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

Abstract

A solid electrolyte membrane, a preparation method thereof, and an all-solid rechargeable batteries are provided, wherein the solid electrolyte membrane comprises a first layer containing solid electrolyte particles, a second layer located on the first layer and containing a composite, and a third layer located on the second layer and containing solid electrolyte particles, the composite including: a core containing diamagnetic particles; and a shell enclosing the core and containing a solid electrolyte.

Description

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

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

[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 capable of improving the ion conductivity and high-rate characteristics of an all-solid-state secondary battery while ensuring the safety of the battery, a method for manufacturing the same, and an all-solid-state secondary battery including the same are provided.

[0005] In one embodiment, the device comprises a first layer comprising solid electrolyte particles; a second layer positioned on the first layer and comprising a complex; and a third layer positioned on the second layer and comprising solid electrolyte particles.

[0006] The above complex provides a solid electrolyte membrane comprising a core including diamagnetic particles; and a shell surrounding the core and including a solid electrolyte.

[0007] In another embodiment, a first layer comprising solid electrolyte particles is formed,

[0008] Forming a second layer containing a complex on the first layer,

[0009] comprising forming a third layer including solid electrolyte particles on the second layer;

[0010] The above complex provides a method for manufacturing a solid electrolyte membrane including a core including diamagnetic particles; and a shell surrounding the core and including a solid electrolyte.

[0011] 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.

[0012] A solid electrolyte membrane according to one embodiment and an all-solid-state secondary battery including the same can improve ion conductivity and high-rate characteristics while ensuring the safety of the battery.

[0013] Figure 1 is a schematic diagram schematically showing a complex (1) according to one embodiment.

[0014] Figure 2 is a schematic diagram showing a solid electrolyte membrane (300) according to one embodiment.

[0015] Figure 3 is a schematic diagram schematically showing the lithium ion movement path within a solid electrolyte membrane (300) that does not include a complex (1).

[0016] Figure 4 is a schematic diagram schematically showing a lithium ion movement path within a second layer (12) according to one embodiment.

[0017] Figure 5 is a perspective view schematically showing a solid electrolyte membrane (300) according to one embodiment.

[0018] Figure 6 is a cross-sectional view schematically showing a second layer (12) in a solid electrolyte membrane (300) according to one embodiment.

[0019] Figures 7 and 8 are cross-sectional views schematically showing an all-solid-state secondary battery (100) according to one embodiment.

[0020] Below, specific implementation examples are described in detail to facilitate their implementation by those skilled in the art. However, the present invention may be implemented in various different forms and is not limited to the implementation examples described herein.

[0021] 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.

[0022] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0023] 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.

[0024] 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.

[0025] “Layer” includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on some surfaces.

[0026] “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.

[0027] “Thickness” may be measured, for example, through photographs taken with an optical microscope such as a scanning electron microscope.

[0028] solid electrolyte membrane

[0029] In one embodiment, a solid electrolyte membrane is provided, comprising: a first layer comprising solid electrolyte particles; a second layer positioned on the first layer and comprising a complex; and a third layer positioned on the second layer and comprising solid electrolyte particles, wherein the complex comprises a core comprising diamagnetic particles; and a shell surrounding the core and comprising a solid electrolyte.

[0030] FIG. 1 is a schematic diagram schematically illustrating a complex (1) included in a second layer (12) in a solid electrolyte membrane (300) according to one embodiment, and FIG. 2 is a schematic diagram schematically illustrating a solid electrolyte membrane (300) according to one embodiment. In addition, FIG. 3 is a schematic diagram schematically illustrating a lithium ion movement path in a solid electrolyte membrane (300) that does not include a complex (1), and FIG. 4 is a schematic diagram schematically illustrating a lithium ion movement path in a second layer (12) according to one embodiment. FIG. 5 is a perspective view schematically illustrating a solid electrolyte membrane (300) according to one embodiment, and FIG. 6 is a cross-sectional view schematically illustrating a second layer (12) included in a solid electrolyte membrane (300) according to one embodiment. FIGS. 7 and 8 are cross-sectional views schematically illustrating an all-solid-state secondary battery (100) according to one embodiment.

[0031] 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 secondary batteries, methods include forming holes or pores and filling them with a solid electrolyte, or adding additives that increase lithium ion conductivity. However, methods of forming holes or pores and filling them with a solid electrolyte have limitations in filling the interior with the solid electrolyte without any gaps. Methods of adding additives that increase ion conductivity also have limitations in the selection of additives because side reactions may occur between the solid electrolyte and the additive, or the properties of the slurry used to form the electrode layer may be affected.

[0032] To shorten the migration path of lithium ions within a solid electrolyte membrane, a composite having a core-shell structure, comprising diamagnetic particles in the core, and a solid electrolyte in the shell, may be considered for use in the solid electrolyte membrane. However, since the composite has electrical conductivity on its own due to the presence of a core comprising diamagnetic particles, there is a risk of internal short circuits occurring in the cell if this is used as is in a solid electrolyte membrane.

[0033] Accordingly, in one embodiment, a solid electrolyte membrane capable of shortening the movement path of lithium ions while suppressing the possibility of occurrence of internal short circuits in the cell is proposed.

[0034] In order to improve ion conductivity and high-rate characteristics by shortening the movement path of lithium ions, a composite (1) as illustrated in Fig. 1 is used as a material of a solid electrolyte membrane. The composite (1) has a core-shell structure having a core (1a) including diamagnetic particles and a shell (1b) surrounding the core and including a solid electrolyte to shorten the movement path of lithium ions. As illustrated in Fig. 4, lithium ions (4) can shorten the movement path through the composite (1), thereby improving ion conductivity and high-rate characteristics. In comparison, as illustrated in Fig. 3, when the composite (1) is not included in the solid electrolyte membrane (300), the movement path of lithium ions (4) is longer than in Fig. 4, and thus the ion conductivity is lowered.

[0035] When using such a complex (1), it is necessary to reduce the risk of internal short circuits in the cell that may occur due to the inclusion of diamagnetic particles as the core (1a). To this end, as illustrated in Fig. 2, a first layer (11) including solid electrolyte particles and a third layer (13) including solid electrolyte particles are laminated on the upper and lower layers of a second layer (12) such that the layer including the complex (1) is positioned in the middle, thereby designing the solid electrolyte membrane (300) as a triple layer.

[0036] 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 (1) itself within the second layer (12) of the solid electrolyte membrane can be designed to be non-spherical. Alternatively, the complex (1) within the second layer (12) can be designed to be non-spherical, and at the same time, the complex can be oriented in a direction perpendicular to or close to the perpendicular direction with respect to the plane direction of the solid electrolyte membrane.

