Negative electrodes for electrochemical devices

Abstract

The negative electrode according to the present invention is manufactured by a dry process using composite particles containing binder particles that satisfy a predetermined particle size range, and therefore the binder polymer is uniformly distributed in the negative electrode active material layer, which results in high binding strength of the negative electrode material, resulting in excellent durability and shape stability of the negative electrode active material layer, and high adhesion strength between the negative electrode active material layer and the current collector.

Description

[Technical Field]

[0001] This application claims priority based on Korean Patent Application No. 10-2022-0182359, filed on December 22, 2022, and the entire contents disclosed in the specification and drawings of that application are incorporated herein by reference.

[0002] The present invention relates to a negative electrode for an electrochemical device, which contains composite particles for a dry electrode. [Background technology]

[0003] The recent dramatic increase in fossil fuel use has led to a growing demand for alternative and clean energy. One of the most active research fields is electrochemical power generation and storage. Currently, secondary batteries are a representative example of electrochemical devices that utilize electrochemical energy, and their range of use is expanding. Lithium secondary batteries, a representative example of secondary batteries, are not only used as energy sources for mobile devices, but are also being used as power sources for electric vehicles and hybrid electric vehicles, which are replacing fossil fuel-powered vehicles such as gasoline and diesel vehicles, which are major causes of air pollution. Their range of use is also expanding to include auxiliary power sources using grids. Such secondary batteries are manufactured through an electrode manufacturing process, an electrode assembly manufacturing process, and a chemical conversion process. Typically, the electrode manufacturing process involves preparing an electrode slurry, coating the slurry on an electrode current collector, and drying the slurry. After drying, subsequent processes such as rolling, slitting, and winding are performed. Among these, the electrode slurry manufacturing process is a process of blending components for forming an electrode active material layer in which an electrochemical reaction actually occurs in the electrode. More specifically, the electrode active material, which is an essential element for an electrode, and other additives such as a conductive material and a filler, a binder for binding the powder particles together and adhering them to the current collector, and a solvent for imparting viscosity and dispersing the powder, are mixed together to produce a slurry having fluidity.

[0004] As described above, in conventional electrodes in which a slurry coating method is used to form an electrode active material layer, the binder material in the electrode cannot be distributed uniformly along the thickness direction of the electrode, and a large amount of the binder material is distributed concentratedly on the surface of the electrode active material layer, resulting in a problem of insufficient bonding strength between the electrode active material layer and the current collector. This is a phenomenon caused by migration of the binder material to the surface layer as the solvent evaporates during drying of the slurry.

[0005] To solve these problems, a method for manufacturing a dry electrode has been proposed in which the electrode material is compressed by a dry method without using a solvent when manufacturing the electrode active material layer. However, in addition to the process method that does not simply use a solvent, it is necessary to establish process conditions suitable for manufacturing a dry electrode so that the dry electrode can achieve a predetermined level of adhesive strength. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a negative electrode containing composite particles containing a negative electrode active material and a polymer for a negative electrode binder.

[0007] Another object of the present invention is to provide a negative electrode in which the binder is uniformly distributed in the negative electrode active material layer, and a constant adhesive strength is ensured in the thickness direction of the negative electrode active material layer. It can be easily understood that the above-mentioned objects and advantages of the present invention can be achieved by the means or methods described in the claims, and combinations thereof. [Means for solving the problem]

[0008] A first aspect of the present invention relates to a negative electrode for an electrochemical element, the negative electrode including a current collector and a negative electrode active material layer formed on at least one surface of the current collector, the negative electrode active material layer contains negative electrode composite particles, the negative electrode composite particles include a negative electrode active material and a negative electrode binder polymer, the negative electrode binder polymer including a sticky rubber-based polymer; The negative electrode binder polymer has a particle shape with a predetermined particle size, and the particle size (D 50 ) is 50 nm or more and less than 300 nm, Meet one or more of the following conditions A) to C), In the following A) to C), X u is the shear force in a section of the negative electrode active material layer from the top to the bottom in the thickness direction, where the thickness is 5% to 10% of the total thickness of the negative electrode active material layer (100%), and X d is the shear force in the section of the negative electrode active material layer from the bottom to the top in the thickness direction, where the thickness is 5% to 10% of the total thickness of the negative electrode active material layer (100%), and X a is the average shear force at any two or more points based on the thickness of the negative electrode active material layer, and X b is the deviation of shear force at any two or more points based on the thickness of the electrode active material layer, and X c means adhesive strength: A) 100.000gf / 20mm*MPa <X c ×X a B) 0 MPa <X b <0.280MPa C) 0 MPa <X d -X u <0.200Mpa.

[0009] A second aspect of the present invention is the above-mentioned first aspect, wherein the negative electrode active material layer satisfies all of the above A) to C).

[0010] In a third aspect of the present invention, in any one of the above-described aspects, the negative electrode active material layer may further satisfy the following condition D): t is the particle size of the binder particles (D 50 , unit: nm): D) 0.500 nm -1<100 / X t <1.500nm -1 .

[0011] A fourth aspect of the present invention is any one of the aforementioned aspects, wherein the composite particles contain the negative electrode active material and the negative electrode binder polymer in a weight ratio of 90:10 to 99.9:0.1.

[0012] A fifth aspect of the present invention is any one of the above aspects, wherein said X u and X d are each independently in the range of 2,000 MPa to 4,000 MPa.

[0013] A sixth aspect of the present invention is any one of the above aspects, wherein the X c is 15,000gf / 20mm~50,000gf / 20mm.

[0014] A seventh aspect of the present invention is any one of the above aspects, wherein said X a and X b are each independently, X u and X d This reflects the value of

[0015] An eighth aspect of the present invention is any one of the above-mentioned aspects, wherein the negative electrode active material is a carbon-based material including at least one selected from graphitizable carbon, non-graphitizable carbon, natural graphite, and artificial graphite; Li x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1), and Sn x Me 1-x Me' y O z(Me is Mn, Fe, Pb, or Ge, and Me' is Al, B, P, Si, an element of Group 1, Group 2, or Group 3 of the periodic table, or a halogen, and 0x≦1, 1≦y≦3, and 1≦z≦8), lithium metal, lithium alloys, silicon-based alloys, tin-based alloys, silicon-based oxides including one or more of SiO, SiO / C, and SiO2, and metal oxides including one or more of SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5.

