Sulfide solid electrolyte, precursor, all-solid-state battery, and method for producing sulfide solid electrolyte

Abstract

To provide mainly a sulfide solid electrolyte having good ion conductivity and water resistance.SOLUTION: Disclosed is a sulfide solid electrolyte comprising Li, P, S and CO32-. The sulfide solid electrolyte includes, as a main phase, a crystal phase having a Li7 P3S11 structure. In an X-ray diffraction measurement with CuKα rays on the sulfide solid electrolyte, when intensity of a peak of Li2S appearing at 2θ=27.0°±0.5°is denoted by IA and intensity of a peak of the crystal phase appearing at 2θ=23.65°±0.50°is denoted by IB, IA / IB is 0 to 0.39. The sulfide solid electrolyte does not have a peak of a heterogenous phase appearing at 2θ=16.5°±0.5°.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a sulfide solid electrolyte having good ionic conductivity and water resistance. [Background technology]

[0002] All-solid-state batteries are batteries that have a solid electrolyte layer between a positive electrode layer and a negative electrode layer, and have the advantage of being easier to simplify safety devices compared to liquid-based batteries that use electrolytes containing flammable organic solvents. Furthermore, sulfide solid electrolytes are known as solid electrolytes used in all-solid-state batteries.

[0003] For example, Patent Document 1 describes Li7P3S 11 In particular, Patent Document 1 discloses a sulfide solid electrolyte of the so-called Li2S-P2S5 system, which uses Li2S and P2S5 as raw materials. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-053850 Summary of the Invention [Problem to be solved by the invention]

[0005] Although Li2S-P2S5-based sulfide solid electrolytes have good ionic conductivity, their high sulfur content leaves room for improvement in water resistance. The present disclosure has been made in light of the above-mentioned circumstances, and a primary object of the present disclosure is to provide a sulfide solid electrolyte having good ionic conductivity and water resistance. [Means for solving the problem]

[0006] In order to solve the above problems, in the present disclosure, Li, P, S and CO3 2- A sulfide solid electrolyte containing Li7P3S 11The main phase is a crystalline phase with the structure, and in X-ray diffraction measurement using CuKα radiation, the peak intensity of Li2S appearing at 2θ=27.0°±0.5° is I A The peak intensity of the above crystalline phase appearing at 2θ = 23.65° ± 0.50° is defined as I B In this case, I A / I B is 0 or more and 0.39 or less, and does not have a peak of a different phase appearing at 2θ=16.5°±0.5°.

[0007] According to this disclosure, CO3 2- Contains Li7P3S 11 It has a crystalline phase with the structure I as the main phase. A / I B is a predetermined value or less and does not have a peak of a different phase, it is possible to obtain a sulfide solid electrolyte having good ionic conductivity and water resistance.

[0008] In the above disclosure, the molar ratio of the S to the P (S / P) may be 3.60 or less.

[0009] In the above disclosure, the ionic conductivity at 25° C. may be 0.11 mS / cm or more.

[0010] In addition, the present disclosure provides a precursor of the sulfide solid electrolyte, wherein the precursor contains the Li, the P, the S, and the CO 2- and the amount of decarboxylation measured by thermogravimetry-differential thermal analysis is 0.49 wt % or more and 1.36 wt % or less.

[0011] According to the present disclosure, the precursor is CO3 2- Since the amount of decarbonation is within a predetermined range, the precursor can be used to obtain a sulfide solid electrolyte having good ionic conductivity and water resistance.

[0012] The present disclosure also provides an all-solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer formed between the positive electrode layer and the negative electrode layer, wherein at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains the sulfide solid electrolyte described above.

[0013] According to the present disclosure, by using the above-described sulfide solid electrolyte, an all-solid-state battery having good ionic conductivity and water resistance can be obtained.

[0014] In addition, in this disclosure, Li, P, S and CO3 2- The method for producing a sulfide solid electrolyte containing Li2CO3 and P2S5 includes the steps of: subjecting a raw material composition containing Li2CO3 and P2S5 to a mechanical milling process to obtain a precursor; and calcining the precursor to obtain Li7P3S. 11 and a firing step of forming a crystalline phase having the structure.

[0015] According to the present disclosure, a raw material composition containing Li2CO3 is used to produce Li7P3S 11 By forming a crystalline phase having such a structure, a sulfide solid electrolyte having good ionic conductivity and water resistance can be obtained.

