Composite binder for dry process, method for preparing composite binder, dry electrode composition containing composite binder, electrode including dry electrode composition, and secondary battery including electrode

Abstract

The present invention relates to technology concerning dry electrode compositions. More specifically, the present invention relates to: a composite binder for a dry process, the composite binder having a novel structure capable of improving adhesion while including a fluorine-based resin; a dry electrode composition containing the composite binder and thus having excellent electrochemical properties as well as superb adhesion; an electrode including the electrode composition; and a secondary battery including the electrode.

Description

Composite binder for a dry process, a method for manufacturing the composite binder, a dry electrode composition comprising the composite binder, an electrode comprising the dry electrode composition, and a secondary battery comprising the electrode.

[0001] The present invention relates to a technology concerning a dry electrode composition, and more specifically, to a composite binder for a dry process having a novel structure capable of improving adhesion while containing a fluorine-based resin, a dry electrode composition containing the same that exhibits excellent adhesion and also excellent electrochemical properties, an electrode containing the electrode composition, and a secondary battery containing the electrode.

[0002] A secondary battery is a type of energy storage device that can be used for a long time through the charging and discharging process. The most common secondary battery is the lithium-ion battery, which is a secondary battery that operates through the movement of metal ions such as lithium ions (Li+) or sodium. The main components constituting the electrode of a secondary battery are three components: an active material that exhibits electrochemical properties, a conductive material to impart electrical conductivity, and a binder used to provide cohesion between these components and adhesion to the metal electrode plate, which is the current collector.

[0003] Conventional electrode manufacturing methods are wet coating methods, in which all components are placed in a solvent and dispersed to form a slurry, which is then formed onto a current collector to a specific thickness to manufacture an electrode. This method requires removing the solvent and recovering the removed solvent, a process that consumes a large amount of energy. However, the dry coating method was developed to minimize this energy consumption. In this method, all components are mixed without using a solvent to create an electrode composition mixture, which is then calendered to form a dry electrode sheet of a specific thickness, and this sheet is attached to a current collector to manufacture the electrode. Since the dry method does not use a solvent, the solvent removal and recovery processes are unnecessary, allowing for the minimization of energy consumption. However, the dry method presents a new challenge: it must create an electrode composition mixture without using a solvent, and it must overcome the need to produce electrodes that satisfy not only electrochemical properties but also adhesion performance, such as adhesion and cohesion, by utilizing a so-called calendering technique that differs from conventional coating processes.

[0004] Fluorinated resin particles known as polytetrafluoroethylene (PTFE) are used as binders in the dry method. However, PTFE has a low solubility parameter, resulting in poor compatibility with other materials. Furthermore, it exhibits poor cohesion with other components and poor adhesion to current collectors. Additionally, there is a very high probability of delamination occurring due to dimensional changes, such as shrinkage and expansion of the electrode layer caused by repeated charging and discharging. This delamination includes micro-delamination between components within the electrode layer and interfacial delamination between the current collector and the electrode layer. Moreover, in the event of a battery fire, gases containing fluorine, such as hydrofluoric acid, are generated, posing a high risk of environmental pollution and human casualties. These disadvantages ultimately act as factors that negatively affect the electrochemical characteristics, long-term reliability, and stability of secondary batteries manufactured from this process.

[0005] To address these issues, a composite binder is sometimes created and used by mixing it with another compound (hereinafter referred to as "other binder") used as a binder for secondary batteries. This method allows for maintaining performance as a battery while reducing the fluorine content within the binder, or addresses the problems associated with existing binders composed of fluorine components. There are various methods for mixing PTFE with other binders, but the simplest method is to manufacture a composite binder by simply mixing PTFE particles and other binder particles using a dry blender. However, this method is difficult to achieve uniform mixing in fine sizes because the shape, size, and electrostatic properties that may occur during mixing of the two particles must be similar. In particular, there is a limitation that the other binder must be in a particulate state.

[0006] Additionally, PTFE particles can be mixed with other binders using the liquid blending method. This method involves preparing an aqueous dispersion of PTFE particles and mixing and stirring it with a binder solution containing dissolved other binders to ensure that the PTFE particles and the other binder molecules are mixed. A significant advantage of this method is that all impurities introduced during the preparation of the PTFE aqueous dispersion can be removed during the washing and purification processes following the mixing of the two materials. While this method yields a more uniform mixture than the particle-to-particle dry blending method, there is a high possibility that achieving a truly uniform mixture is difficult when the solvent systems are different—that is, when mixing an organic binder dissolved in a PTFE aqueous dispersion—because the two materials have a very strong tendency to separate immediately once stirring is stopped.

[0007] To overcome these drawbacks, it is necessary to develop a composite binder by integrally combining fluoropolymer particles, such as PTFE, with other binders suitable for secondary batteries. If such a composite binder with enhanced adhesion is used as a binder for dry electrodes, the adhesion of the dry electrodes will increase, thereby improving long-term electrochemical properties.

[0008] Accordingly, the objective of the present invention is to provide a composite binder for a dry process comprising a new structure capable of improving adhesion while including fluorine-based resin particles, namely a structure in which a membrane-structure formed of a second binder surrounds a plurality of clusters formed by a plurality of first binder particles, which are fluorine-based resins, oriented in a thin and elongated manner, a method for manufacturing the same, and a dry electrode composition comprising the same.

[0009] Another objective of the present invention is to provide a dry electrode manufactured from a dry electrode composition comprising a composite binder for a dry process, wherein the adhesion characteristics of the electrode layer are improved compared to conventional fluoropolymer particle binders.

[0010] Another objective of the present invention is to provide a secondary battery having excellent electrochemical characteristics, such as initial efficiency and capacity retention rate, by including a dry electrode with improved characteristics.

[0011] The objectives of the present invention are not limited to those mentioned above, and may naturally include objectives of the invention that a person skilled in the art can recognize from the description in the detailed description of the invention that follows, even if not explicitly mentioned.

[0012] To achieve the objectives of the present invention as described above, the present invention provides a composite binder for a dry process comprising: a plurality of particle clusters formed by orientation of fluoropolymer particles and / or first binder particles, which are core-shell structure composite binder particles in which the surface of the fluoropolymer particles is wrapped with a second binder; and a plurality of membrane structures formed of a second binder that partially and / or entirely wraps some and / or all of the plurality of clusters.

[0013] In a preferred embodiment, the fluorine resin comprises one or more selected from the group consisting of fluorine homopolymers containing a fluorine component, fluorine copolymers, or combinations thereof.

[0014] In a preferred embodiment, the first binder particle has a diameter of 0.05 to 5.0 microns.

[0015] In a preferred embodiment, the first binder particle comprises polytetrafluoroethylene (PTFE).

[0016] In a preferred embodiment, the second binder comprises one or more of an acrylonitrile-based copolymer in which one or more of a compound having an acrylonitrile group, a compound having a glycol group, a compound having a styrene group, a compound having a butadiene group, and a compound having a carboxyl group are copolymerized, other binder resins for secondary batteries, or combinations thereof.

[0017] In a preferred embodiment, the acrylonitrile-based copolymer is one or more of an acrylonitrile-maleic acid copolymer, an acrylonitrile-acrylic acid copolymer, an acrylonitrile-butadiene copolymer, and an acrylonitrile-ethylene glycol-maleic acid copolymer.

[0018] In a preferred embodiment, the acrylonitrile-based monomer has a form in which a cyano group is attached to a vinyl group as the main chain.

[0019] In a preferred embodiment, the acrylonitrile-maleic acid copolymer is composed of 80-99.98 mol% acrylonitrile-based monomer and 0.02-20 mol% maleic acid-based monomer.

[0020] In a preferred embodiment, the maleic acid monomer is one or more of maleic acid anhydride compounds, which are maleic acid or its salt or anhydrous forms.

[0021] In a preferred embodiment, the maleic acid-based monomer is maleic anhydride.

[0022]

[0023] In a preferred embodiment, the acrylonitrile copolymer has a weight-average molecular weight of 50,000 to 5,000,000 grams / mol.

[0024] In a preferred embodiment, the other binder resin for a secondary battery is one or more selected from the group consisting of polyolefin, polyalkylenes, polyvinylidene fluoride (PVDF), carboxymethylcellulose, styrene-butadiene rubber (SBR), nitrile rubber, styrene-butadiene-styrene copolymer, polyacrylic acid, polyethylene-block-poly(ethylene glycol), poly(ethylene oxide), poly(phenylene oxide), cellulose, derivatives of cellulose or cellulose salts, polyethylene-block-poly(ethylene glycol), polyacrylonitrile (PAN), polydimethylsiloxane and combinations thereof.

[0025] In a preferred embodiment, when the second binder is a combination of the acrylonitrile-based copolymer and another binder resin for a secondary battery, the acrylonitrile-based copolymer and the other binder resin for a secondary battery are included in a weight ratio of 90 to 10:10 to 90.

[0026] In a preferred embodiment, the plurality of clusters and the membrane structure are included in a weight ratio of 10:90 to 90:10.

[0027] In a preferred embodiment, it includes one or more of a core-shell structure and a layered structure.

[0028] In addition, the present invention provides a method for manufacturing a composite binder for a dry process, comprising the steps of: preparing a first binder dispersion by dispersing first binder particles, which are fluorine-based resins, in a solvent; preparing a second binder solution by dissolving a second binder in a solvent; a first stirring step of rotating the first binder dispersion at high speed to form a plurality of clusters formed by the orientation of a plurality of first binder particles; a second stirring step of rotating at high speed while introducing the second binder solution into the first binder dispersion in which the plurality of clusters are formed; and a post-processing step of filtering, washing, and drying the obtained result.

[0029] In a preferred embodiment, the content of the first binder particles dispersed in the first binder dispersion and the second binder dissolved in the second binder solution has a weight ratio of 90 to 10:10 to 90.

[0030] In a preferred embodiment, high-speed rotation in the first stirring step and the second stirring step is performed at a speed of 2,000-30,000 rpm for 10 minutes to 10 hours under temperature conditions of 20-70 degrees.

