Anode and manufacturing method therefor

Abstract

The present invention relates to an anode for a lithium secondary battery, and a manufacturing method therefor. The anode for a lithium secondary battery comprises transition metal particles including iron and / or nickel in a carbon-based anode active material, wherein the concentration ratio of iron to nickel is controlled to satisfy a predetermined range. Therefore, the anode has excellent lifespan characteristics in high-temperature conditions and low electrical resistance in high-rate conditions. In addition, a lithium secondary battery comprising same can have excellent high-temperature lifespan characteristics and high-rate charge / discharge performance.

Description

Cathode and method for manufacturing the same

[0001] The present invention relates to a cathode and a method for manufacturing the same.

[0002] This application claims the benefit of priority from Republic of Korea Patent Application No. 10-2023-0158093, dated November 15, 2023, and all contents of the document in said Korean patent application are incorporated herein by reference.

[0003]

[0004] Lithium secondary batteries are widely used not only in small devices such as portable electronic devices, but also in medium- to large-sized devices such as battery packs for hybrid and electric vehicles and power storage systems. In particular, with growing concern over environmental issues, research is being actively conducted on electric vehicles and hybrid electric vehicles as alternatives to fossil fuel-powered vehicles like gasoline and diesel, a major source of air pollution. Research is also actively underway on high-capacity secondary batteries that power these electric and hybrid electric vehicles.

[0005] Secondary batteries are rechargeable and can include conventional Ni / Cd batteries, Ni / MH batteries, and more recent lithium-ion batteries. Among these secondary batteries, lithium-ion batteries exhibit virtually no memory effect compared to Ni / Cd and Ni / MH batteries, allowing for free charging and discharging, a low self-discharge rate, and high energy density. Furthermore, lithium-ion batteries can be manufactured in small and lightweight designs, making them highly versatile power sources for mobile devices.

[0006]

[0007] [Prior Art Literature]

[0008] Republic of Korea Patent Publication No. 10-2017-0011566

[0009]

[0010] The purpose of the present invention is to provide a cathode having excellent life characteristics under high temperature conditions and excellent electrical performance under high rate conditions, and a method for manufacturing the same.

[0011]

[0012] To solve the above-mentioned problem,

[0013] In one embodiment of the present invention,

[0014] A negative electrode current collector, and a negative electrode active layer provided on at least one surface of the negative electrode current collector and including a carbon-based negative electrode active material;

[0015] The above carbon-based negative electrode active material includes transition metal particles having magnetism;

[0016] The above transition metal particles include iron and nickel;

[0017] The above carbon-based negative electrode active material contains magnetic transition metal particles at a concentration of 1,200 ppm or less;

[0018] A negative electrode is provided, characterized in that the concentration ratio (Fe / Ni) of iron and nickel contained in the above carbon-based negative electrode active material is 2.5 to 13.0.

[0019] The concentration of the iron may range from 0.1 ppm to 1,000 ppm.

[0020] The concentration of the above nickel may range from 0.01 ppm to 500 ppm.

[0021] Additionally, the carbon-based negative electrode active material may include transition metal particles at a concentration ranging from 0.01 ppm to 1,100 ppm.

[0022] In addition, the transition metal particles having the above magnetic properties may contain iron in an amount of 50% or more based on the total weight.

[0023] In addition, the transition metal particles having the above magnetic properties may further include one or more of cobalt, chromium, zinc, magnesium, manganese, and copper.

[0024] In addition, the carbon-based negative electrode active material may be artificial graphite in the form of secondary particles assembled from primary particles.

[0025]

[0026] In addition, in one embodiment of the present invention,

[0027] It comprises a step of forming a negative electrode active layer by applying and drying a negative electrode slurry containing a carbon-based negative electrode active material to at least one surface of a negative electrode current collector,

[0028] The above carbon-based negative electrode active material includes transition metal particles having magnetism,

[0029] The above transition metal particles include iron and nickel,

[0030] The above carbon-based negative electrode active material contains magnetic transition metal particles at a concentration of 1,200 ppm or less,

[0031] A method for manufacturing a negative electrode is provided, characterized in that the concentration ratio (Fe / Ni) of iron and nickel contained in the above carbon-based negative electrode active material is 2.5 to 13.0.

[0032] Here, the carbon-based negative electrode active material can be manufactured by a method including a step (S1) of graphitizing a carbon raw material, and a step (S2) of carbonizing the graphitized carbon raw material, and a step (S3) of applying a magnetic field at least once before and after the carbonizing step to control the concentration of transition metal particles having magnetism present in the carbon raw material.

[0033] The step (S3) of controlling the concentration of the above transition metal particles may be performed by applying a magnetic field with a strength of 1,000 G to 40,000 G for 1 to 600 seconds.

[0034] Additionally, the step (S3) of controlling the concentration of the transition metal particles may be performed before or after the step of carbonizing the graphitized carbon raw material.

[0035] Additionally, the concentration of iron may range from 0.1 ppm to 1,000 ppm.

[0036] The concentration of the above nickel may range from 0.01 ppm to 500 ppm.

[0037] In addition, the transition metal particles having the above magnetic properties may further include one or more of cobalt, chromium, zinc, magnesium, manganese, and copper.

[0038]

[0039] The cathode according to the present invention has the advantages of excellent life characteristics under high-temperature conditions and low electrical resistance under high-rate conditions. Accordingly, a lithium secondary battery containing the cathode can have excellent high-temperature life characteristics and high-rate charge / discharge performance.

[0040]

[0041] The present invention can be modified in various ways and has many embodiments, and specific embodiments will be described in detail in the detailed description.

[0042] However, this is not intended to limit the present invention to a specific embodiment, but should be understood to include all modifications, equivalents, or substitutes included in the technical scope of the present invention.

[0043] In the present invention, it should be understood that terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0044] In addition, in the present invention, "comprising as a main component" may mean comprising a defined component at 50 wt% or more (or 50 vol% or more), 60 wt% or more (or 60 vol% or more), 70 wt% or more (or 70 vol% or more), 80 wt% or more (or 80 vol% or more), 90 wt% or more (or 90 vol% or more), or 95 wt% or more (or 95 vol% or more) of the total weight (or total volume). For example, "comprising graphite as a main component as a negative electrode active material" may mean comprising graphite at 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or 95 wt% or more of the total weight of the negative electrode active material, and in some cases, it may mean that the entire negative electrode active material is made of graphite and comprises 100 wt% of graphite.

