LITHIUM BATTERY

• US 20090068563A1
• Filed: 09/11/2008
• Published: 03/12/2009
• Est. Priority Date: 09/11/2007
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Uemura, Takashi, Ogawa, Mitsuyasu, Yoshida, Kentaro, Ota, Nobuhiro, Kanda, Ryoko
• Granted Patent: US 8,197,970 B2
• Time in Patent Office: Days
• US Class Current: 429/306
• 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 10/0585 of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
• CPC Class Codes: H01M 4/13 Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• CPC Class Codes: H01M 4/485 of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy H01M4/505, H01M4/525 take precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 29/49115 including coating or impregnating

Abstract

A lithium battery includes a substrate, a positive electrode layer, a negative electrode layer, and a sulfide solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, the positive electrode layer, the negative electrode layer, and the sulfide solid electrolyte layer being provided on the substrate. In this lithium battery, the positive electrode layer is formed by a vapor-phase deposition method, and a buffer layer that suppresses nonuniformity of distribution of lithium ions near the interface between the positive electrode layer and the sulfide solid electrolyte layer is provided between the positive electrode layer and the sulfide solid electrolyte layer. As the buffer layer, a lithium-ion conductive oxide, in particular, Li_xLa_(2-x)/3TiO₃ (x=0.1 to 0.5), Li_7+xLa₃Zr₂O_12+(x/2) (−5≦×≦3, preferably −2≦×≦2), or LiNbO₃ is preferably used.

Claims

1. A lithium battery comprising:

a substrate;

a positive electrode layer;

a negative electrode layer; and

a sulfide solid electrolyte layer that mediates conduction of lithium ions between the positive electrode layer and the negative electrode layer, the positive electrode layer, the negative electrode layer, and the sulfide solid electrolyte layer being provided on the substrate,

wherein the positive electrode layer is formed by a vapor-phase deposition method, and

a buffer layer that suppresses nonuniformity of distribution of lithium ions near the interface between the positive electrode layer and the solid electrolyte layer is provided between the positive electrode layer and the solid electrolyte layer.

2. The lithium battery according to claim 1, wherein the buffer layer is made of a lithium-ion conductive oxide.

3. The lithium battery according to claim 2, wherein the lithium-ion conductive oxide is at least one type of compound selected from Li_xLa_(2-x)/3TiO₃ (x=0.1 to 0.5), Li_7+xLa₃Zr₂O_12+(x/2) (−

5≦

×

≦

3), Li₄Ti₅O₁₂, Li_3.6Si_0.6P_0.4O₄, Li_1.3Al_0.3Ti_1.7(PO₄)₃, Li_1.8Cr_0.8Ti_1.2(PO₄)₃, Li_1.4In_0.4Ti_1.6(PO₄)₃, LiTaO₃, and LiNbO₃.

4. The lithium battery according to claim 1, wherein the thickness of the buffer layer is 1 μ

m or less.

5. The lithium battery according to claim 1, wherein the electronic conductivity of the buffer layer is 1×

10<sup>−

5</sup> S/cm or less.

6. The lithium battery according to claim 1, wherein at least one compound constituting the buffer layer has diffused into the positive electrode layer.

7. The lithium battery according to claim 6, wherein the at least one compound includes LiNbO₃, and

the Nb concentration at a position in the positive electrode layer 25 nm from the interface with the buffer layer in the thickness direction is 1×

10<sup>−

3</sup> atomic percent or more and 25 atomic percent or less.

8. The lithium battery according to claim 1, wherein the buffer layer is in an amorphous state.

9. The lithium battery according to claim 8, wherein the buffer layer is made of LiNbO₃, and

no peak having a full width at half maximum of 5°

or less is present in the range of 22°

to 25°

of 2θ

in X-ray diffraction of the buffer layer.

10. The lithium battery according to claim 1, wherein the ab-axis orientation is higher than the c-axis orientation in the positive electrode layer.

11. The lithium battery according to claim 10, wherein an active material of the positive electrode layer is made of a compound having a layered rock-salt structure when crystallized, and

the ratio of plane indices of the positive electrode layer satisfies the relationship (003)/(101)<

10.

12. The lithium battery according to claim 1, wherein the density of the buffer layer is 92% or more of the theoretical density.

13. The lithium battery according to claim 1, wherein an element constituting an active material of the positive electrode layer has diff-used into the buffer layer.

14. The lithium battery according to claim 13, wherein the positive electrode layer contains an active material containing a transition metal element, and

the mass ratio of the transition metal element to lithium in the buffer layer at the interface with the solid electrolyte layer satisfies the following formula:

1×

10<sup>−

4</sup>≦

(transition metal element/lithium)≦

8×

10<sup>−

1</sup>

15. The lithium battery according to claim 1, wherein the surface roughness Ra of the positive electrode layer is 1 nm or more and 40 nm or less.