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: The sulfide solid electrolyte contains Al and N and has a crystal structure. The all-solid-state battery 10 is a secondary battery in which a negative electrode layer 1 and a positive electrode layer 2 are disposed with a solid electrolyte layer 3 interposed therebetween. The negative electrode layer 1 includes a negative electrode substrate layer 4 and a negative electrode mixture layer 5, and the negative electrode substrate layer 4 is the outermost layer of the negative electrode layer 1. The positive electrode layer 2 includes a positive electrode substrate layer 7 and a positive electrode mixture layer 6, and the positive electrode substrate layer 7 is the outermost layer of the positive electrode layer 2. A positive electrode mixture layer 6, a solid electrolyte layer 3, a negative electrode mixture layer 5, and a negative electrode substrate layer 4 are laminated in this order on a positive electrode substrate layer 7, and the negative electrode layer 1, the solid electrolyte layer 3, the positive electrode layer 2, or a combination thereof contains the sulfide solid electrolyte, and initial coulomb efficiency is excellent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Due to their high energy density, 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, automobiles, etc. The non-aqueous electrolyte secondary batteries generally include an electrode assembly having a pair of electrically isolated electrodes and a non-aqueous electrolyte interposed between the electrodes, and are configured to charge and discharge by transferring ions between the electrodes.

[0003] In recent years, with the aim of improving the safety of non-aqueous electrolyte secondary batteries, all-solid-state batteries have been proposed that use sulfide solid electrolytes or the like as the non-aqueous electrolyte instead of liquid electrolytes such as organic solvents (see Patent Document 1).

[0004] One example of a sulfide solid electrolyte is a crystalline sulfide solid electrolyte containing Li, P, S, and N and having a composition expressed by the general formula XLi2S-25P2S5-YLi3N (10≦Y≦15, 67.5≦X+Y≦85) (see Patent Document 2). As sulfide solid electrolytes, 70Li2S·30P2S5 glass ceramics and 60Li2S·25P2S5·10Li3N glass ceramics are used. -3 It has been reported that it exhibits high ionic conductivity of more than 5 S / cm (Non-Patent Document 1).

[0005] First-principles calculations have revealed that such sulfide solid electrolytes inherently have low oxidation and reduction resistance (Non-Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-340257 [Patent Document 2] Japanese Patent Application Publication No. 2018-041671 [Non-Patent Document 1] Solid State Ionics,177,2721(2006), Solid State Ionics,304,85(2016) [Non-patent document 2] ACS Appl.Mater.Interfaces, 7, 23685(2015) Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in light of the above circumstances, and aims 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 problem]

[0008] One aspect of the present invention, which has been made to solve the above-mentioned problems, is a sulfide solid electrolyte having a crystalline structure, which contains N and 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.

[0009] Another aspect of the present invention is a sulfide solid electrolyte containing Al and N and having a crystalline structure. [Effects of the Invention]

[0010] According to the sulfide solid electrolyte according to one or another aspect of the present invention, it is possible to provide a sulfide solid electrolyte with improved reduction resistance. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an all-solid-state battery according to one embodiment of the present invention. [Figure 2] 1 shows X-ray diffraction (XRD) spectra of sulfide solid electrolytes of Examples and Comparative Examples. [Figure 3] 1 shows Raman spectra of sulfide solid electrolytes of Examples and Comparative Examples. [Figure 4] 1 is a graph showing the ionic conductivities at 25° C. of sulfide solid electrolytes of Examples and Comparative Examples. [Figure 5] 1 is a graph showing the initial charge-discharge performance of all-solid-state batteries of Examples and Comparative Examples. [Figure 6] 1 is a graph showing the amount of hydrogen sulfide generated from sulfide solid electrolytes of Examples and Comparative Examples. [Figure 7] 1 is a graph showing the amount of hydrogen sulfide generated from sulfide solid electrolytes of Examples and Reference Examples. [Figure 8] 1 shows X-ray diffraction (XRD) spectra of sulfide solid electrolytes of Examples, Comparative Examples, and Reference Examples. [Figure 9] 1 shows dQ / dV curves of all-solid-state batteries of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0012] A sulfide solid electrolyte according to one embodiment of the present invention is a sulfide solid electrolyte having a crystalline structure, which contains N and 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.

[0013] The present inventors have noticed that nitrides containing any of Al, Si, B, Mg, Zr, Ti, Hf, Ca, Sr, Sc, Ce, Ta, Nb, W, Mo, and V (hereinafter also referred to as element M), which are difficult to use as solid electrolytes due to their low ionic conductivity, exhibit high reduction resistance. Therefore, they have hypothesized that the reduction resistance of a sulfide solid electrolyte may be improved by including nitrogen element (N) and element M in the sulfide solid electrolyte, and have arrived at the present invention.

[0014] The sulfide solid electrolyte contains N and 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 has a crystalline structure, thereby enabling the sulfide solid electrolyte to have improved reduction resistance. In the sulfide solid electrolyte, the element M may be Al. While the reason for this is not clear, the following reason is presumed. When the sulfide solid electrolyte containing the elements M and N is exposed to a reducing atmosphere, a highly reduction-resistant coating containing a nitride of the element M or a lithium nitride of the element M is presumed to be formed on the surface or interface of the sulfide solid electrolyte. This is presumed to improve the reduction resistance of the sulfide solid electrolyte.

[0015] An all-solid-state battery including this sulfide solid electrolyte can be an all-solid-state battery with improved initial coulombic efficiency. Although the reason for this is unclear, the following reason is presumed. It is known that general sulfide solid electrolytes are easily reductively decomposed, and all-solid-state batteries including such sulfide solid electrolytes exhibit a large amount of electricity due to reductive decomposition. However, this sulfide solid electrolyte has high resistance to reduction. Therefore, the initial coulombic efficiency of all-solid-state batteries including this sulfide solid electrolyte can be improved. Furthermore, the sulfide solid electrolyte contains N, which replaces S with N, which has a small ionic radius, reducing the crystal lattice volume. This increases the space for lithium ions to move, improving ionic conductivity. As a result, the initial coulombic efficiency of the all-solid-state battery can be improved while maintaining good ionic conductivity.

[0016] The element M in the sulfide solid electrolyte may be any element that provides a nitride with high reduction resistance. 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 shown by first-principles calculations to provide lithium nitrides containing the element M with high reduction resistance (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 production costs.

[0017] The above crystal structure is Li7P3S 11 Preferably, the crystalline structure has a crystalline phase of Li4P2S6 or β-Li3PS4, or a first crystalline 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 comprises 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 X-ray diffraction measurement, or 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° but no diffraction peak at 30.9°±0.5° in the X-ray diffraction measurement. This configuration further increases the ionic conductivity at 25°C.