[0031] In a preferred embodiment, an interfacial binder comprising fluorine and silicon or titanium may be further added in the first stirring step and the second stirring step.

[0032] In a preferred embodiment, the interface binder is a fluorosilane-based or fluorotitanium-based interface binder and may be added in an amount of 0.1 to 10 parts by weight relative to the weight of the first binder particles.

[0033] In addition, the present invention provides a dry electrode composition comprising an active material, any one of the dry process composite binders described above, a dry process composite binder manufactured by any one of the manufacturing methods described above, and a nanocarbon material.

[0034] In a preferred embodiment, the active material may be included in 85-98% by weight, the composite binder for the dry process in 1.0-10% by weight, and the nanocarbon material in 1.0-5% by weight.

[0035] In a preferred embodiment, the nanocarbon material is any one selected from the group consisting of carbon nanotubes (single-wall, double-wall, multi-wall, and branched), carbon nanoplates, vapor-polymerized carbon nanofibers, carbon nanoribbons, conductive carbon black, graphene nanoplates, carbon balls, and combinations thereof.

[0036] In a preferred embodiment, the nanocarbon material comprises a nanocarbon material having an aspect ratio of 100 or more and a nanocarbon material having an aspect ratio of less than 100 in a weight ratio of 10:90 to 90:10.

[0037] In addition, the present invention provides a dry electrode sheet composed of the dry electrode composition described above.

[0038] In addition, the present invention provides a dry electrode comprising the dry electrode sheet described above.

[0039] In addition, the present invention provides a secondary battery comprising the dry electrode described above.

[0040] The composite binder for a dry process and the method for manufacturing the same according to the present invention described above include a new structure capable of manufacturing a dry electrode with improved adhesion while containing fluorine-based resin particles, namely a structure in which a membrane-structure formed of a second binder surrounds a plurality of clusters formed by a plurality of first binder particles, which are fluorine-based resins, being oriented in a thin and elongated manner.

[0041] In addition, the dry electrode composition of the present invention includes a composite binder for a dry process, and while using a small amount of fluorine-containing organic compounds mainly used as binders in electrode compositions for secondary batteries, it exhibits excellent adhesion and excellent electrochemical properties.

[0042] In addition, the dry electrode of the present invention is manufactured with a dry electrode composition comprising a composite binder for a dry process, and adhesive properties such as binding strength and adhesion strength between components within the electrode layer can be improved compared to conventional fluoropolymer particle binders.

[0043] In addition, the secondary battery of the present invention includes an electrode that maintains long-term reliability stably by improving properties such as adhesion, so it has the advantage of stably maintaining electrochemical properties such as electrical capacity and charge / discharge cycle characteristics.

[0044] These technical effects of the present invention are not limited to the scope mentioned above, and naturally include effects of the invention that a person skilled in the art can recognize from the description of specific details for implementing the invention that follows, even if not explicitly mentioned.

[0045] Figure 1 is an example of the chemical structural formula of the acrylonitrile-maleic anhydride copolymer of the present invention.

[0046] Figure 2 shows a PTFE aqueous dispersion (solid content 50%) according to an embodiment of the present invention.

[0047] FIG. 3 is a view of a PTFE aqueous dispersion rotated at high speed (5,000 rpm) according to an embodiment of the present invention.

[0048] Figure 4 is an electron microscope image of the PTFE particles of the present invention.

[0049] FIG. 5 is an electron microscope image of a composite binder according to an embodiment of the present invention (a shape in which copolymer 1 surrounds a fiberized PTFE particle cluster).

[0050] Figure 6 is an electron microscope image of a composite binder according to an embodiment of the present invention.

[0051] Figure 7 is an enlarged photograph of the PTFE particle cluster of Figure 5.

[0052] Figure 8 shows the FTIR spectrum results for a composite binder containing an acrylonitrile-maleic anhydride copolymer.

[0053] Figure 9 shows the FTIR spectrum results for a composite binder containing an acrylonitrile-ethylene glycol-maleic acid copolymer.

[0054] Figure 10 shows the FTIR spectrum results for a composite binder containing a styrene-butadiene copolymer.

[0055] FIG. 11 is the result of a charge / discharge cycle test for a coin cell according to one embodiment of the present invention.

[0056] The terms used in this invention are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the description of the invention, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0057] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component.

[0058] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this invention.

[0059] In interpreting the components, they shall be interpreted as including a margin of error even without separate explicit notation. In particular, when terms of degree such as "approximately" or "substantially" are used, they may be interpreted as referring to or close to the numerical value where inherent manufacturing and material tolerances are presented.

[0060] In the case of an explanation of a temporal relationship, for example, when the temporal sequence is explained using 'after', 'following', 'next', 'before', etc., it includes cases where the sequence is not continuous unless 'immediately' or 'directly' is used.

[0061] Hereinafter, the technical configuration of the present invention will be described in detail with reference to the attached drawings and preferred embodiments.

[0062] However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Throughout the specification, the same reference numerals used to describe the present invention indicate the same components. Furthermore, in describing the present invention, if it is determined that a detailed description of related known components or functions could obscure the essence of the invention, such detailed description is omitted.

[0063] The technical features of the present invention lie in a composite binder for a dry process and a method for manufacturing the same, comprising a structure in which a plurality of first binder particles, which are composite binder particles having a fluoropolymer resin and / or a core (fluoropolymer resin particle)-shell (second binder) structure, are oriented in a thin and elongated manner and formed into a plurality of clusters, which are then encased by a membrane structure formed of a second binder. Furthermore, the invention relates to a high-adhesion dry electrode composition containing the composite binder for a dry process that exhibits excellent adhesion and excellent electrochemical properties, a dry electrode that possesses high adhesion by enhancing the adhesion between the electrode layer and the current collector and / or the cohesion between the individual components within the electrode by including the high-adhesion dry electrode composition, thereby maintaining stable electrical conductivity, and a secondary battery that maintains stable electrochemical properties such as electrical capacity and charge / discharge cycle characteristics by including the dry electrode that maintains stable electrical conductivity.

[0064] In other words, the present invention develops a composite binder of a novel structure by liquid-fiberizing core-shell structured composite binder particles [i.e., core (fluorine resin particle)-shell (second binder) structured composite binder particles], in which the surface of the fluorine resin particles and / or the fluorine resin particles is wrapped with a second binder, to form multiple thin and elongated oriented clusters, and then wrapping some and / or all of the multiple clusters with a membrane structure formed of the second binder, in order to increase adhesion while using fluorine resin particles; at the same time, it has been experimentally confirmed that a composite binder with improved adhesion can be obtained by using an acrylonitrile-based copolymer containing acrylonitrile groups for some or all of the second binder.

[0065] Accordingly, the composite binder for dry processes according to the present invention comprises: a plurality of clusters formed by orienting a plurality of first binder particles, which are core-shell structured composite binder particles in which the surface of a fluoropolymer resin and / or a fluoropolymer resin particle is wrapped with a second binder; and a plurality of membrane structures formed by a second binder that partially and / or entirely wraps some and / or all of the plurality of clusters. Accordingly, the overall form of the composite binder for dry processes according to the present invention is not limited and can be implemented in various forms as long as the plurality of membrane structures are arranged in a manner that minimizes the exposure of the plurality of clusters and are implemented in a combined form of the plurality of clusters and membrane structures. Furthermore, the composite binder for dry processes according to the present invention may contain a plurality of clusters and membrane structures in a weight ratio of 10:90 to 90:10; however, if the content of the clusters and membrane structures deviates from the set range, the effects obtainable by the composite formation of the two types of binders, namely fiberization performance and adhesion performance, cannot be effectively controlled, which is rather disadvantageous.

[0066] As one embodiment, the composite binder for dry processes of the present invention may be implemented such that a membrane structure made of the second binder partially and / or entirely encloses a plurality of clusters formed of fluoropolymer particles and / or composite binder particles having a core (fluoropolymer particles)-shell (second binder) structure, as shown in FIGS. 5 and 6. Accordingly, as one embodiment, the composite binder for dry processes may be formed in a form in which a membrane structure made of the second binder encloses a portion and / or the entirety of a cluster formed of first binder particles, that is, in a form in which the clusters generally form the core and the membrane structure forms the shell. Additionally, FIG. 7 is an electron microscope image of the PTFE particles of FIG. 5, which shows that, unlike the PTFE particles in the pristine state prior to high-speed rotation of the PTFE aqueous dispersion (Fig. 4), the surface is covered with a different material, and this surface material is a copolymer of the present invention that has strong adhesive properties. Therefore, the PTFE particles within these clusters have a so-called core-shell structure in which PTFE particles are located inside and the surface is wrapped with the copolymer of the present invention. In summary, the composite binder of the present invention can be understood as having a shape in which core-shell structured composite binder particles gather to form a cluster, and the cluster is then wrapped by the copolymer, either wholly or partially, as described above.

[0067] Here, among the first binder particles forming a plurality of clusters included in the composite binder of the present invention, the fluorine resin is not limited to any material that contains a fluorine component and maintains a particulate form in a solvent, but may include one or more of a polymer composed of a fluorine homopolymer, a fluorine copolymer, or a combination thereof. As one embodiment, fluorine resin particles such as polytetrafluoroethylene (PTFE), fluoroethylene propylene (FEP), polyvinylidene fluoride (PVDF), and copolymers thereof may be used, and in particular, may include PTFE. As one embodiment, the diameter of the fluorine resin particles, i.e., the first binder particles, may be 0.05 to 5.0 microns. If the particle size of the first binder is less than 0.05 microns, the particles are too small, making it difficult to form fluorine resin particles or fluorine resin dispersions, which is disadvantageous; and if it is 5 microns or more, the particles are too large, making it difficult to use as a dry binder, which is rather disadvantageous.

