Solid electrolyte, composite material, battery, and method for producing solid electrolyte

Abstract

To provide a solid electrolyte capable of suppressing a decrease in cycle characteristics as a main object.SOLUTION: A solid electrolyte includes Li, a PS43-condition structure, and a BH4- structure, satisfies the following conditions (i) to (iii). Condition (i): an integral area of a peak α having a vertex in a range of 42 ppm±1 ppm in a 11B-NMR measurement is 50% or more with respect to a total integrated area of all peaks. Condition (ii): an integral area of a peak β having the vertex in a range of 90.5 ppm±1 ppm is 50% or more with respect to the total integrated area of all peaks in a 31 P-NMR measurement. Condition (iii): a thermal capacity of an endothermic peak appeared in a range of 115°C±10°C is less than 30 J / g in a temperature increasing step of a DSC measurement.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a solid electrolyte, a composite material, a battery, and a method for manufacturing a solid electrolyte.

Background Art

[0002] In recent years, the development of batteries has been actively carried out. For example, in the automotive industry, the development of batteries used in battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), or hybrid electric vehicles (HEVs) has been promoted. Further, as an electrolyte used in a battery, an inorganic solid electrolyte is known. The inorganic solid electrolyte has an advantage that it is easier to simplify a safety device as compared with an electrolytic solution (liquid electrolyte) containing a flammable organic solvent.

[0003] For example, Patent Document 1 discloses a compound represented by the formula: Li 7-x PS 6-x X x-z (BH4) z (where X is selected from the group consisting of Cl, Br, I, F, and CN, 0 < x ≦ 2, and 0 < z ≦ 0.50).

[0004] Patent Document 2 discloses an alluaudite-type solid electrolyte material containing Li, T, X, and A, where T is at least one element selected from the group consisting of P, As, Si, Ge, Al, and B, X is one or more halogens or BH4, BF4, NH2, or NO3 or a combination thereof, A is one or more of S, Se, and N, and the above solid electrolyte material has peaks at 2θ = 14.6° ± 0.25°, 15.3° ± 0.25°, and 25.1° ± 0.25° in X-ray diffraction measurement using Cu-Kα(1,2) = 1.5418 Å.

[0005] Patent Document 3 discloses a solid electrolyte material containing Li, T, X, and A, in which T contains at least one element selected from the group consisting of Sb, P, As, Si, Ge, Al, B, and W, X contains one or more halogens, pseudohalogens, or N, and A contains one or more of S or Se, and which has peaks at 2θ=14.5°±0.50°, 16.8°±0.50°, 23.9°±0.50°, 28.1°±0.50°, and 32.5°±0.50° in X-ray diffraction measurement using Cu-Kα(1,2)=1.54064 Å. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2020-534245 [Patent Document 2] Special Publication No. 2023-518850 [Patent Document 3] Special Publication No. 2023-543227 Summary of the Invention [Problem to be solved by the invention]

[0007] During the synthesis of a solid electrolyte, some raw materials may remain or impurities may be generated. When a solid electrolyte containing a large amount of raw materials or impurities is used in a battery, the cycle characteristics tend to deteriorate. Specifically, raw materials and impurities are usually electrochemically unstable, so that oxidation or reduction occurs due to changes in potential, and the cycle characteristics tend to deteriorate.

[0008] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a solid electrolyte capable of suppressing deterioration in cycle characteristics. [Means for solving the problem]

[0009] [1] Li and PS4 3- Structure and BH4 -and a structure, The following conditions (i) to (iii) are met: Condition (i): 11 In B-NMR measurement, the integrated area of peak α having an apex in the range of 42 ppm ± 1 ppm is 50% or more of the total integrated area of all peaks. Condition (ii): 31 In P-NMR measurement, the integrated area of peak β having an apex in the range of 90.5 ppm ± 1 ppm is 50% or more of the total integrated area of all peaks. Condition (iii): A solid electrolyte in which the heat capacity of an endothermic peak appearing in the range of 115°C ± 10°C during the temperature rise step of a DSC measurement is less than 30 J / g.

[0010] [2] The solid electrolyte according to [1], wherein the solid electrolyte has an argyrodite-type crystal phase.

[0011] [3] The solid electrolyte according to [1] or [2], wherein, under the condition (i), the integrated area of the peak α is 90% or more of the total integrated area of all peaks.

