All-solid-state battery

Abstract

To provide an anode-free all-solid-state battery that is improved in discharge capacity and cycle characteristics, and also to provide an anode-free all-solid-state battery that can be driven with low constraining pressure.SOLUTION: The present disclosure provides an all-solid-state battery which includes a positive electrode including a positive electrode active material layer, a negative electrode current collector, and a solid electrolyte layer disposed between the positive electrode and the negative electrode current collector. The all-solid-state battery does not contain a negative electrode active material, lithium ions are supplied from the positive electrode active material layer by charging, a lithium metal layer as a negative electrode active material is formed on the negative electrode current collector, and the solid electrolyte layer includes a sulfide-based solid electrolyte containing a group 2 element and having an argyrodite-type crystal structure.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to an all-solid-state battery having an anode-free structure.

Background Art

[0002] For the purpose of achieving high safety, long life, and high energy density, the development of all-solid-state batteries in which the electrolyte of a lithium-ion battery is replaced with a solid electrolyte has been underway. Among several solid electrolytes, sulfide-based solid electrolytes such as Li 10 GeP2S 12 have high ionic conductivity close to that of an electrolyte and have advantages such as being soft and easily obtaining good adhesion to an active material, and the practical application of all-solid-state batteries using sulfide-based solid electrolytes has been expected.

[0003] On the other hand, lithium metal has attracted attention as a negative electrode material for all-solid-state batteries because it can increase the mass energy density (Wh / kg) due to its low mass per unit volume and large theoretical capacity. However, sulfide-based solid electrolytes such as Li 10 GeP2S 12 have low stability against lithium metal and have a problem that it is difficult to use them together with a lithium metal negative electrode.

[0004] Furthermore, when lithium metal is used as a battery negative electrode, generally, a lithium foil is attached onto a planar current collector to manufacture a battery. However, since lithium is an alkali metal and has high reactivity, it explosively reacts with water and also reacts with oxygen in the air, so there is a disadvantage that it is difficult to manufacture and use in a general environment. In particular, when lithium metal is exposed to the air, an oxide film such as LiOH, Li2O, Li2CO3 is formed as a result of oxidation. When the surface oxide film exists on the surface, the oxide film acts as an insulating film and the electrical conductivity decreases, and there occurs a problem that the smooth movement of lithium ions is inhibited and the electrical resistance increases.

[0005] To solve this problem, Patent Documents 1 to 3 disclose an anode-free all-solid-state battery in which a trace amount of a seed metal capable of forming an alloy with lithium such as Ag or Zn is deposited on a negative electrode current collector. However, such an anode-free all-solid-state battery has a problem of high cost because an additional process for applying and sputtering the above metal is required. In addition, an anode-free all-solid-state battery needs to apply a high restraint pressure during battery operation to prevent the growth of lithium dendrites.

[0006] To solve the above problems, as a result of extensive research by the present inventors, in order to fundamentally block the contact of lithium metal with the atmosphere during battery assembly, after assembling the battery, a lithium metal layer is formed on the negative electrode current collector by lithium ions transferred from the positive electrode active material by charging. An anode-free all-solid-state battery was designed. Furthermore, as a solid electrolyte used in the anode-free all-solid-state battery, by using a sulfide-based solid electrolyte containing a polyvalent cation, an anode-free all-solid-state battery having excellent discharge capacity and cycle characteristics and capable of operating at a low restraint pressure was developed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present disclosure is to provide an anode-free all-solid-state battery with improved discharge capacity and cycle characteristics.

[0009] Further, an object of the present disclosure is to provide an anode-free all-solid-state battery that can be driven at a low confinement pressure.

Means for Solving the Problems

[0010] To achieve the above object, the present disclosure provides an all-solid-state battery including a positive electrode including a positive electrode active material layer, a negative electrode current collector, and a solid electrolyte layer disposed between the positive electrode and the negative electrode current collector, wherein the all-solid-state battery does not contain a negative electrode active material, lithium ions are supplied from the positive electrode active material layer upon charging, and a lithium metal layer as a negative electrode active material is formed on the negative electrode current collector, and the solid electrolyte layer includes a sulfide-based solid electrolyte containing a Group 2 element and having an argyrodite-type crystal structure.

[0011] In one embodiment, the negative electrode current collector and the solid electrolyte layer may be in direct contact.

[0012] In one embodiment, the sulfide-based solid electrolyte has the chemical formula Li 7-x-2y M y PS 6-x Ha x and is represented by in the chemical formula, M is one or more elements selected from Group 2 elements, Ha is one or more elements selected from halogen elements, and 0 < x < 2.5 and 0 < y < 0.45 may be satisfied.

[0013] In one embodiment, M may be Ca.

[0014] In one embodiment, the reaction product between the negative electrode current collector and the sulfide-based solid electrolyte may not be included.

[0015] In one embodiment, the all-solid-state battery may be pressed at a pressure of 0.3 MPa or less in the direction in which the positive electrode, the negative electrode current collector, and the solid electrolyte layer are laminated.

[0016] In one embodiment, the positive electrode active material layer may contain the sulfide-based solid electrolyte.

[0017] In one embodiment, the average particle size of the sulfide-based solid electrolyte contained in the solid electrolyte layer may be larger than the average particle size of the sulfide-based solid electrolyte contained in the positive electrode active material layer.

[0018] In one embodiment, the Group 2 element may be present at the 48h site of the argyrodite-type crystal structure.

Advantages of the Invention

[0019] The present disclosure can provide an anode-free all-solid-state battery with improved discharge capacity and cycle characteristics.

[0020] Also, the present disclosure can provide an anode-free all-solid-state battery that can be driven at a low constraint pressure.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0022] Hereinafter, the present disclosure will be described in more detail.

[0023] In the present specification and claims, terms and words used should not be construed in a limited sense in accordance with their ordinary or dictionary meanings. Instead, in accordance with the principle that the inventor can appropriately define the concept of terms in order to explain his invention in the best way, they should be construed in a meaning and concept that conforms to the technical idea of the present disclosure.

[0024] In the drawings, in order to clearly explain the present invention, parts not related to the explanation are omitted, and similar parts throughout the specification are given similar drawing reference numerals. Also, the sizes and relative sizes of the components shown in the drawings are not related to the actual scale and may be reduced or exaggerated for the sake of clarity of the explanation.

[0025] In the present specification, "Dn" means the particle size distribution and means the particle size at the n% point of the cumulative particle number distribution according to the particle size. That is, D50 is the particle size (median diameter, average diameter) at the 50% point of the cumulative particle number distribution according to the particle size, D90 is the particle size at the 90% point of the cumulative particle number distribution according to the particle size, and D10 is the particle size at the 10% point of the cumulative particle number distribution according to the particle size. On the other hand, the particle size distribution may be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (for example, Microtrac S3500), and the difference in the diffraction pattern due to the particle size when the particles pass through the laser beam is measured to calculate the particle size distribution.

[0026] [All-Solid-State Battery] The all-solid-state battery of the present disclosure includes a positive electrode including a positive electrode active material layer, a negative electrode current collector, and a solid electrolyte layer disposed between the positive electrode and the negative electrode current collector. The all-solid-state battery of the present disclosure does not contain a negative electrode active material, and lithium ions are supplied from the positive electrode active material layer during charging, and a lithium metal layer as a negative electrode active material is formed on the negative electrode current collector. The all-solid-state battery of the present disclosure includes a sulfide-based solid electrolyte containing a Group 2 element and having an argyrodite-type crystal structure as the solid electrolyte layer. By having the above configuration, the anode-free all-solid-state battery of the present disclosure can improve the discharge capacity and cycle characteristics. Further, the anode-free all-solid-state battery of the present disclosure can be driven at a low confinement pressure by having the above configuration.

[0027] Note that in the present disclosure, the all-solid-state battery means a state before the first lithium metal deposition (first charging) is performed on the negative electrode current collector (also referred to as an all-solid-state battery precursor).

[0028] The all-solid-state battery may be an all-solid-state lithium secondary battery.

[0029] In order to prevent the growth of lithium dendrites, a confinement pressure is applied during charge and discharge. The confinement pressure can be applied in a direction in which the positive electrode, the negative electrode current collector, and the solid electrolyte layer disposed between the positive electrode and the negative electrode current collector are laminated, that is, in a direction perpendicular to the surface direction of the negative electrode current collector. For example, the confinement pressure can be achieved by fixing with jigs from both the positive electrode side and the negative electrode current collector side of the all-solid-state battery.

[0030] In order to prevent the growth of lithium dendrites, a large confinement pressure is usually applied to the all-solid-state battery. However, the all-solid-state battery of the present disclosure using a sulfide-based solid electrolyte containing a divalent cation may hardly require a confinement pressure.

[0031] The all-solid-state battery may be pressurized at a pressure of 0.3 MPa or less, preferably 0.1 MPa or less, more preferably 0.05 MPa or less, and even more preferably 0.02 MPa or less during charge and discharge. Thus, the anode-free all-solid-state battery of the present disclosure can be driven at a low confinement pressure.

[0032] In a lithium secondary battery, a negative electrode is usually formed on a negative electrode current collector. However, in the present disclosure, after assembling into an anode-free battery structure using only the negative electrode current collector without having metal particles or a coating layer on the surface, lithium ions released from the positive electrode active material by charging form a lithium metal layer as a negative electrode active material on the negative electrode current collector. As a result, a negative electrode having a configuration of a negative electrode current collector / negative electrode active material layer is formed, which constitutes the configuration of a normal lithium secondary battery.

