Nanocarbon dispersion containing non-fluorine-based binder, highly adhesive electrode slurry comprising nanocarbon dispersion, electrode comprising electrode layer formed from electrode slurry, and secondary battery comprising electrode

Abstract

The present invention relates to a technology related to an electrode composition and, more specifically, to an electrode composition containing non-fluorine-based binder, an electrode comprising the electrode composition, and a secondary battery comprising the electrode, the electrode composition exhibiting excellent adhesion and electrochemical properties without using a fluorine-containing organic compound that is mainly used as a binder in electrode compositions for secondary batteries.

Description

A nanocarbon dispersion containing a non-fluorinated binder, a highly adhesive electrode slurry comprising the nanocarbon dispersion, an electrode comprising an electrode layer formed from the electrode slurry, and a secondary battery comprising the electrode.

[0001] The present invention relates to a technology concerning electrode compositions and / or primer compositions, and more specifically, to a nanocarbon dispersion having excellent adhesion and electrochemical properties without using a fluorine-containing organic compound, which is mainly used as a binder in electrode compositions and primer compositions for secondary batteries, an electrode slurry comprising said nanocarbon dispersion, an electrode comprising an electrode layer formed from said electrode slurry, and a secondary battery comprising said electrode.

[0002] Rechargeable batteries, typified by lithium-ion batteries, consist of active materials exhibiting electrochemical properties, conducting additives that impart conductivity, and binders that bind them. The active materials are substances 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), while representative negative electrode active materials are active materials such as graphite, silicon, or silicon oxide. Conducting additives mainly use conductive carbon black or carbon nanotubes. 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.

[0003] 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.

[0004] For example, the binder content tends to be low for active materials with large particle sizes, such as secondary particles; however, it is common practice to increase the binder content when the particles are 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 content of active material, it is essential to enhance the adhesive strength of the binder itself to increase the capacity per unit volume of a secondary battery.

[0005] For anode 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 and are suitable for use as anode binders. However, it is difficult to achieve uniform dispersion of these fluorine-based compounds with nanocarbon materials, such as conductive carbon black or carbon nanotubes, which are used as conductive materials. Furthermore, even if a nanocarbon dispersion is prepared, problems arise where the flowability of the dispersion deteriorates over time. In particular, compounds containing fluorine components also pose the problem of generating toxic gases (hydrogen fluoride; HF) in the event of a fire.

[0006] Therefore, there is a need to develop a nano-carbon dispersion containing a non-fluorine binder that exhibits excellent flowability over time and possesses good adhesion and electrochemical properties, enabling it to be used not only in electrode slurries but also in primer compositions.

[0007] Accordingly, the objective of the present invention is to provide a nano-carbon dispersion containing a non-fluorine binder that exhibits excellent flowability over time and excellent adhesion and electrochemical properties when used in electrode slurries as well as primer compositions, and a method for manufacturing the same.

[0008] Another objective of the present invention is to provide a highly adhesive electrode slurry containing a non-fluorine binder that can reduce the binder content by providing excellent adhesion, such as high adhesion even when using active materials that are in the form of single particles or have a large surface area due to their small particle size, by including a nano-carbon dispersion containing a non-fluorine binder.

[0009] Another objective of the present invention is to provide an electrode in which electrical conductivity is stably maintained due to high adhesion, achieved by enhancing the adhesion between the electrode layer formed from a non-fluorine binder-containing high-adhesion electrode slurry and the current collector, and / or enhancing the cohesion between the components within the electrode.

[0010] 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 an electrode in which electrical conductivity is stably maintained.

[0011] Another objective of the present invention is to provide a current collector comprising a primer layer having excellent adhesion, formed from a nanocarbon dispersion containing a non-fluorine binder.

[0012] 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.

[0013] To achieve the objectives of the present invention described above, the present invention provides a nanocarbon dispersion composed of a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer, a nanocarbon material, and a solvent.

[0014] In a preferred embodiment, the solid content is 0.2 to 20 weight%.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] In a preferred embodiment, the maleic acid-based monomer is maleic anhydride.

[0020] In a preferred embodiment, the copolymer has a weight-average molecular weight of 50,000-3,000,000 grams / mol.

[0021] 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, carbon balls, and combinations thereof.

[0022] In a preferred embodiment, the nanocarbon material is used by mixing a nanocarbon material having an aspect ratio of 100 or more and a nanocarbon material having an aspect ratio of less than 100.

[0023] In a preferred embodiment, the copolymer is included in an amount of 20 to 500 parts by weight per 100 parts by weight of the nanocarbon material.

[0024] In a preferred embodiment, the hydrogen ion index of the nanocarbon dispersion is 5.5 to 7.5.

[0025] In addition, the present invention provides a method for preparing a nanocarbon dispersion, comprising: a first step of preparing a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer; a second step of preparing a precursor solution by dissolving the copolymer in a solvent; a third step of preparing a precursor dispersion by adding a nanocarbon material to the precursor solution and stirring; a fourth step of kneading the precursor dispersion; and a fifth step of re-stirring the kneaded precursor dispersion.

[0026] In a preferred embodiment, in the third step, stirring is performed at 1500 to 3000 rpm for 2 to 7 minutes.

[0027] In a preferred embodiment, in the fourth step, mixing is performed by high-pressure spraying, and in the fifth step, re-stirring is performed at 200 to 900 rpm for 5 to 24 hours.

[0028] In a preferred embodiment, the precursor dispersion has a solid content of 0.2 to 20 weight%, and the solid content comprises 20 to 500 weight parts of the copolymer per 100 weight parts of nanocarbon material.

[0029] In addition, the present invention provides a current collector comprising a primer layer formed from any one of the nano-carbon dispersions described above or a nano-carbon dispersion prepared by any one of the manufacturing methods described above.

[0030] In addition, the present invention provides a dry electrode comprising the above-described current collector.

[0031]

[0032] In addition, the present invention provides an electrode slurry comprising an active material; and any one of the nano-carbon dispersions described above or a nano-carbon dispersion prepared by any one of the manufacturing methods described above.

[0033] In a preferred embodiment, the solid content is 70% by weight or more.

[0034] In a preferred embodiment, the active material is any one selected from the group consisting of alkali metals, alkaline earth metals, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, graphite, silicon, silicon oxide, sulfur, and combinations thereof.

