Acrylic aqueous dispersion, adhesive layer composition, and secondary battery comprising same

Abstract

The present invention, in order to improve the performance and stability of a secondary battery, may provide an adhesive layer formed between a porous substrate and an electrode, and an adhesive layer composition comprising acrylic resin particles and inorganic particles for forming the adhesive layer, and may provide an acrylic aqueous dispersion as a raw material used in the preparation of the adhesive layer composition, wherein the acrylic aqueous dispersion comprises acrylic resin particles prepared from a monomer mixture comprising 50 wt% or more of a C4-C12 cycloalkyl (meth)acrylate and a linear or branched C6-C20 alkyl (meth)acrylate, and an additional monomer including a hydrophilic group-containing (meth)acrylate or a lipophilic monomer, and the acrylic resin particles have a magnesium ion content of 500 ppm or less.

Description

Acrylic aqueous dispersion, adhesive layer composition, and secondary battery containing the same

[0001] The present invention provides an acrylic aqueous dispersion comprising acrylic resin particles included in an adhesive layer formed between an electrode of a secondary battery and a porous substrate.

[0002] In addition, the present invention provides a composition for an adhesive layer comprising the acrylic resin particles and inorganic particles, etc., that form the adhesive layer.

[0003] In addition, the present invention provides a battery, for example, a secondary battery, comprising an adhesive layer formed between the electrode of the battery and a porous substrate.

[0004] Currently, as economic instability caused by the depletion of fossil fuels and environmental pollution resulting from the use of fossil fuels have become major issues, secondary batteries are being used as an energy source to replace fossil fuels.

[0005] In order to replace high-power devices such as automobiles that use fossil fuels, secondary batteries require high charge / discharge capacity, excellent capability-rate (C-rate), and excellent charge / discharge cycle performance. However, for secondary batteries that meet these performance requirements, there is a constant risk of fire and explosion due to heat generation caused by high-density energy storage and high-power charging / discharging.

[0006] As a solution to this problem, a method has been proposed to form an adhesive layer using a fluorine-based resin, such as polyvinyl fluoride (PVDF) or vinyldene fluoride-hexafluoropropylene copolymer (PVDF-HFP), between the electrode and the separator (porous substrate) of a secondary battery. However, the above-mentioned fluorine-based resin is a perfluorinated compound (PFAS, Per- and polyfluoroalkyl substances) and is subject to stricter regulations due to environmental pollution issues. Furthermore, it has low adhesion to the electrode and the porous substrate, and swelling occurs due to the electrolyte in high-temperature environments, and secondary batteries containing it still have stability issues.

[0007] In addition, conventional adhesives used for the electrodes and separators of the aforementioned secondary batteries have the problem of impairing the performance of the secondary batteries manufactured using them, as residual metal ions introduced during the polymerization process remain.

[0008] As another alternative to solve the above problem, there were attempts to use acrylic resins; however, conventional acrylic resins exhibited aggregation, expansion, and precipitation during long-term storage, and still failed to resolve the high-temperature stability issue of secondary batteries.

[0009] In addition, to solve the above problem, the inventors attempted to use a polymerized acrylic resin particle containing (a) 50 weight% or more of C4-C12 cycloalkyl (meth)acrylate and (b) straight-chain or branched-chain C6-C20 alkyl (meth)acrylate as a binder. However, while it is essential to include a magnesium-based dispersant to ensure that the shape and average particle size of the particles are polymerized consistently in the production of the acrylic resin particle, there was a problem in that metal ions such as magnesium ions were present in the produced acrylic resin particle, which degraded the battery performance.

[0010] In other words, since the adhesive layer formed between the electrode and the separator of the secondary battery using the binder invented by the inventors of the present invention contains residual metal ions due to the dispersant introduced during the polymerization process, the secondary battery manufactured has a problem in that its performance is impaired by these metal ions, and therefore a method to solve this is required.

[0011] Accordingly, the present invention may minimize the concentration of metal ions contained in the polymerized acrylic resin particles.

[0012] Specifically, the present invention may include, as residual metal ions of an acrylic resin particle polymerized by including (a) a monomer mixture comprising 50 weight% or more of a C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate and (b) one or more additional monomers selected from a hydrophilic group-containing (meth)acrylate and a lipophilic monomer, in particular magnesium ions at a concentration of 500 ppm or less, preferably 100 ppm or less, and more preferably 50 ppm or less.

[0013] In addition, the present invention can enable an acrylic aqueous dispersion containing the same to have lower swelling properties while having magnesium ions of 500 ppm or less of the polymerized acrylic resin particles, comprising a) a monomer mixture containing 50 weight% or more of C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate and (b) a lipophilic monomer.

[0014] In addition, the present invention may provide large-diameter acrylic resin particles produced by suspension polymerization having significantly larger particles compared to those produced by new emulsion polymerization that imparts the above characteristics as an adhesive to the adhesive layer, and an acrylic aqueous dispersion containing the same.

[0015] In addition, the present invention may provide a new adhesive layer formed between an electrode of a battery and a porous substrate that is a separator, which provides excellent adhesion by bonding the electrode and the porous substrate, provides uniform adhesion without variation in adhesion across the entire adhesive surface, and provides low swelling resistance to the electrolyte.

[0016] In addition, the present invention may provide new acrylic resin particles that impart the above characteristics as an adhesive to the adhesive layer and minimize the content of residual metal ions so as not to affect battery performance, and an acrylic aqueous dispersion containing the same.

[0017] In addition, the present invention may provide an adhesive layer with improved ion mobility, wherein the residual metal ion content of the acrylic resin particles included as the adhesive in the adhesive layer is low.

[0018] In addition, the present invention may provide an adhesive layer disposed between an electrode and a porous substrate, having high adhesion to both the electrode and the porous substrate, and having a low variation in adhesion strength across the entire adhesive surface.

[0019] In addition, the present invention may provide a battery comprising an adhesive layer that improves performance such as thermal stability, electrochemical stability, suppressed swelling with respect to the electrolyte, and interfacial stability.

[0020] In addition, the present invention may provide a secondary battery with excellent stability in that separation between the electrode and the porous substrate does not occur during charge-discharge cycles.

[0021] In addition, the present invention may provide an adhesive layer with excellent ion mobility and a battery with low electrical resistance including the same.

[0022] In addition, the present invention may provide a composition for an adhesive layer with excellent dispersibility comprising inorganic particles and large-diameter acrylic resin particles (binder particles) to form the adhesive layer.

[0023] In addition, the present invention may provide acrylic resin particles having low swelling, low cohesiveness, and high dispersibility included in the adhesive layer, and an acrylic aqueous dispersion containing the same.

[0024] The above acrylic aqueous dispersion may provide excellent redispersibility even after long-term storage.

[0025] The present invention relates to an adhesive layer formed between an electrode and a porous substrate, wherein the adhesive layer is formed by including acrylic resin particles and inorganic particles, and the acrylic resin particles may be prepared by including (a) a monomer mixture comprising 50 weight% or more of C4-C12 cycloalkyl (meth)acrylate and straight-chain or branched-chain C6-C20 alkyl (meth)acrylate; and (b) one or more additional monomers selected from hydrophilic group-containing (meth)acrylate and lipophilic group monomers.

[0026] In one embodiment of the present invention, the acrylic resin particles may contain magnesium ions at a concentration of 500 ppm or less.

[0027] In one aspect of the present invention, the hydrophilic group is a hydroxyl group (*-OH), a carboxylic acid group (*-COOH), an amine group (*-NH2), an amide group (*-CONH2), a thiol group (*-SH), a sulfonic acid group (*-SO3H), a sulfonamide group (*-SO2NH2), or an ammonium group (*-NH3 + It can be ) or a phosphate group (*-PO4H2).

[0028] In one embodiment of the present invention, the lipophilic monomer may be one or more selected from α-olefin, methyl (meth)acrylate, ethyl (meth)acrylate, C6-C20 aryl (meth)acrylate, styrene-based monomer, perfluoroalkyl (meth)acrylate and fluoroalkyl (meth)acrylate.

[0029] In one embodiment of the present invention, the acrylic resin particles may be manufactured by including a step of acid washing and a step of water washing.

[0030] In one embodiment of the present invention, the acrylic resin particles may be prepared by including an additional monomer in an amount of 0.01 to 10 parts by weight per 100 parts by weight of a monomer mixture.

[0031] In one embodiment of the present invention, the acrylic resin particles may have an average particle size (D50) of 0.5 to 10 μm.

[0032] In one embodiment of the present invention, the inorganic particles may have an average particle size (D50) of 10 to 5,000 nm.

[0033] In one embodiment of the present invention, the adhesive layer may comprise 10 to 10,000 parts by weight of inorganic particles with respect to 100 parts by weight of acrylic resin particles.

[0034] In one embodiment of the present invention, the acrylic resin particles may be polymerized by further including 0.1 to 20 parts by weight of a crosslinking agent containing two or more radical reactive groups.

[0035] In one embodiment of the present invention, the adhesive layer may have an adhesion strength of 30 gf / 15 mm or more with a porous substrate as measured by ASTM D3330.

[0036] In one embodiment of the present invention, the adhesive layer may have an adhesion strength of 10 gf / 25 mm or more with respect to the electrode as measured by ASTM D3330.

[0037] In one embodiment of the present invention, the porous substrate having the adhesive layer formed thereon may have a breathability of 150 sec / 100cc or less.

[0038] The present invention provides a battery comprising an adhesive layer.

[0039] The present invention provides an acrylic aqueous dispersion comprising acrylic resin particles, wherein the acrylic resin particles may be prepared by comprising (a) a monomer mixture comprising 50 weight% or more of C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate and (b) an additional monomer of a hydrophilic group-containing (meth)acrylate or a lipophilic group monomer.

[0040] In one embodiment of the present invention, the acrylic resin particles may have a magnesium ion content of 500 ppm or less.

[0041] In one embodiment of the present invention, the acrylic aqueous dispersion further comprises an amphiphilic compound comprising a hydrophilic group and a lipophilic group.

