The demand for lithium-ion batteries as stationary as well as mobile energy storage systems is steadily increasing. The reasons are both the economic growth and the accompanying need for prosperity as well as the ecologization of national economies due to climatic changes. Lithium-ion batteries are therefore of high interest, because lithium has a high specific charge with a low standard potential of -3.05 V against the standard hydrogen electrode. In addition, lithium-ion batteries are reactive, easily scalable and can be installed in a decentralized manner. High research interest exists in the development of energy storage systems with regard to safety, cycle stability and recyclability. Lithium iron phosphate stands out among the various cathode materials because it has high cycling stability and exceptionally high thermal stability. In addition, this type of material can be fast charged and discharged and iron is particularly inexpensive due to its relative abundance in the earth's crust. The disadvantages, such as poorer electrical and lithium-ion conductivity, can also be improved by appropriate measures. There is a need to catch up in regard to a stable recycling process. The different recycling routes can be roughly divided into pyrometallurgy and hydrometallurgy, whereby the hydrometallurgical process route is of high interest for future recycling activities due to the possibility of ensuring high selectivity with corresponding product purity. The aim of this work is to find optimized process parameters for a possible low-cost leaching step within the hydrometallurgical recycling route. The leaching duration and temperature, the solid to liquid ratio, the acid concentration and the necessary amount of oxidant are of importance. Sulfuric acid is used as the leaching agent and hydrogen peroxide as the oxidizing agent in order to achieve an economical process. Within the scope of the work it could be determined, that an economical process mapping is possible by low temperatures with correspondingly long leaching durations at a high acid concentration without the need for additional chemicals. An increase of the solid to liquid ratio can additionally increase the yield. Moreover, an optimized choice of parameters leads to a high lithium yield with low amounts of iron in solution and therefore leads to high selectivity of the leaching process.