Solid electrolyte material, electrode, and lithium ion secondary battery

Abstract

The present disclosure provides a solid electrolyte material which comprises crystals that contain Li, M, O, and X as constituent elements, wherein: the contents of Li, M, O, and X are, in terms of molar ratio, 0.40-1.30:0.80-2.50: 0.01-0.45:3; M includes M1; M1 is at least one element that is selected from the group of elements which have E1 of -500 kJ / mol or less if E1 is the formation energy of MlClx in reaction formula (2 / x)M1 + Cl2 → (2 / x)M1Clx (wherein x is an integer of 1 to 6); and X is at least one element that is selected from the group consisting of F, Br, Cl, and I.

Description

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

[0001] The present disclosure relates to a solid electrolyte material, an electrode, and a lithium-ion secondary battery.

[0002] In recent years, solid electrolytes have been attracting attention as electrolytes for use in electrochemical devices such as lithium-ion batteries. Compared to conventional electrolyte solutions, solid electrolytes have superior high-temperature durability and high-voltage resistance. Therefore, solid electrolytes are considered useful for improving battery performance, such as safety, high capacity, rapid charge / discharge, and pack energy density.

[0003] As a solid electrolyte, Li is used because it has high ionic conductivity close to that of an electrolytic solution and moderate flexibility. １０ GeP ２ S １２ Research on sulfide-based solid electrolytes such as those described in Patent Document 1 is being conducted. ７ La ３ Zr ２ O １２ Oxide-based solid electrolytes such as (LLZO), Li ３ InCl ６ , LiYBr ６ Halide-based solid electrolytes such as the above are also known.

[0004] Halide-based solid electrolytes are considered useful because they have high oxidation resistance, low reactivity with moisture in the atmosphere, are stable, have a monovalent halide ion charge, low activation energy for ion conduction, and are relatively stable at high potentials. Patent Document 2 discloses a lithium ion conductive solid electrolyte material that is composed of Li, La, O, and X, where X is at least one element selected from the group consisting of Cl, Br, and I. Patent Document 3 discloses a solid electrolyte composed of Li, La, O, and I.

[0005] JP 2003-181158 A International Publication No. 2020 / 137043 International Publication No. 2020 / 219846

[0006] Luise M. Riegger, et, al, “Lithium-MetalAnode Instability of the SuperionicHalideSolidElectrolytes and the Implications for Solid-State Batteries”, Angewandte Chemie InternationalEditionVolume 60, Issue 12, p. 6189-6823

[0007] On the other hand, it is known that when a halide-based solid electrolyte comes into contact with a negative electrode material such as lithium or graphite, it undergoes reductive decomposition at the interface, resulting in the generation of lithium chloride and simple metal elements constituting the halide-based solid electrolyte at the interface, which can lead to battery malfunction (e.g., Non-Patent Document 1). A halide-based solid electrolyte with excellent reduction resistance would be useful.

[0008] The present disclosure aims to provide a halide-based solid electrolyte material that is excellent in reduction resistance, and also aims to provide an electrode and a lithium-ion secondary battery that include the above-mentioned halide-based solid electrolyte material.

[0009] The present inventors have found through investigation that the reduction resistance of a halide-based solid electrolyte material is due to the reduction performance of the metal elements themselves, which are the constituent elements, and that the reduction resistance of the solid electrolyte material can be improved by using metal elements that have a large amount of formation energy when forming chlorides of the metal elements and are endothermic, adjusting the content ratio to a predetermined value, and replacing a portion of the halide with oxygen. The present disclosure is based on the above findings.

[0010] The present disclosure provides the following [1].

[0011] [1] A crystal containing Li, M, O, and X as constituent elements, wherein the contents of Li, M, O, and X are in a molar ratio of 0.40 to 1.30:0.80 to 2.50:0.01 to 0.45:3, wherein the M includes M1, and the M1 is represented by the formula (2 / x)M1+Cl. ２ →(2 / x)M1Cl ｘ(wherein x is an integer of 1 to 6) ｘ wherein X is at least one element selected from a group of elements such that, when E1 is the energy of formation of the above-mentioned element, E1 is −500 kJ / mol or less, and X is at least one element selected from the group consisting of F, Br, Cl, and I.

