Solid sulfide electrolytes, batteries, and methods for producing solid sulfide electrolytes.

Abstract

The main purpose of the invention is to propose a solid sulfide electrolyte capable of suppressing the increase in battery resistance (10) with charge and discharge cycles. The invention achieves this purpose by proposing a solid sulfide electrolyte comprising Li, P and S elements, in which, in TOF-SIMS analysis, the ratio (CX / CT) between the total ionic strength (CX) of PO3+, SO42- and PSO+ and the total ionic strength (CT) of all is greater than or equal to 0 and less than 9.10 * 10-3 .

Description

Sulfide solid electrolyte, battery, and method for producing sulfide solid electrolyte

[0001] The present disclosure relates to a sulfide solid electrolyte, a battery, and a method for producing a sulfide solid electrolyte.

[0002] Sulfide solid electrolytes are known as solid electrolytes used in batteries. Sulfide solid electrolytes have the advantage of having higher ionic conductivity than oxide solid electrolytes, for example. Various techniques are known for synthesizing or microparticulating sulfide solid electrolytes. For example, Patent Document 1 discloses a method for producing sulfide glass ceramics, which involves reacting a lithium compound, a phosphorus compound, and a halogen compound in a solvent containing a hydrocarbon and an ether compound to produce sulfide glass, and then heating the resulting sulfide glass to produce sulfide glass ceramics.

[0003] Patent Document 2 discloses a method for producing a sulfide solid electrolyte having a stable crystalline phase, which includes mixing a raw material containing lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms with at least one lithium oxoacid salt selected from lithium nitrate, lithium nitrite, lithium silicate, lithium borate, and lithium carbonate. Patent Document 3 also discloses a method for producing a sulfide solid electrolyte, which includes a micronization step of adding an ether compound to a coarse-grained material of the sulfide solid electrolyte and micronizing the coarse-grained material by a pulverization treatment.

[0004] JP 2017-100907 A JP 2023-097070 A JP 2013-020894 A

[0005] The resistance (internal resistance) of a battery increases as the battery is repeatedly charged and discharged. As a result of extensive research by the present inventors into the factors that cause the battery resistance to increase with the charge-discharge cycle, they have obtained a new finding that the surface state of the sulfide solid electrolyte affects the increase in resistance.

[0006] The present disclosure has been made in view of the above circumstances, and a main object of the present disclosure is to provide a sulfide solid electrolyte that can suppress an increase in battery resistance that occurs with charge / discharge cycles.

[0007] [1] A sulfide solid electrolyte containing Li, P, and S elements, wherein the sum of all ion intensities (C Ｔ ) for PO ３＋ , S.O. ４ ２－ and PSO ＋ The sum of the ionic intensities (C Ｘ ) ratio (C Ｘ / C Ｔ ) is 0 or more, 9.10 x 10 －３ Sulfide solid electrolyte, which is less than

[0008] [2] The above C Ｘ / C Ｔ is 0 or more, 7.57 x 10 －３ The sulfide solid electrolyte according to [1], which is as follows:

[0009] [3] The above C Ｘ / C Ｔ is 0 or more, 6.03 x 10 －３ The sulfide solid electrolyte according to [1] or [2], which is as follows:

[0010] [4] The above C Ｔ The above PO ３＋ Ionic strength (C １ ) ratio (C １ / C Ｔ ) is 5.60 x 10 －４ The sulfide solid electrolyte according to any one of [1] to [3], wherein the sulfide solid electrolyte is less than 100%.

[0011] [5] The above C Ｔ The above SO ４ ２－ Ionic strength (C ２ ) ratio (C ２ / C Ｔ ) is 2.60 x 10 －３ The sulfide solid electrolyte according to any one of [1] to [4], wherein the sulfide solid electrolyte is less than 100%.

[0012] [6] The above C Ｔ The above PSO ＋ Ionic strength (C ３ ) ratio (C ３ / C Ｔ ) is 5.90 x 10 －３The sulfide solid electrolyte according to any one of [1] to [5], wherein the sulfide solid electrolyte is less than 100%.

[0013] [7] The sulfide solid electrolyte according to any one of [1] to [6], wherein the sulfide solid electrolyte has a crystalline phase having peaks at 2θ = 20.2° ± 0.5° and 23.6° ± 0.5° in X-ray diffraction measurement using CuKα radiation. The sulfide solid electrolyte according to any one of [1] to [6].

[0014] [8] The sulfide solid electrolyte according to any one of [1] to [6], wherein the sulfide solid electrolyte has an argyrodite-type crystal phase.

[0015] [9] The sulfide solid electrolyte according to any one of [1] to [6], wherein the sulfide solid electrolyte has an LGPS-type crystal phase.

[0016]

[10] 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, wherein at least one of the positive electrode layer, the negative electrode layer, and the electrolyte layer contains the sulfide solid electrolyte according to any one of [1] to [9].

[0017]

[11] The battery according to

[10] , wherein the electrolyte layer contains the sulfide solid electrolyte.

[0018]

[12] The battery according to

[10] or

[11] , wherein the positive electrode layer contains a positive electrode active material including a rock salt layered active material and the sulfide solid electrolyte, and the negative electrode layer contains a negative electrode active material including Li element and the sulfide solid electrolyte.

[0019]

[13] A method for producing a sulfide solid electrolyte, comprising: a first step of preparing a precursor containing Li, P, and S elements; and a second step of calcining the precursor to obtain a sulfide solid electrolyte, wherein each of the first step and the second step is performed in an environment with an oxygen concentration of less than 254 ppm.

[0020]

[14] The method for producing a sulfide solid electrolyte according to

[13] , wherein each of the first step and the second step is performed in an environment having an oxygen concentration of 176 ppm or less.