[0016] A ninth aspect of the present invention is any one of the preceding aspects, wherein the composite particles have a particle size (D 50 ) is 40 μm to 70 μm.

[0017] A tenth aspect of the present invention is any one of the aforementioned aspects, wherein the polymer for a negative electrode binder contains a diene-based polymer, an acrylate-based polymer, a fluorine-based polymer, a styrene-based polymer, or two or more of these.

[0018] An eleventh aspect of the present invention is any one of the aforementioned aspects, wherein the composite particles have an aspect ratio of 0.5 to 1.0.

[0019] A twelfth aspect of the present invention is any one of the aforementioned aspects, wherein the composite particles further comprise a conductive material for a negative electrode, and the conductive material for a negative electrode is 10% by weight or less based on 100% by weight of the composite particles.

[0020] A thirteenth aspect of the present invention is any one of the aforementioned aspects, wherein the current collector includes a primer layer disposed between the current collector and the negative electrode active material layer, and the primer layer includes a primer layer conductive material and a primer layer binder.

[0021] A fourteenth aspect of the present invention is any one of the aforementioned aspects, wherein the negative electrode active material layer is formed by pressing a plurality of composite particles together.

[0022] A fifteenth aspect of the present invention relates to an electrochemical device comprising the negative electrode according to the present invention. [Effects of the Invention]

[0023] The negative electrode according to the present invention is manufactured by a dry process using composite particles containing binder particles that satisfy a predetermined particle size range, and therefore the binder polymer is uniformly distributed in the negative electrode active material layer, which results in high binding strength between the negative electrode materials and, as a result, excellent durability and shape stability of the negative electrode active material layer. In addition, high adhesion strength is exhibited between the negative electrode active material layer and the current collector.

[0024] The drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further understand the technical concepts of the present invention as well as the content of the invention, and therefore the present invention should not be interpreted as being limited to only the matters depicted in the drawings. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a diagrammatic representation of the distribution of binder particles in a negative electrode active material layer according to the particle diameter of the binder particles. [Figure 2] FIG. 1 is a schematic diagram showing an example of measuring shear strength at each cutting depth while cutting an active material layer with a microblade using a surface and interface properties analyzer (SAICAS). DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention will be described in detail below. However, the present invention is not limited to the following content, and each component may be variously modified or selectively combined as necessary. Therefore, it should be understood that the present invention includes all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention.

[0027] Throughout this specification, when a part is said to "comprise" a certain component, this does not mean that other components are excluded, but that other components may also be included, unless otherwise specified.

[0028] Furthermore, terms and phrases such as "about," "approximately," and "substantially" used throughout this specification mean values ​​at or near the values ​​when manufacturing and material tolerances of the stated meaning are presented, and are used to prevent unscrupulous infringers from unfairly exploiting the contents of the disclosure in which precise or absolute values ​​are stated to aid in the understanding of the present invention.

[0029] Throughout this specification, the phrase "A and / or B" means "A or B or both."

[0030] Certain terminology used herein is for ease of description only and is not limiting. Terms such as "top," "bottom," "right," "left," "front," "rear," "inside," and "outside" may be used to describe relative positions and orientations of components relative to one another or in the drawings to which reference is made, rather than absolute positions. These terms encompass words containing these terms themselves, their derivatives, and words of similar import.

[0031] As used herein, the term "porosity" refers to the ratio of the volume of pores to the total volume of a structure, and is expressed in units of vol%. It can be expressed as terms such as void ratio or net density. In the present invention, the measurement of porosity is not limited to a specific method. For example, in one embodiment of the present invention, porosity can be measured by the Brunauer-Emmett-Teller (BET) method using nitrogen gas or by mercury penetration (Hg porosimeter) according to ASTM D-2873. Alternatively, the true density of the separator can be calculated from the density (apparent density) of the separator, the composition ratio of the materials contained in the separator, and the density of each component, and the porosity of the separator can be calculated from the difference between the apparent density and the true density (net density).

[0032] As used herein, the term "average particle size (D 50 )" means the particle size at 50% of the cumulative distribution of the number of particles according to particle size, and the particle size can be measured using a laser diffraction method. Specifically, the powder to be measured is dispersed in a dispersion medium, and then the powder is taken into a commercially available laser diffraction particle size distribution analyzer (e.g., Microtrac S3500). When the particles pass through a laser beam, the difference in the diffraction pattern according to the particle size is measured to calculate the particle size distribution. By calculating the diameter of the particles at 50% of the cumulative distribution of the number of particles according to particle size in the measuring device, D 50 The particle size can be measured.

[0033] The "thickness" of each layer included in the electrode in this specification may refer to a value measured by a known method for measuring thickness. The method for measuring thickness is not limited thereto, but may be, for example, a value measured using a thickness measuring instrument (VL-50S-B manufactured by Mitutoyo Corporation).

[0034] The "specific surface area" used in this specification may refer to a value measured by a known method for measuring specific surface area. The measurement method for specific surface area is not limited thereto, but may be, for example, a value measured by a flow method or a stationary method.

[0035] The present invention relates to a negative electrode for an electrochemical device and a method for manufacturing the same. The electrochemical device of the present invention encompasses any device in which an electrochemical reaction occurs, and specific examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors such as supercapacitors. In the present invention, the electrochemical device may preferably be a secondary battery, more preferably a lithium ion secondary battery.

[0036] The negative electrode according to the present invention includes a current collector and a negative electrode active material layer formed on at least one surface of the current collector. In the present invention, the negative electrode active material layer may be manufactured by compressing composite particles, which will be described later, in a powder state. That is, the negative electrode active material layer according to the present invention may be manufactured by a dry manufacturing method, rather than a wet manufacturing method in which an electrode material, such as an electrode active material, is prepared using a fluidized wet slurry mixed with a solvent.

[0037] <Dry electrode> The negative electrode active material layer includes negative electrode composite particles, which include a negative electrode active material and a negative electrode binder polymer (first polymer). The composite particles have a particle shape, with the negative electrode active material bound by the negative electrode binder polymer. That is, the composite particles are formed by a plurality of negative electrode active material particles and polymer particles contacting each other and being fixed and bound by the polymer particles to form an aggregate. The term "dry electrode" means that an electrode is manufactured using the negative electrode composite particles, as described in detail below, and that the use of a solvent is eliminated in this process.