[0012] The solid electrolyte material is a halide-based solid electrolyte material containing a halogen element as X and M1 satisfying a predetermined condition as M, and containing oxygen so that Li, M, O, and X have a predetermined content ratio. By having such a configuration, the solid electrolyte material has excellent reduction resistance.

[0013] The above [1] may be the following [2] to [9].

[0014] [2] The M further includes M2, wherein the M2 is an element other than the M1, and the ratio of the M1 to the M2 is a:b in element ratio, and (2 / x)M2+Cl ２ →(2 / x)M2Cl ｘ (wherein x is an integer of 1 to 6) ｘ[1] The solid electrolyte material according to [1], wherein M1 is at least one element selected from the group of elements such that, when the energy of formation of M1 is E2, [a / (a + b)]E1 + [b / (a + b)]E2 is -500 kJ / mol. [3] The solid electrolyte material according to [1] or [2], wherein M1 contains La. [4] The solid electrolyte material according to any one of [1] to [3], wherein X contains Cl, and the proportion of Cl in 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] The solid electrolyte material according to any one of [1] to [5], wherein, in an X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation, when a peak present in a region where the diffraction angle (2θ) is 13.5±1° is defined as Peak A, the half-width of Peak A is 0.80° or less. [7] In an X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation, when a peak existing in a region where the diffraction angle (2θ) is 24.5±1° is defined as Peak B, the half-width of Peak B is 1.58° or less. [8] In an X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation, when a peak existing in a region where the diffraction angle (2θ) is 13.5±1° is defined as Peak A and a peak existing in a region where the diffraction angle (2θ) is 24.5±1° is defined as Peak B, the height H of Peak B is 1.58° or less. Ｂ The height H of the peak A relative to Ａ [9] The solid electrolyte material according to any one of [1] to [7], wherein the ratio of ３ The solid electrolyte material according to any one of [1] to [8],

[0015] The present disclosure also provides the following

[10] to

[12] .

[0016]

[10] An electrode including a solid electrolyte, wherein the solid electrolyte is made of the solid electrolyte material according to any one of [1] to [9].

[11] A lithium ion secondary battery including the electrode according to

[10] .

[12] A lithium ion secondary battery including a solid electrolyte containing the solid electrolyte material according to any one of [1] to [9].

[0017] According to the present disclosure, it is possible to provide a halide-based solid electrolyte material having excellent reduction resistance. According to the present disclosure, it is also possible to provide an electrode and a lithium-ion secondary battery including the above-mentioned halide-based solid electrolyte material.

[0018] FIG. 1 is a graph showing the results of a cyclic voltammetry test when the solid electrolyte materials of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were used.

[0019] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are merely examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

[0020] Unless otherwise specified, the materials exemplified in this specification can be used singly or in combination of two or more. When a plurality of substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified.

[0021] One embodiment of the solid electrolyte material includes a crystal having Li, M, O, and X as constituent elements, where M is a metal element other than Li, and X is at least one selected from the group consisting of F, Br, Cl, and I. Since the solid electrolyte material has a halogen element as X, the solid electrolyte material is a so-called halide-based solid electrolyte. The solid electrolyte material may be a powder that is an aggregate of crystals. Each particle may be polycrystalline.

[0022] In the solid electrolyte material, the M includes M1, and the M1 is expressed as (2 / x)M1+Cl. ２ →(2 / x)M1Cl ｘ (wherein x is an integer of 1 to 6) ｘWhen the energy of formation of the element is E1, the element is at least one selected from the group of elements such that E1 is −500 kJ / mol or less.

