Electrode and electrochemical device including same

Abstract

One aspect of the present invention relates to an electrode for an electrochemical element, the electrode having a characteristic that the ion diffusion rate and the electrode capacity are increased by including a middle region in which the granules contained in the lower region and the upper region are different and which is located between the lower region and the upper region and in which an interface is formed by rectangular recesses and protrusions.

Description

[Technical field]

[0001] The present invention relates to an electrode and an electrochemical device including the same. This application claims priority to Korean Patent Application No. 2022-0095678 filed on August 1, 2022 and Korean Patent Application No. 2022-0105751 filed on August 23, 2022, and the entire contents disclosed in the specification and drawings of said applications are incorporated herein by reference. [Background technology]

[0002] As the use of fossil fuels increases rapidly, the demand for alternative and clean energy is increasing, and one of the most active research fields is the field of power generation and storage using electrochemistry. Currently, a representative example of an electrochemical element that uses such electrochemical energy is a secondary battery, and its range of use is expanding. Lithium secondary batteries, which are representative of such secondary batteries, are not only used as an energy source for mobile devices, but are also being used as a power source for electric vehicles and hybrid electric vehicles that can replace vehicles that use fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, and their range of use is expanding as an auxiliary power source for grid-based power generation.

[0003] Recently, various researches have been conducted on the development of batteries using multiple electrode active materials to improve battery performance. When multiple electrode active materials are mixed to form a single electrode active material layer, the battery performance is deteriorated due to interference between the active materials. Therefore, a method has been considered to improve electrode characteristics and battery performance by forming multiple electrode active material layers and specializing the function of each layer during battery manufacturing.

[0004] In this case, the ion diffusion rate and the electrode capacity per weight or volume usually differ depending on the type of electrode active material. For this reason, there have been attempts to manufacture a multi-layer electrode having one layer composed of an electrode active material with a high ion diffusion rate but a low electrode capacity and another layer composed of an electrode active material with a low ion diffusion rate but a high electrode capacity, but even in this case, an electrode with improved ion diffusion rate and electrode capacity has not been realized. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a multi-layer electrode that realizes both a high ion diffusion rate and a large electrode capacity, and a method for manufacturing the same.

[0006] Another object of the present invention is to provide an electrode having the above-mentioned characteristics and a method for producing the same by using a method that introduces a dry process. [Means for solving the problem]

[0007] In order to achieve the above objectives, According to one aspect of the present invention, there is provided an electrode having the following embodiment.

[0008] The electrode according to the first embodiment is A current collector and an electrode active material layer located on at least one surface of the current collector, the electrode active material layer includes a lower layer region adjacent to a current collector and including a plurality of first granules, an upper layer region located above the lower layer region and including a plurality of second granules, and a middle layer region located between the lower layer region and the upper layer region, in which first unit regions including the first granules and second unit regions including the second granules are alternately arranged n times along a longitudinal direction of the electrode active material layer, where n is an integer of 2 or more, The first unit area and the second unit area each have a rectangular cross-section, the first granule includes a first electrode active material and a first binder binding the first electrode active material, and the second granule includes a second electrode active material and a second binder binding the second electrode active material.

[0009] According to the second embodiment, in the first embodiment, The first and second granules may satisfy at least one of the following characteristics: 1) The first granule and the second granule have different particle sizes. 2) A second characteristic in which the first granules and the second granules have different compositions.

[0010] According to the third embodiment, in the first or second embodiment, The cross-sectional shapes of the first unit region and the second unit region of the intermediate layer region may satisfy the following conditions T1, T2, W1, and W2, respectively: d1≦T1, d2≦T2, 50d1≦W1≦1,000d1, 50d2≦W2≦1,000d2, T1 is the thickness of the first unit area, T2 is the thickness of the second unit area, W1 is the width of the first unit area, W2 is the width of the second unit area, The d1 is the average particle diameter D of the first granule 50 and The d2 is the average particle diameter D of the second granules 50 It is.

[0011] According to the fourth embodiment, in any one of the first to third embodiments, The cross-sectional shapes of the first unit region and the second unit region of the intermediate layer region may satisfy the following conditions T1, T2, W1, and W2, respectively: d1≦T1≦2d1, d2 ≤ T2 ≤ 2d1, 100d1≦W1≦600d1, 100d2≦W2≦600d2.

[0012] According to the fifth embodiment, in any one of the first to fourth embodiments, The average particle size D of the first granules 50 is d1, The average particle size D of the second granules 50 When is d2, It is possible that d2≧d1.

[0013] According to the sixth embodiment, in any one of the first to fifth embodiments, The average particle size D of the first granules 50 is d1, The average particle size D of the second granules 50 When is d2, 15 μm≦d1≦150 μm, It may be 15 μm≦d2≦150 μm.

[0014] According to the seventh embodiment, in any one of the first to sixth embodiments, The electrode active material may include a negative electrode active material.

[0015] According to the eighth embodiment, according to any one of the first to seventh embodiments, The electrode active material may include a positive electrode active material.

[0016] According to the ninth embodiment, in any one of the first to eighth embodiments, At least one of the first electrode active material and the second electrode active material may include a carbon-based compound, and at least one of the first electrode active material and the second electrode active material may include a silicon-based oxide.

[0017] According to the tenth embodiment, in any one of the first to ninth embodiments, The second electrode active material may include SiOx (0≦x≦2).

[0018] According to the eleventh embodiment, in any one of the first to tenth embodiments, The weight of the first granules is 95% by weight or more based on the total weight of the granules contained in the lower layer region; The weight of the second granules may be 95% by weight or more based on the total weight of the granules contained in the upper layer region.

[0019] According to the twelfth embodiment, in any one of the first to eleventh embodiments, The n may be an integer of 15 to 25.

[0020] According to the thirteenth embodiment, in any one of the first to twelfth embodiments, The ion diffusion rate of the intermediate layer region may be greater than the ion diffusion rate of the upper layer region.

[0021] According to the fourteenth embodiment, in any one of the first to thirteenth embodiments, An electrode capacity per unit volume of the upper layer region may be greater than an electrode capacity per unit volume of the lower layer region.

[0022] According to another aspect of the present invention, there is provided a method for manufacturing an electrode according to the following embodiments.

[0023] The electrode manufacturing method according to the fifteenth embodiment includes the steps of: forming an electrode active material layer on at least one surface of a current collector; The process of forming the electrode active material layer includes a step of applying a plurality of first granules to at least one surface of the current collector, a first pressing step of pressing the surface of the applied first granules using a pressing roll having a pattern to form a pattern on the surface of the first granules, a step of applying a plurality of second granules to the surface of the pressed first granules, and a second pressing step of pressing the surface of the applied second granules, The first granules include a first electrode active material and a first binder that binds the first electrode active material, and the second granules include a second electrode active material and a second binder that binds the second electrode active material.

[0024] According to the 16th embodiment, in the 15th embodiment, The first and second granules may satisfy at least one of the following characteristics: 1) The first granule and the second granule have different particle sizes. 2) A second characteristic in which the first granules and the second granules have different compositions.

[0025] According to the seventeenth embodiment, in the fifteenth embodiment or the fifteenth embodiment, The pressure roll may have a projection or mesh pattern.

[0026] According to the 18th embodiment, in any one of the 15th to 17th embodiments, The pressure roll pattern includes a plurality of rectangular protrusions, The shape of the protrusion may satisfy the following conditions W3, W4 and T3: d2≦T3 50d2≦W3≦1,000d2 50d1≦W4≦1,000d1, W3 is the width of the protrusion of the protrusion, W4 is the shortest linear distance between two protrusions, T3 is the thickness of the protrusion, The d1 is the average particle diameter D of the first granule 50 and The d2 is the average particle diameter D of the second granules 50 It is.

[0027] According to the 19th embodiment, in any one of the 15th to 18th embodiments, The electrode active material layer includes a lower layer region adjacent to a current collector and including a plurality of first granules, an upper layer region located above the lower layer region and including a plurality of second granules, and a middle layer region located between the lower layer region and the upper layer region, in which first unit regions including the first granules and second unit regions including the second granules are alternately arranged n times along a longitudinal direction of the electrode active material layer, and the first unit regions and the second unit regions may each have a rectangular cross section.

