Electrochemical stability of bis(trifluoromethanesulfonyl)imide-based ionic liquids at elevated temperature as a solvent for a titanium oxide bronze electrode

Towards Li-Ion Batteries Operating at 80 °C: Ionic Liquid versus Conventional Liquid Electrolytes

“…However, in the scientific literature the term "high temperature cycling" mainly refers to cycling at temperatures at 60 or 70 • C, with only a few reports of battery cycling at 80 • C or higher [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The majority of these studies have been carried out with organic carbonate based electrolytes [7][8][9][10][11][12][13][14][15], but ionic liquid (IL) based electrolytes [16][17][18], solid polymer electrolytes [19], and ternary electrolytes (IL + polymer + Li-salt) [20] have also been explored. The extensive work with traditional carbonate electrolytes has aimed at finding suitable electrolyte additives [7], alternative binders [8], and the failure mechanisms for both the negative [9,10] and positive electrodes [11][12][13] as well as full cells [14,15].…”

“…Work with IL-based electrolytes has, on the other hand, demonstrated promising cycling stabilities for titanium dioxide, TiO 2 (B), and LiFePO 4 (LFP) half-cells at temperatures as high as 120 • C [16][17][18]. The cycling of LIBs at elevated temperatures such as 80 • C is associated with increased risks as the kinetics of any side reaction are enhanced, which could lead to the initiation of heat-generating exothermic reactions and eventually thermal runaway [21].…”

“…The safety of LIBs operating at these temperatures can therefore be significantly improved if more stable IL electrolytes were used. Pyrrolidinium (Pyr) based ILs have been shown to have wide electrochemical stability windows [16,22]. Moreover, TiO 2 electrodes can be cycled at temperatures as high as 120 • C with an electrolyte composed of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in N-methyl-N-propylpyrrolidinium TFSI (Pyr13TFSI) [16].…”

“…Pyrrolidinium (Pyr) based ILs have been shown to have wide electrochemical stability windows [16,22]. Moreover, TiO 2 electrodes can be cycled at temperatures as high as 120 • C with an electrolyte composed of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in N-methyl-N-propylpyrrolidinium TFSI (Pyr13TFSI) [16]. It should be mentioned that the previous studies [16][17][18] were carried out in half-cell configurations with Li metal as the anode material.…”

Graft copolymer-based lithium-ion battery for high-temperature operation

“…Moreover, their battery required extensive modification to the cell construction and was not operational at temperature below the melting point of LiTFSI [29]. Recently, ionic liquids have received much attention for their thermal stability and low flammability, but their electrochemical stability at elevated temperatures remains a challenge [30].…”