Solid electrolyte material, electrode, and lithium-ion secondary battery

Abstract

The present disclosure provides a solid electrolyte material including a crystal having Li, M, O, and X as constituent elements, the contents of Li, M, O, and X being 0.40 to 1.30: 0.80 to 2.50: 0.01 to 0.45: 3 in terms of molar ratio, the above M including M1, the above M1 being at least one selected from the group of elements for which the generation energy of M1Cl in the reaction formula (2 / x)M1+Cl2→(2 / x)M1Cl (in the above reaction formula, x is an integer of 1 to 6) is -500 kJ / mol or less, and the above X being at least one selected from F, Br, Cl, and I. x x The present disclosure provides a solid electrolyte material including a crystal having Li, M, O, and X as constituent elements, the contents of Li, M, O, and X being 0.40 to 1.30: 0.80 to 2.50: 0.01 to 0.45: 3 in terms of molar ratio, the above M including M1, the above M1 being at least one selected from the group of elements for which the generation energy of M1Cl in the reaction formula (2 / x)M1+Cl2→(2 / x)M1Cl (in the above reaction formula, x is an integer of 1 to 6) is -500 kJ / mol or less, and the above X being at least​

Description

Technical Field

[0001] This disclosure relates to solid electrolyte materials, electrodes, and lithium-ion secondary batteries. Background Technology

[0002] In recent years, solid electrolytes have attracted attention as electrolytes used in electrochemical devices such as lithium-ion batteries. Compared with traditional electrolytes, solid electrolytes offer superior high-temperature durability and high-voltage tolerance. Therefore, they are considered useful for improving battery performance, including safety, high capacity, rapid charge and discharge, and battery pack energy density.

[0003] As a solid electrolyte, Li exhibits high ionic conductivity approaching that of liquid electrolytes and moderate flexibility, thus leading to its application in [the study / development]. 10 GeP2S 12 Studies have been conducted on sulfide-based solid electrolytes (e.g., Patent Document 1). Furthermore, Li7La3Zr2O is also known as a lithium-containing solid electrolyte. 12 Oxide-based solid electrolytes such as (LLZO) and halide-based solid electrolytes such as Li3InCl6 and LiYBr6.

[0004] Halogen-based solid electrolytes are considered useful due to their high antioxidant properties, low and stable reactivity with atmospheric moisture, monovalent halide ions, low activation energy in ion conduction, and high stability at high potentials. Patent Document 2 discloses a lithium-ion conductive solid electrolyte material composed of Li, La, O, and X, where X is at least one element selected from Cl, Br, and I. Patent Document 3 discloses a solid electrolyte containing Li, La, O, and I.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2003-181158 Patent Document 2: International Publication No. 2020 / 137043 Patent Document 3: International Publication No. 2020 / 219846 Non-patent literature Non-patent document 1: Luise M. Riegger, et, al, "Lithium-MetalAnodeInstability of the SuperionicHalideSolidElectrolytes andtheImplicationsforSolid-State Batteries", Angewandte ChemieInternationalEditionVolume 60, Issue 12, p.6189-6823 Summary of the Invention

[0006] The problem that the invention aims to solve On the other hand, it is known that when halide-based solid electrolytes come into contact with negative electrode materials such as lithium and graphite, they undergo reduction decomposition at the interface, producing lithium chloride and elemental forms of the metal elements constituting the halide-based solid electrolyte, which may lead to poor battery operation (e.g., Non-Patent Literature 1). The existence of halide-based solid electrolytes with excellent reduction resistance would be useful.

[0007] The purpose of this disclosure is to provide a halide-based solid electrolyte material with excellent reduction resistance. A further purpose of this disclosure is to provide an electrode and a lithium-ion secondary battery comprising the aforementioned halide-based solid electrolyte material.

[0008] Methods for solving problems Through research, the inventors have discovered that the reduction resistance of halide-based solid electrolyte materials originates from the reducing properties of the metal elements themselves. By using metal elements with high energy of formation and endothermic reaction when generating chlorides of these metal elements, and adjusting the content ratio to a predetermined level, and by replacing a portion of the halide with oxygen, the reduction resistance of the solid electrolyte material can be improved. This disclosure is based on the above insights.

[0009] This disclosure provides the following [1]. [1] A solid electrolyte material comprising crystals with Li, M, O, and X as constituent elements. The molar ratios of Li, M, O, and X are 0.40–1.30 : 0.80–2.50 : 0.01–0.45 : 3. The above M includes M1, In the process of transforming (2 / x)M1+Cl2→(2 / x)M1Cl x The reaction formula (in the above reaction formula, x is an integer from 1 to 6) contains M1Cl x When the generation energy is set to E1, M1 is at least one element selected from the group of elements where E1 is below -500 kJ / mol. X is selected from at least one of F, Br, Cl and I.

