CN116783724A

CN116783724A - Electrode

Info

Publication number: CN116783724A
Application number: CN202280010045.XA
Authority: CN
Inventors: 李镐赞; 宋寅宅; 李一何; 李根成; 金起焕; 睦英凤; 朴镇宇
Original assignee: LG Chem Ltd
Current assignee: LG Chem Ltd
Priority date: 2021-01-29
Filing date: 2022-01-28
Publication date: 2023-09-19
Also published as: KR20220109835A

Abstract

The present application relates to an electrode including a current collector and an active material layer, which can provide an electrode capable of securing a high level of inter-particle adhesion and adhesion between the active material layer and the current collector with respect to the content of a binder in the active material layer. The application may also provide the use of the electrode.

Description

Electrode

Technical Field

The present application claims the benefit of priority based on korean patent application No.10-2021-0013168 filed on 29 th 1 st 2021, korean patent application No.10-2021-0013325 filed on 29 th 1 st 2021 and korean patent application No.10-2021-0013326 filed on 29 th 1 st 2021, the disclosures of which are incorporated herein by reference in their entirety.

The present application relates to an electrode, a method of manufacturing the electrode and uses thereof.

Background

The application field of energy storage technology is extended to cell phones, camcorders, notebook computers, electric vehicles, etc.

One of the research fields of energy storage technology is secondary batteries capable of being charged and discharged, and research and development are being conducted to improve the capacity density and specific energy of such secondary batteries.

An electrode (positive electrode or negative electrode) applied to a secondary battery is generally manufactured by forming an active material layer including an electrode active material and a binder on a current collector.

In order to smoothly induce electron movement between active materials and between a current collector and an active material layer in an electrode of a secondary battery, it is necessary to secure adhesion between active material particles and adhesion between an active material layer and a current collector.

Further, when the adhesion between the particles in the active material layer is insufficient, a phenomenon in which the particles fall off from the electrode may occur, wherein the phenomenon deteriorates the stability and performance of the battery. For example, particles that fall off from the surfaces of the negative electrode and the positive electrode due to insufficient adhesion between the particles may cause micro-short circuits or the like inside the battery, thereby causing performance deterioration and ignition due to the short circuits.

When the adhesive force between the active material layer and the current collector is reduced, the moving speed of electrons between the active material layer and the current collector is reduced, which also results in degradation of the speed characteristics and the cycle characteristics.

The adhesive force between the particles in the active material layer or the adhesive force between the active material layer and the current collector is ensured by the binder.

Therefore, if more binder is introduced into the active material layer, higher adhesion can be ensured.

However, in this case, as the proportion of the binder increases, the proportion of the active material decreases, so that there is a problem in that the battery performance is deteriorated due to an increase in electrode resistance, a decrease in conductivity, or the like.

Disclosure of Invention

Technical problem

The present application relates to an electrode, a method of manufacturing the electrode and the use of the electrode. An object of the present application is to provide an electrode capable of securing a high level of inter-particle adhesion and adhesion between an active material layer and a current collector, as compared to the content of a binder in the active material layer.

Technical proposal

Among the physical properties mentioned in the present specification, the physical properties of the measured temperature-affected results are the results measured at room temperature unless otherwise specified.

The term room temperature is a natural temperature without heating or cooling, which refers to, for example, any one of temperatures in the range of 10 ℃ to 30 ℃, or temperatures around about 23 ℃ or about 25 ℃.

In addition, in this specification, unless otherwise indicated, the unit of temperature is degrees celsius (°c).

Among the physical properties mentioned in the present specification, the physical properties of the measurement pressure-affected results are the results measured at normal pressure unless otherwise specified.

The term atmospheric pressure is a natural pressure without pressurization or depressurization, which generally refers to an atmospheric pressure at an atmospheric pressure level, and refers to an atmospheric pressure of, for example, about 740 to 780mmHg or so.

In the case of measuring physical properties of which humidity affects the result, the relevant physical properties are physical properties measured at room temperature and/or at natural humidity without particular control in the normal pressure state.

The electrode of the present application comprises: a current collector; and an active material layer present on one or both sides of the current collector. Fig. 1 shows a structure in which an active material layer 200 is present on one side of a current collector 100. In the electrode structure, the active material layer may also be formed to be in contact with the surface of the current collector, or another layer may also be present between the current collector and the active material layer. For example, as described below, an intermediate layer may also be present between the current collector and the active material layer.

The active material layer may include at least an electrode active material and a binder.

In the present application, by controlling the distribution of the binder in the active material layer, particularly the distribution of the binder in the active material layer adjacent to the current collector, it is possible to ensure high adhesion between particles in the active material layer and at the same time, high adhesion between the active material layer and the current collector. The active material layer basically includes an electrode active material and a binder, wherein the adhesive force is represented by the binder. Therefore, in order to secure the adhesive force, it is necessary to place as much adhesive as possible at a position where the adhesive force is required to be exhibited.

For this reason, the affinity of each component in the slurry for forming the active material layer, or the affinity of each component in the slurry to the current collector must be carefully considered. Since there is a phenomenon in which the binder migrates to the upper portion of the active layer during the formation of the electrode or after the manufacture of the electrode, it is not an easy goal to control the binder so that it can be placed at a position where it is required to exhibit adhesive force, and when the content of the binder in the slurry is small, such control is not even easier. For example, as conceptually shown in fig. 2, a phenomenon in which the binder 2001, which is generally present in the active material layer, migrates to the upper portion of the active material layer occurs during and/or after the electrode manufacturing process, so that it is not easy to properly distribute the binder 2001 between the electrode active materials 1001 and/or between the electrode active materials 1001 and the current collector 100. That is, among the binders distributed on the current collector, the binder contributing to improvement of the adhesion is a part, and when the proportion of the binder in the active material layer is small, this tendency is further increased.

In the present application, by intensively distributing the binder in a portion where improvement of the binding force is required (for example, between the surface of the current collector and the electrode active material, etc.), it is possible to provide an electrode capable of achieving excellent binding force even at a small binder content.

In the present application, the area ratio and the height of the adhesive occupied area confirmed by the standard peeling test are adjusted to a high level as compared with the content of the adhesive contained in the active material layer.

The term area ratio of the adhesive occupied area is a percentage (100×a1/A2) of the area (adhesive occupied area) where the adhesive component is confirmed to be present on the surface of the current collector to the total surface area (A2) of the current collector after a standard peeling test which will be described later. Here, the region where the binder component was confirmed to exist may be confirmed by FE-SEM (field emission scanning electron microscope) analysis in the manner described in the examples. During the validation process, the adhesive is included in the area where the presence of the adhesive component is validated, and in some cases, other additional components (e.g., thickeners, etc.) may also be included.

The term adhesive footprint height is the height of the adhesive footprint, which can be confirmed in the manner described in the examples. Here, in the case where there are a plurality of adhesive occupied regions and the heights of the respective occupied regions are different from each other, the height may be an average height, a maximum height, or a minimum height of the adhesive occupied regions.

In one example, the area ratio (a) of the binder occupying region to the content (W) of the electrode active material in the active material layer (a/W) confirmed in the following standard peeling test performed on the electrode may be 17 or more.

