Aluminum trihydroxide particles, their manufacturing method, separator containing the same, electrode assembly, and lithium secondary battery

Abstract

The present invention provides a fiber having a D50 of about 3.0 μm or less and a BET of about 3.0 μm or less. 2 / g or more and a Li content of about 500 ppm or more, a separator, an electrode assembly, and a lithium secondary battery containing the same are disclosed.

Description

[Technical Field]

[0001] The present invention relates to aluminum trihydroxide particles, a method for producing the same, and a separator, an electrode assembly, and a lithium secondary battery each containing the same.

[0002] This application claims priority based on Korean Patent Application No. 10-2023-0025344 filed on February 24, 2023, and Korean Patent Application No. 10-2024-0001329 filed on January 4, 2024, and the contents disclosed in the specifications and drawings of said applications are incorporated herein in their entirety. [Background technology]

[0003] The separator, which constitutes the electrode assembly of a secondary battery, acts as a separator between the positive and negative electrodes, allowing ions to flow without electrically connecting them. That is, the separator allows the electrolyte to pass through while preventing the electrolyte from diffusing back into the positive and negative electrodes, thereby preventing electrical short circuits between the positive and negative electrodes. Therefore, the separator influences the capacity, charge and discharge speed, and lifespan of a secondary battery, and the material and structure of the separator are therefore considered to be important factors that determine the performance and safety of the secondary battery.

[0004] Polyolefin porous films, which are commonly used as separators in lithium secondary batteries, exhibit significant thermal shrinkage at temperatures above 100°C due to their material properties and manufacturing process characteristics, including elongation, and tend to cause short circuits between the positive and negative electrodes.To solve the safety issues of separators made of polyolefin porous films, separators using inorganic particles have been proposed.

[0005] The inorganic particles are applied to the separator by mixing the inorganic particles with a polymer and coating the surface of a porous polymer film or nonwoven fabric made from a polymer such as a polyolefin, or by mixing the inorganic particles with a polymer, coating the surface of a support, and then peeling the coating off, to form a free-standing separator, or by mixing the inorganic particles with a polymer and coating the surface of the positive electrode, negative electrode, or both electrodes. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide aluminum trihydroxide particles that improve the capacity retention rate of a lithium secondary battery and do not cause side reactions within the lithium secondary battery.

[0007] Another object of the present invention is to provide a method for producing aluminum trihydroxide particles having the above-mentioned properties.

[0008] It is yet another object of the present invention to provide a separator, an electrode assembly, and a lithium secondary battery that include aluminum trihydroxide particles having the above-mentioned properties.

[0009] The objects and advantages of the present invention may be realized by means of the instrumentalities or methods and combinations thereof as set forth in the claims. [Means for solving the problem]

[0010] One aspect of the present invention provides aluminum trihydroxide particles according to the following embodiments.

[0011] The first embodiment is D50 is about 3.0 μm or less, and BET is about 3.0 m 2 / g or more and a Li content of about 500 ppm or more.

[0012] The second embodiment is the same as the first embodiment, The D50 is about 2.5 μm or less and the BET is about 3.5 μm or less. 2 / g or more and a Li content of about 800 ppm or more.

[0013] The third embodiment is the same as the first embodiment, The D50 is about 2.7 μm or less and the BET is about 3.8 μm or less. 2 / g or more and a Li content of about 900 ppm or more.

[0014] The fourth embodiment is the same as the first embodiment, The D50 is about 2.2 μm or less, and the BET is about 4.2 μm or less. 2 / g or more and a Li content of about 1050 ppm or more.

[0015] The fifth embodiment is any one of the first to fourth embodiments, The present invention relates to aluminum trihydroxide particles having a Na content of about 900 ppm or less.

[0016] The sixth embodiment is any one of the first to fourth embodiments, The present invention relates to aluminum trihydroxide particles having a Na content of about 100 ppm or less.

[0017] The seventh embodiment is any one of the first to fourth embodiments, The present invention relates to aluminum trihydroxide particles having a Na content of about 10 ppm or less.

[0018] One aspect of the present invention provides a manufacturing method according to the following embodiment.

[0019] The eighth embodiment is 1. A method for producing aluminum trihydroxide particles, comprising: (S1) A step of adding bauxite to a basic aqueous solution containing Li to obtain a treated solution; (S2) filtering solids from the treated solution to separate an eluate; (S3) precipitating aluminum trihydroxide from the separated eluate; Including, The aluminum trihydroxide particles have a D50 of about 3.0 μm or less and a BET of about 3.0 μm or less. 2 / g or more and a Li content of about 500 ppm or more.

[0020] The ninth embodiment is the same as the eighth embodiment, The method for producing aluminum trihydroxide particles further includes, before step (S3), a step of adding aluminum trihydroxide seeds to the separated eluate, stirring the mixture, and then filtering the aluminum trihydroxide seeds to further separate the eluate.

[0021] The tenth embodiment is the same as the eighth or ninth embodiment, The method for producing aluminum trihydroxide particles includes pulverizing the aluminum trihydroxide precipitated in step (S3), and then adding the pulverized aluminum trihydroxide to step (S1) instead of the bauxite, and repeating steps (S1) to (S3).

