Moisture-Enabled Electric Generator: Bridging Energy Storage and Harvesting

Conventional rechargeable batteries enable reliable energy storage but lack the capability for dynamic energy generation, while emerging energy harvesters harvest ambient energy yet cannot store it sustainably, resulting in intermittent power supply. Moisture-enabled electric generator (MEG) represents a unique solution that bridges the critical gap between energy storage and environmental energy harvesting through humidity-driven ion migration and chemical potential conversion. This review provides a comprehensive overview of the fundamental operating mechanisms of MEG and identifies the two most critical bottlenecks to practical deployment: insufficient electrical output and poor long-term stability. We systematically summarize performance optimization strategies from the perspectives of rational physical architecture design, chemical modification, and innovative structural engineering. Furthermore, we highlight the state-of-the-art applications of MEG in self-powered supplies, flexible sensing, and multifunctional intelligent systems. Finally, we propose an insightful roadmap for future research to address remaining challenges, narrow the performance gap with mature energy technologies, and push MEG toward high-performance, intelligent, and sustainable practical energy systems.