Sulfide solid electrolyte and all-solid-state battery

Abstract

To provide a sulfide solid electrolyte having improved reduction resistance and an all-solid-state battery including the sulfide solid electrolyte.SOLUTION: A sulfide solid electrolyte has a crystal structure and contains Al and N. In an all-solid-state battery 10, an anode layer 1, a solid electrolyte layer 3, a cathode layer 2, or a combination thereof contains the sulfide solid electrolyte.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 having a composition containing Li, P, S, and N and represented by the general formula XLi2S-25P2S5-YLi3N (10≦Y≦15, 67.5≦X+Y≦85) and being a crystalline material is disclosed. (See Patent Document 2) As the sulfide solid electrolyte, 70Li2S·30P2S5 glass ceramics and 60Li2S·25P2S5·10Li3N glass ceramics have been reported to show 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 has low oxidation resistance and reduction resistance in essence. (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 with 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, and 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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Embodiments 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 their low ionic conductivity, exhibit high reduction resistance. Therefore, it was considered that the reduction resistance of the sulfide solid electrolyte could be improved by containing nitrogen element (N) and the element M in the sulfide solid electrolyte, and the present invention was thus achieved.

[0014] When 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, V and N and has a crystal structure, it can be a sulfide solid electrolyte with improved reduction resistance. In the above 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 provided with 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 provided with 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 provided with 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 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, a crystal structure having a crystal phase of Li7P3S 11 , Li4P2S6 or β-Li3PS4, 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 is preferably included. Thereby, the ionic conductivity at 25°C can be increased.

[0018] The first crystal structure preferably includes a specific crystal structure A having diffraction peaks at 2θ = 17.9° ± 0.5°, 19.1° ± 0.5°, 29.1° ± 0.5° and 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 terms of molar ratio, and the content ratio of N to P is preferably 0.02 or more and 1.11 or less in terms of 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 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. 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 is (100 - z)(yLi2S·(1 - y)P2S5)·zLi α M β N (where 0 < z ≤ 40, 0.50 ≤ y ≤ 0.75, α and β are numerical values giving the stoichiometric ratio according to the type of element M), it preferably has a composition represented thereby. 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 10 GeP2S 12Preferably, it includes a structure having a crystal phase.

[0024] Further, the sulfide solid electrolyte contains Li, P, S, N, Ge, and the above element M, and Li 10 GeP2S 12 When it has a crystal phase, 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 GeP2S 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 provided 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 alternating current impedance by the following method. In an argon atmosphere with a dew point of -50°C or lower, 120 mg of sample powder is put into a powder molding machine with an inner diameter of 10 mm, and then uniaxially pressed and formed at a pressure of 50 MPa or less per sample area using a hydraulic press. After releasing the pressure, SUS316L powder is put on the upper and lower surfaces of the sample as a current collector, and then uniaxially pressed and formed for 5 minutes at a pressure of 360 MPa per pellet area 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 alternating current impedance. The measurement conditions are an applied voltage amplitude of 20 mV, a frequency range of 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 contain 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, 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, 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 others, 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, Li7P3S 11 and the Thio-LISICON type, etc. Among these, from the viewpoint of lithium ion conductivity, the crystal structures include the LGPS type, the argyrodite type, and Li7P3S 11 are preferable, and among these, Li7P3S is preferable because of its high stability against Li 11is more preferable. From the viewpoint of stability against the atmosphere, a crystal structure having a crystal phase of Li4P2S6 or β-Li3PS4, 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 is preferably included. Among these, since the lithium ion conductivity is high, 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 is more preferable.

[0034] The above 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 first crystal structure may be within a further range of ±0.3° within the range of the above 2θ, or within a range of ±0.1°.

[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. Using an X-ray diffractometer (Rigaku's "MiniFlex II"), powder X-ray diffraction measurement is performed. 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 crystal structure having the above Li7P3S 11 has diffraction peaks at positions of 2θ = 17.8° ± 0.5°, 18.5° ± 0.5°, 23.7° ± 0.5°, 29.6° ± 0.5°, and 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 GeP2S 12 and the like. The crystal structure having the crystal phase of Li 10 GeP2S 12 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°, and 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 Li6PS5Cl and the like. The crystal structure having the crystal phase of Li6PS5Cl 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°, and 52.5° ± 0.5° in the X-ray diffraction measurement using the above CuKα ray.

