Negative electrode and secondary battery

Abstract

Negative electrode for a secondary battery, comprising: a current collector; and an active material layer of the negative electrode provided on the current collector, comprising an active material of the negative electrode and a conductive material, wherein the conductive material comprises a linear conductive material and a planar conductive material, and wherein the active material layer of the negative electrode has an oriented structure.

Description

Technical field This application claims the priority and benefits of Korean patent application No. 10-2022-0131731, which was filed with the Korean Intellectual Property Office on October 13, 2022. The present invention relates to a negative electrode for a secondary battery and a secondary battery including the same. State of the art Secondary batteries are used not only universally for portable devices, but also for electric vehicles (EVs) and hybrid electric vehicles (HEVs) powered by electric drive sources. The secondary battery is attracting attention as a new energy source for improving environmental friendliness and energy efficiency due to its main advantage of drastically reducing the use of fossil fuels and the benefit of not producing any byproducts resulting from energy consumption. Generally, a secondary battery contains a positive electrode, a negative electrode, a separator inserted between the positive and negative electrodes, an electrolyte, and the like. Furthermore, an electrode, such as a positive electrode and a negative electrode, may include an active material layer of the electrode provided on a current collector. With the increasing use of secondary batteries, different battery performance capabilities are required. To improve battery performance, attempts are made to control the composition of an active material in a positive or negative electrode active material layer or an additive. However, an incorrect material combination can adversely affect the performance of the final battery. Accordingly, research is needed to improve battery performance through the combination of materials for a positive and a negative electrode. Detailed description of the invention Technical problem The present invention is intended to provide a negative electrode for a secondary battery which is capable of providing a secondary battery with improved fast-charging characteristics and a secondary battery including these. Technical solution An exemplary embodiment of the present invention provides a negative electrode for a secondary battery, including: a current collector; and an active material layer of the negative electrode provided on the current collector, comprising an active material of the negative electrode and a conductive material, wherein the conductive material comprises a linear conductive material and a planar conductive material, and wherein the active material layer of the negative electrode has an oriented structure. Another exemplary embodiment of the present invention provides a secondary battery which includes the negative electrode for the secondary battery described above, a positive electrode and a separator. Beneficial effects According to the exemplary embodiments described in this specification, the active material layer of the negative electrode is magnetically aligned, and the linear and planar conductive materials are used simultaneously as conductive materials, thus making it possible to improve the output properties. In particular, compared to the use of a point-like conductive material, the conductive materials also experience an alignment effect when using the linear and planar conductive materials due to the alignment of the active material layer of the negative electrode, resulting in a greater improvement in the output properties. Brief description of the drawings Fig. 1 is a diagram showing the cell resistance as a function of the SOC of negative electrodes prepared in the example and comparison example. Best practice The present invention is described in detail below to facilitate understanding. The present invention can be implemented in various different forms and is not limited to the exemplary embodiments described herein. Furthermore, the terms or words used in the specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but rather as meanings and concepts that correspond to the technical idea of ​​the present invention, based on the principle that an inventor can adequately define terms and concepts to best explain their invention. It is further understood that the terms “include”, “contain” or “have”, when used in this specification, specify the presence of specified features, integers, steps, plant-related elements, and / or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, plant-related elements, and / or combinations thereof. Furthermore, it should be understood that when an element, such as a layer, is described as lying "on" another element, it may lie "directly on" the other element, or there may be an intervening element. Conversely, when an element is described as being "directly on" another element, there are no intervening elements. When an element is described as lying "on" a reference section, the element lies above or below the reference section, and this does not necessarily mean that the element is "above" or "on" a direction opposite to gravity. A negative electrode for a secondary battery according to an exemplary embodiment of the present specification comprises a current collector and an active material layer of the negative electrode, which is provided on the current collector and comprises an active material of the negative electrode and a conductive material, wherein the conductive material comprises a linear conductive material and a planar conductive material, and wherein the active material layer of the negative electrode has an oriented structure due