An electrode and an electrochemical device comprising the same

Abstract

One aspect of the present invention relates to an electrode for an electrochemical device, wherein the electrode is characterized by having an increased ion diffusion rate and electrode capacity by including an intermediate layer region located between the lower and upper regions, wherein the granules included in the lower and upper regions are different, and an interface formed by a square-shaped concave and convex portion is formed therein.

Description

Technology Field

[0001] The present invention relates to an electrode and an electrochemical device including the same. Background Technology

[0002] Due to the rapid increase in the use of fossil fuels, there is a growing demand for alternative and clean energy. As part of this trend, the fields of power generation and energy storage utilizing electrochemistry are among the most actively researched. Currently, secondary batteries are a representative example of electrochemical devices that utilize such electrochemical energy, and their scope of application is steadily expanding. Among these secondary batteries, lithium-ion batteries serve not only as an energy source for mobile devices but are also being realized as power sources for electric and hybrid electric vehicles that can replace fossil fuel-using vehicles, such as gasoline and diesel cars—which are major causes of air pollution. Furthermore, their application is expanding to include auxiliary power sources for grid integration.

[0003] Recently, various studies have been conducted regarding the development of batteries utilizing multiple electrode active materials to enhance performance. However, when multiple electrode active materials are blended to form a single electrode active material layer, a problem has arisen where battery performance deteriorates due to interference effects between the types of active materials. Consequently, methods are being considered to improve electrode characteristics and battery performance by configuring the electrode active material layer into multiple layers during manufacturing and specializing the function of each layer.

[0004] At this time, the ion diffusion rate and electrode capacity per weight or volume typically differ depending on the type of electrode active material. Accordingly, there have been attempts to manufacture multilayer electrodes equipped with one layer of electrode active material having a high ion diffusion rate but a small electrode capacity and one layer of electrode active material having a low ion diffusion rate but a large electrode capacity; however, even in this case, it has not been possible to realize an electrode in which both the ion diffusion rate and electrode capacity are improved simultaneously. The problem to be solved

[0005] Therefore, the problem that the present invention aims to solve is,

[0006] The present invention aims to provide a multilayer electrode that achieves both a high ion diffusion rate and a large electrode capacity, and a method for manufacturing the same.

[0007] In addition, the present invention aims to provide an electrode having the characteristics described above, in which a dry process is introduced, and a method for manufacturing the same. means of solving the problem

[0008] In order to solve the above problem,

[0009] According to one aspect of the present invention, electrodes of the following embodiments are provided.

[0010] The electrode according to the first embodiment is,

[0011] A current collector; and an electrode active material layer located on at least one surface of the current collector; comprising,

[0012] The electrode active material layer comprises: a lower layer region adjacent to a current collector and comprising a plurality of first granules; an upper layer region located on the lower layer region and comprising a plurality of second granules; and an intermediate layer region located between the lower layer region and the upper layer region, wherein a first unit region comprising the first granules and a second unit region comprising the second granules are alternately arranged n times along the longitudinal direction of the electrode active material layer; wherein n is an integer greater than or equal to 2.

[0013] The first unit region and the second unit region each have a square cross-section, and the first granule comprises a first electrode active material and a first binder that binds the first electrode active material, and the second granule comprises a second electrode active material and a second binder that binds the second electrode active material.

[0014] According to the second embodiment, in the first embodiment,

[0015] The first granule and the second granule above may satisfy at least one of the following characteristics.

[0016] 1) A first characteristic in which the particle sizes of the first granule and the second granule are different from each other,

[0017] 2) Second characteristic in which the compositions of the first granule and the second granule are different from each other

[0018] According to the third embodiment, in the first embodiment or the second embodiment,

[0019] The cross-sectional shapes of the first unit area and the second unit area of ​​the above intermediate layer region can each satisfy the conditions of T1, T2, W1, and W2 below.

[0020] d1 ≤ T1,

[0021] d2 ≤ T2,

[0022] 50 d1 ≤ W1 ≤ 1,000 d1,

[0023] 50 d2 ≤ W2 ≤ 1,000 d2,

[0024] The above T1 is the thickness of the first unit region, and

[0025] The above T2 is the thickness of the above second unit area, and

[0026] The above W1 is the width of the first unit area, and

[0027] The above W2 is the width of the above second unit area, and

[0028] The above d1 is the average particle size (D50) of the first granule, and

[0029] The above d2 is the average particle size (D50) of the second granule.

[0030] According to the fourth embodiment, in any one of the first to third embodiments,

[0031] The cross-sectional shapes of the first unit area and the second unit area of ​​the above intermediate layer region can each satisfy the conditions of T1, T2, W1, and W2 below.

[0032] d1 ≤ T1 ≤ 2 d1,

[0033] d2 ≤ T2 ≤ 2 d1,

[0034] 100 d1 ≤ W1 ≤ 600 d1,

[0035] 100 d2 ≤ W2 ≤ 600 d2

[0036] According to the fifth embodiment, in any one of the first to fourth embodiments,

[0037] The average particle size (D50) of the first granule is d1, and

[0038] When the average particle size (D50) of the second granule is d2,

[0039] d2 ≥ d1 may be true.

[0040] According to the 6th embodiment, in any one of the 1st to 5th embodiments,

[0041] The average particle size (D50) of the first granule is d1, and

[0042] When the average particle size (D50) of the second granule is d2,

[0043] 15 μm ≤ d1 ≤ 150 μm, and

[0044] It can be 15 µm ≤ d2 ≤ 150 µm.

[0045] According to the seventh embodiment, in any one of the first to sixth embodiments,

[0046] The above electrode active material may include a negative electrode active material.

[0047] According to the eighth embodiment, in any one of the first to seventh embodiments,

[0048] The above electrode active material may include a positive electrode active material.

[0049] According to the ninth embodiment, in any one of the first to eighth embodiments,

[0050] At least one of the first electrode active material and the second electrode active material comprises a carbon-based compound, and at least one of the first electrode active material and the second electrode active material may comprise a silicon-based oxide.

[0051] According to the 10th embodiment, in any one of the 1st to 9th embodiments,

[0052] The second electrode active material may include SiOx (0≤x≤2).

[0053] According to the 11th embodiment, in any one of the 1st to 10th embodiments,

[0054] Based on the total weight of the granules included in the lower layer region, the weight of the first granule is 95 weight percent or more, and

[0055] Based on the total weight of the granules included in the upper layer region, the weight of the second granule may be 95% or more by weight.

[0056] According to the 12th embodiment, in any one of the 1st to 11th embodiments,

[0057] The above n may be an integer from 15 to 25.

[0058] According to the 13th embodiment, in any one of the 1st to 12th embodiments,

[0059] The ion diffusion rate of the intermediate layer region may be greater than the ion diffusion rate of the upper layer region.

[0060] According to the 14th embodiment, in any one of the 1st to 13th embodiments,

[0061] The electrode capacity per volume of the upper region may be greater than the electrode capacity per volume of the lower region.

[0063] According to another aspect of the present invention, a method for manufacturing an electrode of the following embodiments is provided.

[0064] The method for manufacturing an electrode according to the 15th embodiment is,

[0065] The process includes forming an electrode active material layer on at least one surface of the current collector, and

[0066] The process of forming the electrode active material layer comprises: a step of applying a plurality of first granules on at least one surface of the current collector; a first pressing step of forming a pattern on the surface of the first granules by pressing the surface of the applied first granules using a pressing roll having a pattern formed thereon; a step of applying a plurality of second granules on the surface of the pressed first granules; and a second pressing step of pressing the surface of the applied second granules.

[0067] The first granule comprises a first electrode active material and a first binder that binds the first electrode active material, and the second granule comprises a second electrode active material and a second binder that binds the second electrode active material.

[0068] According to the 16th embodiment, in the 15th embodiment,

[0069] The first granule and the second granule above may satisfy at least one of the following characteristics.

[0070] 1) A first characteristic in which the particle sizes of the first granule and the second granule are different from each other,

[0071] 2) A second characteristic in which the composition of the first granule and the second granule are different from each other.

[0072] According to the 17th embodiment, in the 15th embodiment or the 16th embodiment,

[0073] The pattern of the above-mentioned pressure roll may be a protrusion type or a mesh type.

[0074] According to the 18th embodiment, in any one of the 15th to 17th embodiments,

[0075] The pattern of the above-mentioned pressure roll includes a plurality of square-shaped protrusions, and

[0076] The shape of the above protrusion can satisfy the conditions of W3, W4, and T3 below.

[0077] d2 ≤ T3

[0078] 50 d2 ≤ W3 ≤ 1,000d2,

[0079] 50 d1 ≤ W4 ≤ 1,000 d1,

[0080] The above W3 is the width of the protrusion of the above projection, and

[0081] The above W4 is the shortest straight-line distance between two protrusions, and

[0082] The above T3 is the thickness of the above protrusion, and

[0083] The above d1 is the average particle size (D50) of the first granule, and

[0084] The above d2 is the average particle size (D50) of the second granule.