[0042] In one embodiment of the present invention, the acrylic aqueous dispersion may contain 0.1 to 5 weight percent of an amphiphilic compound based on the total weight.

[0043] In one embodiment of the present invention, the acrylic resin particles may be polymerized by further including 0.1 to 20 parts by weight of a crosslinking agent containing two or more radical reactive groups per 100 parts by weight of a monomer mixture.

[0044] In one embodiment of the present invention, the acrylic aqueous dispersion may have a solid content uniformity of 90 to 110% calculated by Formula 1 below.

[0045] [Equation 1]

[0046]

[0047] (In the above Equation 1, T s ε is the solid content of 100 g of the supernatant extracted from the surface of the acrylic aqueous dispersion in a container with a diameter of 10 cm and a height of 18 cm after placing 1 L of the acrylic aqueous dispersion in the container and letting it stand for 30 minutes, and T dis the solid content of 100 g of the lower liquid extracted from the bottom of the acrylic aqueous dispersion in a container with a diameter of 10 cm and a height of 18 cm, after it has been left to stand for 30 minutes.

[0048] In one embodiment of the present invention, the acrylic aqueous dispersion may have a redispersibility of 130% or less as calculated by the following Formula 2.

[0049] [Equation 2]

[0050]

[0051] (In Equation 2 above, P0 is the average particle size (D50) of acrylic resin particles dispersed in the initial acrylic aqueous dispersion, and P1 is the average particle size (D50) of acrylic resin particles dispersed in the redispersed acrylic aqueous dispersion after leaving the acrylic aqueous dispersion at 25°C for 3 months and then redispersing it at a stirring speed of 200 rpm for 20 minutes.)

[0052] The present invention provides a composition for an adhesive layer for manufacturing an adhesive layer formed between an electrode and a porous substrate, wherein the composition for the adhesive layer may comprise (A) a monomer mixture comprising 50 weight% or more of a C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate; and (b) one or more additional monomers selected from a mixture of hydrophilic group-containing (meth)acrylate and lipophilic monomers, and may comprise acrylic resin particles having a magnesium ion content of 500 ppm or less and (B) inorganic particles.

[0053] In one embodiment of the present invention, the composition for the adhesive layer may comprise 10 to 10,000 parts by weight of inorganic particles with respect to 100 parts by weight of acrylic resin particles.

[0054] In one embodiment of the present invention, the adhesive composition may further comprise an amphiphilic compound comprising a hydrophilic group and a lipophilic group.

[0055] In one embodiment of the present invention, the acrylic resin particles may have an average particle size (D50) of 0.5 to 10 μm.

[0056] In one embodiment of the present invention, the inorganic particles may have an average particle size (D50) of 10 to 5,000 nm.

[0057] The above adhesive layer comprises large-diameter acrylic particles and inorganic particles of a specific composition obtained by suspension polymerization of the present invention, and by using the large-diameter acrylic particles, it can have high adhesion to the electrode and porous substrate even if an excess amount of inorganic particles is included.

[0058] In addition, the adhesive layer may have high adhesion with the porous substrate, with an adhesion strength of 30 gf / 15 mm or more, 40 gf / 15 mm or more, 50 gf / 15 mm or more, 60 gf / 15 mm or more, or up to 70 gf / 15 mm and between these values.

[0059] In addition, the adhesive layer may have high adhesion with the electrode, with an adhesion strength of 10 gf / 25 mm or more, 15 gf / 25 mm or more, 20 gf / 25 mm or more, or up to 25 gf / 25 mm and values ​​different from these.

[0060] In addition, the adhesive layer has excellent adhesion to the electrode and the porous substrate, so it is possible to provide a secondary battery that can prevent fire, explosion, and performance degradation caused by the separation of the electrode and the porous substrate even after long-term use.

[0061] In addition, the porous substrate having an adhesive layer on at least one surface has a permeability of 150 sec / cc or less and 100 sec / cc or less, so that ion movement is not restricted and a secondary battery with low electrical resistance can be manufactured.

[0062] In addition, the above acrylic resin particles may contain residual metal ions in a washing process during the polymerization process, with a residual metal ion content of 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, 100 ppm or less, 50 ppm or less, 30 ppm or less, or in very small amounts where no residual metal ions are detected, and thus a secondary battery capable of stable charging and discharging can be provided by including this as a binder.

[0063] In addition, the acrylic aqueous dispersion may have a redispersibility of acrylic resin particles measured by the measurement method defined in the present invention of 130% or less, 120% or less, preferably 110% or less, more preferably 105% or less, and a value between the above values, thereby preventing expansion and aggregation of particles due to long-term storage, and the adhesive strength of the adhesive layer formed including it and the binding ability of inorganic particles may not be reduced.

[0064] In addition, the acrylic aqueous dispersion may have a measured solid content uniformity of 90 to 110%. This means that the composition for the adhesive layer has excellent dispersibility of inorganic particles and acrylic resin particles, and at the same time, the adhesive layer prepared therefrom can provide uniform adhesion over the entire surface area and provide low deviation in adhesion strength for each part, thereby improving the stability of the battery.

[0065] Unless otherwise defined, technical and scientific terms described in this invention have the meaning commonly understood by those skilled in the art to which this invention pertains, and descriptions of known functions and configurations that could unnecessarily obscure the essence of the invention are omitted in the following description.

[0066] Additionally, the singular form used in the present invention may be intended to include the plural form unless specifically indicated in the context.

[0067] Furthermore, units used in this invention without special mention are based on weight, and for example, units of % or ratio mean weight % or weight ratio, and weight % means the weight percentage of any one component of the entire composition that occupies within the composition unless otherwise defined.

[0068] Additionally, the numerical range used in the present invention includes a lower limit, an upper limit, all values ​​within that range, increments logically derived from the shape and width of the defined range, all of the limited values, and all possible combinations of the upper and lower limits of the numerical ranges limited in different forms.

[0069] Unless otherwise specifically defined in the specification of the present invention, values ​​outside the numerical range that may occur due to experimental error or rounding are also included in the defined numerical range.

[0070] The term "comprising" in the present invention is an open description having an equivalent meaning to expressions such as "comprising," "containing," "having," or "characterizing," and does not exclude elements, materials, or processes not additionally listed.

[0071] The term 'C1-Cn' of the present invention may mean a hydrocarbon having 1 to n carbon atoms.

[0072] The term '(meth)acrylate' of the present invention may be used as 'methacrylate', 'acrylate', or a term including both methacrylate and acrylate.

[0073] The term 'porous substrate' in the present invention refers to a porous film-shaped material made of a polymer resin, such as a polymer film including, for example, a polyolefin-based porous film, and means a substrate used as a separator in the field of secondary batteries, having a thickness of 1 to 200 μm and a porosity of 10 to 70 volume%. Since the porous film-shaped substrate can be manufactured by mixing a polyolefin-based resin and a diluent and then extruding, stretching, and extracting, this is not examined in detail.

[0074] The present invention may provide an adhesive layer having excellent adhesion to both a porous substrate and an electrode, respectively, in order to improve the performance and stability required of a secondary battery; a composition for an adhesive layer having excellent dispersibility even when containing more inorganic particles, a novel acrylic resin particle included in the adhesive composition, and an acrylic aqueous dispersion containing the same.

[0075] The present invention may provide novel acrylic resin particles and an acrylic aqueous dispersion containing the same, which solve the problem of physical properties deteriorating due to aggregation, sedimentation, and expansion during long-term storage.

[0076] The present invention may provide an adhesive layer formed between an electrode and a porous substrate, comprising acrylic resin particles and inorganic particles.

[0077] The above adhesive layer is formed between the electrode and the porous substrate to prevent the electrode and the porous substrate from separating, and even if an excess amount of inorganic particles is included, excellent adhesion can be maintained, and a secondary battery with improved high temperature stability, electrochemical stability, interfacial stability, and low electrical resistance can be provided.

[0078] In one embodiment of the present invention, the composition for the adhesive layer may be prepared by including large-diameter acrylic resin particles of a specific structure of the present invention and inorganic particles. In another embodiment of the present invention, the composition for the adhesive layer may be prepared by including specific acrylic resin particles of the present invention, an amphiphilic compound, and inorganic particles. The composition for the adhesive layer may be prepared by adjusting the solid content by adding an inorganic particle dispersion containing the inorganic particles to an acrylic aqueous dispersion containing the acrylic resin particles and the amphiphilic compound.

[0079] Hereinafter, each of the above components and the present invention will be described in detail.

[0080] The acrylic resin particles of the present invention may be prepared by comprising: a monomer mixture comprising 50% by weight or more of C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate; and one or more additional monomers selected from hydrophilic group-containing (meth)acrylate and lipophilic group monomers.

[0081] Acrylic resin particles produced by polymerizing the above monomer mixture have low swelling and low agglomeration, and also possess excellent adhesion and can firmly bind inorganic particles, making them preferable. In addition, due to the monomer combination described above, the acrylic resin particles can significantly reduce the content of residual magnesium ions, and as a result, the stability of the secondary battery manufactured including them can be improved.

[0082] In one embodiment of the present invention, the additional monomer may be preferred to be a hydrophilic group-containing (meth)acrylate or a lipophilic group monomer, respectively, in order to further enhance the effect of the manufactured acrylic resin particles appearing hydrophilic or lipophilic.

[0083] For example, acrylic resin particles polymerized by including a hydrophilic group-containing (meth)acrylate as the additional monomer can further reduce the residual magnesium ion content through additional processes of acid washing and water washing. In addition, acrylic resin particles polymerized by further including a lipophilic monomer as the additional monomer can be preferred because they can reduce the residual magnesium ion content to 500 ppm or less through acid washing and water washing while maintaining the strong hydrophobicity of the acrylic resin particles, thereby maintaining excellent redispersibility and low swelling properties.

[0084] In one embodiment of the present invention, the acrylic resin particles may have a magnesium ion content measured by an inductively coupled plasma mass spectrometer (ICP-MS, Agilent 7700) of 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, preferably 100 ppm or less, 50 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 1 ppm or more, or no magnesium ions may be detected.

