Ti₃C₂ MXene Based Hybrid Materials:Preparation And Electrochemical Performance

MXene,discovered as a new type of 2D material in 2011,has become a hot scientific topic due to its excellent electrochemical performance,unique and stable layered structure,as well as excellent mechanical and optical properties.Although there are many kinds of MXene,Ti₃C₂ MXene is the most widely studied.Ti₃C₂MXene has a good storage capacity of lithium because of its typical two-dimensional structure and a large specific surface area.Therefore,it has a great application prospect in lithium battery.However,the narrow spacing btween Ti₃C₂ MXene layers inhibits the insertion and diffusion of Li⁺.Furthermore,the specific capacity of Ti₃C₂MXene still need to be improved.This thesis takes Ti₃C₂ MXene as the research object.We carries out three aspects of research work to solve the above problems.Firstly,the alkali metal cation was used to intercalate the interlayers of Ti₃C₂ MXene to adjust the spacing regulation efficitively.We studied the electrochemical performance of the intercalated Ti₃C₂MXene by analysing the change of layer spacing and the functional groups.Furtherly,transition metal cation was used to intercalate the Ti₃C₂ MXene and the electrochemical performance of intercalated Ti₃C₂ MXene was studied.The electrochemical performance of the intercalated Ti₃C₂ MXene was studied by analysing the influence of transition metal cations after characteried.Finally,in view of the high transport capacity,the excellent conductivity and high intrinsic density of Ti₃C₂ MXene,the Fe₃O₄@Ti₃C₂ composites would deliver a high volumetric capacity which was prepared by taking Ti₃C₂MXene as the effective carrier.The specific research contents are as follows.1.Firstly,Ti₃C₂ MXene was intercalated by alkali metal ions such as Li⁺,Na⁺,K⁺and Cs⁺.In the intercalation experiment,the inter layer spacing was changed from 1.01 nm to 1.24 nm(Li⁺),1.22 nm(Na⁺),1.21 nm(K⁺)and 1.28nm(Cs⁺)after intercalation which was calculated by using the Bragg equation through the XRD characterization.The effect of intercalation was obviously.The results of XPS showed that-F groups were reduced and replaced partly by oxygen-containing functional groups.In the test of lithium battery,the reversible specific capacity of the pure Ti₃C₂ MXene is 100.7 mAh g^-1 at 0.1 A g^-1 current density.Due to the influence of intercalation regulation and the change of the group,the Ti₃C₂ MXene intercalated by the alkali metal ion shows a higher reversible specific capacity.The specific capacity of Li⁺@Ti₃C₂,Na⁺@Ti₃C₂,K⁺@Ti₃C₂ and Cs⁺@Ti₃C₂ samples are 160.7 mAh g^-1140 mAh g^-1,153.8 mAh g^-1,153.5 mAh g^-1.2.In the experiment of transition metal ions intercalation,Fe³⁺,Co²⁺and N i²⁺was used to intercalate Ti₃C₂ MXene.The reversible specific capacity of intercalated Ti₃C₂ MXene such as Fe³⁺@Ti₃C₂,Co²⁺@Ti₃C₂ and N i²⁺@Ti₃C₂ is 176.5 mAh g^-1,155 mAh g^-1 and 147.8 mAh g^-1 at the 0.1 A g^-1 current density.After the intercalation and modification of the transition metal cations,the transition metal cations embedded in the Ti₃C₂ MXene layer can be used as an effective charge carrier,which can not only make the conductivity betweent the layers of Ti₃C₂ MXene better,but also provide a fast channel for the insertion and deinsertion of Li⁺.Thus the electrochemical performance of Ti₃C₂ MXene could be improved.3.Fe₃O₄ nanoparticles was prepared by hydrothermal method.And taking Ti₃C₂MXene(Beijing)as the carrier,Fe₃O₄@Ti₃C₂hybrids with different ratios were prepared by a simple ultrasonic method.And they were tested as anode materials for lithium-ion batteries.A series of characterizations such as XRD,SEM,TEM and XPS showed that Fe₃O₄@Ti₃C₂ hybrids were successfully synthesized.The electriochemical properties of the hybrid were also studied.The reversible specific capacity of Fe₃O₄@Ti₃C₂-2:5 is up to 747.4 mAh g^-1 and its volumtric capacity is2038 mAh cm^-3 at 1 C after 1000 cycles.Its reversible specific capacity is 278.3 mAh g^-1 at 5 C after 800 cycles.Ti₃C₂ MXene with the stable layered structure,as an effective carrier to load nanoparticles,can also provide fast transport channel for Li⁺.In the process of charge and discharge,the volume expansion can be suppressed effectively due to the layered stuucture of Ti₃C₂ MXene.Fe₃O₄@Ti₃C₂ hybrids would become anode material with high volumetric capacity for lithium-ion battery due to the high density of Ti₃C₂ MXene.