Method for producing lithium-containing oxide and solid electrolyte

Abstract

A lithium-containing oxide having a garnet structure of cubic crystal, in which 19 The solid was measured under the condition that the resonance frequency of the F nucleus was 564 MHz 19 In the F-NMR spectrum, the chemical shift of the polytetrafluoroethylene was set to -122 ppm, and at least one peak was observed in the range of the chemical shift of -100 to 50 ppm.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing lithium oxide and solid electrolyte. Background Technology

[0002] Solid electrolytes, such as those used as ion-conducting materials, have been actively studied in various fields in recent years. In particular, Li7La3Zr2O... 12 Lithium oxides such as LLZO have attracted particular attention because they are useful as solid electrolyte layers in lithium-ion batteries (Patent Documents 1-7, Non-Patent Documents 1-4). All-solid-state batteries, which replace conventional liquid electrolytes with solid electrolytes, have many advantages: high capacity and rapid charge / discharge can be achieved because no solvent is used; they are flame-retardant and do not decompose like solvents, thus ensuring safety; and they have high-temperature durability, eliminating the need for cooling equipment and improving battery pack energy density.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2015 / 065879

[0006] Patent Document 2: Japanese Patent Application Publication No. 2020-087770

[0007] Patent Document 3: International Publication No. 2015 / 079509

[0008] Patent Document 4: Description of Chinese Patent Application Publication No. 102780028

[0009] Patent Document 5: Chinese Patent Application Publication No. 102780031

[0010] Patent Document 6: Description of Chinese Patent Application Publication No. 102867987

[0011] Patent Document 7: Description of Chinese Patent Application Publication No. 102867988

[0012] Non-patent literature

[0013] Non-patent literature 1: LIU Cai et al., “High Ion Conductivity in Garnet-type F-doped Li7La3Zr2O12”, Journal of Inorganic Materials, Vol.30No.9, p995-1000, Sep., 2015.

[0014] Non-patent document 2: Yao Lu et al., "Effects of Fluorine Doping on Structuraland Electrochemical Properties of Li6.25Ga0.25La3Zr2O12 as Electrolytes for Solid-State Lithium Batteries", ACS Appl.Mater.Interfaces 2019, 11, p2042-2049.

[0015] Non-patent literature 3: Stephen R. Yeandel et al., “Structure and Lithium-Ion Dynamics in Fluoride-Doped Cubic Li7La3Zr2O12(LLZO)Garnet for Li Solid-State Battery Applications”, J. Phys. Chem. C 2018, 122, pp. 27811-27819.

[0016] Non-patent document 4: Qiuying Li et al., "Investigation the electrochemical properties of LiCl-LiBr-LiF-doped Li7La3Zr2O12 electrolyte for lithiumthermal batteries", Ionics (2020), 26, p3875-3882. Summary of the Invention

[0017] The problem that the invention aims to solve

[0018] However, there is still room for improvement in the ionic conductivity of previous solid electrolytes.

[0019] This disclosure is made in view of the above circumstances, with the aim of providing a lithium-containing oxide with excellent ionic conductivity. Furthermore, the aim of this disclosure is to provide a method for manufacturing a solid electrolyte with excellent ionic conductivity.

[0020] Methods for solving problems

[0021] The lithium-containing oxide disclosed herein has a cubic garnet structure, in 19 The solid was measured under the condition that the resonance frequency of the F nucleus was 564 MHz. 19During F-NMR spectroscopy, the chemical shift of polytetrafluoroethylene was set to -122 ppm, and at least one peak was observed within the chemical shift range of -100 to 50 ppm. The lithium-containing oxide is preferably: 6 The solid was measured under the condition that the resonance frequency of the Li nucleus was 44.1 MHz. 6 When performing Li-NMR spectroscopy, the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm, and at least one peak was observed within the chemical shift range of -5 to 15 ppm.

[0022] The lithium-containing oxide disclosed herein can also be: containing fluorine atoms, having a cubic garnet structure, in 6 The solid was measured under the condition that the resonance frequency of the Li nucleus was 44.1 MHz. 6 In Li-NMR spectroscopy, the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm, and at least two peaks were observed within the chemical shift range of -5 to 15 ppm. The lithium-containing oxide is preferably: 19 The solid was measured under the condition that the resonance frequency of the F nucleus was 564 MHz. 19 During F-NMR spectroscopy, the chemical shift of polytetrafluoroethylene was set to -122 ppm, and at least one peak was observed within the chemical shift range of -100 to 50 ppm.

[0023] The preferred lithium-containing oxide disclosed herein is: in 6 The solid was measured under the condition that the resonance frequency of the Li nucleus was 44.1 MHz. 6 When performing Li-NMR spectroscopy, the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm. At least two peaks with a half-maximum amplitude of less than 2 ppm were observed within the chemical shift range of -5 to 15 ppm.

[0024] The preferred lithium-containing oxide disclosed herein is: in 6 The solid was measured under the condition that the resonance frequency of the Li nucleus was 44.1 MHz. 6 During Li-NMR spectroscopy, the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm. Two peaks were observed within the chemical shift range of -5 to 15 ppm. The ratio of the area intensity of the peak with the smaller area intensity to the sum of the area intensities of the two peaks was greater than 0.3%.

[0025] The preferred lithium-containing oxide disclosed herein is one in which, with respect to the ratio of the number of atoms as determined by ICP emission spectroscopy, when La is set to 3, Li is 6 to 12 and Zr is 1 to 3.

[0026] The lithium oxide disclosed herein is preferably such that, in the powder X-ray diffraction pattern, the intensity of the peak at 28.5–29.0° is 0.5 or less relative to the intensity of the peak at 16.0–17.0°.

[0027] The sintered body disclosed herein comprises the aforementioned lithium oxide.