[0035] In addition, the present invention provides an electrode comprising an electrode layer formed from the electrode slurry described above.

[0036] In addition, the present invention provides a secondary battery comprising the electrode described above.

[0037] The nano-carbon dispersion of the present invention described above contains a non-fluorine-based binder and exhibits excellent flowability over time, as well as excellent adhesion and electrochemical properties when used in electrode slurries and primer compositions, and the method for manufacturing the nano-carbon dispersion of the present invention allows for the easy production of a nano-carbon dispersion with excellent properties by using a non-fluorine-based binder as a dispersant.

[0038] In addition, the high-adhesion electrode slurry of the present invention includes a nano-carbon dispersion containing a non-fluorine-based binder, thereby providing excellent adhesion such as high adhesion even when using active materials that are in the form of single particles or have a large surface area due to their small particle size, which allows for a reduction in binder content.

[0039] In addition, the electrode of the present invention has high adhesion through the enhancement of adhesion between the electrode layer formed from a non-fluorine binder-containing high-adhesion electrode slurry and the current collector, and / or the enhancement of cohesion between the components within the electrode, thereby maintaining stable electrical conductivity.

[0040] In addition, since the secondary battery of the present invention includes an electrode in which electrical conductivity is stably maintained, electrochemical characteristics such as electrical capacity and charge / discharge cycle characteristics can be stably maintained.

[0041] In addition, the current collector of the present invention is formed from a nano-carbon dispersion containing a non-fluorine binder and includes a primer layer with excellent adhesive properties, thereby having excellent adhesion to a dry electrode sheet.

[0042] 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.

[0043] FIG. 1 is the chemical structural formula of an acrylonitrile-maleic anhydride copolymer included in a nanocarbon dispersion according to an embodiment of the present invention (a and b are real numbers greater than 0).

[0044] Figure 2 shows the results of measuring the oxidation potential of a nano-carbon dispersion according to an embodiment of the present invention.

[0045] Figure 3 is a photograph showing the flowability of an electrode slurry according to an embodiment of the present invention.

[0046] Figure 4 is a graph showing the charge / discharge cycle test results of a coin cell (active material: NCM811) according to an embodiment of the present invention.

[0047] FIG. 5 is a graph showing the charge / discharge cycle test results of a coin cell (active material: LFP) according to an embodiment of the present invention.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] Hereinafter, the technical configuration of the present invention will be described in detail with reference to the attached drawings and preferred embodiments.

[0054] 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.

[0055] The technical features of the present invention include a nano-carbon dispersion containing a non-fluorine binder that exhibits excellent flowability over time and excellent adhesion and electrochemical properties when used in electrode slurries as well as primer compositions, and a method for manufacturing the same; a highly adhesive electrode slurry containing a non-fluorine binder that can reduce the binder content by providing excellent adhesion, such as high adhesion to active materials with a large surface area due to small particle size or single particle form, without using fluorine-containing organic compounds mainly used as binders in electrode compositions for secondary batteries by including the nano-carbon dispersion; an electrode comprising an electrode layer formed from the electrode slurry; and a secondary battery comprising the electrode.

[0056] In other words, the present invention synthesizes a copolymer (PAM) in which an acrylonitrile-based monomer and a maleic acid-based monomer are copolymerized to enhance adhesion without using fluorine-containing organic compounds, prepares a nanocarbon dispersion using this copolymer as a dispersant, and then prepares an electrode slurry by adding an active material to the nanocarbon dispersion; furthermore, by developing an electrode including an electrode layer formed from the electrode slurry and a secondary battery including the electrode, and by manufacturing a current collector including a primer layer formed from the nanocarbon dispersion, it has been confirmed for the first time through the present invention that the acrylonitrile-maleic acid copolymer not only acts as a dispersant for the nanocarbon dispersion but can also act as a non-fluorine binder with excellent adhesion in the electrode slurry for a secondary battery prepared by adding an active material to the nanocarbon dispersion.

[0057] Accordingly, the nanocarbon dispersion of the present invention may consist of a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer, a nanocarbon material, and a solvent. Here, the nanocarbon dispersion may comprise 0.2-20% by weight of solids (copolymer + nanocarbon material) and the remainder being a solvent. If the solid content is lower than 0.2% by weight, the solution is too dilute, which is disadvantageous as a large amount must be used; if it is 20% by weight or more, the viscosity becomes too high, causing a problem where dispersion becomes difficult. The solid content included in the nanocarbon dispersion may comprise 20-500% by weight of the copolymer per 100% by weight of the nanocarbon material. If the copolymer content is less than 20% by weight, the amount of copolymer used as a dispersant is too low, resulting in reduced dispersibility; if it exceeds 500% by weight, the nanocarbon material content is too low, which is disadvantageous as too large an amount of nanocarbon dispersion must be used.

[0058] The copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer included in the nanocarbon dispersion of the present invention (hereinafter referred to as the "acrylonitrile-maleic acid copolymer") serves as a component that acts not only as a dispersant for nanocarbon materials but also as a binder for secondary batteries. It is not a simple mixture of an acrylonitrile-based polymer and a maleic acid-based polymer, but rather a compound in which an acrylonitrile-based monomer and a maleic acid-based monomer are bonded through a chemical reaction. 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.

[0059] 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.

[0060] 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.

[0061] 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. If the content of the maleic acid component in the copolymer is lower than 0.02 mol%, there is a problem that the adhesive strength enhancement effect is significantly reduced because the content of the maleic acid component is too low, and if it exceeds 20 mol%, there is a problem that the copolymerization reaction becomes too slow. Therefore, 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.

[0062] The weight-average molecular weight of the acrylonitrile-maleic acid copolymer used in the electrode composition of the present invention may be in the range of 50,000 to 3,000,000 grams / mol. If the weight-average molecular weight of the copolymer is less than 50,000 grams / mol, the low molecular weight results in poor physical properties of the electrode layer, which is disadvantageous. If it is 3,000,000 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.

[0063] In the electrode composition of the present invention, the acrylonitrile-maleic acid copolymer is used in a range of 1.0 to 10.0 weight% as described above, and the binder content in the electrode composition can be set differently depending on the shape and size of the active material, or the type and content of the conductive material. Generally, for active materials with small particle sizes, the binder content is relatively high, and a relatively high content of binder is used in dry processes compared to wet processes.

