Hybrid energy cells based on triboelectric nanogenerator: From principle to system

Abstract Usually, plenty of energy forms can be found in our ambient environment including ubiquitous mechanical energies, such as rotation, vibration, and fluctuation energies and other energy forms, such as thermal, solar and chemical energies. Triboelectric nanogenerators (TENGs) that can convert various mechanical energies into electricity have experienced a rapid explosion since 2012 for their potential as a long-term power supply for sensing networks and wearable/portable electronics. To further increase the energy conversion efficiency or expand the application scenes of energy harvesters, hybrid energy harvesting technology based on the TENGs has been developed. In this article, we review the recent progress about the TENG-based hybrid energy cells, including hybrid devices for individually harvesting single energy through multi mechanisms, hybrid counterparts for converting multi-type energies at different situations, and hybridization systems. For single mechanical energy harvesting, the comparison of triboelectric and piezoelectric/electromagnetic generators and their different hybridization modes have been detailed discussed. For multi-type energy harvesting, different structure designs and application scenes are summarized. Finally, integrated hybridization systems are introduced to demonstrate the practicability of the TENG-based self-powered smart system. The summarized development trend and design guidelines will be beneficial to the research of energy harvesters and smart systems, including wearable/portable electronic systems, remote monitoring systems, artificial intelligence and the smart sensing networks, etc.