FORMATION PROCESS FOR LITHIUM-ION BATTERIES

• US 20090274849A1
• Filed: 04/30/2008
• Published: 11/05/2009
• Est. Priority Date: 04/30/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Jain, Gaurav, Scott, Erik R.
• Granted Patent: US 8,980,453 B2
• Time in Patent Office: Days
• US Class Current: 427/457
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/0569 characterised by the solvents
• CPC Class Codes: H01M 10/446 Initial charging measures
• CPC Class Codes: H01M 2010/4292 Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
• CPC Class Codes: H01M 2300/0028 characterised by the solvent
• 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 4/485 of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy H01M4/505, H01M4/525 take precedence
• CPC Class Codes: H01M 4/583 Carbonaceous material, e.g. graphite-intercalation compounds or CFx
• 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
• CPC Class Codes: Y10T 29/49108 Electric battery cell making

Abstract

A method for producing a battery includes providing a battery having a positive electrode, a negative electrode, and an electrolyte that includes a solvent and a salt. The capacity of the negative electrode is less than that of the positive electrode and the negative electrode includes an active material having an average potential versus a lithium reference electrode of greater than approximately 0.2 volts. The method also includes applying an initial charge to the battery at a voltage that is greater than a fully charged voltage of the battery for a sufficient amount of time to cause at least a portion of the solvent to undergo a reduction reaction. The step of applying an initial charge to the battery acts to increase the irreversible capacity loss of the battery during the initial charge and provides the battery with enhanced tolerance to deep discharge conditions.

Claims

1. A method for producing a battery comprising:

providing a battery comprising a positive electrode, a negative electrode, and an electrolyte comprising a solvent and a salt, wherein the capacity of the negative electrode is less than that of the positive electrode and the negative electrode comprises an active material having an average potential versus a lithium reference electrode of greater than approximately 0.2 volts; and

applying an initial charge to the battery at a voltage that is greater than a fully charged voltage of the battery for a sufficient amount of time to cause at least a portion of the solvent to undergo a reduction reaction;

wherein the step of applying an initial charge to the battery acts to increase the irreversible capacity loss of the battery during the initial charge and provides the battery with enhanced tolerance to deep discharge conditions.

2. The method of claim 1, wherein step of applying an initial charge to the battery is performed for a sufficient amount of time to cause the potential of the negative electrode versus a lithium reference electrode to drop to a level such that an irreversible reaction occurs between the electrolyte and the negative electrode.

7. The method of claim 1, wherein during the step of applying the initial charge to the battery, the voltage of the positive electrode versus a lithium reference electrode does not reach a level sufficient to cause oxidation of the electrolyte at the positive electrode.

8. The method of claim 1, wherein step of applying an initial charge to the battery occurs at a charging rate of approximately C/10 or slower.

9. The method of claim 1, wherein the negative electrode comprises an additive configured to enhance the formation of an SEI layer.

10. The method of claim 9, wherein the additive comprises carbon.

11. The method of claim 1, wherein the electrolyte comprises ethylene carbonate.

12. The method of claim 1, wherein the active material of the negative electrode comprises a lithium titanate material.

13. The method of claim 1, wherein the reaction in which a portion of the solvent reduces acts to form a film on the negative electrode.

14. A method for manufacturing a lithium-ion battery comprising:

providing a battery having a positive electrode, a negative electrode, and an electrolyte, the negative electrode configured such that the battery is limited by the capacity of the negative electrode and comprising an active material having an average potential versus a lithium reference electrode of greater than approximately 0.2 volts; and

charging the battery during a formation process with a voltage that is greater than a fully charged voltage of the battery;

wherein during the formation process the voltage of the negative electrode versus a lithium reference electrode drops to a level where a reduction reaction occurs for at least a portion of the electrolyte;

whereby the formation process provides the battery with improved tolerance to overdischarge conditions such that the occurrence of capacity fade with repeated overdischarge cycles is reduced.