[0064] 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), peroxide, oxidizing agent or photoinitiator, ionic polymerization, oxidative polymerization represented by ammonium persulfate, redox polymerization using redox reaction, methods using organic acid-based reaction initiators such as acetic acid or para-toluenesulfonic acid, or thermal polymerization.

[0065] 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 in a molar ratio to a solvent; 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.

[0066] 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.

[0067] The nanocarbon material included in the nanocarbon dispersion of the present invention may be any one selected from the group consisting of conductive carbon black, graphene, carbon nanotubes (single-wall, double-wall, multi-wall, 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, may be mixed with nanocarbon materials with an aspect ratio of less than 100, such as conductive carbon black, carbon balls, and graphene. This is because when nanocarbon materials with a high aspect ratio, such as carbon nanotubes, are dispersed, the particulate nanocarbon material exists between the nanocarbon materials with a high aspect ratio, thereby having the effect of helping to disperse the nanocarbon materials with a high aspect ratio. In the present invention, when the conductive material is a mixture of nanocarbon materials with different aspect ratios, the mixing weight ratio of a nanocarbon material with an aspect ratio of 100 or more and a 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, so it is difficult to obtain the effect of mixing.

[0068] The solvent that can be used in the nanocarbon dispersion of the present invention may be an organic solvent such as NMP or DMF in which the copolymer of the present invention dissolves well. However, if a metal such as lithium is added after hydrogenating the copolymer of the present invention, it may also dissolve in an aqueous solvent; in this case, an aqueous solvent such as water may be used.

[0069] As described below, the nano-carbon dispersion of the present invention can be used as a conductive material for an electrode composition or to form a primer (adhesion promotion) layer for a metal electrode plate such as aluminum or copper foil. In this case, it is preferable to maintain the hydrogen ion index (pH) of the nano-carbon dispersion at 5.5-7.5 to prevent damage to the metal electrode plate. This is because if the hydrogen ion index is 5.5 or lower or 7.5 or higher, the acidity or alkalinity is strong, which may cause damage to the metal electrode plate.

[0070] Next, the method for preparing a nano-carbon dispersion of the present invention may include: a first step of preparing a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer; a second step of preparing a precursor solution by dissolving the copolymer in a solvent; a third step of preparing a precursor dispersion by adding a nano-carbon material to the precursor solution and stirring; a fourth step of kneading the precursor dispersion; and a fifth step of re-stirring the kneaded precursor dispersion.

[0071] In the third step, stirring is performed at 1500 to 3000 rpm for 2 to 7 minutes, and in the fourth step, mixing is performed by high-pressure spraying. In the fifth step, re-stirring can be performed at 200 to 900 rpm for 5 to 24 hours. Re-stirring through the fifth step is effective because it can further reduce the viscosity of the nano-carbon dispersion mixed in the fourth step.

[0072] The precursor dispersion obtained by performing the third step may have a solid content of 0.2 to 20 weight%, wherein the solid content may comprise 20 to 500 weight parts of the copolymer per 100 weight parts of the nanocarbon material. If necessary, a solvent may be further added in the fifth step, and a step for controlling the hydrogen ion index of the nanocarbon dispersion may be further included, wherein the molar ratio of the two monomers may be controlled when preparing the copolymer in the first step, or the hydrogen ion index may be controlled in any one of the second to fifth steps.

[0073] Next, the current collector of the present invention comprises a primer layer formed from a nanocarbon dispersion having any one of the configurations described above or a nanocarbon dispersion prepared by a method for preparing a nanocarbon dispersion having any one of the configurations described above.

[0074] A primer layer is formed on the surface of the current collector, and the thickness of the primer layer can be in the range of 0.1 to 5 µm. This is because if the thickness is less than 0.1 µm, the primer layer is too thin, making the coating process itself difficult and resulting in minimal adhesion enhancement, and if it exceeds 5 µm, it becomes thicker than necessary.

[0075] When a nano-carbon dispersion is formed into a coating with a thickness of 1.0 micron on a polyester film, the surface resistance is 10 7 It can be less than ohms / area, which is intended to facilitate the movement of electrons passing through the primer layer. The surface resistance of a 1.0-micron thick primer layer is 10 7 This is because if the ohm / area is greater than 10, electron movement through the primer layer becomes restricted, which can ultimately lead to a degradation of cell performance. In one embodiment, the surface resistance of a primer layer formed with a thickness of 1.0 micron on a polyester film is 10 7 If it is less than ohms / area, and a primer layer of the same thickness is formed on aluminum or copper foil, the measured surface resistance is 0.003 (3×10⁻⁶). -3 It is measured in ohms / area and is suitable for use.

[0076] Next, the dry electrode of the present invention may include a current collector having the configuration described above. That is, a dry electrode can be finally obtained by going through the steps of attaching a dry electrode sheet onto a current collector having a primer layer formed thereon and performing additional processes such as rolling.

[0077] Next, the electrode slurry of the present invention may comprise an active material; and a nano-carbon dispersion having any one of the compositions described above, or a nano-carbon dispersion prepared by a method for preparing a nano-carbon dispersion having any one of the compositions described above.

[0078] In other words, this is because a high-quality electrode slurry with a high solid content can be simply manufactured by using an acrylonitrile-maleic acid copolymer as a dispersant to prepare a nanocarbon dispersion, appropriately adjusting the content of the nanocarbon material and the acrylonitrile-maleic acid copolymer, and then adding and dispersing only the active material to this dispersion. That is to say, if a nanocarbon dispersion containing acrylonitrile-maleic acid copolymer and nanocarbon material is prepared in proportion to the binder and conductive material content found in general electrode compositions, the dispersion already contains the binder and conductive material; therefore, by simply adding and dispersing the active material to this nanocarbon dispersion, an electrode slurry in which the nanocarbon material is well dispersed can be produced. For example, when the acrylonitrile-maleic acid copolymer of the present invention is used as a binder and carbon nanotubes are used as a conductive material, the nano-carbon dispersion of the present invention is a dispersion in which carbon nanotubes and a binder are pre-dispersed. Therefore, if an active material is further added and dispersed therein, it is equivalent to dispersing carbon nanotubes, which are difficult to disperse, in two stages. Thus, even if the carbon nanotubes have a large aspect ratio, the dispersion state within the electrode slurry becomes very good. Accordingly, it is possible to obtain good electrical conductivity and electrochemical properties even when using a small amount of conductive material.

