electrode for a secondary battery and secondary battery with the same

Abstract

Electrode for a secondary battery, comprising: a current collector; and an electrode active material layer located on at least one surface of the current collector, where the following relation expression 1 is satisfied: [Relationship expression 1] 1.0 ≤ B ei / B ci ≤ 2.0 where in relation expression 1 B ci a surface styrene-butadiene rubber-based binder content of a central section of the electrode active material layer in a lateral direction is and B ei a surface styrene-butadiene rubber-based binder content of a side section of the electrode active material layer in the width direction, where the interface styrene-butadiene rubber-based binder content is an average styrene-butadiene rubber-based binder content in the 10% thickness range based on the total thickness of the electrode active material layer in the thickness direction from the interface between the current collector and the electrode active material layer to the electrode active material layer, where the side section (112) is an area of ​​20% of the side based on the total width of the coated electrode part (11) along the x-axis, wherein the central section (111) is a region that excludes the side section in the coated electrode part (11).

Description

TECHNICAL AREA

[0001] The following disclosure relates to an electrode for a secondary battery with improved fast charging performance and a secondary battery with the same. BACKGROUND

[0002] As regulations regarding fuel efficiency and emissions for automobiles have become stricter worldwide in recent years, the growth of the market for electric vehicles (EVs) equipped with a secondary battery is accelerating. One challenge for EVs is that existing internal combustion engine vehicles can secure the energy required for driving by refueling for a short time, around 5 minutes, whereas charging the secondary batteries of EVs takes a long time, around 6 to 7 hours, based on the 7 kW slow charging method.

[0003] To develop secondary batteries with improved fast-charging performance, a technology is being developed to reduce the binder content by creating a high-adhesion binder. However, there is a limitation to reducing the type of high-adhesion binder and the binder content. If the binder content is too low, a serious problem arises: an electrode active material layer can be detached from a current collector during a notching process or a charge / discharge cycle.

[0004] Accordingly, a technology for the efficient distribution of the binder within the electrode is being developed. Typically, a technology is developed to form an electrode slurry with a high binder content in a lower layer and to apply an electrode slurry with a low binder content in an upper layer to a current collector as a double layer. In this case, the high binder content is formed at an interface between the current collector and the electrode active material layer, making it possible to reduce the binder content throughout the entire electrode active material layer while suppressing delamination of the active material layer, thereby improving battery performance.However, the technology for forming the electrode slurry as the double layer has a process limitation when reducing the thickness of the bottom layer, making it difficult to reduce the thickness of the bottom layer to a certain ratio or less, and thus making it difficult to dramatically reduce the binder content.

[0005] Meanwhile, in addition to the technology for forming the electrode slurry as a double layer, a technology is being developed for forming a binder suspension on the current collector as a thin-film primary layer, followed by the formation of the electrode slurry on a liquid binder suspension primary layer. This allows for more efficient binder distribution within the electrode active material layer. Preparing the electrode active material layer by sequentially applying such a binder suspension electrode slurry can create a thicker electrode slurry with a lower binder content compared to the double-layer coating described above. This significantly reduces the binder content in the electrode active material layer, thereby greatly increasing the battery's resistance and fast-charging performance.

[0006] However, if the electrode slurry is applied to an upper section of the liquid binder suspension, a phenomenon occurs where the liquid binder suspension is forced with fluidity due to a high discharge pressure, leading to the problem of difficulty in maintaining a uniform binder distribution. As a result, a side section of the electrode is coated more thickly than a central section, forming a protruding side ring. This leads to various electrode quality problems, such as uneven distribution of the binder composition between the side and central sections of the electrode, irregularity in the electrode coating width, and dehydration due to the flow of the electrode slurry, thus reducing the electrode's productivity.Particularly if the side ring phenomenon is severe among the problems mentioned above, one problem may be that the current collector is torn during the winding of the electrode manufacturing process, or that the electrode active material layer is pressed in by a rolling roller during rolling.

[0007] Additionally, the technology of preparing the electrode active material layer by sequentially applying the binder suspension electrode slurry can reduce resistance and improve electrode performance by reducing the total binder content in the electrode, but when the binder content is reduced, delamination of the electrode active material layer may still occur due to insufficient adhesion between the current collector and the electrode active material layer.

[0008] As described above, there is a need to develop an electrode capable of solving problems such as the side rings and the separation between the current collector and the electrode active material layer that occur during the electrode manufacturing process, and to improve fast charging performance by optimizing the binder distribution in the electrode and reducing the overall binder content, and to use it in a secondary battery. SUMMARY

[0009] One embodiment of the present invention is directed towards increasing the productivity of an electrode by lowering the binder content in the electrode and optimizing the binder distribution in the electrode in order to solve problems such as a side ring that occur during an electrode manufacturing process, while improving the fast charging performance of a secondary battery.

[0010] In a general aspect, an electrode for a secondary battery comprises: a current collector; and an electrode active material layer located on at least one surface of the current collector, satisfying the following relation expression 1. [Relationship expression 1] 1.0≤Bei / Bci≤2.0

[0011] In relation expression 1, B is ci an interfacial binder content of a central section of the electrode active material layer in a lateral direction and B ei is an interfacial binder content of a side section of the electrode active material layer in the lateral direction.

[0012] The following relationship expression 2 can also be satisfied. [Relationship expression 2] 2.5≤At / Bes≤5.0

[0013] In relation expression 2, B is esa surface binder content of the side section of the electrode active material layer in the lateral direction and B ei is the interfacial binder content of the side section of the electrode active material layer in the lateral direction.

[0014] The electrode active material layer may contain 0.1 to 2 wt.% binder, based on the total weight of the electrode active material layer.

[0015] The electrode active material layer may contain a styrene-butadiene rubber-based binder.

[0016] The electrode may contain an anode.

[0017] The protruding height of the side section of the electrode active material layer in the width direction can be 0 µm or less.

[0018] In another aspect, the manufacture of an electrode for a secondary battery involves: a) applying a binder suspension to at least one surface of a current collector; b) drying a side section of the current collector onto which the binder suspension is applied; c) applying an electrode slurry containing an electrode active material to the binder suspension; and d) drying a result of step c).

[0019] In step a), the binder suspension can be applied evenly to at least one surface of the pantograph.

[0020] In step a), the thickness of the applied binder suspension can be 0.1 to 10 µm.

[0021] The binder suspension applied in step a) may contain 5 to 50 wt.% of the binder, based on a total weight of the binder suspension, and the electrode slurry applied in step c) may contain a binder in an amount of 2.0 wt.% or less, based on the total weight of the electrode slurry.

[0022] Step b) can be performed for 0.001 to 5 seconds at a temperature of 120 to 600 °C.

[0023] Step d) can be performed for 10 to 300 seconds at a temperature of 50 to 300 °C.

