High capacity/high discharge rate rechargeable positive electrode

• US 6,200,704 B1
• Filed: 09/01/1998
• Issued: 03/13/2001
• Est. Priority Date: 09/01/1998
• Status: Expired due to Term

• Current Assignee: PolyPlus Battery Company
• Original Assignee: PolyPlus Battery Company
• Inventors: Katz, Bruce D., Visco, Steven J., De Jonghe, Lutgard C., Chu, May-Ying
• Primary Examiner(s): Kalafut, Stephen
• Assistant Examiner(s): Martin, Angela J.
• Application Number:
  US09/145,484
• Time in Patent Office: 924 Days
• Field of Search: 429/218.1, 429/221, 429/227, 429/231.5, 429/231.95
• US Class Current: 429/218.1
• CPC Class Codes: H01M 10/0436 Small-sized flat cells or batteries for portable equipment
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 2004/028 Positive electrodes
• CPC Class Codes: H01M 4/02 Electrodes composed of, or comprising, active material
• CPC Class Codes: H01M 4/362 Composites
• CPC Class Codes: H01M 4/581 Chalcogenides or intercalation compounds thereof
• CPC Class Codes: H01M 4/5815 Sulfides
• CPC Class Codes: H01M 4/625 Carbon or graphite
• 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

Disclosed is a positive electrode that has a low equivalent weight and high cell voltage and consequently a high specific energy, and a high discharge rate pulse capability. Also disclosed are methods for fabricating active-sulfur-based composite electrodes, and battery cells incorporating such electrodes.

The batteries of this invention are preferably rechargeable and operate at high sulfur utilization over many cycles. Positive electrodes according to the present invention are composed of at least two electrochemically active materials: an “active-sulfur” material, and a second electrochemically active material having a higher discharge rate than the active-sulfur component. The active-sulfur component is also oxidizing with respect to the higher discharge rate material. In operation, the active-sulfur component of the positive electrode discharges to satisfy power demands below its maximum discharge rate. The high discharge rate (but relatively low capacity) material is discharged to satisfy power demands that exceed the active-sulfur'"'"'s discharge rate. The high discharge rate material in the positive electrode may be effectively recharged (or “regenerated”) chemically by oxidation by the active-sulfur material during a “resting” phase, that is, when the power demands on a battery cell in which the cathode is incorporated are low enough that they may be met without exceeding the maximum discharge rate of the active-sulfur component of the positive electrode.

Claims

1. A positive electrode comprising:

a) a first electrochemically active material selected from the group consisting of elemental sulfur, a metal sulfide, a metal polysulfide, and combinations thereof, wherein said metal is selected from the group consisting of alkali metals, alkaline earth metals, and mixtures of alkali and alkaline earth metals; and

b) a second electrochemically active material having a higher discharge rate than said first material, and having a discharge material that is oxidizable by in situ redox reaction with the first electrochemically active material, said discharge material selected from the group consisting of metal sulfides, metal oxides, and conductive polymers.

2. The positive electrode of claim 1, further comprising:

c) an electronically conductive material mixed with the electrochemically active materials so that electrons move between the electrochemically active materials and the electronically conductive material.

3. The positive electrode of claim 2, further comprising:

d) an ionically conductive material mixed with the electrochemically active materials so that ions move between the ionically conductive material and the electrochemically active material.

4. The positive electrode of claim 1, wherein said first electrochemically active material comprises a lithium polysulfide.

5. The positive electrode of claim 1, wherein said second electrochemically active material comprises FeS₂.

6. The positive electrode of claim 1, wherein said second electrochemically active material comprises TiS₂.

7. The positive electrode of claim 2, wherein said electronically conductive material is carbon black.

8. The positive electrode of claim 3, wherein said ionically conductive material is a liquid, gel or solid.

9. The positive electrode of claim 1, wherein said positive electrode comprises from about 20% to 95% (by weight) of said first electrochemically active material, and from about 5% to 80% of said second electrochemically active material.

10. The positive electrode of claim 1, wherein said positive electrode comprises from about 30% to 90% (by weight) of said first electrochemically active material, and from about 10% to 70% of said second electrochemically active material.

11. The positive electrode of claim 1, wherein said positive electrode comprises from about 40% to 80% (by weight) of said first electrochemically active material, and from about 20% to 60% of said second electrochemically active material.

12. The positive electrode of claim 2, wherein said positive electrode comprises from about 0% to 40% (by weight) of the electronically conductive material.

13. The positive electrode of claim 3, wherein said positive electrode comprises from about 5% to 70% (by weight) of the ionically conductive material.

14. A battery cell comprising:

a) a positive electrode comprising a mixture of

i) a first electrochemically active material selected from the group consisting of elemental sulfur, a metal sulfide, a metal polysulfide, and combinations thereof, wherein said metal is selected from the group consisting of alkali metals, alkaline earth metals, and mixtures of alkali and alkaline earth metal, and

ii) a second electrochemically active material having a higher discharge rate than said first material, and having a discharge material that is oxidizable by in situ redox reaction with the first electrochemically active material, said discharge material selected from the group consisting of metal sulfides, metal oxides, and conductive polymers,

b) a current collector electrically connected to the positive electrode;

c) a negative electrode including a metal or metal ion; and

d) an electrolyte separator.

15. The battery cell of claim 14, further comprising:

e) an electronically conductive material mixed with the electrochemically active materials so that electrons move between the electrochemically active materials and the electronically conductive material.

16. The battery cell of claim 14, further comprising:

f) an ionically conductive material mixed with the electrochemically active materials so that ions move between the ionically conductive material and the electrochemically active material.

17. The battery cell of claim 14, wherein said first electrochemically active material is a lithium polysulfide.

18. The battery cell of claim 14, wherein said second electrochemically active material is FeS₂.

19. The battery cell of claim 14, wherein said second electrochemically active material is TiS₂.

20. The battery cell of claim 15, wherein said electronically conductive material is carbon black.

21. The battery cell of claim 16, wherein said ionically conductive material is a liquid, gel or solid.

22. The battery cell of claim 14, wherein said positive electrode comprises from about 20% to 95% (by weight) of said first electrochemically active material, and from about 5% to 80% of said second electrochemically active material.

23. The battery cell of claim 14, wherein said positive electrode comprises from about 20% to 95% (by weight) of said first electrochemically active material, and from about 5% to 80% of said second electrochemically active material.

24. The battery cell of claim 14, wherein said positive electrode comprises from about 30% to 90% (by weight) of said first electrochemically active material, and from about 10% to 70% of said second electrochemically active material.

25. The battery cell of claim 14, wherein said positive electrode comprises from about 40% to 80% (by weight) of said first electrochemically active material, and from about 20% to 60% of said second electrochemically active material.

26. The battery cell of claim 15, wherein said positive electrode comprises from about 0% to 40% (by weight) of the electronically conductive material.

27. The battery cell of claim 16, wherein said positive electrode comprises from about 5% to 70% (by weight) of the ionically conductive material.

28. The battery cell of claim 14, wherein said electrolyte separator is a liquid, gel or solid.

29. The battery cell of claim 14, wherein said battery cell has a thin film format.