[0068] The cluster is a structure formed by the arrangement of multiple first binder particles, and may be in the form of clusters of multiple fluoropolymer particles and / or composite binder particles with a core (fluoropolymer particle)-shell (second binder) structure, clustered in the form of thin, long fibers like a grape cluster. In one embodiment, when PTFE, a fluoropolymer particle, is used as the first binder particle, the cluster can be obtained by liquid phase fibrilization of a PTFE dispersion. The liquid phase fibrilization technique is a method devised in the present invention in which fluoropolymer particles existing in a dispersion state are processed within a solvent to arrange the fluoropolymer particles in a thin, long shape, i.e., to form fibers. As described below, the first binder particles included in the composite binder of the present invention may, as another embodiment, be core-shell structured composite binder particles in which the surface of a plurality of PTFE particles is surrounded by a second binder, and the plurality of clusters may be formed solely of core-shell structured composite binder particles or formed by mixing core-shell structured composite binder particles and PTFE particles. Furthermore, it was experimentally confirmed that a composite binder comprising a structure in which a membrane structure formed by the second binder is arranged to surround part and / or all of a cluster formed by the aggregation of core-shell structured composite binder particles is advantageous for the manufacture of dry electrodes.

[0069] The membrane structure included in the composite binder of the present invention is composed of a second binder and is implemented to have a membrane form that partially and / or entirely encloses a plurality of clusters composed of a plurality of first binder particles, and the overall form is not limited.

[0070] The second binder is a material that forms the shell of the membrane-structure and core-shell structure composite binder particles, and is not limited to a compound that can form a membrane shape by being located on the surface of a cluster of first binder particles and partially and / or wholly surrounding it, but is a polymer that is soluble in organic or aqueous solvents, and may include one or more of the acrylonitrile-based copolymer developed in the present invention, other binder resins for secondary batteries, or combinations thereof.

[0071] Here, the acrylonitrile-based copolymer developed in the present invention may be a polymer in which one or more of a compound having an acrylonitrile group, a compound having a glycol group, a compound having a styrene group, a compound having a butadiene group, and a compound having a carboxyl group are copolymerized. Since the properties of a copolymer can be controlled according to the type and content ratio of the constituent components, the present invention is based on the fact that acrylonitrile groups can impart electrochemical properties. Based on this, an acrylonitrile-based copolymer was developed by selecting a compound having a functional group capable of supplementing flexibility, adhesion, and ion conductivity by copolymerizing it with a compound having an acrylonitrile group. Here, the compound having a glycol group may be a compound such as ethylene glycol or propylene glycol, and the compound having a carboxyl group may be acrylic acid, maleic acid or maleic anhydride, acrylate, etc.

[0072] Specifically, the acrylonitrile-based copolymer may be one or more of acrylonitrile-maleic acid copolymer, acrylonitrile-acrylic acid copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-maleic acid copolymer, and acrylonitrile-ethylene glycol-maleic acid copolymer.

[0073] Here, the weight-average molecular weight of the acrylonitrile copolymer may be in the range of 50,000 to 5,000,000 grams / mol. If the weight-average molecular weight of the copolymer is less than 50,000 grams / mol, the molecular weight is too low, which is disadvantageous as it results in poor mechanical properties of the electrode layer. If it is 5,000,000 grams / mol or more, it is difficult to obtain using a general radical polymerization method, and furthermore, the molecular weight is too high and the viscosity is too high, which makes it difficult to uniformly disperse the active material and the conductive material.

[0074] More specifically, among the acrylonitrile-based copolymers used in the present invention, the acrylonitrile-maleic acid copolymer has particularly strong adhesive strength and is particularly effective in enhancing the adhesion of an electrode layer containing a composite binder; therefore, we will examine the specific composition.

[0075] The acrylonitrile-maleic acid copolymer is a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer. In this invention, it was adopted for the first time as a binder for manufacturing dry electrodes that can be used in electrode compositions for secondary batteries. Through numerous experiments, it was confirmed that, as described above, the acrylonitrile-based monomer can impart electrochemical properties to the electrode, and the maleic acid-based monomer can enhance the binding properties between the metal current collector or the components within the electrode.

[0076] Accordingly, the acrylonitrile-maleic acid copolymer is not limited to being a copolymer obtained by reacting an acrylonitrile-based monomer and a maleic acid-based monomer as shown in FIG. 1, but the content ratio of these components has a wide range of content ratios depending on the type of copolymer, such as a general random copolymer, block copolymer, or graft copolymer. In one embodiment, 80-99.98 mol% of acrylonitrile-based monomer and 0.02-20 mol% of maleic acid-based monomer may be included. This is because if the content of the maleic acid component in the copolymer is lower than 0.02 mol%, the content of the component capable of increasing adhesion is too low, resulting in a significantly reduced effect of enhancing adhesion, and if it exceeds 20 mol%, not only is the increase in adhesion according to the maleic acid content not proportionally large, but the copolymerization reaction becomes too slow. In particular, it may be composed of 85-99.5 mol% of an acrylonitrile-based monomer and 0.5-15 mol% of the maleic acid-based monomer.

[0077] At this time, the acrylonitrile monomer is not limited to being a compound in which a cyanide (-CN) group is attached to a vinyl group (CH2=CH-) as a backbone; for example, any compound having a -CN group on a vinyl group can be used, such as one composed of an acrylonitrile compound alone, one composed together with other compounds as a copolymer, or an acrylonitrile compound in which the -H of the vinyl group constituting the acrylonitrile monomer has a different functional group. A representative example would be CH2=CH-CN.

[0078] Maleic acid monomers are not limited to being composed of two carboxylic acids or having a so-called 5-membered ring structure composed of five carbons and oxygens; as one embodiment, one or more maleic anhydride compounds, such as maleic acid, salts thereof, or anhydrous forms thereof, may be used. Representatively, maleic anhydride (MAH) may be used as a maleic acid monomer. Maleic anhydride is a type of maleic acid with particularly excellent adhesive properties, and can significantly improve adhesion even when used in small amounts; it is a compound that can be produced in the form of graft or random copolymerization.

[0079] Meanwhile, acrylonitrile-maleic acid copolymers can be synthesized by using one or more reaction initiators in combination or sequentially among various methods, such as radical polymerization using 2,2-azobisisobutyronitrile (AIBN), peroxides, oxidizing agents, or photoinitiators; ionic polymerization; oxidative polymerization represented by ammonium persulfate; redox polymerization using redox reactions; methods using organic acid-based reaction initiators such as acetic acid or para-toluenesulfonic acid; or thermal polymerization. Additionally, the copolymers of the present invention may be prepared by emulsion polymerization. However, in emulsion polymerization, emulsifiers or dispersants are used to carry out the copolymerization reaction, and if these additives, such as emulsifiers and dispersants, remain after the reaction, there is a high possibility that they will affect the mechanical properties and electrochemical characteristics of the dry electrode layer. Therefore, it is advantageous to use radical polymerization, which allows the copolymer to be synthesized without using such additives, for all copolymers of the present invention.

[0080] In one embodiment, the present invention comprises a first step of preparing a reaction solution by adding an acrylonitrile monomer and a maleic acid monomer to a solvent in molar ratios; a second step of adding a reaction initiator after raising the reaction solution to a reaction temperature while stirring and heating; and a third step of obtaining the copolymer after a washing process following the completion of the synthesis reaction. That is, the acrylonitrile-based monomer and the maleic acid-based monomer are weighed, placed in a solvent, and raised to a reaction temperature while stirring; then, the copolymer is synthesized by inducing a copolymerization reaction while slowly adding a reaction initiator. As the synthesis reaction proceeds, the viscosity of the reaction solution increases, and in some cases, solidified particles are formed. After the copolymerization reaction is completed, the copolymer is obtained through conventional purification processes such as precipitation with a non-solvent, filtering, and washing.

[0081] In the first step, a reaction solution is prepared using various solvents such as DMF or water, and in the second step, the reaction can be carried out for 1 to 72 hours at a reaction temperature in the range of 50 to 120°C. If the reaction temperature is below 50°C and the reaction time is less than 1 hour, the reaction does not proceed well because the temperature is too low or the reaction time is too short, and if the temperature exceeds 120°C or the reaction time exceeds 72 hours, the reaction may be too rapid or the synthetic product may be deformed due to the reaction taking too long.

[0082] The molecular weight of the synthesized copolymer can be controlled by adjusting the details of the above synthesis reaction, namely the content of reactants and reaction initiators, the order or rate of addition, reaction temperature, time, and other detailed reaction conditions.

[0083] Next, the method for manufacturing a composite binder for a dry process according to the present invention comprises: a step of preparing a first binder dispersion by dispersing first binder particles, which are fluorine-based resins, in a solvent; a step of preparing a second binder solution by dissolving a second binder in a solvent; a first stirring step of forming a plurality of clusters formed by orienting a plurality of first binder particles by rotating the first binder dispersion at high speed; a second stirring step of rotating at high speed while introducing the second binder solution into the first binder dispersion in which the plurality of clusters are formed; and a post-processing step of filtering, washing, and drying the obtained result.

[0084] Here, the content of the first binder particles dispersed in the first binder dispersion and the second binder dissolved in the second binder solution has a weight ratio of 90 to 10:10 to 90. If the content ratio of the first binder and the second binder is outside the set range, the effects obtained by combining the two types of binders, namely fiberization performance and adhesive performance, cannot be effectively controlled, which is rather disadvantageous.

[0085] In the first stirring step and the second stirring step above, high-speed rotation can be performed at a speed of 2,000-30,000 rpm for 10 minutes to 10 hours under temperature conditions of 20-70 degrees.

