Negative Electrode and All-Solid-State Battery Comprising The Same

Abstract

The present invention relates to a cathode comprising a cathode current collector, a first cathode active material layer, and a second cathode active material layer, and an all-solid-state battery comprising the same, wherein the first cathode active material layer comprises a first cathode active material and a conductive material, and the first cathode active material is at least one selected from the group consisting of graphite, silicon, and combinations thereof, and the second cathode active material layer comprises a second cathode active material and a solid electrolyte, and the second cathode active material is silicon. According to the present invention, a novel cathode having high energy density and excellent characteristics regarding charge capacity and Coulomb efficiency over a cycle, and an all-solid-state battery comprising the same can be provided.

Description

Technology Field

[0001] The present invention relates to a cathode and an all-solid-state battery including the same. Background Technology

[0002] Lithium-ion batteries (LIBs) are widely used in electric vehicles, energy storage devices, and electronic equipment due to their high energy density and long lifespan. In particular, graphite, used as the anode material in LIBs, remains a primary anode material to this day due to its stability and excellent performance.

[0003] Conventional liquid electrolyte-based LIB systems feature the electrolyte effectively penetrating the anode, allowing lithium ions to move smoothly through the interlayer structure of graphite. This structural characteristic is one of the key factors enabling graphite anodes to possess superior performance.

[0004] However, when using a graphite anode in an all-solid-state battery, there is a problem due to the limitation that, unlike conventional liquid electrolytes, the solid electrolyte has difficulty effectively securing lithium ion transport pathways within the anode. The problem to be solved

[0005] To solve the above problems, techniques such as mixing a solid electrolyte with the graphite cathode or adding a conductive material were considered.

[0006] However, it has been confirmed that while introducing a solid electrolyte into a single-layer graphite anode can partially improve ionic conductivity within the electrode, there are limitations to performance enhancement due to increased solid-solid interface resistance; and while adding a conductive material to the single-layer graphite anode can contribute to increasing electrical conductivity within the electrode, it leads to problems such as reduced capacity and shortened lifespan due to side reactions and loss of active material.

[0007] Therefore, the present invention aims to solve these problems and provide a new cathode with high energy density and excellent characteristics of charge capacity and Coulomb efficiency according to the cycle, and an all-solid-state battery including the same. means of solving the problem

[0008] The present invention relates to a cathode comprising a cathode current collector, a first cathode active material layer, and a second cathode active material layer, wherein the first cathode active material layer comprises a first cathode active material and a conductive material, and the first cathode active material is at least one selected from the group consisting of graphite, silicon, and combinations thereof, and the second cathode active material layer comprises a second cathode active material and a solid electrolyte, and the second cathode active material is silicon.

[0009] In one embodiment, the first negative electrode active material layer may be characterized by being positioned closer to the negative current collector than the second negative electrode active material layer.

[0010] In one embodiment, the silicon content of the first negative electrode active material layer may be lower than the silicon content of the second negative electrode active material layer.

[0011] In one embodiment, the ratio of the silicon content of the first negative electrode active material layer to the silicon content of the second negative electrode active material layer may be 0.4 or less.

[0012] In one embodiment, the solid electrolyte content of the first cathode active material layer may be lower than the solid electrolyte content of the second cathode active material layer.

[0013] In one embodiment, the Young's Modulus of the solid electrolyte may be characterized as being 18 to 25 GPa.

[0014] In one embodiment, the conductive material content of the second cathode active material layer may be lower than the conductive material content of the first cathode active material layer.

[0015] In one embodiment, the first cathode active material layer may be characterized as not including a solid electrolyte, and the second cathode active material layer may be characterized as not including a conductive material.

[0016] In one embodiment, the first negative electrode active material layer may be characterized by containing 60 weight percent or more of the first negative electrode active material.

[0017] In one embodiment, the first cathode active material layer may be characterized by comprising graphite and silicon.

[0018] In one embodiment, the weight ratio of silicon to graphite in the first cathode active material layer may be characterized as being within the range of 0.005 to 0.5.

[0019] In one embodiment, at least one of the first cathode active material layer and the second cathode active material layer may further include a binder.

[0020] In one embodiment, the ratio of the thickness of the second cathode active material layer to the thickness of the first cathode active material layer may be 2 or less.

[0021] Another aspect of the present invention relates to an all-solid-state battery characterized by comprising an anode, a solid electrolyte layer, and the cathode.

[0022] In one embodiment, the capacity ratio (N / P ratio) of the cathode to the anode may be characterized as being 0.9 to 1.2.

[0023] In one embodiment, the cathode loading amount is 3 to 7 mAh / cm² 2 It can be characterized as being. Effects of the invention

[0024] According to the present invention, a new cathode with high energy density and excellent characteristics of charge capacity and Coulomb efficiency according to the cycle, and an all-solid-state battery including the same can be provided. Brief explanation of the drawing

[0025] FIG. 1 is a schematic diagram of an all-solid-state battery according to one embodiment of the present invention. Figure 2 is a graph showing the results of evaluating the charging cost according to the cycle for the embodiments and comparative examples of the present invention. Figure 3 is a graph showing the results of evaluating the Coulomb efficiency according to the cycle for the embodiments and comparative examples of the present invention. Specific details for implementing the invention

[0026] 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.

[0027] 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.

[0028] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0029] 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 that, for example, a "composition comprising compound A" may also be (essentially / essentially) composed of compound A.

[0030] In this regard, terms such as “to have” or “to possess,” 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.

[0031] In this specification, when it is stated that any layer is located on 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 exists between the two layers.

[0032] 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.

[0033] 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 to 30°C, about 23°C, or about 25°C. Furthermore, unless specifically otherwise specified, the unit of temperature in this specification is °C.

