Method and device for judging the condition of secondary batteries and method for regenerating secondary batteries

• US 20010028238A1
• Filed: 02/09/2001
• Published: 10/11/2001
• Est. Priority Date: 08/10/1998
• Status: Abandoned Application

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Ito, Takashi, Nakamura, Kenji, Minohara, Taketoshi
• Application Number:
  US09/779,466
• Publication Number:
  US 20010028238A1
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: H01M 10/4242 Regeneration of electrolyte or reactants
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The internal resistance related value which is related to the internal resistance of a secondary battery is compared with a previously obtained relation between the internal resistance related value and battery condition to judge the battery condition of the secondary battery. Since the internal resistance related value is a value related to the internal resistance which closely depends on the battery condition, the battery condition can be judged in detail based on the above relation. And the internal resistance related value can be obtained more speedily with a predetermined method. On the other hand, when the level of the degradation of a negative electrode is low, an electrolyte is supplemented, and when the level of the degradation of the negative electrode is high, a reducing agent is added to the electrolyte to regenerate the secondary battery. With this regenerating method, the performance of the negative electrode can be recovered without degrading a positive electrode.

Claims

1. A method for judging the condition of a secondary battery, characterized in that the method comprises the steps of varying a charging current or discharging current of the secondary battery, calculating a quantity of electricity, which is related to a follow-up variation characteristic of a terminal voltage of the secondary battery, relative to a variation of said charging current or discharging current, and judging the condition related to the charging and discharging performance of the secondary battery based on said quantity of electricity.

2. A method as claimed in

claim 1

, wherein said charging current or discharging current is varied stepwise between predetermined two electric currents, and said quantity of electricity is calculated based on a variation wave form of said terminal voltage after the variation of said charging current or discharging current starts stepwise.

3. A method as claimed in

claim 2

, wherein said quantity of electricity includes a first quantity of electricity, which is related to the variation of said terminal voltage at the time said terminal voltage rapidly varies just after the variation of said charging current or discharging current starts stepwise, and a second quantity of electricity, which is related to the variation of said terminal voltage while said terminal voltage gently varies after varying rapidly.

4. A method as claimed in

claim 3

, wherein said quantity of electricity is calculated based on a first quantity of electricity, which is composed of the variation of said terminal voltage at the time said terminal voltage rapidly varies just after the variation of said charging current or discharging current starts stepwise, and/or a second quantity of electricity, which is composed of the variation of said terminal voltage during a predetermined period of time while said terminal voltage gently varies after varying rapidly.

5. A method as claimed in

claim 4

, wherein the battery performance is judged low when said first quantity of electricity or second quantity of electricity exceeds a predetermined threshold.

6. A method as claimed in

claim 2

, wherein said charging current or discharging current is varied stepwise between electric current 0 and a predetermined electric current.

7. A method as claimed in

claim 1

, wherein said quantity of electricity is calculated based on a relation between an AC current component composed of said charging current or discharging current, which periodically varies with a predetermined frequency, and an AC voltage component having the predetermined frequency, which is included in said terminal voltage.

8. A method as claimed in

claim 1

, wherein in the case of an internal impedance of the secondary battery being defined as a parallel impedance composed of a predetermined parallel resistance and parallel electrostatic capacity, which are connected in parallel, and a serial resistance connected in series with the parallel impedance, said quantity of electricity includes a quantity of electricity, which varies with an impedance value of said parallel impedance, or a resistance of said parallel resistance, and a quantity of electricity, which varies with a resistance of said serial resistance.

9. A method as claimed in

claim 8

, wherein the level of the degradation of an ion conduction performance of an electrolyte is estimated based on said resistance of said serial resistance.

10. A method as claimed in

claim 8

, wherein an increase of a film thickness on surfaces of electrodes is estimated based on said impedance value of said parallel impedance or said resistance of said parallel resistance.

11. A method for judging the condition of a secondary battery, characterized in that the method comprises the steps of:

interrupting charging or discharging after charging or discharging with a predetermined current is performed in the secondary battery for a predetermined period of time, obtaining a voltage difference between a terminal voltage measured between a positive electrode terminal and negative electrode terminal when charging or discharging is interrupted, and a terminal voltage measured after charging or discharging is interrupted to obtain an internal resistance related value, which is related to an internal resistance of the secondary battery, based on said voltage difference and said predetermined current; and

comparing said internal resistance related value with a previously obtained relation between said internal resistance related value and battery condition, thereby judging the battery condition of the secondary battery.