[0040] The crystal structure having the crystal phase of the above Li4P2S6 has diffraction peaks at positions of 2θ = 2θ = 16.9° ± 0.5°, 27.1° ± 0.5°, 32.1° ± 0.5°, and 32.5° ± 0.5° in the X-ray diffraction measurement using the above CuKα ray.

[0041] The crystal structure having the crystal phase of the above β-Li3PS4 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 in terms of molar ratio, more preferably 2.36 or more and 3.70 or less, and even more preferably 2.60 or more and 3.40 or less. 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. When the content ratios of Li and N in the sulfide solid electrolyte are within the above ranges, a sulfide solid electrolyte exhibiting good reduction resistance can be obtained. In addition, 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, particularly when the value of y in the general formula is less than 0.75, the so-called cross-linked sulfur P2S7 4- (S3P - S - PS3) decreases and substantially does not contain Li2S which easily reacts with water. Therefore, 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 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, it is preferable because the reduction resistance, air stability, and ionic conductivity at 25 °C can be simultaneously enhanced.

[0045] The sulfide solid electrolyte contains Li, P, S, N, Ge, and the above element M, Li10 GeP2S 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] As the sulfide solid electrolyte, it preferably has a composition represented by the general formula (100 - z)(yLi2S·(1 - y)P2S5)·zLi α M β N (where 0 < z ≤ 40, 0.50 ≤ y ≤ 0.75). By having a composition represented by the above general formula for the sulfide solid electrolyte, the reduction resistance can be further improved. In addition, the initial Coulomb efficiency of the all-solid-state battery including the sulfide solid electrolyte can be further increased.

[0047] In the above 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 above 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 crosslinked sulfur P2S7 4- (S3P - S - PS3) decreases and it substantially does not contain Li2S which easily reacts with water. Therefore, 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. When 1 ≤ z ≤ 30, the ionic conductivity at 25°C can be further increased. When 1 ≤ z ≤ 5 or 10 ≤ z ≤ 30, the ionic conductivity at 25°C can be further increased. When 1 ≤ z ≤ 5 or 10 ≤ z ≤ 25, the ionic conductivity at 25°C can be even further increased.

[0048] In the above general formula, y is preferably 0.50 or more and 0.75 or less, more preferably 0.67 or more and 0.70 or less. When the content ratios of Li2S and P2S5 in the sulfide solid electrolyte are within the above ranges, 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 element M contains Al, α = 1.5 and β = 0.5 may be used.

[0050] When the sulfide solid electrolyte contains Ge, it preferably has a composition represented by the general formula (100 - z)Li 10 GeP2S 12 ·zLi α M β N (where 0 < z ≤ 50, and α and β are numerical values that give a stoichiometric ratio according to the type of element M). For example, when element M contains Al, the sulfide solid electrolyte preferably has a composition represented by the general formula (100 - z)Li 10 GeP2S 12 ·zLi 3 / 2 Al 1 / 2 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 more than 0 and 50 or less, 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, and for example, 0.80 ≦ α ≦ 3.0 and 0.10 ≦ β ≦ 1.2 may be used. In particular, when the element M contains Al, α = 1.5 and β = 0.5 may be used.

[0053] The ionic conductivity of the sulfide solid electrolyte at 25 °C is 0.4×10 -3 S / cm or more, preferably 1.0×10 -3 S / cm or more, 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 provided 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 an all-solid-state battery according to an embodiment of the present invention. The all-solid-state battery 10, which is a secondary battery, has a negative electrode layer 1 and a positive electrode layer 2 disposed with a 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, a positive electrode mixture layer 6, a solid electrolyte layer 3, a negative electrode mixture layer 5, and a 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 contains 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 be used in combination with other solid electrolytes other than the sulfide solid electrolyte. As the other solid electrolyte, it may be a sulfide solid electrolyte other than the sulfide solid electrolyte, or may be an oxide solid electrolyte, a dry polymer electrolyte, a gel polymer electrolyte, or a pseudo solid electrolyte.