[0034] Among the physical properties mentioned in this specification, if the measured pressure affects the physical property, unless otherwise specifically defined, the physical property is measured at normal pressure, that is, atmospheric pressure (about 1 atmosphere).

[0035] Unless otherwise specifically defined in this specification, content means weight %.

[0036] The first aspect of the present invention relates to a cathode.

[0037] The present invention may relate to a cathode comprising, for example, a cathode current collector, a first cathode active material layer, and a second cathode active material layer. As the cathode of the present invention comprises at least two or more cathode active material layers having different characteristics, it can provide a novel cathode having high energy density and excellent characteristics regarding charge capacity and Coulomb efficiency according to the cycle. In this specification, the first cathode active material layer and the second cathode active material layer are distinguished from each other by different types of materials included, combination ratios, and / or placement positions, but may include some identical materials.

[0038] The first cathode active material layer may include, for example, a first cathode active material and a conductive material, and the first cathode active material may be at least one selected from the group consisting of graphite, silicon and combinations thereof.

[0039] The second negative electrode active material layer may include, for example, a second negative electrode active material and a solid electrolyte, and the second negative electrode active material may be characterized as being silicon.

[0040] In this specification, graphite may refer to any one of natural graphite, artificial graphite, and combinations thereof. In this specification, natural graphite may refer to untreated natural graphite or modified natural graphite, and artificial graphite may refer to artificial graphite produced by heating petroleum coke or pitch coke as raw materials in an electric furnace at 2,500°C or higher. The average particle size (D) of each of the natural graphite and artificial graphite 50 ) may be, for example, 10 to 25 μm, but is not limited thereto. The above average particle size (D 50 ) may be measured using, for example, the laser diffraction method or a scanning electron microscope (SEM). The BET specific surface area of ​​the natural graphite is, for example, 1.2 m² 2 It can be greater than / g, and 1.3m in another example.2 / g or more, 1.4m 2 / g or more, 1.5m 2 / g or more or 1.6m 2 / g or more, or 3m 2 / g or less, 2.8 m 2 / g or less, 2.6 m 2 / g or less, 2.4 m 2 / g or less, 2.2 m 2 / g or less, 2.0 m 2 / g or less or 1.8 m 2 It may be less than or equal to / g, but is not limited thereto. The BET specific surface area of ​​the above artificial graphite is, for example, 1 m² 2 It can be less than / g, and 0.9 m in other examples. 2 / g or less or 0.8 m 2 / g or less, or 0.1 m 2 / g or more, 0.2 m 2 / g or more, 0.3 m 2 / g or more, 0.4 m 2 / g or more, 0.5 m 2 / g or more, 0.6 m 2 / g or more or 0.7 m 2 It may be greater than / g but is not limited thereto.

[0041] In this specification, graphite may preferably be a combination of natural graphite and artificial graphite. The graphite may be, for example, a combination of natural graphite and artificial graphite in a weight ratio of 1:1 to 1:9, and in other examples, 1:2 to 1:7 or 1:3 to 1:5. By using a graphite that combines natural graphite and artificial graphite in the above ratios, the present invention can further improve the expression capacity and performance.

[0042] In this specification, silicon may mean, for example, single silicon, silicon alloy, silicon oxide, silicon / carbon composite, and any one of the combinations thereof. The silicon / carbon composite is, for example, carbon being SiOx (0≤x<2) By heat-treating in a state combined with particles, the carbon material becomes SiO x (0≤x<2) Form coated on the particle surface or SiO x (0≤x<2) The particles may have a form in which carbon is dispersed in an atomic state inside, but are not limited thereto. The average particle size (D of the silicon) above 50 ) is, for example, 5 to 20 μm and the maximum particle size (D max ) may be 30 to 40 μm, and the tap density may be 0.1 to 5 g / cm³ 3 It may be, but is not limited thereto. The above average particle size (D 50 ) and maximum particle size (D max ) may be measured using, for example, the laser diffraction method or scanning electron microscope (SEM).

[0043] The first cathode active material layer may be positioned closer to the cathode current collector than, for example, the second cathode active material layer. In other words, the second cathode active material layer may be positioned closer to the solid electrolyte layer described later than, for example, the first cathode active material layer.

[0044] The cathode of the present invention can provide an all-solid-state battery with high energy density and excellent characteristics of charge capacity and Coulomb efficiency over a cycle through a combination of the above configurations.

[0045] The silicon content of the first cathode active material layer may be characterized as being lower than, for example, the silicon content of the second cathode active material layer. In this specification, 'content of B in layer A' may refer, for example, to the weight ratio (weight%) of B contained in layer A relative to the total weight of layer A. By controlling the silicon content of the first cathode active material layer to be lower than the silicon content of the second cathode active material layer, the cathode of the present invention can improve ion conductivity and improve charging speed and energy density by lowering the overvoltage through the alloying reaction between silicon and Li during charging. These effects may be further enhanced by controlling the features described below.

[0046] The ratio of the silicon content of the first negative electrode active material layer to the silicon content of the second negative electrode active material layer may be characterized as being, for example, 0.4 or less. In other examples, the ratio of the silicon content of the first negative electrode active material layer to the silicon content of the second negative electrode active material layer may be characterized as being 0.3 or less, 0.2 or less, 0.1 or less, or 0.09 or less, or 0 or more, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, or 0.08 or more.