[0079] Therefore, by using the nanocarbon dispersion of the present invention, an electrode slurry having a high solid content and a more uniform degree of dispersion can be obtained very effectively. This is because, as described above, the acrylonitrile-maleic acid copolymer of the present invention can be used as a high-quality binder, and at the same time, due to its good compatibility with nanocarbon materials, it has the ability to effectively disperse nanocarbon materials and thus can act as a dispersant.

[0080] The acrylonitrile-maleic acid copolymer of the present invention can be used as a binder for positive and negative electrodes, and can be used as a binder for all secondary batteries that require 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.

[0081] The active material included in the electrode slurry of the present invention may be any one selected from the group consisting of an alkali metal element, an alkaline earth metal element, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, graphite, silicon, silicon oxide, sulfur, and combinations thereof, as an anode active material or a cathode active material. 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).

[0082] In one embodiment, the electrode slurry of the present invention may have a solid content of 70% by weight or more. In this case, the solid content may be an active material, a nanocarbon material, and an acrylonitrile-maleic acid copolymer, wherein the active material may be 85-98% by weight, the nanocarbon material 1.0-5% by weight, and the copolymer 1.0-10% by weight. 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 a secondary battery manufactured with an electrode containing it, and if it exceeds the upper limit, one or more components are excessively included, which may actually impair the properties of the secondary battery. In other words, if the active material content is less than 85 wt%, the electrical capacity of the secondary battery is lowered, which is disadvantageous; if it exceeds 98 wt%, too little binder is included, resulting in poor mechanical properties due to reduced bonding between components and adhesion to the electrode plate. If the content of nanocarbon material is less than 1.0 wt%, the electrical conductivity of the electrode layer is too low, leading to problems such as the electrochemical properties not being properly realized; and if it exceeds 5 wt%, although the electrical conductivity of the electrode layer is good, the content of the active material is relatively low, resulting in a problem of reduced electrical capacity per unit volume. Additionally, if the content of acrylonitrile-maleic acid copolymer is less than 1.0 wt%, the binder content is low, causing the active material electrode layer formed on the electrode plate to detach too easily; and if it exceeds 10 wt%, while there is an advantage of the active material electrode layer adhering strongly to the electrode plate, the relative decrease in active material content ultimately leads to a problem of reduced electrical capacity per unit volume of the electrode.

[0083] Next, the electrode of the present invention may include an electrode layer formed from an electrode slurry having the composition described above. That is, a cathode with an electrode layer of a certain thickness can be manufactured by coating and drying an electrode slurry having the composition described above onto a metal current collector. This method can be similarly applied to other types of secondary batteries, such as all-solid-state batteries, by making an electrode slurry by dispersing components such as an active material, a conductive material, and a solid electrolyte in a solvent, and then coating this onto a current collector to manufacture an all-solid-state electrode with an electrode layer of a certain thickness.

[0084] The secondary battery of the present invention may include an electrode or a dry electrode comprising an electrode layer having the configuration described above.

[0085] Example 1

[0086] 1. Synthesis of Acrylonitrile-Maleic Anhydride Copolymer

[0087] 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 copolymer 1 was obtained through subsequent filtering, washing, and drying processes.

[0088] 2. Preparation of the first precursor solution

[0089] 4g of copolymer 1 was dissolved in 94g of NMP to prepare the first precursor solution.

[0090] 3. Preparation of precursor dispersion

[0091] 2 grams of carbon nanotubes (untreated multi-walled carbon nanotubes, aspect ratio: approximately 1,000) were added to the first precursor solution and high-speed stirred at 2,000 rpm for 5 minutes to prepare a precursor dispersion with a solid content of 2% (based on the weight of carbon nanotubes, total solid content: 6%).

[0092] 4. Mixing stage

[0093] The precursor dispersion was mixed by high-pressure spraying three times at a pressure of 20,000 psi using a microfludizer.

[0094] 5. Re-stirring step

[0095] Nanocarbon dispersion 1 was obtained by stirring the mixed precursor dispersion at 700 rpm for 15 hours. Nanocarbon dispersion 1 contains 200 parts by weight of copolymer 1 as a dispersant and binder per 100 parts by weight of carbon nanotubes, so MWCNT is 2% by weight and copolymer 1 is 4% by weight of the solid content of 6% by weight, and the remaining 94% by weight is composed of NMP as a solvent.

[0096]

[0097] Example 2

[0098] Nanocarbon dispersion 2 was obtained by performing the same method as in Example 1, except that in the precursor dispersion preparation step, carbon nanotubes (untreated multi-walled carbon nanotubes, aspect ratio: 1,000) and conductive carbon black (aspect ratio: less than 10) were mixed in a weight ratio of 1:1 in the first precursor solution. Nanocarbon dispersion 2 consisted of 1 wt% MWCNT, 1 wt% conductive carbon black, and 4 wt% copolymer 1 among 6 wt% solids, and the remainder, i.e., 94 wt%, was composed of NMP as a solvent.

[0099]

[0100] Example 3

[0101] Nanocarbon dispersion 3 was obtained by performing the same method as in Example 1, except that in the first precursor solution preparation step, 8g of copolymer 1 was dissolved in 88g of NMP to prepare the first precursor solution, and in the precursor dispersion preparation step, 4g of carbon nanotubes (untreated multi-walled carbon nanotubes, aspect ratio: 1,000) was used in the first precursor solution. Nanocarbon dispersion 3 consisted of 4% by weight of MWCNT and 8% by weight of copolymer 1 among 12% by weight of solid content, and the remainder, i.e., 88% by weight, was composed of NMP as a solvent.

[0102]

[0103] Example 4

[0104] Nanocarbon dispersion 4 was obtained by performing the same method as in Example 1, except that acrylonitrile-maleic anhydride copolymer 2 was synthesized using 95 mol% acrylonitrile and 5 mol% maleic anhydride. Nanocarbon dispersion 4 consisted of 2 wt% MWCNT and 4 wt% copolymer 2 out of 6 wt% solid content, and the remainder, i.e., 94 wt%, was composed of NMP as a solvent.

