Negative electrode for lithium secondary battery, lithium secondary battery including same, and method for manufacturing negative electrode

Abstract

According to exemplary embodiments, provided is a negative electrode. The negative electrode includes a current collector, a first negative electrode active material layer, and a second negative electrode active material layer, wherein the second negative electrode active material layer includes a plurality of concave portions which are indented toward the first negative electrode active material layer and a plurality of non-concave portions which are not the concave portions, the concave portions and the non-concave portions being alternately arranged in the horizontal direction and the surface of the second negative electrode active material layer having a pattern formed due to the steps.

Description

Anode for a lithium secondary battery, a lithium secondary battery including the same, and a method for manufacturing the anode

[0001] This application claims the benefit of priority from Republic of Korea Patent Application No. 10-2023-0085005, filed on June 30, 2023.

[0002] The present invention relates to a high-loading / high-density negative electrode for satisfying high-energy density, high-output battery specifications, a negative electrode having improved life resistance characteristics according to charge and discharge, a lithium secondary battery including the same, and a method for manufacturing the negative electrode.

[0003] With the recent technological development and increasing demand for mobile devices, the demand for batteries as an energy source is rapidly increasing. As HEV, PHEV, and EV vehicles are gaining attention as future vehicles, various research is being conducted on batteries that can meet these diverse needs.

[0004] In particular, research is actively being conducted on lithium secondary batteries that have high energy density and excellent life and cycle characteristics.

[0005] Conventional lithium secondary batteries primarily use carbon-based compounds as anode active materials, which maintain structural and electrical properties while enabling reversible lithium ion insertion and deintercalation. However, with the growing demand for high-energy-density batteries, extensive research is being conducted on transition metals (Group IV and V), such as silicon and tin, which chemically react with lithium, as well as their alloys and oxides.

[0006] Among them, the above silicon has a theoretical maximum capacity of approximately 4020 mAh / g (9800 mAh / cc, specific gravity 2.23), which is much larger than that of carbon-based materials, and is therefore attracting attention as a high-capacity anode material. However, the silicon or its alloys have a problem in that the anode deteriorates as it repeatedly expands (up to 4 times) and contracts much more than that of carbon-based active materials during charge and discharge, which reduces the cycle life of the battery.

[0007] This phenomenon becomes more pronounced as the content of high-capacity cathode active materials increases, enabling the production of high-energy-density cells. Therefore, research is needed in the field to control volume expansion during charge and discharge, thereby improving electrode structural stability and, consequently, battery performance.

[0008] Furthermore, in response to the growing demand for high-energy-density batteries, development of high-loading and high-density electrodes is primarily underway. However, high-loading / high-density electrodes suffer from increased resistance due to increased pore resistance and longer lithium ion migration paths, which slows the diffusion of lithium ions within the electrode. Therefore, efforts are also needed to improve the resistance increase associated with high-loading / high-density electrodes.

[0009] The technical problem to be solved by the technical idea of ​​the present invention is to provide a lithium secondary battery negative electrode capable of increasing the movement speed of lithium ions in a high-loading negative electrode while improving the deterioration of structural stability due to volume expansion.

[0010] According to one embodiment of the present invention, there is provided an anode for a lithium secondary battery, comprising: a current collector; a first anode active material layer formed on one or both surfaces of the current collector and including a first anode active material, which is a carbon-based compound, as a negative electrode active material; and a second anode active material layer formed on the first anode active material layer and including a second anode active material of a different type from the carbon-based compound as a negative electrode active material, wherein the second anode active material layer includes a plurality of concave portions recessed toward the first anode active material layer and a plurality of non-concave portions that are not the concave portions, wherein the concave portions and the non-concave portions are alternately arranged in a horizontal direction, the concave portions are filled with a conductive layer including a conductive material, and a thickness of the conductive layer filled in the concave portions is smaller than a thickness of the non-concave portions, and a surface of the second anode active material layer is patterned by a step difference between the conductive layer and the non-concave portions.

[0011] In one embodiment, the conductive layer further comprises a negative active material.

[0012] In one embodiment, the conductive layer has the same composition as the second negative electrode active material layer.

[0013] In one embodiment, the weight % of the conductive material included in the conductive layer is greater than the weight % of the conductive material included in the second negative electrode active material layer.

[0014] In one embodiment, the conductive layer comprises 70 to 94 parts by weight of a negative active material; 5 to 20 parts by weight of a conductive agent; and 1 to 10 parts by weight of a binder.

[0015] In one embodiment, the conductive layer does not include a negative active material and includes 80 to 100 parts by weight of a conductive material and 20 parts by weight or less of a binder.

[0016] According to another embodiment of the present invention, there is provided an anode for a lithium secondary battery, comprising: a current collector; a first anode active material layer formed on one or both surfaces of the current collector and including a first anode active material that is a carbon-based compound as a negative electrode active material; and a second anode active material layer formed on the first anode active material layer and including a second anode active material of a different type from the carbon-based compound as a negative electrode active material, wherein the second anode active material layer includes a plurality of concave portions recessed toward the first anode active material layer and a plurality of non-concave portions that are not the concave portions, wherein the concave portions and the non-concave portions are alternately arranged in a horizontal direction, and a surface of the second anode active material layer is patterned by a step difference between the non-concave portions and the concave portions.

[0017] In one embodiment, the horizontal width length of each of the non-concave portions is in the range of 50 μm to 1500 μm.

[0018] In one embodiment, the horizontal width of each of the concave portions is in the range of 10 μm to 800 μm, but is less than or equal to the horizontal width of the non-concave portion.

[0019] In one embodiment, the length of the step is in the range of 5 μm to 60 μm.

[0020] In one embodiment, the negative electrode active material included in the first negative electrode active material layer is composed of a carbon-based first negative electrode active material.

[0021] In one embodiment, the carbon-based first negative electrode active material is a graphite-based negative electrode active material.

[0022] In one embodiment, the second negative electrode active material is Si, SiO x (0 <x<2), Si-C 복합체 및 Si 금속 합금으로 이루어진 군으로부터 선택된 1종 또는 2종 이상의 혼합물일 수 있다.

[0023] In one embodiment, the average value of the total loading amount of the first negative electrode active material layer and the second negative electrode active material layer is 4 mAh / cm2 or more.

[0024] According to another embodiment of the present invention, a lithium secondary battery including the above-described negative electrode is provided.

[0025] According to another embodiment of the present invention, a method for manufacturing an anode for a lithium secondary battery is provided, including: a step of preparing a first anode slurry by mixing and stirring a carbon-based first anode active material, a conductive material, and a binder in a solvent; a step of preparing a second anode slurry by mixing and stirring a second anode active material, a conductive material, and a binder, the second anode active material being different in kind from the carbon-based first anode active material, in a solvent; a step of preparing a slurry for a conductive layer; a first coating step of coating the first anode slurry on a current collector; a second coating step of coating the second anode slurry and the slurry for the conductive layer on the first anode slurry; and a drying step of drying the first anode slurry, the second anode slurry, and the slurry for the conductive layer, wherein the second coating step is characterized in that the second anode slurry and the slurry for the conductive layer are coated so that they are alternately arranged in a horizontal direction.

[0026] In one embodiment, the solids content of the second cathode slurry is greater than the solids content of the slurry for the conductive layer.

[0027] In one embodiment, the secondary coating process includes coating the second cathode slurry and the slurry for the conductive layer using a nozzle printer.

[0028] In one embodiment, the slurry for the conductive layer further comprises a negative active material.

[0029] In one embodiment, the slurry for the conductive layer and the second cathode slurry have the same composition.

[0030] In one embodiment, the weight % of the conductive material included in the solid content of the slurry for the conductive layer is greater than the weight % of the conductive material included in the solid content of the second cathode slurry.

[0031] In one embodiment, the slurry for the conductive layer does not include a negative active material and includes, in the solid content, 80 to 100 parts by weight of a conductive material and 20 parts by weight or less of a binder.

[0032] According to another embodiment of the present invention, a method for manufacturing an anode for a lithium secondary battery is provided, including: a step of preparing a first anode slurry by mixing and stirring a carbon-based first anode active material, a conductive material, and a binder in a solvent; a step of preparing a second anode slurry by mixing and stirring a second anode active material, a conductive material, and a binder, the second anode active material being different in kind from the carbon-based first anode active material, in a solvent; a coating step of coating the first and second anode slurries on a current collector so that the second anode slurry is laminated on the first anode slurry; a step of drying the first and second anode slurries; and a step of etching a second anode active material layer formed by drying the second anode slurry at a predetermined interval and width, and patterning the second anode active material layer so that a concave portion formed by the etching toward the current collector and a non-concave portion that is not the concave portion are alternately arranged in a horizontal direction.

[0033] In one embodiment, the patterning process includes etching using a laser.

[0034] According to one embodiment of the present invention, a negative electrode includes a first negative electrode active material, which is a carbon-based compound having excellent structural stability, in a lower layer, and a second negative electrode active material having excellent capacity and input / output characteristics in an upper layer, so that the problem of the negative electrode active material layer expanding in the thickness direction according to repeated cycles can be alleviated, and resistance and input / output characteristics can be improved even when the negative electrode is highly loaded.

