Electrode material layer composition containing a new binder for dry processes, and lithium ion battery containing the same

Abstract

The present invention relates to technology related to electrodes for lithium ion batteries. More specifically, the present invention relates to an electrode material layer composition including a novel binder that can solve the problem of difficulty in uniformly kneading components in dry processes, rather than wet processes, because existing binders used in manufacturing electrodes by dry processes are solid particles and the components themselves may aggregate or may aggregate due to static electricity generated by friction between particles during dry kneading. The novel binder also has the property of enabling the production of a sheet of an electrode layer material composition with a thickness of less than 100 μm even at a relatively low pressure during production, an electrode including the composition, a method for manufacturing the electrode, and a lithium ion battery including the electrode.

Description

[Technical Field]

[0001] The present invention relates to technology related to electrodes for lithium ion batteries. More specifically, the present invention relates to an electrode material layer composition including a novel binder for a dry process, which can solve the problem of preventing uniform kneading by generating particle aggregation due to static electricity caused by friction of the solid particles during kneading when conventional binders used in manufacturing electrodes by a dry process rather than a wet process are used. The novel binder can also be used to produce a sheet with a thickness of less than 100 μm even at a relatively low pressure during the manufacture of the electrode layer material composition sheet. The electrode includes the novel binder, an electrode including the composition, a method for manufacturing the electrode, and a lithium ion battery including the electrode. [Background technology]

[0002] Lithium-ion batteries are made by mixing lithium-containing compound particles as the positive electrode active material with graphite, a negative electrode active material, and a binder to form an active material layer on a metal foil (plate) such as aluminum or copper, impregnating it with an electrolyte, and then laminating it with a separator in between. Lithium ions operate by repeatedly entering and exiting the positive and negative electrode active material layers (lithiation and delithiation).

[0003] The conventional technology for manufacturing electrode plates is the so-called wet method, in which lubricants, binders, and other additives are dispersed in a solvent to form a slurry, which is then coated to a uniform thickness on a metal electrode plate and dried to form an active material electrode plate. This method has been used for a long time and has the advantage of allowing each component to be mixed uniformly, thereby maximizing battery performance. However, it has the inconvenience of requiring complete removal of the solvent during the drying process and the need to recover all of the solvent, which poses a risk of air pollution, making it a very economical and environmentally inconvenient method.

[0004] A recent technology that has been developed to address these issues is the dry process. The dry process involves dry-mixing active materials and other additives with a binder without the need for a solvent, applying pressure to the mixture to form an active material composition sheet, which is then attached to a metal electrode plate to manufacture the electrode plate. This dry process eliminates the need for a solvent recovery device because it eliminates the complex process of removing and collecting the solvent, making it a more environmentally friendly method than the conventional wet process.

[0005] However, to manufacture an electrode plate using the dry process, the active material, binder, and additive (typically conductive carbon black or carbon nanotubes) must be dispersed dry. Since the active material and conductivity enhancer are already determined, selecting an appropriate binder is crucial in the dry process. Existing binders used in dry processes are all solid particles, but the size and density of each particle vary. In particular, when the components are mixed, friction between the solid particles generates charges on the surface. This generates static electricity, which can lead to particle aggregation and hinder uniform mixing, making it difficult to achieve uniform mixing.

[0006] Therefore, there is an urgent need to develop a new binding technology that can more uniformly mix components such as active materials and conductivity enhancers even in a dry process that does not use a solvent, i.e., a new binder material having properties suitable for use in a dry process, and an electrode material layer composition including the same. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a new use for an acrylate-based compound that exists in a liquid state at room temperature and is post-curable. That is, the conventional binder used in manufacturing electrodes by a dry process without using a solvent is solid particles. During kneading, static electricity occurs due to friction of the solid particles, causing particle aggregation and hindering uniform kneading. In order to solve this problem, the present invention provides an electrode material layer composition containing an acrylic compound as a new binder.

[0008] Another object of the present invention is to provide a method for manufacturing an electrode, which uses an electrode material layer composition that is uniformly kneaded with an acrylate-based compound, which is a new binder for dry processes, thereby enabling the manufacture of a thinner cathode material layer or anode material layer at a lower pressure, and which allows the sheet to be more firmly attached to the electrode plate by attaching the manufactured cathode material layer or anode material layer sheet to the electrode plate and then post-curing the acrylate-based compound contained in the sheet. Also, the present invention provides an electrode manufactured by the method.

[0009] Another object of the present invention is to provide a lithium ion battery that is environmentally friendly and economical because it includes an electrode manufactured by a dry process, thereby eliminating the complicated process of removing and collecting the solvent, and that can be miniaturized due to a thinner cathode material layer or anode material layer.

[0010] The object of the present invention is not limited to the above-mentioned object, and other objects not mentioned above will become clear to those skilled in the art from the following description. [Means for solving the problem]

[0011] To achieve the above object, the present invention first provides a composition for an electrode material layer for a dry process, which comprises an active material for a positive or negative electrode, an acrylate-based compound, and a curing agent for the acrylate-based compound.

[0012] In a preferred embodiment, the acrylate-based compound includes a methacrylate-based compound.

[0013] In a preferred embodiment, the acrylate compound is a monomer or oligomer containing 2 to 16 functional groups and having a main chain containing 2 to 1,000 carbon atoms.

[0014] In a preferred embodiment, the functional groups are 2 to 16 in number and are one or more selected from the group consisting of methylene groups, urethane groups, ester groups, ether groups, oxide groups, ethylene oxide groups, propylene oxide groups, ethylene glycol groups, propylene glycol groups, butadiene groups, imide groups, amine groups, amide groups, epoxy groups, olefin groups, sulfone groups, or combinations thereof.

