METHOD FOR DETERMINING EXTENT AND TYPE OF CAPACITY FADE

• US 20100291417A1
• Filed: 05/15/2009
• Published: 11/18/2010
• Est. Priority Date: 05/15/2009
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Roessler, Mario, Ahmed, Jasim, Christensen, John F.
• Granted Patent: US 8,188,715 B2
• Time in Patent Office: Days
• US Class Current: 429/50
• 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 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method of determining extent and type of capacity fade of an electrochemical cell in one embodiment includes identifying a first volume fraction of an active material in an electrode, identifying a first capacity of the first electrode at another time, identifying a second volume fraction of the first active material based upon the first capacity, identifying a first amount of the first active material lost from the first time to the second time based upon the first volume fraction and the second volume fraction, identifying a third volume fraction of an active material in another electrode, identifying a second capacity of the second electrode at a later time, identifying a fourth volume fraction of the second active material based upon the second capacity, and identifying a second amount of the second active material lost based upon the third volume fraction and the fourth volume fraction.

Claims

1. A method of determining extent and type of capacity fade of an electrochemical cell comprising:

identifying a first volume fraction of a first active material in a first electrode at a first time;

identifying a first capacity of the first electrode at a second time;

identifying a second volume fraction of the first active material based upon the first capacity;

identifying a first amount of the first active material lost from the first electrode from the first time to the second time based upon the first volume fraction and the second volume fraction;

identifying a third volume fraction of a second active material in a second electrode at about the first time;

identifying a second capacity of the second electrode at about the second time;

identifying a fourth volume fraction of the second active material based upon the second capacity; and

identifying a second amount of the second active material lost from the second electrode from about the first time to about the second time based upon the third volume fraction and the fourth volume fraction.

2. The method of claim 1, further comprising:

identifying a fifth volume fraction of a third active material in the first electrode at about the first time;

identifying a third capacity of the first electrode at about the second time;

identifying a sixth volume fraction of the third active material based upon the third capacity; and

identifying a third amount of the third active material lost from the first electrode from about the first time to about the second time based upon the fifth volume fraction and the sixth volume fraction.

3. The method of claim 1, wherein identifying a first volume fraction comprises identifying a relationship between an open cell potential and a state of charge of the first electrode.

4. The method of claim 3, wherein identifying a third volume fraction comprises identifying a relationship between an open cell potential and a state of charge of the second electrode.

5. The method of claim 4, wherein identifying a third volume fraction comprises:

identifying an intrinsic thermodynamic relationship between the open cell potential and the state of charge of the second electrode based upon a material property of the second active material.

6. The method of claim 1, further comprising:

identifying a side reaction loss based upon the identified first amount and the identified second amount.

7. The method of claim 1, wherein the identification of the second volume fraction comprises:

determining a first dimensionless factor (θ

) based upon the identified first capacity; and

wherein the identification of the fourth volume fraction comprises;

determining a second dimensionless factor (θ

) based upon the identified second capacity.

8. The method of claim 7, wherein the identification of the second volume fraction comprises:

determining a state of charge of the first electrode using the first dimensionless factor (θ

); and

wherein the identification of the fourth volume fraction comprises;

determining a state of charge of the second electrode using the second dimensionless factor (θ

).

9. A method of determining extent and type of capacity fade of an electrochemical cell comprising:

quantifying a first change in the volume fraction of active material in a negative electrode;

quantifying a second change in the volume fraction of active material in a positive electrode;

comparing the first change and the second change; and

determining a side reaction loss based upon the comparison.

10. The method of claim 9, wherein the quantification of the first change comprises:

identifying a first volume fraction of a first active material in the negative electrode;

identifying a first capacity of the negative electrode at time later than the first volume fraction identification; and

identifying a second volume fraction of the first active material based upon the first capacity.

11. The method of claim 10, wherein the quantification of the first change further comprises:

identifying a third volume fraction of a second active material in the negative electrode;

identifying a second capacity of the negative electrode at time later than the third volume fraction identification; and

identifying a fourth volume fraction of the second active material based upon the second capacity.

12. The method of claim 10, wherein the quantification of the second change comprises:

identifying a fifth volume fraction of a third active material in the positive electrode;

identifying a third capacity of the positive electrode at time later than the fifth volume fraction identification; and

identifying a sixth volume fraction of the third active material based upon the third capacity.

13. The method of claim 10, wherein identifying a first volume fraction comprises identifying a relationship between an open cell potential and a state of charge of the negative electrode.

14. The method of claim 13, wherein the quantification of the second change comprises:

identifying an initial relationship between an open cell potential and a state of charge of the positive electrode;

identifying a third capacity of the positive electrode at time later than the initial relationship identification; and

identifying a sixth volume fraction of the third active material based upon the third capacity.

15. The method of claim 14, wherein the identification the initial relationship between an open cell potential and a state of charge of the positive electrode comprises:

identifying an intrinsic thermodynamic relationship between the open cell potential and the state of charge of the positive electrode based upon a material property of the active material in the positive electrode.

16. The method of claim 9, wherein the quantification of the first change comprises:

determining a first dimensionless factor (θ

) based upon an identified capacity of the negative electrode; and

wherein the quantification of the second change comprises;

determining a second dimensionless factor (θ

) based upon an identified capacity of the positive electrode.

17. The method of claim 16, wherein the quantification of the first change comprises:

determining a state of charge of the negative electrode using the first dimensionless factor (θ

); and

wherein the quantification of the second change comprises;

determining a state of charge of the positive electrode using the second dimensionless factor (θ

).