Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1999-07-13
2001-05-08
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S231950, C429S245000, C029S002000, C029S623100, C029S623500
Reexamination Certificate
active
06228536
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to batteries, and, more particularly, to the negative current collector in a lithium ion battery cell.
A typical lithium ion battery cell includes a negative electrode, a positive electrode, a separator between the negative electrode and the positive electrode, and an electrolyte that saturates the separator and provides a lithium ion path between the negative electrode and the positive electrode. The negative electrode has a negative current collector contacting the negative electrode active material, and a positive current collector contacting the positive electrode active material. The negative electrode active material releases lithium ions upon discharging of the battery cell and absorbs lithium ions upon charging of the battery cell. The positive electrode active material reacts with lithium ions upon discharging of the battery cell and releases lithium ions upon charging of the battery cell. A lithium ion battery incorporates at least two, and typically a large number, of these cells within a container.
Each current collector provides an electrical current flow path between its respective electrode active material and a terminal, and thence to an external circuit. The current collector is a metal that is resistant to corrosion in the electrolyte, typically copper for the negative current collector and aluminum for the positive current collector. There must be good mechanical adhesion between each of the current collectors and its respective active material. A low electrical resistance at the interface between the current collector and the active material is also important, because the interface is in series with the current flow and imposes an interface impedance on the current flow.
Simultaneously achieving low electrical resistance and good mechanical adhesion between the current collector and the active anode material has been a problem for the case of the copper negative current collector. In one approach, a thin film is applied overlying the copper negative current collector to promote low electrical resistance and good adhesion. However, it is difficult and expensive in a production setting to apply the required thin coating in a precise, controllable, reproducible manner.
There is a need for an improved lithium-ion battery cell in which the interface between the negative current collector and the anode active material has both good adhesion and a low electrical resistance, and which is readily fabricated in production. The present invention fulfills this need, and further provides related advantages.
SUMMARY OF THE INVENTION
The present invention provides a negative current collector useful in a lithium-ion battery, a battery cell assembly using the negative current collector, and a method for their fabrication. The interface between the negative current collector and the negative-electrode active material exhibits both good adhesion and also low electrical resistance. The present invention is compatible with a wide variety of configurations of the negative current collector and of the lithium-ion battery assembly. The approach of the invention is precise, controllable, and reproducible, and is readily applied in a production setting.
In accordance with the invention, a battery cell assembly comprises a battery cell having a negative electrode including a negative-electrode active material that releases lithium ions upon discharging of the battery cell and accepts lithium ions upon charging of the battery cell, and a negative current collector (preferably copper) contacting the negative-electrode active material. The negative current collector has an oxidized/reduced surface, which is preferably prepared by oxidizing a piece of the negative current collector metal, and thereafter reducing the piece of the negative current collector metal. The battery cell further includes a positive electrode comprising a positive-electrode active material that accepts lithium ions upon discharging of the battery cell and releases lithium ions upon charging of the battery cell, and a positive current collector (preferably aluminum) contacting the positive-electrode active material. A separator is disposed between the negative electrode and the positive electrode. The separator is electrically nonconductive to prevent contact between the negative electrode and the positive electrode but is permeable to lithium ions. An electrolyte saturates the electrodes and the separator and provides a lithium ion path between the negative electrode and the positive electrode.
The oxidized/reduced surface on the negative current collector is preferably prepared by immersing a clean and lightly etched negative current collector in an aqueous solution comprising an oxidizer, and thereafter immersing the copper negative current collector in an aqueous solution comprising a reducing agent. Etching prior to oxidation is preferably accomplished by immersing the negative current collector metal. into an acidic aqueous solution. The etching solution may contain sulfuric acid and hydrogen peroxide. The oxidizer may be sodium chlorite, and the reducer may be dimethylamineborane.
REFERENCES:
patent: 5436091 (1995-07-01), Shackle et al.
patent: 5635138 (1997-06-01), Amatucci et al.
Chaney Carol
Gudmestad T.
Hughes Electronics Corporation
Martin Angela J.
LandOfFree
Lithium-ion battery cell having an oxidized/reduced negative... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lithium-ion battery cell having an oxidized/reduced negative..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lithium-ion battery cell having an oxidized/reduced negative... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2512729