[0028] According to another aspect of the present invention, there is provided an electrochemical device having the following embodiments.

[0029] The electrochemical device according to the twentieth embodiment comprises: The battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and at least one of the positive electrode and the negative electrode includes an electrode according to any one of the first to fourteenth embodiments. Effect of the Invention

[0030] The electrode according to one aspect of the present invention provides the advantage of improved ion diffusion rate and / or electrode capacity.

[0031] For example, the electrode according to one embodiment of the present invention has an improved ion diffusion rate or an improved electrode capacity while having a similar level of ion diffusion rate, as compared to not only an electrode composed of a single layer but also a multi-layer electrode having a flat linear shape at the interface of the intermediate layer region.

[0032] In particular, the electrode according to an embodiment of the present invention has an effect of improving the electrode capacity while maintaining a similar level of resistance as compared to a multi-layer electrode having a flat linear shape at the interface of the intermediate layer region.

[0033] A method of manufacturing an electrode according to another aspect of the present invention has the advantage of providing an electrode having the above-mentioned properties.

[0034] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical ideas of the present invention. Therefore, the present invention should not be interpreted as being limited to only the matters described in the drawings. [Brief description of the drawings]

[0035] [Figure 1] FIG. 2 is a schematic diagram of an electrode active material layer in an electrode according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of an electrode active material layer in an electrode according to another embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram of an electrode active material layer in an electrode according to yet another embodiment of the present invention. [Figure 4] FIG. 2 is a schematic diagram of an electrode active material layer in an electrode according to one embodiment of the present invention. [Diagram 5] FIG. 2 is a schematic diagram of an electrode active material layer in an electrode according to one embodiment of the present invention. [Figure 6] 2 is a flow chart of a method for manufacturing an electrode according to one embodiment of the present invention. [Figure 7] 4 is a photograph of a pressure roll pattern used in a method for manufacturing an electrode according to one embodiment of the present invention. [Figure 8] FIG. 2 is a schematic diagram of a patterned pressure roll for use in manufacturing an electrode according to one embodiment of the present invention. [Figure 9] 1 is a schematic diagram of an electrode assembly using an electrode according to an embodiment of the present invention; [Figure 10] FIG. 2 is a schematic diagram of an electrode assembly using an electrode according to Example 1 in the present specification. [Figure 11]FIG. 2 is a schematic diagram of an electrode assembly using an electrode according to Example 2 in this specification. [Figure 12] FIG. 13 is a schematic diagram of an electrode assembly using an electrode according to Example 3 of the present specification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The present invention will be described in detail below. However, the present invention is not limited to the following content, and each component may be modified in various ways or mixed selectively as necessary. Therefore, it should be understood that all modifications, equivalents, or alternatives falling within the spirit and technical scope of the present invention are incorporated.

[0037] In the present specification, when a certain configuration "includes" a certain component, it does not mean that other components are excluded, but that other components may be further included, unless otherwise specified.

[0038] In this specification, the phrase "A and / or B" means A or B, or all of them.

[0039] The present invention relates to an electrode and an electrochemical device including the electrode. The electrochemical device of the present invention includes all devices that perform electrochemical reactions, and specifically includes all types of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors such as supercapacitors. In the present invention, the electrochemical device is preferably a secondary battery, and more preferably a lithium ion secondary battery.

[0040] According to one aspect of the present invention, there is provided an electrode having a multi-layered active material layer. Specifically, the electrode includes a current collector and an electrode active material layer disposed on at least one surface of the current collector.

[0041] In this specification, the vertical direction from the current collector in the electrode to the surface of the electrode active material layer is defined as the "thickness direction" of the electrode active material layer, and the direction perpendicular to the thickness direction is defined as the "longitudinal direction" of the electrode active material layer.

[0042] In one aspect of the present invention, the electrode active material layer includes a lower region adjacent to a current collector and including a plurality of first granules, an upper region disposed above the lower region and including a plurality of second granules, and a middle region disposed between the lower region and the upper region, in which first unit regions including the first granules and second unit regions including the second granules are alternately arranged n times along a longitudinal direction of the electrode active material layer, wherein the first unit regions and the second unit regions each have a rectangular cross section.

[0043] In addition, the first granules include a first electrode active material and a first binder that binds the first electrode active material, and the second granules include a second electrode active material and a second binder that binds the second electrode active material.

[0044] According to one aspect of the present invention, the first granules and the second granules have different sizes.

[0045] In the electrode according to one aspect of the present invention, the intermediate layer region includes an interface having a repeating rectangular shape formed by alternating the first unit regions and the second unit regions.

[0046] According to one aspect of the present invention, the first unit region and the second unit region are formed by granules of different sizes, and an effect of increasing an ion diffusion rate at the interface can be achieved. In particular, compared to a multi-layer electrode including a lower region and an upper region formed by granules of different sizes, in which the interface between the lower region and the upper region is linear, according to one aspect of the present invention, an advantageous effect of increasing an ion diffusion rate can be achieved since the surface area of ​​the interface is wider.

[0047] In particular, according to one embodiment of the present invention, when granules, which are more advantageous in terms of ion diffusion kinetics than the lower layer region, are arranged in the upper layer region, and an interface having a rectangular cross section in which first unit regions and second unit regions are alternately formed in the middle layer region is formed, lithium (ions) can be easily transported in the thickness direction of the electrode, thereby improving the charging capacity of the electrode.

[0048] To this end, according to one embodiment of the present invention, the first granules arranged in the lower layer region and the second granules arranged in the upper layer region may be provided to satisfy at least one of the following characteristics. 1) The first granule and the second granule have different particle sizes. 2) A second characteristic in which the first granule and the second granule have different compositions. In one embodiment of the present invention, the first characteristic may be due to the capacity and / or ion diffusion rate of the granules being varied by varying the size of the granules, regardless of the composition of the granules.

[0049] Regarding the first characteristic, according to an embodiment of the present invention, the first granules and the second granules may have the same composition or different compositions.

[0050] The term "the granules have the same composition" means that the types and weight ratios of the active material, binder, and conductive material (if further included) contained in the granules are the same. Conversely, the term "the granules have different compositions" means that at least one of the active material, binder, and conductive material contained in the granules is different in type, or the types are the same but the weight ratios are different.

[0051] In one embodiment of the present invention, the second property may be due to the capacity and / or ion diffusion rate of the granules being different by varying the composition of the granules, regardless of the size of the granules.

[0052] Regarding the second characteristic, according to an embodiment of the present invention, the first granules and the second granules may be embodied to have the same or similar size, and the similar size may be within ±10% of the particle size difference between them, preferably within ±5%.

[0053] According to an embodiment of the present invention, the first unit area and the second unit area each have a quadrangular cross section, for example, a square cross section or a rectangular cross section. Specifically, the first unit area and the second unit area each have a rectangular cross section in which the heights T1, T2 in the thickness direction are greater than the widths W1, W2 in the longitudinal direction, but the present invention is not limited thereto.

[0054] Furthermore, according to an embodiment of the present invention, the first unit region and the second unit region each have a rectangular cross section, which increases the surface area of ​​the interface 301 of the middle region, thereby providing a more advantageous effect in terms of increasing the ion diffusion rate, compared to electrodes having other shapes (e.g., triangle, trapezoid, etc.). In addition, the increased surface area of ​​the interface 301 of the middle region can provide an advantageous effect in terms of improving the adhesive properties of the lower region and the upper region, but the effects of the present invention are not limited thereto.

[0055] In one aspect of the present invention, the n indicating the number of alternations of the first unit region and the second unit region disposed in the intermediate layer region may be an integer of 2 or more. For example, the 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, and specifically, the n may be an integer of 50 or less within the aforementioned range, but is not limited thereto. For example, the n may be an integer of 10 to 50, 15 to 40, 15 to 25, or 15 to 20.

