Enhanced high voltage performance of LiNi 0.5 Mn 0.3 Co 0.2 O 2 cathode via the synergistic effect of LiPO 2 F 2 and FEC in fluorinated electrolyte for lithium-ion batteries.

LiNi 0.5 Mn 0.3 Co 0.2 O 2 can achieve high energy density due to its merits of high theoretical capacity and a relatively high operating voltage, but the LiNi 0.5 Mn 0.3 Co 0.2 O 2 battery suffers from capacity decay because of the unstable solid electrolyte interface on the cathode. Herein, we investigate the application of a fluorinated electrolyte composed of fluoroethylene carbonate (FEC) as a cosolvent and lithium difluorophosphate (LiPO 2 F 2 ) as a salt-type additive extending the life span of the LiNi 0.5 Mn 0.3 Co 0.2 O 2 cathode. LiNi 0.5 Mn 0.3 Co 0.2 O 2 can achieve and maintain a capacity of 157.7 mA h g -1 over 200 cycles at a 1C rate between 3.0 and 4.4 V, as well as a reversible capacity of 132.7 mA h g -1 even at the high rate of 10C. The enhanced performance can be ascribed to the formation of the robust and protective fluorinated organic-inorganic film on the cathode, which derives from the FEC cosolvent and LiPO 2 F 2 additive and ensures facile lithium-ion transport. The synergistic effect of the cosolvent and additive to boost the electrochemical performance of LiNi 0.5 Mn 0.3 Co 0.2 O 2 cathode will pave a new pathway for high-voltage cathode materials.