Yinglin Xiao

MnFe2O4–graphene nanocomposites with enhanced performances as anode materials for Li-ion batteries

MnFe(2)O(4)-graphene nanocomposites (MnFe(2)O(4)-GNSs) with enhanced electrochemical performances have been successfully prepared through an ultrasonic method, e.g., approximate 1017 mA h g(-1) and 767 mA h g(-1) reversible capacities are retained even after 90 cycles at a current density of 0.1 A g(-1) and 1 A g(-1), respectively. The remarkable improvement in the reversible capacity, cyclic stability and rate capability of the obtained MnFe(2)O(4)-GNSs nanocomposites can be attributed to the good electrical conductivity and special structure of the graphene nanosheets. On the other hand, MnFe(2)O(4) also plays an important role because it transforms into a nanosized hybrid of Fe(3)O(4)-MnO with a particle size of about 20 nm during discharge-charge process, and the in situ formed hybrid of Fe(3)O(4)-MnO can be combined with GNSs to form a spongy porous structure. Furthermore, the formed hybrid can also act as the matrix of MnO or Fe(3)O(4) to prevent the aggregation of Fe(3)O(4) or MnO, and accommodate the volume change of the active materials during the discharge-charge processes, which is also beneficial to improve the electrochemical performances of the MnFe(2)O(4)-GNSs nanocomposites.

3D-hierarchical SnS2 micro/nano-structures: controlled synthesis, formation mechanism and lithium ion storage performances

Three kinds of 3D-hierarchical SnS2 micro/nano-structures were successfully synthesized through a one-pot hydrothermal method by controlling the ratio of SnCl4 and L-cysteine. It was found that these obtained 3D-hierarchical SnS2 structures had great differences in their chemical composition, crystalline property, building blocks, assembling format and porous structure. The formation processes of the hierarchical structures were studied well and the possible mechanisms were also proposed. The lithium storage properties of these 3D-hierarchical SnS2 structures were carefully studied by charge-discharge test and cyclic voltammetry method. The results indicated that the crystalline properties of the electrode materials could influence the initial electrochemical reactivity and the small size of building blocks could greatly improve the reversibility of electrochemical reaction and rate performances. Furthermore, the large surface area, porous structure and free space derived from the 3D hierarchical structures were beneficial to the long-term cycling stability of electrode materials.

3D-hierarchical NiO–graphene nanosheet composites as anodes for lithium ion batteries with improved reversible capacity and cycle stability

3D-hierarchical NiO–graphene nanosheet (GNS) composites as high performance anode materials for lithium-ion batteries (LIBs) were synthesized through a simple ultrasonic method, and characterized by X-ray diffraction, Raman spectrum, field emission scanning electron microscopy and transmission electron microscopy. The results show that the 3D-hierarchical NiO carnations with nanoplates as building blocks are homogeneously anchored onto GNS and act as spacers to reduce the stacking of GNS. Electrochemical performances reveal that the obtained 3D-hierarchical NiO–GNS composites exhibit remarkably high reversible lithium storage capacity, good rate capability and improved cycling stability, e.g. approximate 1065 mA h g−1 of reversible capacity is retained even after 50 cycles at a current density of 200 mA g−1. The remarkable improvement of electrochemical performances of the obtained composites could be attributed to the decrease of the volume expansion and contraction of NiO and the improvement of the electronic conductivity of composites during the cycling process.

Direct growth of SnO2 nanorods on graphene as high capacity anode materials for lithium ion batteries

SnO2 nanorods/graphene nanosheets (GNSs) nanocomposites have been synthesized through a simple ultrasonic combined hydrothermal process, and the formation mechanism of the nanocomposites has been proposed. According to FESEM and TEM analysis, SnO2 nanorods are directly grown and densely distributed on GNSs matrix in such a way that the structure of obtained nanocomposites is analogous to an array structure. The as-prepared nanocomposites exhibit a significantly improved lithium-storage capacity, good cycling stability and high rate capability, e.g. the reversible capacity is kept as high as 1107 mA h g−1 within 100 cycles at a current density of 200 mA g−1, retaining 96.2% of the initial value. The high performance can be ascribed to the unique structure of SnO2 nanorods/GNSs and the synergic effects of GNSs and SnO2 nanorods, in which the direct growth of SnO2 nanorods on GNSs can reduce the stacking of GNSs, provide more reaction sites and facilitate the rapid diffusion of electrons.

Synthesis of Ni-doped NiO/RGONS nanocomposites with enhanced rate capabilities as anode materials for Li ion batteries

Ni-doped NiO–reduced graphene oxide nanosheet (RGONS) nanocomposites as anode materials for Li ion batteries are synthesized through a solvothermal and calcination method. The obtained Ni-doped NiO–RGONS nanocomposites display an improved cycling stability (682 mA h g−1 in the 45th cycle at 200 mA g−1) and an enhanced rate capability (530 mA h g−1 at 1000 mA g−1). NiO–RGONS nanocomposites with a similar structure and RGONS content can also be obtained when the calcinations are performed under air conditions, but they can only keep 292 mA h g−1 and 117 mA h g−1 at 200 mA g−1 and 1000 mA g−1, respectively. The high electrochemical performances of the as-prepared Ni-doped NiO–RGONS nanocomposites could be attributed to their unique structure, in which the highly dispersed Ni NPs have some catalytic effects and improve the electronic conductivity. Also, the layered structure of the NiO nanoplates and RGONSs prevents the aggregation of NiO and decreases the stacking of the RGONSs.

SnO2/C composites fabricated by a biotemplating method from cotton and their electrochemical performances

Biomorphic SnO2/C composites were synthesized by a facile biotemplating method using natural cotton as the structure template and the bio-carbon source. The content of carbon in the composites could be easily adjusted by varying the sintering temperature. Electrochemical tests demonstrated that the content of carbon in the obtained composites had great effects on their electrochemical performances, such that the biomorphic SnO2/C composites prepared at 300 °C exhibited a reversible capacity of 530 mAh g−1 after 100 cycles at a current density of 100 mA g−1. The results suggest that the obtained biomorphic SnO2/C composites prepared by the facile approach may be used as anode materials in practical lithium-ion batteries.

Magnetite modified graphene nanosheets with improved rate performance and cyclic stability for Li ion battery anodes

Magnetite modified graphene nanosheets (MGNSs) were synthesized through a simple ultrasonic method, electrochemical performances indicated that the obtained MGNSs exhibited remarkably high reversible lithium storage capacity (1235 mAh g−1 after 50 cycles at 0.2 A g−1), good rate capability (315 mAh g−1 at 10 A g−1) and improved cycling stability (450 mAh g−1 after nearly 700 cycles at 5 A g−1). The improved electrochemical performances of the obtained MGNSs could be attributed to its inherent electronic conductivity, excellent mechanical properties and expanded (002) interlayer spacing of GNSs. Furthermore, magnetite nanoparticles anchored onto graphene nanosheets (GNSs) could serve as spacers to reduce the stack/restack of GNSs during charge-discharge process and improve their electrochemical performances as anode materials for lithium-ion batteries (LIBs).