[0038] In one embodiment of the present invention, the negative electrode active material and the negative electrode binder polymer may be contained in a weight ratio of 90:10 to 99.9:0.1, preferably 90:10 to 95:5, based on the total weight of the composite particles. Meanwhile, in another embodiment of the present invention, the composite particles may further contain a negative electrode conductive material (first conductive material) as needed. The negative electrode conductive material may be contained in a range of 0.1 wt% to 20 wt% or less, preferably 0.1 wt% to 10 wt% or less, relative to 100 wt% of the composite particles. For example, the conductive material may be contained in the composite particles in a range of approximately 0.1 to 5 wt%.

[0039] Meanwhile, in one embodiment of the present invention, the composite particles may have an aspect ratio of 0.5 to 1.0. The aspect ratio refers to the ratio of the average major axis length to the average minor axis length of the composite particles, where the average minor axis length refers to the average length of the composite particles in the axial direction having the shortest length, and the average major axis length refers to the average length of the composite particles in the axial direction having the longest length. When the aspect ratio of the composite particles satisfies this range, it is advantageous in terms of having sufficient fluidity suitable for the process.

[0040] On the other hand, in one embodiment of the present invention, the particle diameter (D 50 ) is preferably 70 μm or less, and specifically, may be in the range of 40 μm to 70 μm. The lower limit of the particle size can be controlled in consideration of the particle size of the negative electrode active material particles used. In one embodiment of the present invention, the particle size (D 50 ) is in the range of approximately 15 μm to 20 μm, the composite particles have a particle size (D 50 On the other hand, the particle diameter (D 50 If the particle size exceeds 70 μm and becomes excessively large, the flowability of the electrode powder may decrease.

[0041] In one embodiment of the present invention, the negative electrode active material layer may contain the composite particles in an amount of 95 wt % or more relative to 100 wt % of the negative electrode active material layer, and may further contain free negative electrode active material particles derived from the composite particles, binder particles, conductive particles, etc.

[0042] The negative electrode active material layer is formed by accumulating the composite particles in a layered structure, and has pores corresponding to the interstitial volumes between the composite particles, exhibiting porous characteristics derived from such a structure. In one embodiment of the present invention, the negative electrode active material layer preferably has a porosity of 20 vol% to 40 vol%, taking into consideration aspects such as impregnation with an electrolyte, shape stability, and ionic conductivity.

[0043] Meanwhile, according to one embodiment of the present invention, the thickness of the negative electrode active material layer may be, for example, 10 μm to 300 μm or 30 μm to 300 μm, but the present invention is not limited thereto.

[0044] On the other hand, the negative electrode binder polymer (first polymer) has a particle shape with a predetermined particle size (D 50 ) is 50 nm or more and less than 300 nm. The range may be, for example, more than 66 nm and less than 200 nm. When the first polymer has a particle size in the above range, the first binder is uniformly distributed in the negative electrode active material layer, the intervals between particles are short, and the adhesive area with the negative electrode active material increases, thereby enabling a uniform and consistent adhesive force to be exerted in the negative electrode active material layer.

[0045] <Formula condition> In addition, the negative electrode active material layer according to the present invention has a particle size (D 50 In a more specific embodiment, the negative electrode active material layer satisfies all of the following conditions A) to C): A) 100.000gf / 20mm*MPa <X c ×X a B) 0 MPa <X b <0.280MPa C) 0 MPa <X d -X u <0.200Mpa.

[0046] In one embodiment of the present invention, A) is X c ×X a The upper limit may be 1000.000gf / 20mm*MPa or 800.000gf / 20mm*MPa or 600.000gf / 20mm*MPa or 500.000gf / 20mm*MPa or 300.000gf / 20mm*MPa.

[0047] In one embodiment of the present invention, B) is 0 MPa <X b <0.250MPa or 0MPa <X b <0.235MPa or 0MPa <X b <0.210MPa or 0MPa <X b It can be <0.200 MPa.

[0048] Meanwhile, in one embodiment of the present invention, the negative electrode active material layer satisfies at least one of conditions A) to C) and may additionally satisfy the following condition D). Alternatively, in one embodiment of the present invention, the negative electrode active material layer may satisfy all of conditions A) to D).

[0049] D) 0.500 nm -1 <100 / X t <1.500nm -1. In the above condition D), X t is the particle size of the binder particles (D 50 , unit: nm).

[0050] In the above A) to D), X u means a shear force at any one point in a section of the negative electrode active material layer from the top to the bottom in the thickness direction, the section being 5% to 10% of the total thickness of the negative electrode active material layer (100%). uIn this case, a plurality of electrode samples of a predetermined size are secured, the same points are cut for each electrode, and the average value of these can be used as the shear force value.

[0051] X d means a shear force at any one point in a section of the negative electrode active material layer from the bottom to the top in the thickness direction, the section being 5% to 10% of the total thickness of the negative electrode active material layer (100%). d In this case, a plurality of electrode samples of a predetermined size are secured, the same points are cut for each electrode, and the average value of these can be used as the shear force value.

[0052] X a means the average value of shear forces at any two or more points on the thickness of the negative electrode active material layer. a may be the average value of values ​​obtained using multiple electrode samples.

[0053] X b means the standard deviation of the shear force at any two or more points based on the thickness of the electrode active material layer. b may be the average value of values ​​obtained using multiple electrode samples.

[0054] X t means the particle size of the polymer particles contained in the electrode active material layer.

[0055] X c means adhesive strength. The adhesive strength is measured by attaching an electrode of a predetermined size to a substrate using double-sided tape or the like, and peeling the attached electrode at a speed of 180 mm / min to 220 mm / min. The adhesive strength can be obtained by repeatedly measuring it multiple times and averaging the results. In reference to this, the adhesive strength (X c ) may be the peel strength measured at the part of the electrode where the adhesive strength is weakest. cBy applying this to the surface and interface properties analysis system (SAICAS), an equation can be created using the product of the shear stress values ​​obtained, which can then be used to show the adhesive strength in the thickness direction of the negative electrode active material layer.