[0021]

[15] The method for producing a sulfide solid electrolyte according to

[13] , wherein each of the first step and the second step is performed in an environment having an oxygen concentration of 98 ppm or less.

[0022]

[16] The sulfide solid electrolyte has a total ion intensity (C Ｔ ) for PO ３＋ , S.O. ４ ２－ and PSO ＋ The sum of the ionic intensities (C Ｘ ) ratio (C Ｘ / C Ｔ ) is 0 or more, 9.10 x 10 －３

[16] The method for producing a sulfide solid electrolyte according to any one of

[13] to

[15] , wherein the sulfide solid electrolyte is less than 100%.

[0023] The sulfide solid electrolyte according to the present disclosure has the effect of being able to suppress an increase in battery resistance that occurs with charge / discharge cycles.

[0024] FIG. 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. FIG. 2 is a flow diagram illustrating a method for producing a sulfide solid electrolyte according to the present disclosure. FIG. 3 is a result of TOF-SIMS analysis of the sulfide solid electrolytes obtained in Examples 1 to 3 and Comparative Examples 1 to 3. FIG. 4 is a result of TOF-SIMS analysis of the sulfide solid electrolytes obtained in Examples 4 to 6 and Comparative Examples 4 to 6. FIG. 5 is a result of TOF-SIMS analysis of the sulfide solid electrolytes obtained in Examples 7 to 9 and Comparative Examples 7 to 9. FIG. 6 is a result of resistance measurement of the batteries obtained in Examples 1 to 3 and Comparative Examples 1 to 3. FIG. 7 is a result of resistance measurement of the batteries obtained in Examples 4 to 6 and Comparative Examples 4 to 6. FIG. 8 is a result of resistance measurement of the batteries obtained in Examples 7 to 9 and Comparative Examples 7 to 9.

[0025] The sulfide solid electrolyte, the battery, and the method for producing the sulfide solid electrolyte according to the present disclosure will be described in detail below.

[0026] A. Sulfide Solid Electrolyte The sulfide solid electrolyte in the present disclosure contains Li, P, and S. Furthermore, the sulfide solid electrolyte was subjected to TOF-SIMS analysis, and the sum of all ion intensities was calculated as C Ｔ And PO ３＋, S.O. ４ ２－ and PSO ＋ The sum of the ionic intensities of Ｘ In this case, C Ｔ C against Ｘ The ratio (C Ｘ / C Ｔ ) is the predetermined range.

[0027] According to the present disclosure, C Ｘ / C Ｔ is within a predetermined range, the sulfide solid electrolyte can suppress an increase in battery resistance with charge / discharge cycles. As described above, repeated charge / discharge of a battery increases the battery resistance. There is not just one factor that causes the battery resistance to increase with charge / discharge cycles, but multiple factors are assumed. The present inventors have conducted extensive research into factors originating from sulfide solid electrolytes, and have obtained a new finding that the surface state of the sulfide solid electrolyte affects the increase in resistance.

[0028] Specifically, when the surface state of the sulfide solid electrolyte was analyzed by TOF-SIMS, it was found that there was no significant difference in resistance in the early stages of charge and discharge, regardless of whether the proportion of oxides containing at least one of P and S was high or low. Therefore, it was inferred that the proportion of the oxides may not affect the resistance. However, a new finding was obtained that, unexpectedly, the proportion of the oxides has a significant effect on the resistance when charge and discharge are repeated. Therefore, among oxides containing at least one of P and S, PO having a high ionic strength was selected. ３＋ , S.O. ４ ２－ , PSO ＋ As a result, we focused on the following and quantitatively evaluated their ratios. Ｘ / C Ｔ It was confirmed that when the resistance of the battery is within a predetermined range, an increase in the battery resistance due to charge / discharge cycles can be suppressed.

[0029] Here, the TOF-SIMS analysis in the present disclosure will be described in detail. In the present disclosure, the sum of all ion intensities (count numbers) detected by TOF-SIMS is referred to as C Ｔ And PO ３＋The ionic strength of C １ And SO ４ ２－ The ionic strength of C ２ And PSO ＋ The ionic strength of C ３ And PO ３＋ , S.O. ４ ２－ and PSO ＋ The sum of the ionic intensities of Ｘ (C Ｘ =C １ +C ２ +C ３ ) PO ３＋ , S.O. ４ ２－ , PSO ＋ The peak positions (M / Z) of are 37 (=111 / 3), 48 (=96 / 2), and 79 (=79 / 1), respectively.

[0030] In the present disclosure, C Ｘ / C Ｔ is usually 0 or more, 9.10 x 10 －３ Less than. C Ｘ / C Ｔ is 9.00 x 10 －３ or less, 7.57×10 －３ or less, 6.03 × 10 －３ The following may be possible: C Ｘ / C Ｔ If C is too large, it becomes difficult to sufficiently suppress the increase in battery resistance due to charge / discharge cycles. Ｘ / C Ｔ may be 0 or may be greater than 0. In the latter case, C Ｘ / C Ｔ is, for example, 1.00 × 10 －４ or more, 0.50 × 10 －３ or more, 1.00 x 10 －３ It may be more than that.

[0031] In the present disclosure, C １ / C Ｔ is not particularly limited. １ / C Ｔ is, for example, 5.60 × 10 －４ is less than 5.50 × 10－４ or less, 4.50 x 10 －４ or less, 3.40 x 10 －４ The following may be possible: C １ / C Ｔ If C is too large, it becomes difficult to sufficiently suppress the increase in battery resistance due to charge / discharge cycles. １ / C Ｔ may be 0 or may be greater than 0. In the latter case, C １ / C Ｔ is, for example, 1.00 × 10 －５ or more, 0.50 × 10 －４ or more, 1.00 x 10 －４ It may be more than that.