[0024] Secondary battery comprising: the electrode according to any one of claims 1 to 6.

[0025] In yet another aspect, a secondary battery is provided which includes the electrode according to the exemplary embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig.Figure 1 is a perspective view of an electrode according to an exemplary embodiment of the present invention. Fig. 2A is a top view of the electrode of Fig. 1, viewed in a z-axis direction. Fig. 2B is a cross-sectional view of the electrode of Fig. 1 along line I-I'. Fig. Figure 3 is a diagram describing a method for measuring a protruding height of a side section of an electrode active material layer in a lateral direction. Fig. Figure 4 is a diagram reflecting the results of an EDS analysis to evaluate a binder distribution in a thickness direction, depending on whether the side section of the electrode is to be dried. Fig. 5A to Fig.5C are diagrams that represent EDS imaging images for evaluating a binder distribution in the thickness direction, depending on whether the side section is to be dried. Fig. 5A is a diagram representing an EDS imaging image that measures interfacial binder content in a central section of the electrode. Fig. Figure 5B is a diagram representing an EDS imaging image in which an interfacial binder content is measured on a side section of comparison example 1. Fig. 5C is a diagram representing an EDS imaging image in which an interfacial binder content is measured on a side section of Example 1. Fig. Figure 6A is a diagram showing a 3D image of a cross-section of an anode in a lateral direction according to Example 1, analyzed by confocal microscopy. Fig.Figure 6B is a diagram showing a 3D image of a cross-section of an anode in a lateral direction, as shown in Comparative Example 1, obtained through confocal microscopy. Description of reference symbols 1 electrode 11 Coated electrode section 12 Uncoated electrode part 111 Middle section Section 112 DETAILED DESCRIPTION OF EXECUTION FORMS

[0026] Various advantages and features of the present invention and the methods that achieve it will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. However, the present invention is not limited to the exemplary embodiments described below, but can be implemented in various different forms. These exemplary embodiments are provided only to complete the present invention and to enable those skilled in the art to fully understand its scope, and the present invention is defined by the scope of the claims.

[0027] Unless otherwise defined, all terms used in this description (including technical and scientific terms) have the same meanings as those generally known to those skilled in the art in the field to which the present invention relates. Throughout this description, unless otherwise specified, "contains" any component is understood to imply the inclusion of other elements rather than the exclusion of other elements. Additionally, a singular form includes a plural form unless specifically described in the text.

[0028] When an element, such as a layer, film, area, or plate, is described as being "on" or "over" another component, it may be located directly on top of the other element, or there may be elements in between.

[0029] Terms commonly used in this description are first explained with reference to the accompanying drawings to facilitate understanding of the present invention. The accompanying drawings are intended to facilitate understanding of terms, and this does not mean that the terms and technical ideas of the present invention are limited to interpretation only in the accompanying drawings. It should be noted that all content described in this description should be interpreted with due consideration. Regardless of the drawings, the same reference numerals refer to the same components.

[0030] Fig. Figure 1 is a perspective view of an electrode according to an exemplary embodiment of the present disclosure. Fig. 2A is a top view of the electrode of Fig. 1, viewed in a z-axis direction, and Fig.2B is a cross-sectional view of the electrode of Fig. 1 along line I-I'. An area defined by a dotted line in Fig. If 2A is displayed, it may refer to a part that will become an electrode when a battery is installed later.

[0031] With reference to Fig. 1 and Fig.In this description, 2A refers to a “side section” as an end section 112 of a coated electrode part 11 in a lateral direction relative to a side of an uncoated electrode part 12 of an electrode 1, where a direction horizontal to a coating direction of the electrode is referred to as a longitudinal direction (y-axis direction), and a direction perpendicular to the coating direction is referred to as a lateral direction (x-axis direction) during the electrode manufacturing process. In the present invention, the width of the side section 112 may be 20% or less of the total width of the coated electrode part 11 in the lateral direction. Additionally, in this description, the term “middle section” refers to a region 111 that excludes the side section 112 in the lateral direction of the coated electrode part 11.

[0032] With reference to Fig. 1 and Fig. In this description, 2B refers to the “interface binder content” as the average binder content in a section (①') in the thickness direction from an interface between a current collector and an electrode active material layer to the electrode active material layer, where a cross-section (I-I' cross-section) of the electrode active material layer is divided in the thickness direction from the electrode surface to the current collector into 10 sections (①' to ⑩') of the same thickness. In other words, the “interface binder content” refers to the average binder content in the 10% thickness range (①'), relative to the total thickness of the electrode active material layer in the thickness direction from the interface between the current collector and the electrode active material layer to the electrode active material layer.

[0033] Additionally, the "surface binder content" refers to the average binder content in a section (⑩') in the thickness direction from the electrode surface to the electrode active material layer, where the cross-section (I-I' cross-section) of the electrode active material layer is divided into 10 sections (①' to ⑩') of equal thickness in the thickness direction from the electrode surface to the current collector. In other words, the "surface binder content" refers to the average binder content in the 10% thickness range (⑩'), relative to the total thickness of the electrode active material layer in the thickness direction from the electrode surface to the electrode active material layer.

[0034] Additionally, in the present description, the binder content can be a value derived after normalizing the average binder content to 1 in the 30% thickness range (⑧' to ⑩'), based on the total thickness of the electrode active material layer in the thickness direction from the electrode surface to the electrode active material layer. The binder content before normalization is, for example, wt.%, or if, for example, a styrene-butadiene rubber (SBR)-based binder is used, the binder content can be derived as the content (at%) of the adsorbed Os element after exposure of the electrode to Os gas. However, the present invention is not limited to the Os element and can be an element capable of representing the binder depending on the type of binder.

[0035] It goes without saying that the definition of the above-described "side section", "middle section", "interface binder content", "surface binder content", binder content, etc., is applied to the electrode during the coating process that takes place in the electrode assembly process, and as described in Fig. As shown in Figure 2A, the same applies to the part that will become the electrode when the battery is later assembled. For example, for the already assembled battery, after disassembly, each side section, middle section, binder content, etc., can be determined based on the descriptions above. Fig. 1, Fig. 2A, Fig. 2B and terms for the received electrode are defined.

[0036] According to an exemplary embodiment of the present invention, an electrode for a secondary battery comprises a current collector and an electrode active material layer located on at least one surface of the current collector and satisfying the following relation expression 1. [Relationship expression 1] 1.0≤Bei / Bci≤2.0

[0037] In relation expression 1, B is ci a content of an interfacial binder of a central section of the electrode active material layer in a lateral direction and B ei is the content of an interfacial binder of a side section of the electrode active material layer in the lateral direction.

