3D-printed grid electrode integrating both accelerated mass transport and sulfur conversion kinetics for...

Lithium-sulfur (Li-S) batteries have emerged as a highly promising next-generation energy storage system owing to their remarkable advantages of high energy density and low cost. However, the excessive electrolyte dosage severely compromises their practical energy density. Directly reducing the electrolyte dosage will inevitably lead to a significant decline in the practical discharge capacities of Li-S batteries, accompanied by high voltage polarization. This is mainly attributed to the restricted mass transport and sluggish sulfur conversion kinetics under lean electrolyte conditions. In this work, a vanadium carbide (VC) catalyst-modified grid electrode is proposed based on polyvinylidene difluoride (PVDF) phase inversion-assisted 3D printing technology. On the one hand, the spontaneously formed PVDF sheath on the outer layer of printed fine filaments secures the integrity of the grid electrode with ultrahigh sulfur loadings. Meanwhile, the millimeter-scale through-holes perpendicular to the electrode and the micron-scale macropores along the radial direction of the printed filaments jointly construct efficient mass transport channels, ensuring rapid electrolyte infiltration and high-efficiency Li⁺ migration. On the other hand, the VC catalyst demonstrates excellent catalytic activity toward sulfur conversion reactions, especially for the high-energy-barrier processes of Li₂S deposition and decomposition. Theoretical calculations reveal that the spontaneously formed oxide layer plays a crucial role in achieving moderate adsorption of lithium polysulfides (LiPSs) and preventing sulfur poisoning of the catalyst. Based on the above prominent advantages, the VC@carbon nanofiber (CNF)/S grid electrode exhibits outstanding performance in terms of capacity enhancement and cycling stability. At a rate of 0.5C, the electrode with a sulfur loading of 5.9 mg cm^-2 delivers an initial discharge capacity of 824 mAh g^-1 and can maintain stable cycling for 600 cycles, with a capacity decay rate of only 0.07% per cycle. Under the lean electrolyte condition of 7 µL mg^-1, it achieves a discharge capacity of 1116 mAh g^-1 at 0.05C. In addition, under the same lean electrolyte conditions, the fabricated three-layer VC@CNF grid electrode with a sulfur loading of 19.2 mg cm^-2 exhibits an ultrahigh areal capacity of 20.3 mAh cm^-2.