Operando X-Ray Absorption Spectroscopy for Lithium-Sulfur Batteries

<i>Operando</i> sulfur K-edge X-ray Absorption Spectroscopy (XAS) has emerged as a powerful tool to unravel the complex sulfur redox chemistry in lithium-sulfur (Li-S) batteries. Li-S batteries are promosing as a compelling alternative to conventional lithium-ion batteries due to their exceptional theoretical energy density. However, their practical implementation faces challenges related to capacity fading, limited cycle life, and complex sulfur redox chemistry. <i>Operando</i> XAS plays a crucial role in understanding and addressing the above-mentioned challenges.<br/><br/>In this abstract, we first explore the application of <i>operando </i>sulfur K-edge XAS to gain real-time insights into the sulfur redox chemistry occurring at the sulfur cathode during Li-S battery operation. Using <i>operando</i> sulfur K-edge XAS, we revealed the dynamics of intermediate polysulfide species and the sulfur electrochemical conversion. Furthermore, the result guides us to design the multi-metal interaction with polysulfides. Li-S battery performance significantly enhanced by incorporating multi-metal to accelerate the Li-S reaction kinetics.<br/><br/>Then, we designed the cross-sectional Li-S battery cell to quantify polysulfide diffusion rate using sulfur K-edge X-ray spectromicroscopy. We found that elemental sulfur discharged to higher-order polysulfide species (Li₂S₈ and Li₂S₆) on the cathode and quickly diffused to the entire separator. This polysulfide diffusion resulted in the majority capacity decay in Li-S batteries.<br/><br/>In summary, we highlight the crucial role of <i>operando</i> XAS and X-ray spectromicroscopy as a transformative tool to overcome the fundamental challenges in Li-S batteries. Our study offers the potential for high-energy-density and sustainable energy storage solutions.