[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 of

[0024] In addition, 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 of, the content ratio of Li to P is preferably 5.01 or more and 5.61 or less in terms of molar ratio, and the content ratio of N to P is preferably 0.0051 or more and 0.41 or less in terms of molar ratio. Further preferably, the content ratio of Li to P is 5.06 or more and 5.19 or less in terms of molar ratio, and the content ratio of N to P is 0.038 or more and 0.13 or less in terms of 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 that give 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 was determined by measuring AC impedance using the following method. In an argon atmosphere with a dew point of -50°C or lower, 120 mg of sample powder was placed in a powder molder 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 the pressure was released, SUS316L powder was placed on the top and bottom of the sample as current collectors, and then uniaxially pressed for 5 minutes at a pressure of 360 MPa per pellet area to obtain a pellet for ionic conductivity measurement. This pellet for ionic conductivity measurement was inserted into a Hohsen HS cell, and AC impedance measurement was performed. The measurement conditions were an applied voltage amplitude of 20 mV, a frequency range of 1 MHz to 100 mHz, and a measurement temperature of 25°C.

[0028] An all-solid-state battery according to another aspect of the present invention is an all-solid-state battery including an anode layer, a solid electrolyte layer, and a cathode layer, wherein the anode layer, the solid electrolyte layer, the cathode layer, or a combination thereof contains the sulfide solid electrolyte.

[0029] In an all-solid-state battery according to another aspect of the present invention, the negative electrode layer, the solid electrolyte layer, the positive electrode layer, or a combination thereof contains the sulfide solid electrolyte, and therefore the initial coulombic efficiency is excellent. Because the sulfide solid electrolyte has excellent resistance to reduction, it is preferable that the negative electrode layer and / or the solid electrolyte layer contain the sulfide solid electrolyte. This configuration further enhances the effects of the present invention.

[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 crystalline structure. 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 crystalline structure, thereby improving reduction resistance. The sulfide solid electrolyte can be used in any application requiring ionic conductivity. In particular, the sulfide solid electrolyte is preferably used in a lithium all-solid-state battery. Note that in the sulfide solid electrolyte, the element M may be Al.

[0032] The sulfide solid electrolyte has a crystalline structure. Here, "having a crystalline structure" means that, in an X-ray diffraction measurement, peaks derived from the crystalline structure of the sulfide solid electrolyte are observed in the X-ray diffraction pattern. The sulfide solid electrolyte may contain an amorphous portion. A sulfide solid electrolyte having a crystalline 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 LGPS type, argyrodite type, Li7P3S 11 Among these, the crystal structure is preferably the LGPS type, the argyrodite type, or the Li7P3S type from the viewpoint of lithium ion conductivity. 11 Among these, Li7P3S is preferred because it has high stability against Li. 11From the viewpoint of stability to the atmosphere, it is preferable that the material contains a crystal structure having a crystalline 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 radiation, and among these, the 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 more preferable because of its high lithium ion conductivity.

[0034] The first crystal structure may include 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 X-ray diffraction measurement, or 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° but no diffraction peak at 30.9°±0.5° in the X-ray diffraction measurement. This configuration enables the ionic conductivity at 25°C to be increased.

[0035] The diffraction peak of the first crystal structure may be within the range of ±0.3°, or may be within the range of ±0.1° of the 2θ range.

[0036] X-ray diffraction measurements using CuKα radiation are performed as follows: The solid electrolyte powder to be measured is packed into an airtight X-ray diffraction sample holder under an argon atmosphere with a dew point of -50°C or lower. Powder X-ray diffraction measurements are performed using an X-ray diffractometer (MiniFlex II, manufactured by Rigaku). The radiation source is CuKα radiation, the tube voltage is 30 kV, and the tube current is 15 mA. Diffracted X-rays are passed through a 30 μm-thick Kβ filter and detected by a high-speed one-dimensional detector (model number: D / teX Ultra 2). 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 Li7P3S 11 The crystalline structure having this crystalline phase has diffraction peaks at 2θ=17.8°±0.5°, 18.5°±0.5°, 23.7°±0.5°, 29.6°±0.5°, and 30.0°±0.5° in X-ray diffraction measurement using the above CuKα radiation.

[0038] The LGPS-type sulfide solid electrolyte may be, for example, Li 10 GeP2S 12 Li 10 GeP2S 12 The crystalline structure having the above crystalline phase has diffraction peaks at 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 X-ray diffraction measurement using the above CuKα radiation.

[0039] An example of the argyrodite-type sulfide solid electrolyte is Li6PS5Cl, etc. A crystalline structure having a crystalline phase of Li6PS5Cl exhibits diffraction peaks at 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 X-ray diffraction measurement using CuKα radiation.

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

[0041] The crystal structure having the β-Li3PS4 crystalline phase has diffraction peaks at 2θ=17.5°±0.5°, 18.1°±0.5°, 29.1°±0.5°, 29.9°±0.5°, and 31.2°±0.5° in X-ray diffraction measurement using the 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 molar ratio of Li to P in the sulfide solid electrolyte is preferably 1.64 to 4.00, more preferably 2.36 to 3.70, and even more preferably 2.60 to 3.40. The molar ratio of N to P is preferably 0.02 to 1.11, more preferably 0.19 to 1.01, even more preferably 0.22 to 0.71, and particularly preferably 0.28 to 0.65. When the Li and N contents in the sulfide solid electrolyte are within the above ranges, a sulfide solid electrolyte exhibiting good reduction resistance can be obtained. Furthermore, the initial coulombic efficiency of an all-solid-state battery including the sulfide solid electrolyte can be improved.

[0043] Furthermore, from the viewpoint of stability in the atmosphere, it is preferable that the molar ratio of the Li to the P is 2.60 or more and 4.00 or less, and the molar ratio of the N to the P is 0.19 or more and 1.11 or less, and it is more preferable that the molar ratio of the Li to the P is 2.77 or more and 3.38 or less, and the molar ratio of the N to the P is 0.28 or more and 0.65 or less. It is also preferable that the element M contains Al. This prevents the formation of a so-called bridged sulfur P2S7, which is unstable in the atmosphere, particularly when the value of y in the general formula is less than 0.75. 4- Since the sulfide solid electrolyte contains less (S3P-S-PS3) and substantially no Li2S, which is prone to react with water, the atmospheric 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, it is preferable that the molar ratio of the Li content to the P content is 2.77 or more and 3.38 or less, and the molar ratio of the N content to the P content is 0.28 or more and 0.65 or less, because this can simultaneously increase the reduction resistance, atmospheric stability, and ionic conductivity at 25°C.

[0045] The sulfide solid electrolyte contains Li, P, S, N, Ge, and the element M, and 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. Further, the initial Coulomb efficiency of the all-solid-state battery including the sulfide solid electrolyte can be 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, further 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. By z being in the range of more than 0 and 40 or less in the above general formula, the reduction resistance of the sulfide solid electrolyte can be further improved. By 10 ≤ z ≤ 40, so-called cross-linked sulfur P2S7 4- (S3P - S - PS3) decreases and it substantially does not contain Li2S which easily reacts with water, so 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 increased more. 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 increased even 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. 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 Al is included as element M, 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 Al is included as element M, 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 depending on the type of element M. The values ​​of α and β are not particularly limited, but may be, for example, 0.80≦α≦3.0 and 0.10≦β≦1.2. 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 0.4×10 -3 S / cm or more is preferable, and 1.0×10 -3 S / cm or more is more preferable, and 1.5×10 -3 When the ionic conductivity of the sulfide solid electrolyte at 25°C is within the above range, the high-rate discharge performance of an all-solid-state battery including the sulfide solid electrolyte can be improved.

[0054] Thus, the sulfide solid electrolyte can be suitably used as a solid electrolyte for all-solid-state batteries.

