Halide solid electrolyte, positive electrode material, and battery

Abstract

A halide solid electrolyte according to the present disclosure contains Li, Al, M, and X. M is at least one element selected from the group consisting of metal elements (excluding Li and Al) and metalloid elements. X is at least one element selected from the group consisting of F, Cl, Br, and I. The solid electrolyte contains a first particle group that is constituted by first particles composed of a compound A which contains Al and X, and a second particle group that is constituted by second particles composed of a compound B which contains M and X and does not contain Al. In the first particle group, a coefficient of variation CVAl (CVAl=(σAl / AAl)×100) that is obtained using an average AAl and a standard deviation σAl of a mass ratio Al / X is not more than 10%. In the second particle group, a coefficient of variation CVM (CVM=(σM / AM)×100) that is obtained using an average AM and a standard deviation σM of a mass ratio M / X is not more than 20%.

Description

Halide solid electrolytes, cathode materials, and batteries

[0001] The present disclosure relates to halide solid electrolytes, positive electrode materials, and batteries.

[0002] Patent Document 1 discloses a halide-based solid electrolyte material containing Li, Al, Ti, and F. Patent Document 2 discloses a halide-based solid electrolyte material as a solid electrolyte material that coats the surface of a positive electrode active material.

[0003] International Publication No. 2021 / 186809 International Publication No. 2021 / 187391

[0004] An object of the present disclosure is to provide a halide solid electrolyte having excellent ionic conductivity and reliability.

[0005] The halide solid electrolyte of the present disclosure is a halide solid electrolyte containing Li, Al, M, and X, wherein M is at least one element selected from the group consisting of metal elements (excluding Li and Al) and metalloid elements, and X is at least one element selected from the group consisting of F, Cl, Br, and I, and the halide solid electrolyte includes: a first particle group consisting of first particles constituted of a compound A containing Al and the X; and a second particle group consisting of second particles constituted of a compound B not containing Al and containing the M and the X, and wherein in the first particle group, a standard deviation σ of a ratio Al / X of the mass of Al to the mass of X is Al and the average value A of the ratio Al / X Al The coefficient of variation CV is calculated using the following formula (A) Al is 10% or less, and in the second particle group, the standard deviation σ of the ratio M / X of the mass of M to the mass of X is M and the average value A of the ratio M / X M The coefficient of variation CV is calculated using the following formula (B) M is 20% or less. Al = (σ Al / A Al ) × 100 Formula (B): CV M = (σ M / A M ) x 100

[0006] The present disclosure provides a halide solid electrolyte with excellent ionic conductivity and reliability.

[0007] FIG. 1 shows a schematic diagram of the microstructure of a halide solid electrolyte in a first embodiment of the present disclosure. FIG. 2 is a flow diagram of a method for manufacturing a halide solid electrolyte in a first embodiment of the present disclosure. FIG. 3 is a flow diagram of a method for manufacturing a solid electrolyte according to Modification 1. FIG. 4 shows a cross-sectional view of a battery 1000 according to a second embodiment. FIG. 5 is a flow diagram of a method for manufacturing a halide solid electrolyte according to Example 1.

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0009] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, any component that is not described in an independent claim that represents a top concept will be described as an optional component.

[0010] [First Embodiment] A halide solid electrolyte in a first embodiment of the present disclosure contains Li, Al, M, and X. Here, M is at least one element selected from the group consisting of metal elements (excluding Li and Al) and metalloid elements, and X is at least one element selected from the group consisting of F, Cl, Br, and I.

[0011] The halide solid electrolyte in this embodiment includes a first particle group consisting of first particles constituted of a compound A containing Al and X, and a second particle group consisting of second particles constituted of a compound B that does not contain Al and contains M and X.

[0012] In the first particle group, the standard deviation σ of the ratio Al / X of the mass of Al to the mass of X Al and the average value A of the ratio Al / X Al The coefficient of variation CV is calculated using the following formula (A) Al is less than 10%.

[0013] In the second particle group, the standard deviation σ of the ratio M / X of the mass of M to the mass of X M and the average value A of the ratio M / X M The coefficient of variation CV is calculated using the following formula (B) M is 20% or less. When a plurality of elements are contained as M, the mass of M refers to the total mass of all the elements contained as M.

[0014] Formula (A): CV Al = (σ Al / A Al ) × 100 Formula (B): CV M = (σ M / A M ) x 100

[0015] The halide solid electrolyte of this embodiment has the above-described structure, and therefore has excellent ionic conductivity. Furthermore, the halide solid electrolyte of this embodiment also has excellent stability (e.g., heat resistance and atmospheric environment resistance), and can have high reliability. Therefore, the halide solid electrolyte of this embodiment can have excellent ionic conductivity and reliability. For example, the coefficient of variation CV Al is 10% or less, and the coefficient of variation CV M By making the content of SiO 2 equal to or less than 20%, the halide solid electrolyte of this embodiment can achieve a high ionic conductivity of, for example, 1 μS / cm or more.

[0016] The identification of the first and second particles contained in the halide solid electrolyte (i.e., the identification of whether or not Al is contained), the masses of Al and X in the first particles, and the masses of M and X in the second particles can be determined by elemental analysis using energy dispersive X-ray spectroscopy (EDS) or electron probe microanalyzer (EPMA). For example, a cross section of a compact of the halide solid electrolyte is formed using an ion polisher or the like, and a plurality of spots, each having a spot diameter (diameter) of, for example, 1 μm, are set on the cross section. The identification of the first and second particles, the masses of Al and X in the first particles, and the masses of M and X in the second particles may be determined for each of these spots by point analysis using, for example, EPMA. For the spots identified as the first particles, the ratio of the mass of Al to the mass of X, Al / X, is determined from the results of elemental analysis. Similarly, for the spots identified as the second particles, the ratio of the mass of M to the mass of X, M / X, is determined from the results of elemental analysis. Using the results of the ratio Al / X of any 20 spots identified as the first particle, the standard deviation σ of the ratio Al / X Al and average value A Al and from these values, the coefficient of variation CV Al On the other hand, using the results of the ratio M / X of any 20 spots identified as the second particle, the standard deviation σ of the ratio M / X is calculated. M and average value A M and from these values, the coefficient of variation CV is calculated using the above formula (B). M Calculate.

[0017] In order to improve the ionic conductivity, the halide solid electrolyte in this embodiment has a coefficient of variation CV Al In order to improve the ionic conductivity, the coefficient of variation CV in the halide solid electrolyte of this embodiment may be, for example, 9% or less, 8% or less, or 7% or less. M may be, for example, 18% or less, 15% or less, or 12% or less.

[0018] The ratio Al / X is (average value A Al-3 x standard deviation σ Al ) or more and (average value A Al + 3 x standard deviation σ Al ) or less. That is, in the halide solid electrolyte of this embodiment, A Al -3σ Al ≦ratio Al / X≦A Al +3σ Al This reduces particles having a composition with low ionic conductivity, thereby making it possible to obtain a halide solid electrolyte with higher ionic conductivity (for example, 1.0 μS / cm or more, or 3.0 μS / cm or more).

[0019] The above ratio M / X is (average value A M -3 x standard deviation σ M ) or more and (average value A M + 3 x standard deviation σ M ) or less. That is, in the halide solid electrolyte of this embodiment, A M -3σ M ≦Ratio M / X≦A M +3σ M This reduces particles having a composition with low ionic conductivity, thereby making it possible to obtain a halide solid electrolyte with higher ionic conductivity (for example, 1.0 μS / cm or more, or 3.0 μS / cm or more).

[0020] The ratio Al / X is (average value A Al -3 x standard deviation σ Al ) or more and (average value A Al + 3 x standard deviation σ Al ) or less, and the ratio M / X is (average value A M -3 x standard deviation σ M ) or more and (average value A M + 3 x standard deviation σ M This reduces particles having a composition with low ionic conductivity, making it possible to obtain a halide solid electrolyte with higher ionic conductivity (for example, 1.0 μS / cm or more, or 3.0 μS / cm or more).

[0021] The first particles, the second particles, the compound A, the compound B, and the method for producing the halide solid electrolyte will be described in more detail below.

[0022] (First Particles and Second Particles) FIG. 1 is a schematic diagram of the microstructure of the halide solid electrolyte of this embodiment. As shown in FIG. 1, the halide solid electrolyte of this embodiment includes first particles 10 and second particles 20. The halide solid electrolyte of this embodiment is composed of an aggregate of a plurality of particles, including a plurality of first particles 10 (i.e., a first particle group) and a plurality of second particles 20 (i.e., a second particle group). As described above, the first particles 10 are composed of a compound A containing Al and X. The second particles 20 are composed of a compound B that does not contain Al and contains M and X. In FIG. 1, the second particles 20 are hatched to distinguish the first particles 10 from the second particles 20.

[0023] The halide solid electrolyte in this embodiment may be in a powder state or in a compacted powder state.

[0024] The halide solid electrolyte of the present embodiment may be, for example, a compact formed of the first particles 10 and the second particles 20. When the halide solid electrolyte of the present embodiment is, for example, a compact formed of the first particles 10 and the second particles 20, the halide solid electrolyte of the present embodiment can realize a solid electrolyte layer of a battery or a coating layer of active material particles that has excellent ionic conductivity and reliability.

[0025] The first particles 10 and the second particles 20 may each have, for example, an average particle diameter of 0.1 μm or more and 10 μm or less. The first particles 10 and the second particles 20 may each have, for example, a BET specific surface area of ​​0.2 m or more. 2 / g or more and 20m 2 The particle shape of the first particles 10 and the second particles 20 may be any shape such as spherical, needle-like, or scale-like.

