Synergetic electrochemical behavior of magnesium-doped ZnO nanorods with reduced graphene oxide

Abstract

In this study, we synthesized magnesium-doped ZnO (Mg-ZnO) nanorods embedded in reduced oxide graphene layers (rGO) using the simplest one-pot hydrothermal method. The composites ZnO/rGO and Mg-doped ZnO-rGO (Mg-ZnO/rGO) are polycrystalline and showed successful doping of Mg in ZnO lattice which expands the ZnO lattice structure helping lithium storage by providing more sites. Mg doping in the ZnO lattice extenuates ZnO volume contraction and expansion which promotes structural stabilization of the electrode during multiple charging-discharging cycles. In composites, ZnO and Mg-ZnO attain the shape of nanorods and tightly interleaved theirselves in the sheet of rGO. XPS showed the dominant peak of C1s of sp2 bonding supporting the formation of reduced GO along with Zn, O and Mg elements. The performance of the materials is evaluated as anode for LIB. The ZnO/rGO anode exhibits a discharge capacity of 445 mAh/g at 100 mA g−1 that was significantly enhanced to 463 mAh/g after doping ZnO with 2 % Mg. With further increasing the concentration of Mg to 4 %, the Mg-ZnO/rGO anode achieves a higher discharge capacity of 520 mAh g−1 with better rate capability than its counterpart electrodes. The synergistic effects between Mg-ZnO and carbon-based nanomaterials are ascribed to the creation of additional contact sites to penetrate electrolyte ions into the electrode, thus resulting in the fast lithium-ion diffusion rate.