A gamma fluorinated ether as an additive for enhanced oxygen activity in Li-O-2 batteries
2015 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, no 37, 19061-19067 p.Article in journal (Refereed) Published
Perfluorocarbons (PFCs) are known for their high O-2 solubility and have been investigated as additives in Li-O-2 cells to enhance the cathode performance. However, the immiscibility of PFCs with organic solvents remains the main issue to be addressed as it hinders PFC practical application in Li-O-2 cells. Furthermore, the effect of PFC additives on the O-2 mass transport properties in the catholyte and their stability has not been thoroughly investigated. In this study, we investigated the properties of 1,1,1,2,2,3,3,4,4-nonafluoro-6-propoxyhexane (TE4), a gamma fluorinated ether, and found it to be miscible with tetraglyme (TEGDME), a solvent commonly used in Li-O-2 cells. The results show that with the TE4 additive up to 4 times higher O-2 solubility and up to 2 times higher O-2 diffusibility can be achieved. With 20 vol% TE4 addition, the discharge capacity increased about 10 times at a high discharge rate of 400 mA g(C)(-1), corresponding to about 0.4 mA cm(-2). The chemical stability of TE4 after Li-O-2 cell discharge is investigated using H-1 and F-19 NMR, and the TE4 signal is retained after discharge. FTIR and XPS measurements indicate the presence of Li2O2 as a discharged product, together with side products from the parasitic reactions of LiTFSI salt and TEGDME.
Place, publisher, year, edition, pages
2015. Vol. 3, no 37, 19061-19067 p.
IdentifiersURN: urn:nbn:se:uu:diva-265646DOI: 10.1039/c5ta03439fISI: 000361553100032OAI: oai:DiVA.org:uu-265646DiVA: diva2:866643