Sandwich-type porous CoO/N-doped carbon multi-layers can provide 2D electron transfer channels and exhibit super long-term capability for lithium-ion batteries.
The
volume variation of electrode materials will lead to poor cyclability
of lithium-ion batteries during the lithiation/delithiation process.
Instead, inner-stress fragmentation is creatively used to change carbon-layer-capped
Fe3O4 particles ∼30 nm in diameter into
high-density Fe3O4 dots ∼4 nm in size
embedded in ultrathin carbon layers. The optimized structure shows
a remarkable 45.2% enhancement of lithium storage from 804.7 (the
10th cycle) to 1168.7 mA h g–1 (the 250th cycle)
at 500 mA g–1, even retaining 1239.5 mA h g–1 after another 550 cycles. The electrochemical measurements
reveal the enhanced capacitive behavior of the high-density Fe3O4 dots@C layers, which have more extra active
sites for the insertion/extraction of Li+ ions, confirmed
by the differential capacity plots, leading to remarkably increased
specific capacity during cycling. The restructured electrode also
shows a superior rate capacity and excellent cycling stability (938.7
and 815.4 mA h g–1 over 2000 cycles at 1000 and
2000 mA g–1, respectively). X-ray photoelectron
spectroscopy and transmission electron microscopy characterizations
show that the optimized structure has stable structural and componential
stability even at large rates. This work presents an MOF-guided synthesis
of high-density Fe3O4-dots’ anode material
optimized by inner-stress fragmentation, showing a feasible route
to design high-efficiency electrode materials.
Three kinds of hierarchical CuS microflowers composed of thin nanosheets have been synthesized by a simple wet chemical method. It is shown that the CuS microflowers provide suitable substrates to grow nickel nanocrystals. The prepared Ni@CuS hybrids combined with conductive glass (FTO) have been used as counter electrodes for dye-sensitized solar cells (DSSCs). The electrode made of the active material of Ni@CuS microflowers with sparsest petals show an optimal photoelectric conversion efficiency of 4.89%, better than those made of single component of Ni (3.39%) or CuS (1.65%), and other two Ni@CuS composites. The improved performances could be ascribed to the synergetic effect of the catalytic effect towards I[Formula: see text]/I[Formula: see text] from sparse CuS hierarchical structure and uniformly grown Ni nanocrystals. Besides, the introduced Ni nanocrystals could increase the conductivity of the hybrid and facilitate the transport of electrons. The hybrid Ni@CuS composites serving as counter electrodes have much enhanced electrochemical properties, which provide a feasible route to develop high-active non-noble hybrid counter electrode materials.
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