Highly adhesive dry electrode composition, electrode comprising dry electrode composition, and secondary battery comprising electrode

Abstract

The present invention relates to a technology associated with a dry electrode composition and, more specifically, to a highly adhesive dry electrode composition, an electrode comprising the electrode composition, and a secondary battery comprising the electrode, wherein the highly adhesive dry electrode composition uses a composite binder comprising an acrylonitrile-maleic acid-based copolymer, thereby having very excellent adhesiveness and excellent electrochemical properties while using a small amount of a fluorine-containing organic compound.

Description

A highly adhesive dry electrode composition, an electrode comprising the dry electrode composition, and a secondary battery comprising the electrode.

[0001] This invention was supported by the following national research and development project.

[0002] [Project ID] 1415188327

[0003] [Assignment No.] 20024827

[0004] [Ministry Name] Ministry of Trade, Industry and Energy

[0005] [Project Management (Specialized) Agency Name] Korea Institute of Industrial Technology Planning and Evaluation

[0006] [Research Project Title] Development of High-Binding Binder Suitable for Solid Electrolyte Fabrication and Electrode Plate Processing Conditions

[0007]

[0008] The present invention relates to a technology concerning a dry electrode composition, and more specifically, to a highly adhesive dry electrode composition that uses a composite binder containing an acrylonitrile-maleic acid copolymer to provide excellent adhesion while using less fluorine-containing organic compound, and also has excellent electrochemical properties, an electrode comprising said electrode composition, and a secondary battery comprising said electrode.

[0009] Rechargeable batteries, such as lithium-ion batteries, consist of active materials that exhibit electrochemical properties, conducting additives that impart conductivity, and binders that bind them. The active materials are materials that contain metal ions such as lithium or sodium (active materials for the positive electrode) or can accept these ions (active materials for the negative electrode). Representative positive electrode active materials are lithium-cobalt-oxide (LCO) or lithium-nickel-cobalt-manganese (NCM), and representative negative electrode active materials are active materials such as graphite, silicon, or silicon oxide. Conductive carbon black or carbon nanotubes are used as conducting additives. The binder is different for the positive electrode and the negative electrode; polyvinylidenefluoride (PVDF) is mainly used for the positive electrode, while a mixture of styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC), polyacrylic acid (PAA), or other water-based binders is mainly used for the negative electrode.

[0010] These binders bind the active material and the conductive material to impart cohesion between the components, and also serve to provide adhesion properties, such as adhesion between the electrode layer and the current collector. The binder content is adjusted differently depending on various factors, such as the type of active material, particle size, shape, and surface area.

[0011] For example, the binder content tends to be low when the particle size is large, such as in the form of secondary particles where single active particles are clustered together. However, it is generally common to increase the binder content when the particles are single or small, resulting in a large surface area or low surface adhesion. Additionally, the adhesiveness of the binder is a crucial factor; the higher the adhesive strength, the lower the amount of binder required. Since a lower binder content allows for a higher active material content, it is essential to improve the adhesive strength of the binder itself to increase the capacity per unit volume of a secondary battery.

[0012] For positive electrode binders, the main binders are PVDF for wet processes and polytetrafluoroethylene (PTFE) for dry processes, primarily using organic compounds containing fluorine components. Additionally, PTFE is also used as the main binder for dry negative electrodes. These compounds have an oxidation potential of 4.5V or higher, making them suitable for use as positive electrode binders. However, these fluorine-based resins have poor adhesion to other materials, and consequently, dry electrodes manufactured from them also exhibit poor adhesion to current collectors or poor binding strength among the components within the electrode. Furthermore, as the electrodes repeatedly expand and contract during repetitive charge-discharge cycles, the interfaces between the components become slightly separated, which ultimately acts as a factor that degrades the long-term reliability of the secondary battery.

[0013] To compensate for these drawbacks, it is necessary to develop a composite binder for dry electrode manufacturing by combining fluoropolymer particles, such as PTFE, with other binders suitable for secondary batteries. Using such a composite binder with enhanced adhesion as a dry electrode binder will increase the adhesion of the dry electrode and consequently improve long-term electrochemical properties.

[0014] Accordingly, the objective of the present invention is to provide a highly adhesive dry electrode composition having excellent adhesion and excellent electrochemical properties by using a composite binder in which a plurality of clusters formed by the copolymerization of acrylonitrile-based monomers and maleic acid-based monomers surround a plurality of clusters formed by the slender and elongated orientation of fluorine-based resin particles, thereby improving adhesion while including a fluorine-based resin, i.e., a composite binder in which a copolymer containing a film-structure formed by copolymerizing acrylonitrile-based monomers and maleic acid-based monomers is wrapped.

[0015] Another objective of the present invention is to provide a dry electrode in which electrical conductivity is stably maintained due to high adhesion, by including a high-adhesion dry electrode composition to enhance the adhesion between the electrode layer and the current collector and / or the cohesion between the components within the electrode.

[0016] Another objective of the present invention is to provide a secondary battery in which electrochemical characteristics, such as electrical capacity and charge / discharge cycle characteristics, are stably maintained by including a dry electrode in which electrical conductivity is stably maintained.

[0017] 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.

