Facile design and synthesis of nickel foam@Mxene@NiCo layered hydroxides core-sheath nanostructure for high mass-loading of supercapacitors

NiCo layered double hydroxides (NiCo-LDH) represent widespread application in supercapacitor owing to the unique two-dimensional layer structure. However, improving its electrochemical energy storage and cycle stability with high mass-loading remains a huge challenge. By introducing self-assembled Ti3C2Tx (Mxene) on the surface of nickel foam (NF) and then electrodepositing NiCo-LDH, a hierarchical nickel foam@Ti3C2Tx@NiCo layered hydroxides (NF@Mxene@NiCo-LDH) ternary core-sheath nanostructure with high mass-loading is created in this article. The synergistic effect of Mxene and NiCo-LDH greatly improves the cycling stability of the composites. When NF was immersed in Ti3C2Tx solution three times and then electrodeposited for 1000s, the obtained composite electrode NF@Mxene@NiCo-LDH (denoted as M3-NC (1000)) owns a high mass loading up to 14 mg cm−2. The M3-NC (1000) has an areal capacitance of 22.6 F cm−2 at a current density of 5 mA cm−2 and a mass-specific capacitance of 224 mAh g−1 at 0.375 A g−1. The asymmetric supercapacitor with M3-NC (1000) as the positive electrode and AC as the negative electrode achieves an energy density of 3.79 mWh cm−2 at a power density of 3.74 mW cm−2, which is significantly better than the previously reported work of NiCo-LDH. The device also exhibits excellent cycling stability with capacitance retention of 87% after 10,000 cycles at a current density of 200 mA cm−2. This work highlights the design approach of electrode material with high mass-loading for advanced energy applications.