[0105]

[0106] Example 5

[0107] 1. Electrode slurry preparation step

[0108] 9.79 g of active material (NCM811) was added to 3.5 g of nano-carbon dispersion 1 prepared in Example 1 and primary stirring was performed by high-speed stirring (2,000 rpm, 5 minutes). Afterward, the mixture of primary stirring was further dispersed using a Thinky mixer at 2,000 rpm for 10 minutes to obtain electrode slurry 1. At this time, electrode slurry 1 consisted of approximately 75 wt% solids and the remainder being solvent, and the solids in electrode slurry 1 consisted of 97.9 wt% active material (NCM811), 0.7 wt% CNT, and 1.4 wt% copolymer 1.

[0109] 2. Positive electrode preparation stage

[0110] The prepared electrode slurry 1 is applied onto aluminum foil (15 microns), dried (100°C, 30 minutes), then subjected to high-temperature rolling (100°C) and heat-treated again at 100°C for 1 hour until the loading level is ~10 mg / cm² 2 and the electrode density is 2.75 g / cm³ 3 Phosphoric positive electrode plate 1 was manufactured.

[0111] 3. Coin Cell Preparation Phase

[0112] A half-cell structured coin cell 1 (CR2032 type) was prepared as follows using positive electrode plate 1. In this case, lithium metal foil was used as the counter electrode, and the electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a ratio of 30 / 50 / 20, adding 5% fluoroethylene carbonate (FEC) to the mixture, and dissolving 1.15 moles of LiPF6 in this mixture to use as the electrolyte. The coin cell was manufactured using a conventional half-cell structured coin cell manufacturing method in a glove box filled with argon gas.

[0113]

[0114] Example 6

[0115] 1. Electrode slurry preparation step

[0116] Electrode slurry 2 was prepared by performing the same method as in Example 5, except that the nano-carbon dispersion 2 prepared in Example 2 was used. Electrode slurry 2 consisted of approximately 75 wt% solids and the remainder being solvent, and the solids in electrode slurry 2 consisted of 97.9 wt% active material (NCM811), 0.35 wt% MWCNT, 0.35 wt% conductive carbon black, and 1.4 wt% copolymer 1.

[0117] 2. Positive electrode preparation stage

[0118] The prepared electrode slurry 2 is applied onto aluminum foil (15 microns), dried (100°C, 30 minutes), then hot-rolled (100°C) and heat-treated again at 100°C for 1 hour to achieve a loading level of ~11 mg / cm² 2 and the electrode density is 2.73 g / cm³ 3 Phosphoric positive electrode plate 2 was manufactured.

[0119] 3. Coin Cell Preparation Phase

[0120] A coin cell 2 with a half-cell structure was prepared by performing the same method as in Example 5, except that positive electrode plate 2 was used.

[0121]

[0122] Example 7

[0123] 1. Electrode slurry preparation step

[0124] Electrode slurry 3 was prepared by performing the same method as in Example 5, except that 7.0 g of the nano-carbon dispersion 3 prepared in Example 3 was used and 95.8 g of the active material (LFP) was added. Electrode slurry 3 consisted of approximately 75 wt% solids and the remainder being solvent, and the solids in electrode slurry 3 consisted of 95.8 wt% active material (LFP), 1.4 wt% NWCNT, and 2.8 wt% copolymer 1.

[0125] 2. Positive electrode preparation stage

[0126] The prepared electrode slurry 3 is applied onto aluminum foil (15 microns), dried (100°C, 30 minutes), then subjected to high-temperature rolling (100°C) and heat-treated again at 100°C for 1 hour to achieve a loading level of ~10 mg / cm² 2 and the electrode density is 2.4 g / cm³ 3 Phosphoric positive electrode plate 3 was manufactured.

[0127] 3. Coin Cell Preparation Phase

[0128] A coin cell 3 with a half-cell structure was prepared by performing the same method as in Example 5, except that positive electrode plate 3 was used.

[0129]

[0130] Example 8

[0131] Coin cell 4 was prepared by performing the same method as in Example 7, except that nano carbon dispersion 4 obtained in Example 4 was used.

[0132] Comparative Example 1

[0133] 1. Electrode slurry preparation step

[0134] 97 wt% of NCM811, 0.7 wt% of carbon nanotubes (untreated multi-walled carbon nanotubes, aspect ratio: approx. 1,000), and 2.3 wt% of polyacrylonitrile (PAN) homopolymer were weighed and added to NMP to achieve a solid content of 65%, stirred to perform primary dispersion, and then placed into a Thinky mixer and dispersed at 2,000 rpm for 20 minutes to prepare Comparative Electrode Slurry 1.

[0135] 2. Positive electrode preparation stage

[0136] Comparative pre-electrode plate 1 was prepared by performing the same method as in Example 5, except that comparative pre-electrode slurry 1 was used.

[0137] 3. Coin Cell Preparation Phase

[0138] Comparative example coin cell 1 was manufactured by performing the same method as in Example 5, except that comparative example electrode plate 1 was used.

[0139]

[0140] Comparative Example 2

[0141] Comparative Example 2 was prepared by using PVDF, a binder for secondary batteries, as a dispersant for nanocarbon materials according to the method of Example 1 to produce a comparative nanocarbon dispersion 2, and using this, the same method as in Example 5 was performed to produce a comparative electrode plate 2 and a comparative coin cell 2.

[0142]

[0143] Experimental Example 1

[0144] The characteristics of copolymer 1 synthesized in Example 1 and copolymer 2 synthesized in Example 4 were observed and the results were presented.

[0145] First, copolymer 1 was obtained as white particles, and after obtaining the infrared absorption spectrum using Fourier Transfraction (FTIR), the characteristic peaks of each component, e.g., 2244 cm⁻¹ -1 It was confirmed that the copolymer was synthesized by identifying the cyanide group (-CN) nearby and the maleic anhydride peaks near 1630 and 1730 cm⁻¹. In addition, the weight-average molecular weight measured by gel chromatography (GPC) was 725,000 grams / mol.

