Organic-inorganic composite membrane for secondary battery, method for manufacturing same, and lithium secondary battery comprising same

Abstract

The present invention relates to an organic-inorganic composite membrane for a secondary battery, a method for manufacturing the same, and a lithium secondary battery comprising the same, the organic-inorganic composite membrane comprising: a porous matrix containing a fluorine-based copolymer and lithium-lanthanum-zirconium-based oxide particles; and a cross-linked network polymer electrolyte filled in at least one pore of the porous matrix, in which the fluorine-based copolymer contains 10-25% by weight of repeating units derived from hexafluoropropylene.

Description

Technical Field

[0001] This invention relates to an organic-inorganic composite membrane for secondary batteries, its manufacturing method, and a lithium secondary battery including the membrane. Background Technology

[0002] In recent years, with the increasing demand for environmentally friendly energy, research on electrochemical devices has been carried out in many fields, including mobile phones, computers (PCs), and electric vehicles. Lithium-ion batteries, as general-purpose electrochemical devices, typically consist of a lithium transition metal oxide cathode, a graphite-based anode, and an organic electrolyte. To improve electrochemical performance such as high capacity, high power, and long lifespan, as well as external effects such as high / low temperature characteristics, safety, durability, and performance reliability, various types of new materials are being developed and applied to create high-performance next-generation lithium-ion batteries.

[0003] Specifically, to address the safety concerns arising from the flammability, corrosiveness, thermal instability, and high-voltage vulnerability of organic electrolytes, the application of solid electrolytes is being explored. Among these, oxide-based inorganic solid electrolytes exhibit high ionic conductivity, excellent thermal and chemical stability, and superior mechanical strength, thus demonstrating an effect in suppressing lithium dendrite formation. However, they suffer from insufficient film-forming properties, making it difficult to fabricate self-supporting films.

[0004] To address this issue, sometimes the oxide-based inorganic solid electrolyte is coated onto a porous membrane. However, in this case, a sufficient amount of oxide-based inorganic solid electrolyte cannot be contained, resulting in insufficient ionic conductivity and reduced operating efficiency. Alternatively, to improve film-forming properties, sometimes the oxide-based inorganic solid electrolyte is mixed with a polymer to form a membrane. However, in this case, it is difficult to form pores, so it cannot be used as a substitute for the membrane. Furthermore, a separate foaming agent is required to form pores, necessitating additional raw materials or processes, and limitations still exist in controlling the shape or size of the pores.

[0005] Furthermore, in existing technologies, the manufacturing process for slurry compositions containing inorganic solid electrolytes and solvents faces numerous limitations when the inorganic solid electrolyte and solvent are reactive. Therefore, in order to manufacture stable organic-inorganic composite membranes, the interaction between the inorganic solid electrolyte and the solvent must be considered.

[0006] Therefore, there is an urgent need to develop an organic-inorganic composite membrane with high ionic conductivity and excellent chemical stability that can be fabricated into a self-supporting membrane. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] One technical problem of the present invention is to provide a slurry composition for manufacturing organic-inorganic composite membranes and a method for preparing the same. The slurry composition has almost no reactivity between the solvent and the inorganic solid electrolyte particles during preparation, thus exhibiting chemical stability and excellent film-forming properties.

[0009] Furthermore, another technical problem of the present invention is to provide an organic-inorganic composite membrane and a method for manufacturing the same, wherein a self-supporting membrane can be formed from the slurry composition for manufacturing the organic-inorganic composite membrane, and the organic-inorganic composite membrane has excellent ionic conductivity.

[0010] In addition, another technical problem of the present invention is to provide a lithium secondary battery that includes the above-mentioned organic-inorganic composite membrane to replace the existing separator, thereby having excellent high-rate characteristics and battery performance.

[0011] (II) Technical Solution

[0012] The present invention provides an organic-inorganic composite membrane for secondary batteries, the organic-inorganic composite membrane comprising: a porous matrix containing fluorinated copolymer and lithium-lanthanum-zirconium oxide particles; and a cross-linked network polymer electrolyte filling at least one pore of the porous matrix, wherein the fluorinated copolymer contains 10-25% by weight of repeating units derived from hexafluoropropylene.

[0013] According to one specific implementation, the fluorinated copolymer can be polyvinylidene fluoride-hexafluoropropylene.

[0014] According to one specific embodiment, the content of the fluorinated copolymer can be 10-60% by weight relative to the total weight of the porous matrix.

[0015] According to one specific implementation, the lithium-lanthanum-zirconium-based oxide particles can be represented by the following chemical formula 1.

[0016] [Chemical Formula 1]

[0017] Li x M 1a M 2b La y Zr z M 3c O 12

[0018] (In the aforementioned chemical formula 1, 5≤x≤9, 0≤a≤4, 0≤b≤4, 2≤y≤4, 1≤z≤3, 0≤c≤4, and M1 to M3 are independently selected from any one of the elements chosen from Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, and Sn.)

[0019] According to one specific embodiment, the content of the lithium-lanthanum-zirconium-based oxide particles can be 40-90% by weight relative to the total weight of the porous matrix.

[0020] According to one specific embodiment, the porous matrix may consist of a continuous phase comprising a fluorinated copolymer and a dispersed phase comprising lithium-lanthanum-zirconium oxide particles.

[0021] According to one specific embodiment, the cross-linked network polymer electrolyte may comprise an acrylic polymer and a lithium salt.

[0022] According to one specific embodiment, the content of the cross-linked network polymer electrolyte can be 10-80 parts by weight relative to 100 parts by weight of the porous matrix.

[0023] The present invention provides a slurry composition for manufacturing organic-inorganic composite membranes, the slurry composition comprising a fluorinated copolymer, lithium-lanthanum-zirconium oxide particles, a first solvent and a second solvent, wherein the fluorinated copolymer contains 10-25% by weight of repeating units derived from hexafluoropropylene, and the polarity of the second solvent is lower than that of the first solvent.

[0024] According to a specific implementation scheme, the Hansen solubility parameter (δ) of the first solvent Ts1 It can be 18-25MPa 0.5 .

[0025] According to one specific embodiment, the difference in Hansen solubility parameter between the first solvent and the fluorinated copolymer can be 1 MPa. 0.5 Above and below 15.0 MPa 0.5 .

[0026] According to a specific implementation scheme, the Hansen solubility parameter (δ) of the second solvent Ts2 It can be 17MPa 0.5 the following.

[0027] According to one specific embodiment, the dipole moments of the first solvent and the second solvent can be below 2.8 Debye (D), and the dielectric constant can be below 20.

[0028] According to one specific implementation, the first solvent and the second solvent can satisfy a weight ratio of 5 to 50:1.

[0029] The present invention provides a method for manufacturing an organic-inorganic composite membrane for secondary batteries, the method comprising the following steps: (S1) preparing a slurry composition for manufacturing an organic-inorganic composite membrane comprising a fluorinated copolymer, lithium-lanthanum-zirconium oxide particles, a first solvent, and a second solvent; (S2) coating and drying the slurry composition to form a porous matrix; and (S3) impregnating a multifunctional monomer composition into the porous matrix and curing it to form a cross-linked network polymer electrolyte, wherein the fluorinated copolymer contains 10-25% by weight of repeating units derived from hexafluoropropylene.

[0030] According to one specific embodiment, step (S1) may include the following steps: (a) dissolving the fluorinated copolymer in a first solvent; and (b) adding lithium-lanthanum-zirconium-based oxide particles and a second solvent and mixing.

[0031] According to one specific embodiment, step (S2) may include the following steps: drying the first solvent in the slurry composition at a first drying temperature; and drying the second solvent in the slurry composition at a second drying temperature.

[0032] According to one specific implementation, the second drying temperature may be higher than the first drying temperature.

[0033] According to one specific embodiment, the multifunctional monomer composition may comprise a multifunctional acrylic monomer, an initiator, and a lithium salt.

[0034] The present invention provides a lithium secondary battery, wherein the lithium secondary battery comprises the above-mentioned organic-inorganic composite membrane.

[0035] (III) Beneficial Effects

[0036] According to a specific embodiment of the present invention, the organic-inorganic composite membrane can be fabricated as a self-supporting membrane, and the organic-inorganic composite membrane contains micropores, thereby allowing it to replace a separator. Furthermore, the organic-inorganic composite membrane can possess high ionic conductivity, excellent thermal and chemical stability, and superior mechanical strength. Moreover, compared to using an organic electrolyte alone, lithium secondary batteries incorporating the organic-inorganic composite membrane can achieve significantly improved chemical and mechanical stability, and can exhibit superior battery performance with excellent lifespan and high rate capability. Attached Figure Description

[0037] Figure 1This is a graph showing the evaluation results of the film-forming properties of the organic-inorganic composite electrolyte slurry of Example 1 and Comparative Example 1.

