In Situ Growing Te-Doped Ni–Mn Layered Double Hydroxide on a Cetyltrimethylammonium Bromide-Modified MXene Conductive Layer for Binder-Free Supercapacitors

Tellurium-doped nickel manganese layered double hydroxide (Te-NiMn LDH) is synthesized, featuring direct growth on a cetyltrimethylammonium bromide (CTAB)-modified MXene layer (C-MXene) anchored to an ultraviolet-ozone-treated nickel foam (Te-NiMn LDH/C-MXene/NF). This innovative material serves as a high-performance active material in supercapacitors. The modification of MXene using a CTAB-containing ethanol solution leads to increased interlayer spacing, which facilitates ion transport and enhances electrical conductivity. The C-MXene layer on a nickel foam provides an effective conductive substrate that supports the growth of LDH and the incorporation of tellurium and hence eliminates the need for binders or additives. This not only reduces fabrication costs but also minimizes internal resistance. Tellurium doping can increase the electron density within the LDH structure and enhance the valence states and therefore its capacitance. The binder-free Te-NiMn LDH/C-MXene/NF electrode demonstrates a high specific capacitance of 1920 F/g at 2 A/g. Furthermore, the hybrid supercapacitor composed of Te-NiMn LDH/C-MXene/NF and activated carbon electrodes achieves a specific capacitance of 202.6 F/g, maximum energy density of 52.3 Wh/kg, and maximum power density of 6452 W/kg. The excellent cycling stability with a capacitance retention of 77.3% after 10,000 cycles is also obtained for this device.