Application Of Iron-based Selenide Porous Carbon Composites In Energy Storage

In order to achieve the dual-carbon goals of"carbon peak"and"carbon neutrality",lithium-ion batteries have played an irreplaceable role in the rational use of clean and renewable energy.However,with the continuous development of informatization in the current era,the use of portable phones is becoming more and more extensive,and it is difficult for commercial graphite negative electrodes to meet the demand.Therefore,the development of larger capacity,high-performance anode materials is imminent.Among them,iron-based selenides have been widely studied as a high-performance anode material.Iron-based selenides have the characteristics of extensive sources,environmental friendliness,and high theoretical capacity.However,when used as anode materials for lithium-ion batteries,defects such as large volume expansion and low electrical conductivity restrict the development of iron-based selenides to high performance.In order to improve these defects,in this paper,Fe Se@carbon nanorods（Fe Se@C）and Fe Se₂@porous carbon fibers（Fe Se₂@PCF）were prepared by nano-confinement design by combining iron-based selenide with carbon materials.through different electrochemical tests and characterizations to study its lithium storage performance and mechanism.（1）Preparation of porous Fe Se@C nanorods and their lithium storage properties.Nano-confined porous Fe Se@C nanorods were fabricated using Fe-MOF as precursor.In this design,the confinement effect of silica is used to effectively confine Fe Se in the form of nanoparticles inside the carbon shell,avoiding the precipitation and agglomeration of metal particles,and ensuring the electronic and ionic properties of the material.transfer ability.During the calcination process,the silica layer slows down the thermal cracking of the internal organic ligands,and after etching,a protective structure of a double-layer carbon shell is formed,and the outer carbon shell enhances the structural strength and ensures the structural integrity of the material properties,providing the battery with stable cycle performance.The internal porous structure not only provides sufficient buffer space for volume expansion during charge and discharge,but also provides more surface active sites,optimizes the ion transport channel,and ensures the rate capability of the material.Electrochemical performance tests show that after 1000 cycles at a high current density of 5 A g^-1,the discharge capacity remains at 329.7 m Ah g^-1,and the capacity retention rate is 95.9%.（2）Preparation of porous Fe Se₂@PCF and its lithium storage properties.Fe Se₂@PCF with uniform diameter and porous structure was prepared by electrospinning technology and confinement of silica.The confinement effect of silica makes Fe Se₂ evenly dispersed in the carbon fiber with small particles,which improves the electrochemical activity and enables the battery to have excellent rate performance.The one-dimensional carbon fiber shortens the ion transmission path,enhances the electrical conductivity of the material,supports the overall structure of the material,and provides flexibility for the electrode,which can release the mechanical stress during charging and discharging.The large number of micropores also slows down the volume expansion of the material during cycling and improves the cycling performance.Electrochemical performance tests show that at a current density of 1 A g^-1,the Fe Se₂@PCF anode still has a reversible capacity of782.6 m Ah g^-1 and a capacity retention rate of 99.0%after 200 cycles.