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Abstract Heterostructures have broad potential application in energy conversion material and optoelectronic device since of novel interface effect and enhanced electron transport dynamics at heterointerfaces. Herein, we report a heterostructured SnS/SnO 2 /spherical graphene composite, in which ultrafine SnS/SnO 2 nanoparticles with heterostructures are sandwiched between multi-layers of graphene sheets, exhibiting a hollow spherical architecture as a whole. Detailed electrochemical studies indicate that the molar ratio of SnS to SnO 2 has great influence on the charge transport efficiency. Theoretical calculation reveals that SnS and SnO 2 exhibit different work functions and the Fermi level shift is affected by the SnS/SnO 2 molar ratio, thus the hybrid with the ratio close to 1.0 owns the most adsorbed lithium ions, which leads to the highest specific charge-transfer kinetics and lowest ion-diffusion resistance than other samples. Electrochemical tests show that the composite with appropriate composition delivers the best lithium storage rate performance (620 and 312.7 mAh g−1 at 1 C and 10 C). A much stable and high reversible specific capacity of 850 mAh g−1 is obtained after 200 cycles at 0.1 C. The appropriate molar ratio of nano-heterostructures and the novel sandwich hollow spherical composite structure are attributed to the excellent electrochemical performances. Graphical abstract Image 1 Highlights • Heterostructured SnS/SnO 2 /spherical graphene composite is prepared. • Ultrafine SnS/SnO 2 nanoheterostructures are sandwiched between graphene shells. • Fermi level shift is influenced by SnS/SnO 2 molar ratio via DTF calculation. • The composite with molar ratio close to 1 exhibits best charge transfer capability. • Excellent rate performance and cyclic stability is obtained in optimized sample. [ABSTRACT FROM AUTHOR]

Abstract The reunion of Sn is always a troublesome issue when it's used as the energy storage materials, on the one hand it comes from the preparation process due to its low melting point, and on the other hand it comes from the Li-Sn alloying process because of its natural tendency of migration. The Sn/SnO 2 /spherical graphene composite prepared by one-step low temperature hydrothermal reduction method can effectively solve this problem. In the composite, Sn/SnO 2 tiny nanoparticles with average diameter of 5 nm distribute evenly between multilayers of graphene sheets presenting a hollow spherical structure. The introduction of SnO 2 can effectively restrain the agglomeration of Sn nanoparticles during alloying process since an amorphous Li 2 O matrix is formed to separate the adjacent active particles. The sandwich graphene hollow sphere skeleton effectively buffers the volume expansion of Sn/SnO 2 and further restricts their migration and agglomeration. Due to the above advantages, the nano-Li 2 O generating from the decomposition of SnO 2 can contact closely with excessive nano-Sn in restricted area, promoting facile conversed conversion reaction. Therefore, the composite exhibits high reversible capacity and excellent cycle performance. A stable and high specific capacity of 843.8 mAh g−1 is obtained after 100 cycles at 0.1 C. Graphical abstract Image Highlights • Tiny Sn/SnO 2 NPs sandwiching between SG is designed to solve Sn anode's problem. • Sn/SnO 2 /SG is prepared by one-step low temperature hydrothermal reduction method. • Li 2 O generated from SnO 2 acts as buffer matrix for Sn at subsequent alloy process. • Li 2 O and excess nano-sized Sn can react easily to reversibly transform into SnO 2. • Excellent cycle stability is presented in Sn/SnO 2 /SG composite. [ABSTRACT FROM AUTHOR]

Yolk-shell structured nano-Si@void@C can greatly improve the electrical conductivity and buffer the large volume change of silicon nanoparticles, whereas inter poor electrical connection between Si cores and carbon shells still limits the lithium storage performance. Besides, it usually requires complex synthesis conditions and expensive nano-level silicon sources. Herein, we succeed in making the large-size industrial silicon ( ca . 400–500 nm) to a yolk-shell structure with a controllable space buffer layer. Most importantly, an interconnected porous carbon network deriving from the thermal decomposition of carbon chains in silicon sources is formed within the carbon shell simultaneously, which can improve the electrical contact between Si cores and hollow carbon shells and prevent the active particles exposure to the electrolyte. With the help of static outer thin carbon shell, optimized inner void and the flexible electrically conductive carbon network, such yolk-shell structured Si@void@C submicron particles synthesizing by one-step carbon-coating procedure exhibit high initial coulomb efficiency of 62%, good rate performance, and excellent long cycling stability with 950.7 mAh g −1  at 100 mA g −1 after 100 cycles. The low consumption and stable synthesis method make it feasible for large-scale fabrication of the yolk-shell structured Si/C composites as commercial anodes for energy storage. [ABSTRACT FROM AUTHOR]

Exploring versatile strategies for microstructural evolution and surface modification are of fundamental importance in the development of advanced electrode materials. In this work, we report that electron-beam irradiation is a facile approach to perform surface modification for the ultrathin cross-stacked graphene aerogels loaded with SnO 2 quantum dots, resulting in a remarkable modulation on the lithium storage performance. It is found that the as-synthesized SnO 2 /graphene aerogels composites irradiated at 280 kGy exhibit excellent high reversible lithium storage capacity, good rate capability and cycling stability, which retains a discharge capacity of 703 mAh g −1 after 50 cycles at 0.1 C rate. Microstructure analysis indicates that the enhanced electrochemical properties are mainly attributed to the exfoliation of graphene nanosheets, the increase of amorphization, disorder, defects and the removal of partial oxygen-containing functional groups on the surface of graphene nanosheets. The strategy presented here demonstrates that the electron-beam irradiation is a potential strategy to improve the electrochemical performance of graphene-based metal oxides. [ABSTRACT FROM AUTHOR]