Phosphate cathode materials with a stable and open framework structure are expected to be one of the favorable cathode materials for aqueous zinc-ion batteries (AZIBs). However, the slow migration rate of Zn2+ and complex mechanism in aqueous electrolyte are serious problems that limit their application at the present. Here, a new rocking-chair-type cathode material Zn3V4(PO4)6@C (ZVP@C) for AZIBs is synthesized for the first time and evaluated using a composite carbon coating to improve the electronic conductivity. Benefiting from the two-electron reaction of vanadium and the cointercalation of Zn2+/H+, ZVP@C/30%BP delivers a specific capacity as high as 120 mAh·g-1 at 0.04 A·g-1. A good capacity retention of 80% after 400 cycles at 1 A·g-1 is also obtained, which is attributed to the stable crystal structure and the cointercalation reaction of Zn2+/H+. The reaction mechanism is investigated by in situ X-ray diffraction (XRD), ex situ XRD, ex situ X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS). This work not only provides a new phosphate cathode material for AZIBs but also gives a new strategy for improving the specific capacity of phosphate cathode material.
Keywords: Zn2+/H+ cointercalation; Zn3V4(PO4)6; aqueous zinc-ion batteries; high specific capacity; mechanism.