Polyanion-Type Na3V2(PO4)2F3@rGO with High-Voltage and Ultralong-Life for Aqueous Zinc Ion Batteries

Aqueous zinc ion batteries (AZIBs) have attracted much interest in the next generation of energy storage devices because of their elevated safety and inexpensive price. Polyanionic materials have been considered as underlying cathodes owing to the high voltage, large ionic channels and fast ionic kinetics. However, the low electronic conductivity limits their cycling stability and rate performance. Herein, mesoporous Na3V2(PO4)(2)F-3 (N3VPF) nanocuboids with the size of 80-220 nm cladded by reduced graphene oxide (rGO) have been successfully prepared to form 3D composite (N3VPF@rGO) by a novel and fast microwave hydrothermal with subsequent calcination strategy. The enhanced conductivity, strengthened pseudocapacitive behaviors, enlarged D-Zn(2+), and stable structure guarantee N3VPF@rGO with splendid Zn2+ storage performance, such as high capacity of 126.9 mAh g(-1) at 0.5 C (1 C = 128 mA g(-1)), high redox potentials at 1.48/1.57 V, high rate capacity of 93.9 mAh g(-1) at 20 C (short charging time of 3 mins) and extreme cycling stability with capacity decay of 0.0074% per cycle after 5000 cycles at 15 C. The soft package batteries also present preeminent performance, demonstrating the practical application values. In situ X-ray diffraction, ex situ transmission electron microscopy and X-ray photoelectron spectroscopy reveal a reversible Zn2+ insertion/extraction mechanism.

Automated summary

Aqueous zinc ion batteries (AZIBs) have shown promising potential as next-generation energy storage devices due to their high safety and low cost. However, the low electronic conductivity of polyanionic cathode materials has limited their cycling stability and rate performance. In this study, a 3D composite (N3VPF@rGO) consisting of mesoporous Na3V2(PO4)(2)F-3 nanocuboids cladded by reduced graphene oxide (rGO) was successfully synthesized using a novel microwave hydrothermal and subsequent calcination strategy. The N3VPF@rGO composite exhibited enhanced conductivity, pseudocapacitive behavior, enlarged D-Zn(2+), and stable structure, leading to excellent Zn2+ storage performance, including high capacity, high redox potentials, high rate capacity, and extreme cycling stability. The results also demonstrated the practical application values of the soft package batteries. In situ X-ray diffraction, ex situ transmission electron microscopy, and X-ray photoelectron spectroscopy were employed to investigate the reversible Zn2+ insertion/extraction mechanism.