Study of the corrosion behavior of LiFSI based electrolyte for Li-ion cells

The corrosion/passivation phenomenon of Al and stainless steel with 1.25 M LiFSI in ethylene carbonate / ethyl methyl carbonate 30/70 wt% electrolyte was studied in coin cell and pouch cell settings. Our results showed that the LiFSI electrolyte can passivate Al foil in the normal cell operation voltage window 2.8 to 4.3 V. In contrast, no passivation behavior was observed for stainless steel with ever growing current response in cyclic voltammetry test. Corrosion produced Fe/Cr ions were detected on the anode side, which accelerated the electrolyte decomposition reaction. The LiFSI electrolyte was tested in 1.5 Ah pouch cell for long term cycling performance and fast charging capabilities. The capacity retentions after 1000 cycles were 88.5% and 80% for ± 1C and extreme fast charging rates, which demonstrated the suitability of using LiFSI in Li-ion cells without stainless steel components.