Porosity, microstructure and electrochemistry of Na3V2(PO4)2F3/C prepared by mechanical activation

Abstract In this work, a detailed study of the mechanochemical approach to preparation of Na3V2(PO4)2F3/C cathode material with a porous structure is carried out. It is found that mechanical activation (MA) contributes to obtaining a single-phase material with a uniform distribution of elements at the nanoscale, reducing the particle size, and forming a mesoporous structure. On the other hand, a carbon additive prevents iron contamination during MA, suppresses particle growth upon MA and the following annealing, and enhances electrical conductivity. These two factors exhibit a synergetic effect that leads to a significant increase in the specific surface area of the cathode material and facilitate the embedding of carbon particles into the pores of Na3V2(PO4)2F3, thereby improving their contact with the matrix, increasing accessibility of electrolyte to the surface of electrode, and facilitating charge transfer, thus improving electrochemical properties as a result.