Solid electrolyte and solid electrolyte battery

Abstract

This solid electrolyte contains lithium, zirconium, sulfur, oxygen, and chlorine as main elements, and peaks are confirmed at a diffraction angle 2 [theta] of 34.3 DEG + / -0.5 DEG and a diffraction angle 2 [theta] of 50.0 DEG + / -0.5 DEG in an X-ray diffraction pattern using Cu-K [alpha] as a radiation source.

Description

Technical Field

[0001] The present invention relates to a solid electrolyte and a solid electrolyte battery.

[0002] This application claims priority based on Japanese Patent Application No. 2023-019986, filed in Japan on February 13, 2023, and the contents are incorporated herein by reference. Background Art

[0003] In recent years, electronic technology has developed rapidly, enabling portable electronic devices to be smaller, lighter, thinner, and more multifunctional. Consequently, there is a strong desire for batteries, which serve as power sources for these electronic devices, to be smaller, lighter, thinner, and more reliable. Solid electrolyte batteries, which use solid electrolytes as their electrolyte, have attracted considerable attention. Known solid electrolytes include oxide-based solid electrolytes, sulfide-based solid electrolytes, complex hydride-based solid electrolytes, and halide-based solid electrolytes.

[0004] For example, Patent Document 1 discloses a solid electrolyte battery including a halide-based solid electrolyte. 3-2X M X In 1-Y M' Y L 6-Z L' Z In the formula, M and M' are metal elements, L and L' are halogen elements. In addition, X, Y and Z independently satisfy 0≤X<1.5, 0≤Y<1, and 0≤Z≤6.

[0005] In addition, for example, Patent Document 2 discloses a method of 6-3Z Y Z A halide-based solid electrolyte represented by X6, wherein Z satisfies 0<Z<2, and X is Cl or Br.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-244734

[0009] Patent Document 2: International Publication No. 2018 / 025582 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] It is generally believed that halide-based solid electrolytes have higher ion conductivity than oxide-based solid electrolytes, sulfide-based solid electrolytes, complex hydride-based solid electrolytes, etc. However, in order to achieve high discharge energy, an improvement in ion conductivity is required.

[0012] The present invention has been developed in view of the above-mentioned problems, and an object of the present invention is to provide a solid electrolyte and a solid electrolyte battery having excellent ion conductivity.

[0013] Technical means to solve the problem

[0014] In order to solve the above technical problems, the following technical means are provided.

[0015] (1) The solid electrolyte involved in the first embodiment contains lithium, zirconium, sulfur, oxygen and chlorine as main elements, and in the X-ray diffraction pattern of the solid electrolyte using Cu-Kα as the radiation source, peaks are confirmed at diffraction angles 2θ = 34.3°±0.5° and 2θ = 50.0°±0.5°.

[0016] (2) The solid electrolyte of the above-mentioned method (1) may also be such that the intensity Ia of the maximum peak confirmed within the range of the diffraction angle 2θ = 34.3°±0.5° and the intensity Ib of the maximum peak confirmed within the range of the diffraction angle 2θ = 50.0°±0.5° satisfy the relationship 1.020<Ia / Ib≤1.034.

[0017] (3) The solid electrolyte of the above-mentioned method (1) or (2) can also be Li a Zr(SO x ) b Cl4...(1) indicates that the above formula (1) satisfies 0.2≤a≤0.5, 0.1<b≤6.0, and 0<x≤4.0.

[0018] (4) A solid electrolyte battery according to a second aspect comprises a positive electrode, a negative electrode, and a solid electrolyte layer sandwiched between the positive electrode and the negative electrode. The solid electrolyte layer contains the solid electrolyte according to any one of the above aspects (1) to (3).

[0019] Effects of the Invention

[0020] The solid electrolyte of the above embodiment has excellent ion conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 These are the measurement results of the X-ray diffraction pattern of the solid electrolyte according to this embodiment.

[0022] Figure 2 It is a schematic cross-sectional view of the solid electrolyte battery of this embodiment. DETAILED DESCRIPTION

[0023] The present embodiment will be described in detail below with reference to the accompanying drawings as appropriate. The accompanying drawings used in the following description may, for convenience, enlarge portions of the features to facilitate understanding of the features of the present invention, and the dimensional ratios of the various components may differ from actual values. The materials, dimensions, and other figures illustrated in the following description are merely examples, and the present invention is not limited to these figures. The present invention may be implemented with appropriate modifications within the scope of the present invention.

