Preparation And Modification Of Tin-based Anode Materials For Sodium Ion Batteries

Lithium-ion batteries are widely used as energy sources in portable consumer electronic products.However,the high cost and limited availability of lithium salt resources limit the large-scale application of lithium-ion batteries.Sodium-ion batteries have a lower cost,but the energy density is generally lower than lithium ion batteries.In order to improve the energy density of sodium ion batteries,it is necessary to explore the synthesis process of anode materials with high specific capacity.Tin-based materials have a higher specific capacity,but powdering of the material occurs during the cycle,and the cycle stability is poor.This paper has carried out related research on the synthesis of tinbased negative electrode materials and carbon coating modification to improve its performance in sodium ion batteries.First,the synthesis of tin phosphide alloy materials was explored by solvothermal method and ball milling method,and the corresponding characterization was carried out.By controlling the reaction time,pure phase Sn₄P₃ crystal material was obtained.The cycle performance test was conducted,and the first discharge capacity reached 513.43 m Ah/g.When the cycle was 100 cycles,the remaining specific capacity was 60.69 m Ah/g,and the capacity retention rate was 14.41%.Amorphous Sn₄P₃ material was synthesized by ordinary ball milling method,and its particle size was micron.The cycle performance test was carried out,and the first discharge capacity reached 754.48 m Ah/g.When the cycle reached 100 cycles,the remaining specific capacity was less than 10 m Ah/g,and the retention rate was poor.Because the ball milling method is easy to operate,the powder particle size is small and the output is high,it has obvious engineering application advantages,so the ball milling conditions are changed to high-energy wet ball milling,and by controlling the ball milling time,two groups of Sn₄P₃ and Sn P3 phosphating are synthesized Tin material.Among them,the Sn₄P₃-36 h and Sn P3-36 h groups of powders all reached nano-scale particles,and the specific capacity retention rate of 100 cycles of the cycle performance test was more than 60%,which was a significant improvement compared with that.Nano-tin phosphide crystal material is further modified by high-energy ball milling carbon coating method,and a tough carbon layer is coated on the surface to synthesize nano-scale composite material.The modified material has significantly improved cycling performance.The Sn P3/C-36 group has a first discharge specific capacity of 670.02 m Ah/g,a second discharge specific capacity of 498.62 m Ah/g,and a residual specific capacity of 407.91 m Ah/g,81.72% of capacity retention rate after 100 cycles.Sn₄P₃/C-36 group,its first discharge specific capacity is 739.57 m Ah/g,the second discharge specific capacity is 430.74 m Ah/g,the remaining specific capacity after cyclic 100 cycles is 469.29 m Ah/g,the capacity does not decay.In order to pursue a higher specific capacity,we used a high-temperature solid-phase reaction method to synthesize layered Sn Se materials,and modified it with high-energy ball milling-assisted annealing treatment to obtain a reduced-coated carbon layer on the surface of the synthesized Sn Se materials to synthesize Sn Se /C composite material.For the electrochemical performance test,the first discharge specific capacity of Sn Se/C material is 876.58 m Ah/g,and the second discharge specific capacity is 681.61 m Ah/g.After 100 cycles,the remaining specific capacity is 563.74 m Ah/g The capacity retention rate is 82.78%,which has good cycle performance while maintaining a high reversible specific capacity.