12. A method as claimed in

claim 11

, wherein said internal resistance related value is obtained based on said voltage difference obtained in a predetermined period of time when the variation rate of said terminal voltage is a predetermined rate or more after charging or discharging is stopped, and said predetermined electric current.

13. A method as claimed in

claim 11

, wherein said internal resistance related value is obtained based on said voltage difference which is obtained in a predetermined period of time when a variation rate of said terminal voltage is less than a predetermined rate after charging or discharging is interrupted, and said predetermined electric current.

14. A method as claimed in one of claims 12 and 13, wherein said predetermined rate is a variation rate of said terminal voltage at the time an approximately linear variation of said terminal voltage is finished just after charging or discharging is interrupted.

15. A method as claimed in one of claims 12 and 13 wherein said internal resistance related value is a resistance calculated using the formula of (voltage difference/predetermined electric current).

16. A method for judging the condition of a secondary battery, characterized in that the method comprises the steps of detecting a quantity of electricity, which is related to an impedance of the secondary battery, or a quantity of electricity, which is related to a maximum power density by applying an AC voltage to the secondary battery, and judging the performance of the secondary battery based on said detected quantity of electricity.

17. A method as claimed in

claim 16

, wherein said maximum power density as the discharging performance of the secondary battery is obtained based on said quantity of electricity, which is related to said impedance.

18. A method as claimed in

claim 16

, wherein said quantity of electricity is obtained after or while charging and discharging is performed for initial activation of the secondary battery, and an initial power activity of the secondary battery is judged based on the obtained quantity of electricity.

19. A method as claimed in

claim 18

, wherein said initial power activity of the secondary battery is judged to exceed a predetermined level where said quantity of electricity is within a predetermined range to finish charging and discharging for initial activation of the secondary battery.

20. A method as claimed in

claim 18

, wherein said initial power activity of the secondary battery is judged less than a predetermined level where said quantity of electricity is not within a predetermined range to start charging and discharging for initial activation of the secondary battery, again.

21. A method as claimed in

claim 16

, wherein the power degradation of the secondary battery is judged based on the obtained quantity of electricity.

22. A method as claimed in

claim 18

, wherein the life of the secondary battery is judged to end where said quantity of electricity is outside a predetermined range.

23. A method as claimed in one of claims 16 through 22, wherein said quantity of electricity is composed of an AC impedance related quantity of electricity, which is related to an AC impedance component including a component varying with the frequency of the AC voltage, out of the impedance of the secondary battery.

24. A method as claimed in

claim 16

, wherein the quantity of electricity related to the component of the impedance of the secondary battery, which does not vary with the frequency component of the AC voltage, is obtained as a DC impedance related quantity of electricity, the quantity of electricity related to the component of the impedance of the secondary battery, which varies with the frequency component of the AC voltage, is obtained as an AC impedance related quantity of electricity, and the secondary battery is judged good when both said DC impedance related quantity of electricity and said AC impedance related quantity of electricity are respectively predetermined values or less while the secondary battery is judged inferior when both said DC impedance related quantity of electricity and said AC impedance related quantity of electricity are respectively more than predetermined values.

25. A method as claimed in

claim 16

, wherein by applying an AC voltage of a large number of frequency values within a predetermined frequency band to the secondary battery, a real axis component and imaginary axis component of said impedance of the secondary battery are obtained against each frequency value, and said quantity of electricity, which is related to the impedance, is calculated from the obtained real axis component and imaginary axis component.

26. A method as claimed in

claim 25

, wherein said AC impedance component is calculated based on a diameter of a circular arc-shaped locus of said impedance in a two-dimensional plane of which axes are said real axis component and said imaginary axis component.

27. A device for judging the condition of a secondary battery, characterized in that the device comprises:

a voltage applying element for applying AC voltages having a large number of different frequencies to the secondary battery simultaneously or successively;

a terminal voltage detecting element for detecting a terminal voltage of the secondary battery against each frequency;

a current detecting element for detecting the electric current of the secondary battery against each frequency;

an AC impedance component detecting element for detecting the AC impedance component of the secondary battery, which varies with the frequency of the applied AC voltage, based on the detected terminal voltage and electric current; and

a discharging performance judging element for judging at least the discharging performance of the secondary battery based on said AC impedance component.

