MSE Ph.D. Defense - Sihong Wang
Dr. Z.L. Wang (MSE, advisor)
Dr. Meilin Liu (MSE)
Dr. David McDowell (MSE/ME)
Dr. Russell Dupuis (ECE/MSE)
Dr. Mostafa El-Sayed (Chemistry)
Dr. Paul Kohl (ChBE)
Title: Nanogenerator for Energy Harvesting and Its Hybridization with Li-Ion Battery
Energy harvesting and energy storage are two most important technologies in today’s green and renewable energy science. As for energy harvesting, the fundamental science and practically applicable technologies are not only essential in realizing the self-powered electronic devices and systems, but also tremendously helpful in meeting the rapid-growing world-wide energy consumptions. Mechanical energy is one of the most universally-existing, diversely-presenting, but usually-wasted energies in the natural environment. Constantly scavenging energy from ambient mechanical motions could possibly satisfy the energy consumption of a long-term operated electronic system. On the other hand, the electricity generated from environmental energy often needs to be stored in energy storage unit before used to drive electronic devices. For the energy storage units such as Li-ion batteries as the power sources, the limited lifetime is the prominent problem, which drives the major efforts in this field towards the increase of capacity. Hybridizing energy harvesting devices with energy storage units can possibly provide new solution for this.
Recently, based on the well-known phenomenon—the triboelectric effect, a new technology for mechanical energy harvesting—triboelectric nanogenerators (TENGs)—has been developed. In this dissertation, we made important contributions to the development of TENGs in the following aspects. Through rational structural design, we significantly improved the output performance of the contact-mode TENG. The characteristics of such TENGs as a power source have been systematically demonstrated and studied. Beyond this, we have also established the second basic mode for TENG—the lateral sliding mode, and developed sliding-based disk TENGs for harvesting rotational energy and wind-cup-based TENGs for harvesting wind energy. In order to expand the application and versatility of TENG by avoid the connection of the electrode on the moving part, we developed another basic mode—freestanding-layer mode, which is capable of working with supreme stability in non-contact mode and can harvest energy from a free-moving object or a walking human. The new disk TENG constructed based on this mode also displays much improved long-term stability. The above researches have largely propelled the development of TENGs for mechanical energy harvesting and brought a big potential of impacting people’s everyday life.
Targeted at developing sustainable and independent power sources for electronic devices, efforts in this dissertation have been made in this dissertation to develop new fundamental science and new devices that hybridize the mechanical energy harvesting and the energy storage process into a single-step process or in a single device. Through hybridizing a piezoelectric nanogenerator with a Li-ion battery, a self-charging power cell has been demonstrated based on a fundamentally-new mechanical-to-electrochemcial process. The triboelectric nanogenerator as a powerful technology for mechanical energy harvesting has also been hybridized with a Li-ion battery into a self-charging power unit. This new concept of device can sustainably provide a constant voltage for the non-stop operation of electronic devices.