Understanding Piezoionic Effects in Chemo–Mechanical Energy Harvesting by Carbon Nanotube Yarn Twists

Strategies for converting mechanical energy into electrical energy hold significant importance in diverse battery-free and battery-supported applications. Recent studies have demonstrated promising approaches involving the twisting of carbon nanotube yarns, which alter the intrinsic electrochemical capacitance during mechanical motion, thereby generating electrical energy in various aqueous environments. However, the fundamental mechanism of chemo–mechanical energy harvesters based on the nanoscale piezoionic effect, as well as the kinetics of both cations and anions within the system, remains to be clarified. In this study, experimental and computational approaches aimed at fundamentally understanding the piezoionic effect in nanoscale chemo–mechanical dynamics are presented. This phenomenon is analyzed using in situ Raman scattering, piezoelectrochemical impedance spectroscopy, and molecular dynamics simulations. The findings elucidate the collective contributions of cations and anions under mechanical energy inputs and demonstrate the impact of piezoionic kinetics on electrical energy outputs. By gaining a comprehensive understanding of the fundamental piezoionic effect in chemo–mechanical energy harvesting systems, significant advancements in energy sustainability across numerous practical applications are anticipated.