KR20230102940A - Sulfide-based solid electrolyte, all solid secondary battery comprising sulfide-based solid electrolyte, and preparation method thereof - Google Patents

Abstract

A sulfide-based solid electrolyte for an all-solid-state battery, which has an Argyrodite-type crystal structure and includes a compound represented by Formula 1 below, has an average particle diameter of 0.1 μm to 10 μm, and has a 0.01 mS at 25 ° C. It has an ion conductivity of / cm to 3 mS / cm, and in the XRD spectrum of the sulfide-based solid electrolyte, the intensity (Ia) of the first peak at the diffraction angle 2θ = 23 ° ± 0.5 ° and the diffraction angle 2θ = A sulfide-based solid electrolyte for an all-solid-state battery having a ratio (ratio, Ia/Ib) of the intensity (Ib) of the second peak at 25.5°±0.5° of greater than 0 to less than 1, an all-solid secondary battery including the same, and a sulfide-based solid A method for preparing the electrolyte is presented:
<Formula 1>
Li _a M1 _x PS _y M2 _z M3 _w
In the above formula,
M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,
M2 is one or more elements selected from group 17 of the periodic table,
M3 is SO _n ,
4≤a≤8, 0≤x<1, 3≤y≤7, 0<z≤2, 0≤w<2, and 1.5≤n≤5.

Description

Sulfide-based solid electrolyte for all-solid-state battery, all-solid-state secondary battery comprising the same, and preparation method thereof

It relates to a sulfide-based solid electrolyte for an all-solid-state battery, an all-solid-state secondary battery including the same, and a method for manufacturing the same.

An all-solid-state secondary battery includes a solid electrolyte as an electrolyte. All-solid-state secondary batteries have excellent stability because they do not contain flammable organic solvents.

Conventional solid electrolyte materials are pulverized and used to have an average particle diameter within a certain range in order to be applied to all-solid-state secondary batteries, so a lot of energy is consumed.

One aspect is to provide a sulfide-based solid electrolyte having a reduced particle size and excellent lithium ion conductivity at the same time.

Another aspect is to provide an all-solid-state secondary battery including the sulfide-based solid electrolyte.

Another aspect is to provide a method for preparing the sulfide-based solid electrolyte.

according to one side

As a sulfide-based solid electrolyte for an all-solid-state battery,

It includes a compound having an Argyrodite-type crystal structure and represented by Formula 1 below,

The average particle diameter is 0.1 μm to 10 μm,

It has an ion conductivity of 0.01 mS / cm to 3 mS / cm at 25 ° C,

In the XRD spectrum of the sulfide-based solid electrolyte, the ratio of the intensity (Ia) of the first peak at the diffraction angle 2θ = 23° ± 0.5° and the intensity (Ib) of the second peak at the diffraction angle 2θ = 25.5° ± 0.5° A sulfide-based solid electrolyte for an all-solid-state battery in which (ratio, Ia/Ib) is greater than 0 and less than or equal to 1 is provided:

<Formula 1>

Li _a M1 _x PS _y M2 _z M3 _w

In the above formula,

M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,

M2 is one or more elements selected from group 17 of the periodic table,

M3 is SO _n ,

4≤a≤8, 0≤x<1, 3≤y≤7, 0<z≤2, 0≤w<2, and 1.5≤n≤5.

according to the other side

An all-solid-state secondary battery including the sulfide-based solid electrolyte according to the above is provided.

according to another aspect

A cathode layer including a cathode active material layer;

A negative electrode layer including a negative electrode active material layer; and

A solid electrolyte layer disposed between the anode layer and the cathode layer,

An all-solid-state secondary battery including at least one of the positive electrode active material layer and the solid electrolyte layer is provided with the sulfide-based solid electrolyte according to the above.

according to another aspect

providing a first sulfide-based solid electrolyte;

preparing a first solution by dissolving the first sulfide-based solid electrolyte in an organic solvent;

preparing a dried product by drying the first solution; and

Preparing a second sulfide-based solid electrolyte by heat-treating the dried product;

The average particle diameter of the second sulfide-based solid electrolyte is smaller than the average particle diameter of the first sulfide-based solid electrolyte,

The second sulfide-based solid electrolyte,

It includes a compound having an Argyrodite-type crystal structure and represented by Formula 1 below,

The average particle diameter is 0.1 μm to 10 μm,

It has an ion conductivity of 0.01 mS / cm to 3 mS / cm at 25 ° C,

In the XRD spectrum of the sulfide-based solid electrolyte, the ratio of the intensity (Ia) of the first peak at the diffraction angle 2θ = 23° ± 0.5° and the intensity (Ib) of the second peak at the diffraction angle 2θ = 25.5° ± 0.5° A method for producing a sulfide-based solid electrolyte for an all-solid-state battery in which (ratio, Ia/Ib) is greater than 0 and less than or equal to 1 is provided:

<Formula 1>

Li _a M1 _x PS _y M2 _z M3 _w

In the above formula,

M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,

M2 is one or more elements selected from group 17 of the periodic table,

M3 is SO _n ,

4≤a≤8, 0≤x<1, 3≤y≤7, 0<z≤2, 0≤w<2, and 1.5≤n≤5.

According to one aspect, an all-solid-state secondary battery having improved cycle characteristics is provided by including a sulfide-based solid electrolyte having a reduced average particle diameter and excellent lithium ion conductivity.

1a to 1b are powder XRD spectra of dried materials obtained in the process of preparing sulfide-based solid electrolytes in Examples 1 to 2 and Comparative Examples 1 to 4.
2a to 2b are powder XRD spectra of sulfide-based solid electrolytes prepared in Examples 1 to 2 and Comparative Examples 1 to 5;
3A to 3D are scanning electron microscope images of the sulfide-based solid electrolyte and the crude sulfide-based solid electrolyte prepared in Examples 1, 2, and Comparative Example 3;
4a to 4h are external images of a first solution obtained in the process of preparing a sulfide-based solid electrolyte in Examples 1 to 2 and Comparative Examples 1 to 6;
5 is a schematic diagram of an embodiment of an all-solid-state secondary battery.
6 is a schematic diagram of another embodiment of an all-solid-state secondary battery.
7 is a schematic diagram of another embodiment of an all-solid-state secondary battery.

Various implementations are shown in the accompanying drawings. However, this inventive idea may be embodied in many different forms and should not be construed as being limited to the implementations described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive idea to those skilled in the art. Like reference numerals designate like components.

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 another element may be interposed therebetween. In contrast, when an element is referred to as being “directly on” another element, there is no intervening element between them.

Although the terms “first,” “second,” “third,” and the like may be used herein to describe various components, components, regions, layers, and/or regions, these components, components, regions, A layer and/or zone should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or region from another element, component, region, layer or region. Thus, a first component, component, region, layer or region described below could be termed a second component, component, region, layer or region without departing from the teachings herein.

Terms used in this specification are for describing only specific implementations and are not intended to limit the present inventive idea. The singular forms as used herein are intended to include the plural forms including “at least one” unless the context 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. The terms "comprises" and/or "comprising" as used in the Detailed Description specify the presence of specified features, regions, integers, steps, operations, components, and/or components, and one or more other features, regions, integers, or integers. However, it does not exclude the presence or addition of steps, operations, components, components and/or groups thereof.

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

Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It is also understood that terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with that within the context of the related art and the present disclosure, and not in an idealized or overly formal sense. It will be.

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

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

In the present specification, "particle diameter" indicates an average diameter when the particles are spherical, and indicates an average major axis length when the particles are non-spherical. The particle size can be measured using a particle size analyzer (PSA). "Particle diameter" is an average particle diameter, for example. "Average particle diameter" is D50 which is a median particle diameter, for example.

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

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

D10 is a particle size corresponding to a 10% cumulative volume calculated from the side of particles having a 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 an elemental or ionic state.

“Alloy” in this disclosure means a mixture of two or more metals.

In the present disclosure, "electrode active material" means an electrode material capable of undergoing lithiation and delithiation.

In the present disclosure, "cathode active material" means a cathode material capable of undergoing lithiation and delithiation.

In the present disclosure, "negative electrode active material" means a negative electrode material that can undergo lithiation and delithiation.

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

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

In the present disclosure, “anode” and “cathode” refer to an electrode in which electrochemical reduction and lithiation occur during a discharging process.

In the present disclosure, "cathode" and "anode" refer to an electrode in which electrochemical oxidation and delithiation occur during a discharging process.

While particular embodiments have been described, currently unforeseen or unforeseeable alternatives, modifications, variations, improvements, and substantial equivalents may occur to applicants or those skilled in the art. Accordingly, the appended claims as filed and as may be amended are intended to embrace all such alternatives, modifications, variations, improvements and substantial equivalents.

Hereinafter, a sulfide-based solid electrolyte according to one or more exemplary embodiments, an all-solid-state secondary battery including the same, and a manufacturing method of the sulfide-based solid electrolyte will be described in more detail.

[Sulfide-based solid electrolyte]

A sulfide-based solid electrolyte according to an embodiment is a sulfide-based solid electrolyte for an all-solid-state battery, has an argyrodite-type crystal structure, includes a compound represented by Formula 1 below, and has an average particle diameter of 0.1 ㎛ to 10 ㎛, has an ion conductivity of 0.01 mS / cm to 3 mS / cm at 25 ° C, and diffraction angle 2θ = 23 ° ± 0.5 ° in the XRD spectrum of the sulfide-based solid electrolyte First at The ratio (ratio, Ia/Ib) of the intensity (Ia) of the peak and the intensity (Ib) of the second peak at the diffraction angle 2θ = 25.5° ± 0.5° is greater than 0 and less than or equal to 1:

<Formula 1>

Li _a M1 _x PS _y M2 _z M3 _w

In the above formula,

M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,

M2 is one or more elements selected from group 17 of the periodic table,

M3 is SO _n ,

4≤a≤8, 0≤x<1, 3≤y≤7, 0<z≤2, 0≤w<2, and 1.5≤n≤5.

For example, 5≤a≤8, 0≤x≤0.7, 4≤y≤7, 0<z≤2 and 0≤w≤0.5. For example, 5≤a≤7, 0≤x≤0.5, 4≤y≤6, 0<z≤2 and 0≤w≤0.2. For example, 5.5≤a≤7, 0≤x≤0.3, 4.5≤y≤6, 0.2≤z≤1.8 and 0≤w≤0.1. For example, 5.5≤a≤7, 0≤x≤0.1, 4.5≤y≤6, 0.5≤z≤1.8 and 0≤w≤0.1. For example, 5.5≤a≤7, 0≤x≤0.05, 4.5≤y≤6, 1.0≤z≤1.8 and 0≤w≤0.1.

Since the sulfide-based solid electrolyte has a reduced average particle diameter and excellent ion conductivity, cycle characteristics of an all-solid-state secondary battery including the sulfide-based solid electrolyte may be improved.

The average particle diameter of the sulfide-based solid electrolyte is, for example, 0.1 μm to 10 μm, 0.1 μm to 9 μm, 0.1 μm to 8 μm, 0.1 μm to 7 μm, 0.2 μm to 6 μm, 0.2 μm to 5 μm, 0.2 μm to 0.2 μm. 4 μm or 0.5 μm to 2 μm. Since the sulfide-based solid electrolyte has an average particle diameter within this range, it can be suitably used for a cathode layer of an all-solid-state secondary battery. Since the sulfide-based solid electrolyte has an average particle diameter within this range, it is possible to effectively coat the surfaces of the positive electrode active material particles and effectively fill the voids between the positive electrode active material particles. Accordingly, cycle characteristics of an all-solid-state secondary battery employing a cathode layer including such a sulfide-based solid electrolyte may be further improved. If the average particle diameter of the sulfide-based solid electrolyte is excessively increased, it may be difficult to uniformly coat the surface of the positive electrode active material, and the internal resistance of the positive electrode increases as the gap between the particles of the sulfide-based solid electrolyte increases, and the battery including the positive electrode Cycle characteristics of the solid-state secondary battery may deteriorate. If the average particle diameter of the sulfide-based solid electrolyte is excessively reduced, suitability for an electrode manufacturing process may be deteriorated due to aggregation or the like.

The sulfide-based solid electrolyte may have, for example, a narrow particle size distribution. The D90 - D10 value of the sulfide-based solid electrolyte is, for example, 0.1 to 30 μm, 0.1 to 20 μm, 0.1 to 10 μm, 0.1 to 5 μm, 0.1 to 10 μm, 0.1 to 5 μm, 0.1 to 4 μm, 0.1 to 3 μm, 0.1 to 2 μm, or 0.1 to 1 μm. Since the sulfide-based solid electrolyte has a D90-D10 value in such a narrow range, agglomeration of particles may be prevented during the manufacturing process of the positive electrode layer.

The average particle diameter of the sulfide-based solid electrolyte is, for example, 1 μm to 30 μm, 1 μm to 20 μm, 1 μm to 10 μm, 1 μm to 7 μm, 1 μm to 6 μm, 1 μm to 5 μm, or 2 μm. to 4 μm. Since the sulfide-based solid electrolyte has an average particle diameter within this range, it can be suitably used for a solid electrolyte layer of an all-solid-state secondary battery. Accordingly, cycle characteristics of an all-solid-state secondary battery employing a solid electrolyte layer including such a sulfide-based solid electrolyte can be further improved.