[0024] In addition, "a±b" represents a numerical range of not less than (ab) and not more than (a+b).

[0025] Solid electrolyte

[0026] A solid electrolyte is a substance that allows ions to move when an external electric field is applied. High ion conductivity of a solid electrolyte facilitates ion transfer within the solid electrolyte battery, reducing internal resistance.

[0027] The solid electrolyte of this embodiment contains lithium, zirconium, sulfur, oxygen, and chlorine as main elements. Here, the main element is the main element confirmed in the composition analysis, excluding the elements mixed as impurities. The main element is the element clearly detected in the composition analysis. The composition analysis is performed by, for example, X-ray photoelectron spectroscopy (XPS). The main element is, for example, an element that bears the crystalline structure of the solid electrolyte.

[0028] The solid electrolyte may be composed solely of a compound containing lithium, zirconium, sulfur, oxygen, and chlorine as main elements, or may contain substances other than the compound. For example, the substance other than the compound may be a material derived from the raw material powder, such as Li2SO4 or ZrCl4.

[0029] The solid electrolyte may be in the form of a powder (particles) or a sintered body obtained by sintering the powder. Furthermore, the solid electrolyte may be a compact formed by compressing and shaping the powder; a compact formed by shaping a mixture of the powder and a binder; or a coating formed by applying a coating containing the powder, a binder, and a solvent, followed by heating to remove the solvent.

[0030] The solid electrolyte of this embodiment is, for example, Li a Zr(SO x ) b Cl4 ... ... A halide-based solid electrolyte represented by (1): Formula (1) satisfies 0.2≤a<0.5, 0.1<b≤6.0, and 0<x≤4.0.

[0031] In formula (1), Li is a lithium ion. a satisfies 0.2≤a≤0.5, preferably satisfies 0.3≤a≤0.5, and more preferably satisfies 0.4≤a≤0.5. Alternatively, a may be 0.2≤a<0.5. In the compound represented by formula (1), if a is within the above range, the content of Li contained in the compound is appropriate, and the ion conductivity of the solid electrolyte layer becomes high.

[0032] In formula (1), Zr is a zirconium ion and is an element that forms the skeleton of the solid electrolyte.

[0033] In formula (1), SO x is sulfate. x satisfies 0<x≤4.0. x is preferably x=4.0. SO x For example, SO3, SO4, SO5, SO 3 / 2 , SO2, SO 5 / 2 、SO 7 / 2 When the solid electrolyte contains sulfate, the potential window on the reduction side of the solid electrolyte becomes wider and is less likely to be reduced.

[0034] b satisfies 0.1<b≤6.0. The inclusion of sulfate broadens the potential window on the reduction side of the solid electrolyte, and therefore preferably satisfies 0.11≤b. Furthermore, to prevent a decrease in the ionic conductivity of the solid electrolyte due to an excessive sulfate content, b≤1.0 is preferred, b≤0.5 is more preferred, and b≤0.25 is even more preferred.

[0035] In formula (1), Cl represents a chloride ion. Cl ions have a large ionic radius per valence, and the inclusion of this element in the solid electrolyte facilitates the flow of lithium ions.

[0036] Solid electrolytes such as Li 0.5 Zr(SO4) 0.25 Cl4、Li 0.44 Zr(SO4) 0.22 Cl4、Li 0.4 Zr(SO4) 0.2 Cl4、Li 0.36 Zr(SO4) 0.18 Cl4、Li 0.33 Zr(SO4) 0.17 Cl4、Li 0.29 Zr(SO4) 0.14 Cl4、Li 0.22 Zr(SO4) 0.11 Cl4.