[0026] At least one particle selected from the group consisting of the first particles 10 and the second particles 20 may contain an amorphous phase. In this specification, the term "amorphous phase" refers not only to an amorphous phase but also to a phase with disordered crystallinity, in other words, a distorted crystalline phase. This configuration allows for a halide solid electrolyte that combines high ionic conductivity (e.g., 1.0 μS / cm or more) with low electronic conductivity (e.g., 0.01 μS / cm or less). Furthermore, the amorphous phase portion of the particles is generally softer and more easily deformed than the highly crystalline crystalline phase. Therefore, when the first particle group and the second particle group are compacted into a powder body, a halide solid electrolyte having the above configuration is likely to form an interface where the particles are in close contact with each other, which facilitates high density and thin layer formation, and can also be expected to improve ionic conductivity. Therefore, when the halide solid electrolyte having the above configuration is used in, for example, a solid electrolyte layer of a battery, the solid electrolyte layer can be thinned, or it can be suitably used as a coating layer for active material particles.

[0027] The volume of the amorphous phase contained in the second particles 20 may be larger than the volume of the amorphous phase contained in the first particles 10. This configuration can further improve ionic conductivity and reliability. Furthermore, the above configuration makes the halide solid electrolyte softer and more easily deformed, improving the adhesion between particles and reducing voids between particles. Therefore, the halide solid electrolyte having the above configuration can be densified when compacted into a powder. As a result, for example, when used in a solid electrolyte layer of a battery, the solid electrolyte layer can be densified, and the solid electrolyte can be suitably used as a coating layer for active material particles.

[0028] The amorphous phase contained in the first particles 10 may have higher ionic conductivity than the amorphous phase contained in the second particles 20. According to this configuration, the softer second particles 20 can bond between the first particles 10 having higher ionic conductivity, thereby achieving high ionic conductivity.

[0029] The amorphous phase may have lower electronic conductivity than the portions excluding the amorphous phase of the first particle 10 and the second particle 20. When the amorphous phase has lower electronic conductivity (for example, 0.01 μS / cm or less) than the portions excluding the amorphous phase, a halide solid electrolyte with superior ionic conductivity can be obtained.

[0030] When the first particle 10 and / or the second particle 20 contain an amorphous phase, for example, the particle surface layer may contain more amorphous phase than the particle interior. As described above, an amorphous phase is generally softer than a crystalline phase with high crystallinity. Therefore, when the amorphous phase is contained more at the particle surface, the bonding strength (i.e., cohesion) between particles is also stronger. Therefore, by having a configuration in which the amorphous phase is contained more at the particle surface, the halide solid electrolyte of this embodiment can achieve a dense powder structure and improved mechanical strength of the powder compact.

[0031] Furthermore, in the first particle 10 and the second particle 20, the region containing the amorphous phase (e.g., the particle surface layer) may have higher ionic conductivity and lower electronic conductivity than the region not containing the amorphous phase (e.g., the particle interior). For example, the ionic conductivity of the region containing the amorphous phase may be, for example, 1 μS / cm or more. The electronic conductivity of the region containing the amorphous phase may be, for example, 0.01 μS / cm or less. A halide solid electrolyte containing the first particle 10 and the second particle 20 having such a configuration can form a solid electrolyte that is dense in a powder compact, has high ionic conductivity, and has low electronic conductivity, and is useful for improving the performance of batteries. Note that the amorphous region contained in the particle surface layer becomes a bonding interface between particles in the powder compact, and can form a three-dimensional mesh-like network with high ionic conductivity (e.g., 1 μS / cm or more) and low electronic conductivity (e.g., 0.01 μS / cm or less). Such differences in crystallinity between the interior, surface, and interface of a particle can be observed using a high-resolution transmission electron microscope (TEM) as images of highly regular and disordered lattice image regions. Furthermore, the mechanical strength and electrical properties within the particle can be evaluated by mechanical strength measurement such as micro-Vickers or by a nano-prober used in semiconductor evaluation.

[0032] The amorphous nature primarily formed on the particle surface as described above is formed by mechanochemical treatment using a ball mill or the like with typical zirconia balls, starting with the particle surface where impacts act directly. The amorphization of the surface proceeds preferentially over the interior of the particle, facilitating interparticle bonding and reducing interparticle friction during the pressure application process. The mechanochemical treatment method and the zirconia balls used as the grinding media are not limited, and any material that can be amorphized, such as alumina, that is hard and resistant to contamination, can be used.

[0033] It is preferable that the first particles 10 and the second particles 20 having different compositions are uniformly dispersed.

[0034] The dispersibility of the first particles 10 and the second particles 20 can be observed, for example, by elemental analysis (area analysis or point analysis) using EDS or EPMA on a cross section of a powder compact obtained by an ion polisher or the like.

[0035] (Compound A and Compound B) As described above, the first particle 10 is composed of compound A, and the second particle 20 is composed of compound B. Compound A contains Al and X. Compound B does not contain Al, and contains M and X.

[0036] Compound A may be represented by the following composition formula (1), and compound B may be represented by the following composition formula (2): Composition formula (1): Li(Al 1-y1 M y1 ) X6 Composition formula (2): Li2MX6 In composition formula (1), y1 satisfies 0≦y1<1.

[0037] When compound A is represented by the above composition formula (1), the average composition of compound A constituting each first particle 10 may be represented by the above composition formula (1), or compound A in all first particles 10 may be represented by the above composition formula (1). Here, the average composition of compound A constituting first particles 10 can be determined using the results of elemental analysis by EDS or EPMA when identifying the above-mentioned first particles and second particles. For example, the average composition of compound A in first particles 10 can be determined from the results of elemental analysis for any 20 spots identified as first particles 10.

[0038] When compound B is represented by the above composition formula (2), the average composition of compound B constituting each second particle 20 may be represented by the above composition formula (2), or compound B in all second particles 20 may be represented by the above composition formula (2). Here, the average composition of compound B constituting second particles 20 can be determined using the results of elemental analysis by EDS or EPMA when identifying the above-mentioned first particles and second particles. For example, the average composition of compound B in second particles 20 can be determined from the results of elemental analysis for any 20 spots identified as second particles 20.

[0039] According to the above-described configuration, a halide solid electrolyte with improved reliability can be obtained by using a mixed structure of compound A and compound B, which have a high Li ion content and high ionic conductivity.

[0040] The two compounds A and B, which have different compositions, differ from each other in mechanical properties, thermal expansion, heat resistance, and the like. Furthermore, the temperature dependence of these properties also does not match. Therefore, when the halide solid electrolyte of this embodiment is formed into a compact, particles with different properties, such as mechanical properties, thermal expansion, and heat resistance, are dispersed within the compact structure, suppressing critical breakdown and degradation. This is presumably because the dispersed presence of particles with different properties makes damage sporadic and prevents sudden breakdown, making property degradation less likely to become apparent. Therefore, the halide solid electrolyte of this embodiment, which includes the two compounds A and B, which have different compositions, has high ionic conductivity, while also exhibiting improved bending strength, thermal shock resistance, and heat resistance, resulting in high reliability.

[0041] When the halide solid electrolyte of this embodiment includes first particles 10 composed of compound A represented by composition formula (1) and second particles 20 composed of compound B represented by composition formula (2), the halide solid electrolyte of this embodiment can also be represented by the following composition formula (6): Composition formula (6): xLi(Al 1-y1 M y1 )X6-(1-x)Li2MX6 (0<x<1) where, in composition formula (6), x satisfies 0<x<1.

[0042] Compound A may be represented by the following composition formula (3): Composition formula (3): Li3AlX6

[0043] According to the above-described configuration, a halide solid electrolyte with improved reliability can be obtained by using a mixed structure of compound A and compound B, which have a high Li ion content and high ionic conductivity.

[0044] The first particle group may include particles including a first crystal phase represented by the following composition formula (4) and a second crystal phase represented by the following composition formula (5). Composition formula (4): Li(Al 1-y2 M y2 ) X6 Composition formula (5): Li2MX6 In composition formula (4), y2 satisfies 0≦y2<1.

[0045] In the above-described structure, the first crystal phase and the second crystal phase are contained in one particle, and by containing such a particle, a halide solid electrolyte with improved reliability can be obtained.

[0046] In the particles containing the first crystalline phase and the second crystalline phase, the molar ratio of the first crystalline phase to the sum of the first crystalline phase and the second crystalline phase may be 0.05 or more and 0.95 or less. This configuration allows for a halide solid electrolyte having a higher ionic conductivity (e.g., 1.0 μS / cm or more).

[0047] X may contain F. According to this configuration, a halide solid electrolyte with excellent stability (e.g., electrochemical stability and heat resistance) can be obtained due to the strong bond between the most electronegative fluoride ion and other cations. This suppresses fluctuations in characteristics during the manufacturing process, resulting in a battery with excellent performance and reliability. For example, in air, for example, at temperatures between 250°C and 300°C, the ionic conductivity and particle morphology (e.g., BET specific surface area) are stable, resulting in excellent heat resistance. This suppresses deterioration of the properties of the solid electrolyte due to heat generation caused by, for example, drying during slurry coating, warm pressing (e.g., integrating the positive electrode layer, solid electrolyte layer, and negative electrode layer of a battery, or pressing during cell stacking), or friction during coating of the active material.

[0048] M may contain Ti. This configuration allows a halide solid electrolyte to have higher ionic conductivity. Furthermore, by including Ti, the solid-phase reaction temperature can be lowered (for example, to 750°C or less), that is, the reaction can be accelerated. Therefore, a homogeneous halide solid electrolyte with excellent ionic conductivity can be obtained.

[0049] In the composition formula (1), M may contain Ti, and y1 may satisfy the relationship 0≦y1≦0.3. This configuration makes it possible to obtain a halide solid electrolyte having higher ionic conductivity.