[0085] According to the 19th embodiment, in any one of the 15th to 18th embodiments,

[0086] The electrode active material layer comprises: a lower layer region adjacent to a current collector and comprising a plurality of first granules; an upper layer region located on the lower layer region and comprising a plurality of second granules; and an intermediate layer region located between the lower layer region and the upper layer region, wherein a first unit region comprising the first granules and a second unit region comprising the second granules are alternately arranged n times along the longitudinal direction of the electrode active material layer, wherein the first unit region and the second unit region may each have a square cross-section.

[0088] According to another aspect of the present invention, an electrochemical element of the following embodiments is provided.

[0089] The electrochemical device according to the 20th embodiment is,

[0090] The electrode comprises an anode, a cathode, a separator interposed between the anode and the cathode, and an electrolyte, wherein at least one of the anode and the cathode comprises an electrode according to any one of the first to fourth embodiments. Effects of the invention

[0091] An electrode according to one aspect of the present invention has the effect of improving the ion diffusion rate and / or electrode capacity.

[0092] For example, an electrode according to one embodiment of the present invention has the effect of improving the ion diffusion rate compared to an electrode composed of a single layer as well as a multilayer electrode having a flat, straight-line shape at the interface of the intermediate layer region, or improving the electrode capacity while having a similar level of ion diffusion rate.

[0093] In particular, the electrode according to one embodiment of the present invention has the effect of improving electrode capacitance while maintaining a resistance at a similar level compared to a multilayer electrode having a flat, straight-line shape at the interface of the intermediate layer region.

[0094] A method for manufacturing an electrode according to another aspect of the present invention has the effect of providing an electrode having the characteristics described above. Brief explanation of the drawing

[0095] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the aforementioned description; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. FIG. 1 is a schematic diagram of an electrode active material layer within an electrode according to one embodiment of the present invention. FIG. 2 is a schematic diagram of an electrode active material layer within an electrode according to another embodiment of the present invention. FIG. 3 is a schematic diagram of an electrode active material layer within an electrode according to another embodiment of the present invention. FIG. 4 is a schematic diagram of an electrode active material layer within an electrode according to one embodiment of the present invention. FIG. 5 is a schematic diagram of an electrode active material layer within an electrode according to one embodiment of the present invention. FIG. 6 is a flowchart of a method for manufacturing an electrode according to one embodiment of the present invention. FIG. 7 is a photograph of the pattern of a pressure roll used in a method for manufacturing an electrode according to one embodiment of the present invention. FIG. 8 is a schematic diagram of a pressure roll having a pattern formed thereon, used in the manufacture of an electrode according to one embodiment of the present invention. FIG. 9 is a schematic diagram of an electrode assembly using an electrode according to one embodiment of the present invention. FIG. 10 is a schematic diagram of an electrode assembly using an electrode according to Example 1 of the present specification. FIG. 11 is a schematic diagram of an electrode assembly using an electrode according to Example 2 of the present specification. FIG. 12 is a schematic diagram of an electrode assembly using an electrode according to Example 3 of the present specification. Specific details for implementing the invention

[0096] The present invention will be described in detail below. However, the present invention is not limited to the following description, and each component may be modified in various ways or selectively combined as needed. Accordingly, it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0097] In this specification, when a configuration is described as “comprising” a certain component, it means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0098] In this specification, the description “A and / or B” means A or B, or both.

[0099] The present invention relates to an electrode and an electrochemical device comprising said electrode. The electrochemical device of the present invention includes all devices that perform electrochemical reactions, and specific examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors such as supercapacitor devices. In the present invention, preferably, said electrochemical device may be a secondary battery, and more preferably, may be a lithium-ion secondary battery.

[0101] According to one aspect of the present invention, an electrode is provided having an active material layer in a multilayer structure.

[0102] Specifically, the electrode comprises a current collector; and an electrode active material layer located on at least one surface of the current collector.

[0103] In this specification, the vertical direction from the current collector within the electrode to the surface of the electrode active material layer is referred to as the "thickness direction" of the electrode active material layer, and the direction perpendicular to the thickness direction is referred to as the "length direction" of the electrode active material layer.

[0104] In one aspect of the present invention, the electrode active material layer comprises: a lower layer region adjacent to a current collector and comprising a plurality of first granules; an upper layer region located on the lower layer region and comprising a plurality of second granules; and an intermediate layer region located between the lower layer region and the upper layer region, wherein a first unit region comprising the first granules and a second unit region comprising the second granules are alternately arranged n times along the longitudinal direction of the electrode active material layer. In this case, the first unit region and the second unit region each have a square cross-section.

[0105] In addition, the first granule comprises a first electrode active material and a first binder that binds the first electrode active material, and the second granule comprises a second electrode active material and a second binder that binds the second electrode active material.

[0106] In one aspect of the present invention, the size of the first granule and the size of the second granule are different from each other.

[0107] In the electrode according to one aspect of the present invention, the intermediate layer region comprises an interface having a repetitive square shape formed by the alternation of the first unit region and the second unit region.

[0108] According to one embodiment of the present invention, the first unit region and the second unit region are formed by granules of different sizes, and can exhibit an effect of increasing the ion diffusion rate at the interface. In particular, compared to a multilayer electrode comprising a lower region and an upper region formed by granules of different sizes, wherein the interface between the lower region and the upper region is linear in shape, according to one aspect of the present invention, the surface area of ​​the interface is increased, thereby exhibiting an advantageous effect in terms of increasing the ion diffusion rate.

[0109] In particular, according to one embodiment of the present invention, when granules with ion diffusion kinetics more favorable than those in the lower region are arranged in the upper region and an interface with a square cross-sectional shape is formed in the middle region in which a first unit region and a second unit region are alternately formed, the transfer of lithium (ions) in the thickness direction of the electrode is facilitated, and accordingly, the effect of improving the charging capacity of the electrode can be achieved.

[0110] To this end, according to one embodiment of the present invention, a first granule disposed in a lower layer region and a second granule disposed in an upper layer region may be provided to satisfy at least one of the following characteristics.

[0111] 1) First characteristic in which the particle sizes of the first granule and the second granule are different from each other

[0112] 2) Second characteristic in which the compositions of the first granule and the second granule are different from each other

[0113] In one embodiment of the present invention, the first characteristic may be intended to vary the capacity and / or ion diffusion rate of the granules by varying the size of the granules regardless of the composition of the granules.

[0114] Regarding the first characteristic above, according to one embodiment of the present invention, the first granule and the second granule may have the same composition or different compositions.

[0115] The statement that "the composition of the granules is identical" means that the types of active material, binder, (if additionally included) conductive material, etc., contained in the granules, and the weight ratios thereof are identical. Conversely, the statement that "the composition of the granules is different" indicates that at least one type among the active material, binder, and conductive material contained in the granules is different, or that even if each type is identical, the weight ratios thereof are different.

[0116] In one embodiment of the present invention, the second characteristic may be intended to vary the capacity and / or ion diffusion rate of the granules by varying the composition of the granules regardless of the size of the granules.

[0117] Regarding the second characteristic above, according to one embodiment of the present invention, the first granule and the second granule may be implemented with the same or similar size, and the similar size may indicate that the difference in particle size between them is within ±10%, preferably within ±5%.

[0118] According to one embodiment of the present invention, the first unit area and the second unit area each have a rectangular cross-section, and may have, for example, a square cross-section or a rectangular cross-section. Specifically, the first unit area and the second unit area may each have a rectangular cross-section in which the height in the thickness direction (T1, T2) is greater than the width in the length direction (W1, W2), but the present invention is not limited thereto.

[0119] Furthermore, according to one embodiment of the present invention, the first unit region and the second unit region each have a square cross-section, thereby increasing the surface area of ​​the interface (301) of the intermediate layer region compared to electrodes having other shapes (e.g., triangle, trapezoid, etc.), which can provide a more advantageous effect in terms of increasing the ion diffusion rate. Additionally, increasing the surface area of ​​the interface (301) of the intermediate layer region can provide an advantageous effect in terms of improving the adhesion characteristics between the lower layer region and the upper layer region, but the effects of the present invention are not limited thereto.

[0120] In one aspect of the present invention, n, representing the alternating number of a first unit area and a second unit area disposed in the intermediate layer area, is an integer of 2 or more. For example, n may be an integer of 2 or more, an integer of 3 or more, an integer of 4 or more, an integer of 5 or more, or an integer of 10 or more. Specifically, n may be an integer of 50 or less within the range described above, but n is not limited thereto. For example, n may be an integer of 10 to 50, 15 to 40, 15 to 25, or 15 to 20.

[0121] In one embodiment of the present invention, the electrode may have a length of, for example, 5 mm to 1,000 mm, although the size may vary as needed. For example, the length of the electrode may be 10 mm to 700 mm, 50 mm to 600 mm, 100 mm to 600 mm, or 500 mm to 550 mm. In one embodiment of the present invention, when the length of the electrode is 500 mm to 520 mm, for example 509.5 mm, the number of alternating cycles of the first unit area and the second unit area, n, is preferably an integer of 10 to 50, for example 15 to 35, 15 to 30, 20 to 30, or 20 to 25.