[0047] The silicon content of the first negative electrode active material layer may be characterized as, for example, 10 wt% or less. In other examples, the silicon content of the first negative electrode active material layer may be 9.5 wt% or less, 9 wt% or less, 8.5 wt% or less, 8 wt% or less, 7.5 wt% or less, 7 wt% or less, 6.5 wt% or less, 6 wt% or less, 5.5 wt% or less, or 5 wt% or less, or 0 wt% or more, 0.5 wt% or more, 1 wt% or more, 1.5 wt% or more, 2 wt% or more, 2.5 wt% or more, 3 wt% or more, 3.5 wt% or more, 4 wt% or more, or 4.5 wt% or more.

[0048] The silicon content of the second negative active material layer may be characterized as, for example, 15 to 90 weight%. In other examples, the silicon content of the second negative active material layer may be 20 weight% or more, 25 weight% or more, 30 weight% or more, 35 weight% or more, 40 weight% or more, 45 weight% or more, 50 weight% or more, or 55 weight% or more, or 85 weight% or less, 80 weight% or less, 75 weight% or less, 70 weight% or less, 65 weight% or less, or 60 weight% or less.

[0049] The cathode of the present invention may be characterized, for example, in that the solid electrolyte content of the first cathode active material layer is lower than the solid electrolyte content of the second cathode active material layer. By controlling the solid electrolyte content of the first cathode active material layer to be lower than the solid electrolyte content of the second cathode active material layer, the interface between the solid electrolyte layer and the cathode active material layer described later is stably formed, and the volume expansion of silicon can be buffered. This effect can be further maximized by controlling the Young's modulus of the solid electrolyte as described later.

[0050] The Young's Modulus of the solid electrolyte included in the first cathode active material layer or the second cathode active material layer may be characterized as, for example, 18 to 25 GPa. In other examples, the Young's Modulus of the solid electrolyte may be 19 to 24 GPa, 20 to 23 GPa, or 21 to 22 GPa.

[0051] The ratio of the solid electrolyte content of the first cathode active material layer to the solid electrolyte content of the second cathode active material layer may be, for example, 0.1 or less. In other examples, the ratio of the solid electrolyte content of the first cathode active material layer to the solid electrolyte content of the second cathode active material layer may be 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less, 0.001 or less, or 0.0001 or less, and more specifically, 0.

[0052] The solid electrolyte content of the first negative electrode active material layer may be, for example, 3 weight% or less. In other examples, the solid electrolyte content of the first negative electrode active material layer may be 2.5 weight% or less, 2 weight% or less, 1.5 weight% or less, 1 weight% or less, 0.5 weight% or less, 0.1 weight% or less, 0.01 weight% or less, 0.001 weight% or less, or 0.0001 weight% or less, or 0 weight%.

[0053] The solid electrolyte content of the second negative electrode active material layer may be, for example, 10 to 80 weight%. In other examples, the solid electrolyte content of the second negative electrode active material layer may be 15 weight% or more, 20 weight% or more, 25 weight% or more, 30 weight% or more, or 35 weight% or more, or 75 weight% or less, 70 weight% or less, 65 weight% or less, 60 weight% or less, 55 weight% or less, 50 weight% or less, or 45 weight% or less.

[0054] The cathode of the present invention may be characterized, for example, in that the conductive material content of the second cathode active material layer is lower than the conductive material content of the first cathode active material layer. If the conductive material and the solid electrolyte come into direct contact and react, a resistive material may be formed at the interface, which may increase the internal resistance of the all-solid-state battery or degrade output performance, and may also reduce the structural stability of the cathode active material layer. By controlling the conductive material content of the second cathode active material layer, which is positioned closer to the solid electrolyte layer described below, to be lower than the conductive material content of the first cathode active material layer, the present invention suppresses direct contact between the conductive material contained in the first cathode active material layer and the solid electrolyte contained in the solid electrolyte layer, and the resulting electrochemical side reactions, thereby providing an all-solid-state battery with improved performance and lifespan.

[0055] The ratio of the conductive material content of the second cathode active material layer to the conductive material content of the first cathode active material layer may be, for example, 0.1 or less. In other examples, the ratio of the conductive material content of the second cathode active material layer to the conductive material content of the first cathode active material layer may be 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less, 0.001 or less, or 0.0001 or less, and more specifically, 0.

[0056] The conductive material content of the second cathode active material layer may be, for example, 0.1 weight% or less. In other examples, the conductive material content of the second cathode active material layer may be 0.01 weight% or less, 0.001 weight% or less, or 0.0001 weight% or less, and more specifically, 0 weight%.

[0057] The conductive material content of the first cathode active material layer may be, for example, 1 to 10 weight%. In other examples, the conductive material content of the first cathode active material layer may be 1.5 weight% or more, 2 weight% or more, or 2.5 weight% or more, or 9 weight% or less, 8 weight% or less, 7 weight% or less, 6 weight% or less, 5 weight% or less, or 4 weight% or less.

[0058] In order to improve internal ionic conductivity of the electrode and reduce interfacial resistance, while further suppressing the loss of the negative electrode active material and the resulting capacity loss due to side reactions between the conductive material and the solid electrolyte, the present invention may be characterized, for example, in that the first negative electrode active material layer does not contain a solid electrolyte and the second negative electrode active material layer does not contain a conductive material. The negative electrode of the present invention may be characterized in that the conductive material and the solid electrolyte are completely separated and introduced into the first negative electrode active material layer and the second negative electrode active material layer, respectively.

[0059] The first negative active material layer may be characterized by containing, for example, 60 weight% or more of the first negative active material. In other examples, the first negative active material layer may contain 65 weight% or more, 70 weight% or more, 75 weight% or more, 80 weight% or more, 85 weight% or more, or 90 weight% or more, or 99 weight% or less, or 95 weight% or less of the first negative active material.

[0060] The first cathode active material layer of the present invention may be characterized by including, for example, graphite and silicon.

