This thesis investigates the recycling of cathode active powder from LiFePO4 (LFP) Li-ion batteries, with a focus on hydrometallurgical methods, specifically acid leaching. The work addresses the growing need for sustainable and environmentally responsible ways to recycle Li-ion batteries. This topic is becoming increasingly important due to the growth of the electric vehicle market and the European Union's commitment to reducing greenhouse gas emissions. The objective of this study is to recover the main elements of lithium, iron, and phosphorus from LFP batteries using both traditional and greener hydrometallurgical methods, and to compare the efficiency of four different leaching agents. The traditional methods use sulfuric acid (1 M) and hydrochloric acid (0.6 M with NaClO as an oxidizing agent), while the greener methods use citric acid (0.5 M with H2O2 as oxidizing agent) and hydrogen peroxide (20% w/w).