Preparation Of Vanadium Oxide Cathode Materials And Study Of Magnesium Storage Properties

In this paper,in view of the incompatibility between cathode materials and electrolyte,slow kinetics and high polarization of cathode materials,a new type of magnesium ion battery system is proposed.The spinel vanadium oxide and V₂O₅ were selected as cathode materials for magnesium ion batteries,which solved the problems of slow kinetics and high polarization of cathode materials,and applied to magnesium ion batteries and magnesium metal batteries.In this paper,we adjusted the crystal structure and interlayer of vanadium oxide,and studied the reaction mechanism by using advanced characterization methods.In order to realize the reversible and rapid storage of magnesium ions and have great significance for the development of magnesium ion batteries.We selected the degassing spinel oxide Mg(Mg_0.5V_1.5)O₄ and V₂O₅ intercalated with polyaniline as the research objects,and achieved some significant research results have been achieved:（1）Mg(Mg_0.5V_1.5)O₄（MVO）was prepared by hydrothermal synthesis and high temperature calcination as cathode material for magnesium batteries.The results show that the assembled Mg ion battery has high specific capacity(250 m A h g^-1)and stable long cycle performance（up to 500 cycles）.In addition,MVO can still show high rate performance in non corrosive electrolyte,which is superior to the previously reported cathode materials for magnesium batteries.These excellent properties are mainly due to the rapid kinetics of magnesium ions in MVO cathode materials.In addition,a series of characterizations were carried out to verify the magnesium removal process during MVO charging.It is proved that the storage mechanism of Mg ion storage in MVO is the coexistence of two phases and the coexistence of single phase reaction.Full MIBs comprising a MVO cathode,Mg（TFSI）₂/acetonitrile（AN）electrolyte and NTO anode were assembled,and they displayed good electrochemical performance.In this study,a kind of high performance spinel oxide containing removable magnesium ions was introduced in detail as the cathode material of magnesium ion battery,which provided a new idea for the design of cathode material of magnesium ion battery.（2）Polyaniline embedded V₂O₅ superlattice with layered structure was successfully prepared by chemical modification as cathode material for magnesium ion batteries.The introduction of conductive polymer polyaniline not only enlarges the interlayer spacing of V₂O₅,but also improves the conductivity of V₂O₅.It solves the problem that the space between vanadium oxide layers is limited,which is not conducive to the rapid diffusion of magnesium ions.The reversible capacity,Mg²⁺diffusion kinetics and cycling performance of V₂O₅ were significantly improved by inserting polyaniline between V₂O₅layers.The results of X-ray diffraction show that the crystal structure of PVO（V₂O₅―PANI）has no obvious phase transition with the continuous insertion of Mg²⁺,which is due to theπ-πconjugated chain of polyaniline,which makes the structure of PVO flexible,alleviates the interaction between magnesium ions and host,and improves the cycle stability.More importantly,when assembled with magnesium metal as negative electrode,the battery shows a specific discharge cfapacity of 115 m A h g^-1 at a current density of100 m A h g^-1.This study shows that the design organic-inorganic superlattices for magnesium battery cathode materials not only greatly improves its electrochemical performance,but also solves the problem of vanadium oxide matching with magnesium metal anode.The design of this organic-inorganic superlattice structure has made a significant contribution to the development of high-performance magnesium battery.