[0032] In the present disclosure, C ２ / C Ｔ is not particularly limited. ２ / C Ｔ is, for example, 2.60 × 10 －３ is less than 2.50 × 10 －３ or less, 2.30 x 10 －３ or less, 1.90 x 10 －３ The following may be possible: C ２ / C Ｔ If C is too large, it becomes difficult to sufficiently suppress the increase in battery resistance due to charge / discharge cycles. ２ / C Ｔ may be 0 or may be greater than 0. In the latter case, C ２ / C Ｔ is, for example, 0.50 × 10 －４ or more, 1.00 × 10 －４ or more, 5.00 x 10 －４ It may be more than that.

[0033] In the present disclosure, C ３ / C Ｔ is not particularly limited. ３ / C Ｔ For example, 5.90 × 10 －３ is less than 5.70 × 10 －３ or less, 5.50 x 10 －３or less, 4.10 x 10 －３ The following may be possible: C ３ / C Ｔ If C is too large, it becomes difficult to sufficiently suppress the increase in battery resistance due to charge / discharge cycles. ３ / C Ｔ may be 0 or may be greater than 0. In the latter case, C ３ / C Ｔ is, for example, 1.00 × 10 －４ or more, 0.50 × 10 －３ or more, 1.00 x 10 －３ It may be more than that.

[0034] P.O. ３＋ , S.O. ４ ２－ and PSO ＋ The ratio can be controlled by, for example, appropriately adjusting the oxygen ratio in the storage environment of the starting materials, the oxygen concentration in the atmosphere during synthesis, the heating temperature, and the heating time.

[0035] The sulfide solid electrolyte contains at least Li, P, and S. The sulfide solid electrolyte may contain only Li, P, and S, or may contain another element α in addition to Li, P, and S. Examples of the element α include halogen elements such as F, Cl, Br, and I. The sulfide solid electrolyte may contain only one halogen element, or may contain two or more halogen elements.

[0036] Other examples of the element α include, for example, an Me element (Me is Sn, Si, Ge, Ga, B, Al, Zn, In, Bi, As, or Sb). The sulfide solid electrolyte may contain only one Me element, or may contain two or more Me elements. Other examples of the element α include, for example, an O element (oxygen element). In the sulfide solid electrolyte, a portion of the S element may be substituted with an O element.

[0037] The sulfide solid electrolyte may be a glass-ceramic sulfide solid electrolyte, a crystalline sulfide solid electrolyte, or a glass-based (amorphous) sulfide solid electrolyte. Among these, the sulfide solid electrolyte is preferably a glass-ceramic sulfide solid electrolyte or a crystalline sulfide solid electrolyte. That is, the sulfide solid electrolyte preferably has a crystalline phase. Examples of the crystalline phase include an argyrodite-type crystalline phase, an LGPS-type crystalline phase, and a Thio-LISICON-type crystalline phase.

[0038] The sulfide solid electrolyte may have a crystalline phase A having peaks at 2θ = 20.2° ± 0.5° and 23.6° ± 0.5° in XRD measurement using CuKα radiation. In particular, the sulfide solid electrolyte preferably has crystalline phase A as the main phase. The "main phase" refers to the crystalline phase to which the peak with the highest intensity belongs in XRD measurement using CuKα radiation. Crystalline phase A corresponds to, for example, the high Li ion conductive phase described in JP 2015-011898 A. Crystalline phase A typically has peaks at 2θ = 29.4°, 37.8°, 41.1°, and 47.0° in addition to 2θ = 20.2° and 23.6°. The positions of these peaks may also vary within a range of ± 0.5°. The composition of the sulfide solid electrolyte having crystalline phase A is not particularly limited, and it preferably contains the above-mentioned elements. Specific examples of the composition of the sulfide solid electrolyte having the crystalline phase A include xLiI.yLiBr.z (aLi ２ S. (1-a) P ２ S ５) are listed. Here, x + y + z = 100, 0 ≦ x < 100, 0 ≦ y < 100, 0 < z ≦ 100, and 0.70 ≦ a ≦ 0.80. x may be 0 or may be greater than 0. x may be 5 or greater, or may be 10 or greater. x may be 50 or less, or may be 30 or less. y may be 0 or greater than 0. y may be 5 or greater, or may be 10 or greater. y may be 50 or less, or may be 30 or less. z may be 50 or greater, or may be 60 or greater. a may be 0.72 or greater, or may be 0.74 or greater. On the other hand, a may be 0.78 or less, or may be 0.76 or less.

[0039] The sulfide solid electrolyte may have an argyrodite-type crystalline phase. In particular, the sulfide solid electrolyte preferably has the argyrodite-type crystalline phase as the main phase. The argyrodite-type crystalline phase may have peaks at 2θ=15.3°±0.5°, 17.7°±0.5°, 31.1°±0.5°, 44.9°±0.5°, and 47.7°±0.5° in XRD measurement using CuKα radiation. The composition of the sulfide solid electrolyte having the argyrodite-type crystalline phase is not particularly limited, and it preferably contains the elements described above. Specific examples of the composition of the sulfide solid electrolyte having the argyrodite-type crystalline phase include (2-a) Li ２ S-aLiX-Li ３ P.S. ４ Here, X is at least one of Cl, Br, and I, and a may be 0 or greater than 0. In the latter case, a may be 0.5 or greater, or 1.0 or greater. On the other hand, a is, for example, 1.8 or less.

