The present disclosure relates to an invention directed to controlling a viscosity of a slurry used to manufacture an electrochemical device, by adjusting a particle diameter of an inorganic matter that is an ingredient of the slurry, so that a sinking rate of the inorganic particles may remarkably slow down and dispersibility may be dramatically improved, and as a result, the content of the inorganic particles may relatively increase and the inorganic particles may be uniformly distributed in a coating layer on a substrate, thereby preventing a reduction in battery performance.