[0028] The electrolyte composition disclosed herein comprises the above-mentioned lithium oxide.

[0029] The method for manufacturing the solid electrolyte disclosed herein includes a step of performing a topotactic reaction (also known as a localized regulation reaction or localized chemical reaction) on lithium oxide.

[0030] Preferably, the above-mentioned topological chemical reaction is carried out at a temperature below 900°C.

[0031] Preferably, an anion is introduced into a lithium oxide through the above-mentioned topological chemical reaction, the anion containing at least one element selected from the group consisting of halogens, chalcogens, nitrogen, and phosphorus.

[0032] Preferably, in the above-mentioned topological chemical reaction, the lithium oxide is reacted with the metal fluoride.

[0033] Preferably, the metal fluoride is at least one of GaF3, MgF2, NiF2 and ZnF2.

[0034] Preferably, the solid electrolyte described above has a garnet-type structure.

[0035] Invention Effects

[0036] According to this disclosure, a lithium-containing oxide with excellent ionic conductivity can be provided. Furthermore, according to this disclosure, a method for manufacturing a solid electrolyte with excellent ionic conductivity can also be provided. Detailed Implementation

[0037] <Lithium oxides>

[0038] The lithium oxide of this embodiment contains fluorine atoms, has a cubic garnet structure, and satisfies at least one of the following conditions (1) and (2).

[0039] Condition (1): In 19 The solid was measured under the condition that the resonance frequency of the F nucleus was 564 MHz. 19 During F-NMR spectroscopy, the chemical shift of polytetrafluoroethylene was set to -122 ppm, and at least one peak was observed within the chemical shift range of -100 to 50 ppm.

[0040] Condition (2): In 6The solid was measured under the condition that the resonance frequency of the Li nucleus was 44.1 MHz. 6 When performing Li-NMR spectroscopy, the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm, and at least two peaks were observed within the chemical shift range of -5 to 15 ppm.

[0041] Furthermore, in condition (1), the peak of polytetrafluoroethylene, which serves as the benchmark for chemical shift, is the peak of fluorine atoms belonging to the -CF2-CF2- unit.

[0042] Such lithium oxides exhibit excellent ionic conductivity (lithium-ion conductivity). It should be noted that the peaks mentioned in conditions (1) and (2) are NMR resonance peaks, and therefore do not contain rotational sidebands. It should also be noted that, below, solid... 19 Chemical shift in F-NMR spectra refers to... 19 The chemical shift of polytetrafluoroethylene was determined under the condition that the resonance frequency of the F nucleus was 564 MHz, with the chemical shift set to -122 ppm. Furthermore, solid... 6 Chemical shift in Li-NMR spectroscopy refers to... 6 The chemical shift was determined under the condition that the resonance frequency of the Li core is 44.1 MHz, and the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm. Furthermore, as a solid... 19 F-NMR spectroscopy and solid-state 6 Other measurement conditions for Li-NMR spectroscopy, such as those described in the examples, can be listed.

[0043] The reasons for the excellent lithium-ion conductivity of the aforementioned lithium oxide-containing materials are not necessarily clear, but the inventors consider the reasons as follows.

[0044] First, regarding condition (1), in the case of conventional lithium oxides containing fluorine and having a garnet structure (e.g., Comparative Examples 2 and 3), in solid form... 19 No peaks were observed in the F-NMR spectrum within the chemical shift range of -100 to 50 ppm. Therefore, it can be said that at least a portion of the fluorine contained in the lithium oxide of this embodiment is placed in an environment different from that of fluorine in conventional lithium oxides containing fluorine. Consequently, it is believed that this locally affects the crystal structure and charge state of the lithium oxide, and thus influences the distribution or mobility of lithium ions in the compound.

[0045] Furthermore, regarding condition (2), in the case of conventional lithium oxides (e.g., Comparative Example 3), in solid form... 6In the Li-NMR spectrum, only a single peak was observed in the range of -5 to 15 ppm chemical shift. Therefore, it can be said that the lithium-containing oxides satisfying condition (2) contain lithium ions placed in an environment different from that of conventional lithium-containing oxides. It is believed that the lithium ions, due to their high mobility, easily move when a voltage is applied, which contributes to the improvement of lithium-ion conductivity.

[0046] When lithium oxides satisfying condition (1) or (2) have a cubic crystal system, an increase in lithium-ion conductivity can be observed. On the other hand, even if condition (1) or (2) is satisfied, no increase in lithium-ion conductivity can be observed in crystal systems other than cubic, such as tetragonal crystals.

[0047] Regarding condition (1), lithium oxides are used in the determination of solids 19 During F-NMR spectroscopy, it is preferable to observe at least one peak in the range of -75 to 25 ppm, more preferably in the range of -50 to 0 ppm, and even more preferably in the range of -30 to -10 ppm. The number of peaks in these chemical shift ranges is preferably 5 or less, more preferably 3 or less, even more preferably 1 or 2, and particularly preferably 1.

[0048] Regarding condition (2), lithium oxides are used in the determination of solids 6 In Li-NMR spectroscopy, it is preferable to observe at least two peaks in the range of -3 to 12 ppm, more preferably in the range of 0 to 10 ppm, and even more preferably in the range of 1.35 to 5 ppm. The number of peaks within these chemical shift ranges is preferably 5 or less, more preferably 3 or less, and even more preferably 2. Furthermore, within these chemical shift ranges, at least two peaks with a half-maximum amplitude of 2 ppm or less can also be observed.

