Organic pillars pre-intercalated V4+-V2O5·3H2O nanocomposites with enlarged interlayer and mixed valence for aqueous Zn-ion storage

Abstract

As cathodes for aqueous Zn-ion batteries, the repetitive insertion/extraction and strong polarization of Zn2+ during cycles will severely wreck the structure of layered vanadium oxides, resulting in rapid capacity recession. Hence, the ingenious strategy of PAN/THF-pillars intercalation and V4+/V5+ dual-valence regulation was designed to fabricate PAN or THF pre-intercalated V4+-V2O5·3H2O, denoted as P-VO or T-VO. Owing to the interlayer expansion of organic molecules and the electrochemical reactivity enhancement of mixed V4+/V5+ valence, severe structural collapse of cathodes and strong polarization of Zn2+ can be alleviated. Hence, P-VO and T-VO cathodes can exhibit larger interlayer distances of 13.67 and 14.41 Å, more robust construction, faster Zn2+ transmission, and better electrical conductivity. P-VO and T-VO electrodes furnish high zinc storage performance of 251 and 336 mAh g−1 at 500 mA g−1, and persistently maintain considerable reversible capacities of 133 and 100 mAh g−1 after 1000 cycles at a high current density of 10 A g−1. And the capacitive contribution ratios of P-VO and T-VO can reach up to 75% and 86.4%, respectively. Meanwhile, both two cathodes can endure extreme ambient conditions from −15 °C to 45 °C. In addition, the insertion mechanism of Zn2+ was also investigated via in-situ XRD and ex-situ XPS.