Ferroelectric-polarization-induced high-rate performance: 120C achievement with porous Na₃Fe₂(PO₄)P₂O₇ and nano-BaTiO₃ composite cathodes for sodium-ion batteries

Sodium-ion batteries (SIBs) are promising for large-scale energy storage, with cathode materials being key to their electrochemical performance. Recently, Na₃Fe₂(PO₄)P₂O₇ has drawn attention as a potential cathode material for SIBs due to its low cost and stable crystal structure. In this study, we prepared a porous Na₃Fe₂(PO₄)P₂O₇ (NFPP) and introduced nano-BaTiO₃ (BT) to create a composite cathode. The synthesized Na₃Fe₂(PO₄)P₂O₇–3 %BaTiO₃ (NFPP-3BT) delivered a reversible capacity of 62.7 mAh g⁻¹ at an ultra-high rate of 120C and exhibited a long cycle life of 2000 cycles at 10C with a capacity retention of 80.5 %. The high-rate performance is attributed to the synergic effect of the porous structure of NFPP and the polarization electric field from BT's ferroelectricity, enhancing the Na⁺ diffusion. Moreover, the strong adsorption energy for sodium salt anions on the BT surface accelerates the desolvation process and improves the stability of cathode electrolyte interphase (CEI), further improving the rate and cycling performance of NFPP. This work unveils a new strategy for achieving both high-rate capability and excellent cycle stability in SIBs through the synergistic effect of mixed polyanionic cathode materials and ferroelectric materials.