A modified synthesis process of three-dimensional sulfur/graphene aerogel as binder-free cathode for lithium sulfur batteries

摘要

Among the existing rechargeable battery systems, lithium sulfur batteries exhibit ultra-high theoretical specific capacity (1672mAh/g) and specific energy (2600 Wh/kg). However, its practical applications have been limited by several problems, especially the dissolution of lithium polysulfides and shuttle effect, which will cause poor cycling stability. Herein, we synthesized a 3D porous graphene aerogel through a modified two-step hydrothermal reduction method, which has been simultaneously used as the matrix to load sulfur and the shield to constrain the dissolution of polysulfides. The graphene aerogel containing sulfur was mechanically pressed to circular disc and directly used as cathode without any additives, which shows great flexibility and excellent electrical conductivity. Since no extra conductive additives and binder are needed, this binder-free method is also more facile than conventional processes. Meanwhile, the shield was used as lithium polysulfides absorber to suppress the shuttle effect. Compared with conventional lithium sulfur batteries, this novel cathode with unique battery structure enables a higher areal sulfur loading of 2.5mg/cm(2) and initial specific capacity of 1100mAh/g. More importantly, the dissolution and shuttle effect of lithium polysulfides were suppressed effectively by the graphene aerogel matrix and shield, greatly improving the cycling stability. (C) 2018 Elsevier Ltd. All rights reserved.