Polypyride intercalation boosting the kinetics and stability of V3O7·H2O cathodes for aqueous zinc-ion batteries

Abstract

V3O7·H2O (VO) is a high capacity cathode material in the field of aqueous zinc ion batteries (AZIBs), but it is limited by slow ion migration and low electrical conductivity. In this paper, polypyridine (PPyd) intercalated VO with nanoribbon structure was prepared by a simple in-situ pre-intercalation, which is noted VO-PPyd. The total density of states (TDOS) shows that after the pre-intercalation of PPyd, an intermediate energy level appears between the valence band and conduction band, which provides a step that can effectively reduce the band gap and enhance the electron conductivity. Furthermore, the density functional theory (DFT) results found that Zn2+ is more easily de-intercalated from the V-O skeleton, which proves that the embeddedness of PPyd improves the diffusion kinetics of Zn2+. Electrochemical studies have shown that VO-PPyd cathode materials exhibit excellent rate performance (high specific capacity of 465 and 192 mA h g−1 at 0.2 and 10 A g−1, respectively) and long-term cycling performance (92.7% capacity retention rate after 5300 cycles), due to their advantages in structure and composition. More importantly, the energy density of VO-PPyd//Zn at 581 and 5806 W kg−1 is 375 and 247 W h kg−1, respectively. VO-PPyd exhibits excellent electrochemical properties compared to previously reported vanadium based cathodes, which makes it highly competitive in the field of high-performance cathode materials of AZIBs.