[0049] When the peak with the largest area intensity among the peaks observed within the chemical shift range of condition (2) is designated as the first peak, the ratio of the total area intensity of the peaks other than the first peak to the total area intensity of the peaks observed within the chemical shift range of condition (2) is preferably 0.3% or more, more preferably 0.5 to 20%, further preferably 0.7 to 15%, and particularly preferably 1.0 to 12%. When only two peaks are observed within the chemical shift range of condition (2), if the peak with the smaller area intensity is designated as the second peak, the ratio of the area intensity of the second peak to the total area intensity of the first and second peaks is preferably within the range described above. The first peak is preferably a peak originating from lithium occupying 48g of lithium sites. Regarding condition (2), at least one of the observed peaks is preferably observed in the range of -2 to 2.3 ppm, more preferably in the range of 0 to 2 ppm, and further preferably in the range of 1.35 to 2 ppm. Furthermore, regarding condition (2), at least one of the observed peaks preferably has a half-value amplitude of less than 1.3 ppm, more preferably less than 1 ppm. The second peak is preferably observed in the range of -2 to 2.3 ppm and has a half-value amplitude of less than 1.3 ppm, more preferably observed in the range of 1.35 to 2 ppm and has a half-value amplitude of less than 1 ppm.

[0050] Even if only one of conditions (1) and (2) is satisfied, the effects of this disclosure are achieved, but it is more preferable to satisfy both conditions (1) and (2). When condition (1) is satisfied, lithium oxide in solid form... 6 In Li-NMR spectroscopy, when the chemical shift of lithium fluoride is set to 0 ppm, it is preferable to observe at least one peak within the chemical shift range of -5 to 15 ppm, more preferably within the range of -3 to 12 ppm, and even more preferably within the range of 0 to 10 ppm. The number of peaks within these chemical shift ranges is preferably 5 or less, more preferably 3 or less, further preferably 1 or 2, and particularly preferably 1. Furthermore, it is preferable that the peaks within these chemical shift ranges include peaks originating from lithium occupying 48 g of lithium sites.

[0051] The lithium oxide used in this embodiment is not particularly limited, but is preferably a lithium oxide containing La and Zr. Regarding the atomic ratio of Li, La, and Zr in such a lithium oxide, when La is set to 3, it is preferably 5 to 12 Li and 1 to 3 Zr, more preferably 6 to 8 Li and 1 to 2.5 Zr. The atomic ratio of Li, La, and Zr in the lithium oxide can be determined, for example, by ICP emission spectroscopy analysis.

[0052] The lithium oxide of this embodiment may also contain La and Zr, and further contain metal elements other than Li, La, and Zr. Examples of such metal elements include alkaline earth metals such as Mg, Ca, and Sr, as well as metal elements such as Ga, Ta, Nb, and Y. When La is set to 3, the atomic ratio of alkaline earth metals in the lithium oxide may be 0.2 or less, or 0.01 to 0.15. When La is set to 3, the atomic ratio of Ta in the lithium oxide may be 0.01 to 1 or less, or 0.05 to 0.6. When La is set to 3, the atomic ratio of Ga in the lithium oxide may be 0.01 to 1 or less, or 0.1 to 0.6. The lithium oxide of this embodiment may also contain halogen elements other than fluorine, but the content of halogen atoms other than fluorine relative to 100 mol% of fluorine atoms may be 150 mol% or less, 100 mol% or less, or 50 mol% or less.

[0053] The ratio of the number of atoms in lithium oxides can be determined, for example, by ICP (inductively coupled plasma) emission spectroscopy analysis.

[0054] The cubic crystal structure of the lithium-containing oxide in this embodiment can be confirmed, for example, by powder X-ray diffraction. Furthermore, when the lithium-containing oxide of this embodiment is subjected to powder X-ray diffraction using CuKα rays, the intensity of the peak at 28.5–29.0° in the powder X-ray diffraction pattern is preferably 0.5 or less, and can be 0.3 or less, 0.15 or less, or 0.1 or less. Here, the peak intensity refers to the maximum value of each peak in the diffraction pattern. The peak at 28.5–29.0° is considered to be La₂Zr₂O₇ and compounds with similar chemical structures. Such compounds are impurities that do not contribute to the conductivity of lithium ions, and their content is preferably low, more preferably undetectable within the detection limit.

[0055] The lithium-containing oxide of this embodiment is suitable as an ion-conducting material due to its excellent lithium-ion conductivity, and can be used, for example, as a solid electrolyte in lithium-ion batteries.

[0056] The shape of the lithium oxide in this embodiment is not particularly limited; it can be a powder or granules. Furthermore, it can be a sintered body obtained by sintering the powder, or a composite body obtained by bonding the powder with a binder. Additionally, it can be mixed with other components to form a composition for use. Examples of such compositions include electrolyte compositions used as solid electrolytes in lithium-ion batteries. The electrolyte composition may also include ionicly conductive materials, ionic liquids, polymer materials, etc., as components other than the lithium oxide.

[0057] Lithium-ion batteries

[0058] The lithium oxide contained in this embodiment is useful as a solid electrolyte in lithium-ion batteries (all-solid-state batteries). Lithium-ion batteries can be either primary or secondary batteries. When using the lithium oxide contained in this embodiment as a solid electrolyte, since no solvent is required, the solid electrolyte has a wide potential window and is not limited to materials known conventionally used as positive or negative electrodes in lithium-ion batteries that use electrolytes; electrodes with higher potentials can also be used.

[0059] The positive electrode of a lithium-ion battery is not particularly limited and can be any positive electrode containing a positive electrode active material and, if necessary, conductive additives, binders, etc. The positive electrode can be a positive electrode on which a layer containing these materials is formed on the current collector. Examples of positive electrode active materials include lithium (Li) and at least one transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu. Examples of such lithium composite metal oxides include LiCoO2, LiNiO2, LiMn2O4, Li2Mn2O3, and LiNiO2. x Mn y Co 1-x-y O2[0 <x+y<1])、LiNi x Co y Al 1-x-y O2[0 <x+y<1])、LiCr 0.5 Mn 0.5 O2, LiFePO4, Li2FeP2O7, LiMnPO4, LiFeBO3, Li3V2(PO4)3, Li2CuO2, Li2FeSiO4, Li2MnSiO4, etc.

