Polycrystalline material and production method therefor

Patent metadata

Field	Value
Publication number	US-10347912-B2
Application number	US-201515502452-A
Country	US
Kind code	B2
Filing date	Aug 6, 2015
Priority date	Aug 14, 2014
Publication date	Jul 9, 2019
Grant date	Jul 9, 2019

Abstract

Provided are a sodium ion secondary battery and a lithium ion secondary battery capable of undergoing a reversible large-capacity charge/discharge reaction. The sodium and lithium ion secondary batteries each have a positive electrode, a negative electrode, and an electrolyte. The active substance of the positive or negative electrode of these secondary batteries is a single-phase polycrystal represented by the following chemical formula: NaxTi4O9 (2≤x≤3), preferably Na2Ti4O9, having a one-dimensional tunnel type structure, and belonging to a monoclinic crystal system. This polycrystal is obtained by filling a container made of molybdenum or the like with a raw material containing a sodium compound and at least one of a titanium compound and metal titanium, and firing at 800° C. or more but 1600° C. or less.

First claim

What is claimed is:

1. A method of producing a polycrystal, the polycrystal being a single-phase polycrystal represented by the following chemical formula: Na x Ti 4 O 9 (2≤x≤3), having a one-dimensional tunnel type structure, and belonging to a monoclinic crystal system, comprising:
a step of firing a raw material containing a sodium compound and at least one of a titanium compound and metal titanium at 800° C. or more but 1600° C. or less,
wherein the polycrystal is represented by the following formula: Na 2 Ti 4 O 9 and the method further comprises a step of washing, with water, Na y Ti 4 O 9 (2<y≤3) obtained in the firing step.

2. The method of producing a polycrystal according to claim 1 ,
wherein the raw material contains Na 4 Ti 5 O 12 and metal titanium.

3. The method of producing a polycrystal according to claim 1 ,
wherein firing in the firing step is performed in a non-oxidizing atmosphere.

4. The method of producing a polycrystal according to claim 1 ,
wherein in the firing step, firing is performed while filling, with the raw material, a container made of at least one material selected from molybdenum, tungsten, tantalum, iron, nickel, and titanium.

5. A sodium ion secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte,
wherein the positive electrode or negative electrode has, as an active substance thereof, a polycrystal which is a single-phase polycrystal represented by the following chemical formula: Na x Ti 4 O 9 (2≤x≤3), having a one-dimensional tunnel type structure, and belonging to a monoclinic crystal system.

6. A lithium ion secondary battery, comprising a positive electrode, a negative electrode, and an electrolyte,
wherein the positive electrode or negative electrode has, as an active substance thereof, a polycrystal which is a single-phase polycrystal represented by the following chemical formula: Na x Ti 4 O 9 (2≤x≤3), having a one-dimensional tunnel type structure, and belonging to a monoclinic crystal system.

Assignees

• Aist

Inventors

• Kataoka Kunimitsu
• Akimoto Junji

Classifications

• H01M4/485 Primary

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• H01M10/054

  Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium · CPC title

• C01P2002/77

  by unit-cell parameters, atom positions or structure diagrams · CPC title

• C01P2002/72

  by d-values or two theta-values, e.g. as X-ray diagram · CPC title