[0045] Also, in this specification, "average particle diameter (D 50 )" means the particle size at the point where the volume percentage reaches 50% on the cumulative curve when the cumulative curve of the particle size distribution is obtained by taking the total volume as 100%, and means the particle size at the point where the volume becomes 50% when accumulating from the smallest particle size. The above average particle size (D 50 ) can be measured, for example, using a laser diffraction method, which can generally measure particle sizes from the submicron range to several mm, and can obtain results with high reproducibility and high resolution.

[0046] Additionally, in this specification, "magnetism" refers to the property of a material to be magnetized. The magnetism can be classified into diamagnetism, paramagnetism, ferromagnetism, etc. depending on the direction of magnetization according to the direction of the magnetic field when an external magnetic field is applied, or whether an external magnetic field is applied during magnetization.

[0047] As used herein, the terms "about," "approximately," and "substantially" are used to mean a range of or near a numerical value or degree, taking into account inherent manufacturing and material tolerances.

[0048] Lithium secondary batteries are rechargeable power generation devices comprised of a stacked structure of a cathode, separator, and anode. When charging a lithium secondary battery, a lithium desorption reaction occurs at the cathode, oxidizing and releasing lithium contained in the cathode active material. A lithium insertion reaction also occurs at the cathode, reducing lithium and inserting it into the cathode active material.

[0049] The above negative electrode is a material that includes graphite carbon and is widely used as an anode active material. The average potential when a material including graphite carbon releases lithium is about 0.2 V (Li / Li + ) and the discharge potential shows a relatively flat pattern. Therefore, when graphite-based carbon is used as an anode active material, the secondary battery has the advantage of high and constant voltage.

[0050] Amorphous or crystalline carbon is used as the cathode active material, with crystalline carbon being the most commonly used due to its high capacity. Examples of such crystalline carbon include graphite-based carbons, such as natural graphite and artificial graphite.

[0051] Meanwhile, the graphite-based carbon has different characteristics depending on its type. For example, natural graphite is inexpensive and exhibits excellent adhesion to a current collector, but is relatively inferior to artificial graphite in terms of high-rate charge / discharge performance and life characteristics. However, the artificial graphite has a low content of surface defects and functional groups, so when used by mixing propylene carbonate (PC) in the electrolyte for the purpose of improving low-temperature performance, the propylene carbonate may exfoliate and destroy each layer forming the graphite interlayer structure. This exfoliation of graphite deteriorates the life characteristics of the negative electrode under high-temperature conditions and increases resistance under high-rate conditions, which limits rapid charging performance.

[0052] Taking these points into consideration, the present invention provides a secondary battery cathode technology that has excellent life characteristics under high-temperature conditions and can improve electrical performance under high-rate conditions.

[0053]

[0054] Hereinafter, the present invention will be described in more detail.

[0055]

[0056] cathode

[0057] In one embodiment of the present invention,

[0058] A negative electrode current collector, and a negative electrode active layer provided on at least one surface of the negative electrode current collector and including a carbon-based negative electrode active material;

[0059] The above carbon-based negative electrode active material includes transition metal particles having magnetism;

[0060] The above transition metal particles having magnetism include iron and nickel;

[0061] A negative electrode is provided, characterized in that the concentration ratio (Fe / Ni) of iron and nickel contained in the above carbon-based negative electrode active material is 2.5 to 13.0.

[0062]

[0063] The negative electrode according to the present invention may be an negative electrode applied to a lithium secondary battery. The negative electrode includes an negative electrode active layer on at least one surface of the negative electrode current collector. The negative electrode active layer is a layer that implements the electrical activity of the negative electrode, and includes as a main component an negative electrode active material that implements an electrochemical redox reaction during charging and discharging of the battery.

[0064] Here, the negative electrode active material may include a carbon-based negative electrode active material as a main component.

[0065] Specifically, the carbon-based negative electrode active material may be included in an amount of 80 parts by weight to 99.8 parts by weight based on the total weight of the negative electrode active layer. For example, the carbon-based negative electrode active material may be included in an amount of 95 parts by weight or more, 98 parts by weight or more, 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 based on the total weight of the negative electrode active layer.

[0066] In addition, the carbon-based negative electrode active material refers to a material whose main component is carbon atoms, and such carbon-based negative electrode active material may include graphite. The graphite may include at least one of natural graphite and artificial graphite. For example, the carbon-based negative electrode active material may include natural graphite or artificial graphite alone, and in some cases, may include a mixture of natural graphite and artificial graphite.

[0067] For example, the carbon-based negative electrode active material may contain 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, the carbon-based negative electrode active material may strengthen the adhesion between the negative electrode current collector and the negative electrode active layer by containing natural graphite and artificial graphite in the above-mentioned mixing ratio.

[0068] Additionally, the carbon-based anode active material may solely comprise artificial graphite. The present invention, by including artificial graphite solely in the anode active layer, significantly improves the lifespan of the anode, which can be advantageous in conditions such as automobile batteries that must withstand frequent charging for long periods of time. Furthermore, artificial graphite offers the advantages of rapid charging and superior output performance compared to natural graphite.

[0069] The above carbon-based negative electrode active material is preferably a spherical graphite secondary particle formed by aggregating a plurality of flake-shaped graphite primary particles. Examples of the flake-shaped graphite include, in addition to natural graphite and artificial graphite, mesophase calcined carbon (bulk mesophase) made from tar and pitch, and graphitized coke (raw coke, green coke, pitch coke, needle coke, petroleum coke, etc.). In particular, one assembled using a plurality of highly crystalline artificial graphites is preferable. In addition, one graphite assembly can be formed by aggregating 2 to 100, preferably 3 to 20, flake-shaped graphite particles.