[0086] If necessary, an interfacial coupling agent containing fluorine and silicon or titanium may be further added during the first and second stirring steps. This interfacial coupling agent is an additive capable of interfacially bonding the first binder particles, which are fluorine-based resins, and the second binder. It can be used to produce a more uniform composite binder by enhancing the compatibility between the first binder particles and the second binder layer. The interfacial coupling agent can be used without limitation as long as it is a compound in which one side consists of a fluorine component and the other side consists of a component that is compatible with these polar groups. Representative compounds that can be used as interfacial coupling agents are fluorosilane or fluorotitanium-based coupling agents, which are surfactants containing components such as fluorine, silicon, and titanium. When used in small amounts, these interfacial coupling agents can enhance the compatibility between the first binder particles and the second binder, which are fluorine-based resins and have poor compatibility with each other, thereby improving dispersibility and bonding strength. Additives such as interfacial binders may be water-based or organic-based fluorosilane compounds depending on the solvent system. The content of the interfacial binder added may be 0.1 to 10 parts by weight relative to the weight of the first binder particles, and 0.5 to 5 parts by weight may be preferable. If the content of the interfacial binder is less than 0.1 parts by weight, the effect of interfacial bonding is insufficient and is disadvantageous; if it exceeds 10 parts by weight, the effect of enhancing interfacial bonding is insufficient relative to the added content, and there is a concern that an excessive amount may act as an impurity, which is rather disadvantageous.

[0087] The method for manufacturing a composite binder for a dry process according to the present invention described above is implemented by the liquid blending method developed in the present invention. The liquid blending method is a method for manufacturing a composite binder in which two binders are microscopically combined by adding a second binder solution, in which the binder to be combined is dissolved, to a first binder dispersion in which one type of binder in a particulate state is dispersed in a solvent. This method may include a first stirring step and a second stirring step in which liquid fiberization occurs. Since the liquid blending method developed in the present invention is a method of mixing while the binder is dissolved or dispersed in a solvent, it can be used regardless of the type of binder as long as it is soluble in organic and / or water-based solvents. In particular, it has the advantage of being able to manufacture a mixed binder composed of pure polymers by removing impurities that may be included in the manufacture of fluoropolymer particles or other binders during the washing process.

[0088] According to the manufacturing method of the present invention, a microscopically uniformly composited binder having various compositions can be manufactured through a liquid-phase blending method. As one embodiment, a method for manufacturing a composite binder by liquid-phase fibrilizing a PTFE dispersion, which is a fluoropolymer particle, as a first binder is described. The liquid-phase fibrilization technique is a method developed in the present invention in which fluoropolymer particles existing in a dispersion state are rotated at a high speed within a solvent, causing the fluoropolymer particles to be arranged in a thin, long fiber shape in the direction of rotation, thereby causing them to become fibrilized. In other words, liquid-phase fibrilization refers to the clustering of fluoropolymer particles dispersed in a solvent into a thin, long shape, as it is a technique in which a large number of fluoropolymer particles form a cluster formed by being thin and long.

[0089] When the first binder particles are PTFE particles, (1) the step of preparing the first binder dispersion is performed by dispersing PTFE particles in water to prepare a PTFE aqueous dispersion, and if necessary, a commercially available one may be used. (2) The step of preparing the second binder solution can be performed by dissolving the second binder in a solvent to prepare the second binder solution, and the solvent is not limited as long as it can dissolve the second binder, but as one embodiment, it is advantageous to use any one of DMF, NMP, or water. (3) The first stirring step is a step of rotating the first binder aqueous dispersion at high speed to loosen the state in which the PTFE particles are strongly attached to each other. When the first binder particles are dispersed in the solvent and stirred at a very high speed, the first binder particles that were attached by strong molecular forces spread apart and loosen, causing them to swell and simultaneously exist in a form that is thin and long in the direction of stirring. This process can be described as a step of liquid phase fibrilization of PTFE particles, during which multiple PTFE particles are clustered into thin, elongated clusters to exist in the form of secondary particles, namely PTFE clusters. The process conditions for the first stirring step, which enable the PTFE particles to take on this shape, are to rapidly stir the PTFE aqueous dispersion at a speed of 2,000–30,000 rpm at a temperature of 20–70°C for 10 minutes to 10 hours. If the above conditions are below the lower limit or above the upper limit, the first binder particles do not form thin, elongated clusters, so liquid phase fibrilization does not occur, which is disadvantageous; or, due to excessive stirring, the shape of the first binder may be broken, which is actually disadvantageous for forming a composite binder of the desired shape. (4) The second stirring step is a step in which the second binder solution is slowly poured into the liquid fiberized PTFE aqueous dispersion in which a number of clusters are formed, and the mixture is stirred rapidly so that the second binder is positioned between the first binder fibers.At this time, the second binder molecules surround the surface of the first binder particles, forming a so-called core-shell structured particle, in which the first binder particles are located inside and the second binder surrounds the surface. In this way, the core-shell structured composite binder particles gather to form a cluster, and a composite binder can be obtained in which a membrane structure of the second binder surrounds part and / or all of the cluster. The structure of the composite binder obtained at this time may include one or more of a layered structure in which a membrane structure made of the second binder is located between core-shell structured composite binder particle clusters that have been fiberized into a core-shell structure. (5) The post-processing step is a process of obtaining the composite binder particles for the dry process generated in the second stirring step. This step can be performed by filtering the product obtained after stirring is finished to separate the composite binder particles for the dry process from the solvent, washing and purifying them, and then drying them. Here, filtering and washing may be performed one or more times.

[0090] In the present invention, a composite binder can be manufactured by means of the method described above, wherein a membrane structure composed of a second binder surrounds first binder particles and / or core-shell structured composite binder particles, which are fluoropolymer particles and / or core-shell structured composite binder particles constituting a slender, elongated cluster. Unlike a composite binder simply prepared by dry mixing fluoropolymer particles and other binder particles (such as second binder particles), a composite binder with such a structure exhibits better microscopic uniformity. Consequently, it can be easily anticipated that electrochemical properties, such as adhesion or charge-discharge cycle characteristics, are superior and more uniform compared to a simple mixed type binder. In fact, it has been experimentally confirmed that a composite binder using fluoropolymer particles arranged in this manner is advantageous for the manufacture of dry electrodes.

[0091] In the manufacturing method of the present invention, the stirring conditions of the first and second stirring steps were experimentally established. Under conditions below the lower limit of the pre-set stirring conditions, core-shell structure and / or layered structuring reactions did not occur well or were difficult, which was disadvantageous; conversely, under conditions exceeding the upper limit, there was a high possibility that core-shell structuring and / or layered structuring reactions would be hindered, which was rather disadvantageous.

[0092] Next, the dry electrode composition of the present invention may include an active material, any one of the composite binders for a dry process having the composition described above, or a composite binder for a dry process manufactured by any one of the manufacturing methods having the composition described above, and a nanocarbon material.

[0093] Here, the active material may be included in an amount of 85-98 wt%, the nanocarbon material in an amount of 1.0-5 wt%, and the composite binder in an amount of 1.0-10 wt%. The content of each component is determined through experiments. If the content of each component is below the lower limit, there is a problem that it is insufficient to maintain the electrochemical and mechanical properties of the secondary battery manufactured with a dry electrode containing it, and if it exceeds the upper limit, there is a concern that one or more components may be excessively included, thereby impairing the properties of the secondary battery. That is, if the active material used in the dry electrode composition of the present invention is less than 85 weight%, the electrical capacity of the secondary battery is lowered, which is disadvantageous; if it exceeds 98 weight%, the composite binder is inevitably included in too little, resulting in poor mechanical properties due to reduced bonding between components and adhesion to the electrode plate. Additionally, if the nano-carbon material content used in the dry electrode composition of the present invention is less than 1.0 weight%, the surface resistance of the dry electrode layer increases, and if it exceeds 5 weight%, although the surface resistance improves, the content of the active material is relatively lower, resulting in a disadvantageous problem of reduced electrical capacity per unit volume. The content of the composite binder used in the dry electrode composition of the present invention can be set differently depending on the shape and size of the active material or the type and content of the nanocarbon material, but if it is less than 1.0 wt%, there are problems such as the active material electrode layer formed on the electrode plate detaching too easily, and if it exceeds 10 wt%, although there is an advantage that the active material electrode layer adheres strongly to the electrode plate, the relative active material content decreases, and consequently, the problem of the electrical capacitance per unit volume of the electrode decreases.

[0094] To examine in detail each component included in the dry electrode composition of the present invention, first, the active material is a positive active material or a negative active material and may be any one selected from the group consisting of alkali metal elements, alkaline earth metal elements, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, graphite, silicon, silicon oxide, sulfur, and combinations thereof. Here, the alkali metal element may be any one selected from the group including lithium, sodium, potassium, rubidium, cesium, and francium, and the alkaline earth metal element may be any one selected from the group including beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

[0095] The nanocarbon material is a component that imparts electrical conductivity and simultaneously performs the role of a sheet forming agent that substantially aids in the manufacture of dry electrode sheets. It is not limited to being a nano-sized carbon material capable of moving electrons generated from the electrode active material to the current collector, but as one embodiment, it may be any one selected from the group consisting of conductive carbon black, graphene nanoplates, carbon nanotubes (single-wall, double-wall, multi-wall, branched, etc.), carbon nanoplates, vapor-phase polymerized carbon nanofibers, carbon balls, carbon nanoribbons, and combinations thereof. In particular, nanocarbon materials with an aspect ratio of 100 or more, such as carbon nanotubes (single-wall, double-wall, multi-wall, and branched, etc.), carbon nanoplates, vapor-polymerized carbon nanofibers, and carbon nanoribbons, can be mixed with nanocarbon materials with an aspect ratio of less than 100, such as conductive carbon black, carbon balls, and graphene nanoplates. The nanocarbon materials with a low aspect ratio have the effect of helping to disperse the nanocarbon materials with a high aspect ratio, thereby having the effect of slightly lowering the surface resistance of the electrode layer. In the present invention, when the nanocarbon material is a mixture of nanocarbon materials with different aspect ratios, the mixing weight ratio of the nanocarbon material with an aspect ratio of 100 or more and the nanocarbon material with an aspect ratio of less than 100 may be (10-90):(90-10). However, if the content of the two types of nanocarbon materials is less than 10 weight%, it is not a mixture but is similar to a single type of nanocarbon material, making it difficult to obtain the effect of mixing.

