Solid electrolyte and secondary battery

• US 9,812,733 B2
• Filed: 02/03/2015
• Issued: 11/07/2017
• Est. Priority Date: 02/28/2014
• Status: Active Grant

• Current Assignee: Tokyo Institute of Technology (National University Corporation Tokyo Institute of Technology), Ricoh Company Limited
• Original Assignee: Tokyo Institute of Technology (National University Corporation Tokyo Institute of Technology), Ricoh Company Limited
• Inventors: Takeuchi, Shigeo, Yuzurihara, Hajime, Kanno, Ryoji
• Primary Examiner(s): Alejandro, Raymond
• Application Number:
  US14/612,372
• Publication Number:
  US 20150249263A1
• Time in Patent Office: 1,008 Days
• CPC Class Codes: H01B 1/10 sulfides
• CPC Class Codes: H01M 10/054 Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
• CPC Class Codes: H01M 10/0562 Solid materials
• CPC Class Codes: H01M 10/3918 characterised by the electrolyte
• CPC Class Codes: H01M 2300/002 Inorganic electrolyte
• CPC Class Codes: H01M 2300/0068 inorganic
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Provided is a sulfide-based solid electrolyte, including: a Na element; a Ge element; a P element; and a S element, wherein an atomic percentage (at. %) of each of the Na element, the Ge element, the P element, and the S element is as follows when a total of the respective elements is 100 at. %,

• • Na: from 38.8 at. % to 48.4 at. %
  • Ge: from 0.5 at. % to 8.9 at. %
  • P: from 3.9 at. % to 7.9 at. %
  • S: from 43.6 at. % to 48.6 at. %.

Claims

1. A sodium-sulfur based solid electrolyte, comprising:

a Na element;

a Ge element;

a P element; and

a S element,

wherein the sodium-sulfur based solid electrolyte has a Na ion conductivity of 1.5×

10<sup>−

4</sup> S/cm or higher at 25°

C., and

an atomic percentage (at. %) of each of the Na element, the Ge element, the P element, and the S element is as follows when a total of the respective elements in the sodium-sulfur based solid electrolyte is 100 at. %,

Na;

from 38.8 at. % to 48.4 at. %

Ge;

from 0.5 at. % to 8.9 at. %

P;

from 3.9 at. % to 7.9 at. %

S;

from 43.6 at. % to 48.6 at. %.

2. The sodium-sulfur based solid electrolyte according to claim 1,

wherein the atomic percentage (at. %) of each of the Na element, the Ge element, the P element, and the S element is as follows,

Na:

from 40.4 at. % to 44.3 at. %

Ge;

from 3.3 at. % to 6.7 at. %

P;

from 5.5 at. % to 6.7 at. %

S;

from 45.6 at. % to 47.4 at. %.

3. The sodium-sulfur based solid electrolyte according to claim 1,

wherein the sodium-sulfur based solid electrolyte has peaks at 2θ

positions of 29.30°

±

1.00° and

27.20°

±

1.00°

when measured by X-ray diffraction measurement using a Cu-Kα

ray, and

wherein when a diffraction intensity of the peak at the 2θ

position of 29.30°

±

1.00°

is defined as IA and a diffraction intensity of the peak at the 2θ

position of 27.20°

±

1.00°

is defined as IB, a value IB/IA is 0.60 or greater.

4. The sodium-sulfur based solid electrolyte according to claim 1,

wherein the sodium-sulfur based solid electrolyte has a Na ion conductivity of 2.0×

10−

4 S/cm or higher at 25°

C.

5. The sodium-sulfur based solid electrolyte according to claim 1, wherein starting materials for the sodium-sulfur based solid electrolyte include Na₂S.

6. A sodium secondary battery, comprising:

a positive electrode;

a negative electrode; and

a solid electrolyte,

wherein the solid electrolyte in the sodium secondary battery comprises;

a Na element;

a Ge element;

a P element; and

a S element,

wherein an atomic percentage (at. %) of each of the Na element, the Ge element, the P element, and the S element is as follows when a total of the respective elements is 100 at. %,

Na;

from 38.8 at. % to 48.4 at. %

Ge;

from 0.5 at. % to 8.9 at. %

P;

from 3.9 at. % to 7.9 at. %

S;

from 43.6 at. % to 48.6 at. %.

7. The sodium secondary battery according to claim 6,

wherein the positive electrode of the sodium secondary battery includes one or more sodium metallates.

8. The sodium secondary battery according to claim 6, wherein the positive electrode of the sodium secondary battery includes one or more sodium metallates selected from a group consisting of sodium cobaltate, sodium manganate, and sodium nickelate.

9. The sodium secondary battery according to claim 6, wherein the negative electrode of the sodium secondary battery includes an active material selected from a group consisting of a sodium metal, a sodium alloy, and a sodium ion.