Synergistic Cobalt-Manganese Prussian Blue Analogues for Enhanced Polysulfide Conversion in Lithium-Sulfur Batteries

Abstract

The practical deployment of lithium-sulfur (Li-S) batteries is severely impeded by the shuttle effect of soluble lithium polysulfides (LiPSs), which leads to rapid capacity fading and poor Coulombic efficiency. Although Prussian blue analogues (PBA) can physically confine LiPSs within their ordered open frameworks and chemically anchor them via open metal centers, PBA with single-metal active sites often fail to achieve an optimal trade-off between strong adsorption and fast catalytic conversion. Herein, we address this challenge by developing a ternary FeCoMn-PBA host synthesized via room-temperature co-precipitation. This design leverages a multi-metallic synergy: Mn2+ ensures moderate chemical adsorption, Co2+ facilitates superior redox kinetics, and Fe3+ within the rigid framework provides structural stability and additional active sites. Consequently, the FeCoMn-PBA/S cathode demonstrates enhanced electrochemical performance, yielding an average specific capacity of 836.9 mAh g-1 at 2 C and retaining 66.4% of its capacity after 500 cycles at 1 C. The controllable synthesis of these nanocubic PBAs, evolving from binary to ternary compositions, offers practical insights for developing PBA derivatives and designing advanced sulfur host materials.