Abstract:

Aqueous zinc-ion batteries (AZIBs) are an attractive choice for large-scale energy storage in the future. However, suitable cathode materials for Zn²⁺ storage are lacking. This work finds that the cathode material Na₃V₂(PO₄)₃ (NVP) with the natrium super ionic conductor (NASICON) structure can achieve efficient Zn²⁺ storage and ultralong-cycle performance in high-concentration electrolytes. In this paper, a simple sol-gel method is used to prepare a uniform carbon-coated NVP. With the help of X-ray diffraction, scanning electron microscopy, constant current charge-discharge, and other characterization test methods, the structure, morphology, and performance of the NVP materials when used as cathode for AZIBs are analyzed. Additionally, the effects of different concentrations of electrolytes on the electrochemical performances are studied. The results show that NVP materials can provide high-capacity storage, excellent rate performance, and long-cycle life as the electrolyte concentration increases. After 1000 cycles at a high current density of 2000 mA·g^-1, the capacity retention rate is still 77.8%, and the coulombic efficiency per cycle of the material is close to 100%. Furthermore, the kinetic process of the NVP electrode is explored through cyclic voltammetry and galvanostatic intermittent titration technique. Experiments prove that these excellent electrochemical performances can be attributed to the stable and open NASICON framework and excellent kinetic behavior.

Key words: aqueous zinc-ion batteries, cathode materials, Na₃V₂(PO₄)₃, high concentration electrolyte, long cycle life