Battery State of Health Assessment System

• US 20100090650A1
• Filed: 08/07/2009
• Published: 04/15/2010
• Est. Priority Date: 08/03/2005
• Status: Active Grant

• Current Assignee: California Institute of Technology, Centre National De La Recherche Scientifique
• Original Assignee: California Institute of Technology, Centre National De La Recherche Scientifique
• Inventors: McMenamin, Joseph, Yazami, Rachid, Reynier, Yvan, Fultz, Brent T.
• Granted Patent: US 8,446,127 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/443 in response to temperature
• 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: H01M 10/486 for measuring temperature
• CPC Class Codes: H01M 10/657 by electric or electromagnetic means
• CPC Class Codes: H01M 10/6571 Resistive heaters arrangements for heating the battery by its resistance to the internal current H01M10/637
• CPC Class Codes: H01M 10/6572 Peltier elements or thermoelectric devices
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Described herein are systems and methods for accurately characterizing thermodynamic and materials properties of electrodes and electrochemical energy storage and conversion systems. Enhanced sensitivity provided by the present methods and systems combined with measurement conditions that reflect thermodynamically stabilized electrode conditions allow very accurate measurement of thermodynamic parameters, including state functions such as the Gibbs free energy, enthalpy and entropy of electrode/electrochemical cell reactions, that enable prediction of important performance attributes of electrode materials and electrochemical systems, such as the energy, power density, current rate, the cycle life and the state of health of an electrochemical cell. Also provided are systems and methods for charging electrochemical cells; for example, systems and methods for charging an electrochemical according to its state of health.

Claims

1. A method of characterizing the state of health of an electrochemical cell comprising a host material, the method comprising the steps of:

determining Δ

G, Δ

S and/or Δ

H of the electrochemical cell for a plurality of selected electrochemical cell compositions;

determining states of charge of the electrochemical cell for each of the plurality of selected electrochemical cell compositions;

identifying the states of charge and Δ

G, Δ

S and/or Δ

H corresponding to an event or condition of the electrochemical cell; and

comparing the Δ

G, Δ

S and/or Δ

H corresponding to the event or condition of the electrochemical cell to reference Δ

G, Δ

S and/or Δ

H corresponding to the event or condition of a reference electrochemical cell.

2. The method of claim 1, wherein the event or condition is selected from the group consisting of:

a 0% charge state of the electrochemical cell, a 100% charge state of the electrochemical cell, a partial charge state of the electrochemical cell and a phase transition taking place within the electrochemical cell.

3. The method of claim 1, wherein the selected electrochemical cell compositions correspond to compositions of an electrode of the electrochemical cell, compositions of an electrolyte of the electrochemical cell, or compositions or more than one electrode of the electrochemical cell.

4. The method of claim 1, wherein the reference Δ

G, Δ

S and/or Δ

H are Δ

G, Δ

S and/or Δ

H for the electrochemical cell at a previous charge/discharge cycle.

5. The method of claim 1, wherein the plurality of electrochemical cell compositions corresponds to a plurality of states of charge of the electrochemical cell for a single electrochemical cell temperature.

6. The method of claim 1, further comprising a step of controlling and/or monitoring the temperature of the electrochemical cell.

7. The method of claim 1, wherein the step of determining Δ

G, Δ

S and/or Δ

H of the electrochemical cell for a plurality of selected electrochemical cell compositions comprises the steps of;

controlling the composition of the electrochemical cell to establish a plurality of selected electrochemical cell compositions;

controlling the temperature of the electrochemical cell to establish a plurality of selected electrochemical cell temperatures for each of the selected electrochemical cell compositions;

measuring open circuit voltages of the electrochemical cell as a function of time for the selected electrochemical cell compositions and temperatures; and

identifying open circuit voltages for thermochemically stabilized conditions of the electrochemical cell for the selected electrochemical cell compositions and temperatures.

8. The method of claim 7, further comprising the step of:

determining the change in open circuit voltages of the electrochemical cell for thermochemically stabilized conditions between two or more of the selected electrochemical temperatures for each of the selected electrochemical cell compositions.

9. The method of claim 7, further comprising the step of:

generating plots of the open circuit voltages of the electrochemical cell for thermochemically stabilized conditions versus temperature for each of the selected electrochemical cell compositions.

10. The method of claim 9, further comprising the step of:

determining slopes and intercepts for each plot, wherein the slopes correspond to Δ

S and the intercepts correspond to Δ

H.

21. The system of claim 18, wherein the means for characterizing the state of health of the electrochemical cell comprises a system configured for performing the method of claim 1.

11. A method of charging an electrochemical cell comprising a host material, the method comprising the steps of:

characterizing the state of health of the electrochemical cell;

selecting a charging voltage and/or current according to the characterized state of health of the electrochemical cell; and

providing the selected voltage and/or current to electrodes of the electrochemical cell to charge the electrochemical cell.

12. The method of claim 11, wherein the state of health of the electrochemical cell is a function of the number of charge/discharge cycles the electrochemical cell has experienced.

