All‐solid‐state supercapacitors based on yarns of Co3O4-anchored porous carbon nanofibers

[Display omitted] •Structural supercapacitor with high load-bearing and energy storage capabilities.•Synthesis of ultrafine Co3O4-based porous, hollow, nitrogen-doped carbon nanofiber yarns.•All‐solid‐state electrodes for weight-sensitive and volume-restricted applications.•Yarns with remarkable electrochemical properties, cycling stability, energy and power densities. Developing an efficient all‐solid‐state structural supercapacitor with simultaneous high energy storage and load-bearing capabilities for reducing weight/volume in weight-/weight-restricted applicationsremains challenging. Relying only on the solemechanismof theelectrical double layerand the existing trade-offs between load bearing and energy storage requirements have limited the overall performance of carbon-based structural electrodes. Herein, we describe the development of ultrafineCo3O4-anchored highly-porous, hollow, N-doped carbon nanofiber yarns (Co-NCFY) asa high performance multifunctional structural electrode with a remarkable performance index representing mechanical and electrochemical properties. The device is designed to benefit from both the pseudocapacitance and double layer mechanisms to store energy. The Co-NCFY show promising electrochemical properties (electrochemical capacity of 713 F g−1at 1 mV s−1, desirable cycling stability of >92% at 20 A g−1 after >8000 cycles, energy density of 45.4 Wh kg−1 at a power density of 209 W kg−1), and load-bearing capability (strength and young modulus of 87.4 MPa and 26.4 GPa, respectively). Taking into account both electrochemical and mechanical properties, the Co-NCFY outperform recently reported structural electrode materials (see Ashby chart in graphical abstract). These attractive attributes make Co-NCFY a unique structural electrode material for efficient structural energy storage devices.