[0038] Figure 2 This is a graph showing the change in discharge capacity of the organic-inorganic composite electrolytes of Example 1 and Comparative Example 4 according to cycles. Detailed Implementation

[0039] The present invention will now be described in more detail through specific embodiments or implementation schemes. However, the specific embodiments or implementation schemes described below are merely for reference in detailing the present invention, and the present invention is not limited thereto; the present invention can be implemented in various forms.

[0040] Furthermore, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this description is for the purpose of effectively describing specific embodiments only and is not intended to limit the scope of the invention.

[0041] Furthermore, unless otherwise specified in the context, the singular form used in the specification and claims may also include the plural form.

[0042] Furthermore, when describing a part as "containing" or "including" a constituent element, unless otherwise specifically stated to the contrary, it indicates that other constituent elements may be included, rather than excluding other constituent elements.

[0043] Furthermore, unless otherwise specified, all units used in this specification are based on weight. As an example, % or proportion means weight % or weight ratio. Unless otherwise defined, weight % means the weight of any one component in the entire composition.

[0044] Furthermore, in this specification, “~-based polymer,” “~-based copolymer,” and “~-based oxide” are broad concepts that include all “~-based polymer derivatives,” “~-based copolymer derivatives,” and “~-based oxide derivatives.”

[0045] Furthermore, the numerical ranges used in this specification include lower and upper limits, all values ​​within that range, increments logically derived from the form and width of the defined range, all values ​​defined therein, and all possible combinations of upper and lower limits of numerical ranges defined in different forms from each other. In this specification, unless otherwise specifically defined, values ​​outside the defined numerical range that may arise due to experimental errors or rounding are also included within the defined numerical ranges.

[0046] Furthermore, the term "Hansen Solubility Parameters (HSP)" in this specification is used to predict the degree of solubility of a particular substance (solute) in a certain solvent, and refers to the Hansen solubility parameters (proposed by Dr. C. Hansen in 1967) calculated by taking into account three factors: nonpolar dispersive bonds with high degree of bonding within the substance, polar bonds generated by permanent dipoles, and hydrogen bonds.

[0047] In the past, when using oxide-based inorganic electrolytes to manufacture organic-inorganic composite solid electrolytes, excessive side reactions occurred between the solvent and the oxide-based inorganic electrolyte, resulting in increased viscosity of the slurry, making it difficult to form a film and resulting in insufficient film-forming properties, thus making it difficult to produce self-supporting films.

[0048] To address this issue, the oxide-based inorganic solid electrolyte is sometimes coated onto a porous membrane or mixed with a polymer to form a membrane. However, in this case, a sufficient amount of oxide-based inorganic solid electrolyte cannot be contained, resulting in insufficient ionic conductivity and reduced operating efficiency. Furthermore, adding a separate foaming agent to form pores requires additional raw materials or processes, and limitations remain in controlling the shape or size of the pores.

[0049] According to one specific embodiment of the present invention, a porous matrix is ​​manufactured by using a slurry composition comprising a fluorinated copolymer containing a specific amount of repeating units derived from hexafluoropropylene, lithium-lanthanum-zirconium-based oxide particles, and a first solvent and a second solvent meeting specific conditions. This effectively suppresses side reactions between the solvent and the lithium-lanthanum-zirconium-based oxide particles, and the slurry composition exhibits excellent storage stability, processability, and significantly improved film-forming properties, thereby enabling the fabrication of a self-supporting membrane. Furthermore, by utilizing the polarity difference between the first solvent and the second solvent in a two-step or more drying process, the shape and size of the micropores in the porous matrix can be precisely controlled. The first solvent and the second solvent can be solvents that effectively dissolve the fluorinated copolymer while stably dispersing the lithium-lanthanum-zirconium-based oxide particles without reacting with them.

[0050] Furthermore, the first and second solvents can have different polarities, and a porous matrix can be fabricated using phase separation. For example, the first solvent can be a good solvent with higher polarity and better solubility for the fluorinated copolymer compared to the second solvent. Conversely, the second solvent can be a non-solvent with lower polarity compared to the first solvent. This polarity can be expressed by δ, which represents polarity in the Hansen solubility parameter. pThis can be confirmed by parameters, or by the dipole moment and dielectric constant. For example, δ p The difference can be 3 MPa 0.5 Above or approximately 3-8 MPa 0.5 .

[0051] Furthermore, the first solvent and the second solvent can have different polarities and different boiling points, and a porous matrix can be fabricated using phase separation. For example, the first solvent can be a good solvent that dissolves the fluorinated copolymer better than the second solvent due to its higher polarity and lower boiling point. Conversely, the second solvent can be a non-solvent that has lower polarity and a higher boiling point than the first solvent.

[0052] As described above, the fluorinated copolymer contains 10-25% by weight of repeating units derived from hexafluoropropylene, and includes a first solvent and a second solvent under specific conditions, thereby effectively suppressing the side reactions of lithium-lanthanum-zirconium-based oxide particles during slurry preparation. The slurry exhibits excellent storage stability and processability, as well as significantly improved film-forming properties, thus enabling the fabrication of self-supporting membranes.

[0053] Furthermore, the porous matrix produced by the above method has excellent electrolyte impregnation properties, and can be cross-linked network polymer electrolytes by impregnating multifunctional compositions and curing them, and can provide physical properties with excellent ionic conductivity.

[0054] An organic-inorganic composite membrane according to a specific embodiment of the present invention can provide an organic-inorganic composite membrane comprising a porous matrix and a polymer electrolyte. Micropores are uniformly formed in the porous matrix, and the polymer electrolyte is uniformly impregnated within the pores. The polymer electrolyte filling the micropores can act as lithium-ion channels to activate lithium-ion transport, thereby achieving excellent ionic conductivity. The organic-inorganic composite membrane according to a specific embodiment of the present invention exhibits excellent processability, superior electrochemical performance, and excellent chemical and physical stability. Furthermore, it has been discovered that by using the organic-inorganic composite membrane according to a specific embodiment of the present invention, a lithium-ion secondary battery with excellent lifespan and high-rate characteristics can be provided.

[0055] The following describes the various components of the organic-inorganic composite membrane according to a specific embodiment of the present invention.

[0056] The present invention provides an organic-inorganic composite membrane comprising: a porous matrix containing a fluorinated copolymer and lithium-lanthanum-zirconium oxide particles; and a cross-linked network polymer electrolyte filling at least one pore of the porous matrix, wherein the fluorinated copolymer contains 10-25% by weight of repeating units derived from hexafluoropropylene.

[0057] According to one specific embodiment, the fluorinated copolymer in the porous matrix is ​​uniformly mixed with lithium-lanthanum-zirconium-based oxide particles, so that the porous matrix can consist of a continuous phase containing the fluorinated copolymer and a dispersed phase containing lithium-lanthanum-zirconium-based oxide particles. The forms of the continuous and dispersed phases can vary depending on the content of each component. As an example, when the content of lithium-lanthanum-zirconium-based oxide particles is 40% by weight or more, 50% by weight or more, or 60% by weight or more relative to the total weight of the porous matrix, the fluorinated copolymer can act as a binder between the particles, and the oxide particles can be connected, but are not limited thereto. Although there is no upper limit to the content of lithium-lanthanum-zirconium-based oxide particles, the content can be 90% by weight or less, 85% by weight or less, or 80% by weight or less, or any value between these values. For example, the content of lithium-lanthanum-zirconium-based oxide particles can be 40-90% by weight or 50-90% by weight relative to the total weight of the porous matrix.

[0058] According to one specific embodiment, the fluoropolymer can be used without particular restriction as long as it is a fluoropolymer containing repeating units derived from hexafluoropropylene. The content of repeating units derived from hexafluoropropylene in the fluoropolymer can be greater than 5% by weight, more than 6% by weight, more than 10% by weight, more than 15% by weight, less than 35% by weight, less than 34% by weight, less than 33% by weight, less than 32% by weight, less than 31% by weight, less than 30% by weight, less than 25% by weight, or any value between the above values. For example, the content of repeating units derived from hexafluoropropylene in the fluoropolymer can be greater than 5% by weight and less than 35% by weight, 6-34% by weight, 7-33% by weight, 8-32% by weight, 9-31% by weight, 10-30% by weight, 10-25% by weight, or 15-25% by weight. When the content of repeating units derived from hexafluoropropylene in the fluoropolymer meets the above ranges, the miscibility with oxide particles can be improved, thereby achieving excellent film-forming properties. In addition, the content of oxide particles can be 40% or more by weight or 40-90% by weight.

[0059] According to one specific embodiment, the fluorinated copolymer may include any one or more copolymers selected from polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP), tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, and ethylene-vinylidene fluoride-hexafluoropropylene copolymer.

[0060] According to a specific implementation, in addition to the examples described above, the fluorinated copolymer may further include other fluorinated polymers. As an example, it may include any one or more polymers selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), propylene-tetrafluoroethylene-vinylidene fluoride (PTFE-VDF), polyvinylidene fluoride-trifluorochloroethylene (PVDF-CTFE), tetrafluoroethylene-trifluorochloroethylene copolymer (TFE / CTFE), polytrifluorochloroethylene (PCTFE), and ethylene-trifluorochloroethylene copolymer (ECTFE).

