There is provided a method for recovering valuable materials from lithium ion secondary batteries, which includes: a heat-treatment step of performing a heat treatment on a lithium ion secondary battery to obtain a heat-treated product; a first classification step of classifying a crushed product, which is obtained by crushing the heat-treated product, at a classification point of 600 m or greater and 2,400 m or less to obtain a coarse-particle product 1 and a small-particle product; a grinding step of grinding the small-particle product to obtain a ground product; a second classification step of classifying the ground product at one or more classification points that are smaller than the classification point of the first classification step and are 75 m or greater and 1, 200 m or less to obtain a coarse-particle product 2 and a fine-particle product 1; and a magnetic separation step of sorting the fine-particle product 1 obtained in the second classification step using magnetic force.

Methods for extracting a target metal from a mixed metal input are described. The method includes milling the mixed metal input with ammonium bicarbonate to form a milled solid product, aging the milled solid product, and leaching the target metal from the aged solid product.