Constructing Hierarchical CoGa2O4–S@NiCo-LDH Core–Shell Heterostructures with Crystalline/Amorphous/Crystalline Heterointerfaces for Flexible Asymmetric Supercapacitors

The rational design and construction of composite electrodes are crucial for overcoming the issues of poor working stability and slow ionic electron mobility of a single component. Nevertheless, it is a big challenge to construct core-shell heterostructures with crystalline/amorphous/crystalline heterointerfaces in straightforward and efficient methods. Here, we have successfully converted a portion of crystalline CoGa₂O₄ into the amorphous phase by employing a facile sulfidation process (denoted as CoGa₂O₄-S), followed by anchoring crystalline NiCo-layered double hydroxide (denoted as NiCo-LDH) nanoarrays onto hexagonal plates and nucleation points of CoGa₂O₄-S, synthesizing dual-type hexagonal and flower-like 3D CoGa₂O₄-S@NiCo-LDH core-shell heterostructures with crystalline/amorphous/crystalline heterointerfaces on carbon cloth. Furthermore, we further adjust the Ni/Co ratio in LDH, achieving precise and controllable core-shell heterostructures. Benefiting from the abundant crystalline/amorphous/crystalline heterointerfaces and synergistic effect among various components, the CoGa₂O₄-S@Ni₂Co₁-LDH electrode exhibits a specific capacity of 247.8 mAh·g^-1 at 1 A·g^-1 and good rate performance. A CoGa₂O₄-S@Ni₂Co₁-LDH//AC flexible asymmetric supercapacitor provides an energy density of 58.2 Wh·kg^-1 at a power density of 850 W·kg^-1 and exhibits an impressive capacitance retention of 105.7% after 10,000 cycles at 10 A·g^-1. Our research provides profound insights into the design of other similar core-shell heterostructures.