[0038] With reference to Fig. 2A and Fig. 2B refers to the interface binder content B ciof the central section to an average value of the interfacial binder contents measured in a middle (①-①', ②-①' and ③-①') of an area in which the central section is divided into 3 equal parts based on the latitude direction, and the interfacial binder content B ei of the side section refers to an average value of the interfacial binder content measured in the middle (④-①') of the side section.

[0039] In the electrode for a secondary battery that satisfies the relation expression 1 described above, the interface binder content B ei of the side section higher than the interfacial binder content B ciof the central section, so that the interfacial adhesion force of the side section is increased compared to the central section. Accordingly, it is possible to suppress the detachment of the electrode active material layer by effectively supporting a voltage that can occur between the current collector and the electrode active material layer during the battery assembly process and the charging / discharging process.

[0040] From the perspective of further suppressing the detachment of the electrode active material layer, the electrode can be used for a secondary battery that satisfies the relation expression 1 described above, B ei / B ei for example, more than 1.0, for example 1.05 or more, or for example 1.1 or more.

[0041] If the B ei / B eiHowever, if the value is too high, the imbalance between the interfacial binder content and the surface binder content in the central and side sections becomes severe. This can lead to the electrode active material layer detaching from its surface in the form of particles during the notching process, instead of detaching at the interface between the current collector and the electrode active material layer. Additionally, there is a risk of cracking during the drying process due to insufficient surface binder content in the side sections. Considering the above problem, B ei / B ei for example, 2.0 or less, or for example, 1.6 or less, or for example, 1.4 or less.

[0042] Taking into account the effect described above, B ei / B eiSatisfy at least one of the following inequalities. 1.0 < B ei / B ei ≤ 2.0 or 1.05 ≤ B ei / B ei ≤ 2.0 or 1.1 ≤ B ei / B ci ≤ 2.0 or 1.0 < B ei / B ci ≤ 1.6 or 1.05 ≤ B ei / B ci ≤ 1.6 or 1.1 ≤ B ei / B ci ≤ 1.6 or 1.0 < B ei / B ci ≤ 1.4 or 1.05 ≤ B ei / B ci ≤ 1.4 or 1.1 ≤ B ei / B ei ≤ 1.4.

[0043] The electrode can also satisfy the following relation expression 2. [Relationship expression 2] 2.5≤At / Bes≤5.0

[0044] In relation expression 2, B is es a content of a surface binder of the side section of the electrode active material layer in the lateral direction and B ei is the content of the interfacial binder of the side section of the electrode active material layer in the lateral direction.

[0045] With reference to Fig. 2A and Fig. 2B refers to the surface binder content B es of the side section of relation expression 2 to an average value of the surface binder contents measured in the middle (④-⑩') of the side section, and the interfacial binder content B ei of the side section of relation expression 2 refers to an average value of the interfacial binder contents measured in the middle (④-①') of the side section.

[0046] In the electrode for a secondary battery, which also satisfies the relation expression 2 described above, the interface binder content B ei of the side section higher than the surface binder content B es , so that the detachment of the electrode active material layer of the side section can be further suppressed. From the perspective of ensuring such an effect, B ei / B esfor example, 2.5 or more, or for example, 2.75 or more, or for example, 3.0 or more.

[0047] If the B ei / B es However, if the value is too high, not only is the effect of suppressing electrode active material layer detachment saturated, but also, because the surface binder content is too low, detachment occurs in particle or dust form due to cracks in the electrode active material near the surface of the electrode active material layer during the notching process, thus posing a risk of safety problems with the assembled secondary battery. Considering the above problem, B ei / B es for example, 5.0 or less, or for example, 4.5 or less, or for example, 4.0 or less.

[0048] Taking into account the effect described above, B ei / B es Satisfy at least one of the following inequalities. 2.5 ≤ Bei / B es ≤ 5,0, 2, 75 ≤ B ei / B es ≤ 5,0, 3,0 ≤ B ei / B es ≤ 5,0, 2, 5 ≤ B ei / B es ≤ 4,5, 2,75 ≤ B ei / B es ≤ 4,5, 3,0 ≤ B ei / B es ≤ 4,5, 2,5 ≤ B ei / B es ≤ 4,0, 2,75 ≤ B ei / B es ≤ 4,0 oder 3,0 ≤ B ei / B es ≤ 4,0.

[0049] The electrode active material layer can contain 0.1 to 2 wt.%, 0.1 to 1.8 wt.%, 0.5 to 1.8 wt.%, or 0.5 to 1.5 wt.% binder, based on the total weight of the electrode active material layer. In the present invention, by densely distributing the binder at the interface between the current collector and the electrode active material layer and reducing the binder content towards the electrode surface, the total amount of binder contained in the entire active material layer can be significantly reduced. Accordingly, it is possible to improve the adhesion between the current collector and the electrode active material layer and to enhance fast charging performance.

[0050] The electrode active material layer can be formed by applying a binder suspension to at least one surface of the current collector, drying a side section of the current collector onto which the binder suspension is applied in the width direction, and then drying a result obtained by applying the electrode slurry containing the electrode active material to the binder suspension. It should be noted, however, that this is one example of forming the electrode active material layer described above, and the electrode active material layer according to the present invention can be formed by various methods.

[0051] The following section describes in detail the binder suspension, the current collector, and the electrode slurry.

[0052] The binder suspension can contain 5 to 50 wt%, 10 to 50 wt%, 15 to 50 wt%, 10 to 40 wt%, 15 to 40 wt%, 5 to 30 wt%, 10 to 30 wt%, or 15 to 30 wt% binder, based on the total weight of the binder suspension. The binder suspension contains a relatively large amount of binder compared to the electrode slurry, which contains a large amount of the electrode active material, and is therefore applied to the current collector to further increase the adhesion between the current collector and the electrode active material layer.

[0053] The binder may contain a styrene-butadiene rubber (SBR)-based binder, for example styrene-butyl rubber, a styrene-butyl acrylate copolymer, etc., but the present invention is not limited thereto.

[0054] When using an SBR-based binder or similar, the viscosity of the binder suspension is very low because the binder is mixed in particle form. Since the binder particles are small, measuring 200 nm or less, when the electrode slurry is applied to the binder suspension and then dried, the binder particles readily migrate into the electrode slurry, which is located on the upper layer, due to osmotic pressure. Therefore, even after drying, a distinct binder layer cannot form between the binder suspension and the electrode slurry.In addition, the SBR-based binder exhibits good spreadability with the current collector and can therefore be applied uniformly to a relatively thin thickness without forming a separate pattern in the width direction of the current collector, thereby further improving the adhesion between the current collector and the electrode active material layer.