[0096] Meanwhile, the composite binder included in the dry electrode composition of the present invention can be used for both positive and negative electrodes. In the case of the composite binder for the positive electrode, there is no limit to the content range of fluoropolymer particles, but when used for the negative electrode, it is advantageous that the content of fluoropolymer particles does not exceed 50% by weight of the membrane-structure content. This is because when fluoropolymer particles, such as PTFE, are used for the negative electrode, there is a problem of reduced initial efficiency due to the reduction potential, so the content of PTFE can be limited to less than 50%, and in particular, the ratio of fluoropolymer particles can be limited to less than 30%.

[0097] The dry electrode composition of the present invention having the above-described composition can be used to provide a dry electrode in all secondary batteries requiring a binder, such as lithium-ion batteries mainly used in the description of the present invention, as well as other metal-ion batteries such as sodium-ion batteries, sulfide-based or oxide-based all-solid-state batteries, or semi-solid-state batteries.

[0098] Next, the dry electrode sheet of the present invention may include a dry electrode composition having the configuration described above. That is, the dry electrode sheet can be manufactured through a first step of creating a dry electrode composition by placing an active material, a nanocarbon material, and a composite binder for a dry process into a dry mixer and mixing them at high speed, and a second step of calendering the dry electrode composition using a calendering device.

[0099] At this stage, the high-speed mixing conditions for preparing the dry electrode composition involve performing the process for 1 to 60 minutes at a rotational speed of 5,000 to 50,000 rpm. However, caution is required because the surface shape of the active material may be abraded as it collides with other active materials during high-speed mixing. To prevent this, a two-step mixing method is used: first, the composite binder and nanocarbon material are sufficiently stirred and mixed to create a composite binder / nanocarbon material mixture, after which the active material is added and high-speed mixed. This method allows for the production of a dry electrode composition suitable for calendering in a relatively short time. It is further advantageous because the active material in the resulting mixture can maintain a shape similar to its original form. Any mixing device capable of adding each component and mixing it while rotating at high speed can be used.

[0100] As described above, the method of introducing the prepared dry electrode composition into a calendering device to produce a dry electrode sheet may use a previously known calendering method; therefore, the present invention is not limited to any specific method or condition.

[0101]

[0102] Next, the dry electrode of the present invention can be manufactured by including the dry electrode sheet described above. That is, the dry electrode can be finally manufactured by undergoing a third step of attaching a dry electrode sheet having the configuration described above onto a current collector having a primer layer formed thereon, and a fourth step of performing additional processes such as rolling.

[0103] Therefore, each of these steps for manufacturing dry electrode sheets and dry electrodes can be performed in a batch manner, or the dry electrode composition to the dry electrode can be manufactured in a continuous process. Introducing a continuous process would be a more efficient manufacturing process.

[0104] Next, the secondary battery of the present invention may include a dry electrode having the configuration described above. In this case, the secondary battery may be any secondary battery requiring a binder, such as the lithium-ion battery mainly used in the description of the present invention, as well as other metal-ion batteries such as sodium-ion batteries, sulfide-based or oxide-based all-solid-state batteries, or semi-solid-state batteries.

[0105] To specifically explain the above-described technology described below, examples and comparative examples are presented in which an acrylonitrile-maleic acid copolymer, which is an acrylonitrile-based copolymer and has excellent adhesive properties, is used as a second binder capable of producing a composite binder by mixing with fluorine-based resin particles (first binder). However, it is evident that the present invention can be applied not only when the second binder is an acrylonitrile-maleic acid copolymer, but also when it is a mixture of an acrylonitrile-based copolymer and a secondary battery binder, as well as other types of acrylonitrile-based copolymers, other secondary battery binder materials such as polyvinylidene fluoride, or a mixture of an acrylonitrile-based copolymer and a secondary battery binder.

[0106]

[0107] Example 1

[0108] 1. Synthesis of Acrylonitrile-Maleic Anhydride Copolymer

[0109] The acrylonitrile-maleic anhydride copolymer shown in Fig. 1 was synthesized as follows. First, 99 mol% acrylonitrile and 1.0 mol% maleic anhydride were added to ultrapure water to achieve a solid content of 10%, and while stirring, the temperature was raised to 70°C and stirred for 10 minutes. While maintaining this temperature, 1.5 parts by weight of potassium persulfate (KPS), a reaction initiator, were slowly added, and the reaction was carried out for 10 hours. After the reaction was completed, isopropyl alcohol (IPA) was added to the reaction solution to solidify it, and then copolymer 1 was obtained through filtering, washing, and drying processes.

[0110] 2. Preparation of Composite Binder for Dry Processes

[0111] (1) Step of preparing the first binder dispersion

[0112] PTFE particles with an average particle size of 250 nanometers (0.25 microns) were dispersed in water to prepare 20 grams of a first binder aqueous dispersion (50% solid content) (10 grams based on solid content) as shown in Fig. 2.

[0113] (2) Step of preparing the second binder solution

[0114] The obtained copolymer 1 was dissolved in NMP to prepare a second binder solution with a solid content of 10%.

[0115] (3) First stirring stage

[0116] The first binder dispersion was stirred / rotated at 5,000 rpm for 2 hours to induce liquid-phase fiberization, and the first binder dispersion with liquid-phase fiberization was obtained as shown in Fig. 3.

[0117] (4) Second stirring stage

[0118] Then, 100 grams of the second binder solution (10 grams based on solid content) was slowly added to 20 grams of the first binder dispersion (50% solid content) (10 grams based on solid content) and stirred at a speed of 5,000 rpm for 1 hour.

[0119] (5) Post-processing step

[0120] The product obtained from the second stirring step was filtered with a pressurized filter and washed with distilled water twice, and then dried at 50°C to obtain the final reactant, a composite binder 1 for dry processes.

[0121]

[0122] Example 2

[0123] A composite binder 2 for a dry process was obtained by performing the same method as in Example 1, except that a fluorosilane-based coupling agent (trimethoxy (3,3,3-trifluoropropyl)silane, Aldrich) was added in the first stirring step. At this time, the content of the fluorosilane additive was set to 2% by weight relative to the weight of the PTFE particles.

[0124]

[0125] Example 3

[0126] Composite binder 3 for dry processes was obtained by performing the same method as in Example 1, except that the stirring speed in the first stirring step was set to 10,000 rpm.

[0127]

[0128] Example 4

[0129] A copolymer 2 was obtained by performing the same method as in Example 1, except that the molar ratio of acrylonitrile monomer to maleic anhydride monomer was 95:5 mol% during the synthesis of the acrylonitrile-maleic anhydride copolymer, and a composite binder 4 for dry processes containing the same was obtained.

[0130]

[0131] Example 5

[0132] A composite binder 5 for a dry process was obtained by performing the same method as in Example 1, except that an acrylonitrile-ethylene glycol-maleic acid copolymer synthesized as follows was used as the second binder in the second binder solution preparation step.

[0133] The acrylonitrile-ethylene glycol-maleic acid copolymer was obtained by performing the following synthesis process. Maleic acid and ethylene glycol (molecular weight: 4,000 g / mol) were weighed in a molar ratio of 1:2, added to DMF to achieve a solid content of 10 wt%, and mixed by stirring at 90°C for 10 minutes. Subsequently, at the same temperature, 1.5 wt% of para-toluenesulfonic acid (p-CH3CH6CH4SO3H) was slowly added to the mixture as a reaction initiator relative to the weight of the solids, and the reaction was carried out for at least 6 hours. After the reaction was completed, acrylonitrile was added to the mixture, and potassium persulfate (KPS) was slowly added dropwise while stirring for 10 hours to synthesize a ternary copolymer. At this time, the weight ratio of the total weight of the maleic acid and ethylene glycol reacted in the first reaction to the weight of acrylonitrile was set to 1:1, and the content of potassium persulfate, which is the reaction initiator, was set to 1.5% by weight relative to the total solid content. After all reactions were completed, the reaction product was pressurized and the resulting solid was vacuum dried (40°C, 24 hours) to obtain an acrylonitrile-ethylene glycol-maleic acid copolymer.

[0134] Example 6

[0135] A composite binder 6 for a dry process was obtained by performing the same method as in Example 1, except that in the second binder solution preparation step, a styrene-butadiene-styrene copolymer (Aldrich, weight-average molecular weight: 350,000 grams / mol) dissolved in ethyl acetate (EA) with a 10% solid content was used as the second binder solution.

[0136]

[0137] Example 7

[0138] 3 wt% of a composite binder 1 for dry processes and 2 wt% of multi-walled carbon nanotubes were placed in a mixer and mixed at high speed at 10,000 rpm for 10 minutes (5 times of 2 minutes each), then 95 wt% of an active material (NCM811) was added and mixed at high speed for 3 minutes at the same rotational speed to prepare a dry electrode composition 1.

[0139]

[0140] Examples 8 to 12

[0141] Dry electrode compositions 2 to 6 were prepared by performing the same method as in Example 7, except that each of the dry process composite binders 2 to 6 was used.

[0142]

[0143] Example 13

[0144] 95 wt% of active material (NCM811), 2 wt% of multi-walled carbon nanotubes, and 3 wt% of composite binder particles 1 for dry process were placed in a mixer and rotated at high speed at 10,000 rpm for 15 minutes to prepare a dry electrode composition 7.

[0145]

[0146] Example 14

[0147] A dry electrode composition 8 was prepared by performing the same method as in Example 7, except that 94 wt% of active material (LFP), 2 wt% of multi-walled carbon nanotubes, and 4 wt% of composite binder 1 were used. Here, the active material used was lithium iron phosphate (LFP) in a bimodal form (particle size: 1.5 microns and 7 microns) with an average particle size (D50) of 2.2 microns.

[0148]

[0149] Example 15

[0150] In Example 1, a composite binder 7 was prepared by ensuring that the content of PTFE and copolymer 1 was in a weight ratio of 20:80 during the second stirring step, and a dry negative electrode composition was prepared by performing the same method as in Example 7, except that graphite was used as the active material.

