Cycle performance improvement of LiFePO4 cathode with polyacrylic acid as binder

LiFePO4 cathodes with polyacrylic acid (PAA) as binder were prepared with N-methyl-2-pyrrolidone (NMP) as solvent. The cathodes were characterized by peel test, swelling performance test, SEM and electrochemical methods. Compared with conventional poly(vinylidenedifluoride) (PVDF) binder, the PAA binder significantly improves the cycle performance of LiFePO4 cathode. LiFePO4 cathodes with PAA binder can deliver 200 cycles with almost no capacity fading at the current density of 175 mA g−1, which is much better than the cathode with PVDF binder (for the capacity retention 86.6% after 200 cycles). Results show that the PAA binder can not only provide high adhesion strength to ensure good electrical contact between active material and current collector, but also suppress swelling of LiFePO4 cathode with the electrolyte solution compared to the PVDF binder. SEM observation clearly demonstrates that the cracks of the electrodes are effectively suppressed by using the PAA as binder.

► LiFePO4 cathodes with PAA as binder are prepared with NMP solvent. ► The cathodes exhibit reversible cycling behavior with good capacity retention. ► Good mechanical properties and well swelling performance result in the excellent cycle performance. ► Surface morphologies and impedances of the cathode demonstrate PAA can highly improve the cycle performance of LiFePO4 cathode.