[0056] In one embodiment of the present invention, the size of the electrode may vary as necessary, for example, the length of the electrode may be 5 mm to 1,000 mm. 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, based on the length of the electrode being 500 mm to 520 mm, for example 509.5 mm, it is preferable that the n indicating the number of alternations of the first unit region and the second unit region is an integer of 10 to 50, for example, an integer of 15 to 35, 15 to 30, 20 to 30, or 20 to 25.

[0057] According to an embodiment of the present invention, the size of the electrodes may vary as necessary, for example, the width of the electrodes may be 5 mm to 1,000 mm. For example, the width of the electrodes 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.

[0058] According to one embodiment of the invention, the electrodes may be rectangular with a length of 509.3 mm and a width of 93.3 mm.

[0059] In this specification, the length of the electrode refers to the size in the direction in which the first unit regions and the second unit regions are alternately deployed in the electrode active material layer, and may refer to the long side when the electrode is rectangular. The width of the electrode refers to the size in the direction perpendicular to the longitudinal direction of the electrode, and may refer to the short side when the electrode is rectangular.

[0060] The electrode active material layer may include an electrode active material and a binder as electrode materials. Specifically, the electrode material may be included in the electrode active material layer in the form of granules. The granules refer to composite particles including an electrode active material and an electrode binder. In one embodiment of the present invention, the granules may be in the form in which the electrode active material is bound by the electrode binder.

[0061] Meanwhile, the electrode active material layer may further include electrode active material particles in a free state derived from granules.

[0062] In an embodiment of the present invention, the granules may be prepared by mixing the electrode active material with the electrode binder and then granulating the mixture by a spray drying method, but the method for preparing the granules is not limited thereto.

[0063] In one embodiment of the present invention, the granules may be applied to one surface of a current collector and then pressed to form an electrode active material layer without using a separate solvent, but the purpose and use of the granules are not limited thereto.

[0064] The specific structure and composition of the granules will be described later, but first, the structure of the electrode active material layer will be described.

[0065] In the present invention, the electrode active material layer is a layered structure in which a plurality of the granules are accumulated, and has a plurality of micropores provided by interstitial volumes, which are spaces between the granules, and exhibits porous properties due to this structure. In this case, the ion diffusion rate of the electrode active material layer is determined by factors such as the size and number of the micropores, and the electrode capacity of the electrode active material layer is determined by the packing density of the granules.

[0066] The electrode active material layer according to one aspect of the present invention includes a lower layer region, a middle layer region, and an upper layer region, in that order adjacent to the current collector.

[0067] FIG. 1 is a schematic diagram showing a cross section of an electrode active material layer 1 in an electrode according to one embodiment of the present invention.

[0068] 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 above 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.

[0069] In the intermediate layer region 30, first unit regions 301 including the first granules 100 and second unit regions 302 including the second granules 200 are alternately arranged n times along the longitudinal direction of the electrode active material layer 1. In this case, the first unit regions and the second unit regions each have a rectangular cross section, and thus, in the intermediate layer region 30, a continuous rectangular interface is formed by the repetition of the first unit regions 301 and the second unit regions 302.

[0070] In the present invention, the first granules and the second granules have different particle sizes, and FIG. 1 shows a case where the particle size of the second granules 200 is larger than the particle size of the first granules 100 .

[0071] 2 is a schematic diagram showing a cross section of an electrode active material layer 1 in an electrode according to another embodiment of the present invention, in which the particle size of the first granules 100 is larger than the particle size of the second granules 200.

[0072] In one embodiment of the present invention, the first granules and the second granules have different particle sizes, and therefore the electrode according to the embodiment of the present invention exhibits a different electrode capacity than electrodes using only the first granules and the second granules, respectively. In addition, the particle sizes of the granules contained in the upper layer region and the lower layer region are different, and therefore the porosity of the upper layer region and the lower layer region are different. As a result, the electrode according to the embodiment of the present invention exhibits a different ion diffusion rate than electrodes using only the first granules and the second granules, respectively.

[0073] In the past, there have been attempts to realize a multi-layered negative electrode using active material particles of different sizes, but according to the prior art, a flat interface, i.e., a linear interface, is formed between each layer formed using active material particles of different sizes. In this case, the porosity is uniform within each layer, and the porosity of the lower and upper regions may not change significantly based on the interface. Alternatively, if the size of the active material particles constituting the lower region is smaller and the packing density is higher, the porosity of the lower region may decrease based on the interface. In this case, when the electrolyte (electrolytic solution) is impregnated from the upper region close to the surface of the electrode active material layer to the lower region close to the current collector, the impregnation speed of the electrolyte, i.e., the diffusion speed of lithium ions contained in the electrolyte, decreases near the interface, and thus the impregnation time of the electrolyte (diffusion of lithium ions) increases.

[0074] Thus, although the mechanism of the present invention is not limited thereto, according to one aspect of the present invention, a multi-layer electrode having a lower layer region and an upper layer region is provided by using granules having different particle sizes and / or granules having different compositions, and in this case, granules having different particle sizes and / or compositions are mixed between the lower layer region and the upper layer region to provide a continuous quadrangular interface where quadrangular convex and concave portions intersect with each other based on the lower layer region, thereby increasing the surface area of ​​the interface, and thus improving the porosity in the middle of the active material layer, thereby achieving the effect of increasing the ion diffusion rate.

[0075] 3 is a schematic cross-sectional view of an electrode active material layer 1 in an electrode according to an embodiment of the present invention. Referring to FIG. 3, it can be seen that a rectangular interface 310 is formed in an intermediate layer region 30 of the electrode active material layer, where rectangular first and second unit regions are alternately formed. As described above, the interface formed in the intermediate layer region is an interface where the first granules in the first unit region and the second granules in the second unit region have different sizes and / or compositions, and the interface 310 can be confirmed, for example, by visual observation of the electrode or scanning electronic microscopy (SEM) observation.

[0076] In one embodiment of the present invention, the interface may be confirmed by SEM observation. 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 as or different from each other, and the size of the vertical cross-sectional shape of each second unit area may also be the same as or different from each other.

[0077] In one embodiment of the present invention, in the case of an electrode in which the first unit areas and the second unit areas are alternately arranged n times, where n is an even number, the electrode may include n / 2 first unit areas and n / 2 second unit areas.

[0078] In another embodiment of the present invention, in the case of an electrode in which the first unit areas and the second unit areas are alternately arranged n times, where 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.

[0079] 4 is a schematic diagram showing a cross section of an electrode active material layer 1 in an electrode according to an 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, and in this case, each of the first unit regions 301, 301' has a rectangular cross section but may have different sizes, and each of the second unit regions 302, 302' also has a rectangular cross section but may have different sizes.

[0080] In another embodiment of the present invention, the vertical cross-sectional shapes of the first unit regions disposed in the middle layer region 30 may be the same as each other, and the vertical cross-sectional shapes of the second unit regions may be the same as each other.

[0081] In yet another embodiment of the present invention, the shapes of the multiple first unit regions arranged in the intermediate layer region 30 may be the same as each other, and the shapes of the multiple second unit regions may be different from each other, or the shapes of the multiple first unit regions may be different from each other, and the shapes of the multiple second unit regions may be the same as each other. In an embodiment of the present invention, the cross-sectional shapes of the first unit region and the second unit region of the intermediate layer region may each satisfy the following conditions: d1≦T1, d2≦T2, 50d1≦W1≦1,000d1, 50d2≦W2≦1,000d2, T1 is the thickness of the first unit area, T2 is a thickness of the second unit area, W1 is the width of the first unit area, W2 is the width of the second unit area, The d1 is the average particle size D50 of the first granules, The d2 is the average particle size D50 of the second granules.

[0082] In another embodiment of the present invention, the cross-sectional shapes of the first unit region and the second unit region of the intermediate layer region may each satisfy the following conditions.

[0083] d1≦T1≦2d1, d2 ≤ T2 ≤ 2d1, 100d1≦W1≦600d1, 100d2≦W2≦600d2, In one embodiment of the present invention, when W1, W2, T1 and T2 satisfy the above-mentioned conditions, advantageous effects can be obtained in terms of the ion diffusion rate and / or electrode capacity of the electrode, but the present invention is not limited thereto.