[0040] The sulfide solid electrolyte may have an LGPS-type crystalline phase. In particular, the sulfide solid electrolyte preferably has an LGPS-type crystalline phase as a main phase. The LGPS-type crystalline phase may have peaks at, for example, 2θ=17.38°±0.50°, 20.18°±0.50°, 20.44°±0.50°, 23.56°±0.50°, 23.96°±0.50°, 24.93°±0.50°, 26.96°±0.50°, 29.07°±0.50°, 29.58°±0.50°, 31.71°±0.50°, 32.66°±0.50°, and 33.39°±0.50° in an XRD measurement using CuKα radiation. The composition of the sulfide solid electrolyte having an LGPS-type crystalline phase is not particularly limited, and preferably contains the above-mentioned elements. Specific examples of the composition of the sulfide solid electrolyte having an LGPS-type crystalline phase include Li, １０ GeP ２ S １２ LiGePS-based compositions such as Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ LiSiPSCl-based compositions such as Li ９．４２ Si １．０２ P ２．１ S ９．９６ O ２．０４ LiSiPSO based compositions such as the above are exemplified.

[0041] The shape of the sulfide solid electrolyte may be, for example, particulate. ５０ ) is, for example, 0.1 μm or more and 50 μm or less. ５０ The term "particle size" refers to the volume cumulative particle size measured by a laser diffraction / scattering particle size distribution measurement method. The use of the sulfide solid electrolyte is not particularly limited, but it is preferably used in batteries.

[0042] B. Battery Figure 1 is a schematic cross-sectional view illustrating a battery according to the present disclosure. The battery 10 shown in Figure 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 disposed 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 sulfide solid electrolyte described above in "A. Sulfide Solid Electrolyte."

[0043] According to the present disclosure, by using the above-described sulfide solid electrolyte, a battery can be obtained in which an increase in battery resistance due to charge / discharge cycles is suppressed.

[0044] 1. Positive Electrode Layer The positive electrode layer in the present disclosure contains 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 an electrolyte, a conductive material, and a binder.

[0045] The positive electrode active material may be, for example, an oxide active material. Specific examples of the oxide active material include LiCoO ２ , LiMnO ２ , LiNiO ２ , LiVO ２ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ Rock salt layered active materials such as LiMn ２ O ４ , Li(Ni ０．５ Mn １．５ ) O ４ Spinel-type active materials such as LiFePO ４ , LiMnPO ４ , LiNiPO ４ , LiCoPO ４ Examples of the olivine type active materials include:

[0046] 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 LiNbO ３ , Li ３P.O. ４ , LiPON, or other Li ion conductive oxides. The average thickness of the coating layer is, for example, 1 nm or more and 50 nm or less, and may be 1 nm or more and 10 nm or less.

[0047] The shape of the positive electrode active material may be, for example, particulate. ５０ ) is not particularly limited, but may be, for example, 10 nm or more, or may be 100 nm or more. ５０ ) is, for example, 50 μm or less, and may be 20 μm or less.

[0048] The positive electrode layer may contain at least one of an electrolyte, a conductive material, and a binder. Details of the electrolyte are the same as those described in "3. Electrolyte Layer." In particular, the positive electrode layer preferably contains the sulfide solid electrolyte described in "A. Sulfide Solid Electrolyte" above. 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 rubber-based binders and fluoride-based binders. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0049] 2. Negative Electrode Layer The negative electrode layer in the present disclosure contains at least a negative electrode active material. In addition to the negative electrode active material, the negative electrode layer may contain at least one of an electrolyte, a conductive material, and a binder.

[0050] Examples of negative electrode active materials include metal active materials, carbon active materials, and oxide active materials. Examples of metal active materials include Li, Si, Sn, In, and Al. In particular, the metal active material is preferably a Si-based active material, as this can increase the capacity of the battery. The Si-based active material is an active material primarily composed of Si. The Si-based active material may be simple Si, a Si alloy, or a Si oxide. The Si-based active material may also 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 volume change during charging and discharging.

[0051] The Si-based active material preferably has voids inside the primary particles. The presence of voids inside the primary particles can suppress volume changes due to charging and discharging. The proportion of voids in the primary particles (porosity) is, for example, 4% or more, and may be 10% or more. On the other hand, the porosity is, for example, 40% or less, and may be 20% or less. The porosity can be determined, for example, by the following procedure. First, a cross section of the Si-based active material is observed with a scanning electron microscope (SEM) to obtain a photograph of the particles. From the obtained photograph, the silicon portion and the void portion are clearly distinguished using image analysis software and binarized. The areas of the silicon portion and the void portion are determined, and the void portion (%) is calculated using the following formula: Porosity (%) = 100 x (void portion area) / (silicon portion area + void portion area)

[0052] On the other hand, examples of carbon active materials include graphite, hard carbon, and soft carbon, and examples of oxide active materials include lithium titanate.

[0053] The shape of the negative electrode active material may be, for example, particulate. ５０ ) is not particularly limited, but may be, for example, 10 nm or more, or may be 100 nm or more. ５０) is, for example, 50 μm or less, and may be 20 μm or less.

[0054] The negative electrode layer may contain at least one of an electrolyte, a conductive material, and a binder. Details of the electrolyte are the same as those described in "3. Electrolyte Layer." In particular, the negative electrode layer preferably contains the sulfide solid electrolyte described in "A. Sulfide Solid Electrolyte" above. The conductive material and binder are the same as those described in "1. Positive Electrode Layer" above. The thickness of the negative electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0055] 3. Electrolyte Layer The electrolyte layer in the present disclosure is disposed between the positive electrode layer and the negative electrode layer and contains at least an electrolyte. The electrolyte may be a solid electrolyte or a liquid electrolyte (electrolytic solution).

[0056] Examples of the solid electrolyte include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes; and organic polymer electrolytes such as polymer electrolytes and gel electrolytes.

[0057] The sulfide solid electrolyte is an electrolyte containing S as the main anion component. Examples of sulfide solid electrolytes include solid electrolytes containing Li, X (where X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. The sulfide solid electrolyte may further contain at least one of O and a halogen. Examples of halogen include F, Cl, Br, and I. The sulfide solid electrolyte may be glass (amorphous) or glass ceramic. In particular, the electrolyte layer preferably contains the sulfide solid electrolyte described above in "A. Sulfide Solid Electrolyte."

