Solid electrolyte membrane, preparation method thereof, and all-solid rechargeable batteries

Abstract

The present invention relates to a solid electrolyte membrane, a preparation method thereof, and all-solid rechargeable batteries, wherein the solid electrolyte membrane comprises: a core containing a composite and a solid electrolyte, the composite including diamagnetic particles; an insulating layer enclosing the core; and a shell enclosing the insulating layer and containing a solid electrolyte.

Description

Solid electrolyte membrane, method for manufacturing the same, and all-solid-state secondary battery

[0001] The present invention relates to a solid electrolyte membrane, a method for manufacturing the same, and an all-solid-state secondary battery including the same.

[0002] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium-ion batteries are being commercialized not only in information and communication devices, but also in the automotive sector.

[0003] Lithium-ion batteries currently on the market utilize electrolytes, which contain flammable organic dispersions. Therefore, if a short circuit occurs within the battery, overheating and fire are possible. Consequently, all-solid-state secondary batteries using solid electrolytes are being proposed.

[0004] According to one embodiment, a solid electrolyte membrane and an all-solid-state secondary battery capable of improving high-rate characteristics while improving ionic conductivity are provided.

[0005] In one embodiment, a solid electrolyte membrane is provided, comprising a complex and a solid electrolyte, wherein the complex comprises a core including diamagnetic particles; an insulating layer surrounding the core; and a shell surrounding the insulating layer and including a solid electrolyte.

[0006] In another embodiment, an all-solid-state secondary battery is provided, comprising: a positive electrode layer; a negative electrode layer; and the above-described solid electrolyte membrane positioned between the positive electrode layer and the negative electrode layer.

[0007] In another embodiment, a method for producing a solid electrolyte membrane is provided, comprising obtaining a composite including a core including diamagnetic particles, an insulating layer surrounding the core, and a shell surrounding the insulating layer and including a solid electrolyte, preparing a slurry for forming an electrolyte membrane including the composite and the solid electrolyte, and applying the slurry for forming an electrolyte membrane onto a substrate.

[0008] A solid electrolyte membrane according to one embodiment can shorten the lithium ion movement path within the electrolyte membrane and reduce the interfacial contact resistance between electrolytes.

[0009] An all-solid-state secondary battery according to one embodiment can have improved ion conductivity and improved high-rate characteristics.

[0010] Figures 1 and 2 are cross-sectional views schematically showing a complex (1) according to one embodiment.

[0011] Figure 3 is a schematic diagram showing a solid electrolyte membrane (300) according to one embodiment.

[0012] Figure 4 is a perspective view schematically showing a solid electrolyte membrane (300) according to one embodiment.

[0013] Figure 5 is a cross-sectional view schematically showing a solid electrolyte membrane (300) according to one embodiment.

[0014] Figures 6 and 7 are cross-sectional views schematically showing an all-solid-state secondary battery (100) according to one embodiment.

[0015] Below, specific implementation examples are described in detail so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in various different forms and is not limited to the implementation examples described herein.

[0016] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0017] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0018] It should be understood that the terms "include," "comprise," or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0019] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there is another element in between. Conversely, when an element is said to be "directly over" another element, it means that there is no other element in between.

[0020] “Layer” includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on some surfaces.

[0021] “Particle size” or “average particle size” can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope or a scanning electron microscope. Alternatively, the average particle size can be obtained by measuring using dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Unless otherwise defined, the average particle size is the diameter (D) of the particles in the particle size distribution that have a cumulative volume of 50% by volume. 50 ) can mean. In addition, unless otherwise defined, the average particle size is obtained by measuring the size (diameter or length of major axis) of about 20 particles randomly in a scanning electron microscope image to obtain a particle size distribution, and the diameter (D) of the particle having a cumulative volume of 50% by volume in the particle size distribution 50) may be taken as the average particle diameter.

[0022] “Thickness” may be measured, for example, from photographs taken with an electron microscope, such as a scanning electron microscope.

[0023] “Or” is not interpreted as exclusive, for example, “A or B” is interpreted as including A, B, A+B, etc.

[0024] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0025] solid electrolyte membrane

[0026] In one embodiment, a solid electrolyte membrane is provided, comprising a complex and a solid electrolyte, wherein the complex comprises a core including diamagnetic particles; an insulating layer surrounding the core; and a shell surrounding the insulating layer and including a solid electrolyte.

[0027] FIG. 1 and FIG. 2 are cross-sectional views schematically showing a complex (1) included in a solid electrolyte membrane (300) according to one embodiment, FIG. 3 is a diagram schematically showing a solid electrolyte membrane (300) according to one embodiment, FIG. 4 and FIG. 5 are a perspective view and a cross-sectional view schematically showing a solid electrolyte membrane (300) according to one embodiment, respectively, and FIG. 6 and FIG. 7 are cross-sectional views schematically showing an all-solid-state secondary battery (100) including a solid electrolyte membrane (300) according to one embodiment.

[0028] All-solid-state secondary batteries significantly reduce the risk of fire or explosion even in the event of a short circuit by not using flammable organic dispersion media, thereby significantly improving safety compared to lithium-ion batteries. However, solid electrolytes have the problem of lower lithium ion conductivity compared to liquid electrolytes. To shorten the ion migration path within the electrode plates of all-solid-state batteries, methods include forming pores and filling them with a solid electrolyte, or adding additives that increase lithium ion conductivity. However, when forming pores and filling them with a solid electrolyte, there are limitations in filling the pores completely with the solid electrolyte. Even when adding additives that increase ion conductivity, there are limitations in the selection of additives because side reactions may occur between the solid electrolyte and the additive, or the additives may affect the properties of the slurry used to form the electrode layer.

[0029] In order to shorten the movement path of lithium ions in a solid electrolyte membrane, a method of using a composite in the solid electrolyte membrane, in which the solid electrolyte itself has a core-shell structure, the core including diamagnetic particles, and the shell including a solid electrolyte, can be considered. However, since the composite can have electrical conductivity on its own by having a core including diamagnetic particles, there is a risk of internal short circuits occurring in the cell if it is used as is in the solid electrolyte membrane. Therefore, in one embodiment, a solid electrolyte membrane including a composite capable of shortening the movement path of lithium ions while suppressing the possibility of internal short circuits occurring in the cell is proposed.

[0030] According to one embodiment, the complex (1) has a core-shell structure having a core (1a) including diamagnetic particles and a shell (1c) including a solid electrolyte, as illustrated in FIGS. 1 to 3, in order to shorten the movement path of lithium ions (4) within a solid electrolyte membrane (300). In addition, in order to reduce the risk of an internal short circuit of a cell that may occur due to the use of the core (1a) including diamagnetic particles, an insulating layer (1b) surrounding the core is provided between the aforementioned core (1a) and shell (1c). Through this, ion conductivity and high-rate characteristics can be secured through the shortening of the movement path of lithium ions (4), while preventing an internal short circuit of the cell. In addition, since the internal short circuit of the cell can be suppressed even if the solid electrolyte membrane (300) itself is not designed as a multilayer by including an insulating layer (1b) between the core (1a) and the shell (1c), the manufacturing of a thinner solid electrolyte membrane becomes possible and the manufacturing process can also be facilitated.

[0031] According to one embodiment, in order to further improve the ion conductivity and high-rate characteristics of the all-solid-state secondary battery, the complex itself within the solid electrolyte membrane can be made non-spherical, as shown in FIG. 2.

[0032] Alternatively, the complex can be formed into a non-spherical shape within the solid electrolyte membrane, and the complex can be oriented in a direction perpendicular to or close to the plane direction of the solid electrolyte membrane. In a general method of forming a solid electrolyte membrane (300) by applying a slurry for forming a solid electrolyte membrane including the aforementioned non-spherical complex onto a substrate, the non-spherical complex is only randomly distributed within the solid electrolyte membrane (300). That is, in order to align the non-spherical complex within the solid electrolyte membrane (300) in a direction close to the plane direction of the solid electrolyte membrane, a method of applying a slurry for forming a solid electrolyte membrane including the non-spherical complex onto a substrate and then applying a magnetic field can be considered. Here, the reason why the orientation of the complex is controlled by the magnetic field is because the non-spherical complex has a diamagnetic property. Among the currently known solid electrolytes, since they do not exhibit diamagnetic properties, in one embodiment, as shown in FIGS. 1 and 2, the orientation of the complex (1) within the solid electrolyte membrane (300) can be controlled by using a complex (1) having a core (1a) including non-spherical diamagnetic particles. For example, by orienting the complex (1) described above in a direction close to the plane direction of the solid electrolyte membrane (300), the movement path of lithium ions within the solid electrolyte membrane can be shortened, and the interfacial contact resistance between the solid electrolytes can be reduced. An all-solid-state secondary battery (100) including such a solid electrolyte membrane (300) can have improved ion conductivity and enhanced high-rate characteristics.

