Isothermal Sulfur Condensation into Carbon Scaffolds: Improved Loading, Performance, and Scalability for Lithium-Sulfur Battery Cathodes

Here we demonstrate an isothermal technique that enables rapid vapor infiltration of sulfur into carbon templates to overcome scalability and performance bottlenecks associated with common melt infiltration techniques. Building on straightforward thermodynamic principles of capillary condensation, self-limited sulfur loadings up to 82 wt % can be achieved in as little as 10 min at temperatures between 155 and 175 degrees C. We demonstrate a broad range of device performance criteria using a carbon black-single-walled carbon nanotube binder-free cathode framework, including a side-by side comparison to melt infiltrated electrodes with 74 wt % loading that shows improved capacity (1015 mAh/g vs 768 mAh/g), similar to 92% capacity retention after 200 cycles at 0.5 C, and similar to 98% Coulombic efficiency as a result of enhanced uniformity and conductivity. Further, we demonstrate this technique over a range of different electrodes (1) electrodes with high sulfur loading (82 wt %) with high initial discharge capacity of 1340 mAh/g, (2) electrodes with high areal loading of 8 mg/cm(2) sulfur with >6.5 mAh/cm(2) areal capacity, and (3) electrodes based on carbons with microporous confining pores. Most importantly, this vapor infiltration approach requires over 5x less energy input and enables over 60X greater throughput than standard melt infiltration, enabling integration into roll-to-roll rapid processing schemes without compromising device performance. This technique liberates cost and manufacturing barriers to commercialization of Li-S batteries at larger scales while opening new avenues to infiltrate preformed cathode assemblies with sulfur for assessment at lab scales.