to magnetic alignment. The present inventors have found that the improvement in cell resistance by aligning the negative electrode can be further increased when the linear and planar conductive materials are used together as a conductive material, as described above, thereby achieving the present invention. In the exemplary embodiment above, the active material layer of the negative electrode contains a linear conductive material and a planar conductive material. The linear and planar conductive materials are aligned by aligning the active material layer of the negative electrode, thereby improving the battery's performance characteristics. Furthermore, an even greater improvement in performance can be expected when the linear and planar conductive materials are used together. Examples of linear conductive material may include a conductive fiber such as carbon fiber and metal fiber; conductive tubes such as carbon nanotubes, for example, single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs); fluorocarbon; metal powders such as aluminum and nickel powder; a conductive whisker such as zinc oxide and potassium titanate; a conductive metal oxide such as titanium oxide; a conductive material such as a polyphenylene derivative, and the like. Examples of planar conductive materials include graphene and the like. The conductive material may also contain point-like conductive material. Examples of point-like conductive material include graphite, such as natural and synthetic graphite; industrial carbon black, such as acetylene carbon black, Ketjen carbon black, sewer carbon black, furnace carbon black, lamp carbon black, thermal carbon black, and the like. According to one exemplary embodiment, the conductive material can be present in an amount of 0.1 to 5 parts by weight, based on 100 parts by weight of the active material layer of the negative electrode. In this case, the total amount of the linear conductive material and the planar conductive material described above can be 0.1 to 2 parts by weight, based on 100 parts by weight of the active material layer of the negative electrode. The linear conductive material and the planar conductive material can be used in smaller quantities than a point-like conductive material. In an exemplary embodiment of the present specification, the active material of the negative electrode may contain a silicon-based active material and a carbon-based active material, and the carbon-based active material may contain synthetic graphite and natural graphite. In an exemplary embodiment of this specification, the silicon-based active material comprises at least one of SiOx (0 ≤ x < 2), SiMy (M is a metal, 1 ≤ y < 4), and Si / C. The silicon-based active material may comprise only one type or two or more types together. If both active material layers of the negative electrode contain silicon-based active materials, the same type of silicon-based active material, different types, or different combinations of silicon-based active materials may be used for the two active material layers. In an exemplary embodiment of the present specification, the active material layer of the negative electrode may contain 1 to 40 parts by weight, for example 1 to 20 parts by weight of the silicon-based active material, based on a total of 100 parts by weight of the active material of the negative electrode. The active material containing SiOx(0≤x<2) as a silicon-based active material can be a silicon-based composite particle containing SiOx(0 <x<2) und eine Pore enthält. The SiOx(0 <x<2) entspricht einer Matrix in dem siliziumbasierten Verbundpartikel. Das SiOx(0<x<2) könnte eine Form sein, die Si und SiO2enthält, und das Si könnte eine Phase bilden. Das heißt, das x einem Zahlenverhältnis von O zu Si entspricht, die in dem SiOx(0<x<2) enthalten sind. Wenn das silikonbasierte Verbundpartikel das SiOx(0<x<2) enthält, kann eine Entladefähigkeit einer Sekundärbatterie verbessert werden. The silicon-based composite particles can further contain at least one Mg compound and one Li compound. The Mg compound and the Li compound can correspond to the silicon-based composite particle in a matrix. The Mg compound and / or the Li compound can be found in the SIOx(0 <x<2) und / oder auf einer Oberfläche des SiOx(0<x<2) vorhanden sein. Der anfängliche Wirkungsgrad der Batterie kann durch die Mg-Verbindung und / oder die Li-Verbindung verbessert werden. The Mg compound can be at least one selected from the group consisting of Mg silicates, Mg silicides, and Mg oxides. The Mg silicate can contain at least one of Mg₂SiO₄ and MgSiO₃. The Mg silicide can contain Mg₂SiO₄. The Mg oxide can contain MgO. In an exemplary embodiment of this specification, the Mg element may be present in an amount of 0.1 wt.% to 20 wt.% or 0.1 wt.% to 10 wt.% based on a total of 100 wt.% of the silicon-based active material. In particular, the Mg element may be present in an amount of 0.5 wt.% to 8 wt.% or 0.8 wt.% to 4 wt.%. If the above range is met, the Mg compound may be incorporated into the silicon-based active material in a suitable amount so that the volume change of the silicon-based active material during charging and discharging of the battery can be easily suppressed, and the discharge capacity and initial efficiency of the battery can be improved. The lithium compound can be at least one selected from the group consisting of lithium silicate, lithium silicide, and lithium oxide. The lithium silicate can contain at least one of Li₂SiO₃, Li₄SiO₄, and Li₂Si₂O₅. The lithium silicide can contain Li₇Si₂. The lithium oxide can contain Li₂O. In an exemplary embodiment of the present invention, the Li compound can contain a form of lithium silicate. The lithium silicate is described by the formula LiaSibOc(2≤a≤4, 0 <b≤2, 2≤c≤5) dargestellt und kann in kristallines Lithiumsilikat und amorphes Lithiumsilikat eingeteilt werden. Das kristalline Lithiumsilikat kann in den siliziumbasierten Verbundpartikeln in Form von mindestens einem Lithiumsilikat vorhanden sein, das aus der Gruppe bestehend aus Li2SiO3, Li4SiO4und Li2Si2O5ausgewählt ist, und das amorphe Lithiumsilikat kann in Form von LiaSibOc(2≤a≤4, 0<b≤2, 2≤c≤5) vorliegen. Die vorliegende Erfindung ist jedoch nicht darauf beschränkt. In one embodiment of the present specification, the Li element may be present in an amount of 0.1 wt.