Lithium-Sulfur (Li-S) battery is a promising next-generation energy storage device which has the potential to replace the traditional Li-ion battery systems, primarily due to their higher specific capacity (1672 mAh/g) and the low cost of sulfur. However, the sulfur cathode is beset with technical challenges such as poor conductivity and high solubility, resulting in poor capacity retention upon cycling^1-4. Encapsulation of sulfur with carbon allotropes is widely reported as a key strategy to decrease polysulfide solubility and enhance conductivity, with varying degrees of success. The unpredictable performance of carbon allotropes arises from poorly understood interactions with various lithium polysulfide species (Li₂S_n, 2 ≤ n ≤ 8). Multiwall carbon nanotubes (MWCNTs) are a widely used carbon allotrope in sulfur/carbon-based cathodes for Li-S batteries due to their superior electronic conductivity and enhanced diffusivity for Li⁺ cations. In an effort to understand the interaction between highly soluble lithium polysulfides (Li₂S₄, Li₂S_6, and Li₂S₈) and MWCNTs, we performed multimodal spectroscopic analyses including X-ray photoemission spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and ⁷Li nuclear magnetic resonance (NMR) based relaxation (T₁ and T₂) measurements (see Figure 1). This presentation will discuss the multimodal analyses which provide unique access to structural and chemical environments at the polysulfide-MWCNT interfacial region from then atomic to mesoscale level.

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