[0070] The average particle diameter of the above secondary particles (D 50 ) may range from 1 μm to 50 μm. For example, the average particle diameter (D) of the secondary particles 50) may range from 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. Spherical carbon-based negative electrode materials can be advantageous in that the particle size is made smaller to maximize the disorder in the direction of expansion of each particle so as to prevent expansion of the particles due to lithium ion charging. However, when the particle size of the carbon-based negative electrode material is less than 1.0 ㎛, a large amount of binder is required due to the increase in the number of particles per unit volume, and the spheroidization degree and spheroidization yield may be reduced. On the other hand, when the maximum particle size exceeds 50 ㎛, the expansion rate of the negative electrode active material significantly increases during charge and discharge of the secondary battery. Therefore, as charge and discharge are repeated, the adhesion between the negative electrode active material particles and the adhesion between the negative electrode active material particles and the current collector deteriorate, which may significantly reduce the cycle characteristics.

[0071] In addition, the carbon-based negative electrode active material may have a form in which magnetic transition metal particles are uniformly dispersed. The transition metal particles refer to particles containing a transition metal, and the transition metal may be included in the form of a transition metal, a transition metal oxide, a transition metal nitride, a transition metal phosphate, or a transition metal alloy.

[0072] The above-mentioned magnetic transition metal particles include magnetizable transition metals, specifically, iron (Fe) and nickel (Ni). Such transition metal particles may inevitably be included in the manufacturing process of a carbon-based negative electrode active material. The present invention can further improve the charge / discharge performance of the carbon-based negative electrode active material under high-rate conditions and / or high-temperature conditions by including magnetic transition metal particles in the negative carbon-based negative electrode active material. At this time, the transition metal particles may include iron and nickel in predetermined concentration ranges, and these may have a predetermined concentration ratio. The concentration of the transition metal particles and / or the transition metal may be measured using an inductively coupled plasma optical emission spectrometer (ICP-OES), etc.

[0073] For example, the iron may be included in the carbon-based negative electrode active material at a concentration ranging from 0.1 ppm to 1,000 ppm. For example, the iron may be included in the carbon-based negative electrode active material at a concentration ranging 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; It may be included in a concentration range of 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.

[0074] Additionally, the nickel may be included in the carbon-based negative electrode active material in a concentration ranging from 0.01 ppm to 500 ppm. For example, the nickel may be included in a concentration ranging from 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; It may be included in a concentration range of 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.

[0075] The carbon-based negative electrode active material may include, in addition to iron and nickel, a transition metal other than iron and nickel, and may include total transition metal particles having magnetic properties at a concentration of 1,200 ppm or less. For example, the carbon-based negative electrode active material may include 0.01 ppm to 1,200 ppm; 0.01 ppm to 1,100 ppm; 0.05 ppm to 1,050 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; 0.1 ppm to 1 ppm; 0.1 ppm to 5 ppm; 0.1 ppm to 1 ppm; 0.5 ppm to 4 ppm; 110 ppm to 1,000 ppm; The magnetic transition metal particles may be contained therein at a concentration ranging from 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.

[0076] The above transition metal may be a magnetic transition metal, or in some cases, a non-magnetic transition metal, or may include both a magnetic transition metal and a non-magnetic transition metal. For example, the non-magnetic transition metal may exist in the form of an alloy with a magnetic transition metal, and thus may be detected together with the magnetic transition metal during detection. The present invention controls the concentration of the total magnetic transition metal particles other than iron, nickel, and iron and nickel contained in the carbon-based negative electrode active material within the above range, thereby suppressing or preventing the reduction in charge mobility from the positive electrode during charge / discharge of the secondary battery due to an excessive concentration exceeding the above-described upper limit. In particular, when the concentration of the transition metal particles in the carbon-based negative electrode active material exceeds the above-described upper limit, the electrical resistance of the carbon-based negative electrode active material may be somewhat reduced, but this may induce a side reaction with the electrolyte during charge / discharge of the secondary battery, which may lower the initial efficiency. In this case, there is a limitation that the safety of the secondary battery is reduced because gas is generated due to electrolyte decomposition during charging and discharging of the secondary battery. In addition, the present invention can prevent the capacity of the negative electrode from decreasing during high-rate charging and discharging due to a concentration lower than the aforementioned lower limit, or the induction of fire or explosion through various mechanisms of the secondary battery.

[0077] The concentration ratio (Fe / Ni) of iron and nickel contained in the carbon-based negative electrode active material may be in the range of 2.5 to 13.0. For example, the concentration ratio (Fe / Ni) of iron and nickel contained in the carbon-based negative electrode active material may 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 it can be in the range of 3.2 to 7.9.

[0078] The present invention can suppress or prevent an increase in the electrical resistance of the negative electrode during high-rate charge / discharge and a decrease in the lifespan during high-temperature charge / discharge due to a high ratio exceeding the above-described upper limit or a ratio lower than the above-described lower limit by controlling the concentration ratio of iron and nickel contained in the carbon-based negative electrode active material within the above-described range.

[0079] The above-described magnetic transition metal particles may contain transition metal elements in addition to iron and nickel. For example, the above-described transition metal particles may further contain one or more of cobalt, chromium, zinc, magnesium, manganese, and copper. The above-described transition metals may be contained within the particles in the form of transition metals, transition metal oxides, transition metal nitrides, transition metal phosphates, and transition metal alloys.

[0080] In this case, the transition metal particles having magnetism may contain iron at 50% or more by total weight. For example, the transition metal particles having magnetism may contain iron at 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%.

[0081] The present invention has an advantage in that the electrical conductivity of the negative electrode can be increased without causing a side reaction with the electrolyte impregnated in the negative electrode active layer during charging and discharging of the secondary battery by ensuring that the ratio of iron contained in the transition metal particles satisfies the above range.

[0082]

[0083] Meanwhile, the negative electrode active layer according to the present invention may optionally further include a conductive agent, a binder, other additives, etc., as needed, in addition to the carbon-based negative electrode active material as the main component.

[0084] The above-mentioned challenge material may include one or more of carbon black, acetylene black, Ketjen black, carbon nanotubes, carbon fibers, etc., but is not limited thereto.

[0085] For example, the cathode active layer may contain carbon black, carbon nanotubes, carbon fibers, etc. alone or in combination as a conductive material.