[0011] The aforementioned solid electrolyte material is a halide-based solid electrolyte material containing a halogen element as X and M1 meeting specified conditions as M, and containing oxygen in a specified content ratio of Li, M, O, and X. This solid electrolyte material exhibits excellent reduction resistance due to its composition.

[0012] The above [1] can be [2]~[9] below. [2] According to the solid electrolyte material described in [1], wherein, The above M also includes M2, The aforementioned M2 is an element other than M1, and the ratio of the aforementioned M1 to the aforementioned M2 is set as a:b in terms of element ratio, and (2 / x)M2 + Cl2 → (2 / x)M2Cl x The reaction formula (in the above reaction formula, x is an integer from 1 to 6) contains M2Cl x When the generation energy is set to E2, the above M2 is at least one element selected from the group of elements where [a / (a+b)]E1+[b / (a+b)]E2 is -500kJ / mol. [3] According to the solid electrolyte material described in [1] or [2], wherein the M1 mentioned above contains La. [4] The solid electrolyte material according to any one of [1] to [3], wherein the above X contains Cl, and the proportion of Cl in the above X is 50 to 100 mol. [5] The solid electrolyte material according to any one of [1] to [4], wherein the crystal has space group P63 / m symmetry. [6] According to any one of [1] to [5], in the solid electrolyte material, when the peak existing in the region with a diffraction angle (2θ) of 13.5 ± 1° is designated as peak A in the X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα rays, the half-maximum amplitude of the peak A is 0.80° or less. [7] According to any one of [1] to [6], in the solid electrolyte material, when the peak present in the region with a diffraction angle (2θ) of 24.5 ± 1° is designated as peak B in the X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα rays, the half-maximum amplitude of the peak B is 1.58° or less. [8] According to any one of [1] to [7], in the solid electrolyte material, when the peak existing in the region with a diffraction angle (2θ) of 13.5 ± 1° is designated as peak A, and the peak existing in the region with a diffraction angle (2θ) of 24.5 ± 1° is designated as peak B in the X-ray diffraction spectrum obtained by using powder X-ray diffraction with CuKα rays, the height H of the aforementioned peak A is... A The height H relative to the above peak B B The ratio is 0.1 to 1.0. [9] The solid electrolyte material according to any one of [1] to [8] has a density of 2.0 to 5.0 g / cm³. 3 .

[0021] This disclosure also provides the following

[10] ~

[12] .

[10] An electrode comprising a solid electrolyte, wherein, The above-mentioned solid electrolyte is composed of any one of the solid electrolyte materials described in [1] to [9].

[11] A lithium-ion secondary battery having the electrodes described in

[10] .

[12] A lithium-ion secondary battery comprising a solid electrolyte containing any one of the solid electrolyte materials described in [1] to [9].

[0025] Invention Effects According to this disclosure, a halide-based solid electrolyte material with excellent reduction resistance can be provided. According to this disclosure, an electrode and a lithium-ion secondary battery incorporating the aforementioned halide-based solid electrolyte material can also be provided. Attached Figure Description

[0026] Figure 1 The graph shows the results of cyclic voltammetry tests when the solid electrolyte materials of Examples 1, 2, 1, and 2 were used. Detailed Implementation

[0027] The embodiments of this disclosure will now be described. However, the following embodiments are merely illustrative examples of this disclosure and are not intended to limit this disclosure to the following content.

[0028] Unless otherwise specified, the materials illustrated in this specification may be used alone or in combination of two or more. Regarding the content of each component in the composition, in the presence of multiple substances equivalent to each component in the composition, unless otherwise specified, the content refers to the total amount of those multiple substances present in the composition.

[0029] One embodiment of the solid electrolyte material comprises a crystal with Li, M, O, and X as constituent elements, wherein M is a metallic element other than Li, and X is at least one selected from F, Br, Cl, and I. The solid electrolyte material has a halogen element as X, therefore it is a so-called halide-based solid electrolyte. The solid electrolyte material can be a powder that is an aggregate of crystals. Each particle can be polycrystalline.

[0030] For the aforementioned solid electrolyte material, M includes M1, and the reaction (2 / x)M1 + Cl2 → (2 / x)M1Cl x The reaction formula (in the above reaction formula, x is an integer from 1 to 6) contains M1Cl x When the generation energy is set to E1, M1 is at least one element selected from the group of elements with E1 below -500 kJ / mol.

