Negative electrode and method for manufacturing same

Abstract

The invention relates to a negative electrode for a lithium secondary battery and a method for manufacturing the same. The negative electrode for a lithium secondary battery includes transition metal particles containing iron and / or nickel within a carbon-based negative electrode active material, in which the concentration ratio of iron to nickel is controlled so as to satisfy a predetermined range. As a result, the negative electrode has excellent life characteristics under high-temperature conditions, and has low resistance under high-rate conditions. In addition, a lithium secondary battery including the negative electrode for a lithium secondary battery can have excellent high-temperature life characteristics and high-rate charge / discharge performance.

Description

Technical Field

[0001] This invention relates to a negative electrode for secondary batteries and its manufacturing method.

[0002] This application is based on and claims priority to Korean Patent Application No. 10-2023-0158093, filed on November 15, 2023, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Background Technology

[0003] Secondary batteries are widely used not only in small devices such as portable electronic devices, but also in medium and large devices such as battery packs or energy storage devices for hybrid electric vehicles (HEVs) and electric vehicles (EVs). Furthermore, with recent increased attention to environmental issues, research is underway on electric vehicles and hybrid electric vehicles (HEVs) that can replace fossil fuel vehicles such as gasoline and diesel vehicles, which are major contributors to air pollution. Additionally, research is actively being conducted on high-capacity secondary batteries that power EVs and HEVs.

[0004] Secondary batteries are rechargeable batteries and can include conventional Ni / Cd batteries, Ni / MH batteries, and the more recent lithium-ion batteries. Among these, lithium-ion batteries exhibit virtually no memory effect compared to Ni / Cd and Ni / MH batteries. Therefore, lithium-ion batteries can be freely charged and discharged, have a low self-discharge rate, and possess high energy density. Furthermore, lithium-ion batteries can be miniaturized and made lightweight, making them ideal for use as power sources in mobile devices.

[0005] [Existing technical documents]

[0006] [Patent Literature]

[0007] Korean Patent Application Publication No. 10-2017-0011566 Summary of the Invention

[0008] Technical issues

[0009] Therefore, the object of the present invention is to provide a negative electrode for a secondary battery that has excellent life characteristics under high temperature conditions and excellent electrical performance under high rate conditions, as well as a method for manufacturing the same.

[0010] Technical solution

[0011] To solve the above problems,

[0012] This invention provides a negative electrode for a secondary battery, comprising: a negative electrode current collector, and a negative electrode active layer disposed on at least one side of the negative electrode current collector and comprising a carbon-based negative electrode active material. The carbon-based negative electrode active material comprises magnetic transition metal particles, and the transition metal particles comprise iron and nickel. The carbon-based negative electrode active material contains less than 1200 ppm of transition metal particles, and the iron to nickel concentration ratio (Fe / Ni) contained in the carbon-based negative electrode active material is from 2.5 to 13.0.

[0013] The concentration of iron contained in the carbon-based negative electrode active material can be from 0.1 ppm to 1000 ppm.

[0014] The concentration of nickel in the carbon-based anode active material can be from 0.01 ppm to 500 ppm.

[0015] In addition, the carbon-based anode active material may contain transition metal particles at a concentration of 0.01 ppm to 1100 ppm.

[0016] Furthermore, based on the total weight, the transition metal particles may contain more than 50% iron.

[0017] In addition, the transition metal particles may also contain at least one of cobalt, chromium, zinc, magnesium, manganese and copper.

[0018] Furthermore, the carbon-based negative electrode active material can be artificial graphite in the form of secondary particles assembled from primary particles.

[0019] Furthermore, according to one embodiment, the present invention provides a method for manufacturing a negative electrode for a secondary battery, comprising: coating a negative electrode slurry containing a carbon-based negative electrode active material onto at least one side of a negative electrode current collector, and then drying it to form a negative electrode active layer. The carbon-based negative electrode active material contains magnetic transition metal particles, and the transition metal particles contain iron and nickel. The carbon-based negative electrode active material contains less than 1200 ppm of transition metal particles, and the iron to nickel concentration ratio (Fe / Ni) contained in the carbon-based negative electrode active material is 2.5 to 13.0.

[0020] In the method for manufacturing the negative electrode, the carbon-based negative electrode active material is prepared by: (S1) graphitizing the carbon raw material; (S2) carbonizing the graphitized carbon raw material in (S1); and (S3) adjusting the concentration of magnetic transition metal particles present in the carbon raw material by applying a magnetic field at least once before and after (S2).

[0021] In the manufacturing method of the negative electrode, in step (S3), a magnetic field with an intensity of 1000G to 40000G is applied for 1 second to 600 seconds.

[0022] Furthermore, in the manufacturing method of the negative electrode, (S3) is performed before or after (S2).

[0023] Furthermore, in the manufacturing method of the negative electrode, the iron concentration can be from 0.1 ppm to 1000 ppm.

[0024] In the manufacturing method of the negative electrode, the concentration of nickel can be from 0.01 ppm to 500 ppm.

[0025] In addition, in the manufacturing method of the negative electrode, the transition metal particles may also include at least one of cobalt, chromium, zinc, magnesium, manganese and copper.

[0026] Beneficial effects

[0027] The advantages of the negative electrode for secondary batteries of the present invention are: excellent lifespan characteristics under high-temperature conditions and low resistance under high-rate conditions. Therefore, lithium secondary batteries incorporating this negative electrode can have excellent high-temperature lifespan characteristics and high-rate charge-discharge performance. Detailed Implementation

[0028] This invention can be modified in various ways and includes various embodiments, which will be described in detail in the detailed description.

[0029] However, this is not intended to limit the invention to specific embodiments, but should be understood to include all modifications, equivalents or substitutions contained within the technical scope of the invention.

[0030] As used herein, it should be understood that the terms “comprising,” “including,” and “having” are intended to specify the presence of a feature, quantity, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, components, parts, or combinations thereof.

[0031] Furthermore, as used herein, "comprising as a major component" can mean that the total weight (or total volume) contains 50% by weight (or 50% by volume), 60% by weight (or 60% by volume), 70% by weight (or 70% by volume), 80% by weight (or 80% by volume), 90% by weight (or 90% by volume), or 95% by weight (or 95% by volume). For example, "comprising graphite as a major component as a negative electrode active material" can mean that the total weight of the negative electrode active material contains 50% by weight, 60% by weight, 70% by weight, 80% by weight, 90% by weight, or 95% by weight of graphite, and in some cases, it can mean that the negative electrode active material is made entirely of graphite and therefore contains 100% by weight of graphite.

