Conductive material, positive electrode active material layer comprising same, and all-solid-state battery

Abstract

The present invention relates to a conductive material for an all-solid-state battery in which a first binder is coated on at least a portion of the surface of a needle-type conductive material, a positive electrode active material layer for an all-solid-state battery comprising same, and an all-solid-state battery. The all-solid-state battery according to the present invention can exhibit excellent capacity retention during cycling even under low operating voltage, with outstanding high-rate characteristics and adhesion characteristics.

Description

Conductive material, positive active material layer including the same, and all-solid-state battery

[0001] The present invention relates to a conductive material, a positive electrode active material layer comprising the same, and an all-solid-state battery. The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0159456 filed on November 11, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of the specification.

[0002] Recently, all-solid-state batteries with high energy density and stability have been proposed in response to industrial demands, and efforts to further improve these characteristics are ongoing.

[0003] All-solid-state batteries consist of a positive electrode, a solid electrolyte layer, and a negative electrode, and the electrode (positive or negative electrode) is composed of elements such as an active material, a solid electrolyte, a binder, and a conductive material. In this case, the conductive material is important as it plays a role in ensuring conductivity within the electrode, but if an excessive amount of conductive material is included, it causes problems as the battery life is reduced due to side reactions during charging and discharging. Additionally, the binder is important as it plays a role in providing binding force to the components within the electrode, but if an excessive amount of binder is included, it acts as a resistor to ion conduction, which causes problems in degrading battery performance.

[0004] Therefore, in order to manufacture an all-solid-state battery with excellent performance and lifespan, it is necessary to include a conductive material and a binder in appropriate proportions and / or amounts, and to improve the bonding force or interaction between components within the electrode.

[0005] Meanwhile, in the case of all-solid-state batteries, it is necessary to apply pressure of up to tens of megapascals (MPa) during the activation phase, evaluation phase, and / or final product of the battery for stable operation.

[0006] External devices such as pressure jigs are used to maintain this pressure, but because their volume and weight reduce performance characteristics such as energy density and capacity, ensuring stable operation of all-solid-state batteries even under low operating pressure is a key challenge in the commercialization of all-solid-state batteries.

[0007] The present invention aims to solve the above problem by providing a conductive material having excellent capacity retention rate according to the cycle even under low driving pressure, as well as excellent high-rate characteristics and adhesion characteristics, an anode active material layer including the same, and an all-solid-state battery.

[0008] The present invention relates to a conductive material for an all-solid-state battery, characterized in that a first binder is coated on at least a portion of the surface of a linear (needle-type) conductive material.

[0009] In one embodiment, the average length of the particles of the linear conductive material may be 1 μm or more to 60 μm or more.

[0010] In one embodiment, the aspect ratio of the particles of the linear conductive material may be 10 or more to 60 or less.

[0011] In one embodiment, the linear conductive material may be one or more selected from the group comprising carbon nanotubes (CNT), carbon nanofibers (CNF), graphene, and vapor-grown carbon fibers (VGCF).

[0012] In one embodiment, the first binder may be one or more selected from the group consisting of PVDF (poly(vinylidene fluoride)), PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene), P(VDF-TrFE) (Poly(vinylidene fluoride-co-trifluoroethylene)), P(VDF-TrFE-CFE) (Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)), PVDF-CTFE (Poly(vinylidene fluoride-co-chlorotrifluoroethylene)), BR (polybutadiene rubber), NBR (nitrile butadiene rubber), SBR (styrene butadiene rubber), cellulose, and PTFE (polytetrafluoroethylene).

[0013] In one embodiment, the melting temperature of the first binder may be 100°C or higher to 250°C or higher.

[0014] In one embodiment, the first binder may be included in an amount of 10 parts by weight or more to 30 parts by weight or less per 100 parts by weight of conductive material.

[0015] The present invention also relates to a positive active material layer for an all-solid-state battery comprising a positive active material, a solid electrolyte, a conductive material for the all-solid-state battery, and a second binder.

[0016] In one embodiment, the conductive material can form a network structure within the positive active material layer.

[0017] In one embodiment, the second binder may be a rubber-based binder.

[0018] In one embodiment, the weight ratio of the second binder to the first binder may be 0.1 or more to 10 or less.

[0019] In one embodiment, the solid electrolyte may be a sulfide-based solid electrolyte.

[0020] In one embodiment, the sulfide-based solid electrolyte is Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-LiBr-LiI-P2S5, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, and In), Li2S-SiS2-P2S5-LiI, Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are positive numbers), Z is one of Ge, Zn, or Ga, L i2 S-GeS2, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2) and Li 7-x PS 6-x I x It may be one or more selected from a group including (0≤x≤2).

[0021] The present invention also relates to an all-solid-state battery comprising a positive electrode including a positive electrode active material layer according to the above, a solid electrolyte layer, and a negative electrode.

[0022] In one embodiment, the all-solid-state battery may be an anodeless all-solid-state battery.

[0023] In one embodiment, the all-solid-state battery may have a battery driving pressure of 8 MPa or less.

[0024] According to the present invention, a conductive material having excellent capacity retention rate according to the cycle even under low driving pressure, and also excellent high-rate characteristics and adhesion characteristics, a positive electrode active material layer including the same, and an all-solid-state battery can be provided.

[0025] Figure 1 is a scanning electron microscope (SEM) image of a linear conductive material according to an embodiment of the present invention.

[0026] Figure 2 shows the surface SEM (left) and Carbon EDS images of an anode according to an embodiment of the present invention.

[0027] Figure 3 is an image showing an example of a solid-state battery pressurization device.

[0028] Terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0029] Therefore, it should be understood that the configuration of the embodiments described in this specification is merely one of the most preferred embodiments of the present invention and does not represent all of the technical ideas of the present invention, and that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0030] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0031] In this specification, when a part is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Thus, for example, a composition comprising compound A may include compounds other than A. However, the term “comprising” also encompasses, in a more restrictive sense as a specific embodiment thereof, “essentially / essentially composed of” and “composed of,” so, for example, a “composition comprising compound A” may also be (essentially / essentially) composed of compound A.