[0086] At this time, the content of the conductive material may be 0.1 to 10 parts by weight based on 100 parts by weight of the entire negative electrode active layer. For example, the content of the conductive material may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 2 to 6 parts by weight, or 0.5 to 2 parts by weight based on 100 parts by weight of the entire negative electrode active layer. By controlling the content of the conductive material within the above range, the present invention can prevent the resistance of the negative electrode from increasing due to a low content of the conductive material, thereby reducing the charging capacity, and can prevent the problem of the content of the negative electrode active material decreasing due to an excessive amount of the conductive material, thereby reducing the charging capacity, or the problem of the rapid charging characteristics from decreasing due to an increase in the loading amount of the negative electrode active layer.

[0087] The above binder is a component that assists in the bonding of the negative electrode active material and the conductive material and the bonding to the current collector, and can be appropriately applied within a range that does not deteriorate the electrical properties of the electrode. Such binders may include one or more of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVdF), polyacrylonitrile, polymethylmethacrylate, 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 fluoroelastomer.

[0088] The content of the binder may be 0.1 to 10 parts by weight based on 100 parts by weight of the entire negative electrode active layer. For example, the content of the binder may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 2 to 6 parts by weight based on 100 parts by weight of the entire negative electrode active layer. By controlling the content of the binder contained in the negative electrode active layer within the above range, the present invention can prevent the adhesive strength of the active layer from being lowered due to a low content of binder or the electrical properties of the electrode from being lowered due to an excessive amount of binder.

[0089] In addition, the average thickness of the negative electrode active layer may be in the range of 50 ㎛ to 500 ㎛. For example, the average thickness of the negative electrode active layer may be in the range of 100 ㎛ to 400 ㎛; 200 ㎛ to 350 ㎛; 50 ㎛ to 180 ㎛; 80 ㎛ to 150 ㎛; 100 ㎛ to 250 ㎛; 100 ㎛ to 250 ㎛; or 130 ㎛ to 190 ㎛. The average thickness of the negative electrode active layer may be measured through scanning electron microscope (SEM) analysis of a thickness-wise cross-section of the negative electrode. The present invention can not only implement high adhesiveness between the negative electrode active layer and the negative electrode current collector by controlling the average thickness of the negative electrode active layer within the above range, but also implement high energy density of the negative electrode.

[0090] Furthermore, the negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, nickel, titanium, calcined carbon, etc. can be used as the negative electrode current collector, and in the case of copper or stainless steel, a material surface-treated with carbon, nickel, titanium, silver, etc. can also be used. In addition, the average thickness of the negative electrode current collector can be appropriately applied in the range of 1 to 500 ㎛ in consideration of the conductivity and total thickness of the negative electrode to be manufactured.

[0091]

[0092] The cathode according to the present invention, having the above-described configuration, has the advantages of excellent lifespan characteristics under high-temperature conditions and low electrical resistance under high-rate conditions. Accordingly, a lithium secondary battery comprising the cathode can have excellent high-temperature lifespan characteristics and high-rate charge / discharge performance.

[0093]

[0094] Method for manufacturing cathode

[0095] Furthermore, in one embodiment of the present invention,

[0096] A step of forming a negative electrode active layer by applying and drying a negative electrode slurry containing a carbon-based negative electrode active material to at least one surface of a negative electrode current collector;

[0097] The above carbon-based negative electrode active material includes transition metal particles having magnetism;

[0098] The above transition metal particles include iron and nickel;

[0099] A method for manufacturing a negative electrode is provided, characterized in that the concentration ratio (Fe / Ni) of iron and nickel contained in the above carbon-based negative electrode active material is 2.5 to 13.0.

[0100]

[0101] The method for manufacturing an anode according to the present invention refers to the method for manufacturing the anode of the present invention described above. The method for manufacturing the anode can manufacture an anode for a lithium secondary battery by applying a cathode slurry onto a cathode current collector and drying the applied cathode slurry to form a cathode active layer.

[0102] At this time, the negative electrode slurry may include a carbon-based negative electrode active material as a main component, and the carbon-based negative electrode active material may have a form in which magnetic transition metal particles are uniformly dispersed. The transition metal particles refer to particles including a transition metal, and the transition metal may be included in the form of a transition metal, a transition metal oxide, a transition metal nitride, or a transition metal phosphate. At this time, the transition metal particles include a magnetizable transition metal, specifically, iron (Fe) and nickel (Ni).

[0103] In addition, the carbon-based negative electrode active material can be manufactured by a method including a step (S1) of graphitizing a carbon raw material, and a step (S2) of carbonizing the graphitized carbon raw material, and a step (S3) of applying a magnetic field at least once before and after the carbonizing step to control the concentration of transition metal particles having magnetism present in the carbon raw material.

[0104] The above graphitizing step (S1) refers to a process of heat-treating a carbon raw material at a temperature of 2,500°C or higher to convert the disordered structure of the carbon raw material into a graphite structure ordered by van der Waals.

[0105] Here, the “carbon raw material” may include one or more of needle cokes, mosaic cokes, coaltar pitch, and resin pitch.

[0106] The above graphitization step (S1) can be performed using a device such as an Acheson graphitization furnace, a box type graphitization furnace, or a lengthwise graphitization furnace.

[0107] The above graphitizing step (S1) can be applied without particular limitations as long as the heat treatment temperature can induce a physical change in the structure of the irregular carbon raw material into an ordered structure like graphite. For example, the graphitizing step (S1) can be performed at a temperature in the range of 2,000°C to 3,500°C; 2,500°C to 3,500°C; 2,800°C to 3,500°C, or 2,800°C to 3,200°C.

[0108] The present invention facilitates the induction of physical structural changes in carbon raw materials by performing the graphitization step (S1) within the above-described temperature range. The resulting product exhibits high crystallinity, resulting in superior electrical properties when applied to a cathode. Furthermore, the process efficiency is enhanced by suppressing sublimation on the surface of the carbon raw material during heat treatment.

[0109] The carbon raw material obtained in the above graphitizing step (S1) may be a carbon raw material that has been partially removed from the upper portion of the graphitized carbon raw material. When the carbon raw material is graphitized, foreign substances such as transition metals and non-metals present inside the carbon raw material may volatilize. However, some transition metals have boiling points that are equal to or slightly higher than the graphitization temperature, so they may not completely volatilize and may partially remain at the upper portion of the graphitized carbon raw material. Therefore, in this step (S1), when the graphitized carbon raw material is taken out of the reactor, a predetermined portion of the carbon raw material located at the upper portion may be removed and obtained. At this time, the carbon raw material to be removed may be a carbon raw material that has been introduced into the reactor and is present 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 on the surface of the carbon raw material.

