Study On Preparation Of V₅S₈/Carbon And VN/Carbon Anode Materials For Sodium/potassium Storage

The development and storage of renewable energy is an important direction in the field of energy.Electrochemical energy storage technology as an important role is a major growth point.Although lithium ion battery has been successfully industrialized,the scarcity of lithium resources makes it unable to meet the huge market demand.Therefore,new energy storage devices such as sodium/potassium ion batteries with abundant sodium and potassium resources have become new research focuses.Both types of ion batteries require high performance active anode materials to broaden the scope of industrial applications.Vanadium based compound anode materials have high theoretical capacity,but the volume change during the insertion and release process of active ions leads to the instability of the material structure during the cycling process.In order to improve the properties of sodium/potassium storage,the structure of vanadium based compound anode materials were designed by electrostatic spinning method and hydrothermal method,respectively.The details are as follows:（1）V₅S₈ nanoparticles were synthesized with carbon nanofibers（V₅S₈/CNF）by electrostatic spinning and heat treatment.The V₅S₈/CNF anode with three-dimensional network structure shows excellent performance in sodium ion battery with a specific capacity of 351.0 m Ah g^-1 after 400 cycles at 0.2 A g^-1.Similarly,potassium ion battery at 0.2 A g^-1 shows a specific capacity of 289.2 m Ah g^-1 after 200 cycles.The sodium and potassium ion batteries exhibit very stable specific capacities of 251.0and 190.1 m Ah g^-1 after 10000 and 2000 cycles at 2 and 1 A g^-1,respectively.（2）By nitriding the electrospinning precursor,VN/CNF anode material of sodium ion battery was prepared.The material also has fibrous morphology.Carbon skeleton provides a three-dimensional channel for the rapid migration of sodium ions in which vanadium nitride particles anchored.The electrochemical test results show that the unique morphology of the material giving large electrolyte contact area,enlarging the reaction interface,which is conducive to the improvement of material properties.The material exhibits a discharge specific capacity of 230.3m Ah g^-1 at 0.5 A g^-1,and has good cycle stability at large current density.（3）VN/carbon fiber cloth anode material（VN/CFC）was prepared by hydrothermal method and heat treatment.Then,the properties of VN/CFC when used as sodium ion battery and potassium ion battery anode electrodes were explored.VN particles are loaded on each carbon fiber.Due to the unique self-supporting performance of carbon fiber cloth,the volume expansion of the material is effectively alleviated.And the non-binder electrode also reduces the capacity loss with the excellent cycle performances of 368.4 m Ah g^-1 after 100 cycles of 0.1 A g^-1 and 227 m Ah g^-1 discharge specific capacity after 1000 cycles of 2 A g^-1in sodium ion battery.The performances of potassium ion battery are also outstanding.The VN/CFC electrode has excellent cycle performances of 0.1 A g^-1/150cycles/204.9 m Ah g^-1 and 1 A g^-1/1000 cycles/125 m Ah g^-1.