Processing Water-Based Lithium Iron Phosphate (LiFePO₄) Cathodes with CMC Binder: The Impact of Dispersing Methods

Lithium-ion batteries (LIBs) are vital for modern energy storage applications. Lithium iron phosphate (LFP) is a promising cathode material due to its safety, low cost, and environmental friendliness compared to the widely used nickel manganese cobalt oxide (NMC), which contains hazardous nickel and cobalt compounds. However, challenges remain in enhancing the performance of LFP cathodes due to their low electronic and ionic conductivity. To improve both the safety and sustainability of the battery, this work presents a water-based LFP cathode utilizing the bio-based binder carboxymethyl cellulose (CMC), eliminating the need for polyvinylidene fluoride (PVDF) and the toxic solvent N-methyl-2-pyrrolidone (NMP). This study investigates the impact of different dispersing methods—dissolver mixing and wet jet milling—on slurry properties, electrode morphology, and battery performance. Slurries were characterized by rheology, particle size distribution, and sedimentation behavior, while coated and calendered electrodes were examined via thickness measurements and scanning electron microscopy (SEM). Electrochemical performance of the electrodes was evaluated by means of C-Rate testing. The results reveal that dispersing methods significantly influence slurry characteristics but marginally affect electrochemical performance. Compared to dissolver mixing, wet jet milling reduced the median particle size by 39% (ΔD50 = 3.1 µm) and lowered viscosity by 96% at 1 s⁻¹, 80% at 105 s⁻¹, and 64% at 1000 s⁻¹. In contrast, the electrochemical performance of the resulting electrodes differed only slightly, with discharge capacity varying by approximately 12.8% at 1.0 C (Δcapacity = 10.7 mAh g⁻¹). This research highlights the importance of optimizing not only material selection but also processing techniques to advance safer and more sustainable energy storage solutions.