[0031] The element M can be at least one element selected from the group consisting of elements whose upper limit of generation energy E1 is, for example, -550 kJ / mol or less, or -600 kJ / mol or less. If the upper limit of generation energy E1 is within the aforementioned range, the deintercalation / intercalation of halide ions from the solid electrolyte material and the precipitation of M can be further suppressed, thereby further improving the reduction resistance of the solid electrolyte material. The lower limit of generation energy E1 can be, for example, -900 kJ / mol or more, -850 kJ / mol or more, -800 kJ / mol or more, or -750 kJ / mol or more. If the lower limit of generation energy E1 is within the aforementioned range, a layer containing Li elements generated through the reduction decomposition of the solid electrolyte material can be appropriately formed when constructing a battery, thereby improving the operational stability of the battery. The generation energy E1 can be adjusted within the aforementioned range, for example, it can be -900 kJ / mol or more and -500 kJ / mol or less, or -850 kJ / mol or more and -500 kJ / mol or less.

[0032] The formation energies in this specification refer to values ​​calculated using the Gibbs free energy at 0.1 MPa and 298 K. For example, values ​​for the Gibbs free energy can be obtained from NIST-JANAF Thermochemical Tables. The formation energies for chlorides of representative elemental species are shown in Table 1 below.

[0033] From the perspective of further improving reduction resistance, the M1 in the above-mentioned solid electrolyte material may contain La, or may only contain La.

[0034] In addition to M1, the aforementioned solid electrolyte material may also contain M2 as M. Here, M2 is an element other than M1, and the ratio of M1 to M2 is set as a:b in elemental terms, and (2 / x)M2 + Cl2 → (2 / x)M2Cl x The reaction formula (in the above reaction formula, x is an integer from 1 to 6) contains M2Cl x When the generation energy is set to E2, M2 can be at least one element selected from the group where [a / (a+b)]E1 + [b / (a+b)]E2 is -500 kJ / mol. Even if M contains elements other than M1, the decrease in reduction tolerance can be suppressed by adjusting the elemental ratio of M2 to M2 in a manner that satisfies the above conditions.

[0035] When M includes M2, the minimum value of the proportion of M1 (100×a / (a+b)) is determined by the value of [a / (a+b)]E1+[b / (a+b)]E2 being -500 kJ / mol. When this minimum value is set to Q%, the lower limit of the proportion of M1, when M includes M2, can be, for example, Q% or higher, Q+10% or higher, or Q+20%. By keeping the lower limit of the proportion of M1 within the above range, the reduction resistance of the solid electrolyte material can be further improved.

[0036] When M includes M1 and M2, it is preferable that M1 has a larger content. The combined amount of M1 and M2 can be the main element in M. The combined amount of M1 and M2 is based on M, for example, it can be 90 mol% or more, 95 mol% or more, or 100 mol% or more. M1 is preferably the element with the largest amount in M. M2 can be the element with the second largest amount in M. When M includes one element belonging to M1 and one element belonging to M2, the element belonging to M1 can be the element with the largest amount in M, and the element belonging to M2 can be the element with the second largest amount in M.

[0037] From the viewpoint of further improving reduction resistance, the X in the above-mentioned solid electrolyte material preferably contains Cl. When the X contains Cl, the proportion of Cl in the X can be, for example, 50-100 mol%, 70-98 mol%, 80-96 mol%, or 90-94 mol%.

[0038] The aforementioned solid electrolyte material can also be considered as a compound in which a portion of the halogen (X) is replaced by an oxygen (O). In the aforementioned solid electrolyte material, the lower limit of the oxygen content is based on the total content of halogen and oxygen, and can be, for example, 1.0 mol% or more, 4.0 mol% or more, 6.0 mol% or more, or 8 mol% or more. By setting the oxygen content within the above range, the reduction resistance of the solid electrolyte material can be further improved. The upper limit of the oxygen content is based on the total content of halogen and oxygen, and can be, for example, 13.0 mol% or less, 12.5 mol% or less, or 12.0 mol% or less. By setting the oxygen content within the above range, the reduction resistance of the solid electrolyte material can be further improved.

[0039] In the above-mentioned solid electrolyte material, the molar ratio of each element (Li:M:O:X) can be 0.40~1.30:0.80~2.50:0.01~0.45:3, 0.50~1.20:0.84~2.00:0.10~0.42:3, 0.55~1.15:0.86~1.75:0.20~0.40:3, or 0.60~1.00:0.90~1.50:0.30~0.38:3.

