Energy Harvesting Of Ferroelectric Oxide-based Nanogenerators

The invention of piezoelectric nanogenerators is a milestone in the development of nanotechnology.It realizes the conversion from mechanical energy to electric energy at the nanoscale,providing a feasible solution to solve the energy crisis.The electromechanical conversion performance of piezoelectric composites is not only related to the piezoelectric properties of the piezoelectric phase itself,but also closely related to the orientation and distribution of the piezoelectric phase.Currently piezoelectric nanogenerators are mainly prepared by combining piezoelectric materials with a flexible organic matrix.The piezoelectric responses are not concentrated and the load transfer is poor.In order to solve this problem,lithium-doped two-dimensional ZnO micro disks with crystal orientation were prepared and the corresponding nanogenerators were fabricated in the first part of the paper.In the second part,continuous BiFeO₃?BFO?films and Pb(Zr_0.52,Ti_0.48)O₃?PZT?films were grown on glass fiber fabrics?GFF?,and the corresponding nanogenerators were fabricated.The corresponding results are as follows:?1?Self-poled two-dimensional Li-doped ZnO were synthesized via a simple one-step hydrothermal method.The Li-ZnO is self-poled with the d₃₃ of¹5 pm/V.The effect of lithium concentration,precursor concentration,Li-ZnO weight ratio and poling process on the output of nanogenerators based on Li-ZnO has been fully investigated.The output of the LZNGs increased as the concentration of the doping lithium increased;The output of the LZNG based on Li-ZnO micro disks is much higher than those based on Li-ZnO micro rods.This is because Li-ZnO micro disks dispersed in PDMS have the same orientation approximately,achieving macroscopic self-polarization;The LZNG with Li-ZnO weight ratio of 10%obtained the highest output of¹4 V,¹3.18?A/cm²,and⁵.43 mW/cm³ without a poling process.?2?BFO films were grown on the glass fiber fabric?GFF?via a dipping method.The BFO-GFF composites were combined with interdigital electrodes to fabricate flexible nanogenerators?BFO-PENGs?.Ultra-flexible BFO-GFF composite?bending to 180^o?was prepared after an annealing treatment at 550 ^oC for 60 min;BFO-PENG obtained the highest output of¹5 V and⁷1.90?A/cm²,which is an order of magnitude higher than previous works due to the concentrated piezoelectric response and good load transfer of the BFO-GFF composite;Output power test demonstrated the highest power density of².66 mW/cm³.?3?PZT films were grown on the GFF via a dipping method.The PZT-GFF composites were combined with interdigital electrodes and carbon film electrodes to fabricate flexible nanogenerators?IDE-PENG and CFE-PENG?.Ultra-flexible PZT-GFF composite?residual polarization of⁵5?C/cm²?was prepared after an annealing treatment at 650 ^oC for 60 min;The IDE-PENG obtained the highest output of⁶0 V,²45.10?A/cm² and highest power density of¹5.96 mW/cm³,which is two times higher than the PZT powder-based nanogenerator.IDE-PENG clearly shows a linear change of output as a function of strain/load,which is promising to be used as self-powered mechanical sensor;Compared with IDE-PENG,the CFE-PENG advances its application potential with easier fabrication,lower cost,better flexibility and multi size.The CFE-PENG?8cm?8cm?obtained high output of¹10 V and¹.05?A,which can simultaneously light up 20commercial green LEDs.In summary,in this work,we enhanced the piezoelectric output performance and flexibility/durability of ferroelectric oxide-based nanogenerators through morphology control and structural optimization with simplified fabrication process.The research results provide feasible solution for practical application of nanogenerators.