Investigation Of Electrode And Structural Design Of Nanogenerator And Its Applications

In recent years,with the rapid development of the Internet of things,the number of mobile multi-functional electronic devices are increasing explosively.These devices are changing the communicational mode of people to people and people to things.Meanwhile,the traditional power supply units which based on battery are challenged because of its disadvantages such as replacement and maintenance difficult and environmental pollution.It is becoming an urgent issue to develop a suitable energy supply unit.Fortunately,nanogenerators can efficiently convert the mechanical energy in the environment into electrical energy and realize the self-powered electronic devices,and it has lot of merits including lightweight,simple structure,low cost,high efficiency,and diverse material options.Hence,it is an ideal solution for power supply issue of portable electronic devices.However,from experiment to practical application,nanogenerators still face many challenges,and its output performance and stability still need to be further improved.Aiming at improving the output performance and stability of nanogenerator,we design and develop the nanogenerators with novel interdigital electrodes or structure.Firstly,for improving the output performance of Pb(Zr0.52Ti0.48)O3(PZT)based piezoelectric nanogenerators,we develop and optimize the structure of planar interdigital electrode.Secondly,the high performance 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)Ti O3(BZT-BCT)based piezoelectric nanogenerator is achieved by using the optimized interdigital electrode,and a simple solution is proposed for its weak working lifetime.Then,for improving the output performance of triboelectric nanogenerators,we design a novel structure triboelectric nanogenerator with the threedimensional interdigital electrodes.Meanwhile,the mechanism of the high performance of nanogenerators improved by interdigital electrodes structure is deeply analyzed,and this is a novel and effective strategy to increase the output performance of nanogenerator.In addition,aiming to the application requirements of wearable selfpowered electronic devices,we design a fiber-based nanogenerator with semi-supported structure for harvesting human motion energy,which has high stability and working lifetime.The details and main results are as follows:(1)PZT piezoelectric ceramics are widely applied in energy harvesters because of the high piezoelectric coefficient and electro-mechanical coupling coefficient.In order to improve the output performance of the piezoelectric nanogenerator based on PZT,an interdigital electrode structure is designed and optimized.Specifically,the influence of interdigital electrode density on the output performance of piezoelectric nanogenerator is explored,and there is an optimal interdigital electrode density which leading to the best output performance of PZT-based piezoelectric nanogenerator,and the mechanism is explored in detail.Compared with the control group with single pair of electrodes,the output current and charge of piezoelectric nanogenerators with interdigital electrodes are increased by 155 times and 174 times respectively.The high-performance piezoelectric nanogenerator can be used as acoustic energy harvester and wearable hand bending angle monitoring sensor,which show the potential of practical applications.(2)PZT contains lead,which is toxic to the natural environment and human health.In order to reduce environmental pollution and health danger,lead-free BZT-BCT nanowire arrays are successfully synthesized by electrospinning method,and the piezoelectric property is comparable to the piezoelectric ceramics containing lead.Assembled with the optimized interdigital electrode,the BZT-BCT based piezoelectric nanogenerator is completed.And its output voltage,current,charge and power could reach 62 V,0.78 ?A,80 n C,and 31 ?W,respectively.In addition,in order to solve the problem of performance degradation and improve the stability and working lifetime,we configure a triboelectric nanogenerator(TENG)with the BZT-BCT based piezoelectric nanogenerator,and that is repolarized by the TENG at regular intervals.Meanwhile,we explore in detail the polarization effect of the pulse voltage generated by TENG on piezoelectric materials under different conditions.(3)According to the structural characteristics and working mode of triboelectric nanogenerator,we design a novel triboelectric nanogenerator with three-dimensional multiple interdigital electrode structure(MIE-TENG).The same charge quantity can be induced on the surface of multi-layer electrodes by the electrostatic field generated by triboelectric charge,and the output charge can be increased greatly by connecting the multi-layer electrodes.It is a new strategy for improving the output performance of triboelectric nanogenerators.Compared with TENG with single-layer electrode,the output voltage of MIE-TENG with 40 layers electrodes is reduced from 6 k V to 140 V,and the peak current is increased from 0.8 ?A to 60 ?A(the load resistance is 1 M?).Meanwhile,when the load resistance is 10 ?,the maximum peak current of MIE-TENG can reach 14 A,corresponding to 15.6 k A/m2,and the maximum peak power density is 2.18 MW/m2.More importantly,the output charge is increased to 7.2 ?C,corresponding to the output charge density 8 m C/m2.It is a new record.(4)Aiming at the application requirements of wearable self-powered electronic devices,we design a fiber-based nanogenerator by the electret material(FENG)with semi-support structure,which has high stability and working lifetime.The electret material is applied in fiber-based nanogenerators for the first time.The high stability and working lifetime of FENG are owed to the non-contact friction in the work process.The open circuit voltage and short circuit current of FENG can reach 40 V,0.6 ?A.When the load resistance is 400 M?,the output power of FENG reaches 27 ?W? Moreover,no obvious degradation of the output performance under a long-time continuous work(>16 h)and different humidity environments(20-95%RH)is observed,which demonstrates the FENG's good reliability and stability.Many universal materials,such as cotton rope,conductive sewing thread,and polyvinyl chloride tube,have been successfully used to fabricate FENG.Meanwhile,the FENG-based wearable fabric has been successfully developed to effectively harvest mechanical energy of human motion.The FENG is highly effective,reliable,and stable,promoting the development of fiberbased nanogenerators and their applications in self-powered wearable electronics.