The ever-increasing global energy needs and depleting fossil-fuel resources demand the pursuit of sustainable energy alternatives, including both renewable energy sources and sustainable storage technologies. Intensive interest in graphene has centered on its 2D crystal lattice and remarkable properties that offer unique opportunities to address ever-increasing global energy demands. Graphene has shown great potential in electrochemical energy storage and conversion. The high electrochemical theoretical specific capacity, specific capacitance and ultra large surface-to volume ratio, when combined with its remarkable properties, make graphene an ideal material for enhanced energy storage. In this study, reaction mechanisms of SnO2/graphene composite are investigated using generalized gradient approximation implemented in density functional theory. The results show that tensile and compressive strain have negligible effect on electronic properties of graphene. The band structure for the composite materials shows that graphene dominates both the highest occupied and lowest unoccupied states.