Toward 5 V Lithium‐Ion Battery: Exploring the Limit of Charge Cut‐off Voltage of Li‐Rich Layered Oxide Cathode and High‐Voltage Interfacial Processes

Increasing the capacity of Li‐rich layered oxide (LMNC) cathode material for high‐energy density lithium‐ion batteries relies on the increase of charge cut‐off voltage toward 5 V, under the utilization of anodically stable electrolyte component. The utilization of di‐(2,2,2 trifluoroethyl)carbonate (DFDEC)‐containing electrolyte permits significant improvement of anodic stability, cathode–electrolyte interface, and cycling stability of LMNC cathode, with respect to conventional electrolyte. In the present study, the limit of anodic stability of DFDEC under charging to 5.5 V versus Li is explored, and the interfacial processes of DFDEC‐derived surface protection mechanism are investigated, utilizing charge cut‐off voltage‐dependent surface and structural analyses. The oxidative decomposition of DFDEC is found to begin at 4.7 V, producing metal fluorides and CF‐containing organic compounds as the earliest surface species, passivating the cathode surface and reducing metal dissolution, structural transformation, and cathode degradation. The tolerable limit of charge cut‐off voltage of a model electrolyte of 0.1 m LiPF6/DFDEC is determined to be 5.0 V, to which the cathode outperforms conventional electrolyte, delivering discharge capacities of 261–225 mAhg−1 with the capacity retention of 86% at the 50th cycle. The data give an insight into the principles of electrolyte design and high‐voltage cathode–electrolyte interfacial stabilization toward advanced 5 V lithium‐ion batteries. The limit of anodic stability of Li‐rich layered oxide cathode with di‐(2,2,2 trifluoroethyl)carbonate (DFDEC) under charging to 5.5 V versus Li is explored, and initial high‐voltage cathode–electrolyte interfacial processes are investigated. DFDEC oxidation produces metal fluorides and CF‐containing organic compounds as the earliest surface species, which passivates cathode surface and reduces metal dissolution, structural transformation, and degradation of cathode.