Layered double hydroxide with interlayer defects and intralayer defects for high-performance supercapacitors

The layered structure of layered double hydroxides (LDHs) is flexible and adjustable, which makes it have great potential in improving the conductivity, capacitance and cycle stability of materials. However, regulating interlayer activity often requires overcoming charge repulsion within layers. In this study, the dual activity of LDHs was achieved through the design of interlayer defects (intercalation) and intralayer defects (doping and oxygen vacancy). The electronic structure of the substrate was initially improved by one-step sulfidation, in which the insertion of anions (NO₃^– and SO₄^2-) broadened the layer spacing of LDHs and stabilized the microstructure of LDHs, thus exposing more active sites. The addition of La³⁺ not only realizes the above functions, but also increases the concentration of oxygen vacancies, thereby enhancing the electron/ion transport capacity. The addition of reduced graphene oxide (rGO) can improve the electrode material's active area and conductivity. In addition, the electrophoretic tech-fabricated CoS@NiCo-LDH-10La@200rGO electrode shows enhanced electrochemical performance, achieving a specific capacitance of 1632.6 F g⁻¹ and an 80.1 % rate capability. Meanwhile, CoS@NiCo-LDH-10La@200rGO//AC retains 93 % of its initial capacitance after 20,000 cycles. The above excellent electrochemical properties are attributed to a controlled defect design, short electron/ion transfer three-dimensional structure and binder-free electrophoresis technology.