[0055] <All-solid-state battery> The all-solid-state battery includes an anode layer, a solid electrolyte layer, and a cathode layer. FIG. 1 is a schematic cross-sectional view showing an all-solid-state battery according to one embodiment of the present invention. An all-solid-state battery 10, which is a secondary battery, includes an anode layer 1 and a cathode layer 2 arranged with a solid electrolyte layer 3 interposed therebetween. The anode layer 1 includes an anode substrate layer 4 and an anode mixture layer 5, with the anode substrate layer 4 being the outermost layer of the anode layer 1. The cathode layer 2 includes a cathode substrate layer 7 and a cathode mixture layer 6, with the cathode substrate layer 7 being the outermost layer of the cathode layer 2. In the all-solid-state battery 10 shown in FIG. 1, the cathode mixture layer 6, the solid electrolyte layer 3, the anode mixture layer 5, and the anode substrate layer 4 are stacked in this order on the cathode substrate layer 7.

[0056] In the all-solid-state battery, the anode layer 1, the solid electrolyte layer 3, the cathode layer 2, or a combination thereof contains the sulfide solid electrolyte. In the all-solid-state battery, the anode layer 1, the solid electrolyte layer 3, the cathode layer 2, or a combination thereof contains the sulfide solid electrolyte, and therefore the initial coulombic efficiency is excellent. Because the sulfide solid electrolyte has excellent resistance to reduction, it is preferable that the anode layer 1 and / or the solid electrolyte layer 3 contain the sulfide solid electrolyte. With the above configuration, the effects of the present invention are further improved.

[0057] The all-solid-state battery may also use a solid electrolyte other than the sulfide solid electrolyte, which may be a sulfide solid electrolyte other than the sulfide solid electrolyte, an oxide solid electrolyte, a dry polymer electrolyte, a gel polymer electrolyte, or a quasi-solid electrolyte.

[0058] As sulfide solid electrolytes other than the sulfide solid electrolyte, those having high Li ion conductivity are preferred, and examples thereof include 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, and Li2S-P2S5-Z. m S 2n (where m and n are positive numbers, and Z is Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li δ XO ε (where δ and ε are positive numbers, and X is one of P, Si, Ge, B, Al, Ga, and In.) Li 10 GeP2S 12 Among these, Li2S-P2S5 is preferred, and xLi2S·(100-x)P2S5 (70≦x≦80) is more preferred from the viewpoint of good lithium ion conductivity.

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

[0060] (Negative electrode base material layer) The negative electrode substrate layer 4 is a conductive layer. There are no particular limitations on the material of the negative electrode substrate layer 4 as long as it is a conductor. Examples of the material 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, alloys containing one or more of these metals, and stainless steel alloys.

[0061] The lower limit of the average thickness of the negative electrode substrate layer 4 is preferably 3 μm, more preferably 5 μm, and even more preferably 8 μm. The upper limit of the average thickness of the negative electrode substrate layer 4 is preferably 200 μm, more preferably 100 μm, and even more preferably 50 μm. By setting the average thickness of the negative electrode substrate layer 4 to the above lower limit or more, the strength of the negative electrode substrate layer 4 can be sufficiently increased, and the negative electrode layer 1 can be formed well. By setting the average thickness of the negative electrode substrate layer 4 to the above upper limit or less, the volume of the other components can be sufficiently secured.

[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 a negative electrode active material and the sulfide solid electrolyte. The negative electrode mixture may contain optional components such as a solid electrolyte other than the sulfide solid electrolyte, a conductive agent, a binder, a filler, etc., as needed.

[0063] <Negative electrode active material> As the negative electrode active material, a material capable of absorbing and releasing lithium ions is usually used. Specific examples of the negative electrode active material include: Metals or metalloids such as Si, Sn; Metal oxides or semi-metal oxides such as Si oxide and Sn oxide; Polyphosphate compounds; Carbon materials such as graphite and non-graphitic carbon (easily graphitizable carbon or non-graphitizable carbon); Examples include lithium metal composite oxides such as lithium titanate.

[0064] The lower limit of the content of the negative electrode active material in the negative electrode mixture is preferably 10% by mass, more preferably 15% by mass. The upper limit of the content of the negative electrode active material is preferably 60% by mass, more preferably 70% by mass, even more preferably 80% by mass, particularly preferably 90% by mass, and may even be 95% by mass. By setting the content of the negative electrode active material within the above range, the electrical capacity of the all-solid-state battery can be increased.

[0065] <Negative electrode mixture or negative electrode composite> The negative electrode mixture is a mixture prepared by mixing the negative electrode active material and the sulfide solid electrolyte by mechanical milling, etc. For example, the 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 negative electrode composite include a composite in which the negative electrode active material and the sulfide solid electrolyte are chemically or physically bonded, a composite in which the negative electrode active material and the sulfide solid electrolyte are mechanically combined, etc. The composite is one in which the negative electrode active material and the sulfide solid electrolyte are present in a single particle, and examples of the composite include one in which the negative electrode active material and the sulfide solid electrolyte form an aggregated state, and one in which the sulfide solid electrolyte-containing coating is formed on at least a portion of the surface of the negative electrode active material. The negative electrode mixture or negative electrode composite may contain a solid electrolyte other than the sulfide solid electrolyte. The negative electrode active material contained in the negative electrode mixture and the sulfide solid electrolyte constitute a negative electrode mixture or a negative electrode composite, which can improve reduction resistance while maintaining high ionic conductivity, resulting in excellent initial coulombic efficiency.

[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 mass%, preferably 10 mass%. The upper limit of the content of the solid electrolyte in the negative electrode mixture is preferably 90 mass%, more preferably 85 mass%, even more preferably 80 mass%, and particularly preferably 75 mass%. By setting the content of the solid electrolyte in the above range, the electrical capacity 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 mass%, and preferably 10 mass%. The upper limit of the content of the sulfide solid electrolyte in the negative electrode mixture is preferably 90 mass%, more preferably 85 mass%, even more preferably 80 mass%, and particularly preferably 75 mass%. By setting the content of the sulfide solid electrolyte in the negative electrode mixture within the above range, the initial coulombic efficiency of the all-solid-state battery can be further improved when the negative electrode layer contains the sulfide solid electrolyte.

[0068] <Other optional ingredients> The conductive agent is not particularly limited. Examples of such conductive agents include natural or artificial graphite, carbon black such as furnace black, acetylene black, and ketjen black, metals, and conductive ceramics. The conductive agent may be in the form of powder or fiber. The content of the conductive agent in the negative electrode mixture may 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 (binding agent) is not particularly limited, and examples thereof 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, and examples of the main component of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, and carbon.

[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 the above lower limit or more, 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 the above upper limit or less, an all-solid-state battery having an anode with excellent high-rate discharge performance and high active material utilization can be obtained.

[0072] (middle class) The 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 the intermediate layer can be formed, for example, from 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 may 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 be 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, alloys containing one or more of these metals, and stainless steel alloys.