[0035] According to one embodiment of the present invention, the negative electrode has a step pattern formed on the surface of the second negative electrode active material layer, thereby increasing the reaction area of ​​the negative electrode surface, thereby suppressing an increase in resistance due to high loading of the negative electrode, and has excellent structural stability as a result of the step space on the surface of the second negative electrode active material layer acting as a buffer for changes in the volume of the negative electrode active material layer.

[0036] Figure 1 is a top view of a cathode according to one embodiment of the present invention.

[0037] Figure 2 is a vertical cross-sectional view of a cathode according to one embodiment of the present invention.

[0038] Figure 3 is a vertical cross-sectional view of a cathode according to another embodiment of the present invention.

[0039] Figure 4 is a vertical cross-sectional view of a cathode according to another embodiment of the present invention.

[0040] Figure 5 is a flowchart illustrating a method for manufacturing a negative electrode for a lithium secondary battery according to one embodiment of the present invention.

[0041] Figure 6 is a flowchart illustrating a method for manufacturing a negative electrode for a lithium secondary battery according to another embodiment of the present invention.

[0042] FIG. 7 is a drawing illustrating a secondary coating process in a method for manufacturing a cathode according to one embodiment of the present invention.

[0043] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0044] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0045] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0046] In this specification, it should be understood that the terms “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0047] In this specification, the term “combination(s) thereof” included in the surface of the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression of the Makushi format, and means including one or more selected from the group consisting of the above components.

[0048] In this specification, the description of “A and / or B” means “A or B or both.”

[0049] In this specification, “%” means weight percent unless explicitly indicated otherwise.

[0050] In this specification, the specific surface area can be measured using the BET (Brunauer-Emmett-Teller; BET) method. For example, it can be measured using the BET 6-point method by nitrogen gas adsorption flow using a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini).

[0051] In this specification, the average particle diameter (D 50 ) can be defined as the particle diameter at 50% of the particle diameter distribution. The average particle diameter is not particularly limited, but can be measured using, for example, a laser diffraction method or a scanning electron microscope (SEM) photograph. The laser diffraction method can generally measure particle diameters from the submicron range to several mm, and can obtain results with high reproducibility and high resolution.

[0052] In this specification, the full width direction of the cathode is defined as the X-axis direction, the full length direction of the cathode is defined as the Y-axis direction, and the direction perpendicular to the plane resulting from the combination of the X-axis direction and the Y-axis direction is defined as the Z-axis direction, and the X-axis direction and the Y-axis direction are referred to as horizontal directions.

[0053]

[0054] Cathode for lithium secondary batteries

[0055] (First embodiment)

[0056] FIG. 1 is a top view of a cathode according to one embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of a cathode according to one embodiment of the present invention.

[0057] Referring to these drawings, the negative electrode (10, hereinafter referred to as “negative electrode”) for a lithium secondary battery according to the first embodiment includes a first negative electrode active material layer (11) formed on a current collector (13); And it includes a second negative electrode active material layer (12) formed on the first negative electrode active material layer (11), and the second negative electrode active material layer (12) includes a plurality of concave portions (12a) recessed toward the first negative electrode active material layer (11) and a plurality of non-concave portions (12b) other than the concave portions (12b), and the concave portions (12a) and the non-concave portions (12b) are arranged alternately along the horizontal direction (Y-axis direction), and the concave portions (12a) are filled with a conductive layer (14), and the thickness of the conductive layer (14) filled in the concave portions (12a) is smaller than the thickness of the non-concave portions (12b), so that the surface of the second negative electrode active material layer (12) has a pattern formed by the step between the conductive layer (14) and the non-concave portions (12b).

[0058] FIG. 2 illustrates an embodiment in which a first negative electrode active material layer (11) and a second negative electrode active material layer (12) are sequentially formed on one side of a current collector (13), but is not limited thereto, and a first negative electrode active material layer (11) and a second negative electrode active material layer (12) may be sequentially formed on both sides of the current collector (13).

[0059] The first negative electrode active material layer (11) includes a carbon-based first negative electrode active material having excellent structural stability even though the capacity is somewhat small as the negative electrode active material, and the second negative electrode active material layer (12) includes a second negative electrode active material different from the carbon-based compound. In addition, as the second negative electrode active material, an negative electrode active material having a larger capacity and excellent input / output characteristics than the carbon-based first negative electrode active material may be selected. For example, in order to improve the rapid charging performance of the battery, the upper layer of the negative electrode includes a second negative electrode active material such as a transition metal, an oxide thereof, etc., represented by a silicon-based material that is advantageous for the diffusion of lithium ions, and in order to supplement the structural instability problem, which is a disadvantage of these active materials, by including a carbon-based first negative electrode active material in the first negative electrode active material layer, the problem of expansion in the thickness direction of the negative electrode active material layer due to repeated cycles can be alleviated, and the input / output characteristics can be improved even when the negative electrode is highly loaded.

[0060] The above-mentioned concave portion (12a) may be indented toward the first negative electrode active material layer (11) to a thickness corresponding to the thickness of the non-concave portion (12b). That is, as illustrated in FIG. 2, the inside of the concave portion (12a) of the second negative electrode active material layer (12) may have a structure in which the second negative electrode active material layer (12) does not exist, and thus the first negative electrode active material layer (11) is exposed. In addition, a conductive layer (14) may be filled in the inside of the concave portion (12a), and as a result, a structure in which multiple rows of non-concave portions (12b) and multiple rows of conductive layers (14) are alternately arranged on the first negative electrode active material layer (11) may be achieved.

[0061] A plurality of non-concave portions (12b) are spaced apart from each other by a predetermined interval, and a concave portion (12a) is arranged between the non-concave portions (12b) that are spaced apart from each other and an adjacent non-concave portion (12b). The inside of the concave portion (12a) is filled with a conductive layer (14), and the thickness of the conductive layer (14) is smaller than the thickness of the non-concave portion (12b). The step space caused by the difference in thickness between the non-concave portions (12b) and the conductive layer (14) serves to buffer the volume change of the negative electrode active material layer (11, 12) due to repeated charge and discharge, thereby preventing the negative electrode active material from being peeled off during charge and discharge and improving the performance of the battery.

[0062] When a step pattern of a non-concave portion (12b) and a conductive layer (14) is formed, the surface of the second negative electrode active material layer has a wider specific surface area than when there is no such step pattern, so the movement path of lithium ions can be increased, thereby reducing the resistance of the negative electrode and also having the effect of further improving the input / output characteristics.

[0063] In exemplary embodiments, the second negative electrode active material layer (12) and the conductive layer (14) are disposed on the first negative electrode active material layer (11), and the surface of the first negative electrode active material layer (11) is covered by the second negative electrode active material layer (12) and the conductive layer (14). Accordingly, since the second negative electrode active material layer having excellent input / output characteristics is positioned on the surface of the negative electrode, an negative electrode advantageous for rapid charging can be provided.

[0064] The number of rows of the above-described non-concave portions (12b) and concave portions (12a) can be appropriately selected depending on the size of the punched negative electrode and is not particularly limited. Specifically, each of these can be arranged in 100 rows or more, more specifically in 200 to 9000 rows, and even more specifically in 200 to 8000 rows. Here, the punched negative electrode may mean a negative electrode having a predetermined overall width and overall length by notching and cutting an electrode sheet serving as a base material to suit the size of the secondary battery to be assembled (see Fig. 1).

[0065] The horizontal width (X-axis direction or Y-axis direction) of each of the plurality of concave portions (12b) may be in the range of 50 to 1500 ㎛, more specifically 150 to 1250 ㎛, and even more specifically 200 to 1000 ㎛.

[0066] The horizontal direction (X-axis direction or Y-axis direction) width length of each of the plurality of concave portions (12a) may be within a range equal to or less than the horizontal direction width length of the non-concave portion (12b), and may be in a range of 10 to 800 ㎛, more specifically 10 to 600 ㎛, and even more specifically 20 to 400 ㎛.

[0067] When the horizontal width lengths of the non-concave portion (12b) and the concave portion (12a) are within the above range, the input / output characteristics and resistance improvement effect are optimized, and the life characteristics and capacity characteristics can be further improved.

[0068] The length of the step, which is the difference between the thickness of the non-concave portion (12b) and the thickness of the conductive layer (14), may be 5 μm to 60 μm, preferably 7.5 to 40 μm, and more preferably 10 to 30 μm. A negative electrode having a step within the above range can improve the energy density of the battery while exhibiting an excellent resistance improvement effect due to the step. Here, the step refers to the length in the thickness direction (Z direction).

[0069] The above-mentioned concave portion (12a) may be formed at a constant interval, or may be formed at an irregular (random) interval without a constant interval. In addition, the above-mentioned concave portion (12a) may be formed in a constant shape, or may be formed in an irregular shape.

[0070] According to a specific embodiment of the present invention, the negative electrode is a high-loading negative electrode, and the average value of the total loading amount of the first negative electrode active material layer and the second negative electrode active material layer may be 4 mAh / cm2 or more, more specifically, in the range of 4 mAh / cm2 to 8 mAh / cm2.

[0071] In one embodiment of the present invention, the conductive layer (14) may not include a negative electrode active material.