[0060] As the negative electrode of a lithium-ion battery, there are no particular limitations; it can be a negative electrode containing a negative electrode active material and, as needed, conductive additives, binders, etc. The negative electrode can be a negative electrode with a layer containing these materials formed on the current collector. Examples of negative electrode active materials include Nb₂O₅, V₂O₅, TiO₂, In₂O₃, ZnO, SnO₂, NiO, ITO (Indium Tin Oxide), AZO (Al-doped Zinc Oxide), FTO (F-doped Tin Oxide), anatase and rutile phases of TiO₂, and Li₄Ti₅O₂. 12 Lithium composite metal oxides such as Li2Ti3O7, metals such as Li, Si, Sn, Si-Mn, Si-Co, Si-Ni, In, Au and alloys containing these metals, carbon materials such as graphite, and substances in which lithium ions are inserted between the layers of the carbon material.

[0061] There are no particular limitations on the material of the current collector; it can be an element or alloy of metals such as Cu, Mg, Ti, Fe, Co, Ni, Zn, Al, Ge, In, Au, Pt, Ag, and Pd.

[0062] <Methods for manufacturing solid electrolytes>

[0063] The solid electrolyte manufacturing method of this embodiment includes a step of performing a topological chemical reaction on lithium oxide.

[0064] The method for manufacturing the solid electrolyte in this embodiment is also suitable for manufacturing the lithium oxide-containing method described in this embodiment.

[0065] Here, topological chemistry refers to the process by which elements contained in a dopant are introduced into the lithium oxide as anion or other chemical species while maintaining the basic framework of the lithium oxide as the main body. The introduced chemical species can either replace some atoms or groups of atoms in the lithium oxide or insert themselves into the structure of the lithium oxide. It is preferable to introduce anions into the lithium oxide through topological chemistry, and these anions can also replace some of the anions already present in the lithium oxide.

[0066] The crystal structure serving as the basic framework is not particularly limited and can have garnet-type, perovskite-type, layered rock salt-type, NASICON-type, LISICON-type, or olivine-type crystal structures, or it can be amorphous. Crystal structures having garnet-type, perovskite-type, layered rock salt-type, NASICON-type, LISICON-type, or olivine-type crystal structures are particularly preferred.

[0067] The topological chemical reaction is preferably carried out at a temperature below 900°C, more preferably at 50–800°C, even more preferably at 100–700°C, even more preferably at 150–600°C, and particularly preferably at 200–500°C. There is no particular limitation on the duration of the topological chemical reaction, but it can be, for example, 30 minutes to 48 hours, or 5 to 36 hours.

[0068] Lithium oxides can include elements other than lithium. Examples of elements other than lithium include alkali metals, alkaline earth metals, rare earth elements, transition metals, chalcogens, halogens, elements in Group 15 (nitrogen group), Group 14 (carbon group), and Group 13 (boron group) of the periodic table. It should be noted that in this specification, the term "transition metal" refers to elements in Groups 4 to 12 of the periodic table. That is, the term "transition metal" is defined to include elements in the zinc group.

[0069] The alkali metal can be at least one selected from the group consisting of Na, K, Rb and Cs, or it can be at least one selected from the group consisting of Na and K, or it can be Na.

[0070] The alkaline earth metal element can be at least one selected from the group consisting of Be, Mg, Ca, Sr and Ba, or it can be Sr.

[0071] Rare earth elements can be Sc, Y, and lanthanides, or they can be selected from the group consisting of Sc, Y, La, and Nd.

[0072] The transition metal element can be a transition metal element in the 4th to 6th period of the periodic table, and can be at least one selected from the group consisting of Zr, Ta, Ti, V, Sb and Nb, or at least one selected from the group consisting of Zr, Ta and Nb.

[0073] Chalcogens can be at least one selected from the group consisting of O, S, Se, and Te, or at least one of O and S. Halogens can be one selected from the group consisting of F, Cl, Br, and I, or F.

[0074] Elements in Group 15 (Nitrogen Group) of the periodic table can be at least one of N and P, or N alone. Elements in Group 14 (Carbon Group) of the periodic table, C and Ge. Elements in Group 13 (Boron Group) of the periodic table can be at least one selected from the group consisting of B, Al, Ga and In, or Ga alone.

[0075] Lithium oxides can have crystal structures such as garnet, perovskite, layered rock salt, NASICON, LISICON, or olivine, or they can be amorphous. Garnet, perovskite, layered rock salt, NASICON, LISICON, or olivine crystal structures are particularly preferred.

[0076] Lithium-containing oxides with a garnet-type crystal structure include Li7La3Zr2O. 12 Li5La3Nb2O 12 Li5BaLa2TaO 12 Garnet-like crystals obtained by substituting a portion of the elements in these compounds with at least one element selected from the group consisting of N, F, Al, Sr, Sc, Nb, Ta, Sb, and the lanthanides can also be used as the aforementioned lithium-containing oxides. Li can be listed as an example of a lithium-containing oxide with a perovskite-type crystal structure. 0.35 La 0.55 TiO3, Li 0.2 La 0.27 Perovskite-like crystals obtained by substituting a portion of the elements in compounds such as NbO3 with at least one element selected from the group consisting of N, F, Al, Sr, Sc, Nb, Ta, Sb, and the lanthanides can also be used as the aforementioned lithium-containing oxides. Li can be listed as a lithium-containing oxide with a NASICON-type crystal structure. 1.3 Ti 1.7 Al 0.3 (PO4)3, Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li 1.4 Al 0.4 Ti 1.4 Ge 0.2 (PO4)3, etc., can also be used as the aforementioned lithium-containing oxides by substituting a portion of the elements of these compounds with at least one selected from the group consisting of N, F, Al, Sr, Sc, Nb, Ta, Sb, and lanthanides to obtain NASICON-type crystals. Examples of lithium-containing oxides having LISICON-type crystals include Li... 14 ZnGe4O 16 LiSICON-type crystals obtained by substituting a portion of the elements in these compounds with at least one element selected from the group consisting of N, F, Al, Sr, Sc, Nb, Ta, Sb, and the lanthanides can also be used as the aforementioned lithium-containing oxides. Lithium-containing oxides can also be Li... 3.4 V 0.6 Si 0.4 O4, Li 3.6 V 0.4 Ge 0.6 O4, Li 2+x C 1-x B x Compounds with other crystal structures, such as O3.