[0056] The shear force is measured by pressing a blade into the surface of a sample at a constant angle and speed, measuring the vertical and horizontal forces generated, and converting them into shear stress. In one embodiment of the present invention, the shear force can be measured using a SAICAS EN-EX instrument (manufactured by Daipla Wintes Co., Ltd., Japan).

[0057] In one specific embodiment of the present invention, the shear force can be calculated according to the following formula 1 while cutting the electrode active material layer with a microblade at a constant cutting speed using a surface and interface characterization analyzer (SAICAS).

[0058]

number

[0059] FIG. 2 shows a simplified example of measuring the shear strength for each cutting depth while cutting an active material layer with a microblade using a surface and interface physical properties analyzer (SAICAS). As shown in FIG. 2, when measuring the shear strength for each cutting depth of the active material layer, a microblade provided in the surface and interface physical properties analyzer (SAICAS) can be used to cut the active material layer at a constant cutting speed while applying a constant shear angle (φ). In order to maintain a constant cutting speed while proceeding with this cutting, the horizontal force (F) applied to the microblade is adjusted.h ) and normal force (F v ) are measured, and the shear strength (τ s ) can be calculated.

[0060] On the other hand, the X u and X d may each independently be in the range of 2,000 MPa to 4,000 MPa, for example, may have a value in the range of 2,000 MPa to 3,500 MPa.

[0061] On the other hand, the adhesive force c may range from 15,000 gf / 20 mm to 50,000 gf / 20 mm.

[0062] On the other hand, in one embodiment of the present invention, a and X b When calculating the value of X u and X d In other words, X a and X b When cutting to calculate the value of X u and X d This may include cutting locations to calculate the value of

[0063] Furthermore, due to the aforementioned structural characteristics, the negative electrode active material layer according to the present invention has a uniform distribution of the negative electrode binder polymer in the thickness direction. In a specific embodiment, the negative electrode active material layer may have a binder content (wt%) in the upper 100 wt% and the lower 100 wt% of the negative electrode active material layer, with respect to a point 50% from the current collector, that is, a difference of 10 wt% or less. Furthermore, the binder content in the region extending from the current collector to 15% of the thickness of the negative electrode active material layer toward the surface of the negative electrode and the region extending from the surface of the electrode active material layer toward 15% of the thickness of the negative electrode active material layer toward the current collector may have a difference of 10 wt% or less. Such a binder polymer distribution may depend on the particle size range of the binder polymer and the characteristics of the negative electrode active material layer.

[0064] If the shear force and adhesive force are insufficient, the adhesion between the composite particles and the current collector and between the composite particles may decrease, and the deviation of the shear stress depending on the depth from the surface in the thickness of the negative electrode active material layer may increase. In a specific embodiment of the present invention, if the deviation (standard deviation) is 0.200 MPa or more, it is recognized that the binder is not distributed uniformly in the thickness direction of the negative electrode, and the binding force and resistance may decrease. In addition, the difference in shear force (X d -X u The larger the gradient, the more intense the binder migration. Furthermore, the greater the number of binder resin particles relative to a specific unit area of ​​the negative electrode active material layer and the smaller the gradient in the thickness direction, the more uniformly the binder is distributed within the electrode, improving the adhesion of the negative electrode. A small gradient may indicate that binder migration is minimal and the binder is uniformly distributed. On the other hand, a large gradient in the thickness direction may indicate a difference in the binder content ratio between the upper and lower layers of the electrode.

[0065] Meanwhile, in the negative electrode according to the present invention, the negative electrode active material layer may be manufactured by compressing composite particles. As described below, the negative electrode according to the present invention is characterized in that composite particles containing a negative electrode material are manufactured, and then the composite particles are applied to a current collector or the like and pressed to accumulate the composite particles in a layered structure. In a wet electrode manufacturing method involving adding electrode materials to a solvent to prepare a slurry, the evaporation of the solvent during drying of the slurry induces binder migration, resulting in the binder being distributed in a concentrated manner on the surface of the electrode. However, in the present invention, a method is applied in which dry composite particles are compressed and accumulated in a layered structure without using a solvent, so binder migration does not occur. As a result, the binder is uniformly distributed along the thickness of the negative electrode active material layer.

[0066] The negative electrode active material may be, for example, carbon such as non-graphitizable carbon or graphite-based carbon; x Fe2O3(0≦x≦1), Lix WO₂(0 ≦ x ≦ 1), Sn x Me 1-x Me’ y O z (Me is Mn, Fe, Pb, Ge, Me’ is Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 < x ≦ 1, 1 ≦ y ≦ 3, 1 ≦ z ≦ 8), etc. metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; silicon-based oxides such as SiO, SiO / C, SiO₂; metal oxides such as SnO, SnO₂, PbO, PbO₂, Pb₂O₃, Pb₃O₄, Sb₂O₃, Sb₂O₄, Sb₂O₅, GeO, GeO₂, Bi₂O₃, Bi₂O₄, and Bi₂O₅; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; etc. can be used, but the present invention is not limited to only these.

[0067] The conductive material for the negative electrode is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber and metal fiber; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives; etc. can be used. Specifically, for the uniform mixing and improvement of conductivity of the electrode conductive material, it may contain one or more selected from the group consisting of activated carbon, graphite, carbon black, and carbon nanotubes, and more specifically, it may contain activated carbon.

[0068] In the present invention, the polymer for the negative electrode binder is not particularly limited as long as it can be used as a binder material for an electrochemical device. For example, diene-based polymers, acrylate-based polymers, fluorine-based polymers, styrene-based polymers, or may contain two or more of these.

[0069] Examples of the diene polymer include polymers containing monomer units derived from conjugated dienes such as butadiene and isoprene, and hydrogenated products thereof. The proportion of the monomer units derived from conjugated dienes in the diene polymer is usually 40 wt% or more, preferably 50 wt% or more, and more preferably 60 wt% or more.

[0070] Specific examples include conjugated diene homopolymers such as polybutadiene and polyisoprene; aromatic vinyl-conjugated diene copolymers such as styrene-butadiene copolymer (SBR) which may be carboxy-modified; vinyl cyanide-conjugated diene copolymers such as acrylonitrile-butadiene copolymer (NBR); and hydrogenated SBR, hydrogenated NBR.

