Synergistic enhanced kinetics and dual active sites in PANI@V2O5 nanoflower for superior Ca2+ ion storage

Calcium-ion batteries (CIBs) have attracted growing interest owing to abundant Ca resources and its high gravimetric capacity. However, potent electrostatic interactions between Ca2+ ions and host material, can lead to slow diffusion kinetics and crystal structure destabilization. A pre-intercalation strategy involving polyaniline (PANI) was employed in this study to enhance the cathode material performance of PANI@V2O5 (PVO) for CIBs. PANI pre-intercalation improved both the diffusion kinetics and capacity by increasing the distance between the V-O layers (13.8 Å) and significantly enhancing the material conductivity. Meanwhile, the intercalation of PANI as extra active sites also can participate in the redox reaction, providing additional capacity. Moreover, density functional theory calculations demonstrated that the PANI intercalation improved the conductivity and relieved the electrostatic repulsion between Ca2+ ions and the V-O layer. Benefiting from a large layer spacing and dual active sites, PVO achieved a high specific capacity of 205 mAh g−1 at 100 mA g−1. This work provides insight into the mechanism of PANI intercalation to improve electrochemical performance, which sheds light on the rational design of organic–inorganic cathode materials for calcium ion batteries.