Optimization of the cathode porosity via mechanochemical synthesis with carbon black

Abstract

Nanostructured carbon–coated composite cathode materials LiFe0.5Mn0.5PO4/C (LFMP/C) are prepared by the mechanochemically assisted solid-state synthesis using different reagent mixtures and carbon as reducing and covering agent. The effect of the precursors, gas release during the solid-state reaction, and of the intensity of high-energy ball milling on the porous structure and electrochemistry of LFMP/C is studied using DSC/TG/MS, XRD, SEM, TEM, standard contact porosimetry (MSCP), EIS, CV, and GVC. It is shown that the particle size and porosity of LFMP/C strongly depend on the chosen precursors and intensity of mechanical impact. The higher the intensity, the more effective incorporation of carbon black in the pores formed in LFMP, which leads to improved electronic conductivity and better access of the electrolyte to the surface of the electrode, while smaller particles provide improved Li diffusion in the bulk of LFMP. As a result, the cyclability and high-rate performance of the LFMP/C composites are improved.