Design And Electrochemical Zinc Storage Properties Of Manganese/Vanadium Oxide Materials

The development of new energy is inseparable from the energy storage.For the field of energy storage system,secondary battery can provide technical support in the process of implementing the dual-carbon strategy and promoting the development of new energy,so that the field of new energy can enter a stage of rapid development.At the same time,there are still some bottlenecks in the battery industry in the face of huge opportunities.At present,the supply of resources and materials in the battery industry is insufficient,resulting in increased battery costs and there are serious safety problems in commercial lithium-ion batteries.Aqueous zinc-ion batteries（ZIBs）stand out from many secondary batteries and become an electrochemical energy storage system with great potential due to their high safety,low cost,abundant zinc reserves,and simple preparation process.Manganese oxides and vanadium oxides with open framework structures and various oxidation states are currently the most promising cathode materials for Zn-ion batteries.However,their slow diffusion kinetics of zinc ion and material dissolution hinder the further application.In view of this situation,this thesis starts from the aspects of ion pre-intercalation,construction of composite materials to design suitable cathode materials,and the effects of ion pre-intercalation and composite materials on the zinc storage performance of manganese/vanadium oxide materials were investigated.（1）Graphene quantum dots-manganese dioxide composites and their zinc storage propertiesAiming at solving the typical problems of manganese oxides,such as fast capacity fading and slow transport kinetics.A new type of manganese dioxide composites anchored with graphene quantum dots（labeled as Mn O₂-GQDs）were synthesized by a one-step hydrothermal method,which aims to improve the electronic conductivity of manganese dioxide and facilitate the transport kinetics of zinc-ion batteries.Anchoring GQDs on manganese dioxide nanowires can accelerate the transport kinetics of Zn-ion batteries and suppress the manganese dissolution during the cycling process.The as-prepared Mn O₂-40GQDs electrode can exhibit a high specific capacity of 295.7 m Ah g^-1 and excellent capacity retention（88.99%）at a current density of 0.1 A g^-1 after 100 cycles.（2）The design of europium ion pre-intercalation in vanadium pentoxide and its zinc storage performanceIn view of the main problems faced by vanadium-based cathode materials,a europium ion pre-intercalated vanadium oxide material（labeled as Eu-VO）was prepared by pre-intercalating cations into vanadium pentoxide.vanadium pentoxide with open two-dimensional channels can provide intercalation sites for water molecules and cations,which can adjust the original crystal structure for the better insertion/extraction of zinc ions.The as-prepared Eu-VO cathode material delivered a high specific capacity of 489.4 m Ah g^-1 at a current density of0.1 A g^-1,and exhibited excellent rate and cycling performance.Compared with commercial vanadium pentoxide,the vanadium oxide after europium ion pre-intercalation can stably intercalate/extract zinc ions during the first charge and discharge process,which greatly shortens the activation process of zinc intercalation.