[0055] In contrast to the SBR-based binder, polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), carboxymethylcellulose (CMC), etc., which can be used as electrode binders in addition to the SBR-based binder, are applied in a solvent-soluble state. When the electrode is dried, the solvent dries sufficiently, and the phases separate to form a binder layer. For this reason, binders like polyacrylic acid do not readily migrate into the upper electrode active material layer during the drying process. Furthermore, there is a risk of increasing the specific interfacial resistance by forming a distinct binder layer between the current collector and the active material layer. Additionally, a problem arises from the fact that the pattern is not uniformly distributed in the width direction of the current collector (e.g., island type, dot type).Consequently, the adhesion and specific interfacial resistance between the current collector and the electrode active material layer are poor. Therefore, the binder suspension may or may not contain at least one of the following: polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), and carboxymethylcellulose (CMC), in amounts of 5% or less, 4% or less, or 3% or less by weight, respectively, based on the total weight of the binder in the binder suspension.

[0056] The binder suspension can be prepared including a binder and a solvent. The binder suspension refers to a mixture in which the binders are not dissolved and are present in particle form in a solvent. If necessary, a thickener, a conductive material, and the like can be additionally mixed and used.

[0057] The solvent for the anode may be at least one selected from the group consisting of water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol and t-butanol, but is not limited to this group.

[0058] When a thickening agent is added, it can stabilize a solution by increasing the viscosity of the binder suspension. Examples of thickening agents include cellulose-based compounds, specifically one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, alkali metal salts thereof, or similar substances. The alkali metals used could be sodium, potassium, or lithium.

[0059] The conductive material is used to impart conductivity to the electrode and is not particularly limited as long as it is a conventional electronically conductive material that does not cause any chemical changes in the battery. For example, materials selected from the group consisting of natural graphite, synthetic graphite, carbon black, acetylene carbon black, ketone carbon black, carbon fibers, carbon nanotubes, and combinations thereof can be used, but are not limited to these.

[0060] The viscosity of the binder suspension can be 1 to 10,000 cps, 5 to 5,000 cps, or 10 to 2,000 cps. Using a binder suspension with the above viscosity allows for even application to the current collector, and the binder particles can migrate upwards effectively during the drying process.

[0061] The current collector can be, but is not limited to, those selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0062] The electrode slurry may contain 90 wt% or more, 90 to 99.5 wt%, or 95 to 99.5 wt% of the electrode active material, 2.0 wt% or less, 1.5 wt% or less, or 1.0 wt% or less of the binder, or it may not contain any binder at all, and the conductive material and thickener may constitute the remainder, based on the total weight of the electrode slurry. Even when the binder content of the electrode slurry is prepared as low, the adhesion between the current collector and the electrode active material layer can be increased by the migration of binder particles when the binder suspension dries, and the fast charging performance can be improved by lowering the resistance of the electrode surface.

[0063] The electrode slurry may also contain a conductive material, a binder, a thickener, or a combination thereof, if required. The conductive material and the thickener may be the same materials used in the binder suspension described above and may be different or identical, but the present invention is not limited thereto.

[0064] According to the present invention, the electrode active material layer can have a continuous concentration of the binder in the electrode thickness direction. In this description, the "continuous" distribution of the binder means that the binder suspension and the electrode slurry are not formed as separate layers, but the binder is continuous within the electrode active material layer, and thus the concentration of the binder is continuous in the thickness direction of the electrode active material layer.

[0065] According to the present invention, the electrode can be a cathode or an anode.

[0066] If the electrode is a cathode, the electrode active material can be used without restriction, as long as it is a cathode active material typically used in secondary batteries. For example, the electrode active material can contain any cathode active material particle selected from the group consisting of LiCoO2, LiNiO2, LiMn2O4, LiCoPO4, LiFePO4, LiNiMnCoO2, and LiNi 1-x-y-z Co x M 1 y M 2 z O2 consists (M 1 and M 2 are each independently any element chosen from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta and Mg, and x, y and z are each independently an atomic fraction of oxide composition elements and 0 ≤ x < 0.5, 0 ≤ y < 0.5, 0 ≤ z < 0.5, x + y + z ≤ 1) or a mixture of two or more of them.

[0067] If the electrode is an anode, the electrode active material can be used without restriction, as long as it is an anode active material commonly used in secondary batteries. Examples of anode active materials include, but are not limited to, carbon-based anode active materials, silicon-based anode active materials, or a mixture thereof. The carbon-based anode active material can be one or more components selected from synthetic graphite, natural graphite, and hard carbon. The silicon-based anode active material is Si or SiO₂. x(0 < x < 2), a Si-Q alloy (where Q is an element selected from the group consisting of alkali metal, alkaline earth metal, group 13 element, group 14 element, group 15 element, group 16 element, transition metal, rare earth element and combinations thereof, and not Si), a Si-carbon composite or a mixture of at least one of them and SiO2.

[0068] According to an exemplary embodiment of the present invention, it is possible to provide an electrode with improved fast charging performance of a secondary battery by lowering the binder content in the electrode and optimizing the binder distribution in the electrode.

[0069] In the electrode for a secondary battery according to an exemplary embodiment of the present invention, the protruding height of the side section of the electrode active material layer in the lateral direction can be 0 µm or less. If the side ring phenomenon is severe, a problem can arise from the current collector being torn during winding in the electrode manufacturing process, or from the electrode active material layer being indented by a rolling roller during rolling. Considering this, it is preferred that the protruding height of the side section be smaller. According to one example, the protruding height of the side section of the electrode active material layer in the lateral direction can be 0 µm or less, or -0.2 µm or less, or -0.3 µm or less, or -0.5 µm or less.

[0070] A method for measuring a protruding height of a side section of an electrode active material layer in a lateral direction is described with reference to Fig. 3 described in detail. With reference to Fig.3. The protruding height of the side section is obtained by dividing the side section of the electrode active material layer into 8 equal parts in the width direction and then measuring the electrode thickness at the midpoints a to h of the 8 subdivided areas. In the three areas a to c successively, from an outermost side to an inner side of the side section in the width direction, the protruding height of the side section is obtained by subtracting the average thickness value of the electrode thicknesses measured in the remaining areas d to h, excluding the three areas, from the highest thickness value among the measured electrode thicknesses. The electrode thickness can be measured with a micrometer (Grad: 331-261-30) from Mitutoyo Co. with a diameter of 3 mm.

[0071] The manufacture of an electrode for a secondary battery involves: a) applying a binder suspension to at least one surface of a current collector; b) drying a side section of the current collector onto which a binder suspension is applied; c) applying an electrode slurry containing an electrode active material to the binder suspension; and d) drying a result of step c).

[0072] In step a), the current collector is manufactured and the binder suspension is applied to at least one surface of the current collector.

[0073] The types of binder, solvent, and current collector are the same as described above. The known method can be used as the method for preparing a binder suspension. For example, the binder suspension can be prepared by mixing a specific binder, such as the SBR-based binder, in a solvent and diluting the binder to achieve a suitable viscosity, but the present invention is not limited to this.

