Sulfide solid electrolyte and all-solid-state battery

Abstract

To provide a sulfide solid electrolyte with improved reduction resistance and an all-solid-state battery comprising the sulfide solid electrolyte.SOLUTION: A sulfide solid electrolyte contains aluminum (Al) and nitrogen (N), and has a crystalline structure. An all-solid-state battery 10 comprises a negative electrode layer 1, a solid electrolyte layer 3, and a positive electrode layer 2, wherein the negative electrode layer, the solid electrolyte layer, the positive electrode layer, or a combination thereof contains the sulfide solid electrolyte, resulting in superior first coulombic efficiency.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sulfide solid electrolyte and an all-solid-state battery.

Background Art

[0002] Non-aqueous electrolyte secondary batteries typified by lithium-ion non-aqueous electrolyte secondary batteries are widely used in electronic devices such as personal computers and communication terminals, and automobiles because of their high energy density. Generally, the non-aqueous electrolyte secondary battery includes an electrode body having a pair of electrodes electrically isolated from each other, and a non-aqueous electrolyte interposed between the electrodes, and is configured to charge and discharge by transferring ions between both electrodes.

[0003] In recent years, for the purpose of improving the safety of non-aqueous electrolyte secondary batteries, all-solid-state batteries using a sulfide solid electrolyte or the like instead of a liquid electrolyte such as an organic solvent as the non-aqueous electrolyte have been proposed (see Patent Document 1).

[0004] As an example of a sulfide solid electrolyte, a sulfide solid electrolyte containing Li, P, S, and N and having a composition represented by the general formula XLi 2 S-25P 2 S 5 -YLi 3 N (10 ≦ Y ≦ 15, 67.5 ≦ X + Y ≦ 85), which is a crystalline material, is disclosed. (See Patent Document 2) As the sulfide solid electrolyte, 70Li 2 S·30P 2 S 5 glass ceramics and 60Li 2 S·25P 2 S 5 ·10Li 3 N glass ceramics have been reported to exhibit a high ionic conductivity of 10 -3 S / cm or more. (Non-Patent Document 1)

[0005] It has been clarified from first-principles calculations that such a sulfide solid electrolyte is essentially low in oxidation resistance and reduction resistance. (Non-Patent Document 2)

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made based on the above circumstances, and an object thereof is to provide a sulfide solid electrolyte having improved reduction resistance and an all-solid-state battery including the sulfide solid electrolyte.

Means for Solving the Problems

[0008] One aspect of the present invention made to solve the above problems is a sulfide solid electrolyte including at least one element M selected from the group consisting of Al, Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, V and N and having a crystal structure.

[0009] Another aspect of the present invention is a sulfide solid electrolyte including Al and N and having a crystal structure.

Effects of the Invention

[0010] According to the sulfide solid electrolyte according to one aspect or another aspect of the present invention, a sulfide solid electrolyte with improved reduction resistance can be obtained.

Brief Description of the Drawings

[0011]

Figure 1

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Figure 9

Mode for Carrying Out the Invention

[0012] The sulfide solid electrolyte according to one aspect of the present invention is a sulfide solid electrolyte containing at least one element M selected from the group consisting of Al, Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, V and N, and having a crystal structure.

[0013] The inventors focused on the fact that nitrides containing any of Al, Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, V (hereinafter also referred to as element M), which are difficult to apply as solid electrolytes due to low ionic conductivity, exhibit high reducibility resistance. Therefore, the inventors considered that the reducibility resistance of the sulfide solid electrolyte could be improved by containing nitrogen element (N) and the element M in the sulfide solid electrolyte, and thus the present invention was achieved.

[0014] The sulfide solid electrolyte can be a sulfide solid electrolyte with improved reduction resistance by containing at least one element M selected from the group consisting of Al, Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, and V and N and having a crystal structure. In the sulfide solid electrolyte, the element M may be Al. The reason for this is not clear, but the following reasons are speculated. When the sulfide solid electrolyte containing the element M and N is exposed to a reducing atmosphere, it is speculated that a highly reduction-resistant film containing a nitride of the element M, a lithium nitride of the element M, etc. is formed on the surface or interface of the sulfide solid electrolyte. For this reason, it is speculated that the reduction resistance of the sulfide solid electrolyte is improved.

[0015] The all-solid-state battery including the sulfide solid electrolyte can be an all-solid-state battery with improved initial Coulomb efficiency. The reason for this is not clear, but the following reasons are speculated. A general sulfide solid electrolyte is easily reduction-decomposed, and it is known that an all-solid-state battery including such a sulfide solid electrolyte shows a large reduction decomposition charge amount. However, the sulfide solid electrolyte has high reduction resistance. Therefore, the initial Coulomb efficiency of the all-solid-state battery including the sulfide solid electrolyte can be improved. Furthermore, since the sulfide solid electrolyte contains N, S is replaced by N with a small ionic radius, and the crystal lattice volume decreases. Therefore, the space for lithium ions to move becomes larger, and the ionic conductivity can be improved. As a result, the initial Coulomb efficiency of the all-solid-state battery can be improved while maintaining good ionic conductivity.

[0016] In the above sulfide solid electrolyte, the element M only needs to have a high reduction resistance of the nitride. Specifically, it may be at least one element selected from the group consisting of Al, Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, and V. These elements are elements that have been clarified by first-principles calculations to have a high reduction resistance of lithium nitride containing the element M (see Non-Patent Document Adv. Sci., 4, 1600517 (2017)). Among these, Al, B, and Si are preferred because of their low cost and the ability to reduce manufacturing costs.

[0017] As the above crystal structure, it preferably has a crystal structure having a crystal phase of Li 7 P 3 S 11 , Li 4 P 2 S 6 or β-Li 3 PS 4 , or a first crystal structure having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, and 29.8° ± 0.5° in X-ray diffraction measurement using CuKα radiation. This can increase the ionic conductivity at 25°C.

[0018] Preferably, the first crystal structure includes a specific crystal structure A having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, 29.8° ± 0.5°, and 30.9° ± 0.5° in the above X-ray diffraction measurement, or a specific crystal structure B having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, and 29.8° ± 0.5° and not having a diffraction peak at 30.9° ± 0.5° in the above X-ray diffraction measurement. With the above configuration, the ionic conductivity at 25°C can be further increased.

[0019] When the sulfide solid electrolyte contains at least one element M selected from the group consisting of Li, P, S, N, and Al, Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, V, from the viewpoint of reduction resistance, the content ratio of Li to P is preferably 1.64 or more and 4.00 or less in molar ratio, and the content ratio of N to P is preferably 0.02 or more and 1.11 or less in molar ratio. When the content ratios of Li and N in the sulfide solid electrolyte are within the above ranges, the reduction resistance is further improved, and the initial Coulomb efficiency of the all-solid-state battery provided with the sulfide solid electrolyte can be further increased. In the sulfide solid electrolyte, the element M may be Al.

[0020] In the sulfide solid electrolyte, it is more preferable that the content ratio of Li to P is 2.77 or more and 3.38 or less in molar ratio, and the content ratio of N to P is 0.28 or more and 0.65 or less in molar ratio. When the content ratios of Li and N in the sulfide solid electrolyte are within the above ranges, the reduction resistance, the air stability, and the ionic conductivity at 25 °C can be simultaneously increased.

[0021] When the sulfide solid electrolyte has a composition represented by the general formula (100 - z)(yLi 2 S·(1 - y)P 2 S 5 )·zLi α M β N (where 0 < z ≤ 40, 0.50 ≤ y ≤ 0.75, α and β are numerical values giving the stoichiometric ratio depending on the type of element M), it is preferable. When the sulfide solid electrolyte has a composition represented by the above general formula, the reduction resistance is further improved, and the initial Coulomb efficiency of the all-solid-state battery provided with the sulfide solid electrolyte can be further increased.

[0022] The sulfide solid electrolyte may further contain Ge. Even such a sulfide solid electrolyte can enjoy the effects of the present invention.

[0023] When the sulfide solid electrolyte contains Ge, the sulfide solid electrolyte is Li 10GeP 2 S 12 Preferably includes a structure having a crystal phase of

[0024] Further, the sulfide solid electrolyte contains Li, P, S, N, Ge, and the above element M, and Li 10 GeP 2 S 12 When it has a crystal phase of, the content ratio of Li to P is preferably 5.01 or more and 5.61 or less in molar ratio, and the content ratio of N to P is preferably 0.0051 or more and 0.41 or less in molar ratio. Further, it is more preferable that the content ratio of Li to P is 5.06 or more and 5.19 or less in molar ratio, and the content ratio of N to P is 0.038 or more and 0.13 or less in molar ratio.

[0025] When the sulfide solid electrolyte contains Ge, it preferably has a composition represented by the general formula (100 - z)Li 10 GeP 2 S 12 ·zLi α M β N (where 0 < z ≤ 50, α and β are numerical values giving a stoichiometric ratio depending on the type of element M). Among them, in the above general formula, it is particularly preferable that z satisfies 0 < z ≤ 20.

[0026] The ionic conductivity of the sulfide solid electrolyte at 25°C is preferably 1.0×10 -3 S / cm or more. With the above configuration, the high-rate discharge performance of the all-solid-state battery equipped with the sulfide solid electrolyte can be improved.

[0027] The ionic conductivity of the sulfide solid electrolyte at 25°C is determined by measuring the AC impedance by the following method. In an argon atmosphere with a dew point of -50°C or lower, 120 mg of sample powder is introduced into a powder molding machine with an inner diameter of 10 mm, and then uniaxially pressed using a hydraulic press at a pressure of 50 MPa or less per sample area. After releasing the pressure, SUS316L powder is introduced as a current collector on the upper and lower surfaces of the sample, and then uniaxially pressed at a pressure of 360 MPa per pellet area for 5 minutes to obtain a pellet for measuring ionic conductivity. This pellet for measuring ionic conductivity is inserted into an HS cell manufactured by Hokuen Co., Ltd. to measure the AC impedance. The measurement conditions are an applied voltage amplitude of 20 mV, a frequency range from 1 MHz to 100 mHz, and a measurement temperature of 25°C.