[0040] The elemental composition ratios of the solid electrolyte materials in this specification refer to values ​​determined by the following methods. Li and M refer to values ​​determined by high-frequency inductively coupled plasma atomic emission spectrometry (ICP), X refers to values ​​determined by ion chromatography, and O refers to values ​​determined by non-dispersive infrared absorption spectrometry. These values ​​are used to calculate the aforementioned composition ratios. It should be noted that in the case of self-prepared solid electrolyte materials, the composition ratios can be calculated from the elemental composition ratios of the raw materials.

[0041] The aforementioned solid electrolyte material comprises crystals with Li, M, O, and X as constituent elements, and these crystals may be crystals with space group P63 / m symmetry. Alternatively, the aforementioned solid electrolyte may consist solely of this crystal. Whether the aforementioned solid electrolyte contains crystals with space group P63 / m symmetry can be confirmed by performing powder X-ray diffraction using CuKα rays.

[0042] The aforementioned solid electrolyte material may have the same or similar crystal structure as LaCl3, or it may have the same crystal structure as LaCl3. In the X-ray diffraction spectrum obtained by powder X-ray diffraction using CuKα rays, the aforementioned solid electrolyte material may have a peak (hereinafter referred to as peak A) located in the region with a diffraction angle (2θ) of 13.5 ± 1°, or it may have a peak (hereinafter referred to as peak B) located in the region with a diffraction angle (2θ) of 24.5 ± 1°. Peak A originates from the reflection of metal M from the surface of the solid electrolyte along the Li conduction direction, while peak B originates from the reflection of metal M from a direction different from peak A.

[0043] The half-maximum (WHM) of each peak observed in the X-ray diffraction spectrum obtained by powder X-ray diffraction using CuKα rays of a solid electrolyte material can be used as an indicator of the crystallinity of the crystal constituting the solid electrolyte material. That is, the smaller the WHM of a peak, the higher the crystallinity, and the more stably a crystal structure is formed. In the solid electrolyte material disclosed herein, the WHM of the peaks observed in the X-ray diffraction spectrum decreases, increasing crystallinity, thereby reducing the reactivity of the crystal and further improving reduction resistance. On the other hand, a large WHM of the peaks and low crystallinity indicate that the solid electrolyte material has an amorphous structure. Solid electrolyte materials with an amorphous structure exhibit localized fluctuations in the crystal structure, making it difficult to introduce regular lattice defects. Therefore, decomposition starting from lattice defects is less likely to occur, further suppressing the decrease in reduction resistance. The WHM of the peaks, arising from crystallinity, can be adjusted by changing the mass ratio of the raw material composition to the mass of the balls in the ball mill during the manufacture of the solid electrolyte material, the rotational speed of the ball mill, etc.

[0044] In the X-ray diffraction spectrum of the aforementioned solid electrolyte material obtained by powder X-ray diffraction using CuKα rays, the upper limit of the half-maximum amplitude (WHM) of peak A can be, for example, 0.80° or less, 0.75° or less, 0.70° or less, 0.60° or less, 0.50° or less, 0.40° or less, or 0.30° or less. The lower limit of the WHM of peak A is not particularly limited, and can be, for example, 0.22° or more, 0.23° or more, or 0.24° or more.

[0045] In the X-ray diffraction spectrum of the aforementioned solid electrolyte material obtained by powder X-ray diffraction using CuKα rays, the upper limit of the half-maximum amplitude (WHM) of peak B can be, for example, 1.58° or less, 1.40° or less, 1.30° or less, 1.00° or less, 0.90° or less, 0.80° or less, 0.70° or less, 0.60° or less, or 0.50° or less. The lower limit of the WHM of peak B is not particularly limited, and can be, for example, 0.20° or more, 0.23° or more, or 0.25° or more.

[0046] In the X-ray diffraction spectrum obtained by powder X-ray diffraction using CuKα rays on the above-mentioned solid electrolyte material, the height H of the above-mentioned peak A is... A The height H relative to the above peak B B The ratio (H) A / H B The value of H is an indicator of the degree of anisotropy in a crystal structure. It is believed that H... A / H B The higher the value of H, the greater the anisotropy, corresponding to the growth of stable faces of the crystals constituting the solid electrolyte material. Furthermore, through the growth of stable faces of the crystals as described above, reduction resistance is further improved. On the other hand, when anisotropy is too high, the bond energies of interatomic bonds within the crystal structure deviate, reactivity increases, and the reduction resistance of the solid electrolyte material decreases. From the viewpoint of further improving reduction resistance, H... A / H B The value can be, for example, 0.1~1.0, 0.1~0.9, 0.3~0.8, 0.4~0.7 or 0.5~0.7.

