Study On Construction And Lithium Storage Performance Of Titanium Carbide/Iron Oxide Based Anode Materials

Transition metal carbide MXene has excellent electrical conductivity,large specific surface area,high surface structural regulation,unique pseudocapacitive lithium storage behavior and long-cycle stability,making it a research hotspot in secondary ion batteries.However,the following problems still exist in the application:MXene itself has a low capacity,and the structure is easy to stack or collapse during the electrochemical cycle.Although hybrid modification can solve the above-mentioned drawbacks,there are still some problems such as complicated preparation process,limited performance improvement,and unclear modification mechanism.In this paper,the most representative Ti₃C₂ is set as the study object,from the perspective of the structure,morphology,chemical composition,and compounding with low-cost iron-based anode materials,using one-step co-precipitation method to control the preparation of titanium carbide/ferroferric oxide composite anodes.The influence of partial sulfidation and in-situ impregnation on the electrochemical performance and lithium storage mechanism of titanium carbide/iron-based anode materials was also studied.The Ti₃C₂ material with three-dimensional wrinkled structure was successfully prepared by Li F+HCl mixed solution etching and NaOH alkalization treatment.The specific surface area is as high as 29.2 m² g^-1,which is almost twice that of the non-alkalinization treatment.Subsequently,the in situ co-precipitation method was used to successfully grow Fe₃O₄ nanoparticles with a particle size of 20 nm on the three-dimensional Ti₃C₂ matrix.The unique three-dimensional structure not only has good electronic conductivity,but also can buffer the volume expansion of Fe₃O₄ during charging and discharging and prevent the restack of MXene material.The optimized Ti₃C₂/Fe₃O₄ composite material exhibits superior rate performance and cycle stability when worked as the anode composite in lithium ion battery.Notably,it delivers a discharge capacity of 431.2 mAh g^-1 at 10 A g^-1 in the voltage window of 0.01?3.0 V,and remains at 612.3 mAh g^-1 at 1 A g^-1 for 1000 cycles with the retention rate of90.0%.In order to give full play to the lithium storage capacity of Ti ₃C₂ and alleviate the volume expansion of Fe₃O₄ during the cycle,a partial sulfidation method was designed to prepare the three-dimensional structure of S-Ti₃C₂/Fe₃O₄@FeS composite material.The quasi-core-shell Fe₃O₄@FeS nanoparticles were successfully anchored in the three-dimensional open structure of S-functionalized Ti₃C₂,and the degree of sulfidation of the composite material could be controlled by the addition of S.The special structure can not only promote electron transfer and ion diffusion,but also reduce the volume change of oxide/sulfide and maintain the MXene structure.The S-Ti₃C₂/Fe₃O₄@FeS composite electrode with S addition of 30wt.%shows the best cycle performance(the capacity reaching 913.9 mAh^-1 after being cycled 1000 times at 1 A g^-1 in the voltage window of 0.01?3.0 V,)and exceptional rate capability(specific capacity up to 490.4 mAh g^-1 under 10 A g^-1).First-principles calculations demonstrate that the Fe₃O₄@FeS heterostructure has tunable electronic properties,which can induce improved electrochemical kinetics,and provide higher gram capacity based on the conversion reaction;the characteristics of MXene can be adjusted by surface modification with S functional groups,which may help to absorb lithium ions and increase the reversible lithium storage capacity.In-situ XRD and EIS results show that the composite electrode undergoes a gradual conversion reaction of Fe₃O₄-FeO-Feand FeS-Feduring the lithiation process,and a relatively uniform reconversion reaction occurs in the subsequent delithiation process.In order to seek a new way to improve the performance of composite materials,Ti₃C₂/FeOOH quantum dots were prepared by the impregnation method.The open Ti₃C₂ three-dimensional framework provides excellent electronic conductivity and electrolyte channels.The in-situ formed FeOOH quantum dots serve as a support and can inhibit the restack of two-dimensional material.Consequently,the obtained composite electrode shows a superior high-rate performance(286.1 mAh g^-1 at a current density of 10 A g^-1)and long-cycle stability(capacity of 572.3 mAh g^-1 after being cycled 500 times at 0.5 A g^-1).First-principles calculations show that the alkalized Ti₃C₂ and?-FeOOH can form a stable interface structure,and the strong coupling at the interface helps to enhance the charge transfer kinetics and further improve the electrochemical lithium storage reversibility of the composite materials.Subsequently,it was further hybridized with Fe₃O₄ to increase the capacity.The resulting Ti₃C₂/FeOOH/Fe₃O₄ material has a capacity of 510.7 mAh g^-1 at a current density of 10 A g^-1 in the voltage range of 0.01?3.0 V and maintain a discharge capacity of 794.3 mAh g^-1 after being cycled 1000 times under 1 A g^-1.