Application Of Selenium And Selenide In Lithium-ion Batteries

Lithium-ion battery,as a portable energy storage device,has the advantages of high recycling rate,environmental protection and pollution-free,and has become an important energy storage device in the 21^st century.Traditional lithium-ion batteries have the disadvantage of low capacity and have been unable to meet the market demand for electronic products such as mobile electronic devices and electric cars.Therefore,it is of great significance to develop lithium ion battery electrode materials with high capacity and long life.Selenium,as a congener of sulfur,can be used as a positive electrode material for lithium ion batteries,and has attracted the attention of some researchers in recent years.The theoretical specific capacity of selenium element is 675 m A h g-1,and its theoretical specific volume(3260 m A h cm^-3)is the same as that of sulfur(3467 m A h cm^-3).This is because selenium has a higher density.This shows that selenium has the potential as an electrode material.In addition,selenium has a higher electron conductivity(1×10^-3 S m^-1)than sulfur(5×10^-28 S m^-1),which means it has a higher cathode material Utilization.However,from the perspective of chemical similarity,the selenium positive electrode also has the same disadvantages as sulfur:the electrochemical reaction intermediate?polyselenide?can dissolve in the electrolyte and migrate to the negative electrode during the cycling process?shuttle effect?,resulting in irreversible capacity loss.Aiming at this problem,this paper uses metal-organic framework materials as carriers,and cleverly designs sandwich-like sandwich structures to restrain the active substance selenium.In addition,in this paper,the application of selenium in the anode material of lithium ion batteries is studied by rationally designing the iron selenide/carbon composite material?selenium exists in the form of iron selenide?.The main research contents and conclusions of this article are as follows:?1?Using Co-MOF?ZIF-67?as a carrier,the central metal Co²⁺ion is exposed to more active sites through vacuum heating.Then ZIF-67@Se@Mn O₂ composite was successfully prepared by melt diffusion and post-modification methods.After comparison,the pure MOF material does not limit the shuttle effect well,and the ZIF-67@Se@Mn O₂composite material provides more active sites for selenium binding,and the structure of the MOF@Se@oxide is constructed to Limiting polyselenide shuttles.The ZIF-67@Se@Mn O₂ positive electrode exhibited an initial specific discharge capacity of306 m A h g^-1 at 1 C,and the specific discharge capacity remained 83.7%after 100 cycles at the same current density,and the Coulomb efficiency showed Out of nearly 100%high stability.The content of this study shows that constructing a sandwich-like sandwich structure effectively limits the effect of the shuttle effect on the cathode material.?2?Using Zr-MOF?UIO-67?as a carrier,and also vacuum heating,so that the center metal Zr⁴⁺ions expose more active sites.Unlike the previous preparation method,the sandwich-like sandwich structure of the UIO-67@Se@PANI cathode material is achieved by coating with a polyaniline?PANI?layer.The specific capacity of pure UIO-67@Se material decreases rapidly in the cycle,which also proves that MOF material alone cannot well limit the shuttle effect.The specific discharge capacity of the UIO-67@Se@PANI positive electrode at 1 C was 248.3 m A h g^-1,and the specific capacity retention rate after cycling 100 times at this current density was 91.4%,showing excellent electrochemical performance.?3?A high-performance Fe Se₂-C/r GO anode material was prepared by vacuum calcination using metal organic gel?MOG?as a precursor.Thanks to the coating of reduced graphene,not only Fe Se₂ is restricted to a smaller size,but the overall conductivity of the material has been improved.Therefore,Fe Se₂-C/r GO anode materials show excellent cycleability and rate performance in LIB.After 100 cycles,the specific discharge capacity of the battery with Fe Se₂-C/r GO as the anode material at a current density of 100 m A g^-1was 917.7 m A h g^-1,which was almost the same as the initial discharge capacity.Furthermore,it showed a specific discharge capacity of 628.7 m A h g^-1 after 500 cycles under a large current density of 1000 m A g^-1.This research provides new ideas for designing metal selenide electrode materials.