[0085] The reason the above acrylic resin particles contain magnesium ions is that, during polymerization, a magnesium dispersant must be used to obtain acrylic resin particles with a uniform and circular morphology in order to achieve a uniform particle size, and also because when forming an adhesive layer between a separator and an electrode containing such acrylic resin particles, the adhesion and thickness uniformity are excellent. However, when a magnesium dispersant is used for the effects described above, the magnesium ions have a negative effect on the performance of the battery, so the removal of magnesium ions is required.

[0086] To this end, in the present invention, after manufacturing the acrylic resin particles, magnesium ions can be removed through acid washing in an acidic atmosphere and water washing with ion-exchanged water to manufacture acrylic resin particles having the above magnesium ion content.

[0087] At this time, the acrylic resin particles are polymerized by including a monomer mixture comprising 50% by weight or more of C4-C12 cycloalkyl (meth)acrylate and straight-chain or branched-chain C6-C20 alkyl (meth)acrylate, and additional monomers, so that magnesium ions can be effectively washed away by acid washing and water washing. As a result, a battery using the acrylic resin particles as a binder can be stably charged and discharged, which can be preferred.

[0088] In one embodiment of the present invention, the acrylic resin particles may be manufactured by including a step of acid washing one or more times and a step of water washing one or more times for a polymerized product comprising a monomer mixture and a hydrophilic group-containing (meth)acrylate to achieve the magnesium ion content described above, and preferably, the step of water washing may be performed sequentially after the step of acid washing.

[0089] In one embodiment of the present invention, the acidic washing step may involve adding acid dropwise while stirring a slurry containing acrylic resin particles produced by polymerizing a monomer mixture until the pH becomes 8 or lower, and preferably, adding acidic components until the pH becomes 5 to 6.

[0090] The above acrylic resin particles may be preferred to undergo acid washing at a pH of 8 or lower, followed by the water washing described later, so that the magnesium ion content of the manufactured acrylic resin particles can be cleaned to 500 ppm or less. Additionally, the above acid washing may be preferred when performed in an environment of pH 5 to 6 in order to prevent the swollen acrylic resin particles from swelling due to basic components and then shrinking, thereby preventing wrinkles, etc., during the drying step; however, this is not necessarily limited as long as it does not impair the physical properties of the manufactured acrylic resin particles.

[0091] The acidic component used in the above acidic cleaning step is not specifically limited as long as it is an acid usable in this field, but sulfuric acid may be preferred in terms of being able to effectively clean residual acid from the water cleaning step.

[0092] The above water washing step is performed as follows. It may include a process of filtering and separating the slurry of acrylic resin particles acid-washed after polymerization, adding ion-exchanged water to the solid obtained therefrom to re-slurry it, stirring it to wash away residual acidic components and impurities, and then filtering and dewatering.

[0093] The above water washing step may involve adding ion-exchanged water to the solid obtained from the filtration and dewatering process to re-slurry it, and then repeating the water washing step one or more times, two or more times, three or more times, four or more times, or ten or fewer times in the same manner as described above.

[0094] Accordingly, the acrylic resin particles are polymerized with a specific monomer combination and, in the manufacturing process including the acid washing and water washing steps described above, may contain magnesium in very small amounts of 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, 100 ppm or less, preferably 50 ppm or less, and may be preferred as the battery manufactured including the above may have stability, ion transportability, long-term cycle characteristics, and mechanical reliability of the adhesive layer.

[0095] In one embodiment of the present invention, the acrylic resin particles may be polymerized by including an additional monomer of a lipophilic group-containing (meth)acrylate or a lipophilic group monomer in order to solve the problem of excessive residual magnesium ion content due to strong hydrophobicity when polymerized solely by a monomer mixture comprising 50 weight% or more of C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate.

[0096] Acrylic resin particles manufactured by further including the above-mentioned hydrophilic group-containing (meth)acrylate can significantly reduce the residual magnesium ion content through the aforementioned acid washing and water washing. Additionally, acrylic resin particles manufactured by further including the above-mentioned lipophilic monomer may be preferred as they can reduce the residual magnesium ion content to 500 ppm or less while maintaining effects such as redispersibility and low swelling properties resulting from hydrophobicity, but this is not specifically limited as long as it satisfies the magnesium ion content described above.

[0097] In one aspect of the present invention, the hydrophilic group is a hydroxyl group (*-OH), a carboxylic acid group (*-COOH), an amine group (*-NH2), an amide group (*-CONH2), a thiol group (*-SH), a sulfonic acid group (*-SO3H), a sulfonamide group (*-SO2NH2), or an ammonium group (*-NH3 + It may be a phosphate group (*-PO4H2) or a hydroxyl group (*-OH), preferably a carboxylic acid group (*-COOH) or an amine group (*-NH2), and even more preferably a hydroxyl group (*-OH) or a carboxylic acid group (*-COOH).

[0098] The above hydrophilic group-containing (meth)acrylate may be used without limitation as long as it contains the aforementioned hydrophilic group, but as a non-limiting example, it may include one or more selected from (meth)acrylic acid, hydroxy C1-C7 alkyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, and hydroxyphenyl (meth)acrylate.

[0099] In one embodiment of the present invention, the lipophilic monomer may comprise one or more selected from α-olefin, methyl (meth)acrylate, ethyl (meth)acrylate, C6-C20 aryl (meth)acrylate, styrene-based monomer, perfluoroalkyl (meth)acrylate and fluoroalkyl (meth)acrylate, etc., preferably may be a styrene-based monomer, methyl (meth)acrylate or ethyl (meth)acrylate, etc., and more preferably may be a styrene-based monomer.

[0100] Acrylic resin particles prepared by including additional monomers in the above weight range may have low swelling properties and excellent long-term dispersibility in water, and at the same time may be preferred as they may have a magnesium ion content of 500 ppm or less after acid washing and water washing following polymerization.

[0101] In one embodiment of the present invention, the monomer mixture comprising 50 weight% or more of the C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate may include other polymerizable monomers in an amount of 20 weight% or less and 10 weight% or less, but preferably, it may consist only of 50 weight% or more of the C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate.

[0102] In one embodiment of the present invention, the monomer mixture comprising 50 wt% or more of the C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate may comprise, with respect to the total weight, 50 wt% or more, 55 wt% or more, 60 wt% or more, 65 wt% or more, 70 wt% or more, 95 wt% or less, 90 wt% or less, 85 wt% or less, or 80 wt% or less of the C4-C12 cycloalkyl (meth)acrylate, and the values ​​may be different from the above values. For example, it may be 50 to 95 wt%, 55 to 95 wt%, 60 to 95 wt%, 65 to 95 wt%, 70 to 95 wt%, 70 to 90 wt%, 70 to 85 wt%, or 70 to 80 wt%.

[0103] In one embodiment of the present invention, the monomer mixture comprising 50 weight% or more of the C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate may comprise, based on the total weight, 40 weight% or less, 35 weight% or less, 30 weight% or less, 10 weight% or more, 15 weight% or more, or 20 weight% or more of the straight-chain or branched-chain C6-C20 alkyl (meth)acrylate. For example, it may comprise 10 to 40 weight%, 10 to 35 weight%, 10 to 30 weight%, 15 to 30 weight%, or 20 to 30 weight%.

[0104] In one embodiment of the present invention, the acrylic resin particles may be preferred to be polymerized by including 0.05 to 1 weight part of a hydrophilic group-containing (meth)acrylate with respect to 100 weight parts of a monomer mixture comprising 70 to 80 weight% of C4-C12 cycloalkyl (meth)acrylate and 20 to 30 weight% of straight-chain or branched-chain C6-C20 alkyl (meth)acrylate, but this is not necessarily limited to achieving the physical properties of the present invention.

[0105] Acrylic resin particles polymerized from a monomer mixture having the above monomer composition and monomer content can have excellent adhesion between the porous substrate and the electrode and excellent bonding between inorganic particles, and can be preferred as they can have a low magnesium ion content within the aforementioned range during acid washing and water washing in the manufacturing process.

[0106] In addition, the acrylic aqueous dispersion containing the above-mentioned acrylic resin particles, in addition to the effect as a binder described above, has long-term storage stability and excellent dispersibility of the acrylic resin particles, thereby solving the problem of low storage stability of conventional acrylic resin particles.

[0107] In one embodiment of the present invention, the C4-C12 cycloalkyl (meth)acrylate is C5-C 10 It may be a cycloalkyl (meth)acrylate or a C6-C8 cycloalkyl (meth)acrylate. The above C4-C12 cycloalkyl (meth)acrylate may be, as an example, one or more selected from cyclohexyl (meth)acrylate, cyclodecaine (meth)acrylate, and cyclopentane (meth)acrylate, and preferably, cyclohexyl (meth)acrylate may be used alone.

[0108] Acrylic resin particles prepared by including the above-mentioned cyclohexyl (meth)acrylate can prevent expansion and aggregation by water or electrolytes, and an acrylic aqueous dispersion containing the same can have excellent dispersibility without aggregating the acrylic resin particles even during long-term storage.

[0109] In one embodiment of the present invention, the straight-chain or branched-chain C6-C20 alkyl (meth)acrylate may comprise, as a non-limiting example, one or more selected from 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, hexadecanyl (meth)acrylate, nonyl (meth)acrylate, 2-methylheptyl (meth)acrylate, isohexyl (meth)acrylate, and isooctyl (meth)acrylate.

[0110] In particular, the straight-chain or branched-chain C6-C20 alkyl (meth)acrylate may be preferred to include 2-ethylhexyl (meth)acrylate or to use 2-ethylhexyl (meth)acrylate alone due to its excellent processability for forming an adhesive layer, but this is merely an example and is not necessarily limited to cases where physical properties are not compromised.

