KR20240031870A - All Solid secondary battery - Google Patents

Abstract

anode layer; cathode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector, and the positive electrode active material layer A first inert member comprising a lithium-containing sulfide-based positive electrode active material, wherein the lithium-containing sulfide-based positive electrode active material includes Li ₂ S, a Li ₂ S-containing composite, or a combination thereof, and disposed on one side of the positive electrode layer. (inactive member), wherein the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector, and the initial charge capacity (B) of the first negative electrode active material layer and the The ratio (B/A) of the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45, and the initial charge capacity of the positive active material layer is from the first open circuit voltage (1 ^st open circuit voltage) to Li/Li ⁺ is determined at the maximum charging voltage, and the initial charging capacity of the negative electrode active material layer is determined at 0.01 V for Li/Li ⁺ from the ^2nd open circuit voltage, all-solid secondary A battery is presented.

Description

All solid secondary battery

It concerns all-solid-state secondary batteries.

Recently, in response to industrial demands, the development of batteries with high energy density and safety has been actively conducted. For example, lithium batteries are being put to practical use not only in the fields of information-related devices and communication devices, but also in the automotive field. In the automotive field, safety is especially important because it involves life.

Since lithium batteries use an electrolyte containing a flammable organic solvent as an electrolyte, there is a possibility of overheating and fire if a short circuit occurs.

An all-solid-state battery using a solid electrolyte instead of an electrolyte has been proposed.

By not using flammable organic solvents, all-solid-state batteries can greatly reduce the possibility of fire or explosion even if a short circuit occurs. These all-solid-state batteries can greatly increase safety compared to lithium batteries that use electrolytes.

Secondary batteries use sulfur-based materials (e.g., S) as cathode active materials to increase capacity. During the charging and discharging process of a secondary battery, polysulfide is generated from sulfur-based materials, and the generated polysulfide moves to the cathode and reacts with the cathode. These side reactions deteriorate the lifespan characteristics of secondary batteries. A secondary battery that can suppress side reactions between polysulfide and lithium metal is required.

In a secondary battery containing a sulfur-based material (e.g., S), the volume of the sulfur-based material increases during initial discharge and decreases again during the charging process, so in the process of increasing the volume of the sulfur-based material, ions and /Or the electron transmission path may be cut off. Disruption of the ion and/or electron transfer path causes deterioration of the secondary battery. There is a need for a secondary battery that can suppress disruption of the ion and/or electron transfer path.

During the manufacturing process and/or charging and discharging of a secondary battery, defects occur in the solid electrolyte layer, and cracks occur and grow within the solid electrolyte layer from these defects. As lithium grows through these cracks, a short circuit occurs. There is a need for a secondary battery that can suppress the occurrence of such defects during the manufacturing process and/or charging and discharging process of the secondary battery.

One aspect is to prevent side reactions between the electrolyte layer and lithium metal during charging and discharging, suppress disruption of ion and/or electron transfer paths, prevent side reactions caused by polysulfide during charging and discharging, and prevent secondary reactions during manufacturing and/or charging and discharging. The goal is to provide a secondary battery with a new structure that suppresses the occurrence of defects in the battery.

According to one embodiment

anode layer; cathode layer; And a solid electrolyte layer disposed between the anode layer and the cathode layer,

The positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector,

The positive electrode active material layer includes a lithium-containing sulfide-based positive electrode active material, and the lithium-containing sulfide-based positive electrode active material includes Li ₂ S, Li ₂ S-containing composite, or a combination thereof,

comprising a first inactive member disposed on one side of the anode layer,

The negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector,

The ratio (B/A) of the initial charge capacity (B) of the first negative electrode active material layer and the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45,

The initial charging capacity of the positive electrode active material layer is determined from the maximum charging voltage for Li/Li ⁺ from the first open circuit voltage (1 ^st open circuit voltage),

An all-solid-state secondary battery is provided in which the initial charge capacity of the negative electrode active material layer is determined at 0.01 V for Li/Li ⁺ from the ^2nd open circuit voltage.

According to one aspect, according to an all-solid-state secondary battery having a new structure, it is possible to provide an all-solid-state secondary battery with suppressed short circuits and improved cycle characteristics.

1 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.
Figure 2 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.
Figure 3 is a cross-sectional view of a bi-cell all-solid-state secondary battery according to an exemplary embodiment.
Figure 4 is a schematic diagram of an anode layer of an all-solid secondary battery according to an exemplary embodiment.
Figure 5 is a schematic diagram partially showing the interior of an all-solid-state secondary battery according to an exemplary embodiment.
Figure 6 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.
Figure 7 is a cross-sectional view of an all-solid-state secondary battery according to an exemplary embodiment.
Figure 8 is a cross-sectional view of a bi-cell all-solid-state secondary battery according to an exemplary embodiment.
9 is a cross-sectional view of a stacked bi-cell all-solid-state secondary battery stack according to an exemplary embodiment.

Various implementation examples are shown in the accompanying drawings. However, this creative idea can be embodied in many different forms, and should not be construed as limited to the implementation examples described in this specification. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present creative idea to those skilled in the art. Like reference numerals refer to like elements.

It will be understood that when an element is referred to as being “on” another element, it may be directly on top of the other element, or there may be other elements intervening between them. In contrast, when an element is said to be “directly on” another element, there are no intervening elements between them.

Terms such as “first,” “second,” “third,” and the like may be used herein to describe various components, components, regions, layers, and/or sections; Layers and/or zones should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Accordingly, a first component, component, region, layer or section described below may be referred to as a second component, component, region, layer or section without departing from the teachings herein.

The terms used in this specification are intended to describe only specific implementation examples and are not intended to limit the creative idea. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly dictates otherwise. “At least one” should not be construed as limiting to the singular. As used herein, the term “and/or” includes any and all combinations of one or more of the listed items. As used in the detailed description, the terms "comprise" and/or "comprising" specify the presence of a specified feature, area, integer, step, operation, component and/or component, and one or more other features, areas, integers, or elements. , does not exclude the presence or addition of steps, operations, components, ingredients and/or groups thereof.

Spatially relative terms such as “bottom,” “bottom,” “bottom,” “above,” “upper,” etc. are used to facilitate describing the relationship of one component or feature to another component or feature. It can be used here for: It will be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. For example, if the device in the figures were turned over, elements described as “below” or “below” other elements or features would be oriented “above” the other elements or features. Accordingly, the exemplary term “down” can encompass both upward and downward directions. The device can be positioned in different orientations (rotated 90 degrees or rotated in other directions) and the spatially relative terms used herein can be interpreted accordingly.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification have the same meaning as commonly understood by those skilled in the art to which this disclosure pertains. Additionally, it is also understood that terms as defined in commonly used dictionaries should be interpreted as having meanings consistent with their meanings within the context of the related art and present disclosure, and should not be interpreted in an idealized or overly formal sense. It will be.

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

“Group” means a group of the Periodic Table of the Elements according to the International Union of Pure and Applied Chemistry (“IUPAC”) Groups 1-18 grouping system.

In this specification, “particle diameter” refers to the average diameter when the particle is spherical, and refers to the average major axis length when the particle is non-spherical. Particle size can be measured using a particle size analyzer (PSA). “Particle size” is, for example, the average particle size. The “average particle diameter” is, for example, D50, which is the median particle diameter.

D50 is the particle size corresponding to 50% of the cumulative volume calculated from the particle side with the small particle size in the particle size distribution measured by laser diffraction.

D90 is the particle size corresponding to 90% of the cumulative volume calculated from the particle side with the small particle size in the particle size distribution measured by laser diffraction.

D10 is the particle size corresponding to 10% of the cumulative volume calculated from the particle side with the small particle size in the particle size distribution measured by laser diffraction.

In the present disclosure, “metal” includes both metals and metalloids such as silicon and germanium, in elemental or ionic state.

In this disclosure, “alloy” means a mixture of two or more metals.

In the present disclosure, “electrode active material” refers to an electrode material that can undergo lithiation and delithiation.

In the present disclosure, “positive electrode active material” refers to a positive electrode material that can undergo lithiation and delithiation.

In the present disclosure, “negative electrode active material” refers to a negative electrode material that can undergo lithiation and delithiation.

In the present disclosure, “lithiation” and “lithiation” refer to the process of adding lithium to an electrode active material.

In the present disclosure, “delithiation” and “delithiation” refer to a process of removing lithium from an electrode active material.

In the present disclosure, “charging” and “charging” refer to the process of providing electrochemical energy to a battery.

In the present disclosure, “discharge” and “discharge” refer to the process of removing electrochemical energy from a battery.

In the present disclosure, “anode” and “cathode” refer to the electrode where electrochemical reduction and lithiation occur during the discharge process.

In the present disclosure, “cathode” and “anode” refer to the electrode where electrochemical oxidation and delithiation occur during the discharge process.

Although specific embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents not currently contemplated or foreseen may occur to applicants or those skilled in the art. Accordingly, the appended claims, as filed and as modified, are intended to cover all such alternatives, modifications, variations, improvements and substantial equivalents.

Hereinafter, all-solid-state secondary batteries according to example embodiments will be described in more detail.

[All-solid-state secondary battery]

An all-solid-state secondary battery according to one embodiment includes a positive electrode layer; cathode layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector, and the positive electrode active material layer A first inert member comprising a lithium-containing sulfide-based positive electrode active material, wherein the lithium-containing sulfide-based positive electrode active material includes Li ₂ S, a Li ₂ S-containing composite, or a combination thereof, and disposed on one side of the positive electrode layer. (inactive member), wherein the negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector, and the initial charge capacity (B) of the first negative electrode active material layer and the The ratio (B/A) of the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45, and the initial charge capacity of the positive active material layer is from the first open circuit voltage (1 ^st open circuit voltage) to Li/Li ⁺ It is determined at the maximum charging voltage, and the initial charging capacity of the negative electrode active material layer is determined at 0.01 V for Li/Li ⁺ from the ^2nd open circuit voltage.

An all-solid-state secondary battery uses a lithium-containing sulfide-based cathode active material instead of lithium metal as a lithium source. This makes it possible to omit a lithium source, such as lithium metal, from the cathode layer. As the volume of the cathode layer decreases, the energy density of the all-solid secondary battery improves.

An all-solid-state secondary battery includes a lithium-containing sulfide-based cathode active material as a cathode active material. Therefore, disruption of the ion and/or electron transfer path due to an increase in the volume of the lithium-free sulfide-based positive electrode active material, for example, sulfur (S) during initial discharge, is prevented. By preventing disconnection of the ion and/or electron transfer path, the cycle characteristics of the all-solid-state secondary battery are improved.

The all-solid-state secondary battery includes a first negative electrode active material layer having an initial charge capacity in the range of 0.005 to 0.45 compared to the initial charge capacity of the positive electrode active material layer. Since the first negative electrode active material layer has a small initial charge capacity in this range, the negative electrode layer can effectively compensate for changes in the volume of the positive electrode layer during charging and discharging. As a result, the overall volume change of the all-solid-state secondary battery is suppressed during charging and discharging. Deterioration such as cracks due to rapid volume changes during charging and discharging of the all-solid-state secondary battery is prevented, thereby preventing short circuit of the all-solid-state secondary battery and improving cycle characteristics.

Since the all-solid-state secondary battery includes a solid electrolyte layer, the movement of polysulfide generated during charging and discharging of the lithium-containing sulfide-based positive electrode active material to the negative electrode layer is blocked. Therefore, side reactions between polysulfide and the negative electrode active material are suppressed.

By disposing an inert member on one side of the positive electrode layer, cracking of the solid electrolyte layer that occurs during pressurization and/or charging and discharging of the all-solid-state secondary battery is suppressed. Accordingly, cracking of the solid electrolyte layer is suppressed during manufacturing and/or charging and discharging of the all-solid-state secondary battery, thereby suppressing short-circuiting of the all-solid-state secondary battery. As a result, short circuit of the all-solid-state secondary battery is prevented and lifespan characteristics are improved.

1 to 9, the all-solid-state secondary battery 1 includes an anode layer 10; cathode layer (20); and a solid electrolyte layer 30 disposed between the positive electrode layer 10 and the negative electrode layer 20, wherein the positive electrode layer 10 is disposed on the positive electrode current collector 11 and one or both sides of the positive electrode current collector. The positive electrode active material layer 12 includes a sulfide-based positive electrode active material, and the sulfide-based positive electrode active material includes Li ₂ S, Li ₂ S-containing composite, or a combination thereof, and the positive electrode layer It includes a first inactive member 40 disposed on one side of (10), and the negative electrode layer 20 includes a negative electrode current collector 21 and a first negative electrode active material disposed on one side of the negative electrode current collector. It includes a layer 22, and the ratio (B/A) of the initial charge capacity (B) of the first negative electrode active material layer 22 and the initial charge capacity (A) of the positive electrode active material layer 12 is 0.005 to 0.45, The initial charging capacity of the positive electrode active material layer 12 is determined from the maximum charging voltage for Li/Li ⁺ from the first open circuit voltage (1 ^st open circuit voltage), and the first negative active material layer 22 The initial charge capacity of is determined at 0.01 V for Li/Li ⁺ from the ^2nd open circuit voltage.

[Anode layer]

[Anode layer: Anode active material]

1 to 9, the positive electrode active material layer 12 includes, for example, a positive electrode active material and a solid electrolyte. The solid electrolyte included in the positive electrode active material layer 12 is similar to or different from the solid electrolyte included in the solid electrolyte layer 30. For detailed information about the solid electrolyte, refer to the solid electrolyte layer (30).

The cathode active material includes a lithium-containing sulfide-based cathode active material. The lithium-containing sulfide-based positive electrode active material is, for example, an electrode material in which lithium is added to a sulfur-based positive electrode active material. The sulfur-based positive electrode active material includes, for example, a sulfur-based material, a composite containing a sulfur-based material, or a combination thereof. The sulfur-based material may be, for example, inorganic sulfur, Li ₂ S _n (n>1), disulfide compounds, organic sulfur compounds, carbon-sulfur polymers, or combinations thereof. The sulfur-based material-containing composite may be a composite containing inorganic sulfur, Li ₂ S _n (n>1), a disulfide compound, an organic sulfur compound, a carbon-sulfur polymer, or a combination thereof. Composites containing sulfur-based materials include, for example, composites of sulfur-based materials and carbon, composites of sulfur-based materials, carbon and solid electrolytes, composites of sulfur-based materials and solid electrolytes, composites of sulfur-based materials and metal carbides, and sulfur-based materials and It may include a composite of carbon and metal carbide, a composite of a sulfur-based material and a metal nitride, a composite of a sulfur-based material and carbon and metal nitride, or a combination thereof. Since lithium-containing sulfide-based cathode active materials provide higher discharge capacity per unit weight compared to oxide-based cathode active materials, the energy density per unit weight of an all-solid secondary battery containing lithium-containing sulfide-based cathode active materials can be improved.