[0015] In a preferred embodiment, the acrylate compound is contained in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the active material for the positive electrode or negative electrode.

[0016] In a preferred embodiment, the curing agent is one or more of a thermal curing agent and a photocuring agent, and is included in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the acrylate-based compound.

[0017] In a preferred embodiment, the thermal curing agent includes a peroxide or an azo compound, and the light curing agent includes a phenyl ketone compound or a phosphine oxide compound.

[0018] In a preferred embodiment, the composition further comprises at least one binder of a type different from the acrylate-based compound.

[0019] In a preferred embodiment, the acrylate compound and the binder have a weight ratio of 99:1 1:99.

[0020] In a preferred embodiment, the composition further comprises one or more nanocarbon-based conductivity enhancers consisting of conductive carbon black, graphene, and carbon nanotubes.

[0021] In a preferred embodiment, the positive electrode or negative electrode active material comprises one or more selected from the group consisting of lithium, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, a carbon material, silicon, silicon oxide, sulfur, and combinations thereof.

[0022] The present invention also provides an electrode for a lithium ion battery, including a positive electrode material layer or a negative electrode material layer made of any of the electrode material layer compositions for a dry process described above.

[0023] The present invention also provides a method for manufacturing an electrode for a lithium ion battery, including: a composition preparation step of preparing any of the above-described electrode material layer compositions for a dry process; a sheet formation step of forming a positive electrode material layer sheet or a negative electrode material layer sheet from the electrode material layer composition for a dry process; a bonding step of attaching the positive electrode material layer sheet or the negative electrode material layer sheet to a metal electrode plate; a curing step of curing the attached positive electrode material layer sheet or the negative electrode material layer sheet; and a rolling step of the electrode material layer obtained by the curing step.

[0024] In a preferred embodiment, the attaching step includes the steps of forming a primer layer on the metal electrode plate, and placing the positive electrode material layer sheet or the negative electrode material layer sheet on the primer layer and then pressing them together.

[0025] In a preferred embodiment, the curing step is carried out via one or more of heat curing at 50°C to 180°C for 5 minutes to 30 minutes and light curing by UV irradiation.

[0026] The present invention also provides a lithium ion battery including the above-mentioned lithium ion battery electrode.

[0027] The present invention also provides a lithium ion battery including the lithium ion battery electrode manufactured by the above-described manufacturing method. [Effects of the Invention]

[0028] According to the electrode material layer composition of the present invention, the binder contains an acrylate-based compound that is liquid at room temperature. This allows for more uniform kneading of the active material, without the problem of particle aggregation occurring due to static electricity caused by friction of the solid particles during kneading, which hinders uniform kneading, as conventional binders used in electrodes manufactured by dry processes that do not use solvents are solid particles.

[0029] In addition, according to the lithium ion battery electrode and the method for manufacturing the electrode of the present invention, an electrode material layer composition uniformly kneaded with an acrylate-based compound is used, so that a thinner cathode material layer or anode material layer can be manufactured at a low pressure. After the manufactured cathode material layer or anode material layer sheet is attached to an electrode plate, the acrylate contained in the sheet is post-cured to solidify the acrylate, which acts as a binder. This also improves the adhesion of the sheet to the electrode plate, and a rolling process can be performed to increase the electrode density.

[0030] Furthermore, the lithium ion battery of the present invention includes an electrode manufactured by a dry process, which eliminates the need for a complicated process of removing and collecting the solvent, and is therefore environmentally friendly and economical. Furthermore, the thinner cathode and anode material layers allow for miniaturization.

[0031] The effects of the present invention are not limited to those described above, and other effects not described above will be clearly understood by those skilled in the art from the following description. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a graph showing the capacity retention rate according to the number of charge / discharge cycles for an electrode manufactured using Comparative Example 1 of the present invention, which includes PTFE (Polytetrafluoroethylene) particles, a binder for an existing dry process. [Figure 2]1 is a graph showing the capacity retention rate according to the number of charge / discharge cycles of an electrode made of an electrode material layer composition 1 for a dry process according to an embodiment of the present invention and an electrode made of a comparative electrode material layer composition 2 according to Comparative Example 2. [Figure 3] 10 is a graph showing the capacity retention rate according to the number of charge / discharge cycles of an electrode made of electrode material layer composition 2 for a dry process according to another embodiment of the present invention. [Figure 4] 1 is a graph showing the capacity retention rate according to the number of charge / discharge cycles of an electrode made of an electrode material layer composition 3 for a dry process according to another embodiment of the present invention. [Figure 5] 1 is a graph showing the capacity retention rate according to the number of charge / discharge cycles of an electrode made of an electrode material layer composition 4 for a dry process according to another embodiment of the present invention. [Figure 6] 1 is a graph showing the specific capacity of an electrode made of electrode material layer composition 5 for a dry process according to another embodiment of the present invention as a function of the number of charge / discharge cycles. DETAILED DESCRIPTION OF THE INVENTION

[0033] The terms used in this invention are currently selected as widely used general terms as possible while taking into consideration the functions in this invention, but these may change depending on the intentions of engineers engaged in this field, precedents, the emergence of new technologies, etc. In addition, in certain cases, the applicant may arbitrarily select terms, and in such cases, the meanings thereof will be described in detail in the description of the relevant invention.

[0034] When the terms "comprise," "have," "consist of," etc. are used in the present invention, other parts may be added unless "only" is used. When an element is expressed in the singular, it also includes the plural unless otherwise expressly stated.

[0035] When interpreting elements, they are interpreted as including a margin of error even if there is no other explicit description.

[0036] Characteristic parts of each of the several embodiments of the present invention can be partially or wholly combined or combined with each other, and various technical interlocking and driving mechanisms are possible, and each embodiment can be implemented independently of each other or together in a linked relationship.

