Pulse-Charging Energy Storage for Triboelectric Nanogenerator Based on Frequency Modulation

Energy harvesting storage hybrid devices have garnered considerable attention as self-rechargeable power sources for wireless and ubiquitous electronics. Triboelectric nanogenerators (TENGs), a common type of energy harvester, generate alternating current-based, irregular short pulses, posing a challenge for storing the generated electrical energy in energy storage systems that typically operate with direct current (DC)-based low-frequency response. In this study, we propose a new strategy that leverages high-frequency response to develop efficient chargeable TENG-supercapacitor (SC) hybrid devices. A high-frequency SC was fabricated using hollow-structured MXene electrode materials, resulting in a twofold increase in the charging efficiency of the hybrid device compared to a control SC made with conventional carbon electrode materials. For a systematic understanding, the electrochemical interplay between the TENGs and SCs was investigated as a function of the frequency characteristics of SCs (f_SC) and the output pulse duration of TENGs (Δt_TENG). Increasing the f_SC·Δt_TENG enhanced the charging efficiency of the TENG-SC hybrid devices. This study highlights the importance of frequency response design in developing efficient chargeable TENG-SC hybrid devices.