Since the unit of the occupied area ratio A is% and the unit of the adhesive content is% by weight, the unit of the ratio A/W may be% by weight ^-1 (wt ^-1 )。

When the composition of the slurry in the electrode manufacturing process is known, the content of the binder is substantially the same as the content ratio of the binder in the solid content (solvent-excluding portion) of the relevant slurry. In addition, when the composition of the slurry in the electrode manufacturing process is unknown, the content of the binder may be determined by TGA (thermogravimetric analysis) analysis of the active material. For example, when an SBR (styrene-butadiene rubber) binder is applied as the binder, the content of the binder may be determined by the content of the SBR binder obtained by performing TGA analysis on the active material layer and decreasing the temperature-mass curve obtained by increasing the temperature at a rate of 10 ℃/min from 370 ℃ to 440 ℃.

In another example, the ratio a/W may be 17.5 or more, 18 or more, 18.5 or more, 19 or more, 19.5 or more, 20 or more, 20.5 or more, 21 or more, 21.5 or more, 22 or more, 22.5 or more, 23 or more, 23.5 or more, 24 or more, 24.5 or more, 25 or more, or 25.5 or may also be 50 or less, 49 or less, 48 or less, 47 or less, 46 or less, 45 or less, 44 or less, 43 or less, 42 or less, 41 or less, 40 or less, 39 or less, 38 or less, 37 or less, 36 or less, 35 or less, 34 or less, 33 or less, 32 or less, 31 or less, 30 or 29 or less, 28 or less, 27 or 26 or less, 25 or 24 or 23 or less.

At this a/W ratio, an electrode ensuring a high level of adhesion with respect to the applied adhesive content can be provided.

Here, the height of the adhesive occupied area (H _B ) Average particle diameter (B) with particulate binder _D ) Ratio (H) _B /B _D ) May be 0.5 or more. Here, as described below, the average particle diameter of the binder is the particle diameter (median particle diameter) at 50% accumulation in the volume-based accumulation chart obtained by the laser diffraction method. Therefore, in the actual adhesive, there is also an adhesive having a particle size smaller than the average particle size, and the particle size of the adhesive may also beTo be slightly changed by a rolling process or the like of an electrode manufacturing process, so that the ratio (H _B /B _D ) The lower limit of (2) may be 0.5. In another example, the ratio may be 0.6 or more, 0.7 or more, 0.9 or more, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, or 10 or more or less, or may be 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

Standard peel tests were performed using 3M Scotch Magic tape cat.810 r. For the standard peel test, first, the electrode was cut into a size of about 20mm in width and about 100mm in length. The Scotch Magic tape cat.810r was also cut so that the horizontal length was 10mm and the vertical length was 60mm. Subsequently, as shown in fig. 3, scotch Magic tape cat.810r 300 was adhered to the active material layer 200 of the electrode in a crossed state. Adhesion may be performed such that a particular portion of the Magic tape cat.810r 300 used for standard peel tests stands out. Then, the 810r 300 is peeled off by holding the protruding portion. In this case, the peeling rate and the peeling angle are not particularly limited, but the peeling rate may be about 20 mm/sec, and the peeling angle may be about 30 degrees. Furthermore, the adhesion of Scotch Magic tape cat.810r 300 was performed by: once the tape was adhered, the surface of the tape was reciprocated and pressed with rollers having a weight of about 1kg and a radius and width of 50mm and 40mm, respectively.

When the Scotch Magic tape cat.810r 300 is peeled off by the above-described process, the components of the active material layer 200 are peeled off together with the Scotch Magic tape cat.810r 300. Subsequently, the above procedure was repeated using a new Scotch logic tape cat.810r 300.

The standard peeling test may be performed by performing the above-described process until no component peeling of the active material layer 200 is observed on the Scotch Magic tape cat.810r 300.

Regarding the case where there is no falling of the components of the active material layer 200 on the Scotch Magic tape cat.810r 300, when the surface of the Scotch Magic tape peeled from the active material layer is compared with the surface of the unused Scotch Magic tape so that the color tones of the two are substantially the same, it can be determined that the components of the active material layer are not falling (visual observation).

The specific manner in which the standard peel test was performed is described in the examples.

After the standard peel test described above, the area ratio of the adhesive on the current collector can be determined.

There is no particular limitation on the type of current collector used in the present application, wherein known current collectors may be used. In order to achieve the above ratio a/W, the surface characteristics (water contact angle, etc.) of the current collector may be controlled as follows. As the current collector, for example, a film, sheet, or foil made of stainless steel, aluminum, nickel, titanium, baked carbon, copper, carbon, stainless steel surface-treated with nickel, titanium, or silver, aluminum-cadmium alloy, or the like can be used. In order to achieve the desired binder distribution, a current collector having the surface characteristics described below may be selected from current collectors, or the surface characteristics may be adjusted by additional treatments.

The thickness, shape, and the like of the current collector are not particularly limited, and an appropriate type is selected within a known range.

In the electrode of the present application, the surface characteristics of the current collector may be controlled so as to achieve proper distribution of the binder. For example, in the electrode, an intermediate layer may be present between the active material layer and the current collector.

The present application may include, for example, an intermediate layer comprising silicon between the active material layer and the current collector. When the electrode of the present application includes the above-described intermediate layer containing silicon, and at the same time, by controlling the composition of a slurry to be described later (for example, the affinity of a solvent to a binder) and/or the average particle diameter or the like of particulate materials in the slurry, an electrode having excellent adhesion with respect to the binder content can be provided.

The intermediate layer may be, for example, a layer containing a compound of the following formula 1.

[ 1]

In formula 1, R ₁ Is an alkyl group having 11 or less carbon atoms or an alkenyl group having 11 or less carbon atoms, wherein R ₁ Optionally substituted with one or more amino groups, R ₂ To R ₄ Each independently is an alkyl group having 1 to 4 carbon atoms.

The alkyl or alkenyl group in formula 1 may be linear, branched or cyclic, and in suitable examples it may be a linear alkyl or alkenyl group.

In one example, R in formula 1 ₁ A linear alkyl group having 1 to 10 carbon atoms, 1 to 9 carbon atoms, 1 to 8 carbon atoms, 1 to 7 carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 2 to 4 carbon atoms, or a linear alkenyl group having 2 to 10 carbon atoms, 2 to 9 carbon atoms, 2 to 8 carbon atoms, 2 to 7 carbon atoms, 2 to 6 carbon atoms, 2 to 4 carbon atoms, or 2 to 3 carbon atoms, or a linear aminoalkyl group having 1 to 10 carbon atoms, 1 to 9 carbon atoms, 1 to 8 carbon atoms, 1 to 7 carbon atoms, 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 2 to 4 carbon atoms.

The intermediate layer may contain the silane compound of formula 1 as a main component, wherein, for example, the content of the silane compound of formula 1 in the intermediate layer may be about 70 wt% or more, 75 wt% or more, 80 wt% or more, 85 wt% or more, 90 wt% or more, or 95 wt% or more. The upper limit of the content of the silane compound in the intermediate layer is 100% by weight. When a component other than the silane compound of formula 1 is present in the intermediate layer, the component may be a component such as a solvent used in the intermediate layer formation process, or may be an active material layer component that migrates from the active material layer.