[0032] In connection with this, terms such as “comprising” or “having,” as described in this specification, are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0033] In this specification, when any layer is described as being located “on” or “between” another arbitrary layer, this includes not only cases where any layer is in contact with another arbitrary layer, but also cases where another layer or material, etc., exists between the two layers.

[0034] Where in this specification a quantity, concentration, or other value or parameter is given as an enumeration of a range, a preferred range, a preferred upper limit, and a preferred lower limit, it should be understood that any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the range is disclosed separately, specifically discloses all ranges that may be formed. Where a range of numerical values ​​is mentioned in this specification, unless otherwise stated, for example, without limiting terms such as greater than or less than, the range is intended to include its endpoint value and all integers and fractions within that range. The scope of the invention is not intended to be limited to the specific value mentioned when defining the range.

[0035] Among the physical properties mentioned in this specification, if the measured temperature affects the property, the property is measured at room temperature unless specifically otherwise specified. The term "room temperature" refers to a natural temperature that has not been heated or cooled, and may mean, for example, any temperature within the range of about 10°C or higher to 30°C or lower, or about 23°C or about 25°C. Furthermore, unless specifically otherwise specified, the unit of temperature in this specification is °C.

[0036] In addition, among the physical properties mentioned in this specification, if the measured pressure affects the physical property, unless specifically otherwise specified, the physical property is measured at normal pressure, that is, atmospheric pressure (about 1 atmosphere).

[0037] The first aspect of the present invention relates to a conductive material for an all-solid-state battery.

[0038] The above conductive material may, for example, have a first binder coated on at least a portion of the surface of a linear conductive material.

[0039] The average length of the particles of the linear conductive material may, for example, be 1 μm or more to 60 μm or less. In other examples, the average length of the particles of the linear conductive material may be 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, or 8 μm or more, or 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. The average length of the particles of the linear conductive material may be derived by taking an image of the linear conductive material with SEM or TEM, measuring the lengths of several CNFs, and then calculating the average value.

[0040] The average aspect ratio (length of the major axis / length of the minor axis) of the particles of the linear conductive material may be, for example, 10 or more to 60 or less. In other examples, the average aspect ratio of the particles of the linear conductive material may be 15 or more, 20 or more, 25 or more, or 30 or more, or 55 or less, 50 or less, 45 or less, or 40 or less. The average aspect ratio of the particles of the linear conductive material may be derived by taking an image of the linear conductive material with SEM or TEM, measuring the length and diameter of several CNFs to derive the aspect ratio, and then calculating the average value. Alternatively, it may be calculated by obtaining an image of the linear conductive material with SEM and TEM and deriving the average length and average diameter of the linear conductive material using the thresholding method of ImageJ software. By controlling the average length and average aspect ratio of the particles of the linear conductive material as described above, a network structure can be implemented more effectively, and the binding force or interaction between components within the anode active material layer can be further enhanced without degradation of performance.

[0041] In this specification, the terms “linear conductive material” and “point conductive material” can be classified by the shape of the conductive material, for example, if the average aspect ratio is 2 or more, it may be a linear conductive material, and if it is less than 2, it may be a point conductive material. The linear conductive material may have a shape as shown in FIG. 1, for example.

[0042] The above linear conductive material may be one or more selected from the group including, for example, carbon nanotubes (CNT), carbon nanofibers (CNF), graphene, and vapor-grown carbon fibers (VGCF).

[0043] The above point-type conductive material may be one or more selected from the group consisting of, for example, carbon black, acetylene black, Ketjenblack, channel black, furnace black, lamp black, and thermal black.

[0044] The first binder may include, for example, one or more selected from the group consisting of PVDF (poly(vinylidene fluoride)), PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)), BR (polybutadiene rubber), NBR (nitrile butadiene rubber), SBR (styrene butadiene rubber), cellulose, and PTFE (polytetrafluoroethylene). The first binder may have lower solubility in non-polar solvents compared to the second binder described later, for example. The first binder may preferably be a fluorine-based polymer. Since PVDF-HFP has a relatively low melting point due to the amorphous nature of HFP, excellent mechanical strength, better control of shrinkage and expansion of the positive electrode active material during charging and discharging, and high electronic conductivity, the first binder may more preferably be PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)).

[0045] When the first binder is PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)), the weight ratio of PVDF to HFP may be, for example, in the range of 95:5 to 80:20. If PVDF is contained in an amount less than 80 weight%, the crystallinity decreases, the hardness decreases, and the mechanical properties may deteriorate.

[0046] The melting temperature of the first binder may be, for example, 100°C or higher to 250°C or lower. In other examples, the melting temperature of the first binder may be 110°C or higher, 120°C or higher, 130°C or higher, or 140°C or higher, or 240°C or lower, 230°C or lower, 220°C or lower, 210°C or lower, 200°C or lower, or 190°C or lower. The melting temperature of the first binder may be, for example, a value measured by a melting point meter, but is not limited thereto and can be performed by a method commonly known in the art. By introducing a conductive material coated with a first binder having such a melting temperature on at least a portion of the surface of a linear conductive material into an anode active material layer, the present invention can more effectively implement the network structure described below and further improve the bonding force or interaction between components within the anode active material layer without degradation of performance. As a result, the all-solid-state battery according to the present invention can provide a positive electrode with excellent capacity retention rate according to the cycle even under low driving pressure, as well as excellent high-rate characteristics and electrode adhesion. More preferably, the melting temperature of the first binder may be 180°C or lower, 170°C or lower, 160°C or lower, or 150°C or lower in order to further enhance the above effect. Although the reason is not clear, it is expected that even for a first binder with a melting temperature within the above range, if a first binder having a lower melting temperature is introduced, the network structure within the positive electrode active material layer acts more effectively, thereby further mitigating the degradation rate of the all-solid-state battery.

