KR102566410B1 - all solid secondary battery and manufacturing thereof - Google Patents

Abstract

A novel and improved all-solid-state secondary battery capable of preventing short circuits and a method for manufacturing the all-solid-state secondary battery are provided.
In order to solve the above problems, according to one aspect of the present invention, a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer, and the interface between the positive electrode active material layer and the solid electrolyte layer An arithmetic average roughness (Ra) of is 1.0 μm or less, and a solid electrolyte layer has a relative density of 80% or more.

Description

All-solid-state secondary battery and manufacturing method of all-solid-state secondary battery {all solid secondary battery and manufacturing thereof}

The present invention relates to an all-solid-state secondary battery and a method for manufacturing the all-solid-state secondary battery.

In recent years, for example, all-solid-state secondary batteries disclosed in Patent Literatures 1 and 2 have attracted attention. An all-solid-state secondary battery includes a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer. In the all-solid-state secondary battery, a medium that conducts lithium ions is a solid electrolyte.

In order to increase the energy density of such an all-solid-state secondary battery, it has been proposed to use metal lithium as an anode active material. This is because the use of metal lithium as an anode active material can increase the output while flattening the all-solid-state secondary battery.

On the other hand, since the medium for conducting lithium ions in an all-solid-state secondary battery is a solid electrolyte, the characteristics of the battery can be improved by closely clustering the particles constituting the all-solid-state secondary battery. In addition, from the viewpoint of increasing the energy density of an all-solid-state secondary battery, thinning of the solid electrolyte layer is required.

Therefore, when manufacturing an all-solid-state secondary battery, an electrode laminate, which is a laminate of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, is often pressed. Accordingly, particles within each layer and between layers can be densely packed with each other. In addition, the solid electrolyte layer can be thinned. Nevertheless, there is a need for an improved all-solid-state secondary battery and a manufacturing method thereof.

Japanese Patent Application Laid-Open No. 2015-125872 International Publication No. 2014/010042

However, metallic lithium is very fragile. Therefore, the following problems may occur when metal lithium is used as an anode active material. That is, when gaps such as cracks occur on the surface of the solid electrolyte layer, metallic lithium penetrates the gaps during pressing of the electrode laminate. Further, when the gap communicated between the front and back surfaces of the solid electrolyte layer, metallic lithium could reach the positive electrode active material layer. Thus, the all-solid-state secondary battery could be short-circuited. Further, even when the gap does not communicate with the front and back surfaces, the distance between the metal lithium penetrating into the gap and the cathode active material layer is shorter than the distance between the surface of metal lithium and the cathode active material layer. Therefore, current is concentrated in this part during charging, and a short circuit may occur.

In addition, the following problems may occur when the surfaces of the positive electrode active material layer and the solid electrolyte layer are rough. That is, protrusions protruding toward the negative electrode active material layer (ie, metallic lithium) are formed on the surface of the positive electrode active material layer. Therefore, during charging, the distance between the corresponding protrusion and the negative active material layer is shorter than the distance between the other part of the positive active material layer and the negative active material layer. Therefore, current is concentrated in this part during charging, and a short circuit may occur.

As such, a short circuit may occur when metal lithium is used as an anode active material of an all-solid-state secondary battery.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is a new and improved all-solid-state secondary battery and a method for manufacturing the all-solid-state secondary battery capable of preventing short circuits when metal lithium is included in the negative electrode active material layer is to provide

In order to solve the above problems, according to an aspect of the present invention, a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and a solid electrolyte interposed between the positive electrode active material layer and the negative electrode active material layer. An all-solid-state secondary battery comprising a solid electrolyte layer, an arithmetic mean roughness (Ra) at the interface between the positive electrode active material layer and the solid electrolyte layer is 1.0 μm or less, and the solid electrolyte layer density ratio is 80% or more.

In addition, according to one aspect of the present invention, a positive electrode comprising a positive electrode active material layer; a negative electrode including a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector; And an all-solid secondary battery comprising a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer, wherein the negative electrode active material layer includes carbon, and includes a plating layer between the negative electrode current collector and the negative electrode active material layer, , The plating layer contains lithium, the arithmetic average roughness at the interface between the positive electrode active material layer and the solid electrolyte layer is 1.0 μm or less, and the solid electrolyte layer density ratio is 80% or more. do.

According to this aspect, since the arithmetic average roughness (Ra) at the interface between the positive electrode active material layer and the solid electrolyte layer is 1.0 μm or less, current flows more uniformly in the solid electrolyte layer during charging of the solid-state secondary battery. Therefore, since metallic lithium is more uniformly deposited in the negative electrode active material layer, occurrence of a short circuit becomes difficult. Further, since the relative density of the solid electrolyte layers is 80% or more, the gaps between the solid electrolyte layers become smaller and smaller. Therefore, occurrence of short circuit becomes difficult.

Here, the relative density of the positive electrode active material layer may be 60% or more.

According to this point of view, the characteristics of the all-solid-state secondary battery are improved.

In addition, the maximum height roughness (Rz) at the interface between the positive electrode active material layer and the solid electrolyte layer may be 4.5 μm or less.

According to this point of view, current flows more uniformly in the solid electrolyte layer during charging of the all-solid-state secondary battery. Therefore, since metallic lithium is more uniformly deposited on the negative electrode active material layer, occurrence of a short circuit becomes difficult.

Also, the solid electrolyte layer may have a thickness of 100 μm or less.

According to this point of view, the energy density of the all-solid-state secondary battery is improved.

According to another aspect of the present invention, in the all-solid-state secondary battery manufacturing method for manufacturing the all-solid-state secondary battery, providing a positive electrode active material layer; providing an anode active material layer; providing a solid electrolyte layer comprising a solid electrolyte; and pre-pressing the positive electrode active material layer and the solid electrolyte layer; and manufacturing the all-solid-state secondary battery by pressing an electrode laminate comprising a positive electrode active material layer and a solid electrolyte layer pressed in a preliminary press process, and the negative electrode active material layer, wherein the positive electrode active material layer and the solid electrolyte are pressed. The step of pre-pressing is to press the positive electrode active material layer before laminating the pressed positive electrode active material layer on the solid electrolyte layer to provide a pressed positive electrode active material layer, and to laminate the pressed solid electrolyte layer on the negative electrode active material layer There is provided an all-solid-state secondary battery manufacturing method characterized by providing a pressed solid electrolyte layer by pressing the solid electrolyte layer before.

According to this aspect, an all-solid-state secondary battery having the above characteristics can be manufactured.

Here, in the step of pressing the positive electrode active material layer, the positive electrode active material layer may be pressed together with the positive electrode current collector.

According to this aspect, an all-solid-state secondary battery having the above characteristics can be manufactured.

In addition, the pressing of the solid electrolyte layer may include pressing the solid electrolyte layer alone before laminating the positive electrode active material layer in which the solid electrolyte layer is pressed.

According to this aspect, an all-solid-state secondary battery having the above characteristics can be manufactured.

In addition, the step of pressing the solid electrolyte layer may include pressing the solid electrolyte layer alone; And pressing the first intermediate laminate, which is a laminate of the pressed solid electrolyte layer provided by the step of pressing the solid electrolyte layer alone and the pressed positive electrode active material layer provided by the step of pressing the positive electrode active material layer. can include

According to this aspect, an all-solid-state secondary battery having the above characteristics can be manufactured.

In addition, the pressing of the solid electrolyte layer may include pressing the solid electrolyte layer alone; and pressing a second intermediate laminate, which is a laminate of the solid electrolyte layer and the pressed cathode active material layer in the step of pressing the cathode active material layer.

According to this aspect, an all-solid-state secondary battery having the above characteristics can be manufactured.

In addition, in the all-solid-state secondary battery manufacturing method for manufacturing the all-solid-state secondary battery, providing a positive electrode including a positive electrode active material layer, disposing a solid electrolyte layer on the positive electrode; Disposing a negative electrode on the solid electrolyte layer; And providing a voltage between the positive electrode and the negative electrode to form a plating layer between the negative electrode active material layer and the negative electrode current collector to manufacture the all-solid-state secondary battery, wherein the negative electrode includes a negative electrode current collector, A method for manufacturing an all-solid-state secondary battery including a negative electrode active material layer on a negative electrode current collector is provided.

As described above, according to the present invention, when metal lithium is included in the negative electrode active material layer, it will be possible to prevent a short circuit.

1A is a diagram showing a schematic configuration of an all-solid-state secondary battery according to an embodiment of the present invention.
1B is a diagram showing a schematic configuration of an all-solid-state secondary battery according to an embodiment of the present invention.
2 is a diagram showing a solid electrolyte layer and its surrounding structure.
3 is a cross-sectional SEM (electron microscope) photograph showing an interface between a solid electrolyte layer and a positive electrode active material layer and its surrounding structure.
4 is a view for explaining problems of a conventional all-solid-state secondary battery.
5 is a view for explaining problems of a conventional all-solid-state secondary battery.
6 is a diagram for explaining problems of a conventional all-solid-state secondary battery.
7 is a cross-sectional SEM picture for explaining problems of a conventional all-solid-state secondary battery.
8 is a cross-sectional SEM picture for explaining a method of measuring arithmetic average roughness (Ra) at the interface between a solid electrolyte layer and a positive electrode active material layer.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the present specification and drawings, the same reference numerals are given to components having substantially the same functional configuration, thereby omitting redundant description.

It will be understood that when an element is “on” another element, it is directly on the other element, or intervening elements are present therebetween. On the other hand, if a component is "directly on" of another component, it means that there is no intervening configuration between them.