[0016] In the disclosure, the precursor comprises the Li, the P, the S, and the CO 2- and the amount of decarboxylation measured by thermogravimetry-differential thermal analysis may be 0.49% by weight or more and 1.36% by weight or less.

[0017] In the above disclosure, in the amorphization step, the mechanical milling treatment may be performed using a planetary ball mill, the table rotation speed may be 400 rpm or more and 600 rpm or less, and the treatment time may be 18 hours or more and 25 hours or less.

[0018] In the above disclosure, the raw material composition does not necessarily contain Li2S. [Effects of the Invention]

[0019] The present disclosure has an effect of providing a sulfide solid electrolyte having good ionic conductivity and water resistance. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of an all-solid-state battery according to the present disclosure. [Figure 2] 1 is a flowchart illustrating an example of a method for producing a sulfide solid electrolyte according to the present disclosure. [Figure 3] 1 shows the results of XRD measurement of the sulfide solid electrolytes obtained in Example 3 and Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0021] The sulfide solid electrolyte, precursor, all-solid-state battery, and method for producing the sulfide solid electrolyte according to the present disclosure will be described in detail below.

[0022] A. Sulfide solid electrolyte The sulfide solid electrolyte in this disclosure is a composite of Li, P, S, and CO3 2- A sulfide solid electrolyte containing Li7P3S 11 The main phase is a crystalline phase with the structure, and in X-ray diffraction measurement using CuKα radiation, the peak intensity of Li2S appearing at 2θ=27.0°±0.5° is I A The peak intensity of the above crystalline phase appearing at 2θ = 23.65° ± 0.50° is defined as I B In this case, I A / I B is 0 or more and 0.39 or less, and there is no peak of a different phase appearing at 2θ=16.5°±0.5°.

[0023] According to this disclosure, CO3 2- Contains Li7P3S 11 It has a crystalline phase with the structure I as the main phase. A / I Bis a predetermined value or less and does not have a peak of a different phase, it is possible to obtain a sulfide solid electrolyte having good ionic conductivity and water resistance.

[0024] As mentioned above, Patent Document 1 describes Li7P3S 11 In particular, Patent Document 1 discloses a sulfide solid electrolyte having a structure similar to that of Li2S-P2S5, which uses Li2S and P2S5 as raw materials. Although Li2S-P2S5 sulfide solid electrolytes have good ionic conductivity, they have a high sulfur content, so there is room for improvement in water resistance. Specifically, there is room for improvement in water resistance by reducing hydrogen sulfide generated by reaction with water. In contrast, the sulfide solid electrolyte of the present disclosure uses carbonate ions (CO3 2- ), the sulfur content can be reduced. This reduces the amount of hydrogen sulfide generated and improves water resistance. In addition, carbonate ions (CO3 2- ) is a sulfide ion (S - ), the ionic radius of the sulfide solid electrolyte containing carbonate ions is close to that of Li7P3S 11 It is believed that the structure can be maintained. As a result, ionic conductivity is also improved. Furthermore, the sulfide solid electrolyte of the present disclosure can be produced without using expensive LiS as a raw material or by using a small amount of LiS, thereby reducing production costs.

[0025] Although it is not clear how the sulfide solid electrolyte in this disclosure contains carbonate ions, it is speculated as follows. 11 In the crystalline phase, PS4 3- P2S7 unit with bridging sulfur (-S-) 4- Unit (S3P-S-PS3) and PS4 3- :P2S7 4- = 1:1 ratio (Li3PS4 + Li4P2S7 → Li7P3S 11) Bridging sulfur has low stability against water, and it is thought that most of the hydrogen sulfide generated comes from the bridging sulfur. On the other hand, as shown in the examples described later, in the sulfide solid electrolyte of the present disclosure, the amount of hydrogen sulfide generated is significantly small, and therefore carbonate ions are likely to be generated by Li7P3S 11 It is presumed that at least a portion of the bridging sulfur in the crystalline phase is substituted.

[0026] The sulfide solid electrolyte in this disclosure is a composite of Li, P, S, and CO3 2- The sulfide solid electrolyte contains Li, P, S and CO3 2- It may contain only one element, or may contain other elements. Examples of other elements include X (X is a halogen). Examples of halogens include F, Cl, Br, and I. X may be one type, or two or more types.

