Electrolyte with Low Polysulfide Solubility for Li-S Batteries

Sun, Ke; Wu, Qin; Tong, Xiao; Gan, Hong

doi:10.1021/acsaem.8b00317

Title: Electrolyte with Low Polysulfide Solubility for Li-S Batteries

Journal Article · Wed May 23 00:00:00 EDT 2018 · ACS Applied Energy Materials

DOI:https://doi.org/10.1021/acsaem.8b00317· OSTI ID:1439302

Sun, Ke ^[1]; Wu, Qin ^[1]; Tong, Xiao ^[1]; Gan, Hong ^[1]

Brookhaven National Lab. (BNL), Upton, NY (United States)

Here, Li-S battery is one of the most promising next generation rechargeable battery technologies due to its high theoretical energy density and low material cost. While its success is impeded by the low energy efficiency and fast capacity fade primarily caused by the discharge intermediates, Li-polysulfides (PS), dissolution in the electrolyte. Mitigation of PS dissolution in electrolyte involves the search of new electrolyte solvent system that exhibits poor solvation to the PS while still have good solvation ability to the electrolyte salt for high ionic conductivity. Applying co-solvents with reduced solvating power but compatible with the state of art Li-S battery’s ether-based electrolyte is one of the most promising concepts. This route is also advantageous of having a low scale-up cost. With the aids of Quantum Chemical Calculation, we have identified high carbon-to-oxygen (C/O) ratio ethers as co-solvent in the new electrolytes that effectively impede PS dissolution while still maintaining high ionic conductivity. Significantly improved cycle life and cycling Coulombic efficiency are observed for Li-S cells using the new composite electrolytes. Anode analysis with different methods also demonstrate that reducing electrolyte’s PS solubility results in less sulfur total amount on the lithium anode surface and lower ratio of the longer-chain PS, which is probably a sign of suppressed side reactions between the anode and PS in the electrolyte.

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