Preparation And Properties Of ?-Fe₂O₃ Anode Materials For Sodium-Ion Battery

Lithium element will limit the development of lithium batteries in the future due to the high price and shortage of resources.In contrast,sodium has abundant resources,low cost and low toxicity,and similar properties between lithium and sodium,and thus rechargeable sodium-ion batteries have attracted widespread attention.However,the diameter of sodium ions is larger than that of lithium ions,and only a few electrode materials for lithium-ion batteries are suitable for sodium-ion batteries.Therefore,the exploration of electrode materials for sodium-ion batteries with high specific capacity and good cycle stability is highly desired for sodium-ion batteries.Electrode materials for sodium-ion batteries include carbon-based materials,alloys,metal oxides,and sulfide materials.Among them,?-Fe₂O₃ has high potential application with excellent chemical stability,high specific capacity,and ease of preparation.Compared with layered materials,the electrode materials of sodium-ion batteries achieves sodium storage mainly through the formation of Fe nanoparticles dispersed in Na₂O matrix for reversible conversion.However,with the volume change that occurs when the battery is repeatedly charged and discharged,it leads to poor electrical contact and powdering of the electrode.Moreover,owing to the low ionic conductivity of ?-Fe₂O₃ at room temperature,it is difficult to perform an electrochemical oxidation-reduction reaction,which reduces the capacity.The poor cycle stability also which limits its commercial application.Therefore,the main purpose of this paper is to prepare a stable ?-Fe₂O₃ electrode material with cycle stability.The main research is as follows:Firstly,we prepared ?-Fe₂O₃ nanomaterials by the solvothermal method and a calcination process.First-principle calculations are used to study the structure and conductivity of materials.At the current density of 25 m A/g,the sodium-ion cell still has a capacity retention rate of 83% and a reversible capacity of 366.3 m A h/g after 200 cycles.In addition,the effect of the porous structure of ?-Fe₂O₃ nanocrystals on sodium ion transport and circulation capacity was also studied.The results indicate that ?-Fe₂O₃ nanocrystal is a promising candidate for low-cost and pollution-free anode for sodium-ion batteries.Furthermore,in order to alleviate the particle crushing of the ?-Fe₂O₃ material during the charging and discharging process a graphene composite ?-Fe₂O₃ material was prepared by the solvothermal method and the electrochemical performance was studied.The results illustrate that the cycle life and rate performance of composite electrode materials have been improved.Ultimately,the electrochemical characteristics of another phase-type ?-Fe₂O₃ material of iron oxide were prepared by the solid-phase method.By comparison with ?-Fe₂O₃ material,?-Fe₂O₃ material has poor performance.As anodes for sodium-ion batteries,further an improvement is needed.