30. A device as claimed in one of claims 27 through 29, further comprising a bias voltage applying element for applying a bias voltage adapted to hold the secondary battery in a slightly discharging condition at the time the terminal voltage and electric current are detected.

28. A device for judging the condition of the secondary battery, characterized in that the device comprises:

an AC voltage applying element for applying AC voltages having a large number of different frequencies to the secondary battery simultaneously or successively;

a terminal voltage detecting element for detecting a terminal voltage of the secondary battery against each frequency;

a current detecting element for detecting the electric current of the secondary battery against each frequency;

a DC impedance component detecting element for detecting the DC impedance of the secondary battery, which does not vary with the frequency of the applied AC voltage, based on the detected terminal voltage and electric current; and

a discharging performance judging element for determining whether the detected DC impedance related quantity of electricity is a predetermined value or less and judging at least the discharging performance of the secondary battery based on the AC impedance component.

29. A device as claimed in

claim 28

, further comprising an AC impedance component detecting element for detecting the AC impedance component of the secondary battery, which varies with the frequency of the applied AC voltage, based on the detected terminal voltage and electric current, wherein said discharging performance judging element determines whether the detected DC impedance related quantity of electricity and detected AC impedance related quantity of electricity are respectively predetermined values or less and judges at least the discharging performance of the secondary battery.

31. A method for judging the condition of a secondary battery, characterized in that the method comprises the steps of obtaining a first resistance component mainly composed of an ion conduction resistance of an electrolyte by a predetermined method as an internal resistance related value which is related to the internal resistance of the secondary battery, and comparing said first resistance component with a previously obtained relation between the first resistance component and battery condition to judge the condition of the secondary battery.

41. A method as claimed in

claim 31

, wherein charging or discharging is interrupted after charging or discharging of the secondary battery with a predetermined current is performed for a predetermined period of time, a voltage difference between a terminal voltage measured between a positive electrode terminal and negative electrode terminal at the time charging or discharging is interrupted, and a terminal voltage measured after charging or discharging is interrupted, is obtained, and said first resistance component is obtained based on said voltage difference and predetermined current.

42. A method as claimed in

claim 41

, wherein said first resistance component is obtained based on said voltage difference which is obtained in a predetermined period of time when the variation rate of said terminal voltage is a predetermined value or more after charging or discharging is interrupted, along with said predetermined electric current.

45. A method as claimed in

claim 31

, wherein a real axis component value and imaginary axis component value of an impedance are measured against each frequency value by applying AC voltages having a large number of frequency values within a predetermined frequency band to the secondary battery, a circular arc-shaped locus of said impedance is obtained in a plane co-ordinate wherein a real axis and imaginary axis perpendicularly intersect each other with said real axis component value being as the real axis component, and said imaginary axis component value being as the imaginary axis component, and the distance between an intersection of said circular arc-shaped locus and the imaginary axis, and an origin of said plane co-ordinate is obtained, thereby obtaining said first resistance component.

58. A method for regenerating a secondary battery, characterized in that the condition of the secondary battery is judged with the method of one of claims 31 through 50, and when the level of the degradation of a negative electrode is judged low, an electrolyte is only supplied, and when the level of the degradation of said negative electrode is judged high, a reducing agent is added to the electrolyte.

32. A method for judging the condition of a secondary battery, characterized in that the method comprises the steps of obtaining a second resistance component mainly composed of a reaction resistance of electrodes by a predetermined method as an internal resistance related value which is related to the internal resistance of the secondary battery, and comparing said second resistance component with a previously obtained relation between the second resistance component and battery condition to judge the condition of the secondary battery.

43. A method as claimed in

claim 32

, wherein charging or discharging is stopped after charging or discharging with a predetermined current is performed in the secondary battery for a predetermined period of time, a voltage difference between a terminal voltage measured between a positive electrode terminal and negative electrode terminal at the time charging or discharging is interrupted, and a terminal voltage measured after charging or discharging is interrupted, is obtained, and said second resistance component is obtained based on said voltage difference and predetermined electric current.

44. A method as claimed in

claim 43

, wherein said internal resistance related value is obtained based on said voltage difference which is obtained in a predetermined period of time when the variation rate of said terminal voltage is less than a predetermined rate after charging or discharging is stopped, along with the predetermined electric current.