[0058] As the sulfide solid electrolyte other than the sulfide solid electrolyte, it is preferably high in Li ion conductivity. For example, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-Li3N, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S 2n (However, m and n are positive numbers, and Z is any one of Ge, Zn, and Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li δ XO ε (However, δ and ε are positive numbers, and X is any one of P, Si, Ge, B, Al, Ga, and In.), Li 10 GeP2S 12 etc. can be mentioned. Among these, from the viewpoint of good lithium ion conductivity, Li2S-P2S5 is preferable, and xLi2S·(100-x)P2S5 (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 for 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 solid electrolytes other than the sulfide solid electrolyte, conductive agents, binders, and fillers.

[0063] 〈Negative electrode active material〉 As the negative electrode active material, a material that can usually occlude and release lithium ions is generally used. Specific negative electrode active materials include, for example metals or semimetals such as Si and Sn; Metal oxides or metalloid 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 produced 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 obtained by mechanically composite the negative electrode active material and the sulfide solid electrolyte. 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. The shape of the conductive agent includes powder form, fibrous form, etc. 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 thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), 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 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 active material layer 5 is preferably 30 μm, more preferably 60 μm. The upper limit of the average thickness of the negative electrode active material 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 active material 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 active material layer 5 to be equal to or less than the above upper limit, an all-solid-state battery including a negative electrode excellent in high-rate discharge performance and having a high active material utilization rate can be obtained.

[0072] (Intermediate layer) The above intermediate layer is a coating layer on the surface of the negative electrode substrate layer 4, and includes conductive particles such as carbon particles to reduce the contact resistance between the negative electrode substrate layer 4 and the negative electrode active material layer 5. The configuration of the intermediate layer is not particularly limited, and for example, it can be formed of 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 active material 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 active material 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, it can include 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.

[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 not less than the above lower limit, the strength of the positive electrode base material layer 7 can be made sufficiently high, 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 not more than the above upper limit, sufficient volume of other components can be 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. As the above positive electrode active material, for example, Li x MeO y (Me represents at least one transition metal) composite oxide (Li having a layered α-NaFeO2-type crystal structure x CoO2, Li x NiO2, Li x MnO3, Li x Ni α Co (1-α) O2, Li x Ni α Mn β Co (1-α-β) O2, etc., Li x Mn2O4, Li x Ni α Mn (2-α) O4, 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.) Polyanion compounds represented by (such as LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, Li2CoPO4F, etc.) can be mentioned. 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 of them 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 MnO2, FeO2, TiO2, V2O5, V6O 13 , materials such as TiS2 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 also be acceptable. 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 mechanically milling the positive electrode active material, solid electrolyte, etc. in the same manner as in the case of the negative electrode. For example, a mixture of the positive electrode active material and the solid electrolyte, etc. can be obtained by mixing the particulate positive electrode active material and the particulate solid electrolyte, etc. Similar to the case of the negative electrode, the above positive electrode composite includes a composite having a chemical or physical bond between the positive electrode active material and the solid electrolyte, a composite in which the positive electrode active material and the solid electrolyte are mechanically combined, and the like. In the above composite, the positive electrode active material and the solid electrolyte are present within one particle. For example, those in which the positive electrode active material and the solid electrolyte form an aggregated state, those in which a solid electrolyte-containing film 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 contained in the positive electrode binder can maintain high ionic conductivity by constituting the positive electrode mixture or the positive electrode composite. 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.

[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, further 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, and further preferably 200 μm. By setting the average thickness of the positive electrode binder layer 6 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 positive electrode binder layer 6 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.

[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 its 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. Oxides such as Li3PO4, halogens, halogen compounds, etc. may be added to the electrolyte for the solid electrolyte layer.

