In Situ Construction And Lithium Performance Of Ti₃C₂T_x-based Nanocomposites

Demand for novel,low-cost,eco-friendly,high performance energy storage systems has been increasing,to meet the energy needs of modern society and respond to emerging ecological problems.Rechargeable lithium batteries(namely,Li-ion batteries or LIBs)are currently widely used energy storage devices.LIBs are used in widespread applications in portable electronic consumer devices,electric vehicles,and large-scale electricity storage in intelligent grids.However,with the rapid development of technology and increasing living standards,the current lithium-ion batteries still unable to meet contemporary needs.In order to further improve the life and safety of lithium-ion batteries,research on battery electrode materials is of paramount importance.It is well known that small size electroactive materials can provide high electroactive regions,shorten the diffusion and migration path of ions,and mitigate mechanical deformation,all of which are conducive to improving the utilization rate of active materials and improving the stability of electrodes.In this paper,two-dimensional carbide crystal Ti₃C₂T_x was prepared by etching Ti₃Al C₂ with mixed solution of sodium fluoride and hydrochloric acid.In this paper,two-dimensional carbide crystal Ti₃C₂T_xwas prepared by etching Ti₃Al C₂ with mixed solution of sodium fluoride and hydrochloric acid,and Ti₃C₂T_x was exfoliated by dimethyl sulfoxide(DMOS)to obtain d-Ti₃C₂T_x with few layers.d-Ti₃C₂T_x was used as a precursor to prepare MXene nanocomposite,and its electrochemical performance was studied as a anode electrode material for lithium ion battery,the results show that the material exhibits excellent electrochemical performance.Firstly,nanocomposites of LaF₃ decorated on Ti₃C₂T_x(Ti₃C₂T_x@LaF₃)were synthesized using a solid-state sintering method.The physical and electrochemical properties of pristine and Ti₃C₂T_x@LaF₃ anode materials were characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),and electrochemical measurements.The results showed that the heterojunction of LaF₃ nanoparticles with high ionic conductivity was grown on MXene sheet,which was beneficial to shorten the charge transfer distance and improve the charge transfer rate in the electrochemical reaction process.In all cycles,Ti₃C₂T_x@LaF₃ has higher time capacity than pure Ti₃C₂T_x electrodes and exhibit excellent reversible capacity,cycle stability and rate performance.Secondly,this study presents a nanostructured d-Ti₃C₂T_x@Sn O₂ QDs composite through in-situ growth of Sn O₂ QDs on the layer of d-Ti₃C₂T_x nanosheets utilize facile electrostatic attraction under ultrasound irradiation.X-ray diffraction,X-ray photoelectron spectroscopy,and high-resolution transmission electron microscopy results illustrate that Sn O₂ QDs were uniformly distributed on the d-Ti₃C₂T_x layer.The d-Ti₃C₂T_x nanosheets suppress Sn O₂ QDs nanoparticles'volume expansion,agglomeration and accelerate the Li-ion and electron transition process due to the distinguished confinement effect and excellent graphite-like layered structure.Electrochemical results revealed that d-Ti₃C₂T_x@Sn O₂ QDs nanocomposites may greatly improve the reversible capacity compared with pure d-Ti₃C₂T_x and Sn O₂ QDs.Remarkably,the d-Ti₃C₂T_x@Sn O₂ QDs composite maintained 390 mAh·g^-1 with a capacity recovery after 100 cycles at current density of 1000 m A·g^-1.The synergistic effect of Sn O₂ QDs on MXene enlarged the d-spacing of d-Ti₃C₂T_x layers and increased the Li⁺storage,thereby exhibiting excellent electrochemical properties for lithium-ion batteries.Thirdly,d-Ti₃C₂T_x with less layered structure by intercalation and delamination of acoustic degradation method in DMSO(dimethyl sulfoxide).This fabricated fewer sheets samples not only improve the electrical conductibility,specific area,but also reduce the ion diffusion resistance.Novel d-Ti₃C₂T_x@laponite RDS nanocomposites were fabricated by the edge positive RDS nanosheets are assembled on negative MXene nanosheets through electrostatic interaction.The structural characterization and electrochemical performance test results showed that the RDS nanosheets are intimately assembled on the d-Ti₃C₂T_x nanosheets,and RDS in the nanocomposites effectively increases the contact area between the electrode material and the electrolyte,which may decrease the resistance of the material,increase the charge transfer efficiency and promote the rapid charge transfer.d-Ti₃C₂T_x@laponite RDS may deliver an initial specific discharge capacity of 458 mAh·g^-1 under a current density of 50m A·g^-1.And a reversible discharge capacity of 160 mAh·g^-1 at a current density of 1000m A·g^-1,which is significantly higher than that of pure Ti₃C₂T_x,laponite RDS,showing better electrochemical performance.Finally,d-Ti₃C₂T_x@h-BN MXene nanostructured composites with uniform distribution and high density were synthesized by simple liquid phase blending.Through a series of structural characterization and electrochemical properties shown,and the results showed that the d-Ti₃C₂T_x@h-BN nanocomposite with good bonding was successfully prepared,and the h BN was evenly dispersed on the d-Ti₃C₂T_x strip after separation.The d-Ti₃C₂T_x@h-BN nanostructured composite material,as the negative electrode of lithium battery,has a specific capacity of 212 and 403 mAh·g^-1for the first time,respectively.Under high current density,the specific capacity can remain at 80 mAh·g^-1 after 100 cycles,with better performance than pure d-Ti₃C₂T_xmaterial.