[0047] When the first binder is PVDF-HFP, the melting point may vary depending on the weight ratio of PVDF and HFP. For example, if the weight ratio of PVDF is high, the melting point of PVDF-HFP may increase, and if the weight ratio of PVDF is low, the melting point may decrease.

[0048] In the present specification, the statement that the first binder is coated on at least a portion of the surface of the linear conductive material may mean that the first binder covers at least a portion of the surface of the linear conductive material. In the present invention, the number of first binders attached to the surface of the linear conductive material may be, for example, 1.5 times, 2 times, 3 times, 4 times, 5 times, or 10 times the number of second binders attached to the surface of the linear conductive material, but is not limited thereto.

[0049] The first binder may be characterized by being included, for example, in an amount of 10 parts by weight or more to 30 parts by weight or less per 100 parts by weight of the conductive material. In other examples, the first binder may be included in an amount of 12 parts by weight or more, 14 parts by weight or more, 16 parts by weight or more, or 18 parts by weight or more per 100 parts by weight of the conductive material, or in an amount of 28 parts by weight or less, 26 parts by weight or less, 24 parts by weight or less, or 22 parts by weight or less. By controlling the content of the first binder relative to the conductive material in this way, the present invention allows the first binder to be coated in an appropriate amount on the surface of the linear conductive material, thereby increasing the bonding strength between components within the electrode without impairing conductivity. If the first binder is included in a small amount, the bonding ability of the first binder and the conductive material containing it decreases, and if the first binder is included in an excessive amount, the first binder may not easily adhere to the conductive material.

[0050] The above conductive material may be included, for example, in a range of 10 parts by weight or less, 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, 5 parts by weight or less, or 3 parts by weight or less, based on 100 parts by weight of the positive electrode active material, or in a range of 0.1 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, 2 parts by weight or more, 2.5 parts by weight or more, or 3 parts by weight or more.

[0051] A second aspect of the present invention relates to a positive electrode active material layer for an all-solid-state battery.

[0052] The details regarding the first aspect of the present invention may be applied in the same way to the details regarding the second aspect unless specifically described otherwise.

[0053] The positive active material layer of the present invention may include, for example, a positive active material, a solid electrolyte, the aforementioned conductive material for an all-solid-state battery, and a second binder.

[0054] In the present invention, the conductive material may, for example, form a network structure within the positive electrode active material layer. In this specification, the term "network structure" may refer to a structure that is loosely intertwined, for example, like a net, in which one conductive material particle is connected to one or more other conductive material particles to form a three-dimensional net-like structure. In one example, it may refer to a structure having the form shown in FIG. 1, but is not limited thereto. By introducing such a conductive material into the positive electrode active material layer, the present invention may be advantageous for forming a conductive network among the components included in the positive electrode active material layer and may be advantageous for pore development, thereby facilitating the diffusion of lithium ions and reducing diffusion resistance. Furthermore, by forming a network structure as described above, it is possible to provide a positive electrode with excellent capacity retention rate over cycles even under low driving pressure, as well as excellent high-rate characteristics and adhesion characteristics. These effects may be further enhanced by each of the components described below and combinations thereof.

[0055] The positive active material layer of the present invention may include, for example, a positive active material. The positive active material may be characterized by including, for example, one or more positive active materials selected from the group consisting of lithium transition metal oxides, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, and vanadium oxide. The lithium transition metal oxide may be lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganese oxide (lithium manganate), or lithium iron phosphate, or a combination thereof. The positive active material may be, for example, lithium nickel cobalt manganese oxide (NCM). The positive active material is not limited thereto and may be any material used as a positive active material in the relevant technical field. Each positive active material can be used individually or in combination of two or more types.

[0056] The above lithium transition metal oxide is, for example, Li a A 1-b B b D2 (wherein 0.90≤a≤1, and 0≤b≤0.5); Li a Ni 1-b-c Co b B c O 2-α F2(wherein 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0 <α<2); Li a Ni 1-b-c Mn b B c D α (In the above formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0≤α≤2); Li a Ni 1-b-c Co b B c D α(In the above formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a E 1-b B b O 2-c D c (In the above formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05); LiE 2-b B b O 4-c D c (In the above formula, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b B c O 2-α F α (In the above formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a CoG b O2(wherein the above formula, 0.90≤a≤1, 0.001≤b≤0.1); Li a MnG b O2(wherein the above formula, 0.90≤a≤1, 0.001≤b≤0.1); Li a Mn2GbO4 (wherein the above formula, 0.90≤a≤1, 0.001≤b≤0.1); Li a Ni 1-b-c Mn b B c O 2-α F α (In the above formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Mn b B c O 2-α F2(wherein 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni b E c G d O2(wherein 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li a Ni b Co c Mnd GeO2 (wherein the above formula, 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0 ≤d≤0.5, 0.001≤e≤0.1); Li a NiG b O2 (wherein the above equation, 0.90≤a≤1, 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3- f) J2(PO4)3(0≤f≤2); Li (3-f) Fe2(PO4)3(0≤f≤2); it may be a compound represented by any one of the chemical formulas of LiFePO4. In such a compound, A is Ni, Co, Mn, or a combination thereof; B 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; E is Co, Mn, or a combination thereof; F is 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; I is Cr, V, Fe, Sc, Y, or a combination thereof; and J may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof. As a positive electrode active material, a compound having a coating layer added to the surface of such a compound may be used, or a mixture of the compound described above and the compound having a coating layer added may be used. A coating layer added to the surface of such compounds may contain, for example, a lithium ion conductive oxide. The lithium ion conductive oxide is, for example, LiNbO3, Li4Ti5O 12 Examples include Li3PO4, but are not limited thereto. The compounds forming this coating layer may be amorphous or crystalline. Methods for forming the coating layer may include, for example, spray coating or immersion methods, but can be selected without limitation as long as they do not adversely affect the physical properties of the cathode active material.

[0057] When the above-mentioned positive electrode active material is a ternary lithium transition metal oxide such as NCA or NCM and contains nickel (Ni), it may be possible to increase the capacity density of the all-solid-state battery and reduce the metal leaching of the positive electrode active material in the charged state. Accordingly, the cycle characteristics of the all-solid-state battery in the charged state may be improved.

