Regulating Ni3+ contents by a cobalt doping strategy in ternary NixCo3−xAl1-LDH nanoflowers for high-performance charge storage

Abstract

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_xCo_3−xAl₁-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 Ni³⁺ ions to appear on the surface, and higher concentrations of Ni³⁺ ions and more oxygen vacancies play active roles in enhancing the capacitive performances. The Ni₁Co₂Al₁-LDH electrode with a Ni³⁺/Ni²⁺ 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).