The ionic conductivity of the sulfide-based solid electrolyte is, for example, 0.01 mS/cm to 3 mS/cm, 0.01 mS/cm to 2 mS/cm, 0.01 mS/cm to 1.4 mS/cm, and 0.01 mS/cm to 1 mS/cm at 25°C. mS/cm, or from 0.01 mS/cm to 0.5 mS/cm. Since the sulfide-based solid electrolyte has an ionic conductivity in this range, ion transfer between the positive electrode and the negative electrode is effectively performed in an all-solid-state secondary battery including the sulfide-based solid electrolyte, thereby reducing internal resistance between the positive electrode and the negative electrode. . Ionic conductivity can be measured using a DC polarization method. Alternatively, ionic conductivity can be measured using a complex impedance method.

Referring to FIG. 2A, in the XRD spectrum of a sulfide-based solid electrolyte, the intensity (Ia) of the first peak at the diffraction angle 2θ=23.5°±0.5° and the intensity of the second peak at the diffraction angle 2θ=25.5°±0.5° The ratio (Ia/Ib) of (Ib) is greater than 0 and less than or equal to 1. The ratio (Ia/Ib) of the intensity (Ia) of the first peak and the intensity (Ib) of the second peak is, for example, 0.01 to 1, 0.05 to 1, or 0.1 to 1. The first peak may be a peak derived from a non-azirodite crystal structure. The second peak may be a peak derived from the azirodite crystal structure. The first peak may be a peak due to impurities. Referring to FIG. 2A , the first peak is a doublet and the second peak is a singlet.

Referring to FIG. 2A, in the XRD spectrum of the sulfide-based solid electrolyte, the intensity (Ia) of the first peak at the diffraction angle 2θ = 23.5 ° ± 0.5 ° and the intensity of the third peak at the diffraction angle 2θ = 15.5 ° ± 0.5 ° The ratio (Ia/Ic) of (Ic) is greater than 0 and less than or equal to 6. The ratio (Ia/Ic) of the intensity (Ia) of the first peak and the intensity (Ic) of the third peak is, for example, 0.01 to 6, 0.01 to 5, 0.01 to 4, 0.01 to 3, 0.05 to 3, or 0.1 to 3. The third peak may be a peak derived from an azirodite crystal structure. Referring to FIG. 2A , the third peak is a singlet.

A sulfide-based solid electrolyte may have excellent ionic conductivity and chemical stability. Thus, the sulfide-based solid electrolyte can provide improved stability to air and electrochemical stability to metal lithium.

In the compound represented by Formula 1, for example, M1 is Na, K, Mg, Ag, Cu, Hf, In, Ti, Pb, Sb, Fe, Zr, Zn, Cr, B, Sn, Ge, Si, Zr, Ta, Nb, V, Ga, Al, As, or combinations thereof. M1 may be, for example, a monovalent cation or a divalent cation.

In the compound represented by Formula 1, for example, M1 may include Na, K, Cu, Mg, Ag, or a combination thereof. M1 may be, for example, a monovalent cation.

In the compound represented by Formula 1, for example, M2 may include F, Cl, Br, I, or a combination thereof. M2 may be, for example, a monovalent anion.

In the compound represented by Formula 1, for example, SO _n of M3 is S ₄ O ₆ , S ₃ O ₆ , S 2 O _{3 , S 2 O 4 , S 2} O ₅ , _{S 2 O 6} , S ₂ O ₇ , S ₂ O ₈ , SO ₄ , SO ₅ , or combinations thereof. SO _n can be, for example, a divalent anion. SO _n ^2- is for example S ₄ O ₆ ^2- _, S ₃ O ₆ ^2- , S ₂ O ₃ ^2- , S ₂ O 4 ^2- , S ₂ O ₅ ^2- , S ₂ O ₆ ^2- , S ₂ O ₇ ^2- , S ₂ O ₈ ^2- , SO ₄ ^2- , SO ₅ ^2- , or combinations thereof.

The compound represented by Formula 1 may be, for example, a compound selected from compounds represented by Formulas 1a to 1b below:

<Formula 1a>

Li _a PS _y M2 _z

In the above formula,

M2 is one or more elements selected from group 17 of the periodic table,

4≤a≤8, 3≤y≤7, and 0<z≤2.

The compound represented by Formula 1a is a compound containing M2 and not containing M1 and M3,

<Formula 1b>

Li _a M1 _x PS _y M2 _z

In the above formula,

M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,

M2 is one or more elements selected from group 17 of the periodic table,

4≤a≤8, 0<x<1, 3≤y≤7, and 0<z≤2.

The compound represented by Formula 1b is a compound that includes M1 and M2 and does not include M3.

The compound represented by Formula 1 may be, for example, a compound selected from compounds represented by Formulas 1c to 1d below:

<Formula 1c>

Li _a PS _y M2 _z M3 _w

In the above formula,

M2 is one or more elements selected from group 17 of the periodic table,

M3 is SO _n ,

4≤a≤8, 3≤y≤7, 0<z≤2, 0<w<2, and 1.5≤n≤5.

The compound represented by Formula 1c is a compound that does not include M1 and includes M2 and M3,

<Formula 1d>

Li _a M1 _x PS _y M2 _z M3 _w

In the above formula,

M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,

M2 is one or more elements selected from group 17 of the periodic table,

M3 is SO _n ,

4≤a≤8, 0<x<1, 3≤y≤7, 0<z≤2, 0<w<2, and 1.5≤n≤5.

The compound represented by Formula 1c is a compound containing all of M1, M2 and M3.

It may be a compound represented by Formula 1, for example, represented by Formula 2 below:

<Formula 2>

Li _7-m×vz M1 _v PS _6-zw M2 _z M3 _w

In the above formula,

M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table, m is the oxidation number of M1,

M2 is one or more elements selected from group 17 of the periodic table,

M3 is SO _n ,

0≤v<1, 0<z≤2, 0≤w<2, 1.5≤n≤5, 1≤m≤2, and 0<v+w<3.

For example, 0≤v≤0.7, 0<z≤2 and 0≤w≤0.5. For example, 0≤v≤0.5, 0<z≤2 and 0≤w≤0.2. For example, 0≤v≤0.3, 0.2≤z≤1.8 and 0≤w≤0.1. For example, 0≤v≤0.1, 0.5≤z≤1.8 and 0≤w≤0.1. For example, 0≤v≤0.05, 1.0≤z≤1.8 and 0≤w≤0.1.

The compound represented by Formula 1 may be, for example, a compound represented by Formula 2a below:

<Formula 2a>

Li _7-z PS _6-z M2 _z

In the above formula,

M2 is one or more elements selected from group 17 of the periodic table,

0<z≤2.

The compound represented by Formula 2a is a compound containing M2 and not containing M1 and M3.

The compound represented by Formula 1 may be, for example, a compound represented by Formula 2b below:

<Formula 2b>

Li _7-m×vz M1 _v PS _6-z M2 _z

In the above formula,

M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table, m is the oxidation number of M1,

M2 is one or more elements selected from group 17 of the periodic table,

0<v<1, 0<z≤2, and 1≤m≤2.

The solid ion conductor compound represented by Formula 2b is a compound including M1 and M2 but not including M3. M1 may be, for example, one metal element or two or more metal elements.

The compound represented by Formula 1 may be, for example, a compound represented by Formula 2c below:

<Formula 2c>

Li _7-z PS _6-zw M2 _z M3 _w

In the above formula,

M2 is one or more elements selected from group 17 of the periodic table,

M3 is SO _n ,

0<z≤2, 0<w<2, 1.5≤n≤5, and 1≤m≤2.

The compound represented by Formula 2c is a compound that does not include M1 and includes M2 and M3.

The compound represented by Formula 1 may be, for example, a compound represented by Formula 2d below:

<Formula 2d>

Li _7-m×vz M1 _v PS _6-zw M2 _z M3 _w

In the above formula,

M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table, m is the oxidation number of M1,

M2 is one or more elements selected from group 17 of the periodic table,

M3 is SO _n ,

0<v<1, 0<z≤2, 0<w<2, 1.5≤n≤5, and 1≤m≤2.

The solid ion conductor compound represented by Formula 2d is a compound containing M1, M2 and M3. M1 may be, for example, one metal element or two or more metal elements. M2 may be, for example, one kind of halogen element or two or more kinds of halogen elements.

The compound represented by Formula 1 may be, for example, a compound represented by Formula 3 below:

<Formula 3>

Li _7-m×vz M4 _v PS _6-z M5 _z1 M6 _z2

In the above formula,

M4 is Na, K, Mg, Ag, Cu, Hf, In, Ti, Pb, Sb, Fe, Zr, Zn, Cr, B, Sn, Ge, Si, Zr, Ta, Nb, V, Ga, Al, As, or a combination thereof, m is the oxidation number of M4,

M5 and M6 are independently of each other F, Cl, Br, or I,

0<v<0.7, 0<z1<2, 0≤z2<1, 0<z<2, z=z1+z2 and 1≤m≤2.

For example, 0<v≤0.7, 0<z1<2, 0≤z2≤0.5, 0<z<2, and z=z1+z2. For example, 0<v≤0.5, 0<z1<2, 0≤z2≤0.5, 0<z<2 and z=z1+z2. For example, 0<v≤0.3, 0<z1≤1.5, 0≤z2≤0.5, 0.2≤z≤1.8 and z=z1+z2. For example, 0<v≤0.1, 0<z1≤1.5, 0≤z2≤0.5, 0.5≤z≤1.8 and z=z1+z2. For example, 0<v≤0.05, 0<z1≤1.5, 0≤z2≤0.2, 1.0≤z≤1.8 and z=z1+z2. M4 may be, for example, one metal element or two metal elements.

The solid ion conductor compound represented by Chemical Formula 3 may include, for example, one kind of halogen element or two kinds of halogen elements.

The solid ion conductor compound represented by Formula 1 may be, for example, a solid ion conductor compound represented by Formulas 3a to 3f below:

<Formula 3a>

Li _7-z PS _6-z M5 _z1 M6 _z2

<Formula 3b>

Li _7-vz Na _v PS _6-z M5 _z1 M6 _z2

<Formula 3c>

Li _7-vz K _v PS _6-z M5 _z1 M6 _z2

<Formula 3d>

Li _7-vz Cu _v PS _6-z M5 _z1 M6 _z2

<Formula 3e>

Li _7-vz Mg _v PS _6-z M5 _z1 M6 _z2

<Formula 3f>

Li _7-vz Ag _v PS _6-z M5 _z1 M6 _z2

In the above expressions,

M5 and M6 are independently of each other F, Cl, Br, or I,

0<v<0.7, 0<z1<2, 0≤z2<1, 0<z<2 and z=z1+z2. For example, 0<v≤0.7, 0<z1<2, 0≤z2≤0.5, 0<z<2, and z=z1+z2. For example, 0<v≤0.5, 0<z1<2, 0≤z2≤0.5, 0<z<2 and z=z1+z2. For example, 0<v≤0.3, 0<z1≤1.5, 0≤z2≤0.5, 0.2≤z≤1.8 and z=z1+z2. For example, 0<v≤0.1, 0<z1≤1.5, 0≤z2≤0.5, 0.5≤z≤1.8 and z=z1+z2. For example, 0<v≤0.05, 0<z1≤1.5, 0≤z2≤0.2, 1.0≤z≤1.8 and z=z1+z2.