[0037] However, in the general method of forming a solid electrolyte membrane by applying a slurry for forming a solid electrolyte membrane including the aforementioned non-spherical complex onto a substrate, the non-spherical complex (1) is only randomly distributed within the second layer (12). Therefore, in order to distribute the non-spherical complex (1) within the second layer (12) in a direction perpendicular to or close to the perpendicular direction with respect to the plane direction of the solid electrolyte membrane (300), a method of applying a second layer forming slurry including the non-spherical complex onto a substrate and then applying a magnetic field may be considered.

[0038] Here, the reason why the orientation of the non-spherical complex is controlled by the magnetic field is because the non-spherical complex has diamagnetic properties. Since no solid electrolyte known today exhibits diamagnetic properties, in one embodiment, as illustrated in FIG. 1, the orientation of the complex (1) within the solid electrolyte membrane (300) can be controlled using a complex (1) having a core (1a) including non-spherical diamagnetic particles. For example, by orienting the complex (1) within the second layer (12) in a direction perpendicular to or close to the perpendicular direction 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. Accordingly, an all-solid-state secondary battery (100) including a solid electrolyte membrane (300) according to one embodiment can have improved ion conductivity and enhanced high-rate characteristics.

[0039] Hereinafter, the elements constituting the solid electrolyte membrane (300) according to one embodiment will be described in more detail.

[0040] complex

[0041] The complex (1) has a core (1a)-shell (1b) structure, and as illustrated in Fig. 1, the complex (1) includes a core (1a) including diamagnetic particles; and a shell (1b) surrounding the core (1a) and including a solid electrolyte.

[0042] According to one embodiment, in the complex (1), the core (1a) (or the diamagnetic particle included in the core) may be non-spherical. For example, the complex (1) may have an aspect ratio greater than 1, as expressed by the following mathematical formula 1.

[0043] [Mathematical Formula 1]

[0044] Aspect ratio = length of major axis / length of minor axis

[0045] These non-spherical diamagnetic particles and the composite (1) including them can be oriented in a direction perpendicular to or close to perpendicular to the plane direction of the solid electrolyte membrane (for example, at an angle of 50° to 130° with respect to the plane direction of the solid electrolyte membrane (300)) by an externally applied magnetic field. Here, the plane direction (X) of the solid electrolyte membrane (300) refers to a direction parallel to the surface of a wide side of the solid electrolyte membrane. Fig. 5 illustrates a perspective view of the solid electrolyte membrane (300) and the plane direction (X) of the solid electrolyte membrane (300). In addition, Fig. 6 illustrates a cross-sectional view of the second layer (12) included in the solid electrolyte membrane (300), and the plane direction (X) of the solid electrolyte membrane (300) and the direction (Y) perpendicular to the plane direction (X) are each illustrated as lines.

[0046] According to one embodiment, the larger the aspect ratio represented by the above mathematical formula 1, the better the performance of the all-solid-state secondary battery including the solid electrolyte membrane. 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 considering convenience in the manufacturing process and cost reduction effect, the upper limit of the aspect ratio represented by the above mathematical formula 1 may be 5,000 or less, 300 or less, 100 or less, 50 or less, 20 or less, or 10 or less. For example, the aspect ratio of the core (1a) may be 1.1 to 20, or 1.5 to 10, etc.

[0047] According to one embodiment, the major axis length of the complex (1) may be 1 μm to 50 μm, or the minor axis length of the complex (1) may be 0.01 μm to 5 μm. Alternatively, the aspect ratio represented by the above mathematical formula 1, which is the ratio of the major axis length to the minor axis length of the complex (1), may be greater than 1. Here, the major axis length and the minor axis length of the complex mean average values.

[0048] According to one embodiment, in the complex (1), the shell (1b) may be formed with a uniform thickness or may be formed unevenly.

[0049] According to one embodiment, the complex (1) can satisfy at least one of the following mathematical formulas 2 and 3. In other words, it can satisfy either the following mathematical formula 2 or the following mathematical formula 3, or both the following mathematical formulas 2 and 3. In the above range, the orientation effect by the core (1a) of the complex (1) and the lithium ion conductivity effect by the shell (1b) can be harmonized. Here, in the following mathematical formulas 2 and 3, the units of the numerator and denominator only need to be identical to each other, and therefore the units of A1, A2, and B are not particularly limited.

[0050] [Equation 2]

[0051] 0.1 ≤ A1 / B ≤ 100

[0052] [Equation 3]

[0053] 0.01 ≤ A2 / B ≤ 10

[0054] 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 B represents the thickness of the shell (1b).

[0055] 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, or 100 nm to 5 μm, or 1 μm to 4 μm. Alternatively, the thickness of the shell (1b) may be 100 nm to 10 μm, 100 nm to 5 μm, or 300 nm to 3 μm. In this range, the orientation effect by the core (1a) and the lithium ion conduction effect by the shell (1c) can be harmonized. Here, the major axis length of the core (1a), the minor axis length of the core (1a), and the thickness of the shell (1b) mean average values. As a method for measuring the major axis length of the core (1a), the minor axis length of the core (1a), and the thickness of the shell (1b), for example, after obtaining a cross-sectional specimen by cutting the solid electrolyte membrane (500) as in Fig. 6, the composite (1) existing in the second layer (12) within the solid electrolyte membrane (300) can be photographed using a scanning electron microscope (SEM) to observe the composite (1) existing in the second layer (12). In other words, for any ten composites (1) existing in one cross-sectional specimen, the major axis length of each core (1a), the minor axis length of the core (1a), and the thickness of the shell (1b) can be measured, and then the average value can be calculated to obtain the results.

[0056] Alternatively, the weight ratio of the core (1a) and the shell (1b) 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) and the lithium ion conduction effect by the shell (1b) can be harmonized.

[0057] 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 formed by the long axis of the complex (1) with the plane direction (X) of the solid electrolyte membrane (300) can be obtained by measuring the angle formed by the long axis of the complex (1) with the plane direction (X) of the solid electrolyte membrane (or the second layer (12)) indicated by a line, based on the cross-section of the solid electrolyte membrane (300) (or the second layer (12)), as illustrated in FIG. 6.

[0058] For example, the long axis of the complex (1) within the solid electrolyte membrane (300) can 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 effectively shortened, and the interfacial contact resistance between the solid electrolytes can be reduced.