[0012] [4] The solid electrolyte according to any one of [1] to [3], wherein, under the condition (ii), the integrated area of the peak β is 90% or more of the total integrated area of all peaks.

[0013] [5] The solid electrolyte according to any one of [1] to [4], wherein, under the condition (iii), the heat capacity of the endothermic peak is 20 J / g or less.

[0014] [6] The above PS4 3- Structure and above BH4 - The total structure of the PS4 3- The solid electrolyte according to any one of [1] to [5], wherein the molar ratio of the structure is 20% or more and 40% or less.

[0015] [7] The solid electrolyte according to any one of [1] to [6], wherein the solid electrolyte has a composition represented by xLi3PS4-(100-x)LiBH4 (x is 20 or more and 40 or less).

[0016] [8] A composite material comprising the solid electrolyte according to any one of [1] to [7] and at least one of an electrode active material, a conductive material, and a binder.

[0017] [9] A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, At least one of the positive electrode layer, the negative electrode layer, and the electrolyte layer contains the composite material according to [8].

[0018]

[10] The battery according to [9], wherein the electrolyte layer contains a solid electrolyte.

[0019]

[11] A method for producing a solid electrolyte according to any one of [1] to [7], a preparation step of preparing a sulfide solid electrolyte having a composition represented by Li3PS4 and a hydride solid electrolyte having a composition represented by LiBH4; a precursor preparation step of applying mechanical energy to a raw material mixture containing the sulfide solid electrolyte and the hydride solid electrolyte to prepare a precursor; a heat treatment step of heat-treating the precursor to prepare the solid electrolyte; The method for producing a solid electrolyte comprising the steps of:

[0020]

[12]

[11] The method for producing a solid electrolyte according to

[11] , wherein in the preparing step, the sulfide solid electrolyte is amorphous. [Effects of the Invention]

[0021] The present disclosure has an effect of providing a solid electrolyte that can suppress deterioration of cycle characteristics. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. [Figure 2] FIG. 1 is a flow diagram illustrating a method for producing a solid electrolyte according to the present disclosure. [Figure 3] 1 shows the results of 11B-NMR measurement of the solid electrolytes obtained in Example 1, Comparative Example 1, and Comparative Example 2. [Figure 4] 3 shows the results of 31P-NMR measurement of the solid electrolytes obtained in Example 1, Comparative Example 1, and Comparative Example 2. [Figure 5] 1 shows the results of DSC measurements of the solid electrolytes obtained in Example 1, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0023] The solid electrolyte, composite, battery, and method for producing the solid electrolyte according to the present disclosure will be described in detail below.

[0024] A. Solid electrolyte The solid electrolyte in this disclosure is Li and PS4 3- Structure and BH4 - Furthermore, the solid electrolyte of the present disclosure satisfies the following conditions (i) to (iii).

[0025] Condition (i): 11 In B-NMR measurement, the integrated area of peak α having an apex in the range of 42 ppm±1 ppm is 50% or more of the total integrated area of all peaks. Condition (ii): 31 In P-NMR measurement, the integrated area of peak β having an apex in the range of 90.5 ppm±1 ppm is 50% or more of the total integrated area of all peaks. Condition (iii): In the temperature-raising step of the DSC measurement, the heat capacity of the endothermic peak appearing in the range of 115°C ± 10°C is less than 30 J / g.

[0026] According to the present disclosure, the above conditions (i) to (iii) are satisfied, and thus a solid electrolyte capable of suppressing deterioration in cycle characteristics is obtained. During the synthesis of a solid electrolyte, some raw materials may remain or impurities may be generated. When a solid electrolyte containing a large amount of raw materials or impurities is used in a battery, cycle characteristics are likely to deteriorate. Specifically, raw materials and impurities are usually electrochemically unstable, and therefore oxidation or reduction occurs due to changes in potential, making it likely that cycle characteristics will deteriorate. In contrast, the present disclosure satisfies the above conditions (i) to (iii), and therefore few raw materials remain in the solid electrolyte, and the solid electrolyte also contains few impurities. Therefore, oxidation or reduction does not easily occur due to changes in potential, resulting in an electrochemically stable solid electrolyte, and deterioration in cycle characteristics can be suppressed.