[0037] Figure 1 These are the results (XRD chart) of measuring the solid electrolyte of this embodiment by the X-ray diffraction (XRD) method. Figure 1The vertical axis represents intensity, and the horizontal axis represents 2θ. The measurement by X-ray diffraction was performed using a Cu-Kα ray source. Figure 1 The X-ray diffraction pattern shown includes background data of a polyimide tape used in the measurement to prevent contact with the atmosphere. Figure 1 In the figures, the measurement results of XRD patterns of the solid electrolytes of the present embodiment are shown as Examples 1 to 7, and the measurement results of XRD patterns of solid electrolytes of comparative examples that do not satisfy the prescribed requirements are shown as Comparative Examples 1 and 2.

[0038] like Figure 1 As shown, the solid electrolyte of this embodiment shows peaks at diffraction angles 2θ = 34.3° ± 0.5° and 2θ = 50.0° ± 0.5° in the X-ray diffraction pattern measured using a Cu-Kα radiation source. The solid electrolyte of this embodiment has crystallinity. In contrast, no peaks are observed at the aforementioned diffraction angles 2θ in the X-ray diffraction patterns of the solid electrolytes of Comparative Examples 1 and 2. A solid electrolyte having peaks at predetermined positions in an X-ray diffraction pattern has high ionic conductivity.

[0039] Here, the peak with the maximum intensity among the peaks confirmed within the range of diffraction angle 2θ = 34.3° ± 0.5° is called the first peak, and the peak with the maximum intensity among the peaks confirmed within the range of diffraction angle 2θ = 50.0° ± 0.5° is called the second peak. The intensity Ia of the first peak and the intensity Ib of the second peak preferably satisfy the relationship of 1.020 < Ia / Ib ≤ 1.034, more preferably satisfy the relationship of 1.025 ≤ Ia / Ib ≤ 1.034, further preferably satisfy the relationship of 1.027 < Ia / Ib ≤ 1.034, and particularly preferably satisfy 1.029 ≤ Ia / Ib ≤ 1.030. When this relationship is satisfied, the ion conductivity of the solid electrolyte becomes high.

[0040] (Method for producing solid electrolyte)

[0041] In the case where the solid electrolyte of this embodiment is in a powder state, for example, Li2SO4 and ZrCl4, which are raw materials, are mixed in a predetermined molar ratio and reacted. At this time, ZrCl4 is mixed in an excess amount relative to Li2SO4. Specifically, the molar ratio of ZrCl4 is set to be 4 times or more of the molar ratio of Li2SO4. By making the molar ratio of ZrCl4 higher than the molar ratio of Li2SO4, the mixing ratio of Li in the prepared solid electrolyte (the range of a) can be set to a predetermined range.

[0042] The solid electrolyte of this embodiment can be produced by treating a mixture mixed at a predetermined molar ratio using a mechanochemical method and then performing a heat treatment. By adjusting the mechanochemical reaction, a predetermined solid electrolyte with high ion conductivity can be obtained. If the mechanochemical reaction is insufficient, it becomes amorphous as shown in the XRD pattern shown in the comparative example, and sufficient ion conductivity is not found. When synthesized using a planetary ball mill, for example, the mechanochemical reaction can be controlled by the rotation speed, time, medium, and temperature.

[0043] In addition, when the solid electrolyte is obtained as a sintered body, the mixed raw material powder is formed into a specified shape and sintered in a vacuum or in an inert gas atmosphere. When the temperature is increased, ZrCl4 easily evaporates. Therefore, it is preferable to allow halogen gas to coexist in the atmosphere during sintering and to supplement the halogen. In addition, in order to prevent the evaporation of ZrCl4, a hot pressing method using a highly airtight mold can also be used for sintering. In this case, because the mold has a high airtightness, the evaporation of ZrCl4 caused by sintering can be suppressed. By sintering in this way, a solid electrolyte in the form of a sintered body composed of a compound having a specified composition is obtained.

[0044] In addition, in the manufacturing process of the solid electrolyte, heat treatment may be performed as needed. By performing heat treatment, the crystallite size of the solid electrolyte can be adjusted. As a heat treatment, for example, it is preferably performed at 130°C to 650°C in an argon atmosphere for 0.5 to 60 hours, and more preferably at 175°C to 600°C for 1 to 30 hours. By performing heat treatment at 150 to 550°C in an argon atmosphere for 5 to 24 hours, a solid electrolyte having a crystallite size of 5 nm to 500 nm is obtained.

