Lithium-ion conductor and all-solid lithium-ion secondary battery

• US 9,595,736 B2
• Filed: 03/23/2015
• Issued: 03/14/2017
• Est. Priority Date: 10/05/2012
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Yamamoto, Tamotsu, Tanaka, Tsutomu, Homma, Kenji, Watanabe, Satoru
• Primary Examiner(s): Siddiquee, Muhammad
• Application Number:
  US14/665,552
• Publication Number:
  US 20150200421A1
• Time in Patent Office: 722 Days
• US Class Current: 1/1
• CPC Class Codes: H01B 1/10 sulfides
• CPC Class Codes: H01B 1/122 Ionic conductors
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/0562 Solid materials
• CPC Class Codes: H01M 2300/0068 inorganic
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The lithium-ion conductor contains a crystal structure whose composition formula is represented by Li_7+2xP_1-xB_xS₆ (0<x≦1). The crystal structure contains a LiS₄ tetrahedron and a BS₄ tetrahedron, a triangle window of the LiS₄ tetrahedron through which lithium ions pass becomes large caused by the BS₄ tetrahedron, and an ionic conductive path is expanded. Furthermore, lithium ions being a conductive carrier are added corresponding to B quantity x. Consequently, a lithium-ion conductor that exhibits excellent ion conductive property is realized. By using the lithium-ion conductor for a solid electrolyte, an all-solid lithium-ion secondary battery with high characteristics is realized.

Claims

1. A lithium-ion conductor comprising a crystal structure whose composition formula is represented by Li_7+2xP_1-xB_xS₆ (0<

x≦

1).

2. The lithium-ion conductor according to claim 1, wherein a space group of the crystal structure belongs to F-43m.

3. The lithium-ion conductor according to claim 2, wherein, when the crystal structure contains P, the crystal structure contains a LiS₄ tetrahedron in which Li is located at a center of a tetrahedron and S is located at four vertexes, a PS₄ tetrahedron in which P is located at a center of a tetrahedron and S is located at four vertexes and a BS₄ tetrahedron in which B is located at a center of a tetrahedron and S is located at four vertexes, in plural number respectively.

4. The lithium-ion conductor according to claim 3, wherein the crystal structure has a skeleton structure formed of the PS₄ tetrahedron and the BS₄ tetrahedron.

5. The lithium-ion conductor according to claim 3, wherein the crystal structure has a structure in which a pair of the LiS₄ tetrahedrons has two Ss in common.

6. The lithium-ion conductor according to claim 3, wherein the crystal structure has a structure in which the LiS₄ tetrahedron and the BS₄ tetrahedron have two Ss in common.

7. The lithium-ion conductor according to claim 3, wherein the crystal structure has a structure in which a vertex of the PS₄ tetrahedron and a vertex of the BS₄ tetrahedron point to the same direction in a unit lattice.

8. The lithium-ion conductor according to claim 1, further comprising a second crystal structure whose composition formula is Li₃PS₄ and whose space group belongs to Pnma.

9. The lithium-ion conductor according to claim 1, further comprising a third crystal structure whose composition formula is Li₃PS₄ and whose space group belongs to Pmn2₁, or a fourth crystal structure in which a part of Ps of the third crystal structure is substituted by B.

10. An all-solid lithium-ion secondary battery comprising:

a solid electrolyte; and

a pair of electrodes connected to the solid electrolyte,

wherein the solid electrolyte includes a crystal structure whose composition formula is represented by Li_7+2xP_1-xB_xS₆ (0<

x≦

1).

11. The all-solid lithium-ion secondary battery according to claim 10, wherein a space group of the crystal structure belongs to F-43m.

12. The all-solid lithium-ion secondary battery according to claim 11, wherein, when the crystal structure contains P, the crystal structure contains a LiS₄ tetrahedron in which Li is located at a center of a tetrahedron and S is located at four vertexes, a PS₄ tetrahedron in which P is located at a center of a tetrahedron and S is located at four vertexes and a BS₄ tetrahedron in which B is located at a center of a tetrahedron and S is located at four vertexes, in plural number respectively.

13. The all-solid lithium-ion secondary battery according to claim 12, wherein the crystal structure has a skeleton structure formed of the PS₄ tetrahedron and the BS₄ tetrahedron.

14. The all-solid lithium-ion secondary battery according to claim 12, wherein the crystal structure has a structure in which a pair of the LiS₄ tetrahedrons has two Ss in common.

15. The all-solid lithium-ion secondary battery according to claim 12, wherein the crystal structure has a structure in which the LiS₄ tetrahedron and the BS₄ tetrahedron have two Ss in common.

16. The all-solid lithium-ion secondary battery according to claim 12, wherein the crystal structure has a structure in which a vertex of the PS₄ tetrahedron and a vertex of the BS₄ tetrahedron point to the same direction in a unit lattice.

17. The all-solid lithium-ion secondary battery according to claim 10, further comprising a second crystal structure whose composition formula is Li₃PS₄ and whose space group belongs to Pnma.

18. The all-solid lithium-ion secondary battery according to claim 10, further comprising a third crystal structure whose composition formula is Li₃PS₄ and whose space group belongs to Pmn2₁, or a fourth crystal structure in which a part of Ps of the third crystal structure is substituted by B.