[0110] Next, the step (S2) of carbonizing the graphitized carbon raw material refers to a process of assembling and compacting the graphitized carbon raw material. To this end, the present invention can perform carbonization by mixing the graphitized carbon raw material with pitch.

[0111] The carbon raw material graphitized by the above graphitization step (S1) can have a spherical secondary particle shape through the assembly of flaky primary particles. When such graphitized carbon raw material is uniformly mixed with pitch and then carbonized, the mixed pitch fixes the carbon raw materials adsorbed on the surface of the carbon raw material, thereby obtaining more stable spherical secondary particles. In addition, the spherical secondary particles have an increased density due to the pitch on the surface, thereby enabling the realization of a high energy density of the negative electrode active layer.

[0112] The above "pitch" is mainly a material made from coal or petrochemical process by-products, and generally used solid pitch or liquid pitch can be applied. The solid pitch can be obtained by crushing coal tar pitch, petroleum pitch, synthetic pitch, wood tar pitch, etc. The liquid pitch can be manufactured by dissolving liquid resin or solid pitch in a solvent, coating, and then carbonizing. At this time, the solvent that can be used is hexane, toluene, tetrahydrofuran (THF), quinoline, N-methylpyrrolidone (NMP), ethanol, etc.

[0113] The above high-quality pitch is the average particle diameter (D 50 ) may range from 1 to 7 μm, or from 2 to 4 μm. The average particle diameter (D) of the solid pitch 50 ) can be uniformly distributed and mixed among the negative electrode active material particles when satisfying these ranges, thereby coating the surface of the negative electrode active material particles more uniformly.

[0114] The above pitch may be used in an amount of 1 to 10 parts by weight based on 100 parts by weight of the graphitized carbon raw material; alternatively, 3 to 5 parts by weight. The present invention can prevent a significant increase in the content of transition metal particles contained in a carbon-based negative electrode active material produced due to a pitch content higher than the upper limit described above by controlling the mixing amount of pitch during carbonization of the graphitized carbon raw material within the above range. In addition, the present invention can prevent a decrease in structural stability due to lithium insertion / de-insertion of the carbon-based negative electrode active material during charge / discharge of a secondary battery due to a pitch mixing amount lower than the lower limit described above.

[0115] In addition, in this step (S2), the graphitized carbon raw material and pitch can be homogenized using a homogenization device to ensure uniform mixing of the graphitized carbon raw material and pitch. The homogenization device can be applied without particular limitation as long as it is commonly applied in the art. For example, the homogenization device can be a mixing homogenizer (vertical / horizontal mixer), an ultrasonic homogenizer, etc.

[0116] The above carbonization step (S2) can be performed at a predetermined temperature range. For example, the above carbonization step (S2) can be performed at a temperature in the range of 1,000°C to 2,600°C; 1,500°C to 2,000°C; or 1,500°C to 1,600°C.

[0117] Meanwhile, the transition metal particles having the above magnetic properties may be mixed into the carbon raw material by wear of the grinding device during the process of grinding the carbon raw material before graphitizing the carbon raw material, and in some cases, may be mixed into the carbon raw material by wear of the homogenizing device during carbonization of the graphitized carbon raw material. In this way, the introduced transition metal particles may exhibit superior electrical properties at high temperatures and / or conditions, although it is difficult to control the concentration of the transition metal particles compared to the case where the transition metal particles are intentionally mixed into the carbon raw material during the process of manufacturing a carbon-based negative electrode active material.

[0118] Accordingly, the method for manufacturing a negative electrode according to the present invention includes a step (S3) of controlling the concentration of transition metal particles by removing transition metal particles by applying a magnetic field before and / or after the step (S2) of carbonizing a graphitized carbon raw material in order to control the concentration of transition metal particles having magnetism in a carbon-based negative electrode active material.

[0119] For example, the transition metal particles can be removed by applying a magnetic field to the carbon raw material prior to carbonization (S2) of the graphitized carbon raw material.

[0120] Additionally, the above transition metal particles can be removed by applying a magnetic field to the carbon raw material after carbonization (S2) of the graphitized carbon raw material.

[0121] Since the above transition metal particles are magnetic metal particles, they can be easily removed in this step (S3) by applying a magnetic field to the carbon raw material. This allows for controlling the concentration of transition metal particles contained in the carbon-based negative electrode active material produced. However, if a magnetic field is applied twice to the graphitized carbon raw material, the concentration of transition metal particles remaining in the carbon raw material can be significantly reduced. In this case, the concentration ratio of iron and nickel present in the carbon-based negative electrode active material is significantly reduced, which may result in a deterioration in high-temperature charge / discharge performance or an increase in the electrical resistance of the negative electrode under high-rate conditions.

[0122] Here, the step (S3) of controlling the concentration of the transition metal particles can be performed for a certain period of time with a magnetic field strength that satisfies a certain range using an electromagnet or a permanent magnet.

[0123] For example, this step (S3) can be performed by applying a magnetic field with a strength in the range of 1,000 G to 40,000 G (Gauss), and specifically, can be performed by applying a magnetic field with a strength in the range of 5,000 G to 40,000 G; 20,000 G to 40,000 G; or 36,000 G to 40,000 G.

[0124] Additionally, this step (S3) may be performed for 1 second to 600 seconds, specifically, for 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.

[0125] The present invention can more easily control the concentration of transition metal particles in a carbon-based negative electrode active material manufactured by controlling the magnetic field strength and application time in the step (S3) of controlling the concentration of transition metal particles within the above range.

[0126] The carbon-based negative electrode active material manufactured in this way includes transition metal particles, and the transition metal particles may each include iron and nickel in a predetermined concentration range, and these may have a predetermined concentration ratio. Here, the concentration of the transition metal particles and / or the transition metal may be measured using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0127] For example, the iron may be included in the carbon-based negative electrode active material at a concentration ranging from 0.1 ppm to 1,000 ppm. For example, the iron may be included in the carbon-based negative electrode active material at a concentration ranging 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; It may be included in a concentration range of 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.