[0033] That is, the anode-free battery in the present disclosure may be an anode-free battery in which a negative electrode is not formed on the negative electrode current collector at the first assembly, and includes all batteries in which a negative electrode is formed on the negative electrode current collector according to use and may have a negative electrode.

[0034] Further, in the negative electrode of the present disclosure, the form of the lithium metal formed as a negative electrode active material on the negative electrode current collector includes both a form in which the lithium metal is formed in a layer and a structure in which the lithium metal is not formed in a layer (for example, a structure in which the lithium metal is aggregated in a particle form).

[0035] Hereinafter, in the present disclosure, the description will be based on the form of the lithium metal layer formed by the lithium metal in a layer, but it is clear that such a description does not exclude a structure in which the lithium metal is not formed in a layer.

[0036] <Solid electrolyte layer> The solid electrolyte layer contains a solid electrolyte. The solid electrolyte layer can serve as an insulator and an ion conduction channel in an all-solid-state lithium secondary battery.

[0037] The solid electrolyte layer may have a thickness of about 50 μm or less, preferably about 15 μm to 50 μm. The thickness can have an appropriate value within the above-described range in consideration of ion conductivity, physical strength, energy density of the applicable battery, etc. For example, in terms of ion conductivity and energy density, the thickness can be 10 μm or more, 20 μm or more, or 30 μm or more. On the other hand, in terms of physical strength, the thickness can be 50 μm or less, 45 μm or less, or 40 μm or less. Also, the solid electrolyte layer has a thickness range and at the same time, a tensile strength of about 100 kgf / cm 2 to about 2,000 kgf / cm 2 . Also, the solid electrolyte layer can have a porosity of 15 vol% or less, or about 10 vol% or less. Thus, the solid electrolyte layer according to the present disclosure can have high mechanical strength despite being a thin film.

[0038] (Solid electrolyte) The solid electrolyte may include one or more of a sulfide-based solid electrolyte, an oxide-based solid electrolyte, and a polymer-based solid electrolyte. Preferably, the solid electrolyte included in the all-solid-state battery of the present disclosure is a sulfide-based solid electrolyte. The solid electrolyte may be included in the positive electrode active material layer or may be included in the solid electrolyte layer as a separator.

[0039] The average particle size of the solid electrolyte can be controlled according to the application. By controlling the average particle size of the solid electrolyte, the ion conductivity can be improved.

[0040] The average particle size and particle size distribution of the solid electrolyte can be controlled, for example, by changing conditions such as the rotation speed and time of a ball mill apparatus. Thereby, it is possible to produce solid electrolyte coarse powder having a relatively large average particle size, solid electrolyte fine powder having a relatively small average particle size, and solid electrolyte super-coarse powder having a wider particle size distribution than the solid electrolyte coarse powder. For example, the solid electrolyte coarse powder and the solid electrolyte super-coarse powder can be separately produced by controlling the pulverization time of the ball mill apparatus.

[0041] The average particle size of the solid electrolyte coarse powder may be larger than that of the solid electrolyte fine powder. The average particle size of the solid electrolyte coarse powder is 5 to 50 μm, preferably 8 to 30 μm, and more preferably 10 to 20 μm. The average particle size of the solid electrolyte fine powder is 0.1 to 10 μm, preferably 0.5 to 5 μm, and more preferably 1 to 3 μm.

[0042] The average particle size of the solid electrolyte supercoarse powder may be comparable to that of the solid electrolyte coarse powder. That is, the average particle size of the solid electrolyte supercoarse powder is 5 to 50 μm, preferably 8 to 30 μm, and more preferably 10 to 20 μm. The D10 of the solid electrolyte supercoarse powder is smaller than the D10 of the solid electrolyte coarse powder, and the D90 of the solid electrolyte supercoarse powder is larger than the D90 of the solid electrolyte coarse powder. The D10 of the solid electrolyte supercoarse powder is 1 to 6 μm, preferably 2 to 5 μm. The D10 of the solid electrolyte coarse powder is 3 to 8 μm, preferably 4 to 7 μm. The D90 of the solid electrolyte supercoarse powder is 100 to 500 μm, preferably 200 to 400 μm. The D90 of the solid electrolyte coarse powder is 30 to 100 μm, preferably 40 to 80 μm.

[0043] The average particle size of the sulfide-based solid electrolyte contained in the solid electrolyte layer may be larger than that of the sulfide-based solid electrolyte contained in the positive electrode active material layer. Since the solid electrolyte coarse powder and the solid electrolyte supercoarse powder have a large average particle size and few grain boundaries per unit volume, they can exhibit high ionic conductivity when used in the solid electrolyte layer. The solid electrolyte fine powder can enter the gaps between the positive electrode active material particles when used in the positive electrode active material layer, and can provide a lithium ion conduction path for the positive electrode active material. Therefore, by making the average particle size of the sulfide-based solid electrolyte contained in the solid electrolyte layer larger than that of the sulfide-based solid electrolyte contained in the positive electrode active material layer, the discharge capacity and cycle characteristics of the all-solid-state battery can be improved.

[0044] The particle size distribution of the solid electrolyte can affect the discharge capacity and cycle characteristics of the all-solid-state battery. The narrower the particle size distribution of the solid electrolyte, for example, the smaller (D90-D10) / D50 is, the more conducive it is to uniform lithium conduction during charge and discharge, and the discharge capacity can be maintained at a high level. When the particle size distribution of the solid electrolyte becomes wider, the lithium conduction during charge and discharge becomes non-uniform, and the discharge capacity may decrease. (D90-D10) / D50 is from 1 to 30, preferably from 1 to 10, more preferably from 1 to 5. In addition to the average particle size of the solid electrolyte, by controlling the particle size distribution within the above range, the discharge capacity and cycle characteristics of the all-solid-state battery can be further improved.

[0045] The sulfide-based solid electrolyte is not particularly limited as long as it contains sulfur (S), and known sulfide-based solid electrolytes can be used.

[0046] The sulfide-based solid electrolyte may have a crystal structure. The sulfide-based solid electrolyte having a crystal structure can promote the conduction of lithium ions and can have a high lithium ion conductivity.

[0047] The sulfide-based solid electrolyte may have a crystal structure of the argyrodite type, the NASICON type, the perovskite type, the garnet type, or the LGPS type. Preferably, the sulfide-based solid electrolyte has an argyrodite-type crystal structure. The sulfide-based solid electrolyte having an argyrodite-type crystal structure has high stability against lithium metal, making it possible to use lithium metal having a high mass energy density as the negative electrode material.

[0048] The sulfide-based solid electrolyte may be in the form of amorphous, glass, or glass-ceramic.

[0049] Sulfide-based solid electrolytes have ion conductivity of metals belonging to Group 1 or Group 2 of the periodic table, and can include Li-P-S-based glasses and Li-P-S-based glass ceramics. Non-limiting examples of such sulfide-based solid electrolytes include Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, etc., and one or more of these can be included. However, it is not particularly limited to these.

[0050] Sulfide-based solid electrolytes can include a crystalline phase and an amorphous phase. Sulfide-based solid electrolytes can include a crystalline phase having an argyrodite-type crystal structure (also referred to as an argyrodite phase in this specification) and other phases (also referred to as impurity phases or unknown phases in this specification). The argyrodite-type crystal structure is preferably cubic. The other phases may be crystalline phases or amorphous phases. The other phases, regardless of whether they are crystalline phases or amorphous phases, can include Li2S phase, P2S5 phase, LiCl phase, LiBr phase, Li3PS4 phase, MgS phase, CaS phase, SrS phase, BaS phase, CaBr2 phase, etc. Preferably, the sulfide-based solid electrolyte does not contain or substantially does not contain impurity phases other than the argyrodite phase. That is, preferably, the sulfide-based solid electrolyte may consist only of the argyrodite phase. When the sulfide-based solid electrolyte does not contain or substantially does not contain impurity phases, lithium ion conduction is less likely to be inhibited, so the sulfide-based solid electrolyte can have a high lithium ion conductivity.

[0051] The proportion of the crystalline phase contained in the sulfide-based solid electrolyte can be evaluated quantitatively or semi-quantitatively from the XRD pattern. As one method, the proportion of the crystalline phase can be evaluated by comparing the peak intensities (height or area) of the XRD pattern.

[0052] The sulfide-based solid electrolyte has the chemical formula Li 7-x-2y M y PS 6-x Ha x and can be represented by. In the chemical formula, M is one or more elements selected from Group 2 elements, Ha is one or more elements selected from halogen elements, and 0 < x < 2.5, 0 < y < 0.45 can be satisfied. The lattice volume of the sulfide-based solid electrolyte can be 950 Å 3 or more and 980 Å 3 or less. Ha can contain Br. Such a sulfide-based solid electrolyte can have a high lithium ion conductivity. By using a sulfide-based solid electrolyte having a high lithium ion conductivity in an anode-free all-solid-state battery, the discharge capacity and cycle characteristics of the all-solid-state battery can be improved. Further, since the growth of lithium dendrites on the negative electrode current collector is prevented by the sulfide-based solid electrolyte having a high lithium ion conductivity, the anode-free all-solid-state battery of the present disclosure can be driven at a low confinement pressure.