[0058] The shape of the above-mentioned positive active material may be a particle shape, for example, a sphere, an elliptical sphere, etc. The particle size of the positive active material is not particularly limited and must be within a range applicable to the positive active material of a conventional all-solid-state battery. The content of the positive active material of the positive is also not particularly limited and must be within a range applicable to the positive of a conventional all-solid-state secondary battery.

[0059] The positive electrode active material layer of the present invention may include, for example, a solid electrolyte. The solid electrolyte included in the positive electrode may include, for example, an inorganic electrolyte such as a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a phosphoric acid-based solid electrolyte, or a halide-based solid electrolyte, or a polymer electrolyte, but is not limited thereto and may be any electrolyte commonly used in all-solid-state batteries. For example, it may be preferable for the solid electrolyte included in the positive electrode to include a sulfide-based solid electrolyte from the perspective of improving ion conductivity.

[0060] The above sulfide-based solid electrolyte is, for example, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q(p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, and In), Li2S-SiS2-P2S5-LiI, Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are positive numbers), Z is one of Ge, Zn, or Ga, L i2 S-GeS2, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2) and Li 7-x PS 6-x I x It may be one or more selected from (0≤x≤2). Sulfide-based solid electrolytes can be manufactured by processing starting materials, such as Li2S or P2S5, by methods such as melt quenching or mechanical milling. Additionally, heat treatment may be performed after such processing. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In the present invention, the sulfide-based solid electrolyte may, for example, include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the above-mentioned sulfide-based solid electrolyte materials.

[0061] The above sulfide-based solid electrolyte is, for example, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I xIt may be an argyrodite-type compound comprising one or more selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound comprising one or more selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0062] The density of the above-mentioned azyrodite-type solid electrolyte may be, for example, 1.5 to 2.0 g / cc. Since the above-mentioned azyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the solid electrolyte by Li can be effectively suppressed.

[0063] The solid electrolyte included in the above-mentioned positive electrode active material layer may have a smaller average particle size compared to the solid electrolyte included in the solid electrolyte layer described later, for example. For example, the average particle size of the solid electrolyte included in the positive electrode may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the average particle size of the solid electrolyte included in the solid electrolyte layer.

[0064] The above solid electrolyte may be included, for example, in a range of 5 to 50 parts by weight per 100 parts by weight of the positive electrode active material. In other examples, the above solid electrolyte may be included in a range of 10 parts by weight or more or 15 parts by weight or more per 100 parts by weight of the positive electrode active material, or in a range of 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, or 20 parts by weight or less.

[0065] The positive active material layer of the present invention may include, for example, a second binder. The second binder is a component added considering the binding properties of the positive active material, solid electrolyte, and conductive material for the positive electrode of an all-solid-state battery, and any binder known to be usable for electrode formation in the technical field to which the present invention belongs may be used without any particular limitation. The second binder may include components different from the first binder.

[0066] The second binder may be characterized as being soluble in, for example, a non-polar solvent. The second binder may be, for example, a rubber-based binder. Specifically, the second binder may be one or more selected from the group consisting of, for example, butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber.

[0067] The weight ratio of the second binder to the first binder may be, for example, 0.1 or more to 10 or less. In other examples, the weight ratio of the second binder to the first binder may be 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more, or 9 or less, 8 or less, 7 or less, or 6 or less. By controlling the weight ratio of the second binder to the first binder in this way, the present invention can increase the binding strength between components within the electrode. By controlling the weight ratio of the second binder to the first binder as described above, the electrode binding strength is excellent, and the shrinkage and expansion of the anode during charging and discharging can be effectively controlled.

[0068] In addition to the above, the positive active material layer may further include additives such as fillers, coating agents, dispersants, and ion conductivity aids, and these additives may be used without limitation as long as they are known materials generally used in electrodes of all-solid-state batteries.

[0069] The above positive active material layer may be formed by, for example, through a step of applying and / or drying a positive slurry on at least one surface of a positive current collector described later. The application may be performed, for example, by direct gravure coating, micro gravure coating, slot die coating, coma coating, gravure coating, bar coating, roll coating, or slide coating, but is not limited thereto, and may be performed by a method orally known in the art. The above positive slurry may further include, for example, a solvent. The solvent may be water, N-methylpyrrolidone (NMP), etc., but is not limited thereto. The solvent may evaporate during the drying step and thus may not be included in the positive active material layer.

[0070] A third aspect of the present invention relates to an all-solid-state battery.

[0071] The details regarding the first and second aspects of the present invention may be applied equally to the details regarding the third aspect unless specifically described otherwise.

[0072] The all-solid-state battery of the present invention may be characterized by comprising a positive electrode including the aforementioned positive electrode active material layer, a solid electrolyte layer, and a negative electrode.

[0073] The positive electrode of the present invention may further include, for example, a positive current collector. The aforementioned positive active material layer may be formed, for example, on at least one surface of the positive current collector. As the positive current collector, a known metal that can be used as a current collector for an all-solid-state battery may be used. The positive current collector may be, for example, a plate, mesh, or foil made of copper (Cu), nickel (Ni), aluminum (Al), vanadium (V), gold (Au), platinum (Pt), chromium (Cr), iron (Fe), zinc (Zn), indium (In), germanium (Ge), lithium (Li), magnesium (Mg), stainless steel, titanium (Ti), cobalt (Co), or an alloy thereof. The positive current collector may be omitted in some cases.

[0074] The above-mentioned cathode may include a cathode active material layer. The cathode active material layer may include, for example, a cathode active material and may optionally further include a solid electrolyte, a conductive material and / or a binder, etc.

[0075] The above negative electrode active material is, for example, lithium, lithium alloy, carbon, silicon, silicon alloy, or Li4Ti5O. 12 (LTO), etc., or the above lithium, lithium alloy, carbon, silicon, silicon alloy, or Li4Ti5O 12 It can be selected from alloys with at least one metal selected from the group consisting of (LTO), etc., Sn, Ge, and Al.