[0111] In one embodiment of the present invention, the acrylic resin particles may be polymerized by further including a crosslinking agent containing two or more radical reactive groups, and may be polymerized by including the crosslinking agent in an amount of 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, 5 parts by weight or less, 0.1 parts by weight or more, 0.5 parts by weight or more, or 1 part by weight or more with respect to 100 parts by weight of the monomer mixture. For example, the acrylic resin particles prepared in an amount of 0.1 to 20 parts by weight, 0.1 to 15 parts by weight, or 0.5 to 10 parts by weight may preferably be included in an amount of 1 to 5 parts by weight to have high adhesion to both the porous substrate and the electrode.

[0112] Acrylic resin particles polymerized with a crosslinking agent in the above-mentioned range have excellent dispersibility and long-term dispersion stability in an aqueous dispersion, and can also be preferred as an adhesive layer containing them can have high adhesion to a porous substrate and an electrode.

[0113] In one embodiment of the present invention, the acrylic resin particles may have a degree of crosslinking of 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 95% or less, or a value between these values. For example, it may be 45 to 95%, 50 to 95%, 55 to 95%, 60 to 95%, 65 to 95%, 70 to 95%, 75 to 95%, 80 to 95%, or 80 to 95%.

[0114] The degree of crosslinking of the above acrylic resin particles was determined by calculating the dry mass (A0) of the completely dried initial acrylic resin particles, and the initial acrylic resin particles were completely immersed in a mixture of 30 wt% ethylene carbonate (EC) and 70 wt% ethyl methyl carbonate, after which the mixture was filtered and completely dried to obtain a primary residue, and the primary residue was re-immersed in ethanol (ethyl alcohol), and 25 After leaving it at ℃ for 24 hours, the completely dry mass (A1) of the secondary residue is obtained by filtering and completely drying it, and the value may be a percentage of the value obtained by dividing the completely dry mass (A1) of the secondary residue by the dry mass (A0) of the initial acrylic resin particles.

[0115] Acrylic resin particles having a degree of crosslinking within the above range have excellent long-term storage stability, and the rate of change in average particle size (D50) may be low even during long-term storage. In addition, the adhesive layer containing the acrylic resin particles has high adhesive strength and prevents swelling caused by the electrolyte, so it can maintain excellent adhesive strength even when left in the electrolyte for a long period of time, making it a preferred choice.

[0116] The above crosslinking agent may be used without limitation as long as it is a compound containing two or more radical reactive groups, but preferably a compound containing (meth)acrylic groups may be preferred, and as a non-limiting example, it may be one or more selected from 2,2-ethanediol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, divinylbenzene, polyalkylene glycol di(meth)acrylate, and allyl (meth)acrylate.

[0117] In one embodiment of the present invention, the acrylic resin particles may have a glass transition temperature of 10 to 80 ℃, 20 to 70 ℃, 30 to 70 ℃, 40 to 70 ℃, or 50 to 70 ℃.

[0118] In one embodiment of the present invention, when the acrylic resin particles are polymerized without the above-mentioned crosslinking agent, the weight-average molecular weight may be 10,000 to 1,000,000 g / mol, 30,000 to 1,000,000 g / mol, 50,000 to 1,000,000 g / mol, 100,000 to 1,000,000 g / mol, 100,000 to 800,000 g / mol, 200,000 to 700,000 g / mol, 20,000 to 500,000 g / mol, or 100,000 to 1,000,000 g / mol, but is not limited thereto.

[0119] The weight-average molecular weight of the above acrylic resin particles may be measured using GPC (Gel Permeation Chromatography, Waters) after dissolving them in 10 ml of tetrahydrofuran (THF). Since this is specifically described in the examples to be described later, a detailed explanation will be omitted.

[0120] In one embodiment of the present invention, the acrylic resin particles may have an average particle size (D50) of 0.5 μm or more, 1.0 μm or more, 2.0 μm or more, 3.0 μm or more, 10.0 μm or less, 8.0 μm or less, 7.0 μm or less, or a value between these values. For example, it may be 0.5 to 10.0 μm, 1.0 to 10.0 μm, 2.0 to 8.0 μm, or 3.0 to 7.0 μm and a value between these values. Preferably, it may be 1.0 to 10.0 μm, 2.0 to 8.0 μm, or 3.0 to 7.0 μm. In the case of the above values, the adhesion to the electrode is further maintained and combined with inorganic particles, so that the electrode and the separator do not separate and are firmly bonded, the resistance is low, the breathability is excellent, and the charge capacity retention rate is high after manufacturing the battery, so it is further preferred.

[0121] The acrylic resin particles of the present invention are large-diameter particles and can be obtained by suspension polymerization, unlike particles of 300 nm or less, 200 nm or less, 100 nm or less, or 50 nm or less obtained by emulsion polymerization. Since it is difficult to achieve the desired effect of the present invention using the emulsion polymer, the small-diameter particles may be differentiated from the large-diameter particles of the present invention.

[0122] The above acrylic resin particles may be preferred to have an average particle size (D50) in the above range in terms of excellent mixing of the acrylic resin particles and the inorganic particles in the adhesive layer composition further including inorganic particles. In addition, as one embodiment of the present invention, the acrylic resin particles may have a particle size distribution (Span) of 0.5 to 1.5, 0.5 to 1.3, 0.5 to 1.2, 0.5 to 1.1, or 0.5 to 1.05 in terms of having uniform adhesion over the entire surface area of ​​the adhesive layer formed including them.

[0123] The average particle size (D50) and Span value of the above acrylic resin particles were measured using a laser diffraction particle size distribution measuring device (Malvern, MASTERSIZER 3000 hydro) and may have been measured based on a wet measurement method.

[0124] The above "Dn" (n is a real number) refers to the diameter of a particle corresponding to n volume% as an accumulated fraction based on volume. For example, "D50" may refer to the diameter of a particle corresponding to 50 volume% as an accumulated fraction based on volume, and this may be defined as the average particle diameter (D50).

[0125] In addition, the particle size distribution (Span) of the acrylic resin particles is a value calculated as (D90-D10) / D50, which is used to indicate the uniformity of the particle size distribution of the measured acrylic resin particles. For example, the particle size distribution (Span) may mean the value obtained by dividing the difference between the particle diameter (D90) corresponding to 90 volume% in the cumulative fraction and the particle diameter (D10) corresponding to 10 volume% in the cumulative fraction by the average particle diameter (D50) described above, when the measured acrylic resin particles are arranged according to their particle size.

[0126] [Acrylic water dispersion and composition for adhesive layer]

[0127] The present invention provides an acrylic aqueous dispersion containing the large-diameter acrylic resin particles and a composition for an adhesive layer containing the acrylic resin particles and inorganic particles. The composition for an adhesive layer containing the acrylic resin particles can be used in a process in which an adhesive layer is formed between an electrode and a porous substrate by applying the composition to the electrode or a porous substrate, drying it, and then heat-pressing it. Furthermore, the composition for an adhesive layer containing the acrylic resin particles may be preferred because it can form an adhesive layer with high adhesive strength even with a process at a low heat-pressing temperature.

[0128] The above adhesive layer composition can be prepared by adding acrylic resin particles and inorganic particles to water and stirring them, but in order to impart excellent dispersibility, it may be preferred to first prepare an acrylic aqueous dispersion in which the acrylic resin particles are dispersed in water, and then mix it with inorganic particles.

[0129] In another aspect of the present invention, the acrylic aqueous dispersion may be in the form of an acrylic resin particle of the present invention and an amphiphilic compound containing hydrophilic and lipophilic groups mixed and dispersed in water.

[0130] As described above, the acrylic resin particles have an average particle size (D50) of 0.5 μm or more. Therefore, if the aqueous dispersion containing them is left for a long period, trace amounts of the acrylic resin particles may aggregate or precipitate. In the acrylic aqueous dispersion further containing the amphiphilic compound, the amphiphilic compound is bonded to the surface of the acrylic resin particles, so that once dispersed, the acrylic resin particles do not aggregate. Furthermore, the acrylic aqueous dispersion can maintain dispersion stability even when the dispersed acrylic resin particles are stored for a long time, and even if some aggregates occur due to prolonged storage, it has excellent redispersibility, allowing the acrylic particles to be redispersed without aggregation during redispersion.

[0131] Accordingly, the adhesive layer composition prepared including the above acrylic aqueous dispersion has excellent miscibility between inorganic particles and acrylic resin particles and excellent dispersibility, and the adhesive layer prepared therefrom can provide an adhesive layer with high adhesive strength and a very low variation in adhesive strength across the entire bonded area.

[0132] In one embodiment of the present invention, the amphiphilic compound may be used without limitation as long as it is a compound containing lipophilic and hydrophilic groups, but may be, for example, one or more selected from sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium naphthalene sulfonate formaldehyde-based condensation compounds, polyoxyethylene nonylphenyl ether, sorbitan monolaurate, and octadecylamine acetate. More preferably, it may be one or more selected from sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium naphthalene sulfonate formaldehyde-based condensation compounds. The above-mentioned sodium dodecylbenzenesulfonate or sodium naphthalene sulfonate formaldehyde-based condensation compound can be evenly bonded to the surface of the dispersed acrylic resin particles, and thus may be preferred as it may provide excellent dispersibility, redispersibility, and anti-aggregation properties of the aforementioned acrylic resin particles; however, this is not necessarily limited as long as it does not impair the physical properties.

[0133] The above acrylic aqueous dispersion may comprise, with respect to the total weight, acrylic resin particles in an amount of 5 to 70 wt%, 5 to 40 wt%, 5 to 30 wt%, 10 to 30 wt%, 15 to 30 wt%, or 20 to 30 wt%, and values ​​between these values. In one embodiment of the present invention, the above acrylic aqueous dispersion may comprise, with respect to the total weight, an amphiphilic compound in an amount of 20 wt% or less, 15 wt% or less, 10 wt% or less, 5 wt% or less, 0.1 wt% or more, 0.5 wt% or more, or 1 wt% or more, or values ​​between these. For example, it may comprise 0.1 to 20 wt%, 0.1 to 15 wt%, 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 5 wt%, or 0.1 to 3 wt%.