[0128] Additionally, the nickel may be included in the carbon-based negative electrode active material at a concentration of 0.01 ppm to 500 ppm. For example, the nickel may be included in the carbon-based negative electrode active material at a concentration of 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; It may be included in a concentration range of 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.

[0129] In addition, the transition metal particles having the above magnetic properties may include transition metal elements in addition to iron and nickel. For example, the transition metal particles may further include one or more of cobalt, chromium, zinc, magnesium, manganese, and copper. The transition metals may be included in the particle in the form of transition metals, transition metal oxides, transition metal nitrides, and transition metal phosphates.

[0130]

[0131] Meanwhile, the application of the negative electrode slurry can be performed by discharging and coating the negative electrode slurry containing a carbon-based negative electrode active material onto the surface of a moving negative electrode current collector. This process can be applied without particular limitation as long as it is a method commonly applied in the art, but a die coating method can be preferably used. The die coating method can be performed through a slot die having a shim for controlling the discharging conditions of the negative electrode slurry. In this case, by controlling the shape, position, etc. of the shim, the loading amount, coating thickness, etc. of the negative electrode slurry applied onto the negative electrode current collector can be easily controlled.

[0132] In addition, the above-described negative electrode slurry contains a carbon-based negative electrode active material as a main component, and may optionally further contain a conductive agent, a binder, other additives, etc., as needed. At this time, since the composition of the above-described negative electrode slurry has the same composition as the negative electrode active layer formed thereby, a detailed description thereof is omitted.

[0133] In addition, the drying of the cathode slurry can be applied without particular limitation as long as it is a method for drying an electrode active layer commonly used in the art. For example, the drying can be performed by applying heat energy to the cathode slurry using a hot air dryer, a vacuum oven, or the like.

[0134] In addition, the manufacturing method according to the present invention may further include a step of rolling the negative electrode active layer formed by drying the negative electrode slurry. The rolling step is a step of increasing the energy density of the negative electrode active layer by applying pressure to the surface of the formed negative electrode active layer using a roll press or the like. At this time, the rolling may be performed at a temperature higher than room temperature.

[0135] For example, the rolling may be performed at a temperature in the range of 50°C to 100°C, more specifically, at a temperature in the range of 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.

[0136] The above rolling can be performed at a rolling speed in the range of 2 m / s to 7 m / s, and more specifically, can be performed at a rolling speed in the range of 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.

[0137] The above rolling can be performed under pressure conditions ranging from 50 MPa to 200 MPa, and specifically, can be performed 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.

[0138] The present invention can easily increase the energy density of a cathode without damaging the cathode active layer by performing rolling under the above-mentioned temperature, speed and / or pressure conditions.

[0139]

[0140] The method for manufacturing a cathode according to the present invention can include transition metal particles containing iron and nickel at predetermined concentrations and ratios within a carbon-based cathode active material having the above-described composition. Accordingly, the manufactured cathode has the advantages of excellent lifespan characteristics under high-temperature conditions and low electrical resistance under high-rate conditions.

[0141]

[0142] Hereinafter, the present invention will be described in more detail through examples and comparative examples.

[0143] However, the following examples and comparative examples are only illustrative of the present invention, and the content of the present invention is not limited to the following examples and comparative examples.

[0144]

[0145] Examples 1 to 8 and Comparative Examples 1 to 5. Preparation of cathode

[0146] 1) Manufacturing of carbon-based negative electrode active materials

[0147] Coke raw material was prepared as a carbon raw material. The prepared coke raw material had an average particle diameter (D 50 ) was pulverized using a jet mill until it became 10㎛. The pulverized coke raw material was granulated using a horizontal granulator at 800℃ for 24 hours.

[0148] The above-mentioned coke raw material was heat-treated at 2,800°C for 400 hours using an Acheson graphitization device to be graphitized. When the graphitized product was removed from the graphitization device, the upper product from the product surface to a depth of 3% based on the total depth of the product was removed, and the product was obtained. The removal of the upper product is shown in Table 1 below.

[0149] 100 parts by weight of the above graphitized product and 5 parts by weight of solid pitch were mixed using a mixing homogenizer (vertical / horizontal mixer), and carbonized at a temperature of 1,500°C for 24 hours, thereby producing artificial graphite having a spherical secondary particle shape through assembly of flaky primary particles. However, before and / or after the carbonization, a magnetic field of 30,000 to 32,000 G was applied to the graphitized product using an electromagnet for 10 to 300 seconds to control the concentration of transition metal particles present in the product. The concentration control time points are as shown in Table 1 below.

[0150] Inductively coupled plasma optical emission spectrometry (ICP-OES) analysis was performed on the manufactured artificial graphite. Specifically, 100 g of each manufactured artificial graphite was added to 200 ml of ethanol, and a Teflon magnet (magnetic field strength: approximately 5000±100 G) was introduced into the ethanol to which the artificial graphite had been added and mixed for 2 hours. After mixing was completed, the Teflon magnet was removed from the ethanol and placed in a Teflon vial, 15 mL of aqua regia was injected, and then heated at 150°C for 3 hours. The heated aqua regia was cooled to room temperature, and ultrapure water was added to the cooled aqua regia to prepare a sample material with a total volume of 50 mL. Calibration curves were prepared for reference solutions of 0.1 mg / kg, 0.5 mg / kg, and 1.0 mg / kg using an inductively coupled plasma emission spectrometer (Model: OPTIMA AVIO 500, Manufacturer: PERKIN-ELMER), and analysis of the prepared sample material was performed. The method detection limit (MDL) was set to less than 50 μg / kg (< 50 μg / kg).

[0151] As a result, it was confirmed that the artificial graphite had particles containing iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), zinc (Zn), magnesium (Mg), manganese (Mn), and copper (Cu) uniformly dispersed therein. At this time, ① the total concentration of transition metals contained in the artificial graphite, ② the concentrations of each of iron (Fe) and nickel (Ni), and ③ the concentration ratio of iron and nickel are shown in Table 1 below.