[0122] In addition, according to one embodiment of the present invention, the electrode may vary in size as needed, but may have a width of, for example, 5 mm to 1,000 mm. For example, the width of the electrode may be 5 mm to 500 mm, 10 mm to 200 mm, 50 mm to 150 mm, 80 mm to 100 mm, or 90 mm to 100 mm, but is not limited thereto.

[0123] According to one embodiment of the present invention, the electrode may have a rectangular shape with a length of 509.3 mm and a width of 93.3 mm.

[0124] In this specification, the length of the electrode represents the size in the direction in which the first unit region and the second unit region alternating in the electrode active material layer are developed, and, for example, if the electrode has a rectangular shape, it may represent the long side. The width of the electrode represents the size in the direction orthogonal to the length direction of the electrode, and, for example, if the electrode has a rectangular shape, it may represent the short side.

[0125] The electrode active material layer may contain an electrode active material and a binder as electrode materials. Specifically, the electrode materials may be included in the electrode active material layer in the form of granules. The granules represent composite particles comprising an electrode active material and an electrode binder. In one embodiment of the present invention, the granules may be in a form in which the electrode active material is bound by an electrode binder.

[0126] Meanwhile, the above electrode active material layer may further include electrode active material particles in a free state derived from granules.

[0127] In one embodiment of the present invention, the granule may be prepared by mixing the electrode active material with the electrode binder and then granulating it by spray drying, but the method of preparing the granule is not limited thereto.

[0128] In one embodiment of the present invention, an electrode active material layer can be formed without using a separate solvent by applying the granule to one surface of a current collector and then pressing, but the purpose and use of the granule are not limited thereto.

[0129] The specific structure and composition of the above granules will be described later; first, the structure of the electrode active material layer will be explained.

[0130] In the present invention, the electrode active material layer comprises a plurality of granules integrated in a layered structure, having a plurality of micropores provided by the interstitial volume, which is the space between the granules, and exhibiting porous characteristics derived from this structure. At this time, the ion diffusion rate of the electrode active material layer can be determined by factors such as the size and number of micropores, and the electrode capacity of the electrode active material layer can be determined by the packing density of the granules.

[0131] An electrode active material layer according to one aspect of the present invention comprises, in order adjacent to the current collector, a lower layer region, an intermediate layer region, and an upper layer region.

[0132] FIG. 1 shows a schematic diagram of a cross-section of an electrode active material layer (1) within an electrode according to one embodiment of the present invention.

[0133] Referring to FIG. 1, the electrode active material layer (1) includes a lower layer region (10) adjacent to a current collector (not shown) and including a plurality of first granules (100), an upper layer region (20) located on the lower layer region and including a plurality of second granules (200), and an intermediate layer region (30) located between the lower layer region and the upper layer region.

[0134] In the intermediate layer region (30), a first unit region (301) containing the first granule (100) and a second unit region (302) containing the second granule (200) are alternately arranged n times along the longitudinal direction of the electrode active material layer (1). At this time, each of the first unit region and the second unit region has a square cross-section, and thus, a continuous square interface is formed in the intermediate layer region (30) by the repetition of the first unit region (301) and the second unit region (302).

[0135] In the present invention, the particle sizes of the first granule and the second granule are different from each other, and FIG. 1 illustrates a case where the particle size of the second granule (200) is larger than the particle size of the first granule (100).

[0136] FIG. 2 illustrates a schematic cross-section of an electrode active material layer (1) within an electrode according to another embodiment of the present invention. FIG. 2 illustrates a case where the particle size of the first granule (100) is larger than the particle size of the second granule (200).

[0137] In one embodiment of the present invention, the particle sizes of the first granule and the second granule are different from each other, and accordingly, the electrode according to one embodiment of the present invention exhibits an electrode capacity different from that of an electrode using only the first granule and the second granule, respectively. Furthermore, since the particle sizes of the granules included in the upper and lower regions are different from each other, the porosity of the upper and lower regions is formed differently. Accordingly, the electrode according to one embodiment of the present invention exhibits an ion diffusion rate different from that of an electrode using only the first granule and the second granule, respectively.

[0138] Previously, there have been attempts to realize multilayer cathodes using active material particles of different sizes; however, according to conventional technology, a flat interface—that is, an interface with a straight shape—is formed between each layer formed using active material particles of different sizes. In this case, the porosity within each layer is uniform, and a phenomenon may occur where the change in porosity between the lower and upper regions relative to the interface is insignificant. Alternatively, if the size of the active material particles constituting the lower region is smaller and the packing density is higher, a phenomenon may occur where the porosity of the lower region relative to the interface actually decreases. In this case, when the electrolyte is impregnated from the upper region near the surface of the electrode active material layer to the lower region near the current collector, a problem was observed where the impregnation rate of the electrolyte, i.e., the diffusion rate of lithium ions contained in the electrolyte, decreases near the interface, and consequently, the time required for electrolyte impregnation (lithium ion diffusion) increases.

[0139] Accordingly, although the mechanism of the present invention is not limited thereto, according to one aspect of the present invention, a multilayer electrode having a lower region and an upper region is provided by using granules of different particle sizes and / or granules of different compositions, wherein granules of different particle sizes and / or compositions are mixed with each other between the lower region and the upper region to provide a continuous rectangular interface in which a rectangular convex portion and a rectangular concave portion intersect with respect to the lower region, thereby increasing the surface area of ​​the interface and thereby improving the porosity in the middle of the active material layer to exhibit the effect of increasing the ion diffusion rate.

[0140] FIG. 3 illustrates a schematic cross-section of an electrode active material layer (1) within an electrode according to one embodiment of the present invention. Referring to FIG. 3, it can be seen that a square-shaped interface (310) is formed in the intermediate layer region (30) of the electrode active material layer, in which a first unit region and a second unit region are alternately formed. As described above, the interface formed in the intermediate layer region is an interface that appears because the size and / or composition of the first granule of the first unit region and the second granule of the second unit region are different from each other. The interface (310) can be confirmed, for example, through visual observation of the electrode or scanning electronic microscopy (SEM) observation.

[0141] In one embodiment of the present invention, the interface can be confirmed through SEM observation.

[0142] In one embodiment of the present invention, when the first unit area and the second unit area are arranged alternately n times, the size of the vertical cross-sectional shape of each first unit area may be the same or different from each other, and the size of the vertical cross-sectional shape of each second unit area may also be the same or different from each other.

[0143] In one embodiment of the present invention, in the case of an electrode where the first unit area and the second unit area alternate n times and n is an even number, the electrode may include n / 2 first unit areas and n / 2 second unit areas.

[0144] In another embodiment of the present invention, in the case of an electrode where the first unit area and the second unit area alternate n times and n is an odd number, the electrode may include (n-1) / 2 first unit areas and (n+1) / 2 second unit areas, or (n+1) / 2 first unit areas and (n-1) / 2 second unit areas.

[0145] FIG. 4 illustrates a schematic cross-section of an electrode active material layer (1) within an electrode according to one embodiment of the present invention. Referring to FIG. 4, a plurality of first unit regions (301, 301') and a plurality of second unit regions (302, 302') are alternately arranged in the intermediate layer region (30). At this time, each of the first unit regions (301, 301') has a square cross-section, but the sizes of the shapes may differ from each other, and each of the second unit regions (302, 302') also has a square cross-section, but the sizes of the shapes may differ from each other.

[0146] In another embodiment of the present invention, the vertical cross-sectional shapes of a plurality of first unit regions arranged in the intermediate layer region (30) may be equal to each other, and the vertical cross-sectional shapes of a plurality of second unit regions may be equal to each other.

[0147] In another embodiment of the present invention, the shapes of a plurality of first unit regions arranged in the intermediate layer region (30) may be the same size as each other and the shapes of a plurality of second unit regions may be different from each other, or the shapes of a plurality of first unit regions may be different from each other and the shapes of a plurality of second unit regions may be the same size as each other.

[0148] In one embodiment of the present invention, the cross-sectional shape of the first unit region and the second unit region of the intermediate layer region may each satisfy the following conditions.

[0149] d1 ≤ T1,

[0150] d2 ≤ T2,

[0151] 50 d1 ≤ W1 ≤ 1,000 d1,

[0152] 50 d2 ≤ W2 ≤ 1,000 d2,

[0153] The above T1 is the thickness of the first unit region, and

[0154] The above T2 is the thickness of the above second unit area, and

[0155] The above W1 is the width of the first unit area, and

[0156] The above W2 is the width of the above second unit area, and

[0157] The above d1 is the average particle size (D50) of the first granule, and

[0158] The above d2 is the average particle size (D50) of the second granule.

[0160] In another embodiment of the present invention, the cross-sectional shape of the first unit region and the second unit region of the intermediate layer region may each satisfy the following conditions.

[0161] d1 ≤ T1 ≤ 2 d1,

[0162] d2 ≤ T2 ≤ 2 d1,

[0163] 100 d1 ≤ W1 ≤ 600 d1,

[0164] 100 d2 ≤ W2 ≤ 600 d2,

[0165] In one embodiment of the present invention, when W1, W2, T1, and T2 satisfy the conditions described above, advantageous effects may be exhibited in terms of the ion diffusion rate and / or electrode capacitance of the electrode, but the present invention is not limited thereto.

