Electrolytes for Lithium‐Ion Batteries with High‐Voltage Cathodes

The development of a thorough understanding of the reactions of an electrolyte of a lithium-ion battery with the surface of high-voltage cathode materials and the development of novel electrolytes capable of long-term reversible cycling to high voltage is of great current interest. The high oxidation potential of the cathode surface leads to oxidation reactions of the electrolyte components near the interface. An investigation of the thermal stability of the surface layers formed on cathode materials through the combined use of SEM, thermal gravimetric analysis (TGA), and XPS revealed that the cathode particles were found to enhance the thermal stability of the electrolyte at moderately elevated temperatures. Cycling Li-ion cells to high voltage typically results in low coulombic efficiency and poor cycle life. The primary contributor to poor cycling efficiency is the electrochemical oxidation reaction of the electrolytes at high positive potentials.