[0037] The technical configuration of the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0038] However, the present invention is not limited to the embodiments set forth herein and may be embodied in other forms. Like reference numerals used to describe the present invention throughout the specification refer to like elements.

[0039] The present invention provides a new use for an acrylate-based compound that exists as a liquid at room temperature and can be post-cured. The present invention also provides an electrode material layer composition that includes an acrylate-based compound as a new binder so that active materials can be uniformly kneaded using a binder that is liquid at room temperature rather than solid particles when manufacturing an electrode using a dry process that does not use a solvent. The present invention also provides a lithium-ion battery electrode including a positive electrode material layer or a negative electrode material layer made of the composition. Since the electrode material layer composition is uniformly kneaded with the acrylate-based compound, which is a new binder for a dry process, thinner positive electrode material layers or negative electrode material layers can be manufactured at lower pressure. The present invention also provides a method for manufacturing an electrode in which the acrylate-based compound contained in the sheet is post-cured to solidify the acrylate and act as a binder, thereby improving adhesion of the sheet to the electrode plate. The present invention also provides a lithium-ion battery including the electrode.

[0040] That is, as is conventionally known, electrodes, which are one of the important components of lithium-ion batteries, are manufactured by kneading a cathode active material, an anode active material, additives, etc. with a binder to prepare an electrode material layer composition, forming an electrode material layer composition sheet of a desired thickness from the composition, and then attaching the sheet to a metal electrode plate. However, while wet processes for preparing electrode material layer compositions allow for uniform mixing of the components by kneading the components in a solvent, dry processes require the use of only a solid binder without a solvent, making it very difficult to achieve a uniform mixture. In order to obtain an electrode material layer composition with a more uniform mixture, the present invention has developed an electrode material layer composition for a dry process having a new composition including a novel binder for a dry process that allows for more uniform mixing by using an acrylate-based compound, which exists in a liquid state at room temperature but can be made solid through a separate processing step, instead of using a solid binder as in conventional processes.

[0041] As a result, the technology of the present invention provides a new use for an acrylate-based compound that exists in a liquid state at room temperature and is post-curable, i.e., a novel binder that allows a more uniform kneading state when kneading an active material and an additive, and is useful for forming an electrode material layer. Therefore, although the following description of the present invention will be mainly made using a positive electrode, it is obvious that the technology can be commonly applied to active materials for positive and negative electrodes, regardless of the type of active material.

[0042] Therefore, the present invention provides an electrode material layer composition for dry processing, which comprises an active material for a positive or negative electrode, an acrylate-based compound, and a curing agent for the acrylate-based compound.

[0043] Here, the acrylate-based compound is not limited as long as it exists in a liquid state at room temperature and can be solidified through a separate process, i.e., a curing process. However, when an appropriate curing agent is added to an acrylate-based compound that exists in a liquid state at room temperature and cured under appropriate conditions, it becomes solid and converts into a polymer with a three-dimensional network structure. This prevents the acrylate compound from leaching into the electrolyte and thus does not adversely affect battery performance. Furthermore, acrylate-based compounds with appropriate functional groups advantageously form a polymer with a three-dimensional network structure after curing, which can increase adhesion to the metal electrode plate. While the examples primarily focus on acrylate-based compounds, it is understood that methacrylate-based compounds with similar properties are also included. Therefore, the acrylate-based compound used in the present invention should be understood to include not only acrylate-based compounds and methacrylate-based compounds, but also compounds of the same type with other substituents.

[0044] The acrylate compound is not limited to any acrylate compound containing at least two functional groups, and the functional groups contained therein are not limited as long as they can react with heat or light, but may be one or more selected from the group consisting of methylene, urethane, ester, ether, oxide, ethylene oxide, propylene oxide, ethylene glycol, propylene glycol, butadiene, imide, amine, amide, epoxy, olefin, sulfone, or a combination thereof, and may particularly be an acrylate compound containing 2 to 16 functional groups. If the number of functional groups is two or less, it is disadvantageous because it is a monofunctional acrylate with a low curing point and difficult to cure, while if the number of functional groups is 16 or more, it is disadvantageous because there are too many functional groups and it may be converted into a polymer with hard physical properties in a short period of time.

[0045] Additionally, unless otherwise specified, the acrylate-based compound used in the present invention refers to any form of acrylate compound, including monomers and oligomers. In one embodiment, the acrylate-based compound may be in the form of a monomer or oligomer having a main chain of 2 to 1,000 carbon atoms. Main chains with fewer than 2 carbon atoms are disadvantageous because they become very brittle upon post-curing and are unsuitable as binder materials. Main chains with more than 1,000 carbon atoms may cause steric hindrance, which may interfere with the binder's function. Since the main technical feature of the present invention is the use of an acrylate-based compound that exists as a liquid at room temperature and is post-cured through a separate process as a binder, it is clear that the above-mentioned functional groups are merely examples and are not intended to be limiting.

[0046] The acrylate compound used in the present invention may be one or more selected from the group consisting of various aliphatic and aromatic acrylate monomers such as triethylene glycol acrylate, trimethylpropane triacrylate, dipentaerythritol hexaacrylate, trimethylolpropane trimethacrylate, and bisphenol A ethylene oxide dimethacrylate, and oligomers that are complexes formed from two or more units of the main chain monomers constituting these acrylates, such as methylene groups, urethane groups, ester groups, ether groups, oxide groups, ethylene oxide groups, propylene oxide groups, ethylene glycol groups, propylene glycol groups, butadiene groups, imide groups, amine groups, amide groups, epoxy groups, olefin groups, and sulfone groups.

