The Design And Composite Modification Of Erythrocyte Like Fe₂O₃ Anode Materials

In the recent years,due to the rapid development of electric vehicles,the traditional lithium-ion batteries can no longer reach the people’s pursuit of high capacity and rate batteries.In order to improve the performance of lithium ion batteries,the exploration of anode materials for lithium ion batteries has become the focus of current research.The low theoretical specific capacity of conventional graphite anode is the main reason for the limited capacity of conventional lithium-ion battery anode.Generally,transition metal oxides have a high theoretical specific capacity and are a new type of anode material that is expected to replace graphite anodes.Fe₂O₃ has attracted the attention of a large number of researchers due to its high theoretical specific capacity,environmental and chemical stability.However,the large volume strain and low conductivity of Fe₂O₃ anode material during charging and discharging hinder its application in lithium-ion batteries.Currently,the main focus is to improve the electrochemical properties and stability of Fe₂O₃ materials by various modifications.In this paper,we focus on both morphological design and synthesis of composite materials to improve the cycling stability and kinetic performance of Fe₂O₃anode.Firstly,we designed and synthesized erythrocyte-like Fe₂O₃ nanoparticles and investigated the effect of the morphology design on the electrochemical properties of the materials,then we synthesized Fe₂O₃@SnO₂ and Fe₂O₃@SnO₂@GO composites based on the morphology design and investigated the influence of the composite synthesis on the electrochemical properties of the materials.The specific results of the study are as follows:（1）The one-step hydrothermal method was used to synthesize erythrocytic single-crystal Fe₂O₃ nanoparticles,and the stability and rate performance of the erythrocytic Fe₂O₃ anode were found to be improved by electrochemical tests.Its capacity can reach1200.2 m Ah g_-1 after 100 cycles at 0.1 C current density,but there are large fluctuations in the capacity of the battery during charging and discharging.In addition,ex-situ XRD tests and transmission electron microscopy were used to study the transformation of phase and morphology of Fe₂O₃ during charging and discharging,and the lithium storage process of erythrocyte-like Fe₂O₃ anode was found to be controlled by diffusion by CV studies.It is found that the morphology design of erythrocyte-like Fe₂O₃ is beneficial to the performance enhancement of anode materials.（2）Based on the morphological design,Fe₂O₃@SnO₂ composites were synthesized by using hydrothermal method to generate a uniform layer of SnO₂ on the surface of the erythrocyte-like Fe₂O₃.The electrochemical performance analysis revealed that the stability and conductivity of the composites were enhanced by the synergistic effect of the two oxides.After 100 cycles at 0.1 C current density,the specific capacity of the material was stabilized at 675.94 m Ah g^-1,with no significant fluctuation in capacity during the charging and discharging process,and the rate of the composites was also significantly improved.Experiments show that the heterostructure can effectively improve the stability and dynamic properties of the material.（3）The composite Fe₂O₃@SnO₂ was compounded with graphene oxide to enhance the electrical conductivity and stability of the material.When the content of graphene oxide is about 20%,the composite has the most integrated performance.The cycling curve of FSG-20 is relatively smooth and the capacity is stable at 826.2 m Ah g^-1 after100 cycles at 0.1 C current density,and there is no serious degradation of capacity when cycled at current densities from 0.1 C to 2.0 C.The improved electrochemical properties of the composites were attributed to the electronic and ionic conductivity of the composites improved by the excellent electrical conductivity and stability of graphene oxide.It was found that the multi-step modification can effectively improve the electrochemical properties of Fe₂O₃ anode materials and promote the research on the modification of anode materials for lithium-ion batteries.