[0061] The weight ratio of silicon to graphite in the first negative electrode active material layer may be characterized as, for example, 0.005 to 0.5. In other examples, the weight ratio of silicon to graphite in the first negative electrode active material layer may be 0.01 or more, 0.015 or more, 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0.045 or more, or 0.05 or more, or 0.45 or less, 0.4 or less, 0.35 or less, 0.3 or less, 0.25 or less, 0.2 or less, 0.15 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, or 0.06 or less.

[0062] As the first negative active material layer of the present invention includes graphite and silicon as the first negative active material, the capacity and energy density can be improved, and by controlling the weight ratio of silicon to graphite included in the first negative active material layer as described above, the problem of deterioration of cycle characteristics due to the expansion of the silicon active material by charging can be prevented.

[0063] The cathode of the present invention may be characterized, for example, in that at least one of the first cathode active material layer and the second cathode active material layer further comprises a binder. At least one of the first cathode active material layer and the second cathode active material layer may comprise a binder, for example, in an amount of 8 weight% or less. At least one of the first cathode active material layer and the second cathode active material layer may comprise a binder in an amount of 7 weight% or less, 6 weight% or less, 5 weight% or less, or 4 weight% or less, or in an amount of 1 weight% or more, or 2 weight% or more, in other examples. As at least one of the first cathode active material layer and the second cathode active material layer comprises a binder, the bonding force between the electrode materials and / or the interfacial adhesion force between the cathode current collector and the first cathode active material layer, between the first cathode active material layer and the second cathode active material layer, and between the second cathode active material layer and the solid electrolyte layer described later can be improved, thereby providing an all-solid-state battery with excellent stability.

[0064] The ratio of the thickness of the second cathode active material layer to the thickness of the first cathode active material layer may be characterized as being, for example, 2 or less. In this specification, the thickness of each layer may be measured, for example, by a scanning electron microscope (SEM), and the average value of thickness values ​​measured at any 10 locations for each layer may be taken as the thickness of each layer, but is not limited thereto. In other examples, the ratio of the thickness of the second cathode active material layer to the thickness of the first cathode active material layer may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, or 1.0 or more, or 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, or 1.1 or less. By controlling the ratio of the thickness of the second cathode active material layer to the thickness of the first cathode active material layer as described above, the problem of deterioration in cycle characteristics as the silicon active material expands can be prevented.

[0065] The thickness of each of the first negative active material layer and the second negative active material layer may be, for example, 5 to 45 μm. In other examples, the thickness of the second negative active material layer may be 10 to 40 μm, 15 to 35 μm, 20 to 30 μm, 21 to 29 μm, 22 to 28 μm, 23 to 27 μm, or 24 to 26 μm.

[0066] The weight ratio of the second cathode active material layer to the first cathode active material layer may be, for example, 0.5 to 1.5. In other examples, the weight ratio of the second cathode active material layer to the first cathode active material layer may be 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more, or 1.4 or less, 1.3 or less, 1.2 or less, or 1.1 or less.

[0067] For the entire negative electrode active material layer, the negative electrode active material may be included in, for example, 60 weight% or more. For the entire negative electrode active material layer, the negative electrode active material may be included in, in other examples, 65 weight% or more, 70 weight% or more, or 75 weight% or more, or 95 weight% or less, 90 weight% or less, 85 weight% or less, or 80 weight% or less, but is not limited thereto.

[0068] The cathode active material included in the entire cathode active material layer may include, for example, graphite and silicon. For the entire cathode active material layer, the weight ratio of silicon to graphite may be, for example, 0.07 to 7. In the cathode active material layer, the weight ratio of silicon to graphite may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.6 or more, or 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, or 0.7 or less.

[0069] For the entire negative electrode active material layer, the weight ratio of the solid electrolyte to the negative electrode active material may be, for example, 0.05 to 0.72. In the negative electrode active material layer, the weight ratio of the solid electrolyte to the negative electrode active material may, in other examples, be 0.1 or more, 0.15 or more, 0.2 or more, or 0.25 or more, or 0.7 or less, 0.65 or less, 0.6 or less, 0.55 or less, 0.5 or less, 0.45 or less, 0.4 or less, 0.35 or less, or 0.3 or less.

[0070] For the entire negative electrode active material, the weight ratio of the conductive material to the negative electrode active material may be, for example, 0.01 to 0.07. In the negative electrode active material layer, the weight ratio of the conductive material to the negative electrode active material may, in other examples, be 0.011 or more, 0.012 or more, 0.13 or more, 0.014 or more, 0.015 or more, 0.016 or more, 0.017 or more, 0.018 or more, or 0.019 or more, or 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.025 or less, or 0.02 or less.

[0071] For the entire negative electrode active material, the weight ratio of the binder to the negative electrode active material may be, for example, 0.11 or less. In the negative electrode active material layer, the weight ratio of the binder to the negative electrode active material may be 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, or 0.04 or less in other examples.

[0072] The above conductive material can be used to improve the conductivity of the electrode, and can be used without special limitations as long as it is conductive without causing chemical changes. Examples include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskies such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and may include one of these alone or a mixture of two or more.

[0073] The above solid electrolyte may include, for example, sulfide-based solid electrolytes, oxide-based solid electrolytes, polymer-based solid electrolytes, and / or halide-based solid electrolytes, but is not limited thereto.

