The Synthesis And Electrochemical Performances Study Of High-Performance P-Based Anode Materials For Sodium-Ion Battery

In recent decades,the development and advancement of lithium ion battery(LIB)technology have greatly changed people's lives.However,the limited availability of lithium sources,the price of lithium-ion batteries and the sustainability of lithium sources cannot meet the needs of large-scale energy storage systems.Therefore,it is necessary to develop secondary energy storage batteries with excellent performance and low price.Since sodium is abundant in the earth's crust,meanwhile,its chemical properties are similar to lithium-ion batteries.Sodium-ion batteries(SIB)are considered as the best candidates for secondary energy storage batteries.Phosphorus-based materials have excellent sodium storage capacity so that they are seemed as ideal sodium-ion anode materials.However,their conductivity are poor,and the alloying reaction with sodium during charging and discharging produces a large volume expansion in practical applications,resulting in poor cycle reversibility and poor rate performance.In this thesis,the phosphorus-based electrode material was synthesized by designing the morphology.Phosphorus was combined with hierarchy porous hollow CoS,and multi-cavity carbon spheres.The electrochemical properties and its corresponding electrochemical reactions were studied as sodium ion anode materials.The main research contents include:1.Hierarchical and porous hollow CoS with uniform size and diameter between about 200-300 nm was prepared by solvothermal method in hard templating way.Red phosphorus was limited in CoS by vaporization-adsorption method to obtain P@CoS.Due to its unique porous and hierarchical structure,the transmission distance of sodium ions and electrons is effectively shortened,and the migration efficiency of ions and electrons is improved.At the same time,the increased specific surface area provides more active sites for reversible sodium storage.When the electrochemical performance test as sodium-ion anode material exhibited extremely long and stable charge and discharge cycle life.In the electrochemical test,when P@CoS is used as a sodium-ion anode material,the first discharge capacity of the battery is 662.5 mAh·g-1 at the current density of 200 mA g-1.and the capacity can still be maintained 201 mAh·g-1 after about 300 cycles.2.Multi-cavity nano-carbon spheres(MCC)connected porous carbon walls were prepared according to the surface energy-driven self-assembly method.The internal space was divided into multiple small grids connected by multiple porous carbon walls,and the adsorption capacity of the internal space was enhanced.Therefore,P@MCC with high phosphorus loading was obtained by vaporization adsorption.P@MCC composite as anode of Sodium-ion battery,at the current density of 50 mA g",the first discharge specific capacity is 945.4 mAh·g-1.The capacity is maintained at approximately 342.5 mAh·g-1 after 150 cycles,showing excellent cycle performance.