The solid ion conductor compound represented by Formula 1 may be, for example, a solid ion conductor compound represented by the following formulas:

Li _7-vz Na _v PS _6-z F _z1 , Li _7-vz Na _v PS _6-z Cl _z1 , Li _7-vz Na _v PS _6-z Br _z1 , Li _7-vz Na _v PS _6-z I _z1 ,

Li _7-vz Na _v PS _6-z F _z1 Cl _z2 , Li _7-vz Na _v PS _6-z F _z1 Br _z2 , Li _7-vz Na _v PS _6-z F _z1 I _z2 , Li _7-vz Na _v PS _6-z Cl _z1 Br _z2 , Li _7-vz Na _v PS _6-z Cl _z1 I _z2 , Li _7-vz Na _v PS _6-z Cl _z1 F _z2 , Li _7-vz Na _v PS _6-z Br _z1 I _z2 , Li _7-vz Na _v PS _6-z Br _z1 F _z2 , Li _7-vz Na _v PS _6-z Br _z1 Cl _z2 , Li _7-vz Na _v PS _6-z I _z1 F _z2 , Li _7-vz Na _v PS _6-z I _z1 Cl _z2 , Li _7-vz Na _v PS _6-z I _z1 Br _z2 ,

Li _7-vz K _v PS _6-z F _z1 , Li _7-vz K _v PS _6-z Cl _z1 , Li _7-vz K _v PS _6-z Br _z1 , Li _7-vz K _v PS _6-z I _z1 ,

Li _7-vz K _v PS _6-z F _z1 Cl _z2 , Li _7-vz K _v PS _6-z F _z1 Br _z2 , Li _7-vz K _v PS _6-z F _z1 I _z2 , Li _7-vz K _v PS _6-z Cl _z1 Br _z2 , Li _7-vz K _v PS _6-z Cl _z1 I _z2 , Li _7-vz K _v PS _6-z Cl _z1 F _z2 , Li _7-vz K _v PS _6-z Br _z1 I _z2 , Li _7-vz K _v PS _6-z Br _z1 F _z2 , Li _7-vz K _v PS _6-z Br _z1 Cl _z2 , Li _7-vz K _v PS _6-z I _z1 F _z2 , Li _7-vz K _v PS _6-z I _z1 Cl _z2 , Li _7-vz K _v PS _6-z I _z1 Br _z2 ,

Li _7-vz Cu _v PS _6-z F _z1 , Li _7-vz Cu _v PS _6-z Cl _z1 , Li _7-vz Cu _v PS _6-z Br _z1 , Li _7-vz Cu _v PS _6-z I _z1 ,

Li _7-vz Cu _v PS _6-z F _z1 Cl _z2 , Li _7-vz Cu _v PS _6-z F _z1 Br _z2 , Li _7-vz Cu _v PS _6-z F _z1 I _z2 , Li _7-vz Cu _v PS _6-z Cl _z1 Br _z2 , Li _7-vz Cu _v PS _6-z Cl _z1 I _z2 , Li _7-vz Cu _v PS _6-z Cl _z1 F _z2 , Li _7-vz Cu _v PS _6-z Br _z1 I _z2 , Li _7-vz Cu _v PS _6-z Br _z1 F _z2 , Li _7-vz Cu _v PS _6-z Br _z1 Cl _z2 , Li _7-vz Cu _v PS _6-z I _z1 F _z2 , Li _7-vz Cu _v PS _6-z I _z1 Cl _z2 , Li _7-vz Cu _v PS _6-z I _z1 Br _z2 ,

Li _7-vz Mg _v PS _6-z F _z1 , Li _7-vz Mg _v PS _6-z Cl _z1 , Li _7-vz Mg _v PS _6-z Br _z1 , Li _7-vz Mg _v PS _6-z I _z1 ,

Li _7-vz Mg _v PS _6-z F _z1 Cl _z2 , Li _7-vz Mg _v PS _6-z F _z1 Br _z2 , Li _7-vz Mg _v PS _6-z F _z1 I _z2 , Li _7-vz Mg _v PS _6-z Cl _z1 Br _z2 , Li _7-vz Mg _v PS _6-z Cl _z1 I _z2 , Li _7-vz Mg _v PS _6-z Cl _z1 F _z2 , Li _7-vz Mg _v PS _6-z Br _z1 I _z2 , Li _7-vz Mg _v PS _6-z Br _z1 F _z2 , Li _7-vz Mg _v PS _6-z Br _z1 Cl _z2 , Li _7-vz Mg _v PS _6-z I _z1 F _z2 , Li _7-vz Mg _v PS _6-z I _z1 Cl _z2 , Li _7-vz Mg _v PS _6-z I _z1 Br _z2 ,

Li _7-vz Ag _v PS _6-z F _z1 , Li _7-vz Ag _v PS _6-z Cl _z1 , Li _7-vz Ag _v PS _6-z Br _z1 , Li _7-vz Ag _v PS _6-z I _z1 ,

Li _7-vz Ag _v PS _6-z F _z1 Cl _z2 , Li _7-vz Ag _v PS _6-z F _z1 Br _z2 , Li _7-vz Ag _v PS _6-z F _z1 I _z2 , Li _7-vz Ag _v PS _6-z Cl _z1 Br _z2 , Li _7-vz Ag _v PS _6-z Cl _z1 I _z2 , Li _7-vz Ag _v PS _6-z Cl _z1 F _z2 , Li _7-vz Ag _v PS _6-z Br _z1 I _z2 , Li _7-vz Ag _v PS _6-z Br _z1 F _z2 , Li _7-vz Ag _v PS _6-z Br _z1 Cl _z2 , Li _7-vz Ag _v PS _6-z I _z1 F _z2 , Li _7-vz Ag _v PS _6-z I _z1 Cl _z2 , Li _7-vz Ag _v PS _6-z I _z1 Br _z2 ,

In the above equations, 0<v<0.7, 0<z1<2, 0<z2<1, 0<z<2 and z=z1+z2. For example, 0<v≤0.7, 0<z1<2, 0<z2≤0.5, 0<z<2, and z=z1+z2. For example, 0<v≤0.5, 0<z1<2, 0<z2≤0.5, 0<z<2 and z=z1+z2. For example, 0<v≤0.3, 0<z1≤1.5, 0<z2≤0.5, 0.2≤z≤1.8 and z=z1+z2. For example, 0<v≤0.1, 0<z1≤1.5, 0<z2≤0.5, 0.5≤z≤1.8 and z=z1+z2. For example, 0<v≤0.05, 0<z1≤1.5, 0<z2≤0.2, 1.0≤z≤1.8 and z=z1+z2.

The solid ion conductor compound represented by Formula 1 may be, for example, a solid ion conductor compound represented by Formula 4 below:

<Formula 4>

Li _7-m×vz M4 _v PS _6-zw M7 _z (SO ₄ ) _w

In the above formula,

M4 is Na, K, Mg, Ag, Cu, Hf, In, Ti, Pb, Sb, Fe, Zr, Zn, Cr, B, Sn, Ge, Si, Zr, Ta, Nb, V, Ga, Al, As, or a combination thereof, m is the oxidation number of M4,

M7 is F, Cl, Br, or I;

0<v<1, 0<z≤2, 0<w<1, and 1≤m≤2. For example, 0<v≤0.7, 0<z≤2 and 0<w≤0.5. For example, 0<v≤0.5, 0<z≤2 and 0<w≤0.2. For example, 0<v≤0.3, 0.2≤z≤1.8 and 0<w≤0.1. For example, 0<v≤0.1, 0.5≤z≤1.8 and 0<w≤0.1. For example, 0<v≤0.05, 1.0≤z≤1.8 and 0<w≤0.1.

The solid ion conductor compound represented by Formula 1 may be, for example, a solid ion conductor compound represented by Formulas 4a to 4f below:

<Formula 4a>

Li _7-z PS _6-zw M7 _z (SO ₄ ) _w

<Formula 4b>

Li _7-vz Na _v PS _6-zw M7 _z (SO ₄ ) _w

<Formula 4c>

Li _7-vz K _v PS _6-zw M7 _z (SO ₄ ) _w

<Formula 4d>

Li _7-vz Cu _v PS _6-zw M7 _z (SO ₄ ) _w

<Formula 4e>

Li _7-vz Mg _v PS _6-zw M7 _z (SO ₄ ) _w

<Formula 4f>

Li _7-vz Ag _v PS _6-zw M7 _z (SO ₄ ) _w

In the above expressions,

M7 is F, Cl, Br, or I;

0<v<0.7, 0<z≤2, and 0<w<0.2. For example, 0<v≤0.7, 0<z≤2 and 0<w<0.2. For example, 0<v≤0.5, 0<z≤2 and 0<w<0.2. For example, 0<v≤0.3, 0.2≤z≤1.8 and 0<w≤0.1. For example, 0<v≤0.1, 0.5≤z≤1.8 and 0<w≤0.1. For example, 0<v≤0.05, 1.0≤z≤1.8 and 0<w≤0.1.

The compound represented by Formula 1 may be, for example, a compound represented by the following formulas:

Li _7-z PS _6-zw F _z (SO ₄ ) _w , Li _7-z PS _6-zw Cl _z (SO ₄ ) _w , Li _7-z PS _6-zw Br _z (SO ₄ ) _w , Li _{7 -z} PS _6-zw I _z (SO ₄ ) _w

Li _7-vz Na _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz Na _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz Na _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz Na _v PS _6-zw I _z (SO ₄ ) _w ,

Li _7-vz K _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz K _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz K _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz K _v PS _6-zw I _z (SO ₄ ) _w ,

Li _7-vz Cu _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz Cu _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz Cu _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz Cu _v PS _6-zw I _z (SO ₄ ) _w ,

Li _7-vz Mg _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz Mg _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz Mg _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz Mg _v PS _6-zw I _z (SO ₄ ) _w ,

Li _7-vz Ag _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz Ag _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz Ag _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz Ag _v PS _6-zw I _z (SO ₄ ) _w

_{In the above expressions,}

₀ < v < 0.7, 0 < z < 2, and 0 < w < 0.2. For example, 0<v≤0.7, 0<z≤2 and 0<w<0.2. For example, 0<v≤0.5, 0<z≤2 and 0<w<0.2. For example, 0<v≤0.3, 0.2≤z≤1.8 and 0<w≤0.1. For example, 0<v≤0.1, 0.5≤z≤1.8 and 0<w≤0.1. For example, 0<v≤0.05, 1.0≤z≤1.8 and 0<w≤0.1.

The compound represented by Chemical Formula 1 belongs to, for example, a cubic crystal system, and may more specifically belong to the F-43m space group. Also, as described above, the compound represented by Chemical Formula 1 may be an argyrodite-type sulfide having an argyrodite-type crystal structure. The compound represented by Formula 1 includes, for example, at least one of a monovalent cation element and a divalent cation element cation element substituted at a portion of the lithium site in an azirodite-type crystal structure, or includes a heterogeneous halogen element, or , lithium ion conductivity is further improved, and electrochemical stability for lithium metal can be further improved by including SO _n anions substituted at halogen sites.

The compound represented by Formula 1 has, for example, 25.48 ° ± 0.50 °, 30.01 ° ± 1.0 °, 31.38 ° ± 0.50 °, 46.0 ° ± 1.0 °, 48.5 ° ± 1.0 °, and 53.0 ° in the XRD spectrum using CuKα rays. It may have a peak at a position of ±1.0°. Since the compound represented by Formula 1 has an azirodite structure, it may have such a peak in an XRD spectrum using CuKα rays. The compound represented by Formula 1 is, for example, a solid ion conductor compound.

The sulfide-based solid electrolyte may be in the form of a powder or molding. The solid electrolyte in the form of a molding may be in the form of, for example, a pellet, sheet, or thin film, but is not necessarily limited thereto and may have various forms depending on the purpose of use.

[All-solid secondary battery]

An all-solid-state secondary battery according to another embodiment includes a cathode layer including a cathode active material layer; A negative electrode layer including a negative electrode active material layer; and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode active material layer and/or the electrolyte layer include the above-described sulfide-based solid electrolyte. By including the above-described sulfide-based solid electrolyte in the all-solid-state secondary battery, internal resistance of the all-solid-state secondary battery may be reduced and cycle characteristics may be improved.

The positive electrode active material layer includes a third sulfide-based solid electrolyte, and the average particle diameter of the third sulfide-based solid electrolyte may be, for example, 0.1 μm to 10 μm. The electrolyte layer may include a fourth sulfide-based solid electrolyte, and an average particle diameter of the fourth sulfide-based solid electrolyte may be, for example, 1 μm to 30 μm. The average particle diameter of the third sulfide-based solid electrolyte may be smaller than that of the fourth sulfide-based solid electrolyte.

Hereinafter, the all-solid-state secondary battery will be described in more detail.

[Type 1]

The all-solid-state secondary battery may include the above-described sulfide-based solid electrolyte.

An all-solid-state secondary battery may include, for example, a cathode layer including a cathode active material layer; A negative electrode layer including a negative electrode active material layer; and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and the positive electrode active material layer and/or the electrolyte layer may include the above-described sulfide-based solid electrolyte.

An all-solid-state secondary battery according to one embodiment may be prepared as follows.

(solid electrolyte layer)

First, a solid electrolyte layer is prepared.

The solid electrolyte layer may be prepared by mixing and drying a sulfide-based solid electrolyte and a binder, or by rolling powder of a sulfide-based solid electrolyte in a constant shape at a pressure of 1 ton to 10 ton. A sulfide-based solid electrolyte is used as the solid electrolyte.

The average particle diameter of the sulfide-based solid electrolyte is, for example, 1 μm to 30 μm, 1 μm to 20 μm, 1 μm to 10 μm, 1 μm to 7 μm, 1 μm to 6 μm, 1 μm to 5 μm, or 2 μm. to 4 μm. When the solid electrolyte has such an average particle diameter, binding property is improved in the process of forming a sintered body under pressure, and thus ionic conductivity and lifespan characteristics of the solid electrolyte particles can be improved.

The solid electrolyte layer may have a thickness of 10 μm to 200 μm. By having such a thickness of the solid electrolyte layer, a sufficient movement rate of lithium ions is ensured, and as a result, high ionic conductivity can be obtained.

The solid electrolyte layer may further include a solid electrolyte such as a conventional sulfide-based solid electrolyte and/or an oxide-based solid electrolyte in addition to the above-described sulfide-based solid electrolyte.