The thickness of the intermediate layer may be appropriately set in consideration of desired surface characteristics, and may be, for example, in the range of about 0.5 μm to 50 μm.

In another example, the thickness may be about 1 μm or more, 3 μm or more, 5 μm or more, 7 μm or more, or about 9 μm or more, or may be about 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or about 15 μm or less.

In the electrode of the present application, by introducing the intermediate layer between the active material layer and the current collector, the surface characteristics of the current collector can be controlled as described below, and by doing so, the migration phenomenon of the binder to the upper part can be controlled, and the binder can be appropriately distributed at positions where it is necessary to exhibit the adhesion between the particles and/or between the current collector interface and the active material layer. The reason is not clear, but when such a slurry is coated on a current collector whose surface characteristics are controlled as described above, it is possible to expect that the dispersion state of the binder in the slurry, the affinity between the solvent of the slurry and the current collector whose surface characteristics are controlled, the affinity between the current collector whose surface characteristics are controlled and the binder in the slurry, and/or the relationship of particle diameters therebetween in the case of applying a particulate material, etc. are combined with each other to control the position of the binder of a desired shape.

The present application can also more effectively achieve the object by additional control of the composition of the active material layer (e.g., affinity of solvent to binder) and/or particle size characteristics of the particulate material in the slurry, etc.

The active material layer may include, for example, an electrode active material and a binder.

As the binder, a known material may be used, and a component known to contribute to the adhesion of a component (such as an active material in an active material layer) and the adhesion of the active material layer to a current collector may be used. As suitable binders, one or a combination of two or more selected from PVDF (poly (vinylidene fluoride)), PVA (poly (vinyl alcohol)), polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, SBR (styrene-butadiene rubber), fluororubber and other known binders may be used.

For proper adhesive distribution and the like, it is appropriate to use a particulate adhesive as the adhesive.

When a particulate material is used as the electrode active material, the particle diameter ratio between the particulate binder and the electrode active material layer may be controlled so as to control the distribution of the binder in the electrode active material layer.

For example, the ratio (D1/D2) of the average particle diameter (D1, unit nm) of the particulate electrode active material to the average particle diameter (D2, unit nm) of the particulate binder may be in the range of 10 to 1,000. In another example, the ratio (D1/D2) may be 20 or more, 30 or more, 40 or more, 50 or more, 60 or more, 70 or more, 80 or more, 90 or more, 100 or more, 110 or more, 120 or more, or 130 or may be about 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, 400 or less, 300 or less, 200 or less, or 150 or less.

Here, the average particle diameter (D2) of the binder may be in the range of 50nm to 500 nm. In another example, the average particle size (D2) of the binder may be about 70nm or more, about 90nm or more, about 110nm or more, about 130nm or more, or about 140nm or more, or may be about 480nm or less, about 460nm or less, 440nm or less, 420nm or less, 400nm or less, about 380nm or less, about 360nm or less, about 340nm or less, about 320nm or less, about 300nm or less, about 280nm or less, about 260nm or less, about 240nm or less, about 220nm or less, about 200nm or less, about 180nm or less, or about 160nm or less.

Here, the average particle diameter (D1) of the electrode active material may be in the range of 1 μm to 100 μm. In another example, the average particle diameter (D1) may be about 3 μm or more, about 5 μm or more, about 7 μm or more, about 9 μm or more, about 11 μm or more, about 13 μm or more, about 15 μm or more, about 17 μm or more, or about 19 μm or more, or may be about 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, or about 20 μm or less.

Here, the ratio (D90/D10) of the 90% volume cumulative particle diameter (D90) to the 10% volume cumulative particle diameter (D10) of the electrode active material may be 15 or less. In another example, the ratio D90/D10 may be about 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, or 3 or less, or may be greater than 1, 1.5 or more, 2 or more, 2.5 or more, 3 or more, or 3.5 or more.

Here, the 90% volume cumulative particle diameter (D90) of the electrode active material may be in the range of 5 μm to 500 μm. In another example, the particle size (D90) may be about 7 μm or more, about 9 μm or more, about 11 μm or more, about 13 μm or more, about 15 μm or more, about 17 μm or more, about 19 μm or more, about 20 μm or more, about 21 μm or more, about 22 μm or more, about 23 μm or more, about 24 μm or more, or about 25 μm or more, or may be about 450 μm or less, about 400 μm or less, about 350 μm or less, about 300 μm or less, about 250 μm or less, about 200 μm or less, about 150 μm or less, about 100 μm or less, about 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, or about 20 μm or less.

The respective average particle diameters D1 and D2 and the cumulative volume particle diameters D10 and D90 are particle diameters of the respective materials in the slurry applied for preparing the active material layer. Therefore, when the electrode is manufactured through a rolling process, the particle diameters D1, D2, D10, and D90 of the respective components determined in the active material layer may be slightly different.

In this specification, particle diameters D1, D2, D10, and D90 of the particulate matter are particle diameters obtained by a laser diffraction method, and a method of obtaining these particle diameters is described in examples. Further, for example, when the active material layer is a rolled layer, the particle diameter mentioned for the particulate binder and the particulate active material in the active material layer in this specification is the average particle diameter before rolling unless otherwise specified.

In one example, when two types of particulate binders (or electrode active materials) having different particle diameters D1, D2, D10, and D90 are present in the active material layer, the particle diameters D1, D2, D10, and D90 of the two types of particulate binders (or electrode active materials) in consideration of weight fractions may be defined as particle diameters D1, D2, D10, and D90 of the particulate binders (or electrode active materials) in the present specification.

For example, in the case of the average particle diameter, when the particulate binder (or electrode active material) having the average particle diameter Da is present by the weight of W1 and the particulate binder (or electrode active material) having the average particle diameter Db is present by the weight of W2, the average particle diameter D may be defined as d= (da×w1+db×w2)/(w1+w2), which is the same for the particle diameters D10 and D90. Further, at the time of confirmation, the particle diameters Da and Db and the weights W1 and W2 are each numerical values of the same unit as each other.

The reason is not clear, but it is expected that by such particle diameter characteristics, a dispersed state of the binder capable of achieving a desired position of the binder is achieved in the slurry in the electrode manufacturing process, and also migration phenomenon of the binder is properly controlled.

In addition, by the above particle diameter characteristics, it is also possible to prevent problems such as cyclic expansion while securing at most the output and capacity characteristics of the electrode active material.

For proper adhesive distribution, it is advantageous to use an adhesive having solubility parameters within the ranges described below as the adhesive.

In the present application, a relatively small amount of binder can be employed in the active material layer while ensuring a high level of adhesion. For example, the content of the binder in the active material layer may be about 0.5 to 10 wt%. In another example, the ratio may be further controlled within a range of 1 wt% or more, 1.5 wt% or more, 2 wt% or more, 2.5 wt% or more, 3 wt% or more, 3.5 wt% or more, or about 4 wt% or more, and/or within a range of 9.5 wt% or less, 9 wt% or less, 8.5 wt% or less, 8 wt% or less, 7.5 wt% or less, 7 wt% or less, 6.5 wt% or less, 6 wt% or less, 5.5 wt% or less, 5 wt% or less, or about 4.5 wt% or less.

