Design And Electrochemical Performances Of Vanadium Based Cathode Materials For Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries(AZIBs)have recently received much attention because of the advantages of low cost,high security,environmentally friendly,and easy assembly.However,owing to the slow dynamics of Zn2+and the partial dissolution of cathode active materials in the aqueous electrolyte,the achievement of high-performance AZIBs has become an important research topic.Herein,a series of novel vanadium oxide cathode materials were designed and synthesized by ball-milling,hydrothermal and electrospinning routes,and thus the morphology and microstructure were well regulated for optimizing and improving the specific capacity,cycle life and rate performance.The main works are as follows.(1)V2O3@C cathode material.In detail,V2O5 and C6H12O6 were firstly mixed with anhydrous ethanol(C2H6O).After a high-energy ball-milling route and a hightemperature sintering process,the V2O3/carbon composite named as B-V2O3@C was synthesized.Compared with the commercial V2O3 powders,the electrochemical performances of B-V2O3@C achieved a large improvement.It can deliver a highest discharge specific capacity of 430 mAh g-1 at 1000 mA g-1.Even after 2000 cycles at 5000 mA g-1,the capacity retained to 84 mAh g-1.Benefiting from the facile synthesis strategy for large amount product,the B-V2O3@C cathode suggests certain advantages in the large scale application of AZIBs.(2)V2O5 nanofibers cathode material.Typically,the precursor solution includes NH4VO3 and C8H6O4 was treated by a hydrothermal method,and thus the V2O5 nanofibers were obtained.Owing to the unique 1D structure of nanofibers which can offer sufficient reactive sites and reduced ion diffusion paths,efficient Znstorage performance can be achieved for the cathode material.The V2O5 nanofibers can deliver a discharge capacity as high as 264.5 mAh g-1 at 200 mA g-1.Even at 2000 mA g-1,a desirable rate capability of 132.6 mAh g-1 can be obtained.Besides,the V2O5 nanofibers possess a reliable structural stability after repeated cycles.Compared with its counterpart of the commercial V2O5,a competitive advantage is well revealed.(3)Electrospun V2O3@C nanofibers(V2O3@C NFs)as a flexible and binder-free cathode.Specifically,C15H21O6V and PAN were mixed with DMF,and the precursor solution was obtained.By a electrospinning method combined with a stabilization and carbonization process,the final product of V2O3@C NFs was obtained.Due to the structural merits of V2O3@C NFs with nanosized V2O3 crystals uniformly distributed in carbon nanofibers,enhanced charge conductivity can be achieved for desirable transfer kinetics of electrode.The V2O3@C NFs delivers a largest specific capacity of 220 mAh g-1 at 50 mA g-1.Even after 1000 cycles at 200 and 2000 mA g-1,the specific capacity can still be remained with 120 and 100 mAh g-1,respectively.Besides,the V2O3@C NFs can be matched with the flexible Zn anode and thus demonstrates a promising application potential in the field of the flexible electronic devices.