[0059] In the complex (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-like, plate-like, or oval shape. Alternatively, the core (1a) may include a carbon-based material selected from among artificial graphite, natural graphite, graphene, carbon nanotubes (CNTs), carbon fibers, carbon black, or a combination thereof as the diamagnetic particle. At this time, the carbon nanotubes (CNTs) may be S-carbon nanotubes (short length CNTs) or L-carbon nanotubes (long length CNTs).

[0060] According to one embodiment, the shell (1b) may include a solid electrolyte commonly known in the art. For example, the shell (1b) 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. As a representative example, the solid electrolyte included in the shell (1b) may include a sulfide-based solid electrolyte, and the shell (1b) of the composite (1) may include Li6PS5Cl, which is a type of argyrodite-type sulfide-based solid electrolyte. Here, the description of the solid electrolyte particles in the first layer (11), the second layer (12), and the third layer (13) may be equally applied to the solid electrolyte usable in the shell (1b).

[0061] The content of the above complex (1) may be 0.1 wt% to 50 wt%, 0.5 wt% to 40 wt%, 1 wt% to 30 wt%, or 5 wt% to 25 wt% relative to the total weight of the second layer (12). In this range, the effect of improving ion conductivity and high-rate characteristics according to the complex (1) can be further enhanced.

[0062] A solid electrolyte membrane (300) according to one embodiment includes, as illustrated in FIG. 2, a first layer (11) including solid electrolyte particles (2); a second layer (12) positioned on the first layer (11) and including a complex (1); and a third layer (13) positioned on the second layer (12) and including solid electrolyte particles (2) in order to reduce the possibility of occurrence of an internal short circuit in the cell. In this way, by designing the membrane as a triple layer so that the complex (1) having a core including diamagnetic particles capable of electrical conductivity is included in the second layer (12), which is an intermediate layer, the safety of the battery can be ensured.

[0063] 1st and 3rd floors

[0064] The first layer (11) and the third layer (13) include solid electrolyte particles (2). Since the first layer (11) and the third layer (13) include solid electrolyte particles (2), the ionic conductivity of the solid electrolyte membrane can be secured, and unlike the second layer (12), since the first layer (11) and the third layer (13) do not include the complex (1), the occurrence of an internal short circuit of the cell that may result from the complex (1) included in the second layer (12) can be suppressed.

[0065] The solid electrolyte particles (2) included in the first layer (11) and the third layer (13) may include a solid electrolyte commonly known in the art, and for example, the solid electrolyte particles (2) may include a solid electrolyte selected from among a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof.

[0066] Below, the solid electrolyte particles (2) included in the first layer (11) and the third layer (13) are described in detail.

[0067] Sulfide-based solid electrolyte

[0068] 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.

[0069] 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. The ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0070] 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.

[0071] According to one embodiment, sulfide-based solid electrolyte particles 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 first heat treatment result is 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 robustness 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.

[0072] 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.

[0073] The argyrodite-type sulfide-based solid electrolyte particles may include, for example, a compound represented by the following chemical formula 11.

[0074] [Chemical Formula 11]

[0075] (Li a M 1 b M 2 c )(P d M 3 e )(S f M 4 g )X h

[0076] 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.

[0077] 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.

[0078] For example, in chemical formula 11, a+b+c+h=7, d+e=1, and f+g+h=6.

[0079] 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 Cu 0.06 )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.

[0080] 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.

[0081] 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 ㎛. Alternatively, 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 D 50 It may have been calculated.

[0082] Oxide-based solid electrolyte

[0083] 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 yO3(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.

[0084] Halide-based solid electrolyte

[0085] 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.

[0086] 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 may be, 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 0.6 Cl6, or combinations thereof, but is not limited thereto.

[0087] According to one embodiment, the solid electrolyte particles included in the first layer (11) and the third layer (13) may be the same as or different from the solid electrolyte type. Alternatively, the solid electrolyte particles (2) included in the first layer (11) and the third layer (13) may be the same as or different from the solid electrolyte type included in the shell (1b) of the complex (1). For example, the shell (1b) of the complex (1) may be composed of Li6PS5Cl, and the solid electrolyte particles included in the first layer (11) and the third layer (13) may also be composed of Li6PS5Cl.

[0088] According to one embodiment, the first layer (11) and the third layer (13) may each independently further include a binder as an optional component in addition to the aforementioned solid electrolyte particles, and / or further include other components such as an alkali metal salt, an ionic liquid, a conductive polymer, etc. Hereinafter, components that may be additionally included in the first layer (11) and the third layer (13) will be described in detail.

[0089] bookbinder

[0090] The first layer (11) and the third layer (13) may each further include a binder. The binder serves to adhere the solid electrolyte particles (2) to each other well within the first layer (11) and / or the third layer (13). 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.

[0091] The above binder may be included in an amount of 0.1 wt% to 3 wt% relative to the total weight of each of the first layer (11) and the third layer (13), for example, 0.5 wt% to 2 wt%, or 0.5 wt% to 1.5 wt%. Within this range, 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.

[0092] Other ingredients

[0093] The first layer (11) and the third layer (13) may each further include one or more other components selected from alkali metal salts, ionic liquids, and conductive polymers as optional components.

[0094] 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 lithium ion mobility of the solid electrolyte membrane. The lithium salt may be used 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] The first layer (11) and the third layer (13) may each have a weight ratio of solid electrolyte particles to ionic liquid of 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. When the above range is satisfied, the electrochemical contact area with the electrode is improved, so that ionic conductivity can be maintained or improved. Accordingly, the energy density, discharge capacity, rate characteristics, etc. of the all-solid-state secondary battery can be improved.

[0100] According to one embodiment, the average thickness of the first layer (11) may be the same as or different from the average thickness of the third layer (13). For example, each average thickness of the first layer (11) and the third layer (13) may be from 10 μm to 200 μm, for example, from 10 μm to 150 μm, from 10 μm to 100 μm, from 10 μm to 60 μm, from 10 μm to 50 μm, from 10 μm to 34 μm, or from 13 μm to 34 μm, from 15 μm to 34 μm, or from 20 μm to 34 μm.

[0101] 2nd floor

[0102] The second layer (12), as shown in Fig. 2, is positioned between the first layer (11) and the third layer (13), and the second layer (12) includes the aforementioned complex (1). By positioning the complex (1) in the second layer (12), which is an intermediate layer, internal short circuits of the cell can be suppressed, thereby ensuring the safety of the battery. According to one embodiment, the second layer (12) may further include solid electrolyte particles (2) in addition to the aforementioned complex (1).