[0058] The inorganic solid electrolyte other than the sulfide solid electrolyte, the organic polymer electrolyte, and the liquid electrolyte (electrolytic solution) are not particularly limited, and any known electrolytes can be used. The thickness of the electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less.

[0059] 4. Other Configurations The battery according to 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 SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of materials for the negative electrode current collector include SUS, copper, nickel, and carbon. The battery according to the present disclosure may also include an exterior housing that houses an electrode assembly including a positive electrode layer, an electrolyte layer, and a negative electrode layer. The electrode assembly typically further includes a positive electrode current collector and a negative electrode current collector. Examples of exterior housings include a case-type exterior housing and a laminate-type exterior housing.

[0060] The battery according to the present disclosure may further include a confining jig that applies a confining pressure to the electrode assembly along the thickness direction. In particular, when the electrolyte layer is a solid electrolyte layer, applying a confining pressure is preferable to form good ion conduction paths and electron conduction paths. The confining pressure is, for example, 0.1 MPa or more, or may be 1 MPa or more, or may be 5 MPa or more. Meanwhile, the confining pressure is, for example, 100 MPa or less, or may be 50 MPa or less, or may be 20 MPa or less.

[0061] 5. 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 liquid battery containing an electrolytic solution as an electrolyte layer, or may be an all-solid-state battery having a solid electrolyte layer as an electrolyte layer. The battery in the present disclosure may be a primary battery or a secondary battery, but a secondary battery is preferred because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery.

[0062] 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, the battery is preferably 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 (e.g., railways, ships, and aircraft), and may also be used as a power source for electrical appliances such as information processing devices.

[0063] C. Method for Producing Sulfide Solid Electrolyte Figure 2 is a flow diagram illustrating a method for producing a sulfide solid electrolyte according to the present disclosure. As shown in Figure 2, in the first step, a precursor containing Li, P, and S is prepared. Next, in the second step, the precursor is calcined to obtain a sulfide solid electrolyte. In the present disclosure, each of the first and second steps is performed in an environment in which the oxygen concentration is within a predetermined range.

[0064] According to the present disclosure, by performing each of the first step and the second step in an environment in which the oxygen concentration is within a predetermined range, it is possible to obtain a sulfide solid electrolyte that can suppress an increase in battery resistance due to charge / discharge cycles.

[0065] 1. First Step The first step in the present disclosure is a step of preparing a precursor containing Li, P, and S elements. The first step is performed in a space with an adjusted oxygen concentration. Specifically, the first step is performed in an environment where the oxygen concentration is less than 254 ppm. The oxygen concentration may be 176 ppm or less, or 98 ppm or less. The first step is preferably performed in an inert atmosphere such as argon.

[0066] The precursor can be obtained by, for example, amorphizing a raw material mixture containing a Li raw material, a P raw material, and a S raw material. The Li raw material can be, for example, a lithium sulfide (e.g., Li ２ Examples of the P raw material include phosphorus sulfides (e.g., P ２ S ５ , P ２ S ３), and elemental phosphorus. Examples of S raw materials include lithium sulfide (for example, Li ２ S), phosphorus sulfides (e.g., P ２ S ５ , P ２ S ３ ), and elemental sulfur. The raw material mixture may contain another element α in addition to the elements Li, P, and S. The element α is the same as that described above in "A. Sulfide Solid Electrolyte."

[0067] Furthermore, it is preferable that the Li raw material, the P raw material, and the S raw material have a low oxygen concentration in the storage environment. The oxygen concentration in the storage environment of the Li raw material, the P raw material, and the S raw material is preferably 5 ppm or less, respectively. The oxygen concentration in the storage environment of the raw material refers to the oxygen concentration in the storage container. For example, when the raw material is placed in a storage container, if there is a space of 1 L and the space contains 1 cc of oxygen, the oxygen concentration in the storage environment of the raw material corresponds to 1 ppm. The oxygen concentration in the storage environment of the raw material is determined by a GC-TCD (gas chromatography-thermal conductivity detector) method.

[0068] Examples of methods for amorphizing the raw material mixture include mechanical milling using a ball mill, a bead mill, etc. The conditions for mechanical milling are appropriately selected depending on the desired sulfide solid electrolyte.

[0069] On the other hand, the precursor may be obtained by, for example, mixing a raw material mixture containing a Li raw material, a P raw material, and an S raw material in a solvent, followed by filtration. The term "solvent" in the present disclosure refers not only to a solvent in the strict sense, but also to a broader meaning that encompasses a dispersion medium. Examples of the solvent include tetrahydrorane (THF). The solvent preferably has a low oxygen concentration, for example, 5 ppm or less. The amount of the solvent added may be, for example, 20 times or more, or even 30 times or more, by mass ratio, relative to the raw material mixture. On the other hand, the amount of the solvent added may be, for example, 50 times or less, or even 40 times or less, by mass ratio, relative to the raw material mixture.

[0070] The method for mixing the raw material mixture and the solvent is not particularly limited, and examples thereof include a method using a stirrer. The stirring temperature is not particularly limited, and may be, for example, 25°C or higher, 30°C or higher, or 35°C or higher. On the other hand, the stirring temperature is, for example, 50°C or lower, and may be 40°C or lower. The stirring time is not particularly limited, and may be, for example, 48 hours or higher, 60 hours or higher, or 72 hours or higher. On the other hand, the stirring time is, for example, 120 hours or lower, 108 hours or lower, or 96 hours or lower.

[0071] 2. Second Step The second step in the present disclosure is a step of calcining the precursor to obtain a sulfide solid electrolyte. The second step is performed in a space with an adjusted oxygen concentration. Specifically, the second step is performed in an environment where the oxygen concentration is less than 254 ppm. The oxygen concentration may be 176 ppm or less, or 98 ppm or less. The second step may be performed in an inert atmosphere such as argon, or in a reduced pressure atmosphere.

