Engineering Oxygen Vacancies in a Polysulfide-Blocking Layer with Enhanced Catalytic Ability.

The practical application of the lithium-sulfur (Li-S) battery is seriously restricted by its shuttle effect, low conductivity, and low sulfur loading. Herein, first-principles calculations are conducted to verify that the introduction of oxygen vacancies in TiO2 not only enhances polysulfide adsorption but also greatly improves the catalytic ability and both the ion and electron conductivities. A commercial polypropylene (PP) separator decorated with TiO2 nanosheets with oxygen vacancies (OVs-TiO2 @PP) is fabricated as a strong polysulfide barrier for the Li-S battery. The thickness of the OVs-TiO2 modification layer is only 500 nm with a low areal mass of around 0.12 mg cm-2 , which enhances the fast lithium-ion penetration and the high energy density of the whole cell. As a result, the cell with the OVs-TiO2 @PP separator exhibits a stable electrochemical behavior at 2.0 C over 500 cycles, even under a high sulfur loading of 7.1 mg cm-2 , and an areal capacity of 5.83 mAh cm-2 remains after 100 cycles. The proposed strategy of engineering oxygen vacancies is expected to have wide applications in Li-S batteries.