[0061] According to one specific embodiment, the weight-average molecular weight (Mw) of the fluorinated copolymer can be 100,000-5,000,000 g / mol, 200,000-3,000,000 g / mol, 200,000-2,000,000 g / mol, or 300,000-1,000,000 g / mol, but is not limited thereto. Furthermore, the number-average molecular weight (Mn) of the fluorinated copolymer can be 50,000-3,000,000 g / mol, 50,000-1,000,000 g / mol, or 80,000-500,000 g / mol, but is not limited thereto. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) are values ​​measured using gel permeation chromatography (GPC, Waters, Alliance).

[0062] Furthermore, the melting point (Tm) of the fluorinated copolymer can be 50-250°C, 60-170°C, or 80-100°C. This melting point can be measured using conventional methods; for example, it can be measured using a differential scanning calorimetry (DSC, Mettler Toledo, DSC1) at a heating rate of 10°C / min. Meeting these melting points ensures the mechanical properties and flexibility of the formed organic-inorganic composite film.

[0063] According to one specific embodiment, the Hansen solubility parameter (δ) of the fluorinated copolymer can be 10-50 MPa.0.5 15-40MPa 0.5 or 20-35MPa 0.5 For example, the Hansen solubility parameter (δ) of a polyvinylidene fluoride (PVDF) homopolymer with a hexafluoropropylene (HFP) content of 0% by weight is 23.2 MPa. 0.5 Furthermore, the Hansen solubility parameter (δ) decreases with increasing HFP content. Specifically, in one embodiment of the invention, when poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) containing 10-25% by weight of repeating units derived from hexafluoropropylene, δ... d (Dispersion force) can be 16-17 MPa 0.5 δ p (Polarity) can be 10-12 MPa 0.5 δ h (Hydrogen bonds) can be 8-10 MPa 0.5 The solubility parameter (δ) of Hansen can be 23.2 MPa. 0.5 Below or 21-23 MPa 0.5 The Hansen solubility parameter of the fluorinated copolymer can be calculated by the following method, or measured by HSPiP (HansenSolubility Parameters in Practice) software.

[0064] According to one specific embodiment, the content of the fluorinated copolymer, relative to the total weight of the porous matrix, can be 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, less than 80% by weight, less than 70% by weight, less than 60% by weight, less than 50% by weight, less than 40% by weight, less than 35% by weight, less than 30% by weight, or any value between the above values. For example, the content of the fluorinated copolymer can be 5-80% by weight, 10-60% by weight, 10-50% by weight, 10-35% by weight, or 20-30% by weight. When the content of the fluorinated copolymer meets the above ranges, excellent film-forming properties and impregnation properties can be ensured.

[0065] According to one specific embodiment, the lithium-lanthanum-zirconium-based oxide particles are particles containing lithium (Li), lanthanum (La), zirconium (Zr) and oxygen (O) elements, and can be represented by the following chemical formula 1.

[0066] [Chemical Formula 1]

[0067] Li x M 1a M 2b La yZr z M 3c O 12

[0068] In the chemical formula 1, 5≤x≤9, 0≤a≤4, 0≤b≤4, 2≤y≤4, 1≤z≤3, 0≤c≤4, and M1 to M3 are each independently selected from Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, and Sn.

[0069] According to one specific implementation, in the chemical formula 1, M1 to M3 can be independently selected from any element chosen from Ti, Ta, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, and Sn.

[0070] According to a specific implementation scheme, chemical formula 1 can be represented as Li x La y Zr z O 12 Li x Ga a La y Zr z O 12 Or Li x La y Zr z Ta c O 12 , where 5≤x≤9, 0≤a≤4, 2≤y≤4, 1≤z≤3, 0≤c≤4.

[0071] According to one specific implementation, the lithium-lanthanum-zirconium-based oxide particles may be selected from Li7La3Zr2O 12 (LLZO), Li 6.25 Ga 0.25 La3Zr2O 12 (GLLZO) and Li 6.4 La3Zr 1.4 Ta 0.6 O 12 One or more of (LLZTO) etc.

[0072] According to one specific embodiment, the average particle size of the lithium-lanthanum-zirconium-based oxide particles can be 0.01-3 μm, 0.1-1 μm, or 0.2-0.6 μm. The average particle size can be measured according to ISO 13320-1 standard using a particle size analyzer (Microtrac S3500).

[0073] According to one specific embodiment, relative to the total weight of the porous matrix, the content of the lithium-lanthanum-zirconium-based oxide particles can be 20% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, less than 95% by weight, less than 90% by weight, or any value between the above values. For example, the content of the lithium-lanthanum-zirconium-based oxide particles can be 20-95% by weight, 40-90% by weight, 50-90% by weight, 60-90% by weight, 65-90% by weight, or 70-80% by weight. When the content of the lithium-lanthanum-zirconium-based oxide particles meets the above ranges, excellent storage stability can be achieved, and superior electrochemical properties such as ionic conductivity can be realized.

[0074] According to one specific embodiment, in the porous matrix, the content ratio of the fluorine-based copolymer to the lithium-lanthanum-zirconium-based oxide particles can be from 10 to 50: 50 to 90 by weight, and is not limited thereto.

[0075] According to one specific implementation, the thickness of the porous matrix can be 5-100μm, 10-80μm, 15-50μm or 20-30μm, but is not limited thereto.

[0076] According to one specific embodiment, the average pore size of the porous matrix can be 0.01-1 μm, 0.1-0.7 μm, or 0.3-0.6 μm, but is not limited thereto. According to one embodiment, micropores are uniformly formed in the porous matrix, and the polymer electrolyte forms lithium-ion channels, making lithium-ion transport more active, thereby achieving a significant improvement in ionic conductivity.

[0077] According to one specific embodiment, the porosity of the porous matrix can be 10-90%, 20-80%, more than 30%, more than 35%, more than 40%, 40-60%, or less than 60%, and is not limited thereto. When the above porosity is met, an organic-inorganic composite membrane according to one embodiment can be used to replace the existing membrane.

[0078] According to one specific embodiment, the organic-inorganic composite membrane is characterized by comprising a cross-linked network polymer electrolyte impregnated or filled in at least one micropore of the porous matrix. The cross-linked network polymer electrolyte is a gel polymer electrolyte, which can fill the micropores of the porous matrix and act as a connector between pores, thereby serving as a migration channel for lithium ions, thus enabling the fabrication of an organic-inorganic composite membrane with significantly improved ionic conductivity.

[0079] According to one specific embodiment, the cross-linked network polymer electrolyte may comprise a cross-linked network polymer formed by cross-linking the following multifunctional monomers and a lithium salt. The cross-linked network polymer may be formed from monomers containing two or more polymerizable functional groups; as an example, it may comprise any one or more selected from epoxy polymers, vinyl polymers, and acrylic polymers.

[0080] According to one specific embodiment, the cross-linked network polymer electrolyte may contain a lithium salt, and the cross-linked network polymer electrolyte may contain an acrylic polymer and a lithium salt. The acrylic polymer may be formed, for example, from acrylic monomers such as trimethylolpropane ethoxylate triacrylate (TMPETA), trimethylolpropane trimethacrylate (TMPTMA), trimethylolpropane triacrylate (TMPTA), and tetramethylolmethane tetraacrylate (TMMTA), and is not limited thereto. The lithium salt can act as a lithium-ion supply source within the battery, thereby enabling the basic operation of the lithium secondary battery and promoting the migration of lithium ions between the positive and negative electrodes. Non-limiting examples of the lithium salt include LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO3C2F5)2, LiN(CF3SO2)2, LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are natural numbers), LiCl, LiI, LiB(C2O4)2, or combinations thereof, but not limited thereto. The concentration of the lithium salt may be used in the range of 0.1M to 5.0M, 0.1M to 2.0M, or 0.5M to 1.0M, and is not limited thereto.

[0081] According to one specific embodiment, the cross-linked network polymer electrolyte may further comprise a liquid organic electrolyte, and conventional or known liquid organic electrolytes may be used without particular restriction. However, the organic electrolyte may not contain a fluorinated organic electrolyte.

[0082] According to one specific embodiment, the liquid organic electrolyte may comprise carbonate-based solvents, ester-based solvents, ether-based solvents, ketone-based solvents, alcohol-based solvents, or aprotic solvents. These solvents may be used alone or in mixtures of two or more. When two or more solvents are mixed, the mixing ratio can be appropriately adjusted according to the desired battery performance. As an example, any one or more selected from ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and butenyl carbonate (BC) may be used, but not limited to these solvents.

[0083] According to a specific implementation scheme, to improve charge / discharge characteristics, flame retardant properties, etc., the organic electrolyte may further include, as needed, pyridine, triethyl phosphate, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoramide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, etc. In some cases, to impart non-flammability, halogenated solvents such as carbon tetrachloride and trifluoroethylene may be further included, and to improve high-temperature storage characteristics, fluoroethylene carbonate (FEC), propene sultone (PRS), and fluoropropylene carbonate (FPC), etc., may be further included.