[0072] In the second step, the precursor is calcined. The calcination temperature in the second step is preferably, for example, (Tc-10°C) or higher and (Tc+50°C) or lower, based on the crystallization temperature (Tc) of the sulfide solid electrolyte. The calcination time in the second step is, for example, 1 hour or longer, and may be 5 hours or longer. On the other hand, the calcination time in the second step is, for example, 12 hours or shorter, and may be 10 hours or shorter.

[0073] 3. Other Steps The method for producing a sulfide solid electrolyte according to the present disclosure may include a micronization step of micronizing the sulfide solid electrolyte obtained in the second step described above. In the micronization step, it is preferable to micronize the sulfide solid electrolyte by applying mechanical energy to a dispersion in which the sulfide solid electrolyte is added to a dispersion medium. It is preferable that the dispersion medium used in the dispersion medium has a low oxygen concentration. Examples of methods for micronizing the sulfide solid electrolyte include media-type milling using a bead mill, a planetary ball mill, or the like, jet milling, and cavitation milling. The milling conditions can be appropriately set depending on the target particle size.

[0074] 4. Sulfide Solid Electrolyte The sulfide solid electrolyte obtained through the above-described steps is not particularly limited, but is preferably the sulfide solid electrolyte described above in "A. Sulfide Solid Electrolyte."

[0075] 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.

[0076] Example 1 Using a glove box capable of controlling the oxygen concentration, a sulfide solid electrolyte was prepared in an argon atmosphere under conditions of an oxygen concentration of 98 ppm, and a battery was fabricated.

[0077] (Preparation of sulfide solid electrolyte) Li ２ S, P ２ S ５ , LiI and LiBr, 10LiI-15LiBr-75Li ３ P.S. ４ The raw materials were weighed to obtain a raw material mixture. The oxygen concentration in the storage environment of each raw material was 5 ppm or less. This raw material mixture and tetrahydrofuran in a mass ratio of 20 times the raw material mixture were placed in a glass container and stirred at 25°C for 72 hours. The precipitate was then recovered as a precursor of a sulfide solid electrolyte. The recovered precursor was dried in an argon atmosphere at 25°C and then fired at atmospheric pressure at 100°C for 1 hour. The resulting fired body was vacuum-sealed in a quartz tube, and the quartz tube was placed in a muffle furnace and fired at 140°C for 12 hours to obtain a sulfide solid electrolyte. X-ray diffraction measurement using CuKα radiation was performed on the resulting sulfide solid electrolyte, confirming the formation of crystalline phases having peaks at 2θ = 20.2° ± 0.5° and 23.6° ± 0.5°.

[0078] (Fabrication of Battery) First, the positive electrode active material (LiNi １／３ Co １／３ Mn １／３ O ２80.0 g of the sulfide solid electrolyte prepared above, 9.51 g of the sulfide solid electrolyte prepared above, and 2.5 g of the conductive material (VGCF) were weighed and added to a container. Furthermore, a binder solution (a solution containing styrene butadiene rubber at a concentration of 5% by mass) and a dispersion medium (tetralin) were added to the container. The solid content of the resulting mixture was 69% by mass. The resulting mixture was kneaded using a kneading device (Filmix) to obtain a positive electrode slurry. The resulting positive electrode slurry was applied in the form of a film to the surface of a positive electrode current collector (aluminum foil) using a blade coating method with an applicator, and heated at 100 °C for 30 minutes. This resulted in a positive electrode having a positive electrode current collector and a positive electrode layer.

[0079] Next, 18.6 g of the negative electrode active material (Si), 8.69 g of the sulfide solid electrolyte prepared above, and 2.4 g of the conductive material (VGCF) were weighed and added to a container. Furthermore, a binder solution (a solution containing 5% by mass of styrene-butadiene rubber) and a dispersion medium (diisobutyl ketone) were added to the container. The solid content of the resulting mixture was 43% by mass. The resulting mixture was kneaded using a kneading device (Filmix) to obtain a negative electrode slurry. A high-shear PC wheel was used for the kneading device. The resulting negative electrode slurry was applied to the surface of a negative electrode current collector (nickel foil) in the form of a film using a blade coating method with an applicator and heated at 100 °C for 30 minutes. This resulted in a negative electrode having a negative electrode current collector and a negative electrode layer.

[0080] Next, 40 g of the sulfide solid electrolyte prepared above, 8 g of binder solution (hexane solution containing 5% by mass of acrylate butadiene rubber), 25 g of heptane, and 8 g of dibutyl ether were weighed and kneaded using an ultrasonic homogenizer to obtain a slurry for the solid electrolyte layer. The obtained slurry was applied to the surface of aluminum foil in the form of a film using a blade coating method with an applicator, and heated at 100 °C for 30 minutes. This resulted in a transfer member having aluminum foil and a solid electrolyte layer.

[0081] Next, the positive electrode and the transfer member were superimposed so that the positive electrode layer and the solid electrolyte layer faced each other, and pressed with a pressure of 20 kN to transfer the solid electrolyte layer to the positive electrode layer side. Similarly, the negative electrode and the transfer member were superimposed so that the negative electrode layer and the solid electrolyte layer faced each other, and pressed with a pressure of 20 kN to transfer the solid electrolyte layer to the negative electrode layer side. Then, the stack in which the transferred solid electrolyte layers were superimposed was pressed with a pressure of 4 ton / cm to densify. The densified stack was laminated and sealed, and a confining pressure of 5 MPa was applied to obtain a battery (all-solid-state battery). The design capacity of the battery was 0.3 Ah.

[0082] [Examples 2 and 3] Except for changing the oxygen concentration to 33 ppm and 12 ppm, sulfide solid electrolytes were obtained in the same manner as in Example 1. Except for using the obtained sulfide solid electrolytes, batteries were obtained in the same manner as in Example 1.