[0077] Lithium oxides can be compounds obtained by solid-state reactions using compounds containing various elements contained in the lithium oxide as raw materials. Examples of raw materials include compounds containing Li as lithium sources, compounds containing La as lanthanum sources, compounds containing Zr as zirconium sources, and compounds containing Ga as gallium sources.

[0078] Examples of lithium sources include lithium metal salts such as lithium chloride, lithium nitrate, lithium acetate, lithium hydroxide, and lithium carbonate, as well as lithium alkoxides such as lithium methoxide. One or more of these raw materials can be used.

[0079] Examples of lanthanum sources include lanthanum metal salts such as lanthanum chloride, lanthanum nitrate, and lanthanum acetate, and lanthanum alkoxides such as lanthanum trimethylolide. One or more of these raw materials can be used.

[0080] Examples of zirconium sources include zirconium chloride, zirconium oxychloride, zirconium oxynitrate, zirconium hydroxide, zirconium acetate, zirconium metal salts, and zirconium alkoxides such as zirconium tetramethylethanol. One or more of these raw materials can be used.

[0081] Examples of gallium compounds (gallium sources) include gallium metal salts such as gallium bromide, gallium chloride, gallium iodide, and gallium nitrate, as well as gallium alkoxides such as gallium trimethylolpropionate. One or more of these materials can be used.

[0082] The solid-state reaction is carried out by heating the mixture after preparing a mixture of powders of these main raw materials. There are no particular limitations on the heating temperature, but it can be, for example, around 900 to 1200 °C.

[0083] As a dopant, there is no particular problem as long as it is a compound containing the element to be introduced, but for example, a dopant having an anion containing the element to be introduced is preferred. As an anion, it is preferred to have an anion containing one or more elements selected from the group consisting of halogens, chalcogens, nitrogen and phosphorus, more preferably a halide ion, and even more preferably a fluoride ion.

[0084] Metal fluorides can be listed as dopants containing fluoride ions. There are no particular limitations on the metal fluoride, but examples include alkali metal fluorides, alkaline earth metal fluorides, transition metal fluorides, and fluorides of metals in Group 13 of the periodic table. Examples of alkali metal fluorides include LiF, NaF, and KF. Examples of alkaline earth metal fluorides include MgF2, CaF2, SrF2, and BaF2, with MgF2 being preferred. Examples of transition metal fluorides include fluorides of transition metals in periods 4 to 6 of the periodic table, with NiF2 or ZnF2 being preferred. Examples of fluorides of metals in Group 13 of the periodic table include GaF3. The metal fluoride is preferably at least one of GaF3, MgF2, NiF2, and ZnF2. When using a dopant containing fluoride ions, dopants containing other halide ions may not be used. For example, relative to 100 mol% of fluorine atoms in the dopant, the content of other halogen atoms in the dopant can be less than 150 mol%, less than 100 mol%, or less than 50 mol%.

[0085] The amount of dopant used is preferably 0.05 to 25% by mass relative to 100% mass of the total mass of the dopant and the lithium oxide, more preferably 0.1 to 20% by mass, and even more preferably 1 to 18% by mass.

[0086] Topological chemical reactions are preferably carried out by mixing lithium oxide powder and dopant powder and heating. The topological chemical reaction is preferably carried out under reduced pressure, for example, by sealing the lithium oxide powder and dopant powder into a container such as a Pyrex tube under reduced pressure and heating the container. The lithium oxide powder and dopant powder can also be used as a mixture of powders, or they can be shaped into particles or other predetermined forms before being used for the topological chemical reaction.

[0087] The obtained solid electrolyte can also be in the form of powder, but it can also be used as a sintered body obtained by sintering the powder. There are no particular restrictions on the sintering method, but it can be sintered by methods such as discharge plasma sintering.

[0088] The reasons why a solid electrolyte with high ionic conductivity (alkali metal ion conductivity) can be obtained through the manufacturing method of the solid electrolyte disclosed herein are not necessarily clear, but the inventors consider the reasons as follows. First, as described in Patent Documents 1-7 and Non-Patent Documents 1-4, conventional solid electrolytes are synthesized by calcining lithium oxide-containing raw materials together with a compound containing the element to be doped at a high temperature such as 1000°C (high-temperature solid-state reaction) when introducing the element to be doped (e.g., fluorine). On the other hand, in this embodiment, since a topological chemical reaction is performed on the previously synthesized lithium oxide, the reaction can be carried out smoothly while maintaining the basic framework of the lithium oxide. Therefore, it is believed that a quasi-stable phase that cannot be obtained by conventional high-temperature solid-state reactions can be obtained.

[0089] The solid electrolyte in this embodiment is not particularly limited in shape; it can be a powder or granules. Furthermore, it can be a sintered body obtained by sintering powder, or a composite body obtained by bonding powder with a binder. It can also be mixed with other components to form a composition for use. Examples of such compositions include electrolyte compositions used as solid electrolytes in batteries such as lithium-ion batteries and energy storage devices such as capacitors. The electrolyte composition may also contain ionicly conductive materials, ionic liquids, polymer materials, etc., as components other than the solid electrolyte.