[0134] An acrylic aqueous dispersion containing acrylic resin particles and an amphiphilic compound within the above content range may be preferred because the acrylic resin particles can be dispersed with excellent dispersibility, and in particular, after being left for a long period, the redispersed acrylic resin particles can have excellent redispersibility.

[0135] The acrylic aqueous dispersion of the present invention may be prepared by polymerizing an amphiphilic compound when preparing the acrylic resin particles described above, or it may be prepared by separately preparing acrylic resin particles, then adding the prepared acrylic resin particles and an amphiphilic compound to deionized water and mixing them.

[0136] As a specific example, the acrylic aqueous dispersion may be prepared by separating and purifying the reaction product of suspension polymerization by meshing or drying to obtain acrylic resin particles, and then including the obtained acrylic resin particles and an amphiphilic compound.

[0137] As described above, even if the acrylic aqueous dispersion is redispersed after being left for a long period, the acrylic resin particles have excellent redispersibility, and the redispersed acrylic resin particles may not undergo changes in particle size due to aggregation or expansion.

[0138] Therefore, the above acrylic aqueous dispersion can have long-term storage stability, and can be preferred because it can form an adhesive layer without degradation of physical properties such as adhesive strength and breathability even when manufactured using a redispersed acrylic aqueous dispersion after long-term storage.

[0139] In one embodiment of the present invention, the acrylic aqueous dispersion may have a solid content uniformity calculated by Formula 1 below of 90 to 110%, 95 to 105%, or 98 to 102%.

[0140] [Equation 1]

[0141]

[0142] (In the above Equation 1, T s ε is the solid content of 100 g of the supernatant extracted from the surface of the acrylic aqueous dispersion in a container with a diameter of 10 cm and a height of 18 cm after placing 1 L of the acrylic aqueous dispersion in the container and letting it stand for 30 minutes, and T d ...is the solid content of 100 g of the lower liquid extracted from the bottom of the above acrylic aqueous dispersion.)

[0143] The above acrylic aqueous dispersion can contain acrylic resin particles with excellent long-term dispersibility to the extent that there is almost no difference in the solid content between the supernatant and the lower liquid after standing for 30 minutes. Since the above adhesive layer composition is also a water-soluble composition containing acrylic resin particles with excellent dispersibility, when the above coating layer composition is applied to a porous substrate, the acrylic resin particles are uniformly applied over the entire surface area, resulting in minimal variation in adhesive strength and providing excellent adhesion to the electrode and the surface of the porous substrate.

[0144] In one embodiment of the present invention, the acrylic aqueous dispersion may have a redispersibility calculated by the following Formula 2 of 130% or less, 125% or less, 120% or less, 115% or less, 110% or less, 105% or less, or 100% or more. For example, it may be 100 to 130%, 100 to 125%, 100 to 120%, 100 to 115%, 100 to 110%, or 100 to 105%.

[0145] [Equation 2]

[0146]

[0147] (In the above Equation 2, P0 is the average particle size (D50) of acrylic resin particles dispersed in the initial acrylic aqueous dispersion, and P1 is the average particle size (D50) of acrylic resin particles dispersed in the redispersed acrylic aqueous dispersion after leaving the acrylic aqueous dispersion at 25°C for 3 months and then redispersing it at a stirring speed of 200 rpm for 20 minutes.)

[0148] The above acrylic aqueous dispersion does not cause aggregation among acrylic resin particles even when left standing for a long period, and can prevent swelling of the acrylic resin particles caused by deionized water and electrolytes. In addition, since the dispersed acrylic resin particles in the above acrylic aqueous dispersion have low swelling properties with water and electrolytes as described above, it can further prevent changes in the average particle size of the acrylic resin particles dispersed in the redispersed acrylic aqueous dispersion, which may be preferred.

[0149] As such, the above acrylic aqueous dispersion can be usefully used as a binder resin raw material for an adhesive layer composition that bonds a porous substrate and an electrode, and furthermore, it can also be used as a paint, anti-dripping agent, powder coating, fiber coating material, automotive coating agent, or other binder.

[0150] A composition for an adhesive layer comprising the above-mentioned acrylic resin particles and inorganic particles is described below.

[0151] The above adhesive layer composition can be prepared by adding acrylic resin particles and inorganic particles to water and stirring them, but in order to impart excellent dispersibility, it may be preferred to first prepare an acrylic aqueous dispersion in which the acrylic resin particles are dispersed in water, and then mix it with inorganic particles.

[0152] The above acrylic resin particles and acrylic aqueous dispersion are the same as those described above, so further explanation is omitted.

[0153] In the present invention, the inorganic particles are not particularly limited as long as they are inorganic particles used in this field. As a non-limiting example, the inorganic particles may be one or more selected from boehmite, BaTiO3, hafnia (HfO2), CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, and SiC, but are not limited thereto.

[0154] In one embodiment of the present invention, the inorganic particle may have an average particle size (D50) of 5,000 nm or less, 2,000 nm or less, 1,000 nm or less, 500 nm or less, 10 nm or more, 50 nm or more, or 100 nm or more, and a value between the above values. For example, it may be 10 to 5,000 nm, for example, 10 to 2,000 nm, 10 to 1,000 nm, 10 to 500 nm, 50 to 500 nm, 100 to 500 nm, and a value between the above values.

[0155] The above-mentioned inorganic particles may have an average particle size smaller than the average particle size (D50) of the acrylic resin particles described above. Preferably, they may have an average particle size of 4 / 5 or less, 1 / 2 or less, 1 / 3 or less, 1 / 5 or less, 1 / 10 or less, 1 / 20 or less, or 1 / 50 or less relative to the average particle size of the acrylic resin particles, or a value between these values. More preferably, they may have an average particle size of 1 / 2 to 1 / 10. Having a small size of 1 / 2 or less is preferred because it provides excellent adhesion and improves the characteristics of the battery. Furthermore, although not described in a separate example, cases where the size of the inorganic particles is larger than the size of the acrylic resin particles are not preferred because a gap occurs between the electrode and the porous substrate acting as the separator, preventing the battery from fully performing its function.

[0156] That is, the adhesive layer can be mixed with inorganic particles to form an adhesive layer between a porous substrate and an electrode, and to achieve the purpose of improving electrical properties, heat resistance, and dimensional stability, etc., it may be preferred to include acrylic resin particles with an average particle size (D50) larger than the included inorganic particles, while having excellent adhesion to both the porous substrate and the electrode.

[0157] Accordingly, although a composition for an adhesive layer comprising acrylic resin particles and inorganic particles having an average particle size (D50) of the aforementioned range is not disclosed in the present invention, the acrylic resin particles and inorganic particles can be uniformly mixed, and such a composition may be preferred as it can form an adhesive layer having excellent adhesion, excellent breathability, and electrolyte stability as described above on both the porous substrate and the electrode.

[0158] In one embodiment of the present invention, the composition for the adhesive layer may comprise, with respect to 100 parts by weight of acrylic resin particles, inorganic particles in an amount of 10 parts by weight or more, 50 parts by weight or more, 100 parts by weight or more, 200 parts by weight or more, 300 parts by weight or more, 400 parts by weight or more, 10,000 parts by weight or less, 6,000 parts by weight or less, 5,000 parts by weight or less, 4,000 parts by weight or less, 3,000 parts by weight or less, or 2,500 parts by weight or less, and in parts by weight between the above values. For example, it may be included in an amount of 10 to 10,000 parts by weight, 10 to 6,000 parts by weight, 50 to 6,000 parts by weight, 100 to 6,000 parts by weight, 100 to 5,000 parts by weight, 100 to 4,000 parts by weight, 100 to 3,000 parts by weight, 200 to 3,000 parts by weight, 300 to 3,000 parts by weight, 400 to 3,000 parts by weight, or 400 to 2,500 parts by weight. Preferably, it may be included in an amount of 400 to 4,000 parts by weight.

[0159] By using the acrylic resin particles, the above adhesive layer composition can form an adhesive layer that has excellent adhesion to electrodes and porous substrates, and possesses characteristics such as excellent breathability and electrolyte stability, even though it contains a greater number of inorganic particles.

[0160] In one embodiment of the present invention, the composition for the adhesive layer may further include an additional binder component in addition to the acrylic resin particles. The additional binder may be of a non-particulate type or may be a particulate binder other than the acrylic resin particles of the present invention.

[0161] The additional binder mentioned above may comprise one or more selected from polyacrylic, polyester, polyimide, polyamide, polyimideamide, cellulose (including carboxylic cellulose or hydroxyl cellulose), sugar, starch, polyether, and copolymers thereof, provided that it is available for use in this field, although it is not specifically limited.

[0162] In one embodiment of the present invention, the composition for the adhesive layer may further comprise, with respect to 100 parts by weight of the acrylic resin particles, 30 parts by weight or less, 20 parts by weight or less, 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or more of the additional binder. For example, it may further comprise 1 to 30 parts by weight, 1 to 20 parts by weight, 1 to 10 parts by weight, or 1 to 5 parts by weight.

[0163] The composition for the adhesive layer further comprising the above additional binder may be added for various purposes, such as further improving the adhesion of inorganic particles or improving low swelling and heat resistance, but it is not necessarily limited to such additions as long as it can form an adhesive layer that satisfies the physical properties targeted in the present invention.

[0164] In another aspect of the present invention, the composition for the adhesive layer may further include an additive selected from thickeners, thixotropic agents, and defoaming agents. The additive may be preferred to improve coating properties, but this is merely an example and is not necessarily limiting.

[0165] In one embodiment of the present invention, the composition for the adhesive layer may have a solid content of 10 to 70 weight%, 10 to 60 weight%, 20 to 60 weight%, or 30 to 60 weight% in terms of having excellent coating properties, but is not necessarily limited thereto as long as it does not impair physical properties.