[0027] The sulfide solid electrolyte in this disclosure is Li7P3S 11 The crystal phase (hereinafter also referred to as crystal phase A) has the structure Li7P3S 11 It is presumed that at least a part of the bridging sulfur in the crystalline phase is replaced by carbonate ions. Crystalline phase A is Li7P3S 11 It has a peak at the same position as the crystalline phase. 11 Typical peaks of the crystalline phase appear at 2θ=17.8°, 18.2°, 19.8°, 21.8°, 23.8°, 25.9°, 29.5°, and 30.0°. It is preferable that crystalline phase A also has peaks at ±0.5° (preferably ±0.3°) of each of the above positions.

[0028] The sulfide solid electrolyte of the present disclosure has crystalline phase A as a main phase. "Having it as a main phase" means that the proportion (wt %) of the crystalline phase A relative to all crystalline phases contained in the sulfide solid electrolyte is the largest. The proportion of the crystalline phase A relative to all crystalline phases contained in the sulfide solid electrolyte is, for example, 50 wt % or more, or may be 70 wt % or more, or even 90 wt % or more. The proportion of the crystalline phase A can be determined, for example, from the results of synchrotron XRD.

[0029] In addition, in X-ray diffraction measurement using CuKα rays, the sulfide solid electrolyte of the present disclosure has a peak intensity of Li2S appearing at 2θ = 27.0° ± 0.5°. A The crystalline phase A (Li7P3S) appears at 2θ = 23.65° ± 0.50°. 11 The peak intensity of the crystalline phase (having the structure) is I B In this case, I A / I B is less than or equal to a specified value. A / I B A low value means that the amount of Li2S in the sulfide solid electrolyte is low. A / I B is usually 3.9 or less, may be 3.0 or less, may be 2.0 or less, or may be 1 or less. A / I B may be 0 or may be greater than 0. In the present disclosure, when the sulfide solid electrolyte does not have a LiS peak appearing at 2θ=27.0°±0.5°, I A is 0. "No Li2S peak" means that the Li2S peak is so small that it cannot be distinguished from the surrounding noise. A / I B If the value is too large, i.e., if the amount of Li2S present is too large, it may hinder ionic conduction and increase the amount of hydrogen sulfide generated. It may also cause composition deviation.

[0030] Furthermore, the sulfide solid electrolyte of the present disclosure does not have a peak of a different phase appearing at 2θ=16.5°±0.5° in X-ray diffraction measurement using CuKα radiation. The different phase refers to a crystalline phase that does not correspond to either the unreacted raw material or crystalline phase A, and is a crystalline phase that has lower ionic conductivity than crystalline phase A. "Does not have a peak at the position of the different phase" means that the Li2S peak is so small that it cannot be distinguished from surrounding noise. Specifically, the peak intensity of the different phase appearing at 2θ=16.5°±0.5° is expressed as I C In this case, I C / I B is 0.1 or less.

[0031] In the sulfide solid electrolyte, the molar ratio of S to P (S / P) is, for example, 3.60 or less, may be 3.2 or less, may be 3.0 or less, or may be 2.8 or less. 11 The S / P in the crystalline phase is 3.67. On the other hand, the S / P is, for example, 2.0 or more, and may be 2.2 or more.

[0032] In the sulfide solid electrolyte, the molar ratio of Li to the sum of Li and P (Li / (Li+P)) is, for example, 0.65 or more, and may be 0.68 or more. On the other hand, Li / (Li+P) is, for example, 0.75 or less, and may be 0.72 or less. 11 The Li / (Li+P) ratio in the crystalline phase is 0.70. When the sulfide solid electrolyte contains X (X is a halogen), it is preferable that the amount of Li excluding the amount of Li equivalent to X satisfies the above molar ratio (Li / (Li+P)).

[0033] The sulfide solid electrolyte preferably has high ionic conductivity. The ionic conductivity at 25° C. is, for example, 0.11 mS / cm or more, and may be 0.5 mS / cm or more. The ionic conductivity of the sulfide solid electrolyte can be measured, for example, by an AC impedance method.

[0034] The sulfide solid electrolyte may be in the form of particles, for example. 50 ) is, for example, 0.1 μm or more and 50 μm or less. 50 ) can be determined from the results of particle size distribution measurement by laser diffraction scattering. The use of the sulfide solid electrolyte is not particularly limited, but it is preferably used in, for example, all-solid-state batteries.