[0103] For the solid electrolyte particles that can be included in the second layer (12), the description of the solid electrolyte in the shell (1b) of the aforementioned complex (1) and the solid electrolyte particles in the first layer (11) and the third layer (13) can be equally applied.

[0104] As an example, the solid electrolyte particles (2) included in the second layer (12) may be the same as or different from the solid electrolyte particles included in the shell (1b) of the complex (1) and the solid electrolyte particles included in one or more of the first layer (11) and the third layer (13). For example, the shell (1b) of the complex (1) may be composed of Li6PS5Cl, and the solid electrolyte particles included in the second layer (12) may be composed of Li6PS5Cl. Alternatively, the solid electrolyte particles included in the first layer (11) and the third layer (13) may be composed of Li6PS5Cl, and the solid electrolyte particles included in the second layer (12) may be composed of Li6PS5Cl.

[0105] Alternatively, the second layer (12) may further include the aforementioned binder as an optional component, and / or may further include other components such as an alkali metal salt, an ionic liquid, or a conductive polymer. Here, the same content as described above with respect to the first layer (11) and the third layer (13) may be applied to the binder and other components.

[0106] According to one embodiment, the content of the binder included in the second layer (12) may be included in an amount of 0.1 wt% to 3 wt% relative to the total weight of the second layer (12), for example, 0.5 wt% to 2 wt%, or 0.5 wt% to 1.5 wt%. Within this range, the components within the second layer (12) can be well combined without lowering the ionic conductivity of the solid electrolyte, thereby improving the durability and reliability of the battery.

[0107] According to one embodiment, the content of the solid electrolyte particles (2) included in the second layer (12) (i.e., excluding the solid electrolyte included in the shell (1b) of the complex (1)) may be 50 wt% to 99.9 wt% relative to the total weight of the second layer (12), for example, 60 wt% to 99.9 wt%, 65 wt% to 99.5 wt%, 70 wt% to 98 wt%, or 75 wt% to 97 wt%.

[0108] According to one embodiment, the average thickness of the second layer (12) may be the same as or different from the average thickness of one or more of the first layer (11) and the third layer (13). For example, the average thickness of the second layer (12) may be greater than each of the average thicknesses of the first layer (11) and the third layer (13). For example, the average thickness of the second layer (12) may be within a range of 1.2 to 5 times, or within a range of 1.3 to 4.8 times, 1.5 to 4.5 times, or 1.8 to 4 times, the average thickness of the first layer (11) and the third layer (13). Alternatively, the average thickness of the second layer (12) may be 10 μm to 200 μm, for example, 10 μm to 150 μm, 10 μm to 100 μm, 20 μm to 100 μm, 35 μm to 100 μm, 40 μm to 90 μm, or 50 μm to 80 μm. In this range, ionic conductivity due to the complex (1) included in the second layer (12) can be effectively secured.

[0109] According to one embodiment, the average thickness of the first layer (11) and the third layer (13) may be 10 μm to 34 μm, respectively, and the average thickness of the second layer (12) may be 35 μm to 100 μm.

[0110] Method for manufacturing a solid electrolyte membrane

[0111] In another embodiment, a method for manufacturing a solid electrolyte membrane is provided, comprising forming a first layer comprising solid electrolyte particles, forming a second layer comprising a complex on the first layer, and forming a third layer comprising solid electrolyte particles on the second layer, wherein the complex comprises a core comprising diamagnetic particles; and a shell surrounding the core and comprising a solid electrolyte.

[0112] The above description is about a method for manufacturing a solid electrolyte membrane, which is an example of an embodiment. Hereinafter, descriptions that overlap with the above description of the solid electrolyte membrane (300) will be omitted, and the processes for manufacturing the solid electrolyte membrane, which is an example of an embodiment, will be described in more detail.

[0113] The formation of the second layer (12) may include preparing a complex (1), preparing a slurry for forming a second layer (12) including the complex, and applying the slurry for forming the second layer (12) on the first layer (11). The slurry for forming the second layer (12) may further include solid electrolyte particles (2) in addition to the complex (1), and the description given above is equally applicable to the solid electrolyte particles that can be included in the slurry for forming the second layer (12), and therefore, the description thereof is omitted.

[0114] The slurry for forming the second layer (12) can be prepared by mixing the complex (1) and the second solvent. The second solvent is not particularly limited, as any commonly known solvent can be used as long as it can disperse the complex (1). As representative examples, the second solvent may include octyl acetate, isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof.

[0115] Alternatively, when preparing a slurry for forming a second layer (12), one or more components selected from the group consisting of solid electrolyte particles (2), 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 second layer (12), may be further included. In addition, a dispersant (e.g., H-NBR, etc.) commonly known in the art may be further added.

[0116] The slurry for forming the second layer (12) described above can be applied onto the first layer (11), and any method commonly known in the art can be used without limitation as the application method. For example, methods such as bar coating, spin coating, die coating, transfer coating, and spray coating can be used.

[0117] After applying the slurry for forming the second layer described above, drying the applied slurry for forming the second layer may be further included. For example, the drying may be performed in a convection oven, and the temperature of the drying may be 30° C. to 100° C., or 35° C. to 95° C., 40° C. to 90° C., 45° C. to 80° C., 48° C. to 75° C., or 50° C. to 70° C. Alternatively, the drying may be performed for 10 seconds to 20 minutes, or 30 seconds to 15 minutes, 1 minute to 10 minutes, or 2 minutes to 8 minutes.

[0118] According to one embodiment, the method may further include applying a magnetic field to a slurry for forming a second layer (12) applied on either one of the first layer (11) and the third layer (13). When this is satisfied, the complex (1) randomly distributed within the second layer (12) may have an orientation in which it is oriented in a direction (Y) perpendicular to the plane direction (X) of the solid electrolyte membrane (300) or close to the perpendicular direction (Y).

[0119] For example, the strength of the magnetic field may be 0.1 T (Tesla) to 3 T or 0.5 to 2 T. Alternatively, the application time of the magnetic field may be 0.1 seconds to 10 minutes, 30 seconds to 8 minutes, or 1 minute to 5 minutes. The temperature at the time of applying the magnetic field 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 (1) in the second layer (12) due to the application of the magnetic field can be more effectively secured.

[0120] After the application of the magnetic field, the slurry for forming the second layer (12) to which the magnetic field is applied may further be dried. Through the drying, the second layer (12) may be formed on either one of the first layer (11) and the third layer (13). For example, the drying may be performed in a convection oven, and the temperature of the drying may be 30° C. to 100° C., or 35° C. to 95° C., 40° C. to 90° C., 45° C. to 80° C., 48° C. to 75° C., or 50° C. to 70° C. Alternatively, the drying may be performed for 10 seconds to 20 minutes, or may be performed for 30 seconds to 15 minutes, 1 minute to 10 minutes, or 2 minutes to 8 minutes. In this range, it is possible to effectively secure suitable orientation of the complex (1) within the second layer (12).

