Modification Of Ti₃C₂ Lithium-Ion Battery Anode Materials And Electrochemical Performance

With the rapid development of portable and power electronic devices,there are increasing requirements for the comprehensive performance improvement of Lithium-ion batteries.In recent years,Ti₃C₂ nanosheet has received extensive attention in the field of energy conversion and storage owing to its good electrical conductivity,flexibility and high specific surface area.Like other two-dimensional layered materials,such as graphene,Ti₃C₂ also faces the serious stacking problem during the electrochemical reactions.The stacking of electrode materials will directly lead to loss of the ion adsorption sites and increase of ion diffusion resistance,resulting in reduced performance of the related materials accordingly.To reduce Ti₃C₂ from stacking and achieve high performance,it is particularly important to modify the surface of Ti₃C₂.In this thesis,we proposed a series of surface modifications on Ti₃C₂ nanosheets and the specific details are as follows.（1）Titanium dioxide nanoparticles with an average size of 10 nm were in situ grown on the surface of Ti₃C₂ nanosheets by a one-step ethanol-thermal method,and the TiO₂/Ti₃C₂ composite materials were prepared.The composites deliver a reversible specific capacity of 257.3 mAh g^-1 at a small current density of 50 mA g^-1.Moreover,the specific capacity of 141.4 mAh g^-1 with the coulombic efficiency of ～100% can be obtained even after 250 cycles at the current density as high as 1 A g^-1,indicating the good cycling performance and structure stability.（2）Porous Ti₃C₂ nanosheets were prepared via the treatment of tetramethylammonium hydroxide（TMAOH）to Ti₃C₂.The lithium-ion storage performance of Ti₃C₂ nanosheets with and without pores was investigated under varying loading masses from 3.000-6.000 mg cm^-2.The test results indicate that the electrochemical performance of porous Ti₃C₂ nanosheets is better than that Ti₃C₂.（3）Porous Ti₃C₂ nanodots were prepared by modifying the surface of“accordion-like”Ti₃C₂ nanosheets via the treatment of TMAOH.We composited it with graphene oxide（GO）to improve the performance of lithium-ion storage of porous Ti₃C₂ quantum dots.The best lithium-ion storage performance can be obtained when the mass ratio of Ti₃C₂ quantum dots to GO is about 3:1.The composite delivers a reversible specific capacity of 313.47 mAh g^-1 at a low current density of 50 mA g^-1.Moreover,the specific capacity of 97.5 mAh g^-1 with the coulombic efficiency of ～100%can be obtained even after 3000 cycles at the current density as high as 1 A g^-1,indicating the good cycling performance and structure stability.