[0071] The styrene polymer is a polymer having repeating units derived from a styrene monomer, and examples thereof include styrene homopolymers (polystyrene), styrene copolymers, etc. Examples of the styrene copolymer include block copolymers such as styrene-ethylene-butadiene copolymer, styrene-butadiene-propylene copolymer, styrene-isoprene copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-butadiene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-isoprene block copolymer, and styrene-ethylene-propylene-styrene block copolymer.

[0072] Examples of the acrylate polymer include polymers containing monomer units derived from acrylic acid esters and / or methacrylic acid esters, and the proportion of the monomer units derived from acrylic acid esters and / or methacrylic acid esters in the acrylate polymer is usually 40 wt % or more, preferably 50 wt % or more, and more preferably 60 wt % or more. Specific examples of acrylate polymers include crosslinked acrylate polymers such as 2-ethylhexyl acrylate-methacrylic acid-acrylonitrile-ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-methacrylic acid-methacrylonitrile-diethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate-styrene-methacrylic acid-ethylene glycol dimethacrylate copolymer, butyl acrylate-acrylonitrile-diethylene glycol dimethacrylate copolymer, and butyl acrylate-acrylic acid-trimethylolpropane trimethacrylate copolymer; copolymers of ethylene and (meth)acrylic acid esters such as ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-ethyl methacrylate copolymer; and graft polymers in which a radically polymerizable monomer is grafted onto the copolymers of ethylene and (meth)acrylic acid esters. Examples of radically polymerizable monomers used in the graft polymers include methyl methacrylate, acrylonitrile, and methacrylic acid. In addition, copolymers of ethylene and (meth)acrylic acid, such as ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer, can also be used as the dispersible binder.

[0073] The fluoropolymer may include polyvinylidene fluoride copolymers such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), and poly(vinylidene fluoride)-hexafluoropropyl copolymer (PVDF-HFP), specifically, may include polytetrafluoroethylene (PTFE), and more specifically, may be polytetrafluoroethylene (PTFE).

[0074] In one embodiment of the present invention, the polymer for the negative electrode binder may preferably include one or more of a diene-based polymer and a styrene-based polymer, which may be included in an amount of 60 wt% or more of the total weight of the binder polymer for the negative electrode. In a specific embodiment, the negative electrode may include a styrene-butadiene block copolymer in an amount of 60 wt% or more of the total weight of the binder. Meanwhile, the polymer material for the negative electrode binder may further include a fluorine-based copolymer, a polyolefin-based copolymer, polyethylene oxide (PEO), an acrylate-based copolymer, etc.

[0075] In one embodiment of the present invention, the polymer for the negative electrode binder is preferably particulate because it has excellent binding properties and can suppress a decrease in capacitance and deterioration due to repeated charge and discharge. On the other hand, examples of the particulate binder include a binder in a state in which dispersed binder particles are dispersed in water, such as latex, and a powder obtained by drying such a dispersion.

[0076] On the other hand, if necessary, a filler, which is a component that suppresses expansion of the negative electrode active material layer, may be further added to the negative electrode active material layer. The filler is not particularly limited as long as it is a fibrous material that does not cause chemical changes in the battery, and examples of the filler include olefin polymers such as polyethylene and polypropylene, and fibrous materials such as glass fiber and carbon fiber.

[0077] The current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity, and examples thereof include stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or aluminum or stainless steel whose surface has been surface-treated with carbon, nickel, silver, etc. The current collector can also be formed with minute irregularities on its surface to increase the adhesive strength of the electrode active material, and a wide variety of forms such as a film, sheet, foil, mesh, net, porous material, foam, and nonwoven fabric can be used.

[0078] Meanwhile, in one embodiment of the present invention, the current collector may be entirely or partially coated with a conductive primer on the surface on which the negative electrode active material layer is to be formed.

[0079] The primer layer includes a polymer (second polymer) for the primer layer binder and a conductive material (second conductive material), and the content of the binder and conductive material in the primer layer is preferably 90 wt% or more, or 95% or more, of the total weight of the primer layer. The presence of the primer layer between the current collector and the negative electrode active material layer ensures high adhesion between the current collector and the negative electrode active material layer, thereby improving electrochemical effects such as the lifespan of the battery.

[0080] In one embodiment of the present invention, the binder for the primer layer is a material capable of ensuring stability of the primer layer over time. According to another embodiment of the present invention, the binder for the primer layer is, for example, styrene butadiene rubber (SBR), butadiene rubber (BR), nitrile butadiene rubber (NBR), styrene-butadiene-styrene block polymer (SBS), styrene-ethylene-butadiene block polymer (SEB), styrene-(styrene butadiene)-styrene block polymer, natural rubber (NR), isoprene rubber (IR), ethylene-propylene-diene terpolymer (EPDM), poly(ethylene-co-propylene-co-5-methylene-2-norbornene), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyvinyl chloride, or the like. chloride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene, polypropylene, polyethylene-co-vinyl acetate, polyethylene oxide, polypropylene oxideThe binder may include styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR), polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, or two or more of these.

[0081] Meanwhile, the second conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, graphite such as natural graphite or artificial graphite; carbon black-based carbon compounds such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. More specifically, in order to uniformly mix the conductive materials and improve conductivity, the second conductive material may include activated carbon, graphite, carbon black, carbon nanotubes, or a mixture of two or more of these, and more specifically, may include activated carbon.

[0082] Next, a method for producing the composite particles according to the present invention will be described. According to one embodiment of the present invention, the composite particles can be produced by a method including the steps of mixing a negative electrode active material and a first binder with a dispersion medium to produce a slurry, and spray-drying the slurry.

[0083] First, the negative electrode active material and the first binder are added to a solvent and dispersed therein to prepare a slurry for preparing composite particles. At this time, the slurry may further contain a first conductive material or an additive, if necessary.

[0084] The dispersion medium used to obtain the slurry is most preferably water, but organic solvents can also be used. Examples of organic solvents include alkyl alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol; alkyl ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane, and diglyme; amides such as diethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter also referred to as NMP), and dimethylimidazolidinone; and sulfur-based solvents such as dimethyl sulfoxide and sulfolane. Alcohols are preferred. The use of an organic solvent with a boiling point lower than that of water can increase the drying rate during fluidized bed granulation. Furthermore, since the dispersibility or solubility of the negative electrode binder may change, the viscosity and fluidity of the slurry can be adjusted depending on the amount or type of dispersion medium, thereby improving production efficiency.