[0121] Alternatively, the method may further include drying the slurry for forming the second layer (12) to which a magnetic field is applied, forming the second layer (12) on the first layer (11), and then rolling the second layer (12), wherein the conditions for drying and rolling, etc., may be as commonly known in the art.

[0122] Alternatively, after application of the magnetic field, the method may further include removing the substrate as needed.

[0123] According to one embodiment, the preparation of the above-described complex (1) may include preparing a mixed solution by mixing the diamagnetic particles, solid electrolyte particles, and the first solvent, drying the mixed solution, and heat-treating the dried product.

[0124] According to one embodiment, when manufacturing the complex (1), the addition ratio of the diamagnetic particles and the solid electrolyte particles may be 1:1 to 1:500, 1:2 to 1:100, or 1:10 to 1:50.

[0125] The first solvent is not particularly limited, as any commonly known solvent can be used as long as it can disperse the diamagnetic particles and the solid electrolyte particles. However, acetonitrile can be used as a representative example.

[0126] For example, the drying of the slurry for forming the first layer applied as described above can be performed at 80°C to 150°C, 90°C to 140°C, or 100°C to 130°C. Alternatively, the heat treatment can be performed at 200°C to 600°C, 250°C to 550°C, 300°C to 500°C, or 350°C to 450°C. In this range, a composite (1) in which the orientation effect by the core (1a) and the lithium ion conduction effect by the shell (1b) are in harmony can be effectively manufactured.

[0127] The first layer (11) can be formed by preparing a slurry for forming the first layer (11) including solid electrolyte particles and a solvent, and then applying it on a substrate or an already formed second layer (12). Here, the solvent can be any commonly known solvent that can disperse the solid electrolyte particles (2), and is not particularly limited thereto. As a representative example, octyl acetate can be used. As a method for applying the slurry for forming the second layer, any method commonly known in the art can be used without limitation. For example, methods such as bar coating, spin coating, die coating, transfer coating, and spray coating can be used.

[0128] After applying the slurry for forming the first layer, the applied slurry for forming the second layer may be dried to form the first layer. Here, the drying may be performed in a convection oven, and the temperature of the drying may be 30° C. to 100° C., or 35° C. to 95° C., 40° C. to 90° C., 45° C. to 80° C., 48° C. to 75° C., or 50° C. to 70° C. Alternatively, the drying may be performed for 10 seconds to 20 minutes, or 30 seconds to 15 minutes, 1 minute to 10 minutes, or 2 minutes to 8 minutes. Within this range, suitable orientation of the composite (1) within the second layer (12) can be effectively secured.

[0129] Alternatively, after drying the slurry for forming the first layer, rolling the first layer may be further included, if necessary. Here, the rolling conditions may be as commonly known in the art.

[0130] Alternatively, when using a substrate in the formation of the first layer, it may further include removing the substrate as needed.

[0131] Alternatively, the slurry for forming the first layer (11) may further include 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 second layer (12). Alternatively, a dispersant commonly known in the art (e.g., H-NBR, etc.) may be further added.

[0132] In the case of the third layer (13), a slurry for forming the third layer (13) containing solid electrolyte particles and a solvent is prepared, and then the slurry is applied onto a substrate or an already formed second layer (12). Here, the solvent is not particularly limited and any commonly known solvent can be used as long as it is a solvent capable of dispersing the solid electrolyte particles (2), and octyl acetate can be used as a representative example.

[0133] After applying the slurry for forming the third layer, the applied slurry for forming the third layer may be dried to form the third layer. For example, the drying may be performed in a convection oven. The temperature for the drying may be 30° C. to 100° C., or 35° C. to 95° C., 40° C. to 90° C., 45° C. to 80° C., 48° C. to 75° C., or 50° C. to 70° C. Alternatively, the drying may be performed for 10 seconds to 20 minutes, or 30 seconds to 15 minutes, 1 minute to 10 minutes, or 2 minutes to 8 minutes.

[0134] Alternatively, the method may further include drying the slurry for forming the third layer described above to form the third layer (13) on the second layer (12), and then rolling the third layer (13), wherein the conditions for rolling, etc. may be as commonly known in the relevant technical field.

[0135] Alternatively, when using a substrate in forming the third layer, the method may further include removing the substrate as needed.

[0136] Alternatively, the slurry for forming the third layer (13) may further include 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 second layer (12). Alternatively, a dispersant commonly known in the art (e.g., H-NBR, etc.) may be added.

[0137] According to one embodiment, after forming the third layer described above, drying the laminate in which the first layer, the second layer, and the third layer are laminated may be further included. For example, drying the laminate may be performed in a vacuum oven. For example, the temperature of drying for the laminate described above may be higher than the temperature of drying for each of the first layer, the second layer, and the third layer described above. Alternatively, the temperature of drying for the laminate may be performed at 50°C to 150°C, 60°C to 130°C, 70°C to 120°C, or 80°C to 100°C. Alternatively, the time of drying for the laminate may be 30 minutes to 10 hours, 40 minutes to 8 hours, or 1 hour to 5 hours. Within this range, a solid electrolyte membrane (300) in which the first layer, the second layer, and the third layer are laminated can be effectively manufactured.

[0138] All-solid-state secondary battery

[0139] In another embodiment, an all-solid-state secondary battery is provided, which includes 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 of the cell, thereby ensuring the safety of the battery.

[0140] 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 FIGS. 7 and 8.

[0141] The above all-solid-state secondary battery may also be expressed as an all-solid-state battery or an all-solid-state lithium secondary battery.

[0142] Fig. 7 is a cross-sectional view of an all-solid-state battery according to an embodiment. Referring to Fig. 7, 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. 7 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.

[0143] bipolar layer

[0144] 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).

[0145] 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.

[0146] The positive electrode active material layer (203) includes a positive electrode active material and may optionally further include a solid electrolyte, a binder, and / or a conductive material.

[0147] positive electrode active material

[0148] 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.

[0149] 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.

[0150] 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 Nor 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);Li a Nor 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); The a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); The a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); The a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); The a Mn2G b O4(0.90 ≤ a ≤1.8, 0.001 ≤ b ≤ 0.1); The a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5); The (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); The a FePO4(0.90 ≤ to ≤ 1.8)

[0151] 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.