[0053] In the sulfide-based solid electrolyte according to one embodiment of the present disclosure, a part of lithium in Li 7-x PS 6-x Ha x can be substituted with a Group 2 element M that can become a divalent cation. The Group 2 element M that substitutes lithium may be one or more selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). The ionic radius (6 coordination) of lithium (Li) is 90 pm, and the ionic radii (6 coordination) of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba) are 86 pm, 114 pm, 132 pm, and 149 pm, respectively. Based on the valence of the element, two lithiums can be substituted with one Group 2 element M. By substitution with the Group 2 element M, lithium site vacancies are generated, and the lithium ion conductivity can be improved. Further, by substitution with the Group 2 element M, the lattice constant and lattice volume of the sulfide-based solid electrolyte change, and a crystal structure suitable for lithium ion conduction can be obtained.

[0054] In addition, a sulfide-based solid electrolyte according to an embodiment of the present disclosure can be formed by the intrusion of Group 2 element M that can become a divalent cation into the crystal lattice of Li 7-x PS 6-x Ha x The Group 2 element M that intrudes into the crystal lattice may be one or more selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba) can be used alone or in combination. Preferably, the Group 2 element M is magnesium (Mg) or calcium (Ca). Li 7-x PS 6-x Ha x By the intrusion of the Group 2 element M into the crystal lattice of LiPSHa, the lattice constant and lattice volume of the sulfide-based solid electrolyte can change to have a crystal structure suitable for lithium ion conduction. A sulfide-based solid electrolyte containing calcium (Ca) as the Group 2 element M has a high lithium ion conductivity. By using such a sulfide-based solid electrolyte in an anode-free all-solid-state battery, the discharge capacity and cycle characteristics of the all-solid-state battery can be improved. In addition, by using such a sulfide-based solid electrolyte, the growth of lithium dendrites on the negative electrode current collector is prevented, so that the anode-free all-solid-state battery of the present disclosure can be driven at a low confinement pressure.

[0055] The Group 2 element M may be located at the interstitial sites of the sulfide-based solid electrolyte having an argyrodite-type crystal structure. When the Group 2 element M is located at the interstitial sites of the argyrodite-type crystal structure, at least a part of the Group 2 element M can move away from the interstitial sites during charge and discharge of the all-solid-state battery. A part of the Group 2 element M that has left the interstitial sites can be deposited at the interface between the negative electrode current collector and the solid electrolyte layer and / or at the interface between the positive electrode active material layer and the solid electrolyte layer. Also, a part of the Group 2 element M that has left the interstitial sites can return to the original interstitial sites or other interstitial sites. In the all-solid-state battery of the present disclosure, since the addition amount y of the Group 2 element M contained in the sulfide-based solid electrolyte is small, even if the Group 2 element M leaves the interstitial sites, the argyrodite-type crystal structure of the sulfide-based solid electrolyte can be maintained. The Group 2 element M can move as a carrier of the all-solid-state battery together with lithium during charge and discharge of the all-solid-state battery. The position of the Group 2 element M can be determined by measurement techniques known to those skilled in the art, for example, neutron diffraction analysis.

[0056] Preferably, the Group 2 element M is magnesium (Mg) and / or calcium (Ca), and particularly preferably, calcium (Ca). When the Group 2 element M is magnesium (Mg) and / or calcium (Ca), the sulfide-based solid electrolyte can have a high degree of crystallinity, and therefore, the sulfide-based solid electrolyte can have a high ionic conductivity. This is considered to be because the ionic radius of lithium (Li) is 90 pm, and the ionic radii of magnesium (Mg) and calcium (Ca) are 86 pm and 114 pm, respectively, which are close values, so the argyrodite-type crystal structure is likely to be maintained even after substitution by the Group 2 element M.

[0057] Chemical formula Li 7-x-2y M y PS 6-x Ha xThe addition amount y of Group 2 element M satisfies 0 < y < 0.45, preferably, y satisfies 0 < y < 0.1, more preferably, 0.005 ≤ y ≤ 0.04, and even more preferably 0.01 ≤ y ≤ 0.03. When y satisfies the above range, the sulfide-based solid electrolyte can have high ionic conductivity. When y is 0, no change in the crystal structure due to the substitution of Group 2 element M can be obtained, and the ionic conductivity may be low. When y is 0.45 or more, the argyrodite-type crystal structure of the sulfide-based solid electrolyte may not be maintained, and the ionic conductivity may decrease. Also, the impurity phase that inhibits lithium ion conduction in the sulfide-based solid electrolyte may increase, and the ionic conductivity may decrease.

[0058] Chemical formula Li 7-x-2y M y PS 6-x Ha x The halogen (Ha) in is one or more elements selected from halogen elements. Preferably, the halogen (Ha) contains chlorine (Cl) and / or bromine (Br). When sulfur (S) is a divalent anion, it has a stronger ability to attract lithium ions than monovalent halogen and can greatly inhibit the movement of lithium ions. By including bromine (Br), the sulfur (S) occupancy at specific sites in the argyrodite-type crystal structure decreases, the halogen increases, and the lithium ion mobility around the bromine (Br) site can become active. As a result, the lithium ion conductivity can be improved. Also, bromine (Br) can combine with Li in the sulfide-based solid electrolyte to form lithium bromide (LiBr), which is a water-absorbing substance. Lithium bromide (LiBr) can adsorb moisture that can decrease the lithium ion conductivity and improve the lithium ion conductivity of the sulfide-based solid electrolyte.

[0059] Chemical formula Li 7-x-2y M y PS 6-x Ha xThe ratio x of halogen (Ha) satisfies 0 < x < 2.5, preferably satisfies 1.0 < x < 2.0, and more preferably satisfies 1.3 < x < 1.8. When x satisfies the above range, the argyrodite-type crystal structure is stabilized, and the sulfide-based solid electrolyte can have high ionic conductivity.

[0060] The Group 2 element M contained in the sulfide-based solid electrolyte can move during the operation of the all-solid-state battery. Preferably, the Group 2 element M contained in the sulfide-based solid electrolyte can move in the form of a divalent cation.

[0061] At least a part of the Group 2 element M can move toward the negative electrode during charging of the all-solid-state battery and can be deposited at the interface between the negative electrode current collector and the solid electrolyte layer. When there is another intermediate layer between the negative electrode current collector and the solid electrolyte layer, the Group 2 element M can be deposited at the interface between the negative electrode current collector and the intermediate layer. A part of the Group 2 element M can also be deposited inside the intermediate layer.

[0062] At least a part of the Group 2 element M can move toward the positive electrode during discharging of the all-solid-state battery and can be deposited at the interface between the positive electrode active material layer and the solid electrolyte layer. When there is another intermediate layer between the positive electrode active material layer and the solid electrolyte layer, the Group 2 element M can be deposited at the interface between the positive electrode current collector and the intermediate layer. A part of the Group 2 element M can also be deposited inside the intermediate layer.

[0063] The Group 2 element M can be deposited on each of the above interfaces in one or more forms selected from the group consisting of the Group 2 element M alone, an alloy with lithium, and a compound containing the Group 2 element M. By depositing the Group 2 element M on each of the above interfaces during charge and discharge, the adhesion at each of the above interfaces is improved, and the ionic conduction path and / or the electrical conduction path across each of the above interfaces is maintained. Thereby, the all-solid-state battery of the present disclosure has improved discharge capacity and cycle characteristics. Furthermore, the all-solid-state battery of the present disclosure can perform charge and discharge without a high constraint pressure of several MPa or more required during the operation of a conventional all-solid-state battery.

[0064] The Group 2 element M is preferably present at the 48h site of the argyrodite-type crystal structure. A part of the Group 2 element M present at the 48h site of the argyrodite-type crystal structure can move to the negative electrode side during charging of the all-solid-state battery and to the positive electrode side during discharging of the all-solid-state battery without destroying the argyrodite-type crystal structure.

[0065] The alloy of the Group 2 element M and lithium can include MLi x (1 ≤ x ≤ 2). Preferably, the alloy of the Group 2 element M and lithium can include CaLi x (1 ≤ x ≤ 2). More preferably, the alloy of the Group 2 element M and lithium can include at least one selected from the group consisting of CaLi and CaLi2. Also, CaLi3 and Ca3Li may be included.

[0066] The compound of the Group 2 element M and lithium can include the compound of calcium and lithium. Also, the compound of magnesium and lithium can be included.

[0067] The ionic conductivity of the sulfide-based solid electrolyte can be affected by the crystallinity of the sulfide-based solid electrolyte. The crystallinity can be evaluated from the XRD pattern. In the XRD pattern, when no other phases (crystalline phases or amorphous phases such as Li2S phase, P2S5 phase, LiCl phase, LiBr phase, Li3PS4 phase, MgS phase, CaS phase, SrS phase, and BaS phase) other than the argyrodite crystal phase are observed or hardly observed, the sulfide-based solid electrolyte can have high ionic conductivity.

[0068] The lattice volume of the sulfide-based solid electrolyte can change due to the substitution of lithium sites by the Group 2 element M. Although not bound by theory, it is considered that when the Group 2 element M exhibits the characteristics of a divalent cation, the interaction with other anions present in the sulfide-based solid electrolyte is strengthened, and the lattice volume changes, that is, increases or decreases. Such a change in the lattice volume leads to a crystal structure suitable for lithium ion conduction, and the sulfide-based solid electrolyte can have high ionic conductivity.

[0069] The lattice volume of the sulfide-based solid electrolyte is 950 Å 3 or more and 980 Å 3 or less, preferably 958 Å 3 or more and 966 Å 3 or less, more preferably 960 Å 3 or more and 964 Å 3 or less, even more preferably 961 Å 3 or more and 963 Å 3 or less. The lattice constant and lattice volume can be evaluated from the XRD pattern. The lattice volume of the sulfide-based solid electrolyte can vary depending on the firing temperature even with the same composition. When the lattice volume satisfies the above range, lithium ion conduction in the sulfide-based solid electrolyte is promoted, and the sulfide-based solid electrolyte can have a high ionic conductivity.

