The influence of the slurry mixing procedure on the homogeneity and electrochemical performance of composite electrodes for Li-ion batteries was studied. MCMB graphite and Co3O4 were used as probe active materials, since they exhibit different reaction mechanisms with lithium. Three different mixing procedures were used, (i) magnetic stirring, (ii) magnetic stirring with additional sonication steps and (iii) ball milling. SEM studies allow to determine that the mixing procedure has a significant effect in the microstructure of the active material. Indeed, ball milling was found to destroy the pristine MCMB microstructure and to induce agglomeration in nanosized Co3O4. While magnetic stirring is much less aggressive to that respect, sonication steps were found to enhance the homogeneity of the mixture without inducing major modifications in the microstructure of the materials and hence to have a beneficial impact in the final electrochemical performance.