[0045] As described above, the solid electrolyte of this embodiment has a specific peak confirmed in the X-ray diffraction pattern, indicating high ion conductivity. The reason why the ion conductivity increases when the solid electrolyte has a specific peak in the X-ray diffraction pattern is unclear, but it is believed that the confirmation of the peak is due to the formation of a specific crystal plane, which ensures a path for lithium ion conduction.

[0046] Solid electrolyte battery

[0047] Figure 2 1 is a schematic cross-sectional view of a solid electrolyte battery 100 according to this embodiment. Figure 2 The solid electrolyte battery 100 shown includes a power generation element 40 and an exterior body 50. The exterior body 50 surrounds the power generation element 40. The power generation element 40 is connected to the outside via a pair of terminals 60 and 62 connected to the power generation element 40. Figure 2A laminated battery is shown in FIG. 1 , but a wound battery may also be used. The solid electrolyte battery 100 is used for, for example, a laminate battery, a rectangular battery, a cylindrical battery, a coin battery, a button battery, and the like.

[0048] <Power generation element>

[0049] The power generation element 40 includes a solid electrolyte layer 10, a positive electrode 20, and a negative electrode 30. The power generation element 40 is charged or discharged by transferring ions between the positive electrode 20 and the negative electrode 30 via the solid electrolyte layer 10 and transferring electrons via an external circuit.

[0050] (Solid electrolyte layer)

[0051] The solid electrolyte layer 10 is sandwiched between the positive electrode 20 and the negative electrode 30. The solid electrolyte layer 10 includes a solid electrolyte that can move ions by an externally applied voltage. For example, the solid electrolyte conducts lithium ions and blocks the movement of electrons.

[0052] The solid electrolyte layer 10 includes, for example, the above-mentioned solid electrolyte. The solid electrolyte layer 10 may also include a binder in addition to the above-mentioned solid electrolyte. The binder described below can be used.

[0053] (positive electrode)

[0054] like Figure 2 As shown, the positive electrode 20 includes a plate-shaped (foil-shaped) positive electrode current collector 22 and a positive electrode mixture layer 24. The positive electrode mixture layer 24 is in contact with at least one surface of the positive electrode current collector 22.

[0055] The positive electrode current collector 22 can be made of any electronically conductive material that is resistant to oxidation during charging and does not corrode easily. Examples of the positive electrode current collector 22 include metals such as aluminum, stainless steel, nickel, and titanium, as well as conductive resins. The positive electrode current collector 22 can also be in the form of powder, foil, punched sheets, or expanded sheets.

[0056] The positive electrode mixture layer 24 contains a positive electrode active material and, if necessary, a solid electrolyte, a binder, and a conductive additive.

[0057] The positive electrode active material is not particularly limited as long as it can reversibly absorb and release, insert and deintercalate (intercalation and deintercalation) lithium ions, and the positive electrode active material used in known solid electrolyte batteries can be used. As the positive electrode active material, for example, metal oxides containing lithium, metal phosphates containing lithium, etc. can be mentioned.

[0058] Lithium-containing metal oxides include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese spinel (LiMn2O4), and lithium nickel oxide (LiNiO2). x Co y Mnz O2 (x + y + z = 1) represented by a composite metal oxide, lithium vanadium compounds (LiVOPO4, Li3V2 (PO4) 3), olivine-type LiMPO4 (wherein M represents at least one selected from Co, Ni, Mn, Fe), lithium titanate (Li4Ti5O 12 )wait.

[0059] In addition, the positive electrode active material may not contain lithium. Examples of such positive electrode active materials include metal oxides that do not contain lithium (MnO2, V2O5, etc.), metal sulfides that do not contain lithium (MoS2, etc.), and fluorides that do not contain lithium (FeF3, VF3, etc.). When using a positive electrode active material that does not contain lithium, the negative electrode is pre-doped with lithium ions, or a negative electrode containing lithium ions is used.

[0060] The solid electrolyte contained in the positive electrode 20 is, for example, the solid electrolyte described above. The solid electrolyte contained in the positive electrode 20 may be a halide-based solid electrolyte other than the solid electrolyte described above.

[0061] The content of the solid electrolyte in the positive electrode mixture layer 24 is not particularly limited, but is preferably 1% to 50% by mass, more preferably 5% to 30% by mass, based on the total mass of the positive electrode active material, solid electrolyte, conductive additive, and binder.

