Vanadium Phosphate Cathode Material For The Study Of Aqueous Multivalent Ion Batteries

The exploration of more efficient energy storage devices has been spurred on by the growing need for renewable energy storage.In recent years,rechargeable aqueous zinc-ion batteries and aqueous aluminum-ion batteries have many advantages,such as safety,environmental protection and cost effectiveness,and have the possibility of gradually becoming substitutes for the original lithium ion batteries.However,they still have problems such as low discharge specific capacity of cathode materials and dissolution in the cycle process.Although a lot of research has been carried out in the past,the development of aqueous multivalent state ion battery is still in its initial stage.Therefore,it is necessary to find the cathode material with excellent long cycle stability and high working voltage.In order to find cathode materials that can meet the requirements of both aqueous zinc ion battery and aqueous aluminum ion battery,we selected vanadium oxygen phosphate as the basic cathode material,because its layered structure can meet the requirements of intercalation of multivalent ions.However,as a typical phosphate cathode,vanadium phosphate has inherent low conductivity and structural dissolution problems in electrochemical reactions,which limits its development.In this paper,in order to solve these problems,the carbon composite modified VOPO₄ is specifically applied in the aqueous zinc ion battery and the aqueous aluminum ion battery,the specific research content is as follows:（1）First of all,we modified the carbon of vanadium phosphate,increased the interlayer distance,and constructed a conductive carbon network between the interlayer and the surface,and successfully prepared VOPO₄/C,which not only improved the electron conductivity of the cathode,but also effectively inhibited the dissolution of VOPO₄ in the aqueous electrolyte.Provide new solutions for the optimization of VOPO₄.（2）The carbon composite modified VOPO₄/C is applied to the aqueous zinc ion battery.At a current density of 100 mA g^-1,the aqueous zinc ion battery can achieve a specific discharge capacity of 141 mA h g^-1,which is twice that of the pure VOPO₄ cathode material.It has a marked enhancement in multiplier performance and long cycle performance,as well as a notable improvement in the kinetics of zinc ion migration.The structural stability of the composites is good after circulation,and there is no structural dissolution problem.It contributes a new strategy for the development of aqueous zinc ion cathode.（3）Using the carbon composite modified VOPO₄/C as the cathode of the aqueous aluminum ion battery,the electrochemical performance of the composite material has been significantly improved compared with the simple vanadium oxyphosphate.Moreover,the structure of the electrode was complete after circulation,and no structural dissolution problem appeared.The migration rate of Al³⁺in the cathode material is greatly improved,and the mechanism of Al³⁺intercalating and de-intercalating in the cathode material is studied.After charge and discharge cycle,there is no other aluminum oxide and other byproducts on the aluminum metal anode,indicating that VOPO₄/C can be used as a cathode of aluminum ion material for further exploration.