Synthesis Of New MXenes-based Nanocomposites Materials And Its Capacitor Performance

As human demand grows,the demand for energy storage devices is getting higher and higher.Supercapacitor,a new type of electrochemical energy storage device,between the dielectric capacitor and battery,with a high power density almost comparable to the traditional dielectric capacitor,and a relatively high energy density,is particularly suitable for high pulse current discharge.MXenes material is a kind of newly discovered two-dimensional material,with high structure stability,good electrical conductivity and abundant surface functional groups,which have showed excellent application prospect in the field of supercapacitor.However,the MXenes material has the disadvantages of easy agglomeration?easy agglomeration and low capacity and.How to improve the electrochemical performance of MXenes is a hot topic in current research.In this paper,the d-Ti₃C₂T_x is obtained from Ti₃AlC₂ by etching and ultrasonic.Based on this,two new MXenes-based nano-composite materials:d-Ti₃C₂T_x/?-Fe₂O₃and 3D RGO/d-Ti₃C₂T_x,are prepared,and the effects of material composition on the structure morphology and electrochemical performance of the materials are studied.?1?d-Ti₃C₂T_x:Ti₃AlC₂ is etched by LiF/HCl,NH₄HF₂/HCl and HF.The three etching solutions are able to etch the Al elements completely.The structure of ml-Ti₃C₂T_x?The etching products?is a typical layered structure,which can obviously see the gap between layers.Ml-Ti₃C₂T_x can be further separated by ultrasonography to obtain a single layer or a less layer of d-Ti₃C₂T_x.The electrochemical performance test shows that d-Ti₃C₂T_x has a typical double layer capacitance.At the current density of 1A/g,the mass ratio of d-Ti₃C₂T_x is 83.7 F/g.The results of EIS also show that the internal resistance and contact resistance of d-Ti₃C₂T_x are small and the diffusion resistance is also very small,which is consistent with the literature reports.?2?d-Ti₃C₂T_x/?-Fe₂O₃:We synthesize MXenes?Ti₃C₂T_x?/?-Fe₂O₃ nanocomposite by a self-assembly method via electrostatic attraction.The characterizations show that these?-Fe₂O₃ nanoparticles are covered by d-Ti₃C₂Tx nanosheets completely.This structure improves the conductivity of the whole material,improves the electron transfer rate,and inhibits the dissolution of iron oxide,thus improving the electrochemical properties of the material.In consequence,as negative electrode materials,the as-prepared nanocomposites deliver a much-enhanced electrochemical performance,including a wide operating potential of 1.2 V?-1.2V⁰V?,a high specific capacitance of 405.4 F/g at the current density of 2 A/g and a specific capacitance of197.62 F/g even at the current density of 20 A/g.In addition,the nanocomposites possessed a high cycling stability with 97.7%capacitance retention of the initial capacitance after 2000 cycles.The excellent electrochemical performance of the MXenes/?-Fe₂O₃ nanocomposites demonstrates their potential as negative electrode materials for supercapacitors.?3?3D RGO/d-Ti₃C₂T_x:with the help of CTAB,d-Ti₃C₂T_x and GO are combined in water,and then the heat reaction is launched under the condition of adding hydrazine hydrate as reducing agent.Finally,3D RGO/d-Ti₃C₂T_x is obtained by freeze-drying..SEM results shows that with the introduction of d-Ti₃C₂T_x,the pore structure became rich and the number of pore increase.As a self-supporting material,the material can be used as electrode directly,which greatly reduces the volume of the device and saves the cost.The results of electrochemical test shows that the specific capacity of the material can reach to 164.9 F/g at a scan rate of 2 mV/s.When the scan rate increased to 300mV/s,the specific capacity of the material is still 117.72 F/g?the capacity retention rate is 71.4%?.The recycling performance of the materials is also excellent.the nanocomposites possessed a high cycling stability with 98.3%capacitance retention of the initial capacitance after 5000 cycles.This indicates that 3D RGO/d-Ti₃C₂T_x has great application prospect in the field of flexible devices and consumer electronics products.