Preparation And Research On Carbon-based Composite Cathode Materials For Li/Na-Se Batteries

Lithium-ion batteries?LIBs?are widely used in portable electronic devices due to its high energy density and long cycle life.With the development of electric vehicles and clean energy in recent years,secondary battery systems with higher energy and power density have received widespread attention.Conventional LIBs cathode materials,such as LiFePO₄,LiCoO₂,and LiMnO₂,cannot meet the demand for use due to the limitations of theoretical specific capacity.Therefore,it is crucial to develop new battery systems with high energy density.At the same time,sodium ion batteries?SIBs?are considered a promising battery for large-scale energy storage due to the low raw material price and abundant reserves.Therefore,the development of high specific capacity and high energy density LIBs and NIBs cathode materials is imminent.In recent years,selenium?Se?cathode materials have been considered to be promising due to their high theoretical volumetric specific capacity(3253 mAh cm^-3)and high electrical conductivity.However,the application of selenium cathode still faces some problems,such as large volume expansion during charge and discharge,irreversible capacity attenuation caused by"shuttle effect",and low utilization rate of bulk selenium.Based on the above problems,this paper studied the effect of different carbon matrix for anchoring Se and discussed the effect of heteroatom doping.In addition,the MoSe₂@CNT/GO composite interlayer was also studied to enhance the cycle performance.The main research results are as follows:?1?Hierarchical radial-structured zinc glutamate?Zn-Glu?MOF precursor was prepared by precipitation method and pyrolyzed at high temperature to obtain nitrogen-doped microporous carbon.Se@N-HRMC was obtained by melt diffusion method.A series of characterization and analysis show that abundant micropores can well limit selenium and alleviate volume expansion.Small pore size can greatly increase the activity of selenium and improve the utilization of active materials.Doped nitrogen atoms can provide additional chemical adsorption to enhances the affinity of the matrix to the active material,and Se@N-HRMC exhibits excellent lithium storage and sodium storage properties.?2?A melamine-based porous organic skeleton was synthesized by hydrothermal method,which was pyrolyzed at high temperature to obtain a N,O,S-codoped porous carbon,and selenium was loaded by melting method.The DFT calculation shows that the rich hatereatoms doping can effectively enhance the affinity between the carbon material and the active material,and the porous structure can effectively alleviate the volume expansion and fully infiltrate the electrolyte.A series of electrochemical performance tests show that the prepared NOS-PC electrode has excellent lithium storage and sodium storage properties.?3?A porous organic polymer precursor was synthesized by Schiff base condensation reaction based on the polymerization of terephthalaldehyde and m-phenylenediamine in dioxane.The carbon microspheres with macropores and micropores was obtained by pyrolysis.When testing the lithium storage performance after loading selenium,it was found that the capacity was attenuate severe.Therefore,we designed a MoSe₂@CNT/GO composite interlayer to improve the utilization of active materials.A series of comparative studies on its electrochemical properties show that the MoSe₂@CNT/GO interlayer can greatly improve the stability of cycle peerformance.