Electrochemical-thermal modeling of lithium plating/stripping of Li (Ni0.6Mn0.2Co0.2)O2/Carbon lithium-ion batteries at subzero ambient temperatures

Electrochemical performance of lithium-ion batteries drops significantly at low temperatures, especially under charging, because the lithium ions are prone to deposit as lithium metal on instead of intercalating into the solid matrix of anode. At discharging, the existence of lithium stripping leads to the capacity reversed partially, whose amount is proportional to the width of extra voltage plateau displayed at the beginning. A physics-based electrochemical-thermal model considering effects of lithium plating/stripping is developed and validated to explore the degradation mechanism and behaviors of NMC/Carbon cells undergoing prolonged cycling. The temporal and spatial analyses of overpotential of lithium plating and surface concentration in solid phase at various operating conditions demonstrate that lithium plating starts to take place at the interface between composite anode and separator, and the degradation can be accelerated by the decreasing ambient temperatures and increasing charging current rates. The degradation effects including loss of recyclable lithium ions, loss of anode active material, growth of plated lithium and secondary solid electrolyte interphase (SEI) and consumption of electrolyte solvents are considered. The model is capable of estimating capacity as a function of cycle number with an overall accuracy of 3% if the capacity fade is less than 30%.