[0035] B. Precursor The precursor of the sulfide solid electrolyte in the present disclosure is the precursor of the sulfide solid electrolyte described above, and the precursor contains the Li, P, S, and CO 2- The amount of decarboxylation measured by thermogravimetry-differential thermal analysis is within a predetermined range.

[0036] According to the present disclosure, the precursor is CO3 2- Since the amount of decarbonation is within a predetermined range, the precursor can be used to obtain a sulfide solid electrolyte having good ionic conductivity and water resistance.

[0037] The amount of decarboxylation is usually 0.49% by weight or more, and may be 0.6% by weight or more, or 0.7% by weight or more. On the other hand, the amount of decarboxylation is usually 1.36% by weight or less, and may be 1.3% by weight or less, or 1.1% by weight or less, or 0.9% by weight or less. The amount of decarboxylation is calculated by thermogravimetry-differential thermal analysis (TG-DTA).

[0038] The precursor in the present disclosure is typically an amorphous sulfide glass. Amorphous means that X-ray diffraction (XRD) analysis reveals no crystalline periodicity, but rather a halo pattern. The precursor is typically used to obtain the sulfide solid electrolyte described above in "A. Sulfide Solid Electrolyte."

[0039] C. All-solid-state battery Fig. 1 is a schematic cross-sectional view showing an example of an all-solid-state battery according to the present disclosure. The all-solid-state battery 10 shown in Fig. 1 includes a positive electrode layer 1, a negative electrode layer 2, a solid 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, a negative electrode current collector 4 that collects current from the negative electrode layer 2, and a battery case 6 that houses these components. Furthermore, at least one of the positive electrode layer 1, the negative electrode layer 2, and the solid electrolyte layer 3 contains the sulfide solid electrolyte described above in "A. Sulfide Solid Electrolyte."

[0040] According to the present disclosure, by using the above-described sulfide solid electrolyte, an all-solid-state battery having good ionic conductivity and water resistance can be obtained.

[0041] 1. Positive electrode layer The positive electrode layer in the present disclosure is a layer containing at least a positive electrode active material. In addition to the positive electrode active material, the positive electrode layer may contain at least one of a solid electrolyte, a conductive material, and a binder.

[0042] 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, Li(Ni 0.5 Mn 1.5 )O4, and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCuPO4.

[0043] The surface of the positive electrode active material may be coated with a coating layer, which can suppress the reaction between the positive electrode active material and the sulfide solid electrolyte. Examples of materials for the coating layer include Li-ion conductive oxides such as LiNbO3, Li3PO4, and LiPON. The average thickness of the coating layer is, for example, 1 nm or more and 20 μm or less, and may be 1 nm or more and 10 nm or less.

[0044] The positive electrode layer in the present disclosure preferably contains the above-mentioned sulfide solid electrolyte. Examples of the conductive material include carbon materials. Examples of the carbon material include particulate carbon materials such as acetylene black (AB) and ketjen black (KB), and fibrous carbon materials such as carbon fiber, carbon nanotubes (CNT), and carbon nanofibers (CNF). Examples of the binder include fluorine-based binders such as polyvinylidene fluoride (PVDF). The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0045] 2. Negative electrode layer The negative electrode layer in the present disclosure is a layer containing at least a negative electrode active material. In addition to the negative electrode active material, the negative electrode layer may also contain at least one of a solid electrolyte, a conductive material, and a binder.

[0046] Examples of negative electrode active materials include metal active materials and carbon active materials. Examples of metal active materials include In, Al, Si, and Sn. Examples of carbon active materials include mesocarbon microbeads (MCMB), highly oriented pyrolytic graphite (HOPG), hard carbon, and soft carbon.

[0047] The solid electrolyte, conductive material, and binder are the same as those described above. The negative electrode layer in the present disclosure preferably contains the sulfide solid electrolyte described above. The thickness of the negative electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0048] 3.Solid electrolyte layer The solid electrolyte layer in the present disclosure is a layer formed between the positive electrode layer and the negative electrode layer, and contains at least a solid electrolyte. The solid electrolyte layer may also contain a binder in addition to the solid electrolyte. The solid electrolyte and the binder are the same as those described above. The solid electrolyte layer in the present disclosure preferably contains the sulfide solid electrolyte described above. The thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less.

