Preparation And Electrochemical Properties Of Modified Ti₃C₂ Based Anode Materials

This work is based on lithium-ion battery,choosing one of the most representative MXene materials Ti₃C₂ as research object.The main purpose of this research is to improve the electrochemical performance of Ti₃C₂ anode material.In this work,the effect of molecular intercalation on electrochemical properties of Ti₃C₂ material is studied systematically.Three kinds of composites MoS₂/p-Ti₃C₂,Ag₂S@MoS₂/p-Ti₃C₂ and CoMoO₄/c-Ti₃C₂?p-Ti₃C₂ and c-Ti₃C₂ represent mild and severe oxidized Ti₃C₂ at high temperature,respectively.?are prepared by using MoS₂,Ag₂S and CoMoO₄ as intercalation agents.The influence of the kind and content of intercalation agents on the comprehensive electrochemical properties of Ti₃C₂ materials are investigated.In order to improve the cyclic stability of MoS₂/p-Ti₃C₂ composite,carboxymethyl cellulose,glucose and hexadecyl trimethyl ammonium bromide are selected as carbon sources to fabricate three types of carbon encapsulated MoS₂/p-Ti₃C₂ composites.The impact of carbon sources on the cyclic stability of MoS₂/p-Ti₃C₂ composites is also explored.Experimental results show that the introduction of intercalation agent significantly increases the layer spacing of Ti₃C₂.With the intercalation of MoS₂,the interlayer spacing of Ti₃C₂ increases by 0.2324 nm.And the common intercalation of Ag₂S and MoS₂ enlarges the interlayer spacing of the Ti₃C₂ from 0.9888 nm to 1.229nm.As can be seen from the scanning electron microscope diagram,MoS₂,Ag₂S and CoMoO₄ molecules are uniformly grown on the interlayer and surface of the p-Ti₃C₂or c-Ti₃C₂,forming close contact between the interface,which is beneficial to the transmission of electrons in materials.Test results exhibit that both MoS₂/p-Ti₃C₂ and CoMoO₄/c-Ti₃C₂ composites show the optimal electrochemical performance when the content of intercalation agents is 20%.The synergistic effect of p-Ti₃C₂ and 20 wt%MoS₂ endows composite?T20?with maximum discharge capacity of 656 mAh g^-1 at 50 mA g^-1,which is significantly higher than the theoretical capacity of Ti₃C₂(320 mAh g^-1).The sample also shows excellent cycling stability at 500 mA g^-1.Even at high current density of 3000 mA g^-1,a stable specific capacity of 153 mAh g^-1 is obtained.From the impedance diagram,it can be analyzed that T20 sample has the highest ions and electrons transfer rates.At the current density of 50 mA g^-1,the discharge specific capacity of 20%CoMoO₄ intercalated c-Ti₃C₂ composite(M-2,412.8 mAh g^-1)is much higher than that of Ti₃C₂ anode material without intercalation(231.9mAh g^-1).M-2 specimen also reveals excellent stability during cycle and rate performance test.