A fluorinated electrolyte stabilizing high-voltage graphite/NCM811 batteries with an inorganic-rich electrode-electrolyte interface

Increasing the operating voltage of Ni-rich cathode materials is a promising route to achieve lithium-ion batteries with a high energy density. However, the unstable electrode–electrolyte interface (EEI) caused by the decomposition of carbonate-based electrolytes at high voltage is a major obstacle. Herein, it is reported that the superior electrochemical performance of the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode at 4.6 V is achievable using a novel electrolyte system containing fluorinated carbonate and fluorinated carboxylate with a lithium difluoro(oxalate)borate (LiDFOB) additive. The stable B- and F-rich inorganic EEI at high voltage can reduce electrochemical polarization while also preventing the collapse of the cathode structure and continuous dissolution of transition metal ions. As a result, our designed fluorinated electrolyte enables Li/NCM811 half-cells to deliver a high specific capacity (247.2 mAh g−1), superior cyclability (81.4% retention at 200 cycles, 0.5C) and rate performance (154.5 mAh g−1 at 5C) at 4.6 V. The designed electrolyte also enables graphite (Gr)/NCM811 full cells with high loading cathode (≈ 9.5 mg cm−2) to achieve a high capacity retention of 83.3% (0.5C) after 100 cycles at 4.6 V. This work provides a new method to achieve high energy density Gr/NCM811 batteries at high voltage.