[0070] The ionic conductivity of the sulfide-based solid electrolyte (also referred to as "lithium ion conductivity" in this specification) means the ionic conductivity at room temperature (25 °C, 298 K) and normal pressure (1 atm) unless otherwise specified. When the sulfide-based solid electrolyte is used in an all-solid-state battery, it is preferably 4 mS / cm or more in practical use. The ionic conductivity of the sulfide-based solid electrolyte according to one embodiment of the present disclosure is 2 mS / cm or more, preferably 4 mS / cm or more, more preferably 10.8 mS / cm or more, even more preferably 12 mS / cm or more, and most preferably 13 mS / cm or more.

[0071] The sulfide-based solid electrolyte according to one embodiment of the present disclosure can be obtained by a manufacturing method including a step of mixing a lithium source, a Group 2 element source, a phosphorus source, a sulfur source, and a halogen source to obtain a mixture, and a step of firing the mixture at a temperature of 250 °C to 600 °C. The firing of the mixture may be performed in an inert atmosphere such as argon gas and nitrogen gas.

[0072] The lithium source, Group 2 element source, phosphorus source, sulfur source, and halogen source may be compounds such as sulfides, oxides, nitrides, etc. Lithium sulfide (Li2S) can be used as the lithium source, diphosphorus pentasulfide (P2S5) can be used as the phosphorus source, and lithium halides (LiHa) such as lithium chloride (LiCl) and lithium bromide (LiBr) can be used as the halogen source. For example, a sulfide can be used as the Group 2 element source. Alternatively, sulfur can be supplied from other element sources. That is, one or more of the lithium source, Group 2 element source, phosphorus source, and halogen source may also serve as the sulfur source.

[0073] In the case of a sulfide-based solid electrolyte having an argyrodite-type crystal structure, the firing temperature is preferably 350°C to 550°C, more preferably 400°C to 500°C, and even more preferably 410°C to 470°C. When the firing temperature satisfies the above range, the formation of the argyrodite-type crystal structure is promoted, and the sulfide-based solid electrolyte can have a high crystallinity. Thereby, a sulfide-based solid electrolyte having a high ionic conductivity can be obtained.

[0074] The solid electrolyte layer can further contain a binder for the solid electrolyte layer. The binder for the solid electrolyte layer can be introduced for binding between the solid electrolytes and for binding between the solid electrolyte layer and battery elements (for example, a positive electrode, a negative electrode, etc.) laminated on both sides thereof.

[0075] The material for the binder of the solid electrolyte layer is not particularly limited and can be appropriately selected within the range of components used as the binder for the solid electrolyte in the all-solid-state lithium secondary battery. Specifically, the binder for the solid electrolyte layer can include at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), nitrile butadiene rubber (NBR), fluorine rubber, and acrylic binders.

[0076] The solid electrolyte layer may not contain the binder for the solid electrolyte layer. When the solid electrolyte layer does not contain the binder for the solid electrolyte layer, the content of the solid electrolyte contained in the solid electrolyte layer can be increased, and the ionic conductivity of the solid electrolyte layer can be improved.

[0077] <Negative electrode> Before the first lithium metal deposition (first charge) is performed, the negative electrode does not contain a negative electrode active material.

[0078] During charging, lithium ions are supplied from the positive electrode active material contained in the positive electrode active material layer, and a lithium metal layer as the negative electrode active material is formed on the negative electrode current collector. Specifically, in an all-solid-state battery having an anode-free battery structure, when a voltage above a certain level is applied for charging, lithium ions are desorbed from the positive electrode active material in the positive electrode, and the desorbed lithium ions pass through the solid electrolyte layer and move to the negative electrode current collector side, forming a lithium metal layer consisting only of pure lithium on the negative electrode current collector to form the negative electrode. The formation of such a lithium metal layer by charging has the advantage that a thin film layer can be formed compared to the conventional negative electrode in which a lithium metal layer is sputtered on the negative electrode current collector or a lithium foil and the negative electrode current collector are laminated, and the adjustment of the interface characteristics is very easy.

[0079] In particular, since it is formed with an anode-free battery structure and no exposure of lithium metal to the atmosphere occurs during the battery assembly process, problems such as the formation of an oxide film on the surface due to the high reactivity of lithium itself and the resulting reduction in the lifespan of the lithium secondary battery can be fundamentally eliminated.

[0080] The formed lithium metal layer forms a uniform continuous or discontinuous layer on the negative electrode current collector. As an example, when the negative electrode current collector is in foil form, it can have a continuous thin film form, and when the negative electrode current collector has a three-dimensional porous structure, the lithium metal layer may be formed discontinuously. That is, the discontinuous layer is distributed in a discontinuous form, where there are regions where the lithium metal layer exists and regions where it does not exist within a specific region, and the regions where the lithium metal layer does not exist isolate, sever, or separate the regions where the lithium compound exists in an island-like manner, meaning that the regions where the lithium metal layer exists are distributed without continuity.

[0081] The lithium metal layer formed through such charge and discharge has a thickness of at least 50 nm and at most 100 μm, preferably 1 μm to 50 μm, in order to function as a negative electrode. If the thickness is less than the above range, the charge and discharge efficiency of the battery will decrease rapidly. Conversely, if it exceeds the above range, although the lifespan characteristics and the like are stable, there is a problem that the energy density of the battery becomes low.

[0082] In particular, the lithium metal layer shown in the present disclosure is manufactured as an anode-free battery without lithium metal during battery assembly. Compared with a lithium secondary battery assembled using a conventional lithium foil, almost no or hardly any oxide layer is formed on the lithium metal layer during the assembly process. Thereby, the degradation phenomenon of the battery lifespan due to the above oxide layer can be prevented.

[0083] The charging range for forming a lithium metal layer in the present disclosure is within a voltage range of 4.5 V to 2.5 V, and one charge is performed at 0.01 to 0.2 C. If the charging is performed below the above range, it becomes difficult to form a lithium metal layer. Conversely, if it exceeds the above range, after battery damage and over-discharge occur, charging and discharging cannot be performed properly.

[0084] The negative electrode can include a negative electrode current collector. The negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the all-solid-state battery and has conductivity. As the negative electrode current collector, iron, stainless steel, aluminum, nickel, titanium, fired carbon, or those obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used.

[0085] In particular, it is preferable that the negative electrode current collector of the present disclosure does not react with the sulfide-based solid electrolyte. In other words, it is preferable that the all-solid-state battery of the present disclosure does not contain a reaction product between the negative electrode current collector and the sulfide-based solid electrolyte. The fact that the reaction product between the negative electrode current collector and the sulfide-based solid electrolyte is not contained can be confirmed, for example, by observing a cross-section of the all-solid-state battery with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). XRD measurement may be used to confirm that the above reaction product is not contained. Before the first lithium metal deposition (first charge), the negative electrode current collector and the sulfide-based solid electrolyte may be in direct contact. Also, after discharging the battery, lithium metal as the negative electrode active material moves to the positive electrode side, and there is almost no or no negative electrode active material on the negative electrode current collector. When a side reaction occurs between the negative electrode current collector and the sulfide-based solid electrolyte, by-products such as hydrogen sulfide are generated, which can have an adverse effect on the performance of the all-solid-state battery. To prevent such side reactions, it is preferable that the negative electrode current collector has high stability against the sulfide-based solid electrolyte. Since the negative electrode current collector does not react with the sulfide-based solid electrolyte, the anode-free type all-solid-state battery of the present disclosure can improve the discharge capacity and cycle characteristics. Also, since the negative electrode current collector does not react with the sulfide-based solid electrolyte and does not generate side reaction products, the anode-free type all-solid-state battery of the present disclosure can be driven at a low restraint pressure.

[0086] The negative electrode current collector may have a thickness of 3 μm to 500 μm.

[0087] The negative electrode current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric body, etc. with fine irregularities formed on the surface.

[0088] The negative electrode current collector may be in direct contact with the solid electrolyte layer. The negative electrode current collector may be in direct contact with the sulfide-based solid electrolyte contained in the solid electrolyte layer. By directly contacting the negative electrode current collector and the solid electrolyte layer without an intermediate layer, the thickness of the all-solid-state battery can be reduced, and the volume energy density of the all-solid-state battery can be improved. Since the amount of active material that can be mounted increases and the growth of lithium dendrites is prevented, the discharge capacity and cycle characteristics of the all-solid-state battery can be improved. Also, the all-solid-state battery can be driven at a low confinement pressure.

[0089] The negative electrode current collector does not necessarily have to be in direct contact with the solid electrolyte layer. An intermediate layer may be formed between the negative electrode current collector and the solid electrolyte layer. When the intermediate layer is formed, the lithium metal layer is formed on the negative electrode current collector as lithium ions supplied from the positive electrode active material layer pass through the intermediate layer. That is, the lithium metal layer is formed between the negative electrode current collector and the intermediate layer during charging.

[0090] Here, the intermediate layer can be any as long as lithium ions can be smoothly transmitted, and materials used for lithium ion conductive polymers and / or inorganic solid electrolytes may be used, and if necessary, may further contain a lithium salt.

[0091] The intermediate layer may contain a metal that forms an alloy with lithium. Examples of the metal that forms an alloy with lithium include germanium, tin, zinc, indium, gallium, antimony, lead, gold, silver, aluminum, platinum, palladium, etc.

