Interconnected highly graphitic carbon nanosheets derived from wheat stalk have been successfully synthesized via a combined hydrothermal and graphitization process.
A facile process is developed to prepare SnO-based composites through using metal-organic frameworks (MOFs) as precursors. The nitrogen-doped graphene wrapped okra-like SnO composites (SnO@N-RGO) are successfully synthesized for the first time by using Sn-based metal-organic frameworks (Sn-MOF) as precursors. When utilized as an anode material for lithium-ion batteries, the SnO@N-RGO composites possess a remarkably superior reversible capacity of 1041 mA h g at a constant current of 200 mA g after 180 charge-discharge processes and excellent rate capability. The excellent performance can be primarily ascribed to the unique structure of 1D okra-like SnO in SnO@N-RGO which are actually composed of a great number of SnO primary crystallites and numerous well-defined internal voids, can effectively alleviate the huge volume change of SnO, and facilitate the transport and storage of lithium ions. Besides, the structural stability acquires further improvement when the okra-like SnO are wrapped by N-doped graphene. Similarly, this synthetic strategy can be employed to synthesize other high-capacity metal-oxide-based composites starting from various metal-organic frameworks, exhibiting promising application in novel electrode material field of lithium-ion batteries.
To address the huge volumetric change and unstable solid electrolyte interphase (SEI) issues of Sn-based anodes, this paper proposes a Sn-Co-C ternary composite with a cubic yolk-shell structure. The proposed Sn-Co nanoalloys encapsulated in N-doped carbon hollow cubes (Sn-Co@C) are simply synthesized by the conformal polydopamine coating of home-made CoSn(OH) hollow nanocubes subsequent with hydrogen reduction. The cubic Sn-Co@C yolk-shell structure possessing an optimized carbon shell thickness displays excellent cyclic performance and superior rate capability when utilized as an anode for lithium-ion batteries. The composite shows an initial discharge capacity of 885 mA h g at 200 mA g with a high capacity retention of ∼91.2% after 180 cycles. It can still deliver a considerable capacity of 560 mA h g at a high current density of 1 A g after 200 cycles. This attractive electrochemical characteristic can be ascribed to the distinct cubic yolk-shell architecture, in which the inner inactive Co can buffer the volumetric expansion of Sn, the void can provide external space for the volumetric change of Sn, and the outer carbon shell can effectively prevent the agglomeration of Sn-Co nanoalloys and maintain the stability of SEI films.
Silicon
(Si) attracts extensive attention as the advanced anode material for
lithium (Li)-ion batteries (LIBs) because of its ultrahigh Li storage
capacity and suitable voltage plateau. Hollow porous structure and
dopant-induced lattice expansion can enhance the cycling stability
and transporting kinetics of Li ions. However, it is still difficult
to synthesize the Si anode possessing these structures simultaneously
by a facile method. Herein, the lightly boron (B)-doped spherical
hollow-porous Si (B-HPSi) anode material for LIBs is synthesized by
a facile magnesiothermic reduction from B-doped silica. B-HPSi exhibits
local lattice expansion located on boundaries of refined subgrains.
B atoms in Si contribute to the increase of the conductivity and the
expansion of lattices. On the basis of the first-principles calculations,
the B dopants induce the conductivity increase and local lattice expansion.
As a result, B-HPSi electrodes exhibit a high specific capacity of
∼1500
mAh g–1 at 0.84 A g–1 and maintains
93% after 150 cycles. The reversible capacities of ∼1250, ∼1000,
and ∼800 mAh g–1 can be delivered at 2.1,
4.2, and 8.4 A g–1, respectively.
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