[0022] One aspect of the present invention provides a separator according to the following embodiment.

[0023] The eleventh embodiment is A separator, a porous polymer film; an organic / inorganic composite coating layer formed on at least one surface of the porous polymer film, the organic / inorganic composite coating layer including a mixture of inorganic particles and a polymer; The separator relates to the inorganic particles comprising aluminum trihydroxide particles according to any one of the first to seventh embodiments.

[0024] The twelfth embodiment is A separator, Nonwoven fabric and an organic / inorganic composite coating layer containing a mixture of inorganic particles and a polymer, coated on at least one surface of the nonwoven fabric; The separator relates to the inorganic particles comprising aluminum trihydroxide particles according to any one of the first to seventh embodiments.

[0025] The thirteenth embodiment is A separator comprising a free-standing organic / inorganic composite film containing a mixture of inorganic particles and a polymer, The inorganic particles relate to a separator comprising aluminum trihydroxide particles according to any one of the first to seventh embodiments.

[0026] One aspect of the present invention provides an electrode assembly according to the following embodiments.

[0027] The fourteenth embodiment is An electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, The electrode assembly relates to the separator, which is a separator according to any one of the eleventh to thirteenth embodiments.

[0028] The fifteenth embodiment is An electrode assembly including a separator, The separator has a porous organic / inorganic composite coating layer containing a mixture of inorganic particles and a binder polymer; The electrode assembly relates to the inorganic particles comprising aluminum trihydroxide particles according to any one of the first to seventh embodiments.

[0029] One aspect of the present invention provides a lithium secondary battery according to the following embodiments.

[0030] The sixteenth embodiment relates to a lithium secondary battery including the electrode assembly according to the fourteenth or fifteenth embodiment. [Effects of the Invention]

[0031] According to one embodiment of the present invention, aluminum trihydroxide particles having D50 and BET controlled within a predetermined range and containing a predetermined or greater amount of Li, the Li impurity remaining in the particles does not cause a side reaction in the lithium secondary battery, and instead improves the capacity retention rate of the lithium secondary battery.

[0032] The effects of each component of the present invention will be described in detail below. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best explain the invention. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical ideas of the present invention, and therefore, various equivalents and modifications that can be substituted therefor may exist at the time of filing this application.

[0034] Throughout this specification, the term "comprises" or "has" a part means that it does not exclude other elements, but may further include or further comprise other elements, unless otherwise specified.

[0035] Throughout this specification, the property of having pores means that the object contains a plurality of pores, the interconnected structure of which allows gaseous and / or liquid fluids to pass from one side of the object to the other.

[0036] Throughout this specification, particles refer to small, almost invisible objects having a diameter of a few micrometers or less, regardless of their shape, such as spherical, ellipsoidal, or irregular.

[0037] As used herein, the terms "about," "approximately," and "substantially" are used to mean a range of or approximation to a numerical value or degree, taking into account inherent manufacturing and material tolerances, and are used to prevent infringers from unfairly using disclosure content in which exact or absolute numerical values ​​are mentioned, provided to aid in the understanding of the present invention.

[0038] Throughout this specification, the separator is a porous material containing a plurality of pores, and serves as a porous ion-conducting barrier that blocks electrical contact between the negative electrode and the positive electrode in an electrochemical device and allows ions to pass through.

[0039] When inorganic particles are used to form separators, various types of inorganic particles that are electrochemically stable within the operating voltage of lithium secondary batteries have been proposed. Among these, aluminum trihydroxide (ATH) is an inorganic particle that has attracted attention due to its flame retardancy.

[0040] ATH is produced by adding the raw material bauxite powder to an aqueous NaOH solution to dissolve the aluminum component, obtaining an eluate, and then precipitating ATH from the eluate and pulverizing it.

[0041] Because an aqueous NaOH solution is used in the bauxite powder leaching process, sodium remains as an impurity in the resulting ATH. The sodium remaining in ATH does not contribute to improving performance such as the capacity retention rate of lithium secondary batteries, but may instead cause side reactions within the battery.

[0042] As described above, in order to solve the performance and safety problems of lithium secondary batteries, a separator using ATH particles, which is a flame-retardant inorganic material, has been proposed.

[0043] On the other hand, because ATH particles are produced using an aqueous NaOH solution, the resulting ATH contains residual Na as an impurity. The Na remaining in ATH does not contribute to improving performance such as the capacity retention rate of lithium secondary batteries, but may instead cause side reactions within the battery, potentially affecting its performance and safety.

[0044] In the present invention, a LiOH aqueous solution is used instead of a NaOH aqueous solution during the preparation of ATH, so that the impurities remaining in the prepared ATH are Li components rather than Na components. Unlike Na impurities, Li impurities do not cause side reactions in lithium secondary batteries and increase the ionic conductivity of the lithium secondary battery, thereby improving the capacity retention rate. Note that the basic aqueous solution in one embodiment is not limited to LiOH. For example, any basic aqueous solution containing Li, other than LiOH aqueous solution, can be applied to the present invention.

[0045] According to one aspect of the present invention, inorganic particles have an average particle size D50 of about 3.0 μm or less and a specific surface area BET of 3.0 m 2 / g or more and a Li content of 500 ppm or more is provided.