[0075] The lower limit of the average thickness of the positive electrode substrate layer 7 is preferably 3 μm, more preferably 5 μm. The upper limit of the average thickness of the positive electrode substrate layer 7 is preferably 200 μm, more preferably 100 μm, and even more preferably 50 μm. By making the average thickness of the positive electrode substrate layer 7 equal to or greater than the above lower limit, the strength of the positive electrode substrate layer 7 can be sufficiently increased, allowing the positive electrode layer 2 to be formed satisfactorily. By making the average thickness of the positive electrode substrate layer 7 equal to or less than the above upper limit, sufficient volume for the 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 solid electrolyte, the sulfide solid electrolyte may be used, but it is more preferable to use a solid electrolyte with high oxidation resistance. Like the negative electrode mixture, the positive electrode mixture forming the positive electrode mixture layer 6 contains 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 not contain a solid electrolyte.

[0077] <Cathode active material> The positive electrode active material contained in the positive electrode mixture layer 6 can be a known material that is commonly used in all-solid-state batteries. x MeO y (Me represents at least one transition metal) 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) Li with spinel-type crystal structure, such as O2 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 (LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, Li2CoPO4F, etc.) in which 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 may be used in combination.

[0078] Positive electrode active materials include 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, and Li-Ba, as well as compounds other than those represented by the above general formula, such as MnO2, FeO2, TiO2, V2O5, and VO 13 A material having a redox potential higher than that of the negative electrode material, such as TiS2, can be used.

[0079] The lower limit of the content of the positive electrode active material in the positive electrode mixture is preferably 10% by mass, more preferably 15% by mass. The upper limit of the content of the positive electrode active material is preferably 60% by mass, more preferably 70% by mass, even more preferably 80% by mass, particularly preferably 90% by mass, and may even be 95% by mass. By setting the content of the positive electrode active material within the above range, the electrical capacity of the all-solid-state battery can be increased.

[0080] <Positive Electrode Mixture or Positive Electrode Composite> As in the case of the negative electrode, the positive electrode mixture is a mixture prepared by mixing a positive electrode active material, a solid electrolyte, etc. by mechanical milling, etc. For example, the mixture of a positive electrode active material and a solid electrolyte, etc. can be obtained by mixing a particulate positive electrode active material and a particulate solid electrolyte, etc. As in the case of the negative electrode, the positive electrode composite may be a composite having a chemical or physical bond between the positive electrode active material and the solid electrolyte, etc., or a composite obtained by mechanically combining the positive electrode active material and the solid electrolyte, etc. The composite is one in which the positive electrode active material and the solid electrolyte, etc. are present within a single particle, and examples thereof include a composite in which the positive electrode active material and the solid electrolyte, etc. are in an aggregated state, and a composite in which a coating containing the solid electrolyte, etc. is formed on at least a portion of the surface of the positive electrode active material. The cathode active material and the solid electrolyte contained in the cathode mixture constitute a cathode mixture or a cathode composite, thereby maintaining high ionic conductivity. Note that, although the sulfide solid electrolyte may be used as the solid electrolyte, it is more preferable to use a solid electrolyte having high oxidation resistance.

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

[0082] The lower limit of the average thickness of the positive electrode mixture layer 6 is preferably 30 μm, more preferably 60 μm. The upper limit of the average thickness of the positive electrode mixture layer 6 is preferably 1000 μm, more preferably 500 μm, and even more preferably 200 μm. By setting the average thickness of the positive electrode mixture 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 mixture 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. In addition to the sulfide solid electrolyte described above, examples of the electrolyte for the solid electrolyte layer include oxide solid electrolytes, other sulfide solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, and pseudo-solid electrolytes. Among these, sulfide solid electrolytes are preferred, and sulfide solid electrolytes are more preferred, from the viewpoints of good ionic conductivity and ease of interface formation. By including the sulfide solid electrolyte in the solid electrolyte layer 3, the solid electrolyte layer maintains high ionic conductivity while improving reduction resistance, thereby improving the initial coulombic efficiency of the all-solid-state battery.

[0084] The electrolyte for the solid electrolyte layer may have a crystalline structure or may be amorphous without a crystalline structure. The electrolyte for the solid electrolyte layer may contain an oxide such as Li3PO4, a halogen, a halogen compound, or the like.

[0085] The lower limit of the average thickness of the solid electrolyte layer 3 is preferably 1 μm, more preferably 3 μm. The upper limit of the average thickness of the solid electrolyte layer 3 is preferably 50 μm, more preferably 20 μm. By setting the average thickness of the solid electrolyte layer 3 to the above lower limit or more, it is possible to reliably insulate the positive electrode and the negative electrode. By setting the average thickness of the solid electrolyte layer 3 to the above upper limit or less, it is possible to increase the energy density of the all-solid-state battery.

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

[0087] (Sulfide solid electrolyte manufacturing process) In this step, the sulfide solid electrolyte is produced, for example, by the following procedure. (1) Nitride (Li 3 / 2 Al 1 / 2 Preparation of N) Li3N and AlN are mixed in a mortar and then pelletized. Then, heat treatment is performed to form Li 3 / 2 Al 1 / 2 N is produced. 3 / 2 Al 1 / 2 N" is written as "Li3AlN2". (2) Preparation of sulfide solid electrolyte The above Li in a given molar ratio 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. Methods for preparing the sulfide solid electrolyte precursor include mechanical milling and melt quenching. When preparing a sulfide solid electrolyte, a sulfide solid electrolyte precursor is prepared and then heat-treated at a temperature equal to or higher than the crystallization temperature, whereby the sulfide solid electrolyte can be prepared.

[0088] The crystallization temperature can be determined by measurement using a differential scanning calorimeter (DSC). 11 To obtain the β-Li3PS4 crystal structure, the heat treatment temperature is preferably 250°C or higher and 400°C or lower. To obtain the β-Li3PS4 crystal structure, the heat treatment temperature is preferably 200°C or higher and 400°C or lower. This is because heat treatment at a high temperature such as 500°C may result in a phase transition to the stable phase Li4P2S6. For example, 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° in X-ray diffraction measurement using CuKα radiation, the heat treatment temperature is preferably 250°C or higher and 400°C or lower.

[0089] In the above-described preparation process, a sulfide solid electrolyte containing Al as the element M is prepared. However, by using a similar method to the above-described preparation process, a sulfide solid electrolyte having a crystalline structure containing N and 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 can be prepared. For example, the nitride in the above-described preparation process can be Li. 3 / 2 Al1 / 2 Li instead of N 3 / 2 B 1 / 2 N and Li 5 / 3 Si 1 / 3 N, Li 9 / 5 Si 3 / 10 By using N, etc., it is possible to prepare a sulfide solid electrolyte containing elements such as B and Si as well as N. In addition to the nitrides mentioned above, other nitrides that can be used in the above preparation process include 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 Examples include N.

[0090] Furthermore, in the above-described fabrication process, a nitride composed of elements M, Li, and N was used as the starting material, but the method for fabricating the sulfide solid electrolyte of this embodiment is not limited to this.