[0074] The above sulfide-based solid electrolyte contains sulfur atoms (S), has ionic conductivity of metals belonging to Group 1 or Group 2 of the periodic table, and may have electronic insulation properties. The above sulfide-based solid electrolyte preferably contains at least Li, S, and P as elements and has lithium ion conductivity, but may include other elements other than Li, S, and P depending on the purpose or case. As the above-mentioned sulfide-based solid electrolyte, for example, Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-H2S, Li2S-P2S5-H2S-LiCl, Li2S-LiI-P2S5, Li2S-LiI-Li2OP2S5, Li2S-LiBr-P2S5, Li2SLi2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, Li2SGa2S3, Li2S-GeS2-Ga2S3, Li2S-GeS2-P2S5, Li2S-GeS2-Sb2S5, Li2S-GeS2-Al2S3, Li2SSiS2, Li2S-Al2S3, Li2S-SiS2-Al2S3, Li2S-SiS2-P2S5, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-LiI, Li2S-SiS2-Li4SiO4, Li2SSiS2-Li3PO4, or Li 10 GeP2S 12The above may include the above. The above sulfide-based solid electrolyte may include an azirodite-based solid electrolyte comprising one or more selected from Li6PS5F, Li6PS5Cl, Li6PS5Br, Li6PS5I, or Li6PS5X (where X is two or more selected from F, Cl, Br, and I). Alternatively, the above sulfide-based solid electrolyte may include an amorphous sulfide glass manufactured using Li2S, P2S5, etc. as a raw material, or may include a glass ceramic obtained by heat treating the sulfide glass, but is not limited thereto.

[0075] The above oxide-based solid electrolyte is, for example, LiPON, Li 3x La (2 / 3-x)(1 / 3-2x) TiO3(0.04 <x<0.16), Li 1+x Al x Ti 2-x (PO4)3(0 <x<2), Li 1+x Al x Ge 2-x (PO4)3(0 <x<2), 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, Pb 1-x La x Zr 1-y Ti y O3(0≤x<1, 0≤y<1), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3, HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<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), Li x La y TiO3(0 <x<2, 0<y<3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2, Li 3+x La3M2O 12 (M is Te, Nb, or Zr, 1≤x≤10), Li7La3Zr2O 12 , Li 3+x La3Zr 2-a M a O 12 (M is Ga, W, Nb, Ta, or Al, 0 <a<2, 1≤x≤10) 또는 이들의 조합을 포함할 수 있다. 또한 산화물계 고체 전해질은 Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12 (M-doped LLZO, M=Ga, W, Nb, Ta, or Al, 0 <a<2, 1≤x≤10) 중에서 선택된 가넷계(Garnet-type) 고체 전해질, 또는 리튬-알루미늄-티타늄 인산염계(LATP, Li 1+x Al x Ti 2-x (PO4)3), lithium-aluminum-germanium phosphate system (LAGP, Li 1.5 Al 0.5 Ge 1.5 It may include a NASICON-based solid electrolyte selected from (PO4)3-based, lithium-silicon-titanium phosphate-based (LSTP, LiSiO2TiO2(PO4)3), or a combination thereof, but is not limited thereto.

[0076] The above oxide-based solid electrolyte may be crystalline, amorphous, glassy, ​​or glass-ceramic, and may have various crystalline states depending on the manufacturing method and composition.

[0077] The above-mentioned polymer-based solid electrolyte is not particularly limited to any polymer material that is an ion-conducting material and is commonly used as a solid electrolyte material for all-solid-state batteries. The above-mentioned polymer-based solid electrolyte may include, for example, polyether-based polymers, polycarbonate-based polymers, acrylate-based polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene oxide (PEO), polyethylene derivatives, alkylene oxide derivatives, phosphate ester polymers, polyaisation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, or polymers containing ionic dissociators. Alternatively, the above-mentioned polymer-based solid electrolyte may include, as a polymer resin, a branched copolymer, a comb-like polymer, and a cross-linked polymer resin, etc., in which an amorphous polymer such as polymethyl methacrylate (PMMA), polycarbonate, polysiloxane, and / or phosphazene is copolymerized as a comonomer to a polyethylene oxide (PEO) main chain.

[0078] The above-mentioned halide-based solid electrolyte may, for example, contain a halogen element as the main component of anion. Containing a halogen element as the main component of anion may mean that the proportion (molar ratio) of the halogen element is the highest among all anions constituting the halide-based solid electrolyte. The ratio of the halogen (X) element to all anions constituting the above-mentioned halide-based solid electrolyte may, for example, be 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. The halogen element may be one or more types. The above-mentioned halide-based solid electrolyte may, for example, not contain a sulfur element (S element). The above-mentioned halide-based solid electrolyte may, for example, contain a Li element, an M element (M is a metal other than Li), and an X element. X may, for example, be F, Cl, Br, I, or a combination thereof. The above halide-based solid electrolyte may include, for example, Br or Cl as X. The above halide-based solid electrolyte may include, for example, a metal element such as Sc, Y, B, Al, Ga, or In as M. The composition of the above halide-based solid electrolyte is, for example, Li 6-3a M a Br b Cl c (M is a metal other than Li, and 0 <a<2, 0≤b≤6, 0≤c≤6, b+c=6)일 수 있다. 상기 할라이드계 고체 전해질은 예를 들어 Li3YBr6, Li3YCl6, 또는 Li3YBr2C l4 It could be the back.

[0079] More specifically, the solid electrolyte may include a sulfide-based solid electrolyte in terms of achieving high energy density and stability. Specifically, the solid electrolyte may include an azirodite-based sulfide solid electrolyte, but is not limited thereto.

[0080] The binders included in the first cathode active material layer and the second cathode active material layer may be the same or different. Examples of the binders include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol (PVA), polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used.

[0081] The above cathode may additionally include, for example, additives. The additives may be, for example, fillers, coating agents, dispersants, thickeners, ion conductivity aids, etc., but are not limited thereto, and any known material generally used for cathodes may be used without limitation.