[0047] The acrylate compound may be included in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the positive or negative electrode active material. If the amount of the acrylate compound is less than 0.1 parts by weight, the amount of the acrylate compound is too low and its role as a binder is negligible, which is disadvantageous for kneading. If the amount of the acrylate compound is more than 20 parts by weight, the amount of the active material is relatively low, which may result in a low electrical capacity relative to the total volume, which may result in a decrease in the performance of the lithium ion battery.

[0048] The acrylate curing agent is a component used to convert an acrylate compound, which exists as a liquid at room temperature, into a polymer with a three-dimensional network structure by kneading it and then curing it through a separate process. One or more of a thermal curing agent and a photocuring agent can be used. That is, when photocuring is not successful, especially when the electrode layer is thick, it is more effective to use a photocuring agent (photoinitiator) and a thermal curing agent in combination. Any type of curing agent can be used as long as it generates radicals when exposed to heat or light.

[0049] More specifically, the thermal initiator is a curing agent containing a peroxide or an azo compound, and is not limited to a specific type as long as it decomposes at 50°C to 180°C to generate a reaction initiator. In one embodiment, a peroxide initiator may be benzyl peroxide (BP), which generates oxygen radicals. An azo compound curing agent such as 2,2-azobisisobutyronitrile (AIBN) can be used. If the decomposition temperature of the curing agent is less than 50°C, the decomposition temperature is too low and the reaction initiator is easily generated, which is disadvantageous. If the decomposition temperature is greater than 180°C, the temperature required for the curing reaction is too high, which is disadvantageous in terms of cost. Preferably, a curing agent that decomposes at a temperature between 50°C and 150°C is used.

[0050] The photoinitiator may be a curing agent containing a phenyl ketone compound or a phosphine oxide compound that generates radicals when irradiated with light such as UV. In one embodiment, solid or liquid photoinitiators such as hydroxycyclohexyl phenyl ketone, hydroxydimethylacetophenone, trimethylbenzoyldiphenylphosphine oxide, or methylbenzoyl formate may be used.

[0051] The curing agent may be included in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the acrylate-based compound. If the curing agent content is less than 0.1 part by weight, the acrylate-based compound may not harden and may remain in a liquid state even after the curing reaction, which is disadvantageous. If the curing agent content exceeds 20 parts by weight, the compound may become too hard due to over-curing, or radicals generated from the curing agent that does not fully participate in the curing reaction may cause a side reaction, which may further deteriorate the binder contained therein.

[0052] If necessary, one or more other types of binders may be included in addition to the acrylate-based compound. Here, the weight ratio of the acrylate-based compound to the binder may be 99:11:99. Preferably, the weight ratio of the acrylate-based compound to the binder may be 80:20 to 20:80. If the weight ratio exceeds the upper and lower limits, the resulting mixture is not essentially a mixture but is essentially the same as a single binder, which is disadvantageous as it has little function as a mixed binder.

[0053] Here, other types of binders may be used, including any known binder that can be used in a dry process, and a mixture of two or more binders. In one embodiment, the binder may include polytetrafluoroethylene (PTFE), polyolefin, polyalkylene, polyether, styrene-butadiene rubber (SBR), polysiloxane and polysiloxane copolymer, branched polyether, polyvinylether, polyacrylic acid, polyvinylcarbonate, copolymers thereof, and / or mixtures thereof. The one or more binders can further include guar, alginic acid, poly[(isobutylene-alt-maleic acid, ammonium salt)-co-isobutylene-alt-maleic anhydride)], poly(ethylene-alt-maleic anhydride), poly(methyl vinyl ether-alt-maleic anhydride), polyacrylonitrile (PAN), poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC), and polyvinyl ether. The binder can include cellulose. In some embodiments, the polyolefin can include polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), copolymers thereof, and / or mixtures thereof.For example, the binder can include polyvinylidene chloride, poly(phenylene oxide) (PPO), polyethylene-block-poly(ethylene glycol), poly(ethylene oxide) (PEO), polydimethylsiloxane (PDMS), polydimethylsiloxane-co-alkylmethyl siloxane, copolymers thereof, and / or mixtures thereof. In certain embodiments, the fibrillizable binder is PTFE. The binder can include cellulose or a cellulose derivative. Derivatives of cellulose can include, for example, cellulose esters such as cellulose acetate; cellulose ethers such as methylcellulose, ethylcellulose, hydroxypropylcellulose (HPC), hydroxypropylmethylcellulose, or hydroxyethylcellulose (HEC); cellulose nitrate; cellulose chitosan such as carboxymethylcellulose chitosan; or carboxyalkyl cellulose such as carboxymethylcellulose (CMC), carboxyethylcellulose, carboxypropylcellulose, or carboxyisopropylcellulose. In additional embodiments, the cellulose or cellulose derivative can include a cellulose salt. In another embodiment, the cellulose salt cation can be selected from sodium, ammonium, calcium, or lithium.For example, the cellulose or cellulose derivative can include sodium cellulose or a sodium cellulose derivative selected from sodium cellulose ester, sodium cellulose ether, sodium cellulose nitrate, or sodium carboxyalkyl cellulose. The CMC can include sodium carboxymethyl cellulose. In some embodiments, the one or more binders include CMC, PVDF, and / or PTFE.

[0054] In some cases, the electrode material layer composition of the present invention may include a nanocarbon-based conductivity enhancer. The nanocarbon-based conductivity enhancer is not limited to any nano-sized carbon material, but in one embodiment, may be one or more selected from the group consisting of conductive carbon black, graphene, and carbon nanotubes (single-walled, double-walled, multi-walled, etc.). For example, carbon nanotubes are advantageous because of their very large aspect ratio. In the case of carbon nanotubes, one or more of single-walled, double-walled, and multi-walled nanotubes may be used in combination. The content of the nanocarbon-based conductivity enhancer may range from 0.05 to 300 parts by weight per 100 parts by weight of the acrylate-based compound or the acrylate-based compound and other types of binder. If the content of the nanocarbon-based conductivity enhancer is less than 0.05 parts by weight, the content is too small and the conductivity enhancement effect is insignificant, which is disadvantageous. If the content is 300 parts by weight or more, the content is too high and the viscosity of the entire active material slurry becomes too high or the density of the electrode layer made of the active material may decrease, which is disadvantageous.