A conventional sulfide-based solid electrolyte may include, for example, lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or a combination thereof. Conventional sulfide-based solid electrolyte particles may include Li ₂ S, P ₂ S ₅ , SiS ₂ , GeS ₂ , B ₂ S ₃ or a combination thereof. Conventional sulfide-based solid electrolyte particles may be Li ₂ S or P ₂ S ₅ . Conventional sulfide-based solid electrolyte particles are known to have higher lithium ion conductivity than other inorganic compounds. For example, a conventional sulfide-based solid electrolyte includes Li ₂ S and P ₂ S ₅ . When the sulfide solid electrolyte material constituting the conventional sulfide-based solid electrolyte includes Li ₂ SP ₂ S ₅ , the mixing molar ratio of Li ₂ S to P ₂ S ₅ is, for example, about 50:50 to about 90:10. range can be In addition, Li ₃ PO ₄ , halogen, halogenated compounds, Li _2+2x Zn _1??x GeO ₄ (“LISICON”), Li _3+y PO _4-x N _{x (} “LIPON”), Li _3.25 Ge _0.25 P _0.75 S ₄ ("ThioLISICON"), Li ₂ O-Al ₂ O ₃ -TiO ₂ -P ₂ O _{5 (} "LATP"), etc. Li ₂ SP ₂ S ₅ , SiS ₂ , GeS ₂ , B ₂ S ₃ , Alternatively, an inorganic solid electrolyte prepared by adding a combination thereof to an inorganic solid electrolyte may be used as a conventional sulfide solid electrolyte. Non-limiting examples of conventional sulfide solid electrolyte materials include Li ₂ SP ₂ S ₅ ; Li ₂ SP ₂ S ₅ -LiX (X=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 S -P ₂ S ₅ -Z _m S _n (0<m<10, 0<n<10, Z=Ge, Zn or Ga); Li ₂ S-GeS ₂ ; Li ₂ S-SiS ₂ -Li ₃ PO ₄ ; and Li ₂ S-SiS ₂ -Li _p MO _q (0<p<10, 0<q<10, M=P, Si, Ge, B, Al, Ga or In). In this regard, a conventional sulfide-based solid electrolyte material is a raw material starting material (eg, Li ₂ S, P ₂ S ₅ , etc.) of a sulfide-based solid electrolyte material is melt quenched (melt quenching method), mechanical milling method etc. can be produced by processing. Also, calcinations may be performed after the treatment.

The binder included in the solid electrolyte layer, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol It is not limited to the like or these, and all are possible as long as they are used as binders in the art. The binder of the solid electrolyte layer may be the same as or different from the binders of the positive electrode layer and the negative electrode layer.

(anode layer)

Next, an anode layer is prepared.

The cathode layer may be prepared by forming a cathode active material layer containing a cathode active material on a current collector. The average particle diameter of the cathode active material may be, for example, 2 μm to 10 μm.

Any positive electrode active material may be used without limitation as long as it is commonly used in a secondary battery. For example, it may be a lithium transition metal oxide or a transition metal sulfide. For example, one or more types of composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used, and specific examples thereof include Li _a A _1-b B _b D ₂ (above In the formula, 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5); Li _a E _1-b B _b O _2-c D _c (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE _2-b B _b O _4-c D _c (wherein 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _b E _c G _d O ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a CoG _b O ₂ (wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a MnG _b O ₂ (wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (wherein 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₂ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); A compound represented by any one of the chemical formulas of LiFePO ₄ may be used. In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or combinations thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or combinations thereof. For example, LiCoO ₂ , LiMn _x O _2x (x=1, 2), LiNi _1-x Mn _x O _2x (0<x<1), Ni _1-xy Co _x Mn _y O ₂ (0≤x≤ 0.5, 0≤y≤0.5), Ni _1-xy Co _x Al _y O ₂ (0≤x≤0.5, 0≤y≤0.5), LiFePO ₄ , TiS ₂ , FeS ₂ , TiS ₃ , FeS _{3 ,} and the like. In these compounds, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or combinations thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or combinations thereof. It is also possible to use a compound in which a coating layer is added to the surface of such a compound, and it is also possible to use a mixture of the above-mentioned compound and a compound in which a coating layer is added. The coating layer applied to the surface of such a compound includes, for example, a coating element compound of an oxide, a hydroxide, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compound constituting the coating layer is amorphous or crystalline. The coating elements included in the coating layer include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer formation method is selected within a range that does not adversely affect the physical properties of the cathode active material. The coating method is, for example, spray coating, dipping method or the like. Since a specific coating method can be well understood by those skilled in the art, a detailed description thereof will be omitted.

The cathode active material includes, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the above-described lithium transition metal oxides. "Layered rock salt structure" means, for example, that an oxygen atom layer and a metal atom layer are arranged alternately and regularly in the <111> direction of a cubic rock salt type structure, whereby each atomic layer is formed on a two-dimensional plane. It is a structure that forms "Cubic rock salt structure" refers to a NaCl type structure, which is a type of crystal structure, and specifically, face centered cubic lattice (fcc) formed by positive and negative ions, respectively, unit lattice ) shows a structure displaced by 1/2 of the ridge. A lithium transition metal oxide having such a layered rock salt structure is, for example, LiNi _x Co _y Al _z O ₂ (NCA) or LiNi _x Co _y Mn _z O ₂ (NCM) (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1) is a ternary lithium transition metal oxide. When the cathode active material includes a ternary lithium transition metal oxide having a layered rock salt structure, energy density and thermal stability of the all-solid-state secondary battery are further improved.

As described above, the cathode active material may be covered by the coating layer. Any coating layer may be used as long as it is known as a coating layer of a positive electrode active material for an all-solid-state secondary battery. The coating layer is, for example, Li ₂ O-ZrO ₂ (LZO) or the like.

When the cathode active material includes, for example, nickel (Ni) as a ternary lithium transition metal oxide such as NCA or NCM, it is possible to increase the capacity density of an all-solid-state secondary battery and reduce metal elution of the cathode active material in a charged state. . As a result, cycle characteristics of the all-solid-state secondary battery in a charged state are improved.

The shape of the positive electrode active material is, for example, a particle shape such as a spherical sphere or an elliptical sphere. The particle size of the positive electrode active material is not particularly limited, and is within a range applicable to the positive electrode active material of a conventional all-solid-state secondary battery. The content of the positive electrode active material in the positive electrode layer is also not particularly limited, and is within a range applicable to the positive electrode layer of a conventional all-solid-state secondary battery. The content of the positive electrode active material in the positive electrode active material layer may be, for example, 50 to 95% by weight.

The positive electrode active material layer may additionally include a sulfide-based solid electrolyte.

The cathode active material layer may include a binder. The binder is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or the like.

The cathode active material layer may include a conductive material. The conductive material is, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder or the like.

The cathode active material layer may further include additives such as a filler, a coating agent, a dispersant, and an ion conductive auxiliary agent in addition to the above-described cathode active material, solid electrolyte, binder, and conductive material.

As fillers, coating agents, dispersants, ion conductivity aids, etc. that may be included in the cathode active material layer, known materials generally used in electrodes of solid-state secondary batteries may be used.

The cathode current collector is, for example, aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), A plate or foil made of zinc (Zn), germanium (Ge), lithium (Li) or an alloy thereof is used. The positive electrode current collector may be omitted.

The cathode current collector may further include a carbon layer disposed on one side or both sides of the metal substrate. By additionally disposing the carbon layer on the metal substrate, it is possible to prevent the metal of the metal substrate from being corroded by the solid electrolyte included in the positive electrode layer and to reduce interface resistance between the positive electrode active material layer and the positive electrode current collector. The thickness of the carbon layer may be, for example, 1 μm to 5 μm. If the thickness of the carbon layer is too thin, it may be difficult to completely block contact between the metal substrate and the solid electrolyte. If the thickness of the carbon layer is too thick, the energy density of the all-solid-state secondary battery may decrease. The carbon layer may include amorphous carbon, crystalline carbon, and the like.

(cathode layer)

Next, the cathode layer is prepared.

The negative electrode layer may be manufactured in the same manner as the positive electrode layer, except that the negative electrode active material is used instead of the positive electrode active material. The negative electrode layer may be prepared by forming a negative electrode active material layer containing the negative electrode active material on the negative electrode current collector.

The negative electrode active material layer may additionally include the above-described sulfide-based solid electrolyte.

The anode active material may be lithium metal, a lithium metal alloy, or a combination thereof.

The anode active material layer may further include a conventional anode active material in addition to lithium metal, a lithium metal alloy, or a combination thereof. Conventional anode active materials may include, for example, at least one selected from the group consisting of metals alloyable with lithium, transition metal oxides, non-transition metal oxides, and carbon-based materials. Metals alloyable with lithium are, for example, Ag, Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloys (wherein Y is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth element or a combination thereof, but not Si), a Sn-Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, but not Sn) ) and the like. The element Y is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, It may be Se, Te, Po, or a combination thereof. The transition metal oxide may be, for example, lithium titanium oxide, vanadium oxide, lithium vanadium oxide, or the like. The non-transition metal oxide may be, for example, SnO ₂ , SiO _x (0<x<2), or the like. The carbon-based material may be, for example, crystalline carbon, amorphous carbon or mixtures thereof. Crystalline carbon may be graphite such as amorphous, plate-shaped, flake-shaped, spherical or fibrous natural graphite or artificial graphite, and the amorphous carbon may be soft carbon (low-temperature calcined carbon) or hard carbon ), mesophase pitch carbide, calcined coke, and the like.

Referring to FIG. 5, the all-solid-state secondary battery 40 according to an embodiment includes a solid electrolyte layer 30, a positive electrode layer 10 disposed on one surface of the solid electrolyte layer 30, and a solid electrolyte layer 30. and a cathode layer 20 disposed on the other side. The positive electrode layer 30 includes a positive electrode active material layer 12 in contact with the solid electrolyte layer 30 and a positive electrode current collector 11 in contact with the positive electrode active material layer 12, and the negative electrode layer 20 includes a solid electrolyte layer 30 ) and a negative electrode active material layer 22 in contact with the negative electrode current collector 21 in contact with the negative electrode active material layer 22 . In the all-solid-state secondary battery 40, for example, the positive active material layer 12 and the negative active material layer 22 are formed on both sides of the solid electrolyte layer 30, and the positive active material layer 12 and the negative active material layer 22 ), the positive electrode current collector 11 and the negative electrode current collector 21 are respectively formed on the solid-state secondary battery 30 is completed. Alternatively, the anode active material layer 22, the solid electrolyte layer 30, the cathode active material layer 12, and the cathode current collector 11 are sequentially stacked on the anode current collector 21 to form an all-solid-state secondary battery 40 is completed

In the all-solid-state secondary battery 40, the average particle diameter of the third sulfide-based solid electrolyte included in the positive electrode active material layer 12 is, for example, 0.1 μm to 10 μm, 0.5 μm to 7 μm, 0.5 μm to 6 μm, or 0.5 μm. μm to 5 μm, 0.5 μm to 4 μm, 0.5 μm to 3 μm, or 0.5 μm to 2 μm. In the all-solid-state secondary battery 40, the average particle diameter of the fourth sulfide-based solid electrolyte included in the solid electrolyte layer 30 is, for example, 1 μm to 30 μm, 1 μm to 20 μm, 1 μm to 10 μm, 1 μm to 7 μm, 1 μm to 6 μm, 1 μm to 5 μm, or 2 μm to 4 μm. The cycle of the all-solid-state secondary battery 40 by having the third sulfide-based solid electrolyte and the fourth sulfide-based solid electrolyte included in the positive electrode active material layer 12 and/or the solid electrolyte layer 30 each have a particle size within this range. characteristics can be further improved.

In the all-solid-state secondary battery 40, the average particle diameter of the third sulfide-based solid electrolyte in the positive electrode active material layer 12 may be smaller than the average particle diameter of the fourth sulfide-based solid electrolyte included in the solid electrolyte layer 30. Since the average particle diameter of the third sulfide-based solid electrolyte in the positive electrode active material layer 12 is smaller than the average particle diameter of the fourth sulfide-based solid electrolyte included in the solid electrolyte layer 30, the all-solid-state secondary battery 40 including these The cycle characteristics of can be further improved.

[Type 2]

6 to 7, the all-solid-state secondary battery 1 includes, for example, a positive electrode layer 10 including a positive electrode active material layer 12 disposed on a positive electrode current collector 11; a negative electrode layer 20 including a negative electrode active material layer 22 disposed on the negative electrode current collector 21; and an electrolyte layer 30 disposed between the positive electrode layer 10 and the negative electrode layer 20, and the positive electrode active material layer 12 and/or the electrolyte layer 30 may include a sulfide-based solid electrolyte.

An all-solid-state secondary battery according to another embodiment may be prepared as follows.

The positive electrode layer and the solid electrolyte layer are manufactured in the same manner as in the above-described all-solid-state secondary battery.

(cathode layer)

Next, the cathode layer is prepared.

6 to 7, the negative electrode layer 20 includes a negative electrode current collector 21 and a negative electrode active material layer 22 disposed on the negative electrode current collector 21, and the negative electrode active material layer 22 is, for example, For example, a negative electrode active material and a binder are included.