[0032] In addition, as used in this article, “average particle size (D)” 50 "50% of the total volume" refers to the particle size at the point on the cumulative particle size distribution curve where the volume percentage reaches 50% when the total volume is 100%. This means the particle size at the point where the volume becomes 50% when accumulating from smaller particle sizes. Average particle size (D) 50 Particle sizes can be measured using methods such as laser diffraction, which can typically measure particle sizes from submicron to several millimeters and yield results with high reproducibility and high resolution.

[0033] Furthermore, as used herein, "magnetic" or "magnetic property" refers to the property of the material to be magnetized. Based on the relationship between the direction of the external magnetic field and the magnetization direction when an external magnetic field is applied, or whether an external magnetic field is applied during the magnetization process, magnetism can be classified as diamagnetic, paramagnetic, and ferromagnetic.

[0034] As used in this article, the terms “about,” “approximately,” and “basically” are intended to indicate that, taking into account inherent manufacturing and material tolerances, the values ​​or degrees of tolerances are within or near the range of values.

[0035] A lithium-ion secondary battery is a rechargeable electrical energy generating device with a stacked structure of positive electrode, separator, and negative electrode. When a lithium-ion secondary battery is charged, a lithium desorption reaction occurs at the positive electrode, where lithium contained in the positive electrode active material is oxidized and released, while a lithium intercalation reaction occurs at the negative electrode, where lithium is reduced and intercalated into the negative electrode active material.

[0036] For the negative electrode, materials containing graphitic carbon are widely used as active materials. The average potential for lithium release from materials containing graphitic carbon is approximately 0.2V (based on Li / Li). + Furthermore, the discharge potential exhibits a relatively flat pattern. Therefore, when graphitic carbon is used as the negative electrode active material, the advantage lies in the relatively high and constant voltage of the secondary battery.

[0037] The anode active material used is either amorphous carbon or crystalline carbon, with crystalline carbon being the primary choice due to its higher capacity. These crystalline carbons include graphitic carbons, such as natural graphite and synthetic graphite.

[0038] Meanwhile, the properties of graphitic carbon vary depending on the type. For example, natural graphite is inexpensive and exhibits excellent adhesion to current collectors, but it is relatively inferior to synthetic graphite in terms of high-rate charge-discharge performance or lifetime characteristics. However, because synthetic graphite has fewer surface defects or functional groups, when used to improve low-temperature performance by mixing propylene carbonate (PC) into the electrolyte, the PC can strip and disrupt the layers that form the interlayer structure of graphite. This stripping of graphite degrades the lifetime characteristics of the negative electrode under high-temperature conditions and increases resistance under high-rate conditions, which limits fast-charging performance.

[0039] In view of this, the present invention provides a technology for a negative electrode for secondary batteries, which can improve life characteristics under high temperature conditions and electrical performance under high rate conditions.

[0040] The invention will be described in more detail below.

[0041] negative electrode

[0042] According to one embodiment, the present invention provides a negative electrode for a secondary battery, comprising: a negative electrode current collector; and a negative electrode active layer disposed on at least one side of the negative electrode current collector and comprising a carbon-based negative electrode active material. The carbon-based negative electrode active material comprises transition metal particles, the transition metal particles comprising iron and nickel. The iron to nickel concentration ratio (Fe / Ni) contained in the carbon-based negative electrode active material is from 2.5 to 13.0.

[0043] The negative electrode for secondary batteries of the present invention can be a negative electrode for lithium secondary batteries. The negative electrode includes a negative electrode active layer on at least one side of the negative electrode current collector. The negative electrode active layer realizes the electroactivity of the negative electrode and contains a negative electrode active material that realizes electrochemical redox reactions during the charging and discharging process of the battery as a main component.

[0044] The negative electrode active material may contain carbon-based negative electrode active materials as the main component.

[0045] For example, based on the total weight of the negative electrode active layer, the content of carbon-based negative electrode active material can be from 80 parts by weight to 99.8 parts by weight. Alternatively, based on the total weight of the negative electrode active layer, the content of carbon-based negative electrode active material can be more than 95 parts by weight, more than 98 parts by weight, 84 parts by weight to 99.8 parts by weight, 90 parts by weight to 99.8 parts by weight, 94 parts by weight to 99.8 parts by weight, 88 parts by weight to 96 parts by weight, or 92 parts by weight to 97.5 parts by weight.

[0046] Furthermore, carbon-based anode active materials refer to materials containing carbon atoms as the main component, and such carbon-based anode active materials may contain graphite. Graphite may contain any and more of natural graphite and artificial graphite. For example, carbon-based anode active materials may contain only natural graphite or artificial graphite, and in some cases, may contain a mixture of natural graphite and artificial graphite.

[0047] For example, carbon-based anode active materials may comprise natural graphite and artificial graphite in a weight ratio of 5 to 50:50 to 95, 20 to 45:55 to 80, or 30 to 50:50 to 70. In this case, by including natural graphite and artificial graphite in the above mixing ratios, carbon-based anode active materials can enhance the adhesion between the anode current collector and the anode active layer.

[0048] Furthermore, carbon-based negative electrode active materials may contain only artificial graphite. According to one embodiment of the invention, when only artificial graphite is contained in the negative electrode active layer, the lifespan of the negative electrode is significantly improved, which may be advantageous in conditions such as automotive batteries that must withstand frequent charging over long periods. Moreover, compared to batteries using natural graphite, batteries using artificial graphite are advantageous for fast charging and exhibit superior output performance.

[0049] Carbon-based anode active materials can be spherical secondary graphite particles formed from assemblies of multiple flake-shaped primary graphite particles. Besides natural and artificial graphite, examples of flake graphite include mesophase calcined carbon (bulk mesophase) using tar and pitch as raw materials and graphitized coke (e.g., coke, green coke, pitch coke, needle coke, and petroleum coke), and can be assembled, for example, from multiple highly crystalline artificial graphite particles. Furthermore, a graphite assembly can be formed from 2 to 100 or 3 to 20 flake-shaped graphite particles.

[0050] The average particle size (D) of secondary particles 50 The average particle size (D) of secondary particles can range from 1 μm to 50 μm. For example, the average particle size (D) of secondary particles can be... 50 The particle size can be 1 μm to 40 μm; 1 μm to 30 μm; 10 μm to 40 μm; 15 μm to 30 μm; 25 μm to 50 μm; 11 μm to 19 μm; 15 μm to 25 μm; 20 μm to 30 μm; 1 μm to 20 μm; 1 μm to 10 μm; 5 μm to 15 μm; 10 μm to 20 μm; 15 μm to 30 μm; 15 μm to 20 μm; 21 μm to 26 μm; 25 μm to 30 μm; 11 μm to 17 μm; 16 μm to 23 μm; 2 μm to 7 μm; 0.5 μm to 5 μm; or 1 μm to 3 μm. To maximize the disorder of each particle in the expansion direction, thereby suppressing particle expansion caused by lithium-ion charging, it is advantageous to have a smaller particle size. However, when the particle size of carbon-based anode active materials is less than 1.0 μm, the number of particles per unit volume increases, requiring a large amount of binder, and the sphericity and sphericity yield may decrease. On the other hand, when the maximum particle size exceeds 50 μm, the expansion rate of the anode active material during the charge and discharge process of the secondary battery increases significantly, and with repeated charge and discharge, the adhesion between anode active material particles and the adhesion between anode active material particles and current collector deteriorates, which may significantly reduce cycle characteristics.