The electrode active material contained in the active material layer may be a positive electrode active material or a negative electrode active material, and is not particularly limited to a specific type. For example, as the positive electrode active material, a material including LiCoO may be used ₂ 、LiNiO ₂ 、LiMn ₂ O ₄ 、LiCoPO ₄ 、LiFePO ₄ 、LiNiMnCoO ₂ And LiNi _1-x-y-z Co _x M1 _y M2 _z O ₂ (M1 and M2 are each independently selected from Al, ni,Co, fe, mn, V, cr, ti, W, ta, mg and Mo, x, y and z are each independently an atomic fraction of an oxide constituent element, satisfying that O.ltoreq.x < 0.5, 0.ltoreq.y < 0.5, 0.ltoreq.z < 0.5,0 < x+y+z.ltoreq.1), etc., and as the negative electrode active material, natural graphite, artificial graphite, carbonaceous materials may be used; lithium-containing titanium composite oxide (LTO), si, sn, li, zn, mg, cd, ce, ni, or Fe metal (Me); an alloy consisting of a metal (Me); an oxide (MeOx) of a metal (Me); and active materials such as metal (Me) and carbon complexes.

In the present application, it is possible to ensure excellent adhesion while maintaining a relatively high proportion of active material in the active material layer.

For example, the active material in the active material layer may be in the range of 1000 to 10000 parts by weight with respect to 100 parts by weight of the binder. In another example, the ratio may be 1500 parts by weight or more, 2000 parts by weight or more, 2500 parts by weight or more, 3000 parts by weight or more, 3500 parts by weight or more, 4000 parts by weight or more, or 4500 parts by weight or more, or 9500 parts by weight or less, 9000 parts by weight or less, 8500 parts by weight or less, 8000 parts by weight or less, 7500 parts by weight or less, 7000 parts by weight or less, 6500 parts by weight or less, 6000 parts by weight or less, 5500 parts by weight or less, 5000 parts by weight or less, 4500 parts by weight or less, 4000 parts by weight or less, 3500 parts by weight or less, 3000 parts by weight or less, or about 2500 parts by weight or less.

The active material layer may contain other necessary components in addition to the above-described components. For example, the active material layer may further include a conductive material. As the conductive material, for example, a known composition may be used without any particular limitation as long as it exhibits conductivity without causing chemical changes in the current collector and the electrode active material. For example, as the conductive material, one or a mixture of two or more selected from the following may be used: graphite, such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black or summer black; conductive fibers such as carbon fibers or metal fibers; a fluorocarbon powder; metal powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives, and the like.

The content of the conductive material is controlled as needed without particular limitation, but it may be generally contained in an appropriate proportion in the range of 0.1 to 20 parts by weight or 0.3 to 12 parts by weight with respect to 100 parts by weight of the active material. A method of determining the content of the conductive material at an appropriate level in consideration of the cycle life of the battery and the like is known.

The active material layer may contain other necessary known components (for example, a thickener such as carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, or the like) in addition to the above-described components.

The thickness of the active material layer is not particularly limited, and may be controlled to a thickness of an appropriate level in consideration of desired properties.

For example, the thickness of the active material layer may be in the range of about 10 μm to 500 μm. In another example, the thickness may be approximately 30 μm or more, 50 μm or more, 70 μm or more, 90 μm or more, or about 100 μm or more, or may be approximately 450 μm or less, 400 μm or less, 350 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, or about 150 μm or less.

The active material layer may be formed to have a certain level of porosity. Porosity is typically controlled by rolling during the fabrication of the electrode. The porosity of the active material layer may be about 35% or less. The porosity may be adjusted in a range of 33% or less, 31% or less, 29% or less, or 27% or less, and/or in a range of 5% or more, 7% or more, 9% or more, 11% or more, 13% or more, 15% or more, 17% or more, 19% or more, 21% or more, 23% or more, or 25% or more. As described below, a rolling process controlled to have the porosity described above may help to form the binder distribution desired in the present application. Here, the porosity is a value calculated by a method of comparing the ratio of the actual density of the active material layer to the difference between the densities after rolling, and a method of calculating the porosity of the active material layer in this way is known.

The application also relates to a method of manufacturing an electrode. The above-described electrode may be manufactured in a manner to be described later. Typically, the electrode is manufactured by applying a slurry on a current collector, drying it, and then performing a rolling process.

Accordingly, the method of manufacturing an electrode may include a step of forming a slurry layer on the current collector.

In the present application, a desired binder distribution can be formed by controlling the composition of the slurry, the surface characteristics of the current collector on which the slurry is coated, the drying conditions, and/or the rolling conditions in the above-described process.

For example, in the production method of the present application, as the slurry, a slurry in which a relatively hydrophobic binder (suitably, a particulate binder having a specific average particle diameter and simultaneously having relatively hydrophobicity) is dispersed in a relatively polar solvent in a certain amount may be applied. As described below, this slurry is coated on a current collector whose surface characteristics are controlled. The reason is not clear, but when such a slurry is coated on a current collector, it is expected that the dispersion state of the binder in the slurry, the affinity of the solvent of the slurry to the surface of the current collector, the affinity of the surface of the current collector to the binder in the slurry, and/or the particle size relationship between them in the case of applying a particulate material, etc. are combined with each other to control the position of the binder of a desired shape.

For example, the affinity of a solvent to a current collector surface affects the contact angle of the solvent on the current collector surface, wherein the contact angle may create a force in a particular direction in the slurry due to capillary action or the like upon evaporation of the solvent. The affinity of the binder to the solvent and the amount of the binder (and, in the case of a particulate binder, the particle size) influence the dispersion state of the binder in the slurry, and the affinity of the binder to the current collector surface influences the dispersion state of the binder in the slurry, the distribution shape of the binder entering the current collector surface, and the like.

In the present application, it has been confirmed that a desired adhesive arrangement is achieved by the dispersion state of the adhesive and the evaporation state of the solvent when forming a slurry of the following composition on a current collector having the following surface characteristics, and the shearing force in the slurry generated thereby.

For example, the slurry applied to the manufacturing process may contain a solvent. As the solvent, a solvent capable of appropriately dispersing a slurry component such as an electrode active material is generally used, and examples thereof are water, methanol, ethanol, isopropanol, acetone, dimethyl sulfoxide, formamide, dimethylformamide, and the like.

In the present application, it may be necessary to use a solvent having a dipole moment of about 1.3D or more in the solvent. In another example, the dipole moment of the solvent may also be controlled to be in a range of about 1.35D or more, 1.4D or more, 1.45D or more, 1.5D or more, 1.55D or more, 1.6D or more, 1.65D or more, 1.7D or more, 1.75D or more, 1.8D or more, or 1.85D or more and/or in a range of about 5D or less, 4.5D or less, 4D or less, 3.5D or less, 3D or less, 2.5D or less, 2D or less, or 1.9D or less. For each solvent, the dipole moment of the solvent is known.