[0084] According to one specific embodiment, the content of the cross-linked network polymer electrolyte can be 5-100 parts by weight, 10-80 parts by weight, or 20-70 parts by weight relative to 100 parts by weight of the porous matrix. When the content of the cross-linked network polymer electrolyte meets the above ranges, a significant improvement in film-forming properties, impregnation properties, and ionic conductivity can be achieved.

[0085] According to one specific embodiment, the organic-inorganic composite film can possess superior surface properties compared to existing technologies. These surface properties can be confirmed by the appearance of the organic-inorganic composite film or the high-rate characteristics of batteries manufactured using the organic-inorganic composite film. By manufacturing the organic-inorganic composite film using the following method, side reactions between oxide particles and the solvent can be minimized, thus allowing the formation of a self-supporting film with excellent surface properties and good mechanical and physical properties, and with uniform micropores. If excessive side reactions occur between oxide particles and the solvent, the viscosity of the slurry composition increases sharply, leading to poor film-forming properties, making it impossible to form a film, and the pore shape may become irregular. Furthermore, lithium-ion migration is restricted, resulting in unstable and insufficient charge-discharge characteristics of the battery at high rates. However, the organic-inorganic composite film according to one embodiment is manufactured using solvents under specific conditions, thus effectively suppressing side reactions with oxide particles, thereby exhibiting excellent film-forming properties. Furthermore, by simultaneously using a fluorinated copolymer containing a specific amount of repeating units with the solvent and manufacturing a composite film using the following manufacturing method, it is possible to improve the dispersibility of the oxide particles and form uniform micropores. Moreover, in lithium-ion secondary batteries manufactured using the organic-inorganic composite film, lithium-ion migration becomes more active, thereby achieving excellent battery performance and high-rate characteristics.

[0086] The following provides a more detailed description of a slurry composition for manufacturing an organic-inorganic composite membrane according to one embodiment.

[0087] In one specific embodiment of the present invention, the slurry composition for manufacturing a porous matrix of an organic-inorganic composite membrane may comprise 10-25% by weight of a fluorinated copolymer containing repeating units derived from hexafluoropropylene, lithium-lanthanum-zirconium-based oxide particles, a first solvent and a second solvent, wherein the polarity of the second solvent may be lower than that of the first solvent.

[0088] In one specific embodiment of the present invention, the slurry composition for manufacturing a porous matrix of an organic-inorganic composite membrane may comprise 10-25% by weight of a fluorinated copolymer derived from repeating units of hexafluoropropylene, lithium-lanthanum-zirconium oxide particles, a first solvent and a second solvent, wherein the polarity of the second solvent may be lower than that of the first solvent, and the boiling points of the first solvent and the second solvent may be different from each other.

[0089] The organic-inorganic composite membrane described above can be manufactured using the slurry composition for manufacturing organic-inorganic composite membranes.

[0090] According to one specific embodiment, in order to form a self-supporting film using the lithium-lanthanum-zirconium-based oxide particles and a fluorinated copolymer containing 10-25% by weight of repeating units derived from hexafluoropropylene, the first solvent and the second solvent are preferably solvents with different polarities. For example, the first solvent can be a solvent with a Hansen solubility parameter close to that of the fluorinated copolymer and a lower boiling point. Because the first solvent has a Hansen solubility parameter close to that of the fluorinated copolymer, it can dissolve the fluorinated copolymer well, and because the first solvent has a lower boiling point, it can evaporate quickly. Furthermore, the second solvent can be a solvent with lower polarity and a higher boiling point compared to the first solvent.

[0091] Furthermore, the polarity of the first solvent and the second solvent can be represented by the Hansen solubility parameter, and the polarity can be represented by δ in the Hansen solubility parameter. p It can also be expressed using dipole moment and dielectric constant.

[0092] According to one specific embodiment, the slurry composition for manufacturing the organic-inorganic composite membrane comprises a fluorinated copolymer, lithium-lanthanum-zirconium-based oxide particles, a first solvent, and a second solvent. The descriptions of the fluorinated copolymer and the lithium-lanthanum-zirconium-based oxide particles are the same as described above and are therefore omitted.

[0093] According to one specific embodiment, the first solvent can be a good solvent with higher polarity and better solubility for the fluorinated copolymer compared to the second solvent. Furthermore, the second solvent can be a non-solvent with lower polarity compared to the first solvent. This polarity can be represented by δ, which is expressed in the Hansen solubility parameter. p This can be confirmed by parameters, or by the dipole moment and dielectric constant. For example, δ p The difference can be 3 MPa 0.5 Above or approximately 3-8 MPa 0.5 .

[0094] Furthermore, the first solvent and the second solvent can have different polarities and different boiling points, and a porous matrix can be fabricated using phase separation. For example, the first solvent can be a good solvent that has higher polarity and a lower boiling point than the second solvent, thus dissolving the fluorinated copolymer better. Furthermore, the second solvent can be a non-solvent that has lower polarity and a higher boiling point than the first solvent. According to one specific embodiment, the Hansen solubility parameter (δ) of the first solvent... Ts1 It can be 18-25MPa 0.5 18.5-23MPa 0.5Or 19.0-20MPa 0.5 When the Hansen solubility parameter of the first solvent meets the above range, a self-supporting film can be formed, and the electrolyte impregnation can be improved, thereby achieving excellent ionic conductivity and high rate performance.

[0095] According to one specific embodiment, the difference in Hansen solubility parameter between the first solvent and the fluorinated copolymer can be 1 MPa. 0.5 Above and less than 15MPa 0.5 1-14MPa 0.5 1-10MPa 0.5 1-8MPa 0.5 1.5-8MPa 0.5 1.5-5MPa 0.5 Or 1.5-3.5MPa 0.5 When the difference in the Hansen solubility parameters meets the above-mentioned range, the solubility of the fluorinated copolymer can be improved. The Hansen solubility parameters can be calculated using the following method or confirmed using HSPiP (Hansen Solubility Parameters in Practice) software.

[0096] According to one specific implementation, the boiling point of the first solvent can be below 110°C, 0-80°C, 10-80°C, or 20-70°C.

[0097] According to a specific implementation scheme, the vapor pressure of the first solvent at room temperature can be above 25 mmHg or 50-150 mmHg.

[0098] According to one specific embodiment, the dipole moments of the first solvent and the second solvent can be less than 2.8 Debye (D), and the dielectric constant can be less than 20. For example, the dipole moments of the first solvent and the second solvent can be 0-2 Debye (D), and the dielectric constant can be from 1 to 20.

[0099] According to one specific implementation, the dipole moment of the first solvent can be 0.1-10 Debye (D), 0.5-5 Debye (D), or 1-2.5 Debye (D).

[0100] According to one specific embodiment, the dielectric constant of the first solvent can be 1 to 20, 2 to 15, or 5 to 10. When a first solvent satisfying the above range is used, appropriate interaction occurs with the fluorinated copolymer, thereby enabling the preparation of a slurry composition capable of forming a self-supporting film.

[0101] According to one specific implementation, the dipole moment of the second solvent can be 0-2.85 Debye (D), 0-2 Debye (D), 0-1.5 Debye (D), or 0-1 Debye (D).

[0102] According to one specific implementation, the dielectric constant of the second solvent can be 1 to 20, 1 to 10, or 1 to 5.

[0103] According to one specific implementation, the first solvent may be a polar organic solvent, a polar protic organic solvent, a polar aprotic organic solvent, or a mixture thereof. Non-limiting examples of the aforementioned polar organic solvents include N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), cyclohexyl-pyrrolidone (CHP), N-dodecyl-pyrrolidone (N12P), benzyl benzoate, N-octyl-pyrrolidone (N8P), dimethyl-imidazolidinone (DMEU), cyclohexanone, dimethylacetamide (DMA), and N-methylformamide (NMP). Formamide (NMF), bromobenzene, chloroform, benzonitrile, quinoline, benzyl ether, ethanol, isopropanol, methanol, butanol, 2-ethoxyethanol, 2-butoxyethanol, 2-methoxypropanol, tetrahydrofuran (THF), ethylene glycol, pyridine, N-vinylpyrrolidone, methyl ethyl ketone (butanone), α-terpineol, formic acid, ethyl acetate, and acrylonitrile, etc., but not limited to these.

[0104] According to one specific embodiment, the first solvent may be an ether-based organic solvent. The ether-based organic solvent may be a non-cyclic ether-based organic solvent, a cyclic ether-based organic solvent, or a mixture thereof. Non-limiting examples of the ether-based organic solvent include 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, and tetraethylene glycol diethyl ether. ether), 1,3-dioxolane, 4,5-dimethyl-dioxolane, 4,5-diethyl-dioxolane, 4-methyl-1,3-dioxolane, 4-ethyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2,5-dimethoxytetrahydrofuran tetrahydrofuran), 2-ethoxytetrahydrofuran, 2-methyl-1,3-dioxolane, 2-vinyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 2-methoxy-1,3-dioxolane, 2-ethyl-2-methyl-1,3-dioxolane3-Dioxolane, tetrahydropyran, 1,4-dioxane, 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene, isosorbide dimethyl ether, etc.

