Study On High-Performance Triboelectric Nanogenerators Based On Enclosed Structural Designs

The triboelectric nanogenerator(TENG)can effectively collect irregular or low-frequency mechanical energy and convert it into electrical energy.It has been considered as one of the effective means to obtain environmental energy and achieve self-powered sensing,providing a new idea for the development of new green energy.Generally,TENG can only provide stable output in a relatively dry environment.The presence of moisture in the environment will greatly reduce the triboelectric charge on the surface of the material and affect the output of electrical properties.In addition to being used in conventional environments,in order for TENG to adapt to complex environments such as rain,snow,and implantation in the body,it can be sealed to avoid the external environment's influence on internal materials.Therefore,on the one hand,the device needs to have good sealing properties to isolate the influence of the external environment;on the other hand,it is necessary to design a well-designed internal structure to improve the output performance of the device,so as to well collect various mechanical energy.In this thesis,the output performance of TENG has been improved from material modification,structural design to environmental gas changes,an enclosed interconnected TENG array is prepared,which can be adapted to various complex environments.The contents of the full text study include:Adding closed-cell microspheres to the silicone rubber to build a microscopic closed-cell structure to increase charge capture: The closed-cell expandable microspheres are used to modify the silicone rubber,and a closed-cell structure is built inside the silicon rubber microstructure,which can be used as a trap capture more charges to increase the surface charge density,thereby effectively improving the output performance of TENG.At a working frequency of 2.5 Hz,the optimal TENG assembled by the microsphere-modified silicone rubber composite film has the best electrical performance output,the voltage and current are 300 V and 4.2 ?A,respectively.Compared with silicone rubber-based TENG,the voltage and current are increased by 230% and 60%,respectively.In addition,thermoplastic polyurethane(TPU)/multi-walled carbon nanotubes(MWCNTs)flexible electrodes are prepared,and a fully flexible single-electrode model TENG can be used as an electronic skin to collect the human body's mechanical energy and convert it into electrical energy.Add a dielectric layer between the triboelectric material and the electrode to optimize the TENG trap distribution: add a dielectric layer between the triboelectric material and the electrode,including polyimide(PI),polypropylene(PP),polyamide(PA)),polyethylene(PE),dense polytetrafluoroethylene(PTFE),polyoxymethylene(POM)and silicone rubber can change the trap distribution of TENG,increase charge retention and reduce charge dissipation,thereby effectively improving the output performance of TENG.In the tested dielectric layer,PI proved to have the largest charge trap density and trap energy level.From the analysis of the isothermal surface potential decay(ISPD)model,it can be seen that deeper storage depths will have the best electrical performance output.The working frequency is 2.5 Hz,and the output voltage(1500 V),output current(23 ?A)and transfer charge density(200 n C)of TENG composed of a PI dielectric layer under TPU and porous PTFE are compared with those without a dielectric layer,increases were 88%,260% and 200%,respectively.Further studies have shown that the performance enhancement mechanism of the added dielectric layer in this system has nothing to do with the electrical positive and negative properties of the troboelectric material,but is closely related to its volume conductivity.Optimizing the volume conductivity of the triboelectric material has proved to be beneficial to the output of electrical properties.Fill the enclosed structure with high-dielectric-strength gas to improve the air breakdown: an enclosed nested cubic TENG composed of an inner shell and an outer shell is made,and different gases such as helium(He),argon(Ar),air(Air),nitrogen(N2),carbon dioxide(CO2),freon(CHCl F2)and sulfur hexafluoride(SF6),their output performance has varying degrees of change.The prepared enclosed cubic TENG is not affected by the environmental humidity.When the cubic TENG is shaken,the energy of the four directions of vibration in the horizontal space can be collected as a self-powered device.Among them,when the working frequency is 3 Hz,when filled with SF6 gas with high dielectric strength,it can generate a maximum output voltage of 500 V and a short current of 11 ?A,which are 67% and 120% higher than that in an air atmosphere.The theoretical model of "gas discharge" predicts and explains the relationship between the gas atmosphere and the enhanced output performance of the cubic TENG.Vent holes are constructed between TENG units to increase the sensitivity of the TENG array: a novel flexible and closed interconnected TENG array is designed.This structure can more easily obtain electrical performance output and can work under high humidity conditions,even use it in water.Each TENG unit uses a microsphere-modified silicone rubber composite film as the triboelectric negative material,TPU is used as the triboelectric positive material,and a dielectric layer is added between it and the electrode.Multiple TENG units are connected by vents to form a interconnected TENG array,and finally filled with SF6 gas inside.Compared with the common independent TENG array,when one of the units is pressed,the internal gas will diffuse to the other units,showing higher output performance and sensitivity.In addition,the influence of the structural factors of each TENG unit on the output performance is analyzed.When the top layer thickness is 0.8 mm and the air gap distance is 4 mm,there is an optimal voltage output.This interconnected TENG array can be used for gait monitoring,emergency fall detection/alarm systems for healthcare,and smart window sensors in smart residential systems.Therefore,the optimal conditions for enclosed structure TENG were explored from material modification,structural design and gas atmosphere changes,and flexible enclosed TENG units were prepared.Units and units were connected by air vents,and a novel enclosed interconnected TENG array was designed.It has good output performance and sensitivity,and can be adapted to various complex environments.