Facile fabrication of a fully biodegradable and stretchable serpentine-shaped wire supercapacitor

With the rapidly growing interest and usage in wearable electronics, considerable attention has been paid to the environmental concern caused by electronic waste and the toxicity of constituent materials. In this study, we report the facile fabrication of a fully biodegradable and stretchable serpentine-shaped wire supercapacitor by using a water-soluble molybdenum (Mo) wire, polyvinyl-alcohol-based biodegradable gel polymer electrolyte, and biodegradable elastomer—poly(1,8-octanediol-co-citrate) (POC). A thin oxide layer grown on a Mo wire via simple anodization drastically improves the electrochemical capacitance by inducing pseudocapacitance. As a result, the fabricated supercapacitor exhibits areal capacitance of 4.15 mF cm⁻² at 0.05 mA cm⁻², energy density of 0.37 µWh cm⁻², and power density of 0.8 mW cm⁻². The design of the serpentine-shaped wire supercapacitor encapsulated with POC gives mechanical and electrochemical stability against deformations of repetitive stretching. The biodegradable property of the supercapacitor is confirmed by the measurements of the change in mass of its constituent materials with elapsed time in water. Furthermore, the transient electrochemical performance of the fabricated wire supercapacitor in water over a certain period of time is observed to depend on the encapsulation.