[0072] When the negative active material is not included in the conductive layer (14), lithium ions can move quickly through the conductive layer (14), which can be more advantageous in improving resistance and input / output characteristics. However, since there is no negative active material in the conductive layer (14) that can absorb lithium, there is a concern about lithium plating. Therefore, in this case, it is preferable to design the horizontal width (X-axis direction or Y-axis direction) of the conductive layer to be smaller than the horizontal width of the concave portion (12a) described above. Specifically, the horizontal width of the conductive layer (14) may be 10 µm to 400 µm, preferably 10 µm to 300 µm, and more preferably 20 µm to 200 µm.

[0073] When the negative electrode active material is not included in the conductive layer (14), the conductive layer (14) according to one embodiment may include 80 to 100 parts by weight of a conductive material and 20 parts by weight or less of a binder. The conductive material and binder are not particularly limited and may be known materials used in negative electrodes for lithium secondary batteries. Specific examples of the conductive material include carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material, etc., and among them, carbon nanotube, carbon nanofiber, and carbon black are preferable as the conductive material of the conductive layer.

[0074] In another embodiment of the present invention, the conductive layer (14) may further include a negative electrode active material.

[0075] When the above conductive layer (14) includes a negative electrode active material, the conductive layer contributes to the capacity development of the negative electrode, so there is a more advantageous advantage in terms of high loading of the electrode. In addition, since a negative electrode active material capable of absorbing lithium is present in the conductive layer (14), the risk of lithium plating is low.

[0076] In one embodiment, the negative electrode active material included in the conductive layer (14) may include the same compound as the second negative electrode active material included in the non-concave portion (12b), and may further include the first negative electrode active material, which is a carbon-based compound.

[0077] In an exemplary embodiment, the conductive layer (14) may have the same composition as the second negative electrode active material layer. Here, having the same composition means that the negative electrode active material, conductive material, and binder constituting the conductive layer (14) and the negative electrode active material, conductive material, and binder constituting the second negative electrode active material layer are each the same compound and have the same weight ratio. When the conductive layer (140) and the second negative electrode active material layer (12) have the same composition, the method for manufacturing the negative electrode can be simpler.

[0078] When the conductive layer (14) includes a negative electrode active material, the negative electrode according to one embodiment may have a weight % of the conductive material included in the conductive layer (14) greater than a weight % of the conductive material included in the second negative electrode active material layer (12). In this case, the excellent electrical conductivity of the conductive layer (14) may alleviate the phenomenon of structural destruction of the conductive network due to a change in the volume of the negative electrode active material layer. In one embodiment, the conductive layer (14) may include, with respect to 100 wt. of the conductive layer, 70 to 94 wt. parts of the negative electrode active material; 5 to 20 wt. parts of the conductive material; and 1 to 10 wt. parts of the binder. In a preferred embodiment, the conductive layer (14) may include 80 to 93 wt. parts of the negative electrode active material; 5.5 to 15 wt. parts of the conductive material; and 2 to 9 wt. parts of the binder, more preferably, 82 to 92 wt. parts of the negative electrode active material; 6 to 10 wt. parts of the conductive material; and may contain 2.5 to 8 parts by weight of a binder.

[0079] In order to control the electrical conductivity of the above conductive layer (14) to be greater than the electrical conductivity of the negative electrode active material layer (12), the content of the conductive material in the conductive layer may be increased as described above, or a conductive material having a characteristic greater than the electrical conductivity of the conductive material included in the second negative electrode active material layer (12b) may be selected as the conductive material of the conductive layer (14).

[0080] The above current collector (13) is a metal having high conductivity and to which the slurry of the electrode active material can easily adhere, and any metal that is non-reactive within the voltage range of the battery can be used. Specifically, copper, stainless steel, aluminum, nickel, titanium, sintered carbon; stainless steel surface-treated with carbon, nickel, titanium or silver; aluminum-cadmium alloy; non-conductive polymer surface-treated with a conductive material; or conductive polymer can be used. In addition, the bonding strength of the negative electrode active material can be strengthened by forming fine irregularities on the surface, and can be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0081] The above first negative electrode active material layer (11) may include a carbon-based first negative electrode active material as the negative electrode active material. The carbon-based first negative electrode active material has superior structural stability to the second negative electrode active material included in the second negative electrode active material layer described below, and thus does not experience a large volume change due to repeated charging and discharging, making it preferable as the negative electrode active material included in the lower layer.

[0082] Specifically, both low-crystalline carbon and high-crystalline carbon can be used as the above-mentioned carbon-based first negative electrode active material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and examples of high-crystalline carbon include calcined carbon such as natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and petroleum or coal tar pitch derived cokes. Specifically, graphite-based negative electrode active materials such as natural graphite or artificial graphite are more preferable because they can reversibly insert and de-insert lithium ions while maintaining structural and electrical properties.

[0083] Typically, to address the lack of adhesion between the negative electrode active material and the negative electrode current collector, methods such as adding additional binder or further rolling the negative electrode are employed. However, if the porosity of the negative electrode active material layer is reduced by increasing the binder content or increasing the degree of rolling of the negative electrode, the diffusion of lithium ions from the surface of the negative electrode active material layer into the negative electrode active material layer becomes difficult, resulting in increased negative electrode resistance and deterioration of the performance of the secondary battery.

[0084] When natural graphite having excellent adhesive strength or a graphite-based negative electrode active material having a high degree of sphericity is included in the first negative electrode active material layer positioned between the second negative electrode active material layer and the current collector, the adhesive strength between the negative electrode active material and the negative electrode current collector can be improved without increasing the binder or negative electrode rolling as described above.

[0085] In one embodiment of the present invention, in order to improve adhesion while maintaining an appropriate range of output characteristics, the first negative electrode active material layer may be composed of natural graphite and / or artificial graphite as the negative electrode active material. In particular, to maximize adhesion, the carbon-based first negative electrode active material may be composed of natural graphite.

[0086] In one embodiment of the present invention, the graphite-based active material has an average particle diameter (D) of 1 ㎛ to 30 ㎛ 50 ) and may have an average particle diameter (D) of specifically 5 ㎛ to 25 ㎛, more specifically 7 ㎛ to 23 ㎛ 50 ) can have.

[0087] When the graphite-based active material included in the first negative electrode active material layer has an average particle diameter within the above numerical range, the first negative electrode active material layer can be appropriately formed on the current collector while exhibiting an appropriate electrode density.

[0088] In one embodiment of the present invention, the natural graphite may have a specific surface area of ​​1.5 m2 / g to 8 m2 / g, specifically 2.1 m2 / g to 4.5 m2 / g, and more specifically 2.5 m2 / g to 4 m2 / g. When the natural graphite has the specific surface area range, it can provide adhesiveness to the negative electrode due to the specific surface area above a certain level, while preventing the initial irreversible capacity during charge and discharge from increasing excessively due to the specific surface area.

[0089] In addition, the natural graphite may have a tap density of 0.9 g / cc to 1.3 g / cc, specifically, a tap density of 0.92 g / cc to 1.2 g / cc, and more specifically, a tap density of 0.95 g / cc to 1.15 g / cc. When the natural graphite has a tap density within the above range, the first negative electrode active material may have appropriate negative electrode adhesiveness and excellent energy density.

[0090] In one embodiment of the present invention, the artificial graphite may have a specific surface area of ​​0.4 m2 / g to 5.0 m2 / g, specifically 0.5 m2 / g to 4.0 m2 / g, and more specifically 0.6 m2 / g to 3.0 m2 / g. When the artificial graphite has the specific surface area range, the initial irreversible capacity during charge and discharge may be prevented from increasing.

[0091] In addition, the artificial graphite may have a tap density of 0.7 g / cc to 1.1 g / cc, specifically, a tap density of 0.75 g / cc to 1.05 g / cc, and more specifically, a tap density of 0.8 g / cc to 1.0 g / cc. When the artificial graphite has a tap density within the above range, the first negative electrode active material may have excellent energy density.

[0092] In one embodiment of the present invention, the graphite-based negative electrode active material included in the first negative electrode active material layer may have a sphericity of 0.8 or more, preferably a sphericity of 0.85 to 1, and more preferably a sphericity of 0.9 to 1.

[0093] The higher the degree of sphericity of the graphite-based negative electrode active material, the more the binder is properly attached to the surface of the negative electrode active material, and is smoothly dispersed without causing clumping or agglomeration, thereby improving the adhesive strength of the entire first negative electrode active material layer.

[0094] The above sphericity may be a value obtained by dividing the circumference of a circle having the same area as the projected image when the graphite-based negative electrode active material is projected by the perimeter of the projected image, and may be specifically expressed by the following mathematical formula 1. The above sphericity may be measured using a particle shape analyzer, such as a sysmex FPIA3000 manufactured by Malvern.

[0095] [Mathematical Formula 1]

[0096] Sphericity = Circumference of a circle with the same area as the projected image of the graphite-based active material / Perimeter of the projected image

[0097] In one embodiment of the present invention, it is preferable that the negative electrode active material included in the first negative electrode active material layer (11) be composed only of the carbon-based first negative electrode active material described above, in terms of structural stability and capacity retention rate of the negative electrode.

[0098] In one embodiment of the present invention, the first negative electrode active material layer (11) may have a thickness of 200 μm or less, specifically a thickness of 20 μm to 150 μm, and more specifically a thickness of 30 μm to 100 μm.

[0099] When the first negative electrode active material layer has a thickness within the above range, the first negative electrode active material layer can be appropriately formed on the negative electrode current collector to provide appropriate adhesive force between the negative electrode current collector and the second negative electrode active material layer.

