Florea Ileana1 Mariam Ezzedine1 Leandro Sacco1 Mihai Zamfir1 Costel Cojocaru1 2

1, Ecole Polytechnique, Palaiseau, , France
2, CNRS, Palaiseau, , France

Liquid electron microscopy is a new TEM-based characterization technique that allows us to apply the powerful capabilities of an electron microscope to probe/ image and understand real-time nanoscale morphological and structural evolution of nano-systems under certain electrochemical conditions (operando).[1] For in situ electrochemical experiments, the importance of using the liquid cell is related to the fact that experiments in liquid environments enable direct imaging of the key phenomena taking place during the battery operation, stage crucial for establishing a good correlation between the microstructure of nanocomposites and the performances of the aimed devices. The main challenge of our work is the assessment of the batteries performances when nanostructured electrode materials are considered for both the anode and the cathode. Nanostructured materials show great promise; they can open new possibilities for enhancing the energy density of Li-ion batteries.
The present study is focused on the realization of the in – situ liquid TEM observation using a closed electrochemical cell [2] of the electrochemical technique that activate the nanoparticle nucleation/growth mechanism of under certain electrochemical conditions (operando ) as the ionic solution is introduced into the cell(unit) [3, 4].
From the experimental point of view, two electrodeposition approaches have been used: the cycling voltammetry and pulsed chronoamperometry modes both under constant flow. The interpretation and the analyses of the recorded current versus time curves allowed us observing that the nucleation mode is strongly related to the deposition conditions. Thus we noticed when the pulsed chronoamperometry mode is used we have a homogeneous NP deposition on the working electrode. The NPs size is depending on the cycle number and the liquid flow rate within the cell. In contrast, under cycling voltammetry mode, we observe an inhomogeneous deposition of the NPs generated by the oxidation of different organic species that can be formed after the first cycle.

[1] Gohier A., Laïk B, Kim K., Maurice J.-L., Pereira-Ramos, J-P., Cojocaru C. S., Advanced Materials 84 (2012) 2592-2597
[2] Unocic R. R., Sacci R. L., Brown G. M., Veith G. M., Dudney N. J., More K. L., Walden II F. S., Gardiner D. S., and Nackashi D. P. Microscopy and Microanalysis( 2014), 20, 452-461.
[3] Zaluzec N. J., Burke M. G., Haigh S. J., Kulzick M. A. Microscopy and Microanalysis( 2014), 20, 323-329