High Yield Preparation Of MXene And Its Application In Supercapacitor And Zinc Ion Battery

Two-dimensional(2D)transition metal carbides and nitrides,known as MXene,are a large family that possesses stable phase structure,tunable interlayer spacing,large specific surface area,high conductivity and hydrophilicity.These physical and chemical properties make them perfect candidates for different applications,such as energy storage devices,catalysis,optics and so on.However,the low yield of MXene in traditional synthesis limits its further applications on the industrial level.In this thesis,we have successfully resolved the low synthesis yield issue of MXene by using a hydrothermal-assisted intercalation method.Based on this novel method,we further explore the potential application of MXene in supercapacitor and aqueous zinc ion battery.The corresponding research contents and results are as follows:(1)Study on the high yield synthesis of Ti₃C₂T_X nanosheets via hydrothermal-assisted intercalation.The low yield of Ti₃C₂T_X nanosheets is largely due to the strong interactions between adjacent 2D layers,for example,the residual Ti-Al bond.In order to break these interactions,a hydrothermal-assisted intercalation method is proposed by using tetramethylammonium hydroxide(TMAOH)and vitamin C(AA)as intercalator and antioxidant,respectively,which can achieve a high yield of Ti₃C₂T_X.The experimental results showed that TMAOH can effectively intercalate into the 2D layers of Ti₃C₂T_X under high temperature and thus widen interlayer distance,while addition of AA can improve the thermal stability of Ti₃C₂T_X and avoid its spontaneous oxidation.Thus,the yield of Ti₃C₂T_X nanosheets can reach a high value of 74% with the optimal conditions(140 ?,24 h).(2)The application of Ti₃C₂T_X in supercapacitor.MXene is an ideal electrode material for high-performance supercapacitors because of its high conductivity,abundant surface functional groups and large surface area.Herein,a highly conductive electrode with continuous network for supercapacitors is designed by combining Ti₃C₂T_X nanosheets with carbon nanotubes(CNTs).The experimental results showed that the porous electrode can avoid the compact stacking of Ti₃C₂T_X nanosheets,thus promoting rapid electron and ion transport,which results in high specific capacity and high rate capability.The Ti₃C₂T_X&CNT electrode can achieve a high capacitance of 473 F g-1 at a current density of 1 A g-1 and 340 F g-1 even at 10 A g-1,when the weight ratio of CNT to Ti₃C₂T_X is 3:4.(3)The application of vanadium carbide(V₂CT_X)in aqueous zinc ion batteries.Vanadium based compounds have high capacity theoretically which makes them ideal cathode materials for high performance zinc ion batteries.Herein,the potential application of 2D V2 CTX as cathode material for zinc ion battery is studied in detail.The experimental results showed that V2 CTX achieved high specific capacity with the spontaneous oxidation of V,while its unique layered structure could solve the problem of poor cycling stability of traditional vanadiumbased compounds.Thus,the zinc ion battery based on V2 CTX cathode achieved a high specific capacity of 460 m Ah g-1 at the current density of 0.5 A g-1,and the capacity retention rate was almost 100% after 2000 cycles.