Study On Aerosol Jet Printing Of MXene-based Electrode Film And Microstructure Regulation

Aerosol jet printing（AJP）is an emerging additive manufacturing technology characterized by an annular sheath gas that creates a micro-scale confinement space that constrains the transport of aerosol droplets,and the micro-reaction process of droplets will directly affect the morphology and structure of the formed material film,providing significant benefits in controlling the structure of materials at the micro-nano scale and developing new materials.This thesis,based on AJP,uses the two-dimensional structure MXene as an ink substance,which has recently received a lot of interest.A series of MXene microelectrodes with a variety of microstructural characteristics were successfully fabricated,and their formation mechanism and electrochemical performance were systematically studied,using droplets as microreactors,regulating the process of solvent evaporation and solute migration of droplets on the deposition surface,and in situ controlling the aggregate morphology and structure of MXene nanosheets.The following are the important points:The Al atomic layer was removed by etching Ti₃Al C₂ powders with a mixed system of Li F+HCl,and the solution in the middle part was preferably freeze-dried following ultrasonic peeling and centrifugation,yielding high-quality few-layer Ti₃C₂T_xnanosheets with a size of several hundreds of nanometers.AJP’s Ti₃C₂T_x film electrodes have excellent electrochemical performance,with mass specific capacitances of 315.00F g^-1@0.5 A g^-1 and 298.68 F g^-1@1 A g^-1,respectively.MXene’s self-stacking feature limits future performance improvements in MXene-based energy devices.Aerosol jet printing was used to create MXene films having an orientated tubular structure.The MXene film with an oriented tubular structure was effectively created on the PET substrate using a few-layer Ti₃C₂T_x nanosheets aqueous solution as the AJP ink,by regulating the carrier gas and sheath gas,when the focusing ratio FR is 1.5,and the formation mechanism was explored.Aerosol droplets wrapped in MXene nanosheets created a quasi-conical fibers array on the deposition surface during the printing process.The retreating of several unidirectional tiny meniscus-shaped gas-liquid-solid three-phase contact lines（TCL）results in oriented tubular-like Ti₃C₂T_x nanostructures,which curve and have a directional layout.This structure has double the specific surface area(25.92 m² g^-1)and more evident graded pores than the Ti₃C₂T_x structure used in vacuum-assisted filtration.The manufactured tubular-like Ti₃C₂T_x electrode,based on this structure,can allow the electrolyte to permeate between layers better while shortening the ion transport channel,maximizing the role of active elements.AJP also produced tubular-like Ti₃C₂T_x microsupercapacitor electrodes with an interdigitated structure,and evaluated the impact of electrode structural factors such interdigital width,interdigital spacing,and electrode thickness on device performance.The areal capacitance of the manufactured Ti₃C₂T_x microsupercapacitor,which has an interdigital width of 250μm,interdigital spacing of 170μm,and 50 printing cycles,is34.87 m F cm^-2,which is much better than MXene devices obtained using conventional additive manufacturing processes.MXene nanosheets’self-stacking capabilities are successfully suppressed by the spherical-like structure.The 3D crumpled Ti₃C₂T_x nanospheres were created and their formation mechanism explored by altering the carrier gas and sheath gas,and employing the limited flux of microscale aerosol droplets as microreactors to control the migration and assembly of Ti₃C₂T_x nanosheets.A temperature differential along the gas-liquid interface between the apex and bottom of the droplet might cause Marangoni flow within the droplet during the printing process.The MXene nanosheets inside the droplets migrate to the edge under the influence of thermocapillary flow,where they are shaped and assembled along the droplet’s surface,while the TCL of the droplet rapidly recedes due to competing pinning and capillary forces,resulting in Ti₃C₂T_xnanospheres with a 3D crumpled structure.The interlayer spacing of crumpled Ti₃C₂T_xnanospheres can be controlled simply by changing the deposition temperature.The size of crumpled Ti₃C₂T_x nanospheres can be adjusted by altering the ink concentration.The interdigitated electrodes made from crumpled Ti₃C₂T_x nanospheres effectively facilitate ion transport,and the resulting microsupercapacitor has a remarkable electrochemical performance with an area capacitance of 112.74 m F cm^-2@0.05 m A cm^-2.Another typical technique for efficiently suppressing the self-stacking capabilities of MXene nanosheets is heterostructure.By incorporating C,Ag nanoparticles,and Ag nanowires,films with hybrid structure or heterostructures such as Ti₃C₂T_x/C,Ag NPs-Ti₃C₂T_x,and Ag NWs-Ti₃C₂T_x were produced using AJP technology.The results reveal that adding C to Ti₃C₂T_x nanosheets during the manufacturing process significantly inhibits self-stacking.Meanwhile,the attached C can be employed as an adhesive to connect neighboring Ti₃C₂T_x nanosheets and nanospheres,boosting the electrochemical performance of the Ti₃C₂T_x interdigital electrodes by maintaining integrity.The areal capacitance can reach 64.58 m F cm^-2@0.05 m A cm^-2 when the Ti₃C₂T_x and C mass ratios are 1:1.AJP makes it simple to deposit a range of materials in situ to build heterogeneous structures films.For Ti₃C₂T_x supercapacitors,pre-deposited Ag NPs or Ag NWs thin films can be employed as current collectors to improve the conductivity and electrochemical performance of the interdigital electrodes.By controlling the migration and assembly of MXene nanosheets induced by solvent evaporation during the printing process,tubular-like Ti₃C₂T_x structure,3D crumpled Ti₃C₂T_x nanospheres structure,and heterostructures such as Ti₃C₂T_x/C,Ag NPs-Ti₃C₂T_x,and Ag NWs-Ti₃C₂T_x were fabricated for the development of high-performance energy devices.The manufactured microsupercapacitor devices have exceptional performance because to the effective suppression of MXene’s self-stacking features.This research exploits the AJP process’s enormous potential as a promising additive manufacturing technology for the development of functional devices with multi-scale structure feature,which will open up new avenues for low-cost,controllable fabrication of high-performance energy devices,and has significant implications for future practical applications in energy,optics,electronics,and catalysis.