[0166] FIG. 5 illustrates the width (W1) and thickness (T1) of the first unit area (301) and the width (W2) and thickness (T2) of the second unit area (302).

[0167] In one embodiment of the present invention, when the average particle size (D50) of the first granule is d1 and the average particle size (D50) of the second granule is d2, d2 ≥ d1 may be true. Specifically, d1 may be 15 μm to 150 μm and d2 may be 15 μm to 150 μm. When the sizes of the first granule and the second granule satisfy these conditions, an advantageous effect may be exhibited in terms of ease of classification of the first granule and the second granule and ease of electrode manufacturing, and an advantageous effect may also be exhibited in terms of ion diffusion rate, but the present invention is not limited thereto.

[0168] In another embodiment of the present invention, d1 ≥ d2, wherein d1 is 15 μm to 150 μm and d2 is 15 μm to 150 μm.

[0169] In one embodiment of the present invention, 15 μm ≤ d1 ≤ 60 μm, 15 μm ≤ d2 ≤ 60 μm, and d1 ≥ d2. Also, 30 μm ≤ d1 ≤ 60 μm, 30 μm ≤ d2 ≤ 60 μm, and d1 ≥ d2. Also, 45 μm ≤ d1 ≤ 55 μm, 45 μm ≤ d2 ≤ 55 μm, and d1 ≥ d2. In another embodiment, d1 > d2.

[0170] In one embodiment of the present invention, d1 and d2 may each have a particle size of 2 to 5 times the particle size of the electrode active material included in the first granule and the second granule, and may, for example, have a particle size of 3 to 4 times.

[0171] The "average particle size (D50)" of the above granules refers to the particle size at the 50% point of the cumulative distribution of the number of particles according to particle size, and the particle size may be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) to measure the difference in diffraction patterns according to particle size as the particles pass through the laser beam, thereby calculating the particle size distribution. The D50 particle size can be measured by calculating the particle diameter at the point that is 50% of the cumulative distribution of the number of particles according to particle size in the measuring device.

[0172] In one embodiment of the present invention, T1 and T2 may each be, for example, 1 μm to 1,000 μm. Preferably, T1 may be equal to or greater than the average particle size (D50) of the first granule and equal to or less than the height of the electrode, and T2 may be equal to or greater than the average particle size (D50) of the second granule and equal to or less than the height of the electrode.

[0173] In one embodiment of the present invention, T1 and T2 may each be, for example, 1 μm to 500 μm and 20 μm to 100 μm, and specifically, 25 μm to 75 μm, 25 μm to 70 μm, 25 μm to 65 μm, 25 μm to 60 μm, 30 μm to 60 μm, 40 μm to 60 μm, 50 μm to 60 μm, or 50 μm to 55 μm, but are not limited thereto.

[0174] In one embodiment of the present invention, the lower layer region may further include a second granule for forming the upper layer region in a predetermined amount, but it may be preferable in terms of the ion diffusion rate of the electrode that the weight of the first granule is, for example, 95 wt% or more, 96 wt% or more, 97 wt% or more, 98 wt% or more, 99 wt% or more, 99.5 wt% or more, or 100 wt% (i.e., composed only of the first granule) based on the total weight of the granules included in the lower layer region.

[0175] In another embodiment of the present invention, the upper layer region may further include a first granule for forming the lower layer region in a predetermined amount, but it may be preferable in terms of the ion diffusion rate of the cathode that the weight of the second granule is, for example, 95 wt% or more, 96 wt% or more, 97 wt% or more, 98 wt% or more, 99 wt% or more, 99.5 wt% or more, or 100 wt% (i.e., composed only of the second granule) based on the total weight of the granules included in the upper layer region.

[0176] In another embodiment of the present invention, the weight of the first granule may be 95% by weight or more based on the total weight of the granules included in the lower layer region, and the weight of the second granule may be 95% by weight or more based on the total weight of the granules included in the upper layer region.

[0177] In another embodiment of the present invention, the weight of the first granule may be 100% by weight based on the total weight of the granules included in the lower layer region, and the weight of the second granule may be 100% by weight based on the total weight of the granules included in the upper layer region.

[0178] In one embodiment of the present invention, as the number of repetitions n of the first unit region and the second unit region increases, the surface area of ​​the interface formed in the intermediate layer region increases. Accordingly, the effect of increasing the rate of increase of the ion diffusion rate by the interface can be exhibited.

[0179] In one embodiment of the present invention, when the size of the second granule included in the upper region is larger than the size of the first granule included in the lower region, the upper region may exhibit high porosity due to an increase in interstitial volume compared to the lower region. Accordingly, the ion diffusion rate of the upper region may be greater than the ion diffusion rate of the lower region. When the ion diffusion rate of the upper region is greater than the ion diffusion rate of the lower region, it may suppress lithium bonding on the surface of the electrode and facilitate ion diffusion, thereby improving the charging performance of the battery, but the present invention is not limited thereto.

[0180] The above ion diffusion rate refers to the degree of ion diffusion within a specific material. Specifically, in this specification, unless otherwise defined, the ion diffusion rate refers to the diffusion rate of lithium ions.

[0181] The method for measuring the above ion diffusion rate is not particularly limited and, for example, can be measured using the GITT (Galvanostatic Intermittent Titration Technique) method in a charge / discharge state. According to one embodiment of the present invention, the ion diffusion rate can be measured through the GITT method under SOC 50% conditions and can be expressed in units of cm2 / s, but is not limited thereto.

[0182] In another embodiment of the present invention, the ion diffusion rate of the intermediate layer region is greater than the ion diffusion rate of the upper layer region. This may be a result derived from the fact that the parking density of granules in the intermediate layer region is lower than that of the upper layer region, and consequently, the porosity of the intermediate layer region is increased compared to the upper layer region, but the mechanism of the present invention is not limited thereto.

[0183] The above porosity refers to the ratio of the volume occupied by pores to the total volume of a structure. The unit of the above porosity is volume %, and it can be used interchangeably with terms such as porosity and porosity. The porosity of the above cathode can be measured, for example, by the BET (Brunauer-Emmett-Teller) measurement method using nitrogen gas or the mercury infiltration method (Hg porosimeter) and ASTM D-2873. Alternatively, it can be measured by calculating the true density of the electrode from the electrode density (apparent density) and the composition ratio of the materials contained in the electrode and the density of each component, and then calculating the porosity of the electrode from the difference between the apparent density and the true density (net density). For example, porosity can be calculated by the following Equation 1.

[0184] [Equation 1]

[0185] Porosity (Volume %) = {1 - (Apparent Density / True Density)} * 100

[0186] In the above Equation 1, the apparent density can be calculated from the following Equation 2.

[0187] [Equation 2]

[0188] Apparent density (g / cm³) = (Weight of porous substrate (g)) / {(Thickness of porous substrate (cm)) x (Area of ​​porous substrate (cm²))}

[0189] In one embodiment of the present invention, the porosity of the intermediate layer region may be, for example, 10 volume% to 50 volume% or 20 volume% to 40 volume%, but is not limited thereto.

[0190] In one embodiment of the present invention, the porosity of the intermediate layer region is higher than the porosity of the upper layer region and the lower layer region, and for example, the porosity of the intermediate layer region may have a value increased by 10% to 200%, for example, 30% to 100%, relative to the porosity of the upper layer region and the lower layer region, respectively, but the present invention is not limited thereto.

[0191] In one embodiment of the present invention, by using a second granule included in the upper region that has a lower ion diffusion rate than the first granule included in the lower region, the effect of having a lower ion diffusion rate in the upper region than in the lower region can be achieved. When the ion diffusion rate in the upper region is low, the lithium binding amount in the upper region is increased, and accordingly, the effect of improving the energy density of the electrode in the upper region can be achieved. As a result, the effect of the upper region having an improved electrode capacity compared to the lower region can be achieved.

[0192] In another embodiment of the present invention, the electrode capacity per volume of the upper layer region may exhibit a characteristic greater than the electrode capacity per volume of the lower layer region.

[0193] In one embodiment of the present invention, by using a first granule included in the lower region having a lower ion diffusion rate than a second granule included in the upper region, the ion diffusion rate of the lower region can be lower than that of the upper region. When the ion diffusion rate in the lower region is low, the lithium binding amount in the lower region is increased, and accordingly, the energy density of the electrode in the lower region can be improved. As a result, the lower region can have an improved electrode capacity compared to the upper region.

[0194] In another embodiment of the present invention, the electrode capacity per volume of the lower layer region may exhibit a characteristic greater than the electrode capacity per volume of the upper layer region.

[0195] The electrode capacity per volume above represents the electrode capacity measured based on the same volume of the electrode, and the electrode capacity can be measured by measuring the discharge capacity under charge-discharge conditions. Although the measurement method is not limited thereto, for example, the electrode capacity per volume above can be measured as the discharge capacity when electrode samples prepared with the same volume are charged at 25°C with a constant current (CC) of 0.1C until they reach 3.0 V (vs Li / Li+), and discharged at a current density of 0.1C until they reach 1.7 V (vs Li / Li+).