[0074] Step a) can consist of applying the binder suspension uniformly to the entirety of at least one surface of the pantograph. In this description, uniform application of the binder suspension means applying the binder suspension uniformly to the pantograph so that the binder does not form a specific pattern.

[0075] According to an exemplary embodiment, in step a), the binder suspension can be applied to a thickness of 0.1 to 10 µm after drying. The application thickness of the binder suspension can be, for example, 0.5 to 5 µm, 0.5 to 3 µm, or 0.5 to 1 µm. If the thickness of the applied binder suspension is excessive, the binder suspension will not mix well with the electrode slurry, so that after drying the binder suspension, the separation between the layers is clear and the binder layer, which is an insulator, forms within the electrode active material layer, thus increasing the specific interfacial resistance. On the other hand, if the application thickness of the binder suspension is less than 0.1 µm, it may be difficult to achieve the intended purpose of the present invention.This means it is possible to prevent an increase in the specific interfacial resistance in the thickness range described above, to improve the interfacial adhesion between the current collector and the electrode active material layer, and to improve process defects such as electrode detachment.

[0076] According to an exemplary embodiment, the binder suspension may contain 5 to 50 wt.%, 10 to 50 wt.%, 15 to 50 wt.%, 10 to 40 wt.%, 10 to 40 wt.%, 15 to 40 wt.%, 5 to 30 wt.%, 10 to 30 wt.%, or 15 to 30 wt.% of binder, based on the total weight of the binder suspension. The electrode slurry may contain or not contain 2.0 wt.% or less, 1.5 wt.% or less, or 1.0 wt.% or less of the binder, based on the total weight of the electrode slurry.

[0077] In step b), the side section of the current collector, onto which the binder suspension is applied, is dried. According to the exemplary embodiment of the present invention, during the drying of the electrode active material layer, onto which the binder suspension electrode slurry is sequentially applied in step d) after drying in step b), the fluidity of the binder suspension in the side section of the electrode is reduced, thereby solving problems that occur in the manufacturing process, such as the side ring.Additionally, it is possible to suppress the uneven distribution of the binder composition of the electrode in the width direction due to the difference in the migration rate of the binder in the side section and the middle section of the electrode, thereby increasing the interfacial adhesion of the side section of the electrode and improving process defects such as the detachment of the electrode active material layer.

[0078] The drying time of step b) can be, for example, 0.001 to 5 seconds, 0.001 to 3 seconds, 0.001 to 2 seconds, 0.001 to 1 second, 0.005 to 5 seconds, 0.005 to 3 seconds, 0.005 to 2 seconds, 0.005 to 1 second, 0.015 to 5 seconds, 0.015 to 3 seconds, 0.015 to 2 seconds, 0.015 to 1 second, 0.03 to 5 seconds, 0.03 to 3 seconds, 0.03 to 2 seconds or 0.03 to 1 second.

[0079] The drying temperature of step b) can be, for example, 120 to 600 °C, 120 to 500 °C, 120 to 450 °C, 120 to 400 °C, 150 to 600 °C, 150 to 500 °C, 150 to 450 °C, 150 to 400 °C, 200 to 600 °C, 200 to 500 °C, 200 to 450 °C or 200 to 400 °C.

[0080] The drying time or drying temperature of step b) can be changed depending on the production rate of the electrode and the amount of binder applied.

[0081] If the drying temperature is too high or the drying time is too long, not only the side section but also the middle section may dry, or an insulating layer may form due to excessive drying of the binder, causing problems by increasing the electrode's resistance. Conversely, if the drying temperature is too low or the drying time is too short, the side section will not dry sufficiently, increasing the risk of process defects such as side ring failure. In an exemplary embodiment, the drying of step b) can be performed at a temperature of 120 to 600 °C for 0.001 to 5 seconds.

[0082] In step c), the electrode slurry containing the electrode active material is applied to the binder suspension. The electrode active material is the same as described above. Any method known to be used to produce the electrode slurry for a secondary battery can be used.

[0083] Any application method known to form a film by the general application of a liquid phase may be used for applying the binder suspension in step a) and the electrode slurry in step c). This includes, but is not limited to, spray coating, dip coating, rotary coating, gravure coating, doctor blade coating, roller coating, inkjet printing, slot die coating, flexographic printing, screen printing, electrostatic printing, microcontact printing, embossing, reverse offset printing, rotary doctor blade coating, gravure offset printing, etc.

[0084] In step d), the result from step c) is dried.

[0085] The drying of step d) can be carried out for 10 to 300 seconds, for example 10 seconds or more, 20 seconds or more or 30 seconds or more, for example 300 seconds or less, 280 seconds or less, 260 seconds or less, 240 seconds or less, 220 seconds or less, 200 seconds or less, 180 seconds or less, 160 seconds or less, 150 seconds or less, 140 seconds or less, 130 seconds or less, 120 seconds or less or 110 seconds or less.

[0086] Additionally, the drying of step d) can be carried out at a temperature of 50 to 300 °C, for example 50 °C or higher, 60 °C or higher, 70 °C or higher, 80 °C or higher or 90 °C or higher, for example 300 °C or lower, 280 °C or lower, 260 °C or lower, 240 °C or lower, 220 °C or lower or 200 °C or lower.

[0087] If the drying temperature of step d) is too high or the drying time is very short, the migration of the binder particles is excessive and interfacial adhesion cannot be sufficiently achieved. In an exemplary embodiment, the drying of step d) can be carried out at a temperature of 50 to 600 °C for 10 to 300 seconds.

[0088] Then, by rolling the dried electrode under suitable conditions, an electrode with an electrode active material layer formed on the current collector can be produced. In this case, any known rolling method can be used for the rolling process, and the present invention is not limited thereto.

[0089] In the production of an electrode for a secondary battery, the binder suspension, which contains a relatively large amount of binder, is applied first. Then, the electrode slurry, which contains a relatively small amount of binder (present in the upper part of the binder suspension) and a large amount of electrode active material, is applied. This ensures that the binder is distributed densely at the interface between the current collector and the electrode active material layer, and in the adjacent area. Consequently, it is possible to suppress delamination of the electrode active material layer and improve the battery's fast-charging performance by reducing the binder content across the entire electrode active material layer.

[0090] Additionally, in the production of a secondary battery electrode, during the drying of the electrode active material layer, onto which the binder suspension electrode slurry from subsequent step d) is applied, it is possible to solve problems that arise in the manufacturing process, such as side rings, by reducing the fluidity of the binder suspension in the side ring section. Furthermore, it is possible to suppress the uneven distribution of the electrode's binder composition in the lateral direction, caused by the difference in the binder migration rate between the side and central sections of the electrode. This increases the interfacial adhesion of the electrode's side section and improves process defects such as electrode active material layer delamination.