[0055] The method of kneading the nanocarbon-based conductivity enhancer such as carbon nanotubes can be a method of first kneading the conductivity enhancer such as carbon nanotubes or conductive carbon black with the active material, and then adding a liquid acrylate-based compound thereto and kneading it finally. Alternatively, the conductivity enhancer such as carbon nanotubes or conductive carbon black can be first kneaded with the acrylate-based compound, and then kneading it again with the active material to prepare a final kneaded product.

[0056] The positive or negative electrode active material may be any active material known in the art that is suitable for use in a positive or negative electrode of a lithium ion battery, and may, in one embodiment, be one or more selected from the group consisting of lithium, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, carbon materials, silicon, silicon oxide, sulfur, and combinations thereof.

[0057] The carbon material can be selected from, for example, graphitic materials, graphite, graphene-containing materials, hard carbon, soft carbon, carbon nanotubes, porous carbon, conductive carbon, or combinations thereof. Graphite can be synthetic or naturally derived. Activated carbon can be derived from a steam process or an acid / etching process. In some embodiments, the graphitic material can be a surface-treated material. In some embodiments, the porous carbon can comprise activated carbon. In some embodiments, the porous carbon can comprise hierarchically structured carbon. In some embodiments, the porous carbon can comprise structured carbon nanotubes, structured carbon nanowires, and / or structured carbon nanosheets. In some embodiments, the porous carbon can comprise graphene sheets. In some embodiments, the porous carbon can be surface-treated carbon.

[0058] Next, the electrode for a lithium ion battery of the present invention includes a positive electrode material layer or a negative electrode material layer made of any one of the electrode material layer compositions for dry processing described above. The positive electrode material layer or the negative electrode material layer has a thickness of less than 100 μm, and since the electrode material layer composition for dry processing contains an acrylate-based compound, an electrode film with a thinner thickness and excellent properties can be manufactured.

[0059] Next, the method for manufacturing an electrode for a lithium ion battery according to the present invention may include the steps of: preparing an electrode material layer composition for dry processing according to any one of the above; forming a positive electrode material layer sheet or a negative electrode material layer sheet using the electrode material layer composition for dry processing; attaching the positive electrode material layer sheet or the negative electrode material layer sheet to a metal electrode plate; curing the attached positive electrode material layer sheet or the negative electrode material layer sheet; and rolling the electrode material layer obtained by the curing step. Here, each of these steps may be processed in a batchwise manner or may be a continuous process to manufacture a final electrode plate. The use of a continuous process may be the most efficient manufacturing process.

[0060] The composition preparation step can be performed using any known kneading method as long as all components, i.e., the negative or positive electrode active material, the liquid acrylate compound, and the acrylate compound curing agent, are mixed and kneaded under dry shear. Various kneading methods can be used, including mixers (low-speed and high-speed mixers) such as a Hensel mixer equipped with an appropriate blade, or extruder-type mixers capable of continuous processing. Typical examples of effective mixers include a single-screw extruder, twin-screw extruder, or continuous kneader equipped with a kneading function.

[0061] A sheet of the active material composition having a predetermined thickness can be formed using a die capable of forming a sheet of an appropriate thickness at the end of the continuous kneading apparatus, and the sheet can be rolled multiple times to form a sheet of the desired thickness. In the examples and comparative examples described below, a calendering method was used in which the active material composition is passed between two rolls designed to have a predetermined gap therebetween.

[0062] The attaching step may include forming a primer layer on a metal electrode plate, and placing the positive electrode material layer sheet or the negative electrode material layer sheet on the primer layer and then pressing them together. In a continuous process, the attaching step may be performed on a metal electrode plate supplied via a separate supply device.

[0063] The curing step is a process for curing the positive electrode material layer sheet or the negative electrode material layer sheet attached to the metal electrode plate in the attaching step to solidify the acrylate compound so that it acts as a binder and strengthens the adhesion of the sheet to the metal electrode plate, and may be performed by either heat curing at 50°C to 180°C for 5 minutes to 30 minutes and / or photo curing by UV irradiation.

[0064] The rolling step may be performed to finally press the electrode material layer obtained after the hardening step with an appropriate force to increase the electrode density. [Example]

[0065] NCM811 (95.0 wt%), which is a positive electrode active material, 2.5 wt% of an acrylate-based compound (a 1:1 mixture of an ethylene glycol-based bifunctional monomer and a hexafunctional ethylene glycol-based oligomer), 0.05 wt% of an azo-based curing agent (AIBN) which is a thermal curing agent, 0.05 wt% of a phosphine oxide-based curing agent (trimethylbenzoyldiphenylphosphine oxide) which is a photocuring agent, and 2.4 wt% of conductive carbon black were placed in a kneader and kneaded at room temperature at 20 rpm for 10 minutes to prepare electrode material layer composition 1 for dry processing. [Example]

[0066] An electrode material layer composition 2 for dry processing was prepared in the same manner as in Example 1, except that no photocuring agent was used and 0.1 wt % of an azo-based curing agent (AIBN) as a thermal curing agent was used. [Example]

[0067] An electrode material layer composition 3 for dry machining was prepared in the same manner as in Example 1, except that an acrylate-based compound and PTFE mixed in a weight ratio of 1:1 were used instead of an acrylate-based compound. [Example]

