  Supercapacitors or ultracapacitors are promising for efficient energy storage
applications, owing to their high power density, high charge-discharge rates,
and long cycle life performance. To achieve this goal, a large specific surface
area, an high electronic conductivity and a fast cation intercalation
de-intercalation process are generally required in the design and preparation
of materials for high-performance supercapacitors. Recently, core-shell
heterostructures with multifunctionalities are regarded as one of promising
materials for supercapacitors or ultracapacitors applications. In particular,
one-dimensional (1D) core-shell heterostructures have sparked great scientific
and technological interests due to their high versatility and applicability as
the essential components in nanoscale electronics, catalysis, chemical sensing,
and energy conversion storage devices. Various metal metal oxide, metal metal,
metal oxide metal oxide and metal oxide conductive polymers so far have been
investigated. Transition metal hydroxide oxide Co3O4, Co(OH)2, MnO2, Mn(OH)2,
NiO, Ni(OH)2 and their compounds storing energy by surface faradaic (redox)
reactions were generally integrated with conducting scaffold to build
core-shell structure. Intensive studies show that an enlarged active surface
area of transition metal hydroxide oxide enables a promoted surface redox
reaction and enhanced electrochemical performance. Therefore, controllable
synthesis of a hierarchically porous construction with high surface areas is
critically important for energy storage.