[0091] Meanwhile, if the binder suspension is applied to the current collector without performing step b) described above, in the case where the electrode can be produced by applying the binder suspension with a high binder content to the side section and applying a binder suspension with a low binder content to the middle section, the manufacturing problem may arise that requires two facilities to apply two different suspensions in the width direction. When two suspensions are applied, a large difference may occur at the interface of the applied suspensions, or defects may occur due to non-coating.

[0092] According to an exemplary embodiment of the present invention, a secondary battery is provided which includes the electrode according to the exemplary embodiment of the present invention. The secondary battery may also include a separator and an electrolyte solution. The electrode is the same as described above.

[0093] The separator is not particularly limited as long as it is a known separation membrane in the field. For example, it can be selected from fiberglass, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or a combination thereof, and can be in the form of a nonwoven or woven fabric, and can optionally be used in a single-layer or multi-layer structure.

[0094] The electrolyte solution comprises a non-aqueous organic solvent and an electrolyte solution salt. The non-aqueous organic solvent is ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane (DME), γ-butyrolactone (BL), tetrahydrofuran (THF), 1,3-dioxolane (DOL), diethyl ether (DEE), methyl formate (MF), methyl propionate (MP), sulfolane (S), dimethyl sulfoxide (DMSO), acetonitrile (AN), or a mixture thereof, but is not limited to these. The electrolyte solution salt is a material dissolved in the non-aqueous organic solvent and thus serves as a source of electrolyte metal ions in the battery to enable basic secondary battery operation and promote the movement of electrolyte metal ions between the cathode and the anode.As a non-restrictive example, if the electrolyte metal is lithium, the electrolyte salt is LiPF6, LiBF4, LiTFSI, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiSbF6, LiAlO4, LiAlCl4, LiN(C. x F 2x+1 SO2) (C y F 2y+1 SO2) (where x and y are natural numbers), LiCl, LiI, or a mixture thereof, but is not limited to these. Additionally, the electrolyte solution salt may use the known material in a concentration suitable for the purpose and may, if necessary, also include the known solvent or additive to improve charging / discharging properties, flame retardancy, and the like.

[0095] To solve the above problem, the battery can be manufactured by forming an electrode assembly by sequentially stacking a manufactured anode, a separator, and a cathode, placing the manufactured electrode assembly into a cylindrical battery casing or a prismatic mold, and then injecting an electrolyte solution. Alternatively, the battery can be manufactured by stacking the electrode assembly, impregnating the electrode assembly in the electrolyte solution, and placing the resulting assembly into a battery casing and sealing it.

[0096] For the battery casing used in the present invention, any type commonly used in the field can be employed, and there is no restriction in appearance according to the battery's intended use. For example, a cylindrical type, a can-shaped type, a prismatic type, a pouch type, a coin-shaped type, etc., can be used.

[0097] The secondary battery according to the present invention can be used not only in a battery cell that serves as an energy source for a small device, but can also preferably be used as a unit cell in a medium-sized battery module comprising a plurality of battery cells. Preferred examples of the medium-sized device include, but are not limited to, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an energy storage system, etc.

[0098] The present invention is described in detail below with reference to examples, but these serve to describe the present invention in more detail, and the scope of the present invention is not limited by the following examples. Examples (Example 1)<Herstellung der Anode>

[0099] A binder suspension was prepared by diluting an SBR (Zeon BM451B) suspension as a binder and a CMC thickener with pure water, such that the SBR suspension and the CMC thickener have a weight ratio of 99:1.

[0100] An anode active material in which artificial graphite (D50:13 µm) and natural graphite (D50:10 µm) are mixed in a weight ratio of 5:5, a CMC thickening agent and an SBR binder were added to water in a weight ratio of 98.5:1:0.5 to produce an anode slurry with a viscosity of 5,000 cps.

[0101] The binder suspension, prepared on the surface of a copper pantograph (copper foil 8 µm thick), was applied to a thickness of 1 µm using a gravure coating process. Side sections on both sides of the copper pantograph, in the width direction to which the binder suspension was applied, were then dried. The prepared anode slurry was applied to a thickness of 83 µm using a slot nozzle and dried. The binder suspension and the anode slurry were then applied to another surface and dried in the same manner. In this case, drying was carried out under the conditions described in Table 1 below. After drying, the rollers were rolled (roll density: 1.68 g / cm³). 3 ) carried out to produce an anode with an anode active material layer formed on it.

[0102] In this case, the anode used an electrode with a width of 100 mm, based on a coated electrode part, and the side section was an area with a width of 20 mm at an end section in the width direction, and the middle section was an area with a width of 80 mm, excluding the side section. <Herstellung der Kathode>

[0103] A slurry was prepared by Li[Ni 0,88 Co 0,1 Mn 0,02 ]O2 as a cathode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed in a weight ratio of 96.5:2:1.5. The slurry was applied uniformly to a 12 µm thick aluminum foil and vacuum-dried to produce a cathode for a secondary battery. <Herstellung der Sekundärbatterie>

[0104] The cathode and anode are stacked to a predetermined size by means of notches, and a separator (polyethylene, 13 µm thick) is placed between the cathode and anode to form an electrode cell. Each tab section of the cathode and anode is then welded. The welded cathode / separator / anode assembly is placed in a bag, and three sides are sealed, except for one electrolyte solution injection side. In this case, the electrode tab section is included in the sealed portion. An electrolyte solution is injected through the remaining surfaces, except for the sealed portion, and the remaining surfaces are sealed and then impregnated for 12 hours or more. When the electrolyte solution was dissolved, 1 M LiPF6 was used in a mixed solvent of EC / EMC / DEC (25 / 45 / 30; volume ratio). The electrodes used had a wt% vinylene carbonate (VC) and 0.5 wt% LiPF6 dissolved in a diluent of 1 M ...-% 1,3-propanesultone (PRS) and 0.5 wt% lithium bis(oxalato)borate (LiBOB), based on a total weight of the electrolyte solution, were added.

[0105] Afterwards, pre-charging was performed for 36 minutes at a current corresponding to 0.25C. Following degassing after 1 hour and aging for more than 24 hours, chemical charging and discharging were carried out (charging condition CC-CV 0.2C 4.2V 0.05C CUT-OFF, discharging condition CC 0.2C 2.5V CUT-OFF).

[0106] Afterwards, standard charging and discharging were performed (charging condition CC-CV 0.33C 4.2V 0.05C CUT-OFF, discharging condition CC 0.33C 2.5V CUT-OFF). (Examples 2 and 3, comparison examples 1 to 3)

[0107] Examples 2 and 3 and comparative examples 1 to 3 were carried out under the same manufacturing conditions as in Example 1, except that the conditions for drying the side section during the manufacture of the anode were carried out under the conditions described in Table 1.