[0068] An electrode material layer composition 4 for dry machining was prepared in the same manner as in Example 1, except that an acrylate-based compound and an ethylene glycol-based copolymer (a ternary copolymer of ethylene glycol-maleic anhydride-acrylonitrile, CNP Solutions, Korea) were mixed in a weight ratio of 1:1 instead of an acrylate-based compound. [Example]

[0069] 95.0 wt% of a mixed active material of graphite and silicon oxide (SiOx) (graphite:SiOx = 90:10 (weight ratio), theoretical capacity: 470 mAh / g) as the negative electrode active material, 3.5 wt% of a hexafunctional urethane oligomer, 0.05 wt% of an azo-based curing agent (AIBN) as a thermal curing agent, 0.05 wt% of a phosphine oxide-based curing agent (trimethylbenzoyldiphenylphosphine oxide) as a photocuring agent, 1.4 wt% of carbon black, and 0.5 wt% of single-walled carbon nanotubes were placed in a kneader as a kneading machine and kneaded at room temperature at 20 rpm for 10 minutes to prepare electrode material layer composition 5 for dry processing. [Example]

[0070] 1. Composition Preparation Step

[0071] An electrode material layer composition 1 was prepared in the same manner as in Example 1.

[0072] 2. Positive electrode material layer sheet formation step

[0073] Electrode material layer composition 1: 7 kgf / cm 2 The sheet was rolled several times while applying a pressure of 1000 kJ / cm to form a positive electrode material layer sheet having a thickness of 70 μm.

[0074] 3. Adhesion Step

[0075] (I) Primer layer formation step

[0076] To attach the positive electrode material layer sheet to the aluminum electrode plate, a primer layer was formed on the surface of the electrode plate as follows. The primer for the positive electrode plate was prepared by adding carbon nanotubes to NMP together with ethylene glycol-maleic anhydride-acrylonitrile copolymer (CNP Solutions, Korea), stirring at room temperature for 10 minutes, and then dispersing the mixture using a pressurized spray method to prepare a primer solution. The carbon nanotube content in the binder was 20 wt% based on the total weight of the copolymer, and the solid content in the dispersion was 4 wt%. The primer layer was formed to a thickness of approximately 1.0 μm using a bar coater (drying: 130°C, 2 minutes). A tape test of the primer layer confirmed that it adhered well and did not peel off from the electrode plate. Furthermore, the surface resistance of the electrode plate on which the primer layer was formed was 2×10 -3 The surface resistance was Ω / area, which was similar to that of the aluminum electrode plate.

[0077] (II) Crimping step

[0078] A temporary positive electrode was formed by placing a positive electrode material layer sheet on the aluminum electrode plate on which the primer layer was formed and pressing the sheet together.

[0079] 4. Curing step

[0080] The temporary positive electrode was treated at a temperature of 120 °C for 10 minutes and then irradiated with UV (700 mJ / cm 2) causes the acrylate compounds, a bifunctional ethylene glycol monomer and a hexafunctional ethylene glycol oligomer, to harden, allowing the acrylate compound used as a binder to function as a binder that does not dissolve in the electrolyte.

[0081] 5. Rolling step

[0082] The electrode material layer after the curing step has an electrode density of 1.0 g / cm 3 Thus, a positive electrode 1 for a lithium ion battery including a positive electrode material layer sheet having a thickness of 70 μm was finally manufactured. [Example]

[0083] A positive electrode 2 for a lithium ion battery including a positive electrode material layer sheet having a thickness of 70 μm was manufactured in the same manner as in Example 6, except that an electrode material layer composition 2 was prepared in the composition preparation step, and only thermal curing (120°C, 10 minutes) was performed without UV irradiation in the curing step. [Example]

[0084] In the composition preparation step, an electrode material layer composition 3 was prepared, and the rolling pressure was 7 kgf / cm 2 A positive electrode 3 for a lithium ion battery including a positive electrode material layer sheet having a thickness of 75 μm was produced in the same manner as in Example 6, except that the electrode material layer was formed as follows. [Example]

[0085] In the composition preparation step, an electrode material layer composition 5 is prepared, and in the sheet formation step, a rolling pressure of 7 kgf / cm 2 A negative electrode for a lithium ion battery including a 65 μm thick negative electrode material layer sheet was manufactured in the same manner as in Example 6, except that a negative electrode material layer sheet was formed as the negative electrode material layer sheet and copper foil was used as the metal electrode plate in the attachment step.

[0086] <Comparative Example 1> NCM811 (95.0 wt %), which is a positive electrode active material, 3.5 wt % of PTFE, and 1.5 wt % of conductive carbon black were mixed and stirred at 300 rpm for 10 minutes to prepare Comparative Electrode Material Layer Composition 1.

[0087] <Comparative Example 2> Comparative electrode material layer composition 2 was prepared in the same manner as in Example 1, except that 0.001 wt % of an azo-based curing agent (AIBN), 0.001 wt % of a phosphine oxide-based curing agent (trimethylbenzoyldiphenylphosphine oxide), and 2.498 wt % of conductive carbon black were used in the composition preparation step.

[0088] <Comparative Example 3> In the composition preparation step, comparative electrode material layer composition 1 was prepared, and in the sheet formation step, the rolling pressure was 20 kgf / cm 2 Comparative Example 1 was produced in the same manner as in Example 6, except that a positive electrode material layer sheet was formed as described above and the curing step was not performed. The thickness of the positive electrode material layer sheet formed during the production of Comparative Example 1 was 110 μm.

[0089] <Comparative Example 4> Comparative positive electrode 2 including a positive electrode material layer sheet having a thickness of 80 μm was produced in the same manner as in Example 6, except that comparative electrode material layer composition 2 was prepared in the composition preparation step.