[0028] The all-solid-state battery according to another aspect of the present invention includes a negative electrode layer, a solid electrolyte layer, and a positive electrode layer, and is an all-solid-state battery in which the negative electrode layer, the solid electrolyte layer, the positive electrode layer, or a combination thereof contains the sulfide solid electrolyte.

[0029] Since the all-solid-state battery according to another aspect of the present invention has the negative electrode layer, the solid electrolyte layer, the positive electrode layer, or a combination thereof containing the sulfide solid electrolyte, the initial Coulomb efficiency is excellent. Since the sulfide solid electrolyte is excellent in reduction resistance, it is preferable that the negative electrode layer and / or the solid electrolyte layer contains the sulfide solid electrolyte. With the above configuration, the effect of the present invention becomes even more excellent.

[0030] Hereinafter, embodiments of the sulfide solid electrolyte and the all-solid-state battery according to the present invention will be described in detail.

[0031] <Sulfide solid electrolyte> The sulfide solid electrolyte contains at least one element M selected from the group consisting of Al, Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, and V, and N, and has a crystal structure. By containing at least one element M selected from the group consisting of Al, Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, and V, and N, and having a crystal structure, the reduction resistance can be improved. The sulfide solid electrolyte can be used in any application that requires ionic conductivity. Among them, the sulfide solid electrolyte is preferably used in a lithium all-solid-state battery. In the above sulfide solid electrolyte, the element M may be Al.

[0032] The sulfide solid electrolyte has a crystal structure. Here, "having a crystal structure" means that in X-ray diffraction measurement, peaks derived from the crystal structure of the sulfide solid electrolyte are observed in the X-ray diffraction pattern. The sulfide solid electrolyte may contain an amorphous part. The sulfide solid electrolyte having a crystal structure can be obtained, for example, by crystallizing an amorphous sulfide solid electrolyte by heat treatment or the like.

[0033] Examples of the crystal structure of the sulfide solid electrolyte include the LGPS type, the argyrodite type, Li 7 P 3 S 11 and the Thio-LISICON system, etc. Among these, from the viewpoint of lithium ion conductivity, the LGPS type, the argyrodite type, and Li 7 P 3 S 11 are preferable, and among these, Li 7 P 3 S 11 is more preferable because of its high stability against Li. From the viewpoint of stability against the atmosphere, Li 4 P 2 S 6 or β-Li 3 PS 4It preferably includes a crystal structure having the crystal phase or a first crystal structure having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, and 29.8° ± 0.5° in X-ray diffraction measurement using CuKα rays. Among these, since it has high lithium ion conductivity, it is more preferably a first crystal structure having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, and 29.8° ± 0.5° in X-ray diffraction measurement using CuKα rays.

[0034] The above-mentioned first crystal structure may include a specific crystal structure A having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, 29.8° ± 0.5°, and 30.9° ± 0.5° in the above X-ray diffraction measurement or a specific crystal structure B having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, and 29.8° ± 0.5° and not having a diffraction peak at 30.9° ± 0.5° in the above X-ray diffraction measurement. With the above configuration, the ionic conductivity at 25°C can be increased.

[0035] The diffraction peaks in the above-mentioned first crystal structure may be within a further range of ±0.3° or within a range of ±0.1° within the range of the above 2θ.

[0036] The X-ray diffraction measurement using the above CuKα rays is performed according to the following procedure. A hermetic X-ray diffraction measurement sample holder is filled with a solid electrolyte powder to be measured under an argon atmosphere with a dew point of -50°C or lower. Powder X-ray diffraction measurement is performed using an X-ray diffractometer ("MiniFlex II" manufactured by Rigaku). The radiation source is CuKα rays, the tube voltage is 30 kV, the tube current is 15 mA, and the diffracted X-rays are detected by a high-speed one-dimensional detector (model number: D / teX Ultra 2) through a Kβ filter with a thickness of 30 μm. The sampling width is 0.01°, the scan speed is 5° / min, the divergence slit width is 0.625°, the receiving slit width is 13 mm (OPEN), and the scattering slit width is 8 mm.

[0037] The above Li 7P 3 S 11 The crystal structure having the crystal phase of S has diffraction peaks at positions of 2θ = 17.8° ± 0.5°, 18.5° ± 0.5°, 23.7° ± 0.5°, 29.6° ± 0.5°, 30.0° ± 0.5° in the X-ray diffraction measurement using the above CuKα ray.

[0038] Examples of the above LGPS type sulfide solid electrolyte include Li 10 GeP 2 S 12 and the like. Li 10 GeP 2 S 12 The crystal structure having the crystal phase of S has diffraction peaks at positions of 2θ = 14.4° ± 0.5°, 20.1° ± 0.5°, 20.4° ± 0.5°, 26.9° ± 0.5°, 29.5° ± 0.5°, 47.3° ± 0.5° in the X-ray diffraction measurement using the above CuKα ray.

[0039] Examples of the above argyrodite type sulfide solid electrolyte include Li 6 PS 5 Cl and the like. Li 6 PS 5 The crystal structure having the crystal phase of Cl has diffraction peaks at positions of 2θ = 15.6° ± 0.5°, 25.5° ± 0.5°, 30.0° ± 0.5°, 31.4° ± 0.5°, 45.0° ± 0.5°, 52.5° ± 0.5° in the X-ray diffraction measurement using the above CuKα ray.

[0040] The above Li 4 P 2 S 6 The crystal structure having the crystal phase of S has diffraction peaks at positions of 2θ = 2θ = 16.9° ± 0.5°, 27.1° ± 0.5°, 32.1° ± 0.5°, 32.5° ± 0.5° in the X-ray diffraction measurement using the above CuKα ray.

[0041] The above β-Li 3 PS 4The crystal structure having the crystal phase has diffraction peaks at positions of 2θ = 17.5° ± 0.5°, 18.1° ± 0.5°, 29.1° ± 0.5°, 29.9° ± 0.5°, and 31.2° ± 0.5° in the X-ray diffraction measurement using the above CuKα ray.

[0042] The sulfide solid electrolyte preferably contains Li, P, S, N, and element M. In this case, from the viewpoint of reduction resistance, the content ratio of Li to P in the sulfide solid electrolyte is preferably 1.64 or more and 4.00 or less, more preferably 2.36 or more and 3.70 or less, and even more preferably 2.60 or more and 3.40 or less in terms of molar ratio. The content ratio of N to P is preferably 0.02 or more and 1.11 or less, more preferably 0.19 or more and 1.01 or less, even more preferably 0.22 or more and 0.71 or less, and particularly preferably 0.28 or more and 0.65 or less. By the content ratios of Li and N in the sulfide solid electrolyte being within the above ranges, a sulfide solid electrolyte showing good reduction resistance can be obtained. Also, the initial Coulomb efficiency of the all-solid-state battery including the sulfide solid electrolyte can be increased.

[0043] Furthermore, from the viewpoint of air stability, the content ratio of Li to P is preferably 2.60 or more and 4.00 or less in terms of molar ratio, and the content ratio of N to P is preferably 0.19 or more and 1.11 or less in terms of molar ratio. More preferably, the content ratio of Li to P is 2.77 or more and 3.38 or less in terms of molar ratio, and the content ratio of N to P is 0.28 or more and 0.65 or less in terms of molar ratio. Also, it is preferable to contain Al as element M. Thereby, especially when the value of y in the general formula is less than 0.75, so-called cross-linked sulfur P 2 S 7 4- (S 3 P - S - PS 3 ) decreases, and since it substantially does not contain Li 2 S which is likely to react with water, the air stability of the sulfide solid electrolyte is improved, and the generation of hydrogen sulfide due to the reaction between moisture in the air and S in the sulfide solid electrolyte can be suppressed.

[0044] In particular, when the content ratio of Li to P is 2.77 or more and 3.38 or less in molar ratio, and the content ratio of N to P is 0.28 or more and 0.65 or less in molar ratio, it is preferable because the reduction resistance, the air stability, and the ionic conductivity at 25 °C can be enhanced simultaneously.

[0045] The sulfide solid electrolyte contains Li, P, S, N, Ge, and the element M, and Li 10 GeP 2 S 12 When it has a crystal phase of, from the viewpoint of reduction resistance, the content ratio of Li to P is preferably 5.01 or more and 5.61 or less in molar ratio, and the content ratio of N to P is preferably 0.0051 or more and 0.41 or less in molar ratio. Further, it is more preferable that the content ratio of Li to P is 5.06 or more and 5.19 or less in molar ratio, and the content ratio of N to P is 0.038 or more and 0.13 or less in molar ratio.

[0046] The sulfide solid electrolyte preferably has a composition represented by the general formula (100 - z)(yLi 2 S·(1 - y)P 2 S 5 )·zLi α M β N (where 0 < z ≤ 40, 0.50 ≤ y ≤ 0.75). By having the composition represented by the general formula for the sulfide solid electrolyte, the reduction resistance can be further improved. Further, the initial Coulomb efficiency of the all-solid-state battery including the sulfide solid electrolyte can be further increased.

[0047] In the general formula, z is preferably more than 0 and 40 or less, more preferably 1 or more and 30 or less, still more preferably 1 or more and 5 or 10 or more and 30 or less, and even more preferably 1 or more and 5 or 10 or more and 25 or less. When z in the general formula is in the range of more than 0 and 40 or less, the reduction resistance of the sulfide solid electrolyte can be further improved. When 10 ≤ z ≤ 40, so-called cross-linked sulfur P which is unstable in air 2 S 7 4- (S 3P-S-PS 3 ) decreases, and Li which easily reacts with water 2 Since it substantially does not contain S, the air stability of the sulfide solid electrolyte is improved, and the generation of hydrogen sulfide due to the reaction between moisture in the air and S in the sulfide solid electrolyte can be suppressed. By 1 ≦ z ≦ 30, the ionic conductivity at 25 °C can be further increased. By 1 ≦ z ≦ 5 or 10 ≦ z ≦ 30, the ionic conductivity at 25 °C can be further increased. By 1 ≦ z ≦ 5 or 10 ≦ z ≦ 25, the ionic conductivity at 25 °C can be further increased more.