[0108] In Table 1 below, drying was carried out using a hot air blower, taking into account the drying conditions, such as the temperature.

[0109] The binder content was derived by exposing the electrode to sufficient Os gas and then using the content (at%) of the adsorbed Os element, and B ei / B ei and B ei / B es were derived by using the binder content and the contents described in the comparative expressions 1 and 2 above in this description.

[0110] Here is B cithe interfacial binder content of the central section of the electrode active material layer in the lateral direction, B ei is the interfacial binder content of the side section of the electrode active material layer in the lateral direction and B es is the surface binder content of the side section of the electrode active material layer in the width direction, and each binder content was measured by the procedure described above in this description and then calculated to derive each value.

[0111] The “protruding height of the side section” in Table 1 is the protruding height of the side section of the electrode active material layer in the lateral direction and was measured according to the procedure for measuring the protruding height of a side section in a lateral direction described in this specification. The electrode thickness can be measured with a 3 mm diameter micrometer (Grad: 331-261-30) from Mitutoyo Co.

[0112] In Table 1, “whether embossing has occurred” was evaluated as dents if the number of dents on the electrode due to the shedding of electrode active material particles during a 200 m rolling operation running at a speed of 20 m / min using a roll-to-roll press was 3 times or more.

[00137] [Table 1] Drying conditions of the side section Binder distribution protruding height of the side section (µm) Whether a dent occurs (O / x) Whether carried out Temperature (°C) B ei / B ei B ei / B es should(◯ / ×) Example 1 ◯ 200 1,26 3,16 -0, 7 × Example 2 ◯ 500 1,34 3,22 -1,0 × Example 3 ◯ 400 1,39 3,18 -3,2 × Comparative example 1 × - 0,71 2,15 15,6 ◯ Comparative example 2 ◯ 50 0,82 1,95 2,6 ◯ Comparative example 3 ◯ 100 0,73 1,89 2,7 ◯

[0113] The "electrode adhesion" in Table 2 below was measured between the anode active material layer of the fabricated anode and the anode current collector using an electrode substrate adhesion tester (IMADA DS2-50N). In the measurement procedure, after a double-sided tape was attached to the adhesion tester and the fabricated anode current collector was positioned on the tape, the roller moved the fabricated anode current collector back and forth 10 times to secure the anode current collector. The tape was then cut to a width of 18 mm and attached to the central section of the tester with the tape side facing down. The adhesion to the anode active material layer was then measured while the adhesion tester was moved at a speed of 300 rpm in a direction perpendicular to 90° of the adhesion surface.

[0114] The “specific interfacial resistance” of Table 2 below was measured by applying a measuring current of 10 mA to the manufactured anode using an electrode resistance measuring device of the XF057 battery from HIOKI Co.

[0115] For "Cell Resistance (DC-IR)" in Table 2 below, the cell resistance of the manufactured secondary battery was measured. The cell resistance was measured using the following procedure. The manufactured secondary batteries of each example and comparison example were charged (0.3C CC / CV charge, 4.2V, 0.05C cut), left to rest for 10 minutes, and discharged (0.3C CC discharge, SOC50 cut). The secondary battery was left to rest at SOC50 for 1 hour, discharged at 1C for 10 seconds, and then left to rest again for 10 seconds. In this case, the cell resistance (DC-IR) was calculated by dividing the difference between the voltage after resting at SOC50 for 1 hour and the voltage after the 1C discharge for 10 seconds by a current. [Table 2] Electrode adhesion (N / cm) specific surface resistivity (Ω·cm) 2 ) Cell wide resistance DC-IR(mΩ) Middle section Page section Middle section Page section Example 1 0,22 0,31 0,018 0, 016 1,34 Example 2 0,21 0,24 0,02 0, 019 1, 33 Example 3 0,22 0,33 0,014 0, 014 1,31 Comparative example 1 0,22 0,16 0,013 0,013 1,35 Comparative example 2 0,21 0,17 0,019 0,02 1,36 Comparative example 3 0,20 0,16 0,016 0,018 1,33

[0116] The results from Tables 1 and 2 are compared and evaluated. Referring to Tables 1 and 2, in Examples 1 to 3 of the present invention, the protruding height of the side section was 0 µm or less, and the electrode active material layer did not detach, so that no dent occurred during rolling.

[0117] On the other hand, in comparative example 1, drying of the side section was not performed, and when the entire electrode active material layer of the binder suspension-anode slurry was dried, the side section dried quickly, and the migration of the binder in the side section was more active compared to the center section. Since the migration rate of the binder in the side section and the center section differed, the binder distribution in the electrode active material layer became uneven. Consequently, the B ei / B ei-value less than 1.0 and the B ei / B es The value was less than 2.5, thus reducing the adhesion between the electrode active material layer and the current collector in the side section. Additionally, the protruding height of the side section significantly exceeded 0 µm, and numerous particle indentations occurred during rolling.

[0118] Comparative Examples 2 and 3 dried the side section, but the drying temperature was lower than the temperature limited by the present invention. Consequently, the side section was not dried sufficiently, so that the B ei / B ei -value less than 1.0 and the B ei / B esThe pH value was less than 2.5, thus reducing the adhesion between the electrode active material layer and the current collector in the side section. Additionally, the side section was not dried sufficiently, so the protruding height of the side section exceeded 0 µm, and numerous particle indentations occurred during rolling.

[0119] Fig. 4 and Fig. 5A to Fig. Figure 5C are diagrams reflecting the results of an EDS analysis to evaluate the binder distribution in the thickness direction, depending on whether the side section is to be dried, and EDS imaging images. For the EDS analysis, the manufactured electrode was sufficiently exposed to Os gas, and then the analysis was performed on the Os element.

[0120] Fig.Figure 4 is a diagram reflecting the results of an EDS analysis to evaluate a binder distribution in a thickness direction, depending on whether the side section of the electrode is to be dried. Fig.Figure 4 shows a line from "Example 1" indicating the distribution of the binder content of the side section of Example 1 in the thickness direction, and a line from "Comparison Example 1" indicates the distribution of the binder content of the side section of Comparison Example 1 in the thickness direction. A line from the "Middle" indicates the binder content distribution of the middle section of Example 1 in the thickness direction. Since the line from the "Middle" shows little change in the binder content distribution depending on whether the side section is dried, the distribution of the binder content of the side sections of Example 1 and Comparison Example 1, depending on whether the side section is dried, was evaluated using the distribution of the binder content of the middle section of Example 1 in the thickness direction. In a horizontal axis "Thickness Range" of the diagram of Fig.3 was “0”, the interface between the current collector and the electrode active material layer, and “1” was the surface of the electrode active material layer, so that the binder distribution in the thickness direction from the interface to the surface was specified. A vertical axis “intensity” of the diagram of Fig. 3 is an index used to assess the relative amount of binder content and indicates the EDS intensity for the Os element. The higher the intensity value, the higher the binder content in the corresponding thickness range.

