In this study L‐(+)‐tartaric acid was used to extract metals from either pure cathode material (NMC111) or black mass from spent lithium‐ion batteries. The leaching efficiencies of Li, Co, Ni, and Mn from NMC111 are >87 % at 70 °C, with an initial solid to liquid ratio of 17, and >72.4±1.0 % from black mass under corresponding conditions. The metals tend to form mixed phases in antisolvent crystallization and seeding has a minimal effect on the final solid composition. Impurities influence both crystal nucleation and growth. By controlling the antisolvent addition rate crystal growth can be promoted. The theoretical dielectric constant of the solution is shown to correlate excellently to the recovery efficiency across different antisolvents, where a value <52 results in over 95 % total transition metal recovery efficiency. The correlation can be a powerful tool for quantitative prediction of optimal solvent composition for effective antisolvent crystallization.