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.