[0082] The above-mentioned cathode current collector may have one or more shapes selected from, for example, thin, plate, mesh, punched metal, and foam. The above-mentioned cathode current collector may be, for example, a metal foil or metal mesh, or a carbon sheet. Examples of metals constituting the cathode current collector include at least one selected from copper, nickel, chromium, gold, platinum, silver, aluminum, iron, titanium, zinc, cobalt, vanadium, magnesium, lead, germanium, indium, tin, zirconium, and stainless steel. The above-mentioned cathode current collector may include at least one metal selected from copper, nickel, and stainless steel in order to ensure reduction resistance. The cathode current collector may, for example, have a carbon coating layer on its surface. The cathode current collector may also be, for example, a metal foil or a substrate on which the above-mentioned metal is plated or deposited. The thickness of the cathode current collector may be, for example, 0.1 μm or more or 1 μm or more, 1 mm or less or 100 μm or less, but is not limited thereto.

[0083] A second aspect of the present invention relates to an all-solid-state battery comprising a positive electrode, a solid electrolyte layer, and a negative electrode. The details of the first aspect of the present invention may be applied in the same way to the details of the second aspect unless specifically described otherwise.

[0084] The above anode may include, for example, an anode current collector and an anode active material layer located on at least one surface of the anode current collector.

[0085] The above positive active material layer may optionally include, for example, a binder, a conductive material, a solid electrolyte and / or additives together with the positive active material.

[0086] The above-mentioned positive electrode active material reversibly absorbs and desorbs lithium ions. The above-mentioned positive electrode active material may be, for example, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide, but is not limited thereto; any material used as a positive electrode active material in the relevant technical field may be used. The above-mentioned positive electrode active material may be used individually or in a mixture of two or more types.

[0087] 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 Mn d 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 bO2 (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.

[0088] When the above-mentioned positive 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 active material in the charged state, and accordingly, the cycle characteristics of the all-solid-state battery in the charged state may be improved.

[0089] 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 secondary 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.

[0090] For the above binder, for example, the details regarding the binder described above may be applied in the same way, and the binder included in the first and / or second negative active material layer and the binder included in the positive active material layer may each be the same or different from each other.

[0091] For the above-mentioned conductive material, for example, the matters concerning the conductive material described above may be applied in the same way, and the conductive material included in the first and / or second negative active material layer and the conductive material included in the positive active material layer may each be the same or different from one another.

[0092] For example, the solid electrolyte included in the positive electrode active material layer may be subject to the same provisions as the solid electrolyte included in the negative electrode active material layer described above, and the solid electrolyte included in the negative electrode active material layer and the solid electrolyte included in the positive electrode active material layer may be the same or different from each other.

[0093] For the above additives, for example, the details regarding the aforementioned additives may be applied in the same way, and the additive included in the first and / or second negative active material layer and the additive included in the positive active material layer may each be the same or different from one another.

[0094] The thickness of the above positive active material layer may be, for example, 50 μm to 200 μm, more specifically 70 μm to 150 μm, and more specifically 80 μm to 110 μm, but is not limited thereto.

[0095] The loading amount of the above positive active material layer is, for example, 1.0 mAh / cm² 2 Up to 6.0mAh / cm² 2 It could be, specifically 2.5mAh / cm 2 Up to 5.0mAh / cm² 2 It could be, and more specifically, 3.5mAh / cm 2 Up to 4.5mAh / cm 2 It may be, but is not limited to this.

[0096] The anode current collector may have one or more shapes selected from, for example, thin, plate, mesh, punched metal, and foam. The anode current collector may be composed of, for example, a metal foil or a metal mesh, and may be a metal foil for ease of handling, but is not limited thereto. Examples of metals constituting the anode current collector include at least one selected from copper, nickel, chromium, gold, platinum, silver, aluminum, iron, titanium, zinc, cobalt, vanadium, magnesium, lead, germanium, indium, tin, zirconium, and stainless steel. The anode current collector may include aluminum for the purpose of ensuring oxidation resistance. The anode current collector may, for example, have a carbon coating layer on its surface. The anode current collector may also be, for example, a metal foil or a substrate on which the metal is plated or deposited. The thickness of the anode current collector may be, for example, 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less, but is not limited thereto.

[0097] For example, the same provisions regarding the solid electrolyte included in the above-mentioned solid electrolyte layer may apply to the solid electrolyte included in the aforementioned cathode or anode active material layer, and the solid electrolyte included in the above-mentioned solid electrolyte layer and the solid electrolyte included in the cathode or anode active material layer may be the same or different from each other. However, the average particle size of the solid electrolyte included in the cathode or anode active material layer may be smaller than the average particle size of the solid electrolyte included in the solid electrolyte layer.

[0098] In the all-solid-state battery of the present invention, the capacity ratio of the negative electrode to the positive electrode (N / P ratio) may be, for example, 0.9 to 1.2. In the all-solid-state battery of the present invention, the capacity ratio of the negative electrode to the positive electrode may be 0.91 or more, 0.92 or more, 0.93 or more, 0.94 or more, 0.95 or more, 0.96 or more, 0.97 or more, 0.98 or more, 0.99 or more, 1 or more, 1.01 or more, 1.02 or more, 1.03 or more, 1.04 or more, 1.05 or more, 1.06 or more, or 1.07 or more, or 1.19 or less, 1.18 or less, 1.17 or less, 1.16 or less, 1.15 or less, 1.14 or less, 1.13 or less, 1.12 or less, 1.11 or less, 1.1 or less, or 1.09 or less. When the N / P ratio satisfies the above range, lithium dendrite formation is suppressed and energy density per volume is increased, thereby securing a high capacity retention rate, and lifespan characteristics and battery stability can be improved.