[0049] 4. Other configurations The all-solid-state battery of the present disclosure typically includes a positive electrode current collector that collects current from the positive electrode layer and a negative electrode current collector that collects current from the negative electrode layer. Examples of materials for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Examples of materials for the negative electrode current collector include SUS, copper, nickel, and carbon. Furthermore, a typical battery case, such as a SUS battery case, can be used.

[0050] 5.All-solid-state battery The all-solid-state battery in the present disclosure is preferably an all-solid-state lithium-ion battery. The all-solid-state battery may be either a primary battery or a secondary battery, but is preferably a secondary battery. This is because it can be repeatedly charged and discharged, making it useful, for example, as an in-vehicle battery. The term "secondary battery" also includes secondary batteries used as primary batteries (used for only one discharge after charging). Examples of the shape of the all-solid-state battery include coin-type, laminate-type, cylindrical, and prismatic types.

[0051] D. Manufacturing method of sulfide solid electrolyte FIG. 2 is a flowchart showing an example of a method for producing a sulfide solid electrolyte according to the present disclosure. In FIG. 2, first, a raw material composition containing Li2CO3 and P2S5 is prepared. Next, the raw material composition is subjected to a mechanical milling process to obtain a precursor. Next, the obtained precursor is calcined to obtain Li7P3S 11 A crystalline phase having a structure is formed, thereby obtaining a sulfide solid electrolyte.

[0052] According to the present disclosure, a raw material composition containing Li2CO3 is used to produce Li7P3S 11 By forming a crystalline phase having the structure, a sulfide solid electrolyte having good ionic conductivity and water resistance can be obtained. Furthermore, in the present disclosure, the above-mentioned sulfide solid electrolyte can be produced without using, or using a reduced amount of, expensive LiS as a raw material, thereby reducing production costs.

[0053] 1. Amorphization process The amorphization step is a step of obtaining a precursor by performing a mechanical milling treatment on a raw material composition containing Li2CO3 and P2S5.

[0054] The raw material composition contains at least Li2CO3 and P2S5. The raw material composition may or may not contain Li2S, but the latter is preferred because it allows the sulfur content of the sulfide solid electrolyte to be reduced. On the other hand, in the former case, the ratio of Li2S to the total of Li2CO3 and Li2S is, for example, 50 mol% or less, or may be 30 mol% or less, or may be 10 mol% or less. On the other hand, the ratio is, for example, 1 mol% or more.

[0055] The raw material composition may further contain LiX (X is a halogen). Examples of LiX include LiF, LiCl, LiBr, and LiI. The raw material composition may or may not contain an oxide such as LiO.

[0056] The molar ratio of S to P (S / P) in the raw material composition is, for example, 3.60 or less, may be 3.2 or less, may be 3.0 or less, or may be 2.8 or less. 11 The S / P in the crystalline phase is 3.67. On the other hand, the S / P is, for example, 2.0 or more, and may be 2.2 or more.

[0057] In the raw material composition, the molar ratio of Li to the total of Li and P (Li / (Li+P)) is, for example, 0.65 or more, and may be 0.68 or more. On the other hand, Li / (Li+P) is, for example, 0.75 or less, and may be 0.72 or less. 11 The Li / (Li+P) ratio in the crystalline phase is 0.70. When the raw material composition contains X (X is a halogen), it is preferable that the Li content excluding the Li content equimolar to X satisfies the above-mentioned molar ratio (Li / (Li+P)).

[0058] In addition, the mechanical milling is not particularly limited as long as it is a method that can impart mechanical energy, and examples thereof include a ball mill, a vibration mill, a turbo mill, a mechanofusion, and a disk mill. The mechanical milling may be a dry type or a wet type, but the latter is preferred from the viewpoint of uniform processing. The type of dispersion medium used in the wet mechanical milling method is not particularly limited.

[0059] 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 composition and milling balls are added and processed at a predetermined rotation speed and time. The rotation speed of the table of the planetary ball mill is, for example, 300 rpm or more, and may be 400 rpm or more. On the other hand, the rotation speed of the table of the planetary ball mill is, for example, 600 rpm or less, and may be 550 rpm or less. Furthermore, the processing time of the planetary ball mill is, for example, 10 hours or more, may be 18 hours or more, or may be 20 hours or more. On the other hand, the processing time may be, for example, less than 30 hours, and may be 25 hours or less.

[0060] The precursor obtained by the amorphization step is the same as that described in "B. Precursor of sulfide solid electrolyte," and therefore will not be described here.