[0050] In the composition formula (4), M may contain Ti, and y2 may satisfy the relationship 0≦y2≦0.3. This configuration makes it possible to obtain a halide solid electrolyte having higher ionic conductivity.

[0051] Compound A represented by composition formula (3) may have a monoclinic crystal structure. This configuration allows a halide solid electrolyte to be obtained that has higher ionic conductivity (e.g., 1.0 μS / cm or more).

[0052] In the particles containing the first crystal phase and the second crystal phase, the first crystal phase may have an orthorhombic crystal structure. This configuration allows for a halide solid electrolyte with higher ionic conductivity (e.g., 3.0 μS / cm or higher). In this case, M may contain Ti. In this case, by including Ti in M, a halide solid electrolyte with even higher ionic conductivity (e.g., 6.0 μS / cm or higher) can be obtained.

[0053] (Characteristics of Halide Solid Electrolyte) The halide solid electrolyte compact of this embodiment can be used, for example, as a solid electrolyte layer of a battery, a coating layer that coats an active material of a battery, and a composite material for an electrode layer. The halide solid electrolyte of this embodiment can be formed into a dense compact (e.g., a relative density of 95% or more) by improving packing. This results in a compact with high ionic conductivity and excellent mechanical performance (e.g., high flexural strength and high impact resistance). Meanwhile, reducing the relative density of the solid electrolyte (e.g., 90% or less) reduces its heat capacity, thereby improving its thermal shock resistance. The density of such a solid electrolyte compact can be controlled, for example, by the pressure used to form the compact. The halide solid electrolyte of this embodiment is a material with excellent interparticle adhesion, allowing a wide density range to be controlled depending on the intended application. Furthermore, when the solid electrolyte of this embodiment is used in a coating layer of an active material, densification can be achieved by increasing the shear stress applied when coating the active material. The shear stress is, for example, 29.4 MPa or more and 980 MPa or less. Furthermore, by incorporating an amorphous phase into the first particles 10 and / or the second particles 20, the particles become softer, enhancing the adhesion between the particles. This also provides the effect of suppressing the destruction of the active material particles due to the stress during coating, thereby suppressing the deterioration of properties due to the destruction of the active material particles. Furthermore, the friction between the particles is reduced, thereby suppressing the generation of heat between the particles during pressure application or coating. This suppresses the thermal denaturation of the solid electrolyte and the active material, thereby suppressing the deterioration of properties and changes in particle shape.

[0054] The melting point of compound A represented by composition formula (1) in the atmosphere is, for example, 750°C or higher and 800°C or lower. The melting point of compound B represented by composition formula (2) in the atmosphere is, for example, around 700°C. In this case, when compound A and compound B are compared, compound B, which has a lower melting point, tends to be softer. For this reason, when compound A and compound B are contained together and subjected to a pulverization (amorphization) treatment in the same batch, amorphization of compound B tends to progress. Therefore, in this case, the amorphous phase in the particle surface of compound B is large, or there are many amorphized particles in the second particles 20 composed of compound B. For this reason, in a solid electrolyte obtained by mixing first particles 10 composed of compound A and second particles 20 composed of compound B and subjecting them to a mechanochemical treatment, the amorphization of the particle surface of the second particles 20 progresses more, resulting in the effect of improving the binding strength of the bonding interface with the particles. For example, in a powder compact, the effect is obtained in which the soft particles of compound B are preferentially deformed and filled into the gaps between the particles of compound A. In this way, by including the second particles 20 made of compound B in the first particles 10 made of compound A, it becomes easier to obtain a solid electrolyte that is dense and has excellent mechanical properties. A solid electrolyte that includes such first particles 10 made of compound A and second particles 20 made of compound B and has a coefficient of variation CV that provides high ionic conductivity is obtained. Al and the coefficient of variation CV M For example, a powder density of 1.942 g / cm 3 By mixing LiAlF powder and LiTiF powder in a molar ratio of, for example, 75:25, 3 The density is improved.

[0055] (Method for Producing Halide Solid Electrolyte) The halide solid electrolyte of this embodiment can be produced, for example, by the following method.

[0056] 2 is a flow diagram of a method for producing a halide solid electrolyte according to an embodiment of the present disclosure. The method for producing a halide solid electrolyte according to this embodiment will be described below with reference to FIG. 2.

[0057] A plurality of batches having an average composition of the target compound A, for example, composition formula (1), but differing slightly in their Al components, are synthesized to produce first particles 10 composed of compound A. Meanwhile, a plurality of batches having an average composition of the target compound B, for example, composition formula (2), but differing slightly in their M components, are synthesized to produce second particles 20 composed of compound B. The resulting first particles 10 and second particles 20 are mixed in a predetermined ratio to synthesize the halide solid electrolyte of this embodiment. Note that the synthesis method is not limited to this, and as long as the solid electrolyte of this embodiment is ultimately synthesized, the synthesis route is not limited to this embodiment.

[0058] A specific example of a method for producing the first particles 10 is as follows.

[0059] A plurality of batches are pre-synthesized with slight variations in the Al component so that the average composition corresponds to the composition of the target compound A. The average composition of the mixture of these pre-synthesized batches corresponds to the composition of the target compound A. As an example, as shown in FIG. 2 , three batches A1, A2, and A3 are prepared, each with a slight variation in the Al component. The batch Al is prepared by mixing the starting materials so that the Al content is -a% compared to the composition of the target compound A, i.e., the mixing ratio of the starting materials is a molar ratio in which the Al content is reduced by a% compared to the amount of Al charged when synthesizing the target composition. The batch A2 is prepared by mixing the starting materials in a ratio that results in the composition of the target compound A. In other words, the variation in Al content of the batch A2 from the target composition is ±0%. Badge A3 is a mixture of starting materials so that it has a composition in which Al is +a% from the composition of the target compound A, i.e., the mixing ratio of the starting materials is a molar ratio in which Al is increased by a% compared to the amount of Al charged when synthesizing the target composition. a can be adjusted, for example, within a range of 0.001% or more and 10% or less. Starting materials serving as Li, Al, and M sources are charged at the respective ratios, and preliminary synthesis A (synthesis of badges A1, A2, and A3) is performed, for example, by mechanochemical synthesis. The starting materials may be, for example, halides such as their respective fluorides (e.g., LiF, AlF3, and fluorides of M), but are not limited to halides such as fluorides. For example, any raw material form, such as oxides, carbonates, or fluorinated oxides, can be used as long as it can synthesize the solid electrolyte of this embodiment. Sub-components (i.e., Nb and Ga components) may be included in the starting materials, which can promote the synthesis reaction (for example, LiF+AlF3 → Li3AlF6).

[0060] After pre-synthesis of badges A1, A2, and A3, badges A1, A2, and A3 are weighed in a molar ratio of A1:A2:A3 = 1:1:1, and then uniformly dry-mixed for approximately 30 minutes using, for example, a mortar and pestle (synthesis step A). ​​This synthesis step A produces a powder whose average composition is that of the target compound A. This powder corresponds to first particles 10. The particle size of the powder may be any size that is easy to handle during the manufacturing process, and may be, for example, an average particle size of 0.5 μm or more and 3.0 μm or less. While an example of synthesis using three badges A1, A2, and A3 has been given, this is not limiting and three or more badges may be used.

[0061] A specific example of a method for producing the second particles 20 is as follows.

[0062] A plurality of batches are pre-synthesized with slight variations in the M component so that the average composition corresponds to the composition of the target compound B. The average composition of the mixture of these pre-synthesized batches corresponds to the composition of the target compound B. As an example, as shown in FIG. 2 , three batches B1, B2, and B3 are prepared, each with a slight difference in the M component. In badge B1, the starting materials are mixed so that the M is −b % from the composition of the target compound A, i.e., the mixing ratio of the starting materials is such that the M is reduced by b % in molar ratio from the amount of M charged when synthesizing the target composition. In badge B2, the starting materials are mixed in a ratio that results in the composition of the target compound B. In other words, in badge B2, the change in M ​​from the target composition is ±0%. Badge B3 is a mixture of starting materials so that it has a composition in which M is +b% relative to the composition of the target compound B, i.e., so that the mixing ratio of the starting materials is such that M is increased by b% in molar ratio compared to the amount of M charged when synthesizing the target composition. b can be adjusted, for example, within a range of 0.001% or more and 15% or less. Starting materials serving as Li and M sources are charged at the respective ratios, and preliminary synthesis B (synthesis of badges B1, B2, and B3) is performed, for example, by mechanochemical synthesis. The starting materials may be in the form of their respective fluorides (e.g., LiF, fluorides of M), but are not limited to fluorides. For example, any raw material form, such as oxide, carbonate, or fluorinated oxide, can be used as long as it can synthesize the solid electrolyte of this embodiment. Sub-components (i.e., Nb and Ga components) may be included in the starting materials, which can promote the synthesis reaction (for example, LiF+AlF3 → Li3AlF6).

[0063] After pre-synthesis of badges B1, B2, and B3, badges B1, B2, and B3 are weighed in a molar ratio of B1:B2:B3 = 1:1:1, and then uniformly dry-mixed for approximately 30 minutes using, for example, a mortar and pestle (synthesis step B). This synthesis step B produces a powder whose average composition corresponds to the target compound A. This powder corresponds to first particles 10. The particle size of the powder may be any size that is easy to handle during the manufacturing process, and may be, for example, 0.5 μm or more and 3.0 μm or less. While an example of synthesis using three badges B1, B2, and B3 has been given, the present invention is not limited to this, and three or more badges may be used.