[0047] The powder X-ray diffraction measurements using CuKα rays described in this specification were performed under the conditions described in the examples. The half-maximum (FWHM) of a peak in this specification refers to the full width at half maximum (FWHM), which is determined by fitting a spectrum obtained by removing background signals from the X-ray diffraction spectrum obtained through the powder X-ray diffraction measurements described above. An X-ray diffraction apparatus was used for the powder X-ray diffraction measurements. For example, the "Ultima IV" (trade name) manufactured by Rigaku Corporation can be used. Data analysis can be performed using, for example, the analysis software "PDXL2" included with the "Ultima IV" (trade name) manufactured by Rigaku Corporation.

[0048] The density of the aforementioned solid electrolyte material can be, for example, 2.0~5.0 g / cm³. 3 2.5~4.8g / cm 3 2.8~4.6g / cm 33.0~4.4g / cm 3 Or 3.5~4.4g / cm 3 If the density of the solid electrolyte material is within the above range, the density of the solid electrolyte can be further increased when the solid electrolyte material is compressed and formed, and the reduction resistance can be further improved by forming a more uniform and stable interface with the electrode.

[0049] The density in this specification refers to the value calculated by measuring the volume of a test sample prepared by filling 100 mg of the above-mentioned solid electrolyte material into an insulating cylinder with an inner diameter of 10 mm, applying a pressure of 370 MPa.

[0050] One example of a method for manufacturing a solid electrolyte material involves modifying a raw material composition comprising a lithium source and a compound having a metal element M as a constituent element by a mechanochemical method. Examples of lithium sources include lithium halides and lithium oxide. Examples of compounds having a metal element M as a constituent element include halides of metal element M and oxides of metal element M. At least one of the lithium source and the compound having a metal element M as a constituent element is a halide, and preferably, the compound having at least a metal element M as a constituent element contains a halide. The metal element M at least includes M1 as described above.

[0051] In mechanochemical methods, for example, a ball mill can be used to supply mechanical energy to the raw material solids through collisions, shearing, and friction. Ball milling can be carried out dry. Before ball milling, the raw material composition can be mixed (pre-mixed) in a mortar or other container for at least one minute. This pre-mixing homogenizes the raw material composition fed into the container during ball milling, resulting in better uniformity of the solid electrolyte material obtained through ball milling and further improved reduction resistance.

[0052] Zirconia balls can be used in ball mills. The diameter of the balls can be, for example, 1~15mm, 2~10mm, or 2~5mm.

[0053] The filling rate of balls in the container during ball milling can be adjusted by the filling amount of the raw material composition. The ratio of the mass of the raw material composition to the mass of the balls (100 [total mass of the raw material composition] / [total mass of the balls]) can, for example, be 5.0% by mass or less, 4.5% by mass or less, 3.0% by mass or less, 2.8% by mass or less, 2.6% by mass or less, or 2.5% by mass or less. If the ratio is within the above range, the impact of the balls can be supplied to the raw material composition more fully. The ratio of the mass of the raw material composition to the mass of the balls can, for example, be 0.3% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 1.5% by mass or more, or 1.8% by mass or more. If the lower limit of the above ratio is within the above range, the incorporation of impurities accompanying the collision of the balls into the solid electrolyte material can be further reduced, the generation of crystal defects accompanying the incorporation of impurities can be suppressed, and the reduction in reduction resistance can be more effectively suppressed.

[0054] The rotational speed of the ball mill can be, for example, 200~700 rpm, 200~500 rpm, or 250~350 rpm.

[0055] The processing time using a ball mill can be, for example, 24 hours or more, or 24 to 72 hours or 36 to 60 hours. By limiting the processing time to within the above range, the raw material solids are more thoroughly mixed, and the elemental substitution using the mechanochemical method becomes more complete, thereby further improving the reduction resistance of the obtained solid electrolyte material.

[0056] The aforementioned solid electrolyte materials exhibit excellent reduction resistance, making them useful as materials for forming solid electrolyte layers or electrodes in batteries. Furthermore, these solid electrolyte materials also possess excellent reduction resistance, making them useful as constituent materials for lithium-ion secondary batteries.

