Tuning Lithium-Sulfur Battery Electrolytes for Improved Performance

Snapshots of calculated structures for electrolytes with different solvent/salt ratios (left), and saturated polysulfide solutions (right, top), which demonstrate the sparingly polysulfide solubility of the lowest solvent/salt ratio (0.8:1) owing to the lack of “free” solvent. The electrolyte with a ratio of 0.8:1 yielded greatly improved performance in cell tests for 100 cycles (right, bottom).

Scientific Achievement

The electrolyte of the lithium-sulfur (Li-S) battery was tuned to both overcome the need for a high electrolyte/sulfur ratio and inhibit the lithium dendrite growth on the anode at the same time.

Significance and Impact

Achieving a Li-S battery that operates for numerous charge-discharge cycles with a minimal amount of electrolyte is an important step in the development of low-cost, high energy density batteries.

Research Details

  • This new electrolyte consists of an ether (“diglyme”) solvent with a lithium salt, where the solvent/salt ratio is tuned to minimize the solvent activity.
  • This tuning transforms the sulfur reaction pathway at the cathode in such a way that the related polysulfide dissolution reactions occur partially in the solid state, as opposed to just in the liquid electrolyte.
  • As shown by experimental and computational studies, the resulting lowered activity for the solvent along with an extended electrolyte network structure curtail the need for high electrolyte volumes.
  • In addition, the optimized electrolyte structure avoids the problem with electrolyte solvent degradation by suppressing dendrite formation, greatly improving cycle life.

DOI: 10.1038/s41560-018-0214-0

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