The anode active material included in the anode active material layer 22 has a particle form, for example. The average particle diameter of the particle-shaped negative electrode active material is, for example, 4 μm or less, 3 μm or less, 2 μm or less, 1 μm or less, or 900 nm or less. The average particle diameter of the particle-shaped negative electrode active material is, for example, 10 nm to 4 μm or less, 10 nm to 3 μm or less, 10 nm to 2 μm or less, 10 nm to 1 μm or less, or 10 nm to 900 nm or less. . When the anode active material has an average particle diameter within this range, reversible absorbing and/or desorbing of lithium may be more easily performed during charging and discharging. The average particle diameter of the negative electrode active material is, for example, a median diameter (D50) measured using a laser type particle size distribution analyzer.

The anode active material included in the anode active material layer 22 includes, for example, at least one selected from a carbon-based anode active material and a metal or metalloid anode active material.

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), graphene ), etc., but are not necessarily limited to these, and all are possible as long as they are classified as amorphous carbon in the art. Amorphous carbon has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon.

Metal or metalloid cathode 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 thereto, and can be used as a metal anode active material or a semi-metal anode active material forming an alloy or compound with lithium in the art. For example, nickel (Ni) is not a metal anode active material because it does not form an alloy with lithium.

The anode active material layer 22 includes one kind of anode active material among these anode active materials or a mixture of a plurality of different anode active materials. For example, the anode active material layer 22 includes only amorphous carbon, or may include gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), or bismuth (Bi). ), at least one selected from the group consisting of tin (Sn) and zinc (Zn). Alternatively, the anode active material layer 22 may include amorphous carbon, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin ( Sn) and a mixture with at least one selected from the group consisting of zinc (Zn). The mixing ratio of the mixture of amorphous carbon and gold is, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 as a weight ratio, but is not necessarily limited to these ranges, and the required total It is selected according to the characteristics of the solid secondary battery (1). Cycle characteristics of the all-solid-state secondary battery 1 are further improved by having such a composition of the negative electrode active material.

The anode active material included in the anode 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), tin (Sn ) and zinc (Zn). Metalloids are otherwise semiconductors. The content of the second particles is 8 to 60% by weight, 10 to 50% by weight, 15 to 40% by weight, or 20 to 30% by weight based on the total weight of the mixture. By having the content of the second particles within this range, for example, cycle characteristics of the all-solid-state secondary battery 1 are further improved.

The binder included in the negative active material layer 22 is, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride/ Hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but not necessarily limited thereto, are all possible as long as they are used as binders in the art. The binder may be single or composed of a plurality of different binders.

As the negative active material layer 22 includes a binder, the negative active material layer 22 is stabilized on the negative electrode current collector 21 . In addition, cracking of the anode active material layer 22 is suppressed despite a change in volume and/or relative position of the anode active material layer 22 during charging and discharging. For example, when the anode active material layer 22 does not contain a binder, the anode active material layer 22 can be easily separated from the anode current collector 21 . When the anode active material layer 22 is separated from the anode current collector 21, a short circuit occurs when the anode current collector 21 contacts the solid electrolyte layer 30 at the exposed portion of the anode current collector 21. Chances increase. The negative electrode active material layer 22 is manufactured, for example, by applying a slurry in which materials constituting the negative electrode active material layer 22 are dispersed onto the negative electrode current collector 21 and drying it. Stable dispersion of the negative active material in the slurry is possible by including the binder in the negative active material layer 22 . For example, when the slurry is applied on 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).

The negative electrode 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 auxiliary agents.

The thickness of the 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 layers 12, 12a, 12b. The thickness of the negative electrode active material layer 22 is, for example, 1 um to 20 um, 2 um to 10 um, or 3 um to 7 um. If the thickness of the negative electrode active material layer 22 is too thin, lithium dendrites formed between the negative electrode active material layer 22 and the negative electrode current collector 21 collapse the negative electrode active material layer 22 to form an all-solid-state secondary battery 1 It is difficult to improve the cycle characteristics of If the thickness of the negative electrode active material layer 22 is excessively increased, the energy density of the all-solid-state secondary battery 1 is lowered and the internal resistance of the all-solid-state secondary battery 1 by the negative electrode active material layer 22 increases, resulting in an all-solid-state secondary battery The cycle characteristics of (1) are difficult to improve.

When the thickness of the negative active material layer 22 decreases, for example, the charging capacity of the negative active material layer 22 also decreases. The charge capacity of the negative electrode active material layer 22 is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 2% compared to the charge capacity of the positive electrode active material layer 12. below The charge capacity of the negative electrode active material layer 22 is, for example, 0.1% to 50%, 0.1% to 40%, 0.1% to 30%, 0.1% to 20%, 0.1% compared to the charge capacity of the positive electrode active material layer 12. to 10%, 0.1% to 5%, or 0.1% to 2%. If the charge capacity of the negative electrode active material layer 22 is too small, the thickness of the negative electrode active material layer 22 becomes very thin, so lithium formed between the negative electrode active material layer 22 and the negative electrode current collector 21 during repeated charging and discharging processes. Since dendrites collapse the anode active material layer 22 , it is difficult to improve cycle characteristics of the all-solid-state secondary battery 1 . If the charging capacity of the negative electrode active material layer 22 is excessively increased, the energy density of the all-solid secondary battery 1 is lowered and the internal resistance of the all-solid secondary battery 1 by the negative electrode active material layer 22 increases. The cycle characteristics of the battery 1 are difficult to improve.

The charge capacity of the positive electrode active material layer 12 is obtained by multiplying the charge capacity density (mAh/g) of the positive electrode active material layer by the mass of the positive electrode active material in the positive electrode active material layer 12 . When several types of positive electrode active materials are used, a charge capacity density × mass value is calculated for each positive electrode active material, and the sum of these values is the charge capacity of the positive electrode active material layer 12 . The charge capacity of the negative electrode active material layer 22 is also calculated in the same way. That is, the charge capacity of the negative active material layer 22 is obtained by multiplying the charge capacity density (mAh/g) of the negative active material layer by the mass of the negative active material in the negative active material layer 22 . When several types of anode active materials are used, a charge capacity density x mass value is calculated for each anode active material, and the sum of these values is the capacity of the anode active material layer 22 . Here, the charge capacity densities of the positive electrode active material and the negative electrode active material are capacities estimated using an all-solid half-cell using lithium metal as a counter electrode. The charge capacities of the positive active material layer 12 and the negative active material layer 22 are directly measured by measuring the charge capacities using an all-solid half-cell. When the measured charge capacity is divided by the mass of each active material, the charge capacity density is obtained. Alternatively, the charge capacities of the positive electrode active material layer 12 and the negative electrode active material layer 22 may be initial charge capacities measured during the first cycle charge.

Referring to FIG. 7 , the all-solid-state secondary battery 1a may further include, for example, a metal layer 23 disposed between the negative electrode current collector 21 and the negative electrode active material layer 22 . The metal layer 23 may be a metal foil or a plated metal layer. The metal layer 23 includes lithium or a lithium alloy. Thus, the metal layer 23 acts, for example, as a lithium reservoir. 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 all are possible as long as they are used as lithium alloys in the art. The metal layer 23 may be made of one of these alloys or lithium, or made of several types of alloys.

The thickness of the metal layer 23 is not particularly limited, but is, for example, 1 μm to 200 μm, 1 μm to 100 μm, 1 μm to 70 μm, 1 μm to 50 μm, 1 μm to 30 μm, or 1 μm to 1 μm. It is 20 μm. If the thickness of the metal layer 23 is too thin, it is difficult to perform the role of a lithium reservoir by the metal layer 23 . If the thickness of the metal layer 23 is excessively thick, the mass and volume of the all-solid-state secondary battery 1 may increase and cycle characteristics may deteriorate. The metal layer 23 may be, for example, a metal foil having a thickness within this range.

In the all-solid-state secondary battery (1a), the metal layer 23 is disposed between the negative electrode current collector 21 and the negative electrode active material layer 22 before assembly of the all-solid-state secondary battery 1, for example, or the all-solid-state secondary battery 1 After assembly, it is deposited between the negative electrode current collector 21 and the negative electrode active material layer 22 by charging. When the metal layer 23 is disposed between the negative electrode current collector 21 and the negative electrode active material layer 22 before assembling the all-solid-state secondary battery 1a, since the metal layer 23 is a metal layer containing lithium, a lithium reservoir works as For example, lithium foil is disposed between the anode current collector 21 and the anode active material layer 22 before assembling the all-solid-state secondary battery 1a. As a result, cycle characteristics of the all-solid-state secondary battery 1a including the metal layer 23 are further improved. If the metal layer 23 is deposited by charging after assembly of the all-solid-state secondary battery 1a, since the metal layer 23 is not included during assembly of the all-solid-state secondary battery 1a, the energy of the all-solid-state secondary battery 1a density increases. For example, when charging the all-solid-state secondary battery 1, the charge exceeds the charge capacity of the negative electrode active material layer 22. That is, the negative electrode active material layer 22 is overcharged. At the beginning of charging, lithium is occluded in the negative electrode active material layer 22 . The anode active material included in the anode active material layer 22 forms an alloy or compound with lithium ions transferred from the cathode layer 10 . When charging exceeds the capacity of the negative electrode active material layer 22, for example, lithium is deposited on the back side of the negative electrode active material layer 22, that is, between the negative electrode current collector 21 and the negative electrode active material layer 22, and the deposited A metal layer corresponding to the metal layer 23 is formed by lithium. The metal layer 23 is a metal layer mainly composed of lithium (ie, metal lithium). This result is obtained by, for example, the anode active material included in the anode active material layer 22 is composed of a material forming an alloy or compound with lithium. During discharge, lithium in the negative active material layer 22 and the metal layer 23, that is, the metal layer is ionized and moves toward the positive electrode layer 10. Therefore, it is possible to use lithium as an anode active material in the all-solid-state secondary battery 1a. In addition, since the negative electrode active material layer 22 covers the metal layer 23, it serves as a protective layer for the metal layer 23, that is, the metal layer, and at the same time suppresses precipitation growth of lithium dendrite. Therefore, short circuit and capacity reduction of the all-solid-state secondary battery 1a are suppressed, and as a result, cycle characteristics of the all-solid-state secondary battery 1a are improved. In addition, when the metal layer 23 is disposed by charging after assembly of the all-solid-state secondary battery 1a, the negative electrode current collector 21 and the negative electrode active material layer 22 and the region between them are, for example, the all-solid-state secondary battery It is a Li-free region that does not contain lithium (Li) in the initial state of (1a) or the state after discharge.

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

The all-solid-state secondary battery 1 may further include, for example, a thin film (not shown) including an element capable of forming an alloy with lithium on the negative electrode current collector 21 . The thin film is disposed between the anode current collector 21 and the anode active material layer 22 . The thin film contains an element capable of forming an alloy with, for example, lithium. Elements capable of forming an alloy with lithium include, for example, gold (Au), silver (Ag), zinc (Zn), tin (Sn), indium (In), silicon (Si), aluminum (Al), Bismuth (Bi), etc., but is not necessarily limited thereto, and any element capable of forming an alloy with lithium in the art is possible. The thin film is composed of one of these metals or an alloy of several metals. By placing the thin film on the negative electrode current collector 21, for example, the deposition form of the metal layer 23 deposited between the thin film 24 and the negative electrode active material layer 22 is further flattened, and the all-solid secondary battery 1 ) cycle characteristics 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. When the thickness of the thin film is less than 1 nm, it may be difficult to exhibit the function of the thin film. If the thickness of the thin film is excessively thick, the thin film itself occludes lithium and the amount of lithium precipitated from the negative electrode decreases, thereby reducing the energy density of the all-solid-state battery and deteriorating cycle characteristics of the all-solid-state secondary battery 1 . The thin film may be disposed on the anode current collector 21 by, for example, a vacuum deposition method, a sputtering method, a plating method, etc., but is not necessarily limited to this method, and any method capable of forming a thin film in the art is possible.

[Method for manufacturing sulfide-based solid electrolyte]

A method of manufacturing a solid ion conductor compound according to another embodiment includes providing a first sulfide-based solid electrolyte; preparing a first solution by dissolving the first sulfide-based solid electrolyte in an organic solvent; preparing a dried product by drying the first solution; and preparing a second sulfide-based solid electrolyte by heat-treating the dried product, wherein the average particle diameter of the second sulfide-based solid electrolyte is smaller than the average particle diameter of the first sulfide-based solid electrolyte, and the second sulfide-based solid electrolyte The electrolyte has an Argyrodite-type crystal structure and includes a compound represented by Formula 1 below, has an average particle diameter of 0.1 μm to 7 μm, and is 0.01 mS/cm to 3 mS/cm at 25° C. It has an ion conductivity of cm, and in the XRD spectrum of the sulfide-based solid electrolyte, the intensity (Ia) of the first peak at the diffraction angle 2θ = 23.0 ° ± 0.5 ° and the diffraction angle 2θ = 25.5 ° ± 0.5 ° The ratio (ratio, Ia/Ib) of the intensity (Ib) of the second peak of is greater than 0 and less than or equal to 1:

<Formula 1>

Li _a M1 _x PS _y M2 _z M3 _w

In the above formula,

M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,

M2 is one or more elements selected from group 17 of the periodic table,

M3 is SO _n ,

4≤a≤8, 0≤x<1, 3≤y≤7, 0<z≤2, 0≤w<2, and 1.5≤n≤5.