[0196] In one embodiment of the present invention, by placing an intermediate layer region between two electrode active material layers having a difference in electrode capacity per volume as described above, and increasing the effective surface area of ​​the interface between the upper layer region and the lower layer region, an advantageous effect can be achieved in terms of efficiently improving the electrode capacity per total volume of the electrode.

[0197] In one embodiment of the present invention, the total thickness of the electrode active material layer may be, for example, 50 μm to 120 μm, specifically 70 μm to 112 μm. At this time, based on the total thickness of the electrode active material layer, the thickness of the intermediate layer region may be, for example, 15 μm to 40 μm, specifically 20 to 40 μm or 27 μm to 37 μm, and the thickness of each of the upper layer region and the lower layer region may be, for example, 15 μm to 40 μm, specifically 20 to 40 μm or 27 μm to 37 μm.

[0198] The total “thickness” of the electrode active material layer, or the “thickness” of each layer included therein, or W1, W2, T1, and T2 may represent values ​​measured by a known method for measuring thickness. The method of measuring thickness is not limited to this, but may be, for example, a value measured using a thickness gauge (Mitutoyo, VL-50S-B).

[0200] Next, the structure and composition of the granules included in the electrode active material layer will be described in detail.

[0201] In this specification, a granule included in the lower layer region of the electrode active material layer is named the first granule, and a granule included in the upper layer region is named the second granule, wherein the first granule and the second granule indicate that their particle sizes are different from each other. The intermediate layer region includes both the first granule and the second granule, and is each included by a first unit region containing the first granule and a second unit region containing the second granule.

[0202] The above granule comprises an electrode active material and a binder, and may further comprise a conductive material as needed. In this specification, the electrode active material, binder, and conductive material included in the first granule are respectively referred to as the first electrode active material, the first binder, and the first conductive material, and the electrode active material, binder, and conductive material included in the second granule are respectively referred to as the second electrode active material, the second binder, and the second conductive material.

[0203] The above granules are formed by binding the electrode active material and / or conductive material by the binder to form a set of particles, and the electrode active material layer comprises a plurality of granules.

[0204] In one embodiment of the present invention, the content (wt%) of the binder relative to the total weight of the active material, binder, and conductive material included in the granule (100wt%) may be higher in the surface portion (102) than in the center portion (101) of the granule.

[0205] Here, the surface portion refers to an area near the surface of the granule up to a predetermined depth from the surface of the granule toward the center of the granule, and the center refers to a portion other than the surface portion. In one embodiment of the present invention, the surface portion may refer to an area from the center of the particle diameter of the granule to the surface of the granule after 70% of the radius, preferably after 85% of the radius, or after 90%, or after 95% of the radius.

[0206] In one embodiment of the present invention, the content of the binder relative to the total weight of the granules in the region from the center of the granule particles to the surface of the granules after 90% radius may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0207] In another embodiment of the present invention, the content of the binder relative to the total weight of the granules in the region from the center of the granule to the surface of the granule after 95% of the particle radius may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more.

[0208] To describe the granule in more detail, the granule may comprise a central part containing a plurality of electrode active materials; and a surface part containing a binder located on all or part of the outer side of the central part and binding the electrode active materials. That is, in the central part of the granule, a plurality of electrode active materials form an aggregate by making surface contact, line contact, point contact, or two or more of these contacts with each other, and in the surface part of the granule, a binder is located on all or part of the outer side of such aggregate, thereby fixing and binding the plurality of electrode active materials in the central part of the granule.

[0209] According to one embodiment of the present invention, a small amount of binder may also be included in the central portion to serve to connect and fix a plurality of electrode active materials in the central portion. However, in the central portion of the granule, a plurality of electrode active materials form an aggregate by making surface contact, line contact, point contact, or two or more of these contacts with each other, and in the surface portion of the granule, a binder may be located on a part or all of the outer side of such aggregate, thereby fixing and binding a plurality of electrode active materials in the central portion of the granule.

[0210] In one embodiment of the present invention, the granule may have an aspect ratio of 0.5 to 1.5. The closer the aspect ratio is to 1, the more spherical the granule may be. Specifically, the aspect ratio of the granule may be 0.8 to 1.2. More specifically, the aspect ratio of the granule may be 0.95 to 1.05. The aspect ratio refers to the ratio of the major axis length to the minor axis length of the granule, wherein the minor axis length represents the average value of the length in the axial direction having the shortest length of 10 granules, and the major axis length represents the average value of the length in the axial direction having the longest length of 10 granules. When the aspect ratio of the granule satisfies this range, it is advantageous in terms of having sufficient fluidity suitable for the process.

[0211] Meanwhile, if the above granule further includes a conductive material, the conductive material may be fixed within the granule by binding between the conductive material and the electrode active material particles or between the conductive material particles by the binder.

[0212] In one embodiment of the present invention, the electrode may be a negative electrode, and the electrode active material may be a negative electrode active material.

[0213] In one embodiment of the present invention, when the electrode is a negative electrode, the first negative electrode active material and the second negative electrode active material may be of the same or different types, for example, carbonaceous compounds such as non-graphitizable carbon, graphite-based carbon, etc.; LixFe2O3(0≤x≤1), LixWO2(0≤x≤1), SnxMe1-xMe'yOz (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Group 1, Group 2, and Group 3 of the periodic table, halogen; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SiO, SiO / C, SiO2등의 실리콘계 산화물; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5 등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 또는 이들 중 2 이상의 혼합물 중에서 선택되는 것일 수 있으나, 이에 한정되는 것은 아니다.

[0214] In one embodiment of the present invention, the first cathode active material and the second cathode active material may each comprise a carbon-based compound.

[0215] In one embodiment of the present invention, at least one of the first negative electrode active material and the second negative electrode active material comprises a carbon-based compound, and at least one of the first negative electrode active material and the second negative electrode active material may comprise a silicon-based compound.

[0216] In another embodiment of the present invention, the first negative electrode active material is composed solely of a carbon-based compound, and the second negative electrode active material may be composed of a mixture of a carbon-based compound and a silicon-based oxide (SiOx (0≤x≤2)).

[0217] In another embodiment of the present invention, the first negative electrode active material is composed of a mixture of a carbon-based compound and a silicon-based oxide, and the second negative electrode active material may be composed solely of a carbon-based compound.

[0218] In one embodiment of the present invention, when at least one of the first negative electrode active material and the second negative electrode active material comprises a mixture of a carbon-based compound and a silicon-based compound, the mixing ratio of the carbon-based compound and the silicon-based compound may be 9:1 to 1:9, 9:1 to 5:5, 9:1 to 6:4, 9:1 to 7:3, or 9:1 to 8:2 as a weight ratio of the carbon-based compound to the silicon-based compound, but the present invention is not limited thereto.

[0219] In one embodiment of the present invention, the first negative electrode active material may be composed solely of artificial graphite, and the second negative electrode active material may be composed of a mixture of SiO and artificial graphite. Specifically, the first negative electrode active material may be composed solely of artificial graphite, and the second negative electrode active material may be composed of a mixture of artificial graphite and SiO, for example, a mixture having a weight ratio of artificial graphite to SiO of 9:1 to 5:5 or 9:1.

[0220] In one embodiment of the present invention, the electrode may be a positive electrode, and the electrode active material may be a positive electrode active material.

[0221] In one embodiment of the present invention, when the electrode is a positive electrode, the first positive electrode active material and the second positive electrode active material may be of the same or different types, for example, each may include a lithium transition metal oxide; a lithium metal iron phosphate; a lithium nickel-manganese-cobalt oxide; an oxide in which a portion of the lithium nickel-manganese-cobalt oxide is substituted with another transition metal; or two or more of these, but are not limited thereto. Specifically, the positive electrode active material may include, for example, a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium manganese oxide such as the chemical formula Li1+xMn2-xO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; a lithium copper oxide (Li2CuO2); or a vanadium oxide such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; Ni-site type lithium nickel oxide represented by the chemical formula LiNi1-xMxO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); lithium manganese composite oxide represented by the chemical formula LiMn2-xMxO2 (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); lithium metal phosphate LiMPO4 (where M = Fe, CO, Ni, or Mn); Lithium nickel-manganese-cobalt oxide Li1+x(NiaCobMnc)1-xO2(x = 0 ~ 0.03, a = 0.3 ~ 0.95, b = 0.01 ~ 0.35, c = 0.01 ~ 0.5, a+b+c=1); Lia[NibCocMndAle]1-fM1fO2, an oxide in which a portion of lithium nickel-manganese-cobalt oxide is substituted with aluminum (M1 is one or more selected from the group consisting of Zr, B, W, Mg, Ce, Hf, Ta, La, Ti, Sr, Ba, F, P, and S, and 0.8≤a≤1.2, 0.5≤b≤0.99, 0 <c<0.5, 0<d<0.5, 0.01≤e≤0.1, 0≤f≤0.1); 리튬 니켈-망간-코발트 산화물에 일부가 다른 전이금속으로 치환된 산화물 Li1+x(NiaCobMncMd)1-xO2(x = 0 ~ 0.03, a = 0.3 ~ 0.95, b = 0.01 ~ 0.35, c = 0.01 ~ 0.5, d = 0.001 ~ 0.03, a+b+c+d=1, M은 Fe, V, Cr, Ti, W, Ta, Mg 및 Mo로 이루어진 군으로부터 선택된 어느 하나임), 디설파이드 화합물; Fe2(MoO4)3 또는 이들 중 2 이상의 혼합물 중에서 선택되는 것일 수 있으나, 이에 한정되는 것은 아니다.