[0091] The above-mentioned preparation process has been described using an Li2S-P2S5-based sulfide solid electrolyte as an example, but LGPS-type or argyrodite-type sulfide solid electrolytes can also be prepared using similar preparation processes. For example, in the above manufacturing process, the starting material is Li 3 / 2 Al 1 / 2 Although N, Li2S, and P2S5 were used, a Ge-containing compound such as GeS2 may be further added to prepare a LGPS-type sulfide solid electrolyte containing Ge. More specifically, starting materials are mixed in a predetermined molar ratio in a mortar or the like, and then subjected to mechanical milling, such as ball milling or vibration milling, to produce a sulfide solid electrolyte precursor, which is then heat-treated at a predetermined temperature or higher to produce the sulfide solid electrolyte. For example, Li 10 GeP2S 12 When preparing a sulfide solid electrolyte having a crystalline 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, further preferably 400° C. or higher and 650° C. or lower, and particularly preferably 450° C. or higher and 600° C. The heat treatment may be carried out under a reduced pressure atmosphere or an inert gas atmosphere.

[0092] (Negative electrode mixture production process) In this step, an anode mixture for forming the anode layer is prepared. When the anode mixture contains a mixture or composite including an anode active material and the sulfide solid electrolyte, this step includes mixing the anode active material and the sulfide solid electrolyte by, for example, mechanical milling to prepare a mixture or composite of the anode active material and the sulfide solid electrolyte.

[0093] (Electrolyte manufacturing process for solid electrolyte layer) In this step, the above-mentioned solid electrolyte layer electrolyte for forming the solid electrolyte layer is prepared. In this step, the predetermined material for the solid electrolyte layer electrolyte can be obtained by processing the predetermined material for the solid electrolyte layer electrolyte by a mechanical milling method. The predetermined material for the solid electrolyte layer electrolyte may be prepared by a melt quenching method, where the predetermined material for the solid electrolyte layer electrolyte is heated to above its melting temperature, melt-mixed in a predetermined ratio, and then quenched. Other methods for synthesizing the solid electrolyte layer electrolyte include, for example, a solid-phase method in which the solid electrolyte layer electrolyte is sintered under reduced pressure, a liquid-phase method such as solution deposition, a vapor-phase method (PLD), and mechanical milling followed by sintering in an argon atmosphere. Note that when the solid electrolyte layer electrolyte is a sulfide solid electrolyte, the above-mentioned sulfide solid electrolyte preparation step is performed in the preparation step for the solid electrolyte layer electrolyte.

[0094] (Positive electrode mixture production process) In this step, a cathode mixture for forming a cathode layer is prepared. The method for preparing the cathode mixture is not particularly limited and can be appropriately selected depending on the purpose. Examples include compression molding of a cathode active material, mechanical milling of a predetermined material for the cathode mixture, and sputtering using a target material for the cathode active material. When the cathode mixture contains a mixture or composite containing a cathode active material and the sulfide solid electrolyte, this step includes mixing the cathode active material and the sulfide solid electrolyte using, for example, mechanical milling to prepare a mixture or composite of the cathode active material and the sulfide solid electrolyte.

[0095] (Lamination process) In this step, an anode layer having an anode substrate layer and an anode mixture layer, a solid electrolyte layer, and a cathode layer having a cathode substrate layer and a cathode mixture layer are laminated. In this step, the anode layer, the solid electrolyte layer, and the cathode layer may be formed sequentially or in reverse, and the order of forming the layers is not particularly important. The anode layer is formed by pressure molding the anode substrate and the anode mixture, the solid electrolyte layer is formed by pressure molding an electrolyte for the solid electrolyte layer, and the positive electrode layer is formed by pressure molding the positive electrode substrate and the cathode mixture.

[0096] The anode layer, the solid electrolyte layer, and the positive electrode layer may be laminated by simultaneously pressure-molding the anode substrate, the anode mixture, the electrolyte for the solid electrolyte layer, the cathode substrate, and the positive electrode mixture. The positive electrode layer, the anode layer, or these layers may be molded in advance, and then pressure-molded together with the solid electrolyte layer to laminate them.

[0097] [Other embodiments] The present invention is not limited to the above-described embodiment, and can be implemented in various other forms, including those described above, with various modifications and improvements.

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

[0099] <Example> The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0100] [Example 1] The following process yields 99(0.70Li2S·0.30P2S5)·1Li 3 / 2 Al 1 / 2 N was synthesized. LiN and AlN were weighed out to a molar ratio of 1.2:1, mixed in a mortar, and then pelletized. Then, the mixture was heat-treated at 750°C for 1 hour to obtain LiN. 3 / 2 Al 1 / 2 N was prepared. 3 / 2 Al 1 / 2 XRD measurement revealed that the main phase of N is Li. 3 / 2 Al 1 / 2 It was confirmed that N. Next, Li2S (99.98%, Aldrich), P2S5 (99%, Aldrich), and Li3 / 2Al were mixed in a glove box with an argon atmosphere at a dew point of -50 °C or less. 1 / 2 The sulfide solid electrolyte of Example 1 was obtained by weighing N to a molar ratio of 69.3:29.7:1.0 and then mixing them in a mortar. This mixed sample was placed in a sealed 80 mL zirconia pot containing 160 g of 4 mm diameter zirconia balls. Milling was performed for 45 hours at an orbital speed of 510 rpm using a planetary ball mill (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 but not higher than 100°C above the crystallization temperature. The crystallization temperature was determined by DSC measurement. The DSC measurement was performed under the following conditions: A DSC apparatus (Rigaku, Thermo Plus DSC8230) was used, and a stainless steel sealed pan was used, and the temperature was increased from room temperature to 400°C at a rate of 10°C / min.

[0101] [Examples 2 to 9] The composition of sulfide solid electrolyte is (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, or 40.

[0102] [Example 10] Li2S, P2S5 and Li are used as raw materials for sulfide solid electrolytes. 3 / 2 Al 1 / 2 N to Li2S:P2S5:Li 3 / 2 Al 1 / 2 The sulfide solid electrolyte of Example 10 was synthesized in the same manner as in Example 1, except that the components were weighed out so that N=67.5:22.5:10.0 (mol %).

[0103] [Example 11] Li2S, P2S5 and Li are used as raw materials for sulfide solid electrolytes. 3 / 2 Al 1 / 2 N to Li2S:P2S5:Li 3 / 2 Al 1 / 2 A sulfide solid electrolyte of Example 11 was synthesized in the same manner as in Example 1, except that the components were weighed so that N=35.0:35.0:30.0 (mol %).

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

[0105] [Example 13] Li2S, P2S5 and Li are used as raw materials for sulfide solid electrolytes. 3 / 2 Al 1 / 2 N to Li2S:P2S5:Li 3 / 2 Al 1 / 2 A sulfide solid electrolyte of Example 13 was synthesized in the same manner as in Example 1, except that the components were weighed out so that N=50.3:24.7:25.0 (mol %).

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

[0107] [Examples 15 to 18] LiN and BN were weighed out to a molar ratio of 1.1:1, mixed in a mortar, pelletized, and then heat-treated at 800°C for 10 minutes to obtain Li 3 / 2 B 1 / 2 N was prepared. 3 / 2 B 1 / 2 XRD measurement revealed that the main phase of N is Li. 3 / 2 B 1 / 2 It was confirmed that N. Next, Li 3 / 2 Al 1 / 2 Li above instead of N 3 / 2 B 1 / 2 N was used, and the sulfide solid electrolyte had the composition formula (100-z)(0.70Li2S·0.30P2S5)·zLi 3 / 2 B 1 / 2 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 N was changed to 1, 10, 20, or 30. [Examples 19 to 23] Li3N and Si3N4 were weighed out to a molar ratio of 5.1:1, mixed in a mortar, pelletized, and then heat-treated at 800°C for 10 minutes to obtain Li 5 / 3 Si 1 / 3 N was prepared. 5 / 3 Si 1 / 3 XRD measurement revealed that the main phase of N is Li. 5 / 3 Si 1 / 3 It was confirmed that N. Next, Li 3 / 2 Al 1 / 2 Li above instead of N 5 / 3 Si 1 / 3N was used, and the sulfide solid electrolyte had the composition formula (100-z)(0.70Li2S·0.30P2S5)·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, or 45.

