Giorgia Zampardi

Determination of the formation and range of stability of the SEI on glassy carbon by local electrochemistry

The solid electrolyte interphase (SEI) is an electronic insulating and ionic conducting layer that is of main importance in lithium-ions batteries, since it critically affects the final performance of the battery system. The formation of this electronic insulating layer was determined in operando on a glassy carbon electrode by means of a microelectrode positioned in close proximity to its surface using scanning electrochemical microscopy (SECM). Glassy carbon was chosen as an ideal model system for carbonaceous materials, since it forms a SEI similar in composition to the one on graphite but concomitantly shows negligible intercalation of lithium ions. Moreover, the stability of the SEI was analysed depending on different potential ranges and the role of the cations on the insulating character of the SEI was investigated.

Wet Nanoindentation of the Solid Electrolyte Interphase on Thin Film Si Electrodes

The solid electrolyte interphase (SEI) film formed at the surface of negative electrodes strongly affects the performance of a Li-ion battery. The mechanical properties of the SEI are of special importance for Si electrodes due to the large volumetric changes of Si upon (de)insertion of Li ions. This manuscript reports the careful determination of the Youngs modulus of the SEI formed on a sputtered Si electrode using wet atomic force microscopy (AFM)-nanoindentation. Several key parameters in the determination of the Youngs modulus are considered and discussed, e.g., wetness and roughness-thickness ratio of the film and the shape of a nanoindenter. The values of the Youngs modulus were determined to be 0.5-10 MPa under the investigated conditions which are in the lower range of those previously reported, i.e., 1 MPa to 10 GPa, pointing out the importance of the conditions of its determination. After multiple electrochemical cycles, the polymeric deposits formed on the surface of the SEI are revealed, by force-volume mapping in liquid using colloidal probes, to extend up to 300 nm into bulk solution.

Solid electrolyte interphase in semi-solid flow batteries: a wolf in sheep's clothing

The formation of the alkyl carbonate-derived solid electrolyte interphase (SEI) enables the use of active materials operating at very cathodic potentials in Li-ion batteries. However, the SEI in semi-solid flow batteries results in a hindered electron transfer between a fluid electrode and the current collector restricting the operating potentials to ca. 0.8 V vs. Li/Li(+) for EC-based electrolytes.

Potassium (De-)insertion Processes in Prussian Blue Particles: Ensemble versus Single Nanoparticle Behaviour

Potassium (de-)insertion from Prussian blue (PB) is investigated at the single and multi-particle scale. The electrochemical behaviour is found to differ between the two measurement types. At the single particle level, oxidation of the PB nanoparticles with concomitant K+ deinsertion occurs more readily than the associated reduction, relating to K+ insertion. In contrast, the cyclic voltammetry of PB in a composite electrode containing conductive additives and polymeric binder suggests the opposite behaviour. Implications for assessing battery materials are discussed.

Electrochemical Behavior of Single CuO Nanoparticles: Implications for the Assessment of their Environmental Fate

The electrochemical behavior of copper oxide nanoparticles is investigated at both the single particle and at the ensemble level in neutral aqueous solutions through the electrode-particle collision method and cyclic voltammetry, respectively. The influence of Cl- and NO3- anions on the electrochemical processes occurring at the nanoparticles is further evaluated. The electroactivity of CuO nanoparticles is found to differ between the two types of experiments. At the single-particle scale, the reduction of the CuO nanoparticles proceeds to a higher extent in the presence of chloride ion than of nitrate ion containing solutions. However, at the multiparticle scale the CuO reduction proceeds to the same extent regardless of the type of anions present in solution. The implications for assessing realistically the environmental fate and therefore the toxicity of metal-based nanoparticles in general, and copper-based nanoparticles in particular, are discussed.