All-Fluorinated Electrolyte Enables Safe LiNi<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>O<sub>2</sub>|Graphite Pouch Cells with Stable High-Voltage Operation
Fu-Kui Zhang, Changjun Wu, Yu Wu, Xinrui Su, Tao Deng
Abstract
The poor safety and stability of conventional carbonate-based electrolytes at high voltage hinders the exploration of higher-nickel lithium-ion batteries. The all-fluorinated electrolytes are expected to suppress thermal hazards and enhance the high-voltage (up to 4.5 V) performance. In this study, an all-fluorinated electrolyte was proposed for a LiNi0.8Co0.1Mn0.1O2 (NCM811) pouch battery using a single-crystal cathode, which operates stably under high voltage. The high-voltage capacity retention of the cell using the all-fluorinated electrolyte after 300 cycles was 97.88%, while that of the cell using a conventional electrolyte was only 89.79%. Compared with the conventional electrolytes, all-fluorinated electrolytes increased the thermal runaway (TR) initial temperature of the battery by 15.4 °C and reduced the TR maximum temperature by 83.3 °C. Material characterization demonstrates that the cathode and anode interface rich in friendly elements (F and B) helped suppress the crosstalk of oxygen and hydrogen from the intrinsic level, thereby reducing the strength of the chain reaction during the TR process. This research provides new engineering guidance for solving the thermal safety problems of high-voltage NCM811/graphite pouch cells.