[0027] Condition (i) in this disclosure is: 11 In B-NMR measurement, the integrated area of peak α, which has its apex in the range of 42 ppm ± 1 ppm, is specified to be 50% or more of the total integrated area of all peaks. Peak α is BH4 - This peak is due to B in the structure. The proportion of the integrated area of peak α may be 70% or more, 80% or more, 90% or more, or 95% or more.

[0028] Condition (ii) in this disclosure is: 31 In P-NMR measurement, the integrated area of peak β, which has its apex in the range of 90.5 ppm ± 1 ppm, is 50% or more of the total integrated area of all peaks. 3- This peak is due to P in the structure. The proportion of the integrated area of peak β may be 70% or more, 80% or more, or 90% or more.

[0029] The condition (iii) in the present disclosure specifies that the heat capacity of the endothermic peak appearing in the temperature rising step of the DSC measurement in the range of 115°C ± 10°C is less than 30 J / g. The above-mentioned condition (i) specifies that the BH4 contained in the raw material (e.g., LiBH4) remaining in the solid electrolyte is - The conditions also include the above. On the other hand, since the raw materials remaining in the solid electrolyte are usually thermochemically unstable compared to the target solid electrolyte, DSC measurement can distinguish between the raw materials remaining in the solid electrolyte and the target solid electrolyte. The heat capacity of the endothermic peak may be 25 J / g or less, or may be 20 J / g or less.

[0030] The solid electrolyte of the present disclosure preferably has an argyrodite-type crystalline phase. The presence of an argyrodite-type crystalline phase in a solid electrolyte can be confirmed by X-ray diffraction (XRD) measurement. In XRD measurement using CuKα radiation, the solid electrolyte preferably has peaks at 2θ=17.0°±0.5°, 24.1°±0.5°, 28.3°±0.5°, 29.6°±0.5°, and 38.6°±0.5°. These peaks are typical peaks of an argyrodite-type crystalline phase. The positions of these peaks may be within a range of ±0.3° or ±0.1°, respectively.

[0031] The solid electrolyte of the present disclosure preferably contains an argyrodite-type crystalline phase as a major phase. The "major phase" refers to the crystalline phase having the highest peak intensity in XRD measurement using CuKα radiation. Furthermore, it is preferable that the solid electrolyte does not exhibit a Li2S peak in XRD measurement. Similarly, it is preferable that the solid electrolyte does not exhibit a P2S5 peak in XRD measurement.

[0032] Solid electrolyte is PS4 3- Structure and BH4 - PS4 with structure 3- Structure and BH4 - PS4 for the total structure 3-The molar ratio of the structure is, for example, 20% or more, or may be 23% or more, or may be 25% or more, while the molar ratio is, for example, 40% or less, or may be 38% or less, or may be 35% or less.

[0033] The solid electrolyte preferably has a composition represented by xLi3PS4-(100-x)LiBH4. In this composition, x is typically 20 or more, and may be 23 or more, or 25 or more. On the other hand, x is typically 40 or less, and may be 38 or less, or 35 or less.

[0034] The solid electrolyte of the present disclosure preferably has high ionic conductivity. The ionic conductivity at 25°C is, for example, 1×10 -4 S / cm or more, 5×10 -4 The average particle diameter (D 50 ) is, for example, 0.1 μm or more and 50 μm or less. 50 ) refers to the volume cumulative particle size measured by a laser diffraction / scattering particle size distribution analyzer. The use of the solid electrolyte is not particularly limited, but it is preferably used in, for example, a battery.

[0035] B. Composite material The composite material in the present disclosure contains the above-described solid electrolyte and at least one of an electrode active material, a conductive material, an electrolyte, and a binder.

[0036] According to the present disclosure, the use of the above-described solid electrolyte provides a composite that can suppress deterioration of cycle characteristics. Examples of the composite in the present disclosure include a positive electrode composite used in a positive electrode layer of a battery, a negative electrode composite used in a negative electrode layer of a battery, and an electrolyte layer composite used in an electrolyte layer of a battery.

[0037] 1. Cathode mixture The positive electrode mixture usually contains at least the above-described solid electrolyte and a positive electrode active material. The positive electrode mixture may further contain at least one of a conductive material and a binder.

[0038] The solid electrolyte is the same as that described above in "A. Solid Electrolyte." The proportion of the solid electrolyte in the positive electrode composite is, for example, 10% by weight or more, or may be 20% by weight or more, or may be 30% by weight or more. On the other hand, the proportion of the solid electrolyte in the positive electrode composite is, for example, 50% by weight or less.

