Improving High-Voltage Performance of Lithium-Ion Batteries with Sulfolane as an Electrolyte Additive

Sulfolane (SL) is investigated as an electrolyte additive for LiNi1/3Co1/3Mn1/3O2/ graphite cell cycled in the voltage range of 3.0–4.6 V (vs. Li+/Li). The cyclic stability of LiNi1/3Co1/3Mn1/3O2/graphite cells is improved by using 2 vol.% SL. Charge–discharge tests on graphite/Li and LiNi1/3Co1/3Mn1/3O2/Li cells show that the cyclic improvement of the full cell results from the contribution of SL on the enforced stability of both graphite anode and LiNi1/3Co1/3Mn1/3O2 cathode. Linear sweep voltammetry data indicate that SL can improve the oxidation potential of the reference electrolyte, that is, 1.0 M LiPF6 in ethylene carbonate/dimethyl carbonate (1/1, by volume). Cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy indicate that an SL-containing electrolyte is likely to form low impedance, as well as a protective and stable film on both cathode and anode electrodes, which improves the stability of the electrode and electrolyte during cycling.