Defect‐Engineered CoSe ₂ Quantum Dots Exposing Highly Active (111) Facets with Lithiophilic‐Sulfurophilic Functionality for High‐Energy Lithium–Sulfur Batteries

The shuttle of lithium polysulfides (LiPSs) and sluggish redox kinetics have posed significant barriers to advancing lithium-sulfur batteries. The design of lithiophilic-sulfiphilic cathode show great promise, however, the integration of these multifunction through precise atomic-level synergy remains a critical challenge. Herein, defective CoSe₂ quantum dots (QDs) confined within carbon microspheres (CoSe₂@C) are prepared as sulfur cathode host material. The exposure of the highly active (111) facets provides more active sites and accelerates the catalytic conversion kinetics of LiPSs. Additionally, the abundant selenium vacancies exhibit dual-bonding capability with Li and S atoms, thereby improving the adsorption of LiPSs and lowering the reaction energy barrier. Moreover, the carbon microspheres matrix effectively alleviates the aggregation of CoSe₂ QDs and increases the specific surface area. Benefiting from the above merits, the titled cathode exhibits enhanced conductivity and charge transfer, which effectively enhances the dynamics and alleviates shuttle effects. Consequently, the Li-S batteries assembled with CoSe₂@C cathodes show extraordinary performance with an initial specific capacity of 1397 mAh g^-1 at 0.2 C, a decay rate of 0.029% per cycle after 1000 cycles at 2 C. This work offers viewpoint for designing highly efficient catalysts for Li-S batteries.