<p>This paper investigates the synthesis of iron phosphate (FePO₄) for lithium-ion battery cathodes from various raw materials as iron sources. FeSO₄·7H₂O offers a simple and cost-effective precursor for the FePO₄ precipitation method, though pH sensitivity can lead to uneven particle growth. FeCl₃ as an Fe source for FePO₄ synthesis through the hydrothermal method provides precise control over the morphology of the synthesized particle but requires longer reaction times. Fe₂O₃, commonly used in solid-state synthesis methods, ensures uniform particle distribution but reacts slowly. Fe(NO₃)₃ easily dissolves in water, allowing for controlled reactivity, though it is hygroscopic and produces toxic nitrogen oxide gas. Fe(NH₄)₂(SO₄)₂·6H₂O enables low-temperature synthesis but results in amorphous materials that lead to lower cell performance. Fe₃O₄ offers high stability and uniform particle size of the synthesized FePO₄ but requires energy-intensive reduction. FeC₂O₄·2H₂O facilitates the production of high-quality LiFePO₄, though its sintering process demands high temperatures. FeCO₃ exhibits a slow synthesis process and gives impurity challenges. Fe(OH)₃ is cost-effective but often yields amorphous and thermally unstable products. Beyond these conventional precursors, sustainable alternatives such as FeNi alloys from nickel laterite ore processing and Fe–P industrial waste are also considered. The transformation of FeNi alloys into FePO₄ and NiSO₄·6H₂O provides a dual benefit by supplying precursors for both LFP and NMC cathode materials, while valorizing industrial byproducts. This approach highlights a promising and sustainable route for future cathode material development.</p>