Bifunctional Separator with Nest-like MnOOH Network via Facile In-situ Synthesis for Highly Stable and “Li-dendrite free” Lithium-sulfur Batteries

The slow redox kinetics in the sulfur cathode and lithium (Li)-dendrite growth on the lithium anode leads to significant capacity degradation and serious safety incidents for lithium-sulfur (Li-S) batteries. Herein, a bifunctional polypropylene separator with nest-like MnOOH network synergistic carbon layer (MnOOH/C/PP) via facile in-situ synthesis method was designed as an effective host for both sulfur cathode and lithium anode. A series of electrochemical tests and non-in situ SEM characterization confirmed that the as-prepared MnOOH/C layer has good physical/chemical adsorption and catalytic activity of polysulfides. Furthermore, the Li||Li symmetric batteries exhibited inhibited dendrite growth even after undergoing cycling for more than 2200 h at 1 mA cm^-2. Consequently, the Li-S battery based on a functional MnOOH/C/PP separator shows high discharge capacity (1358 mAh g^-1 at 0.1 C), good rate capability (755 mAh g^-1 at 3 C) and stable cyclability (0.049% decay per cycle over 700 cycles). Particularly, an areal capacity can reach 3.55 mA h cm^-2 even at a high sulfur loading of 7.02 mg cm^-2 and a high-capacity retention rate of 90.2% remained over 200 cycles, demonstrating the viability of this simple and efficient strategy for creating highly stable and safe Li-S batteries.