Facile Formation of a LiF-Carbon Layer as an Artificial Cathodic Electrolyte Interphase through Encapsulation of a Cathode with Carbon Monofluoride

Lithium batteries that utilize a lithium anode and a high voltage cathode are highly required to meet the growing demand for electrification of transportation. High voltage lithium cobalt oxide (LiCoO2, LCO) can be a promising choice for lithium batteries with high energy and power. However, intrinsic structural instability at high voltages (>4.2 V) leads to significant capacity loss during the repeated cycles of charge-discharge. Herein, a simple and effective method has been proposed to prepare an artificial protective layer of LCO, enabling the LCO to achieve long-term cycle stability at 4.5 V. It is found that carbon monofluoride reacts with LCO via defluorination at 400 degrees C to form a LiF-C layer on LCO, which suppresses side reactions at the electrolyte/electrode interface. Moreover, the LiF-C layer plays a key role in not only facilitating charge transport but also restricting Co dissolution from the cathode. The Li//LiF-C coated LCO cells deliver an initial discharge capacity of 186 mAh g(-1) at 0.1C and exhibit excellent cycling and rate performance: 161 mAh g(-1) after 180 cycles (90% of the initial value at 0.5C) and 115 mAh g(-1) at 10C (63.2% of the 0.1C capacity).

Automated summary

The study successfully improved the cycling stability of lithium batteries by forming an artificial protective layer on high voltage lithium cobalt oxide, enhancing the performance of the batteries.