The Effect of Electrolyte Additives upon Lithium Plating during Low Temperature Charging of Graphite-LiNiCoAlO₂ Lithium-Ion Three Electrode Cells

The effects of lithium-ion electrolyte additives in ester-rich low temperature electrolyte blends, including vinylene carbonate (VC), lithiuma bis(oxalato) borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), propane sultone (PS) and lithium bis(fluorosulfonyl)imide (LiFSI), upon the likelihood of lithium plating are investigated in graphite-LiNiCoAlO₂ three-electrode cells. Although metallic lithium is generally absent in lithium-ion cells, certain conditions, particularly charging at low temperature and/or at high rate, can lead to lithium metal plating on the surface rather than intercalating into the carbon anode. Metallic lithium reacts with the electrolyte and forms dendrites upon continuous plating, which can lead to cell shorting and capacity loss. The type of carbon anode, electrolyte, and solid-electrolyte-interphase (SEI) all influence this behavior. SEI stabilizing additives are generally detrimental to low temperature charging performance, however, 0.1 M LiFSI was found to be advantageous to low temperature charging. When charged at a C/5 rate to 4.10 V, lithium plating was evident at ∼20 °C higher temperature with VC and LiBOB additives compared to the baseline electrolyte without any additives (plating appears at −10 °C rather than −30 °C with the baseline electrolyte). In contrast, the cell containing 0.10 M LiFSI as an additive did not display lithium plating until −40 °C, or 10 °C lower than the baseline cell.