Although the terms "first", "second", "third", etc. may be used herein, it is intended to describe various components, components, regions, layers, and/or portions, but such components, components, components , regions, layers, and/or portions are not intended to be limited by these terms. These terms are only intended to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a “first component”, “component”, “region”, “layer”, or “portion” discussed below may be referred to as a second component, component, region, layer, or section without departing from the teachings herein. can be named

The terminology used herein is only for the purpose of describing a particular embodiment, and not for the purpose of limiting it. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural, including “at least one,” unless the context clearly dictates otherwise. “At least one” should not be limited to “one” or “an”. "or" means "and/or" As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. When the terms "comprise" and/or "comprising", or "includes" and/or "including" are used herein, the indicated features, regions, numbers , states the presence of steps, acts, elements, and/or ingredients, but does not preclude the presence or addition of one or more other features, regions, numbers, steps, acts, elements, components, and/or groups thereof. .

Furthermore, the relative concepts of "lower" or "below" and "upper" or "above" are intended to describe a relationship between one component and another component as shown in the drawings. Relative concepts are intended to include other arrangements of the device other than the arrangement shown in the figures. For example, if the device in either figure is turned over, a component described as being on the "lower" side of other components would be arranged on the "upper" side of the other components. Thus, the exemplary term “lower” may encompass both “lower” or “upper” arrangements, depending on the particular arrangement of the figures. Similarly, if the device in either figure is turned over, components that are “below” other components will be arranged “above” the other components. Thus, the exemplary term “below” can encompass both arrangements below and above.

As used herein, "about" or "approximately" means a given within an acceptable error range for a particular value determined by the skilled person, taking into account measurement errors and errors associated with the measurement of a particular quantity (i.e., limitations of the measurement system). Include values and averages. For example, "about" can mean within one or more standard deviations, or within 30%, 20%, 10% or 5% of a given value.

Unless defined otherwise, all terms (technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. In addition, terms such as those defined in commonly used dictionaries should be interpreted in a meaning consistent with their meaning in the context of the related technical literature and the present application, and unless specifically defined herein, interpreted in an ideal or excessively formal meaning. It shouldn't be.

Exemplary implementations are described herein with reference to cross-sectional views that are schematic representations of idealized implementations. As such, variations from the shape of the illustration as a result of, for example, manufacturing techniques and/or tolerances, should be expected. Accordingly, the implementations described herein should not be construed as limited to the particular shape of the region as shown herein, but should include deviations in shape resulting, for example, from manufacturing. For example, areas depicted or depicted as flat may typically have rough and/or non-linear features. Moreover, the sharp angles illustrated may be rounded. Accordingly, the regions depicted in the drawings are schematic in nature and the shapes are not intended to illustrate the exact shape of the region and are not intended to limit the scope of the present claims.

An electrode laminate of an all-solid-state secondary battery, which is a laminate of a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, is pressed in the manufacture of an all-solid-state battery. Thus, particles in each of the layers and between the layers can be compacted and brought into contact with each other. In addition, the solid electrolyte layer may be a thin film type.

< 1. All-solid-state battery >

As a result of earnestly examining the problems of an all-solid-state secondary battery using metal lithium as a negative electrode active material, the inventors of the present invention came up with an all-solid-state secondary battery according to this embodiment. Therefore, first, the examination performed by the inventor will be described.

4 to 7, a conventional all-solid-state secondary battery 100 using metal lithium as an anode active material includes a cathode active material layer 112, a cathode active material layer 122, and a solid electrolyte layer 130. Here, FIGS. 4 to 6 are diagrams showing the configuration of a conventional all-solid-state secondary battery 100, and FIG. 7 shows cross-sectional SEM pictures corresponding to FIGS. 5 to 6. The cathode active material layer 112 includes a cathode active material 112a and a solid electrolyte 112b. The solid electrolyte layer 130 includes a solid electrolyte 130a. The anode active material layer 122 is made of metal lithium.

A short circuit may occur when gaps 123 such as cracks are formed on the surface of the solid electrolyte layer 130 . A situation in which a short circuit occurs will be described based on FIG. 4 . As shown in FIG. 4, a gap 123 is formed in the solid electrolyte layer 130 (eg, extending from the upper surface of the solid electrolyte layer 130 to the lower surface of the solid electrolyte layer 130) communicating from the front and back surfaces, there is. When the electrode laminate, which is a laminate of the positive electrode active material layer 112, the negative electrode active material layer 122, and the solid electrolyte layer 130, is pressed, metal lithium penetrates into the gap between the solid electrolyte layer 130. Since the gap of the solid electrolyte layer 130 communicates with the front and back surfaces of the solid electrolyte layer 130 (eg, extends from the upper surface of the solid electrolyte layer 130 to the lower surface of the solid electrolyte layer 130), the metal Lithium could reach the cathode active material layer 112 . Thus, the all-solid-state secondary battery could be short-circuited. In addition, even when the gap of the solid electrolyte layer 130 is not in communication with the front and back surfaces, the distance between the metal lithium penetrating into the gap and the cathode active material layer 112 is the distance between the metal lithium in the other part and the cathode active material layer 112. become shorter Therefore, current is concentrated in this portion (eg, gap) during charging, and a short circuit may occur.

When the interface between the positive electrode active material layer 112 and the solid electrolyte layer 130 is rough, a short circuit may occur. A situation in which a short circuit occurs will be further described with reference to FIGS. 5 to 7. The interface B between the positive electrode active material layer 112 and the solid electrolyte layer 130 is rough, so that protrusions 112c are formed on the surface of the positive electrode active material layer 112 . Therefore, during charging, the distance between the corresponding protrusion 112c and the negative active material layer 122 is shorter than the distance between the other part of the positive active material layer and the negative active material layer 122 . Therefore, at the time of charging, current is concentrated in this part (the part indicated by frame A in Fig. 6). That is, a high current density flows in the portion marked with frame A. As a result, there has been a case where metallic lithium is locally deposited in the corresponding portion (for example, on the surface thereof), resulting in a short circuit.

In this way, when metallic lithium is used as the negative electrode active material of an all-solid-state secondary battery, a short circuit may occur. Therefore, the present inventors have considered increasing the density of the solid electrolyte layer 130 and flattening the interface between the positive electrode active material layer 112 and the solid electrolyte layer 130 in order to prevent a short circuit. When the density of the solid electrolyte layer 130 is high, the gap in the solid electrolyte layer 130 can be reduced and becomes smaller. Furthermore, when the interface between the positive electrode active material layer 112 and the solid electrolyte layer 130 is flat, the possibility of a phenomenon in which a large current locally flows is reduced. As a result, the present inventors came up with an idea for an all-solid-state secondary battery according to this embodiment. Hereinafter, this embodiment will be described in detail.

< 2. Rating Criteria: Configuration of All-Solid-State Secondary Batteries >

Next, the configuration of the all-solid-state secondary battery 1 according to the present embodiment will be described based on FIGS. 1A to 3. As shown in FIG. 1A, the all-solid-state secondary battery 1 includes a positive electrode 10, a negative electrode 20, and a solid electrolyte layer 30. In one embodiment, the negative electrode 20 of the all-solid-state secondary battery includes an anode active material layer 22 on a negative electrode current collector 21 . As shown in FIG. 1B , after charging, the all-solid-state secondary battery further includes a plating layer between the anode active material layer 22 and the anode current collector 21 .

(2-1. Anode)

The positive electrode 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 . Examples of the positive electrode current collector 11 include indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), plate-like bodies or thin bodies made of zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof; and the like. Combinations comprising at least one of the foregoing may be used. The cathode current collector 11 may be omitted.

The cathode active material layer 12 may include a cathode active material 12a and a solid electrolyte 12b. In this case, resistance between the positive electrode active material layer and the solid electrolyte layer may be lowered. In addition, the solid electrolyte 12b included in the positive electrode 10 may be of the same type as or not the same as the solid electrolyte 12b included in the solid electrolyte layer 30 . Details of the solid electrolyte 12b will be described in detail in the section on the solid electrolyte layer 30 .

The cathode active material may be a cathode active material capable of reversibly intercalating and releasing lithium ions.

For example, the cathode active material may use at least one of cobalt, manganese, nickel, and a composite oxide of a metal selected from combinations thereof and lithium. In one embodiment, the cathode active material may be a compound represented by any of the following formulas: Li _a A _1-b B ¹ _b D ¹ ₂ (wherein 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5 ); Li _a E _1-b B ¹ _b O _2-c D ¹ _c (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE _2-b B ¹ _b O _4-c D ¹ _c (wherein 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05); Li _a Ni _1-bc Co _b B ¹ _c D ¹ _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Co _{b B} ¹ _c O _2-α F ¹ _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Co _{b B} ¹ _c O _2-α F ¹ ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B ¹ _c D ¹ _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Mn _b B ¹ _c O _2-α F ¹ _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B ¹ _c O _2-α F ¹ ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _b E _c G _d O ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a CoG _b O ₂ (wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a MnG _b O ₂ (wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiI ¹ O ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); A compound represented by any of the chemical formulas of LiFePO ₄ may be used:

In the above formula, 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 combinations thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or combinations thereof.

For example, the cathode active material is lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, nickel cobalt aluminum lithium (NCA), nickel cobalt lithium manganate (NCM) , lithium manganate, lithium iron phosphate, and the like, nickel sulfide, copper sulfide, sulfur, iron oxide, or vanadium oxide. These cathode active materials may be used alone or in combination of two or more.

In addition, the cathode active material is preferably formed by including a lithium salt of a transition metal oxide having a layered rock salt structure among the above-mentioned lithium salts. Here, "layered" indicates a thin sheet shape. In addition, "rock salt structure" refers to a sodium chloride type structure, which is a type of crystal structure, specifically, a structure in which face-centered cubic lattices formed by cations and anions, respectively, are arranged so that the edges of the unit lattice are offset by only 1/2 of each other indicates

As a lithium salt of a transition metal oxide having such a layered halite-type structure, for example, LiNi _x Co _y Al _z O ₂ (NCA) (0 < x < 1, 0 < y < 1, 0 < z < 1 , and x + y + z = 1), LiNi _x' Co _y' Mn _z' O ₂ (NCM) (0 <x'< 1, 0 <y'< 1, 0 <z'< 1, and x' + y' + z' = 1), or a lithium salt of a ternary transition metal oxide in combination thereof.

