Trimetallic oxides/hydroxides as hybrid supercapacitor electrode materials: a review

Environmentally friendly energy sources such as solar and wind power as alternatives to fossil fuels are strategic for meeting the energy needs of an increasingly demanding population, but they are periodic or intermittent in nature, making energy storage devices fundamental for the realization of a sustainable society. Thus, the quest for much higher power and energy dense devices, especially hybrid supercapacitors, as alternatives to lithium-ion batteries, has been scaling up since the combining of the outstanding power density of supercapacitive materials with the high energy density of battery-type materials into a single device. Despite their high resistance, transition metal oxides are promising electrode materials for use in devices, since their rich electrochemistry can be activated by three main strategies to boost the specific charge capacity, charge-discharge and ion diffusion kinetics, and cyclability of devices via : (a) the incorporation of hetero-atoms that generate trimetallic oxides, (b) nanostructuration via hierarchical core@shell furry and mesoporous systems, and (c) combination with other materials to generate nanocomposites. These strategies, especially those leading to highly porous 3D core@shell architecture nanomaterials, are very successful, where trimetallic oxides, and ternary T LDHs and multicomponent systems, realized via the combination of mono- and/or bimetallic oxides and hydroxides, have demonstrated exceptionally good performances as electrode materials, presenting bright new perspectives for the future of hybrid energy storage devices. The main strategies to impart synergistic catalytic effects to trimetallic oxide/layered double hydroxide materials are discussed: (a) heteroatom incorporation, (b) the formation of nanocomposites, and (c) hierarchical core@shell nanostructuration.