[0061] 2. Firing process In the calcination step, the precursor is calcined to obtain Li7P3S 11 This is a process for forming a crystalline phase having a structure.

[0062] The calcination temperature was set to the crystallization temperature (T c ) or higher. c ) is, for example, 170°C or higher and 280°C or lower. c ) can be determined by differential thermal analysis (DTA). The firing temperature is, for example, T cThe firing temperature is, for example, 200°C or higher and 320°C or lower.

[0063] The heating time is not particularly limited as long as it is a time that allows the desired sulfide solid electrolyte to be obtained. The heating time is, for example, from 1 minute to 24 hours, and may be from 1 minute to 10 hours. Furthermore, heating is preferably performed in an inert gas atmosphere (e.g., an Ar gas atmosphere) or a reduced pressure atmosphere (e.g., in a vacuum), as this can prevent deterioration (e.g., oxidation) of the sulfide solid electrolyte. The heating method is not particularly limited, but examples include a method using a calcination furnace.

[0064] 3.Sulfide solid electrolyte By the above-mentioned process, Li, P, S and CO3 2- The sulfide solid electrolyte is preferably the same as that described above in "A. Sulfide solid electrolyte."

[0065] 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]

[0066] [Example 1] A sulfide solid electrolyte was prepared using Li2CO3 (Kojundo Chemical) and P2S5 (Aldrich) as raw materials as follows. First, 0.8736 g of Li2CO3 and 1.1264 g of P2S5 were weighed and mixed. The resulting raw material composition (70Li2CO3-30P2S5) was placed in a zirconia pot (45 ml) containing 5 mm diameter zirconia balls, and 4 g of dehydrated heptane (Kanto Chemical) was added and the pot was covered. This was then placed in a planetary ball mill (Fritch P-7) and mechanically milled at a rotation speed of 500 rpm for 18 hours to obtain a precursor (glass). Next, the resulting precursor was fired in an inert atmosphere at 300°C, above the crystallization temperature, for 3 hours. It was then cooled to produce a glass-ceramic sulfide solid electrolyte. The sulfide solid electrolyte thus obtained was heated, and the released gas was analyzed by gas chromatography. Carbon dioxide was detected as the main component, confirming that the sulfide solid electrolyte contained carbonate ions.

[0067] [Comparative Example 1] As raw materials, 0.6508 g of Li2S (Furuuchi Chemical) and 1.3492 g of P2S5 were weighed and mixed. A sulfide solid electrolyte was produced in the same manner as in Example 1, except that the obtained raw material composition (70Li2S-30P2S5) was used.

[0068] [Examples 2 to 3 and Comparative Examples 2 to 3] A sulfide solid electrolyte was produced in the same manner as in Example 1, except that the treatment time of mechanical milling was changed to the time shown in Table 1.

[0069] [evaluation] (XRD measurement) X-ray diffraction (XRD) measurements using CuKα radiation were performed on the sulfide solid electrolytes obtained in Examples 1 to 3 and Comparative Examples 1 to 3. The results of Example 3 and Comparative Example 3 are shown in Figure 3 as representative results. As indicated by the arrows in Figure 3(a), in Example 3, Li7P3S 11A crystalline phase having the structure was confirmed. In Example 3, no peak due to a different phase was observed near 2θ=16.5°. On the other hand, as shown in FIG. 3(b), in Comparative Example 3, a peak due to a different phase was observed near 2θ=16.5°. In addition, from the XRD chart, it was found that I A / I B was calculated to be 0.39 for Example 3 and 1.41 for Comparative Example 3. C / I B was calculated to be 0.098 for Example 3 and 0.61 for Comparative Example 3.

[0070] (thermogravimetric-differential thermal analysis) The crystallization temperature (T c The amount of decarboxylation was calculated using a TG-DTA device (manufactured by Rigaku) ​​by heating the precursor from room temperature to 400°C at a rate of 10°C / min, and then calculating the amount of decarboxylation from the TG curves around the crystallization temperature. The results are shown in Table 1.

[0071] (Ionic conductivity measurement) Ion conductivity measurements (25°C) were carried out on the sulfide solid electrolytes obtained in Examples 1 to 3 and Comparative Examples 1 to 3. 100 mg of the obtained sulfide solid electrolyte powder was pelletized under a pressure of 6 ton / cm using a pellet molding machine. 2 The pellets were pressed at 100°C to prepare pellets. The resistance of the pellets was measured by the AC impedance method, and the ionic conductivity was calculated from the thickness of the pellets. The results are shown in Table 1.