46. A method as claimed in

claim 32

, wherein a real axis component value and imaginary axis component value of an impedance are measured against each frequency value by applying AC voltages having a large number of frequency values within a predetermined frequency band to the secondary battery, a circular arc-shaped locus of said impedance is obtained in a plane co-ordinate wherein a real axis and imaginary axis perpendicularly intersect each other with said real axis component value being as the real axis component, and said imaginary axis component value being as the imaginary axis component, and the diameter of a circular component of a circular arc-shaped locus is obtained, thereby obtaining said second resistance component.

47. A method as claimed in

claim 46

, wherein the condition of the secondary battery is judged by comparing said second resistance component of the secondary battery with a previously obtained relation between the second resistance component and the maximum power density.

33. A method for judging the condition of a secondary battery, characterized in that the method comprising the steps of obtaining a first resistance component mainly composed of a ion conduction resistance of an electrolyte, and a second resistance component mainly composed of a reaction resistance of electrodes respectively by a predetermined method as the internal resistance related values which are related to the internal resistance of the secondary battery, and comparing both the first and second resistance components with a previously obtained relation between the first and second resistance components and the battery condition to judge the condition of the secondary battery.

36. A method as claimed in

claim 33

, wherein a degradation judgement standard of a sum of said first resistance component and second resistance component, which is a border value between a normal condition and degraded condition of a reference battery equivalent to the secondary battery, is previously obtained, and said sum of said first and second resistance components which are obtained in the secondary battery is compared with said degradation judgement standard to judge whether the secondary battery is in a normal condition or degraded condition.

34. A method for judging the condition of a secondary battery, characterized in that the method comprises the steps of obtaining a first resistance component mainly composed of a ion conduction resistance of an electrolyte, and a second resistance component mainly composed of a reaction resistance of electrodes respectively by a predetermined method as the internal resistance related values which are related to the internal resistance of the secondary battery, and obtaining a resistance component ratio showing the ratio of the first resistance component and second resistance component, and comparing said resistance component ratio with a previously obtained relation between the resistance component ratio and the battery condition to judge the condition of the secondary battery.

35. A method as claimed in

claim 34

, wherein said resistance component ratio is calculated by the formula of arctan (second resistance component/first resistance component).

37. A method as claimed in one of claims 34 and 35, wherein said degraded condition is divided into a first degraded condition which is mainly caused by an increase of an ion conduction resistance, a second degraded condition which is mainly caused by an increase of both the ion conduction resistance and an increase of a reaction resistance, and a third degraded condition which is mainly caused by an excessive increase of the reaction resistance when the secondary battery is judged to be in the degraded condition, a first border value as a border value between said first degraded condition and second degraded condition relative to said previously obtained resistance component ratio, and a second border value as a border value between said second degraded condition and third degraded condition relative to said previously obtained resistance component ratio are respectively obtained, the resistance component ratio obtained in the secondary battery is compared with said first border value and second border value to judge whether the secondary battery is in said first degraded condition, second degraded condition or third degraded condition.

59. A method for regenerating a secondary battery, characterized in that the condition of the secondary battery is judged with the method of

claim 37

or

40

, and when the secondary battery is judged to be in the first degraded condition, an electrolyte is only supplied, and when the secondary battery is judged to be in the second degraded condition, a reducing agent is added to the electrolyte.

60. A method for regenerating a secondary battery, characterized in that the condition of the secondary battery is judged with the method of

claim 37

or

40

, and when the secondary battery is judged to be in the first degraded condition, an electrolyte is only supplied, and when the secondary battery is judged to be in the second degraded condition, a negative electrode is taken from a battery container and is subjected to a reducing treatment.

61. A method for regenerating a secondary battery, characterized in that the condition of the secondary battery is judged with the method of

claim 37

or

40

, and when the secondary battery is judged to be in the first degraded condition, an electrolyte is only supplied, when the secondary battery is judged to be in the second degraded condition, a negative electrode is taken from a battery container and is subjected to a reducing treatment, and in said reducing treatment, a negative electrode active material is mechanically separated from said negative electrode in a non oxidized liquid and is subjected to the reducing treatment.

