Fabrication Of Fibrous Asymmetric Supercapacitors And Investigation Of Their Electrochemical Properties

With the increasing rapidly for technologies of micro-intelligent chips,sensors and wireless communication devices.The intelligent flexible wearable devices are developing for integrated muti-functions more and more.Benefited from this advantage,flexible wearable devices not only applied in frontier field such as aviation and aerospace,but also widely applied in civilian market.Smart bracelet,human health monitor as a representative of intelligent flexible wearable devices,which can be prompted convenient of people live greatly.In addition,energy supply module is very important to multifunctional integrated device.However,traditional columnar,block and button-type batteries with large volume,heavy mass and unable to fold,which makes them unsuitable as energy supply devices for wearable lightweight electronic integrated devices.Therefore,a major of challenge of limiting development of lightweight and multifunctional electronic integrated devices is to design suitable wearable energy storage devices.Different from wire-shaped batteries,wire-shaped supercapacitor has unique advantage,which is high power density,long cycle stability,high safety,small light weight,easy knitting and tailoring,and environmental friendliness.So that they are expected to become a new generation of flexible wearable energy storage devices.Unfortunately,the lower energy density are limits the further development of fibrous supercapacitors in practical applications.How to increase the energy density without affecting the power density of device has become a significant problem need researcher to solve.So far,there are mainly two ways of improve to device energy density,which have been affirmed by researchers.On the one hand,through the development of asymmetrical structure of supercapacitor devices,it can be promoted device voltage.On the other hand,optimizing electrode materials to increase the specific capacity of the positive and negative electrode materials.Based on these two methods,this thesis designs and constructs fibrous asymmetric supercapacitors with high energy density,and uses efficient and fast additive manufacturing technology to reach rapid and large-scale preparation.The main research contents are as follows:(1)MnO₂ and MoS₂ nanosheets with high theoretical capacity were synthesized by a simple and effective hydrothermal method.In addition,the organic materials was heat-treated to obtain nitrogen-doped porous carbon.Through a series steps of agitating and ultrasound,MnO₂ and MoS₂ nanosheets are uniformly mixed with the graphene nanosheets to obtain a printable ink with high rheological properties,respective.Finally,3D printing was used to obtained coaxial positive electrode composite fibers and negative electrode composite fibers.The PVA/KOH composite gel as the gel electrolyte,a winding fibrous asymmetric supercapacitor device was prepared after a series of treatments.Our assembled supercapacitor has satisfactory electrochemical performance,and positive and negative electrode was protected by coating of carbon,which leaded excellent long-cycle stability of device.(2)In order to solve the problems of the cumbersome preparation process of traditional fibrous supercapacitors and the mismatch of Young's modulus caused by the loosening of the electrode interface after long time bending.We use 3D printing multi-ink direct writing technology to obtain a coaxial fiber with a compact structure and good scalability via designing structure of multi-core shell coaxial print nozzle and adjusting the rheological properties of the ink and the supply rate of the multi-ink.Due to the immiscibility between the inks of different components,the electrode and the electrolyte cam be tightly combined,leading the device has good electrochemical performance.(3)The multi-ink 3D printing coaxial fibrous asymmetric supercapacitors as the power supply unit.And then,a self-powered and self-monitored integrated system was constructed through series-parallel connection.Investigating the feasibility of integrating high-energy density,high-voltage fibrous asymmetric supercapacitors and chip-type micro-solar charging panels in practical applications(such as electric vehicles,micro water pumps,sightseeing cable cars and other energy-consuming devices)in series and parallel connections.In addition,a bionic-based pressure sensor with high-sensitivity,low-detection limit was constructed to form a self-energy pressure monitoring device,which maintained good stability performance under 600 times repeated loading/uploading.