[0222] In one embodiment of the present invention, the first binder and the second binder may be of the same or different types and have adhesive properties, are stable in electrochemical reactions, and can bind electrode materials such as the electrode active material and conductive material to maintain a granular form, and can integrate into a layered structure and maintain a stable form by binding the granules to each other by compression, and are not limited to specific components.The first binder and the second binder are, for example, styrene butadiene rubber (SBR), butadiene rubber (BR), nitrile butadiene rubber (NBR), styrene butadiene styrene block polymer (SBS), styrene ethylene butadiene block polymer (SEB), styrene-(styrene butadiene)-styrene block polymer, natural rubber (NR), isoprene rubber (IR), ethylene-propylene-diene terpolymer (EPDM), poly(ethylene-co-propylene-co-5-methylene-2-norbornene) polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyvinyl chloride, polyvinylidene fluoride-co-hexafluoropropylene, It may be polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene, polypropylene, ethylene vinyl acetate copolymer (polyethylene-co-vinyl acetate), polyethylene oxide, polypropylene oxide, polyarylate, cyanoethylpullulan, cyanoethylpolyvinyl alcohol, or may contain two or more of these.Specifically, the binder may be selected from styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), polymethylmethacrylate, polyethylhexyl acrylate, polybutyl acrylate, or a mixture of two or more of these, but is not limited thereto.

[0223] In one embodiment of the present invention, the first conductive material and the second conductive material may be of the same or different types, and are not particularly limited as long as they possess conductivity without causing chemical changes in the battery. Examples of the first conductive material and the second conductive material include, for instance, graphite such as natural graphite or artificial graphite; carbon black-based carbon compounds such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. In a specific embodiment, the first conductive material and the second conductive material may each be one selected from these or a mixture of two or more, but are not limited thereto.

[0224] In one embodiment of the present invention, the granules may be obtained by applying a method of preparing a fluidized slurry by mixing an electrode active material and a binder with a solvent, and spray-drying the slurry. As described above, the granules may be manufactured to further include a conductive material as needed. Additionally, they may be manufactured to further include other additives for performance improvement.

[0225] First, the electrode active material and binder, and optionally a conductive material and additional additives are dispersed or dissolved in a dispersion medium (a solvent for the electrode binder) to obtain a slurry in which the electrode active material and binder are dispersed or dissolved.

[0226] Water is most suitable as the dispersion medium used to obtain the above slurry, but an organic solvent may also be used. Examples of organic solvents include alkyl alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol; alkyl ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane, and diglyme; amides such as diethylformamide, dimethylacetoamide, N-methyl-2-pyrrolidone (hereinafter also referred to as NMP), and dimethylimidazolidinone; and sulfur-based solvents such as dimethyl sulfoxide and sulfolain, but alcohols are preferred. If an organic solvent with a boiling point lower than that of water is used in combination, the drying speed during flow granulation can be accelerated. In addition, since the dispersibility or solubility of the cathode binder can be changed, the viscosity or fluidity of the slurry can be adjusted according to the amount or type of dispersion medium, thereby improving production efficiency.

[0227] The amount of dispersion medium used when preparing the above slurry may be an amount such that the solid content concentration of the slurry is usually in the range of 1 to 50 wt%, or 5 to 50 wt%, or 10 to 30 wt%.

[0228] The method or sequence of dispersing or dissolving the electrode active material and binder, etc., in the dispersion medium is not particularly limited. Examples include a method of adding and mixing the electrode active material and binder in the dispersion medium, or a method of dissolving or dispersing the binder in the dispersion medium and then finally adding and mixing the electrode active material. If conductive materials or additives are included, these components may be added at the time of adding the electrode active material. Mixing means may include, for example, mixing equipment such as a ball mill, sand mill, bead mill, pigment disperser, stone mill, ultrasonic disperser, homogenizer, or planetary mixer. Mixing may be performed, for example, for 10 minutes to several hours in the range of room temperature to 80°C.

[0229] Next, the above slurry is spray-dried. The spray drying method is a method of drying by spraying the slurry into hot air. An atomizer can be cited as a representative example of a device used in the spray drying method. There are two types of atomizers: a rotary disc type and a pressurized type. The rotary disc type is a method in which the slurry is introduced near the center of a high-speed rotating disc, and the slurry is placed outside the disc by the centrifugal force of the disc, thereby drying it in a mist form. The rotation speed of the disc depends on the size of the disc, but is usually 5,000 to 35,000 rpm, preferably 15,000 to 30,000 rpm. On the other hand, the pressurized method is a method in which the slurry is pressurized and dried in a mist form from a nozzle.

[0230] The temperature of the sprayed slurry is usually room temperature, but it may be heated to above room temperature. The temperature of the hot air during spray drying can be controlled to 80°C to 250°C, preferably 100°C to 250°C, based on the reactor inlet temperature (at input), in order to form a granule structure with a high binder content on the surface. According to one embodiment of the present invention, considering the gradient of the binder content and the aspect ratio of the granules, the temperature can be controlled to preferably 175°C to 250°C, more preferably 180°C to 250°C. In the spray drying method, the method of sucking in the hot air is not particularly limited and may include, for example, a method in which the hot air and the spray direction flow parallel in the transverse direction, a method in which the spray is sprayed at the top of the drying tower and descends together with the hot air, a method in which the sprayed droplets and the hot air come into counter-flow contact, or a method in which the sprayed droplets flow parallel with the hot air first and then fall by gravity to come into counter-flow contact. Meanwhile, in one embodiment of the present invention, the outlet temperature of the reactor (hot air temperature discharged from the reactor) during spray drying can be controlled to 90°C to 130°C.

[0231] If the outlet temperature and / or △T, which is the difference between the inlet and outlet temperatures, is low, drying is not done properly, resulting in the formation of particles with a large amount of residual solvent. Consequently, uniform spherical particles are not formed, and the granules may clump together or be formed in an amorphous state. On the other hand, if the inlet temperature is too high and △T is large, over-drying prevents the granules from agglomerating, and particles with a very small particle size (D50) and a low aspect ratio may be produced. Therefore, in order to control the particle size to an appropriate level with high sphericity and minimal binder clumping, it is necessary to control the inlet and outlet temperatures within an appropriate range.

[0232] In addition, the surface of the product obtained by optional spray drying, i.e., the granule, can be heat-treated to harden it, and the heat treatment temperature can usually be 80°C to 300°C.

[0233] In one embodiment of the present invention, the current collector may be used without particular limitation as long as it has high conductivity without causing chemical changes in the battery. For example, the current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The current collector may also have fine irregularities formed on its surface to increase the adhesion of the active material, and may take various forms such as a film, sheet, foil, net, porous body, foam, or nonwoven fabric. Meanwhile, in one embodiment of the present invention, the current collector may have a thickness of 10 μm to 50 μm, but is not particularly limited thereto. For example, the current collector may have a thickness of 10 μm to 20 μm.

[0234] In one embodiment of the present invention, the current collector may have a primer layer formed on at least one surface that covers all or at least a portion of the surface. The primer layer may be introduced to improve the bonding strength and electrical conductivity between the current collector and the electrode active material layer. The primer layer may include a binder and a conductive material, and regarding the binder and conductive material, the contents of the binder and conductive material of the electrode active material layer described above may be adapted.

[0235] In one embodiment of the present invention, the primer layer may further include, for example, a dispersant for dispersing the binder and conductive material in addition to the above.

[0236] In one embodiment of the present invention, the primer layer comprises the composition described above, and its thickness may be 300 nm to 1.5 μm, specifically 700 nm to 1.3 μm, but is not limited thereto.

[0237] The electrode active material layer of the electrode according to one aspect of the present invention described above may exhibit a higher ion diffusion rate compared to an electrode active material layer composed of a single layer and / or multiple layers, wherein the interface between layers is provided in the form of a horizontal straight line or has other shapes such as a triangle or a trapezoid. Alternatively, when having a similar ion diffusion rate, it may exhibit an improved electrode capacity per unit volume.

[0239] According to another aspect of the present invention, a method for manufacturing an electrode is provided.

[0240] A method for manufacturing an electrode according to another aspect of the present invention includes a process of forming an electrode active material layer on at least one surface of a current collector.

[0241] According to another aspect of the present invention, the process of forming the electrode active material layer comprises the following steps:

[0242] (S1) A step of applying a plurality of first granules on at least one surface of the above-mentioned current collector;

[0243] (S2) A first pressing step of forming a pattern on the surface of the first granule by pressing the surface of the first granule using a pressing roll having a pattern formed thereon;

[0244] (S3) A step of applying a plurality of second granules on the surface of the first granule that has been pressurized; and

[0245] (S4) A second pressing step of pressing the surface of the second granule applied above.

