IN-SITU BATTERY DIAGNOSIS METHOD USING ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY

• US 20120078552A1
• Filed: 09/22/2011
• Published: 03/29/2012
• Est. Priority Date: 09/27/2010
• Status: Active Grant

• Current Assignee: IFP Energies Nouvelles
• Original Assignee: IFP Energies Nouvelles
• Inventors: Sauvant-Moynot, Valérie, MINGANT, Remy, Bernard, Julien
• Granted Patent: US 8,849,598 B2
• Time in Patent Office: Days
• US Class Current: 702/63
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

Method of estimating the internal state of an electrochemical system for electric power storage, such as a battery.

The SoC and the electrochemical impedance are determined for various internal states of an electrochemical system of the same type as the electrochemical system studied. An electrochemical impedance model is then defined as a function of the SoC and of parameters. These parameters are calibrated through adjustment on the electrochemical impedance measurements obtained for the various internal states. The electrochemical impedance Z of the system studied is determined and its SoC is estimated using the model applied to electrochemical impedance Z.

Claims

1. A method of estimating an internal state of at least a first electrochemical system for electric power storage, wherein at least one property relative to the internal state of said first electrochemical system is estimated from electrochemical impedance measurements, characterized in that it comprises the following stages:

for various internal states of at least a second electrochemical system of the same type as said first electrochemical system;

-measuring said property relative to the internal state of said second system; and

-measuring the electrochemical impedance of said second electrochemical system at least at one frequency;

defining an electrochemical impedance model as a function of said property and of parameters, and calibrating said parameters by means of an adjustment on said electrochemical impedance measurements obtained for said internal states;

determining an electrochemical impedance Z of said first electrochemical system for at least one frequency,

estimating the internal state of said first electrochemical system by estimating said property relative to the internal state of said electrochemical system using said model and said electrochemical impedance Z.

2. A method as claimed in claim 1, wherein said property relative to the internal state of said electrochemical system is estimated by means of the following stages:

i. selecting an initial value for said property;

ii. applying said model to said initial value for modelling an electrochemical impedance Zm of said first system for at least one frequency;

iii. adjusting said value so that the modelled electrochemical impedance Zm corresponds to the measured electrochemical impedance Z.

3. A method as claimed in claim 1, wherein said electrochemical impedance model is constructed by carrying out the following stages:

i. selecting a representative impedance diagram curve shape obtained on an electrochemical system of the same type as said first electrochemical system

ii. defining said model by a formula allowing to reproduce said curve shape.

4. A method as claimed in claim 3, wherein a model of the type as follows is used:

5. A method as claimed in claim 1, wherein said various internal states are obtained through accelerated aging of a second electrochemical system for electric power storage of the same type as said first electrochemical system.

6. A method as claimed in claim 1, wherein said various internal states are obtained by selecting a set of second electrochemical systems of the same type as said first electrochemical system, said systems of said set having different internal states.

7. A method as claimed in claim 1, wherein at least one of the properties relative to the internal state of said electrochemical system is calculated:

a state of charge (SoC) of said system, a state of health (SoH) of said system.

8. A method as claimed in claim 1, wherein the electrochemical impedance is determined for various frequencies by measuring electric impedance diagrams obtained by adding an electric signal to a current running through said electrochemical system.

9. A method as claimed in claim 8, wherein said electric impedance diagrams are measured by applying a sinusoidal current perturbation to said electrochemical system and by measuring an induced sinusoidal voltage at the terminals of said electrochemical system.

10. A method as claimed in claim 8, wherein said electric impedance diagrams are measured by applying a current perturbation in form of a superposition of several sinusoids or in form of a white noise, on said electrochemical system, and by measuring an induced sinusoidal voltage at the terminals of said electrochemical system.

11. A method as claimed in claim 1, wherein the electrochemical impedance is determined for several frequencies by measuring electric impedance diagrams obtained using a non-invasive method comprising processing the voltage signal and the current signal as a function of time.

12. A method as claimed in claim 1, wherein said electrochemical system is at rest or in operation.

13. A method as claimed in claim 1, wherein said electrochemical system is a battery or an element of a pack.

14. A method as claimed in claim 1, wherein a failure of at least one element of a battery pack is detected by determining the state of function (SoF) of at least one element of said pack.

15. A system of estimating an internal state of an electrochemical system for electric power storage, comprising:

at least one detector (G) including a means of measuring or estimating the electrochemical impedance of said electrochemical system;

a memory allowing to store an electrochemical impedance model as a function of said property, said model being first calibrated by means of measurements for various internal states of at least a second electrochemical system of the same type as said electrochemical system;

means for calculating a property relative to the internal state of said electrochemical system using said model.

16. A smart battery management or charge/discharge system comprising a system for estimating an internal state of said battery as claimed in claim 15.