Reinforced polysulfide barrier by g-C3N4/CNT composite towards superior lithium-sulfur batteries

Abstract The notorious shuttle effect has long been obstructing lithium-sulfur (Li-S) batteries from yielding the expected high energy density and long lifespan. Herein, we develop a multifunctional polysulfide barrier reinforced by the graphitic carbon nitride/carbon nanotube (g-C3N4/CNT) composite toward inhibited shuttling behavior and improved battery performance. The obtained g-C3N4 delivers a unique sponge-like architecture with massive ion transfer pathways and fully exposed active interfaces, while the abundant C-N heteroatomic structures impose strong chemical immobilization toward lithium polysulfides. Combined with the highly conductive agent, the g-C3N4/CNT reinforced separator is endowed with great capability of confining and reutilizing the active sulfur within the cathode, thus contributing to an efficient and stable sulfur electrochemistry. Benefiting from these synergistic attributes, Li-S cells based on g-C3N4/CNT separator exhibit an excellent cyclability with a minimum decay rate of 0.03% per cycle over 500 cycles and decent rate capability up to 2 C. Moreover, a high areal capacity of 7.69 mAh cm−2 can be achieved under a raised sulfur loading up to 10.1 mg cm−2, demonstrating a facile and efficient pathway toward superior Li-S batteries.