[0084] In FIG. 5, 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 are shown.

[0085] In one embodiment of the present invention, when the average particle diameter D50 of the first granule is d1 and the average particle diameter D50 of the second granule is d2, d2≧d1 may be satisfied. 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 such conditions, advantageous effects can be obtained in terms of the ease of classification of the first granule and the second granule and the manufacture of the electrode. In addition, advantageous effects can be obtained in terms of the ion diffusion rate, but the present invention is not limited thereto.

[0086] In another embodiment of the present invention, d1≧d2, in which case, d1 may be 15 μm to 150 μm, and d2 may be 15 μm to 150 μm.

[0087] 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.

[0088] In one embodiment of the present invention, d1 and d2 may have a particle size that is 2 to 5 times, for example, 3 to 4 times, the particle size of the electrode active material contained in the first granule and the second granule, respectively.

[0089] The "average particle size D50" of the granules means the particle size at 50% of the cumulative particle number distribution according to particle size, and the particle size may be measured using a laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium, and then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500). When the particles pass through a laser beam, the diffraction pattern difference according to the particle size is measured to calculate the particle size distribution. The D50 particle size can be measured by calculating the particle diameter at the 50% point of the cumulative particle number distribution according to particle size in the measuring device.

[0090] In one embodiment of the present invention, each of T1 and T2 may be, for example, 1 μm to 1,000 μm. Desirably, T1 may be equal to or larger than the average particle diameter D50 of the first granules and equal to or smaller than the height of the electrode. T2 may be equal to or larger than the average particle diameter D50 of the second granules and equal to or smaller than the height of the electrode.

[0091] In one embodiment of the present invention, each of T1 and T2 may be, for example, 1 μm to 500 μm or 20 μm to 100 μm, and specifically, may be 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 is not limited thereto.

[0092] In one embodiment of the present invention, the lower layer region may further include a predetermined amount of second granules for forming the upper layer region, and it is preferable in terms of the ion diffusion rate of the electrode that the weight of the first granules based on the total weight of the granules included in the lower layer region 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., consisting of only the first granules).

[0093] In another embodiment of the present invention, the upper layer region may further include a predetermined amount of first granules for forming the lower layer region, and it is preferable in terms of the ion diffusion rate of the negative electrode that the weight of the second granules based on the total weight of the granules included in the upper layer region 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., consisting of only the second granules).

[0094] In yet another embodiment of the present invention, the weight of the first granules may be 95% by weight or more based on the total weight of the granules contained in the lower layer region, and the weight of the second granules may be 95% by weight or more based on the total weight of the granules contained in the upper layer region.

[0095] In yet another embodiment of the present invention, the weight of the first granules may be 100% by weight based on the total weight of the granules contained in the lower layer region, and the weight of the second granules may be 100% by weight based on the total weight of the granules contained in the upper layer region.

[0096] In an 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, thereby increasing the rate of increase in the ion diffusion rate through the interface.

[0097] In one embodiment of the present invention, when the size of the second granules in the upper region is larger than the size of the first granules in the lower region, the upper region may exhibit higher porosity due to an increase in interstitial volume compared to the lower region. This provides an effect that the ion diffusion rate of the upper region is higher than that of the lower region. When the ion diffusion rate of the upper region is higher than that of the lower region, lithium bonding on the surface of the electrode is suppressed and ion diffusion is facilitated, thereby improving the charging performance of the battery, but the present invention is not limited thereto.

[0098] The ion diffusion rate refers to the degree of diffusion of ions in a specific material. Specifically, unless otherwise defined in this specification, the ion diffusion rate refers to the diffusion rate of lithium ions.

[0099] The method for measuring the ion diffusion rate is not particularly limited. For example, the ion diffusion rate may be measured using a Galvanostatic Intermittent Titration Technique (GITT) method in a charge / discharge state. According to an embodiment of the present invention, the ion diffusion rate is measured by the GITT method under a condition of SOC 50% and expressed as cm 2 The unit may be expressed in units of, but is not limited to, s.

[0100] In another embodiment of the present invention, the ion diffusion rate of the middle layer region is greater than that of the upper layer region, which may be due to the fact that the parking density of granules in the middle layer region is lower than that of the upper layer region, resulting in an increase in porosity in the middle layer region compared to the upper layer region, but the mechanism of the present invention is not limited thereto.

[0101] The porosity means the ratio of the volume of pores to the total volume of a structure. The unit of the porosity is volume %, and it may be used interchangeably with terms such as void ratio and porosity. The porosity of the negative electrode may be measured, for example, by a BET (Brunauer-Emmett-Teller) measurement method using nitrogen gas or a mercury penetration method (Hg porosimeter) and ASTM D-2873. Alternatively, the porosity of the electrode may be measured by calculating the true density of the electrode from the density (apparent density) of the electrode, the composition ratio of the materials contained in the electrode, and the density of each component, and calculating the porosity of the electrode from the difference between the apparent density and the true density (net density). For example, the porosity may be calculated according to the following Equation 1. (Formula 1) Porosity (volume%) = {1-(apparent density / true density)} x 100 The apparent density in Equation 1 can be calculated from Equation 2 below. (Formula 2) Apparent density (g / cm 3 ) = (weight of porous substrate (g)) / {(thickness of porous substrate (cm)) × (area of ​​porous substrate (cm 2 ))} In one embodiment of the present invention, the porosity of the intermediate layer region may be, for example, 10% by volume to 50% by volume or 20% by volume to 40% by volume, but is not limited thereto.

[0102] In one embodiment of the present invention, the porosity of the middle layer region may be higher than the porosity of the upper layer region and the lower layer region. For example, the porosity of the middle layer region may be 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.

[0103] In one embodiment of the present invention, the second granules contained in the upper region have a lower ion diffusion rate than the first granules contained in the lower region, so that the ion diffusion rate of the upper region can be made lower than that of the lower region. When the ion diffusion rate in the upper region is low, the amount of lithium bonded in the upper region can be increased, thereby improving the energy density of the electrode in the upper region. This allows the upper region to have an improved electrode capacity compared to the lower region.

[0104] In another embodiment of the present invention, the upper region may exhibit a characteristic that the electrode capacity per volume is greater than the electrode capacity per volume of the lower region.

[0105] In one embodiment of the present invention, the first granules in the lower region have a lower ion diffusion rate than the second granules in the upper region, so that the ion diffusion rate of the lower region can be lower than that of the upper region. If the ion diffusion rate in the lower region is low, the amount of lithium binding in the lower region can be increased, thereby improving the energy density of the electrode in the lower region. This allows the lower region to have an improved electrode capacity compared to the upper region.

[0106] In another embodiment of the present invention, the electrode capacitance per volume of the lower layer region may be greater than the electrode capacitance per volume of the upper layer region.

[0107] The electrode capacity per volume refers to an electrode capacity measured based on the same volume of the electrode, and the electrode capacity may be measured by measuring a discharge capacity under charge and discharge conditions. Although the measurement method is not limited thereto, for example, the electrode capacity per volume may be measured as a discharge capacity when electrode samples prepared in the same volume are charged at a constant current of 0.1 C CC at 25° C. to 3.0 V (vs Li / Li+) and discharged at a current density of 0.1 C to 1.7 V (vs Li / Li+).

[0108] In one embodiment of the present invention, by disposing an intermediate layer region between two electrode active material layers having a difference in electrode capacity per volume as described above, the surface area of ​​the interface between the upper layer region and the lower layer region can be increased, which can provide an advantageous effect in terms of efficiently improving the electrode capacity per total volume of the electrode.

[0109] 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. In this case, based on the total thickness of the electrode active material layer, the thickness of the middle layer region may be, for example, 15 μm to 40 μm, specifically 20 μm 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 μm to 40 μm or 27 μm to 37 μm.

