Closed‐Loop Wearable Energy Management: From Biomechanical Energy Harvesting to Full‐Cycle Battery Charging

Biomechanical energy is abundant but irregular and low-grade, posing a significant challenge for wearable electronics, where existing energy-harvesting solutions are mainly limited to charging capacitors via physical storage, falling short of achieving a full chemical-charging cycle for practical batteries. To bridge this gap, we developed a closed-loop strategy that integrates an optimized triboelectric nanogenerator, a dedicated lithium-ion battery charge-management system, and fiber lithium-ion batteries (FLIBs). This system achieved a 22.7-fold increase in the root-mean-square current and an 800-fold reduction in the optimal load resistance. Consequently, the charging rate is increased by a factor of 38.8, allowing, for the first time, the full electrochemical charging cycle of 20 and 50 cm FLIBs to be completed within 2.37 ± 0.10 and 6.06 ± 0.11 h, respectively. The self-powered backpack system demonstrated practical viability by powering real-time positioning and outdoor data transmission, marking a decisive advance from energy harvesting to full energy autonomy for wearables.