[0023] The M may be at least one element selected from a group of elements such that the upper limit of the generation energy E1 is, for example, -550 kJ / mol or less, or -600 kJ / mol or less. When the upper limit of the generation energy E1 is within the above range, detachment of halide ions from the solid electrolyte material and precipitation of M can be further suppressed, thereby further improving the reduction resistance of the solid electrolyte material. The lower limit of the generation energy E1 may be, for example, -900 kJ / mol or more, -850 kJ / mol or more, -800 kJ / mol or more, or -750 kJ / mol or more. When the lower limit of the generation energy E1 is within the above range, a layer containing Li element generated by reductive decomposition of the solid electrolyte material can be appropriately formed when a battery is constructed, thereby improving the operational stability of the battery. The generation energy E1 may be adjusted within the above range, for example, from −900 kJ / mol to −500 kJ / mol, or from −850 kJ / mol to −500 kJ / mol.

[0024] The formation energy in this specification refers to a value calculated using Gibbs free energy at 0.1 MPa and 298 K. The Gibbs free energy value can be obtained from, for example, the NIST-JANAF Thermochemical Tables. The formation energies for producing chlorides of representative element species are shown in Table 1 below.

[0025]

[0026] From the viewpoint of further improving reduction resistance, M1 in the solid electrolyte material may contain La or may consist of La alone.

[0027] The solid electrolyte material may further contain M2 as the M in addition to M1. Here, M2 is an element other than M1, and the ratio of M1 to M2 is a:b in terms of element ratio, where (2 / x)M2+Cl２ →(2 / x)M2Cl ｘ (wherein x is an integer of 1 to 6) ｘ When the energy of formation of M is E2, [a / (a+b)]E1+[b / (a+b)]E2 is −500 kJ / mol. Even when M contains an element other than M1, the reduction resistance can be suppressed by adjusting the element ratio of M2 and M2 so as to satisfy the above-mentioned condition.

[0028] When the M contains the M2, the minimum value of the proportion of the M1 (100 × a / (a+b)) is determined so that the value of [a / (a+b)]E1 + [b / (a+b)]E2 is −500 kJ / mol. When this minimum value is Q%, when the M contains the M2, the lower limit of the proportion of the M1 may be, for example, Q% or more, Q+10% or more, or Q+20%. When the lower limit of the proportion of the M1 is within the above range, the reduction resistance of the solid electrolyte material can be further improved.

[0029] When the M includes M2 in addition to M1, it is preferable that the content of M1 is greater, and the total amount of M1 and M2 may be a major element in the M. The total amount of M1 and M2 may be, for example, 90 mol % or more, 95 mol % or more, or 100 mol % based on the M. The M1 is preferably the element species that is most abundant among the M. The M2 may be the element species that is second most abundant among the M. When the M consists of two elements, one element belonging to the M1 group and one element belonging to the M2 group, the element belonging to the M1 group may be the element that is most abundant among the M, and the element belonging to the M2 group may be the element that is second most abundant among the M.

[0030] From the viewpoint of further improving reduction resistance, X in the solid electrolyte material preferably contains Cl. When X contains Cl, the proportion of Cl in X may be, for example, 50 to 100 mol%, 70 to 98 mol%, 80 to 96 mol%, or 90 to 94 mol%.

[0031] The solid electrolyte material can also be considered as a compound in which a portion of the halogen (X) is substituted with oxygen (O). In the solid electrolyte material, the lower limit of the oxygen content may be, for example, 1.0 mol% or more, 4.0 mol% or more, 6.0 mol% or more, or 8 mol% or more, based on the total content of the halogen and oxygen. 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 may be, for example, 13.0 mol% or less, 12.5 mol% or less, or 12.0 mol% or less, based on the total content of the halogen and oxygen. By setting the oxygen content within the above range, the reduction resistance of the solid electrolyte material can be further improved.

[0032] In the solid electrolyte material, the ratio of the contents of the elements Li, M, O, and X (Li:M:O:X) may be, in molar ratio, 0.40 to 1.30:0.80 to 2.50:0.01 to 0.45:3, 0.50 to 1.20:0.84 to 2.00:0.10 to 0.42:3, 0.55 to 1.15:0.86 to 1.75:0.20 to 0.40:3, or 0.60 to 1.00:0.90 to 1.50:0.30 to 0.38:3.