[0085] The amount of the dispersion medium used when preparing the slurry can be an amount such that the solids concentration of the slurry is usually in the range of 1 to 50 wt %, or 5 to 50 wt %, or 10 to 30 wt %.

[0086] The method or order for dispersing or dissolving the negative electrode materials, such as the negative electrode active material and the first polymer, in the dispersion medium is not particularly limited. Examples include a method in which the negative electrode active material and the first polymer are added to the dispersion medium and mixed, or a method in which the first binder is dissolved or dispersed in the dispersion medium, and then the negative electrode active material is added and mixed. If the slurry contains a conductive material and / or additives, these components may be added when the negative electrode active material is added. Examples of mixing methods include mixing equipment such as a ball mill, sand mill, bead mill, pigment disperser, stone mill, ultrasonic disperser, homogenizer, and planetary mixer. Mixing may be performed, for example, at room temperature to 80°C for 10 minutes to several hours.

[0087] Next, the slurry is spray-dried. The spray drying method is a method in which a slurry is sprayed into hot air and dried. Atomizers are a typical example of a device used in the spray drying method. There are two types of atomizers: a rotating disk type and a pressing type. The rotating disk type is a method in which the slurry is taken into the approximate center of a disk rotating at high speed, and the slurry is placed on the outside of the disk by the centrifugal force of the disk, at which point it is atomized and dried. The rotation speed of the disk depends on the size of the disk, but is usually 5,000 to 35,000 rpm, preferably 15,000 to 30,000 rpm. On the other hand, the pressing type is a method in which the slurry is pressed and atomized from a nozzle, and then dried.

[0088] The temperature of the slurry to be sprayed is usually room temperature, but may be heated to above room temperature. The temperature of the hot air during spray drying is usually 80°C to 250°C, preferably 100°C to 200°C. In the spray drying method, the method of sucking in the hot air is not particularly limited, and examples include a method in which the hot air and the spray direction flow sideways in parallel, a method in which the slurry is sprayed from the top of the drying tower and descends together with the hot air, a method in which the sprayed droplets come into countercurrent contact with the hot air, and a method in which the sprayed droplets first flow parallel to the hot air and then fall by gravity and come into countercurrent contact.

[0089] Alternatively, the spray-dried product, i.e., the composite particles, may be heat-treated to harden the surface thereof, and the heat-treatment temperature may be generally 80°C to 300°C.

[0090] The composite particles prepared as described above can be used to prepare a negative electrode. A method for preparing a negative electrode according to one embodiment of the present invention will now be described in detail.

[0091] For example, the negative electrode may be manufactured by a method including the steps of coating a plurality of composite particles on a current collector and pressing the coated composite particles to form a negative electrode active material layer.

[0092] First, the composite particles prepared by the above-described method are applied onto a current collector, and at least one surface of the current collector may be provided with a primer layer containing the second conductive material and the second binder, as described above, on all or part of the surface.

[0093] According to one embodiment of the present invention, a negative electrode active material layer can be formed by supplying a plurality of prepared composite particles to a roll-type press molding device using a feeder such as a screw feeder, and at this time, by feeding a current collector to the rolls of the press molding device simultaneously with the supply of the composite particles, the negative electrode active material layer can be laminated directly on the current collector. Alternatively, the composite particles can be dispersed on the current collector, and the composite particles can be uniformly leveled with a blade or the like to adjust the thickness, and then molded using a press device to form the negative electrode active material layer.

[0094] In these methods, the temperature during roll press molding is usually 0°C to 200°C, preferably higher than the melting point or glass transition temperature of the first binder, and more preferably 20°C or more higher than the melting point or glass transition temperature. The molding speed in roll press molding can usually be 0.1 to 20 m / min, or 1 to 10 m / min. The linear pressure between the rolls can usually be 0.2 to 30 kN / cm, or 0.5 to 10 kN / cm.

[0095] To eliminate variations in the thickness of the molded negative electrode and increase the density of the negative electrode active material layer to achieve high capacity, further pressing (post-pressing) can be performed as necessary. Such post-pressing typically involves a roll pressing process. In the roll pressing process, two cylindrical rolls are arranged parallel to each other with a narrow gap between them, rotated in opposite directions, and the electrode is sandwiched between them and pressed. The temperature of the rolls may be adjusted by heating or cooling.

[0096] According to another embodiment of the present invention, there is provided a secondary battery in which an electrode assembly including the positive electrode, the negative electrode, and a separator is housed in a battery case (cylindrical case, prismatic case, pouch, etc.) together with a lithium-containing non-aqueous electrolyte, and an energy storage device including the same as a unit battery, wherein at least one of the positive electrode and the negative electrode may be the above-described electrode.

[0097] The positive electrode may include a current collector and a positive electrode active material layer formed on at least one surface of the current collector. The positive electrode active material layer may include a positive electrode active material, a third conductive material, and a third polymer for a positive electrode binder in a predetermined ratio. The positive electrode active material is not particularly limited as long as it is in the form of a lithium transition metal oxide, lithium metal iron phosphate, or metal oxide, and examples thereof include layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; 1+x Mn 2-x Lithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3); 2-x M xLithium manganese composite oxides represented by Li2Mn3MO8 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); Li in which part of the Li in the chemical formula is replaced by an aluminum ion; 1+x (Ni a Co b Mn c Al d ) 1-x O2 (x = 0-0.03, a = 0.3-0.95, b = 0.01-0.35, c = 0.01-0.5, d = 0.001-0.03, a + b + c + d = 1); lithium metal phosphate LiM P O4 (where M=Fe, CO, Ni, or Mn), disulfide compounds; and Fe2(MoO4)3; however, the present invention is not limited to these.

[0098] Meanwhile, the third conductive material and the third polymer may be used without particular limitations as long as they are generally applicable to a positive electrode, and a person skilled in the art to which the present invention pertains may select and apply an appropriate one. For example, the third conductive material may be selected as a component suitable for a positive electrode with reference to the first or second conductive material. Also, the third polymer may be selected as a component suitable for a positive electrode with reference to the first or second polymer.

