Method for producing secondary battery electrodes
A method for producing secondary battery electrodes includes a step of preparing a moisture powder formed of aggregated particles that contain a plurality of electrode active material particles, a binder resin, and solvent, wherein the solid phase, liquid phase, and gas phase in at least 50 number % or more of the aggregated particles in the moisture powder form a pendular state or a funicular state; a step of forming a coating film composed of the moisture powder on an electrode current collector, while the gas phase remains present; a step of forming a depression in the coating film by carrying out, using a die having an elevation of prescribed height, depression/elevation transfer into the coating film; and a step of carrying out depression/elevation transfer, using a die having an elevation higher than the elevation of prescribed height, by pressing the higher elevation into the depression that has been formed.
1. A method for producing a secondary battery electrode, comprising:
a step of preparing a moisture powder that is formed of aggregated particles that at least contain a plurality of electrode active material particles, a binder resin, and solvent, wherein a solid phase, liquid phase, and gas phase in at least 50 number % or more of the aggregated particles in the moisture powder form a pendular state or a funicular state;
a step of forming, using the moisture powder, a coating film composed of the moisture powder, on an electrode current collector, while the gas phase remains present;
a step of forming a depression in the coating film by carrying out, using a die having an elevation of prescribed height, depression/elevation transfer into a surface region of the coating film that has been formed;
a step of carrying out depression/elevation transfer, using a die having an elevation higher than the elevation of prescribed height, by pressing the higher elevation into the depression that has been formed; and
a step of forming an electrode active material layer by removing the solvent.
2. The method for producing a secondary battery electrode according to claim 1 , wherein
if the bulk specific gravity measured by placing an amount (g) of the moisture powder in a container having a prescribed volume (mL) and then leveling the moisture powder without applying a force is referred to as the loose bulk specific gravity X (g/mL), and
the specific gravity calculated from the composition of the moisture powder on the assumption that no gas phase is present is referred to as the true specific gravity Y (g/mL), then
the ratio of the loose bulk specific gravity X and the true specific gravity Y (Y/X) is 1.2 or more.
3. The method for producing a secondary battery electrode according to claim 1 , wherein the step of carrying out depression/elevation transfer is carried out such that the aspect ratio of the depression formed by the step of forming a depression is increased more than 1-fold and not more than 2-fold.
4. The method for producing a secondary battery electrode according to claims 1 , wherein the dies used in the step of forming a depression in the coating film and the step of carrying out depression/elevation transfer are each a roll die.