By this manufacturing method, a sulfide-based solid electrolyte having a reduced particle size can be simply manufactured.

First, a first sulfide-based solid electrolyte is provided. The first sulfide-based solid electrolyte includes, for example, a compound having the composition of Chemical Formula 1 and has a larger average particle diameter than the second sulfide-based solid electrolyte. The method of providing the first sulfide-based solid electrolyte is not limited. It may be prepared from a precursor of a sulfide-based solid electrolyte in a wet and/or dry manner. Alternatively, the first sulfide-based solid electrolyte is commercially available.

Next, a first solution is prepared by dissolving the first sulfide-based solid electrolyte in an organic solvent.

The organic solvent can be, for example, a polar solvent. The relative polarity of the organic solvent may be, for example, 0.5 to less than 1, 0.55 to less than 1, 0.6 to less than 1, 0.6 to 0.9, or 0.6 to 0.8.

When the organic solvent has a relative polarity within this range, the first sulfide-based solid electrolyte can be effectively dissolved. When the organic solvent is a non-polar solvent, the relative polarity of the organic solvent is excessively low, and thus the solubility of the first sulfide-based solid electrolyte may decrease.

The organic solvent may be inert to the first sulfide-based solid electrolyte, for example. If the organic solvent is active against the first sulfide-based solid electrolyte, the first sulfide-based solid electrolyte is decomposed, making it impossible to prepare the second sulfide-based solid electrolyte.

The organic solvent may be, for example, a hydroxyl solvent. The hydroxyl solvent may be, for example, a solvent containing a hydroxyl group and an alkyl group.

The hydroxyl solvent can be, for example, an alkanol containing 1 to 8 carbon atoms. Organic solvents are for example methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 1-hexanol, 2-hexanol , 3-hexanol, 1-heptanol and 1-octanol may include at least one selected from.

Referring to FIGS. 4A and 4B , the first solution may be transparent or partially transparent. A transparent or translucent first solution indicates that the first sulfide-based solid electrolyte is mostly or completely dissolved in the organic solvent.

The amount of the first sulfide-based solid electrolyte dissolved in the first solution may be 30 wt% or less, 20 wt% or less, or 15 wt% or less based on the total weight of the first solution. The content of the first sulfide-based solid electrolyte dissolved in the first solution and included in the first solution may be 0.1 to 30 wt%, 1 to 20 wt%, or 5 to 15 wt% based on the total weight of the first solution. When the first solution includes the first sulfide-based solid electrolyte within this range, the first solution may be transparent or translucent.

Next, the first solution is dried to prepare a dried product. The first solution may be a slurry prepared by volatilizing the solvent at 100 °C to 200 °C, 500 °C to 200 °C, or 170 °C to 200 °C, for example.

The slurry can then be dried to prepare a dried product. Drying of the slurry may be performed at a temperature of, for example, 100 °C to 180 °C, 120 °C to 160 °C, or 130 °C to 150 °C. Drying of the slurry may be performed for, for example, 1 hour to 100 hours, 1 to 50 hours, 10 to 30 hours, or 20 to 30 hours. Drying can be carried out, for example, in a vacuum oven.

The degree of crystallinity of the dry matter may be, for example, 50% or less, 40% or less, 30% or less, or 20% or less. The degree of crystallinity of the dry matter may be, for example, 1% to 50%, 5% to 40%, 5% to 30%, or 5% to 20%. The crystallinity of the dried product can be calculated, for example, as the intensity ratio of peaks at specific diffraction angles in the XRD spectrum of the dried product with respect to 100% crystallinity.

Subsequently, a second sulfide-based solid electrolyte may be prepared by heat-treating the dried product. Heat treatment of the dry matter can be carried out, for example, in an inert gas atmosphere or in vacuum. The inert gas is, for example, argon, nitrogen, etc., but is not limited thereto. Heat treatment of the dried material may be performed at a temperature of, for example, 350 °C to 750 °C, 450 °C to 650 °C, or 500 °C to 600 °C. Dry heat treatment may be performed for, for example, 30 minutes to 100 hours, 30 minutes to 50 hours, 1 hour to 20 hours, or 1 hour to 12 hours.

The average particle diameter of the prepared second sulfide-based solid electrolyte may be smaller than that of the first sulfide-based solid electrolyte. The average particle diameter of the prepared second sulfide-based solid electrolyte may be 95% or less, 90% or less, 80% or less, 70% or less, 50% or less, 30% or less, or 10% or less of the average particle diameter of the first sulfide-based solid electrolyte. there is. The average particle diameter of the prepared second sulfide-based solid electrolyte is 1% to 95%, 1% to 90%, 1% to 80%, 5% to 70%, 5% to 50% of the average particle diameter of the first sulfide-based solid electrolyte. %, 5% to 30% or 5% to 10%.

The prepared second sulfide-based solid electrolyte may be, for example, powder. The prepared second sulfide-based solid electrolyte powder may be additionally classified using a classifier. The classifier is not particularly limited and may be, for example, a mesh or the like. The classified second sulfide-based solid electrolyte may have a more uniform particle size distribution. For example, coarse particles included in the second sulfide-based solid electrolyte may be selectively removed by further classification.

Through the following Examples and Comparative Examples, this creative idea will be explained in more detail. However, the examples are for exemplifying the present creative idea, and the scope of the present creative idea is not limited only to them.

(Manufacture of solid ion conductor compound)

Example 1: Li using methanol ₆ PS ₅ Preparation of Cl

All manufacturing processes were carried out in a glove box under a dry argon atmosphere.

A Li ₆ PS ₅ Cl first sulfide-based solid electrolyte powder having a D50 average particle diameter of 30 μm was prepared.

A first solution was prepared by adding the first sulfide-based solid electrolyte powder to methanol, an organic solvent, and stirring at room temperature for 24 hours to dissolve the first sulfide-based solid electrolyte. The content of the first sulfide-based solid electrolyte powder included in the first solution was 10 wt%.

As shown in Figure 4a, the first solution was transparent to the extent that the back of the beaker could be seen.

The first solution was removed by evaporating the organic solvent at 180°C, and then left to stand at 140°C for 24 hours in a vacuum oven to obtain a dried product.

1a and 1b are XRD spectra of dry matter. As shown in Figure 1a, the peak intensity of the dried product obtained by using the methanol solvent was low due to the low crystallinity of the dried product.

The degree of crystallinity of the dried product obtained using methanol was less than 20%.

The dried material was put into a furnace under an argon atmosphere and heat-treated at 550° C. for 3 hours to obtain Li ₆ PS ₅ Cl second sulfide-based solid electrolyte powder. The D50 average particle diameter of the second sulfide-based solid electrolyte powder was 6 μm.

As shown in the scanning electron microscope image of the second sulfide-based solid electrolyte powder in FIG. 3a and the scanning electron microscope image of the first sulfide-based solid electrolyte powder in FIG. 3c, the second sulfide-based solid electrolyte powder prepared using methanol The average particle diameter of was decreased compared to the first sulfide-based solid electrolyte powder.

The relative polarity of methanol to water was 0.76, and the boiling point was 64.7 °C. The relative polarity of water is 1.

Example 2: Li using ethanol ₆ PS ₅ Preparation of Cl

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that ethanol was used instead of methanol as an organic solvent. The crystallinity of the dried product was less than 20%.

The relative polarity of ethanol to water was 0.65, and the boiling point was 78.4 °C. The relative polarity of water is 1.

Comparative Example 1: Li using acetonitrile ₆ PS ₅ Preparation of Cl

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that acetonitrile (ACN) was used instead of methanol as an organic solvent.

The relative polarity of acetonitrile (ACN, acetonitrile) to water was 0.46, and the boiling point was 82.1 °C. The relative polarity of water is 1.

Comparative Example 2: Li using acetone ₆ PS ₅ Preparation of Cl

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that acetone was used instead of methanol as an organic solvent.

The relative polarity of acetone to water was 0.36, and the boiling point was 56.0 °C. The relative polarity of water is 1.

Comparative Example 3: Li using tetrahydrofuran ₆ PS ₅ Preparation of Cl

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that tetrahydroputan (THF) was used as an organic solvent instead of methanol.

The relative polarity of tetrahydrofuran to water was 0.21, and the boiling point was 66.0 °C. The relative polarity of water is 1.

Comparative Example 4: Li with Heptane ₆ PS ₅ Preparation of Cl

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that heptane was used instead of methanol as an organic solvent.

The relative polarity of heptane to water was 0.01, and the boiling point was 98.4 °C. The relative polarity of water is 1.

Comparative Example 5: Li using NMP ₆ PS ₅ Preparation of Cl

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that N-methylpyrrolidone (NMP) was used instead of methanol as an organic solvent.

The relative polarity of N-methylpyrrolidone (NMP) to water was 0.67, and the boiling point was 202.0 °C. The relative polarity of water is 1.

Comparative Example 6: Li using toluene ₆ PS ₅ Preparation of Cl

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that toluene was used instead of methanol as an organic solvent.

The relative polarity of toluene to water was 0.099, and the boiling point was 100.6 °C. The relative polarity of water is 1.

Example 3: Manufacturing all-solid-state secondary battery

(Anode layer manufacturing)

Cathode active material LiNi _0.8 Co _0.15 Al _0.05 O ₂ (NCA) (D50 = 14 μm), carbon nanofibers as a conductive material, polytetrafluoroethylene (PTFE) as a binder, and the second sulfide-based solid electrolyte prepared in Example 1 ( D50 = 6 μm), and then xylene was added to prepare a cathode slurry. A positive electrode sheet was prepared by molding the prepared positive electrode slurry into a sheet shape. The mixed weight ratio of the opposing positive electrode active material and the small particle positive electrode active material was 3:1. The mixed weight ratio of cathode active material: conductive material: binder: solid ion conductor compound was 84:0.2:1.0:14.8. The prepared cathode sheet was pressed onto an anode current collector of 18 μm thick aluminum foil, placed in a batch-type oil chamber, and warm isostatic press (WIP) at 90° C. for 1 hour at a pressure of 500 MPa. A positive electrode layer was prepared by performing the process.

(Manufacture of solid electrolyte layer)

A solid electrolyte layer was prepared as follows using the first sulfide-based solid electrolyte (D50 = 30 μm) used in Example 1 as a solid electrolyte powder.

A mixture was prepared by mixing the solid electrolyte prepared in Example 1 and an acrylic resin (manufactured by Xeon) as a binder in a weight ratio of 98.5:1.5. Isobutyl isobutyrate (IBIB), a solvent, was added to the prepared mixture and stirred to prepare a solid electrolyte slurry. The solid electrolyte slurry was placed on a polyethylene nonwoven fabric and dried in air at 25° C. for 12 hours and vacuum dried at 70° C. for 2 hours. A solid electrolyte layer in the form of a sheet formed on the polyethylene nonwoven fabric was prepared by the above process.

(cathode layer manufacturing)

A Ni foil (thickness: 10 μm) was prepared as an anode current collector. Ag particles (average primary particle diameter of about 60 nm) and carbon black (average primary particle diameter of about 35 nm) were mixed at a weight ratio of 25:75 to prepare mixed powder as an anode active material. Mixed powder prepared in a container and polyvinylidene fluoride (PVDF) binder (# 9300, Kureha Co.) were put into N-methylpyrrolidone (NMP) and stirred to prepare an anode slurry. The binder content was 7% by weight based on the total dry weight of the negative electrode layer. The prepared anode slurry was applied on Ni foil using a blade coater, and dried in air at 80° C. for 20 minutes and vacuum dried at 100° C. for 12 hours to prepare a cathode layer.

(Manufacture of all-solid-state secondary battery)

After stacking the positive electrode layer, the solid electrolyte layer, and the negative electrode layer in order, they are pressed and placed in a batch-type oil chamber, and a warm isotactic press (WIP) process is performed at 90 ° C for 1 hour at a pressure of 500 MPa. Thus, an all-solid-state secondary battery having an area of 4 cm ² was manufactured.

Example 4

An all-solid-state secondary battery was manufactured in the same manner as in Example 3, except that the sulfide-based solid electrolyte powder prepared in Example 2 was used in the positive electrode layer instead of the sulfide-based solid electrolyte powder prepared in Example 1.

Comparative Examples 7 to 12

An all-solid-state secondary battery was manufactured in the same manner as in Example 3, except that the sulfide-based solid electrolyte powder prepared in Comparative Examples 1 to 6 was used for each positive electrode layer instead of the sulfide-based solid electrolyte powder prepared in Example 1. .

Evaluation Example 1: First Solution Appearance Evaluation

4a to 4h show the appearance of the first solutions prepared in Examples 1 to 2 and Comparative Examples 1 to 6.