[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) After mixing Li3N and AlN in a mortar or the like, they are pelletized. Next, heat treatment is performed to produce Li 3 / 2 Al 1 / 2 N. In general, "Li 3 / 2 Al 1 / 2 N" is denoted as "Li3AlN2". (2) Preparation of Sulfide Solid Electrolyte The above-mentioned Li 3 / 2 Al 1 / 2 N, Li2S and P2S5 are mixed in a mortar or the like, and then a sulfide solid electrolyte precursor is prepared. As a method for preparing the sulfide solid electrolyte precursor, for example, a mechanical milling method, a melt quenching method, or the like can be used. When preparing a sulfide solid electrolyte, after preparing the sulfide solid electrolyte precursor, the sulfide solid electrolyte can be prepared 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 Li7P3S 11 crystal structure, the heat treatment temperature is preferably 250 °C or higher and 400 °C or lower. In order to obtain a β-Li3PS4 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 Li4P2S6, which is a stable phase. 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 preparation process, the case of preparing a sulfide solid electrolyte containing Al as element M has been described. However, by the same method as the above preparation 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, V, and N can be used to prepare a sulfide solid electrolyte having a crystal structure. For example, as the nitride in the above preparation process, Li 3 / 2 Al1 / 2 Replace N with Li 3 / 2 B 1 / 2 N or Li 5 / 3 Si 1 / 3 N, Li 9 / 5 Si 3 / 10 By using N etc., 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 elements M, Li, and N was used as the starting material, but the production method of the sulfide solid electrolyte of this embodiment is not limited to this.

[0091] In the above production process, a Li2S-P2S5-based sulfide solid electrolyte was used 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 production process, Li 3 / 2 Al 1 / 2 N, Li2S and P2S5 were used, but a Ge-containing LGPS-type sulfide solid electrolyte containing Ge may also be produced by adding a Ge-containing compound such as GeS2. More specifically, after mixing starting materials in a predetermined molar ratio in a mortar or the like, a mechanical milling method, for example, ball milling treatment or vibration milling treatment, etc. is performed to produce a sulfide solid electrolyte precursor. Then, the precursor is heat-treated at a predetermined temperature or higher to produce a sulfide solid electrolyte. For example, Li 10 GeP2S 12 When producing a sulfide solid electrolyte having a 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, even 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 carried out under a reduced pressure atmosphere or under an inert gas atmosphere.

[0092] (Negative electrode binder production process) In this process, a negative electrode binder for forming a negative electrode layer is produced. When the negative electrode binder 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, and a mixture or composite of the negative electrode active material and the sulfide solid electrolyte is produced.

[0093] (Solid electrolyte layer electrolyte production 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 treating it by a mechanical milling method. The electrolyte for the solid electrolyte layer may be produced by heating a predetermined material of the electrolyte for the solid electrolyte layer above the melting temperature and melting and mixing the two at a predetermined ratio by the melt quenching method and then quenching. Other synthesis methods of the electrolyte for the solid electrolyte layer include, for example, a solid phase method of firing under reduced pressure encapsulation, a liquid phase method such as dissolution precipitation, a vapor phase method (PLD), and firing under an argon atmosphere after mechanical milling. 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 carried out.

[0094] (Positive electrode binder production process) In this process, a positive electrode mixture for forming a positive electrode layer is produced. The method for producing the positive electrode mixture is not particularly limited and can be appropriately selected according to the purpose. For example, compression molding of a 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 a 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 to produce a mixture or composite of the positive electrode active material and the sulfide solid electrolyte.

[0095] (Lamination process) In this process, a negative electrode layer having a negative electrode substrate layer and a negative electrode mixture layer, a solid electrolyte layer, and a positive electrode layer having a positive electrode substrate 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 sequentially formed, 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 a negative electrode substrate and a negative electrode mixture, the above solid electrolyte layer is formed by pressure molding an electrolyte for the solid electrolyte layer, and the above positive electrode layer is formed by pressure molding a positive electrode substrate and a positive electrode mixture.