[0121] With reference to Fig. 4 was the interface binder content B in Example 1. ei of the side section higher than the interfacial binder content B ciof the central section, and the adhesion between the current collector and the electrode active material layer of the side section was measured as higher than that in the central section. On the other hand, in comparative example 1, the interface binder content B ei of the side section lower than the interfacial binder content B ci of the central section, such that the adhesion between the current collector and the electrode active material layer of the side section was measured as lower than the adhesion in the central section. As a result, the risk of electrode active material layer detachment during the secondary battery assembly process or cycle evaluation of the secondary battery was relatively high.

[0122] Fig. 5A to Fig. 5C are diagrams that represent EDS imaging images for evaluating a binder distribution in the thickness direction, depending on whether the side section is to be dried. Fig.5A is an EDS imaging image in which the interfacial binder content of the central section is measured, Fig. 5B is an EDS imaging image in which the interfacial binder content of the side section of comparison example 1 is measured, and Fig. Figure 5C is an EDS imaging image showing the interfacial binder content of the side section of Example 1. With reference to Fig. 5C under the accompanying drawings, it can be visually confirmed that the interfacial binder content of the side section is high in the case of Example 1, in which the drying of the side section is carried out.

[0123] Fig. 6A and Fig. Figure 6B are 3D images obtained by analyzing the cross-section of the anode in the width direction according to Example 1 and Comparative Example 1. With reference to Fig. 6A and Fig.In comparison example 1 (6B), it can be visually confirmed that the thickness of the side section of the anode is significantly thicker than the thickness of the middle section.

[0124] According to an exemplary embodiment of the present invention, it is possible to provide an electrode with improved fast charging performance of a secondary battery by lowering the binder content in the electrode and optimizing the binder distribution in the electrode.

[0125] The production of an electrode for a secondary battery involves applying a binder suspension containing a relatively large amount of binder, drying a side section of a current collector onto which the binder suspension is applied, and applying an electrode slurry containing a large amount of electrode active material. Accordingly, it is possible to resolve problems that arise in a manufacturing process, such as side rings, by addressing issues of uneven thickness and uneven distribution of the binder composition in a lateral direction of an electrode. These issues can arise due to a difference in the binder migration rate between a side section and a central section of the electrode. This can be achieved by drying an electrode active material layer onto which a binder suspension electrode slurry is sequentially applied.

Claims

[1] Electrode for a secondary battery, comprising: a current collector; and an electrode active material layer located on at least one surface of the current collector, where the following relation expression 1 is satisfied: [Relationship expression 1] 1.0≤Bei / Bci≤2.0 where in relation expression 1 B ci a surface styrene-butadiene rubber-based binder content of a central section of the electrode active material layer in a lateral direction is and B ei a surface styrene-butadiene rubber-based binder content of a side section of the electrode active material layer in the width direction, where the interface styrene-butadiene rubber-based binder content is an average styrene-butadiene rubber-based binder content in the 10% thickness range based on the total thickness of the electrode active material layer in the thickness direction from the interface between the current collector and the electrode active material layer to the electrode active material layer, where the side section (112) is an area of ​​20% of the side based on the total width of the coated electrode part (11) along the x-axis, wherein the central section (111) is a region that excludes the side section in the coated electrode part (11). [2] Electrode according to claim 1, wherein the following relation expression 2 is also satisfied: [Relationship expression 2] 2.5≤At / Bes≤5.0 where in relation expression 2 B esa surface styrene-butadiene rubber-based binder content of the side section of the electrode active material layer in the width direction is and B ei the interface styrene-butadiene rubber-based binder content of the side section of the electrode active material layer in the width direction is, where the surface styrene-butadiene rubber-based binder content is an average styrene-butadiene rubber-based binder content in the 10% thickness range based on the total thickness of the electrode active material layer in the thickness direction from the surface of the electrode (1) to the electrode active material layer. [3] Electrode according to claim 1, wherein the electrode active material layer contains 0.1 to 2 wt.% styrene-butadiene rubber-based binder based on a total weight of the electrode active material layer. [4] Electrode according to claim 1, wherein the electrode includes an anode. [5] Electrode according to claim 1, wherein, when the side section (112) of the electrode active material layer is divided into 8 equal parts in the width direction (x-axis), the value obtained by subtracting the average thickness of the electrode thickness measured in the remaining areas excluding the following three areas is equal to or greater than the highest thickness among the electrode thicknesses measured in three successive areas from the outermost to the innermost area. [6] Electrode for a secondary battery, comprising: a current collector; and an electrode active material layer located on at least one surface of the current collector, where the following relation expression 1 is satisfied: [Relationship expression 1] 1.0≤Bei / Bci≤2.0 where in relation expression 1 B cia surface styrene-butadiene rubber content of a central section of the electrode active material layer in a lateral direction is and B ei a surface styrene-butadiene rubber content of a side section of the electrode active material layer in the lateral direction, where the interface styrene-butadiene rubber content is an average styrene-butadiene rubber content in the 10% thickness range based on the total thickness of the electrode active material layer in the thickness direction from the interface between the current collector and the electrode active material layer to the electrode active material layer, where the side section (112) is an area of ​​20% of the side based on the total width of the coated electrode part (11) along the x-axis, wherein the central section (111) is a region that excludes the side section in the coated electrode part (11). [7] Electrode according to claim 6, wherein the following relation expression 2 is also satisfied: [Relationship expression 2] 2.5≤At / Bes≤5.0 where in relation expression 2 B es a surface styrene-butadiene rubber content of the side section of the electrode active material layer in the width direction is and B ei the interface styrene-butadiene rubber content of the side section of the electrode active material layer in the lateral direction is, where the surface styrene butadiene rubber content is an average styrene butadiene rubber content in the 10% thickness range based on the total thickness of the electrode active material layer in the thickness direction from the surface of the electrode (1) to the electrode active material layer. [8] Electrode according to claim 6, wherein the electrode active material layer contains 0.1 to 2 wt% styrene-butadiene rubber based on a total weight of the electrode active material layer. [9] Electrode according to claim 6, wherein the electrode includes an anode. [10] Electrode according to claim 6, wherein, when the side section (112) of the electrode active material layer is divided into 8 equal parts in the width direction (x-axis), the value obtained by subtracting the average thickness of the electrode thickness measured in the remaining areas excluding the following three areas is equal to or greater than the highest thickness among the electrode thicknesses measured in three successive areas from the outermost to the innermost area. [11] Secondary battery comprising the electrode according to any one of claims 1 to 10.

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