[0099] The separator may be a conventional porous polymer film, such as a porous polymer film made from a polyolefin polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, either alone or in combination. Alternatively, an insulating thin film having high ion permeability and mechanical strength may be used. The separator may include a safety reinforced separator (SRS), in which a ceramic material is thinly coated on the surface of the separator. Alternatively, a conventional porous nonwoven fabric, such as a nonwoven fabric made from high-melting-point glass fiber or polyethylene terephthalate fiber, may be used, but the present invention is not limited thereto.

[0100] The electrolytic solution is an electrolyte and includes a lithium salt and an organic solvent for dissolving the lithium salt.

[0101] The lithium salt may be any one that is commonly used in electrolytes for secondary batteries. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C- , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - One selected from the group consisting of:

[0102] The organic solvent contained in the electrolytic solution may be any commonly used organic solvent without any limitation, and may typically be at least one selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ-butyrolactone, propylene sulfite, and tetrahydrofuran.

[0103] In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are highly viscous organic solvents with high dielectric constants, and are therefore suitable for use because they effectively dissociate lithium salts in the electrolyte. When such cyclic carbonates are mixed in an appropriate ratio with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, an electrolyte solution having high electrical conductivity can be prepared, making them even more suitable for use.

[0104] Optionally, the electrolyte stored according to the present invention may further contain additives such as overcharge inhibitors that are typically contained in electrolytes.

[0105] The lithium secondary battery according to one embodiment of the present invention may be completed by forming an electrode assembly by disposing a separator between a positive electrode and a negative electrode, placing the electrode assembly in, for example, a pouch, a cylindrical battery case, or a prismatic battery case, and then injecting an electrolyte. Alternatively, the electrode assemblies may be stacked, impregnated with an electrolyte, and then placed in a battery case and sealed to complete the lithium secondary battery.

[0106] At this time, the specific structures of the secondary battery and the energy storage device are well known and therefore will not be described in this specification.

[0107] The present invention will be described in more detail below with reference to examples to facilitate a better understanding of the present invention. However, the examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples detailed below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0108] Example Example 1 (1) Preparation of current collector with primer layer Carbon black (specific surface area: 30 m) as a conductive material for the primer layer 2 / g, particle size: (70 nm)) 30 parts by weight, styrene-butadiene rubber (SBR) (T g A primer layer slurry was prepared by mixing 69 parts by weight of acrylic acid (-15°C) and 1 part by weight of carboxymethyl cellulose (CMC) as a dispersant with water as a dispersion medium. The content ratio of the conductive material, binder, and dispersant in the slurry was the same as the content ratio of the conductive material, binder, and dispersant in the primer layer to be subsequently formed. The solid content of the primer layer slurry was 7 wt%.

[0109] The prepared primer layer slurry was applied to one side of a copper current collector (thickness: 10 μm) and dried at a temperature of 130° C. to form a primer layer on the entire surface of the copper current collector.

[0110] (2) Manufacturing of composite particles The negative electrode active material contained 1.91 parts by weight of natural graphite with a spheroidization degree of 0.95 and 76.5 parts by weight of artificial graphite with an average spheroidization degree of 0.9, carbon black (Super C65) as a negative electrode conductive material, and modified styrene butadiene copolymer (D 50 A carboxymethyl cellulose solution (Daicel® 2200, solids concentration: 1.5 wt%) and a carboxymethyl cellulose solution (Daicel® 2200, solids concentration: 1.5 wt%) serving as a dispersant were mixed in a weight ratio of 95.6:1.0:2.3:1.1 together with water serving as a dispersant, and a slurry with a viscosity of approximately 3000-5000 cp was produced using a homogenizer. At this time, the solids content in the slurry was 53 wt%, and further water was added to adjust the solids content to 20 wt%. At this time, the viscosity was at a level of 1000 cps or less.

[0111] The slurry prepared above was dried using a spray dryer to prepare composite particles. The conditions of the spray dryer were controlled to an inlet temperature of 180°C and an outlet temperature of 100°C, and the operation was carried out for 3 hours with a rotation speed of 20,000 rpm. Large powders of 150 μm or more were removed from the obtained composite particles using an industrial sieve. The average particle size (D 50 ) was 78 μm.

[0112] (3) Manufacturing of the negative electrode One side of the current collector having the primer layer is coated with a thickness adjusting bar over an area of ​​25 cm 2 The composite particles prepared above were uniformly applied in an amount of 380 mg per layer, and pressed using a roll-to-roll hot rolling molding machine (sheeting machine) at a pressure of 0.7 ton per cm and a temperature of 60°C at a speed of 2 m (meters) per minute to form a negative electrode active material layer, thereby manufacturing a negative electrode.

[0113] Example 2 First polymer D 50A negative electrode was produced in the same manner as in Example 1, except that the thickness of the conductive layer was 90 nm.

[0114] Comparative Example 1 The negative electrode active material contained 1.91 parts by weight of natural graphite with a spheroidization degree of 0.95 and 76.5 parts by weight of artificial graphite with an average spheroidization degree of 0.9, carbon black (Super C65) as a negative electrode conductive material, and modified styrene butadiene copolymer (D 50 A carboxymethyl cellulose solution (Daicel® 2200, solids concentration: 1.5 wt%) and a carboxymethyl cellulose solution (Daicel® 2200, solids concentration: 1.5 wt%) serving as a dispersant were mixed with water serving as a dispersion medium in a weight ratio of 95.6:1.0:2.3:1.1, and a slurry with a viscosity of approximately 3000-5000 cPs was prepared using a homogenizer. The solids content in the slurry was 53 wt%. The slurry was coated on one side of a 10 μm-thick copper (Cu) thin film serving as a negative electrode current collector using a coater. The coating speed was 0.3 m / s, and the coating was dried at a temperature of 120°C using a drying device equipped with a hot air blower and an IR heater. The resultant was rolled using a roll pressing method to obtain a dry film with a dried weight per unit area of ​​380 mg / 25 cm. 2 A negative electrode having a negative electrode active material layer with a loading amount of 10 ...

[0115] Comparative Example 2 First polymer D 50 A negative electrode was produced in the same manner as in Comparative Example 1, except that the thickness was set to 90 nm.

[0116] Comparative Example 3 First polymer D 50 A negative electrode was produced in the same manner as in Comparative Example 1, except that the thickness of the conductive layer was 250 nm.

