Freestanding strontium vanadate/carbon nanotube films for long-life aqueous zinc-ion batteries

Aqueous rechargeable zinc-ion battery (ZIB) is considered to be a potential energy storage system for large-scale applications due to its environmental friendliness, high safety, and low cost. However, it remains challenging to develop suitable cathode materials with high specific capacity and long-term cyclic stability. Herein, we have fabricated freestanding Sr0.19V2O5·1.3H2O/carbon nanotubes (SrVO/CNTs) composite films with different mass ratios by incorporating SrVO into CNTs network. The synthesized SrVO possesses a large interlayer spacing of 1.31 nm, which facilitates Zn2+ diffusion. Furthermore, the SrVO/CNTs composite film with conductive network structure promotes electron transfer and ensures good contact between SrVO and CNTs during the long-term cycling process. As a result, the battery based on the SrVO/CNTs composite cathode with a mass ratio of 7:3 delivers a specific capacity of 326 mAh·g−1 at 0.1 A·g−1 and 145 mAh·g−1 at 5 A·g−1, demonstrating a high capacity and excellent rate capability. Remarkably, the assembled ZIB shows good capacity retention of 91% even after ultra-long cycling for 7500 cycles at a high current rate of 5 A·g−1. More importantly, the battery also delivers a high energy density and power density, as 290 Wh·kg−1 at 125 W·kg−1 (0.1 A·g−1), or 115 Wh·kg−1 at 6078 W·kg−1 (5 A·g−1). The results demonstrate that the SrVO/CNTs composite is a promising cathode toward large-scale energy storage applications.