[0033] The composition ratios of elements in the solid electrolyte material in this specification refer to values ​​measured by the following method. Li and M are values ​​determined by inductively coupled plasma atomic emission spectroscopy (ICP), X is a value determined by ion chromatography, and O is a value determined by non-dispersive infrared absorption spectroscopy. The composition ratios are calculated using these values. When the solid electrolyte material is prepared by oneself, the composition ratios can be calculated from the composition ratios of elements in the raw materials.

[0034] The solid electrolyte material contains crystals having Li, M, O, and X as constituent elements, and the crystals may have space group P63 / m symmetry. The solid electrolyte may consist solely of the crystals. Whether the solid electrolyte contains crystals having space group P63 / m symmetry can be confirmed by powder X-ray diffraction measurement using CuKα radiation.

[0035] The solid electrolyte material is LaCl ３ and may have the same or similar crystal structure as LaCl ３ The solid electrolyte material may have the same crystal structure as that of the solid electrolyte material. In an X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation, the solid electrolyte material may have a peak (hereinafter also referred to as Peak A) present in a region where the diffraction angle (2θ) is 13.5±1°, and may also have a peak (hereinafter also referred to as Peak B) present in a region where the diffraction angle (2θ) is 24.5±1°. Peak A is a peak derived from reflection of metal M on a surface along the Li conduction direction of the solid electrolyte, and Peak B is a peak derived from reflection of metal M in a direction different from Peak A.

[0036] The half-width of each peak observed in the X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation for a solid electrolyte material can be used as an index for measuring the crystallinity of the crystals constituting the solid electrolyte material. In other words, the smaller the half-width of the peak, the higher the crystallinity and the more stable the crystal structure formed. In the solid electrolyte material according to the present disclosure, the half-width of the peak observed in the X-ray diffraction spectrum is reduced, and by increasing the crystallinity, the reactivity of the crystal is reduced, thereby further improving the reduction resistance. On the other hand, a large half-width of the peak and low crystallinity indicate that the solid electrolyte material has an amorphous structure. A solid electrolyte material with an amorphous structure has localized fluctuations in the crystal structure within the material, making it difficult to introduce regular lattice defects. This makes it difficult for decomposition originating from lattice defects to occur, and thus reduces the decrease in reduction resistance. The half-width of the peak is due to crystallinity and can be adjusted by changing the ratio of the mass of the raw material composition to the mass of the balls in the ball mill when producing the solid electrolyte material, the rotation speed of the ball mill, etc.

[0037] In the solid electrolyte material, in an X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation, the upper limit of the half width of the peak A may 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 half width of the peak A is not particularly limited, but may be, for example, 0.22° or more, 0.23° or more, or 0.24° or more.

[0038] In the solid electrolyte material, in an X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation, the upper limit of the half width of the peak B may 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 half width of the peak B is not particularly limited, and may be, for example, 0.20° or more, 0.23° or more, or 0.25° or more.

[0039] In the X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation for the solid electrolyte material, the height H of the peak B Ｂ The height H of the peak A relative to Ａ The ratio (H Ａ / H Ｂ The value of H is an index showing the degree of anisotropy of the crystal structure. Ａ / H Ｂ The larger the value of H, the higher the anisotropy, which is thought to correspond to the progress of growth of stable crystal planes constituting the solid electrolyte material. The growth of stable crystal planes as described above further improves reduction resistance. On the other hand, if the anisotropy is too high, variations occur in the bond energy of interatomic bonds within the crystal structure, increasing reactivity and resulting in a decrease in the reduction resistance of the solid electrolyte material. Ａ / H Ｂ From the viewpoint of further improving reduction resistance, the value of may be, for example, 0.1 to 1.0, 0.1 to 0.9, 0.3 to 0.8, 0.4 to 0.7, or 0.5 to 0.7.

[0040] Powder X-ray diffraction measurements using CuKα radiation in this specification are performed under the conditions described in the Examples. The half-width of a peak in this specification refers to the full width at half maximum (FWHM), and is determined from a spectrum obtained by the above powder X-ray diffraction measurement, in which background signals have been removed and fitting has been performed. An X-ray diffractometer is used for powder X-ray diffraction measurements. Examples of X-ray diffractometers that can be used include the "Ultima IV" (trade name) manufactured by Rigaku Corporation. For data analysis, the analysis software "PDXL2" included with the "Ultima IV" (trade name) manufactured by Rigaku Corporation can be used.