The lithium-containing sulfide-based positive electrode active material includes, for example, Li ₂ S, Li ₂ S-containing composite, or a combination thereof. By including Li ₂ S, Li ₂ S-containing composite or a combination thereof having high capacity as a lithium-containing sulfide-based cathode active material, the use of lithium metal can be omitted when manufacturing an all-solid-state secondary battery. Since lithium metal has high reactivity and great ductility, it can reduce mass productivity during battery manufacturing. Therefore, the mass productivity of all-solid-state secondary batteries can be improved. Since lithium metal is omitted from the negative electrode layer, the volume of the negative electrode layer is reduced, thereby improving the energy density per unit volume of the all-solid-state secondary battery, and an all-solid-state secondary battery with a simpler structure can be constructed.

For example, the volume of a lithium-containing sulfide-based cathode active material (eg, Li ₂ S) decreases as it undergoes delithiation during initial charging, and then increases in volume through relithiation during subsequent discharge. Therefore, since the volume of the lithium-containing sulfide-based positive electrode active material changes while the ion and/or electron transfer path due to the conductive material disposed around the lithium-containing sulfide-based positive electrode active material is maintained, the ion and/or electron transfer path may be cut off. Unlikely. On the other hand, the sulfur-based positive electrode active material (eg, S) increases in volume as it undergoes lithiation during initial discharge, for example, and decreases in volume through delithiation again during subsequent charging. Therefore, the initial ion and/or electron transfer path due to the conductive material disposed around the sulfur-based positive electrode active material may be collapsed due to an increase in the initial volume of the sulfur-based positive electrode active material, so there is a possibility that the ion and/or electron transfer path will be disconnected. high.

The particle size of the lithium-containing sulfide-based positive electrode active material may be, for example, 1 nm to 50 ㎛, 10 nm to 50 ㎛, 50 nm to 40 ㎛, 100 nm to 30 ㎛, 500 nm to 30 ㎛, or 1 ㎛ to 20 ㎛. there is. When the lithium-containing sulfide-based cathode active material has a particle size in this range, the cycle characteristics of an all-solid-state secondary battery containing the lithium sulfide-based cathode active material can be further improved. Li2S-containing composites are, for example, composites of Li2S and conductive materials. The conductive material is, for example, an ionically conductive material, an electronically conductive material, or a combination thereof.

The electronic conductivity of the electronically conductive material is, for example, greater than or equal to 1.0×10 ³ S/m, 1.0×10 ⁴ S/m, or 1.0×10 ⁵ S/m. The form of the electronic conductive material is, for example, particulate electronic conductive material, plate-shaped electronic conductive material, rod-shaped electronic conductive material, or a combination thereof, but is not necessarily limited to these. The electronically conductive material may be, for example, carbon, metal powder, metal compound, etc. When carbon is included as an electronic conductive material, carbon has high electronic conductivity and is light, so an all-solid-state secondary battery with high energy density per unit mass can be implemented. The electronically conductive material may have pores. By having pores, the electronic conductive material can contain Li2S in the pores, thereby increasing the contact area between Li2S and the electronic conductive material and increasing the specific surface area of Li2S. The pore capacity is, for example, 0.1 cc/g to 20.0 cc/g, 0.5 cc/g to 10 cc/g, or 0.5 cc/g to 5 cc/g. The average pore diameter is, for example, 1 nm to 100 nm, 1 nm to 50 nm, or 1 nm to 20 nm. The BET specific surface area of the electronically conductive material having pores is 200 m ² /g to 4500 m 2 /g when the average pore diameter is 15 nm or less, and 100 m ^{2 /g to 4500 m 2 /} g when the average pore diameter is greater than 15 nm. It is 2500 m ² /g. BET specific surface area, pore diameter, pore capacity and average pore diameter can be determined using, for example, a nitrogen adsorption method.

The ionic conductivity of the ion conductive material is, for example, at least 1.0×10 ^-5 S/m, 1.0×10 ^-4 S/m, or 1.0×10 ^-3 S/m. The ionically conductive material may have pores. By having pores, Li2S can be included in the pores, thereby increasing the contact area between Li2S and the ion conductive material and increasing the specific surface area of Li2S. The form of the ion conductive material is, for example, particulate ion conductive material, plate-shaped electronic conductive material, rod-shaped electronic conductive material, or a combination thereof, but is not necessarily limited to these. The ion conductive material may be, for example, a sulfide-based solid electrolyte or an oxide-based solid electrolyte. When a sulfide-based solid electrolyte is included as an ion conductive material, the sulfide-based solid electrolyte has high ionic conductivity and can be molded into various shapes, so an all-solid-state secondary battery with a large capacity can be implemented.

Li2S-containing composites include, for example, a composite of Li2S and carbon, a composite of Li2S, carbon and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S, carbon and a lithium salt, a composite of Li2S and a lithium salt, a composite of Li2S and a metal carbide, It includes a complex of Li2S and carbon and metal carbide, a complex of Li2S and metal nitride, a complex of Li2S and carbon and metal nitride, or a combination thereof. Li2S-containing composites are distinguished from simple mixtures of Li2S, carbon, solid electrolyte, lithium salt, metal carbide, and metal nitride. Simple mixtures of Li2S, carbon, solid electrolyte, lithium salt, metal carbide, and metal nitride provide high interfacial resistance by failing to maintain a dense interface between Li2S and these other components, resulting in a shortened lifespan of the all-solid-state secondary battery. It may deteriorate the characteristics.

The complex of Li2S and carbon contains carbon. Carbon, for example, is a material containing carbon atoms and can be used as a conductive material in the relevant technical field. The carbon may be, for example, crystalline carbon, amorphous carbon, or combinations thereof. Carbon may be, for example, a calcined product of a carbon precursor. The carbon may be, for example, a carbon nanostructure. The carbon nanostructure may be, for example, a one-dimensional carbon nanostructure, a two-dimensional carbon nanostructure, a three-dimensional carbon nanostructure, or a combination thereof. The carbon nanostructure may be, for example, carbon nanotubes, carbon nanofibers, carbon nanobelts, carbon nanorods, graphene, or combinations thereof. The carbon may be, for example, porous carbon or non-porous carbon. Porous carbon may contain, for example, periodic and ordered two-dimensional or three-dimensional pores. Porous carbon includes, for example, carbon black such as Ketjen black, acetylene black, Denka black, thermal black, and channel black; It may be graphite, activated carbon, or a combination thereof. The form of carbon is, for example, particle form, sheet form, flake form, etc., but is not limited to these, and any carbon that is used in the art is possible. The manufacturing method of the Li2S and carbon composite may be a dry method, a wet method, or a combination thereof, but is not limited to these. In the art, the manufacturing method of the Li2S and carbon composite may include, for example, milling, heat treatment, deposition, etc., but is not limited to these. It is not limited to and any method used in the relevant technical field is possible.

The composite of Li2S, carbon, and solid electrolyte includes carbon and solid electrolyte. Carbon refers to the complex of Li2S and carbon described above. The solid electrolyte can be, for example, any material used as an ion conductive material in the art. The solid electrolyte is, for example, an inorganic solid electrolyte. The solid electrolyte is, for example, a crystalline solid electrolyte, an amorphous solid electrolyte, or a combination thereof. The solid electrolyte is, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a combination thereof. The sulfide-based solid electrolyte includes, for example, Li, S, and P, and may optionally further include a halogen element. The sulfide-based solid electrolyte may be selected from sulfide-based solid electrolytes used in the solid electrolyte layer. For example, the sulfide-based solid electrolyte may have an ionic conductivity of 1×10 ^-5 S/cm or more at room temperature. The oxide-based solid electrolyte includes, for example, Li, O, and transition metal elements, and may optionally further include other elements. For example, the oxide-based solid electrolyte may be a solid electrolyte having an ionic conductivity of 1×10 ^-5 S/cm or more at room temperature. The oxide-based solid electrolyte may be selected from oxide-based solid electrolytes used in the solid electrolyte layer.

The complex of Li2S and solid electrolyte includes a solid electrolyte. The solid electrolyte refers to the complex of Li2S, carbon, and solid electrolyte described above.

The complex of Li2S with carbon and lithium salt contains Li2 with carbon and lithium salt. Carbon refers to the complex of Li2S and carbon described above. Lithium salt is a compound that does not contain sulfur (S). For example, the lithium salt may be a binary compound consisting of lithium and one element selected from groups 13 to 17 of the periodic table of elements. Binary compounds are for example LiF, LiCl, LiBr, LiI, LiH, Li ₂ S, Li ₂ O, Li ₂ Se, Li ₂ Te, _{Li 3 N, Li 3} P, Li ₃ As, Li ₃ Sb, Li ₃ It may include one or more selected from Al ₂ and LiB ₃ . For example, the lithium salt may be a ternary compound consisting of lithium and two types of elements selected from groups 13 to 17 of the periodic table of elements. Ternary compounds are for example Li ₃ OCl, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiNO ₃ , Li ₂ CO ₃ , LiBH ₄ , Li ₂ SO ₄ , Li ₃ It includes one or more selected from BO ₃ , Li ₃ PO ₄ , Li ₄ NCl, Li ₅ NCl ₂ and Li ₃ BN ₂ . The lithium salt is particularly one or more lithium halide compounds selected from LiF, LiCl, LiBr, and LiI. The complex of Li2S, carbon, and lithium salt may be, for example, a complex of Li2, carbon, and lithium halide. The complex of Li2, carbon, and lithium salt can provide improved ionic conductivity by including a lithium halide compound. The complex of Li2S with carbon and lithium salt is distinct from the simple mixture of Li2S with carbon and lithium salt. A simple mixture of Li2S, carbon, and lithium salt provides high interfacial resistance by failing to maintain a dense interface between Li2S, carbon, and lithium salt, and as a result, may reduce the lifespan characteristics of the all-solid-state secondary battery.

The complex of Li2S and lithium salt includes lithium salt. Lithium salt refers to the lithium salt used in the above-mentioned Li2s and a composite of carbon and lithium salt.

The complex of Li2S and metal carbide includes metal carbide. Metal carbide is, for example, a two-dimensional metal carbide. Two-dimensional metal carbides are, for example, M _n+1 C _{n T} x is the number of terminal groups). Two- _{dimensional metal} carbides _{are for} example _{Ti 2} CT _{x , (} Ti _{0.5 , Nb 0.5 ) 2 CT 2} T _x , Ti ₃ CNT _x , Ta ₄ C ₃ T _x , Nb ₄ C ₃ T _x , or a combination thereof. The surfaces of two-dimensional metal carbides are terminated with O, OH and/or F.

The composite of Li2S and carbon and metal carbide contains carbon and metal carbide. Carbon refers to the complex of Li2S and carbon described above. Metal carbide refers to the complex of Li2S and metal carbide described above.

The complex of Li2S and metal nitride includes metal nitride. The metal nitride is, for example, a two-dimensional metal nitride. Two-dimensional metal nitrides are, for example, M _{n + 1} N _{n T} , x is the number of terminal groups). The surface of the two-dimensional metal nitride is terminated with O, OH and/or F.

The complex of Li2S and carbon and metal nitride contains carbon and metal nitride. Carbon refers to the complex of Li2S and carbon described above. Metal carbide refers to the complex of Li2S and metal nitride described above.

The content of the sulfide-based positive electrode active material included in the positive electrode active material layer 12 is, for example, 10 wt% to 90 wt%, 10 wt% to 80 wt%, and 10 wt% to 70 wt of the total weight of the positive electrode active material layer 12. %, 10 wt% to 60 wt%, or 10 wt% to 50 wt%.

The positive electrode active material layer 12 may additionally include, for example, a sulfide-based compound that is distinct from Li2S. The sulfide-based compound may be, for example, a compound containing a metal element other than Li and a sulfur element. For example, the sulfide-based compound may be a compound containing a metal element belonging to groups 1 to 14 of the periodic table of elements with an atomic weight of 10 or more and a sulfur element. The sulfide-based compound may be, for example, FeS ₂ , VS ₂ , NaS, MnS, FeS, NiS, CuS, or a combination thereof. By additionally including a sulfide-based compound in the positive electrode active material layer, the cycle characteristics of the all-solid-state secondary battery can be further improved. The content of the sulfide-based compound, which is distinct from Li2S contained in the positive electrode active material layer 12, may be 10 wt% or less, 5 wt% or less, 3 wt% or less, or 1 wt% or less of the total weight of the positive electrode active material layer 12. .

[Anode layer: solid electrolyte]

The positive electrode active material layer 12 may further include, for example, a solid electrolyte. The solid electrolyte may be, for example, a sulfide-based solid electrolyte. The solid electrolyte included in the positive electrode layer 10 may be the same as or different from the solid electrolyte included in the solid electrolyte layer 30. For detailed information about the solid electrolyte, refer to the solid electrolyte layer (30).

The solid electrolyte included in the positive electrode active material layer 12 may have a D50 average particle diameter smaller than that of the solid electrolyte included in the solid electrolyte layer 30. For example, the D50 average particle diameter of the solid electrolyte included in the positive electrode active material layer 12 is 90% or less, 80% or less, 70% or less, and 60% of the D50 average particle diameter of the solid electrolyte included in the solid electrolyte layer 30. It may be 50% or less, 40% or less, 30% or less, or 20% or less. The D50 average particle diameter is, for example, the median particle diameter (D50). The median particle diameter (D50) is the particle size corresponding to 50% of the cumulative volume calculated from the particle side with the small particle size in the particle size distribution measured, for example, by laser diffraction.

The solid electrolyte content included in the positive electrode active material layer 12 is, for example, 1 wt% to 40 wt%, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or It may be 1 wt% to 10 wt%.

[Anode layer: conductive material]

The positive electrode active material layer 12 may further include a conductive material. The conductive material may be, for example, a carbon-based conductive material, a metal-based conductive material, or a combination thereof. The carbon-based conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or a combination thereof, but is not limited to these and can be any carbon-based conductive material used in the art. possible. The metal conductive material may be a metal powder, a metal fiber, or a combination thereof, but is not limited to these, and any metal conductive material used in the art is possible. The content of the conductive material included in the positive electrode active material layer 12 is, for example, 1 wt% to 30 wt%, 1 wt% to 20 wt%, or 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12. You can.

[Anode layer: binder]

The positive electrode active material layer 12 may further include a binder. The binder is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these and is used as a binder in the art. Everything is possible. The binder content included in the positive electrode active material layer 12 may be, for example, 1 wt% to 10 wt% of the total weight of the positive electrode active material layer 12. The binder can be omitted.