[0064] First particles 10 composed of compound A obtained in the synthesis step A and second particles 20 composed of compound B obtained in the synthesis step B are weighed in a predetermined ratio (e.g., first particles 10:second particles 20 = 7:3 (molar ratio)), and similarly to the mixing in the synthesis steps A and B, a general alumina mortar and pestle are used to uniformly dry mix the mixture for, for example, 20 to 40 minutes. The mixture is then placed in a planetary ball mill (capacity 300 mL) together with zirconia balls (diameter 0.5 mm to 3 mm, 100 g to 400 g), and subjected to dry mechanochemical treatment (e.g., 20 to 60 hours) as the main synthesis step, thereby synthesizing a solid electrolyte containing amorphous Al and M with a compositional variation. In this manner, the solid electrolyte according to this embodiment can be synthesized.

[0065] In addition, minor components (Nb, Ga components (e.g., NbF, GaF)) may be added in this synthesis step. For example, the minor components may be added separately during the synthesis of compound A, the synthesis of compound B, and the main mixing step of mixing compound A (i.e., first particles 10) and compound B (i.e., second particles 20). Adding the minor components separately can achieve the effect of uniformly dispersing the minor components in the solid electrolyte. The minor components (Nb, Ga) have the effect of promoting the solid-phase reaction (the reaction of synthesizing compound A and compound B from the starting materials). In addition, the minor components are preferably in the form of fine particles to prevent the formation of unnecessary precipitates. For example, it is desirable for the minor components to be smaller particles (e.g., an average particle diameter of 0.1 μm or more and 1 μm or less) than the starting materials (e.g., LiF, AlF, and TiF).

[0066] In the above example, a fluoride was used as the starting material, but a halide corresponding to the halogen element contained in X can be used.

[0067] The number of divided batches is not limited to three, but may be two or more, or may be four or more. In dry mixing or mechanochemical processing, powder does not have the fluidity of a liquid, so by increasing the number of divided batches (and increasing the number of divided batches), it becomes easier to synthesize a limited composition range or a homogeneous solid electrolyte. However, since an increase in the number of divided batches leads to a decrease in workability, the number of divided batches may be set in consideration of productivity. The number of divided batches may be different between compound A and compound B.

[0068] In this manner, the solid electrolyte according to the present embodiment can be synthesized. However, when all of the starting materials are combined into one batch for synthesis as described in Patent Documents 1 and 2, homogenization may be difficult, and the uneven composition may easily produce an unnecessary precipitate phase, resulting in large composition fluctuations.

[0069] The diameter of the zirconia balls can be any size to adjust the amount of powder and the crushing force.

[0070] The mixing of composition A, which includes a compositional difference, and compound B is not limited to a ball mill, and may be performed by wet mixing using, for example, a V blender or a disper mill using a solvent such as ethanol. The dispersion state and compositional difference (Al and Ti) of compound A and compound B in the solid electrolyte can be evaluated by elemental analysis (area analysis or point analysis) using, for example, EPMA or EDS.

[0071] In the above example, a halide such as a fluoride was used as the starting material. However, as a first modification of the manufacturing method, an oxide may be used as the starting material, and a precursor of the oxide of compound A and a precursor of the oxide of compound B may be halogenated (fluorinated). In the following example, a fluorination treatment is performed as the halogenation.

[0072] 3 is a flow diagram of a method for producing a solid electrolyte according to Modification 1. Modification 1 differs in that Compound A and Compound B, which have different compositions, are synthesized from starting materials, such as powders of chemically pure oxides and carbonates of LiCO, TiO, and AlO, to form oxide precursors (Compound A and Compound B), which are then mixed with NHF powder and heat-treated to fluorinate the oxide precursors, thereby synthesizing a solid electrolyte.

[0073] As precursors of compound A (composition ratio that results in LiAlO), five badges with slightly different Al components are pre-synthesized (A1 to A5 precursors) using LiCO and AlO, and then multiple pre-synthesized badges are synthesized (mixed together) to obtain precursors of compound A with Al composition differences that result in an average composition of A (composition ratio that results in LiAlO).

[0074] Specifically, the five compositional components are Al = -2%, -1%, ±0%, +1%, and +2%, as in the examples. The starting materials are weighed out on a 30 g scale in a normal atmospheric environment (e.g., a temperature of 22°C to 26°C and a humidity of 30% to 50%) so as to achieve the respective ratios, and then wet-mixed and pulverized (20 hours) using a 600 ml ball mill (using φ1 mm zirconia balls and pure water (60 ml)). The resulting powders are then air-dried in a dryer (at 200°C for 20 hours), yielding pre-synthesized powders A1, A2, A3, A4, and A5, which are then dry-mixed (using a mortar and pestle) to obtain a precursor powder of compound A.

[0075] On the other hand, as a precursor of compound B (composition ratio that becomes LiTiO), five badges with slightly changed Ti components are pre-synthesized (precursors B1 to B5) using LiCO and TiO (for example, anatase type), and then multiple pre-synthesized badges are dry-synthesized (mixed together) to obtain a precursor of compound B that includes Ti composition differences and has an average composition of B (composition ratio that becomes LiTiO).

[0076] Specifically, the five compositional components are Ti = -3%, -1%, ±0%, +1%, +3%, as in the examples. The starting materials were weighed out in a normal atmospheric environment on a 30 g scale to achieve the respective ratios, and then wet-mixed and pulverized (20 hours) using a 600 ml ball mill (using φ1 mm zirconia balls and 60 ml of pure water). The mixture was then air-dried in a dryer (at 200°C for 20 hours) to obtain precursor powders of pre-synthesized B1, B2, B3, B4, and B5. The obtained pre-synthesized B1, B2, B3, B4, and B5 powders were dry-mixed (using a mortar and pestle) to obtain a precursor powder of compound B.

[0077] Thereafter, the precursor powder of the above-mentioned compound A (preliminary synthesis A1, A2, A3, A4, and A5) and the precursor powder of compound B (preliminary synthesis B1, B2, B3, B4, and B5) were dry-mixed in a predetermined ratio using a mortar and pestle for about 10 minutes to obtain a precursor mixed powder of compound A and compound B. Next, a predetermined amount of NH4F powder as a fluoride source and the precursor mixed powder of compound A and compound B were weighed out in a predetermined ratio so that the total amount was 30 g, and the mixture was dry-mixed for about 10 minutes using a mortar and pestle.

[0078] Next, the powder mixed with NH4F (NH4F + compound A precursor + compound B precursor) is placed in a high-purity (SSA-H) alumina crucible and converted into a fluoride by heat treatment at 330°C for 5 hours in a nitrogen atmosphere using a general electric furnace. Thereafter, the obtained fluoride is subjected to mechanochemical treatment in the same manner as in the embodiment.

[0079] In this way, the solid electrolyte of this embodiment is obtained by the manufacturing method of Modification 1. The diameter of the zirconia balls can be any size to adjust the amount of powder and the grinding force. The precursor may also be a fluoride oxide (e.g., TiF2O).

[0080] The fluorination method is not limited to the above method, and fluorination may be carried out by generating fluorine gas by heat treating a fluorination source and bringing the fluorine gas into contact with the object to be fluorinated.

[0081] Specifically, the precursor mixed powder of compound A and compound B is placed on a mesh such as a fine-mesh nickel netting, and the fluoride source (ammonium fluoride) is placed underneath, but they are not in direct contact with each other. By heat treatment, fluorine gas is generated, which passes through the mesh and synthesizes the precursor mixed powder of compound A and compound B into a fluoride. Any fluoride source can be used as long as it is thermally decomposable. In particular, since the mixed powder and the fluoride source are not in direct contact with each other, the fluoride source may contain inorganic residues (e.g., CuF2, which emits F as a gas upon heating). While heat treatment in a nitrogen or reducing atmosphere is preferable to prevent oxidation of the nickel netting, heat treatment in air is also possible if repeated several times.

[0082] Second Embodiment A second embodiment will be described below, and the matters described in the first embodiment will be omitted as appropriate.

[0083] The battery according to the second embodiment includes a positive electrode, an electrolyte layer, and a negative electrode. The electrolyte layer is disposed between the positive electrode and the negative electrode.

[0084] At least one selected from the group consisting of the positive electrode, the electrolyte layer, and the negative electrode contains the halide solid electrolyte according to the first embodiment.

[0085] The battery according to the second embodiment has excellent charge / discharge characteristics because it contains the halide solid electrolyte according to the first embodiment.

[0086] FIG. 4 shows a cross-sectional view of a battery 1000 according to a second embodiment.

[0087] The battery 1000 according to the second embodiment includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is provided between the positive electrode 201 and the negative electrode 203.

[0088] The positive electrode 201 may include a positive electrode material including the halide solid electrolyte according to the first embodiment. The positive electrode 201 includes a positive electrode active material 204 and a solid electrolyte 100.

[0089] The electrolyte layer 202 contains an electrolyte material.

[0090] The negative electrode 203 contains a negative electrode active material 205 and a solid electrolyte 100 .

[0091] The solid electrolyte 100 includes, for example, the halide solid electrolyte according to the first embodiment. The solid electrolyte 100 may be particles containing the halide solid electrolyte according to the first embodiment as a main component. Particles containing the halide solid electrolyte according to the first embodiment as a main component refer to particles in which the component contained in the largest amount by molar ratio is the halide solid electrolyte according to the first embodiment. The solid electrolyte 100 may be particles made of the halide solid electrolyte according to the first embodiment.

[0092] The positive electrode 201 contains a material capable of absorbing and releasing metal ions (e.g., lithium ions). The material is, for example, a positive electrode active material 204.

[0093] Examples of the positive electrode active material 204 include a lithium-containing transition metal oxide, a transition metal fluoride, a polyanion, a fluorinated polyanion material, a transition metal sulfide, a transition metal oxyfluoride, a transition metal oxysulfide, or a transition metal oxynitride. Examples of the lithium-containing transition metal oxide include Li(Ni,Co,Mn)O, Li(Ni,Co,Al)O, or LiCoO.

