A Green and Environment-Friendly Route to Make High-Efficiency Lithium Sulfur Batteries with the Spent Graphite as Sulfur Host

The resourceful treatment of spent lithium-ion batteries is becoming increasingly important, and the recycling of spent graphite is already the utmost urgency. Carbon materials are gaining much attention as good sulfur hosts for applications in lithium-sulfur batteries with excellent theoretical specific capacity. However, the preparation of related carbon materials is an energy-consuming and environmentally unfriendly process. Spent graphite without complex treatment can be applied directly as a sulfur host with porous structure and defects. After multiple charge/discharge not only does the spent graphite surface form rich polar functional groups, but also contain Ni, Co and Mn introduced by the dissolution of cathode active materials. These properties increase the electrical conductivity and shuttle effect and promote polysulfide conversion kinetics. Here, spent graphite recovered from spent lithium-ion batteries was compounded with sulfur as cathode material for lithium-sulfur batteries for the first time. Additionally, the SG/S with high sulfur content of 78.4% obtained an initial discharge capacity of 1377 mAh g −1 at the rate of 0.2 C with an excellent cycling stability. Even after 500 cycles, the cathode specific capacity remained as high as 765 mAh g −1 at a low decay rate (0.006% per cycle) at 0.5 C. The work in this paper not only recovers spent graphite resourcefully, but also obtains lithium-sulfur batteries with excellent electrochemical performance.