[Anode layer: Other additives]

In addition to the positive electrode active material, solid electrolyte, binder, and conductive material described above, the positive electrode active material layer 12 may further include additives such as filler, coating agent, dispersant, and ion conductivity auxiliary agent.

As fillers, coating agents, dispersants, ion conductive auxiliaries, etc. that the positive electrode active material layer 12 may contain, known materials generally used in electrodes of all-solid-state secondary batteries can be used.

[Anode layer: Anode current collector]

The positive electrode current collector 11 is, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc ( A plate or foil made of Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof is used. The positive electrode current collector 11 can be omitted. The thickness of the positive electrode current collector 11 is, for example, 1 μm to 100 μm, 1 μm to 50 μm, 5 μm to 25 μm, or 10 μm to 20 μm.

The positive electrode current collector 11 may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or combinations thereof. The base film may be an insulator, for example. Since the base film contains an insulating thermoplastic polymer, when a short circuit occurs, the base film softens or liquefies and blocks battery operation, thereby suppressing a rapid increase in current. The metal layer is, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum ( Al), germanium (Ge), or alloys thereof. The metal layer acts as an electrochemical fuse and is cut in the event of overcurrent, thereby performing a short circuit prevention function. The limit current and maximum current can be adjusted by adjusting the thickness of the metal layer. The metal layer may be plated or deposited on the base film. As the thickness of the metal layer decreases, the limiting current and/or maximum current of the positive electrode current collector 11 decreases, so the stability of the lithium battery in the event of a short circuit may be improved. A lead tab may be added on the metal layer for connection to the outside. The lead tab may be welded to the metal layer or metal layer/base film laminate by ultrasonic welding, laser welding, spot welding, etc. During welding, the base film and/or metal layer melts and the metal layer may be electrically connected to the lead tab. To make the welding of the metal layer and the lead tab more robust, a metal chip may be added between the metal layer and the lead tab. The metal piece may be a thin piece of the same material as the metal of the metal layer. The metal piece may be, for example, metal foil, metal mesh, etc. The metal piece may be, for example, aluminum foil, copper foil, SUS foil, etc. The lead tab may be welded to the metal piece/metal layer laminate or the metal piece/metal layer/base film laminate by placing the metal piece on the metal layer and then welding it with the lead tab. During welding, the base film, metal layer, and/or metal piece melt and the metal layer or metal layer/metal piece laminate may be electrically connected to the lead tab. Metal chips and/or lead tabs may be added to a portion of the metal layer. The thickness of the base film may be, for example, 1 to 50 μm, 1.5 to 50 μm, 1.5 to 40 μm, or 1 to 30 μm. By having the base film have a thickness within this range, the weight of the electrode assembly can be more effectively reduced. The melting point of the base film may be, for example, 100 to 300°C, 100 to 250°C or less, or 100 to 200°C. Because the base film has a melting point in this range, the base film melts during the process of welding the lead tab and can be easily coupled to the lead tab. To improve the adhesion between the base film and the metal layer, surface treatment such as corona treatment may be performed on the base film. The thickness of the metal layer may be, for example, 0.01 to 3 μm, 0.1 to 3 μm, 0.1 to 2 μm or 0.1 to μm. When the metal layer has a thickness within this range, the stability of the electrode assembly can be ensured while maintaining conductivity. The thickness of the metal piece may be, for example, 2 to 10 μm, 2 to 7 μm, or 4 to 6 μm. When the metal piece has a thickness within this range, the connection between the metal layer and the lead tab can be performed more easily. By having the positive electrode current collector 11 having this structure, the weight of the positive electrode can be reduced and, as a result, the energy density of the positive electrode and the lithium battery can be improved.

[Anode layer: first inert member]

Referring to FIG. 1, the positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on one surface of the positive electrode current collector. A first inactive member 40 is disposed on one side of the anode layer 10. The first inert member 40 is disposed on one side of the positive electrode active material layer 12 and the positive electrode current collector 11. Referring to FIG. 2, the first inert member 40 is disposed on one side of the positive electrode active material layer 12 and is disposed on the solid electrolyte layer 40 and the positive electrode current collector 11 facing the solid electrolyte layer 40. placed in between. The first inert member 40 is not disposed on one side of the positive electrode current collector 11.

By including the first inert member 40, cracking of the solid electrolyte layer 30 is prevented during manufacturing and/or charging and discharging of the all-solid-state secondary battery 1, resulting in the cycle of the all-solid-state secondary battery 2. Characteristics are improved. In the all-solid secondary battery 1 that does not include the first inert member 40, the solid electrolyte layer 30 is in contact with the positive electrode layer 10 during manufacturing and/or charging and discharging of the all-solid secondary battery 1. As uneven pressure is applied, cracks occur in the solid electrolyte layer 30, and the growth of lithium metal through the cracks increases the possibility of a short circuit occurring.

In the all-solid-state secondary battery 1, the thickness T2 of the first inert member 40 is greater than the thickness T1 of the positive electrode active material layer 12 or is equal to the thickness T1 of the positive electrode active material layer 12. In the all-solid-state secondary battery 1, the thickness T2 of the first inert member 40 is substantially equal to the thickness T3 of the positive electrode layer 10. The thickness T2 of the first inert member 40 is the same as the thickness T3 of the anode layer 10, so that uniform pressure is applied between the anode layer 10 and the solid electrolyte layer 30 and the anode layer 10 ) and the solid electrolyte layer 30 are sufficiently brought into close contact, so that the interfacial resistance between the anode layer 10 and the solid electrolyte layer 30 is reduced. In addition, the solid electrolyte layer 30 is sufficiently sintered during the pressurized manufacturing process of the all-solid-state secondary battery 1, thereby reducing the internal resistance of the solid electrolyte layer 30 and the all-solid secondary battery 1 including the same.

The first inert member 40 surrounds the side surface of the positive electrode layer 10 and is in contact with the solid electrolyte layer 30. During the pressing process in the solid electrolyte layer 30 that is not in contact with the anode layer 20, the first inert member 40 surrounds the side of the anode layer 10 and contacts the solid electrolyte layer 30. Cracks in the solid electrolyte layer 30 caused by pressure differences can be effectively suppressed. The first inert member 40 surrounds the side of the positive electrode layer 10 and is separated from the negative electrode layer 20, or more specifically, the first negative electrode active material layer 22. The first inert member 40 surrounds the side surface of the anode layer 10, contacts the solid electrolyte layer 30, and is separated from the cathode layer 20. Accordingly, the possibility of a short circuit occurring due to physical contact between the positive electrode layer 10 and the first negative electrode active material layer 22 or overcharging of lithium is suppressed. For example, the inert member 40 is disposed on one side of the positive electrode active material layer 12 and at the same time is disposed on one side of the positive electrode current collector 11, thereby forming the positive electrode current collector 11 and the negative electrode layer ( 20) It more effectively suppresses the possibility of a short circuit due to contact.

1 to 5, the first inert members 40, 40a, and 40b extend from one side of the anode layer 30 to the distal end of the solid electrolyte layer 30. By extending the first inert member 40 to the distal end of the solid electrolyte layer 30, cracking occurring at the distal end of the solid electrolyte layer 30 can be suppressed. The distal end of the solid electrolyte layer 30 is the outermost part in contact with the side of the solid electrolyte layer 30. The first inert member 40 extends to the outermost portion in contact with the side surface of the solid electrolyte layer 30. The first inert member 40 is separated from the negative electrode layer 20, and more specifically, the first negative electrode active material layer 22. The first inert member 40 extends to the distal end of the solid electrolyte layer 30, but does not contact the cathode layer 20. The first inert member 40 fills the space extending from one side of the anode layer 30 to the distal end of the solid electrolyte layer 30, for example.

Referring to FIGS. 1 and 2, the width (W2) of the first inert member 40 extending from one side of the anode layer 10 to the distal end of the solid electrolyte layer 30 is, for example, the anode layer 10 ) 1 to 30%, 1 to 25%, 1 to 20%, 1 to 15%, 1 to 10% or 1 to 5 of the width (W1) between one side of and the other side opposite to the one side. %am. If the width (W2) of the first inert member 40 is too large, the energy density of the all-solid-state secondary battery 1 is reduced. If the width (W2) of the first inert member 40 is too small, the effect of disposing the first inert member 40 is insignificant.

The area S1 of the anode layer 10 is smaller than the area S3 of the solid electrolyte layer 30 in contact with the anode layer 10. A flame-retardant inert member 40 is disposed surrounding the side of the anode layer 10 to compensate for the difference in area between the anode layer 10 and the solid electrolyte layer 30. The area S2 of the flame-retardant inert member 40 compensates for the difference between the area S1 of the anode layer 10 and the area S3 of the solid electrolyte layer 30, thereby responding to the pressure difference during the pressing process. It effectively suppresses cracks in the solid electrolyte layer 30 caused by this. For example, the sum of the area S1 of the positive electrode layer 10 and the area S2 of the inert member 40 is equal to the area S3 of the solid electrolyte layer 30.

The area S1 of the anode layer 10 is, for example, less than 100%, 99% or less, 98% or less, 97% or less, 96% or less, or 95% or less of the area S3 of the solid electrolyte layer 30. am. The area S1 of the anode layer 10 is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, or 60% to 97% of the area S3 of the solid electrolyte layer 30. , 70% to 96%, 80% to 95%, or 85% to 95%.

If the area (S1) of the positive electrode layer (10) is equal to or larger than the area (S3) of the solid electrolyte layer (30), a short circuit occurs due to physical contact between the positive electrode layer (10) and the first negative electrode active material layer (22). Otherwise, the possibility of a short circuit occurring due to overcharging of lithium increases. The area S1 of the positive electrode layer 10 is, for example, the same as the area of the positive electrode active material layer 12. The area S1 of the positive electrode layer 10 is, for example, the same as the area 11 of the positive electrode current collector.

The area S2 of the first inert member 40 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the area S1 of the anode layer 10. The area S2 of the first inert member 40 is, for example, 1% to 50%, 5% to 40%, 5% to 30%, 5% to 20% of the area S1 of the anode layer 10. , or 5% to 15%.

The area S1 of the positive electrode layer 10 is smaller than the area S4 of the negative electrode current collector 21. The area S1 of the positive electrode layer 10 is, for example, less than 100%, less than 99%, less than 98%, less than 97%, less than 96%, or less than 95% of the area S4 of the negative electrode current collector 21. am. The area S1 of the positive electrode layer 10 is, for example, 50% to less than 100%, 50% to 99%, 55% to 98%, or 60% to 97% of the area S4 of the negative electrode current collector 21. , 70% to 96%, 80% to 95%, or 85% to 95%. The area S4 of the negative electrode current collector 21 is, for example, the same as the area of the negative electrode layer 20. The area S4 of the negative electrode current collector 21 is, for example, the same as the area of the first negative electrode active material layer 22.

As used herein, "same" area, length, width, thickness and/or shape means "substantially the same" area, length, width, thickness and/or shape, except where the area, length, width, thickness and/or shape are intentionally different. Includes all instances of width, thickness and/or shape. “Same” area, length, width and/or thickness refers to the extent to which the unintentional difference in area, length, width and/or thickness of the compared objects is, for example, less than 1%, less than 0.5%, or less than 0.1%. Includes.

For example, the thickness of the first inert member 40 is greater than the thickness of the first negative electrode active material layer 22. The thickness of the first negative electrode active material layer 22 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the first inert member 40. The thickness of the first negative electrode active material layer 22 is, for example, 1% to 50%, 1% to 40%, 1% to 30%, 1% to 20%, or 1% of the thickness of the first inert member 40. % to 10%.

The negative electrode layer 20 includes a negative electrode current collector 21 and a first negative electrode active material layer 22 disposed on one surface of the negative electrode current collector 21. For example, the first negative electrode active material layer 22 is free on the other side opposite to one side of the negative electrode current collector 21. For example, the first negative electrode active material layer 22 is disposed on only one side of the negative electrode current collector 21, and the first negative electrode active material layer 22 is not disposed on the other side.

The first inert member 40 may be a gasket. By using a gas cat as the inert member 40, cracking of the solid electrolyte layer 30 caused by pressure difference during the pressing process can be effectively suppressed.

The first inert member 40 has, for example, a single-layer structure. Alternatively, although not shown in the drawings, the first inert member 40 may have a multi-layer structure. In the first inert member 40 having a multi-layer structure, each layer may have a different composition. The first inert member having a multi-layer structure may have, for example, a two-layer structure, a three-layer structure, a four-layer structure, or a five-layer structure. The first inert member 40 having a multilayer structure may include, for example, one or more adhesive layers and one or more support layers. The adhesive layer effectively prevents separation between the positive electrode layer 10 and the solid electrolyte layer 30 due to a change in the volume of the positive electrode layer 10 that occurs during charging and discharging of the all-solid-state secondary battery 10, for example. The inert member 40 film strength is improved by providing cohesion between the support layer and other layers. The support layer provides support to the first inert member 40, prevents uneven pressure applied to the solid electrolyte layer 30 during the pressurization process or charge/discharge process, and forms the all-solid-state secondary battery 1 to be manufactured. Prevent deformation.

Referring to FIG. 3, the all-solid-state secondary battery 1 includes a positive electrode layer 10, a negative electrode layer 20, and a solid electrolyte layer 30 disposed between them, and the positive electrode layer 10 serves as a positive electrode house. It includes a first positive electrode active material layer 12a and a second positive electrode active material layer 12b disposed on both sides of the entire body 11 and the positive electrode current collector 11, respectively, and the solid electrolyte layer 30 is the first positive electrode. Each includes a first solid electrolyte layer 30a in contact with the active material layer 12a and a second solid electrolyte layer 30b in contact with the second positive electrode active material layer 12b, and the negative electrode layer 20 is a first solid electrolyte layer 20. Each includes a first cathode layer 20a in contact with the solid electrolyte layer 30a and a second cathode layer 20b in contact with the second solid electrolyte layer 30b, and the first inert member 40 is connected to each other. It is disposed surrounding the side of the anode layer 10 between the opposing first solid electrolyte layer 30a and the second solid electrolyte layer 30b. The first inert member 40 includes, for example, a 1a inert member 40a in contact with the first solid electrolyte layer 30a and a 1b inert member 40b in contact with the second solid electrolyte layer 30b. do. Therefore, the all-solid-state secondary battery 1 has a bi-cell structure. Because the all-solid-state secondary battery 1 has this bi-cell structure, the solid electrolyte layer 30 and the cathode layer 20 are symmetrically arranged to face each other around the anode layer 10. Therefore, structural deformation due to pressure applied during manufacturing of the all-solid-state secondary battery 1 is more effectively suppressed. Accordingly, cracking of the solid electrolyte layer 30 is suppressed during the manufacturing process and/or charging and discharging of the all-solid secondary battery 1, thereby preventing short circuiting of the all-solid secondary battery 1, and resulting in all-solid secondary battery 1. The cycle characteristics of the battery 1 are further improved. Additionally, since only one positive electrode current collector 11 is used for the plurality of positive electrode active material layers 12a and 12b, the energy density of the all-solid-state secondary battery 1 increases.