[0092] As the lithium ion conductive polymer, for example, any one selected from the group consisting of polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polyvinylidene fluoride - hexafluoropropylene (PVDF - HFP), or a mixture of two or more of these may be used, but it is not limited thereto. Any polymer having lithium ion conductivity can be used without limitation.

[0093] When using a lithium ion conductive polymer, in order to further increase the lithium ion conductivity, it may further contain a substance used for such a purpose.

[0094] As an example, it may further contain lithium salts such as LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, LiSCN, LiC(CF3SO2)3, (CF3SO2)2NLi, (FSO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, lithium imide, etc.

[0095] The inorganic solid electrolyte is a ceramic - based material, and a crystalline or amorphous material may be used. Thio - LISICON (Li 3.25 Ge 0.25 P 0.75 S4), Li2S - SiS2, LiI - Li2S - SiS2, LiI - Li2S - P2S5, LiI - Li2S - P2O5, LiI - Li3PO4 - P2S5, Li2S - P2S5, Li3PS4, Li7P3S 11 , Li2O - B2O3, Li2O - B2O3 - P2O5, Li2O - V2O5 - SiO2, Li2O - B2O3, Li3PO4, Li2O - Li2WO4 - B2O3, LiPON, LiBON, Li2O - SiO2, LiI, Li3N, Li5La3Ta2O 12 、Li7La3Zr2O 12, Li6BaLa2Ta2O 12 , Li3PO (4-3 / 2w) Nw (where w < 1), Li 3.6 Si 0.6 P 0.4 Inorganic solid electrolytes such as O4 are possible. At this time, when using an inorganic solid electrolyte, if necessary, it may further contain a lithium salt.

[0096] The inorganic solid electrolyte can be mixed with known substances such as a binder and applied in the form of a thick film through slurry coating. Also, if necessary, it can be applied in the form of a thin film through a vapor deposition process such as sputtering. The slurry coating method to be used can be appropriately selected based on the coating method, drying method, and content of the solvent mentioned for the lithium ion conductive polymer.

[0097] The intermediate layer containing the aforementioned lithium ion conductive polymer and / or inorganic solid electrolyte can increase the transfer rate of lithium ions and facilitate the formation of the lithium metal layer. At the same time, when using the lithium metal layer / negative electrode current collector as the negative electrode, it can simultaneously ensure the effect of suppressing or preventing the generation of lithium dendrites.

[0098] In order to ensure the above effects, it is necessary to limit the thickness of the intermediate layer.

[0099] The lower the thickness of the intermediate layer, the more advantageous it is for the output characteristics of the battery. However, if it is not formed with a certain thickness or more, the side reaction between lithium and the electrolyte formed on the negative electrode current collector later cannot be suppressed, and furthermore, the dendrite growth cannot be effectively blocked. In the present disclosure, the thickness of the intermediate layer may preferably be 10 nm to 50 μm. If the thickness of the intermediate layer is less than the above range, the side reaction and exothermic reaction between lithium and the electrolyte that increase under conditions such as overcharging or high-temperature storage cannot be effectively suppressed, so the improvement in safety cannot be achieved. Also, if it exceeds the above range, the thickness of the all-solid-state battery increases, and the volume energy density of the all-solid-state battery may decrease.

[0100] <Positive electrode> The positive electrode can include a positive electrode active material layer and a positive electrode current collector.

[0101] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change to the positive electrode or the battery and has high conductivity. For example, it can include at least one selected from the group consisting of iron, stainless steel, copper, aluminum, nickel, titanium, and fired carbon, and specifically can include aluminum. The positive electrode current collector can include a carbon-based conductive material and a binder, and can further include a primer layer coated on the surface of the positive electrode current collector. Thereby, the adhesion and electrical conductivity between the positive electrode active material layer and the current collector can be greatly improved.

[0102] The positive electrode active material layer can be disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer can be disposed on one or both surfaces of the positive electrode current collector.

[0103] The positive electrode active material layer can include a positive electrode active material. The lithium source for forming the lithium metal layer in the anode-free battery structure of the present disclosure is the positive electrode active material, and the positive electrode active material contains lithium. That is, when the lithium ions in the positive electrode active material are charged in a specific voltage range, the lithium ions are desorbed to form a lithium metal layer on the negative electrode current collector.

[0104] The positive electrode active material can be used without limitation as long as it can be used as a positive electrode active material for a lithium-ion secondary battery. The positive electrode active material includes layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x O4 (where x is 0 to 0.33), lithium manganese oxides including LiMnO3, LiMn2O3, LiMn2O4, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M xNi-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, P, Mg, Ca, Zr, Ti, Ru, Nb, W, B, Si, Na, K, Mo, V or Ga and x = 0.01 to 0.3); chemical formula LiMn 1-x M x Lithium manganese composite oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiNi x Mn 2-x Spinel-structured lithium manganese composite oxide represented by O4; LiMn2O4 in which part of Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compound; LiMn x Fe 1-x PO4 (0 ≦ x ≦ 0.9); It can contain Fe2(MoO4)3 etc. However, it is not limited to these only.

[0105] The positive electrode active material can contain Li 1+x M y O 2+z where M can be at least one element selected from the group consisting of Ni, Co, Mn, Fe, P, Al, Mg, Ca, Zr, Zn, Ti, Ru, Nb, W, B, Si, Na, K, Mo, and V, and 0 ≦ x ≦ 5, 0 < y ≦ 2, 0 ≦ z ≦ 2 can be satisfied. Specifically, the above Li 1+x M y O 2+z is LiCoO2, LiNiO2, LiMnO2, Li[Ni 0.5 C o0.3 Mn 0.2 O2, Li[Ni 0.6 Co 0.2 Mn 0.2 O2, Li[Ni 0.7 Co 0.1 Mn 0.2 O2, Li[Ni 0.8 Co 0.1 Mn 0.1 O2, Li[Ni 0.9 Co 0.05 Mn 0.05O2, LiMn2O4, LiFePO 4、0.5 Li2MnO3·0.5Li[Mn 0.4 Ni 0.3 Co 0.3 O2 can include at least any one selected from the group consisting of. Preferably, the above Li 1+x M y O 2+z is the above Li[Ni 0.6 Co 0.2 Mn 0.2 O2, Li[Ni 0.7 Co 0.1 Mn 0.2 O2, Li[Ni 0.8 Co 0.1 Mn 0.1 O2, Li[Ni 0.9 Co 0.05 Mn 0.05 O2. Since the positive electrode active material contains Li 1+x M y O 2+z , lithium can be sufficiently supplied to the negative electrode, and Li 1+x M y O 2+z does not cause a decrease in the overall performance of the battery and shows electrochemical activity after the first cycle, so the loss of battery capacity due to the irreversible capacity of the negative electrode can be eliminated. The above Li 1+x M y O 2+z can be in the form of secondary particles formed by binding or granulating primary particles, or, alternatively, can be in the form of single particles.

[0106] The positive electrode active material can be contained in the positive electrode active material layer in an amount of 50% to 95% by weight, specifically 60% to 90% by weight.

[0107] Also, the average particle size of the positive electrode active material is 1 to 30 μm, and according to one embodiment, it is 8 to 12 μm. When the average particle size of the positive electrode active material is within the above range, the capacity characteristics of the battery are excellent.

[0108] The positive electrode active material layer can further include a positive electrode conductive material.

[0109] The positive electrode conductive material is not particularly limited as long as it does not cause a chemical change to the positive electrode or the battery and has conductivity. For example, the positive electrode conductive material includes graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; graphene; conductive fibers such as carbon nanofibers and carbon nanotubes; carbon fluoride; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives, and can include one or more mixtures selected therefrom.

[0110] The positive electrode conductive material can be contained in the positive electrode active material layer in an amount of 1% to 30% by weight.

[0111] The positive electrode active material layer can further include a positive electrode binder.

[0112] The positive electrode binder is not particularly limited as long as it is a component useful for binding the positive electrode active material, the positive electrode conductive material, etc., and binding to the current collector. Specifically, it can include at least one selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene (PTFE), polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), styrene-butadiene rubber (SBR), and fluororubber.

[0113] The positive electrode binder can be contained in the positive electrode active material layer in an amount of 1% to 30% by weight.

[0114] The positive electrode active material layer can contain one or more additives such as an oxidation stability additive, a reduction stability additive, a flame retardant, a heat stabilizer, and an anti-fogging agent, if necessary.

[0115] The positive electrode active material layer can further contain a sulfide-based solid electrolyte. The sulfide-based solid electrolyte contained in the positive electrode active material layer may have the same composition as the sulfide-based solid electrolyte contained in the solid electrolyte layer, or may have a different composition.

[0116] The positive electrode active material layer can contain 5% to 60% by weight, specifically 10% to 40% by weight, of the sulfide-based solid electrolyte.

[0117] The average particle size of the positive electrode active material may be larger than the average particle size of the solid electrolyte contained in the positive electrode active material layer. In this case, the solid electrolyte can enter the gaps between the positive electrode active material particles and provide a lithium ion conduction path for the positive electrode active material.

[0118] The present disclosure provides a secondary battery having the above-described structure. Further, the present disclosure provides a battery module including the secondary battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. At this time, specific examples of the device include power tools driven by receiving power from an electric motor; electric vehicles including electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), etc.; electric two-wheel vehicles including electric bicycles (E-bike) and electric scooters (E-scooter); electric golf carts; power systems, etc., but are not limited thereto.