[0033] Hereinafter, the elements constituting the solid electrolyte membrane (300) according to one embodiment will be described in more detail.

[0034] complex

[0035] As shown in FIGS. 1 and 2, the complex (1) includes a core (1a) including diamagnetic particles; an insulating layer (1b) surrounding the core; and a shell (1c) surrounding the insulating layer and including a solid electrolyte. That is, the complex (1) has a core-shell structure, and includes a core (1a) including diamagnetic particles, a shell (1c) including a solid electrolyte, and at the same time, an insulating layer (1b) between the aforementioned core (1a) and shell (1c).

[0036] According to one embodiment, in the complex (1), the core (1a) (or the diamagnetic particle included in the core) may be non-spherical. The core (1a) may have an aspect ratio greater than 1, as expressed by the following mathematical formula 1. Here, in the following mathematical formula 1, the units of the major axis length and the minor axis length need only be identical, and therefore are not particularly limited.

[0037] [Mathematical Formula 1]

[0038] Aspect ratio = length of major axis / length of minor axis

[0039] In the above mathematical expression 1, the length of the major axis and the length of the minor axis represent values ​​for the core (1a). Such non-spherical diamagnetic particles and the composite (1) including the same can be oriented in a direction perpendicular to or close to the perpendicular direction (for example, 50 to 130° with respect to the surface direction (X) of the solid electrolyte membrane (300)) with respect to the surface direction of the solid electrolyte membrane by an externally applied magnetic field. Here, the surface direction (X) of the solid electrolyte membrane (300) refers to a direction parallel to the surface of the wide side of the solid electrolyte membrane. Fig. 4 illustrates a perspective view of the solid electrolyte membrane (300) and the surface direction (X) of the solid electrolyte membrane (300) described above. In addition, a cross-sectional view in the thickness direction of the solid electrolyte membrane (300) is shown in Fig. 5, and the surface direction (X) of the solid electrolyte membrane (300) and the direction (Y) perpendicular to the surface direction (X) are each drawn as lines.

[0040] As the aspect ratio represented by the above mathematical formula 1 increases, the performance of the all-solid-state secondary battery including the solid electrolyte membrane according to one embodiment can be improved. For example, the aspect ratio represented by the above mathematical formula 1 may be 1.1 or more, 1.2 or more, 1.3 or more, 1.5 or more, 2 or more, or 3 or more. The upper limit of the aspect ratio represented by the above mathematical formula 1 may not be particularly limited, but may be 5,000 or less, 300 or less, 100 or less, 50 or less, 20 or less, or 10 or less in consideration of convenience in the manufacturing process and cost reduction effect. For example, the aspect ratio of the core (1a) may be 1.1 to 20, or 1.5 to 10, etc.

[0041] According to one embodiment, the length of the major axis of the complex may be from 1 μm to 50 μm, or the length of the minor axis of the complex may be from 0.01 μm to 5 μm. Alternatively, the aspect ratio, which is the ratio of the length of the major axis to the length of the minor axis of the complex, may be greater than 1.

[0042] According to one embodiment, the complex may be included in an amount of 0.1 wt% to 50 wt% relative to 100 wt% of the solid electrolyte membrane.

[0043] According to one embodiment, in the complex (1), the insulating layer (1b) may be formed with a uniform thickness or may be formed unevenly. Alternatively, the shell (1c) may also be formed with a uniform thickness or may be formed unevenly.

[0044] According to one embodiment, the complex (1) can satisfy the following mathematical formula 2 or the following mathematical formula 3, or can satisfy both the following mathematical formulas 2 and 3. In this range, the complex (1) can be effectively oriented so that its long axis is perpendicular to or close to the perpendicular direction to the plane direction of the solid electrolyte membrane by an externally applied magnetic field. Here, in the following mathematical formulas 2 and 3, since the units of the numerator and denominator only need to be identical to each other, the units of A1, A2, and C are not particularly limited.

[0045] [Equation 2]

[0046] 0.1 ≤ A1 / C ≤ 100

[0047] [Equation 3]

[0048] 0.01 ≤ A2 / C ≤ 10

[0049] In the above mathematical expressions 2 and 3, A1 represents the major axis length of the core (1a), A2 represents the minor axis length of the core (1a), and C represents the thickness of the shell (1c).

[0050] Alternatively, the complex (1) can satisfy the following mathematical formula 4. In this range, the orientation effect by the core (1a) of the complex (1), the internal short-circuit suppression effect by the insulating layer (1b), and the lithium ion conduction effect by the shell (1c) can be harmonized. Here, in the following mathematical formula 4, the units of the numerator and denominator only need to be identical, so the units of A1, B, and C are not particularly limited.

[0051] [Mathematical Formula 4] 0.05 ≤ A1 / (B + C) ≤ 500

[0052] In the above mathematical expression 4, the definitions of A1 and C are as described above, and B represents the thickness of the insulating layer (1b).

[0053] According to one embodiment, the major axis length of the core (1a) may be 1 μm to 50 μm, 1 μm to 20 μm, 2 μm to 15 μm, or 3 μm to 12 μm. Alternatively, the minor axis length of the core (1a) may be 10 nm to 5 μm, 100 nm to 5 μm, or 1 μm to 4 μm. Alternatively, the thickness of the shell (1c) may be 10 nm to 10 μm, 100 nm to 5 μm, or 1 μm to 3 μm. The thickness of the insulating layer (1b) may be 10 nm to 10 μm, 100 nm to 5 μm, or 1 μm to 3 μm. In this range, the orientation effect by the core (1a), the internal short-circuit suppression effect by the insulating layer (1b), and the lithium ion conduction effect by the shell (1c) can be harmonized. Meanwhile, the major axis length of the core (1a), the minor axis length of the core (1a), the thickness of the shell (1c), and the thickness of the insulating layer (1b) mean average values. As for the measuring method of the major axis length of the core (1a), the minor axis length of the core (1a), the thickness of the shell (1c), and the thickness of the insulating layer (1b), for example, after obtaining a cross-sectional specimen by cutting the solid electrolyte membrane (300) as in Fig. 5, the composite (1) existing in the solid electrolyte membrane (300) can be measured by photographing it with a scanning electron microscope (SEM) so that it can be observed. In other words, for any 10 complexes (1) present in one cross-sectional specimen, the major axis length of each core (1a), the minor axis length of the core (1a), the thickness of the insulating layer (1b), and the thickness of the shell (1c) can be measured and then the average value can be calculated.

[0054] Alternatively, the weight ratio of the core (1a) and the shell (1c) in the complex (1) may be 1:1 to 1:500, 1:2 to 1:100, or 1:10 to 1:50. In this range, the orientation effect by the core (1a), the internal short-circuit suppression effect by the insulating layer (1b), and the lithium ion conduction effect by the shell (1c) can be harmonized.

[0055] According to one embodiment, the long axis of the complex (1) within the solid electrolyte membrane (300) can be oriented in a direction (Y) perpendicular to or close to the direction (Y) perpendicular to the plane direction (X) of the solid electrolyte membrane (300). The orientation angle that the long axis of the complex (1) forms with the plane direction (X) of the solid electrolyte membrane (300) can be obtained by measuring the angle that the long axis of the complex (1) forms with the plane direction (X) of the solid electrolyte membrane in the cross-section of the solid electrolyte membrane (300) based on the plane direction (X) of the solid electrolyte membrane (in the cross-sectional view of the solid electrolyte membrane, the plane direction of the solid electrolyte membrane is indicated by a line as X in FIG. 5) as shown in FIG. 4.

[0056] For example, the long axis of the complex (1) within the solid electrolyte membrane (300) may be oriented in a range of 50° to 130° with respect to the plane direction (X) of the solid electrolyte membrane (300), or in a range of 70° to 110°, or in a range of 85° to 95°, or in a substantially vertical (90°) direction (Y). In this range, the lithium ion migration path within the solid electrolyte membrane can be shortened, and the interfacial contact resistance between the solid electrolytes can be reduced.

[0057] In the composite (1), the shape of the diamagnetic particle of the core (1a) is not particularly limited as long as it is non-spherical and has an aspect ratio greater than 1 as expressed by the above mathematical formula 1. For example, the core (1a) may include a diamagnetic particle having a needle-shaped, plate-shaped, or oval shape. Alternatively, the core (1a) may include a carbon-based material selected from among artificial graphite, natural graphite, graphene, carbon nanotubes (CNTs), L-carbon nanotubes (Long length CNTs), carbon fibers, carbon black, or a combination thereof as the diamagnetic particle.

