In this work we analyzed the influence of precursor selection on the performance of lithium iron phosphate (LFP) cathode active material (CAM). We used different iron oxide battery grades from the LANXESS portfolio of, as well as an iron phosphate as precursor material for lithium iron phosphate cathode materials and tested the resulting lithium iron phosphate materials in coin cells in a half-cell design with lithium anodes.
The LFP-synthesis was based on a carbo thermal reduction with a premixing of the lithium-, iron-, phosphorus- and carbon-source, spray-drying and calcination. The Li:Fe:P ratio was kept the same for all materials, the Fe:C ratio was varied for iron phosphate. The calcination times and temperatures were chosen based on available syntheses methods in literature. The finished LFP cathode active material was then mixed with polyvinylidene fluoride (PVDF), carbon black and N-methyl-2-pyrrolidone (NMP) and prepared as a cathode for electrochemical cycling.
The results showed clear differences in the resulting LFP materials, based on their precursors. Different iron oxides and iron phosphate cause different electrochemical properties. Some precursors elevate the rate capacity of the resulting cathode active material significantly while others increase the maximum charge capacity or increase the first cycle efficiency and charge retention of multiple cycles.
These results highlight the importance of precursor choice for a given synthesis and can help improve battery performance based on a given target system.