[0051] Furthermore, carbon-based anode active materials can have a form in which transition metal particles are uniformly dispersed. Transition metal particles refer to particles containing transition metals, and the transition metals can be contained in the form of transition metals or transition metal alloys, transition metal oxides, transition metal nitrides, or transition metal phosphates.

[0052] According to one embodiment, the transition metal particles comprise magnetizable transition metals, such as iron (Fe) and nickel (Ni). These transition metal particles can be included in the manufacturing process of the carbon-based anode active material. By including transition metal particles in the carbon-based anode active material, the present invention can also improve the charge-discharge performance of the carbon-based anode active material under high-rate conditions and / or high-temperature conditions. The transition metal particles may each comprise predetermined concentrations of iron and nickel, and the iron and nickel may have a predetermined concentration ratio. The concentration of the transition metal particles and / or the transition metal can be measured using, for example, inductively coupled plasma optical emission spectrometry (ICP-OES).

[0053] For example, carbon-based anode active materials may contain iron at concentrations ranging from 0.1 ppm to 1000 ppm. Specifically, carbon-based anode active materials may contain iron at the following concentrations: 0.1 ppm to 900 ppm; 0.1 ppm to 900 ppm; 0.1 ppm to 750 ppm; 0.1 ppm to 500 ppm; 0.1 ppm to 250 ppm; 0.1 ppm to 100 ppm; 0.1 ppm to 50 ppm; 0.1 ppm to 10 ppm; 0.1 ppm to 5 ppm; 0.1 ppm to 1 ppm; 0.5 ppm to 4 ppm; 10 ppm to 990 ppm; 100 ppm to 990 ppm; 200 ppm to 990 ppm; 500 ppm to 990 ppm; 750 ppm to 990 ppm; 1.0 ppm to 4.9 ppm; 0.3 ppm to 1.8 ppm; or 0.1 ppm to 0.9 ppm.

[0054] In addition, carbon-based anode active materials may contain nickel at concentrations ranging from 0.01 ppm to 500 ppm. For example, they may contain nickel at the following concentrations: 0.01 ppm to 300 ppm; 0.01 ppm to 200 ppm; 0.01 ppm to 150 ppm; 0.01 ppm to 115 ppm; 0.01 ppm to 100 ppm; 0.01 ppm to 75 ppm; 0.01 ppm to 50 ppm; 0.01 ppm to 25 ppm; 0.01 ppm to 10 ppm; 0.01 ppm to 5 ppm; 0.01 ppm to 3 ppm; 0.01 ppm to 1.5 ppm; 1 ppm to 3 ppm; 10 ppm to 200 ppm; 50 ppm to 200 ppm; 80 ppm to 150 ppm; 110 ppm to 190 ppm; 0.10 ppm to 0.95 ppm; or 0.2 ppm to 1.1 ppm.

[0055] Carbon-based anode active materials can contain all transition metal particles, including iron, nickel, and other transition metals other than iron and nickel, at a concentration of less than 1200 ppm. For example, the following concentrations of transition metal particles may be included in carbon-based anode active materials: 0.01 ppm to 1200 ppm; 0.01 ppm to 1100 ppm; 0.05 ppm to 1050 ppm; 0.1 ppm to 990 ppm; 0.1 ppm to 500 ppm; 0.1 ppm to 100 ppm; 0.1 ppm to 50 ppm; 0.1 ppm to 10 ppm; 0.1 ppm to 5 ppm; 0.1 ppm to 1 ppm; 0.5 ppm to 4 ppm; 110 ppm to 1000 ppm; 110 ppm to 800 ppm; 110 ppm to 600 ppm; 110 ppm to 400 ppm; 200 ppm to 650 ppm; 200 ppm to 990 ppm; 500 ppm to 990 ppm; 800 ppm to 990 ppm; 1.0 ppm to 4.9 ppm; 0.8 ppm to 2.3 ppm; or 0.1 ppm to 0.9 ppm.

[0056] According to one embodiment, the transition metal can be a magnetic transition metal (magnetic transition metal), or in some cases, a non-magnetic transition metal (non-magnetic transition metal). Alternatively, the transition metal can comprise both magnetic and non-magnetic transition metals. For example, the non-magnetic transition metal can exist in the form of an alloy with the magnetic transition metal, and therefore can be detected together with the magnetic transition metal during the detection process.

[0057] By controlling the concentration of all transition metal particles, including iron, nickel, and additionally contained transition metals, in the carbon-based negative electrode active material within the aforementioned range, this invention can suppress or prevent the reduction in charge mobility migrating from the positive electrode due to excessively high concentrations exceeding the aforementioned upper limit during the charging and discharging process of the secondary battery. For example, by controlling the concentration of transition metal particles in the carbon-based negative electrode active material within the aforementioned range, side reactions between the secondary battery and the electrolyte during charging and discharging are suppressed, thereby suppressing or preventing the reduction in initial efficiency, and also suppressing gas generation caused by electrolyte decomposition, thereby enhancing the safety of the secondary battery. Furthermore, it can suppress or prevent the capacity reduction of the negative electrode during high-rate charging and discharging, or fire or explosion due to various mechanisms of the secondary battery.

[0058] According to one embodiment, the iron to nickel concentration ratio (Fe / Ni) in the carbon-based negative electrode active material can be from 2.5 to 13.0. For example, the iron to nickel concentration ratio (Fe / Ni) in the carbon-based negative electrode active material can be 2.5 to 12.0; 2.5 to 10.0; 2.5 to 8.0; 2.5 to 5.5; 2.5 to 4.5; 2.5 to 4.1; 2.5 to 3.9; 3.2 to 8.5; 3.2 to 6.5; 3.2 to 4.5; 3.2 to 3.9; 3.5 to 8.5; 4.0 to 5.5; 5.0 to 8.5; 6.0 to 13.0; 9.0 to 13.0; 2.8 to 12.5; or 3.2 to 7.9.