As shown in FIG. 4a, the first solution prepared in Example 1 was transparent enough to see the back side. In Example 1, the sulfide-based solid electrolyte was dissolved in a solvent.

As shown in FIG. 4B, the first solution prepared in Example 2 was partially transparent to the extent that the bottom surface was visible. In Example 1, the sulfide-based solid electrolyte was dissolved in a solvent.

As shown in FIGS. 4c to 4h, the first solutions prepared in Comparative Examples 1 to 6 were opaque. In Comparative Examples 1 to 4 and Comparative Example 6, the sulfide-based solid electrolytes were not dissolved in the solvent but dispersed.

As shown in Figure 4g, the color of the first solution prepared in Comparative Example 5 was completely changed. The sulfide-based solid electrolyte prepared in Comparative Example 5 reacted with the solvent (NMP) and was completely decomposed.

Evaluation Example 2: X-ray diffraction test of dried material

For the dried powders obtained by drying the first solutions in Examples 1 to 2 and Comparative Examples 1 to 4, the powder XRD spectrum was measured, and the results are shown in FIGS. 1A to 1B. Cu Kα radiation was used to measure the XRD spectrum.

As shown in FIG. 1a, the dried products of Examples 1 and 2 had relatively weak peak intensities due to the low crystallinity of the dried products.

As shown in FIG. 1A, the dry materials of Comparative Examples 1 and 3 did not dissolve in the first solution but were dispersed and then dried, resulting in little change in the peak intensity and crystal structure of the sulfide-based solid electrolyte.

As shown in FIG. 1B, in the dry products of Comparative Examples 2 and 4, almost no peaks for the azirodite crystal structure were observed due to the collapse of the azirodite crystal structure.

Evaluation Example 3: X-ray diffraction test of second sulfide-based solid electrolyte

For the second sulfide-based solid electrolyte powder prepared in Examples 1 and 2, Comparative Example 1, and Comparative Example 5, powder XRD spectra were measured, and the results are shown in FIGS. 2A and 2B. Cu Kα radiation was used to measure the XRD spectrum.

The sulfide-based solid electrolytes of Examples 1 and 2 belong to the F-23m space group, have a structure belonging to a cubic crystal system, and include sulfide having an Argyrodite type crystal structure. Confirmed.

As shown in FIG. 2A, the sulfide-based solid electrolytes prepared in Examples 1 to 2 and Comparative Examples 1 and 3 exhibit peaks corresponding to the azirodite-type crystal structure, and contain sulfides having an azirodite-type crystal structure. It was confirmed that

As shown in FIG. 2B, in the products prepared in Comparative Examples 2, 4, and 5, the azirodite-type crystal structure is collapsed, so that no peak corresponding to the azirodite-type crystal structure is observed, and non-aziro A peak for an impurity phase having a dite crystal structure was mainly observed.

The second sulfide-based solid electrolyte prepared in Example 1 has the intensity (Ia) of the first peak at the diffraction angle 2θ = 23 ° ± 0.5 ° and the intensity of the second peak at the diffraction angle 2θ = 25.5 ° ± 0.5 ° ( The ratio (Ia/Ib) of Ib) was 0.73. The first peak was a doublet peak. The second peak was a singlet peak, and the average of the doublets was used as the first peak intensity (Ia). The first peak was a peak derived from an impurity having a non-azirodite crystal structure. The second peak was derived from a sulfide having an azirodite crystal structure.

In the XRD spectrum of the second sulfide-based solid electrolyte prepared in Example 1, the intensity (Ia) of the first peak at the diffraction angle 2θ=23°±0.5° and the third peak at the diffraction angle 2θ=15.5°±0.5° The ratio (ratio, Ia/Ic) of the intensity (Ic) of was 1.05. The third peak was derived from a sulfide having an azirodite crystal structure.

The second sulfide-based solid electrolyte prepared in Example 2 has the intensity (Ia) of the first peak at the diffraction angle 2θ = 23 ° ± 0.5 ° and the intensity of the second peak at the diffraction angle 2θ = 25.5 ° ± 0.5 ° ( The ratio (Ia/Ib) of Ib) was 0.25. The first peak was a doublet peak. The second peak was a singlet peak, and the average of the doublets was used as the first peak intensity (Ia). The first peak was a peak derived from an impurity having a non-azirodite crystal structure. The second peak was derived from a sulfide having an azirodite crystal structure.

In the XRD spectrum of the second sulfide-based solid electrolyte prepared in Example 2, the intensity (Ia) of the first peak at the diffraction angle 2θ=23.5°±0.5° and the third peak at the diffraction angle 2θ=15.5°±0.5° The ratio (ratio, Ia/Ic) of the intensity (Ic) of was 0.45. The third peak was derived from a sulfide having an azirodite crystal structure.

It was determined that some impurities were generated in the process of recrystallization after the second sulfide-based solid electrolyte prepared in Examples 1 and 2 was dissolved.

In the second sulfide-based solid electrolytes prepared in Comparative Examples 1 and 3, the first peak at the diffraction angle 2θ=23°±0.5° was not observed. Accordingly, the ratio (Ia/Ib) between the intensity (Ia) and intensity (Ib) of the first peak was zero. Since the second sulfide-based solid electrolytes prepared in Comparative Examples 1 and 3 did not substantially dissolve in the solvent, it was determined that they had substantially the same peak as the first sulfide-based solid electrolyte.

The second sulfide-based solid electrolytes prepared in Comparative Examples 2, 4 and 5 have the intensity (Ia) of the first peak at the diffraction angle 2θ=23°±0.5° and the second peak at the diffraction angle 2θ=25.5°±0.5°. The peak intensity (Ib) ratio (ratio, Ia/Ib) was 1.1 or more. In the sulfide-based solid electrolytes prepared in Comparative Examples 2 and 4, the crystal structure of azirodite was mostly collapsed by reaction with the solvent, resulting in excessive impurities, and it was determined that the peaks for the impurities appeared larger.

Evaluation Example 4: Measurement of ionic conductivity

After preparing the second sulfide-based solid electrolyte powders prepared in Examples 1 to 2 and Comparative Examples 1 to 6, 200 mg of the powder was pressed at a pressure of 4 ton/cm ² for 2 minutes to obtain a thickness of about 100 μm and a diameter of about 13 mm. A pellet specimen was prepared. Symmetry cells were prepared by disposing indium (In) electrodes having a thickness of 50 μm and a diameter of 13 mm on both sides of the prepared specimen, respectively. The preparation of the symmetric cell was carried out in an Ar atmosphere glover box.

The impedance of the pellets was measured by a two-probe method using an impedance analyzer (Material Mates 7260 impedance analyzer) for the specimens with indium electrodes disposed on both sides. The frequency range was 0.1 Hz to 1 MHz, and the amplitude voltage was 10 mV. It was measured at 25°C in an Ar atmosphere. The resistance value was obtained from the arc of the Nyguist plot for the impedance measurement results, and the ionic conductivity was calculated considering the area and thickness of the specimen. The measurement results are shown in Table 1 below.

Ionic conductivity [mS/cm] Example 1 0.21 Example 2 0.8 Comparative Example 2 0.05 Comparative Example 4 0.04 Comparative Example 5 not measurable

As shown in Table 1, the second sulfide-based solid electrolytes prepared in Examples 1 and 2 had improved ionic conductivity at 25 ° C. compared to the second sulfide-based solid electrolytes prepared in Comparative Examples 2, 4 and 5. .

Evaluation Example 5: Particle size measurement

D50 values of the second sulfide-based solid electrolyte particles prepared in Examples 1 to 2 and Comparative Examples 1 to 6 were measured using a particle size analyzer (PSA). The measurement solvent was xylene.

The median particle diameter, which is the D50 value of the prepared solid ion conductor compound particles, was taken as the average particle diameter. Some of the measurement results are shown in Table 2 below.

Scanning electron microscope images of the second sulfide-based solid electrolytes prepared in Examples 1, 2, and Comparative Example 3 are shown in FIGS. 3A to 3C.

A scanning electron microscope image of the first sulfide-based solid electrolyte used in the preparation of the second sulfide-based solid electrolyte is shown in FIG. 3D.

D50
[um] Example 1 6 Example 2 10 Comparative Example 3 30 First sulfide-based solid electrolyte
(crude Li ₆ PS ₅ Cl) 30

As shown in Table 2, the second sulfide-based solid electrolytes prepared in Examples 1 and 2 exhibited an average particle diameter (D50) of 10 μm or less.

The second sulfide-based solid electrolyte prepared in Examples 1 and 2 had a reduced average particle diameter compared to the first sulfide-based solid electrolyte.

The average particle diameter of the sulfide-based solid electrolyte of Comparative Example 3 was increased compared to the first sulfide-based solid electrolyte.

Therefore, the particle size of the sulfide-based solid electrolyte can be easily reduced by the method for preparing the sulfide-based solid electrolyte of the present invention.

Evaluation Example 6: Evaluation of Life Characteristics

Life characteristics of the all-solid-state secondary batteries of Examples 3 to 4 and Comparative Examples 7 to 12 were evaluated. The charge/discharge test was performed by putting the all-solid-state secondary battery in a chamber at 45°C.

The battery was charged with a constant current of 0.33C until the voltage reached 4.25V, and charged until the current value reached 0.1C at a constant voltage of 4.25V. Subsequently, discharging was performed at a constant current of 0.33 C until the battery voltage reached 2.5 V. Fifty such charge/discharge cycles were performed. A 10-minute rest period was placed after the charge and discharge steps for each cycle.

Capacity retention rates of the all-solid-state secondary batteries prepared in Examples 3 to 4 and Comparative Examples 7 to 12 were measured. The capacity retention rate is calculated from Equation 2 below.

<Equation 1>

Capacity retention rate (%) = [discharge capacity of the 50th cycle / discharge capacity of the first cycle] × 100

The all-solid-state secondary batteries of Examples 3 to 4 had improved capacity retention rates compared to the all-solid-state secondary batteries of Comparative Examples 8, 10, and 11 having a positive electrode layer containing a sulfide in which the azirodite structure was collapsed.

1, 1a, 40 All-solid-state secondary battery 10 Cathode layer
11 positive electrode current collector 12 positive electrode active material layer
20 negative electrode layer 21 negative electrode current collector
22 anode active material layer 23 metal layer
30 solid electrolyte layer

Claims (20)

