Dicarbonate Compounds as Electrolyte Solvents for Li-ion Cell Operation

Novel dicarbonate compounds were explored as a new class of electrolyte solvents for Li-ion batteries. Dimethyl-2,5-dioxahexane carboxylate (DMOHC) has been shown to be a high viscosity solvent that provides exceptional lifetime for Li-ion cells during elevated temperature cycling. Here, various dicarbonates were synthesized and screened for their physical properties, such as viscosity melting point and boiling point. Then, Li[Ni 0.6 Mn 0.4 Co 0.0 ]O 2 /graphite (NMC640), Li[Ni 0.83 Mn 0.06 Co 0.11 ]O 2 /graphite (Ni83), and LiFePO 4 /graphite (LFP) Li-ion pouch cells were used to evaluate the suitability of the various dicarbonates as electrolyte solvents for Li-ion cells. Cell testing was performed at 70 and 85 °C with various C-rate testing conditions. These novel dicarbonates were also blended with diethyl carbonate and dimethyl carbonate to lower viscosity and increase ionic conductivity. The findings suggest that several dicarbonate compounds can be viable electrolyte solvents for Li-ion cells operating only at elevated temperatures (70 °C+). It may not be possible to find a dicarbonate compound with low viscosity suitable as the main electrolyte solvent for Li-ion cells designed to operate at room temperature.