[0090] <Experimental Example 1> To confirm that the electrode material layer was well adhered to the metal electrode plate, an adhesion test using Scotch tape was performed on the lithium-ion battery positive electrodes 1 and 5 and the comparative positive electrodes 1 and 2. To do this, 3M Scotch tape was applied to the surface of the electrode material layer, and the degree of adhesion was determined by whether the electrode material layer peeled off from the electrode plate during the peeling process.

[0091] The results of the adhesion test using Scotch tape confirmed that the electrode material layer adhered well to the electrode plate for both the lithium-ion battery positive electrode 15 and the comparative positive electrode 1. However, in the case of the comparative positive electrode 2, the active material layer adhered to the positive electrode plate was not firm, and the surface remained sticky.

[0092] In other words, the electrode material layer of the lithium-ion battery positive electrode 1 adhered well to the electrode plate, was flexible, and the surface was not sticky. In particular, the positive electrode material layer sheet processability was excellent. Because acrylate compounds are liquid at room temperature, it is presumed that processing such as kneading and rolling of the active material composition, which is mostly composed of inorganic particles, is much easier.

[0093] The surface of the electrode material layer of the lithium-ion battery positive electrode 2 was not sticky, adhered well to the electrode plate, and was relatively flexible. However, it was observed that the electrode material layer was slightly less rigid than that of Example 1 (when both a thermal curing agent and a photocuring agent were used).

[0094] In the positive electrode 3 for a lithium ion battery, the electrode material layer was firmly attached to the electrode plate, the electrode plate was flexible when bent, and the surface was not sticky.

[0095] In the case of the positive electrode 4 for a lithium ion battery, the active material composition sheet was easily formed into a sheet having a thickness of 70 μm, and in addition to having excellent adhesive strength to the electrode plate, a hard electrode material layer was obtained.

[0096] The negative electrode for lithium-ion batteries also exhibits flexible bending properties, and adhesion tests for the electrode material layer confirmed that the electrode material layer adhered well to the electrode plate.

[0097] <Experimental Example 2> An experiment was conducted to measure and compare the pressure applied during the process of forming the electrode material layer and the final thickness formed for lithium ion battery positive electrodes 1 and 5 and comparative positive electrodes 1 and 2.

[0098] Experimental results showed that when only a solid binder (PTFE) was used in the electrode material layer composition (Comparative Example 1), high pressure rolling was required to form a positive electrode material layer sheet in the sheet formation step, and even when rolling at higher pressures, it was difficult to form a positive electrode material layer sheet with a thickness of 100 μm or less. In contrast, when an acrylate-based compound was included in the electrode material layer composition as in Examples 1 to 5 and Comparative Example 2, the rolling pressure for forming a positive electrode material layer sheet in the sheet formation step was significantly lower, and it was easy to form a positive electrode material layer sheet with a thickness of 100 μm or less (typically 60 to 80 μm).

[0099] <Experimental Example 3> The lithium ion battery positive electrode 15 and the comparative positive electrodes 1 and 2 were subjected to a charge-discharge cycle test as follows, and the results are shown in FIGS. 1 and 6, respectively.

[0100] The cell performance test for the positive electrode was as follows. A half-cell coin cell (CR2032) was fabricated and subjected to a charge-discharge cycle test at a 1.0C rate. A lithium metal foil was used as the counter electrode, and the electrolyte was a solution of 1.15 mol of LiPF6 dissolved in a mixed solvent of carbonates, such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), vinylene carbonate (VC), and fluoroethylene carbonate (FEC) (weight ratio: EC / DEC / VC / FEC = 3 / 7 / 0.05 / 0.05). The coin cell was fabricated in a glove box filled with argon gas.

[0101] In the charge-discharge cycle test of the present invention, the rate was initially increased to 0.1 C to 1.0 C, and then a life test was performed at a rate of 1.0 C. The discharge capacity after four cycles was taken as the initial capacity, and this initial capacity was compared with the discharge capacity after 50 to 100 cycles to calculate the capacity retention rate.

[0102] As shown in FIG. 1, in the case of Comparative Example Positive Electrode 1, the capacity decreased after about 40 to 50 cycles.

[0103] As a result of a charge-discharge cycle test on the positive electrode 1 for a lithium ion battery according to Example 6 of the present invention, it was measured that the initial capacity was maintained at about 89% after 100 cycles, as shown in Figure 2. On the other hand, in the case of the positive electrode 2 according to Comparative Example 4, the capacity retention rate after 100 cycles was also about 70%, indicating a decrease in capacity. These results indicate that the acrylate-based compound must be sufficiently cured in order to function as a binder.

[0104] As shown in FIG. 3, the charge-discharge cycle test result of the positive electrode 2 for a lithium ion battery according to Example 7 of the present invention was about 87%, which was a slightly lower capacity retention rate than the result of Example 1.

[0105] Referring to Figure 4, which shows the charge-discharge cycle test results for the lithium-ion battery positive electrode 3 according to Example 8 of the present invention, the capacity retention rate after 100 cycles was about 90%, which was similar to the result for the lithium-ion battery positive electrode 1 according to Example 6. Comparing the results for the lithium-ion battery positive electrode 3 according to the present invention with the comparative positive electrode 1, it can be seen that the use of PTFE mixed with the acrylate binder of the present invention improves the rapid decrease in capacity observed in the case of PTFE alone.

[0106] FIG. 5 shows the results of a charge-discharge cycle test of a lithium ion battery positive electrode 4 prepared in the same manner as in Example 8, except that the electrode material layer composition 4 of the present invention was used. It can be seen that the capacity retention rate after 100 cycles was approximately 91%, which is an excellent result.

