Low temperature synthesis of hierarchically porous carbon host for durable lithium-sulfur batteries

Abstract

Porous carbons with abundant pores and good conductivity are the dominant sulfur host in lithium sulfur batteries. Herein, a facile simultaneous activation/carbonization with inexpensive FeCl3 and ZnCl2 as activators is employed to prepare sucrose derived porous carbon at low temperature of 600 °C. The as-prepared carbon materials not only have partial graphitization due to the FeCl3 catalysis, but also show abundant hierarchical porous structure with high specific surface area of 2104 m2 g−1 and large pore volume of 1.29 cm3 g−1, whilst obtaining a high yield of about 30 wt%. When used to encapsulate sulfur, the abundant porous structure is conductive to immobilizing polysulfides and buffering volume effect during charge/discharge. Owing to these structure merits and good electrical conductivity, the corresponding porous carbon/sulfur cathode with a sulfur content of 53 wt% delivers high first discharge capacity of 811 mAh g−1 at 0.2C. Even with 75 wt% sulfur, the reversible capacity of 446 mAh g−1 are also obtained after 200 cycles at 0.2C. Especially, a durable long life of 1000 cycles with a low capacity decay of 0.035% per cycle can be achieved at 1C when the sulfur content is 45 wt%. This work provides a scientific foundation for preparing high-performance porous carbon applied in energy-related storage/conversion.