[0110] The total "thickness" of the electrode active material layer, or the "thickness" of each layer contained therein, or the W1, W2, T1, and T2 may indicate values ​​measured by a known method for measuring thickness. The method for measuring thickness may be, but is not limited to, for example, a value measured using a thickness meter (Mitutoyo, VL-50S-B).

[0111] Next, the structure and composition of the granules contained in the electrode active material layer will be described.

[0112] In the present specification, the granules included in the lower layer region of the electrode active material layer are referred to as first granules, and the granules included in the upper layer region are referred to as second granules, and the first granules and the second granules have different particle sizes. The middle layer region includes both the first granules and the second granules, and is included by a first unit region including the first granules and a second unit region including the second granules, respectively.

[0113] The granules include an electrode active material and a binder, and may further include a conductive material, if necessary. In this specification, the electrode active material, binder, and conductive material contained in the first granules are referred to as a first electrode active material, a first binder, and a first conductive material, respectively, and the electrode active material, binder, and conductive material contained in the second granules are referred to as a second electrode active material, a second binder, and a second conductive material, respectively.

[0114] The granules are formed by binding the electrode active material and / or conductive material with the binder, and the electrode active material layer includes a plurality of granules.

[0115] In an embodiment of the present invention, the granule may have a higher content (wt%) of the binder at the surface than at the center, relative to 100 wt% of the total weight of the active material, the binder, and the conductive material (if included).

[0116] Here, the surface portion means a region near the surface of the granule from the surface of the granule to a predetermined depth toward the center of the granule, and the central portion means a portion other than the surface portion. In one embodiment of the present invention, the surface portion may mean a region from the particle diameter center of the granule to the surface of the granule at a radius of 70% or more, preferably a region from the particle diameter center of the granule to the surface of the granule at a radius of 85% or more, or 90% or more, or 95% or more.

[0117] In one embodiment of the present invention, in a region from the center of the granule particle to the surface of the granule at a radius of 90% or more, the binder content may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more relative to 100 wt% of the total weight of the granule.

[0118] In another embodiment of the present invention, in a region from the center of the granule to the surface of the granule at 95% or more of the particle radius, the binder content may be 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, or 90 wt% or more, based on 100 wt% of the total weight of the granule.

[0119] To describe the granule in more detail, the granule may have a center portion including a plurality of electrode active materials, and a surface portion including a binder located on all or a part of the outside of the center portion and binding the electrode active materials. That is, in the center portion of the granule, the plurality of electrode active materials form an aggregate by surface contact, line contact, point contact, or two or more of these contacts, and in the surface portion of the granule, a binder is disposed on all or a part of the outside of the aggregate, thereby fixing and binding the plurality of electrode active materials in the center portion of the granule to each other.

[0120] According to an embodiment of the present invention, the center portion may further include a small amount of binder to connect and fix the plurality of electrode active materials in the center portion. However, in the center portion of the granule, the plurality of electrode active materials may be in surface contact, line contact, point contact, or contact with two or more of them to form an aggregate, and in the surface portion of the granule, the binder may be located on a part or the whole of the outside of such an aggregate, thereby fixing and binding the plurality of electrode active materials in the center portion of the granule to each other.

[0121] 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 shortened length of the granule to the length of the long axis, in which the shortened length indicates the average length of the 10 granules in the axial direction having the shortest length, and the long axis length indicates the average length of the 10 granules in the axial direction having the longest length. When the aspect ratio of the granule satisfies such a range, it is advantageous in terms of having sufficient fluidity suitable for processing.

[0122] On the other hand, when the granules further contain a conductive material, the conductive material may be fixed in the granules by the binder through binding between the conductive material and the electrode active material particles or between the conductive material particles.

[0123] 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.

[0124] In an 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 the same or different from each other. For example, each of them may be a carbon-based compound such as non-graphitizable carbon or graphitic carbon; Li x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1), Sn x Me 1-x Me' y O z(Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≤ 1; 1 ≤ y ≤ 3; 1 ≤ z ≤ 8), etc. metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; silicon-based oxides such as SiO, SiO / C, SiO2; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; or it can be selected from mixtures of two or more of these, but is not limited thereto.

[0125] In one embodiment of the present invention, the first negative electrode active material and the second negative electrode active material may each contain a carbon-based compound.

[0126] In one embodiment of the present invention, at least one of the first negative electrode active material and the second negative electrode active material contains a carbon-based compound, and at least one of the first negative electrode active material and the second negative electrode active material may contain a silicon-based compound.

[0127] In another embodiment of the present invention, the first negative electrode active material may be composed only 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)).

[0128] In still another embodiment of the present invention, the first negative electrode active material may be composed of a mixture of a carbon-based compound and a silicon-based oxide, and the second negative electrode active material may be composed only of a carbon-based compound.

[0129] 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 contains 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 a weight ratio of carbon-based compound: silicon compound of 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, but the present invention is not limited thereto.

[0130] In one embodiment of the present invention, the first negative electrode active material may be composed of only 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 of only 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:SiO of 9:1 to 5:5, or 9:1.

[0131] 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.

[0132] 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 the same or different from each other. For example, each may include, but is not limited to, lithium transition metal oxide; lithium metal iron phosphate; lithium nickel-manganese-cobalt oxide; an oxide in which a part of lithium nickel-manganese-cobalt oxide is substituted with another transition metal; or two or more of these. Specifically, the positive electrode active material may be, 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; 1+x Mn 2-x Lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x M x Lithium nickel oxide with Ni site represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x=0.01 to 0.3); 2-x M xO2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 - 0.1), or lithium manganese composite oxide represented by 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 Li 1+x (Ni a Co b Mn c ) 1-x O2 (x = 0 - 0.03, a = 0.3 - 0.95, b = 0.01 - 0.35, c = 0.01 - 0.5, a + b + c = 1); oxide in which part of lithium nickel - manganese - cobalt oxide is substituted by aluminum Li a [Ni b Co c Mn d Al e ) 1-f M 1 f O2 (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, 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); oxide in which part of lithium nickel - manganese - cobalt oxide is substituted by other fibrous metal Li 1+x (Ni a Co b Mn c M d ) 1-x O2 (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, M is any one selected from the group consisting of Fe, V, Cr, Ti, W, Ta, Mg and Mo). A disulfide compound; It can be selected from Fe2(MoO4)3 or a mixture of two or more of these, but is not limited thereto.

[0133] In one embodiment of the present invention, the first binder and the second binder may be the same or different, and are not limited to a specific component as long as they have adhesiveness, are stable in an electrochemical reaction, bind the electrode active material and an electrode material such as a conductive material to maintain a granular form, and are capable of accumulating the granules into a layered structure by binding them to each other through compression to maintain a stable form.The first binder and the second binder may be, 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-hexafluoropropylene ... The polymer may include polyvinyl fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyethylhexylacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene, polypropylene, ethylene-vinyl acetate, polyethylene oxide, polypropylene oxide, polyarylate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, or two or more thereof.Specifically, the binder may be selected from, but is not limited to, styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), polymethylmethacrylate, polyethylhexylacrylate, polybutylacrylate, or a mixture of two or more thereof.

[0134] In one embodiment of the present invention, the first conductive material and the second conductive material may be the same or different, and are not particularly limited as long as they do not induce chemical changes in the battery and have conductivity. Examples of the first conductive material and the second conductive material include graphite such as natural graphite and artificial graphite; carbon black-based carbon compounds such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and 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 or a mixture of two or more selected from the above, but are not limited thereto.

[0135] In one embodiment of the present invention, the granules are obtained by mixing an electrode active material and a binder with a solvent to prepare a fluidized slurry, and then spray-drying the slurry. As described above, the granules may further include a conductive material, if necessary. In addition, the granules may further include other additives for improving performance.

[0136] First, the electrode active material and binder, and optionally a conductive material and additional additives, are dispersed or dissolved in a dispersion medium (solvent for the electrode binder) to obtain a slurry in which the electrode active material and binder are dispersed or dissolved.

