Enhanced Polysulfide Trapping and Conversion by Amorphous-Crystalline Heterostructured MnO2 Interlayers for Li-S Batteries.

ABSTRACT

The practical application of lithium-sulfur batteries (LSBs) is still hindered by several technical issues, including severe polysulfide shuttling and sluggish redox kinetics, which reduces the sulfur utilization and further results in low energy density. Herein, amorphous-crystalline heterostructured MnO2 (ACM) prepared through a simple calcination process was employed as the functional interlayer to play a double role as effective trapper and multifunctional electrocatalyst for LSBs. ACM not only combines the strong sulfur chemisorption of the amorphous MnO2 (AM) and fast Li+ transportation of the crystalline MnO2(CM) but also accelerates the interface charge transfer at the amorphous/crystalline interfaces. The LSBs with such unique interlayer exhibited an excellent rate performance of 1155.5 mAh·g-1 at 0.2 C and 692.9 mAh·g-1 at 3 C and a low decay rate of 0.071% per cycle over 500 cycles at 0.5 C. Even for a high sulfur loading of 5 mg·cm-2 at 0.1 C, a high capacity retention of 92.3% could also be achieved after 100 cycles. The concept of amorphous-crystalline heterostructures prepared by crystallization regulation might also be used for other electronic devices and catalyst designs.