SECONDARY BATTERY

• US 20140162109A1
• Filed: 07/07/2011
• Published: 06/12/2014
• Est. Priority Date: 07/07/2011
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Ueki, Tomoyoshi, Shimamura, Harunari, Fukumoto, Yusuke
• Granted Patent: US 9,660,240 B2
• Time in Patent Office: Days
• US Class Current: 429/144
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 50/417 Polyolefins
• CPC Class Codes: H01M 50/457 comprising three or more layers
• CPC Class Codes: H01M 50/46 Separators, membranes or diaphragms characterised by their combination with electrodes
• CPC Class Codes: H01M 50/489 Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
• CPC Class Codes: H01M 50/491 Porosity
• CPC Class Codes: H01M 50/581 in response to temperature
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Provided is a very safe secondary battery that can prevent the occurrence of battery abnormalities even when the internal battery temperature increases due to, for example, overcharging. A separator 70 in this secondary battery has a laminated structure that is provided with at least two porous layers 76A, 72, 76B, wherein one of these layers forms a porous electroconductive layer 72 in which an electroconductive material 74 is dispersed in the porous layer.

Claims

1-9. -9. (canceled)

10. A secondary battery comprising:

a positive electrode;

a negative electrode; and

a porous separator made of a polymer and interposed between the positive electrode and the negative electrode,

wherein the separator has a porous electroconductive layer in which an electroconductive material is dispersed, and electroconductive material-free porous layers laminated on two sides of the porous electroconductive layer, and

the melting point of the polymer constituting the porous electroconductive layer is lower than the melting point of the polymer constituting the electroconductive material-free porous layers.

11. The secondary battery according to claim 10, wherein the polymer constituting the porous electroconductive layer is polyethylene and the polymer constituting the electroconductive material-free porous layers is polypropylene.

12. The secondary battery according to claim 10, wherein, when the porous electroconductive layer is made 100 mass %, the percentage content of the electroconductive material present in the porous electroconductive layer is greater than 3 mass % and less than 50 mass %.

13. The secondary battery according to claim 12, wherein the percentage content of the electroconductive material is from at least 8 mass % to not more than 40 mass %.

14. The secondary battery according to claim 10, wherein the electroconductive material is a carbon material.

15. The secondary battery according to claim 10, wherein the average pore diameter of the electroconductive material-free porous layer is 0.05 μ

m to 0.5 μ

m, and the average particle diameter of the electroconductive material present in the porous electroconductive layer is 0.01 μ

m to 0.1 μ

m and is not larger than the average pore diameter.

16. The secondary battery according to claim 10, fabricated as a lithium ion secondary battery using a positive electrode that contains a positive electrode active material usable in a lithium ion secondary battery, a negative electrode that contains a negative electrode active material usable in a lithium ion secondary battery, and an electrolyte solution.