[0152] 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.

[0153] [Chemical Formula 21]

[0154] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0155] 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.

[0156] 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.

[0157] [Chemical Formula 22]

[0158] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0159] 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 M 3 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.

[0160] [Chemical Formula 23]

[0161] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0162] 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.

[0163] [Chemical Formula 24]

[0164] Li a4 Ni x4 Mny4 M 5 z4 O 2-b4 X b4

[0165] 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.

[0166] The average particle diameter (D) of the above positive electrode active material 50 ) may be 1 μm to 25 μm, for example, 3 μm to 25 μm, 1 μm to 20 μm, 1 μm to 18 μm, 3 μm to 15 μm, or 5 μm to 15 μm. 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.

[0167] 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.

[0168] 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.

[0169] 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%.

[0170] bookbinder

[0171] 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.

[0172] Challenge

[0173] 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.

[0174] 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).

[0175] The 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 materials, binders, and conductive agents. 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.

[0176] solid electrolyte

[0177] 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 descriptions thereof are equally applicable to the description of 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.

[0178] As for the solid electrolyte included in the positive electrode active material layer (203), the description of the solid electrolyte included in the shell (1b) of the above-described complex (1) or the solid electrolyte particles included in the first layer (11) to the third layer (13) in the solid electrolyte membrane (300) can be equally applied.

[0179] For example, the solid electrolyte included in the positive electrode active material layer (203) may be the same as the solid electrolyte included in the shell (1b) of the aforementioned complex (1), or the solid electrolyte particles included in the first layer (11) to the third layer (13) 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.

[0180] In the 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.

[0181] cathode layer

[0182] The negative electrode layer may include, for example, a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] 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.

[0192] The above binder serves to adhere the negative active material particles well to each other and also to adhere the negative active material well to the current collector. The binder may include an insoluble binder, a water-soluble binder, or a combination thereof.

[0193] 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.

[0194] 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.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] Fig. 8 is a schematic cross-sectional view of an all-solid-state battery including a precipitated negative electrode layer. Referring to Fig. 8, the precipitated negative electrode layer (400') may include a negative electrode current collector (401) and a negative electrode coating layer (405) positioned on the negative electrode current collector. In an all-solid-state battery including such a precipitated negative electrode layer (400'), initial charging begins in a state in which no negative electrode active material is present, and upon charging, 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.

[0200] The above cathode coating layer (405) may include a lithium-philic metal, carbon material, or a combination thereof that acts as a catalyst.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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 ㎛.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] Hereinafter, examples and comparative examples of the present invention are described. The following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0211] Example 1

[0212] (1) Manufacturing of complex

[0213] As diamagnetic particles, needle-shaped artificial graphite having an aspect ratio of 4.0, a minor axis length of 1 μm, and a major axis length of 4 μm was prepared. In addition, as a raw material for a solid electrolyte, a mixture of Li2S, P2S5, and LiCl in a molar ratio of 5:1:2 was prepared. In the presence of acetonitrile as a solvent, the solid electrolyte raw material and the diamagnetic particles were mixed in a weight ratio of 30:1, magnetically stirred for 2 hours, dried at 120°C, and then heat-treated at 400°C. Accordingly, a solid electrolyte composite was obtained, including a core including needle-shaped artificial graphite; and a shell surrounding the core and including a Li6PS5Cl solid electrolyte.

[0214] (2) Preparation of slurry for forming the second layer

[0215] Under the solvent octyl acetate, 20 wt% of the complex, 78.3 wt% of the argyrodite-type crystals Li6PS5Cl solid electrolyte particles (D 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 a second layer.

[0216] (3) Manufacturing of the first layer

[0217] An acrylic binder (SX-A334, Zeon Co., Ltd.) was added to octyl acetate to prepare a 4 wt% binder solution. Li6PS5Cl solid electrolyte particles (D) which are argyrodite-type crystals 50 = 3㎛) was added to the prepared acrylic binder solution and mixed with a thin mixer to prepare a slurry. The slurry contained 1.5 parts by weight of acrylic binder relative to 98.5 parts by weight of the solid electrolyte. The prepared slurry was applied onto a nonwoven fabric using a bar coater and dried in a convection oven at 50°C for 5 minutes to obtain a laminate.

[0218] (4) Manufacturing of the second layer

[0219] The manufactured slurry for forming the second layer was applied onto the aforementioned first layer using a bar coater, and a magnetic field was applied at a strength of 1 T at 25°C for 2 minutes. After the application of the magnetic field, the slurry to which the magnetic field was applied was dried in a convection oven at 50°C for 5 minutes. Through the above process, a laminate in which a second layer was formed on the first layer was manufactured.

[0220] (5) Manufacturing of the third layer

[0221] Subsequently, an acrylic binder (SX-A334, Zeon Co., Ltd.) was added to octyl acetate to prepare a 4 wt% binder solution. Li6PS5Cl solid electrolyte particles (D) which are argyrodite-type crystals 50 = 3㎛), the prepared acrylic binder solution was added and mixed with a sink mixer to prepare a slurry for forming the third layer. The slurry for forming the third layer contained 1.5 parts by weight of the acrylic binder relative to 98.5 parts by weight of the solid electrolyte. The prepared slurry for forming the third layer was applied onto the second layer using a bar coater and dried in a convection oven at 50°C for 5 minutes to obtain a laminate in which the first layer, the second layer, and the third layer were sequentially laminated.

[0222] Afterwards, the laminate was dried in a vacuum oven at 80°C for more than 2 hours to manufacture a solid electrolyte membrane (300).

[0223] (6) Manufacturing of the anode layer

[0224] Using octyl acetate as a solvent, a solid electrolyte of Li6PS5Cl (D) containing 13.5 wt% of argyrodite-type crystals 50 =3㎛), 85 wt% of positive electrode active material (LiNi 0.8 Co 0.1 Al 0.1O2), 1.0 wt% PVDF binder, and 0.5 wt% carbon nanotubes were mixed to prepare a cathode slurry. The cathode slurry was applied onto one side of a cathode current collector made of aluminum foil, and then dried and rolled to prepare a cathode layer.

[0225] (7) Manufacturing of cathode layer

[0226] 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.

[0227] A mixed powder of 0.25 g of 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. Subsequently, 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 nickel foil 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 8 hours or more, i.e., 10 hours. By the above process, a negative electrode layer having a negative electrode coating layer formed on a negative electrode current collector was prepared.