[0100] The above carbon-based first negative electrode active material is capable of reversible insertion and deintercalation of lithium ions while maintaining structural and electrical properties as a negative electrode active material, but has a small capacity, which limits the production of a battery with high energy density. The present invention solves the above problem by including a second negative electrode active material of a different type from the above carbon-based first negative electrode active material in the second negative electrode active material layer.

[0101] In one embodiment of the present invention, the second negative electrode active material may be at least one active material particle selected from the group consisting of a transition metal, a transition metal oxide, a transition metal alloy, an oxide of a transition metal alloy, and a transition metal-containing composite. The transition metal may be any one of a Group 14 or Group 15 transition metal, and specifically, the transition metal may be any one of a silicon-based material, a tin-based material, and a germanium-based material. The transition metal included in the transition metal oxide, the transition metal alloy, the oxide of a transition metal alloy, and the transition metal-containing composite may be the above-described transition metal.

[0102] For example, if the transition metal is a silicon-based material, the second negative electrode active material is Si, SiO x (0 <x<2), Si-C 복합체 및 Si 금속 합금으로 이루어진 군으로부터 선택된 1종 또는 2종 이상의 혼합물일 수 있고, 구체적으로 실리콘 산화물 입자(SiO x , 0 <x<2)일 수 있으며, 상기 실리콘 산화물 입자(SiO x , 0 <x<2)는 결정형 SiO2및 비정형 Si로 구성된 복합물일 수 있다.

[0103] The metal of the above Si-metal alloy may be an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, excluding Si. Specific examples of the metal include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0104] The above silicon particles have an average particle diameter (D) of 1 ㎛ to 30 ㎛ 50 ) and may have an average particle diameter (D) of specifically 3 ㎛ to 20 ㎛, more specifically 4 ㎛ to 10 ㎛ 50 ) can have the average particle diameter (D) of the above silicon particles. 50 ) is too small, the side reaction with the electrolyte may increase and the life performance may decrease, and the average particle diameter (D 50) is excessively large, the volume expansion during charge and discharge is large, which may cause particle cracks, thus reducing the life performance. Therefore, when the silicon-based particles satisfy the above range, the side reaction with the electrolyte and the volume expansion of the silicon-based particles can be maintained at an appropriate level, so that the battery including the silicon-based particles can exhibit excellent life performance.

[0105] In one embodiment of the present invention, the second negative electrode active material layer may further include, in addition to the second negative electrode active material, the carbon-based first negative electrode active material as the negative electrode active material. The carbon-based first negative electrode active material included in the second negative electrode active material layer may be specifically one or two materials selected from the natural graphite and artificial graphite.

[0106] In one embodiment of the present invention, the second negative electrode active material layer (11) may have a thickness of 200 μm or less, specifically a thickness of 20 μm to 150 μm, and more specifically a thickness of 30 μm to 100 μm.

[0107] The first negative electrode active material layer and the second negative electrode active material layer may optionally additionally include a binder, a conductive material, a filler, and other additives in addition to the negative electrode active material.

[0108] The above binder is not particularly limited as long as it is a component that assists in the bonding of the active material and the conductive material and the bonding to the current collector, and examples thereof include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

[0109] The above binder may typically be included in an amount of 1 to 30 wt% based on the total weight of the first negative electrode active material layer or the second negative electrode active material layer.

[0110] The conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, paneth black, lamp black, thermal black, and the like; conductive fibers such as carbon fiber or metal fiber; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0111] The above-mentioned conductive material may typically be included in an amount of 1 to 30 wt% based on the total weight of the first negative electrode active material layer or the second negative electrode active material layer.

[0112] The above filler is optionally used as a component that suppresses expansion of the electrode, and is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery. For example, olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber are used.

[0113]

[0114] (Second embodiment)

[0115] FIG. 3 is a vertical cross-sectional view of a cathode according to another embodiment of the present invention, and FIG. 4 is a vertical cross-sectional view of a cathode according to another embodiment of the present invention.

[0116] Referring to these drawings, the negative electrode (10) according to the present invention includes a first negative electrode active material layer (11) formed on a current collector (13); and a second negative electrode active material layer (12) formed on the first negative electrode active material layer (11), wherein the second negative electrode active material layer (12) includes a plurality of concave portions (12a) recessed toward the first negative electrode active material layer (11) and a plurality of non-concave portions (12b) other than the concave portions (12b), wherein the concave portions (12a) and the non-concave portions (12b) are alternately arranged in a horizontal direction (Y-axis direction), and the surface of the second negative electrode active material layer may have a structure in which a pattern is formed by a step difference between the non-concave portions and the concave portions.

[0117] The second negative electrode active material layer (12) has a plurality of concave portions (12a) having steps and a plurality of non-concave portions (12b) alternately arranged so that a step pattern is formed on the entire surface of the second negative electrode active material layer (12). Accordingly, the negative electrode according to the present invention has an increased reactive surface area of ​​the negative electrode surface compared to a negative electrode in which the surface of the negative electrode active material layer is entirely flat, thereby suppressing an increase in resistance due to high loading of the negative electrode, and the step space of the surface of the second negative electrode active material layer (12) acts as a buffer against changes in the volume of the negative electrode active material layers (11, 12), resulting in excellent structural stability.

[0118] In particular, the cathode (10) according to the second embodiment can be more effective in alleviating stress due to volume expansion of the non-concave portion (12b) because the interior of the concave portion (12a) is a hollow space.

[0119] The first negative electrode active material layer (11) above includes a first negative electrode active material that is a carbon-based compound with excellent structural stability even though the capacity is somewhat small, and the second negative electrode active material layer (12) may include a second negative electrode active material with a large capacity and excellent input / output characteristics. Since the first negative electrode active material and the second negative electrode active material have been described in detail above, a duplicate description will be omitted.

[0120] In exemplary embodiments, the second negative electrode active material layer (12) is disposed on the first negative electrode active material layer (11), and the surface of the first negative electrode active material layer (11) is covered by the second negative electrode active material layer (12). Accordingly, since the second negative electrode active material layer with excellent input / output characteristics is located on the surface of the negative electrode, an negative electrode advantageous for rapid charging can be provided.

[0121] The cross-sectional shape of the above concave portion (12a) may have an inverted triangle shape as shown in Fig. 3, or a trapezoid shape as shown in Fig. 4. However, it is not limited thereto.

[0122] The above-mentioned concave portion (12a) may be formed at a constant interval, or may be formed at an irregular (random) interval without a constant interval. In addition, the above-mentioned concave portion (12a) may be formed in a constant shape, or may be formed in an irregular shape.

[0123] The horizontal direction (Y-axis direction) width of the above-mentioned non-concave portion (12b) may be in the range of 50 to 1500 ㎛, more specifically 150 to 1250 ㎛, and even more specifically 200 to 1000 ㎛.

[0124] The horizontal direction (Y-axis direction) width of the above concave portion (12a) may be within a range equal to or less than the horizontal direction width of the above non-concave portion (12b), and may be in a range of 10 to 800 ㎛, more specifically 10 to 600 ㎛, and even more specifically 20 to 400 ㎛.

[0125] The number of rows of the above-mentioned non-concave portion (12b) and concave portion (12a) can be appropriately selected depending on the size of the punched electrode and is not particularly limited. Specifically, each of these can be arranged in 100 rows or more, more specifically in 200 to 9,000 rows, and even more specifically in 200 to 8,000 rows.

[0126] The concave portions (12b) of the plurality of rows are spaced apart at a predetermined interval, and the concave portions (12a) are arranged between the mutually spaced concave portions and the adjacent concave portions, and the inside of the concave portions (12a) has a non-filled structure, unlike the first embodiment.

[0127] The length of the step, which is the difference between the thickness of the non-concave portion (12b) and the thickness of the concave portion (12a), may be in the range of 5 µm to the thickness of the non-concave portion (12b), and may be in the range of 5 µm to 60 µm, preferably 7.5 to 40 µm, and more preferably 10 to 30 µm. Here, the step may be defined as a value obtained by subtracting the minimum value of the thickness of the concave portion (12a) from the maximum value of the thickness of the non-concave portion (12b). A negative electrode having a step within the above range can improve the energy density of a battery while exhibiting an excellent resistance improvement effect due to the step.

[0128] Meanwhile, although FIGS. 3 and 4 illustrate an embodiment in which the second negative electrode active material layer is exposed in the concave portion (12a), the present invention does not exclude an embodiment in which the first negative electrode active material layer is exposed along with the second negative electrode active material layer. However, since the diffusion rate of lithium ions in the first negative electrode active material layer is slower than that in the second negative electrode active material layer, it is preferable that the first negative electrode active material layer is not exposed or that the exposed area of ​​the first negative electrode active material layer is smaller.

[0129] The negative electrode according to the second embodiment of the present invention is a high-loading negative electrode, and the average value of the total loading amount of the first negative electrode active material layer and the second negative electrode active material layer may be 4 mAh / cm2 or more, more specifically, in the range of 4 mAh / cm2 to 8 mAh / cm2.

[0130] In the negative electrode according to the second embodiment, the contents of the current collector and the first and second negative electrode active material layers are the same as those of the negative electrode according to the first embodiment, so any duplicated contents thereon are omitted.