[0099] In the all-solid-state battery of the present invention, the loading amount of the negative electrode active material layer is, for example, 3 to 7 mAh / cm² 2The loading amount of the cathode active material layer may be 3.1 or more, 3.2 or more, 3.3 or more, 3.4 or more, 3.5 or more, 3.6 or more, 3.7 or more, 3.8 or more, 3.9 or more, 4 or more, 4.1 or more, 4.2 or more, 4.3 or more, or 4.4 or more in other examples, or 6.8 or less, 6.6 or less, 6.4 or less, 6.2 or less, 6 or less, 5.8 or less, 5.6 or less, 5.4 or less, 5.2 or less, 5 or less, 4.8 or less, or 4.6 or less.

[0100] 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.

[0101] Example.

[0102] (cathode)

[0103] A slurry for the first negative electrode active material layer was prepared by mixing graphite, silicon, a conductive material, and a binder with NMP (N-methyl-2-pyrrolidone) in a weight ratio of 89.3:4.7:3:3. At this time, a mixture of artificial graphite and natural graphite in a weight ratio of 8:2 was used as the graphite, a silicon / carbon composite was used as the silicon, carbon black was used as the conductive material, PVDF was used as the binder, and the solid content ratio of the slurry for the first negative electrode active material layer was 60%.

[0104] The above slurry for the first cathode active material layer was uniformly coated onto a copper foil with a thickness of 15 μm using a blade coater, and vacuum dried at 120°C for 10 minutes to obtain a structure having a first cathode active material layer formed thereon.

[0105] A slurry for the second negative electrode active material layer was prepared by mixing silicon, a solid electrolyte, and a binder with NMP (N-methyl-2-pyrrolidone) in a weight ratio of 57:40:3. At this time, a silicon / carbon composite was used as the silicon, an azirodite-based (Li6PS5Cl) sulfide solid electrolyte was used as the solid electrolyte, and PVDF was used as the binder, and the solid content ratio of the slurry for the second negative electrode active material layer was 60%.

[0106] The slurry for the second cathode active material layer was uniformly applied onto the first cathode active material layer using a blade coater and vacuum dried at 120°C for 10 minutes. Subsequently, a cathode was obtained by pressing with a roll press to sequentially form the first cathode active material layer and the second cathode active material layer on a copper foil. At this time, the thickness ratio and weight ratio of the first cathode active material layer and the second cathode active material layer were 1:1, and for the entire cathode active material layer, the weight ratio of graphite:silicon:solid electrolyte:conductive material:binder was 44.6:30.9:20:1.5:3, and the sum of the loading amounts of the first cathode active material layer and the second cathode active material layer was 4.43 mAh / cm² 2 It was.

[0107] (anode)

[0108] LiNi as the positive active material 0.8 Co 0.15 Mn 0.05 O2 (NCM), an azirodite-based (Li6PS5Cl) sulfide solid electrolyte, carbon nanofiber (CNF) as a conductive material, and polytetrafluoroethylene (Teflon binder) as a binder were prepared. The above materials were mixed in a weight ratio of positive active material : solid electrolyte : conductive material : binder = 83.7 : 14.9 : 0.2 : 1.2, and then formed into a large sheet to produce a positive electrode sheet. Subsequently, the positive electrode sheet was compressed onto a 12 µm thick aluminum foil to produce a positive electrode. The loading amount of the positive active material layer (positive electrode sheet) was 4.1 mAh / cm². 2It was.

[0109] (Solid electrolyte layer)

[0110] As a solid electrolyte layer, a solid electrolyte layer with a thickness of 10 μm was used, comprising an azirodite-based (Li6PS5Cl) sulfide solid electrolyte and a binder.

[0111] (Solid-state battery)

[0112] An all-solid-state battery was fabricated by stacking a positive electrode, a solid electrolyte layer, and a negative electrode, and sealing them in a pouch under vacuum. The N / P ratio of the fabricated all-solid-state battery was 1.08.

[0113] Here, each part of the positive current collector and the negative current collector was protruded out of the pouch to maintain the vacuum of the battery. These protrusions were used as the positive and negative terminals. In addition, this all-solid-state battery was subjected to hydrostatic pressure treatment at 500 MPa for 30 minutes.

[0114] Comparative Example 1

[0115] An all-solid-state battery was manufactured in the same manner as in the example, except that a slurry for the negative electrode active material layer was prepared by mixing graphite, a solid electrolyte, and a binder in a weight ratio of 77:20:3 with NMP (N-methyl-2-pyrrolidone), and a single layer of the negative electrode active material layer was formed on a copper foil. The loading amount of the negative electrode active material layer was 4.43 mAh / cm² 2 It was.

[0116] Comparative Example 2

[0117] An all-solid-state battery was manufactured in the same manner as in the example, except that a slurry for the negative electrode active material layer was prepared by mixing graphite, a solid electrolyte, a conductive material, and a binder in a weight ratio of 75.5:20:1.5:3 with NMP (N-methyl-2-pyrrolidone), and a single layer of the negative electrode active material layer was formed on a copper foil. The loading amount of the negative electrode active material layer was 4.43 mAh / cm² 2 It was.

[0118] Comparative Example 3

[0119] An all-solid-state battery was manufactured in the same manner as in the example, except that graphite was introduced instead of silicon when preparing the slurry for the second negative electrode active material layer, and the mixture was prepared such that the weight ratio of graphite : solid electrolyte : binder within the second negative electrode active material layer was 57 : 40 : 3. At this time, the thickness ratio and weight ratio of the first negative electrode active material layer and the second negative electrode active material layer were 1 : 1, and the weight ratio of graphite : silicon : solid electrolyte : conductive material : binder over the entire negative electrode active material layer was 73.2 : 2.3 : 20 : 1.5 : 3, and the sum of the loading amounts of the first negative electrode active material layer and the second negative electrode active material layer was 4.42 mAh / cm² 2 It was.