[0018] To achieve the objectives of the present invention described above, the present invention provides a dry electrode composition comprising an active material, a composite binder containing a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer, and a nanocarbon material.

[0019] In a preferred embodiment, the active material may be included in 85-98% by weight, the nanocarbon material in 1.0-5% by weight, and the composite binder in 1.0-10% by weight.

[0020] In a preferred embodiment, the copolymer is composed of 80-99.98 mol% of the acrylonitrile-based monomer and 0.02-20 mol% of the maleic acid-based monomer.

[0021] In a preferred embodiment, it consists of 85-99.5 mol% of the acrylonitrile-based monomer and 0.5-15 mol% of the maleic acid-based monomer.

[0022] 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.

[0023] 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.

[0024] In a preferred embodiment, the maleic acid-based monomer is maleic anhydride.

[0025] In a preferred embodiment, the copolymer has a weight-average molecular weight of 50,000 to 5,000,000 grams / mol.

[0026] In a preferred embodiment, the composite binder has a structure in which a membrane structure containing the copolymer partially and / or entirely encloses a portion and / or the entirety of a plurality of clusters formed by the orientation of fluoropolymer particles and / or core-shell structured composite binder particles.

[0027] In a preferred embodiment, the composite binder has a structure including one or more of a core-shell structure and a layered structure.

[0028] In a preferred embodiment, the plurality of clusters and the membrane structure are included in a weight ratio of 10:90 to 90:10.

[0029] In a preferred embodiment, the membrane structure further comprises another binder resin for a secondary battery.

[0030] 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.

[0031] In a preferred embodiment, the nanocarbon material comprises 1 to 60 parts by weight of a nanocarbon material having an aspect ratio of less than 100 per 100 parts by weight of a nanocarbon material having an aspect ratio of 100 or more.

[0032] In addition, the present invention provides a dry electrode sheet composed of any one of the dry electrode compositions described above.

[0033] In addition, the present invention provides a dry electrode comprising the dry electrode sheet described above.

[0034] In addition, the present invention provides a secondary battery comprising the dry electrode described above.

[0035] The high-adhesion dry electrode composition of the present invention described above utilizes a composite binder in which a copolymer-containing membrane structure, formed by copolymerizing acrylonitrile-based monomers and maleic acid-based monomers, surrounds a plurality of clusters formed by oriented thinly and elongatedly of fluorine-based resin particles, thereby providing excellent adhesion and excellent electrochemical properties.

[0036] In addition, the dry electrode of the present invention includes a highly adhesive dry electrode composition, thereby enhancing the adhesion between the electrode layer and the current collector and / or the cohesion between the components within the electrode, so that the electrical conductivity can be stably maintained.

[0037] In addition, the secondary battery of the present invention includes a dry electrode in which electrical conductivity is stably maintained, so it has the advantage that electrochemical characteristics such as electrical capacity and charge / discharge cycle characteristics can be stably maintained.

[0038] 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.

[0039] Figure 1 is an example of the chemical structural formula of the acrylonitrile-(anhydrous)maleic acid copolymer of the present invention.

[0040] Figure 2 shows the appearance of a PTFE aqueous dispersion according to an embodiment of the present invention.

[0041] Figure 3 shows a high-speed rotated PTFE aqueous dispersion according to an embodiment of the present invention.

[0042] Figure 4 is an electron microscope image of PTFE particles according to an embodiment of the present invention (original shape of fluoropolymer particles).

[0043] FIG. 5 is an electron microscope image of a composite binder according to an embodiment of the present invention (shape in which a copolymer surrounds a fiberized PTFE particle cluster).

[0044] Figure 6 is an enlarged electron microscope image of a PTFE particle cluster according to an embodiment of the present invention.

[0045] FIG. 7 is an infrared spectroscopic spectrum (FTIR spectrum) of a composite binder containing a copolymer according to an embodiment of the present invention.

[0046] Figure 8 is the result of a charge / discharge cycle test according to an embodiment of the present invention.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] Hereinafter, the technical configuration of the present invention will be described in detail with reference to the attached drawings and preferred embodiments.

[0053] 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.

[0054] The technical feature of the present invention lies in a highly adhesive dry electrode composition having excellent adhesion and excellent electrochemical properties, by using a composite binder in which a core (fluorine resin particle)-shell (second binder) structure is surrounded by a copolymer-containing membrane structure formed by copolymerizing an acrylonitrile-based monomer and a maleic acid-based monomer, and a new structure capable of improving adhesion while containing a fluorine resin, namely a fluorine resin particle cluster formed by fluorine resin particles oriented in a thin and elongated manner and / or a form in which a second binder surrounds the fluorine resin particles, i.e., a core (fluorine resin particle)-shell (second binder) structure surrounded by a copolymer containing an acrylonitrile-based monomer and a maleic acid-based monomer. In addition, there is a dry electrode having high adhesion, which maintains stable electrical conductivity by including a high-adhesion dry electrode composition to enhance the adhesion between the electrode layer and the current collector and / or the cohesion between the components within the electrode, and a secondary battery having electrochemical characteristics such as electrical capacity and charge / discharge cycle characteristics that maintain stable electrical conductivity, by including the dry electrode having stable electrical conductivity.

