A stretchable, asymmetric, coaxial fiber-shaped supercapacitor for wearable electronics

Fiber-shaped supercapacitors (FSCs), owing to their high-power density and feasibility to be integrated into woven clothes, have drawn tremendous attentions as a key device for flexible energy storage. However, how to store more energy while withstanding various types of mechanical deformation is still a challenge for FSCs. Here, based on a magnetron sputtering method, different pseudocapacitive materials are conformally coated on self-supported carbon nanotube aligned films. This fabrication approach enables a stretchable, asymmetric, coaxial fiber-shaped supercapacitors with high performance. The asymmetric electrode configuration that consists of CNT@NiO@MnO_x cathode and CNT@Fe₂O₃ anode successfully extends the FSC’s electrochemical window to 1.8 V in an aqueous electrolyte. As a result, a high specific capacitance of 10.4 F·cm^-3 is achieved at a current density of 30 mA·cm^-3 corresponding to a high energy density of 4.7 mWh·cm^-3. The mechanical stability of the stretchable FSC is demonstrated with a sustainable performance under strains up to 75% and a capacitance retention of 95% after 2,000 cycles under 75% strain.