[0039] Examples of the positive electrode active material include oxide active materials, such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 )O4, and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0040] A coating layer containing a Li-ion conductive oxide may be formed on the surface of the oxide active material. This is because it can suppress the reaction between the oxide active material and the solid electrolyte (especially a sulfide solid electrolyte). An example of the Li-ion conductive oxide is LiNbO3. The thickness of the coating layer is, for example, 1 nm or more and 30 nm or less. Furthermore, Li2S, for example, can also be used as the positive electrode active material.

[0041] The positive electrode active material may be in the form of particles, for example. 50 ) is not particularly limited, but may be, for example, 10 nm or more, or may be 100 nm or more. On the other hand, the average particle diameter (D 50 ) is, for example, 50 μm or less, and may be 20 μm or less.

[0042] The proportion of the positive electrode active material in the positive electrode mixture is, for example, 30% by weight or more, or alternatively, 50% by weight or more, or even 70% by weight or more, while the proportion of the positive electrode active material in the positive electrode mixture is, for example, 99% by weight or less.

[0043] Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNT), and carbon nanofibers (CNF). Examples of binders include rubber-based binders and fluoride-based binders.

[0044] 2.Negative electrode composite material The negative electrode mixture typically contains at least the above-described solid electrolyte and a negative electrode active material. The negative electrode mixture may further contain at least one of a conductive material and a binder.

[0045] The solid electrolyte is the same as that described above in "A. Solid Electrolyte." The proportion of the solid electrolyte in the negative electrode composite is, for example, 10% by weight or more, or may be 20% by weight or more, or may be 30% by weight or more. On the other hand, the proportion of the solid electrolyte in the negative electrode composite is, for example, 50% by weight or less.

[0046] Examples of the negative electrode active material include Li-based active materials such as Li and Li alloys, Si-based active materials, carbon active materials such as graphite, and Li4Ti5O 12Examples of oxide active materials include: Among these, the negative electrode active material is preferably a Si-based active material, since this allows for a high battery capacity. The Si-based active material is an active material whose main component is Si. The Si-based active material may be simple Si, a Si alloy, or a Si oxide. The Si-based active material may have a diamond-type crystalline phase, a clathrate I crystalline phase, or a clathrate II crystalline phase. In the clathrate I or II crystalline phase, multiple Si elements form a polyhedron (cage) containing pentagons or hexagons. This polyhedron has a space inside that can encapsulate metal ions such as Li ions, thereby suppressing volumetric changes during charging and discharging.

[0047] The negative electrode active material may be in the form of particles, for example. 50 ) is not particularly limited, but may be, for example, 10 nm or more, or may be 100 nm or more. On the other hand, the average particle diameter (D 50 ) is, for example, 50 μm or less, and may be 20 μm or less.

[0048] The proportion of the negative electrode active material in the negative electrode composite is, for example, 30% by weight or more, or may be 50% by weight or more, or may be 70% by weight or more. On the other hand, the proportion of the negative electrode active material in the negative electrode composite is, for example, 99% by weight or less. The conductive material and binder used in the negative electrode composite are the same as those described for the positive electrode composite above.

[0049] 3.Mixture material for electrolyte layer The electrolyte layer composite material contains, for example, the above-described solid electrolyte and a binder.

[0050] The solid electrolyte is the same as that described above in "A. Solid Electrolyte." The proportion of the solid electrolyte in the electrolyte layer composite is, for example, 70% by weight or more, or may be 80% by weight or more, or may be 90% by weight or more. On the other hand, the proportion of the solid electrolyte in the electrolyte layer composite is, for example, 99% by weight or less. The binder is the same as that described above in the positive electrode composite.

[0051] C.Battery Fig. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. The battery 10 shown in Fig. 1 includes a positive electrode layer 1 containing a positive electrode active material, a negative electrode layer 2 containing a negative electrode active material, an electrolyte layer 3 formed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode current collector 4 that collects current from the positive electrode layer 1, and a negative electrode current collector 5 that collects current from the negative electrode layer 2. Furthermore, at least one of the positive electrode layer 1, the negative electrode layer 2, and the electrolyte layer 3 contains the composite material described above in "B. Composite Material."

