Enhanced high voltage performance of LiNi0.5Mn0.3Co0.2O2 cathode via the synergistic effect of LiPO2F2 and FEC in fluorinated electrolyte for lithium-ion batteries

LiNi_0.5Mn_0.3Co_0.2O₂ can achieve high energy density due to its merits of high theoretical capacity and a relatively high operating voltage, but the LiNi_0.5Mn_0.3Co_0.2O₂ 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 (LiPO₂F₂) as a salt-type additive extending the life span of the LiNi_0.5Mn_0.3Co_0.2O₂ cathode. LiNi_0.5Mn_0.3Co_0.2O₂ 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 LiPO₂F₂ additive and ensures facile lithium-ion transport. The synergistic effect of the cosolvent and additive to boost the electrochemical performance of LiNi_0.5Mn_0.3Co_0.2O₂ cathode will pave a new pathway for high-voltage cathode materials.