X.Y. Liu

Hierarchical NiCo2O4@NiCo2O4 Core/Shell Nanoflake Arrays as High-Performance Supercapacitor Materials

Hierarchical NiCo2O4@NiCo2O4 core/shell nanoflake arrays on nickel foam for high-performance supercapacitors are fabricated by a two-step solution-based method which involves in hydrothermal process and chemical bath deposition. Compared with the bare NiCo2O4 nanoflake arrays, the core/shell electrode displays better pseudocapacitive behaviors in 2 M KOH, which exhibits high areal specific capacitances of 1.55 F cm(-2) at 2 mA cm(-2) and 1.16 F cm(-2) at 40 mA cm(-2) before activation as well as excellent cycling stability. The specific capacitance can achieve a maximum of 2.20 F cm(-2) at a current density of 5 mA cm(-2), which can still retain 2.17 F cm(-2) (98.6% retention) after 4000 cycles. The enhanced pseudocapacitive performances are mainly attributed to its unique core/shell structure, which provides fast ion and electron transfer, a large number of active sites, and good strain accommodation.

Facile synthesis of Ni-coated Ni2P for supercapacitor applications

Ni2P particles are coated homogenously with amorphous Ni by an electroless plating process. The Ni coating exhibits a nanoflake morphology and has 20–30 nm in thickness after plating for 10 min. As electrochemical capacitor materials, the pseudocapacitor behaviors are investigated by cyclic voltammograms and galvanostatic charge–discharge tests in 2 M LiOH. The Ni-coated Ni2P delivers high specific capacitances of 581 F g−1 at 1 A g−1 and 464 F g−1 at 40 A g−1, respectively, and also exhibits superior cycling performance. The specific capacitance can achieve a maximum of 1115 F g−1 at 2 A g−1, which can still maintain 1029 F g−1 (92.3% capacity retention) after 3000 cycles. The enhanced pseudocapacitive performances are mainly attributed to its flake-like Ni coating which can provide fast ion and electron transfer and large amounts of active sites.