[0120] Evaluation Example 1. Energy Density Evaluation

[0121] The results of calculating the volume energy density for the all-solid-state batteries prepared in the above examples and comparative examples 1 to 3 are as shown in Table 1 below.

[0122] The volumetric energy density (Wh / L) of the battery is measured according to Equation 1 below.

[0123] [Equation 1]

[0124] Volumetric energy density = (Q Х V ave ) / Volume of battery (L)

[0125] In Equation 1 above, Q is the discharge capacity (Ah) of the battery, and V ave This is the nominal voltage, which corresponds to the average operating voltage during battery discharge.

[0126] In Evaluation Example 1, charging and discharging were performed in a cell having an arbitrary discharge capacity within the range of 3 to 4.25 V, and the measured nominal voltage (V ave The volume energy density was calculated by substituting ) into Equation 1.

[0127] division Energy density (Wh / L) Examples 628 Comparative Example 1 521 Comparative Example 2 516 Comparative Example 3 533

[0128] As shown in Table 1 above, in the case of the example, the energy density is 628 Wh / L, and it can be confirmed that it has a high energy density value compared to Comparative Examples 1 to 3.

[0129] Evaluation Example 2. Evaluation of charging capacity and Coulomb efficiency according to cycle

[0130] For the above Examples and Comparative Example 3, the charging specific capacity (mAh / g) and Coulombic efficiency (%) were measured at the following operating voltage range and operating temperature of 60°C. The specific charging and discharging conditions are as follows.

[0131] (Charging / Discharging Conditions)

[0132] Charging: 0.33 C 4.2V CC / CV, 0.1C cut-off

[0133] Discharge: 0.33C, 3.0V, CC

[0134] Under the conditions described above, 30 charge-discharge cycles were repeated, and the charge capacity and Coulomb efficiency were measured for each cycle. The results are shown in Table 2, Figure 2, and Figure 3 below. Here, Coulomb efficiency is a value calculated as the ratio (%) of the discharge capacity to the charge capacity for each cycle.

[0135] division Coulomb efficiency (%) (0.33C, 30 cycles) Examples 99.7 Comparative Example 3 35.2 @ 6 cycle (shortcut)

[0136] As shown in Table 2 and Figure 3 above, in the case of Comparative Example 3, the Coulomb efficiency was 93.1% in the first cycle, 98.6% in the second cycle, 96.2% in the third cycle, 88.9% in the fourth cycle, 88.1% in the fifth cycle, and 35.2% in the sixth cycle, indicating that it was overcharged and showed unstable Coulomb efficiency from the first cycle, with a short circuit occurring in the sixth cycle. In contrast, in the case of the embodiment including the configuration of the present invention, the Coulomb efficiency remained stable at 99.7% throughout the cycle, and normal charging behavior was observed. Explanation of the symbols

[0137] 10 : Whole house 201: First cathode active material layer 202: Second negative electrode active material layer 30: Solid electrolyte layer

Claims

Claim 1 A cathode comprising a cathode current collector, a first cathode active material layer, and a second cathode active material layer, wherein the first cathode active material layer comprises a first cathode active material and a conductive material, and the first cathode active material is at least one selected from the group consisting of graphite, silicon, and combinations thereof, and the second cathode active material layer comprises a second cathode active material and a solid electrolyte, and the second cathode active material is silicon. Claim 2 In claim 1, the cathode is characterized in that the first cathode active material layer is positioned closer to the cathode current collector than the second cathode active material layer. Claim 3 A cathode according to claim 1, characterized in that the silicon content of the first cathode active material layer is lower than the silicon content of the second cathode active material layer. Claim 4 A cathode according to claim 3, characterized in that the ratio of the silicon content of the first cathode active material layer to the silicon content of the second cathode active material layer is 0.4 or less. Claim 5 A cathode according to claim 1, characterized in that the solid electrolyte content of the first cathode active material layer is lower than the solid electrolyte content of the second cathode active material layer. Claim 6 A cathode according to claim 1, characterized in that the Young's Modulus of the solid electrolyte is 18 to 25 GPa. Claim 7 A cathode according to claim 1, characterized in that the conductive material content of the second cathode active material layer is lower than the conductive material content of the first cathode active material layer. Claim 8 A cathode according to claim 1, characterized in that the first cathode active material layer does not include a solid electrolyte and the second cathode active material layer does not include a conductive material. Claim 9 A cathode according to claim 1, characterized in that the first cathode active material layer comprises 60 weight% or more of the first cathode active material. Claim 10 A cathode according to claim 1, characterized in that the first cathode active material layer comprises graphite and silicon. Claim 11 A cathode according to claim 10, characterized in that the weight ratio of silicon to graphite in the first cathode active material layer is within the range of 0.005 to 0.

5. Claim 12 A cathode according to claim 1, characterized in that at least one of the first cathode active material layer and the second cathode active material layer further comprises a binder. Claim 13 A cathode according to claim 1, characterized in that the ratio of the thickness of the second cathode active material layer to the thickness of the first cathode active material layer is 2 or less. Claim 14 All-solid-state battery characterized by comprising a positive electrode, a solid electrolyte layer, and a negative electrode according to claim 1. Claim 15 An all-solid-state battery according to claim 14, characterized in that the capacity ratio (N / P ratio) of the cathode to the anode is 0.9 to 1.

2. Claim 16 In claim 14, the cathode loading amount is 3 to 7 mAh / cm 2 A solid-state battery characterized by being.

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