% to 20 wt.% or 0.1 wt.% to 10 wt.% based on a total of 100 wt.% of the silicon-based active material. More specifically, the Li element may be present in an amount of 0.5 wt.% to 8 wt.%, and more precisely, 0.5 wt.% to 4 wt.%. If the above range is met, the Li compound may be present in a suitable amount in the silicon-based active material such that the volume change of the active material of the negative electrode during charging and discharging of the battery can be easily suppressed, and the discharge capacity and initial efficiency of the battery can be improved. The concentration of the Mg or Li element can be confirmed by ICP analysis. For ICP analysis, a predetermined amount (approximately 0.01 g) of an active material from the negative electrode is precisely aliquoted, transferred to a platinum crucible, and completely decomposed on a hot plate by adding nitric, hydrofluoric, and sulfuric acids. Subsequently, a reference calibration curve is obtained using an inductively coupled plasma atomic emission spectrometer (ICP-AES, Perkin-Elmer 7300) by measuring the intensity of a standard liquid prepared with a standard solution (5 mg / kg) at an intrinsic wavelength of the Mg or Li element.Subsequently, a pretreated sample solution and a blank sample are introduced into the spectrometer, and by measuring the intensity of each component to calculate an actual intensity, calculating the concentration of each component based on the obtained calibration curve, and then performing a conversion so that the sum of the calculated concentrations of the components corresponds to a theoretical value, the Mg element or Li element content in the prepared silicon-based active material can be analyzed. In an exemplary embodiment of this specification, a carbon layer may be provided on a surface of the silicon-based composite particle and / or within the pore. The carbon layer imparts conductivity to the silicon-based composite particle, thus improving the initial efficiency, lifetime characteristics, and battery capacity characteristics of a secondary battery containing the active material of the negative electrode, including the silicon-based composite particle. The total amount of the carbon layer may range from 5 wt% to 40 wt% based on 100 wt% of the total value of the silicon-based composite particle. In an exemplary embodiment of the present specification, the carbon layer may contain at least one of amorphous carbon or crystalline carbon. An average particle diameter (D50) of the silicon-based active material can range from 2 µm to 15 µm, specifically from 3 µm to 12 µm, and even more specifically from 4 µm to 10 µm. If the above range is met, a side reaction between the silicon-based composite particle and the electrolyte solution is controlled, and the discharge capacity and initial efficiency of the battery can be effectively achieved. In this specification, an average particle diameter (D50) can be defined as a particle diameter that corresponds to 50% of the cumulative volume in a particle diameter distribution curve. The average particle diameter (D50) can be measured, for example, using a laser diffraction method. Laser diffraction generally allows the measurement of particle diameters in the submicron range up to several millimeters, yielding results with high reproducibility and resolution. The active material, including Si / C as the silicon-based active material, is a composite of Si and C and is to be distinguished from silicon carbide, which is designated SiC. The silicon-carbon composite can be a composite of silicon, graphite, and the like, and can form a structure in which a core composite of silicon, graphite, and the like is surrounded by graphene, amorphous carbon, or the like. In the silicon-carbon composite, silicon can be nanosilicon. In an exemplary embodiment of this specification, the synthetic graphite and the natural graphite may be present in amounts of 60 parts by weight or more and 99 parts by weight or less, respectively, based on 100 parts by weight of the negative electrode active material. The synthetic graphite and the natural graphite may be present in a weight ratio of 1:9 to 9:1, for example, 2:8 to 8:2. In an exemplary embodiment of the present specification, the active material of the negative electrode may be contained in an amount of 80 parts by weight or more and 99.9 parts by weight or less, and preferably in an amount of 80 parts by weight or more and 90 parts by weight or less, based on 100 parts by weight of the active material layer of the negative electrode. According to another exemplary embodiment of the present specification, the negative electrode active material layer can also contain a binder for the negative electrode in addition to the negative electrode active material. The binder for the negative electrode can serve to improve the adhesion between the particles of the negative electrode active material and the adhesive force between the particles of the negative electrode active material and the negative electrode current collector. Binders known according to the prior art can be used for the negative electrode.Non-exhaustive examples may include at least one selected from the group consisting of: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene propylene diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid and the above-mentioned materials in which a hydrogen atom is replaced by Li, Na, Ca, etc., and may also include various copolymers