[0046] For example, ATH particles have a D50 of about 2.5 μm or less and a BET of about 3.5 μm. 2 / g or more and the Li content may be about 800 ppm or more.

[0047] Alternatively, the ATH particles have a D50 of about 2.7 μm or less and a BET of about 3.8 μm or less. 2 / g or more and the Li content may be about 900 ppm or more.

[0048] In yet another example, the D50 is about 2.2 μm or less and the BET is about 4.2 μm or less. 2 / g or more and the Li content can be about 1,050 ppm or more. In yet another example, the D50 can be about 1.2 μm or less and the BET can be about 7.8 μm or less. 2 / g or more and the Li content may be about 1,910 ppm or more.

[0049] If the Li content of the ATH particles is less than 500 ppm, the low Li content limits the improvement in the capacity retention rate of the lithium secondary battery. Also, if the D50 of the ATH particles exceeds 3.0 μm or the BET is too small, it is difficult to produce ATH particles with a Li content of 500 ppm or more.

[0050] The Li content of the ATH particles may be 500 ppm or more, and there is no upper limit. For example, the upper limit of the Li content of the ATH particles may be 10,000 ppm, but is not limited to this.

[0051] The smaller the D50 of the ATH particles, the larger the BET, and conversely, the larger the BET, the smaller the D50. Therefore, the lower limit of the D50 and the upper limit of the BET of the ATH particles are not limited. For example, the lower limit of the D50 of the ATH particles is 0.01 μm, and the upper limit of the BET is 20,000 g / m 2 It can be, but is not limited to,

[0052] If the D50 of the ATH particles exceeds 3.0 μm, the BET becomes too small, and in this case, it is difficult to produce ATH particles having a Li content of 500 ppm or more.

[0053] According to one embodiment, the ATH particles can be prepared as follows: First, bauxite, a mineral rich in aluminum, is introduced into an aqueous LiOH solution to obtain a treated solution (S1). This step dissolves the aluminum component of the bauxite. In one example, the treated solution can be produced by powdering the bauxite, then introducing it into a high-pressure reactor together with the aqueous LiOH solution and stirring at high temperature.

[0054] Subsequently, the solid content is filtered from the treated solution of (S1) to separate the eluate (S2).

[0055] Thereafter, ATH is precipitated from the separated eluate (S3). For example, ATH can be precipitated by lowering the temperature of the separated eluate and then stirring it.

[0056] Before step (S3), ATH seeds may be added to the separated eluate, followed by stirring, and the ATH seeds may be filtered to separate the eluate further, which is then fed to step S2.

[0057] The ATH precipitated in step (S3) may be pulverized, and the pulverized ATH may be added to step (S1) instead of the bauxite, and steps (S1) to (S3) may be repeated one or more times. The Li content and other impurity contents in the ATH may be adjusted by repeating these steps.

[0058] Meanwhile, when preparing the ATH particles of the present invention, bauxite powder, a mineral rich in aluminum, may be subjected to the aforementioned leaching and precipitation processes using an aqueous LiOH solution, and the resulting precipitate may then be subjected to further leaching and precipitation processes using an aqueous NaOH solution to produce an ATH precipitate. The ATH obtained in this manner contains Li impurities of about 500 ppm or more and also contains residual Na impurities. In this case, the Na content may be about 900 ppm or less to minimize side reactions in lithium secondary batteries due to the Na impurities. In one embodiment, the Na content may be about 100 ppm or less, or about 10 ppm or less.

[0059] The ATH precipitate obtained by the above process can be washed with distilled water and then pulverized using a pulverizer such as a bead mill to obtain ATH particles of a desired particle size.

[0060] The term "D50" as used herein means the average particle size of inorganic particles, as described above, and refers to the particle size of particles that accounts for 50% of the total volume when particle sizes are measured using a particle size analyzer and the volumes are accumulated starting from the smallest particle.

[0061] In the present invention, the average particle size can be measured using a laser diffraction method, which is generally capable of measuring particle sizes from the submicron range to several nanometers, and provides results with high reproducibility and high resolution.

[0062] In the present invention, the BET (specific surface area) of the particles is measured from the amount of nitrogen gas adsorbed using a specific surface area analyzer.

[0063] In the present invention, the contents of Li and Na impurities are measured using ICP-OES (Inductively Coupled Plasma-Optical Emission Spectroscopy).

[0064] The ATH particles of the present invention can be used in lithium secondary batteries, particularly as separators for lithium secondary batteries, for example, but not limited to, in the form of an organic / inorganic composite layer containing a mixture of inorganic particles and a polymer, as described below.

[0065] In a first embodiment, the separator includes a porous polymer film and an organic / inorganic composite coating layer formed on at least one surface of the porous polymer film, the organic / inorganic composite coating layer containing a mixture of inorganic particles and a polymer, wherein the inorganic particles include the ATH particles of the present invention described above.

[0066] Examples of porous polymer film substrates include porous polymer films made of polyolefins such as polyethylene, polypropylene, polybutene, and polypentene, and such polyolefin porous polymer films exhibit a shutdown function at temperatures of, for example, approximately 80°C to 130°C.