[0048] In the above general formula, y is preferably 0.50 or more and 0.75 or less, and more preferably 0.67 or more and 0.70 or less. Li in the sulfide solid electrolyte 2 S and P 2 S 5 When the content ratio of is in the above range, the ionic conductivity of the sulfide solid electrolyte at 25 °C is improved.

[0049] In the above general formula, α and β are numerical values that give a stoichiometric ratio according to the type of element M. The values of α and β are not particularly limited. For example, 0.80 ≦ α ≦ 3.0 and 0.10 ≦ β ≦ 1.2 may be used. In particular, when Al is included as element M, α = 1.5 and β = 0.5 may be used.

[0050] When the sulfide solid electrolyte contains Ge, the general formula (100 - z)Li 10 GeP 2 S 12 ·zLi α M β N (where 0 < z ≦ 50, α and β are numerical values that give a stoichiometric ratio according to the type of element M) preferably has a composition represented by. For example, when Al is included as element M, the sulfide solid electrolyte has the general formula (100 - z)Li 10 GeP 2 S 12 ·zLi 3 / 2 Al 1 / 2It preferably has a composition represented by N (where 0 < z ≤ 50). When the sulfide solid electrolyte has such a composition, the ionic conductivity at 25°C can be increased.

[0051] In the above general formula, z is greater than 0 and less than or equal to 50, preferably 1 or more and 45 or less, more preferably 3 or more and 35 or less, still more preferably 5 or more and 25 or less, and even more preferably 7 or more and 20 or less. When z in the above general formula is within the above range, the reduction resistance and the ionic conductivity at 25°C can be further increased.

[0052] In the above general formula, α and β are numerical values that give a stoichiometric ratio according to the type of element M. The values of α and β are not particularly limited. For example, 0.80 ≤ α ≤ 3.0 and 0.10 ≤ β ≤ 1.2 may be used. In particular, when Al is included as element M, α = 1.5 and β = 0.5 may be used.

[0053] The ionic conductivity of the sulfide solid electrolyte at 25°C is preferably 0.4×10 -3 S / cm or more, more preferably 1.0×10 -3 S / cm or more, and still more preferably 1.5×10 -3 S / cm or more. When the ionic conductivity of the sulfide solid electrolyte at 25°C is the above value, the high-rate discharge performance of the all-solid-state battery equipped with the sulfide solid electrolyte can be improved.

[0054] Thus, the sulfide solid electrolyte can be suitably used as the solid electrolyte of an all-solid-state battery.

[0055] <All-solid-state battery> The all-solid-state battery includes a negative electrode layer, a solid electrolyte layer, and a positive electrode layer. FIG. 1 is a schematic cross-sectional view showing the all-solid-state battery according to an embodiment of the present invention. The all-solid-state battery 10, which is a secondary battery, has the negative electrode layer 1 and the positive electrode layer 2 disposed with the solid electrolyte layer 3 therebetween. The negative electrode layer 1 has a negative electrode base material layer 4 and a negative electrode mixture layer 5, and the negative electrode base material layer 4 is the outermost layer of the negative electrode layer 1. The positive electrode layer 2 has a positive electrode base material layer 7 and a positive electrode mixture layer 6, and the positive electrode base material layer 7 is the outermost layer of the positive electrode layer 2. In the all-solid-state battery 10 shown in FIG. 1, the positive electrode mixture layer 6, the solid electrolyte layer 3, the negative electrode mixture layer 5, and the negative electrode base material layer 4 are laminated in this order on the positive electrode base material layer 7.

[0056] In the all-solid-state battery, the negative electrode layer 1, the solid electrolyte layer 3, the positive electrode layer 2, or a combination thereof contains the sulfide solid electrolyte. Since the negative electrode layer 1, the solid electrolyte layer 3, the positive electrode layer 2, or a combination thereof in the all-solid-state battery contains the sulfide solid electrolyte, the initial Coulomb efficiency is excellent. Since the sulfide solid electrolyte is excellent in reduction resistance, it is preferable that the negative electrode layer 1 and / or the solid electrolyte layer 3 contain the sulfide solid electrolyte. With the above configuration, the effects of the present invention become even more excellent.

[0057] The all-solid-state battery may also use other solid electrolytes in addition to the sulfide solid electrolyte. As the other solid electrolyte, a sulfide solid electrolyte other than the sulfide solid electrolyte may be used, or an oxide solid electrolyte, a dry polymer electrolyte, a gel polymer electrolyte, or a pseudo solid electrolyte may be used.

[0058] As the sulfide solid electrolyte other than the sulfide solid electrolyte, it is preferable that it has high Li ion conductivity. For example, Li 2 S-P 2 S 5 、Li 2 S-P 2 S 5 -LiI、Li 2 S-P 2 S 5 -LiCl、Li 2 S-P 2 S 5 -LiBr、Li 2 S-P2 S 5 -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-P 2 S 5 -Li 3 N, Li 2 S-SiS 2 , Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 -LiI, Li 2 S-SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3 , Li 2 S-P 2 S 5 -Z m S 2n (However, m, n are positive numbers, and Z is any one of Ge, Zn, Ga.), Li 2 S-GeS 2 , Li 2 S-SiS 2 -Li 3 PO 4 , Li 2 S-SiS 2 -Li δ XO ε (However, δ, ε are positive numbers, and X is any one of P, Si, Ge, B, Al, Ga, In.), Li 10 GeP 2 S 12 etc. can be mentioned. Among these, from the viewpoint of good lithium ion conductivity, Li 2 S-P 2 S 5 is preferable, and xLi 2 S·(100 - x)P 2 S5 (70 ≦ x ≦ 80) is more preferable.

[0059] [Negative electrode layer] The negative electrode layer 1 includes a negative electrode base material layer 4 and a negative electrode mixture layer 5 laminated on the surface of the negative electrode base material layer 4. The negative electrode layer 1 may have an intermediate layer (not shown) between the negative electrode base material layer 4 and the negative electrode mixture layer 5.

[0060] (Negative electrode base material layer) The negative electrode base material layer 4 is a layer having conductivity. The material of the negative electrode base material layer 4 is not limited as long as it is a conductor. For example, one or more metals selected from the group consisting of copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, gold, silver, iron, platinum, chromium, tin, indium, and alloys containing one or more of these, and stainless alloys can be mentioned.

[0061] As the lower limit of the average thickness of the negative electrode base material layer 4, 3 μm is preferable, 5 μm is more preferable, and 8 μm is even more preferable. As the upper limit of the average thickness of the negative electrode base material layer 4, 200 μm is preferable, 100 μm is more preferable, and 50 μm is even more preferable. By setting the average thickness of the negative electrode base material layer 4 to be not less than the above lower limit, the strength of the negative electrode base material layer 4 can be made sufficiently high, so that the negative electrode layer 1 can be formed well. By setting the average thickness of the negative electrode base material layer 4 to be not more than the above upper limit, sufficient volume of other components can be ensured.

[0062] (Negative electrode mixture layer) The negative electrode mixture layer 5 can be formed from a so-called negative electrode mixture containing a negative electrode active material. The negative electrode mixture may contain a negative electrode mixture or a negative electrode composite containing the negative electrode active material and the sulfide solid electrolyte. The negative electrode mixture may optionally contain optional components such as a solid electrolyte other than the sulfide solid electrolyte, a conductive agent, a binder, and a filler.

[0063] 〈Negative electrode active material〉 As the negative electrode active material, a material that can usually occlude and release lithium ions is used. Specific negative electrode active materials include, for example Metals or semi-metals such as Si and Sn; Metal oxides or semi-metal oxides such as silicon oxide and tin oxide; Polyphosphoric acid compounds; Carbon materials such as graphite (graphite), non-graphitic carbon (easily graphitizable carbon or hardly graphitizable carbon); Examples include lithium metal composite oxides such as lithium titanate.

[0064] As the lower limit of the content of the negative electrode active material in the negative electrode binder, 10% by mass is preferable, and 15% by mass is more preferable. As the upper limit of the content of the negative electrode active material, 60% by mass is preferable, 70% by mass is more preferable, 80% by mass is further preferable, 90% by mass is particularly preferable, and 95% by mass may be used. By setting the content of the negative electrode active material within the above range, the capacitance of the all-solid-state battery can be increased.

[0065] 〈Negative electrode mixture or negative electrode composite〉 The above-mentioned negative electrode mixture is a mixture prepared by mechanically milling the negative electrode active material and the sulfide solid electrolyte. For example, a mixture of the negative electrode active material and the sulfide solid electrolyte can be obtained by mixing particulate negative electrode active material and particulate sulfide solid electrolyte. Examples of the above-mentioned negative electrode composite include a composite having a chemical or physical bond between the negative electrode active material and the sulfide solid electrolyte, and a composite in which the negative electrode active material and the sulfide solid electrolyte are mechanically combined. The above composite is one in which the negative electrode active material and the sulfide solid electrolyte are present in one particle. For example, those in which the negative electrode active material and the sulfide solid electrolyte form an aggregated state, and those in which a sulfide solid electrolyte-containing film is formed on at least a part of the surface of the negative electrode active material. The above-mentioned negative electrode mixture or negative electrode composite may contain a solid electrolyte other than the sulfide solid electrolyte. Since the negative electrode active material and the sulfide solid electrolyte contained in the negative electrode binder constitute the negative electrode mixture or negative electrode composite, the reduction resistance can be improved while maintaining high ionic conductivity, so the initial Coulomb efficiency is excellent.

