Regulating Ni 3+ contents by a cobalt doping strategy in ternary Ni x Co 3- x Al 1 -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 Ni x Co 3- x Al 1 -LDHs ( x = 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, etc. However, incorporating more cobalt ions into NiCoAl-LDHs will generate more oxygen vacancies, causing more Ni 3+ ions to appear on the surface, and higher concentrations of Ni 3+ ions and more oxygen vacancies play active roles in enhancing the capacitive performances. The Ni 1 Co 2 Al 1 -LDH electrode with a Ni 3+ /Ni 2+ ratio of 1.44 and an oxygen vacancy concentration of 54.83% delivers a high specific capacitance (728 C g -1 at 1 A g -1 ) and excellent capacitance retention (93.18% of initial capacitance at 30 A g -1 after 10 000 cycles).