Andreas Hofmann¹,*, Michael Schulz¹, Thomas Hanemann^1,2

2. EXPERIMENTAL

N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)azanide

(DMMA-TFSA, IoLiTec, >99%), lithium bis(trifluoromethanesulfonyl)azanide (LiTFSA, IoLiTec, > 99%), and propylene carbonate (PC, Sigma-Aldrich, anhydrous, 99.7%) were dried at 110°C by means of a continuous flow of dried air. The water content of the solvents was determined by coulombmetric Karl Fischer titration to be less than 10 ppm. Vinylene carbonate (Aldrich, 97%), lithium tetrafluoroborate (Aldrich, anhydrous, 99.998% trace metals basis), lithium triflate (LiOTf, Aldrich, 99.995% trace metals basis), lithium hexafluorophosphate (ABCR, battery grade, 20 ppm H2O max), lithium perchlorate (Aldrich, 99.99% trace metals basis), lithium foil (Alfa Aesar, 0.75 mm thick), and hexamethyldisilazane (Aldrich, >99%) were used as received. The preparation of the electrolytes was performed in a vacuum glove box (Xiamen Tmaxcn Inc.) with oxygen and water levels below 0.5 ppm. Calandered electrodes based on graphite and NMC with a content of approximately 90% of active material were provided in cooperation.

In this study common coin cells (type: CR 2032, Hohsen Corp.) were used with a coin cell crimper from Xiamen TMAX Battery Equipments Limited. The cells were assembled in an argon-filled glove box according to standard procedures. Precisely, a graphite anode (Ø = 15 mm), a NMC cathode (Ø = 14 cm), and a glass fiber separator (Whatman®, GF/B and QMA 450; Ø =16 mm) were used inside a coin type cell with one coin cell case (Xiamen Tmaxcn Inc.) and one stainless steel spacer.