This report summarizes the experimental activities carried out in the framework of Work Package 1, Activity 1.4, whose main objectives were: i) to define the level of reproducibility achieved by the process developed by RSE for the preparation of MXenes, also taking into account the intrinsic variability of the electrochemical characterization techniques, and ii) to study the effects induced by the SPS synthesis and exfoliation processes on the electrochemical properties of MXenes in order to identify possible innovative variants to maximize their final storage performance.

With regard to the first point, the experimental activity has consolidated what has been achieved in previous years in order to be able to implement in the coming years a production of MAXphase/MXenes at the scale of kg/day in the RSE laboratories; an essential condition for the production of NIB batteries with MXene-based anodes in larger formats (pouch) than the one tested so far (button). With regard to the SPS process for the synthesis of the original MAXPhases, the main objects of study were: i) the overall reproducibility of the process, in order to be able to evaluate, on a statistically significant basis, the influence of the various preparation parameters, ii) the correlation between process parameters (load, residual argon pressure in the chamber), quality of the MAXPhases (purity) and electrochemical performances of the respective MXenes, and iii) the effect of possible variations to which the SPS process may be subject (e.g. different powder suppliers, etc.).

As regards the activities carried out in order to correlate the parameters of the exfoliation processes with the storage performances of the MXenes thus obtained, we: i) studied the effect of post-exfoliation thermal treatments in HF; ii) conducted studies on the reproducibility of the process in HCl NaF until we identified process parameters capable of returning MXenes with performances similar to those in HF; iii) carried out solid-state NMR measurements to study how the exfoliation processes functionalize the MXene lamellae; and, iv) tested a new type of etching based on NH4HF2.