1 to 5, the first inert member 40 is, for example, a flame-retardant inert member. By providing flame retardancy, the flame retardant inert member can prevent the possibility of thermal runaway and ignition of the all-solid-state secondary battery 1. As a result, the safety of the all-solid-state secondary battery 1 is further improved. The flame retardant inert member absorbs residual moisture in the all-solid secondary battery 1, thereby preventing deterioration of the all-solid secondary battery 1 and improving the lifespan characteristics of the all-solid secondary battery 1.

Flame retardant inert members include, for example, matrices and fillers. The matrix includes, for example, a substrate and reinforcement. The matrix includes, for example, a fibrous substrate and fibrous reinforcement. By including a substrate in the matrix, the matrix can be elastic. Therefore, the matrix effectively accommodates volume changes during charging and discharging of the all-solid-state secondary battery 1 and can be placed in various positions. The substrate comprising the matrix comprises, for example, a first fibrous material. By including the first fibrous material, the substrate effectively accommodates the volume change of the positive electrode layer 30 that occurs during the charging and discharging process of the all-solid-state secondary battery 1, and first inactivates the positive electrode layer 30 due to the volume change. Deformation of the member 40 can be effectively suppressed. The first fibrous material is, for example, a material having an aspect ratio of at least 5, at least 20, or at least 50. The first fibrous material is, for example, a material having an aspect ratio of 5 to 1000, 20 to 1000, or 50 to 1000. The first fibrous material is, for example, an insulating material. Since the first fibrous material is an insulating material, it is possible to effectively prevent short circuit between the positive electrode layer 30 and the negative electrode layer 20 due to lithium dendrites, etc., which occur during charging and discharging of the all-solid-state secondary battery 1. The first fibrous material includes, for example, one or more selected from pulp fibers, insulating polymer fibers, and ion-conducting polymer fibers. The strength of the matrix is improved by the inclusion of reinforcement in the matrix. Therefore, the matrix can prevent excessive volume change during charging and discharging of the all-solid-state secondary battery 1 and prevent deformation of the all-solid-state secondary battery 1. The reinforcement comprised by the matrix comprises, for example, a second fibrous material. The strength of the matrix can be increased more uniformly by the reinforcing material including the second fibrous material. The second fibrous material is, for example, a material with an aspect ratio of 3 or more, 5 or more, or 10 or more. The first fibrous material is, for example, a material having an aspect ratio of 3 to 100, 5 to 100, or 10 to 100. The second fibrous material is, for example, a flame retardant material. Since the second fibrous material is a flame retardant material, ignition due to thermal runaway occurring during the charging and discharging process of the all-solid-state secondary battery 1 or due to external shock can be effectively suppressed. The second fibrous material is, for example, glass fiber, metal oxide fiber, ceramic fiber, etc.

The flame retardant inert member includes a filler in addition to the matrix. The filler may be disposed within the matrix, on the surface of the matrix, or on both the interior and the surface. Fillers are for example inorganic materials. The filler contained by the flame retardant inert member is, for example, a moisture getter. For example, the filler prevents deterioration of the all-solid-state secondary battery 1 by removing moisture remaining in the all-solid-state secondary battery 1 by adsorbing moisture at a temperature of less than 100°C. In addition, when the temperature of the all-solid secondary battery (1) increases above 150°C due to thermal runaway occurring during the charge/discharge process of the all-solid secondary battery (1) or an external shock, the filler releases the adsorbed moisture to form an all-solid secondary battery (1). Ignition of the secondary battery 1 can be effectively suppressed. That is, the filler is, for example, a flame retardant. The filler is, for example, a metal hydroxide having moisture adsorption properties. Metal hydroxides contained in the filler include, for example, Mg(OH) ₂ , Fe(OH) ₃ , Sb(OH) ₃ , Sn(OH) ₄ , TI(OH) ₃ , Zr(OH) ₄ , Al(OH) ₃ or a combination thereof. The content of the filler contained in the flame retardant inert member is, for example, 10 to 80 parts by weight, 20 to 80 parts by weight, 30 to 80 parts by weight, 40 to 80 parts by weight, 50 to 100 parts by weight, based on 100 parts by weight of the flame retardant inert member (4). 80 parts by weight, 60 to 80 parts by weight, or 65 to 80 parts by weight.

The flame retardant inert member may further comprise, for example, a binder. The binder may include, for example, a curable polymer or a non-curable polymer. A curable polymer is a polymer that hardens by heat and/or pressure. Curable polymers are solid, for example at room temperature. The flame retardant inert member 40 includes, for example, a heat pressure curable film and/or a cured product thereof. A thermo-pressure curable polymer is, for example, TSA-66 from Toray.

The flame retardant inert member may additionally include other materials in addition to the above-described substrate, reinforcing material, filler, and binder. The flame retardant inert member may further include, for example, one or more selected from among paper, insulating polymer, ion conductive polymer, insulating inorganic material, oxide-based solid electrolyte, and sulfide-based solid electrolyte. The insulating polymer may be, for example, an olefin-based polymer such as polypropylene (PP) or polyethylene (PE).

The density of the base material or the reinforcing material included in the flame-retardant inert member is, for example, 10% to 300%, 10% to 150%, 10% to 140%, and 10% of the density of the positive electrode active material included in the positive electrode active material layer 12. It may be from 130% to 130%, or from 10% to 120%.

The first inert member 40 is a member that does not contain an electrochemically active material, for example, an electrode active material. Electrode active material is a material that absorbs/releases lithium. The first inert member 40 is a member made of a material other than the electrode active material and used in the relevant technical field.

[Cathode layer]

[Cathode layer: Negative active material]

1 to 5, the negative electrode layer 20 includes a first negative electrode active material layer 22. The first negative electrode active material layer 22 includes, for example, a negative electrode active material and a binder.

The negative electrode active material included in the first negative electrode active material layer 22 is, for example, a negative electrode material that can form an alloy or compound with lithium.

The negative electrode active material included in the first negative electrode active material layer 22 has, for example, a particle form. The average particle diameter of the negative electrode active material in particle form is, for example, 4 ㎛ or less, 3 ㎛ or less, 2 ㎛ or less, 1 ㎛ or less, 500 nm or less, 300 nm or less, or 100 nm or less. The average particle diameter of the negative electrode active material in particle form is, for example, 10 nm to 4 ㎛, 10 nm to 3 ㎛, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 300 nm, or It is 10 nm to 100 nm. Because the negative electrode active material has an average particle size in this range, reversible absorption and/or desorbing of lithium can be facilitated more easily during charging and discharging. The average particle diameter of the negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size distribution meter.

The negative electrode active material included in the first negative electrode active material layer 22 includes, for example, one or more selected from carbon-based negative electrode active materials and metal or metalloid negative electrode active materials.

Carbon-based negative active materials include, for example, amorphous carbon, crystalline carbon, porous carbon, or combinations thereof.

The carbon-based negative electrode active material is particularly amorphous carbon. Amorphous carbon is, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene. ), etc., but is not necessarily limited to these, and any carbon that is classified as amorphous carbon in the relevant technical field is possible. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity and is distinguished from crystalline carbon or graphitic carbon.

The carbon-based negative active material may be, for example, porous carbon. The pore volume contained in the porous carbon is, for example, 0.1 cc/g to 10.0 cc/g, 0.5 cc/g to 5 cc/g, or 0.1 cc/g to 1 cc/g. The average pore diameter of porous carbon is, for example, 1 nm to 50 nm, 1 nm to 30 nm, or 1 nm to 10 nm. The BET specific surface area of the porous carbon is, for example, from 100 m ² /g to 3000 m ² /g.

Metal or metalloid anode active materials include gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). ), but is not necessarily limited to these, and any metal negative active material or metalloid negative electrode active material that forms an alloy or compound with lithium in the art can be used. For example, nickel (Ni) does not form an alloy with lithium, so it is not a metal anode active material.

The first negative electrode active material layer 22 includes one type of negative electrode active material among these negative electrode active materials, or a mixture of a plurality of different negative electrode active materials. For example, the first negative active material layer 22 contains only amorphous carbon, or gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), and bismuth. (Bi), tin (Sn), and zinc (Zn). Alternatively, the first negative electrode active material layer 22 is made of amorphous carbon, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), It includes a mixture with one or more selected from the group consisting of tin (Sn) and zinc (Zn). The mixing ratio of the mixture of amorphous carbon and gold, etc. is a weight ratio, for example, 99:1 to 1:99, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1. The range is not limited and is selected depending on the characteristics of the all-solid-state secondary battery (1) required. When the negative electrode active material has this composition, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

The negative electrode active material included in the first negative electrode active material layer 22 includes, for example, a mixture of first particles made of amorphous carbon and second particles made of metal or metalloid. Metals or metalloids include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), and tin (Sn). ) and zinc (Zn). Metalloids, on the other hand, are semiconductors. The content of the second particles is 1 to 99%, 1 to 60%, 8 to 60%, 10 to 50%, 15 to 40%, or 20 to 30% by weight, based on the total weight of the mixture. . By having the content of the second particles in this range, for example, the cycle characteristics of the all-solid-state secondary battery 1 are further improved.

Alternatively, the first negative electrode active material layer 22 includes a composite negative electrode active material. The composite anode active material may include, for example, a carbon-based support and a metal-based anode active material supported on the carbon-based support. As the composite negative electrode active material has this structure, localization of the metal-based negative electrode active material within the first negative electrode active material layer can be prevented and uniform distribution can be obtained. As a result, the cycle characteristics of the all-solid-state secondary battery 1 including the first negative electrode active material layer 22 are further improved.

The metal-based negative electrode active material supported on the carbon-based support includes, for example, a metal, a metal oxide, a complex of a metal and a metal oxide, or a combination thereof. Metals include, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and tellurium (Te). and zinc (Zn). Metal oxides include, for example, gold (Au) oxide, platinum (Pt) oxide, palladium (Pd) oxide, silicon (Si) oxide, silver (Ag) oxide, aluminum (Al) oxide, bismuth (Bi) oxide, tin ( Sn) oxide, tellurium (Te) oxide, zinc (Zn) oxide, etc. _{Metal oxides} are _, for _{example , Au} ≤1, 0<y≤1), Si _x O _y (0<x≤1, 0<y≤2), Ag _x O _y (0<x≤2, 0<y≤1), Al _x O _y (0<x≤2, 0<y≤3), Bi _x O _y (0<x≤2, 0<y≤3), Sn _x O _y (0<x≤1, 0<y≤2), It may include Te _x O _y (0<x≤1, 0<y≤3), Zn _x O _y (0<x≤1, 0<y≤1), or a combination thereof. Complexes of metals and metal oxides are, for example, Au and Au _x O _y (0<x≤2, 0<y≤3), Pt and Pt _x O _y (0<x≤1, 0<y≤2 ), a complex of Pd and Pd _x O _y (0<x≤1, 0<y≤1), a complex of Si and Si _x O _y (0<x≤1, 0<y≤2), Ag and Complex of Ag _x O _y (0<x≤2, 0<y≤1), complex of Al and Al _x O _y (0<x≤2, 0<y≤3), Bi and Bi _x O _y (0 <x≤2, 0<y≤3), complex of Sn and Sn _x O _y (0<x≤1, 0<y≤2), complex of Te and Te _x O _y (0<x≤1, 0 <y≤3), a complex of Zn and Zn _x O _y (0<x≤1, 0<y≤1), or a combination thereof.

The carbon-based support is, for example, amorphous carbon. Amorphous carbon is, for example, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), graphene, activated carbon ( activated carbon), carbon nanofibers (CNF), carbon nanotubes (CNT), etc., but are not necessarily limited to these and can be anything that is classified as amorphous carbon in the relevant technical field. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity and is distinguished from crystalline carbon or graphitic carbon. The carbonaceous material is, for example, a carbon-based negative electrode active material.

The composite anode active material has a particle form, for example. The particle size of the composite anode active material having a particle shape is, for example, 10 nm to 4 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. Because the composite anode active material has a particle size in this range, reversible absorption and/or desorbing of lithium can be facilitated more easily during charging and discharging. The metal-based negative active material supported on the support may, for example, have a particle form. The particle size of the metal-based negative electrode active material may be, for example, 1 nm to 200 nm, 1 nm to 150 nm, 5 nm to 100 nm, or 10 nm to 50 nm. The carbon-based support may, for example, have a particle form. The particle size of the carbon-based support may be, for example, 10 nm to 2 ㎛, 10 nm to 1 ㎛, 10 nm to 500 nm, 10 nm to 200 nm, or 10 nm to 100 nm. By having the carbon-based support having a particle size within this range, it can be more uniformly disposed within the first negative electrode active material layer. The carbon-based support may be, for example, nanoparticles with a particle diameter of 500 nm or less. The particle size of the composite negative electrode active material, the particle size of the metal-based negative electrode active material, and the particle size of the carbon-based support are, for example, average particle sizes. The average particle diameter is, for example, the median diameter (D50) measured using a laser particle size distribution meter. Alternatively, the average particle size can be determined automatically using software, for example from an electron microscope image, or manually by manual means.

[Cathode layer: binder]

The binder included in the first negative electrode active material layer 22 is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and vinylidene fluoride. It is not necessarily limited to ride/hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., and any binder used in the art can be used. The binder may be single or composed of multiple different binders.

Since the first negative electrode active material layer 22 includes a binder, the first negative electrode active material layer 22 is stabilized on the negative electrode current collector 21. In addition, cracking of the first negative electrode active material layer 22 is suppressed despite changes in the volume and/or relative position of the first negative electrode active material layer 22 during the charging and discharging process. For example, when the first negative electrode active material layer 22 does not include a binder, it is possible for the first negative electrode active material layer 22 to be easily separated from the negative electrode current collector 21. At the portion where the negative electrode current collector 21 is exposed due to the separation of the first negative electrode active material layer 22 from the negative electrode current collector 21, the negative electrode current collector 21 contacts the solid electrolyte layer 30, causing a short circuit. The likelihood of this occurring increases. The first negative electrode active material layer 22 is manufactured, for example, by applying a slurry in which the material constituting the first negative electrode active material layer 22 is dispersed onto the negative electrode current collector 21 and drying it. By including a binder in the first negative electrode active material layer 22, stable dispersion of the negative electrode active material in the slurry is possible. For example, when the slurry is applied onto the negative electrode current collector 21 by screen printing, it is possible to suppress clogging of the screen (for example, clogging by aggregates of the negative electrode active material).

