In-situ electrochemical conversion of V2O3@C into Zn3(OH)2V2O7·2H2O@C for high-performance aqueous Zn-ion batteries

Abstract

Open-framework crystal structured vanadates have been extensively investigated as cathode materials for aqueous zinc-ion batteries (ZIBs). However, the inherent challenges of poor electronic conductivity and structural instability compromise the rate capability and overall cycle life. Herein, we first successfully synthesized octahedral MIL-101(V) and prepared the Zn₃(OH)₂V₂O₇·2H₂O@C (ZVOH@C) composite by in-situ electrochemical conversion of MIL-101(V)-derived crystalline V₂O₃ and carbon composite (V₂O₃@C). The ZVOH@C composite of open-framework crystal structured Zn₃(OH)₂V₂O₇·2H₂O and conductive carbon skeleton not only possesses more active sites, more stable crystal structure and higher electrical conductivity, but also provides faster Zn²⁺ diffusion kinetics. As expected, the ZVOH@C composite electrode exhibits excellent capacity of 506.3 mAh/g at a current density of 1.0 A/g, exceptional rate performance (375.7 mAh/g at 20.0 A/g), and impressive long-term cycling stability, maintaining 314.5 mAh/g over 5000 cycles at 20.0 A/g. This study demonstrates a promising method for designing new cathode materials through in-situ electrochemical synthesis for ZIBs.