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To overcome the low electrical conductivity weakness of layered double hydroxide and to improve the electrochemical energy storage performance as supercapacitor electrodes, NiAl layered double hydroxide (NiAl‐LDH) flowers with ultrathin structure grown on three‐dimensional graphene (3DG) was constructed via a facile hydrothermal strategy. The NiAl‐LDH/3DG composites as binder‐free supercapacitor electrode showed a high specific capacitance of 884.5 F g–1 at 1 A g–1. Excellent cycle stability retaining 90 % of the initial capacitance after 7000 cycles at 5 A g–1 was also demonstrated, with the coulombic efficiency stayed above 95 % during the whole cycling process. The excellent performances should be ascribed to the synergistic effect of NiAl‐LDH and 3DG, in which the NiAl‐LDH ultrathin nanoflake petals provide sufficient pseudocapacitive sites; while 3DG provides robust and highly interconnected skeleton for efficient mass/charge transport. [ABSTRACT FROM AUTHOR]

To accommodate large volume change of Cu2O for improving its supercapacitor performances, Cu2O@Ni-Al LDH core-shell structure was designed and prepared through nickel-aluminum double hydroxide grown on cubic Cu2O via a simple solvent process. The Cu2O core was wrapped by Ni-Al LDH shell, which provides a high specific area for electrochemical reaction. The results show that the specific capacitance and cycle stability of Cu2O@Ni-Al LDH are superior to those of Cu2O cubic particles. The specific capacitance of Cu2O@Ni-Al LDH hybrid electrode was up to 389 F g−1 at 1 A g−1. Furthermore, a reversible capacitance of 457 F g−1 was obtained after 12,000 cycles at a much higher current density of 10 A g−1. The enhanced performances were ascribed to the unique core-shell structure and the synergistic effects of Cu2O and Ni-Al LDH, which alleviated volume expansion and provided abundant electrochemical active sites. [ABSTRACT FROM AUTHOR]

Abstract Transition metal oxides have received considerable attention as promising electrode materials for the next generation high performance lithium-ion batteries and supercapacitors. However, transition metal oxides electrodes usually suffer from severe volume expansion and poor electrical conductivity, leading to fast capacity fading and low rate capability, which limit their commercialization in energy storage devices. Herein, we develop a bifunctional ZnO NiO microsphere electrode with yolk-shelled structure for lithium-ion batteries and supercapacitors by annealing tetracyanide-metallic-frameworks precursor of Zn[Ni(CN) 4 ]. Benefiting from its unique structure and composition, the yolk-shelled ZnO NiO microspheres as anode for lithium-ion batteries exhibits a high lithium storage capacity (978 mAh g−1 at 0.25 C) and superior rate performance (628 mAh g−1 at 2.5 C after 300 cycles). While for supercapacitors electrode, it delivers a high specific capacitance of 1350 F g−1 at a current density of 3.0 A g−1 and an excellent cycling stability with a capacity retention of 92.8% over 6000 cycles. The excellent electrochemical performance is ascribed to the synergistic effect between ZnO and NiO, and the yolk-shelled structure, which can provide rich active sites for electrochemical reaction, and effectively alleviate the volume expansion and structural pulverization of the electrode during charge-discharge cycling. Graphical abstract Image 1 Highlights • Yolk-shelled ZnO NiO bifunctional electrode was prepared by Zn[Ni(CN) 4 ] precursor. • It shows enhanced cycle performances with 628 mAh g−1 at 2.5 C after 300 cycles. • It exhibits high specific capacitance and an ultralong cycling lifetime for SCs. • The excellent performance is due to the unique structure and synergistic effect. [ABSTRACT FROM AUTHOR]