[Cathode layer: Other additives]

The first negative active material layer 22 may further include additives used in the conventional all-solid-state secondary battery 1, such as fillers, coating agents, dispersants, and ion conductivity auxiliaries.

[Cathode layer: solid electrolyte]

The first negative electrode active material layer 22 may further include a solid electrolyte. The solid electrolyte may be, for example, a material selected from solid electrolytes included in the solid electrolyte layer 30. The solid electrolyte included in the first negative electrode active material layer 22 acts as a reaction point where the formation of lithium metal begins within the first negative electrode active material layer 22, acts as a space where the formed lithium metal is stored, or acts as a space for storing lithium ions. It can act as a transmission path. Solid electrolyte can be omitted.

In the first negative electrode active material layer 22, for example, the content of the solid electrolyte may be high in the area adjacent to the solid electrolyte layer 30 and low in the area adjacent to the negative electrode current collector 21. The solid electrolyte in the first negative electrode active material layer 22 may have, for example, a concentration gradient in which the concentration decreases from an area adjacent to the solid electrolyte layer 30 to an area adjacent to the negative electrode current collector 21.

[Cathode layer: first cathode active material layer]

The ratio (B/A) of the initial charge capacity (B) of the first negative electrode active material layer 22 and the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45. The initial charging capacity of the positive electrode active material layer 12 is determined from the first open circuit voltage (1 ^st open circuit voltage) to the maximum charging voltage for Li/Li ⁺ . The initial charge capacity of the first negative active material layer 22 is determined at 0.01 V for Li/Li ⁺ from the ^2nd open circuit voltage.

The maximum charging voltage is determined by the type of cathode active material. The maximum charging voltage may be, for example, 1.5 V, 2.0 V, 2.5 V, 3.0 V, 3.5 V, 4.0 V, 4.2 V, or 4.3 V. For example, the maximum charging voltage of Li2S or Li2S composite may be 2.5 V relative to Li/Li ⁺ . For example, the maximum charging voltage of Li2S or Li2S composite may be 3.0 V for Li/Li ⁺ . The ratio (B/A) of the initial charge capacity (B) of the first negative electrode active material layer 22 and the initial charge capacity (A) of the positive electrode active material layer is, for example, 0.01 to 0.3, 0.01 to 0.2, or 0.05 to 0.1. .

The initial charge capacity (mAh) of the cathode active material layer 12 is obtained by multiplying the charge specific capacity (mAh/g) of the cathode active material by the mass (g) of the cathode active material in the cathode active material layer 12. When multiple types of positive electrode active materials are used, the charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values is the initial charge capacity of the positive electrode active material layer 12. The initial charge capacity of the first negative electrode active material layer 22 is also calculated in the same way. The initial charge capacity of the first negative electrode active material layer 22 is obtained by multiplying the charge capacity density (mAh/g) of the negative electrode active material by the mass of the negative electrode active material in the first negative electrode active material layer 22. When several types of negative electrode active materials are used, the charge capacity density × mass value is calculated for each negative electrode active material, and the sum of these values is the initial charge capacity of the first negative electrode active material layer 22. The charge capacity density of each positive electrode active material and negative electrode active material can be measured using an all-solid half-cell using lithium metal as a counter electrode. The initial charge capacity of each of the positive electrode active material layer 12 and the first negative electrode active material layer 22 can be directly measured using an all-solid half-cell at a constant current density, for example, 0.1 mA/cm ^2. there is. For the anode, the measurement can be performed for operating voltages from the first open circuit voltage (OCV) up to the maximum charging voltage, for example 3.0 V (vs. Li/Li ⁺ ). For the cathode, the measurement can be performed for operating voltages from the second open circuit voltage (OCV) up to 0.01 V for the cathode, for example lithium metal. For example, the all-solid-state half-cell having a positive electrode active material layer is charged with a constant current of 0.1 mA/cm ² from the first open circuit voltage to 3.0 V, and the all-solid-state half-cell having the first negative electrode active material layer is charged from the second open circuit voltage. It can be charged at a constant current of 0.1 mA/cm ² up to 0.01 V. The current density during constant current charging may be, for example, 0.2 mA/cm ² or 0.5 mA/cm ² . The all-solid-state half-cell having a positive electrode active material layer can be charged, for example, from a first open-circuit voltage to 2.5 V, 2.0 V, 3.5 V, or 4.0 V. The maximum charging voltage of the positive electrode active material layer can be determined by the maximum voltage of the battery that satisfies the safety conditions according to JISC8712:2015 of the Japanese Standards Association.

If the initial charge capacity of the first negative electrode active material layer 22 is too small, the thickness of the first negative electrode active material layer 22 becomes very thin, so that the first negative electrode active material layer 22 and the negative electrode current collector ( 21) The lithium dendrite formed between the first negative electrode active material layer 22 collapses, making it difficult to improve the cycle characteristics of the all-solid-state secondary battery 1. If the charging capacity of the first negative electrode active material layer 22 increases excessively, the energy density of the all-solid-state secondary battery 1 decreases and the internal resistance of the all-solid-state secondary battery 1 due to the first negative electrode active material layer 22 increases. Therefore, it is difficult to improve the cycle characteristics of the all-solid-state secondary battery 1.

The thickness of the first negative electrode active material layer 22 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer 12. The thickness of the first negative electrode active material layer 22 is, for example, 1 to 50%, 1 to 40%, 1 to 30%, 1 to 20%, 1 to 10%, or 1 to 1% of the thickness of the positive electrode active material layer 12. It is 5%. The thickness of the first negative electrode active material layer 22 is, for example, 1 μm to 20 μm, 2 μm to 15 μm, or 3 μm to 10 μm. If the thickness of the first negative electrode active material layer 22 is too thin, the lithium dendrites formed between the first negative electrode active material layer 22 and the negative electrode current collector 21 collapse the first negative electrode active material layer 22, causing electric shock. It is difficult to improve the cycle characteristics of the solid secondary battery 1. If the thickness of the first negative electrode active material layer 22 increases excessively, the energy density of the all-solid-state secondary battery 1 decreases and the internal resistance of the all-solid-state secondary battery 1 due to the first negative electrode active material layer 22 increases. It is difficult to improve the cycle characteristics of the all-solid-state secondary battery (1). If the thickness of the first negative electrode active material layer 22 decreases, for example, the initial charge capacity of the first negative electrode active material layer 22 also decreases.

[Cathode layer: second cathode active material layer]

Although not shown in the drawing, the all-solid-state secondary battery 1 further includes a second negative electrode active material layer disposed, for example, between the negative electrode current collector 21 and the first negative electrode active material layer 22 after being charged. . The second negative electrode active material layer is a metal layer containing lithium or a lithium alloy. The metal layer includes lithium or a lithium alloy. Therefore, since the second negative electrode active material layer is a metal layer containing lithium, it functions as a lithium reservoir, for example. Lithium alloys include, for example, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc. It is not limited to, and any lithium alloy used in the relevant technical field is possible. The second negative electrode active material layer may be made of one of these alloys or lithium, or may be made of several types of alloys. The second negative electrode active material layer is, for example, a plated layer. For example, the second negative electrode active material layer is deposited between the first negative electrode active material layer 22 and the negative electrode current collector 21 during the charging process of the all-solid-state secondary battery 1.

The thickness of the second negative electrode active material layer is not particularly limited, but is, for example, 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 150 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the second negative electrode active material layer is too thin, it is difficult for the second negative electrode active material layer to function as a lithium reservoir. If the thickness of the second negative active material layer is too thick, the mass and volume of the all-solid-state secondary battery 1 may increase and the cycle characteristics of the all-solid-state secondary battery 1 may actually deteriorate.

Alternatively, in the all-solid secondary battery 1, the second negative electrode active material layer may be disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22, for example, before assembly of the all-solid secondary battery 1. there is. When the second negative electrode active material layer 23 is disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22 before assembly of the all-solid-state secondary battery 1, the second negative electrode active material layer contains lithium. Because it is a metal layer, it acts as a lithium reservoir. For example, before assembling the all-solid-state secondary battery 1, lithium foil may be placed between the negative electrode current collector 21 and the first negative electrode active material layer 22.

If the second negative electrode active material layer is precipitated by charging after assembling the all-solid secondary battery (1), the all-solid secondary battery (1) does not include the second negative electrode active material layer when assembling the all-solid secondary battery (1). The energy density increases. When charging the all-solid-state secondary battery 1, the charge exceeds the charging capacity of the first negative electrode active material layer 22. That is, the first negative electrode active material layer 22 is overcharged. At the beginning of charging, lithium is stored in the first negative electrode active material layer 22. The negative electrode active material included in the first negative electrode active material layer 22 forms an alloy or compound with lithium ions that have migrated from the positive electrode layer 10. When charging exceeds the capacity of the first negative electrode active material layer 22, for example, lithium is formed on the back of the first negative electrode active material layer 22, that is, between the negative electrode current collector 21 and the first negative electrode active material layer 22. This precipitates, and a metal layer corresponding to the second negative electrode active material layer is formed by the precipitated lithium. The second negative electrode active material layer is a metal layer mainly composed of lithium (i.e., metallic lithium). This result is obtained, for example, when the negative electrode active material included in the first negative electrode active material layer 22 includes a material that forms an alloy or compound with lithium. During discharge, lithium in the first negative electrode active material layer 22 and the second negative electrode active material layer, that is, the metal layer, is ionized and moves toward the positive electrode layer 10. Therefore, it is possible to use lithium as a negative electrode active material in the all-solid-state secondary battery 1. In addition, since the first negative electrode active material layer 22 covers the second negative electrode active material layer, it serves as a protective layer for the second negative electrode active material layer, that is, the metal layer, and also serves to suppress the precipitation growth of lithium dendrites. Perform. Therefore, short circuit and capacity reduction of the all-solid-state secondary battery 1 are suppressed, and as a result, the cycle characteristics of the all-solid-state secondary battery 1 are improved. In addition, when the second negative electrode active material layer is disposed by charging after assembling the all-solid-state secondary battery 1, the negative electrode layer 20, that is, the negative electrode current collector 21 and the first negative electrode active material layer 22, and between them The area is a Li-free area that does not contain lithium (Li) in the initial state or after complete discharge of the all-solid-state secondary battery 1.

[Cathode layer: Cathode current collector]

The negative electrode current collector 21 is made of a material that does not react with lithium, that is, does not form any alloy or compound. Materials constituting the negative electrode current collector 21 include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but are not necessarily limited to these. Anything that can be used as an electrode current collector in the technical field is possible. The negative electrode current collector 21 may be composed of one of the above-described metals, an alloy of two or more metals, or a coating material. The negative electrode current collector 21 is, for example, in the form of a plate or foil.

For example, although not shown in the drawing, the all-solid-state secondary battery 1 may further include a thin film containing an element capable of forming an alloy with lithium on one surface of the negative electrode current collector 21. The thin film is disposed between the negative electrode current collector 21 and the first negative electrode active material layer 22. The thin film contains elements that can form alloys, for example with lithium. Elements that can form an alloy with lithium include, for example, gold, silver, zinc, tin, indium, silicon, aluminum, and bismuth, but are not necessarily limited to these, and elements that can form an alloy with lithium are known in the art. Any element is possible. The thin film is composed of one of these metals or an alloy of several types of metals. By placing the thin film on one side of the negative electrode current collector 21, for example, the precipitated shape of the second negative electrode active material layer deposited between the thin film 24 and the first negative electrode active material layer 22 is further flattened, The cycle characteristics of the solid secondary battery 1 can be further improved.

The thickness of the thin film is, for example, 1 nm to 800 nm, 10 nm to 700 nm, 50 nm to 600 nm, or 100 nm to 500 nm. If the thickness of the thin film is less than 1 nm, it may be difficult for the thin film to function. If the thickness of the thin film is too thick, the thin film itself may occlude lithium, thereby reducing the amount of lithium precipitated at the negative electrode, thereby lowering the energy density of the all-solid-state battery and the cycle characteristics of the all-solid-state secondary battery 1. The thin film may be disposed on the negative electrode current collector 21 by, for example, vacuum deposition, sputtering, plating, etc., but it is not necessarily limited to these methods and any method that can form a thin film in the art is possible.

Although not shown in the drawing, the negative electrode current collector 21 may include, for example, a base film and a metal layer disposed on one or both sides of the base film. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or combinations thereof. The polymer may be an insulating polymer. Since the base film contains an insulating thermoplastic polymer, when a short circuit occurs, the base film softens or liquefies and blocks battery operation, thereby suppressing a rapid increase in current. The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or alloys thereof. The negative electrode current collector 21 may additionally include metal pieces and/or lead tabs. For more detailed information about the base film, metal layer, metal chip, and lead tab of the negative electrode current collector 21, refer to the positive electrode current collector 11 described above. When the negative electrode current collector 21 has this structure, the weight of the negative electrode can be reduced and, as a result, the energy density of the negative electrode and the lithium battery can be improved.

[Cathode layer: second inert member]

Referring to FIGS. 6 to 9 , the all-solid secondary battery 1 further includes second inert members 50, 50a, 50b, and 50c disposed on the other side of the negative electrode current collector 21.

The second inert member 50 is different from the first inert member 40 in that it has conductivity by additionally containing a conductive material. The second inert member 50 is, for example, a conductive flame retardant inert member.

Conductive materials include, for example, graphite, carbon black, acetylene black, Ketjen black, Denka black, carbon fiber, carbon nanotubes (CNT), graphene, metal fiber, metal powder, etc. The 25°C electronic conductivity of the second inert member 50 is, for example, 100 times, 1,000, or 10,000 times the electronic conductivity of the first inert member 40 at 25°C.

The second inert member 50 includes, for example, matrix, filler, and conductive material. The matrix includes, for example, a substrate and reinforcement. The second inert member 50 may further include filler, binder, etc. The content of the conductive material included in the second inert member 50 is, for example, 1 to 30 parts by weight, 1 to 20 parts by weight, 1 to 15 parts by weight, and 1 to 10 parts by weight, based on 100 parts by weight of the second inert member 50. parts by weight, 5 to 40 parts by weight, 5 to 30 parts by weight, or 5 to 35 parts by weight.