[0067] In this case, the polyolefin porous polymer film may be formed from a polyolefin polymer such as polyethylene (e.g., high density polyethylene, linear low density polyethylene, low density polyethylene, ultra-high molecular weight polyethylene), polypropylene, polybutylene, polypentene, or the like, either alone or in combination of two or more thereof.

[0068] In addition to the polyolefin-based materials, the porous polymer film may be formed from a heat-resistant polymer having a melting point of 200°C or higher, such as polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, or the like, either individually or in combination, but is not limited thereto.

[0069] The porous polymer film may be formed into a structure in which two or more film layers are laminated, and each film layer may be formed from a polymer such as the above-mentioned polyolefin or polyester, either alone or in a mixture of two or more of these polymers.

[0070] An organic / inorganic composite coating layer containing inorganic particles containing the ATH of the present invention and a polymer mixture as main components is formed on at least one surface of the porous polymer film.

[0071] The ATH of the present invention described above contributes to improving the flame retardancy of the separator and also to improving the capacity retention rate of the lithium secondary battery.

[0072] In addition to ATH, other inorganic particles may be mixed in. The inorganic particles suppress the thermal shrinkage of the porous polymer film during thermal runaway of the battery, and prevent direct contact between the positive and negative electrodes even if the polymer film melts down, thereby contributing to preventing battery explosion.

[0073] The inorganic particles to be mixed in addition to ATH are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention are those that are within the operating voltage range (e.g., Li / Li) of the applied lithium secondary battery. + There are no particular limitations on the dielectric constant, as long as oxidation and / or reduction reactions do not occur at a potential of 0 to 5 V relative to the reference voltage. In particular, when inorganic particles with a high dielectric constant are used as the inorganic particles, they can contribute to an increase in the degree of dissociation of the electrolyte salt, for example, lithium salt, in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte solution.

[0074] For the reasons mentioned above, the inorganic particles may include inorganic particles with a high dielectric constant, such as a dielectric constant of about 5 or more, or about 10 or more. Non-limiting examples of inorganic particles with a dielectric constant of about 5 or more include BaTiO3, Pb(Zr x , Ti 1-x )O3(PZT, where 0 <x<1である。)、Pb 1-x La x Zr 1-y Ti y O3(PLZT, where 0 <x<1、0<y<1である。)、(1-x)Pb(Mg 1 / 3 Nb 2 / 3 )O 3-xPbTiO3 (PMN-PT, where 0 < x < 1), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite, AlOOH, SiC, and TiO2, and can be any one inorganic particle selected from the group consisting of these or a mixture of two or more thereof.

[0075] Also, as the inorganic particles, inorganic particles having lithium ion transfer ability, that is, inorganic particles containing lithium element but having a function of moving lithium ions without storing lithium can be used. Non-limiting examples of inorganic particles having lithium ion transfer ability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y -based glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), Li 3.25 Ge 0.25 P 0.75 S4, etc., such as lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), SiS2-based glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5-based glass (Li x Py S z Examples include (0 < x < 3, 0 < y < 3, 0 < z < 7) or mixtures of two or more of these.

[0076] The inorganic particles are mixed with a polymer and coated on at least one surface of the porous polymer substrate. Non-limiting examples of polymers include polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloro ethylene, polyvinylidene fluoride-co-chlorotrifluoro ethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples of suitable polymers include acrylic acid, acrylic acid copolymer, acrylic acid ester, acrylic acid ester copolymer ...

[0077] The inorganic particles may be disposed in substantial contact with one another, and when the mixed polymer is formed as a coating layer on some or all of the surfaces of the inorganic particles, the polymer may connect and fix the inorganic particles together so that the inorganic particles remain bound to one another.

[0078] The separator of the first type can be manufactured by further dispersing inorganic particles in a slurry in which a polymer is dissolved or dispersed in a solvent, coating the slurry on at least one side of a porous polymer film, and drying the coating to form an organic / inorganic composite coating layer.

[0079] In a second type of separator comprising a porous polymer nonwoven fabric and an organic / inorganic composite coating layer containing a mixture of inorganic particles and a polymer coated on at least one surface of the porous polymer nonwoven fabric, the inorganic particles include the ATH particles of the present invention described above.

[0080] The porous polymer nonwoven fabric refers to a porous polymer nonwoven fabric in which pores are formed between the fibers that make up the nonwoven fabric, and examples thereof include spunbond nonwoven fabrics, meltblown nonwoven fabrics, etc. The nonwoven fabric refers to a fabric formed by entanglement of fibers, rather than a fabric woven with warp and weft threads using a loom or a knitted fabric using a knitting machine.

[0081] The fibers constituting the nonwoven fabric are preferably made from the heat-resistant polymers described above, and fibers made from polyolefin-based polymers may be used alone or in combination with heat-resistant polymer fibers.

[0082] As the inorganic particles and polymer, the inorganic particles and polymer described above may be used.

[0083] This second type of separator can be manufactured by dispersing inorganic particles in a slurry prepared by dissolving or dispersing a polymer in a solvent, coating the slurry on at least one surface of a porous polymer nonwoven fabric, and then drying the coated slurry to form an organic / inorganic composite coating layer. Depending on the size of the pores in the porous polymer nonwoven fabric, the organic / inorganic composite coating layer may be disposed only on the surface, or may be disposed both on the surface and in the pores inside the porous polymer nonwoven fabric, or may be disposed primarily inside the porous polymer nonwoven fabric.