[0094] In the present disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0095] The shape of the positive electrode active material 204 is not limited to a specific shape. The positive electrode active material 204 may be particles. The positive electrode active material 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material 204 has a median diameter of 0.1 μm or more, the positive electrode active material 204 and the solid electrolyte 100 can be well dispersed in the positive electrode 201. This improves the charge / discharge characteristics of the battery 1000. When the positive electrode active material 204 has a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material 204 improves. This allows the battery 1000 to operate at a high output.

[0096] The positive electrode active material 204 may have a larger median diameter than the solid electrolyte 100. This allows the positive electrode active material 204 and the solid electrolyte 100 to be dispersed well in the positive electrode 201.

[0097] In order to improve the energy density and output of the battery 1000, in the positive electrode 201, the ratio of the volume of the positive electrode active material 204 to the sum of the volume of the positive electrode active material 204 and the volume of the solid electrolyte 100 may be 0.30 or more and 0.95 or less.

[0098] A coating layer may be formed on at least a portion of the surface of the positive electrode active material 204. The coating layer may be formed on the surface of the positive electrode active material 204, for example, before mixing with the conductive additive and the binder. Examples of coating materials included in the coating layer include a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte. When the solid electrolyte 100 contains a sulfide solid electrolyte, the coating material may contain the halide solid electrolyte according to the first embodiment to suppress oxidative decomposition of the sulfide solid electrolyte. When the solid electrolyte 100 contains the halide solid electrolyte according to the first embodiment, the coating material may contain an oxide solid electrolyte to suppress oxidative decomposition of the solid electrolyte. Lithium niobate, which has excellent stability at high potentials, may be used as the oxide solid electrolyte. By suppressing oxidative decomposition, an increase in overvoltage of the battery 1000 can be suppressed.

[0099] As described above, when the positive electrode 201 includes a positive electrode material including the halide solid electrolyte according to the first embodiment, the positive electrode material may include the halide solid electrolyte according to the first embodiment as the solid electrolyte 100, or may include the halide solid electrolyte according to the first embodiment as a coating material that coats the positive electrode active material 204.

[0100] To improve the energy density and output of the battery 1000, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

[0101] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte. The solid electrolyte may include the halide solid electrolyte according to the first embodiment. The electrolyte layer 202 may be a solid electrolyte layer.

[0102] The electrolyte layer 202 may contain 50 mass % or more of the halide solid electrolyte according to the first embodiment. The electrolyte layer 202 may contain 70 mass % or more of the halide solid electrolyte according to the first embodiment. The electrolyte layer 202 may contain 90 mass % or more of the halide solid electrolyte according to the first embodiment. The electrolyte layer 202 may be made of only the halide solid electrolyte according to the first embodiment.

[0103] Hereinafter, the halide solid electrolyte according to the first embodiment will be referred to as a first solid electrolyte, and a solid electrolyte different from the first solid electrolyte will be referred to as a second solid electrolyte.

[0104] The electrolyte layer 202 may contain not only the first solid electrolyte but also the second solid electrolyte. The first solid electrolyte and the second solid electrolyte may be uniformly dispersed in the electrolyte layer 202. A layer made of the first solid electrolyte and a layer made of the second solid electrolyte may be stacked along the stacking direction of the battery 1000.

[0105] The battery according to the second embodiment may include a positive electrode 201, a second electrolyte layer, a first electrolyte layer, and a negative electrode 203, in this order. The solid electrolyte contained in the first electrolyte layer may have a lower reduction potential than the solid electrolyte contained in the second electrolyte layer. This allows the solid electrolyte contained in the second electrolyte layer to be used without being reduced. As a result, the charge / discharge efficiency of the battery 1000 can be improved. For example, when the second electrolyte layer contains the first solid electrolyte, the first electrolyte layer may contain a sulfide solid electrolyte to suppress reductive decomposition of the solid electrolyte. This allows the charge / discharge efficiency of the battery 1000 to be improved. The second electrolyte layer may contain the first solid electrolyte. The first solid electrolyte has high oxidation resistance, thereby achieving a battery with excellent charge / discharge characteristics.

[0106] The electrolyte layer 202 may consist of only the second solid electrolyte.

[0107] The electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less. When the electrolyte layer 202 has a thickness of 1 μm or more, the cathode 201 and the anode 203 are less likely to short-circuit. When the electrolyte layer 202 has a thickness of 1000 μm or less, the battery 1000 can operate at high power.

[0108] Examples of the second solid electrolyte are LiMgX, LiFeX, Li(Al,Ga,In)X, Li(Al,Ga,In)X, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I.

[0109] To improve the energy density and power output of the battery 1000, the electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less.

[0110] The negative electrode 203 contains a material capable of absorbing and releasing metal ions (e.g., lithium ions). The material is, for example, a negative electrode active material 205.

[0111] Examples of the negative electrode active material 205 include a metal material, a carbon material, an oxide, a nitride, a tin compound, or a silicon compound. The metal material may be a simple metal or an alloy. An example of the metal material is lithium metal or a lithium alloy. Examples of the carbon material are natural graphite, coke, partially graphitized carbon, carbon fiber, spherical carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, suitable examples of the negative electrode active material are silicon (i.e., Si), tin (i.e., Sn), a silicon compound, or a tin compound.

[0112] The anode active material 205 may be selected taking into consideration the reduction resistance of the solid electrolyte contained in the anode 203. For example, when the anode 203 contains a first solid electrolyte, the anode active material 205 may be a material capable of absorbing and releasing lithium ions at 0.27 V or more relative to lithium. Examples of such anode active materials include titanium oxide, indium metal, or a lithium alloy. An example of titanium oxide is Li4Ti5O 12 , LiTiO, or TiO. By using the above-mentioned negative electrode active material, it is possible to suppress the reductive decomposition of the first solid electrolyte contained in the negative electrode 203. As a result, it is possible to improve the charge / discharge efficiency of the battery 1000.

[0113] The shape of the negative electrode active material 205 is not limited to a specific shape. The negative electrode active material 205 may be particles. The negative electrode active material 205 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material 205 has a median diameter of 0.1 μm or more, the negative electrode active material 205 and the solid electrolyte 100 can be well dispersed in the negative electrode 203. This improves the charge / discharge characteristics of the battery 1000. When the negative electrode active material 205 has a median diameter of 100 μm or less, the lithium diffusion rate within the negative electrode active material 205 improves. This allows the battery 1000 to operate at high power.

[0114] The negative electrode active material 205 may have a larger median diameter than the solid electrolyte 100. This allows the negative electrode active material 205 and the solid electrolyte 100 to be dispersed well in the negative electrode 203.

[0115] In order to improve the energy density and output of the battery 1000, in the negative electrode 203, the ratio of the volume of the negative electrode active material 205 to the sum of the volume of the negative electrode active material 205 and the volume of the solid electrolyte 100 may be 0.30 or more and 0.95 or less.

[0116] To improve the energy density and output of the battery 1000, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less.

[0117] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a second solid electrolyte for the purpose of increasing ionic conductivity, chemical stability, and electrochemical stability.

[0118] The second solid electrolyte may be a sulfide solid electrolyte.

[0119] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, or Li 10 GeP2S 12 is.

[0120] When the electrolyte layer 202 contains the first solid electrolyte, the negative electrode 203 may contain a sulfide solid electrolyte to suppress reductive decomposition of the solid electrolyte. The electrochemically stable sulfide solid electrolyte covers the negative electrode active material, thereby preventing the first solid electrolyte from contacting the negative electrode active material. As a result, the internal resistance of the battery 1000 can be reduced.

[0121] The second solid electrolyte may be an oxide solid electrolyte.

[0122] Examples of oxide solid electrolytes include: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutions; (ii) perovskite-type solid electrolytes such as (LaLi)TiO3; (iii) Li 14 ZnGeO 16 LISICON-type solid electrolytes such as LiSiO, LiGeO or elemental substitutions thereof; (iv) LiLaZrO 12 or an element-substituted product thereof, or (v) a garnet-type solid electrolyte such as Li3PO4 or an N-substituted product thereof.

[0123] As mentioned above, the second solid electrolyte may be a halide solid electrolyte.

[0124] Examples of halide solid electrolytes are LiMgX, LiFeX, Li(Al,Ga,In)X, Li(Al,Ga,In)X, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I.

[0125] Other examples of halide solid electrolytes include Li a Me b Y cZ6, where a + mb + 3c = 6 and c > 0 are satisfied. Me is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Y. Z is at least one selected from the group consisting of F, Cl, Br, and I. m represents the valence of Me. "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metal elements" are all elements included in Groups 1 to 12 of the periodic table (excluding hydrogen) and all elements included in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0126] In order to improve the ionic conductivity of the halide solid electrolyte, Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0127] The halide solid electrolyte may be Li3YCl6 or Li3YBr6.

[0128] The second solid electrolyte may be an organic polymer solid electrolyte.

[0129] Examples of organic polymer solid electrolytes are compounds of polymer compounds and lithium salts.

[0130] The polymer compound may have an ethylene oxide structure. A polymer compound having an ethylene oxide structure can contain a large amount of lithium salt, and therefore can further increase ionic conductivity.

[0131] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOF, LiN(SOCF), LiN(SOCF), LiN(SOCF)(SOCF), or LiC(SOCF). One lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used.

[0132] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid to facilitate the exchange of lithium ions and improve the output characteristics of the battery.

[0133] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0134] Examples of non-aqueous solvents are cyclic carbonate ester solvents, chain carbonate ester solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, or fluorine-containing solvents. Examples of cyclic carbonate ester solvents are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of chain carbonate ester solvents are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of chain ether solvents are 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a chain ester solvent is methyl acetate. Examples of fluorine-containing solvents are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or two or more non-aqueous solvents selected from these may be used in combination.

