Preparation,Characterization And Electrochemistry Properties Of Two-Dimensional Ti₃C₂-Based Composites For Energy Storage

Lithium-ion battery is the most widely used secondary batteries and become the most potential energy storage devices,which can properly satisfied the capability requirements of energy storage equipment for the developing society.However,the short storage and high cost of the lithium limit its further application and development.In this,the sodium ion battery with excellent energy storage property and good environmental compatibility has begun to appear on the field of energy storage,and is expected to become the next generation of new energy storage battery instead of lithium ion battery.The anode of battery always play an important role in lithium/sodium ion battery,and anode material has always been an important factor restricting its development.Among the anode materials,the transition metal carbon nitride?MXenes?has emerged as the research hotspot due to its unique two-dimensional structure,excellent comprehensive performance and diversity,and become one of the most promising candidates to replace the traditional commercial graphite anode materials.In this article,the design of the structure for Ti₃C₂ electrode is optimized,and based on it,a very high-performance anode material in lithium?sodium?ion battery has been designed.It explores the possibility to modify the transitional metallic carbon nitrous oxide?MXenes?for further applications as energy storage materials.The concrete research content is as follows:?1?The different ethcing time and temperature of the Ti₃AlC₂ are carried out to exploring the principle of Ti₃C₂T_X etching process from Ti₃AlC₂ phase,and the optimal etching condition was determined by comparing the topography structure of the final product.The etched Ti₃C₂T_X material and a simple one-step hydration reaction are used to prepare TiO₂/Ti₃C₂ composite material with a layer size of about 30 nm on the base of the original accordion Ti₃C₂T_X material.The hydrothermal process expands the interlayer spacing of Ti₃C₂T_X materials,reduces the various functional groups on its surface,and the uniform distribution of TiO₂ particles improve the microstructure of the raw materials together,so it is more conducive to the electrochemical reaction.It can be seen from the results of the electrochemical storage test that TiO₂/Ti₃C₂ exhibits a higher reversible specific capacity of267 mAh g^-1after 500 cycles at current density of 200 mA g^-1?203 mAh g^-11 for Ti₃C₂T_X?,and at the same time it exhibits better cyclic stability and electron conductivity than the Ti₃C₂T_X material.?2?In this chapter,the Ti₃C₂T_X material with proper etching is used,through a simple solvent thermal process,which leads to the formation of NaTi₂?PO₄?₃ phase with high crystallinity on the expanded layered Ti₃C₂ nanosheet,and finally the NaTi₂?PO₄?₃/Ti₃C₂composite material is generated.And the sodium ion cell battery was tested using a control sample of different composition ratios,and the most potential composite material with the best sodium storage performance is obtained by analyzing the electrochemical results.At the appropriate proportion,the NaTi2?PO4?3 phase provides a higher sodium storage capacity.At the same time,with the good stability of the Ti₃C₂T_X material improved its poor stability,as well as the good changes in the synthetic process,the sodium ion electrode material with more reasonable structure and better performance has been formed finally.The results of the electrochemical performance tests show that the structure stability,the electrochemical stability and the conductivity of the Na Ti₂?PO₄?₃/Ti₃C₂ composites are improved to a certain extent,and also exhbits an excellent rate capability.The reversible capacity increased to 121 mAh g^–1after 500 cycles at the current density of 200 mA g^–1?79 mAh g^-11 for Ti₃C₂T_X?,which has a strong improvement of about 50%.What's more,a very stable circulation can be found after 2000 cycles at the high current density of 2000 mA g^–1,demonstrate its excellent performance of sodium reserves.?3?Based on TiO₂/Ti₃C₂ composite materials,during the hydrothermal reaction,the TiO₂ and Ti elements on the substrate react with the high concentration NaOH solution to form Na₂Ti₃O₇ and coated on the original layer Ti₃C₂T_X,and the Na₂Ti₃O₇/Ti₃C₂ composite is finally obtained.Based on the optimization of TiO2/Ti3C2 composite structure,the alkalization further improves its structure.The sodium ion battery is assembled for the electrochemical storage test,and the results are analyzed to prove the excellent performance of Na₂Ti₃O₇/Ti₃C₂ composite material.The reversible capacity of 118 mAh g^-1after 500 cycles at the current density of 200 mA g^-1,which has a strong improvement compared with the original Ti₃C₂T_X material(75 mAh g^-1)and Ti O₂/Ti₃C₂ composite materials(101 mAh g^-1),and it has a very excellent magnification performance.Meanwhile,it also shows its excellent sodium storage performance under the condition of large current and long circulation.