[0052] According to the present disclosure, by using the composite material described above, a battery can be obtained that can suppress deterioration in cycle characteristics.

[0053] 1. Positive electrode layer, negative electrode layer, and electrolyte layer The positive electrode layer in the present disclosure may contain the above-described positive electrode composite. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less. The negative electrode layer in the present disclosure may contain the above-described negative electrode composite. The thickness of the negative electrode layer is, for example, 0.1 μm or more and 1000 μm or less. The electrolyte layer in the present disclosure may contain the above-described electrolyte layer composite. The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less.

[0054] 2. Other configurations The battery in the present disclosure typically includes a positive electrode current collector that collects current from the positive electrode active material and a negative electrode current collector that collects current from the negative electrode active material. Examples of materials for the positive electrode current collector include stainless steel, aluminum, nickel, iron, titanium, and carbon. Examples of materials for the negative electrode current collector include stainless steel, copper, nickel, and carbon.

[0055] 3.Battery The type of battery in the present disclosure is not particularly limited, but is typically a lithium-ion battery. The battery in the present disclosure may be a primary battery or a secondary battery, with secondary batteries being preferred. This is because they can be repeatedly charged and discharged, making them useful, for example, as automotive batteries. The battery in the present disclosure may also be a solid-state battery whose electrolyte layer contains a solid electrolyte (particularly an inorganic solid electrolyte). Examples of solid-state batteries include all-solid-state batteries and semi-solid-state batteries.

[0056] Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, it is preferable that the battery be used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for mobile objects other than vehicles (for example, trains, ships, and aircraft), or as a power source for electrical appliances such as information processing devices. The method for manufacturing the battery is not particularly limited, and known methods can be used.

[0057] D. Manufacturing method of solid electrolyte Fig. 2 is a flow diagram illustrating a method for producing a solid electrolyte according to the present disclosure. As shown in Fig. 2, first, a sulfide solid electrolyte having a composition represented by Li3PS4 and a hydride solid electrolyte having a composition represented by LiBH4 are prepared (preparation step). Next, mechanical energy is applied to a raw material mixture containing the sulfide solid electrolyte and the hydride solid electrolyte to produce a precursor (precursor preparation step). Next, the precursor is heat-treated to produce the solid electrolyte described above in "A. Solid Electrolyte" (heat treatment step).

[0058] According to the present disclosure, by carrying out the above-described steps, a solid electrolyte capable of suppressing deterioration in cycle characteristics can be obtained.

[0059] 1. Preparation process The preparation step in the present disclosure is a step of preparing a sulfide solid electrolyte having a composition represented by Li3PS4 and a hydride solid electrolyte having a composition represented by LiBH4. The sulfide solid electrolyte and the hydride solid electrolyte may be prepared by self-synthesis or may be purchased from a third party.

[0060] The sulfide solid electrolyte has a composition represented by Li3PS4. Preferably, the sulfide solid electrolyte is amorphous. When an amorphous sulfide solid electrolyte is measured by XRD using CuKα radiation, a halo pattern is observed. Preferably, when an amorphous sulfide solid electrolyte is measured by XRD using CuKα radiation, Li2S peaks (2θ=27.0°, 31.2°, 44.8°, 53.1°) are not observed. In addition, when the sulfide solid electrolyte is measured by XRD using CuKα radiation, a halo pattern is observed at 417 cm -1 The intensity at I 417 Height: 402cm -1 The intensity at I 402 In this case, I 402 / I 417 The peak of PS4 is 417 cm -1 The S3P-S-PS3 peak is observed around 402 cm -1 Also, at 402cm -1 In this case, the shoulder of the PS4 peak overlaps with the S3P-S-PS3 peak. Therefore, even if the S3P-S-PS3 peak does not exist, for example, the peak at 402 cm -1 The strength of the

[0061] The hydride solid electrolyte has a composition represented by LiBH4, which may be crystalline or amorphous.

[0062] 2. Precursor preparation process The precursor preparation step in the present disclosure is a step of applying mechanical energy to a raw material mixture containing a sulfide solid electrolyte and a hydride solid electrolyte to prepare a precursor.

[0063] The raw material mixture may contain only the sulfide solid electrolyte and the hydride solid electrolyte, or may further contain other substances. Examples of methods for applying mechanical energy include mechanical milling methods such as ball mills and vibration mills. The mechanical milling method may be either a dry method or a wet method, with the latter being preferred from the viewpoint of uniform processing. The type of dispersion medium used in the wet mechanical milling method is not particularly limited.