[0062] The binder binds the positive electrode active material, solid electrolyte, and conductive additive to each other within the positive electrode mixture layer 24 and firmly bonds the positive electrode mixture layer 24 to the positive electrode current collector 22. The positive electrode mixture layer 24 preferably contains a binder. The binder preferably has antioxidant properties and good adhesive properties.

[0063] Examples of the binder used in the positive electrode mixture layer 24 include polyvinylidene fluoride (PVDF) or its copolymers, polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyamideimide (PAI), polybenzimidazole (PBI), polyethersulfone (PES), polyacrylic acid (PA) and its copolymers, metal ion crosslinked products of polyacrylic acid (PA) and its copolymers, maleic anhydride grafted polypropylene (PP), maleic anhydride grafted polyethylene (PE), or mixtures thereof. Among these, PVDF is particularly preferably used as the binder.

[0064] The binder content in the positive electrode mixture layer 24 is not particularly limited, but is preferably 0.3% to 10% by mass, more preferably 0.3% to 5% by mass, based on the total mass of the positive electrode active material, solid electrolyte, conductive additive, and binder. If the binder content is too low, sufficient bonding strength may not be achieved in the positive electrode 20. Conversely, if the binder content is too high, conventional binders are electrochemically inert and do not contribute to discharge capacity, making it difficult to achieve sufficient volumetric or gravimetric energy density.

[0065] The conductive additive improves the electron conductivity of the positive electrode mixture layer 24. Known conductive additives can be used. Examples of conductive additives include carbon materials such as carbon black, graphite, carbon nanotubes, and graphene; metals such as aluminum, copper, nickel, stainless steel, iron, and amorphous metals; conductive oxides such as ITO; or mixtures thereof. The conductive additive can also be in the form of powder or fiber.

[0066] The content of the conductive additive in the positive electrode mixture layer 24 is not particularly limited. When a conductive additive is added, the mass ratio of the conductive additive is preferably 0.5% to 20% by mass, and more preferably 1% to 5% by mass, based on the total mass of the positive electrode active material, solid electrolyte, conductive additive, and binder.

[0067] (negative electrode)

[0068] like Figure 2 As shown, the negative electrode 30 includes a negative electrode current collector 32 and a negative electrode mixture layer 34 . The negative electrode mixture layer 34 is in contact with the negative electrode current collector 32 .

[0069] The negative electrode current collector 32 only needs to have electron conductivity. The negative electrode current collector 32 can be made of a metal such as copper, aluminum, nickel, stainless steel, or iron, or a conductive resin. The negative electrode current collector 32 can also be in the form of powder, foil, punched sheet, or expanded material.

[0070] The negative electrode mixture layer 34 contains a negative electrode active material and, if necessary, a solid electrolyte, a binder, and a conductive additive.

[0071] The negative electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions, and insert and extract lithium ions. A known negative electrode active material used in solid electrolyte batteries can be used as the negative electrode active material.

[0072] The negative electrode active material is a carbon material such as natural graphite, artificial graphite, mesocarbon microbeads, mesocarbon fibers (MCF), coke, glassy carbon, organic compound calcined products, Si, SiO x , Sn, aluminum and other metals that can be combined with lithium, their alloys, composite materials of these metals and carbon materials, lithium titanate (Li4Ti5O 12), oxides such as SnO2, metallic lithium, etc. The negative electrode active material is preferably natural graphite.

[0073] The solid electrolyte contained in the negative electrode 30 is, for example, the solid electrolyte described above. The solid electrolyte contained in the negative electrode 30 may be a halide-based solid electrolyte other than the solid electrolyte described above.

[0074] The binder and the conductive additive contained in the negative electrode 30 are the same as those contained in the positive electrode 20 .

[0075] <Exterior body>

[0076] The outer casing 50 houses the power generation element 40. The outer casing 50 prevents moisture and the like from entering from the outside. Figure 2 As shown, the exterior body 50 includes a metal foil 52 and a resin layer 54 laminated on each surface of the metal foil 52. The exterior body 50 is a metal laminate film in which the metal foil 52 is coated with the resin layer 54 from both sides.

