Author: Daniel Tevik Rogstad
Title: Performance of Si anodes in ionic liquid electrolytes with added carbonates
Affiliation: Norwegian University of Science and Technology
Electrolytes consisting of the lithium bis(fluorosulfonyl)imide (LiFSI) salt and the room temperature ionic liquid N-Propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR13FSI) were made with and without the addition of dimethyl carbonate (DMC) and fluoroethylene carbonate (FEC). EL-CELL® PAT-cells were assembled using a 73 wt% µ-Si electrode in pseudo full cell setup with a capacitively oversized LiFePO4 cathode to determine the effect of the electrolytes on rate performance and cycling stability. Silicon electrodes were extracted from cells cycled 1, 11 and 51 cycles and the composition and growth of the SEI layer was analyzed using XPS.
It is shown that mixing small amounts of carbonate into ionic liquid electrolytes can have a positive effect on the rate capability of silicon electrodes in Li-ion batteries as compared to electrolytes of pure ionic liquids. The addition of FEC in addition to DMC seems to be essential to also retain a good cycling stability.