Electrochemical Performance Of Ti₃C₂T_x And Its Composite Material As Anode For Li-ion Batteries

In recent years,Ti₃C₂T_x,have received significant research interests as ideal matrices for active electrode materials in rechargeable ion batteries,thanks to its hydrophilic surface,excellent electrical conductivity,larger volume capacity,larger interlayer distance,and lower lithium ion diffusion barrier.However,due to the large number of surface functional groups on the surface of the Ti₃C₂T_x prepared by the wet method,its mass specific capacitance is impaired,and its conductivity and lithium storage performance are greatly reduced,so it is difficult to meet the design requirements of high-performance lithium-ion battery electrodes.In response to these problems,the following researches are carried out in this paper:First,two different preparation processes of Ti₃C₂T_x were compared.Ti₃C₂T_x was prepared by etching with two different etchants,HF and HCL+LiF,respectively.Then,the crystal structure,morphology and surface characteristics of Ti₃C₂T_x prepared by the two methods were analyzed and compared.The research results show that when HF is used as an etchant,a layered accordion-like Ti₃C₂T_x can be obtained,but its surface is relatively complicated with a large number of-F functional groups,which is an obstacle to energy storage.However,Ti₃C₂T_x etched by HCl+LiF has fewer layers,more regular crystal structure,and simpler chemical surface,and can exist stably in the form of colloid in water.Then,the electrochemical performance of two Ti₃C₂T_x materials was investigated by assembling lithium-ion batteries.In general,Ti₃C₂T_x with fewer layers shows better lithium storage performance and rate performance.Ti₃C₂T_x with fewer layers delivered higher capacities of 255 mAh g^-1 at 0.1 A g^-1.Even after 1000 cycles,the specific capacity of the Ti₃C₂T_x with fewer layers is still up to 205 mAh g^-1 at 1 A g^-1.At the same time,we performed a kinetic analysis of two Ti₃C₂T_x electrode materials.Ti₃C₂T_x with few layers showed a larger pseudocapacitive contribution within a scan rate of 0.1～2mV s^-1.Most of the current during the electrochemical reaction came from due to the fast capacitance control process,it has better dynamic behavior.Secondly,SiO₂/Ti₃C₂T_x nanosheets were prepared by a simple liquid phase method,and a fast and continuous three-dimensional electronic/ion conductive network structure was constructed.Then,the electrochemical performance of SiO₂/Ti₃C₂T_x material was studied by assembling a lithium-ion battery.At a current density of 100 mA g^-1,the first discharge/charge specific capacity of SiO₂/Ti₃C₂T_x was 1387.3/447.5 mAh g^-1.SiO₂/Ti₃C₂T_x can provide a high capacity of 366 mAh g^-1 after 300 charge and discharge cycles at a current density of 1 A g^-1,compared with the Ti₃C₂T_x with fewer layers under the same conditions(190 mAh g^-1),the specific capacity is increased by176 mAh g^-1.By analyzing the kinetics of charge storage of SiO₂/Ti₃C₂T_x nanosheets and the contribution ratio of rubidium capacitance,it is proved that the ratio of the capacitance control capacity of the SiO₂/Ti₃C₂T_x electrode material increases with the increase of the scan rate,indicating that at higher scan rates,the capacitance behavior will be store/release Li⁺more efficiently.