Titanic-acid-based solid electrolyte material

Abstract

Provided is a titanic-acid-based solid electrolyte material that does not generate hydrogen sulfide, does not contain rare earth elements, and has exceptional thermal stability.　This titanic-acid-based solid electrolyte material 1 comprises a titanate having a structure in which: a plurality of host layers 2 are stacked, each host layer being formed by two-dimensionally linking, in a ridge-sharing manner, octahedrons in each of which 6 oxygen atoms are coordinated to a titanium atom; and lithium ions 3 and divalent or higher valent cations (α) 4 are arranged between the host layers 2, the titanate being such that some of the titanium sites in the host layers 2 are substituted with monovalent to trivalent cations (β) and / or vacancies, wherein the titanic-acid-based solid electrolyte material 1 is characterized in that the titanate is obtained by treating a lepidocrocite-type titanate in the presence of a mixed molten salt of a lithium salt and a salt of the cations (α) 4.

Claims

1. A titanate-based solid electrolyte material having a structure in which multiple host layers are stacked, each host layer is formed by a chain of octahedrons, each host atom having six oxygen atoms coordinated to a titanium atom, with the octahedrons sharing edges and operating in a two-dimensional direction, and lithium ions and divalent or higher cations (α) are arranged between the host layers, wherein a portion of the titanium sites in the host layers is replaced with a titanate salt in which at least one of monovalent to trivalent cations (β) and vacancies, and the titanate salt is obtained by treating a lepidocrocite-type titanate salt in the presence of a mixed molten salt of a lithium salt and a salt of cations (α).

2. The titanate-based solid electrolyte material according to claim 1, wherein the cation (α) is at least one cation selected from group 2 element ions.

3. The titanate-based solid electrolyte material according to claim 1 or 2, wherein the content of lithium ions present between the layers of the host layer is 5 mol% to 70 mol% relative to 100 mol% of ions present between the layers of the host layer.

4. The titanate-based solid electrolyte material according to claim 1 or 2, wherein the content ratio of the cation (α) to the lithium ion present between the layers of the host layer (cation (α) / lithium ion) is 1 / 4 to 12 in molar ratio.

5. The titanate-based solid electrolyte material according to claim 1 or 2, wherein the interlayer distance of the host layer is 6 Å to 13 Å.

6. The titanate-based solid electrolyte material according to claim 1 or 2, wherein the cation (β) is at least one ion selected from the group consisting of lithium ions, magnesium ions, zinc ions, copper ions, and nickel ions.

7. The titanate-based solid electrolyte material according to claim 1 or 2, wherein the lithium salt is lithium nitrate.

8. The titanate-based solid electrolyte material according to claim 1 or 2, wherein the salt of the cation (α) is a nitrate of the cation (α).

9. The titanate-based solid electrolyte material according to claim 1 or 2, wherein the total amount of ions in the lithium salt and the salt of the cation (α) is 10 to 40 equivalents relative to the exchangeable cation capacity of the lepidocrocite-type titanate.

10. The titanate-based solid electrolyte material according to claim 1 or 2, wherein a portion of the titanium sites in the host layer are replaced with a titanate salt in which monovalent to trivalent cations (β).

11. The empirical formula is A ０．０１～０．１５ Li ０．０５～０．３５ M ０．２０～０．８０ Ti １．６～１．８３ O ３．７～４．０ A titanate-based solid electrolyte material according to claim 1 or 2, represented by the formula [wherein A is one or more alkali metals other than Li, and M is one or more selected from Mg, Zn, Ga, Ni, Cu, Fe, Al, Mn, Co, and Nb].

12. The compositional formula is A ０．０１～０．２０ Li ０．０５～０．３５ M ０．２０～０．８０ □ ０．１５～０．４０ Ti １．６～１．８３ O ３．７～４．０ [wherein, A is one or more kinds of alkali metals excluding Li, M is one or more kinds selected from Mg, Zn, Ga, Ni, Cu, Fe, Al, Mn, Co and Nb, and □ is a pore.] The titanium-based solid electrolyte material according to claim 1 or 2.

13. A method for producing a titanate-based solid electrolyte material according to claim 1 or 2, comprising the steps of mixing a lepidocrocite-type titanate, a lithium salt, and a salt of a cation (α), and then heat-treating the mixture.

14. A solid electrolyte containing the titanate-based solid electrolyte material described in claim 1 or 2.

15. A lithium-ion secondary battery comprising the solid electrolyte described in claim 14.

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