Engineering Dynamic Electrolyte Microenvironments via Double-Shell Hosts for Practical Lithium-Sulfur Batteries

The practical deployment of lithium-sulfur (Li-S) batteries is hampered by the shuttle effect of lithium polysulfides (LiPSs) and sluggish kinetics of sulfur redox reaction. While prevailing research focuses on maximizing the intrinsic activity of catalysts, the critical role of the host architecture in modulating the local reaction microenvironment remains overlooked. Herein, we report a facile ion-exchange strategy to synthesize double-shell hollow Prussian blue analogue derivative (Co_2.5Fe/NC) as advanced sulfur hosts by precisely controlling the Co/Fe molar ratio at 2.5. Finite element simulations and in situ diagnostics reveal that the double-shell structure orchestrates a self-propelled electrolyte flow within the nanoreactor during operation. This dynamic flow effectively mitigates the spatial concentration heterogeneity of LiPSs, especially near the catalysts, thereby preventing active material passivation and ensuring sustained high catalytic efficiency. Consequently, even with a catalyst of moderate intrinsic activity, the Co_2.5Fe/NC cathode achieves exceptional stability under lean electrolyte conditions (0.016% decay per cycle over 1000 cycles at 2 C). More importantly, an Ah-level pouch cell delivers a high energy density of 454.7 Wh kg⁻¹. This work shifts the paradigm from solely pursuing catalytic activity to designing host structures that intelligently manage the electrochemical microenvironment, offering a new avenue toward practical Li-S batteries.