[0152] Whether the top of the graphitized product was removed? Magnetic field application Transition metal particle component analysis results [Unit: ppm] Application time Application time Total concentration Fe concentration Ni concentration Fe / Ni Manufacturing example 1O Before carbonization Approximately 300 seconds 10.6 0.23 Manufacturing example 2O After carbonization Approximately 300 seconds 21.3 0.4 3.25 Manufacturing example 3O After carbonization Approximately 150 seconds 53.9 0.9 4.33 Manufacturing example 4O After carbonization Approximately 80 seconds 1612.9 2.9 4.44 Manufacturing example 5O After carbonization Approximately 15 seconds 91767.1 10.70 Manufacturing example 6X After carbonization Approximately 10 seconds 16095303.17 Manufacturing example 7X After carbonization Approximately 300 seconds 1,0008601107.82 Manufacturing example 8X After carbonization Approximately 200 seconds 1,0008307411.22 Manufacturing example 9O Before and after carbonization about 300 seconds 0.10.070.032.33 Manufacturing example 10X Before and after carbonization about 300 seconds 5004052913.97 Manufacturing example 11X Before carbonization about 300 seconds 2,00017901909.42 Manufacturing example 12OX-4,00034803709.41 Manufacturing example 13XX-6,00052705609.41

[0153]

[0154]

[0155] 2) Cathode manufacturing

[0156] Carboxymethylcellulose (CMC) and styrene butadiene rubber (SBR) were prepared as binders. Then, 96 parts by weight of the artificial graphite of Manufacturing Examples 1 to 10 prepared above, 1.5 parts by weight of carboxymethylcellulose (CMC), and 2.5 parts by weight of styrene butadiene rubber (SBR) were mixed with water to a solid content of 50% to prepare a negative electrode slurry.

[0157] The manufactured cathode slurry was applied onto a copper foil (thickness: 10 μm) being transported roll-to-roll (transport speed: 5 m / min) using a die coater.

[0158] The applied negative electrode slurry was dried with hot air to form a negative electrode active layer on the negative electrode current collector. The formed negative electrode active layer was rolled at 50±1℃ under a pressure of 100 to 150 MPa and a conveying speed of 3 m / s to manufacture a negative electrode for a lithium secondary battery (average thickness of the negative electrode active layer: 160±5 μm). The types of artificial graphite applied to each negative electrode are shown in Table 2 below.

[0159] Types of applied artificial graphiteExample 1 Artificial graphite manufactured in Manufacturing Example 1Example 2 Artificial graphite manufactured in Manufacturing Example 2Example 3 Artificial graphite manufactured in Manufacturing Example 3Example 4 Artificial graphite manufactured in Manufacturing Example 4Example 5 Artificial graphite manufactured in Manufacturing Example 5Example 6 Artificial graphite manufactured in Manufacturing Example 6Example 7 Artificial graphite manufactured in Manufacturing Example 7Example 8 Artificial graphite manufactured in Manufacturing Example 8Comparative Example 1 Artificial graphite manufactured in Manufacturing Example 9Comparative Example 2 Artificial graphite manufactured in Manufacturing Example 10Comparative Example 3 Artificial graphite manufactured in Manufacturing Example 11Comparative Example 4 Artificial graphite manufactured in Manufacturing Example 12Comparative Example 5 Artificial graphite manufactured in Manufacturing Example 13

[0160]

[0161]

[0162] Examples 9 to 16 and Comparative Examples 6 to 10. Manufacturing of lithium secondary batteries.

[0163] LiNi with a particle size of 5㎛ as a cathode active material 0.7 Co 0.1 Mn 0.1 Al 0.1 O2 was prepared, and polyvinylidene fluoride as a carbon-based conductive agent and binder was mixed with N-methyl pyrrolidone (NMP) in a weight ratio of 94:3:3 to form a slurry, which was cast on an aluminum sheet, dried in a vacuum oven at 120°C, and then rolled to manufacture a cathode.

[0164] A separator made of 18 μm polypropylene was interposed between the positive electrode obtained above and the negative electrode manufactured in Examples 1 to 8 and Comparative Examples 1 to 5, respectively, and inserted into a case, and then an electrolyte composition was injected to assemble a monocell for a lithium secondary battery.

[0165] At this time, the types of negative electrodes applied to each lithium secondary battery are shown in Table 3 below.

[0166] Type of applied cathode Example 9 The cathode manufactured in Example 1 Example 10 The cathode manufactured in Example 2 Example 11 The cathode manufactured in Example 3 Example 12 The cathode manufactured in Example 4 Example 13 The cathode manufactured in Example 5 Example 14 The cathode manufactured in Example 6 Example 15 The cathode manufactured in Example 7 Example 16 The cathode manufactured in Example 8 Comparative Example 6 The cathode manufactured in Comparative Example 1 Comparative Example 7 The cathode manufactured in Comparative Example 2 Comparative Example 8 The cathode manufactured in Comparative Example 3 Comparative Example 9 The cathode manufactured in Comparative Example 4 Comparative Example 10 The cathode manufactured in Comparative Example 5

[0167]

[0168] Experimental example.

[0169] In order to evaluate the performance of the negative electrode according to the present invention, the following experiments were conducted on each negative electrode and lithium secondary battery manufactured in the examples and comparative examples.

[0170]

[0171] 1) Evaluation of high-rate DC resistance of secondary batteries

[0172] Monocells manufactured in Examples 9 to 16 and Comparative Examples 6 to 10 were activated by charging at 0.1 C in constant current-constant voltage (CC-CV) mode at 25°C until 4.25 V, and then discharging at a constant current of 0.1 C until 3.0 V.

[0173] Each activated monocell was charged at a constant current of 2.5 C at 25°C for 30 seconds to a 50% state of charge (SOC), while measuring the direct current resistance (DC-IR). The measured results are shown in Table 4 below.

[0174]

[0175] 2) High temperature life evaluation

[0176] Monocells manufactured in Examples 9 to 16 and Comparative Examples 6 to 10 were activated by charging at 0.1 C in constant current-constant voltage (CC-CV) mode at 25°C until 4.25 V, and then discharging at a constant current of 0.1 C until 3.0 V.

[0177] Afterwards, a constant current (CC) charge of 1C at 45℃ and a constant current (CC) discharge of 1C were set as one cycle, and 300 cycles of charge and discharge were performed on each monocell. At this time, 1 charge and discharge cycle of each monocell st Charging capacity of the cycle and 300 th The charging capacity of the cycle was measured. The measured 1 st 300 based on the charging capacity of the cycle th The high-temperature life of each monocell was evaluated by calculating the cycle-specific charge capacity retention rate. The results are shown in Table 4 below.