[0166] [Formation of an adhesive layer and a battery including the same]

[0167] In one embodiment of the present invention, the adhesive layer may be formed by applying and drying a composition for an adhesive layer and then pressing. The pressing may be performed by thermal pressing. The thermal pressing may be performed at a melting temperature of 50°C or higher, 55°C or higher, 60°C or higher, 65°C or higher, 80°C or lower, or 75°C or lower, as long as it is above the temperature at which the acrylic resin particles can melt, although this is not specifically limited. Additionally, the thermal pressing may be performed for 0.5 to 5 seconds at a pressure of 4.0 to 10.0 MPa, 5.0 to 8.0 MPa, or 6.0 to 7.0 MPa, but this is not specifically limited as long as it does not impair the physical properties of the manufactured adhesive layer.

[0168] In one embodiment of the present invention, the method for forming the adhesive layer may first apply the composition for the adhesive layer described above to a porous substrate and dry it to produce a thickness of 1.0 μm or more, 2.0 μm or more, 3.0 μm or more, 10.0 μm or less, or 8.0 μm or less, and then laminate it with an electrode and heat-press it to bond, but the bonding method is not necessarily limited as long as it is within a range recognizable by a person skilled in the art.

[0169] Accordingly, the adhesive layer can have effects such as adhesion and high breathability depending on the characteristics of the acrylic resin particles described above, and can also firmly bind inorganic particles, thereby providing a battery with further enhanced stability.

[0170] In one embodiment of the present invention, the adhesive layer may have an adhesion strength with a porous substrate measured by ASTM D3330 of 30 gf / 15 mm or more, 35 gf / 15 mm or more, 40 gf / 15 mm or more, 45 gf / 15 mm or more, 48 gf / 15 mm or more, 50 gf / 15 mm or more, 52 gf / 15 mm or more, 55 gf / 15 mm or more, 58 gf / 15 mm or more, 80 gf / 15 mm or less, 75 gf / 15 mm or less, 70 gf / 15 mm or less, 65 gf / 15 mm or less, or 60 gf / 15 mm or less. For example, it may be 30 to 80 gf / 15 mm, 35 to 80 gf / 15 mm, 40 to 80 gf / 15 mm, 45 to 80 gf / 15 mm, 50 to 80 gf / 15 mm, or 55 to 80 gf / 15 mm.

[0171] In one embodiment of the present invention, the adhesive layer may have an adhesion strength of an electrode such as a cathode, measured by ASTM D3330, of 10 gf / 25 mm or more, 12 gf / 25 mm or more, 15 gf / 25 mm or more, 18 gf / 25 mm or more, 20 gf / 25 mm or more, and 50 gf / 25 mm or less. For example, it may be 10 to 50 gf / 25 mm, 15 to 50 gf / 25 mm, or 20 to 50 gf / 25 mm.

[0172] The adhesion strength of the above adhesive layer, porous substrate, and electrode may be measured from an adhesive layer formed from an adhesive layer composition containing 500 parts by weight of inorganic particles per 100 parts by weight of acrylic resin particles.

[0173] That is, the adhesive layer has excellent adhesion to both the porous substrate and the electrode even when containing a large amount of inorganic particles for high-temperature stability, and can evenly contain inorganic particles on the surface of the porous substrate, thereby providing a battery with improved stability.

[0174] In one embodiment of the present invention, the porous substrate forming the adhesive layer may have a breathability of 150 sec / 100cc or less, 140 sec / 100cc or less, 130 sec / 100cc or less, 120 sec / 100cc or less, 110 sec / 100cc or less, 100 sec / 100cc or less, or 50 sec / 100cc or more, and between these. For example, it may be 50 to 200 sec / 100cc, 50 to 150 sec / 100cc, 50 to 140 sec / 100cc, 50 to 130 sec / 100cc, 50 to 120 sec / 100cc, 50 to 110 sec / 100cc, or 50 to 100 sec / 100cc.

[0175] The porous substrate forming the adhesive layer described above has excellent air permeability as per the above range, and the secondary battery manufactured including it does not impede the mobility of ions passing through the adhesive layer and the porous substrate, thereby enabling the manufacture of a battery with low electrical resistance. Accordingly, even though the adhesive layer contains a large amount of inorganic particles for high-temperature stability, it has excellent adhesion to the porous substrate and electrode, low adhesion variation, and low air permeability, and it is advantageous to manufacture a battery having high stability and low electrical resistance.

[0176] The present invention may provide a battery comprising the adhesive layer, and the battery may be a half battery, a primary battery, or a secondary battery.

[0177] In one embodiment of the present invention, the adhesive layer is formed on both sides of a porous substrate corresponding to a separator, and the electrode laminate may be in the form of an electrode laminate in which the adhesive layer is bonded to the cathode and the anode.

[0178] That is, in one embodiment of the present invention, the battery may be a secondary battery comprising a porous substrate, an adhesive layer formed on one or both sides of the porous substrate, and an electrode formed on the adhesive layer.

[0179] In one embodiment of the present invention, the electrode may be a cathode or an anode, and the adhesive layer may be formed on both sides of a porous substrate and used for bonding both the cathode and the anode.

[0180] The above anode may be manufactured by including an anode active material, a conductive material, and an anode binder, and the above cathode may be manufactured by including a cathode active material, a conductive material, and a cathode binder; however, since the above anode and cathode may be used without limitation as long as they are recognizable by a person skilled in the art, further explanation is not provided regarding this.

[0181] The porous substrate may be in the form of a polyolefin-based breathable film or a nonwoven fabric, and any material commonly adopted in this field may be used without limitation. For example, the porous substrate may be a porous polyolefin-based film. The porous polyolefin-based film may be manufactured, for example, by feeding and mixing a polyolefin and a diluent into an extruder, extruding the mixture, and then performing an extraction and stretching process, but is not limited thereto.

[0182] The above polyolefin may include, but is not limited to, polyethylene; polypropylene; polybutylene; polypentene; polyhexene; polyoctene; copolymers of two or more α-olefin monomers such as ethylene, propylene, butene, pentene, 4-methylpentene, hexene, and octene; or mixtures thereof.

[0183] As another example, the above porous substrate may be manufactured by including one or two polymers selected from polyethylene terephthalate, polybutyl terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride-hexafluoropropylene copolymer, and polystyrene, but is not necessarily limited thereto.

[0184] In one embodiment of the present invention, when the battery is a coin-type half-cell having an adhesive layer formed on one surface of a porous substrate and a negative electrode formed on the formed adhesive layer, the measured electrical resistance may be 1.50 Ω or less, 1.30 Ω or less, 1.10 Ω or less, 1.00 Ω or less, 0.80 Ω or less, 0.60 Ω or less, 0.30 Ω or more, 0.40 Ω or more, 0.45 Ω or more, and a value between these values. For example, it may be 0.30 to 1.50 Ω, 0.30 to 1.40 Ω, 0.30 to 1.30 Ω, 0.30 to 1.20 Ω, 0.30 to 1.10 Ω, 0.30 to 1.00 Ω, 0.30 to 0.90 Ω, 0.30 to 0.80 Ω, 0.30 to 0.70 Ω, or 0.30 to 0.60 Ω.

[0185] The present invention will be described in more detail through the following examples. However, the following examples are merely for reference to explain the present invention in detail and are not limited thereto, and the present invention may be implemented in various forms. Furthermore, unless otherwise defined, all technical and scientific terms have the same meaning as generally understood by one of the art to which the present invention pertains. Additionally, the terms used in the description of the present invention are intended merely to effectively describe specific embodiments and are not intended to limit the present invention.

[0186] [measurement method]

[0187] 1. Measurement of magnesium ion concentration

[0188] The acrylic resin particles prepared in the following preparation examples and comparative preparation examples were measured using an inductively coupled plasma mass spectrometer (ICP-MS, Agilent 7700) to determine the content (ppm) of the magnesium ions contained therein.

[0189] 2. Measurement of Average Particle Size (D50) and Span Value

[0190] Resin particles were measured using a laser diffraction particle size distribution measuring device (Malvern, MASTERSIZER 3000 hydro), and the average particle size and Span value (average particle size distribution width) were measured based on the wet measurement method.

[0191] The average particle size of the resin particles was determined using the D50 value, which is the average particle size measured by volume (where Dn represents the particle diameter corresponding to n% of the cumulative fraction, "D50" corresponds to 50% of the cumulative fraction based on volume). Subsequently, the particle size distribution (Span) of the resin particles was calculated from the dispersion of the measured acrylic resin particles using (D90-D10) / D50. The measured resin particles were then photographed using a scanning electron microscope (Hitachi, SEM) to confirm that they were similar to the average particle size (D50).

[0192] 3. Glass transition temperature

[0193] After measuring each resin particle for 2 cycles under a heating condition of 10 ℃ / min using a differential scanning calorimeter thermogravimetric analyzer (TA, Q20), the inflection point of the second cycle was calculated using the half Cp method.

[0194] 3. Measurement of weight-average molecular weight

[0195] 10 mg of resin particles were each dissolved in 10 ml of tetrahydrofuran (THF), filtered using a 0.2 µm Teflon filter, and then measured using GPC (Gel Permeation Chromatography, Waters).

[0196] 4. Measurement of solid content

[0197] 100 g of aqueous dispersion was stirred for 10 minutes, then placed in a drying oven at 105 ℃ and dried for 24 hours. After drying, the container was removed and cooled in a desiccator at room temperature to measure the weight of the remaining solids, and the solid content was determined from the weight of the initial aqueous dispersion and the weight of the solids.

[0198] 1 L of the above aqueous dispersion was placed in a container with a diameter of 10 cm and a height of 18 cm, and after standing for 30 minutes, the solid content (weight%) of 100 g of the supernatant extracted from the surface of the acrylic aqueous dispersion in the container was measured in the same manner as the method used to measure the solid content of the initial aqueous dispersion. In addition, the solid content of 100 g of the lower liquid extracted from the bottom of the container of the aqueous dispersion after standing for 30 minutes was also calculated in the same way.

[0199] Subsequently, the above supernatant solid content (T s ) and lower liquid high-molecular content (T d The uniformity of solid content (%) was calculated by calculating ) using the following Equation 1.

