METHOD FOR DETERMINING A STATE VARIABLE OF AN ELECTROCHEMICAL CELL USING COMPLEX IMPEDANCE AT RADIOELECTRIC FREQUENCIES

• US 20130162258A1
• Filed: 12/21/2012
• Published: 06/27/2013
• Est. Priority Date: 12/23/2011
• Status: Active Grant

• Current Assignee: SAFT SA (Totalenergies Se)
• Original Assignee: SAFT SA (Totalenergies Se)
• Inventors: DESPREZ, Philippe, PATIN, Alain, FLEUREAU, Patrice, REBOUSSIN, Loc
• Granted Patent: US 9,453,884 B2
• Time in Patent Office: Days
• US Class Current: 324/427
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00
• CPC Class Codes: G01R 27/28 Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response in line transmission systems H04B3/46
• CPC Class Codes: G01R 31/001 Measuring interference from external sources to, or emission from, the device under test, e.g. EMC, EMI, EMP or ESD testing measuring electromagnetic fields G01R29/08; circuits for generating HV pulses in dielectric strength testing G01R31/14
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• 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 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A method is provided for determining a state variable such as aging of an electrochemical cell comprising an electrode plate group, that includes analyzing at least a portion of a response spectrum of the electrochemical cell to application of an electromagnetic wave in a frequency ranging from 10 kHz to 10 GHz, so as to determine an indicator of the value of the state variable.

Claims

1-17. -17. (canceled)

18. A method for determining a state variable of an electrochemical cell comprising an electrode plate group, said method comprising analyzing at least a portion of a response spectrum of the electrochemical cell to application of an electromagnetic wave in a frequency ranging from 10 kHz to 10 GHz, so as to determine an indicator of the value of said state variable.

19. The method according to claim 18, wherein the frequency ranges from 100 kHz to 10 GHz, preferably between 1 MHz to 1 GHz, more preferably between 10 MHz to GHz.

20. The method according to claim 18, wherein the value of the state variable is compared with a reference value and the electrochemical cell is considered to be defective if a difference between the value of the state variable and the reference value exceeds a predetermined threshold.

21. The method according to claim 18, wherein the value of the state variable is obtained by comparing a plot of variation of an indicator value of the state variable with a plot of the change of said indicator obtained from measurement of complex impedance of a reference cell.

22. The method according to claim 21, wherein the state variable is a parameter which varies during use of the electrochemical cell, such as its capacity, internal resistance, its state of charge, the state of aging of its electrodes, the state of aging of the electrolyte or the state of aging of the separator.

23. The method according to claim 18, comprising the steps of:

measuring complex impedance of the electrode plate group;

plotting a complex impedance spectrum of the electrode plate group, and

determining at least one resonance frequency f₀ of the complex impedance spectrum which is a frequency at which the imaginary part of the complex impedance is zero.

24. The method according to claim 23, wherein the complex impedance spectrum of the electrode plate group is plotted for a range of frequencies between 200 MHz and 1 GHz, preferably between 300 MHz and 600 MHz and wherein within said range at least one resonance frequency f₀ exists, in order to determine the state variable corresponding to the height of the electrode plate group.

25. The method according to claim 23, wherein the complex impedance spectrum of the electrode plate group is plotted for a range of frequencies between 10 MHz and 200 MHz, preferably between 50 MHz to 200 MHz and wherein within the said range at least one resonance frequency f₀ exists, in order to determine the state variable corresponding to the length of the unwound electrode plate group.

26. The method according to claim 18, comprising the steps of:

measuring complex impedance of the electrode plate group;

plotting variation for a frequency ranging from 0.01 MHz to 10 MHz, preferably between 0.1 MHz to 1 MHz, of at least one indicator selected from the real part of the complex impedance, the imaginary part of the complex impedance or a combination of these, such as the argument of the complex impedance, so as to determine a state variable, preferably aging of the electrochemical cell.

27. The method according to claim 26, including comparing a plot of variation in at least one of said indicators to a plot of variation in the same indicator or indicators obtained from measurement of complex impedance of a reference electrode plate group.

28. The method according to claim 26, wherein variation in the real part of the complex impedance as a function of frequency is represented and at least one peak exists such that a ratio:

(Remax-Max (Re1, Re2))/Remax is greater than 0.5, preferably greater than 0.75

where

Remax denotes the real part at the peak;

Re1 and Re2 denote the real parts of both bases at the peak, and

Max (Re1, Re2) denotes the maximum value of Re1 and Re2.

29. The method according to claim 27, wherein variation in the imaginary part of the complex impedance is represented as a function of frequency and at least one peak exists such that a ratio:

(Immax-Max. (Im1, Im2))/Immax is greater than 0.5, preferably greater than 0.75

where

Immax denotes the imaginary part at the peak;

Im1 and Im2 denote the imaginary parts at the two bases at the peak, and

Max (Im1, Im2) represent a maximum value of Im1 and Im2.

30. The method according to claim 18, wherein the electrochemical cell is a lithium cell, preferably a cell of the lithium-ion type.

31. A method of monitoring the manufacture of electrochemical cells, implementing a method for determining a state variable of an electrochemical cell comprising an electrode plate group, said method comprising analyzing at least a portion of a response spectrum of the electrochemical cell to application of an electromagnetic wave in a frequency ranging from 10 kHz to 10 GHz, so as to determine an indicator of the value of said state variable, wherein:

the value of the state variable is measured on each cell manufactured;

a cell is rejected if the difference between the value of the state variable measured and a reference value exceeds a predetermined threshold.

32. The monitoring method according to claim 31, comprising statistical sampling of electrochemical cells on a production line in order to monitor changes in the cells produced.

33. A computer program product comprising at least one sequence of instructions stored and accessible to a processor, wherein operation of the processor leads to the implementation of a method for determining a state variable of an electrochemical cell comprising an electrode plate group, said method comprising analyzing at least a portion of a response spectrum of the electrochemical cell to application of an electromagnetic wave in a frequency ranging from 10 kHz to 10 GHz, so as to determine an indicator of the value of said state variable.

34. A computer-readable data carrier suitable to implement at least one of the sequences of instructions of the computer program product of claim 33.