[0178] Type of cathode DC resistance [mΩ] Capacity retention rate [%] at 300 cycles Example 9 Cathode manufactured in Example 1 178384.6 Example 10 Cathode manufactured in Example 2 178085.5 Example 11 Cathode manufactured in Example 3 176086.9 Example 12 Cathode manufactured in Example 4 175486.5 Example 13 Cathode manufactured in Example 5 177284.8 Example 14 Cathode manufactured in Example 6 182579.8 Example 15 Cathode manufactured in Example 7 179084.0 Example 16 Cathode manufactured in Example 8 180582.9 Comparative Example 6 Cathode manufactured in Comparative Example 1 183182.6 Comparative Example 7Cathode manufactured in Comparative Example 2 195177.7Comparative Example 8Cathode manufactured in Comparative Example 3 191379.9Comparative Example 9Cathode manufactured in Comparative Example 4 192179.1Comparative Example 10Cathode manufactured in Comparative Example 5 194678.6

[0179]

[0180] As shown in Table 4 above, it can be seen that the negative electrode for a lithium secondary battery according to the present invention has low DC resistance during high-rate charge / discharge and excellent high-temperature charge / discharge performance.

[0181] Specifically, the secondary battery of the embodiment in which the concentration and concentration ratio of iron and nickel contained in the carbon-based negative electrode active material satisfied a predetermined range had a low DC resistance of less than 1810 mΩ during high-rate charge / discharge of 2.5C, and a high capacity retention rate of about 83% or more during high-temperature charge / discharge.

[0182] On the other hand, the secondary battery of Comparative Example 6 had a significantly lower concentration of transition metal particles in the carbon-based negative electrode material compared to the examples, but the concentration ratio of iron and nickel was significantly lower, so that the DC resistance exceeded 1800 mΩ during high-rate charge / discharge and the capacity retention rate was confirmed to be less than 83% during high-temperature charge / discharge.

[0183] This means that even if a carbon-based negative electrode active material contains a certain amount of transition metal particles, if the concentration of iron and nickel and their concentration ratio satisfy a certain range, the DC resistance during high-rate charge / discharge of the negative electrode and the capacity retention rate during high-temperature charge / discharge can be improved.

[0184] From these results, it can be seen that the negative electrode for a lithium secondary battery according to the present invention has the advantages of excellent life characteristics under high temperature conditions and low electrical resistance under high rate conditions.

[0185]

[0186] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that the present invention can be variously modified and changed within a scope that does not depart from the technical scope of the present invention as set forth in the claims to be described below.

[0187] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the patent claims.

Claims

1. A negative electrode current collector, and a negative electrode active layer provided on at least one surface of the negative electrode current collector and including a carbon-based negative electrode active material; The above carbon-based negative electrode active material includes transition metal particles having magnetism; The above transition metal particles contain iron and nickel; The above carbon-based negative electrode active material contains transition metal particles in a concentration range of 1,200 ppm or less; A cathode characterized in that the concentration ratio of iron and nickel (Fe / Ni) contained in the carbon-based cathode active material is in the range of 2.5 to 13.

0.

2. In paragraph 1, An anode having a concentration of iron contained in the above carbon-based anode active material in the range of 0.1 ppm to 1,000 ppm.

3. In paragraph 1, An anode having a concentration of nickel contained in the above carbon-based anode active material in the range of 0.01 ppm to 500 ppm.

4. In paragraph 1, The above carbon-based negative electrode active material is a negative electrode containing magnetic transition metal particles in a concentration range of 0.01 ppm to 1,100 ppm.

5. In paragraph 1, A cathode in which the transition metal particles having magnetism included in the above carbon-based cathode active material contain iron at 50% or more by total weight.

6. In paragraph 1, A cathode further comprising at least one of cobalt, chromium, zinc, magnesium, manganese, and copper as the magnetic transition metal particles included in the above carbon-based cathode active material.

7. In paragraph 1, The above carbon-based negative electrode active material is a negative electrode characterized in that it is an artificial graphite in the form of secondary particles in which primary particles are assembled.

8. A step of forming a negative electrode active layer by applying and drying a negative electrode slurry containing a carbon-based negative electrode active material to at least one surface of a negative electrode current collector; The above carbon-based negative electrode active material includes transition metal particles having magnetism; The above transition metal particles contain iron and nickel; The above carbon-based negative electrode active material contains transition metal particles in a concentration range of 1,200 ppm or less; A method for manufacturing a cathode, characterized in that the concentration ratio (Fe / Ni) of iron and nickel contained in the carbon-based cathode active material is in the range of 2.5 to 13.

0.

9. In paragraph 8, The above carbon-based negative electrode active material is, Step of graphitizing carbon raw material (S1), and Comprising a step (S2) of carbonizing a graphitized carbon raw material; A method for manufacturing a cathode, wherein the graphitized carbon raw material is manufactured by a method including a step (S3) of controlling the concentration of transition metal particles having magnetism present in the carbon raw material by applying a magnetic field at least once before and after the carbonization step.

10. In paragraph 9, The step (S3) of controlling the concentration of transition metal particles included in the above carbon-based negative electrode active material is a method for manufacturing a negative electrode in which a magnetic field is applied with a strength ranging from 1,000 G to 40,000 G for 1 second to 600 seconds.

11. In paragraph 9, A method for manufacturing a cathode, wherein the step (S3) of controlling the concentration of transition metal particles included in the above carbon-based cathode active material is performed before or after the step of carbonizing the graphitized carbon raw material.

12. In paragraph 8, A method for manufacturing a negative electrode, wherein the concentration of iron contained in the above carbon-based negative electrode active material is in the range of 0.1 ppm to 1,000 ppm.

13. In paragraph 8, A method for manufacturing a negative electrode, wherein the concentration of nickel contained in the above carbon-based negative electrode active material is in the range of 0.01 ppm to 500 ppm.

14. In paragraph 8, A method for manufacturing a cathode, wherein the transition metal particles included in the above carbon-based cathode active material further include at least one of cobalt, chromium, zinc, magnesium, manganese, and copper.