[0059] By adjusting the iron and nickel concentration ratio in the carbon-based negative electrode active material to the above-mentioned range, the present invention can suppress or prevent the increase in resistance of the negative electrode during high-rate charge and discharge processes and the reduction in lifespan during high-temperature charge and discharge processes.

[0060] Transition metal particles may additionally contain transition metal elements other than iron and nickel. For example, transition metal particles may also contain one or more of cobalt, chromium, zinc, magnesium, manganese, and copper. Transition metals may be contained in the particles in the form of transition metals or alloys, transition metal oxides, transition metal nitrides, or transition metal phosphates.

[0061] In this case, based on the total weight, the iron content of the magnetic transition metal particles can be 50% or more. For example, the iron content of the transition metal particles can be 50% to 95%; 50% to 90%; 55% to 90%; 60% to 90%; 65% to 90%; 75% to 90%; 80% to 90%; 55% to 85%; 55% to 80%; 60% to 80%; 60% to 70%; 70% to 85%; 58% to 69%; 62% to 81%; or 76% to 89%.

[0062] The advantage of this invention is that by ensuring that the ratio of iron contained in the transition metal particles meets the above-mentioned range, the conductivity of the negative electrode can be improved without causing side reactions with the electrolyte impregnated in the negative electrode active layer during the charging and discharging process of the secondary battery.

[0063] Additionally, when necessary, in addition to the carbon-based anode active material as the main component, the anode active layer of the present invention may optionally contain conductive materials, binders, and other additives.

[0064] Conductive materials may include, but are not limited to, one or more of carbon black, acetylene black, Ketjen black, carbon nanotubes and carbon fibers.

[0065] As an example, the negative electrode active layer may contain only carbon black, carbon nanotubes and carbon fibers or a combination thereof as conductive materials.

[0066] At this point, based on a total of 100 parts by weight of the negative electrode active layer, the content of conductive material can be from 0.1 parts by weight to 10 parts by weight. For example, based on a total of 100 parts by weight of the negative electrode active layer, the content of conductive material can be from 0.1 parts by weight to 8 parts by weight, 0.1 parts by weight to 5 parts by weight, 0.1 parts by weight to 3 parts by weight, 2 parts by weight to 6 parts by weight, or 0.5 parts by weight to 2 parts by weight. By controlling the content of conductive material within the above range, the present invention can suppress the increase in negative electrode resistance caused by a low content of conductive material, thereby suppressing the decrease in charging capacity, and can also suppress the decrease in the content of negative electrode active material caused by excessive conductive material, thereby suppressing the decrease in charging capacity, or suppressing the decrease in fast charging characteristics caused by an increase in the load of the negative electrode active layer.

[0067] Adhesives are components that facilitate the bonding of negative electrode active materials and conductive materials to the current collector. Adhesives can be appropriately applied within a range that does not degrade the electrical properties of the electrode. Adhesives may include one or more of the following: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVdF), polyacrylonitrile, poly(methyl methacrylate), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber (SBR), and fluororubber.

[0068] Based on a total of 100 parts by weight of the negative electrode active layer, the binder content can be from 0.1 parts by weight to 10 parts by weight. For example, based on a total of 100 parts by weight of the negative electrode active layer, the binder content can be from 0.1 parts by weight to 8 parts by weight, 0.1 parts by weight to 5 parts by weight, 0.1 parts by weight to 3 parts by weight, or 2 parts by weight to 6 parts by weight. By controlling the binder content in the negative electrode active layer within the above ranges, the present invention can suppress the degradation of the adhesion of the active layer caused by a low binder content, or suppress the degradation of the electrical properties of the electrode caused by an excessive amount of binder.

[0069] Furthermore, the average thickness of the negative electrode active layer can be from 50 μm to 500 μm. For example, the average thickness of the negative electrode active layer can be from 100 μm to 400 μm; 200 μm to 350 μm; 50 μm to 180 μm; 80 μm to 150 μm; 100 μm to 250 μm; or 130 μm to 190 μm. By controlling the average thickness of the negative electrode active layer within the above range, the present invention can achieve high adhesion between the negative electrode active layer and the negative electrode current collector, and achieve high energy density of the negative electrode.

[0070] Furthermore, there are no particular limitations on the negative electrode current collector, as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, nickel, titanium, and calcined carbon can be used as negative electrode current collectors, and in the case of copper or stainless steel, materials surface-treated with carbon, nickel, titanium, or silver can also be used. Moreover, considering the conductivity and total thickness of the negative electrode to be manufactured, the average thickness of the negative electrode current collector can be appropriately applied within the range of 1 μm to 500 μm.

[0071] With the above configuration, the negative electrode of the present invention exhibits excellent lifespan characteristics under high-temperature conditions and low resistance under high-rate conditions. Therefore, a lithium secondary battery incorporating the negative electrode of the present invention can possess excellent high-temperature lifespan characteristics and high-rate charge-discharge performance.

[0072] Method for manufacturing the negative electrode

[0073] According to one embodiment, the present invention provides a method for manufacturing a negative electrode for a secondary battery, comprising: coating a negative electrode slurry comprising a carbon-based negative electrode active material onto at least one side of a negative electrode current collector, and then drying it to form a negative electrode active layer. The carbon-based negative electrode active material comprises magnetic transition metal particles, and the transition metal particles comprise iron and nickel. The iron to nickel concentration ratio (Fe / Ni) contained in the carbon-based negative electrode active material is from 2.5 to 13.0.

[0074] The method for manufacturing the negative electrode of the present invention refers to the method for manufacturing the negative electrode described above. The method for manufacturing the negative electrode involves coating a negative electrode slurry onto a negative electrode current collector and drying the coated negative electrode slurry to form a negative electrode active layer, thereby manufacturing a negative electrode for lithium secondary batteries.

[0075] The negative electrode slurry may contain carbon-based negative electrode active materials as the main component, and these materials may have uniformly dispersed transition metal particles. Transition metal particles refer to particles comprising magnetic or non-magnetic transition metals, or both, and the transition metals may be contained in the form of transition metals, alloys of both magnetic and non-magnetic transition metals, transition metal oxides, transition metal nitrides, or transition metal phosphates. The transition metal particles may contain iron (Fe) and nickel (Ni) as magnetizable transition metals.

[0076] The carbon-based negative electrode active material is prepared by: (S1) graphitizing the carbon raw material; (S2) carbonizing the graphitized carbon raw material in (S1); and (S3) adjusting the concentration of magnetic transition metal particles present in the carbon raw material by applying a magnetic field at least once before and after (S2).

[0077] According to one embodiment, the graphitization step (S1) refers to the process of heat-treating carbon raw materials at a temperature above 2500°C to transform the disordered carbon raw material structure into a graphite structure ordered by van der Waals forces.