As the binder contained in the slurry, an appropriate one of the above types of binders may be selected and used. In order to achieve the desired dispersion in the solvent, it may be necessary to use a solubility parameter of about 10 to 30MPa ^1/2 The left and right adhesives act as adhesives. In another example, the solubility parameter may be 11MPa ^1/2 Above, 12MPa ^1/2 Above, 13MPa ^1/2 Above, 14MPa ^1/2 Above 15MPa ^1/2 Above, or 16MPa ^1/2 Above, or may be 28MPa ^1/2 Below, 26MPa ^1/2 Below, 24MPa ^1/2 Below, 22MPa ^1/2 Below, 20MPa ^1/2 Below, or 18MPa ^1/2 The following is given. The solubility parameters of such adhesives can be confirmed by literature (e.g., yanlong Luo et al, 2017, etc.). For example, in the above type of adhesive, the type having such a solubility parameter may be selected.

As the binder, a particulate binder may be used, for example, a particulate binder having an average particle diameter of the above average diameter may be used.

The binder content in the slurry can be controlled in consideration of the desired dispersion state. For example, the binder may be contained in the slurry such that the concentration of the binder (=100×b/(b+s), where B is the weight (g) of the binder in the slurry and S is the weight (g) of the solvent in the slurry) is about 0.1 to 10% with respect to the solvent. In another example, the concentration may be 0.5% or more, 1% or more, 1.5% or more, 2% or more, 2.5% or more, 3% or more, or 3.5% or more, or may be about 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, or 2.5% or less.

In addition to the above components, the slurry may contain an electrode active material. As the electrode active material, an appropriate type may be selected from the above types, and in consideration of contribution to a desired dispersion state, an electrode active material in the form of particles having an average particle diameter (D50 particle diameter) and a D10-D90 particle diameter relationship in the above range and having a ratio to the average particle diameter of the binder in the above range may be used.

The proportion of the electrode active material in the slurry may be adjusted so that the proportion of the electrode active material in the active material layer may be achieved.

In addition to the above components, the slurry may contain other components including the above conductive materials, thickeners, and the like, depending on the purpose.

The method of manufacturing an electrode of the present application may include, for example, a step of forming a slurry layer on the current collector. The slurry may be coated on the surface of the current collector. In this process, there is no particular limitation on the coating method, and a known coating method, for example, a method such as spin coating, comma coating, or bar coating may be applied.

The surface characteristics of the current collector coated with the slurry can be controlled.

For example, the surface of the current collector coated with the slurry may have a water contact angle of 50 degrees or more. In another example, the water contact angle may also be controlled within a range of 100 degrees or less, 95 degrees or less, 90 degrees or less, 85 degrees or less, 80 degrees or less, or 75 degrees or less and/or within a range of 55 degrees or more, 60 degrees or more, 65 degrees or more, 70 degrees or more, 75 degrees or more, 85 degrees or more, or 90 degrees or more.

For example, the surface of the current collector coated with the slurry may have a DM (diiodomethane) contact angle of 30 degrees or more. In another example, the DM contact angle may also be controlled within a range of 70 degrees or less, 65 degrees or less, 60 degrees or less, 55 degrees or less, 50 degrees or less, or 45 degrees or less and/or within a range of 35 degrees or more, 40 degrees or more, 45 degrees or more, 50 degrees or more, 55 degrees or more, or 60 degrees or more.

For example, the surface of the current collector coated with the slurry may have a surface energy of 65mN/m or less. The surface energy may be 60mN/m or less, 55mN/m or less, 50mN/m or less, 45mN/m or less, 40mN/m or less, 35mN/m or less, or about 30mN/m or less, or may be 25mN/m or more, 27mN/m or more, or 29mN/m or more.

For example, the surface of the current collector coated with the slurry may have a dispersion energy of less than 45 mN/m. In another example, the dispersion energy may be 40mN/m or less, 35mN/m or less, or about 30mN/m or less, or may be about 23mN/m or more, 25mN/m or more, or about 27mN/m or more.

For example, the surface of the current collector coated with the slurry may have a polar energy of 20mN/m or less. In another example, the polar property may be 18mN/m or less, 16mN/m or less, 14mN/m or less, 12mN/m or less, 10mN/m or less, 8mN/m or less, 6mN/m or less, 4mN/m or less, 2mN/m or less, or 1.5mN/m or less, or may also be 0.5mN/m or more, 1mN/m or more, 1.5mN/m or more, 2mN/m or more, 2.5mN/m or more, 3mN/m or more, 3.5mN/m or more, 4mN/m or more, 4.5mN/m or more, 5mN/m or more, 5.5mN/m or more, 6mN/m or 6.5mN/m or 7mN/m or more.

Here, the surface energy, the dispersion energy, and the polarity energy are physical quantities that can be obtained by an OWRK (Owens-Wendt-Rabel-Kaelble) method based on the water contact angle and the DM contact angle.

By applying the above slurry to the surface of a current collector that satisfies at least one, two or more or all of the above surface characteristics, a desired active material layer can be obtained.

Among the above-mentioned current collectors, a current collector exhibiting the water contact angle or the like may be selected, but there are cases where the current collector does not generally satisfy the above-mentioned characteristics, and therefore, surface treatment may also be performed to satisfy desired surface characteristics.

For example, the above-described silicon-containing layer may be formed on the surface of the current collector.

As for the silicon-containing layer (intermediate layer), for example, a step of coating a coating solution containing a silicon compound on the surface of the current collector may be included. As for the content of the silicon-containing layer, the above-described content can be applied in the same manner. The coating method is not particularly limited, and for example, a method such as spin coating, comma coating, or bar coating may be employed.

The solvent may be, for example, ethanol or the like, and is not particularly limited as long as the silicon compound can be appropriately dispersed.

The silicon compound may be contained in the solvent, for example, in a range of 0.1 to 10% by weight. In another example, the compound of formula 1 may be present in an amount of 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, or 0.9 wt% or more, or 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5 wt% or less, 4 wt% or less, 3 wt% or less, or 2 wt% or less, relative to the solvent.

The step of forming the intermediate layer may include, for example, two or more drying steps.

The step of forming the intermediate layer may include a first drying step. For example, the first drying process may be performed at a temperature ranging from 40 ℃ to 250 ℃. In another example, the first drying process may be performed at a temperature of 45 ℃ or more, 50 ℃ or more, 55 ℃ or more, 60 ℃ or more, 65 ℃ or more, 70 ℃ or more, 75 ℃ or more, 80 ℃ or more, 85 ℃ or more, 90 ℃ or more, or 95 ℃ or more, or may be performed at a temperature of 240 ℃ or less, 230 ℃ or less, 220 ℃ or less, 210 ℃ or less, 200 ℃ or less, 190 ℃ or less, 180 ℃ or less, 170 ℃ or less, 160 ℃ or less, 150 ℃ or less, 140 ℃ or less, 130 ℃ or less, 120 ℃ or less, or 110 ℃ or less. Further, the first drying process may be performed, for example, for a time ranging from 1 minute to 15 minutes. In another example, the annealing may be performed for 2 minutes or more, 3 minutes or more, or 4 minutes or more, or may be performed for 14 minutes or less, 13 minutes or less, 12 minutes or less, 11 minutes or less, 10 minutes or less, 9 minutes or less, 8 minutes or less, 7 minutes or less, or 6 minutes or less.