[0228] (8) Manufacturing of all-solid-state secondary batteries

[0229] A laminate was prepared by placing the solid electrolyte membrane (300) 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 min 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 103 μm, the thickness of the negative electrode coating layer was 7 μm, and the thickness of the solid electrolyte membrane was 60 μm.

[0230] Additionally, for the aforementioned solid electrolyte membrane (300) in which the first layer (11), the second layer (12), and the third layer (13) are sequentially laminated, a cross-sectional specimen was prepared so that the cross-section could be observed, and then photographed and observed using a scanning electron microscope (SEM). The average thickness of the first layer measured by SEM was 30 μm, the average thickness of the second layer was 60 μm, and the average thickness of the third layer was 30 μm. At this time, the average thicknesses of the first layer, the second layer, and the third layer were obtained by measuring the thickness at 10 random points at equal intervals and calculating the average value.

[0231] In addition, among the cross-sectional specimens, 10 random complexes existing in the second layer (12) were selected, the thickness of the shell of each complex was measured, and the average value was calculated. The average shell thickness was 0.5 ㎛.

[0232] Comparative Example 1

[0233] A solid electrolyte membrane and an all-solid-state secondary battery of Comparative Example 1 were manufactured in substantially the same manner as Example 1, except that a single-layer solid electrolyte membrane containing only solid electrolyte particles (Li6PS5Cl) was used instead of a triple-layer solid electrolyte membrane.

[0234] Comparative Example 2

[0235] In the preparation of the slurry for forming the second layer, a solid electrolyte membrane and an all-solid-state secondary battery of Comparative Example 2 were prepared in substantially the same manner as Example 1, except that only 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 used instead of the composite and a shell was not formed.

[0236] Comparative Example 3

[0237] In the manufacture of the composite, a solid electrolyte membrane and an all-solid-state secondary battery of Comparative Example 3 were manufactured in substantially the same manner as in Example 1, except that needle-shaped artificial graphite having an aspect ratio of 1.0, a short-axis length of 3.5 μm, and a long-axis length of 3.5 μm was used and a shell was not formed.

[0238] For reference, the structure of the solid electrolyte (or composite) formed by Example 1 and Comparative Examples 1 to 3, the structure of the solid electrolyte membrane, the shape of the diamagnetic particles, the aspect ratio of the diamagnetic particles, the short axis length and long axis length of the diamagnetic particles, and the weight ratio of the core and shell in the composite are shown in Table 1 below.

[0239] Structure of solid electrolyte (or composite)Solid electrolyte membrane structureDiamagnetic particle core: solid electrolyte shellWeight ratioShapeAspect ratioMinor axis lengthMajor axis lengthExample 1Diamagnetic particle core-solid electrolyte shell3-layeredacrylic4.01 ㎛4 ㎛1:30Comparative example 1Solid electrolyte single-layeredamorphous----Comparative example 2Diamagnetic particle single-layeredacrylic4.01 ㎛4 ㎛-Comparative example 3Diamagnetic particle single-layeredspherical1.03.5 ㎛3.5 ㎛-

[0240] Evaluation Example 1: Ionic Conductivity of the Anode Layer

[0241] For each solid electrolyte membrane of the examples and comparative examples, ionic conductivity was evaluated.

[0242] Specifically, each solid electrolyte membrane obtained from the aforementioned examples and comparative examples 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.

[0243] Ionic Conductivity (mS / cm) (@ 45℃)Example 10.41Comparative Example 10.34Comparative Example 20.4Comparative Example 30.32

[0244] 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 to 3.

[0245] In Example 1, a solid electrolyte membrane was manufactured using a core-shell structured composite including a core comprising diamagnetic particles having an aspect ratio greater than 1; and a shell surrounding the core and containing a solid electrolyte. Accordingly, when a magnetic field was applied during the manufacturing process of Example 1, the composite was oriented within the second layer (12) of the solid electrolyte membrane within an angle of 50 to 130° with respect to the plane direction of the solid electrolyte membrane. The orientation of the composite 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 described above, it was confirmed that the lithium ion path was shortened and the solid electrolyte membrane according to Example 1 had high ionic conductivity.

[0246] On the other hand, Comparative Example 1 is a case where a single-layer solid electrolyte membrane was used instead of the triple-layer solid electrolyte membrane of Example 1, and an amorphous solid electrolyte itself was used instead of the composite of Example 1. Accordingly, during the process of manufacturing the solid electrolyte membrane obtained from Comparative Example 1, it was confirmed that even when a magnetic field was applied, the amorphous solid electrolyte within the solid electrolyte membrane did not exhibit a specific orientation and was oriented randomly.

[0247] Comparative Example 2 is an example in which only needle-shaped artificial graphite without a solid electrolyte shell formed was used instead of the composite present in the second layer of Example 1. Accordingly, during the process of manufacturing the solid electrolyte membrane obtained from Comparative Example 2, the orientation of the needle-shaped artificial graphite without a solid electrolyte shell formed may be close to vertical within the second layer of the solid electrolyte membrane due to the applied magnetic field. However, in the case of Comparative Example 2, it was found that a battery safety problem occurred in Evaluation Example 2 below due to the fact that the solid electrolyte shell was not formed.

[0248] Meanwhile, in the solid electrolyte membrane according to Comparative Example 3, the complex did not exhibit orientation even when a magnetic field was applied. Accordingly, no increase in ionic conductivity was observed compared to Comparative Example 1.

[0249] Evaluation Example 2: Evaluation of high-rate characteristics and occurrence of internal short circuits in all-solid-state secondary batteries.

[0250] For each all-solid-state secondary battery of the examples and comparative examples, high-rate characteristics were evaluated.

[0251] Specifically, in a constant temperature bath at 45°C, the battery was charged at a constant current of 0.1 C until the battery voltage reached 4.25 V, and discharged at a constant current of 0.1 C until the battery voltage reached 2.5 V (first cycle); charged at a constant current of 0.1 C until the battery voltage reached 4.25 V, and discharged at a constant current of 0.33 C until the battery voltage reached 2.5 V (second cycle); charged at a constant current of 0.1 C until the battery voltage reached 4.25 V, and discharged at a constant current of 1.0 C until the battery voltage reached 2.5 V (third cycle).

[0252] 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 4.

[0253] [Equation 4]

[0254] High rate characteristics [%] = [Discharge capacity in the 3rd cycle (1C rate) / Discharge capacity in the 1st cycle (0.1C rate)] × 100 [%]

[0255] 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.