[0078] "Carbon feedstock" may include at least one of needle coke, embedded coke, coal tar pitch and resin pitch.

[0079] The graphitization step (S1) can be carried out using equipment such as an Acheson graphitization furnace, a box-type graphitization furnace, or a vertical graphitization furnace.

[0080] The graphitization step (S1) can be applied at any heat treatment temperature capable of inducing physical changes in the structure of irregular carbon raw materials into an ordered structure (e.g., graphite), without particular limitation. For example, the graphitization step (S1) can be carried out at temperatures of 2000°C to 3500°C; 2500°C to 3500°C; 2800°C to 3500°C; or 2800°C to 3200°C.

[0081] By performing the graphitization step (S1) within the aforementioned temperature range, the present invention can readily induce changes in the physical structure of the carbon raw material. Therefore, the resulting product exhibits high crystallinity and thus excellent electrical properties when coated onto the negative electrode. Furthermore, since sublimation of the carbon raw material surface is suppressed during heat treatment, it offers the advantage of excellent process efficiency.

[0082] The carbon raw material obtained in the graphitization step (S1) can be a carbon raw material from which a portion of the carbon raw material present on top of the graphitized carbon raw material has been removed. When the carbon raw material is graphitized, foreign substances present inside the carbon raw material, such as transition metals and nonmetals, volatilize. However, in the case of certain transition metals, since their boiling points are equal to or slightly higher than the graphitization temperature, the transition metals may not completely volatilize and may partially remain on top of the graphitized carbon raw material. Therefore, in step (S1), when the graphitized carbon raw material is removed from the reactor, the predetermined carbon raw material located on top can be removed and the carbon raw material to be removed can be carbon raw material that has already been introduced into the reactor and exists at a depth ratio of 10% or less, 5% or less, or 3% or less based on the total depth of the carbon raw material.

[0083] Next, the step (S2) of carbonizing the graphitized carbon raw material refers to the process of assembling and compacting the graphitized carbon raw material. Therefore, the present invention allows carbonization to be performed while the graphitized carbon raw material is mixed with pitch.

[0084] The graphitized carbon raw material, through the graphitization step (S1), can have a spherical secondary particle shape formed by assembling sheet-like primary particles. When the graphitized carbon raw material is uniformly mixed with pitch and then carbonized, the mixed pitch fixes the carbon raw material adsorbed on the surface of the carbon raw material, thus obtaining more stable spherical secondary particles. Furthermore, since the pitch on the surface increases the density of the spherical secondary particles, a high energy density of the negative electrode active layer can be achieved.

[0085] "Bitten material" is primarily made from byproducts of coal or petrochemical processes and can be either solid or liquid bitten material. Solid bitten material can be obtained by crushing coal tar pitch, petroleum pitch, synthetic pitch, or wood tar pitch. Liquid bitten material can be manufactured by dissolving liquid resin or solid bitten material in a solvent, followed by coating and carbonization. Solvents that can be used include hexane, toluene, tetrahydrofuran (THF), quinoline, N-methylpyrrolidone (NMP), or ethanol.

[0086] The average particle size (D) of solid asphalt 50 The average particle size of solid asphalt can range from 1 μm to 7 μm or from 2 μm to 4 μm. 50 When this range is met, solid asphalt can be evenly distributed and mixed between the negative electrode active material particles. As a result, the surface of the negative electrode active material particles can be coated more evenly.

[0087] Based on 100 parts by weight of graphitized carbon raw material, the amount of pitch can be 1 to 10 parts by weight; or 3 to 5 parts by weight. By controlling the amount of pitch mixed during the carbonization process of the graphitized carbon raw material within the above range, the present invention can suppress or prevent a significant increase in the content of transition metal particles in the manufactured carbon-based anode active material caused by the pitch content exceeding the upper limit. Furthermore, the present invention can suppress or prevent the degradation of structural stability of the carbon-based anode active material due to lithium intercalation / desorption during the charging and discharging process of the secondary battery caused by the pitch mixing amount falling below the lower limit.

[0088] Furthermore, in step (S2), a homogenization device can be used to homogenize the graphitized carbon raw material and the pitch to uniformly mix them. The homogenization device can be any homogenization device commonly used in the art, without particular limitation. For example, the homogenization device can be a mixing homogenizer (vertical / horizontal mixer) or an ultrasonic homogenizer.

[0089] The carbonization step (S2) can be carried out within a predetermined temperature range. For example, the carbonization step (S2) can be carried out at a temperature of 1000°C to 2600°C; 1500°C to 2000°C; or 1500°C to 1600°C.

[0090] Meanwhile, during the grinding process of the carbon raw material before graphitization, transition metal particles can be mixed into the carbon raw material due to wear of the grinding equipment. Furthermore, in some cases, they can be mixed into the carbon raw material during the carbonization process of the graphitized carbon raw material due to wear of the homogenization equipment. In this way, compared to intentionally mixing transition metal particles into the carbon raw material during the manufacturing process of carbon-based anode active materials, although it is difficult to control the concentration of transition metal particles, the introduced transition metal particles can exhibit better electrical properties under high-temperature conditions.

[0091] Therefore, a method for manufacturing a negative electrode according to one embodiment of the present invention includes step (S3): before and / or after the step (S2) of carbonizing the graphitized carbon raw material, transition metal particles are removed by applying a magnetic field to the carbon raw material to adjust the concentration of transition metal particles in the carbon-based negative electrode active material.

[0092] For example, transition metal particles can be removed by applying a magnetic field to the carbon feedstock before carbonizing the graphitized carbon feedstock (S2).

[0093] Furthermore, transition metal particles can be removed by applying a magnetic field to the carbon feedstock after the graphitized carbon feedstock has been carbonized (S2).

[0094] According to one embodiment, when the transition metal particles are magnetic metal particles, in this step (S3), the transition metal particles can be easily removed by applying a magnetic field to the carbon raw material. This allows for adjustment of the concentration of transition metal particles contained in the carbon-based anode active material to be manufactured. However, when a magnetic field is applied twice to the graphitized carbon raw material, the concentration of the remaining transition metal particles in the carbon raw material can be significantly reduced. In this case, since the iron to nickel concentration ratio present in the carbon-based anode active material is significantly reduced, the high-temperature charge-discharge performance may deteriorate, or the resistance of the anode may increase under high-rate conditions. Therefore, appropriate adjustments are required.

[0095] The step (S3) of adjusting the concentration of transition metal particles can be performed for a certain duration using an electromagnet or permanent magnet under a magnetic field strength within a certain range.

[0096] For example, step (S3) can be performed by applying a magnetic field with a strength of 1000G to 40000G (Gauss). According to one embodiment, step (S3) can be performed by applying a magnetic field with a strength of 5000G to 40000G, 20000G to 40000G, or 36000G to 40000G.

