| The increasing shortage limitation of lithium resources has promoted the extensive research of sodium/potassium ion batteries,but the poor reaction kinetics and low specific capacity of sodium/potassium ion batteries limit their development.In this thesis,Li1.3Al0.3Ti1.7(PO4)3(LATP)with high sodium diffusion coefficient and NiCo2O4/NiCo2Se4 with high theoretical specific capacity are synthesized,and sodium/potassium storage is studied in detail.(1)The low electronic conductivity of LATP doesn't benefit the Faraday reaction,with poor electrochemical activity.Coating carbon on the surface of LATP can significantly overcome this disadvantage.The electronic conductivity of LATP@C composite material is highly improved,which is beneficial of the cathode materials for sodium ion batteries.(2)The sodium diffusion coefficient and sodium diffusion activation energy of 7.8 wt%carbon coated LATP are 3.32×10-8 cm2s-1 and 0.179 eV at room temperature,respectively.7.8 wt%carbon coated LATP shows the best electrochemical performance:the capacity retention rates are 99.56%,99.4%and 99.4%after 1000 cycles at various rates of 5C,10C and 20C,respectively.The initial discharge specific capacity of 7.8 wt%carbon coated LATP is about 108.9 mAh g-1 at 20C,and the capacity almost remains unchanged at different rates from 1C up to 20C.(3)The synthesized NiCo2O4 is with core-shell structure,flower-shaped spherical structure,three-dimensional flower-shaped spherical structure,and its derivative NiCo2Se4 shows similar structured morphology.As the anode materials for potassium ion batteries,the flower-shaped spherical structure can significantly improve the utilization rate and discharge specific capacity.More interestingly,the substitution of Se for O can increase the electronic conductivity and chemical reaction kinetics of the anode materials.The flower-shaped spherical NiCo2Se4 is with an initial discharge specific capacity of 751 mAh g-1 at a current density of 100 mA g-1. |
PDF Full Text Request