Research On The Preparation Of Three-dimensional Iron Oxide And Its Performance As An Anode For Quasi-solid-state Batteries

Benefiting from the progress of human technology and civilization,the booming development of potable and wearable electronic devices has promoted the research of flexible energy storage devices（FESDs）.The design and development of efficient,safe,and environmentally friendly FESDs have become a global hot spot.With the characteristics of environmental protection,low cost,high safety,and large capacity,nickel/iron（Ni/Fe）batteries have a broad application prospect in FESDs.However,the Fe-based anode of conventional Ni/Fe batteries suffers from passivation,hydrogen evolution,and volume expansion during the cycling progress,which greatly affects the Coulombic efficiency and long cyclic stability of Ni/Fe batteries.As one of the transition metal oxides,iron oxide（Fe₂O₃）has attracted much attention because of its high theoretical capacity,high hydrogen precipitation potential,and abundant resources,but the problems of poor electrical conductivity and particle agglomeration have limited its further development.To address the problems of Fe-based anode and the great potential of Ni/Fe batteries in FESDs applications.To address the problems of Fe-based anode and the great potential of Ni/Fe batteries for FESDs,this paper uses nanostructure design and modification strategies to build a 3D structural surface that provides sufficient electron/ion transport pathways for the electrochemical reactions of Fe₂O₃active materials,thus constructing flexible Ni/Fe batteries with high energy storage characteristics.The specific contents are as follows:（1）Through a combination of gel coating and high-temperature etching,a carbon-coated Fe/Fe₂O₃ nanoparticles（3D-Fe/Fe₂O₃@C）anode with a 3D structure was constructed in situ on a flexible carbon cloth.The Fe/Fe₂O₃ heterostructure was uniformly dispersed within the carbon layer skeleton,which improves the carrier density and conductivity of the electrode.The porous3D structure of the electrode surface resulted in a significant increase in hydrophilicity and electroactive surface areas（ECSAs）,exhibiting an area-specific capacity of 3.07 m Ah cm^-2 as well as improved rate performance and Coulombic efficiency.When assembled with a Ni Co₂O₄as a semi-solid Ni/Fe battery,it provides an energy density of 15.53 m Wh cm^-3 and a power density of 761.91 Wh cm^-3.In addition,the flexible Ni/Fe battery has good electrochemical properties and mechanical stability even after bending at arbitrary angles and 20000 cycles,which provides new insights into the design and preparation of a new generation of FESDs.（2）Through a Two-step electrodeposition process,a 3D layered structure containing Fe₂O₃ nanosheets and Ti₃C₂T_x MXene nanosheets（3D-MXene/Fe₂O₃）were prepared on the surface of carbon fiber.The interaction between Fe₂O₃ nanosheets and functional groups on Ti₃C₂T_x nanosheets greatly enhances the ion/electron transport efficiency of Ti₃C₂T_x.The maximum volume-specific capacity of the prepared 3D-MXene/Fe₂O₃ anode can reach 37.4m Ah cm^-3.The fibrous Ni/Fe battery assembled with 3D-MXene/Fe₂O₃ as an anode,Ni Co O as a cathode,and PVA/KOH as the gel electrolyte has a maximum volumetric capacity of 35.1m Ah cm^-3 and a maximum energy density of 56.2 m Wh cm^-3.Moreover,this fibrous Ni/Fe battery has remarkable cyclic stability and mechanical flexibility,providing a reference for the design and improvement of Fe-based anode for next-generation flexible Ni/Fe batteries.