[0137] The dispersion medium used to obtain the slurry is most preferably water, but an organic solvent may 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, dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter also referred to as NMP), and dimethylimidazolidinone; sulfur-based solvents such as dimethyl sulfoxide and sulfolane; and the like, with alcohols being preferred. The combined use of an organic solvent with a boiling point lower than that of water can increase the drying speed during fluidized granulation. In addition, the dispersibility or solubility of the negative electrode binder can change, so that the viscosity and fluidity of the slurry can be adjusted according to the amount or type of the dispersion medium, thereby improving production efficiency.

[0138] The amount of the dispersion medium used when preparing the slurry may be an amount such that the solids concentration of the slurry is usually in the range of 1 to 50 wt%, or 5 to 50 wt%, or 10 to 30 wt%.

[0139] The method or order of dispersing or dissolving the electrode active material and binder in the dispersion medium is not particularly limited, and examples thereof include a method of adding the electrode active material and binder to the dispersion medium and mixing them, and a method of dissolving or dispersing the binder in the dispersion medium and then adding the electrode active material and mixing them. When a conductive material or additive is included, these components may be added when the electrode active material is added. Examples of mixing means include mixing devices such as a ball mill, a sand mill, a bead mill, a pigment disperser, a stone mill, an ultrasonic disperser, a homogenizer, and a planetary mixer. Mixing may be performed, for example, at room temperature to 80° C. for 10 minutes to several hours.

[0140] Next, the slurry is spray-dried. The spray-drying method is a method of spraying the slurry into hot air and drying it. A typical example of a device used in the spray-drying method is an atomizer. There are two types of atomizers: a rotating disk type and a pressurized type. The rotating disk type is a method in which the slurry is introduced almost at the center of a disk rotating at high speed, and the slurry is atomized and dried when it leaves the disk due to the centrifugal force of the disk. The rotation speed of the disk depends on the size of the disk, but is usually 5,000 to 35,000 rpm, preferably 15,000 to 30,000 rpm. On the other hand, the pressurized type is a method in which the slurry is pressurized and sprayed in a mist form from a nozzle to dry it.

[0141] The temperature of the slurry to be sprayed is usually room temperature, but may be heated to room temperature or higher. The hot air temperature during spray drying may be controlled to 80°C to 250°C, preferably 100°C to 250°C, based on the inlet temperature of the reactor (at the time of introduction) in order to form a granule structure with a high binder content on the surface. According to one embodiment of the present invention, the temperature may be controlled to 175°C to 250°C, more preferably 180°C to 250°C, taking into consideration the gradient of the binder content and the aspect ratio of the granules. In the spray drying method, the method of inhaling the hot air is not particularly limited, and examples thereof include a method in which the hot air and the spray direction flow sideways in parallel, a method in which the sprayed droplets are sprayed from the top of the drying tower and fall together with the hot air, a method in which the sprayed droplets come into countercurrent contact with the hot air, and a method in which the sprayed droplets flow parallel to the initial hot air and then fall by gravity to come into countercurrent contact. Meanwhile, in one embodiment of the present invention, during the spray drying, the outlet temperature of the reactor (the temperature of hot air discharged from the reactor) may be controlled to 90°C to 130°C.

[0142] If the outlet temperature and / or ΔT, which is the difference between the inlet temperature and the outlet temperature, is low, the drying is not performed properly, particles with a lot of residual solvent are formed, and uniform spherical particles are not produced, and the granules may aggregate or be formed in an irregular state. On the other hand, if the inlet temperature is too high and ΔT is large, over-drying occurs, granules are not granulated, and particles with a very small particle size D50 and a low aspect ratio may be produced. Therefore, in order to achieve high sphericity, little binder aggregation, and control the particle size to an appropriate level, it is necessary to control the inlet temperature and outlet temperature within an appropriate range.

[0143] Optionally, the product obtained by spray drying, i.e., the granules, may be heat-treated to harden the surface thereof. In this case, the heat-treatment temperature may be generally 80°C to 300°C.

[0144] In one embodiment of the present invention, the current collector can be used without any particular limitation as long as it does not induce chemical changes in the battery and has high conductivity. The current collector can be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The current collector can also be formed with fine irregularities on its surface to increase the adhesive strength of the active material, and can be in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc. Meanwhile, in one embodiment of the present invention, the current collector can have a thickness of 10 μm to 50 μm, Although not particularly limited thereto, the current collector may have a thickness of, for example, 10 μm to 20 μm.

[0145] In one embodiment of the present invention, a primer layer may be formed on at least one surface of the current collector to cover all or at least a portion of the surface. The primer layer may be introduced to improve the adhesive 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 the binder and conductive material may be the same as those described above for the binder and conductive material of the electrode active material layer.

[0146] In an embodiment of the present invention, the primer layer may further include, for example, a dispersant for dispersing the binder and the conductive material.

[0147] In one embodiment of the present invention, the primer layer includes the above-mentioned composition and has a thickness of 300 nm to 1.5 μm, specifically, 700 nm to 1.3 μm, but is not limited thereto.

[0148] The electrode active material layer of the electrode according to one aspect of the present invention may be composed of a single electrode active material layer and / or multiple layers, and may have a higher ion diffusion rate than an electrode active material layer having an interlayer interface in the form of a horizontal straight line or other shape such as a triangle or trapezoid, or may have an improved electrode capacity per volume when the interlayer interface has a similar ion diffusion rate. According to another aspect of the invention, a method of manufacturing an electrode is provided.

[0149] A method for producing an electrode according to another aspect of the present invention includes forming an electrode active material layer on at least one surface of a current collector.

[0150] According to another aspect of the present invention, the step of forming the electrode active material layer comprises the steps of: (S1) applying a plurality of first granules to at least one surface of the current collector; (S2) A first pressing step of pressing the surface of the applied first granules using a pressing roll having a pattern to form a pattern on the surface of the first granules. (S3) applying a plurality of second granules onto the surface of the compressed first granules; (S4) A second pressurizing step of pressing the surface of the applied second granules. The first granules include a first electrode active material and a first binder that binds the first electrode active material, and the second granules include a second electrode active material and a second binder that binds the second electrode active material.

[0151] According to an embodiment of the present invention, the first granules and the second granules may satisfy at least one of the following characteristics: 1) The first granule and the second granule have different particle sizes. 2) A second characteristic in which the first granules and the second granules have different compositions.

[0152] The step of forming the electrode active material layer is a step for forming an electrode active material layer including the above-mentioned lower layer region, upper layer region, and middle layer region located between the lower layer region and the upper layer region, in which the middle layer region is arranged such that first unit regions including the first granules and second unit regions including the second granules 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.

[0153] FIG. 6 is a flow chart illustrating a method for manufacturing an electrode according to one embodiment of the present invention.

[0154] Referring to FIG. 6, a method for manufacturing an electrode according to an embodiment of the present invention includes the steps of (a) applying a plurality of first granules 100 to a current collector 2, (b) pressing the surface of the applied first granules using a pressure roll 1000 having a pattern formed thereon, (d) applying a plurality of second granules 200 onto the surface of the pressed first granules, and (e) pressing the surface of the applied second granules.

[0155] Specifically, a plurality of first granules 100 are applied to at least one surface of the current collector 2, and then the surface of the applied first granules is pressed using a patterned roll 1000 to form a pattern on the surface of the first granules. At this time, the pattern formed on the surface of the first granules serves as a pre-pattern for the interface of the intermediate layer region in the electrode active material to be manufactured.

[0156] Conventionally, in a method for manufacturing a multilayer electrode by applying an electrode active material to a current collector and applying pressure thereto, and then applying another electrode active material thereto and applying pressure thereto, a pressure roll having a smooth surface has been used to flatten the interlayer interface.

[0157] In the present invention, in order to increase the surface area of ​​the interface between the electrode active material layers, a roll having a pattern formed on its surface is used as the pressure roll.

[0158] FIG. 7 is a photograph of the surface of a pressure roll having a pattern formed thereon that can be used in step S2 according to an embodiment of the present invention.

