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Polysulfide’s impact on physical and electrochemical properties of ionic liquid electrolytes

Filippa Lundin
Göteborg : Chalmers tekniska högskola, 2017. 58 s.
[Examensarbete på avancerad nivå]

The Lithium-Sulfur battery is in need of a new safer electrolyte. For this, ionic liquids are considered a promising candidate. But how does the electrolyte react when polysulfides (PS) dissolves into it? This thesis investigates how an addition of PS affect phase transitions, ionic conductivity, mobility and SEI-formation of ionic liquid electrolytes. In the study the properties of 1-Propyl-1-methyl-pyrrolidinium Bis(fluorosulfonyl)imide (P13FSI) and 1-Butyl-1-methyl-pyrrolidinium Bis(trifluoromethanesulfonyl)imide (P14TFSI) with their corresponding anion lithium salt are compared with and without polysulfide additives. For these ionic liquid electrolytes the solubility of PS is low, hence the impact of the PS presence is small. The phase transitions, investigated by DSC, were found to be unaffected upon addition of polysulfides for P13FSI based electrolytes, while the crystallisation temperature increases for P14TFSI based samples when polysulfides are present.The conductivity increases when PS are present in the P13FSI electrolyte, while for the P14TFSI electrolyte the conductivity decreases in the presence of PS. From diffusion coefficients the mobility of all electrolyte components was found to increase upon addition of PS for P13FSI. In the P14TFSI electrolyte the mobility decreases in the presence of PS in agreement with the result for the conductivity. From cycling and impedance data the solid electrolyte interphase (SEI) layer was found to form faster and found to have a lower resistance with PS than without for the P13FSI electrolyte. The presence of PS didn’t affect the formation for the P14TFSI electrolyte. Based on this study the properties of the ionic liquid electrolytes does not change considerably when PS is introduced, making it a promising candidate as electrolyte for Lithium-Sulfur batteries.

Nyckelord: Ionic liquid, Li-S battery, Polysulfides, P13FSI, P14TFSI.

Publikationen registrerades 2018-11-27. Den ändrades senast 2018-11-27

CPL ID: 256352

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