Formulating a Non-Flammable Highly Concentrated Dual-Salt Electrolyte for Wide Temperature High-Nickel Lithium Ion Batteries

With the ever-increasing energy density of lithium ion batteries (LIBs), the safety concerns have aroused great interests. It is well known that electrolytes play a crucial role in determining the safety of LIBs. Here, a non-flammable highly concentrated dual-salt electrolyte is formulated by dissolving 2 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 2 M lithium difluoro(oxalate)borate (LiDFOB) in trimethyl phosphate (TMP) and gamma-butyrolactone (GBL). Encouragingly, this delicately tailored concentrated dual-salt electrolyte possesses high compatibility with high-nickel LIB systems of LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622)/mesocarbon microbeads (MCMB), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811)/MCMB, LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA)/MCMB. Especially, NCM622/MCMB full cell using this electrolyte delivers excellent electrochemical performances over a wide temperature range (−30 °C ∼ 90 °C). It is revealed that thermally stable dual-salt of LiTFSI and LiDFOB will form favorable synergistic effects on electrode interfaces. This paper will guide the formulation of highly safe electrolytes for next generation high energy high nickel LIBs.