[0055] In other words, the present invention devises a dry electrode composition using a copolymer (hereinafter referred to as "PAM," "acrylonitrile-(anhydrous)maleic acid copolymer," or "copolymer of the present invention") in which an acrylonitrile-based monomer and a maleic acid-based monomer are copolymerized to increase adhesion while using a fluorine-containing organic compound, and composites this with fluorine-based resin particles to create a composite binder of a new structure, namely a composite binder in which a plurality of clusters formed by the copolymer-containing membrane structure of the present invention are oriented in a thin and long manner, wherein the fluorine-based resin particles and / or the fluorine-based resin particles are surrounded by the copolymer of the present invention, and a dry electrode comprising the same and a secondary battery comprising the dry electrode have been developed.

[0056] Accordingly, the dry electrode composition of the present invention comprises an active material, a composite binder containing a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer, and a nanocarbon material.

[0057] 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; and if the nano-carbon material content used in the dry electrode composition of the present invention is less than 1.0 weight%, the electrical conductivity of the electrode layer is low, so electron movement through the electrode layer is not smooth, which is a problem of degraded electrochemical properties; and if it exceeds 5 weight%, it is disadvantageous because the content of the active material is lowered due to the use of an excessive amount, resulting in a lower electrical capacity. 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.

[0058] 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).

[0059] 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 assisting in the formation of dry electrode sheets while performing the role of transferring electrons generated from the electrode active material to the current collector. However, as one embodiment, it may be any one selected from the group consisting of conductive carbon black, graphene nanoplates, carbon nanotubes (single-walled, double-walled, multi-walled, branched, etc.), carbon nanoplates, vapor-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, because the effect of enhancing the conductivity of the electrode layer is greater than that of using a single type of nanocarbon material. In the present invention, when the nanocarbon material is a mixture of nanocarbon materials with different aspect ratios, the amount of nanocarbon material with an aspect ratio of less than 100 may be 1 to 60 parts by weight per 100 parts by weight of nanocarbon material with an aspect ratio of 100 or more. This is because using a large amount of nanocarbon material with an aspect ratio of 100 or more helps in forming a dry electrode surface.

[0060] In the dry electrode composition of the present invention, the composite binder contains the copolymer of the present invention, namely a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer. In particular, the form is not limited as long as the acrylonitrile-maleic acid copolymer or the composition containing the acrylonitrile-maleic acid copolymer is arranged in a form that minimizes the exposure of the fluorine resin and is implemented in a combined form between the copolymer or the composition containing the copolymer and the fluorine resin. In the composite binder of the present invention, the fluorine resin and the acrylonitrile-maleic acid copolymer or the composition containing the acrylonitrile-maleic acid copolymer may be included in a weight ratio of 10:90 to 90:10.

[0061] As one embodiment, the composite binder may be implemented to have a structure in which a membrane structure containing an acrylonitrile-maleic acid copolymer partially and / or wholly encloses a plurality of clusters formed by orientation of fluoropolymer particles (Fig. 4; electron microscope image of PTFE particles) and / or core (fluoropolymer particles)-shell (second binder) structured composite binder particles (Fig. 6; enlarged image of a portion of Fig. 5), as shown in FIG. 5 (electron microscope image of the composite binder of the present invention). Here, FIG. 4 is the original shape of the fluoropolymer particles, FIG. 5 is an electron microscope image of the composite binder manufactured using the technology of the present invention, and FIG. 6 is an enlarged image of the particle portion of FIG. 5. As shown in FIGS. 4 to 6, although the PTFE particles themselves are spherical particles with a size of about 0.25 microns, when processed by the method of the present invention, a core-shell structured composite binder is formed in which the surface of the PTFE particles is covered by the copolymer of the present invention, and a composite binder is formed in which a plurality of composite binder particles gather to form a cluster, and a membrane structure containing the copolymer of the present invention partially or entirely covers the cluster. More specifically, if the shape of the composite binder is specified, it may be formed in a form in which a membrane structure containing an acrylonitrile-maleic acid copolymer covers part and / or all of a plurality of clusters formed by fluoropolymer particles and / or core (fluoropolymer particles)-shell (second binder) structured composite binder particles.

[0062] Here, the fluorine resin included in the composite binder of the present invention is not limited to any material containing a fluorine component, 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), and polyvinylidene fluoride (PVDF) may be used, and in particular, may include PTFE. As one embodiment, the diameter of the fluorine resin particles may be 0.05 to 5.0 microns. If the particle size of the fluorine resin is less than 0.05 microns, the particles are too small, making it difficult to form fluorine resin particles or to form a fluorine resin dispersion, 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.