The drying step may include, for example, a second drying step. The second drying step may, for example, be performed at the same temperature and/or time as the first drying step.

A washing process may be further included between the first drying step and the second drying step. The washing process may be performed using, for example, a solvent such as ethanol.

The present application may relate to a method of manufacturing an electrode including the step of forming a slurry layer on a current collector. The step of forming the slurry layer may be performed according to the above-described coating method.

After the slurry is applied, for example, a drying process of the slurry may be performed. The conditions under which the drying process is performed are not particularly limited, but the drying temperature may be appropriately adjusted in a range of about 150 to 400 ℃ in consideration of a desired position of the binder, etc. In another example, the drying temperature may be about 170 ℃ or more, 190 ℃ or more, 210 ℃ or more, or 225 ℃ or more, or 380 ℃ or less, 360 ℃ or less, 340 ℃ or less, 320 ℃ or less, 300 ℃ or less, 280 ℃ or less, 260 ℃ or less, or 240 ℃ or less.

The drying time may also be controlled in consideration of the desired position of the binder, etc., in consideration of the dispersion state, and may be adjusted in the range of about 10 seconds to 200 seconds, for example. In another example, the time may also be controlled in a range of 20 seconds or more, 30 seconds or more, 40 seconds or more, 50 seconds or more, 60 seconds or more, 70 seconds or more, 80 seconds or more, or 85 seconds or more, and/or in a range of 190 seconds or less, 180 seconds or less, 170 seconds or less, 160 seconds or less, 150 seconds or less, 140 seconds or less, 130 seconds or less, 120 seconds or less, 110 seconds or less, 100 seconds or less, or 95 seconds or less.

After the drying process, a rolling process may be performed. In this case, even by the rolling conditions (for example, pressure during rolling, etc.), the position of the adhesive, etc. can be adjusted.

For example, rolling may be performed such that the porosity of the rolled slurry (active material layer) is about 35% or less. By performing the pressure or the like applied at the time of rolling with such porosity, a desired adhesive distribution can be effectively formed. In another example, the porosity may be further controlled in a range of 33% or less, 31% or less, 29% or less, or 27% or less, and/or in a range of 5% or more, 7% or more, 9% or more, 11% or more, 13% or more, 15% or more, 17% or more, 19% or more, 21% or more, 23% or more, or 25% or more.

The thickness of the rolled slurry (i.e., the active material layer) is within the thickness range of the active material layer as described above.

In the manufacturing process of the electrode of the present application, necessary additional processes (e.g., a cutting process, etc.) may be performed in addition to the slurry coating, drying, and rolling.

The application also relates to an electrochemical element, e.g. a secondary battery, comprising such an electrode.

The electrochemical element may include the electrode as a positive electrode and/or a negative electrode. Other configurations or manufacturing methods of the electrochemical element are not particularly limited as long as the electrode of the present application is used as the negative electrode and/or the positive electrode, and known methods may be applied.

Advantageous effects

The present application relates to an electrode including a current collector and an active material layer, which can provide an electrode capable of securing a high level of inter-particle adhesion and adhesion between the active material layer and the current collector with respect to the binder content in the active material layer.

Drawings

Fig. 1 is a cross-sectional view of an exemplary electrode of the present application.

Fig. 2 is a conceptual diagram of a state of formation of an active material layer in the related art.

Fig. 3 is a conceptual diagram of a state in which a standard peeling test is performed.

Fig. 4 to 9 are FE-SEM images of the current collector surfaces of examples 1 to 6, respectively.

Fig. 10 and 11 are FE-SEM images of the current collector surfaces of comparative examples 1 and 2, respectively.

[ description of reference numerals ]

100: current collector

200: active material layer

300: scotch Magic tape

1001; electrode active material

2001: adhesive agent

Detailed Description

Hereinafter, the present application will be described in more detail by way of examples and comparative examples, but the scope of the present application is not limited to the following examples.

1. Measurement of contact angle and surface energy

Contact angle and surface energy were measured using a droplet shape analyzer device of KRUSS (manufacturer: KRUSS, trade name: DSA 100). 3. Mu.l of water or DM (diiodomethane) droplets were added dropwise at a rate of about 3. Mu.l/sec, respectively, and the respective contact angles were measured by chamfer measurements. The surface energy, dispersion energy and polar properties were calculated by the OWRK (Owens-Wendt-Rabel-Kaelble) method, by the contact angle of water and DM, respectively.

2. Standard peel test

Standard peel tests were performed using 3M Scotch Magic tape cat.810r. To obtain a sample, the electrodes prepared in examples or comparative examples were cut into a size of about 20mm in width and about 100mm in length. The Scotch Magic tape cat.810r was adhered to the active material layer of the obtained sample by reciprocating and pressing a roller having a weight of 1kg, a radius of 50mm and a width of 40mm once. At this time, the Scotch Magic tape was cut to a width of about 10mm and a length of about 60mm and used, and as shown in fig. 3, the Scotch Magic tape and the electrode active material layer were cross-adhered to a length of about 20mm and the protruding portion was fixed and peeled off. At this time, the peeling rate and the peeling angle were set to a speed of about 20 mm/sec and an angle of about 30 degrees. A new high tape was replaced and used each time the strip was peeled off. The above procedure was repeated until the components of the active material layer were not exposed on the surface of the Scotch Magic tape. Whether the components of the active material layer were exposed or not was visually observed, and when the color tone was not significantly changed as compared with the unused tape, it was determined that the components of the active material layer were not exposed.

3. Determination of the area of the adhesive occupied area

After standard peel tests, the area of the adhesive was confirmed from the surface of the current collector. After the standard peeling test, the surface of the current collector was photographed at 500 times magnification using an FE-SEM (field emission scanning electron microscope) apparatus (manufacturer: HITACHI, trade name: S4800) to obtain an image. The area of the surface where the current collector was not observed due to the presence of the adhesive and the area of the surface where the current collector was observed were divided using Image J software (manufacturer: image J) Trainable Weka Segmentation Plug-in, and the occupation area of the adhesive was measured based on these areas. In the above method, based on the luminance, a portion having a luminance of 80 or less and a portion having a luminance of 160 or more due to the height within the closed curve composed of the relevant portions are defined as a portion occupied by the adhesive, and the other area is designated as an area without the adhesive.

4. Height determination of adhesive footprint

After the standard peeling test, the surface of the current collector was observed with a confocal laser beam-splitting microscope (manufacturer: keyenece, product name: VK-X200), 5 or more images were obtained at a magnification of 3000 times, and the height of the adhesive occupied area was measured at 3 or more positions and 20 or more positions in total for each image, whereby the arithmetic average thereof was designated as the height of the adhesive occupied area.