[0097] Furthermore, step (S3) can be performed for 1 second to 600 seconds, for example, 10 seconds to 600 seconds; 30 seconds to 600 seconds; 60 seconds to 600 seconds; 100 seconds to 500 seconds; 200 seconds to 400 seconds; or 250 seconds to 350 seconds.

[0098] By adjusting the magnetic field strength and application time of step (S3) to adjust the concentration of transition metal particles to the above range, the present invention can more easily adjust the concentration of transition metal particles in the carbon-based anode active material to be prepared.

[0099] The carbon-based anode active material prepared in this way contains transition metal particles, which may contain iron and nickel in a predetermined concentration range, and the iron and nickel may have a predetermined concentration ratio. The concentration of the transition metal particles and / or the transition metal can be measured using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0100] For example, the iron concentration in carbon-based anode active materials can be from 0.1 ppm to 1000 ppm. For example, the iron concentration in carbon-based anode active materials can be from 0.1 ppm to 900 ppm; 0.1 ppm to 900 ppm; 0.1 ppm to 750 ppm; 0.1 ppm to 500 ppm; 0.1 ppm to 250 ppm; 0.1 ppm to 100 ppm; 0.1 ppm to 50 ppm; 0.1 ppm to 10 ppm; 0.1 ppm to 5 ppm; 0.1 ppm to 1 ppm; 0.5 ppm to 4 ppm; 10 ppm to 990 ppm; 100 ppm to 990 ppm; 200 ppm to 990 ppm; 500 ppm to 990 ppm; 750 ppm to 990 ppm; 1.0 ppm to 4.9 ppm; 0.3 ppm to 1.8 ppm; or 0.1 ppm to 0.9 ppm.

[0101] Furthermore, the concentration of nickel in carbon-based anode active materials can range from 0.01 ppm to 500 ppm. For example, the concentration of nickel in carbon-based anode active materials can be 0.01 ppm to 300 ppm; 0.01 ppm to 200 ppm; 0.01 ppm to 150 ppm; 0.01 ppm to 115 ppm; 0.01 ppm to 100 ppm; 0.01 ppm to 75 ppm; 0.01 ppm to 50 ppm; 0.01 ppm to 25 ppm; 0.01 ppm to 10 ppm; 0.01 ppm to 5 ppm; 0.01 ppm to 3 ppm; 0.01 ppm to 1.5 ppm; 1 ppm to 3 ppm; 10 ppm to 200 ppm; 50 ppm to 200 ppm; 80 ppm to 150 ppm; 110 ppm to 190 ppm; 0.10 ppm to 0.95 ppm; or 0.2 ppm to 1.1 ppm.

[0102] In addition to magnetic iron and nickel, transition metal particles may additionally contain transition metal elements. For example, the additionally contained transition metal particles may also include at least one of magnetic cobalt and non-magnetic chromium, zinc, magnesium, manganese, and copper. Transition metals may be contained in the particles in the form of transition metals or alloys of transition metals, transition metal oxides, transition metal nitrides, or transition metal phosphates. As mentioned above, non-magnetic transition metals exist in the form of alloys with magnetic transition metals, and therefore can be detected together with magnetic transition metals, for example, during capture processes used for measurement.

[0103] Simultaneously, the coating of the negative electrode slurry can be performed by discharging and coating the negative electrode slurry containing carbon-based negative electrode active material onto the surface of a moving negative electrode current collector. This process can be applied in any manner commonly practiced in the art without limitation, but die coating can be used. Die coating can be performed using a slit die with a gasket for controlling the discharge conditions of the negative electrode slurry. In this case, by controlling the shape and position of the gasket, the loading amount and coating thickness of the negative electrode slurry coated on the negative electrode current collector can be easily controlled.

[0104] Furthermore, the negative electrode slurry contains carbon-based negative electrode active materials as the main component, and may further contain conductive materials, binders, and other additives if necessary. Since the composition of the negative electrode slurry is the same as that of the negative electrode active layer formed therefrom, further description is omitted.

[0105] Furthermore, the drying of the negative electrode slurry can be applied in any manner commonly practiced in the art for drying the active layer of the electrode without limitation. For example, drying can be performed by applying heat to the negative electrode slurry using a hot air dryer, a vacuum oven, or the like.

[0106] Furthermore, the manufacturing method of the present invention may also include a step of calendering the negative electrode active layer formed by drying the negative electrode slurry. The calendering step is a step of applying pressure to the surface of the formed negative electrode active layer using a rolling mill or the like to increase the energy density of the negative electrode active layer. In this case, calendering can be performed at a temperature above room temperature.

[0107] For example, calendering can be carried out at temperatures ranging from 50°C to 100°C, such as 60°C to 100°C; 75°C to 100°C; 85°C to 100°C; 50°C to 90°C; 60°C to 80°C; or 65°C to 90°C.

[0108] Rolling can be carried out at rolling speeds of 2 m / s to 7 m / s, for example, 2 m / s to 6.5 m / s; 2 m / s to 6 m / s; 2 m / s to 5.5 m / s; 2 m / s to 5 m / s; 2 m / s to 4.5 m / s; 2 m / s to 4 m / s; 2.5 m / s to 4 m / s; 2.5 m / s to 3.5 m / s; 3.5 m / s to 5 m / s; 5 m / s to 7 m / s; 5.5 m / s to 6.5 m / s or 6 m / s to 7 m / s.

[0109] The rolling process can be carried out under pressure conditions ranging from 50 MPa to 200 MPa, for example, under pressure conditions ranging from 50 MPa to 150 MPa; 50 MPa to 100 MPa; 100 MPa to 200 MPa; 150 MPa to 200 MPa; or 80 MPa to 140 MPa.

[0110] By calendering under the temperature, speed, and / or pressure conditions described above, the present invention can easily increase the energy density of the negative electrode without damaging the negative electrode active layer.

[0111] The above-described configuration of the anode manufacturing method of the present invention allows for the inclusion of transition metal particles containing iron and nickel at predetermined concentrations and ratios in the carbon-based anode active material. Therefore, the advantages of the manufactured anode are: excellent lifetime characteristics at high temperatures and low resistance at high rates.

[0112] The invention will be described in more detail below with reference to examples and comparative examples.

[0113] However, the following embodiments and comparative examples are only used to illustrate the present invention, and the content of the present invention is not limited to the following embodiments and comparative examples.

[0114] Manufacturing of negative electrode

[0115] 1) Preparation of carbon-based anode active materials

[0116] As a carbon feedstock, coke feedstock is prepared. The prepared coke feedstock is ground using a jet mill until the average particle size (D) is reached. 50 The coke raw material was reduced to 10 μm. The pulverized coke raw material was granulated at 800℃ for 24 hours using a horizontal granulator.