[0063] In addition, the membrane structure that partially and / or wholly encases the fluorine resin may be formed in the form of a thin film consisting solely of an acrylonitrile-maleic acid copolymer or mixed with one or more other secondary battery binder resins, and the other secondary battery binders may include all types of binders that are polymers soluble in organic or aqueous solvents and have been used as electrode binders in the past, are currently being used, or have the potential to be used in the future. Representative binder materials may be binder materials composed of components such as polyolefins like ethylene, polyalkylenes, styrene-butadiene rubber (SBR), nitrile rubber, polyacrylic acid, polyacrylonitrile (PAN), acrylonitrile copolymers, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and cellulose. The mixing ratio of the acrylonitrile-maleic acid copolymer constituting the membrane structure and other binder compounds for secondary batteries may be (90-10):(10-90) by weight. This mixing ratio is a formulation determined through experiments to impart the properties of the acrylonitrile-maleic acid copolymer while utilizing the various advantages (physicochemical properties or economic advantages, etc.) of other binder resins for secondary batteries, because basically, the membrane structure must contain at least 10% by weight of the acrylonitrile-maleic acid copolymer to exhibit excellent adhesive properties.

[0064] More specifically, regarding the acrylonitrile-maleic acid copolymer included in the composite binder of the present invention, the acrylonitrile-maleic acid copolymer is not a simple mixture of acrylonitrile-based polymers and maleic acid-based polymers, but rather a compound in which acrylonitrile-based monomers and maleic acid-based monomers are bonded through a chemical reaction. In the present invention, it is adopted for the first time as a binder that can be used in an electrode composition for a secondary battery. Through numerous experiments, it has been confirmed that the acrylonitrile-based monomer constituting the copolymer can impart electrochemical properties to the electrode, and the maleic acid-based monomer can enhance the bonding between the metal current collector or the components within the electrode.

[0065] Here, 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 the acrylonitrile compound alone, one composed with other compounds such as in a copolymer form, 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.

[0066] 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. In 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 even a small amount can significantly improve adhesion. It is advantageous to produce it in the form of graft or random copolymerization, because if other additives such as emulsifiers or dispersants are used, such as in emulsion polymerization, these additives may affect the electrochemical properties of the electrode if they are not completely removed.

[0067] In the present invention, 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 as one embodiment, it may contain 80-99.98 mol% of an acrylonitrile-based monomer and 0.02-20 mol% of a maleic acid-based monomer. Since there is a problem that the adhesive strength enhancement effect is significantly reduced if the content of the maleic acid component in the copolymer is lower than 0.02 mol%, and there is a problem that the copolymerization reaction becomes too slow if it exceeds 20 mol%, 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.

[0068] The weight-average molecular weight of the acrylonitrile-maleic acid copolymer used in the dry electrode composition of the present invention may be in the range of 50,000 to 5,000,000 grams / mol. This is because if the weight-average molecular weight of the copolymer is less than 50,000 grams / mol, the molecular weight is too low and the physical properties of the electrode layer deteriorate, which is disadvantageous, and if it is 5,000,000 grams / mol or more, it is difficult to obtain using a general radical polymerization method, and there is a problem that it is difficult to uniformly disperse the active material and the conductive material due to the high molecular weight and high viscosity.

[0069] In addition, the acrylonitrile-maleic acid copolymer used in the dry electrode composition of the present invention can be synthesized by combining or sequentially using one or more reaction initiators from various forms, such as radical polymerization using 2,2-azobisisobutyronitrile (AIBN), peroxide, oxidizing agent or photoinitiator, ionic polymerization, oxidative polymerization represented by ammonium persulfate, redox polymerization using redox reaction, a method using organic acid-based reaction initiators such as acetic acid or para-toluenesulfonic acid, or thermal polymerization.

[0070] 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.

[0071] At this time, 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 4 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 4 hours, the reaction does not proceed well because the temperature is too low or the reaction time is too short; if the temperature exceeds 120°C or the reaction time exceeds 72 hours, there is a possibility that the synthetic product may be deformed due to an overly rapid reaction or a reaction for a long time. The molecular weight of the synthesized copolymer can be controlled by adjusting detailed reaction conditions of the above synthesis reaction, such as the content of reactants and reaction initiators, the order or rate of addition, the reaction temperature, and the time.

[0072] The acrylonitrile-maleic acid copolymer-containing composite binder of the present invention having the composition described above can be used to manufacture a composite binder for manufacturing dry electrodes by using a liquid-phase blending method together with a fluoropolymer binder having excellent fiberization performance.

[0073] The liquid blending method is a process for manufacturing a composite binder by microscopically combining two binders by adding a second binder solution, in which the binder to be combined is dissolved, to a first binder dispersion, in which a single type of binder in a particulate state is dispersed in a solvent. Since the liquid blending method involves mixing binders while they are 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 aqueous solvents. In particular, it has the advantage of enabling the production of a mixed binder composed of pure polymers by removing impurities that may be present during the manufacturing of fluoropolymer particles or other binders during the washing process.