[0058] According to one embodiment, the insulating layer (1b) may include an insulating material. As the insulating material, any material known to have insulating properties may be used without limitation. Representative examples include polymers, and the polymer may include at least one selected from polyethylene oxide (PEO), hydrogenated nitrile butadiene rubber (HNBR), styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), or a combination thereof. By including the polymer in the insulating layer (1b), the orientation effect by the core (1c) of the composite (1) can be secured, while effectively suppressing internal short circuits of the all-solid-state secondary battery.

[0059] Alternatively, in the complex (1), the weight ratio of the core and the insulating layer may be 1:0.01 to 1:50, or 1:0.01 to 1:10, 1:0.05 to 1:5, or 1:0.08 to 1:1. In this range, the orientation effect by the core and the effect of suppressing the occurrence of internal short circuit by the insulating layer can be harmonized.

[0060] In addition, in the complex (1), the shell (1c) may include a solid electrolyte commonly known in the art. For example, the shell may include a solid electrolyte selected from a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof, and the following description is equally applicable to this.

[0061] As a representative example, the solid electrolyte included in the shell (1c) may include a sulfide-based solid electrolyte, and the shell (1c) of the complex (1) may include Li6PS5Cl, which is a type of argyrodite-type sulfide-based solid electrolyte.

[0062] Meanwhile, the content of the complex (1) may be 0.1 wt% to 50 wt%, 0.5 wt% to 20 wt%, or 1 wt% to 10 wt% relative to the total weight of the solid electrolyte membrane (300). In this range, the improvement effect of ion conductivity and high-rate characteristics according to the complex (1) can be further enhanced.

[0063] solid electrolyte

[0064] In addition to the composite (1), the solid electrolyte membrane (300) essentially includes a solid electrolyte (2). By including the solid electrolyte, the ionic conductivity of the solid electrolyte membrane can be secured. The solid electrolyte may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof. The aforementioned solid electrolytes are described below.

[0065] Sulfide-based solid electrolyte

[0066] Sulfide-based solid electrolytes include, for example, Li2S-P2S5, Li2S-P2S5-LiX (where X is a halogen element, for example, I or Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z. m S n (m, n are integers, Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are integers, and M is P, Si, Ge, B, Al, Ga or In), or a combination thereof.

[0067] Alternatively, the sulfide-based solid electrolyte can be obtained by, for example, mixing Li2S and P2S5 in a molar ratio of 50:50 to 90:10, or a molar ratio of 50:50 to 80:20, and optionally heat-treating the mixture. Within the above mixing ratio range, a sulfide-based solid electrolyte having excellent ionic conductivity can be produced. Here, the ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0068] Methods for mixing sulfur-containing raw materials for producing sulfide-based solid electrolytes include mechanical milling or the solution method. Mechanical milling involves placing raw materials in a ball mill reactor and vigorously stirring them to finely atomize and mix them. Using the solution method, the raw materials are mixed in a solvent to obtain a solid electrolyte as a precipitate. Furthermore, heat treatment after mixing can solidify the crystals of the solid electrolyte and improve ionic conductivity. For example, a sulfide-based solid electrolyte can be produced by mixing sulfur-containing raw materials and heat-treating them twice or more, resulting in a sulfide-based solid electrolyte with high ionic conductivity and robustness.

[0069] According to one embodiment, a sulfide-based solid electrolyte particle can be manufactured through, for example, a first heat treatment in which sulfur-containing raw materials are mixed and calcined at 120°C to 350°C, and a second heat treatment in which the results of the first heat treatment are mixed and calcined at 350°C to 800°C. The first heat treatment and the second heat treatment can each be performed in an inert gas or nitrogen atmosphere. The first heat treatment can be performed for 1 to 10 hours, and the second heat treatment can be performed for 5 to 20 hours. The first heat treatment can have the effect of milling small raw materials, and the second heat treatment can synthesize the final solid electrolyte. Through two or more such heat treatments, a high-performance sulfide-based solid electrolyte with high ionic conductivity and durability can be obtained, and such a solid electrolyte can be said to be suitable for mass production. The temperature of the first heat treatment may be, for example, 150°C to 330°C, or 200°C to 300°C, and the temperature of the second heat treatment may be, for example, 380°C to 700°C, or 400°C to 600°C.

[0070] For example, the sulfide-based solid electrolyte particles may include argyrodite-type sulfides. The argyrodite-type sulfide-based solid electrolyte particles may have an ionic conductivity of 10, which is the ionic conductivity of a typical liquid electrolyte at room temperature. -4 10 inland -2 It has a high ionic conductivity approaching the S / cm range, can form a close bond between a positive electrode active material and a solid electrolyte without causing a decrease in ionic conductivity, and can further form a close interface between an electrode layer and a solid electrolyte membrane. An all-solid-state secondary battery including this can have improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0071] The argyrodite-type sulfide-based solid electrolyte particles may include, for example, a compound represented by the following chemical formula 11.

[0072] [Chemical Formula 11]

[0073] (Li a M 1 b M 2 c )(P d M 3 e )(S f M 4 g )X h

[0074] In the above chemical formula 11, 4≤a≤8, and M 1 is Mg, Cu, Ag, or a combination thereof, and 0≤b<0.5, and M 2 is Na, K, or a combination thereof, 0≤c<0.5, and M 3 is Sn, Zn, Si, Sb, Ge, or a combination thereof, and 0 <d<4, 0≤e<1 이고, M 4 is O, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤12, 0≤g<2, and X is F, Cl, Br, I, or a combination thereof, and 0≤h≤2.

[0075] For example, in chemical formula 11, a halide element (X) may be included as an essential element, in which case 0 <h≤2로 표시될 수 있다. 일 예로 화학식 11에 M 1 Elements may be required, in which case 0 <b<0.5로 표시될 수 있다. 화학식 11에서 M 3 can be understood as an element substituted in place of P and 0 <e<1일 수 있다. 화학식 11에서 M 4 is substituted in the S position, for example, 0 <g<2일 수 있으며 S의 비율인 f는 예를 들어 3≤f≤7일 수 있다. M 4 Go SO n If SO n It can be, for example, S4O6, S3O6, S2O3, S2O4, S2O5, S2O6, S2O7, S2O8, SO4, or SO5, and can be, for example, SO4.

[0076] For example, in chemical formula 11, a+b+c+h=7, d+e=1, and f+g+h=6.

[0077] As a specific example, argyrodite-type sulfide-based solid electrolyte particles include Li3PS4 and Li7P3S. 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 , Li 5.75 PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )PS 4.75 Cl 1.25 , (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.70 (SO4) 0.05 )Cl 1.25 , (Li 5.69 Cu0.06 )P(S 4.60 (SO4) 0.15 )Cl 1.25 , (Li 5.72 Cu 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , (Li 5.72 Na 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , Li 5.75 P(S 4.725 (SO4) 0.025 )Cl 1.25 , or combinations thereof, but are not limited thereto.

[0078] An argyrodite-type sulfide-based solid electrolyte can be manufactured, for example, by mixing lithium sulfide and phosphorus sulfide, optionally a lithium halide. After mixing these, a heat treatment may be performed. The heat treatment may include, for example, two or more heat treatment processes. Here, manufacturing an argyrodite-type sulfide-based solid electrolyte may include, for example, a first heat treatment of mixing raw materials and calcining at 120°C to 350°C, and a second heat treatment of mixing the resultant of the first heat treatment again and calcining at 350°C to 800°C.

[0079] Average particle diameter (D) of sulfide-based solid electrolyte particles 50 ) may be, for example, 0.1 ㎛ to 5.0 ㎛ or 0.1 ㎛ to 3.0 ㎛, may be small particles of 0.1 ㎛ to 1.9 ㎛, or may be large particles of 2.0 ㎛ to 5.0 ㎛. The sulfide-based solid electrolyte particles may be a mixture of small particles having an average particle diameter of 0.1 ㎛ to 1.9 ㎛ and large particles having an average particle diameter of 2.0 ㎛ to 5.0 ㎛. The average particle diameter of the sulfide-based solid electrolyte particles may be measured by an electron microscope image, and for example, a particle size distribution is obtained by measuring the size (diameter or major axis length) of about 20 particles in a scanning electron microscope image, where D50 It may have been calculated.

