High-Capacity LiNi_0.8Co_0.1Mn_0.1O₂ Positive-Electrodes in the Nearly Saturated and Fluorinated Acetate-Diluted Electrolyte Solutions

Abstract

Six kinds of acetic acid esters substituted with a different number of fluorine atoms were systematically investigated as a diluent for the nearly saturated LiBF 4 -based electrolyte solutions. Of these, only one fluorinated acetic acid ester was found to be suitable for the dilution and to greatly improve the charge− discharge cycle performance of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) electrodes. The charging voltage was raised to 4.6 V to increase the discharge capacities. The structure and thermal stability of the diluted electrolyte solutions, as well as the surface of the NCM811 electrodes after repeated charge/discharge cycles, were analyzed to elucidate the mechanism for the improved performance.