[0096] The negative electrode layer, the solid electrolyte layer, and the positive electrode layer may be laminated by pressure molding the negative electrode substrate, the negative electrode mixture, the electrolyte for the solid electrolyte layer, the positive electrode substrate, and the positive electrode mixture at once. The positive electrode layer, the negative electrode layer, or these layers may be pre-formed and laminated by pressure molding with the solid electrolyte layer.

[0097] [Other embodiments] The present invention is not limited to the above embodiments, and can be implemented in various modified and improved forms 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 for example, it may include other layers other than the negative electrode layer, the positive electrode layer, and the solid electrolyte layer, such as an intermediate layer and an adhesive layer.

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

[0100] [Example 1] By the following process, 99(0.70Li2S·0.30P2S5)·1Li 3 / 2 Al 1 / 2 N was synthesized. Li3N 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. The produced 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, Li2S (99.98%, Aldrich), P2S5 (99%, Aldrich) and Li3 / 2Al 1 / 2 N were weighed so that the molar ratio was 69.3:29.7:1.0, 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 45 hours at a revolution speed of 510 rpm using a planetary ball mill (manufactured by FRITSCH, model number Premium line P-7). Heat treatment was performed for 2 hours to obtain the sulfide solid electrolyte of Example 1. This heat treatment was performed at a temperature equal to or higher than the crystallization temperature and not more than 100 °C higher than the crystallization temperature. The crystallization temperature was determined by measuring DSC. The DSC measurement was performed 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 10 °C / min.

[0101] [Examples 2 to 9] Composition formula of sulfide solid electrolyte (100 - z)(0.70Li2S·0.30P2S5)·zLi 3 / 2 Al 1 / 2The sulfide solid electrolytes of Examples 2 to 9 were synthesized in the same manner as in Example 1, except that the value of z in N was changed to 5, 7, 10, 15, 20, 25, 30, and 40.

[0102] [Example 10] As raw materials for the sulfide solid electrolyte, Li2S, P2S5, and Li 3 / 2 Al 1 / 2 N was weighed so that Li2S:P2S5:Li 3 / 2 Al 1 / 2 N = 67.5:22.5:10.0 (mol%). 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, Li2S, P2S5, and Li 3 / 2 Al 1 / 2 N was weighed so that Li2S:P2S5:Li 3 / 2 Al 1 / 2 N = 35.0:35.0:30.0 (mol%). The sulfide solid electrolyte of Example 11 was synthesized in the same manner as in Example 1.

[0104] [Example 12] As raw materials for the sulfide solid electrolyte, Li2S, P2S5, and Li 3 / 2 Al 1 / 2 N was weighed so that Li2S:P2S5:Li 3 / 2 Al 1 / 2 N = 53.6:26.4:20.0 (mol%). The sulfide solid electrolyte of Example 12 was synthesized in the same manner as in Example 1.

[0105] [Example 13] As raw materials for the sulfide solid electrolyte, Li2S, P2S5, and Li 3 / 2 Al 1 / 2 N was weighed so that Li2S:P2S5:Li 3 / 2 Al 1 / 2 N = 50.3:24.7:25.0 (mol%). The sulfide solid electrolyte of Example 13 was synthesized in the same manner as in Example 1.

[0106] [Example 14] As raw materials for the sulfide solid electrolyte, Li2S, P2S5, and Li 3 / 2 Al 1 / 2 N were weighed so that Li2S:P2S5:Li 3 / 2 Al 1 / 2 N = 46.9:23.1:30 (mol%). The sulfide solid electrolyte of Example 14 was synthesized in the same manner as in Example 1, except for this weighing.

[0107] [Examples 15 to 18] Li3N 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 to have the main phase of Li 3 / 2 B 1 / 2 N by XRD measurement. Next, instead of Li 3 / 2 Al 1 / 2 N, the above Li 3 / 2 B 1 / 2 N was used, and the 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)(0.70Li2S·0.30P2S5)·zLi 3 / 2 B 1 / 2 N was changed to 1, 10, 20, and 30. [Examples 19 to 23] Li3N and Si3N4 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 to have the main phase of Li 5 / 3 Si 1 / 3 N by XRD measurement. Next, instead of Li 3 / 2 Al 1 / 2 N, the above Li 5 / 3 Si 1 / 3Using N, the composition formula of the sulfide solid electrolyte is (100 - z)(0.70Li2S·0.30P2S5)·zLi 5 / 3 Si 1 / 3 Except for changing the value of z in N to 1.5, 15, 20, 30, and 45, the sulfide solid electrolytes of Examples 19 to 23 were synthesized in the same manner as in Example 1.