[0090] Example

[0091] <Example 1>

[0092] First, 1.30 g of Li₂CO₃, 2.46 g of La₂O₃, and 1.24 g of ZrO₂ were mixed while being pulverized. The resulting powder was then calcined in air in an MgO crucible at 1000 °C for 10 hours to obtain undoped Li₇La₃Zr₂O. 12 (LLZO).

[0093] In the obtained LLZO, GaF3 was added as a metal fluoride at a rate of 10% by mass relative to 100% by mass of LLZO, and the mixture was pulverized and mixed simultaneously. The resulting powder was shaped into particles with a diameter of approximately 6 mm. The particles were placed in a Pyrex tube, which was then degassed and sealed. The particles in the Pyrex tube were heated at 400 °C for 24 hours, and then removed and pulverized to obtain powdered fluorine-doped LLZO (solid electrolyte).

[0094] solid 19 F-NMR determination >

[0095] The solid electrolyte of Example 1 was subjected to solidification under the following conditions. 19Determination by F-NMR.

[0096] Device: JNM-ECZ600R (manufactured by Nippon Electronics Co., Ltd.)

[0097] Observation kernel: 19 F (with) 19 The resonant frequency of the F core is 564MHz.

[0098] Magic Angle Rotation (MAS) frequency: 20kHz

[0099] Measurement method: Hahn echo method

[0100] Waiting time and cumulative number of attempts: 15 seconds or 60 seconds, 128 attempts

[0101] Measurement temperature: room temperature

[0102] Reference material: The chemical shift of the peak of fluorine atoms from the -CF2-CF2- unit of polytetrafluoroethylene was set to -122 ppm.

[0103] It should be noted that, regarding polytetrafluoroethylene, the data obtained separately from the samples under the same conditions as those of the examples and comparative examples were used as the benchmark (i.e., used as an external standard).

[0104] The PTFE samples were obtained by finely cutting Valqua tape seals (model 20-E).

[0105] solid 6 Li-NMR Measurement

[0106] The solid electrolyte of Example 1 was subjected to solidification under the following conditions. 6 Li-NMR determination.

[0107] Device: AVANCE300 (manufactured by Bruker)

[0108] Observation kernel: 6 Li (with) 6 The resonance frequency of the Li nucleus is 44.1 MHz.

[0109] Magic Angle Rotation (MAS) frequency: 10kHz

[0110] Measurement method: Single-pulse method (using Bruker's standard pulse sequence zg)

[0111] Excitation pulse amplitude: π / 4 pulse

[0112] Waiting time and cumulative number of attempts: 40 seconds, 2048 times

[0113] Measurement temperature: room temperature

[0114] Reference substance: the peak observed for 1 mol / L LiCl aqueous solution is set as 1.19 ppm

[0115] In the obtained solid 6 Li-NMR spectrum, two peaks of different intensities are observed within a chemical shift range of -5 to 15 ppm. Here, the area intensity of the large peak is calculated by fitting the large peak with a Gaussian program via the least square method.

[0116] Furthermore, for the area intensity of the small peak, it is calculated by fitting, via the least square method using a Gaussian program, the spectrum obtained by subtracting the spectrum of the large peak obtained by the fitting method described above from the original spectrum. The peak with a larger area intensity is defined as a first peak, and the peak with a smaller area intensity is defined as a second peak. Table 1 shows the respective positions and half-widths of the first and second peaks.

[0117] Furthermore, the ratio of the area intensity of the second peak to the sum of the area intensities of the first peak and the second peak (also abbreviated as the area ratio) is shown in Table 1.

[0118] In the solid 19 F-NMR spectrum, one peak is observed within a chemical shift range of -100 to 50 ppm. Specifically, a peak is observed at a position of -24.1 ppm.

[0119] <Measurement of Powder X-ray Diffraction>

[0120] Measurement of powder X-ray diffraction was performed using an apparatus: Ultima IV (manufactured by Rigaku Corporation, radiation source: CuKα radiation). In the powder X-ray diffraction pattern of the solid electrolyte of Example 1, since a single peak is observed at 2θ = 16.0 to 17.0°, it is confirmed to have a cubic garnet-type structure. Furthermore, undoped LLZO is confirmed to have a tetragonal garnet-type structure.

[0121] Furthermore, in the powder X-ray diffraction pattern, a peak is observed at 2θ = 28.5 to 29.0°. The intensity ratio of this peak to the intensity of the peak at 16.0 to 17.0° (hereinafter also abbreviated as peak intensity ratio) is calculated. The results are shown in Table 1.

[0122] <ICP Emission Spectrometry>

[0123] Apparatus used: ICP-AES (Agilent Technologies 5110) was used to perform ICP emission spectroscopy analysis on the solid electrolyte of Example 1 to determine the content ratios of Li, La, and Zr (with La content set to 3). The analytical method was performed by pressurized acid decomposition followed by ICP-AES. Pretreatment conditions were implemented by decomposing a mixed acid (hydrochloric acid and sulfuric acid in a 3:1 molar ratio) at 100°C for 20 hours. The results are shown in Table 1.

[0124] <Determination of Ionic Conductivity>

[0125] The solid electrolyte device LABOX-325R (manufactured by SinterLand Co., Ltd.) of Example 1 was subjected to discharge plasma sintering under vacuum conditions at 1100°C for 3 minutes and a pressure of 40 MPa to obtain a disk-shaped sintered body with a thickness of 0.5 mm and a diameter of 3-5 mm. Gold layers were then formed on the two opposing circular surfaces of the sintered body by sputtering to obtain evaluation test pieces.