[0080] Oxide-based solid electrolyte

[0081] Oxide-based solid electrolytes include, for example, Li 1+x Ti 2-x Al(PO4)3(LTAP)(0≤x≤4), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 <x<2, 0≤y<3), BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0≤x<1, 0≤y<1), PB(Mg3Nb 2 / 3 )O3-PbTiO3(PMN-PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0 <x<2, 0<y<3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0≤x≤1, 0≤y≤1), lithium lanthanum titanate (Li x La y TiO3, 0 <x<2, 0<y<3), Li2O, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2계 세라믹스, 가넷(Garnet)계 세라믹스 Li 3+x La3M2O 12 (M= Te, Nb, or Zr; x is an integer from 1 to 10), or mixtures thereof.

[0082] Halide-based solid electrolyte

[0083] The solid electrolyte membrane may include, for example, a halide-based solid electrolyte. The halide-based solid electrolyte contains a halogen element as a main component, and may mean that the ratio of the halide element to all elements constituting the solid electrolyte is 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. For example, the halide-based solid electrolyte may not contain a sulfur element.

[0084] The halide-based solid electrolyte may contain lithium element, a metal element other than lithium, and a halogen element. The metal element other than lithium may be Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof. The halogen element may be F, Cl, Br, I, or a combination thereof, and may be Cl, Br, or a combination thereof. The halide-based solid electrolyte may contain, for example, Li a M1X6 (M is Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof, X is F, Cl, Br, I, or a combination thereof, and 2≤a≤3) can be represented. The halide-based solid electrolyte is, for example, Li2ZrCl6, Li 2.7 Y 0.7 Zr 0.3 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 In 0.5 Zr 0.5 Cl6, Li2In 0.5 Zr 0.5 Cl6, Li3YBr6, Li3YCl6, Li3YBr2Cl4, Li3YbCl6, Li 2.6 Hf 0.4 Yb 0.6Cl6, or combinations thereof, but is not limited thereto.

[0085] The solid electrolyte (2) included in the solid electrolyte membrane (300) may be the same as or different from the solid electrolyte included in the shell (1c) of the complex (1). For example, the shell (1c) of the complex (1) and the solid electrolyte (2) included in the solid electrolyte membrane (300) may each include an argyrodite-type sulfide-based solid electrolyte.

[0086] The content of the solid electrolyte (2) included in the solid electrolyte membrane (300) (excluding the solid electrolyte included in the shell (1c) of the composite (1)) may be 50 wt% to 99.9 wt% relative to the total weight of the solid electrolyte membrane (300), and may be, for example, 80 wt% to 99.9 wt%, 90 wt% to 99.5 wt%, 95 wt% to 98 wt%, or 96 wt% to 97 wt%.

[0087] The solid electrolyte (2) included in the solid electrolyte membrane (300) may be in the form of particles and its average particle diameter (D 50 ) may be 0.1 ㎛ to 5.0 ㎛, 0.5 ㎛ to 5.0 ㎛, 0.5 ㎛ to 4.0 ㎛, 0.5 ㎛ to 3.0 ㎛, 0.5 ㎛ to 2.0 ㎛, or 0.5 ㎛ to 1.0 ㎛. The average particle diameter of the solid electrolyte particles may be measured by an SEM image, and for example, the particle size distribution is obtained by measuring the size (diameter or length of the major axis) of about 20 particles in the SEM image, where D 50 It may have been calculated.

[0088] bookbinder

[0089] In addition, the solid electrolyte membrane may further include a binder as an optional component. The binder serves to ensure that the composite (1) particles and the solid electrolyte (2) particles adhere well to each other. Such binders include, for example, nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, natural rubber, polydimethylsiloxane, polyethylene oxide, polyvinylpyrrolidone, polyvinylpyridine, chlorosulfonated polyethylene, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, polyamideimide, polyimide, acrylic resin, poly(meth)acrylate, polyacrylonitrile, polystyrene, It may include polyurethanes, copolymers thereof, or combinations thereof.

[0090] The above binder may be included in an amount of 0.1 wt% to 3 wt% relative to the total weight of the solid electrolyte membrane (300), for example, 0.5 wt% to 2 wt%, or 0.5 wt% to 1.5 wt%. When the binder is included in the above range, the components within the solid electrolyte membrane can be well combined without lowering the ionic conductivity of the solid electrolyte, thereby improving the durability and reliability of the battery.

[0091] Other ingredients

[0092] The solid electrolyte membrane may optionally further include one or more other components selected from the group consisting of alkali metal salts, ionic liquids, and conductive polymers.

[0093] The alkali metal salt may be, for example, a lithium salt. The content of the lithium salt in the solid electrolyte membrane may be 1 M or more, for example, 1 M to 4 M. In this case, the lithium salt may improve ion conductivity by enhancing the lithium ion mobility of the solid electrolyte membrane.

[0094] The lithium salt may be applied without limitation on type, and may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiSCN, LiN(CN)2, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, or a combination thereof.

[0095] For example, the lithium salt may be an imide-based lithium salt such as LiTFSI, LiFSI, LiBETI, or a combination thereof. The imide-based lithium salt can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0096] Ionic liquids are salts or molten salts that are composed only of ions and are liquid at room temperature, with a melting point below room temperature.

[0097] The ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, trizolium, and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6- , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br - , I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may be a compound containing one or more anions selected from among:

[0098] The ionic liquid may be at least one selected from the group consisting of, for example, N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide.

[0099] In the solid electrolyte membrane, the weight ratio of the solid electrolyte to the ionic liquid may be 0.1:99.9 to 90:10, for example, 10:90 to 90:10, 20:80 to 90:10, 30:70 to 90:10, 40:60 to 90:10, or 50:50 to 90:10. A solid electrolyte membrane satisfying the above range can maintain or improve ionic conductivity by improving the electrochemical contact area with the electrode. Accordingly, the energy density, discharge capacity, rate characteristics, etc. of the all-solid-state secondary battery can be improved.

[0100] Method for manufacturing a solid electrolyte membrane

[0101] In another embodiment, a method for manufacturing a solid electrolyte membrane is provided, comprising obtaining a composite including a core including diamagnetic particles, an insulating layer surrounding the core, and a shell surrounding the insulating layer and including a solid electrolyte, preparing a slurry for forming an electrolyte membrane including the composite and the solid electrolyte, and applying the slurry for forming an electrolyte membrane on a substrate. The above description relates to a method for manufacturing a solid electrolyte membrane, which is an embodiment, and hereinafter, any description overlapping with the above will be omitted, and a process for manufacturing a solid electrolyte membrane, which is an embodiment, will be described in more detail.

[0102] The above complex can be obtained by mixing diamagnetic particles and an insulating material in a first solvent, then drying the mixture, mixing the result of the first drying with a solid electrolyte raw material in a second solvent, then drying the mixture, and heat-treating the result of the second drying.

[0103] According to one embodiment, the weight ratio of the diamagnetic particles and the insulating material may be 1:0.01 to 1:50, or 1:0.01 to 1:10, 1:0.05 to 1:5, or 1:0.08 to 1:1.

[0104] The first solvent is a solvent that disperses diamagnetic particles and insulating materials, and the second solvent is a solvent that can disperse the obtained product and the solid electrolyte raw material. Since any commonly known solvent can be used, there is no particular limitation. As a representative example, an organic solvent such as N-methyl-2-pyrrolidone (NMP) can be used as the first solvent, and acetonitrile can be used as the second solvent.

[0105] According to one embodiment, the first drying and the second drying may be performed at, for example, 80°C to 150°C, 90°C to 140°C, or 100°C to 130°C. Alternatively, the heat treatment may be performed at, for example, 200°C to 600°C, 250°C to 550°C, 300°C to 500°C, or 350°C to 450°C. Alternatively, the temperatures of the first drying and the second drying may be the same or different from each other.

[0106] A complex (1) can be obtained by this method, and the structure of the complex (1) thus obtained is as described above.

[0107] Next, a slurry for forming an electrolyte membrane including the complex and a solid electrolyte is prepared. The slurry for forming an electrolyte membrane can be prepared by mixing the complex, the solid electrolyte, and a third solvent.

[0108] As the third solvent, any commonly known solvent capable of dispersing the complex and the solid electrolyte may be used, and is not particularly limited. Representative examples of the third solvent include octyl acetate, isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof.

[0109] When preparing the slurry for forming the above-mentioned electrolyte membrane, one or more components selected from the group consisting of a binder, an alkali metal salt, an ionic liquid, and a conductive polymer, which are previously mentioned as components that can be included in the solid electrolyte membrane, may be further included. In addition, a dispersant commonly known in the art (e.g., H-NBR, etc.) may be further added.