[0159] As shown in Fig. 7(a), according to one embodiment of the present invention, the pressure roll pattern may be a protrusion type in which the pattern protrudes outward from a central rod. In particular, a roll having a rectangular protrusion pattern formed thereon may be used so that the first unit area and the second unit area each have a rectangular cross section.

[0160] As shown in FIG. 7(b), according to another embodiment of the present invention, the pressure roll pattern may be a mesh type in which the pattern is recessed inward from a central bar.

[0161] In one embodiment of the present invention, the pressure roll pattern may include a plurality of square-shaped protrusions.

[0162] Fig. 8 shows a cross-sectional shape of a pressure roll having a predetermined protrusion width and including parallel protrusions (protrusions) along the longitudinal direction of a cylindrical rolling roll according to one embodiment of the present invention. As shown in Fig. 8, a pattern of recesses and protrusions can be formed in the longitudinal direction (or machine direction (MD)) of an electrode using a pressure roll having parallel protrusions along the longitudinal direction of the cylindrical pressure roll.

[0163] In another embodiment of the present invention, a pattern of recesses and protrusions can be formed on the electrode using a pressure roll including parallel protrusions (protrusions) along a direction perpendicular to the longitudinal direction of the cylindrical pressure roll and parallel to the cylindrical upper and lower surfaces (not shown). In this case, a pattern of recesses and protrusions can be formed in the width direction (or transverse direction (TD)) of the electrode.

[0164] Referring to FIG. 8, the rectangular protrusion may satisfy the following conditions W3, W4, and T3: d2≦T3 50d2≦W3≦1,000d2 50d1≦W4≦1,000d1.

[0165] The W3 is the width of the protruding portion of the protrusion, the W4 is the shortest linear distance between two protrusions, the T3 is the thickness of the protruding portion of the protrusion, the d1 is the average particle size D50 of the first granule, and the d2 is the average particle size D50 of the second granule.

[0166] In one embodiment of the present invention, a rectangular prepattern is formed on the surface of the first granules pressed by the protruding pressure roll in the middle layer region of the electrode active material layer. When the second granules are applied to the surface of the first granules on which the prepattern is formed, the second granules are applied to the surface of the first granules pressed by the protruding parts of the pressure roll, thereby forming a second unit region in the middle layer region of the electrode active material layer.

[0167] The second granules are applied to the surface of the first granules on which the prepattern is formed, and then pressed to manufacture an electrode having an electrode active material layer including the lower layer region, the middle layer region, and the upper layer region.

[0168] In this case, the pressing step S4 may be performed using a pair of rolling rolls having flat surfaces, as shown in FIG. 6(e).

[0169] According to another embodiment of the present invention, after applying the second granules, the second granules are further pressed using a pressure roll having a pattern formed thereon, which is used in the pressing step S2, and then the third granules are applied, thereby producing an electrode active material layer including two or more intermediate layer regions.

[0170] In addition, the temperature and pressure conditions in the granule coating process and the pressurizing process in each of the steps S1 to S4 can be performed according to normal conditions, and are not particularly limited in the present invention.

[0171] In accordance with yet another aspect of the present invention, there is provided an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

[0172] FIG. 9 is a schematic diagram of an electrode assembly according to one aspect of the present invention.

[0173] Referring to FIG. 9, the electrode assembly may include a positive electrode and a negative electrode on either side of a separator in the center, and each of the positive electrode and the negative electrode may include an active material layer formed on a current collector, and the current collector may include a non-coated portion (or tab) on which no active material layer is formed.

[0174] According to one embodiment of the present invention, at least one of the positive electrode and the negative electrode may be an electrode that does not include a current collector (not shown).

[0175] In the present invention, at least one of the positive electrode and the negative electrode is the above-mentioned electrode, which is characterized in that it is an electrode including an upper layer region, a lower layer region and a middle layer region.

[0176] According to one embodiment of the present invention, as shown in 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, or 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.

[0177] 10 to 12 are schematic diagrams showing an electrode assembly including an electrode according to one embodiment of the present invention, in which either the positive electrode or the negative electrode includes an upper layer region, a lower layer region, and a middle layer region.

[0178] According to yet another aspect of the present invention, there is provided an electrochemical device comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode comprises the above-described electrode.

[0179] In one embodiment of the present invention, the separator and the electrolyte may be any suitable material that can be used in a typical electrochemical device without sacrificing the object of the present invention, and therefore, the specific types of the separator and the electrolyte will not be described here.

[0180] In one embodiment of the present invention, the electrochemical device may have a shape such as a coin shape, a cylindrical shape, a pouch shape, a square shape, etc., and the shape of the battery is not particularly limited. In addition, the electrochemical device can be used not only as a battery cell used as a power source for a small device, but also as a unit battery for a medium- to large-sized battery module including a plurality of battery cells, and the form of use is not particularly limited.

[0181] In order to aid in the understanding of the present invention, examples, comparative examples and experimental examples are presented below. However, the following experimental examples are merely examples relating to the configuration and effects of the present invention, and the scope and effects of the present invention are not limited thereto.

[0182] Experimental example 1. Evaluation of charging speed depending on interface height [Electrode manufacturing] Preparation of the first granule (lower layer area) 95.6wt% of artificial graphite (D50: 15μm) as electrode active material, 1.0wt% of carbon black (SuperC65) as electrode conductive material, 1.1wt% of carboxymethylcellulose (daicel2200, aqueous solution form, solid concentration 1.5wt%) as electrode dispersant, and 2.3wt% of modified styrene butadiene copolymer (Grade Name AX-B119) as electrode binder were mixed with water as a dispersion medium to prepare a slurry with a viscosity of about 1000cPs using a homogenizer. At this time, the solid content of the slurry was 30wt%. In the above weight ratio, the carboxymethylcellulose was calculated based on the solid content.

[0183] The prepared slurry was dried by feeding it into a spray dryer together with hot air under a pressure range of -40 mmH2O. In this case, the conditions of the spray dryer were controlled as follows: inlet temperature 250°C, outlet temperature 100°C, and rotation speed 18,000 rpm. The obtained granules were sieved through an industrial sieve to remove coarse powder of 150 μm or more. The granules had a central portion including a plurality of electrode active materials and electrode conductive materials, and a surface portion including an electrode binder arranged outside the central portion and binding the electrode active materials and the electrode conductive materials. The obtained first granules had an average particle size D50 of 50.1 μm and an aspect ratio of 1.04. Preparation of the second granule (upper layer) The second granules were prepared in the same manner as the first granules, except that a mixture of artificial graphite (D50: 15 μm):SiO (D50: 6 μm) (weight ratio 9:1) was used as the electrode active material. The average particle size D50 of the obtained second granules was 48.28 μm, and the aspect ratio was 1.01. Electrode fabrication The electrodes were manufactured according to the sequence shown in FIG.

[0184] A thickness adjustment bar is used on one side of the copper collector (thickness 10 μm) to adjust the current collector to 25 cm 2The first granules prepared above were uniformly spread in an amount of 200 mg per cm, and pressed at a speed of 2 m per minute under conditions of 60°C and a pressure of 0.1 ton per cm using a rolling machine. Then, a current collector of 25 cm was placed on the pressed surface. 2 The second granules prepared above were uniformly spread in an amount of 200 mg per cm, and then pressed at a speed of 2 m per min under conditions of 0.5 ton per cm and 60° C. using a rolling machine equipped with smooth surface rolls to manufacture an electrode.

[0185] The cross-sectional schematic diagram of the pressure roll used is shown in Figure 8. A pressure roll was used in which the protrusions that appeared in the cross section in the longitudinal direction of the cylindrical roll were formed in parallel with the same width. The width of the protrusions was kept constant, and the thickness of the protrusions was varied to produce three electrodes with different interface shapes in the middle layer region. The schematic diagrams of the three electrodes are shown in Figure 10 (Example 1), Figure 11 (Example 2), and Figure 12 (Example 3), respectively.

[0186] The electrodes in Figures 10 to 12 were formed with a total length of 509.5 mm, a width of 93.3 mm, and the first and second unit regions were arranged alternately 30 times. The thicknesses T1, T2 of the first and second unit regions were 3 μm (Figure 10, Example 1), 27 μm (Figure 11, Example 2), and 54 μm (Figure 12, Example 3), respectively.