[0074] A microscopically uniformly composited composite 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 aqueous dispersion (Fig. 2), which is a fluoropolymer particle, as a first binder is described. The liquid-phase fibrilization technique is a method devised in the present invention, which processes fluoropolymer particles existing in a dispersion state within a solvent to arrange the fluoropolymer particles into a thin, long shape, that is, to make them fibrilized. This involves a PTFE aqueous dispersion of 20-70 o This can be implemented by rotating at a speed of 2,000–30,000 rpm for 10 minutes–10 hours at a temperature of C. However, under rotation conditions below the lower limit or above the upper limit of the above conditions, liquid fiberization does not occur properly, or problems such as heat generation due to excessive rotation or the liquid fiberized first binder particles unraveling occur, making it disadvantageous. This is a technique in which rotating the PTFE aqueous dispersion at a high speed forms a cluster of thin, long fibers in the direction of rotation, similar to a grape cluster, where numerous fluoropolymer particles form a cluster (Fig. 3). A second binder solution is added to the liquid fiberized PTFE particle cluster, and under the same rotation conditions (2,000–30,000 rpm, 20–70 oA composite binder (Fig. 5) can be manufactured by further rotating the material (C, 10 min - 10 hours) to form a multitude of particles constituting a thin, elongated cluster, in which a membrane structure containing an acrylonitrile-maleic acid copolymer is wrapped around them. Experiments have confirmed that a composite binder using fluoropolymer particles arranged in a fibrous manner in this form is advantageous for manufacturing dry electrodes. If the particles in Fig. 5 are observed in more detail, they have a shape in which the copolymer of the present invention is wrapped around the surface of fluoropolymer particles, such as PTFE, and they are not circular but are attached to each other. This is because PTFE is located inside, and its surface is wrapped by the copolymer of the present invention, which has high adhesive strength. Therefore, the shape of the composite binder exhibited by the composite binder of the present invention can be described as a composite binder in which a membrane structure containing the copolymer of the present invention surrounds part and / or the whole of a composite binder particle cluster formed by the aggregation of composite binder particles having a core (fluoropolymer particle)-shell (copolymer of the present invention) structure.

[0075] 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%.

[0076] 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.

[0077] 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 containing an acrylonitrile-maleic acid copolymer into a dry mixer and mixing them at high speed, and a second step of calendering the dry electrode composition using a calendering device.

[0078] 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.

[0079]

[0080] 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.

[0081] 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.

[0082] 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.

[0083] Example 1

[0084] 1. Synthesis of Acrylonitrile-Maleic Anhydride Copolymer

[0085] The acrylonitrile-maleic anhydride copolymer shown in Fig. 1 was synthesized as follows. First, 99.5 mol% acrylonitrile and 0.5 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.

[0086] 2. Preparation of a composite binder containing an acrylonitrile-maleic anhydride copolymer

[0087] As shown in Fig. 2, a first binder dispersion composed of PTFE particles with a solid content of 50% was prepared by dispersing PTFE particles in water. A second binder solution with a solid content of 10% was prepared by dissolving copolymer 1 in a DMF solution. Subsequently, the first binder dispersion was stirred and rotated at 5,000 rpm for 2 hours to induce liquid-phase fiberization (Fig. 3). Afterward, the second binder solution was added to the first binder dispersion while stirring at the same speed for 1 hour to mix the two components, and then filtered, washed, and dried to obtain composite binder 1 (Fig. 5). At this time, the content of PTFE and copolymer 1 was set to a weight ratio of 50:50.

[0088] 3. Preparation of dry electrode composition

[0089] A dry electrode composition 1 comprising 95 wt% of active material (NCM811), 2 wt% of multi-walled carbon nanotubes, and 3 wt% of composite binder 1 was prepared as follows. First, the composite binder 1 and multi-walled carbon nanotubes were placed in a mixer and mixed by high-speed rotation at 10,000 rpm for 10 minutes. Afterward, the active material was added, and the mixture was rotated and mixed at the same rotation speed for another 3 minutes to prepare the dry positive electrode composition 1.

[0090] Example 2

[0091] Acrylonitrile-maleic anhydride copolymer 2 was synthesized in the same manner as in Example 1, except that 95 mol% acrylonitrile and 5 mol% maleic anhydride were used, and then a composite binder 2 was prepared in the same manner as in Example 1, and then a dry positive electrode composition 2 was prepared.

[0092] Example 3

[0093] A dry positive electrode composition 3 was prepared by performing the same method as in Example 1 after preparing the composite binder 1, except that 94 wt% of the active material (LFP), 2 wt% of multi-walled carbon nanotubes, and 4 wt% of the composite binder 1 were used. Here, the active material used was lithium iron phosphate (LFP) in a bimodal form with an average particle size (D50) of 2.5 microns.

[0094] Example 4

[0095] A composite binder 3 was prepared by having the content of PTFE and copolymer 1 in a weight ratio of 20:80, and a dry negative electrode composition was prepared by performing the same method as in Example 1, except that graphite was used as the active material.

[0096] Example 5

[0097] After preparing composite binder 1 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. The composite binder 1, conductive carbon black, and solid electrolyte were placed in a mixer and mixed at 10,000 rpm for 10 minutes, after which the active material was added and mixed again for 3 minutes to prepare the dry electrode composition for a sulfide-based solid-state battery.

[0098] Example 6

[0099] 1. Dry positive electrode sheet preparation step

[0100] Dry positive electrode sheet 1 was prepared using the dry positive electrode composition 1 and the calendering method in a dry electrode manufacturing apparatus.

[0101] 2. Dry positive electrode preparation step

[0102] Dry positive electrode 1 was manufactured by attaching a dry positive electrode sheet 1 onto a current collector having a primer layer formed thereon in a continuous process. The attachment of the dry positive electrode sheet and the current collector was achieved by passing them between rolls set to be 30% thinner than the total thickness of the current collector and the dry positive electrode at a high temperature (100°C), and then the dry positive electrode 1 was manufactured by rolling at a high temperature (100°C).