[0200] [Equation 1]

[0201]

[0202] 5. Storage Stability Evaluation

[0203] After the acrylic aqueous dispersion prepared in the examples and comparative examples was left standing at 25°C for 3 months, it was redispersed for 20 minutes at a stirring speed of 200 rpm, and the average particle size (D50, P1) of the resin particles dispersed in the acrylic aqueous dispersion was measured. After measuring the average particle size (D50, P0) of the acrylic resin particles dispersed in the initial acrylic aqueous dispersion, the redispersibility of the acrylic resin particles was calculated using the following Equation 2. At this time, the method for measuring the average particle size (D50) is the same as the method for measuring the average particle size (D50) described above.

[0204] [Equation 2]

[0205]

[0206] 6. Measurement of electrode and porous adhesion strength

[0207] The laminates prepared in the examples and comparative examples were tested according to ASTM D3330, and the 180° peel force between the adhesive layer, the cathode, and the porous substrate was measured using a Shimadzu EZTest / CE (Japan) measuring instrument capable of measuring within the range of 0-100 N.

[0208] 7. Breathability Measurement

[0209] After removing the cathode from the laminate prepared in the following examples and comparative examples, a measurement sample having an adhesive layer formed on a porous substrate was fixed to a Gurley Densometer, and 100 cc of air was passed through at a pressure of 1 atmosphere, and the air permeability was determined by measuring the time it took for 100 cc of air to pass through.

[0210] 8. Measurement of Resistance Value of Coin-Type Half-Battery

[0211] The laminates prepared in the following examples and comparative examples were cut to fit the size of a coin shell case. Then, the cut laminates were placed in a stainless steel coin shell case equipped with spacers and springs, and a lithium electrolyte in which 1.0 M concentration of LiPF6 was dissolved in a solvent mixed with ethylene carbonate and dimethyl carbonate in a volume ratio of 3:7 was injected, and the coin shell case was compressed with a press to produce a coin-type half-cell.

[0212] Subsequently, the manufactured coin-type half-cell was measured using an impedance analyzer. Specifically, the manufactured coin-type half-cell was driven at a voltage of 10 mV in a frequency range of 1 Hz to 1 MHz, and a Nyquist plot was generated to analyze the real part and imaginary part components. Subsequently, the resistance of the cell was calculated using the real part values ​​obtained in the low-frequency range from the measured Nyquist plot.

[0213] [Preparation Example 1]

[0214] (Manufacture of acrylic resin particles)

[0215] A colloidal dispersion containing magnesium hydroxide as a metal hydrate was prepared by adding a sodium hydroxide aqueous solution with a concentration of 10 wt% to a mixed aqueous solution of magnesium hexahydrate with a concentration of 8.2 wt% and sodium lauryl sulfate with a concentration of 0.002 wt% and stirring. The colloidal dispersion was prepared by mixing the mixed aqueous solution of magnesium hexahydrate and sodium lauryl sulfate with the sodium hydroxide aqueous solution in a weight ratio of 3.7:1.

[0216] In addition, a monomer required for the polymerization of acrylic resin particles was prepared by mixing 1 part by weight of 2-hydroxyethyl methacrylate with 100 parts by weight of a monomer mixture composed of 75% by weight of cyclohexyl methacrylate (CHMA) and 25% by weight of 2-ethylhexyl acrylate (2-EHA).

[0217] Subsequently, the above colloidal dispersion and monomer mixture were introduced into a reactor in a weight ratio of 2.6:1, and 2 parts by weight of benzoyl peroxide were introduced for every 100 parts by weight of the introduced monomer mixture, and then high-shear stirring was performed for 10 minutes at a rotation speed of 16,000 rpm using a high-shear emulsifying disperser (manufactured by IKA, T 25 digital ULTRA-TURRAX) to form droplets of the monomer composition.

[0218] A reactor in which droplets of the above monomer composition were formed was heated to 80°C and reacted for 1 hour, and then heated again to 105°C and polymerized for 20 minutes to obtain a slurry containing acrylic resin particles.

[0219] Subsequently, the above slurry was acid-washed by stirring while maintaining the temperature at 25°C and adding a dilute aqueous sulfuric acid solution dropwise until the pH reached 6, and the slurry after the acid washing was completed was filtered to obtain a solid. Ion-exchanged water was added to the solid obtained from the acid washing treatment to re-slurry it, and a water washing treatment was performed 5 times by stirring for 20 minutes and then filtering. Afterward, the solid obtained after the acid washing and water washing were placed in a dryer and dried at 35°C for 24 hours to finally obtain acrylic resin particles.

[0220] (Preparation of acrylic aqueous dispersion)

[0221] 76 wt% of ion-exchanged water, 25 wt% of the above acrylic resin particles, and 2.5 wt% of dodecylbenzenesulfonic acid sodium salt (SDBS) were added to a high-shear emulsion disperser (manufactured by IKA, T 25 digital ULTRA-TURRAX) and stirred sufficiently for 2 hours to prepare an acrylic aqueous dispersion.

[0222] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0223] [Preparation Example 2]

[0224] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that 1 part by weight of methacrylic acid was used instead of 1 part by weight of 2-hydroxyethyl acrylate.

[0225] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0226] [Preparation Example 3]

[0227] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that 1 part by weight of acrylonitrile (AN) was used instead of 1 part by weight of 2-hydroxyethyl acrylate.

[0228] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0229] [Preparation Example 4]

[0230] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that 1 part by weight of acrylamido-2-methylpropanesulfonic acid (AMPS) was used instead of 1 part by weight of 2-hydroxyethyl acrylate.

[0231] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0232] [Preparation Example 5]

[0233] Acrylic resin particles and an acrylic aqueous dispersion containing the same were prepared in the same manner as in Preparation Example 1 above, except that cyclopentyl methacrylate was used instead of cyclohexyl methacrylate (CHMA) included in the monomer mixture.

[0234] Subsequently, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0235] [Preparation Example 6]

[0236] Acrylic resin particles and an acrylic aqueous dispersion containing the same were prepared in the same manner as in Preparation Example 1 above, except that hexadecanyl acrylate was used instead of 2-ethylhexyl acrylate (2-EHA) included in the monomer mixture.

[0237] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0238] [Preparation Example 7]

[0239] Acrylic resin particles and an acrylic aqueous dispersion containing the same were prepared in the same manner as in Preparation Example 1 above, except that cyclopentyl methacrylate was used instead of cyclohexyl methacrylate (CHMA) included in the monomer mixture, and hexadecanyl acrylate was used instead of 2-ethylhexyl acrylate (2-EHA).

[0240] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0241] [Preparation Example 8]

[0242] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that 1 part by weight of α-styrene was used instead of 1 part by weight of 2-hydroxyethyl acrylate.

[0243] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0244] [Preparation Example 9]

[0245] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that 1 part by weight of methyl methacrylate was used instead of 1 part by weight of 2-hydroxyethyl acrylate.

[0246] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0247] [Preparation Example 10]

[0248] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that 1 part by weight of ethyl acrylate was used instead of 1 part by weight of 2-hydroxyethyl acrylate.

[0249] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0250] [Preparation Example 11]

[0251] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that 1 part by weight of benzyl acrylate was used instead of 1 part by weight of 2-hydroxyethyl acrylate.

[0252] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0253] [Preparation Example 12]

[0254] Acrylic resin particles and an acrylic aqueous dispersion containing the same were prepared in the same manner as in Preparation Example 8 above, except that cyclopentyl methacrylate was used instead of cyclohexyl methacrylate (CHMA) included in the monomer mixture.

[0255] Subsequently, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0256] [Preparation Example 13]

[0257] Acrylic resin particles and an acrylic aqueous dispersion containing the same were prepared in the same manner as in Preparation Example 8 above, except that hexadecanyl acrylate was used instead of 2-ethylhexyl acrylate (2-EHA) included in the monomer mixture.

[0258] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0259] [Preparation Example 14]

[0260] Acrylic resin particles and an acrylic aqueous dispersion containing the same were prepared in the same manner as in Preparation Example 8 above, except that cyclopentyl methacrylate was used instead of cyclohexyl methacrylate (CHMA) included in the monomer mixture, and hexadecanyl acrylate was used instead of 2-ethylhexyl acrylate (2-EHA).

[0261] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0262] [Comparative Manufacturing Example 1]

[0263] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that acid washing was not performed.

[0264] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0265] [Comparative Manufacturing Example 2]

[0266] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that physical cleaning was not performed.

[0267] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0268] [Comparative Manufacturing Example 3]

[0269] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 1 above, except that neither acidic purification nor physical cleaning was performed.

[0270] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0271] [Comparative Manufacturing Example 5]

[0272] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 8 above, except that acid washing was not performed.

[0273] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0274] [Comparative Manufacturing Example 6]

[0275] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 8 above, except that physical cleaning was not performed.

[0276] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0277] [Comparative Manufacturing Example 7]

[0278] Acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner as in Preparation Example 8 above, except that neither acidic purification nor physical cleaning was performed.

[0279] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0280] [Comparative Manufacturing Example 8]

[0281] In the above Preparation Example 8, acrylic resin particles and an acrylic aqueous dispersion were prepared in the same manner, except that alkaline washing was performed to achieve a pH of 9.

[0282] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0283] After that, the acrylic resin particles and acrylic aqueous dispersion prepared above were measured using the measurement method described above, and the results are shown in Table 1 below.

[0284]

[0285]

[0286] In Table 1 above, the acrylic aqueous dispersions of Preparation Examples 1 to 14 were found to contain acrylic resin particles with a very uniform average particle size (D50) having an average particle size (D50) of 5.0 to 7.0 μm and a span value of less than 1.5, and were also confirmed to contain Mg ions of 500 ppm or less, preferably 400 ppm or less, after acid washing and water washing treatments.

[0287] In addition, it was confirmed that the acrylic aqueous dispersions of Preparation Examples 1 to 14 had a solid content uniformity of 90 to 110%, and that over time, acrylic resin particles did not settle and had excellent long-term dispersibility, and after being left for 30 days, the rate of change in the redispersed average particle size was 130% or less, and there was almost no expansion of the redispersed acrylic resin particles or aggregation between the acrylic resin particles, thereby maintaining the average particle size of the initial acrylic resin particles.