[0119] Hereinafter, for easy understanding of the present invention, preferred embodiments are shown. However, it is obvious to those skilled in the art that the following embodiments are merely illustrative of the present invention and various changes and modifications can be made within the scope of the present invention and the scope of the technical idea. It is natural that such deformations and modifications belong to the appended claims.

[0120] (Synthesis of Solid Electrolyte) Production Example 1 As raw materials, lithium sulfide (Li2S, Mitsuwa Chemical), phosphorus pentasulfide (P2S5, Aldrich), calcium sulfide (CaS, high-purity chemical), lithium chloride (LiCl, Aldrich), and lithium bromide (LiBr, Aldrich) were used to obtain a composition of Li 5.4-2y M y PS 4.4 Cl 1.0 Br 0.6 (where the addition amount y of Group 2 element M = 0.025). Weighing and mortar mixing were carried out in an Ar gas flow glove box to obtain a mixed powder. This mixed powder was placed in a ZrO2 pot together with ZrO2 balls to obtain a sealed pot. This sealed pot was installed in a planetary ball mill apparatus and ball milled at 380 rpm for 20 hours. Then, the pot was opened in the glove box and the powder was recovered. This powder was placed in a carbon crucible, sealed, and then fired at 430 °C for 8 hours while flowing Ar gas. The fired powder was pulverized in a mortar for 10 minutes to obtain a solid electrolyte crude powder containing divalent cations.

[0121] Production Example 2 The solid electrolyte crude powder containing divalent cations obtained in Production Example 1 was placed in a ZrO2 pot together with ZrO2 balls and anisole solvent, and wet pulverization was carried out at 250 rpm for 1 hour to obtain a solid electrolyte fine powder containing divalent cations.

[0122] Production Example 3 A solid electrolyte super-crude powder containing divalent cations was obtained in the same manner as in Production Example 1, except that the fired powder was pulverized in a mortar for 1 minute.

[0123] Comparative Production Example 1 A solid electrolyte crude powder not containing divalent cations was obtained in the same manner as in Example 1, except that calcium sulfide (CaS, high-purity chemical) was not used. The composition of the solid electrolyte obtained in Comparative Production Example 1 was Li 5.4 PS 4.4 Cl 1.0 Br 0.6 .

[0124] Comparative Production Example 2 The solid electrolyte coarse powder without divalent cations obtained in Comparative Production Example 1 was placed in a ZrO₂ pot together with ZrO₂ balls and anisole solvent, and wet pulverization was carried out at 250 rpm for 1 hour to obtain a solid electrolyte fine powder without divalent cations.

[0125] [Evaluation] Using the obtained solid electrolyte, the following evaluations were carried out.

[0126] (XRD measurement) A predetermined amount of the solid electrolyte was placed in a sealed holder in an Ar gas flow glove box, and XRD measurement was performed. The lattice constant, lattice volume, and full width at half maximum were calculated from the obtained XRD (X-ray diffraction) pattern. The full width at half maximum was calculated from the (311) plane crystal peak of the argyrodite-type crystal structure observed near 2θ = 30° in Fig. 4.

[0127] The measuring apparatus and conditions are as follows. · X-ray diffractometer: Rigaku Smartlab · Radiation source: Cu-Kα ray (λ = 1.5418 Å) · Voltage: 45 kV · Current: 200 mA · Scan range (2θ): 10 - 60° · Step size: 0.01°

[0128] (Particle size distribution measurement) The solid electrolyte was put into a heptane solvent, and a solid electrolyte dispersion solution was prepared using Span 80 as a dispersant. Using the dispersion solution, the particle size distribution was measured with a particle size measuring apparatus Mastersizer 3000. Data analysis was performed with the refractive index of the solid electrolyte being 2.16.

[0129] (Ionic conductivity measurement) A predetermined amount of solid electrolyte was placed inside a Macor tube. The Macor tube and a pellet forming jig (upper press pin and lower press pin) were combined and pressed at approximately 370 MPa using a uniaxial press. Thereafter, a predetermined amount of gold powder was placed on both sides of the pellet, and then pressed at approximately 554 MPa using a uniaxial press to obtain a Macor tube cell. The obtained Macor tube cell was installed in an electrochemical measurement jig cell, and pressurized up to 80 MPa using a torque wrench to obtain an ion conductivity measurement cell. The obtained ion conductivity measurement cell was connected to an impedance measurement device, and the resistance value of the solid electrolyte pellet was measured at room temperature (298 K) and normal pressure (1 atm) to derive the ion conductivity [mS / cm] of the solid electrolyte.

[0130] (Neutron diffraction measurement) A predetermined amount of solid electrolyte was placed inside a neutron diffraction measurement device, and neutron diffraction measurement was performed. From the obtained neutron diffraction pattern, the crystal structure was determined using Z-Rietveld of a crystal structure analysis program, and the lattice constant, element position, occupancy, and atomic displacement parameter were calculated.

[0131] The measurement device and conditions are as follows. · Neutron diffraction device: High Energy Accelerator Research Organization J-PARC BL09 SPICA · Neutron source: TOF (Time of Fly) type · Sample amount: Approximately 0.6 g · Measurement d range: 0.3 - 3.7 Å

[0132] [Evaluation results] (Crystal phase) Table 1 shows the evaluation results of the crystal phases (crystal structures) identified from the XRD patterns by XRD measurement. The measured XRD patterns are shown in Fig. 4. As can be seen from Table 1 and Fig. 4, for the solid electrolytes obtained in Production Examples 1 and 2 and Comparative Production Examples 1 and 2, almost no impurity phase (also called unknown phase) was observed, and there were only peaks of almost the argyrodite phase. A sulfide-based solid electrolyte having an argyrodite-type crystal structure without or with almost no impurity phase was obtained. A sulfide-based solid electrolyte with a high degree of crystallinity can promote the hopping conduction of lithium ions and contribute to an increase in ionic conductivity.

[0133] (Lattice volume) The lattice constants derived from the XRD patterns were in the range of 9.8698 Å to 9.8700 Å in Production Examples 1 and 2, and the lattice volume was 961.4 Å 3 to 961.5 Å 3 On the other hand, in Comparative Production Examples 1 and 2 where the lithium sites of the sulfide-based solid electrolyte were not substituted by the Group 2 element M, the lattice constants were in the range of 9.9467 Å to 9.9470 Å, and the lattice volume was 984.1 Å 3 to 984.2 Å 3 It was shown that substituting the lithium sites of the argyrodite-type crystal structure with the Group 2 element M reduced the crystal volume by about 2.3%. Although not bound by theory, it is considered that one of the two lithium sites was substituted by the Group 2 element M and the other became a lithium vacancy, thereby changing the crystal volume of the sulfide-based solid electrolyte. The lithium vacancy serves as a path for the hopping conduction of lithium ions and is considered to contribute to an increase in ionic conductivity. In addition, the Group 2 element M substituted at the lithium site can have a divalent valence, and the force attracting anions around the Group 2 element M site can change compared to the monovalent lithium ion. As a result, the crystal volume of the sulfide-based solid electrolyte changes, and it is considered to have a structure suitable for the hopping conduction of lithium ions.

[0134] The full width at half maximum of the (311) plane crystal peak of the argyrodite crystal structure was 0.06° in Production Examples 1 and 2. On the other hand, it was 0.08° in Comparative Production Examples 1 and 2. In Production Examples 1 and 2, which are solid electrolytes containing divalent cations, the full width at half maximum is small. A small full width at half maximum corresponds to a large crystallite size and is considered to contribute to an increase in ionic conductivity. Also, it was found that the crystallinity and crystal size of the solid electrolyte do not change due to the pulverization process.

[0135]

Table 1

[0136] (Particle size distribution) The particle size distribution measurement results are shown in Table 2. The average particle size D50 was 15.1 μm for the solid electrolyte coarse powder containing divalent cations in Production Example 1, 1.66 μm for the solid electrolyte fine powder containing divalent cations in Production Example 2, and 14.5 μm for the solid electrolyte ultra-coarse powder containing divalent cations in Production Example 3. Also, it was 14.7 μm for the solid electrolyte coarse powder without divalent cations in Comparative Production Example 1 and 1.42 μm for the solid electrolyte fine powder without divalent cations in Comparative Production Example 2. It was confirmed that the solid electrolyte coarse powder could be pulverized into a solid electrolyte fine powder by additional wet pulverization.

[0137]

Table 2

[0138] (Ionic conductivity) The measurement results of the ionic conductivity are shown in Table 1. The solid electrolyte coarse powder containing divalent cations in Production Example 1 was 13.24 mS / cm, the solid electrolyte fine powder containing divalent cations in Production Example 2 was 4.32 mS / cm, and the solid electrolyte ultra-coarse powder containing divalent cations in Production Example 3 was 13.20 mS / cm. Also, the solid electrolyte coarse powder without divalent cations in Comparative Production Example 1 was 9.91 mS / cm, and the solid electrolyte fine powder without divalent cations in Comparative Production Example 2 was 3.3 mS / cm. Regardless of the presence or absence of divalent cations, the solid electrolyte coarse powder had a higher ionic conductivity than the solid electrolyte fine powder. When the solid electrolyte coarse powder was used, it was considered that the ionic conductivity was high because there were fewer grain boundaries per unit volume. Regardless of the average particle size of the solid electrolyte, the solid electrolyte containing divalent cations had a higher ionic conductivity than the solid electrolyte without divalent cations.