38. A method for judging the condition of a secondary battery, characterized in that the method comprises the steps of obtaining a first resistance component mainly composed of an ion conduction resistance of an electrolyte, and a second resistance component mainly composed of a reaction resistance of electrodes respectively by a predetermined method as the internal resistance related value which is related to the internal resistance of the secondary battery, plotting an internal resistance co-ordinate showing a co-ordinate of the internal resistance of the secondary battery in a plane co-ordinate of which one axis component is the first resistance component and the other axis component is the second resistance component, and comparing the internal resistance co-ordinate with a previously obtained relation between the internal resistance co-ordinate and battery condition, which has been previously plotted on the plane co-ordinate, to judge the condition of the secondary battery.

39. A method as claimed in

claim 38

, wherein a normal region as a set region of the internal resistance co-ordinate where a reference battery equivalent to the secondary battery is in a normal condition, and a degradation region as a set region of the internal resistance co-ordinate where the reference battery is in a degraded condition, are previously investigated and plotted in said plane co-ordinate, the position of the internal resistance co-ordinate of the secondary battery relative to said normal region and degradation region is investigated to judge whether the secondary battery is in a normal condition or degraded condition.

40. A method as claimed in one of claims 38 and 39, wherein the degraded condition is divided into a first degraded condition which is mainly caused by an increase of an ion conduction resistance, a second degraded condition which is mainly caused by an increase of the ion conduction resistance and a reaction resistance, and a third degraded condition which is mainly caused by an excessive increase of the reaction resistance when the secondary battery is judged to be in the degraded condition, a first degradation region as a set region of the internal resistance co-ordinate where a reference battery equivalent to the secondary battery is in the first degraded condition, a second degradation region as a set region of the internal resistance co-ordinate where the reference battery is in a second degraded condition and a third degradation region as a set region of the internal resistance co-ordinate where the reference battery is in a third degraded condition are previously investigated respectively, and plotted in the plane co-ordinate, the position of the internal resistance co-ordinate of the secondary battery relative to the first degradation region, second degradation region and third degradation region is investigated to judge whether the secondary battery is in the first degradation region, second degradation region or third degradation region.

48. A method for judging the condition of a secondary battery, characterized in that the method comprises the steps of judging the level of the degradation of a negative electrode low when the average thickness of an oxidized layer formed on a surface of an active material of said negative electrode of the secondary battery is less than a predetermined standard, and judging the level of the degradation of the negative electrode high when the average thickness of said oxidized layer is the predetermined standard or more.

49. A method as claimed in

claim 48

, wherein said predetermined standard is the average thickness of said oxidized layer, which is measured at the time a discharge capacity of a reference battery equivalent to the secondary battery rapidly decreases or an internal resistance of the reference battery rapidly increases.

50. A method as claimed in

claim 49

, wherein the average thickness of said oxidized layer as the standard is 1000 nm.

51. A method for regenerating a secondary battery, characterized in that an electrolyte is only supplemented when the level of the degradation of a negative electrode is low, and a reducing agent is added to said electrolyte when the level of the degradation of said negative electrode is high.

52. A method as claimed in

claim 51

, wherein the level of the degradation of said negative electrode is judged low, and said electrolyte is only supplied when the average thickness of said oxidized layer which is formed on said surface of said active material of said negative electrode is less than a predetermined standard, and the level of the degradation of said negative electrode is judged high, and the reducing agent is added to the electrolyte when the average thickness of said oxidized layer is the predetermined standard or more.

53. A method as claimed in

claim 52

, wherein said standard is the average thickness of said oxidized layer, which is measured at the time the discharge capacity of a reference battery equivalent to the secondary battery rapidly decreases or the internal resistance of the reference battery rapidly increases.

54. A method as claimed in

claim 53

, wherein the average thickness of said oxidized layer as said standard is 1000 nm.

57. A method as claimed in one of claims 51 through 56, wherein said secondary battery is a nickel-hydrogen battery including a negative electrode of which a negative electrode active material is a hydrogen-occluding alloy, and an electrolyte interposed between a positive electrode and said negative electrode.

55. A method for regenerating a secondary battery, characterized in that an electrolyte is only supplemented when the level of the degradation of a negative electrode is low, and said negative electrode is taken from a battery container and is subjected to a reducing treatment when the level of the degradation of said negative electrode is high.

56. A method as claimed in

claim 55

, wherein a negative electrode active material is mechanically separated from said negative electrode in a nonoxidized liquid, and is subjected to a reducing treatment.