Crystal Phase Dominance Over Structural Confinement of ZrO 2 for Enhanced Polysulfide Immobilization in Lithium–Sulfur Batteries

The conversion‐based electrochemical energy storage mechanism of lithium–sulfur batteries (LSBs) involves lithium polysulfides (LiPSs) as the reaction intermediates. LiPSs dissolve in the electrolyte, leading to capacity losses and the shuttle effect. To tackle this, the physical confinement of sulfur and LiPSs using nitrogen‐doped Ketjenblack and chemical anchoring via different crystal phases of ZrO 2 is investigated. By combining theoretical analysis and experimental verification, a clear correlation between the electronic structure of ZrO 2 crystal phases and their actual performance in LSBs is established. Compared to the cubic ZrO 2 crystal phase, the monoclinic phase shows stronger binding energy with Li 2 S 6 and a higher density of states near the Fermi level, which translates into more efficient redox kinetics and shuttle suppression as well as enhanced sulfur utilization in practical cells. Li–S coin cells assembled with an electrode containing monoclinic ZrO 2 as the sulfur host provided a high initial discharge capacity of 1207 mAh g −1 at 0.05 C, demonstrating stable long‐term cycling at 2 C over 500 cycles with 84% capacity retention and a capacity loss of 0.03% per cycle. This demonstrates the promise of the monoclinic ZrO 2 crystal phase for the chemical confinement of LiPSs in LSBs.