[0105] According to a specific implementation scheme, the Hansen solubility parameter (δ) of the second solvent Ts2 It can be 17MPa 0.5 Below, 1-17MPa 0.5 7-17MPa 0.5 or 10-17MPa 0.5 When the Hansen solubility parameter of the second solvent meets the above range, a self-supporting film can be formed, and the electrolyte impregnation can be improved, thereby achieving excellent ionic conductivity and high rate performance.

[0106] According to one specific embodiment, the boiling point of the second solvent can be above 100°C, 100-300°C, or 110-230°C. As an example, the second solvent and the first solvent can have different boiling points from each other, with a boiling point difference of more than 50°C, for example, 50-200°C.

[0107] According to one specific implementation, the vapor pressure of the second solvent at room temperature can be below 15 mmHg or 0.05-10 mmHg.

[0108] According to one specific implementation, the dipole moment of the second solvent can be 0-2 Debye (D), 0-1 Debye (D), or 0-0.5 Debye (D).

[0109] According to one specific embodiment, the dielectric constant of the second solvent can be 0.1 to 10, 0.5 to 5, or 0.5 to 3.

[0110] According to a specific implementation scheme, the second solvent may be a hydrocarbon-based organic solvent, or may be any one or a combination of two or more selected from aliphatic hydrocarbon-based organic solvents (hexane, octane, heptane, etc.), alicyclic hydrocarbon-based organic solvents (cyclohexane, cyclohexene, ethylcyclohexane, methylcyclohexane, methylcyclohexene, etc.) and aromatic hydrocarbon-based organic solvents (benzene, toluene, xylene, ethylbenzene, diethylbenzene, trimethylbenzene, triethylbenzene, etc.).

[0111] According to a specific implementation plan, the hydrocarbon-based organic solvent can be C 3-30Hydrocarbon-based organic solvents or C 5-12 Hydrocarbon-based organic solvent. Alternatively, the second solvent may be any one or a combination of two or more selected from pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, etc.

[0112] According to a specific implementation scheme, the Hansen solubility parameter (δ) of the first solvent Ts1 The Hansen solubility parameter (δ) of the second solvent Ts2 The Hansen solubility parameter (δ) of fluorinated copolymers. Tm ) can satisfy δ Ts2 <δ Ts1 δ Ts2 ≤δ Tm -5.9MPa 0.5 <δ Ts1 or δ Ts2 ≤δ Tm -3.7MPa 0.5 <δ Ts1 .

[0113] According to one specific embodiment, the weight ratio of the first solvent to the second solvent can be 0.1 to 100:1, 1 to 80:1, 5 to 50:1, or 10 to 30:1. When the above weight ratio meets the above range, film-forming properties and impregnation properties can be improved simultaneously, thus enabling the manufacture of organic-inorganic composite films with excellent battery characteristics.

[0114] According to one specific embodiment, the content of the fluorinated copolymer may be 1-50 parts by weight, 3-30 parts by weight, or 5-20 parts by weight relative to 100 parts by weight of the first solvent.

[0115] According to one specific embodiment, the content of the fluorinated copolymer may be 5-100 parts by weight, 10-60 parts by weight, or 15-45 parts by weight relative to 100 parts by weight of the lithium-lanthanum-zirconium-based oxide particles.

[0116] According to one specific embodiment, the solids content of the slurry composition for manufacturing organic-inorganic composite membranes, based on dry weight, can be 10-70% by weight, 15-50% by weight, or 25-45% by weight.

[0117] The above-described organic-inorganic composite membrane can be manufactured using the above-described slurry composition for manufacturing organic-inorganic composite membranes. In the organic-inorganic composite membrane, by simultaneously using a solvent that satisfies the above conditions and lithium-lanthanum-zirconium-based oxide particles, side reactions can be effectively suppressed. Furthermore, by using the solvent and a fluorinated copolymer containing a specific amount of repeating units derived from hexafluoropropylene (HFP), a matrix with uniformly dispersed oxide particles can be manufactured based on excellent solubility.

[0118] According to one specific implementation scheme, the ionic conductivity of the organic-inorganic composite membrane can be 1×10⁻⁶. -5 S / cm or higher, 1×10 -4 S / cm or higher, 5×10 -4 S / cm or higher, 7×10 -4 S / cm or higher, 9×10 -4 S / cm or higher or 1×10 -3 For membranes with a conductivity of S / cm or higher, the upper limit of the ionic conductivity is not particularly limited, but the ionic conductivity of the organic-inorganic composite membrane can be 1×10⁻⁶. -2 S / cm or less or 5×10 -4 S / cm to 1×10 -2 S / cm.

[0119] This invention provides a lithium secondary battery comprising the above-described organic-inorganic composite membrane. The type of lithium secondary battery is not particularly limited, but as a non-limiting example, a lithium-ion battery can be cited. The lithium-ion battery is a well-known battery, and its structure is also known; therefore, it will not be specifically described in this invention.

[0120] According to one embodiment, a lithium secondary battery can use an organic-inorganic composite membrane according to one embodiment between the positive and negative electrodes. In this case, the positive and negative electrodes can be used without restriction, as long as they are commonly used in lithium secondary batteries. The organic-inorganic composite membrane according to one embodiment can replace the separator and can simultaneously function as both an electrolyte and a separator.

[0121] A lithium secondary battery according to a specific embodiment can have excellent life characteristics, and according to the evaluation method below, the capacity retention rate of the lithium secondary battery after 200 cycles can be above 80%, above 85%, above 90%, or below 99.9%, but is not limited thereto.

[0122] According to a specific embodiment, the lithium secondary battery can have excellent high-rate characteristics. According to the following evaluation method, the discharge capacity of the lithium secondary battery at 2C can be above 50 mAh / g, above 90 mAh / g, above 100 mAh / g, above 120 mAh / g, or below 200 mAh / g, but is not limited thereto.

[0123] The following provides a more detailed description of a method for manufacturing an organic-inorganic composite membrane according to one embodiment.

[0124] This invention provides a method for manufacturing an organic-inorganic composite membrane, the method comprising the following steps: (S1) preparing a slurry composition for manufacturing an organic-inorganic composite membrane comprising a fluorinated copolymer, lithium-lanthanum-zirconium-based oxide particles, a first solvent, and a second solvent; (S2) coating and drying the slurry composition to form a porous matrix; and (S3) impregnating a multifunctional monomer composition into the porous matrix and curing it to form a cross-linked network polymer electrolyte, wherein the fluorinated copolymer contains 10-25% by weight of repeating units derived from hexafluoropropylene. The descriptions of the fluorinated copolymer, lithium-lanthanum-zirconium-based oxide particles, porous matrix, cross-linked network polymer electrolyte, and slurry composition for manufacturing the organic-inorganic composite membrane are the same as described above and are therefore omitted.

[0125] According to one specific embodiment, step (S1) may include the following steps: (a) dissolving the fluorinated copolymer in a first solvent; and (b) adding lithium-lanthanum-zirconium-based oxide particles and a second solvent and mixing. 1-50% by weight or 5-20% by weight of the fluorinated copolymer may be dissolved in the first solvent. After complete dissolution, the lithium-lanthanum-zirconium-based oxide particles and the second solvent may be added and stirred. The stirring method may use conventional or known methods.

[0126] According to one specific embodiment, the porous matrix can be manufactured using methods for manufacturing porous membranes or known methods, specifically, a dry phase inversion method.

[0127] According to one specific embodiment, step (S2) can be divided into a coating step of the prepared slurry composition and a drying step. The coating can be performed using conventional or known coating methods without particular limitation. For example, methods such as spin coating, dip coating, ink-jet printing, spray coating, screen printing, drop casting, or doctor blade coating can be used. Furthermore, the coating amount can be easily adjusted according to the thickness of the electrolyte membrane to be manufactured.

[0128] According to one specific embodiment, the object coated with the slurry composition can be an electrode or a release film.

[0129] According to one specific embodiment, the drying step in step (S2) may include the following steps: drying the first solvent in the slurry composition at a first drying temperature (hereinafter referred to as primary drying); and drying the second solvent in the slurry composition at a second drying temperature (hereinafter referred to as secondary drying).

[0130] According to one specific embodiment, the second drying temperature can be higher than the first drying temperature. The first and second drying temperatures can be varied depending on the types and boiling points of the first and second solvents. The first drying step is the drying of the first solvent, and the first drying temperature can be, for example, 0-80°C, 10-50°C, or room temperature (20-25°C). The second drying step is the drying of the second solvent, and the second drying can be carried out at a temperature higher than or equal to the boiling point of the first solvent. For example, the second drying temperature can be 70-300°C, 80-300°C, 90-150°C, or 100-130°C. Through this step (S2), a porous matrix satisfying the above-mentioned physical properties can be manufactured.