[0110] The aforementioned slurry for forming an electrolyte membrane can be applied to a substrate. Any method commonly known in the art can be used without limitation as the application method. For example, bar coating, spin coating, die coating, transfer coating, spray coating, and the like can be used. Any material commonly known in the art can be used as the substrate without limitation.

[0111] According to one embodiment, the method may further include applying a magnetic field to the slurry for forming an electrolyte film applied on the substrate. When this is satisfied, the complex (1) that was randomly distributed within the solid electrolyte film (300) can be oriented in a direction perpendicular (Y) or close to a direction perpendicular to the plane direction (X) of the solid electrolyte film (300).

[0112] For example, the strength of the magnetic field may be 0.1 T (Tesla) to 3 T, or 0.5 T to 2 T, and the application time of the magnetic field may be 0.1 second to 10 minutes. The temperature at which the magnetic field is applied is not particularly limited, but the higher the temperature, the weaker the magnetic field strength may be. By appropriately controlling the strength and application time of the magnetic field, the orientation of the composite in the solid electrolyte membrane due to the application of the magnetic field can be more effectively secured.

[0113] According to one embodiment, after applying the magnetic field, the method may include drying the slurry for forming the electrolyte membrane to which the magnetic field has been applied to form a solid electrolyte membrane. Alternatively, the method may further include performing drying and rolling after applying the magnetic field.

[0114] For example, the method may further include drying a slurry for forming an electrolyte membrane to which a magnetic field is applied, forming a solid electrolyte membrane on the substrate, and rolling the solid electrolyte membrane. Here, conditions such as drying and rolling may be as commonly known in the art. Alternatively, the method may further include removing the substrate, if necessary, after applying the magnetic field.

[0115] All-solid-state secondary battery

[0116] In another embodiment, an all-solid-state secondary battery is provided, comprising: a positive electrode layer; a negative electrode layer; and the aforementioned solid electrolyte membrane positioned between the positive electrode layer and the negative electrode layer. Since the all-solid-state secondary battery includes the solid electrolyte membrane according to the aforementioned embodiment, it exhibits excellent ion conductivity and high-rate characteristics, while effectively suppressing internal short circuits in the cell.

[0117] Hereinafter, descriptions overlapping with the above will be omitted, and components of an all-solid-state secondary battery, which is an example of an implementation, will be described in more detail with reference to FIG. 6.

[0118] The above-mentioned all-solid-state secondary battery may also be expressed as an all-solid-state battery or an all-solid-state lithium secondary battery.

[0119] Fig. 6 is a cross-sectional view of an all-solid-state battery according to an embodiment. Referring to Fig. 6, the all-solid-state battery (100) may have a structure in which an electrode assembly in which a negative electrode layer (400) including a negative electrode current collector (401) and a negative electrode active material layer (403), a solid electrolyte membrane (300), and a positive electrode layer (200) including a positive electrode active material layer (203) and a positive electrode current collector (201) are laminated is housed in a case such as a pouch. The all-solid-state battery (100) may further include an elastic layer (500) on the outer side of at least one of the positive electrode layer (200) and the negative electrode layer (400). Meanwhile, although Fig. 6 illustrates one electrode assembly including a negative electrode layer (400), a solid electrolyte membrane (300), and a positive electrode layer (200), an all-solid-state battery may be manufactured by laminating two or more electrode assemblies.

[0120] bipolar layer

[0121] The positive electrode layer may include, for example, a positive electrode current collector (201); and a positive electrode active material layer (203) positioned on the positive electrode current collector (201).

[0122] The positive electrode current collector (201) may be selected from the group consisting of aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof. Aluminum foil may be used as the positive electrode current collector, but is not limited thereto.

[0123] The positive electrode active material layer (203) includes a positive electrode active material and may optionally include a solid electrolyte, a binder, and / or a conductive material.

[0124] A compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) can be used as a cathode active material. Specifically, one or more of a composite oxide of lithium and a metal selected from the group consisting of cobalt, manganese, nickel, and combinations thereof can be used.

[0125] The above composite oxide may be a lithium transition metal composite oxide, and specific examples thereof include lithium nickel-based oxides, lithium cobalt-based oxides, lithium manganese-based oxides, lithium iron phosphate-based compounds, cobalt-free nickel-manganese-based oxides, lithium-rich layered oxides, or combinations thereof. For example, the positive electrode active material may be a high-nickel-based positive electrode active material in which the nickel content is 80 mol% or more with respect to 100 mol% of metals excluding lithium in the lithium transition metal composite oxide. The nickel content in the high-nickel-based positive electrode active material may be 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and may be 99 mol% or less with respect to 100 mol% of metals excluding lithium. The high-nickel-based positive electrode active material can realize high capacity and thus can be applied to high-capacity, high-density lithium secondary batteries.

[0126] As a more specific example, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Mn 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤0.5, 0 < α < 2);Li a Ni 1-b-c Mn b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2);Lia Ni b Co c L 1 d G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.1); Li a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(0.90 ≤ a ≤1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); Li a FePO4(0.90 ≤ a ≤ 1.8)

[0127] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; Z is Cr, V, Fe, Sc, Y, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0128] The cathode active material may include, for example, a lithium nickel-based oxide represented by the following chemical formula 21, a lithium cobalt-based oxide represented by the following chemical formula 22, a lithium iron phosphate-based compound represented by the following chemical formula 23, a cobalt-free lithium nickel-manganese-based oxide represented by the following chemical formula 24, or a combination thereof.

[0129] [Chemical Formula 21]

[0130] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0131] In the above chemical formula 21, 0.9≤a1≤1.8, 0.3≤x1≤1, 0≤y1≤0.7, 0≤z1≤0.7, 0.9≤x1+y1+z1≤1.1, and 0≤b1≤0.1, and M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0132] In the above chemical formula 21, 0.6≤x1≤1, 0≤y1≤0.4, and 0≤z1≤0.4, or 0.8≤x1≤1, 0≤y1≤0.2, and 0≤z1≤0.2.

[0133] [Chemical Formula 22]

[0134] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0135] In the above chemical formula 22, 0.9≤a2≤1.8, 0.7≤x2≤1, 0≤y2≤0.3, 0.9≤x2+y2≤1.1, and 0≤b2≤0.1, and M3 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0136] [Chemical Formula 23]

[0137] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0138] In the above chemical formula 23, 0.9≤a3≤1.8, 0.6≤x3≤1, 0≤y3≤0.4, and 0≤b3≤0.1, and M 4 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0139] [Chemical Formula 24]

[0140] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0141] In the above chemical formula 24, 0.9≤a2≤1.8, 0.8≤x4<1, 0 <y4≤0.2, 0≤z4≤0.2, 0.9≤x4+y4+z4≤1.1, 및 0≤b4≤0.1이고 M 5 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0142] The average particle diameter (D) of the above positive electrode active material 50 ) may be 1 ㎛ to 25 ㎛, for example, 3 ㎛ to 25 ㎛, 1 ㎛ to 20 ㎛, 1 ㎛ to 18 ㎛, 3 ㎛ to 15 ㎛, or 5 ㎛ to 15 ㎛. For example, the positive electrode active material may have an average particle diameter (D 50 ) with small particles of 1 ㎛ to 9 ㎛ and an average particle diameter (D 50 ) may include particles having a particle size range of 10 ㎛ to 25 ㎛. The positive electrode active material having such a particle size range can be harmoniously mixed with other components in the positive electrode active material layer and can realize high capacity and high energy density. Here, the average particle size is obtained by selecting 20 or so random particles from a scanning electron microscope image of the positive electrode active material, measuring their particle sizes (diameter, or major axis, or major axis length), and then obtaining a particle size distribution, and in the particle size distribution, the diameter (D) of the particles having a cumulative volume of 50% by volume 50 ) may be taken as the average particle diameter.

[0143] The above-mentioned positive electrode active material may be in the form of a secondary particle formed by agglomeration of a plurality of primary particles, or may be in the form of a single particle. In addition, the above-mentioned positive electrode active material may be spherical or nearly spherical in shape, or may be polyhedral or irregular in shape.

[0144] Meanwhile, the positive electrode active material may include a buffer layer on the particle surface. The buffer layer may be expressed as a coating layer, a protective layer, etc., and may play a role in lowering the interfacial resistance between the positive electrode active material and the sulfide-based solid electrolyte particles. For example, the buffer layer may include a lithium-metal-oxide, wherein the metal may be one or more elements selected from the group consisting of Al, B, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, and Zr. The lithium-metal-oxide is excellent in lowering the interfacial resistance between the positive electrode active material and the solid electrolyte particles while improving the performance of the positive electrode active material by facilitating the movement of lithium ions and electron conduction.

