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.