Ionic Liquids as Cathode Additives for High Voltage Lithium Batteries

Abstract

Two oxalatoborate ionic liquids (ILs), which are commonly utilized as electrolyte additives that form a protective layer on the cathode surface, are investigated for the first time as electrode additives. Cathodes based on LiNi0.5Mn1.5O4 (LNMO) containing 3 wt% ILs, i.e., "IL‐enriched cathodes", exhibit capacity values above 120 mAh/g with high Coulombic efficiencies throughout cycling over 200 times. A cathode without ILs also exhibits a capacity of 119 mAh/g but its Coulombic efficiency becomes low and unstable after 109 cycles. In addition, when 0.3 M ILs are added to conventional carbonate‐based electrolytes, the battery cycle life improves but there is a reduction in the capacity probably due to low ionic conductivity of the electrolyte mixtures. Post‐mortem analyses of electrodes retrieved from cycled cells highlight less electrolyte decomposition and less cathode corrosion, enabled by using the IL as the additive in LNMO, which are confirmed by a particle shape with smooth surface identical to the fresh cathode. The study demonstrates that oxalatoborate ILs can be used as the electrode additive, and this provides a new concept for cathode formulations for high performance batteries with a small amount of ILs.

Fluorinated Fullerenes as Electrolyte Additives for High Ionic Conductivity Lithium-Ion Batteries

“…It thereby facilitates the enhancement of the energy density, power density, and cycle stability of the battery or electrochemical system [15,16]. In addition, some additives can have a significant effect on the electrode, forming a protective layer on the electrode surface to reduce electrolyte decomposition and electrode corrosion, thus further optimizing the electrochemical performance [17]. Moreover, additives are employed to enhance the high-temperature, freezing, or flame-retardant properties of electrolytes, enabling them to meet specific application requirements.…”