thereof. The binder for the positive electrode can be contained in an amount of 0.1 parts by weight or more and 20 parts by weight or less, for example preferably 0.3 parts by weight or more and 20 parts by weight or less, and more preferably 0.5 parts by weight or more and 10 parts by weight or less, based on 100 parts by weight of the active material layer of the negative electrode. In an exemplary embodiment of the present specification, the thickness of the active material layer of the negative electrode can be 5 µm or more and 300 µm or less, for example 10 µm or more and 150 µm or less. In an exemplary embodiment of this specification, the current collector of the negative electrode is not particularly limited, as long as it exhibits conductivity without causing a chemical change in the battery. Examples of materials suitable for use as a current collector include copper, stainless steel, aluminum, nickel, titanium, burnt carbon, aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like. In particular, transition metals that readily adsorb carbon, such as copper and nickel, may be used for the current collector. The thickness of the current collector may range from 1 µm to 500 µm, but is not limited to this range. Another exemplary embodiment of the present specification provides a secondary battery which includes the negative electrode according to the exemplary embodiments described above, a positive electrode and a separator. In an exemplary embodiment of this specification, the positive electrode can include a positive electrode current collector and an active material layer of the positive electrode formed on the positive electrode current collector and containing the active material of the positive electrode. The thickness of the active material layer of the positive electrode can be 20 µm or more and 500 µm or less. The positive electrode current collector is not particularly limited as long as it exhibits conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, burnt carbon, aluminum, or stainless steel with a surface treated with carbon, nickel, titanium, silver, or similar materials can be used. Furthermore, the positive electrode current collector typically has a thickness of 1 to 500 µm, and its surface can be formed with microscopic irregularities to enhance the adhesion of the active material. For example, the positive electrode current collector can be used in various forms, such as a film, sheet, foil, mesh, porous body, foam body, or non-woven fabric body. In an exemplary embodiment of this specification, the positive electrode may contain a lithium composite transition metal compound comprising nickel (Ni) and cobalt (Co) as active materials. The lithium composite transition metal compound may further comprise at least one manganese and one aluminum. The lithium composite transition metal compound may contain 80 mol% or more, for example, 80 mol% or more and less than 100 mol% nickel, as well as metals other than lithium. In an exemplary embodiment, the active material of the positive electrode can be contained in an amount of 80 parts by weight or more and 99.9 parts by weight or less, for example preferably 90 parts by weight or more and 99.9 parts by weight or less, more preferably 95 parts by weight or more and 99.9 parts by weight or less, and most preferably 98 parts by weight or more and 99.9 parts by weight or less, based on 100 parts by weight of the active material layer of the positive electrode. According to a further exemplary embodiment of the present specification, the active material layer of the positive electrode according to the exemplary embodiment described above may further contain a binder for the positive electrode and a conductive material. The binder for the positive electrode can serve to improve the adhesion between particles of the active material of the positive electrode and the adhesive force between particles of the active material of the positive electrode and the current collector of the positive electrode. Materials known in the prior art can be used for the binder of the positive electrode. Non-restrictive examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, various copolymers thereof, and the like. One of these or a mixture of two or more of them can be used. The binder for the positive electrode can be contained in an amount of 0.1 parts by weight or more and 50 parts by weight or less, for example preferably 0.3 parts by weight or more and 35 parts by weight or less, and more preferably 0.5 parts by weight or more and 20 parts by weight or less, based on 100 parts by weight of the active material layer of the positive electrode. The conductive material contained in the active material layer of the positive electrode is used to impart conductivity to the electrode and can be used without particular restriction as long as the conductive material exhibits electronic conductivity without causing a chemical change in a battery. Specific examples may include graphite such as natural graphite and synthetic graphite; a carbon-based material such as carbon black, acetylene carbon black, ketjen carbon black, sewer carbon black, furnace carbon black, flame carbon black, thermal carbon black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; a conductive whisker such as zinc oxide and potassium titanate; a conductive metal oxide such as titanium oxide; or a conductive polymer such as a polyphenylene derivative, and the like, and any of these, or a mixture of two or more, may be used. In particular, in an exemplary embodiment, the conductive material can comprise one or more single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The conductive material can be present in an amount of 0.1 parts by weight or more and 2 parts by weight or less, for example preferably 0.3 parts by weight or more and 1.5 parts by weight or less, and more preferably 0.5 parts by weight