METHOD OF ESTIMATING AN INTERNAL TEMPERATURE OF A LITHIUM-ION CELL

[0001] Method of estimating an internal temperature of a lithium-ion cell (1), comprising steps of:
a) carrying out an electrochemical impedance spectroscopy measurement on said cell (1) at a known internal temperature so as to determine a phase of impedance at a plurality of electrochemical impedance spectroscopy frequencies;
b) carrying out a distribution of relaxation times analysis on said electrochemical impedance spectroscopy measurement;
c) determining a characteristic frequency corresponding to an electrochemical impedance spectroscopy frequency associated with movement of lithium ions through a solid electrolyte interface layer of said cell, on the basis of said distribution of relaxation times analysis;
d) providing a correlation curve representative of the relationship between the impedance phase at said characteristic frequency and internal temperature for said cell (1), and carrying out a calibration of said correlation curve on the basis of said impedance phase as measured in step a) at said characteristic frequency and said known internal temperature;
e) repeatedly, carrying out electrochemical impedance spectroscopy at said characteristic frequency to determine an impedance phase at said characteristic frequency;
f) on the basis of said impedance phase at said characteristic frequency as determined out in step e), estimating said internal temperature based on said correlation curve as calibrated in step d);
g) repeatedly, updating said characteristic frequency and updating said calibration by repeating steps a)-d).