When the cathode active material includes the lithium salt of the ternary transition metal oxide having the layered halite structure, energy density and thermal stability of the all-solid-state secondary battery 1 may be improved.

The cathode active material may be covered by a coating layer. Here, the coating layer of the present embodiment is preferably any one known as a coating layer of a cathode active material of an all-solid-state secondary battery. Examples of the coating layer include, for example, Li ₂ O-ZrO ₂ and the like.

In addition, when the cathode active material is formed of a lithium salt of a ternary transition metal oxide such as NCA or NCM, and nickel (Ni) is included as the cathode active material, the capacity density of the all-solid-state secondary battery 1 is increased, resulting in a state of charge. It is possible to reduce metal elution from the cathode active material in As a result, the all-solid-state secondary battery 1 according to the present embodiment can improve long-term stability and cycle characteristics in a charged state.

Here, examples of the shape of the positive electrode active material include particle shapes such as true spherical and elliptical spherical shapes. In addition, the particle size of the cathode active material is not particularly limited and may be within a range applicable to the cathode active material of a conventional all-solid-state secondary battery. In addition, the content of the positive electrode active material of the positive electrode 10 is not particularly limited and may be within a range applicable to the positive electrode of a conventional all-solid-state secondary battery.

In addition, additives such as a conductive agent, a binder, a filler, a dispersant, and an ion conductive agent may be appropriately mixed with the positive electrode 10 in addition to the above-described positive electrode active material and the solid electrolyte 12b.

Examples of the conductive agent that can be incorporated into the positive electrode 10 include graphite, carbon black, acetylene black, ketjen black, carbon fiber, and metal powder. In addition, examples of binders that can be mixed with the positive electrode 10 include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and the like. can In addition, as fillers, dispersants, ion conducting agents, and the like that can be incorporated into the positive electrode 10, known materials commonly used in electrodes of lithium ion secondary batteries can be used.

When the cathode active material layer 12 includes the cathode active material, the solid electrolyte 12b, and the binder, the cell capacity (capacity per unit cell) of the all-solid-state secondary battery 1 may be increased.

For example, the binder may be a vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, styrene butadiene rubber-based polymer, and Mixtures thereof may be used, but are not limited thereto, and any materials that can be used as binders in the art may be used.

In addition, the relative density of the positive electrode active material layer 12 may be 60% or more. For example, the relative density of the positive electrode active material layer 12 is 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88% , 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, and may be less than 100% or less than 99.5%. For example, about 60% to about 99.5%, about 65% to about 98%, or about 70% to about 95%. Relative densities as used herein follow Equation 1 below.

<Equation 1>

Relative Density = (Measured Density/Theoretical Density) x 100%

The measured density can be determined by dividing the mass of a sample of material by the volume (eg, dividing the mass of a pellet material by the volume). The theoretical density is the density of a material having zero porosity, which can be determined, for example, by calculating the density based on the crystal structure of the material or by calculating the density based on SEM analysis.

In this case, the battery characteristics of the all-solid-state secondary battery 1 are improved. Here, the relative density of the positive electrode active material layer 12 is the ratio of the density to the theoretical density of the positive electrode active material layer 12 . The theoretical density of the positive electrode active material layer 12 is calculated according to the nominal density of each material constituting the positive electrode active material layer and the mass ratio of these materials. In addition, a cross section of the positive electrode active material layer 12 was observed by SEM to measure the content of the positive electrode active material layer 12, and the corresponding content was determined as a relative density.

Here, as a method of setting the relative density of the positive electrode active material layer 12 to a value within the above range, a method of pressing the positive electrode active material layer 12 in the manufacturing process of the all-solid-state secondary battery 1 may be mentioned. In this embodiment, the positive electrode active material layer 12 is pressed before laminating the positive electrode active material layer 12 on the solid electrolyte layer 30 . As a result, the relative density of the positive electrode active material layer 12 can be set to a value within the above range, and as will be described in detail later, the interface B between the positive electrode active material layer 12 and the solid electrolyte layer 30 (see FIGS. 2 and 3) ) can be flattened. The upper limit of the relative density is not particularly limited, but is preferably 95% or less when the positive electrode active material is crystalline such as a lithium salt of a transition metal oxide. If the relative density exceeds 95%, the cathode active material layer 12 may crack. Also, when a crack occurs in the positive electrode active material layer 12, battery characteristics may deteriorate. In addition, when the cathode active material is amorphous such as sulfur, the relative density may be less than 100% or less than 99.5% due to limitations such as performance of manufacturing equipment.

(2-2. Cathode)

The negative electrode 20 includes a negative electrode current collector 21 and a negative electrode active material layer 22 . The negative current collector 21 includes indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), A plate-like body or a thin body made of aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof, and the like may be exemplified. The negative electrode current collector 21 can be omitted.

The negative electrode active material layer 22 includes metal lithium. The negative electrode active material layer 22 may include metal lithium, or metal lithium or a metal active material other than metal lithium (indium (In), aluminum (Al), tin (Sn), silicon (Si), or a combination thereof). ) can be composed of an alloy with Preferably, the negative electrode active material layer 22 may include metal lithium. In this way, the energy density of the all-solid-state secondary battery 1 can be improved.

In one embodiment, the negative electrode active material layer 22 includes carbon. Carbon may be amorphous or graphitic. Examples of carbon include ketjen black, carbon black, graphite, carbon nanotubes, carbon fibers, mesoporous carbon, mesocarbon microbeads (MCMB), oil furnace black, extra-conductive Extra-conductive black, acetylene black, lamp black, non-graphitizing carbon, graphitizing carbon, cracked carbon, coke, glassy carbon, and activated carbon. The coke includes pitch coke, needle coke, and petroleum coke. Combinations comprising at least one of the foregoing may be used.

The negative electrode active material layer 22 may include a binder. Examples of the binder are not particularly limited, and may include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. Combinations comprising at least one of the foregoing may be used.

(2-3. Solid electrolyte layer)

The solid electrolyte layer 30 is formed between the anode 10 and the cathode 20 and includes a solid electrolyte 30a.

The solid electrolyte 30a is made of, for example, a sulfide-based solid electrolyte material. As the sulfide-based solid electrolyte material, for example, Li _7-a PS _6-a X _a (X is a halogen atom, for example, F, Cl, Br, I, or a combination thereof, 0≤a<2) ,c(0<a<1), aLi ₂ S-bP ₂ S ₅ -cLiX (X is a halogen atom, eg F, Cl, Br, I, or a combination thereof, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1), aLi ₂ S-bP ₂ S ₅ -cLi ₂ O (0<a<1, 0<b<1, 0<c <1, and a+b+c=1), aLi ₂ S-bP ₂ S ₅ -cLi ₂ O-dLiI (0<a<1, 0<b<1, 0<c<1, 0<d< 1 and a+b+c+d=1), aLi ₂ S-(1-a)SiS ₂ (0<a<1), aLi2 _S -bSiS ₂ -cLiI (0<a<1, 0<b< 1, 0<c<1, and a+b+c=1), aLi ₂ S-bSiS ₂ -cLiBr (0<a<1, 0<b<1, 0<c<1, and a+b+ c=1), aLi ₂ S-bSiS ₂ -cLiCl (0<a<1, 0<b<1, 0<c<1, and a+b+c=1), aLi ₂ S-bSiS ₂ -cB ₂ S ₃ -dLiI (0<a<1, 0<b<1, 0<c<1, 0<d<1 and a+b+c+d=1), aLi ₂ S-bSiS ₂ -cP ₂ S ₅ -dLiI (0<a<1, 0<b<1, 0<c<1, 0<d<1 and a+b+c+d=1), aLi ₂ S-(1-a)B ₂ S ₃ (0<a<1), aLi ₂ S-bP ₂ S ₅ -cZ _m S _n (m and n are independently positive integers from 1 to 10, and Z is Ge, Zn, or Ga; , 0<a<1, 0<b<1, 0<c<1, and a+b+c=1), aLi ₂ S-(1-a)GeS ₂ (0<a<1), aLi ₂ S-bSiS ₂ -cLi ₃ PO ₄ (0<a<1, 0<b<1, 0<c<1, and a+b+c=1), and aLi ₂ S-bSiS ₂ -cLi _P MO _q (p and q are independently positive integers from 1 to 10, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1, M is P, Si , Ge, B, Al, Ga or In) and the like. Here, the sulfide-based solid electrolyte material is prepared by treating a starting material (eg, Li ₂ S, P ₂ S ₅ , etc.) by a melt quenching method or a mechanical milling method. Further, an additional heat treatment may be applied after this treatment. The solid electrolyte may be amorphous or crystalline, or a mixture thereof.

In addition, as the solid electrolyte 30a, it is preferable to use a sulfide solid electrolyte material containing sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements, particularly including Li ₂ SP ₂ S ₅ It is more preferable to use the

Here, when using a sulfide-based solid electrolyte material containing Li ₂ SP ₂ S ₅ as the sulfide-based solid electrolyte material forming the solid electrolyte 30a, the mixing molar ratio of Li ₂ S and P ₂ S ₅ is, for example, Li ₂ S :P ₂ S ₅ = Can be selected from the range of 50:50 to 90:10. In addition, the solid electrolyte layer 30 may further include a binder. The binder included in the solid electrolyte layer 30 may include, for example, styrene-butadiene (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or a combination thereof. can The binder in the solid electrolyte layer 30 may be the same as or different from the binder in the positive electrode active material layer 12 .

The relative density of the solid electrolyte layer 30 is 80% or more. For example, the relative density of the solid electrolyte layer 30 is 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, It may be greater than 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, and may be less than 100% or less than 99.5%. For example, from about 80% to about 99.5%, or from about 85% to about 98%.