[0246] The first granule comprises a first electrode active material and a first binder that binds the first electrode active material, and the second granule comprises a second electrode active material and a second binder that binds the second electrode active material.

[0247] According to one embodiment of the present invention, the first granule and the second granule may satisfy at least one of the following characteristics.

[0248] 1) A first characteristic in which the particle sizes of the first granule and the second granule are different from each other,

[0249] 2) Second characteristic in which the compositions of the first granule and the second granule are different from each other

[0250] The process of forming the above electrode active material layer is intended to form an electrode active material layer comprising the aforementioned lower layer region, upper layer region, and an intermediate layer region located between the lower layer region and the upper layer region. In this case, the intermediate layer region is formed such that a first unit region containing the first granule and a second unit region containing the second granule are alternately arranged n times along the longitudinal direction of the electrode active material layer, thereby forming an interface having a continuous rectangular cross-section.

[0251] FIG. 6 illustrates a flowchart of a method for manufacturing an electrode according to one embodiment of the present invention.

[0252] Referring to FIG. 6, a method for manufacturing an electrode according to one embodiment of the present invention comprises the steps of: (a) applying a plurality of first granules (100) on a current collector (2); (b) applying pressure to the surface of the applied first granules using a pressure roller (1000) having a pattern formed thereon; (c) applying pressure to the surface of the applied first granules; (d) applying a plurality of second granules (200) to the surface of the applied first granules; and (e) applying pressure to the surface of the applied second granules.

[0253] Specifically, after applying a plurality of first granules (100) on at least one surface of a current collector (2), a pattern is formed on the surface of the first granules by applying pressure to the surface of the applied first granules using a patterned roll (1000). At this time, the pattern formed on the surface of the first granules functions as a pre-pattern of the interface of the intermediate layer region of the electrode active material being manufactured.

[0254] In a conventional method for manufacturing multilayer electrodes by applying an electrode active material onto a current collector and applying pressure, and then applying and applying the electrode active material again, a pressure roll having a smooth surface was used to flatten the interface between layers.

[0255] In the present invention, a roll having a pattern formed on its surface is used as a pressure roll to increase the surface area of ​​the interface between the electrode active material layers.

[0256] FIG. 7 is a surface photograph of a pressure roll having a pattern formed thereon that can be used in step (S2) according to one embodiment of the present invention.

[0257] Referring to FIG. 7, in one embodiment of the present invention, the pattern of the pressure roll may be a protrusion type (a) in which the pattern protrudes outward from a central rod. In particular, a roll having a square-shaped protrusion pattern formed thereon may be used such that the first unit area and the second unit area each have a square-shaped cross-section.

[0258] Referring to FIG. 7, in another embodiment of the present invention, the pattern of the pressure roll may be a mesh type (b) in which the pattern is indented inward from a central rod.

[0259] In one embodiment of the present invention, the pattern of the pressure roll may include a plurality of square-shaped protrusions.

[0260] FIG. 8 illustrates the cross-sectional shape of a pressure roll having a projection (protrusion) parallel along the longitudinal direction of a cylindrical rolling roll having a predetermined projection width according to one embodiment of the present invention. With reference to FIG. 8, a pattern of concave and convex portions can be formed in the longitudinal direction (or machine direction (MD)) of an electrode by using a pressure roll having a projection parallel along the longitudinal direction of the cylindrical pressure roll.

[0261] In another embodiment of the present invention, a pattern of concave and convex portions may be formed on an electrode using a pressure roll that includes a projection (protrusion) parallel to the upper and lower surfaces of the cylinder and perpendicular to the longitudinal direction of the cylindrical pressure roll (not shown). In this case, a pattern of concave and convex portions may be formed in the width direction (or transverse direction (TD)) of the electrode.

[0262] Referring to FIG. 8, the square-shaped protrusion may satisfy the conditions of W3, W4, and T3 below:

[0263] d2 ≤ T3

[0264] 50 d2 ≤ W3 ≤ 1,000d2,

[0265] 50 d1 ≤ W4 ≤ 1,000 d1

[0266] W3 is the width of the protrusion of the projection, W4 is the shortest straight distance between two projections, T3 is the thickness of the protrusion of the projection, d1 is the average particle size (D50) of the first granule, and d2 is the average particle size (D50) of the second granule.

[0267] In one embodiment of the present invention, a square-shaped pre-pattern is formed on the surface of the first granule pressed by the protruding pressure roll. When the second granule is applied to the surface of the first granule having the pre-pattern formed thereon, the second granule is applied to the surface of the first granule pressed by the protrusion of the pressure roll to form a second unit region in the intermediate layer region of the electrode active material layer.

[0268] As described above, by applying a second granule to the surface of a first granule on which a pre-pattern is formed and then applying pressure, an electrode having an electrode active material layer having the lower layer region, middle layer region, and upper layer region formed as described above can be manufactured.

[0269] At this time, the pressurization step of (S4) above can be performed using a pair of rolling rolls with flat surfaces as shown in (e) of Fig. 6.

[0270] According to another embodiment of the present invention, an electrode active material layer may be manufactured by applying a second granule, then applying pressure using a pressure roller formed with a pattern used during the pressure application of step (S2), and then applying a third granule.

[0271] In addition, the temperature and pressure conditions of the granule coating process and the pressurization process, respectively, in each of the steps (S1) to (S4) above can be performed according to normal conditions and are not specifically limited in the present invention.

[0273] According to another aspect of the present invention, an electrode assembly comprising an anode, a cathode, and a separator interposed between the anode and the cathode is provided.

[0274] FIG. 9 shows a schematic diagram of an electrode assembly according to one aspect of the present invention.

[0275] Referring to FIG. 9, the electrode assembly may include a positive electrode and a negative electrode on each side of the separator based on the central separator, and the positive electrode and the negative electrode may each include an active material layer formed on a current collector, and the current collector may include a non-active portion (or tab) where the active material layer is not formed.

[0276] According to one embodiment of the present invention, at least one of the anode and the cathode may be an electrode that does not include a current collector (not shown).

[0277] In the present invention, at least one of the anode and cathode is characterized as being an electrode comprising an upper layer region, a lower layer region, and an intermediate layer region as described above.

[0278] In one embodiment of the present invention, with reference to FIG. 9, the electrode located on the upper surface of the separator may be a negative electrode and the electrode located on the lower surface of the separator may be a positive electrode, and conversely, the electrode located on the upper surface of the separator may be a positive electrode and the electrode located on the lower surface of the separator may be a negative electrode, but is not limited thereto.

[0279] FIGS. 10 to 12 illustrate a schematic diagram of an electrode assembly including an electrode according to one embodiment of the present invention, wherein one of the positive and negative electrodes includes an upper layer region, a lower layer region, and an intermediate layer region.

[0281] According to another aspect of the present invention, an electrochemical device is provided comprising an anode, a cathode, a separator interposed between the anode and the cathode, and an electrolyte, wherein at least one of the anode and the cathode comprises the electrode described above.

[0282] In one embodiment of the present invention, the separator and electrolyte may be used without particular limitation as long as they are usable in conventional electrochemical devices within a range that does not impede the purpose of the present invention; therefore, a description of specific types thereof is omitted.

[0283] In one embodiment of the present invention, the external shape of the electrochemical element may be, for example, coin-shaped, cylindrical, pouch-shaped, or prismatic, and the external shape of the battery is not particularly limited. Furthermore, the electrochemical element may be used not only as a battery cell used as a power source for small devices but also as a unit cell in a medium-to-large battery module containing a plurality of battery cells, and the form of use is not particularly limited.

[0285] Hereinafter, examples, comparative examples, and experimental examples are presented to aid in understanding the contents of the present invention. However, the following test examples correspond only to a few test examples regarding the composition and effects of the present invention, and the scope and effects of the present invention are not limited thereto.

[0286] Experimental Example 1. Evaluation of filling speed according to the height of the interface shape

[0287] [Manufacturing of Electrodes]

[0288] Preparation of the first granule (lower layer area)

[0289] 95.6 wt% of artificial graphite (D50 15 μm) as the electrode active material, 1.0 wt% of carbon black (Super C65) as the electrode conductive material, 1.1 wt% of carboxymethylcellulose (daicel2200, aqueous solution form, solid content 1.5 wt%) as the electrode dispersant, and 2.3 wt% of modified styrene butadiene copolymer as the electrode binder were mixed with water as the dispersion medium to prepare a slurry with a viscosity of approximately 1000 cPs using a homogenizer. At this time, the solid content of the slurry was 30 wt%. Among the above weight ratios, the carboxymethylcellulose was calculated based on the solid content.

[0290] The manufactured slurry was introduced into a spray dryer with hot air under pressure conditions of -40 mmH2O and dried. At this time, the conditions of the spray dryer were controlled to an inlet temperature of 250°C, an outlet temperature of 100°C, and a rotation speed of 18,000 rpm. The obtained granules were cleaned using an industrial sieve to remove particles larger than 150 μm. The granules had a central portion containing a plurality of electrode active materials and electrode conductive materials, and a surface portion containing an electrode binder located on the outer side of the central portion that binds the electrode active materials and electrode conductive materials. The average particle size (D50) of the first obtained granules was 50.1 μm, and the aspect ratio was 1.04.