[0139] (Neutron diffraction measurement) The results of the neutron diffraction measurement are shown in Tables 3 and 4. Table 3 is the crystal structure analysis result of the solid electrolyte coarse powder in Production Example 1. Table 4 is the crystal structure analysis result of the solid electrolyte coarse powder in Comparative Production Example 1. In each table, the site is represented by a combination of numbers and English notations. The number represents the number of positions where an element can be placed in the crystal structure, and the English notation is the crystallographic symmetry defined for that site, assigned in the order of a, b, c, d... from the highest crystallinity. g means the occupancy of each site. x, y, and z are parameters determined by the site, and the position where the element is located is the value represented by the ratio of the lattice constants in the x, y, and z directions. B iso is the atomic displacement parameter and represents the distribution of displacements due to the thermal vibration of atoms.

[0140] As shown in Table 3, it was confirmed that calcium (Ca) was present at the 48h site of the aldite-type crystal structure in the solid electrolyte coarse powder of Production Example 1. The occupancy g of calcium (Ca) at the 48h site was 0.003 ± 0.002. When calculating the addition amount of Group 2 element M in the solid electrolyte coarse powder of Production Example 1 composed of the crystal structure, it was 0.036 ± 0.024, and the charged addition amount (y = 0.025) was within that range. Since the solid electrolyte coarse powder of Comparative Production Example 1 did not use calcium as a raw material, calcium (Ca) is not shown in the analysis results of Table 4.

[0141]

Table 3

Table 4

[0142] Example 1 After weighing 90 mg of the solid electrolyte coarse powder containing divalent cations obtained in Production Example 1, it was placed in a molding jig and pressure-molded at 110 MPa for 1 minute to obtain a solid electrolyte pellet.

[0143] An NCM-based cathode active material with an Ni content of 80 mol%, a solid electrolyte fine powder containing divalent cations obtained in Production Example 2, and a conductive material were weighed at a mass ratio of 60:35:5. These were mixed to obtain a cathode mixture.

[0144] On one surface of the solid electrolyte pellet, 17 mg of the positive electrode mixture was placed. After that, the SUS press pin of the molding jig was pressed against it to flatten it, and then it was pressure-molded at 110 MPa for 1 minute to obtain a positive electrode active material layer formed on the solid electrolyte layer. An SUS plate as a positive electrode current collector was placed on the positive electrode active material layer, and an SUS plate as a negative electrode current collector was placed so as to be in direct contact with the solid electrolyte layer on the side opposite to the positive electrode active material layer. This was pressure-molded at 554 MPa for 1 minute to obtain a laminate. The obtained laminate was combined with an SUS press pin to fabricate a Macall tube cell. The obtained Macall tube cell was installed in a battery cell, and a low restraint pressure of about 0.005 MPa was applied to obtain an all-solid-state battery. That is, the all-solid-state battery of Example 1 contains a solid electrolyte coarse powder containing a divalent cation in the solid electrolyte layer 2 and a solid electrolyte fine powder containing a divalent cation in the positive electrode active material layer.

[0145] The all-solid-state battery of Example 1 is shown in FIG. 1. As shown in FIG. 1, the negative electrode current collector 1 and the solid electrolyte layer 2 containing a solid electrolyte containing a divalent cation are in direct contact. The all-solid-state battery of Example 1 is in the state of a battery precursor before the first charge and does not include a negative electrode active material layer. The all-solid-state battery of Example 1 is an all-solid-state battery with an anode-free structure.

[0146] Example 2 In the step of obtaining the solid electrolyte pellet, an all-solid-state battery was obtained in the same manner as in Example 1, except that the solid electrolyte fine powder containing a divalent cation obtained in Production Example 2 was used instead of the solid electrolyte coarse powder containing a divalent cation obtained in Production Example 1. That is, the all-solid-state battery of Example 2 contains a solid electrolyte fine powder containing a divalent cation in the solid electrolyte layer 2 and the positive electrode active material layer 3.

[0147] Example 3 In the step of obtaining the all-solid-state battery, an all-solid-state battery was obtained in the same manner as in Example 1, except that a restraint pressure of about 8 MPa was applied instead of a restraint pressure of about 0.005 MPa.

[0148] Example 4 In the step of obtaining the solid electrolyte pellet, an all-solid-state battery was obtained in the same manner as in Example 1, except that the super-coarse solid electrolyte powder containing divalent cations obtained in Production Example 3 was used instead of the coarse solid electrolyte powder containing divalent cations obtained in Production Example 1. That is, the all-solid-state battery of Example 4 contains the super-coarse solid electrolyte powder containing divalent cations in the solid electrolyte layer 2 and the fine solid electrolyte powder containing divalent cations in the positive electrode active material layer 3.

[0149] Comparative Example 1 In the step of obtaining the solid electrolyte pellet, the coarse solid electrolyte powder not containing divalent cations obtained in Comparative Production Example 1 was used instead of the coarse solid electrolyte powder containing divalent cations obtained in Production Example 1, and in the step of obtaining the positive electrode mixture, the fine solid electrolyte powder not containing divalent cations obtained in Comparative Production Example 2 was used instead of the fine solid electrolyte powder containing divalent cations obtained in Production Example 2. An all-solid-state battery was obtained in the same manner as in Example 1. That is, as shown in FIG. 2, the all-solid-state battery of Comparative Example 1 contains the coarse solid electrolyte powder not containing divalent cations in the solid electrolyte layer 5 and the fine solid electrolyte powder not containing divalent cations in the positive electrode active material layer 3.

[0150] Comparative Example 2 In the step of obtaining the all-solid-state battery, an Ag-C intermediate layer was installed on the solid electrolyte layer on the side opposite to the positive electrode active material layer, and a SUS plate as a negative electrode current collector was installed on the Ag-C intermediate layer, and an all-solid-state battery was obtained in the same manner as in Comparative Example 1 except that a confinement pressure of about 4 MPa was applied. The Ag-C intermediate layer was prepared by dissolving a predetermined amount of Ag and C (carbon black) in N-methylpyrrolidone added with 7 wt% of PVDF and then applying it on the SUS plate. That is, as shown in FIG. 3, the all-solid-state battery of Comparative Example 2 contains the coarse solid electrolyte powder not containing divalent cations in the solid electrolyte layer 5, the fine solid electrolyte powder not containing divalent cations in the positive electrode active material layer 3, and an intermediate layer 6 is installed between the solid electrolyte layer 5 and the negative electrode current collector 1.

[0151] [All-Solid-State Battery Evaluation] (Charge and Discharge Test) Using the obtained all-solid-state battery, a charge-discharge test was conducted at 25°C. The voltage range was 4.25V - 3.0V, the charging conditions were CC(0.05C)-CV(0.01C cut-off), and the discharging conditions were CC(0.05C). From the obtained charge-discharge curves, the charge capacity and discharge capacity were determined. Also, the discharge capacity retention rate (%) at 25°C under the charging conditions CC(0.05C)-CV(0.01C) and discharging conditions CC(0.05C) was derived according to the following formula.

[0152] Discharge capacity in each cycle / Discharge capacity in the first cycle × 100

[0153] [Evaluation Results] (All-solid-state battery characteristics) The initial discharge capacity relative ratio of the all-solid-state battery capacity of Example 1 to that of Comparative Example 1 was 103%. The initial discharge capacity relative ratio of the all-solid-state battery capacity of Example 2 to that of Comparative Example 1 was 103%. The initial discharge capacity relative ratio of the all-solid-state battery capacity of Example 3 to that of Comparative Example 1 was 101%.

[0154] Thus, the all-solid-state batteries of Examples 1 to 3 containing a sulfide-based solid electrolyte in which the solid electrolyte layer contains a Group 2 element and has an argyrodite-type crystal structure were able to increase the discharge capacity compared to the all-solid-state battery of Comparative Example 1 that does not contain the sulfide-based solid electrolyte of the present disclosure.

[0155] Figures 5 and 6 are graphs showing the discharge capacity retention rates of the all-solid-state batteries of Examples 1 to 4 and Comparative Examples 1 and 2. The scales of the vertical axes of Figure 5 and Figure 6 are different. The discharge capacity retention rate at the third cycle was 99.5% for Example 1, 99.2% for Example 2, 99.2% for Example 3, 97.9% for Example 4, 78.8% for Comparative Example 1, and 92.4% for Comparative Example 2. The discharge capacity retention rate in the 8th cycle was 98.6% in Example 1, 65.5% in Example 4, and 84.2% in Comparative Example 2. In Example 4, the discharge capacity decreased after 4 cycles. The solid electrolyte ultra-coarse powder used in the solid electrolyte layer of Example 4 has an average particle size similar to that of the solid electrolyte coarse powder used in Example 1, but has a wider particle size distribution. This wide particle size distribution is considered to lead to non-uniform lithium ion conduction during charge and discharge, for example, by deteriorating the smoothness of the surface of the solid electrolyte layer, resulting in a decrease in the discharge capacity. In Comparative Example 1, the discharge capacity decreased rapidly after 4 cycles, making it impossible to measure the discharge capacity. Different from Comparative Example 1, in Comparative Example 2, an intermediate layer 6 is provided between the solid electrolyte layer 5 and the negative electrode current collector 1. Since the intermediate layer 6 suppressed the growth of lithium dendrites, Comparative Example 2 is considered to have shown better cycle characteristics than Comparative Example 1.

[0156] Thus, all solid-state batteries of Examples 1 to 3 containing a sulfide-based solid electrolyte in which the solid electrolyte layer contains a Group 2 element and has an argyrodite-type crystal structure were able to enhance cycle characteristics more than all solid-state batteries of Comparative Examples 1 and 2 that do not contain the sulfide-based solid electrolyte of the present disclosure. The all-solid-state battery of Example 4 was able to enhance cycle characteristics more than all solid-state batteries of Comparative Examples 1 and 2 at a low number of cycles.