[0126] The ionic conductivity of the test pieces used for evaluation was measured at room temperature (25°C) using an impedance analyzer (Sl1260, Sl1296, Solartron) at a frequency of 0.1–1 MHz and an amplitude of 10 mV. The ionic conductivity was determined by fitting the obtained Nyquist plot to an assumed equivalent circuit. The results are shown in Table 1.

[0127] <Comparative Example 1>

[0128] For the undoped LLZO produced in Example 1, various measurements were performed in the same manner as in Example 1. The results are shown in Tables 1 and 2. It should be noted that the powder X-ray diffraction results showed two split peaks at the 16-17° position, thus confirming a tetragonal garnet-type structure. Furthermore, the ionic conductivity was measured for a disk-shaped sintered body obtained by pressing and then firing it in air at 1000°C for 10 hours. Other results are shown in Tables 1 and 2.

[0129] <Example 2>

[0130] First, 1.16 g of Li₂CO₃, 2.37 g of La₂O₃, 1.17 g of ZrO₂, 0.12 g of Ga₂O₃, 0.07 g of SrCO₃, and 0.11 g of Ta₂O₅ were mixed while being pulverized. The resulting powder was then calcined in air in an MgO crucible at 1000 °C for 10 hours to obtain Li. 6.25 Ga 0.25 La2.9 Sr 0.1 Zr 1.9 Ta 0.1 O 12 .

[0131] In the obtained Li 6.25 Ga 0.25 La 2.9 Sr 0.1 Zr 1.9 Ta 0.1 O 12 In, relative to Li 6.25 Ga 0.25 La 2.9 Sr 0.1 Zr 1.9 Ta 0.1 O 12 100% by mass of GaF3 was added as a metal fluoride, and the mixture was pulverized and mixed. The resulting powder was shaped into particles with a diameter of approximately 6 mm. The particles were placed in a Pyrex tube, which was then degassed and sealed. The particles in the Pyrex tube were heated at 400°C for 24 hours, then removed and pulverized to obtain a powdered fluorine-doped lithium oxide (solid electrolyte). Various measurements were performed on the obtained solid electrolyte in the same manner as in Example 1. The powder X-ray diffraction results showed a single peak observed at 16–17°, thus confirming a cubic garnet-type structure. Furthermore, the above-mentioned Li... 6.25 Ga 0.25 La 2.9 Sr 0.1 Zr 1.9 Ta 0.1 O 12 It also has a cubic garnet-type structure. Other results are shown in Tables 1 and 2.

[0132] <Example 3>

[0133] First, 1.29 g of Li₂CO₃, 2.34 g of La₂O₃, 0.95 g of ZrO₂, and 0.42 g of Ta₂O₅ were mixed while being pulverized. The resulting powder was then calcined in air in an MgO crucible at 1000 °C for 10 hours to obtain Li. 6.6 La3Zr 1.6 Ta 0.4 O 12 .

[0134] In the obtained Li 6.6 La3Zr 1.6 Ta 0.4 O 12 In, relative to Li6.6 La3Zr 1.6 Ta 0.4 O 12 MgF2 was added as a metal fluoride at a rate of 100% by mass and 2% by mass, and the mixture was pulverized and mixed. The resulting powder was shaped into particles with a diameter of approximately 6 mm. The particles were placed in a Pyrex tube, which was then degassed and sealed. The particles in the Pyrex tube were heated at 400°C for 24 hours, then removed and pulverized to obtain a powdered fluorine-doped lithium oxide (solid electrolyte). Various measurements were performed on the obtained solid electrolyte in the same manner as in Example 1. The powder X-ray diffraction results showed a single peak observed at 16–17°, thus confirming a cubic garnet-type structure. Furthermore, the above-mentioned Li... 6.6 La3Zr 1.6 Ta 0.4 O 12 It also has a cubic garnet-type structure. Other results are shown in Tables 1 and 2.

[0135] <Example 4>

[0136] MgF2 was used as the metal fluoride, and the amount added was 20% by mass relative to 100% by mass of LLZO. Otherwise, the solid electrolyte was synthesized in the same manner as in Example 1, and various determinations were performed. The results are shown in Tables 1 and 2.

[0137] <Comparative Example 2>

[0138] As raw materials, 1.13 g of Li₂CO₃, 2.49 g of La₂O₃, 1.25 g of ZrO₂ and 0.13 g of LiF were mixed and calcined in air in an MgO crucible at 1000 °C for 10 hours to obtain Li₆La₃Zr₂O. 11 The solid electrolyte powder is composed of F. The solid electrolyte is manufactured by the same method as that used in International Publication No. 2015 / 065879 (particularly Example 2, etc.). The obtained solid electrolyte powder was subjected to discharge plasma sintering and various measurements by the same method as in Example 1. The results are shown in Tables 1 and 2.

[0139] <Comparative Example 3>

[0140] Li was synthesized using the same method as in Example 3 of Japanese Patent Application Publication No. 2020-087770. 5.55 Ga 0.5 La 2.95 Ca 0.05 Zr2O 11F. That is, 0.87g of Li₂CO₃, 2.48g of La₂O₃, 1.27g of ZrO₂, 0.24g of Ga₂O₃, 0.02g of CaF₂, and 0.12g of LiF are mixed and calcined in air in an MgO crucible at 1000℃ for 10 hours to obtain Li. 5.55 Ga 0.5 La 2.95 Ca 0.05 Zr2O 11 The composition of F is a solid electrolyte powder. For the determination of ionic conductivity, a disc-shaped sintered body obtained by pressing and firing in air at 1000°C for 10 hours was used. The results are shown in Tables 1 and 2.

