Method of charging secondary battery by varying current or voltage at an inflection point in a storage region before full charge and device therefor

• US 6,377,030 B1
• Filed: 07/29/1999
• Issued: 04/23/2002
• Est. Priority Date: 07/31/1998
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kawakami, Soichiro, Asao, Masaya
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/362,889
• Time in Patent Office: 999 Days
• Field of Search: 320/127, 320/128, 320/135, 320/148, 320/156, 320/157, 320/160, 320/161, 320/162, 320/164
• US Class Current: 320/161
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/446 Initial charging measures
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0069 Charging or discharging for charge maintenance, battery initiation or rejuvenation
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• 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

Provided is a charging method of a secondary battery capable of reducing the irreversible quantity in initial charge and discharge cycles after production of the battery and improving charge and discharge cycle characteristics. The secondary battery is at least comprised of an anode, a cathode, and an electrolyte and has a curve of anode potential or cathode potential against storage quantity, or an open-circuit voltage curve against storage quantity with inflection points. A charging operation of the secondary battery is carried out in a predetermined wave form at least until the inflection point. After passing the inflection point, until a fully charged state is achieved, the charging is performed in a different pattern from that before the inflection point.

Claims

1. A charging method for a secondary battery comprising an anode, a cathode, and an electrolyte and having an inflection point in a storage region before full charge in a potential curve of the anode, a potential curve of the cathode or an open-circuit voltage curve of the battery against storage quantity,

wherein the battery is charged while at least one of a charging current and a charging voltage is subjected to variation with time, at least until the inflection point and, after the inflection point, a charging pattern selected from the group consisting of a charging voltage and a current waveform is changed.

2. The charging method for the secondary battery according to claim 1, wherein said variation is at least one of an increase and a decrease.

3. The charging method for the secondary battery according to claim 2, wherein a waveform of said variation is selected from the group consisting of a rectangular wave, a step wave, a sawtooth wave, a sine wave, and a combination of two or more thereof.

4. The charging method for the secondary battery according to any one of claims 1 to 3, wherein said variation includes a discharge process.

5. The charging method for the secondary battery according to any one of claims 1 to 3, wherein said variation includes a rest process in which neither charge nor discharge is carried out.

6. The charging method for the secondary battery according to claim 5, wherein the secondary battery is charged at least at one of a constant current and a constant voltage, after passing over the inflection point.

7. The charging method for the secondary battery according to claim 1, wherein said charging method is used for initial charge and discharge cycles after assembly of the secondary battery.

8. The charging method for the secondary battery according to claim 7, wherein said initial charge and discharge cycles consist of 10 or fewer cycles.

9. The charging method for the secondary battery according to claim 8, wherein said initial charge and discharge cycles consist of 5 or fewer cycles.

10. The charging method for the secondary battery according to claim 1, wherein said inflection point is a point of change caused by molecular structural change of an active material forming the anode or the cathode.

11. The charging method for the secondary battery according to claim 1, wherein said inflection point is a point of change from convex to concave or from concave to convex in a function curve representing a relation of potential of the anode or potential of the cathode or open-circuit voltage of the secondary battery against storage quantity of the secondary battery, or a point at which a slope of said function curve becomes constant.

12. The charging method for the secondary battery according to claim 1, wherein the secondary battery employs an oxidation-reduction reaction of lithium ions.

13. The charging method for the secondary battery according to claim 1, wherein said anode is an electrode structure at least comprised of a current collector and a material capable of absorbing and desorbing lithium ions, which is placed on one surface or on both surfaces of the current collector, said material being selected from the group consisting of a metal, an alloy thereof, a metal oxide, a metal nitride, a carbon material, silicon, and a combination thereof.

14. The charging method for the secondary battery according to claim 13, wherein said metal or the alloy thereof is tin or a tin alloy.

15. The charging method for the secondary battery according to claim 13, wherein said metal or the alloy thereof is lithium or a lithium alloy.

16. The charging method for the secondary battery according to claim 13, wherein said inflection point and the storage quantity corresponding to the inflection point are values preliminarily measured based on a secondary battery sample having the same structure as a secondary battery subjected to a charging process.

17. A charging device for charging a secondary battery, said device comprising:

a connection portion at least capable of electrically being connected to input and output terminals of a cathode and an anode of the secondary battery;

charging means for charging the secondary battery via the connection portion;

variation means for effecting variation with time of at least one of a charging current and a charging voltage of the charging means; and

switching means for switching a charge pattern of the charging means before a predetermined charge quantity to that after said charge quantity, wherein said predetermined charge quantity is a charge quantity corresponding to an inflection point in a storage region before full charge in a potential curve of the anode, a potential curve of the cathode or an open-circuit voltage curve of the battery against storage quantity.

19. The charging device according to claim 17, said device having means for detecting at least one of a current flowing in said secondary battery and a voltage of said secondary battery.

20. The charging device according to claim 17, wherein said variation is at least one of an increase and a decrease.

21. The charging device according to claim 17, wherein a waveform of said variation is selected from the group consisting of a rectangular wave, a step wave, a sawtooth wave, a sine wave, and a combination of two or more thereof.

22. The charging device according to claim 17, wherein said variation includes a discharge process.

23. The charging device according to claim 17, wherein said variation includes a rest process in which the secondary battery is kept in an open state.

24. The charging device according to claim 17, wherein the secondary battery is charged at least at one of a constant current and a constant voltage after passing over said predetermined charge quantity.

27. The charging device according to claim 17, wherein said secondary battery has a battery pack structure in which one secondary battery or a plurality of secondary batteries connected in parallel or in series are inserted in a package.

28. The charging device according to claim 27, said device comprising means for communication with said battery pack.

18. An activation device for activating a secondary battery after assembly by charge and discharge, said device comprising:

a connection portion at least capable of electrically being connected to input and output terminals of a cathode and an anode of the secondary battery;

charging means for charging the secondary battery via the connection portion;

variation means for effecting variation with time of at least one of a charging current and a charging voltage of the charging means;

switching means for switching a charge pattern of the charging means before a predetermined charge quantity to that after said charge quantity, wherein said predetermined charge quantity is a charge quantity corresponding to an inflection point in a storage region before full charge in a potential curve of the anode, a potential curve of the cathode or an open-circuit voltage curve of the battery against storage quantity;

discharging means for discharging the secondary battery; and

second switching means for switching electrical connection or disconnection between the secondary battery and the charging means or the discharging means.

25. The activation device according to claim 18, wherein the secondary battery is subjected to repetition of 10 or fewer cycles of charge and discharge to charge the secondary battery after assembly up to a predetermined charge quantity and thereafter discharge the secondary battery down to a predetermined potential or discharge a predetermined electricity quantity.

26. The activation device according to claim 25, wherein the secondary battery is subjected to repetition of 5 or fewer cycles of charge and discharge.