Surface Modification of Tin Oxide Through Reduced Graphene Oxide As a Highly Efficient Cathode Material for Magnesium-Ion Batteries

Among post-lithium ion technologies, magnesium-ion batteries (MIBs) are receiving great concern in recent years. However, MIBs are mainly restrained by the lack of cathode materials, which may accommodate the fast diffusion kinetics of Mg2+ ions. To overcome this problem, herein we attempt to synthesize a reduced graphene oxide (rGO) encapsulated tin oxide (SnO2) nanoparticles composites through an electrostatic-interaction-induced-self-assembly approach at low temperature. The surface modification of SnO2 via carbonaceous coating enhanced the electrical conductivity of final composites. The SnO2-rGO composites with different weight ratios of rGO and SnO2 are employed as cathode material in magnesium-ion batteries. Experimental results show that MIB exhibits a maximum specific capacity of 222 mAhg-1 at the current density of 20 mAg-1 with a good cycle life (capacity retention of 90%). Unlike Li-ion batteries, no SnO2 nanoparticles expansion is observed during electrochemical cycling in all-phenyl-complex (APC) magnesium electrolytes, which ultimately improves the capacity retention. Furthermore, ex-situ x-ray diffraction and scanning electron microscopy (SEM) studies are used to understand the magnesiation/de-magnesiation mechanisms. At the end, SnO2-rGO composites are tested for Mg2+/Li+ hybrid ion batteries and results reveal a specific capacity of 350 mAhg-1 at the current density of 20 mAg-1. However, hybrid ion battery exhibited sharp decay in capacity owing to volume expansion of SnO2 based cathodes. This work will provide a new insight for synthesis of electrode materials for energy storage devices.