[0145] The content of the positive electrode active material may be included within a range known in the art and is not particularly limited. For example, the positive electrode active material may be included in an amount of 55 wt% to 99.5 wt% relative to the total weight of the positive electrode active material layer, for example, 65 wt% to 95 wt%, or 75 wt% to 91 wt%.

[0146] bookbinder

[0147] The binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the positive electrode current collector (201). Representative examples of the binder include, but are not limited to, one or more selected from among polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, polyacrylonitrile, polymethyl methacrylate, vinylidene fluoride / hexafluoropropylene copolymer, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0148] Challenge

[0149] Conductive materials are used to impart conductivity to electrodes, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0150] The content of the binder and the conductive material may be 0.1 wt% to 10 wt% and 0.1 wt% to 5 wt%, respectively, based on the total weight of the positive electrode active material layer (203).

[0151] The above-described positive electrode active material layer (203) may further include additives such as fillers, coating agents, dispersants, and ion-conducting aids, in addition to the aforementioned positive electrode active material, binder, and conductive agent. As fillers, coating agents, dispersants, and ion-conducting aids that may be included in the positive electrode layer, known materials generally used in positive electrodes of all-solid-state secondary batteries may be used.

[0152] solid electrolyte

[0153] The positive electrode active material layer (203) may optionally further include a solid electrolyte. The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof, and the specific description thereof is identical to the description given above for the solid electrolyte membrane (300). As a representative example, when the positive electrode active material layer (203) further includes a sulfide-based solid electrolyte, the ionic conductivity of the positive electrode layer may be further improved.

[0154] The solid electrolyte included in the positive electrode active material (203) may be the same as the solid electrolyte included in the shell (1b) of the above-described complex (1) or the solid electrolyte included in the solid electrolyte membrane (300). For example, when the shell (1b) of the complex (1) is composed of Li6PS5Cl, the sulfide-based solid electrolyte included in the positive electrode active material layer (203) may also be composed of Li6PS5Cl.

[0155] In the above positive electrode active material layer (203), the content of the solid electrolyte may be 0.5 wt% to 30 wt% relative to the total weight of the positive electrode active material layer (203), for example, 1 wt% to 5 wt%. When the solid electrolyte is included in the positive electrode active material layer (203) in such a content, the efficiency and life characteristics of the all-solid-state secondary battery can be improved without reducing the capacity.

[0156] cathode layer

[0157] The negative electrode layer (400) may include, for example, a current collector (401) and a negative electrode active material layer (403) positioned on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder, a conductive material, and / or a solid electrolyte.

[0158] The above negative active material may include a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0159] The material capable of reversibly intercalating / deintercalating the lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0160] As the above lithium metal alloy, an alloy of lithium and one or more metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0161] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x(0<x<2), Si-Q 합금(상기 Q는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님), 상기 Sn계 음극 활물질로는 Sn, SnO2, Sn-R 합금(상기 R은 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Sn은 아님) 등을 들 수 있고, 또한 이들 중 적어도 하나와 SiO2를 혼합하여 사용할 수도 있다. 상기 원소 Q 및 R로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, 및 이들의 조합으로 이루어진 군에서 선택되는 것을 사용할 수 있다.

[0162] The silicon-carbon composite may be, for example, a silicon-carbon composite including a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer positioned on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. As the amorphous carbon precursor, coal pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, or a polymer resin such as a phenol resin, a furan resin, or a polyimide resin may be used. At this time, the content of silicon may be 10 wt% to 50 wt% with respect to the total weight of the silicon-carbon composite. In addition, the content of the crystalline carbon may be 10 wt% to 70 wt% with respect to the total weight of the silicon-carbon composite, and the content of the amorphous carbon may be 20 wt% to 40 wt% with respect to the total weight of the silicon-carbon composite. In addition, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm.

[0163] The average particle diameter (D) of the above silicon particles 50 ) may be 10 nm to 20 μm, for example, 10 nm to 500 nm. The silicon particles may exist in an oxidized form, and at this time, the atomic content ratio of Si:O in the silicon particles, which indicates the degree of oxidation, may be 99:1 to 33:67. The silicon particles may be SiO x It can be a particle, in which case SiO x In the range x can be greater than 0 and less than 2. Here, the average particle diameter (D 50 ) is measured by a particle size analyzer using laser diffraction and means the diameter of particles with a cumulative volume of 50% in the particle size distribution.

[0164] The above Si-based negative electrode active material or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material. The mixing ratio of the Si-based negative electrode active material or Sn-based negative electrode active material and the carbon-based negative electrode active material can be 1:99 to 90:10 by weight.

[0165] The content of the negative active material in the above negative active material layer may be 95 wt% to 99 wt% with respect to the total weight of the negative active material layer.

[0166] In one embodiment, the negative electrode active material layer may further include a binder and optionally further include a conductive material. The content of the binder in the negative electrode active material layer may be 1 wt% to 5 wt% based on the total weight of the negative electrode active material layer. In addition, when the negative electrode active material layer further includes a conductive material, the negative electrode active material layer may include 90 wt% to 98 wt% of the negative electrode active material, 1 wt% to 5 wt% of the binder, and 1 wt% to 5 wt% of the conductive material.

[0167] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector. The binder may include an insoluble binder, a water-soluble binder, or a combination thereof.

[0168] The above-described non-aqueous binder may include, for example, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer comprising ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0169] The water-soluble binder may be a rubber-based binder or a polymer resin binder. The rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0170] When a water-soluble binder is used as the negative electrode layer binder, a thickener capable of imparting viscosity may be used together, and the thickener may include, for example, a cellulose-based compound. The cellulose-based compound may include carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, an alkali metal salt thereof, or a combination thereof. Na, K, or Li may be used as the alkali metal. The amount of the thickener used may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0171] The conductive material is used to provide conductivity to the electrode, and may include, for example, carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, and carbon nanotubes; metal-based materials in the form of metal powder or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0172] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0173] As another example, the cathode layer may be a precipitation-type cathode layer. The precipitation-type cathode layer refers to a cathode layer that does not include a cathode active material when the battery is assembled, but in which lithium metal or the like is precipitated when the battery is charged, and this acts as a cathode active material.

[0174] Fig. 7 is a schematic cross-sectional view of an all-solid-state battery including a precipitated negative electrode layer. Referring to Fig. 7, the precipitated negative electrode layer (400') may include a current collector (401) and a negative electrode coating layer (405) positioned on the current collector. An all-solid-state battery including such a precipitated negative electrode layer (400') is initially charged in a state in which no negative electrode active material is present, and upon charging, a high-density lithium metal or the like is precipitated between the current collector (401) and the negative electrode coating layer (405) to form a lithium metal layer (404), which may function as a negative electrode active material. Accordingly, in an all-solid-state battery that has been charged at least once, the precipitated negative electrode layer (400') may include a current collector (401), a lithium metal layer (404) positioned on the current collector, and a negative electrode coating layer (405) positioned on the metal layer. The above lithium metal layer (404) refers to a layer in which lithium metal, etc. is precipitated during the charging process of the battery, and may be referred to as a metal layer or a negative electrode active material layer.

[0175] The above cathode coating layer (405) may include a metal, a carbon material, or a combination thereof that acts as a catalyst.

[0176] The metal may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one of these or of several types of alloys. When the metal is present in particle form, its average particle diameter (D 50 ) may be less than about 4 μm, for example, 10 nm to 4 μm.

[0177] The carbon material may be, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may be, for example, natural graphite, artificial graphite, mesophase carbon microbeads, or a combination thereof. The amorphous carbon may be, for example, carbon black, activated carbon, acetylene black, Denka black, Ketjen black, or a combination thereof.

[0178] When the above-described negative electrode coating layer (405) includes both the metal and the carbon material, the mixing ratio of the metal and the carbon material may be, for example, a weight ratio of 1:10 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state battery can be improved. The above-described negative electrode coating layer (405) may include, for example, a carbon material supported with a catalytic metal, or may include a mixture of metal particles and carbon material particles.

[0179] The above cathode coating layer (405) may include, for example, the metal and amorphous carbon, in which case it can effectively promote the precipitation of lithium metal.

[0180] The above cathode coating layer (405) may further include a binder, and the binder may be a conductive binder. In addition, the above cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0181] The thickness of the cathode coating layer (405) may be, for example, 100 nm to 20 ㎛, or 500 nm to 10 ㎛, or 1 ㎛ to 5 ㎛.

