We succeed in the controllable synthesis, topotactic phase transformation and chemical exfoliation of highly crystallized layered hydroxides with various metallic compositions (Fe, Co, Ni, Zn, Al, etc.), by rationally designing the oxidation state as well as by modifying the coordination geometry of metal cations. These transition metal hydroxides, consisting of redoxable host slabs (M2+(OH)2⇔M3+OOH⇔M4+O2) and large interlayer spacing for ionic accessibility, afford a high potential in utilizing as active electrode materials for Faradaic pseudocapacitors. Especially, by exfoliating them into unilamellar nanosheets with a molecular thickness of ~0.8 nm, the electrochemical reactivity can be further enhanced due to an utmost high surface area as well as shortest path of electron transfer and ion diffusion. To harvest a synergistic effect, we fabricated for the first time a genuine superlattice nanocomposite through molecular-scale hetero-assembly of cationic hydroxide nanosheets and anionic conductive graphene, achieving hybrid supercapacitors with both high capacity and high power rate.

We succeed in the controllable synthesis, topotactic phase transformation and chemical exfoliation of highly crystallized layered hydroxides with various metallic compositions (Fe, Co, Ni, Zn, Al, etc.), by rationally designing the oxidation state as well as by modifying the coordination geometry of metal cations. These transition metal hydroxides, consisting of redoxable host slabs (M2+(OH)2⇔M3+OOH⇔M4+O2) and large interlayer spacing for ionic accessibility, afford a high potential in utilizing as active electrode materials for Faradaic pseudocapacitors. Especially, by exfoliating them into unilamellar nanosheets with a molecular thickness of ~0.8 nm, the electrochemical reactivity can be further enhanced due to an utmost high surface area as well as shortest path of electron transfer and ion diffusion. To harvest a synergistic effect, we fabricated for the first time a genuine superlattice nanocomposite through molecular-scale hetero-assembly of cationic hydroxide nanosheets and anionic conductive graphene, achieving hybrid supercapacitors with both high capacity and high power rate.