[0117] granular coke feedstock was graphitized by heat treatment at 2800°C for 400 hours using an Acheson graphitization apparatus. When the graphitized product was removed from the apparatus, the upper portion of the product, extending from the product surface to a depth equal to 3% of the total product depth, was removed, yielding the remaining product. Whether the top product was removed is shown in Table 1 below.

[0118] Artificial graphite in the form of spherical secondary particles was prepared by assembling flake-like primary particles through mixing 100 parts by weight of graphitized product and 5 parts by weight of solid pitch in a vertical / horizontal mixer and carbonizing the mixture at 1500°C for 24 hours. However, before and / or after carbonization, a magnetic field of 30,000 G to 32,000 G was applied to the graphitized product for 10 to 300 seconds using an electromagnet, thereby adjusting the concentration of transition metal particles present in the product. The time points for adjusting the concentration are shown in Table 1 below.

[0119] The prepared artificial graphite was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES). For example, 100 g of each prepared artificial graphite was added to 200 mL of ethanol, and a Teflon magnet (magnetic field strength: approximately 5000 G ± 100 G) was introduced into the ethanol containing the artificial graphite, and the mixture was stirred for 2 hours. After mixing, the Teflon magnet was removed from the ethanol, placed in a Teflon vial, and 15 mL of aqua regia was added. The vial was then heated at 150 °C for 3 hours. The heated aqua regia system was cooled to room temperature, and ultrapure water was added to the cooled aqua regia system, with a total volume of 50 mL, to prepare the sample material. Calibration curves for reference solutions of 0.1 mg / kg, 0.5 mg / kg, and 1.0 mg / kg were prepared using an inductively coupled plasma optical emission spectrometer (model: OPTIMAAVIO 500, manufacturer: PERKIN-ELMER), and the prepared sample material was analyzed. At this point, the method detection limit (MDL) is set to less than 50 μg / kg (<50 μg / kg).

[0120] As a result, it was confirmed that the artificial graphite contained uniformly dispersed particles of iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), zinc (Zn), magnesium (Mg), manganese (Mn), and copper (Cu). The total concentration of transition metals contained in the artificial graphite, the corresponding concentrations of iron (Fe) and nickel (Ni), and the concentration ratio of iron to nickel are shown in Table 1 below.

[0121] [Table 1]

[0122]

[0123] 2) Manufacturing of the negative electrode

[0124] Carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) were prepared as binders. Then, 96 parts by weight of the artificial graphite manufactured in Preparation Examples 1 to 10, 1.5 parts by weight of carboxymethyl cellulose (CMC) and 2.5 parts by weight of styrene-butadiene rubber (SBR) were mixed with water to make the solid content 50%, thereby preparing a negative electrode slurry.

[0125] The prepared negative electrode slurry was coated onto copper foil (thickness: 10 μm) that was conveyed by roller to roller using a die coating machine (conveyor speed: 5 m / min).

[0126] The coated negative electrode slurry is dried with hot air to form a negative electrode active layer on the negative electrode current collector. The formed negative electrode active layer is calendered at 50±1℃, 100MPa-150 MPa pressure and 3m / s conveying speed to manufacture a negative electrode for lithium secondary batteries (average thickness of negative electrode active layer: 160±5μm). The types of artificial graphite coated onto each negative electrode are shown in Table 2 below.

[0127] [Table 2]

[0128] Types of artificial graphite Example 1 Artificial graphite prepared in Preparation Example 1 Example 2 Artificial graphite prepared in Preparation Example 2 Example 3 Artificial graphite prepared in Preparation Example 3 Example 4 Artificial graphite prepared in Preparation Example 4 Example 5 Artificial graphite prepared in Preparation Example 5 Example 6 Artificial graphite prepared in Preparation Example 6 Example 7 Artificial graphite prepared in Preparation Example 7 Example 8 Artificial graphite prepared in Preparation Example 8 Comparative Example 1 Artificial graphite prepared in Preparation Example 9 Comparative Example 2 Artificial graphite prepared in Preparation Example 10 Comparative Example 3 Artificial graphite prepared in Preparation Example 11 Comparative Example 4 Artificial graphite prepared in Preparation Example 12 Comparative Example 5 Artificial graphite prepared in Preparation Example 13

[0129] Manufacturing of lithium secondary batteries

[0130] LiNi with a particle size of 5 μm was prepared as the positive electrode active material. 0.7 Co 0.1 Mn 0.1 Al 0.1 O2 is mixed with carbon-based conductive agents and polyvinylidene fluoride as a binder in N-methylpyrrolidone (NMP) at a weight ratio of 94:3:3 to form a slurry, which is then cast onto an aluminum sheet, dried in a vacuum oven at 120°C, and then calendered to produce the negative electrode.

[0131] A separator made of 18 μm polypropylene was placed between the positive electrode obtained above and the negative electrode manufactured in Examples 1 to 8 and Comparative Examples 1 to 5, and placed in a housing. Then, an electrolyte composition was injected to assemble a single cell for a lithium secondary battery.

[0132] The types of negative electrodes used in various lithium secondary batteries are shown in Table 3 below.

[0133] [Table 3]

[0134] Types of negative electrodes used Example 9 The negative electrode prepared in Example 1 Example 10 The negative electrode prepared in Example 2 Example 11 The negative electrode prepared in Example 3 Example 12 The negative electrode prepared in Example 4 Example 13 The negative electrode prepared in Example 5 Example 14 The negative electrode prepared in Example 6 Example 15 The negative electrode prepared in Example 7 Example 16 The negative electrode prepared in Example 8 Comparative Example 6 The negative electrode prepared in Comparative Example 1 Comparative Example 7 The negative electrode prepared in Comparative Example 2 Comparative Example 8 The negative electrode prepared in Comparative Example 3 Comparative Example 9 The negative electrode prepared in Comparative Example 4 Comparative Example 10 The negative electrode prepared in Comparative Example 5

[0135] Experimental Example

[0136] To evaluate the performance of the negative electrode of the present invention, the following experiments were conducted on the negative electrodes and lithium secondary batteries prepared in the examples and comparative examples.

[0137] 1) Evaluation of the high-rate DC resistance of secondary batteries

[0138] The single cells manufactured in Examples 9 to 16 and Comparative Examples 6 to 10 were charged to 4.25V at 0.1C in constant current-constant voltage (CC-CV) mode at 25°C, and then discharged to 3.0V at a constant current of 0.1C to activate the single cell.

