Power capability of LiTDI-based electrolytes for lithium-ion batteries

Abstract

We report results obtained with lithium 4,5-dicyano-2-(trifluoromethyl) imidazolide (LiTDI), which we believe is a promising lithium salt for electrolytes in lithium-ion batteries. This “Hückel”- type salt has high charge delocalizations which contribute to good lithium-ion dissociation. In addition, it has high thermal stability and safer degradation products compared to LiPF6, which were identified by TGA-MS. It also does not corrode but passivate the aluminum current collector. Cyclic voltammetry measurements showed a stability up to 4.5 V, which is sufficient for use with standard cathode materials. The power capability of half cells containing LiTDI in EC/DEC was evaluated with standard cathodes used in lithium-ion batteries: LFP, NMC, LCO and LMO. Two LiTDI concentrations were investigated: 1 M and 0.6 M and compared with a reference electrolyte: 1 M LiPF6. In spite of a slightly lower conductivity than the LiPF6, LiTDI (1 M and 0.6 M) shows similar power capability up to 2C with LFP (84% of specific capacity recovered), 10C with NMC (61% of specific capacity recovered), and up to 20C for LMO (88% of specific capacity recovered). Furthermore, better power capability was obtained with 0.6 M LiTDI with LCO, which yielded 82% of specific capacity recovered at 1C (67% for 1 M LiTDI and 1 M LiPF6).