Construction of phosphatized cobalt nickel-LDH nanosheet arrays as binder-free electrode for high-performance battery-like supercapacitor device

Cobalt-nickel bimetallic phosphide intersectional nanosheet arrays are fabricated on carbon fiber cloth (CoNi-LDH-350P@CFC) via facile one-step hydrothermal synthesis of CoNi-LDH and a sequent phosphating at an optimal temperature (350 °C). Phosphating temperature is proven to be crucial in modulating the morphology and structure of phosphatized LDHs. The CoNi-LDH-350P@CFC nanosheet arrays not only provide sufficient redox-active sites but also boost the electrical conductivity and facilitate the ion and charge transport. Consequently, the CoNi-LDH-350P@CFC as a self-supported electrode could deliver an ultrahigh specific capacity of 803 C g⁻¹ (or 223 mAh g⁻¹) at a current density of 0.5 A g⁻¹ and superior rate retention of 70% at a high rate of 30 A g⁻¹. Furthermore, the assembled CoNi-LDH-350P@CFC//active carbon (AC) asymmetric supercapacitors (ASCs) can exhibit an impressive energy density of 42 Wh kg⁻¹ at a power density of 400.4 W kg⁻¹ with acceptable cycling stability of 87.7% capacitance retention after 3000 cycles at 10 A g⁻¹.