As a sulfide-based solid electrolyte for an all-solid-state battery,
It includes a compound having an Argyrodite-type crystal structure and represented by Formula 1 below,
The average particle diameter is 0.1 μm to 10 μm,
It has an ion conductivity of 0.01 mS / cm to 3 mS / cm at 25 ° C,
In the XRD spectrum of the sulfide-based solid electrolyte, the ratio of the intensity (Ia) of the first peak at the diffraction angle 2θ = 23° ± 0.5° and the intensity (Ib) of the second peak at the diffraction angle 2θ = 25.5° ± 0.5° (ratio, Ia / Ib) is greater than 0 to less than 1, sulfide-based solid electrolyte for all-solid-state batteries:
<Formula 1>
Li _a M1 _x PS _y M2 _z M3 _w
In the above formula,
M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,
M2 is one or more elements selected from group 17 of the periodic table,
M3 is SO _n ,
4≤a≤8, 0≤x<1, 3≤y≤7, 0<z≤2, 0≤w<2, and 1.5≤n≤5. The sulfide-based solid electrolyte according to claim 1, wherein a ratio (Ia/Ib) of the intensity (Ia) of the first peak and the intensity (Ib) of the second peak is 0.01 to 1. The sulfide system according to claim 1, wherein the first peak is a peak derived from the non-azirodite crystal structure, and the second peak is a peak derived from the azirodite crystal structure. solid electrolyte. The sulfide-based solid electrolyte for an all-solid-state battery according to claim 1, wherein the first peak is a doublet and the second peak is a singlet. According to claim 1, in the XRD spectrum of the sulfide-based solid electrolyte, the intensity (Ia) of the first peak at the diffraction angle 2θ = 23 ° ± 0.5 ° and the third peak at the diffraction angle 2θ = 15.5 ° ± 0.5 ° A sulfide-based solid electrolyte for an all-solid-state battery, wherein the ratio (Ia/Ic) of intensity (Ic) is greater than 0 and less than or equal to 6. The sulfide-based solid electrolyte according to claim 3, wherein the third peak is a peak derived from an azirodite crystal structure. The method of claim 1, wherein M1 is Na, K, Cu, Mg, Ag, Cu, Hf, In, Ti, Pb, Sb, Fe, Zr, Zn, Cr, B, Sn, Ge, Si, Zr, Ta , Nb, V, Ga, Al, As, or a combination thereof,
M2 includes F, Cl, Br, I or a combination thereof,
_{SO n} of M3 is S ₄ O ₆ , S ₃ O ₆ , S 2 O 3 , S ₂ O ₄ , S ₂ O ₅ , S ₂ O ₆ , S ₂ O ₇ , _{S 2 O 8} , SO ₄ , SO ₅ , or a combination thereof, a sulfide-based solid electrolyte for an all-solid-state battery. The sulfide-based solid electrolyte for an all-solid-state battery according to claim 1, wherein the compound represented by Formula 1 is selected from compounds represented by Formulas 1a to 1b:
<Formula 1a>
Li _a PS _y M2 _z
In the above formula,
M2 is one or more elements selected from group 17 of the periodic table,
4≤a≤8, 3≤y≤7, and 0<z≤2,
<Formula 1b>
Li _a M1 _x PS _y M2 _z
In the above formula,
M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,
M2 is one or more elements selected from group 17 of the periodic table,
4≤a≤8, 0<x<1, 3≤y≤7, and 0<z≤2, The sulfide-based solid electrolyte for an all-solid-state battery according to claim 1, wherein the compound represented by Formula 1 is selected from compounds represented by Formulas 1c to 1d:
<Formula 1c>
Li _a PS _y M2 _z M3 _w
In the above formula,
M2 is one or more elements selected from group 17 of the periodic table,
M3 is SO _n ,
4≤a≤8, 3≤y≤7, 0<z≤2, 0<w<2, and 1.5≤n≤5,
<Formula 1d>
Li _a M1 _x PS _y M2 _z M3 _w
In the above formula,
M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,
M2 is one or more elements selected from group 17 of the periodic table,
M3 is SO _n ,
4≤a≤8, 0<x<1, 3≤y≤7, 0<z≤2, 0<w<2, and 1.5≤n≤5. The sulfide-based solid electrolyte for an all-solid-state battery according to claim 1, wherein the compound represented by Formula 1 is represented by the following formulas:
Li _7-z PS _6-z F _z1 , Li _7-z PS _6-z Cl _z1 , Li _7-z PS _6-z Br _z1 , Li _7-z PS _6-z I _z1 ,
Li _7-z PS _6-z F _z1 Cl _z2 , Li _7-z PS _6-z F _z1 Br _z2 , Li _7-z PS _6-z F _z1 I _z2 , Li _7-z PS _6-z Cl _z1 Br _z2 , Li _7-z PS _6-z Cl _z1 I _z2 , Li _7-z PS _6-z Cl _z1 F _z2 , Li _7-z PS _6-z Br _z1 I _z2 , Li _7-z PS _6-z Br _z1 F _z2 , Li _7-z PS _6-z Br _z1 Cl _z2 , Li _7-z PS _6-z I _z1 F _z2 , Li _7-z PS _6-z I _z1 Cl _z2 , Li _7-z PS _{6- z} I _z1 Br _z2 ,
Li _7-vz Na _v PS _6-z F _z1 , Li _7-vz Na _v PS _6-z Cl _z1 , Li _7-vz Na _v PS _6-z Br _z1 , Li _7-vz Na _v PS _6-z I _z1 ,
Li _7-vz Na _v PS _6-z F _z1 Cl _z2 , Li _7-vz Na _v PS _6-z F _z1 Br _z2 , Li _7-vz Na _v PS _6-z F _z1 I _z2 , Li _7-vz Na _v PS _6-z Cl _z1 Br _z2 , Li _7-vz Na _v PS _6-z Cl _z1 I _z2 , Li _7-vz Na _v PS _6-z Cl _z1 F _z2 , Li _7-vz Na _v PS _6-z Br _z1 I _z2 , Li _7-vz Na _v PS _6-z Br _z1 F _z2 , Li _7-vz Na _v PS _6-z Br _z1 Cl _z2 , Li _7-vz Na _v PS _6-z I _z1 F _z2 , Li _7-vz Na _v PS _6-z I _z1 Cl _z2 , Li _7-vz Na _v PS _6-z I _z1 Br _z2 ,
Li _7-vz K _v PS _6-z F _z1 , Li _7-vz K _v PS _6-z Cl _z1 , Li _7-vz K _v PS _6-z Br _z1 , Li _7-vz K _v PS _6-z I _z1 ,
Li _7-vz K _v PS _6-z F _z1 Cl _z2 , Li _7-vz K _v PS _6-z F _z1 Br _z2 , Li _7-vz K _v PS _6-z F _z1 I _z2 , Li _7-vz K _v PS _6-z Cl _z1 Br _z2 , Li _7-vz K _v PS _6-z Cl _z1 I _z2 , Li _7-vz K _v PS _6-z Cl _z1 F _z2 , Li _7-vz K _v PS _6-z Br _z1 I _z2 , Li _7-vz K _v PS _6-z Br _z1 F _z2 , Li _7-vz K _v PS _6-z Br _z1 Cl _z2 , Li _7-vz K _v PS _6-z I _z1 F _z2 , Li _7-vz K _v PS _6-z I _z1 Cl _z2 , Li _7-vz K _v PS _6-z I _z1 Br _z2 ,
Li _7-vz Cu _v PS _6-z F _z1 , Li _7-vz Cu _v PS _6-z Cl _z1 , Li _7-vz Cu _v PS _6-z Br _z1 , Li _7-vz Cu _v PS _6-z I _z1 ,
Li _7-vz Cu _v PS _6-z F _z1 Cl _z2 , Li _7-vz Cu _v PS _6-z F _z1 Br _z2 , Li _7-vz Cu _v PS _6-z F _z1 I _z2 , Li _7-vz Cu _v PS _6-z Cl _z1 Br _z2 , Li _7-vz Cu _v PS _6-z Cl _z1 I _z2 , Li _7-vz Cu _v PS _6-z Cl _z1 F _z2 , Li _7-vz Cu _v PS _6-z Br _z1 I _z2 , Li _7-vz Cu _v PS _6-z Br _z1 F _z2 , Li _7-vz Cu _v PS _6-z Br _z1 Cl _z2 , Li _7-vz Cu _v PS _6-z I _z1 F _z2 , Li _7-vz Cu _v PS _6-z I _z1 Cl _z2 , Li _7-vz Cu _v PS _6-z I _z1 Br _z2 ,
Li _7-vz Mg _v PS _6-z F _z1 , Li _7-vz Mg _v PS _6-z Cl _z1 , Li _7-vz Mg _v PS _6-z Br _z1 , Li _7-vz Mg _v PS _6-z I _z1 ,
Li _7-vz Mg _v PS _6-z F _z1 Cl _z2 , Li _7-vz Mg _v PS _6-z F _z1 Br _z2 , Li _7-vz Mg _v PS _6-z F _z1 I _z2 , Li _7-vz Mg _v PS _6-z Cl _z1 Br _z2 , Li _7-vz Mg _v PS _6-z Cl _z1 I _z2 , Li _7-vz Mg _v PS _6-z Cl _z1 F _z2 , Li _7-vz Mg _v PS _6-z Br _z1 I _z2 , Li _7-vz Mg _v PS _6-z Br _z1 F _z2 , Li _7-vz Mg _v PS _6-z Br _z1 Cl _z2 , Li _7-vz Mg _v PS _6-z I _z1 F _z2 , Li _7-vz Mg _v PS _6-z I _z1 Cl _z2 , Li _7-vz Mg _v PS _6-z I _z1 Br _z2 ,
Li _7-vz Ag _v PS _6-z F _z1 , Li _7-vz Ag _v PS _6-z Cl _z1 , Li _7-vz Ag _v PS _6-z Br _z1 , Li _7-vz Ag _v PS _6-z I _z1 ,
Li _7-vz Ag _v PS _6-z F _z1 Cl _z2 , Li _7-vz Ag _v PS _6-z F _z1 Br _z2 , Li _7-vz Ag _v PS _6-z F _z1 I _z2 , Li _7-vz Ag _v PS _6-z Cl _z1 Br _z2 , Li _7-vz Ag _v PS _6-z Cl _z1 I _z2 , Li _7-vz Ag _v PS _6-z Cl _z1 F _z2 , Li _7-vz Ag _v PS _6-z Br _z1 I _z2 , Li _7-vz Ag _v PS _6-z Br _z1 F _z2 , Li _7-vz Ag _v PS _6-z Br _z1 Cl _z2 , Li _7-vz Ag _v PS _6-z I _z1 F _z2 , Li _7-vz Ag _v PS _6-z I _z1 Cl _z2 , Li _7-vz Ag _v PS _6-z I _z1 Br _z2 ,
In the above equations, 0<v<0.7, 0<z1<2, 0≤z2<1, 0<z<2 and z=z1+z2. The sulfide-based solid electrolyte for an all-solid-state battery according to claim 1, wherein the compound represented by Formula 1 is represented by the following formulas:
Li _7-z PS _6-zw F _z (SO ₄ ) _w , Li _7-z PS _6-zw Cl _z (SO ₄ ) _w , Li _7-z PS _6-zw Br _z (SO ₄ ) _w , Li _{7 -z} PS _6-zw I _z (SO ₄ ) _w
Li _7-vz Na _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz Na _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz Na _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz Na _v PS _6-zw I _z (SO ₄ ) _w ,
Li _7-vz K _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz K _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz K _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz K _v PS _6-zw I _z (SO ₄ ) _w ,
Li _7-vz Cu _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz Cu _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz Cu _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz Cu _v PS _6-zw I _z (SO ₄ ) _w ,
Li _7-vz Mg _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz Mg _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz Mg _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz Mg _v PS _6-zw I _z (SO ₄ ) _w ,
Li _7-vz Ag _v PS _6-zw F _z (SO ₄ ) _w , Li _7-vz Ag _v PS _6-zw Cl _z (SO ₄ ) _w , Li _7-vz Ag _v PS _6-zw Br _z (SO ₄ ) _w , Li _7-vz Ag _v PS _6-zw I _z (SO ₄ ) _w
In the above expressions,
0<v<0.7, 0<z≤2, and 0<w<0.2. A cathode layer including a cathode active material layer;
A negative electrode layer including a negative electrode active material layer; and
A solid electrolyte layer disposed between the anode layer and the cathode layer,
An all-solid-state secondary battery comprising at least one of the positive electrode active material layer and the solid electrolyte layer comprising the sulfide-based solid electrolyte according to any one of claims 1 to 11. According to claim 12,
The positive electrode active material layer includes a third sulfide-based solid electrolyte, and the average particle diameter of the third sulfide-based solid electrolyte is 0.1 μm to 10 μm,
The electrolyte layer includes a fourth sulfide-based solid electrolyte, and the average particle diameter of the fourth sulfide-based solid electrolyte is 1 μm to 30 μm,
An all-solid-state secondary battery wherein the average particle diameter of the third sulfide-based solid electrolyte is smaller than the average particle diameter of the fourth sulfide-based solid electrolyte. providing a first sulfide-based solid electrolyte;
preparing a first solution by dissolving the first sulfide-based solid electrolyte in an organic solvent;
preparing a dried product by drying the first solution; and
Preparing a second sulfide-based solid electrolyte by heat-treating the dried product;
The average particle diameter of the second sulfide-based solid electrolyte is smaller than the average particle diameter of the first sulfide-based solid electrolyte,
The second sulfide-based solid electrolyte,
It includes a compound having an Argyrodite-type crystal structure and represented by Formula 1 below,
The average particle diameter is 0.1 μm to 10 μm,
It has an ion conductivity of 0.01 mS / cm to 3 mS / cm at 25 ° C,
In the XRD spectrum of the sulfide-based solid electrolyte, the ratio of the intensity (Ia) of the first peak at the diffraction angle 2θ = 23° ± 0.5° and the intensity (Ib) of the second peak at the diffraction angle 2θ = 25.5° ± 0.5° Method for producing a sulfide-based solid electrolyte for an all-solid-state battery in which (ratio, Ia/Ib) is greater than 0 and less than or equal to 1:
<Formula 1>
Li _a M1 _x PS _y M2 _z M3 _w
In the above formula,
M1 is one or more metal elements other than Li selected from groups 1 to 15 of the periodic table,
M2 is one or more elements selected from group 17 of the periodic table,
M3 is SO _n ,
4≤a≤8, 0≤x<1, 3≤y≤7, 0<z≤2, 0≤w<2, and 1.5≤n≤5. 15. The method of claim 14, wherein the organic solvent is a polar solvent, and the relative polarity of the organic solvent is from 0.5 to less than 1,
The manufacturing method, wherein the organic solvent is inert to the first sulfide-based solid electrolyte. 15. The method of claim 14, wherein the organic solvent is a hydroxyl solvent and the hydroxyl solvent is an alkanol containing 1 to 8 carbon atoms,
The organic solvent is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 1-hexanol, 2-hexanol, 3 - A manufacturing method comprising at least one selected from hexanol, 1-heptanol and 1-octanol. 15. The method of claim 14, wherein the first solution is transparent or partially transparent,
The content of the first sulfide-based solid electrolyte dissolved in the first solution is 30 wt% or less based on the total weight of the first solution. The method according to claim 14, wherein the degree of crystallinity of the dried product is 50% or less. The manufacturing method according to claim 14, wherein the heat treatment is performed at a temperature of 350°C to 750°C for 30 minutes to 12 hours under an inert gas atmosphere or vacuum. The manufacturing method according to claim 14, wherein the second sulfide-based solid electrolyte is a powder, and further comprising a step of classifying the second sulfide-based solid electrolyte.

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