[0084] The inorganic particles may be disposed in substantial contact with one another, except for a state in which fibers are interposed between the inorganic particles.

[0085] In a third type of separator having a free-standing organic / inorganic composite film containing a mixture of inorganic particles and a polymer, the inorganic particles contain the ATH particles of the present invention described above.

[0086] The term "free-standing" refers to a form in which the separator maintains its shape by itself without being coated or attached to another support.

[0087] As the inorganic particles and polymer, the inorganic particles and polymer described above may be used.

[0088] This third type of separator can be produced by dispersing inorganic particles in a slurry prepared by dissolving or dispersing a polymer in a solvent, coating the resulting slurry on a support such as polytetrafluoroethylene, drying the resulting slurry, and then peeling the resulting slurry from the support. In this case, the inorganic particles of the free-standing organic / inorganic composite film may be in substantial contact with each other. When the mixed polymer is formed as a coating layer on some or all of the surfaces of the inorganic particles, the polymer may connect and fix the inorganic particles together so that the inorganic particles remain bonded to each other.

[0089] The fourth type may be a separator in the form of a porous organic / inorganic composite coating layer containing a mixture of inorganic particles and a binder polymer, formed on at least one surface of the positive electrode, the negative electrode, or both the positive electrode and the negative electrode.

[0090] As the inorganic particles and polymer, the inorganic particles and polymer described above may be used.

[0091] The separator of the fourth type can be manufactured by further dispersing inorganic particles in a slurry in which a polymer is dissolved or dispersed in a solvent, coating the slurry on at least one surface of the positive electrode, the negative electrode, or both the positive electrode and the negative electrode, and drying the coating to form an organic / inorganic composite coating layer.

[0092] In the separators of the first to fourth types described above, the organic / inorganic composite coating layer or organic / inorganic composite film may be porous. The weight ratio of inorganic particles to polymer may be, but is not limited to, about 99:1 to 50:50. The thickness of the separator may be, but is not limited to, about 1 to 30 μm.

[0093] In this case, the pores formed in the organic / inorganic composite coating layer or organic / inorganic composite film may be formed in the polymer matrix by extracting a plasticizer, or may be formed by spaces formed between inorganic particles when the inorganic particles are arranged in substantial contact with each other.

[0094] The separator of the present invention described above can be applied to an electrode assembly as follows, but is not limited thereto.

[0095] The separator of any one of the first to third types is laminated and interposed between a positive electrode, a negative electrode, and the positive and negative electrodes, and is manufactured as an electrode assembly by bonding them together by a process such as lamination.

[0096] The separator of the fourth type is interposed in the form of a coating layer on at least one surface of the positive electrode, the negative electrode, or both the positive electrode and the negative electrode, and is manufactured as an electrode assembly by bonding them together by a process such as lamination.

[0097] If necessary, in addition to the separator described above, a conventional separator may be further interposed between the positive electrode and the negative electrode.

[0098] The positive and negative electrodes that constitute the electrode assembly will be described below by way of example.

[0099] The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.

[0100] The positive electrode current collector in the positive electrode is not particularly limited as long as it does not induce chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The positive electrode current collector typically has a thickness of about 3 μm to 500 μm, and the surface of the positive electrode current collector may be provided with fine irregularities to enhance the adhesive strength of the positive electrode active material. For example, the positive electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0101] The positive electrode active material layer may include a known positive electrode active material, a conductive material, and a binder.

[0102] Positive electrode active materials include layered compounds such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; 1+x Mn 2-x Lithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; and the chemical formula LiNi1-x M x Ni-site lithium nickel oxide represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3). 2-x M x Examples of suitable lithium manganese oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and x is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4, in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0103] The conductive material is used to impart conductivity to the electrode. Any conductive material can be used without particular limitations, as long as it does not undergo chemical changes in the resulting battery and has electronic conductivity. Examples include black black (e.g., natural black or artificial black); carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or fibers (e.g., copper, nickel, aluminum, and silver); conductive whiskers (e.g., zinc oxide and potassium titanate); conductive metal oxides (e.g., titanium oxide); and conductive polymers (e.g., polyphenylene derivatives). These materials can be used alone or in combination. The conductive material is typically present in an amount of about 1% to 30% by weight based on the total weight of the positive electrode active material layer.

[0104] The binder functions to improve adhesion between positive electrode active material particles and between the positive electrode current collector. Examples of binders include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. One or more of these may be used alone or in combination. The binder may be present in an amount of about 1 wt% to 30 wt% based on the total weight of the positive electrode active material layer.

[0105] The positive electrode may be fabricated by a conventional method for fabricating a positive electrode. For example, the positive electrode may be fabricated by applying a composition for forming a positive electrode active material layer, including a positive electrode active material and, optionally, a binder and a conductive material, to a positive electrode current collector, followed by drying and rolling. In this case, the types and amounts of the positive electrode active material, binder, and conductive material are as described above.

[0106] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and may be used alone or in combination. The amount of the solvent used may be such that the viscosity is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and to provide a suitable thickness uniformity during application to produce a positive electrode, taking into consideration the coating thickness of the slurry and the production yield.

