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

Abstract

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.