Piezoelectric nano-generator output of electrical energy for the pulse form, which in most cases can not directly power the electronic devices, so it is necessary to first collect the energy stored in the storage device, that is, the battery can be directly converted to electrical energy and storage, to achieve the battery of self charge. Based on the new technology of battery charging, this kind of self charging battery can greatly broaden the application range of the self driven working mode, especially the self drive of the electronic devices with larger power. By integrating the piezoelectric film with the lithium battery, the researchers designed a battery with a self charging function. The battery can be recharged continuously when it is subjected to a cyclic force, thus enabling direct conversion of the mechanical energy to the energy stored in the battery. They used the porous PVDF material commonly used in the lithium battery structure as a diaphragm, but the PVDF films were polarized and the piezoelectric potential of the vertical film direction could be produced in the event of stress. The principle is that the PVDF film is placed between the anode and cathode of the lithium battery and is tightly jointed, when subjected to compressive stress, the piezoelectric potential of the film can drive the li+ of the electrolyte to migrate and combine with the anode material, when the ionic equilibrium state breaks, the lithium cobalt acid in the cathode breaks down, releasing some li+ into the electrolyte; After the stress is withdrawn, some li+ will return, however, it does not affect the charging effect in this cycle. The battery can be recharged continuously by applying stress over the cycle. It is noteworthy that the charging efficiency of this direct integrated rechargeable battery is higher than the charging method of parallel between the nano-generator and the battery, because it eliminates the energy loss of the intermediate links such as rectification and transmission.
Piezoelectric nano-Generators after 10 years of development, through the optimization of materials and the innovation of structure, there has been a great development in performance improvement, which shows great research value and application foreground in energy collection, information sensing, environmental monitoring and biomedicine, but there are still many problems needing further study.
1. Piezoelectric composites
Most of the traditional piezoelectric materials are inorganic ceramic materials, their mechanical stability is poor, and the existing flexible polymer piezoelectric materials have low piezoelectric properties. Therefore, how to design both flexible and good piezoelectric properties of composite materials can greatly broaden the application of piezoelectric nano-generators.
2. Piezoelectric nano-generator matching circuit design
Piezoelectric nano-generators output is the pulse signal, whether it is stored in the electrical energy storage equipment or directly to the electronic devices to power supply, all need to design the relevant circuit to make the output more stable, and improve its use efficiency.
3. Application of micro-Nano energy
The advantage of piezoelectric nano-generators over macroscopic generators lies in their energy collection advantages in micro-na scale, so we should continuously seek the energy acquisition and self driving application of piezoelectric nano-generators within the micro-NA range. Energy technology is in a period of vigorous development, the need for more innovative work to promote nano-generators to the direction of industrialization. With the development of new material technology, it is believed that piezoelectric nano-generators and their self driven systems will be used in the revolutionary application of the wave of science and technology.