Efficient Charging of Li-Ion Batteries with Pulsed Output Current of Triboelectric Nanogenerators

The triboelectric nanogenerator (TENG) is a promising mechanical energy harvesting technology, but its pulsed output and the instability of input energy sources make associated energy-storage devices necessary for real applications. In this work, feasible and efficient charging of Li-ion batteries by a rotating TENG with pulsed output current is demonstrated. In-depth discussions are made on how to maximize the power-storage efficiency by achieving an impedance match between the TENG and a battery with appropriate design of transformers. With a transformer coil ratio of 36.7, similar to 72.4% of the power generated by the TENG at 250 rpm can be stored in an LiFePO4-Li4Ti5O12 battery. Moreover, a 1 h charging of an LiCoO2-C battery by the TENG at 600 rpm delivers a discharge capacity of 130 mAh, capable of powering many smart electronics. Considering the readily scale-up capability of the TENG, promising applications in personal electronics can be anticipated in the near future.