A flexible lithium-ion battery with quasi-solid gel electrolyte for storing pulsed energy generated by triboelectric nanogenerator

Sustainable operation of flexible and wearable electronic devices is possible with energy harvested from environment, but such power could be in the form of pulses with varying amplitude and frequency. In this work, we prepared quasi-solid lithium-ion batteries (LIBs) for storing the energy generated by a triboelectric nanogenerator (TENG). The lithium-ion batteries composed of a gel electrolyte, LiFePO4 cathode and metallic lithium anode can deliver a capacity of ~ 140 mA h g−1 at 0.2 C rate and ~ 120 mA h g−1 at 1 C rate. A flexible pouch cell was further fabricated with this quasi-solid electrolyte, which shows good flexibility, high mechanical strength and excellent safety against the nail puncture. The flexible LIB was used to store the pulse form energy harvested by a TENG to provide more stable power output sustainably. The quasi-solid LIB can be charged by TENG directly for three times with a capacity loss of 17%. Importantly, a power management unit (PMU) was designed to make the output of TENG to be more suitable for charging the flexible LIBs. Our results show that this PMU is beneficial for decreasing the output voltage of TENGs, thus improving the cyclability of the cell, which may be utilized in various systems consisting of different batteries and TENGs.