5. Determination of particle size (D10, D50 and D90 particle size) of particulate Binder and electrode active Material

The average particle size (D50 particle size) of the particulate binder and electrode active material was measured according to ISO-13320 standard using a Marvern MASTERSIZER3000 apparatus. At the time of measurement, water was used as a solvent. When a material to be measured (a particulate binder or an electrode active material) is dispersed in a solvent and irradiated with laser light, the laser light is scattered by the binder dispersed in the solvent, and the intensity and directivity values of the scattered laser light vary according to the size of particles, so that the average particle diameter can be obtained by analyzing these by the mie scattering theory. By the above analysis, a volume-based cumulative chart of particle size distribution was obtained by converting into particle sizes of spheres having the same volume as the dispersed binder, and the particle size (median particle size) at 50% accumulation of the chart was designated as the average particle size (D50 particle size).

Further, the particle diameter at 90% accumulation based on the volume accumulation map is designated as 90% volume accumulation particle diameter (D90), and the particle diameter at 10% accumulation is designated as 10% volume accumulation particle diameter (D10).

6. Measuring adhesion

After rolling, the electrode was cut to have a width of about 20mm, and the adhesive force was measured according to a known method for measuring adhesive force of an active material layer. When the adhesive force was measured, the peeling angle was 90 degrees, and the peeling rate was about 5 mm/sec. After the measurement, the peak-stabilized portions were averaged and defined as adhesion.

Example 1

Copper foil (Cu foil) was used as a current collector, and after the surface characteristics were adjusted in the following manner, it was applied to manufacturing an electrode.

First, a coating liquid in which ethyltrimethoxysilane was dispersed in ethanol as a solvent at a concentration of about 1 wt% was coated on the surface of a copper foil to a thickness of about 10 μm using a bar coater. After coating, it was annealed at 100 ℃ for about 5 minutes, washed with ethanol, and then dried again at 100 ℃ for about 5 minutes to form a silane coating. The surface energy of the silane coating was about 29.7. 29.7 mN/m (dispersion energy was about 28.3mN/m, and polar properties were about 1.4 mN/m). Further, the water contact angle is about 95 degrees, and the DM contact angle is about 60.4 degrees.

The slurry was prepared by mixing water, SBR (styrene-butadiene rubber) binder, thickener (CMC, carboxymethyl cellulose), electrode active material (1) (artificial Graphite (GT), average particle size (D50 particle size): 20 μm) and electrode active material (2) (natural graphite (PAS), average particle size (D50 particle size): 15 μm) in a weight ratio of 51:2:0.6:37.1:9.3 (water: SBR: CMC: active material (1): active material (2)). Here, the average particle diameter (D50 particle diameter) of the electrode active material (1) (GT) is about 20 μm, the D10 particle diameter is about 8 μm, and the D90 particle diameter is about 28 μm. Here, the average particle diameter (D50 particle diameter) of the electrode active material 2 (PAS) is about 15 μm, the D10 particle diameter is about 6 μm, and the D90 particle diameter is about 25 μm.

Here, water is a solvent having a dipole moment of about 1.84 and D, and SBR binder has a solubility parameter of about 16.9 MPa ^1/2 Left and right adhesives. The solubility parameter of the SBR adhesive is the value described in Yanlong Luo et al, 2017. The SBR binder was a particulate binder having an average particle diameter (D50 particle diameter, median particle diameter) of about 150 nm.

The slurry was coated on the surface of the silane coating layer to a thickness of about 280 μm by a gap coating method and dried at a temperature of about 230 ℃ for about 90 seconds. After drying, a slurry layer having a thickness of about 180 μm was obtained, and the dried slurry layer was rolled with a conventional electrode mill to have a final thickness of about 100 μm and a porosity of about 24%, thereby forming an active material layer.

The porosity of the active material layer is a value calculated by comparing the ratio of the difference between the true density and the density after rolling. Further, when considering the composition of the slurry, the content of SBR binder in the active material layer of the electrode is about 4 wt%, and the content of the electrode active material (gt+pas) is about 95 wt%.

Example 2

Copper foil (Cu foil) was used as a current collector, which was applied to manufacture of an electrode after the surface characteristics were adjusted in the following manner.

A coating liquid in which allyltrimethoxysilane was dispersed in ethanol as a solvent at a concentration of about 1 wt% was coated on the surface of the copper foil to a thickness of about 10 μm using a bar coater. After coating, it was annealed at 100 ℃ for about 5 minutes, washed with ethanol, and then dried again at 100 ℃ for about 5 minutes to form a silane coating. The surface energy of the silane coating was about 30.6. 30.6 mN/m (dispersion energy was about 29.5mN/m, and polar properties were about 1.1 mN/m). Further, the water contact angle was about 95.8 degrees, and the DM contact angle was about 58.4 degrees.

Subsequently, the same slurry as used in example 1 was coated on the surface of the silane coating layer to a thickness of about 280 μm by a gap coating method, and dried at a temperature of about 230 ℃ for about 90 seconds. After drying, a slurry layer having a thickness of about 180 μm was obtained, and the dried slurry layer was rolled with a conventional electrode mill to have a final thickness of about 100 μm and a porosity of about 24%, thereby forming an active material layer.

The calculation method of the porosity of the active material layer and the content of SBR binder and electrode active material in the active material layer of the electrode were the same as in example 1.

Example 3

A coating liquid in which 3-aminopropyl trimethoxysilane was dispersed in ethanol as a solvent at a concentration of about 1 wt% was coated on the surface of the copper foil to a thickness of about 10 μm using a bar coater. After coating, it was annealed at 100 ℃ for about 5 minutes, washed with ethanol, and then dried again at 100 ℃ for about 5 minutes to form a silane coating. The surface energy of the silane coating was about 28.3mN/m (dispersion energy was about 27.1mN/m, and polar properties were about 1.2 mN/m). Further, the water contact angle was about 96.8 degrees, and the DM contact angle was about 62.6 degrees.

Subsequently, the same slurry as used in example 1 was coated on the surface of the silane coating layer to a thickness of about 280 μm by a gap coating method, and dried at a temperature of about 230 ℃ for about 90 seconds. After drying, a slurry layer having a thickness of about 180 μm was obtained, and the dried slurry layer was rolled with a conventional electrode mill to have a final thickness of about 110 μm and a porosity of about 26%, thereby forming an active material layer.

Example 4

Copper foil whose surface characteristics were controlled in the same manner as in example 1 was used as a current collector.

The slurry was prepared by mixing water, SBR (styrene-butadiene rubber) binder, thickener (CMC, carboxymethyl cellulose), electrode active material (1) (artificial Graphite (GT), average particle size (D50 particle size): 20 μm) and electrode active material (2) (natural graphite (PAS), average particle size (D50 particle size): 15 μm) in a weight ratio of 48.5:1:0.5:45:5 (water: SBR: CMC: active material (1): active material (2)). Here, water is a solvent having a dipole moment of about 1.84D, and SBR binder has a solubility parameter of about 16.9MPa ^1/2 Left and right adhesives. The solubility parameter of the SBR adhesive is the value described in Yanlong Luo et al, 2017. The SBR binder was a particulate binder having an average particle diameter (D50 particle diameter, median particle diameter) of about 150 nm.