[0135] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOCF, LiN(SOCF), LiN(SOCF), LiN(SOCF)(SOCF), or LiC(SOCF). A single lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L or more and 2 mol / L or less.

[0136] The gel electrolyte may be a polymer material impregnated with a non-aqueous electrolyte, such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0137] Examples of cations contained in the ionic liquid are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium; (ii) aliphatic cyclic ammonium such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, or piperidiniums; or (iii) nitrogen-containing heterocyclic aromatic cations such as pyridiniums or imidazoliums.

[0138] An example of an anion contained in an ionic liquid is PF6 - , BF4 - , SbF6 - , AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - is.

[0139] The ionic liquid may contain a lithium salt.

[0140] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder to improve adhesion between particles.

[0141] Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl ester of acrylic acid, polyethyl ester of acrylic acid, polyhexyl ester of acrylic acid, polymethacrylic acid, polymethyl ester of methacrylic acid, polyethyl ester of methacrylic acid, polyhexyl ester of methacrylic acid, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethyl cellulose. Copolymers can also be used as binders. Examples of such binders include copolymers of two or more materials selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Mixtures of two or more materials selected from these may also be used as binders.

[0142] At least one selected from the positive electrode 201 and the negative electrode 203 may contain a conductive additive to improve electronic conductivity.

[0143] Examples of the conductive additive include (i) graphites such as natural graphite or artificial graphite, (ii) carbon blacks such as acetylene black or ketjen black, (iii) conductive fibers such as carbon fiber or metal fiber, (iv) carbon fluoride, (v) metal powders such as aluminum, (vi) conductive whiskers such as zinc oxide or potassium titanate, (vii) conductive metal oxides such as titanium oxide, or (viii) conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene. For cost reduction, the conductive additives (i) or (ii) may be used.

[0144] In addition, a separator impregnated with an electrolytic solution may be used instead of the electrolyte layer, or the exterior housing containing the positive electrode, separator portion, and negative electrode may be filled with the electrolytic solution. The electrolytic solution may be, for example, the nonaqueous electrolytic solution described above. Examples of the shape of the battery according to the second embodiment include a coin type, a cylindrical type, a prismatic type, a sheet type, a button type, a flat type, and a laminate type.

[0145] The battery according to the second embodiment may be manufactured, for example, by preparing a material for forming a positive electrode, a material for forming an electrolyte layer, and a material for forming a negative electrode, and by using a known method to fabricate a laminate in which the positive electrode, the electrolyte layer, and the negative electrode are arranged in this order.

[0146] [Other Embodiments] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0147] (Technology 1) A halide solid electrolyte containing Li, Al, M, and X, wherein M is at least one element selected from the group consisting of metal elements (excluding Li and Al) and semimetal elements, and X is at least one element selected from the group consisting of F, Cl, Br, and I, and the halide solid electrolyte includes: a first particle group consisting of first particles constituted of a compound A containing Al and the X; and a second particle group consisting of second particles constituted of a compound B not containing Al and containing the M and the X, and wherein in the first particle group, a standard deviation σ of a ratio Al / X of the mass of Al to the mass of X is Al and the average value A of the ratio Al / X Al The coefficient of variation CV is calculated using the following formula (A) Al is 10% or less, and in the second particle group, the standard deviation σ of the ratio M / X of the mass of M to the mass of X is M and the average value A of the ratio M / X M The coefficient of variation CV is calculated using the following formula (B) M The halide solid electrolyte is represented by the formula (A): CV Al = (σ Al / A Al ) × 100 Formula (B): CV M = (σM / A M ) x 100

[0148] The above-described configuration allows for the production of a halide solid electrolyte having excellent ionic conductivity. Furthermore, the above-described configuration allows for the production of a highly reliable halide solid electrolyte having excellent stability (e.g., heat resistance and atmospheric environment resistance). Therefore, the above-described configuration allows for the production of a halide solid electrolyte having excellent ionic conductivity and reliability.

[0149] (Technology 2) The halide solid electrolyte according to Technology 1, wherein the compound A is represented by the following composition formula (1), and the compound B is represented by the following composition formula (2). Composition formula (1): Li(Al 1-y1 M y1 ) X6 Composition formula (2): Li2MX6 In the composition formula (1), y1 satisfies 0≦y1<1.

[0150] According to the above-described configuration, a halide solid electrolyte with improved reliability can be obtained by using a mixed structure of compound A and compound B, which have a high Li ion content and high ionic conductivity.

[0151] (Technology 3) The halide solid electrolyte according to Technology 2, wherein the compound A is represented by the following composition formula (3): Composition formula (3): Li3AlX6

[0152] According to the above-described configuration, a halide solid electrolyte with improved reliability can be obtained by using a mixed structure of compound A and compound B, which have a high Li ion content and high ionic conductivity.

[0153] (Technology 4) The halide solid electrolyte according to Technology 1, wherein the first particle group includes particles including a first crystalline phase represented by the following composition formula (4) and a second crystalline phase represented by the following composition formula (5). Composition formula (4): Li(Al 1-y2 M y2 ) X6 Composition formula (5): Li2MX6 In the composition formula (4), y2 satisfies 0≦y2<1.

[0154] In the above-described structure, the first crystal phase and the second crystal phase are contained in one particle, and by containing such a particle, a halide solid electrolyte with improved reliability can be obtained.

[0155] (Technology 5) The halide solid electrolyte according to Technology 4, wherein in the particles containing the first crystal phase and the second crystal phase, a molar ratio of the first crystal phase to a total of the first crystal phase and the second crystal phase is 0.05 or more and 0.95 or less.

[0156] According to the above-described configuration, a halide solid electrolyte having higher ionic conductivity (for example, 1.0 μS / cm or more) can be obtained.

[0157] (Technology 6) The halide solid electrolyte according to any one of Techniques 1 to 5, wherein the X contains F.

[0158] According to the above-described configuration, a halide solid electrolyte having excellent stability (for example, electrochemical stability and heat resistance) can be obtained due to the strong bond between the fluoride ion, which has the highest electronegativity, and other cations.

[0159] (Technology 7) The halide solid electrolyte according to any one of Techniques 1 to 6, wherein the M contains Ti.

[0160] The above-described structure allows a halide solid electrolyte to be obtained that has higher ionic conductivity. Furthermore, the inclusion of Ti lowers the solid-phase reaction temperature (for example, to 750°C or less), which means that the reaction can be accelerated. Therefore, a homogeneous halide solid electrolyte with excellent ionic conductivity can be obtained.

[0161] (Technology 8) The halide solid electrolyte according to Technology 2 or 3, wherein the M contains Ti, and the y1 satisfies 0≦y1≦0.3.

[0162] With the above-described configuration, a halide solid electrolyte having higher ionic conductivity can be obtained.

[0163] (Technology 9) The halide solid electrolyte according to Technology 4 or 5, wherein M contains Ti, and y2 satisfies 0≦y2≦0.3.

[0164] With the above-described configuration, a halide solid electrolyte having higher ionic conductivity can be obtained.

[0165] (Technology 10) The halide solid electrolyte according to Technology 3, wherein the compound A represented by the composition formula (3) has a monoclinic crystal structure.

[0166] With the above-described configuration, a halide solid electrolyte having higher ionic conductivity (for example, 1.0 μS / cm or more) can be obtained.

[0167] (Technology 11) The halide solid electrolyte according to Technology 4, wherein the first crystal phase has an orthorhombic crystal structure.

[0168] With the above-described configuration, a halide solid electrolyte having higher ionic conductivity (for example, 3.0 μS / cm or higher) can be obtained.

[0169] (Technology 12) The halide solid electrolyte according to Technology 11, wherein the M contains Ti.

[0170] With the above-described configuration, a halide solid electrolyte having even higher ionic conductivity (for example, 6.0 μS / cm or more) can be obtained.

[0171] (Technology 13) The ratio Al / X is (the average value A Al -3 x the standard deviation σ Al ) or more and (the average value A Al + 3 × the standard deviation σ Al 13. The halide solid electrolyte according to any one of claims 1 to 12, wherein:

[0172] With the above-described configuration, particles having a composition with low ionic conductivity are reduced, and therefore a halide solid electrolyte with higher ionic conductivity (for example, 1.0 μS / cm or more, or 3.0 μS / cm or more) can be obtained.

[0173] (Technique 14) The ratio M / X is (the average value A M-3 x the standard deviation σ M ) or more and (the average value A M + 3 × the standard deviation σ M 14. The halide solid electrolyte according to any one of claims 1 to 13, wherein:

[0174] With the above-described configuration, particles having a composition with low ionic conductivity are reduced, and therefore a halide solid electrolyte with higher ionic conductivity (for example, 1.0 μS / cm or more, or 3.0 μS / cm or more) can be obtained.

[0175] (Technology 15) The ratio Al / X is (the average value A Al -3 x the standard deviation σ Al ) or more and (the average value A Al + 3 × the standard deviation σ Al ) or less, and the ratio M / X is (the average value A M -3 x the standard deviation σ M ) or more and (the average value A M + 3 × the standard deviation σ M 15. The halide solid electrolyte according to any one of claims 1 to 14, wherein:

[0176] With the above-described configuration, particles having a composition with low ionic conductivity are reduced, and therefore a halide solid electrolyte with higher ionic conductivity (for example, 1.0 μS / cm or more, or 3.0 μS / cm or more) can be obtained.

[0177] (Technology 16) The halide solid electrolyte according to any one of Techniques 1 to 15, wherein at least one particle selected from the group consisting of the first particles and the second particles includes an amorphous phase.