[0108] [Comparative Example 1] The raw material for sulfide solid electrolyte is Li 3 / 2 Al 1 / 2 A 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 mechanical milling. In an argon atmosphere glove box with a dew point below -50°C, the raw materials for the sulfide solid electrolyte, Li2S and P2S5, were weighed out to a ratio of Li2S:P2S5 = 75:25 (mol%) and then mixed in an agate mortar. The mixture was placed in a sealed 80 mL zirconia pot containing 160 g of 4 mm diameter zirconia balls. Milling was performed for 45 hours at an orbital speed of 510 rpm using a planetary ball mill (FRITSCH, model number Premium line P-7). This process yielded the sulfide solid electrolyte of Reference Example 1.

[0110] [Reference example 2] Li 3 / 2 Al 1 / 2 A sulfide solid electrolyte of Reference Example 2 was synthesized in the same manner as in Example 1, except that LiN was used instead of N and the value of z in the composition formula of the sulfide solid electrolyte (100-z)(0.70LiS 0.30P2S5) zLi3N was changed to 20.

[0111] [Example 24] By the following process, 87.6(Li10GeP2S12) 12.4Li 3 / 2 Al 1 / 2 N was synthesized. LiN and AlN were weighed out to a molar ratio of 1.2:1, mixed in a mortar, and then pelletized. Then, the mixture was heat-treated at 750°C for 1 hour to obtain LiN. 3 / 2 Al 1 / 2 N was produced. Next, in a glove box with an argon atmosphere at a dew point of -50 °C or less, Li2S (99.98%, Aldrich), P2S5 (99%, Aldrich), GeS2 (99.99%, High Purity Chemical Laboratory), and Li 3 / 2 Al 1 / 2 The sulfide solid electrolyte of Example 24 was obtained by weighing out N to a molar ratio of 5:1:1:0.14 and then mixing them in a mortar. This mixed sample was placed in a sealed 80 mL zirconia pot containing 160 g of 4 mm diameter zirconia balls. It was milled for 40 hours at an orbital speed of 370 rpm using a planetary ball mill (FRITSCH, model number Premium line P-7). It was then heat-treated at 550°C for 8 hours to obtain the sulfide solid electrolyte of Example 24.

[0112] [Example 25, Example 26, Comparative Example 2] The composition formula of sulfide solid electrolyte is (100-z)(Li 10 GeP2S 12 )·zLi 3 / 2 Al 1 / 2 The sulfide solid electrolytes of Examples 25 and 26 and Comparative Example 2 were synthesized in the same manner as in Example 1, except that the value of z in N was changed to 30.2, 42.5, and 60.9. Comparative Example 3 The raw material for sulfide solid electrolyte is Li 3 / 2 Al 1 / 2 A sulfide solid electrolyte of Comparative Example 3 was synthesized in the same manner as in Example 24, except that N was not used. [Reference example 3] The raw material for sulfide solid electrolyte is Li 3 / 2 Al 1 / 2 The sulfide solid electrolyte of Reference Example 3 was synthesized in the same manner as in Example 24, except that LiO (99%, Kojundo Chemical Laboratory) was used instead of N and weighed out so that the ratio of LiS:P2S5:GeS2:Li2O was 4.86:1:1:0.14 (mol%). [Reference example 4] The raw material for sulfide solid electrolyte is Li 3 / 2 Al 1 / 2 A 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 out so that the ratio of Li2S:P2S5:GeS2:Al2S3 was 5:1:0.93:0.035 (mol%).

[0113] [evaluation] (1)XRD analysis X-ray diffraction measurements were performed using the following method. An airtight sample holder for X-ray diffraction measurements was filled with the sulfide solid electrolyte powders of the examples and comparative examples in an argon atmosphere with a dew point of -50°C or lower. Powder X-ray diffraction measurements were performed using an X-ray diffractometer ("miniFlex II" manufactured by Rigaku). The radiation source was CuKα radiation, the tube voltage was 30 kV, and the tube current was 15 mA. Diffracted X-rays were passed through a 30 μm-thick Kβ filter and detected with a high-speed one-dimensional detector (model number: D / teX Ultra2). 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] 2 shows X-ray diffraction (XRD) spectra in the range of 2θ=10° to 40° for Examples 1 to 3, 6, 8, 9, 10, and 11 and Comparative Example 1. Table 1 shows the crystal structures identified from the XRD spectra for 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 for Examples 24 to 26, Comparative Examples 2 and 3, and Reference Examples 3 and 4. Note that "Unknown" in Table 2 indicates that a diffraction peak was observed that could not identify the crystal structure.

[0116] (2) Raman spectroscopy The Raman spectrum was measured using a laser Raman spectrophotometer (Horiba Ltd., "LabRAM HR Revolution") at 100 cm under the conditions of an excitation laser wavelength of 532 nm (YAG laser) and a grating of 600 gr / mm. -1 From 1800cm -1 Raman spectroscopy was performed in the wavenumber range of

[0117] 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 at 25° C. by measuring AC impedance using a Bio-Logic VMP-300 according to the method described above.

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

[0120] FIG. 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 and activation energies at 25° C. for Examples 24 to 26, Comparative Examples 2 and 3, and Reference Examples 3 and 4.

[0122] (4) Initial coulombic efficiency and charge / discharge performance (4-1) Preparation of positive electrode active material A LiNbO3 precursor solution was prepared by dissolving metallic Li in ultra-dehydrated ethanol, followed by dissolving niobium ethoxide (Nb(OC2H5)5). A rolling fluidized coating device (FD-MP-01F) manufactured by Powrex Corporation was used to coat LiNi 0.8 Co 0.15 Al 0.05The particle surface of O2 (NCA) was coated with LiNbO3 precursor. The LiNbO3-coated NCA was fabricated by heat-treating the NCA coated with 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 to a ratio of LiNbO3-coated NCA:Li3PS4 = 70:30 (mass%) and then mixed in an agate mortar. The sulfide solid electrolyte of Example 1 was placed in a powder molding machine with an inner diameter of 10 mm and then pressure-molded using a hydraulic press. After releasing the pressure, the NCA-Li3PS4 mixed powder was placed on one side of the solid electrolyte layer of Example 1 and pressure-molded at 360 MPa per sample area for 5 minutes. After releasing the pressure, a metal Li foil was attached 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-sealed in an aluminum laminate cell and pressed using a stainless steel plate to obtain an all-solid-state battery cell (Li-NCA half cell).

[0124] All-solid-state battery cells (Li-NCA half cells) including the sulfide solid electrolytes of Examples 2, 4, and Comparative Example 1 were obtained by performing the same operation as in Example 1, except that the sulfide solid electrolyte of Example 1 was replaced with the sulfide solid electrolytes of Examples 2, 4, and Comparative Example 1.

