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 (Ea) 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.