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 scanning electron microscope 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/cm2. Consequently, the Li–S battery based on a functional MnOOH/C/PP separator shows high discharge capacity (1358 mAh/g at 0.1 C), good rate capability (755 mAh/g at 3 C) and stable cyclability (0.049 % decay per cycle over 700 cycles). Particularly, an areal capacity can reach 3.55 mAh/cm2 even at a high sulfur loading of 7.02 mg/cm2 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.