[0064] Various conditions for mechanical milling are set so as to obtain the desired precursor. For example, when using a planetary ball mill, the raw material mixture and milling balls are added to a pot and processed at a predetermined rotation speed and time. The rotation speed of the table of the planetary ball mill is, for example, 200 rpm or more and 500 rpm or less. The processing time of the planetary ball mill is, for example, 1 hour or more and 50 hours or less, or may be 5 hours or more and 30 hours or less.

[0065] 3.Heat treatment process The heat treatment step in the present disclosure is a step of heat treating a precursor to produce a solid electrolyte. The heat treatment temperature is preferably, for example, a temperature equal to or higher than the crystallization temperature of the precursor. The heat treatment temperature is, for example, 160°C or higher and 250°C or lower. The heat treatment time is, for example, 1 hour or higher and 10 hours or lower. The heat treatment atmosphere can be, for example, an inert gas atmosphere or a vacuum.

[0066] 4.Solid electrolyte The solid electrolyte obtained by each of the above steps is the same as that described above in "A. Solid Electrolyte." The present disclosure can also provide a method for producing a solid electrolyte, which includes a preparation step of preparing Li3PS4 and LiBH4, a precursor preparation step of applying mechanical energy to a raw material mixture containing the Li3PS4 and LiBH4 to prepare a precursor, and a heat treatment step of heat-treating the precursor to prepare the solid electrolyte, wherein the raw material mixture has a composition represented by xLi3PS4-(100-x)LiBH4 (x is 20 or more and 40 or less).

[0067] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0068] [Example 1] ZrO2 balls were added to a 500ml pot, and then a total of 30g of Li2S and P2S5 was added to achieve a molar ratio of Li2S:P2S5 = 3:1, followed by 100g of heptane. The pot was then placed in a planetary ball mill and ball milled at 300 rpm for 20 hours. This resulted in the synthesis of amorphous Li3PS4 (sulfide solid electrolyte).

[0069] The LiBH4 (hydride solid electrolyte) was then dried using a hot plate at 150°C for 1 hour. ZrO2 balls were added to the pot, and a total of 10g of Li3PS4 and LiBH4 was added to achieve a Li3PS4:LiBH4 = 25:75 molar ratio, followed by 100g of heptane. The pot was then placed in a planetary ball mill and ball milled at 300 rpm for 20 hours to synthesize a precursor. The precursor was then heat-treated using a hot plate at 180°C for 3 hours to obtain a solid electrolyte.

[0070] [Examples 2 and 3 and Comparative Examples 1 and 2] A solid electrolyte was obtained in the same manner as in Example 1, except that the ratio of Li3PS4 and LiBH4 was changed to the ratio shown in Table 1.

[0071] Comparative Example 3 ZrO2 balls were added to a 500 ml pot, and a total of 10 g of Li2S, P2S5, and LiBH4 was added to achieve a molar ratio of Li2S:P2S5:LiBH4 = 18.75:6.25:75. 100 g of heptane was then added. The pot was then placed in a planetary ball mill and ball milled at 300 rpm for 20 hours to synthesize a precursor. The precursor was then heat-treated on a hot plate at 180 °C for 3 hours to obtain a solid electrolyte.

[0072] Comparative Example 4 ZrO2 balls were added to a 500 ml pot, and then a total of 10 g of P2S5 and LiBH4 was added to achieve a molar ratio of P2S5:LiBH4 = 10:90. 100 g of heptane was then added. The pot was then placed in a planetary ball mill and ball milled at 300 rpm for 20 hours to synthesize a precursor. The precursor was then heat-treated on a hot plate at 200 °C for 3 hours to obtain a solid electrolyte.