The elastic modulus (Young's modulus) of the second inert member 50 is, for example, smaller than that of the negative electrode current collector 21 . The elastic modulus (Young's modulus) of the second inert member 50 is, for example, 50% or less, 30% or less, 10% or less, or 5% or less of the elastic modulus of the negative electrode current collector 21. The elastic modulus (Young's modulus) of the second inert member 50 is, for example, 0.01% to 50%, 0.1 to 30%, 0.1 to 10%, and 1 to 5% of the elastic modulus of the negative electrode current collector 21. The elastic modulus of the second inert member 50 is, for example, 100 MPa or less, 50 MPa or less, 30 MPa or less, 10 MPa or less, or 5 MPa or less. The elastic modulus of the second inert member 50 is, for example, 0.01 to 100 MPa, 0.1 to 50 MPa, 0.1 to 30 MPa, 0.1 to 10 MPa, or 1 to 5 MPa.

Since the second inert members 50, 50a, and 50b are conductive, they can function as the negative electrode current collector 50. In addition, since the second inert members 50, 50a, and 50b have a lower elastic modulus than the negative electrode current collector 50, the change in volume of the negative electrode layer 20 during charging and discharging of the all-solid-state secondary battery 1 can be observed. can be accommodated effectively. As a result, the second inert members 50, 50a, and 50b effectively relieve the internal stress caused by the change in volume of the all-solid secondary battery 1 during charging and discharging of the all-solid secondary battery 1, thereby producing an all-solid secondary battery ( 1) The cycle characteristics can be improved.

For example, the thickness of the second inert member 50 is greater than the thickness of the first negative electrode active material layer 22. Since the second inert member 50 has a greater thickness than the first negative electrode active material layer 22, it can more effectively accommodate changes in the volume of the negative electrode layer 20 during charging and discharging. The thickness of the first negative electrode active material layer 22 is 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less of the thickness of the second inert member 50. The thickness of the first negative electrode active material layer 22 is, for example, 1% to 50%, 1% to 40%, 1% to 30%, 1% to 20%, or 1% of the thickness of the second inert member 50. % to 10%. The thickness of the second inert member 50 is, for example, 1 μm to 300 μm, 10 μm to 300 μm, 50 μm to 300 μm, or 100 μm to 200 μm. If the thickness of the second inert member 50 is too thin, it may be difficult to provide the intended effect, and if the thickness of the second inert member 50 is too thick, the energy density of the all-solid-state secondary battery 1 may decrease. there is. The shape of the second inert member 50 is not particularly limited and may be selected depending on the shape of the all-solid-state secondary battery 1. The second inert member 50 may be, for example, in the form of a sheet, a rod, or a gas cat.

The second inert member 50 may be disposed, for example, on one side or both sides of one all-solid-state secondary battery 1. The second inert member 50 may be disposed, for example, between a plurality of stacked all-solid-state secondary batteries 1 . The second inert member 50 may be disposed, for example, between each of the plurality of stacked all-solid-state secondary batteries 1, on the uppermost surface and/or on the lowermost surface.

The ratio of the volume of the all-solid-state secondary battery 1 before charging to the volume of the all-solid-state secondary battery 1 after charging, and the volume expansion rate, may be, for example, 15% or less, 10% or less, or 5% or less.

The increase in volume of the cathode layer 20 when charging the all-solid-state secondary battery 1 is offset by the decrease in volume of the anode layer 10, and the second inert member 50 reduces the volume change of the cathode layer 20. By housing, the change in volume of the all-solid-state secondary battery 1 before and after charging is alleviated.

The energy density per unit volume of the all-solid-state secondary battery 1 may be, for example, 500 to 900 Wh/L, 500 to 800 Wh/L, or 500 to 700 Wh/L. The energy density per unit weight of the all-solid-state secondary battery 1 may be, for example, 350 to 600 Wh/g, 350 to 580 Wh/g, 350 to 570 Wh/g, or 350 to 550 Wh/g. Since the all-solid-state secondary battery 1 has an energy density in this range, it can provide improved energy density compared to a conventional secondary battery.

[Solid electrolyte layer]

[Solid electrolyte layer: solid electrolyte]

Referring to Figures 1 to 5, the solid electrolyte layer 30 includes a solid electrolyte disposed between the anode layer 10 and the cathode layer 20.

The solid electrolyte may include, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof.

The solid electrolyte is, for example, a sulfide-based solid electrolyte. Sulfide-based solid electrolytes are, for example, Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiX, X is a halogen element, Li ₂ SP ₂ S ₅ -Li ₂ O, Li ₂ SP ₂ S ₅ -Li ₂ O -LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI , Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ SB ₂ S ₃ , Li ₂ SP ₂ S ₅ -Z _m S _n , m, n are positive numbers, Z is Ge, Zn or Ga. One, Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li _p MO _q , p, q are positive numbers, M is P, Si, Ge, B , Al, one of Ga In, Li _7-x PS _6-x Cl _x , 0(x(2, Li _7-x PS _6-x Br _x , 0(x(2, and Li _7-x PS _{6- x I ​ ​ ​} In addition, after this treatment, heat treatment can be performed. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may be, for example, one of the above-mentioned sulfide-based solid electrolyte materials. It may contain at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, the solid electrolyte may be a material containing Li ₂ SP ₂ S _5. Forming a solid electrolyte When using a sulfide-based solid electrolyte material containing Li ₂ SP ₂ S ₅ , the mixing molar ratio of Li ₂ S and P ₂ S ₅ is, for example, Li ₂ S: P ₂ S ₅ = 20: 80 to It ranges from 90:10, 25:75 to 90:10, 30:70 to 70:30, and 40:60 to 60:40.

The sulfide-based solid electrolyte may include, for example, an argyrodite type solid electrolyte represented by the following formula (1):

<Formula 1>

_Li ^{+ 12} _{- nx} A ^{n +}

where A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta, X is S, Se or Te, and Y is Cl, Br, I, F , CN, OCN, SCN, or N ₃ , and 1(n(5, 0(x(2. The sulfide-based solid electrolyte is, for example, Li _7-x PS _6-x Cl _x , 0≤x≤2, Argyrodite-type containing one or more selected from Li _7-x PS _6-x Br _x , 0≤x≤2, and Li _7-x PS _6-x I _x , 0≤x≤2 The sulfide-based solid electrolyte is, for example, an argyrodite-type containing one or more selected from Li ₆ PS ₅ Cl, Li ₆ PS ₅ Br, and Li ₆ PS ₅ I. ) may be a compound.

The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g/cc. Argyrodite-type solid electrolyte has a density of 1.5 g/cc or more, which reduces the internal resistance of the all-solid secondary battery and effectively suppresses penetration of the solid electrolyte layer by Li. can do.

Oxide-based solid electrolytes are, for example, Li _1+x+y Al _x Ti _2-x Si _y P _3-y O ₁₂ (0<x<2, 0≤y<3), BaTiO ₃ , Pb(Zr,Ti _{) O 3 ( PZT} ), _{Pb 1 - x} La PbTiO ₃ (PMN-PT), HfO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , Na ₂ O, MgO, NiO, CaO, BaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , SiO ₂ , Li ₃ PO ₄ , Li _x Ti _y (PO ₄ ) ₃ (0<x<2, 0<y<3), Li _x Al _y Ti _z (PO ₄ ) ₃ (0<x<2, 0 <y<1, 0<z<3), Li _1+x+y (Al, Ga) _x (Ti, Ge) _2-x Si _y P _3-y O ₁₂ (0≤x≤1 0≤y≤ _{1 ) , Li ​ ​ ​ ​ ​ ​ ​ 2} O ₅ -TiO ₂ -GeO ₂ , Li _3+x La ₃ M ₂ O ₁₂ (M = Te, Nb, or Zr, 0≤x≤10), or a combination thereof. Oxide-based solid electrolytes are manufactured by, for example, a sintering method.

Oxide-based solid electrolytes are, for example, Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO) and Li _3+x La ₃ Zr _2-a M _a O ₁₂ (M doped LLZO, M=Ga, W, Nb, Ta, or It is a garnet-type solid electrolyte selected from Al, 0<a<2, 0≤x≤10).

The polymer solid electrolyte may include, for example, a dry polymer electrolyte, a gel polymer electrolyte, or a combination thereof.

A dry polymer electrolyte is an electrolyte that is, for example, a mixture of a lithium salt and a polymer. A dry polyelectrolyte is, for example, a polyelectrolyte that does not contain a liquid electrolyte. Polymers contained in the dry polymer electrolyte are, for example, polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), and poly(styrene). -b-ethylene oxide) block copolymer (PS-PEO), poly(styrene-butadiene), poly(styrene-isoprene-styrene), poly(styrene-b-divinylbenzene) block copolymer, poly(styrene-ethylene) oxide-styrene) block copolymer, or a combination thereof.

A gel polymer electrolyte is an electrolyte that contains a liquid electrolyte and a polymer. Liquid electrolytes are, for example, mixtures of lithium salts and organic solvents. The polymer contained in the gel polymer electrolyte may be selected from polymers contained in the dry polymer electrolyte.

The solid electrolyte layer 30 may be impermeable to lithium polysulfide. Therefore, it is possible to block side reactions between lithium polysulfide and the negative electrode layer generated during charging and discharging of the sulfide-based positive electrode active material. Accordingly, the cycle characteristics of the all-solid-state secondary battery 1 including the solid electrolyte layer 30 can be improved.

[Solid electrolyte layer: binder]

The solid electrolyte layer 30 may include, for example, a binder. The binder included in the solid electrolyte layer 30 is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is limited to these. It does not work, and any binder used in the relevant technical field can be used. The binder of the solid electrolyte layer 30 may be the same as or different from the binder included in the positive electrode active material layer 12 and the negative electrode active material layer 22. The binder can be omitted.

The binder content included in the solid electrolyte layer 30 is 0.1 to 10 wt%, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 1 wt%, 0 to 0.5 wt, based on the total weight of the solid electrolyte layer 30. %, or 0 to 0.1 wt%.

This creative idea is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the creative idea, and the scope of the creative idea is not limited to these alone.

Example 1: Mono-cell all-solid-state secondary battery, sulfide-based cathode active material (Li ₂ S-CNF composite), flame retardant first inert member

(Cathode layer manufacturing)

SUS foil with a thickness of 10 μm was prepared as a negative electrode current collector. Additionally, carbon black (CB) particles with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as negative electrode active materials.

4 g of mixed powder of carbon black (CB) and silver (Ag) particles mixed at a weight ratio of 3:1 was placed in a container, and 4 g of NMP solution containing 7% by weight of PVDF binder (# 9300 from Kureha) was added to it. A mixed solution was prepared by addition. Next, NMP was added little by little to the mixed solution while stirring the mixed solution to prepare a slurry. The prepared slurry was applied to a SUS sheet using a bar coater and dried in air at 80°C for 10 minutes. The laminate thus obtained was vacuum dried at 40°C for 10 hours. The dried laminate was cold roll pressed at a pressure of 5 ton·f/cm ² at a speed of 5 m/sec to flatten the surface of the first negative electrode active material layer of the laminate. A cathode layer was produced through the above process. The thickness of the first negative electrode active material layer included in the negative electrode layer was about 15 ㎛. The areas of the first negative electrode active material layer and the negative electrode current collector were the same.

(Anode layer manufacturing)

Li2S-CNF composite was prepared as a positive electrode active material. The Li2S-CNF composite was prepared according to the method disclosed in Electrochimica Acta 230 (2017) 279-284, except that vapor grown carbon fiber (VGCF) was changed to carbon nanofiber (CNF). Li ₆ PS ₅ Cl (D50=3.0um, crystalline), an argyrodite type crystal, was prepared as a solid electrolyte. Ketjen black was prepared as a challenge. A positive electrode mixture was prepared by mixing these materials in a weight ratio of positive electrode active material: solid electrolyte: conductive agent = 40:50:10. The positive electrode mixture was obtained by dry mixing using a ball mill. The positive electrode mixture obtained by ball milling formed an ionic and electronic conductive network.

The positive electrode mixture was placed on one side of a positive electrode current collector made of aluminum foil or SUS coated with carbon on one side, and a positive electrode layer was manufactured by plate pressing at a pressure of 200 MPa for 10 minutes. The thickness of the anode layer was about 120 μm. The thickness of the positive electrode active material layer was about 100 ㎛, and the thickness of the carbon-coated aluminum foil was about 20 ㎛. The areas of the positive electrode active material layer and the positive electrode current collector were the same.

(Manufacture of solid electrolyte layer)

A mixture was prepared by adding 1.5 parts by weight of an acrylic binder based on 98.5 parts by weight of the solid electrolyte to Li ₆ PS ₅ Cl solid electrolyte (D ₅₀ = 3.0 (m, crystalline), which is an argyrodite type crystal. Octyl acetate was added to the prepared mixture and stirred to prepare a slurry. The prepared slurry was applied using a bar coater on a 15 (m) thick nonwoven fabric placed on a 75 (m) thick PET substrate. A laminate was obtained by applying and drying in air for 10 minutes at 80° C. The obtained laminate was vacuum dried for 2 hours at 80° C. A solid electrolyte layer was manufactured through the above process.

(Inert flame retardant member)

A slurry containing pulp fiber, glass fiber, aluminum hydroxide (Al(OH) ₃ ), an acrylic binder, and a solvent was molded into a gas cat shape and the solvent was removed to prepare a flame-retardant inert member. .

The weight ratio of pulp fiber, glass fiber, aluminum hydroxide (Al(OH) ₃ ), and acrylic binder was 20:8:70:2. The thickness of the inert member was 120 μm.

Before placing the prepared flame-retardant inert member on the solid electrolyte layer, it was subjected to vacuum heat treatment at 80° C. for 5 hours to remove moisture, etc. from the flame-retardant inert member.

(Manufacture of all-solid-state secondary batteries)

Referring to FIG. 1, a solid electrolyte layer was placed on the negative electrode layer so that the first negative electrode active material layer was in contact with the solid electrolyte layer, and a positive electrode layer was placed on the solid electrolyte layer. A laminate was prepared by placing a gas cat around the anode layer and in contact with the solid electrolyte layer. The thickness of the gas cat was about 120 ㎛. The above flame retardant inert member was used as a gas cat. A gas cat was placed in contact with the side of the anode layer and the solid electrolyte layer. The anode layer was placed in the center of the solid electrolyte layer, and the gas cat surrounded the anode layer and extended to the end of the solid electrolyte layer. The area of the anode layer was about 90% of the area of the solid electrolyte layer, and a gas cat was placed over the remaining 10% of the area of the solid electrolyte layer where the anode layer was not placed.