[0107] In another method, the positive electrode can be produced by casting the composition for forming the positive electrode active material layer onto a separate support, peeling the composition from the support, and laminating the resulting film onto a positive electrode current collector.

[0108] The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0109] The negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy may be used. The negative electrode current collector typically has a thickness of about 3 μm to 500 μm. As with the positive electrode current collector, the surface of the current collector may be formed with fine irregularities to enhance the binding strength of the negative electrode active material. The negative electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0110] The negative electrode active material layer includes a negative electrode active material and, optionally, a binder and a conductive material. For example, the negative electrode active material layer can be fabricated by applying a negative electrode-forming composition including the negative electrode active material and, optionally, the binder and the conductive material to a negative electrode current collector and drying the composition, or by casting the negative electrode-forming composition on a separate support, peeling it off from the support, and laminating the resulting film on the negative electrode current collector.

[0111] The negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium, such as carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; SiO βExamples of the negative electrode active material include metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide (0<β<2); or composites containing the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites. These may be used alone or in combination. A thin film of metallic lithium may also be used as the negative electrode active material. Both low-crystalline carbon and high-crystalline carbon may also be used as the carbon material. Typical low-crystalline carbons include soft carbon and hard carbon, and typical high-crystalline carbons include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-fired carbons such as petroleum or coal tar pitch-derived cokes.

[0112] The binder and conductive material may be the same as those described above for the positive electrode.

[0113] Meanwhile, a lithium secondary battery according to one aspect of the present invention includes the above-described electrode structure.

[0114] The lithium secondary battery includes the electrode structure and electrolyte described above. Examples of the electrolyte used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten polymer electrolytes that can be used in manufacturing lithium secondary batteries.

[0115] In one embodiment, the electrolyte may include an organic solvent and a lithium salt.

[0116] The organic solvent may be any solvent that functions as a medium through which ions involved in the electrochemical reaction of the battery can move. For example, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone, or ε-caprolactone; an ether solvent such as dibutyl ether or tetrahydrofuran; a ketone solvent such as cyclohexanone; an aromatic hydrocarbon solvent such as benzene or fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylene carbonate (EC), or propylene carbonate. Examples of suitable solvents include carbonate-based solvents such as ethylene carbonate (PC), alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group that may contain a double-bonded aromatic ring or ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with low viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) that have high ionic conductivity and a high dielectric constant, which can improve the charge / discharge performance of batteries, are more preferred. In this case, mixing the cyclic carbonate and the chain carbonate in a volume ratio of about 1:1 to about 1:9 can result in excellent electrolyte performance.

[0117] The lithium salt may be any compound capable of providing lithium ions used in lithium secondary batteries. For example, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably within the range of about 0.1M to 2.0M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, resulting in good electrolyte performance and efficient lithium ion migration.

[0118] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethyl alcohol amine, cyclic ethers, ethylenediamine, m-glyme (n-glyme), hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride, to improve battery life characteristics, suppress battery capacity loss, and improve battery discharge capacity. In this case, the additives may be contained in an amount of about 0.1 wt % to 5 wt % based on the total weight of the electrolyte.

[0119] The lithium secondary battery according to the present invention is useful in portable devices such as mobile phones, notebook computers, and digital cameras, and in electric vehicles such as hybrid electric vehicles (HEVs).

[0120] While the present invention may be embodied in many different forms, it is to be understood that the invention is not limited to the specific embodiments set forth herein.

[0121] Example 1 [Production of aluminum trihydroxide particles] (1) Dissolution stage 100 g of bauxite, which had been crushed and pulverized in a ball mill, and a 40% LiOH aqueous solution were added to a high-pressure reactor and stirred at 200°C for 1 hour to prepare an eluate. The ratio of bauxite to LiOH added was adjusted to 0.6.

[0122] (2) Precipitation stage After filtering the solid red mud from the eluate, 40 g of ATH seeds were mixed with the separated solution and stirred at 80°C for 1.5 hours. After filtering the aluminum trihydroxide seeds, the filtrate was stirred at 50°C for 12 hours or more to prepare an ATH precipitate. The produced ATH precipitate was washed with distilled water.

[0123] (3) Iterative phase The ATH precipitate obtained in step (2) was crushed and pulverized, and the resulting powder was added instead of the bauxite in step (1), and steps (1) and (2) were repeated. By repeating this process, the Li content and the contents of other impurities could be adjusted.

[0124] (4) Crushing stage Distilled water was added to the ATH precipitate obtained by the above process to a solid content of approximately 40% and then crushed using a bead mill. The bead size was 0.7 mm, the bead filling rate was 75%, and the linear speed was 700 rpm for three passes (the crushing step was repeated three times). After the bead milling process, a slurry containing dispersed ATH particles was obtained, which was then dried at 120°C to obtain ATH particles.

