Research On Material Interface Regulation And Electrical Performance Of Nanogenerator

The advent of the Internet of Things（Io T）era facilitates human life,making intelligence popularized to every aspect,including transportation,medical care,industrial production and so on.As the basis for information acquisition in Io T,sensing system always plays an important role.The rapid development of the Io T requires a rapid increase in the number of sensors.Although the power consumption of electronic devices is getting smaller and smaller,the energy supply of sensors is still an urgent problem to be solved due to the huge number and wide distribution.At present,the batteries for sensors need to be replaced or recharged regularly,consuming a lot of manpower and material resources.The self-powered system can harvest the energy in environment and convert it into electrical energy.After combining self-powered system with sensing system,self-powered sensing system can be developed to solve this problem effectively.In the energy harvesting unit,piezoelectric nanogenerator（PENG）and triboelectric nanogenerator（TENG）stand out because of its advantages,such as high output,simple structure,and so on.Although nanogenerator has rapid developement,the electrical output performance is still a key factor limiting the development and practical application.In this paper,starting from the theoretical source of nanogenerator,a series of projects based on displacement current is designed.The method of material interface regulation is applied to enhance electrical performance.It lays the foundation for application of TENG in self-powered sensing system.The main researches are listed as follows:The polarization charge density of displacement current in piezoelectric nano generator is improved and the electrical performance is enhanced.Polyvinylidene fluoride（PVDF）crystal nanosheets are constructed by high-pressure melting method.By adjusting the anisotropy of the crystal nanosheets interface,the polarization charge density in displacement current can be effectively enhanced.And the high-performance piezoelectric materials can be obtained.By comparing different preparation methods,it is proved that the high-pressure melting method also has a significant improvement on crystallinity（65.54%）andβphase content（86.48%）.The problem of low PVDF’s piezoelectric properties is fundamentally solved with polarization process avoided.PVDF based on this method has good stability（97%）,and the acceleration sensor has high sensitivity of 2.405 n A s² m^-1,which could be used for dynamic acceleration monitoring.This easy process method has great potential commercial production of PVDF.In TENG,the enhancement effect of fluorine-containing groups on triboelectric charge density is investigated.New two-dimensional transition metal carbide（MXene）films and alkalized MXene films are prepared.By adjusting the fluorine-containing groups at the interface between MXene and nylon,the effect of fluorine-containing groups on triboelectric charge density of displacement current is verified.The power output of the TENG made of MXene and nylon under different loads is investigated.In addition,the conductivity of MXene can reduce the matching impedance from 100 MΩto 10 MΩ.As a new material,MXene can put forward a new path for development of TENG.The triboelectric charge density of displacement current in TENG is improved.A free-fixed rotational TENG is proposed.By magnetic structure design,a free-fixed rotational TENG is proposed.By regulating the interaction force between triobelectric layers,effective contact area of tribo-material interface is enhanced,leading to improved triboelectric charge density.The device can deliver a short-circuit current of 55μA,open-circuit voltage of 500 V,and transfer charge of 235 n C at 400 rpm.And the influence mechanism of rotation speed on electrical performance is clarified.The experiments verify that the fabricated device can harvest rotational energy effectively and supply power for a wireless temperature sensor through the power management circuit.This study takes a revolutionary step for TENG in self-powered wheel sensing field.The dielectric property of tribo-materials in TENG is enhanced,resulting in improved displacement current.The interface polarization is realized by doping active carbon in PVDF with micro capacitance structure constructed.Thus,the dielectric property of the materials is adjusted,and the displacement current of TENG is enhanced.The influence of different active carbon contents on various properties is investigated.Compared with the pure PVDF,TENG by the 0.8%active carbon doped PVDF obtains an enhancement in voltage,current,and power by 2.5,3.5,and 9.8 times,respectively.The experiments verify that the micro capacitor structure constructed by this method can effectively enhance the dielectric performance,which is conducive to the enhancement of TENG electrical performance.The theoretical analysis of materials and devices are carried out systematically to explain the enhancement mechanism of TENG based on composite film.The fabricated TENG has good performance both in energy harvesting and active sensing.This study breaks a new way to enhance output performance of TENG by material interface science.The displacement current and conduction current are directly superimposed to improve the electrical performance.A maglev electromagnetic-triboelectric nanogenerator is designed.Based on magnetic structure design,the magnet is introduced to reduce the energy loss caused by impact during vibration.And the variable magnetic field can form electromagnetic generator（EMG）.Thus,the hybrid of TENG and EMG can make the displacement current and conduction current superimposed directly,effectively improving the efficiency and the output density of the whole device.TENG can reach 0.34 m W/g at 50mΩ,while EMG can reach 0.12 m W/g at 700Ω.The influence of different vibration frequencies on output performance is investigated,revealing the action law of superposition of displacement current and conduction current to improve TENG electrical performance This study paves a new way for hybrid of TENG and other power generation methods.Based on the above works,a double-layer wave-structure hybrid nanogenerator is designed.On one hand,the wave structure can combine multiple working modes to improve the triboelectric charge density at the interface,enhancing the displacement current furthermore.On the other hand,the double-layer structure can improve the power density of the whole device.And the magnet is introduced to hybrid TENG and EMG,superimposing displacement current and conduction current for higher power density,as 167.22 W/m³.The influence of vibration frequency on output performance is investigated.The experiments verify that the self-powered safety helmet based on the fabricated device can harvest the energy when people exercise.This study provides a new idea for combination of multiple working modes of TENG.