[0107] From the results of FIGS. 4 and 5, it is clear that the acrylate binder of the present invention can be used in combination with other dry binders.

[0108] Referring to FIG. 6 showing the charge-discharge cycle test results of the negative electrode for a lithium ion battery according to Example 9 of the present invention, the discharge capacity after 4 cycles was measured to be 415 mAh / g, and the discharge capacity after 50 cycles was measured to be 397 mAh / g, indicating a capacity retention rate of about 96%.

[0109] From the above experimental results, when an acrylate-based compound is used as a binder in the electrode material layer composition for dry processing and a curing agent for the acrylate-based compound is used in combination, the electrode material layer composition containing the positive or negative electrode active material can be uniformly mixed because the acrylate-based compound is liquid at room temperature, and the processability of the electrode sheet made of the electrode material layer composition, i.e., the positive electrode material layer sheet or the negative electrode material layer sheet, is also excellent. 2 It was confirmed that an electrode layer material composition sheet having a relatively thin thickness of less than 100 μm can be produced even at a relatively low pressure of less than 100 μm, and that after a final curing step, the electrode material layer sheet has excellent adhesion to the metal electrode plate and can maintain a high capacity retention rate during a charge-discharge cycle test.

[0110] Therefore, when an acrylate-based compound and a curing agent for the acrylate-based compound are included as a binder in an electrode material layer composition for a dry process as in the present invention, not only the physical properties but also the capacity retention rate in a cycle test can be maintained at a fairly high level, regardless of the curing method, such as a thermal curing method or a photocuring method, as long as curing is performed. In particular, it has been confirmed that using a mixture of a photoinitiator and a thermal curing agent as a curing agent is very effective in maintaining the physical properties of the electrode material layer.

[0111] The electrode material layer composition of the present invention can be used to form a positive electrode material layer and a negative electrode material layer, and can be used in a variety of common lithium-ion batteries that use active materials. In addition, the lithium-ion battery of the present invention can be used in various battery-based devices, such as electric vehicles, mobile phones, and laptops.

[0112] Although the present invention has been illustrated and described with reference to preferred embodiments as described above, it is not limited to the above-described embodiments, and various changes and modifications may be made by those skilled in the art to which the invention pertains without departing from the spirit of the invention.

Claims

1. An electrode material layer composition for a dry process, comprising: an active material for a positive electrode or a negative electrode; an acrylate-based compound; and a curing agent for the acrylate-based compound.

2. The electrode material layer composition for a dry process according to claim 1, wherein the acrylate-based compound comprises a methacrylate-based compound.

3. 10. The composition for an electrode material layer according to claim 1, wherein the acrylate-based compound is a monomer or oligomer having 2 to 16 functional groups and a main chain having 2 to 1,000 carbon atoms.

4. 4. The electrode material layer composition for a dry process according to claim 3, wherein the functional groups are at least one selected from the group consisting of a methylene group, a urethane group, an ester group, an ether group, an oxide group, an ethylene oxide group, a propylene oxide group, an ethylene glycol group, a propylene glycol group, a butadiene group, an imide group, an amine group, an amide group, an epoxy group, an olefin group, a sulfone group, or a combination thereof, and the functional groups are in a number of 2 to 16.

5. 10. The electrode material layer composition for a dry process according to claim 1, wherein the acrylate-based compound is contained in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the positive or negative electrode active material.

6. 10. The electrode material layer composition for a dry process according to claim 1, wherein the curing agent is at least one of a thermal curing agent and a photocuring agent, and is included in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the acrylate-based compound.

7. 7. The electrode material layer composition for a dry process according to claim 6, wherein the thermal curing agent comprises a peroxide or an azo compound, and the photocuring agent comprises a phenyl ketone-based compound or a phosphine oxide-based compound.

8. The composition for an electrode material layer for a dry process according to claim 1, further comprising at least one binder different from the acrylate-based compound.

9. 9. The electrode material layer composition for a dry process according to claim 8, wherein the acrylate compound and the binder have a weight ratio of 99:1 to 1:

99.

10. The electrode material layer composition for a dry process according to claim 1, further comprising one or more nanocarbon-based conductivity enhancers selected from conductive carbon black, graphene, and carbon nanotubes.

11. 2. The electrode material layer composition for a dry process according to claim 1, wherein the positive or negative electrode active material comprises at least one selected from the group consisting of lithium, manganese, nickel, cobalt, aluminum, iron, phosphorus, tin, titanium, a carbon material, silicon, silicon oxide, sulfur, and combinations thereof.

12. An electrode for a lithium ion battery, comprising at least one of a positive electrode material layer and a negative electrode material layer made of the electrode material layer composition for a dry process according to any one of claims 1 to 11.

13. A composition preparation step of preparing the electrode material layer composition for a dry process according to any one of claims 1 to 11; forming a positive electrode material layer sheet or a negative electrode material layer sheet using the electrode material layer composition for the dry process; a step of attaching the positive electrode material layer sheet or the negative electrode material layer sheet to a metal electrode plate; a curing step of curing the attached positive electrode material layer sheet or negative electrode material layer sheet; and rolling the electrode material layer obtained by the curing step.

14. 14. The method of claim 13, wherein the attaching step includes the steps of: forming a primer layer on the metal electrode plate; and placing the positive electrode material layer sheet or the negative electrode material layer sheet on the primer layer and then pressing the sheet together.

15. 14. The method of claim 13, wherein the curing step is performed through at least one of thermal curing at 50°C to 180°C for 5 minutes to 30 minutes and photocuring by UV irradiation.

16. A lithium ion battery comprising the lithium ion battery electrode according to claim 12.

17. A lithium ion battery comprising an electrode for a lithium ion battery manufactured by the manufacturing method according to claim 13.

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