[0187] In order to compare the effect with an electrode in which the interface between the lower layer region and the upper layer region has a linear shape, an electrode was prepared by rolling using a normal flat pressure roll without any protrusions on the surface as Comparative Example 1. Except for the different shape of the pressure roll, the electrode was manufactured in the same manner as described above.

[0188] [Physical property evaluation] The prepared electrode (negative electrode) was sandwiched between a polyethylene porous membrane and placed in contact with a reference positive electrode and pressurized, and then immersed in an electrolyte and charged at rates of 0.5C and 1C, respectively, to measure the time required to reach a SOC of 100%. The results are shown in Table 1 below.

[0189] In addition, in order to compare and evaluate the resistance of each electrode, a current of 2.5 C was applied for 30 seconds, and the resistance value according to V=IR was calculated and shown in Table 1 below.

[0190] [Table 1] From the results of Table 1, it was confirmed that the order of improvement in charge capacity was Example 3 > Example 2 > Example 1. From this, it was confirmed that the granules, which are advantageous in terms of kinetics in improving battery capacity, are arranged in the upper layer, and lithium is more easily transferred through the interface in the middle layer region, thereby improving the final charge capacity of the battery without increasing resistance.

[0191] In particular, it was confirmed that when the intermediate layer region has a parallel interface, the charge capacity is deteriorated and the resistance value is increased. Experimental example 2. Evaluation of charging speed according to the width of the unit area (number of alternations n) The electrodes were prepared by varying the widths W1 and W2 of the first and second unit regions while maintaining the length of the electrode, and varying the number of alternations n of the first and second unit regions. The electrodes were then charged at rates of 0.5C, 1C, and 2C in the same manner as in Experimental Example 1, and the time it took to reach a SOC of 100% was measured, and the results are shown in Table 2 below.

[0192] In addition, in order to compare and evaluate the resistance of each electrode, a current of 2.5 C was applied for 30 seconds, and the resistance value according to V=IR was calculated. The results are shown in Table 2 below.

[0193] [Table 2] From the results in Table 2, it was confirmed that when n is 20, the charging time is the longest when charging at a rate of 0.5 C to 2 C, and thus the electrode is most excellent in terms of final charge capacity. In particular, it was confirmed that the electrode according to the present invention can improve the electrode capacity without increasing the resistance value, since the resistance value does not change significantly even when the number of n is changed. [Explanation of symbols]

[0194] 1 Electrode active material layer 2 Current collector 10 Lower area 20 Upper area 30 Middle class area 100 1st Granule 200 2nd Granule 301, 301' First unit area 302, 302' Second unit area 310 Interface 1000 patterns formed on the pressure roll 2000, 3000 Rolling mill

Claims

1. A current collector; an electrode active material layer located on at least one surface of the current collector, The electrode active material layer is a lower layer region adjacent to the current collector and including a plurality of first granules; an upper layer region located above the lower layer region and including a plurality of second granules; a middle layer region located between the lower layer region and the upper layer region, in which first unit regions including the first granules and second unit regions including the second granules are alternately arranged n times along the longitudinal direction of the electrode active material layer, where n is an integer of 2 or more; the first unit area and the second unit area each have a rectangular cross section, The first granules include a first electrode active material and a first binder that binds the first electrode active material, The second granules include a second electrode active material and a second binder binding the second electrode active material.

2. 2. The electrode of claim 1, wherein the first granules and the second granules satisfy at least one of the following characteristics: 1) The first granule and the second granule have different particle sizes. 2) A second characteristic in which the first granules and the second granules have different compositions.

3. 2. The electrode according to claim 1, wherein the cross-sectional shapes of the first unit region and the second unit region of the intermediate layer region satisfy the following conditions T1, T2, W1 and W2, respectively: d1≦T1, d2≦T2, 50d1≦W1≦1,000d1, 50d2≦W2≦1,000d2, T1 is the thickness of the first unit area, T2 is a thickness of the second unit region, W1 is the width of the first unit area, W2 is the width of the second unit area, The d1 is the average particle diameter D of the first granule ５０ and The d2 is the average particle diameter D of the second granule ５０ It is.

4. 4. The electrode according to claim 3, wherein the cross-sectional shapes of the first unit region and the second unit region of the intermediate layer region satisfy the following conditions T1, T2, W1 and W2, respectively: d1≦T1≦2d1, d2≦T2≦2d1, 100d1≦W1≦600d1, 100d2≦W2≦600d2.

5. The average particle size D of the first granule ５０ is d1, The average particle size D of the second granules ５０ When is d2, 2. The electrode according to claim 1, wherein d2 > d1.

6. The average particle size D of the first granule ５０ is d1, The average particle size D of the second granules ５０ When is d2, 15 μm≦d1≦150 μm, 2. The electrode according to claim 1, characterized in that 15 μm≦d2≦150 μm.

7. The electrode of claim 1 , wherein the electrode active material layer comprises a negative electrode active material.

8. The electrode of claim 1 , wherein the electrode active material layer comprises a positive electrode active material.

9. At least one of the first electrode active material and the second electrode active material includes a carbon-based compound; The electrode of claim 1 , wherein at least one of the first electrode active material and the second electrode active material comprises a silicon-based oxide.

10. 2. The electrode of claim 1, wherein the second electrode active material comprises SiOx, where 0≦x≦2.

11. The weight of the first granules is 95% by weight or more based on the total weight of the granules contained in the lower layer region; 2. The electrode according to claim 1, wherein the weight of the second granules is 95% by weight or more based on the total weight of the granules contained in the upper layer region.

12. 2. The electrode according to claim 1, wherein n is an integer from 15 to 25.

13. 2. The electrode of claim 1, wherein the ion diffusion rate of said middle layer region is greater than the ion diffusion rate of said upper layer region.

14. 2. The electrode according to claim 1, wherein the electrode capacitance per volume of the upper layer region is greater than the electrode capacitance per volume of the lower layer region.

15. forming an electrode active material layer on at least one surface of a current collector; The step of forming an electrode active material layer includes: applying a plurality of first granules to at least one surface of the current collector; a first pressing step of pressing the surface of the applied first granules using a pressure roll having a pattern to form a pattern on the surface of the first granules; applying a plurality of second granules onto the surface of the compressed first granules; A second pressurizing step of pressing the surface of the applied second granules, The first granules include a first electrode active material and a first binder that binds the first electrode active material, the second granules include a second electrode active material and a second binder that binds the second electrode active material.

16. 16. The method for manufacturing an electrode according to claim 15, wherein the first granules and the second granules satisfy at least one of the following characteristics: 1) The first granule and the second granule have different particle sizes. 2) A second characteristic in which the first granules and the second granules have different compositions.

17. The method for manufacturing an electrode according to claim 15, wherein the pressure roll has a protrusion-type or mesh-type pattern.

18. the pressure roll pattern includes a plurality of rectangular protrusions; The method for manufacturing an electrode according to claim 15, characterized in that the shape of the protrusion satisfies the following conditions W3, W4 and T3: d2≦T3 50d2≦W3≦1,000d2 50d1≦W4≦1,000d1, W3 is the width of the protrusion of the protrusion, W4 is the shortest linear distance between the two protrusions, T3 is the thickness of the protruding portion of the protrusion, The d1 is the average particle diameter D of the first granule ５０ and The d2 is the average particle diameter D of the second granule ５０ It is.

19. The electrode active material layer is a lower layer region adjacent to the current collector and including a plurality of first granules; an upper layer region located above the lower layer region and including a plurality of second granules; a middle layer region located between the lower layer region and the upper layer region, in which first unit regions including the first granules and second unit regions including the second granules are alternately arranged n times along the longitudinal direction of the electrode active material layer, The method of claim 15, wherein the first unit area and the second unit area each have a rectangular cross section.

20. The battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte solution, 15. An electrochemical element, characterized in that at least one of the positive electrode and the negative electrode comprises the electrode according to claim 1.

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