[0057] One embodiment of the electrode is an electrode comprising a solid electrolyte. The solid electrolyte is composed of the aforementioned solid electrolyte material. The electrode comprises an electrode active material (positive electrode active material or negative electrode active material).

[0058] One embodiment of a lithium-ion secondary battery includes the aforementioned electrode. The electrode can be either a positive or negative electrode, but due to the excellent reduction resistance of the aforementioned solid electrolyte material, the advantages of this disclosure are more pronounced when it is used as a negative electrode.

[0059] Positive electrode active materials can be exemplified by lithium-containing composite metal oxides comprising lithium (Li) and at least one transition metal selected from V, Cr, Mn, Fe, Co, Ni, and Cu. Examples of such lithium composite metal oxides include LiCoO2, LiNiO2, LiMn2O4, Li2MnO3, and LiNiO2.x Mn y Co 1-x-y O2[0 <x+y<1])、LiNi x Co y Al 1-x-y O2[0 <x+y<1])、LiCr 0.5 Mn 0.5 O2, LiFePO4, Li2FeP2O7, LiMnPO4, LiFeBO3, Li3V2(PO4)3, Li2CuO2, Li2FeSiO4 and Li2MnSiO4, etc.

[0060] Examples of negative electrode active materials include metals such as Li, Si, Sn, Si-Mn, Si-Co, Si-Ni, In, and Au, as well as alloys containing these metals, carbon materials such as graphite, and materials in which lithium ions are embedded in the interlayer of the carbon material.

[0061] In addition to the solid electrolyte and electrode active material described above, the electrode may also contain other components. Examples of such other components include solid electrolyte compounds other than the solid electrolyte material, conductive additives, and binders.

[0062] As a conductive material contained in the positive electrode, the conductive additive can be a carbon material. Examples of carbon materials include graphene, graphite, carbon black, fullerene, carbon nanotubes, and carbon fibers. Examples of graphite include natural graphite (flake graphite, etc.) and artificial graphite. Examples of carbon black include acetylene black, Ketjen black, channel black, furnace black, lamp black, and pyrolysis black. Examples of carbon fibers include vapor-grown carbon fibers (VGCF), etc.

[0063] Examples of binders (adhesives) include fluorinated resins and synthetic rubbers. Fluorinated resins are preferably resins with a carbon chain as the main chain. The carbon chain can be formed by free radical polymerization of a compound having olefinically unsaturated groups. Examples of fluorinated resins include poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and polyvinylidene fluoride (PVDF). Examples of synthetic rubbers include SBR (styrene-butadiene rubber).

[0064] The electrode may have a structure in which a layer comprising the above-mentioned solid electrolyte material and electrode active material is disposed on the current collector. The material of the current collector is not particularly limited and may be an element or alloy of metals such as Cu, Mg, Ti, Fe, Co, Ni, Zn, Al, Ge, In, Au, Pt, Ag, and Pd.

[0065] Another embodiment of the lithium-ion secondary battery includes a solid electrolyte comprising the aforementioned solid electrolyte material. The lithium-ion secondary battery may have a stacked structure comprising a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in sequence. Because the lithium-ion secondary battery of this embodiment includes the aforementioned solid electrolyte material in the solid electrolyte layer, even when the solid electrolyte layers containing this solid electrolyte material are disposed in direct contact with the negative electrode, no excess metal M1 deposition due to a reduction reaction will occur, and stable operation can be expected.

[0066] Several embodiments have been described above, but this disclosure is not limited to any of the above embodiments. Furthermore, the descriptions of the above embodiments are interchangeable.

[0067] Example The present disclosure will now be described in more detail with reference to embodiments and comparative examples. However, the present disclosure is not limited to the embodiments described below.

[0068] (Example 1) In an argon atmosphere with a dew point below -70°C (hereinafter referred to as a dry argon atmosphere), LiCl, Li₂O, and LaCl₃ were weighed in the proportions shown in Table 2 to prepare a raw material composition. The raw material composition was mixed for 1 minute using a mortar and pestle in a dry argon atmosphere. 1.6 g of the mixed raw material composition was placed in a zirconia jar, and 65 g of zirconia balls with a diameter of 4 mm were further added to the jar. Then, the mixture was ball-milled using a planetary ball mill at 300 rpm for 24 hours to obtain a solid electrolyte material. The planetary ball mill used was a "PM 400" (product name) manufactured by Verder Scientific Co., Ltd.

[0069] (Example 2) As shown in Table 2, the composition and dosage of the raw material composition were changed, and otherwise, the solid electrolyte material was obtained in the same manner as in Example 1.

