Study On The Performance And Application Of Organic/Inorganic Composites Based Triboelectric Nanogenerators

With the booming era of Internet of Things and 5G,billions of distributed electronic devices and sensor networks are used in major fields.Solving the energy supply problem of the massive wireless electronic devices and sensors is an essential factor in promoting the development of the information age.And the traditional energy supply method can no longer meet its development needs.Therefore,new energy supply methods are one of the main directions of current research.Triboelectric nanogenerator（TENG）is a new energy harvesting technology based on the coupling effect of contact electrification and electrostatic induction,which converts tiny mechanical energy in the environment into electrical energy,with the advantages of wide operating frequency,abundant choice of materials,easy fabrication and low production cost.It is a potential green energy supply method for microelectronic devices.However,there are problems such as low output performance and short lifetime.To address these problems,this thesis adopts high dielectric constant ferroelectric Bi Fe O₃（BFO）and electron trapping MoS₂ nanosheets as doping materials to regulate the surface charge density of organic polymer triboelectric materials.It improves the mechanical durability of the materials with the excellent lubrication property of MoS₂,providing a new idea for preparing new triboelectric materials.The TENG constructed with it has high output performance and long service life,which is of great practical significance to promote the practicalization of TENG.Meanwhile,a piezoelectric-triboelectric hybrid nanogenerator was designed based on(K_0.45Na_0.55)_0.98Li_0.02Nb_0.76Ta_0.18Sb_0.06O₃（KNLNTS）ferroelectric ceramic sheets,which effectively improved the output performance of the generator and carried out research on its application in self-driven sensing such as power supply of microelectronic devices and monitoring of human motion status.（1）BFO nanoceramic particles with high dielectric constant were introduced into polydimethylsiloxane（PDMS）to modulate the surface charge density of the material,which in turn enhanced the output performance of TENG.The organic/inorganic composite triboelectric material made of BFO and PDMS was used as the negative triboelectric material of the TENG,and Aluminium（Al）foil was used as the positive triboelectric material and electrode to construct the TENG in contact-separation mode.This thesis investigated the effects of composite film thickness,BFO doping ratio,external force magnitude and contact-separation frequency on the output performance of TENG.The results showed that the best output performance of the BFO/PDMS composite-based TENG was achieved when the composite film thickness of 200μm,the doping amount of BFO was 3 wt%,and the external force and frequencie of 3.5 N and 3 Hz,respectively.The maximum output voltage and current were about 180 V and30μA,which are 200%and 500%higher than the PMDS-based TENG under the same conditions.Furthermore,the TENG can charge a commercial capacitor of 10μF to 2.5V in 120 s and power an electronic watch or 52 LEDs in series.（2）High-performance and long-life TENGs that can harvest wind energy were constructed using PVDF/MoS₂ composite film and nylon（PA）film as triboelectric materials,respectively,with PVDF/MoS₂ composite film as negative triboelectric material and PA film as positive triboelectric material.This thesis investigated the effects of composite film thickness,MoS₂ doping ratio,and wind speed on the output performance of TENG.The results show that the best output performance is achieved when the thickness of the composite film is 30μm,the MoS₂ doping ratio is 2 wt%,and the wind speed is 16.5 m/s.The device output voltage,current,and power are 410V,48μA,and 5.37 m W,respectively.In addition,the capacitor with a capacity of 3300μF could be charged from 0 V to 3 V in 31 s.The reason for the improved output performance of the PVDF/MoS₂ composite film-based TENG is also explained using an electron cloud-potential well model.In addition,the tribological property tests of PVDF film and PVDF/MoS₂ composite film show that the MoS₂ reduces the material friction coefficient and decreases the abrasion effectively.Compared with the PVDF film,the friction coefficient of the composite film was reduced by 0.08.The stability test shows that the PVDF/MoS₂ composite film-based TENG maintains excellent stability after 20 h of continuous operation.（3）The(K_0.45Na_0.55)_0.98Li_0.02Nb_0.76Ta_0.18Sb_0.06O₃（KNLNTS）lead-free piezoelectric ceramic powder was prepared by solid-phase reaction method,and KNLNTS piezoelectric ceramic sheets were obtained after pressing,sintering and polarization.PDMS polymer was used as its flexible shell to construct KNLNTS-based piezoelectric nanogenerator（PENG）.The results showed that the output voltage and current of the PENG were 2.6 V and 78 n A,respectively,under an external force of 10.8 N.The device maintained excellent stability after 2 h of continuous operation.A contact-separation TENG was constructed using one side of the PDMS case as the negative triboelectric material,the FEP film as the positive triboelectric material,and Al foil as electrode,resulting in an optimum output voltage and current of 38 V and 5.8μA,respectively.The PENG and TENG were connected in parallel to form a piezoelectric-triboelectric hybrid nanogenerator（HG）,which could charge a commercial capacitor of 10μF to 1.56 V within 120 s.HG’s charging rate was significantly higher than that of PENG and TENG alone.At the same time,the device can be used as a flexible wearable sensor for dynamic monitoring of information such as the pulse rate before and after human exercise.