[0131]

[0132] lithium secondary battery

[0133] Next, a lithium secondary battery according to the present invention will be described.

[0134] A lithium secondary battery according to one embodiment of the present invention may include a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.

[0135] The lithium secondary battery of the present invention can be manufactured using conventional methods known in the art. For example, it can be manufactured by inserting a separator between the positive and negative electrodes and injecting an electrolyte.

[0136] In the lithium secondary battery, the negative electrode is as described above. For example, the negative electrode may include a current collector; a first negative electrode active material layer formed on one or both surfaces of the current collector and including a first negative electrode active material, which is a carbon-based compound, as a negative electrode active material; and a second negative electrode active material layer formed on the first negative electrode active material layer and including a second negative electrode active material of a different type from the carbon-based compound as a negative electrode active material, wherein the second negative electrode active material layer includes a plurality of concave portions recessed toward the first negative electrode active material layer and a plurality of non-concave portions that are not the concave portions, wherein the concave portions and the non-concave portions are alternately arranged in a horizontal direction, and the concave portions are filled with a conductive layer including a conductive material, and a thickness of the conductive layer filled in the concave portions is smaller than a thickness of the non-concave portions, so that a surface of the second negative electrode active material layer may be a negative electrode in which a pattern is formed by a step difference between the conductive layer and the non-concave portions.

[0137] In addition, the negative electrode may include a current collector; a first negative electrode active material layer formed on one or both sides of the current collector and including a first negative electrode active material that is a carbon-based compound as a negative electrode active material; and a second negative electrode active material layer formed on the first negative electrode active material layer and including a second negative electrode active material of a different type from the carbon-based compound as a negative electrode active material, wherein the second negative electrode active material layer includes a plurality of concave portions recessed toward the first negative electrode active material layer and a plurality of non-concave portions that are not the concave portions, wherein the concave portions and the non-concave portions are alternately arranged in a horizontal direction, and a surface of the second negative electrode active material layer may be a negative electrode in which a pattern is formed by a step difference between the non-concave portions and the concave portions.

[0138] The first negative electrode active material layer (11) may include a carbon-based first negative electrode active material having excellent structural stability even though the capacity is somewhat small, and the second negative electrode active material layer (12) may include a second negative electrode active material having a large capacity and excellent input / output characteristics.

[0139] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0140] In the above positive electrode, the positive electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0141] The positive electrode active material is not particularly limited, and compounds known in the art that are capable of reversible intercalation and deintercalation of lithium can be used without limitation. Specifically, the positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); LiV3O8, LiV3O4, V2O5, Cu2V2O Vanadium oxide, chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); chemical formula LiMn 2-x M x Lithium manganese composite oxides expressed as O2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x It may include, but is not limited to, lithium manganese composite oxides having a spinel structure represented by O4; LiMn2O4 in which a portion of Li in the chemical formula is replaced by an alkaline earth metal ion; disulfide compounds; lithium iron phosphate represented by LiFePO4; disulfide compounds; Fe2(MoO4)3, etc.

[0142] However, it is important for the battery to which the present invention is applied to improve energy density, and therefore, the positive electrode active material may be a lithium transition metal oxide with a high Ni content represented by the following chemical formula 1.

[0143] Li 1+x Nia Co b Mn c M 1-(a+b+c) O 2-y A y (1)

[0144] In the above formula,

[0145] M is at least one selected from the group consisting of Cu, Ti, Mg, Al, Pt, and Zr,

[0146] A is an oxygen-substituting halogen,

[0147] 0≤x≤0.5, 0.8≤a≤1, 0≤b≤0.2, 0≤c≤0.2, 0.9≤a+b+c≤1, and 0≤y≤0.001.

[0148] More specifically, the above a may be 0.88≤a<1.

[0149] Additionally, the lithium transition metal oxide represented by the above chemical formula 1 may be mixed and used with other active materials.

[0150] The above-described positive electrode active material layer may include a positive electrode conductive material and a positive electrode binder together with the positive electrode active material described above.

[0151] The above-mentioned positive electrode conductive material is used to provide conductivity to the electrode, and carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material, etc. can be used. Products currently sold as conductive materials include acetylene black series (products of Chevron Chemical Company or Gulf Oil Company, etc.), Ketjen Black EC series (product of Armak Company), Vulcan XC-72 (product of Cabot Company), and Super P (product of MMM). Among these, carbon nanotubes, carbon nanofibers, and carbon black are preferable as the conductive material of the present invention, and carbon nanotubes are most preferable. The conductive network of carbon nanotubes is most preferable as a conductive material included in the positive electrode of the present invention because it can alleviate the phenomenon of binder lifting during the drying process of the positive electrode slurry.

[0152] The BET specific surface area of ​​the above carbon nanotube may be 100 m2 / g to 1000 m2 / g, 150 m2 / g to 800 m2 / g, 150 m2 / g to 500 m2 / g, 150 m2 / g to 300 m2 / g, or 150 m2 / g to 200 m2 / g.

[0153] The above-mentioned positive electrode conductive material may be included in the positive electrode active material layer in an amount of 0.1 to 30 wt%, specifically 0.1 to 10 wt%, and more specifically 0.5 to 5 wt%.

[0154] The above-mentioned positive electrode binder may be any binder polymer that is commonly used without limitation. For example, various types of binder polymers such as polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, styrene butadiene rubber (SBR), and carboxyl methyl cellulose (CMC) may be used.

[0155] The above positive electrode binder may be included in the positive electrode active material layer in an amount of 0.1 to 30 wt%, specifically 0.1 to 10 wt%, and more specifically 0.5 to 5 wt%.

[0156] The above separator can be any porous substrate typically used as a separator in lithium secondary batteries. Examples include, but are not limited to, a polyolefin-based porous membrane or non-woven fabric. In particular, one having low resistance to electrolyte ion movement and excellent electrolyte moisture retention capacity is preferred.

[0157] Examples of the above polyolefin porous membrane include a membrane formed from a single or mixed polymer of polyolefin polymers such as polyethylene, polypropylene, polybutylene, polypentene, etc., such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene.

[0158] The above nonwoven fabric may include, in addition to polyolefin-based nonwoven fabrics, nonwoven fabrics formed from polymers such as polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, and polyethylenenaphthalene, either singly or in combination. The structure of the nonwoven fabric may be a spunbond nonwoven fabric composed of long fibers or a meltblown nonwoven fabric.

[0159] The thickness of the porous substrate is not particularly limited, but may be 5 to 50 μm, and the pore size and pore content present in the porous substrate are also not particularly limited, but may be 0.01 to 50 μm and 10 to 95%, respectively.

[0160] Meanwhile, in order to improve the mechanical strength of the separator composed of the porous substrate and to suppress short circuits between the anode and cathode, a porous coating layer including inorganic particles and a binder polymer may be further included on at least one side of the porous substrate.

[0161] Meanwhile, in the lithium secondary battery, the electrolyte may include an organic solvent and lithium salt commonly used in electrolytes, and is not particularly limited.

[0162] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC) can be used.

[0163] Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0164] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. It is preferable that the lithium salt be included in the electrolyte at a concentration of approximately 0.6 mol% to 2 mol%.

[0165] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0166] The lithium secondary battery of the present invention can be manufactured by forming an electrode assembly by placing a separator between the positive and negative electrodes, placing the electrode assembly in a cylindrical or square battery case, and then injecting an electrolyte. Alternatively, the electrode assembly can be manufactured by stacking the electrode assembly, impregnating it with an electrolyte, and placing the resulting product in a battery case and sealing it.

[0167] When manufacturing the lithium secondary battery of the present invention, the electrode assembly may be dried to remove one or more organic solvents selected from the group consisting of N-methyl-2-pyrrolidone (NMP), acetone, ethanol, propylene carbonate, ethyl methyl carbonate, ethylene carbonate, and dimethyl carbonate used in manufacturing the positive electrode. If an electrolyte having the same composition as the organic solvent used in manufacturing the positive electrode is used as the electrolyte, the process of drying the electrode assembly may be omitted.

[0168] Unlike the lithium secondary battery described above, a lithium secondary battery according to another embodiment of the present invention may be an all-solid-state battery.

[0169] The above battery case can be adopted as one commonly used in the field, and there is no limitation on the external shape according to the use of the battery. For example, it can be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0170] The lithium secondary battery according to the present invention stably exhibits excellent resistance characteristics, discharge capacity, output characteristics, and capacity retention rate, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in electric vehicles such as energy storage systems (ESS) and hybrid electric vehicles (HEVs).

[0171]

[0172] Method for manufacturing a negative electrode for a lithium secondary battery

[0173] Next, a method for manufacturing a negative electrode for a lithium secondary battery according to the present invention will be described.

[0174] Figure 5 is a flowchart illustrating a method for manufacturing a negative electrode for a lithium secondary battery according to one embodiment of the present invention.

[0175] Referring to FIG. 5, a method for manufacturing a cathode according to one embodiment may include a process for manufacturing a first cathode slurry (P11), a process for manufacturing a second cathode slurry (P12), a process for manufacturing a slurry for a conductive layer (P13), a first coating process for coating the first cathode slurry (P14), a second coating process for coating the second cathode slurry and the slurry for a conductive layer (P15), and a drying process for drying the first cathode slurry, the second cathode slurry, and the slurry for a conductive layer (P16).