[0151]

[0152] Example 16

[0153] After preparing Composite Binder 1 for the dry process in the same manner as in Example 1, a dry electrode composition for a sulfide-based solid-state battery was prepared as follows using 70 wt% of a positive electrode active material (NCM811), 27.5 wt% of a sulfide-based solid electrolyte (LPSCl; Li6PS5Cl), 1.5 wt% of conductive carbon black, and 1.0 wt% of Composite Binder 1. Composite Binder 1 for the dry process, conductive carbon black, and solid electrolyte were placed in a mixer and mixed at 10,000 rpm for 10 minutes, then the active material was added and mixed again for 3 minutes to prepare the dry electrode composition for a sulfide-based solid-state battery.

[0154]

[0155] Example 17

[0156] 1. Dry electrode sheet preparation step

[0157] Dry electrode sheet 1 was prepared using the calendering method in a dry electrode manufacturing apparatus using dry electrode composition 1.

[0158] 2. Dry electrode preparation step

[0159] Place the dry electrode sheet 1 on an aluminum foil with a primer layer formed as a current collector, and at 100℃, ~10kgf / cm² 2 After attachment under the conditions, rolled at a high temperature (100℃) to produce dry positive electrode 1 (loading level: ~20 mg / cm² 2 , electrode density: ~3.0 g / cm³ 3 Manufactured ).

[0160]

[0161] Examples 18 to 24

[0162] Dry electrode sheets 2 to 8 were prepared by performing the same method as in Example 17, except that dry electrode compositions 2 to 8 were used respectively, and then dry positive electrodes 2 to 8 were prepared. Here, the loading level of dry positive electrode 8 was ~16.1 mg / cm² 2 , electrode density is ~2.1 g / cm³ 3 am.

[0163]

[0164] Example 25

[0165] A dry negative electrode sheet was prepared by performing the same method as in Example 17, except that the dry negative electrode composition prepared in Example 15 was used, and then a dry negative electrode was prepared. At this time, a copper foil with a primer layer formed with a thickness of 1-2 microns was used as the current collector to make the negative electrode.

[0166]

[0167] Example 26

[0168] A dry electrode composition for sulfide-based solid-state batteries is calendered using a dry electrode manufacturing device to produce an all-solid-state battery electrode sheet, and then subjected to pressurization at a pressure of 430 MPa to produce an all-solid-state battery dry electrode (loading level: ~16 mg / cm² 2 , electrode density: ~2.4 g / cm³ 3 Made ).

[0169]

[0170] Example 27

[0171] A half-cell structured coin cell (CR2032 type) 1 was manufactured using a dry positive electrode 1. In this case, lithium metal foil was used as the counter electrode, and 1.15 mol of LiPF6 was dissolved in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) (volume ratio: 3 / 5 / 2) mixed with 5% fluoroethylene carbonate (FEC) relative to the total solvent weight. The coin cell was manufactured according to a conventional coin cell manufacturing method in a glove box filled with argon gas.

[0172]

[0173] Examples 28 to 34

[0174] Half-cell structured coin cells (CR2032 type) 2 to 8 were manufactured by performing the same method as in Example 27, except that each of the dry positive electrodes 2 to 8 was used.

[0175]

[0176] Example 35

[0177] A negative electrode coin cell with a half-cell structure was manufactured by performing the same method as in Example 27, except that a dry negative electrode was used.

[0178]

[0179] Example 36

[0180] An all-solid-state pressure cell was manufactured by stacking as follows using an all-solid-state dry electrode.

[0181] It was manufactured by assembling in the order of a negative electrode (nickel foil), lithium-indium (counter electrode, lithium: Honjo, nickel: Nilaco), solid electrolyte layer (Li6PS5Cl) (separator, 100 mg), all-solid-state battery dry electrode, and positive electrode (aluminum foil). At this time, the aluminum foil used as the positive electrode current collector had a primer layer with a thickness of 1.5 microns formed on one side.

[0182]

[0183] Comparative Example 1

[0184] A comparative dry electrode composition comprising 95 wt% of an active material (NCM811), 2 wt% of multi-walled carbon nanotubes, and 3 wt% of PTFE, a fluoropolymer particle, was prepared as follows. First, PTFE and carbon nanotubes were placed in a mixer and mixed by high-speed rotation at 10,000 rpm for 10 minutes (5 times of 2 minutes each). Afterward, the active material was added, and the mixture was rotated and mixed at the same rotation speed for another 3 minutes to prepare comparative dry electrode composition 1.

[0185]

[0186] Comparative Example 2

[0187] A comparative example dry electrode composition 2 for an all-solid-state battery was prepared by performing the same method as in Example 16, except that PTFE was used instead of a composite binder 1 for the dry process.

[0188]

[0189] Comparative Example 3

[0190] Comparative dry electrode sheet 1 was prepared in the same manner as in Example 17, except that Comparative dry electrode composition 1 was used, and then Comparative dry electrode 1 was prepared.

[0191]

[0192] Comparative Example 4

[0193] Comparative dry electrode sheet 2 was prepared in the same manner as in Example 26, except that Comparative dry electrode composition 2 was used, and then Comparative dry electrode 2 was prepared.

[0194]

[0195] Comparative Example 5

[0196] A comparative example coin cell 1 with a half-cell structure was prepared by performing the same method as in Example 27, except that a comparative example dry positive electrode 1 was used.

[0197]

[0198] Comparative Example 6

[0199] A comparative pre-pressure cell was manufactured by performing the same method as in Example 36, except that comparative pre-dry electrode 2 was used.

[0200]

[0201] Experimental Example 1

[0202] In Examples 1 and 3, composite binders 1 and 3 were prepared using acrylonitrile-maleic anhydride copolymer 1 in the form of white particles, respectively. Since composite binders 1 and 3 of the present invention are identical to those in Example 1 except for the rotational speed during preparation, the synthesis of the composite binder was confirmed by obtaining the Fourier Transistor (FTIR) spectrum of the composite binder in Example 1 and analyzing the characteristic peaks of the spectrum. As a result of the FTIR measurement (Fig. 8) for composite binder 1 containing the acrylonitrile-maleic anhydride copolymer of Example 1, the PTFE ranged from 1150 to 1200 cm⁻¹. -1 It exhibits a large absorption peak at , and the acrylonitrile component at 2244 cm⁻¹. -1It is measured in the vicinity, which is the characteristic pit of the cyanide group (-CN). Furthermore, maleic anhydride changes into maleic acid when the synthesis reaction takes place in ultrapure water; therefore, when acrylonitrile monomer and maleic anhydride monomer are reacted, the synthesized copolymer becomes an acrylonitrile-maleic acid copolymer. The presence of maleic acid or maleic anhydride components in the copolymer of the present invention is determined by the infrared spectroscopic spectrum at 1600–1750 cm⁻¹. -1 It was confirmed that a carbonyl peak in the region was observed. In the infrared spectroscopic spectrum of the composite binder 1 of the present invention, characteristic peaks of the PTFE component, cyanide group, and maleic acid or maleic anhydride component were confirmed to be present; thus, it was confirmed that the composite binder 1 composed of PTFE and an acrylonitrile-maleic anhydride copolymer component was successfully synthesized. For reference, the weight-average molecular weight (GPC method) of copolymer 1 was measured to be 725,000 grams / mol (Example 1).

[0203]

[0204] Experimental Example 2

[0205] The morphology of the composite binders 1 to 6 for dry processes prepared in Examples 1 to 6 was observed. First, Fig. 2 shows the appearance of the PTFE aqueous dispersion obtained in the step of preparing the first binder dispersion of Example 1, and Fig. 3 is a photograph of the first binder dispersion after high-speed rotation of the PTFE aqueous dispersion at 5,000 rpm for 2 hours, i.e., liquid-fiberized first binder dispersion. As can be seen in Fig. 3, it can be seen that the PTFE aqueous dispersion has become liquid-fiberized and the PTFE has swollen significantly. The electron microscope observation results of the composite binder 1 obtained after the reaction was terminated and a washing process was performed, while slowly pouring the second binder solution, i.e., the copolymer 1 of the present invention dissolved in DMF, into this expanded PTFE aqueous dispersion and maintaining a high-speed stirring state for 1 hour, are shown in Figs. 4 to 7. Figure 4 shows PTFE particles in their original state without high-speed rotation, and it can be seen that the PTFE particles in their original state are spherical particles with a particle size of about 0.25 microns. Figure 5 is an electron microscope image of a composite binder obtained by high-speed rotation of a first binder dispersion and then high-speed rotation again while adding a second binder solution, and Figure 6 is a further magnified view of a part of Figure 5. Looking at the results in Figures 5 and 6, it can be seen that the composite binder of the present invention consists of small particles gathered to form a long band shape, with the second binder covering part and / or the entire surface. In addition, the electron microscope image in Fig. 7 is a magnified view of the small particles in Fig. 5, showing that the particles within the cluster are not simply the original PTFE particles but have a shape in which the surface is covered with another material. This indicates that the particles have a core-shell structure, meaning that PTFE particles are located inside and a second binder is wrapped around the surface, i.e., composite binder particles formed by combining PTFE and the second binder.Accordingly, it can be seen that the composite binder of the present invention has a structure in which a plurality of clusters of core-shell structured composite binder particles (core-shell structured particles in which PTFE particles are inside and the second binder surrounds the surface) are formed by the penetration of a second binder into a state in which PTFE particles are linearly oriented, and a membrane structure comprising a second binder, i.e., an acrylonitrile-based copolymer, partially and / or wholly surrounds the clusters. It can be seen that the composite binder has a structure in which either a core-shell structure or a layered structure, or a composite form thereof.

[0206] As such, the microstructure of the composite binder of the present invention includes one or more of a core-shell and layered structure, and is a microstructure that is completely different from that of a general dry-blended mixed binder, which is a form in which particles are simply dry-blended, that is, a form in which a mass of another binder is located around a mass of PTFE particles that are gathered together. As a result, since the composite binder of the present invention is microscopically composited as shown in FIGS. 5 to 7, it can be said that it is suitable for manufacturing a more uniform electrode composition mixture than a mixed binder obtained by a general dry-blending method when mixing a dry electrode composition.