[0146] In addition, although the synthesis rate of copolymer 2 was slower than that of copolymer 1, it was successfully synthesized. The synthesis of the copolymer was confirmed by identifying acrylonitrile groups and maleic anhydride components through FTIR spectral analysis. Furthermore, the weight-average molecular weight was confirmed to be 850,000 grams / mol by GPC.

[0147]

[0148] Experimental Example 2

[0149] The characteristics of the nano-carbon dispersions 1 to 4 prepared in Examples 1 to 4 were observed, and the dispersion state, viscosity (spindle #64), and hydrogen ion index were measured, and the results are shown in Table 1.

[0150] Classification Dispersion State Viscosity (cPs) Hydrogen Ion Index Nano-carbon dispersion 1 Good 18,000 6.3 Nano-carbon dispersion 2 Good 22,000 6.1 Nano-carbon dispersion 3 Good 24,000 5.9 Nano-carbon dispersion 4 Good 23,000 6.5

[0151]

[0152] Nano-carbon dispersions 1 to 4 prepared according to the method of the present invention all had very good dispersion states, with the nano-carbon material uniformly dispersed even without separate additives. In addition, nano-carbon dispersions 1 to 4 were thinly coated onto aluminum foil, and the oxidation potential was measured, and the results for nano-carbon dispersion 1 are shown in FIG. 2.

[0153] As shown in Figure 2, in the case of nano-carbon dispersion 1, the oxidation potential was measured to be very high at approximately 5.8V, indicating that it can be sufficiently used as a binder for the anode. Although the results for nano-carbon dispersions 2 to 4 are not shown, they all exhibited values ​​of 5.0V or higher, thus confirming that they can all be used as binders for the anode or as dispersants for nano-carbon materials for the anode.

[0154]

[0155] Experimental Example 3

[0156] The electrode slurries 1 to 4 prepared in Examples 5 to 8 were visually observed, and a representative result photograph (electrode slurry 1) is shown in FIG. 3.

[0157] As shown in Fig. 3, the electrode slurry prepared according to the method of the present invention was found to be very suitable for wet electrode manufacturing as it has a honey-like, flowing shape. In particular, the solid content of the electrode slurry was about 75%, which is a very high solid content compared to the electrode slurry of the prior art, which generally has a solid content of up to 65% by weight as in the comparative example.

[0158] In other words, in the conventional method of manufacturing electrode slurries, an active material, a binder (or a binder solution in which the binder is pre-dissolved in the solvent), and a conductive material (or a dispersion in which the conductive material is pre-dispersed) are all added to a solvent and mixed at once. However, since all materials, especially nanocarbon materials, must be well dispersed, it was difficult to significantly increase the viscosity of the slurry. However, since the nanocarbon dispersion of the present invention pre-disperses nanocarbon materials, which are very difficult to disperse, into a copolymer that can be used as a binder for secondary batteries, an electrode slurry with higher homogeneity can be manufactured by adding and dispersing an active material to this dispersion. In this case, since there is no need to further disperse the nanocarbon materials, the electrode slurry can have flowability suitable for coating even with a high solid content.

[0159] As described above, since a nano-carbon dispersion is prepared by pre-dispersing carbon nanotubes with a copolymer and then adding and dispersing only the active material to obtain an electrode slurry, the effect of increasing the solid content of the electrode for the wet process can be obtained through the electrode slurry according to the present invention.

[0160]

[0161] Experimental Example 4

[0162] To confirm the characteristics of the positive electrodes 1 to 4 prepared in Examples 5 to 8 and the comparative positive electrodes 1 to 2 prepared in Comparative Examples 1 to 2, the surfaces were visually observed, and the adhesion, binding strength, and surface resistance were measured as follows, and the results are shown in Table 2.

[0163] The adhesion to the electrode was evaluated using Scotch tape (3M Scotch Tape; width: 18 mm). After attaching the electrode to a glass substrate using double-sided tape, Scotch tape was applied to the electrode layer on the upper surface. After 30 minutes, the adhesive strength was determined by measuring the force required to peel the tape while pulling it with a tensile testing machine. The cohesion was classified as "strong," "moderate," or "weak" based on the amount of electrode layer material adhering to the tape. Although this method is subjective, it is sufficient for assessing cohesion within a short period of time.

[0164] To exclude the influence of the metal electrode plate during surface resistance measurement, the electrical conductivity (surface resistance) of the electrode layer was formed on aluminum foil. After attaching and removing tape from the surface of the electrode layer, the surface resistance of the electrode layer attached to the tape was measured and used as the surface resistance of the electrode layer. Although this method is complex, it is effective because it allows for the measurement of the adhesion of the electrode layer while simultaneously measuring the surface resistance of the electrode layer in a state where the influence of the metal foil is excluded (Measuring instrument: Mitsubishi surface resistance meter, 4-point probe method, round tip used).

[0165] Classification Surface Condition Adhesion (N / mm) Bonding Strength Surface Resistance (Ohms / Area) Positive Electrode Plate 1 Good 0.078 Strong ~10 2 Positive electrode plate 2 Good 0.065 Strong~10 2 Positive electrode plate 3 Good 0.054 Strong~10 2 Positive electrode plate 4 Good 0.085 Strong~10 2 Comparison Old Plate 1 Good 0.022 Average~10 2 Comparison Old Plate 2 Good 0.025 Average~10 5

[0166]

[0167] Looking at the results in Table 2, it can be seen that the adhesion of positive electrode plates 1 to 4 is significantly higher than that of comparative pre-electrode plates 1 and 2. In particular, comparing the results of positive electrode plate 1 with comparative pre-electrode plate 1, it can be seen that the copolymer formed by copolymerizing acrylonitrile with maleic anhydride (a type of maleic acid) exhibits significantly higher adhesion than in the case of acrylonitrile homopolymer. Comparing the adhesion of positive electrode plate 1 and positive electrode plate 4, the adhesion of positive electrode plate 4 was measured to be superior, which is due to the higher content of maleic anhydride in the copolymer. Furthermore, it can be seen that adhesion is not particularly high when PVDF, a conventional binder for secondary batteries, is used as a nanocarbon material dispersant (comparative pre-electrode plate 2). In addition, regarding the surface resistance of all positive electrode plates, the surface resistance of the electrode layer itself is several hundred (10 2 It was measured as ohms / area. However, when PVDF was used as a dispersant (Comparative Example Nano-carbon Dispersion 2), the surface resistance was measured to be significantly higher compared to the copolymer of the present invention (10 5 (Ohms / Area). As such, the low adhesion and high surface resistance observed when PVDF is used as a nanocarbon dispersant are thought to be due to the fact that PVDF cannot effectively disperse carbon nanotubes, which are nanocarbon materials, at low concentrations. This indicates that the acrylonitrile-maleic acid copolymer of the present invention is a highly effective compound as a dispersant for nanocarbon materials, and furthermore, that the copolymer of the present invention is highly effective as a binder for secondary batteries.

