In next-generation energy storage systems, Na-ion batteries have attracted attention as an alternative to Li-ion batteries due to the low cost and abundant natural reserves of metallic Na. Transition metal selenides, as anode materials for sodium-ion batteries, have attracted much attention from researchers due to their high theoretical capacity. Due to the large volume change of metal selenides during cycling, it is easy to destroy the material structure and the instability of the SEI film, resulting in fast capacity decay and poor rate performance of Na-ion batteries during cycling. To make better use of the advantages of transition metal selenides, it is necessary to modify transition metal selenides. Based on the above background, a series of selenide composite materials were prepared by adjusting the atomic ratio, doping, and other strategies, and applied to sodium-ion batteries. The research content and results are as follows: (1) Using K3[Fe(CN)6] as the precursor, first calcined at high temperature, and then selenized at different temperatures, a series of FeSe/N-doped carbon composite materials and electrode materials were obtained. The results show that when the atomic ratio of Fe and Se is 1:2, the resulting product/NC exhibits the best electrochemical performance and still maintains the g-1 discharge-specific capacity.  There are three main reasons for the improved sodium storage performance of /NC electrode materials: 1) the high content of pyridine nitrogen and pyrrole nitrogen provides more active sites for Na+; 2) the high content of carbon structure defects is beneficial to improve the conductivity of the material, At the same time, the existence of carbon nanotubes can also effectively alleviate the volume change during charge and discharge; 3) /NC has strong conductivity, and the phase change resistance during charge and discharge is small, which makes the diffusion of Na+ smoother, thereby improving the electrochemical performance.

(2) Vulcanize /NC to obtain .4S1.6/NC solid solution composite material, which is used as anode material for sodium-ion batteries. The results found that, compared with /NC and FeS2/NC, the .4S1.6/NC solid solution composite electrode material exhibited better electrochemical sodium storage performance. When the current density is 10.0A g-1, the discharge-specific capacity of g-1 is still maintained after 7000 cycles, and the Coulomb efficiency is stable, indicating that the 4S1.6/NC solid solution composite electrode material has very good cycle stability. .4S1 .6/The main reasons for the improvement of the sodium storage performance of NC electrode materials: 1) The incorporation of anions (S2-) improves the conductivity, enhances the electron transfer ability, and greatly improves the electrochemical performance; 2) Compared with undoped and FeS2 Compared with .4S1.6/NC, the content of pyridinic nitrogen and pyrrole nitrogen is higher, which can provide more active sites and thus improve the electrochemical activity. This study provides an effective method and strategy for the development of Na-ion batteries.  (3) Preparation of Cu2-xSe/(Co, Cu)Se2 solid solution composites by high-temperature calcination and selenization. The temperature was found to be an important factor in the formation of Cu2-xSe/(Co, Cu)Se2.  The Cu2-xSe/(Co, Cu)Se2 solid solution composite exhibits significantly better sodium storage performance than /and, and the discharge specific capacity can still reach g-1 after 3000 cycles at a current density of 10.0A g-1, namely The excellent electrochemical activity benefits from the synergistic effect between atoms after the solid solution is formed, which improves the kinetics of the sodium ion storage reaction. The doping of copper can improve the cycle life and rate performance of the electrode material, which is beneficial to the Na+ in the lattice. Diffusion quickly. And enhance the conductivity of the electrode. This indicates that the synergy between atoms after the formation of a solid solution plays a crucial role in the improvement of sodium storage performance. Expand▼