[0077] The metal foil 52 is, for example, aluminum foil or stainless steel foil. The resin layer 54 can be made of, for example, a resin film such as polypropylene. The material constituting the resin layer 54 may be different on the inside and outside. For example, the outside material may be a high-melting-point polymer such as polyethylene terephthalate (PET) or polyamide (PA), while the inside material may be polyethylene (PE) or polypropylene (PP).

[0078] <Terminal>

[0079] Terminals 60 and 62 are connected to the negative electrode 30 and the positive electrode 20, respectively. Terminal 62 connected to the positive electrode 20 is the positive electrode terminal, and terminal 60 connected to the negative electrode 30 is the negative electrode terminal. Terminals 60 and 62 provide electrical connections to the outside world. They are formed from conductive materials such as aluminum, nickel, and copper. Connections can be made by welding or screwing. To prevent short circuits, terminals 60 and 62 are preferably protected by insulating tape.

[0080] [Method for manufacturing solid electrolyte battery]

[0081] The positive electrode is produced by applying a paste containing a positive electrode active material onto the positive electrode current collector 22 and drying it to form the positive electrode mixture layer 24. The above-mentioned solid electrolyte may be added to the paste containing the positive electrode active material.

[0082] Next, the negative electrode 30 is prepared. The negative electrode is produced by applying a paste containing a negative electrode active material onto the negative electrode current collector 32 and drying it to form a negative electrode mixture layer 34. The above-mentioned solid electrolyte may be added to the paste containing the negative electrode active material.

[0083] The power generation element 40 can be produced using a powder molding method, for example. A guide having a hole is placed on the positive electrode 20, and the guide is filled with a solid electrolyte. The surface of the solid electrolyte is then flattened, and the negative electrode 30 is stacked on top of the solid electrolyte. This sandwiches the solid electrolyte between the positive electrode 20 and the negative electrode 30. The solid electrolyte is then press-formed by applying pressure to the positive electrode 20 and the negative electrode 30. This press-forming process produces a laminated body in which the positive electrode 20, the solid electrolyte layer 10, and the negative electrode 30 are stacked in this order.

[0084] Next, external terminals are welded to the positive electrode collector 22 of the positive electrode 20 and the negative electrode collector 32 of the negative electrode 30, respectively, forming the stack, by a known method, thereby electrically connecting the positive electrode collector 22 or the negative electrode collector 32 to the external terminals. The stack connected to the external terminals is then housed in the outer casing 50, and the opening of the outer casing 50 is heat-sealed to seal the stack. Through the above steps, the solid electrolyte battery 100 of this embodiment is obtained.

[0085] Since the solid electrolyte battery 100 of the present embodiment includes the above-described solid electrolyte, the conduction of Li ions is smooth and the internal resistance is low.

[0086] The embodiments of the present invention have been described in detail above with reference to the drawings. However, each structure in each embodiment and their combination are merely examples, and additions, omissions, substitutions, and other modifications of the structure are possible without departing from the scope of the present invention.

[0087] Example

[0088] "Example 1"

[0089] (Preparation of Solid Electrolyte)

[0090] In a glove box with a dew point of about -75°C, raw material powders of lithium sulfate (Li2SO4) and zirconium chloride (ZrCl4) are weighed in a molar ratio of 1:4. Next, the raw material powder is added to a zirconia sealed container for a planetary ball mill in which 5mmΦ zirconia balls are pre-placed. Next, the sealed container is covered, the lid is screwed to the container body, and then the lid and the container are sealed with a polyimide tape. The polyimide tape has the effect of blocking moisture. Next, the zirconia sealed container is placed in the planetary ball mill. The rotation speed is set to 450rpm, the revolution speed is set to 450rpm, the rotation direction of the rotation and the rotation direction of the revolution are set to opposite directions, and the mechanochemical reaction is carried out for 48 hours, and then each container is placed in a constant temperature bath at 120°C for 1 hour for heat treatment, thereby generating a solid electrolyte (Li 0.5 Zr(SO4) 0.25 Cl4).

