Non-crystallizing solvent mixtures and lithium electrolytes for low temperatures

• Published in: Solid state ionics Vol. 308; pp. 22 - 26
• Main Authors: Kasprzyk, Marta, Zalewska, Aldona, Niedzicki, Leszek, Bitner, Anna, Marcinek, Marek, Wieczorek, Wladyslaw
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2017; Elsevier BV
• Subjects: Batteries; Conductivity; Dimethyl ether; Electrochemical analysis; Electrolyte; Electrolytes; Energy storage; Lithium; Lithium-ion batteries; Low temperature; Non-crystallizing; Performance enhancement; Polyethylene glycol; Rechargeable batteries; Solvents; Studies; Temperature; Non-crystallizing; Conductivity; Lithium; Electrolyte; Low temperature
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2017.05.014

A new class of solvent mixture and new liquid electrolytes are reported. New non-crystallizing materials may improve the performance of lithium-ion batteries at extremely low temperatures. Solvents were prepared by mixing EC (ethylene carbonate) with PEG250 (poly(ethylene glycol) dimethyl ether with an average molar mass of 250gmol−1). Some of these mixtures show only a glass transition, which takes place at temperatures below −70°C. It is possible to prepare such non-crystallizing electrolytes with both the novel imidazolide lithium salt LiTDI (lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide) and the benchmark commercial salt LiPF6 (lithium hexafluorophosphate). Most state-of-the-art electrolytes crystallize at temperatures above −40°C. Thus, below this temperature a rapid decrease in conductivity is observed. New solutions show very good thermal and electrochemical properties (for instance: high conductivity, wide range of electrochemical stability window). This type of electrolyte may also reach high conductivity values of around 0.014mScm−1 at −60°C. This new class of electrolyte may be the answer to the numerous present issues with applications below 0°C, and also gives the possibility of battery storage at low temperature without cell damage. •First studies on non-crystallizing mixtures of solvents EC:PEG250•First studies on lithium electrolytes based on such mixtures with Tg<−80°C•Lithium conducting electrolytes based on such solvents do not crystallize.•Conductivity of new electrolyte based on such mixtures is 0.014mScm−1 at −60°C.