[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 N was not used.

[0109] [Reference Example 1] 75Li2S·25P2S5 (Li3PS4) was synthesized by the mechanical milling method. In an argon atmosphere glove box with a dew point of -50°C or lower, Li2S and P2S5, which are the raw materials of the sulfide solid electrolyte, were weighed so that Li2S:P2S5 = 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, Li3N 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)(0.70Li2S·0.30P2S5)·zLi3N of the sulfide solid electrolyte was changed to 20.

[0111] [Example 24] By the following treatment, 87.6(Li10GeP2S12)·12.4Li 3 / 2 Al 1 / 2 N was synthesized. Li3N 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. Next, in a glove box with an argon atmosphere having a dew point of -50 °C or lower, Li2S (99.98%, Aldrich), P2S5 (99%, Aldrich), GeS2 (99.99%, High Purity Chemical Laboratory), 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 sulfide solid electrolyte of the composition formula (100 - z)(Li 10 GeP2S 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] For the raw material of the sulfide solid electrolyte, except that Li 3 / 2 Al 1 / 2 N was replaced with Li2O (99%, High Purity Chemical Laboratory) and weighed so that Li2S:P2S5:GeS2:Li2O = 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. [Reference Example 4] As a raw material for the sulfide solid electrolyte, Li 3 / 2 Al 1 / 2 The sulfide solid electrolyte of Reference Example 4 was synthesized in the same manner as in Example 24, except that Al2S3 (98%, Aldrich) was used instead of N, and weighed so that Li2S:P2S5:GeS2:Al2S3 = 5:1:0.93:0.035 (mol%).

[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 ("miniFlex II" manufactured by Rigaku). 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. In Table 2, "Unknown" indicates that diffraction peaks whose crystal structures could not be identified were confirmed.

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

[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] Figure 4 shows the ionic conductivities at 25°C of Examples 1 to 9 and Comparative Example 1, and Table 1 shows the ionic conductivities at 25°C of Examples 1 to 23, Comparative Example 1, and Reference Example 2.

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

[0122] (4) Initial Coulomb efficiency and charge-discharge performance (4-1) Preparation of the positive electrode active material After dissolving metallic Li in ultradehydrated ethanol, niobium ethoxide (Nb(OC2H5)5) was dissolved to prepare a LiNbO3 precursor solution. Using a rolling fluid coating device (FD-MP-01F) manufactured by Pauleck, LiNi 0.8 Co 0.15 Al 0.05The surface of O2(NCA) particles was coated with a LiNbO3 precursor. LiNbO3-coated NCA was prepared by heat-treating the NCA coated with the LiNbO3 precursor at 350 °C for 1 hour. This LiNbO3-coated NCA was used as the positive electrode active material.

[0123] (4-2) Fabrication of all-solid-state battery cell (Li-NCA half-cell) LiNbO3-coated NCA and the sulfide solid electrolyte (Li3PS4) of Reference Example 1 were weighed so that LiNbO3-coated NCA:Li3PS4 = 70:30 (mass %), and then mixed in an agate mortar. After the sulfide solid electrolyte of Example 1 was put into a powder molding machine with an inner diameter of 10 mm, it was pressure-molded using a hydraulic press. After releasing the pressure, the NCA-Li3PS4 mixed powder was put on one side of the solid electrolyte layer of Example 1 and pressure-molded at 360 MPa for 5 minutes per sample area. After releasing the pressure, a metal Li foil was bonded to the opposite side of the sulfide solid electrolyte layer of Example 1 and pressure-molded 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-encapsulated 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 replaced with the sulfide solid electrolytes of Example 2, 4, and Comparative Example 1 to obtain all-solid-state battery cells (Li-NCA half-cells) equipped with the sulfide solid electrolytes of Example 2, 4, and Comparative Example 1.