[0041] The density of the solid electrolyte material is, for example, 2.0 to 5.0 g / cm ３ , 2.5-4.8g / cm ３ , 2.8-4.6g / cm ３ , 3.0-4.4g / cm ３ , or 3.5 to 4.4 g / cm ３ When the density of the solid electrolyte material is within the above range, the density of the solid electrolyte can be further improved when the solid electrolyte material is subjected to compression molding or the like, and a more uniform and stable interface can be formed between the solid electrolyte material and the electrode, thereby further improving reduction resistance.

[0042] The density in this specification refers to a value calculated by filling 100 mg of the solid electrolyte material into an insulating cylinder having an inner diameter of 10 mm, applying a pressure of 370 MPa to prepare a measurement sample, measuring the volume of the measurement sample, and calculating the density.

[0043] An example of a method for producing a solid electrolyte material includes modifying a raw material composition containing a lithium source and a compound having a metal element M as a constituent element by a mechanochemical method. Examples of the lithium source include lithium halide and lithium oxide. Examples of the compound having the metal element M as a constituent element include a halide of the metal element M and an oxide of the metal element M. At least one of the lithium source and the compound having the metal element M as a constituent element is a halide, and it is preferable that at least the compound having the metal element M as a constituent element contains a halide. The metal element M contains at least the above-mentioned M1.

[0044] In the mechanochemical method, for example, a method of supplying mechanical energy such as collision, shear, and friction between raw material solids using a ball mill can be employed. The treatment using the ball mill may be performed dry. Before the treatment using the ball mill, the raw material composition may be mixed (pre-mixed) for 1 minute or more in a mortar or the like. By performing such pre-mixing, the raw material composition charged into the container during the ball mill treatment is homogenized, and the solid electrolyte material obtained by the ball mill treatment also has even better homogeneity, thereby further improving reduction resistance.

[0045] The balls used in the ball mill may be zirconia balls, and the diameter of the balls may be, for example, 1 to 15 mm, 2 to 10 mm, or 2 to 5 mm.

[0046] The filling rate of the balls in the container during ball milling may be adjusted by the amount of the raw material composition filled. 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]) may be, for example, 5.0 mass% or less, 4.5 mass% or less, 3.0 mass% or less, 2.8 mass% or less, 2.6 mass% or less, or 2.5 mass% or less. When the ratio is within the above range, the impact of the balls can be more sufficiently applied to the raw material composition. The ratio of the mass of the raw material composition to the mass of the balls may be, for example, 0.3 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 1.5 mass% or more, or 1.8 mass% or more. When the lower limit of the ratio is within the above range, the incorporation of impurities into the solid electrolyte material due to collisions between the balls can be further reduced, the occurrence of crystal defects associated with the incorporation of impurities can be suppressed, and a decrease in reduction resistance can be more sufficiently suppressed.

[0047] The rotation speed of the ball mill may be, for example, 200 to 700 rpm, 200 to 500 rpm, or 250 to 350 rpm.

[0048] The time for the treatment with the ball mill may be, for example, 24 hours or more, 24 to 72 hours, or 36 to 60 hours. When the treatment time with the ball mill is within the above range, the raw material solids are mixed more thoroughly, the element substitution by the mechanochemical method is more sufficient, and the reduction resistance of the obtained solid electrolyte material can be further improved.

[0049] The solid electrolyte material has excellent reduction resistance and is therefore useful as a material for forming a solid electrolyte layer in a battery or for forming an electrode. The solid electrolyte material also has excellent reduction resistance and is therefore useful as a constituent material of a lithium ion secondary battery.

[0050] One embodiment of the electrode is an electrode including a solid electrolyte. The solid electrolyte is made of the above-described solid electrolyte material. The electrode includes an electrode active material (a positive electrode active material or a negative electrode active material).

[0051] One embodiment of a lithium ion secondary battery includes the electrode. The electrode may be either a positive electrode or a negative electrode, but the effects of the present disclosure are more pronounced when the electrode is a negative electrode because the solid electrolyte material has excellent reduction resistance.

