Electrochemical Analysis of Factors Affecting the Kinetic Capabilities of an Ionic Liquid Electrolyte

Abstract

As an alternative to conventional carbonate-based electrolytes, ionic liquid (IL) electrolytes exhibit several advantageous characteristics including non-flammability, negligible volatility, high electrochemical and thermal stability, and the ability to form robust yet conductive passivation layers on a number of high-energy electrode materials. However, IL electrolytes traditionally suffer from poor rate performance owing to their high viscosity and low ionic conductivity as compared to traditional electrolyte solutions. The following study will assess the kinetic capabilities of an IL electrolyte paired with a high-energy, nickel-rich layered cathode. The effects of temperature, electrode mass loading, and electrode composition are investigated in order to form an understanding of the kinetically limiting factors. Cycling tests performed at elevated temperatures not only show that IL electrolytes enable stable high-temperature operation but that elevated temperatures facilitate substantial improvements in rate capabilities. Analysis by electrochemical impedance spectroscopy ultimately illuminates a critical correlation between electrode wettability and rate performance. The trends established by this study will to help inform the optimal performance of IL electrolytes in high-rate applications.