Making Stretchable Hybrid Supercapacitors by Knitting Non‐Stretchable Metal Fibers

Abstract To obtain supercapacitors for wearable electronic devices, highly conductive stretchable electrode substrates with excellent tensile recovery are required. However, the simultaneous realization of the above mentioned characteristics is difficult. In this study, tough stainless‐steel fibers (SSFs) are employed as the substrates for knitting into stainless‐steel meshes (SSMs), for the fabrication of textile electrodes with typical 2D‐interconnected networks. The obtained knitted networks can transform the angular elasticity of SSFs into the stretchability of the textile electrodes. The electrodes based on the SSM substrates can be obtained via the in situ growth of NiCo 2 S 4 nanosheets covered by CoS 2 nanowires, which exhibit a high specific capacity, high rate capability, and excellent cycling stability. Moreover, the first stretchable solid‐state hybrid supercapacitors based on SSM display excellent performances with respect to a high energy density (60.2 Wh kg −1 at 800 W kg −1 ), remarkable tensile recovery (≤40% elongation), and high stability (≈76.4% capacity retention at 30% strain for 1000 stretching cycles). The highly stretchable supercapacitor is sewn on the elbow of a garment to drive a light‐emitting diode, and it maintains a high performance with respect to the repetitive process of bending and straightening, thus demonstrating the high applicability of the designed SSMs to wearable electronics.