Study On The Preparation And Energy Storage Mechanism Of Zinc-Based Selenide

Sodium-ion batteries are the most promising alternatives to Lithium-ion batteries due to their low cost and abundant sodium resources.ZnSe has a higher theoretical capacity,but it also has a lower cycle life due to its poor electrical conductivity and larger volume expansion during sodium storage.Based on the advantages and disadvantages of ZnSe,this paper improves the ZnSe anode material performance by means of valence bond cross-connection,spatial confinement,nano-micro-tuning,energy band reconfiguring,to improve the electron and ion transfer rate,and relieve the volume expansion.The sodium storage mechanism of ZnSe,CuZnSe@NC and the interfacial behavior with carbon-based materials are elucidated,revealing the deep influence of the second metal ion on the morphology,energy band,electronic structure of ZnSe nanoribbons.The main findings are as follows:（1）Using the complexation effect of citric acid,ZnSe/C composites with 3D hierarchical structure were successfully prepared by calcination.The experimental along with calculations results reveal Zn-O-C bonds served as electron/charge bridge accelerate charge/ion transfer,indicating fast reaction kinetics.The 3D carbon network improves structure stability by restricting volume expansion.Under the combined effect of Zn-O-C bond and steric confinement effect,ZnSe/C composites show an ultra-long lifetime of 1000 cycles at 5 A g^-1 with a capacity of 281 m A h g^-1.（2）Bimetal Selenide Heterojunction CuZnSe@NC nanobelts with unique structures were designed and fabricated by cation exchange method.Due to the Cu²⁺partial replacement Zn²⁺in the ZnSe@NC,the lattice distortion resulting from the mismatch of lattice parameters provides abundant active sites.After the construction of the heterojunction,the difference in work function leads to charge rearrangement,the band structure of the material is reconfigured,and the overall performance and electrochemical environment are optimized.When used as a negative electrode material for Na-ion batteries,CuZnSe@NC has a stable capacity of 411.5 m A h g^-1 after 1000 cycles at 1 A g^-1,and still has an ultra-high specific capacity of 361.8 m A h g^-1 at a large current density of 5 A g^-1.This thesis includes 48 figures,5 tables and 139 references.