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The increasing demand for high performance lithium ion batteries (LIBs) has aroused great interest in developing high specific capacity, cycle performance and rate capability anode materials. Transition metal oxides (TMOs) have attracted much attention as promising anode materials for rechargeable LIBs owing to their high theoretical capacity. Here, a general strategy has been developed to fabricate high-performance fibrous TMO anodes such as elemental Ni doped NiO fibre (NiO/Ni/C-F), yolk–shell structured carbon@Fe2O3 fibre (C@Fe2O3-F), and hollow CuO fibre (CuO-HF) with controllable nanostructures by using alginate microfibres as templates. The key to the formation of various TMO micro-/nano-structures is the templating ability of the natural structure of long alginate molecular chains, where the metal cations can be confined in an “egg-box”via coordination with negatively charged α-l-guluronate blocks. When tested as anode materials for LIB half cells, these fibrous electrodes deliver excellent cycling performance with no capacity decrease after 200 cycles (793 mA h g−1, NiO/Ni/C-F, 0.072 A g−1; 1035 mA h g−1, C@Fe2O3-F, 0.1 A g−1; 670 mA h g−1, CuO-HF, 0.067 A g−1), and demonstrate great rate performance at different current densities. This finding highlights a general, green and eco-friendly strategy for the scale-up production of potential high-performance TMO anodes for LIBs. [ABSTRACT FROM AUTHOR]

A high-performance one-dimensional (1D) nanofibrillar N–Co–C oxygen reduction reaction (ORR) catalyst was fabricated via electrospinning using renewable natural alginate and multiwalled carbon nanotubes (MWCNTs) as precursors, where Co nanoparticles (NPs) are encapsulated by nitrogen (N)-doped amorphous carbon and assembled on MWCNTs. The 1D morphology not only prevents the aggregation of the Co NPs, but also provides a typical multimodal mesoporous structure which is beneficial for the O2 diffusion and the migration of adsorbed superoxide. In combination with the high conductivity of CNTs, the N-doped amorphous carbon shell can exert electron release on the encapsulated Co NPs, and thus enhance the ORR activity. It is also a protective layer that stabilizes the Co NPs, which ensures a high ORR activity of the catalysts in both alkaline and acid media and long-term durability. So compared with a commercial Pt/C catalyst, as expected, the N–Co–C nanofiber reported herein exhibited a comparable current density and onset potential (−0.06 V), with better durability in alkaline and acid solutions and better resistance to crossover effects in the ORR. [ABSTRACT FROM AUTHOR]

Cobalt tetroxide (Co3O4) has attracted much attention as a promising anode material for rechargeable lithium-ion batteries (LIBs) owing to its high theoretical capacity (890 mA h g−1). However, its poor electronic conductivity and weak ability to accommodate large volume changes during a repeated charging–discharging process, which results in the poor cycling performance, have hindered the practical application of Co3O4. In this article, Co3O4/C fibres were prepared by simple pyrolysis of wetspun cobalt alginate fibres. The composites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). It was found that the resulting material possesses a unique hierarchical nano/microstructure in which Co3O4 nanoparticles (NPs) are capsulated in a micro-sized carbonaceous fibrous matrix. This nano/microstructure can combine the merits of the Co3O4 nanostructure and the carbonaceous microfibre matrix, and thus exhibits a high reversible capacity of 780 mA h g−1 at 89 mA g−1 after 100 cycles as well as excellent cycling stability and rate performance when used as an anode material. This finding could open up a new direction in sustainable use of natural seaweed resources as new energy storage materials. [ABSTRACT FROM AUTHOR]