[0073] [evaluation] ( 11 B-NMR measurement) For the solid electrolytes obtained in Examples 1 to 3 and Comparative Examples 1 to 4, 11 B-NMR measurements were performed. 11 B-NMR measurements were carried out under the following conditions. Measured nuclides: 11 B (solid) Magnetic field strength: 11.747T ( 11 160.36MHz on B nucleus) Observation frequency range: -750ppm~750ppm Number of data points: 2048 points Measurement mode: Single pulse Repeat time: 1 sec Number of times accumulated: 128 times Reference material: Adamantane signal (13C nucleus 29.5 ppm) to adjust shim Z0 Rotation speed: 18 kHz Measurement temperature: room temperature

[0074] The obtained peaks were fitted, and the ratio of the integrated area of peak α having a peak in the range of 42 ppm±1 ppm to the total integrated area of all peaks (main phase ratio) was calculated. The results are shown in Table 1. In addition, as a representative result, FIG. 3 shows the ratio of the integrated area of peak α to the total integrated area of all peaks for the solid electrolytes obtained in Example 1, Comparative Example 1, and Comparative Example 2. 11 The results of B-NMR measurements are shown in Figures 3(a) and 3(b). As shown in Figures 3(a) and 3(b), it was confirmed that the ratio of the integrated area of peak α was high in Example 1 and Comparative Example 1. On the other hand, as shown in Figure 3(c), in Comparative Example 2, the ratio of the integrated area of peak α was low, confirming the presence of a phase due to impurities.

[0075] ( 31 P-NMR measurement) For the solid electrolytes obtained in Examples 1 to 3 and Comparative Examples 1 to 4, 31 P-NMR measurements were performed. 31 P-NMR measurements were carried out under the following conditions. Measured nuclides: 31 P (solid) Magnetic field strength: 11.747T ( 31 202.4MHz with P nucleus) Observation frequency range: -450ppm~550ppm Number of data points: 2048 points Measurement mode: Single pulse Repeat time: 300 sec Number of measurements: 64 (5.5 hours) Reference substance: Ammonium dihydrogen phosphate (external standard: 1.33 ppm) Rotation speed: 18kHz Measurement temperature: room temperature

[0076] The obtained peaks were fitted, and the ratio of the integrated area of peak β having a peak in the range of 90.5 ppm±1 ppm to the total integrated area of all peaks (main phase ratio) was calculated. The results are shown in Table 1. In addition, as a representative result, FIG. 4 shows the ratio of the integrated area of peak β to the total integrated area of all peaks for the solid electrolytes obtained in Example 1, Comparative Example 1, and Comparative Example 2. 31The results of P-NMR measurements are shown in Figures 4(a) and 4(b). As shown in Figures 4(a) and 4(b), it was confirmed that the ratio of the integrated area of peak β was high in Example 1 and Comparative Example 1. On the other hand, as shown in Figure 4(c), in Comparative Example 2, the ratio of the integrated area of peak β was low, confirming the presence of a phase due to impurities.

[0077] (DSC measurement) Differential scanning calorimetry (DSC) was performed on the solid electrolytes obtained in Examples 1 to 3 and Comparative Examples 1 to 4. The DSC measurements were performed under the following conditions. Equipment: Rigaku DSC-60 Plus Heating rate: 10℃ / min Reference material: Al2O3

[0078] The results are shown in Table 1. Furthermore, as representative results, FIG. 5 shows the results of DSC measurements of the solid electrolytes obtained in Example 1, Comparative Example 1, and Comparative Example 2. As shown in FIG. 5(a), in Example 1, a small endothermic peak appeared in the range of 115°C ± 10°C. As shown in FIG. 5(b), in Comparative Example 1, a large endothermic peak appeared in the range of 115°C ± 10°C, suggesting that a large amount of residual raw material (LiBH4) was contained. On the other hand, as shown in FIG. 5(c), in Comparative Example 2, no endothermic peak was observed in the range of 115°C ± 10°C.

[0079] (Capacity retention rate measurement) All-solid-state batteries were fabricated using the solid electrolytes obtained in Examples 1 to 3 and Comparative Examples 1 to 4. Specifically, the solid electrolyte, a negative electrode active material (Si), and a conductive material (VGCF) were mixed to obtain a negative electrode mixture. Next, the solid electrolyte and a positive electrode active material (LiNi coated with LiNbO3) were mixed to obtain a negative electrode mixture. 1 / 3 Co 1 / 3 Mn 1 / 3 O2) and a conductive material (VGCF) were mixed to obtain a positive electrode composite. Next, the positive electrode composite, the above solid electrolyte, and the negative electrode composite were stacked in an alumina cylinder with a diameter of 11.28 mm and pressed at a pressure of 6 tons to obtain a laminate having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. Furthermore, the laminate was restrained at 6 N to obtain an all-solid-state battery for evaluation.

