Succinic Anhydride as an Enabler in Ethylene Carbonate-Free Linear Alkyl Carbonate Electrolytes for High Voltage Li-Ion Cells

Abstract

Ethylene carbonate-free electrolytes containing 1 M LiPF6 in ethyl methyl carbonate with succinic anhydride as an enabler exhibited promising cycling and storage performance in Li(Ni0.4Mn0.4Co0.2)O2/graphite pouch type Li-ion cells tested to 4.5 V. Although cells using 1 M LiPF6 in EMC can barely function due to the poor passivation of the graphite electrode, the addition of 1% succinic anhydride allows cells to operate well. Compared to other enablers such as vinylene carbonate, succinic anhydride provides similar cycling and storage performance at 40◦C and improved storage or cycling performance at 60◦C. Succinic anhydride also limits gas evolution, especially at high temperatures where cells with vinylene carbonate normally produces large amounts of gas. Symmetric cell studies showed that adding succinic anhydride to cells greatly increased the impedance of the graphite electrode after formation. However, the impedance of the graphite electrode decreased substantially during cycling, leading to a significant decrease of impedance in the full pouch cells. With succinic anhydride as an enabler, ethylene carbonate-free linear alkyl carbonate electrolytes may be suitable for high temperature applications in some Li-ion cells.