[0288] In contrast, it was confirmed that the acrylic aqueous dispersions of Comparative Manufacturing Examples 1 to 8 had a magnesium ion content of dispersed acrylic resin particles exceeding 500 ppm, and also did not satisfy the uniformity of solid content of the acrylic aqueous dispersion and the rate of change in average particle size of the acrylic resin particles of the redispersed acrylic aqueous dispersion targeted by the present invention.

[0289] [Examples 1 to 14 and Comparative Examples 1 to 8]

[0290] An acrylic aqueous dispersion and an inorganic particle dispersion of the preparation example and comparative example shown in Table 2 below were mixed in a stirrer to prepare an adhesive layer composition with a solid content of 55 wt%. The adhesive layer composition was prepared such that, for every 100 parts by weight of acrylic resin particles, 500 parts by weight of alumina particles (Sumitomo Chemical, AKP-50, volume average particle size: 0.2 μm) as inorganic particles, 15 parts by weight of Toyo Chem CSB 130 (solid content 40%, average particle size 177 nm) as an additional binder, and 1.5 parts by weight of carboxymethyl cellulose as a thickener.

[0291] Afterwards, the above adhesive layer composition was applied to one surface of a porous substrate (Celgard, Celgard® 2400) to a thickness of 5.9 μm and dried, and a cathode was placed so that the cathode active material layer of the cathode was in contact with the dried adhesive layer composition, and then heat-pressed at 60°C and 6.5 MPa for 1 second to produce a laminate having an adhesive layer formed between the porous substrate and the cathode.

[0292] The above cathode was manufactured by applying the cathode slurry to a copper foil, which is a cathode collecting agent, at a rate of 98 g / m², followed by drying, cold pressing, and slitting processes. The cathode slurry was prepared such that it has a solid content of 63 wt%, and the solid composition consists of 96.1 wt% artificial graphite as the cathode active material, 1.0 wt% acetylene black as the conductive agent, 1.6 wt% styrene-butadiene rubber (SBR) as the binder, and 1.2 wt% sodium carboxymethylcellulose (CMC-Na) as the thickener.

[0293] The adhesive layer manufactured above and the laminate formed including it were measured using the measurement method described above, and the results are shown in Table 2 below.

[0294]

[0295]

[0296] As can be seen from Table 2 above, it was confirmed that the adhesive layers of Examples 1 to 14 have excellent adhesion to both the electrode and the porous substrate, with an adhesion strength of 10 gf / 25 mm or more to the cathode and an adhesion strength of 30 gf / 15 mm or more to the porous substrate.

[0297] In addition, the porous substrate formed with the adhesive layer of Examples 1 to 14 has excellent air permeability with an air permeability of 150 sec / cc or less, and it was confirmed that the coin-type half-sheet manufactured including it has a very low electrical resistance of 1.5 Ω or less.

[0298] In contrast, compared to the adhesive layer of Comparative Examples 1 to 8, it was confirmed that the adhesive layer has low adhesion to the cathode and porous substrate and low air permeability, and that the coin-type half-paper containing it has a very high electrical resistance value exceeding 1.5 Ω.

[0299] Accordingly, according to one embodiment of the present invention, the adhesive layer has excellent adhesion to both the electrode and the porous substrate despite containing a large amount of inorganic particles, and also has excellent breathability, so a secondary battery manufactured including the same can have excellent high-temperature stability, electrical resistance stability and surface stability, and can have low electrical resistance.

[0300] In addition, the acrylic aqueous dispersion used as a raw material for the adhesive layer composition of the present invention contains acrylic resin particles having a uniform particle size, and the included acrylic resin particles have excellent dispersibility and excellent redispersibility, thereby solving the problem of performance degradation caused by sedimentation, expansion, and aggregation of conventional acrylic binders.

[0301] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical concept or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not limited to one.

Claims

As an adhesive layer formed between an electrode and a porous substrate, The above adhesive layer is formed by including acrylic resin particles and inorganic particles, and The above acrylic resin particles are prepared by comprising: (a) a monomer mixture comprising at least 50 weight% of C4-C12 cycloalkyl (meth)acrylate and a straight-chain or branched-chain C6-C20 alkyl (meth)acrylate; and (b) one or more additional monomers selected from hydrophilic group-containing (meth)acrylates and lipophilic group monomers; and The above acrylic resin particles are an adhesive layer containing magnesium ions at a concentration of 500 ppm or less. In Article 1, The above hydrophilic groups are hydroxyl groups (*-OH), carboxylic acid groups (*-COOH), amine groups (*-NH2), amide groups (*-CONH2), thiol groups (*-SH), sulfonic acid groups (*-SO3H), sulfonamide groups (*-SO2NH2), and ammonium groups (*-NH3 + Adhesive layer consisting of ) or phosphate groups (*-PO4H2). In Article 1, The above lipophilic monomer is one or more selected from α-olefin, methyl (meth)acrylate, ethyl (meth)acrylate, C6-C20 aryl (meth)acrylate, styrene-based monomer, perfluoroalkyl (meth)acrylate, and fluoroalkyl (meth)acrylate, forming an adhesive layer. In Article 1, The above acrylic resin particles are an acrylic aqueous dispersion manufactured by including a step of acid washing and a step of water washing. In Article 1, The above acrylic resin particles are an adhesive layer prepared by including an additional monomer in an amount of 0.01 to 10 parts by weight per 100 parts by weight of a monomer mixture. In Article 1, The above acrylic resin particles are an adhesive layer having an average particle size (D50) of 0.5 to 10 μm. In Article 1, The above inorganic particles are an adhesive layer having an average particle size (D50) of 10 to 5,000 nm. In Article 1, The adhesive layer comprises 10 to 10,000 parts by weight of inorganic particles per 100 parts by weight of acrylic resin particles. In Article 1, The above acrylic resin particles are an adhesive layer polymerized by further including 0.1 to 20 parts by weight of a crosslinking agent containing two or more radical reactive groups. In Article 1, The above adhesive layer is an adhesive layer having an adhesion strength of 30 gf / 15 mm or more with a porous substrate as measured by ASTM D3330. In Article 1, The above adhesive layer is an adhesive layer having an adhesion strength of 10 gf / 25 mm or more with respect to an electrode as measured by ASTM D3330. In Article 1, The porous substrate having the above adhesive layer formed thereon is an adhesive layer having a breathability of 150 sec / 100cc or less. A battery comprising an adhesive layer selected from any one of claims 1 to 12. As an acrylic aqueous dispersion containing acrylic resin particles, The above acrylic resin particles are prepared by comprising (a) a monomer mixture comprising 50 weight% or more of C4-C12 cycloalkyl (meth)acrylate and straight-chain or branched-chain C6-C20 alkyl (meth)acrylate and (b) one or more additional monomers selected from hydrophilic group-containing (meth)acrylate and lipophilic group monomers, and The above acrylic resin particles are an acrylic aqueous dispersion having a magnesium ion content of 500 ppm or less. In Article 14, The above acrylic aqueous dispersion is an acrylic aqueous dispersion that further comprises an amphiphilic compound including hydrophilic and lipophilic groups. In paragraph 15, The above acrylic aqueous dispersion is an acrylic aqueous dispersion containing 0.1 to 5 weight percent of an amphiphilic compound based on the total weight. In Paragraph 14, The above acrylic resin particles are an acrylic aqueous dispersion polymerized by further including 0.1 to 20 parts by weight of a crosslinking agent containing two or more radical reactive groups per 100 parts by weight of a monomer mixture. In Paragraph 14, The above acrylic aqueous dispersion is an acrylic aqueous dispersion having a solid content uniformity of 90 to 110% calculated by Formula 1 below. [Equation 1] In the above Equation 1, T s is the solid content of 100 g of the supernatant extracted from the surface of the acrylic aqueous dispersion in a container with a diameter of 10 cm and a height of 18 cm after placing 1 L of the acrylic aqueous dispersion in the container and letting it stand for 30 minutes, and T d 1 L of acrylic aqueous dispersion is placed in a container with a diameter of 10 cm and a height of 18 cm, and after standing for 30 minutes, the solid content of 100 g of the lower liquid extracted from the bottom of the acrylic aqueous dispersion in the container is used. In Article 14, The above acrylic aqueous dispersion is an acrylic aqueous dispersion having a redispersibility of 130% or less calculated by the following Formula 2. [Equation 2] In the above Equation 2, P0 is the average particle size (D50) of acrylic resin particles dispersed in the initial acrylic aqueous dispersion, and P1 is the average particle size (D50) of acrylic resin particles dispersed in the redispersed acrylic aqueous dispersion after leaving the acrylic aqueous dispersion at 25°C for 3 months and then redispersing it at a stirring speed of 200 rpm for 20 minutes. A composition for an adhesive layer for manufacturing an adhesive layer formed between an electrode and a porous substrate, The above adhesive layer composition is prepared by polymerizing (A)(a) a monomer mixture comprising 50 weight% or more of C4-C12 cycloalkyl (meth)acrylate and straight-chain or branched-chain C6-C20 alkyl (meth)acrylate; and (b) one or more additional monomers selected from hydrophilic group-containing (meth)acrylates and lipophilic group monomers; and acrylic resin particles having a magnesium ion content of 500 ppm or less; and (B) A composition for an adhesive layer comprising inorganic particles. In Article 20, The above adhesive layer composition comprises 10 to 10,000 parts by weight of inorganic particles per 100 parts by weight of acrylic resin particles. In Article 20, The above adhesive composition is an adhesive layer composition that further comprises an amphiphilic compound including a hydrophilic group and a lipophilic group. In Article 20, The above acrylic resin particles are an adhesive composition having an average particle size (D50) of 0.5 to 10 μm. In Article 20, The above inorganic particles are a composition for an adhesive layer having an average particle size (D50) of 10 to 5,000 nm.

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