[0131] According to one specific embodiment, step (S3) may include the steps of preparing a multifunctional monomer composition and impregnating it into the porous matrix, as well as the step of curing it.

[0132] According to one specific embodiment, the multifunctional monomer composition may comprise a multifunctional acrylic monomer, an initiator, and a lithium salt. The multifunctional acrylic monomer may be an acrylic monomer containing two or more acrylic functional groups, specifically, it may be a combination of one or more selected from diacrylate monomers, triacrylate monomers, and tetraacrylate monomers. Non-limiting examples of the multifunctional acrylic monomer include, but are not limited to, polyethylene glycol diacrylate (PPGDA), polypropylene glycol diacrylate (PPGDA), polyethylene glycol dimethacrylate (PPD), trimethylolpropane triacrylate (PPD), trimethylolpropane ethoxylate triacrylate (PPD), dipentaerythritol penta- / hexa-acrylate (PPD), and pentaerythritol tetraacrylate (PPD).

[0133] According to one specific embodiment, the content of the polyfunctional acrylic monomer can be 1-50% by weight or 2-30% by weight relative to the total weight of the polyfunctional monomer composition.

[0134] According to one specific embodiment, the initiator is not limited to any initiator capable of initiating photocuring or thermocuring, and the initiator can be selected and used according to the type of the aforementioned multifunctional monomer. For example, the initiator can be tert-butyl peroxy pivalate (t-BPP), benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), etc., and is not limited to these. The content of the initiator can be 0.5-2% by weight of the multifunctional acrylic monomer content; for example, relative to the total weight of the multifunctional monomer composition, the content of the initiator can be 0.01-10% by weight or 0.05-5% by weight.

[0135] According to one specific embodiment, the multifunctional monomer composition may further comprise the aforementioned liquid organic electrolyte. In this case, the content of the organic electrolyte may be 50-99% by weight or 70-98% by weight relative to the total weight of the multifunctional monomer composition.

[0136] According to one specific embodiment, the method of impregnating the multifunctional monomer composition into the matrix can be any method used in the same technical field without limitation, and can be easily selected and performed according to well-known methods. The specific execution conditions are well known, and therefore will not be specifically described in this invention.

[0137] According to one specific embodiment, the multifunctional monomer composition is injected into the aforementioned porous matrix and cured to prepare a cross-linked network polymer electrolyte filling at least one pore of the porous matrix. The multifunctional monomer composition can be injected or impregnated according to conventional or known methods used in the art. Thus, the multifunctional monomer can cross-link to form a network polymer, which in turn can form a cross-linked network polymer electrolyte with lithium salt or lithium salt and organic electrolyte filling the spaces between the network polymers.

[0138] The present invention will now be described in more detail based on embodiments and comparative examples. However, the embodiments and comparative examples below are merely examples to illustrate the present invention in more detail, and the present invention is not limited to the embodiments and comparative examples below.

[0139] First, the methods for measuring and evaluating the physical properties of the diaphragm are explained.

[0140] (Methods for evaluating physical properties)

[0141] 1. Electrolyte impregnation amount (uptake, %)

[0142] The porous substrates prepared in the examples and comparative examples were impregnated in a liquid electrolyte, and the amount of liquid electrolyte impregnation (absorption, %) was measured by the following calculation formula 1, and is shown in Table 2. The liquid electrolyte used was an electrolyte containing 5% by weight FEC and 1.0 M LiPF6 dissolved in a mixed solvent of EC / EMC at a volume ratio of 3:7.

[0143] [Calculation Formula 1]

[0144] Liquid electrolyte impregnation amount (%) = (W - W0) / W0 × 100

[0145] W0 represents the weight (mg) of the porous matrix before impregnation with the liquid electrolyte, and W represents the weight (mg) of the porous matrix after impregnation with the liquid electrolyte.

[0146] 2. Ionic conductivity [S / cm]

[0147] The organic-inorganic composite film manufactured in the examples and comparative examples was placed between stainless steel (1 mm thick) to fabricate a coin cell. The ionic conductivity of the fabricated cell was measured by electrochemical impedance spectroscopy (EIS) analysis (measurement conditions: frequency 1.0 MHz to 0.1 Hz, amplitude potential 10 mV) and calculation formula 2 below, and is shown in Table 3 below.

[0148] [Calculation Formula 2]

[0149] Ionic conductivity (S / cm) = L / (R×A)

[0150] R represents the impedance measurement resistance (Ω), L represents the thickness of the sample (electrolyte layer) (cm), and A represents the area of ​​the sample (cm²). 2 ).

[0151] 3. Evaluation of lifespan characteristics and high-rate characteristics

[0152] The organic-inorganic composite membranes manufactured in the examples and comparative examples were placed between stainless steel (1 mm thick) to manufacture coin-shaped batteries, and the discharge capacity of the manufactured coin-shaped batteries was evaluated.

[0153] Coin-type batteries consist of a graphite anode / organic-inorganic composite film / LiNi 0.8 Mn 0.1 Co 0.1The positive electrode is composed of O2. The manufacturing methods for the aforementioned negative and positive electrodes are as follows.

[0154] A negative electrode slurry is prepared by mixing graphite (as the negative electrode active material), styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) (as binders), and carbon black (as a conductive material) in a weight ratio of 96:3:1. The negative electrode slurry is then uniformly coated onto a 10 μm copper foil, followed by drying and calendering to manufacture the negative electrode.

[0155] LiNi will be used as the positive electrode active material 0.8 Mn 0.1 Co 0.1 O2 powder and carbon black are uniformly mixed at a weight ratio of 90:5, and then a polyvinylidene fluoride (PVDF) solution is added as a binder, resulting in a positive electrode active material: carbon black: binder weight ratio of 90:5:5, thereby preparing a slurry for forming the positive electrode active material layer. The prepared slurry is coated onto a 12 μm thick aluminum substrate serving as the positive electrode current collector using a doctor blade, and then dried under reduced pressure at 120°C. It is then calendered by roll forming to form a sheet, thus manufacturing a positive electrode with both a positive electrode current collector and a positive electrode active material layer.

[0156] For the manufactured coin-shaped battery, under charging and discharging conditions within a voltage range of 2.5V to 4.2V, five charge-discharge cycles were performed at current densities of 0.1C, 0.2C, 0.3C, 0.5C, 1.0C, 2.0C, and 5.0C, respectively. Changes were observed, and the discharge capacity [mAh / g] at 0.1C and 2.0C, as well as the percentage (%) of the discharge capacity at 2C relative to the discharge capacity at 0.1C, were measured and recorded in Table 3 below. Next, 70 charge-discharge cycles were performed under 0.5C charging and discharging conditions, and the change in discharge capacity measured in each cycle was observed. Furthermore, Figure 2 The figure shows the change in discharge capacity [mAh / g] of Example 1 and Comparative Example 4 according to the cycle.

[0157] 4. Confirmation of the content of repeating units derived from hexafluoropropylene in fluoropolymers

[0158] Prepare 20 mg of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer sample and mix it with 1 mL of tetrahydrofuran-d8 (THF-d8) or acetone-d6 (Acetone-d6), stirring until completely dissolved. Transfer the sample to a fluorine-19 nuclear magnetic resonance spectrometer (NMR spectrometer). 19 The sample was placed in an F NMR tube and then measured using a 400 MHz nuclear magnetic resonance spectrometer.19 F NMR spectrum. Measurement temperature set to 25℃.

[0159] In measurement 19 In the 180 nm NMR spectrum, the -CF2- signal of the vinylidene fluoride (VDF) unit appears at approximately -90 ppm to -130 ppm, the -CF3 signal of the hexafluoropropylene (HFP) unit appears at approximately -68 ppm to -80 ppm, and the -CF- signal appears at approximately -180 ppm to -190 ppm. The HFP content (mol%) was obtained by calculating the -CF3 peak area, and then converted to the mass percentage (wt%) to confirm the content.

[0160] 5. Hansen's solubility parameter (HSP)

[0161] The Hansen solubility parameter is a parameter for determining the solubility of a specific substance by comprehensively considering its dispersion force, dipole-dipole interaction, and hydrogen bonding force. The Hansen solubility parameter can be expressed by the following formula.

[0162] [Mode]

[0163]

[0164] In the formula, δ T This represents the total Hansen solubility parameter, with the meanings of each item as follows: δ d δ is the dispersion parameter originating from intermolecular dispersion forces. p δ is the polar parameter originating from the interaction between permanent dipoles. h These are hydrogen bonding parameters derived from hydrogen bonds. The units for all solubility parameters are in MPa. 0.5 .

[0165] 6. Stability of oxide particles in the slurry composition

[0166] To evaluate the oxide stability of the slurry compositions prepared in the examples and comparative examples, phase changes were observed after standing at room temperature for 1 hour. If no change occurred after standing, it was rated as "good"; if gelation, precipitation, or phase separation occurred after standing, it was rated as "poor".