[0125] (4-3) Charge / discharge test A 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 conducted in a thermostatic chamber at 50°C. Charging was performed using constant current / constant voltage (CCCV) charging with a charging current of 0.125 mA / cm2 and an upper charge voltage limit of 4.35 V. The charge termination condition was that the charging current reached 0.0625 mA / cm2. Discharging was performed using constant current (CC) discharging with a discharge current of 0.125 mA / cm2 and an end-of-discharge voltage of 2.85 V. The rest time between charging and discharging was 30 minutes. The percentage of the above initial discharge capacity relative to the amount of electricity in the initial charge at this time was calculated as the "initial coulombic efficiency (%)."

[0126] 5 shows the initial charge-discharge performance of Examples 1, 2, 4 and Comparative Example 1. Table 1 shows the initial coulombic efficiencies (%) of Examples 1, 2, 4 and Comparative Example 1.

[0127] (5) Reduction resistance of sulfide solid electrolyte (5-1) Evaluation test using reduction resistance evaluation cell In a glove box with an argon atmosphere and a dew point of −50°C or less, the sulfide solid electrolyte of Example 1 and SUS316L powder were weighed out to a mass ratio of 1:4 and then mixed in an agate mortar. The sulfide solid electrolyte (Li3PS4) of Reference Example 1 was placed in a powder molding machine with an inner diameter of 10 mm and then pressure-molded using a hydraulic press. After releasing the pressure, a mixed powder of the SUS316 powder and the sulfide solid electrolyte powder of Example 1 was placed on one side of the Li3PS4 layer and pressure-molded at 360 MPa for 5 minutes. After releasing the pressure, a metallic Li foil was attached to the opposite side of the Li3PS4 layer and pressure-molded to obtain a laminate of the sulfide solid electrolyte mixture layer of Example 1, the Li3PS4 layer, and the metallic Li foil. This laminate was sealed under reduced pressure in an aluminum laminate cell and compressed using a stainless steel plate to obtain a cell for evaluating reduction resistance, in which the mixture layer of the sulfide solid electrolyte of Example 1 was used as a working electrode and a metallic Li foil was used as a counter electrode. The charging test conditions were a measurement temperature of 50°C, constant current constant voltage (CCCV) charging, and a charging current of 0.1 mA / cm 2The minimum charge potential was 0.01 V, and the total charge time was 100 hours. Here, the reaction in which the mixture layer of the sulfide solid electrolyte in Example 1 is reduced is referred to as "charging." The amount of charge electricity 20 hours after the start of charging was taken as the reductive decomposition capacity (mAh / g) of the sulfide solid electrolyte after 20 hours. Because the SUS316L powder is stable at a potential of 0 V vs. Li / Li+, the only redox species is the sulfide solid electrolyte. Therefore, the amount of electricity flowing through this evaluation cell represents the amount of reductive decomposition of the sulfide solid electrolyte. Using the same procedure, the sulfide solid electrolytes of Examples 2, 4, 8 to 17, 19, 20, and 22 and Comparative Example 1 were evaluated for reduction resistance.

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

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

[0130] Graphite particles (Gr) and sulfide solid electrolyte (Li) of Example 24 10.21 GeP2Al 0.07 S 12 N 0.14 ) to Gr:Li 10.21 GeP2Al 0.07 S 12 N 0.14 After weighing the two components so that the ratio was 60:40 (mass%), they were mixed in an agate mortar. Li3PS4 was placed in a powder molding machine with an inner diameter of 10 mm, and then pressure-molded using a hydraulic press. After releasing the pressure, Gr-Li was applied to one side of the Li3PS4 layer. 10.21 GeP2Al 0.07 S 12 N 0.14The mixed powder was charged and pressure-molded. After the pressure was released, a metallic Li foil was attached to the opposite surface of the Li3PS4 layer and pressure-molded to obtain a laminate of the sulfide solid electrolyte mixture layer of Example 24, the Li3PS4 solid electrolyte layer, and the metallic Li foil. This laminate was sealed under reduced pressure in an aluminum laminate cell and pressed using a stainless steel plate to obtain an all-solid-state battery cell (Li-Gr half cell) with the sulfide solid electrolyte mixture layer of Example 24 as the working electrode and the metallic Li foil as the counter electrode.

[0131] All-solid-state battery cells (Li-Gr half cells) including the sulfide solid electrolytes of Examples 25, 26, and Comparative Example 3 were obtained by the same operation as in Example 24, except that the sulfide solid electrolyte of Example 24 was replaced with the sulfide solid electrolytes of Examples 25, 26, and Comparative Example 3.

[0132] A discharge test (lithiation of Gr) was conducted on the above all-solid-state battery cell (Li-Gr half cell) under the following conditions. The discharge test was conducted in a thermostatic chamber at 50°C. The discharge current was 0.125 mA / cm. 2 The discharge capacity Q was differentiated with respect to the voltage V to obtain the differential value dQ / dV, and a graph (dQ / dV curve) was plotted showing the relationship between the voltage V and the differential value dQ / dV.

[0133] 9 shows the dQ / dV curves of Examples 24 to 26 and Comparative Example 3. Table 2 shows the dQ / dV curves of Examples 24 to 26 and Comparative Example 3, where dQ / dV=-100 mAhg. -1 V -1 The figure shows the value of the voltage V at 0.4V. It can be seen from Figure 9 that the amount of change in dQ / dV is large around 0.4V. The lithiation potential of Gr is about 0.1V vs Li / Li. + Therefore, it is presumed that the change in dQ / dV around 0.4 V is due to the reductive decomposition of the sulfide solid electrolyte. Therefore, the dQ / dV of the all-solid-state battery cell (Li-Gr half cell) of this example is -100 mAhg -1 V -1 The shift in the value of the voltage V at 1000 kJ / cm2 in the less noble direction means that the reductive decomposition potential of the sulfide solid electrolyte has shifted in the less noble direction, that is, the reduction resistance has improved.

[0134] (6) Atmospheric stability assessment To evaluate the chemical stability of sulfide solid electrolytes in the atmosphere, the amount of hydrogen sulfide generated was measured. In a glove box with an argon atmosphere and a dew point of -50°C or less, 100 mg of sulfide solid electrolyte powders from the Examples and Comparative Examples were uniaxially pressed for 5 minutes at 360 MPa per sample area using a powder press with an inner diameter of 10 mm to obtain pellets. The pellets were then placed in a sealed desiccator (effective volume 2100 cm). 3 The hydrogen sulfide generated was measured using a hydrogen sulfide sensor (TPA-5200E). The measurement was stopped when the hydrogen sulfide sensor's upper detection limit of 50 ppm was reached or when 40 minutes had elapsed. Amount of hydrogen sulfide generated from 1g of solid electrolyte V (cm 3 / g) is the obtained concentration C (ppm), the actual volume of the desiccator L (cm 3 ) and the mass m (g) of the pellet, using the following formula: V(cm 3 / g) = C × L × 10 -6 / m

[0135] 6 and 7 show the relationship between the time of exposure to the atmosphere (minutes) and the amount of hydrogen sulfide generated (cm ) for the sulfide solid electrolyte pellets of the above-mentioned Examples and Comparative Examples. 3 1 is a graph showing the relationship between the temperature and the pressure (MPa) and the pressure (MPa). FIG. 6 shows the amount of hydrogen sulfide generated in Example 4, Example 6, and Comparative Example 1 up to 20 minutes of exposure to the atmosphere, and FIG. 7 shows the amount of hydrogen sulfide generated in Example 6 and Reference Example 1 up to 40 minutes of exposure to the atmosphere.