[0066] When the negative electrode mixture contains a solid electrolyte, the lower limit of the content of the solid electrolyte in the negative electrode mixture may be 5% by mass, and preferably 10% by mass. The upper limit of the content of the solid electrolyte in the negative electrode mixture is preferably 90% by mass, more preferably 85% by mass, still more preferably 80% by mass, and particularly preferably 75% by mass. By setting the content of the solid electrolyte within the above range, the capacitance of the all-solid-state battery can be increased.

[0067] When the negative electrode layer contains the sulfide solid electrolyte, the lower limit of the content of the sulfide solid electrolyte in the negative electrode mixture may be 5% by mass, and preferably 10% by mass. The upper limit of the content of the sulfide solid electrolyte in the negative electrode mixture is preferably 90% by mass, more preferably 85% by mass, still more preferably 80% by mass, and particularly preferably 75% by mass. By setting the content of the sulfide solid electrolyte in the negative electrode mixture within the above range, when the negative electrode layer contains the sulfide solid electrolyte, the initial Coulomb efficiency of the all-solid-state battery can be further improved.

[0068] 〈Other optional components〉 The conductive agent is not particularly limited. Examples of such conductive agents include carbon blacks such as natural or artificial graphite, furnace black, acetylene black, and ketjen black, metals, and conductive ceramics. Examples of the shape of the conductive agent include powder form and fibrous form. The content of the conductive agent in the negative electrode mixture can be, for example, 0.5% by mass or more and 30% by mass or less. The negative electrode mixture may not contain a conductive agent.

[0069] The binder is not particularly limited. Examples include fluororesins (such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF)), thermoplastic resins such as polyethylene, polypropylene, polyimide, and polyacrylic acid; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0070] The above-mentioned filler is not particularly limited. Examples of the main component of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, carbon, and the like.

[0071] The lower limit of the average thickness of the negative electrode mixture layer 5 is preferably 30 μm, more preferably 60 μm. The upper limit of the average thickness of the negative electrode mixture layer 5 is preferably 1000 μm, more preferably 500 μm, and even more preferably 200 μm. By setting the average thickness of the negative electrode mixture layer 5 to be equal to or greater than the above lower limit, an all-solid-state battery having a high energy density can be obtained. By setting the average thickness of the negative electrode mixture layer 5 to be equal to or less than the above upper limit, an all-solid-state battery having excellent high-rate discharge performance and a negative electrode with a high active material utilization rate can be obtained.

[0072] (Intermediate layer) The above-mentioned intermediate layer is a coating layer on the surface of the negative electrode substrate layer 4, and contains conductive particles such as carbon particles to reduce the contact resistance between the negative electrode substrate layer 4 and the negative electrode mixture layer 5. The configuration of the intermediate layer is not particularly limited, and for example, it can be formed by a composition containing a resin binder and conductive particles.

[0073] [Positive electrode layer] The positive electrode layer 2 includes a positive electrode substrate layer 7 and a positive electrode mixture layer 6 laminated on the surface of the positive electrode substrate layer 7. Similar to the negative electrode layer 1, the positive electrode layer 2 may have an intermediate layer between the positive electrode substrate layer 7 and the positive electrode mixture layer 6. This intermediate layer can have the same configuration as the intermediate layer of the negative electrode layer 1.

[0074] (Positive electrode substrate layer) The positive electrode substrate layer 7 can have the same configuration as the negative electrode substrate layer 4. The material of the positive electrode substrate layer 7 is not limited as long as it is a conductor. For example, one or more metals selected from the group consisting of copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, gold, silver, iron, platinum, chromium, tin, indium, and alloys containing one or more of these, and stainless steel alloys can be mentioned.

[0075] As the lower limit of the average thickness of the positive electrode base material layer 7, 3 μm is preferable, and 5 μm is more preferable. As the upper limit of the average thickness of the positive electrode base material layer 7, 200 μm is preferable, 100 μm is more preferable, and 50 μm is even more preferable. By setting the average thickness of the positive electrode base material layer 7 to be equal to or greater than the above lower limit, the strength of the positive electrode base material layer 7 can be sufficiently increased, so that the positive electrode layer 2 can be formed well. By setting the average thickness of the positive electrode base material layer 7 to be equal to or less than the above upper limit, the volume of other components can be sufficiently ensured.

[0076] (Positive electrode mixture layer) The positive electrode mixture layer 6 can be formed from a so-called positive electrode mixture containing a positive electrode active material. The positive electrode mixture may contain a positive electrode mixture or a positive electrode composite containing a positive electrode active material and a solid electrolyte. As the above solid electrolyte, the sulfide solid electrolyte may be used, but it is more preferable to use a solid electrolyte with high oxidation resistance. The positive electrode mixture forming the positive electrode mixture layer 6, like the negative electrode mixture, may contain optional components such as a solid electrolyte, a conductive agent, a binder, and a filler as necessary. Note that the positive electrode mixture layer may be in a form that does not contain a solid electrolyte.

[0077] 〈Positive electrode active material〉 As the positive electrode active material contained in the positive electrode mixture layer 6, known ones usually used in all-solid-state batteries can be used. Examples of the above positive electrode active material include Li x MeO y (Me represents at least one transition metal) composite oxide (layered α-NaFeO 2 type crystal structure Li x CoO 2 , Li x NiO 2 , Li x MnO 3 , Li x Ni α Co (1-α) O 2 , Li x Ni α Mn β Co (1-α-β) O 2 etc., spinel-type crystal structure Li x Mn 2 O 4 , Li xNi α Mn (2-α) O 4 etc., Li w Me x (AO y ) z (Me represents at least one transition metal, and A represents, for example, P, Si, B, V, etc.) a polyanion compound represented by (LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 , Li 3 V 2 (PO 4 ) 3 , Li 2 MnSiO 4 , Li 2 CoPO 4 F, etc.). The elements or polyanions in these compounds may be partially substituted with other elements or anion species. In the positive electrode active material layer, one of these compounds may be used alone, or two or more thereof may be mixed and used.

[0078] As the positive electrode active material, lithium alloys such as Li-Al, Li-In, Li-Sn, Li-Pb, Li-Bi, Li-Ga, Li-Sr, Li-Si, Li-Zn, Li-Cd, Li-Ca, Li-Ba, etc., and MnO 2 , FeO 2 , TiO 2 , V 2 O 5 , V 6 O 13 , TiS 2 , etc., materials with a redox potential nobler than that of the negative electrode material can be used.

[0079] As the lower limit of the content of the positive electrode active material in the positive electrode binder, 10% by mass is preferable, and 15% by mass is more preferable. As the upper limit of the content of the positive electrode active material, 60% by mass is preferable, 70% by mass is more preferable, 80% by mass is further preferable, 90% by mass is particularly preferable, and 95% by mass may be used. By setting the content of the positive electrode active material within the above range, the capacitance of the all-solid-state battery can be increased.

[0080] <Positive electrode mixture or positive electrode composite> The above positive electrode mixture is a mixture prepared by mixing a positive electrode active material, a solid electrolyte, etc. by mechanical milling or the like, similar to the case of the negative electrode. For example, a mixture of a positive electrode active material and a solid electrolyte or the like can be obtained by mixing particulate positive electrode active material and particulate solid electrolyte or the like. The above positive electrode composite also includes, similar to the case of the negative electrode, a composite having a chemical or physical bond between a positive electrode active material and a solid electrolyte or the like, a composite obtained by mechanically compositing a positive electrode active material and a solid electrolyte or the like, and the like. The above composite is one in which a positive electrode active material and a solid electrolyte or the like are present in one particle. For example, those in which a positive electrode active material and a solid electrolyte or the like form an aggregated state, those in which a solid electrolyte-containing film or the like is formed on at least a part of the surface of the positive electrode active material, and the like can be mentioned. The positive electrode active material and the solid electrolyte or the like contained in the positive electrode binder can constitute a positive electrode mixture or a positive electrode composite, thereby maintaining high ionic conductivity. As the above solid electrolyte, the sulfide solid electrolyte may be used, but it is more preferable to use a solid electrolyte having high oxidation resistance.

[0081] When the positive electrode binder contains a solid electrolyte, the lower limit of the content of the solid electrolyte may be 5% by mass, and 10% by mass is preferable. The upper limit of the content of the solid electrolyte in the positive electrode binder is preferably 90% by mass, more preferably 85% by mass, still more preferably 80% by mass, and particularly preferably 75% by mass. By setting the content of the solid electrolyte within the above range, the electric capacity of the all-solid-state battery can be increased.

[0082] The lower limit of the average thickness of the positive electrode binder layer 6 is preferably 30 μm, and more preferably 60 μm. The upper limit of the average thickness of the positive electrode binder layer 6 is preferably 1000 μm, more preferably 500 μm, still more preferably 200 μm. By setting the average thickness of the positive electrode binder layer 6 to be not less than the above lower limit, an all-solid-state battery having a high energy density can be obtained. By setting the average thickness of the positive electrode binder layer 6 to be not more than the above upper limit, an all-solid-state battery having excellent high-rate discharge performance and a high active material utilization rate can be obtained.

[0083] [Solid electrolyte layer] The solid electrolyte layer 3 contains an electrolyte for the solid electrolyte layer. Examples of the electrolyte for the solid electrolyte layer include, in addition to the above-mentioned sulfide solid electrolyte, for example, oxide solid electrolytes, other sulfide solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, pseudo solid electrolytes, and the like. Among these, sulfide solid electrolytes are preferred from the viewpoints of good ionic conductivity and easy interface formation, and the sulfide solid electrolyte is more preferred. By the solid electrolyte layer 3 containing the sulfide solid electrolyte, the solid electrolyte layer can maintain high ionic conductivity while improving the reduction resistance, so that the initial Coulomb efficiency of the all-solid-state battery can be improved.

