Cell Chemistry Considerations for Long-Lived Li-Ion Cells at High Temperatures

This study aimed to improve the high-temperature performance of Li-ion cells with liquid electrolyte to enable long lifetimes with wide operable temperature ranges. Three different positive electrode chemistries (Li[Ni 0.5 Mn 0.3 Co 0.2 ]O 2 , Li[Ni 0.83 Mn 0.06 Co 0.11 ]O 2 , Li[Ni 0.6 Mn 0.4 Co 0.0 ]O 2 ), six different electrolyte solvent blends (combining ethylene carbonate (EC), dimethyl carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dimethyl-2,5-dioxahexane carboxylate), and 10 different electrolyte additive combinations (combining vinylene carbonate (VC), ethylene sulfate (DTD), prop-1-ene-1,3-sultone, and tris(trimethylsilyl) phosphite) were cycled at C/3 and 85 °C. Selected electrode and electrolyte combinations were cycled at C/3 and 20 °C. The charge transfer resistance of all cells was measured at 10 °C. It was determined that gas production in the pouch cells increases with the Ni content in the positive electrode. The most optimal electrolyte solvent combination is EC:DEC. EC:EMC possibly enhances low-temperature performance without significant lifetime cost at 85 °C. Lowering the EC content in Ni83 cells reduces gas production and extends lifetime. The best-performing electrolyte additive combination was 2 wt% VC 1 wt% DTD.