The prepared laminate was plate pressed at 85 ^o C and a pressure of 500 MPa for 30 min. Through this pressure treatment, the solid electrolyte layer is sintered and battery characteristics are improved. The thickness of the sintered solid electrolyte layer was about 45 ㎛. The density of Li ₆ PS ₅ Cl solid electrolyte, which is an argyrodite type crystal, included in the sintered solid electrolyte layer was 1.6 g/cc. The area of the solid electrolyte layer was the same as the area of the cathode layer.

The pressurized laminate was placed in a pouch and vacuum sealed to produce an all-solid-state secondary battery. Parts of the positive electrode current collector and negative electrode current collector were extended outside the sealed battery and used as the positive electrode layer terminal and the negative electrode layer terminal.

Example 2: Sulfide-based positive electrode active material (Li ₂ S-CNF composite), flame retardant first inert member, conductive flame retardant second inert member

Before putting the pressurized laminate in a pouch, a conductive flame retardant member in the form of a sheet having the same area and shape as the laminate was additionally placed on the negative electrode current collector of the pressurized laminate and vacuum sealed to manufacture an all-solid-state secondary battery. An all-solid-state secondary battery was manufactured in the same manner as in Example 1, except that. The conductive flame retardant inert member sheet was prepared by the following method. The conductive flame retardant inert member sheet can act as an elastic sheet.

(conductive flame retardant inert member)

A slurry mixed with pulp fiber, glass fiber, aluminum hydroxide (Al(OH) ₃ ), acrylic binder, conductive material (Denka black), and solvent is formed into a sheet and then dried. A flame retardant inert member was manufactured. The weight ratio of pulp fiber, glass fiber, aluminum hydroxide (Al(OH) ₃ ), acrylic binder, and conductive material was 20:8:50:2:20. The thickness of the conductive flame retardant inert member was 120 μm. The manufactured conductive flame retardant inert member was vacuum heat treated at 80° C. for 5 hours before being placed on the negative electrode current collector to remove moisture, etc. from the conductive flame retardant inert member.

Example 3: Sulfide-based positive electrode active material (Li ₂ S-CNF composite), non-flammable first inert member

An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that the flame-retardant inert member was changed to a non-flammable inert member.

The non-flammable inert member contained pulp fibers and an acrylic binder at a weight ratio of 98:2, and did not contain glass fibers or Al(OH) ₃ . The thickness of the non-flammable inert member was 120 μm.

Example 4: Sulfide-based positive electrode active material (Li ₂ S-C-Li ₆ P.S. ₅ Cl complex), flame retardant first inert member

An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that Li ₂ SC-Li ₆ PS ₅ Cl composite was used as the positive electrode active material instead of Li2S-VGCF composite.

The Li ₂ SC-Li ₆ PS ₅ Cl complex was manufactured by Nano Lett. It was prepared according to the method disclosed in 2016, 16, 7, 4521??4527.

Example 5: Sulfide-based positive electrode active material (Li ₂ S-C composite), first negative electrode active material layer (Ag-supported carbon), flame retardant first inert member, conductive flame retardant second inert member

An all-solid-state secondary battery was manufactured in the same manner as in Example 2, except that carbon black supported with silver particles below was used as the negative electrode active material instead of a mixture of carbon black and silver particles.

(Production of silver particle-supported carbon black)

Carbon black was dispersed in a 1.0 M sulfuric acid solution and stirred for 2 hours, then filtered and dried to prepare acid-treated carbon black.

10 g of acid-treated carbon black was added to a mixed solvent of 1500 g of distilled water, 1500 g of ethanol, and 30 g of glycerol and stirred. Then, 2 g of AgNO ₃ was added and stirred to prepare a mixed solution. The particle size of carbon black was 80 nm. A reducing agent was added to the mixed solution, and silver ions were reduced and supported on carbon black. Carbon black carrying silver-containing particles was filtered, washed, and dried to prepare a composite anode active material. As a result of scanning electron microscopy and XPS measurement, it was confirmed that a plurality of silver-containing particles were supported on the carbon black particles. The silver-containing particles were silver particles, silver oxide (Ag ₂ O) particles, and composite particles of silver (Ag) and silver oxide (Ag ₂ O). The content of silver-containing particles contained in the composite anode active material was 5 wt%. The average particle diameter of the silver particles was 10 nm.

Example 6: Sulfide-based positive electrode active material (Li ₂ S-C-LiI complex), flame retardant first inert member

An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that Li ₂ SC-LiI composite was used instead of Li 2 S-VGCF composite as the positive electrode active material.

Li ₂ SC-LiI complex is Nano Lett, except that Li ₆ PS ₅ Cl is changed to LiI. It was prepared according to the method disclosed in 2016, 16, 7, 4521??4527.

Comparative Example 1: Sulfide-based positive electrode active material, no inert member used (free)

An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a flame-retardant inert member (i.e., gasket) was not used when manufacturing the all-solid-state secondary battery.

Comparative Example 2: Oxide-based positive electrode active material, flame retardant first inert member

An all-solid-state secondary battery was manufactured in the same manner as Example 1, except that a positive electrode containing lithium transition metal oxide was used instead of a positive electrode containing Li2S positive electrode active material.

A positive electrode containing lithium transition metal oxide was prepared by the following method.

(Anode layer manufacturing)

LiNi _0.8 Co _0.15 Al _0.05 O ₂ (NCA) coated with Li ₂ O-ZrO ₂ (LZO) was prepared as a positive electrode active material. The LZO-coated positive electrode active material was manufactured according to the method disclosed in Korean Patent Publication No. 10-2016-0064942. Li ₆ PS ₅ Cl (D50=0.5um, crystalline), an argyrodite type crystal, was prepared as a solid electrolyte. A polytetrafluoroethylene (PTFE) binder (Teflon binder from DuPont) was prepared as a binder. Carbon nanofibers (CNF) were prepared as a conductive agent. These materials were mixed with xylene solvent in a weight ratio of cathode active material: solid electrolyte: conductive agent: binder = 84:11.5:3:1.5. The mixture was molded into a sheet and vacuum dried at 40°C for 8 hours. A positive electrode sheet was manufactured. The positive electrode sheet was placed on one side of a positive electrode current collector made of aluminum foil coated with carbon on one side, and the positive electrode layer was manufactured by plate pressing at a pressure of 200 MPa for 10 minutes. The thickness of the anode layer was about 120 μm. The thickness of the positive electrode active material layer was about 100 ㎛, and the thickness of the carbon-coated aluminum foil was about 20 ㎛. The areas of the positive electrode active material layer and the positive electrode current collector were the same.

Example 7: One bi-cell all-solid-state secondary battery, sulfide-based cathode active material (Li ₂ S-CNF composite), flame retardant first inert member

(Manufacture of bi-cell all-solid-state secondary battery)

The positive electrode layer was prepared in the same manner as Example 1, except that the positive electrode active material layer was prepared on both sides of the positive electrode current collector.

The total thickness of the anode layer was about 220 μm. The thickness of the positive electrode active material layer was about 100 ㎛, and the thickness of the carbon-coated aluminum foil was about 20 ㎛.

Two cathode layers, solid electrolyte layers, and flame retardant inert members were prepared in the same manner as in Example 1.

Referring to FIG. 3, a solid electrolyte layer was placed on the negative electrode layer so that the first negative electrode active material layer was in contact with the solid electrolyte layer, and a positive electrode layer was placed on the solid electrolyte layer. The positive electrode layer had a structure in which a positive electrode active material layer was disposed on both sides of the positive electrode current collector. A gas cat was placed around the anode layer, surrounding the anode layer and in contact with the solid electrolyte layer. The thickness of the gas cat was approximately 220 ㎛. For example, the gasket may have a structure in which two gaskets with a thickness of 110 ㎛ are stacked, or a gasket with a thickness of 220 ㎛ may be one sheet. The above flame retardant inert member was used as a gas cat.

A gas cat was placed in contact with the side of the anode layer and the solid electrolyte layer. The anode layer was placed in the center of the solid electrolyte layer, and the gas cat surrounded the anode layer and extended to the end of the solid electrolyte layer. The area of the anode layer was about 90% of the area of the solid electrolyte layer, and a gas cat was placed on the entire remaining 10% of the area of the solid electrolyte layer where the anode layer was not placed. A laminate was prepared by placing a solid electrolyte layer on the anode layer and the gas cat, and placing a cathode layer on the solid electrolyte layer.

The prepared laminate was plate pressed at 85 ^o C and a pressure of 500 MPa for 30 min. Through this pressure treatment, the solid electrolyte layer is sintered and battery characteristics are improved. The thickness of one sintered solid electrolyte layer was about 45 ㎛. The density of Li ₆ PS ₅ Cl solid electrolyte, which is an argyrodite type crystal, included in the sintered solid electrolyte layer was 1.6 g/cc. The area of the solid electrolyte layer was the same as the area of the cathode layer.

The pressurized laminate was placed in a pouch and vacuum sealed to produce an all-solid-state secondary battery. Parts of the positive electrode current collector and negative electrode current collector were extended outside the sealed battery and used as the positive electrode layer terminal and the negative electrode layer terminal.

Example 8: Sulfide-based positive electrode active material (Li ₂ S-CNF composite), flame retardant first inert member, conductive flame retardant second inert member

Before putting the pressurized laminate in a pouch, a conductive flame-retardant inert member in the form of a sheet having the same area and shape as the laminate is additionally placed on one side of the pressurized laminate and the other side opposite to the one side, and vacuum-sealed to form an all-solid form. An all-solid-state secondary battery was manufactured in the same manner as Example 7, except that the secondary battery was manufactured. The conductive flame retardant inert member was prepared in the same manner as Example 2.

Evaluation Example 1: Calculation of volume change rate when charging an all-solid-state secondary battery

[Al current collector (10 ㎛) / LiNi _0.8 Co _0.15 Al _0.05 O ₂ (NCA) positive electrode active material layer (100 ㎛) / Li ₆ PS ₅ Cl solid electrolyte layer (32 ㎛) / first negative electrode active material layer (7 ㎛) /SUS current collector (10 ㎛)] The initial first volume of the first all-solid secondary battery of the structure, and the first all-solid lithium metal layer with a thickness of 30 ㎛ deposited between the first negative electrode active material layer and the SUS current collector by charging. From the second volume after charging of the secondary battery, the change in volume of the first all-solid-state secondary battery during charging was calculated and shown in Table 1 below. It was assumed that there was no change in the thickness of the NCA cathode active material layer before and after charging.

[Al current collector (10 ㎛)/Li2S (60wt%)-carbon (40wt%) positive electrode active material layer (50 ㎛)/Li ₆ PS ₅ Cl solid electrolyte layer (32 ㎛)/first negative electrode active material layer (7 ㎛) /SUS current collector (10 ㎛)] The initial first volume of the second all-solid secondary battery of the structure, and the second all-solid material in which a 30 ㎛ thick lithium metal layer is deposited between the first negative electrode active material layer and the SUS current collector by charging. From the second volume after charging of the secondary battery, the change in volume of the second all-solid-state secondary battery during charging was calculated and shown in Table 1 below. It was assumed that the thickness of Li2S (60wt%)-carbon (40wt%) after charging decreased by 15 ㎛ from 50 ㎛ to 35 ㎛. It was assumed that all lithium contained in Li2S moves to the cathode. It was assumed that the positive electrode active material layer of the second all-solid-state secondary battery consisted only of Li2S and carbon. It was assumed that the positive electrode active material layer of the first all-solid-state secondary battery was made of NCA.

Initial cell thickness
[㎛] thickness change
[㎛] Volume expansion rate
[%] 1st all-solid-state secondary battery
(NCA anode) 159 30 18.9 2nd all-solid secondary battery
(Li2S anode) 109 15 13.9

As shown in Table 1, in the second all-solid-state secondary battery having a positive electrode active material layer containing Li2S, the volume of the negative electrode layer increases due to precipitation of the lithium metal layer, but the volume of the positive electrode active material layer decreases, resulting in an all-solid secondary battery. The overall volume increase of the secondary battery was suppressed. On the other hand, in the first all-solid-state secondary battery equipped with a cathode active material layer containing lithium transition metal oxide, the volume change of the cathode active material layer was minimal, so the overall volume of the all-solid-state secondary battery due to precipitation of the lithium metal layer was significant. .

Therefore, it was confirmed that the second all-solid-state secondary battery can effectively prevent deterioration, such as cracks, of the all-solid-state secondary battery by mitigating the volume change that occurs during charging and discharging of the all-solid-state secondary battery by the first all-solid-state secondary battery. did.

Evaluation Example 2: Charge/discharge test

The charge/discharge characteristics of the all-solid-state secondary batteries prepared in Examples 1 to 8 and Comparative Example 1 were evaluated by the following charge/discharge test. The charge/discharge test was performed by placing the all-solid-state secondary battery in a constant temperature bath at 45°C.

The first cycle was charging for 12.5 hours at a constant current of 0.1C until the battery voltage reached 2.5 V to 2.8 V. Subsequently, discharge was performed for 12.5 hours at a constant current of 0.1C until the battery voltage reached 0.5V.

The second cycle was charging for 12.5 hours at a constant current of 0.33C until the battery voltage reached 2.5 V to 2.8 V. Subsequently, discharge was performed for 12.5 hours at a constant current of 0.33C until the battery voltage reached 0.5V.

The third cycle was charging for 12.5 hours at a constant current of 1.0C until the battery voltage reached 2.5 V to 2.8 V. Subsequently, discharge was performed for 12.5 hours at a constant current of 1.0C until the battery voltage reached 0.5V.

The charge/discharge characteristics of the all-solid-state secondary battery prepared in Comparative Example 2 were evaluated by the following charge/discharge test. The charge/discharge test was performed by placing the all-solid-state secondary battery in a constant temperature bath at 45°C.

The first cycle was charging for 12.5 hours at a constant current of 0.1C until the battery voltage reached 3.9V to 4.25V. Subsequently, discharge was performed for 12.5 hours at a constant current of 0.1C until the battery voltage reached 2.5V.

The second cycle was charging for 12.5 hours at a constant current of 0.33C until the battery voltage was 3.9V to 4.25V. Subsequently, discharge was performed for 12.5 hours at a constant current of 0.33C until the battery voltage reached 2.5V.

The third cycle was charging for 12.5 hours at a constant current of 1.0C until the battery voltage reached 3.9V to 4.25V. Subsequently, discharge was performed for 12.5 hours at a constant current of 1.0C until the battery voltage reached 2.5V.

The presence of a short circuit, initial discharge capacity, and high rate characteristics during the charge/discharge process up to the third cycle are shown in Table 2 below.

Whether or not a short circuit occurs is ○ if the short circuit occurs before the first cycle is completed, △ if the short circuit occurs in the second cycle, and × if the short circuit does not occur until the third cycle is completed.

