Optimization of graphene dose for improved electrochemical performance of silicon–graphene negative electrodes in lithium batteries

Abstract Different percentages of nanoparticles graphene (G) were mixed with nano-micron sized silicon (Si) particles as follows: 10, 20, 30 and 40 wt% graphene to silicon ratios. The crystal structure of pure Si powder pattern has cubic phase SEM, TEM/SAED and XPS equipments were implemented to study the surface properties of the prepared G@Si composites. Cyclic voltammetry (CV) measurement for the G@Si cell revealed two broad cathodic peaks, related to the deposition of Li 2 O thin layer on Si particles and the lithiation process of Si to form lithium silicide. Meanwhile, the oxidation of Li x Si into Si and Li ionis confirmed by the anodic strong peak at 0.56 V. Electrochemical impedance spectroscopy (EIS) measurements revealed high interfacial resistance ~ 1825 Ω for pure Si anode in comparison with that of G@Si composite anode. It is concluded that graphene acts as a conductive shielding pathway to inhibit the large volume change and minimize the capacity fading during successive galvanostatic cycling of G@Si composite anode materials versus Li/Li + . Accordingly, the specific discharge capacity of 30%G@Si cell delivered about 1240 and 900 mAhg −1 for 1st and 100th charge–discharge cycles, respectively.