[0070] (Comparative Example 1) Under a dry argon atmosphere, LiCl and InCl3 were weighed in the amounts specified in Table 3 to prepare the raw material composition. The raw material composition was mixed for 1 minute using a mortar and pestle under a dry argon atmosphere. 1.2 g of the mixed raw material composition was placed in a zirconia jar, and 65 g of zirconia balls with a diameter of 4 mm were further added to the jar. The mixture was then ball-milled using a planetary ball mill at 300 rpm for 24 hours to obtain a crude product. The obtained crude composition was then heated at 230°C for 5 hours under an argon atmosphere to prepare a solid electrolyte material. The planetary ball mill used was a "PM 400" (product name) manufactured by Verder Scientific Co., Ltd.

[0071] (Comparative Examples 2-3) As shown in Table 3, the composition and dosage of the raw material composition were changed, and otherwise, the solid electrolyte material was obtained in the same manner as in Example 1.

[0072] <Composition of Solid Electrolyte Materials> The elemental composition ratios (molar ratios) of the solid electrolyte materials obtained in Examples 1-2 and Comparative Examples 1-3 were calculated from the elemental ratios in the raw materials. The results are shown in Table 4.

[0073] <Crystal Structure Analysis of Solid Electrolyte Materials> For the solid electrolyte materials obtained in Examples 1-2 and Comparative Examples 1-3, powder X-ray diffraction measurements were performed at 25°C to determine the half-maximum amplitude (WMA) of peak A in the region with a diffraction angle (2θ) of 13.5 ± 1°, the WMA of peak B in the region with a diffraction angle (2θ) of 24.5 ± 1°, the height ratio (intensity ratio) of peak A to peak B, and the symmetry of the crystal. The WMA of the peaks was obtained by removing the background signal and fitting the data. The results are shown in Table 4. It should be noted that the measurement conditions for the powder X-ray diffraction measurements were set as follows.

[0074] Measuring device: Ultima IV (manufactured by Rigaku Co., Ltd.) X-ray generator: CuKα ray source, voltage 40kV, current 40mA X-ray detector: scintillation counter or semiconductor detector Measurement range: Diffraction angle 2θ = 5° ~ 80° Scanning speed: 4° / minute <Density Measurement of Solid Electrolyte Materials> For the solid electrolyte materials obtained in Examples 1-2 and Comparative Examples 1-3, 100 mg of the solid electrolyte material was filled into an insulating cylinder with an inner diameter of 10 mm, and a pressure of 370 MPa was applied to prepare test samples. The volume of the test samples was measured, and the density was calculated. The results are shown in Table 4.

[0075] Evaluation of Solid Electrolyte Materials as Solid Electrolytes: Evaluation of Reduction Resistance The reduction resistance of the solid electrolyte materials obtained in Examples 1-2 and Comparative Examples 1-3 was evaluated by the methods shown below.

[0076] [Evaluation of battery manufacturing] The following battery manufacturing process was carried out entirely within a glove box purged with an inert gas. First, 100 mg of the aforementioned solid electrolyte material was filled into an insulating cylinder with an inner diameter of 10 mm, and a pressure of 123 MPa was applied, thereby forming the first solid electrolyte layer. Next, 60 mg of Li6PS5Cl, a sulfide solid electrolyte, was added in contact with the first solid electrolyte layer, and a pressure of 123 MPa was applied, thereby forming the second solid electrolyte layer (Li6PS5Cl layer).

[0077] Next, 37 parts by weight of SUS powder and 63 parts by weight of the aforementioned solid electrolyte material were weighed and mixed in an agate mortar to prepare a mixture. 30 mg of the mixture was then filled into the first solid electrolyte layer on the side opposite to the second solid electrolyte layer, and a pressure of 370 MPa was applied to form the working electrode layer. Separately, 6 mg of Li foil was placed in contact with and covered the second solid electrolyte layer on the side opposite to the first solid electrolyte layer, and a pressure of 50 MPa was applied to form the reference electrode layer.

[0078] A current collector made of stainless steel is attached to the side of the working electrode layer and the reference electrode layer opposite to the solid electrolyte side, as described above, and leads are installed on the current collectors to make an evaluation battery.

[0079] Cyclic Voltammetry Test Using the evaluation battery prepared as described above, the leads electrically connected to the current collector in contact with the working electrode layer and the leads electrically connected to the current collector in contact with the reference electrode layer were electrically connected to an impedance analyzer (Solatron Analytical, product name: Sl1260) and a potentiometer (Solatron Analytical, product name: Sl1287A), and a cyclic voltammetry test was performed under the following conditions.

