Classifier for positive electrode active material and method for regenerating lithium precursor by using same

A method for regenerating a lithium precursor, the method comprising:

• preparing a cathode active material mixture that comprises an active material powder including lithium composite oxide particles and dust particles;
• collecting the active material powder by separating the dust particles from the cathode active material mixture using a classifier;
• reducing the active material powder to form a preliminary precursor mixture;
• and
• recovering a lithium precursor from the preliminary precursor mixture,
• wherein the collecting comprises classifying the active material powder into a first active material powder and a second active material powder and collecting each of the first active material powder and the second active material powder,
• wherein the collected first active material powder is subjected to a reductive treatment to form the preliminary precursor mixture, and
• wherein the separation of the dust particles and the classification of the first active material powder and the second active material powder are performed together in the classifier,
• wherein the collected second active material powder is treated with an acid solution.