Entrapment of sulfur in hierarchical porous graphene for lithium-sulfur batteries with high rate performance from -40 to 60°C

The Li-S battery is with a much greater theoretical energy density than those of conventional lithium ion batteries. The key to achieve a high performance electrode for Li-S battery lies in the arrangement of the building blocks into a well-designed structure, in which the nanocarbon framework not only acts as an electronic conduit to the encapsulated active materials but also serves as a mini-electrochemical reaction chamber. Therefore, a nanocomposite with sulfur entrapped into hierarchical porous graphene was proposed and fabricated for Li-S batteries. The nanocomposite electrode exhibits high discharging capacitance of 1068 and 543mAhg^-1 at a current density of 0.5 and 10C, respectively. The discharging capacity of 386mAhg^-1 can be presented at ultra-low temperature of -40°C, which far exceeds the operating range of conventional lithium-ion batteries. The large scale produced hierarchal graphene was mainly decorated with epoxy and hydroxyl groups, which can enhance the binding of S to the C-C bonds due to the induced ripples by the functional groups. These results provided a promising electrode material for energy storage device with high capacitance, which is important for the increasing demands of power sources in cold environments, such as battery systems for electric vehicles in cold zone or for aeronautic applications.