Improving Linear Alkyl Carbonate Electrolytes with Electrolyte Additives

The effectiveness of some selected electrolyte additives were studied in ethylene carbonate-free linear alkyl carbonate electrolyte mixtures containing 1 M LiPF6/ethylmethyl carbonate: vinylene carbonate (98:2 w:w). The electrolytes were used in Li(Ni0.4Mn0.4Co0.2)O2/graphite pouch type Li-ion cells tested to 4.5 V at elevated temperature. The results showed that cells with linear alkyl carbonate electrolytes outperformed cells with EC-based electrolytes having state-of-the-art additive blends and cells with fluorinated electrolytes during short-term and long-term cycling at elevated temperatures. The addition of triallyl phosphate or pyridine phosphorus pentafluoride as electrolyte additives to the EC-free electrolyte provided cells with better capacity retention during long-term cycling than cells containing vinylene carbonate alone. These results suggest that small quantities of electrolyte additives can be used to create EC-free, linear alkyl carbonate electrolytes that perform well at high voltages.