Synthesis And Lithium (Sodium) Storage Performance Of Copper-based Chalcogenide Composites

Owning to the popularity of electric vehicles and the development of large-scale energy storage applications,it is urgent to develop high-performance lithium-ion batteries（LIBs）and sodium-ion batteries（SIBs）to satisfy continuously surging market demand.As the essential component of batteries,anode materials play a critical role in battery performance.Therefore,the exploration of anode materials,possessing high specific capacity and good cycle stability is of great importance to energy storage.Copper-based chalcogenides have been considered a promising anode material for lithium/sodium ion batteries based on their high theoretical capacity and unique physicochemical properties.However,the crushing and dissolution of the electrodes caused by the structural rearrangement and large volume expansion during cycling will lead to rapid capacity decay.This dissertation chose copper-based chalcogenides as the research object.Various optimization strategies,such as nanostructural construction,carbon coating and composition modification,were employed to prepare high-performance Cu₉S₅/CNFs and Cu_2-xSe/Mo Se₂/CNFs composites,and their lithium（sodium）storage behaviors were investigated simultaneously.The main contents of this work are as follows:（1）Cu₉S₅ nanoparticles embedded in N,S co-doped carbon nanofibers（Cu₉S₅/CNFs）were fabricated by electrospinning assistance with high-temperature sulfuration process.By facilely adjusting the annealing temperature,the controllable fabrication of morphology and heteroatom doping could be achieved.With the unique hierarchical structure and heteroatom doping,the Cu₉S₅/CNFs-600 electrode delivers a high capacity of 709.2 m A h g^-1 at 0.1 A g^-1 after 100 cycles for LIBs.When used as the anode material for sodium-ion batteries,the electrode maintains a reversible capacity of 231.8 m A h g^-1 after 1500 cycles at a current density of 1.0 A g^-1（with 90.5%capacity retention）.It also shows good stability in the full cell paired with Li Fe PO4 cathode.（2）To overcome the problems associated with poor cycling stability and low utilization of active materials in single-phase copper-based chalcogenides anode materials.Cu_2-xSe/MoSe₂/CNFs composite was synthesized by compounding Cu_2-xSe with MoSe₂ using electrospinning combined with high-temperature selenization process.With the introduction of Cu_2-xSe/MoSe₂ heterointerface,the improved electrochemical activity of the electrode can be achieved.That led to the faster electrochemical reaction kinetics,which further enhances the pseudocapacitive effect of the electrode.In addition,nitrogen and selenium co-doped carbon nanofibers can not only improve the electrical conductivity of the material,but also act as a buffer matrix to deliver better cycling stability.Based on the above merits,the Cu_2-xSe/MoSe₂/CNFs electrode can achieve a reversible capacity of 1121.3 m A h g^-1 after 150 cycles at 0.1 A g^-1 for LIBs.Furthermore,When used as the anode materials for sodium-ion batteries,it exhibits a remarkable cycling life with a reversible capacity of 259.2 m A h g^-1 at a current density of 1.0 A g^-1 over 2000 cycles,with a capacity retention rate of 93.5%.