Intraparticle Sulfur Distribution Effects in Dry-Processed Polymer-Free Sulfur Electrodes for High-Performance Lithium-Sulfur Batteries

초록

Solvent- and polymer-binder-free fabrication of sulfur positive electrode by heat-roll-pressed powder-bed lamination relies on sulfur–carbon (S/C) composites in which sulfur must function as both active material and a thermally activated binding phase. Yet, how intraparticle sulfur distribution governs powder-bed consolidation and the durability of the resulting electrode film remains unclear. Here, we compare two S/C composites with identical sulfur content (∼70 wt.%) but contrasting architectures, a ball-milled composite (B-S/C) with surface-aggregated sulfur and a melt-infiltrated composite (T-S/C) with uniformly confined sulfur in a porous carbon framework. Structural and rheological analyses reveal that the B-S/C, containing larger sulfur aggregates, exhibits higher cohesion and compressibility, which is favorable for interparticle bonding, yet forms sulfur-depleted rims and crack-prone crusts during heat-roll pressing. In contrast, uniformly confined sulfur in T-S/C enables cohesive interparticle fusion into a continuous porous network. Electrochemically, T-S/C electrodes deliver improved rate capability and durable cycling in both coin-type and pouch-type Li/S batteries, markedly outperforming B-S/C-based Li/S batteries. These results establish homogeneous intraparticle sulfur distribution as a key design rule to preserve porosity during dry compaction and enable reliable manufacturing of high-performance polymer-binder-free sulfur positive electrodes for lithium/sulfur batteries.

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