[0125] (4-3) Charge-discharge test The charge-discharge test was conducted on the above all-solid-state battery cell (Li-NCA half-cell) under the following conditions. The charge-discharge test was carried out 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 set to 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-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. After the sulfide solid electrolyte (Li3PS4) of Reference Example 1 was put into a powder molding die with an inner diameter of 10 mm, it was pressure-molded using a hydraulic press. After releasing the pressure, a mixed powder of the above SUS316 powder and the sulfide solid electrolyte powder of Example 1 was put on one side of the Li3PS4 layer and pressure-molded at 360 MPa for 5 minutes. After releasing the pressure, a metal Li foil was bonded to the opposite side of the Li3PS4 layer and pressure-molded to obtain a laminate of the mixture layer of the sulfide solid electrolyte of Example 1, the Li3PS4 layer, and the metal Li foil. This laminate was vacuum-sealed in an aluminum laminate cell and compressed using a stainless steel plate to obtain a cell for evaluating reducing resistance with the mixture layer of the sulfide solid electrolyte of Example 1 as the working electrode and the metal Li foil as the counter electrode. The charging test conditions were a measurement temperature of 50°C, and charging was performed as constant current-constant voltage (CCCV) charging with a charging current of 0.1 mA / cm 2The lower limit charging 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 taken as the reduction decomposition capacity (mAh / g) of the sulfide solid electrolyte 20 hours later. 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. Using 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 capacities 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 using all-solid-state battery cells (Li-Gr half-cells) 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 according to the procedure shown below.

[0130] Graphite particles (Gr) and the sulfide solid electrolyte of Example 24 (Li 10.21 GeP2Al 0.07 S 12 N 0.14 ) were weighed so that Gr:Li 10.21 GeP2Al 0.07 S 12 N 0.14 = 60:40 (mass %), and then mixed in an agate mortar. After Li3PS4 was put 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 Li3PS4 layer, Gr-Li 10.21 GeP2Al 0.07 S 12 N 0.14The mixed powder was introduced and pressure-molded. After releasing the pressure, a metal Li foil was laminated on the opposite side of the Li3PS4 layer and pressure-molded to obtain a laminate of the mixture layer of the sulfide solid electrolyte, the Li3PS4 solid electrolyte layer, and the metal Li foil of Example 24. 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) having 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 carried out 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) provided 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 (Gr lithiation) was carried out under the following conditions. The discharge test was conducted in a constant temperature bath at 5 2 0 °C. Discharge was performed at a constant current (CC) with a discharge current of 0.125 mA / cm

[0133] Figure 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 . From Figure 9, it is confirmed 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 + , the change in dQ / dV near the above 0.4 V is presumed to be due to the reductive decomposition of the sulfide solid electrolyte. Therefore, the shift of the value of the voltage V at dQ / dV = -100 mAhg -1 V -1 in the all-solid-state battery cell (Li-Gr half cell) of this example 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 Atmospheric Stability To evaluate the chemical stability of the sulfide solid electrolyte in the atmosphere, 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 , temperature 20°C, relative humidity approximately 90%), and a hydrogen sulfide sensor (TPA-5200E) was used to measure the amount of hydrogen sulfide generated. The measurement was terminated when the detected upper limit value of the hydrogen sulfide sensor, 50 ppm, was reached or when the measurement time had elapsed for 40 minutes. The amount of hydrogen sulfide generated V (cm 3 / g) per gram of the solid electrolyte was determined 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 amount of hydrogen sulfide generated (cm 3 / g) for the sulfide solid electrolyte pellets of the above examples and comparative examples. Figure 6 shows the amount of hydrogen sulfide generated up to an atmospheric exposure time of 20 minutes in Example 4, Example 6, and Comparative Example 1, and Figure 7 shows the amount of hydrogen sulfide generated up to an atmospheric exposure time of 40 minutes in Example 6 and Reference Example 1.