[0136] [Table 1]

[0137] As shown in Table 1, the sulfide solid electrolytes of the Examples, which contained N and any one of Al, B, or Si as the element M and had a crystalline structure, had a suppressed reductive decomposition capacity 20 hours after the start of charging and excellent initial coulombic efficiency compared to the sulfide solid electrolyte of Comparative Example 1. The sulfide solid electrolytes of Examples 1, 2, 4 to 8, 10, 12 to 17, and 19 to 22 also had good ionic conductivity at 25°C. On the other hand, the sulfide solid electrolyte of Comparative Example 1, which did not contain the elements M and N, had good ionic conductivity, but the reductive decomposition capacity 20 hours after the start of charging was large and the initial coulombic efficiency was poor.

[0138] From Table 1, when the molar ratio of Li to P is 2.77 or more and 3.38 or less, and the molar ratio of N to P is 0.28 or more and 0.65 or less, 10 -3 Scm -1 A sulfide solid electrolyte having a structure that is expected to exhibit the above ionic conductivity and good atmospheric stability was obtained, and it was therefore confirmed that the composition of the sulfide solid electrolyte having such values ​​is particularly preferable. Furthermore, when the sulfide solid electrolyte contained Al as the element M, LiS did not precipitate even when the content ratios of Li and N were large, such as when the molar ratio of Li to P was 3.40 and the molar ratio of N to P was 0.71. This suggests that it is particularly preferable to contain Al as the element M.

[0139] As shown in Figure 2, peaks were observed in the XRD spectrum of the sulfide solid electrolytes of all Examples and Comparative Examples, confirming that they had a crystalline structure. 11The sulfide solid electrolytes of Examples 4 to 9 had a specific crystal structure A with diffraction peaks at 2θ = 17.9°, 19.1°, 29.1°, 29.8°, and 30.9°. The sulfide solid electrolyte of Example 10 had a specific crystal structure B with diffraction peaks at 2θ = 17.9°, 19.1°, 29.1°, and 29.8°.

[0140] As shown in the Raman spectrum of FIG. 3, the sulfide solid electrolyte of the example becomes more and more bridging sulfur P2S7 as z increases, i.e., as the nitrogen (N) content increases. 4- Raman shift of 406 cm -1 The peak around the 3- Raman shift of 423cm -1 Therefore, the molecular structures of Examples 1 and 15 in Table 1 based on the Raman spectra are PS4 3- , P2S7 4- and P2S6 4- The molecular structures of Examples 7 to 9, Examples 11 to 14, and Examples 20 to 22 based on Raman spectroscopy are presumed to be composed of PS4 3- It is assumed to consist of

[0141] 6 and 7, it was confirmed that the amounts of hydrogen sulfide generated in Example 4 and Example 6 were smaller than the amount of hydrogen sulfide generated in Comparative Example 1. In particular, Example 6, where z = 20, exhibited a superior effect of suppressing hydrogen sulfide generation compared to Comparative Example 1 and Reference Example 1. This suggests that the sulfide solid electrolyte not only has high reduction resistance but also excellent atmospheric stability. The reason why the sulfide-based solid electrolyte has a high suppression effect on hydrogen sulfide generation is presumed to be as follows: As shown in the Raman spectrum in FIG. 3, the sulfide solid electrolyte of the example has a tendency to exhibit a high suppression effect on hydrogen sulfide generation. As z increases, that is, as the N content increases, the sulfide solid electrolyte of the example exhibits a tendency to exhibit a high suppression effect on hydrogen sulfide generation. 4- Raman shift of 406 cm -1The peaks around the region where the sulfide solid electrolyte is used are reduced. In addition, in the XRD (X-ray diffraction) spectrum shown in FIG. 2, the sulfide solid electrolyte of the example does not show any peaks derived from Li2S. From these facts, it can be seen that by increasing the N content, the sulfide solid electrolyte can prevent the formation of so-called bridged sulfur P2S7, which is unstable in the atmosphere. 4- It is presumed that the effect of suppressing the generation of hydrogen sulfide can be improved because (S3P-S-PS3) is reduced and Li2S, which easily reacts with water, is not substantially contained. In addition, Example 6 (z=20) is a cross-linked sulfur P2S7 4- The reason why the amount of hydrogen sulfide generated is less than that in Reference Example 1, which does not have N, is thought to be because the introduction of N into the structure of the solid electrolyte forms a three-dimensional network, strengthening the bonds. It is generally known that the introduction of N into oxynitride glass, in which part of the O in oxide glass is replaced with N, improves water resistance.

[0142] Comparing Examples 6, 17, and 21 with Reference Example 2, in which the N content was fixed at z=20 and y=0.70, it was found that Li2S precipitated only in Reference Example 2, which did not contain the element M. This suggests that the inclusion of the element M can suppress the precipitation of Li2S.

[0143] The reason why the sulfide solid electrolyte containing element M can suppress the precipitation of Li2S is thought to be as follows. When Li3N is used as the starting material for a sulfide-based solid electrolyte containing N, Li3N reacts dramatically with P2S5, releasing N2 and causing Li2S to precipitate. This is thought to be because the energy of N defect formation in Li3N is small. In contrast, in the present invention, α M β Since the N defect formation energy of N is greater than that of Li3N, it is thought that the reaction proceeds slowly during the synthesis of sulfide-based solid electrolytes, suppressing the release of N2 and the precipitation of Li2S. The "defect formation energy" referred to here is 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 defect atom, and refers to 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 crystalline structure had excellent ionic conductivity at 25°C. Also, dQ / dV=-100mAhg -1 V -1 The shift of the value of the voltage V at 1000 kJ / cm2 in the less noble direction means that the reductive decomposition potential of the sulfide solid electrolyte has shifted in the less noble direction, i.e., that the reduction resistance has improved. Therefore, the sulfide solid electrolytes of the examples were also excellent in reduction resistance. In particular, the sulfide solid electrolyte of Example 24 was found to exhibit superior ionic conductivity at 25°C compared to the sulfide solid electrolytes of Reference Examples 3 and 4.

[0146] The above results demonstrate that the sulfide solid electrolyte according to the present invention has high reduction resistance and can improve the initial coulombic efficiency of an all-solid-state battery including the sulfide solid electrolyte. The results also demonstrate that the sulfide solid electrolyte according to the present invention can improve atmospheric stability. [Industrial Applicability]

[0147] The all-solid-state battery including the sulfide solid electrolyte according to the present invention has excellent initial coulombic efficiency, and is therefore suitable for use as, for example, a lithium-ion all-solid-state battery for HEVs. [Explanation of symbols]

[0148] 1. Negative electrode layer 2 Positive electrode layer 3 Solid electrolyte layer 4 Negative electrode base material layer 5. Negative electrode mixture layer 6 Positive electrode mixture 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 crystalline structure.

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