New class of nonaqueous electrolytes for long-life and safe lithium-ion batteries

Long-life and safe lithium-ion batteries have been long pursued to enable electrification of the transportation system and for grid applications. However, the poor safety characteristics of lithium-ion batteries have been the major bottleneck for the widespread deployment of this promising technology. Here, we report a novel nonaqueous Li2B12F12-xHx electrolyte, using lithium difluoro(oxalato) borate as an electrolyte additive, that has superior performance to the conventional LiPF6-based electrolyte with regard to cycle life and safety, including tolerance to both overcharge and thermal abuse. Cells tested with the Li2B12F9H3-based electrolyte maintained about 70% initial capacity when cycled at 55 degrees C for 1,200 cycles, and the intrinsic overcharge protection mechanism was active up to 450 overcharge abuse cycles. Results from in situ high-energy X-ray diffraction showed that the thermal decomposition of the delithiated Li1-x[Ni(1/3M)n(1/3)Co(1/3)](0.9)O-2 cathode was delayed by about 20 degrees C when using the Li2B12F12-based electrolyte.