Oxalate-derived NiO@NiAl-layered double hydroxide core-shell material for supercapacitors

Abstract

NiO as an appealing electrode material has been used for supercapacitors due to its high theoretical capacity and easy availability, but intrinsically low electrical conductivity and insufficient redox active sites restrict its further applications. In this work, a novel oxalate-derived NiO@NiAl-layered double hydroxide (LDH) with 3D core-shell structure (denoted as NiO_OA@LDH) was prepared via hydrothermal calcination method, where the oxalate-derived porous C-doping NiO (NiO_OA) grown on nickel foam (NF) was constructed using NiC₂O₄ as a sacrificial template and carbon source. The deposition of the ultrathin NiAl-LDH nanosheets on the NiO_OA was conducive to forming robust adhesion between the core and the shell, which promoted effective electron/ion transfer and structure stability. Benefiting from the unique 3D core-shell structure and complementary compositional features, the NiO_OA@LDH gave a high specific charge of 1347.0C g⁻¹ at 1 A g⁻¹, prominent rate performance (68.5 % retention at 15 A g⁻¹) and cycle stability (91.1 % retention at 5 A g⁻¹ after 5000 cycles). Furthermore, the as-assembled NiO_OA@LDH//activated carbon (AC) device achieved a high energy density of 45.6 Wh kg⁻¹ at a power density of 557.8 W kg⁻¹ and an outstanding cycle stability (93.1 % retention at 5 A g⁻¹ after 10,000 cycles).