[0168]

[0169] Experimental Example 5

[0170] The electrochemical characteristics of coin cells 1 to 4 prepared in Examples 5 to 8 and comparative example coin cells 1 to 2 prepared in the comparative example were measured as follows, and the results are shown in Table 3 and Figure 4. Figure 4 shows the charge-discharge cycle test results of coin cell 1 (Example 5) and comparative example coin cell 2. For reference, the charge-discharge test results of coin cells 2, 4 and comparative example coin cell 1 were similar to the results of coin cell 1 and were therefore not included in Figure 4.

[0171] Charge-discharge cycle tests were performed on half-cell structured coin cells (CR2032 type) 1 to 4 and comparative example coin cells as follows. The charge-discharge cycle test was performed by first undergoing a formation process at 0.1C and a 0.1C rate, and then performing the charge-discharge cycle test at a 1.0C rate. During the charge-discharge cycle test, the discharge or charge capacity of the positive electrode after 3-4 cycles was set as the initial capacity, and the capacity retention rate (%) was calculated by comparing it with the capacity after 50 cycles.

[0172] Category Initial Capacity (mAh / g) Reverse Capacity after 50 Cycles (mAh / g) Capacity Retention Rate (%) Coin Cell 1188 18297 Coin Cell 2187 17996 Coin Cell 3148 148 100 Coin Cell 4186 17896 Comparison Example Coin Cell 1180 17396 Comparison Example Coin Cell 2183 8245

[0173]

[0174] The results of a charge-discharge cycle test for coin cells 1 to 4, each containing an electrode prepared using an electrode slurry prepared with the nano-carbon dispersion liquid of the present invention. The initial capacity of coin cells 1, 2, and 4 was approximately 180-190 mAh / g, and the discharge capacity after 50 cycles was measured to be approximately 178-187 mAh / g, showing a capacity retention rate of over 95%. In addition, when an acrylonitrile homopolymer other than a copolymer was used as the dispersant and binder, the charge-discharge cycle characteristics were similar to those of coin cell 1 using a copolymer. From this, it can be seen that the maleic acid used in the copolymer of the present invention has the effect of increasing only the adhesion strength without impairing the electrochemical properties at all.

[0175] In addition, it was confirmed that when PVDF, a conventional binder for secondary batteries, was used as the dispersant, the capacity retention rate decreased sharply to less than 50% after 50 cycles. Upon investigating the cause of this difference, it was found that when PVDF was used as the dispersant, dispersion appeared to be good during the initial stages, but over time, the conductive nano-carbon dispersion liquid showed signs of separating from the active material. Therefore, it was found that PVDF has poor compatibility with the carbon nanotubes used as the conductive material in this experiment, and since it separates immediately after dispersion, the surface resistance of the electrode layer increases, resulting in a significant decrease in electrochemical performance. This phenomenon is observed in the composition ratio tested in this invention. That is, while the basic composition ratio of conventional lithium-ion batteries using PVDF as a binder is 96 wt% active material, 2 wt% conductive material, and 2 wt% binder, the composition ratio of the present invention is 97.9 wt% active material, 0.7 wt% conductive material, and 1.4 wt% binder, which is a composition ratio in which the content of the active material is increased by 1.9% compared to the composition ratio of conventional lithium-ion batteries. This can be described as an extreme composition ratio in which the content of the binder and conductive material is very low. In such cases, the binder must have very good compatibility with the nanocarbon material and the active material, as well as excellent adhesion, so that characteristics such as the surface resistance and adhesion of the electrode can be maintained even with a small amount of binder. Therefore, in the case of such extreme compositional ratios, the acrylonitrile-maleic anhydride copolymer of the present invention is a more effective binder than conventional PVDF, and the method of pre-dispersing nanocarbon materials using this copolymer as a dispersant and then adding an active material thereto can be considered an effective method for preparing an electrode slurry with a high solid content.

[0176] In particular, in the case of Coin Cell 3 using LFP active material, as shown in Fig. 5, the initial capacity is low at approximately 148 mAh / g, but after 50 cycles, the capacity retention rate is 148 mAh / g, confirming that there is almost no capacity decay (capacity retention rate: 100%).

[0177] On the other hand, when an acrylonitrile homopolymer other than the copolymer of the present invention was used, it was measured to exhibit an electrical capacitance similar to that of Coin Cell 1. When comparing this result (Table 3) with the result of Experimental Example 3 (Table 2), it can be seen that the maleic acid used in the copolymer of the present invention has the effect of increasing only the adhesion without impairing the electrochemical properties at all. On the other hand, as shown in Figure 4, in the case of Comparative Example Coin Cell 2, which was prepared using Comparative Example Nano-Carbon Dispersion Liquid 2 in which carbon nanotubes were dispersed using PVDF, a conventional binder for secondary batteries, as a dispersant, the electrical properties decreased rapidly at the beginning of the charge-discharge test, and the capacity retention rate was measured to decrease to about 45% after 50 cycles.

[0178] Example 9

[0179] The nano-carbon dispersion 1 obtained in Example 1 was used as a primer solution for a current collector to obtain a current collector 1 with a primer layer formed as follows.

[0180] Nano carbon dispersion 1 was applied onto aluminum foil using a bar coater and dried to form a 1.0 micron primer layer.

[0181]

[0182] Example 10

[0183] A current collector 2 with a 1.5-micron primer layer formed thereon was obtained by performing the same method as in Example 9, except that the nano-carbon dispersion 2 obtained in Example 2 was used.

