NEGATIVE ELECTRODE FOR LITHIUM SECONDARY BATTERY AND METHOD FOR PRODUCING SAME

• US 20120214063A1
• Filed: 11/10/2010
• Published: 08/23/2012
• Est. Priority Date: 11/16/2009
• Status: Active Grant

• Current Assignee: Gunma University, National University Corporation
• Original Assignee: Gunma University, National University Corporation
• Inventors: Morimoto, Hideyuki, Tobishima, Shin-ichi
• Granted Patent: US 8,986,883 B2
• Time in Patent Office: Days
• US Class Current: 429/211
• CPC Class Codes: H01M 2004/027 Negative electrodes
• CPC Class Codes: H01M 4/131 Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/1391 of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/621 Binders
• CPC Class Codes: H01M 4/622 being polymers
• 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

Abstract

A negative electrode for a lithium secondary battery, in which α-Fe₂O₃ that is low in cost, has little environmental impact and has high theoretical capacity is used as an active material, maintains high adhesiveness between a current collector and an electrode layer, and can simultaneously achieve both of an improvement in the cycle characteristics and high capacity. In a negative electrode for a lithium secondary battery, which is configured of a current collector, and an electrode layer that is formed on the current collector and contains at least a negative electrode active material, a conductive assistant and a binder component, the negative electrode active material is composed of α-Fe₂O₃ particles that generate a conversion electrode reaction, the binder component is a mixture of polyamide acid and partially imidized polyamide acid. The electrode layer is configured so that a concentration of the binder component decreases as distanced from the current collector.

Claims

1. A negative electrode for a lithium secondary battery, comprising:

a current collector; and

an electrode layer that is formed on the current collector and contains at least a negative electrode active material, a conductive assistant and a binder component,

wherein the negative electrode active material is composed of α

-Fe₂O₃ particles that generate a conversion electrode reaction, and the binder component is a mixture of polyamide acid and partially imidized polyamide acid.

2. The negative electrode for the lithium secondary battery according to claim 1, wherein a concentration of the binder component of the electrode layer is configured so that the concentration decreases as distanced from the current collector.

3. The negative electrode for the lithium secondary battery according to claim 1, wherein a content of the binder component configuring the electrode layer is 3 to 20% by weight.

4. A lithium secondary battery that uses the negative electrode according to claim 1.

7. The negative electrode for the lithium secondary battery according to claim 2, wherein a content of the binder component configuring the electrode layer is 3 to 20% by weight.

8. A lithium secondary battery that uses the negative electrode according to claim 2.

9. A lithium secondary battery that uses the negative electrode according to claim 3.

10. A lithium secondary battery that uses the negative electrode according to claim 7.

5. A method for producing a negative electrode for a lithium secondary battery, comprising:

coating a slurry containing at least a negative electrode active material, a conductive assistant, a binder and a solvent on a current collector; and

vacuum drying and pressing the current collector having a coating film to form an electrode layer containing at least the negative electrode active material, the conductive assistant and the binder component on the current collector,

wherein as the negative electrode active material configuring the slurry, α

-Fe₂O₃ particles that generate a conversion electrode reaction are used, and as the binder configuring the slurry, polyamide acid is used, the slurry is adjusted to low viscosity of 2 to 3 Pa·

s at room temperature, the binder is allowed to naturally sediment in the coating film formed by coating the prepared low viscosity slurry, thereby a concentration of the binder component in the electrode layer formed on the current collector is configured so as to decrease as distanced from the current collector, and

the binder is partially imidized by vacuum drying and pressing to render the binder component contained in the electrode layer to a mixture of polyamide acid and partially imidized polyamide acid.

6. The method for producing the negative electrode for the lithium secondary battery according to claim 5, wherein a content of the binder component configuring the electrode layer is 3 to 20% by weight.