A hollow MOF-derived capsular VxO3@CN cathode with high capacity and ultralong lifespan for aqueous zinc ion batteries

Abstract

To attain the practical use of rechargeable aqueous zinc batteries (RAZBs), cathode materials with both high density Zn²⁺ storage sites and high Zn²⁺ transport kinetics are required. However, combining these key elements in metal oxide-based cathode materials is highly challenging due to the compact structure. Herein, we have reported a high-performance V_xO₃@CN (CN = nitrogen-doped carbon) cathode with uniform capsular morphology, highly conductive CN substrates and vanadium defects. Without extra templates and severe synthesis conditions, a tailored MOF precursor was converted to V_xO₃@CN with superior electrolyte wettability, fast charge, and ion transfer kinetics. The vanadium defect and CN substrate with high electron conductivity modified the transport resistance of Zn²⁺ and electrons in V_xO₃, resulting in the formation of efficient Zn²⁺ channels and better utilization of high-density active sites. As a result, V_xO₃@CN attained a capacity of 365 mA h g⁻¹ at 0.5 A g⁻¹ after 800 cycles and a capacity of 210 mA h g⁻¹ at 2.0 A g⁻¹ after 5000 cycles. Combining the in/ex situ characterization studies and DFT calculations, the formation mechanism of capsular V_xO₃@CN and the effect of defects on the high-performance Zn²⁺ transport and storage are revealed.