[0292] Preparation of the second granule (upper region)

[0293] A second granule was prepared according to the same method as the first granule, except that a mixture of artificial graphite (D50 15㎛):SiO (D50 6㎛) (9:1 weight ratio) was used as the electrode active material. The average particle size (D50) of the obtained second granule was 48.28㎛, and the aspect ratio was 1.01.

[0295] Manufacturing of electrodes

[0296] The electrode was manufactured as follows according to the sequence shown in Fig. 6.

[0297] An electrode was manufactured by evenly dispersing the previously prepared first granules on one surface of a copper current collector (thickness 10 μm) in an amount of 200 mg per 25 cm2 of the current collector using a thickness control bar, applying pressure at a speed of 2 m / min at a pressure of 0.1 ton per cm and a temperature of 60°C using a rolling device, then evenly dispersing the previously prepared second granules on the pressured surface in an amount of 200 mg per 25 cm2 of the current collector, and then applying pressure at a speed of 2 m / min at a pressure of 0.5 ton per cm and a temperature of 60°C using a rolling device equipped with a smooth surface roll.

[0298] At this time, a cross-sectional schematic diagram of the pressure roll used is shown in FIG. 8, and a pressure roll was used in which protrusions appearing in the cross-section along the longitudinal direction of the cylindrical roll were formed parallel to each other with the same width. Three electrodes were manufactured with different shapes of the interfaces in the intermediate layer region by maintaining the width of the protrusions constant and varying the thickness of the protrusions, and schematic diagrams of the three electrodes are shown in FIG. 10 (Example 1), FIG. 11 (Example 2), and FIG. 12 (Example 3), respectively.

[0299] The electrodes of FIGS. 10 to 12 were formed with a total length of 509.5 mm and a width of 93.3 mm, with the first unit area and the second unit area alternating 30 times, and the thicknesses (T1, T2) of the first unit area and the second unit area were manufactured to be 3 μm (Fig. 10, Example 1), 27 μm (Fig. 11, Example 2), and 54 μm (Fig. 12, Example 3), respectively.

[0300] To compare the effect with an electrode having a straight shape at the interface between the lower and upper regions, a rolled electrode was prepared as Comparative Example 1 using a conventional flat pressure roll without protrusions on its surface. The electrode was manufactured using the same method as above, except that the shape of the pressure roll was different.

[0302] [Physical Property Evaluation]

[0303] The electrode (cathode) prepared above was placed in contact with a reference anode with a polyethylene porous membrane in between and pressurized, then immersed in an electrolyte and charged at rates of 0.5C and 1C, respectively, and the time required to reach a state of 100% SOC was measured, and the results are shown in Table 1 below.

[0304] In addition, to compare and evaluate the resistance values ​​of each electrode, a current of 2.5C was applied for 30 seconds, and the resistance values ​​were calculated according to V=IR and shown together in Table 1 below.

[0305] n number Thickness of T1, T2 (㎛) 0.5C charging time(s) 1C charging time(s) 2.5C 30s pulse resistance (Ω) Comparative Example 1 0 0 5500 - 3.910 Example 1 30 3 5650 2000 3.801 Example 2 30 27 5718 2000 3.800 Example 3 30 54 5740 2120 3.800

[0306] Through the results of Table 1 above, it was confirmed that the charging capacity is improved in the order of Example 3 > Example 2 > Example 1.

[0307] Through this, it was confirmed that the final charge capacity of the battery is improved without increasing resistance, as granules that are kinetically more advantageous for improving battery capacity are placed in the upper layer and lithium is transported more easily through the interface of the middle layer region.

[0308] In particular, it was confirmed that when an interface parallel to the intermediate layer region is present, the charge capacity is inferior and the resistance value also increases.

[0310] Experimental Example 2. Evaluation of charging speed according to the width of the unit area (alternating cycles n)

[0311] After preparing electrodes by maintaining the length of the electrode and varying the widths (W1, W2) of the first and second unit regions and varying the alternating number n of the first and second unit regions, the time required to reach a SOC of 100% was measured by charging at speeds of 0.5C, 1C, and 2C according to the same method as in Experimental Example 1, and the results are shown in Table 2 below.

[0312] In addition, to compare and evaluate the resistance values ​​of each electrode, a current of 2.5C was applied for 30 seconds, and the resistance values ​​were calculated according to V=IR and shown together in Table 1 below.

[0314] n number Thickness of T1, T2 (㎛) Charging time(s) 2.5C 30s pulse resistance (Ω) 0.5C 1C 2C Example 4 4 54 5605 2040 480 3.801 Example 5 8 54 5730 2070 490 3.800 Example 6 12 54 5771 2070 490 3.800 Example 7 16 54 5796 2090 490 3.801 Example 8 20 54 5797 2090 500 3.800 Example 9 32 54 5783 2080 490 3.800

[0315] Through the results of Table 2 above, it was confirmed that when n is 20, charging at a rate of 0.5C to 2C results in the highest charging time, which is the best in terms of the final charging capacity of the electrode.

[0316] In particular, it was confirmed that the electrode according to the present invention can improve electrode capacitance without increasing the resistance value by showing that the resistance value does not change significantly even when the number of n changes. Explanation of the symbols

[0318] 1 - Electrode active material layer 2- The whole house 10 - Lower area 20 - Upper area 30 - Intermediate layer area 100 - 1st Granule 200 - 2nd Granule 301, 301' - 1st unit area 302, 302' - Second unit area 310 - Interface 1000 - Pattern-formed pressure roll 2000, 3000 - Rolled Roll

Claims

Claim 1 A current collector; and an electrode active material layer located on at least one surface of the current collector; wherein the electrode active material layer comprises: a lower layer region adjacent to the current collector and comprising a plurality of first granules; and an upper layer region located on the lower layer region and comprising a plurality of second granules. The electrode comprises: an intermediate layer region located between the lower layer region and the upper layer region, wherein a first unit region including the first granule and a second unit region including the second granule are alternately arranged n times along the longitudinal direction of the electrode active material layer, wherein n is an integer greater than or equal to 2, wherein the first unit region and the second unit region each have a square cross-section, wherein the first granule includes a first electrode active material and a first binder that binds the first electrode active material, and the second granule includes a second electrode active material and a second binder that binds the second electrode active material, and wherein the ion diffusion rate of the intermediate layer region is greater than the ion diffusion rate of the upper layer region, or the electrode capacity per volume of the upper layer region is greater than the electrode capacity per volume of the lower layer region. Claim 2 An electrode according to claim 1, wherein the first granule and the second granule satisfy at least one of the following characteristics: 1) a first characteristic in which the particle sizes of the first granule and the second granule are different from each other, and 2) a second characteristic in which the compositions of the first granule and the second granule are different from each other. Claim 3 An electrode according to claim 1, characterized in that the cross-sectional shapes of the first unit region and the second unit region of the intermediate layer region each satisfy the conditions T1, T2, W1, and W2 below: d1 < T1, d2 < T2, 50 d1 ≤ W1 ≤ 1,000 d1, 50 d2 ≤ W2 ≤ 1,000 d2, wherein T1 is the thickness of the first unit region, T2 is the thickness of the second unit region, W1 is the width of the first unit region, W2 is the width of the second unit region, and d1 is the average particle size (D) of the first granule. 50 ) and the above d2 is the average particle size (D of the second granule) 50 )am. Claim 4 An electrode according to claim 3, characterized in that the cross-sectional shape of the first unit region and the second unit region of the intermediate layer region each satisfies the conditions of T1, T2, W1, and W2 below: d1 < T1 ≤2 d1,d2 < T2 ≤2 d1,100 d1 ≤ W1 ≤ 600 d1,100 d2 ≤ W2 ≤ 600 d2. Claim 5 In claim 1, the average particle size (D) of the first granule 50 ) is d1, and the average particle size (D) of the second granule is 50 An electrode characterized in that when ) is d2, d2 ≥ d1. Claim 6 In claim 1, the average particle size (D) of the first granule 50 ) is d1, and the average particle size (D) of the second granule is 50 An electrode characterized in that when ) is d2, 15 μm ≤ d1 ≤ 150 μm and 15 μm ≤ d2 ≤ 150 μm. Claim 7 An electrode according to claim 1, characterized in that the electrode active material comprises a negative electrode active material or a positive electrode active material. Claim 8 An electrode according to claim 1, wherein at least one of the first electrode active material and the second electrode active material comprises a carbon-based compound, and at least one of the first electrode active material and the second electrode active material comprises a silicon-based oxide. Claim 9 An electrode according to claim 1, characterized in that the square shape is a square or a rectangular shape. Claim 10 An electrochemical device comprising an anode, a cathode, a separator interposed between the anode and the cathode, and an electrolyte, wherein at least one of the anode and the cathode comprises an electrode according to any one of claims 1 to 9.

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