Study of the Electrochemical Behavior of Dual-Graphite Cells Using Ionic Liquid-Based Electrolytes

Abstract

Dual-ion cells based on the anion intercalation into a graphite positive electrode have been proposed as electrochemical energy storage devices. In this set-up, the electrolyte, in this case a mixture of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (Pyr14TFSI) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) acts not only as charge carrier, but also as active material. Since the compatibility of this ionic liquid-based electrolyte mixture with graphitic anodes is relatively poor and not sufficient, the selection of the anode materials for the dual-ion system was limited to metallic lithium or Li4Ti5O12 so far. In this work, we present promising results concerning the use of graphite as both the anode and cathode material in a so-called “dual-graphite cell”. The Pyr14TFSI-LiTFSI ionic liquid electrolyte is used in combination with the SEI-forming additive ethylene sulfite (ES) and allows a stable and highly reversible lithium ion and TFSI- anion intercalation/de-intercalation into the graphite anode and cathode, respectively.

A Dual‐graphite Battery with Pure 1‐Butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl) Imide as the Electrolyte

“…Therefore, the optimum upper cut‐off voltage was chosen to be 4.6 V for the Pyr 14 TFSI‐DGB system. Compared with batteries based on lithium salt electrolytes (i. e., the electrolyte of mixture Pyr 14 TFSI‐LiTFSI with additives) in literature,, this Pyr 14 TFSI‐DGB system shows a distinct advantage in that the pure Pyr 14 TFSI electrolyte has a lower viscosity and higher conductivity.…”

Intercalation manners of perchlorate anion into graphite electrode from organic solutions

“…Graphite is called a redox-amphoteric material, because it can be reduced as well as oxidized electrochemically and chemically, accompanying intercalation of various cations or anions, and leading to so-called donor-type or acceptor-type graphite intercalation compounds (GICs) [1]. Among numerous GICs, lithiumgraphite intercalation compound (Li-GIC) has been the most attractive in the past few decades.…”

“…Recently, much attention has been focused on ionic liquids which allow reliable operation in highly oxidizing circumstance [1,2,5,[8][9][10][12][13][14][15][16]. However, the drawbacks such as relatively poor compatibility with graphitic electrodes and high viscosity at room temperature may become problems in practical applications [10].…”

Electrolytes for Dual‐Carbon Batteries

“…Directly adding low concentrations of SEI‐forming additives into IL‐based electrolytes is an effective method of suppressing the solvent co‐intercalation. Winter's group proved that adding 2 wt.% of ethylene sulfite (ES) into Pyr 14 TFSI IL can largely enhance the reversible capacity and cycling stability of DCBs based on either LiTFSI, NaTFSI, or KTFSI salt . For instance, the discharge capacity of Li/KS6L batteries increased from 50 mAh g −1 to 97 mAh g −1 after 2 wt.% ES was added into 1 M LiTFSI/Pyr 14 TFSI electrolytes.…”