Carbon Layer Induced the Formation of an Oxygen Vacancy-Rich γ-MnO2 Porous Network on the Separator for Enhancing Lithium–Sulfur Battery Performance

Abstract

Oxygen vacancy materials have been proven to exhibit rapid capture and catalytic conversion ability toward lithium polysulfides in lithium–sulfur (Li–S) batteries. Herein, the γ-MnO₂ porous network with rich oxygen vacancies is simply prepared on a polypropylene separator by using a carbon layer as a growth medium (MnO₂/C/PP) and applied in Li–S batteries. By contrast, no obvious γ-MnO₂ porous network can be observed without the carbon layer. Besides, the presence of rich oxygen vacancies in γ-MnO₂ is proven by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). A series of experimental results confirm that the modified separators MnO₂/C/PP have strong anchoring and catalytic effects on polysulfides. As a result, the battery with a MnO₂/C/PP separator shows a specific discharge capacity of 919 mAh g^–1 at 0.5 C and maintains a reversible capacity of 464 mAh g^–1 after 600 cycles with a capacity decay rate of 0.082% per cycle. This work provides an effective new strategy for the preparation of high-activity manganese-based catalysts with good application prospects for energy storage devices.