Doping effect and oxygen vacancy engineering in nickel-manganese layered double hydroxides for high-performance supercapacitors

Design of electrode materials with high electrochemical capacitance and long lifetime remains a challenging issue for high-performance supercapacitors . Herein, we successfully synthesized a binder-free composite electrode comprising oxygen vacancy-abundant NiMnMg-layered double hydroxides grown on 3D graphene foam (Vo-NiMnMg-LDH@3DG) by Mg doping during hydrothermal process and subsequently Ar plasma etching . Thanks to the incorporation of electrochemically inert Mg element, the enhanced charge transfer capability, and enriched active sites that induced by plentiful oxygen vacancies, Vo-NiMnMg-LDH@3DG manifests a high specific capacity of 374.8 mAh g −1 at a current density of 1 A g −1 and satisfactory rate performance (74.26% at 20 A g −1 ). Furthermore, the asymmetric supercapacitor (ASC) assembled with Vo-NiMnMg-LDH@3DG cathode and activated carbon anode exhibits a specific capacitance up to 171 F g −1 at 1 A g −1 , achieving a maximum energy density of 53.62 Wh kg −1 and the highest power density of 7500 W kg −1 . This work not only provides innovative approaches for preparing oxygen vacancy-rich LDH materials, but also offers insights for the design and improvement of energy storage devices based on transition metal-based LDH. • Oxygen vacancy-abundant NiMnMg-LDH in-situ grown on graphene foam was successfully fabricated. • Doping of inactive Mg stabilize the crystal lattice of NiMn-LDH, enhancing the cycling stability. • Mg doping and plasma treatment induce abundant oxygen vacancies, facilitating charge transfer and improving capacity.