[0080] In the cyclic voltammetry test, the scan rate was set to 1 mV / s, and the current flowing through the working electrode was measured when the potential of the working electrode changed relative to the reference electrode (Li+ / Li). More specifically, first, the potential of the working electrode was increased to 4.8 V relative to the reference electrode (Li) using the open-circuit voltage as a starting point, and then decreased to 0 V in reverse. The current value when the voltage relative to the Li metal reference becomes 1 V was determined as the evaluation index of reduction resistance. The results are shown in Table 4. Additionally, for reference, Figure 1 The results of cyclic voltammetry tests using the solid electrolyte materials of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are shown.

[0081] As shown in Table 4, in the cyclic voltammetry test of the evaluation battery for the solid electrolyte material of the embodiment that satisfies the conditions of the present disclosure by using a specified amount of the metal element M1 specified in this disclosure and by replacing a portion of the halogen with oxygen, it was confirmed that the current value at 1V was sufficiently low. On the other hand, in the cyclic voltammetry test of the evaluation battery for the solid electrolyte material of the comparative example, it was confirmed that the current value at 1V became relatively high. That is, it was confirmed that the reaction of the solid electrolyte material of the embodiment was suppressed even at a voltage of 1V, and its reduction resistance was superior to that of the solid electrolyte material of the comparative example.

[0082] Industrial availability According to this disclosure, a halide-based solid electrolyte material with excellent reduction resistance can be provided. According to this disclosure, an electrode and a lithium-ion secondary battery incorporating the aforementioned halide-based solid electrolyte material can also be provided.

Claims

1. A solid electrolyte material comprising crystals with Li, M, O, and X as constituent elements, The molar ratios of Li, M, O, and X are 0.40–1.30 : 0.80–2.50 : 0.01–0.45 :

3. The M includes M1, In the process of transforming (2 / x)M1+Cl2→(2 / x)M1Cl x The reaction formula (in which x is an integer from 1 to 6) contains M1Cl x When the generation energy is set to E1, M1 is at least one element selected from the group where E1 is below -500 kJ / mol. X is selected from at least one of F, Br, Cl and I.

2. The solid electrolyte material according to claim 1, wherein, The M also includes M2. M2 is an element other than M1, and the ratio of M1 to M2 is set as a:b in terms of element ratio, and (2 / x)M2 + Cl2 → (2 / x)M2Cl x The reaction formula (in which x is an integer from 1 to 6) contains M2Cl x When the generation energy is set to E2, M2 is at least one element selected from the group [a / (a+b)]E1+[b / (a+b)]E2 where -500kJ / mol.

3. The solid electrolyte material according to claim 1 or 2, wherein, M1 contains La.

4. The solid electrolyte material according to claim 1 or 2, wherein, X contains Cl, and the proportion of Cl in X is 50-100 moles.

5. The solid electrolyte material according to claim 1 or 2, wherein, The crystal has space group P63 / m symmetry.

6. The solid electrolyte material according to claim 1 or 2, wherein, In the X-ray diffraction spectrum obtained by powder X-ray diffraction using CuKα rays, when the peak existing in the region with a diffraction angle (2θ) of 13.5 ± 1° is designated as peak A, the half-maximum amplitude of peak A is less than 0.80°.

7. The solid electrolyte material according to claim 1 or 2, wherein, In the X-ray diffraction spectrum obtained by powder X-ray diffraction using CuKα rays, when the peak present in the region with a diffraction angle (2θ) of 24.5 ± 1° is designated as peak B, the half-maximum amplitude of peak B is less than 1.58°.

8. The solid electrolyte material according to claim 1 or 2, wherein, In the X-ray diffraction spectrum obtained by powder X-ray diffraction using CuKα rays, peak A is designated as the peak present in the region with a diffraction angle (2θ) of 13.5 ± 1°, and peak B is designated as the peak present in the region with a diffraction angle (2θ) of 24.5 ± 1°. The height H of peak A is... A Relative to the height H of peak B B The ratio is 0.1 to 1.

0.

9. The solid electrolyte material according to claim 1 or 2, wherein the density is 2.0~5.0 g / cm³. 3 .

10. An electrode comprising a solid electrolyte, wherein, The solid electrolyte is composed of the solid electrolyte material as described in claim 1 or 2.

11. A lithium-ion secondary battery comprising the electrode as described in claim 10.

12. A lithium-ion secondary battery comprising a solid electrolyte containing the solid electrolyte material of claim 1 or 2.

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