[0207] The aforementioned phenomenon was also observed in the preparation of composite binder particles using the remaining copolymers, namely acrylonitrile-ethylene glycol-maleic acid copolymer and styrene-butadiene-styrene copolymer. Specifically, it was confirmed that when a PTFE dispersion is rotated at high speed, a second binder solution is poured in, and high-speed rotation continues, composite binder particles in which PTFE particles are wrapped by the second binder gather and arrange in the form of secondary particles, and a composite binder having a shape in which the second binder wraps over them again is formed. Therefore, it can be seen that the composite binder manufacturing technique of the present invention is applicable to any binder for secondary batteries that can be dissolved in a solvent.

[0208] The synthesis of the above composite binder could be confirmed by obtaining an infrared spectroscopic spectrum (FTIR spectrum), similar to Experimental Example 1. Specifically, Fig. 8 shows the FTIR spectrum for the dry process composite binder 1 obtained in Example 1, which was explained in Experimental Example 1. Similarly, in the case of the dry process composite binder 5 obtained in Example 5 (second binder: acrylonitrile-ethylene glycol-maleic acid copolymer), in addition to the characteristic peak in Fig. 8, 1103 cm⁻¹ -1 The ethylene glycol component peak in the vicinity (Fig. 9), and in the case of the dry process composite binder 6 of Example 6, the PTFE component (1150-1200 cm⁻¹) -1 , 600-700cm -1 ), Styrene component (2800-3100cm -1 , 700cm -1 ), butadiene component (1600-1650cm -1 By confirming the presence of the peak, it was confirmed that the composite binder 6 for the dry process is a composite binder composed of PTFE, styrene, and butadiene components (Fig. 10).

[0209] Experimental Example 3

[0210] The dry electrode state, adhesion strength, and surface resistance characteristics were measured for the dry electrode sheets 1 to 8 and dry positive electrodes 1 to 8 prepared in Examples 17 to 24, and the comparative example dry electrode sheet 1 and comparative example dry positive electrode 1 of Comparative Example 3.

[0211] Similar to Comparative Example Dry Sheet 1 obtained in Comparative Example 3 using the conventional dry binder PTFE, all dry electrode sheets 1-8 obtained in Examples 17 to 24 could be produced as high-quality dry electrode sheets with a thickness of approximately 70-90 microns using the calendering method, resulting in a clean surface. Therefore, it can be confirmed that the composite binder of the present invention produces dry electrode sheets well without any difference from the conventional dry binder PTFE. Furthermore, Comparative Example Dry Electrode 1 and Dry Electrode Sheets 1-8 could be manufactured by attaching Comparative Example Dry Sheet 1 and Dry Electrode Sheets 1-8 to a current collector at high temperature without any particular difficulty, and the loading levels of these electrodes 1-7 were approximately 20 mg / cm². 2 , electrode density is 3.0 g / cm³ 3 , the loading level of positive electrode 8 is ~16.1 mg / cm² 2 , and the electrode density is ~2.1 g / cm³ 3 It was confirmed to be.

[0212] The surface resistance and adhesion of these positive electrode plates were measured.

[0213] The surface resistance of the electrode layer of dry electrode sheet 1 (4-point probe method, measurement tip: round shape) is ~90 ohms / area, and the surface resistance of the electrode layer of dry positive electrode 1 manufactured by attaching this dry electrode sheet 1 to a current collector is 10 -3 It was measured in ohms / area. The low surface resistance of dry positive electrode 1 is thought to be due to the influence of the aluminum metal located beneath the electrode layer. Dry positive electrodes 2 to 8 and comparative example dry positive electrode 1 exhibited characteristics very similar to those of the above dry positive electrode 1. This is because surface resistance is a characteristic determined by the content and dispersion of carbon nanotubes used as a conductive material; it appears that all the above positive and negative electrodes have similar surface resistance values ​​because they use the same amount of conductive material and have very similar dispersions.

[0214] Adhesion strength tests for dry positive electrodes were performed as follows. First, one side of double-sided tape was attached to the metal foil of dry positive electrode 1, and the other side was attached to a glass substrate. Subsequently, tape (3M Scotch Tape, width: 18 mm) was attached to the opposite electrode layer of dry positive electrode 1, and after 30 minutes, the peel strength of the tape was measured using a tensile tester, and the value divided by the width of the tape was defined as the adhesion strength (N / mm). The adhesion strength of dry positive electrode 1 was measured to be ~0.078 N / mm, while the comparative example dry positive electrode 1 showed a relatively low adhesion strength of ~0.01 N / mm. This appears to be due to the high release characteristics of the fluorine component in the case of PTFE. Dry positive electrodes 2, 3, and 7 showed adhesion strength similar to that of dry positive electrode 1, which is thought to be because the composition and content of these electrode layers are similar. However, in the case of dry electrode 4, the adhesive strength is 0.087 N / mm, showing higher adhesion compared to other dry electrodes. This is thought to be because the maleic acid content (5 mol%) is higher than that of other electrode plates (1 mol%). However, in the case of dry electrode 5 (second binder: acrylonitrile-ethylene glycol-maleic acid copolymer) and dry electrode 6 (second binder: styrene-butadiene-styrene copolymer), the adhesive strength was approximately 0.058 N / mm, showing lower adhesion than dry electrode 1. Meanwhile, from the results of the comparative example dry electrode 1, it was observed that the composite binder prepared using the liquid fiberization technique of the present invention showed higher adhesion compared to PTFE.

[0215] Therefore, it was confirmed that different adhesive strengths were observed depending on the type of components constituting the composite binder.

[0216]

[0217] Experimental Example 4

[0218] Charge-discharge cycle tests were performed on coin cells 1-8 and comparative example coin cell 1. The charge-discharge cycle test was conducted by undergoing the formation process twice at a rate of 0.1C, followed by a cycle test at a rate of 1.0C. The discharge capacity after 3 cycles was set as the initial capacity, and the capacity retention rate (%) was calculated by comparing it with the discharge capacity after 50 cycles.

[0219] The charge / discharge cycle test results for the above coin cell 7 are shown in FIG. 11, and the results for the remaining coin cells are summarized in Table 1. That is, the measured values ​​for coin cells 1 to 8 and comparative example coin cell 1 are summarized in Table 1.

[0220] Initial Efficiency (FCE, %) Initial Capacity (mAh / g) 50-Cycle Capacity (mAh / g) Capacity Retention Rate (%) Coin Cell 193 185 17293 Coin Cell 294 192 18194 Coin Cell 393 191 18094 Coin Cell 494 191 17993 Coin Cell 594 189 17894 Coin Cell 694 188 17794 Coin Cell 792 192 18194 Coin Cell 893 149 14899 Comparison Coin Cell 190 189 17392

[0221]

[0222] As shown in Figure 11 and Table 1, for Coin Cell 7, the initial efficiency (FCE) during the 0.1C rate formation process was 92%, the initial capacity after 3 cycles was 192 mAh / g, and the capacity after 50 cycles was 181 mAh / g, showing a capacity retention rate of approximately 94%. The results for the remaining Coin Cells 1 to 3 were measured to be similar. This is thought to be because the electrical capacitance characteristics that can be realized are similar since the composition of the electrode layer of each coin cell is identical. When comparing these results with Comparative Coin Cell 1, the initial efficiency (FCE) of the Comparative Coin Cell during the 0.1C rate formation process was 90%, the initial capacity after 3 cycles was 189 mAh / g, and the capacity after 50 cycles was 173 mAh / g, with a capacity retention rate of approximately 92%. From Table 1, it can be seen that the initial efficiency (FCE) of Coin Cells 1 to 6 and 8 is higher than that of Coin Cell 7. This implies that the manufacturing method of the dry electrode composition affects the initial efficiency. In other words, the results show that the method of preparing the dry electrode composition by first high-speed mixing the carbon nanotubes and composite binder, followed by the addition of the active material and high-speed mixing, is more effective in increasing initial efficiency than the method of placing the active material, carbon nanotubes, and composite binder into a container and high-speed mixing them all at once.

[0223] In addition, the results of the characteristic test on a cell, namely Coin Cell 8, for LFP, another type of active material, show that although the initial electrical capacitance is lower than that of NCM811, the capacity retention rate is almost 99%, indicating almost no loss. From this, it can be seen that the composite binder of the present invention can be applied to both NCM and LFP.

[0224] Comparing the above results, it can be seen that the composite binder of the present invention exhibits better electrochemical characteristics than a dry electrode using only PTFE, indicating that the technology of the present invention is capable of compensating for the shortcomings of existing PTFE.

[0225]

[0226] Experimental Example 5

[0227] The dry negative electrode obtained in Example 25 showed good adhesion of approximately 0.065 N / mm, and the surface resistance of the dry negative electrode sheet itself was 50 ohms / area, while the resistance of the electrode layer attached to the current collector was 10 -3 It was measured at a level. In addition, as a result of the charge-discharge cycle test for the negative electrode coin cell, the initial efficiency was measured at 90%, the initial capacity at 340 mAh / g, and the capacity after 50 cycles at 339 mAh / g, indicating that the capacity retention rate is nearly 100%.

[0228] These results demonstrate that even if the first binder particles and the second binder included in the composite binder for the dry process of the present invention are identical, they can be used as binder materials for manufacturing dry positive electrodes and dry negative electrodes by varying the relative content ratios.

[0229] In other words, the present invention utilizes a composite binder for a dry electrode composed of PTFE and an acrylonitrile-based copolymer, varying their relative ratios to serve as a dry binder for a positive electrode and a negative electrode. This is because it can be seen that when a weight ratio of PTFE / copolymer 1 was used as the positive electrode binder at 50:50 and a weight ratio of 20:80 as the negative electrode binder, both the dry positive electrode 1 (Experimental Examples 3 to 4) and the dry negative electrode (Experimental Example 5) obtained very good results in electrochemical properties such as adhesion, surface resistance, and charge / discharge cycle characteristics. In this case, for the negative electrode, the ratio of PTFE to copolymer 1 was set to 20:80 in order to reduce the content of PTFE, as the reduction potential of PTFE showed a relatively high value.

