Doped sulfone electrolytes for high voltage Li-ion cell applications

We show that, with appropriate doping, the ethersulfone-based electrolytes that we earlier reported to have 5.6 V electrochemical windows but poor cycling performance in Li-ion cells, can succeed. We show they can be used to make cells that, at C/20 charge/discharge rates, have cycling performance equal to those with the standard LiPF6-carbonate electrolytes. A difference in performance that develops at higher C is removed by substituting an ethersulfone with one fewer methyl groups, for lower viscosity.