Interfacial Polysulfide Confinement via Spatially Controlled Sulfonated Metal-Organic Polyhedra Coatings in Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries offer a high theoretical specific energy of 2600 Wh kg-1, yet commercialization remains limited by poor sulfur conductivity and structural instability of sulfur electrodes due to polysulfide (Li-PS) dissolution and shuttling. Here, a sulfonated zirconium-based metal organic polyhedron (SMOP) is introduced as a molecularly dispersible additive for nanoscale interfacial engineering at 3 wt.% in the sulfur-carbon composite. Two placement modes are implemented, where SMOP is assembled as a conformal interfacial coating on sulfur-loaded hollow carbon spheres (SMOP-S-HCS), whereas SMOP is introduced by co-deposition/physical blending with Ketjen black (SMOP-S-KB), producing a dispersed/buried distribution without a defined surface layer. SMOP-S-HCS delivers a low shuttle charge (QPS) of 54.0 mAh gS -1, whereas SMOP-S-KB exhibits approximately 1.7-fold higher QPS despite identical SMOP loading during the Li-PS shuttle current measurement. SMOP-S-HCS delivers robust rate capability with discharge capacity ranging from ∼1500 to ∼800 mAh gS -1 from 0.05 to 2C and sustained discharge capacity of 850 mAh gS -1 after 400 cycles at 0.3C. Ex situ sulfur K-edge XAS confirms the effectiveness of SMOP functional barrier against Li-PS shuttling by probing more reversible sulfur speciation and reduced oxidized sulfur buildup during cycling.