[0178] The above configuration makes it possible to obtain a halide solid electrolyte that combines high ionic conductivity (e.g., 1.0 μS / cm or more) and low electronic conductivity (e.g., 0.01 μS / cm or less). Furthermore, in the halide solid electrolyte, the amorphous phase portion is soft and easily deformed. Therefore, when the halide solid electrolyte of Technology 16 is compacted, an interface where particles are in close contact with each other is likely to form, which facilitates high density and thin layer formation, and further improves ionic conductivity. Therefore, when the halide solid electrolyte of Technology 16 is used in, for example, a solid electrolyte layer of a battery, the solid electrolyte layer can be thinned, or it can be suitably used as a coating layer for active material particles.

[0179] (Technology 17) The halide solid electrolyte according to Technology 16, wherein the volume of the amorphous phase contained in the second particles is larger than the volume of the amorphous phase contained in the first particles.

[0180] According to the above-mentioned configuration, ionic conductivity and reliability can be further improved. Furthermore, according to the above-mentioned configuration, the halide solid electrolyte becomes softer and more easily deformed, improving the adhesion between particles and reducing voids between particles. Therefore, the halide solid electrolyte according to Technique 17 can be densified when compacted into a powder. This allows, for example, when used in a solid electrolyte layer of a battery, the solid electrolyte layer can be densified, and the solid electrolyte can be suitably used as a coating layer for active material particles.

[0181] (Technology 18) The halide solid electrolyte according to Technology 16 or 17, wherein the amorphous phase contained in the first particles has higher ionic conductivity than the amorphous phase contained in the second particles.

[0182] According to the above configuration, the softer second particles can bind the first particles having higher ionic conductivity, thereby achieving high ionic conductivity.

[0183] (Technology 19) The halide solid electrolyte according to any one of Technologies 16 to 18, wherein the amorphous phase has lower electronic conductivity than portions of the first particles and the second particles other than the amorphous phase.

[0184] When the amorphous phase has lower electronic conductivity (for example, 0.01 μS / cm or less) than the portion other than the amorphous phase, a halide solid electrolyte having superior ionic conductivity can be obtained.

[0185] (Technology 20) The halide solid electrolyte according to any one of claims 1 to 19, which is a compact formed of the first particles and the second particles.

[0186] According to the above-described configuration, it is possible to realize a solid electrolyte layer of a battery or a coating layer of active material particles that has excellent ionic conductivity and reliability.

[0187] (Technology 21) The halide solid electrolyte according to any one of Techniques 1 to 20, wherein the halide solid electrolyte contains at least one selected from the group consisting of Nb and Ga.

[0188] According to the above-mentioned configuration, the synthesis reaction from the starting material to the halide solid electrolyte is accelerated, and a halide solid electrolyte having excellent ionic conductivity and reliability can be efficiently obtained.

[0189] (Technology 22) A positive electrode material comprising the solid electrolyte according to any one of Technology 1 to Technology 21.

[0190] The positive electrode material according to Technology 22 can realize a high-performance battery having excellent charge / discharge characteristics.

[0191] (Technology 23) A battery comprising a positive electrode containing the positive electrode material according to Technology 22.

[0192] This configuration makes it possible to provide a battery with excellent charge / discharge characteristics.

[0193] (Technology 24) A battery comprising: a positive electrode; a negative electrode; and an electrolyte layer provided between the positive electrode and the negative electrode, wherein at least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte according to any one of Technologies 1 to 21.

[0194] This configuration makes it possible to provide a high-performance battery having excellent charge / discharge characteristics.

[0195] While the solid electrolyte and the manufacturing method thereof according to the present disclosure have been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as they do not deviate from the gist of the present disclosure, various modifications conceivable by a person skilled in the art to the embodiments and other forms constructed by combining some of the components of the embodiments are also included in the scope of the present disclosure.

[0196] Furthermore, the above-described embodiments can be modified, replaced, added, omitted, and the like in various ways within the scope of the claims or their equivalents.

[0197] The present disclosure will now be described in more detail with reference to examples.

[0198] <Synthesis of halide solid electrolyte> (Example 1) Fig. 5 is a flow diagram of a method for producing a halide solid electrolyte in Example 1. In Example 1, the compound A constituting the first particles is Li3(Al 0.85 Ti 0.15 In Example 1, a halide solid electrolyte was synthesized in which the compound B constituting the second particles was represented by the composition formula LiTiX. That is, in Example 1, M was Ti. In Example 1, the compound A was Li(Al 0.85 Ti 0.15 )F6 and compound B, Li2TiX6, in a molar ratio of Li3(Al 0.85 Ti 0.15 ) A halide solid electrolyte was synthesized so that F:LiTiX = 0.75:0.25.

[0199] Chemically high-purity powders of LiF, TiF, and AlF were prepared as starting materials. First particles composed of compound A and second particles composed of compound B were fabricated using these starting materials.

[0200] In the preparation of the first particles, first, the average composition is set to the target composition of compound A, Li3(Al 0.85 Ti 0.15 ) F6, and five badges A1, A2, A3, A4, and A5, each slightly different in Al content, were pre-synthesized.

[0201] In the badge A1, the composition of the target compound A, Li3 (Al 0.85 Ti 0.15 )F6 to have a composition in which Al is -2%, that is, the mixing ratio of the starting materials is Li3(Al 0.85 Ti 0.15 The starting materials were mixed so that the amount of Al was reduced by 2% in molar ratio compared to the amount of Al charged when F6 was the target.

[0202] In badge A2, the composition of the target compound A, Li3 (Al 0.85 Ti 0.15 )F6 to have a composition in which Al is -1%, that is, the mixing ratio of the starting materials is Li3(Al 0.85 Ti 0.15 The starting materials were mixed so that the amount of Al was reduced by 1% in molar ratio compared to the amount of Al charged when F6 was the target.

[0203] In badge A3, the composition of the target compound A, Li3 (Al 0.85 Ti 0.15 The starting materials were mixed in a ratio such that the composition of the target compound A was Li3(Al 0.85 Ti 0.15 ) The change in Al from F6 was 0%.

[0204] In badge A4, the composition of the target compound A, Li3 (Al 0.85 Ti 0.15 )F6 to have a composition in which Al is +1%, that is, the mixing ratio of the starting materials is Li3(Al 0.85 Ti 0.15 ) The starting materials were mixed so that the amount of Al was increased by 1% in molar ratio compared to the amount of Al charged when F6 was the target.

[0205] In badge A5, the composition of the target compound A, Li3 (Al 0.85 Ti 0.15 )F6 to have a composition in which Al is +2%, that is, the mixing ratio of the starting materials is Li3(Al 0.85 Ti 0.15 ) The starting materials were mixed so that the amount of Al was increased by 2% in molar ratio compared to the amount of Al charged when F6 was the target.

[0206] For each of batches A1 to A5, 30 g of the mixed powder of starting materials was weighed out in a normal atmospheric environment and pre-synthesized for 10 hours by dry mechanochemical treatment in a 300 mL planetary ball mill (using 1 mm diameter zirconia balls). Five grams of each of the resulting pre-synthesized products A1, A2, A3, A4, and A5 were combined and placed in a 600 mL ball mill with a zirconia inner wall together with 5 mm diameter zirconia balls and dry mixed for 20 hours. This resulted in first particles. The first particles had an average particle size of approximately 0.7 μm. The average particle size of the first particles was determined by the intercept method using scanning electron microscope (SEM) images of the first particles (magnification: 2000x).

[0207] To prepare the second particles, first, five particles B1, B2, B3, B4, and B5 were preliminarily synthesized, each having an average composition Li2TiX6, the composition of the target compound B, but with slightly different Ti components.

[0208] In batch B1, the starting materials were mixed so that the composition of the target compound B, Li2TiX6, would have a Ti content of -3%. In other words, the starting materials were mixed so that the mixing ratio of the starting materials would be 3% less Ti in molar ratio than the amount of Ti charged when Li2TiX6 was the target.

[0209] In batch B2, the starting materials were mixed so that the composition would be such that Ti was -1% of the composition Li2TiX6 of the target compound B, that is, the mixing ratio of the starting materials was such that Ti was reduced by 1% in molar ratio compared to the amount of Ti charged when Li2TiX6 was the target.

[0210] In batch B3, the starting materials were mixed in a ratio that resulted in the composition Li2TiX6 of the target compound B. That is, in batch B3, the change in Ti from the composition Li2TiX6 of the target compound B was 0%.

[0211] In batch B4, the starting materials were mixed so that the composition of the target compound B, Li2TiX6, would have a Ti content of +1%. In other words, the starting materials were mixed so that the mixing ratio of the starting materials would be such that the amount of Ti added was increased by 1% in molar ratio compared to the amount of Ti charged when Li2TiX6 was the target.

[0212] In batch B5, the starting materials were mixed so that the composition of the target compound B, Li2TiX6, would have a Ti content of +3%, i.e., the mixing ratio of the starting materials would be such that the amount of Ti added was increased by 3% in molar ratio compared to the amount of Ti charged when Li2TiX6 was the target.

[0213] For each batch B1 to B5, 30 g of the mixed powder of starting materials was weighed out under normal atmospheric conditions and pre-synthesized for 10 hours by dry mechanochemical treatment in a 300 mL planetary ball mill (using 1 mm diameter zirconia balls). Five grams of each of the resulting pre-synthesized products B1, B2, B3, B4, and B5 were combined and placed in a 600 mL ball mill with a zirconia inner wall along with 5 mm diameter zirconia balls and dry mixed for 20 hours. This resulted in second particles. The second particles had an average particle size of approximately 0.66 μm. The average particle size of the second particles was determined by the intercept method using SEM images of the second particles (magnification: 2000x).

