Biaxial Stretchability in High‐Performance, All‐Solid‐State Supercapacitor with a Double‐Layer Anode and a Faradic Cathode Based on Graphitic‐2200 Knitted Carbon Fiber

Abstract Large reversible biaxial (xy) stretching in energy storage devices is now an urgent requirement for the field of stretchable electronics to enable reliability in practical applications. Here, a fascinating stretching machine is designed and used for xy‐stretching of a high‐performance supercapacitor device without performance degradation. A trimetallic metal organic framework (MOF)‐derived ternary metal oxide on graphitic‐2200 knitted carbon fiber (MOF‐ZNCO@g‐KCF), activated carbon loaded onto drilled knitted carbon fiber (AC@g‐KCF‐d), and a poly‐vinyl alcohol, poly‐ethylene oxide, and potassium hydroxide (PVA/PEO/KOH) based hydrogel polymer film are used as a faradic cathode, a double layer anode, and an electrolyte, respectively, to integrate the biaxially stretchable asymmetric supercapacitor (BSASC) device. The fabricated MOF‐ZNCO@g‐KCF//AC@g‐KCF‐d BSASC maintains an outstanding performance consistency at different xy‐stretched conditions, even after repeated deformations. Notably, after 10 000 galvanostatic charge–discharge cycles, the BSASC in the xy‐biaxial stretched condition is retained at 93.7%, and after 100 successive stretch–relax cycles for the same stretching dimension it still retains a 92.48% capacity, demonstrating excellent mechanical and electrochemical stability. The exceptional performance consistency in the xy‐stretched position, demonstrates that the BSASC is one of the best performers among the stretchable supercapacitors reported to date.