[0230] As is well known, in the wet method, different solvents are used to prepare the positive electrode slurry and the negative electrode slurry, so the binder for the positive electrode and the binder for the negative electrode must inevitably be different. However, since the dry method does not use solvents, the same type of binder can be used for both the positive and negative electrodes. In particular, in the case of a composite binder in which two materials, namely PTFE and an acrylate copolymer, are combined as in the present invention, it was found that it can be applied to both electrodes by adjusting the relative content of the two materials.

[0231]

[0232] Experimental Example 6

[0233] All-solid-state battery electrode sheets and all-solid-state battery dry electrodes were made using a dry electrode composition for sulfide-based all-solid-state batteries containing a composite binder 1 for dry process, and an all-solid-state battery pressure cell was made from the same as in Example 36, and a charge-discharge cycle test was performed on the pressure cell.

[0234] The electrochemical characteristics of the all-solid-state battery pressure cell were tested by subjecting the pressure cell to a formation process three times at a rate of 0.05C, followed by a cycle test at a rate of 0.2C. Subsequently, the electrical capacity of one cycle at a rate of 0.2C was set as the initial capacity, and after measuring the discharge capacity after 50 cycles, it was divided by the initial capacity to determine the capacity retention rate.

[0235] The sulfide-based all-solid-state battery dry electrode had a clean surface and good appearance, and the adhesion strength, measured by the method of Experimental Example 3, showed a good value of ~0.05 N / mm. The charge-discharge cycle test results for the all-solid-state battery pressure cell were compared with the results of the comparative pre-pressure cell obtained in Comparative Example 6. In the case of the all-solid-state battery pressure cell, the initial capacity at a rate of 0.05 C was 225 mAh / g, and the initial efficiency (FCE) according to charge-discharge was ~90%. The initial capacity for one cycle at a rate of 0.2 C was 180 mAh / g, and the discharge capacity after 50 cycles was 170 mAh / g, showing a capacity retention rate of approximately 90%. The comparative pre-pressure cell was manufactured using only PTFE in the same way, and the charge-discharge cycle test was performed in the same way. As a result of measurement, all characteristics were similar to the results of the all-solid-state battery pressure cell, except that the initial capacity at a rate of 0.05 C was slightly lower at approximately 222 mAh / g.

[0236] From the experimental results described above, it was confirmed that the present invention manufactures a composite binder for a dry process using a liquid fiberization technique for PTFE and a second binder, and that this can be utilized as a binder for manufacturing dry electrodes. It was also confirmed that the dry electrode composition of the present invention can be applied as a composite binder for both positive and negative electrodes by adjusting the content of one or more of the first binder (fluoropolymer particles) and the second binder (shell material and membrane structure) constituting the included composite binder.

[0237] In particular, since the composite binder included in the dry electrode composition of the present invention is manufactured in a liquid phase, unlike the method of simply mixing particles with a dry blender, it is evident that more uniform compounding is possible at a microscopic level, and thus, more uniform characteristics can be realized.

[0238] Meanwhile, in the above-described embodiment, the fluoropolymer particles located in the core or on the inside were specified as PTFE, and the second binder constituting the shell or membrane structure was specified as an acrylonitrile-maleic acid copolymer; however, it can be easily implemented using other fluoropolymer particles as well as acrylonitrile-based copolymers, other binders for secondary batteries, or mixtures thereof mixed in a certain proportion as the second binder forming the shell or membrane structure.

[0239]

[0240] Although the present invention has been illustrated and described with reference to preferred embodiments as described above, it is not limited to the aforementioned embodiments, and various changes and modifications may be made by those skilled in the art within the scope of the invention without departing from the spirit of the invention.

Claims

1. A plurality of particle clusters formed by orientation of fluoropolymer particles and / or first binder particles, which are core-shell structured composite binder particles in which the surface of the fluoropolymer particles is wrapped with a second binder; and A composite binder for a dry process comprising: a plurality of membrane-structures formed of a second binder that partially and / or entirely encloses some and / or all of the plurality of clusters.

2. In Paragraph 1, A composite binder for dry processes characterized by comprising one or more selected from the group consisting of a fluorine-containing homopolymer, a fluorine-containing copolymer, or a combination thereof, the above-mentioned fluorine-based resin.

3. In Paragraph 1, A composite binder for dry processes, characterized in that the first binder particles have a diameter of 0.05 to 5.0 microns.

4. In Paragraph 1, A composite binder for dry processes characterized in that the first binder particles include polytetrafluoroethylene (PTFE).

5. In Paragraph 1, The above second binder is a composite binder for a dry process characterized by comprising one or more of the following: an acrylonitrile-based copolymer in which one or more of a compound having an acrylonitrile group, a compound having a glycol group, a compound having a styrene group, a compound having a butadiene group, and a compound having a carboxyl group are copolymerized; other binder resins for secondary batteries; or a combination thereof.

6. In Paragraph 5, A composite binder for dry processes characterized in that the acrylonitrile-based copolymer is one or more of acrylonitrile-maleic acid copolymer, acrylonitrile-acrylic acid copolymer, acrylonitrile-butadiene copolymer, and acrylonitrile-ethylene glycol-maleic acid copolymer.

7. In Paragraph 6, A composite binder for dry processes characterized by the acrylonitrile-based monomer having a structure in which a cyano group is attached to a vinyl group as the main chain.

8. In Paragraph 6, A composite binder for dry processes characterized in that the above acrylonitrile-maleic acid copolymer is composed of 80-99.98 mol% acrylonitrile-based monomer and 0.02-20 mol% maleic acid-based monomer.

9. In Paragraph 8, A composite binder for dry processes characterized in that the above maleic acid monomer is one or more of maleic acid, its salt, or an anhydrous maleic acid compounds in the form of the anhydrous forms thereof.

10. In Paragraph 9, A composite binder for dry processes characterized in that the above maleic acid-based monomer is maleic anhydride.

11. In Paragraph 5, A composite binder for dry processes characterized by the acrylonitrile-based copolymer having a weight-average molecular weight of 50,000 to 5,000,000 grams / mol.

12. In Paragraph 5, The above-mentioned binder resin for a secondary battery is a composite binder for a dry process characterized by being one or more selected from the group consisting of polyolefin, polyalkylenes, polyvinylidene fluoride (PVDF), carboxymethylcellulose, styrene-butadiene rubber (SBR), nitrile-based rubber, styrene-butadiene-styrene copolymer, polyacrylic acid, polyethylene-block-poly(ethylene glycol), poly(ethylene oxide), poly(phenylene oxide), cellulose, derivatives of cellulose or cellulose salts, polyethylene-block-poly(ethylene glycol), polyacrylonitrile (PAN), polydimethylsiloxane, and combinations thereof.

13. In Paragraph 5, A composite binder for a dry process, characterized in that when the second binder is a combination of the acrylonitrile-based copolymer and a binder resin for a secondary battery, the acrylonitrile-based copolymer and the binder resin for a secondary battery are included in a weight ratio of 90 to 10:10 to 90.

14. In Paragraph 1, A composite binder for dry processes characterized by comprising the plurality of clusters and the membrane structure in a weight ratio of 10:90 to 90:

10.

15. In any one of paragraphs 1 through 14, A composite binder for dry processes characterized by including one or more of a core-shell structure and a layered structure.

16. A step of preparing a first binder dispersion by dispersing first binder particles, which are fluorine-based resins, in a solvent; A step of preparing a second binder solution by dissolving the second binder in a solvent; A first stirring step of rotating a first binder dispersion at high speed to form a plurality of clusters formed by orienting a plurality of first binder particles; A second stirring step of high-speed rotating while introducing a second binder solution into a first binder dispersion having a plurality of clusters formed therein; and A method for manufacturing a composite binder for a dry process, comprising a post-processing step of filtering and washing the obtained result and then drying it.

17. In Paragraph 16, A method for manufacturing a composite binder for a dry process, characterized in that the content of the first binder particles dispersed in the first binder dispersion and the second binder dissolved in the second binder solution has a weight ratio of 90 to 10:10 to 90.

18. In Paragraph 16, A method for manufacturing a composite binder for a dry process, characterized in that high-speed rotation in the first stirring step and the second stirring step is performed at a speed of 2,000-30,000 rpm for 10 minutes to 10 hours under temperature conditions of 20-70 degrees.

19. In Paragraph 16, A method for manufacturing a composite binder for a dry process, characterized by further adding an interfacial binder containing fluorine and silicon or titanium in the first stirring step and the second stirring step.

20. In Paragraph 19, A method for manufacturing a composite binder for a dry process, characterized in that the above-mentioned interfacial binder is a fluorosilane-based or fluorotitanium-based interfacial binder and is added in an amount of 0.1 to 10 parts by weight relative to the weight of the first binder particles.

21. A dry electrode composition comprising an active material, a dry process composite binder according to any one of claims 1 to 14 or a dry process composite binder manufactured by a method according to any one of claims 16 to 20, and a nanocarbon material.

22. In Paragraph 21, A dry electrode composition characterized by comprising 85-98% by weight of the above active material, 1.0-10% by weight of the above composite binder for dry process, and 1.0-5% by weight of the above nanocarbon material.

23. In Paragraph 21, A dry electrode composition characterized in that the above nanocarbon material is any one selected from the group consisting of carbon nanotubes (single-wall, double-wall, multi-wall, and branched), carbon nanoplates, vapor-polymerized carbon nanofibers, carbon nanoribbons, conductive carbon black, graphene nanoplates, carbon balls, and combinations thereof.

24. In Paragraph 23, The above-mentioned nanocarbon material comprises a nanocarbon material having an aspect ratio of 100 or more and a nanocarbon material having an aspect ratio of less than 100 in a weight ratio of 10:90 to 90:10, characterized as a dry electrode composition.

25. A dry electrode sheet made of the dry electrode composition of claim 21.

26. A dry electrode comprising the dry electrode sheet of claim 25.

27. A secondary battery comprising the dry electrode of claim 26.

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