[0176] The above method for manufacturing the negative electrode is for manufacturing the negative electrode according to the first embodiment described above, and is characterized in that the second negative electrode slurry and the slurry for the conductive layer are coated so that they are alternately arranged in the horizontal direction during the second coating process. That is, the second negative electrode slurry is coated in multiple rows at predetermined intervals, and the slurry for the conductive layer is also coated in multiple rows at predetermined intervals, but the second negative electrode slurry and the slurry for the conductive layer are coated in a form in which they are alternately arranged.

[0177] The second negative electrode slurry coated in multiple rows is dried to become a non-concave portion (12b) of the second negative electrode active material layer, and the conductive layer slurry coated in multiple rows is dried to become a conductive layer (14). In addition, the conductive layer (14) fills a portion of the interior of the concave portion (12a), which is a space between mutually spaced non-concave portions and adjacent non-concave portions.

[0178] The above method for manufacturing a cathode has the advantage of saving manufacturing costs because there is no problem of the cathode active material layer being lost compared to the manufacturing method of forming a pattern on the surface of the cathode active material layer by laser etching described later.

[0179] The process for preparing the first negative electrode slurry (P11) may include a process of mixing and stirring a carbon-based first negative electrode active material, a conductive material, and a binder in a solvent. Since the carbon-based first negative electrode active material has superior structural stability compared to the second negative electrode active material, it is less likely to be detached from the current collector, and is therefore preferable as the negative electrode active material of the first negative electrode slurry for forming the first negative electrode active material layer close to the current collector.

[0180] The carbon-based first negative electrode active material, conductive material, and binder included in the first negative electrode slurry have been described in detail above, so redundant descriptions are omitted.

[0181] The process for manufacturing the second negative electrode slurry (P12) may include a process of mixing and stirring the second negative electrode active material, conductive material, and binder in a solvent.

[0182] The above carbon-based first negative electrode active material is capable of reversible insertion and de-insertion of lithium ions while maintaining structural and electrical properties as a negative electrode active material, but has a small capacity, which limits the production of a battery having a high energy density. Therefore, by including a second negative electrode active material of a different type from the carbon-based first negative electrode active material in the second negative electrode slurry for forming two negative electrode active material layers, an negative electrode suitable for a battery having a high energy density can be produced.

[0183] The second negative electrode active material, conductive material, and binder included in the second negative electrode slurry have been described in detail above, so redundant descriptions are omitted.

[0184] The process (P13) for preparing the slurry for the above-mentioned conductive layer may include a process of mixing and stirring the electrode material in a solvent.

[0185] As previously mentioned, the conductive layer may or may not include a negative electrode active material, so in one embodiment, the slurry for the conductive layer may include a negative electrode active material, and in another embodiment, the slurry for the conductive layer may not include a negative electrode active material.

[0186] In one embodiment where the slurry for the conductive layer includes a negative electrode active material, the slurry for the conductive layer may include the same compound as the second negative electrode active material included in the second negative electrode slurry as the negative electrode active material, and may further include the carbon-based first negative electrode active material.

[0187] In one embodiment where the slurry for the conductive layer includes a negative electrode active material, the slurry for the conductive layer and the second negative electrode slurry may have the same composition. Here, having the same composition means that the negative electrode active material, conductive material, and binder constituting the conductive layer (14) and the negative electrode active material, conductive material, and binder constituting the second negative electrode active material layer are each the same compound and have the same weight ratio.

[0188] In one embodiment where the slurry for the conductive layer includes a negative electrode active material, the weight % of the conductive material included in the solid content of the slurry for the conductive layer may be greater than the weight % of the conductive material included in the solid content of the second negative electrode slurry.

[0189] The slurry for the conductive layer may not contain a negative electrode active material to maximize the buffering effect against volume changes of the second negative electrode active material layer. In this embodiment, the slurry for the conductive layer may contain 80 to 100 parts by weight of a conductive material and 20 parts by weight or less of a binder in the solid content.

[0190] Since the above challenge material and binder have been described in detail above, redundant descriptions will be omitted.

[0191] The solvent for preparing the first cathode slurry, the second cathode slurry, and the slurry for the conductive layer may be a solvent generally used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and one of these may be used alone or a mixture of two or more thereof may be used.

[0192] Meanwhile, in order to form a step between the non-concave portion of the second negative electrode active material layer formed from the second negative electrode slurry and the conductive layer formed from the slurry for the conductive layer, the solid content of the second negative electrode slurry may be greater than the solid content of the slurry for the conductive layer. Accordingly, after drying, the thickness of the second negative electrode active material layer formed from the second negative electrode slurry may be greater than the thickness of the conductive layer formed from the slurry for the conductive layer. In other words, the level of the step between the non-concave portion and the conductive layer can be controlled by adjusting the respective solid contents of the second negative electrode slurry and the slurry for the conductive layer.

[0193] The above first coating process (P14) is a process of coating the first negative electrode slurry on the current collector (13). The coating method of the first negative electrode slurry can be used without limitation as a coating method generally used in the relevant technical field. For example, the first negative electrode slurry can be coated using a slot die coater.

[0194] The above-described second coating process (P15) is a process of coating the second cathode slurry and the slurry for the conductive layer on the first cathode slurry. After the above-described first coating process (P14), the second coating process (P15) may be performed without drying the first cathode slurry, or after the above-described first coating process (P14), the second coating process (P15) may be performed after drying the first cathode slurry.

[0195] In the above-described secondary coating process (P15), the second cathode slurry may be coated in multiple rows at predetermined intervals along the transverse direction (CD) to have a predetermined width length. The coating width length of the cathode slurry in one row may be in the range of 50 to 1500 μm, more specifically 150 to 1250 μm, and more specifically 200 to 1000 μm.

[0196] In the above-described second coating process (P15), the slurry for the conductive layer may be coated in multiple rows at predetermined intervals along the transverse direction (CD) to have a predetermined width length. The coating width length of the slurry for the conductive layer of one row may be in the range of 10 μm to 800 μm, more specifically 10 to 600 μm, and even more specifically 20 to 400 μm, within the range of the coating width length of the second negative electrode slurry. Meanwhile, when the second negative electrode slurry does not include a negative electrode active material, the coating width length of the slurry for the conductive layer may be further reduced. Specifically, the coating width length of the slurry for the conductive layer may be in the range of 10 μm to 400 μm, preferably 10 μm to 300 μm, and even more preferably 20 μm to 200 μm.

[0197] In one embodiment, the coating width length of the slurry for the conductive layer is consistent with the coating interval of the second cathode slurry, so that the first cathode slurry or the first cathode mixture layer is almost covered by the second cathode slurry and the slurry for the conductive layer, which is preferable in terms of capacity and input / output characteristics of the cathode.

[0198] In one embodiment of the present invention, the second coating process (P15) may use a nozzle printer to alternately coat the second cathode slurry and the slurry for the conductive layer.

[0199] Figure 7 is a drawing illustrating the secondary coating process. Figure 7 illustrates a process of simultaneously coating the second cathode slurry and the slurry for the conductive layer using a nozzle printer as a coating device.

[0200] Referring to FIG. 7, the nozzle printer is capable of continuously discharging the second negative electrode slurry (21) and the conductive layer slurry (22) in line units having a predetermined width, and it is easy to control the coating width according to the coating speed, so it is preferable as a coating device for alternately pattern-coating the second negative electrode slurry and the conductive layer slurry. The nozzle printer may include two or more nozzles, and may be configured so that the second negative electrode slurry (21) and the conductive layer slurry (22) are discharged from each of the plurality of nozzles (First nozzle, Second nozzle). The second negative electrode slurry (21) is dried to become a non-concave portion (12b) of the second negative electrode active material layer, and the conductive layer slurry (22) is dried to become a conductive layer (14).

[0201] In exemplary embodiments, the ratio of the total loading amount of the second cathode slurry and the slurry for the conductive layer to the loading amount of the first cathode slurry may be in the range of 3:1 to 1:3, specifically 2:1 to 1:2, and more specifically 6:4 to 4:6. When the ratio of the loading amounts is in the above numerical range, the structural stability and rate characteristics of the cathode are excellent.

[0202] The above drying process (P16) is a drying process to remove the solvent in the first cathode slurry, the second cathode slurry, and the slurry for the conductive layer. The first cathode slurry, the second cathode slurry, and the slurry for the conductive layer can be dried all at once after the first and second coating processes, or the drying process can be performed after the first coating process and after the second coating process, respectively.

[0203]

[0204] Figure 6 is a flowchart illustrating a method for manufacturing a cathode according to another embodiment of the present invention.

[0205] Referring to FIG. 6, a method for manufacturing a negative electrode according to another embodiment of the present invention may include a process of manufacturing a first negative electrode slurry (P21), a process of manufacturing a second negative electrode slurry (P22), a process of coating the first and second negative electrode slurries (P23), a process of drying the first and second negative electrode slurries (P24), and a process of etching the second negative electrode active material layer to pattern it so that concave portions and non-concave portions are alternately arranged (P25).

[0206] The process for manufacturing the first cathode slurry (P21) and the process for manufacturing the second cathode slurry (P22) are the same as the process for manufacturing the cathode of the embodiment described above, so duplicate descriptions are omitted.

