Preparation Of MXene Based Conductive Ink And Study On Performance Of 3D Printed Micro-Supercapacitors

Micro-supercapacitor with high power density,long cycle life,and fast charge and discharge is the current focus of research as an energy storage device.In the process of fabricating micro-supercapacitor,3D printing technology can be used for the printing and molding of electrodes and electrolytes because it can achieve the goal of high-resolution printing and patterns on demand.However,the lack of functional ink with excellent functionality,printability and no complicated post-processing steps is a difficult problem to be solved urgently at present.MXene is a new class of new materials with great application prospects in energy storage,electromagnetic shielding,catalysis,hydrogen storage,sensing and other fields.However,the sheet stacking problem,poor mechanical stability and limited refined molding methods of MXene materials have limited its development in wearable fields such as flexible supercapacitors.In this paper,two-dimensional MXene nanosheets are used as the base material,and a cross-linking agent is introduced to construct additional interfacial interactions between MXene materials to build a stable and dynamically recoverable MXene three-dimensional cross-linked network,which promotes the gelation of its dispersion to obtain colloids with reliable printability and excellent intrinsic properties,and to realize the refinement,customized and controllable molding of MXene materials through 3D printing technology;The construction of stable three-dimensional network to suppress MXene stacking and enhance the functionality and mechanical stability of printing structure;MXene ink was applied to the customized printing construction of wearable supercapacitors through 3D printing technology,and the electrochemical performance was studied.The main research contents are as follows:（1）The Preparation and study of 3D printing of MXene-BPEI aqueous colloidal ink.We synthesized few-layers Ti₃C₂T_x nanosheets by etching,and constructed additional crosslinking points between MXene nanosheets to promote the self-assembly of MXene materials into a dynamic and recoverable three-dimensional crosslinking network by introducing amino crosslinking agents such as BPEI.On the one hand,the surface tension of the materials in the network would hinder the flow of liquid,so as to form a high viscosity colloid that can be printed.On the other hand,the stacking phenomenon of nanosheets could be prevented.The effects of the ratio of each component,the type of crosslinking agent and interface effect on the rheological behavior,electrical conductivity and mechanical stability of the printed structure were further studied.The results showed that the amount of crosslinking agent introduced will have a great impact on the rheological behavior:A little amount of crosslinking agent can’t form high viscosity colloid,but excessive crosslinking agent will cause more serious agglomeration of Ti₃C₂T_x.The best mass ratio of Ti₃C₂T_x to BPEI is1:0.00048,and the ink viscosity can reach 19489.3 Pa·s.The ink can be used to print complex patterns.FT-IR and XPS characterization confirmed that the hydrogen bond between MXene and BPEI was the driving force for the formation of colloid.Due to the low content of crosslinking agent,the ink can show excellent functionality only by drying at low temperature,and the ink has high electrical conductivity up to 8032.12 S cm^-1.The printed structure shows good mechanical stability,the storage modulus can reach 2.4 MPa,which is much larger than the loss modulus,and the loss coefficient is relatively low,which is basically maintained at around 0.17.The above results provide a simple and feasible strategy for the preparation of 2D MXene functional materials towards high-efficiency,high-resolution patterning and complex structures.（2）The construction and performance study of 3D printed MXene based micro-supercapacitors.The interdigital electrodes were prepared by 3D printing and freeze-drying.And the micro-supercapacitor was prepared by adding PVA/H₂SO₄electrolyte.Freeze-drying endows the electrode with a porous structure.The construction of a three-dimensional cross-linked network suppresses sheet stacking,further enhancing the contact between the active material and the gel electrolyte.At the same time,the introduction of additional crosslinking point enhances the stability of electrode structure,hence capacitors can work normally under large current.Therefore,MXene-BPEI based micro-supercapacitor has good electrochemical performance.Its area capacitance can reach 3783.53 m F cm^-2 at 1 m V s^-1,which is nearly twice that of pure MXene based supercapacitor.Even if the scan rare is increased to 100 m V s^-1,it can achieve 924.06 m F cm^-2.The device can also have 99.44%capacitance retention after 10000 cycles,reflecting good cycle stability.Additionally,the device has a maximum energy density of 99.41μWh cm^-2 and a maximum power density of 18 m W cm^-2.The micro-supercapacitors showed good flexibility.After bending in the range of 0°to 180°,the capacity remains above 90%.In addition,we explored the feasibility of connecting supercapacitors in series and parallel to meet the practical application.The results showed that the working voltage of the series device reaches 1.2 V,which is twice that of the single device.The working voltage of the parallel device does not change,but the capacity becomes twice that of the single device.The series and parallel devices can work normally,showing great potential in practical application.