Topic 01-29 : Highly concentrated electrolytes dedicated to lithium-sulfur batteries

As outlined above, one main problem of Li-S batteries is themany different polysulfides formed during the discharge process and their solubilities in the electrolytes employed.Here we suggest to limit their transport, close to immobilizing them,by employing novel highly concentrated electrolytes based on a new family of lithium salts developed at WUT having nitrile functional groups - with the hypothesis of beneficial interactions with the polysulfides. ThisESR project contains comprehensive basic research (synthesis, characterisation, testing) on model systems and working electrolytes as well as synthesis of sulfides and polysulfides.In addition also important phenomena at the two interfaces, metallic lithium electrode / electrolyte and sulfur electrode / electrolyte, will be investigated by electrochemical techniques as function of reversible electrochemical deposition and dissolution of lithium (containing) species. By techniques such as operando Raman spectroscopy the ESR will be trained in monitoring the polysulfides during cell operation and as function of electrolyte composition - including also specific molecular level interactions present.

Two particular targets are to: i) balance the concentration of the novel salts vs. Li-S cell performance and ii) to investigate also the role of different solvents to reduce the polysulfide solubility. The selection of the latter from databases will be assisted by advanced polysulfide solubility calculations based on DFT and statistical mechanics at Chalmers. At WUT special care will be taken to create lab cells and systems that closely mimick commercially realistic solutions.
The secondments at Chalmers aim for the ESR to learn to design highly concentrated electrolytes based on polysulfide solubility and the nature of charge carriers including how to employ advanced operando Raman spectroscopy to verify hypotheses on immobilisation and specific interactions.

Mobility scheme: Y1: 1 month at Chalmers: learning basics of electrolyte design, use of (results from) computational techniques - pending the ESR skill-set, Y2: 2 months at Chalmers: performing operando Raman spectroscopy on model and Gen1 electrolytes, Y3: 2 months at Chalmers: performing operando Raman spectroscopy on Gen2/final electrolytes.