[0167] 7. Film-forming properties

[0168] Using a doctor blade coating method, the slurry compositions prepared in the examples and comparative examples were cast onto a polyethylene terephthalate release film. After a single drying at room temperature, a second drying was performed at 80°C under vacuum to form a porous substrate with a thickness of 20 μm. To evaluate the film-forming properties of the slurry composition, its surface condition and the mechanical and physical properties of the coating were assessed after casting.

[0169] When the coated surface is smooth and a self-supporting film can be formed after drying, it is rated as "excellent". When a self-supporting film cannot be formed or the surface is very rough and produces a large number of pores, it is rated as "poor".

[0170] [Example 1]

[0171] 1) Fabrication of porous matrix

[0172] 2g of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) (HFP 10% by weight) as a fluorine-based copolymer was added to 20g of the first solvent (tetrahydrofuran (THF)). The mixture was then dissolved at approximately 50°C for 1 hour. Subsequently, 8g of LLZTO oxide particles (Li) with an average particle size D50 of 300nm were added. 6.4 La3Zr 1.4 Ta 0.6 O 12 A slurry composition was prepared by stirring / ball milling 1.5 g of a first solvent and 1.5 g of a second solvent (dodecane) at room temperature for 24 hours. The weight ratio of the first solvent to the second solvent was 13.3:1, and the weight ratio of the fluorinated copolymer to the LLZTO oxide particles was 20:80.

[0173] The stability of the oxide particles in the prepared slurry composition was evaluated and recorded in Table 2 below.

[0174] The prepared slurry composition was cast onto a release film (polyethylene terephthalate (PET) release film) using a doctor blade coating method. It was then dried once at room temperature, followed by a second drying at 80°C under vacuum to form a porous matrix with a thickness of 20 μm. The film-forming properties and liquid electrolyte impregnation properties of the slurry composition were then evaluated and are shown in Table 2.

[0175] 2) Manufacturing of organic-inorganic composite membranes

[0176] A multifunctional monomer composition was impregnated into the porous matrix, and then thermosetting was performed at 70°C for 1 hour to obtain an organic-inorganic composite membrane with a thickness of 20 μm. The multifunctional monomer composition consisted of 94.95 wt% liquid electrolyte, 5 wt% ethoxylated trimethylolpropane triacrylate (TMPETA) monomer, and 0.05 wt% thermosetting initiator tert-butyl peroxypentanoate (t-BPP). The liquid electrolyte used was an electrolyte containing 5 wt% FEC and 1.0 M LiPF6 dissolved in a mixed solvent comprising EC / EMC at a volume ratio of 3:7.

[0177] The ionic conductivity and discharge capacity of the manufactured organic-inorganic composite membrane were evaluated and are shown in Table 3 below.

[0178] [Example 2]

[0179] The organic-inorganic composite membrane was manufactured using the same method as in Example 1, except that the fluorinated copolymer used was poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) (HFP was 15% by weight). The stability of the oxide particles in the slurry composition, the film-forming properties of the slurry composition, and the impregnation properties in the liquid electrolyte were evaluated and are shown in Table 2. Furthermore, the ionic conductivity and discharge capacity of the manufactured organic-inorganic composite membrane were evaluated and are shown in Table 3 below.

[0180] [Example 3]

[0181] The organic-inorganic composite membrane was manufactured using the same method as in Example 1, except that the fluorinated copolymer used was poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) (HFP was 25% by weight). The stability of the oxide particles in the slurry composition, the film-forming properties of the slurry composition, and the impregnation properties in the liquid electrolyte were evaluated and are shown in Table 2. Furthermore, the ionic conductivity and discharge capacity of the manufactured organic-inorganic composite membrane were evaluated and are shown in Table 3 below.

[0182] [Example 4]

[0183] The organic-inorganic composite membrane was manufactured using the same method as in Example 1, except that 5 g of fluorinated copolymer and 5 g of LLZTO oxide particles were used to adjust the solid content of the LLZTO oxide particles to 50% by weight. The stability of the oxide particles in the slurry composition, the film-forming properties of the slurry composition, and the impregnation properties in the liquid electrolyte were evaluated and are shown in Table 2. Furthermore, the ionic conductivity and discharge capacity of the manufactured organic-inorganic composite membrane were evaluated and are shown in Table 3 below.

[0184] [Example 5]

[0185] The organic-inorganic composite membrane was manufactured using the same method as in Example 1, except that 1 g of fluorinated copolymer and 9 g of LLZTO oxide particles were used to adjust the solid content of the LLZTO oxide particles to 90% by weight. The stability of the oxide particles in the slurry composition, the film-forming properties of the slurry composition, and the impregnation properties in the liquid electrolyte were evaluated and are shown in Table 2. Furthermore, the ionic conductivity and discharge capacity of the manufactured organic-inorganic composite membrane were evaluated and are shown in Table 3 below.

[0186] [Comparative Example 1]

[0187] The procedure was performed using the same method as in Example 1, except that a poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) (HFP was 5% by weight) was used as the fluorinated copolymer. The stability of the oxide particles in the slurry composition, the film-forming properties of the slurry composition, and the impregnation properties in the liquid electrolyte were evaluated and are shown in Table 2. Furthermore, the ionic conductivity and discharge capacity of the manufactured organic-inorganic composite membrane were evaluated and are shown in Table 3 below.

[0188] However, the fluorinated copolymers failed to dissolve well in the first solvent and failed to form a good film.

[0189] [Comparative Example 2]

[0190] The procedure was performed using the same method as in Example 1, except that the fluorinated copolymer used was poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)) (HFP was 35% by weight). The stability of the oxide particles in the slurry composition, the film-forming properties of the slurry composition, and the impregnation properties in the liquid electrolyte were evaluated and are shown in Table 2. Furthermore, the ionic conductivity and discharge capacity of the manufactured organic-inorganic composite membrane were evaluated and are shown in Table 3 below.

[0191] [Comparative Example 3]

[0192] The process was carried out using the same method as in Example 1, except that acetone was used as the first solvent. The stability of the oxide particles in the slurry composition, the film-forming properties of the slurry composition, and the impregnation properties with the liquid electrolyte were evaluated and are shown in Table 2. Furthermore, the ionic conductivity and discharge capacity of the manufactured organic-inorganic composite membrane were evaluated and are shown in Table 3 below.

[0193] However, the LLZTO oxide particles react with the solvent, causing the slurry composition to gel, making it impossible to manufacture a film.

[0194] [Comparative Example 4]

[0195] The procedure was performed using the same method as in Example 1, except that LLZTO oxide particles were not added. The stability of the oxide particles in the slurry composition, the film-forming properties of the slurry composition, and the impregnation properties in the liquid electrolyte were evaluated and are shown in Table 2. Furthermore, the ionic conductivity and discharge capacity of the manufactured organic-inorganic composite membrane were evaluated and are shown in Table 3 below.

[0196] [Table 1]

[0197]

[0198] Figure 1 The diagram shows the coatings obtained by casting the slurry compositions of Example 1 and Comparative Example 1 to evaluate film-forming properties. The slurry composition of Example 1 has a smooth surface after coating and good mechanical and physical properties after drying, thus forming a self-supporting film. On the other hand, in the case of Comparative Example 1, the surface is very rough, and a large number of irregular pores are observed on the surface. The slurry composition of Comparative Example 2 has a good surface condition, but its mechanical and physical properties are excessively reduced after drying, making it impossible to form a self-supporting film. Furthermore, in Comparative Example 3, the LLZTO oxide particles react with the solvent, causing the slurry composition to gel, thus preventing film formation. The mechanical and physical properties refer to tensile strength, which is evaluated by the degree to which the film can withstand manual stretching of both sides after formation. When the mechanical and physical properties are good, a self-supporting film can be formed.

[0199] The physical properties of the oxide particles, film-forming properties, and impregnation amount of the composite membranes according to Examples 1 to 5 and Comparative Example 4 were analyzed / measured and are shown in Table 2 below. However, in the cases of Comparative Examples 1 to 3, since the membrane could not be manufactured, the impregnation amount and ionic conductivity could not be measured.

[0200] Furthermore, the Hansen solubility parameter (δ) of poly(vinylidene fluoride) (P(VDF)) (HFP = 0 wt%), a fluorine-based copolymer, is 23.2 MPa. 0.5 In the above embodiments, the Hansen solubility parameter (δ) of tetrahydrofuran (THF), used as the first solvent, is 19.5 MPa. 0.5 In Hansen's solubility parameter, δ represents polarity. p 5.7 MPa 0.5 δ represents the dispersion force. d 16.8 MPa 0.5 δ represents the hydrogen bond h 8.0 MPa 0.5 Furthermore, its dipole moment is 1.75D and its dielectric constant is 7.6.

