New methodology of electrochemical noise analysis and applications for commercial Li-ion batteries

Electrochemical noise analysis (ENA) is performed on ICR 18650 commercial lithium-ion batteries. The interest of ENA relates with the possibility of in-situ diagnostics during charging or discharging of the battery. Thus, the extraction of small voltage fluctuations should take into account the time evolution of the mean signal. The non-stationary character of the phenomenon (charging and discharging battery) limits the use of traditional methods of signal filtering and attenuation, so a special methodology has been developed to calculate the noise standard deviation (STD). A good reproducibility of the results has been demonstrated, and V-shape form curves have been obtained with a minimum STD value at about 55 % of state of charge (SOC). It can be noted also that fast discharge provided with 3.3 Omega load is noisier than the slow one with 5 Omega load. Some promising results have been obtained regarding the possibility of battery state of health determination.