Qigang Han

Facile fabrication of SnO2@TiO2 core–shell structures as anode materials for lithium-ion batteries

A novel strategy to fabricate SnO2@TiO2 composite was developed by combining the glucose-mediated hydrothermal method along with a sol–gel step, followed by a sintering process. Herein, glucose was found to play dual roles of facilitating the rapid precipitation of polycrystalline SnO2 nanocolloids in the hydrothermal process and act as a pore-forming material to leave behind nanopores when it is combusted in the sintering process. Due to the combined superiority of TiO2 as a inert nanoshell and SnO2 as a core with a high theoretical specific capacity, together with the combustion-formed carbon-derived voids with many extra free spaces to buffer the volume change, the obtained SnO2@TiO2 composite has potential for use as an anode material for lithium-ion batteries with enhanced electrochemical performances. A high reversible capacity of 910 mA h g−1 was maintained over 300 cycles at a current density of 100 mA g−1. Even at a high current density of 1000 mA g−1, the substantial discharge capacity could still reach 617 mA h g−1 after 1000 repeated cycles. Such excellent cycling stability and remarkable rate capability of the designed SnO2@TiO2 composite can be attributed to its novel structure and the synergistic effects between the SnO2 core and TiO2 shell.

Simple preparation of Cu6Sn5/Sn composites as anode materials for lithium-ion batteries

Cu6Sn5/Sn composites are directly fabricated by a high energy mechanical milling technique and subsequent heat treatment. In particular, the effects of the ratios of Sn to Cu6Sn5 (CuxSny, x = 10 − y, y = 4.5, 7 and 9) on the lithium-ion batteries performances are investigated. The results show that the sample with y = 4.5 is a single-phase Cu6Sn5, the sample with y = 7 is slightly Sn rich in the Cu6Sn5 (Sn Cu6Sn5). Furthermore, the Cu6Sn5/Sn composite has an obvious structure of a core–shell, only when y = 7. As an anode material for lithium-ion batteries, the Cu6Sn5/Sn composite with y = 7 exhibits a discharge capacity of 761.6 mA h g−1 after the first cycle, 457.8 mA h g−1 after 20th cycles, and an initial coulombic efficiency of 91.37%, which shows a better electrochemical performance than that of y = 4.5 or 9. In addition, after adding 15 wt% of graphite, the sample with y = 7 maintains a discharge capacity of 605.8 mA h g−1 after 100 repeated cycles, higher than many reported Cu–Sn-based anode materials.

Synthesis of polygonal Co3Sn2 nanostructure with enhanced magnetic properties

A one-pot solvothermal route is employed to fabricate polygonal Co3Sn2 nanostructures. The obtained product exhibits anisotropic structure and morphology, which endow the Co3Sn2 nanostructure with enhanced coercivity of 131.5 Oe, four times as high as the cubic cobalt sample (31.3 Oe).

Gd–Sn alloys and Gd–Sn–graphene composites as anode materials for lithium-ion batteries

Due to its high theoretical capacity as high as 990 mA h g−1, Sn is considered as a potential anode material for high-capacity lithium-ion batteries (LIBs). However, the huge volume expansion during the alloying/dealloying process causes poor cycling stability and low rate capability. To address this gap, Gd doped Gd–Sn alloys are introduced in this work. Herein, the Gd–Sn alloys are prepared by arc-melting two different starting bulk metals Gd and Sn with atomic ratios of Gd : Sn = 1 : 3 and 1 : 6. Then, the obtained Gd–Sn powders mixed with graphene at a mass ratio of 1 : 10 are deployed to prepare the Gd–Sn–graphene composites by a ball-milling route. XRD results show that the characteristic peaks of the obtained Gd–Sn–graphene composites are consistent with GdSn3, β-Sn, and graphene phases, where the well-dispersed Gd–Sn alloy particles are distributed with sizes of about hundreds of nanometers. In addition, graphene was homogeneously dispersed with the GdSn3 and Sn particles, when the composite has an atomic ratio of Gd : Sn = 1 : 6 and graphene content of 9 wt% (GdSn6/G composite). The electrochemical characterization shows that the GdSn6/G composite has a higher reversible discharge capacity than that of the Gd–Sn powders. At a current density of 100 mA g−1, the first charge and discharge capacities are 547.1 and 900.2 mA h g−1, and a stable capacity of 455.3 mA h g−1 could be maintained after 30 cycles. Even at a current density of 500 mA g−1 (about 1C rate), a good reversible capacity of 403.9 mA h g−1 could be achieved. The enhanced performance may be attributed to the rare earth metal Gd with good toughness, and graphene with good electrical conductivity and mechanical strength.