Direct Wet-spinning Assembly And Performance Of Fiber-shaped Flexible Graphene-based Supercapacitors

Graphene fiber-shaped supercapacitors have a wide application in the field of flexible wearable divice due to their lightweight,programmable and high-power density properties.However,the complex assembly process,the thick electrolyte layer,insufficient contact with the electrode,and the high risk of short circuit in severe deformations all limit the practical application of graphene fiber-shaped supercapacitors at present.In view of these problems,this paper constructs fiber-shaped flexible graphene-based supercapacitors with coaxial and twisting structures by direct wet-spinning,regulating their microstructure and studing the electrochemical properties and stability.The specific research content is as follows:（1）PVDF nanofibers with good hydrophilia,acid and base resistance,average length and diameter of 165μm and 750 nm respectively,were obtained by electrospinning and shear homogenization.Taking PVDF nanofiber/CMC as spinning dope,the PVDF nanofiber separator with uniform,continuous,controllable thickness and interlaced internal fibers was obtained by wet-spinning.（2）PVDF nanofiber/CMC and GO solution were used as inner and outer layer spinning dope respectively.A coaxial graphene fiber-shaped supercapacitor based on PVDF nanofiber separator was obtained by direct wet-spinning with a coaxial needle.The porous PVDF nanofiber membrane embedded between the graphene fiber electrodes has a thin and highly folded network structure,enabling the electrode to be fully chemically reduced without damaging the structure of separator,with good contact interface,rapid transport of electrolyte ions,and the device to be free from the risk of short-circuit.The electrochemical test results show that the supercapacitor has excellent electrochemical performance,good bending and cyclic stability,and its specific capacitance and energy density can reach 346.5 mF cm^-2 and 30.8 Wh cm^-2,respectively.After the 10000 times cyclic test,the capacitance retention rate reached 94%.When doped with MnO₂,the specific capacitance can be increased to 410.7 mF cm^-2.（3）Taking GO/CNT/VC dispersion solution and CMC/H₃PO₄ solution as electrode and gel electrolyte separator spinning dope,respectively.The twisting-structured graphene/CNT composite fiber-shaped supercapacitors were obtained by direct wet-spinning with side-by-side the multi-channel needle.The continuous,thin and folded electrolyte layer is integrated with the high porosity electrode,which is conducive to the rapid penetration of electrolyte ions to the contact between the electrode and the electrolyte interface and the inside of the electrode.The electrochemical test results show that the specific capacitance and energy density of the supercapacitor can reach 186.9 mF cm^-2 and 4.16 Wh cm^-2,respectively,and good bending and cyclic stability of the device.When doped with MnO₂,the specific area capacitance can be increased to 267.2 mF cm^-2.