[0139] Each activated cell was charged at a constant current of 2.5C for 30 seconds at 25°C until its state of charge (SOC) reached 50%, and its DC internal resistance (DCIR) was measured. The measurement results are shown in Table 4 below.

[0140] 2) High-temperature life assessment

[0141] The single cells manufactured in Examples 9 to 16 and Comparative Examples 6 to 10 were charged to 4.25V at 0.1C in constant current-constant voltage (CC-CV) mode at 25°C, and then discharged to 3.0V at a constant current of 0.1C to activate the single cell.

[0142] After activating a single cell, a cycle was defined as charging and discharging at a constant current of 1C at 45°C and a constant current of 1C at 1C, and each cell underwent 300 charge-discharge cycles. The charge capacity of each cell was measured during the first and third cycles. Based on the measured charge capacity of the first cycle, the charge capacity retention rate of the third cycle was calculated to evaluate the high-temperature life of each cell. The results are shown in Table 4 below.

[0143] [Table 4]

[0144] Types of negative electrodes DC resistance [mΩ] Capacity retention rate after 300 cycles [%) Example 9 The negative electrode prepared in Example 1 1783 84.6 Example 10 The negative electrode prepared in Example 2 1780 85.5 Example 11 The negative electrode prepared in Example 3 1760 86.9 Example 12 The negative electrode prepared in Example 4 1754 86.5 Example 13 The negative electrode prepared in Example 5 1772 84.8 Example 14 The negative electrode prepared in Example 6 1825 79.8 Example 15 The negative electrode prepared in Example 7 1790 84.0 Example 16 The negative electrode prepared in Example 8 1805 82.9 Comparative Example 6 The negative electrode prepared in Comparative Example 1 1831 82.6 Comparative Example 7 The negative electrode prepared in Comparative Example 2 1951 77.7 Comparative Example 8 The negative electrode prepared in Comparative Example 3 1913 79.9 Comparative Example 9 The negative electrode prepared in Comparative Example 4 1921 79.1 Comparative Example 10 The negative electrode prepared in Comparative Example 5 1946 78.6

[0145] As shown in Table 4 above, it can be seen that the negative electrode for lithium secondary batteries of the present invention has low DC resistance during high-rate charging and discharging, and excellent high-temperature charging and discharging performance.

[0146] For example, a secondary battery in which the concentration and ratio of iron and nickel contained in a carbon-based negative electrode active material meet a predetermined range has a low DC resistance of less than 1810 mΩ during high-rate charge-discharge at 2.5C and a high capacity retention of more than 83% during high-temperature charge-discharge.

[0147] Meanwhile, compared with the examples, the secondary battery of Comparative Example 6 has a significantly lower concentration of transition metal particles in the carbon-based anode material, but the iron to nickel concentration ratio is significantly lower. Therefore, the DC resistance exceeds 1800 mΩ during high-rate charge and discharge, and the capacity retention is less than 83% during high-temperature charge and discharge.

[0148] This means that even if carbon-based anode active materials contain a certain amount of transition metal particles, when the concentrations of iron and nickel and their concentration ratio meet certain ranges, the DC resistance of the anode during high-rate charge and discharge processes and the capacity retention rate during high-temperature charge and discharge processes can be improved.

[0149] Therefore, the negative electrode for lithium secondary batteries of the present invention has excellent life characteristics under high temperature conditions and low resistance under high rate conditions.

[0150] As can be understood from the foregoing, various embodiments of the present invention have been described herein for illustrative purposes, and various modifications may be made without departing from the scope and spirit of the present invention.

[0151] Therefore, the technical scope of this invention should not be limited to the content described in the detailed description of the specification, but should be defined by the scope of the claims.

Claims

1. A negative electrode for a secondary battery, the negative electrode comprising: Negative current collector; and A negative electrode active layer comprising a carbon-based negative electrode active material is disposed on at least one side of the negative electrode current collector. in, The carbon-based negative electrode active material contains magnetic transition metal particles. The transition metal particles comprise iron and nickel. The concentration of the transition metal particles contained in the carbon-based anode active material is below 1200 ppm, and The iron / Ni concentration ratio of the carbon-based negative electrode active material is between 2.5 and 13.

0.

2. The negative electrode for a secondary battery as described in claim 1, wherein, The concentration of iron in the carbon-based negative electrode active material is from 0.1 ppm to 1000 ppm.

3. The negative electrode for a secondary battery as described in claim 1, wherein, The concentration of nickel in the carbon-based anode active material is from 0.01 ppm to 500 ppm.

4. The negative electrode for a secondary battery as described in claim 1, wherein, The concentration of the transition metal particles contained in the carbon-based negative electrode active material is from 0.01 ppm to 1100 ppm.

5. The negative electrode for a secondary battery as described in claim 1, wherein, Based on total weight, the magnetic transition metal particles contain more than 50% iron.

6. The negative electrode for a secondary battery as described in claim 1, wherein, The magnetic transition metal particles contained in the carbon-based negative electrode active material also include at least one of cobalt, chromium, zinc, magnesium, manganese, and copper.

7. The negative electrode for a secondary battery as described in claim 1, wherein, The carbon-based negative electrode active material is artificial graphite in the form of secondary particles assembled from primary particles.

8. A method for manufacturing a negative electrode for a secondary battery, the method comprising: A negative electrode slurry containing a carbon-based negative electrode active material is coated onto at least one side of a negative electrode current collector, and then the negative electrode slurry coated onto the negative electrode current collector is dried to form a negative electrode active layer. The carbon-based negative electrode active material contains magnetic transition metal particles. The transition metal particles comprise iron and nickel. The concentration of the transition metal particles contained in the carbon-based anode active material is below 1200 ppm, and The iron / Ni concentration ratio of the carbon-based negative electrode active material is between 2.5 and 13.

0.

9. The method of claim 8, wherein, The carbon-based anode active material is prepared by the following method: (S1) Graphitize carbon raw materials; (S2) Carbonize the graphitized carbon raw material in (S1); and (S3) The concentration of magnetic transition metal particles present in the carbon raw material is adjusted by applying a magnetic field at least once before and after (S2).

10. The method of claim 9, wherein, In (S3), a magnetic field with an intensity of 1000G to 40000G is applied for 1 second to 600 seconds.

11. The method of claim 9, wherein, (S3) is performed before or after (S2).

12. The method of claim 8, wherein, The concentration of iron in the carbon-based negative electrode active material is from 0.1 ppm to 1000 ppm.

13. The method of claim 8, wherein, The concentration of nickel in the carbon-based anode active material is from 0.01 ppm to 500 ppm.

14. The method of claim 8, wherein, The transition metal particles contained in the carbon-based negative electrode active material also include at least one of cobalt, chromium, zinc, magnesium, manganese, and copper.

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