Electrochemical performances and interfacial properties of graphite electrodes with ionic liquid and alkyl-carbonate hybrid electrolytes

The electrochemical and thermal properties of carbon microbeads (CMB) electrodes with the hybrid electrolytes consisting of varying proportions of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13TFSI) and alkyl-carbonate organic solvent are investigated. Particularly, the interfacial properties of CMB/hybrid electrolytes are explored by means of morphologic observations and spectroscopic technologies. It is found that, after the addition of lithium salt to pure PP13TFSI, the decomposition of more TEST- anions possibly is a new reason for the increased sharply interfacial resistance. By contrast, the hybrid electrolytes with 50-70 wt% alkyl-carbonate co-solvents have advantages of high ionic conductivity and excellent thermal safety combined. Another even more important is that, due to theirs low viscosity and assistant CMB passivation, they have the superiorities in Li+ mobility, particle wettability and solid electrolyte interphase (SEI) film etc., and then show the improved charge-discharge performances. These results clearly prove the advantage of the use of hybrid electrolytes on the performance of the CMB electrode. (C) 2013 Elsevier Ltd. All rights reserved.