[0182] The above-described precipitated negative electrode layer (400') may further include, for example, a thin film on the surface of the current collector, i.e., between the current collector and the negative electrode coating layer. The thin film may include an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one of these or may be composed of several types of alloys. The thin film may further flatten the precipitated form of the lithium metal layer (404) and further improve the characteristics of the all-solid-state battery. The thin film may be formed by, for example, a vacuum deposition method, a sputtering method, a plating method, etc. The thickness of the thin film may be, for example, 1 nm to 500 nm.

[0183] The above-mentioned all-solid-state secondary battery may be a unit cell having a structure of positive electrode layer / solid electrolyte membrane / negative electrode layer, a bi-cell having a structure of negative electrode layer / solid electrolyte membrane / positive electrode layer / solid electrolyte membrane / negative electrode layer, or a laminated battery in which the structure of the unit cell is repeated.

[0184] The shape of the above-described all-solid-state secondary battery is not particularly limited, and may be, for example, coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, flat, etc. In addition, the above-described all-solid-state battery can be applied to large-scale batteries used in electric vehicles, etc. For example, the above-described all-solid-state battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring large amounts of power storage, and for example, it can be used in electric bicycles or power tools.

[0185] The following examples and comparative examples are described. The following examples are merely examples and the present invention is not limited to the examples described below.

[0186] Example 1

[0187] (1) Manufacturing of complex

[0188] As a diamagnetic particle of the core, needle-shaped artificial graphite having an aspect ratio of 4.0, a short axis length of 1 μm, and a long axis length of 4 μm was prepared, a PVDF binder (#9300 from Kureha) was prepared as an insulating material, and a solid electrolyte raw material of Li2S, P2S5, and LiCl was prepared in a molar ratio of 5:1:2.

[0189] To a solution containing 8 wt% PVDF binder dissolved in NMP as a solvent, the needle-shaped artificial graphite was added at 20 wt%, magnetically stirred for 1 hour, filtered, and dried at 120°C to obtain needle-shaped artificial graphite coated with PVDF binder as a precursor. Subsequently, in the presence of acetonitrile as a solvent, the solid electrolyte raw material and the precursor were mixed at a weight ratio of 30:1, magnetically stirred for 2 hours, dried at 120°C, and heat-treated at 400°C. A composite was obtained, comprising: a needle-shaped artificial graphite core; a PVDF binder layer surrounding the core; and a Li6PS5Cl layer surrounding the PVDF binder layer.

[0190] (2) Preparation of slurry for forming electrolyte membrane

[0191] Solid electrolyte (D) of Li6PS5Cl, 20 wt% complex, 78.3 wt% argyrodite type crystals in octyl acetate as solvent 50 =3㎛), 1.3 wt% of acrylic binder (SX-A334, Zeon Co., Ltd) and 0.4 wt% of dispersant (H-NBR) were added, and then mixed with a sinky mixer to prepare a slurry for forming an electrolyte membrane.

[0192] (3) Manufacturing of solid electrolyte membrane

[0193] The prepared slurry was applied onto a non-woven fabric using a bar coater, and a magnetic field was applied at 25°C and 1 T for 2 minutes. After the magnetic field was applied, the slurry was dried in a convection oven at 50°C for 5 minutes to obtain a laminate. The obtained laminate was dried in a vacuum oven at 40°C for more than 10 hours. A solid electrolyte membrane was prepared through the above process. For the obtained solid electrolyte membrane, cross-sectional specimens were prepared so that the cross-section could be observed, and then images were taken using an SEM. Ten random composites were selected, and the thickness of the shell and the thickness of the insulating layer of each composite were measured, and the average values ​​were calculated. The average thickness of the shell was 0.5 μm, and the average thickness of the insulating layer was 0.1 μm.

[0194] (4) Manufacturing of the anode layer

[0195] A solid electrolyte of Li6PS5Cl containing 13.5 wt% argyrodite-type crystals (D 50 =1um), 85 wt% of cathode active material (LiNi 0.8 Co 0.1 Al 0.1 O2), 1.0 wt% PVDF binder, and 0.5 wt% carbon nanotube conductive agent were mixed to prepare a cathode slurry. The cathode slurry was applied onto one side of an aluminum foil cathode current collector, followed by drying and rolling to prepare a cathode layer.

[0196] (5) Manufacturing of cathode layer

[0197] A nickel foil with a thickness of 12.5 ㎛ was prepared as a negative electrode current collector. In addition, D was used as a material to form a negative electrode coating layer. 50 Carbon black (CB) and D with a particle size of approximately 30 nm 50 Silver (Ag) particles with a diameter of approximately 60 nm were prepared.

[0198] A 0.25 g composite powder containing carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 2 g of an NMP solution containing 7 wt% PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. A slurry was prepared by stirring the mixed solution while adding NMP little by little to the mixed solution. The prepared slurry was applied to a nickel foil current collector using a bar coater and dried in a convection oven at 80°C for 10 minutes to obtain a laminate. The obtained laminate was vacuum-dried at 100°C for 10 hours, and a negative electrode layer was prepared by forming a negative electrode coating layer on the negative electrode current collector through the above process.

[0199] (6) Manufacturing of all-solid-state secondary batteries

[0200] A laminate was prepared by placing the solid electrolyte membrane between the positive electrode layer and the negative electrode layer. The prepared laminate was hot-plate pressed at 80°C and a pressure of 500 MPa for 30 minutes to manufacture an all-solid-state secondary battery. This pressurization process sintered the solid electrolyte membrane, thereby improving battery characteristics. The thickness of the pressed positive electrode active material layer was approximately 105 μm, the thickness of the negative electrode coating layer was 8 μm, and the thickness of the solid electrolyte membrane was 62 μm.

[0201] Comparative Example 1

[0202] Without adding a complex to the slurry for forming the electrolyte membrane, 97.5 wt% Li6PS5Cl solid electrolyte (D 50 =3㎛), 2 wt% of an acrylic binder (SX-A334, Zeon Co., Ltd) and 0.5 wt% of a dispersant (H-NBR) were mixed with a sinky mixer to prepare a slurry for forming an electrolyte membrane, and a solid electrolyte membrane and an all-solid-state secondary battery of Comparative Example 1 were manufactured in substantially the same manner as in Example 1, except that the slurry was mixed with a sinky mixer to prepare a slurry for forming an electrolyte membrane.

[0203] Comparative Example 2

[0204] In the manufacture of the composite, the needle-shaped artificial graphite was replaced with spherical artificial graphite having an aspect ratio of 1.0, a short axis length of 3.5 ㎛, and a long axis length of 3.5 ㎛, and a composite consisting of a diamagnetic particle core and a solid electrolyte shell surrounding it was used without forming an insulating layer, and a composite, a solid electrolyte membrane, and an all-solid-state secondary battery were manufactured in the same manner as in Example 1.

[0205] Comparative Example 3

[0206] A composite, a solid electrolyte membrane, and an all-solid-state secondary battery were manufactured in the same manner as in Example 1, except that a composite consisting of a diamagnetic particle core and a solid electrolyte shell surrounding the core was used without forming an insulating layer during the manufacture of the composite.

[0207] The structure of the solid electrolyte (or complex) formed by the aforementioned Example 1 and Comparative Examples 1 to 3; the shape, aspect ratio, short axis length, and long axis length of the core are shown in Table 1 below.

[0208] Structure of the composite in the solid electrolyte membrane Core shape Aspect ratio Short axis length Long axis length Example 1 Diamagnetic particle core - insulating layer - solid electrolyte shell Needle-shaped 4.01 ㎛ 4 ㎛ Comparative example 1 Solid electrolyte alone----Comparative example 2 Diamagnetic particle core - solid electrolyte shell Spherical 1.0 3.5 ㎛ 3.5 ㎛ Comparative example 3 Diamagnetic particle core - solid electrolyte shell Needle-shaped 4.01 ㎛ 4 ㎛

[0209] Evaluation Example 1: Evaluation of ionic conductivity

[0210] For each solid electrolyte membrane of the examples and comparative examples, ionic conductivity was evaluated. Each solid electrolyte membrane obtained from Example 1 and Comparative Examples 1 to 3 was placed in a mold with a diameter of 10 mm and pressed at a pressure of 350 mPa to form a pellet. An indium (In) thin film was coated on both sides of the pellet to prepare a sample for measuring ionic conductivity. The impedance of the prepared sample was measured using an AUTOLAB PGSTAT30 (Metrohm Autolab Co. Ltd.) potentiostat, and a Nyquist plot was plotted, from which the ionic conductivity was measured at 45°C. The results are shown in Table 2 below.