In this case, the gap in the solid electrolyte layer 30 becomes smaller and smaller. Therefore, occurrence of short circuit becomes difficult. Here, the relative density of the solid electrolyte layer 30 is the density with respect to the theoretical density of the solid electrolyte layer 30 . The theoretical density of the solid electrolyte layer 30 can be calculated based on the nominal density of each material constituting the solid electrolyte layer 30 and the mass ratio of each material, and a cross section of the solid electrolyte layer 30 is observed by SEM. The content of the solid electrolyte layer 30 may be measured and the content may be regarded as a relative density.

Here, as a method of setting the relative density of the solid electrolyte layer 30 to a value within the above range, there is a method of pressing the solid electrolyte layer 30 in the manufacturing process of the all-solid-state secondary battery 1 . In this embodiment, prior to laminating the solid electrolyte layer 30 on the negative electrode active material layer 22, the solid electrolyte layer 30 is pressed. As a result, the relative density of the solid electrolyte layer 30 can be set to a value within the above range. The upper limit of the relative density is not particularly limited, but the relative density may be less than 100% or, for example, 99.5% or less due to limitations such as the performance of the manufacturing apparatus.

In addition, the thickness of the solid electrolyte layer 30 may be 100 μm or less. For example, the solid electrolyte layer 30 may have a thickness of 100 μm, 95 μm, 90 μm, 85 μm, 80 μm, 75 μm, 70 μm, 65 μm, 60 μm, 55 μm, or 50 μm or less. , but is not limited thereto, and may be, for example, about 5 μm to about 100 μm, or about 10 μm to about 90 μm. Accordingly, the energy density of the all-solid-state secondary battery 1 can be increased. In addition, as a method of setting the thickness of the solid electrolyte layer 30 to a value within the above range, there is a method of pressing the solid electrolyte layer 30 .

(2-4. Interface state of cathode active material layer and solid electrolyte layer)

In this embodiment, as shown in FIGS. 2 and 3, the interface B between the positive electrode active material layer 12 and the solid electrolyte layer 30 is flat. Specifically, the arithmetic mean roughness (Ra) of the interface B is 1.0 µm or less. For example, the Ra may be 1.0 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, or 0.1 μm or less, such as from about 0.01 μm to about 1 μm. μm, about 0.05 μm to about 0.9 μm, about 0.1 μm to about 0.8 μm, or about 0.15 μm to about 7 μm. The maximum height roughness (Rz) of interface B may be 4.5 μm or less. For example, the Rz is 4.5 μm, 4.4 μm, 4.3 μm, 4.2 μm, 4.1 μm, 4.0 μm, 3.9 μm, 3.8 μm, 3.7 μm, 3.6 μm, 3.5 μm, 3.4 μm, 3.3 μm, 3.2 μm, 3.1 μm, 3.0 μm, 2.9 μm, 2.8 μm, 2.7 μm, 2.6 μm, 2.5 μm, 2.4 μm, 2.3 μm, 2.2 μm, 2.1 μm, 2.0 μm, 1.9 μm, 1.8 μm, 1.7 μm, 1.6 μm, 1.5 μm, 1.4 μm, 1.3 μm, 1.2 μm, 1.1 μm, 1.0 μm, 0.9 μm, 0.8 μm, 0.7 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.2 μm, 0.1 μm or less, for example, about 0.01 μm to about 4.5 μm, about 0.05 μm to about 4 μm or about 0.1 μm to about 3.5 μm.

The arithmetic mean roughness (Ra) is statistically an arithmetic average of deviations of the roughness curve from the mean line. The maximum height roughness (Rz) means the vertical distance between two parallel lines parallel to the center line of the roughness curve at the interface and passing through the highest and lowest points of the curve.

Here, based on Fig. 8, the method of measuring the arithmetic mean roughness Ra and the maximum height roughness Rz of the interface B will be explained. Fig. 8 shows a cross-sectional SEM photograph in the vicinity of interface B. First, an SEM photograph of the all-solid-state secondary battery 1 is acquired. Then, a portion near the interface B (for example, a portion shown in Fig. 8) is taken from the cross-sectional SEM photograph. In addition, this process may be omitted. Subsequently, the cathode active material 12a in contact with the solid electrolyte layer 30 is extracted from the cross-sectional SEM photograph. Next, a point P closest to the solid electrolyte layer 30 is extracted from these positive electrode active materials 12a. Then, a roughness curve passing through this point P is measured, and an arithmetic average roughness (Ra) and a maximum height roughness (Rz) are measured based on this roughness curve. Specific measurement can be performed using ImageJ, an analysis software of the National Institutes of Health (NIH, http://imagej.nih.gov/ij/). In Examples described later, the arithmetic mean roughness (Ra) and the maximum height roughness (Rz) were measured by this method. Further, the roughness curve represents the interface B described above.

In this embodiment, since the arithmetic average roughness (Ra) of the interface B is 1.0 μm or less, current flows more uniformly in the solid electrolyte layer 30 during charging of the all-solid-state secondary battery 1 . As a result, since metal lithium is uniformly deposited on the negative electrode active material layer 22, it is difficult to cause a short circuit.

Further, even when the arithmetic mean roughness (Ra) is 1.0 µm or less, the maximum height roughness (Rz) may be large. Also, there is a possibility that the current is concentrated in a portion where the maximum height illuminance Rz is large. For this reason, it is preferable that the maximum height roughness (Rz) be 4.5 μm or less. As a result, when the all-solid-state secondary battery 1 is charged, current flows more uniformly in the solid electrolyte layer 30 . Since the arithmetic mean roughness (Ra) and the maximum height roughness (Rz) are smaller, the lower limit is not particularly limited. However, due to limitations such as the performance of the manufacturing apparatus, the arithmetic mean roughness (Ra) may be 0.2 μm or more, and the maximum height roughness (Rz) may be 1.5 μm or more.

< 3. Manufacturing method of lithium ion secondary battery >

Next, a method for manufacturing the all-solid-state secondary battery 1 according to the present embodiment will be described. The all-solid-state secondary battery 1 according to the present embodiment can be manufactured by manufacturing the positive electrode 10, the negative electrode 20, and the solid electrolyte layer 30, respectively, and then laminating each of the above layers. The positive electrode 10, the negative electrode 20 and the solid electrolyte layer 30 can be manufactured by a known method.

(3-1. Anode manufacturing process)

The cathode active material can be prepared by a known method. Then, the prepared cathode active material, the solid electrolyte prepared by the method described below, and various additives are mixed and added to a non-polar solvent to form a slurry or paste. In addition, the positive electrode 10 can be obtained by applying the obtained slurry or paste onto the positive electrode current collector 11, drying it, and rolling it. The positive electrode 10 may be manufactured by compacting and molding a mixture of a positive electrode active material and various additives in a pellet form without using the positive electrode current collector 11 .

(3-2. Cathode manufacturing process)

The negative electrode 20 is manufactured by laminating a metal foil (eg, metallic lithium in the form of a metal foil) as the negative electrode active material layer 22 on the negative electrode current collector 21 .

By using metallic lithium foil as the negative electrode active material layer, it is easy to manufacture a high-capacity battery.

(3-3. Solid Electrolyte Layer Manufacturing Process)

The solid electrolyte layer 30 may be made of a solid electrolyte formed from a sulfide-based solid electrolyte material.

First, the starting raw material is treated by a melt quenching method or a mechanical milling method.

For example, in the case of using the melt quenching method, a starting material (eg, Li ₂ S, P ₂ S ₅ , etc.) is mixed in a predetermined amount, and the pelletized product is reacted at a predetermined reaction temperature in vacuum, followed by rapid cooling. Thus, a sulfide-based solid electrolyte material can be manufactured. Further, the reaction temperature of the mixture of Li ₂ S and P ₂ S ₅ is preferably 400°C to 1000°C, more preferably 800°C to 900°C. In addition, the reaction time is preferably 0.1 hour to 12 hours, more preferably 1 hour to 12 hours. Then, the cooling temperature of the reactants is usually 10 ° C or less, preferably 0 ° C or less, and the cooling rate is usually 1 ° C / sec to 10000 ° C / sec, preferably 1 ° C / sec to 1000 ° C / sec.

In addition, in the case of using a mechanical milling method, a sulfide-based solid electrolyte material can be produced by stirring and reacting starting materials (eg, Li ₂ S, P ₂ S ₅ , etc.) using a ball mill or the like. In addition, the stirring speed and stirring time of the mechanical milling method are not particularly limited, but the faster the stirring speed, the faster the production speed of the sulfide-based solid electrolyte material. You can increase your call rate.

Thereafter, a solid electrolyte in a particulate state can be prepared by heat-treating the mixed raw material obtained by the melt quenching method or the mechanical milling method at a predetermined temperature and then pulverizing the mixture. When a solid electrolyte has a glass transition point, it may change from amorphous to crystalline by heat treatment.

Then, the solid electrolyte layer 30 is produced by forming a film using a known film formation method such as an aerosol deposition method, a cold spray method, and a sputtering method, for example, of the solid electrolyte obtained by the above method. can Also, the solid electrolyte layer 30 is made by pressurizing solid electrolyte particles alone. In addition, the solid electrolyte layer 30 may be produced by mixing a solid electrolyte, a solvent, and a binder, coating, drying, and pressurizing. The specifics of the film formation method can be determined by a person skilled in the art without undue experimentation, and therefore, for clarity, will not be further described.

(4. Press process)

Then, a press process is performed. The press process of this embodiment is divided into a preliminary press process and a main press process.

(4-1. Preliminary press process)

In the preliminary press step, the positive electrode active material layer and the solid electrolyte layer are pressed in advance. Specifically, the preliminary press process includes a positive electrode active material layer press process and a solid electrolyte layer press process.

