| Lithium-ion batteries（LIBs）with high energy density have garnered considerable attention in energy applications.However,the limited reserves and uneven distribution of lithium result in high costs,thus impeding sustainable application of LIBs in the energy sector,particularly in electronic devices and electric vehicles.Sodium presents several advantages,including abundant reserves,uniform distribution,and physical and chemical properties akin to lithium,making sodium-ion batteries（SIBs）a promising contender for the next-generation energy storage technology.Nonetheless,Na+has a larger ionic radius of 0.0102?compared to Li+at 0.0076?,resulting in slower diffusion kinetics of Na+in the active electrode material and increased likelihood of volume changes during charging and discharging.These factors significantly affect the cycling stability of SIBs,rendering the search for a suitable and structurally stable electrode material an urgent need for the development of sodium-ion batteries.Transition metal phosphides（TMPs）and sulfides（TMDs）have high specific capacity and suitable redox potential as anode materials for SIBs.However,when used as anode materials for sodium-ion batteries,TMPs and TMDs present several issues:（1）poor electrical conductivity and ion diffusion properties lead to slow charge and discharge rates,limiting their application in high multipliers.（2）The structure of electrode materials tends to pulverize due to significant volume changes during the charging/discharging process,resulting in a reduced cycle life.To address the issues faced by both materials mentioned above,this dissertation takes a comprehensive approach,starting with structural design and material compounding.1.Preparation of CoP@NC nanosheets and the study of sodium storage properties.CoP@NC nanosheets were prepared by a combination of solvothermal and calcination treatments.The nanosheet structure of CoP@NC greatly reduces the ion and electron transport paths and provides abundant active sites.The nitrogen-doped carbon coating substantially enhances the negative electrode’s reversible capacity and cycling stability in sodium-ion batteries,resulting in exceptional electrochemical performance of CoP@NC as an anode material.Even after 100 cycles at a current density of 0.1 A g-1,CoP@NC exhibits a high reversible capacity of 265.1 m Ah g-1.The excellent multiplicative performance of CoP@NC is evident from the specific capacities of 258.3m Ah g-1 and 101.1 m Ah g-1 displayed by the electrodes at current densities of 0.1 A g-1and 2 A g-1,respectively.This performance is considerably superior to the published related work.2.Preparation of C u S nanowires by metal organic gels derivatization and their sodium storage properties.Cu-based metal organic gels were prepared by complexation of metal ions with1,3,5-tri（4-carboxyphenyl）benzene（H3BTB）at room temperature,and the nanowires of CuS were obtained after sulfidation of the gel.the nanowire structure of CuS greatly reduces the ion as well as electron transport paths.Based on the above advantages,CuS nanowires shows excellent sodium storage performance(reversible capacity remains380.3 m Ah g-1 and 297.4 m Ah g-1 after 200 cycles at current densities of 0.1 A g-1 and0.5 A g-1,respectively)and excellent cycle stability(specific capacity decay rate of about5.4%after 750 cycles at current densities of 2 A g-1)when used as the anode of sodium ion batteries. |
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