[0103] Example 7

[0104] Dry positive electrode sheet 2 was prepared in the same manner as in Example 6, except that dry positive electrode composition 2 was used, and then dry positive electrode 2 was prepared.

[0105] Example 8

[0106] Dry positive electrode sheet 3 was prepared in the same manner as in Example 6, except that dry positive electrode composition 3 was used, and then dry positive electrode 3 was prepared.

[0107] Example 9

[0108] 1. Dry negative electrode sheet preparation step

[0109] A dry negative electrode sheet was produced using a dry negative electrode composition and the calendering method in a dry electrode manufacturing device.

[0110] 2. Dry negative electrode preparation step

[0111] A dry negative electrode was manufactured by attaching a dry negative electrode sheet onto a current collector having a primer layer formed thereon in a continuous process. At this time, a copper foil with a primer layer formed thereon with a thickness of 1-2 microns was used as the current collector to make the negative electrode. The dry negative electrode sheet and the current collector were attached by passing them between rolls set to be 30% thinner than the total thickness of the current collector and the dry electrode at a high temperature (100℃), and then the dry negative electrode (thickness: ~50 microns) was manufactured by rolling at a high temperature (100℃).

[0112] Example 10

[0113] 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 ).

[0114] Example 11

[0115] 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.

[0116] Example 12

[0117] A coin cell (CR2032 type)2 with a half-cell structure was manufactured by performing the same method as in Example 11, except that a dry positive electrode 2 was used.

[0118] Example 13

[0119] Coin cell 3 was manufactured by performing the same method as in Example 11, except that a dry positive electrode 3 was used.

[0120] Example 14

[0121] A negative electrode coin cell with a half-cell structure was manufactured using the same method as in Example 11, except that a dry negative electrode was used.

[0122] Example 15

[0123] An all-solid-state pressure cell was manufactured by stacking as follows using an all-solid-state dry electrode.

[0124] 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.

[0125] Comparative Example 1

[0126] A comparative pre-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 multi-walled carbon nanotubes were placed in a mixer and mixed by high-speed rotation at 10,000 rpm for 10 minutes. Afterward, the active material was added, and the mixture was further rotated and mixed at the same rotation speed for 23 minutes to prepare the comparative pre-dry anode composition 1.

[0127] Comparative Example 2

[0128] A comparative dry electrode composition 2 for an all-solid-state battery was prepared by performing the same method as in Example 5, except that PTFE was used instead of composite binder 1.

[0129] Comparative Example 3

[0130] Comparative example dry positive electrode sheet 1 was prepared in the same manner as in Example 6, except that comparative example dry positive electrode composition 1 was used, and then comparative example dry positive electrode 1 was prepared.

[0131] Comparative Example 4

[0132] Comparative pre-dry positive electrode sheet 2 was prepared in the same manner as in Example 6, except that Comparative pre-dry positive electrode composition 2 was used, and then Comparative pre-dry positive electrode 2 was prepared.

[0133] Comparative Example 5

[0134] A comparative example coin cell with a half-cell structure was prepared by performing the same method as in Example 11, except that a comparative example dry positive electrode 1 was used.

[0135] Comparative Example 6

[0136] A comparative pre-pressure cell was manufactured by performing the same method as in Example 15, except that a comparative pre-dry positive electrode 2 was used.

[0137] Experimental Example 1

[0138] In Examples 1 and 2, acrylonitrile-maleic anhydride copolymers 1 and 2 in the form of white particles were synthesized, respectively, and composite binders 1 and 2 were obtained based on this. Since composite binders 1 and 2 differ only in the content of maleic anhydride, the explanation for determining whether the composite binder of the present invention has been synthesized will be explained using the infrared spectroscopic spectrum (FTIR spectrum) of composite binder 1.

[0139] Figure 7 shows the FTIR spectrum for composite binder 1. Looking at this spectrum, the characteristic peak of PTFE is at 1150–1200 cm⁻¹. -1 This can be confirmed by the measurement of a large peak at , and the acrylonitrile component is at 2244 cm⁻¹. -1 It is measured in the vicinity, which is the characteristic pit of the cyanide group (-CN). And the presence of maleic acid or maleic anhydride components is determined by the 1600–1750 cm⁻¹ range of the infrared spectroscopic spectrum. -1 It was confirmed that a carbonyl peak was observed in the region (Fig. 7). Since the composite binder 2 using copolymer 2 of the present invention has the same components, it is observed at the same location. For reference, the weight-average molecular weight (GPC method) of the two copolymers was measured as 725,000 grams / mol for copolymer 1 (Example 1) and 850,000 grams / mol for copolymer 2. From these results, it was confirmed that the composite binders 1 and 2 of the present invention were successfully synthesized.

[0140] Experimental Example 2

[0141] In Examples 1 and 2, composite binders 1 and 2 were prepared by using a PTFE aqueous dispersion (Fig. 2), which is a fluoropolymer particle, and copolymer 1 or copolymer 2 dissolved in DMF, respectively.