[0125] The D50, BET, and Li content of the ATH obtained by the above treatment were measured and are shown in Table 1. [Separator manufacturing] A dispersion of 20 g of the ATH particles obtained by the above process, approximately 1.0 g of a polyacrylic acid dispersant solution (42% solids by weight), and 20 g of 0.5 mm diameter beads for dispersion were added to 30.5 g of a water:ethanol dispersion at a weight ratio of approximately 95:5. The mixture was then stirred for 2 hours using a paint shaker to prepare an ATH particle dispersion. Next, a particulate acrylic polymer (150 nm particle diameter, Tg: -25°C) dispersed in water at approximately 40% by weight and 0.24 g of a surfactant (3M FC4430, 90% solids by weight) were added to the dispersion and shaken to prepare a coating slurry.

[0126] The prepared coating slurry was filtered through a 200-mesh filter and then coated onto one side of a wet-laid porous polyethylene film (SEMCORP, porosity 45%, thickness 9 μm) using a bar coater, dried, and then coated on the other side of the film under the same conditions to produce a double-sided coated separator. The total thickness of the coating layer formed on both sides of the film after coating is shown in Table 1.

[0127] [Manufacturing lithium secondary batteries] (Cathode manufacturing) LiNi 0.8 Co 0.1 Mn 0.1 A slurry for forming a positive electrode active material layer was prepared by mixing O2 positive electrode active material, carbon black conductive material, a binder (a mixture of PVDF-HFP copolymer and PVDF), and a dispersant with water in a weight ratio of 97.5:0.7:1.66:0.14, so that the total amount of the remaining components excluding water was 50 wt%. The slurry was then applied to a 10 μm thick aluminum thin film current collector and dried to produce a positive electrode with a 120 μm thick positive electrode active material layer.

[0128] (Anode manufacturing) A slurry for forming a negative electrode active material layer was prepared by mixing graphite (a mixture of natural graphite and artificial graphite) anode active material, carbon black conductive material, a binder (a mixture of PVDF-HFP copolymer and PVDF), and a dispersant with water in a weight ratio of 97.5:0.7:1.66:0.14 so that the total amount of the remaining components excluding water was 50 wt %. The slurry was then applied to a 10 μm-thick copper thin film current collector and dried to prepare a negative electrode with a 120 μm-thick negative electrode active material layer.

[0129] (Manufacturing of single cells) The separator prepared by the above-described method was laminated between the positive electrode and the negative electrode, and the sides were fixed with polyimide tape to prepare an electrode assembly, which is a single cell.

[0130] (Lithium secondary battery manufacturing) An electrolyte solution in which about 1M LiPF6 was dissolved in a solvent in which ethylene carbonate / ethyl methyl carbonate was mixed at a volume ratio of 3:7 was injected into the single cell to manufacture a lithium secondary battery.

[0131] Example 2 The same procedure as in Example 1 was carried out, except that in the milling step (4) of [Preparation of ATH particles], the bead size was changed to 1 mm and a total of two passes (the milling step was repeated twice) were carried out.

[0132] Example 3 The same procedure as in Example 2 was carried out, except that the repeating step (3) in [Production of ATH particles] was omitted.

[0133] (Comparative Example 1) The same procedure as in Example 2 was carried out, except that in the repeating step (3) of [Preparation of ATH particles], an aqueous NaOH solution was used instead of an aqueous LiOH solution in the dissolution step (1).

[0134] (Comparative Example 2) The same procedure as in Example 1 was carried out, except that in the dissolution step (1) of [Preparation of ATH particles], an aqueous NaOH solution was used instead of an aqueous LiOH solution.

[0135] (Comparative Example 3) The same procedure as in Example 2 was carried out, except that the dissolution step (1) of [Preparation of ATH particles] was carried out using an aqueous NaOH solution instead of an aqueous LiOH solution.

[0136] Measurement method for D50 of aluminum trihydroxide particles The D50 of the ATH particles was measured by putting them into a wet particle size analyzer (Mastersizer 3000, Malvern) and using the laser diffraction method.

[0137] BET measurement method for aluminum trihydroxide particles The BET of the ATH particles was measured from the amount of adsorbed nitrogen gas using a BET analyzer (BELSORP-mini II, BEL).

[0138] Method for measuring the Li content of aluminum trihydroxide particles Approximately 0.1 g of ATH particles were dispensed into a coming tube and its weight was accurately measured. Then, 1.5 mL of concentrated hydrochloric acid and 0.2 mL of hydrogen peroxide were added, and the mixture was shaken and mixed. After that, the mixture was placed in a water bath for dissolution (at 130°C for more than 4 hours).

[0139] The eluted product was then cooled to room temperature, and 200 μL of hydrofluoric acid was added, sealed, and reacted at room temperature for 3 hours.

[0140] Thereafter, 1 mL of boric acid and approximately 0.2 mL of an internal standard substance (Scandium; Sc) were added to the reaction product, and the reaction product was diluted with 20 mL of ultrapure water.

[0141] The diluted resultant was filtered through a 0.45 μm filter to prepare a sample.

[0142] The Li content and Na content in the ATH particles of the sample were measured using an ICP-OES device (OPTIMA 5300 OV, Perkin Elmer).

[0143] Heat shrinkage measurement method The separators of the examples and comparative examples were left in an oven at 150° C. for 30 minutes, and then the thermal shrinkage was measured.

