Titanium-oxo cluster reinforced gel polymer electrolyte enabling lithium-sulfur batteries with high gravimetric energy densities

Lithium-sulfur (Li-S) battery research has flourished by upgrading the performances of sulfur cathodes and Li metal anodes under flooded electrolyte conditions. However, since high gravimetric energy density can only be achieved at a low electrolyte/sulfur (E/S) ratio, the severe performance degradation under lean electrolyte conditions is becoming a bottleneck in the development of Li-S batteries. Here we propose a new class of gel polymer electrolytes by using titanium-oxo clusters as reinforcements to construct low E/S batteries. The developed electrolyte has favorable mechanical properties and high Li-ion conductivity, as well as excellent capabilities to block polysulfide shuttling and suppress Li dendrite formation, enabling low E/S batteries to exhibit enhanced capacities and cycling stabilities. Remarkably, the low E/S (3 μL mg S −1 ) battery fabricated with high sulfur loading (10 mg S cm −2 ) and low negative/positive capacity ratio (1/1) can deliver a gravimetric energy density of 423 W h kg −1 and continue to operate for 100 cycles. This study provides a new avenue for high-energy-density Li-S batteries. A titanium-oxo cluster-reinforced gel polymer electrolyte is developed to improve the performance of high-sulfur-loading lithium-sulfur batteries under lean electrolyte conditions.