WP 4. Insights into Redox Reactions

Objectives: (i) deciphering of the mechanism of the electrochemical intercalation of Li+ and Na+ ions into different classes of materials by integrating in-depth physicochemical, electrochemical and theoretical studies; (ii) selection materials with colossal intercalation capacity.

Tasks and justification: the ingenuity of the investigation consists of the utilization of a smart combination of in-situ and ex-situ physicochemical methods for monitoring the structural and chemical changes in the bulk and at the surface of the compounds resulting from the intercalation reactions. The amalgamation of experimental and theoretical data will allow a new level of comprehension of the intercalation reaction mechanism.

Task 4.1 in-situ and ex-situ Diffraction and Spectroscopic methods for monitoring of the structural changes occurring in the bulk of materials during intercalation reactions

4.1.1 Determination of the phase composition and structural peculiarities at the macro-level for different classes of materials after intercalation reaction on the basis of data from ex-situ X-ray powder diffraction.

4.1.2 Probing of intercalation-induced changes in the structure at the nano-level by selected area electron diffraction (SAED) and transmission electron microscopy with high-resolution (HRTEM). Evaluation of the chemical elements distribution in a nano-scale region by BF-STEM.

4.1.3 Monitoring of the oxidation state and the local symmetry of transition metal ions in the course of the intercalation reaction by utilization of in-situ and ex-situ EPR spectroscopy.

4.1.4 in-situ Raman spectroscopy for local structural analysis of intercalation materials.

Task 4.2 ex-situ X-ray photoelectron spectroscopy for quantification of chemical changes on the surface of materials during electrochemical reaction.

Task 4.3 Summarizing of experimental and theoretical data in order to get insight into the mechanism of intercalation reactions:

4.3.1 Extracting experimental correlations between bulk and surface characteristics for each class of studied compounds and their intercalation properties.

4.3.2 Establishing relations between the redox activities of the cations and anions and the intercalation properties of studied compounds: experimental and theoretical data analysis.

Milestones for WP4: development of in-situ methods of characterization.

Main result of WP4: (i) acquisition of new knowledge on the mechanism of intercalation reactions of Li+ and Na+ into layered oxides and MOFs by integrating in-depth physicochemical, electrochemical and theoretical studies; (ii) new concept on the synergism between cation and anion redox reactions in materials with colossal intercalation capacity.

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