[0076] The above-mentioned solid electrolyte, conductive material, and / or binder, etc., may be one of the types included in the aforementioned positive electrode active material layer or the solid electrolyte layer described below, but is not limited thereto; any material used as a solid electrolyte, conductive material, and / or binder, etc. in the relevant technical field may be used. The solid electrolyte, conductive material, and / or binder included in the negative electrode active material layer may be the same as or different from the solid electrolyte, conductive material, and / or binder included in the positive electrode active material layer, solid electrolyte layer, etc. As a binder included in the above-mentioned cathode active material layer, one or more selected from, for example, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, cellulose diacetate, poly(vinylidene fluoride), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylate styrene-butadiene rubber, epoxy resin, and nylon may be used, but are not limited thereto. As a conductive material included in the above-mentioned cathode active material layer, one or more selected from the group consisting of, for example, graphite; carbon black such as acetylene black, Ketjenblack, channel black, furnace black, lamp black, thermal black; or carbon fiber; may be used, but are not limited thereto.

[0077] The above-mentioned negative electrode active material layer may also further include, for example, other additives. These additives may be used without limitation as long as they are known materials commonly used in electrodes of all-solid-state batteries.

[0078] The negative electrode may also further include, for example, a negative current collector. As the negative current collector, a known metal that can be used as a current collector for an all-solid-state battery may be used. For example, the negative current collector may be a material that does not form alloys or compounds with lithium. For example, the negative current collector may be selected from the group consisting of copper (Cu), nickel (Ni), aluminum (Al), vanadium (V), gold (Au), platinum (Pt), magnesium (Mg), iron (Fe), titanium (Ti), cobalt (Co), chromium (Cr), zinc (Zn), germanium (Ge), indium (In), and stainless steel, but is not limited thereto; any material used as an electrode current collector in the relevant technical field may be used as long as it does not impede the purpose of the present invention. The negative current collector may be composed of one of the metals described above, or may be composed of an alloy of two or more metals or a coating material. The above-mentioned cathode current collector may be in the form of, for example, a plate, mesh, or foil, but is not limited thereto.

[0079] The all-solid-state battery of the present invention may be, for example, an anodeless all-solid-state battery.

[0080] In an anodeless all-solid-state battery, for example, when the negative electrode uses lithium or a lithium alloy as the negative electrode active material, the negative electrode may include lithium or a lithium alloy as the negative electrode active material layer during the battery manufacturing process (from the initial manufacturing), or a lithium layer may be formed during the charging process without forming a separate negative electrode active material layer during the battery manufacturing process.

[0081] In the above battery manufacturing process, if a separate negative electrode active material layer is not formed, the all-solid-state battery of the present invention may include a metal layer between the solid electrolyte layer and the negative electrode current collector, or, if there is no negative electrode current collector, on the surface of the non-negative electrode coating layer described later that is opposite to the solid electrolyte layer.

[0082] In this specification, the term "non-cathode coating layer" refers to a coating layer formed between the non-cathode coating layer and the solid electrolyte layer, or on one side of the solid electrolyte layer in the absence of the non-cathode coating layer, in the case of a solid-state battery in which lithium is adsorbed during charging and the charging capacity of the non-cathode coating layer is exceeded, and lithium is precipitated between the negative current collector and the non-cathode coating layer or, in the case of no negative current collector, on the side of the non-cathode coating layer opposite to the solid electrolyte layer to form a metal layer, and in the case of discharge, lithium in the non-cathode coating layer and the lithium metal layer is ionized and moves toward the positive electrode. The composition and operating mechanism may differ from the aforementioned negative active material layer. The non-cathode coating layer can cover the lithium metal layer during the charging process to serve as a protective layer for the lithium metal layer and can suppress the precipitation growth of lithium dendrites, thereby suppressing short circuits and capacity degradation of the solid-state battery and improving performance.

[0083] The above-mentioned anode coating layer may include, for example, amorphous carbon. The amorphous carbon included in the above-mentioned anode coating layer may be, for example, one or more selected independently from the group consisting of hard carbon, soft carbon, amorphous carbon film, and carbon black (e.g., acetylene black, furnace black, Ketjen black, etc.), but is not limited thereto, and any amorphous carbon that can be used in an anode all-solid-state battery may be used without limitation.

[0084] The above-mentioned non-cathode coating layer may further include, for example, a lithium-affinity element that forms an alloy or compound with lithium. The lithium-affinity element may be, for example, one or more metals, metalloids, or combinations thereof selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn).

[0085] The particle size of the above lithium-affinity element may, for example, be in the range of 10 nm or more to 1000 nm or less. The above particle size may refer to a maximum particle size, a minimum particle size, or an average particle size. In other examples, the particle size of the above lithium-affinity element may be 20 nm or more, 30 nm or more, 40 nm or more, or 50 nm or more, or 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less.

[0086] The above-mentioned non-cathode coating layer may also further include, for example, a binder. The binder may be selected from the binders mentioned as being included in the aforementioned positive active material layer, negative active material layer, and solid electrolyte layer described later, or any known binder may be used without limitation without being limited thereto.

[0087] The above cathode may, for example, optionally further include a cathode current collector on one surface of a non-cathode coating layer, and the aforementioned cathode current collector may be used without limitation.

[0088] When an all-solid-state battery includes a negative electrode coating layer, the all-solid-state battery may further include a thin film containing an element capable of forming an alloy with lithium, for example. The thin film may be included between the negative electrode current collector and the negative electrode coating layer, or, in the absence of a negative electrode current collector, on at least one surface of both sides of the negative electrode coating layer. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., but is not limited thereto; any element capable of forming an alloy with lithium in the relevant art field may be used. The thin film may be composed of one of the above examples or may be composed of various types of alloys. As the all-solid-state battery of the present invention further includes such a thin film, the cycle characteristics of the all-solid-state battery may be further improved.