[0072] (Measurement of hydrogen sulfide generation amount) The water resistance of the sulfide solid electrolytes obtained in Example 2 and Comparative Example 1 was evaluated by measuring the amount of hydrogen sulfide generated as follows. A 1.5 L desiccator was placed in a dry air glove box set to a dew point of -30°C, and an Al container containing 2 mg of sulfide solid electrolyte was placed in the desiccator. The desiccator was then left exposed for 30 minutes with the fan running and the lid closed. The hydrogen sulfide generated during this process was monitored with a sensor. The results are shown in Table 1.

[0073] [Table 1]

[0074] As shown in Table 1, in Comparative Example 1, the ionic conductivity was high, but the amount of hydrogen sulfide generated was large. -1 A good ionic conductivity of at least mS / cm was obtained. Furthermore, in Example 2, the amount of hydrogen sulfide generated was significantly lower than in Comparative Example 1. Although the amount of hydrogen sulfide generated was not measured in Examples 1 and 3, it is believed that similar results to those in Example 1 were obtained because the raw material compositions were the same.

[0075] In addition, the ionic conductivity of Comparative Examples 2 and 3 was lower than that of Examples 1 to 3. In Comparative Example 2, the amount of decarbonation was extremely large. This is presumably because the treatment time was short and carbonate ions were not incorporated into the glass. Thus, the sulfide solid electrolyte obtained in Comparative Example 2 had a low ionic conductivity of carbonate ions (CO3 2- ) was not contained. In addition, in Comparative Example 2, the ionic conductivity was one order of magnitude smaller than that in Examples 1 to 3. Therefore, it was suggested that the sulfide solid electrolyte obtained in Comparative Example 2 did not contain Li7P3S 11 On the other hand, in Comparative Example 3, as shown in Table 1, it was suggested that there was no crystalline phase having the I structure. A / I B was larger than that of Example 3, suggesting that the water resistance was low. In addition, in Comparative Example 3, a peak of a different phase was confirmed, which suggests that the different phase caused a decrease in ionic conductivity. [Explanation of symbols]

[0076] 1...Positive electrode layer 2...Anode layer 3...Solid electrolyte layer 4...Positive electrode current collector 5...Negative electrode current collector 6... Battery case 10...All-solid-state battery

Claims

1. Li, P, S and CO ３ ２－ A sulfide solid electrolyte comprising: The sulfide solid electrolyte contains the CO 3 2− in its crystals, The ionic conductivity at 25°C is 0.11 mS / cm or more, A sulfide solid electrolyte, wherein when 2 mg of the sulfide solid electrolyte is placed in a 1.5 L desiccator and exposed for 30 minutes in an environment with a dew point of −30° C., the amount of hydrogen sulfide generated is 100 ppm or less.

2. 2. The sulfide solid electrolyte according to claim 1, wherein the amount of hydrogen sulfide is 1.0 ppm or less.

3. A sulfide solid electrolyte containing Li, P, S, and CO 3 2− , The sulfide solid electrolyte contains bridging sulfur (—S—), The ionic conductivity at 25°C is 0.11 mS / cm or more, A sulfide solid electrolyte, wherein when 2 mg of the sulfide solid electrolyte is placed in a 1.5 L desiccator and exposed for 30 minutes in an environment with a dew point of −30° C., the amount of hydrogen sulfide generated is 0.4 ppm or less.

4. A sulfide solid electrolyte containing Li, P, S, and CO 3 2− , The ionic conductivity at 25°C is 0.11 mS / cm or more, the amount of hydrogen sulfide generated when 2 mg of the sulfide solid electrolyte is placed in a 1.5 L desiccator and exposed for 30 minutes in an environment with a dew point of −30° C. is 100 ppm or less; Li ７ P ３ S １１ The main phase of the crystalline phase has the structure In X-ray diffraction measurement using CuKα radiation, Li appears at 2θ = 27.0° ± 0.5° ２ The peak intensity of S is I Ａ The peak intensity of the crystalline phase appearing at 2θ=23.65°±0.50° is defined as I Ｂ In this case, I Ａ / I Ｂ is equal to or greater than 0 and equal to or less than 0.39, A sulfide solid electrolyte that does not have a peak of a different phase appearing at 2θ=16.5°±0.5°.

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