Discretized Analysis of Polysulfide Shuttle Dynamics in Lithium-Sulfur Batteries

The polysulfide shuttle effect remains a fundamental challenge in lithium-sulfur batteries, particularly for high-energy-density applications where conventional mitigation strategies prove insufficient. Here, we introduce a state-resolved methodology for quantifying shuttle current by analyzing Coulombic efficiency across discretized charging blocks, addressing limitations in traditional voltage-dependent measurement techniques. Through systematic analysis of cells with and without LiNO3 additive, we demonstrate that shuttle activity peaks at 60%-70% state-of-charge (SOC), correlating with maximum Li2S4 concentration as confirmed by UV-vis spectroscopy. The block efficiency analysis reveals distinct patterns: cells without LiNO3 show efficiency dropping to 60% in the mid-SOC region, while LiNO3-containing cells maintain minimum efficiency around 80%, demonstrating approximately 70% suppression of peak shuttle current. Electrochemical impedance analysis further reveals how polysulfide evolution affects transport processes, with bulk resistance peaking at mid-SOC due to pore blockage, while interfacial resistance changes reflect the transition between different polysulfide species. By correlating block efficiency with polysulfide speciation, we establish that Li2S4 drives shuttle activity through its optimal balance of solubility and mobility, while larger Li2S8 species contribute less despite higher solubility. This work provides quantitative insights into shuttle current distribution across different SOC ranges while establishing a robust methodology for evaluating shuttle suppression strategies.