[0089] The thickness of the thin film may be, for example, 1 nm or more to 800 nm or less, 10 nm or more to 700 nm or less, 50 nm or more to 600 nm or less, or 100 nm or more to 500 nm or less. The thin film may be formed by, for example, vacuum deposition, sputtering, plating, etc., but is not limited thereto, and any method capable of forming a thin film in the relevant technical field is possible.

[0090] When the above-mentioned anode coating layer is included, the all-solid-state battery may further include, upon charging, a metal and / or a metal layer containing lithium or a lithium alloy, for example, between the negative electrode current collector and the anode coating layer, on the side of the anode coating layer opposite to the solid electrolyte layer, and / or within the anode coating layer. The lithium alloy may be, for example, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., but is not limited thereto; any alloy used as a lithium alloy in the relevant technical field is acceptable. The metal or metal layer included between the negative electrode current collector and the anode coating layer and / or within the anode coating layer may be composed of one of these alloys or lithium, or may be composed of various types of alloys.

[0091] The thickness of the metal layer containing the lithium or lithium alloy may be, for example, within a range of 1 μm or more to 1000 μm or less, 1 μm or more to 500 μm or less, 1 μm or more to 200 μm or less, 1 μm or more to 150 μm or less, 1 μm or more to 100 μm or less, or 1 μm or more to 50 μm or less. It is necessary to control the thickness as above so that the metal layer can perform its role as a lithium reservoir well and improve cycle characteristics.

[0092] The above metal layer may be formed, for example, by precipitation between the negative electrode current collector and the non-negative electrode coating layer, or on the side of the non-negative electrode coating layer opposite to the solid electrolyte layer, by charging after assembly of the all-solid-state battery. When the metal layer is formed by charging after assembly of the all-solid-state battery, the region between the negative electrode current collector and the non-negative electrode coating layer, or on the side of the non-negative electrode coating layer opposite to the solid electrolyte layer, may, for example, be a lithium-free region that does not contain lithium in the initial state or after discharge of the all-solid-state battery.

[0093] The above solid electrolyte layer may include, for example, at least one of the examples of solid electrolytes included in the aforementioned positive electrode active material layer, and this may be the same as or different from the solid electrolyte included in the positive electrode active material layer. The solid electrolyte included in the solid electrolyte layer may have an average particle size (D50) of, for example, in the range of 0.5 μm or more to 4 μm or less. The above solid electrolyte may be used as a single type or as two or more types. If the solid electrolyte layer includes two or more types of solid electrolytes, the two or more types of solid electrolytes may be mixed in one layer, or a separate layer containing each solid electrolyte may be formed to create a multilayer structure, or each solid electrolyte may be mixed and a separate layer may be formed with the same or different mixing ratio to create a multilayer structure. In this specification, the average particle diameter (D50) may refer to the diameter at which the cumulative volume of particles becomes half (50%) of the total volume when the particle diameters of the particles, measured by laser diffraction scattering particle diameter distribution measurement, are arranged in order of smallest to largest.

[0094] The above solid electrolyte layer may preferably include a sulfide-based solid electrolyte in order to achieve high ionic conductivity and energy density.

[0095] The solid electrolyte layer may further contain, for example, a binder. For example, a water-based binder, an organic binder, or a combination thereof may be used as the binder. The binder may be, for example, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, cellulose diacetate, poly(vinylidene fluoride), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylate styrene-butadiene rubber, epoxy resin, nylon, or a combination thereof. For example, styrene-butadiene rubber, carboxymethylcellulose, or a combination thereof may be used as the water-based binder. For example, the organic binder may be polytetrafluoroethylene, poly(vinylidene fluoride), or a combination thereof, but is not limited thereto, and known binders may be used without limitation as long as they do not impede the purpose of the present invention. The solid electrolyte layer may contain, for example, 5 weight percent or less of the binder.

[0096] The thickness of the above solid electrolyte layer is not particularly limited, but can typically be in the range of 0.1 μm or more to 1 mm or less.

[0097] The all-solid-state battery of the present invention may also, for example, have a battery operating pressure of 8 MPa or less. In this specification, "battery operating pressure" may refer to pressure applied to the all-solid-state battery during the activation stage, evaluation stage, and / or final product stage for stable operation of the all-solid-state battery. The pressurization may be performed using an external device (e.g., a pressurizing jig) such as that shown in FIG. 3, but is not limited thereto, and any known pressurizing device may be used without limitation. Generally, for all-solid-state batteries, it is necessary to apply pressure reaching tens of megapascals (MPa) for stable operation; however, the present invention can provide an all-solid-state battery capable of exhibiting stable and excellent performance even under low battery operating pressure through a combination of the aforementioned configurations.

[0098] In the following, the present invention is described in detail with reference to examples to specifically explain the disclosure of the present invention as described above and the intended functions and effects of the present invention. However, the examples may be modified in various different forms, and the scope of this specification is not to be interpreted as being limited only to these examples. It is emphasized that the examples are provided to represent the present invention and to explain it more specifically to those skilled in the art.

[0099] Example 1.

[0100] (anode)

[0101] A PAN / pitch solution was prepared by mixing an electrospinning solution in which 10 wt% of polyacrylonitrile (PAN) was dissolved in dimethylformamide (DMF) with a solution in which 20 wt% of pitch was dissolved in tetrahydrofuran (THF) such that the mass ratio of PAN / pitch was 7 / 3. Subsequently, the PAN / pitch solution was electrospun into nanofibers using an electrospinning device. The electrospun nanofibers were stabilized in air at 280°C for 1 hour using a high-temperature furnace, and then carbonized at 800°C for 1 hour in an N2 atmosphere to produce carbon nanofibers (CNF). The average length of the CNF was approximately 9 μm, the average aspect ratio was approximately 35, and the bulk density was 2 g / cc to 3 g / cc. Subsequently, a certain amount of dry CNF powder was dispersed in acetone using an ultrasonic probe to prepare a 5 wt% CNF solution. PVDF-HFP (melting temperature: 140°C), corresponding to 20 wt% of the weight of CNF, was added to the prepared CNF solution and stirred for 90 minutes to prepare a CNF / PVDF-HFP solution. Subsequently, acetone was removed using a rotary evaporator. Finally, the CNF / PVDF-HFP mixture was left in a flask overnight at 60°C under vacuum to remove acetone residue, thereby preparing a conductive material mixed with CNF (linear conductive material) and PVDF-HFP (first binder). The prepared conductive material had a structure in which PVDF-HFP covered approximately 5% to approximately 10% of the entire surface of the CNF.