[0084] The electrolyte for the solid electrolyte layer may have a crystal structure or may be amorphous without a crystal structure. Additives such as oxides such as Li 3 PO 4 and halogens, halogen compounds, etc. may be added.

[0085] As the lower limit of the average thickness of the solid electrolyte layer 3, 1 μm is preferred, and 3 μm is more preferred. As the upper limit of the average thickness of the solid electrolyte layer 3, 50 μm is preferred, and 20 μm is more preferred. By setting the average thickness of the solid electrolyte layer 3 to be equal to or greater than the above lower limit, it becomes possible to surely insulate the positive electrode and the negative electrode. By setting the average thickness of the solid electrolyte layer 3 to be equal to or less than the above upper limit, it becomes possible to increase the energy density of the all-solid-state battery.

[0086] [Manufacturing method of all-solid-state battery] The manufacturing method of the all-solid-state battery mainly includes, for example, a sulfide solid electrolyte manufacturing step of manufacturing the sulfide solid electrolyte, a negative electrode mixture manufacturing step, an electrolyte manufacturing step for the solid electrolyte layer, a positive electrode mixture manufacturing step, and a lamination step of laminating the negative electrode layer, the solid electrolyte layer, and the positive electrode layer.

[0087] (Sulfide solid electrolyte manufacturing step) In this step, for example, the sulfide solid electrolyte is manufactured by the following procedure. (1) Preparation of Nitride (Li 3 / 2 Al 1 / 2 N) Li 3 N and AlN are mixed in a mortar or the like and then pelletized. Next, heat treatment is performed to produce Li 3 / 2 Al 1 / 2 N. Note that generally, "Li 3 / 2 Al 1 / 2 N" is denoted as "Li 3 AlN 2 ". (2) Preparation of Sulfide Solid Electrolyte The above-mentioned Li 3 / 2 Al 1 / 2 N, Li 2 S and P 2 S 5 are mixed in a mortar or the like, and then a sulfide solid electrolyte precursor is produced. As a method for producing the sulfide solid electrolyte precursor, for example, a mechanical milling method, a melt quenching method, or the like can be used. When producing a sulfide solid electrolyte, after producing the sulfide solid electrolyte precursor, the sulfide solid electrolyte can be produced by heat treatment at a temperature equal to or higher than the crystallization temperature.

[0088] The above-mentioned crystallization temperature can be determined by measurement using a differential scanning calorimeter (DSC). For example, in order to obtain a Li 7 P 3 S 11 crystal structure, the heat treatment temperature is preferably 250°C or higher and 400°C or lower. In order to obtain a β-Li 3 PS 4 crystal structure, the heat treatment temperature is preferably 200°C or higher and 400°C or lower. This is because when heat treatment is performed at a high temperature such as 500°C, there is a possibility of phase transition to the stable phase Li 4 P 2 S 6 . For example, in X-ray diffraction measurement using CuKα radiation, in order to obtain a first crystal structure having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5°, and 29.8° ± 0.5°, the heat treatment temperature is preferably 250°C or higher and 400°C or lower.

[0089] In the above production process, the case of producing a sulfide solid electrolyte containing Al as the element M has been described. However, by the same method as the above production process, at least one element M selected from the group consisting of Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, and V, and N can be included to produce a sulfide solid electrolyte having a crystal structure. For example, as the nitride in the above production process, Li 3 / 2 Al 1 / 2 N can be replaced with Li 3 / 2 B 1 / 2 N or Li 5 / 3 Si 1 / 3 N, Li 9 / 5 Si 3 / 10 N, etc. By using these, a sulfide solid electrolyte containing elements such as B and Si and N can be produced. As the nitrides that can be used in the above production process, in addition to those described above, LiMgN, LiCaN, LiHf 1 / 2 N, Li 3 / 2 Sc 1 / 2 N, LiZr 1 / 2 N, Li 5 / 3 Ti 1 / 3 N, Li 4 / 3 Ta 1 / 3 N, Li 7 / 4 Ta 1 / 4 N, Li 7 / 4 Nb 1 / 4 N, Li 3 / 2 W 1 / 4 N, Li 7 / 4 V 1 / 4 N, etc. can be exemplified.

[0090] Also, in the above production process, a nitride composed of the element M, Li, and N was used as the starting material, but the production method of the sulfide solid electrolyte of the present embodiment is not limited to this.

[0091] In the above production process, Li 2 S-P 2 S 5 Based sulfide solid electrolyte has been described as an example, but LGPS type or argyrodite type sulfide solid electrolytes can also be produced by a similar production process. For example, in the above manufacturing process, Li is used as the starting material. 3 / 2 Al 1 / 2 N, Li 2 S and P 2 S 5 However, by adding a Ge-containing compound such as GeS 2 etc., the LGPS-type sulfide solid electrolyte containing Ge may be produced. More specifically, after mixing starting materials in a mortar or the like at a predetermined molar ratio, mechanical milling methods such as ball milling treatment or vibration milling treatment are performed to produce a sulfide solid electrolyte precursor. Thereafter, the sulfide solid electrolyte can be produced by heat-treating the precursor at a predetermined temperature or higher. For example, when producing a sulfide solid electrolyte having a Li 10 GeP 2 S 12 crystal structure, the heat treatment temperature is preferably 300°C or higher and 1000°C or lower, more preferably 350°C or higher and 700°C or lower, still more preferably 400°C or higher and 650°C or lower, and particularly preferably 450°C or higher and 600°C or lower. The heat treatment may be performed under a reduced pressure atmosphere or an inert gas atmosphere.

[0092] (Negative electrode mixture preparation process) In this process, a negative electrode mixture for forming a negative electrode layer is produced. When the negative electrode mixture contains a mixture or composite containing a negative electrode active material and the sulfide solid electrolyte, in this process, for example, the negative electrode active material and the sulfide solid electrolyte are mixed using a mechanical milling method or the like to produce a mixture or composite of the negative electrode active material and the sulfide solid electrolyte.

[0093] (Solid electrolyte layer electrolyte preparation process) In this process, the electrolyte for the solid electrolyte layer for forming the solid electrolyte layer is produced. In this process, a predetermined material of the electrolyte for the solid electrolyte layer can be obtained by processing it by the mechanical milling method. The predetermined material of the electrolyte for the solid electrolyte layer may be heated to a temperature equal to or higher than the melting temperature by the melt quenching method, and the two may be melt-mixed at a predetermined ratio and then quenched to produce the electrolyte for the solid electrolyte layer. As other synthesis methods of the electrolyte for the solid electrolyte layer, for example, a solid phase method of encapsulating under reduced pressure and firing, a liquid phase method such as dissolution precipitation, a vapor phase method (PLD), firing in an argon atmosphere after mechanical milling, etc. can be mentioned. In addition, when the electrolyte for the solid electrolyte layer is the sulfide solid electrolyte, in the production process of the electrolyte for the solid electrolyte layer, the above-mentioned sulfide solid electrolyte production process is performed.

[0094] (Positive electrode mixture preparation process) In this process, a positive electrode mixture for forming a positive electrode layer is produced. The production method of the positive electrode mixture is not particularly limited and can be appropriately selected according to the purpose. For example, compression molding of the positive electrode active material, mechanical milling treatment of a predetermined material of the positive electrode mixture, sputtering using a target material of the positive electrode active material, etc. can be mentioned. When the positive electrode mixture contains a mixture or composite containing the positive electrode active material and the sulfide solid electrolyte, in this process, for example, the positive electrode active material and the sulfide solid electrolyte are mixed using a mechanical milling method or the like, and a mixture or composite of the positive electrode active material and the sulfide solid electrolyte is produced.

[0095] (Lamination process) In this process, a negative electrode layer having a negative electrode base material layer and a negative electrode mixture layer, a solid electrolyte layer, and a positive electrode layer having a positive electrode base material layer and a positive electrode mixture layer are laminated. In this process, the negative electrode layer, the solid electrolyte layer, and the positive electrode layer may be formed sequentially, or vice versa, and the order of formation of each layer is not particularly limited. The above negative electrode layer is formed by pressure molding the negative electrode base material and the negative electrode mixture, the above solid electrolyte layer is formed by pressure molding the electrolyte for the solid electrolyte layer, and the above positive electrode layer is formed by pressure molding the positive electrode base material and the positive electrode mixture.

[0096] The negative electrode substrate, negative electrode mixture, electrolyte for the solid electrolyte layer, positive electrode substrate, and positive electrode mixture may be pressure-molded at once so that the negative electrode layer, solid electrolyte layer, and positive electrode layer are laminated. The positive electrode layer, negative electrode layer, or these layers may be pre-molded and pressure-molded with the solid electrolyte layer for lamination.

[0097] [Other Embodiments] The present invention is not limited to the above embodiments, and can be implemented in various modified and improved embodiments in addition to the above aspects.

[0098] The configuration of the all-solid-state battery according to the present invention is not particularly limited, and it may include other layers other than the negative electrode layer, positive electrode layer, and solid electrolyte layer, such as an intermediate layer or an adhesive layer.

[0099] [Examples] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples.

