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Nickel-cobalt oxides/hydroxides have been considered as promising electrode materials for a high-performance supercapacitor. However, their energy density and cycle stability are still very poor at high current density. Moreover, there are few reports on the fabrication of mixed transition-metal oxides with multishelled hollow structures. Here, we demonstrate a new and flexible strategy for the preparation of hollow Ni-Co-O microspheres with optimized Ni/Co ratios, controlled shell porosity, shell numbers, and shell thickness. Owing to its high effective electrode area and electron transfer number (n(3/2) A), mesoporous shells, and fast electron/ion transfer, the triple-shelled Ni-Co1.5-O electrode exhibits an ultrahigh capacitance (1884 F/g at 3A/g) and rate capability (77.7%, 3-30A/g). Moreover, the assembled sandwiched Ni-Co1.5-O//RGO@Fe3O4 asymmetric supercapacitor (ACS) retains 79.4% of its initial capacitance after 10 000 cycles and shows a high energy density of 41.5 W h kg(-1) at 505 W kg(-1). Importantly, the ACS device delivers a high energy density of 22.8 W h kg(-1) even at 7600 W kg(-1), which is superior to most of the reported asymmetric capacitors. This study has provided a facile and general approach to fabricate Ni/Co mixed transition-metal oxides for energy storage.

In this article, double carbon shell hollow spheres which provide macropores (mC) for ultrasmall FeO nanoparticle (10-20 nm) encapsulation individually were first prepared (FeO@mC). The well-constructed FeO@mC electrode materials offer the feasibility to study the volume change, aggregation, and pulverization process of the active FeO nanoparticles for Li-ion storage in a confined space. FeO@mC exhibits excellent electrochemical performances and delivers a high capacity of 645 mA h g at 2 A g after 1000 cycles. Even at 10 A g or after 1000 cycles at 2 A g, the porous carbon structure was well maintained and no obvious aggregation and pulverization of the FeO nanoparticles was observed, although the volume of the active FeO particles was expanded to 40-60 nm compared to that of the original particles (10-20 nm). This can be due to the in situ embedment of one FeO nanoparticle into one macropore individually. The uniform dispersion and confinement of the FeO nanoparticles in the macropores of the carbon shell could effectively accommodate severe volume variations upon cycling and prevent self-aggregation and spreading out from the carbon shell during the expansion process of the nanoscale FeO particles, leading to improved capacity retention. Our work confirms the effectiveness for pulverization control by confining FeO nanoparticles individually into macropores to improve its Li-ion storage properties, providing a novel strategy for the design of new-structured anode materials for Li-ion batteries.

Interpenetrated networks between graphitic carbon infilling and ultrafine TiO nanocrystals with patterned macropores (100-200 nm) were successfully synthesized. Polypyrrole layer was conformably coated on the primary TiO nanoparticles (∼8 nm) by a photosensitive reaction and was then transformed into carbon infilling in the interparticle mesopores of the TiO nanoparticles. Compared to the carbon/graphene supported TiO nanoparticles or carbon coated TiO nanostructures, the carbon infilling would provide a conductive medium and buffer layer for volume expansion of the encapsulated TiO nanoparticles, thus enhancing conductivity and cycle stability of the C-TiO anode materials for lithium ion batteries (LIBs). In addition, the macropores with diameters of 100-200 nm in the C-TiO anode and the mesopores in carbon infilling could improve electrolyte transportation in the electrodes and shorten the lithium ion diffusion length. The C-TiO electrode can provide a large capacity of 192.8 mA h g after 100 cycles at 200 mA g, which is higher than those of the pure macroporous TiO electrode (144.8 mA h g), C-TiO composite electrode without macroporous structure (128 mA h g), and most of the TiO based electrodes in the literature. Importantly, the C-TiO electrode exhibits a high rate performance and still delivers a high capacity of ∼140 mA h g after 1000 cycles at 1000 mA g (∼5.88 C), suggesting good lithium storage properties of the macroporous C-TiO composites with high capacity, cycle stability, and rate capability. This work would be instructive for designing hierarchical porous TiO based anodes for high-performance LIBs.

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Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) is a kind of novel non-fluorine polymer, whose high proton conductivity is dependent on high degree of sulfonation, which resulting in loss of dimensional stability. SPPESK/superacid sulfated zirconia (SZrO 2 ) composite proton exchange membranes are fabricated first. The composite membrane shows good dimensional stability, ascribing to the restriction effect of hydrogen bonding force on the mobility and relaxation of polymer chains. Introducing SZrO 2 simultaneously enhances the conductivity and anti-methanol permeation, owing to the connected ion domains, enlarged and aggregated ion clusters, excess proton conduction sites, and good blocking effect to methanol of SZrO 2 . For composite membrane containing 1.5 wt % SZrO 2 , the highest conductivity of 180 mS cm −1 is obtained at 80 C. Compared with pristine SPPESK and Nafion 115, the methanol permeability is reduced by 54 and 77%, and the maximum power density of direct methanol fuel cell is enhanced by 133 and 25%.