3. The method of claim 17 wherein the fully charged voltage of the battery is between approximately 2.5 and 3.0 volts and the step of applying an initial charge to the battery utilizes a voltage of between approximately 3.4 and 3.8 volts.

4. The method of claim 3, wherein the positive electrode comprises an active material and the step of applying an initial charge to the battery increases the zero volt crossing potential of the battery to a level that is greater than a decomposition potential of the active material of the positive electrode.

5. The method of claim 4, wherein the zero volt crossing potential of the battery after the step of applying the initial charge to the battery is greater than approximately 3.0 volts.

6. The method of claim 3, wherein the step of applying an initial charge to the battery is performed for a sufficient amount of time to cause the potential of the negative electrode versus a lithium reference electrode to drop to a level below approximately 0.9 volts.

15. The method of claim 14, wherein the fully charged voltage of the battery is between approximately 2.5 and 3.0 volts and the voltage applied to the battery during the formation process is between approximately 3.4 and 3.8 volts.

16. The method of claim 15, wherein the positive electrode comprises an active material and as a result of the formation process, the zero volt crossing potential of the battery is increased to a level that is greater than a decomposition potential of the active material of the positive electrode.

17. The method of claim 16, wherein the zero volt crossing potential of the battery after the formation process is greater than approximately 3.0 volts.

18. The method of claim 17, wherein the zero volt crossing potential of the battery after the formation process is greater than approximately 3.5 volts.

19. The method of claim 14, wherein during the formation process the voltage of the negative electrode versus a lithium reference electrode drops to a level below approximately 0.9 volts.

20. The method of claim 14, wherein during the formation process, the voltage of the positive electrode versus a lithium reference electrode does not reach a level sufficient to cause oxidation of the electrolyte at the positive electrode.

21. The method of claim 14, wherein the formation process uses a charging rate of approximately C/10 or slower.

22. The method of claim 14, wherein the negative electrode comprises an additive configured to enhance the formation of an SEI layer.

23. The method of claim 22, wherein the additive comprises carbon.

24. The method of claim 14, wherein the electrolyte comprises ethylene carbonate.

25. The method of claim 14, wherein the active material for the negative electrode comprises a lithium titanate material.

26. The method of claim 14, wherein the reduction of a portion of the electrolyte contributes to the formation of a film on the negative electrode.

31. The method of claim 26, wherein during the step of applying the initial charge, the voltage of the negative electrode versus a lithium reference electrode drops to less than approximately 0.9 volts.

27. A method for producing a battery comprising:

applying an initial charge to a lithium-ion battery that comprises an electrolyte, a positive electrode, and a negative electrode, the negative electrode having a lower capacity than the positive electrode and comprising a negative active material that has an average potential of greater than approximately 0.2 volts versus a lithium reference electrode;

wherein the step of applying an initial charge utilizes a voltage that is greater than a fully charged voltage of the battery and is performed for a sufficient amount of time to form a film at the negative electrode that results from the reduction of the electrolyte;

whereby the zero volt crossing potential for the battery is increased to a level greater than the decomposition potential of an active material provided on the positive electrode to provide enhanced tolerance to repeated overdischarge conditions.

28. The method of claim 27, wherein the fully charged voltage of the battery is between approximately 2.5 and 3.0 volts and step of applying an initial charge utilizes a voltage that is between approximately 3.4 and 3.8 volts.

29. The method of claim 28, wherein the positive electrode comprises an active material and after the step of applying the initial charge, the zero volt crossing potential of the battery is increased to a level that is greater than a decomposition potential of the active material of the positive electrode.

30. The method of claim 29, wherein the zero volt crossing potential of the battery after the step of applying the initial charge is greater than approximately 3.0 volts.

32. The method of claim 27, wherein the negative electrode comprises an additive configured to enhance the formation of an SEI layer.

33. The method of claim 27, wherein the negative active material comprises a lithium titanate material.

34. The method of claim 27, wherein the electrolyte comprises ethylene carbonate.