Method of producing electrode

A method of producing an electrode comprising:

• (a) preparing an active material powder, the active material powder including a foreign particle and an active material particle;
• (b) preparing a first electrode material including the active material powder;
• (c) performing a dry classification treatment on the first electrode material to separate out coarse particles and decrease the foreign particle included in the first electrode material, wherein the dry classification treatment is performed with a cut size greater than a D99 of the active material powder, where D99 refers to a particle size in a volume-based particle size distribution at which cumulative frequency of particle sizes accumulated from a small size side reaches 99% of all particles;
• and
• (d) forming an active material layer including the first electrode material after the dry classification treatment by:
• (d1) performing a magnetic separation treatment on a conductive material to decrease a magnetic metal particle included in the conductive material;
• (d2) preparing a powdery and granular composition by mixing the first electrode material after the dry classification treatment with a second electrode material comprising the conductive material;
• and
• (d3) coating a surface of a substrate with the powdery and granular composition by electrostatic coating,
• wherein:
• the first electrode material is in powder form,
• the foreign particle includes a metal foreign object and is a coarse particle;
• and
• coating the surface of the substrate with the powdery and granular composition by electrostatic coating comprises:
• feeding the powdery and granular composition into a vessel;
• adsorbing the powdery and granular composition from the vessel onto a first roll by a magnetic force of the first roll;
• conveying the substrate, using a second roll, to a roll gap between the first roll and a third roll, wherein the first roll, the second roll, and the third roll have parallel axes;
• supporting the substrate on a surface of the third roll;
• and
• forming an electric field between the first roll and the third roll such that an electrostatic force pulls the powdery and granular composition toward the third roll and causes the powdery and granular composition to become adhered to the substrate.