[0100] [Example 1] By the following treatment, 99(0.70Li 2 S·0.30P 2 S 5 )·1Li 3 / 2 Al 1 / 2 N was synthesized. Li 3 N and AlN were weighed so that the molar ratio was 1.2:1, mixed in a mortar, and then pelletized. Next, heat treatment was performed at 750 ° C for 1 hour to prepare Li 3 / 2 Al 1 / 2 N. The prepared Li 3 / 2 Al 1 / 2 N was confirmed to have a main phase of Li 3 / 2 Al 1 / 2 N by XRD measurement. Next, in a glove box with an argon atmosphere having a dew point of -50 ° C or lower, Li 2 S(99.98%, Aldrich), P2S5(99%, Aldrich) and Li3 / 2Al 1 / 2After weighing N so that the molar ratio was 69.3:29.7:1.0, it was mixed in a mortar. This mixed sample was put into a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. Milling treatment was carried out for 45 hours at a revolution speed of 510 rpm using a planetary ball mill (manufactured by FRITSCH, model number Premium line P-7). After heat treatment for 2 hours, the sulfide solid electrolyte of Example 1 was obtained. This heat treatment was carried out at a temperature equal to or higher than the crystallization temperature and not exceeding 100 °C above the crystallization temperature. The crystallization temperature was determined by measuring DSC. The DSC measurement was carried out under the following conditions. That is, using a DSC apparatus (manufactured by Rigaku, Thermo Plus DSC8230), using a sealed pan made of SUS, the temperature was raised from room temperature to 400 °C at a rate of 10 °C / min.

[0101] [Examples 2 to 9] Composition formula of sulfide solid electrolyte (100 - z)(0.70Li 2 S·0.30P 2 S 5 )·zLi 3 / 2 Al 1 / 2 Except that the value of z in N was changed to 5, 7, 10, 15, 20, 25, 30, 40, the sulfide solid electrolytes of Examples 2 to 9 were synthesized in the same manner as in Example 1.

[0102] [Example 10] As raw materials for the sulfide solid electrolyte, Li 2 S, P 2 S 5 and Li 3 / 2 Al 1 / 2 N were weighed so that Li 2 S:P 2 S 5 :Li 3 / 2 Al 1 / 2 N = 67.5:22.5:10.0 (mol%), and the sulfide solid electrolyte of Example 10 was synthesized in the same manner as in Example 1.

[0103] [Example 11] As raw materials for the sulfide solid electrolyte, Li 2 S, P 2 S5 and Li 3 / 2 Al 1 / 2 N were weighed so that the ratio of Li 2 S:P 2 S 5 :Li 3 / 2 Al 1 / 2 N was 35.0:35.0:30.0 (mol%). The sulfide solid electrolyte of Example 11 was synthesized in the same manner as in Example 1, except for the weighing.

[0104] [Example 12] As raw materials for the sulfide solid electrolyte, Li 2 S, P 2 S 5 and Li 3 / 2 Al 1 / 2 N were weighed so that the ratio of Li 2 S:P 2 S 5 :Li 3 / 2 Al 1 / 2 N was 53.6:26.4:20.0 (mol%). The sulfide solid electrolyte of Example 12 was synthesized in the same manner as in Example 1, except for the weighing.

[0105] [Example 13] As raw materials for the sulfide solid electrolyte, Li 2 S, P 2 S 5 and Li 3 / 2 Al 1 / 2 N were weighed so that the ratio of Li 2 S:P 2 S 5 :Li 3 / 2 Al 1 / 2 N was 50.3:24.7:25.0 (mol%). The sulfide solid electrolyte of Example 13 was synthesized in the same manner as in Example 1, except for the weighing.

[0106] [Example 14] As raw materials for the sulfide solid electrolyte, Li 2 S, P 2 S 5 and Li 3 / 2 Al 1 / 2 N were weighed so that the ratio of Li 2 S:P 2 S 5 :Li 3 / 2 Al1 / 2 A sulfide solid electrolyte of Example 14 was synthesized in the same manner as in Example 1, except that the weighing was performed so that N = 46.9:23.1:30 (mol%).

[0107] [Examples 15 to 18] Li 3 N and BN were weighed so that the molar ratio was 1.1:1, mixed in a mortar, pelletized, and then heat-treated at 800 °C for 10 minutes to prepare Li 3 / 2 B 1 / 2 N. The prepared Li 3 / 2 B 1 / 2 N was confirmed by XRD measurement to have a main phase of Li 3 / 2 B 1 / 2 N. Next, instead of Li 3 / 2 Al 1 / 2 N, the above Li 3 / 2 B 1 / 2 N was used, and sulfide solid electrolytes of Examples 15 to 18 were synthesized in the same manner as in Example 1, except that the value of z in the composition formula (100 - z)(0.70Li 2 S·0.30P 2 S 5 )·zLi 3 / 2 B 1 / 2 N was changed to 1, 10, 20, and 30. [Examples 19 to 23] Li 3 N and Si 3 N 4 were weighed so that the molar ratio was 5.1:1, mixed in a mortar, pelletized, and then heat-treated at 800 °C for 10 minutes to prepare Li 5 / 3 Si 1 / 3 N. The prepared Li 5 / 3 Si 1 / 3 N was confirmed by XRD measurement to have a main phase of Li 5 / 3 Si 1 / 3 N. Next, instead of Li 3 / 2 Al 1 / 2 N, the above Li 5 / 3 Si 1 / 3 N was used, and the composition formula of the sulfide solid electrolyte (100 - z)(0.70Li 2 S·0.30P2 S 5 )·zLi 5 / 3 Si 1 / 3 The sulfide solid electrolytes of Examples 19 to 23 were synthesized in the same manner as in Example 1, except that the value of z in N was changed to 1.5, 15, 20, 30, and 45.

[0108] [Comparative Example 1] For the raw material of the sulfide solid electrolyte, Li 3 / 2 Al 1 / 2 The sulfide solid electrolyte of Comparative Example 1 was synthesized in the same manner as in Example 1, except that Li

[0109] [Reference Example 1] 75Li 2 S·25P 2 S 5 (Li 3 PS 4 ) was synthesized by the mechanical milling method. In an argon atmosphere glove box with a dew point of -50°C or lower, Li 2 S and P 2 S 5 were weighed so that Li 2 S:P 2 S 5 = 75:25 (mol%), and then mixed in an agate mortar. The mixture was put into a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. Milling treatment was performed for 45 hours at a revolution speed of 510 rpm using a planetary ball mill (manufactured by FRITSCH, model number Premium line P-7). By the above treatment, the sulfide solid electrolyte of Reference Example 1 was obtained.

[0110] [Reference Example 2] Li 3 / 2 Al 1 / 2 Instead of N, Li 3 N was used, and the sulfide solid electrolyte of Reference Example 2 was synthesized in the same manner as in Example 1, except that the value of z in the composition formula (100 - z)(0.70Li 2 S·0.30P 2 S 5 )·zLi 3 was changed to 20.

[0111] [Example 24] Through the following process, 87.6(Li10GeP2S12)·12.4Li 3 / 2 Al 1 / 2 N was synthesized. Li 3 N and AlN were weighed so that the molar ratio was 1.2:1, mixed in a mortar, and then pelletized. Next, heat treatment was performed at 750 °C for 1 hour to produce Li 3 / 2 Al 1 / 2 N. Next, in a glove box with an argon atmosphere where the dew point is -50 °C or lower, Li 2 S (99.98%, Aldrich), P 2 S 5 (99%, Aldrich), GeS 2 (99.99%, High Purity Chemical Research Institute) and Li 3 / 2 Al 1 / 2 N were weighed so that the molar ratio was 5:1:1:0.14, and then mixed in a mortar. This mixed sample was put into a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. Milling treatment was performed for 40 hours at a revolution speed of 370 rpm using a planetary ball mill (manufactured by FRITSCH, model number Premium line P-7). Then, heat treatment was performed at 550 °C for 8 hours to obtain the sulfide solid electrolyte of Example 24.

[0112] [Example 25, Example 26, Comparative Example 2] For the composition formula of the sulfide solid electrolyte (100-z)(Li 10 GeP 2 S 12 )·zLi 3 / 2 Al 1 / 2 N, except that the value of z was changed to 30.2, 42.5, and 60.9, the sulfide solid electrolytes of Example 25, Example 26, and Comparative Example 2 were synthesized in the same manner as in Example 1. [Comparative Example 3] For the raw material of the sulfide solid electrolyte, except that Li 3 / 2 Al 1 / 2 N was not used, the sulfide solid electrolyte of Comparative Example 3 was synthesized in the same manner as in Example 24. [Reference Example 3] As the raw material of the sulfide solid electrolyte, Li 3 / 2 Al 1 / 2 Instead of N, Li 2 O (99%, High Purity Chemical Laboratory) was used, and Li 2 S:P 2 S 5 :GeS 2 :Li 2 O = 4.86:1:1:0.14 (mol%). The sulfide solid electrolyte of Reference Example 3 was synthesized in the same manner as in Example 24, except that the weighing was performed so that the ratio was obtained. [Reference Example 4] As the raw material of the sulfide solid electrolyte, Li 3 / 2 Al 1 / 2 Instead of N, Al 2 S 3 (98%, Aldrich) was used, and Li 2 S:P 2 S 5 :GeS 2 :Al 2 S 3 = 5:1:0.93:0.035 (mol%). The sulfide solid electrolyte of Reference Example 4 was synthesized in the same manner as in Example 24, except that the weighing was performed so that the ratio was obtained.

[0113] [Evaluation] (1) XRD Analysis X-ray diffraction measurement was performed by the following method. Using an airtight sample holder for X-ray diffraction measurement, the sulfide solid electrolyte powders of the examples and comparative examples were filled under an argon atmosphere with a dew point of -50°C or lower. Powder X-ray diffraction measurement was performed using an X-ray diffractometer (Rigaku "miniFlex II"). The radiation source was CuKα radiation, the tube voltage was 30 kV, the tube current was 15 mA, and the diffracted X-rays were detected by a high-speed one-dimensional detector (model number: D / teX Ultra2) through a Kβ filter with a thickness of 30 μm. The sampling width was 0.01°, the scan speed was 5° / min, the divergence slit width was 0.625°, the receiving slit width was 13 mm (OPEN), and the scattering slit width was 8 mm.

[0114] Figure 2 shows the X-ray diffraction (XRD) spectra in the range of 2θ = 10° to 40° for Examples 1 to 3, 6, 8, 9, 10, 11 and Comparative Example 1. Table 1 shows the crystal structures identified from the XRD spectra of Examples 1 to 23, Comparative Example 1 and Reference Example 2.