[0201] In the case of acetone used in Comparative Example 3, the Hansen solubility parameter (δ) was 20.3 MPa.0.5 But polarity (δ) p =10.4MPa 0.5 The polarity is very high, with a dipole moment of 2.88D and a dielectric constant of 20.7. This excessive polarity leads to side reactions in the oxide particles in the slurry, resulting in reduced storage stability and making it unsuitable for membrane fabrication.

[0202] [Table 2]

[0203]

[0204] As shown in Table 2 above, in Examples 1 to 5, the oxide particles exhibited good stability and excellent film-forming properties. Furthermore, experiments using octane and decane instead of dodecane in Example 1 also demonstrated good stability and excellent film-forming properties of the oxide particles, and the liquid electrolyte impregnation amount showed similar values ​​to that in Example 1.

[0205] Based on the above results, it can be confirmed that the combination of a fluorinated copolymer containing 10-25% by weight of repeating units derived from hexafluoropropylene and a specific solvent results in excellent dispersibility of oxide particles and suppression of side reactions, thus exhibiting excellent stability. Furthermore, it can be confirmed that a two-step drying process using two solvents with different polarities and boiling points can form uniform micropores and lithium-ion flow channels within the composite membrane, resulting in uniform electrolyte distribution, promoting active lithium-ion migration, and achieving high ionic conductivity.

[0206] Coin-shaped batteries were manufactured using the composite films prepared according to Examples 1 to 5 and Comparative Example 4. The ionic conductivity and discharge capacity of the manufactured coin-shaped batteries were evaluated and are shown in Table 3 below.

[0207] [Table 3]

[0208]

[0209] As shown in Table 3 above, compared with the comparative examples, the battery comprising the organic-inorganic composite electrolyte according to an embodiment of the present invention exhibits a very high discharge capacity even at high rates, and the percentage (%) of discharge capacity at 2C relative to discharge capacity at 0.1C is superior. Specifically, in the organic-inorganic composite membranes according to Examples 1 to 5, by using a combination of a fluorinated copolymer with an HFP content of 10-25% by weight and a specific solvent, the side reactions of lithium-lanthanum-zirconium-based oxide particles are effectively suppressed, and the fluorinated copolymer with an HFP content of 10-25% by weight has excellent solubility, thereby enabling the fabrication of a matrix with uniformly dispersed oxide particles. Furthermore, through a two-step drying process, micropores are uniformly formed, thereby activating lithium-ion transport of the electrolyte filling the pores, thus exhibiting superior high-rate characteristics and more stable charge-discharge performance compared to the comparative examples.

[0210] Therefore, it can be confirmed that when a lithium secondary battery is manufactured by including an organic-inorganic composite film according to one embodiment, significantly improved lifespan and high rate performance can be achieved.

[0211] Therefore, according to a specific embodiment, the organic-inorganic composite membrane is manufactured by the following method: a porous matrix with uniform micropores is formed from a slurry composition comprising a first solvent satisfying the above conditions, a second solvent, a fluorine-based copolymer having a specific HFP content, and a lithium-lanthanum-zirconium-based oxide; and a polymer electrolyte containing a lithium salt is filled into the pores of the porous matrix to manufacture the organic-inorganic composite membrane. This allows for the formation of a self-supporting membrane and minimizes side reactions between the solvent and the lithium-lanthanum-zirconium-based oxide, thus achieving a significant improvement in ionic conductivity. Furthermore, it has been confirmed that when a lithium secondary battery is manufactured using an organic-inorganic composite electrolyte including the aforementioned organic-inorganic composite membrane, it can exhibit superior lifespan and high-rate characteristics compared to existing lithium secondary batteries.

[0212] As described above, this invention has been illustrated with specific content and limited embodiments, but this is only provided to help to understand the invention more fully. The invention is not limited to the above embodiments, and those skilled in the art can make various modifications and variations based on these descriptions.

[0213] Therefore, the present invention should not be limited to the embodiments described above, and all contents that are equivalent to or have equivalent variations of the claims are within the scope of the present invention.

Claims

1. An organic-inorganic composite membrane for secondary batteries, comprising: A porous matrix comprising a fluorine-based copolymer and lithium-lanthanum-zirconium-based oxide particles; and A cross-linked network polymer electrolyte, wherein the cross-linked network polymer electrolyte fills at least one pore of the porous matrix. in, The fluoropolymer contains 10-25% by weight of repeating units derived from hexafluoropropylene.

2. The organic-inorganic composite membrane for secondary batteries according to claim 1, wherein, The fluorinated copolymer is polyvinylidene fluoride-hexafluoropropylene.

3. The organic-inorganic composite membrane for secondary batteries according to claim 1, wherein, The content of the fluorinated copolymer is 10-60% by weight relative to the total weight of the porous matrix.

4. The organic-inorganic composite membrane for secondary batteries according to claim 1, wherein, The lithium-lanthanum-zirconium-based oxide particles are represented by the following chemical formula 1. [Chemical Formula 1] Lie down x I 1a I 2b Go away. y Zr z I 3c Oh 12 In the chemical formula 1, 5≤x≤9, 0≤a≤4, 0≤b≤4, 2≤y≤4, 1≤z≤3, 0≤c≤4 M1 to M3 are each independently selected from any one of the elements selected from Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Co, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, and Sn.

5. The organic-inorganic composite membrane for secondary batteries according to claim 1, wherein, The content of the lithium-lanthanum-zirconium-based oxide particles is 40-90% by weight relative to the total weight of the porous matrix.

6. The organic-inorganic composite membrane for secondary batteries according to claim 1, wherein, The porous matrix consists of a continuous phase containing fluorine-based copolymers and a dispersed phase containing lithium-lanthanum-zirconium-based oxide particles.

7. The organic-inorganic composite membrane for secondary batteries according to claim 1, wherein, The cross-linked network polymer electrolyte comprises an acrylic polymer and a lithium salt.

8. The organic-inorganic composite membrane for secondary batteries according to claim 1, wherein, The content of the cross-linked network polymer electrolyte is 10-80 parts by weight relative to 100 parts by weight of the porous matrix.

9. A slurry composition for manufacturing an organic-inorganic composite membrane, comprising a fluorine-based copolymer, lithium-lanthanum-zirconium-based oxide particles, a first solvent, and a second solvent. in, The fluoropolymer contains 10-25% by weight repeating units derived from hexafluoropropylene. The polarity of the second solvent is lower than that of the first solvent.

10. The slurry composition for manufacturing organic-inorganic composite membranes according to claim 9, wherein, The Hansen solubility parameter δ of the first solvent Ts1 18-25MPa 0.5 .

11. The slurry composition for manufacturing organic-inorganic composite membranes according to claim 9, wherein, The difference in Hansen solubility parameters between the first solvent and the fluorinated copolymer is 1 MPa. 0.5 Above and below 15.0 MPa 0.5 .

12. The slurry composition for manufacturing organic-inorganic composite membranes according to claim 9, wherein, The Hansen solubility parameter δ of the second solvent Ts2 17MPa 0.5 the following.

13. The slurry composition for manufacturing organic-inorganic composite membranes according to claim 9, wherein, The dipole moments of the first solvent and the second solvent are less than 2.8 Debye (D) and the dielectric constant is less than 20.

14. The slurry composition for manufacturing organic-inorganic composite membranes according to claim 9, wherein, The content ratio of the first solvent to the second solvent is satisfied with a weight ratio of 5 to 50:

1.

15. A method for manufacturing an organic-inorganic composite membrane for secondary batteries, comprising the following steps: (S1) Prepare an organic-inorganic composite membrane manufacturing slurry composition comprising a fluorine-based copolymer, lithium-lanthanum-zirconium-based oxide particles, a first solvent and a second solvent; (S2) Coating and drying the slurry composition to form a porous matrix; and (S3) Impregnate the multifunctional monomer composition into the porous matrix and cure it to form a cross-linked network polymer electrolyte. The fluorinated copolymer contains 10-25% by weight of repeating units derived from hexafluoropropylene.

16. The method for manufacturing an organic-inorganic composite membrane for secondary batteries according to claim 15, wherein, Step (S1) includes the following steps: (a) Dissolving the fluorinated copolymer in a first solvent; and (b) Add lithium-lanthanum-zirconium-based oxide particles and a second solvent and mix.

17. The method for manufacturing an organic-inorganic composite membrane for secondary batteries according to claim 15, wherein, Step (S2) includes the following steps: The first solvent in the slurry composition is dried at a first drying temperature; and The second solvent in the slurry composition is dried at a second drying temperature.

18. The method for manufacturing an organic-inorganic composite membrane for secondary batteries according to claim 17, wherein, The second drying temperature is higher than the first drying temperature.

19. The method for manufacturing an organic-inorganic composite membrane for secondary batteries according to claim 15, wherein, The multifunctional monomer composition comprises a multifunctional acrylic monomer, an initiator, and a lithium salt.

20. A lithium secondary battery comprising an organic-inorganic composite membrane for secondary batteries according to any one of claims 1 to 8.

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