Regulating Ni contents by a cobalt doping strategy in ternary NiCoAl-LDH nanoflowers for high-performance charge storage.

NiAl-LDH and CoAl-LDH as typical two-dimensional layered materials have been widely used as supercapacitor cathodes due to their special composition, morphology and rich electrochemically active centers. However, a clear strategy to enhance their electrochemical performances remains lacking. Here, with NiCoAl-LDHs ( = 1, 1.5 and 2, in short: NiCoAl-LDHs) as examples, a Co/Ni ion co-incorporation strategy was used to study the possible effects on their capacitive performance. Our work demonstrated that different cobalt contents in NiCoAl-LDHs show no obvious changes in their crystal structure, morphology, surface area, However, incorporating more cobalt ions into NiCoAl-LDHs will generate more oxygen vacancies, causing more Ni ions to appear on the surface, and higher concentrations of Ni ions and more oxygen vacancies play active roles in enhancing the capacitive performances. The NiCoAl-LDH electrode with a Ni/Ni ratio of 1.44 and an oxygen vacancy concentration of 54.83% delivers a high specific capacitance (728 C g at 1 A g) and excellent capacitance retention (93.18% of initial capacitance at 30 A g after 10 000 cycles).