[0091] The planetary ball mill is set up in a normal atmosphere (air). The zirconia sealed container used in the planetary ball mill is screwed in and further sealed with polyimide tape. When the zirconia sealed container is placed in the planetary ball mill, it is believed that even in a normal atmosphere, moisture is unlikely to enter the zirconia sealed container from the air because the zirconia sealed container is firmly pressed and fixed.

[0092] [XRD measurement]

[0093] In a glove box with a dew point of about -70°C where argon gas is circulated, the prepared solid electrolyte is filled into a holder for XRD measurement. Then, a polyimide tape (a tape dried in vacuum at 70°C for 16 hours) is pasted to cover the filling surface to seal it against moisture, and an XRD measurement sample is prepared. Next, it is taken out in the atmosphere and an X-ray diffractometer (X'PertPro manufactured by PANalytical) is used to measure the XRD pattern. The X-ray source uses Cu-Kα rays.

[0094] The X-ray diffraction pattern of the produced solid electrolyte had peaks at diffraction angles 2θ=34.3°±0.5° and 2θ=50.0°±0.5°.

[0095] [Measurement of ionic conductivity]

[0096] Next, in a glove box with a dew point of approximately -70°C and circulating argon gas, the obtained solid electrolyte powder was filled into a press-molding die and press-molded using a weight of approximately 30 kN to produce a cell for measuring ion conductivity.

[0097] The die for press molding was composed of a PEEK (polyetheretherketone) cylinder with a diameter of 10 mm, and an upper punch and a lower punch made of SKD11 material with a diameter of 9.99 mm.

[0098] Next, prepare a stainless steel disc and a Teflon (registered trademark) disc with four screw holes, each 50 mm in diameter and 5 mm thick. Place the press mold as follows. Load the disc in the order of stainless steel disc / Teflon (registered trademark) disc / press mold / Teflon (registered trademark) disc / stainless steel disc. Tighten the screws at all four locations with a torque of approximately 3 N·m. Furthermore, insert screws into the screw holes on the sides of the upper and lower punches to create external connection terminals.

[0099] The external connection terminals were connected to a potentiostat equipped with a frequency response analyzer (VersaSTAT3, manufactured by Princeton Applied Research), and the ionic conductivity was measured using the impedance measurement method. Measurements were performed in the measurement frequency range of 1 MHz to 0.1 Hz, with an amplitude of 10 mV and a temperature of 25°C. The ionic conductivity of the solid electrolyte of Example 1 was 0.39 mS / cm.

[0100] "Examples 2 to 7"

[0101] Examples 2 to 7 differ from Example 1 in that the materials and molar ratios of the raw material powders were changed. The properties of the solid electrolytes were measured in Examples 2 to 7 in the same manner as in Example 1. The molar ratios of lithium sulfate (Li2SO4) and zirconium chloride (ZrCl4) used in the production of Examples 2 to 7 are shown below.

[0102] Example 2 Li2SO4:ZrCl4=1:4.5

[0103] Example 3 Li2SO4:ZrCl4=1:5.0

[0104] Example 4 Li2SO4:ZrCl4=1:5.5

[0105] Example 5 Li2SO4:ZrCl4=1:6.0

[0106] Example 6 Li2SO4:ZrCl4=1:7.0

[0107] Example 7 Li2SO4:ZrCl4=1:9.0

[0108] Furthermore, XRD and ion conductivity measurements were performed on the solid electrolytes prepared in Examples 2 to 7 in the same manner as in Example 1. In all of the solid electrolytes in Examples 2 to 7, peaks were observed at diffraction angles 2θ = 34.3° ± 0.5° and 2θ = 50.0° ± 0.5° in the X-ray diffraction patterns.

[0109] The compositions and ion conductivities of the solid electrolytes prepared in Examples 2 to 7 are shown below.

[0110] Example 2Li 0.44 Zr(SO4) 0.22 Cl4 0.27mS / cm

[0111] Example 3Li 0.4 Zr(SO4) 0.2 Cl4 0.17mS / cm

[0112] Example 4Li 0.36 Zr(SO4)0.18 Cl4 0.10mS / cm

[0113] Example 5Li 0.33 Zr(SO4) 0.17 Cl4 0.02mS / cm

[0114] Example 6Li 0.29 Zr(SO4) 0.14 Cl4 0.07mS / cm

[0115] Example 7Li 0.22 Zr(SO4) 0.11 Cl4 0.01mS / cm

[0116] "Comparative Example 1"

[0117] Comparative Example 1 differs from Example 1 in that the rotation speed was set to 250 rpm and the revolution speed was set to 250 rpm during production, and no subsequent heat treatment was performed. The composition of the solid electrolyte in Comparative Example 1 was the same as that in Example 1.