[0256] 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 119718417287.3X Comparative example 119518316886.2X Comparative example 2----O Comparative example 3----O

[0257] According to Table 3 above, in the case of Example 1, compared to the cases of Comparative Examples 1 to 3, not only the discharge capacity in each cycle but also the high-rate characteristics were superior, and internal short circuits did not occur. Through this, it can be seen that, as in Example 1, by forming a solid electrolyte membrane into a triple layer using a composite, the high-rate characteristics of the all-solid-state secondary battery are improved and there is an effect of suppressing internal short circuits.

[0258] In contrast, in the case of Comparative Example 1, no internal short circuit occurred in the cell, but as confirmed in Evaluation Example 1 above, the ionic conductivity was low, and in the cases of Comparative Examples 2 and 3, it was confirmed that an internal short circuit occurred in the cell.

[0259] 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.

[0260] [Explanation of symbols]

[0261] 1: composite, 1a: core, 1b: shell, 2: solid electrolyte particle, 4: lithium ion, 11: first layer, 12: second layer, 13: third layer, 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. A first layer comprising solid electrolyte particles; A second layer located on the first layer and comprising a complex; and a third layer positioned on the second layer and including solid electrolyte particles, The above complex comprises a core including diamagnetic particles; and a shell surrounding the core and including a solid electrolyte.

2. In paragraph 1, The above diamagnetic particles are 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 long axis of the above complex 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 complex is a solid electrolyte membrane comprising a core and a shell in a weight ratio of 1:1 to 1:

500.

5. In paragraph 1, The above diamagnetic particles are a solid electrolyte membrane having a needle-like, plate-like or oval shape.

6. In paragraph 1, The above core is a solid electrolyte membrane comprising a carbonaceous material selected from among artificial graphite, natural graphite, graphene, carbon nanotubes (CNTs), carbon fibers, carbon black, or a combination thereof as diamagnetic particles.

7. In paragraph 1, The above shell is a solid electrolyte membrane including a solid electrolyte selected from a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof.

8. In paragraph 1, The above complex is a solid electrolyte membrane satisfying at least one of the following mathematical formulas 2 and 3: [Equation 2] 0.1 ≤ A1 / B ≤ 100 [Equation 3] 0.01 ≤ A2 / B ≤ 10 In the above mathematical expressions 2 and 3, A1 represents the major axis length of the core, A2 represents the minor axis length of the core, and B represents the thickness of the shell.

9. In paragraph 1, The second layer is a solid electrolyte membrane further comprising solid electrolyte particles.

10. In paragraph 1, The above solid electrolyte particles are solid electrolyte membranes that are sulfide-based solid electrolyte particles.

11. In paragraph 1, The longitudinal length of the core is 1 ㎛ to 50 ㎛, A solid electrolyte membrane having a short axis length of the core of 10 nm to 5 μm.

12. In paragraph 1, A solid electrolyte membrane comprising the above complex in an amount of 0.1 wt% to 50 wt% relative to the total weight of the second layer.

13. In paragraph 1, The average thickness of the first layer is 10 ㎛ to 200 ㎛, A solid electrolyte membrane having an average thickness of the third layer of 10 ㎛ to 200 ㎛.

14. In paragraph 1, A solid electrolyte membrane wherein the average thickness of the second layer is greater than the average thicknesses of each of the first layer and the third layer.

15. In paragraph 1, A solid electrolyte membrane wherein the average thickness of the second layer is within a range of 1.2 to 5 times the average thickness of each of the first and third layers.

16. In paragraph 1, The average thickness of the first layer is 10 ㎛ to 34 ㎛, The average thickness of the second layer is 35 ㎛ to 100 ㎛, A solid electrolyte membrane having an average thickness of the third layer of 10 ㎛ to 34 ㎛.

17. In paragraph 1, A solid electrolyte membrane in which the content of the binder included in the second layer is 0.1 wt% to 3 wt% relative to the total weight of the second layer.

18. In paragraph 1, A solid electrolyte membrane in which the content of solid electrolyte particles included in the second layer is 50 wt% to 99.9 wt% relative to the total weight of the second layer.

19. Forming a first layer containing solid electrolyte particles, Forming a second layer containing a complex on the first layer, comprising forming a third layer including solid electrolyte particles on the second layer; A method for manufacturing a solid electrolyte membrane, wherein the complex comprises a core including diamagnetic particles; and a shell surrounding the core and including a solid electrolyte.

20. In paragraph 19, The formation of the second layer is A composite is prepared, comprising: a core including diamagnetic particles; and a shell surrounding the core and including a solid electrolyte; A slurry for forming a second layer including the above complex is prepared, A method for manufacturing a solid electrolyte membrane, comprising applying a slurry for forming the second layer on the first layer.

21. In paragraph 20, A method for manufacturing a solid electrolyte membrane, further comprising applying a magnetic field to a slurry for forming a second layer applied on the first layer.

22. In paragraph 21, A method for manufacturing a solid electrolyte membrane, further comprising drying a slurry for forming a second layer to which the magnetic field is applied.

23. In paragraph 19, The manufacture of the above complex is as follows: By mixing the above diamagnetic particles, solid electrolyte and first solvent, a mixed solution is prepared, Dry the above mixed solution, A method for producing a solid electrolyte membrane, comprising heat-treating the obtained product of the above drying.

24. In paragraph 20, A method for producing a solid electrolyte membrane, wherein the slurry for forming the second layer is produced by mixing the complex and the second solvent.

25. In paragraph 21, A method for manufacturing a solid electrolyte membrane wherein the strength of the magnetic field is 0.1 to 3 T.

26. In paragraph 21, A method for manufacturing a solid electrolyte membrane, wherein the application time of the magnetic field is 0.1 seconds to 10 minutes.

27. In paragraph 19, After the formation of the third layer, the laminate is further dried, in which the first layer, the second layer, and the third layer are laminated. A method for manufacturing a solid electrolyte membrane, wherein the drying temperature for the above laminate is higher than the drying temperature for each of the first layer, the second layer, and the third layer.

28. In paragraph 27, A method for manufacturing a solid electrolyte membrane, wherein the drying temperature of the above laminate is 70°C to 120°C.

29. Bipolar layer; cathode layer; and An all-solid-state secondary battery comprising a solid electrolyte membrane according to any one of claims 1 to 18 positioned between the positive electrode layer and the negative electrode layer.

30. In paragraph 29, The negative electrode comprises a negative electrode current collector; and a negative electrode coating layer positioned on the negative electrode current collector and including a lithium-philic metal, a carbon material, or a combination thereof; An all-solid-state secondary battery comprising a lithium metal layer formed by charging between the negative electrode current collector and the negative electrode coating layer.

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