or more and 1.2 parts by weight or less, based on 100 parts by weight of the composition for an active material layer of the positive electrode. The positive and negative electrodes can be manufactured using a typical positive and negative electrode manufacturing process, except that the aforementioned positive and negative electrode active materials are used. Specifically, the electrodes can be manufactured by applying an active material layer composition, including the active material described above and optionally a binder and a conductive material, to a current collector, followed by drying and rolling. In this case, the types and contents of the active materials of the positive and negative electrodes, the binder, and the conductive material are as described above.The solvent can be a solvent commonly used in the field; for example, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, or a mixture of any one of these or two or more may be used. A sufficient amount of solvent is required if it can dissolve or disperse the active material, the conductive material, and the binder, taking into account the applied thickness of the slurry and the production yield, and then achieve a viscosity that provides excellent thickness uniformity when used to produce a positive and a negative electrode.Alternatively, the positive electrode and the negative electrode can be produced by laminating a film onto a current collector, which is obtained by pouring the composition for the formation of an active material layer onto a separate substrate and peeling it off the substrate. Another exemplary embodiment of the present specification provides a method for manufacturing the positive electrode for a secondary battery according to the exemplary embodiments described above. The manufacturing method includes coating a composition comprising an active material of the negative electrode and a conductive material onto a current collector, magnetically aligning the composition simultaneously with or after coating, and performing rolling to form an active material layer of the negative electrode, wherein the conductive material comprises a linear conductive material and a planar conductive material. The type of conductive material of the respective active material layers of the negative electrode, as described above, and the manufacturing process in which the magnetic alignment is carried out, can control a degree of alignment of the active material layer of the negative electrode. The separator serves to separate the negative electrode from the positive electrode and to provide a migration path for lithium ions. Any separator can be used without particular restrictions, as long as it is typically used as a separator in a secondary battery. In particular, a separator with high moisture retention capacity for an electrolyte solution and low resistance to electrolyte ion migration is preferred. Specifically, a porous polymer film, for example, a porous polymer film made from a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure with two or more layers thereof, can be used.Furthermore, an ordinary porous nonwoven fabric, such as one made from high-melting-point glass fiber, polyethylene terephthalate fiber, or similar materials, can also be used. Additionally, a coated separator comprising a ceramic component or polymer material can be employed to ensure heat resistance or mechanical strength, and the separator, with its single-layer or multi-layer structure, can be used selectively. Examples of the electrolyte may include, but are not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten-type inorganic electrolyte that can be used to manufacture the lithium secondary battery. In particular, the electrolyte may contain a non-aqueous organic solvent and a metal salt. For example, a non-aqueous organic solvent such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methylformate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, or ethyl propionate can be used. Particularly among carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are highly viscous organic solvents and can be preferred due to their high permittivity for dissociating lithium salts effectively. When the cyclic carbonate is mixed and used in a suitable ratio with a linear carbonate of low viscosity and low permittivity, such as dimethyl carbonate and diethyl carbonate, an electrolyte with high electrical conductivity can be produced and is therefore preferentially used. A lithium salt can be used as the metal salt, wherein the lithium salt is a material that dissolves readily in the non-aqueous electrolyte solution, wherein, for example, one or more from the group consisting of F-, Cl-, I-, NO3-, N(CN)2-, BF4-, ClO4-, PF6-, (CF3)2PF4-, (CF3)3PF3-, (CF3)4PF2-, (CF3)5PF-, (CF3)6P-, CF3SO3-, CF3CF2SO3-, (CF3SO2)2N-, (FSO2)2N-, CF3CF2(CF3)2CO-, (CF3SO2)2CH-, (SF5)3C-, (CF3SO2)3C-, CF3(CF2)7SO3-, CF3CO2-, CH3CO2-, SCN- and (CF3CF2SO2)2N-, are used as the anion of the lithium salt. can be. One or more additives, for example a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glymer, hexaphosphotriamide, a nitrobenzene derivative, sulfur, a quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, an ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride, may be further incorporated into the electrolyte in addition to the electrolyte components described above to improve the battery's lifetime characteristics, suppress a reduction in battery capacity, improve the battery's discharge capacity, and the like. The secondary battery according to an exemplary embodiment of the present invention comprises an assembly including a positive electrode, a negative electrode, a separator and an electrolyte, and may be a lithium secondary battery. Another exemplary embodiment of the present invention provides a battery module comprising the secondary battery described above as an element cell, as