Short circuit or not Example 1 (mono-cell/Li2S-C composite/flame retardant anode gasket) × Example 2 (mono-cell/Li2S-C composite/flame retardant anode gasket/Ag+C mixture/cathode sheet) × Example 3 (mono-cell/Li2S-C composite/non-flammable anode gasket) × Example 4 (mono-cell/Li2S-C-Li6PS5Cl composite/flame retardant anode gasket) × Example 5 ((mono-cell/Li2S-C composite/flame retardant anode gasket/Ag supported C/cathode sheet) × Example 6 (mono-cell/Li2S-C-LiI composite/flame retardant anode gasket) × Example 7 (bi-cell/Li2S-C composite/flame retardant anode gasket) × Example 8 (bi-cell/Li2S-C composite/flame retardant anode gasket/cathode sheet) × Comparative Example 1 (mono-cell/Li2S-C composite/-) ○ Comparative Example 2 (mono-cell/NCA/flame retardant anode gasket) ×

As shown in Table 2, the all-solid-state secondary batteries of Examples 1 to 8 showed improved cycle characteristics compared to the all-solid-state secondary battery of Comparative Example 1.

Evaluation Example 3: High temperature lifespan characteristics test

The charge/discharge characteristics of the all-solid-state secondary batteries prepared in Examples 1 to 8 and Comparative Example 1 were evaluated by the following charge/discharge test. The charge/discharge test was performed by placing the all-solid-state secondary battery in a constant temperature bath at 45°C.

The first cycle was charging for 12.5 hours at a constant current of 0.6 mA/cm ² until the battery voltage was 2.5 V to 2.8 V. Subsequently, discharge was performed for 12.5 hours at a constant current of 0.6 mA/cm ² until the battery voltage reached 0.5V.

The charge/discharge characteristics of the all-solid-state secondary battery prepared in Comparative Example 2 were evaluated by the following charge/discharge test. The charge/discharge test was performed by placing the all-solid-state secondary battery in a constant temperature bath at 45°C.

The first cycle was charging for 12.5 hours at a constant current of 0.6 mA/cm ² until the battery voltage was 3.9V to 4.25V. Subsequently, discharge was performed for 12.5 hours at a constant current of 0.6 mA/cm ² until the battery voltage reached 2.5V.

The discharge capacity of the first cycle was taken as the standard capacity. After the second cycle, charging and discharging were performed up to 150 cycles under the same conditions as the first cycle. The measurement results are shown in Table 3 below.

It was considered to have superior lifespan characteristics as the number of cycles required for the discharge capacity to decrease to 95% of the standard capacity after the second cycle increased.

In the all-solid-state secondary battery of Comparative Example 1, a short circuit occurred before the first cycle was completed, making it impossible to measure lifespan characteristics.

number of cycles
[episode] Example 1 (mono-cell/Li2S-C composite/flame retardant anode gasket) 301 Example 2 (mono-cell/Li2S-C composite/flame retardant anode gasket/Ag+C mixture/cathode sheet) 415 Example 3 (mono-cell/Li2S-C composite/non-flammable anode gasket) 220 Example 4 (mono-cell/Li2S-C-Li6PS5Cl composite/flame retardant anode gasket) 302 Example 5 (mono-cell/Li2S-C composite/flame retardant anode gasket/Ag supported C/cathode sheet) 580 Example 6 (mono-cell/Li2S-C-LiI composite/flame retardant anode gasket) 820 Example 7 (bi-cell/Li2S-C composite/flame retardant anode gasket) 450 Example 8 (bi-cell/Li2S-C composite/flame retardant anode gasket/cathode sheet) 510 Comparative Example 1 (mono-cell/Li2S-C composite/-) not measurable Comparative Example 2 (mono-cell/NCA/flame retardant anode gasket) 200

As shown in Table 3, the lifespan characteristics of the all-solid-state secondary batteries of Examples 1 to 8 were improved compared to the all-solid-state secondary batteries of Comparative Example 2.

The all-solid-state secondary battery of Example 6 contained Li2S-C-LiI complex as a positive electrode active material, and thus had better lifespan characteristics compared to Example 1 containing Li2S-C complex and Example 4 containing Li2S-C-Li6PS5Cl complex. improved.

The all-solid-state secondary batteries of Examples 1 to 6 containing Li2S were determined to have improved lifespan characteristics due to reduced volume changes during charging and discharging compared to the all-solid-state secondary batteries of Comparative Example 2 containing an oxide-based positive electrode active material.

The all-solid-state secondary batteries of Examples 7 and 8 have a bi-cell structure in which the components are arranged symmetrically, thereby reducing the volume change during charge and discharge compared to the all-solid-state secondary batteries of Examples 1 to 4, which have a monocell structure. It was judged to have improved lifespan characteristics through effective mitigation.

The all-solid-state secondary batteries of Examples 1, 2, and 4 were determined to have improved lifespan characteristics by including a flame-retardant inert member compared to Example 3, which included a non-flammable inert member.

The all-solid-state secondary battery of Example 8 has improved lifespan characteristics compared to the all-solid-state secondary battery of Example 7 because the second inert member is additionally disposed on the negative electrode current collector, effectively relieving the stress of the negative electrode layer where volume changes are concentrated. It was judged to have. The all-solid-state secondary battery of Example 2 was also judged to have improved lifespan characteristics compared to Examples 1, 3, and 4 for the same reason. The all-solid-state secondary battery of Example 5 was judged to have improved lifespan characteristics compared to Example 2, which was a simple mixture of silver particles and carbon particles, by using carbon loaded with silver particles.

As described above, the all-solid-state secondary battery according to this embodiment can be applied to various portable devices, vehicles, etc.

Although an exemplary embodiment has been described in detail with reference to the attached drawings, the creative idea is not limited to this example. It is obvious that anyone with ordinary knowledge in the technical field to which this creative idea belongs can derive various examples of changes or modifications within the scope of the technical idea described in the patent claims, and these are naturally within the technical scope of this creative idea. belongs to

1 All-solid-state secondary battery 10 Anode layer
11 Positive electrode current collector 12 Positive electrode active material layer
20 cathode layer 21 cathode current collector
22 First negative electrode active material layer 30 Solid electrolyte layer
40 First inert member
50 Second inert member

Claims (20)

anode layer; cathode layer; And a solid electrolyte layer disposed between the anode layer and the cathode layer,
The positive electrode layer includes a positive electrode current collector and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector,
The positive electrode active material layer includes a lithium-containing sulfide-based positive electrode active material, and the lithium-containing sulfide-based positive electrode active material includes Li ₂ S, Li ₂ S-containing composite, or a combination thereof,
comprising a first inactive member disposed on one side of the anode layer,
The negative electrode layer includes a negative electrode current collector and a first negative electrode active material layer disposed on one surface of the negative electrode current collector,
The ratio (B/A) of the initial charge capacity (B) of the first negative electrode active material layer and the initial charge capacity (A) of the positive electrode active material layer is 0.005 to 0.45,
The initial charging capacity of the positive electrode active material layer is determined from the maximum charging voltage for Li/Li ⁺ from the first open circuit voltage (1 ^st open circuit voltage),
The initial charge capacity of the first negative active material layer is determined at 0.01 V for Li/Li ⁺ from the ^2nd open circuit voltage. The method of claim 1, wherein the Li2S-containing composite is a composite of Li2S and carbon, a composite of Li2S, carbon, and a solid electrolyte, a composite of Li2S and a solid electrolyte, a composite of Li2S, carbon, and a lithium salt, a composite of Li2S and a lithium salt, and a composite of Li2S and a metal. An all-solid-state secondary battery comprising a composite of carbide, a composite of Li2S, carbon, and metal carbide, a composite of Li2S and metal nitride, a composite of Li2S, carbon, and metal nitride, or a combination thereof. The all-solid-state secondary battery of claim 1, wherein the positive electrode active material layer further includes FeS ₂ , VS ₂ , NaS, MnS, FeS, NiS, CuS, or a combination thereof. The method of claim 1, wherein the positive electrode active material layer further includes one or more selected from a solid electrolyte, a conductive material, and a binder,
An all-solid-state secondary battery, wherein the solid electrolyte includes a sulfide-based solid electrolyte, and the conductive material includes a carbon-based conductive material. The method of claim 1, wherein the first inert member surrounds a side of the anode layer and is in contact with the solid electrolyte layer,
The first inert member extends from one side of the positive electrode layer along the surface of the solid electrolyte layer to the distal end of the solid electrolyte layer,
The area of the positive electrode active is smaller than the area of the solid electrolyte layer in contact with the positive electrode layer,
An all-solid-state secondary battery, wherein the first inert member is disposed surrounding a side of the positive electrode layer to compensate for an area difference between the positive electrode layer and the solid electrolyte layer. The method of claim 1, wherein the thickness of the first inert member is greater than the thickness of the first negative electrode active material layer,
The thickness of the first negative electrode active material layer is 50% or less of the thickness of the first inert member,
An all-solid-state secondary battery in which a negative electrode active material layer is absent on the other side of the negative electrode current collector. The method of claim 1, wherein the positive electrode layer includes a positive electrode current collector and a first positive electrode active material layer and a second positive electrode active material layer respectively disposed on both sides of the positive electrode current collector,
The solid electrolyte layer includes a first solid electrolyte layer and a second solid electrolyte layer in contact with the first positive electrode active material layer and the second positive electrode active material layer, respectively,
The cathode layer includes a first cathode layer and a second cathode layer in contact with the first solid electrolyte layer and the second solid electrolyte layer, respectively,
An all-solid-state secondary battery, wherein the inert member is disposed between the first and second solid electrolyte layers opposing each other and surrounding a side of the positive electrode layer. The all-solid-state secondary battery of claim 1, wherein the first inert member includes a flame-retardant inert member, and the flame-retardant inert member includes a matrix and a filler. 9. The method of claim 8, wherein the matrix includes a substrate and reinforcement,
The substrate includes a first fibrous material, the first fibrous material is an insulating material, and the first fibrous material includes one or more selected from pulp fibers, insulating polymer fibers, and ion conductive polymer fibers,
An all-solid-state secondary battery, wherein the reinforcing material includes a second fibrous material, the second fibrous material is a flame retardant material, and the second fibrous material includes one or more selected from glass fiber and ceramic fiber.
The filler is a moisture getter, and the filler contains a metal hydroxide,
The metal hydroxide is one or more selected from Mg(OH) ₂ , Fe(OH) ₃ , Sb(OH) ₃ , Sn(OH) ₄ , TI(OH) ₃ , Zr(OH) ₄ , and Al(OH) ₃ . An all-solid secondary battery including. The method of claim 1, wherein the first negative electrode active material layer includes a negative electrode active material and a binder,
An all-solid-state secondary battery in which the negative electrode active material has a particle form and an average particle diameter of the negative electrode active material is 4 ㎛ or less. The method of claim 10, wherein the negative electrode active material includes at least one selected from carbon-based negative electrode active materials and metal or metalloid negative electrode active materials,
The carbon-based negative electrode active material includes amorphous carbon, crystalline carbon, porous carbon, or a combination thereof,
The metal or metalloid negative electrode active material is gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), zinc ( Zn) or a combination thereof, an all-solid secondary battery. The method of claim 10, wherein the negative electrode active material includes a mixture of first particles made of amorphous carbon and second particles made of metal or metalloid,
The all-solid-state secondary battery wherein the content of the second particles is 1 to 60 wt% based on the total weight of the mixture. The all-solid-state secondary battery of claim 1, wherein the first negative electrode active material layer further includes a solid electrolyte. The method of claim 1, wherein the negative electrode active material includes: a carbon-based support; and a gold-based negative electrode active material supported on the carbon-based support,
The metal-based negative electrode active material includes metal, metal oxide, a complex of metal and metal oxide, or a combination thereof,
The metal-based negative electrode active material has a particle shape, and the particle size of the metal-based negative electrode active material is 1 nm to 200 nm,
The carbon-based support has a particle shape, the particle size of the carbonaceous material is 10 nm to 2 ㎛, and after the all-solid-state battery is charged, the second negative electrode current collector is disposed between the negative electrode current collector and the first negative electrode active material layer. Further comprising a negative electrode active material layer,
The second negative electrode active material layer is a metal layer, and the metal layer includes lithium or a lithium alloy. The method of claim 1, further comprising a second inert member disposed on the other side of the negative electrode current collector,
An all-solid-state secondary battery, wherein the second inert member includes a conductive flame retardant inert member. According to claim 15,
The elastic modulus (Young's modulus) of the second inert member is smaller than the elastic modulus of the negative electrode current collector,
The elastic modulus of the second inert member is 100 MPa or less,
The thickness of the second inert member is greater than the thickness of the first negative electrode active material layer,
An all-solid-state secondary battery, wherein the thickness of the first negative electrode active material layer is 50% or less of the thickness of the second inert member. The method of claim 1, wherein the volume expansion rate of the all-solid-state secondary battery after charging is 15% or less,
An all-solid-state secondary battery having an energy density of 500 to 900 Wh/L or 350 to 600 Wh/kg. The method of claim 1, wherein the solid electrolyte layer includes a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a polymer solid electrolyte, or a combination thereof,
The polymer solid electrolyte includes a dry polymer electrolyte, a gel polymer electrolyte, or a combination thereof,
An all-solid secondary battery in which the solid electrolyte layer is impermeable to lithium polysulfide. The method of _claim 1, wherein the sulfide _- based solid electrolyte _{is Li 2} SP ₂ S _{5 , Li 2 SP 2 S 5} -LiX, -Li ₂ O-LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ SB ₂ S ₃ , Li ₂ SP ₂ S ₅ -Z _m S _n , m, n are positive numbers, Z is Ge, either Zn or Ga, Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li _p MO _q , p, q are positive numbers, M is P, Si , one of Ge, B, Al, Ga In, Li _7-x PS _6-x Cl _x , 0≤x≤2, Li _7-x PS _6-x Br _x , 0≤x≤2, and Li _{7- x} PS _6-x I _x , 0≤x≤2, one or more selected from
The sulfide-based solid electrolyte is an argyrodite-type solid electrolyte containing at least one selected from Li ₆ PS ₅ Cl, Li ₆ PS ₅ Br and Li ₆ PS ₅ I,
An all-solid-state secondary battery wherein the argyrodite-type solid electrolyte has a density of 1.5 to 2.0 g/cc. The method of claim 1, wherein at least one of the positive electrode current collector and the negative electrode current collector includes a base film and a metal layer disposed on one or both sides of the base film,
The base film includes a polymer, and the polymer is polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. Includes,
The metal layer is made of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), and aluminum (Al). , an all-solid-state secondary battery containing germanium (Ge), lithium (Li), or alloys thereof.

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