Solvent-Free Manufacturing of Lithium Iron Phosphate Cathodes via Binder Fibrillation for Li-Ion Batteries

Solvent-free electrode manufacturing reduces cost and carbon emissions in Li-ion battery production via eliminating the electrode drying and toxic solvent recovery processes in conventional manufacturing. Herein, lithium iron phosphate-based cathodes are solvent-free manufactured via binder fibrillation. Effects of electrode thickness, porosity, and composition on cell performance are investigated for electrode optimization. By balancing the electrode thickness and porosity, the areal capacity exhibits a collective increase under different C-rates, such as 2.0–2.6 mAh cm ⁻² uplifting from 0.1 to 0.75 C. These results are different from increasing electrode thickness alone where the increasing tendency in areal capacity becomes flattened with C-rate, indicating the reduction of active material unitization in thick electrodes. Adhesive lamination of electrode sheets on current collectors is found to improve C-rate and cycling performance in comparison to non-laminated electrodes, and the improvement is more effective at higher C-rates. Four-probe electrode sheet resistance tests reveal that the resistivity of dry electrodes is independent of electrode thickness when the composition is fixed, which indicates the uniformity and reproducibility the dry electrodes. By increasing the carbon to binder ratios while keeping the active material fraction the same, the electrode resistivity is decreased by 30% which leads to the improvement of C-rate performance.