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, 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 GdSn, 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 GdSn and Sn particles, when the composite has an atomic ratio of Gd:Sn = 1:6 and graphene content of 9 wt% (GdSn/G composite). The electrochemical characterization shows that the GdSn/G composite has a higher reversible discharge capacity than that of the Gd-Sn powders. At a current density of 100 mA g, the first charge and discharge capacities are 547.1 and 900.2 mA h g, and a stable capacity of 455.3 mA h g could be maintained after 30 cycles. Even at a current density of 500 mA g (about 1C rate), a good reversible capacity of 403.9 mA h g 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.