(4-1-1. Cathode active material layer press process)

In the positive electrode active material layer press process, the positive electrode active material layer 12 is pressed prior to laminating the positive electrode active material layer 12 on the solid electrolyte layer 30 . Here, the positive electrode active material layer 12 is pressed together with the positive electrode current collector 11 . As a result, the surface of the positive electrode active material layer 12 can be flattened, but the arithmetic mean roughness (Ra) and maximum height roughness (Rz) of the interface B can be set to values within the above-mentioned range. In addition, even if the solid electrolyte layer 30 is laminated on the positive electrode active material layer 12 and then the laminate is pressed, the arithmetic average roughness (Ra) and maximum height roughness (Rz) of the interface B are set to values within the above-mentioned range. Can not.

A method of pressing the positive electrode active material layer 12 is not particularly limited, and a press method used in the manufacture of a conventional all-solid-state secondary battery is sufficient. For example, the positive electrode active material layer 12 may be pressed by a roll press or the like.

The specific press pressure may vary depending on the press device, the material of the positive electrode active material layer 12, and the like. However, since the arithmetic average roughness (Ra) and maximum height roughness (Rz) of interface B tend to decrease as the press pressure increases, the arithmetic average roughness (Ra) and maximum height roughness (Rz) of interface B are What is necessary is just to adjust the press pressure so that it may become a value within a range.

The positive electrode active material layer may increase the relative density of the active material through a preliminary press process. In addition, interfacial resistance may be reduced by reducing the arithmetic surface roughness of the positive electrode surface including the positive electrode active material.

(4-1-2. Solid electrolyte layer press process)

In the solid electrolyte layer pressing process, the solid electrolyte layer 30 is pressed before the solid electrolyte layer 30 is laminated on the negative electrode active material layer 22 . As a result, the relative density of the solid electrolyte layer 30 can be set to a value within the above range. In addition, even if the solid electrolyte layer 30 is laminated on the negative electrode active material layer 22 and then the laminate is pressed, the relative density of the solid electrolyte layer 30 cannot be set to a value within the above-described range. The solid electrolyte layer press process is divided into the following three types. Any method can obtain the effect of the present embodiment, and the second method is the most effective among them.

A specific pressing method for performing the solid electrolyte layer pressing process is not particularly limited, and a conventional pressing method used in the manufacture of an appropriate all-solid-state secondary battery is sufficient. For example, the solid electrolyte layer 30 may be pressed by a roll press or the like.

The specific press pressure may vary depending on the press device, the material of the solid electrolyte layer 30, and the like. However, since the relative density of the solid electrolyte layer 30 tends to increase as the press pressure increases, the press pressure may be adjusted so that the relative density of the solid electrolyte layer 30 falls within the above range.

(4-1-2-1. First press method)

The first press method includes a step of pressing the solid electrolyte layer alone ("solid electrolyte layer single press process"). In the solid electrolyte layer single press process, the solid electrolyte layer 30 is pressed before laminating the solid electrolyte layer 30 on the positive electrode active material layer 12 pressed in the positive electrode active material layer press process. Therefore, in the first pressing method, the solid electrolyte layer 30 is pressed before laminating the solid electrolyte layer 30 on the negative electrode active material layer 22 . As a result, the relative density of the solid electrolyte layer 30 can be set to a value within the above range. In addition, in the first pressing method, the solid electrolyte layer 30 is pressed alone before laminating the solid electrolyte layer 30 on the positive electrode active material layer 12 . Therefore, the relative density of the solid electrolyte layer 30 can be increased more reliably. In addition, in this pressing process described later, since the solid electrolyte layer 30 after pressing is laminated on the positive electrode active material layer 12, the arithmetic average roughness (Ra) and maximum height roughness (Rz) of the interface B can be more reliably reduced. And, since the first press method does not involve the first intermediate laminate press process to be described later, the relative density of the solid electrolyte layer 30 tends to be somewhat lower than that of the second press method.

(4-1-2-2. Second press method)

The second pressing method includes the aforementioned solid electrolyte layer single press process and the first intermediate laminate press process. In the solid electrolyte layer single press process, the solid electrolyte layer 30 is pressed before laminating the solid electrolyte layer 30 on the positive electrode active material layer 12 pressed in the positive electrode active material layer press process. In the first intermediate laminate press process, the first intermediate laminate, which is a laminate of the solid electrolyte layer 30 pressed in the solid electrolyte layer single press process and the positive electrode active material layer 12 pressed in the positive electrode active material layer press process, is pressed. .

In the second pressing method, the solid electrolyte layer 30 is pressed before laminating the solid electrolyte layer 30 on the negative electrode active material layer 22 . As a result, the relative density of the solid electrolyte layer 30 can be set to a value within the above range. In addition, in the second pressing method, the solid electrolyte layer 30 is pressed alone before the solid electrolyte layer 30 is laminated on the positive electrode active material layer 12 . Therefore, not only the relative density of the solid electrolyte layer 30 is increased more reliably, but also the arithmetic average roughness (Ra) and maximum height roughness (Rz) of the interface B can be reduced more reliably.

(4-1-2-3. Third press method)

The third press method presses the second intermediate laminate, which is a laminate of the solid electrolyte layer 30 and the positive electrode active material layer 12 pressed in the positive electrode active material layer pressing step. The third pressing method may be referred to as a method excluding the solid electrolyte layer alone pressing process from the second pressing method.

In the third pressing method, the solid electrolyte layer 30 before pressing is laminated on the positive electrode active material layer 12 . Therefore, in some cases, the solid electrolyte layer 30 having a rough surface is laminated on the positive electrode active material layer 12 . However, the solid electrolyte layer 30 is softer than the positive electrode active material layer 12 , and the surface shape of the solid electrolyte layer 30 may follow the surface shape of the positive electrode active material layer 12 . Therefore, the arithmetic average roughness (Ra) and maximum height roughness (Rz) of the interface B fall within the above range. As a result, since the solid electrolyte layer alone press step is omitted, the arithmetic mean roughness (Ra) and maximum height roughness (Rz) of the interface B tend to be slightly higher than those of the first press and the second press methods. However, since the solid electrolyte layer 30 is pressed before laminating the solid electrolyte layer 30 on the negative electrode active material layer 22, the same effect as the first press method and the second press method is obtained.

In addition, the relative density of the positive electrode active material layer 12 and the solid electrolyte layer 30 is preferably within the above-mentioned numerical range (60% or 80% or more) at the time when the preliminary press process is finished.

(4-2. Main press process)

In this press process, the positive electrode active material layer 12 (ie, the positive electrode 10), the solid electrolyte layer 30, and the negative electrode active material layer 22 (ie, the negative electrode 20) pressed in the preliminary press process are laminated. to produce an electrode laminate. Next, the electrode laminate is pressed. Through the above steps, the all-solid-state secondary battery 1 is produced. A specific press method for performing this press process is not particularly limited, and a press method used in the manufacture of a conventional all-solid-state secondary battery is sufficient. For example, this press process can be performed by a roll press or the like.

In one embodiment, an all-solid-state secondary battery including a plating layer between the negative electrode current collector and the negative electrode active material layer, providing a positive electrode including a positive electrode active material layer; disposing a solid electrolyte layer on the anode; disposing a negative electrode on the solid electrolyte layer, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, wherein the negative electrode active material layer includes carbon; and forming a plating layer between the negative electrode active material layer and the negative electrode current collector by providing a voltage between the positive electrode and the negative electrode.

[Example]

(1. Example 1)

Next, examples of this embodiment will be described. In Example 1, an all-solid-state secondary battery was manufactured by the following process.

(1-1. Anode manufacturing)

LiNi _0.8 Co _0.15 Al _0.5 O ₂ (NCA) three-component powder as a positive electrode active material, Li ₂ SP ₂ S ₅ (molar ratio 75:25) crystalline powder as a sulfide-based solid electrolyte, and vapor phase growth as a conductive agent The carbon fiber powder was weighed out in a mass ratio of 60:35:5 and mixed using an auto-revolution mixer.

Next, a dehydrated xylene solution in which SBR was dissolved as a binder was added to the mixed powder so that the SBR was 5.0% by mass based on the total mass of the mixed powder, thereby producing a primary mixture. In addition, a secondary mixture was produced by adding an appropriate amount of dehydrated xylene for viscosity adjustment to the obtained primary mixture. In addition, in order to improve the dispersibility of the mixed powder, zirconia balls with a diameter of 5 mm were added to the secondary mixture in an amount of space, mixed powder, and zirconia balls, each occupying 1/3 of the total volume of the kneading vessel. . The resulting tertiary mixture was put into a rotating, rotating, or mixer, and stirred at 3000 rpm for 3 minutes to produce a coating solution for the cathode active material layer.

Subsequently, an aluminum foil current collector having a thickness of 20 μm is prepared as a cathode current collector, the anode current collector is placed on a desktop screen printer, and a metal mask having a diameter of 2.0 cm x 2.0 cm and a thickness of 150 μm is used. Thus, the cathode active material layer coating solution was coated on the sheet. Thereafter, the sheet coated with the positive electrode active material layer coating solution was dried on a hot plate at 60° C. for 30 minutes and then vacuum dried at 80° C. for 12 hours. Thus, a positive electrode active material layer was formed on the positive electrode current collector. The total thickness of the positive electrode current collector and the positive electrode active material layer after drying was about 165 μm.

(1-2. Solid Electrolyte Layer Preparation)

As a sulfide-based solid electrolyte, a dehydrated xylene solution in which SBR is dissolved in Li ₂ SP ₂ S ₅ (molar ratio 75:25) crystalline powder is added so that SBR is 2.0% by mass based on the total mass of the mixed powder, to obtain a primary mixture. Created. In addition, a secondary mixture was produced by adding an appropriate amount of dehydrated xylene for viscosity adjustment to the obtained primary mixture. In addition, in order to improve the dispersibility of the mixed powder, zirconia balls with a diameter of 5 mm were added to the tertiary mixture in an amount of 1/3 of the total volume of the kneading vessel for the space, composite powder, and zirconia balls. The resulting tertiary mixture was put into a rotating, rotating, or mixer, and stirred at 3000 rpm for 3 minutes to produce an electrolyte layer coating solution.

