Lithium Difluorophosphate As a Promising Electrolyte Lithium Additive for High-Voltage Lithium-Ion Batteries

Lithium difluorophosphate (LiDFP), the decomposition product of LiPF6, was evaluated in high-voltage LiNi1/3Co1/3Mn1/3O2/graphite pouch cells. We report that conventional carbonate-based electrolytes containing 1 wt % LiDFP can notably enhance the cyclability and rate capability of the battery at 4.5 V. Its capacity retention maintained 92.6% after 100 cycles, whereas it is only 36.0% for the additive-free battery. Even after 200 cycles, the capacity retention remained 78.2%. The EIS measurements performed by three-electrode graphite/Li/LiNi1/3Co1/3Mn1/3O2 pouch batteries indicate that LiDFP can efficiently restrain the breakdown of the electrolyte on the LiNi1/3Co1/3Mn1/3O2 electrode surface and relieve the increase of cathode resistance. Additionally, a uniform and stable SEI film modified by LiDFP on the anode can effectively remit the electrode/electrolyte interfacial reaction and relieve the increase of anode resistance during cycling. Further evidence for the beneficial effect of LiDFP in inhibiting...