[0157] The all-solid-state batteries of Example 1 and Example 3 include solid electrolyte coarse powder containing divalent cations, that is, the solid electrolyte coarse powder of Production Example 1, in the solid electrolyte layer. The all-solid-state battery of Example 2 includes solid electrolyte fine powder containing divalent cations, that is, the solid electrolyte fine powder of Production Example 2, in the solid electrolyte layer. The all-solid-state battery of Example 4 includes solid electrolyte super-coarse powder containing divalent cations, that is, the solid electrolyte super-coarse powder of Production Example 3, in the solid electrolyte layer. As shown in Table 1, the solid electrolyte coarse powder of Production Example 1 and the solid electrolyte super-coarse powder of Production Example 3 exhibit an ionic conductivity that is approximately three times higher than that of the solid electrolyte fine powder of Production Example 2. As shown in FIG. 6, the all-solid-state battery of Example 1 exhibited better cycle characteristics than the all-solid-state battery of Example 2. The excellent cycle characteristics of the all-solid-state battery of Example 1 are considered to be due to the high ionic conductivity of the solid electrolyte coarse powder containing divalent cations. Although the all-solid-state battery of Example 4 has a solid electrolyte super-coarse powder with high ionic conductivity, its cycle characteristics are inferior to those of the all-solid-state battery of Example 2. This is presumably because large particles such as aggregates contained in the solid electrolyte super-coarse powder of Example 4, which has a wide particle size distribution, deteriorate the smoothness of the surface of the solid electrolyte layer, and the lithium ion conduction during charge and discharge becomes non-uniform.

[0158] Normally, during charge and discharge of a solid battery, a high confinement pressure is applied to suppress the growth of lithium dendrites on the negative electrode current collector. However, as can be seen from FIG. 6, the all-solid-state battery of Example 1 to which a confinement pressure of about 0.005 MPa was applied exhibited better discharge capacity and cycle characteristics than the all-solid-state battery of Example 3 to which a confinement pressure of about 8 MPa was applied. This is presumably due to the use of a solid electrolyte containing divalent cations in the solid electrolyte layer and the positive electrode active material layer. Thus, the all-solid-state battery of the present disclosure can be driven at a low confinement pressure.

[0159] FIG. 7 is an SEM image showing the calcium distribution in the all-solid-state battery of Example 1. The left image in FIG. 7 represents a cross-sectional view of the all-solid-state battery before the first charge. The central image in FIG. 7 represents a cross-sectional view of the all-solid-state battery after the first charge. The right image in FIG. 7 represents a cross-sectional view of the all-solid-state battery after the first discharge. In each SEM image, calcium (Ca) is shown in white. The negative electrode current collector was peeled off for SEM observation.

[0160] As can be seen from the left image in FIG. 7, before the first charge of the all-solid-state battery, calcium (Ca) contained in the solid electrolyte layer is distributed throughout the solid electrolyte layer. However, it should be noted that the white dots observed in the region of the "state where the current collector has peeled off" are derived from calcium (Ca) in the depth direction of the solid electrolyte layer, and there is no calcium (Ca) in the region of the "state where the current collector has peeled off".

[0161] As can be seen from the central image in FIG. 7, after the first charge of the all-solid-state battery, a part of calcium (Ca) has moved to the interface between the negative electrode current collector and the solid electrolyte layer. As can be seen from the right image in FIG. 7, after the first discharge of the all-solid-state battery, a part of calcium (Ca) has moved to the interface between the positive electrode active material layer (also referred to as the "positive electrode layer") and the solid electrolyte layer. Even during the charge and discharge after the second time, calcium moves to the interface between the negative electrode current collector and the solid electrolyte layer during charging, and moves to the interface between the positive electrode active material layer and the solid electrolyte layer during discharging. Thus, it was suggested that calcium (Ca), which is a Group 2 element, moves between the electrodes together with lithium, which is a charge carrier, in the anode-free structure all-solid-state battery of Example 1.

[0162] FIG. 8 is an SEM image (left) of the negative electrode current collector side and a graph (right) showing the calcium line analysis result after the first charge of the all-solid-state battery of Example 1. The negative electrode current collector was peeled off for SEM observation.

[0163] As can be seen from the left - hand image in Fig. 8, after the first charge of the all - solid - state battery, a precipitate was formed between the negative electrode current collector and the solid electrolyte layer. The results of line analysis of calcium (SEM - EDX analysis) across the solid electrolyte layer - precipitate - negative electrode current collector are shown in the right - hand image of Fig. 8. It can be seen that calcium (Ca) is distributed across the solid electrolyte layer and the precipitate. In particular, it can be seen that a large amount of calcium (Ca) is present at the interface between the precipitate and the negative electrode current collector. It is considered that the formation of the precipitate between the precipitate and the negative electrode current collector improves the adhesion between the negative electrode current collector and the solid electrolyte layer through the precipitate.

[0164] Since lithium is formed between the negative electrode current collector and the solid electrolyte layer during charging of the anode - free all - solid - state battery, the precipitate shown in Fig. 8 is considered to contain lithium. Also, from the SEM - EDX analysis, the precipitate shown in Fig. 8 is considered to contain elemental calcium (Ca), or an alloy or compound of calcium (Ca) and lithium. In particular, since calcium (Ca) is present on the negative electrode current collector side in the precipitate, it is considered that the calcium (Ca) contained in the precipitate improves the adhesion / adhesiveness between the negative electrode current collector and the solid electrolyte layer through the precipitate. As a result, it is considered that the all - solid - state battery of Example 1 has excellent discharge capacity, cycle characteristics, and drivability at a low constraint pressure. Although further analysis is required, it is considered that the precipitate formed between the positive electrode active material layer and the solid electrolyte layer during discharge of the all - solid - state battery also has a similar form and characteristics to the above - mentioned precipitate formed between the negative electrode current collector and the solid electrolyte layer.

[0165] In conventional anode-free batteries, lithium-containing precipitates such as lithium metal formed between the negative electrode current collector and the solid electrolyte layer after charging destroy the ion conduction path and / or the electrical conduction path between the negative electrode current collector and the solid electrolyte layer, causing a decrease in ion conductivity and a decrease in cycle characteristics. However, in the all-solid-state battery of the present disclosure, the Group 2 element contained in the solid electrolyte layer accumulates between the negative electrode current collector and the solid electrolyte layer during charging, improving the adhesion between them and enabling high discharge capacity and cycle characteristics to be maintained. Further, in the all-solid-state battery of the present disclosure, the Group 2 element contained in the solid electrolyte layer accumulates between the positive electrode active material layer and the solid electrolyte layer during discharge, improving the adhesion between them and enabling high discharge capacity and cycle characteristics to be maintained. Furthermore, in the all-solid-state battery of the present disclosure, the adhesion between the solid electrolyte layer and the electrode is improved by the deposit containing the Group 2 element, and it can be driven at a low restraint pressure such as about 0.005 MPa.

[0166] As described above, the present disclosure has been described by way of limited embodiments and drawings. However, the present disclosure is not limited thereto, and it goes without saying that various modifications and variations can be made by those having ordinary knowledge in the technical field to which the present disclosure pertains within the equivalent scope of the technical idea of the present disclosure and the appended claims.

Explanation of Reference Numerals

[0167] 1 Negative electrode current collector 2 Solid electrolyte layer containing a solid electrolyte containing divalent cations 3 Positive electrode active material layer 4 Positive electrode current collector 5 Solid electrolyte layer containing a solid electrolyte not containing divalent cations 6 Intermediate layer

Claims

1. An all-solid-state battery including a positive electrode containing a positive electrode active material layer, a negative electrode current collector, and a solid electrolyte layer disposed between the positive electrode and the negative electrode current collector, wherein the all-solid-state battery does not contain a negative electrode active material, lithium ions are supplied from the positive electrode active material layer upon charging, and a lithium metal layer as a negative electrode active material is formed on the negative electrode current collector, the solid electrolyte layer contains a sulfide-based solid electrolyte containing a Group 2 element and having an argyrodite-type crystal structure. An all-solid-state battery.

2. The all-solid-state battery according to claim 1, wherein the negative electrode current collector and the solid electrolyte layer are in direct contact.

3. wherein the sulfide solid electrolyte has the chemical formula Li ７－ｘ－２ｙ M ｙ PS ６－ｘ Ha ｘ and is represented by In the chemical formula, M is one or more elements selected from Group 2 elements, Ha is one or more elements selected from halogen elements, The all-solid-state battery according to claim 1, satisfying 0 < x < 2.5 and 0 < y < 0.

45.

4. The all-solid-state battery according to claim 3, wherein M is Ca.

5. The all-solid-state battery according to claim 1, which does not contain a reaction product between the negative electrode current collector and the sulfide-based solid electrolyte.

6. The all-solid-state battery according to claim 1, wherein the all-solid-state battery is pressurized at a pressure of 0.3 MPa or less in the direction in which the positive electrode, the negative electrode current collector, and the solid electrolyte layer are laminated.

7. The all-solid-state battery according to claim 1, wherein the positive electrode active material layer contains the sulfide-based solid electrolyte.

8. The all-solid-state battery according to claim 1, wherein the average particle diameter of the sulfide-based solid electrolyte contained in the solid electrolyte layer is larger than the average particle diameter of the sulfide-based solid electrolyte contained in the positive electrode active material layer.

9. The all-solid-state battery according to claim 1, wherein the Group 2 element is present at the 48h site of the argyrodite-type crystal structure.

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