[0083] [Comparative Examples 1 to 3] Except for changing the oxygen concentration to 342 ppm, 501 ppm, and 254 ppm, sulfide solid electrolytes were obtained in the same manner as in Example 1. Except for using the obtained sulfide solid electrolytes, batteries were obtained in the same manner as in Example 1.

[0084] [Example 4] A battery was obtained in the same manner as in Example 1, except that the preparation of the sulfide solid electrolyte was changed as follows: Li ２ S, P ２ S ５ and LiCl, Li ２ S-LiCl-Li ３ P.S. ４ (Li ６ P.S. ５The raw materials were weighed to obtain a composition of 100% by mass of ammonium hydroxide, ammonium hydroxide, and ammonium hydroxide. The oxygen concentration in the storage environment of each raw material was 5 ppm or less. The obtained raw material mixture was placed in a zirconia pot together with zirconia balls, which was then set in a planetary ball mill (Fritch P-5) and mechanically milled at a rotation speed of 300 rpm for 20 hours to obtain a precursor. The obtained precursor was heated at 550°C for 6 hours in an Ar flow atmosphere to obtain a sulfide solid electrolyte. X-ray diffraction measurement using CuKα radiation was performed on the obtained sulfide solid electrolyte, and it was confirmed that an argyrodite-type crystalline phase was formed.

[0085] [Examples 5 and 6] Except for changing the oxygen concentration to 33 ppm and 12 ppm, sulfide solid electrolytes were obtained in the same manner as in Example 4. Except for using the obtained sulfide solid electrolytes, batteries were obtained in the same manner as in Example 1.

[0086] [Comparative Examples 4 to 6] Except for changing the oxygen concentration to 342 ppm, 501 ppm, and 254 ppm, sulfide solid electrolytes were obtained in the same manner as in Example 4. Except for using the obtained sulfide solid electrolytes, batteries were obtained in the same manner as in Example 1.

[0087] [Example 7] A battery was obtained in the same manner as in Example 1, except that the preparation of the sulfide solid electrolyte was changed as follows: Li ２ S, GeS ２ and P ２ S ５ Li ４ GeS ４ -2Li ３ P.S. ４ (Li １０ GeP ２ S １２) to obtain a raw material mixture. The oxygen concentration in the storage environment of each raw material was 5 ppm or less. The obtained raw material mixture was placed in a zirconia pot together with zirconia balls, which was then set in a planetary ball mill (Fritch P-5) and mechanically milled at a rotation speed of 370 rpm for 40 hours to obtain a precursor. The obtained precursor was placed in a carbon-coated quartz tube and vacuum-sealed. The pressure of the vacuum-sealed quartz tube was approximately 30 Pa. Next, the quartz tube was placed in a firing furnace and fired at 550 °C for 8 hours to obtain a sulfide solid electrolyte. X-ray diffraction measurement using CuKα radiation was performed on the obtained sulfide solid electrolyte, and it was confirmed that an LGPS-type crystalline phase was formed.

[0088] [Examples 8 and 9] A sulfide solid electrolyte was obtained in the same manner as in Example 7, except that the oxygen concentration was changed to 33 ppm and 12 ppm. A battery was obtained in the same manner as in Example 1, except that the obtained sulfide solid electrolyte was used.

[0089] [Comparative Examples 7 to 9] Sulfide solid electrolytes were obtained in the same manner as in Example 7, except that the oxygen concentration was changed to 342 ppm, 501 ppm, and 254 ppm. Batteries were obtained in the same manner as in Example 1, except that the obtained sulfide solid electrolytes were used.

[0090] [Evaluation] (TOF-SIMS Analysis) The surface state of the sulfide solid electrolytes obtained in Examples 1 to 9 and Comparative Examples 1 to 9 was measured by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Specifically, the sulfide solid electrolyte powder was pelletized, and Bi was used as the primary ion. ３＋ The measurement was carried out using a ion beam splitter, with the irradiation current value set to 0.3 pA and the analysis area set to 300 μm. The total of all detected ion intensities (count numbers) was calculated as C Ｔ And PO ３＋ The ionic strength of C １ And SO ４ ２－ The ionic strength of C ２ And PSO ＋The ionic strength of C ３ Then, C １ , C ２ and C ３ The sum of C Ｘ The results are shown in Table 1 and Figures 3 to 5. The bar graphs shown in Figures 3 to 5 show, from the left, C １ / C Ｔ , C ２ / C Ｔ , C ３ / C Ｔ and C Ｘ / C Ｔ This shows:

[0091]

[0092] As shown in Table 1 and FIG. 3, Examples 1 to 3 have a higher C Ｘ / C Ｔ It was confirmed that the value of C was small. １ , C ２ and C ３ In contrast, in Comparative Examples 1 to 3, the values ​​of C １ , C ２ and C ３ All of the values ​​were large. ３ (PSO ＋ 4 and 5, a similar tendency was confirmed in the relationship between Examples 4 to 6 and Comparative Examples 4 to 6, and in the relationship between Examples 7 to 9 and Comparative Examples 7 to 9.

[0093] (Measurement of Ionic Conductivity) The ionic conductivity of the sulfide solid electrolytes obtained in Examples 1 to 9 and Comparative Examples 1 to 9 was measured. First, two sheets of carbon-coated aluminum foil were stacked on top of each other, and a 6 ton / cm ２ The cell was pressed at a pressure of 59 kN and restrained at 6 N m, and the thickness was measured. The McCor cell was also restrained at 6 N m, and the thickness was measured. These thicknesses were used as blanks. Next, 150 mg of sulfide solid electrolyte powder was placed in the compaction cell, and the pressure was 1 ton / cm. ２Carbon-coated aluminum foil was placed on both sides of the obtained powder compact, and the powder compact was pressed under the conditions of 6 ton / cm ２ The cell was then restrained with a pressure of 6 N·m, and the thickness was measured. The cell was then sealed in a desiccator together with a Molle-Silar cube. Then, an electrochemical measurement was performed using a Solartron measuring instrument at frequencies of 0.1 Hz to 10 ６ The impedance was measured under the conditions of a frequency of 10 Hz, an amplitude of 10 mV, and a temperature of 25° C., and the ionic conductivity was determined. The results are shown in Table 2.

