Electrochemical tests galvanostatic measurements

Pitting and crevice corrosion are associated with the breakdown of passivity [SO]. Electrochemical tests for evaluating the susceptibility of a material to pitting and to crevice corrosion include potentiodynamic, potentiostatic, scratch potentiostatic, potentiostaircase, tribo-eUipsometric methods, pit-propagation rate curves, galvanostatic, and electrochemical noise measurements [80-S2]. 

Most electrochemical testing conducted to date has used various DC approaches. The most common methods involve linear polarization (to determine the polarization resistance for calculation of corrosion current via the Stem-Geary equation) [44] and potentiodynamic polarization (to determine breakdown and repassivation potentials). Other tests are also conducted, however. For example, long-term open circuit potential versus time measurements, potentiostatic chronoamperometry, and galvanostatic measurements are occasionally conducted for specialized purposes. 

To validate the Pxy-TFSI- RTIL mixtures as electrolytes for batteries Li-ion application, tests of cycling ability are required, after the determination of their electrochemical window. The quality of the passivating protective layer, and its stability at the graphite electrode, must be checked by mean of galvanostatic chronopotentiometric measurements. The Pxy-TFSI- RUL contents lower than 20 % (w/w) are not of a real interest, in spite of an ionic conductivity over the standard electrolyte one, because the phenomenon of self-extinguished flame becomes striking only from 20 % of Pxy-TFSI. For between 20 % and 30 % Pxy-TFSI- RUL, the performances are optimized from the point of view of the ionic transpxjrt, of the thermal stability and of the material wettability Beyond these contents, up to 50 %, the increase of the viscosity of mixtures can limit their applications at room temperature (mainly because of the decrease of the performances of ionic transport), but their use can be considered for higher temperature applications. 

The electrochemical window determination shows that all the studied pyrrolidinium imides can be incorporated in the electrolyte for Li-ion battery except the P13-TFSI RTIL if a graphite electrode is used as negative electrode. These results are confirmed by the galvanostatic chronopotentiometric measurements to test the cycling ability with the electrolyte imder consideration. The best electrochemical performances are achieved in the presence of the 20%or 30% P14-TFSI RTIL mixtures... 

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