Solvothermal-localized selenylation transformation of cobalt nickel MOFs templated heterointerfaces enriched monoclinic Co3Se4/CoNi2Se4@activated knitted carbon cloth for flexible and bi-axial stretchable supercapacitors

The main barrier to the development of modern electronic gadgets is their limited flexibility and stretchability to the X- and Y-directions. Here, a two-step solvothermal technique was used to synthesize monoclinic heterointerface-enriched Co3Se4/CoNi2Se4 2D nanosheet arrays on a flexible and bi-axial stretchable activated knitted carbon cloth substrate (AKCC) for flexible and bi-axial symmetric supercapacitors (SSCs). By optimizing the molar ratio of cobalt and nickel (Co: Ni = 4: 0, 3: 1, 1:1, 1:3, and 0:4), the inherent bimetallic LDH and selenide formation and charge storage mechanism were examined. According to the experimental investigation, selenide with a ratio of Co: Ni = 1:1 (Co3Se4/CoNi2Se4@AKCC) possessed superior electrochemical activities in term of specific capacity, rate capability, and cycle longevity. Homogenous growth of 2D nanosheet arrays with 3D superstructures, modulated electronic structure, possible valence interchange or/and charge hopping effect between Co and Ni cations, built-in electric fields, and suitable lateral size/thickness of nanosheet arrays realized sufficient charge storage capability, ion transport, and reaction kinetics. Moreover, Co: Ni = 1:1 selenide showed performance consistency at different modes of flexibility (bending and twisting,) and stretchability conditions (X- and Y-directions). A high-performance flexible and bi-axial stretchable SSCs was assembled, which delivered outstanding energy density at different mode of flexibility and stretchability conditions.