[0142] First, when the PTFE aqueous dispersion (Fig. 2) is rotated at a high speed, the PTFE particles align in the direction of rotation to form a fibrous structure. As shown in Fig. 3, water penetrates between the PTFE particles, widening the gaps between them and solidifying. In other words, the PTFE particles are arranged in long, thin lines through liquid-phase fiberization; since this resembles a grape cluster, it will be referred to as a PTFE particle cluster. When a solution containing copolymer 1 or copolymer 2 is added and the mixture is rotated at a high speed, the two substances—the PTFE particle cluster and the copolymer—mix and align again in the direction of rotation. At this point, the copolymer, acting as the second binder, partially or entirely encases the particle cluster (Fig. 5). Furthermore, when the particle cluster in Fig. 5 is observed under magnification (Fig. 6), the particles in Fig. 6 appear irregular and attached to each other, unlike the circular PTFE particles in Fig. 4. This demonstrates that when a PTFE aqueous dispersion is rotated at high speed, a second binder solution is added to it, and the mixture is rotated again, the resulting structure is a core-shell composite binder particle cluster in which PTFE particles are located inside and the second binder surrounds the surface. Therefore, the composite binder of the present invention is formed in a form in which composite binder particles with a core (fluoropolymer particles)-shell (copolymer of the present invention) structure gather to form clusters, and the copolymer of the present invention is positioned between some and / or all of these clusters or between already formed composite binder particle clusters; that is, a composite binder having one or more microstructures among a core-shell and a layered structure is produced. From this, it can be seen that the composite binder of the present invention is obtained in a form in which PTFE particles in a dispersion state undergo liquid phase fibrilization by high-speed rotation and are surrounded by the copolymer of the present invention.

[0143] The microstructure of the composite binder comprising one or more of the core-shell and layered structures of the present invention 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 and 6, 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.

[0144] Experimental Example 3

[0145] Similar to Comparative Example Dry Anode Sheet 1 obtained in Comparative Example 3 using the conventional dry binder PTFE, both Dry Anode Sheets 1-2 obtained in Examples 6 and 7 could be produced as high-quality dry electrode sheets with clean surfaces using the calendering method. Therefore, it can be confirmed that the composite binder of the present invention produces dry anode sheets without any difference from the conventional dry binder PTFE. Furthermore, Comparative Example Dry Anode Sheet 1 and Dry Anode Sheets 1 and 2 could be manufactured by attaching them to a current collector at high temperature without any particular difficulty, and the loading level of these anodes was ~20 mg / cm² 2 , and the electrode density is 3.0 g / cm³ 3 It was confirmed to be.

[0146] The surface resistance and adhesion of these positive electrode plates were measured.

[0147] The surface resistance of dry positive 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 positive electrode sheet 1 to a current collector is 10 -3It 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 electrode 2, dry positive electrode 3, the all-solid-state battery dry positive electrode, and the comparative example dry positive electrode 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.

[0148] The adhesion test for the above dry positive electrode 1 was performed as follows. First, the current collector side of the dry positive electrode 1 was attached to a glass substrate using double-sided tape. Then, a tape (3M Scotch tape; width: 18 mm) was attached to the electrode layer on the opposite side, and after 30 minutes, the peel strength was measured using a tensile testing machine. The value obtained by dividing this by the tape width (18 mm) was expressed as the adhesion strength (N / mm). The adhesion strength of the 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 is because, in the case of PTFE, a low value is measured due to the release characteristics of the fluorine component, and the copolymer 1 of the present invention is a compound copolymerized with a component having strong adhesive properties. In the case of dry positive electrode 2, the adhesion strength is 0.087 N / mm, which is higher than that of dry positive electrode 1. This is predicted to be because the maleic acid content (5 mol%) is higher than that of dry positive electrode 1 (0.5 mol%).

[0149] Synthesizing the above results, it was found that as the content of maleic acid copolymerized with acrylonitrile in the acrylonitrile-maleic acid copolymer of the present invention increases, the adhesive strength of the copolymer of the present invention also increases. From these results, it was confirmed that the composite binder using the acrylonitrile-maleic acid copolymer of the present invention meets the purpose of enhancing the adhesive strength of the electrode layer.

[0150] Experimental Example 4

[0151] A charge-discharge cycle test, which is one of the electrochemical characteristics, was performed on Coin Cell 1-2 and Comparative Example Coin Cell. The charge-discharge cycle test was performed by undergoing the formation process twice at a rate of 0.1C and then performing 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.

[0152] From the charge / discharge cycle test results for Coin Cell 1 shown in Fig. 8, 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 94%. Coin Cell 2 also showed similar results to Coin Cell 1. This suggests that since cell performance is largely determined by the active material, even if the binder components differ slightly, if the type and content of the active material are the same, the cells exhibit similar performance.

[0153] On the other hand, in the case of the comparative example coin cell, the initial efficiency was 90%, the capacity after 3 cycles was 189 mAh / g, and the capacity after 50 cycles was 173 mAh / g, showing a capacity retention rate of 92%, which was lower than that of coin cells 1 and 2. This result demonstrates that even if the active material content is the same, different cell characteristics can be observed depending on the type of binder, and it can be seen that the composite binder using the copolymer of the present invention exhibits superior cell characteristics compared to the standard sample PTFE.