[0214] Next, the first particles (i.e., compound A) and the second particles (i.e., compound B) are mixed in a solution of compound A, Li(Al 0.85 Ti 0.15 )F6 and compound B, Li2TiX6, in a molar ratio of Li3(Al 0.85 Ti 0.15The first particles and the second particles were weighed and mixed so that the ratio of F:LiTiX was 0.75:0.25 and the total weight was 30 g. The first particles and the second particles were placed in a 600 mL ball mill with a zirconia inner wall together with 5 mm diameter zirconia balls and dry mixed for 20 hours, and the mixed powder was recovered as the halide solid electrolyte of Example 1. This dry ball mill treatment including mechanochemical treatment also promoted amorphization simultaneously with the synthesis of the halide solid electrolyte. That is, the obtained halide solid electrolyte of Example 1 contained an amorphous phase.

[0215] Comparative Example 1 A halide solid electrolyte was synthesized using a method similar to that used for the solid electrolyte material of the example described in Patent Document 1. Specifically, fluoride was used as the starting material, and the halide solid electrolyte of Comparative Example 1 was produced by mechanochemical synthesis. Specifically, LiF, TiF4, and AlF3 were prepared in a molar ratio of LiF:TiF4:AlF3 = 2.75:0.25:0.75. 30 g of a mixture of these materials was placed in a 500 mL planetary ball mill together with 200 g of φ5 mm zirconia balls in an Ar atmosphere and sealed. The mixture was then subjected to mechanochemical milling in the planetary ball mill for 12 hours at 500 rpm. In this manner, the solid electrolyte of Comparative Example 1 was synthesized. The synthesized product was removed from the Ar atmosphere and recovered.

[0216] <Evaluation of Solid Electrolytes> The halide solid electrolytes of Example 1 and Comparative Example 1 synthesized as described above were evaluated for ionic conductivity, electronic conductivity, coefficient of variation CV Al , and the coefficient of variation CV M asked for.

[0217] (Ionic Conductivity) The ionic conductivity was calculated from the area, thickness, and room temperature impedance characteristics of a compacted powder sample obtained by placing a halide solid electrolyte powder in a 10 mm diameter mold and applying a pressure of approximately 3 t / cm using a uniaxial hydraulic press. Impedance measurements were performed at room temperature while applying pressure. The impedance measurements were performed at a measurement frequency of 10 Hz to 10 MHz, a measurement voltage of 1 Vrms, and no DC bias. Misalignment in the electrical length of the cable and measuring jig was offset and evaluated. The ionic conductivity of the halide solid electrolyte of Example 1 was 7.1 μS / cm, and the ionic conductivity of the halide solid electrolyte of Comparative Example 1 was 0.93 μS / cm.

[0218] (Electronic Conductivity) The electronic conductivity was calculated from DC voltage and current characteristics. The electronic conductivity of the halide solid electrolyte of Example 1 was <0.01 μS / cm. The electronic conductivity of the halide solid electrolyte of Comparative Example 1 was 0.017 μS / cm.

[0219] (Coefficient of variation CV Al and the coefficient of variation CV M The coefficient of variation CV for the halide solid electrolyte obtained in Example 1 and the halide solid electrolyte obtained in Comparative Example 1 was Al and the coefficient of variation CV M was calculated in the following way.

[0220] First, a compacted sample of the halide solid electrolyte was prepared in the same manner as the compacted sample prepared in the measurement of ionic conductivity. A cross section of the compacted sample was formed using a cross-section polisher (CP). The cross section was subjected to elemental analysis (point analysis) by EPMA at a spot diameter (diameter) of 1 μm for a plurality of randomly selected spots. The spots identified as first particles and the spots identified as second particles by the elemental analysis by EPMA were separated, and 20 spots were randomly selected from each of the spots identified as first particles and the spots identified as second particles. The standard deviation σ of the ratio Al / X was calculated using the elemental analysis results of the 20 randomly selected spots measured as first particles. Al and average value A AlCalculate the coefficient of variation CV Al The standard deviation σ of the ratio M / X was calculated using the elemental analysis results of the second particles and 20 randomly measured spots. M and average value A M Calculate the coefficient of variation CV M was calculated.

[0221] For the halide solid electrolyte obtained in Example 1, the standard deviation σ Al is 0.01013, average value A Al is 0.1512, the coefficient of variation CV Al is 6.7%, and the standard deviation σ M is 0.01683, average value A M is 0.1503, the coefficient of variation CV M was 11.2%.

[0222] For the halide solid electrolyte obtained in Comparative Example 1, the standard deviation σ Al is 0.02084, average value A Al is 0.1408, the coefficient of variation CV Al is 14.8%, and the standard deviation σ M is 0.03711, average value A M is 0.139, the coefficient of variation CV M was 26.7%.

[0223] As mentioned above, the coefficient of variation CV Al is 10% or less, and the coefficient of variation CV M The halide solid electrolyte of Example 1, in which the coefficient of variation CV Al exceeds 10% and the coefficient of variation CV M The ionic conductivity was higher than that of the halide solid electrolyte of Comparative Example 1, in which the ionic conductivity exceeded 20%.

[0224] The halide solid electrolyte according to the present disclosure can be used, for example, as a solid electrolyte for secondary batteries such as all-solid-state batteries used in various electronic devices or automobiles.

Claims

1. A halide solid electrolyte comprising Li, Al, M, and X, wherein M is at least one element selected from the group consisting of metal elements (excluding Li and Al) and semimetal elements, and X is at least one element selected from the group consisting of F, Cl, Br, and I, the halide solid electrolyte comprising: a first particle group consisting of first particles constituted of a compound A containing Al and the X; and a second particle group consisting of second particles constituted of a compound B not containing Al and containing the M and the X, wherein in the first particle group, a standard deviation σ of a ratio Al / X of the mass of Al to the mass of X is Al and the average value A of the ratio Al / X Al The coefficient of variation CV is calculated using the following formula (A) Al is 10% or less, and in the second particle group, the standard deviation σ of the ratio M / X of the mass of M to the mass of X is M and the average value A of the ratio M / X M The coefficient of variation CV is calculated using the following formula (B) M is 20% or less. Al = (σ Al / A Al ) × 100 Formula (B): CV M = (σ M / A M ) x 100 2. The halide solid electrolyte according to claim 1, wherein the compound A is represented by the following composition formula (1), and the compound B is represented by the following composition formula (2). Composition formula (1): Li3(Al 1-y1 M y1 ) X6 Composition formula (2): Li2MX6 In the composition formula (1), y1 satisfies 0≦y1<1.

3. The halide solid electrolyte according to claim 2, wherein the compound A is represented by the following composition formula (3): Li3AlX6 4. The halide solid electrolyte according to claim 1, wherein the first particle group includes particles including a first crystal phase represented by the following composition formula (4) and a second crystal phase represented by the following composition formula (5). Composition formula (4): Li3(Al 1-y2 M y2 ) X6 Composition formula (5): Li2MX6 In the composition formula (4), y2 satisfies 0≦y2<1.

5. The halide solid electrolyte according to claim 4, wherein in the particles containing the first crystal phase and the second crystal phase, a molar ratio of the first crystal phase to a sum of the first crystal phase and the second crystal phase is 0.05 or more and 0.95 or less.

6. The halide solid electrolyte according to claim 1, wherein X includes F.

7. The halide solid electrolyte according to claim 1, wherein M includes Ti.

8. The halide solid electrolyte according to claim 2, wherein M contains Ti, and y1 satisfies 0≦y1≦0.

3.

9. The halide solid electrolyte according to claim 4, wherein M contains Ti, and y2 satisfies 0≦y2≦0.

3.

10. The halide solid electrolyte according to claim 3, wherein the compound A represented by the composition formula (3) has a monoclinic crystal structure.

11. The halide solid electrolyte according to claim 4, wherein the first crystal phase has an orthorhombic crystal structure.

12. The halide solid electrolyte according to claim 11, wherein M includes Ti.

13. The ratio Al / X is (the average value A Al -3 x the standard deviation σ Al ) or more and (the average value A Al + 3 × the standard deviation σ Al 2. The halide solid electrolyte according to claim 1, wherein the average molecular weight of the halide solid electrolyte is 1.0 or less.

14. The ratio M / X is (the average value A M -3 x the standard deviation σ M ) or more and (the average value A M + 3 × the standard deviation σ M 2. The halide solid electrolyte according to claim 1, wherein the average molecular weight of the halide solid electrolyte is 1.0 or less.

15. The ratio Al / X is (the average value A Al -3 x the standard deviation σ Al ) or more and (the average value A Al + 3 × the standard deviation σ Al ) or less, and the ratio M / X is (the average value A M -3 x the standard deviation σ M ) or more and (the average value A M + 3 × the standard deviation σ M 2. The halide solid electrolyte according to claim 1, wherein the average molecular weight of the halide solid electrolyte is 1.0 or less.

16. The halide solid electrolyte of claim 1, wherein at least one particle selected from the group consisting of the first particles and the second particles includes an amorphous phase.

17. The halide solid electrolyte according to claim 16, wherein the volume of the amorphous phase contained in the second particles is greater than the volume of the amorphous phase contained in the first particles.

18. The halide solid electrolyte according to claim 16, wherein the amorphous phase contained in the first particles has a higher ionic conductivity than the amorphous phase contained in the second particles.

19. The halide solid electrolyte according to claim 16, wherein the amorphous phase has lower electronic conductivity than the portions of the first particles and the second particles other than the amorphous phase.

20. The halide solid electrolyte according to claim 1, which is a compact formed of the first particles and the second particles.

21. The halide solid electrolyte according to claim 1, wherein the halide solid electrolyte contains at least one selected from the group consisting of Nb and Ga.

22. A positive electrode material comprising the halide solid electrolyte of claim 1.

23. A battery comprising a positive electrode comprising the positive electrode material of claim 22.

24. A battery comprising: a positive electrode; a negative electrode; and an electrolyte layer provided between the positive electrode and the negative electrode, wherein at least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the halide solid electrolyte according to claim 1.

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