[0207] The process of coating the first and second negative electrode slurries (P23) is a process of coating the first negative electrode slurry and the second negative electrode slurry on the current collector. After coating the first negative electrode slurry, the second negative electrode slurry may be coated, or the first negative electrode slurry and the second negative electrode slurry may be simultaneously coated using equipment such as a dual slot die configured to discharge the first negative electrode slurry and the second negative electrode slurry simultaneously.

[0208] In exemplary embodiments, the loading ratio of the first cathode slurry and the second cathode slurry may be in the range of 3:1 to 1:3, specifically 2:1 to 1:2, and even more specifically 6:4 to 4:6. When the loading ratio is in the above numerical range, the structural stability and rate characteristics of the cathode are excellent.

[0209] The above drying process (P24) is a process for drying the first and second cathode slurries. After coating and drying the first cathode slurry, the second cathode slurry may be coated and dried, or the first and second cathode slurries may be coated simultaneously, and then the first and second cathode slurries may be dried at the same time.

[0210] The above drying process (P24) can be performed according to a general method well known in the art.

[0211] The above patterning process (P25) is a process of forming a pattern by alternately arranging concave and non-concave portions on the surface of the second negative electrode active material layer by irradiating a laser on the second negative electrode active material layer formed by drying the second negative electrode slurry to form concave portions directed toward the first negative electrode active material layer.

[0212] The area irradiated with the laser is detached from the second negative electrode active material layer and becomes a concave portion (12a) having an inward shape toward the first negative electrode active material layer, as shown in FIGS. 3 and 4.

[0213] Since the width direction length of the above-mentioned non-concave portion (12a) and the width direction length of the concave portion have been described in detail above, redundant descriptions are omitted.

[0214] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention solely to these examples.

[0215]

[0216] Example 1: Preparation of the cathode

[0217] (Preparation of the first cathode slurry)

[0218] Natural graphite (D) with a sphericity of 0.9 as a negative electrode active material 50 15㎛), styrene butadiene rubber (SBR) as a binder, carboxymethyl cellulose (CMC) as a thickener, and carbon nanotubes as a conductive material were mixed and stirred in water at a weight ratio of 94:3:1.5:1.5 to prepare a first cathode slurry (solid content: 50 wt%).

[0219] (Manufacture of the second cathode slurry)

[0220] Natural graphite (D) with a sphericity of 0.9 50 Artificial graphite (D) with a particle size of 16㎛, a specific surface area of ​​3.0㎡ / g, and a tap density of 1.1g / cc) 10 wt% and a sphericity of 0.85 5023㎛, specific surface area 1.0㎡ / g, tap density 0.9g / cc) 85 wt% and average particle size (D ) of 6㎛ 50 ) having silicon oxide particles (SiO x , 0 <x<2) 5 중량%로 이루어진 음극 활물질을 준비하였다. 상기 음극 활물질, 바인더로서 스티렌 부타디엔 러버(SBR), 증점제로서 카르복시메틸셀룰루오스(CMC), 도전재로서 탄소나노튜브를 95:2:1.5:1.5의 중량비로 물에 혼합 및 교반하여 제2 음극 슬러리를 제조하였다(고형분 함량: 50 중량%).

[0221] (Manufacturing of cathode)

[0222] The first and second negative electrode slurries were simultaneously coated on a copper current collector having a thickness of 20 μm using a dual slot die coater. At this time, the first negative electrode slurry was laminated on the copper current collector, and the second negative electrode slurry was laminated on the first negative electrode slurry. At this time, the loading ratio of the first negative electrode slurry and the second negative electrode slurry was 1:1. Afterwards, drying and rolling were performed at a temperature of 80 to 90°C.

[0223] After rolling, the second negative electrode slurry was dried and formed on the second negative electrode active material layer, and concave portions with a width of 30 ㎛ were formed by etching at intervals of 200 ㎛ using a laser to indent toward the first negative electrode active material layer. In the manufactured negative electrode, the total thickness of the negative electrode active material layer was 110 ㎛, and the step difference between the concave portion and the non-concave portion was 31 ㎛.

[0224]

[0225] Example 2: Preparation of the cathode

[0226] (Manufacture of the first and second cathode slurries)

[0227] In the same manner as in Example 1, the first cathode slurry and the second cathode slurry were prepared.

[0228] (Manufacture of slurry for the conductive layer)

[0229] It has the same composition as the second cathode slurry, but the solid content was changed to 40 wt%.

[0230] (Manufacturing of cathode)

[0231] On a copper current collector having a thickness of 20 μm, the first negative electrode slurry was coated using a single slot die coater and then dried to form a first negative electrode active material layer. The second negative electrode slurry and the slurry for the conductive layer were simultaneously coated on the first negative electrode active material layer using a nozzle printer, such that the second negative electrode slurry and the slurry for the conductive layer were alternately arranged along the width direction (CD) of the current collector, and the horizontal width length of the second negative electrode slurry forming one row was 200 μm, and the horizontal width length of the slurry for the conductive layer forming one row was 20 μm. At this time, the loading ratio of the first negative electrode slurry, the second negative electrode slurry, and the slurry for the conductive layer was set to 1:1. Thereafter, the negative electrode was manufactured by drying and rolling at a temperature of 80 to 90°C.

[0232] The total thickness of the negative electrode active material layer in the manufactured negative electrode was 110 μm, and the step difference between the non-concave portion formed by drying the second negative electrode slurry and the conductive layer formed by drying the slurry for the conductive layer was 31 μm.

[0233]

[0234] Comparative example: Manufacturing of cathode

[0235] (Manufacture of the first and second cathode slurries)

[0236] The first cathode slurry and the second cathode slurry were prepared in the same manner as in Example 1.

[0237] (Manufacturing of cathode)

[0238] The first and second negative electrode slurries were simultaneously coated on a copper current collector having a thickness of 20 μm using a dual slot die coater. At this time, the first negative electrode slurry was laminated on the copper current collector, and the second negative electrode slurry was laminated on the first negative electrode slurry, and the loading ratio of the first negative electrode slurry and the second negative electrode slurry was 1:1. Afterwards, the negative electrode was dried and rolled at a temperature of 80 to 90°C to manufacture a negative electrode having a total thickness of the negative electrode active material layer of 110 μm.

[0239]

[0240] Experimental Example 1: Capacity Retention Rate Evaluation According to Cycles

[0241] (Manufacturing of half cells)

[0242] A lithium (Li) metal thin film was used as an anode. An electrode assembly was manufactured by interposing a polyethylene separator (20 μm thick) between the anode and the respective negative electrodes manufactured in Examples 1 to 2 and Comparative Examples. The electrode assembly was inserted into a pouch-type battery case, and an electrolyte was injected to manufacture a half-cell. At this time, the electrolyte was an electrolyte in which 1 M LiPF6 was dissolved in an organic solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70.

[0243] (Capacity retention rate evaluation)

[0244] For each half-cell manufactured using the cathodes of Examples 1 to 2 and the comparative example, 500 cycles of charge and discharge were performed at a temperature of 25 degrees Celsius under the following conditions, and the capacity retention rate was calculated by substituting the results into the following equation. The results are shown in Table 1.

[0245] Charge: 0.7C CC / CV, 4.2V, 0.05C cut-off

[0246] Discharge: 0.5C, CC, 2.5V cut-off

[0247] The capacity retention rate was calculated as follows, and the results are shown in Table 1.

[0248] Capacity retention rate (%) = (500 cycle discharge capacity / 1 cycle discharge capacity) × 100

[0249]

[0250] Experimental Example 2: Measurement of Constant Current Charging Capacity Ratio

[0251] Half cells were manufactured using the same method as in Experimental Example 1. For each half cell manufactured using the negative electrodes of Examples 1 to 2 and the Comparative Example, constant current charging was performed at 0.5 C, cut-off was reached when 4.2 V was reached, and CC charge capacity was measured. Thereafter, constant voltage charging was performed, cut-off was reached when 0.02 C was reached, and CC-CV charge capacity was measured. Then, the constant current charge capacity ratio was calculated by substituting it into the following equation. A larger constant current charge capacity ratio means better resistance characteristics and rate characteristics (charge speed).

[0252] Constant current charging capacity ratio (%) = CC charging capacity / CC-CV charging capacity) × 100

[0253] The above process was performed by changing the charging speed to 1.0C and 2.0C, respectively, to calculate the constant current charging capacity, and the results are shown in Table 1.

[0254] Capacity retention rate (%) Constant current charge capacity ratio (%) 0.5C 1.0C 2.0C Example 189876735 Example 290887040 Comparative example 7070285

[0255] Referring to Table 1 above, the half-cell including the negative electrode according to Examples 1 and 2 was found to have superior capacity retention rate and constant current charge capacity ratio compared to the half-cell including the negative electrode according to the comparative example.

[0256]

[0257] Experimental Example 3: Resistance Characteristic Evaluation

[0258] (Manufacturing of positive electrode)

[0259] LiNi as a cathode active material 0.8 Co 0.1 Mn 0.1 O2, carbon black as a conductive agent, and PVDF as a binder were mixed / stirred in a weight ratio of 97:1.5:1.5 in an N-methylpyrrolidone solvent to prepare a cathode slurry.

[0260] The positive electrode slurry was coated on an aluminum current collector having a thickness of 20 μm, and dried and rolled at a temperature of 130°C to manufacture a positive electrode.