[0117] Comparative Example 4 First polymer D 50 A negative electrode was produced in the same manner as in Example 1, except that the thickness of the negative electrode was set to 250 nm.

[0118] Measurement method using the Surface and Interface Properties Analysis System (SAICAS) A surface and interfacial cutting analysis system (SAICAS) was used to measure the shear force due to cutting at each point in the thickness of the anode active material layer. The measurement device used was the SAICAS-DN (manufactured by Daipla Wintes Co., Ltd., Japan). The boron nitride blade (blade width: 1 mm, rake angle: 20°, clearance angle: 10°) was set to move at 2 μm / s horizontally and 0.2 μm / s vertically. The mechanical properties between the constituent elements within the anode were measured every 10 μm depth within the anode. The normal and horizontal forces generated during the blade pressing process were measured and converted into shear stress.

[0119] Adhesion strength measurement method A 4cm x 2cm piece of double-sided tape was attached to a glass slide, and a 20mm x 12cm piece was cut. The negative electrode was attached to the double-sided tape using a 2kg roller with a constant force. The glass slide with the negative electrode attached was then placed horizontally at a 180° angle, and the attached negative electrode was peeled off at a rate of 200mm / min, while the force was measured. This was repeated five times, and the average values ​​are shown in the table.

[0120] [Table 1]

[0121] [Table 2] As is clear from the above, it was confirmed that the adhesive strength was reduced compared to the Examples when the particle size of the first binder polymer was excessively large, as in Comparative Examples 3 and 4. On the other hand, in the cases of Comparative Examples 1 and 2, the particle size of the first binder polymer was at a level substantially equivalent to that of Examples 1 and 2, but Comparative Examples 1 and 2 in particular had a large standard deviation, which was confirmed to be the cause of the reduced adhesive strength.

Claims

1. a current collector and a negative electrode active material layer formed on at least one surface of the current collector, the negative electrode active material layer contains negative electrode composite particles, the negative electrode composite particles include a negative electrode active material and a negative electrode binder polymer, the negative electrode binder polymer including a sticky rubber-based polymer; The negative electrode binder polymer has a particle shape with a predetermined particle size, and the particle size (D ５０ ) is 50 nm or more and less than 300 nm, Satisfy one or more of the following conditions A) to C): In the following A) to C), X ｕ is the shear force in a section of the negative electrode active material layer from the top to the bottom in the thickness direction, the thickness of which is 5% to 10% of the total thickness of the negative electrode active material layer (100%), and X ｄ is the shear force in a section of the negative electrode active material layer from the bottom to the top in the thickness direction, the thickness of which is 5% to 10% of the total thickness of the negative electrode active material layer (100%), and X ａ is the average of shear forces at any two or more points based on the thickness of the negative electrode active material layer, and X ｂ is the deviation of shear force at any two or more points based on the thickness of the electrode active material layer, and X ｔ is the particle size of the binder, and X ｃ means adhesive strength, negative electrode: A) 100.000gf / 20mm*MPa<X ｃ ×X ａ B) 0MPa<X ｂ <0.280MPa C) 0Mpa<X ｄ -X ｕ <0.200Mpa。

2. 2. The negative electrode according to claim 1, wherein the negative electrode active material layer satisfies all of conditions A) to C).

3. The negative electrode active material layer further satisfies condition D), and X ｔ is the particle size of the binder particles (D ５０ 3. The negative electrode according to claim 1 or 2, wherein the surface roughness is 100 nm. D)0.500nm －１ <100 / X ｔ <1.500nm －１ 。

4. 2. The negative electrode of claim 1, wherein the composite particles contain the negative electrode active material and the negative electrode binder polymer in a weight ratio of 90:10 to 99.9:0.

1.

5. The X ｕ and X ｄ and each independently is 2.000 MPa to 4.000 MPa.

6. The X ｃ The negative electrode according to claim 1, wherein the surface tension is 15,000 gf / 20 mm to 50,000 gf / 20 mm.

7. The X ａ and X ｂ are each independently X ｕ and X ｄ The negative electrode according to claim 1 , wherein the value of

8. The negative electrode active material may be a carbon-based material including at least one selected from the group consisting of graphitizable carbon, non-graphitizable carbon, natural graphite, and artificial graphite; ｘ Fe ２ O ３ (0≦x≦1), Li ｘ WO ２ (0≦x≦1), and Sn ｘ Me １－ｘ Me' ｙ O ｚ (Me is Mn, Fe, Pb, or Ge, and Me' is Al, B, P, Si, an element of Group 1, Group 2, or Group 3 of the periodic table, or a halogen, and 0x≦1, 1≦y≦3, and 1≦z≦8.), lithium metal, lithium alloys, silicon-based alloys, tin-based alloys, SiO, SiO / C, and SiO ２ Silicon-based oxides containing one or more of the following: SnO, SnO ２ , PbO, PbO ２ , Pb ２ O ３ , Pb ３ O ４ , Sb ２ O ３ , Sb ２ O ４ , Sb ２ O ５ , GeO, GeO ２ , Bi ２ O ３ , Bi ２ O ４ and Bi ２ O ５ 2. The negative electrode according to claim 1, comprising at least one selected from the group consisting of:

9. The composite particles have a particle size (D ５０ 2. The negative electrode according to claim 1, wherein the thickness of the first electrode is 40 μm to 70 μm.

10. The negative electrode according to claim 1 , wherein the polymer for the negative electrode binder comprises a diene-based polymer, an acrylate-based polymer, a fluorine-based polymer, a styrene-based polymer, or two or more of these.

11. 2. The negative electrode according to claim 1, wherein the composite particles have an aspect ratio of 0.5 to 1.

0.

12. 2. The negative electrode according to claim 1, wherein the composite particles further contain a conductive material for a negative electrode, and the conductive material for a negative electrode is 10% by weight or less based on 100% by weight of the composite particles.

13. 2. The negative electrode according to claim 1, wherein the current collector includes a primer layer disposed between the current collector and the negative electrode active material layer, the primer layer including a primer layer conductive material and a primer layer binder.

14. The negative electrode according to claim 1 , wherein the negative electrode active material layer is formed by pressing a plurality of composite particles together.

15. An electrochemical element comprising the negative electrode according to claim 1 , a positive electrode, and a separator sandwiched between the negative electrode and the positive electrode.

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