Controlled Hierarchical Construction of Ultrahomogeneous Co₉S₈@CoAl-LDH/NF Layered Core–Shell Heterostructures for High-Performance Asymmetric Supercapacitors

The rational collocation and construction of multiphase composite electrode materials with ingenious structures is a key strategic to enhance the electrochemical performance of supercapacitors (SCs). Within this project, a unique Co₉S₈@CoAl-LDH/NF core-shell heterostructure consisting of CoAl-LDH/NF ultrathin nanosheets sturdily attached to Co₉S₈/NF needle-like nanorods is grown in situ on self-supported conductive substrate nickel foam (NF) by an effortless and productive multistep hydrothermal method. The construction of the core-shell structure can effectively enhance the capacitive properties as well as the mechanical strength of the material. Compared with the single-component materials Co₉S₈/NF (1769.6 mF cm^-2 and 91.6%) and CoAl-LDH/NF (858 mF cm^-2 and 85.2%), the Co₉S₈@CoAl-LDH/NF composites have excellent capacitance properties (5052.4 mF cm^-2) along with exceptional capacitance retention (5000 cycles) 98.5% even after undergoing charging and discharging. Furthermore, the asymmetric SCs fabricated with Co₉S₈@CoAl-LDH/NF and AC/NF exhibit an energy density of 0.17 mWh cm^-2 at 3.20 mW cm^-2. Therefore, the innovative core-shell heterostructure of Co₉S₈@CoAl-LDH/NF presented in this study holds immense practical potential as a groundbreaking electrode material in the realm of SCs.