[0144] The thermal shrinkage rate was calculated by marking two arbitrary points in each of the MD (Machine Direction) and TD (Transverse Direction) directions of the separator, and calculating the rate of increase or decrease in the distance (gauge length) between these points using the following formula 1. <Expression 1> Heat shrinkage rate (%) = {(BA) / A} x 100 In the above formula 1, A is the gauge length before the separator is left at a high temperature, and B is the gauge length after the separator is left at a high temperature for 30 minutes.

[0145] Capacity retention rate measurement method The lithium secondary batteries of the examples and comparative examples prepared by the above methods were repeatedly charged and discharged at 25°C at a rate of 1C (current) in the range of 2.5V to 4.25V, and the capacity retention was measured by calculating the ratio of the discharge capacity after 200 cycles to the initial discharge capacity. Here, 1C is a unit that defines the charge / discharge rate of a secondary battery, and refers to the rate at which a battery is fully charged or discharged when charged or discharged within one hour. For example, if a secondary battery has a capacity of 1,000mA and is fully charged in one hour, it is said to have been charged at a rate of 1C, and if it is fully charged in 30 minutes, it is said to have been charged at a rate of 2C.

[0146] [Table 1] As can be seen from Table 1, in Examples 1 to 3 in which the present invention was applied, the capacity retention rates were 96%, 95%, and 93%, respectively, which was significantly improved over the 88%, 86%, and 83% of the comparative examples.

[0147] Although the present invention has been described above with reference to preferred embodiments, it will be understood by those skilled in the art or those with ordinary skill in the art to which the invention pertains that various modifications and variations of the present invention are possible within the scope of the spirit and technical scope of the present invention as set forth in the claims below. Therefore, the technical scope of the present invention should not be limited to the content of the detailed description of the invention, but should be determined by the claims.

Claims

1. D50 is about 3.0 μm or less, and BET is about 3.0 μm or less ２ / g or more and a Li content of about 500 ppm or more.

2. The D50 is about 2.5 μm or less, and the BET is about 3.5 μm or less. ２ 2. The aluminum trihydroxide particles of claim 1, wherein the aluminum trihydroxide has a surface area of ​​about 1000 nm / g or more and a Li content of about 800 ppm or more.

3. The D50 is about 2.7 μm or less, and the BET is about 3.8 μm or less. ２ 2. The aluminum trihydroxide particles of claim 1, wherein the aluminum trihydroxide has a surface area of ​​about 1000 nm / g or more and a Li content of about 900 ppm or more.

4. The D50 is about 2.2 μm or less, and the BET is about 4.2 μm or less. ２ 2. The aluminum trihydroxide particles of claim 1, wherein the aluminum trihydroxide has a surface area of ​​about 1000 nm / g or more and a Li content of about 1050 ppm or more.

5. 2. The aluminum trihydroxide particles of claim 1, wherein the Na content is about 900 ppm or less.

6. 2. The aluminum trihydroxide particles of claim 1, wherein the Na content is about 100 ppm or less.

7. 2. The aluminum trihydroxide particles of claim 1, wherein the Na content is about 10 ppm or less.

8. 1. A method for producing aluminum trihydroxide particles, comprising: (S1) A step of adding bauxite to a basic aqueous solution containing Li to obtain a treated solution; (S2) filtering the solid content from the treated solution to separate the eluate; (S3) precipitating aluminum trihydroxide from the separated eluate; Including, The aluminum trihydroxide particles have a D50 of about 3.0 μm or less and a BET of about 3.0 μm or less. ２ / g or more and a Li content of about 500 ppm or more.

9. The method for producing aluminum trihydroxide particles according to claim 8, wherein the basic aqueous solution containing Li is LiOH.

10. 9. The method for producing aluminum trihydroxide particles according to claim 8, further comprising, before step (S3), adding aluminum trihydroxide seeds to the separated eluate, stirring the mixture, and then filtering the aluminum trihydroxide seeds to further separate the eluate.

11. 9. The method for producing aluminum trihydroxide particles according to claim 8, wherein the aluminum trihydroxide precipitated in step (S3) is pulverized, and the pulverized aluminum trihydroxide is introduced into step (S1) instead of the bauxite, and steps (S1) to (S3) are repeated.

12. A separator, a porous polymer film or nonwoven fabric; an organic / inorganic composite coating layer formed on at least one surface of the porous polymer film or nonwoven fabric, the organic / inorganic composite coating layer including a mixture of inorganic particles and a polymer; Equipped with A separator, wherein the inorganic particles include the aluminum trihydroxide particles according to claim 1 .

13. A separator comprising a free-standing organic / inorganic composite film containing a mixture of inorganic particles and a polymer, A separator, wherein the inorganic particles include the aluminum trihydroxide particles according to claim 1 .

14. An electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, An electrode assembly, wherein the separator is the separator according to claim 12.

15. An electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, An electrode assembly, wherein the separator is the separator of claim 13.

16. An electrode assembly including a separator, The separator has a porous organic / inorganic composite coating layer containing a mixture of inorganic particles and a binder polymer; An electrode assembly, wherein the inorganic particles include the aluminum trihydroxide particles according to claim 1 .

17. A lithium secondary battery comprising the electrode assembly according to claim 14.

18. A lithium secondary battery comprising the electrode assembly according to claim 15.

19. A lithium secondary battery comprising the electrode assembly according to claim 16.

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