13. The method of claim 11, wherein the voltage and/or current provided to the electrochemical cell is preselected according to the number of charge/discharges cycles the electrochemical cell has experienced.

14. The method of claim 11, wherein the step of characterizing the state of health of the electrochemical cell comprises the steps of:

determining Δ

G, Δ

S and/or Δ

H of the electrochemical cell for a plurality of selected electrochemical cell compositions;

determining states of charge of the electrochemical cell for each of the plurality of selected electrochemical cell compositions;

identifying the states of charge and Δ

G, Δ

S and/or Δ

H corresponding to an event or condition of the electrochemical cell; and

comparing the Δ

G, Δ

S and/or Δ

H corresponding to the event or condition of the electrochemical cell to reference Δ

G, Δ

S and/or Δ

H corresponding to the event or condition of a reference electrochemical cell.

15. The method of claim 11, wherein when the characterized state of health corresponds to a first state of health of the electrochemical cell, a first charging voltage is selected and wherein when the characterized state of health corresponds to a second state of health of the electrochemical cell, a second charging voltage less than the first charging voltage is selected.

16. The method of claim 11, wherein when the characterized state of health corresponds to a charge/discharge cycle number of 20 to 2000, the charging voltage is selected over the range of 1.5-5.5 volts.

17. The method of claim 11, wherein when the characterized state of health corresponds to a charge/discharge cycle number of 200 to 1000, the charging voltage is selected over the range of 2.5-5.3 volts.

18. A system for charging an electrochemical cell comprising a host material, the system comprising:

means for delivering a voltage and/or current to electrodes of the electrochemical cell;

means for characterizing a state of health of the electrochemical cell; and

a control circuit for;

receiving the characterized state of health; and

controlling the means for delivering a voltage and/or current.

19. The system of claim 18, wherein the means for delivering a voltage and/or current comprises a voltage and/or current source.

20. The system of claim 18, wherein the means for delivering a voltage and/or current comprises a voltage and/or current controller.

22. The system of claim 18, wherein the means for characterizing the state of health of the electrochemical cell comprises a system configured for performing a method comprising the steps of:

determining changes in entropy, enthalpy or free energy of the electrochemical cell for a plurality of selected electrochemical cell compositions;

determining states of charge of the electrochemical cell for each of the plurality of selected electrochemical cell compositions;

identifying the states of charge and changes in entropy, enthalpy or free energy corresponding to an event or condition of the electrochemical cell; and

comparing the changes in entropy, enthalpy or free energy corresponding to the event or condition of the electrochemical cell to reference changes in entropy, enthalpy or free energy corresponding to the event or condition of a reference electrochemical cell.

23. The system of claim 18, wherein the means for characterizing the state of health of the electrochemical cell comprises:

a means for measuring open circuit voltages of the electrochemical cell as a function of time;

a composition controller electrically connected to the electrochemical cell for establishing selected electrochemical cell compositions corresponding to different stoichiometries of a species incorporated with a host material of the electrochemical cell, the composition controller configured for establishing a plurality of the selected compositions;

a temperature controller in thermal contact with the electrochemical cell for establishing a plurality of selected electrochemical cell temperatures for each of the selected compositions, thereby establishing a plurality of selected electrochemical cell temperature and composition combinations; and

an open circuit voltage analyzer for receiving open circuit voltage measurements as a function of time from the means for measuring open circuit voltages and for identifying open circuit voltages for thermochemically stabilized conditions of the electrochemical cell for the selected electrochemical cell temperature and compositions combinations.

24. The system of claim 18, wherein the control circuit selectively provides voltage and/or current to electrodes of the electrochemical cell from the means for delivering a voltage and/or current.

25. The system of claim 18, wherein the voltage and/or current delivered to the electrodes of the electrochemical cell from the means for delivering a voltage and/or current is determined by the control circuit based upon the characterized state of health of the electrochemical cell.

26. The system of claim 18, wherein the electrochemical cell is a battery in a mobile electronic device.

27. The system of claim 18, wherein the system comprises a component of a mobile electronic device.

28. The system of claim 18, configured for performing a method comprising the steps of:

characterizing the state of health of the electrochemical cell;

selecting a charging voltage and/or current according to the characterized state of health of the electrochemical cell; and

providing the selected voltage and/or current to electrodes of the electrochemical cell to charge the electrochemical cell.

29. The method of claim 28, wherein the monitoring step comprises measuring a plurality of open circuit voltages of the electrochemical cell.

30. The method of claim 28, further comprising the step of monitoring a voltage profile of the electrochemical cell over at least one charge cycle.

31. The method of claim 28, further comprising the step of monitoring a temperature of the electrochemical cell over at least one discharge cycle.

32. The method of claim 28, further comprising the step of monitoring a temperature of the electrochemical cell over at least one charge cycle.

28-1. A method of charging an electrochemical cell in a mobile electronic device, the method comprising the steps of:

monitoring a voltage profile of the electrochemical cell over at least one discharge cycle;

determining a charging voltage and/or current based upon the monitored discharge voltage profile; and

providing the charging voltage and/or current to electrodes of the electrochemical cell, thereby charging the electrochemical cell.