Cost-Efficient Film-Forming Additive for High-Voltage Lithium-Nickel-Manganese Oxide Cathodes.

The operating voltage of lithium-nickel-manganese oxide (LiNiMnO, LNMO) cathodes far exceeds the oxidation stability of the commercial electrolytes. The electrolytes undergo oxidation and decomposition during the charge/discharge process, resulting in the capacity fading of a high-voltage LNMO. Therefore, enhancing the interphasial stability of the high-voltage LNMO cathode is critical to promoting its commercial application. Applying a film-forming additive is one of the valid methods to solve the interphasial instability. However, most of the proposed additives are expensive, which increases the cost of the battery. In this work, a new cost-efficient film-forming electrolyte additive, 4-trifluoromethylphenylboronic acid (4TP), is adopted to enhance the long-term cycle stability of LNMO/Li cell at 4.9 V. With only 2 wt % 4TP, the capacity retention of LNMO/Li cell reaches up to 89% from 26% after 480 cycles. Moreover, 4TP is effective in increasing the rate performance of graphite anode. These results show that the 4TP additive can be applied in high-voltage LIBs, which significantly increases the manufacturing cost while improving the battery performance.