Characterization of LTO//NMC Batteries Containing Ionic Liquid or Carbonate Electrolytes after Cycling and Overcharge
Résumé
Electrochem. stabilities under cycling and overcharge of Li4Ti5O12 (LTO)//LiNi1/3Mn1/3Co1/3O2 (NMC) batteries with two ionic liq.-based electrolytes and a com. electrolyte were investigated at 25 and 60°. The electrolytes were constituted of ethylene carbonate/di-Me carbonate mixts. with LiPF6, and of imidazolium and pyrrolidinium-based ionic liqs. contg. the bis(trifluoromethanesulfonyl)imide anion (NTf2) assocd. to LiNTf2 salt. The expts. were performed in coin and pouch cells in order to follow the evolution of the stability of both solid, liq., and gas phases. The decompn. products and stability of the electrolytes was assessed by gas chromatog. coupled with IR spectroscopy. The characterization of the electrode surfaces by SEM, XRD, and XPS techniques was reported, after cycling and overcharge. The XPS anal. of both electrodes indicated that their surfaces were covered by an IL film in the case of NMC, and by several NTf2 anion decompn. products in the case of LTO. This work highlights the difference between thermal and electrochem. stability, esp. for imidazolium-based electrolytes. [on SciFinder(R)]