Freestanding agaric-like molybdenum carbide/graphene/N-doped carbon foam as effective polysulfide anchor and catalyst for high performance lithium sulfur batteries

Developing high energy density lithium-sulfur (Li–S) batteries mainly relies on the design of the electrode matrix which can accommodate high sulfur loading and still remain high utilization of active materials. Herein, a 3D hierarchical graphitic carbon foam supported graphene@Mo₂C (GCF-G@Mo₂C) heterostructure is introduced as a freestanding electrode for Li–S batteries with a facile and cost-effective method. The N-doped carbon foam wrapped by graphene sheets with agaric-like porous structure could promote fast electron and ion transport, meanwhile effectively anchor the polysulfides through physical confinement and chemical adsorption by strongly polar-polar interactions. More importantly, the Mo₂C nanoparticles can act as the chemical anchoring center to provide strong polysulfide adsorption, as testified by experimental data and first-principle calculations. Moreover, the catalytic effect of Mo₂C also accelerates the redox kinetics of polysulfide conversion, contributing to enhanced rate performance. As a result, the cell with GCF-G@Mo₂C displays an initial capacity as high as 862 mAh g⁻¹ and a retained capacity of 597 mAh g⁻¹ after 600 cycles with only 0.051% capacity fade per cycle at 1C rate, presenting good cycling stability. In addition, the GCF-G@Mo₂C substrate with high sulfur content (70 ​wt%) and sulfur loading (10.5 ​mg ​cm⁻²) achieves an ultra-high areal capacity of 12.6 mAh cm⁻² at 0.1 ​C, offering a competitive cathode for high-performance Li–S batteries.