[0154] Experimental Example 5

[0155] As in Examples 3 and 13, the composite binder 1 of the present invention was applied to LFP, a different type of active material, to manufacture a dry positive electrode 3 and a coin cell 3, and charge-discharge cycle tests were performed on them. As a result of measurement, the initial efficiency was approximately 93%, the initial capacity was 149 mAh / g, and the capacity after 50 cycles was 148 mAh / g, showing a capacity retention rate of nearly 100%. This result demonstrates the characteristics of a typical LFP active material, which has a very high capacity retention rate despite having a lower electrical capacity than NCM811. From this, it is shown that the composite binder containing the copolymer of the present invention can be applied to LFP active materials and, furthermore, to other types of active materials. In the wet method, completely different binders must be used depending on whether it is for the positive electrode or the negative electrode because the solvent system is different; however, since the dry method does not use a solvent, the range of binder selection is much wider. In addition, it can be confirmed that the composite binder using the copolymer of the present invention is a binder that can be applied not only to NCM but also to LFP and furthermore to other types of active materials.

[0156] Experimental Example 6

[0157] The dry negative electrode composition obtained in Example 4 is an example in which a binder material of the same type as the composite binder used in the dry positive electrode composition is utilized with a different relative content ratio. That is, for the positive electrode, the weight ratio of PTFE constituting the composite binder to the copolymer of the present invention was set to 50:50, and for the negative electrode, it was set to 20:80. In this case, the content ratio of PTFE to copolymer 1 was set to 20:80 for the negative electrode to reduce the content of PTFE, as the reduction potential of PTFE showed a relatively high value.

[0158] The dry negative electrode sheet exhibited good adhesion with an adhesion strength of approximately 0.065 N / mm, and the surface resistance was measured to be approximately 100 ohms / area. In addition, the charge-discharge cycle test results for the negative electrode coin cell showed an initial efficiency of 90%, an initial capacity of 340 mAh / g after 3 cycles, and a capacity of 339 mAh / g after 50 cycles, demonstrating a capacity retention rate of nearly 100%.

[0159] Experimental Example 7

[0160] A dry electrode for a sulfide-based solid-state battery containing composite binder 1 as in Example 5 was prepared as in Example 10, and a pressure cell for a solid-state battery was prepared therefrom as in Example 15, and a charge-discharge cycle test was performed on the pressure cell.

[0161] 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.

[0162] The all-solid-state battery dry electrode had a clean surface and a 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 94%. 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.

[0163] From the experimental results described above, it was confirmed that the present invention can prepare a composite binder using a liquid-phase fiberization technique for PTFE and an acrylonitrile-maleic acid copolymer, and utilize it 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 fluoropolymer particles, shells, and membrane structures constituting the included composite binder.

[0164] 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.

[0165] 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 dry electrode composition comprising an active material, a composite binder containing a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer, and a nanocarbon material.

2. In Paragraph 1, A dry electrode composition characterized by comprising 85-98 wt% of the above active material, 1.0-5 wt% of the above nanocarbon material, and 1.0-10 wt% of the above composite binder.

3. In Paragraph 1, A dry electrode composition characterized by the copolymer comprising 80-99.98 mol% of the acrylonitrile-based monomer and 0.02-20 mol% of the maleic acid-based monomer.

4. In Paragraph 3, A dry electrode composition characterized by being composed of 85-99.5 mol% of the acrylonitrile-based monomer and 0.5-15 mol% of the maleic acid-based monomer.

5. In Paragraph 1, A dry electrode composition characterized in that the above-mentioned acrylonitrile-based monomer has a form in which a cyano group is attached to a vinyl group as the main chain.

6. In Paragraph 1, A dry electrode composition 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 anhydrous form thereof.

7. In Paragraph 6, An electrode composition characterized in that the above maleic acid-based monomer is maleic anhydride.

8. In Paragraph 1, The above copolymer is a dry electrode composition characterized by having a weight-average molecular weight of 50,000-5,000,000 grams / mol.

9. In Paragraph 1, The above composite binder is a dry electrode composition characterized by having a structure in which a membrane structure containing the copolymer partially and / or entirely encloses a plurality of clusters formed by the orientation of fluoropolymer particles and / or core-shell structured composite binder particles.

10. In Paragraph 9, The above composite binder is a dry electrode composition characterized by having a structure including one or more of a core-shell structure and a layered structure.

11. In Paragraph 9, A dry electrode composition characterized by comprising the plurality of clusters and the membrane structure in a weight ratio of 10:90 to 90:

10.

12. In Paragraph 9, A dry electrode composition characterized in that the above membrane structure further comprises another binder resin for secondary batteries.

13. In Paragraph 1, 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.

14. In Paragraph 13, A dry electrode composition characterized by comprising 1 to 60 parts by weight of a nanocarbon material having an aspect ratio of less than 100 per 100 parts by weight of a nanocarbon material having an aspect ratio of 100 or more.

15. A dry electrode sheet composed of a dry electrode composition according to any one of claims 1 to 14.

16. A dry electrode comprising the dry electrode sheet of claim 15.

17. A secondary battery comprising the dry electrode of claim 16.

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