The intercalation cathode of MOFs-driven vanadium-based composite embedded in N-doped carbon for aqueous zinc ion batteries

The materials driven by metal-organic frameworks (abbreviated MOFs) and their derivatives   can prevent self-aggregation and inherit their original morphology. The adjustable porosity features of pristine MOFs can achieve an outstanding electrochemical performance. Herein, we report a novel cathode material of V 2 O 3 /V 3 O 5 /Zn 2 VO 4 @NC composite (abbreviated ZnVO-800) with hierarchical structure and heterojunction derived from zeolitic imidazolate framework-8 (abbreviated ZIF-8) by self-sacrificed route. The ZnVO-800 cathode undergoes two- step reactions in relation with H + and Zn 2+ synergistic insertion/extraction and exhibits rapid Zn 2+ diffusion kinetics and high electrochemical activity after activation. Specifically, the reversible capacity of the activated electrode reaches up to 314.0 mAh·g −1 at the initial discharge of 0.5A·g −1 as it applies to aqueous zinc ion batteries (abbreviated AZIBs). Remarkably, it exhibits a high reversible capacity of 100.1 mAh·g −1 and an excellent cycleability with a capacity retention of 90.8 % even after 3000 cycles. The electrochemical mechanism reveals that the ZnVO-800 with poor electrochemical characteristics is transformed into Zn x V 2 O 5 ·nH 2 O with high electrochemical activity by in-situ electrochemical activation process. Subsequently, Zn 2+ /H + is reversibly inserted/extracted in the cathode material. The heterojunction with hierarchical structure can not only increase the contact interface between electrolyte and cathode materials, but also shorten the ions diffusion path, which is conducive to rapid dynamics and long-term cycleability.