[0052] The positive electrode active material may be, for example, a lithium-containing composite metal oxide containing lithium (Li) and at least one transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu. Examples of such lithium composite metal oxides include LiCoO ２ , LiNiO ２ , LiMn ２ O ４ , Li ２ MnO ３ , LiNi ｘ Mn ｙ Co １－ｘ－ｙ O ２ [0<x+y<1]), LiNi ｘ Co ｙ Al １－ｘ－ｙ O ２ [0<x+y<1]), LiCr ０．５ Mn ０．５ O ２ , LiFePO ４ , Li ２ FeP ２ O ７ , LiMnPO ４ , LiFeBO ３ , Li ３ V ２ (P.O. ４ ) ３ , Li ２ CuO ２ , Li ２ FeSiO ４ , and Li ２ MnSiO ４ Examples include:

[0053] Examples of the negative electrode active material include metals such as Li, Si, Sn, Si—Mn, Si—Co, Si—Ni, In, and Au, alloys containing these metals, carbon materials such as graphite, and substances in which lithium ions are inserted between layers of the carbon materials.

[0054] The electrode may contain other components in addition to the solid electrolyte and electrode active material, such as a solid electrolyte compound other than the solid electrolyte material, a conductive additive, and a binder.

[0055] The conductive material contained in the positive electrode may be, for example, a carbon material. Examples of the carbon material include graphene, graphite, carbon black, fullerene, carbon nanotubes, and carbon fibers. Examples of graphite include natural graphite (such as flake graphite) and artificial graphite. Examples of carbon black include acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Examples of carbon fibers include vapor-grown carbon fiber (VGCF).

[0056] Examples of the binder include fluorine-based resins and synthetic rubbers. The fluorine-based resin is preferably a resin having a carbon chain as the main chain. The carbon chain may be formed by radical polymerization of a compound having an ethylenically unsaturated group. Examples of the fluorine-based resin include poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and polyvinylidene fluoride (PVDF). Examples of the synthetic rubber include SBR (styrene butadiene rubber).

[0057] The electrode may have a configuration in which a layer of a composition containing the above-mentioned solid electrolyte material and an electrode active material is provided on a current collector. The material of the current collector is not particularly limited, and may be a simple metal or an alloy of metals such as Cu, Mg, Ti, Fe, Co, Ni, Zn, Al, Ge, In, Au, Pt, Ag, and Pd.

[0058] Another embodiment of the lithium-ion secondary battery includes a solid electrolyte containing the above-described solid electrolyte material. The lithium-ion secondary battery may have a laminated structure including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order. Since the lithium-ion secondary battery according to this embodiment includes the above-described solid electrolyte material in the solid electrolyte layer, even if the solid electrolyte layer containing the solid electrolyte material is provided so as to be in direct contact with the negative electrode, deposition of excess metal M1 due to a reduction reaction does not occur, and stable operation can be expected.

[0059] Although several embodiments have been described above, the present disclosure is not limited to the above embodiments. Furthermore, the descriptions of the above embodiments can be applied to each other.

[0060] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

[0061] Example 1 In an argon atmosphere having a dew point of −70° C. or less (hereinafter referred to as a dry argon atmosphere), LiCl, Li ２ O, and LaCl ３ The raw material composition was prepared by weighing out the ingredients in the amounts shown in Table 2. The raw material composition was mixed in a mortar for 1 minute in a dry argon atmosphere. 1.6 g of the mixed raw material composition was placed in a zirconia pot, and 65 g of zirconia balls with a diameter of 4 mm were further added to the pot. The mixture was then subjected to ball milling treatment in 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 K.K.

[0062] Example 2 A solid electrolyte material was obtained in the same manner as in Example 1, except that the components and blending amounts of the raw material composition were changed as shown in Table 2.