[0115] Figure 8 shows the X-ray diffraction (XRD) spectra in the range of 2θ = 10° to 60° for Example 24, Comparative Example 3 and Reference Examples 3 and 4. Table 2 shows the crystal structures identified from the XRD spectra of Examples 24 to 26, Comparative Examples 2 and 3, and Reference Examples 3 and 4. Note that "Unknown" in Table 2 indicates that diffraction peaks for which the crystal structure could not be identified were confirmed.

[0116] (2) Raman spectroscopy The Raman spectra were measured by the following method. Using a laser Raman spectrophotometer ("LabRAM HR Revolution" manufactured by Horiba, Ltd.), Raman spectroscopic measurements were performed in the wavenumber range of 100 cm -1 to 1800 cm -1 under the conditions of an excitation laser wavelength of 532 nm (YAG laser) and a grating of 600 gr / mm.

[0117] Figure 3 shows the Raman spectra of Examples 2 to 6 and Comparative Example 1. Table 1 shows the molecular structures identified from the Raman spectra of Examples 1 to 23, Comparative Example 1 and Reference Example 2.

[0118] (3) Ionic conductivity (σ) The ionic conductivity (σ) was determined by measuring the alternating current impedance by the above method using "VMP-300" manufactured by (Bio-Logic) at 25°C.

[0119] For Examples 24 to 26, Comparative Examples 2 and 3, and Reference Examples 3 and 4, the ionic conductivities at each temperature of -30°C, -20°C, -10°C, 0°C, and 50°C were also measured, and the activation energy was calculated by the Arrhenius equation.

[0120] Example 1 to 9 and Comparative Example 1 shown in Fig. 4, and Example 1 to 23, Comparative Example 1 and Reference Example 2 shown in Table 1 show the ionic conductivity at 25°C.

[0121] Table 2 shows the ionic conductivity and activation energy at 25°C of Example 24 to 26, Comparative Example 2, 3, and Reference Example 3, 4.

[0122] (4) Initial Coulomb efficiency and charge-discharge performance (4-1) Preparation of the positive electrode active material After dissolving metallic Li in ultra-dehydrated ethanol, niobium ethoxide (Nb(OC 2 H 5 ) 5 ) was dissolved to prepare a LiNbO 3 precursor solution. Using a rolling fluid coating device (FD-MP-01F) manufactured by Paulic, a coating of the LiNbO 0.8 Co 0.15 Al 0.05 O 2 (NCA) precursor was coated on the particle surface of LiNbO 3 . The NCA coated with the LiNbO 3 precursor was heat-treated at 350°C for 1 hour to prepare LiNbO 3 coated NCA. This LiNbO 3 coated NCA was used as the positive electrode active material.

[0123] (4-2) Preparation of all-solid-state battery cell (Li-NCA half cell) LiNbO 3 coated NCA and the sulfide solid electrolyte of Reference Example 1 (Li 3 PS 4 ) were weighed so that LiNbO 3 coated NCA:Li 3 PS 4 =70:30 (mass%) and then mixed in an agate mortar. After putting the sulfide solid electrolyte of Example 1 into a powder molding machine with an inner diameter of 10 mm, it was pressure-molded using a hydraulic press. After releasing the pressure, on one side of the solid electrolyte layer of Example 1, NCA-Li 3 PS 4The mixed powder was introduced and pressed at 360 MPa for 5 minutes per sample area. After pressure release, a metal Li foil was laminated on the opposite side of the sulfide solid electrolyte layer of Example 1 and pressed to obtain a laminate of the positive electrode mixture layer, the sulfide solid electrolyte layer of Example 1, and the metal Li foil. This laminate was vacuum-sealed in an aluminum laminate cell and compressed using a stainless steel plate to obtain an all-solid-state battery cell (Li-NCA half cell).

[0124] The same operations as in Example 1 were performed except that the sulfide solid electrolyte of Example 1 was changed to the sulfide solid electrolytes of Example 2, 4, and Comparative Example 1, to obtain all-solid-state battery cells (Li-NCA half cells) provided with the sulfide solid electrolytes of Example 2, 4, and Comparative Example 1.

[0125] (4-3) Charge and discharge test The above all-solid-state battery cell (Li-NCA half cell) was subjected to a charge and discharge test under the following conditions. The charge and discharge test was conducted in a thermostat at 50 °C. Charging was performed as constant current constant voltage (CCCV) charging with a charging current of 0.125 mA / cm2 and a charging upper limit voltage of 4.35 V. The charging termination condition was until the charging current reached 0.0625 mA / cm2. Discharging was performed as constant current (CC) discharging with a discharging current of 0.125 mA / cm2 and a discharging termination voltage of 2.85 V. The rest time between charging and discharging was 30 minutes. The percentage of the above first discharge capacity with respect to the first charge amount was determined as the "first Coulomb efficiency (%)".

[0126] Figure 5 shows the first charge and discharge performance of Example 1, Example 2, Example 4, and Comparative Example 1. Table 1 shows the first Coulomb efficiency (%) of Example 1, Example 2, Example 4, and Comparative Example 1.

[0127] (5) Reducing resistance of sulfide solid electrolyte (5-1) Evaluation test using a cell for evaluating reducing resistance In a glove box with an argon atmosphere having a dew point of -50 °C or lower, the sulfide solid electrolyte of Example 1 and SUS316L powder were weighed so that the mass ratio was 1:4, and then mixed in an agate mortar. The sulfide solid electrolyte of Reference Example 1 (Li 3PS 4 ) was introduced, and then pressure molding was carried out using a hydraulic press. After pressure release, Li 3 PS 4 A mixed powder of the above SUS316 powder and the sulfide solid electrolyte powder of Example 1 was introduced onto one side of the layer and pressure molded at 360 MPa for 5 minutes. After pressure release, Li 3 PS 4 By laminating and pressure molding a metallic Li foil on the opposite side of the layer, a laminate of the mixture layer of the sulfide solid electrolyte of Example 1, Li 3 PS 4 layer and the metallic Li foil was obtained. This laminate was vacuum-encapsulated in an aluminum laminate cell and compressed using a stainless steel plate to obtain a cell for evaluating the reduction resistance with the mixture layer of the sulfide solid electrolyte of Example 1 as the working electrode and the metallic Li foil as the counter electrode. The charging test conditions were a measurement temperature of 50 °C, charging was carried out by constant current constant voltage (CCCV) charging, the charging current was 0.1 mA / cm 2 , the charging lower limit potential was 0.01 V, and the total charging time was 100 hours. Here, the reaction in which the mixture layer of the sulfide solid electrolyte of Example 1 is reduced is defined as "charging". The amount of charging electricity 20 hours after the start of charging was defined as the reduction decomposition capacity (mAh / g) of the sulfide solid electrolyte after 20 hours. Since the SUS316L powder is stable at a potential of 0 V vs. Li / Li+, the redox species is only the sulfide solid electrolyte. Therefore, the amount of electricity flowing through this evaluation cell represents the reduction decomposition amount of the sulfide solid electrolyte. By the same procedure, the reduction resistance of the sulfide solid electrolytes of Examples 2, 4, 8 to 17, 19, 20, 22 and Comparative Example 1 was evaluated.

[0128] Table 1 shows the reduction decomposition capacity of the sulfide solid electrolytes of Examples 1, 2, 4, 8 to 17, 19, 20, 22 and Comparative Example 1 20 hours after the start of charging.

[0129] (5-2) Evaluation test by all-solid-state battery cell (Li-Gr half cell) For the sulfide solid electrolytes of Examples 24 to 26, Comparative Examples 2 and 3, and Reference Examples 3 and 4, the reduction resistance was evaluated by the following procedure.

[0130] Graphite particles (Gr) and the sulfide solid electrolyte of Example 24 (Li 10.21 GeP 2 Al 0.07 S 12 N 0.14 ) were weighed so that Gr:Li 10.21 GeP 2 Al 0.07 S 12 N 0.14 = 60:40 (mass %), and then mixed in an agate mortar. After putting Li 3 PS 4 into a powder molding machine with an inner diameter of 10 mm, it was pressure-molded using a hydraulic press. After releasing the pressure, Gr-Li 3 PS 4 mixed powder was put on one side of the Li 10.21 GeP 2 Al 0.07 S 12 N 0.14 layer and pressure-molded. After releasing the pressure, a metal Li foil was bonded to the opposite side of the Li 3 PS 4 layer and pressure-molded to obtain a laminate of a mixture layer of the sulfide solid electrolyte of Example 24, a Li 3 PS 4 solid electrolyte layer, and a metal Li foil. This laminate was hermetically sealed under reduced pressure in an aluminum laminate cell and compressed using a stainless steel plate to obtain an all-solid-state battery cell (Li-Gr half-cell) with the mixture layer of the sulfide solid electrolyte of Example 24 as the working electrode and the metal Li foil as the counter electrode.

[0131] The same operations as in Example 24 were performed except that the sulfide solid electrolyte of Example 24 was changed to the sulfide solid electrolytes of Examples 25, 26, and Comparative Example 3, to obtain all-solid-state battery cells (Li-Gr half-cells) equipped with the sulfide solid electrolytes of Examples 25, 26, and Comparative Example 3.

[0132] Regarding the above all-solid-state battery cell (Li-Gr half-cell), a discharge test (lithiation of Gr) was conducted under the following conditions. The discharge test was carried out in a constant temperature bath at 50 °C. The discharge was performed with a discharge current of 0.125 mA / cm 2Then, constant current (CC) discharge was performed. At this time, a graph (dQ / dV curve) showing the relationship between the differential value dQ / dV obtained by differentiating the discharge capacity Q with respect to the voltage V and the voltage V was plotted.