The slurry was coated on the surface of the silane coating layer to a thickness of about 280 μm by a gap coating method and dried at a temperature of about 230 ℃ for about 90 seconds. After drying, a slurry layer having a thickness of about 180 μm was obtained, and the dried slurry layer was rolled with a conventional electrode mill to have a final thickness of about 110 μm and a porosity of about 26%, thereby forming an active material layer.

The method of calculating the porosity of the active material layer is the same as in example 1. Further, when considering the composition of the slurry, the content of SBR binder in the active material layer of the electrode was about 2 wt% and the content of the electrode active material was about 97 wt%.

Example 5

Copper foil whose surface characteristics were controlled in the same manner as in example 2 was used as a current collector.

Subsequently, the same slurry as used in example 4 was coated on the surface of the silane coating layer to a thickness of about 280 μm by a gap coating method, and dried at a temperature of about 230 ℃ for about 90 seconds. After drying, a slurry layer having a thickness of about 180 μm was obtained, and the dried slurry layer was rolled with a conventional electrode mill to have a final thickness of about 110 μm and a porosity of about 26%, thereby forming an active material layer.

The calculation method of the porosity of the active material layer and the content of SBR binder and electrode active material in the active material layer of the electrode were the same as in example 4.

Example 6

Copper foil whose surface characteristics were controlled in the same manner as in example 3 was used as a current collector.

Comparative example 1

Copper foil (Cu foil) as a current collector was directly applied to electrode fabrication without separate treatment. The surface energy of the untreated copper foil surface was about 71.2mN/m (dispersion energy was about 45mN/m, and polar properties were about 26.2 mN/m).

Subsequently, the same paste as used in example 1 was coated on the surface of the copper foil to a thickness of about 280 μm by a gap coating method, and dried at a temperature of about 230 ℃ for about 90 seconds. After drying, a slurry layer having a thickness of about 180 μm was obtained, and the dried slurry layer was rolled with a conventional electrode mill to have a final thickness of about 110 μm and a porosity of about 26%, thereby forming an active material layer.

Comparative example 2

Copper foil (Cu foil) as a current collector was directly applied to electrode fabrication without separate treatment. The surface energy of the untreated copper foil surface was about 71.2mN/m, the dispersion energy was about 45mN/m, and the polar properties were about 26.2 mN/m.

Subsequently, the same paste as used in example 4 was coated on the surface of the copper foil to a thickness of about 280 μm by a gap coating method, and dried at a temperature of about 230 ℃ for about 90 seconds. After drying, a slurry layer having a thickness of about 180 μm was obtained, and the dried slurry layer was rolled with a conventional electrode mill to have a final thickness of about 110 μm and a porosity of about 26%, thereby forming an active material layer.

The calculation method of the porosity of the active material layer and the content of SBR binder and electrode active material in the electrode active material layer were the same as in example 4.

Test example 1 determination of the area and height of the adhesive occupied area

Standard peel tests were performed on the electrodes of examples and comparative examples in the above manner, and the area of the occupied area of the adhesive and the height of the occupied area were confirmed. Fig. 4 to 9 are FE-SEM images of examples 1 to 6, respectively, and fig. 10 and 11 are FE-SEM images of comparative examples 1 to 2, respectively.

The results are described in table 1 below.

TABLE 1

From table 1, it is confirmed that, in the case of the examples, a high occupation area ratio of the binder is ensured with respect to the binder content in the active material layer.

Test example 2 determination of adhesion

The results of evaluating the adhesive force (unit: gf/20 mm) of examples and comparative examples are shown in Table 2 below.

TABLE 2

As can be confirmed from table 2, in the case of examples, high adhesion was ensured with respect to the binder content in the active material layer.

Claims

1. An electrode, comprising:

a current collector; and

an active material layer on one or both sides of the current collector,

wherein the active material layer contains an electrode active material and a particulate binder,

wherein the ratio A/W of the area ratio A of the occupied area of the binder on the current collector to the binder content W in the active material layer is 17 or more, which is determined according to the following standard peeling test, and

wherein the ratio of the height of the adhesive occupied area to the average particle diameter of the particulate adhesive is 0.5 or more:

standard peel test: the process of adhering the Scotch Magic tape cat.810r on the active material layer and then peeling it off was repeated until no component of the active material layer was observed on the Scotch Magic tape cat.810 r.

2. The electrode of claim 1, further comprising a silicon-containing layer between the active material layer and the current collector.

3. The electrode according to claim 1 or 2, wherein the current collector is a film, sheet or foil made of one or more selected from stainless steel, aluminum, nickel, titanium, baked carbon, copper, carbon, stainless steel surface-treated with nickel, titanium or silver, and aluminum-cadmium alloy.

4. An electrode according to any one of claims 1 to 3, wherein the binder comprises one or more selected from PVDF (poly (vinylidene fluoride)), PVA (poly (vinyl alcohol)), polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulphonated EPDM, SBR (styrene-butadiene rubber) and fluororubber.

5. The electrode according to any one of claims 1 to 4, wherein the binder has an average particle diameter of 50 to 500 nm.

6. The electrode according to any one of claims 1 to 5, wherein the electrode active material and the binder are fine particles, and a ratio D1/D2 of an average particle diameter D1 of the electrode active material to an average particle diameter D2 of the binder is 10 to 1000.

7. The electrode according to claim 6, wherein the electrode active material has an average particle diameter in a range of 1 μm to 100 μm.

8. The electrode according to claim 6, wherein a ratio D90/D10 of a 90% volume cumulative particle diameter D90 to a 10% volume cumulative particle diameter D10 in the electrode active material is 15 or less.

9. The electrode according to any one of claims 1 to 8, wherein the binder in the active material layer has a content in the range of 0.5 to 10 wt%.

10. The electrode according to any one of claims 1 to 9, wherein the electrode active material is contained in the active material layer in an amount of 1000 to 10000 parts by weight with respect to 100 parts by weight of the binder.

11. The electrode according to any one of claims 1 to 10, wherein the active material layer has a thickness in a range of 10 μm to 500 μm.

12. A method of manufacturing an electrode according to any one of claims 1 to 11, comprising:

a slurry layer is formed on the current collector,

wherein the slurry contains a solvent having a dipole moment of 1.3D or more, the binder, and the electrode active material, and

wherein a silicon-containing layer is on the surface of the current collector on which the slurry layer is formed.

13. A method of manufacturing an electrode according to any one of claims 1 to 11, comprising:

A slurry layer is formed on the current collector,

wherein the slurry comprises a solvent having a dipole moment of 1.3D or more and a solubility parameter of 10 to 30MPa ^1/2 Is within the range of the binder and the electrode active material, and

wherein the surface of the current collector on which the slurry layer is formed has a water contact angle of 50 degrees or more.

14. An electrochemical element comprising the electrode according to any one of claims 1 to 11 as a positive electrode or a negative electrode.

15. A secondary battery comprising the electrode according to any one of claims 1 to 11 as a negative electrode or a positive electrode.