[0063]

[0064] Comparative Example 1: LiCl and InCl were mixed under a dry argon atmosphere. ３The raw material composition was prepared by weighing out the ingredients in the amounts shown in Table 3. The raw material composition was mixed in a mortar for 1 minute in a dry argon atmosphere. 1.2 g of the mixed raw material composition was placed in a zirconia pot, and 65 g of zirconia balls with a diameter of 4 mm were added to the pot. A crude product was then obtained by ball milling using a planetary ball mill at 300 rpm for 24 hours. The obtained crude composition was heat-treated at 230°C for 5 hours in an argon atmosphere to prepare a solid electrolyte material. A "PM 400" (product name) manufactured by Verder Scientific K.K. was used as the planetary ball mill.

[0065] Comparative Examples 2 and 3 Solid electrolyte materials were obtained in the same manner as in Example 1, except that the components and blending amounts of the raw material composition were changed as shown in Table 3.

[0066]

[0067] <Composition of Solid Electrolyte Material> The composition ratio (molar ratio) of each element in the solid electrolyte materials obtained in Examples 1 and 2 and Comparative Examples 1 to 3 was calculated from the element ratio in the raw materials. The results are shown in Table 4.

[0068] <Crystal Structure Analysis of Solid Electrolyte Material> Powder X-ray diffraction measurement was performed at 25°C for each of the solid electrolyte materials obtained in Examples 1 and 2 and Comparative Examples 1 to 3 to determine the half-width of Peak A present in the region where the diffraction angle (2θ) is 13.5±1°, the half-width of Peak B present in the region where the diffraction angle (2θ) is 24.5±1°, the height ratio (intensity ratio) of Peak A to Peak B, and the symmetry of the crystal. The half-width of the peaks was determined by removing the background signal and performing fitting. The results are shown in Table 4. The measurement conditions for the powder X-ray diffraction measurement were as follows: Measurement apparatus: Ultima IV (manufactured by Rigaku Corporation) X-ray generator: CuKα radiation source, voltage 40 kV, current 40 mA X-ray detector: scintillation counter or semiconductor detector Measurement range: diffraction angle 2θ = 5° to 80° Scan speed: 4° / min

[0069] <Measurement of Density of Solid Electrolyte Material> For each of the solid electrolyte materials obtained in Examples 1 and 2 and Comparative Examples 1 to 3, 100 mg of the solid electrolyte material was filled into an insulating cylinder having an inner diameter of 10 mm, and a pressure of 370 MPa was applied to prepare a measurement sample. The volume of the measurement sample was measured, and the density was calculated. The results are shown in Table 4.

[0070] <Evaluation of Solid Electrolyte Materials as Solid Electrolytes: Evaluation of Reduction Resistance> The reduction resistance of each of the solid electrolyte materials obtained in Examples 1 and 2 and Comparative Examples 1 to 3 was evaluated by the method described below.

[0071] [Preparation of Evaluation Cell] The preparation process of the evaluation cell described below was all carried out in a glove box purged with an inert gas. First, 100 mg of the solid electrolyte material was filled into an insulating cylinder with an inner diameter of 10 mm, and a pressure of 123 MPa was applied to form a first solid electrolyte layer. Next, Li, a sulfide solid electrolyte, was added. ６ P.S. ５ 60 mg of Cl was filled onto the first solid electrolyte layer so as to be in contact with it, and a pressure of 123 MPa was applied to form the second solid electrolyte layer (Li ６ P.S. ５ A Cl layer was formed.

[0072] Next, 37 parts by weight of SUS powder and 63 parts by weight of the above solid electrolyte material were weighed and mixed in an agate mortar to prepare a mixture. 30 mg of the above mixture was filled onto the surface of the first solid electrolyte layer opposite the second solid electrolyte layer, and a pressure of 370 MPa was applied to form a working electrode layer. Additionally, 6 mg of Li foil was placed onto the surface of the second solid electrolyte layer opposite the first solid electrolyte layer, covering it, and a pressure of 50 MPa was applied to form a reference electrode layer.

[0073] A current collector made of stainless steel was attached to each of the surfaces of the working electrode layer and the reference electrode layer formed as described above, opposite to the solid electrolyte side, and a lead wire was attached to each of the current collectors to prepare an evaluation cell.

