negative electrode A negative electrode slurry was prepared by adding the negative electrode active material produced in Example 1, styrene-butadiene rubber as a binder, carbon black as a conductive material, and carboxymethylcellulose (CMC) as a thickener in a weight ratio of 94:3:1:2 to water as a solvent. The negative electrode slurry was then added to a copper foil (negative electrode current collector) with a thickness of 8 μm at a concentration of 14 mg / cm². 2 After coating with the specified loading amount, the material was dried, with the circulating air temperature at 130°C. Next, the current collector coated with the negative electrode slurry was rolled (roll press), dried in a 30°C vacuum oven for 1 hour, and then rolled to 15.2 cm. 2 The negative electrode of Example 1 (rolling density: 1.78 g / cc) containing the negative electrode active material layer was manufactured by punching out a rectangular shape.

[0152] The negative electrodes of Examples 2-5 and Comparative Examples 1-9 were manufactured using the same method as the negative electrode manufacturing method of Example 1, except that the negative electrode active materials of Examples 2-5 and Comparative Examples 1-9 were used instead of the negative electrode active material of Example 1.

[0153] Experimental Example 1: Evaluation of Output Performance <Manufacturing of full-cell secondary batteries> A cathode slurry was prepared by mixing the cathode active material LCO, a carbon black-based conductive material, and a binder PVDF powder in a weight ratio of 92:2:6 with the solvent N-methyl-2-pyrrolidone.

[0154] The manufactured positive electrode slurry is loaded onto a positive electrode current collector with a thickness of 15 μm (mg / cm²). 2 The material was applied to a surface area of ​​23 mg per unit area, dried in a vacuum oven at 130°C for 1 hour, and then rolled at a pressure of 15 MPa between rolls heated to 80°C to produce a cathode with a final rolled density of 3.8 g / cc.

[0155] After positioning porous polyethylene separators between the negative and positive electrodes produced in Examples 1-5 and Comparative Examples 1-9, electrode assemblies were manufactured using a stacking method. These electrode assemblies were then placed in aluminum pouch-type battery cases, and full-cell secondary batteries were manufactured by injecting electrolyte (ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 1:4 (volume ratio), lithium hexafluorophosphate (LiPF 61 mol), vinylene carbonate (VC) content 0.5 wt) based on the weight of the electrolyte.

[0156] <Evaluation of output performance> As described above, the full-cell secondary batteries of Examples 1-5 and Comparative Examples 1-9 were charged to 0.33C and 4.4V. After adjusting the State of Charge (SOC) to 50%, the voltage drop during discharge with a 2.5C pulse for 10 seconds was used to measure the resistance increase rate (%), which is calculated as voltage decrease / applied current. The results are shown in Table 4 below.

[0157] Experiment Example 2: Evaluation of rapid charging performance For the full-cell secondary batteries of Examples 1-5 and Comparative Examples 1-9 manufactured in Experimental Example 1, the capacity retention rate after 100 cycles of cycle charging and discharging at 45°C was measured to evaluate the rapid charging performance.

[0158] Specifically, the full-cell secondary batteries of Examples 1-5 and Comparative Examples 1-9 were charged and discharged for 100 cycles under the following conditions: charge (CC / CV mode, 1C charge, cut-off at 0.005V and 0.005C) and discharge (CC mode, 0.5C discharge, cut-off at 1.5V).

[0159] The capacity retention rate was evaluated using the following formula, and the results are shown in Table 4.

[0160] Capacity retention rate (%) = {(Discharge capacity at the 100th cycle) / (Discharge capacity at the first cycle)} × 100

[0161] [Table 4]

[0162] Referring to Table 4, it can be confirmed that Examples 1 to 5, which are negative electrodes according to the present invention, exhibit significantly superior output performance and rapid charging performance compared to the negative electrodes of Comparative Examples 1 to 9.

Claims

1. Negative electrode current collector and The negative electrode current collector includes a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, The aforementioned negative electrode active material layer contains a negative electrode active material, The aforementioned negative electrode active material includes a first negative electrode active material and a second negative electrode active material. The first negative electrode active material is coated artificial graphite particles, which include primary artificial graphite particles and an amorphous carbon coating layer located on the primary artificial graphite particles. The second negative electrode active material is an uncoated artificial graphite particle in the form of a secondary particle obtained by granulating two or more primary artificial graphite particles. The average particle size (D) of the first negative electrode active material ５０ ) with respect to the average particle size (D ５０ The ratio of ) is 1.2 to 4.7, The average particle size (D) of the first negative electrode active material ５０ ) are 4 μm to 13 μm, The average particle size (D) of the second negative electrode active material ５０ ) is 15 μm to 25 μm, The negative electrode has a BET specific surface area of ​​0.1 m² / g to 3.0 m² / g.

2. The average particle size (D) of the first negative electrode active material ５０ ) with respect to the average particle size (D ５０ The negative electrode according to claim 1, wherein the ratio of ) is 2.0 to 3.

5.

3. The anode according to claim 1, wherein the amorphous carbon coating layer is contained in the first anode active material in an amount of 1% to 10% by weight.

4. The negative electrode according to claim 1, wherein the second negative electrode active material consists of the uncoated artificial graphite particles.

5. The aforementioned uncoated artificial graphite particles have an average particle size (D ５０ The negative electrode according to claim 1, wherein two or more primary artificial graphite particles having a size of 7 μm to 10 μm are granulated.

6. The negative electrode according to claim 1, wherein the first negative electrode active material and the second negative electrode active material are included in the negative electrode active material layer in a weight ratio of 10:90 to 80:

20.

7. The average particle size (D) of the negative electrode active material ５０ The negative electrode according to claim 1, wherein the diameter is 12 μm to 20 μm.

8. The negative electrode according to claim 1, wherein the crystal size La(100) in the a-axis direction determined by XRD analysis of the negative electrode active material is 200 nm to 300 nm, and the crystal size Lc(002) in the c-axis direction is 50 nm to 100 nm.

9. The negative electrode according to claim 1, wherein the tap density of the negative electrode active material is 1.00 g / cc to 1.20 g / cc.

10. The negative electrode according to claim 1, wherein the rolling density of the negative electrode is 1.5 g / cc to 2.0 g / cc.

11. A negative electrode according to any one of claims 1 to 10, A positive electrode opposite the negative electrode, A separator interposed between the negative electrode and the positive electrode, A secondary battery containing an electrolyte.

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