[0184]

[0185] Experimental Example 6

[0186] The characteristics of the primer layers obtained in Examples 9 and 10 were investigated, and the results are shown in Table 4.

[0187] Classification Surface Condition Thickness Adhesion (N / mm) Surface Resistance (Ohms / Area) Total Current Collector 1 Good 1.0 0.1 95 2×10 -3 Total house size 2 (good) 1.5 0.2 5 4 1.7 × 10 -3

[0188]

[0189] As shown in Table 4, the appearance of the primer layer was very clean, and as a result of the tape test conducted on current collectors 1 and 2 using the same method as in Experimental Example 4—that is, on the primer layer formed on aluminum foil—the adhesion was excellent to the extent that it did not peel off the tape. In addition, the surface resistance of the primer layer (primer layer formed on the metal electrode plate) was 10 -3 It was measured to possess good electrical conductivity in terms of ohms / area. As described above, the present invention explains that not only can a nanocarbon dispersion liquid be prepared very easily by using an acrylonitrile-maleic acid (or maleic anhydride) copolymer as a dispersant for nanocarbon materials, but an electrode prepared from an electrode slurry obtained by adding an active material to said nanocarbon dispersion liquid can also significantly improve adhesive properties, such as the binding force of each component within the electrode and the adhesion force between the current collector and the electrode, thereby enabling the manufacture of a secondary battery with stable mechanical properties. In other words, the present invention confirmed that the acrylonitrile-maleic acid copolymer not only acts as a dispersant for nanocarbon materials but also exhibits excellent performance as a binder for secondary batteries such as lithium-ion batteries. Furthermore, it was confirmed that the nanocarbon dispersion liquid containing the acrylonitrile-maleic acid copolymer of the present invention as a dispersant can be used as an electrode slurry for secondary batteries and a primer solution for current collectors by adjusting the ratio of each component and the solid content. In particular, it was confirmed that by using an acrylonitrile-maleic acid copolymer as a dispersant and appropriately adjusting the ratio of the dispersant to the nanocarbon material to create a nanocarbon dispersion, and then adding and dispersing only the active material into this dispersion, an electrode slurry with high solid content and excellent homogeneity can be produced, and the electrochemical properties of the electrode prepared therefrom are also very excellent. Furthermore, it was confirmed that when the copolymer of the present invention is used as a nanocarbon material dispersant, the content of the conductive material and binder in the electrode slurry can be lowered, and thus the content of the active material can be increased, thereby increasing the electrical capacitance per unit volume.

[0190]

[0191] 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 nanocarbon dispersion composed of a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer, a nanocarbon material, and a solvent.

2. In Paragraph 1, A nano-carbon dispersion characterized by having a solid content of 0.2 to 20 weight%.

3. In Paragraph 1, The above copolymer is a nano-carbon dispersion characterized by being composed of 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 nano-carbon dispersion 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, The above acrylonitrile-based monomer is characterized by having a structure in which a cyano group is attached to a vinyl group as the main chain, forming a nano-carbon dispersion.

6. In Paragraph 1, A nano-carbon dispersion characterized in that the above maleic acid monomer is one or more of maleic acid, its salt, or anhydrous maleic acid compounds in their anhydrous forms.

7. In Paragraph 6, A nano-carbon dispersion characterized in that the above maleic acid-based monomer is maleic anhydride.

8. In Paragraph 1, The above copolymer is a nano-carbon dispersion characterized by a weight-average molecular weight of 50,000-3,000,000 grams / mol.

9. In Paragraph 1, The nanocarbon dispersion is 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, carbon balls, and combinations thereof.

10. In Paragraph 1, The above nanocarbon material is a nanocarbon dispersion liquid characterized by using a mixture of a nanocarbon material having an aspect ratio of 100 or more and a nanocarbon material having an aspect ratio of less than 100.

11. In Paragraph 2, A nanocarbon dispersion liquid characterized by containing 20 to 500 parts by weight of the copolymer per 100 parts by weight of the nanocarbon material.

12. In Paragraph 1, A nano-carbon dispersion characterized by having a hydrogen ion index of 5.5 to 7.

5.

13. A first step of preparing a copolymer of an acrylonitrile-based monomer and a maleic acid-based monomer; A second step of preparing a precursor solution by dissolving the above copolymer in a solvent; A third step of preparing a precursor dispersion by adding a nanocarbon material to the above precursor solution and stirring; A fourth step of kneading the above precursor dispersion; and A method for preparing a nano-carbon dispersion, comprising: a fifth step of re-stirring the above-mentioned mixed precursor dispersion.

14. In Paragraph 13, A method for preparing a nano-carbon dispersion, characterized in that, in the third step above, stirring is performed at 1500 to 3000 rpm for 2 to 7 minutes.

15. In Paragraph 13, In the above fourth step, mixing is performed by a high-pressure spray method, and A method for preparing a nano-carbon dispersion liquid, characterized in that, in the above 5th step, re-stirring is performed at 200 to 900 rpm for 5 to 24 hours.

16. In Paragraph 13, A method for preparing a nanocarbon dispersion, characterized in that the precursor dispersion has a solid content of 0.2 to 20 weight%, and the solid content comprises 20 to 500 weight parts of the copolymer per 100 weight parts of nanocarbon material.

17. A current collector comprising a primer layer formed of a nanocarbon dispersion liquid according to any one of claims 1 to 12 or a nanocarbon dispersion liquid prepared by the manufacturing method according to any one of claims 13 to 16.

18. A dry electrode comprising the current collector of paragraph 17.

19. Active material; and An electrode slurry comprising: a nano-carbon dispersion of any one of claims 1 to 12 or a nano-carbon dispersion prepared by the manufacturing method of any one of claims 13 to 16.

20. In Paragraph 19, An electrode slurry characterized by having a solid content of 70% by weight or more.

21. In Paragraph 19, The electrode slurry is characterized in that the active material is any one selected from the group consisting of alkali metals, alkaline earth metals, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, graphite, silicon, silicon oxide, sulfur, and combinations thereof.

22. An electrode comprising an electrode layer formed from the electrode slurry of claim 19.

23. A secondary battery comprising the electrode of claim 18.

24. A secondary battery comprising the electrode of claim 22.

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