[0102] Next, the positive electrode active material (LiNi 0.8 Co 0.15 Mn 0.05 An anode slurry was prepared by mixing O2 (NCM), a solid electrolyte (Li6PS5Cl, which is an argyrodite-type crystal), the conductive material, and a second binder (BR) (weight average molecular weight 300,000 to 500,000) in a solvent (a non-polar solvent such as xylene) in a weight ratio of 80:15:2.5:2.5.

[0103] After that, the above anode slurry was applied onto an aluminum foil with a thickness of 18 μm, and then dried at 100°C for 12 hours under an atmospheric environment to obtain an anode comprising an anode active material layer with a thickness of 150 μm or more to 200 μm or less.

[0104] (Solid electrolyte layer)

[0105] A solid electrolyte layer containing Li6PS5Cl was used.

[0106] (cathode)

[0107] 6 g of amorphous carbon (average particle size 41 nm), 2 g of silver (Ag) nanoparticles (average particle size 60 nm), 9.33 g of PVdF solution (solid content 6%), and 7.19 g of NMP solution were placed in a Thinky mixer container and mixed 12 times for 3 minutes at 2000 rpm. Subsequently, 5 g of NMP solution was added, and mixing was performed 5 times for 3 minutes at 2000 rpm to prepare a cathode-free coating layer slurry. Next, the slurry was coated onto a SUS foil with a thickness of 10 μm using a bar coater, dried in air at 80°C for 20 minutes, and then vacuum dried at 100°C for 12 hours. Through this process, a cathode was obtained in which a cathode-free coating layer with a thickness of 14.0 μm and a porosity of 67.1% was formed on the SUS foil.

[0108] (Manufacturing of electric batteries)

[0109] An all-solid-state battery was manufactured in which a negative electrode, a solid electrolyte layer, and a positive electrode were sequentially stacked. Here, parts of the positive current collector and the negative current collector were protruded outward from the pouch to maintain a vacuum in the battery. These protrusions served as the positive and negative terminals. Additionally, this all-solid-state battery was subjected to hydrostatic pressure treatment at 500 MPa for 30 minutes.

[0110] Example 2.

[0111] An all-solid-state battery was manufactured in the same manner as in Example 1, except that PVDF-HFP with a melting temperature of 190°C was used as the first binder when manufacturing the conductive material.

[0112] Comparative Example 1.

[0113] An all-solid-state battery was manufactured in the same manner as in Example 1, except that carbon nanofibers (CNF) were used as the conductive material.

[0114] Comparative Example 2.

[0115] An all-solid-state battery was manufactured in the same manner as in Example 1, except that carbon black (Super C65), a point-type conductive material, was used as the conductive material.

[0116] Comparative Example 3.

[0117] An all-solid-state battery was manufactured in the same manner as in Example 1, except that a structure was used in which PVDF-HFP, as a conductive material, covered about 5% to about 10% of the entire surface of carbon black (Super C65), which is a point-type conductive material.

[0118] The above conductive material was manufactured as follows.

[0119] A certain amount of dry carbon black (Super C) powder was dispersed in acetone using an ultrasonic probe to prepare a 5 wt% solution. PVDF-HFP (melting temperature: 140°C), corresponding to 20 wt% of the weight of the carbon black, was added to the prepared carbon black solution and stirred for 90 minutes to prepare a Super C65 / PVDF-HFP solution. Subsequently, acetone was removed using a rotary evaporator. Finally, the Super C65 / PVDF-HFP mixture was left in a flask overnight at 60°C under vacuum to remove acetone residue, thereby producing a conductive material mixed with Super C (point-type conductive material) and PVDF-HFP (first binder).

[0120] Evaluation Example 1. Capacity retention rate characteristics according to driving pressure

[0121] The all-solid-state battery (pouch-type monocell) of the above example and comparative example was connected between the first plate (12) and the second plate (13) of the cell jig (10) as shown in FIG. 3, and the battery driving pressure was controlled to 7 MPa or 10 MPa, and the battery was driven under the following charge / discharge conditions with an operating voltage range of 4.25 V-3.0 V and a driving temperature of 60°C to evaluate the capacity retention rate according to the cycle, and the results are shown in Table 1 below.

[0122] Charging conditions: 0.33C, 4.25V CC / CV, 0.05C cut-off

[0123] Discharge conditions: 0.33C, 3.0V, CC

[0124] Classification Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Capacity Retention Rate (%) @ 190 cycle, 10MPa 87.4 87.1 86.2 89.4 88.1 Capacity Retention Rate (%) @ 190 cycle, 7MPa 87.6 86.3 84.5 Short Circuit Occurrence 84.4 Driving Pressure 10MPa → 7MPa Capacity Retention Rate Change Rate (%p) 0.2 -0.8 -1.7 / -3.7

