A novel route to constructing high-efficiency lithium sulfur batteries with spent graphite as the sulfur host

Abstract

The recovery treatment of spent lithium-ion batteries (LIBs) is becoming increasingly crucial, and it is of the utmost urgency to recycle spent graphite. Carbon materials are gaining more and more attention for applications in lithium-sulfur batteries acting as the sulfur (S) hosts with excellent theoretical capacity. However, the preparation of related carbon materials is energy-consuming and tedious. Herein, by directly using spent graphite (SG) from the spent LIBs without complex treatment as a substrate, a SG/S cathode has been prepared for lithium-sulfur batteries for the first time. Repeated charge/discharge cycles bring the SG surface not only rich functional polar groups, but also metal elements like Ni, Co and Mn through the dissolution of active cathode materials (in LIBs). These factors increase the conductivity, and efficiently promote the lithium polysulfide (LiPS) conversion kinetics in a way that the SG effectively adsorbs and fixes LiPS to reduce the shuttle effect in lithium sulfur batteries. Additionally, the SG/S cathode with high sulfur content of 78.4% has 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 remains as high as 765 mAh g−1 with a low average decay rate (0.006% per cycle) at 0.5 C. This work not only realizes the re-utilization of spent graphite, but also fabricates lithium-sulfur batteries with excellent electrochemical performances.