[0133] Fig. 9 shows the dQ / dV curves of Examples 24 to 26 and Comparative Example 3. Table 2 shows the values of the voltage V at dQ / dV = -100 mAhg -1 V -1 In addition, it is confirmed from Fig. 9 that the change amount of dQ / dV near 0.4 V is large. Since the lithiation potential of Gr is about 0.1 V vs Li / Li + it is estimated that the change in dQ / dV near 0.4 V is due to the reductive decomposition of the sulfide solid electrolyte. Therefore, the shift of the voltage V value of the all-solid-state battery cell (Li-Gr half-cell) of this example at dQ / dV = -100 mAhg -1 V -1 in the lower direction means that the reductive decomposition potential of the sulfide solid electrolyte has shifted in the lower direction, that is, the reduction resistance has improved.

[0134] (6) Evaluation of air stability In order to evaluate the chemical stability of the sulfide solid electrolyte in the air, the amount of hydrogen sulfide generated was measured. Inside a glove box with an argon atmosphere at a dew point of -50 °C or lower, 100 mg of the sulfide solid electrolyte powder of the examples and comparative examples was uniaxially pressed at 360 MPa for 5 minutes using a powder molding machine with an inner diameter of 10 mm to obtain pellets. Then, the obtained pellets were placed inside a sealed desiccator (substantially 2100 cm 3 in volume, temperature 20 °C, relative humidity about 90%), and a hydrogen sulfide sensor (TPA-5200E) was used to measure the amount of hydrogen sulfide generated. The measurement was terminated when the detection upper limit value of the hydrogen sulfide sensor, which is 50 ppm, was reached or when 40 minutes had elapsed. The amount of hydrogen sulfide generated V (cm 3 / g) per gram of the solid electrolyte was obtained from the following formula using the obtained concentration C (ppm), the substantial volume L (cm 3 ) of the desiccator, and the mass m (g) of the pellet. V (cm 3 / g) = C × L × 10 -6 / m

[0135] Figures 6 and 7 are graphs showing the relationship between the atmospheric exposure time (minutes) and the hydrogen sulfide generation amount (cm 3 / g) for the sulfide solid electrolyte pellets of the above Examples and Comparative Examples. Figure 6 shows the hydrogen sulfide generation amounts up to 20 minutes of atmospheric exposure in Example 4, Example 6, and Comparative Example 1, and Figure 7 shows the hydrogen sulfide generation amounts up to 40 minutes of atmospheric exposure in Example 6 and Reference Example 1.

[0136]

Table 1

[0137] As shown in Table 1, the sulfide solid electrolyte of the Example containing any one of the elements Al, B, or Si as element M and N and having a crystal structure had a reduced decomposition capacity after 20 hours from the start of charging suppressed as compared with the sulfide solid electrolyte of Comparative Example 1, and an excellent initial Coulomb efficiency. The sulfide solid electrolytes of Example 1, Example 2, Example 4 to Example 8, Example 10, Example 12 to Example 17, Example 19 to Example 22 also had good ionic conductivity at 25°C. On the other hand, the sulfide solid electrolyte of Comparative Example 1 not containing elements M and N had good ionic conductivity, but had a large reduced decomposition capacity after 20 hours from the start of charging and inferior initial Coulomb efficiency.

[0138] From Table 1, when the content ratio of Li to P is 2.77 or more and 3.38 or less in molar ratio, and the content ratio of N to P is 0.28 or more and 0.65 or less in molar ratio, 10 -3 Scm -1 A sulfide solid electrolyte having a structure that is expected to exhibit ionic conductivity of 10 or more and good air stability was obtained. Therefore, it was confirmed that it is particularly preferable that the composition of the sulfide solid electrolyte is such a value. Also, when the sulfide solid electrolyte contains Al as element M, even when the content ratio of Li to P is 3.40 in molar ratio and the content ratio of N to P is 0.71 in molar ratio, and the content ratios of Li element and N are large, Li 2 S did not precipitate. From this, it was suggested that it is particularly preferable to contain Al as element M.

[0139] As shown in FIG. 2, it was confirmed that the sulfide solid electrolytes of all examples and comparative examples had peaks observed in the XRD spectrum and had a crystal structure. Example 1 and Example 2 were Li 7 P 3 S 11 , Example 3 was β-Li 3 PS 4 , Example 11 had the crystal structure of Li 4 P 2 S 6 . The crystal structures of the sulfide solid electrolytes of Examples 4 to 9 were a specific crystal structure A having diffraction peaks at 2θ = 17.9°, 19.1°, 29.1°, 29.8° and 30.9°. It was confirmed that the crystal structure of the sulfide solid electrolyte of Example 10 was a specific crystal structure B having diffraction peaks at 2θ = 17.9°, 19.1°, 29.1° and 29.8°.

[0140] As shown by the Raman spectrum of FIG. 3, in the sulfide solid electrolyte of the example, as z increases, that is, as the nitrogen (N) content increases, the Raman shift around 406 cm 2 S 7 4- derived from cross-linked sulfur P -1 decreases, and a peak around the Raman shift of 423 cm 3- derived from PS4 -1 appears. Therefore, the molecular structures according to the Raman spectra of Example 1 and Example 15 in Table 1 are PS4 3- , P 2 S7 4- and P 2 S 6 4-is presumed to be composed of. The molecular structures based on the Raman spectra of Examples 7 to 9, Examples 11 to 14, and Examples 20 to 22 are PS4 3- is presumed to be composed of.

[0141] As shown in FIGS. 6 and 7, it was confirmed that the amount of hydrogen sulfide generated in Examples 4 and 6 was less than that in Comparative Example 1. In particular, Example 6 with z = 20 had an excellent inhibitory effect on hydrogen sulfide generation compared to Comparative Example 1 and Reference Example 1. Therefore, it was suggested that the sulfide solid electrolyte not only has high reduction resistance but also excellent air stability. The reason why the sulfide-based solid electrolyte has a high inhibitory effect on the generation of hydrogen sulfide is presumed as follows. As shown by the Raman spectrum in FIG. 3, in the sulfide solid electrolyte of the example, as z increases, that is, as the nitrogen content increases, the cross-linked sulfur P 2 S 7 4- The peak around the Raman shift of 406 cm derived from -1 decreases. Also, in the XRD (X-ray diffraction) spectrum shown in FIG. 2 of the sulfide solid electrolyte of the example, the peak derived from Li 2 S did not appear. From these facts, the sulfide solid electrolyte increases the nitrogen content, so-called cross-linked sulfur P 2 S 7 4- (S 3 P-S-PS 3 ) decreases, and since Li 2 S that easily reacts with water is not substantially contained, it is presumed that the inhibitory effect on the generation of hydrogen sulfide can be improved. In addition, in Example 6 (z = 20), the cross-linked sulfur P 2 S 7 4-The reason why the amount of hydrogen sulfide generated is less than that in Comparative Example 1 without [substance] is considered to be that a three-dimensional network is formed by introducing N into the structure of the solid electrolyte, resulting in stronger bonding. In an oxynitride glass in which part of the O of the oxide glass is replaced by N, it is generally known that the water resistance is improved by introducing N.

[0142] When Comparative Example 2 without element M, and Examples 6, 17, and 21 with the N content fixed with z = 20 and y = 0.70 are compared, it can be seen that Li 2 S is deposited only in Comparative Example 2 without element M. From this, it is considered that the deposition of Li 2 S can be suppressed by including element M.

[0143] The reason why the deposition of Li 2 S can be suppressed by the sulfide solid electrolyte containing element M is considered as follows. As a starting material for the sulfide-based solid electrolyte containing N, when Li 3 N is used, Li 3 N and P 2 S 5 react violently and N 2 is released, and Li 2 S is deposited. This is considered to be because the N defect generation energy of Li 3 N is small. In contrast, in the present invention, since the N defect generation energy of Li α M β N is larger than the N defect generation energy of Li 3 N, the reaction proceeds gently during the synthesis process of the sulfide-based solid electrolyte, and the release of N 2 and the deposition of Li 2 S are considered to be suppressed. Here, the "defect generation energy" means a value calculated using the total energy Eperfect of the crystal structure without defects, the total energy Evacancy of the crystal structure with defects, and the chemical potential μ of the defect atoms, and means a parameter defined by the following formula. E defect = (E vacancy + μ) - Eperfect

[0144]

Table 2

[0145] As is clear from Table 2, the sulfur-based sulfide solid electrolyte containing Li, P, S, Ge, Al, and N and having a crystal structure had excellent ionic conductivity at 25°C. Also, dQ / dV = -100 mAhg -1 V -1 The shift of the voltage V value in the negative direction at V means that the reduction decomposition potential of the sulfide solid electrolyte has shifted in the negative direction, that is, the reduction resistance has improved. Therefore, the sulfide solid electrolyte of the example was also excellent in reduction resistance. Among them, it was confirmed that the sulfide solid electrolyte of Example 24 exhibited excellent ionic conductivity at 25°C compared to the sulfide solid electrolytes such as those of Reference Examples 3 and 4.

[0146] From the above results, it was shown that the sulfide solid electrolyte according to the present invention has high reduction resistance and can improve the initial Coulomb efficiency of all-solid-state batteries equipped with the sulfide solid electrolyte. Also, it was shown that the sulfide solid electrolyte according to the present invention can also be improved in terms of air stability.

Industrial Applicability

[0147] Since the all-solid-state battery equipped with the sulfide solid electrolyte according to the present invention has excellent initial Coulomb efficiency, it is suitably used, for example, as a lithium-ion all-solid-state battery for HEV.

Explanation of Signs

[0148] 1 Negative electrode layer 2 Positive electrode layer 3 Solid electrolyte layer 4 Negative electrode substrate layer 5 Negative electrode binder layer 6 Positive electrode binder layer 7 Positive electrode substrate layer 10 All-solid-state battery

Claims

[Claim 1] A sulfide solid electrolyte containing Al and N and having a crystal structure.

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