[0211] Ionic Conductivity (mS / cm) (@ 45℃)Example 10.44Comparative Example 10.34Comparative Example 20.31Comparative Example 30.40

[0212] According to Table 2 above, the solid electrolyte membrane obtained from Example 1 exhibited higher ionic conductivity than the solid electrolyte membranes of Comparative Examples 1 and 2. In Example 1, a solid electrolyte membrane was manufactured using a composite including a core comprising diamagnetic particles having an aspect ratio greater than 1. Accordingly, when a magnetic field was applied during the manufacturing process of the solid electrolyte membrane, the composite was oriented in the range of 50 to 130° with respect to the plane direction of the solid electrolyte membrane. This was confirmed by manufacturing a cross-sectional specimen of the solid electrolyte membrane, photographing it with a scanning electron microscope (SEM), measuring the orientation angle for 10 random composites, and calculating the average value. According to the orientation of the composites within the solid electrolyte membrane, it was confirmed that the lithium ion path was shortened and the solid electrolyte membrane according to Example 1 had high ionic conductivity.

[0213] On the other hand, Comparative Example 1 is a case where the composite was not applied to the solid electrolyte membrane, and it was confirmed that even if a magnetic field was applied during the process of manufacturing the solid electrolyte membrane, the solid electrolyte particles did not show a specific orientation but were oriented randomly within the solid electrolyte membrane. In addition, Comparative Example 2 is a case where a spherical diamagnetic particle was applied as the core of the composite, and even if a magnetic field was applied during the process of manufacturing the solid electrolyte membrane, it did not show a specific orientation within the solid electrolyte membrane, and the effect of increasing ionic conductivity was not observed.

[0214] Evaluation Example 2: Evaluation of high-rate characteristics and occurrence of short circuits

[0215] For each all-solid-state secondary battery of Examples and Comparative Examples, in order to evaluate the discharge capacity and high-rate characteristics, the battery was charged at a constant current of 0.1 C until the battery voltage became 4.25 V in a constant-temperature chamber at 45°C, and discharged at a constant current of 0.1 C until the battery voltage became 2.5 V (first cycle); charged at a constant current of 0.1 C until the battery voltage became 4.25 V, and discharged at a constant current of 0.33 C until the battery voltage became 2.5 V (second cycle); charged at a constant current of 0.1 C until the battery voltage became 4.25 V, and discharged at a constant current of 1.0 C until the battery voltage became 2.5 V (third cycle). The discharge capacity and high-rate characteristics in each cycle are shown in Table 2 below. Here, the high-rate characteristics are defined by the following mathematical expression 5.

[0216] [Equation 5]

[0217] High rate characteristics [%] = [Discharge capacity in the 3rd cycle (1C rate) / Discharge capacity in the 1st cycle (0.1C rate)] × 100 [%]

[0218] In addition, in the charge / discharge cycle described above, the case where no internal short circuit occurred was evaluated as 'X', and the case where an internal short circuit occurred was evaluated as 'O', and these are shown in Table 3 below.

[0219] 0.1C discharge capacity (mAh / g) 0.33C discharge capacity (mAh / g) 1C discharge capacity (mAh / g) High rate characteristics (%) Whether internal short circuit occurs Example 119418517389.2X Comparative example 119518316886.2X Comparative example 2----O Comparative example 3----O

[0220] According to Table 3 above, in the case of Example 1, compared to Comparative Examples 1 to 3, not only was the discharge capacity in each cycle superior, but also the high-rate characteristics were superior, and internal short circuits did not occur. This indicates that the use of the composite according to one embodiment improves the high-rate characteristics of the all-solid-state secondary battery and has the effect of suppressing internal short circuits.

[0221] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the present invention.

[0222] [Explanation of symbols]

[0223] 1: composite, 1a: core, 1b: insulating layer, 1c: shell, 2: solid electrolyte, 4: lithium ion, 100: all-solid-state secondary battery, 200: cathode layer, 201: cathode current collector, 203: cathode active material layer, 300: solid electrolyte membrane, 400: anode layer, 400': precipitation-type anode layer, 401: anode current collector, 403: anode active material layer, 404: lithium metal layer, 405: anode coating layer, 500: elastic layer

Claims

1. Containing a complex and solid electrolyte, The above complex is A core containing diamagnetic particles; an insulating layer surrounding the core; and A solid electrolyte membrane comprising a shell surrounding the insulating layer and containing a solid electrolyte.

2. In paragraph 1, The above core is a solid electrolyte membrane having an aspect ratio greater than 1, as expressed by the following mathematical formula 1: [Mathematical Formula 1] Aspect ratio = length of major axis / length of minor axis.

3. In paragraph 2, A solid electrolyte membrane in which the major axis of the core is oriented in a range of 50° to 130° with respect to the plane direction of the solid electrolyte membrane.

4. In paragraph 1, The above core is a solid electrolyte membrane having a needle-like, plate-like or oval shape.

5. In paragraph 1, A solid electrolyte membrane comprising the above diamagnetic particles comprising a carbonaceous material, wherein the carbonaceous material comprises artificial graphite, natural graphite, graphene, carbon nanotubes (CNTs), L-carbon nanotubes (long length CNTs), carbon fibers, carbon black, or a combination thereof.

6. In paragraph 1, A solid electrolyte membrane wherein the insulating layer comprises a polymer, and the polymer comprises polyethylene oxide, hydrogenated nitrile rubber, styrene-butadiene rubber, polyvinylidene fluoride, or a combination thereof.

7. In paragraph 1, A solid electrolyte membrane in which the weight ratio of the core and the insulating layer is 1:0.01 to 1:

50.

8. In paragraph 1, The solid electrolyte of the above shell is a solid electrolyte membrane including a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof.

9. In paragraph 1, A solid electrolyte membrane in which the weight ratio of the core and the shell is 1:1 to 1:

500.

10. In paragraph 1, The length of the major axis of the above core is 1 ㎛ to 50 ㎛, A solid electrolyte membrane having a shortened length of the core of the above-mentioned type of membrane of 0.01 ㎛ to 5 ㎛.

11. In paragraph 1, A solid electrolyte membrane, wherein the complex is included in an amount of 0.1 wt% to 5 wt% based on 100 wt% of the solid electrolyte membrane.

12. In paragraph 1, The solid electrolyte of the above solid electrolyte membrane includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof, and is in the form of particles having an average particle diameter (D 50 ) is a solid electrolyte membrane having a thickness of 0.1 ㎛ to 5.0 ㎛.

13. Obtaining a composite including a core containing diamagnetic particles, an insulating layer surrounding the core, and a shell surrounding the insulating layer and containing a solid electrolyte, A slurry for forming an electrolyte membrane comprising the above complex and a solid electrolyte is prepared, A method for manufacturing a solid electrolyte membrane, comprising applying a slurry for forming the electrolyte membrane on a substrate.

14. In paragraph 13, A method for manufacturing a solid electrolyte membrane, further comprising applying a magnetic field to a slurry for forming an electrolyte membrane applied on a substrate.

15. In paragraph 14, The strength of the above magnetic field is 0.1 T to 3 T, A method for manufacturing a solid electrolyte membrane, wherein the application time of the magnetic field is 0.1 seconds to 10 minutes.

16. In paragraph 14, A method for manufacturing a solid electrolyte membrane, further comprising drying a slurry for forming an electrolyte membrane to which a magnetic field is applied to form a solid electrolyte membrane.

17. In paragraph 13, The above complex is After mixing the diamagnetic particles and insulating material in the first solvent, first drying is performed, The result of the first drying and the solid electrolyte raw material are mixed in a second solvent and then dried a second time. A method for producing a solid electrolyte membrane obtained by heat treating the result of the second drying.

18. In paragraph 17, A method for producing a solid electrolyte membrane, wherein the production of the slurry for forming the above electrolyte membrane is performed by producing a slurry by mixing the above complex, a solid electrolyte, and a third solvent.

19. In paragraph 17, A method for manufacturing a solid electrolyte membrane, wherein the first drying is performed at 80°C to 150°C.

20. In paragraph 17, A method for manufacturing a solid electrolyte membrane, wherein the second drying is performed at 80°C to 150°C.

21. In paragraph 17, A method for manufacturing a solid electrolyte membrane, wherein the above heat treatment is performed at 200°C to 600°C.

22. Bipolar layer; cathode layer; and An all-solid-state secondary battery comprising a solid electrolyte membrane according to any one of claims 1 to 12 positioned between the positive electrode layer and the negative electrode layer.

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