[0136]

Table 1

[0137] As shown in Table 1, the sulfide solid electrolytes of the examples containing any one of Al, B, or Si as element M and N and having a crystal structure had a reduced decomposition capacity suppressed 20 hours after the start of charging compared to the sulfide solid electrolyte of Comparative Example 1, and 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, and 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 that does not contain element M and N had good ionic conductivity, but had a large reduced decomposition capacity 20 hours after 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 Scm 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 ratios of Li and N are large such that 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, Li2S 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, peaks were observed in the XRD spectra of the sulfide solid electrolytes of all examples and comparative examples, and it was confirmed that they have a crystal structure. Examples 1 and 2 are Li7P3S 11, Example 3 had the crystal structure of β-Li3PS4, and Example 11 had the crystal structure of Li4P2S6. 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 in Fig. 3, in the sulfide solid electrolytes of the examples, as z increases, that is, as the nitrogen (N) content increases, the cross-linked sulfur P2S7 4- Raman shift 406 cm derived from -1 The peak near decreases, and PS4 3- Raman shift 423 cm derived from -1 The peak near appears. Therefore, the molecular structures based on the Raman spectra of Example 1 and Example 15 in Table 1 are PS4 3- , P2S7 4- And P2S6 4- It 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 presumed to be composed of PS4 3- From.

[0141] As shown in Figs. 6 and 7, it was confirmed that the hydrogen sulfide generation amounts of Examples 4 and 6 were less than that of 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 had 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 electrolytes of the examples, as z increases, that is, as the N content increases, the cross-linked sulfur P2S7 4- Raman shift 406 cm derived from -1The nearby peaks are decreasing. Also, in the XRD (X-ray diffraction) spectrum shown in Fig. 2 for the sulfide solid electrolyte of the example, the peaks derived from Li2S did not appear. From these facts, it is considered that by increasing the content of N in the sulfide solid electrolyte, the so-called crosslinked sulfur P2S7 4- (S3P-S-PS3) decreases, and since it substantially does not contain Li2S which easily reacts with water, it is presumed that the inhibitory effect on the generation of hydrogen sulfide can be improved. In addition, for Example 6 (z = 20), the reason why the generation amount of hydrogen sulfide is less than that of Reference Example 1 which does not have crosslinked sulfur P2S7 4- 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 oxynitride glass in which part of O of the oxide glass is replaced by N, it is generally known that the water resistance is improved by introducing N.

[0142] Comparing Example 6, Example 17, Example 21, and Reference Example 2 with z = 20 and y = 0.70 where the content of N is fixed, it can be seen that Li2S is deposited only in Reference Example 2 which does not contain element M. From this, it is considered that the deposition of Li2S can be suppressed by including element M.

[0143] As the reason why the deposition of Li2S can be suppressed by the sulfide solid electrolyte containing element M, the following can be considered. When Li3N is used as the starting material for the sulfide-based solid electrolyte containing N, Li3N and P2S5 react violently to release N2 and Li2S is deposited. This is considered to be because the N defect generation energy of Li3N is small. In contrast, in the present invention, the N defect generation energy of Li α M β N is larger than the N defect generation energy of Li3N, so the reaction proceeds gently during the synthesis process of the sulfide-based solid electrolyte, and the release of N2 and the deposition of Li2S are suppressed. Here, the "defect generation energy" refers to a value calculated using the total energy Eperfect of a crystal structure without defects, the total energy Evacancy of a crystal structure with defects, and the chemical potential μ of the defective atom, and means a parameter defined by the following formula. E defect = ( E vacancy + μ ) - E perfect

[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, the fact that the value of the voltage V at dQ / dV = -100 mAhg -1 V -1 shifts in the lower direction means that the reduction decomposition potential of the sulfide solid electrolyte has shifted in the lower 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 an all-solid-state battery including the sulfide solid electrolyte. Also, it was shown that the sulfide solid electrolyte according to the present invention can be improved in terms of air stability.

Industrial Applicability

[0147] Since the all-solid-state battery including 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 Symbols

[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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