A polyethylene terephthalate (PET) acid substrate (PET substrate) was placed in a desktop screen printing machine, and an electrolyte layer coating solution was coated on the PET substrate using a metal mask with a hole diameter of 2.5 cm x 2.5 cm and a thickness of 300 μm. Then, it was dried on a hot plate at 40°C for 10 minutes and vacuum dried at 40°C for 12 hours. Thus, a solid electrolyte layer was formed. The total thickness of the solid electrolyte layer after drying was around 180 μm.

(1-3. Cathode manufacturing)

A nickel foil current collector having a thickness of 20 μm was prepared as the negative electrode current collector, and a metal lithium foil having a width of 2.2 cm x 2.2 cm and a thickness of 30 μm was adhered to the negative electrode current collector to manufacture a negative electrode.

(1-4. Rating standard: production of all-solid-state secondary batteries)

In Example 1, the preliminary press process of the following process was performed. That is, the positive electrode was pressed at a pressure of 10 tons with a single screw press. Thus, the positive electrode active material layer press process was performed. The bulk density of the positive electrode active material layer after pressing was 2.23 g/cc. The pressed positive electrode active material layer was cut with a φ 10 mm Thomson knife and the height and mass were measured. The bulk density of the positive electrode active material layer was calculated by dividing the mass of the cut electrode layer by the volume.

Then, a solid electrolyte layer press process was performed. In Example 1, the second method was employed as the solid electrolyte layer fabrication process. Specifically, the solid electrolyte layer was pressed at a pressure of 10 tons with a single screw press (solid electrolyte layer single press process). The solid electrolyte layer was pressed together with the PET substrate. The bulk density of the solid electrolyte layer after pressing was 1.53 g/cc. The bulk density of the solid electrolyte layer was calculated using the same method as the method for calculating the bulk density of the positive electrode active material.

Subsequently, the positive electrode was cut with a φ 11 mm Thomson knife, and the solid electrolyte layer and the positive electrode on the PET substrate were laminated so that the solid electrolyte layer and the positive electrode active material layer faced each other. Subsequently, the solid electrolyte layer and the positive electrode were adhered according to a dry lamination method using a roll press machine with a roll spacing of 150 μm. This produced the 1st intermediate|middle laminated body. Subsequently, the first intermediate laminate was pressed at a pressure of 10 tons using a single screw press (first intermediate laminate press step). The bulk density of the positive electrode active material layer after pressing was 2.27 g/cc, and the bulk density of the solid electrolyte layer was 1.56 g/cc. In addition, the thickness of the solid electrolyte layer was 90 μm. A preliminary press process according to the above process was performed.

Then, the relative densities of the positive electrode active material layer and the solid electrolyte layer were calculated based on the bulk density after the preliminary press step. Specifically, the nominal densities of NCA, Li ₂ SP ₂ S ₅ (molar ratio 75:25) crystalline powder and conductive agent were 4.6 g/cc, 1.8 g/cc, and 2.1 g/cc, respectively. Therefore, the theoretical density of the positive electrode active material layer was 3.50 g/cc (=4.6x0.6+1.8x0.35+2.1x0.05), and the theoretical density of the solid electrolyte layer was 1.8 g/cc. Therefore, the relative density of the positive electrode active material layer was 64.9% (= 2.27/3.50), and the relative density of the solid electrolyte layer was 86.7% (= 1.56/1.8). In addition, in this embodiment, in order to simplify the calculation, the binder was not taken into account in the calculation of the theoretical density. The amount of binder used is small compared to other components, so even if the binder is not considered, it has little effect on the result. In addition, if the relative density at this point is a value within the above-mentioned numerical range, the relative density after the main pressing process will inevitably fall within the above-mentioned numerical range.

Next, the arithmetic mean roughness (Ra) and maximum height roughness (Rz) of the interface B were measured in the following steps. That is, the cross section of the first intermediate laminate was obtained by cutting using ion milling (E-3500, manufactured by Hitachi High Technologies). Next, the cross-section was observed with FE-SEM (Japan Electronics: JSM-7800F), and a cross-sectional SEM image was acquired. 3 is a cross-sectional SEM image of Example 1. Then, the arithmetic average roughness (Ra) and maximum height roughness (Rz) of interface B were measured by the method described above.

Then, the negative electrode was cut with a φ 13 mm Thomson knife, and the first intermediate laminate and the negative electrode were laminated so that the solid electrolyte layer and the negative electrode active material layer faced each other, to prepare an electrode laminate. Then, the electrode laminate was pressed at a pressure of 3 tons by a single screw press. That is, this press process was performed. The thickness of the solid electrolyte layer after this pressing process was 85 μm.

Subsequently, after the press process, the electrode laminate was placed in an aluminum laminate film equipped with terminals and evacuated to 100 Pa with a vacuum. Then, the electrode laminate was enclosed in a laminate film using a heat seal. Thus, an all-solid-state secondary battery (test cell) was produced.

(1-5. With or without paragraph)

Whether or not the test cell was short-circuited was determined by the open circuit voltage of the test cell. Specifically, the closed-circuit voltage of the test cell was measured, and it was determined that a short circuit had occurred when the voltage was 2.4 V or less. Those with short circuits were not subjected to the following cycle life test.

(1-6. Cycle life test)

The obtained test cell was charged at 45°C with a constant current of 0.13 mA to an upper limit voltage of 4.0 V, and a charge/discharge cycle of discharging at 0.13 mA to a discharge end voltage of 2.5 V was repeated 50 cycles. And, the ratio of the discharge capacity at the 50th cycle to the discharge capacity at the first cycle (initial capacity) was taken as the retention rate of the discharge capacity. The measurement of discharge capacity is in accordance with TOSCAT-3100, a charge-discharge evaluation device of Dongyang System. The retention rate of discharge capacity is a parameter representing cycle characteristics. The larger this value, the better the cycle characteristics. The characteristics and evaluation results of each Example and Comparative Example are summarized in Table 1. In one embodiment, the capacity retention rate of the all-solid-state secondary battery may exceed about 75% after 50 charge/discharge cycles.

(2. Example 2)

The same test as in Example 1 was performed except that the third method was performed in the solid electrolyte layer press process. Specifically, in Example 2, the following preliminary press process was performed.

The positive electrode 10 was pressed with a uniaxial press at a pressure of 10 tons (positive electrode active material layer press process). The bulk density of the positive electrode active material layer after pressing was 2.26 g/cc.

Subsequently, the positive electrode was cut with a φ 11 mm Thomson knife, and the solid electrolyte layer and the positive electrode on the PET substrate were laminated so that the solid electrolyte layer and the positive electrode active material layer faced each other. Subsequently, the solid electrolyte layer and the positive electrode were adhered according to a dry lamination method using a roll press machine with a roll spacing of 150 μm. This produced the 2nd intermediate|middle laminated body. Next, the second intermediate laminate was pressed at a pressure of 10 tons with a single screw press (second intermediate laminate press step). The bulk density of the positive electrode active material layer after pressing was 2.29 g/cc, and the bulk density of the solid electrolyte layer was 1.55 g/cc. A preliminary press process according to the above process was performed. After that, the same process as in Example 1 was performed. In addition, the arithmetic mean roughness (Ra) and maximum height roughness (Rz) of the interface B were measured using the second intermediate laminate after preliminary pressing. The results are summarized in Table 1.

(3. Example 3)

The same test as in Example 1 was performed except that the first method was performed in the solid electrolyte layer press process. Specifically, in Example 3, the following preliminary press process was performed.

That is, the positive electrode 10 was pressed at a pressure of 10 tons using a single screw press (positive electrode active material layer press step). The bulk specific gravity of the positive electrode active material layer after pressing was 2.24 g/cc.

Next, the solid electrolyte layer was pressed at a pressure of 10 tons by a single screw press (solid electrolyte layer single press process). The solid electrolyte layer was pressed together with the PET substrate. The bulk density of the solid electrolyte layer after pressing was 1.53 g/cc. A preliminary press process according to the above process was performed.

Then, the positive electrode and the negative electrode were cut with the Thomson knife used in Example 1, and the positive electrode, the solid electrolyte layer, and the negative electrode were laminated so that the solid electrolyte layer and each active material layer faced each other, to prepare an electrode laminate. Then, the electrode laminate was pressed at a pressure of 3 tons with a single screw press. That is, this press process was performed. After that, the same test as in Example 1 was performed. In addition, the arithmetic mean roughness (Ra) and maximum height roughness (Rz) of the interface B were measured using the electrode laminate after main pressing.

(4. Example 4)

The same test as in Example 1 was performed except that the press pressure of the first intermediate laminate press process was 15 tons.

(5. Example 5)

The same test as in Example 1 was performed except that the press pressure of the positive electrode active material layer press process and the solid electrolyte layer alone press process was set to 7 tons.

(6. Example 6)

The same test as in Example 2 was performed except that the press pressure of the positive electrode active material layer press process was set to 7 tons.

(7. Example 7)

In Example 7, the positive electrode active material layer and the solid electrolyte layer were produced by the following process. That is, except for NCA three-component powder, Li ₂ SP ₂ S ₅ (molar ratio 75:25) amorphous powder as a sulfide-based solid electrolyte, and vapor-grown carbon fiber powder as a conductive agent in a mass ratio of 90:7:3. Then, a positive electrode active material layer was prepared in the same process as in Example 4. In addition, a solid electrolyte layer was fabricated in the same process as in Example 4, except that Li ₂ SP ₂ S ₅ (molar ratio: 75:25) amorphous powder was used as a sulfide-based solid electrolyte.