[0118] The solid electrolyte of Comparative Example 1 was also subjected to XRD and ionic conductivity measurements in the same manner as in Example 1. In the X-ray diffraction pattern of the solid electrolyte of Comparative Example 1, no peaks were observed at diffraction angles 2θ = 34.3° ± 0.5° and 2θ = 50.0° ± 0.5°. Furthermore, the ionic conductivity of the solid electrolyte of Comparative Example 1 was 0.003 mS / cm.

[0119] "Comparative Example 2"

[0120] Comparative Example 2 differs from Example 2 in that the rotation speed was set to 250 rpm and the revolution speed was set to 250 rpm during production, and no subsequent heat treatment was performed. The composition of the solid electrolyte in Comparative Example 2 was the same as that in Example 2.

[0121] The solid electrolyte of Comparative Example 2 was also subjected to XRD and ionic conductivity measurements in the same manner as in Example 1. In the X-ray diffraction pattern of the solid electrolyte of Comparative Example 2, no peaks were observed at diffraction angles 2θ = 34.3° ± 0.5° and 2θ = 50.0° ± 0.5°. Furthermore, the ionic conductivity of the solid electrolyte of Comparative Example 2 was 0.002 mS / cm.

[0122] The results of Examples 1 to 7 and Comparative Examples 1 and 2 are summarized in the following Table 1. In Table 1, the first peak is a peak within the range of a diffraction angle 2θ = 34.3° ± 0.5°, the second peak is a peak within the range of a diffraction angle 2θ = 50.0° ± 0.5°, and Ia / Ib is the intensity ratio of the intensity Ia of the maximum peak confirmed within the range of a diffraction angle 2θ = 34.3° ± 0.5° to the intensity Ib of the maximum peak confirmed within the range of a diffraction angle 2θ = 50.0° ± 0.5°.

[0123] [Table 1]

[0124]

[0125]

[0126] The solid electrolytes of Examples 1 to 7, in which the first and second peaks were confirmed, had higher ion conductivities than the solid electrolytes of Comparative Examples 1 and 2, in which the first and second peaks were not confirmed.

[0127] Industrial applicability

[0128] The solid electrolyte of this embodiment has excellent ion conductivity and is suitable for solid electrolyte batteries.

[0129] Explanation of symbols

[0130] 10…solid electrolyte layer, 20…positive electrode, 22…positive electrode current collector, 24…positive electrode mixture layer, 30…negative electrode, 32…negative electrode current collector, 34…negative electrode mixture layer, 40…power generating element, 50…external body, 52…metal foil, 54…resin layer, 60, 62…terminals, 100…solid electrolyte battery.

Claims

1. A solid electrolyte, wherein: Contains lithium, zirconium, sulfur, oxygen and chlorine as main elements, In the X-ray diffraction pattern using Cu—Kα as a radiation source, peaks were confirmed at diffraction angles 2θ=34.3°±0.5° and 2θ=50.0°±0.5°.

2. The solid electrolyte according to claim 1, wherein The intensity Ia of the maximum peak confirmed within the range of the diffraction angle 2θ = 34.3°±0.5° and the intensity Ib of the maximum peak confirmed within the range of the diffraction angle 2θ = 50.0°±0.5° satisfy the relationship 1.020<Ia / Ib≤1.

034.

3. The solid electrolyte according to claim 1, wherein The solid electrolyte is represented by the following formula (1): Lee a Zr(SO x ) b Cl4……(1), The formula (1) satisfies 0.2≤a≤0.5, 0.1<b≤6.0, and 0<x≤4.

0.

4. A solid electrolyte battery, wherein: A positive electrode, a negative electrode, and a solid electrolyte layer sandwiched between the positive electrode and the negative electrode. The solid electrolyte layer includes the solid electrolyte according to claim 1 .

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