[0125] (In Table 1 above, “capacity retention rate (%)@190 cycle 10MPa” refers to the percentage of the capacity after 190 cycles relative to the capacity after 1 cycle evaluated by the above method while controlling the battery driving pressure to 10MPa, and “capacity retention rate (%)@190 cycle 7MPa” refers to the percentage of the capacity after 190 cycles relative to the capacity after 1 cycle evaluated by the above method while controlling the battery driving pressure to 7MPa, and “driving pressure 10 MPa → 7 MPa capacity retention rate change rate” refers to the difference between “capacity retention rate (%)@190 cycle 7MPa” and “capacity retention rate (%)@190 cycle 10MPa”.) It can be confirmed that Example 1 and Example 2 each have a superior capacity retention rate over cycles compared to Comparative Example 1, in both cases where the driving pressure is high (10MPa) and low (7MPa). This is presumed to be because the linear conductive material coated with the first binder in Examples 1 and 2 formed a network structure within the positive active material layer, thereby mitigating the degradation rate of the all-solid-state battery. In particular, it was confirmed that the degradation of the all-solid-state battery proceeded the least in Example 1, which used a linear conductive material coated with a first binder having a lower melting temperature as the conductive material. This is presumed to be because the conductive material with the first binder having a low melting temperature further enhanced the bonding strength between the components within the positive active material layer. Meanwhile, in the case of Comparative Example 2, a short circuit occurred when operating under a condition of 7 MPa with reduced battery operating pressure, and in the case of Comparative Example 3, it was confirmed that the capacity retention rate was significantly lower compared to the examples when operating under a condition of 7 MPa with reduced battery operating pressure. This is presumed to be because there was no effect of forming a network structure within the positive active material layer, causing the degradation of the all-solid-state battery to proceed rapidly when the operating pressure was reduced.

[0126] Evaluation Example 2. Capacity retention rate characteristics during high-rate discharge

[0127] The capacity retention rate during high-rate discharge was evaluated by measuring the 1.0C discharge capacity relative to the 0.1C discharge capacity under an operating voltage range of 4.25V-3.0V and an operating temperature of 60℃, and the results are shown in Table 2 below.

[0128] Classification Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Capacity retention rate (%) during high-rate charging 939 2.99 2.79 1.59 0.3

[0129] (The capacity retention rate during high-rate charging refers to the percentage ratio of the 1.0C discharge capacity to the 0.1C discharge capacity.)

[0130] Evaluation Example 3. Anodic Adhesion

[0131] The adhesion strength of the above anode was measured using the 90° Peel Test method. Specifically, double-sided tape was attached to a slide glass, and an electrode punched to 20mm × 180mm was placed on top of it. After adhesion was achieved by reciprocating 10 times with a 2kg roller, the peeling force from the slide glass was measured by pulling at 200mm / min using a UTM (TA) machine. At this time, the measurement angle between the slide glass and the electrode was 90°. The measurement results are shown in Table 3 below.

[0132] Classification Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Anode Adhesion (gf / cm) 56.3 50.2 44.4 28.8 35.7

[0133] It was confirmed that Examples 1 and 2 had superior adhesion compared to Comparative Examples 1 to 3. In the case of Comparative Examples 2 and 3, which used point-type conductive materials, it is presumed that the adhesion was low because a network structure was not formed. Meanwhile, it was confirmed that the adhesion was the best in Example 1, which used a linear conductive material coated with a first binder having a low melting temperature as the conductive material. This is presumed to be because the conductive material incorporating the first binder having a low melting temperature further enhanced the bonding strength between the components within the anode active material layer.

Claims

1. A conductive material for an all-solid-state battery, wherein at least a portion of the surface of the linear (needle type) conductive material is coated with a first binder.

2. In Paragraph 1, A conductive material for an all-solid-state battery, wherein the average length of the particles of the linear conductive material is 1 μm or more to 60 μm or less.

3. In Paragraph 1, A conductive material for an all-solid-state battery, wherein the average aspect ratio of the particles of the linear conductive material is 10 or more to 60 or less.

4. In Paragraph 1, The above linear conductive material is a conductive material for an all-solid-state battery, comprising one or more selected from the group including carbon nanotubes (CNT), carbon nanofibers (CNF), graphene, and vapor-grown carbon fibers (VGCF).

5. In Paragraph 1, A conductive material for an all-solid-state battery, wherein the first binder comprises one or more selected from the group consisting of PVDF (poly(vinylidene fluoride)), PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)), P(VDF-TrFE) (Poly(vinylidene fluoride-co-trifluoroethylene)), P(VDF-TrFE-CFE) (Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)), PVDF-CTFE (Poly(vinylidene fluoride-co-chlorotrifluoroethylene)), BR (polybutadiene rubber), NBR (nitrile butadiene rubber), SBR (styrene butadiene rubber), cellulose, and PTFE (polytetrafluoroethylene).

6. In Paragraph 1, A conductive material for an all-solid-state battery, wherein the melting temperature of the first binder is 100°C or higher to 250°C or lower.

7. In Paragraph 1, A conductive material for an all-solid-state battery, characterized in that the first binder is included in an amount of 10 parts by weight or more to 30 parts by weight or less per 100 parts by weight of the conductive material.

8. A positive active material layer for an all-solid-state battery comprising a positive active material, a solid electrolyte, a conductive material for an all-solid-state battery according to claim 1, and a second binder.

9. In Paragraph 8, The above conductive material forms a network structure within the positive active material layer for an all-solid-state battery.

10. In Paragraph 8, The above second binder is a rubber-based binder, a positive active material layer for an all-solid-state battery.

11. In Paragraph 8, A positive electrode active material layer for an all-solid-state battery, wherein the weight ratio of the second binder to the first binder is 0.1 or more to 10 or less.

12. In Paragraph 8, The above-mentioned solid electrolyte is a sulfide-based solid electrolyte, a positive electrode active material layer for an all-solid-state battery.

13. In Paragraph 12, The above sulfide-based solid electrolyte is Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-LiBr-LiI-P2S5, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, and In), Li2S-SiS2-P2S5-LiI, Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are positive numbers), Z is one of Ge, Zn, or Ga, L i2 S-GeS2, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2) and Li 7-x PS 6-x I x A positive electrode active material layer for an all-solid-state battery, comprising one or more selected from the group including (0≤x≤2).

14. An all-solid-state battery comprising a positive electrode including a positive active material layer according to claim 8, a solid electrolyte layer, and a negative electrode.

15. In Paragraph 14, A solid-state battery, an anodeless solid-state battery.

16. In Paragraph 14, All-solid-state battery with a battery operating pressure of 8 MPa or less.

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