Improvements in Mechano-Electrochemical Energy Harvesting Performance of Carbon Nanotube Yarns via Poly(sodium 4-styrenesulfonate) Coating

Mechano-electrochemical energy harvesters have attracted increasing attention owing to their superior energy density in the low-frequency range compared to conventional mechanical energy harvesters. However, their inherently low voltage output remains a critical limitation, posing challenges for practical applications. Herein, we enhanced the energy harvesting performance of a coiled carbon nanotube (CNT) yarn harvester using a polyelectrolyte coating. The negatively charged poly(sodium 4-styrenesulfonate) (PSS) shifts the potential of zero charge of the harvester beyond the electrochemically stable potential window and increases the self-bias voltage used for harvesting. As a result, the maximum open-circuit voltage and peak power increased by 1.87 and 3.76 times, respectively, compared to those of a pristine CNT harvester. In addition, the direction of voltage generation is reversed; therefore, using the pristine CNT yarn as the positive electrode and the PSS@CNT yarn as the negative electrode effectively doubles the output voltage through the additive contribution of the voltages generated by each electrode. The peak power of the asymmetric harvester is 91.6 W/kg. The asymmetric harvester can be fabricated in a textile form and attached to clothing such as swimsuits, enabling its application in wearable devices for power supply or self-powered motion tracking sensor.