In addition, the following process was performed as a preliminary press process. That is, the positive electrode was pressed at a pressure of 15 tons using a single screw press under vacuum (positive electrode active material layer press process). Subsequently, the solid electrolyte layer was pressed under vacuum with a single screw press at a pressure of 15 tons (solid electrolyte layer single press process). Thereafter, the same process as in Example 4 (specifically, the first intermediate laminate press process) was performed. The preliminary press process of the above process was performed. The bulk density of the positive electrode active material layer after the preliminary press process was 3.82 g/cc. In addition, the bulk density of the solid electrolyte layer after preliminary pressing was 1.77 g/cc. At this time, the theoretical density of the positive active material layer was 4.33 g/cc (=4.6x0.9+1.8x0.07+2.1x0.03) and the relative density was 88.2% (=3.82/4.33). In addition, the theoretical density of the solid electrolyte layer was 98.3% (= 1.77/1.8). Processes other than the above were the same as in Example 4.

(8. Example 8)

The same experiment as in Example 1 was conducted except that the cathode layer was produced by the following steps. A nickel foil having a thickness of 20 μm was prepared as the negative electrode current collector. In addition, as a negative electrode active material, acetylene black powder (AB) having a primary particle size of 35 nm was prepared. 2 g of AB was placed in a container, and an NMP solution in which PVDF as a binder was dissolved was added so that the PVDF was 3.0% by mass with respect to the total mass of the mixed powder, and a primary liquid mixture was generated. A secondary liquid mixture was generated by adding an appropriate amount of NMP to this primary liquid mixture for viscosity adjustment. The secondary liquid mixture thus produced was put into a rotating and rotating mixer, and stirred at 2000 rpm for 5 minutes to generate a negative electrode layer coating liquid.

This slurry was applied onto NI foil using a blade coater, dried on a hot plate at 100°C for 30 minutes, and then vacuum dried at 180°C for 12 hours. A cathode layer was produced through the above steps. The total thickness of the negative electrode current collector and the negative electrode active material layer after drying was about 30 μm. The all-solid-state battery produced in Example 8 was charged only once under the same conditions as in Example 1.

Thereafter, the battery was disassembled in a dry atmosphere, and the cross section of the all-solid-state battery was polished with an ion milling device, and then observed by SEM. As a result, it was observed that lithium precipitated at the interface between the nickel foil and the AB layer by charging.

(9. Comparative Example 1)

The same test as in Example 1 was performed except that the positive electrode active material layer press process and the solid electrolyte layer alone press process were not performed. Figure 7 shows a cross-sectional SEM photograph used to measure the arithmetic mean roughness (Ra) and maximum height roughness (Rz) of Comparative Example 1.

(10. Comparative Example 2)

The same test as in Example 1 was performed except that all press pressures in the preliminary press process were set to 3 tons.

(11. Comparative Example 3)

The same test as in Example 1 was performed except that the positive electrode active material layer press process was not performed.

(12. Comparative Example 4)

The same test as in Example 3 was performed except that the positive electrode active material layer press process was not performed.

(13. Comparative Example 5)

The same test as in Example 3 was performed except that the solid electrolyte layer alone press process was not performed.

(14. Comparative Example 6)

The same test as in Comparative Example 1 was performed except that a metal mask having a thickness of 600 μm was used in the preparation of the solid electrolyte layer.

(15. Comparative Example 7)

The same test as in Example 3 was performed except that the preliminary press process was not performed. That is, in Comparative Example 7, only the press process was performed. The bulk density of each layer, the arithmetic mean roughness (Ra) of interface B, and the maximum height roughness (Rz) were measured using the electrode laminate after main pressing.

(16. Comparative Example 8)

The same test as in Example 8 was performed except that the positive electrode active material layer press process and the solid electrolyte layer alone press process were not performed.

(17. Reference example 1)

The same test as in Comparative Example 1 was performed, except that a metal mask having a thickness of 1200 μm was used to prepare the solid electrolyte layer.

(18. Reference Example 2)

The same test as in Comparative Example 1 was performed except that the negative electrode was manufactured by the following process. That is, graphite powder (vacuo-dried at 80° C. for 24 hours) as a negative electrode active material and polyvinylidene fluoride (PVdF) as a binder were weighed at a mass ratio of 95.0:5.0. In addition, these materials and an appropriate amount of N-methyl-2-pyrrolidone (NMP) were put into a rotating, rotating, mixer, stirred at 3000 rpm for 3 minutes, and then degassed for 1 minute to produce a negative electrode active material coating solution.

Subsequently, a nickel foil current collector having a thickness of 20 μm was prepared as an anode current collector, and an electrolyte layer coating liquid was coated on the nickel current collector using a metal mask having a hole diameter of 2.2 cm x 2.2 cm and a thickness of 250 μm. The sheet coated with the negative electrode active material coating solution was stored in a dryer heated at 80° C. and dried for 15 minutes. Furthermore, the sheet after drying was vacuum dried at 80°C for 24 hours. This produced a cathode. The thickness of the cathode was around 140 μm.

(17. Reference Example 3)

In Reference Example 3, a non-aqueous electrolyte secondary battery was produced by the following process. After that, a cycle life test was conducted in the same manner as in Example 1.

(17-1. Manufacture of anode)

NCA three-component powder as a positive electrode active material and acetylene black as a conductive agent were weighed in a mass ratio of 97:3 and mixed. Next, an NMP solution in which PVdF was dissolved as a binder was added to this mixed powder so that PVdF was 3.0% by mass with respect to the total mass of the mixed powder, thereby producing a primary mixture. In addition, an appropriate amount of NMP was added to the obtained primary mixture to adjust the viscosity to produce a secondary mixture. The resulting secondary mixture was put into a rotating, rotating, or mixer, and stirred at 2000 rpm for 3 minutes to produce an anode coating solution.

Subsequently, an aluminum foil current collector with a thickness of 20 μm was prepared as the positive electrode current collector, the positive electrode current collector was placed on a tabletop screen printer, and the positive electrode active material coating liquid was applied on the sheet using a metal mask having a hole diameter of 2.0 cm x 2.0 cm and a thickness of 150 μm. coated Thereafter, the sheet coated with the cathode active material coating solution was dried on a hot plate at 100° C. for 30 minutes and vacuum dried at 180° C. for 12 hours. Thus, a positive electrode active material layer was formed on the positive electrode current collector. The total thickness of the positive electrode current collector and the positive electrode active material layer after drying was around 120 μm.

A first pressure molding was performed at a pressure of 3 tons using a single screw press for the positive electrode. The density of the positive electrode after compression was 2.33 g/cc. The anode was cut with a Thompson blade of φ 11 mm.

(17-2. Manufacturing of negative electrode)

A copper foil current collector with a thickness of 20 μm was prepared as the negative electrode current collector, and metal lithium gold with a thickness of 30 μm was bonded thereto to prepare a negative electrode. The cathode was cut with a Thompson blade of φ 13 mm.

(17-3. Manufacture of non-aqueous electrolyte secondary battery)

A porous polyethylene film (φ 15.5 mm, thickness 12 μm) was used as the separator. An electrode laminate was produced by interposing a separator between the positive electrode and the negative electrode. The electrode laminate was processed into a 2032 coin half cell.

Subsequently, lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a non-aqueous solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3:7 to a concentration of 1.3 mol/L to prepare an electrolyte did By injecting the prepared electrolyte solution into a 2032 coin half cell, the electrolyte solution was impregnated with the separator. Thus, a non-aqueous electrolyte secondary battery was manufactured.

The nominal densities of NCA and acetylene black were 4.6 g/cc and 2.1 g/cc, respectively. Therefore, the theoretical density of the positive electrode active material layer was 4.53 g/cc (=4.6x0.97+2.1x0.03), and the relative density was 51.4% (=2.33/4.53).

According to Table 1, Examples 1 to 7 satisfy the requirements of the present embodiment, do not generate a short circuit immediately after production, and have a high retention rate (in other words, short circuits are less likely to occur). Also, in Example 7, an amorphous solid electrolyte was used, so the initial capacity was slightly lower than that of other Examples. However, it was not a value that was a problem in practice. In Comparative Example 1 related to this, the positive electrode active material layer press process and the solid electrolyte layer alone press process were not performed, so the interface B became rough. For this reason, a short circuit occurred at an early stage during charging and discharging.

In Comparative Example 2, since the press pressure was low, the interface B became rough and the relative density of each layer decreased. For this reason, a short circuit occurred immediately after the test cells were fabricated. In Comparative Examples 3 and 4, the positive electrode active material layer press process was not performed, so the interface B became rough. For this reason, a short circuit occurred at an early stage during charging and discharging. In Comparative Example 4, the first intermediate laminate press process was not performed, so the relative density of the positive electrode active material layer was also reduced. In Comparative Example 5, the solid electrolyte layer alone was not pressed, so the relative density of the solid electrolyte layer was reduced. For this reason, a short circuit occurred immediately after the test cells were fabricated. In addition, the thickness of the solid electrolyte layer also increased. In Comparative Example 6, since the solid electrolyte layer was thicker than in Comparative Example 1, the number of cycles until short circuit increased slightly, but short circuit could not be avoided. In Comparative Example 7, the pre-pressing process was not performed, so not only the interface B became rough, but also the relative density of each layer was reduced. Because of this, a short circuit occurred immediately after the test cells were manufactured.

In Reference Example 1, the solid electrolyte layer in Comparative Example 1 was made very thick. Short circuit could be suppressed by making the solid electrolyte layer very thick, but the energy density became very small. So, it's not practical. In Reference Example 2, the negative electrode active material in Comparative Example 1 was graphite-based. When the negative electrode active material is made of graphite, there is no problem that the present embodiment focuses on, but the energy density is reduced. Reference Example 3 is a non-aqueous electrolyte secondary battery. Compared with Examples 1 to 7, Examples 1 to 7 obtained characteristics similar to those of Reference Example 3. Therefore, Examples 1 to 7 can enjoy the advantages (eg, higher safety) of the all-solid-state secondary battery while considering the characteristics of the battery similar to that of the non-aqueous electrolyte secondary battery.

