Lithium ion secondary battery

Patent metadata

Field	Value
Publication number	US-9160004-B2
Application number	US-201214345590-A
Country	US
Kind code	B2
Filing date	Sep 13, 2012
Priority date	Sep 22, 2011
Publication date	Oct 13, 2015
Grant date	Oct 13, 2015

Abstract

In a lithium ion secondary battery including a positive electrode, a separator, and a negative electrode opposed to the positive electrode with an intervention of the separator, the negative electrode includes a negative electrode active material including a silicon compound, and a negative electrode binder including a particular polyimide, and lithium is occluded in both the negative electrode active material and the negative electrode binder even during discharge.

First claim

The invention claimed is:

1. A lithium ion secondary battery comprising a positive electrode, a separator, and a negative electrode opposed to the positive electrode with an intervention of the separator, wherein
the negative electrode comprises a negative electrode active material comprising at least a silicon compound, and a negative electrode binder,
the negative electrode binder comprises a polyimide represented by formula (1):

wherein R 1 and R 2 each independently represent an alkyl group, an alkoxy group, an acyl group, a phenyl group, or a phenoxy group, and
lithium is occluded in both the negative electrode active material and the negative electrode binder even during discharge.

2. The lithium ion secondary battery according to claim 1 , wherein the polyimide can form a lithium polyimide represented by formula (2):

wherein R 1 and R 2 represent the same groups as R 1 and R 2 in formula (1), respectively,
by a reversible reaction with lithium ions, with charge and discharge.

3. The lithium ion secondary battery according to claim 1 , wherein R 1 and R 2 in formula (1) are each independently an alkyl group or an alkoxy group.

4. The lithium ion secondary battery according to claim 1 , wherein R 1 and R 2 in formula (1) are each independently a methyl group or a methoxy group.

5. The lithium ion secondary battery according to claim 1 , wherein the negative electrode binder comprises a polyimide represented by formula (3) or formula (4):

6. The lithium ion secondary battery according to claim 1 , wherein the negative electrode is doped with lithium.

7. The lithium ion secondary battery according to claim 1 , wherein the following formula (i) is satisfied:
1.2 ≦M a /M c ≦1.9   (i)

wherein an amount of lithium inserted into the negative electrode until the negative electrode reaches a potential of 0.02 V with respect to metal lithium is M a (a number of atoms), and an amount of lithium released from the positive electrode until the positive electrode reaches a potential of 4.3 V with respect to metal lithium is M c (a number of atoms).

8. The lithium ion secondary battery according to claim 1 , wherein the following formula (ii) is satisfied:
2 ≦A/B≦ 20   (ii)

wherein an amount of lithium (a number of atoms) in the negative electrode active material and an amount of lithium (a number of atoms) in the negative electrode binder during discharge when battery voltage is 3.0 V or less are A and B, respectively.

9. The lithium ion secondary battery according to claim 1 , wherein the silicon compound is silicon oxide.

10. The lithium ion secondary battery according to claim 1 , wherein the negative electrode further comprises carbon as the negative electrode active material.

11. The lithium ion secondary battery according to claim 10 , wherein a content of the carbon is 1% by mass or more and 10% by mass or less with respect to the entire negative electrode active material.

12. The lithium ion secondary battery according to claim 1 , wherein a content of the negative electrode binder is 5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the negative electrode active material.

Assignees

• Kasahara Ryuichi
• Iriyama Jiro
• Inoue Kazuhiko
• Nec Corp

Inventors

• Kasahara Ryuichi
• Iriyama Jiro
• Inoue Kazuhiko

Classifications

• H01M4/364

  as mixtures · CPC title

• H01M4/382

  Lithium (H01M4/405 takes precedence) · CPC title

• H01M4/622 Primary

  being polymers · CPC title

• H01M2004/027

  Negative electrodes · CPC title

• H01M10/052

  Li-accumulators · CPC title