[0080] The obtained all-solid-state battery was subjected to 50 CCCV charge-discharge cycles at a charge-discharge rate of 1 / 3C at room temperature, and the ratio of the discharge capacity after 50 cycles to the initial discharge capacity was calculated as the "capacity retention rate." The results are shown in Table 1.

[0081] [Table 1]

[0082] As shown in Table 1, it was confirmed that Examples 1 to 3 had higher capacity retention rates and better cycle characteristics than Comparative Examples 1 to 4. On the other hand, in Comparative Example 1, the heat capacity of the endothermic peak in the DSC measurement was large, and it is presumed that the solid electrolyte contained a large amount of residual raw material (LiBH4), which resulted in the low capacity retention rate. In Comparative Example 2, the proportions of the integrated areas of peaks α and β were small, and it is presumed that the solid electrolyte contained a large amount of impurities, which resulted in the low capacity retention rate. In Comparative Examples 3 and 4, the proportions of the integrated area of peak β were small, and it is presumed that the solid electrolyte contained a large amount of impurities, which resulted in the low capacity retention rate. In this way, it was confirmed that by satisfying the above-mentioned conditions (i) to (iii), it is possible to suppress the deterioration of cycle characteristics. [Explanation of symbols]

[0083] 1 ... Positive electrode layer 2...Anode layer 3 … Electrolyte layer 4 … Positive electrode current collector 5 … Negative electrode current collector 10...battery

Claims

1. Li and P.S. ４ ３－ Structure and BH ４ － and a structure, The following conditions (i) to (iii) are satisfied: Condition (i): １１ In B-NMR measurement, the integrated area of peak α having an apex in the range of 42 ppm ± 1 ppm is 50% or more of the total integrated area of all peaks. Condition (ii): ３１ In P-NMR measurement, the integrated area of peak β having an apex in the range of 90.5 ppm ± 1 ppm is 50% or more of the total integrated area of all peaks. Condition (iii): A solid electrolyte in which the heat capacity of an endothermic peak appearing in the range of 115°C ± 10°C during the temperature-raising step of DSC measurement is less than 30 J / g.

2. The solid electrolyte of claim 1 , wherein the solid electrolyte has an argyrodite-type crystalline phase.

3. 2. The solid electrolyte according to claim 1, wherein, under the condition (i), the integrated area of the peak α is 90% or more of the total integrated area of all peaks.

4. 2. The solid electrolyte according to claim 1, wherein, under the condition (ii), the integrated area of the peak β is 90% or more of the total integrated area of all peaks.

5. 2. The solid electrolyte according to claim 1, wherein, under the condition (iii), the heat capacity of the endothermic peak is 20 J / g or less.

6. Said P.S. ４ ３－ Structure and the BH ４ － The PS relative to the total structure ４ ３－ The solid electrolyte according to claim 1 , wherein the molar ratio of the structure is 20% or more and 40% or less.

7. The solid electrolyte is xLi ３ P.S. ４ -(100-x)LiBH ４ 2. The solid electrolyte according to claim 1, having a composition represented by the formula: (x is 20 or more and 40 or less).

8. A composite material comprising the solid electrolyte according to any one of claims 1 to 7 and at least one of an electrode active material, a conductive material, and a binder.

9. A battery having a positive electrode layer, a negative electrode layer, and an electrolyte layer disposed between the positive electrode layer and the negative electrode layer, A battery, wherein at least one of the positive electrode layer, the negative electrode layer, and the electrolyte layer contains the composite material according to claim 8 .

10. 10. The battery of claim 9, wherein the electrolyte layer comprises a solid electrolyte.

11. A method for producing a solid electrolyte, comprising the steps of: producing the solid electrolyte according to any one of claims 1 to 7; Li ３ P.S. ４ A sulfide solid electrolyte having a composition represented by the formula: ４ a preparation step of preparing a hydride solid electrolyte having a composition represented by the formula: a precursor preparation step of applying mechanical energy to a raw material mixture containing the sulfide solid electrolyte and the hydride solid electrolyte to prepare a precursor; a heat treatment step of heat-treating the precursor to prepare the solid electrolyte; The method for producing a solid electrolyte comprising the steps of:

12. The method for producing a solid electrolyte according to claim 11 , wherein in the preparing step, the sulfide solid electrolyte is amorphous.

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