Although preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited thereto. Since it is clear that a person with ordinary knowledge in the technical field to which the present invention belongs can consider various changes or modifications within the scope of the technical idea described in the claims, these are naturally within the technical scope of the present invention. understood to belong to

1 All-solid-state secondary battery
10 anode
11 positive current collector
12 cathode active material layer
20 cathode
21 negative current collector
22 anode active material layer
30 solid electrolyte layer

Claims (31)

A positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and a solid electrolyte layer including a solid electrolyte interposed between the positive electrode active material layer and the negative electrode active material layer,
The arithmetic mean roughness (Ra) at the interface between the positive electrode active material layer and the solid electrolyte layer is 1.0 μm or less, the relative density of the solid electrolyte layer is 80% or more, and the interface between the positive electrode active material layer and the solid electrolyte layer is An all-solid-state secondary battery, characterized in that the maximum height roughness (Rz) is 4.5 μm or less. According to claim 1,
The all-solid-state secondary battery, characterized in that the negative electrode active material layer contains lithium. According to claim 1,
The negative electrode active material layer is an all-solid-state secondary battery, characterized in that it contains carbon. According to claim 3,
The carbon is ketjen black, carbon black, graphite, carbon nanotube, carbon fiber, mesoporous carbon, mesocarbon microbeads (MCMB), oil furnace black, extra-conductive black (extra-conductive black), acetylene black, lamp black, non-graphitizing carbon, graphitizing carbon, cracked carbon, coke, glassy An all-solid-state secondary battery comprising glassy carbon or activated carbon. According to claim 1,
All-solid-state secondary battery, characterized in that the relative density of the positive electrode active material layer is 60% or more. delete According to claim 1,
The cathode active material layer is an all-solid-state secondary battery, characterized in that it comprises a cathode active material and a solid electrolyte. According to claim 1,
The cathode active material layer is an all-solid-state secondary battery, characterized in that it comprises a lithium transition metal oxide having a layered halite-type structure. According to claim 1,
The cathode active material layer includes a compound represented by LiNi _x Co _y Al _z O ₂ , LiNi _x' Co _y' Mn _z' O ₂ , or a combination thereof;
0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1, and 0 <x'< 1, 0 <y'< 1, 0 <z'< 1, and An all-solid-state secondary battery, characterized in that it satisfies x' + y' + z' = 1. According to claim 1,
The cathode active material layer includes a compound represented by LiNi _x Co _y Al _z O ₂ , LiNi _x' Co _y' Mn _z' O ₂ , or a combination thereof;
0.7 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1, and 0.7 <x'< 1, 0 <y'< 1, 0 <z'< 1, and An all-solid-state secondary battery, characterized in that it satisfies x' + y' + z' = 1. According to claim 1,
The positive electrode active material layer is an all-solid-state secondary battery, characterized in that it further comprises a binder. According to claim 11,
The binder is a vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, a styrene butadiene rubber-based polymer, or a combination thereof. All-solid-state secondary battery comprising a. According to claim 1,
All-solid-state secondary battery, characterized in that the thickness of the solid electrolyte layer is 100 μm or less. According to claim 1,
The solid electrolyte layer is Li _7-a PS _6-a X _a (X is F, Cl, Br, I, or a combination thereof, 0≤a<2), aLi ₂ S-(1-a)P ₂ S ₅ (0<a<1), aLi ₂ S-bP ₂ S ₅ -cLiX (X is F, Cl, Br, I, or a combination thereof, 0<a<1, 0<b<1, 0<c <1, and a+b+c=1), aLi ₂ S-bP ₂ S ₅ -cLi ₂ O (0<a<1, 0<b<1, 0<c<1, and a+b+c = 1), aLi ₂ S-bP ₂ S ₅ -cLi ₂ O-dLiI (0<a<1, 0<b<1, 0<c<1, 0<d<1 and a+b+c+d = 1), aLi ₂ S-(1-a)SiS ₂ (0<a<1), aLi2 _S -bSiS ₂ -cLiI (0<a<1, 0<b<1, 0<c<1, and a+b+c=1), aLi ₂ S-bSiS ₂ -cLiBr (0<a<1, 0<b<1, 0<c<1, and a+b+c=1), aLi ₂ S- bSiS ₂ -cLiCl (0<a<1, 0<b<1, 0<c<1, and a+b+c=1), aLi ₂ S-bSiS ₂ -cB ₂ S ₃ -dLiI (0<a <1, 0<b<1, 0<c<1, 0<d<1 and a+b+c+d=1), aLi ₂ S-bSiS ₂ -cP ₂ S ₅ -dLiI (0<a< 1, 0<b<1, 0<c<1, 0<d<1 and a+b+c+d=1), aLi ₂ S-(1-a)B ₂ S ₃ (0<a<1 ), aLi ₂ S-bP ₂ S ₅ -cZ _m S _n (m and n are independently positive integers from 1 to 10, Z is Ge, Zn, or Ga, and 0<a<1, 0<b<1,0<c<1, and a+b+c=1), aLi ₂ S-(1-a)GeS ₂ (0<a<1), aLi ₂ S-bSiS ₂ -cLi ₃ PO ₄ (0<a<1, 0<b<1, 0<c<1, and a+b+c=1), or aLi ₂ S-bSiS ₂ -cLi _P MO _q (p and q are independently 1 to 10, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1, M is P, Si, Ge, B, Al, Ga or An all-solid-state secondary battery comprising In). According to claim 1,
The solid electrolyte layer is an all-solid-state secondary battery, characterized in that it comprises a solid electrolyte material containing sulfur (S), phosphorus (P) and lithium (Li). According to claim 1,
The all-solid secondary battery further comprises a positive electrode current collector. According to claim 1,
The all-solid-state secondary battery, characterized in that the capacity retention rate after 50 cycles of the all-solid-state secondary battery exceeds 75%. According to claim 1,
The all-solid-state secondary battery is an all-solid-state secondary battery, characterized in that the closed circuit voltage exceeds 2.4V.
A positive electrode including a positive electrode active material layer;
A negative electrode including a negative electrode current collector, a negative electrode active material layer on the negative electrode current collector, and a plating layer between the negative electrode current collector and the negative electrode active material layer, wherein the negative electrode active material layer contains carbon and the plating layer contains lithium. ; and
a solid electrolyte layer between the positive active material layer and the negative active material layer;
including,
An all-solid-state secondary battery, characterized in that the arithmetic mean roughness (Ra) at the interface between the positive electrode active material layer and the solid electrolyte layer is 1.0 μm or less, and the relative density of the solid electrolyte layer is 80% or more. According to claim 19,
The all-solid secondary battery, characterized in that the carbon is amorphous. According to claim 19,
The plating layer is an all-solid-state secondary battery, characterized in that consisting of lithium. According to claim 19,
The solid electrolyte layer is an all-solid-state secondary battery, characterized in that it comprises a sulfide solid electrolyte. A method of manufacturing the all-solid-state secondary battery according to any one of claims 1 to 5 and 7 to 18, the method comprising:
providing a cathode active material layer;
providing an anode active material layer;
Providing a solid electrolyte layer comprising a sulfide-based solid electrolyte;
Pre-pressing the positive electrode active material layer and the solid electrolyte layer, and
Preparing an all-solid-state secondary battery by pressing an electrode laminate including the pre-pressed cathode active material layer, the pre-pressed solid electrolyte layer, and the anode active material layer;
The step of pre-pressing the positive electrode active material layer and the solid electrolyte
Prior to laminating the pressed cathode active material layer on the solid electrolyte layer, pressing the cathode active material layer to provide a pressed cathode active material layer; and
The manufacturing method of an all-solid-state secondary battery comprising the step of providing a pressed solid electrolyte layer by pressing the solid electrolyte layer before laminating the pressed solid electrolyte layer on the negative electrode active material layer. According to claim 23,
In the step of pressing the positive electrode active material layer, the method of manufacturing an all-solid-state secondary battery, characterized in that the positive electrode active material layer is pressed together with the positive electrode current collector. According to claim 23,
Pressing the solid electrolyte layer,
The method of manufacturing an all-solid-state secondary battery comprising the step of pressing the solid electrolyte layer alone before laminating the pressed cathode active material layer. According to claim 25,
Pressing the solid electrolyte layer,
Pressing the solid electrolyte layer alone, and
The method of manufacturing an all-solid-state secondary battery comprising the step of pressing the first intermediate laminate comprising the pressed solid electrolyte layer and the pressed positive electrode active material layer. According to claim 23,
Pressing the solid electrolyte layer,
The method of manufacturing an all-solid-state secondary battery comprising the step of pressing the second intermediate laminate comprising the pressed solid electrolyte layer and the pressed positive electrode active material layer. According to claim 23,
The negative electrode active material layer is located on the negative electrode current collector,
The method of manufacturing an all-solid-state secondary battery, characterized in that it further comprises the step of providing a plating layer between the negative electrode active material layer and the negative electrode current collector by charging the all-solid-state secondary battery. A method for manufacturing an all-solid-state secondary battery according to any one of claims 19 to 22,
providing a cathode comprising a cathode active material layer;
disposing a solid electrolyte layer on the anode;
disposing a negative electrode on the solid electrolyte layer, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, and the negative electrode active material layer includes carbon; and
The method of manufacturing an all-solid-state secondary battery comprising the step of manufacturing the all-solid-state secondary battery by providing a voltage between the positive electrode and the negative electrode to form a plating layer between the negative electrode active material layer and the negative electrode current collector. According to claim 29,
The method of manufacturing an all-solid-state secondary battery, characterized in that the carbon is amorphous carbon. According to claim 29,
The method of manufacturing an all-solid-state secondary battery, characterized in that the plating layer is composed of lithium.

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