An additive-free and free-standing GPE with excellent Li+ mobility and polysulfide localization is prepared via a facile route.

The inhibition of polysulfides by a MOF composite separator with an ion sieve effect, and physical and chemical adsorption is illustrated.

A monolayer poly(vinyl alcohol) (PVA)-based separator with pendant sulfonate/carboxylate groups and compact morphology is synthesized to suppress the essential lithium polysulfide permeation in lithium sulfur batteries (LSBs). The Li transference number is significantly increased to 0.8, much higher than that of a commercial separator (0.43). The polysulfide retention is verified by idle test in a polysulfide-rich electrolyte under the internal electric field of the cell. The LSB with an additive-free electrolyte attains a Coulombic efficiency around 98% and delivered capacity of 804 mA h g at 2.5 A g. After 500 cycles, it retains 901 mA h g at 1.5 A g with extra low fading rate of 0.016% per cycle. Overall, this monolayer PVA-based separator provides a facile and effective technique to assemble highly stable LSBs.

A simple one-pot hydrothermal method is developed for fabrication of MoS2@rGO nanoflakes using the economical MoO3 as the molybdenum source. Benefiting from the unique nanoarchitecture, high MoS2 loading (90.3 wt%) and the expanded interlayer spacing, the as-prepared MoS2@rGO nanoflakes exhibit greatly enhanced sodium storage performances including a high reversible specific capacity of 441 mAh g−1 at a current density of 0.2 A g−1, high rate capability, and excellent capacity retention of 93.2% after 300 cycles.

The practical use of the rechargeable lithium-sulfur (Li-S) battery is still restricted by poor cycle life and rate performance caused by the shuttle of soluble redox intermediates and low conductivity of S/Li2S. A comprehensive approach is to tune the multi-electron redox reactions and construct reversible chemical bonds with polysulfide intermediates. In this study, RuO2 nano dots (NDs) are proposed to anchor polysulfides, trigger the surface-mediated reduction of polysulfides and to facilitate the formation of Li2S2/Li2S through its catalytic effect for the first time. When serving as the sulfur host, the RuO2 NDs can retard the shuttle of polysulfides, accelerate the redox reaction of polysulfides, and therefore result in improved sulfur utilization and enhanced rate performance. The designed RuO2@NMCs/S ternary electrodes with high sulfur loading of 70 wt% could achieve a low decay rate of 0.07% per cycle for 500 cycles at a 0.5 C-rate. Realized by fast electrode kinetics, the reversible capacity of 634 mA h g-1 is attained at a high C-rate of 5 C. Overall, this strategy sheds new light on the oxide mediators for reversible modulation of electrochemical reactions in lithium-sulfur (Li-S) batteries.