[0094] (Resistance Measurement) Resistance measurements were performed using the batteries obtained in Examples 1 to 9 and Comparative Examples 1 to 9. First, the batteries were charged to 4.55 V, then discharged to 2.5 V, and discharged from that voltage at 1.7 C. The resistance (resistance before endurance testing) was calculated from the voltage change over 10 seconds and the current value. Then, CCCV charging and discharging was performed for 1000 cycles under the conditions of upper limit voltage: 4.55 V, lower limit voltage: 2.5 V, and rate: 0.1 C. The resistance after 1000 cycles (resistance after endurance testing) was calculated in the same manner as above. The results are shown in Table 2 and Figures 6 to 8.

[0095]

[0096] As shown in Table 2 and FIG. 6, in Examples 1 to 3 and Comparative Examples 1 to 3, the ionic conductivity and the resistance of the battery before endurance testing were both comparable. In other words, it was confirmed that the surface state of the sulfide solid electrolyte has little effect on the resistance of the battery before endurance testing. In contrast, as shown in Table 2 and FIG. 6, it was confirmed that the resistance of the battery after endurance testing in Examples 1 to 3 can be significantly reduced compared to the resistance in Comparative Examples 1 to 3. In this way, C Ｘ / C Ｔ It was confirmed that the use of a sulfide solid electrolyte in which the value of β-type sulfide is adjusted to fall within a predetermined range can suppress the increase in battery resistance due to charge / discharge cycling. Furthermore, as shown in Figures 7 and 8, a similar tendency was confirmed in the relationship between Examples 4 to 6 and Comparative Examples 4 to 6, and in the relationship between Examples 7 to 9 and Comparative Examples 7 to 9.

[0097] 1 ... positive electrode layer 2 ... negative electrode layer 3 ... electrolyte layer 4 ... positive electrode current collector 5 ... negative electrode current collector 10 ... battery

Claims

1. A sulfide solid electrolyte containing Li, P and S elements, wherein the sum of all ion intensities (C Ｔ ) to PO ３＋ , S.O. ４ ２－ and PSO ＋ The sum of the ionic intensities (C Ｘ ) ratio (C Ｘ / C Ｔ ) is 0 or more, 9.10 x 10 －３ A sulfide solid electrolyte that is less than 2. Above C Ｘ / C Ｔ is 0 or more, 7.57 x 10 －３ The sulfide solid electrolyte according to claim 1, wherein:

3. Above C Ｘ / C Ｔ is 0 or more, 6.03 x 10 －３ The sulfide solid electrolyte according to claim 1, wherein:

4. Above C Ｔ The PO for ３＋ Ionic strength (C １ ) ratio (C １ / C Ｔ ) is 5.60 x 10 －４ The sulfide solid electrolyte of claim 1 . 5.C above Ｔ The SO ４ ２－ Ionic strength (C ２ ) ratio (C ２ / C Ｔ ) is 2.60 x 10 －３ The sulfide solid electrolyte of claim 1 .

6. Above C Ｔ The PSO for ＋ Ionic strength (C ３ ) ratio (C ３ / C Ｔ ) is 5.90 x 10 －３ The sulfide solid electrolyte of claim 1 .

7. The sulfide solid electrolyte according to claim 1, wherein the sulfide solid electrolyte has a crystalline phase having peaks at 2θ = 20.2° ± 0.5° and 23.6° ± 0.5° in X-ray diffraction measurement using CuKα radiation.

8. The sulfide solid electrolyte of claim 1, wherein the sulfide solid electrolyte comprises an argyrodite-type crystal phase.

9. The sulfide solid electrolyte of claim 1, wherein the sulfide solid electrolyte comprises an LGPS-type crystal phase.

10. 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, wherein at least one of the positive electrode layer, the negative electrode layer, and the electrolyte layer contains the sulfide solid electrolyte according to any one of claims 1 to 9.

11. The battery of claim 10, wherein the electrolyte layer contains the sulfide solid electrolyte.

12. The battery according to claim 10, wherein the positive electrode layer contains a positive electrode active material including a rock salt layered type active material and the sulfide solid electrolyte, and the negative electrode layer contains a negative electrode active material including Li element and the sulfide solid electrolyte.

13. A method for producing a sulfide solid electrolyte, comprising: a first step of preparing a precursor containing Li, P and S elements; and a second step of calcining the precursor to obtain a sulfide solid electrolyte, wherein each of the first step and the second step is performed in an environment in which the oxygen concentration is less than 254 ppm.

14. The method for producing a sulfide solid electrolyte according to claim 13, wherein the first step and the second step are each carried out in an environment having an oxygen concentration of 176 ppm or less.

15. The method for producing a sulfide solid electrolyte according to claim 13, wherein the first step and the second step are each carried out in an environment having an oxygen concentration of 98 ppm or less.

16. The sulfide solid electrolyte is analyzed by TOF-SIMS, and the sum of all ion intensities (C Ｔ ) to PO ３＋ , S.O. ４ ２－ and PSO ＋ The sum of the ionic intensities (C Ｘ ) ratio (C Ｘ / C Ｔ ) is 0 or more, 9.10 x 10 －３ The method for producing a sulfide solid electrolyte according to claim 13, wherein the sulfide solid electrolyte is less than 100% by mass.

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