An organic nickel salt-based electrolyte additive boosts homogeneous catalysis for lithium-sulfur batteries

The shuttling of soluble lithium polysulfides (LiPSs) intermediates bottlenecks practical uses of lithium-sulfur (Li-S) batteries. A commercial organometallic salt, nickel chloride dimethoxyethane adduct (NiDME), is introduced as the homogenous catalyst dissolved in the electrolyte to suppress the shuttle effect. A very small amount of catalyst (only 0.5 wt% additive relative to the electrolyte) brings the battery capacity a big rise from 408 to 784 mAh g⁻¹ over 500 cycles at 1 C. More promisingly, the required amount of electrolyte is greatly reduced, and the battery works well with a lean electrolyte (5 μL_{(electrolyte)}/mg_(sulfur)). The improved performance is attributed to the catalyst-accelerated LiPS conversion which is characterized by largely decreased activation energy (E_a) of the sulfur redox reaction, especially for Li₂S deposition, and much reduced accumulation of LiPSs intermediates. Specially, the NiDME additive captures LiPSs in the electrolyte, accelerates the redox reactions homogeneously and regulates a uniform and fast deposition of Li₂S, all these contributing to a perfect catalytic cycle with less LiPS shuttling. This work deepens our understanding on catalysis in accelerating sulfur redox conversion and indicates homogeneous catalysis as a simple yet fundamental solution to shuttle effect of LiPSs intermediates, which boosts practical Li-S batteries with less electrolyte needs and long working life.