well as a battery pack containing this secondary battery. The battery module and battery pack contain the secondary battery, which has high capacity, high rate characteristics, and high cycle characteristics. The battery module and battery pack can be used as an energy source for a medium to large device selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and an energy storage system. Since the secondary battery, according to the exemplary embodiments of the present invention, stably exhibits excellent discharge capacity, performance characteristics, and cycle performance, the secondary battery can be used as a power source for a portable device such as a mobile phone, a laptop computer, and a digital camera, as well as for a medium-sized to large device selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and an energy storage system. For example, the battery module or battery pack can be used as a power source for a medium-sized to large device, for one or more power tools; an electric vehicle, including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or an energy storage system. Type of invention Preferred examples are provided below to better understand the present invention. It will be obvious to those skilled in the art that the examples are provided only to illustrate the present invention, and that various modifications and alterations are possible within the scope and technical spirit of the present invention. Such changes and modifications naturally fall within the scope of the claims contained herein. Example 1 The first active material layer of the negative electrode was coated to a thickness of 100 µm on the negative electrode current collector, then rolled and dried at room temperature. A magnetic alignment process was applied during the coating process. A composition was used to prepare the active material layer of the negative electrode, containing a negative electrode active material including synthetic graphite, natural graphite, and SiO₂, a conductive material (including a linear conductive material (CNT) and a planar conductive material (graphene) in a weight ratio of 1:1), a binder (SBR), and a thickener in a weight ratio of 96:1:2:1. The degree of orientation was confirmed by ratio calculation using XRD. A positive electrode was prepared by coating a positive electrode current collector with a composition containing Li1.0Ni0.86Co0.08Mn0.06O2, a conductive material (CNT) and a binder (PVDF) in the respective weight ratio of 97:1:2, and subsequently carrying out drying and rolling. A battery was prepared by stacking the positive and negative electrodes with an intermediate separator and injecting an electrolyte solution. The electrolyte solution contained 1M LiPF6, EC (ethylene carbonate) / EMC (ethyl methyl carbonate) (in a volume ratio of 3 / 7), 1.5 wt% VC (vinyl carbonate), and 0.5 wt% PS (propanesultone). Comparative example 1 The same procedure as in Example 1 was carried out, except that only a point-like conductive material (soot) was used as the conductive material of the active material layer of the negative electrode. Fig. 1 shows the cell resistance as a function of the state of charge (SOC) of the negative electrodes prepared in the example and the comparison example. Fig. 1 confirmed that, compared to the negative electrode on which only the point-like conductive material was applied, as in the comparison example, the negative electrode on which the linear and planar conductive materials were applied showed a greater improvement in cell resistance when magnetic alignment was applied. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature KR 10-2022-0131731

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Claims

Negative electrode for a secondary battery, comprising: a current collector; and an active material layer of the negative electrode provided on the current collector, comprising an active material of the negative electrode and a conductive material, wherein the conductive material comprises a linear conductive material and a planar conductive material, and wherein the active material layer of the negative electrode has an oriented structure. Negative electrode for a secondary battery according to claim 1, wherein the active material of the negative electrode comprises a silicon-based active material, synthetic graphite and natural graphite. Negative electrode for a secondary battery according to claim 2, wherein the conductive material is contained in an amount of 1 to 40 parts by weight, based on 100 parts by weight of the active material layer of the negative electrode. Negative electrode for a secondary battery according to claim 1, wherein the conductive material is contained in an amount of 0.1 to 5 parts by weight, based on 100 parts by weight of the active material layer of the negative electrode. Negative electrode for a secondary battery according to claim 1, wherein the linear conductive material is selected from at least one of the following: a conductive fiber; a conductive tube; a metal powder; a conductive whisker; a conductive metal oxide; a polyphenylene derivative. Negative electrode for a secondary battery according to claim 1, wherein the planar conductive material comprises graphene. Negative electrode for a secondary battery according to claim 1, wherein the conductive material further comprises a point-like conductive material. Secondary battery comprising the negative electrode according to any one of claims 1 to 7, a positive electrode and a separator. Secondary battery according to claim 8, wherein the positive electrode comprises a lithium composite transition metal compound containing nickel (Ni) and cobalt (Co) as an active material. Secondary battery according to claim 9, wherein the lithium composite transition metal compound further comprises at least one of manganese and aluminium.

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