Design of Ti4+/Zr4+ as Dual-Supporting Sites in Na3V2(PO4)3 for the Advanced Aqueous Zinc-Ion Battery Cathode

Thedevelopment of aqueous zinc-ion batteries (AZIBs)still facesa huge challenge due to poor cycling stability and slow kinetics ofthe cathode material. In this work, we report an advanced cathodeof Ti4+/Zr4+ as dual-supporting sites in Na3V2(PO4)(3) with an expandedcrystal structure, exceptional conductivity, and superior structuralstability for AZIBs, which exhibits fast Zn2+ diffusionand excellent performance. The results of AZIBs afford remarkablyhigh cycling stability (91.2% retention rate over 4000 cycles) andexceptional energy density (191.3 W h kg(-1)), outperformingmost Na+ superionic conductor (NASICON)-type cathodes.Furthermore, different in/ex situ characterization techniques andtheoretical studies reveal the reversible storage mechanism of Zn2+ in an optimal Na2.9V1.9Ti0.05Zr0.05(PO4)(3) (NVTZP) cathode anddemonstrate that Na+ defects together with Ti4+/Zr4+ sites can intrinsically contribute to the high electricalconductivity and low Na+/Zn2+ diffusion energybarrier of NVTZP. Moreover, the flexible soft-packaged batteries furtherdemonstrate a superior capacity retention rate of 83.2% after 2000cycles from the perspective of practicality.

Automated summary

In this work, an advanced cathode material of Ti4+/Zr4+ supported Na3V2(PO4)(3) was reported for aqueous zinc-ion batteries (AZIBs), exhibiting fast zinc ion diffusion and excellent performance. The AZIBs showed high cycling stability (91.2% retention rate over 4000 cycles) and exceptional energy density (191.3 W h kg(-1)), outperforming most Na+ superionic conductor cathodes. The reversible storage mechanism of zinc ions in an optimal Na2.9V1.9Ti0.05Zr0.05(PO4)(3) (NVTZP) cathode with Na+ defects and Ti4+/Zr4+ sites was demonstrated.