[0074] [Cyclic Voltammetry Test] Using the evaluation cell prepared as described above, the lead wires electrically connected to the current collector in contact with the working electrode layer and the lead wires electrically connected to the current collector in contact with the reference electrode layer were electrically connected to an impedance analyzer (manufactured by Solatron Analytical, product name: S11260) and a potentiostat (manufactured by Solatron Analytical, product name: S11287A), and a cyclic voltammetry test was carried out under the following conditions.

[0075] The cyclic voltammetry test was performed at a sweep rate of 1 mV / s, and the current flowing when the potential of the working electrode relative to the reference electrode (Li / Li) was measured. More specifically, the potential of the working electrode relative to the reference electrode (Li) was first increased to 4.8 V starting from the open circuit voltage, and then reduced back to 0 V. The current value when the voltage relative to Li metal became 1 V was determined as an evaluation index of reduction resistance. The results are shown in Table 4. For reference, FIG. 1 shows the results of the cyclic voltammetry test using the solid electrolyte materials of Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

[0076]

[0077] As shown in Table 4, in a cyclic voltammetry test on an evaluation cell using a solid electrolyte material of an example that satisfies the conditions of the present disclosure, including containing a predetermined amount of a predetermined metal element M1 and substituting a portion of the halogen with oxygen, it was confirmed that the current value at 1 V was sufficiently low. On the other hand, in a cyclic voltammetry test on an evaluation cell using a solid electrolyte material of a comparative example, it was confirmed that the current value at 1 V was relatively high. In other words, it was confirmed that the solid electrolyte material of the example inhibited reaction even at a voltage of 1 V and had better reduction resistance than the solid electrolyte material of the comparative example.

[0078] According to the present disclosure, it is possible to provide a halide-based solid electrolyte material having excellent reduction resistance. According to the present disclosure, it is also possible to provide an electrode and a lithium-ion secondary battery including the above-mentioned halide-based solid electrolyte material.

Claims

1. A crystal containing Li, M, O, and X as constituent elements, wherein the contents of Li, M, O, and X are 0.40-1.30:0.80-2.50:0.01-0.45:3 in molar ratio, and the M includes M1, and the M1 is (2 / x)M1+Cl. ２ →(2 / x)M1Cl ｘ (wherein x is an integer of 1 to 6) ｘ wherein X is at least one element selected from a group of elements such that, when E1 is the energy of formation of the above-mentioned element, E1 is −500 kJ / mol or less, and X is at least one element selected from the group consisting of F, Br, Cl, and I.

2. The M further includes M2, and the M2 is an element other than the M1, and the ratio of the M1 to the M2 is a:b in element ratio, and (2 / x)M2+Cl ２ →(2 / x)M2Cl ｘ (wherein x is an integer of 1 to 6) ｘ The solid electrolyte material according to claim 1, wherein the solid electrolyte material is at least one element selected from the group of elements such that [a / (a+b)]E1+[b / (a+b)]E2 is −500 kJ / mol when the formation energy of the above is E2.

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 to 100 mol %.

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 an X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation, when a peak present in a region where the diffraction angle (2θ) is 13.5±1° is defined as Peak A, the half-value width of Peak A is 0.80° or less.

7. The solid electrolyte material according to claim 1 or 2, wherein, in an X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation, when a peak present in a region where the diffraction angle (2θ) is 24.5±1° is defined as Peak B, the half-value width of Peak B is 1.58° or less.

8. In an X-ray diffraction spectrum obtained by powder X-ray diffraction measurement using CuKα radiation, when a peak existing in the region where the diffraction angle (2θ) is 13.5±1° is defined as Peak A and a peak existing in the region where the diffraction angle (2θ) is 24.5±1° is defined as Peak B, the height H of Peak B is Ｂ The height H of the peak A relative to Ａ The solid electrolyte material according to claim 1 or 2, wherein the ratio is 0.1 to 1.

0.

9. Density: 2.0 to 5.0 g / cm ３ The solid electrolyte material according to claim 1 or 2, 10. An electrode comprising a solid electrolyte, wherein the solid electrolyte is made of the solid electrolyte material according to claim 1 or 2.

11. A lithium ion secondary battery comprising the electrode according to claim 10.

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

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