Battery Cathode Material Production from Waste

This Master’s thesis investigates the sustainable synthesis of lithium iron phosphate, LiFePO4 (LFP), as a cathode material for lithium-ion batteries using waste-derived iron phosphate, FePO4, as the main precursor. The work is motivated by the growing demand for LFP batteries and the need to develop more circular and environmentally responsible routes for battery material production. In particular, the study explores the possibil- ity of using phosphorus- and iron-containing waste streams recovered from wastewater treatment as alternative raw materials for cathode synthesis. Recovered FePO4 precursor was first evaluated and processed before LiFePO4 synthe- sis. Thermogravimetric analysis showed that the recovered precursor contained water and was therefore treated as hydrated FePO4·nH2O. To improve precursor quality, the material was dehydrated and purified using hydrochloric acid leaching followed by pH-controlled re-precipitation with ammonia. ICP analysis showed that aluminium and sodium impu- rities detected in the non-purified precursor were reduced to below the detection limit after purification. X-ray diffraction further confirmed that the purified FePO4 retained the iron phosphate phase while showing a cleaner diffraction pattern. LiFePO4 was synthesized from both non-purified and purified FePO4 precursors using a solid-state synthesis route with lithium sources including LiOH·H2O and Li2CO3. XRD analysis showed that LiFePO4 phase formation was achieved, but the sample prepared from non-purified FePO4 contained additional minor peaks, suggesting the presence of secondary phases. In contrast, LiFePO4 synthesized from purified FePO4 showed a cleaner diffraction pattern, indicating improved phase formation. SEM analysis showed irregular and agglomerated particle morphology for both samples, with no major morphological difference observed after purification. Overall, the results demonstrate that wastewater-derived FePO4 can be used as a pre- cursor for LiFePO4 synthesis, provided that an appropriate purification step is included. The study shows that precursor purification plays a critical role in improving chemical purity and phase formation of the final LFP material. Electrochemical testing of the syn- thesized material was carried out externally and remained pending at the time of writing; therefore, this work primarily establishes the feasibility of synthesis and structural char- acterization, while full battery-performance evaluation is recommended as future work.