[0141] Table 1

[0142]

[0143] Table 2

[0144]

[0145] NT: Not measured

[0146] The solid electrolytes of Examples 1-4, synthesized via topological chemical reactions, all exhibited higher ionic conductivity than the solid electrolytes of Comparative Examples 1-3, obtained via high-temperature solid-phase synthesis. Furthermore, regarding the solid electrolytes of Examples 1, 3, and 4, in solid... 19 In the F-NMR spectrum, peaks were observed in the range of -100 to 50 ppm chemical shift, and in solid-state... 6 Two peaks were observed in the Li-NMR spectrum within a chemical shift range of -5 to 15 ppm. On the other hand, regarding Comparative Example 3, synthesized using a conventional method, in solid... 19 No peaks were observed in the F-NMR spectrum within the chemical shift range of -100 to 50 ppm in the solid state. 6 Only one peak was observed in the Li-NMR spectrum within the chemical shift range of -5 to 15 ppm. Furthermore, regarding Comparative Example 2, synthesized using a conventional method, in solid... 19 No peaks were observed in the F-NMR spectrum within the chemical shift range of -100 to 50 ppm, although in solid-state... 6 Two peaks were observed in the Li-NMR spectrum within a chemical shift range of -5 to 15 ppm, but the crystal system was tetragonal. This indicates that the environment in which fluorine was placed in the solid electrolytes of Examples 1, 3, and 4 differed from previous methods. Furthermore, a comparison between Examples 1-4 and Comparative Example 3 revealed that the environment in which lithium was placed in the cubic phase was different.

Claims

1. A lithium oxide having a cubic garnet structure, exist 19 The solid was measured under the condition that the resonance frequency of the F nucleus was 564 MHz. 19 During F-NMR spectroscopy, the chemical shift of polytetrafluoroethylene was set to -122 ppm, and at least one peak was observed within the chemical shift range of -30 to -10 ppm.

2. The lithium-containing oxide according to claim 1, wherein, exist 6 The solid was measured under the condition that the resonance frequency of the Li nucleus was 44.1 MHz. 6 When performing Li-NMR spectroscopy, the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm, and at least one peak was observed within the chemical shift range of -5 to 15 ppm.

3. The lithium-containing oxide according to claim 2, wherein it contains fluorine atoms. exist 6 The solid was measured under the condition that the resonance frequency of the Li nucleus was 44.1 MHz. 6 When performing Li-NMR spectroscopy, the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm, and at least two peaks were observed within the chemical shift range of -5 to 15 ppm.

4. The lithium-containing oxide according to claim 3, wherein, exist 6 The solid was measured under the condition that the resonance frequency of the Li nucleus was 44.1 MHz. 6 When performing Li-NMR spectroscopy, the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm. At least two peaks with a half-maximum amplitude of less than 2 ppm were observed within the chemical shift range of -5 to 15 ppm.

5. The lithium-containing oxide according to claim 3 or 4, wherein, exist 6 The solid was measured under the condition that the resonance frequency of the Li nucleus was 44.1 MHz. 6 During Li-NMR spectroscopy, the chemical shift of a 1 mol / L LiCl aqueous solution was set to 1.19 ppm. Two peaks were observed within the chemical shift range of -5 to 15 ppm. The ratio of the area intensity of the peak with the smaller area intensity to the sum of the area intensities of the two peaks is 0.3% or more.

6. The lithium-containing oxide according to claim 5, wherein, exist 19 The solid was measured under the condition that the resonance frequency of the F nucleus was 564 MHz. 19 During F-NMR spectroscopy, the chemical shift of polytetrafluoroethylene was set to -122 ppm, and at least one peak was observed within the chemical shift range of -100 to 50 ppm.

7. The lithium-containing oxide according to any one of claims 1 to 4, wherein, Regarding the ratio of the number of atoms measured by ICP emission spectroscopy, when La is set to 3, Li is 5 to 12 and Zr is 1 to 3.

8. The lithium-containing oxide according to any one of claims 1 to 4, wherein, In the powder X-ray diffraction pattern, the intensity of the peak at 28.5–29.0° is less than 0.5 compared to the intensity of the peak at 16.0–17.0°.

9. The lithium-containing oxide according to any one of claims 1 to 4, comprising one selected from the group consisting of Sc, Y, La and Nd.

10. The lithium-containing oxide according to any one of claims 1 to 4, comprising at least one selected from the group consisting of Zr, Ta, Ti, V, Sb and Nb.

11. The lithium oxide according to any one of claims 1 to 4, wherein it comprises selected La and Zr.

12. A sintered body comprising any one of claims 1 to 11 containing a lithium oxide.

13. An electrolyte composition comprising any one of claims 1 to 11 containing a lithium oxide.

14. A method for manufacturing a solid electrolyte, comprising: a step of carrying out a solid-phase reaction at 900-1200°C using a compound comprising various metal elements contained in a lithium oxide according to any one of claims 1 to 11 as a raw material; and a step of introducing anions by carrying out a topological chemical reaction on the obtained lithium oxide at a temperature below 900°C.

15. The method for manufacturing a solid electrolyte according to claim 14, wherein, The topological chemical reaction is carried out at a temperature of 50–700 °C.

16. The method for manufacturing a solid electrolyte according to claim 14 or 15, wherein, The anion contains fluorine.

17. The method for manufacturing a solid electrolyte according to claim 14 or 15, wherein, The anion is a fluoride ion.

18. The method for manufacturing a solid electrolyte according to claim 14 or 15, wherein, In the aforementioned topological chemical reaction, the lithium-containing oxide is reacted with a metal fluoride.

19. The method for manufacturing a solid electrolyte according to claim 18, wherein, The metal fluoride is at least one of GaF3, MgF2, NiF2 and ZnF2.

20. The method for manufacturing a solid electrolyte according to claim 14 or 15, wherein, The solid electrolyte has a garnet-type crystal structure.

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