Synthesis Of Vanadium Oxides Nanomaterrials And The Electrochemical Performance For Zinc-ion Batteries

With the development of energy conversion systems and energy storage technologies,more and more attention has been paid to various types of new metal ion batteries.Among them,rechargeable aqueous zinc ion batteries?RAZIBs?are considered to be one of the most promising energy storage systems.Because of its lots of advantages,such as high safety,low cost,environment friendliness,convenient assembly,abundant zinc reserves in nature,large theoretical capacity,and high ionic conductivity of aqueous electrolyte(10^–1?6 S cm^–1).Continuous research and development of high-performance cathode materials have great significance for the commercial application of RAZIBs.At present,vanadium oxides materials are considered to be the most promising cathode materials for RAZIBs due to their rich reserves,low cost,multivalent state of vanadium,and high theoretical zinc ion storage capacity(589 mAh g^–1).However,there are some problems in vanadium oxide materials,such as low conductivity,complex energy storage mechanism,and slow diffusion kinetics of zinc ions.Which makes performance of the RAZIBs is unsatisfactory.In this paper,the synthesis of silver vanadate@hydrated vanadium pentoxide(Ag_0.333V₂O₅@V₂O₅·nH₂O)core-shell coaxial nanocable structure,conjugated polyaniline and water molecules are co-intercalated in vanadium pentoxide to obtain the large layer spacing rose-like polyaniline and water co-intercalated vanadium oxide?PVO?structure and porous carbon/hydrated vanadium oxide nanosheets?PC/V₂O₅·nH₂O?to improve the conductivity of vanadium oxide,zinc ion diffusion rate and zinc ion storage kinetics.And the above materials are tested for electrochemical performance and zinc storage mechanism of RAZIBs.The specific research contents of this article are as follows:?1?Through a simple one-step hydrothermal treatment process,Ag_0.333V₂O₅@V₂O₅·nH₂O coaxial nanocables are obtained as the positive electrode of RAZIBs.Such a dense electrode architecture constructed by the silver vanadium oxide@water-pillared vanadium oxide core-shell(Ag_0.333V₂O₅@V₂O₅·nH₂O)coaxial nanocables that maintains optimal ion/electron percolation without admixing the additional inert component.This electrochemically-robust architecture is composed of a highly electronic conductive phase of silver vanadate and a highly ionic conductive phase of structure water-pillared V₂O₅·nH₂O,which synergistically form a coaxial nanocables structure benefiting for ion/electron contact and penetration in practically thick electrode.Compared with pure Ag_0.333V₂O₅ and V₂O₅/V₂O₅·nH₂O electrode materials,the Ag_0.333V₂O₅@V₂O₅·nH₂O coaxial nanocables deliver higher reversible capacity(312.1 mAh g^-1 at 0.5 A g^-1),excellent rate capability(196.7 mAh g^-1 at 3.0A g^-1)and more stable cycling performance(261.7 mAh g^-1 at 0.5 A g^-1 after 100cycles).Our work emphasizes the design of the binary mixture of ion and electron conduction to enhance the storage performance of zinc ions.And the feasible strategy of constructing effectively ionic/electronic percolating thick electrodes to boost the reaction kinetics that can also be applied to other active materials for practical multivalent batteries.?2?A conjugated polyaniline intercalating strategy is firstly proposed to improve the zinc ion storage properties for low cost vanadium oxide.The rose-like polyaniline-intercalating vanadium oxide?PVO?architectures have been successfully synthesized through a facile in-situ oxidative/intercalative polymerization of aniline into vanadium oxide.During the intercalation processes of aniline,the valence of vanadium reduces to V⁴⁺and simultaneously the polyaniline could be formed in the interlayers of the vanadium oxide host.After the conjugated polyaniline intercalation,the interlayer spacing of the layered materials increases from 5.77 to 14.02?.The rose-like PVO architectures deliver an outstanding specific discharge capacity(420.4mAh g^-11 at 0.5 A g^-1),superior long cycle performance(400 mAh g^-11 at 5 A g^-1),high capacity retention rate?87.5%after 600 cycles?and greatly improved rate performance(288.9 mAh g^-11 at 20 A g^-1).The electrochemical results show that the rose-like polyaniline-intercalating vanadium oxide architectures display unprecedented zinc-ion storage performances,outperforming most of guest ion/small molecular-intercalating vanadium-based compounds.Furthermore,a unique intercalation-conversion zinc-ion storage mechanism has been firstly proposed.This strategy paves an avenue to tune electronic structure,interlayer spacing and microstructure towards advanced energy storage applications.?3?The porous carbon/V₂O₅·nH₂O nanosheets?PC/V₂O₅·nH₂O?is prepared by an extremely simple magnetic stirring mothed.Utilize porous carbon nanosheets as a supporting framework,hydrated V₂O₅ is uniformly loaded on porous carbon.Which is not only effectively inhibits the aggregation and stacking of V₂O₅·nH₂O,but also increases the contact area between the active substance and the electrolyte,which is more conducive to the transport of zinc ions and improves the electrochemistry of RAZIBs.As anticipated that the PC/V₂O₅·nH₂O displays excellent rate performance(325.3 mAh g^-1 at high current density 20 A g^-1),high specific discharge capacity of415.4 mAh g^-1 at 0.5 A g^-1 than the stacked V₂O₅·nH₂O(240 mAh g^-1 at 0.5 A g^-1),outstanding cyclic stability and capacity retention?after 1000 cycles the capacity retention rate about 97.1%?.The investigation of the reaction mechanism shows a reversible intercalation&conversion.This material design method provides ideas for the design of cathode materials for multivalent batteries,which need to be prepared in large quantities in practical applications.