[0261] (Manufacturing of full cells)

[0262] An electrode assembly was manufactured by interposing a polyethylene separator (20 μm thick) between each of the negative electrodes of Examples 1 to 2 and the comparative example and the positive electrode. The electrode assembly was inserted into a pouch-type battery case, and an electrolyte was injected to manufacture a full cell. At this time, the electrolyte was an electrolyte prepared by dissolving 1 M LiPF6 in an organic solvent mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70.

[0263] (DCIR measurement)

[0264] When each full cell was charged to 50% SOC at room temperature and discharged at 2.5C for 10 seconds, the voltage drop that occurred was recorded, and the resistance value (mOhm) of each coin-type full cell was measured using R=V / I, and the results are shown in Table 2.

[0265] Charge: 0.5C, CC / CV, 4.2V, 0.05C cut-off

[0266] Discharge: 0.5C, CC, 2.5V cut-off

[0267]

[0268] Experimental Example 4: Rapid Charging Performance Evaluation

[0269] Each of the above full cells was charged to 4.2 V at a constant current of 0.33 C at a temperature of 25 degrees Celsius, charged until the current value became 0.05 C at a constant voltage of 4.2 V, rested for 10 minutes, and then discharged to 2.5 V at a constant current of 0.33 C.

[0270] Then, the battery was charged as described above and discharged at a constant current of 2C until it reached 2.5 V to evaluate the discharge rate characteristics, and the results are shown in Table 2.

[0271]

[0272] DCIR(mohm) Rate Characteristics(%)0.33C / 2.0C vs.0.33C / 0.33CCas. Example 11.0275as. Example 21.0178as. Comparative Example 1.167

[0273] Referring to Table 2, in the case of the negative electrodes according to Examples 1 and 2, since the second negative electrode active material layer has concave and non-concave portions alternately arranged to form a pattern on the negative electrode surface, the full cell manufactured using the negative electrodes according to Examples 1 and 2 was found to have superior resistance characteristics and rate characteristics compared to the full cell manufactured using the negative electrode of the comparative example.

[0274]

[0275] The present invention has been described in more detail through drawings and examples. However, the configurations described in the drawings or examples described in this specification are merely embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of this application.

[0276]

[0277] [Explanation of symbols]

[0278] 10: Cathode

[0279] 11: First negative electrode active material layer

[0280] 12: Second negative electrode active material layer

[0281] 12a: Concave

[0282] 12b: Non-concave area

[0283] 13: Whole house

Claims

1. Whole house; A first negative electrode active material layer formed on one or both sides of the above-described collector and including a first negative electrode active material that is a carbon-based compound as a negative electrode active material; and A second negative electrode active material layer is formed on the first negative electrode active material layer and includes a second negative electrode active material of a different type from the carbon-based compound as the negative electrode active material. The second negative electrode active material layer includes a plurality of concave portions and a plurality of non-concave portions that are not the concave portions and are arranged alternately in a horizontal direction, and The above concave portion is filled with a conductive layer including a conductive material, A negative electrode for a lithium secondary battery, characterized in that the thickness of the conductive layer filled in the concave portion is smaller than the thickness of the non-concave portion, and the surface of the second negative electrode active material layer has a pattern formed by the step between the conductive layer and the non-concave portion.

2. In claim 1, A negative electrode for a lithium secondary battery, wherein the above conductive layer further comprises a negative electrode active material.

3. In claim 2, A negative electrode for a lithium secondary battery, characterized in that the conductive layer has the same composition as the second negative electrode active material layer.

4. In claim 2, A negative electrode for a lithium secondary battery, wherein the weight % of the conductive material included in the conductive layer is greater than the weight % of the conductive material included in the second negative electrode active material layer.

5. In claim 4, The above conductive layer comprises 70 to 94 parts by weight of a negative electrode active material; 5 to 20 parts by weight of the challenge agent; and A negative electrode for a lithium secondary battery comprising 1 to 10 parts by weight of a binder.

6. In claim 1, The above conductive layer does not contain a negative active material, 80 to 100 parts by weight of a conductive agent and A negative electrode for a lithium secondary battery containing a binder of 20 parts by weight or less.

7. Whole house; A first negative electrode active material layer formed on one or both sides of the above-described collector and including a first negative electrode active material that is a carbon-based compound as a negative electrode active material; and A second negative electrode active material layer is formed on the first negative electrode active material layer and includes a second negative electrode active material of a different type from the carbon-based compound as the negative electrode active material. The second negative electrode active material layer includes a plurality of concave portions recessed toward the first negative electrode active material layer and a plurality of non-concave portions other than the concave portions, wherein the concave portions and non-concave portions are arranged alternately in a horizontal direction, A negative electrode for a lithium secondary battery, characterized in that the surface of the second negative active material layer has a pattern formed by a step difference between the non-concave portion and the concave portion.

8. In any one of claims 1 to 7, A negative electrode for a lithium secondary battery, characterized in that each of the above-mentioned non-concave portions has a horizontal width length in the range of 50 ㎛ to 1500 ㎛.

9. In any one of claims 1 to 7, A negative electrode for a lithium secondary battery, characterized in that the horizontal width of each of the above concave portions is in the range of 10 µm to 800 µm, but is less than or equal to the horizontal width of the non-concave portion.

10. In any one of claims 1 to 7, A negative electrode for a lithium secondary battery, characterized in that the length of the step is in the range of 5㎛ to 60㎛.

11. In any one of claims 1 to 7, A negative electrode for a lithium secondary battery, wherein the negative electrode active material included in the first negative electrode active material layer is composed of a carbon-based first negative electrode active material.

12. In any one of claims 1 to 7, The above carbon-based first negative electrode active material is a negative electrode for a lithium secondary battery that is a graphite-based negative electrode active material.

13. In any one of claims 1 to 7, The above second negative electrode active material is Si, SiO x (0 <x<2), Si-C 복합체 및 Si 금속 합금으로 이루어진 군으로부터 선택된 1종 또는 2종 이상의 혼합물인 리튬 이차전지용 음극.

14. In any one of claims 1 to 7, A negative electrode for a lithium secondary battery, wherein the average value of the total loading amount of the first negative electrode active material layer and the second negative electrode active material layer is 4 mAh / ㎠ or more.

15. A lithium secondary battery comprising a negative electrode according to any one of claims 1 and 7.

16. A process for preparing a first negative electrode slurry by mixing and stirring a carbon-based first negative electrode active material, a conductive agent, and a binder in a solvent; A process for preparing a second negative electrode slurry by mixing and stirring a second negative electrode active material, a conductive material, and a binder of a different type from the above carbon-based first negative electrode active material in a solvent; Process for manufacturing slurry for a conductive layer; A first coating process of coating a first cathode slurry on the entire collector; A secondary coating process of coating a second cathode slurry and a slurry for a conductive layer on the first cathode slurry; and A drying process comprising drying the first cathode slurry, the second cathode slurry, and the slurry for the conductive layer, A method for manufacturing a negative electrode for a lithium secondary battery, characterized in that the above-mentioned secondary coating process coats the second negative electrode slurry and the slurry for the conductive layer so that they are alternately arranged in a horizontal direction.

17. In claim 16, A method for manufacturing a negative electrode for a lithium secondary battery, characterized in that the solid content of the second negative electrode slurry is greater than the solid content of the slurry for the conductive layer.

18. In claim 16, A method for manufacturing a negative electrode for a lithium secondary battery, characterized in that the above secondary coating process coats the second negative electrode slurry and the slurry for the conductive layer using a nozzle printer.

19. In claim 16, A method for manufacturing a negative electrode for a lithium secondary battery, wherein the slurry for the above-mentioned conductive layer further includes a negative electrode active material.

20. In claim 19, A method for manufacturing a negative electrode for a lithium secondary battery, characterized in that the slurry for the above-mentioned conductive layer and the second negative electrode slurry have the same composition.

21. In claim 19, A method for manufacturing an anode for a lithium secondary battery, wherein the weight % of the conductive material included in the solid content of the slurry for the conductive layer is greater than the weight % of the conductive material included in the solid content of the second anode slurry.

22. In claim 16, The slurry for the above-mentioned conductive layer does not contain a negative electrode active material, In the solid content, 80 to 100 parts by weight of conductive agent and A method for manufacturing a negative electrode for a lithium secondary battery comprising a binder of 20 parts by weight or less.

23. A process for preparing a first negative electrode slurry by mixing and stirring a carbon-based first negative electrode active material, a conductive agent, and a binder in a solvent; A process for preparing a second negative electrode slurry by mixing and stirring a second negative electrode active material, a conductive material, and a binder of a different type from the above carbon-based first negative electrode active material in a solvent; A coating process for coating the first and second cathode slurries so that the second cathode slurry is laminated on the first cathode slurry on the current collector; Process for drying the first and second cathode slurries; and A method for manufacturing a negative electrode for a lithium secondary battery, comprising a process of etching a second negative electrode active material layer formed by drying a second negative electrode slurry at a predetermined interval and width, and patterning the second negative electrode active material layer so that a concave portion formed toward a current collector by the etching and a non-concave portion that is not the concave portion are alternately arranged in a horizontal direction.

24. In claim 23, A method for manufacturing a negative electrode for a lithium secondary battery, characterized in that etching is performed using a laser during the above patterning process.

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