Nanotextured alpha Ni( ii )–Co( ii ) hydroxides as supercapacitive active phases

A family of monophasic nanoplatelets of Ni( ii )–Co( ii ) layered hydroxides, were obtained by a one-pot room temperature homogeneous alkalinization driven by the the epoxide route with glycidol. Both cations precipitate in the form of solid solutions, giving the general formula Ni 1−x Co x (OH) 2−y Cl y · n H 2 O. Co( ii )-rich samples developed the simonkolleite-like alpha structure in which cations can adopt either octahedral (Oh) or tetrahedral (Td) environments, according to the formula (Ni,Co)Oh1− x CoTd2 x (OH) 2−2x (Cl) 2x · n H 2 O. Ni( ii )-rich ones resulted in ill-crystallized turbostratic (Ni,Co) 1−x (OH) 2−x (Cl) x · n H 2 O. Despite the inherent differences in the crystallochemical nature of theses phases, electrochemical measurements depict a monotonous behavior in terms of their capacitance. An optimum performance was observed for samples with X Ni(II) = 0.83 under most of the experimental conditions explored. This sample reaches a maximum specific capacitance of 2091 F g −1 , registered at a discharge current density of 0.5 A g −1 , while an energy density of 80.7 W h kg −1 was recorded at a power density of 960.4 W kg −1 .